Bimetallic Nickel Complexes Containing Benzotriazole-Derived Diamine-Bisphenolate Ligands as Highly Active Catalysts for the Copolymerization of Carbon Dioxide with Cyclohexene Oxide: Synthesis, Catalysis, and Kinetics

Abstract

We reported the syntheses of a family of structurally well defined dicarboxylate and dinitrate dinickel complexes coordinated on ethyl N-substituted benzotriazole-containing diamine-bisphenolate derivatives. Dinickel carboxylate complexes 1−8 were highly active catalysts for CO 2 copolymerization with cyclohexene oxide. Specifically, the trifluoroacetate-supported Ni complex 1 enabled the mediation of such a CO 2 copolymerization with a high turnover frequency of up to 2521 h −1 under the optimized conditions, affording the related CO 2 -based polycarbonates having "controllable" and "immortal" characters. The kinetics of CO 2 /cyclohexene oxide copolymerization by 1 was systematically investigated, and this kind of copolymerization catalysis showed a first-order dependence on both the nickel catalyst and monomer concentrations.

Dinuclear Nickel Complexes Using Hexadentate Benzothiazole-Based Diamine-Bisphenolate Ligands: Highly Active Catalysts for Copolymerization of Carbon Dioxide with Epoxides

“…We therefore integrated the overall rate equation of CO 2 -copolymerization as −d­[CHO]/d t = k p [ 2 ] 1 [CHO] 1 [CO 2 ] 0 , and the kinetic investigations showed a first-order dependence on both complex and CHO concentration as well as the zero order on carbon dioxide. The kinetics of such polymerization catalysis are in accord with previous reports for nickel-catalyzed CO 2 /CHO copolymerization by salen-type or salan-type complexes. ,, To further obtain the activation parameters (Δ H ‡ , Δ S ‡ , and Δ G ‡ ) of CO 2 /CHO copolymerization by 2 , kinetic experiments were performed at different temperatures (Table S5). Figure S10 illustrates the linear relationship between ln­[CHO] 0 /[CHO] t and time at varying temperatures, and these copolymerizations also follow first-order kinetics in CHO concentration.…”

Well-Defined and Highly Effective Nickel Catalysts Coordinated on Tridentate SNO Schiff-Base Derivatives for Alternating Copolymerization of Epoxides and Anhydrides

“…The geometry around the Ni­(II) center was a distorted octahedron constructed with two S atoms, two N atoms, and two O atoms of two tridentate SNO ligands and was confirmed by the average bond angles (172.09° for 1 , 171.68° for 2 , 175.18° for 3 , 171.16° for 4 , and 171.33° for 5 ) from the axial axes of S2–Ni1–O2, N1–N1–N2, and O1–Ni1–S1. The six-coordinate Ni-involved bond lengths were all within normal ranges, according to those previously reported of Ni­(II) complexes. − Notably, the single-crystal structures of complexe 6 were further confirmed to be a rare heptanuclear nickel­(II) octacarboxylate species in the air-yielded crystals of a structurally complex heptanuclear Ni7 cluster. In addition, all the Ni atoms exhibited a distorted octahedral geometry, as shown in Figure .…”

“…Our research group previously investigated dinuclear and trinuclear Ni CO 2 –epoxide ROCOP catalysts with high copolymerization selectivity that can operate without cocatalysts . Furthermore, Ko et al studied bimetallic Ni complexes consisting of benzotriazole phenolate derivatives and used these complexes for anhydride–epoxide and CO 2 –epoxide copolymerization without a cocatalyst to yield polymers with only moderate dispersity. − However, most metal complexes are based on hard oxygen- or nitrogen-based polydentate donors, and few studies have explored catalysts bearing softer donors, such as sulfur. − This paper reports a series of Ni complexes with simple tridentate SNO ligands that can serve as active and controllable catalysts for the anhydride–epoxide ROCOP. The use of these catalysts can greatly affect the rate of polymerization.…”

Bimetallic Nickel Complexes as Effective and Versatile Catalysts for Copolymerization of Epoxides with Carbon Dioxide or Phthalic Anhydride: Catalysis and Kinetics

“…However, the other nickel atom, Ni(2), adopts a distorted octahedral geometry, which was composed of two N atoms of benzotriazole groups and two O atoms of phenolate in equatorial position as well as the axial positions were occupied by the iodide group and O atom of the THF molecule. Not surprisingly, the average bond lengths between the five-coordinate Ni atom with O­(phenoxy) and N­(amine) in 3 are 2.026(4) Å and 2.090(5) Å, respectively, which are shorter than those values of the dinickel dicarboxylate analogues having two six-coordinate Ni atoms incorporated by benzotriazole-derived diamine-bisphenolate ligands. ,, Note that the average bond distance between the nickel ion and bonded halide for 3 was found to be 2.7230(8) Å, which was significantly longer than 2.3278(10) Å for 1 and 2.517(3) Å for 2 , respectively. This result is consistent with the ionic radius trend of halide ions and indicates that the more labile I – group may behave a good nucleophile during epoxide copolymerization catalysis.…”