[Li{CH(Me)P(Ph)2(NCO2Me)}2(THF)2]:  Crystal, Solution, and Calculated Structure of a N-Delocalized Lithium Phosphazene

The first crystal structure of the lithium complex of a P-alkyl-P,P-diphenyl(N-methoxycarbonyl)phosphazene has been characterized. It is dimeric, with the anion chelating the lithium in an unusual six-membered ring. A monomer−dimer equilibrium has been identified in THF solution. Ab initio calculations indicated that the six-membered ring is electronically favored over an alternative Li−C−P−N four-membered ring.