Isolation, bonding and reactivity of a monomeric stibine oxide

In contrast to phosphine oxides and arsine oxides, which are common and exist as stable monomeric species featuring the corresponding pnictoryl functional group (Pn=O/Pn⁺-O^-; Pn = P, As), stibine oxides are generally polymeric, and the properties of the unperturbed stiboryl group (Sb=O/Sb⁺-O^-) remain unexplored. We now report the isolation of the monomeric stibine oxide, Dipp₃SbO (where Dipp = 2,6-diisopropylphenyl). Spectroscopic, crystallographic and computational studies provide insight into the nature of the Sb=O/Sb⁺-O^- bond. Moreover, isolation of Dipp₃SbO allows the chemistry of the stiboryl group to be explored. Here we show that Dipp₃SbO can act as a Brønsted base, a hydrogen-bond acceptor and a transition-metal ligand, in addition engaging in 1,2-addition, O-for-F₂ exchange and O-atom transfer. In all cases, the reactivity of Dipp₃SbO differed from that of the lighter congeners Dipp₃AsO and Dipp₃PO.