Synthesis, characterisation and reactivity of group six alkylidynes bearing the tridentate phosphine PPh(C2H4PPh2)2-'triphos'. Crystal structure of mer-[W(NCMe)(≡CC6H4Me-4){PPh(C2H4PPh2)2}(CO)][BF4]

Article abstract of DOI:10.1016/S0022-328X(97)00412-9

Reaction between [WBr(≡CC₆H₄Me-4)(NC₅H₅Me-4)₂(CO)₂] and the tridentate, linear, phosphine PPh(CH₂CH₂PPh₂)₂ (triphos) in refluxing toluene affords mer-[WBr(≡CC₆H₄Me-4){PPh(C₂H₄PPh₂)₂}(CO)], 1. Halide abstraction (with TIBF₄) in CH₂Cl₂ solvent results in carbonyl scavenging to afford the cationic dicarbonyl species fac-[WBr(≡CC₆H₄Me-4){PPh(C₂H₄PPh₂)₂}(CO)₂][BF₄], 2, whereas removal of the halide in acetonitrile solvent affords the complex mer-[W(NCMe)(≡CC₆H₄Me-4){PPh(C₂H₄PPh₂)₂}(CO)][BF₄], 3. Protonation of 1 (with HBF₄ · OEt₂) results in the formation of the alkylidene complex mer-[WBr{=C(H)C₆H₄Me-4}{PPh(C₂H₄PPh₂)₂}(CO)][BF₄], 4. Methylation of 1 affords the methyl/alkylidyne complex mer-[WCH₃(≡CC₆H₄Me-4){PPh(C₂H₄PPh₂)₂}(CO)], 5, which can be protonated to form [WCH₃{=C(H)C₆H₄Me-4}{PPh(C₂H₄PPh₂)₂}(CO)][BF₄], 6. The new complexes have been fully characterised by multinuclear NMR spectroscopy and, additionally, for 3 by a single crystal X-ray diffraction study.