Trans–cis C–Pd–C rearrangement in hemichelates. Issue 25 (2nd June 2017) - Werlé, Christophe
Abstract : In the transition state of the trans – cis isomerization process, hemichelation dynamically offers alternative coordination positions to the Pd center. Abstract : Kinetically unstable heteroleptic trans -bispalladacycles were isolated by using hemichelation. Three structures of trans isomers and five of cis isomers were characterized by X-ray diffraction analysis. The ready trans -to- cis isomerization of such hemichelates that was monitored by variable temperature NMR experiments is facilitated dynamically because the Pd(ii ) center can preserve its square planar coordination in a rather low lying transition state, which was localized by methods of the density functional theory. This process is not achievable in the isomerization of conventional homoleptic trans -bispalladacycles since it involves the preliminary partial chelate decoordination and an unfavorable high-lying planar trigonal coordinated – or Y-shaped-Pd(ii ) transition state according to DFT investigations.