SYNTHESIS AND PROPERTIES OF ALKYL AND ETA-2-ACYL COMPLEXES OF TUNGSTEN - CRYSTAL AND MOLECULAR-STRUCTURE OF W(CH3)(ACAC)(CO)2(PME3)2

The acyl complexes W(eta-2-C(O)R)Cl(CO)(PMe3)3 react with NaS2CNMe2 with formation of the new acyls W(eta-2-C(O)R)(S2CNMe2)(CO)(PMe3)2 (R = CH2CMe3 (2), CH2CMe2Ph (3)), but the (trimethylsilyl)methyl derivative affords an equilibrium mixture of an analogous bidentate acyl 1b and of the alkyl isomer W(CH2SiMe3)(S2CNMe2)(CO)2(PMe3)2 (1a). Other dithiocarbamate and xanthate salts react similarly with W(eta-2-C(O)CH2SiMe3)Cl(CO)(PMe3)3 to yield analogous equilibrium mixtures of the alkyl, W(CH2SiMe3)(S2CX)(CO)2(PMe3)2 (4a-6a), and acyl, W(eta-2-C(O)CH2SiMe3)(S2CX)(CO)(PMe3)2 (4b-6b), isomers. Carbonylation of compounds 1 furnishes exclusively the bidentate acyl W(eta-2-C(O)CH2SiMe3)(S2CNMe2)(CO)2(PMe3) (7). The CH2SiMe3 group in acyls W(eta-2-C(O)CH2SiMe3)(S2CX)(CO)(PMe3)2 is extremely prone to hydrolytic cleavage of the CH2-SiMe3 bond and undergoes facile rupture in the presence of small amounts of water with formation of the methyl derivatives W(CH3)(S2CX)(CO)2(PMe3)2 The reaction of W(eta-2-C(O)CH2SiMe3)Cl(CO)(PMe3)3 with Tl(acac) gives directly W(CH3)(acac)(CO)2(PMe3)2 (13), which has been structurally characterized by X-ray crystallography. Crystals of 13 are orthorhombic, space group Pbca, with unit cell constants a = 11.110 (2) angstrom, b = 13.779 (3) angstrom, c = 26.813 (5) angstrom, and D(calcd) = 1.64 g cm-3 for Z = 8.