E versus Z isomers of Fischer aminocarbene complex [Mo(CO)(4)(PPh3){C(NHCy)(2-furyl)}]: N-H center dot center dot center dot O versus C-H center dot center dot center dot O intramolecular hydrogen bonds

摘要

A density functional theory (DFT) calculated conformation analysis of the twelve possible conformations of [Mo(CO)(4)(PPh3){C(NHCy)(2-furyl)}], 1, utilizing different DFT methods, showed that both the cis-syn,Z (2), 1-Z, and the cis-syn,Z (2), 1-E, conformations of this aminocarbene complex have similar electronic and Gibbs free energies. The solid-state crystal structure of the 1-Z is presented in this study and compared to the structure of the 1-E conformation. The stability of 1-Z, versus the previously published solid-state structure of conformer 1-E, is ascribed to stabilization of the N-H center dot center dot center dot O-Fu intramolecular bond. This is evidenced by a shorter H center dot center dot center dot O intramolecular bond in the experimental crystal structure of 1-Z. The stability of the 1-Z and 1-E conformations were analyzed and compared by density functional theory, quantum theory of atoms in molecules (QTAIM) and natural bond orbital (NBO) methods. The NBO analysis reveals similar but stronger donor-acceptor interactions in 1-Z than in 1-E. QTAIM calculations indicate 6 and 5 bond critical points related to intramolecular bonds stabilizing the orientation of 2-furyl and NHCy in 1-Z and 1-E respectively. (C) 2015 Elsevier B.V. All rights reserved.