Reactivity of the Carbyne Complexes [W2(μ-COR)(η5-C5H5)2(CO)2(μ-Ph2PCH2PPh2)]+(R = H, Me) toward Diazomethane

Abstract

Reaction of [W2(μ-COH)Cp2(CO)2(μ-dppm)]BF4 (Cp = η5-C5H5; dppm = Ph2PCH2PPh2) with CH2N2 in the presence of CuCl at −75 °C leads to the methoxycarbyne cluster [CuW2Cl(μ3-COMe)Cp2(CO)2(μ-dppm)]BF4. Copper(I) chloride can be cleanly removed from the latter upon addition of PPh3, thus giving the methoxycarbyne complex [W2(μ-COMe)Cp2(CO)2(μ-dppm)]BF4. In the absence of CuCl, either the hydroxy or the methoxycarbyne ditungsten cations react with CH2N2 to give a mixture of the μ-methylene, μ-alkenyl compound [W2(μ-CH2){μ-η1:η2-C(OMe)CH2}Cp2(CO)2(μ-dppm)]BF4, which has been characterized through an X-ray study, and the μ-alkyne, μ-alkenyl species [W2{μ-η1:η2-C(OMe)CH}{μ-η1:η2-C(OMe)CH2}Cp2(CO)(μ-dppm)]BF4, the latter being the result of the addition of four molecules of CH2N2 to the starting hydroxycarbyne compound. The influence of experimental conditions on the above reactions has been analyzed through separate experiments. For example, the use of tetrahydrofuran as solvent almost suppresses the formation of t...