Substrate-Gated Transformation of a Pre-Catalyst into an Iron-Hydride Intermediate [(NO)(CO)Fe(μ-H)Fe(CO)(NO)] for Catalytic Dehydrogenation of Dimethylamine Borane.

Continued efforts are made on the development of earth-abundant metal catalysts for dehydrogenation/hydrolysis of amine boranes. In this study, complex [K-18-crown-6-ether][(NO)Fe(μ-Pyr)(μ-CO)Fe(NO)] (, Pyr = 3-methylpyrazolate) was explored as a pre-catalyst for the dehydrogenation of dimethylamine borane (DMAB). Upon evolution of H from DMAB triggered by , parallel conversion of into [(NO)Fe(,'-PyrBHNMe)] () and an iron-hydride intermediate [(NO)(CO)Fe(μ-H)Fe(CO)(NO)] () was evidenced by X-ray diffraction/nuclear magnetic resonance/infrared/nuclear resonance vibrational spectroscopy experiments and supported by density functional theory calculations. Subsequent transformation of into complex [(NO)Fe(μ-CO)Fe(NO)] () is synchronized with the deactivated generation of H. Through reaction of complex [Na-18-crown-6-ether][(NO)Fe(η-BH)] () with CO as an alternative synthetic route, isolated intermediate [Na-18-crown-6-ether][(NO)(CO)Fe(μ-H)Fe(CO)(NO)] () featuring catalytic reactivity toward dehydrogenation of DMAB supports a substrate-gated transformation of a pre-catalyst [(NO)Fe(μ-Pyr)(μ-CO)Fe(NO)] () into the iron-hydride species as an intermediate during the generation of H.