Unusual Reactivity of the Unsaturated Dimolybdenum Complex [Mo₂(η⁵-C₅H₅)₂{μ-OP(OEt)₂}{μ-P(OEt)₂}(CO)₂]

Abstract

Reaction of the doubly metal−metal bonded compound [Mo2Cp2{μ-OP(OEt)2}{μ-P(OEt)2}(CO)2] with [Fe2(CO)9] leads to the 46 e- cluster [FeMo2Cp2{μ-OP(OEt)2}{μ-P(OEt)2}(CO)5]. By contrast, reaction of [Mo2Cp2{μ-OP(OEt)2}{μ-P(OEt)2}(CO)2] with SnCl2 leads to the incorporation of two molecules of reagent: one molecule inserts into the Mo−O bond, and the other one adds to the MoMo double bond to finally yield the tetranuclear compound [Mo2Cp2{μ-(EtO)2POSnCl2}{μ-P(OEt)2}(μ-SnCl2)(CO)2] as confirmed by an X-ray diffraction study. Complex [Mo2Cp2{μ-OP(OEt)2}{μ-P(OEt)2}(CO)2] reacts with HCC(p-C6H4Me) to give a mixture of the alkyne-bridged compound [Mo2Cp2{μ-η2:η2-HCC(p-C6H4Me)}{μ-(EtO)2POP(OEt)2}(CO)2] and the alkenyl-bridged [Mo2Cp2{μ-η1,κ1:η2-OP(OEt)2CHC(p-C6H4Me)}{μ-P(OEt)2}(CO)2] (structure confirmed through an X-ray diffraction study). This requires either P−O reductive elimination between phosphonate and phosphido ligands or insertion of the incoming alkyne into the Mo−P (phosphonate) bond, all these uncommon processes occurring at room temperature. The solution structure of the new compounds is analyzed on the basis of their IR and NMR data and X-ray diffraction studies, and the reaction pathways prevalent for the title compound are discussed on the basis of the data available.