Two isomeric Ru(II) complexes containing the dinucleating Hbpp (3,5-bis(2-pyridyl)pyrazole) ligand together with Cl and dmso ligands have been prepared and their structural, spectroscopic, electrochemical, photochemical, and catalytic properties studied. The crystal structures of trans, cis-[RuIICl2(Hbpp)(dmso)2], 2a, and cis(out),cis-[RuIICl2-(Hbpp)(dmso)2], 2b, have been solved by means of single-crystal X-ray diffraction analysis showing a distorted octahedral geometry for the metal center where the dmso ligands coordinate through their S atom. 1D and 2D NMR spectroscopy corroborates a similar structure in solution for both isomers. Exposure of either 2a or 2b in acetonitrile solution under UV light produces a substitution of one dmso ligand by a solvent molecule generating the same product namely, cis(out)-[RuIICl2(Hbpp)(MeCN)(dmso)], 4. While the 1 e- oxidation of 2b or cis(out),- cis-[RuIICl2(bpp)(dmso)2]+, 3b, generates a stable product, the same process for 2a or trans, cis-[RIICl2(bpp)(dmso)2]+, 3a, produces the interesting linkage isomerization phenomenon where the dmso ligand switches its bond from Ru-S to Ru-O (KIIIo→s = 0.25 ± 0.025, kIIIo→s = 0.017 s-1, and kIIIs→o = 0.065 s-1; KIIo→s = 6.45 × 109, kIIo→s = 0.132 s-1, kIIs→o = 2.1 × 10-11 s-1). Finally complex 3a presents a relatively high activity as hydrogen transfer catalyst, with regard to its ability to transform acetophenone into 2-phenylethyl alcohol using 2-propanol as the source of hydrogen atoms.
|Publication status||Published - 24 Mar 2003|