Important Coordination Compounds Formulas for JEE and NEET

 Page 1


  
COORDINATION COMPOUNDS
ADDITION COMPOUNDS :
They are formed by the combination of two or more stable
compounds in stoichiometric ratio.These are
(1) Double salts and (2) Coordination compounds
DOUBLE SALTS :
Those addition compounds which lose their identity in solutions
eg. K
2
SO
4
 , Al
2
(SO
4
)
3
COORDINATION COMPOUNDS :
Those addition compounds which retain their identity (i.e. doesn?t lose
their identity) in solution are
Fe(CN)
2
 + 4KCN ?? ? Fe(CN)
2
 . 4KCN
or K
4
 [Fe(CN)
6
] (aq.)  4K
+
 (aq.) + [Fe(CN)
6
]
4?
 (aq.)
Central Atom/Ion :
In a coordination entity?the atom/ion to which are bound a fixed number of
ligands in a definite geometrical arrangement around it.
Ligands :
The neutral molecules, anions or cations which are directly linked with
central metal atom or ion in the coordination entity are called ligands.
Chelate ligand :
Chelate ligand is a di or polydentate ligand which uses its two or more
donor atoms to bind a single metal ion producing a ring.
Ambidentate Ligand :
Ligands which can ligate through two different atoms present in it
nitrito-N ; M ? O?N=O
nitrito-O
M ? SCN thiocyanato or thiocyanato-S ; 
M ? NCS isothiocyanato or thiocyanato-N
Coordination Number :
The number of ligand donor atoms to which the metal is directly attached.
Oxidation number of Central Atom :
The oxidation number of the central atom is defined as the charge it would
carry if all the ligands are removed along with the electron pairs that are
shared with the central atom. [Fe(CN)
6
]
3?
 is +3 and it is written as Fe(III).
Page 2


  
COORDINATION COMPOUNDS
ADDITION COMPOUNDS :
They are formed by the combination of two or more stable
compounds in stoichiometric ratio.These are
(1) Double salts and (2) Coordination compounds
DOUBLE SALTS :
Those addition compounds which lose their identity in solutions
eg. K
2
SO
4
 , Al
2
(SO
4
)
3
COORDINATION COMPOUNDS :
Those addition compounds which retain their identity (i.e. doesn?t lose
their identity) in solution are
Fe(CN)
2
 + 4KCN ?? ? Fe(CN)
2
 . 4KCN
or K
4
 [Fe(CN)
6
] (aq.)  4K
+
 (aq.) + [Fe(CN)
6
]
4?
 (aq.)
Central Atom/Ion :
In a coordination entity?the atom/ion to which are bound a fixed number of
ligands in a definite geometrical arrangement around it.
Ligands :
The neutral molecules, anions or cations which are directly linked with
central metal atom or ion in the coordination entity are called ligands.
Chelate ligand :
Chelate ligand is a di or polydentate ligand which uses its two or more
donor atoms to bind a single metal ion producing a ring.
Ambidentate Ligand :
Ligands which can ligate through two different atoms present in it
nitrito-N ; M ? O?N=O
nitrito-O
M ? SCN thiocyanato or thiocyanato-S ; 
M ? NCS isothiocyanato or thiocyanato-N
Coordination Number :
The number of ligand donor atoms to which the metal is directly attached.
Oxidation number of Central Atom :
The oxidation number of the central atom is defined as the charge it would
carry if all the ligands are removed along with the electron pairs that are
shared with the central atom. [Fe(CN)
6
]
3?
 is +3 and it is written as Fe(III).
  
DENTICITY AND CHELATION :
Table : 1
Common Monodentate Ligands
Common Name IUPAC Name Formula
 methyl isocyanide methylisocyanide CH
3
NC
triphenyl phosphine triphenyl phosphine/triphenyl phosphane PPh
3
pyridine pyridine C
5
H
5
N (py)
ammonia ammine NH
3
methyl amine methylamine MeNH
2
water aqua or aquo H
2
O
carbonyl carbonyl CO
thiocarbonyl thiocarbonyl CS
nitrosyl nitrosyl NO
fluoro fluoro or fluorido* F
?
chloro chloro or chlorido* Cl
?
bromo bromo or bromido* Br
?
iodo iodo or iodido* I
?
cyano cyanido or cyanido-C* (C-bonded) CN
?
isocyano isocyanido or cyanido-N* (N-bonded) NC
?
thiocyano thiocyanato-S(S-bonded) SCN
?
isothiocyano thiocyanato-N(N-bonded) NCS
?
cyanato (cyanate) cyanato-O (O-bonded) OCN
?
isocyanato (isocyanate) cyanato-N (N-bonded) NCO
?
hydroxo hydroxo or hydroxido* OH
?
nitro nitrito?N (N?bonded) NO
2
?
nitrito nitrito?O (O?bonded) ONO
?
nitrate nitrato NO
3
?
amido amido NH
2
?
imido imido NH
2?
nitride nitrido N
3?
azido azido N
3
?
hydride hydrido H
?
oxide oxido O
2?
peroxide peroxido O
2
2?
superoxide superoxido O
2
?
acetate acetato CH
3
COO
?
sulphate sulphato SO
4
2?
thiosulphate thiosulphato S
2
O
3
2?
sulphite sulphito SO
3
2?
hydrogen sulphite hydrogensulphito HSO
3
?
sulphide sulphido or thio S
2?
hydrogen sulphide hydrogensulphido or mercapto HS
?
thionitrito thionitrito (NOS)
?
nitrosylium nitrosylium or nitrosonium NO
+
nitronium nitronium NO
2
+
* The 2004 IUPAC draft recommends that anionic ligands will end with-ido.
Page 3


  
COORDINATION COMPOUNDS
ADDITION COMPOUNDS :
They are formed by the combination of two or more stable
compounds in stoichiometric ratio.These are
(1) Double salts and (2) Coordination compounds
DOUBLE SALTS :
Those addition compounds which lose their identity in solutions
eg. K
2
SO
4
 , Al
2
(SO
4
)
3
COORDINATION COMPOUNDS :
Those addition compounds which retain their identity (i.e. doesn?t lose
their identity) in solution are
Fe(CN)
2
 + 4KCN ?? ? Fe(CN)
2
 . 4KCN
or K
4
 [Fe(CN)
6
] (aq.)  4K
+
 (aq.) + [Fe(CN)
6
]
4?
 (aq.)
Central Atom/Ion :
In a coordination entity?the atom/ion to which are bound a fixed number of
ligands in a definite geometrical arrangement around it.
Ligands :
The neutral molecules, anions or cations which are directly linked with
central metal atom or ion in the coordination entity are called ligands.
Chelate ligand :
Chelate ligand is a di or polydentate ligand which uses its two or more
donor atoms to bind a single metal ion producing a ring.
Ambidentate Ligand :
Ligands which can ligate through two different atoms present in it
nitrito-N ; M ? O?N=O
nitrito-O
M ? SCN thiocyanato or thiocyanato-S ; 
M ? NCS isothiocyanato or thiocyanato-N
Coordination Number :
The number of ligand donor atoms to which the metal is directly attached.
Oxidation number of Central Atom :
The oxidation number of the central atom is defined as the charge it would
carry if all the ligands are removed along with the electron pairs that are
shared with the central atom. [Fe(CN)
6
]
3?
 is +3 and it is written as Fe(III).
  
DENTICITY AND CHELATION :
Table : 1
Common Monodentate Ligands
Common Name IUPAC Name Formula
 methyl isocyanide methylisocyanide CH
3
NC
triphenyl phosphine triphenyl phosphine/triphenyl phosphane PPh
3
pyridine pyridine C
5
H
5
N (py)
ammonia ammine NH
3
methyl amine methylamine MeNH
2
water aqua or aquo H
2
O
carbonyl carbonyl CO
thiocarbonyl thiocarbonyl CS
nitrosyl nitrosyl NO
fluoro fluoro or fluorido* F
?
chloro chloro or chlorido* Cl
?
bromo bromo or bromido* Br
?
iodo iodo or iodido* I
?
cyano cyanido or cyanido-C* (C-bonded) CN
?
isocyano isocyanido or cyanido-N* (N-bonded) NC
?
thiocyano thiocyanato-S(S-bonded) SCN
?
isothiocyano thiocyanato-N(N-bonded) NCS
?
cyanato (cyanate) cyanato-O (O-bonded) OCN
?
isocyanato (isocyanate) cyanato-N (N-bonded) NCO
?
hydroxo hydroxo or hydroxido* OH
?
nitro nitrito?N (N?bonded) NO
2
?
nitrito nitrito?O (O?bonded) ONO
?
nitrate nitrato NO
3
?
amido amido NH
2
?
imido imido NH
2?
nitride nitrido N
3?
azido azido N
3
?
hydride hydrido H
?
oxide oxido O
2?
peroxide peroxido O
2
2?
superoxide superoxido O
2
?
acetate acetato CH
3
COO
?
sulphate sulphato SO
4
2?
thiosulphate thiosulphato S
2
O
3
2?
sulphite sulphito SO
3
2?
hydrogen sulphite hydrogensulphito HSO
3
?
sulphide sulphido or thio S
2?
hydrogen sulphide hydrogensulphido or mercapto HS
?
thionitrito thionitrito (NOS)
?
nitrosylium nitrosylium or nitrosonium NO
+
nitronium nitronium NO
2
+
* The 2004 IUPAC draft recommends that anionic ligands will end with-ido.
  
Table : 2
Common Chelating Amines
Table : 3
Common Multidentate (Chelating) Ligands
Common Name          IUPAC Name Abbreviation Formula Structure
acetylacetonato
2,4-pentanediono
or acetylacetonato
acac CH 3 COCHCOCH 3
?
2,2'-bipyridine 2,2'-bipyridyl bipy C 10 H 8 N 2
oxalato oxalato ox C 2 O 4
2?
dimethylglyoximato
butanedienedioxime
or dimethylglyoximato
DMG HONC(CH
3
)C(CH
3
)NO
?
ethylenediaminetetraacetato
1,2-ethanediyl
(dinitrilo)tetraacetato
or 
ethylenediaminetetraacetato
EDTA (
?
OOCCH
2
)
2
NCH
2
CH
2
N(CH
2
COO
?
)
2
?
OCH C 2
?
OCH C
2
CH CO 2
?
CH CO 2
?
||
O
||
||
O
O
||
O
:
:
Homoleptic and heteroleptic complexes
Complexes in which a metal is bound to only one type of donor groups,
e.g., [Cr(NH
3
)
6
]
3+
, are known as homoleptic. Complexes in which a metal
is bound to more than one type of donor groups, e.g., [Co(NH
3
)
4
Br
2
]
+
, are
known as heteroleptic.
Page 4


  
COORDINATION COMPOUNDS
ADDITION COMPOUNDS :
They are formed by the combination of two or more stable
compounds in stoichiometric ratio.These are
(1) Double salts and (2) Coordination compounds
DOUBLE SALTS :
Those addition compounds which lose their identity in solutions
eg. K
2
SO
4
 , Al
2
(SO
4
)
3
COORDINATION COMPOUNDS :
Those addition compounds which retain their identity (i.e. doesn?t lose
their identity) in solution are
Fe(CN)
2
 + 4KCN ?? ? Fe(CN)
2
 . 4KCN
or K
4
 [Fe(CN)
6
] (aq.)  4K
+
 (aq.) + [Fe(CN)
6
]
4?
 (aq.)
Central Atom/Ion :
In a coordination entity?the atom/ion to which are bound a fixed number of
ligands in a definite geometrical arrangement around it.
Ligands :
The neutral molecules, anions or cations which are directly linked with
central metal atom or ion in the coordination entity are called ligands.
Chelate ligand :
Chelate ligand is a di or polydentate ligand which uses its two or more
donor atoms to bind a single metal ion producing a ring.
Ambidentate Ligand :
Ligands which can ligate through two different atoms present in it
nitrito-N ; M ? O?N=O
nitrito-O
M ? SCN thiocyanato or thiocyanato-S ; 
M ? NCS isothiocyanato or thiocyanato-N
Coordination Number :
The number of ligand donor atoms to which the metal is directly attached.
Oxidation number of Central Atom :
The oxidation number of the central atom is defined as the charge it would
carry if all the ligands are removed along with the electron pairs that are
shared with the central atom. [Fe(CN)
6
]
3?
 is +3 and it is written as Fe(III).
  
DENTICITY AND CHELATION :
Table : 1
Common Monodentate Ligands
Common Name IUPAC Name Formula
 methyl isocyanide methylisocyanide CH
3
NC
triphenyl phosphine triphenyl phosphine/triphenyl phosphane PPh
3
pyridine pyridine C
5
H
5
N (py)
ammonia ammine NH
3
methyl amine methylamine MeNH
2
water aqua or aquo H
2
O
carbonyl carbonyl CO
thiocarbonyl thiocarbonyl CS
nitrosyl nitrosyl NO
fluoro fluoro or fluorido* F
?
chloro chloro or chlorido* Cl
?
bromo bromo or bromido* Br
?
iodo iodo or iodido* I
?
cyano cyanido or cyanido-C* (C-bonded) CN
?
isocyano isocyanido or cyanido-N* (N-bonded) NC
?
thiocyano thiocyanato-S(S-bonded) SCN
?
isothiocyano thiocyanato-N(N-bonded) NCS
?
cyanato (cyanate) cyanato-O (O-bonded) OCN
?
isocyanato (isocyanate) cyanato-N (N-bonded) NCO
?
hydroxo hydroxo or hydroxido* OH
?
nitro nitrito?N (N?bonded) NO
2
?
nitrito nitrito?O (O?bonded) ONO
?
nitrate nitrato NO
3
?
amido amido NH
2
?
imido imido NH
2?
nitride nitrido N
3?
azido azido N
3
?
hydride hydrido H
?
oxide oxido O
2?
peroxide peroxido O
2
2?
superoxide superoxido O
2
?
acetate acetato CH
3
COO
?
sulphate sulphato SO
4
2?
thiosulphate thiosulphato S
2
O
3
2?
sulphite sulphito SO
3
2?
hydrogen sulphite hydrogensulphito HSO
3
?
sulphide sulphido or thio S
2?
hydrogen sulphide hydrogensulphido or mercapto HS
?
thionitrito thionitrito (NOS)
?
nitrosylium nitrosylium or nitrosonium NO
+
nitronium nitronium NO
2
+
* The 2004 IUPAC draft recommends that anionic ligands will end with-ido.
  
Table : 2
Common Chelating Amines
Table : 3
Common Multidentate (Chelating) Ligands
Common Name          IUPAC Name Abbreviation Formula Structure
acetylacetonato
2,4-pentanediono
or acetylacetonato
acac CH 3 COCHCOCH 3
?
2,2'-bipyridine 2,2'-bipyridyl bipy C 10 H 8 N 2
oxalato oxalato ox C 2 O 4
2?
dimethylglyoximato
butanedienedioxime
or dimethylglyoximato
DMG HONC(CH
3
)C(CH
3
)NO
?
ethylenediaminetetraacetato
1,2-ethanediyl
(dinitrilo)tetraacetato
or 
ethylenediaminetetraacetato
EDTA (
?
OOCCH
2
)
2
NCH
2
CH
2
N(CH
2
COO
?
)
2
?
OCH C 2
?
OCH C
2
CH CO 2
?
CH CO 2
?
||
O
||
||
O
O
||
O
:
:
Homoleptic and heteroleptic complexes
Complexes in which a metal is bound to only one type of donor groups,
e.g., [Cr(NH
3
)
6
]
3+
, are known as homoleptic. Complexes in which a metal
is bound to more than one type of donor groups, e.g., [Co(NH
3
)
4
Br
2
]
+
, are
known as heteroleptic.
  
Nomenclature of Coordination Compounds
Writing the formulas of Mononuclear Coordination Entities :
(i) The central atom is placed first.
(ii) The ligands are then placed in alphabetical order. The placement
of a ligand in the list does not depend on its charge.
(iii) Polydentate ligands are also placed alphabetically. In case of
abbreviated ligand, the first letter of the abbreviation is used to
determine the position of the ligand in the alphabetical order.
(iv) The formula for the entire coordination entity, whether charged or
not, is enclosed in square brackets. When ligands are polyatomic,
their formulas are enclosed in parentheses. Ligands abbreviations
are also enclosed in parentheses.
(v) There should be no space between the ligands and the metal
within a coordination sphere.
(vi) When the formula of a charged coordination entity is to be written
without that of the counter ion, the charge is indicated outside the
square brackets as a right superscript with the number before the
sign. For example, [Co(H
2
O)
6
]
3+
, [Fe(CN)
6
]
3?
 etc.
(vii) The charge of the cation(s) is balanced by the charge of the
anion(s).
Writing the name of Mononuclear Coordination Compounds :
(i) Like simple salts the cation is named first in both positively and
negatively charged coordination entities.
(ii) The ligands are named in an alphabetical order (according to the
name of ligand, not the prefix) before the name of the central
atom/ion.
(iii) Names of the anionic ligands end in ?o and those of neutral ligands
are the same except aqua for H
2
O, ammine for NH
3
, carbonyl for
CO, thiocarbonyl for CS and nitrosyl for NO. But names of cationic
ligands end in?ium.
(iv) Prefixes mono, di, tri, etc., are used to indicate the number of the
one kind of ligands in the coordination entity. When the names of
the ligands include a numerical prefix or are complicated or
whenever the use of normal prefixes creates some confusion, it is
set off in parentheses and the second set of prefixes is used.
2 di bis
3 tri tris
4 tetra tetrakis
5 penta pentakis
6 hexa hexakis
7 hepta heptakis
Page 5


  
COORDINATION COMPOUNDS
ADDITION COMPOUNDS :
They are formed by the combination of two or more stable
compounds in stoichiometric ratio.These are
(1) Double salts and (2) Coordination compounds
DOUBLE SALTS :
Those addition compounds which lose their identity in solutions
eg. K
2
SO
4
 , Al
2
(SO
4
)
3
COORDINATION COMPOUNDS :
Those addition compounds which retain their identity (i.e. doesn?t lose
their identity) in solution are
Fe(CN)
2
 + 4KCN ?? ? Fe(CN)
2
 . 4KCN
or K
4
 [Fe(CN)
6
] (aq.)  4K
+
 (aq.) + [Fe(CN)
6
]
4?
 (aq.)
Central Atom/Ion :
In a coordination entity?the atom/ion to which are bound a fixed number of
ligands in a definite geometrical arrangement around it.
Ligands :
The neutral molecules, anions or cations which are directly linked with
central metal atom or ion in the coordination entity are called ligands.
Chelate ligand :
Chelate ligand is a di or polydentate ligand which uses its two or more
donor atoms to bind a single metal ion producing a ring.
Ambidentate Ligand :
Ligands which can ligate through two different atoms present in it
nitrito-N ; M ? O?N=O
nitrito-O
M ? SCN thiocyanato or thiocyanato-S ; 
M ? NCS isothiocyanato or thiocyanato-N
Coordination Number :
The number of ligand donor atoms to which the metal is directly attached.
Oxidation number of Central Atom :
The oxidation number of the central atom is defined as the charge it would
carry if all the ligands are removed along with the electron pairs that are
shared with the central atom. [Fe(CN)
6
]
3?
 is +3 and it is written as Fe(III).
  
DENTICITY AND CHELATION :
Table : 1
Common Monodentate Ligands
Common Name IUPAC Name Formula
 methyl isocyanide methylisocyanide CH
3
NC
triphenyl phosphine triphenyl phosphine/triphenyl phosphane PPh
3
pyridine pyridine C
5
H
5
N (py)
ammonia ammine NH
3
methyl amine methylamine MeNH
2
water aqua or aquo H
2
O
carbonyl carbonyl CO
thiocarbonyl thiocarbonyl CS
nitrosyl nitrosyl NO
fluoro fluoro or fluorido* F
?
chloro chloro or chlorido* Cl
?
bromo bromo or bromido* Br
?
iodo iodo or iodido* I
?
cyano cyanido or cyanido-C* (C-bonded) CN
?
isocyano isocyanido or cyanido-N* (N-bonded) NC
?
thiocyano thiocyanato-S(S-bonded) SCN
?
isothiocyano thiocyanato-N(N-bonded) NCS
?
cyanato (cyanate) cyanato-O (O-bonded) OCN
?
isocyanato (isocyanate) cyanato-N (N-bonded) NCO
?
hydroxo hydroxo or hydroxido* OH
?
nitro nitrito?N (N?bonded) NO
2
?
nitrito nitrito?O (O?bonded) ONO
?
nitrate nitrato NO
3
?
amido amido NH
2
?
imido imido NH
2?
nitride nitrido N
3?
azido azido N
3
?
hydride hydrido H
?
oxide oxido O
2?
peroxide peroxido O
2
2?
superoxide superoxido O
2
?
acetate acetato CH
3
COO
?
sulphate sulphato SO
4
2?
thiosulphate thiosulphato S
2
O
3
2?
sulphite sulphito SO
3
2?
hydrogen sulphite hydrogensulphito HSO
3
?
sulphide sulphido or thio S
2?
hydrogen sulphide hydrogensulphido or mercapto HS
?
thionitrito thionitrito (NOS)
?
nitrosylium nitrosylium or nitrosonium NO
+
nitronium nitronium NO
2
+
* The 2004 IUPAC draft recommends that anionic ligands will end with-ido.
  
Table : 2
Common Chelating Amines
Table : 3
Common Multidentate (Chelating) Ligands
Common Name          IUPAC Name Abbreviation Formula Structure
acetylacetonato
2,4-pentanediono
or acetylacetonato
acac CH 3 COCHCOCH 3
?
2,2'-bipyridine 2,2'-bipyridyl bipy C 10 H 8 N 2
oxalato oxalato ox C 2 O 4
2?
dimethylglyoximato
butanedienedioxime
or dimethylglyoximato
DMG HONC(CH
3
)C(CH
3
)NO
?
ethylenediaminetetraacetato
1,2-ethanediyl
(dinitrilo)tetraacetato
or 
ethylenediaminetetraacetato
EDTA (
?
OOCCH
2
)
2
NCH
2
CH
2
N(CH
2
COO
?
)
2
?
OCH C 2
?
OCH C
2
CH CO 2
?
CH CO 2
?
||
O
||
||
O
O
||
O
:
:
Homoleptic and heteroleptic complexes
Complexes in which a metal is bound to only one type of donor groups,
e.g., [Cr(NH
3
)
6
]
3+
, are known as homoleptic. Complexes in which a metal
is bound to more than one type of donor groups, e.g., [Co(NH
3
)
4
Br
2
]
+
, are
known as heteroleptic.
  
Nomenclature of Coordination Compounds
Writing the formulas of Mononuclear Coordination Entities :
(i) The central atom is placed first.
(ii) The ligands are then placed in alphabetical order. The placement
of a ligand in the list does not depend on its charge.
(iii) Polydentate ligands are also placed alphabetically. In case of
abbreviated ligand, the first letter of the abbreviation is used to
determine the position of the ligand in the alphabetical order.
(iv) The formula for the entire coordination entity, whether charged or
not, is enclosed in square brackets. When ligands are polyatomic,
their formulas are enclosed in parentheses. Ligands abbreviations
are also enclosed in parentheses.
(v) There should be no space between the ligands and the metal
within a coordination sphere.
(vi) When the formula of a charged coordination entity is to be written
without that of the counter ion, the charge is indicated outside the
square brackets as a right superscript with the number before the
sign. For example, [Co(H
2
O)
6
]
3+
, [Fe(CN)
6
]
3?
 etc.
(vii) The charge of the cation(s) is balanced by the charge of the
anion(s).
Writing the name of Mononuclear Coordination Compounds :
(i) Like simple salts the cation is named first in both positively and
negatively charged coordination entities.
(ii) The ligands are named in an alphabetical order (according to the
name of ligand, not the prefix) before the name of the central
atom/ion.
(iii) Names of the anionic ligands end in ?o and those of neutral ligands
are the same except aqua for H
2
O, ammine for NH
3
, carbonyl for
CO, thiocarbonyl for CS and nitrosyl for NO. But names of cationic
ligands end in?ium.
(iv) Prefixes mono, di, tri, etc., are used to indicate the number of the
one kind of ligands in the coordination entity. When the names of
the ligands include a numerical prefix or are complicated or
whenever the use of normal prefixes creates some confusion, it is
set off in parentheses and the second set of prefixes is used.
2 di bis
3 tri tris
4 tetra tetrakis
5 penta pentakis
6 hexa hexakis
7 hepta heptakis
  
(v) Oxidation state of the metal in cation, anion or neutral coordination
entity is indicated by Roman numeral in the parentheses after the
name of metal.
(vi) If the complex ion is a cation, the metal is named same as the
element. For example, Co in a complex cation is called cobalt
and Pt is called platinum. If the complex ion is an anion, the
name of the metal ends with the suffix - ate. For example, Co in a
complex anion, [Co(SCN)
4
]
2?
 is called cobaltate. For some metals,
the Latin names are used in the complex anions.
iron (Fe) ferrate lead (Pb) plumbate
silver (Ag) argentate tin (Sn) stannate
gold (Au) aurate
(vii) The neutral complex molecule is named similar to that of the
complex cation.
Werner's Theory :
According to Werner most elements exhibit two types of valencies :
(a) Primary valency and (b) Secondary valency.
(a) Primary valency :
This corresponds to oxidation state of the metal ion. This is also called
principal, ionisable or ionic valency. It is satisfied by negative ions and its
attachment with the central metal ion is shown by dotted lines.
(b) Secondary or auxiliary valency :
It is also termed as coordination number (usually abbreviated as CN) of
the central metal ion. It is non-ionic or non-ionisable (i.e. coordinate covalent
bond type). In the modern terminology, such spatial arrangements are
called coordination polyhedra and various possibilities are
C.N. = 2 linear C.N. = 3 Triangular
C.N. = 4    tetrahedral or square planar C.N. = 6 octahedral.
Effective Atomic Number Rule given by Sidgwick :
Effective Atomic Number (EAN) = Atomic no. of central metal ? Oxidation
state of central metal + No. of electrons donated by ligands.
Valence Bond Theory :
The model utilizes hybridisation of  (n-1) d, ns, np or ns, np, nd orbitals of
metal atom or ion to yield a set of equivalent orbitals of definite geometry
to account for the observed structures such as octahedral, square planar
and tetrahedral, and magnetic properties of complexes. The number of
unpaired electrons, measured by the magnetic moment of the compounds
determines which d-orbitals are used.