Indicate the coordination number and the oxidation number of the metal for each of the following complexes: (a) \(\mathrm{K}_{3}\left[\mathrm{Co}(\mathrm{CN})_{6}\right]\) (b) \(\mathrm{Na}_{2}\left[\mathrm{CdBr}_{4}\right]\) (c) \(\left[\mathrm{Pt}(\mathrm{en})_{3}\right]\left(\mathrm{ClO}_{4}\right)_{4}\) (d) \(\left[\mathrm{Co}(\mathrm{en})_{2}\left(\mathrm{C}_{2} \mathrm{O}_{4}\right)\right]^{+}\) (e) \(\mathrm{NH}_{4}\left[\mathrm{Cr}\left(\mathrm{NH}_{3}\right)_{2}(\mathrm{NCS})_{4}\right]\) (f) \(\left[\mathrm{Cu}(\mathrm{bipy})_{2} \mathrm{I}\right] \mathrm{I}\)

First, we identify the metal atom and ligands in the complex. In this case, cobalt (Co) is the central metal atom with six cyanide (CN) ligands surrounding it.

The coordination number is the number of ligand atoms bonded to the central metal atom. Since there are six cyanide (CN) ligands surrounding cobalt, the coordination number of Co is 6.

The overall charge of the complex ion is -3 since there are three potassium (K) counterions with a +1 charge each. Therefore, Co must have an oxidation number that allows the complex ion to have a -3 charge. Since each of the six cyanide ligands has a -1 charge: \[Oxidation \,number\, of\, Co + 6(-1) = -3\] The oxidation number of cobalt (Co) is +3.

In this complex, cadmium (Cd) is the central metal atom, with four bromide (Br) ligands surrounding it.

There are four bromide ligands bonded to the central metal atom. Hence the coordination number of Cd is 4.

The overall charge of the complex ion is -2 due to the two sodium (Na) counterions with a +1 charge each. Each of the four bromide ligands has a -1 charge. Thus: \[Oxidation\, number\, of\, Cd + 4(-1) = -2\] The oxidation number of cadmium (Cd) is +2.

In this complex, platinum (Pt) is the central metal atom, surrounded by three ethylenediamine (en) ligands.

Each ethylenediamine (en) ligand has two donor atoms (nitrogen), so the coordination number of Pt is 3 × 2 = 6.

The overall charge of the complex ion is +4 because there are four perchlorate (ClO4) counterions with a -1 charge each. Assuming all ligands are removed: \[Oxidation\, number\, of\, Pt = +4\] The oxidation number of platinum (Pt) is +4. Consider the following sections for the remaining complexes: (d) [Co(en)2(C2O4)]+: Coordination Number: 5 (2 en ligands with two donor atoms each, and 1 oxalate ligand with two donor atoms) Oxidation Number: +3 (assuming all ligands are removed, the overall charge of the complex ion is +1) (e) NH4[Cr(NH3)2(NCS)4]: Coordination Number: 6 (2 ammonia ligands with one donor atom each, and 4 thiocyanate ligands with one donor atom each) Oxidation Number: +3 (assuming all ligands are removed, the overall charge of the complex ion is -1 and balancing with +1 ammonium counterion) (f) [Cu(bipy)2 I]I: Coordination Number: 5 (2 bipyridine ligands with two donor atoms each, and 1 iodide ligand with one donor atom) Oxidation Number: +2 (assuming all ligands are removed, the overall charge of the complex ion is 0 and balancing with -1 iodide counterion)