Electrochemistry and [60]fullerene displacement reactions of (dihapto-[60]fullerene) pentacarbonyl metal(0) (M = Cr, Mo, W)

Abstract

Cyclic voltammetry (CV) measurements on (eta(2)-C(60))M(CO)(5) complexes (M = Cr, Mo, W) in dichloromethane show three [60]fullerene-centered and reversible reduction/oxidation waves. The E(1/2) values of these waves are shifted to positive values relative to the corresponding values of the uncoordinated [60]fullerene in the same solvent. A Jahn-Teller type distortion of the spherical surface of [60]fullerene promoted by [60]fullerene-metal pi-backbonding may explain the observed positive shifts. Lewis bases (L = piperidine and triphenyl phosphine) displace [60]fullerene from (eta(2)-C(60))M(CO)(5) complexes. Analysis of the activation parameters for the metal-[60]fullerene dissociation, the metal-[60]fullerene bond enthalpies (from DFT computations), and metal-solvent (benzene) bond enthalpies (from DFT computations) suggests appreciable solvent contribution to the transition state leading to formation of the intermediate species solvent-M(CO)(5). Appreciable transition state stabilization due to solvation of the intermediate species is inferred for M = Mo and W. For M = Cr, stabilization of the intermediate species due to solvation is not accompanied by the corresponding transition state stabilization.

Solvent/C60 exchange on Ir(CO)(PPH3)2(Cl)(η2-C60) and solvent/solvent’ exchange on Ir(CO)(PPH3)2(Cl)(solvent)

“…Moreover, the observed relative k solvent =k 0 solvent ratios (i.e. k benzene =k 0 benzene % 10; k cyclohexane = k 0 cyclohexane % 4; k chlorobenzene =k 0 chlorobenzene % 6; k toluene =k 0 toluene % 8) are in line with the expectation that the Ir-C 60 bond is stronger than Ir-solvent bonds [12].…”

“…enthalpy of activation value (DH à = 136(15) kJ/mol), in the vicinity of the enthalpies of activation for C 60 dissociation from (g 2 -C 60 )M(CO) 5 (M = Cr, Mo, W) complexes and to thermodynamic M-C 60 bond enthalpies obtained by DFT methods [12], also supports a dissociative mechanism interpretation.…”

New Ruthenium Bis(terpyridine) Methanofullerene and Pyrrolidinofullerene Complexes: Synthesis and Electrochemical and Photophysical Properties

“… a Conditions: potentials referenced to Fc + /Fc; scan rate 200 mV s –1 ; glassy-carbon-disk working electrode; AgCl/Ag reference electrode; Pt-rod counter electrode; 0.1 M Bu 4 NPF 6 in dichloromethane. b Taken from ref . c Irreversible process. The peak potential is shown. d Two processes. e Not detectable. …”

Consecutive C60 Fullerene Dissociation from Ir(η2-C60)(CO)(Cl)(PPh3)2 and the Oxidative Addition of Benzene

“…propose a plausible mechanism and relate the enthalpies of activation to bonding enthalpies in the corresponding transition states and to thermodynamic bond enthalpies where appropriate .…”