Novel Heterobimetallic Manganese-Chromium and Rhenium-Chromium Complexes

Abstract

A characteristic property of transition metal π-complexes with polycyclic aromatic ligands is their ability to undergo haptotropic rearrangements; the metal fragment is considered as the moveable functional group that is shifted between two non-equivalent rings of an oligocyclic ligand. <br /> We decided to add second different metal units coordinated to the (polyarene)Cr(CO)₃ complexes in order to study their influences on the migration of the chromium moiety. In this context, we synthesized the first <i>syn </i>and<i> anti</i> heterobimetallic Cr(CO)₃-Mn(CO)₃ and Cr(CO)₃-Re(CO)₃ oligocyclic fused-arene complexes. Moreover, we investigated a novel synthesis of (<i>N</i>-heterocyclic polyarene)Cr(CO)₃ and cyclomanganated (<i>N</i>-heterocyclic polyarene)Cr(CO)₃ complexes. In all binuclear cases, the chromium-templated-[3+2+1] benzannulation of <i>Fischer</i> arylcarbenes bearing an additional metal label was employed to introduce the chromium moiety. <br /> The thermo-induced haptotropic chromium migrations along the π-face of the platforms were performed with all these complexes and yielded in most case to the desired thermodynamic haptotropomers. The intramolecular courses of the chromium fragment were confirmed by NMR-studies which revealed first order kinetics. Besides, all the heterobimetallic structures were determined by X-ray analyses.