Cobalt , magnetic susceptibility compounds

JFiq. X-l.—Curves showing the reciprocal of molar magnetic susceptibility of compounds of cobalt(II) as a function of the absolute temperature. 

The active C(j-bromoamminebis(ethylenediamine)cobalt(III) salts, like the racemic compounds, are similar in properties to the corresponding cis-chloroamminebis(ethylenediamine)cobalt(III) salts, but they have been less extensively investigated. They are quite stable, and their solutions do not race-mize on standing at room temperature or even on heating to incipient boil-ing.i They can be converted from one salt to another without loss of optical activity. Treatment of the active bromide or(+)-a-bromocamphor- r-sulfonate with liquid ammonia yields the corresponding optically active cw-diammine-bis(ethylenediamine)cobalt(III) salts. A partial resolution of the racemic bromide into optical isomers on ( +)- and ( — )-quartz has been reported.The specific magnetic susceptibility has been found to be 3.49 X... 

The only known solid compounds containing the ion Co(H20)6 are the sulfate Co2(S04)3 18H20 and its alums. Although the first synthesizer of the sulfate reported he was able to store it in a stoppered tube for months without visible decomposition, later authors stated that this compound and the ammonium alum decompose at laboratory temperature within a few hours. By an improved drying procedure, the cesium alum is readily obtained in a form in which even the magnetic susceptibility (a very sensitive criterion for the presence of dipositive cobalt) shows that only very slow decomposition occurs. Use of this... 

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...

---