Artetxe Beñat, Reinoso Santiago, San Felices Leire, Vitoria Pablo, Pache Aroa, Martín-Caballero Jagoba, Gutiérrez-Zorrilla Juan M
Departamento de Química Inorgánica, Facultad de Ciencia y Tecnología, Universidad del País Vasco UPV/EHU , P.O. Box 644, 48080 Bilbao, Spain.
Inorg Chem. 2015 Jan 5;54(1):241-52. doi: 10.1021/ic502232v. Epub 2014 Nov 14.
The first organic derivatives of 3d-metal-disubstituted Krebs-type polyoxometalates have been synthesized under mild bench conditions via straightforward replacement of labile aqua ligands with N,O-chelating planar anions on either preformed or in situ-generated precursors. Nine hybrid clusters containing carboxylate derivatives of five- or six-membered aromatic N-heterocycles as antenna ligands have been obtained as pure crystalline phases and characterized by elemental and thermal analyses, infrared spectroscopy, and single-crystal X-ray diffraction. They all show the general formula {M(II)L(H2O)}2(WO2)2(B-β-XW9O33)2 and can be classified as follows: 1-SbM, where L = 1H-imidazole-4-carboxylate (imc), X = Sb(III), n = 12, and M(II) = Mn, Co, Ni, Zn; 1-TeM, where L = imc, X = Te(IV), n = 10, and M(II) = Mn, Co; 2-SbNi, where L = 1H-pyrazole-3-carboxylate (pzc), X = Sb(III), n = 12, and M(II) = Ni; and 3-SbM, where L = pyrazine-2-carboxylate (pyzc), X =Sb(III), n = 12, and M(II) = Co, Zn. The 3d-metal-disubstituted tungstotellurate(IV) skeleton of compounds 1-TeM is unprecedented in polyoxometalate chemistry. The stability of these hybrid Krebs-type species in aqueous solution has been confirmed by (1)H NMR spectroscopy performed on the diamagnetic 1-SbZn and 3-SbZn derivatives. Our systematic study of the reactivity of disubtituted Krebs-type polyoxotungstates toward diazole-, pyridine-, and diazinecarboxylates demonstrates that organic derivatization is strongly dependent on the nature of the ligand, as follows: imc displays a "universal ligand" character, as functionalization takes place regardless of the external 3d metal and heteroatom; pzc and pyzc show selectivity toward specific 3d metals; pyridazine-3-carboxylate and pyrimidine-4-carboxylate promote partial decomposition of specific precursors, leading to [M(II)L2(H2O)2] complexes; and picolinate is inert under all conditions tested.
3d 金属双取代的克雷布斯型多金属氧酸盐的首批有机衍生物已在温和的实验室条件下合成，方法是在预制或原位生成的前体上，用 N,O - 螯合平面阴离子直接取代不稳定的水合配体。已获得九个含有五元或六元芳香族 N - 杂环羧酸盐衍生物作为天线配体的杂化簇，为纯晶相，并通过元素分析、热分析、红外光谱和单晶 X 射线衍射进行了表征。它们都具有通式{M(II)L(H₂O)}₂(WO₂)₂(B - β - XW₉O₃₃)₂，可分类如下：1 - SbM，其中 L = 1H - 咪唑 - 4 - 羧酸盐（imc），X = Sb(III)，n = 12，且 M(II) = Mn、Co、Ni、Zn；1 - TeM，其中 L = imc，X = Te(IV)，n = 10，且 M(II) = Mn、Co；2 - SbNi，其中 L = 1H - 吡唑 - 3 - 羧酸盐（pzc），X = Sb(III)，n = 12，且 M(II) = Ni；以及 3 - SbM,其中 L = 吡嗪 - 2 - 羧酸盐（pyzc）,X = Sb(III),n = 12,且 M(II) = Co、Zn。化合物 1 - TeM 的 3d 金属双取代钨碲酸盐(IV)骨架在多金属氧酸盐化学中是前所未有的。通过对抗磁性的 1 - SbZn 和 3 - SbZn 衍生物进行的¹H NMR 光谱，证实了这些杂化克雷布斯型物种在水溶液中的稳定性。我们对双取代克雷布斯型聚氧钨酸盐与二唑、吡啶和二嗪羧酸盐反应性的系统研究表明，有机衍生化强烈依赖于配体的性质，具体如下：imc 表现出“通用配体”特征，因为无论外部 3d 金属和杂原子如何，功能化都会发生；pzc 和 pyzc 对特定的 3d 金属表现出选择性；哒嗪 - 3 - 羧酸盐和嘧啶 - 4 - 羧酸盐会促进特定前体的部分分解，生成[M(II)L₂(H₂O)₂]配合物；而吡啶甲酸酯在所有测试条件下都是惰性的。
