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Title: Chapter%20Nine%20%20%20%20%20%20%20Coordination%20Compounds


1
Chapter Nine Coordination Compounds
Coordination Compound a compound in which a
central metal ion is attached to a group of
surrounding molecules or ions by coordinate
covalent bonds.
2
Anemia(???)
3
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4
CH2OH CHSH CH2SH
CH2OH CHS CH2S
Hg
Hg
  • Anti-tumour(??) agent

5
Coordination Compounds
  • 9-1 Basic Concepts
  • 9-2 The Chemical Bond Theory
  • 9-2.1 Valence Bond Theory
  • 9-2.2 Crystal Field Theory
  • 9-3 Coordination Equilibrium
  • 9-4 Chelates

6
9-1 Basic Concepts  
  • An introduction to complex ions with an
    explanation of what ligands are and how they bond
    to the central metal ion.
  • central metal ion
  • transition
    metals (but not all)
  • complex ion
  • ligands (anions or
    polar

  • molecules)

7
Transition Metals (T.M.)
  • This gives rise to the following properties
  • Distinctive color
  • paramagnetic compounds
  • catalytic activity
  • great tendency to form complex ions
  • Zn, Cd, Hg are not considered T.M.

8
Ligands and Donor atom
  • Ligands ions or molecules that is bound directly
    to the metal atom. e.g. NH3, CN-, H2O, Cl-, I-
  • Donor atom the atom in a ligand that is bound
    directly to the metal atom , has lone electron
    pairs.
  • e.g. C, N, O, S, F, Cl, Br, I

9
Ligands
  • Depending on the number of donor atoms present
    in the molecule or ion, ligands can be classified
    as
  • monodentate (H2O NH3 )
  • bi dentate (H2N-CH2-CH2-NH2 )
  • polydentate (EDTA)
  • also called chelating agents

10

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Coordination number
  • Coordination number the number of donor atoms
    surrounding the central metal atom in a complex
    ion. Commonly, it is 2, 4 ,5 or 6
  • For monodentate Cu(NH3)4 SO4 ,
    Fe(CN)64-
  • Coordination number ligand number
  • For bidentate or polydentate
  • Coordination number ? ligand number
  • e.g. Cu(en)2SO4 ( en H2N-CH2-CH2-NH2)
  • Coordination number 4 ? 2

13
Charges of coordination ion
Charges of coordination ion the sum of
charges of central ion and ligands
  • e.g. K3Fe(CN)6 Fe3
  • Fe(H2O)6Cl3 Fe3
  • K4Fe(CN)6 Fe2

14
The features of coordination ion
  • Contains a complicated ion - coordination ion
  • Cu(NH3)42 , Ag(NH3)2,
    Fe(CN)64-
  • Metal ion bonded with other ion or molecule by
    coordination bond
  • Has definite stability
  • KClMgCl2 6H2O K, Cl-,
    Mg2
  • KAl(SO4) 12H2O K,
    Al3, SO42

15
Simple ion and complex ion
  • CuSO4

BaCl2
Cu(NH3)4 SO4 Ag(NH3)2Cl
BaSO4
NaOH
CuSO4
Cu(OH)2
NH3H2O
NH3H2O
CuSO4
Cu(OH)2
Blue
Cu2 4NH3 Cu(NH3)42
Complex ion
NH3H2O
NaCl
AgNO3
Ag(NH3)2
AgCl
16
The composition of coordination compound
  • the coordination sphere
  • 1. The central metal and the ligands bound
  • to it constitute.
  • 2. square brackets to set off the groups
  • within the coordination sphere from
  • other parts of the compound.
  • for example Co(NH3)6Cl3
  • PtCl62

17
coordination atom or donor atom
Inner sphere coordination sphere
Outer sphere
  • Cu(NH3)42 SO42-

Charges of coordination ion
Central ion or atom
Ligand
Coordination number
18
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bidentate
20
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21
What are the oxidation numbers of the central
metal in the complexes below?
  • K3FeF6
  • Na2Ni(CN)4

22
??????
  • 1. ?????
  • ????????-??????
  • CuCl2 BaSO4
  • Pt(en)2Cl2 Cu(NH3)4SO4
    K4Fe(CN)6
  • 2. ?? ?????

???-????-?-??????(???)
Cu(NH3)42 ? ? ? ?(?)?? Fe(CN)64-
? ? ? ?(?)????
23
3.???????????????????????????????????????????
??????NH3?H2O Co(H2O)(NH3)3Cl2Cl
??????????(?) Pt(NH3)4(NO2)ClCO3
???????????(?) Cu(NH3)4(OH)2 ???????(?)
KPt(NH3)Cl5 ??????(?)??
FeFe(CN)6 ????(?)?? Fe2Fe(CN)6
????(?)??? Pt(NH3)2Cl2 ??????(?)
Ni(CO)4 ?????

24
Naming of Coordination Compounds
  • the International Union of Pure and Applied
    Chemistry (IUPAC)
  • 1. The cation is named before the anion.
  • NaCl sodium choride
  • 2. Within a complex ion the ligands are named
  • first, in alphabetical order, and the
    metal ion is
  • named last.
  • 3. To name the ligands
  • anionic ligands end in -o
  • neutral ligands usually called the name of
    the

  • molecule

25
LIGAND Name of Ligand in Coord.
Cpd. Bromide, Br- Bromo Chloride,
Cl- Chloro Cyanide, CN- Cyano Hydorxide,
OH- Hydroxo Oixde, O2- Oxo Carbonate,
CO32- Carbanato Nitrite, NO3- Nitro Oxolate,
C2O42- Oxolato Ammonia, NH3 Ammine Carbon
monoxide, CO Carbonyl Water, H2O Aquo Ethylenedi
amine(en) Ethylenediamine
Naming Coordination Compounds
26
  • 4. When several ligands of a particular kind are
    present, we use the Greek prefixes to name them.
  • Di (2)
  • tri (3)
  • tetra (4)
  • Penta (5)
  • Hexa (6)

Co(NH3)4Cl2are tetraamminedichloro
If the ligand itself contains a Greek prefix, we
use the prefixes bis, tris, tetrakis to indicate
the number of ligands present. e.g.
Cu(en)22 bis(ethylenediamine)
27
5. The oxidation number of the metal is written
in Roman numerals following the name of
the metal. Cr(NH3)4Cl2, which is
called tetraamminedichlorochromium(?) ion.
6. If the complex ion is an anion, its name ends
in - ate. K4Fe(CN)6 the anion Fe(CN)64
- is called hexacyanoferrate(II) ion.
28
Metal in anion complex Aluminum
Aluminate Chromium Chromate Cobalt
Cobaltate Copper Cuprate Gold Aurate Iron
Ferrate Lead Plumbate
Metal in anion complex Manganese Manganate Nickel
Nickelate Silver Argentate Tin
Stannate Tungsten Tungstate Zinc Zincate
29
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31
  • Example 9-1
  • (a) Ni(CO)4, (b)
    Co(NH3)4Cl2Cl,
  • (c) K3Fe(CN)6, (d) Cr(en)3Cl3.
  • Solution
  • (a) tetracarbonylnickel(0)
  • (b) tetraamminedichlorocobalt( ?) chloride
  • (c) potassium hexacyanoferrate(?).
  • potassium ferricyanide
  • (d) tris(ethylenediamine) chromium(?)
  • chloride.

32
. tetraamminedichlorochromium(?) ion.
hexacyanoferrate(II) ion.

the cation Cr(NH3)4Cl2
the anion Fe(CN)64 -
33
  • Give the formula for the following coordination
    compounds.
  • tetracarbonylnickel(0)
  • tetraammineaquochlorocobalt(III) chloride

Ni(CO)4,
Co(NH3)4H2OClCl2
How did I know there had to be two chlorides at
the end?
34
9-2 The Chemical Bond Theory
  • Several different bonding theories have been
    applied to transition-metal coordination
    compounds. We shall consider two of these.
  • the valence-bond theory being covalent and
    examines the hybridization of orbitals on the
    metal.
  • the crystal-field theory from an ionic point of
    view and focuses on(??) the effect of the
    surrounding ligands on the energies of the metal
    d orbitals

35
  • 9-2.1 Valence Bond Theory
  • Magnetism
  • Isomerism (???)
  • stability
  • 9-2.2 Crystal Field Theory
  • The Splitting(??) of the d orbitals in
  • octahedral Field
  • High-spin and Low-Spin
  • Coordination Compounds
  • The color of coordination compounds

36
9-2.1 the valence-bond theory
  • a ligand orbital containing two electrons
    overlaps an unoccupied orbital on the metal atom.
  • donate a pair of electrons into a suitable empty
    hybrid orbital on the metal,

37
the valence-bond theory Outline
  • 1. Central ion bonds with ligands by
  • coordination bond.
  • 2. The empty orbitals of central ion must
  • hybridize to increase bonding ability.
  • 3. There are two types of coordination
    compounds
  • _ outer-orbital coordination compounds
  • _ inner-orbital coordination compounds

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39
Example Ag(NH3)2
  • 47Ag Kr4d105s1
  • Central ion Ag 4d105s05p0

Ag
hybrid
2 NH3
sp hybridization( outer orbital )
Ag(NH3)2(linear)
40
Ni(NH3)42 28Ni 3d84s2
  • Central ion Ni2 3d8 4s0 4p0

4 NH3
hybrid
sp3 hybridization( outer orbital )
Ni(NH3)4 2 (tetrahedral)
41
Ni
Ni
42
Ni(CN)4 2-
  • Central ion Ni2 3d8 4s0 4p0

realignment
hybrid
4 CN-
dsp2 hybridization inner orbital
Ni(CN)4 2-( square planar)
43
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44
Co(NH3)6 3
  • Co atom
  • Co3 ion
  • Co(NH3)63

3d74s2
3d6
6 NH3
d2sp3 hybridization
(inorbital complex)
Co(NH3)6 3 (octahedral)
45
CoF63
4d
  • Co atom 3d74s2
  • Co3 ion
  • CoF63

3d 4s 4p
3d6
6 F-
sp3d2 hybridization
(octahedral)
46
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47
Magnetism
  • Paramagnetism substances containing unpaired
    electrons are paramagnetic.
  • diamagnetic substances without unpaired
    electrons are diamagnetic.
  • magnetic moment µ
  • µvn (n2)
  • n is the number of unpaired electrons

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49
  • Example For Fe(H2O)6SO4
  • µ5.26B.M
  • according to above equation, n 4 ,so there
    are 4 unpaired electrons in this coordination
    compound.
  • Example For K4Fe(CN)6
  • µ0 B.M
  • according to above equation, n 0 ,so there
    are 0 unpaired electrons in this coordination
    compound.

50
  • Example For Fe(H2O)6SO4 , µ5.26B.M
  • according to above equation, n 4 ,so there
    are 4 unpaired electrons in this coordination
    compound.

26Fe 3d64s24p04d0
3d 4s 4p
4d
Fe2 3d6 4s04p04d0






Sp3d2 hybridization
outer orbital
51
  • Example For K4Fe(CN)6 , µ0 B.M
  • according to above equation, n 0 ,so there
    are 0 unpaired electrons in this coordination
    compound.

Fe2 3d64s04p04d0
3d 4s 4p







d2sp3 hybridization, inner orbital
52
Table 9-4 Some common types of hybridization and
geometries.
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54
Isomerism(???)
  • Isomers Two or more compounds that have the
    same formula but a different structure (that is,
    the same collection of atoms but arranged in
    different ways) are called isomers.
  • Isomers

Structural isomers
Geometric isomers (Stereo?? isomers)
Optical isomers
55
Structural isomerism
  • Structural isomers are that differ in how the
    atoms are joined together.
  • Example Co(NH3)5(SO4)Br red
  • Co(NH3)5 Br SO4
    violet
  • CH3-CH2-CH2-COOH
  • CH3-CH-COOH
  • CH3

56
??????(?)
???????(?)
57
Geometric isomerism (Stereoisomerism,
cis-trans isomerism)
  • are isomers that have the same chemical bonds
    but different special arrangements.
  • the isomer with like groups close together is
    called the cis-isomer.
  • whereas the one with like groups far apart is
    called the trans-isomer.

58
Geometric Isomerism (stereoisomerism)
  • Pt(NH3)2Cl2
  • Cl NH3
  • cis Pt
  • Cl NH3

NH3 Cl trans Pt Cl
NH3
59
both coordination compounds are named
diamminedichloroplatinum(II)
trans
cis
cis-diamminedichloroplatinum(II)
60
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Optical Isomerism
63
??????????
???????????,??????????????????????????
64
????????????
?????,??????,???????,??????????????????????????
?????????????????????
65
9-2.2 Crystal Field Theory(??P217)
  • 1. the ligands in a transition-metal complex are
    treated as point charges. Thus, a ligand anion
    becomes simply a point of negative charge. metal
    ion becomes simply a point of positive charged.
  • 2. For the formation of a complex ion or
    molecule is the electrostatic attraction
  • 3. this theory explains both the paramagnetism
    and color observed in certain complexes.

66
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????d???????
69
The Splitting of the d Orbitals in Octahedral
Field
70
eg (d?)orbitals
? eg - t2g
t2g (de)orbitals
71
crystal field splitting energy, ?
????????????t2g?????eg ?????????
72
High-Spin and Low-Spin Coordination Compounds
  • Fe(H2O)62 Fe 3d64s2 Fe2
    3d6

Figure Occupation of the 3d orbitals in
complexes of Fe2. (a) Low spin. (b) High
spin.
73
pairing energy P
  • pairing energy P the energy required to put
    two electrons into the same orbital.
  • 1. P gt ? the fourth electron will go into one
    of the higher d orbitals.
  • a high-spin complex
  • 2. P lt? an electron in one of the lower
    energy orbitals.
  • a low spin complex

74
?????(?)???
? ??
???????????,???????
? ????
?????,????????,????
75
? ?? spectrochemical series,
which is a list of ligands arranged in order of
their abilities to split the d orbitals
  • Weak-bonding ligands Strong-bonding
    ligands
  • I lt Br lt Cl lt SCNlt F lt OH lt H2O ltNCS
  • lt edta lt NH3 lt en lt
    NO2lt CN lt CO
  • Increasing ? ?

Co(H2O)63
Co(NH3)63 Co(CN)63- ?o /cm-1
13000 22900
34000
  • ???o gt P low-spin complex
  • ???o lt P high-spin complex

76
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  • ? ?????M ?????

79
  • ?????????,d-d????(?? ?)????( )
  • a. Fe(H2O)6 2 b. Fe(H2O)6 3
  • c. FeF6 4- d. FeF6 3-

80
????????t 2g?eg??????
81
1. Crystal Field Stabilization Energy(CFSE)
????????
  • A measure of the net energy of stabilization
    gained by a metal ion's nonbonding d electrons as
    a result of complex formation.

? ????????(Crystal field stabilization energy,
CFSE)?????????d?????????? ????????? ?
82
  • ligand field stabilization energy
  • a measure of the increased stability of a
    complex showing ligand field splitting.

In general, CFSE ( electrons in t2g)
(-0.4 ? 0 ) (electrons in
eg) (0.6 ? 0 )
83
CFSE 6 (-0.4 ? 0 ) 0 (0.6 ? 0
) -2.4 ? 0
CFSE 4 (-0.4 ? 0 ) 2 (0.6 ? 0
) -0.4 ? 0
84
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85
2. ??????????
?????????????d???d???????(d-d??)?
? ???????????? ???? ? ???????????? ??
h? ?
86
The larger the crystal-field splitiing (??), the
higher will be the frequency of light absorbed
most strongly(??), and the shorter its
wavelength(??).
87
The color of coordination compound
  • Many of the colors of octahedral transition-metal
    compounds arise from the excitation of an
    electron from an occupied lower energy orbital to
    an empty higher energy orbital.
  • The frequency (?) of light that is capable of
    inducing such a transition is related to the
    energy difference between the two states, which
    is the crystal-field splitting energy.
  • h? ?

88
h? ?
?? ?? ??
?? ?? ??
89
  • As we have noted earlier, strong-field ligands
    cause a large split in the energies of the d
    orbitals of the central metal atom.
  • Transition metal coordination compounds with
    these ligands are yellow, orange, or red since
    they absorb higher-energy violet or blue light.
  • On the other hand, coordination compounds of
    transition metals with weak-field ligands are
    blue-green, blue, or indigo since they absorb
    lower-energy yellow, orange, or red light.

90
  • Co(NH3)5Cl2 Purple compound
  • absorbs yellow green
    region
  • ( wavelength
    of 530 nm)
  • Co(NH3)63 orange compound
  • absorbs violet region
  • (wavelength
    of 410nm)
  • d10 (Zn2, Ag complexes) is colorless

91
  • Ti33d1,
  • Ti(H2O)63
  • ???????????,
  • ???????
  • ? 492.7nm (???),
  • Eh? 242.79 kJmol-1,
  • ??1/?20300cm-1
  • (1cm-111.96Jmol-1),
  • ?????????????o20 300 cm-1

92
???Fe(CN)63-?FeF63-??????1.7?B?5.9 ?B,
(1) ??????????????????? (2) ??????d????????
(3) ????????????,?????
? (1)Fe(CN)63-?,?vn (n2)1.7B.M, ?n1
FeF63?,?vn(n2) 5.9B.M, ?n5 (2)
Fe(CN)63-?,d????????t2g5eg0,
FeF63?,d????????t2g3eg2, (3)
Fe(CN)63-??????,???????
FeF63-??????,????????
93
9-3 Coordination equilibrium

  • coordination
  • Cu2(aq) 4NH3(aq) Cu(NH3)42
    (aq)
  • ionization
  • Cu(NH3)42
    Cu2NH34
  • Ks -------------------- Kis
    -------------------
  • Cu2NH34
    Cu(NH3)4 2

Stability constant or formation constant(Kf)
Instability constant
94
ßn --Accumulate stability constant
Cu(NH3)2
Cu2NH3 Cu(NH3)2
K1
Cu2NH3
Cu(NH3)22
Cu(NH3)2NH3 Cu(NH3)22
K2
Cu(NH3)2NH3
Cu(NH3)32
Cu(NH3)22NH3 Cu(NH3)32
K3
Cu(NH3)22NH3
Cu(NH3)42
Cu(NH3)32NH3 Cu(NH3)42
K4
Cu(NH3)32NH3
95
Cu2(aq) NH3(aq) Cu(NH3)2
(aq)
K11.4104 Cu2(aq)
2NH3(aq) Cu(NH3)22 (aq)

K23.17103 Cu2(aq) 3NH3(aq)
Cu(NH3)32 (aq)

K37.76102 Cu2(aq) 4NH3(aq)
Cu(NH3)2 (aq)
K41.39102
ß2 K1 K2
ß3 K1 K2 K3
lgß4 lgK1lgK2lgK3lgK4
96
  • Generally, for the same type complex ions
  • the larger value of Ks(Kf), the great
  • stability of the complex ion in solution and
  • accounts for the very low concentration of
  • metal ions at equilibrium.
  • For the different type complex ions
  • you need compare their stability by
    calculation.(???p224??9-1?)

97
1. Influence of acidity on coordination
equilibrium
  • Fe(C2O4)33- Fe3 3C2O42-

  • Equilibrium shift
    6H

  • 3H2C2O4

??? ????????,H????????????,???????????,?????????
???????????????????????.
???? ?????????OH-????????????????????????
98
2. Influence of precipitation on coordination
equilibrium
  • Ag(NH3)2 Ag 2NH3
  • Equilibrium shift Br-
  • AgBr
  • AgBr(s) AgBr-

  • Equilibrium shift 2S2O32-
  • Ag(S2O3)23-

????????????,?????????????????????????????????????
???Ag????? Cl-ltNH3ltBr-ltS2O32-ltI-ltCN-ltS2- ??????
????????KSP???????KS????
99
?9-2 ?Ag(CN)2-?CN-?????0.10molL-1?????NaCl,?
???AgCl??? ???Na2S,????Ag2S???
  • ???????????
  • Ag CN-
    Ag(CN)2- KS1.010 21
  • ?????


  • (molL-1)
  • ??AgCl?????? Ag Cl-gtKSP1.7710-10
  • ????NaCl????????,???AgCl??,?
  • Cl-gt
    (molL-1)
  • ??????NaCl????Cl-gt1.771010molL-1?
  • ????????NaCl?????AgCl???

100
  • ??Na2S??Ag2S??????
  • Ag2 S2- gt
    KSP6.6910-50
  • S2- gt
  • ????Na2S??????????,??
  • S2- gt
    (molL-1)
  • ??Na2S??????? S2-gt6.6910-10 molL-1,
  • ????????Na2S????Ag2S???

101
?9-3 25?,?1L????0.1molAgCl????,????
??????molL-1 ?
  • ??????????

  • KSP1.810-10

  • KS1.6107
  • ???????????

??????????
102
  • ?????Ag?????Ag(NH3)2???,?Ag(NH3)2Cl-0.1
    molL-1
  • ?????????????NH3????
  • NH3
    (molL-1)
  • ?????? ????

1.8620.12.06(molL-1)
??????????AgI ?? ?
103
Influence of redox on coordination equilibrium
  • Fe3 I- Fe2 1/2I2
  • 6F- Equilibrium shift
  • FeF63-
  • FeCl4- Fe3 4Cl-
  • Equilibrium I-
  • Shift
  • Fe2 1/2I2

????,????????????????,????????I-??FeCl4-????Fe3
??? Fe2,???FeCl4-?????.
??????????? gt
, ???NaF???,Fe3?F-????FeF63-???, ?Fe3?????
?,Fe3/ Fe2????????????,?Fe3/ Fe2???????I2/
I-??????,?????????????.
104
?????? Cu/ Cu
Ag/Ag Au3/Au F0/v
0.52 0.799 1.50
Cu(CN)2-/Cu Ag(CN)2-/Ag
Au(CN)2/Au -0.43
-0.31 -0.58
105
Influence of on coordination equilibrium
  • Ag(NH3)2 2CN- Ag(CN)2-
    2NH3
  • Mn(en)32 Ni2
    Ni(en)32 Mn2

??KS??????????????????
106
?9-4 ?HgCl42-?????????KI??,
????HgI42-????
  • ??????????
  • ???? HgI42- KS 6.81029HgCl42- KS
    1.171015
  • ?????
  • K???,???HgCl42-???HgI42-?????????

107
9-4 Chelates
  • polydentate ligands have two or more donor atoms
    situated so that they can simultaneously
    coordinate to a metal ion.
  • chelating agents appear to grasp the metal
    between two or more donor atoms.
  • claw NH2-CH2-CH2-H2N

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110
polydentate ligand is the ethylenediaminetetraace
tate ion
  • This ion, abbreviated EDTA4 -, has six donor
    atoms. It can wrap around a metal ion using all
    six of these donor atoms as shown in figure (9-9).

111
  • Figure 9-9
  • The CoEDTA- ion showing how the ethylenediamine-
  • tetraacetate ion is able to wrap around a
    metal ion, occupying six positions in the
    coordination-sphere.

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116
  • In general, chelating agents form coordination
    compounds containing rings, these coordination
    compounds are called chelates.
  • The chelates are more stable than related
    monodentate ligands, which is called chelating
    effect.

117
  • Ni2(aq) 6NH3(aq) Ni(NH3)62(aq) K 4
    108
  • Ni2(aq) 3en (aq) Ni(en)32(aq) K
    2 1018
  • Although the donor atom is nitrogen (N) in both
    instances, Ni(en)32 has a stability constant
    nearly 1010 times larger than Ni(NH3)62.

118
  • The stability of chelate depends on the number
    and size of chelate ring.
  • The larger number of chelate ring, the more
    stable chelate is.
  • When the chelate ring is formed by 5 or 6
    members, the chelate is most stable.

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