LAUSR

Understanding the formation of metal-metal bonds and their electronic structures is still a scientific task. We herein report on the stepwise synthesis of boryl-substituted antimony compounds in which the antimony atoms adopt four different oxidation states (+III, +II, +I, +I/0). Sb-C bond homolysis of Cp*[(HCNDip)2B]SbCl (1; Cp* = C5Me5; Dip = 2,6-iPr2C6H3) gave diboryldichlorodistibane [(HCNDip)2BSbCl]2 (2), which reacted with KC8 to form diboryldistibene [(HCNDip)2BSb]2 (3) and traces of cyclotetrastibane [(HCNDip)2B]3Sb4Cl (5). One-electron reduction of 3 yielded the potassium salt of the diboryldistibene radical anion [(HCNDip)2BSb]2̇-, [K(18-c-6)(OEt2)][{(HCNDip)2BSb}2] (4), which exhibits an unprecedented inequivalent spin localization on the Sb-Sb bond and hence an unsymmetric electronic structure. Compounds 1-4 were characterized by heteronuclear nuclear magnetic resonance (NMR) (1H, 13C, 11B), infrared (IR), ultraviolet-visible (UV-vis) spectroscopy (3, 4), and single crystal X-ray diffraction (sc-XRD, 1-5), while the bonding nature of 3 and 4 was analyzed by quantum chemical calculations. EPR spectroscopy resolves the dissimilar Sb hyperfine tensors of 4, reflecting the inequivalent spin distribution, setting 4 uniquely apart from all previously characterized dipnictene radical anions.