Ring flipping in heterobimetallic Re-Ir complexes and its effect on structural isomerism: Dynamic NMR and DFT study

Abstract

Experimental and DFT study on the ring flipping phenomenon from the two fused puckered five–membered rings in complex [PNP(Me)(CH3CN)Ir-ReO3][PF6] (2) and its derivative [PNP(Me)(CNtBu)Ir-ReO3][PF6] (3) is reported here. Dynamic NMR studies from 31P{1H}NMR on ring flipping revealed that complexes 2 and 3 possess ΔG‡ value of 11.2 ± 0.3 and 9.2 ± 0.3 kcal/mol at 298 K respectively. Density Functional Theory (DFT) calculations concurred with the Potential Energy (PE) values of 12.36 and 8.09 kcal/mol respectively for the same phenomena. Also, DFT studies revealed that ring flipping and structural isomerism between 2 and its isomer [PNP(H)Ir-μ(CH2)-μ(O)-Re(O)2][PF6] (1) possess distinct transition states and can occur concurrently as observed experimentally.