An-Najah Staff

The novel trans-[Ru^(II)Cl₂(H₂C=C(CH₂PPh₂)₂)(diamine)]1-3complexes {diamine is1,2-ethanediamine1,1,3-propanediamine2and2,2-dimethyl-1,3-propanediamine3}were obtained by reacting trans-[RuCl₂[H₂C=C(CH₂PPh₂)₂]₂ with an excess amount of corresponding diaminein CH₂Cl₂as solvent. One of the diphosphine ligands was quantitatively replaced by the corresponding diamine, even when excess diamine was added. In solution only the trans-[RuCl₂(H₂C=C(CH₂PPh₂)₂)(diamine)] isomer configuration was confirmed by NMR spectroscopyand theX-ray crystal structure of 2.These diphosphine complexes have exhibited significant activity and selectivity as hydrogenation catalystsfor a,ß-unsaturated ketone.The catalytic activity were compared to an analogous trans–[Ru^(II)Cl₂(H₂C(CH₂PPh₂)₂)(diamine)]4-6 {diamine is 1,2-ethanediamine 4 ,1,3-propanediamine5and2,2-dimethyl-1,3-propanediamine6}.Complexes 1-3 werecatalyzeda,ß-unsaturated ketone faster than the previously reported complexes 4-6. Density functional theory (DFT) calculationshave been carried out to study the shift in the Ru(III)/Ru(II) couple and the  catalytic activity for the two representative complexes 2 and 5.

Three complexes of the general formula trans/cis-[Ru^(II)(dppme)(N–N)Cl₂] {dppme is H₂C=C(CH₂PPh₂)₂ and N–N is 1,2-diaminocyclohexane (trans/cis-(1)) and 1-methyl-1,2-diaminopropane (trans-(2)} were obtained by reacting trans-[RuCl₂(dppme)₂] with an excess amount of corresponding diamine in CH₂Cl₂ as  a solvent. The complexes were characterized by an elemental analysis, IR, ¹H, ¹³C and ³¹P{1H}NMR, FAB-MS and Uv-visible. The trans-(1) (kinetic product) readily isomerizes to the cis-(1) (thermodynamic product) and this process was followed by using ³¹P{¹H} NMR, cyclic voltammetry  and UV–vis. The electrochemical studies on complex (1) reveal that the Ru(III)/Ru(II) couples are sensitive to the isomer (trans/cis) formed. The structureof cis-(1) isomer was confirmed by X-ray analysis and ³¹P{¹H} NMR. Transfer-hydrogenation reactions for reduction of trans-4-phenyl-3-butene-2-one were conducted using complexes trans/cis-(1) and trans-(2). The electronic spectra of cis/trans-(1) in dichloromethane were calculated with the use of time-dependent DFT methods.

Novel Ru(II) complex-based hybrid inorganic-organic materials immobilized via a diamine co-ligand site instead of the conventional diphosphine ligand have been prepared. The complexes were prepared by two different methods: sol-gel and surface modification techniques. The structures of the desired materials were deduced by several available physical measurements like elemental analyses, infrared, FAB-MS and 1H-, 13C- and 31P-NMR spectroscopy. Due to a lack of solubility the structures of xerogel 3 and modified 4 were studied by solid state 13C-, 29Si- and 31P-NMR spectroscopy, infrared spectroscopy and EXAFS. These materials were stable enough to serve as hydrogenation catalysts. Selective hydrogenation of functionalized carbonyls in a,b-unsaturated compounds was successfully carried out under mild conditions in a basic medium using these complexes as catalysts.

Syntheses of four new ruthenium(II) complexes of the [RuCl2(P)2(N)2] type using 2-(diphenylphosphino)ethyl methyl ether (P~O) as ether-phosphine and triphenylphosphine (PPh3) as monodentate phosphine ligands in the presence of [3-(2-aminoethyl)aminopropyl]trimethoxysilane as diamine co-ligand are presented for the first time. The reactions were conducted at room temperature and under an inert atmosphere. Due to the presence of the trimethoxysilane group in the backbone of complexes 1 and 2 they were subjected to an immobilization process using the sol-gel technique in the presence of tetraethoxysilane as cross-linker. The structural behavior of the phosphine ligands in the desired complexes during synthesis were monitored by 31P{1H}-NMR. Desired complexes were deduced from elemental analyses, Infrared, FAB-MS and 1H-, 13C- and 31P-NMR spectroscopy, xerogels X1 and X2 were subjected to solid state, 13C-, 29Si- and 31P-NMR spectroscopy, Infrared and EXAF. These complexes served as hydrogenation catalysts in homogenous and heterogeneous phases, and chemoselective hydrogenation of the carbonyl function group in trans-4-phenyl-3-butene-2-al was successfully carried out under mild basic conditions.

The diamine (Nsingle bondN) co-ligand 2,2-dimethyl-1,3-propanediamine and 2,3-diaminophathalene react individually with [RuCl2(dppb)2(μ-dppb)] to afford complexes with kinetically stable trans-[Cl2Ru(dppb)(Nsingle bondN)] as the favoured isomer. The thermodynamically stable cis-[Cl2Ru(dppb)(Nsingle bondN)] isomer of complex 1 was formed from the trans-1 isomer. The trans to cis isomerization reaction was conducted in CHCl3 at RT and monitored by 31P{1H} NMR. The structures of the desired complexes were characterized via elemental analyses, IR and, UV–visible spectroscopy, FAB-MS and NMR. The structure of the cis-1 isomer was determined by single crystal X-ray measurements. Both the trans-1 and cis-1 isomers were shown to have a significant catalytic role in selective hydrogenation reactions under mild conditions using cinnamic aldehyde as typical model reaction.