- Syntheses, structures and catalytic properties of ruthenium(II) nitrosyl complexes with bidentate and tetradentate Schiff base ligands
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Treatment of Ru(NO)Cl3·xH2O with 1 equiv. bidentate Schiff bases in the presence of triethylamine in DMF/THF afforded a series of anionic ruthenium(II) nitrosyl complexes of the type [Et3NH][Ru(κ2-N,O-LR)(NO)Cl3] (HLR = 2-butyliminomethyl-phenol 1, 2-(benzylimino-methyl)-phenol 2, 2-[(4-chloro-phenylimino)-methyl]-phenol 3, 2-[(4-nitro-phenylimino)-methyl]-phenol 4, 2-[(2,6-diisopropyl-phenylimino)-methyl]-phenol 5). Interaction of Ru(NO)Cl3·xH2O and 1 equiv. tetradentate Schiff bases under the same condition led to isolation of an anionic complex [Et3NH][Ru(κ2-N,O-L-CH2CH2-NOH)-(NO)Cl3] (HL-CH2CH2-NOH = N,N′-disalicylidene-1,2-ethanediamine 6) and a neutral complex [Ru(salen-phn)(NO)Cl] (H2salen-phn = N,N′-disalicylidene-1,2-phenyldiamine 7). The molecular structures of 1·?C2H5OH, 2–6, and 7·CH2Cl2 have been determined by single-crystal X-ray crystallography. Investigation of the catalytic properties of ruthenium(II) nitrosyl complexes 1–7 showed that they are efficient catalytic precursors for the transfer hydrogenation of acetophenone.
- Wu, Fule,Wang, Chang-Jiu,Lin, Hui,Jia, Ai-Quan,Zhang, Qian-Feng
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- Modulation of imine chemistry with intramolecular hydrogen bonding: Effects from ortho-OH to NH
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Salicylaldehyde derivatives and their imines are important building blocks in organic and supramolecular chemistry. In an effort to expand structural diversity in the current work we changed ortho-OH in salicylaldehyde to NH of amide/sulfonamide and investigated the effect of resulting intramolecular hydrogen bonds on imine dynamic covalent chemistry (DCC). A suite of ortho-aminobenzaldehydes were readily synthesized, and X-ray and NMR data validated the existence of NH?O intramolecular hydrogen bonds. The formation and exchange of imines were then studied in acetonitrile, and the acidity of OH/NH significantly influenced the thermodynamics and kinetics of imine reactions. Furthermore, the role of OH/NH?N hydrogen bonds on imines was elucidated by the shift of aldehyde exchange equilibrium. Finally, the formation of imines was achieved in aqueous solutions. The mechanistic insights could pave the way for future applications in assembly and labelling.
- Chen, Hang,Feng, Zelin,Jia, Shuaipeng,You, Lei
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supporting information
(2020/03/24)
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- Anagostic, mono- and hexahapta interactions in Tl(I) dithiocarbamates: A new precursor for the preparation of Tl2S nanoparticles
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Two new homoleptic complexes, [Tl(bzfdtc)]2 (1) and [Tl(bu2-OHbzdtc)]2 (2) (where bzfdtc = N-benzyl-N-furfuryldithiocarbamate and bu2-OHbzdtc = (N-butyl-N-(2-hydroxybenzyl)dithiocarbamate), have been prepared an
- Gomathi, Govindaraju,Thirumaran, Subbiah,Ciattini, Samuele
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p. 424 - 433
(2015/11/11)
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- DNA binding properties of two ruthenium(III) complexes containing schiff bases derived from salicylaldehyde: Spectroscopic and electrochemical evidence of CT DNA intercalation
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The interaction of CT DNA by two anionic Ru(III) complexes with N-substituted salicylidenimine ligands was investigated by spectroscopic titration and cyclic voltammetry. The result gives a surprising evidence for intercalation of DNA by the negatively ch
- Ljubijankic, Nevzeta,Zahirovic, Adnan,Turkusic, Emir,Kahrovic, Emira
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p. 215 - 222
(2013/11/06)
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- Chemical reactivity and skin sensitization potential for benzaldehydes: Can Schiff base formation explain everything?
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Skin sensitizers chemically modify skin proteins rendering them immunogenic. Sensitizing chemicals have been divided into applicability domains according to their suspected reaction mechanism. The widely accepted Schiff base applicability domain covers aldehydes and ketones, and detailed structure-activity-modeling for this chemical group was presented. While Schiff base formation is the obvious reaction pathway for these chemicals, the in silico work was followed up by limited experimental work. It remains unclear whether hydrolytically labile Schiff bases can form sufficiently stable epitopes to trigger an immune response in the living organism with an excess of water being present. Here, we performed experimental studies on benzaldehydes of highly differing skin sensitization potential. Schiff base formation toward butylamine was evaluated in acetonitrile, and a detailed SAR study is presented. o-Hydroxybenzaldehydes such as salicylaldehyde and the oakmoss allergens atranol and chloratranol have a high propensity to form Schiff bases. The reactivity is highly reduced in p-hydroxy benzaldehydes such as the nonsensitizing vanillin with an intermediate reactivity for p-alkyl and p-methoxy-benzaldehydes. The work was followed up under more physiological conditions in the peptide reactivity assay with a lysine-containing heptapeptide. Under these conditions, Schiff base formation was only observable for the strong sensitizers atranol and chloratranol and for salicylaldehyde. Trapping experiments with NaBH3CN showed that Schiff base formation occurred under these conditions also for some less sensitizing aldehydes, but the reaction is not favored in the absence of in situ reduction. Surprisingly, the Schiff bases of some weaker sensitizers apparently may react further to form stable peptide adducts. These were identified as the amides between the lysine residues and the corresponding acids. Adduct formation was paralleled by oxidative deamination of the parent peptide at the lysine residue to form the peptide aldehyde. Our results explain the high sensitization potential of the oakmoss allergens by stable Schiff base formation and at the same time indicate a novel pathway for stable peptide-adduct formation and peptide modifications by aldehydes. The results thus may lead to a better understanding of the Schiff base applicability domain.
- Natsch, Andreas,Gfeller, Hans,Haupt, Tina,Brunner, Gerhard
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p. 2203 - 2215
(2013/01/15)
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- Carbon dioxide as a carbonylating agent in the synthesis of 2-oxazolidinones, 2-oxazinones, and cyclic ureas: Scope and limitations
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Carbon dioxide can be used as a convenient carbonylating agent in the synthesis of 2-oxazolidinones, 2-oxazinones, and cyclic ureas. The transient carbamate anion generated by treating a primary or secondary amine group in basic media can be activated with phosphorylating agents such as Diphenylphosphoryl azide (DPPA) and Diphenyl chlorophosphate (DPPCl) but also with other types of electrophiles such as SOCl2, TsCl, or AcCl. The intramolecular trapping of the activated carbamate by a hydroxyl group leads to the formation of 2-oxazolidinones or 2-oxazinones in good to excellent yields. This methodology was successfully applied to the synthesis of cyclic ureas up to 7-membered rings from the corresponding diamines.
- Paz, Jairo,Perez-Balado, Carlos,Iglesias, Beatriz,Munoz, Luis
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experimental part
p. 3037 - 3046
(2010/07/15)
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- Selective Functionalisation. Part 11. Selective Hydrogenation by a Novel Palladium Salicylidene-ethylenediamine Complex and the Properties of Derivatives of some Square Planar Homogenous Hydrogenation Catalysts.
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Analogues of two reported homogenous hydrogenation catalysts based upon square planar palladium complexes have been prepared with a view to modifying the structures to permit the control of selectivity by micellar interactions.Derivatives of bisacetylacetonatopalladium(II) in which the diketone was alkylated at C-3 or C-5 were prepared but no useful catalytic activity was observed for the reduction of nitrobenzene to aniline in the presence of pyridine.Complexes were also prepared from bisacetylacetonatopalladium(II) with 4-substituted pyridines as ligands; 4-tridecylpyridine afforded an unstable complex but 4-decylaminopyridine afforded a stable complex with low catalytic activity.A series of salicylidene imine palladium(II) complexes was prepared.Contrary to previous reports, the well-known salicylidene-ethylenediaminepalladium(II) complex was not a catalyst for homogenous hydrogenation but a new oligomeric green heterogenous complex with selective hydrogenation properties was discovered.This green complex was selective for the hydrogenation of alkynes, especially terminal alkynes, and reduced few other functional groups (ArNO2, ArCHO).Many variations on this structure were investigated in an attempt to discover a soluble or crystalline analogue of the green complex but no complexes with improved properties were isolated.
- Kerr, James M.,Suckling, Colin J.,Bamfield, Peter
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p. 887 - 895
(2007/10/02)
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- Coordination Compounds of Tantalum(V)
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Ta(OPri)4(SB), Ta(OPri)3(SB)2 and Ta(OPRi)2(SB)3 types of complexes of tantalum with aldimines (SBH) of the type o-OHC6H4CH:NC6H4CH3-o, o-OHC6H4CH:NC4H9-n, C6H5CH:NNHCONH2 and C6H5CH:NNHCSNH2 have been synthesized by the reactions of tantalum pentaisopropoxide.The aldimines were obtained by the condensation of salicylaldehyde with o-methylaniline and n-butylamine and of benzaldehyde with semicarbazide hydrochloride and thiosemicarbazide.The complexes have been fully characterised by their analytical data, conductance, magnetic and molecular weight measurement and IR, electronic and PMR data.
- Mookerjee, M. N.,Singh, R. V.,Tandon, J. P.
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p. 521 - 522
(2007/10/02)
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- X-Ray Structures of Several Bis(N-alkylsalicylaldiminato)zinc(II) Complexes
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X-Ray structures of five bis(N-R-salicylaldiminato)zinc(II) complexes with R = ethyl, n-propyl, i-propyl, n-butyl and 4-thia-n-hexyl were determined.The N2O2 coordination geometry is in all cases quasi-tetrahedral with the dihedral angle between the plane
- Dreher, Michael,Elias, Horst,Paulus, Helmut
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p. 707 - 710
(2007/10/02)
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- SOLVENT EFFECT IN THE AMINE EXCHANGE OF SCHIFF BASES, II. RELATIONSHIP BETWEEN THE RATE CONSTANT AND THE ACTIVITY COEFFICIENT OF ETHANOL IN ETHANOL-CYCLOHEXANE MIXTURE
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The rate of amine exchange has been investigated in the reaction of Schiff bases with primary amines in ethanol-cyclohexane mixtures.The rate constant depends, according to the folowing equation, on the rate constants measured in ethanol and cyclohexanol (k1*, k2*), on the composition of solvent mixture (x1, x2) and on the activity coefficient of ethanol (γ1): log k=x1 logk1* + x2 logk2* + (a+bγ1)x1x2.The validity of the equation is interpreted by the hydrogen bond formed between the ethanol and Schiff base molecules.
- Nagy, P.
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p. 461 - 468
(2007/10/02)
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- Synthesis and Reactions of Coumarin-3-N-bromoarylcarboxamides
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Various coumarin-3-N-bromoarylcarboxamides (Ia-h) have been prepared and their reactions with aliphatic amines and hydrazines studied.Some acridinyl derivatives (XIa-f) of coumarin-3-carboxamide (Ii) have also been prepared.
- Islam, A. M.,Bedair, A. H.,Aly, F. M.,El-Sharief, A. M. Sh.,El-Masry, F. M.
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p. 224 - 226
(2007/10/02)
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- N-Substituted Salicylaldimines Derivatives of Germanium(IV)
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Hexa-coordinated Schiff base complexes of germanium of the general type Ge(OC2H5)2(SB)2 (SB(-) is the anion of the monofunctional bidentate Schiff base, SBH) have been synthesized by the reaction between ethyl-orthogermanate and the Schiff base in benzene
- Singh, R. V.,Tandon, J. P.
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p. 1391 - 1398
(2007/10/02)
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