Cobalt coordination complex

Albeit with less overall success, trifluoromethyl iodide has also been employed to effect oxidative trifluoromethylations of elemental copper and a few chromium and cobalt coordination complexes and to oxidatively cleave metal—metal bonds in complexes like Ni2(CO)2(Cp)2, Co2(CO)g, and GeMe3Fe(CO)2Cp. One of the first examples of this type of reaction is (22)... 

E8.24 The ratio of cobalt to acetylacetone in the complex is 3 1. Converting the given mass percents of Co and C to moles of Co and C, we find that for every one mole of Co in the product we have 15 moles of C moles of Co = 0.28 mol moles of C = 4.2 mol. Considering that every acac" ligand has five carbon atoms, it is obvious that for each mole of Co we have three moles of acac, This ratio is consistent with the formula Co(acac)j. (Consult Section 7.1 for more detail on the acetylacetonate ligand and cobalt coordination complexes.)... 

Brink NG, Kuehl FA and Folkers K (1950). Vitamin Bi2 The identification of vitamin B12 as a cyano-cobalt coordination complex. Science, 112, 354. 

FIGURE 1. (a) POM-supported cobalt coordination complexes in the polyoxocation, [PMo Mo2 V 044 Co(2,2 -bipy)2(H20) 4f, showing the tetra-capping and tetra-sup-porting connection mode and disordered P tetrahedron, (b) The same is shown in the polyhedral representation of the polyoxocation. (Reprinted with permission from ref. 27.). 

When, however, the ligand molecule or ion has two atoms, each of which has a lone pair of electrons, then the molecule has two donor atoms and it may be possible to form two coordinate bonds with the same metal ion such a ligand is said to be bidentate and may be exemplified by consideration of the tris(ethylenediamine)cobalt(III) complex, [Co(en)3]3+. In this six-coordinate octahedral complex of cobalt(III), each of the bidentate ethylenediamine molecules is bound to the metal ion through the lone pair electrons of the two nitrogen atoms. This results in the formation of three five-membered rings, each including the metal ion the process of ring formation is called chelation. 

Structural types for organometallic rhodium and iridium porphyrins mostly comprise five- or six-coordinate complexes (Por)M(R) or (Por)M(R)(L), where R is a (T-bonded alkyl, aryl, or other organic fragment, and Lisa neutral donor. Most examples contain rhodium, and the chemistry of the corresponding iridium porphyrins is much more scarce. The classical methods of preparation of these complexes involves either reaction of Rh(III) halides Rh(Por)X with organolithium or Grignard reagents, or reaction of Rh(I) anions [Rh(Por)] with alkyl or aryl halides. In this sense the chemistry parallels that of iron and cobalt porphyrins. 

The hexamine cobalt (II) complex is used as a coordinative catalyst, which can coordinate NO to form a nitrosyl ammine cobalt complex, and O2 to form a u -peroxo binuclear bridge complex with an oxidability equal to hydrogen peroxide, thus catalyze oxidation of NO by O2 in ammoniac aqueous solution. Experimental results under typical coal combusted flue gas treatment conditions on a laboratory packed absorber- regenerator setup show a NO removal of more than 85% can be maitained constant. 

Recent years, the authors have innovatively proposed a method by using the aqueous ammonia liquor containing hexamine cobalt (II) complex to scrub the NO-containing flue gases[6-9], since several merits of this complex have been exploited such as (1) activation of atmospheric O2 to a peroxide to accelerate the O2 solubility, (2) coordination of NO, as NO is a stronger ligand than NH3 and H2O of Co( II) complexes to enhance the NO absorption and (3), catalysis of NO oxidation to further improve the absorption both of O2 and NO. Thus, a valuable product of ammonium nitrate can be obtained. 

Preparations of heterocyclic thiosemicarbazone complexes with cobalt(II) salts of weakly coordinating anions (e.g., perchlorate and tetrafluoroborate) often result in cobalt(III) complexes due to air oxidation. The first 2-acetylpyridine thiosemicarbazone cobalt(III) complex was the diamagnetic [Co(15b-H)2]C104... 

Methyl-3-formylpyrazole 4-phenylthiosemicarbazone, 45, also coordinates as a deprotonated NNS ligand to form spin-paired cobalt(III) complexes [200]. Values of Dq and B are 2500 and 550 cm , respectively, indicating less covalency than the complexes of 40. Analogous complexes have been isolated with the related 41 having values of Dq and B of 2460 and 580 cm respectively, for [Co(41-H)2 ] [191]. 

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