Synthesis, Structure, and Bonding Properties of Ruthenium Complexes Possessing a Boron-Based PBP Pincer Ligand and Their Application for Catalytic Hydrogenation

Abstract

In addition to our previous works for PBP-pincer metal complexes, four PBP-pincer Ru complexes, [PBP]Ru(Cl)(CO) (2), [PBP]Ru(CO)(η2-BH4) (3), [PBP](μ-H)2Ru(OAc-κ2O) (4), and [PBP](μ-H)2Ru(η2-BH4) (5) were synthesized. All the obtained complexes were characterized by NMR and IR spectroscopy, X-ray crystallography, elemental analysis, and DFT calculation with AIM analysis. Through the structural analysis, two types of interaction between boron atoms and ruthenium atoms in 3–5 were revealed. One is the typical two-center–two-electron bond between the boron atom of the PBP ligand and the Ru atom, associated with bridging hydride ligand(s) on the Ru(IV) center. The other is an ionic interaction between the Ru fragment and the tetrahydroborate anion. On comparison of the structural features, vibrational analysis, NBO analysis, and AIM analysis of the obtained compounds with those of the previously reported complexes having “similar” interactions among B, H, and Ru atoms, the interactions in 4 and 5 were proven ...