Transcript Document 7300079

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.
Anemia(贫血症)
CH2OH
CH2OH
CHSH
CH2SH
+ Hg
CHS
CH2S
•Anti-tumour（肿瘤） agent
Hg
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
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)
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.
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
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
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)6]4Coordination number = ligand number
For bidentate or polydentate：
Coordination number ≠ ligand number
e.g. [Cu(en)2]SO4 ( en = H2N-CH2-CH2-NH2)
Coordination number = 4 ≠ 2
Charges of coordination ion:
Charges of coordination ion =
the sum of charges of central ion and ligands
e.g.
K3[Fe(CN)6]
Fe3+
[Fe(H2O)6]Cl3 Fe3+
K4[Fe(CN)6]
Fe2+
• The features of coordination ion
• Contains a complicated ion - coordination ion
[Cu(NH3)4]2+ ,
[Ag(NH3)2]+,
[Fe(CN)6]4-
• Metal ion bonded with other ion or molecule
by coordination bond
• Has definite stability:
KCl•MgCl2 • 6H2O :
K+, Cl-, Mg2+
KAl(SO4) • 12H2O :
K+, Al3+, SO42+
Simple ion and complex ion
CuSO4 BaCl2
BaSO4
[Cu(NH3)4] SO4
[Ag(NH3)2]Cl
NaOH
CuSO4
Cu(OH)2
CuSO4 NH3•H2O Cu(OH)2 NH3•H2O Blue
Cu2+ + 4NH3 == [Cu(NH3)4]2+ Complex ion
AgNO3 NaCl AgCl NH3•H2O [Ag(NH3)2]+
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)6]Cl3
[PtCl6]2+
coordination
Inner sphere
Outer sphere
atom or
coordination sphere
donor atom
[Cu(NH3)4]2+
Central Ligand
ion
or atom
Coordination
number
SO42Charges of
coordination ion
bidentate
What are the oxidation numbers of the
central metal in the complexes below?
• K3[FeF6]
• Na2[Ni(CN)4]
 中文命名原则:
1. 内界和外界:
同一般简单化合物-某化某;某酸某
CuCl2 ;
BaSO4
[Pt(en)2]Cl2 ; [Cu(NH3)4]SO4 ;
K4[Fe(CN)6]
2. 内界: 按下列次序:
配体数-配体名称-“合”-中心离子名称(氧化
数)
[Cu(NH3)4]2+: 四 氨 合 铜(Ⅱ)离子
[Fe(CN)6]4- : 六 氰 合 铁(Ⅱ)酸根离子
3.当有多种配体时:先无机后有机;先阴性离子后
中性分子;先简单后复杂;先常见后不常见;同类
按配位原子字母顺序;如先NH3后H2O
[Co(H2O)(NH3)3Cl2]Cl: 氯化二氯三氨一水合钴(Ⅲ)
[Pt(NH3)4(NO2)Cl]CO3 :碳酸一氯一硝基四氨合铂(Ⅳ)
[Cu(NH3)4](OH)2 : 氢氧化四氨合铜(Ⅱ)
K[Pt(NH3)Cl5] : 五氯一氨合铂(Ⅲ)酸钾
Fe[Fe(CN)6] : 六氰合铁(Ⅲ)酸铁
Fe2[Fe(CN)6] : 六氰合铁(Ⅱ)酸亚铁
[Pt(NH3)2Cl2] : 二氯二氨合铂(Ⅱ)
[Ni(CO)4]
: 四羰基合镍
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
Naming Coordination
Compounds
LIGAND
Name of Ligand in Coord. Cpd.
Bromide, BrBromo
Chloride, ClChloro
Cyanide, CNCyano
Hydorxide, OHHydroxo
Oixde, O2Oxo
Carbonate, CO32Carbanato
Nitrite, NO3Nitro
Oxolate, C2O42Oxolato
Ammonia, NH3
Ammine
Carbon monoxide, CO Carbonyl
Water, H2O
Aquo
Ethylenediamine(en)
Ethylenediamine
4. When several ligands of a particular kind are
present, we use the Greek prefixes to name
them.
•
•
•
•
•
Di
tri
tetra
Penta
Hexa
(2)
(3)
(4)
(5)
(6)
[Co(NH3)4Cl2]+are
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)2]2+ bis(ethylenediamine)
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(Ⅲ) ion.
6. If the complex ion is an anion, its name ends in ate. K4[Fe(CN)6] the anion [Fe(CN)6]4 - is
called
hexacyanoferrate(II) ion.
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
• Example 9-1 :
(a) Ni(CO)4,
(b) [Co(NH3)4Cl2]Cl,
(c) K3[Fe(CN)6], (d) [Cr(en)3]Cl3.
• Solution:
(a) tetracarbonylnickel(0)
(b) tetraamminedichlorocobalt( Ⅲ) chloride
(c) potassium hexacyanoferrate(Ⅲ).
potassium ferricyanide
(d) tris(ethylenediamine) chromium(Ⅲ)
chloride.
.
tetraamminedichlorochromium(Ⅲ) ion.
the cation [Cr(NH3)4Cl2]+
hexacyanoferrate(II) ion.
the anion [Fe(CN)6]4 -
Give the formula for the following coordination
compounds.
tetracarbonylnickel(0)
Ni(CO)4,
tetraammineaquochlorocobalt(III) chloride
[Co(NH3)4H2OCl]Cl2
How did I know there had to be two
chlorides at the end?
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(集中) the effect of the
surrounding ligands on the energies of the
metal d orbitals
9-2.1 Valence Bond Theory
• Magnetism
• Isomerism (异构体)
• stability
9-2.2 Crystal Field Theory
• The Splitting（分裂） of the d orbitals in
octahedral Field
• High-spin and Low-Spin
Coordination Compounds
• The color of coordination compounds
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,
 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
Example [Ag(NH3)2]+
• 47Ag [Kr]4d105s1
• Central ion: Ag+ 4d105s05p0
2 electron clouds
Ag+:
hybrid
2 : NH3
sp hybridization( outer orbital )
[Ag(NH3)2]+（linear）
Ni(NH3)42+
28Ni
3d84s2
• Central ion: Ni2+ 3d8 4s0 4p0
hybrid
4 :NH3
sp3 hybridization( outer orbital )
[Ni(NH3)4 ]2+ (tetrahedral)
[Ni
Ni
[Ni(CN)4 ]2• Central ion: Ni2+ 3d8 4s0 4p0
realignment
hybrid
4 :CNdsp2 hybridization inner orbital
[Ni(CN)4 ]2-( square planar)
[Co(NH3)6] 3+
• Co atom
3d74s2
• Co3+ ion
3d6
• [Co(NH3)6
6 :NH3
]3+
d2sp3 hybridization
(inorbital complex)
Co(NH3)6 3+ (octahedral)
CoF63+
4d
• Co atom 3d74s2
• Co3+ ion
3d
4s
4p
3d6
6 :F
-
• CoF63+
sp3d2 hybridization
(octahedral)
Magnetism
• Paramagnetism: substances containing
unpaired electrons are paramagnetic.
• diamagnetic: substances without unpaired
electrons are diamagnetic.
• magnetic moment: μ
μ=√n (n+2)
• n : is the number of unpaired electrons
• Example : For [Fe(H2O)6]SO4
μ=5.26B.M
according to above equation, n = 4 ,so there are 4
unpaired electrons in this coordination compound.
• Example : For K4[Fe(CN)6]
μ=0 B.M
according to above equation, n = 0 ,so there are 0
unpaired electrons in this coordination compound.
• Example : For [Fe(H2O)6]SO4 , μ=5.26B.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
• Example : For K4[Fe(CN)6] , μ=0 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
Table 9-4: Some common types of hybridization and
geometries.
 Isomerism(异构体)
• 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立体 isomers)
Optical isomers
• Structural isomerism
• Structural isomers are that differ in how
the atoms are joined together.
• Example: [Co(NH3)5(SO4)]Br
[Co(NH3)5 Br] SO4
CH3-CH2-CH2-COOH
CH3-CH-COOH
CH3
red
violet
硝基四氨合钴（Ⅲ）
亚硝酸四氨合钴（Ⅲ）
• 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.
Geometric Isomerism (stereoisomerism)
• Pt(NH3)2Cl2
Cl
cis
NH3
Pt
Cl
NH3
NH3 Cl
trans
Pt
Cl
NH3
both coordination compounds are
named: diamminedichloroplatinum(II)
cis
cis-diamminedichloroplatinum(II)
trans
Optical Isomerism
“反应停”的手性结构分子
化学名称叫做酞胺呱啶酮，是一种常用于
安定精神和抑制妊娠恶心的镇静药和催眠药。
被反应停夺去胳膊的孩子们
“海豹”式畸形，不是手足全无，就是缺胳膊少腿，甚至手
掌直接长在肩膀上；或者出现心脏等内脏器官畸形、脑障碍、
听力或视力丧失、发生自痹症和癫痫症等
9-2.2 Crystal Field Theory（中文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.
中心离子d轨道角度分布图
The Splitting of the d Orbitals in Octahedral Field
eg (dγ)orbitals
Δ = eg - t2g
t2g (dε)orbitals
crystal field splitting energy, Δ
Δ在数值上等于一个电子由t2g轨道跃迁到eg 轨道所需的激发能。
E (deg )  E (dt2 g )  0  10Dq
2E (deg )  3E (dt2 g )  0
solution :
E (d eg )  0.6 0 (increase energy)
E (d t2 g )  0.4 0 (decrease energy)
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
.
pairing energy P
• pairing energy P: the energy required to
put two electrons into the same orbital.
• 1. P > Δ : the fourth electron will go into
one of the higher d orbitals.
a high-spin complex
2. P <Δ : an electron in one of the lower
energy orbitals.
a low spin complex
影响分裂能()的因素
① 配体：
中心离子和配体构型一定，值与配体有关：
② 中心离子
配体固定时，中心离子电荷越高，值越大
① 配体： 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 – < Br – < Cl– < SCN–< F –< OH – < H2O <NCS–
< edta < NH3 < en < NO2–< CN –< CO
Increasing Δ →
[Co(H2O)6]3+
o /cm-1
13000
[Co(NH3)6]3+
22900
[Co(CN)6]334000
强场：o > P :
low-spin complex
弱场：o < P:
high-spin complex
F- is a weakfield ligand
CN- is a
strong-field
ligand
● ②中心离子M 对的影响：
电荷Z增大， o增大:
o /cm-1
[Cr (H2O)6]3+
17600
[Cr (H2O)6]2＋
14000
主量子数n增大， o增大:
o /cm-1
[CrCl6]3-
[MoCl6]3-
13600
19200
例：下列四种络合物中，d-d跃迁能量(分裂
能)最低的是( )
a. [Fe(H2O)6] 2+ b. [Fe(H2O)6] 3+
c. [FeF6] 4d. [FeF6] 3-
八面体场中电子在t 2g和eg轨道中的分布
只
有
一
种
排
列
高
d1
d2
1
2
d9
d8
d3
1
2
3
d5
d6
d7
4
5
4
3
2
1
0
1
d4
自
旋
低
自
旋
晶体场理论的应用
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.
● 定义:晶体场稳定能(Crystal field stabilization energy,
CFSE)是指电子占据分裂的d轨道后而产生的高于平
均能量的额外稳定能 。
• 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 Δ 0 )
+ (#electrons in eg) × (0.6 Δ 0 )
CFSE= 6 × (-0.4 Δ 0 )
+ 0 × (0.6 Δ 0 )
= -2.4 Δ 0
CFSE= 4 × (-0.4 Δ 0 )
+ 2 × (0.6 Δ 0 )
= -0.4 Δ 0
2.
解释配合物离子的颜色
过渡金属配合物的颜色产生于d电子在d轨道之间的
跃迁（d-d跃迁）。
▲ 所吸收光子的频率与分裂能
大小有关
▲ 颜色的深浅与跃迁电子数目
有关
hν = Δ
ΔO
hν
The larger the crystal-field splitiing （Δ大）, the
higher will be the frequency of light absorbed most
strongly（ν大）, and the shorter its wavelength（λ
短）.
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 (ν) 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.
hν = Δ
hν = Δ
Δ大
ν大
λ短
Δ小
ν小
λ长
•On the other hand,
coordination compounds of
transition metals with weakfield ligands are blue-green,
blue, or indigo since they
absorb lower-energy yellow,
orange, or red light.
• 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 higherenergy violet or blue
light.
[Co(NH3)5Cl]2+
absorbs
Purple compound
yellow green region
( wavelength of 530 nm)
[Co(NH3)6]3+
absorbs
orange compound
violet region
(wavelength of 410nm)
d10 (Zn2+, Ag+ complexes) is colorless
Ti3+：3d1，
[Ti(H2O)6]3+
吸收可见光中蓝绿色的光，
使溶液呈红色。
= 492.7nm (蓝绿色)，
E=h = 242.79 kJ·mol-1，
波数1/=20300cm-1
(1cm-1=11.96J·mol-1)，
恰好等于该配离子的分裂能
Δo=20 300 cm-1
例：已知[Fe(CN)6]3-和[FeF6]3-的磁矩分别为1.7B和5.9 B，
(1) 计算这两种络离子中心离子未成对电子数。
(2) 写出中心离子d轨道上电子排布。
(3) 它们是强场还是弱场络合物，说明原因。
解：
(1)[Fe(CN)6]3-中，由√n ×（n＋2）=1.7B.M, 得n=1
[FeF6]3中，由√n×（n＋2）= 5.9B.M, 得n=5
(2) [Fe(CN)6]3-中，d轨道上电子排布为t2g5eg0，
[FeF6]3中，d轨道上电子排布为t2g3eg2，
(3) [Fe(CN)6]3-是强场络合物，因为强场低自旋；
[FeF6]3－是弱场络合物，因为弱场高自旋。
9-3 Coordination equilibrium
coordination
Cu2+(aq) + 4NH3(aq)
[Cu(NH3)4]2+ (aq)
ionization
[Cu(NH3)4]2+
• Ks = -------------------[Cu2+][NH3]4
[Cu2+][NH3]4
Kis= ------------------[ Cu(NH3)4] 2 +
Stability constant
or formation constant(Kf)
Instability constant
βn --Accumulate stability constant
Cu2+＋NH3
Cu(NH3
)2+＋NH
Cu(NH3)2
Cu(NH3
Cu(NH3)2
3
2+＋NH
3
Cu(NH3)32+＋NH3
[Cu(NH3)2+]
K1＝——————————
[Cu2+]×[NH3]
)2+
[Cu(NH3)22+]
K2＝————————————
[Cu(NH3)2+][NH3]
2+
Cu(NH3)3
2+
Cu(NH3)4
2+
[Cu(NH3)32+]
K3＝————————————
[Cu(NH3)22+][NH3]
[Cu(NH3)42+]
K4＝————————————
[Cu(NH3)32+][NH3]
Cu2+(aq) + NH3(aq)
[Cu(NH3)]2+ (aq)
K1=1.4×104
Cu2+(aq) + 2NH3(aq)
[Cu(NH3)2]2+ (aq)
β2= K1 • K2
Cu2+(aq) + 3NH3(aq)
K2=3.17×103
[Cu(NH3)3]2+ (aq)
β3= K1 • K2 • K3
Cu2+(aq) + 4NH3(aq)
K3=7.76×102
[Cu(NH3)]2+ (aq)
 4  K1  K 2  K3  K 4  K s
lgβ4 ＝lgK1＋lgK2＋lgK3＋lgK4
K4=1.39×102
• 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.（见中文p224【例9-1】）
1. Influence of acidity on coordination
equilibrium
• [Fe(C2O4)3]3-
Equilibrium shift
Fe3+ + 3C2O42+
6H+
3H2C2O4
酸效应: 当溶液酸度增大时，H+离子可与配体结合生成弱酸，
使配离子向解离方向移动，配离子的稳定性降低。这种因溶
水解效应: 因金属离子与溶液中OH－结合而使配离
液酸度增大而使配合物稳定性降低的现象.
子离解的作用叫做金属离子的水解效应。
2. Influence of precipitation on coordination
equilibrium
[Ag(NH3)2]+
Ag+ + 2NH3
+
Equilibrium shift
BrAgBr
• AgBr(s)
Ag++Br+
Equilibrium shift
2S2O32[Ag(S2O3)2]3-
配位平衡与沉淀平衡的转化，取决于沉淀剂与配位剂争夺金属
离子能力的大小及其浓度。实验证明一些阴离子或分子争夺Ag+
离子的能力： Cl－＜NH3＜Br－＜S2O32－＜I－＜CN－＜S2－
这个顺序与形成难溶盐的溶度积KSP和形成配离子的KS大小有关
[例9-2] 向[Ag(CN)2]－和CN－的浓度均为0.10mol·L-1溶液中加入
NaCl，能否产生AgCl沉淀？ 若改加Na2S，能否产生Ag2S沉淀？
解：溶液中有下列配位平衡：
Ag+
+
CN－
[Ag(CN)2]－
KS＝1.0×10 21
由平衡式得：

[
Ag
(
CN
)
0.1

 20
-1)
2]
(mol·L
[ Ag ] 


1
.
0

10
K s [CN  ]2 1.0  10 21  (0.10) 2
生成AgCl沉淀的条件是 [Ag+][ Cl－]＞KSP＝1.77×10－10
假设加入NaCl后溶液体积无变化，要生成AgCl沉淀，则:
10
10
1
.
77

10
1
.
77

10
10
[Cl－]＞
(mol·L-1)


1
.
77

10
[ Ag  ]
1.0  10 20
显然仅靠加入NaCl是无法使[Cl－]＞1.77×1010mol·L-1。
所以向上述溶液加NaCl不可能产生AgCl沉淀。
加入Na2S产生Ag2S沉淀的条件是:
[Ag+]2 [ S2-]
[
S2-]
＞ KSP＝6.69×10-50
＞
K sp
[ Ag  ]
假设加入Na2S后溶液体积无明显变化，则有
50
6
.
69

10
10
-1)

6
.
69

10
[S2－] ＞
(mol·L
(1.0 1020 ) 2
加入Na2S很容易使溶液中[ S2-]＞6.69×10-10 mol·L-1，
因此向上述溶液加Na2S时可产生Ag2S沉淀。
[例9-3] 25℃，在1L氨水中使0.1molAgCl固体溶解，氨水的浓
度至少为多少mol·L-1 ？
• 解：在溶液中有两个平衡：
AgCl (s)
Ag   2 NH3
Ag   Cl[Ag(NH 3 ) 2 ]
KSP＝1.8×10-10
KS＝1.6×107
将两式相加得总的平衡式：
AgCl(s) + 2NH3
[Ag(NH3)2]+ + Cl-
此反应的平衡常数式为：
[ Ag ( NH 3 ) 2 ][Cl  ] [ Ag ( NH 3 ) 2 ][Cl  ][ Ag  ]
K

2
[ NH 3 ]
[ NH 3 ]2 [ Ag  ]
K  K SP  K S
• 设溶解了的Ag+全部转化为[Ag(NH3)2]+配离子，则
[Ag(NH3)2+]＝[Cl-]＝0.1mol·L-1
• 由平衡常数表示式解出平衡时NH3的浓度为： K  K SP  K S
[NH3]＝
[ Ag ( NH 3 ) 2 ][Cl  ]
0.1 0.1
-1)


1
.
86
(mol·L
K s  K sp
1.6  10 7  1.8  10 10
• 氨水的总浓度
c NH 3至少应为:
-1）
c NH＝1.86＋2×0.1＝2.06（mol·L
3
计算说明氨水能否溶解AgI 沉淀 ？
Influence of redox on coordination equilibrium
Fe3+ + IFe2++ 1/2I2
另一方面，配位平衡也可以
+
转化为氧化还原平衡，使配
6F- Equilibrium
shift
－
离子离解。如I 可使[FeCl4]
－配离子中Fe3+还原成
Fe2+，
[FeCl4]Equilibrium
Shift
从而使[FeCl4]－配离子离解.
[FeF6]3-

Fe3 / Fe2 
 I
Fe3+ + 4Cl+
I-
Fe2+ + 1/2I2

根据标准电极电势表得知 
＞
，
2 /I
当加入NaF晶体时，Fe3+与F－结合生成[FeF6]3－配离子，
使Fe3+离子浓度降低，Fe3+/ Fe2+电对的电极电势也随之降低，当
Fe3+/ Fe2+的电极电势小于I2/ I－的电极电势时，则氧化还原反应方
向发生改变.
电极电势改变
Cu+/ Cu
Φ0/v
0.52
[Cu(CN)2]-/Cu
-0.43
Ag+/Ag
0.799
[Ag(CN)2]-/Ag
-0.31
Au3+/Au
1.50
[Au(CN)2]+/Au
-0.58
Influence of on coordination equilibrium
• [Ag(NH3)2]+ +2CN-
[Ag(CN)2]- + 2NH3
• [Mn(en)3]2+ + Ni2+
[Ni(en)3]2+ + Mn2+
利用KS值可以判断配位平衡转化的方向和程度。
[例9-4]
在[HgCl4]2-配离子的溶液中加入KI溶液，
能否生成[HgI4]2-配离子？
解：溶液中存在下列平衡：
[HgCl4]2- + 4I-
[HgI4]2- + 4Cl-
[ HgI 42 ][Cl  ]4 [ HgI 42 ][Cl  ]4 [ Hg 2 ] K [ HgI4 ]2 
K


2
 4
2
 4
2
[ HgCl 4 ][ I ]
[ HgCl 4 ][ I ] [ Hg ] K [ HgCl ]2 
4
查表得知 [HgI4]2－ KS = 6.8×1029；[HgCl4]2－ KS = 1.17×1015
29
6
.
8

10
14
代入上式得： K 

5
.
8

10
1.17  1015
K值很大，说明由[HgCl4]2－转化为[HgI4]2－的反应完全可以实现
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∶
polydentate ligand is the
ethylenediaminetetraacetate 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).
• Figure 9-9:
• The CoEDTA- ion
showing how the
ethylenediaminetetraacetate ion is
able to wrap around
a metal ion,
occupying six
positions in the
coordination-sphere.
• 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.
Ni2+(aq) + 6NH3(aq) =[Ni(NH3)6]2+(aq) K = 4 ×108
Ni2+(aq) + 3en (aq) = [Ni(en)3]2+(aq)
K = 2 ×1018
• Although the donor atom is nitrogen (N) in both
instances, [Ni(en)3]2+ has a stability constant
nearly 1010 times larger than [Ni(NH3)6]2+.
• 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.