Chapter 12 Coordination Compound Main topics: Fundamental Concepts of CC Crystal Field Theory of CC Valence Bond Theory of CC Coordination compounds(or

Chapter 12

Coordination Compound

Main topics: Fundamental Concepts of CC

Crystal Field Theory of CC

Valence Bond Theory of CC

Coordination compounds(or complexs) are closely related to the

chemistry of transition metals

Why Study chemistry of complex Transition metals are found in nature

– Rocks and minerals contain transition metals– The color of many gemstones is due to the presence

of transition metal ions• Rubies(红宝石 ) are red due to Cr(chromium)

• Sapphires(蓝宝石 ) are blue due to Fe and Ti(titanium)

– Many biomolecules contain transition metals that are involved in the functions of these biomolecules

• Vitamin B12 contains Co(cobalt)

• Hemoglobin, myoglobin, and cytochrome C contain Fe

Colour of transition metal complexes

Ruby

Corundum

Al2O3 with Cr3+ impurities

Sapphire

Corundum

Al2O3 with Fe2+ and Ti4+ impurities

Emerald

Beryl

AlSiO3 containing Be with Cr3+ impurities

octahedral metal centre

coordination number 6

Transition metals and their compounds have many useful applications– Fe is used to make steel and stainless steel

– Ti is used to make lightweight alloys

– Transition metal compounds are used as pigments

• TiO2 = white

• PbCrO4 = yellow

• Fe4[Fe(CN)6]3 (prussian blue, 普鲁士蓝 )= blue

– Transition metal compounds are used in many industrial processes

Why Study chemistry of complex

To understand the uses and applications

of transition metals and their

compounds, we need to understand their

chemistry.

Our focus will be on the 4th period

transition elements.

Why Study chemistry of complex

Fig. 23.1

Fig. 23.3

Fig. 23.4

f block transition elements

d block transition elements

Periodic Table

General Properties– Have typical metallic properties– Not as reactive as Grp. IA, IIA metals– Have high MP’s, high BP’s, high density,

and are hard and strong– Have 1 or 2 s electrons in valence shell– Differ in # d electrons in n-1 energy level– Exhibit multiple oxidation states

Transition Metals

Sc Ti V Cr Mn Fe Co Ni Cu Zn

Y Zr Nb Mo Tc Ru Rh Pd Ag Cd

La Hf Ta W Re Os Ir Pt Au Hg

IIIB IVB VB VIB VIIB IB IIBVIIIB

d-Block Transition Elements

Most have partially occupied d subshells in common oxidation states

Electronic Configurations

Sc [Ar]3d14s2

Ti [Ar]3d24s2

V [Ar]3d34s2

Cr [Ar]3d54s1

Mn [Ar]3d54s2

Element Configuration

[Ar] = 1s22s22p63s23p6

(p. 1012)

Aqueous Oxoanions of V, Cr, and Mn in their Highest Oxidation States

Fig 23.5

Fe [Ar] 3d64s2

Co [Ar] 3d74s2

Ni [Ar] 3d84s2

Cu [Ar]3d104s1

Zn [Ar]3d104s2

Element Configuration

[Ar] = 1s22s22p63s23p6

Electronic Configurations

Transition Metals

• Characteristics due to d electrons:– Exhibit multiple oxidation states– Compounds typically have color– Exhibit interesting magnetic properties

• Paramagnetism(顺磁性 )• Ferromagnetism(铁磁性 )

3/7/01 Ch. 24 11

Oxidation States of Transition Elements

+3+3+3+3+3+3+3+3+3

+7

+6+6+6

+5+5+5+5

+4+4+4+4+4+4

+2+2+2+2+2+2+2+2+2

+1+1

ZnCuNiCoFeMnCrVTiSc

loss of ns e-sloss of ns and (n-1)d e-s

Electronic configuration of Fe2+

Electronic Configurations of Transition Metal Ions

valence ns e-’s removed first

Fe – 2e- Fe2+

[Ar]3d64s2 [Ar]3d6

Electronic configuration of Fe3+

Fe – 3e- Fe3+

[Ar]3d64s2 [Ar]3d5

valence ns e-’s removed first, then n-1 d e-’s

Electronic configuration of Co3+

Co – 3e- Co3+

[Ar]3d74s2 [Ar]3d6

valence ns e-’s removed first, then n-1 d e-’s

A Brief Review for Concepts of acids and bases

Historically, chemists have sought to relate the properties of acids and bases to their compositions and molecular structures.

■ Arrhenius concept of acids and bases — In the 1880s the Swedish chemist Svante Arrhenius(1859-1927, 1903 Nobel Prize in

chemistry) linked acid behavior with the presence of H+ ions and base behavior with the presence of OH-

(hydroxyl ion ) ions in aqueous solution. He defined acids as substances that produce H+ ions in water, and base as substances that produce OH- ions in water. Over time his concept of acids and bases came to be stated in the following way: Acids are substances that, when dissolved in water, increase the concentration of H+ ions. Likewise, bases are substances that, when dissolved in water, increase the concentration of OH- ions.

■ Bronsted concept of acids and bases — In the 1923 Danish chemist Johannes Bronsted (1879-1947) and English chemist Thomas Lowry (1874-1936) proposed a more general definition of acids and bases. Their concept is based on the fact that acid-base reactions involve the transfer of H+ ions from one substance to another.Bronsted and Lowry proposed that acids and bases be defined in terms of their ability to transfer protons. Their definition is: an acid is a substance(molecule or ion) that can transfer a proton to another substance. Likewise, a base is a substance that can accept a proton.

■ Lewis(1875-1946) concept of acids and bases — For a substance to be a proton acceptor(a Bronsted-Lowry base), that substance must possess an unshared pair of electrons for binding the proton. For example, NH3

(ammonia)acts as a proton acceptor when it reacts with H+ to form NH4

+ (ammonium ion). G.N. Lewis was the first to notice this aspect of acid-base reactions. He proposed a definition of acid and base that emphasizes the shared electron pair. A Lewis acid is defined as an electron-pair acceptor, and a Lewis base is defined as an electron-pair donor. The Lewis definition therefore greatly increases the number of species that can be considered acids.

　　　 Transition metals act as Lewis acids• Form complexes/complex ions

Fe3+(aq) + 6CN-(aq) Fe(CN)63-(aq)

Ni2+(aq) + 6NH3(aq) Ni(NH3)62+(aq)

Complex contains central metal ion bonded to one or Complex contains central metal ion bonded to one or more molecules or anionsmore molecules or anions

Lewis acid = metal = center of coordinationLewis acid = metal = center of coordination

Lewis base = ligand = molecules/ions covalently Lewis base = ligand = molecules/ions covalently bonded to metal in complexbonded to metal in complex

Lewis acid Lewis base Complex ion


Transition metals act as Lewis acids

• Form complexes/complex ions

Fe3+(aq) + 6CN-(aq) [Fe(CN)6]3-(aq)

Ni2+(aq) + 6NH3(aq) [Ni(NH3)6]2+(aq)



★ There is a rich and important chemistry associated with such complex assemblies of metals surrounded by molecules and ions.

Metal compounds of this kind are called:

配位化合物coordination compounds

Addition of base， ammonium hydrate(氨水 ) to an aqueous solution of Cu2+ ions causes precipitation(沉淀 ) of Cu(OH)2

(copper hydroxide). When the base is continually added in, the precipitation will dissolved and form a transparent (透明的 ) solution with dark blue color. If ethanol(乙醇 ) is added in this transparent solution, again, the dark blue precipitation appears. chemical analysis tells us the precipitate is Cu(NH3)4]SO4•H2O.

★ Species such as [Cu(NH3)4]2+ that are assemblies of a central metal ion bonded to a group of surrounding molecules or ions are called metal complexes or merely complexes (复合物 ). If the complex carries a net electric charge, it is generally called a complex ion (复合离子 )。

Compounds that contain complexes are known as

coordination compounds ( CC, 配合物 )☞Although transition metals excel in forming coordination compounds, other metals can form them as well.

§12.1 fundamental Concepts of CC

1.1 composition of complexes

中心原子配体

配位键

内层（ inner sphere）外层（ outer sphere）

配合物

[ Cu ( NH3 )4 ]2+ SO42-

离子键

★ coordination molecules have no outer sphere but inner sphere

coordination bond

ionic bond

coordination compounds

The molecules or ions that surround a

metal ion in a complex are called

ligands(配体 ). Ligands may be anions

or polar molecules. Some common

ligands are water (水 ), ammonia (氨 ),

hydroxide (氢氧化物 ), cyanide (氰化物 ), and chloride (氯化物 ).

Each of these has at least one unshared pair

of electrons that can be used to coordinate

(form a coordinate covalent bond (配位共价键 ) to the metal ion). Metal ions can act as

Lewis acids, accepting electrons from ligands,

which act as Lewis bases. The atom that is

bound directly to the metal ion is called the

donor atom(供电子原子 ). It's the atom that

donates a lone pair of electrons to the metal

ion.

[ Cu（ NH3） 4 ] 2+ [ Fe(H2O) 6]3+ [ SiF6 ] 2-

中心原子

配体

配位原子

Cu( ) Ⅱ Fe( ) Ⅲ Si(Ⅳ)

NH3 H2O F-

N O F

中心原子： cations or atoms offering empty orbitals

配体： the molecules or ions that surround the metal ion in a complex

配位原子： the atoms of ligand bound directly to the metal

（ central atom）

（ Ligand）

（ donor atom）

★ Ligand is from the Latin word ligare, meaning “to bind”

Coordination sphere– Metal and ligands bound to it

Coordination number– number of donor atoms bonded to the central

metal atom or ion in the complex• Most common = 4, 6• Determined by ligands

– Larger ligands and those that transfer substantial negative charge to metal favor lower coordination numbers

Ligands– classified according to the number of donor

atoms– Examples

• monodentate = 1• bidentate = 2• tetradentate = 4• hexadentate = 6• polydentate = 2 or more donor atoms

Coordination Compounds

Common ligands:

– water H - O - H

– ammonia NH3

– chloride ion Cl -

– cyanide ion C N -

• Monodentate– Examples:

• H2O, CN-, NH3, NO2-, SCN-, OH-, X- (halides),

CO, O2-

– Example Complexes• [Co(NH3)6]3+

• [Fe(SCN)6]3-

单齿配体（monodentate ligand )： — the ligands possess a single donor atom and

are able to occupy only one site in a coordination sphere

– Examples• oxalate ion = C2O4

2-

• ethylenediamine (en) = NH2CH2CH2NH2

• ortho-phenanthroline (o-phen)

– Example Complexes• [Co(en)3]3+

• [Cr(C2O4)3]3-

• [Fe(NH3)4(o-phen)]3+

二齿配体（ bidentate ligand )： — the ligands possess two donor atoms

N - CH2- CH2 - N H

H H

H

Ethylenediamine (en)

oxalate ion(草酸根 )

Ortho-phenanthroline(邻二氮杂菲 )

carbonate ion(碳酸根 )

bipyridine(联二吡啶 )

Structures of other bidentate ligands. The coordinating atoms are shown in blue.

N - CH2- CH2 - N H

H H

HEthylenediamine (en)

ethylenediaminetetraacetate (EDTA) = (O2CCH2)2N(CH2)2N(CH2CO2)2

4-

– Example Complexes• [Fe(EDTA)]-1

• [Co(EDTA)]-1

六齿配体（ hexadentate ligand )： — the ligands possess six donor atoms

Coordination Compounds

Uses for EDTA– Used in food products to complex metals that

promote decomposition reactions– Used to remove toxic heavy metals from the

body– Used to complex metal ions that inhibit or

promote polymerization reactions

EDTA

N

NH NH

N

Porphine(卟啉 ), an important chelating agent

found in nature

N

N N

N

Fe2+

Metalloporphyrin（铁卟啉）

Coordination Compounds • Porphyrins are naturally occurring

complexes derived from porphin.– Heme (Fe2+)– Chlorophyll (Mg2+)

Myoglobin(肌红蛋白 ), a protein that stores O2 in cells

Coordination Environment of Fe2+ in Oxymyoglobin (氧肌红蛋白 ), and Oxyhemoglobin (氧血红蛋白 )

Ferrichrome(铁血素 )

(Involved in Fe transport in bacteria)

常见的单基配体

常见的多基配体

☛ The charge on a central metal ion can be determined in much the same way that

oxidation numbers are determined in molecular compounds. It is important to recognize common molecules, to remember that they are neutral, and to know the charges on both monoatomic and polyatomic ions. The sum of charges on the metal ion and the ligands must equal the net charge on the complex.

Complex charge

[Fe(CN)6]3-

Complex charge = sum of charges on the metal and the ligands

+3 6(-1)

[Co(NH3)6]Cl2

Neutral charge of coordination compound = sum of charges on metal, ligands, and counterbalancing ions

neutral compound

+2 6(0) 2(-1)

常见金属离子的配位数

☛ Coordination numbers of 2, 4, and 6 are common. The geometry of a complex is determined in part by its coordination number. (Size of the ligands can also impact the geometry.)

Coordination Number

Geometry

2 Linear

4 Tetrahedral(more common) or square planar

6 Octahedral

(p. 1017)

Structures of (a) [Zn(NH3)4]2+ and (b) [Pt(NH3)4]

2+,

illustrating the tetrahedral and square-planar geometries, respectively. These are the two common geometries for complexes in which the metal ion has a coordination number of 4. The shaded surfaces shown in the figure are not bonds; there are included merely to assist in visualizing the shape of the metal complex.

Two representations of an octahedral coordination sphere, the common geometric arrangement for complexes in which the metal ion has a coordination number of 6.

Attentions:

In mono-core coordination compounds, each donor atom can only bind directly to one central atom to form coordination bond.

Though some ligands have two or more donor atoms, they are still monodentate ligand because only one donor atom can form bond with central atom.

e.g： H2O 、 F-

e.g： SCN- 、 NCS- 、NO2

- 、 ONO-

1.2 types of CC

1. Simple complex

— The one formed by central metal atom and monodentate ligand.

[Cu(NH3)4]SO4、 K[Ag(CN)2] 、K2[PtCl4]、 etc.

e.g:

许多水合结晶盐都含有水合配离子 .

如 : FeCl3· 6H2O 为 [Fe(H2O)6]Cl3；

CuSO4·5H2O 为 [Cu(H2O)4]SO4·H2O 。

H2O分子是单基配体，配位原子是 O原

子。

2. 螯合物 (Chelate compound)

Polydentate ligands (多基配体 ) tend to

coordinate more readily and form more

stable complexes than monodentate

ligands (单基配体 ). This phenomenon is

known as the chelate effect (螯合效应 ) .

— — the ringed coordination compounds the ringed coordination compounds formed by metal atom and polydentateformed by metal atom and polydentate

Cd2+

螯合剂螯合剂 (chelating agents)(chelating agents)

— — polydentate ligands are polydentate ligands are also known as chelating also known as chelating agents which are agents which are usually organic ligands usually organic ligands possessing donor atoms possessing donor atoms like Nlike N、、 PP、、 OO、、 S.S.

The [CoEDTA]– ion, showing how theEthylene diamine tetraacetate (乙二胺四乙酸 ) ion is able to wrap around a metal ion, occupying six positions in the coordination sphere.

3. 特殊配合物 (special complex)

M ← C间的键

M→C间的反馈键

1) 羰合物 (carboxide) — the complex formed when carbon

monoxide acts as the ligand

NaClFeHCFeClNaHC 2)(2 255255

The first sandwich complex discovered was ferrocene (二茂铁 ). Ferrocene and its derivative are used as additive of rocket fuel, aging agent of silicon resin and rubber and absorbant of ultraviolet light.

2) 夹心配合物(Sandwich complex)

Fe(C5H5)2

3) 原子族状化合物

原子簇状化合物是指具有两个或两个以上金属 —原子以金属金属键（M—M）直接结合而形成的化合物，简称簇合物。双核簇合物 [Re2Cl8]

2 －

是最简单的双核簇合物。

[Re2Cl8]2 －的结构

4) 大环配合物 (marcocyclic complex)— Ringed coordination compounds formed by

metal atom and polydentate ligands with O、 N、 P、 S or As(arsenic) atoms on their ring frameworks

There are two types of macrocyclic complex:

冠醚（ Crown ether）

穴醚（ Hole ether）

The cation is named before the anion

When naming a complex:– Ligands are named first

• alphabetical order

– Metal atom/ion is named last• oxidation state given in Roman numerals follows

in parentheses

– Use no spaces in complex name

1.3 Nomenclature of CC (IUPAC Rules)

[Co(NH3)5Cl]2+ Pentaamminechlorocobalt (III) 五氨氯钴 (III)

The names of anionic ligands end with the suffix -o– -ide suffix changed to

-o

– -ite suffix changed to -ito

– -ate suffix changed to -ato

Ligand Name

bromide, Br- bromo

chloride, Cl- chloro

cyanide, CN- cyano

hydroxide, OH-

hydroxo

oxide, O2- oxo

fluoride, F- fluoro

Nomenclature of CC (IUPAC Rules)

Ligand Name

carbonate, CO32- carbonato

oxalate, C2O42- oxalato

sulfate, SO42- sulfato

thiocyanate, SCN- thiocyanato

thiosulfate, S2O32- thiosulfato

Sulfite, SO32- sulfito


Neutral ligands are referred to by the usual name for the molecule

– Example• ethylenediamine

– Exceptions• water, H2O = aqua

• ammonia, NH3 = ammine

• carbon monoxide, CO = carbonyl


Greek prefixes are used to indicate the number of each type of ligand when more than one is present in the complex– di-, 2; tri-, 3; tetra-, 4; penta-, 5; hexa-, 6

If the ligand name already contains a Greek prefix, use alternate prefixes:– bis-, 2; tris-, 3; tetrakis-,4; pentakis-, 5; hexakis-, 6

– The name of the ligand is placed in parentheses


[Co(en)3]Cl3－ tris(ethylenediamine)cobalt(III) chloride

e.g:

K4[Fe(CN)6] potassium hexacyanoferrate(II)

[ 六氰合亚铁 (II)酸钾 ][CoCl4]2- tetrachlorocobaltate(II) ion

[四氯合钴 (II)酸根离子 ].

If a complex is an anion, its name ends with the -ate

– appended to name of the metal


e.g:

Transition Metal

Name if in Cationic Complex

Name if in Anionic Complex

Sc Scandium Scandate

Ti titanium titanate

V vanadium vanadate

Cr chromium chromate

Mn manganese manganate

Fe iron ferrate

Co cobalt cobaltate

Ni nickel nickelate

Cu Copper cuprate

Zn Zinc zincate


★ Some names of coordination compounds

[Co(NH3)4Cl2]Cl: tetraamminedichlorocobalt(Ⅲ) chloride

[Pt(NH3)2Cl2]: diamminedichloroplatinum(Ⅱ)

K[Ni(C2O4)2]: potassium bisoxalatonicketate(Ⅱ) oxalic acid(草酸 )

[Cr (NH3)5H2O](NO3)3: pentaammineaquachromium (Ⅲ) nitrate

Questions

1. Which name is correct for the coordination compound [Fe(en)2Cl2]Cl?

A dichlorobisethylenediamineiron(III) chloride

B diethylenediaminechlorineiron(I) chloride

C iron(III) bisethylenediaminedichloro chloride

D iron(III) trichloridebisethylenediamine

总称阴离子在前，阳离子在后◆ 含配阳离子：

某酸某某化某氢

氧化某◆ 含配阴离子：

某酸某某酸

◆中性配位分子

[Co(NH3)4Cl2]Cl氯化二氯四氨合钴（ III）

[Ag(NH3)2]OH氢氧化氨合银 ( )Ⅰ

[Cu(NH3)4]SO4 硫酸四氨合铜（ II）

K4[Fe(CN)6]六氯合铁（ II）酸钾H2[PtCl6]六氯合铂（ IV）酸

配合物的命名nomdenclature of complex

[Co(NH3)4(NO2)Cl]NO3

硝酸氯硝基四氨合钴（ III）

NH4[Co(NO2)4(en)]

四硝基（乙二胺）合钴（ III）酸铵

[Co(NH3)3(H2O)Cl2]Cl[Co(NH3)3(H2O)Cl2]Cl

氯化二氯三氨水合钴（ III）氯化二氯三氨水合钴（ III）

[Co (NO2)(NH3)4Cl]NO3[Co (NO2)(NH3)4Cl]NO3

硝酸氯硝基四氨合钴（ III）硝酸氯硝基四氨合钴（ III）

注意：配体次序　　　　　　　　　　　

　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　

　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　

　　　　　　

1) 　　　　　先无机配体后有机配体　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　

　　　　　　　　　　　　　　　　　　　　　　　　　　　　　 2)先阴　　　　　　　　　　　　　　　　　　　离子后中性分子

　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　

　　　　　　　　　　　　　 3)若配体均为阴离　子或中性分子可按配位原子

　　　　　　元素符号的英文字母顺序　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　

　　　　 4)同类配体中若配位原子相同，则将含较少原子数的配体排在前面，较多原子数

　　　　　　　　　　　　　　　　　的配体列后 5)

复杂配体均加圆括号，以免混淆

[Cu（ NH3） 4]2+

四氨合铜（ II）离子

[CoCl2（ NH3） 4

]+

二氯四氨合钴（ III）离子

[Fe（ en） 3]Cl3

氯化三（乙二胺）合钴（ III）

四氨铜（ II）

四氨二氯合钴（ III）离子

氯化三乙二胺合钴（ III）

[Ag（ NH3） 2]OH

氢氧化二氨合银（ I）

氢氧化氨合银

H2[PtCl6]

六氯合铂（ IV）酸

[Co（ NH3） 5（ H2O） ]2（ SO4

） 3

硫酸五氨水合钴（ III）

六氯合铂酸（ IV）

硫酸一水五氨合钴（ III）

[Co（ NH3） 2（ en） 2]Cl3

氯化二氨二（乙二胺）合钴（ III）

[Ni（ CO） 4]

四羰基合镍

氯化二（乙二胺）二氨合钴（ III）

四羰基合镍（ 0）

[Cu（ NH3） 4]2+

加少量加少量 NaOH NaOH 加少量加少量 NaNa22S S

无明显现象无明显现象黑色沉淀黑色沉淀

Ksp(Ksp(Cu(OH)Cu(OH)22)=5.6×10)=5.6×10-20-20

Cu(OH)Cu(OH)22 IP< Ksp IP< KspKsp(Ksp(CuS CuS )=6.3×10)=6.3×10-36-36

CuSCuS IP > Ksp IP > Ksp

说明：说明：配离子在溶液中仍或多或少的离解配离子在溶液中仍或多或少的离解出出 Cu2+

Cu2++4NH3 [Cu(NH3)4]2+ 配位 kf

解离 kd

kf=[Cu(NH3)4

2+]

[Cu2+][NH3]4

Formation constant of cc Kf

同类 kf 配合物稳定性↗

Kf[Ag(CN)2]-=1.31021 Kf[Ag(NH3)2]+=1.1107

稳定性 [Ag(CN)2]- [Ag(NH3)2]+

1.4 Equilibrium of CC

1. Kd and Kf of coordination compounds

Kf1

Cu2+ ＋NH3

[Cu(NH3)]2+

Kf2

[Cu(NH3)2]2+ [Cu(NH3)]2+ ＋ NH3

Kf3

[Cu(NH3)3]2+ [Cu(NH3)2]2+ ＋ NH3

Kf4

[Cu(NH3)4]2+ [Cu(NH3)3]2+ ＋ NH3

Kf 也叫配合物的稳定常数 (KS) 或积累稳定常数 (Kβ)

KKff = K = Kf1f1×K×Kf2f2×K×Kf3f3×K×Kf4 f4 = = 1Kd

Comparison of stability of CC ions:Comparison of stability of CC ions:

KKs s [ M[ Mn+ n+ ]]

（（ 11）） same typesame type：：■■Ag(NHAg(NH3 3 ))22

+ + 1.11.1× × 10107 7 9.19.1× × 1010-9-9

■■ Ag(CN)Ag(CN)22- - 1.31.3× × 101021 21

7.77.7× × 1010-23-23

（（ 22）） different typedifferent type：：■■ CuYCuY2- 2- 6.36.3××101018 18 1.31.3× × 1010-10-10

■■ Cu(en)Cu(en)222+ 2+ 44××10101919

8.68.6× × 1010-8-8

Comparison of stability of CC ions:Comparison of stability of CC ions:

KKs s [ M[ Mn+ n+ ]]

（（ 11）） same typesame type：：■■Ag(NHAg(NH3 3 ))22

+ + 1.11.1× × 10107 7 9.19.1× × 1010-9-9

■■ Ag(CN)Ag(CN)22- - 1.31.3× × 101021 21

7.77.7× × 1010-23-23

（（ 22）） different typedifferent type：：■■ CuYCuY2- 2- 6.36.3××101018 18 1.31.3× × 1010-10-10

■■ Cu(en)Cu(en)222+ 2+ 44××10101919

8.68.6× × 1010-8-8

2. Shift of coordination equilibrium

1) coordination equili- and acid-base equili-

2) coordination equili- and precipitate equili-

3) coordination equili- and redox equili-

Common characteristic ：

multiple equilibrium

[Cu（ NH3） 4]2+ Cu2++4NH3

+4H+

4NH4+

shift

(1) Effect of Acidity (1) Effect of Acidity

Acidity （ pH ） stabilityAcidity （ pH ） stability ↘↘

1) coordination equilibrium and acid-base equilibrium

[FeF6]3- Fe3+ + 6F- [H[H+]>0.5 ]>0.5 mol/Lmol/L酸效应酸效应+

6H+

6HF

Acidity ↓ stability of CC ↑Acidity ↓ stability of CC ↑

+3OH-

Fe(OH)3

水水解解效效应应

一般：在保证不生成氢氧化物沉淀的前提下一般：在保证不生成氢氧化物沉淀的前提下尽量提高尽量提高 PHPH值，以保证配合物的稳定性值，以保证配合物的稳定性

(2) Effect of hydrolysis(2) Effect of hydrolysis

KspAgBr= 5.0×10KspAgBr= 5.0×10-13-13

+ + 2NH2NH33

[Ag(NH[Ag(NH33))22]]++

AgClAgCl AgAg+ + + Cl+ Cl-- KspAgCl=1.8×10KspAgCl=1.8×10-10-10

AgAg+ + + 2NH+ 2NH33

+ + BrBr--

AgBrAgBr

Ks=1.1×10Ks=1.1×1077

争取争取 AgAg++能力：能力：ClCl- - <NH<NH3 3 < Br< Br--

< I< I- - < CN< CN- - < S< S2-2-

注意注意：同类型的物质才能由平衡常数作判据：同类型的物质才能由平衡常数作判据

2) coordination equilibrium and precipitate equilibrium

12-7

例：计算 298.15K时， AgCl在 1L 6molL-

1NH3 溶液中的溶解度。

解解：先写出此溶液主要存在的平衡反应：先写出此溶液主要存在的平衡反应

11））沉淀平衡：沉淀平衡：AgClAgCl （（ ss））

AgAg+ + + Cl+ Cl-- KspAgCl=1.77×10KspAgCl=1.77×10-10-10

22））配位平衡：配位平衡：Ks=1.1×10Ks=1.1×1077AgAg+ + + 2NH+ 2NH33 [Ag(NH[Ag(NH33))22]]++

两式相加：两式相加：AgCl (s) +2NHAgCl (s) +2NH33 [Ag(NH[Ag(NH33))22]]+ + + Cl+ Cl--

KK

AgCl (s) +2NHAgCl (s) +2NH33 [Ag(NH[Ag(NH33))22]]+ + + Cl+ Cl--KK

s s6-2ss

K= KsKsp = 1.1107 1.77 10-10

S = 0.24（mol L-1）

K =[Ag(NH3)2

+][Cl-]

[NH3]2

[Ag(NH3)2+][Ag+][Cl-]

[Ag+][NH3]2= = KsKsp

=s2

(6-2s)2

所以：

沉淀溶解条件 Ks Ksp 沉淀生成条件 Ks Ksp

当加入配合剂使沉淀溶解时，最有利于沉淀转化为配合物的条件是（）

1） Ks 大 2） Ks 小 3） Ksp 大 4） Ksp小

A. 1） 2） 3 ） B. 1） 3 ） C. 2） 4 ） D. 4 ） E. 1） 2） 3） 4）

B

AgCl (s) + 2NHAgCl (s) + 2NH33 [Ag(NH[Ag(NH33))22]]+ + + Cl+ Cl--KK

K =KsKsp

[Ag(NH3)2]+ + Br- AgBr + 2NH3

K′=1

KsKsp

解：

若在上述溶液中加入 NaBr固体使 Br-浓度为 0.1 molL-

1（忽略加入引起的体积变化）问有无 AgBr沉淀生成？

（ Ks[Ag（ NH3） 2]+=1.1107、 KspAgCl=1.77

10-10 、 KspAgBr=5.35 10-13）s=0.24（mol L-1）

[Ag（ NH3） 2]+ + Br-

AgBr + 2NH3

6-2 0.240.10.24

KsKsp

= 1 103 QK

反应向右进行 AgBr生成有

K=1

=5.53 10-13 1.1107

1=1.7105

Q =（ 6-2 0.24） 20.24 0.1

解：溶液中的平衡为Ag + +2NH3

[Ag(NH3)2]+

例：在 100.0ml含有过量 NH3• H2O 的

AgNO3混合溶液中，加入 0.1molL-1NaCl溶

液 100.0ml时无 AgCl沉淀生成 , 计算混合液中 NH3的平衡浓度至少为多少？

Ks[Ag(NH3)2]+ = 1.1107、

KspAgCl = 1.8 10-10

∵无 AgCl ∴ 沉淀 [Ag+][Cl-] ≤ KspAgCl

[Ag+] ≤ KspAgCl ⁄ [Cl-]

[Cl-]= 0.1×100/200=0.05 molL-1

∴[Ag+] ≤ 1.8 10-10 ⁄ 0.05 = 3.6× 10-9molL-1

[Ag(NH3)2]+ = 0.1×100 ⁄ 200 － [Ag+] ≈ 0.05 molL-1

由配位平衡

得： [NH3]min = 1.12 molL-1

{[Ag(NH3)2]+}

[Ag+]•[NH3]2Ks =

若用若用 NaBrNaBr代替代替 NaClNaCl情况如何？情况如何？

[Ag[Ag++] ≤ KspAgBr ] ≤ KspAgBr ／／ [Br[Br--]]

[Ag[Ag++] ≤ 5.0 ] ≤ 5.0 1010-13-13 ／／ 0.05 = 1.0× 100.05 = 1.0× 10-11-11molmolLL-1-1

∵ ∵ 浓浓 NHNH33•• HH22OO的浓度仅为的浓度仅为 15mol 15mol LL-1-1

∴∴上述条件下用上述条件下用 NHNH33•• HH22OO 不可能阻止不可能阻止

AgBrAgBr沉淀沉淀

{[Ag(NH3)2]+}

[Ag+]•[NH3]2Ks =

[NH[NH33]min ≈21.3 mol]min ≈21.3 molLL-1-1

在在 0.1mol0.1molLL-1-1 [Zn(NH[Zn(NH33))44]]2+2+ 溶液中通入溶液中通入 HH22SS至至SS2-2-浓度为浓度为 :1.0×10:1.0×10-10 -10 molmolLL-1-1 ,,问是否有问是否有 ZnZnSS沉淀沉淀析出？析出？Ks [Zn(NHKs [Zn(NH33))44]]2+2+=5.0=5.0101088 、、 Ksp ZnKsp ZnSS =1.2 =1.21010-23-23

解解：未通：未通 HH22SS前前设设0.1mol0.1molLL-1-1 [Zn(NH[Zn(NH33))44]]2+2+ 溶液中溶液中 [[ZnZn2+2+]] = = x x molmolLL-1 -1 则：则： [[NHNH33]] = 4= 4x x molmolLL-1-1

通通HH22SS IP IP = = CCZnZn2+ 2+ •• CCSS2- 2- = 3.8×10= 3.8×10-3-3 × × 1.0×101.0×10-10 -10

IPIP = 3.8×10= 3.8×10-13 -13 ＞＞ Ksp ZnKsp ZnSS

∴∴上述条件下有上述条件下有 ZnZnSS沉淀沉淀析出析出

ZnZn2+2+ +4NH +4NH33[Zn(NH[Zn(NH33))44]]2+2+

[Zn(NH[Zn(NH33))44]]2+2+ = = 0.10.1－－ x ≈ x ≈ 0.10.1 molmolLL-1-1

代入代入 Ks = {[Zn(NHKs = {[Zn(NH33))44]]2+2+} } ⁄⁄ [[ZnZn2+2+]]•• [[NHNH33]]44

得：得： x≈ x≈ 3.8×103.8×10-3-3 mol molLL-1-1

4Au+O2+2H2O 4OH-+4Au+

Au+/Au=1.692v O2/OH- =0.401v

4Au + O2 + 2H2O + 8CN- 4[Au(CN)2]- + 4OH-

shift

[Au（ CN） 2]-/Au=-0.574v O2/OH-=0.401v forward

2[Au(CN)2]- + Zn [Zn (CN)4]2- + 2Au

ºº

º º

3) coordination equilibrium and redox equilibrium

Fe3+ + I- Fe2++1/2 I2

[FeF6]3-

+6F-

[FeCl4]- Fe3++4Cl-

+ I-

Fe2++1/2 I2

在某一配位平衡体系中，加入另一种能与中在某一配位平衡体系中，加入另一种能与中

心原子心原子 ((或配体或配体 ))形成配合物的配体（或中形成配合物的配体（或中

心原子）配位平衡是否变化，可根据它们的心原子）配位平衡是否变化，可根据它们的

KsKs值相对大小值相对大小 ((同类型同类型 ))及计算来判断。及计算来判断。

4) coordination equilibrium and other coordination equilibrium

1. 已知 Ks[Ag （ CN ） 2]-

Ks[Ag（ NH3） 2]+，

反应

[Ag （ CN ） 2]- + 2NH3 [Ag （ NH3 ） 2]+

+2CN- 将（）

A. 正向自发进行 B. 处于平衡状

态

C. 逆向自发进行 D. 无法判定

C

Questions:

2. 在 [Cu（ NH3） 4]SO4溶液中存在平衡

[Cu（ NH3） 4]2+ Cu2++4NH3

若向该溶液中分别加入以下试剂，能使平衡右移的

是（）

1 ）盐酸 2 ）氨水 3） Na2S 4） Na2SO4

A. 1） 2） 3 ） B. 1） 3 ）

C. 2） 4 ） D. 4 ）

E. 1） 2） 3） 4）

B

isomer(异构体 ) ： Two or more

compounds with the same elemental

composition but different arrangements of

atoms.

✽ Isomerism of CC

— Major Types

structural isomers

stereoisomers

1.4.1 Structural Isomers

structural isomers(结构异构体 ) ： — isomers that have different bonds.

1. Coordination-sphere isomers– differ in a ligand bonded to the metal in the

complex, as opposed to being outside the coordination-sphere

• Example

[Co(NH3)5Cl]Br vs. [Co(NH3)5Br]Cl

— Consider ionization in water

[Co(NH3)5Cl]Br [Co(NH3)5Cl]+ + Br-

[Co(NH3)5Br]Cl [Co(NH3)5Br]+ + Cl-

[Co(NH3)5Cl]Br vs. [Co(NH3)5Br]Cl

— Consider precipitation

[Co(NH3)5Cl]Br(aq) + AgNO3(aq) [Co(NH3)5Cl]NO3(aq) + AgBr(s)

[Co(NH3)5Br]Cl(aq) + AgNO3(aq) [Co(NH3)5Br]NO3(aq) + AgCl(aq)

2. Linkage isomers

— differ in the atom of a ligand bonded to the metal in the complex

Example:

– [Co(NH3)5(ONO)]2+ vs. [Co(NH3)5(NO2)]2+

Example:

– [Co(NH3)5(SCN)]2+ vs. [Co(NH3)5(NCS)]

Co-SCN vs. Co-NCS

stereoisomers(立体异构体 )

1.4.2 Stereoisomers

— isomers with the same bonds but different spatial arrangements of those bonds.

1. Geometric isomers

－ Have different chemical/physical properties different colors, melting points, polarities, solubilities, reactivities, etc.

－ Differ in the spatial arrangements of the ligands

cis isomer, 顺式

trans isomer，反式

Pt(NH3)2Cl2

Geometric Isomers

[PtCl2(NH3)2]的顺式异构体

称为顺铂 (cisplatin), 是一个很好的抗癌药物，当它进入人体后，能迅速而又牢固地与 DNA(脱氧核糖核酸 )

结合成为一种隐蔽的 cis-

DNA加合物，干扰 DNA的复制，阻止癌细胞的再生。

[PtCl2(NH3)2]的反式异构体

没有抗癌功能。

cis isomer trans isomer

[Co(H2O)4Cl2]+

Geometric Isomers

2. Optical isomers

– isomers that are nonsuperimposable mirror images

• said to be “chiral” (handed)

• referred to as enantiomers

– A substance is “chiral” if it does not have a “plane of symmetry”

Fig. 23.12

mirror p

lane

cis-[Co(en)2Cl2]+

Example 1

180 °

rotate mirror image 180°Example 1

Nonsuperimposable, enantiomers

cis-[Co(en)2Cl2]+

Example 1

mirror p

lane

trans-[Co(en)2Cl2]+

Example 2

Example 2

180 °

rotate mirror image 180°

trans-[Co(en)2Cl2]+

Example 2

Superimposable-not enantiomers

trans-[Co(en)2Cl2]+

Properties of Optical Isomers

Enantiomers – possess many identical properties

• solubility, melting point, boiling point, color, chemical reactivity (with nonchiral reagents)

– different in:• interactions with plane polarized light• reactivity with “chiral” reagents

Example

Optical Isomers

light source

unpolarized light

polarizing filter plane

polarized light

(random vibrations) (vibrates in one plane)

(+) dextrorotatory (right rotation )(-) levorotatory(left rotation )

Optical Isomers

optically active sample in solution

rotated polarized light

polarizing filterplane

polarized light

optically active sample in solution

rotated polarized light

polarizing filterplane

polarized light

Dextrorotatory (d) = right rotation

Levorotatory (l) = left rotation

Racemic mixture = equal amounts of two enantiomers; no net rotation

— theory of bonds between metal atoms and donor atoms

§12.2 Valence Bond Theory of Coordination Compounds

主价副价理论 (main valence and auxiliary vanlence theory)

价键理论 (valence bond theory) 晶体场理论 (crystal field theory) 分子轨道理论 (molecular orbital theory) 配位场理论 (coordination field theory)

Werner's name will always be associated with the theory of coordination which he established and with his work on the spatial relationships of atoms in the molecule, the foundations of which were laid in the work he did, when he was only 24, for his doctorate thesis in 1892. In this work he formulated the idea that, in the numerous compounds of tervalent(三价的 ) nitrogen, the three valence bonds of the nitrogen atom are directed towards the three corners of a tetrahedron, the fourth corner of this being occupied by the nitrogen atom.

Alfred Werner (1866 - 1919)The founder coordination compound

1913 Nobel Prize in chemistry

In 1891 he had published a paper on the

theory of affinity and valence, in which he

substituted for Kekulé's conception of

constant valence, the idea that affinity is an

attractive force exerted from the centre of the

atom which acts uniformly towards all parts

of the surface of the atom.

Some Coordination Compounds of Cobalt Studied by Werner

Werner’s Data*Traditional Total Free Modern Charge ofFormula Ions Cl- Formula Complex Ion

CoCl3 6 NH3 4 3 [Co(NH3)6]Cl3 3+

CoCl3 5 NH3 3 2 [Co(NH3)5Cl]Cl2 2+

CoCl3 4 NH3 2 1 [Co(NH3)4Cl2]Cl 1+

CoCl3 3 NH3 0 0 [Co(NH3)3Cl3] ---

.

.

.

.

L· Pauling H· Bethe J· H· Van Vleck

Valence bond theory

1931年Crystal field theory

1929→1950S

20s of 20 century20s of 20 century

一 . Valence Bond Theory一 . Valence Bond Theory

Central atomCentral atom ligandligandligandligand

Coordination Coordination bondbond

Coordination Coordination bondbond

Equivalent hybridization

Equivalent hybridization

Lone electron pairLone electron pair

main concepts: － hybridization －coordination bond

Geometry of NH3

Zn2+

NH3

NH3 NH3

NH3

2+

[Zn(NH[Zn(NH33))44] ] 2+2+

3030ZnZn2+2+ [Ar] [Ar]1818

3d3d10104s4s 4p4p

等性等性 spsp33杂杂化化

3d3d10104 4 个个 spsp33 杂化轨杂化轨道道

[Ar][Ar]1818

Tetrahedron Tetrahedron

Geometry of [Zn(NHGeometry of [Zn(NH33))44] ] 2+2+

Atoms in the third period and beyond can also

use d orbitals to form hybrid orbitals. Mixing

one s orbital, three p orbitals, and one d

orbital leads to five sp3d hybrid orbitals. These

hybird orbitals are directed toward the

vertices(顶点 ) of a trigonal bipyramid(三角双锥 ). The formation sp3d hybrids is

exemplified by the phosphorus (磷 ) atom in

PF5 , phosphorus pentafluoride .

How to use VSEPR method to predict the molecular shape of PF5 ?

Similarly, mixing one s orbital, three p orbitals, and two d orbitals gives six sp3d2 hybrid orbitals, which are directed toward the vertices of an octahedron(八面体 ). The use of d orbitals in constructing hybrid orbitals nicely corresponds to the notion of an expanded valence shell.

Geometry of coordination compounds depends on the geometry of hybrid orbitals of central atoms !

Common hybridization types of metals and the Geometries of the Complexes

Linear

Coordination Number Geometry

2examples:

[Ag(NH3)2]+

[Ag(CN)2]-

[Cu(NH3)2]+

sp hybridization



3Example:

[Cu(CN)3]2-

sp2 hybridization


4 tetrahedral

square planar

Example:

[Ni(CN)4]2-

Examples:

[Zn(NH3)4]2+,

[FeCl4]-


sp3

dsp2



5Examples:

[Ni(CN)5]3-

[Fe(CO)5]

dsp3


6 octahedral

[FeF6]3- sp3d2


Examples:

[Fe(CN)6]3- d2sp3

[Cr(NH3)6]3+ sp3d2

Hybrid Orbitals and Bonding in the Tetrahedral [Zn(OH)4]2- ion

30Zn [Ar]3d104s2

Hybrid Orbitals and Bonding in the Square Planar [Ni(CN)4]2- Ion

28Ni [Ar]3d84s2

Valence Bond TheoryHybrid Orbitals and Bonding in the Octahedral

[Cr(NH3)6]3+ Ion

24Cr [Ar]3d54s1

Factors affecting the geometry of complexs

Electronic configuration of central atoms (metal atoms)

electronegativity of donor atoms

1. outer-orbital coordination compound(high-spin complexs)

When the electronegativity of donor atoms like halogen and oxygen is high, it is uneasy for them to lose the lone electron pairs. So the donor atoms can not disorder(push) the valence electrons in metal atoms. Under this circumstance the central atoms only offer their outer-orbitals to form hybrid orbitals, sp,sp2,sp3, sp3d2 ,sp2d3..

Since the electrons in valence shell of the metal atoms are not rearranged, there are relatively more unpaired d electrons in their valence shell. So these complexs are called high-spin complexs.

[FeF[FeF66] ] 3-3- FF- - 1s1s2 2 2s2s2 2 2p2p66

2626Fe [Ar]Fe [Ar]18 18 3d3d6 6 4s4s2 2 → Fe→ Fe3+3+ [Ar] [Ar]18 18 3d3d554s4s0 0

3d3d55 4s4s00 4p4p 4d4d

Equivalent Equivalent sp3d2 hybridization hybridization

3d3d55

4d4dSpSp33dd22 hybridization orbital hybridization orbital

high-spin complexs

3d3d55

4d4d

Because bonding orbitals is relatively far Because bonding orbitals is relatively far

away from the nuclei, the bonding electron away from the nuclei, the bonding electron

pairs are not firmly held by the nuclei. So, the pairs are not firmly held by the nuclei. So, the

bond energy of outer-orbital complexs is low bond energy of outer-orbital complexs is low

and consequently they are not so stable, and consequently they are not so stable,

having a high solubility in water. having a high solubility in water.

SpSp33dd22 hybridization orbitalhybridization orbital

2. inner-orbital coordination compound(low-spin complexs)

When the electronegativity of donor atoms like carbon (CNcarbon (CN--) ) ，， nitrogen(-NOnitrogen(-NO2-2-) ) is not so high, it is easy for them to lose the lone electron pairs. So the donor atoms can not push the valence electrons into inner orbitals of metal atoms. Under this circumstance the central atoms can offer inner-orbitals to form hybrid orbitals, (n-1)dsp2,(n-1)d2sp3..

Since the electrons in valence shell of the metal atoms are rearranged, there are relatively less unpaired d electrons in their valence shell. So these complexs are called low-spin complexs.

[Fe(CN)[Fe(CN)66] ] 3-3-

26Fe [Ar]26Fe [Ar]18 18 3d3d6 6 4s4s2 2 → Fe→ Fe3+3+ [Ar] [Ar]18 18 3d3d554s4s0 0

3d3d55 4s4s00 4p4p

3d3d55

3d3d55 dd22spsp33杂化轨道杂化轨道

low-spin complexs

3d3d55 dd22spsp33杂化轨道杂化轨道

Because bonding orbitals is relatively closer Because bonding orbitals is relatively closer to the nuclei, the bonding electron pairs are to the nuclei, the bonding electron pairs are firmly held by the nuclei. So, the bond energy firmly held by the nuclei. So, the bond energy of low-orbital complexs is comparatively high of low-orbital complexs is comparatively high and consequently they are stable and have a and consequently they are stable and have a low solubility in water. low solubility in water.

Strength of ligand:CNCN-- > NO > NO22

- - > SO> SO332- 2- > en > NH> en > NH33

> EDTA> H> EDTA> H22OO

> OH> OH-- > F > F -- > SCN > SCN- - > Cl > Cl -- > Br > Br -- > > I I --

越强越易使中心原子电子重排并成对越强越易使中心原子电子重排并成对。。

Outer-orbital Vs. Inner-orbital hybridization

Outer-orbital Vs. Inner-orbital hybridization

Outer orbital:

Inner orbital:

spd

(n-1)dsp

sp3d2、 sp、 sp3

dsp2、 d2sp3

Requirement for formation of inner-oribtal complexs — The energy released during the bonding between donor atoms and metal atoms is more than that released during formation of outer-orbital complex after offseting the energy for electron pairing.

3d3d55 dd22spsp33—inner-orbital—inner-orbital[Fe(CN)[Fe(CN)66] ] 3-3-

3d3d55

4d4dspsp33dd22—outer-orbital—outer-orbital

[FeF[FeF66] ] 3-3-

3d3d55 4s4s00 4p4p

FeFe3+3+ 1818[Ar][Ar]

High-spin

low-spin

Generally, coordination compounds formed by inner Generally, coordination compounds formed by inner orbitals are stabler than those formed by outer orbitals are stabler than those formed by outer orbitals, but the coordination compound formed orbitals, but the coordination compound formed contains empty (n-1)d orbitals, it will be unstable.contains empty (n-1)d orbitals, it will be unstable.

[V(NH[V(NH33))66]]3+3+

VV3+3+

1818[Ar][Ar] 3d3d224s4s 4p4p

dd22spsp33杂化杂化

1818[Ar][Ar]

3d3d22 dd22spsp33杂化杂化

We know that the existence of unpaired electrons in a molecule causes the molecule

to exhibit paramagnetism(顺磁性 ). Paramagnetic substances are attracted by a magnetic field. The magnitude of this attraction can provide evidence of the number of unpaired electrons in the substance.

2. Magnetism of complexs

★ 未成对 d 电子数与配合物磁矩的关系： B——玻尔磁子 (B.M)

1B =9.27×10-24 B.M

■ ■ 形成外轨型配合物时，一般形成外轨型配合物时，一般 n n 值不变：值不变： [Fe(H[Fe(H22O)O)66]]2+ 2+ 实测 =5.70 B

■ ■ 形成内轨型配合物时，一般形成内轨型配合物时，一般 n n 值减小：值减小： [Fe(CN)[Fe(CN)66]]3+ 3+ 实测 =2.25B

)2( nnm

n 1 2 3 4 5 6 7

m 1.73 2.83 3.87 4.90 5.92 6.93 7.49

（ 1） [26Fe（ H2O） 6]3+ =5.9

Fe3+ 1s22s22p63s23p6 3d 5

sp3d23d外轨八面体

配合物的电子结构和磁矩

已知 [26Fe（ CN） 6]3-的磁矩 = 3 ， Fe3+ 采用（）已知 [29Cu（ NH3） 4]2+为内轨型配离子， Cu2+空轨

道的杂化类型为（）

A. sp3 杂化 B. dsp2 杂化 C. sp3不等性杂化

D. dsp2 不等性杂化 E. d2sp3 杂化 F. sp3d2

杂化

E

Cu2+ 1s22s22p63s23p63d9

3d 激发dsp2

3d4p

B

Measurement of the magnetic properties of coordination complexes gives some interesting results. Two complexes containing the cobalt(III) ion exhibit different magnetic properties. The complex ion [Co(NH3)6]

3+ is diamagnetic(反磁性的 ). It contains no unpaired electrons. The complex ion [CoF6]

3– is paramagnetic (顺磁性的 ). In fact, its degree of paramagnetism is such that we know it contains four unpaired electrons.

The fact that the cobalt(III) ion has different numbers of unpaired electrons in different compounds indicates that the free ion's electron configuration is not the only determining factor in the number of unpaired electrons in a complex. Crystal-field theory helps explain these observations.

Assumes bonding is covalent

Does not account for colour of complexes

Can predict magnetism wrongly

Does not account for spectrochemical

series

Limitations of VB theory

When ligands coordinate to a metal ion, they increase the energies of the metal‘s d orbitals by ligand d-orbital repulsion. Because of their spatial arrangement, the d orbitals do not all experience the same increase in energy. If we consider the formation of an octahedral(八面体的 ) complex in which the ligands approach the metal ion along the x, y, and z axes, we see that only orbitals that lie along the axes (the dz2 and dx2-y2) are approached directly.

§12.3 Crystal-Field Theory

(红宝石 )

Crystal-Field TheoryCrystal-Field Theory Crystal field theory describes bonding in

transition metal complexes. The formation of a complex is a Lewis acid-base

reaction. Both electrons in the bond come from the ligand

and are donated into an empty, hybridized orbital on the metal.

Charge is donated from the ligand to the metal. Assumption in crystal field theory: the

interaction between ligand and metal is electrostatic.

The more directly the ligand attacks the metal orbital, the higher the energy of the d orbital.

ligands approach along x, y, z axes

(-) Ligands attracted to (+)

metal ion; provides stability

Octahedral Crystal Field

d orbital e-’s repulsed by (–) ligands; increases d orbital

potential energy

+

-

- -

-

-

-

Crystal Field Theory

greater electrostatic repulsion = higher potential energy

less electrostatic repulsion = lower potential energy

The complex metal ion has a lower energy than the separated metal and ligands.

In an octahedral field, the five d orbitals do not have the same energy: three degenerate orbitals are higher energy than two degenerate orbitals.

The energy gap between

them is called , the crystal field splitting energy.

3.1 Splitting of d orbital of metal atoms

Splitting of d-orbital Energies by a Tetrahedral Field and a Square Planar

Field of Ligands

分裂能△ o的大小与配体的场强、中心离子

的电荷数及中心离子在周期表中的位置等因素有关。

3.2 Factors affecting the magnitude of ∆

1. effect of ligands

中心离子相同，配体不同，则由配体所产生的晶体场分裂能力越强，所产生的晶体场场强越大，分裂能

越大。同一种金属离子分别与不同的配体生成一系列八面体配合物，用电子光谱法分别测定它们在八面体场中

△的分裂能（ o），按由小到大的次序排列，得如下序

列：

光谱化学序列

2. Effect of metal atoms配体相同，中心金属离子相同时，金属离子价态越高，分裂能越大。例如： [Co(H2O)6]

3+ △ o=18600 cm － 1

[Co(H2O)6]2+ △ o= 9300 cm － 1

[Co(NH3)6]3+ △ o= 23000 cm － 1

[Co(NH3)6]2+ △ o= 10100 cm － 1

配体相同，中心金属离子价态相同且为同族元素时，从上到下分裂能增大。例如： [Co(NH3)6]

3+ △ o=23000 cm － 1

[Rh(NH3)6]3+ △ o= 33900 cm － 1

[Ir(NH3)6]3+ △ o= 40000 cm － 1

3.3 Electronic Configurations of Transition Metal Complexes

• Expected orbital filling tendencies for e-’s:– occupy a set of equal energy orbitals one at a time

with spins parallel (Hund’s rule) • minimizes repulsions

– occupy lowest energy vacant orbitals first

• These are not always followed by transition metal complexes.

d orbital occupancy depends on and pairing energy, P– e-’s assume the electron configuration with the

lowest possible energy cost

– If > P ( large; strong field ligand)

• e-’s pair up in lower energy d subshell first

– If < P ( small; weak field ligand)

• e-’s spread out among all d orbitals before any pair up

d-orbital energy level diagramsoctahedral complex

d1

d2


d3


d4

high spin < P

low spin

> P


d5

high spin < P

low spin

> P


d6

high spin < P

low spin

> P


d7

high spin < P

low spin

> P


d8


d9


d10


Electronic Configurations of Transition Metal Complexes

Determining d-orbital energy level diagrams:– determine oxidation # of the metal

– determine # of d e-’s

– determine if ligand is weak field or strong field

– draw energy level diagram

High-spin and low-spin complex ions of Mn2+

Orbital Occupancyfor High- and Low-Spin Complexes of d4 Through d7 MetalIons

d4

d6

d7

d5

High spin weak-field

ligand

Low spin strong-field

ligand

Crystal field theory can offer a good

explanation of many properties of

transition metal, such as

stability、 spectrum、 and

magnetism.

3.4 Application of crystal field theory

Properties of Transition Metal Complexes

Properties of transition metal complexes:– usually have color

• dependent upon ligand(s) and metal ion– many are paramagnetic

• due to unpaired d electrons• degree of paramagnetism dependent on

ligand(s)– [Fe(CN)6]3- has 1 unpaired d electron– [FeF6]3- has 5 unpaired d electrons

Crystal Field Theory– Can be used to account for

• Colors of transition metal complexes– A complex must have partially filled d

subshell on metal to exhibit color– A complex with 0 or 10 d e-s is colorless

• Magnetic properties of transition metal complexes

– Many are paramagnetic– # of unpaired electrons depends on the

ligand

Compounds/complexes that have color:– absorb specific wavelengths of visible light (400 –

700 nm)

• wavelengths not absorbed are transmitted• color observed = complementary color of color

absorbed

1. Account for the color of complexs

Visible Spectrum

White = all the colors (wavelengths)

400 nm 700 nm

wavelength, nm

higher energy

lower energy

(Each wavelength corresponds to a different color)

absorbed color

observed color

Relation Between Absorbed and Observed Colors

Absorbed ObservedColor (nm) Color (nm)

Violet 400 Green-yellow 560Blue 450 Yellow 600 Blue-green 490 Red 620Yellow-green 570 Violet 410Yellow 580 Dark blue 430Orange 600 Blue 450Red 650 Green 520

Color & Visible SpectraColor & Visible Spectra

Color& SpectraColor& Spectra The plot of absorbance versus

wavelength is the absorption spectrum.

—For example, the absorption spectrum for [Ti(H2O)6]3+ has

a maximum absorption occurs at 510 nm (green and yellow).

—So, the complex transmits all light except green and yellow.

—Therefore, the complex appears to be purple.

Absorption of UV-visible radiation by atom, ion, or molecule:– Occurs only if radiation has the energy needed

to raise an e- from its ground state to an

excited state• i.e., from lower to higher energy orbital• light energy absorbed = energy difference

between the ground state and excited state • “electron jumping”

white light

red light absorbed

green light observed

For transition metal complexes, corresponds to

energies of visible light.

Absorption raises an electron from the lower d subshell to the higher d

subshell.

Many coordination compounds exhibit vivid colors. Pigments in paint are often coordination complexes, as are the colorants（着色剂） in stained glass（彩色玻璃） . The colors exhibited by coordination compounds can be explained in terms of the electron configurations of their central metal ions.It is generally necessary for a metal ion to have a partially filled d subshell for it to be colored. In fact, most transition-metal ions have a partially filled d subshell. Compounds of metal ions with empty d subshells, such as Al3+ and Ti4+ are typically colorless. Compounds of metal ions with completely filled d subshells, such as Zn2+, also tend to be colorless.

Objects and substances appear colored by virtue of

reflection or absorption of visible light. An opaque

（不透明的） object may appear yellow because

it reflects only yellow light and absorbs all other

colors; or, it may appear yellow because it absorbs

just the complementary color （补色） of yellow,

which is violet . A translucent （半透明的）material may transmit only green light, or it may

transmit all colors but red, the complementary

color of green. Either way, it will appear green to

our eyes.

violet

Different complexes exhibit different colors because:– color of light absorbed depends on

• larger = higher energy light (Shorter wavelengths) absorbed

• smaller = lower energy light(Longer wavelengths) absorbed

– magnitude of depends on:• ligand(s)• metal

white light

red light absorbed

(lower energy light)

green light observed

[M(H2O)6]3+

white light

blue light absorbed (higher energy light)

orange light observed

[M(en)3]3+

Colors of Transition Metal Complexes

配离子显色的原因如下：

如果配合物中心离子的 t2g轨道和 eg轨道没有

充满，通过吸收可见光（或紫外光）区的某一波长的光波，就可以使 d电子从 t2g轨道跃迁到 eg轨

道，我们称之为 d-d 跃迁。包含所有可见光波长的白光，照射配离子的水溶液时，因为配离子发生 d—d跃迁而吸收了部分波长，透过余下的光波，溶液便呈现出不同的颜色。

因为产生 d—d跃迁所吸收的能量与配离子的分裂能有关，所以分裂能不同的配离子会显示不同的颜色。

Colour of transition metal complexes

Ruby

Corundum

Al2O3 with Cr3+ impurities

Sapphire

Corundum

Al2O3 with Fe2+ and Ti4+ impurities

Emerald

Beryl

AlSiO3 containing Be with Cr3+ impurities

octahedral metal centrecoordination number 6

(红宝石 ) (刚玉 )

(蓝宝石 )

(绿宝石 ,翡翠 )

(绿玉 )

The wavelength of light absorbed depends on the size of the energy gap, ∆ , between lower- and higher-energy d orbitals. The size of ∆ depends in part on the identity of the ligands coordinating to the metal ion. Figure below shows a series of four chromium(III) complexes, each with a different ∆ value.

green yellow yellow

∆3

violet violetvioletyellowred

∆1∆2

∆4

24Cr3+ 3d3

例如， [Ti(H2O)6]3+ △的分裂能 o =20400 cm―1对

波长为 490 nm（波数为 20400 cm―1）的光有最大吸收峰，相当于吸收了蓝绿色的光，该配合物呈现出紫红色。

The energy gap between the three lower-energy d orbitals and the two higher-energy d orbitals is such that visible light causes this electron promotion. Thus, a particular wavelength of visible light is absorbed, giving a coordination complex its characteristic color. The gap between lower- and upper-level d orbitals in the [Ti(H2O)6]

3+ ion is of the magnitude that light of

510 nm wavelength promotes an electron. Absorption of this wavelength of light (510 nm is

a green wavelength) gives the ion its

characteristic red color.

22Ti [Ar]3d24s2

22Ti3+ [Ar]3d14s0

Ti: titanium

[Ti(H2O)6]3+, 红色

★ 因为 Zn2+为 d10构型，不会发生 d—d跃迁，所以 [ Zn(H2O)6]

2+离子为无色溶液。

“ ”光谱化学序列就是利用这一原理测出来的。需要指出的是，过渡金属离子颜色不一定都是 d—d 跃迁的结果。

• Color of a complex depends on: (i) the metal and (ii) its oxidation state.

• Pale blue [Cu(H2O)6]2+ can be converted into dark blue [Cu(NH3)6]2+ by adding NH3(aq).

• A partially filled d orbital is usually required for a complex to be colored.

• So, d 0 metal ions are usually colorless. Exceptions: MnO4

- and CrO42-.

• Colored compounds absorb visible light.

• The color our eye perceives is the sum of the light not absorbed by the complex.

2. Account for the stability of complexs

1．配合物稳定性的示方法

在 [Cu(NH3)4]SO4溶液中，实际上存在着如

下平衡：

[Cu(NH3)4]2+ ⇌ Cu2++4NH3

Cu2++4NH3 ⇌ Cu(NH3)4]2+

[Cu(NH3)4]2+ ⇌ Cu2++4NH3

Cu2++4NH3 ⇌ Cu(NH3)4]2+

前者是配离子的解离反应，后者则是配离子的生成反应。与之相应的标准平衡常数分别为叫做配离子的解离常数 (dissociation constant)和生成常数 (formation constant)，分别用符号Kd和 Kf 表示。 Kd是配离子不稳定性的量

度，对相同配位数的配离子来说， Kd越大，

表示配离子越易解离。

Kf 是配离子稳定性的量度， Kf值越大，表

示该配离子在水中越稳定，因而 Kd和 Kf又

分别称为不稳定常数 (unstable constant)和

稳定常数 (stable costant)。

显然任何一个配离子的与互为倒数关

系：

Kd × Kf = 1

在溶液中配离子的生成是分步进行的，每一步都有一个对应的稳定常数，我们称它为逐级稳定常数 (stepwise stable constants)（或分步稳定常数）。逐级稳定常数越大表示该级配合物越稳定，例如：

Cu2+ + NH3 ⇌ [Cu(NH3)]2+

10

/)( /) (

/))]( ([ 31.4

0

3

02

02

30

1

cNHccCuc

cNHCucK

同理有：

[Cu(NH3)]2+ + NH3 ⇌ [Cu(NH3)2]2+ K2

0 = 10 3.67

[Cu(NH3)2]2+ + NH3 ⇌ [Cu(NH3)3]2+ K30 = 10 3.04

[Cu(NH3)3]2+ + NH3 ⇌ [Cu(NH3)4]2+ K40 = 10 2.3

多配体配离子的总稳定常数（或累积稳定常数）等于逐级稳定常数的乘积：

[Cu]2+ + 4NH3 ⇌ [Cu(NH3)4]2+

32.1340

302

02430

403

02

01

0 10/)( /)(

/)])(([

cNHccCuc

cNHCucKKKKK f

一些常见配离子的稳定常数

☛ 在晶体场中，中心离子的 d 电子从假如未分裂的 d轨道（能量为 Es的 d轨道）进入分裂后的 d轨道所产生的能量下降低值，称为晶体场稳定化能 (crystal field stability energy) 。

d6

除了 Ni2+和 Cu2+的顺序反常外，弱场中配离子的稳定性顺序与 CFSE顺序基本一致，即 CFSE愈大，配合物愈稳定。 Cu2+的稳定性大于 Ni2+是由于Cu2+的八面体配离子产生了杨 -泰勒效应的结果 .

在价键理论中，需要借助配离子的磁性实验数据推测中心离子 d 轨道中的未成对电子数，从而判断中心离子属于何种杂化类型，该配合物属于何种配合物。

△在晶体场理论中，只要知道分裂能（ o）和电

子成对能（ P）数据，就可以判断该配离子属于

强场或弱场离子，并进一步写出 d电子在 t2g轨道

和 eg轨道上的分布情况，判断成单电子数，并利

用公式 3-12计算出该配离子磁矩的理论值。

3. Account for the magnetism of complexs

Magnetism• Many transition metal complexes are

paramagnetic (i.e. they have unpaired electrons).

• There are some interesting observations. Consider a d6 metal ion:– [Co(NH3)6]3+ has no unpaired electrons, but [CoF6]3-

has four unpaired electrons per ion.

• We need to develop a bonding theory to account for both color and magnetism in transition metal complexes.

Documents

Chapter 12 Coordination Compound Main topics: Fundamental Concepts of CC Crystal Field Theory of CC Valence Bond Theory of CC Coordination compounds(or