title: The unexpected mechanism underlying the high-valent mono-oxo-rhenium(V) hydride catalyzed hydrosilylation of C=N functionalities: insights from a DFT study.
abstract: In this study, we theoretically investigated the mechanism underlying the high-valent mono-oxo-rhenium(V) hydride Re(O)HCl2(PPh3)2 (1) catalyzed hydrosilylation of C=N functionalities. Our results suggest that an ionic S(N)2-Si outer-sphere pathway involving the heterolytic cleavage of the Si-H bond competes with the hydride pathway involving the C=N bond inserted into the Re-H bond for the rhenium hydride (1) catalyzed hydrosilylation of the less steric C=N functionalities (phenylmethanimine, PhCH=NH, and N-phenylbenzylideneimine, PhCH=NPh). The rate-determining free-energy barriers for the ionic outer-sphere pathway are calculated to be ∼28.1 and 27.6 kcal mol(-1), respectively. These values are slightly more favorable than those obtained for the hydride pathway (by ∼1-3 kcal mol(-1)), whereas for the large steric C=N functionality of N,1,1-tri(phenyl)methanimine (PhCPh=NPh), the ionic outer-sphere pathway (33.1 kcal mol(-1)) is more favorable than the hydride pathway by as much as 11.5 kcal mol(-1). Along the ionic outer-sphere pathway, neither the multiply bonded oxo ligand nor the inherent hydride moiety participate in the activation of the Si-H bond.
authors.affiliation: Jiangsu Collaborative Innovation Center of Biomedical Functional Materials, Jiangsu Provincial Key Laboratory for NSLSCS, Nanjing Normal University, Nanjing 210097 (China).
authors.forename: Jiandi
authors.initials: J
authors.lastname: Wang
authors.forename: Wenmin
authors.initials: W
authors.lastname: Wang
authors.forename: Liangfang
authors.initials: L
authors.lastname: Huang
authors.forename: Xiaodi
authors.initials: X
authors.lastname: Yang
authors.forename: Haiyan
authors.initials: H
authors.lastname: Wei
mesh_terms: D002384:Catalysis; D006859:Hydrogen / Q000737:chemistry; D007097:Imines / Q000737:chemistry; D008024:Ligands; D008958:Models, Molecular; D017601:Oxygen Compounds / Q000737:chemistry; D011789:Quantum Theory; D012211:Rhenium / Q000737:chemistry*; D012821:Silanes / Q000737:chemistry*; D013816:Thermodynamics
chemical_list: D007097:Imines; D008024:Ligands; D017601:Oxygen Compounds; D012821:Silanes; D012211:Rhenium; D006859:Hydrogen
keywords: catalysis; density functional theory; hydrosilylation; mechanism; rhenium