Catalytic Homologation of Vinyltributylstannane to Allyltributylstannane by Mo(IV) Complexes in the Presence of Ethylene

Abstract
We have found that CH2CHSnBu3 is converted into CH2CHCH2SnBu3 catalytically in the presence of Mo(IV) olefin complexes such as Mo(NAr)(CH2CH2)[biphen] (where Ar = 2,6-i-Pr2C6H3 and [biphen]2- = 3,3‘-di-tert-butyl-5,5‘,6,6‘-tetramethyl-1,1‘-biphenyl-2,2‘-diolate). The proposed mechanism involves formation of a metalacyclopentane (MC4) complex from ethylene and CH2CHSnBu3, “contraction” of this MC4 complex to a metalacyclobutane (MC3) complex, and finally metathesis of the MC3 complex to give CH2CHCH2SnBu3 and Mo(NAr)(CH2)[biphen]. These new findings suggest (inter alia) that contraction of an MC4 ring to an MC3 ring may be a much more common mode of decomposition of metalacyclopentane rings in d0 complexes than previously believed.