title: Structurally diverse copper complexes bearing NNO-tridentate Schiff-base derivatives as efficient catalysts for copolymerization of carbon dioxide and cyclohexene oxide.
abstract: Structurally diverse copper acetate complexes based on NNO-tridentate Schiff-base ligands were synthesized and characterized as mono-, di-, and trinuclear complexes with respect to varied ancillary ligands. Treatment of the ligand precursors (L(1)-H = 2-(1-((2-(dimethylamino)ethyl)imino)ethyl)-4-methylphenol, L(2)-H = 4-chloro-2-(1-((2-(dimethylamino)ethyl)imino)ethyl)phenol, and L(3)-H = 2-(1-((2-(dimethylamino)ethyl)imino)ethyl)-5-methylphenol) with Cu(OAc)2·H2O (1 equiv) in refluxing ethanol afforded five-coordinate mono- or bimetallic copper complexes ([(L(1))Cu(OAc)(H2O)] (1); [(L(2))Cu(OAc)(H2O)] (2); [(L(3))2Cu2(OAc)2] (3)) in high yields. Dinuclear copper acetate analogue [(L(1))2Cu2(OAc)2] (4) resulted from treatment of L(1)-H as the ligand precursor in refluxing anhydrous MeOH with equimolar proportions of metal acetate salt under a dry nitrogen atmosphere. However, a trinuclear complex, [(L(4))2Cu3(OAc)4] (5), was obtained on utilizing 2-(1-((2-(dimethylamino)ethyl)imino)ethyl)-5-methoxyphenol (L(4)-H) as the proligand under the same synthetic route of 1-3; this complex was also synthesized in the reaction of L(4)-H and copper(II) acetate monohydrate in the ratio of 2:3, giving a quantitative yield. All complexes are active catalysts for copolymerization of cyclohexene oxide (CHO) and CO2 without cocatalysts. In particular, dinuclear Cu complex 3 performed satisfactorily to produce polycarbonates with controllable molecular weights and high carbonate linkages. These copper complexes are the first examples that are effective for both CO2/CHO copolymerization and formation of polymers in a controlled fashion.
authors.affiliation: Department of Chemistry and ‡Center of Nanoscience & Nanotechnology, National Chung Hsing University , Taichung 402, Taiwan.
authors.forename: Chen-Yen
authors.initials: CY
authors.lastname: Tsai
authors.forename: Bor-Hunn
authors.initials: BH
authors.lastname: Huang
authors.forename: Mon-Wei
authors.initials: MW
authors.lastname: Hsiao
authors.forename: Chu-Chieh
authors.initials: CC
authors.lastname: Lin
authors.forename: Bao-Tsan
authors.initials: BT
authors.lastname: Ko
mesh_terms: D000577:Amides / Q000737:chemistry; D002245:Carbon Dioxide / Q000737:chemistry*; D002384:Catalysis; D003300:Copper / Q000737:chemistry*; D053138:Cyclohexenes / Q000737:chemistry*; D007097:Imines / Q000737:chemistry; D008958:Models, Molecular; D015394:Molecular Structure; D009942:Organometallic Compounds / Q000737:chemistry*; D010636:Phenols / Q000737:chemistry; D058105:Polymerization; D011108:Polymers / Q000138:chemical synthesis / Q000737:chemistry; D012545:Schiff Bases / Q000737:chemistry*
chemical_list: D000577:Amides; D053138:Cyclohexenes; D007097:Imines; D009942:Organometallic Compounds; D010636:Phenols; D011108:Polymers; D012545:Schiff Bases; D002245:Carbon Dioxide; C007193:cyclohexene oxide; D003300:Copper