Magnetic moments of octahedral complexes

The magnetic moment of octahedral complexes can often be used to distinguish between those in which there are d sp octahedral bonds and... 

Table 5-3.—Observed Magnetic Moments of Octahedral Complexes of Transition Elements ...

Thus the magnetic moments of tetrahedral complexes lie in the range 4.4-4.8 BM, whereas those of octahedral complexes are around 4,8-5.2 BM at room temperature, falling off appreciably as the temperature is reduced. 

The neutral complex NiL2py2-py (201 L = 9,10-phenanthrenequinone in the mononegative semiquinone form) has a cis octahedral structure.1602 The magnetic moment of the complex (4.20 BM) has been attributed to the sum of one 5 = 1 and two S = i non-interacting spin systems which allowed the description of the complex as a nickel(II)-semiquinone system. The same holds for other neutral complexes of the types NiLz and NiL bipy), as confirmed by IR... 

Fig. 64 Effective magnetic moment of octahedral Mn(III) complexes for various crystal-field strengths showing the spin-transition...

Magnetic moments of octahedral Ni(II) complexes are usually close to the spin-only value of 2.83 b- In contrast, tetrahedral complexes possess magnetic moments 4 b due to orbital contributions (see Section 20.8), and square... 

Most Fe complexes are octahedral but several other stereochemistries are known (Table 25.3). [FeX4] (X = Cl, Br, I, NCS) are tetrahedral. A single absorption around 4000 cm due to the T2 E transition is as expected, but magnetic moments of these and other apparently tetrahedral complexes are reported to lie in the range 5.0-5.4BM, and the higher values are difficult to explain. 

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