IIT JEE , AIEEE Forum - Chemistry , Inorganic Chemistry

Werewolf

I am having difficulty in finding the following for a complex compound :

1) Number of unpaired electrons

2) Hybridization

3) Geometry

Please give me a general stepwise approach( filling of orbitals, effects of strong/weak field ligands and what all ligands can be considered strong and which all can be considered weak,when to pair up electrons and when not to pair them up ) to find these mentioned things.

Also I will be obliged if someone explains me how do complex compounds show colour due to charge transfer.

srini

Hey,

Consider an element in an oxidation state say fe in +2... electronic configuration of fe is 3d6 4s2, in fe+2 the electrons of outermost electrons are removed, so the electronic configuration is fe 3d6 4s0, or like...there are four unpaired electrons.

(psst.. these are supposed to be orbitals!! he he..)

junglejalebi

sabse pehele yaad kar ki
only co no nh3 en cn are strong ligands hote hai
>>>>>>>
jab yaad ho jai tab age bATATA HOON

Werewolf

I want more elaborate explanation

Werewolf

ok jungle jalebi go ahead

ashgirl

see for finding unpaired no of electrons, first find the charge on metal ligand, then after dat write its electronic configuration and check the number of unpaired electrons ...... u can draw and do it too!!

hybridization-

if coordination number is 4, then hybridization possible are sp3(tetrahedral) and dsp2(square planar)

if coordination number is 6, then hybridization possible are d2sp3(octahedral) and sp3d2(octahedral).

Werewolf

But its not like that , we have to consider many effects like what are the ligands and other factors , pairing and in some cases pairing also doesnt happen inspite of strong filed ligands , I want this explanation

ashgirl

a strong ligand is capable of forcing the electrons to pair up and a weak ligand is incapable of doing that.

strong - CN- , CO, en,NH3,H2O,NO2-,Py

weak- I-,Br-,Cl-,F-,NO3-,OH-,C2O4 2-,NH3,H2O

remember pairing is done only to the extent required...according to the coordination number!!

by knowing the magnetic moment, u can get to know the geometry and also whether it acts as strong or weak ligand..........

ashgirl

is it clear now?? or do u wanna know sumthing else too??

Werewolf

Why is NH₃ and H₂O both in weak and strong ?

Werewolf

And before pairing the electrons up do we consider the electrons donated by the ligands to the central metal ion or we pair up the electrons of only metal ion without considering electrons donated by the ligand?

Why don't you tell me all the steps that you follow for such problems?

madmax

I Just wanna stress tht there are some exceptions to these like jumping of electrons across d and p orbitals and these are generally seen with COBALT

Also note tht Water and NH3 can act as both strong and weak field ligands

Werewolf

3 new doubts arise , please don't mind people

1) before pairing the electrons up do we consider the electrons donated by the ligands to the central metal ion or we pair up the electrons of only metal ion without considering electrons donated by the ligand?

2) When do NH₃ and H₂O act as weak and when strong?

3) When does electrons jump d and p orbitals ?

madmax

OK let me answer your questions
1) We only consider the electrons of the ionized CENTRAL atom and then arrange the ligands depending on whether the ligands are strong (i.e. cause pairing of unpaired electrons) or weak ligands (no pairing)

2) NH3 and H2O act as strong ligands when the electron pairing energy is less than the energy derived from the Crystal Field Splitting However if it is more then they act as weak ligands

3)This is not actually known.....Chemists hypothetise the jump of electrns based upon exprimental observations lyk spectroscopic evidence....These jumps happen rarely

Buddy I'm sorry if this sounds rude or sumthing,I am just trying to tell U..........I think your concepts are pretty poor in Coordinatn Chem.....SO I think you shud refer atleast the NCERT book b4 thnking of anythng else

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