Kinetic and Thermodynamic Control of Nitrile Dissociation in the Complexes (R_Fe,R_C)/(S_Fe,R_C)-[CpFe(Prophos)NCR]X (X = I, PF₆) by the Inductive Effect

Abstract

The chiral-at-metal complexes (R Fe ,R C )/(S Fe ,R C )-[CpFe(Prophos)-NCR]X (X = I, PF 6 ; R = Et, Ph, p-substituted Ph) were prepared, and the diastereomers were separated by fractional crystallization. Eight diastereomerically pure complexes (S Fe ,R C )-[CpFe(Prophos)NCR]X could be characterized by X-ray crystallography. The kinetics of epimerization with respect to the labile Feconfiguration in CDCl 3 at ambient temperatures was measured for the EtCN, PhCN, and (p-C 6 H 4 NMe 2 ) complexes. The half-lives of 162 and 760 min of the first-order reactions of (S Fe ,R C )-[CpFe(Prophos)NCPh]PF 6 and (S Fe ,R C )-[CpFe-(Prophos)NC(p-C 6 H 4 NMe 2 )]PF 6 at 293 K demonstrate the importance of the inductive effect in the rate-determining cleavage of the Fe−NCR bond. The diastereomer ratios of 5:95 to 10:90 at equilibrium under thermodynamic control were strongly in favor of the (S Fe ,R C )-[CpFe(Prophos)NCR]X diastereomers. In ligand exchange reaction reactions, (R Fe ,R C )/(S Fe ,R C ) diastereomer ratios of up to 35:65 were observed under kinetic control.

Structural conversion of three copper(ii) complexes with snapshot observations based on the different crystal colours and morphology

“…Generally, it is difficult to capture or only capture one dynamic product as an intermediate product. [28][29][30][31] Identifying the crystal structure of dynamic product can provide a basis for fully understanding the synthesis process of single crystal. Two continuous intermediate state kinetic products and one nal state thermodynamic product were captured for the rst time, which provided an excellent basis for exploring the structural evolution of complexes.…”