Redox and anion exchange chemistry of a stibine-nickel complex: writing the L, X, Z ligand alphabet with a single element.

According to the covalent bond classification (CBC) method, two-electron donors are defined as L-type ligands, one-electron donors as X-type ligands, and two-electron acceptors as Z-type ligands. These three ligand functions are usually associated to the nature of the ligating atom, with phosphine, alkyl, and borane groups being prototypical examples of L-, X- and Z-ligands, respectively. A new SbNi platform is reported in which the ligating Sb atom can assume all three CBC ligand functions. Using both experimental and computational data, it is shown that PhICl2 oxidation of (o-(Ph2P)C6H4)3SbNi(PPh3) (1) into [(o-(Ph2P)C6H4)3ClSb]NiCl (2) is accompanied by a conversion of the stibine L-type ligand of 1 into a stiboranyl X-type ligand in 2. Furthermore, the reaction of 2 with the catecholate dianion in the presence of cyclohexyl isocyanide results in the formation of [(o-(Ph2P)C6H4)3(o-O2C6H4Sb)]Ni(CNCy) (4), a complex featuring a nickel atom coordinated by a Lewis acidic, Z-type, stiborane ligand.