Chemistry of di-and tri-metal complexes with bridging carbene or carbyne ligands. Part 37. Methylene group transfer to carbon–metal multiple bonds; crystal structures of [TiW{µ-C(C6H4Me-4)Ch2}(µ-CO)(CO)(η-C5H5)3] and [PtW{µ-C(C6H4Me-4)CH2}(CO)2(PMe3)2(η-C5H5)]

Abstract

The compounds [W(CR)(CO)₂(η-C₅H₅)](R = C₆H₄Me-4 or Me) and [[graphic omitted]H₂}(η-C₅H₅)₂] react in toluene, in the presence of tetrahydrofuran, to afford the bridged vinyl complexes [TiW{µ-C(R)CH₂}(µ-CO)(CO)(η-C₅H₅)₃]. The compound with R = C₆H₄Me-4 may also be prepared by treating [TiW(µ-CC₆H₄Me-4)(µ-CO)(CO)(µ-C₅H₅)₃] with the titanium reagent. It has been structurally characterised by X-ray diffraction. The Ti–W bond [3.082(2)Å] is spanned by a σ:η²-CO ligand [W–C–O 173.4(3)°, Ti–C 2.222(4), Ti–O– 2.285(3)Å] and by a σ:η²-C(C₆H₄Me)CH₂ group, σ bonded to titanium and η² co-ordinated to tungsten [Ti–C 2.290(4), CC 1.441(6), W–C 2.199(5) and 2.268(6)Å]. The tungsten atom carries a terminally bound CO ligand and a C₅H₅ group, and the titanium atom is ligated by two C₅H₅ groups. Reactions between the dimetal compounds [PtW(µ-CR)(CO)₂(PMe₃)₂(η-C₅H₅)] and [[graphic omitted]H₂}(η-C₅H₅)₂] afford the complexes [PtW{µ-C(R)CH₂}(CO)₂(PMe₃)₂(η-C₅H₅)]. An X-ray diffraction study on the platinum–tungsten species with R = C₆H₄Me-4 established the structure as one in which the Pt–W bond [2.820(1)Å] is bridged by a C(C₆H₄Me-4)CH₂ group, as in the titanium–tungsten compound, being σ bonded to the platinum and η² co-ordinated to the tungsten. The metal–metal bond is semi-bridged by one CO ligand [W–C–O 166(1)°], while the remaining CO is terminally bound to tungsten, which also carries the C₅H₅ group. The platinum is ligated by two PMe₃ ligands, and is in a distorted square-planar environment defined by the two phosphorus atoms, and the µ-C atoms of the semi-bridging carbonyl and the vinyl group. Spectroscopic properties of the new dimetal compounds are reported, and their mechanisms of formation discussed in the light of ¹H and ¹³C-{¹H} n.m.r. studies on reaction mixtures.