Synthesis and reactivity of water-soluble arene-ruthenium(II) complexes and dimerization of terminal alkynes in organic and aqueous media

Treatment of the dimeric precursor [{RuCl(mu-Cl) (eta(6)-C6H5OCH2CH2OH)}(2)] (1) with HN=CPh2 in the presence of H2O afforded the arene-ruthenium(II) complex [(eta(6)-C(6)H(5)OCH(2)CH2OH) (HN=CPh2) RuCl2] (2), as well as the aquo-species [(eta(6)-C6H5OCH2CH2OH) (H2O)RuCl2] (3). The hydroxyethoxy substituent on the arene induces water-solubility of the resulting complexes. Reaction of 2 with HC C(O)OR1 in R2OH afforded the chelate vinyl ether complexes [Tp(PPh3) Ru-C(OR2) CHC(O) OR1] (4a, R-1 = Me, R-2 = Me; 4b, R-1 = Et, R-2 = Me; 4c, R-1 = Et, R-2 = Et; 4d, R-1 = Me, R-2 = Et), respectively. Preliminary results on the catalytic activity of 2 are also accessible. Intriguingly, complex 2 catalyzes the dimerization of some terminal alkynes HC CR in organic and aqueous medium. Whereas with R = COOMe, E-selective head-to-head dimerization takes place exclusively, in the case of R = SiMe3, t-Bu isomeric mixtures of head-to-head and head-to-tail coupling products are obtained. The structure of 3 has been determined by X-ray diffraction analysis. (C) 2014 Elsevier B.V. All rights reserved.