Synthesis and Catalytic Properties of Rhodium(I) and Copper(I) Complexes Bearing Dipyrido-Annulated <i>N</i>-Heterocyclic Carbene Ligands

Starting from the in situ generated free carbenes dipyrido[1,2-c;2′,1′-e]imidazolin-6-ylidene (dipiy) and 2,10-di-tert-butyldipyrido[1,2-c;2′,1′-e]imidazolin-6-ylidene (dipiytBu), the synthesis of the new carbene complexes [RhCl(COD)(dipiy)] and [RhCl(COD)(dipiytBu)] can be achieved. Upon chloride abstraction and coordination of phosphine, a very active precursor for the catalytic hydrosilylation of ketones is formed. The reaction was also followed by NMR spectroscopy. In addition the respective CuI(dipiytBu) complex was synthesized and fully characterized. X-ray structure analysis reveals this compound to be a trimer [CuI(dipiytBu)]3 with two Cu−Cu bonds in the solid state. However, unlike the imidazolinylidene analogues, this complex and in situ prepared CuX(dipiy) complexes (X = I, Cl) were found to be inactive in the hydrosilylation of ketones.