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].