Carbene adducts of dimethylcadmium

The first examples of carbene-cadmium complexes are reported from the react ions of a variety of imidazol-2-ylidenes or imidazolin-2-ylidenes with dime thylcadmium. Four new carbene complexes are characterized by NMR spectrosco py (H-1, C-13 and Cd-113). The cadmium centers are strongly shifted downfie ld(100 - 150 ppm) by interaction with the carbenes. X-ray structures are re ported for three carbene-cadmium 1:1 adducts. The cadmium centers exhibit d istorted trigonal-planar geometries in which the carbene ligands have an av erage 18.2 pm longer bond distance to cadmium compared to the methyl groups . The planes of cadmium coordination are twisted with respect to the plane of the imidazole ring. The more basic imidazolin-2-ylidene is shown to disp lace imidazol-2-ylidenes from the cadmium center.