Question

please do answer all the questions below. thank you

For each of the following complexes, draw the molecular structure and determine the effective atomic numbers. (i) Na[Fe(CN)s(NH3)3l (i) [Cr(H2O)2(NH3)2(en)]Cl (ii) [Co(o-phen)2(NHs)(NCS))CI (iv) (n3-C3Hs)Co(CO)2] (v) [Fe(diphos)(CO)sl in which diphos Ph2PCH2CH2PPh2 and Ph CsHs (10 marks) (i)/ The K for Fe(OH)4]2-is found to be higher than that found in (5 marks) Zn(OH)4]2-and [Cr(OHM. Explain . Cho and coworkers used the following ligand to react with cobalt. Predict how this ligand would bind to Co2*. (4 marks)

Answer 1

The molecular structures are shown below:

NAs NH Na H2 N cN NG Fe Fe NC CN CA NHs mx-TRANS ace c CIS NMs Hs en CH NH3 o-Phin NCS

ALLYL Co oc cO CO Co - fe - cD dithe

Effective atomic number for each molecule

1). Na[Fe(CN)3(NH3)3]

Oxidation state of Fe=

X + 3(-1) + 3(0) = -1

X= +2

Atomic number of Fe. = 26

No. Of electrons in Fe2+=24

Electrons from 3 CN-. =6

Electrons from 3 NH3. =6

EAN. = 36(EAN is obeyed)

2). [Cr(H2O)2(NH3)2(en)]Cl3

Oxidation state of Cr=

X +2(0)+2(0)+0=+3

X=+3

Atomic number of Cr. = 24

No. Of electrons in Cr3+. = 21

Electrons from 2 H2O. = 4

Electrons from 2 NH3. =4

Electrons from en. =4

EAN. = 35(EAN not obeyed)

3). [Co (o-phen)2(NH3)(NCS)]Cl

Oxidation state of Co=

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

X=+2

Atomic number of Co =27

No. Of electrons in Co2+=25

Electrons from 2 o- phen =8

Electrons from NH3 =2

Electrons from NCS=2

EAN. = 37(EAN not obeyed)

4).[(n3-C3H5)Co (CO)2]

Oxidation state of Co = 0

Atomic number of Co= 27

No. Of electrons in Co = 27

Electrons from n3-C3H5=3

Electrons from 2CO =4

EAN. =34(EAN not obeyed)

5). [Fe(diphos)(CO)3]-

Oxidation state of Fe=

X=-1

Atomic number of Fe=26

No. Of electrons in Fe-1= 27

Electrons from diphos=4

Electrons from 3 CO= 6

EAN. = 37(EAN not obeyed)

B). Kf is the rate of formation.

It is said that kf is higher for [Fe(OH-]2- than for [Zn(OH-)4 and

[Cr(OH-)4]-

In each oxidation state is given as:

Fe =+2 3d6

Zn=+2 3d10

Cr=+3 3d3

OH- is a strong field ligand and cause pairing of electrons.

In cause of Zn pairing is impossible high spin complex is formed.

Cr3+ has only 3 electrons on 3d and hence pairing occurs easily.

Fe2+ requires more pairing energy hence Kf is greater.

C). Rotation alon CH2-CH2 bond is possible so as to cause all the Nitrogens in same plane to bind the Co.