Pd and Ni complexes of a novel vinylidene β‐diketimine ligand: Their application as catalysts in Heck coupling and alkyne trimerization

Abstract

A β‐diketimine ligand with vinylidene substitution at γ‐carbon, CH2C(CH3CNAr)2 (Ar = 2,6‐diisopropylphenyl) (L2), was synthesized by treating β‐diketimine H2C(CH3CNAr)2 with n‐BuLi followed by paraformaldehyde. L2 formed the homobimetallic ether‐bridged β‐diketiminate complex [O{(CH2‐β‐diketiminate)Pd(OAc)}2] (1) with (PdOAc)2. It also gave complexes [L2PdCl2] (2) and [L2NiBr2] (3) when treated with PdCl2(CH3CN)2 and NiBr2(dimethoxyethane), respectively. All the compounds were characterized using 1H/13C NMR spectroscopy and single‐crystal X‐ray diffraction studies. The catalytic activity of Pd and Ni complexes 1, 2 and 3 was explored in Heck coupling and alkyne trimerization reactions and it was found that they are very good catalysts. The results are reported in detail.