Institut für Anorganische und Analytische Chemie, Albert-Ludwigs-Universität Freiburg, Albertstr. 21, D-79104, Freiburg, Germany.
Dalton Trans. 2010 May 21;39(19):4495-507. doi: 10.1039/b925107c.
The coordination chemistry of the ligand 3-(2-pyridyl)-[1,2,4]triazolo[4,3-a]pyridine (L¹⁰) has been investigated and iron(II), cobalt(II), nickel(II) and copper(II) complexes featuring diverse structural motifs have been prepared. In the 2 : 1-type complexes Co(II)(L¹⁰)₂(MeOH)₂₂ (20), Ni(II)(L¹⁰)₂(MeOH)₂₂ (21), Cu(II)(L¹⁰)₂(MeOH)₂₂ (22), Co(II)(L¹⁰)₂(H₂O)₂₂ (23) and [Cu(II)(L¹⁰)₂(ClO₄)₂] (24) the metal centres are N₄O₂ octahedrally coordinated with two N²,N(pyr) bidentate ligands L¹⁰ in the equatorial positions. In the N₆ octahedral 4 : 1-type complex Co(II)(L¹⁰)₄₂·H₂O (25) both axially coordinating N¹ unidentate and equatorially bound N²,N(pyr) bidentate ligands L¹⁰ are observed. The N₆ octahedral 3 : 1-type complex Fe(II)(L¹⁰)₃₂·1.5MeCN·0.13H₂O·0.87MeO(t)Bu (27) features three N²,N(pyr) bidentate ligands L¹⁰ in the mer configuration. The two closely related N₆ octahedral complexes [Fe(II)(L¹⁰)₂(NCS)₂] (29) and [Fe(II)(L¹⁰)₂(dca)₂] (30) have fundamentally different structures. While complex 29 features two equatorially bound N²,N(pyr) bidentate ligands L¹⁰ and axial NCS⁻ co-ligands, complex 30 is a one-dimensional doubly μ1,5-dicyanamido-bridged polymer with N¹ unidentate ligands L¹⁰ in the axial positions. Temperature-dependent magnetic susceptibility measurements of the iron(II) complexes 28 and 29 have shown the 3 : 1-type complex Fe(II)(L¹⁰)₃₂·H₂O (28) to be in the low-spin state over the range 300-2 K and the 2 : 1-type complex 29 to be a spin crossover compound with T(1/2) = 269 K whereas the dicyanamido-bridged complex 30 remains in the high-spin state even down to 113 K, according to X-ray diffraction data. A single end-to-end bridging NCS⁻ co-ligand is found in the N₄S square-pyramidal complex [Cu(II)(L¹⁰)(NCS)₂] (31) which shows Curie-Weiss behaviour over the range 300-2 K. A brief review of the coordination chemistry of triazolopyridines is given.
已研究了配体 3-(2-吡啶基)-[1,2,4]三唑并[4,3-a]吡啶 (L¹⁰) 的配位化学，并制备了具有不同结构特征的铁(II)、钴(II)、镍(II)和铜(II)配合物。在 2:1 型配合物 Co(II)(L¹⁰)₂(MeOH)₂₂ (20)、Ni(II)(L¹⁰)₂(MeOH)₂₂ (21)、Cu(II)(L¹⁰)₂(MeOH)₂₂ (22)、Co(II)(L¹⁰)₂(H₂O)₂₂ (23) 和 [Cu(II)(L¹⁰)₂(ClO₄)₂] (24) 中，金属中心以 N₄O₂ 八面体配位，两个 N²,N(pyr) 双齿配体 L¹⁰ 在赤道位置。在 N₆ 八面体 4:1 型配合物 Co(II)(L¹⁰)₄₂·H₂O (25) 中，观察到两个轴向配位的 N¹ 单齿和赤道结合的 N²,N(pyr) 双齿配体 L¹⁰。N₆ 八面体 3:1 型配合物 Fe(II)(L¹⁰)₃₂·1.5MeCN·0.13H₂O·0.87MeO(t)Bu (27) 具有三个在 mer 构型中的 N²,N(pyr) 双齿配体 L¹⁰。两个密切相关的 N₆ 八面体配合物 [Fe(II)(L¹⁰)₂(NCS)₂] (29) 和 [Fe(II)(L¹⁰)₂(dca)₂] (30) 具有根本不同的结构。虽然配合物 29 具有两个赤道结合的 N²,N(pyr) 双齿配体 L¹⁰ 和轴向 NCS⁻ 共配体，但配合物 30 是具有轴向 N¹ 单齿配体 L¹⁰的一维双μ1,5-二氰基酰胺桥联聚合物。铁(II)配合物 28 和 29 的温度依赖性磁化率测量表明，3:1 型配合物 Fe(II)(L¹⁰)₃₂·H₂O (28) 在 300-2 K 的范围内处于低自旋态，2:1 型配合物 29 是自旋交叉化合物，T(1/2) = 269 K，而二氰基酰胺桥联配合物 30 即使在 113 K 以下仍保持高自旋态，根据 X 射线衍射数据。在 N₄S 四方锥配合物 [Cu(II)(L¹⁰)(NCS)₂] (31) 中发现了一个单端到端桥联的 NCS⁻ 共配体，该配合物在 300-2 K 的范围内表现出居里-外斯行为。对三唑并吡啶的配位化学进行了简要综述。
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