PROTONATION OF THE ALKYLIDYNETUNGSTEN COMPLEXES [W(CR)(CO)2(ETA-C5H5)] (R = C6H4ME-2, C6H3ME2-2,6 OR C6H4OME-2)

The complexes [W(= CR)(CO)2(eta-C5H5)] (R = C6H4Me-2 or C6H3Me2-2,6) react with 2 equivalents of CF3CO2H in CH2Cl2 to afford [W(O2CCF3)2(CO)(eta-2-COCH2R)(eta-C5H5)], and with 2 equivalents of HBF4.Et2O in NCMe to give the salts [W(CO)(NCMe)2(eta-2-COCH2R)(eta-C5H5)][BF4]2. Treatment of [W(= CC6H4OMe-2)(CO)2(eta-C5H5)] with ca. 0.5 equivalent of HBF4.Et2O in CH2Cl2 at ca. -78-degrees-C gives the salt [W{= C(H)C6H4OMe-2}(CO)2(eta-C5H5)][BF4]. However, if the reaction of [W(= CC6H4OMe-2)(CO)2(eta-C5H5)] with 1 equivalent of HBF4.Et2O is carried out in the presence of PPh3 or Ph2PCH2PPh2 the complexes [W{sigma,eta-2-CH(PPh3)C6H4OMe-2}(CO)2(eta-C5H5)][BF4] and [W{CH(C6H4OMe-2)PPh2CH2PPh2}(CO)2(eta-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-degrees), and by a CH(PPh3)C6H4OMe-2 fragment. The latter is attached to the metal in a sigma,eta-2-bonding mode via a W-CH(PPh3) linkage [2.16(3) angstrom] and connectivities to two carbon atoms of the C6H4OMe-2 ring [W-C1 2.31(3) and W-C6 2.65(4) angstrom].