An-Najah Staff

Thiomorpholine (tetrahydro-1,4-thiazine), in the presence of Os(VIII) as catalyst, is oxidized by alkaline hexacyanoferrate(III) to 2-hydroxythiomorpholine. There is a first-order dependence in [Fe(CN)₆^3-] and [Os(VIII)] and zero-order dependence in [thiomorpholine] and [OH^-]. The observed rate constant was dependent on [Fe(CN)₆^4-] the type of electrolyte and the permitivitty of the reaction medium (10-40% ethanol). The proposed mechanism includes the formation of a transient [OsO₄(OH)₂ ]^2--thiomorpholine complex prior to the rate-determining regeneration of Os^VIII by [Fe(CN)₆^3-]. The values of the enthalpy and entropy of activation are calculated from rate constant values measured at different temperatures (20-40 ° C).

The T—silyl functionalized diamine-bis(ether-phosphine)ruthenium(II) complexes 1a(T°) — 1g(T°) (Scheme 1) were sol-gel processed in the presence of different amounts of the co-condensation agents CH3Si(OMe)3(Me—T°) and (MeO)2SiMe—(CH2)6—MeSi(OMe)2(D°—C6—D°) to produce a library of the interphase catalysts X1a — X1c, X2a — X2g, and X3a — X3g. Due to the remarkable electronic and steric effects of the co-ligands on the catalytic activity of such complexes, a series of aliphatic and aromatic diamines was selected. The new polymers were investigated by multinuclear CP/MAS solid-state NMR spectroscopy as well as by EXAFS, EDX, SEM, and BET methods. Selected interphase catalysts show high activities and selectivities in the hydrogenation of trans-4-phenyl-3-butene-2-one.

Diamineruthenium(II) complexes containing the hemilabile methoxyethyldimethylphosphine ligand, [Cl2Ru(Ln)(η1-Me2PCH2CH2OMe)2] (2Ln) (n = 1-12, Scheme 1), have been synthesized from the starting materials Me2PCH2CH2OMe, [Ru(COD)Cl2]n, and the respective diamines L1-L12. The structure of complex 2L5 reveals that two chlorides are in trans position, while in complex 2L11 the two chlorides favor a cis configuration. Most of the complexes are highly catalytic active in the hydrogen transfer reduction of acetophenone. The experimental study indicates that the replacement of phenyl groups for methyl functions in the ether-phosphine ruthenium(II) complexes resulted in a switch of the hydrogenation mechanism from direct hydrogenation to transfer hydrogenation. The reason is attributed to the better donor ability of methyl groups compared to phenyl substitutents. Thus the metal center becomes more electron-rich and inhibits the binding of dihydrogen to the ruthenium(II) complex fragment.

Molecular rutheniumcomplexesarecurrentlyusedascatalysts to promote avariety of reactions with novel activation routes. Coordination and organometallic complexes of rutheniumhave unfolded wide possibilities for acollection of catalytic organic processes, taking advantages of the development in the

Reaction of the ruthenium phosphine complex [RuCl2(PPh3)3] 1 with an unsaturated functionalized diphosphine ligand, namely 1,1-bis(diphenyl-phosphinomethyl)ethene, H2C=C(CH2PPh2)2, (dppme) gave trans-Cl2Ru(dppme)2 2. Complex 2 served as a precursor for the synthesis of trans-Cl2Ru(dppme)(alkylamine)2 complexes 3–5 by reaction with RNH2. All these complexes were characterized by spectroscopic techniques and by elemental analysis. The solid-state structure of complex 2 was determined by X-ray crystallography.