Reactivity and mechanism in reactions of methylene halides with cycloneophylplatinum(II) complexes: Oxidative addition and methylene insertion

Abstract

ABSTRACT The reactions of methylene halides, CH2X2, with cycloneophylplatinum(II) complexes [Pt(CH2CMe2C6H4)(NN)], NN = 4,4’-di-t-butyl-2,2’-bipyridine or 3,4,7,8-tetramethyl-1,10-phenanthroline, gave either the product of cis oxidative addition [PtX(CH2X)(CH2CMe2C6H4)(NN)] or of cis oxidation with methylene insertion [PtX2(CH2CMe2C6H4CH2)(NN)]. By monitoring the reactions by NMR spectroscopy, it was shown that the major route to the methylene insertion product was by rearrangement of the initial product of oxidative addition. When X = I and NN = 4,4’-di-t-butyl-2,2’-bipyridine, the products of trans oxidative addition and methylene insertion were also detected in solution at intermediate stages of reaction. The methylene insertion step was strongly retarded in the presence of free halide, indicating that reaction occurred by way of a cationic intermediate formed by halide dissociation from [PtX(CH2X)(CH2CMe2C6H4)(NN)]. The chemistry gives useful insight into the possible mechanisms operating in catalytic chemistry involving methylene halides as methylene insertion reagents.