Thienyl-Substituted Allenylideneruthenium(II) Complexes: Synthesis, Spectroscopic Characterization, and Electrochemical Studies

Two propargylic alcohols incorporating a thienyl moiety were synthesized, and their subsequent reaction to form allenylideneruthenium(II) complexes is reported. The alkynol 4-hydroxy-4-ethynylcyclopenta[2,1-b:3,4-b′]dithiophene (4) reacts with cis-[RuCl2(P∩P)2] (P∩P = dppm, dppe) to afford the allenylidene complexes trans-[RuCl(P∩P)2{CCC(4-cyclopentadithiophene)}]PF6 (P∩P = dppm, 5a; dppe, 5b). Similar reactions of cis-[RuCl2(P∩P)2] with 1,1-di(2′-thienyl)prop-2-yn-1-ol (2) yield products consistent with formulation as an allenylideneruthenium(II) complex, although with no identifiable counteranion. In contrast the reaction of 2 with [RuClCp(dppe)] readily affords the deep purple complex [RuCp(dppe){CCC(2-thienyl)2}]PF6. The complexes have been characterized by spectroscopy and mass spectrometry, and a single-crystal X-ray structural determination of complex 5a was undertaken. The allenylidene complexes obtained in a pure state have also been investigated through cyclic voltammetry, and preliminary investigations illustrate their potential as synthons for organometallic polymers via electropolymerization.本工作合成了两种带有噻吩基（thienyl）片段的炔丙醇（propargylic alcohol），并报道了它们用于构建亚丙二烯基钌(II)配合物（allenylideneruthenium(II) complex）的后续反应。炔醇4-羟基-4-乙炔基环戊二[2,1-b:3,4-b′]二噻吩（4）与顺式-[RuCl₂(P∩P)₂]（双齿膦配体（P∩P）= dppm（双(二苯基膦)甲烷）、dppe（双(二苯基膦)乙烷））反应，得到亚丙二烯基配合物反式-[RuCl(P∩P)₂{=C=C=C(4-环戊二噻吩基)}]PF₆（其中P∩P为dppm时对应产物5a，为dppe时对应产物5b）。顺式-[RuCl₂(P∩P)₂]与1,1-二(2'-噻吩基)丙-2-炔-1-醇（2）的类似反应所得产物符合亚丙二烯基钌(II)配合物的组成特征，尽管未分离得到可识别的抗衡阴离子。与之相反，化合物2与[RuClCp(dppe)]（其中Cp为环戊二烯基（Cyclopentadienyl））的反应可便捷地得到深紫色配合物[RuCp(dppe){=C=C=C(2-噻吩基)₂}]PF₆。已通过光谱学与质谱法对上述配合物进行表征，并对配合物5a开展了单晶X射线结构测定。以纯品形式获得的亚丙二烯基配合物还通过循环伏安法（cyclic voltammetry）进行了研究，初步研究结果表明，它们有望作为通过电聚合法（electropolymerization）制备有机金属聚合物（organometallic polymer）的合成子（synthon）。