Dinuclear and Trinuclear Nickel Complexes as Effective Catalysts for Alternating Copolymerization on Carbon Dioxide and Cyclohexene Oxide

详细信息    查看全文

• 作者：Chen-Yen Tsai ; Fu-Yin Cheng ; Kuan-Yeh Lu ; Jung-Tsu Wu ; Bor-Hunn Huang ; Wei-An Chen ; Chu-Chieh Lin ; Bao-Tsan Ko
• 刊名：Inorganic Chemistry
• 出版年：2016
• 出版时间：August 15, 2016
• 年：2016
• 卷：55
• 期：16
• 页码：7843-7851
• 全文大小：564K
• 年卷期：0
• ISSN：1520-510X

文摘

A series of novel nickel complexes 1–9 supported by NNO-tridentate Schiff-base derivatives have been synthesized and characterized. Treatment of the pro-ligands [L¹-H = 2,4-di-tert-butyl-6-(((2-(dimethylamino)ethyl)imino)methyl)phenol, L²-H = 2-(((2-(dimethylamino)ethyl)imino)methyl)-4,6-bis(2-phenylpropan-2-yl)phenol, L³-H = 2-(((2-(dimethylamino)ethyl)imino)methyl)phenol] with Ni(OAc)₂·4H₂O in refluxing ethanol afforded mono- or bimetallic nickel complexes {[(L¹)Ni(OAc)] (1); (L²)Ni(OAc)] (2); (L³)₂Ni₂(OAc)₂(H₂O)] (3)}. Alcohol-solvated trimetallic nickel acetate complexes {[(L³)₂Ni₃(OAc)₄(MeOH)₂] (4); (L³)₂Ni₃(OAc)₄(EtOH)₂] (5)} could be generated from the reaction of L³-H and anhydrous nickel(II) acetate with a ratio of 2:3 in refluxing anhydrous MeOH or EtOH. The reaction of nickel acetate tetrahydrate and L⁴-H to L⁶-H [L⁴-H = 2-(((2-(dimethylamino)ethyl)imino)methyl)-5-methoxyphenol, L⁵-H = 2-(((2-(dimethylamino)ethyl)imino)methyl)-4-methoxy-phenol, L⁶-H = 2-(((2-(dimethylamino)ethyl)imino)(phenyl)methyl)phenol] produced, respectively, the alcohol-free trinuclear nickel complexes {[(L⁴)₂Ni₃(OAc)₄] (7); [(L⁵)₂Ni₃(OAc)₄] (8); [(L⁶)₂Ni₃(OAc)₄] (9)} with the same ratio in refluxing EtOH under the atmospheric environment. Interestingly, recrystallization of [(L³)₂Ni₃(OAc)₄(MeOH)] (4) or [(L³)₂Ni₃(OAc)₄(EtOH)] (5) in the mixed solvent of CH₂Cl₂/hexane gives [(L³)₂Ni₃(OAc)₄] (6), which is isostructural with analogues 7–9. All bi- and trimetallic nickel complexes exhibit efficient activity and good selectivity for copolymerization of CO₂ with cyclohexene oxide, resulting in copolymers with a high alternating microstructure possessing ≥99% carbonate-linkage content. This is the first example to apply well-defined trinuclear nickel complexes as efficient catalysts for the production of perfectly alternating poly(cyclohexene carbonate).