Cobalt imidazole

Fig. 16 Views and magnetic properties of the open-framework coordination polymers based on cobalt imidazolates. (a) Evacuated [Co(im)J-0 5Ch. (b) [Co(im)j4- (c) [Co(im)j]j. (d) [Co5(im)j 0.4Mb]j. (e) Plots of temperature dependence of ac susceptibility obtained at 0.1 Oe field for [Co(im)J 0.5Ch. A peak appears at 15 K, which is indicative of the ferromagnetic character of this compound, (f) Plot of the thermal evolution of the for [CoCiml lj at 10 kOe field. The inset shows the hysteresis loop at 1.8 K ( ) and 5.0 K (o). (Co, blue O, red C, brown N, violet H, white. Solvent guest molecules in (d) are represented as spheres) Reprinted from ref 168 [Tian YQ, Cai C-X, Ren X-M, Duan C-Y, Xu Y, Gao S, You X-Z, The SUica-Like Extended Polymorphism of Cobalt(ll) Imidazolate Three-Dimensional Erameworks X-ray Single-Crystal Structures and Magnetic Properties (2003) Chem Eur 1 9 5673]. Copyright WUey-VCH Verlag GmbH Co. KGaA. Reproduced with permission...

As a result of solvothermal syntheses using IM and MelM, EtIM and PhIM derivatives, a family of zinc and cobalt imidazolates with porous topology types observed for zeolites has been discovered. Among the microporous solids... 

Ma S, Goenaga GA, Call AV, Liu D-J (2011) Cobalt imidazolate framework as precursor for oxygen reduction reaction electrocatalysts. Chem Eur J 17 2063-2067... 

C, but it played a key role in generating a high density of catalytic sites with proper accessibility for oxygen. The choice of cobalt imidazolate MOF precursor was explained by its analogous structure with the C0N4 (or FeN4) macromolecules precursors for nonprecious metal catalysts for the ORR.131... 

Resorcinol or hydroquinone production from m- or -diisopropylben2ene [100-18-5] is realized in two steps, air oxidation and cleavage, as shown above. Air oxidation to obtain the dihydroperoxide (DHP) coproduces the corresponding hydroxyhydroperoxide (HHP) and dicarbinol (DC). This formation of alcohols is inherent to the autooxidation process itself and the amounts increase as DIPB conversion increases. Generally, this oxidation is carried out at 90—100°C in aqueous sodium hydroxide with eventually, in addition, organic bases (pyridine, imidazole, citrate, or oxalate) (8) as well as cobalt or copper salts (9). 

Despite the weak basicity of isoxazoles, complexes of the parent methyl and phenyl derivatives with numerous metal ions such as copper, zinc, cobalt, etc. have been described (79AHC(25) 147). Many transition metal cations form complexes with Imidazoles the coordination number is four to six (70AHC(12)103). The chemistry of pyrazole complexes has been especially well studied and coordination compounds are known with thlazoles and 1,2,4-triazoles. Tetrazole anions also form good ligands for heavy metals (77AHC(21)323). 

The structure of the diamagnetic, cherry-red vitamin B12 is shown in Fig. 26.6 and it can be seen that the coordination sphere of the cobalt has many similarities with that of iron in haem (see Fig. 25.7). In both cases the metal is coordinated to 4 nitrogen atoms of an unsaturated macrocycle (in this case part of a corrin ring which is less symmetrical and not so unsaturated as the porphyrin in haem) with an imidazole nitrogen in the fifth position. A major... 

The ONIOM protein system contains the substrate, methylmalonyl-CoA, bound to the active site, the cofactor (AdoCbl) and all amino acids within a 15-A radius from the cobalt atom. The active-site selection contains a truncated AdoCbl and the imidazole ring of its lower ligand. The QM part was calculated using the BP86 functional [31, 72] because it gives better agreement with experimental Co—C bond energies [73, 74], This a different choice of functional compared to the other studies in the present review. 

Table 12 shows the cis effect of the axial ligand X or L on the optical spectrum of cobalt(III) etioporphyrin derivatives Co(Etio-I)LX [32a-h] which behave similarly to the corresponding rhodium(III) complexes (Table 4). Analogous trends are found in the Co(TTP)LX series (133). The only notable feature is the large bathochromic shift caused by benzimidazole in [32h] obviously this ligand is far more different from pyridine than imidazole, the condensed ring system acting as a stronger 7r-acceptor.

Cobalt, Co " (cf ) 4, tetrahedral 5 -Thiolate, thioether, N-imidazole Alkyl group transfer, oxidases... 

Reactions of cobalt porphyrin with p-fluoranyl or phenyl-A -butylimidazole proceeds analogously—both fluoranyl and imidazole coordinate with the cobalt contained in the porphyrin complex, but fluoranyl was fixed in its semiquinone, anion-radical form (Okamoto and Fukuzumi 2003). 

The complexes [LCo(p-02)(p-OH)CoL] [L = en, trien, dien, tetra-ethylenepentamine, or tris-(2-aminoethyl)amine] have been studied, and the new complexes [[Co(imidazole)(gly)2 202],4H20 [ Co2(imidazole)2-(gly)402 0H],3H20, and [Co(imidazole)(gly)2(02)H20] have been prepared The spectroscopic properties of various p-peroxo- and p-superoxo-cobalt(iii) complexes have been examined. The singly-bridged p-peroxo-compounds have a strong band at 300 nm, whereas this falls at 350 nm for p-peroxo-p-hydroxo-complexes and two peaks at 480 and 700 nm are observed for p-superoxo-species. The i.r. spectra of p-peroxo-bridged complexes of cobalt(iii)-cyclam have been reported. ... 

Die Umsetzung von Benzylamin mit Tctrachlormcthan unter Kohlenmonoxid- oder Stickstoff-Druck von etwa 7500 Torr (5000 kPa) bei 150° fuhrt unter (Catalyse mit Carbonyl-cobalt- Oder Carbonyl-molybdan-Komplexen zu Gemischen aus 2,4.5-Triphenyl1-Benzyl-2,4,5-triphenyl-imidazol, 2,4,5-Triphenyl-4,5-dihydro- und l-Benzyl-2,4,5-tripheny -4,5-dihydro-imidazol °. 

More recent studies of the kinetics of bromination of imidazoles coordinated to cobalt(III) have implied that, in aqueous solution, proton-abstraction from a Wheland intermediate is rate-determining at acidic pH values. In more nearly neutral conditions bromine addition becomes rate-... 

The structure of the E. coli enzyme (Fig. 16-24) shows methylcobalamin bound in a base-off conformation, with histidine 759 of the protein replacing dimethylbenzimidazole in the distal coordination position on the cobalt. This histidine is part of a sequence Asp-X-His-X-X-Gly that is found not only in methionine synthase but also in methylmalonyl-CoA mutase, glutamate mutase, and 2-methyleneglutarate mutase. However, diol dehydratase lacks this sequence and binds adenosylcobalamin with the dimethylbenz-imidazole-cobalt bond intact.417... 

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