Readily accessible nitrilium triflates are convenient imine building blocks for the expedient synthesis of a novel class of 1,3-P,N ligands as demonstrated for the reaction with primary phosphanes. This procedure allows variation of all substituents. X-ray crystal structures are reported for nitrilium ions, phosphaamidines, and three phosphaamidinate complexes. The lithium phosphaamidinate is N coordinated and its reaction with [AuCl(tht)] (tht = tetrahydrothiophene) gives a unique P-bridged gold trimer, while a P,N-bidentate complex results from [{RhCl(cod)}2]. The nitrilium ion methodology allows extension of the 1,3-P,N motive to bis(imino)phosphanes, which are the neutral phosphorus analogues of the valuable β-diketiminate ligand.

The sodium salt of the new bis(mesitoyl)phosphinic acid (BAPO-OH) can be prepared in a very efficient one-pot synthesis. It is well soluble in water and hydrolytically stable for at least several weeks. Remarkably, it acts as an initiating agent for the surfactant-free emulsion polymerization (SFEP) of styrene to yield monodisperse, spherical nanoparticles. Time-resolved electron paramagnetic resonance (TR-EPR) and chemically induced electron polarisation (CIDEP) indicate preliminary mechanistic insights.

The P-coordinated boryl radical [Ph2P(naphthyl)BMes]˙ (Mes=mesityl) was prepared by (electro)chemical reduction of the corresponding borenium salt or bromoborane. Electron paramagnetic resonance (EPR) analysis in solution and DFT calculations indicate large spin density on boron (60-70%) and strong P-B interactions (P→B σ donation and B→P negative hyperconjugation). The radical is persistent in solution and participates in a Gomberg-type dimerization process. The associated quinoid-type dimer has been characterized by single-crystal X-ray diffraction.