Trapping of a Late-Metal Terminal Sulfido Intermediate with Phenyl Isothiocyanate

Abstract

Nickel–sulfur bonds play key roles in catalysis and biological systems. In most metal complexes, sulfur acts as a bridge joining metal centers, rather than as a terminal sulfide ligand. The addition of phenyl isothiocyanate to Ni(dcpe)(Ph)(SH) afforded the dithiocarbamate complex Ni(dcpe)(κ2-S2C═NPh) with the loss of benzene. The reaction was monitored by UV–visible spectroscopy under pseudo-first-order rate conditions and showed limited dependence on isothiocyanate concentration, suggesting that the reaction proceeds through an intermediate terminal sulfido nickel complex. The values of ΔH⧧ and ΔS⧧ for the reaction were found to be 18.6 ± 1.5 kcal/mol and −17.8 ± 4.7 eu, respectively. Full characterization of Ni(dcpe)(κ2-S2C═NPh), including a single-crystal X-ray structure determination, was achieved.