Chemistry of di- and tri-metal complexes with bridging carbene or carbyne ligands. Part 6. Synthesis of platinum–chromium and –tungsten compounds. X-Ray crystal structure of [(Me3P)(OC)4W{µ-C(OMe)C6H4Me-4}Pt(PMe3)2]

Abstract

Addition of light petroleum solutions of [M{C(OMe)C₆H₄R-4}(CO)₅](M = Cr or W, R = Me or CF₃) to ethylene-saturated solutions of [Pt(cod)₂](cod = cyclo-octa-1,5-diene), to which two molar equivalents of tertiary phosphine had been added, afforded the heteronuclear dimetal complexes [(OC)₅[graphic omitted](PR₃)₂](R = Me, PR₃ PMe₃ or PMe₂Ph; R = CF₃, PR₃= PMe₃) and [(OC)₅[graphic omitted](PR₃)₂](R = Me or CF₃, PR₃= PMe₃ or PMe₂Ph), characterised by ³¹P and ¹H n.m.r. spectroscopy. The compounds [(OC)₅[graphic omitted](PMe₂Ph)₂], [(OC)₅[graphic omitted](PMe₂Ph)₂], and [(OC)₅[graphic omitted](PMe₃)₂] were similarly obtained from [W{C(OMe)Me}(CO)₅], [Cr([graphic omitted]H₂)(CO)₅], and [W(CPh₂)(CO)₅], respectively. Although [PtW(µ-CPh₂)(CO)₅(PMe₃)₂] is a relatively unstable complex, reaction with trimethylphosphine affords air-stable [(Me₃P)(OC)₄[graphic omitted](PMe₃)₂] as a single isomer. A similar enhanced thermal and oxidative stability relative to the pentacarbonyl species is also observed with the compounds [(Me₃P)(OC)₄[graphic omitted](PMe₃)₂] and [(R₃P)(OC)₄[graphic omitted](PR₃)₂](PR₃= PMe₃ or PMe₂Ph). A single-crystal X-ray diffraction study on the complex [PtW{µ-C(OMe)-C₆H₄Me-4}(CO)₄(PMe₃)₃]shows that the tungsten–platinum bond [2.825(1)Å] is asymmetrically bridged by a C(OMe)C₆H₄Me-4 group [C–W 2.37(1)Å; C–Pt 2.03(1)Å], that the co-ordination of the W atom is close to octahedral, and that the Pt atom is in a near-planar environment. The crystals are orthorhombic, space group Pna2₁(no. 33), with Z= 4 in a unit cell of dimensions a= 18.180(6), b= 10.720(3), c= 14.697(4)Å. The structure has been elucidated by heavy-atom methods from 3 882 independent intensities measured to 2θ= 60° at 200 K, and refined to R 0.044.