Unusual coordination mode of thiosemicarbazone ligands. A search for the origin
Unusual coordination mode of thiosemicarbazone ligands. A search for the origin
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DOI：
10.1021/ic991083r
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发表时间：
2000-03-20
影响因子：
4.6
通讯作者：
Bhattacharya, S
中科院分区：
文献类型：
--
作者：
Basuli, F;Peng, SM;Bhattacharya, S
本文合成了12个钌和锇的混配缩氨基硫脲配合物，其中10个为[M（bpy）（2）-（bztsc-R）] ClO_4（M = Ru，Os; bpy = 2，2 ′-联吡啶，Hbztsc-R =苯甲醛缩氨基硫脲），2个为[M（bpy）（2）（actsc）] ClO_4（Hactsc =丙酮缩氨基硫脲）。所有的配合物都是抗磁性的（低自旋d（6），S = 0），在乙腈溶液中，在可见光区显示出几个强烈的金属-配体电荷转移（MLCT）跃迁。用X射线晶体学方法测定了Hbztsc-OMe、[Ru（bpy）（2）（bztsc-NO2）] ClO 4和[Ru（bpy）（2）（actsc）] ClO 4的晶体结构。苯甲醛缩氨基硫脲以顺式存在，苯基反式位于肼氮上。苯甲醛缩氨基硫脲配体通过肼基氮和硫以近似67度的咬合角与金属配位，形成四元螯合环。然而，actsc配体通过亚胺氮和硫配位，形成具有类似于81度的咬角的五元螯合环。研究了两类缩氨基硫脲配体的配位方式的差异，bztsc-R和actsc，似乎是由于芳基和甲基反式肼氮的空间体积的差异。在乙腈溶液中，它们都显示出在0.18-0.58 V vs SCE范围内的可逆金属（II）-金属（III）氧化，随后在1.11-1.60 V vs SCE范围内的不可逆氧化。在-1.53 ~-1.96VvsSCE范围内，还观察到配位联吡啶的两个连续单电子还原。
Twelve mixed-ligand thiosemicarbazone complexes of ruthenium and osmium, ten of general formula [M(bpy)(2)-(bztsc-R)]ClO4, (M = Ru, Os; bpy = 2,2'-bipyridine, Hbztsc-R = benzaldehyde thiosemicacbazone) and two of type [M(bpy)(2)(actsc)]ClO4 (Hactsc = acetonethiosemicarbazone), have been synthesized and characterized. All the complexes are diamagnetic (low-spin d(6), S = 0) and in acetonitrile solution show several intense metal-to-ligand charge-transfer (MLCT) transitions in the visible region. Structures of Hbztsc-OMe, [Ru(bpy)(2)(bztsc-NO2)]ClO4 and [Ru(bpy)(2)(actsc)]ClO4 have been determined by X-ray crystallography. Benzaldehyde thiosemicarbazone exists in the thione form with the phenyl group trans to the hydrazinic nitrogen. The benzaldehyde thiosemicarbazone ligand coordinates to the metals through the hydrazinic nitrogen and sulfur with a bite angle of similar to 67 degrees, forming a four-membered chelate ring. However, the actsc ligand coordinates through the imine nitrogen and sulfur, forming a five-membered chelate ring with a bite angle of similar to 81 degrees. The difference in coordination modes of two types of thiosemicarbazone ligands, viz., bztsc-R and actsc, appears to result from the difference in steric bulk of the aryl and methyl group trans to the hydrazinic nitrogen. In acetronitrile solution they all show a reversible metal(II)-metal(III) oxidation in the range 0.18-0.58 V vs SCE followed by an irreversible oxidation in the range 1.11-1.60 V vs SCE. Two successive one-electron reductions of the coordinated bipyridine are also observed in the range -1.53 to -1.96 V vs SCE.