Halogeno Metal Carbonyls and Related Compoundsf F. C A L D E R A Z ZO Cyanamid European Research Institute, Cologny, Geneva, Switzerland

Halogeno Metal Carbonyls and Related Compoundsf

F . C A L D E R A Z Z O

Cyanamid European Research Institute, Cologny, Geneva, Switzerland

1. I n t r o d u c t i o n . . . . . . . . . . · 3 8 3 2. M e t h o d s o f P r e p a r a t i o n . . . · 3 8 5 A . C o p p e r S u b g r o u p . . . · . . 3 9 1

B . N i c k e l S u b g r o u p 3 9 2 C . C o b a l t S u b g r o u p 3 9 4 D . I r o n S u b g r o u p . . . · 3 9 6

E . M a n g a n e s e S u b g r o u p . . . · · · 3 9 9 F . C h r o m i u m S u b g r o u p . . . 4 0 1 3. C h e m i c a l a n d P h y s i c a l P r o p e r t i e s . . . 4 0 2

4. S t r u c t u r e s 4 0 3 A . X - R a y D e t e r m i n a t i o n s . . . 4 0 3

B . S t r u c t u r e I n v e s t i g a t i o n s b y P h y s i c a l M e t h o d s . . . 4 0 5 5. R e a c t i o n s o f H a l o g e n o M e t a l C a r b o n y l s . . . . . . . . . . . . 4 1 2 A . M o n o n u c l e a r C o m p o u n d s . . . . . . . . . . . . 4 1 2 B . P o l y n u c l e a r C o m p o u n d s . . . 4 1 9 C . A n i o n i c C o m p o u n d s . . . 4 2 3 6. M e c h a n i s t i c S t u d i e s . . . 4 2 3

7. S t a b i l i t y o f H a l o g e n o M e t a l C a r b o n y l s 4 2 6 R e f e r e n c e s . . . . . . . . . 4 3 0

1 . Introduction

T r a n s i t i o n m e t a l s form halogeno m e t a l carbonyls in which b o t h carbon m o n o x i d e a n d halogens are b o n d e d t o t h e central m e t a l a t o m . F o r some of t h e V I I I g r o u p m e t a l s (platinum, palladium) a n d copper a n d gold t h e carbonyls h a v e n o t y e t b e e n r e p o r t e d . Nevertheless, halogeno carbonyls of these m e t a l s a r e k n o w n .

T h e formal charge carried b y t h e halogen c a n be i n t e r n a l l y neutralized b y t h e central m e t a l a t o m , in such a w a y t h a t t h e o x i d a t i o n s t a t e of t h e m e t a l is equal t o t h e n u m b e r of halogen groups present. This is t h e case of u n c h a r g e d halogeno m e t a l carbonyls. So, for e x a m p l e , Fel2(CO)4

I T h e f o l l o w i n g a b b r e v i a t i o n s a r e u s e d : M e , m e t h y l ; E t , e t h y l ; P h , p h e n y l ; B u t , n - b u t y l ; d i p y , 2 , 2 ' - d i p y r i d y l ; p y , p y r i d i n e ; d i p h o s , l , 2 - b i s - ( d i p h e n y l p h o s p h i n o ) e t h a n e ; d i a r s , o - p h e n y l e n e b i s - ( d i m e t h y l a r s i n e ) ; p h e n , 1,1 O - p h e n a n t h r o l i n e ; T T A S , b i s - ( o - d i m e t h y l a r s i n o p h e n y l ) m e t h y l a r s i n e ; d i t h i a n , 1 , 4 - d i t h i a n e .

3 8 3

384 Γ. CALDERAZZO

can be considered as a coordination c o m p o u n d of iron in a formal oxidation s t a t e 2 + . H o w e v e r , anionic halogeno carbonyl m e t a l l a t e s also are k n o w n . I n these c o m p o u n d s t h e oxidation s t a t e of t h e m e t a l is given b y t h e n u m b e r of halogen groups p r e s e n t t o which t h e n u m b e r of negative charges of t h e complex are t o be s u b t r a c t e d . E x a m p l e s of this t y p e are t h e anions [PtClsiCO)]-, [IrBr4(CO)2]- a n d [MnClaiCO)^- which should be considered as coordination c o m p o u n d s of P t ( I I ) , I r ( I I I ) a n d Mn(I) respectively. I t will be noticed t h a t for anionic halogeno m e t a l carbonyls, zero oxidation states are possible a n d are actually k n o w n . [ C r X ( C 0) 5 ] - is such a case.

A few examples of cationic halogeno m e t a l carbonyls are k n o w n b u t these are of t h e s u b s t i t u t e d t y p e , such as [PtCl(dipy)(CO)]+ isolated b y I r v i n g a n d Magnusson. <^^) T h e oxidation s t a t e of t h e m e t a l is in this case given b y t h e n u m b e r of halogens present in t h e coordination sphere of t h e m e t a l t o which t h e positive charges of t h e complex cation are t o be a d d e d . T h e complex of p l a t i n u m a n d t h e complexi^^^) [CrBr(diars)2(CO)2]+ b o t h contain t h e m e t a l in oxidation s t a t e 2 + .

Dinuclear a n d polynuclear halogeno m e t a l carbonyls are also k n o w n . B o t h carbon m o n o x i d e a n d halogens are in principle capable of acting as bridging groups b e t w e e n t w o m e t a l s . Despite t h a t , t h e r e are n o a u t h e n t i c a t e d cases k n o w n of bridging CO groups in halogeno m e t a l carbonyls. I t is a quite general feature t h a t t h e b o n d s between m e t a l a t o m s are preferably o b t a i n e d b y direct m e t a l - m e t a l b o n d s (as p r o b ­ ably in [Mn2X2(CO)8]^"") or, m o r e often, b y halogen bridges (as for e x a m p l e in [MnBr(CO)4]2).

Although double halogen bridges are m o s t c o m m o n l y encountered in dinuclear halogeno m e t a l carbonyls, t h e r e are few cases k n o w n of bridges between t w o m e t a l s t h r o u g h one single halogen. This is p r o b a b l y t h e case for GÎ ^I ( C O) ^ O ^ ^ ' ) a n d for [ F e, X ( C, I i, U C O ) , ] + , ( ' ^ > ' ^ ' ' ^ - ) for which s t r u c t u r e s of t h e t y p e shown below h a v e been proposed.

oc- Α Α

- C r - - C r - -CO

0 c

- F e - - F e -

Halogeno m e t a l carbonyls are low-spin complexes, i.e. t h e halogens a n d CO groups provide a strong ligand field for t h e central m e t a l a t o m . T h u s , if we consider, for example, t h e (Z^-system of Fel2(CO)4, we observe t h a t this c o m p o u n d is diamagnetic. <i^^'^^^) T h e same is t r u e for t h e ci ^-system of PtCl 2( 0 0) 2 , whose m a g n e t i c susceptibility h a s been

HALOGENO METAL CARBONYLS 385

qCÎ ^ CI ' CI

is such a n e x a m p l e .

Also included b o t h in t h e discussion a n d in t h e t a b l e s are e x a m p l e s of s u b s t i t u t e d halogeno m e t a l carbonyls. These are c o m p o u n d s n o t necessarily directly p r e p a r e d from halogeno m e t a l carbonyls b y s u b ­ s t i t u t i o n reactions, w h i c h contain, in a d d i t i o n t o c a r b o n m o n o x i d e a n d halogen groups, o t h e r ligands such as t r i p h e n y l p h o s p h i n e , cyclo- p e n t a d i e n y l rings, aliphatic a n d a r o m a t i c amines a n d so on. T h e r e a d e r should, however, be a w a r e of t h e fact t h a t only t h e m o s t r e p r e s e n t a t i v e e x a m p l e s of substituted halogeno m e t a l carbonyls are r e p o r t e d in Tables I I a n d I V , a n d t h e e x a m p l e s given t h e r e should n o t be considered e x h a u s t i v e of t h e subject.

2. Methods of P r e p a r a t i o n

H a l o g e n o m e t a l carbonyls can be p r e p a r e d b y t w o m a i n p r o c e d u r e s : (a) b y t r e a t m e n t of t h e m e t a l halide w i t h c a r b o n m o n o x i d e a t high t e m p e r a t u r e or (b) b y o x i d a t i o n of t h e m e t a l carbonyl w i t h halogens.

T h e first m e t h o d h a s been used p a r t i c u l a r l y w i t h t h e g r o u p V I I I second a n d t h i r d row t r a n s i t i o n elements, whose m e t a l carbonyls are n o t k n o w n or n o t readily p r e p a r e d . T h e a d d i t i o n of a halogen a c c e p t o r m a y b e necessary if a halide of t h e m e t a l in a higher oxidation s t a t e is used as s t a r t i n g m a t e r i a l . Copper is usually e m p l o y e d for this purpose.

m e a s u r e d b y K l e m m a n d co-workers. (^^^> Low-spin p a r a m a g n e t i c halogeno m e t a l carbonyls h a v e also been r e p o r t e d . B o t h CrI(CO)5(2^) a n d Cr2l(CO)io^^^) are p a r a m a g n e t i c w i t h a m a g n e t i c m o m e n t corre­

sponding t o one u n p a i r e d electron. I n t h e l a t t e r c o m p o u n d one of t h e t w o c h r o m i u m a t o m s should be considered as being in a n oxidation s t a t e 1 + , a n d t h e o t h e r in a zero o x i d a t i o n s t a t e : a n d d^ respectively.

T h e empirical inert-gas rule is rarely applied t o halogeno m e t a l carbonyls, especially those containing g r o u p V I I I second a n d t h i r d row m e t a l s . T a k i n g into a c c o u n t t h a t , once t h e o x i d a t i o n s t a t e s h a v e been assigned t o t h e m e t a l s , bridging halogen a t o m s should b e correctly considered as four-electron donors (two electrons t o each of t h e t w o m e t a l a t o m s forming t h e bridge), several e x a m p l e s are found of t h e b r e a k d o w n of such a rule. T h e p l a t i n u m ( I I ) d e r i v a t i v e [PtCl2(CO)]2, t o which I r v i n g a n d Magnusson (^^) h a v e assigned t h e s y m m e t r i c trans- configuration

CI CI

\ / \ /

P t P t

386 F. CALDERAZZO

S o m e t i m e s t h e use of a halogen acceptor is unnecessary, since carbon m o n o x i d e itself can a c t as a n acceptor b y forming in t h e reaction con­

ditions phosgene or phosgene analogues, COXg.

TABLE I . H a l o g e n o m e t a l c a r b o n y l s

C o m p o u n d C o l o u r M . P . (°C) R e f e r e n c e s

C u C l ( C O ) c o l o u r l e s s d e c . a t r o o m t e m p . 167 C u C l ( C O ) . 2 H 2 0 c o l o u r l e s s d e c . a t r o o m t e m p . 98, 1 2 0

A u C l ( C O ) c o l o u r l e s s ^ΊΟ s u b l i m e s 102, 122

A u B r ( C O ) c o l o u r l e s s s u b l i m e s 102

[ P d C l , ( C O ) ] „ y e l l o w - b r o w n 6 0 d e c . 126

[ P d , C l ( C O ) , ] „ y e l l o w 150 d e c . 5 5

[ P d, C l 4( C O) 2 ? - g r e e n y e l l o w — ^{6 4}

coloin-less 103 114, 116, 152

P t B r 2( C 0 ) i , c o l o u r l e s s 7 5 s u b l i m e s 116

P t I a i C O ) , r u b y r e d 4 0 s u b l i m e s 116

[ P t C l , ( C O ) ] , r e d 195 116, 152

[ P t B r , ( C 0) ] 2 r e d 187 116, 130, 145

[ P t I , ( C O ) ] , v i o l e t 1 4 0 - 1 5 0 d e c . 116, 130

P t j C l i { C O ) , o r a n g e 1 2 3 116, 152

P t j B r 4( C O) 3 b r i c k r e d 142 116

[ P t C l a i C O ) ] - y e l l o w 2 2 0 a 6 3 , 116, 130

[ P t B r 3( C 0 ) ] - g o l d e n y e l l o w 245^ 116, 130

[ P t l 3( C 0 ) ] - o r a n g e 230^ 116, 130

[ P t ( N C S) 3( C 0 ) ] - — — ^{1 3 0}

P t F , ( C O ) , p a l e y e l l o w s u b l i m e s 153

C o I j ( C O ) b l a c k b r o w n d e c . a t r o o m t e m p . 1 5 0

[ R h C l ( C O ) , ] „ r u b y r e d 125-5 58, 108

[ R h B r ( C O ) j ] „ y e l l o w - r e d 118 58, 108

[ R h I ( C O ) J „ y e l l o w 114 108

[ R h ( C N ) { C O ) , ] „ b l u e — ^{1 0 8 a}

[ R h C l , ( C O) 2 ] - p a l e y e l l o w 81 dec,^ 109, 161

[ R h B r , ( C 0) 2 ] - p a l e y e l l o w 86 d e c . b 161

[ R h I , ( C O ) , ] - m u s t a r d y e l l o w 78 d e c . b 161

[Rh^Br^iCO)^]^- o r a n g e r e d 174 d e c . b 161

[ R h , I , ( C 0) 2 ] ^ - r e d d i s h b r o w n — ¹⁶¹

[ R h l j C O ] - d a r k b r o w n — ¹⁶¹

[ R h F 3( C O ) , ] , o r a n g e r e d — ¹⁵³

I r C l a l C O ) ^ c o l o u r l e s s 1 4 0 d e c . 88, 121

I r B r a l C O ) ^ p a l e y e l l o w — ⁸⁸

I r I , ( C O ) , l i g h t y e l l o w — ⁸⁸

I r C l ( C O) 3 l i g h t b r o w n — ⁸⁸

I r B r ( C 0) 3 b r o w n — ⁸⁸

I r I ( C O) 3 d e e p b r o w n — ⁸⁸

I r l 3( C O) 3 d e e p r e d

—

[ I r l 3( C O ) , ] , b r o w n r e d — ¹¹⁸

d a r k r e d — ¹¹⁸

[ I r I , ( C O ) , ] - g r e e n y e l l o w 158* 118

[ I r B r 3( C O ) , ] - y e l l o w 175* 115

H A L O G E N O M E T A L C A R B O N Y L S 387

TABLE I —c o n t i n u e d

C o m p o u n d C o l o u r M. P . (°C) R e f e r e n c e s

[ I r l g C O ] - b r o w n 2 5 6 » 1 1 8

[ I r l . C O ] - r e d 273a 118, 132

[ I r B r , ( C 0 ) 2 ] - c a n a r y - y e l l o w 190C ^{1 1 5}

[ I r l ^ i C O ) ^ ] - r e d 210» 1 1 5 , 1 1 8

[ I r C l , ( C 0 ) ] 2 - p i n k 2 6 2 » 1 1 8

[lvBT,{CO)f~ p i n k 2 9 3 » 1 1 8

[IvUCO)Y- b r o w n r e d 3 0 8 » 1 1 8

[ I r ^ C l ^ i C O ) , ] - b r o w n 2 2 5 d e c . » 1 1 5

[ I r ^ B r ^ i C O J - d a r k b r o w n 2 5 0 » 1 1 5

t o b a c c o > 2 0 0 < i d e c . 1 1 5

l i g h t r e d 2 8 4 » 1 1 8

F e l 2 ( C O) 5 — — ^{6 6 a ,} 170

F e C l 2 ( C O) 4 y e l l o w 10 d e c . 6 6

F e B r 2 ( C O) 4 b r o w n r e d 5 5 d e c . 6 6 , 129

F e l 2 { C O) 4 r e d 7 5 d e c . 6 6

F e I C l ( C 0) 4 d e e p y e l l o w — ^{8 4}

F e I B r ( C 0) 4 r e d b r o w n — ^{8 4}

F e C l 2 ( C O ) 2 d e e p b r o w n — ^{8 4}

F e l 2 ( C O ) 2 d e e p b r o w n — ^{7 6}

F e I ( C 0 ) 2 — — ⁷⁶

F e 2 l 2 ( C O) 8 w h i t e - 5 39

I l u l 2 ( C O) 4 g o l d e n y e l l o w 140 d e c . 37

[ R u C l 2 ( C O ) 2] n l e m o n y e l l o w — ^{1 2 3}

[ R u B r 2 ( C O ) 2 ] „ l i g h t o r a n g e — ^{1 2 3}

[ R u l 2 { C O ) 2] n o c h r e — 9 4 , 1 2 3

[ R u B r ( C O ) ] „ c o l o u r l e s s — ¹¹⁹

O s C l 2 ( C O) 4 c o l o u r l e s s — ^{8 2}

O s B r 2 ( C O) 4 c o l o u r l e s s a n d — ^{8 2}

l i g h t y e l l o w

O s l 2 ( C O) 4 y e l l o w a n d — ^{8 2}

d e e p y e l l o w

[ O s B r ( C O ) j 2 c a n a r y - y e l l o w — ^{8 2}

[ O s I ( C O) 4] 2 y e l l o w o r a n g e — ^{8 2}

[ O s C l 2 ( C O) 3 ] / c o l o u r l e s s 2 6 9 - 2 7 3 1 2 4

[ O s B r 2 ( C O) 3 ] . « y e l l o w — ^{8 2}

[ O s l 2 ( C O) 3 ] « « d e e p y e l l o w — ^{8 2}

O s B r 2 ( C O ) 2 y e l l o w i s h — ^{8 2}

O s l 2 ( C O ) 2 l i g h t y e l l o w — ^{8 2}

M n C l ( C 0) 5 p a l e y e l l o w

—

M n B r ( C 0) 5 y e l l o w — ²

M n I ( C 0) 5 o r a n g e - r e d 1 1 5 d e c . 2, 27

M n C N ( C O) 5 p a l e y e l l o w — Ί 8 0 d e c . 3 3 a

M n ( S C N ) ( C 0) 5 g o l d e n y e l l o w — ^{4 6 , 171}

[ M n C l ( C O) 4] 2 o r a n g e — ²

[ M n B r ( C O) 4] 2 b r o w n — ²

[ M n I ( C O) 4] 2 d a r k b r o w n — ²

[ E t 4 N ] [ M n C l 2 ( C O) 4 ] p a l e y e l l o w — ^{1, 8}

[ E t 4 N ] [ M n B r 2 ( C O) 4 ] y e l l o w — ^{1, 8}

[ E t 4 N ] [ M n l 2 ( C O) 4 ] d e e p r e d — ^{1, 8}

388 Γ. CALDERAZZO TABLE I —c o n t i n u e d

C o m p o u n d C o l o u r M . P . (°C) R e f e r e n c e s

[ E t ^ N l a i M n ^ C l ^ i C O l s ] y e l l o w

—

[ E t . N J ^ E M n ^ B r ^ i C O s ]

— —

[ E t , N] 2[ M n, l 2( C O) 8 ] r e d

—

T c C l ( C 0) 5 c o l o u r l e s s 9 2

T c B r ( C 0) 5

—

T c I ( C 0) 5 f

—

[ T c C l ( C O ) J /

—

[ T c B r ( C 0) j 2 ^

—

[ T c I ( C 0) j 2 ^

—

I l e C l ( C 0) 5 c o l o u r l e s s 15, 8 9 , 1 5 1

R e B r ( C 0) 5 c o l o u r l e s s 89, 151

R e I ( C 0) 5 c o l o u r l e s s 2 7 , 8 9 , 1 5 1

[ R e C l ( C O) 4 ] 2 c o l o u r l e s s 3

[ R e B r ( C 0) j 2 c o l o u r l e s s 3

[ R e I ( C 0) j 2 y e l l o w 3

[ R e I , ( C O ) J - c o l o u r l e s s l a

[ R e l 3( C O) 3 ] ^ - c o l o u r l e s s l a

[Re^BrgCCO),]- c o l o u r l e s s l a

[ R e , I , ( C 0 ) s] 2 - c o l o u r l e s s l a

C r I ( C 0) 5 d e e p b l u e d e c . a t r o o m t e m p . 2 0

C r C N ( C 0) 5 d e e p g r e e n 1 8 a

C r N C S ( C 0) 5 d e e p r e d 1 8 a

Cr2l(CO)io r e d d e c . a t r o o m t e m p . 19

C r 2( N C S ) ( C O) i o r e d 2 0 - 4 0 d e c . 1 9 a

[ C r C l ( C 0) 5 ] - y e l l o w 5

[ C r B r ( C 0) 5 ] - y e l l o w 5

[ C r I ( C 0) 5 ] - y e l l o w 5, 5 2

[ C r ( N C S ) ( C 0) 5 ] - d e e p y e l l o w 172

—

[ M o C l ( C O) 5 ] - y e l l o w 5

[ M o B r ( C O) 5 ] - y e l l o w 5

[ M o I ( C O) 5 ] - y e l l o w 4, 5, 5 2

[ M o ( N C S ) ( C O) 5 ] - d e e p y e l l o w 172

[ M o B r 3(CO) 4 ] - y e l l o w o r a n g e 57

[ M o I a i C O J - y e l l o w o r a n g e 5 7 , 1 0 3

[ W C 1 ( C 0 ) J - y e l l o w 5

[ W B r i C O J - y e l l o w 5

[ W I ( C 0) 5 ] - y e l l o w 5, 5 2

[ W ( N C S ) ( C 0) 5 ] - d e e p y e l l o w 172

[ W B r 3( C O) 4 ] - y e l l o w o r a n g e 57

[ W l 3( C 0 ) J - y e l l o w o r a n g e 57, 1 0 3

* F o r t h e t e t r a p h e n y l a r s o n i u m s a l t .

^ F o r t h e t e t r a e t h y l a m m o n i u m s a l t .

^ F o r t h e t e t r a b u t y l a m m o n i u m s a l t , d F o r t h e p o t a s s i u m s a l t ,

e P r o b a b l y χ = 2.

' I d e n t i f i e d b y i n f r a r e d s p e c t r u m o n l y .

HALOGENO METAL CARBONYLS 389

TABLE I I . S u b s t i t u t e d h a l o g e n o m e t a l c a r b o n y l s

C o m p o u n d C o l o u r M . P . ( ° C ) R e f e r e n c e s

m - i P t C l g P E t g i C O ) ] c o l o u r l e s s m - C P t B r a P E t a i C O ) ] c o l o u r l e s s [ P t C l d i p y ( C O ) ] + y e l l o w C o I( P P h 3) ( C O) 3 d a r k b r o w n C o B r( P P h 3 ) 2( C O) 2 » b r o w n CoI( P P h 3 ) 2(CO) 2 ^ b r o w n C o l 2( C p ) ( C O ) d a r k p u r p l e F 3 C C o I( C p ) ( C O ) b l a c k CoCl2(PEt3)2(CO) — R h C l( P E t 3 ) 2( C O )

R h C l( P P h 3 ) 2( C O ) F 3 C R h I( C p ) ( C 0 ) I r C l ( p- t o l u i d i n e) ( C 0) 2 I r l 3 ( N H 3 ) 2(CO) I r l 2 d i p y( C O) 2 I r I( P P h 3 ) 2( C O) 2 H3CIrClI(PPh3)2(CO) H 3 C O C R h C l I ( P B u t 3 ) 2(CO) I r C l( P P h 3 ) 2( C O )

I r B r( P P h 3 ) 2( C O ) I r I( P P h 3 ) 2( C O ) IrCl3(PEt3)2(CO) [ I r l 3 P( O E t) 3( C O) ] 2 FeBr2(AsPh3)2(CO)2 F e l 2 ( S b P h 3) ( C O) 3 F e B r 2 ( T e P h 2) ( C O) 3 F e l 2 ( T e P h 2) ( C O) 3 F e C l 2 ( P E t 2 P h)(CO) 2 [ F e 2 B r C p 2( C O) 4 ] + [ F e 2 l( C p) 2( C O ) J + F e C l ( C p ) ( C O ) » F e I C p ( P h N C ) ( C O ) ci5.[RuCl2(PEt2Ph)2(CO)2^

R u H C l( P E t 2 P h ) 3( C O p R u l 2 p y 2( C O) 2 Rul2{PPh3)2(CO)2 O s H C l( P P h 3 ) 3{ C O ) O s H B r( P P h 3 ) 3( C O ) OsCl3(PPh3)2(CO) OsBr3(PPh3)2(CO) O s B r ( C p ) ( C O) 2 M n B r( d i p h o s) ( C O) 3 M n I( d i p h o s) ( C O) 3 [Mn( d i p h o s ) 2(CO) 2 l C l

y e l l o w d a r k r e d b l u e d a r k r e d r e d a n d y e l l o w o r a n g e p a l e y e l l o w o r a n g e l e m o n y e l l o w y e U o w p a l e y e l l o w r e d

b r o w n b r o w n b l a c k o r a n g e r e d b r o w n d e e p r e d r e d b r o w n c o l o u r l e s s c o l o u r l e s s o r a n g e o c h r e

c o l o u r l e s s b r o w n p u r p l e l i g h t y e l l o w l i g h t o r a n g e o r a n g e y e l l o w - o r a n g e

1 3 4 - 1 3 6 1 1 8 - 1 2 0

185 d e c . 1 0 7 - 1 0 8 d e c . 9 7 - 1 0 0 d e c . 185 d e c . - 1 4 5 d e c .

5 8 7 5 - 7 6 1 9 5 - 2 0 0 d e c . 1 6 8 - 1 6 9

2 2 8 2 4 0 d e c . 2 6 8 - 2 6 9 d e c . 8 2 - 5 - 8 5 d e c . 3 2 3 - 3 2 5 2 5 6 - 2 6 0 d e c . 1 5 9 - 1 6 1 2 2 0 d e c .

1 6 0

108 1 4 4 - 1 4 6 9 9 - 1 0 1

2 7 6 2 3 5 2 3 0 1 2 0 - 1 2 1 1 8 2 - 1 8 3 179 1 9 1 - 1 9 2

3 2 3 2 9 5 67 67, 1 4 8 6 7 , 1 4 8 6 2 , 1 0 4 105 2 5 2 8 9 0 , 1 5 9 128 13 131 14 14 61 61 1 3 7 , 1 6 5 13 3 3 b 31 173 8 3 8 3 7 4 7 4 2 5 5 0 5 1 , 5 1 a 6 0 , 1 4 4 1 0 0 2 9 , 3 3 2 8 , 3 3 9 4 71 139, 1 6 4 139, 1 6 2 , 1 6 4 162

162 4 7

140 1 4 0 1 4 1 , 1 4 9

390 Γ.CALDERAZZO TABLE I I —c o n t i n u e d

C o m p o u n d C o l o u r M . P . (°C) R e f e r e n c e s

M n C l ( P P h 3 ) ( C O) 4 y e l l o w 91

c* 5- M n B r ( P P h 3 ) ( C O) 4 — — 9, 9 7 a

i m n 5- M n B r ( P P h 3 ) ( C O) 4 o r a n g e — 9 7 a

M n B r ( P P h 3 ) 2 ( C O) 3 « l i g h t b r o w n — ²

M n B r ( A s P h 3 ) 2 ( C O) 3 c o r a n g e — 2

M n B r ( P h N C ) ( C 0) 4 y e l l o w 8 6 - 8 7 100

M n B r ( P h N C ) 2 ( C O) 3 p a l e y e l l o w 8 4 - 8 6 1 0 0

M n B r ( P h N C) 3( C O ) 2 y e l l o w 1 2 9 - 1 3 0 1 0 0

M n B r ( p y ) 2 ( C O) 3 o r a n g e — 2, 8 0

M n B r d i p y ( C 0) 3 y e l l o w o r a n g e — 2, 8 0

M n B r ( d i t h i a n ) ( C 0) 3 o r a n g e 1 3 5 - 1 3 6 127

c i s - I l e B r ( P P h 3 ) ( C O) 4 c o l o u r l e s s 146 9 7 a i m n 5- R e B r ( P P h 3 ) ( C O) 4 c o l o u r l e s s 134 9 7 a

R e C l ( d i a r s ) ( C 0) 3 ^ c o l o u r l e s s — 106

R e C l ( d i a r s) 2( C 0 ) ^ c o l o u r l e s s — 106

ReClpy2(CO)3^ c o l o u r l e s s 2, 7 0

R e I d i p y ( C 0) 3 y e l l o w — 2

R e I ( P P h 3 ) 2 ( C O) 3 — — 2

c î 5- R e I ( d i p h o s ) ( C O) 3 c o l o u r l e s s — 5 6 a

[ C r I ( T T A S ) ( C O) 3 ] l 3 b r o w n 36

[ C r B r ( d i a r s) 2( C O) 2] B r p a l e y e l l o w — 112

M o B r 2 d i p y(CO) 3 d e e p y e l l o w 155

M o C l ( C p ) ( C O) 3 o r a n g e r e d 145 d e c . 1 4 4 a

[ M o I ( T T A S ) ( C O) 3] I o r a n g e — 3 6

W B r 2 d i p y( C O) 3 d e e p y e U o w 1 5 5

[ W I ( T T A S ) ( C 0) 3] I o r a n g e — ³⁶

W B r 2( d i a r s ) ( C O) 3 y e l l o w — ¹¹¹

[ W B r 2( d i a r s ) ( C O) 3] B r y e l l o w g r e e n — ¹¹¹

[ W I ( d i a r s ) ( C O) 4 ] l 3 r e d b r o w n — ¹¹¹

C p = c y c l o p e n t a d i e n y l .

a- A c c o r d i n g t o r e f e r e n c e 6 7 t h e c o m p o u n d c r y s t a l l i z e s w i t h o n e m o l e o f b e n z e n e .

^ B r o m o a n d i o d o d e r i v a t i v e s a l s o d e s c r i b e d , c I o d o d e r i v a t i v e a l s o r e p o r t e d , b u t n o t t h e c h l o r o .

A n inspection of Table I shows t h a t , a m o n g t h e m e t a l s k n o w n t o give m e t a l carbonyls, nickel, cobalt a n d v a n a d i u m d o n o t form easily isolable a n d well characterized halogeno carbonyls. T h e carbonyls of these t h r e e m e t a l s r e a c t r a p i d l y w i t h halogens giving t h e corresponding m e t a l halides. I n t h i s case t h e oxidation of t h e m e t a l carbonyls is t h e r e ­ fore n o t a practical w a y for p r e p a r i n g t h e so far u n k n o w n halogeno carbonyls. I t is n o t impossible, however, t h a t oxidation a t low t e m p e r a ­ t u r e s m i g h t yield t h e desired p r o d u c t s , a l t h o u g h t h e i r t h e r m a l stability is n o t e x p e c t e d t o b e high.

I t will also b e noticed t h a t palladium a n d p l a t i n u m , t h e carbonyls of

H A L O G E N O M E T A L C A R B O N Y L S 391

which h a v e n o t y e t b e e n p r e p a r e d , give a large v a r i e t y of halogeno carbonyls. F o r silver, n o halogeno carbonyls h a v e y e t been isolated. I t h a s been r e p o r t e d , i^^ea) however, t h a t a solution of silver s u l p h a t e in c o n c e n t r a t e d sulphuric acid absorbs c a r b o n m o n o x i d e in t h e r a t i o 2 AgrCO; from this it h a s been inferred t h a t a c o m p o u n d h a v i n g t h e stoichiometry A g 2 S 0 4. C O m a y be p r e s e n t in solution b u t no p r o d u c t h a s been isolated from it.

S u b s t i t u t e d halogeno m e t a l carbonyls can be p r e p a r e d either b y r e p l a c e m e n t of one (or more) CO groups from t h e halogeno m e t a l carbonyl

M X „ ( C O ) „ + L — ^ M X ^ ( C O ) „ _ i L + C O (1) or b y o x i d a t i o n of a s u b s t i t u t e d m e t a l carbonyl w i t h halogen. Some

special cases will be discussed separately.

A. Copper subgroup

Chloro- a n d b r o m o c a r b o n y l s of gold, AuCl(CO) a n d AuBr(CO) of u n ­ k n o w n molecular weight, were o b t a i n e d for t h e first t i m e b y M a n c h o t a n d Gall, w h o t r e a t e d a n h y d r o u s AuClg or AuCl in a s t r e a m of d r y CO a t 115-120°. <i22)

A b e t t e r m e t h o d of p r e p a r a t i o n is t h e t r e a t m e n t a t r o o m t e m p e r a t u r e of a suspension of AuCl in benzene w i t h carbon m o n o x i d e a t a t m o s p h e r i c pressure. This m e t h o d t a k e s a d v a n t a g e of t h e fact t h a t AuCl(CO) is soluble in benzene, a n d a p r o d u c t completely free from metallic gold is so o b t a i n e d . Care m u s t be t a k e n t o use d r y benzene since AuCl(CO) is v e r y readily decomposed b y w a t e r . <i^2) A small yield of a crystalline s u b l i m a t e h a s been o b t a i n e d b y t r e a t i n g AuBrg w i t h a s t r e a m of c a r b o n m o n o x i d e in t h e d r y s t a t e , i^^^) N o AuI(CO) h a s been r e p o r t e d t o b e formed b y t h e action of carbon m o n o x i d e on A u l . T h e chlorocarbonyl of gold h a s been r e p o r t e d t o b e volatile a n d m o n o m e r i c in benzene. I t loses CO in vacuo, b u t it sublimes in a s t r e a m of carbon m o n o x i d e .

W a g n e r i^^^) observed t h a t finely divided cuprous chloride a b s o r b e d carbon m o n o x i d e a t r o o m t e m p e r a t u r e w h e n a pressure of 100 a t m w a s used. H e w a s able t o d e t e r m i n e t h a t t h e a m o u n t of CO a b s o r b e d corre­

s p o n d e d t o t h a t required for t h e formation of t h e c o m p o u n d CuCl(CO).

T h e p r o d u c t o b t a i n e d b y this m e t h o d w a s a colourless p o w d e r t h a t lost CO w h e n t h e pressure was released; t h e evolution of CO w a s r a p i d a n d complete a t 60°. T h e loss of CO from CuCl(CO) w a s r e p o r t e d t o b e slow u n d e r a n a t m o s p h e r e of carbon m o n o x i d e a n d t o be accelerated b y light.

CuCl(CO) is also found as b y - p r o d u c t of t h e p r e p a r a t i o n u n d e r CO pressure of m e t a l carbonyls or halogeno m e t a l carbonyls s t a r t i n g from t h e m e t a l halide w h e n copper is used as halogen acceptor.

392 F. CALDERAZZO

B. Nickel subgroup

W h i l e halogeno m e t a l carbonyls of nickel are n o t k n o w n , several c o m p o u n d s of p a l l a d i u m a n d p l a t i n u m h a v e been r e p o r t e d .

A c o m p o u n d of formula PdCl2(C0) was o b t a i n e d b y M a n c h o t a n d K o n i g (12^) b y t h e action of c a r b o n m o n o x i d e s a t u r a t e d w i t h m e t h a n o l on d r y p a l l a d i u m ( I I ) chloride a t r o o m t e m p e r a t u r e . T h e c o m p o u n d is readily decomposed b y w a t e r . A l t h o u g h its molecular weight is n o t k n o w n , it is p r o b a b l y a d i m e r similar t o t h e analogous p l a t i n u m com­

p o u n d (vid. inf.). I t is slowly decomposed b y m o i s t u r e a t r o o m t e m p e r a ­ t u r e . W h e n d r y it s t a r t s decomposing a t 60°.

A chlorocarbonyl c o m p o u n d of formula Pd2Cl(CO)2 h a s been o b t a i n e d b y Fischer a n d Vogler b y t r e a t m e n t of PdCl2(PhCN)2 w i t h CO. <^5> This c o m p o u n d is d i a m a g n e t i c b u t its molecular weight is u n k n o w n .

A p r o b a b l y polymeric chlorocarbonyl of p a l l a d i u m of formula PdCl(CO) h a s been o b t a i n e d b y t r e a t i n g PdCl2 w i t h carbon m o n o x i d e in m e t h a n o l in t h e presence of small a m o u n t s of w a t e r , i^^^*) T h e violet c o m p o u n d so o b t a i n e d is u n s t a b l e t o w a r d s w a t e r , insoluble in all com­

m o n organic solvents a n d n o t volatile. A n infrared C — 0 s t r e t c h i n g v i b r a t i o n w a s observed a t 1975 cm-^ w i t h shoulders a t 1925 a n d 1892 cm-^.

T h e [Pd2Cl4(CO)2]^~ anion w a s r e p o r t e d t o be o b t a i n e d b y t h e action of c a r b o n m o n o x i d e on a s a t u r a t e d solution of a m m o n i u m chloro- p a l l a d a t e in c o n c e n t r a t e d HC1.<^^^ H o w e v e r , I r v i n g a n d Magnusson i^"^) h a v e a r g u e d t h a t this c o m p o u n d was a c t u a l l y NH4+[PdCl3(CO)]~, w h i c h yielded [PdCl(en)C0][PdCl3(C0)] b y reaction w i t h ethylenedi­

a m i n e .

T h r e e t y p e s of halogeno carbonyls of p l a t i n u m , PtX2(CO)2, [PtX2(CO)]2 a n d Pt2X4(CO)3, are k n o w n from t h e studies of Schiitzen- berger w h o p r e p a r e d t h e chloro derivatives b y passing CO a n d chlorine over p l a t i n u m s p o n g e a t 250°. I n addition, t h e anions [ P t X g i C O ) ] "

h a v e been described. All t h e u n c h a r g e d halogeno carbonyls of p l a t i n u m a r e volatile a n d soluble in t h e c o m m o n organic solvents. T h e resistance t o hydrolysis decreases in t h e order [ P t X 3 ( C 0 ) ] - > [PtX2(CO)]2 >

Pt2X4(CO)3 > PtX2(CO)2; t h e t h e r m a l stability usually increases from A halogeno carbonyl of copper of formula C u C l ( C O ) . 2 H 2 0 w a s o b t a i n e d b y s a t u r a t i n g a n a q u e o u s solution of cuprous chloride w i t h c a r b o n m o n o x i d e , i^^'^^o) I d e n t i c a l results were o b t a i n e d in n e u t r a l , acid or slightly alkaline solution. This chlorocarbonyl of copper also de­

composes readily unless it is k e p t in a p r o t e c t i v e a t m o s p h e r e of carbon m o n o x i d e .

H A L O G E N O M E T A L C A R B O N Y L S 393

t h e iodo t o t h e chloro derivatives. I t is w o r t h m e n t i o n i n g t h a t r e c e n t l y t h e c o m p o u n d PtF8(CO)2 h a s been r e p o r t e d as a yellow sublimable solid. <^^2> This c o m p o u n d , o b t a i n e d from P t F 4 a n d CO u n d e r pressure is, w i t h R h F 3( C O ) 2 , t h e first k n o w n e x a m p l e of a fluoro c a r b o n y l com­

p o u n d . A p l a t i n u m ( I V ) formulation (C0F)+2 (PtFe)^- h a s been, however, suggested for t h i s c o m p o u n d b y Jorgensen.i^^^)

PtX^iCO)^. Of this series, in a d d i t i o n t o t h e chloro, t h e b r o m o a n d iodo d e r i v a t i v e s are also k n o w n . L u t t o n a n d P a r r y i^^^) r e p o r t e d t h e p r e p a r a t i o n of PtCl2(CO)2 in 5 0 - 7 5 % yields b y r e a c t i n g PtClg w i t h CO a t 40-120 a t m a n d 100°. A t high t e m p e r a t u r e s lower yields were o b t a i n e d d u e t o t h e relatively low t h e r m a l stability of t h e c o m p o u n d . T h e b r o m o a n d iodo d e r i v a t i v e s were p r e p a r e d b y M a l a t e s t a a n d Naldini<i^6) b y t h e action of CO u n d e r pressure (180-210 a t m ) a t a b o u t 105° on H2PtBr6 a n d P t l 2 , respectively. T h e iodo c o m p o u n d is t h e r ­ m a l l y t h e least stable a n d is easily c o n v e r t e d even a t r o o m t e m p e r a t u r e i n t o [Ptl2(CO)]2, w i t h evolution of CO. T h e chloro d e r i v a t i v e also loses CO, slowly on s t a n d i n g in vacuo or u n d e r nitrogen, i^^^) r a p i d l y a t high t e m p e r a t u r e ; it m e l t s a t 103° b u t t h e n solidifies again, t h e n e x t m e l t i n g p o i n t being 195°. This is d u e t o t h e r e a c t i o n :

2 PtX2(CO)2 > 2 C 0 + [PtX2(CO)]2 (2) [PtX^{ΟΟ)]^. T h e b r o m o a n d iodo d e r i v a t i v e s were o b t a i n e d from t h e

corresponding chloro d e r i v a t i v e b y t r e a t m e n t w i t h h y d r o g e n b r o m i d e a n d iodide, respectively. These c o m p o u n d s can be, however, p r e ­ p a r e d also b y reaction(2). T h e b r o m o d e r i v a t i v e [PtBr2(CO)]2 w a s also r e p o r t e d b y Pullinger<^^^) w h o p r e p a r e d it b y r e a c t i n g p l a t i n u m ( I I ) b r o m i d e w i t h a s t r e a m of d r y CO a t 180°. A l t h o u g h these c o m p o u n d s were initially a s s u m e d t o b e dimeric, only r e c e n t l y h a s t h e molecular c o m p l e x i t y as [PtCl2(CO)]2 been established b y I r v i n g a n d M a g n u s - son. I n a g r e e m e n t w i t h t h e s t r u c t u r e p r o p o s e d b y these a u t h o r s (see p . 385) t h e c o m p o u n d should be correctly d e n o t e d as 5i/m-im7i5-di-ju,- c h l o r o d i c h l o r o d i c a r b o n y l d i p l a t i n u m ( I I ) .

[PtX^iCO)]-, T h e anions [ P t X 3 ( C 0 ) ] - w i t h X Cl, B r , a n d I were described b y Mylius a n d F o e r s t e r . i^^^) T h e first one w a s o b t a i n e d b y r e a c t i n g [PtCl2(CO)]2 w i t h HCl, t h e o t h e r t w o from [ P t C l 3 ( C 0 ) ] - b y e x c h a n g e w i t h H B r a n d H I , respectively. M a l a t e s t a a n d N a l d i n i h a v e s h o w n( i i 6 ) t h a t t h e reactions of d r y HgPtCle, K2PtCl4, H a P t B r g a n d H2PtIg w i t h CO give, a m o n g o t h e r p r o d u c t s , t h e anions [PtX3(C0)]~.

H e r m a n< ^ 3 ) o b t a i n e d t h e anion [ P t C l 3 ( C 0 ) ] - also from a n acid a q u e o u s solution of Na2PtCl6 a n d CO. B y successive a d d i t i o n of p y r i d i n e t h e anion w a s s e p a r a t e d as t h e p y r i d i n u m salt [pyH][PtCl3(C0)].

394 F . CALDERAZZO

Pt^XJ^GO)^. T h e i o d o d e r i v a t i v e o f t h i s c l a s s h a s n o t y e t b e e n r e p o r t e d . T h e c h l o r o a n d b r o m o d e r i v a t i v e s w e r e o b t a i n e d i n a p u r e s t a t e b y c o n t r o l l e d d e c o m p o s i t i o n a t r o o m t e m p e r a t u r e o f s o l u t i o n s o f t h e c o r r e ­ s p o n d i n g PtX2(CO)2 i n a n h y d r o u s b e n z e n e . N o t m u c h i s k n o w n a b o u t t h e s t r u c t u r e o f t h e s e c o m p o u n d s . H o w e v e r , s i n c e t h e i n f r a r e d s p e c t r u m d o e s n o t s h o w b a n d s a t t r i b u t a b l e t o CO b r i d g i n g s t r e t c h i n g v i b r a t i o n s , t h e c o m p o u n d s s h o u l d c o n t a i n c h l o r i n e b r i d g e s r a t h e r t h a n a CO b r i d g e a s p r e v i o u s l y p r o p o s e d . <^^2)

C. Cobalt subgroup

N o s t a b l e h a l o g e n o c a r b o n y l s o f c o b a l t a r e k n o w n . S o m e y e a r s a g o a c o m p o u n d , u n s t a b l e a t r o o m t e m p e r a t u r e a n d h a v i n g t h e c o m p o s i t i o n

Col2(CO), w a s , h o w e v e r , o b t a i n e d f r o m t h e r e a c t i o n o f C0I2 w i t h CO

u n d e r p r e s s u r e a t r o o m t e m p e r a t u r e . <i^^)

I t i s i n t e r e s t i n g t o n o t e t h a t a n i o d o d e r i v a t i v e b e c o m e s i s o l a b l e w h e n t r i f l u o r o p h o s p h i n e , i n s t e a d o f c a r b o n m o n o x i d e , i s a l i g a n d f o r c o b a l t . K r u c k a n d L a n g <i^^^) h a v e i s o l a t e d CoI(PF3)4, a b r o w n s o l i d d e c o m ­ p o s i n g a t 7 ° , f r o m t h e r e a c t i o n o f C0I2 w i t h

PF3

T h e h a l o g e n a t i o n o f [ C o( P P h 3 ) ( C O) 3 ] - w i t h

CF3I

A p r o d u c t r e p o r t e d a s h a v i n g t h e c o m p o s i t i o n R h 2 C l 2 0. 3 C O w a s o b t a i n e d < i 2 5 ) from R h C l 3 . H 2 0 a n d CO a t 140°: t h i s c o m p o u n d i s p r o b a b l y i d e n t i c a l w i t h [ R h C l( C 0) 2] n l a t e r p r e p a r e d b y L a g a l l y . <^^^) H e o b t a i n e d [ R h C l( C 0)2] n from h y d r a t e d RhClg a n d CO a t a t m o s p h e r i c p r e s s u r e : t h e r e a c t i o n i s p r o m o t e d b y s a t u r a t i n g t h e CO s t r e a m w i t h m e t h y l a l c o h o l . A l m o s t q u a n t i t a t i v e y i e l d s w e r e o b t a i n e d f r o m a n ­ h y d r o u s R h C l 3 a n d CO u n d e r p r e s s u r e (200-240 a t m ) a t 150°.

T h e b r o m o a n d i o d o d e r i v a t i v e s w e r e a l s o p r e p a r e d b y L a g a l l y . ^ ^ ^ ^ ) T h e b e s t r e s u l t s w e r e o b t a i n e d i n t h e s e c a s e s b y u s i n g h i g h p r e s s u r e t e c h n i q u e s . I n p a r t i c u l a r [ R h I ( C 0) 2 ] w h i c h c o u l d n o t b e o b t a i n e d a t a t m o s p h e r i c p r e s s u r e o f CO, w a s p r e p a r e d i n q u a n t i t a t i v e y i e l d s f r o m r h o d i u m c h l o r i d e a n d CO u n d e r p r e s s u r e a t 150-180° i n t h e p r e s e n c e o f a l a r g e e x c e s s o f i o d i n e . T h e r e a c t i o n w a s c a r r i e d o u t i n a c o p p e r - l i n e d a u t o c l a v e w h i c h m a d e t h e e l i m i n a t i o n o f c h l o r i n e ( w i t h f o r m a t i o n o f CuCl(CO) ) m o r e e a s y .

I n t h e r h o d i u m s e r i e s , i n g e n e r a l t h e t e n d e n c y t o h a l o g e n o c a r b o n y l s f o r m a t i o n d e c r e a s e s i n t h e o r d e r CI > B r > I .

T h e s e c o m p o u n d s a r e v o l a t i l e s u b s t a n c e s , s o l u b l e i n c o m m o n o r g a n i c

H A L O G E N O M E T A L C A R B O N Y L S 395

solvents. Surprisingly, t h e i n t e n s i t y of t h e colour decreases in t h e series Cl (ruby red), B r (yellow red), I (yellow).

T h e halogeno carbonyls of r h o d i u m dissolve readily in cold w a t e r c o n t a i n i n g h y d r o g e n halides w i t h f o r m a t i o n of dihalogenodicarbonyl rhodates.<^^^'^^^) Loss of c a r b o n m o n o x i d e yields t h e t e t r a h a l o g e n o d i - c a r b o n y l d i r h o d a t e anions :

[RhX(CO)2]2 + 2 X - > 2[RhX2(CO)2]- (3) 2[RhX2(CO)2]- > [Rh2X4(CO)2]2- + 2 CO ( 4 )

H a l o g e n o carbonyl derivatives of cobalt <i^^) a n d r h o d i u m c o n t a i n ­ ing a perfluoroalkyl g r o u p σ-bonded t o t h e m e t a l were p r e p a r e d b y r e a c t i n g M(C5H5)(CO)2 (M = Co, R h ) w i t h perfluoroalkyl iodide. F o r e x a m p l e

CF3I + CoC5H5(CO)2 > F3CCoI(C5H5)(CO) + CO ( 5 ) T h e s u b s t i t u t e d halogeno c a r b o n y l of r h o d i u m RhCl(PPh3)2(CO) can b e c o n v e n i e n t l y p r e p a r e d b y t r e a t i n g RhCl3.3H20 w i t h t r i p h e n y l p h o s ­ p h i n e in 2- m e t h o x y e t h a n o l a t reflux t e m p e r a t u r e .a ) g o m e n o n - completely clarified m e c h a n i s m , d e c a r b o n y l a t i o n of t h e alcohol a n d r e d u c t i o n of t h e m e t a l occur.

T h e halogeno carbonyl c o m p o u n d s of iridium were first described b y M a n c h o t a n d H i e b e r a n d t h e i r co-workers. ^^^^'^^^ Their c h e m i s t r y h a s been extensively s t u d i e d b y M a l a t e s t a a n d co-workers a n d several n e w t y p e s of c o m p o u n d s discovered. A wide r a n g e of halogeno carbonyls of iridium are n o w k n o w n , including some anionic species. T h e dihalogeno d i c a r b o n y l c o m p o u n d s IrX2(CO)2 a n d t h e t r i c a r b o n y l s I r X( C 0) 3 were p r e p a r e d from t h e reaction of I r X g w i t h CO a t o r d i n a r y pressure a t a b o u t 1 5 0 ° . (121,88) IrX2(CO)2 a n d I r X( C 0) 3 are decomposed r a p i d l y b y w a t e r . T h e iodo c a r b o n y l c o m p o u n d s of iridium Irl3(CO)3, [Irl3(CO)2]2 a n d Ir2X6(00)3 h a v e b e e n obtained<ii^) b y t h e r e a c t i o n of iridium tri- a n d t e t r a i o d i d e s w i t h CO a t high t e m p e r a t u r e a n d pressure.

Chlorotricarbonyliridium, IrCl(C0)3, which is completely insoluble in t h e u s u a l organic solvents, h a s b e e n suggested(^^^) t o b e p o l y m e r i c .

Anionic halogeno carbonyls of iridium were first o b t a i n e d b y Mala­

t e s t a a n d Sandroni^ii'^) b y r e a c t i n g m i x t u r e s of I r l 3 - K I w i t h CO u n d e r pressure a t 8 0 - 2 5 0 ° . T h e t w o p o t a s s i u m salts K[Irl4(CO)2] a n d K2[Irl5(CO)] were o b t a i n e d in t h i s m a n n e r . T h e relative a m o u n t s of t h e t w o salts o b t a i n e d d e p e n d on t h e r a t i o I r l 3 : K I e m p l o y e d ; <i^i) t h e a d d i t i o n of a halogen a c c e p t o r such as copper h a s n o effect o n t h e reaction.

396 F . C A L D E R A Z Z O

Cu

rBr^iCO)] (6)

The intermediate formation of K3[IrBr6], K2[IrBr5(CO)] and K[IrBr4(CO)2] was indicated b y the fact that these salts were actually separated when the reaction of K2[IrBrg] with CO was carried out in the absence of copper.

The infrared spectrum of K2[Ir2Br5(CO)4] where the t w o iridium atoms are in an average oxidation state + 1* 5 , does n o t show the presence of bridging CO groups. This suggested a bromine-bridged structure.

D. Iron subgroup

The three dihalogeno tetracarbonyls of iron FeX2(CO)4 have been prepared b y the action of halogens on Fe(C0)5.<^^'^^^) The reaction with iodine t o obtain Fel2(CO)4 is usually carried out in diethyl ether or aliphatic hydrocarbons at about room temperature using a slight excess of F e( C 0) 5 . The product can be recovered from the reaction mixture b y sublimation after evaporation of the solvent. FeCl2(CO)4 a n d F e B r 2 ( C O ) 4 can be prepared similarly b u t their isolation in a pure state is better obtained b y crystallization techniques because of their lower thermal stability.

Although the preparation of the halogeno carbonyls of iron from F e( C 0) 5 is n o w the most convenient method due to the commercial availability of the pentacarbonyl, it is worth mentioning that Fel2(CO)4 can be directly prepared in excellent yield from F e l 2 and CO under pressure, i^*^) I n diethyl ether as solvent at 110 a t m and in 10 h the yields were reported to be quantitative.

The halogeno tetracarbonyls are reasonably soluble in the common organic solvents. The resistance to heat and hydrolysis increases from the chloro to the iodo derivative. FeCl2(CO)4 and FeBr2(CO)4 are rapidly

T h e presence of copper has, however, a marked influence on the reaction of potassium hexabromoiridate with CO.i^^^) I n the presence of copper, K2[Ir2Br5(CO)4] is obtained in practicahy quantitative yields.

T h e reaction scheme proposed is the following:

K2[Ir2Br,(CO)4]

Î

Cu

K[IrBr4(CO)2] ^ K [ I r B r 3 ( C O ) 2 ] CO + K2[IrBre]

K3[IrBre] —

H A L O G E N O M E T A L C A R B O N Y L S 397

d e c o m p o s e d b y w a t e r , w h e r e a s Fel2(CO)4 is h y d r o l y s e d only u p o n h e a t i n g .

H i e b e r suggested t h a t t h e reaction leading t o t h e f o r m a t i o n of Fel2(CO)4 goes t h r o u g h a n i n t e r m e d i a t e ' ' a d d u c t " Fe(CO)5.l2, s t a b l e only a t v e r y low t e m p e r a t u r e . Fel2(CO)5 is also m e n t i o n e d in t h e a b s t r a c t of a p a p e r b y Wojcicki a n d Faronai^'^^) a n d further r e p o r t s on t h i s subject a r e p r o b a b l y t o b e e x p e c t e d .

I t h a s also b e e n reported(^^) t h a t b y r e a c t i n g Fe3(CO)i2 w i t h iodine in t e t r a h y d r o f u r a n , Fe2l2(CO)8 is o b t a i n e d as a w h i t e solid below its m e l t i n g p o i n t (—5°).

H a l o g e n o carbonyls of iron w i t h a lower c o n t e n t of c a r b o n m o n o x i d e , Fel2(CO)2 a n d FeI(C0)2 h a v e also b e e n r e p o r t e d (see T a b l e I) b u t t h e i r s t r u c t u r e s h a v e n o t b e e n investigated. T h e y were p r e p a r e d from Fel2(CO)4 b y h e a t i n g a t 120° in a h y d r o g e n s t r e a m or in a CO2 a t m o ­ sphere, respectively.

A p r o d u c t h a v i n g t h e composition FeCl2(CO)2 w a s r e p o r t e d b y H i e b e r a n d W i r s c h i n g : it w a s o b t a i n e d in q u a n t i t a t i v e yields a n d in a p u r e s t a t e b y t h e slow reaction (3-4 days) of Fel2(CO)4 w i t h t h i o n y l chloride. This c o m p o u n d does n o t a p p e a r t o h a v e been further in­

v e s t i g a t e d .

T h e halogeno carbonyls of r u t h e n i u m [RuX2(CO)2]n were o b t a i n e d b y M a n c h o t a n d K o n i g i^^^) b y t h e a c t i o n of a c a r b o n m o n o x i d e s t r e a m o n a n h y d r o u s r u t h e n i u m trihalides a t 210-290°.

T h e t e n d e n c y t o halogeno c a r b o n y l f o r m a t i o n is lower for RuClg t h a n for R u B r g a n d R u l g . T h e conversion of RuClg is low a n d incom­

plete a t 270°: after 8 h of reaction small a m o u n t s of [Rul2(CO)2]n were o b t a i n e d . W i t h R u l g t h e conversion i n t o t h e iodocarbonyl w a s re­

p o r t e d t o b e complete in 30 m i n a t 240-250°. These r u t h e n i u m com­

p o u n d s show a r e m a r k a b l e resistance t o h y d r o l y s i s ; t h e iodo d e r i v a t i v e is a t t a c k e d only w i t h difficulty b y d i l u t e d sulphuric a n d hydrochloric acids.

A halogeno c a r b o n y l of r u t h e n i u m w i t h a lower c o n t e n t of c a r b o n m o n o x i d e , [RuBr(CO)]^ h a s also b e e n described. <ii^) I t is p r o b a b l y polymeric. I t w a s o b t a i n e d b y t r e a t m e n t of R u B r g w i t h CO u n d e r pressure a t a b o u t 185° for 8 h. W h e n freshly p r e p a r e d , t h i s b r o m o c a r b o n y l is colourless a n d crystalline. I t dissolves, a l t h o u g h w i t h difficulty, in a n h y d r o u s alcohol a n d h e a t e d a t 200° gives r u t h e n i u m m e t a l a n d RuBr2(CO)2:

200°

2[ R u B r( C 0 ) ] ^ nUu +n RuBr2(CO)2 (7) R u t h e n i u m , unlike iron, did n o t a p p e a r t o form halogeno carbonyls

of t h e t y p e RuX2(CO)4 u n t i l D a h l a n d co-workers r e c e n t l y p r e p a r e d t h e

398 F . C A L D E R A Z Z O

2[RuHCl(CO)(PEt2Ph)3] + 2CH4 + 2KC1 + 2H2O (8) The formation of the final product is believed to take place via an

initial ethoxide-ruthenium complex, followed b y hydride transfer to the ruthenium. I n a second step methane elimination and carbonyl complex formation take place. Rusina and Vlcek^^^'^) have later shown that carbonylation reactions of this type do not occur exclusively in iodo derivative Rul2(CO)4 by treating Rulg with CO under pressure at 170° in the presence of copper for 24 h.

Calderazzo and L'Eplattenier^^^^) have obtained RuBr2(CO)4 and Rul2(CO)4 by oxidation of Ru(C0)5 with the corresponding halogen.

Halogeno carbonyls of osmium, OsX2(CO)4, OsX2(CO)3, OsX2(CO)2 and [OsX(CO)4]2 have been described by Hieber<«2) and Manchot <i24)

and their co-workers. The reaction of OsCla with dry CO at atmospheric pressure at 270° yielded a colourless compound to which Manchot and Konig (124) assigned the formula OsCl2(CO)3.

Hieber and Stallmann^^^) prepared all the other known halogeno carbonyls of osmium by using either the high pressure techniques or reactions of the metal halide with CO at atmospheric pressure. The bromo derivatives were obtained from the reaction of Os2Br9 at high temperature and pressure, whereas the iodo derivatives were obtained from an osmium iodide of not well defined composition.

Substituted halogeno hydrido carbonyls of bivalent ruthenium and osmium of formula MHX(CO)(PPh3)3 have been obtained (i^^) by heating (NH4)20sX6 or RUCI3 with the phosphorus ligand in alcohol solution (2-methoxyethanol or ethylene glycol). In a closely related reaction OsHCl(CO)(PEt2Ph)3 is obtained by boiling OsCl3(PEt2Ph)3 with KOH in ethyl alcohol, i^^) Substituted non-hydridic halogeno carbonyls of ruthenium RuCl2(PR3)2(CO)2 in both cis and trans forms were obtained (29.33) ^y boiling the complex salt [Ru2Cl3(PEt2Ph)6]Cl with potassium hydroxide in allyl alcohol.

The very interesting question of the origin of the hydrido and carbon monoxide groups in these complexes has been partially answered.

Vaska and DiLuzio^^^^) found by deuteration methods that in the system K2lrCl6 - EtOH - PPh3 the hydrogen in the final complex IrHCl2(PPh3)3 originated from the α-hydrogens of the alcohol. Chatt, Shaw and Field<33) studied the reaction of [Ru2Cl3(PEt2Ph)6]Cl with EtOH in the presence of alkali and found that methane was formed.

The reaction was therefore proposed to occur according to the following stoichiometry:

[Ru2Cl3(PEt2Ph)6]Cl + 2 K 0 H + 2C2H5OH >

HALOGENO METAL CARBONYLS 399

alcoholic solvents. T h e y h a v e , for e x a m p l e , p r e p a r e d RhCl(PPh3)2(CO) from r h o d i u m ( I I I ) chloride a n d t r i p h e n y l p h o s p h i n e in d i m e t h y l f o r m a ­ m i d e as solvent.

E. Manganese subgroup

H a l o g e n o carbonyls of m a n g a n e s e , t e c h n e t i u m a n d r h e n i u m of t h e t y p e s M X ( C 0) 5 a n d [MX(CO)4]2 h a v e b e e n r e p o r t e d . M n I ( C 0) 5 w a s first isolated from t h e p r o d u c t s of t h e c a r b o n y l a t i o n of Mnl2 u n d e r CO pressure, i^"^)

T h e anionic t y p e s [MnX2(CO)4]- a n d [Mn2X2(CO)8]2- a r e also k n o w n . <i'^)

I n t h e u n c h a r g e d series, t h e resistance t o h e a t a n d hydrolysis in­

creases from t h e chloro t o t h e iodo d e r i v a t i v e s .

T h e m o n o m e r i c M X ( C 0) 5 a r e n o w usually o b t a i n e d b y t r e a t m e n t of t h e corresponding m e t a l p e n t a c a r b o n y l s w i t h halogens. <2,27,69,92)

[M(CO)5]2 + X2 > 2 M X ( C 0) 5 (9)

I n t h e case of m a n g a n e s e , r e a c t i o n (9) is usually carried o u t in a solvent a t r o o m t e m p e r a t u r e . T h e isolation of M n B r ( C 0) 5 a n d M n I ( C 0) 5 is t h e n b e t t e r o b t a i n e d b y s u b l i m a t i o n of t h e solid residue after e v a p o r a t i o n of t h e solvent. T h e r e a c t i o n of Mn2(CO)io w i t h chlorine is a c c o m p a n i e d b y some decomposition t o t h e m e t a l h a l i d e ; t h e s a m e is t r u e for t h e s u b l i m a t i o n of M n C l ( C 0) 5 .

T h e dimeric [MnX(CO)4]2 h a v e b e e n o b t a i n e d i^) b y t h e r m a l decom­

position of t h e corresponding halogeno m e t a l p e n t a c a r b o n y l s . T h e t e m p e r a t u r e r e q u i r e d is a b o u t 120° a n d t h e r e a c t i o n is carried o u t in a n i n e r t solvent.

2 M n X ( C 0) 5 ^ [MnX(CO)4]2 + 2 CO (10) T h e yields are only a r o u n d 4 0 % because of p a r t i a l t h e r m a l decomposi­

t i o n of t h e p e n t a c a r b o n y l . R e a c t i o n (10) w a s s h o w n t o b e reversible. <2) T h e anions [MnX2(CO)4]- a n d [Mn2X2(CO)8]2- were o b t a i n e d b y t h e a c t i o n of t e t r a - a l k y l a m m o n i u m halides on M n X ( C 0) 5 a n d Mn2(CO)io, respectively: (i'^>

R4NX + M n X ( C 0) 5 > R4N[MnX2(CO)4] + CO (11) 2 R4NX + Mn2(CO)io > (R4N)2[Mn2X2(CO)8] + 2 C 0 (12) A n iodine-bridged carbonyl d e r i v a t i v e of m a n g a n e s e w a s o b t a i n e d

400 F. CALDERAZZO

T h e dimeric t e c h n e t i u m c o m p o u n d s [TeX(CO)4]2 h a v e been o b ­ t a i n e d <^2) b y t h e r m a l decomposition of t h e halogeno p e n t a c a r b o n y l s according t o a r e a c t i o n similar t o (10). V e r y small a m o u n t s of t h e s e c o m p o u n d s were p r e p a r e d , sufficient, however, t o fully characterize t h e m b y infrared spectroscopy.

T h e t h r e e r h e n i u m derivatives R e X ( C 0) 5 were originally p r e p a r e d directly from t h e c a r b o n y l a t i o n respectively of ReClg, R e B r 3 a n d KgReIg a t 200-230° a t 200 a t m , in t h e presence of copper a s halogen acceptor. (1^1) H i e b e r et alA^^^ r e p o r t e d t h a t t h e t e n d e n c y t o t h e forma­

t i o n of t h e halogeno c a r b o n y l s increases in t h e o r d e r Cl < B r < I . F r o m K2Rel6 in t h e presence of copper, R e I ( C 0) 5 is formed a t 200°

a l r e a d y a t a t m o s p h e r i c pressure of CO; on t h e o t h e r h a n d , a pressure of 30 a t m is necessary for t h e f o r m a t i o n of R e C l ( C 0) 5 from K2ReCl6 a t 230°, copper being still p r e s e n t . Good yields of R e C l ( C 0) 5 ( 7 0 % ) a n d R e B r ( C 0) 5 ( 8 5 - 9 0 % ) were o b t a i n e d from active r h e n i u m m e t a l in p r e ­ sence of c o p p e r ( I I ) halides:

R e + CuX2 + 6 CO > R e X ( C 0) 5 + CuX(CO) (13)

R e C l ( C 0) 5 w a s also r e p o r t e d t o b e o b t a i n e d in 3 0 % yield b y t h e reaction of F e ( C 0) 5 w i t h ReCla a t 70-145° in diethyl ether, i^^)

T h e dihalogeno t e t r a c a r b o n y l derivatives of r h e n i u m [ReX2(CO)4]2 were o b t a i n e d b y t h e r m a l decomposition of t h e corresponding halogeno p e n t a c a r b o n y l c o m p o u n d s :

2 BeX(CO)J-^^~-^ [ReX(CO)4]2 + 2 CO (14) T h e p r o d u c t s of t h i s reaction a r e colourless solids w h e n p u r e , sparingly soluble in organic solvents.

b y E m e l é u s a n d Grobe<45) b y t r e a t i n g Mn2(CO)io w i t h (CP3)2PI. T o t h e p r o d u c t o b t a i n e d , of formula Mn2lP(CF3)2(CO)8, w a s assigned t h e following s t r u c t u r e :