2- Vinylpyridine, ruthenium complexes

Moreno-Manas et al. [98] reported on a similar effect of triphenylphosphine for the Michael addition of active methylene compounds to n-acceptor olefins such as methyl vinyl ketone, acrylonitrile, and 2-vinylpyridine and dialkyl azodi-carboxylates. They compared the reactivity of RuH2(PPh3)4, RuCl2(PPh3)3, and PPh3 and concluded that for /5-diketones, ketoesters, and ketoamides, triphenylphosphine released from the ruthenium complexes contributes totally or partially to the catalysis. 

Nakahira, T. Graetzel, M. Visible light sensitization of platinized T102 photocatalyst by surface-adsorbed poly(4-vinylpyridine) derivatized with ruthenium trisbipyridyl complex, Makromol. Chem., Rapid Commun. 1985, 6, 341. 

Another example is the ruthenium-catalysed alkenylation of pyridine which is performed in the presence of the same catalyst precursor RuCl(Cp)(PPh3)2 (20 mol %)/NaPF6 (20 mol %) at 150 °C [63]. The use of trimethylsilylalkynes, which are also known to produce vinylidene complexes rather than terminal alkynes, avoids the dimerization of the alkyne and favours the formation of the (E)-vinylpyridine (Scheme 17). The reaction has been applied to a variety of silylated alkynes and substituted pyridines (Fig. 8). 

Electropolymerization of 4-Vinylpyridine Complexes. Investigations of Structural and Electronic Influences on Thin Film Formation. The recent discovery of the reductive polymerization of complexes containing vinylpyridyl ligands (lg), such as Ru -(bpy)2(vpy)22+ has led to the preparation of homogeneous thin layers of very stable electroactive polymers. This method has been extended to 4-vinyl-4 -methyl-2,2 -bipyridine (lg, 21a) and 4-vinyl-l,10-phenanthroline (21b) on both ruthenium and iron. In the following section we discuss our results on thin films derived from the polymerizable ligands BPE and the trans-4 -X-stilbazoles, (4 -X-stilb X - Cl, OMe, CN and H). 

The Dublin group has also reported a three-color electrochromic metallopoly mer 6 based on a ruthenium phenolate complex bound to poly(4-vinylpyridine). The reversible color changes (wine red to green) are associated with the Ru(II) oxidation, whereas the mixed redox state produces a red-orange. The charge transport parameters of the polymer were thoroughly characterized [27,28]. 

D. Abruna, P. Denisevich, M. Umana, T. J. Meyer, and R. W. Murray, Rectifying interfaces using two-layer films of electrochemically polymerized vinylpyridine and vinylbipyridine complexes of ruthenium and iron on electrodes, J.Am.Chem.Soc., 103 1 (1981). 

Castro-Rodrigo R, Esteruelas MA, Fuertes S, Lopez AM, Mozo S, Onate E. Olefin-alkylidene equilibrium of 2-vinylpyridine in osmimn- and ruthenium-hydrido-tris (pyrazolybborate and osmium-cyclopentadienyl complexes. Organometallics. 2009 28 594-5951. 

Photosubstitution at ruthenium(II)-bipyridyl complexes has been described for the polymer-bound complex [Ru (bipy)2 (pvp)2f", where pvp is poly(4-vinylpyridine). Reactivity is lower here than for equivalent monomeric complexes. " Photoisomerization cis trans) of [Ru(bipy)2(OH2)2] has been studied at the surface of hectorite, a layer silicate, and the results compared with those for aqueous solution. " ... 

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