Copper complexes of 2,6-bis(iminomethyl)pyridine derivatives and of 1,3-bis(pyridin-2-yl)pyrazole. Effects of ligand bulk and conformational strain on the ground state of a six-co-ordinate copper(II) ion
作者:Joanne M. Holland、Xiaoming Liu、Jing P. Zhao、Frank E. Mabbs、Colin A. Kilner、Mark Thornton-Pett、Malcolm A. Halcrow
DOI:10.1039/b005105p
日期:——
Complexation of hydrated Cu(BF4)2 by 2 molar equivalents of L2R (L2Me = 2,6-bismethyliminomethyl}pyridine, L2Cy = 2,6-biscyclohexyliminomethyl}pyridine, L2But = 2,6-bistert-butyliminomethyl}pyridine) afforded [Cu(L2R)2][BF4]2 (R = Me, 1; Cy, 2; or But, 3) in moderate yields. EPR spectroscopy in solution and the solid state demonstrates that 1 and 2 adopt the expected dy2 − z2}1 electronic ground state, and that the pseudo-Jahn–Teller elongation axis is fluxional in solid 1 and static in solid 2. In contrast, 3 exhibits a dz2}1 ground state by EPR. The crystal structures of 2·MeNO2 and 3·½Me2CO contain rhombic six-co-ordinate copper(II) ions, which differ principally in the length of the Cu–N bonds close to the molecular y axis. Treatment of [Cu(NCMe)4]BF4 with varying ratios of L2R yields [Cu(L2R)2]BF4 (R = Me, 4; Mes, 5; or Cy, 6: L2Mes = 2,6-bis2,4,6-trimethylphenyliminomethyl}pyridine) or [Cu(L2But)}2][BF4]27. The single crystal structure of 5·MeCN shows a flattened tetrahedral copper(I) centre with two bidentate L2Mes ligands. Reaction of hydrated Cu(ClO4)2 with 2 molar equivalents of L3 (1,3-bispyridin-2-yl}pyrazole) yields [Cu(L3)2][ClO4]28, whose crystal structure demonstrates a six-co-ordinate copper(II) ion with long Cu–Npyridine} bonds. Powder EPR spectroscopy demonstrates a dz2}1 ground state for 8 in the solid.
2 摩尔当量的 L2R(L2Me = 2,6-双甲基亚氨甲基}吡啶,L2Cy = 2,6-双环己基亚氨甲基}吡啶,L2But = 2,6-双叔丁基亚氨甲基}吡啶)络合水合 Cu(BF4)2,以中等产率得到 [Cu(L2R)2][BF4]2(R = Me,1;Cy,2;或 But,3)。溶液和固态的 EPR 光谱显示,1 和 2 采用了预期的 dy2 - z2}1 电子基态,在固态 1 中,伪贾恩-泰勒伸长轴是通态的,而在固态 2 中,伪贾恩-泰勒伸长轴是静态的。2-MeNO2 和 3-½Me2CO 的晶体结构包含菱形六配位铜(II)离子,它们的主要区别在于靠近分子 y 轴的 Cu-N 键的长度不同。用不同比例的 L2R 处理 [Cu(NCMe)4]BF4,可得到 [Cu(L2R)2]BF4(R = Me,4;Mes,5;或 Cy,6:L2Mes = 2,6-双2,4,6-三甲基苯基亚氨基甲基}吡啶)或 [Cu(L2But)}2][BF4]27。5-MeCN 的单晶结构显示了一个扁平的四面体铜(I)中心和两个双齿 L2Mes 配体。水合 Cu(ClO4)2 与 2 摩尔当量的 L3(1,3-双吡啶-2-基}吡唑)反应产生了 [Cu(L3)2][ClO4]28,其晶体结构显示了一个具有长 Cu-Npyridine} 键的六配位铜(II)离子。粉末 EPR 光谱显示 8 在固体中处于 dz2}1 基态。