11

The chemistry of the The chemistry of the transition metalstransition metals

Chapter 22Chapter 22

22

Electron configurationsElectron configurations

• Let’s write the 3d metals’ and their Let’s write the 3d metals’ and their ions’ eions’ e-- configurations configurations

• Sc, V, Cr, Fe, Ni, Cu, ZnSc, V, Cr, Fe, Ni, Cu, Zn

33

Atomic sizeAtomic size

• Atomic size decreases across Atomic size decreases across period & increases down a period & increases down a columncolumn

• Not a big change to the radii Not a big change to the radii across the rowacross the row– Due to eDue to e--’s being stable in ’s being stable in

outermost orbital (4s) while outermost orbital (4s) while adding to 3dadding to 3d

• But 3But 3rdrd row roughly same as 2 row roughly same as 2ndnd, , not largernot larger– Due to eDue to e--’s going into 4f ’s going into 4f – The f-subshell is ineffective The f-subshell is ineffective

at shielding outer eat shielding outer e--’s from ’s from nuclear chargenuclear charge• Outer eOuter e--’s held more ’s held more

tightly by nucleustightly by nucleus– Called Called lanthanide lanthanide

contractioncontraction

44

Ionization energyIonization energy

• Increase across rowIncrease across row

• But increase smaller But increase smaller than for main-group than for main-group elementselements

• Also, 3Also, 3rdrd transition row transition row has higher ionization E has higher ionization E (generally) than first 2 (generally) than first 2 rowsrows– Runs counter to main-Runs counter to main-

group elementsgroup elements• Due to outer eDue to outer e--’s being ’s being

held more tightlyheld more tightly

55

Electronegativity Electronegativity

• Increase across row, same as main-groupIncrease across row, same as main-group

• However, increase going down a groupHowever, increase going down a group– Conversely, main-group decrease going down a Conversely, main-group decrease going down a

groupgroup

• 11stst & 2 & 2ndnd rows different, but 2 rows different, but 2ndnd & 3 & 3rdrd same same– Due to small change in atomic size going down Due to small change in atomic size going down

group w/large increase in nuclear chargegroup w/large increase in nuclear charge

• Au = 2.4 !Au = 2.4 !

• AuAu-- found to exist! found to exist!

66

Oxidation statesOxidation states

• VariableVariable– Up to +8 in Os & RuUp to +8 in Os & Ru

• Re has widest range: -3 Re has widest range: -3 +7 ! +7 !

77

Coordination compoundsCoordination compounds

• Can form Can form complex ionscomplex ions– Ion containing central metal ion bound to Ion containing central metal ion bound to

one or more one or more ligandsligands•Lewis base (or eLewis base (or e-- donor) that forms bond donor) that forms bond

w/metalw/metal

• When complex ion combines When complex ion combines w/counter-ions (non-ligands) they w/counter-ions (non-ligands) they yield a neutral compoundyield a neutral compound– Coordination compoundCoordination compound

88

Its historyIts history

• Alfred WernerAlfred Werner

• Central metal ion has 2 types of interactions:Central metal ion has 2 types of interactions:

• 1. 1. primary valenceprimary valence: oxidation state on : oxidation state on central metal atomcentral metal atom

• 2. 2. secondary valencesecondary valence: # of molecules/ions : # of molecules/ions bound to metal atom, called bound to metal atom, called coordination #coordination #..

• Ex: CoClEx: CoCl33 6NH 6NH33 has primary valence of 3 and has primary valence of 3 and coordination # of 6coordination # of 6

99

More More

• Can think of metal-Can think of metal-ligand complex as ligand complex as Lewis acid/base Lewis acid/base adductadduct– Since ligand Since ligand

donates edonates e- - pair to pair to empty orbital on empty orbital on metalmetal• Called Called coordinate coordinate

covalent bondcovalent bond

1010

More on ligandsMore on ligands

• Those that donate one eThose that donate one e-- pair = pair = monodentatemonodentate (why is it CO and not OC?) (why is it CO and not OC?)

• Those that donate 2 = Those that donate 2 = bidentatebidentate• More than 2 = More than 2 = polydentatepolydentate

• Latter two called Latter two called chelateschelates• Coordinating ligand = Coordinating ligand = chelating agentchelating agent

1111

Naming coordination Naming coordination compoundscompounds

1.1. Name ligandsName ligands– Neutral ligands named as molecules Neutral ligands named as molecules

except for Hexcept for H22O (aqua), NHO (aqua), NH33 (ammine), (ammine), and CO (carbonyl)and CO (carbonyl)

– Anionic ligands have suffix changes:Anionic ligands have suffix changes:• -ide -ide -o -o fluoride fluoride fluoro fluoro• -ate -ate -ato -ato sulfate sulfate sulfato sulfato• -ite -ite -ito -ito nitrite nitrite nitrito nitrito

1212

Naming coordination Naming coordination compoundscompounds

2.2. List names of ligands in alphabetical List names of ligands in alphabetical order before name of metal cationorder before name of metal cation

– For example: ammine comes before bromoFor example: ammine comes before bromo

3.3. Use prefix to indicate # of ligandsUse prefix to indicate # of ligands– 2 2 di di diamminediammine– 3 3 tri tri triiodotriiodo– 4 4 tetra tetra tetranitritotetranitrito– 5 5 penta penta– 6 6 hexa hexa

1313

Naming coordination Naming coordination compoundscompounds

– If the ligand name already has a number If the ligand name already has a number prefix, put () around ligandprefix, put () around ligand

– 2 2 bis bis bis(ethylenediamine)bis(ethylenediamine)– 3 3 tris tris tris(edta)tris(edta)– 4 4 tetrakis tetrakis– Prefixes don’t affect order in which Prefixes don’t affect order in which

ligands listedligands listed

1414

Naming coordination Naming coordination compoundscompounds

4.4. Name metalName metal– When complex ion is When complex ion is cationcation, use name of , use name of

metal followed by oxidiation state metal followed by oxidiation state w/Roman numeralw/Roman numeral• PtPt2+2+ = platinum (II) = platinum (II)

– If complex ion If complex ion anionicanionic, drop ending of , drop ending of metalmetal• Add –ate followed by oxid. state w/Roman Add –ate followed by oxid. state w/Roman

numeralnumeral– PtPt2+2+ = platinate(II) = platinate(II)

1515

Naming coordination Naming coordination compoundscompounds5.5. Write entire name by listing ligands first then Write entire name by listing ligands first then

metalmetal– Chemical formula: Chemical formula:

• Symbol of metal first, then neutral molecules and anions Symbol of metal first, then neutral molecules and anions last (all one word!)last (all one word!)– Hexaamminecobalt(III) ion= [Co(NHHexaamminecobalt(III) ion= [Co(NH33))66]]3+3+

– Diamminetetrachloroplatinate(II) ion = [Pt(NHDiamminetetrachloroplatinate(II) ion = [Pt(NH33))22ClCl44]]2-2-

– If more than one anion or neutral molecule in ligand, list If more than one anion or neutral molecule in ligand, list in alphabetical order in alphabetical order based on chemical symbolbased on chemical symbol

• [Mn(CO)(NH[Mn(CO)(NH33))55]SO]SO4 4 is correctis correct• [Mn(NH[Mn(NH33))55(CO)]SO(CO)]SO44 is is incorrectincorrect

– SOSO4 4 is called a “counter-ion”is called a “counter-ion” There should be a space between the complex ion and the There should be a space between the complex ion and the

counter-ioncounter-ion

1616

Practice namingPractice naming

• [Cr(H[Cr(H22O)O)55Cl]ClCl]Cl22

• KK33[Fe(CN)[Fe(CN)66]]

• NaNa22[PtCl[PtCl44]]

• [Mn(CO)(NH[Mn(CO)(NH33))55]SO]SO44

1717

Practice writing chemical Practice writing chemical formulaeformulae

• Tetraaquaplatinum(II) Tetraaquaplatinum(II) hexachloroplatinate(IV)hexachloroplatinate(IV)

• Ammonium Ammonium diaquatetrabromovanadate(III)diaquatetrabromovanadate(III)

• Tris(ethylenediamine)cobalt(III) Tris(ethylenediamine)cobalt(III) trioxalatoferrate(III)trioxalatoferrate(III)

1818

Structure and isomerizationStructure and isomerization

• 3 categories3 categories1.1. Structural isomers: atoms connected in Structural isomers: atoms connected in

different waysdifferent ways1.1. Coordination isomersCoordination isomers2.2. Linkage isomersLinkage isomers

2.2. Geometric isomers: ligands have different Geometric isomers: ligands have different spatial arrangementspatial arrangement1.1. Cis-trans isomersCis-trans isomers2.2. Octahedral complex isomersOctahedral complex isomers

3.3. Optical isomers: nonsuperimposable mirror-Optical isomers: nonsuperimposable mirror-images (enantiomers)images (enantiomers)

1919

Structural isomerism: Structural isomerism: coordination isomerscoordination isomers

• Coordination isomersCoordination isomers– Coordination ligand exchanges places Coordination ligand exchanges places

w/uncoordinated counter-ionw/uncoordinated counter-ion

• Ex: [Co(NHEx: [Co(NH33))55Br]Cl vs. [Co(NHBr]Cl vs. [Co(NH33))55Cl]BrCl]Br

2020

Structural isomerism: linkage Structural isomerism: linkage isomersisomers

• Either one of atoms in NOEither one of atoms in NO22-- can bond can bond

to metalto metal– When O, nitrito: ONOWhen O, nitrito: ONO--

– When N, nitro: NOWhen N, nitro: NO22--

• Different color compounds (page Different color compounds (page 1089)1089)

2121

Geometric isomerism: cis-trans Geometric isomerism: cis-trans isomersisomers

• Occurs in sq-planar: MAOccurs in sq-planar: MA22BB22

• And octahedral complexes: MAAnd octahedral complexes: MA44BB22

2222

Geometric isomerism: Geometric isomerism: octahedral complex isomersoctahedral complex isomers

• MXMX33YY33

• Fac (facial) isomerFac (facial) isomer– Three identical ligands at corners of a Three identical ligands at corners of a

triangular triangular faceface of octahedron of octahedron

• Mer (meridian) isomerMer (meridian) isomer– Three identical ligands at corners of a Three identical ligands at corners of a

triangular triangular meridianmeridian (inside octahedron) (inside octahedron)

2323

Optical isomerismOptical isomerism

• Nonsuperimposable mirror-imagesNonsuperimposable mirror-images– EnantiomersEnantiomers

• Have chirality/chiral centerHave chirality/chiral center

• Rotation of plane-polarized light in Rotation of plane-polarized light in opposite directionsopposite directions

2424

Geometries Geometries

• Depend in part on coordination #Depend in part on coordination #

• Coordination #Coordination # ShapeShape ExampleExample

• 22 linear linear [Ag(NH[Ag(NH33))22]]++

• 44 dd88 sq planar sq planar [PdCl[PdCl44]]2-2-

• 44 dd1010 tetrahedral [Zn(NH tetrahedral [Zn(NH33))44]]2+2+

• 66 octahedral [Fe(H octahedral [Fe(H22O)O)66]]3+3+

2525

Bonding in coordination Bonding in coordination compoundscompounds

• Valence Bond Theory: hybridization Valence Bond Theory: hybridization of orbitals (CHEM&141)of orbitals (CHEM&141)

• Filled orbital on ligandFilled orbital on ligand

• Empty orbital on metal cation Empty orbital on metal cation – Lead to hybridized orbitalsLead to hybridized orbitals

2626

Hybridizations of complex Hybridizations of complex ionsions

Geometry Geometry HybridizationHybridization

• LinearLinear spsp

• TetrahedralTetrahedral spsp33

• Square planarSquare planar dspdsp22

• OctahedralOctahedral dd22spsp33

2727

Crystal Field TheoryCrystal Field Theory

• VB theory can’t explain color and VB theory can’t explain color and magnetism of coordination compoundsmagnetism of coordination compounds

• Basically, complex ions form due to Basically, complex ions form due to attractions between eattractions between e-- on ligands and on ligands and positive charge on metal ionpositive charge on metal ion– Yet, eYet, e-- on ligands repel e on ligands repel e-- in in unhybridized unhybridized metal metal

d-orbitalsd-orbitals

• Crystal Field Theory (CFT) focuses on Crystal Field Theory (CFT) focuses on these repulsionsthese repulsions

2828

Ligands attack on x, y, z Ligands attack on x, y, z axesaxes

• Notice how ligands interact most strongly with top two orbitals’ lobesNotice how ligands interact most strongly with top two orbitals’ lobes– Greater interactionsGreater interactions

• Higher repulsionsHigher repulsions

• In below three, orbitals lie between axes & have nodes directly on axesIn below three, orbitals lie between axes & have nodes directly on axes– Less interactionsLess interactions

• Lower repulsionsLower repulsions

2929

More…More…

• D-orbitals end up being split into low- and D-orbitals end up being split into low- and high-E orbitalshigh-E orbitals– Based on spatial arrangement of ligandsBased on spatial arrangement of ligands

• High-E orbitals are top two (see previous figure)High-E orbitals are top two (see previous figure)• Low-E orbitals are bottomw three (see previous Low-E orbitals are bottomw three (see previous

figure)figure)

• Diff in E between split d-orbitalsDiff in E between split d-orbitals– Crystal field splitting ECrystal field splitting E– = = ∆∆

• Magnitude of ∆ depends on particular complex Magnitude of ∆ depends on particular complex (mostly its ligands)(mostly its ligands)

3030

Octahedral geometryOctahedral geometry

3131

Tetrahedral Tetrahedral

• Based on how ligands interact with Based on how ligands interact with orbital lobesorbital lobes

3232

Square planarSquare planar

• Again, based on how ligands overlap Again, based on how ligands overlap with orbital lobeswith orbital lobes

3333

Comparing all 3 ligand Comparing all 3 ligand geometriesgeometries

3434

Calculate Calculate ∆ (crystal field ∆ (crystal field splitting E)splitting E)

• Using EUsing Ephotonphoton = h = h = hc/ = hc/ = = ∆∆

• [Ti(H[Ti(H22O)O)66]]3+3+ has max abs @ 498 nm has max abs @ 498 nm

• What is the CFSE in kJ/mol?What is the CFSE in kJ/mol?

• Calculate it!Calculate it!

3535

Solution Solution

photon

34 8

9

-19 -19 -22

-22 23

hcE = h = =

m(6.626 10 J s)(3.00 10 )hc s = 498 10 m

3.99 10 J = 3.99 10 J/ion = 3.99 10 kJ/ion

kJ ions kJ3.99 10 6.022 10 240ion mol mol

3636

Magnitude of CFSEMagnitude of CFSE

• Depends largely on ligands involvedDepends largely on ligands involved– Spectroscopic studies of various ligands Spectroscopic studies of various ligands

attached to same metal attached to same metal •Yield Yield Spectrochemical seriesSpectrochemical series

– Arranged from ligands that result in Arranged from ligands that result in largest ∆ to smallestlargest ∆ to smallest

3737

Spectrochemical seriesSpectrochemical series

• CNCN-- > NO > NO22-- > en > NH > en > NH33 > (typically > (typically

strong-field ligands)strong-field ligands)

• HH22O > OHO > OH-- > F > F-- > Cl > Cl--> Br> Br--> I> I-- (typically weak-field ligands)(typically weak-field ligands)

• Large ∆ = strong-field ligandsLarge ∆ = strong-field ligands

• Small ∆ = weak-field ligandsSmall ∆ = weak-field ligands

3838

More More

• Also, as oxidation state increases, so Also, as oxidation state increases, so does ∆does ∆– Draws ligands closer to metal, increases Draws ligands closer to metal, increases

nodal repulsionsnodal repulsions

3939

Magnetic propertiesMagnetic properties

• Magnitude of Magnitude of ∆ ∆ determines d-orbital determines d-orbital occupancy and # of occupancy and # of unpaired eunpaired e--’s’s

• Large ∆ = strong-Large ∆ = strong-field ligands: field ligands: – Low-spin complexesLow-spin complexes

• Small ∆ = weak-field Small ∆ = weak-field ligands:ligands:– High-spin High-spin

complexescomplexes

4040

Magnetic propertiesMagnetic properties

• Low-spin complexes tend to be diamagneticLow-spin complexes tend to be diamagnetic• High-spin complexes tend to be paramagneticHigh-spin complexes tend to be paramagnetic

• dd11, d, d22, d, d33, d, d88, d, d99, and d, and d1010 do not rely on ligand splitting do not rely on ligand splitting strengthstrength

• Why?Why?

• Practice: Practice: • How many unpaired eHow many unpaired e--’s would one expect for ’s would one expect for

[FeCl[FeCl66]]3-3-??• How many unpaired eHow many unpaired e--’s would one expect for ’s would one expect for

[Co(CN)[Co(CN)66]]4-4-??

4141

Color of complex ionsColor of complex ions

• The color wheel: absorption of color The color wheel: absorption of color appears as complementary colorappears as complementary color

4242

Color of complex ionsColor of complex ions

• Color Color inin causes lower d-orbital e causes lower d-orbital e-- to to go up to higher d-orbital statego up to higher d-orbital state– Specific wavelength of light kicked outSpecific wavelength of light kicked out

•The complement of color absorbedThe complement of color absorbed

• Colorless complexes are either dColorless complexes are either d00 or or dd1010

– Don’t have d-orbital eDon’t have d-orbital e--’s to move up’s to move up

4343

Problem Problem

• Two ligands form complexes with Two ligands form complexes with same metal ion. The first ligand, A, same metal ion. The first ligand, A, complexes a red soln, while the complexes a red soln, while the second ligand, B, complexes a yellow second ligand, B, complexes a yellow soln. soln.

• Which ligand produces the larger Which ligand produces the larger ∆?∆?