EaSTCHEM School of Chemistry, University of St Andrews, St Andrews, Fife, UK.
Dalton Trans. 2012 Mar 21;41(11):3154-65. doi: 10.1039/c2dt12031c. Epub 2012 Jan 30.
Sterically crowded peri-substituted selenium and tellurium acenaphthene donors D1-D7 [Acenap(EPh)(Br) E = Se, Te; Acenap(SePh)(EPh) E = Se, S; Acenap(TePh)(EPh) E = S, Se, Te] react with dibromine and diiodine acceptors to afford a group of structurally diverse addition products 1-12, comparable in some cases to previously reported naphthalene analogues. Tellurium donors D4-D6 react conventionally with the dihalogens to afford insertion adducts 6-11 (X-R(2)Te-X) exhibiting molecular see-saw geometries, characterised by hypervalent X-Te-X quasi-linear fragments. The reactions of selenium donors D1-D3 with diiodine afford expected neutral charge-transfer (CT) spoke adducts 1, 4 and 5 (R(2)Se-I-I) containing quasi-linear Se-I-I alignments. Conversely, treatment of D2 and D3 with dibromine results in the formation of two tribromide salts 2 and 3 containing bromoselanyl cations R(2)Se-Br···Br-Br(2), each exhibiting a quasi-linear three-body Br-Se···E (E = Se, S) fragment. The peri-bonding in these species can be thought of as a weak hypervalent G···Se-X three-centre, four-electron (3c-4e) type interaction, closely related to the T-shaped 3c-4e interaction. Density-functional calculations performed on 2 and 3 and their bare cations (2a and 3a) reveal Wiberg bond indices of 0.25-0.37, suggesting substantial 3c-4e character in these systems. The presence of such an interaction operating in 2 and 3 alleviates steric strain within the peri-region and minimises the degree of molecular distortion required to achieve a relaxed geometry. Ditellurium donor D7 reacts with dibromine to afford an unorthodox insertion adduct 12 containing a Te-O-Te bridge and two quasi-linear Br-Te-O fragments, with the central tellurium atoms assuming a molecular see-saw geometry. Whilst DFT calculations indicate 12 is thermodynamically unfavourable, its formation is viable under experimental conditions.
位阻拥挤的取代硒和碲吖啶供体 D1-D7 [吖啶（EPh）（Br）E = Se，Te；吖啶（SePh）（EPh）E = Se，S；吖啶（TePh）（EPh）E = S，Se，Te] 与二溴和二碘受体反应，生成一组结构多样的加成产物 1-12，在某些情况下与先前报道的萘类似物相当。碲供体 D4-D6 与二卤化物反应常规生成插入加合物 6-11（X-R(2)Te-X），具有分子跷跷板几何形状，由高价 X-Te-X 准线性片段特征。硒供体 D1-D3 与二碘反应生成预期的中性电荷转移（CT）辐条加合物 1、4 和 5（R(2)Se-I-I），其中包含准线性 Se-I-I 排列。相反，D2 和 D3 与二溴反应生成含有溴代硒𬭩阳离子R(2)Se-Br···Br-Br(2)的两种三溴化物盐 2 和 3，每个都含有准线性三原子 Br-Se···E（E = Se，S）片段。这些物种中的近键可以被认为是弱超价 G···Se-X 三中心、四电子（3c-4e）型相互作用，与 T 形 3c-4e 相互作用密切相关。对 2 和 3 及其裸露阳离子（2a 和 3a）进行的密度泛函计算显示 Wiberg 键指数为 0.25-0.37，表明这些体系中存在大量 3c-4e 特征。这种相互作用的存在在 2 和 3 中减轻了近位区域内的空间拥挤，并最小化了实现松弛几何所需的分子变形程度。双碲供体 D7 与二溴反应生成含有 Te-O-Te 桥和两个准线性 Br-Te-O 片段的非正统插入加合物 12，其中中心碲原子采用分子跷跷板几何形状。虽然 DFT 计算表明 12 在热力学上是不利的，但在实验条件下其形成是可行的。
