**Structure of K2NiF6 complex:**

The K2NiF6 complex is formed by the combination of potassium ions (K+) and nickel(II) fluoride (NiF6^2-) ions. It has a cubic crystal structure with each nickel ion surrounded by six fluoride ions in an octahedral arrangement. The potassium ions are located in the voids between the octahedral units.

**Hybridization in K2NiF6 complex:**

In the K2NiF6 complex, the nickel ion is in the +2 oxidation state, which means it has lost two electrons. The electronic configuration of nickel in the ground state is [Ar]3d^84s^2. However, in the complex, the nickel ion undergoes hybridization to form six sigma bonds with the fluoride ions. This leads to the promotion of two 4s electrons to the 4p orbital, resulting in the formation of six sp^3d^2 hybrid orbitals. These hybrid orbitals are then used to form sigma bonds with the fluoride ions.

**Magnetic property of K2NiF6 complex:**

The effective magnetic moment (μeff) of a complex depends on the number of unpaired electrons present. Unpaired electrons contribute to the magnetic moment because of their spin. In the K2NiF6 complex, the nickel ion is in the +2 oxidation state, which means it has lost two electrons.

Nickel has an atomic number of 28, and in its ground state, it has two unpaired electrons. However, in the complex, the nickel ion undergoes hybridization, and the unpaired electrons are involved in bonding, resulting in the formation of a diamagnetic complex.

A diamagnetic complex has all paired electrons, and as a result, it does not have any net magnetic moment. Therefore, the K2NiF6 complex shows a 0.0 BM effective magnetic moment.

In conclusion, the K2NiF6 complex has a cubic crystal structure with an octahedral arrangement of fluoride ions around the nickel ion. The nickel ion undergoes sp^3d^2 hybridization to form sigma bonds with the fluoride ions. The complex is diamagnetic, with a 0.0 BM effective magnetic moment, due to the pairing of all the electrons in the hybridized orbitals.

Uhmm K2NiF6 maybe