TY - JOUR
T1 - Bioinspired catalytic conjugate additions of thiophenols to α,β-enones by a disubstituted benzoate-bridged nickel mimic for the active site of urease
AU - Lee, Way Zen
AU - Tseng, Huan Sheng
AU - Wang, Tzu Li
AU - Tsai, Hui Lien
AU - Kuo, Ting Shen
PY - 2010/7/12
Y1 - 2010/7/12
N2 - A disubstituted benzoate polydentate ligand, 2,6-bis[bis(pyridinyl-2- methyl)aminoethoxyl]benzoate (HL), was prepared to synthesize nickel mimics for the active site of urease. Reaction of the deprotonated L- with Ni(ClO4)2 · 6H2O afforded a dinickel complex, [LNi2(CH3CN)(THF)](ClO4)3 (1), characterized by UV/vis spectroscopy and X-ray crystallography. Addition of urea to an acetonitrile solution of 1 afforded a dinickel urea adduct, [LNi2(urea)2](ClO4)3 · 2CH3CN (2), which was structurally and spectroscopically characterized. 1H NMR and ESI-MS spectra of 2 both evidenced that urea molecules remained coordinated to the nickel centers of 2 in solution. With the inspiration of urea coordination to the nickel centers of 1, the conjugate additions of thiophenols to α,β-enones catalyzed by complex 1 were examined and found to proceed in good yields. In contrast, the same catalytic reaction by Ni(ClO4)2 · 6H2O and HL was far less effective. Also, addition of NaOAc or NaOAcPh2 to an acetonitrile solution of 1 gave tetranuclear nickel complexes, [LNi 2-(μ-OAc)]2(ClO4)4 · 3H2O (3) and [LNi2(μ-OAcPh2)] 2(ClO4)4 · 5CH3CN · 2THF (4), and their molecular structures determined by X-ray diffraction can be described as dimers of dimers. Each dinickel core of 3 and 4 closely mimics the active site of urease. The magnetic data of 1, 3, and 4 exhibited a very weak antiferromagnetic coupling (J =-0.72 cm-1 for 1,-0.65 cm-1 for 3 and 4) between two metal centers in the dinickel core.
AB - A disubstituted benzoate polydentate ligand, 2,6-bis[bis(pyridinyl-2- methyl)aminoethoxyl]benzoate (HL), was prepared to synthesize nickel mimics for the active site of urease. Reaction of the deprotonated L- with Ni(ClO4)2 · 6H2O afforded a dinickel complex, [LNi2(CH3CN)(THF)](ClO4)3 (1), characterized by UV/vis spectroscopy and X-ray crystallography. Addition of urea to an acetonitrile solution of 1 afforded a dinickel urea adduct, [LNi2(urea)2](ClO4)3 · 2CH3CN (2), which was structurally and spectroscopically characterized. 1H NMR and ESI-MS spectra of 2 both evidenced that urea molecules remained coordinated to the nickel centers of 2 in solution. With the inspiration of urea coordination to the nickel centers of 1, the conjugate additions of thiophenols to α,β-enones catalyzed by complex 1 were examined and found to proceed in good yields. In contrast, the same catalytic reaction by Ni(ClO4)2 · 6H2O and HL was far less effective. Also, addition of NaOAc or NaOAcPh2 to an acetonitrile solution of 1 gave tetranuclear nickel complexes, [LNi 2-(μ-OAc)]2(ClO4)4 · 3H2O (3) and [LNi2(μ-OAcPh2)] 2(ClO4)4 · 5CH3CN · 2THF (4), and their molecular structures determined by X-ray diffraction can be described as dimers of dimers. Each dinickel core of 3 and 4 closely mimics the active site of urease. The magnetic data of 1, 3, and 4 exhibited a very weak antiferromagnetic coupling (J =-0.72 cm-1 for 1,-0.65 cm-1 for 3 and 4) between two metal centers in the dinickel core.
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U2 - 10.1021/om100103u
DO - 10.1021/om100103u
M3 - Article
AN - SCOPUS:77955824840
SN - 0276-7333
VL - 29
SP - 2874
EP - 2881
JO - Organometallics
JF - Organometallics
IS - 13
ER -