Establishing the Coordination Chemistry of Antimony(V) Cations: Systematic Assessment of Ph 4 Sb(OTf) and Ph 3 Sb(OTf) 2 as Lewis Acceptors

The coordination chemistry of the stiboranes Ph 4 Sb(OTf) ( 1 a , OTf = OSO 2 CF 3 ) and Ph 3 Sb(OTf) 2 ( 3 ) with Lewis bases has been investigated. The significant steric encumbrance of the Sb center in 1 a precludes interaction with most ligands, but the relatively low steric demands of 4‐methylpyridine‐ N ‐oxide (OPyrMe) and OPMe 3 enabled the characterization of [Ph 4 Sb(OPyrMe)][OTf] ( 2 a ) and [Ph 4 Sb(OPMe 3 )][OTf] ( 2 b ), rare examples of structurally characterized complexes of stibonium acceptors. In contrast, 3 was found to engage a variety of Lewis bases, forming stable isolable complexes of the form [Ph 3 Sb(donor) 2 ][OTf] 2 [donor=OPMe 3 ( 6 a ), OPCy 3 ( 6 b , Cy=cyclohexyl), OPPh 3 ( 6 c ), OPyrMe ( 6 d )], [Ph 3 Sb(dmap) 2 (OTf)][OTf] ( 6 e , dmap=4‐(dimethylamino)pyridine) and [Ph 3 Sb(donor)(OTf)][OTf] [donor=1,10‐phenanthroline ( 7 a ) or 2,2′‐bipy ( 7 b , bipy=bipyridine)]. These compounds exhibit significant structural diversity in the solid‐state, and undergo ligand exchange reactions in line with their assignment as coordination complexes. Compound 3 did not form stable complexes with phosphine donors, with reactions instead leading to redox processes yielding SbPh 3 and products of phosphine oxidation.