Ch23 coordination(a)
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Transcript of Ch23 coordination(a)
Transition Metals and Coordination Chemistry
Chapter 23Chapter 23
Transition Metals
Similarities Similarities within a given period within a given period
and and within a given group. within a given group.
Last electrons added are inner electrons (Last electrons added are inner electrons (dd’s, ’s, ff’s).’s).
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Ce
Th
Pr
Pa
Nd
U
Pm Sm
Pu
Eu
Am
Gd
Cm
Tb
Bk
Dy
Cf
Ho
Es
Er
Fm
Tm
Md
Yb
No
Lu
Lr
Sc
Y
La
Ac
Ti
Zr
Hf
Unq
V
Nb
Ta
Unp
Cr
Mo
W
Unh
Mn
Tc
Re
Uns
Fe
Ru
Os
Co
Rh
Ir
Ni
Pd
Pt
Cu
Ag
Au
Zn
Cd
Hg
Uno Une Uun Uuu
Np
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Sc
Y
La*
Ac†
Ti
Zr
Hf
Unq
V
Nb
Ta
Unp
Cr
Mo
W
Unh
Mn
Tc
Re
Fe
Ru
Os
Co
Rh
Ir
Ni
Pd
Pt
Cu
Ag
Au
Zn
Cd
Hg
Ce
Th
Pr
Pa
Nd
U
Pm
Np
Sm
Pu
Eu
Am
Gd
Cm
Tb
Bk
Dy
Cf
Ho
Es
Er
Fm
Tm
Md
Yb
No
Lu
Lr
d-block transition elements
*Lanthanides
† Actinides
f-block transition elements
Uns Uno Une Uun Uuu
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0.2
Ato
mic
rad
ii (n
m)
Atomic number
La
Hf
TaW
Re OsIr Pt
Au
Zr
Y
NbMo
Tc Ru
Rh Pd
Ag
Sc
Ti
VCr
Mn Fe Co NiCu
1st series (3d)
2nd series (4d)
3rd series (5d)
0.1
0.15
Multiple Oxidation States
Metallic Behavior/Reducing StrengthLower oxidation state = more metallicLower oxidation state = more metallic
Color and Magnetism
e- in partially filled d sublevel absorbs visible light moves to slightly higher energy d orbital
Magnetic properties due to unpaired electrons
Electronegativity increases down column
ChromiumChemical properties reflect oxidation state
Valence-State Electronegativity
Electronegativity, ENElectronegativity, EN::
electron “pulling power”electron “pulling power”
Valence-state ENValence-state EN::
metal in higher oxidation statemetal in higher oxidation state
is more positiveis more positive
has stronger pull on electronshas stronger pull on electrons
is more electronegativeis more electronegative
““Effective ENEffective EN””
Manganese
Silver
Weak Reducing Agent, H2Q
Mercury
Coordination Compound
Consist of a Consist of a complex ion complex ion and necessary and necessary counter ionscounter ions
[Co(NH[Co(NH33))55Cl]ClCl]Cl22
Complex ion:Complex ion: [Co(NH[Co(NH33))55Cl]Cl]2+2+
CoCo3+3+ + 5 NH + 5 NH33 + Cl + Cl--
== 1(3+) + 5 (0) + 1(1-)1(3+) + 5 (0) + 1(1-)
= 2+= 2+
Counter ions:Counter ions: 2 Cl2 Cl--
Complex ion remains intact upon dissolution in water
[Co(NH3)6]Cl3 [Pt(NH3)4]Br2
Complex Ion
Species where transition metal ion is surrounded Species where transition metal ion is surrounded by a certain number of ligands.by a certain number of ligands.
Transition metal ion:Transition metal ion: Lewis acidLewis acid
Ligands:Ligands: Lewis basesLewis bases
Co(NHCo(NH33))663+3+
Pt(NHPt(NH33))33BrBr++
Ligands
Molecule or ion having a lone electron pair that Molecule or ion having a lone electron pair that can be used to form a bond to a metal ion can be used to form a bond to a metal ion
((Lewis baseLewis base).).
coordinate covalent bondcoordinate covalent bond: metal-ligand bond: metal-ligand bond
monodentatemonodentate: one bond to metal ion: one bond to metal ion
bidentatebidentate: : two bond to metal iontwo bond to metal ion
polydentatepolydentate: : more than two bonds to a metalmore than two bonds to a metal
ion possibleion possible
Formulas of Coordination Compounds
1.1. Cation then anionCation then anion
2.2. Total charges must balance to zeroTotal charges must balance to zero
3.3. Complex ion in bracketsComplex ion in brackets
KK22[Co(NH[Co(NH33))22ClCl44]]
[Co(NH[Co(NH33))44ClCl22]Cl]Cl
Names of Coordination Compounds
1.1. Cation then anionCation then anion
2.2. LigandsLigands
in alphabetical order before metal ionin alphabetical order before metal ion
neutral:neutral: molecule name*molecule name*
anionic:anionic: -ide -ide -o -o
prefix indicates number of eachprefix indicates number of each
3.3. Oxidation stateOxidation state of metal ion in () only if more of metal ion in () only if more than one possiblethan one possible
4.4. If complex ion = anion, metal ending If complex ion = anion, metal ending -ate -ate
Examples
KK22[Co(NH[Co(NH33))22ClCl44]]
potassium diamminetetrachlorocobaltate(II)potassium diamminetetrachlorocobaltate(II)
[Co(NH[Co(NH33))44ClCl22]Cl]Cl
tetraamminedichlorocobalt(III) chloridetetraamminedichlorocobalt(III) chloride
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Isomers(same formula but different properties)
Stereoisomers(same bonds, differentspatial arrangements)
Structuralisomers
(different bonds)
Opticalisomerism
Geometric(cis-trans)isomerism
Linkageisomerism
Coordinationisomerism
Structural Isomerism 1
Coordination isomerism: Coordination isomerism:
Composition of the complex ion varies.Composition of the complex ion varies.
[Cr(NH[Cr(NH33))55SOSO44]Br ]Br
and and [Cr(NH[Cr(NH33))55Br]SOBr]SO44
Structural Isomerism 2
Ligand isomerism: Ligand isomerism:
Same complex ion structure but point of Same complex ion structure but point of attachment of at least one of the ligands differs.attachment of at least one of the ligands differs.
[Co(NH[Co(NH33))44(NO(NO22)Cl]Cl)Cl]Cl
andand [Co(NH[Co(NH33))44(ONO)Cl]Cl(ONO)Cl]Cl
Linkage Isomers
[Co(NH[Co(NH33))55(NO(NO22)]Cl)]Cl22
Pentaamminenitrocobalt(III)Pentaamminenitrocobalt(III)chloridechloride
[Co(NH[Co(NH33))55(ONO)]Cl(ONO)]Cl22
Pentaamminenitritocobalt(III)Pentaamminenitritocobalt(III)chloridechloride
Stereoisomerism 1
Geometric isomerism (cis-trans):Geometric isomerism (cis-trans):
Atoms or groups arranged differently spatially Atoms or groups arranged differently spatially relative to metal ionrelative to metal ion
Pt(NHPt(NH33))22ClCl22
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H3N
Co
H3N
NH3
NH3
Cl
Cl
H3N
Co
H3N
NH3
Cl
Cl
NH3
Cl
Cl
Co
Cl
Cl
Co
(a) (b)
Stereoisomerism 2Optical isomerismOptical isomerism: :
Have opposite effects on plane-polarized lightHave opposite effects on plane-polarized light(no superimposable mirror images)(no superimposable mirror images)
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Unpolarizedlight
Polarizingfilter
Polarizedlight
Tubecontainingsample
Rotatedpolarized light
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Left hand Right hand
Mirror imageof right hand
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N
N
N
N
N
NCo
N
N
N
N
N
NCo
Mirror imageof Isomer I
Isomer I Isomer II
N
N
N
N
N
NCo
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Cl
Cl
N
N
N
NCo
Cl
Cl
N
N
N
NCo
Cl
Cl
N
N
N
NCo
Cl
Cl
N
N
N
NCo
Cl
Cl
N
N
N
NCo
Isomer IIIsomer I
cistrans
Isomer II cannot besuperimposed exactlyon isomer I. They arenot identical structures.
The trans isomer andits mirror image areidentical. They are notisomers of each other.
Isomer II has the samestructure as the mirrorimage of isomer I.(b)(a)
Crystal Field Theory
Focus:Focus: energies of the energies of the dd orbitals orbitals
AssumptionsAssumptions
1.1. Ligands:Ligands: negative point negative point chargescharges
2.2. Metal-ligand bonding:Metal-ligand bonding: entirely ionicentirely ionic
strong-fieldstrong-field (low-spin): large splitting of (low-spin): large splitting of dd orbitals orbitals
weak-fieldweak-field (high-spin): small splitting of (high-spin): small splitting of dd orbitals orbitals
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eg(dz2, dx2 – y2)
t2g(dxz, dyz, dxy)
Free metal ion3d orbitalenergies
E
= crystal field splitting
High spin Low spin
[V(H2O)6]2+ [V(H2O)6]3+
[Cr(NH3)6]3+ [Cr(NH3)5Cl]2+s
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–
–
–
––
–– ––
–
dz2 dx2 – y2
dxy dyzdxz
(a) (b)
Tetrahedral Complexes
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E
Free metal ion Complex
dz2
dxy
dxz dyz
dx2 - y2
M z
(b)
Free metal ion Complex
dx2 - y2
dxydz2
dxz dyz
M
(a)
x
y
E
Square Planar & Linear Complexes
Approach along x-and y-axes Approach along z-axis
Hemoglobin & Oxyhemoglobin