Iridium Insertion to Triosmium Cluster Containing Unsaturated Os–Os Bonds

Stereoregular CO2 Copolymers from Epoxides with an Electron-Withdrawing Group: Crystallization and Unexpected Stereocomplexation

“…In 2008, Lee et al investigated the coupling of CO 2 and styrene oxide using zinc-based catalyst systems, but they generally suffered from low activity, poor polymer selectivity, and the concomitant formation of ether linkage units . Prior to this study, well-defined β-diiminate–zinc complexes reported by the Coates group proved to be efficient in catalyzing this reaction at ambient temperature and 2.0 MPa, but the selectivity for copolymer was only 35% .…”

“…The production of degradable polycarbonates via the alternating copolymerization of epoxides and carbon dioxide (CO 2 ), the renewable C1 feedstock, has received considerable attention from both academic and industrial researchers in recent decades. − Numerous catalyst systems have been developed for this transformation by improving activity, suppressing ether linkages, increasing polymer selectivity, and enhancing polymer property. − Notably, the recently developed single-site metal catalysts with well-defined structure were found to be active under mild reaction conditions and thereby in some instances affording regio- and/or stereoselective copolymers. − Significant progress has been made in the formation of CO 2 copolymers (CO 2 -based polycarbonates) from aliphatic or alicyclic epoxides with electron-donating groups; however, very limited reports regard the selective synthesis of CO 2 copolymers from epoxides with electron-withdrawing groups, such as styrene oxide. − Being different from the terminal epoxides with an electron-donating group such as propylene oxide, the nucleophilic ring-opening of styrene oxide predominantly occurs at the methine C α –O bond rather than the methylene C β –O bond due to the electron-withdrawing nature of the aromatic ring. As a consequence, cyclic styrene carbonate is easily produced via backbiting of the propagating polycarbonate anion to the benzyl carbon of the adjacent carbonate unit .…”

Geometric structures and electron affinities of chlorine-doped silicon clusters

“…In recent years, considerable interest, both experimentally and theoretically, has focused on small atomic clusters [1][2][3][4][5][6][7][8][9][10]. The interest is in how the structures and properties of clusters approach those of the bulk material as the size increases.…”