Synthesis, Structure, and Spectroscopic, Photochemical, Redox, and Catalytic Properties of Ruthenium(II) Isomeric Complexes Containing Dimethyl Sulfoxide, Chloro, and the Dinucleating Bis(2-pyridyl)pyrazole Ligands.

Two isomeric Ru(ll) complexes containing the dinucleating Hbpp (3,5-bis(2-pyridyl)pyrazole) ligand together with CI and dmso ligands have been prepared and their structural, spectroscopic, electrochemical, photochemical, and catalytic properties studied. The crystal structures of trans, cis-[Ru[sup II]CI[sub 2](Hbpp)(dmso)[sub 2]], 2a, and cis(out),cis-[Ru[sup II]Cl[sub 2](Hbpp)(dmso)[sub 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)-[Ru[sup II[CI[sub 2](Hbpp)(MeCN)(dmso)], 4. While the 1 e[sup -] oxidation of 2b or cis(out),cis-[Ru[sup II]Cl[sub 2](bpp)(dmso)[sub 2]][sup +], 3b, generates a stable product, the same process for 2a or trans, cis-[R[sup II]Cl[sub 2](bpp)(dmso)[sub 2]][sup +], 3a, produces the interesting linkage isomerization phenomenon where the dmso ligand switches its bond from Ru-S to Ru-O (K[sup III, sub O→S] = 0.25 ± 0.025, k[sup III, sub O → S] = 0.017 s[sup -1], and k[sup III, sub S → O] = 0.065 s[sup -1] k[sup II, sub O → S] = 6.45 × 10[sup 9]. k[sup II, sub O → S] = 0.132 s[sup -1], k[sup II, sub S → O] = 2.1 × 10[sup -11] s[sup -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. [ABSTRACT FROM AUTHOR]