The spin only magnetic moment of `[MnBr_(4)]^(2-)` is 5.9 BM. Predict the geometry of the complex ion.

Explanation

Magnetic moment of a transition metal complex is given by `mu=sqrt(n(n+2))BM`, where n = no. of unpaired electrons in metal ion. Magnetic moment (5.9 BM) of `[MnBr_(4)]^(2-)` corresponds to n = 5. Since coordination number of `Mn^(2+)` in the given complex is 4, geometry can be either tetrahedral (`sp^(3)` - hybri - disation ) or square planar (`dsp^(2)` hybridisation). It must have tetrahedral geometry rather than square planar, in order to account for presence of 5 unpaired electrons in d - orbitals.