Synthesis and conformational studies of (diphenylphosphinoamino)-cyclodiphosph(III)azanes

Abstract

A series of 2,4-bis(diphenylphosphinoalkylamino)-1,3-di-t-butylcyclodiphosph(III)azanes, [(Ph₂P)RNPNBu^t]₂[R = Me or Et (cis- and trans-isomers); R = Prⁱ or Bu^t(cis-isomers)], have been prepared by the reactions of N-lithiated alkyl-N-(diphenylphosphino) amines, N (PPh₂)(R)(Li), with 2-cis-4-dichloro-1,3-di-t-butylcyclodiphosph(III)azane, (ClPNBu^t)₂, in benzene solution. Hydrogen-1, 13_C and ³¹P n.m.r. spectroscopy show that these compounds are cyclodiphosph(III)azenes rather than phosph(III)azenes, (Ph₂P)RNPNBu^t, in solution, and variable temperature ^3lP n.m.r. data have enabled the preferred conformations of the exo-P–N–P skeletons to be identified. In the case of [(Ph₂P)RNPNBu^t]₂(R = Prⁱ and Bu^t) more than one conformer can be distinguished at sub-ambient temperatures.