A new class of ligand derived from the reactions of bis(dialkylphosphino)amines and 9-diazofluorene: preparation, structure and reactivity

The reaction of tetra(isopropyl)diphosphazane (iPr-PNP) or tetraphenyldiphosphazane (Ph-PNP) with 9-diazofluorene (9-DAF) affords new chelating phosphazene ligands [F(NN)P(R)2NP(R)2(NHN)F] where F = fluorenylidene and R = iPr (1a) or Ph (1b). 1b has been shown to react with ZnEt2 and AlMe3 giving mononuclear organometallic complexes 4 and 5, respectively, while the reaction with NaH generates the chelated sodium complex 6. The complexes have been fully characterized and their solid-state structures have been authenticated using single-crystal X-ray diffraction. Complexes 4 and 5 have been used as catalysts for the ring-opening copolymerization (ROCOP) of cyclohexene oxide (CHO) and phthalic anhydride (PA). These complexes selectively gave polyesters through the ROCOP of PA and CHO in the presence of bis(triphenylphosphine)iminium chloride (PPNCl) as a nucleophilic co-catalyst, yielding moderate molar mass polyesters with narrow dispersity (e.g. Mn = 10.1 kg mol−1 and Đ = Mw/Mn = 1.25).