Rigid Acridane-Based Pincer Supported Rare-Earth Complexes for -1,4-Polymerization of 1,3-Conjugated Dienes.

A convenient synthetic route has been developed for preparing the novel rigid 4,5-(PR)2-2,7,9,9-tetramethylacridane-based pincer ligands (PNP; R = Pr and Ph), and the first rare-earth (Ln = Y, Lu) alkyl complexes bearing the PNP ligands were synthesized by a salt metathesis reaction (for the isopropyl-substituent PNP complexes, ) or direct alkylation (for the phenyl-substituent PNP complexes, ). For both and , the NMR spectroscopy and X-ray diffraction study confirmed the successful coordination of the PNP ligand to the central metal ion in a tridentate manner via the two phosphine and the nitrogen donors. In contrast to that are solvent-free complexes, the metal centers in are each coordinated with one tetrahydrofuran molecule. Upon activation by [PhC][B(CF)], and could catalyze the living polymerization of isoprene and β-myrcene with high catalytic activity and high -1,4-selectivity (up to 92.3% for isoprene and 98.5% for β-myrcene). Moreover, the /[PhC][B(CF)] catalytic system also could promote the polymerization of butadiene and its copolymerization with isoprene to produce copolymers with high -1,4-selectivity and narrow polydispersity.