Tris amine, formation complexes

Structures have been determined for [Fe(gmi)3](BF4)2 (gmi = MeN=CHCF[=NMe), the iron(II) tris-diazabutadiene-cage complex of (79) generated from cyclohexanedione rather than from biacetyl, and [Fe(apmi)3][Fe(CN)5(N0)] 4F[20, where apmi is the Schiff base from 2-acetylpyridine and methylamine. Rate constants for mer fac isomerization of [Fe(apmi)3] " were estimated indirectly from base hydrolysis kinetics, studied for this and other Schiff base complexes in methanol-water mixtures. The attenuation by the —CH2— spacer of substituent effects on rate constants for base hydrolysis of complexes [Fe(sb)3] has been assessed for pairs of Schiff base complexes derived from substituted benzylamines and their aniline analogues. It is generally believed that iron(II) Schiff base complexes are formed by a template mechanism on the Fe " ", but isolation of a precursor in which two molecules of Schiff base and one molecule of 2-acetylpyridine are coordinated to Fe + suggests that Schiff base formation in the presence of this ion probably occurs by attack of the amine at coordinated, and thereby activated, ketone rather than by a true template reaction. ... 

Involvement of two nucleophilic nitrogen atoms is thus typical for the amino heterocycles. The mutual disposition of the pyridine and amine nitrogen atoms allows the formation of chelate structures for the cobalt complexes of purine, 221 and 222. Structures with the N, iV -five-membered metal cycles were proven for the tri- and tetranuclear complexes of silver ) with 8-aminoquinoline (223) (92IC4370), and polymeric copper- and rhodium-acetate clusters (224). Another coordination mode can be found in the complexes of 4-amino-3,5-bis(pyridin-2-yl)-l,2,4-triazole, (225 or... 

The circular dichroism (CD) spectra of optically active di-, tri-, and tetranuclear complexes of chromium(III) and cobalt(III) have been reported and used to establish the complexes absolute configurations (55 59, 111, 115, 116, 152-157). The changes in circular dichroism resulting from ion pairing have been studied for the tetranuclear hexol Co j(OH)2Co(NH,)4J, h+ and have been shown to be attributable to the vicinal effect of the chiral oxygen centers produced stereospecifically by the ion-pair formation (56). For a series of trinuclear cobalt (III) amine complexes, cis-Co(CN)2[(OH)2Co(N4)2 J3 +, it was shown that the main CD contributions due to the two chiral Co(OH)4(CN)2 and Co(N4)(OH)2 centers are additive (155). In the case of the related tetranuclear complex Co((OH)2Co(en)2J,< + this postulate of additivity of CD spectra proved unsatisfactory (57). 

The choice of tridentate amine has a critical impact on the coordination mode of the ambidentate nitrite ligand, N02.499,500 Complexes with substituted tri- and tetraamines have shown that bulky substituents may prevent the formation of the -N02 bridged polymeric complexes, and the intramolecular hydrogen network may stabilize N coordination of nitrite. 

Bulk electrochemical reduction of the platinum(IV) complex of the tridentate ligand l,l,l-tris(aminomethyl)ethane(tame), [Pt(tame)2]4+, leads to the quantitative formation of [Pt(tame)2]2+ (28), in which one of the amine donor groups in tame remains noncoordinated.141 The X-ray structure of the diprotonated complex [Pt(Htame)2]4+, as its tetrachlorozincate(II) salt, is also reported. 

A similar reaction mechanism was proposed by Chin et al. [32] for the hydrolysis of the biological phosphate monoester adenosine monophosphate (AMP) by the complex [(trpn) Co (OH2)]2+ [trpn = tris(ami-nopropyl)amine]. Rapid cleavage is observed only in the presence of 2 equiv metal complex. It is evident from 31P NMR spectra that on coordination of 1 equiv (trpn)Co to AMP a stable four-membered chelate complex 4 is formed. The second (trpn)Co molecule may bind to another oxygen atom of the substrate (formation of 5) and provide a Co-OH nucleophile which replaces the alkoxy group. The half-life of AMP in 5 is about 1 h at pD 5 and 25 °C. 

Kinetics of formation of the dinuclear iron(III) complex [(tpa)Fe (p-0)(p-urea)Fe(tpa)]s+ tpa = tris(2-pyridylmethyl)amine were investigated in relation to the suggestion that urease action in vivo involves an intermediate containing Ni (p - O H) (p -ur e a) Ni. The mechanism of formation of the di-iron species from [(tpa)(H20)Fe(p-0)Fe(0H)(tpa)]3+ is proposed to involve three reversible steps (350). Three kinetically distinct steps are also involved in the deposition of FeO(OH) in... 

The elimination of HC1 was proposed to occur also during the H2 activation with the [Pd(PNP)Cl]Cl complexes (PNP = bis-2-(diphenylphosphino)ethyl benzy-lamine, bis-2-(diphenylphosphino)ethyl amine or tris-2-(diphenylphosphino)ethyl amine) [24, 25]. Based on the findings of 31P 1H - and 1H-NMR investigations, the hydride [HPd(PNP)]Cl was detected under H2 atmosphere. The alternative mechanism which involves the oxidative addition of H2 with formation of a Pd(IV)-dihydride intermediate, appeared less likely on the basis of thermodynamic considerations. 

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