SPONTANEOUS FORMATION OF A DICOORDINATE IMINOPHOSPHINE FROM A TRICOORDINATE TRIAMINOPHOSPHINE VIA A TETRACOORDINATE PHOSPHORANE

The unexpected thermodynamic preference for a dicoordinate iminophosphine over a tricoordinate triaminophosphine is demonstrated by the spontaneous elimination of HNR2 from four derivatives of (NR2)2P-N(H)Mes. (1) (NR2 = NMe2, NEt2, piperidino, NiPr2) under ambient conditions. More surprising is the observation of the tetracoordinate phosphorane tautomer 2 as an intermediate in the elimination reaction which ultimately gives 3. The potential for tetracoordination in the presence of the sterically demanding (2,4,6-tri-tert-butylphenyl)-imino substituent is confirmed in the crystal structure of the thermally stable iminochlorophosphorane (NEt2)2P(Cl)=NMes..