Department of Chemistry, North Eastern Hill University, Shillong, 793022, Meghalaya, India.
Center for Computational Quantum Chemistry, University of Georgia, Athens, GA, 30602, USA.
Chemphyschem. 2021 Oct 5;22(19):2014-2024. doi: 10.1002/cphc.202100121. Epub 2021 Aug 18.
Vanadium forms binuclear complexes with a variety of ligands often containing V≡V triple bonds. Many tetragonal divanadium paddlewheel complexes with bridging bidentate ligands have been experimentally characterized. This research exhaustively treats model tetragonal, trigonal, and digonal paddlewheel-type divanadium complexes V L (L=formamidinate, guanidinate, and carboxylate; x=2, 3, 4), each in the three lowest-energy spin states. The V-V formal bond orders are obtained from metal-metal MO diagrams for representative structures. A number of short V-V multiple bonds of order 3, 3.5, and 4 are found in these model complexes. The short V≡V triple bonds and singlet ground state predicted here for the model tetragonal complexes correspond well with the limited experimental results for the series of known tetragonal paddlewheels. Digonal divanadium lanterns with very short V-V quadruple bonds are predicted as interesting synthetic targets. The V-V bond distances are categorized into distinct ranges according to the formal bond order values from 0.5 to 4. These bond length ranges are compared with the ranges compiled for other divanadium complexes including carbonyl complexes.
钒可以与多种配体形成双核配合物，这些配体通常含有 V≡V 三键。许多具有桥联双齿配体的四方双钒桨轮配合物已被实验表征。本研究详尽地处理了模型四方、三角和二角桨轮型双钒配合物 VL（L=甲酰胺基、胍基和羧酸盐；x=2、3、4），每个配合物都处于三种最低能量自旋态。代表性结构的金属-金属 MO 图得到了 V-V 形式键序。在这些模型配合物中发现了许多短的 V-V 多重键，其键序为 3、3.5 和 4。此处预测的模型四方配合物中的短 V≡V 三键和单线态基态与已知四方桨轮系列的有限实验结果非常吻合。具有非常短 V-V 四重键的二角双钒灯笼被预测为有趣的合成目标。V-V 键距离根据形式键序值（0.5 至 4）分为不同的范围。这些键长范围与为包括羰基配合物在内的其他双钒配合物编制的范围进行了比较。
