Cobalt monovalent, complexes

In some instances the metal complex may become the anode instead of the cathode. The acidic radicles have, in this case, increased at the expense of ammonia until there is a greater number of acidic radicles in the complex than corresponds to the valency of the metallic atom thus [Co(NH8)s.(NO,)J. If valency is determined by the above method it is found, since cobalt is trivalent, and (N02)4 has a total valency of four, that the valency of the complex, namely, three minus four, has a unit negative value. The complex is thus anodic and unites with one atom of a monovalent metal or its equivalent. The complex radicle cited, therefore, united with potassium yields the substance [Co(NH.))2.(N02)4]K, or potassium tctranitrito-diammino-eobalt,. 

Such a configuration should on replacement of one ammonia molecule by acidic or other monovalent radicle yield only one compound, and this is proved to be the case. On the other hand, if two acidic, or other groups replace two ammonia groups in the complex, isomerism should be possible, yielding two isomers of the formula [M(NII3)4R2 R. In the case of dinitro-tctrammino-cobaltic nitrate, [Co(NIi2)4(N02)2 N03, two isomeric forms are known to exist, one brown in colour, the other yellow. The two substances may be represented by the following formula —... 

It has been shown, that a divalent acidic radicle may occupy one or two co-ordinate positions. In this case, therefore, the divalent radicle occupies only one co-ordinate position, but as a divalent radicle it satisfies two principal valencies of the cobalt atom, and hence the complex cation is monovalent. 

Ammino-derivatives op Cobalt Salts—Cobaltous Salt Ammines—Cobaltic Salt Ammines—Mononuclear Cobalt-ammines containing One Atom of Cobalt in the Molecule—Cobaltic Salts with Trivalent Cation—Cobalt-ammines Containing Divalent Cation—Cobalt-ammines containing Monovalent Cation—Cobalt-ammines consisting of Non-dissociable Complex— Cobalt-ammines containing Monovalent Anion—Cobalt Salts containing Trivalent Anion—Polynuclear Cobalt-ammines containing Two or more Cobalt Atoms in the Molecule—Cobalt-ammines of Unknown Constitution— Ionisation Metamerism—Polymerisation Isomerism—Valency Isomerism —Co-ordination Position Isomerism—Isomerism due to Asymmetric Cobalt Atoms. 

The classical dc polarography of vitamins A, B, B2, B6, BI2, and C, nicotinamide, tocopherols, and naphthoquinones has been reviewed [55]. Other studies have examined in detail the cyclic voltammetry of vitamin B12 employing rapid-scan voltammetry at the DME [90] and the HMDE [91]. Vitamin B12 is complexed with trivalent cobalt ion at the heterocyclic nitrogen atoms. As a result of the complexation, a catalytic hydrogen wave is formed for the compound. In addition to the catalytic wave, a wave corresponding to the reduction of the trivalent cobalt to the monovalent state is observed. 

Among the electrochemical syntheses related to the change of metal oxidation number, we emphasize obtaining acetylacetonates of divalent iron, cobalt, and nickel [551,623]. The method of alternating-current electrochemical synthesis was applied to isolate Ji-complexes of monovalent copper with allylamines, allylimines, and ally-lurea from the salts of divalent copper [624-628], We note that the same method was used for preparation of analogous ji-complexes with copper(II) halides (X = Cl, Br) [629a]. Other electrochemical syntheses with participation of metal salts and complexes are described in monographs [201,202] and literature cited therein. 

K2[Fe(NO)2(CN)2]. My former co-worker R. Nast (83) showed that the reaction of carbon monoxide with K4[Ni2I(CN)6] and K4[Ni°(CN)4] in liquid ammonia gave nickel cyanocarbonyl complexes with monovalent and zero-valent metal atoms. The isoelectronic hexacyanoiron(III) or tetra-cyanonickel(II) complexes correspond to the cyanocarbonyls [Feu(CN)5 CO]3-, [Ni (CN)3CO]2-, or [Ni°(CN)2(CO)2]2-. Cobalt is analogous to nickel in forming the complex [Co(CN)3CO]2-. According to our earlier work, [Fe"(CN)5CO]3- and [Fem(CN)6]3- are isosteric (87). Other structural investigations were concerned with tetracyano and tetracarbonyl complexes (88). 

Two perfectly reversible one-electron reduction steps are observed for Co.S ", at —0.53 V (Co +/+) and 1.205 V (Co+/ ). Comparison of the electrochemical properties of the cobalt catenate with the previously reported data for cobalt bpy or phen complexes [31, 32] shows here again a strong stabilization of the reduced states, Co and Co". Other sterically constrained polyimine ligands also lead to stabilized monovalent cobalt complexes [33-37]. Remarkable also is the drastic structural effect of the catenate on the Co +/-+ redox potential whereas bpy or phen complexes of cobalt(II) can easily be oxidized to octahedral cobalt(III) [36, 38], the redox potential value of the Co + -+ couple being close to 0 V, no oxidation peak is observed for Co.5 + prior to ligand oxidation (Ep > 1.6 V). The destabilization effect of Co " due to tetrahedral environment provided by the entwined and interlocked structure of 5 is thus very large (>1.5 V). 

All of the above ligands (H2P) contain on the central nitrogens two extremely weakly acidic protons, which can be substituted by two monovalent metal ions (M21—P) or one divalent metal ion (M11—P). If the central ion has an oxidation state of +3, an extra monovalent anion (X) is added to it in a plane perpendicular to the porphyrin plane (MmX—P), if the oxidation state is +4, two extra monovalent anions join the metal on both sides of the porphyrin plane (MIVX2—P), or there is one divalent anion, usually oxygen, e.g. (MoIV0—P). Very often the coordination sites 5 and 6 of bivalent central ions are occupied by rather firmly bound neutral extra ligands. Familiar examples are CO, H2O2 and O2 in iron, O2 in cobalt, pyridine and water in almost all metal complexes of the porphyrins. 

Platinates, bis(oxalato)-, 139 cadmium complexes superstructure, 142 cobalt complexes, 140 electrical conductivity, 14] superstructure, 141 thermopower, 141 divalent cation salts, 140 iron complexes structure, 142 lead complexes superstructure, 142 magnesium complexes, 140 electrical conduction, 142 structure, 142 thermopower, 142 modulated superstructure, 139 monovalent cation salts, 139 nickel complexes structure, 141 partially oxidized, 139 Platinates, tetracyano-, 136 anion-deficient salts, 136 electrical conduction, 138 optical properties, 138 cation-deficient salts, 138 oxidation states, 136 partially oxidized, 138 semiconductors, 134 Platinum colloidal... 

The various aspects of oxidative polymerization of phenols have been thoroughly reviewed. Most commonly PPEs are produced by the self-con-densation of a monovalent phenol in the presence of oxygen and a metal-amine-complex catalyst. Manganese, copper and cobalt can be used as the metal in the catalyst. Cu+ is most commonly utilized. For example, the preparation of the catalyst can be achieved by stirring cuprous bromide and di-n-butyl amine in toluene. ... 

Additionally, acetylene may be also cocyclized with nitriles to form substituted pyridines using Co - zeolites as with soluble cobaltous complexes. Only Co is active in this reaction which needs an insertion of the nitrile into the M pentacycle. Apparently this is the element that enables competition of the nitrile with acetylene. It also appeared that the cobalt centers had to swing between the trivalent and monovalent states (45). The use of substituted acetylenes showed that the 2-, 5-substituted pyridines are significantly favoured by comparison with homogeneous media. 

The Co-Na-MOR and Co-H-MOR were prepared by ion exchange of Na-MOR and H-MOR with Co(acetate)2 solutions at 350 K [10P2]. In the Co-Na-MOR and Co-H-MOR samples exchanged to various extents with cobalt (Co/Al = 0.1 0.5), isolated Co was the most abundant species, whereas the residual cobalt was present as [Co-O-Co]. The FTIR results demonstrated that in all Co-MOR samples, irrespective of the cobalt content, cobalt is almost exclusively located inside the mordenite chaimels. In the presence of monovalent cobalt complex with EDMA, zeolites have been synthesized from aluminosilicate gels in hydrothermal conditions [llKlj. Three kinds of zeolites, i.e., MOR-, MFI-, and ANA-types were obtained. The cobalt atoms have been shown to be located in the MOR-framework, through Co-atom substitution and not in micropores as a complex. 

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