Coordination compound notes

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4. Naming of Ambidentate ligands :-

1.	NC- ---->	cynido/cyno or cynido - C
	CN- ---->	isocynido or cynido - N
2.	ONO- ---->	nitrito or nitroto - O
	OO-N ---->	nitro or nitrito - N
3.	NCO- ---->	cynato or cynato - O
	OCN- ---->	isocynito or cynato - N
4.	NCS- ---->	thiocynato or thiocynato - S
	SCN- ---->	isothiocynato or thiocynato - N

IUPAC Names of Compound
	K4[Fe(CN)6]	Potassium hexacynidoferrate(ii)
	[Co(en)3]Cl3	Tris(ethylenediamine)cobalt(iii)chloride
	[Fe(H2O)5NO]SO4	Pentaaquanitrosoniumiron(i)sulphate
	Na2[Fe(CN)5NO]	Sodium heptacynidonitrisoniumferrate(ii)
	K2[HgI4]	Potassium tetraiodidomercurate(ii)
	[Fe(en)2ClBr]NO3	Bromochlorobis(ethylenediamine)iron(iii)nitrate
	[Ni(CO)4]	Tetracarbonylnickel
	Li[AlH4]SO4	Lithium tetrahydridoaluminate(iii)
	H2[PtCl6]	Hexachloroplatenic acid
	H[AuCl4]	Tetrachloroauric acid
	CuSO4.5H2O water of crystallisation [Cu(H2O)4]SO4.H2O	Tetraaquacuprate(ii)sulphate monohydrate
	FeSO4.7H2O [Fe(H2O)6]SO4.H2O	Hexaaquaferrate(ii)sulphate monohydrate
	[(NH3)4PtCl2Pt(NH3)4](SO4)3	Tetraammineplatinum(iv)di(u-chlorido) tetraammineplatinum(iv) sulphate or di(u-chlorido)octaamminediplatinum(iv)sulphate or di-u-chloridobis-(tetraammineplatinum(iv))sulphate or bis-(u-chloridotetraammineplatinum(iv))sulphate
	Note :- In case of breezing ligands, prefix 'u (mu)' is attached. In last example, Cl2 act as breezing ligand with both Pt.

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------------------:Hybridisation of Coordination Compound :-------------------
-:Crystal field theory :-

• In presence of ligands, degeneracy of 5 d orbitals destroy said to be Crystal field splitting.
  
• Magnitude of Crystal field splitting depend on the nature of ligands.
  According to Spectrochemical series, ligands are of two type :-
  
• Strong field ligand :- They pair up unpaired electrons present in inner d-subshell.
  
• Weak field ligand :- They do not disturb the original configuration of inner d-subshell. They do not pair up unpaired electrons.
  According to Spectrochemical series,
  

  Increasing order of strength
  Weak field ligand -	I- < Br- < SCN- < Cl- < S2- < NO3- < F- < OH- < CH3OO- < C2O42- < H2O
  Strong field ligands -	NCS- < edta4- < NH3 < py < en < dipy < NO2- < CN- < CO
  Weak field ligands -	O2-
  	NO+
  	PPH3
  Strong field ligands -	dmg-
  	gly-

  Crystal field theory for Coordination Number = 6 :-
  
  • Possible geometry of Coordination number 6 is octahedral.
    
  • Bond angle will be 90^o and 180^o.
    
  • Ligands will approches axially so, energy of 'eg' set of orbitals will increases more than energy of 't₂g' shell of orbitals.
  
  
  In presence of any ligand, 1^st electron goes in dxy, 2^nd electron goes to dyz, 3^rd electron goes to dx orbital, but in case of Strong field ligand, 4^th electron will pair up or goes in dxy, 5^th electron will pair up in dyz, 6^th electron will pair up in dx orbitals. After that 7^th electron goes to dx²y², 8^th electron goes to dz², 9^th electron will pair up or goes in dx²y² and 10^th electron will pair up or goes in dz² orbital. It means, in presence of Strong field ligand, pairing of electrons take place.
  But in presence of Weak field ligand, first all orbitals will filled up by one electron each. It means if 5 electrons are present, then all five orbitals will contain one electron each. After that if 6^th electron will come, then it will pair up in dxy orbital (1^st orbital) and so on.
  

  d-subshell	Strong field Ligand	Hybridization	Weak field Ligand	Hybridization
  d1	t2g1 eg0	d2sp3	t2g1 eg0	d2sp3
  d2	t2g2 eg0		t2g2 eg0
  d3	t2g3 eg0	d2sp3	t2g3 eg0	d2sp3
  d4	t2g4 eg0		t2g3 eg1	sp3d2
  d5	t2g5 eg0		t2g3 eg2
  d6	t2g6 eg0		t2g4 eg2
  d7	t2g6 eg1	sp3d2	t2g5 eg2	sp3d2
  d8	t2g6 eg2		t2g6 eg2
  d9	t2g6 eg3		t2g6 eg3
  d10	t2g6 eg4		t2g6 eg4

  Result -> configuration in d¹, d², d³, d⁸, d⁹, d¹⁰ doesn't depend on the nature of ligand.

  --: Calculation of Magnetic Moment :--
  

  if n = number of unpaired electron, then
  

  Magnetic Moment (mu), u = {n(n+2)}1/2

  
  Total spin (s) = n * 1/₂
  High spin = higher number of unpaired electron
  Low spin = lower number of unpaired electron

  d-subshell	Strong field Ligand		Weak field Ligand
  	unpaired electron	High or Low spin	unpaired electron	High or Low spin
  d1	1	Not define	1	Not define
  d2	2	Not define	2	Not define
  d3	3	Not define	3	Not define
  d4	2	Low spin	4	High spin
  d5	1	Low spin	5	High spin
  d6	0	Low spin	4	High spin
  d7	1	Low spin	3	High spin
  d8	2	Not define	2	Not define
  d9	1	Not define	1	Not define
  d10	0	Not define	0	Not define
  High spin and Low spin is defined only for d4, d5, d6 and d7.
  For Strong Field Ligand, it is Low spin and for Weak Field Ligand, it is High spin.

  --: Calculation of Hybridization :--
  

  
  
  Note :-- Only 'eg' set of (n-1)d orbital can be used in Hybridization.
  Example :--
  

  K3[Fe(CN)6]	[Fe(SCN)6]-3
  26Fe = [Ar] 4s2 3d6	26Fe = [Ar] 4s2 3d6
  Primary valancy = +3	Primary valancy = +3
  26Fe+3 = [Ar] 4s0 3d5	26Fe+3 = [Ar] 4s0 3d5
  As CN- is a strong field ligand, it will pair up 4 electrons in 3d orbital. 1 remain unpair because there is no more single electron for pairing.	As SCN- is a weak field ligand, it does not change the original configuration of electrons. 5 electrons remain unpaired.
  All electron will lie in 't2g' set. t2g 5 eg0	3 electron electron will lie in 't2g' and 2 electron will lie in 'eg' set. t2g 3 eg 2
  On pairing of electron, 2 orbitals of 3d will contain 2-2 electrons (paired electrons) and 1 orbital contain 1 electron. Here 2 orbitals are vacant which accept loan pair given by ligand. So 2 orbitals which accept loan pair will participate in Hybridization.	All 5 orbitals of 3d will contain 1 unpaired electron. Here no orbital is vacant, so no one will accept loan pair given by ligand. So none of 3d orbital will participate in Hybridization.
  Hybridization = d2sp3	Hybridization = sp3d2
  unpaired electron = 1	unpaired electron = 5
  Magnetic Moment, u = {n(n+2)}1/2 u = {1(1+2)}1/2 = 31/2	Magnetic Moment, u = {n(n+2)}1/2 u = {5(5+2)}1/2 = (35)1/2
  Low spin	High spin

  Complex	d-subshell	Hybridization	unpaired electron	Magnetic Moment	High or Low spin
  [Fe(en)3]+2	d6	d2sp3	0	0	Low spin
  [CoF6]-3	d6	sp3d2	4	(24)1/2	High spin
  [Fe(en)2ClBr]NO3	d5	d2sp3	1	31/2	Low spin
  [Ni(H2O)6]+2	d8	sp3d2	2	81/2	Not define
  [Fe(H2O)6]+3	d5	sp3d2	5	(35)1/2	High spin
  [V(H2O)6]+3	d2	d2sp3	2	81/2	Not define
  [Cr(NH3)6]+3	d3	d2sp3	3	151/2	Not define
  [Co(en)3]+2	d7	d2sp3	1	31/2	Low spin
  Transference of electron in d7 :- like in [Co(en)3]+2 Condition for transference are :- Only one electron is transferred All the ligands must be strong filled ligand After transference, orbital left vacant must be used in hybridization. After transference, electron of 3d7 will goes to or lie in 4d1 in case of [Co(en)3]+2. Hence two orbitals or 'eg' set is vacant in case of [Co(en)3]+2. Hence, Hybridization is d2sp3
  [Mn(H2O)6]+2	d5	sp3d2	5	(35)1/2	High spin
  Na2[Fe(CN)5NO]	d6	d2sp3	0	0	Low spin
  [Fe(NH3)6]+3	d5	d2sp3	1	31/2	Low spin
  [Co(NO2)6]-3	d6	d2sp3	0	0	Low spin

  -: Limitation of Crystal Field Theory :-
  

  1. NH₃ is a Weak Field Ligand with Fe⁺² and Mn⁺² if coordination number is 6.
     
  2. [Cr(H₂O)₆]⁺³, hybridization of this compound should be 'd²sp³', but actual hybridization of this compound is 'sp³d²'.
     
  3. For 4-d and 5-d series elements, all the ligands are acting as Strong Field Ligand due to their higher Z-effective.
     
  4. For Co⁺³, if coordination number is 6, then all the ligands written on the right side of the ' floride ' are Strong Field Ligand.
  Crystal field theory for Coordination Number = 4 :-
  
  Case : 1
  In Presence of Strong Field Ligands :-
  
  • Possible geometry = Square Planar.
    
  • Hybridization = dsp²

  Orbitals	Hybridization
  d0 - d8	dsp2
  d9	dsp2 (transference of electron)
  d10	sp3

  Case : 2

  In Presence of Weak Field Ligands :-
  
  • Possible Geometry = Tetrahedral.
    
  • Hybridization = d³s / sp³.

  Orbitals	Hybridization
  d0, d1, d2	d3s
  d3 ... d10	sp3

  Complex	d-subshell	Hybridization	Unpaired electron
  [MnCl4]-2	d5	sp3	5
  [Ni(CN)4]-2	d8	dsp2	0
  [NiCl4]-2	d8	sp3	2
  [Cu(NH3)4]+2	d9	dsp2	1
  [Cu(CN)4]-3	d10	sp3	0
  [PtCl4]-2	d8	dsp2	0
  [Zn(NH3)4]+2	d10	sp3	0
  [Ni(en)Cl2]	d8	dsp2	0
  [Ni(PPH3)Cl2]	d8	sp3	2
  [Ni(dmg)2]	d8	dsp2	0
  [CoCl4]-2	d7	sp3	3
  [Rh(PPH3)Cl] Wilkinson's catalyst	d8	dsp2	0
  [Ni(CO)4]	d10	sp3	0
  NOTE :- s electron are remaining if any, are transferred to d-subshell.