SYNTHESIS, CHARACTERIZATION AND REACTIVITY OF GROUP-6 ALKYLIDYNES BEARING THE TRIDENTATE PHOSPHINE PPH(C2H4PPH2)(2) TRIPHOS - CRYSTAL-STRUCTURE OF ER-[W(NCME)(CC6H4ME-4)(PPH(C2H4PPH2)(2))(CO)][BF4]

Reaction between [WBr(=CC6H4Me-4)(NC5H5Me-4)(2)(CO)(2)] and the triden tate, linear, phosphine PPh(CH2CH2PPh2)(2) (triphos) in refluxing tolu ene affords mer-[WBr(=CC6H4Me-4){PPh(C2H4PPh2)(2)}(CO)] 1. Halide abst raction (with TIBF4) in CH2Cl2 solvent results in carbonyl scavenging to afford the cationic dicarbonyl species -[WBr(=CC6H4Me-4){PPh(C2H4PP h2)(2)}(CO)(2)][BF4],2 whereas removal of the halide in acetonitrile s olvent affords the complex r-[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(C-2 H4PPh2)(2)}( CO)][BF4] 4. Methylation of 1 affords the methyl/alkylidyne complex me r-[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 c omplexes have been fully characterised by multinuclear NMR spectroscop y and, additionally, for 3 by a single crystal X-ray diffraction study . (C) 1997 Elsevier Science S.A.