Oxidative Dimerization of Arylalkynyl–Ruthenium Complexes

Chemical oxidation of Ru(CCPh)(PPh3)2Cp with [FeCp2]PF6 affords the binuclear cationic complexes [Cp(PPh3)2Ru{CCHC6H4CPhC}Ru(PPh3)2Cp](PF6)2 (2) and [Cp(PPh3)2Ru{CC(C6H4)CPhC}Ru(PPh3)2Cp]PF6 (3) by radical coupling at sites shown to be electron-rich by DFT studies, particularly involving the acetylide Cβ and Ph Cpara atoms and, to a lesser extent, the Cp carbon atoms. Complexes 2 and 3 are related by facile deprotonation/protonation reactions. When the 4-position of the Ph group is blocked, attack by Cβ upon the Cp group occurs to give the bis(vinylidene) [Ru{CC(C6H4Me-4)-η-C5H4[Ru(PPh3)2{CCH(C6H4Me-4)}(PPh3)2Cp]}](PF6)2 (4), which can be deprotonated to give [Ru{CC(C6H4Me-4)-η-C5H4[Ru(PPh3)2{CC(C6H4Me-4)}(PPh3)2Cp]}]PF6 (5). Complex 4 is rapidly oxidized during workup to form [Ru{CC(C6H4Me)-η-C5H4[Ru(CO)(PPh3)2]}(PPh3)2Cp](PF6)2 (6). Single-crystal X-ray structure determinations of the salts 2, 3, and 6 are reported.

以六氟磷酸二茂铁([FeCp₂]PF₆)对(苯乙炔基)双(三苯基膦，triphenylphosphine, PPh₃)环戊二烯基(cyclopentadienyl, Cp)合钌进行化学氧化，通过自由基偶联反应得到双核阳离子配合物[Cp(PPh₃)₂Ru{=C=CHC₆H₄CPh=C=}Ru(PPh₃)₂Cp](PF₆)₂（产物2）与[Cp(PPh₃)₂Ru{C≡C(C₆H₄)CPh=C=}Ru(PPh₃)₂Cp]PF₆（产物3）；该自由基偶联发生在经密度泛函理论（Density Functional Theory, DFT）研究证实为富电子的位点，尤其涉及乙炔基的Cβ原子与苯环的对位碳原子，环戊二烯基碳原子的参与程度相对较弱。配合物2与3可通过简便的脱质子/质子化反应相互转化。当苯环（Ph基团）的4位被取代基占据时，Cβ原子会进攻环戊二烯基配体，得到双(亚乙烯基，vinylidene)配合物[Ru{=C=C(C₆H₄Me-4)-η-C₅H₄[Ru(PPh₃)₂{=C=CH(C₆H₄Me-4)}(PPh₃)₂Cp]}](PF₆)₂（产物4）；该配合物可经脱质子反应得到[Ru{=C=C(C₆H₄Me-4)-η-C₅H₄[Ru(PPh₃)₂{C≡C(C₆H₄Me-4)}(PPh₃)₂Cp]}]PF₆（产物5）。配合物4在后处理过程中会被快速氧化，生成[Ru{=C=C(C₆H₄Me)-η-C₅H₄[Ru(CO)(PPh₃)₂]}(PPh₃)₂Cp](PF₆)₂（产物6）。本文报道了盐类2、3与6的单晶X射线衍射结构解析结果。