Ch8 Coordination [호환 모드]chem.yonsei.ac.kr/~mhmoon/pdf/General_Oxtoby/Ch8_Coordination.pdf · 8.3 8.1 chemistry of Transition Metals transition metal elements : partially filled

8.1

Chapter 8Bonding in Transition Metal

C d & C di i C lCompounds & Coordination Complexes Emerald: Beryllium aluminum silicatey

Prof. Myeong Hee Moon

8.2

Chapter Outline

• Chemistry of transition metals

• Bonding in simple molecules that contain treansition metals

• Introduction to coordination chemistry

St t f di ti l• Structures of coordination complexes

• crystal field theory : optical & magnetic properties

• optical properties & spectrochemical series

• Bonding in coordination complexes• Bonding in coordination complexes


8.3

8.1 chemistry of Transition Metals

transition metal elements : partially filled d-electron shells wide variety of geometric strctures colors magnetic propwide variety of geometric strctures, colors, magnetic prop

• physical properties: IE & IE increases across: IE1 & IE2 increases across: atomic and ionic radii decrease due to increase of eff nuclear charge

but at end, repulsion between electrons increases radii increase


8.4

physical properties: sizes, m.p.

• lanthanide contraction: 3rd transition (6th period)

• melting point: metal-metal bond: higher m.p. for elements with: 3 transition (6 period)

atomic radii of 3rd tran. are not muchdifferent from 2nd (4d, 5th period) tran.due to diffused f orbital poor screening

g pmore unpaired electrons

- # covalent bond characters

due to diffused f orbital.- poor screening


8.5

physical properties: hydration enthalpy

• enthalpy of hydration : energy change when a metal is hydrated.py y gy g y

M2+ (g) M2+ (aq)

Strength of the interactions increases as the ionic radii decrease allowing

predicted

as the ionic radii decrease, allowing water molecules to approach the ions more closely.

Exp data

-Deviations show that factors otherthan ionic radii are important.

t d f C M Z Exp data-note: no dev for Ca, Mn, Znhalf or full filled d orbital


8.6

physical properties: oxidation statesof transition-metal elementsof transition metal elements

• higher ox state – relatively covalent, Mn2O7 (liq at rom temp)• lower ox. State – relatively ionic, Mn3O4 (m.p. 1564oC)


8.7

8.2 Bonding in simple molecules that containTransition Metals

1) Homonuclear diatomic molecules: formed at high temp in gas phase Cu Ag: formed at high temp in gas phase. Cu2, Ag2,

• two requirements to make diatomic moleculestwo requirements to make diatomic molecules- energy level order of tra.metals - ignor mixing of 4s orbital and 3d orbitals

psd 443 εεε <<23

zd

• typical overlap of 3d orbitals between two metals

ddand :*σσ

yzyzxzxz

zz

dddd

dd

−−

−

or and

and 22

:

:*ππ

σσ

xyxyyxyxdddd −−

−− or and 2222:*δδ


8.8

MO formed from d-orbital overlap

and :*δδ

yxyx

dd

dd −−−

or

and

2222

:δδ

xyxy dd −

dddd or

and :*ππ

yzyzxzxz dddd −− or

22:*

zzdd −σσ and


8.9

Orbital correlation diagram for Homonuclear diatomic molecules of tr metals

C molec le stabe in gas phase [Ar]3d10 4s1 22 e for bonding• Cu2 molecule: stabe in gas phase. : [Ar]3d10 4s1. 22 e for bondingall orbitals filled except 4σ*. 2σ Filled with each 4s1.

B.O. = 1. single bond


8.10

Heteronuclear diatomic molecules

• metal oxide

O in match or

O in match

nod

nod

xy

yx

nb

−

−− 22:δ

and xxz pd 23:* −ππ

y

or yyz pd 23 −

zzpd 23: 2

* −σσ and


8.11

Heteronuclear diatomic molecules

• ScO - (Sc: 4s2 3d1), (O:2s2 2p4) - total 9 electrons.t t (1 nb)2(2 )2(1 )4(3 nb)1 B O 3 ( i il t N )gr.state : (1σnb)2(2σ)2(1π)4(3σnb)1 B.O.=3 (similar to N2)

b i ith S 2+ (3d1) d O2 (2 2 2 6)• begin with Sc2+ (3d1) and O2-(2s2 2p6)

O 2s electrons ScO 1 σnb

O 2pz electrons contribute – 2σ orbitalsLigand-to-metal (L M) σ donationg ( )dative bond


8.12

8.3 Introduction to Coordination Chemistry

• Formation of coordination complexes found by Werner: ti f C b lt h l id ( NH ) ith HCl( ): reaction of Cobalt chrloride (w NH3) with HCl(aq)

– NH3 was not removed. NH3 is bound: treated with AgNO3 at 0oC.

comp 1 : all Cl precipitated, comp2: 2/3 of Cl, comp3: 1/3, comp4:no primary valences (nondirectional) + secondary valences (well defined)

coordination complexes

Comp 1: CoCl3·6NH3 (orange-yellow) [Co(NH3)6]3+ Cl-3Comp 1: CoCl3 6NH3 (orange yellow) [Co(NH3)6] Cl 3

Comp 2: CoCl3·5NH3 (purple) [Co(NH3)5 Cl]2+ Cl-2Comp 3: CoCl3·4NH3 (green) [Co(NH3)4 Cl2]+ Cl-

Comp 4: CoCl ·3NH (green) [Co(NH ) Cl ]Comp 4: CoCl3 3NH3 (green) [Co(NH3)3 Cl3]

• Central metal atom – transition metal. Coordinate covalent bond


8.13

Coordination complex

• Werner tested electrical conductivity[Co(NH ) ]3+ Cl- similar to conductivity of Al(NO )[Co(NH3)6]3 Cl 3 similar to conductivity of Al(NO3)3

[Co(NH3)5 Cl]2+ Cl-2 similar to conductivity of Mg(NO3)2

[Co(NH3)4 Cl2]+ Cl- similar to conductivity of NaNO3

[C (NH ) Cl ] l l t i l d ti it[Co(NH3)3 Cl3] very low electrical conductivityC.N. : 1~16, mostly 6, commonly as 2~4, 5

• Ligands: anion or neutral compound Lewis bases (e donors)Ligands: anion or neutral compound, Lewis bases (e donors)

H2O: or :NH3. [Cu(NH3)]2+ , [Fe(CN)6]3-

Bidentate : ethylenediamine (en),

chelates: polydentate ligands


8.14

Coomon Ligands


8.15

chelates

Trisoxalatocopper(III) ion


8.16

Oxidation states

Ex) Determine the oxidation state of the coordinated metal atom in each of the followingsin each of the followingsa) K[Co(NH3)2 (CN)4] b) Os(CO)5, c) Na[Co(H2O)3 (OH)3]

Pt(NH3)2 Cl2 [Pt(NH3)3Cl][Pt(NH3)Cl3][Pt(NH ) Cl] [PtCl ] [Pt(NH ) ][Pt(NH )Cl ][Pt(NH3)3Cl]2 [PtCl4] [Pt(NH3)4][Pt(NH3)Cl3]2


8.17

Naming Coordination Compounds

1. In a coordination complex, single word. name ligand (w numbers) first and metalname ligand (w numbers) first and metal.

2. Name the compound with positive ion first followed (w space) negative ion.) g[Pt(NH3)3Cl]Cl :triaminechloroplatinum chloride

3. Anionic ligands named by putting suffix –o. f t l li d h dnames of neutral ligands – unchanged

common names for water – aqua, NH3-amine, see Table4 di tri tetra penta -- (bis tris tetrakis pentakis -- for4. di, tri, tetra, penta (bis, tris, tetrakis, pentakis, for

complicated ligand)5. list ligands in alphabetical order 6. A Roman numeral placed after the metal – oxidation states

If complex ion – negative : put –ate at the metal.


8.18

Sample problem

Name the following coordination compounds:[Co(H2O)2Cl2]Cl diaquadichlorocobalt(III) chloride[Co(H2O)2Cl2]Cl diaquadichlorocobalt(III) chloride

K3[Fe(CN)6] potassium hexacyanoferrate(III)

Sodium hexafluorocobaltate(III) Na3[CoF6]Sodium hexafluorocobaltate(III) Na3[CoF6]

Bisethylenediaminecopper(II) chloride [Cu(en)2]Cl2


Dithiosulfatoargentate(I) ethylenediaminetetraacetato calciate(II)

8.19

Ligand Substitution Rxn

• Exchange of ligands : NH3 and Cl- in Weernewr’s cobalt complexes

NiSO ( ) 6 H O ( ) [Ni(H O) ] SO ( )

Yellow colorless Green

NiSO4(s) + 6 H2O (g) [Ni(H2O)6] SO4(s)

Yellow colorless Blue-violet

NiSO4(s) + 6 NH3 (g) [Ni(NH3)6] SO4(s)

green colorless Blue-violet

[Ni(H2O)6]2+(aq) + 6 NH3 (g) [Ni(NH3 )6]2+(aq) + 6 H2O

green colorless Blue-violet

• Chelate effect[C (H O) ]2+ 4NH [C (NH ) ]2+ 4H O K 4 108[Cu(H2O)4]2+ + 4NH3 → [Cu(NH3)4]2+ + 4H2O K=4x108

[Ni(NH3)6]2+ + 3en → [Ni(en)3]2+ +6NH3

Chelate effect (entropy) K 5x109


Chelate effect (entropy) K=5x109

8.20

8.4 Structures of Coordination Complexes

•[Co(NH ) ]3+ structure ?•[Co(NH3)6]3+ structure ?

• CN = 2 – linear complex, 180op ,

• CN = 4 – tetrahedral complex, 109op– square planar complex (nd8electron configuration),

90o bond angles.CN 6• CN = 6 – octahedral complex, 90o bond angles.


8.21

CN = 4

Tetrahedral Square planar2

eg) Zn(NH3)42+, CoCl4

2- cf) VSEPR Modeleg) Cu(NH3)4

2+, Ni(II), Pd(II), Pt(II)


tetraaminezinc(II) tetraamineplatinum(II)

8.22

Sample Problem

Predict the geometry of the following complexes:

[Ni(NH3)6]2+ [Pt(NH3)2 Cl2][Au(CN)2]+ CN 6 h d l[ ( )2] CN = 6, octahedral

CN = 4, square planar[Ni(NH3)6]2+

[Pt(NH3)2Cl2]CN = 2, linear

[Pt(NH3)2Cl2]

[Au(CN)2]+


8.23

Geometric Isomers - Oh

Cis-[Co(NH3)4Cl2]+ and trans- [Co(NH3)4Cl2]+


8.24

Structural isomers

fac-triaminetrichlorocobalt(III)


8.25

Chiral Structures(optical isomerism)(optical isomerism)


8.26

Optical isomers

All i [C (NH ) (H O) Cl ]+


All cis-[Co(NH3)2(H2O)2Cl2]+

8.27

Co-EDTA : chiral complex


8.28

Ionization Isomers


pentaaminesulfatocobalt(III) chloride pentaaminechlorocobalt(III) sulfate

8.29

Coordination (sphere) isomers

T t i l ti (II) t t hl t (II)Tetraamineplatinum(II) tetrachlorocuprate(II)


pentaaminenitrocobalt(III) aminepentanitrochromate(III)

8.30

Coordination complexes ion Biology

• 9 essential transition elements in life : V Cr Mn Fe Co Ni Cu Zn Mo: V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Mo

BacteriochlorophyllHemoglobin : carries 4 hemes.

Bacteriochlorophyll: related to photosynthesis


8.31

8.5 Crystal field theory: optical and magnetic p.

• Why does Ni(II) form octahedral, square-planar, tetrahedral complexes ?crystal field splitting theory (CFST)y p g y ( )

: explains electronic, optical, & magnetic propertiesbased on the interaction between metal – ligand

: In the presence of ligands,

- the d orbital of the metal are split by a slight energy difference ∆by a slight energy difference, ∆o

- electron in two orbitals

222 &zyx

dd−

experiences strong repulsion

with electrons from ligand

i i th f bit l

y

raising the energy of orbitals


8.32

Crystal Field Modely

Approach of six ligands to transition metal cation splits d orbitals into two sets of different energy: explain color and magnetic propertiessets of different energy: explain color and magnetic properties

eg

E d

x2−y2 , dz2

ΔoΔo

dxy , dyz , dxz

3/5△o

2/5△o

Free metal ion in Spherical field in Oh fieldt2g

Free metal ion in Spherical field in Oh fieldsmall Δo large Δo

•Cristal field splitting energy Δ Cristal Field Stabilization Energy


•Cristal field splitting energy Δo , Cristal Field Stabilization Energy

8.33

high spin vs low spin

Cr3+: d3 paramagneticMn3+: d4 two gr states

• when Δ0 large: low spin comp.strong field

Mn : d two gr. states

strong field• when Δ0 small: high spin comp.

weak fieldweak field


8.34

CFSE

• crystal field stabilization energy (CFSE)


8.35

SN=4, square planar vs. tetrahedral


8.36

Magnetic Properties

• Ferromagnetism, Paramagnetism, Diamagnetism

Strong field Weak fieldHund’s Rule, strong paramagnetic


Hund s Rule, strong paramagnetic

8.37

Magnetic Properties

• Ferromagnetism, Paramagnetism, Diamagnetism


8.38

8.6 Optical Properties & Spectrochemical Series

• colors: by ox state of metal, # & nature of ligand, geometry of complex.

Strong Field Ligand vs Weak Field LigandStrong Field Ligand vs. Weak Field Ligand

[Co(H2O)6]2+

[CoCl4]2-


8.39Effect of Ligands onthe Colors of Coordination Compoundsp

Spectrochemical series : the nature of the ligand determines the magnitude of the crystal field splitting, ∆omagnitude of the crystal field splitting, ∆o

: small size halide approaches metal more closely greater repulsion

I- < Br- < Cl- < F- < OH- < H2O < NH3 < NCS- < N < H3en < CO, CN-

weak field intermediate strong-field ligand (low spin)


8.40

Absorption wavelengths


8.41

8.7 Bonding in Coordination Complexes

• hybrid orbitals

dsp3 : PF5

d2sp3: SF6


8.42

• Hybrid orbitals


8.43

Orbital CorrelationDiagram of [CrCl ]-3Diagram of [CrCl6]-3

Cr

6Cl-

Cr


8.44

Homework

10, 11, 12, 13, 14, 18, 22, 24, 33, 34, 36, 44


Documents

Ch8 Coordination [호환 모드]chem.yonsei.ac.kr/~mhmoon/pdf/General_Oxtoby/Ch8_Coordination.pdf · 8.3 8.1 chemistry of Transition Metals transition metal elements : partially filled