Chapter Nine Coordination Compounds Coordination Compound a compound

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Chapter Nine Coordination Compounds Coordination Compound: a compound in which a central metal ion

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)

Anemia(贫血症)

CH 2 OH CHSH CH 2 SH + Hg CHS CH 2 S •

CH 2 OH CHSH CH 2 SH + Hg CHS CH 2 S • Anti-tumour(肿瘤) agent Hg

Coordination Compounds • 9 -1 Basic Concepts • 9 -2 The Chemical Bond Theory

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

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: –

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

Ligands and Donor atom • Ligands: ions or molecules that is bound directly to the metal atom. e. g. NH 3, CN-, H 2 O, 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

Ligands • Depending on the number of donor atoms present in the molecule or ion, ligands can be classified as: monodentate : (H 2 O: : NH 3 ) bi dentate :(H 2 N-CH 2 -NH 2 ) polydentate: (EDTA) also called chelating agents

Coordination number • Coordination number: the number of donor atoms surrounding the central metal

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(NH 3)4] SO 4 , [Fe(CN)6]4 Coordination number = ligand number For bidentate or polydentate: Coordination number ≠ ligand number e. g. [Cu(en)2]SO 4 ( en = H 2 N-CH 2 -NH 2) Coordination number = 4 ≠ 2

Charges of coordination ion: Charges of coordination = the sum of charges of central

Charges of coordination ion: Charges of coordination = the sum of charges of central ion and ligands e. g. K 3[Fe(CN)6] Fe 3+ [Fe(H 2 O)6]Cl 3 Fe 3+ K 4[Fe(CN)6] Fe 2+

 • The features of coordination • Contains a complicated ion - coordination [Cu(NH

• The features of coordination • Contains a complicated ion - coordination [Cu(NH 3)4]2+ , [Ag(NH 3)2]+, [Fe(CN)6]4 - • Metal ion bonded with other ion or molecule by coordination bond • Has definite stability: KCl • Mg. Cl 2 • 6 H 2 O : K+, Cl-, Mg 2+ KAl(SO 4) • 12 H 2 O : K+, Al 3+, SO 42+

Simple ion and complex ion Cu. SO 4 Ba. Cl 2 Ba. SO 4

Simple ion and complex ion Cu. SO 4 Ba. Cl 2 Ba. SO 4 [Cu(NH 3)4] SO 4 [Ag(NH 3)2]Cl Na. OH Cu. SO 4 Cu(OH)2 Cu. SO 4 NH 3 • H 2 O Cu(OH)2 NH 3 • H 2 O Blue Cu 2+ + 4 NH 3 == [Cu(NH 3)4]2+ Complex ion Ag. NO 3 Na. Cl Ag. Cl NH 3 • H 2 O [Ag(NH 3)2]+

The composition of coordination compound • the coordination sphere: 1. The central metal and

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(NH 3)6]Cl 3 [Pt. Cl 6]2+

coordination Inner sphere atom or coordination sphere Outer sphere donor atom [Cu(NH 3)4]2+ SO

coordination Inner sphere atom or coordination sphere Outer sphere donor atom [Cu(NH 3)4]2+ SO 42 - Central Ligand ion or atom Coordination number Charges of coordination

 bidentate

bidentate

What are the oxidation numbers of the central metal in the complexes below? •

What are the oxidation numbers of the central metal in the complexes below? • K 3[Fe. F 6] • Na 2[Ni(CN)4]

Naming of Coordination Compounds • the International Union of Pure and Applied Chemistry (IUPAC)

Naming of Coordination Compounds • the International Union of Pure and Applied Chemistry (IUPAC) • 1. The cation is named before the anion. Na. Cl: 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, Br. Bromo Chloride,

Naming Coordination Compounds LIGAND Name of Ligand in Coord. Cpd. Bromide, Br. Bromo Chloride, Cl. Chloro Cyanide, CNCyano Hydorxide, OHHydroxo Oixde, O 2 Oxo Carbonate, CO 32 Carbanato Nitrite, NO 3 Nitro Oxolate, C 2 O 42 Oxolato Ammonia, NH 3 Ammine Carbon monoxide, CO Carbonyl Water, H 2 O Aquo Ethylenediamine(en) Ethylenediamine

4. When several ligands of a particular kind are present, we use the Greek

4. When several ligands of a particular kind are present, we use the Greek prefixes to name them. • • • Di (2) tri (3) tetra (4) Penta (5) Hexa (6) [Co(NH 3)4 Cl 2]+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

5. The oxidation number of the metal is written in Roman numerals following the name of the metal. [Cr(NH 3)4 Cl 2]+, which is called tetraamminedichlorochromium(Ⅲ) ion. 6. If the complex ion is an anion, its name ends in ate. K 4[Fe(CN)6] the anion [Fe(CN)6]4 - is called hexacyanoferrate(II) ion.

Metal in anion complex Aluminum Aluminate Chromium Chromate Cobaltate Copper Cuprate Gold Aurate Iron

Metal in anion complex Aluminum Aluminate Chromium Chromate Cobaltate Copper Cuprate Gold Aurate Iron Ferrate Lead Plumbate Metal in anion complex Manganese Manganate Nickelate Silver Argentate Tin Stannate Tungsten Tungstate Zincate

 • Example 9 -1 : (a) Ni(CO)4, (b) [Co(NH 3)4 Cl 2]Cl, (c)

• Example 9 -1 : (a) Ni(CO)4, (b) [Co(NH 3)4 Cl 2]Cl, (c) K 3[Fe(CN)6], (d) [Cr(en)3]Cl 3. • 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(NH 3)4 Cl 2]+ hexacyanoferrate(II) ion. the anion [Fe(CN)6]4

. tetraamminedichlorochromium(Ⅲ) ion. the cation [Cr(NH 3)4 Cl 2]+ 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(NH 3)4

Give the formula for the following coordination compounds. tetracarbonylnickel(0) Ni(CO)4, tetraammineaquochlorocobalt(III) chloride [Co(NH 3)4 H 2 OCl]Cl 2 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

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

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

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,

l the valence-bond theory Outline : 1. Central ion bonds with ligands by coordination

l 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(NH 3)2]+ • 47 Ag [Kr]4 d 105 s 1 • Central ion:

Example [Ag(NH 3)2]+ • 47 Ag [Kr]4 d 105 s 1 • Central ion: Ag+ 4 d 105 s 05 p 0 Ag+: hybrid 2 : NH 3 sp hybridization( outer orbital ) [Ag(NH 3)2]+(linear)

 Ni(NH 3)42+ 28 Ni 3 d 84 s 2 • Central ion: Ni

Ni(NH 3)42+ 28 Ni 3 d 84 s 2 • Central ion: Ni 2+ 3 d 8 4 s 0 4 p 0 hybrid 4 : NH 3 sp 3 hybridization( outer orbital ) [Ni(NH 3)4 ]2+ (tetrahedral)

[Ni Ni

[Ni Ni

[Ni(CN)4 ]2 - • Central ion: Ni 2+ 3 d 8 4 s 0

[Ni(CN)4 ]2 - • Central ion: Ni 2+ 3 d 8 4 s 0 4 p 0 realignment hybrid 4 : CNdsp 2 hybridization inner orbital [Ni(CN)4 ]2 -( square planar)

[Co(NH 3)6] 3+ • Co atom 3 d 74 s 2 • Co 3+

[Co(NH 3)6] 3+ • Co atom 3 d 74 s 2 • Co 3+ ion 3 d 6 • 6 : NH 3 [Co(NH 3)6]3+ d 2 sp 3 hybridization (inorbital complex) Co(NH 3)6 3+ (octahedral)

Co. F 63+ 4 d • Co atom 3 d 74 s 2 3

Co. F 63+ 4 d • Co atom 3 d 74 s 2 3 d 4 s 4 p • Co 3+ ion 3 d 6 6 : F - • Co. F 63+ sp 3 d 2 hybridization (octahedral)

Magnetism • Paramagnetism: substances containing unpaired electrons are paramagnetic. • diamagnetic: substances without unpaired

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(H 2 O)6]SO 4 μ=5. 26 B. M according

• Example : For [Fe(H 2 O)6]SO 4 μ=5. 26 B. M according to above equation, n = 4 , so there are 4 unpaired electrons in this coordination compound. • Example : For K 4[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(H 2 O)6]SO 4 , μ=5. 26 B. M

• Example : For [Fe(H 2 O)6]SO 4 , μ=5. 26 B. M according to above equation, n = 4 , so there are 4 unpaired electrons in this coordination compound. 26 Fe: 3 d 64 s 24 p 04 d 0 3 d 4 s 4 p 4 d Fe 2+: 3 d 6 4 s 04 p 04 d 0 • • • Sp 3 d 2 hybridization outer orbital

 • Example : For K 4[Fe(CN)6] , μ=0 B. M according to above

• Example : For K 4[Fe(CN)6] , μ=0 B. M according to above equation, n = 0 , so there are 0 unpaired electrons in this coordination compound. Fe 2+: 3 d 64 s 04 p 04 d 0 3 d 4 s 4 p • • • d 2 sp 3 hybridization, inner orbital

Table 9 -4: Some common types of hybridization and geometries.

Table 9 -4: Some common types of hybridization and geometries.

l Isomerism(异构体) • Isomers : Two or more compounds that have the same formula

l 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

• Structural isomerism • Structural isomers are that differ in how the atoms are joined together. • Example: [Co(NH 3)5(SO 4)]Br red [Co(NH 3)5 Br] SO 4 violet CH 3 -CH 2 -COOH CH 3 -CH-COOH CH 3

 • Geometric isomerism (Stereoisomerism, cis-trans isomerism) • are isomers that have the same

• 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(NH 3)2 Cl 2 Cl NH 3 cis Pt Cl

Geometric Isomerism (stereoisomerism) • Pt(NH 3)2 Cl 2 Cl NH 3 cis Pt Cl NH 3 Cl trans Pt Cl NH 3

both coordination compounds are named: diamminedichloroplatinum(II) cis-diamminedichloroplatinum(II) trans

both coordination compounds are named: diamminedichloroplatinum(II) cis-diamminedichloroplatinum(II) trans

Optical Isomerism

Optical Isomerism

9 -2. 2 Crystal Field Theory(中文P 217) Ø 1. the ligands in a transition-metal

9 -2. 2 Crystal Field Theory(中文P 217) Ø 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. Ø 2. For the formation of a complex ion or molecule is the electrostatic attraction Ø 3. this theory explains both the paramagnetism and color observed in certain complexes.

The Splitting of the d Orbitals in Octahedral Field

The Splitting of the d Orbitals in Octahedral Field

eg (dγ)orbitals Δ = eg - t 2 g (dε)orbitals

eg (dγ)orbitals Δ = eg - t 2 g (dε)orbitals

High-Spin and Low-Spin Coordination Compounds • Fe(H 2 O)62+ Fe 3 d 64 s

High-Spin and Low-Spin Coordination Compounds • Fe(H 2 O)62+ Fe 3 d 64 s 2 Fe 2+ 3 d 6 Figure: Occupation of the 3 d orbitals in complexes of Fe 2+. (a) Low spin. (b) High spin.

 pairing energy P • pairing energy P: the energy required to put two

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

① 配体: spectrochemical series, which is a list of ligands arranged in order of

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 – < H 2 O <NCS– < edta < NH 3 < en < NO 2–< CN –< CO Increasing Δ → [Co(H 2 O)6]3+ o /cm-1 13000 [Co(NH 3)6]3+ 22900 [Co(CN)6]334000 强场: o > P : low-spin complex 弱场: o < P: high-spin complex

晶体场理论的应用 1. Crystal Field Stabilization Energy(CFSE) • A measure of the net energy of

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

• ligand field stabilization energy: a measure of the increased stability of a complex showing ligand field splitting. In general, CFSE = (# electrons in t 2 g) × (-0. 4 Δ 0 ) + (#electrons in eg) × (0. 6 Δ 0 )

The larger the crystal-field splitiing (Δ大), the higher will be the frequency of light

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

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

 • As we have noted earlier, strong-field ligands cause a large split in

• 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 • On the other hand, ligands are yellow, coordination compounds of orange, or red since transition metals with weakfield ligands are blue-green, they absorb higherenergy violet or blue, or indigo since they light. absorb lower-energy yellow, orange, or red light.

[Co(NH 3)5 Cl]2+ Purple compound absorbs yellow green region ( wavelength of 530 nm)

[Co(NH 3)5 Cl]2+ Purple compound absorbs yellow green region ( wavelength of 530 nm) [Co(NH 3)6]3+ orange compound absorbs violet region (wavelength of 410 nm) d 10 (Zn 2+, Ag+ complexes) is colorless

9 -3 Coordination equilibrium coordination Cu 2+(aq) + 4 NH 3(aq) [Cu(NH 3)4]2+ (aq)

9 -3 Coordination equilibrium coordination Cu 2+(aq) + 4 NH 3(aq) [Cu(NH 3)4]2+ (aq) ionization [Cu(NH 3)4]2+ [Cu 2+][NH 3]4 • Ks = ---------- Kis= ---------- [Cu 2+][NH 3]4 [ Cu(NH 3)4] 2 + Stability constant or formation constant(Kf) Instability constant

βn --Accumulate stability constant Cu 2++NH 3 Cu(NH 3)22++NH 3 Cu(NH 3)32++NH 3 [Cu(NH

βn --Accumulate stability constant Cu 2++NH 3 Cu(NH 3)22++NH 3 Cu(NH 3)32++NH 3 [Cu(NH 3)2+] K 1=——————— 2+]×[NH ] [Cu 3 ——— 2+] [Cu(NH ) 2+ 3 2 Cu(NH 3)2 K 2=———— 2+][NH ] [Cu(NH ) 3 3 ———— 2+] [Cu(NH ) 2+ 3 3 Cu(NH 3)3 K 3=———— 2+][NH ] [Cu(NH ) 3 2 3 ———— Cu(NH 3)2+ Cu(NH 3)4 2+ [Cu(NH 3)42+] K 4=———— 2+][NH ] [Cu(NH ) 3 ———— 3 3

Cu 2+(aq) + NH 3(aq) [Cu(NH 3)]2+ (aq) K 1=1. 4× 104 Cu 2+(aq)

Cu 2+(aq) + NH 3(aq) [Cu(NH 3)]2+ (aq) K 1=1. 4× 104 Cu 2+(aq) + 2 NH 3(aq) [Cu(NH 3)2]2+ (aq) 3 β 2= K 1 • K 2 K =3. 17× 10 2 Cu 2+(aq) + 3 NH 3(aq) [Cu(NH 3)3]2+ (aq) 2 β 3= K 1 • K 2 • K 3 K =7. 76× 10 3 Cu 2+(aq) + 4 NH 3(aq) [Cu(NH 3)]2+ (aq) K 4=1. 39× 102 lgβ 4 =lg. K 1+lg. K 2+lg. K 3+lg. K 4

 • Generally, for the same type complex ions: the larger value of Ks(Kf),

• 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p 224【例9 -1】)

电极电势改变 Cu+/ Cu Ag+/Ag Au 3+/Au Φ 0/v 0. 52 0. 799 1. 50

电极电势改变 Cu+/ Cu Ag+/Ag Au 3+/Au Φ 0/v 0. 52 0. 799 1. 50 [Cu(CN)2]-/Cu [Ag(CN)2]-/Ag [Au(CN)2]+/Au -0. 43 -0. 31 -0. 58

Influence of on coordination equilibrium • [Ag(NH 3)2]+ +2 CN- [Ag(CN)2]- + 2 NH

Influence of on coordination equilibrium • [Ag(NH 3)2]+ +2 CN- [Ag(CN)2]- + 2 NH 3 • [Mn(en)3]2+ + Ni 2+ [Ni(en)3]2+ + Mn 2+ 利用KS值可以判断配位平衡转化的方向和程度。

9 -4 Chelates • polydentate ligands have two or more donor atoms situated so

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 ∶NH 2 -CH 2 -H 2 N∶

 polydentate ligand is the ethylenediaminetetraacetate ion: • This ion, abbreviated EDTA 4 -,

polydentate ligand is the ethylenediaminetetraacetate ion: • This ion, abbreviated EDTA 4 -, 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 Co. EDTA- ion showing how the ethylenediamine

• Figure 9 -9: • The Co. EDTA- ion showing how the ethylenediamine tetraacetate 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

• 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.

 Ni 2+(aq) + 6 NH 3(aq) =[Ni(NH 3)6]2+(aq) K = 4 × 108

Ni 2+(aq) + 6 NH 3(aq) =[Ni(NH 3)6]2+(aq) K = 4 × 108 Ni 2+(aq) + 3 en (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(NH 3)6]2+.

 • The stability of chelate depends on the number and size of chelate

• 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.