below for [NiCl ] - . Here nickel is in + oxidation state and the ion has the electronic configuration . The hybridisation scheme is as shown in diagram. Each Cl – ion donates a pair of electrons.
The compound is paramagnetic since it contains two unpaired electrons. Similarly, [Ni(CO) ] has tetrahedral geometry but is diamagnetic since nickel is in zero oxidation state and contains no unpaired electron. Orbitals of Ni ion dsp hybridised orbitals of Ni [Ni(CN) ] (low spin complex) – s p Four pairs of electrons from CN groups dsp hydrid p p . .
Magnetic Properties of In the square planar complexes, the hybridisation involved is dsp . An example is [Ni(CN) ] – . Here nickel is in + oxidation state and has the electronic configuration d . The hybridisation scheme is as shown in diagram: Each of the hybridised orbitals receives a pair of electrons from a cyanide ion.
The compound is diamagnetic as evident from the absence of unpaired electron. It is important to note that the hybrid orbitals do not actually exist. In fact, hybridisation is a mathematical manipulation of wave equation for the atomic orbitals involved. The magnetic moment of coordination compounds can be measured by the magnetic susceptibility experiments.
The results can be used to obtain information about the number of unpaired electrons and hence structures adopted by metal complexes. A critical study of the magnetic data of coordination compounds of metals of the first transition series reveals some complications. For metal ions with upto three electrons in the d orbitals, like Ti + ( d ); V ( d ); Cr + ( d ); two vacant d orbitals are available for octahedral hybridisation with s and p orbitals. The magnetic behaviour of these free ions and their coordination entities is similar.
When more than three d electrons are present, the required pair of d orbitals for octahedral hybridisation is not directly available (as a consequence of