Crystal Structure of the Phosphinyl-stabilised Ylide Me3NNP(=O)Ph2 ⋅ H2O

Crystals of trimethylammonio-P,P-diphenylphosphinamidate hydrate, Me3NNP(=O)Ph2 ⋅ H2O, are held together by hydrogen bonds which link two Me3NNP(=O)Ph2 and two water molecules to form a centrosymmetric O4H4 ring belonging to graph set R2 4(8). Each P=O oxygen atom can thereby act as acceptor to two hydrogen bonds, rather than to only one, as in the two-fold symmetric P=O⋅⋅⋅H–O–H⋅⋅⋅O=P motif commonly found in phosphine oxide hemihydrates. The unusual P–N bond in Me3NNP(=O)Ph2 is short enough 1.614(3) Å to indicate some multiple character