Fluxional Pd(II) NHC complexes – Synthesis, structure elucidation and catalytic studies

Abstract

Four catalytically relevant Pd(II) complexes involving N-heterocyclic carbenes (NHCs) and bidentate N- and P-donor ligands were synthesized and characterized. The structures and conformations of the complexes were elucidated on the basis of combination of dynamic NMR and DFT studies. Conformational studies in respect to hindered rotation around C-Ndonor and Pd-CNHC bonds were performed resulting in surprisingly good agreement between the calculated and the experimental results. The results from dynamic NMR and DFT studies confirm hindered rotation around the C-N bond in 1,3-disubstituted imidazole complexes. The fluxional behavior of P-donor ligands includes exchange between left-handed and right-handed phosphine propellers. The catalytic studies of 1,3-disubstituted 4,5-fused imidazole complexes produced excellent activities in Suzuki–Miyaura Reaction.