The complex ion NiCl4^2- has two unpaired electrons, whereas Ni(CN)4^2- is diamagnetic. Propose

The complex ion NiCl4^2- has two unpaired electrons, whereas...

Key Concepts

Electronic Configuration and Magnetism

The electronic configuration of the central metal ion, combined with the crystal field splitting induced by various ligands, directly influences the magnetic properties of a complex. For a d? metal like Ni(II), the arrangement of electrons in the split d orbitals differs between high-spin and low-spin configurations. In a tetrahedral geometry with weak field ligands, the d electrons are less paired, resulting in unpaired electrons and paramagnetism, whereas in a square planar geometry with strong field ligands, a low-spin configuration with all electrons paired results in diamagnetism.

Ligand Field Strength

Ligand field strength, which is related to the position of ligands in the spectrochemical series, determines the magnitude of the crystal field splitting. Strong field ligands, such as cyanide, produce a larger splitting which can favor low-spin configurations with paired electrons, leading to diamagnetism. In contrast, weak field ligands, like chloride, result in a smaller crystal field splitting, which can lead to high-spin configurations featuring unpaired electrons.

Coordination Geometry

Coordination geometry refers to the three-dimensional arrangement of ligands around a central metal ion. In the context of the two nickel complexes, the NiCl?²? ion adopts a tetrahedral geometry while the Ni(CN)?²? ion adopts a square planar geometry. These geometries significantly influence the distribution of electrons in the metal’s d orbitals and hence determine the magnetic properties of the complexes.

Crystal Field Theory

Crystal field theory explains how the electrostatic interactions between the ligands and the central metal ion lead to energy splitting of the metal's d orbitals. The extent and pattern of this splitting depend on the geometry of the complex and the nature of the ligands. In these nickel complexes, the different splitting schemes in tetrahedral versus square planar environments account for the presence or absence of unpaired electrons.

Transcript

00:04 Here the question is the complex ion nicl 4 2 negative has two unpaired electrons whereas nicn4 2 negative is diamagnetive proposed structures for these two complex ions so first we are taking nicl 4 2 negative 2 negative in this complex we know one thing that c l minus is weak ligate and when it is weakligent crystal field splitting energy will build us now how the electrons are arranged in it atomic number number of nickel is 28 outer electronic configuration is after a which should be 4 s2 3d8 and when nickel is at plus 2 state its configuration is 4 s0 3d8 so how the splitting is taking place when the coordination number is 4 splitting is octahedral splitting.

02:49 So d x square minus y square and d z square will be lower energy level and d x y d y z and d x y z and d x z will be higher level but this splitting energy delta e delta zero should be less in case of cl complex and that is why the electronic configuration should be electrons are first filled singly and then pairing is taking place so eight electrons we have to arrange one two three four five then six 7, 8 and by this we can understand that how in nickel chlorine complex, first complex, two unpaired electrons are present and because of that it should be paramagnetic.

04:22 Now when it is paramagnetic, d orbitals are not disturbed.

04:26 That means the hybridization should be sp3 when hybridization is sp3 the geometry is tetrahedral nickel at the center and all the chlorine one chlorine should be above the plane other chlorine should be below the plane and all other chlorine are arranged tetrahedral and this whole complex should be inside the bracket and outside it should be too negative.

05:12 So geometry is tetrahedral and hybridization is as quickly.

05:25 In case of first complex.

05:28 Now in second complex what happens, complex is nic -c -n -4.

05:46 So when the complex is n nickel cn4, cnn, cn ligand we know already that it is strong ligate.

06:03 Minus 2 should be the charge over it.

06:07 And here when cn is strong ligand, splitting should be maximum.

06:26 That means more than the chlorine...

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