Reactivity studies of pincer bis-protic N-heterocyclic carbene complexes of platinum and palladium under basic conditions.

David C Marelius,Douglas B Grotjahn,Curtis E Moore,Arnold L Rheingold

doi:10.3762/bjoc.12.126

Abstract

Bis-protic N-heterocyclic carbene complexes of platinum and palladium (4) yield dimeric structures 6 when treated with sodium tert-butoxide in CH2Cl2. The use of a more polar solvent (THF) and a strong base (LiN(iPr)2) gave the lithium chloride adducts monobasic complex 7 or analogous dibasic complex 8.

Highlights

N-Heterocyclic carbenes (NHCs) have been extensively researched for a number of purposes since 1991 when Arduengo first isolated free NHCs [1,2,3]
50 years of NHC ligand research have demonstrated the importance of the electronic and steric effects that can be modified by altering the alkyl or aryl groups on each nitrogen atom
With only a few papers exploring the utility of these imidazol2-yl complexes, we aim to extend this to our recently reported pincer bis PNHC complexes 4-PdCl and 4-PtCl and their triflato analogs [14]

Summary

Introduction

N-Heterocyclic carbenes (NHCs) have been extensively researched for a number of purposes since 1991 when Arduengo first isolated free NHCs [1,2,3]. NHCs as ligands have been known even longer. In 1968, Wanzlick and Öfele separately synthesized mercury(II) and chromium(0) imidazol-2ylidene complexes [3]. 50 years of NHC ligand research have demonstrated the importance of the electronic and steric effects that can be modified by altering the alkyl or aryl groups on each nitrogen atom. Less common are protic imidazol-2ylidene (PNHC) ligands with a hydrogen atom on one or both of the stabilizing nitrogens. The synthesis of PNHC complexes has proven to be a challenge, which has limited studies of their reactivity [4,5,6,7,8]

Objectives

Results

Conclusion