Question

Indicate the coordination number of the metal and the oxidation number of the metal in each of the following complexes: (a) \(\mathrm{Na}_{2}\left[\mathrm{CdCl}_{4}\right]\) (b) \(\mathrm{K}_{2}\left[\mathrm{MoOCl}_{4}\right]\) (c) \(\left[\mathrm{Co}\left(\mathrm{NH}_{3}\right)_{4} \mathrm{Cl}_{2}\right] \mathrm{Cl}\) (d) \(\left[\mathrm{Ni}(\mathrm{CN})_{5}\right]^{3-}\) (e) \(\mathrm{K}_{3}\left[\mathrm{~V}\left(\mathrm{C}_{2} \mathrm{O}_{4}\right)_{3}\right]\) (f) \(\left[\mathrm{Zn}(\mathrm{en})_{2}\right] \mathrm{Br}_{2}\)

Short answer

The coordination and oxidation numbers for the given complexes are: (a) \(CdCl_4^{2-}\): Coordination number = 4, Oxidation number = +2 (b) \(MoOCl_4^{2-}\): Coordination number = 5, Oxidation number = +2 (c) \(Co(NH_3)_{4}Cl_2^{+}\): Coordination number = 6, Oxidation number = +3 (d) \(Ni(CN)_{5}^{3-}\): Coordination number = 5, Oxidation number = +2 (e) \(V(C_2O_4)^{3-}_3\): Coordination number = 6, Oxidation number = +3 (f) \(Zn(en)_2\): Coordination number = 4, Oxidation number = +2

Step-by-step solution

Metal and ligands identification

In this complex, the metal is Cadmium (Cd) and the ligands are Chloride ions (Cl).

Coordination number

There are 4 Chloride ions directly bonded to Cadmium, so the coordination number is 4

Oxidation number

The overall charge of the complex is -2. Since 4 chloride ions contribute -4 charge, the oxidation number of the metal (Cd) is +2. (b) \(\mathrm{K}_{2}\left[\mathrm{MoOCl}_{4}\right]\)

Metal and ligands identification

In this complex, the metal is Molybdenum (Mo) and the ligands are Chloride ions (Cl) and Oxygen atoms (O).

Coordination number

There are four Chloride ions and one Oxygen directly bonded to Molybdenum, so the coordination number is 5.

Oxidation number

The overall charge of the complex is -2. Two potassium ions contribute +2 charge and oxygen contributes -2 charge, so the oxidation number of Molybdenum (Mo) is +2. (c) \(\left[\mathrm{Co}\left(\mathrm{NH}_{3}\right)_{4} \mathrm{Cl}_{2}\right]\mathrm{Cl}\)

Metal and ligands identification

In this complex, the metal is Cobalt (Co) and the ligands are Ammine (NH3) and Chloride ions (Cl).

Coordination number

There are 4 Ammine molecules and 2 Chloride ions directly bonded to Cobalt, so the coordination number is 6.

Oxidation number

The overall charge of the complex is +1. The two chloride ions outside the square brackets contribute -1 charge, so the oxidation number of Cobalt (Co) is +3. (d) \(\left[\mathrm{Ni}(\mathrm{CN})_{5}\right]^{3-}\)

Metal and ligands identification

In this complex, the metal is Nickel (Ni) and the ligands are Cyanide ions (CN).

Coordination number

There are 5 Cyanide ions directly bonded to Nickel, so the coordination number is 5.

Oxidation number

The overall charge of the complex is -3. Since 5 cyanide ions contribute -5 charge, the oxidation number of Nickel (Ni) is +2. (e) \(\mathrm{K}_{3}\left[\mathrm{~V}\left(\mathrm{C}_{2}\mathrm{O}_{4}\right)_{3}\right]\)

Metal and ligands identification

In this complex, the metal is Vanadium (V) and the ligands are Oxalate ions (C2O4).

Coordination number

There are 3 Oxalate ions directly bonded to Vanadium, so the coordination number is 6.

Oxidation number

The overall charge of the complex is -3. Three potassium ions contribute +3 charge and 3 oxalate ions contribute -6 charge, so the oxidation number of Vanadium (V) is +3. (f) \(\left[\mathrm{Zn}(\mathrm{en})_{2}\right] \mathrm{Br}_{2}\)

Metal and ligands identification

In this complex, the metal is Zinc (Zn) and the ligands are Ethylenediamine (en).

Coordination number

There are 2 Ethylenediamine molecules directly bonded to Zinc, so the coordination number is 4.

Oxidation number

Since the complex has a neutral charge and the two bromide ions outside the square brackets contribute -2 charge, the oxidation number of Zinc (Zn) is +2.