Heterobimetallic Complexes Bridged by Imidazol{[4,5-f][1,10]-phenanthrolin}-2-ylidene: Synthesis and Catalytic Activity in Tandem Reactions

###EgeUn###A series of monometallic complexes obtained by metalation of the phenanthrolin donor in 1,3-dibutyl-1H-imidazol[4,5-f][1,10]phenanthrolin}ium hexafluorophospate 1 (M = Pd 2, Ru 3, Ir 4) have been prepared. Subsequently, the imidazolium moiety of complexes 2-4 was metalated with M', leading to the heterobimetallic phenanthroline/NHC complexes (M/M' = Pd/Rh 5, Pd/Ir 6, Pd/Ru 7, Ru/Pd 8, Ir/Pd 9) and the homobimetallic complex (M/M' = Ir/Ir 10). The new complexes were characterized by elemental analysis, FTIR, UV-vis, and NMR spectroscopy. The molecular structures of the heterobimetallic complexes 5 and 6 were determined by X-ray diffraction studies. The catalytic activity of the heterobimetallic complexes 5-9 were tested in selected tandem reactions (dehalogenation/transfer hydrogenation and Suzuki-Miyaura coupling/transfer hydrogenation). It was found that the M/M' heterobimetallic complexes display higher catalytic activities when compared to equimolar mixtures of the mononuclear complexes M and M', thus indicating that an increase in the number of metal atoms in one complex leads to an increased activity in the tandem reactions.Ege UniversityEge University [2012-BIL-042, 2013 FEN 062]; TUBITAKTurkiye Bilimsel ve Teknolojik Arastirma Kurumu (TUBITAK) [111T398]; Dokuz Eylul UniversityDokuz Eylul University [2010.KB.FEN.13]; Deutsche ForschungsgemeinschaftGerman Research Foundation (DFG) [SFB 858, IRTG 2027]Financial support from Ege University (Project 2012-BIL-042; 2013 FEN 062) and TUBITAK (111T398) is gratefully acknowledged. The authors acknowledge Dokuz Eylul University for the use of the Oxford Rigaku Xcalibur Eos Diffractometer (purchased under University Research Grant No 2010.KB.FEN.13). F.E.H. thanks the Deutsche Forschungsgemeinschaft (SFB 858 and IRTG 2027)