Problem 13 - Chemistry Central Science

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) \(\left[\mathrm{Zn}(\mathrm{en})_{2}\right] \mathrm{Br}_{2}\)

Step-by-Step Solution

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 1: Metal and ligands identification

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

Step 2: Coordination number

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

Step 3: 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) \(\mathrm{K}_{2}\left[\mathrm{MoOCl}_{4}\right]\)

Step 4: Metal and ligands identification

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

Step 5: Coordination number

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

Step 6: 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) \(\left[\mathrm{Co}\left(\mathrm{NH}_{3}\right)_{4} \mathrm{Cl}_{2}\right]\mathrm{Cl}\)

Step 7: Metal and ligands identification

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

Step 8: Coordination number

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

Step 9: 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) \(\left[\mathrm{Ni}(\mathrm{CN})_{5}\right]^{3-}\)

Step 10: Metal and ligands identification

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

Step 11: Coordination number

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

Step 12: 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) \(\mathrm{K}_{3}\left[\mathrm{~V}\left(\mathrm{C}_{2}\mathrm{O}_{4}\right)_{3}\right]\)

Step 13: Metal and ligands identification

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

Step 14: Coordination number

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

Step 15: 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) \(\left[\mathrm{Zn}(\mathrm{en})_{2}\right] \mathrm{Br}_{2}\)

Step 16: Metal and ligands identification

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

Step 17: Coordination number

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

Step 18: 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.