Facile Activation of Triarylboranes by Rhenium(V) Oxo Imido Complexes

We report the synthesis and reactivity studies of a pair of rhenium­(V) oxo imido complexes. Oxidation of the rhenium­(III) terminal oxo ORe­(η2-DHF)­(BDI) (DHF = dihydrofulvalene, BDI = N,N′-bis­(2,6-diisopropylphenyl)-3,5-dimethyl-β-diketiminate) with organic azides R-N3 (R = tBu, 2,6-diisopropylphenyl) yields the title complexes. Computational studies confirm that the rhenium oxo moieties of these complexes are polarized and correspondingly nucleophilic, owing to the preferential π bonding of the imido ligand to the Re center. This asymmetry in the metal–ligand multiple bond electronic structure facilitates the ready activation of B–C bonds in triarylboranes (BPh3 and B­(C6F5)3), yielding rhenium­(V) aryl borinate complexes. In the case of BPh3, subsequent cyclometalation of the 1,2-addition products was found to take place upon heating, ejecting benzene to form bidentate diphenylborinate complexes.