Chemistry of di- and tri-metal complexes with bridging carbene or carbyne ligands. Part 30. Synthesis of the vanadium–tungsten complexes [VW(µ-CR)(CO)2(η-C5H5)3](R = C6H4Me-4 or Me) and the crystal structure of the tolylmethylidyne compound

Abstract

The compounds [W(CR)(CO)₂(η-C₅H₅)](R = C₆H₄Me-4 or Me) and [V(η-C₅H₅)₂] react slowly at 0 °C in light petroleum to give black crystalline dimetal compounds [VW(µ-CR)(CO)₂(η-C₅H₅)₃] in good yield. Whereas in the solid state the compounds are reasonably stable, in solution they partially dissociate into the precursors. Spectroscopic data are reported and discussed, including e.s.r. studies which confirm the expected paramagnetism of the complexes. The molecular structure of the complex [VW(µ-CC₆H₄Me-4)(CO)₂(η-C₅H₅)₃] has been established by single-crystal X-ray diffraction. As expected, the vanadium–tungsten bond [2.994(5)Å] is bridged by the CC₆H₄Me-4 ligand [V–C 2.21(2) and W–C 1.86(1)Å]. One of the two CO ligands on tungsten semi-bridges the V–W bond [W–C–O 167(3)°, V–C(O) 2.63(3) and W–C(O) 1.97(3)Å]. The vanadium and tungsten atoms are also η₅-bonded to two and one cyclopentadienyl groups, respectively. Crystals of [VW(µ-CC₆H₄Me-4)(CO)₂(η-C₅H₅)₃] are monoclinic, space group P2₁/c(no. 14) and the structure has been refined to R 0.097 (R′ 0.093) for 1 699 reflections measured to 2θ= 50° at room temperature.