Nickel complexes, magnetic moments

Nickel(II) complexes of (505) exhibit spin equilibria in solution.1355 With the bidentate analogues (506), complexes [Ni(506)2] have been isolated.1356 When Rj = Ph, the complex is tetrahedral in solution. It has a temperature independent magnetic moment of 2.75pB- When R = Me, the complex exhibits square planar-tetrahedral equilibrium in solution. Both are, however, diamagnetic in the solid state. 

Barefield, Busch and Nelson (1968) Iron, cobalt and nickel complexes having anomalous magnetic moments [202]. 

The only apparently mononuclear complex of nickel(I) so far discovered is K3Ni(CN)4 (187). It is an extremely reactive substance obtained by reduction of K2Ni(CN)4 in strongly alkaline solution it has a magnetic moment of 1.73 B.M., which is the value expected for one unpaired electron. This compound may be compared with the complex acetylides prepared by... 

Griffith el al. (Ill, 112) have shown that the blue compounds obtained by the interaction of nitric oxide and nickel carbonyl in the presence of water or an alcohol (68) have the general formula Ni(NO)(OR)3, and are probably tetrahedral. The N—0 stretching frequency of 1828 cm-1 in Ni(NO)(OH)3 indicates coordination of N0+ the spectra show absorption at 15,500 cm-1, in agreement with other such complexes, but the magnetic moment of Ni(NO)(OH)3 is only 2.97 B.M., which indicates considerable distortion. 

The first observation of an abnormal magnetic moment, in the sense intended here, was made by French et al. (90), who found that the normally diamagnetic bis(formylcamphor)ethylenedi-imine nickel(II) had a magnetic moment of 1.9 B.M. in methanol. They suggested that a fraction of the complex molecules were fully paramagnetic in the solution, an idea which is still universally accepted. Willis and Mellor (261) developed this theme and found that the phenomenon covered a wide range of nickel chelates and also of solvents. The moments developed were larger in pyridine than in inert solvents like benzene or chloroform, and the moments in pyridine often corresponded to complete conversion into para-... 

Analytical data on the soluble products isolated from chloroform are in excellent agreement with the composition 1 Ni+2 1 monoalkylated ligand 1 I or Br. The magnetic moment of this methylated complex was found to be 1.89 Bohr magnetons per nickel (II). The molar conductivities of the methylated and benzylated complexes in methanol at 25° C. are 75.4 and 68.4 ohm-1, respectively. These values approximate those expected for uni-univalent electrolytes in this solvent. The formulation of these alkylated compounds as dimeric electrolytes (structure VII) does not appear to be totally consistent with their physical properties. One or both halide ions may be bound to the metal ion. These results lead to the easily understood generalization that terminal sulfur atoms alkylate more readily than bridged mercaptide groups. 

The reaction of NUeoKU with U yields, i diamagnetic complex of formulation Miten l. What is the oxidation state of ruckcl in this complex ts your answer consistent with the absence of j magnetic moment. The complex. lNi <>-CriHj[Pg.848]

Nickel(II) in tetrahedral symmetry has an orbitally degenerate ground state and the magnetic moments of tetrahedral complexes are expected to be substantially higher than those of six-coordinate complexes because of the larger orbital contribution. The magnetic moments are usually found to be in the range 3.3-4.0 BM at room temperature and tend to zero at very low temperatures. 

The theory of the magnetic susceptibility of nickel(II) complexes is well established and several review articles have already appeared.375-379 A quantity of interest in studying the magnetic properties of nickel(II) complexes is the effective magnetic moment p = (8xT). 

Table 25 Typical Values of the Effective Magnetic Moment at Room Temperature of Nickel(ll) Complexes in Various Coordination Environments...

Table 30 Magnetic Moments and Spectral Parameters for some Pseudotetrahedral Nickel(II) Complexes ...

Table 32 Magnetic Moments and Spectra) Parameters for some High-spin Five-coordinate Nickel(Il) Complexes with Nearly Square Pyramidal Geometry 1... 

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