Enabling and Probing Oxidative Addition and Reductive Elimination at a Group 14 Metal Center: Cleavage and Functionalization of E-H Bonds by a Bis(boryl)stannylene

摘要

By employing strongly σ-donating boryl ancillary ligands, the oxidative addition of H_2 to a single site Sn~Ⅱ system has been achieved for the first time, generating (boryl)_2SnH_2. Similar chemistry can also be achieved for protic and hydridic E-H bonds (N-H/O-H, Si-H/B-H, respectively). In the case of ammonia (and water, albeit more slowly), E-H oxidative addition can be shown to be followed by reductive elimination to give an N- (or O-)borylated product. Thus, in stoichiometric fashion, redox-based bond cleavage/formation is demonstrated for a single main group metal center at room temperature. From a mechanistic viewpoint, a two-step coordination/ proton transfer process for N-H activation is shown to be viable through the isolation of species of the types Sn(boryl)_2·NH_3 and [Sn(boryl)_2(NH_2)]~- and their onward conversion to the formal oxidative addition product Sn(boryl)_2(H)(NH_2).