The copolymerization of carbon dioxide with epoxides is an industrially relevant means to valorize wastes and improve sustainability in polymer manufacturing, and may also provide an economic benefit to CO2 capture and storage technologies. The efficiency of the process depends upon the catalyst used; previously Zn(II)Mg(II) heterodinuclear catalysts showed good performances at low CO2 pressures, which has been attributed to synergic interactions between the metals. Here we report a Mg(II)Co(II) catalyst for the production of polyols by copolymerization of CO2 with cyclohexene oxide that exhibits significantly better activity (turn-over-frequency over 12,000 h-1), high CO2 utilization (over 99 %) and high polymer selectivity (over 99 %). Detailed kinetic investigations show a second-order rate law, independent of CO2 pressure from 1 to 40 bar. Investigations of the synergy between the metal centres showed that epoxide coordination occurs at Mg(II) with reduced transition state entropy, which the carbonate attack step is accelerated at Co(II) through lowering of the transition state enthalpy. functionalization of alternating polyesters: selective patterning of (AB)n sequences.

The uranium complexes [U(η8-C8H6(1,4-SiMe3)2)(η5-CpMe4R)] can be tuned to selectively reduce CO2, giving U(iv) complexes incorporating bridging oxo, carbonate, or oxalate groups.

The reactivity of the bis(pentalene)dititanium double-sandwich compound Ti2Pn†2 (1) (Pn† = 1,4-{SiiPr3}2C8H4) with CO2 is investigated in detail using spectroscopic, X-ray crystallographic, and computational studies. When the CO2 reaction is performed at −78 °C, the 1:1 adduct 4 is formed, and low-temperature spectroscopic measurements are consistent with a CO2 molecule bound symmetrically to the two Ti centers in a μ:η2,η2 binding mode, a structure also indicated by theory. Upon warming to room temperature the coordinated CO2 is quantitatively reduced over a period of minutes to give the bis(oxo)-bridged dimer 2 and the dicarbonyl complex 3. In situ NMR studies indicated that this decomposition proceeds in a stepwise process via monooxo (5) and monocarbonyl (7) double-sandwich complexes, which have been independently synthesized and structurally characterized. 5 is thermally unstable with respect to a μ-O dimer in which the Ti–Ti bond has been cleaved and one pentalene ligand binds in an η8 fashion to each of the formally TiIII centers. The molecular structure of 7 shows a “side-on” bound carbonyl ligand. Bonding of the double-sandwich species Ti2Pn2 (Pn = C8H6) to other fragments has been investigated by density functional theory calculations and fragment analysis, providing insight into the CO2 reaction pathway consistent with the experimentally observed intermediates. A key step in the proposed mechanism is disproportionation of a mono(oxo) di-TiIII species to yield di-TiII and di-TiIV products. 1 forms a structurally characterized, thermally stable CS2 adduct 8 that shows symmetrical binding to the Ti2 unit and supports the formulation of 4. The reaction of 1 with COS forms a thermally unstable complex 9 that undergoes scission to give mono(μ-S) mono(CO) species 10. Ph3PS is an effective sulfur transfer agent for 1, enabling the synthesis of mono(μ-S) complex 11 with a double-sandwich structure and bis(μ-S) dimer 12 in which the Ti–Ti bond has been cleaved.

An insoluble form of methylaluminoxane, also known as solid polymethylaluminoxane (sMAO), has been synthesized by the controlled hydrolysis of trimethylaluminum (TMA) with benzoic acid, followed by thermolysis. Characterization of sMAO by multinuclear NMR spectroscopy in solution and the solid state reveals an aluminoxane structure that features "free" and bound TMA and incorporation of a benzoate residue. Total X-ray scattering (or pair distribution function, PDF) measurements on sMAO allow comparisons to be made with simulated data for DFT modeled structures of MAO. Several TMA-bound (AlOMe) n cage and nanotubular structures with n>10 are consistent with the experimental data. The measured Brunauer-Emmett-Teller (BET) surface area of sMAO ranges between 312 -606 m 2 g -1 and shows an N 2 adsorption/desorption isotherm consistent with a non-porous material. sMAO can be utilized to support metallocene pre-catalysts in slurry-phase ethylene polymerization reactions. Metallocene pre-catalyst rac-ethylenebis(1-indenyl)dichlorozirconium, rac-(EBI)ZrCl 2 was immobilized on sMAO samples, to afford solids which showed very high polymerization activities in hexane, comparable to those of the respective homogeneous catalysts formed by treatment of the pre-catalysts with MAO. rac-(EBI)ZrCl 2 immobilized on an sMAO containing an Al:O ratio of 1.2 gave the highest ethylene polymerization activity.