Westerhausen Matthias
Institute of Inorganic and Analytical Chemistry, Friedrich-Schiller-Universität Jena, August-Bebel-Str. 2, D-07743, Jena, Germany.
Dalton Trans. 2006 Oct 28(40):4755-68. doi: 10.1039/b609040k. Epub 2006 Sep 5.
Heterobimetallic compounds of the alkaline-earth metals show a wide structural variety with strongly differing reactivity patterns. The combination of magnesium and alkali metal amides yields cyclic molecules with an extreme high reactivity which often are considered as "inverse crowns" with the metal atoms as coordination sites for Lewis bases. In other metallates of the alkaline-earth metals an activation of alkyl groups succeeds. In alkaline-earth metal zincates an inverse coordination of the type M(2)(mu-R)(2)ZnR is observed and the alkyl groups are in bridging positions between zinc and the s-block metals thus forming a very reactive M-C-Zn three-center-two-electron bond. Furthermore, the metals of the carbon group form alkaline-earth metal-silicon, -germanium and -tin bonds or, in the presence of very strong Lewis bases, even solvent-separated ion pairs. For electronegative substituents at tin an inverse coordination mode such as M(mu-R)(2)SnR is observed.
碱土金属的异双金属化合物展现出广泛的结构多样性以及截然不同的反应模式。镁与碱金属酰胺的组合会生成具有极高反应活性的环状分子，这些分子常被视为“反冠醚”，其中金属原子作为路易斯碱的配位位点。在碱土金属的其他金属酸盐中，烷基得以活化。在碱土金属锌酸盐中，观察到了M(2)(μ-R)(2)ZnR这种类型的反向配位，且烷基处于锌与s区金属之间的桥连位置，从而形成非常活泼的M-C-Zn三中心两电子键。此外，碳族金属会形成碱土金属 - 硅、 - 锗和 - 锡键，或者在存在极强路易斯碱的情况下，甚至会形成溶剂分隔的离子对。对于锡上的电负性取代基，观察到了诸如M(μ-R)(2)SnR这样的反向配位模式。
