The influence of phosphine cone angle on the synthesis and structures of [Rh(PR3)(Binor–S)]+ complexes that show C–C sigma interactions

Complexes that show C–C···Rh sigma interactions have been synthesized and characterised by NMR spectroscopy and X–ray diffraction: [Rh(PR3)(Binor–S)][BArF4], R = PtBu2Me, PCy2Ph; Ar = C6H3(CF3)2, Binor–S = 1,2,4,5,6,8-dimetheno-S-indacene. These studies, in concert with previously published work, show that there is a rather narrow window of phosphine steric profile that supports the isolation of these interesting complexes, with the phosphine cone angle lying between 160° and 170°.