Miller Joel S
Department of Chemistry, University of Utah, Salt Lake City, UT 84112-0850, USA.
Angew Chem Int Ed Engl. 2006 Apr 10;45(16):2508-25. doi: 10.1002/anie.200503277.
Tetracyanoethylene (TCNE) undergoes numerous reactions and is reported to exist in many structural motifs. Identification of these forms and motifs can be challenging. Nonetheless, the number of nu(CN) absorptions and their frequencies provide insight with respect to the specific forms and charge on the TCNE fragment. Particularly informative is the average of the fundamental nu(CN) bands, as well as the length of the central C-C bond. This Review discusses the assignment of structure and formal charge for TCNE-containing compounds. Scrutiny of previous assignments reveals some discrepancies which are discussed, and provides a basis for further study of TCNE structure-function relationships. Several multimetal complexes with bridging TCNE units exhibit mixed valency and extensive delocalization. The scarcity of suitable model compounds, especially those with M(d(pi-pi*)) backbonding to the CN groups, have thwarted the detailed description of these valence ambiguous compounds; thus, new well-characterized polynuclear compounds are needed.
四氰基乙烯（TCNE）会发生多种反应，据报道存在于许多结构基序中。识别这些形式和基序可能具有挑战性。尽管如此，ν(CN)吸收峰的数量及其频率能为TCNE片段的特定形式和电荷提供线索。特别有信息量的是基本ν(CN)带的平均值以及中心C-C键的长度。本综述讨论了含TCNE化合物的结构和形式电荷的归属。对先前归属的审查揭示了一些差异并进行了讨论，为进一步研究TCNE结构-功能关系提供了基础。几种具有桥连TCNE单元的多金属配合物表现出混合价态和广泛的离域。合适的模型化合物稀缺，尤其是那些具有M(d(π-π*))与CN基团反馈键合的化合物，阻碍了对这些价态不明确化合物的详细描述；因此，需要新的特征明确的多核化合物。
