Low-spin complexes Co

For a d6 ion such as Co3+, a low-spin complex would contain no unpaired electrons, whereas the high-spin case would contain four unpaired electrons. The low-spin complex [Co(NH3)6]C13 has a magnetic moment of 0, whereas that of K3[CoF6] is 4.36 BM in accord with these predictions. 

The five-co-ordinate, low-spin complexes [Co(Me6[14]l,4,8,ll-tetraeneN4)X] (ClOJj (X Cl, Br, CIO4, HjO, or MeCN) have been made by using a template reaction to make the corresponding [FeL(MeCN)2](PFg)2 complex followed by displacement of the ligand from Fe and reaction with cobalt(ii). A kinetics and mechanism study of the irreversible oxidation of the diaquacobalt(ii), perchlorate complex of (13) revealed that the process is accelerated by X and increases in acidity. 

Substantial contact contribution to the isotropic shifts have been observed in variable temperature H n.m.r. studies of low-spin complexes Co(BAE) and Co(F3BAE) (18). ... 

For the low-spin complex [Co(en)(NH3)2Cl2]C104, identify the following ... 

The trans isomer Cu(en)2Cl2, where en stands for H2NCH2CH2NH2, is more stable than the cis isomer. Rationalize this in terms of (i) the classical ionic model, and (ii) the crystal field theory. Which of the above arguments is apphcable to the low-spin complex [Co(en)2Cl2]+ ... 

Co(c-Hx2 tc)3BF4 is a 1 1 electrolyte in nitromethane and has a magnetic moment of 3.48 BM at room temperature, which is in between the value for a high-spin and a low-spin complex. 

Complexes of metals like Co3+ that exhibit more than one spin state are classified as high-spin or low-spin. A high-spin complex, such as [CoF6]3, is one in which the d electrons are arranged according to Hund s rule to give the maximum number of unpaired electrons. A low-spin complex, such as [Co(CN)6]3-, is one in which the d electrons are paired up to give a maximum number of doubly occupied d orbitals and a minimum number of unpaired electrons. 

The term cobaloximes refers to that class of cobalt complexes in which two dimethylglyoximato or other glyoximato monoanions occupy four coordination positions about cobalt and in which the four N donors are in essentially the same plane. A neutral octahedral low-spin d6 Co(III) cobaloxime is shown in Figure 1. Cobaloximes with this oxidation state have been studied most extensively since these are more stable than the oxidation state I, II, and IV compounds. The chemistry of these latter oxidation state compounds will be reviewed... 

Determine the ground-state electron configuration and spectral term of the following octahedral complexes low-spin Fe(CN)g- low-spin Cr(CO)6 high-spin Cr(H20)g+. 

The new low-spin complexes [Fe(43)L1L2](PF6)2 (Lt = L2 = imidazole, MeCN Lj = MeCN, L2 = CO) have been isolated. The bis-acetonitrile complexes undergo reversible substitution reactions with both CO and imidazole. In the case of imidazole substitution, one or more of the following are present in solution depending on the substrate concentration [Fe(43)(MeCN)2]2 +, [Fe(43)(MeCN)(imid)]2 +, and [Fe(43)-(imid)2]2 +. For CO substitution, only [Fe(43)(MeCN)2J2+ and [Fe(43)(CO)-(MeCN)]2+ are present in solution when the pressure of CO gas is less than or equal to one atmosphere.218 The structure of high-spin [FeIICl(44)]I has been determined... 

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