Theoretical and Experimental Investigations on Hypoelectronic Heterodimetallaboranes of Group 6 Transition Metals

Density functional theory (DFT) has been used to probe the bonding and electronic properties of dimolybdaborane [(Cp*Mo)2B5H9], 1 (Cp* = η5-C5Me5), and several other heterodimolybdaborane clusters, such as [(Cp*Mo)2B5(μ3-OEt)­H7] (2), [(Cp*Mo)2B5(μ3-OEt)­(n-BuO)­H6] (3), [(η5-C5H5W)2B4H4S2] (4), and [(Cp*Mo)2B4H4E2] (5–7, where, for 5, E = S, for 6, E = Se, and for 7, E = Te). The DFT results were also used to address some key points such as (i) the metal–metal bond length, (ii) the location and number of bridging and terminal hydrogen atoms, (iii) the molecular orbital analysis, and (iv) the assignment of 11B and 1H NMR chemical shifts. These studies further provide meticulous insight into similarities and differences between various dimetallaborane clusters 1–7. In addition, the crystal structures of 5 and 7 are reported, which come on top of the already existing literature of dimetallaboranes and support the theoretical findings.本研究采用密度泛函理论（Density functional theory，DFT）对二钼硼烷类化合物[(Cp*Mo)₂B₅H₉]（1，其中Cp*为η⁵-五甲基环戊二烯基，即η⁵-C₅Me₅）以及其他若干杂二钼硼烷簇合物开展了成键与电子性质的探究，所涉簇合物包括[(Cp*Mo)₂B₅(μ₃-OEt)H₇]（2）、[(Cp*Mo)₂B₅(μ₃-OEt)(n-BuO)H₆]（3）、[(η⁵-C₅H₅W)₂B₄H₄S₂]（4）以及[(Cp*Mo)₂B₄H₄E₂]（5~7，其中5的E为S，6为Se，7为Te）。本研究同时利用DFT计算结果对若干关键科学问题进行了系统探讨，具体包括：(i) 金属-金属键长；(ii) 桥氢与端基氢的位置及数目；(iii) 分子轨道分析；(iv) ¹¹B与¹H核磁共振化学位移的归属。上述研究进一步细致阐明了1~7号各类二金属硼烷簇合物之间的异同点。此外，本研究还报道了5号与7号化合物的晶体结构，该结果补充了已有的二金属硼烷类化合物相关文献，并为本次理论计算结果提供了实验支撑。