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

Abstract

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 (H[1a]) or Ph (H[1b]). H[1b] has been shown to react with ZnEt₂ and AlMe₃ giving mononuclear organometallic complexes ZnEt[1b] (4) and AlMe₂[1b] (5), respectively, while the reaction with NaH generates the chelated sodium complex Na(THF)₂[1b] (6). Complexes 4, 5, and 6 have been fully characterized, and the solid-state structures of all complexes in this study have been authenticated using single-crystal X-ray diffraction. Complexes 4 and 5 catalyze the ring-opening copolymerization (ROCOP) of cyclohexene oxide (CHO) and phthalic anhydride (PA) giving polyesters in the presence of bis(triphenylphosphine)iminium chloride (PPNCl) as a nucleophilic co-catalyst, yielding moderate molar masses with narrow dispersities.