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, Dipp 3 SbO (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 Dipp 3 SbO allows the chemistry of the stiboryl group to be explored. Here we show that Dipp 3 SbO can act as a Brønsted base, a hydrogen-bond acceptor and a transition-metal ligand, in addition engaging in 1,2-addition, O-for-F 2 exchange and O-atom transfer. In all cases, the reactivity of Dipp 3 SbO differed from that of the lighter congeners Dipp 3 AsO and Dipp 3 PO.