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

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)A] is bridged by the CC6H4Me-4 ligand [V–C 2.21(2) and W–C 1.86(1)A]. 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)A]. 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.