Synthesis, characterisation and reactivity of group six alkylidynes bearing the tridentate phosphine PPh(C 2H 4PPh 2) 2-‘triphos’. Crystal structure of mer-[W(NCMe)(≡CC 6H 4Me-4)PPh(C 2H 4PPh 2) 2(CO)][BF 4

Abstract

Reaction between [WBr(≡CC 6H 4Me-4)(NC 5H 5Me-4) 2(CO) 2] and the tridentate, linear, phosphine PPh(CH 2CH 2PPh 2) 2 (triphos) in refluxing toluene affords mer-[WBr(≡CC 6H 4Me-4)PPh(C 2H 4PPh 2) 2(CO)], 1. Halide abstraction (with TlBF 4) in CH 2Cl 2 solvent results in carbonyl scavenging to afford the cationic dicarbonyl species fac-[WBr(≡CC 6H 4Me-4)PPh(C 2H 4PPh 2) 2(CO) 2][BF 4], 2, whereas removal of the halide in acetonitrile solvent affords the complex mer-[W(NCMe)(≡CC 6H 4Me-4)PPh(C 2H 4PPh 2) 2(CO)][BF 4], 3. Protonation of 1 (with HBF 4 · OEt 2) results in the formation of the alkylidene complex mer-[WBr≡C(H)C 6H 4Me-4PPh(C 2H 4PPh 2) 2(CO)][BF 4], 4. Methylation of 1 affords the methyl/alkylidyne complex mer-[WCH 3(≡CC 6H 4Me-4)PPh(C 2H 4PPh 2) 2(CO)], 5, which can be protonated to form [WCH 3=C(H)C 6H 4Me-4PPh(C 2H 4PPh 2) 2(CO)][BF 4], 6. The new complexes have been fully characterised by multinuclear NMR spectroscopy and, additionally, for 3 by a single crystal X-ray diffraction study.