Planar tetracoordinate carbon species involving beryllium substituents.
Planar tetracoordinate carbon species involving beryllium substituents.
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DOI：
10.1021/ic7017709
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发表时间：
2008-01
影响因子：
4.6
通讯作者：
Zhi‐Xiang Wang;Chenggen Zhang;Zhongfang Chen;P. Schleyer
中科院分区：
文献类型：
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作者：
Zhi‐Xiang Wang;Chenggen Zhang;Zhongfang Chen;P. Schleyer
平面四配位碳（ptC）的安排，可以通过采用基于铍的多个取代基，尽管其相当弱的π受体的能力。通过在B3 LYP/6-311++G（3df，2 p）和MP2/6-311 ++ G（3df，2 p）理论水平上详细阐述平面C（BeH）4（2-）原型，计算设计了各种含ptC的例子，其中一些具有多于一个ptC。原型更喜欢D（2 h）顺磁三重基态由于洪德规则，而不是一个单线态。高度极化的C-Be键大大削弱了T（d）C（BeH）4中四面体碳的刚性，而额外电子对C-Be和Be 4外围共价键的增强最终稳定了ptC。两个p π电子的离域性是适度的，但它们在最负电性的碳原子上的密度有助于稳定ptC排列。这与使p（pi）孤对离域以稳定ptC排列的常规策略相反。各种策略，以实现与PTC中性衍生物的证明。
Planar tetracoordinate carbon (ptC) arrangements can be achieved by employing multiple substituents based on beryllium, despite its rather weak pi-acceptor ability. A variety of ptC-containing examples, some with more than one ptC, have been designed computationally by elaborating the planar C(BeH) 4 (2-) prototype at B3LYP/6-311++G(3df,2p) and MP2/6-311++G(3df,2p) levels of theory for some small ptC representatives. The prototype prefers a D(2h) paramagnetic triplet ground state due to Hund's rule, rather than a singlet. The highly polarized C-Be bonding weakens the rigidity of the tetrahedral carbon in T(d)C(BeH) 4 enormously, and the enhancement of both C-Be and Be 4 peripheral covalent bonding exerted by the extra electrons stabilizes the ptC eventually. The delocalization of the two p pi electrons is only modest, but their density on the most electronegative carbon atom helps stabilize the ptC arrangement. This is in contrast to the conventional strategy to delocalize p(pi) lone pairs for stabilizing the ptC arrangement. Various strategies to achieve neutral derivatives with ptCs are demonstrated.