6337-28-6Relevant articles and documents
Iridium(I) homobinuclear complexes containing salen-type ligands as bridge
Alvarado-Monzón, José C.,López, Jorge A.,de Riquer, Gabriel A. Andreu,Cristobal, Crispin,Flores-Alamo, Marcos,Ruiz-Azuara, Lena
, p. 243 - 250 (2019/02/01)
New binuclear iridium(I) complexes with general formula [Ir2(η4-cod)2(μ-SB)] (1–12) derived from the reactions of tetradentate Schiff bases ligands [N,N′-ethylenebis(5-R-salicylideneimine)] (5,5′-R-salenH2), [N,N′-1,3-propylenebis(5-R-salicylideneimine)] (5,5′-R-salpenH2), and [N,N′-o-phenylenebis(5-R-salicylideneimine)] (5,5′-R-salphenH2) (R = H, MeO, Cl, NO2) with [Ir(cod)(μ-Cl)]2 were synthesized. The homobinuclear nature of this iridium complexes was supported by elemental analysis, FAB-Mass and 1H NMR spectrometry. Full characterization was accomplished by IR spectroscopy, 13C NMR and bidimensional NMR experiments (COSY, HSQC, HMBC and NOESY). In addition, iridium complex [(Ir(η4-cod)2(μ-5,5′-MeO-salen)] (2) was characterized by X-ray crystallography, showing that ethylene bridge is a s-trans conformation, and that the Schiff base ligand act as a bridging N,O-bidentate ligand toward two iridium atoms, and 1,5-cyclooctadiene (cod) ligand complete the coordination sphere of metal center. The effect of the substituent groups on salicylaldiminate fragments has been studied by 13C{1H} NMR shift and Hammett sigma correlations for each series of complexes.
Oxovanadium(IV)-salen ion catalyzed H2O2 oxidation of tertiary amines to n-oxides- critical role of acetate ion as external axial ligand
Mathavan, Alagarsamy,Ramdass, Arumugam,Ramachandran, Mohanraj,Rajagopal, Seenivasan
, p. 315 - 326 (2015/04/14)
The oxovanadium(IV)-salen ion catalyzed H2O2 oxidation of N,N-dimethylaniline forms N-oxide as the product of the reaction. The reaction follows Michaelis-Menten kinetics and the rate of the reaction is accelerated by electron donating groups present in the substrate as well as in the salen ligand. This peculiar substituent effect is accounted for in terms of rate determining bond formation between peroxo bond of the oxidant and the N-atom of the substrate in the transition state. Trichloroacetic acid (TCA) shifts the λmax value of the oxidant to the red region and catalyzes reaction enormously. The cleavage of N￡O bond by vanadium complex leads to moderate yield of the product. But the percentage yield of the product becomes excellent in the presence of TCA.
Electronic and steric effects in manganese Schiff-base complexes as models for the water oxidation complex in photosystem II. The isolation of manganese-(II) and -(III) complexes of 3- and 3,5-substituted N,N′-bis(salicylidene)ethane-1,2-diamine (H2salen) ligands
Bermejo, Manuel R.,Castineiras, Alfonso,Garcia-Monteagudo, Juan C.,Rey, Manuel,Sousa, Antonio,Watkinson, Michael,McAuliffe, Charles A.,Pritchard, Robin G.,Beddoes, Roy L.
, p. 2935 - 2944 (2007/10/03)
Manganese-(II) and -(III) complexes of substituted N,N′-bis(salicylidene)ethane-1,2-diamine (H2salen) ligands H2L (substituents are in the 3, 5 or 3,5 positions of the phenyl rings of the salen moiety) have been prepared and thoroughly characterised. The reaction of Mn(ClO4)2·6H2O with H2L in ethanol in air normally leads to manganese(III) complexes ligated by both the N2O2 ligand and water molecule(s). However, by employing electron-withdrawing substituents on the ligand, e.g. 3-Br,5-NO2, a manganese(II) complex can be obtained. A 'borderline' ligand is represented by the 5-NO2 derivative (nsalen), which produces a manganese(II) complex contaminated with a small amount of a manganese(III) species. Using a more rigorous oxidising agent in the synthesis, [Fe(η-C5H5)2][FeCl4], drives the reaction totally to a manganese(III) complex [Mn(nsalen)Cl(H2O)]. In addition to magnetic susceptibility studies, cyclic voltammetry has been employed. All the complexes exhibit an oxidation and reduction peak, the reversible character being confirmed by pulse voltammetry. Pulse voltammetry also confirmed the nature of the manganese(II) species [Mn(bnsalen)(H2O)2]·2H2O [H2bnsalen = N,N′-bis(3-bromo-5-nitrosalicylidene)ethane-1,2-diamine] and that a slight amount of a manganese(III) species is present in [Mn(nsalen)(H2O)2]·2H2O. Six complexes have been crystallographically characterised. Despite the retention of an octahedral manganese environment in all of them, the supramolecular structures exhibit a wide diversity. The 3,5-dichloro and 5-bromo salen complexes containing co-ordinated water display combined π and hydrogen bonding, as well as dimerisation. The complex [{Mn(μ-dbsalen)(μ-O)}2] (dbsalen = 3,5-dibromo derivative) offers an alternative bridging arrangement, and [Mn(bsalen)(MeOH)(OClO3)]·H2O (bsalen = 5-bromo derivative) highlights the versatility of the manganese centre in these systems where, unexpectedly, perchlorate is co-ordinated in place of a lattice water. A more subtle rearrangement of supramolecular structure is obtained in [Mn(nsalen)Cl(H2O)] where the usual combination of π- or hydrogen-bonding interaction is modified by the corresponding ability of the 5-NO2 substituent.
