Protonation of the alkylidynetungsten complexes [W(CR)(CO)2(η-C5H5)](R = C6H4Me-2, C6H3Me2-2,6 or C6H4OMe-2)

Abstract

The complexes [W(CR)(CO)₂(η-C₅H₅)](R = C₆H₄Me-2 or C₆H₃Me₂-2,6) react with 2 equivalents of CF₃CO₂H in CH₂Cl₂ to afford [W(O₂CCF₃)₂(CO)(η²-COCH₂R)(η-C₅H₅)], and with 2 equivalents of HBF₄·Et₂O in NCMe to give the salts [W(CO)(NCMe)₂(η²-COCH₂R)(η-C₅H₅)][BF₄]₂. Treatment of [W(CC₆H₄OMe-2)(CO)₂(η-C₅H₅)] with ca. 0.5 equivalent of HBF₄·Et₂O in CH₂Cl₂ at ca. –78 °C gives the salt [W{C(H)C₆H₄OMe-2}(CO)₂(η-C₅H₅)][BF₄]. However, if the reaction of [W(CC₆H₄OMe-2)(CO)₂(η-C₅H₅)] with 1 equivalent of HBF₄·Et₂O is carried out in the presence of PPh₃ or Ph₂PCH₂PPh₂ the complexes [W{σ,η²-CH(PPh₃)C₆H₄OMe-2}(CO)₂(η-C₅H₅)][BF₄] and [[graphic omitted]Ph₂}(CO)₂(η-C₅H₅)][BF₄], respectively, are obtained. The structure of the former has been established by X-ray diffraction. In the cation the tungsten atom is ligated by the cyclopentadienyl group, two CO molecules (W–C–O average 176°), and by a CH(PPh₃)C₆H₄OMe-2 fragment. The latter is attached to the metal in a σ,η²-bonding mode via a W–CH(PPh₃) linkage [2.16(3)Å] and connectivities to two carbon atoms of the C₆H₄OMe-2 ring [W–C¹ 2.31(3) and W–C⁶ 2.65(4)Å].