Question

Identify the charge on the transition metal center and the number of valence d electrons it has.

1. [Cu(en)₂(H₂O)₂]I₂

2. [Co(NH₃)₅(NO₂)]Cl₂

3. [Co(en)₂Cl₂]Cl^-

4. Mo(bipy)(pph₃)(CO)₃

Answer 1

1. [Cu(en)2(H2O)2]I2

Let the charge on Cu be 'x'

en and H2O are neutral ligands and charge on iodine is -1. Hence

x + 0+0+2*(-1) = 0

=> x = +2

Hence charge on Cu is +2 and the cation is Cu²⁺

Electronic configuration of Cu is [Ar] 3d¹⁰ 4S¹

Hence electronic configuration of Cu²⁺ is [Ar] 3d⁹ 4S⁰

Hence number of valence d electrons = 9

2.[Co(NH3)5(NO2)]Cl2

Let the charge on Co be 'x'

NH3is a neutral ligand, NO₂^- is a monoanionic ligand and charge on chloride is -1. Hence

x + 0 -1+2*(-1) = 0

=> x = +3

Hence charge on Co is +3 and the cation is Co³⁺

Electronic configuration of Co is [Ar] 3d⁷ 4S²  

Hence electronic configuration of Co³⁺ is [Ar] 3d⁶ 4S⁰

Hence number of valence d electrons = 6

3.  [Co(en)2Cl2]Cl^-

Let the charge on Co be 'x'

en is a neutral ligand, Cl^- is a monoanionic ligand and charge on chloride is -1. Hence

x + 0 + 2x(-1) + ( -1) = -1

=> x = +2

Hence charge on Co is +2 and the cation is Co³⁺

Electronic configuration of Co is [Ar] 3d⁷ 4S²  

Hence electronic configuration of Co²⁺ is [Ar] 3d⁷ 4S⁰

Hence number of valence d electrons = 6

4.4.Mo(bipy)(pph3)(CO)3

Let the charge on Co be 'x'

bipy, pph3 and CO are neutral ligands. Hence

x + 0 + 0+0 = 0

=> x = 0

=> x = +2

Hence charge on Mo is 0 and the metal is neutral.

Electronic configuration of Mo is [Kr] 4d⁵ 5S¹   

Hence number of valence d electrons = 6