Bis-Adducts of Substituted Phenylethynyl on a Ru₂(DMBA)₄ Core: Effect of Donor/Acceptor Modifications

The reactions between arylethynes (either BuLi activated or Et3N assisted) and Ru2(RDMBA)4X2, where RDMBA is either N,N‘-dimethylbenzamidinate (R = H) or N,N‘-dimethyl-m-methoxybenzamidinate (R = m-MeO) and X is either Cl- or NO3-, resulted in the compounds Ru2(RDMBA)4(C⋮CC6H4Y)2 (Y = H (1a,b), 4-NO2 (2a,b), 4-CN (3a,b), 3-CN (4a,b), 4-NMe2 (5a,b); R = H (a), m-MeO (b)). The single-crystal X-ray diffraction study of 1b and 2a revealed the linear alignment of the arylethynyl ligands along the Ru−Ru vector. All of the compounds display two Ru-based one-electron processes, an oxidation and a reduction, and their electrode potentials correlate linearly with the Hammett constants of substituent Y. Compounds 5a,b display an additional pair of one-electron processes attributed to the oxidation of 4-NMe2 groups, on the basis of which an extensive electron delocalization along the metallayne backbone was inferred.以经正丁基锂（BuLi）活化或三乙胺（Et3N）辅助的芳基乙炔与Ru₂(RDMBA)₄X₂为反应物，其中RDMBA可为N,N'-二甲基苯甲脒（R=H）或N,N'-二甲基间甲氧基苯甲脒（R=m-MeO），X可为Cl⁻或NO₃⁻，反应得到系列化合物Ru₂(RDMBA)₄(C≡CC₆H₄Y)₂（Y = H（1a,b）、4-NO₂（2a,b）、4-CN（3a,b）、3-CN（4a,b）、4-NMe₂（5a,b）；R=H对应a系列，m-MeO对应b系列）。 对1b和2a的单晶X射线衍射（single-crystal X-ray diffraction）研究表明，芳基乙炔基配体沿Ru-Ru键轴呈线性排布。 所有目标化合物均表现出两个基于Ru的单电子氧化还原过程（一个氧化过程与一个还原过程），其电极电势与取代基Y的哈密特常数（Hammett constants）呈线性相关。 化合物5a与5b额外呈现出一对单电子过程，该过程可归因为4-NMe₂基团的氧化；据此可以推断，电子沿金属炔基骨架存在广泛离域。