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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.

Rapid intramolecular oxidation of the car-banion (NH3)5CoNCHPh generated in [(NH3)5Co-NC–CH2Ph]3+ yields the nitrile radical which immedi-ately dimerises to stilbene dinitrile.

Crystal structure determinations have been carried out on recrystallized samples of the ‘brown’ and ‘green’ forms of the title compound [CO(O·C6H4·CH:N·[CH2]3·S·[CH2]2·S·[CH2]3·N:CH·C6H4·O)]+I–. (I) and (II) respectively, by X-ray diffraction, using diffractometer data, and refined by least squares to R 0.043 (I) and 0.042 (II) for 581 and 3 427 reflections. Crystals of (I) are monoclinic, space group C2, a= 13.155(6), b= 11.915(4), c= 7.685(3)A, β= 106.69(4)°, Z= 2. Crystals of (II) are triclinic, space group P, a= 20.010(8), b= 13.321(4), c= 10.086(4)A, α= 68.74(3), β= 93.41(3), γ= 92.90(3)°, Z= 4. (II) contains a methanol solvent molecule in the lattice and comprises two types of cation, one in which the S,O,N from the same half of the ligand are coplanar, and a second, identical with that found in (I), in which the two ligand oxygen atoms are mutually trans. An absolute configuration is suggested for (I). Both cation types contain two-fold rotation axes, that in (I) being Imposed crystallographically.

Il semblerait ne pas y avoir de relation entre la loi de vitesse et la distribution des produits pour l'hydrolyse basique de [(NH 3 ) 5 CoX] n+ en presence d'anions Y m−

Synthese de (dinitro-1,12 hexaazapentacyclodotriacontane) Co(III) 3+ . La reduction par Zn et HCl donne les complexes de Co(II) et reduit les groupes nitro en groupes amino

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

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.

Le compose cristallise dans le systeme monoclinique, groupe P2 1 /c avec Z=4. Coordination octaedrique autour du cation. Etude electrochimique et photochimique

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