Structural diversity in iron(<scp>ii</scp>) complexes of 2,6-di(pyrazol-1-yl)pyridine and 2,6-di(3-methylpyrazol-1-yl)pyridine
作者:Jérôme Elhaïk、Colin A. Kilner、Malcolm A. Halcrow
DOI:10.1039/b510370c
日期:——
The syntheses, magnetochemistry and crystallography of [Fe(L1)2]I0.5[I3]1.5 (1), [Fe(L1)2][Co(C2B9H11)2]2 (2) and [Fe(L2)2][SbF6]2 (3) (L1 = 2,6-di(pyrazol-1-yl)pyridine; L2 = 2,6-di(3-methylpyrazol-1-yl)pyridine) are described. Compounds 1 and 3 are high-spin between 5–300 K. For 1, this reflects a novel variation of an angular Jahn–Teller distortion at the iron centre, which traps the molecule in its high-spin state. No such distortion is present in 3; rather, the high-spin nature of this compound may reflect ligand conformational strain caused by an intermolecular steric contact in the crystal lattice. Compound 2 exhibits a gradual high → low spin transition upon cooling with T½ = 318 ± 3 K, that is only 50% complete. This reflects the presence of two distinct, equally populated iron environments in the solid. One of these unique iron centres adopts the same angular structural distortion shown by 1 and so is trapped in its high-spin state, while the other, which undergoes the spin-crossover, has a more regular coordination geometry. In contrast with 3, the solvated salts [Fe(L2)2][BF4]2·4CH3CN and[Fe(L2)2][ClO4]2·(CH3)2CO both undergo gradual thermal spin-transitions centred at 175 ± 3 K.
本文描述了[Fe(L1)2]I0.5[I3]1.5 (1), [Fe(L1)2][Co(C2B9H11)2]2 (2) 和 [Fe(L2)2][SbF6]2 (3) (L1 = 2,6-双(吡唑-1-基)吡啶; L2 = 2,6-双(3-甲基吡唑-1-基)吡啶)的合成、磁化学和晶体学。化合物 1 和 3 在 5-300 K 范围内为高自旋。对于 1,这反映了铁中心处角向 Jahn-Teller 畸变的一种新型变化,这种畸变使分子处于其高自旋态。3 中不存在这种畸变;相反,该化合物的高自旋性质可能反映了晶格中分子间空间接触引起的配体构象应变。化合物 2 在冷却过程中逐渐发生高自旋 → 低自旋转变,T½ = 318 ± 3 K,仅完成 50%。这反映了固体中存在两种截然不同、数量相等的铁环境。其中一个独特的铁中心采用了与 1 相同的角向结构畸变,因此被固定在其高自旋态,而另一个发生自旋交叉的铁中心则具有更规则的配位几何结构。与 3 相反,溶剂化盐 [Fe(L2)2][BF4]2·4CH3CN 和 [Fe(L2)2][ClO4]2·(CH3)2CO 均在 175 ± 3 K 处发生渐进式热自旋转变。