Triadic coupling between hydride, acetylide and alkyne on the complex WRe(eta-C5Me5)O(CO)(4)(mu-H)(CCPh). Crystal structures of complexes containing a substituted cyclopentadienylidene ligand or a folded metallacyclopentadienyl fragment

摘要

[[abstract]]The reaction of the dinuclear oxoacetylide complex [WRe(eta-C5Me5)O(CO)(4)(mu-H)(mu-CCPh)] 1 with dimethyl acetylenedicarboxylate afforded the bis(alkylidene) complex [WRe(eta-C5Me5)O(CO)(3)(mu-CHPh){mu-C-5(CO2Me)(4)}] 2, generated by formal co-ordination of two alkynes and cleavage of a C-C bond. In contrast, treatment of 1 with an excess of di-p-tolylacetylene in refluxing toluene gave three complexes [WRe(eta-C5Me5)O(CO)(3){CH(Ph)CC(C6H4Me-p) CH(mu-eta(2)-C6H3Me)}] 3, [WRe(eta-C5Me5)O(CO)(3){mu-C4Ph[C2H(C6H4Me-p)(2)](C6H4Me-p)(2)}] 4 and [WRe(eta-C5Me5)O(CO)(3){mu-C-4[C2H(C6H4Me-p)(2)]Ph(C6H4Me-p)(2)}] 5. Compounds 4 and 5, which possess a folded metallacyclopentadienyl fragment, are produced by hydride migration to alkyne, giving a cis-ditolylalkenyl substituent, followed by coupling with acetylide and a second ditolylacetylene molecule. Compound 3 is probably produced by a distinct sequence, involving initial formation of a C(C6H4Me-p)C(C6H4Me-p)CCHPh linkage, followed by orthometallation and hydrogen transfer. Single-crystal structural analyses of 2-5 have been performed and the possible reaction mechanisms leading to their isolation are presented.