ETA-2-ACYL AND METHYL COMPLEXES OF TUNGSTEN - CRYSTAL AND MOLECULAR-STRUCTURES OF W(ETA-2-C(O)CH2SIME3)CL(CO)(PME3)3 AND W(CH3)(S2CNME2)(CO)2(PME3)2

Treatment of WCl2(CO)2(PMe3)3 with Grignard reagents affords the formally six-coordinate bidentate acyls W(eta-2-C(O)R)Cl(CO)(PMe3)3 (R = CH2SiMe3 (1a), CH2CMe3 (1b), CH2CMe2Ph (1c)), whereas the analogous reaction with LiMe furnishes a seven-coordinate methyl complex of composition W(CH3)Cl(CO)2(PMe3)3 (1d). Addition of Me2PCH2CH2PMe2 (dmpe) to solutions of 1d effects PMe3 substitution and formation of W(CH3)Cl(CO)2(PMe3)(dmpe) (2), but further reaction with dmpe does not take place even under rather forcing conditions (excess dmpe, 50-degrees-C, 24 h). A related bis-dmpe complex, [W(CH3)(CO)2(dmpe)2]Cl (3), is obtained, however, by reaction of 1a with 2 equiv of dmpe. Facile desilylation of 1a to other related methyl complexes is also observed under appropriate conditions. Carbonylation of compounds 1b-d under ambient conditions yields the eta-2-acyl complexes W(eta-2-C(O)R)Cl(CO)2(PMe3)2 (R = CH2CMe3 (5b), CH2CMe2Ph (5c), CH3 (5d)), while the Me3SiCH2 derivative 1a again undergoes desilylation and furnishes the acetyl 5d. The methyldithiocarbamate compound W(CH3)(S2CNMe2)(CO)2(PMe3)2 (4), prepared from 1a and NaS2CNMe2, also converts into an acetyl complex, W(eta-2-C(O)CH3)(S2CNMe2)(CO)2(PMe3) (6), upon reaction with CO. The eta-2-acyl complex 1a and the methyl complex 4 have been characterized by X-ray studies. la is orthorhombic, P2(1)2(1)2(1), with a = 10.717 (5) angstrom, b = 12.526 (5) angstrom, c = 18.870 (7) angstrom, Z = 4, and R = 0.027, while 4 is monoclinic, P2(1)/c, with a = 14.318 (8) angstrom, b = 9.140 (2) angstrom, c = 16.267 (6) angstrom, beta = 106.08 (4)-degrees, Z = 4, and R = 0.029.