Chemistry of di- and tri-metal complexes with bridging carbene or carbyne ligands. Part 17. Reactions of the compounds [Ru3(CO)12], [Os3(µ-H)2(µ-CH2)(CO)10], and [Os3(CO)10(cyclo-C8H14)2] with [W(CC6H4Me-4)(CO)2(η-C5H5)]; crystal structures of [OsW2{µ3-C2(C6H4Me-4)2}(CO)7(η-C5H5)2](two isomers) and [Os3W(µ3-CC6H4Me-4)(CO)11(η-C5H5)]

Abstract

Reactions between [W(CR)(CO)₂(η-C₅H₅)](R = C₆H₄Me-4) and [Os₃(µ-H)₂(µ-CH₂)(CO)₁₀] or [Ru₃(CO)₁₂], in tetrahydrofuran and toluene, respectively, afford the cluster compounds [MW₂(µ₃-RC₂R)(CO)₇(η-C₅H₅)₂](M = Os or Ru). The molecular structure of the osmiumditungsten compound was established by a single-crystal X-ray diffraction study, which shows that the crystallographic asymmetric unit contains two distinct isomeric molecules (1a) and (1b). In both isomers a OsW₂ triangle is µ₃-(η²-‖) bridged by the C₂(C₆H₄Me-4)₂ ligand but in (1a) the vector joining the ligated carbon atoms of the alkyne lies essentially parallel to the W–W edge [3.159(2)Å], whereas in (1b) it lies essentially parallel to an Os–W edge [2.981(2)Å]. In both isomers the osmium and tungsten atoms carry three and two CO ligands, respectively, but in (1b) one of these groups is strongly semi-bridging [W–C–O 156(3)°]. The isomers (1a) and (1b) undergo interesting dynamic processes in solution as deduced by variable-temperature ¹H n.m.r. studies. The compounds [W(CR)(CO)₂(η-C₅H₅)] and [Os₃(CO)₁₀(η₂-C₈H₁₄)₂] react slowly in toluene at room temperature to afford the tetranuclear cluster [Os₃W(µ₃-CR)(CO)₁₁(η-C₅H₅)], the structure of which was established by X-ray diffraction. The molecule has an essentially Os₃W tetrahedral core, with an Os₂W face capped by the tolylidyne ligand. Each osmium carries three terminal CO groups and the tungsten atom is bonded to a η-C₅H₅ ligand as well as to two CO groups, one of which is semi-bridging [W–C–O 159(2)°]. The Os–Os edge [2.795(1)Å] of the capped face is marginally longer than the non-bridged Os-Os edges [2.790(1) and 2.791 (1)Å]. In contrast, the Os–W edges [2.874(1) and 2.867(1)Å] of the capped face are shorter than the remaining Os–W separation [2.915(1)Å]. The µ₃-CR ligand is slightly asymmetrically bridging: µ₃-C–Os 2.142(14) and 2.048(15), µ3-C–W 2.138(15)Å.