s, or keywords if they used Heck-type chemistry in their syntheses, because it became one of basic tools of organic preparations, a natural way to

http://aether.cmi.ua.ac.be/artikels/Artikels%20Gitte/Artikels/Reviews/Heck%20reactie%20Beletskaya%20%20Chem.%20Rev.%20003009.pdf

The heck reaction as a sharpening stone of palladium catalysis.

Dioxygen activation at mononuclear nonheme iron active sites: enzymes, models, and intermediates.

Conversion constants for redox potentials measured versus different reference electrodes in acetonitrile solutions at 25°C

Artificial photosynthesis: molecular systems for catalytic water oxidation.

Dialkylbiaryl phosphines are a valuable class of ligand for Pd-catalyzed amination reactions and have been applied in a range of contexts. This perspective attempts to aid the reader in the selection of the best choice of reaction conditions and ligand of this class for the most commonly encountered and practically important substrate combinations.

Dialkylbiaryl phosphines in Pd-catalyzed amination: a user's guide

Les coordinats N, O concernes sont: R-quinoleinol-8, et N-arylsalicylaldimine. On synthetise les complexes MQ 3 (M=Ru, Os), RuL 3 et [Et 4 N][OsX 2 Q 2 ] et [RuL 3 ]PF 6 , [OsQ 3 ]ClO 4 et OsX 2 Q 2 . Donnees IR, RPE et comportement electrochimique

Ruthenium and osmium complexes of N,O chelators: syntheses, oxidation levels, and distortion parameters

Twelve mixed-ligand thiosemicarbazone complexes of ruthenium and osmium, ten of general formula [M(bpy)2(bztsc-R)]ClO4, (M = Ru, Os; bpy = 2,2'-bipyridine, Hbztsc-R = benzaldehyde thiosemicacbazone) and two of type [M(bpy)2(actsc)]ClO4 (Hactsc = acetonethiosemicarbazone), have been synthesized and characterized. All the complexes are diamagnetic (low-spin d6, S = 0) and in acetonitrile solution show several intense metal-to-ligand charge-transfer (MLCT) transitions in the visible region. Structures of Hbztsc-OMe, [Ru(bpy)2(bztsc-NO2)]ClO4 and [Ru(bpy)2(actsc)]ClO4 have been determined by X-ray crystallography. Benzaldehyde thiosemicarbazone exists in the thione form with the phenyl group trans to the hydrazinic nitrogen. The benzaldehyde thiosemicarbazone ligand coordinates to the metals through the hydrazinic nitrogen and sulfur with a bite angle of approximately 67 degrees, forming a four-membered chelate ring. However, the actsc ligand coordinates through the imine nitrogen and sulfur, forming a five-membered chelate ring with a bite angle of approximately 81 degrees. The difference in coordination modes of two types of thiosemicarbazone ligands, viz., bztsc-R and actsc, appears to result from the difference in steric bulk of the aryl and methyl group trans to the hydrazinic nitrogen. In acetronitrile solution they all show a reversible metal(II)-metal(III) oxidation in the range 0.18-0.58 V vs SCE followed by an irreversible oxidation in the range 1.11-1.60 V vs SCE. Two successive one-electron reductions of the coordinated bipyridine are also observed in the range -1.53 to -1.96 V vs SCE.

Unusual coordination mode of thiosemicarbazone ligands. A search for the origin.

Reaction of Hsaltsc (1) with [M(PPh3)3X2] (M = Ru, Os; X = Cl, Br) in ethanol affords complexes of the type [M(PPh3)2(saltsc)2] (2), where the saltsc ligand is coordinated, in spite of having the phenolic oxygen as a potential third donor site, as a bidentate N,S-donor ligand forming a four-membered chelate ring.

Steric Control of the Coordination Mode of the Salicylaldehyde Thiosemicarbazone Ligand. Syntheses, Structures, and Redox Properties of Ruthenium and Osmium Complexes

Tris(3,5-di-tert-butylbenzoquinone) complexes of Ru and Os have been synthesized in the interest of investigating periodic trends in charge distribution for tris(quinone) complexes of second- and third-row transition metals. Infrared spectra of the two complexes are similar but differ from spectra obtained on related semiquinone (Fe(DBSQ){sub 3}) and catecholate (Re(DBCat){sub 3}) complexes. Both complexes undergo two oxidation and two reduction reactions at similar potentials. Crystallographic characterization on the cis and trans isomers of Ru(DBQ){sub 3} and on trans-Os(DBQ){sub 3} at {minus}60{degree}C shows short M-O bond lengths, typical of complexes containing high oxidation state forms of Ru and Os. Ligand C-O bond lengths are found to be intermediate between semiquinone and catecholate values, with lengths that are more semiquinone-like for Ru(DBQ){sub 3} and more catecholate-like for Os(DBQ){sub 3}. This subtle difference in charge distribution between the second- and third-row metals appears to contribute to marked differences in the stereodynamic properties of the two complexes. Both are diamagnetic and show sharp NMR spectra at room temperature. Eight tert-butyl and eight ring proton resonances are observed for Ru(DBQ){sub 3} at room temperature, indicating the presence of stereochemically rigid cis and trans isomers. Two tert-butyl and two ring proton resonances are observed for Os(DBQ){sub 3}more » at room temperature. At {minus}85{degree}C eight tert-butyl and eight ring proton resonances appear as molecular rearrangement rates decrease on the NMR time scale. Analysis of the temperature dependence of the spectrum of Os(DBQ){sub 3} has indicated racemization by a trigonal twist mechanism at lower temperatures, with structural isomerization and racemization by a rhombic twist mechanism at higher temperatures.« less

Periodic trends in charge distribution for transition-metal complexes containing catecholate and semiquinone ligands. Synthetic, physical, and stereodynamic properties of the tris(3,5-di-tert-butylquinone) complexes of ruthenium and osmium

Reaction of benzaldehyde semicarbazone (HL-R, where H is a dissociable proton and R is a substituent (R = OMe, Me, H, Cl, NO 2 ) at the para position of the phenyl ring) with [Ru(PPh 3 ) 3 Cl 2 ] and [Ru(PPh 3 ) 2 (CO) 2 Cl 2 ] has afforded complexes of different types. When HL-NO 2 and [Ru(PPh 3 ) 3 Cl 2 ] react in solution at ambient temperature, trans-[Ru(PPh 3 ) 2 (L-NO 2 )Cl] is obtained. Its structure determination by X-ray crystallography shows that L-NO 2 is coordinated as a tridentate C,N,O-donor ligand. When reaction between HL-NO 2 and [Ru(PPh 3 ) 3 Cl 2 ] is carried out in refluxing ethanol, a more stable cis isomer of [Ru(PPh 3 ) 2 (L-NO 2 )Cl] is obtained. The trans isomer can be converted to the cis isomer simply by providing appropriate thermal energy. Slow reaction of HL-R with [Ru(PPh3)2(CO)2Cl2] in solution at ambient temperature yields 5-[Ru(PPh 3 ) 2 (L-R)(CO)Cl] complexes. A structure determination of 5-[Ru(PPh 3 ) 2 (L-NO 2 )(CO)Cl] shows that the semicarbazone ligand is coordinated as a bidentate N,O-donor, forming a five-membered chelate ring. When reaction between HL-R and [Ru(PPh 3 ) 2 (CO) 2 Cl 2 ] is carried out in refluxing ethanol, the 4-[Ru(PPh 3 ) 2 (L-R)(CO)Cl] complexes are obtained. A structure determination of 4-[Ru(PPh 3 ) 2 (L-NO 2 )(CO)Cl] shows that a semicarbazone ligand is bound to ruthenium as a bidentate N,O-donor, forming a four-membered chelate ring. All the complexes are diamagnetic (low-spin d 6 , S = 0 ). The trans- and cis-[Ru(PPh 3 ) 2 (L-NO 2 )Cl] complexes undergo chemical transformation in solution. The 5- and 4-[Ru(PPh 3 ) 2 (L-R)(CO)Cl] complexes show sharp NMR signals and intense MLCT transitions in the visible region. Cyclic voltammetry of the 5-[Ru(PPh 3 ) 2 (L-R)(CO)Cl] and 4-[Ru(PPh 3 ) 2 (L-R)(CO)Cl] complexes show the Ru(II)-Ru(III) oxidation to be within 0.66-1.07 V. This oxidation potential is found to linearly correlate with the Hammett constant of the substituent R.

Samaresh Bhattacharya

Papers

Ruthenium and osmium complexes of N,O chelators: syntheses, oxidation levels, and distortion parameters

Unusual coordination mode of thiosemicarbazone ligands. A search for the origin.

Steric Control of the Coordination Mode of the Salicylaldehyde Thiosemicarbazone Ligand. Syntheses, Structures, and Redox Properties of Ruthenium and Osmium Complexes

Periodic trends in charge distribution for transition-metal complexes containing catecholate and semiquinone ligands. Synthetic, physical, and stereodynamic properties of the tris(3,5-di-tert-butylquinone) complexes of ruthenium and osmium

Chemical control on the coordination mode of benzaldehyde semicarbazone ligands. synthesis, structure, and redox properties of ruthenium complexes.