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.