1005144-16-0Relevant articles and documents
Ruthenium complexes with vinyl, styryl, and vinylpyrenyl ligands: A case of non-innocence in organometallic chemistry
Maurer, Joerg,Linseis, Michael,Sarkar, Biprajit,Schwederski, Brigitte,Niemeyer, Mark,Kaim, Wolfgang,Zalis, Stanislav,Anson, Chris,Zabel, Manfred,Winter, Rainer F.
, p. 259 - 268 (2008/09/21)
We herein describe a systematic account of mononuclear ruthenium vinyl complexes L-{Ru}-CH=CH-R where the phosphine ligands at the (PR′ 3)2Ru(CO)Cl={Ru} moiety, the coordination number at the metal (L = 4-ethylisonicotinate or a vacant coordination site) and the substituent R (R = nbutyl, phenyl, 1-pyrenyl) have been varied. Structures of the enynyl complex Ru(CO)Cl(PPh3)2(η 1:η2-nBuHC=CHC≡CnBu), which results from the coupling of the hexenyl ligand of complex 1a with another molecule of 1-hexyne, of the hexenyl complexes (nBuCH=CH)Ru(CO) Cl(PiPr3)2 (1c) and (nBUCH=CH)RU(CO) Cl(PPh3)2(NC5H4COOEt-4) (1b), and of the pyrenyl complexes (1-Pyr-CH=CH)Ru(CO)Cl(PiPr3) 2 (3c) and (1-Pyr-CH=CH)Ru(CO)Cl(PPh3)3 (3a-P) have been established by X-ray crystallography. All vinyl complexes undergo a one-electron oxidation at fairly low potentials and a second oxidation at more positive potentials. Anodic half-wave or peak potentials show a progressive shift to lower values as π-conjugation within the vinyl ligand increases. Carbonyl band shifts of the metal-bonded CO ligand upon monooxidation are significantly smaller than is expected of a metal-centered oxidation process and are further diminished as the vinyl CH=CH entity is incorporated into a more extended π-system. ESR spectra of the electrogenerated radical cations display negligible g-value anisotropies and small deviations of the average g-value from that of the free electron. The vinyl ligands thus strongly contribute to or even dominate the anodic oxidation processes. This renders them a class of truly non-innocent ligands in organometallic ruthenium chemistry. Experimental findings are fully supported by quantum chemical calculations: The contribution of the vinyl ligand to the HOMO increases from 46% (Ru-vinyl delocalized) to 84% (vinyl dominated) as R changes from nbutyl to 1-pyrenyl.