Bis(diphenylphosphino)acetonitrile oxides, -sulfides and -imines: Their formation and structural features, and the remarkable structures of two lithiated derivatives

Oxidation of bis(diphenylphosphino)acetonitrile (dppmCN, 8) yields the corresponding bis-phosphinoxide system (9). Analogously, treatment of dppmCN with sulfur gave bis(diphenylphosphinsulfido)acetonitrile (10). Both compounds show very similar structures in the solid state, featuring strongly distorted U-shaped conformations. The Staudinger reaction of dppmCN with phenylazide gives rise to the formation of the bis(diphenylphosphinimino)acetonitrile product that was obtained in its ylidic P–NH tautomer form in solution and in the crystalline state. Deprotonation of the bis(diphenylphosphinchalcogenido)acetonitriles 9 and 10 gave the corresponding [NC–(Ph2PX)2]− anions (X = O, S). Their lithio compounds show a remarkable structural diversity in dependence of the chalcogene element used. The oxygen-containing compound (13) forms an oxygen-coordinated Li+-bridged 12-membered heteromacrocyclic structure, whereas Li+ avoids sulfur coordination in 14 and exhibits a THF-stabilized Li+–NC–R adduct structure in the crystal.