A convenient synthetic route has been developed for preparing the novel rigid 4,5-(PR2)­2–2,7,9,9-tetramethylacridane-based pincer ligands (acri‑RPNP; R = i Pr and Ph), and the first rare-earth (Ln = Y, Lu) alkyl complexes bearing the acri‑RPNP ligands were synthesized by a salt metathesis reaction (for the isopropyl-substituent acri‑iPrPNP complexes, 1-Ln) or direct alkylation (for the phenyl-substituent acri‑PhPNP complexes, 2-Ln). For both 1-Ln and 2-Ln, the NMR spectroscopy and X-ray diffraction study confirmed the successful coordination of the acri‑RPNP ligand to the central metal ion in a tridentate manner via the two phosphine and the nitrogen donors. In contrast to 1-Ln that are solvent-free complexes, the metal centers in 2-Ln are each coordinated with one tetrahydrofuran molecule. Upon activation by [Ph3C]­[B­(C6F5)4], 1-Y and 2-Lu could catalyze the living polymerization of isoprene and β-myrcene with high catalytic activity and high cis-1,4-selectivity (up to 92.3% for isoprene and 98.5% for β-myrcene). Moreover, the 1-Y/[Ph3C]­[B­(C6F5)4] catalytic system also could promote the polymerization of butadiene and its copolymerization with isoprene to produce copolymers with high cis-1,4-selectivity and narrow polydispersity.

We have reported the synthesis of a family of diarylamido-based rare-earth complexes and their stereoselective polymerization of isoprene.

With an objective to reduce petrochemical dependency, synthesis of biobased polymers from renewable feedstocks has been widely investigated. In this study, we report that living and highly 3,4-isoselective polymerization of the biobased monomer βfarnesene (100% 3,4-, >99% mmmm) can be realized at room temperature using a phosphine-functionalized fluorenyl-ligated yttrium catalytic system with ultrahigh activity. Detailed investigations suggested that the coordinated phosphine group plays a pivotal role in the high regio-and stereoselectivity of 1-Y-catalyzed β-farnesene polymerization, and the density functional density (DFT) calculation offered important insights into the 3,4-isoselectivity. Additionally, block copolymers featuring rigid 3,4isospecific polyisoprene blocks and amorphous 3,4-isospecific polyfarnesene blocks were successfully prepared. The morphology and mechanical properties of these elastomeric copolymers were studied by using atomic force microscopy and stress−strain experiments, respectively.