A Group IV transition metal cation M^ 2+ reacts with...

The formation of a brilliant red precipitate with dimethylglyoxime (DMG) in an ammoniacal medium indicates that the metal cation $\text{M}^{2+}$ is $\text{Ni}^{2+}$. The complex formed is bis(dimethylglyoximato)nickel(II), $[\text{Ni}(\text{DMG})_2]$.

In this complex, Nickel is in a $+2$ oxidation state with a $3\text{d}^{8}$ electronic configuration.

Although DMG is generally a weak field ligand, in this specific complex it acts as a strong field ligand due to the extra stability provided by intramolecular hydrogen bonding between the two DMG ligands. This causes the pairing of the two unpaired $3\text{d}$ electrons, leaving one inner $3\text{d}$ orbital empty.

The empty $3\text{d}$, one $4\text{s}$, and two $4\text{p}$ orbitals undergo $\text{dsp}^{2}$ hybridization to form a square planar complex. Since all electrons are paired, the complex is diamagnetic.

Answer: $\text{dsp}^{2}$, diamagnetic