The Magnetic Criterion for Bond Type

Quadricovalent complexes of silver(II) should have the same planar configuration as those of copper(II). This has been verified33 for the silver(II) salt of picolinic acid, which is isomorphous with the cop-per(II) salt and which shows moreover the high birefringence expected for a parallel arrangement of planar molecules with the structure 

Sidgwick, The Electronic Theory of Valency, Clarendon Press, Oxford, 1927. 

This simple rule is satisfactory for many substances, but there are also many exceptions. For example, the complex [Ni(CN)4] is diamagnetic, although the rule would make it paramagnetic (resembling Se, Z = 34, with magnetic moment about 2.8 magnetons). 

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Complex Bond Orbitals The Magnetic Criterion for Bond Type... 

These complexes and others of similar character are discussed further in Chapter 5, in which a magnetic criterion for bond type applicable to complexes of the transition elements is described. 

The hybrid bond orbitals discussed in the preceding chapter have been described as having only a small amount of d and / character. The bonds in many molecules and complex ions, especially those involving atoms of the transition elements, can be discussed in a simple way in terms of hybrid orbitals with a large amount of d character (and, in a few cases, / character). These bonds and a magnetic criterion for bond type are discussed in the following sections. 

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