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.