Bimetallic Co-M (M = Cu, Ag, and Au) Carbonyl Complexes Supported by N-Heterocyclic Carbene Ligands: Synthesis, Structures, Computational Investigation, and Catalysis for Ammonia Borane Dehydrogenation

The reaction of Na[Co(CO)(4)] with M(IPr)CI (M = Cu, Ag, and Au; IPr C3N2H2((C6H3Pr2)-Pr-i)(2)) affords the neutral heterometallic complexes [Co(CO)(4){M-(IPr)}] (M = Cu, 1; Ag, 2; and Au, 3). Formation of 2 is accompanied by traces of [Ag(IPr)(2)] [Ag{Co(CO)(4)}(2)] (4). The reaction of Na[Co(CO)(4)] with M(IMes)CI (IMes = C3N2H2(C6H2Me3)(2)) results in mixtures of [Co(CO)(4){M(IMes)}] (M = Cu, 5; Ag, 6; and Au, 7) and [M(IMes)(2)] [M{Co(CO)(4)}(2)] (M = Cu, 8; Ag, 9; and Au, 10). In the cases of Cu and Ag, ionic complexes 8 and 9 are the major products, whereas neutral species 7 is the major product for Au. All species 1-10 have been spectroscopically characterized by IR and H-1 and C-13{H-1} NMR spectroscopy. Moreover, the molecular structures of 2, 3, and 8 have been determined by single-crystal X-ray diffraction (SC-XRD). Bimetallic Co-M-NHC complexes 1-3 and 7-9 have been tested as catalysts for the dehydrogenation of ammonia-borane (AB) in THE as solvent, and their performances compared to [Fe(CO)(4){M(NHC)}(2)], M(NHC)Cl, and Na[Co(CO)(4)]. DFT computations have been performed to provide information on the structure, IR spectroscopy, and the thermodynamics of Co-M carbonyl clusters.

Automated summary

This study focuses on the reaction of Na[Co(CO)(4)] with different ligands M(IPr) and M(IMes) in the presence of Cu, Ag, and Au metals, resulting in the formation of various neutral and ionic heterometallic complexes. The synthesized products were characterized using spectroscopic techniques, and the molecular structures of some complexes were determined by X-ray diffraction. The catalytic performances of these bimetallic complexes were evaluated for the dehydrogenation of ammonia-borane and compared with other compounds. Additionally, DFT calculations were performed to provide information on the structure, IR spectroscopy, and thermodynamics of Co-M carbonyl clusters.