15496-36-3Relevant academic research and scientific papers
Mononuclear, dinuclear, and pentanuclear [{N,S(thiolate)}iron(II)] complexes: Nuclearity control, incorporation of hydroxide bridging ligands, and magnetic behavior
Krishnamurthy, Divya,Sarjeant, Amy N.,Goldberg, David P.,Caneschi, Andrea,Totti, Federico,Zakharov, Lev N.,Rheingold, Arnold L.
, p. 7328 - 7341 (2005)
The mixed N3S(thiolate) ligand 1-[bis(2-(pyridin-2-yl)ethyl} amino]-2-methylpropane-2-thiol (Py2SH) was used in the synthesis of four iron(II) complexes: [(Py2S)FeCl] (1), [(Py2S)FeBr] (2), [(Py2S)4Fe5II(μ-OH) 2]-(BF4)4 (3). and [(Py2S) 2Fe2II(μ-OH)]BF4 (4). The X-ray structures of 1 and 2 revealed monomeric iron(II)-alkylthiolate complexes with distorted trigonal-bi-pyramidal geometries. The paramagnetic 1H NMR spectra of 1 and 2 display resonances from δ = -25 ppm to + 100 ppm, consistent with a high-spin iron(II) ion (S=2). Spectral assignments were made on the basis of chemical shift information and T1 measurements and show the monomeric structures are intact in solution. To provide entry into hydroxide-containing complexes, a novel synthetic method was developed involving strict aprotic conditions and limiting amounts of H2O. Reaction of Py2SH with NaH and Fe-(BF4)2·6H 2O under aprotic conditions led to the isolation of the pentanuclear, μ-OH complex 3, which has a novel dimer-of-dimers type structure connected by a central iron atom. Conductivity data on 3 show this structure is retained in CH2Cl2. Rational modification of the ligand-to-metal ratio allows control over the nuclearity of the product, yielding the dinuclear complex 4. The X-ray structure of 4 reveals an unprecedented face-sharing, biooctahedral complex with an [S2O] bridging arrangement. The magnetic properties of 3 and 4 in the range 1.9-300 K were successfully modeled. Dinuclear 4 is antiferromagnetically coupled [J = -18.8(2) cm-1]. Pentanuclear 3 exhibits ferrimagnetic behavior, with a high-spin ground state of ST=6, and was best modeled with three different exchange parameters [J= -15.3(2), J′ = -24.7(3), and J″ = -5.36(7) cm-1]. DFT calculations provided good support for the interpretation of the magnetic properties.
A strategic approach for the synthesis of new porphyrin rings, attractive for heme model purpose
Ladomenou, Kalliopi,Charalambidis, Georgios,Coutsolelos, Athanassios G.
, p. 2882 - 2887 (2007/10/03)
Novel complexes have been efficiently synthesized with a facile route using two different atropisomers of the same porphyrin. These compounds feature a tridentate binding site, a tyrosine molecule, and a proximal base, all bound to the porphyrin ring in different fashions, making them attractive for heme modeling purposes.
Dioxygen mediated oxo-transfer to an amine and oxidative N-dealkylation chemistry with a dinuclear copper complex
Zhang,Liang,Kim,Gan,Tyeklar,Lam,Rheingold,Kaderli,Zuberbuehler,Karlin
, p. 631 - 632 (2007/10/03)
Reaction of dioxygen with a dinuclear copper(I) complex of a new binucleating ligand is described, wherein a peroxodicopper(II) (Cu2-O2) intermediate leads to an oxo-transfer reaction to give an N-oxide of an N-benzyl internal ligand
Mechanism of aromatic hydroxylation in a copper monooxygenase model system. 1,2-methyl migrations and the NIH shift in copper chemistry
Nasir, M. Sarwar,Cohen, Brett I.,Karlin, Kenneth D.
, p. 2482 - 2494 (2007/10/02)
The NIH shift mechanism appears to be operative in a copper monooxygenase model system involving dicopper ion complex mediated O2 hydroxylation of an arene substrate. Previous studies have shown that when a dicopper(I) complex containing two tridentate PY2 units (PY2 = bis[2-(2-pyridyl)ethyl]amine) which are linked by a m-xylyl group, i.e., [Cu2(XYL-H)]2+ (1), is reacted with dioxygen, a Cu2O2 intermediate forms and hydroxylation in the intervening 2-xylyl position occurs. Here, corresponding reactions of 2-methyl substituted analogues [Cu2(Me2XYL-CH3)]2+ (4) and [Cu2(XYL-CH3)]2+ (5) are described in detail. Oxygenation of these causes xylyl hydroxylation reactions producing new phenol products, with concomitant 1,2-migration of the methyl group, loss of one PY2 ligand arm, and formaldehyde formation. Manometric O2 uptake experiments and an 18O2 labeling study confirm that the stoichiometry of these reactions are consistent with that observed for monooxygenases. A reaction carried out using a dinucleating ligand which has been deuterated in benzylic positions confirms that the CH2O product is derived from this carbon atom, a result also consistent with migration of the 2-methyl group. A small yield of methylbis[2-(2-pyridyl)ethyl]amine (MePY2) is consistently obtained, and experiments suggest this may be derived from the reduction of an intermediate iminium salt [CH2=N[CH2CH2PY]2]+ (PY = 2-pyridyl). The hydroxylation induced 1,2-methyl migrations observed here are reminiscent of the NIH shift reactions previously observed only in iron hydroxylases and suggest that the copper ion mediated reactions proceed by the electrophilic attack of a Cu2O2 intermediate upon the proximate aromatic substrate. A detailed mechanism is proposed and discussed in terms of the known O2 reactivity and structure of these dinuclear copper complexes. The biological relevance and significance of this monooxygenase model system is also discussed.
SYNTHESIS OF FUNCTIONALLY SUBSTITUTED PYRIDINES AND DIPYRIDYL-SUBSTITUTED COMPOUNDS WITH THE AID OF LOW-VALENCE COMPOLEXES
Selimov, F. A.,Khafizov, V. R.,Dzhemilev, U. M.
, p. 290 - 295 (2007/10/02)
The possibility of the preparation of oxygen, nitrogen, and sulfur-containing pyridines and dipyridyl-substituted compounds by the cyclocotrimerization of substituted propionitriles with acetylene under the influence of a Co(2-ethylhexanoate)2-Al(C2H5)3 catalyst was demonstrated.It was established that the nature of the heteroatom in substituted propionitriles has virtually no effect on the direction of the reaction.
Ionization and Intramolecular Reactions of N,N-Bis- and N,N-Bismaleamic Acids. An Enzyme Model
Suh, Junghun,Kim, Mahn Joo,Seong, Nak Jin
, p. 4354 - 4358 (2007/10/02)
N,N-Bismaleamic acid (1) and N,N-bismaleamic acid (2) underwent exclusive amide hydrolysis and intramolecular Michael-type addition, respectively.The pH profile of the pseudo-first-order rate constant for the reaction of 1 was a simple descending sigmoid inflecting at the pKa of the carboxyl group.The pH profile of 2 was a composite of two bell-shaped curves which disclosed the abnormally low pKa's of the carboxyl group and one of the two pyridinium groups.The change in the reaction path and the abnormal pKa's observed withthe structural variation in maleamic acid derivatives suggest that the change in enzyme specificity and the perturbed pKa's of the active site functional groups can be achieved with a relatively loose geometry of the enzyme-substrate complex.The failure to observe the metal ion catalysis of the amide hydrolysis of 1 and 2 indicates that the metal complexation of the compounds is inefficient.
