PROTONATION OF THE ALKYLIDYNETUNGSTEN COMPLEX [W(CC6H4CH2OME-2)(CO)2(ETA-C5H5)]

The complex [W(= CC6H4CH2OMe-2)(CO)2(eta-C5H5)] has been prepared and its protonation with HBF4.Et2O and aqueous Hl investigated. In CH2Cl2 at -78-degrees-C mixtures of the alkylidynetungsten compound and PPh3 on treatment with HBF4.Et2O afford the complex [W(CO)2{eta-4-C6H4(CH2)[CH(PPh3)]1,2}(eta-C5H5)][BF4]2, the structure of which has been established by X-ray crystallography. The C6H4-(CH2)[CH(PPh3)]-1,2 ligand is eta-4-co-ordinated to the tungsten via the carbon atoms of the ortho CH and CH2 substituents of the C6H4 group and their respective ring carbons [W-C 2.30(2) to 2.41(2) angstrom]. The terminal CH fragment carries a PPh3 group P-C [1.81(2) angstrom]. The tungsten atom is also ligated by the C5H5 ring and two CO groups in the usual manner. Treatment of [W(= CC6H4CH2OMe-2)(CO)2(eta-C5H5)] with aqueous Hl affords sequentially the alkylidene complex [W{= C(H)C6H4CH2OMe-2}-l(CO)2(eta-C5H5)] and the acyl compound [Wl2(CO)(eta-2-COCH2C6H4CH2OMe-2)(eta-C5H5)]. Possible pathways to the new compounds are discussed, and their H-1 and C-13-{H-1} NMR spectra are reported.