Organometallics 1989,8, 2751-2754 however, the radical decays within -2 h. No ESR could be observed in solvents such as acetic acid and pyridine, showing that the radical stability is solvent dependent and it is best produced in a solvent like benzene. The bluish powder" of the complex obtained by evaporating a benzene solution of hexaphenylditin(I1) and aminophenol(1) in equivalent amounts gives intense ESR signal as shown by solid lines in Figure 1. The stability of the radical is probably in part due to steric reasons associated with the p-tert-butyl group. Other spectroscopic measurements on this complex will be discussed later. Under similar conditions, 2-aminophenol and 4-aminophenol failed to produce any radical complex a t room temperature. When irradiated, 4-aminophenol gave only its phenoxyradicals, probably by reaction with 'SnPh3 radical (Sn-Sn bond dissociation energy is 53 kcal mol-').14 ESR signal obtained by ground-state interactions between ABP and organoditin is enhanced by W irradiation for a short period of time (- 10 presumably due to the formation of reactive 'SnPh3 radicals which subsequently reacts with ABP. The radical complex is, therefore, produced not only thermally but also photochemically.6J0 The optical absorption spectra of the radical complex has been recorded in various solvents. It has characteristic bands with A, at -393 and 578 nm in benzene. The Aof ABP itself in benzene occurs a t 292 nm. The broad band a t 578 nm is probably due to metal-ligand charge transfer in this complex supporting our ESR observation of appreciable metal d orbital participation in the stability of the radical. The near-IR measurements show overtone bands a t 6060 cm-' and two combination bands of the aromatic C-H vibrations a t 4650 and 4059 cm-'.
Conclusion The spontaneous ground-state reaction of the organotin compounds with 2-amino-4-tert-butylphenol a t room temperature is demonstrated by ESR measurements, taking hexaphenylditin as the model organotin compound. A very (17) The solid sample can be stored for days without any indication of decaying as measured by ESR signal intensity. (18) CJDEP measurements done in the laboratory of Dr.J. K. S. Wan of Queen's University show that the photochemical formation of the radical occurs with weak polarization in the emissive mode.
2751
stable radical complex, in which tin is probably coordinated to the oxygen and nitrogen of the aminophenol, is formed. 2-Aminophenol and 4-aminophenol do not react under similar conditions. The radical complex has been characterized by UV-visible and near-IR absorption spectrophotometry.
Experimental Section 2-Amii~4tert-butylphenol,2-aminophenol, and 4aminophenol were purchased from Aldrich Chemicals and were purified by
sublimation. Hexaphenylditin, tti-tert-butyltinhydride and other organometallic compounds were supplied by Alfa Inorganics and were used as received. All solvents were purified by standard procedure^.'^ The purity of the reagents used in this study were checked by IR using a Nicolet BDXB FT-IR spectrometer and by NMR using a GE QE-300 FT-NMR spectrometer. CW-ESR spectra were recorded with 100 kHz magnetic field modulation on a Varian E-109 X-band spectrometer equipped with Varian E-272B FieldfFrequency lock assembly and a Nicolet 1280 computer for data acquisition and manipulations.20 Standard sample of DPPH was used as g marker and for magnetic field calibration. All measurements were carried out at room temperature ( 296 K). A standard sample consisted of about l-mL solution containing 10-2M aminophenol and 5 X 10-3M organcditin in a 4 m m quartz tubing which was thoroughly degassed with nitrogen and sealed closed. The sample was irradiated in situ in the ESR cavity by using a high-pressure mercury arc lamp. The UV-visible and near-IR absorption spectra of sample solutions were recorded on a Perkin-Elmer DU-7 and on a Coleman Model EPS-3T spectrophotometers. N
Acknowledgment. A part of this research was funded by the National Scientific and Engineering Research Council of Canada. S.S. wishes to thank the Department of Chemistry of the University of Oregon for financial support during the completion of this work. Several important comments by two reviewers have led to the refinements in the text. Registry No. I, 1199-46-8; 11, 1064-10-4; IV, 123125-63-3; 2-aminophenol, 95-55-6;4-aminophenol, 123-30-8; hexamethylditin, 661-69-8; tri-tert-butyltin hydride, 16216-29-8. (19) Particular care was taken to dry solventa used in this study. Benzene was dried over sodium and distilled. The radical complexes are rather unstable in polar solvents. (20) Sur, S. K.; Cooney, T. C. Phys. Chem. Miner. 1989, in press.
Synthesis and Characterization of Dimethyltin(I V ) Derivatives of Fluoro- and Oxyfluorochromates Siva P. Mallela and Jean'ne M. Shreeve" Department of Chemism, university of Idaho, Moscow, Idaho 83843 Received April 25, 1989
Dimethyltin(IV) fluoride reach with CrOzFzto yield a (CH&Sn-containing derivative, while with CrOFl and CrFs only (CHJfinF derivatives are obtained. Anhydrous HF is found to be necessary for the reactions to proceed at room temperature, and, in its absence, (CH3),SnF2did not react with CrOzFzeven at high temperature. The vibrational data are consistent with a linear C-Sn-C group in each of these derivatives. Reaction of CrOzFzwith elemental fluorine in the presence of either CsF or NOF provides a one-step direct route to CsCrOF5or NOCrOF5salts. Reaction of either CrOzFzor CrOs with COFz in the presence of CsF is another simple, convenient, new synthetic route to the CsCrOF5 salt.
Introduction While the dark violet-red crystalline solid Cr02Fz(mp 31.6 OC, to yield an orangered liquid and red-brown vapor) can be obtained in a variety of ways, the most convenient and nearly quantitative synthetic route is the fluorination 0276-7333/89/2308-2751$01.50/0
of Cr03 with carbonyl difluoride.' Salts of the type MZCrO2F4can be conveniently obtained from CrO2FZand alkali-metal fluoride^.^^^ The interesting oxofluoride (1)Gard, G. L. Znorg. Synth. 1986, 24, 67.
0 1989 American Chemical Society
2752 Organometallics, Vol.8,No.12,1989 CrOF, was recently obtained by a new preparative route from the fluorination of CrzOzF2with KrF2 in anhydrous HF., Earlier it was prepared by the direct fluorination of Cr03 with Fz a t 140 0C.596 This procedure requires careful temperature control, since chromium(V) fluoride, which is very difficult to separate from CrOF,, also forms as a byproduct a t higher temperatures.6 We have also reported a very convenient synthetic route for the preparation of CrOF, by catalytic fluorination of Cr02Fzwith F2.7 Although CrOF, behaves as a strong Lewis acid and forms stable salts with FNO' and CsF? it also reacts with the Lewis acid SbF, in anhydrous H F to yield an adduct CrOF4-SbF5which has a fluorine-bridged structure.8 Chromium(V) fluoride is a very stable, red sticky solid that can be obtained quantitatively in high purity by the fluorination of Cr02F2with elemental f l ~ o r i n e .A~ powerful oxidizing and fluorinating reagent, it forms an adduct of the composition CrF5.2SbF,B with SbF5and fluorinates Xe to XeF2 and XeF2 to XeFklOJ1 Its reactions with Lewis bases have also been studied exten~ively.~ Recently the stable compound NF4CrF6was synthesized in anhydrous HF, and its reactions with ClF,, FNO, Cl,, CFCl,, and KrF2 were examined.12 Few oxyhalides of chromium(\') of the type &OX3 where X = F or C1 have been reported,13-15 and thus, few salts that contain [CrOF,]- have been characterized. Our present investigation examined the reactivity of oxyfluorochromates(VI)and chromium(\r) fluorides toward organometallic fluorides, such as (CH3)2SnF2. To our knowledge no such reactions have been reported for compounds that contain 3d transition metals. Only metal pentafluorides of the type MF, with M a group 5 or group 15 metal have been studied to generate the (CH3)2Sn2+ cation.16 We also investigated the existence of other possible cations such as (CH3),SnF+ in anhydrous H F in the presence of chromium oxyfluorides and chromium(V) fluoride similar to the superacid systems reported earlier.17-20 The obvious advantage of choosing anhydrous HF
(2) Brown, S. D.; Gard, G. L. Inorg. Chem. 1973,12,483. (3) Brown, S. D.; Green, P. J.; Gard, G. L. J. Fluorine Chem. 1975,5, 203. (4) Christe, K. 0.;Wilson, W. W.; Bougon, R. A. Inorg. Chem. 1986, 25, 2163. (5) Edwards, A. J.; Falconer, W. E.; Sunder, W. A. J. Chem. SOC., Dalton Trans. 1974, 541.
(6) Hope, E. G.; Jones, P. J.; Levason, W.; Ogden, J. S.; Tajik, M.; Turff, J. W. J. Chem. SOC.,Dalton Trans. 1985, 529. (7) Mallela, S. P.; Shreeve, J. M. Inorg. Synth., submitted to Vol. 28. (8) Wilson, W. W.; Christe, K. 0. J. Fluorine Chem. 1987, 35, 531. (9) Brown, S. D.; Loehr, T. M.; Gard, G. L. J. Fluorine Chem. 1976, 7, 19. (10) Zemva, B.; Zupan, J.; Slivnik, J. J. Inorg. Nucl. Chem. 1973,35, 3941. (11) Brown, S. D.; Gard, G. L. Inorg. Nucl. Chem. Lett. 1975,11,19. (12) Bougon, R.; Wilson, W. W.; Christe, K. 0. Inorg. Chem. 1985,24, 2286. (13) Levason, W.; Ogden, J. S.; Rest, A. J. J . Chem. SOC., Dalton Trans. 1980, 419 and references there in. (14) Green, P. J.; Johnson, B. M.; Loehr, T. M.; Gard, G. L. Inorg. Chem. 1982,21,3562. (15) Hope, E. G.; Jones, P. J.; Levason, W.; Ogden, J. S.; Tajik, M.; Turff, J. W. J. Chem. SOC.,Dalton Trans. 1984, 2445. (16) Mallela, S. P.; Yap, S.; Sams, J. R.; Aubke, F. Reu. Chim. Miner. 1986, 23, 572. (17) Schlemper, E. 0.; Hamilton, W. C. Inorg. Chem. 1966, 5, 995. (18) Levchuk, L. E.; Sams, J. R.; Aubke, F. Inorg. Chem. 1972,11,43. (19) Mallela, S. P.; Tomic, S. T.; Lee, K.; Sams, J. R.; Aubke, F. Inorg. Chem. 1986,25, 2939. (20) Mallela, S. P.; Yap, S.; Sams, J. R.; Aubke, F. Inorg. Chem. 1986, 25, 4074.
Mallela and Shreeve
is that all the reagents, Cr02F2, CrOF,, CrF,, and (CH,),SnF2, are easily soluble a t room temperature, and hence heating to higher temperature to enhance solubility, which could produce decomposition of the expected products, is precluded. In addition to the reaction chemistry of oxyfluorochromates we have also focused our attention on the easy direct synthetic preparative routes for the known oxyfluorochromate(V1) salts of the type MCrOF6 where M = Cs or NO.
Experimental Section Chemicals. Literature methods were used to prepare Cr02F$ and (CH3)2SnF2.21CrF, and CrOF, were prepared by the fluorination of Cr02F2with elemental fluorine! Anhydrous hydrogen fluoride (99.9%) was obtained from Matheson. Carbonyl difluoride used was supplied by PCR Research Chemicals. General Methods. Reactkns in anhydrous H F were performed in vessels made from Kel-F tubes (Zeus). Kel-F vessels of 20-mL volume were equipped with Teflon-coated magnetic spin bars and fitted with Monel Swagelock fittings and a Whitey Monel valve. A Monel metal vacuum line' that was passivated with CiF was used to transfer volatile materials (PVT technique). Highpressure reactions were carried out either in a prepassivated Hoke Monel cylinder (when fluorine was used) or in a Hoke stainless-steel vessel (for COF2) equipped with Whitey valves and Swagelock fittings. Hygroscopic solids were manipulated in an inert-atmosphere box fiied with purified dry nitrogen. Chemical analysis for C and H was performed at the University of British Columbia. Additional microanalyses were carried out by Beller Mikroanalytisches Laboratorium, Gottingen, FRG. A PerkinElmer 1710 Fourier transform infrared spectrometer and a Biorad Digilab IR FTS 15/80 spectrometer were used with samples pressed between AgBr windows (Harshaw Chemicals) for infrared spectra recordings. Raman spectra were obtained on a Spex Ramalog 5 spectrometer equipped with an argon ion h e r (Spectra Physics Model 164) operating at 514.5 nm. Individual Preparations. Dimethyltin(1V) Dioxotetrafluorochromate(VI), (CH3)2SnCr02F,. A Kel-F vessel with Swagelock fittings and containing a Teflon-coated magnetic stirring bar was loaded with 546.9 mg (2.9 mmol) of (CH3)2SnF2. T o this was distilled about 3 mL of anhydrous HF. Then, 378.2 mg (3.1 mmol) of CrOzF2 was added. After the mixture was allowed to warm to room temperature, the contents were stirred vigorously. Within 10 min, a purple solution was obtained. After the solution was stirred vigorously for 45 min, an orange-yellow solid began to precipitate. After the solution was stirred for an additional 11 h, a n almost colorless solution and a yellow solid were obtained. All of the volatile materials were removed under vacuum a t room temperature. The remaining light brownish yellow hygroscopic solid (669 mg,2.2 "01) changes to light yellow a t 165-175 "C to light green at 245 "C and finally decomposes a t 312 "C with concomitant glass attack. An identical product was obtained when the ratio of Cr02F2to (CH3),SnF2 was 2:l. Infrared spectral data obtained are (below lo00 cm-'): 1016 vvw, 972 m, 900 sh, 785 vs, 669 m, 658 w, 626 ms, 597 s, 519 vs, 430 w, 419 m cm-'. Anal. Calcd for C2&SnCrO2F4: C, 7.78; H, 1.96; F, 24.61. Found: C, 7.70; H, 2.00; F, 25.0. The (CH3)#nF,-Cr02F2System. Into a 150-mL Monel metal container at -196 "C that contained (CH3),SnF2 (1000 mg, 5.32 "01) was condensed Cr02F2(712.4 mg, 5.84 mmol). No solvent was used. The mixture was heated at 100 "C for 90 h. After the reaction the infrared spectrum of volatile materials showed bands due only t o Cr02F2that was recovered quantitatively. The (CH3)2SnF2-Cr02F2-COF2 System. Onto a mixture of (CH3)2SnF2(lo00 mg, 5.32 mmol) and Cr02F2(1494.3 mg, 12.25 mmol) in a Monel metal cylinder was condensed COF, (12.42 "01) a t -196 "C. The container was warmed slowly to ambient temperature and later heated a t 150 "C for 90 h. After the reaction, the infrared spectra of the materials volatile at -78 "C showed bands due to C 0 2 and COF? The materials volatile at (21) Huang, J.; Hedberg, K.; Chem., 1988,27, 4633.
Shreeve, J. M.; Mallela, S. P. Inorg.
Synthesis of Dimethyltin(IV) Derivatives -78 "C were removed under vacuum. On the basis of the CrOzFz (7.21 "01) that was recovered at room temperature, (CH&SnFZ had reacted with 5.04 mmol of CrO2F2. Analysis of the yellowish
brown hygroscopic solid product was close to that expected for a mixture of (CH3)2SnFzand (CH3)zSnF.CrF50. Fluorodimethyltin(1V) Oxopentafluorochromate(VI), (CH3)zSnFCrOF5.Equimolar amounts of (CH3)$nFz (140 mg, 0.75 mmol) and CrOF4(110 mg, 0.76 mmol) were charged into a Kel-F vessel, and -2 mL of anhydrous HF'was transferred onto the mixture at -196 "C. The contents were stirred vigorously at room temperature, and initially a clear purple solution was obtained. A yellowish brown solid precipitated within 35 min. After the solution was stirred for 9 h, all of the volatile materials were removed under vacuum at 25 "C. The yellowish brown hygroscopic solid (270 mg, 0.8 mmol) decomposed at 280 "C to a green product when heated in a glass capillary. Infrared spectral data obtained are (below 1000 cm-I): 997 8,824 s, 697 8,669 w, 560 vs br, 425 w, 410 vw,371 w cm-'. And. cdcd for C&,hCrOF6: C, 7.26; H, 1.83. Found: C, 7.00; H, 1.75. Fluorodimethyltin(1V) Hexafluorochromate(V), (CH3)zSnFCrF8. To a Kel-F vessel equipped with a Teflon-coated magnetic stirring bar were transferred CrF5(250 mg, 1.7 mmol) and (CH&SnF2(317.6 mg, 1.7 mmol). About 5 mL of anhydrous HF was added to the mixture at -196 O C . On warming slowly a reddish yellow solution developed at ambient temperature and almost immediately a yellow solid precipitated. The reaction mixture was stirred vigorously for 5 h at 25 "C to give a clear, colorless solution and a yellow solid. After all of the volatile materials were removed, a yellow hygroscopic solid (CH,)8nFCrF6 (550 mg, 1.65 mmol) was obtained. On heating in a glass capillary tube the color changed from yellow to brown at 190 O C and decomposed at 280-290 "C. Infrared spectral data obtained are (below 1000 cm-'): 780 vs br, 669 w, 629 w, 597 s, 518 s br (531 m, Raman), 380 s, 280 m cm-'. Anal. Calcd for CzH8SnCrF7:C, 7.20; H, 1.81; F, 39.84. Found: C, 6.98; H, 1.73; F, 38.2. The (CH3),SnFz4:rF5-HF System. In an attempt to prepare (CH3)zSn(CrF6)z, 2 equiv of CrF6(90 mg, 0.61 "01) and 1 equiv of (CH3)zSnFz (57.1 mg, 0.3 "01) were stirred vigorously in about 4 mL of anhydrous HF for 20 h. The light yellow hygroscopic product obtained was identified as (CH3)&3nFCrF6. Preparation of NOCrOFs and CsCrOF6. Equimolar amounts of CrOzFz(618.5 mg, 5.07 mmol) and NOF (248.4 mg, 5.07 mmol) were vacuum transferred into a 100-mL Hoke Monel vessel (prepassivated with F2). About 120 mmol of elemental fluorine was then introduced at -196 O C . The vessel was allowed to warm very slowly to 25 "C and then was heated in an oven maintained at 80 "C for 65 h. The excess fluorine and other volatile materials were removed first at -196 "C and later at -78 "C. The light purple hygroscopic solid obtained was identified as NOCrOF, by its IR spectrum., Oven dried, finely ground CsF (757.7 mg, 4.99 "01) and 619.7 mg (5.08 "01) of CrOzFzwere treated exactly as described above except the heating time was 88 h. The yellow hygroscopic solid obtained was identified by IR spectrum as CsCrOFb6 In an alternate preparative route to CsCrOF5,500 mg (5 mmol) of Cr03 (oven dried at 100 "C for 24 h and finely ground) and 759 mg (5 mmol) of dried powdered CsF were heated in presence of 990 mg (15.0 mmol) of COFzin a 75-mL Hoke steel container at 90 "C for 20 h. On removal of the volatile materials (C02 and COFz), a yellow hygroscopic solid obtained was identified as CsCrOF5 similar to the one described above. The yellow solid on heating in a glass capillary tube melts at 300 "C.
Results and Discussion Chromium(V1) difluoride dioxide, Cr02F2,reacts with group 1 and group 2 metal fluorides2 to form solid fluorochromates as follows. 2MF
-
+ Cr02F2 60 "C
M2Cr02F4 M = Na, K, Cs 30 'C
MCr02F4 MFz + Cr02F2 M = Ca, Mg These salts can be prepared directly, but in some cases,
Organometallics, Vol. 8, No. 12, 1989 2753 for example, where M = Ca and Mg, the presence of a solvent such as perfluoroheptane facilitates the reaction. CrOzFzalso reacts with organometallic fluorides, such as (CH3)2SnF2in anhydrous hydrogen fluoride (AHF) at room temperature.
AHF, 1.5 h
(CH3)2SnF2+ Cr02F2 (CH3),SnCr02F4 The light brownish yellow hygroscopic solid is very reactive with water producing a yellow dichromate solution. An excess of Cr02F2has no effect on the reaction and is recovered quantitatively. Without solvent, the reaction does not proceed even after 90 h at 150 "C. However, AHF is a suitable reaction medium for this system. The advantages of AHF as solvent include its ability to dissolve both the dimethyltin(1V) fluoride with the dimethyltin(1V) moiety being stable toward further solvolysis1s and the chromium compounds Cr02F2,CrOF,, and CrF,. In all cases, purple or reddish yellow solutions were observed before precipitation of the product occurred. A clear solution was present when the reaction was completed. In the presence of carbonyl fluoride (COF2) the expected reaction of Cr02F2with (CH3)2SnF2according to 150 "C
(CH3)2SnF2+ 2Cr02F2+ 2COF2 gh (CH3)2Sn(CrOF5)2+ 2C02 did not occur. The infrared spectrum of the yellowish brown solid that was formed showed the presence of the [CrOF5]- anion as well as frequencies due to (CH3)2SnF2. Elemental analysis confirmed the product to be a mixture of (CH3)2SnFCrOF5and unreacted (CH3)2SnF2. In view of these observations, the possibility of the formation of the (CH3)2SnF+seemed likely in this system. This has been confirmed by the direct reaction of (CH3)$3nF2with CrOF4 in AHF according to (CH3)2SnF2+ CrOF,
9h
(CH3),SnFCrOF5
The material isolated was analyzed and characterized to be (CH3)2SnFCrOF5by infrared and Raman spectroscopy. A similar reaction occurred with CrF5, where (CH3)$3nF2 and CrF, were reacted in a 1:l ratio according to (CH3),SnF2 + CrF,
AHF 7 (CH3)2SnFCrF6
Unlike other pentafluorides,16such as NbF5, TaF,, or SbF,, apparently CrF5 stabilizes the (CH3)2SnF+cation in anhydrous HF. It is rather surprising that the attempted synthesis of (CH3)2Sn(CrF6)2,by reacting 2 equiv of CrF, with 1equiv of (CHJ2SnF2,was not successful, and instead only (CH3),SnFCrF6 was formed. Spectral as well as elemental analysis confirmed this formulation for the product obtained. All of the dimethyltin(IV) chromates decompose around 300 "C that is well below the decomposition of (CH3)2SnF,.18 This thermal behavior is another indication that the compounds are not simple mixtures containing- unreacted (CH;),SnF,. Although a large number of salts with Cr09F9have been reportedonly two derivatives are known for-C%OF4. The recently reported NOCrOF5 has been prepared4 by the direct reaction of CrOF4 with FNO according to CrOF, + FNO NOCrOF, The other reported derivative containing the [CrOFJ ion was obtained by heating CrOF, and CsF a t 100 oC.6 In both cases, CrOF, was prepared separately before reacting with the base. Our one-step synthetic approach differs significantly, and the starting material is the very easily obtainable
-
2754 Organometallics, Vol. 8, No. 12, 1989
Mallela and Shreeue
CrOzF2or Crop The following two procedures were used to prepare the known derivatives. 1. Fluorination of Cr02Fzwith elemental fluorine in the presence of a base NOF (or CsF) according to Cr02F2+ NOF
FZ
NOCrOF,
+ 0.502
2. Fluorination of Cr03 (or Cr02F2) with carbonyl fluoride in the presence of a stoichiometric amount of CsF, according to Cr03
+ CsF + 2COF2
24 h
CsCrOF,
+ 2C02
Both of these compounds were characterized by comparison of infrared spectra and physical properties, such as melting points, reported in the literature. The success of these fluorination reactions, we believe is that the CrOF4 formed in situ, reacted readily with the available base to yield the solid products. In a separate fluorination of Cr02F2 with elemental fluorine in the presence of catalytic amounts of CsF we did, in fact, isolate pure CrOF47that was studied via electron diffraction.21 Similar efforts to obtain pure CrOF, with carbonyl difluoride were not successful.22
Vibrational Spectra Metal oxy complexes show strong characteristic bands for stretching and deformation vibrations of metal-oxygen bonds in both IR and Raman spectra. In the absence of other spectroscopic techniques, vibrational spectroscopy is an excellent tool for the structural characterization of metal oxy and dioxy complexes. These bands are generally multiple. Their vibrational frequencies are expected to be sensitive to changes in the degree of metal-oxygen 7~ bonding. The M = O stretches are found near 950 cm-' for monooxy c ~ m p l e x e s . These ~ ~ ~ ~are ~ observed at 820 cm-' for trans-dioxo and near 930 and 890 cm-' for cis-dioxo
specie^.^^?^^ The infrared frequencies for dimethyltin(1V) oxyfluorochromates are given. Efforts to obtain good quality Raman spectra were not successful due to the strong fluorescence effect for all these compounds. Griffith and Wickins26i28showed that octahedral mononuclear transition-metal (do)dioxo complexes have a cis structure. For cis-dioxo species (symmetry C2J vsym(M02) and 6(M02)are Al mode and v,,(M02) is B, mode. All three are IR and Raman active.n On the basis of Griffth's assignment, Brown et al.3 have concluded that alkali-metal oxyfluorochromates (Cr(VI), do) possess the cis-dioxo structure. The additional bands observed for alkali-metal fluorochromates have been attributed to the interactions between Cr=O groups in neighboring mole~ules.~ Assuming an octahedral cis-dioxo structure for (CH3)2SnCr02F4,the bands a t 972 and 900 cm-' can tentatively be assigned to u,,(Cr02) and v,,(CrO2), respectively. These are in good agreement with that of Na2W02F4, N B ~ M O O ~and F ~Cs2Cr02Fk3 ,~~ The strong v(Cr=O) vibration for the monooxyfluorochromate (CH3),SnFCrOF5is observed at 997 cm-', which is again in agreement with the assignment for &OF,(22) Mallela, S. P.; G u D ~0. , D.; Shreeve. J. M. Inora. Chem. 1988. 27, 208. (23) Brown, D. J. Chem. SOC.1964, 4944. (24) Selbin, J.; Holmes, C. H.; McGlynn, S. P. J. Inorg. NucE. Chem. 1963,25, 1359. (25) Griffith, W. P.; Wickins, T.D. J. Chem. SOC.1968,400. (26) Johnson, N. P.; Lock, C. J.; Wilkinson, G. J. Chem. SOC.1964, 1054. (27) Griffith, W. P. J . Chem. SOC.A 1969, 211.
(C4,L4 The increase in C r = O stretching frequency by 42 cm-' from C S C ~ O F(955 , ~ cm-') to (CH3)2SnFCrOF5(997 cm-l) may be due to the cation-anion interactions in the dimethyltin complex. A similar increase of 26 cm-' is observed for v,,(Cr02) in the dioxo compound (CH3)2SnCr02F4. Thus, metal oxygen vibrational frequencies clearly differentiate between monooxy- and diooxyfluorochromate anions with octahedral coordination. The bands due to the dimethyltin(1V) moiety are very weak for all these dimethyltin derivatives. These are observed a t -3035 and -2925 cm-' (CH3 stretch) and at -1273 and -1210 cm-' (CH3 bending) and are in agreement with literature reports.16,28-34 A very strong band at 785 cm-' due to Sn-CH3 rocking is observed for (CH3)2SnCr02F4. The asymmetric stretching vibration for Sn-C is very well resolved a t 597 cm-', and the v(CrF) vibration is found a t 519 cm-'. On the other hand, for (CH3)2SnFCrOF5the Sn-CH3 rocking vibration is observed at 824 cm-l, but the Sn-C asymmetric stretch and u(CrF) vibrations are not resolved and are observed as a very broad strong band centered a t -560 cm-'. The additional bands observed are possibly due to solid-state effects, since the infrared spectra were obtained as films pressed between AgBr windows. In the absence of high-quality Raman spectra these bands could not be assigned. The lack of a strong band a t -360 cm-' in (CH3)2SnCr02F4confirms the presence of the ( C H 3 ) ~ n 2 + cation, since the Sn-F stretching vibration for (CH,),SnFCrOF5 is found a t 371 cm-'. The infrared spectrum (CH3)2SnFCrF6is relatively simple compared to the other two oxyfluorochromates. For the octahedral CrF6- (0,) anion the two infrared active modes are v3(FlV)and v ~ ( F ~ ~These ) . ~ two J ~ IR active modes have been found for CsCrF6 (600, 295 cm-') and NO2CrF6(600, 275 cm-') and were assigned to v,,(CrF) and G(Cr-F), respecti~ely.~ The expected two frequencies for the CrF6- anion in (CH3)&hd?CrF6were found at 597 cm-' u3 (uWw(Cr-F))and 280 cm-' (G((3r-F)) and were in agreement with reported frequencies? Very strong bands at 780 cm-' (Sn-CH3rock) and 518 cm-I (Sn-C asym str) expected for the (CH3)2SnF+ moiety have been found to be in excellent agreement with previous assignment^.'^,^^-^ The Raman active v(Sn-C) symmetric stretching frequency was observed at 531 cm-I in the Raman spectrum suggesting a linear CH3-Sn-CH, group. The strong band observed a t 380 cm-' in the IR spectrum can be assigned to Sn-F stretching. This band has been observed a t -360 cm-l for (CH3),SnF2. It is interesting to note that this band observed a t around 380 cm-' in the (CH3)2SnF+cationic species is absent in (CH3)2Sn2+. The formulation of the resulting solid products as (CH3)2SnFCrOF, and (CH3)2SnFCrF6as suggested earlier appears to be reasonable. Acknowledgment is made to the donors of the Petroleum Research Fund, administered by the American Chemical Society, to NSF Grants CHE-8404974 and CHE-8703790, and to AFOSR 87-0067. We are grateful to Dr. F. Aubke of the University of British Columbia for helpful discussions. (28) Clark, H. C.; Goel, R. G. J. Organomet. Chem. 1964, 7, 263. (29) Clark, H. C.; OBrien, R. J. Inorg. Chem. 1963,2, 1020. (30) Clark, H. C.; O'Brien, R. J. Inorg. Chem. 1963,2, 740. (31) Clark, H. C.; O'Brien, R. J.; Trotter, J. J. Chem. SOC.1964,2332. (32) Yeata, P. A.; Ford, B. F. E.; Sams, J. R.; Aubke, F. J. Chem. SOC., Chem. Commun. 1969,791. (33) Yeats, P. A.; Sams, J. R.; Aubke, F. Inorg. Chem. 1972,11,2634. (34) Tan,T. H.; Dalziel, J. R.; Yeata, P. A.; S ~ SJ.,R.; Thompson, R. C.; Aubke, F. Can. J . Chem. 1972,50, 1843.
