Chemistry of di- and tri-metal complexes with bridging carbene or carbyne ligands. Part 29. Synthesis of rhenium–tungsten compounds; X-ray crystal structures of [ReW2(µ-Br)(µ-L)(µ-CC6H4Me-4)(µ3-CC6H4Me-4)(CO)3(η-C5H5)2](L = CO or O)

Abstract

The compound [W(CR)(CO)₂(η-C₅H₅)](R = C₆H₄Me-4) reacts with the rhenium compounds [Re₂(CO)₁₀], [Re₂(µ-Br)₂(thf)₂(CO)₆](thf = tetrahydrofuran), and [ReBr(NCMe)₂(CO)₃] to afford, respectively, the cluster complexes [Re₂W(µ₃-CR)(CO)₁₀(η-C₅H₅)], [Re₂W(µ-Br)₂(µ₃-CR)-(CO)₇(η-C₅H₅)], and [ReW₂(µ-Br)(µ-CR)(µ₃-CR)(µ-CO)(CO)₃(η-C₅H₅)₂]. The latter compound has been structurally characterised by an X-ray diffraction study. A ReW₂ triangle of metal atoms [W–W 2.620(1), Re–W 2.867(1) and 2.912(1)Å] is asymmetrically capped by a CC₆H₄Me-4 ligand [µ₃-C–Re 2.248(12), µ₃-C–W 2.035(14) and 2.050(11)Å], and is edge-bridged by CC₆H₄Me-4, Br, and CO groups, with the latter being asymmetrically bound [W–C–O 155(1)°].The two tungsten atoms carry cyclopentadienyl ligands, and the rhenium atom three terminally bound CO groups. The compound [ReW₂(µ-Br)(µ-CR)(µ₃-CR)(µ-CO)(CO)₃(η-C₅H₅)₂] readily oxidises in air to afford the oxo-bridged species [ReW₂(µ-Br)(µ-O)(µ-CR)(µ₃-CR)(CO)₃(η-C₅H₅)₂] which was also characterised by X-ray diffraction. This complex is structurally similar to its precursor but with the significant differences of the µ-CO ligand being replaced by µO and the capping CC₆H₄Me-4 being very asymmetrically bound to the metal triangle [µ₃-C–Re 2.515(20), µ₃-C–W 2.017(19) and 2.114(18)Å]. In addition to reacting with oxygen, the compound [ReW₂(µ-Br)(µ-CR)(µ₃-CR)(µ-CO)(CO)₃(η-C₅H₅)₂] reacts with sulphur. The nature of the product is described, and the n.m.r. spectra (¹H and ¹³C-{¹H}) of all the new compounds are reported and discussed in relation to their established or proposed structures.