Preparation and structure elucidation of novel organoruthenium amidinates bearing η4-diene ligands

A series of novel ruthenium amidinate complexes bearing η4-cyclooctadiene (COD) or η4-norbornadiene (NBD) ligand was prepared, and their structures were elucidated by spectroscopy and crystallography. A disilver amidinate, Ag2{μ2,η-PhNC(H)NPh}2, was treated with either (η4-COD)Ru(MeCN)2Cl2 or (η4-NBD)Ru(pyridine)2Cl2 to form the corresponding bisamidinate complex, (η4-COD)Ru{η2-PhNC(H)NPh}2 (5a) or (η4-NBD)Ru{η2-PhNC(H)NPh}2 (5a′), respectively, in moderate to good yield. Alternatively, (η4-COD)Ru{η2-iPrNC(Me)NiPr}2 (5b) or (η4-NBD)Ru{η2-iPrNC(Me)NiPr}2 (5b′) was synthesized by reaction of [(η4-COD)RuCl2]n or (η4-NBD)Ru(pyridine)2Cl2 with Li{iPrNC(Me)NiPr}. Careful treatment of (η4-NBD)Ru(pyridine)2Cl2 with one equivalent of Li{iPrNC(Me)NiPr} resulted in the formation of a monoamidinate complex, (η4-NBD)Ru{η2-iPrNC(Me)NiPr}(pyridine)Br (6) as a good precursor for a mixed amidinate complex, (η4-NBD)Ru{η2-iPrNC(Me)NiPr}{η2-PhNC(H)NPh} (5c′), which was obtained by the reaction of 6 with Ag2{μ2,η-PhNC(H)NPh}2. Crystal structures of these complexes revealed the octahedral arrangement of the ligands.