Twists and Turns of Platinum-Allene Complexes: NMR Techniques for the Study of the Dynamic Behavior in Solution

Classic (dynamic exchange line-shape analysis) and novel (SSTD NMR) NMR techniques have been applied in order to obtain the kinetic and thermodynamic parameters of the three main processes occurring in the fluxional behavior of Pt-allene complexes with N-containing ligands, in four and five coordination mode, in solution. Our results show intramolecular helical and rotational movements closely related to each other, confirming eta(1)-staggered structures as possible intermediates. The ligand exchange in these complexes seems to occur via a ligand-independent dissociative mechanism, where coordinating solvents might be involved in the stabilization of the intermediates. The differences observed in the interaction of allenes with other metals could be the basis to explain the divergent reactivity observed in platinum-catalyzed processes.