Explain the following giving reasons
(a) `[NiCI_(4)]^(2-)` is tetrahedral and paramagnetic whereas `[Ni(CN)_(4)]^(2-)` is square plannar and dimagnetic
(b) `[Fe(H_(2)O)_(6)]^(3+)` ion is more paramagnetic than `[Fe(CN)_(6)]^(3-)` ion
(c ) `Ni(CO)_(4)` is tetrahedral while `[Ni(CN)_(4)]^(2-)` ion is square planar
(d) `[Co(F_(6))]^(3-)` is a high spin complex whereas `[Co(CN)_(6)]^(3-)` ion is a low spin complex .