Organometallics 1982, 1, 453-459
Experimental Section The infrared spectrum was recorded on a Perkin-Elmer 521 spectrometer. NMR spectra were recorded at 15.08 MHz in the Fourier transform mode on a Bruker WP60 spectrometer. All reported shifta are downfield relative to tetramethylsilane. The mass spectrum were measured on an AEI MS-9 high-resolution mass spectrometerwith a DS-30 data system. An ionizing voltage of 70 eV was used. Reagents obtained from the indicated sources were used without further purification: hexaethylbenzene, Cr(CO)6 (Pfaltz & Bauer); PEG (Fluka). Tricarbonyl(hexaethylbenzene)chromium(O) (3) was prepared as described previously.2 Dicarbonyl(hexaethylbenzene)(triethylphosphine) chromium(0) (1) was prepared by UV irradiation for 1 h of a freeze-thaw degassed pentane (30 ml) solution of 3 (0.18 g, 0.47 mmol) and PEG (0.1 g, 0.68 mmol) contained in a quartz vessel. The pentane solution was filtered under a nitrogen atmosphere and the solvent removed. The solid residue was recrystallized from pentane to give orange crystals of 1: IR (KBr) 1789,1846, 1857,1948 cm-'; 13C(1H)NMR (CD2C12,ambient temperature) b 6.5, 15.2, 16.1, 21.2, 22.5 (ethyl),lS 106.9 (C& 244.3 (CO, 2Jpc= 22 Hz); mass spectrum, mle (relative intensity) 472 (M', 8),416 (M' - 2C0,45), 326 (M' - CO - PEG, 7), 298 (M' - 2CO - PEG, 57), 246 (M+ - 2CO - PEt, - Cr, 100); mass spectrum (high resolution), mle 472.2560 (472.2562 calcd for C2eH45S2Cr02P). Crystallography. Crystals of 1, obtained by slow evaporation of a pentane solution, are monoclinic: F'2,lc; a = 9.729 (4) A, b (17) Crystal packing effects are also unlikely to play a significant role in determining the conformations of 1 and 2, since there are no intermolecular H-H contecta shorter than 2.3 A. (18)Absorptions from the ethyl groups of HEB overlap with those of triethylphoephine, and no attempt was made to assign individual CHBand CH2 signals.
453
= 18.353 (6) A, c = 29.869 (12) A, /3 = 98.26 (2)'; d d d = 1.189 g cm-, for 2 = 8 (C2eHISCr02P,mol wt 472.61). The intensity data were measured on a Hilger-Watts diffractometer (Ni-filtered Cu K a radiation, 8-28 scans, pulse-height discrimination). The size of the crystal used for data collection waa approximately0.15 X 0.15 X 0.5 mm; the data were corrected for absorption (JI = 44.4 cm-'). A total of 4951 independent reflections were measured for 8 < 48O, of which 4015 were considered to be observed (I> 2.50(0). The structure was solved by the heavy-atom method after the positions of the four chromium and phosphorus atoms had been obtained from an E map. A block-diagonalleashquarea, in which the matrix was partitioned into two blocks, was used for the final refinement. Two reflections which were strongly affected by extinction were excluded from the final refinement and difference map. Anisotropicthermal parameters were used for nonhydrogen atoms and isotropic temperature factors were used for hydrogen atoms in the final refinement. The hydrogen atoms were included in the structure factor calculations, but their parameters were not refined. The final discrepancy indices are R = 0.041 and R , = 0.044 for the 4013 observed reflections. The final difference map has no peaks greater than h0.5 e A-3,
Acknowledgment. We thank the National Science Foundation (Grant CHE8009670) for support of this work and Stella Denmanla for experimental and technical assistance. Registry No. 1, 80462-12-0;3, 47378-46-1.
Supplementary Material Available: Final anisotropic thermal parameters and atomic parameters for hydrogen atoms, with standard deviations for 1A and 1B and a structure factor table for 1 (20 pages). Ordering information is given on any current masthead page.
The Series RU(CO),,[P(OM~)~], ( n = 1-5). Migration in Ru[ P(OMe),I5
Methyl
Randy F. Alex and Roland K. Pomeroy' Depaflment of Chemistv, Simon Fraser Universiw, Burnaby, British Columbia, Canada V5A 1S6 Received August 14, 198 1
Pentakis(trimethy1 phosphite)ruthenium, Ru[P(OMe),], (5), has been prepared by the ultraviolet irradiation of a hexane solution of RU,(CO)~~ and excess P(OMeI3. When the reaction was followed by 31P(1H) NMR spectroscopy, the stepwise formation of RU(CO)~,,[P(OM~)~],, (n = 1-5) was indicated. Alternative syntheses for the derivatives with n = 1-4 are reported. As previously found for Ru(CO),[P(OMe),], Ru(CO)~JP(OM~),],(n = 3,4) are probably fluxional, on the NMR time scale, in solution. When 5, in hexane solution, was heated to 120 "C, it isomerized to Ru[P(OM~),],(CH,)[P(O)(OM~)~] (59. Treatment of either 5 or 5i with Me1 gave ( R U [ P ( O M ~ ) ~ ] ~ ( C HThe ~ ) )preparation I. of the ortho-metalated compound,
,
,
(H)Ru [ (C6H40)P(OPh)2][P ( OMe),] , from Ru(CO)z[P(OMe) ,] and P(OPh), is also described.
Introduction I n t h e past several years i t has become apparent t h a t phosphites, and trimethyl phosphite in particular, are able to stabilize transition metals in low, or formally zero, oxidation states. These complexes (e.g., Cr[P(OMe)&,l W[P(OMe)&,2 Co[P(0Ph),l4H3) have stoichiometries that resemble the corresponding carbonyl derivatives. However, due to the different electronic and steric properties of the CO and P(OR)3 ligands, i t would be expected that the two
types of compounds would have different chemical properties. Two groups have reported the synthesis of Fe[P(OMe),], and described aspects of its ~ h e m i s t r y . ~The . ~ preparation of t h e ruthenium analogue, Ru[P(OMe),], (5), has also been mentioned together with its temperature-dependent 31P(1H} N M R spectrum.6 The preparation involved t h e sodium amalgam reduction of Ru[P(OMe),I4Cl2 in t h e (4) Tolman, C. A,; Yarbrough, L. W.; Verkade, J. G. Inorg. Chem. 1977,16,479. Jesson, J. P.; Cushing, M. A.; Ittel, S. D. Zmrg. Synth. 1981,
(1)Van-Catledge, F. A,; Ittel, S. D.; Tolman, C. A.; Jesson, J. P. J. Chem. Soc., Chem. Commun. 1980, 254. (2) Choi, H. W.; Gavin, R. M.; Muetterties, E. L. J.Chem. SOC.,Chem. Commun. 1979, 1085. (3) Conder, H.L.; Courtney, A. R.; DeMarco, D. J.Am. Chem. SOC. 1979, 101, 1606.
0276-7333/82/2301-0453$01.25/0
20. _ _79. ,
( 5 ) Harris,T. V.; Rathke, J. W.; Muetterties, E. L. J. Am. Chem. Soc. 1978,100,6966. (6) English, A. D.; Ittel, S. D.; Tolman, C. A.; Meakin, P.; Jesson, J. P. J. Am. Chem. SOC.1977,99, 117. Jesson, J. P.; Cushing, M. A.; Ittel, S. D. Znorg. Synth. 1981,20,80.
0 1982 American Chemical Society
Alex and Pomeroy
454 Organometallics, Vol. 1, No. 3, 1982
presence of excess trimethyl phosphite. During our study7 of the preparation of some Ru(CO)~Lderivatives, it was noted that 5 could be prepared by the ultraviolet irradi) ~ ~excess Pation of a hexane solution of R u ~ ( C Oand (OMe)3. This method is similar to that used by Mathieu ~]~, it does and PoilblancB to prepare M O [ P ( O M ~ ) although not appear to have been exploited since this original report. In this paper we describe the details of the preparation of Ru[P(OMe),], using this method, along with the synthesis of the other members of the series Ru(CO),,[P(OMe)d, (n = 1-5). The isomerization of 5 to Ru[P(OMe)3]4(Me)[P(0)(OMe)2] is also reported. This work has been the subject of a preliminary communi~ation.~ Experimental Section General Procedure. Unless otherwise stated, reactions (and the purification of solvents) were carried out under a nitrogen atmosphere with use of standard Schlenk techniques. Hexane was refluxed over potassium, distilled, and stored over type 4A molecular sieves before use. Dodecacarbonyltriruthenium was prepared by a literature method.1° Trimethyl phosphite, as obtained commercially, was transferred under nitrogen to a 500-mL round-bottom flask fitted with a Teflon valve and stored under nitrogen before use; it was pure by ,lP(lH} NMR spectroscopy. Previously, impure trimethyl phosphite was purified by distillation from sodium (under nitrogen). The ultraviolet irradiations were carried out with use of a Hanovia 200-W lamp inside a water-cooled, quartz jacket. The reactanta were contained in thick-walled Pyrex, Carius tubes (30 cm X 3 cm diameter) fitted at one end with a Teflon valve. There was approximately 3 cm between the edge of the UV source and the edge of the solution. Infrared spectra were recorded with a Perkin-Elmer 237 spectrometer fitted with an external recorder. The spectra (carbonyl region) were calibrated by using carbon monoxide. Phosphorus NMR spectra were obtained on a Varian XL 100 instrument (operating in the Fourier transform mode, with proton decoupling). An internal reference of P(OMe), was used, and the chemical shifts referred to H3P04 (6 0, downfield negative) by taking the 31P resonance of trimethyl phosphite (in hexane, ambient temperature) as -140.5 ppm. Proton NMR spectra were obtained on the same instrument with the exception of the spectrum of Ru[P(OMe)3]4(CH3)[P(0)(OMe)2] shown in Figure 2. This spectrum was obtained on the Bruker 4ooMHz instrument at the University of Alberta; the spectrum was recorded with the phosphorus nuclei partially decoupled. Mass spectra were obtained on a HewlettPackard 5985 GC-MS system with an ionization voltage of 80 eV except in the cases of Ru[P(OMe),], and Ru[P(0Me),l4(CH3)[P(0)(OMe)2]2where chemical ionization (with CH5+)was used. Microanalyses were performed by Mr. M. K. Yang of the microanalytical laboratory of Simon Fraser University or by Canadian Microanalytical Service Ltd., Vancouver, B.C. Melting points were measured in sealed capillaries under nitrogen on a Gallenkamp apparatus. R u ( C O ) ~ [ P ( O M ~and ) ~ ] R u ( C O ) ~ [ P ( O M ~A ) ~g]h~a Carius tube containing RU,(CO)~~ (0.32 g, 0.50mmol) and P(OMe), (2.5 mL, 21 mmol) in hexane (20 mL) was cooled to -196 "C and evacuated; the solution was degaased with two freeze-thaw cycles. The solution was stirred at room temperature for 24 h. An infrared spectrum (carbonyl region), after this period, of the orange-red solution indicated the presence of Ru(CO),[P(OMe),] (1) and RU(CO)~[P(OM~),]~ (2) in an approximate 2 1 ratio. There were also other absorptions of weak intensity which indicated the presence of other ruthenium-carbonyl species. An infrared spectrum of a reaction solution which had been stirred for a further 96 h revealed a slight decrease in the intensity of the bands due to 1, with a corresponding increase in those due to 2. The solution was also a much paler red color. (7) Cobbledick, R. E.; Einstein, F. W. B.; Pomeroy, R. K.; Spetch, E. R.J . Organomet. Chem. 1980,195, 77. (8) Mathieu, R.; Poilblanc, R. Inorg. Chem. 1972,If, 1858. (9) Pomeroy, R. K.; Alex, R. F. J. Chem. SOC.Chem. Commun. 1980,
1114. (10)Mantovani, A.; Cenini, S. Inorg. Synth. 1976,16, 47.
The monosubstituted complex, 1, may be separated from 2 by fractional sublimation a t
