"Bent bonds" between bismuth and carbon atoms as a result of C-H activation in Mo-Bi complexes.
"Bent bonds" between bismuth and carbon atoms as a result of C-H activation in Mo-Bi complexes.
复制标题
Mo-Bi 络合物中 C-H 活化导致铋和碳原子之间形成“弯曲键”。
作者：
S. Roggan;G. Schnakenburg;C. Limberg;S. Sandhöfner;H. Pritzkow;B. Ziemer
钼二氢化合物与两个等价物[Bi(OtBu)(3)]通过乙醇消除反应，生成含有两个Mo-Bi金属键的化合物[Cp(2)Mo{Bi(OtBu)(2)}(2)](1)。如果两种试剂以1：1的比例使用，则会发生连续缩合反应。这些最初导致[{Cp(2)Mo}(2){Mu-Bi(OtBu)}(2)](2)，然而，它在溶液中非常不稳定并且通过额外的醇消除而分解：络合物诱导的邻近效应促进了残留的醇氧配体在环戊二烯配体内的C-H键的断裂，从而自发地释放了另外两个等价醇，从而得到两个具有桥联钼铋金属键的CP配体的异构体化合物3和4：第一异构体(3)包含两个Mu(2)-ETA(5)：ETA(1)-C(5)H(4)，第二异构体(4)包含一个桥联Mu(3)-ETA(5)：ETA(1)：ETA(1)-C(5)H(3)配体。这些配体同时与钼和铋原子结合是通过铋和某些碳中心之间的“弯曲键”实现的。通过基于密度泛函理论(DFT)、分子中原子理论(AIM)、自然键序(NBO)和电子局域函数(ELF)的计算，分析了这些不寻常的成键情况。根据结果，可以根据碳离子中心与铋离子相互作用(即闭壳相互作用)来理解这些键。用理论方法研究了这些键的形成以及从2到3和4所涉及的热力学/动力学，从而使产物的形成合理化。测定了所有四个新化合物的晶体结构。并以[(Me)Cp(2)MoH(2)]/[Bi(OtBu)(3)]体系的相应结果为背景，讨论了这些结构的性质和形成机理。
The reaction of molybdocenedihydride with two equivalents of [Bi(OtBu)(3)] proceeds via alcohol elimination and provides the compound [Cp(2)Mo{Bi(OtBu)(2)}(2)] (1), which contains two Mo--Bi metal bonds, in good yields. If the two reagents are employed in a 1:1 ratio continuative condensation reactions occur. These initially lead to [{Cp(2)Mo}(2){mu-Bi(OtBu)}(2)] (2), which, however, is very unstable in solution and decomposes via additional alcohol elimination: Complex-induced proximity effects facilitate the cleavage of C--H bonds within the cyclopentadienyl ligands by the residual alkoxide ligands, so that spontaneously two further equivalents of alcohol are released, thereby yielding two isomeric compounds 3 and 4 with Cp ligands bridging Mo--Bi metal bonds: The first isomer (3) contains two mu(2)-eta(5):eta(1)-C(5)H(4) ligands, the second isomer (4) contains one bridging mu(3)-eta(5):eta(1):eta(1)-C(5)H(3) ligand. The binding of these ligands to molybdenum and bismuth atoms at the same time is made possible through "bent bonds" between the bismuth and certain carbon centres. These unusual bonding situations were analysed by means of calculations based on density functional theory (DFT), the atoms in molecules (AIM) theory, natural bond order (NBO) considerations and the electron localisation function (ELF). According to the results the bonds can be understood in terms of carbanionic centres interacting with bismuth cations (i.e. closed-shell interactions). The formation of these bonds and the thermodynamics/kinetics involved on going from 2 to 3 and 4 were also studied by theoretical methods, so that the product formation is rationalised. The crystal structures of all four new compounds were determined. These structures but also the properties and mechanisms of formation are discussed against the background of the corresponding results obtained while studying the system [(Me)Cp(2)MoH(2)]/[Bi(OtBu)(3)].