Manganous fluoride, MnF2, was found to have a melting point of 929.5 ± 0.5 and a density at 25° of 3.922 ± 0.004 by Griffei and Stout*2 8 0) who made single crystals and studied the crystal structure. Stout and Reed*7 2 2) and Baur*55) also studied its crystal structure. Its absorption spectra is reported by both Parkinson and Williams*5 2 8) and by Stout*7 2 0).
The structure of MnF3 was studied by Hepworth and Jack*3 1 7), and M n F4 was sought for but not found by Gutman and Emeleus*2 8 3). It has been reported by Hoppe and Klemm*3 4 3 a) to result from the direct fluorination of Li2MnF6 at 550°. It sublimed and was very reactive with water and air.
Permanganyl fluoride MnOsF was prepared by Engelbrecht and Grosse*2 0 8) by either of the two reactions:
K M n 04 + 2 H F -> M n O s F + K F + H20 K M n 04 + 2 S 03H F -> M n O s F + K S 03F + H2SO4
They preferred the second reaction. The compound is unstable above room temperature and decomposes to MnF2, M n 02, and O2. Its melting point is —38°, its vapor pressure from —15 to +10° is given by the equation, logio Pmm = 8.2 — 1770/T which would indicate a boiling point of about 60° and a heat of vaporization of 8100 cal per mole. It is stable at Dry Ice temperature. Aynsley*25) prepared the compound along with I02F by the action of I F5 on K M n 04 at about 40°.
The X-ray spectra of some double fluorides of bivalent manganese were studied by Simonov, Batsanova, and Korba*6 8 0) such as NaMnF3, K M n F3, N H4M n F3, RbMnF3, and CsMnF3. Ryss and Vitukhnovskaya*609) prepared Cs2MnFs • H2O from CsF and a chromic salt in aqueous H F solution and MnF3CrF3 • 6H2O in a similar method using MnF3.
The fluoromanganates of the alkali metals were studied by Hoppe et #/.*3 4 3 b). From a MnCl2 solution and the alkali fluoride they obtained M M n F3 where M = Na, K, Rb, Cs, and N H4. By direct fluorination with elementary fluorine at 500° of K M n F3, RbMnF3, and C s M n F3 they obtained KMnFs, RbMnFs and CsMnFs. Upon reduction with hydrogen KMnFs and RbMnFs gave K M n F4 and RbMnF4. The magnetic properties of KMnF3 have been studied by Pearson( 5 4 0 a), Beckman*5 5 6), and Heeger et #/.*315a).
76 J. H. SIMONS
Potassium pentrafluoromanganate (III), anhydrous, K^MnFs, was prepared by Peacock*540) from K^MnFs • H2O by treatment with KHF2 and heating to 400°. K^MnFe was prepared from KMnC>4 by reduction with H2O in a hydrofluoric acid solution containing KHF2, by Bode, Jenssen, and Bandte*6 8). The crystal structures of K^MnFe, Rf^MnFe, and C s 2 M n F 6 were reported by Bode and Wendt*7 6). Hoppe and Blinne*3 4 1) prepared MgMnF6, CaMnF6, SrMnF6, and BaMnF6 by treating a mixture of sulfates or chlorides of the alkaline earth metal and of man
ganese with fluorine at temperatures from 20 to 200°. Crocket and Haendler*1 5 2) prepared K M n F3 and RbMnF3.
Rhenium pentrafluoride, ReFs, was prepared by Hargreaves and Peacock*301) by the reaction of R e F 6 with tungsten carbonyl, W(CO)6.
It is a yellow green crystalline solid that melts at 48° and boils at 240°
where it disproportionates to the tetra and hexafluorides.
Rhenium tetrafluoride, ReFj, obtained from the pentafluoride is a pale blue powder. It sublimed at about 300° in a high vacuum.
Rhenium oxytetrafluoride, R e O F 4 , was also obtained by the reaction of ReF6 with metal carbonyls such as Re2(CO)i0, W(CO)6, and Mo(CO)6. It is a blue crystalline solid which melts at 108° and boils at 171°. It reacts with Pyrex glass at 250° to form R e O F 3 .
Rhenium hexafluoride, R e F 6 , was reported to be the highest fluoride of rhenium obtained by the reaction of fluorine on the metal by Aynsley, Peacock, and Robinson*29). Malm, Selig, and Fried*4 5 0) reported that at 400°, R e F 6 will absorb more fluorine to give R e F 7 and that at the same temperature the R e F 7 will react with the metal to produce R e F 6 . They are both yellow solids, R e F 6 melting at 18.6°, and R e F 7 melting at 48.3.
They have different infrared spectra. Preliminary vapor pressures of
R e F 6 show for the solid at 0.0, 9.4, and 14.9° the pressures are 167, 272, and 356 mm, respectively, and for the liquid at 20.3, 26.9, and 30.9°, the pressures 454, 590, and 686 mm, respectively; and for R e F 7 solid at 0.0, 10.1, 15.2, 25.2, and 34.2, the pressures are 25, 46, 61, 106, and 165 mm, respectively. The infrared spectrum of R e F 6 is reported by Gaunt*2 5 5) and the absorption spectrum by Goodman, Fred, and Weinstock*2 7 4).
Nikolaev and Ippolitov*5 0 7 a) reported R e F 6 prepared by the reaction of the metal and CIF3 at 300°. The crude product was crystallized from HF, vacuum treated at — 70°, and distilled under a hydrogen atmosphere in a platinum tube to give yellow crystalline R e F 6 .
Cady and Hargreaves*1 0 6 a) reported the physical properties of R e O F 4 ,
ReOF5, R e 02F3, ReF5, and ReF6. See Table page 77.
Oxyfluoridesof rhenium have been prepared and studied. By the reaction of either rhenium dioxide or potassium perrhenate with fluorine at 100°, Aynsley, Peacock, and Robinson*29) prepared rhenium oxypentafluoride
R e O F4 R e O F s R e 02F3 R e F5 R e F6
Boiling point (°C) 171.7 73.0 185.4 221.3 33.8 Triple point (°C) 107.8 40.8 90.0 48.0 18.7
( m m ) 45.2 237.1 436.3
Transition point (°C) 30.0 - 1 . 9
( m m ) 144.6 153.1
Heat of fusion 3,230 1,220 940
(Cal per mole)
AS of fusion 8,478 3.886 3.21 (Cal per mole per deg)
Heat of transition 1,338 2,090
(Cal per mole)
2,090
AS transition 3.868 7.71
Heat of vaporization 14,590 7,720 15,700 13,880 6,860 (Cal per mole)
6,860 Heat of sublimation
A b o v e transition 17,820 8,940 7,800
Below transition 10,280 9,890
Entropy of vaporization 32.7 22.3 34.3 28.1 22.3
Vapor pressures follow the equations below in the stated temperature range
Liquid R e O F4 (108 to 172°) logio Pmm = 10.09 - 3 , 2 0 6 7 " ! Solid R e O F4 (50 to 107°) logio Pmm = 11.88 - 3 , 8 8 8 7 - ! Liquid R e O F5 (41 to 73°) logio Pmm 7.727 - l , 6 7 8 . 6 T - i Solid R e O F5 (30 to 41°) logio Pmm = 8.620 - 1 , 9 5 8 . 5 7 - ! Solid R e O F5 (0 to 30°) logio Pmm = 9.581 - 2 , 2 5 0 . 1 7 - 1 Liquid R e 02F3 (90 to 170°) logio Pmm 10.36 - 3 , 4 3 7 7 " ! Liquid R e F5 (48.0 to 140°) logio Pmm = 9.024 -- 3 , 0 3 7 7 " ! Liquid R e F6 (19.0 to 33.8°) logio Pmm = 7.732 -- 1 , 4 8 9 . 1 7 - 1 Solid R e F6 ( - 1 . 9 to 18.0°) logio Pmm 8.539 -- 1 , 7 2 4 . 7 7 - 1 Solid R e F6( - 5 . 0 t o - 1 . 9 ° ) logio Pmm 10.110 -- 2 , 1 5 1 . 2 7 - 1
ReOFs and rhenium dioxytrifluoride ReC^Fs. The former melts at 34.5° and boils at 55°. It hydrolyzes easily and is readily reduced.
Perrhenyl fluoride, ReOsF, was prepared by Engelbrecht and Grosse*2 0 8) by the reaction of ReOaCl with anhydrous H F followed by vacuum sublim
ation. It is a yellow solid which melts at 147° and boils at 164° with slight decomposition. It is very reactive as an oxidizing agent and is hydrolyzed easily. Aynsley, and Hair*26) prepared ReC^F and IOF3 by the action of IF5 on KReC>4 under reflux at 97°. The melting point of ReC^Fs is found to be 95° and its boiling point 126°. The microwave spectrum and structure of perrhenyl fluoride are reported by Lotspeich, Javan, and Engelbrecht*4 3 9).
78 J. H . SIMONS
Fluoroherrates of quadrivalent rhenium have been prepared by Peacock*536). Potassium bifluoride was heated with ammonium iodorhe-nate (IV), (NH^ReFe, at 250°. The latter compound was made by the reduction of (NH^ReCU with hydroiodic acid in the presence of ammonium iodide. The K^ReFe was recrystallized from hot water. Rb2ReF6 and Cs2ReF6 were prepared in a similar manner. These are all soluble in water.
By adding barium or hexamminocobaltic chlorides to a solution of the potassium salts BaReF6 and Co(NH3)eReF6 were formed. Using a strongly ammoniacal nickel sulfate solution Ni(NH3)eReF6 was crystallized. The acid in aqueous solution was obtained from a solution of K^ReFe by ion exchange. Addition of ammonium carbonate or sodium carbonate to such a solution and evaporating resulted in (NH^ReFe and Na2ReF6. The free acid could not be obtained by careful drying of its aqueous solution.
Crystal structures of the salts were determined. Weise*7 6 8) obtained K2ReF6 and Rb2ReF6 by reaction of K2ReBr6 and Rb2ReBr6 with HF at 450°, for Cs2ReF6 only 350° was required.
Alkali hexafluororhenates (V) were prepared by Peacock*539) by mixing a solution of ReF6 in SO2 at —65° with a solution in SO2 of the alkali iodide. The compounds all hydrolyze with water. Crystal structures for NaReF6, KReF6, RbReF6, and CsReF6 are given.
Some complex oxyfluorides of septavalent rhenium were prepared by Peacock*534) by the action of bromide trifluoride on metallic perrhenates.
The following were obtained relatively pure: KRe02F4, RbReC>2F4, CsRe02F4, AgRe02F4, and Ba(Re02F4)2. They hydrolyze. Ca(Re02F4)2, Sr(Re02F4)2, and NaReC^Ei were prepared but in less pure condition.