Examining the stability of phospha(III)guanidines: Formation of a formamidinium:phosphinate ion-pair and an N-protonated phospha(III)guanidinium chloride

Reaction of the phospha(III)guanidine, Ph2PC{NCy}{NHCy}, with tert-butyl hydroperoxide resulted in isolation of [HC{NHCy}2][O2PPh2] via cleavage of the P–Camidine bond. The crystal structure shows chains of ion-pairs linked by NH⋯O hydrogen-bonding in the solid-state. Protonation of the starting material using anhydrous HCl afforded the phospha(III)guanidinium chloride, [Ph2PC{NHCy}2][Cl] in which the integrity of the P–Camidine bond was maintained. The crystal structure reveals a single hydrogen-bonding interaction between NH and the chloride ion.

Ph2PC{NCy}{NHCy} (A) reacted with tert-butyl hydroperoxide via cleavage of the P–Camidine bond to afford [HC{NHCy}2][O2PPh2], consisting of ion-pairs linked by NH⋯O hydrogen-bonds. Protonation of A with anhydrous HCl afforded the phospha(III)guanidinium chloride, [Ph2PC{NHCy}2][Cl] which retains the P–Camidine bond. The crystal structure of this salt shows a hydrogen-bond between the NH and the chloride.Figure optionsDownload as PowerPoint slideHighlights
► Examination of stability of Ph2PC{NCy}{NHCy} towards O2 and H2O.
► Decomposition via cleavage of the P–Camidine bond.
► [HC{NHCy}2][O2PPh2] formation as products using t-BuOOH(aq).
► Hydrochloride salt [Ph2PC{NHCy}2][Cl] from reaction with anhydrous HCl.