Question

1. Consider an octahedral coordination compound with formula [M(NH₃)₄Cl₂]SO₄ (M is unknown but it is in the second transition metal series (Zr to Cd). Answer the following questions.

1. What is the oxidation state of the metal M?
2. It is found that this compound has an effective magnetic moment of 2.83 B.M. Identify the metal and justify your answer.
3. How many geometric isomers are possible? Explain
4. Are optical isomers possible? Explain.

Answer 1

a. Let the oxidation state of the metal be x.

So, x+ (4×0)+ (-1×2)=2 (charge of Cl=-1, NH3 neutral molecule)

x= 4 implies metal is in +4 oxidation state.

b. Metal is Molebdnum(Mo). Mo is in 5s^1 4d^5 configuration. We know metal is in +4 oxidation state. Hence metal would be in 4d^2 configuration. So two unpaired electrons are present in d orbital. For 2 unpaired electron the magnetic moment would be 2.83 BM which is equal to the given magnetic moment. Hence we xan confirm that fiven metal is Mo.

c. Two geometrical isomers are possible. One is cis isomer and other is trans isomer. In cis isomer two chlorine are placed in adjacent position whereas in trans isomer chlorine are present trans to each other.

d. Optical isomers are not possible, because octahedral compound with bidentate ligand shows optical isomerism.The given compound doesn't contain any bidentate ligand, also it has symmetrical geometry.Thus optical isomerism are not possible for this.