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Synthese de [(NH 3 ) 5 CoNCN(CH 3 ) 2 ] 3+ et loi de vitesse de son hydrolyse basique. Le produit d'hydrolyse [(NH 3 ) 5 CoNHCON(CH 3 ) 2 ] 2+ est stable en solution basique mais s'isomerise rapidement en [(NH 3 ) 5 CoOC(NH 2 )N(CH 3 ) 2 ] 3+ en solution acide. Spectres RMN de 1 H

Revue des phenomenes associes a la chimie des ions metalliques mettant en jeu des hexaazamacropolycycles

Le phosphate de dinitro-2,4 phenyle coordine au reste Co(NH 3 ) 5 3+ est decompose dans une base aqueuse en phosphoramidate (lie par N et O) et dinitro-2,4 phenolate. Le cycle chelate s'ouvre ensuite en phosphoramidate monodente. Mecanisme

The intramolecular condensation of monodentate (aminomethyl) carbonyl ligand NH 2 CH 2 C(=O)R (R=H, CH 3 , phenyl) with quadridentate amines such as tren (tris-(2-aminoethyl) amine) and trien (1,8-diamino-3,6-diazaoctane) bound to cobalt(III) ions is explored in terms of controlling the regiospecificity and stereospecificity of such condensations

The redox chemistry of the mixed nitrogen-sulfur donor cobalt(III) complexes with the macrobicyclic ligands 8-methyl-6, 10, 19-trithia-l, 3, 14, 16-tetraazabicyclo[6.6.6]icosane (azacapten), l-methyl-8-nitro-3, 13, 16-trithia-6, 10, 19-triazabicyclo[6.6.6]icosane ((NO)capten), and 8-ammonio-1-methyl-3, 13, 16-trithia-6, 10, 19-triazabicyclo[6.6.6]icosane ((NH )capten) qnd of the hexadentate precursor ligand 5-(4-amino-2-thiabutyl)-5-methyl-3,7-dithia-l,9-nonanediamine (ten) has been investigated in aqueous and aprotic solutions. The macrobicyclic complexes exhibit a chemically and electrochemically reversible Co(III)/Co(II) couple near 0 V in aqueous (NHE) and aprotic solutions (Ag/AgCl) and a chemically irreversible but elctrochemically reversible 1-e couple near-1 V, nominally Co(II)/Co(I). In addition, a further multielectron couple is observed for the azacapten complex at more negative potentials. No evidence for oxidation processes was forthcoming. The low-spin d cobalt(II) complex of (NH )capten has been characterized by ESR spectroscopy at 4.2 K, and the nominally d cobalt(I) complex, at 100 K. The former compound exhibits g values at 1.94, 2.21, and 4.22, while the latter compound shows an eight-line pattern at g = 2.17 (A = 67 G) consistent with its formulation as d Co(I) and not as a d Co(II)-S radical state.

Die Hydrolyse der im Titel genannten Spezies wird in 0,5 bis 1,0m HClO4 unter Zusatz von NaClO4 im Temperaturbereich von 60 bis 80°C untersucht.

Spectroscopic and structural data of series of complexes with widely varied metal centers (d0 to d10) and an identical ligand sphere (figure) are presented. The structures comprise a range from near octahedral to near trigonal prismatic geometries and also involving additional small tetragonal perturbations. The complete series allows for an analysis of the various influences, viz. bonding and non-bonded interactions which dictate the compromise structure. Axial and rhombic distortions in solution and solid state of selected examples are discussed on the basis of electronic and EPR spectroscopy and trigonal distortions are analyzed on the basis of twist angles calculated from X-ray data.

The single crystal axial CD of three Co(III) completes has been measured between 295 and 9 K. For Λ-Co (sepulchrate) (NO3)3 the rotational strength R(1T1(E) ← 1A1) decreases from ≈11 × 10−40 c.g.s. units at 295 K to ≈0 at 80 K. The main features of the single crystal CD spectra can be explained by a static coupling model of optical activity.

Synthese et hydrolyse basique. La coordination a l'ion metallique resulte en un fort accroissement de la vitesse d'hydrolyse des coordinats coordines. Parametres d'activation

Synthese des complexes M(NH 3 ) 5 (OSO 2 CF 3 ) n+ , M(NH 2 CH 3 ) 5 (OSO 2 CF 3 ) 2+ , cis-M(en) 2 (OSO 2 CF 3 ) 2 + et trans-M(en) 2 Cl(OSO 2 CF 3 ) + avec M=metal trivalent. Constantes de vitesse d'aquation

This paper examines regio-and stereo-specificity for reactions of coordinated organic substrates. The reactions involve addition of coordinated nucleophiles where the specificity arises from non-bonded interactions, substituent effects on the metal, orbital steering directed by the chelates and electronic effects imparted by the geometry required for chelation. The reactions examined include hydration of olefins, addition of nucleophiles at coordinated imines, oxidation and alkylation of coordinated mercaptide ions, stereo-specific deuteration for chelated N-benzyl glycine and amine synthesis organised by the metal.

The postulated formation of the superoxide radical anion, O/sub 2//sup -/-, as an intermediate in the reaction of Co(sep)/sup 2 +/ (sep = sepulchrate) with molecular oxygen has now been confirmed by a trapping reaction with Cu/sup 2 +/. In the absence of Cu/sup 2 +/, O/sub 2//sup -/-oxidizes a second Co(sep)/sup 2 +/ to Co(sep)/sup 3 +/. The latter reaction, studied directly by use of the flash photolytic technique, has at 25/sup 0/C a rate constant of (4.6+/-1.1) x 10/sup 7/M/sup -1/s/sup -1/, independent of pH in the range 11.3-12.6. Nitrogen perdeuteration yields d(N)/sup 6 -/Co(sep)/sup 2 +/, which reacts with O/sub 2/ at the same rate but with O/sub 2//sup -/ 2.1 times more slowly. The proposed mechanism of the O/sub 2//sup -/ reaction consists of the hydrogen atom abstraction from a N-H bond of Co(sep)/sup 2 +/ by O/sub 2//sup -/, followed by the rapid protonation of the products, Co/sup III/(sep-H)/sup 2 +/ and HO/sub 2/, to form Co(sep)/sup 3 +/ and H/sub 2/O/sub 2/. In contrast, the reaction between Co(sep)/sup 2 +/ and O/sub 2/, which shows no kinetic isotope effect, occurs by outer-sphere electron transfer.

The paper reviews and discusses some aspects of substitution of octahedral complexes in aqueous solution. The areas considered primarily are anation, aquation and substitution in labile and kinetically robust systems. The evidence for the existence of intermediates of reduced coordination number, the characteristics and properties of such intermediates and the implications of these properties in the aforementioned processes are considered. A discussion of some primary aspects of base hydrolysis in octahedral complexes is included. The intermediates derived from these processes and details concerning their lifetime and structure are discussed. Finally, the use of such intermediates for synthesis of labile and thermodynamically unstable products is exemplified. The dissociative character of all this chemistry is offset against the comparative absence of nucleophilic characteristics. The point is made that the absence of nucleophilic paths for electronically rich systems should lead more commonly to the observation of electrophilic reactions and some of the evidence for these is presented.

The base hydrolysis of acetonitrile to acetamide is catalyzed by a factor of 2 X l0(6) on coordination to CO(NH3)5 8+. Hydroxide appears to attack the carbon atom of the nitrile group, while in a separate and concurrent process the methyl protons exchange. On addition of acid to the acetamido complex produced, protonation occurs on the carbonyl oxygen (pKa = 3.02; μ = 1.0 M, NaC104; T = 25°) rather than on the amide nitrogen atom.