Chemistry of di- and tri-metal complexes with bridging carbene or carbyne ligands. Part 18. Synthesis of the complexes [MW(µ-CC6H4Me-4){µ-(σ : η2-CO)}(CO)(η-C5H5)3](M = Ti or Zr) and the crystal structure of the titanium–tungsten compound

Abstract

The compounds [M(CO)₂(η-C₅H₅)₂](M = Ti or Zr) react with [W(CC₆H₄Me-4)(CO)₂(η-C₅H₅)] when heated in toluene to give the dimetal compounds [MW(µ-CC₆H₄Me-4)(µ-CO)(CO)(η-C₅H₅)₃], characterised by n.m.r. and i.r. spectroscopy. The structure of the titanium–tungsten compound has been established by a single-crystal X-ray diffraction study. As expected, the titanium–tungsten bond [2.977(4)Å] is bridged by the CC₆H₄Me-4 ligand [Ti–C 2.19(3) and W-C 1.91(2)Å, with double-bond character in the linkage to tungsten], and one of the two linear terminal carbonyl ligands on the W atom forms a η²-donor bond to the Ti atom. The bridge system itself is nearly planar; but although the two cyclopentadienyl ligands on the Ti atom are at normal bonding distances and are approximately equivalently related to the bridge plane, they are in a staggered orientation to one another. The third cyclopentadienyl ligand completes the bonding around the W atom. The high thermal stability and relative inertness of the molecule can be ascribed, at least in part, to the compact arrangement of inert bulky ligands around the metal centres.