Reactions of co-ordinated ligands. Part 44. The reactivity of the carbyne complex [Mo(CCH2But){P(OMe)3}2(η-C5H5)] towards protonic acids, diphenylphosphine, and the π-acid tetracyanoethylene; formation and crystal structures of [MoH(CCH2But){P(OMe)3}2(η-C5H5)][BF4], [Mo{σ-OC(O)CF3}{η2-HOC(O)CF3}{P(OMe)3}2(η-C5H5)], and [Mo(CCH2But){η2-C2(CN)4}{P(OMe)3}{η-C5H5)]

Abstract

Reaction of [Mo(CCH₂Bu^t){P(OMe)₃}₂(η-C₅H₅)] with HBF₄·(MeCO)₂O affords the crystallographically identified hydrido–carbyne [MoH(CCH₂Bu^t){P(OMe)₃)₂(η-C₅H₅)][BF₄][Mo–H, 1.74(3)Å]. In contrast, reaction with CF₃CO₂H or CF₃SO₃H leads to loss of the carbyne fragment and the formation of [Mo{σ-OC(O)CF₃){η²-HOC(O)CF₃}{P(OMe)₃}₂(η-C₅H₅)] and [Mo(σ-OSO₂CF₃)(η²-HOSO₂CF₃){P(OMe)₃}₂(η-C₅H₅)], the former being structurally identified by X-ray crystallography. The reaction of [Mo(CCH₂Bu^t){P(OMe)₃}₂(η-C₅H₅)] with Ph₂PH and tetracyanoethylene was also examined. The phosphine reaction also leads to loss of the CCH₂Bu^t group, with formation of [Mo(PPh₂)(HPPh₂){P(OMe)₃}(η-C₅H₅)] and [Mo(PPh₂){P(OMe)₃}₂(η-C₅H₅)]. Both of these complexes are also formed on reaction of Ph₂PH with [Mo(η³-1 -MeC₃H₄){P(OMe)₃}₂(η-C₅H₅)]. Tetracyanoethylene reacts at room temperature with the carbyne to displace one of the trimethyl phosphite ligands with formation of the X-ray crystallographically characterised alkene-carbyne complex [Mo(CCH₂Bu^t){η²-C₂(CN)₄}{P(OMe)₃}(η-C₅H₅)]. The carbon-carbon bond of the co-ordinated tetracyanoethylene is orthogonal to the MOC vector.