COORDINATION CHEMISTRY OF C=S-FUNCTIONAL COMPOUNDS .10. CATIONIC RUTHENIUM-THIOBENZALDEHYDE COMPLEXES - SYNTHESIS BY HYDRIDE ABSTRACTION FROM BENZYLTHIOLATE COMPLEXES, STRUCTURE, DYNAMIC BEHAVIOR AND REACTIONS

Hydride abstraction from [Cp(R3P)2Ru(SCH2C6H4X)] [R3P = Ph3P, Me3P, (M eO)3P; (R3P)2 = Ph2PCH2PPh2 (dppm), Ph2PC2H4PPh2(dppe), Ph2PC2H4PMe2 ( dpme), Me2PC2H4PMe2(dmpe); X = H, Cl, OMe] using triphenylcarbenium he xafluorophosphate yields ionic thiobenzaldehyde complexes [Cp(R3P)2Ru( S = CHC6H4X)]PF6. With bulky ligands R3P only eta1(S) isomers are form ed, whereas a dynamic eta1/eta2 equilibrium is observed for (R3P)2 = ( Me3P)2, dmpe. An X-ray structure determination was carried out on [Cp( dppe)Ru(S=CHC6H4OMe)]PF6 . 0.5 Et2O (triclinic, space group P1BAR, a = 11.372(4) angstrom, b = 12.782(5) angstrom, c = 14.548(4) angstrom, a lpha = 70.33(l), beta = 80.61(2)-degrees, gamma = 81.91(2)-degrees, Z = 2): Ru-PI: 2.296(l) angstrom, Ru-P2: 2.301(l) angstrom, Ru-S: 2.314( l) angstrom, S-C6: 1.632(5) angstrom. Control experiments show that th e beta-hydride abstraction is initiated by single electron oxidation o f the thiolate complex to give a radical cation intermediate. A fairly large kinetic isotope effect (KIE) of the H-transfer step (k(H)/k(D) = 5.6 using [Ph3C]+ and 7.4 using [CP2Fe]+ as oxidant) demonstrates th at the ruthenium atom is not involved. The thiobenzaldehyde complexes readily add nucleophiles such as H-, D-, PMe3, OR-, SR-, and carbanion s. With (R3P)2 = dpme, moderate diastereoselectivities are found in so me of these reactions. [4 + 2]-Cycloadditions have been carried out wi th 2,3-dimethylbutadiene and cyclopentadiene. The latter are moderatel y diastereoselective for (R3P)2 = dpme and highly exo-selective for (R 3P)2 = dppm. An X-ray structure determination of [Cp(dppm)-Ru(SC6H7C6H 4Cl)]PF6 . MeCN (monoclinic, space group P2 1/c, a = 13.463(6) angstro m, b = 16.071(3) angstrom, c = 20.813(9) angstrom, beta = 92.30(2)-deg rees, Z = 4) reveals that the E configuration of the C = S bond is ret ained in the Diels-Alder adduct.