Bispidine copper(II) compounds: Effects of the rigid ligand backbone

被引:61
作者
Comba, P [1 ]
Lienke, A [1 ]
机构
[1] Heidelberg Univ, Inst Anorgan Chem, D-69120 Heidelberg, Germany
关键词
D O I
10.1021/ic010200r
中图分类号
O61 [无机化学];
学科分类号
070301 ; 081704 ;
摘要
Approximative density-functional theory calculations indicate that the tetradentate ligand L (L = 2,4-bis-(2-pyridyl)-3,7-diaza-[3.3.1]-bicyclononane) enforces an unusual and strong binding of a co-ligand (substrate) to a copper(II) center. The co-ligand in [Cu(L)(CI)II completes a square-pyramidal coordination around copper(II) and binds in the equatorial plane rather than on the apical position. This configuration is a stable geometric isomer for the model complex [Cu(NH3)(2)(imine)(2)(Cl)](+), but it is disfavored by approximately 10 kJ mol(-1) and not commonly observed for CuN4 chromophores with a monodentate co-ligand. The equatorial coordination increases the bond energy of the copper(II) -chloride bond by approximately 80 kJ mol-1, and similar results are expected for other copper(II)-L-substrate complexes, some of which show strong catalytic activity or unusual stability. Despite the enforced configuration, L does not impose significant steric strain on the copper(II) center but is well preorganized for the Jahn-Teller labile ion in this unusual geometry. The preorganization extends to the orientation of the pyridine donors (torsion angle around the copper-pyridine bond), and this seems to be of importance in the reactivity of the copper-L complexes and their derivatives.
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页码:5206 / 5209
页数:4
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