Heterobimetallic complexes containing an N-heterocyclic carbene based multidentate ligand and catalyzed tandem click/Sonogashira reactions

Mono- and polynuclear complexes containing 3-(1,10-phenanthrolin-2-yl)-1-(pyridin-2-ylmethyl)-imidazolylidene (L), [NiL2](PF6)(2) (2), [CoL2](PF6)(3) (3), [PtLCl](PF6) (4), [PdAgL2](PF6)(3) (5), [PdCuL2](PF6)(3) (6), [Pd2L2Cl2](PF6)(2) (7), and [Pd3L2Cl4](PF6)(2) (8)have been prepared and fully characterized by NMR, ESI-MS spectroscopy, and X-ray crystallography. In complexes 2-4, the ligand binds to metals in a pincer NNC fashion with the pyridine group uncoordinated. Complexes 5 and 6 are isostructural to each other in which the palladium ions are surrounded by two pyridines and two imidazolylidenes and Ag(I)or Cu(I)is coordinated by two 1,10-phenanthroline moieties. In the trinuclear palladium complex 8, one palladium ion has an identical coordination mode as in 5 and 6, and the other two palladium ions are bonded to the 1,10-phenanthroline. Complex 6 exhibits excellent catalytic activity for the tandem click/Sonogashira reaction of 1-(bromomethyl)-4-iodobenzene, NaN3, and ethynylbenzene in which three C-N bonds and one C-C bond are formed in a single flask.