Protonation of the alkylidynetungsten complex [W(CC6H4CH2OMe-2)(CO)2(η-C5H5)]

Abstract

The complex [W(CC₆H₄CH₂OMe-2)(CO)₂(η-C₅H₅)] has been prepared and its protonation with HBF₄·Et₂O and aqueous HI investigated. In CH₂Cl₂ at –78 °C mixtures of the alkylidynetungsten compound and PPh₃ on treatment with HBF₄·Et₂O afford the complex [W(CO)₂{η⁴-C₆H₄(CH₂)[CH(PPh₃)]-1,2}(η-C₅H₅)][BF₄]₂, the structure of which has been established by X-ray crystallography. The C₆H₄(CH₂)[CH(PPh₃)]-1,2 ligand is η⁴-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)Å]. The terminal CH fragment carries a PPh₃ group P–C [1.81 (2)Å]. The tungesten atom is also ligated by the C₅H₅ ring and two CO groups in the usual manner. Treatment of [W(CC₆H₄CH₂OMe-2)(CO)₂(η-C₅H₅)] with aqueous HI affords sequentially the alkylidene complex [W{C(H)C₆H₄CH₂OMe-2}I(CO)₂(η-C₅H₅)] and the acyl compound [WI₂(CO)(η²-COCH₂C₆H₄CH₂OMe-2)(η-C₅H₅)]. Possible pathways to the new compounds are discussed, and their ¹H and ¹³C-{¹H} NMR spectra are reported.