Mono-, di-, tetra- and heptanuclear copper(II) complexes with 4-(3,5-di-R-1H-pyrazol-1-yl)-6-methyl-2-(pyridin-2-yl)pyrimidines (R=H, Me): Syntheses, crystal structures and electrospray ionization mass spectrometry
作者:Mark B. Bushuev、Yuri V. Gatilov、Elena B. Nikolaenkova、Vladimir G. Vasiliev、Viktor P. Krivopalov
DOI:10.1016/j.ica.2012.10.018
日期:2013.1
A series of mono- and oligonuclear copper(II) complexes with new hybrid NNN-tridentate 4-(1H-pyrazol-1-yl)-2-(pyridin-2-yl)pyrimidine ligands, 4-(1H-pyrazol-1-yl)-2-(pyridin-2-yl)-6-methylpyrimidine (L-1) and 4-(3,5-dimethyl-1H-pyrazol-1-yl)-2-(pyridin-2-yl)-6-methylpyrimidine (L-2), have been synthesized. The reaction of CuCl2 with L-1 in EtOH in the 1: 1 metal-to-ligand molar ratio affords the mononuclear complex [(CuLCl2)-Cl-1]center dot 0.5H(2)O (1). An increase of the metal-to-ligand molar ratio up to 4: 1 as well as the use of less polar mixed solvent, EtOH/CHCl3, leads to mononuclear complex [(CuLCl2)-Cl-1] (2). Attempts to crystallize di- or oligonuclear copper(II) complex with L-1 (the 8:1 metal-to-ligand molar ratio, EtOH/CHCl3) resulted in the formation of ionic halocuprate compound, [(CuL14Cl12)-L-7][Cu2Cl6] (3), containing unique heptanuclear cation, [(CuL4Cl12)-L-7-Cl-1](2+), and dinuclear anion [Cu2Cl6](2) . The reaction of CuCl2 with L-2 in EtOH in the 1:1 metal-to-ligand molar ratio affords mononuclear complex [CuL2Cl2] (4). Di- and tetranuclear complexes, [Cu2L2Cl4] (5) and [(Cu4L2Cl8)-Cl-2] (6), can be crystallized from ethanolic solution when the 2: 1 metal-to-ligand molar ratio is used. The former is the product of kinetic control, while the latter is that of thermodynamic one. Being coordinated, the molecules of L-1 and L-2 adopt tridentate chelating coordination mode binding copper atoms through pyrazolyl N-2, pyrimidine N-3 and pyridinyl N atoms and forming thus two five-membered chelate rings (CuN3C and CuN2C2). Depending on the metal-to-ligand molar ratio in the solution, electrospray ionization mass spectrometry (ESI-MS) evidenced the presence of mono- and oligonuclear copper species in the CuCl2-L-1 and CuCl2-L-2 solutions. The isolation of oligonuclear species in the solid state seems to be related with the absence of hydrogen-bond donor groups in the molecules of 4-(1H-pyrazol-1-yl)-2-(pyridin-2-yl) pyrimidine ligands. (C) 2012 Elsevier B. V. All rights reserved.