CHAPTER 16 THE ELEMENTS: THE d BLOCK · 2010-04-12 · Textbook: P. Atkins / L. Jones, Chemical Principles, 4th ed., Freeman (2008) Chapter 16 3 16.2 Trends in Chemical Properties

2009년도 제2학기 화 학 2 담당교수: 신국조 Textbook: P. Atkins / L. Jones, Chemical Principles, 4th ed., Freeman (2008) Chapter 16

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CHAPTER 16 THE ELEMENTS: THE d BLOCK

THE d-BLOCK ELEMENTS AND THEIR COMPOUNDS

◆ Transition metals (전이금속,轉移金屬)

Groups 3 ~ 11(12)

Fe: Steel, blood

Cu: superconductors

V, Pt: catalysts

Ti: airplanes

Ag, Au, Pt: precious metals

Co, Mo, Zn: vitamins,

essential enzymes

Colors of glass (Co blue),

potteries, pigments

Group 12 elements: Zn, Cd, Hg

filled d-orbitals

▶ Inner transition metals: 4f-orbitals

Lanthanoids (Lanthanides)

(“rare earths,희토류,稀土類”)

Actinoides (Actinides)

Fig. 16.1 d-block and f-block elements.

16.1 Trends in Physical Properties

Energy levels: orbitals < ( 1)n d− − ns − orbitals

Electronic configurations:

Sc: , Sc1 2[Ar]3 4d s +: 1 1[Ar]3 4d sTi: 2 2[Ar]3 4d sV: 3 2[Ar]3 4d sCr: 5 1[Ar]3 4d sMn: 5 2[Ar]3 4d sFe: 6 2[Ar]3 4d sCo: 7 2[Ar]3 4d sNi: 8 2[Ar]3 4d sCu: 10 1[Ar]3 4d sZn: 10 2[Ar]3 4d s

Fig. 16.2 The atomic radii (in pm) of elements of the 1st row in d-block.

Common properties: Good electrical conductors, malleable, ductile, lustrous, silver-white color (except Au, Cu)

☺ Malleability(전성,展性), Ductility(연성,延性)


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▶ Shape of d-orbitals affects the properties

(1) Widely separate lobes of two d-orbitals

Weak repulsion between occupying electrons

(2) Low electron density near the nucleus

Ineffective shielding of nucleus

Initial decrease and then increase of atomic

radii of d-metals in the same period:

▶ Similar radii of d-metals wide range of alloys

Fig. 16.3 Alloys between d-metals due to similar atomic radii.

◆ Lanthanum contraction

Increase in atomic radii of 2nd row d-metals (Period 5) from the 1st row (Period 4) Similar atomic radii of 2nd (Period 5) and 3rd row (Period 6) d-metals due to the lanthanide contraction

Decrease in radius along the first row of the f-block due to increasing nuclear charge along the period and poor shielding of f-electrons

Resulted in (1) high density and (2) nobility of Period 6 elements

Fig. 16.4 The atomic radii (in pm) of the d-block elements.

Fig. 16.5 The densities (in g·cm–3) of the d-metals at 25oC.


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16.2 Trends in Chemical Properties

▶ More than one common oxidation states for the d-block elements:

1. Widest range of oxidation states for the central elements of each row Mn, Ru, Os

Only one oxidation state for elements at the end of each row

2. Higher oxidation states for elements in the 2nd and 3rd rows than those in the 1st row Os vs. Fe

Fig. 16.6 The oxidation numbers of the d-block elements. The brown block marks the common numbers.

▶ An element in a high oxidation state easily reduced strong oxidant

2MnO ( ) 8 H ( ) 5 Mn ( ) 4 H O( )aq aq e aq l− + − ++ + ⎯⎯→ +4 2 , o 1.51 VE = +

▶ An element in a low oxidation state easily oxidized strong reducing agent

3+ 2Cr ( ) Cr ( )aq e s− ++ ⎯⎯→ , o 0.41 VE = −

▶ Acidity of d-metallic oxides increased as oxidation states CrO +2 basic Cr2O3 +3 amphoteric CrO3 +6 acidic

▶ Elements on RHS (LHS) of d-block easy (difficult) to extract from ores

Bronze Age: bronze (Cu/Sn), brass (Cu/Zn) Iron Age Ti

leftward in d-block as the reducing technique developed

SELECTED ELEMENTS: A SURVEY

16.3 Scandium Through Nickel

Similar melting and boiling points but gradual increase in density


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▶ Scandium, Sc discovered by Nilson (1879) from Scandinavian ores

Reactive metal, Strongly hydrated Sc3+ ion, [Sc(H2O)6]3+

▶ Titanium, Ti discovered by Gregor (1791)

Light and strong metal: airplanes, dental fixtures

Resistant to corrosion: passivated by its oxide

Ores: ilmenite, FeTiO3; rutile, TiO2

Obtained first by treating ores with Cl2 in the presence of coke to form TiCl4

followed by reduction:

o700 C4 2TiCl ( ) 2 Mg( ) Ti( ) 2 MgCl ( )g l s+ ⎯⎯⎯→ + s

s

Oxide, TiO2 : white pigments in paints and paper

semiconductor in the presence of light : converting solar radiation into electrical energy in solar cells

Titanate (oxoanion of Ti)

BaTiO3 (barium titanate) piezoelectric (압전성,壓電性): mechanical viration electrical signal

Used as a underwater sound detection

▶ Vanadium, V discovered by del Rio (1801), rediscovered by Sefstrom (1831)

☺ ‘Vanadis’ (Norse goddess of beauty and fertility)

Obtained by reducing its oxide:

2 5V O ( ) 2 Ca( ) 2 V( ) 5 CaO( )s l s∆+ ⎯⎯→ +


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Used in making tough steel for truck springs

Oxide, V2O5

Orange-yellow solid

Catalyst in Contact process for sulfuric acid

Compounds: used in pottery glazes (유약,釉藥)

Fig. 16.7 Vanadium compounds in water. Blue colors are due to the vanadyl ion, VO2+.

▶ Chromium, Cr Lehmann (1761), Siberian red lead, Vauquelin (1798), first isolation

Greek word "chrōma" (χρωµα), meaning “color”

Stainless steel, chromium plating

Reduction of its ore, chromite, FeCr2O4

with carbon in electric furnace:

2 4FeCr O ( ) 4 C( ) Fe( ) 2 Cr( ) 4 CO( )s s l l∆+ ⎯⎯→ + + g

l

2

Reduction of its oxide by aluminum in the thermite process:

2 3 2 3Cr O ( ) 2 Al( ) Al O ( ) 2 Cr( )s s s∆+ ⎯⎯→ +

► CrO2 :

ferromagnetic, used for coating “chrome” recording tape

► Na2CrO4 : yellow solid

2 2+4 2 72 CrO ( ) 2 H ( ) Cr O ( ) H O( )aq aq aq l

− −+ ⎯⎯→ +

Fig. 16.8 Yellow chromate (CrO42–) ion acid⎯⎯⎯→Orange dichromate (Cr2O72–) ion

2 + 3+2 7 2Cr O ( ) 14 H ( ) 6 2 Cr ( ) 7 H O( )aq aq e aq l

− −+ + ⎯⎯→ + , o 1.33 VE = +

http://en.wikipedia.org/wiki/Color


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▶ Manganese, Mn Gahn (1774), first isolation

Manganese steel

Manganese bronze

39% Zn, 1% Mn, small amount of Fe & Al, rest Cu

corrosion resistive, used for propellers of ships

Alloy with Al stiff cans with thinner walls

Ores: Nodules on the ocean floor

Thermite process from pyrolusite(軟망간石), MnO2

Fig. 16.9 The manganese nodules on the ocean floor.

2 23 MnO ( ) 4 Al( ) 3 Mn( ) 2 Al O ( )s s l∆+ ⎯⎯→ + 3 s

Manganese dioxide, MnO2

Brown-black solid used in dry cells

Decolorizer to conceal green tint of glass

Potassium permanganate, KMnO4

Strong oxidant in acidic solution, Mild disinfectant, Versatile adaptability to variety of mechanisms

▶ Iron, Fe

Most abundant on Earth, Second most abundant in the Earth’s crust

Ores: hematite(적철광,赤鐵鑛), Fe2O3; magnetite(자철광,磁鐵鑛), Fe3O4 ; Pyrite(황철광,黃鐵鑛), FeS2

Passivated by oxidizing acids such as HNO3


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Reacts with nonoxidizing acids evolving H2 and forming iron(II) salts

readily oxidized to iron(III) salts

32 6

pale pur

22 5

yelle w

2

o

3

pl

[FeOH(H O) ] ( )H O( ) H O ( )[Fe(H O) ] ( ) l a aaq qq+ ++⎯⎯→+ +←⎯⎯

Fe3+ ions in amethyst(자수정,紫水晶) purple color

Zero oxidation number compound: iron pentacarbonyl, Fe(CO)5 yellow molecular liquid

Human body contains 3g of iron as hemoglobin

Daily loss 1 mg in sweat, feces, hairs

Monthly loss 20 mg for 女人

Anemia (빈혈증,貧血症)

▶ Cobalt, Co Silver-grey metal Brandt (1735), first isolation

Ore: cobaltite(輝코발트鑛), CoAsS

Byproducts from mining of Cu and Ni

Alnico steel (Al/Ni/Co steel) : permanent magnets for loud speakers

Cobalt steel : surgical steels, drill bits, lathe(선반,旋盤) tools

Vitamin B12

▶ Nickel, Ni Cronstedt (1751), first isolation

Stainless steel, Cupronickel : alloy for making nickel coins (5 cents), 25% Ni + 75% Cu

Nicad batteries

Catalyst for hydrogenation reactions

► Mond process (1899): Ludwig Mond(獨,1839-1909)

(1) o, 200 C

2 2NiO( ) H ( ) Ni( ) H O( )s g s∆+ ⎯⎯⎯⎯→ + g

g

g

(2) o50 60

4Ni( , impure) 4 CO( ) Ni(CO) ( )Cs g −+ ⎯⎯⎯⎯→

(3) o, 220-250 C

4Ni(CO) ( ) Ni( , pure) 4 CO( )g s∆⎯⎯⎯⎯⎯→ +

Green color of [Ni(H2O)6]2+


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16.4 Groups 11 and 12

◆ Group 11 elements: Cu, Ag, Au coinage(주화,鑄貨) metals, , Low reactivity 10 1( 1)n d ns−

▶ Copper, Cu

Ores: Chalcopyrite(황동광,黃銅鑛),CuFeS2;

Malachite(공작석,孔雀石), CuCO3·Cu(OH)2;

Chalcocite(휘동광,輝銅鑛), Cu2S.

Separation of crushed sulfide ores from excess rocks

by froth flotation(포말부유선광,泡沫浮遊選鑛) process: ● Powdered ores combined with oil, water, and detergent. ● Air is blown through the mixture. ● Oil-coated sulfide ores float to the surface with the froth. ● Unwanted copper-poor residue, gangue (맥석,脈石), sinks to the bottom.

bubbles ores rocks

▶ Extraction of metals from its ores: ► Pyrometallurgy(건식야금법,乾式冶金法) Roasting of enriched ore:

2 2

2

2 CuFeS ( ) 3 O ( ) 2 CuS( ) 2 FeO( ) 2 SO ( )

s gs s∆ g

+

⎯⎯→ + +

Smelting(용융,鎔融) of CuS reduction by heating with coke (C)

Oxidation of S to SO2:

2 2CuS( ) O ( ) Cu( ) SO ( )s g l∆+ ⎯⎯→ + g

blister copper(조동,粗銅)

Fig. 16.10 Chalcopyrite, Malachite, Chalcocite

Fig. 16.11 The froth flotation process.

Fig. 16.12 Industrial-scale copper refinery. Molten copper poured into molds.


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► Hydrometallurgy(습식야금법,濕式冶金法)

(1) Extraction of metal ions by sulfuric acid on ores

(2) Reduction of metal ions to metals

2Cu ( ) H ( ) Cu( ) 2 H ( )aq g s aq+ ++ ⎯⎯→ + , o 65 kJG∆ = −

o 2(Cu / Cu) 0.34 VE + = +

☺ Zn and Ni can not be extracted by hydrometallurgically. o 2(Zn / Zn) 0.76 VE + = − , o 2(Ni / Ni) 0.23 VE + = −

● Purification of impure copper by electrolysis.

● Alloys of copper: Bronze (Cu/Sn) and Brass (Cu/Zn)

● Corrosion in moist air:

2 2 3

basic cop

2 2 2

per carbonate

Cu (OH) C2 Cu( ) H O( ) O ( ) CO )( O ()s l g sg+ + + ⎯⎯→

Fig. 16.13 The passivating patina (박막,薄膜) of pale green copper carbonate.

● Disproportionation of copper(I) compound in water:

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2 6[Cu(H2 Cu O)( ) 6 H O( ) ) (( u] C )aq l saq+ ++ ⎯⎯→ +

● Copper is essential in animal metabolism Octopus, arthropods(절지동물,節肢動物:게,새우) Transportation of oxygen in green blood ! (Fe Cu)

▶ Silver (은,銀), Ag Peru, Mexico Byproduct of refining copper and lead, Germicide utensils, ‘은-나노 세탁기’, ‘은나노폰’ Recycling from photoindustry

Ag ( ) Ag( )aq e s+ −+ ⎯⎯→ , o 0.80 VE = +

can not reduce H+ to H2. Reacts with sulfur and sulfur compounds Oxidation number +1 AgNO3 and AgF soluble, other silver salts are sparingly soluble in water

▶ Gold, Au South Africa Pure gold : 24-karat gold

karat (purity) X = 24×(Mg / Mm) Mg(m): mass of gold (material)

carat (mass) 1 carat = 200 mg Malleable : 1 g 1 m2

Ductile: 1 g 2 km

Fig. 16.14 The color of gold: 8K, 14K, white gold, 18K, 24K


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2 l

aq

gg

g

2 g

2 g

l

Noble metal:

Au ( ) Au( )aq e s+ −+ ⎯⎯→ , o 1.69 VE = +

3Au ( ) 3 Au( )aq e s+ −+ ⎯⎯→ , o 1.40 VE = +

3 2NO ( ) 4 H ( ) 3 NO( ) 2 H O( )aq aq e g l− + −+ + ⎯⎯→ + , o 0.96 VE = +

Reacts with ‘aqua regia (王水)’ mixture of conc HNO3 and conc HCl (1:3 by volume)

3 4 2Au( ) 6 H ( ) 3 NO ( ) 4 Cl ( ) [AuCl ] ( ) 3 NO ( ) 3 H O( )s aq aq aq aq g−+ − −+ + + ⎯⎯→ + +

Reacts with NaCN in aerated aqueous solution:

2 2 24 Au( ) 8 NaCN( ) O ( ) 2 H O( ) 4 Na[Au(CN) ]( ) 4 NaOH( )s aq g l aq+ + + ⎯⎯→ +

◆ Group 12 elements: Zn, Cd, Hg 10 2( 1)n d ns−

▶ Zinc, Zn Ore: sphalerite(섬아연광,閃亞鉛鑛), ZnS

Preparation: froth-flotation, roasting, smelting with coke

2 22 ZnS( ) 3 O ( ) 2 ZnO( ) 2 SO ( )s g s∆+ ⎯⎯→ +

ZnO( ) C( ) Zn( ) CO( )s s l∆+ ⎯⎯→ + Amphoteric

22Zn( ) 2 HCl( ) Zn ( ) 2 Cl ( ) H ( )s aq aq aq

+ −+ ⎯⎯→ + + 2

2 4

zincate ion

Zn( ) 2 OH ( ) 2 H O( ) [Zn(OH) ] ( ) H ( )s aq l aq− −+ + ⎯⎯→ +

Alloy: Brass (Cu/Zn) Essential mineral: growth retardation, diarrhea, infection susceptibility for children Enzymes: alcohol dehydrogenase Muscle cramp : Treat with ZnSO4▶ Cadmium, Cd Byproduct of zinc production Used for Ni/Cd batteries, pigments, corrosion-resistant plating on steel Very toxic: softening bones, destroy kidney and lung ▶ Mercury (수은,水銀), Hg Ore: cinnabar(진사,辰砂), HgS

Froth-flotation, roasting in air

2HgS( ) O ( ) Hg( ) SO ( )s g g∆+ ⎯⎯→ + distilled and condensed

Reacts with nitric acid: 2+

3 23 Hg( ) 8 H ( ) 2 NO ( ) 3 Hg ( ) 2 NO( ) 4 H O( )l aq aq aq g−++ + ⎯⎯→ + +

Oxidation states: Hg22+ (+1, Hg2Cl2), Hg2+ (+2, HgCl2) Wide liquid range: – 39oC (m.p.) ~ 357oC (b.p.)


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COORDINATION COMPOUNDS

d-metal (Lewis acid) vs. ligands (Lewis base) covalent bonds

complexes of d-metals : colorful, magnetic

[Cu(H2O)6]2+ (blue), hexaaquacopper(II) ion

[Fe(CN)6]4+ hexacyanoferrate(II) or ferrocyanide ion, K4[Fe(CN)6] (lemon-yellow)

[Fe(CN)6]3+ hexacyanoferrate(III) or ferricyanide ion, K3[Fe(CN)6] (bright red)

BOX 16.1 WHAT HAS THIS TO DO WITH……STAYING ALIVE

◈ Metalloprotein: Large organic molecule made of folded polymerized chains of amino acids including metal atoms

Ex. 1. Hemoglobin : contains 4 planar heme groups Central Fe(II) at the center of a heme group surrounded by 4 N atoms from amine groups An O2 molecule as a fifth ligand Can transport 4 O2 molecules cf. Myoglobin : contains 1 heme group can bind only one O2 molecule

Ex. 2. Cobalamin (Vitamin B12) Central Co(III) at the center of an octahedral complex surrounded by 5 N atoms from amine groups – CH2 – group as a sixth ligand formation of a carbon-cobalt bond (metal-carbon bond)

Ex 3. Zinc-containing enzymes Play important roles in various metabolisms “master hormone” Decrease in intracelluar zinc concentration related to “aging” ▶ Chromium(III) : regulation of glucose metabolism ▶ Copper(I) : essential nutrient for healthy cells

◆ Nobel Laureates in Chemistry (1962) "for their studies of the structures of globular proteins"

Max F. Perutz John C. Kendrew (英,1914-2002) (英,1917-1997) Hemoglobin Myoglobin

Oxygen transport by a heme group of hemoglobin


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◆ Nobel Laureate in Chemistry (1964) "for her determinations by X-ray techniques of the structures of important biochemical substances"

Pennicilin & Vitamin B12

Dorothy C. Hodgkin (英,1910-1994)

Vitamin B12 with a carbon-cobalt bond 16.5 Coordination Complexes (배위착물,配位錯物)

◆ Nobel Laureate in Chemistry (1913) "in recognition of his work on the linkage of atoms in molecules by which he has thrown new light on earlier investigations and opened up new fields of research especially in inorganic chemistry"

Alfred Werner Fig. 16.15 (a) Six-coordinate octahedral, (b) four-coordinate tetrahedral, (瑞西,1866-1919) (c) four coordinate square planar complexes.

▶ Central d-metal (Lewis acid) vs. ligands (Lewis base) coordinate covalent bonds

Coordination sphere (배위권,配位圈) Coordination number (배위수,配位數) (number of ligands attached to the central metal atom)Octaheral 6

Tetrahedral 4

Square planar 4

▶ Ligands (L. ligandus, “to bind”)

Neutral molecule: CO in Ni(CO)4, Ions : CN– in [Fe(CN)6]4– , Cl– in [FeCl(H2O)5]+

▶ Preparation of complex ions: 2 4

2 6 6 2[Fe(H O) ] ( ) 6 CN ( ) [Fe(CN) ] ( ) 6 H O( )aq aq aq l+ − −+ ⎯⎯→ +

2

2 6 2 5 2[Fe(H O) ] ( ) Cl ( ) [FeCl(H O) ] ( ) H O( )aq aq aq l+ − ++ ⎯⎯→ + incomplete substitution


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◈ Werner’s Findings:

Chemical formulas Compound 1: CoCl3·6NH3 orange-yellow Compound 2: CoCl3·5NH3 purple Compound 3: CoCl3·4NH3 green Compound 4: CoCl3·3NH3 green

▶ Treatment with HCl did not remove NH3 ▶ Treatment with AgNO3(aq)

Compound 1 All of the chloride present precipitated as AgCl. Compound 2 2/3 of ...... Compound 3 1/3 of ...... Compound 4 no reaction ! ◆ Werner’s analysis: Octahedral complexes

Compound 1: [Co(NH3)6]3+(Cl–)3 ↔ Conductivity of Al(NO3)3Compound 2: [Co(NH3)5Cl]2+(Cl–)2 ↔ Conductivity of Mg(NO3)2Compound 3: [Co(NH3)4Cl2]+(Cl–) ↔ Conductivity of NaNO3Compound 4: [Co(NH3)4Cl3] ↔ Nonelectrolyte


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Fig. 16.16 Formation of hexacyanoferrate(II) ion, [Fe(CN)6]4– Fig. 16.17 The colored d-metal complexes: by adding KCN(aq) to FeSO4(aq). The blue Prussian blue is [Fe(SCN)(H2O)5]2+, [Co(SCN)4(H2O)2]2–, [Cu(NH3)4(H2O)2]2+, [CuBr4]2–

formed by polymerization of the complex ion.


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TOOLBOX 16.1 NOMENCLATURE OF d-METAL COMPLEXES AND COORDINATION COMPOUNDS

1. Name the ligands first and then the metal atom or ion.

2. Neutral ligands: H2NCH2CH2NH2(ethylenediamine, en), H2O(aqua), NH3(ammine), CO(carbonyl), NO(nitrosyl)

3. Anionic ligands: –ide, –ate, –ite –o, –ato, –ito Cl–(chloro), SO42–(sulfato), NO2–(nitrito)

4. Number of ligands: Greek prefixes 2 (di-), 3 (tri-), 4 (tetra-), 5 (penta-), 6 (hexa-), …

For complex ligands already containing Greek prefixes: 2 (bis-), 3 (tris-), 4(tetrakis-), …

5. Name the ligands in alphabetical order neglecting the Greek prefixes.

6. Chemical symbols of anionic ligands first then neutral ones.

7. The Roman numeral for the oxidation state of the cental metal.

[FeCl(H2O)5]+ pentaaquachloroiron(II) ion

[CrCl2(NH3)4]+ tetraamminedichlorochromium(III) ion

[Co(en)3]3+ tris(ethylenediamine)cobalt(III) ion

8. For an anionic complex, the suffix –ate is added to the stem of the name of metal.

[Ni(CN)4]2–, tetracyanickelate(II) ion

If the name of metal is originated from Latin, use the Latin stem.

[Fe(CN)6]4–, hexacyanoferrate(II) ion Iron (Fe) : ferrum

9. When naming the coordination compound, name the cation before the anion.

NH4[PtCl3(NH3)] ammonium ammintrichloroplatinate(II)

[Cr(OH)2(NH3)4]Br tetraamminedihydroxochromium(III) bromide

Ex. 16.1 Naming complexes and coordination compounds

(a) [Co(NH3)3(H2O)3]2(SO4)3 Triamminetriaquacobalt(III) sulfate

(b) Sodium dichlorobis(oxalato)palatinate(IV) Na2[PtCl2(ox)2]

[Co(NH3)3(H2O)3]3+ [PtCl2(ox)2]2–


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16.6 The Shapes of Complexes

[Fe(CN)6]4– [CoCl4]2– [Pt(NH3)2Cl2] Linear complex

Mo or W complexes

▶ Metallocene: sandwich compounds

Ex. Ferrocene : an iron atom in between two cyclopentadienyl ligands with 10 links

◆ Polydentate (“many toothed”) ligands Forming chelates (L. “claw”)

▶ Bidentate ligands: Ethylenediamine (en)

▶ Hexadentate ligands: Ethlenediaminetetraacetic acid (EDTA) antidote to lead poisoning

Sodium iminodisuccinate scavenging metal ions to remove ☺ succinic acid(호박산,琥珀酸)


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16.7 Isomers (이성질체,異性質體)

Compounds that contain the same numbers of the same atoms but in different arrangements.

◈ Types of isomers:

Fig. 16.18 The various types of isomerism in coordination compounds

◆ Structural isomers (구조이성질체) atoms connected to different partners different chemical formulas

▶ Ionization isomers (이온화이성질체)

Exchange of a ligand with an anion or a neutral molecule outside the coordination sphere

Ex. (1) [CoBr(NH3)5]SO4 and (2) [CoSO4(NH3)5]Br (1) precipitates with Ba2+(aq)


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▶ Hydrate isomers (수화水化이성질체)

Exchange of an H2O molecule with another ligand in the coordination sphere

Ex. (1) [Cr(H2O)6]Cl3 (2) [CrCl(H2O)5]Cl2·H2O (3) [CrCl2(H2O)4]Cl·2H2O

Precipitation of 3, 2, and 1 mols AgCl from 1 mol of (1), (2), and (3), respectively

Fig. 16.19 Hydrate isomers. Fig. 16.20 Linkage isomers.

▶ Linkage isomers (결합이성질체)

differing in the identity of the atom used by a given ambidentate (양쪽자리성) ligand

to attach to the metal ion

Ex. (1) SCN– (thiocyanato-), NCS– (isothiocyanato) (2) CN– (cyano-), NC– (isocyano-)

(3) NO2– (nitro-), ONO– (nitrito) ex. [CoCl(NO2)(NH3)4]+ and [CoCl(ONO)(NH3)4]+

▶ Coordination isomers (배위이성질체)

differing by the exchange of one or more ligands between a cationic complex and an

anionic complex ex. [Cr(NH3)6][Fe(CN)6] and [Cr(NH3)5CN][Fe(CN)5(NH3)]

Fig. 16.21 Coordination isomers. Exchange of a ligand between cationic and anionic complexes.

◆ Steroisomers (입체이성질체) atoms with the same partner but with different arrangements in space

same chemical formula


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▶ Geometrical isomers (기하이성질체)

atoms are bonded to the same neighbors but have different locations relative to each other

occur for octahedral and square planar complexes but not for tetrahedral complexes

Used for chemotherapy therapeutically inactive

▶ Optical isomers (광학이성질체)

Nonsuperimposable mirror images of each other

Fig. 16.22 Optical isomers. Mirror images.

Louis Pasteur (佛, 1822-1895)

Discovered chirality and explained optical activity

Both geometrical and optical isomerism can occur in octahedral complexes

Geometrical isomerism: trans isomer: (a) (green) , cis isomers: (b) and (c) (both violet)

Optical isomerism: between (b) and (c)

Optical isomers can occur for tetrahedral complexes but not for square planar complexes


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◆ Chiral (Ancient Greek χείρ, “hand”) complex cf. chirality (handedness)

A molecule is chiral if it is nonsuperimposable on its mirror image.

cis isomers of [CoCl2(en)2]+ (b) and (c) are chiral.

trans isomer of [CoCl2(en)2]+ (a) is superimposable on its mirror image “achiral”

▶ Optical activity : ability of chiral molecules to rotate the plane of polarized light

▶ Enantiomers (거울상이성질체: Greek, ἐνάντιος, “opposite”, and µέρος, “part” or “portion”):

a chiral complex and its mirror image

Enantiomers rotate the polarized plane clockwise (+, or d- ) cf. dextro- (L. ‘on the right side’)

or counterclockwise (–, or l- ) with the same amount. cf. levo- (L. ‘on the left side’)

▶ Racemic mixture: a mixture of enantiomers in equal amount

The first racemic compound is ‘racemic acid (tartaric acid)’

obtained from grape juice (L. racemus, “grape”).

tartaric acid

BOX 16.2 HOW DO WE KNOW…THAT A COMPLEX IS OPTICALLY ACTIVE?

◆ Polarimetry (편광측정,偏光測定)

Fig. 16.23 Rotation of a plane-polarized light by an optically active substance. Polarimeter

Ex. 16.2 Identifying optical isomerism


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Compound Chirality Compound / Its mirror image

Rotating the mirror image along A – A gives identical to the original.

superimposable achiral

The mirror image is superimposable on the original

achiral

No rotation allows the complex superimposable on the original

chiral

(c) (c)*

No rotation allows the complex superimposable on the original

chiral

(d) (d)* Rotating (c)* by 90o

along the vertical B – D axis gives (d).

(c) and (d) are a pair of enantiomers


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THE ELECTRONIC STRUCTURES OF COMPLEXES

16.8 Crystal Field Theory

(1) Metal atom (or ion) at the center of an octahedron (or a tetraheron)

(2) Ligands: negative point charges surrounding the metal

(3) Interaction with electrons of d-orbitals depending on the orientation of d-orbitals

Fig. 16.24 The crystal field theory representation of electron pairs as point charges.

▶ Octahedral complex: [Ti(H1d 2O)6]3+ cf. Ti: 2 2[Ar]3 4d s

Fig. 16.25 The classification of d-orbitals in to two groups.

Three 2 gt -orbitals ( ) : lobes directed between the point charges Low energy , ,xy yz xzd d d Two ge -orbitals ( ) : lobes point directly toward the point charges High energy 2 2,z x yd d − 2

t : three orbitals, : second set of three orbitals, : two orbitals, 2t e(gerade)g : even, : odd upon inversion (ungerade)u

Fig. 16.26 The energy levels of the d-orbitals in an octahedral complex with the ligand field splitting, . O∆

Electron configuration of 1d -complex of [Ti(H2O)6]3+

Fig. 16.27 The excitation of an electron to a upper orbital upon absorbing a photon of light.


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Ex. 16.3 Determining the ligand field splitting

The complex [Ti(H2O)6]3+ absorbs light of wavelength 510 nm.

What is the ligand field splitting of the complex?

[Solution] ohν = ∆ , /cλ ν= o A /N hc λ∆ =

( ) ( ) ( )23 1 34 8 17

6.022 10 mol 6.626 10 J s 2.998 10 m s5.10 10 mo

− −

−

× × × ⋅ × ×∆ =

×

−⋅

1235 kJ mol−= ⋅

▶ Terahedral complex

Fig. 16.28 The energy levels of the d-orbitals in a tetrahedral complex with the ligand field splitting, T∆ . In general, . O T∆ > ∆

16.9 The Spectrochemical Series

Arranging ligands according to the relative magnitudes of the ligand field splittings

Fig. 16.29 The spectrochemical series.

Colors and magnetic properties of complexes : Magnitude of O∆ and electron configurations

Strong-field ligand Weak-field ligand Low-spin complex High-spin complex

Ex. 16.4 Predicting the electron configuration of a complex

Predict the electron configuration of an octahedral -complex with (a) strong- and (b) weak-field ligands. 5d


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(a) 52gt ; one unpaired electron (b) 3 2

2g gt e ; five unpaired electrons

16.10 The Colors of Complexes

▶ Complementary colors (보색,補色)

One of pair of colors that white light

appears when the other is removed.

Red Green ↔

Blue Orange ↔

Fig. 16.30 A color wheel: Fig. 16.31 Violet [Ti(H2O)6]3+Color of absorbed light is absorbs yellow-green ight. opposite the color perceived.

▶ Color of the complex depends on ligand field splitting ▶ Ligand-to-metal charge-transfer transition

Fig. 16.32 The effect on the color of the octahedral Co(III) complexes Fig. 16.33 Charge-transfer transition with different ligands. Ligand field strengths increase from left to right. in MnO4–.


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16.11 Magnetic Properties of Complexes

▶ Paramagnetism (상자기성,常磁氣性) : unpaired electrons, attracted to a magnet

▶ Diamagnetism (반자기성,反磁氣性) : paired electrons, repulsed by a magnet

Fig. 16.34 Detecting magnetic character of a complex by a Guoy balance. (a) A sample is inserted between electromagnets. (b) Paramagnetic drawing and (c) Diamagnetic repulsion.

▶ High spin complex

more unpaired electrons

strongly paramagnetic

complexes of weak-field ligands 4 ~d d 7

7

▶ Low spin complex

less unpaired electrons

weakly paramagnetic

complexes of strong-field ligands 4 ~d d

Fig. 16.35 (a) Strong field ligand (low-spin complex); (b) Weak-field ligand (high-spin complex).

Ex. 16.5 Predicting the magnetic properties of a complex.

Fe (a) [Fe(H2O)6]2+ (b) [Fe(CN)6]4–

Fe2+ ion ( ion) H6d 2O: weak field ligand CN– : strong field ligand

4 2

2g gt e , high spin 6

2gt , low spin 4 unpaired electrons no unpaired electrons paramagnetic diamagnetic


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16.12 Ligand Field Theory

d-orbitals of central metal + ligand orbitals

Consider an octahedral complex of a d-metal in 4th period

Nine 4s-, 4p-, 3d-orbitals from central metal ion

Six ligand orbitals, one from each ligand:

Cl3p-orbital from Cl– ligand or Nsp3 lone pair from NH3 ligand

Cylindrical symmetry along metal-ligand axis

Forming six σ -bonds

15 MOs from 9 metal orbitals and 6 ligand orbitals

( 6 σ -bonding, 3 nonbonding, 6 antibonding )

three t2g-orbitals of the metal nonbonding

▶ Aufbau principle

Number of available electrons in a complex : 12 + n nd n electrons from the metal

12 electrons from six ligands

First 12 electrons fill six bonding orbitals: 1 1, ,g u ga t e

n electrons fill 3 nonbonding ( 2gt ) and 2 antibonding ( ge ) MOs

☺ ligand field splitting energy separation between

nonbonding and antibonding MOs

Fig. 16.36 The six orbitals provided by ligands in octahedral complex.

Fig. 16.37 The MO energy level diagram for an octahedral complex.

▶ Effect of π -bonding formed from a p-orbital of a ligand and a t2g orbital of metal

Fig. 16.38 The effects of π –bonding on ligand field splitting.

(a) Occupied π -orbital and (b) unoccupied *π -orbital of a ligand overlap with 2gt orbital of a metal in the complex. Ligand field splitting decreases in (a) but increases in (b).


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► Why is Cl– a weak field ligand? Fig.16.38(a)

Cl3p-orbital is full and contributes 2 electrons filling the bonding π -orbital

n d-electrons of the metal filling the antibonding *π -orbital ligand filed splitting decreased !

Cl– a weak field ligand despite its negative charge

► Why is CO a strong field ligand? Fig.16.38(b)

Empty antibonding *π -orbital of the ligand closer in energy to 2gt orbital of a metal

Formation of a bonding π -orbital and an antibonding *π -orbital of the complex

n d-electrons of the metal filling the bonding π -orbital ligand field splitting increased !

CO is a strong field ligand despite being electrically neutral

THE IMPACT ON MATERIALS

16.13 Steel

Blast furnace: 40 m high

For 1 kg of steel, we need

1.75 kg ore, 0.75 kg coke, 0.25 kg limestone.

3 2CaCO ( ) CaO( ) CO ( )s s∆⎯⎯→ + g

l

l

l

▶ Impurities removed by CaO as slag:

2 3CaO( ) SiO ( ) CaSiO ( )s s∆+ ⎯⎯→

2 3 2 2CaO( ) Al O ( ) Ca(AlO ) ( )s s∆+ ⎯⎯→

4 10 3 4 2CaO( ) P O ( ) 2 Ca (PO ) ( )s s∆+ ⎯⎯→

Fig. 16.39 Reduction of iron ores in a blast furnace.

▶ Molten iron obtained through a series of reactions in the four main temperature zones in the furnace.

Zone A : C + O2o1900 C⎯⎯⎯→ CO2

Zone B: CO2 + C 2 CO, Feo1300 C⎯⎯⎯→ 2O3 + 3 CO 2 Fe + 3 CO⎯⎯→ 2 , FeO + CO Fe + CO⎯⎯→ 2

Zone C & D: 800 ~ 1000oC

3 Fe2O3 + CO 2 Fe⎯⎯→ 3O4 + CO2, Fe3O4 + CO 3 FeO + CO⎯⎯→ 2 , CaCO3 CaO + CO⎯⎯→ 2


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▶ Molten pig iron (선철,銑鐵) flows from Zone C to Zone A. 90-95 % Fe, 3-5 % C, 2% Si

Pure Fe: m.p.1540oC, Fe(4% C): m.p. 1015oC

▶ Cast iron (주철,鑄鐵) fewer impurities with 2% C, brake drum, engine blocks, transmission housings

◆ Basic oxygen process :

Purification (impurities: Si, P, S) of molten pig iron with a blast of oxygen and powdered limestone

2 Fe + O2 2 FeO ⎯⎯→

Si + O2 SiO⎯⎯→ 2

2 FeO + Si 2 Fe + SiO⎯⎯→ 2

SiO2 + CaO CaO· SiOIn slag⎯⎯⎯→ 2

5 FeO + 2 P + 3 CaO 5 Fe + (CaO)In slag⎯⎯⎯→ 3·P2O5(l)

C + FeO Fe + CO ⎯⎯→

C + 1/2 O2 CO ⎯⎯→

Fig. 16.40 The basic oxygen process.

▶ Carbon contents in steel

16.14 Nonferrous Alloys

▶ One-phase homogeneous alloys substitutional alloys

brass, bronze, gold coinage alloy

▶ Heterogeneous mixtures of different crystalline phases:

tin-lead solder, mercury-silver amalgams

16.15 Magnetic Materials Fig. 16.41 The atomic radii of Cu and Zn.

▶ Paramagnetism (상자성,常磁性) : unpaired electrons, disappears when the field is turned off

▶ Ferromagnetism (강자성,强磁性) : Fe, Co, Ni, permanent magnet, cassette tape, computer disks

domain(regions of aligned spins;자구,磁區) survives after the applied field is turned off.


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Fig. 16.42 Ferromagnetic material before(a) and after (b) magnetization.

▶ Antiferromagnetism (반강자성,反强磁性): Mn or ‘ferrimagnetism’

Neighboring spins are locked into an antiparallel arrangements magnetic moments cancel

▶ Ceramic magnet : refrigerator magnet, brittle, cheap

Barium ferrite, (BaO·nFe2O3) or Strontium ferrite (SrO·nFe2O3)

Compressing powdered ferrites in a magnetic field and heating it until it hardens.

▶ Ferrofluid: ferromagnetic fluid

Suspension of finely powdered magnetite, Fe3O4, in a viscous, oily liquid that contains a detergent

(oleic acid)

Forming an inverted micelles

Used in braking system of exercise machines

The stronger the magnetic field, the greater the resistance to motion.

▶ Molecular magnets

d-block metal atoms bonded to groups of nonmetal atoms (C,H,O)

d-block metal atoms are imbedded in cage-like structures nano-size molecular magnets

Fig. 16.43 The ferrofluid drawn by a magnet. Fig. 16.44 Molecular magnet: Nano-size molecular torus of 84 Mn atoms.

◈ Magnetic susceptibility and Curie temperature (Exercise 16.77)

Magnetic susceptibility (자화율,磁化率) :

degree of magnetization of a material in response to an applied magnetic field.

number of unpaired electrons

▶ Curie temperature, TC (768oC for Fe)

Ferromagnetic material becomes paramagnetic above Tc

2nd order phase transition

Documents

CHAPTER 16 THE ELEMENTS: THE d BLOCK · 2010-04-12 · Textbook: P. Atkins / L. Jones, Chemical Principles, 4th ed., Freeman (2008) Chapter 16 3 16.2 Trends in Chemical Properties