无机化学课件：15 Ch 22 Coordination Chemistry

1、Chemistry: Atoms FirstJulia Burdge & Jason OverbyChapter 22Coordination ChemistryCoordination Chemistry2222.1 Coordination CompoundsProperties of Transition MetalsLigandsNomenclature of Coordination Compounds22.2Structure of Coordination Compounds22.3Bonding in Coordination Compounds: Crystal Field

2、TheoryCrystal Field Splitting in Octahedral ComplexesColorMagnetic PropertiesTetrahedral and Square-Planar Complexes22.4Reactions of Coordination Compounds22.5Applications of Coordination CompoundsCoordination Compounds22.1Coordination compounds contain coordinate covalent bonds formed by the reacti

3、ons of metal ions with groups of anions or polar molecules.A coordinate covalent bond is a covalent bond in which one of the atoms donates both of the electrons that constitute the bond.Ammonia, a Lewis baseBoron trifluoridea Lewis acidempty unhybridized 2pz orbitalA coordinate covalent bondCoordina

4、tion CompoundsCoordination compounds may consist of a complex ion and one or more counter ions.K2PtCl6The compound consists of the complex ion PtCl62 and two K+ counter ions.Some coordination compounds do not contain complex ions.Coordination CompoundsMost of the metals in coordination compounds are

5、 transition metals.Coordination CompoundsProperties of transition metals include:incompletely filled d subshellsreact to form ions with incompletely filled d subshelldistinctive colorsparamagnetismcatalytic activitytendency to form complex ionsexhibit variable oxidation stateCoordination CompoundsCo

6、ordination CompoundsCoordination CompoundsCoordination CompoundsThe molecules or ions that surround the metal in a complex ion are called ligands.Ligands must contain at least one unshared pair of valence electrons.The atom in the ligand directly bonded to the metal atom is called the donor atom.Coo

7、rdination CompoundsCoordination CompoundsThe coordination number in a coordination compound refers to the number of donor atoms surrounding the central metal atom in a complex ion.Coordination CompoundsBidentate and polydentate ligands are also called chelating agents Coordination CompoundsBidentate

8、 and polydentate ligands are also called chelating agents Worked Example 22.1Strategy Identify the components of each compound, and use known oxidation states and charges to determine the oxidation state of the metal.Determine the oxidation state of the central metal atom in each of the following co

9、mpounds: (a) Ru(NH3)5(H2O)Cl2, (b) Cr(NH3)6(NO3)3, and (c) Fe(CO)5.Solution (a) Ru(NH3)5(H2O)Cl2 consists of a complex ion (the part of the formula enclosed in a square brackets) and two Cl- counter ions. Because the overall charge on the compound is zero, the complex ion is Ru(NH3)5(H2O)2+. There a

10、re six ligands: five ammonia molecules and one water molecule. Each molecule has a zero charge (i.e., each ligand is neutral), so the charge on the metal is equal to the overall charge on the complex ion. Ru has an oxidation state of +2.(b) Cr(NH3)6(NO3)3 consists of a complex ion and three NO3- ion

11、s, making the complex ion Cr(NH3)63+. Each of the six ammonia molecule ligands is neutral (i.e., each has a zero charge), making the charge on the metal equal to the overall charge on the complex ion. Cr has an oxidation state of +3. Worked Example 22.1 (cont.)Solution (c) Fe(CO)5 does not contain a

12、 complex ion. The ligands are CO molecules, which has a zero charge, so the central metal also has a zero charge. Fe has an oxidation state of 0.Think About It To solve a problem like this, you must be able to recognize the common polyatomic ions and you must know the charges.Coordination CompoundsN

13、omenclature of Coordination Compounds The cation is named before the anion, as in other ionic compounds. Within a complex ion, the ligands are named first, in alphabetical order; the metal ion is named last. The names of anionic ligands end with the letter o, whereas neutral ligands are usually call

14、ed by the names of the molecules. When two or more of the same ligand are present use Greek prefixes di, tri, tetra, penta and hexa, to specify their number. The oxidation number of the metal is indicated in Roman numerals immediately following the name of the metal. The names of anions end in ate.M

15、ultiplicityMonodentatemono = 1di = 2tri = 3tetra = 4penta = 5hexa = 6Bi- or tri- dentatebis = 2tris = 3tetrakis = 4Coordination CompoundsCoordination Compounds Worked Example 22.2Strategy For each compound, name the cation first and the anion second. Refer to Tables 22.4 and 22.5 for the names of li

16、gands and anions containing metal atoms.Write the names of the following coordination compounds: (a) Co(NH3)4Cl2Cl and (b) K3Fe(CN)6.Solution (a) The cation is a complex ion containing four ammonia molecules and two chloride ions. The counter ion is chloride (Cl-), so the charge on the complex catio

17、n +1, making the oxidation state of cobalt +3.The compound is named tetraamminedichlorocobalt(III) chloride.(b) The cation is K+, and the anion is a complex ion containing six cyanide ions. The charge on the complex ion is 3, making the oxidation state of iron +3.The compound is named potassium hexa

18、cyanoferrate(III).Think About It When the anion is a complex ion, its name must end in ate, followed by the metals oxidation state in Roman numerals. Also, do not use prefixes to denote numbers of counter ions. Worked Example 22.3Strategy If you cant remember them yet, refer to Tables 22.4 and 22.5

19、for the names of ligands and anions containing metal atoms.Write formulas for the following compounds: (a) pentaamminechlorocobalt(III) chloride and (b) dichlorobis(ethylenediamine)platinum(IV) nitrate.Solution (a) There are six ligands: five NH3 molecules and one Cl- ion. The oxidation state of cob

20、alt is +3, making the overall charge on the complex ion +2. Therefore, there are two chloride ions as counter ions.The formula is Co(NH3)5ClCl2.(b) There are four ligands: two bidentate ethylenediamines and two Cl- ions. The oxidation state of platinum is +4, making the overall charge on the complex

21、 ion +2. Therefore, there are two nitrate ions as counter ions.The formula is Pt(en)2Cl2(NO3)2.Think About It Although ligands are alphabetized in a compounds name, they do not necessarily appear in alphabetical order in the compounds formula.配位化合物中文命名法配离子的命名配离子命名顺序：1、配体，2、中心离子，中间加一“合”字，配体的数目用汉字写在配体

22、的前面，中心离子的氧化数用罗马字写在中心离子名称的后面，并加括弧；Co(NH3)63+ 六氨合钴(III)离子若有两种或以上配体时，先写阴离子，再写中性分子，中间加圆点“”分开。若阴离子不止一种时，则先写简单的，再写复杂的，最后写有机酸根离子；CoCl(SCN)(en)2+一氯硫氰酸根二（乙二胺）合钴（III）离子当中性分子不止一种时，则按配原子元素符号顺序排列；Co(NH3)5H2O3+ 五氨水合钴（III）离子含配阳离子配合物的命名1、外界阴离子，2、配体，3、中心离子， 1，2 之间加一“化”字或不加字没有外界的配合物可不必标明中心离子的氧化态含配阴离子配合物的命名1、配体，2、中心离子

23、，3、外界的金属离子。 2，3 之间加一“酸”字The geometry of a coordination compound plays a significant role in determining its properties.Structure of Coordination Compounds22.2Coordination NumberStructure2Linear4Tetrahedral or square planar6OctahedralCompounds that differ in the arrangement of ligands around the cent

24、ral atom are known as stereoisomers.Stereoisomers have different chemical and physical properties.Structure of Coordination CompoundsStereoisomers may exhibit two types of stereoisomerism: geometric and optical.Geometrical isomers are stereoisomers that cannot be interconverted without breaking chem

25、ical bonds. Geometric isomers come in pairs.Structure of Coordination CompoundsStereoisomers may exhibit two types of stereoisomerism: geometric and optical.Structure of Coordination CompoundsOptical isomers are nonsuperimposable mirror images.Stereoisomers may exhibit two types of stereoisomerism:

26、geometric and optical.Structure of Coordination CompoundsOptical isomers are nonsuperimposable mirror images.Structure of Coordination CompoundsOptical isomers nonsuperimposable mirror imagesTermed chiralRotate polarized light in different directionsRotation to the right dextrorotatory (d isomer)Rot

27、ation to the left levorotatory (l isomer)Enantiomers a pair of d and l isomersRacemic mixture equimolar mixture of two enantiomersNet rotation of polarized light is zeroStructure of Coordination CompoundsStructure of Coordination CompoundsValence Bond Theory Bonding in Coordination Compounds: Crysta

28、l Field TheoryCrystal field theory explains the bonding in complex ions purely in terms of electrostatic forces.Attraction between the metal ion (atom) and the ligands22.3Repulsion between the lone pairs on the ligands and the electrons in the d orbitals of the metal.In the absence of ligands, the d

29、 orbitals are degenerate.Bonding in Coordination Compounds: Crystal Field TheoryIn the presence of ligands, electrons in d orbitals experience different levels of repulsion for the ligand lone pairs.As a result (depending on the geometry) some d orbitals attain higher energy and others lower energy.

30、The five d-orbitals in an octahedral field of ligandsBonding in Coordination Compounds: Crystal Field TheoryIn an octahedral complex: The electrons in the d orbitals located along the coordinate axes experience stronger repulsions and increase in energy.The electrons in the d orbitals 45o from the c

31、oordinate axes experience weaker repulsions and decrease in energy.The energy difference between the two sets of orbitals is the crystal field splitting ().depends on the nature of metal and ligandsdetermines color and magnetic propertiesBonding in Coordination CompoundsSpherical Fieldtransition met

32、alatomBondedtransition metalatom Crystal field splitting ( D) is the energy difference between two sets of d orbitals in a metal atom when ligands are presentBonding in Coordination Compounds: Crystal Field TheoryColorAs with reflected light, transmitted light of selected wavelengths is responsible

33、for color.The color of observed light is the complementary color to the light absorbed.Bonding in Coordination Compounds: Crystal Field TheoryThe process of photoabsorption:An absorption spectrum of Ti(H2O)63+ The energy of the incoming photon is equal to the crystal field splitting.Bonding in Coord

34、ination Compounds: Crystal Field TheorySpectroscopic measurements of D allow an ordering of ligands ability to split the d orbitals called a spectrochemical series.strong field ligandweak field ligandincreasingsmall Dlarge DThe spectrochemical seriesFor a given ligand, the color depends on the oxida

35、tion state of the metal ion.For a given metal ion, the color depends on the ligand.I- Cl- F- OH- H2O SCN- NH3 en NO2- CN- COWEAKER FIELDSTRONGER FIELDLARGER DSMALLER DLONGER SHORTER Back-bonding 反馈键Bonding in Coordination Compounds: Crystal Field TheoryMagnetic PropertiesThe magnitude of the crystal

36、 field splitting also determines the magnetic properties of a complex ion.The electron configuration of the ion is a balance between:The energy to promote an electron to a higher energy d orbitalStability gained by maximum number of unpaired spinsBonding in Coordination Compounds: Crystal Field Theo

37、ry Worked Example 22.3Strategy The magnetic properties of a complex ion depend on the strength of the ligands. Strong-field ligands, which cause a high degree of splitting among the d orbital energy levels, result in low-spin complexes. Weak-field ligands, which cause only a small degree of splittin

38、g among the d orbital energy levels, result in high-spin complexes.Predict the number of unpaired spins in the Cr(en)32+ ion.Solution The electron configuration of Cr2+ is Ar3d4; and en is a strong-field ligand. Because en is a strong-field ligand, we expect Cr(en)32+ to be a low-spin complex. Accor

39、ding to Figure 22.18, all four electrons will be placed in the lower-energy d orbitals (dxy, dyz, and dxz) and there will be a total of two unpaired spins.Think About It It is easy to draw the wrong conclusion regarding high- and low-spin complexes. Remember that the term high spin refers to the num

40、ber of spins (unpaired electrons), not to the energy levels of the d orbitals. The greater the energy gap between the lower-energy and higher-energy d orbitals, the greater the chance that the complex will be low spin.Splitting of d-orbital energies by a tetrahedral field and a square planar field o

41、f ligandstetrahedralsquare planarBonding in Coordination Compounds: Crystal Field TheoryTetrahedral and square planar complexesProximity of the ligands to d orbitals changes with the geometry of the complexd electrons in orbitals more closely associated with the lone pairs of ligand electrons attain

42、 higher energiesSplitting patterns reflect this repulsionTetrahedral fieldBonding in Coordination Compounds: Crystal Field TheoryTetrahedral and square planar complexesProximity of the ligands to d orbitals changes with the geometry of the complexd electrons in orbitals more closely associated with

43、the lone pairs of ligand electrons attain higher energiesSplitting patterns reflect this repulsionSquare planar fieldt = 4/9 o MOElectronic SpectraLambert-Beer Law Relaxation of Selection RulesOctahedral complexes: centrosymmetric Laporte rule relaxed by vibronic coupling Tetrahedral complexes: non-

44、centrosymmetric Laporte rule relaxed by orbital mixingSelection RulesSpin Selection RuleDS = 0There must be no change in spin multiplicity during an electronic transitionLaporte Selection RuleD l = 1There must be a change in parity during an electronic transitiond5 complexes: vibronic coupling and S

45、pin-orbit couplingSelection RulesTransitionecomplexesSpin forbidden10-3 1Many d5 Oh cxsLaporte forbidden Mn(OH2)62+ Spin allowedLaporte forbidden1 10Many Oh cxsNi(OH2)62+10 100 Some square planar cxs PdCl42-100 10006-coordinate complexes of low symmetry, many square planar cxs particularly with orga

46、nic ligandsSpin allowed102 103Some MLCT bands in cxs with unsaturated ligandsLaporte allowed102 104Acentric complexes with ligands such as acac, or with P donor atoms103 106 Many CT bands, transitions in organic speciesCHARGE-TRANSFER SPECTRAJahn Teller EffectsFor a non-linear molecule that is in an

47、 electronically degenerate state, distortion must occur to lower the symmetry, remove the degeneracy, and lower the energy.Jahn-Teller effects do not predict which distortion will occur other than that the center of symmetry will remain.The distortion by the unsymmetrical distribution of electrons i

48、n eg orbital is stronger than that of t2g.Jahn-Teller Theorem If the ground electronic configuration of a nonlinear molecule is degenerate, the molecule will distort so as to remove a degeneracy and achieve a lower energy.e.g. Octahedral Cu(II) complexes (d9) Two degenerate ground electronic configu

49、rations: d8 d9 d10 Degenerate No Yes No configuration J-T distortion No Yes No The geometry of some six-coordinatedCu(II) complexes is tetragonal instead of octahedral.Solid-state structure of Cu(NH3)62+Elongation of the two axial bonds leads to stabilization of z2 and destabilization of x2-y2.Overa

50、ll, the tetragonal geometry is more stable than the octahedral analogue by (21 1) or 0.5 1N.B. Distortion by either elongation or compression of the axial bonds will remove the degeneracy and results in stabilizationJ-T theorem cannot predict which way it will takeTetragonal geometry for 6-coordinated Cu(II) complexes Broadening of absorption band for