Zinc complexes bearing BIAN ligands as efficient catalysts for the formation of cyclic carbonates from CO₂ and epoxides

Abstract

Herein, we present the synthesis of three new neutral aryl-BIAN ZnCl2 complexes (where aryl-BIAN = bis(aryl-imino)acenaphthene) with formulations [Zn(4-iPrC6H4-BIAN)Cl2] (1), [Zn(2-iPrC6H4-BIAN)Cl2] (2) and [Zn(4-NO2C6H4-BIAN)Cl2] (3) obtained through a green synthesis...

Halogen Bonding in the Decoration of Secondary Coordination Sphere of Zinc(II) and Cadmium(II) Complexes: Catalytic Application in Cycloaddition Reaction of CO2 with Epoxides

“…Inspired on the reported ,− transition metal complex catalyzed reaction mechanism for cycloaddition of CO 2 with epoxides, we propose that the reaction proceeds as shown in Scheme , according to the following main steps with postulated involvement of iodo bonding: (i) ring opening in epoxide though its coordination to a metal center and conceivable halogen bonding with an iodo-substituent ( I ) and nucleophilic attack by halide anion; (ii) insertion of CO 2 possibly through the negative charge assisted halogen and tetrel bonding ( II ); (iii) ring-closing ( III ) with liberation of cyclic carbonate and regeneration of the catalyst as well as of the halide anion (conceivably assisted by halogen bonding with a second catalyst molecule). Although the electron-withdrawing ability of the iodo-substitents in the ligand phenyl ring may increase the Lewis acidity of the metal center and thus promote the activation of the epoxide, we believe that this effect is much lower than that of the proposed iodo-bonding in view of the long distance of the iodo-substituents to the metal ion center (5 or 7 nonconjugated bonds), in contrast with the proposed iodo-bonding directly involving the epoxide.…”

“…The axial positions are occupied by two oxygen atoms (O13 and O15) from water molecules, with bond lengths of 2.165(4) and 2.138(4) Å, respectively. In both coordinated ligands in Zn2 the resonance assisted hydrogen bond ( (24) ring motifs, 60 resulting in a 1D supramolecular chain (Figure S1).…”

“…The yields of 4-methyl-1,3-dioxolan-2-one (97%, entry 1) and 4-ethyl-1,3-dioxolan-2-one (93%, entry 3) observed in this work are higher than those reported 70 for a pyrrole-Schiff base zinc complex (74 and 81%, respectively) in the presence of cocatalyst TBABr, in which the use of dichloromethane as a solvent can also be considered a disadvantage in comparison to our solvent-free system. Relatively to Zn4 (94%, entry 5, Table 4), the conversion of 2-phenyloxirane is also lower in the Zn(II)-N,N-bis(2-pyridinecarboxamide)-1,2-benzene/TBABr (27%), 71 Zn(II)-bis-thiosemicarbazonate/TBAI (29%), 72 Zn-(II)-bis(arylimino) acenaphthene)/TBABr (70%), 24 zinc(II)azatrane/TBAI (75%), 73 and Zn(II)-[2-(4,5-diphenyl-1Himidazol-2-yl)-4-((triphenylphosphonio)methyl)phenolate chloride] 2 (86%) 74 catalyzed systems.…”

“…Due to the high bonding enthalpy of the CO double bond (+805 kJ mol –1 ) and the linear molecular configuration of centrosymmetric CO 2 , a catalyst is generally required to bring down the energy barrier in its chemical transformations. The organocatalytic and metal complex catalyzed conversion of CO 2 , as an abundant, inexpensive, nontoxic, nonflammable, and renewable C1 source/building unit (instead of the commonly used phosgene, COCl 2 ) in chemical synthesis has already been recognized as a powerful synthetic strategy. − For example, metal complex-catalyzed cycloaddition of CO 2 with epoxides leads to cyclic and/or polymeric carbonates, − which find a variety of applications in the pharmaceutical industry, − electrolytes in lithium ion batteries, , paint-strippers, aprotic polar solvents in organic synthesis, , intermediates in the synthesis of carbamates, , etc. The search for a new effective, environmentally friendly, and inexpensive catalytic system is a tremendous challenge in the synthesis of cyclic carbonates from the CO 2 and epoxides.…”

A Family of Cagelike Mn-Silsesquioxane/Bathophenanthroline Complexes: Synthesis, Structure, and Catalytic and Antifungal Activity

“…In particular, catalytic cycloaddition of CO 2 with epoxides into cyclic carbonates is a very attractive transformation, the products of which are being widely used as raw materials for production of electrolyte solvents in lithium-ion batteries, engineering plastics, building blocks for organic and pharmaceutical synthesis, etc . Numerous catalysts, such as metal complexes including coordination polymers and metal organic frameworks, ionic liquids, cellulose/KI, ion exchange resins, quaternary ammonium and phosphonium salts, etc., have been explored for efficient synthesis of cyclic carbonates from CO 2 and epoxides. − However, there is only a recent example of the cycloaddition reaction of CO 2 with small epoxides catalyzed by CLMS (Eu 13 -based complex) …”