Chapter 9 Chemistry of Coordination Compounds(配位化合物).ppt

1、1,Chapter 9 Chemistry of Coordination Compounds(配位化合物),9.1 The Basic Concepts of Coordination Compounds (配位化合物的基本概念) * 9.2 Isomerism(异构现象) 9.3 Covalent Bond of Coordination Compound (配位化合物的价键理论) * 9.4 Crystal-Field Theory(晶体场理论) 9.5 Chelates(螯合物) 9.6 The Coordination Equilibrium(配位平衡),2,9.1 The Basi

2、c Concepts of Coordination Compounds(配位化合物的基本概念),9.1.1 The Composition(组成) of Coordination Compounds,A metal complex, or simply a complex(络合物), is a metal ion bound to a group of surrounding ions or molecules. When a complex is charged, it is called a complexion. Coordination compounds(配位化合物) are co

3、mpounds that contain complexes.,The metal ions are called centre ions(中心离子), it is the core part of a Coordination compounds. The transition metal ion is most common. If metal or nonmetal atoms(no charges) is the core, called centre atom(中心原子).,3,The metal ion and the ligands that are covalently bou

4、nd to it make up the coordination sphere(配位层) of the complex. The number of donor atoms bound to the metal ion is the coordination number (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 i

5、mpact the geometry.),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, ammonia, hydroxide, cyanide(氰化物), and chloride. Each of these has at least one unshared pair of electrons that can be use

6、d to coordinate(配位) (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(配位原子). Its the atom that donates(提供) a lone pair of

7、electrons to the metal ion.,4,Coordination Number Geometry(几何构型) 2 Linear(直线型) 4 Tetrahedral(more common) or square planar (平面四方型) 6 Octahedral(八面体),5,Cu(NH3)4SO4,K4 Fe(CN)6,6,Questions,1. What is the charge on the nickel ion in the complex ion Ni(NH3)6 2+? (1) +6; (2) +2; (3) +8; (4) 4;,2. What is

8、the coordination number of chromium in the complex ion Cr(H2O)4Cl2+? (1) 2; (2) 4; (3) 5; (4) 6,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

9、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.,3. What is the coordination number of iron in Fe(en)2Cl2Cl? (1) 2; (2) 4; (3) 6; (4) 8,7,9.1.2 Nomenclature(命名法) of Coordination

10、Compounds,1. 中文命名规则,配位化合物的命名与无机盐的命名规则相似,阴离子在前,阳离子在后. 配离子或中性配位化合物的命名顺序为:配体-合-中心离子或原子 (氧化数) .不同配体之间用圆点分开,阴离子配体在前,中性配体在后;配位数用汉字表示(二、三等),氧化数用带括号的罗马字表示.,配阴离子配合物 某酸盐,K2SiF6,KPtCl5(NH 3),NaCo(CO)4,六氟合硅()酸钾,五氯 氨合铂()酸钾,四羰基合钴(-)酸钠,8,Zn(NH3)4Cl2,配阳离子配合物酸某盐,CoCl(NH3)5Cl2,Co (NH3)2(en)2 (NO3)3,二氯化四氨合锌(),二氯化一氯 五氨

11、合钴(),硝酸二氨 二(乙二胺) 合钴(),中性配合物,PtCl2(NH3)2,Co(NO2)3(NH3)3,二氯二氨合铂(),三硝基 三氨合钴(),9,The system for naming coordination compounds is as follows:,2. Within a complex ion or molecule, the ligands are named before the metal. Ligands are listed in alphabetical order(字母顺序), regardless of the charge on the ligand

12、. Prefixes that give the number of ligands are not considered part of the ligand name in determining alphabetical order. Thus, in the Co(NH3)5Cl2+ ion we name the ammonia ligands first, then the chloride, then the metal: pentaamminechlorocobalt(III). Note, however, that in writing the formula, the m

13、etal is listed first.,*2. 英文命名规则(self-study ),1. In naming salts, the name of the cation is given before the name of the anion. Thus, in Co(NH3)5ClCl2 we name the Co(NH3)5Cl2+ and then the Cl.,10,4. A Greek prefix (for example, di-, tri-, tetra-, penta-, and hexa-) is used to indicate the number of

14、each kind of ligand when more than one is present. Therefore, in the name for Co(NH3)5Cl2+ we have pentaammine, indicating five ligands. If the name of the ligand itself contains a Greek prefix, such as mono- or di-, the name of the ligand is enclosed in parentheses, and alternate prefixes (bis-, tr

15、is- tetrakis-, pentakis-, and hexakis-) are used. For example, the name for Co(en)3Cl3 is tris(ethylenediamine)cobalt(III) chloride.,3. The names of the anionic ligands end in the letter o, whereas neutral ones ordinarily bear the name of the molecule. Special names are given to H2O (aqua) and NH3 (

16、ammine). For example, the terms chloro and ammine occur in the name for Co(NH3)5ClCl2,11,6. The oxidation number of the metal is given in parentheses in Roman numerals following the name of the metal. For example, the Roman numeral III is used to indicate the +3 oxidation state of cobalt in Co(NH3)5

17、Cl2+.,5. If the complex is an anion, its name ends in -ate. For example, in K4Fe(CN)6 the anion is called the hexacyanoferrate(II) ion. The suffix -ate is often added to the Latin stem, as in this example.,Co(NH3)4Cl2Cl,tetraamminedichlorocobalt()chloride,Pt(NH3)2Cl2,diamminedichloroplatinum(),K2Ni(

18、C2O4)2,potassium bisoxalatonickelate(),Cr(NH3)5H2O(NO3)3,pentaammineaquachromium() nitrate,Samples,12,*9.2 Isomerism(异构现象),Two or more compounds with the same elemental composition but different arrangements of atoms are called isomers(异构体). Structural isomers(结构异构体) are isomers that have different

19、bonds. Stereoisomers(立体异构体) are isomers with the same bonds but different spatial arrangements of those bonds.,Two types of structural isomers are linkage isomers(链异构体) and coordination-sphere isomers(配位层异构体). Linkage isomers differ only in which atom of a ligand serves as the donor atom. A common e

20、xample of linkage isomerism can occur in compounds with a nitrite ion ligand. The nitrite ion can coordinate through the oxygen atom, in which case the ligand is called nitro (硝基), or it can coordinate through a nitrogen, in which case it is called nitrito亚硝酸(基). In order to distinguish these two, t

21、he nitro ligand is generally written as NO2- , whereas the nitrito ligand is written as ONO- .,13,(a) Yellow N-bound and (b) red O-bound isomers of Co(NH3)5NO22+,Coordination-sphere isomers differ in what ions are bound to the metal ion inside the coordination sphere and what ions are outside the co

22、ordination sphere, held there by electrostatic attraction. Three coordination-sphere isomers exist for the compound CrCl3(H2O)6. One is a violet compound. The other two are green.,14,Two types of stereoisomerism are geometrical isomerism(几何异构体) and optical isomerism(旋光异构体). Geometrical isomerism is

23、possible in square planar complexes and in octahedral complexes. An isomer with particular groups adjacent to each other is called a cis(顺式) isomer, while one with particular groups across from each other are called trans(反式).,(a) Cis and (b) trans geometric isomers of the square-planar Pt(NH3)2Cl2,

24、(a) Cis and (b) trans geometric isomers of the octahedral Co(NH3)4Cl2+ ion. (The symbol N represents the coordinated NH3 group.),15,Optical isomers are mirror images that cannot be superimposed(叠加) on each other. They are called enantiomers(对映异构体).,Enantiomers are distinguished from each other by th

25、e way they rotate the plane of plane-polarized light. The isomer that rotates the light one way is called dextrorotatory(右旋), and the isomer that rotates it the other way is called levorotatory(左旋). Such isomers are said to be optically active(光学活性). When equal amounts of the two isomers are present

26、, there is no net rotation. Such a mixture, which is not optically active, is called racemic(外消旋).,16,9.3 Covalent Bond of Coordination Compound(配位化合物的价键理论),Donor atom(配位原子) in ligands(配体) has unshared pair of electrons(lone pair electrons孤对电子). Centre ion(or atom) has empty orbits in valence shell

27、and will Hybridize (杂化) in forming coordination compound.,The orbitals of ligands with lone pair electrons will overlap with the empty hybrid orbitals of centre ion(or atom), forming a coordinate covalent bond(配位共价键),If the orbitals of centre ion are all outer orbitals(ns,np,nd) in hybridization, it

28、 is called outer orbital(外轨型) coordination compound. If it has inner orbitals(n-1)d participle in hybridization, it is called inner orbital(内轨型) coordination compound.,17,Formation of Ag(NH3)2+ - Linear(直线形),Linear(直线形),Formation of Zn(NH3)42+- Tetrahedral(四面体),Tetrahedral(四面体),18,Octahedral(八面体),Fo

29、rmation of FeF63- - Octahedral(八面体),Outer orbital coordination compound (外轨型配位化合物),19,Formation of Fe(CN)63- - Octahedral(八面体),Inner orbital coordination compound (内轨型配位化合物),Octahedral(八面体),20,Square planar (平面正方形),Formation of Ni(CN)42- - Square planar(平面正方形),Inner orbital coordination compound (内轨

30、型配位化合物),The Geometry and Coordination Number of coordination ions are determined by the hybridization type of centre ions (as shown follow) .,21,22,Contrast(比较) of Outer orbital(外轨型) and Inner orbital(内轨型) coordination compound,Outer orbital(外轨型) has the largest number of unshared electron, which is

31、 paramagnetism(顺磁性). Inner orbital(内轨型) has the smallest number of unshared electron, which is weak magnetism or diamagnetism(抗磁性). The electron configurations of centre ion is (n-1)d10 , could form Outer orbital(外轨型) only, as Ag+,Zn2+,Hg2+ etc. and (n-1)d47 has two possibility. F-,OH-,H2O as ligand

32、s(配体) is apt to form Outer orbital(外轨型) ; CN-, CO as ligands is apt to form Inner orbital(内轨型); NH3, Cl- has two possibility. Outer orbital(外轨型) is less than Inner orbital(内轨型) in stability.,23,Magnetism and type of bond(磁性与键型),Example,By experimental, the magnetism moment of Fe(H2O)62+ and Fe(CN)64

33、 - are = 5.0B and = 0B , guess the bond types of the two compounds.,Fe(H2O)62+,Fe(CN)64 -,= 5.0B , n = 4,= 0B , n = 0,24,Electron configuration about Fe and their ions,Fe :Ar3d64s2,Fe2+ :Ar3d6,3d,4s,4p,4d,Fe(H2O)62+,Fe(CN)64 -,sp3d2杂化,Outer orbital (外轨型),Inner orbital (内轨型),d2sp3杂化,The Fe(CN)64 - is

34、 more than the Fe(H2O)62+ in stability,25,*9.4 Crystal-Field Theory(晶体场理论),When ligands coordinate to a metal ion, they increase the energies of the metals d orbitals by ligand d-orbital repulsion. Because of their spatial arrangement, the d orbitals do not all experience the same increase in energy

35、. If we consider the formation of an octahedral 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.,The d orbitals that are approached directly by ligands exhibit a greater inc

36、rease in energy than do the others. This causes an energy separation or splitting(分裂) of the d orbitals. This is the basis of the transition-metal bonding model known as crystal-field theory (晶体场理论).,26,Notice that the lobes of the dz2 and dx2-y2 orbitals (b and c) point toward the charges. The lobe

37、s of the dxy, dyz, and dxz orbitals (df) point between the charges.,(a) An octahedral array of negative charges approaching metal ion. (bf) The orientations of the d orbitals relative to the negatively charged ligands.,27,At the same time, the energies of the metal d electrons are increased by the r

38、epulsive interaction between these electrons and the electrons of the ligands. These repulsive interactions give rise to the splitting of the metal d-orbital energies.,In the crystal-field model, the bonding between the metal ion and donor atoms is considered to be largely electrostatic. The energy

39、of the metal ion plus coordinated ligands is lower than that of the separated metal ion plus ligands because of the electrostatic attraction.,28,We can now explain why complexes of metals with partially filled d orbitals exhibit the colors that they do. An electron in one of the lower-energy d orbit

40、als can be promoted (or excited ) to one of the higher-energy d orbitals by absorption of the correct wavelength of light.,Energies of the d orbitals in an octahedral crystal field,29,The energy gap between the three lower-energy d orbitals and the two higher-energy d orbitals is such that visible l

41、ight 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)63+ ion is of the magnitude that light of 510 nm wavelength promotes an electron. A

42、bsorption of this wavelength of light (510 nm is a green wavelength) gives the ion its characteristic red color,30,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 coordinat

43、ing to the metal ion. Figure below shows a series of four chromium(III) complexes, each with a different value,31,The relative values of for complexes of a given metal ion can be predicted using the spectrochemical series(光谱化学序列). This is a list of common ligands arranged in order of increasing . Li

44、gands that cause larger splitting of d orbital energies are called strong-field ligands. Those that cause smaller splitting are called weak-field ligands.,Cl F H2O NH3 en NO2 (N-bonded) CN,Magnetic properties of transition-metal complexes can also be explained using crystal-field theory. Recall the

45、example in the previous section regarding magnetism, where two cobalt(III) complexes had different numbers of unpaired electrons. Co(NH3)63+ contains no unpaired electrons while CoF63 contains four unpaired electrons. You now know that the fluoride ion is a weaker-field ligand than ammonia, so you e

46、xpect to be larger in the ammine complex than in the fluoro complex.,32,Tetrahedral and square-planar complexes also exhibit splitting of d-orbital energies, but the spatial arrangements of ligands relative to d orbitals result in different splitting patterns for these two geometries. Tetrahedral co

47、mplexes exhibit splitting such that there are two d orbitals at a lower level and three d orbitals at a higher level. The magnitude of in tetrahedral complexes is always sufficiently small that all tetrahedral complexes are high spin.,Questions,Which of the following cannot have both high-spin and l

48、ow-spin complexes? Cr3+ () Fe2+ Fe3+ Mn2+,33,9.5 Chelates(螯合物),Each of the ligands encountered so far has been a monodentate ligand(单齿配体), meaning that they each have only one donor atom. Polydentate ligand(多齿配体) have two or more donor atoms and are also known as chelating agents(螯合剂). A common poly

49、dentate ligand is the molecule ethylenediamine(乙二胺), abbreviated en,Each of ethylenediamines nitrogen atoms has an unshared pair of electrons that can be donated to a metal ion. Ethylenediamine is a bidentate(双齿) ligand. Another common chelating agent is the ethylenediaminetetraacetate ion or EDTA.

50、EDTA has six potential donor atoms: four oxygens and two nitrogens. EDTA is a hexadentate (六齿) ligand and is able to wrap around a metal ion, coordinating to it with all six donor atoms.,34,The CoEDTA ion, showing how the ethylenediaminetetraacetate ion is able to wrap around a metal ion, occupying

51、six positions in the coordination sphere.,Structures of other bidentate ligands. The coordinating atoms are shown in blue.,Polydentate ligands tend to coordinate more readily and form more stable complexes than monodentate ligands. This phenomenon is known as the chelate effect(螯合效应).,35,9.6 The Coo

52、rdination Equilibrium(配位平衡),9.6.1 The Coordination Equilibrium and constant Kfo , Kdo,Kfo = Cu(NH3)42+/Cu2+NH34,Cu2+(aq) + 4NH3(aq) Cu(NH3)42+(aq),At equilibrium,Kfo is coordination formation constant(配离子的形成常数) The larger the Kfo, the more stable the coordination. The formation of coordination compo

53、und is stepwise(分步) reaction.,Cu(NH3)42+(aq) Cu2+(aq) + 4NH3(aq),Kdo = Cu2+NH34/ Cu(NH3)42+,At equilibrium,Kdo is coordination dissociation constant(配离子的离解常数) The larger the Kdo, the more un-stable the coordination. The dissociation of coordination compound is also stepwise (分步) reaction.,Converse,3

54、6,Cu2+(aq) + NH3(aq) Cu(NH3)2+(aq),Cu(NH3)2+(aq) + NH3(aq) Cu(NH3)22+(aq),Cu(NH3)22+(aq) + NH3(aq) Cu(NH3)32+(aq),Cu(NH3)32+(aq) + NH3(aq) Cu(NH3)42+(aq),k1 = Cu(NH3)2+/Cu2+NH3,k2 = Cu(NH3)22+/ Cu(NH3)2+ NH3,k3 = Cu(NH3)32+/ Cu(NH3)22+ NH3,k4 = Cu(NH3)42+/ Cu(NH3)32+ NH3,k1 . k2 . k3. k4 are called stepwise formation constants(逐级形成常数),Kfo = k1 k2 k3 k4,k1. k2 . k3. k4 are called stepwise dissociation constants(逐级离解常数),Kdo = k1 k2 k3 k4,37,Kfo = 1/ Kdo,k1 =1/ k4 , k2 =1/ k3 , k3 =1/ k2 , k4 =1/ k1,We have,What is the concentration of Ag+ at equilibrium with 1.0 mL 0.040 M AgNO3 after the a