Synthesis of Pd phosphine-imine complexes and their reactivity with base

Abstract

Two phosphine-imine ligands were synthesized in which the heteroatoms were connected by an ethyl (1a) or a propyl (1b) linker. Both ligands were reacted with PdCl(Me)(COD), which gave the square planar complexes PdCl(Me)(κ2-P,N-1a) (2a) and PdCl(Me)(κ2-P,N-1b) (2b). Both complexes were treated with base in pyridine in an effort to prepare phosphine 1-azaallyl complexes of the type Pd(Me)(κ2-P,N-L)(py). Deprotonation of 2a gave an intractable mixture of products. In contrast, deprotonation of 2b afforded a new product 4b. However, the site of deprotonation was the methylene adjacent to the phosphine rather than Cα to the imine carbon, deprotonation of which would have afforded a 1-azaallyl moiety.