III cation

Compounds that have the empirical formulas MCr02 and DCr204 where M is a monovalent and D a divalent cation, are known as chromites. These are actually mixed oxides and probably are better written as M20-Cr203 and D0-Cr203, respectively. The oxides of D are largely spinels, ie, the oxygen atoms define a close-packed cubic array having the octahedral holes occupied by the Cr(III) cation and the tetrahedral holes occupied by D (54). Chromite ore is an important member of this class of oxides. 

Group III sulfides and hydroxides. /Left) Five Group III cations precipitatB as sulfides. These are NiS. CoS. and FeS (all of which are black], MnS (salmon), and ZnS (white). (Right) Jvio cations precipitate as hydroxides. AIIOHfo (white) and Cr(0H)3 (gray-green). 

Note Iron(III) cations also react and give the well known deep red iron(III) isothiocyanate. 

There have been no reports of complexes of " JV-substituted thiosemicarbazones derived from 2-formylpyridine, but 2-acetylpyridine JV-methyl-thiosemicarbazone, 3a, formed [Fe(3a-H)2]C104 and [Fe(3a-H)2]FeCl4 [117]. The nature of these two species was established by partial elemental analyses, molar conductivities, magnetic moments, electronic, infrared, mass and electron spin resonance spectra. A crystal structure of a related selenosemicarbazone complex confirmed the presence of a distorted octahedral iron(III) cation coordinated by two deprotonated anions so that each ligand is essentially planar and the azomethine nitrogens are trans to each other the pyridyl nitrogen and selenium donors are both cis. 

A warmed alcoholic solution of cobalt(Il) nitrate and 2-formylpyridine S-methyldithiocarbazate, 6, yielded diamagnetic [Co(6-H)2]N03 [126]. However, cobalt(II) chloride, bromide and thiocyanate yielded complexes with cobalt(III) cations and cobalt(II) anions, [Co(9-H)2]2 [C0A4]. 

Very recently, Chant et al. (65) reported the existence of a bis-chelated Fe(III) cation, obtained by titrating Fe(i-Pr2 tc)3 with Fe(III)-ions to the endpoint corresponding with [FeO —Pr2perchlorate acid hydrolysis of Q i Pr2dtc. ... 

Due to the high charge-to-radius ratio, a hexaaqua Cr(III) cation loses protons to form olates (3atb) in this hydrolysis process. One, two and three protons can be lost from Cr-coordinated HgO to yield the mono-, di- and tri- hydroxides of hydrous Cr species,... 

Olated Cr(III) reagents were prepared according to Equation 2 by reacting CrtNOg) with a calculated equivalent of NaOH. Chromic nitrate was used Decause the freshly prepared solution affords the hexaaqua Cr(III) cations. 

The reactive Cr(III) species in polymer crosslinking are the dates derived from the hydrolysis of hydrated Cr(III) cations. 

Clark and co-workers have reported reactions of Ir(III) cations with terminal alkynes in methanol in which alkoxycarbene complexes are formed (60). By analogy with a more extensively studied Pt(II) system (61), it has been concluded that cationic vinylidene complexes, e.g., 35, are reaction intermediates, e.g.,... 

GFP hopo ICBP IP3 Ln3+ mal memal MLCK nota oxine par pdta pmea py quin-2 green fluorescent protein hydroxypyridinon(at)e intestinal calcium-binding protein inositol 1,4,5-triphosphate a lanthanide(III) cation malonate methylmalonate myosin light chain kinase 1,4,7-triazacyclononane-l,4,7-triacetate 8- hydroxyquinoline pyridine-2-azo-4 -dimethylaniline propylene-1,2-diaminetetraacetate 9- [2-(phosphonomethoxy)ethyl] adenine pjrridine pjrridyl 8-amino-2- [(2-amino-5-methylphenoxy )methyl] -6-methoxyquinoline-ATJV -tetraacetate 2- [ [2-[his(carboxymethyl)amino]-5-methyl-phenoxy] methyl] -6-methoxy-8- [bis(carboxymethyl) amino] quinoline]... 

Bailey, N.A., Blunt, E.H., Fairhurst, G., and White, C., Reactions of the r 6-benzene(ri5-ethyltetramethylene cyclopentadie3nyl) rhodium(III) cation and related species with nucleophilies, /. Chem. Soc., Dalton, 829, 1980. 

Dichromate anions are readily absorbed under acidic conditions by wool that has been dyed with chrome dyes. The chromium(VI) on the fibre is then gradually reduced by the cystine residues in wool keratin to chromium(III) cations, which react with the dye ligands to form a stable complex. In this way the cystine disulphide bonds are destroyed, resulting in oxidative degradation of the wool fibres [71]. 

The chromium (III) cations then combine with the carboxylate groups in the wool fibre (Scheme 5.20). 

Fig. 8. Structures of the biferrocenylene (II, III) cation (a) and the biferrocene (II, III) cation (b). Reproduced with permission from Ref.5)...

Inert M(III) cations will exchange their ligands faster once they are adsorbed to an oxide surface. 

---