Electrochemical Behavior of Phosphine-Substituted Ruthenium(II) Polypyridine Complexes with a Single Labile Ligand

A series of phosphine-substituted
ruthenium polypyridine complexes, cis­(P,Cl)-[Ru­(trpy)­(Pqn)­Cl]­PF6 (cis-Cl), trans­(P,MeCN)-[Ru­(trpy)­(Pqn)­(MeCN)]­(PF6)2 (trans-PN), cis­(P,MeCN)-[Ru­(trpy)­(Pqn)­(MeCN)]­(PF6)2 (cis-PN), and [Ru­(trpy)­(dppbz)­(MeCN)]­(PF6)2 (PP), were synthesized and crystallographically
characterized (trpy = 2,2′:6′,2″-terpyridine,
Pqn = 8-(diphenylphosphanyl)­quinoline, and dppbz = 1,2-bis­(diphenylphosphanyl)­benzene).
In electrochemical measurements for cis-PN and PP, the reduction of cis-PN resulted in the formation of trans-PN via cis–trans isomerization and that of PP proceeded via a two-electron-transfer reaction. The mechanism of
the electrochemical behaviors is discussed through consideration of
five-coordinated species, [Ru­(trpy)­(Pqn)]n+ or [Ru­(trpy)­(dppbz)]n+ (n = 0–2), formed by liberation of a monodentate labile ligand.

本研究合成了一系列膦取代（phosphine-substituted）钌多吡啶配合物（ruthenium polypyridine complexes），并通过单晶X射线衍射对其进行了结构表征，具体包括顺式(P,Cl)-[Ru(trpy)(Pqn)Cl]PF₆（记为cis-Cl）、反式(P,MeCN)-[Ru(trpy)(Pqn)(MeCN)](PF₆)₂（记为trans-PN）、顺式(P,MeCN)-[Ru(trpy)(Pqn)(MeCN)](PF₆)₂（记为cis-PN）以及[Ru(trpy)(dppbz)(MeCN)](PF₆)₂（记为PP）。其中trpy为2,2':6',2''-三联吡啶（2,2':6',2''-terpyridine），Pqn为8-(二苯基膦基)喹啉（8-(diphenylphosphanyl)quinoline），dppbz为1,2-双(二苯基膦基)苯（1,2-bis(diphenylphosphanyl)benzene）。
针对cis-PN与PP的电化学测试结果表明，cis-PN在还原过程中会通过顺反异构化反应转化为trans-PN，而PP的还原则通过双电子转移反应进行。本研究通过考察解离单齿易脱落配体后生成的五配位物种[Ru(trpy)(Pqn)]ⁿ⁺或[Ru(trpy)(dppbz)]ⁿ⁺（n=0~2），对上述电化学行为的反应机理展开了讨论。