Coordination Geometry of NiCl2 {P(C2H5)2(C6H5)}2

In order to determine the coordination geometry of Ni2+ in NiCl2 {P(C2H5)2(C6H5)}2, we need to analyze the structure and electronic configuration of the complex.

Structure of the complex:
The complex consists of a central nickel ion (Ni2+) surrounded by ligands. The ligands in this case are two chloride ions (Cl-) and two bidentate ligands, P(C2H5)2(C6H5). The ligands form coordination bonds with the central metal ion through their lone pairs of electrons.

Electronic configuration of Ni2+:
The electronic configuration of Ni2+ is [Ar] 3d8. In this configuration, there are eight electrons in the d orbital. According to Hund's rule, these electrons will occupy different d orbitals before pairing up, resulting in unpaired electrons.

Temperature-dependent magnetic behavior:
In paramagnetic substances, the presence of unpaired electrons leads to the alignment of the spins of these electrons in the presence of a magnetic field. This alignment results in a net magnetic moment, causing the substance to be attracted to a magnetic field. On the other hand, diamagnetic substances have no unpaired electrons and are not attracted to a magnetic field.

Coordination geometry in the paramagnetic state:
In the paramagnetic state, the complex exhibits temperature-dependent magnetic behavior due to the presence of unpaired electrons. The coordination geometry of Ni2+ in the paramagnetic state is tetrahedral.

Explanation:
The tetrahedral coordination geometry is observed when the ligands around the central metal ion are arranged in a tetrahedral shape. In the case of NiCl2 {P(C2H5)2(C6H5)}2, the two chloride ions and two bidentate ligands (P(C2H5)2(C6H5)) form a tetrahedral arrangement around the Ni2+ ion.

Coordination geometry in the diamagnetic state:
In the diamagnetic state, the complex does not exhibit temperature-dependent magnetic behavior due to the absence of unpaired electrons. The coordination geometry of Ni2+ in the diamagnetic state is square planar.

Explanation:
The square planar coordination geometry is observed when the ligands around the central metal ion are arranged in a square planar shape. In the absence of unpaired electrons, the ligands form a square planar arrangement around the Ni2+ ion.

Conclusion:
In NiCl2 {P(C2H5)2(C6H5)}2, the coordination geometry of Ni2+ in the paramagnetic state is tetrahedral, while in the diamagnetic state, it is square planar. The presence or absence of unpaired electrons determines the magnetic behavior and, consequently, the coordination geometry of the complex.