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Four N,O‐Bidentate‐Chelated Ligand‐Tunable Copper(II) Complexes: Synthesis, Structural Characterization and Exceptional Catalytic Properties for Chan–Lam Coupling Reactions
Author(s) -
Jia Xuefeng,
Peng Pai,
Cui Jing,
Xin Nana,
Huang Xianqiang
Publication year - 2018
Publication title -
asian journal of organic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.846
H-Index - 44
eISSN - 2193-5815
pISSN - 2193-5807
DOI - 10.1002/ajoc.201800153
Subject(s) - chemistry , denticity , morpholine , copper , square pyramidal molecular geometry , crystallography , coordination geometry , crystal structure , octahedral molecular geometry , ligand (biochemistry) , pyrrolidine , octahedron , catalysis , stereochemistry , medicinal chemistry , hydrogen bond , molecule , organic chemistry , biochemistry , receptor
Four N,O‐bidentate chelating ligands [ L 1 = N ‐(4‐thiazolylmethyl)morpholine‐ N ‐oxide, L 2 = N ‐(2‐pyridylmethyl)pyrrolidine‐ N ‐oxide, L 3 = N ‐(4‐thiazolylmethyl)pyrrolidine‐ N ‐oxide, and L 4 = N ‐(2‐pyridylmethyl)morpholine‐ N ‐oxide] were designed and synthesized. The treatment of N,O‐bidentate ligands with CuCl 2 in ethanol at room temperature afforded four new copper complexes—[Cu( L 1 ) 2 ]Cl 2 ( I ), [Cu( L 2 ) 2 ][CuCl 4 ] ( II ), [Cu( L 3 ) 2 Cl] 2 [CuCl 2 (H 2 O) 2 ]Cl 2 ⋅ 10 H 2 O ( III ) and [Cu( L 4 ) 2 ][Cu( L 4 ) 2 (CH 3 OH) 2 ][CuCl 4 ] 2 ( IV )—which were fully characterized by single‐crystal X‐ray diffraction, IR spectroscopy and elemental analyses. Most interestingly, the single‐crystal X‐ray diffraction analyses revealed that the N,O‐bidentate ligands L 1 – L 4 can tune the corresponding geometry configuration of copper atoms in complexes I – IV . The copper atoms in I and II showed four‐coordinated distorted square planar geometry, whereas the central copper atom in III adopted a distorted square pyramidal geometry. It should be noted that complex IV was constructed by a distorted square planar CuN 2 O 2 unit, one octahedral CuN 2 O 4 unit and two [CuCl 4 ] 2− anions. Importantly, these copper(II) complexes, especially complex IV , showed high catalytic activity in Chan–Lam coupling reactions of primary or secondary amines with arylboronic acid under mild conditions. Substrates with many functional groups were tolerated and the C–N coupling products were afforded in good to excellent yields (up to 96 % yield).