Polynuclear Enantiopure Salen-Mesoionic Carbene Hybrid Complexes

Salen ligands and mesoionic carbene (MIC) ligands constitute important ligand classes in homogeneous catalysis. In this article we describe the first integration of a salen moiety and MIC donors in the same catalyst entity. Homo- and heterometallic polynuclear metal complexes could be selectively prepared by first installing a metal center (Ni(II), Pd(II)) in the N2O2 salen sphere followed by metalation of the mesoionic carbenes (Ag(I), Pd(II)). The silver complexes could be used for transmetalations to form Au(III) complexes. Several complexes showed catalytic activity in the 1,4-addition of an oxindole to a nitroolefin.