Supported Single-Site Ti(IV) on a Metal–Organic Framework for the Hydroboration of Carbonyl Compounds

A stable and structurally well-defined titanium alkoxide catalyst supported on a metal–organic-framework (MOF) of UiO-67 topology (ANL1-Ti­(O i Pr) 2 ) was synthesized and fully characterized by a variety of analytical and spectroscopic techniques, including BET, TGA, PXRD, XAS, DRIFT, SEM, and DFT computations. The Ti-functionalized MOF was demonstrated active for the catalytic hydroboration of a wide range of aldehydes and ketones with HBpin as the boron source. Compared to traditional homogeneous and supported hydroboration catalysts, ANL1-Ti­(O i Pr) 2 is completely recyclable and reusable, making it a promising hydroboration catalyst alternative for green and sustainable chemical synthesis. In addition, ANL1-Ti­(O i Pr) 2 catalyst exhibits remarkable hydroboration selectivity toward aldehydes vs ketone in competitive study. DFT calculations suggest that the catalytic hydroboration proceeds via a (1) hydride transfer between the active Ti-hydride species and a carbonyl moiety (rate-determining step) and (2) alkoxide transfer (intramolecular σ-bond metathesis) to generate the borate ester product.