Today’s(Topics!Coordination)Chemistry)II" "• Ligands(

• Naming(coordination(compounds(

• Valence(bond(theory(and(bonding(in(coordination(compounds(

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Related(Problems(from(Spring(2008(Final(Exam:(34(&(Spring(2009(Final(Exam:(33(

Corresponding(Connect(Problems:(Set(9:(8,(9,(10,(13 (

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(Figures(and(tables(taken(from(Chemistry,(4th(ed.(by(J.(McMurray(and(R.(C.(Fay,(PrenticeMHall,(2004.(All,materials,are,©,2012–2013,Lynmarie,A.,Posey,and,Michigan,State,University,unless,otherwise,noted;,all,rights,reserved.,

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Learning(Objectives((Lecture(24)" You(should:(

1. understand(what(linkage(isomerism(is(and(be(able(to(identify(ambidentate(ligands.(

2. be(able(classify(ligands(as(monodentate,(bidentate,(tridentate,(tetradentate,(or(hexadentate.(

3. know(how(to(name(coordination(compounds(and(be(able(to(write(formulas(for(coordination(compounds(based(on(names.(

4. be(prepared(to(apply(the(effective(atomic(number(rule(to(understand(bonding(in(coordination(compounds.(

5. be(able(to(apply(valence(bond(theory(to(predict(transition(metal(hybridization(and(geometries(in(coordination(compounds.(

6. understand(the(significance(of(the(spectrochemical(series(in(terms(of(how(it(applies(to(the(strength(of(ligand(bonding(and(the(splitting(of(transitionMmetal(d(orbitals.(

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( ( (3(

Linkage(Isomerism" "Some(ligands(have(more(than(one(atom(with(a(lone(pair(of(electrons(available(to(form(a(coordinate(bond(with(a(transition(metal.(The(compound(formed(and(its(properties(depend(on(which(atom(coordinates(to(the(metal.((

Ex:(NO!!((nitrite)(in(the(compounds([Co(NH3)5NO2]Cl2((pentaamminenitrocobalt(III)(chloride,(mustard(color)(and([Co(NH3)5ONO]Cl2(pentaamminenitritocobalt(III)(chloride,(dark(orange).((

When(ligands(can(coordinate(by(more(than(one(atom,(they(are(called(ambidentate.(Ex:(SCN:!((isothiocyanate,(coordinates(using(N)(vs.(: SCN!((thiocyanate,(coordinates(using(S)(

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(FigureMMcMurray(&(Fay)(

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( ( (4(

Ligands" "Ligands(are(classified(based(on(the(number(of(electron(pairs(with(which(they(coordinate(to(the(metal.(

Monodentate"• coordinate(through(a(single(electron(pair((FigureMMcMurray(&(Fay)(

(The(ligands(CN!((cyanideMcoordinates(using(C(vs.(isocyanideMcoordinates(using(N)(and(SCN!((thiocyanate(vs.(isothiocyanate)(are(ambidentate.(While(CO(has(two(available(pairs(of(electrons,(CO(bonds(preferentially(to(transition(metals(via(the(lone(pair(on(the(less(electronegative(C(atom.(

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( ( (5(

Bidentate"• coordinate(through(two(electron(pairs(on(different(donor(atoms((FigureMMcMurray(&(Fay)(

(( (

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( ( (6(

• The(polydentate(ligands(often(serve(as(chelating,agents(and(form(chelates((complexes(formed(by(a(polydentate(ligand(and(a(single(metal).(The(term(chelate(is(derived(from(the(Greek(word(“chele,”(which(means(claw.(

Note:(Some(ligands,(such(as(: SCN:!,(which(have(more(than(one(lone(pair(of(electrons(can(behave(as(bidentate(ligands;(however,(they(cannot(chelate(because(the(distance(between(the(two(donor(atoms(is(not(large(enough(to(permit(the(ligand(to(bond(to(two(coordination(sites(on(the(same(metal.(: SCN:!(can(only(act(as(a(bidentate(ligand(when(bridging(between(two(transitionMmetal(atoms.(

Tridentate"• coordinates(through(three(donor(atoms(

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Tetradentate"• coordinates(through(four(donor(atoms(

• interesting(tetradentate(ligands,(such(as(porphyrins,(are(macrocyclic(

When(the(porphyrin(coordinates(to(the(metal,(the(H(atoms(bonded(to(two(of(the(four(coordinating(N(atoms(are(lost.((FigureMMcMurray(&(Fay)(

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Hexadentate"• coordinates(through(six(donor(atoms((FigureMMcMurray(&(Fay)(

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Naming'Coordination'Compounds" "Rules"1. When(the(compound(is(a(salt,(name(the(cation(first.(

2. Name(the(ligands(in(alphabetical(order.(

3. If(the(ligand(is(an(anion,(change(the(ending(to(Mo((TableMMcMurray(&(Fay)(

–ite(to(–ito/(–ate(to(–ato/(–ide(to(–o(

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( ( (10(

4. If(the(ligand(is(neutral,(use(its(ordinary(name(except(for(

water(is(called(aqua(

ammonia(is(called(ammine(

carbon(monoxide(is(called(carbonyl(

5. Indicate(the(number(of(ligands(by(the(prefixes(

two:(di(or(bis(

three:(tri(or(tris(

four:(tetra(or(tetrakis(

five:(penta(or(pentakis(

six:(hexa(or(hexakis(The(second(prefix(given(is(used(when(confusion(would(result(from(using(the(simpler((first)(prefix.(When(the(prefixes(from(the(second(group(are(used,(the(name(of(the(ligand(is(enclosed(in(parentheses.(

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( ( (11(

6. If(the(complex(is(anionic,(add(the(suffix(Mate(to(the(metal.((TableMMcMurray(&(Fay)(

7. Denote(the(oxidation(state(of(the(metal(by(Roman(numerals(in(parentheses(following(the(name(of(the(metal.(

8. Waters(of(crystallization(•n(H2O(are(specified(at(the(end(of(the(name(with(the(appropriate(prefix(to(indicate(the(number(of(water(molecules(per(formula(unit(followed(by(hydrate.(

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( ( (12(

Example:)Naming)Coordination)Compounds" 1. Name(the(following(coordination(compounds:(

(a) Na2[Pt(CN)4](

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(b) K3[Fe(C2O4)3]•3H2O(

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(c) [Fe(OH)(H2O)5](NO3)2(

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(d) [Co(NH3)4(CH3NH2)2]Br3(

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2. Write(formulas(for(the(following(coordination(compounds:(

(a) hexaamminenickel(II)(sulfate(

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(b) sodium(tetrachlorocuprate(II)(

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( ( (13(

Bonding'in!Transition)Metal)Complexes" N."V."Sidgewick"and"Lowry’s"Effective"Atomic"Number"(EAN)"Rule"• application(of(Lewis’(ideas((octet(rule)(to(coordination(compounds(

• Since(ligands(are(Lewis(bases,(they(contribute(a(pair(of(electrons(for(each(bond(formed(with(the(transitionMmetal(ion.(Stable,coordination,compounds,are,formed,when,the,compound,achieves,a,nobleFgas,configuration,about,the,metal,ion,,giving,rise,to,the,effective,atomic,number,rule.(In(other(words,(when(the(number(of(electrons(in(the(transitionMmetal(ion(plus(the(number(contributed(by(the(ligands(adds(up(to(36((Kr),(54((Xe),(or(86((Rn),(the(compound(is(especially(stable.(

• most(useful(for(predicting(stable(organometallic(compounds(

• unfortunately,(many(exceptions(

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( ( (14(

Application*of*the$Effective(Atomic(Number(Rule" Coordination"Compounds:"Find(number(of(ligands(coordinated(with(the(transition(metal.(

Co(III)(+(NH3(

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Ag(I)(+(NH3(

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( ( (15(

Organometallic"Compounds"Find(the(oxidation(state(of(the(transition(metal(in(these(compounds(and(the(charge(on(the(coordination(complex.(

[Ni(CO)4](

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[Mn(CO)5](

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( ( (16(

Valence&Bond&Theory&&&Transition!metal%Complexes" "Orbitals(on(the(transition(metal(that(accept(electrons(from(the(ligands(are(hybridized.(

Hybridization( #,of,Charge,Clouds( Shape(

sp( 2( linear(

sp2( 3( trigonal(planar(

sp3( 4( tetrahedral(

dsp2( 4( square(planar(

dsp3( 5( trigonal(bipyramidal(or(square(pyramid(

d2sp3( 6( octahedral(

d4sp( 6( trigonal(prism(

d3sp3( 7( capped(ocatahedral(

d5p3( 8( square(antiprism(

d5sp3( 9( tricapped(trigonal(prism(

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( ( (17(

Application*of*Valence*Bond*Theory" "Apply(valence(bond(theory(to(predict(hybridization(and(geometries(for(the(following(coordination(complexes:(

Cr(CO)6((diamagneticMall(electrons(on(metal(paired)(

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[NiCl!]!!((paramagneticMunpaired(electrons(on(metal)((

(( (

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( ( (18(

[Ni(CN)!]!!((diamagnetic)((

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[CoF!]!!((paramagnetic,(highMspin(or(spinMfree)((

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( ( (19(

[Co(NH!)!]!!((diamagnetic,(lowMspin(or(spinMpaired)((

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Note:(Pairing(of(electrons(requires(energy.(In(the(diamagnetic(compounds,(the(pairing(energy(is(supplied(by(the(energy(released(in(bond(formation.(Because(NH!(and(CN!(form(stronger(bonds(than(!!(and(!"!(there(is(enough(energy(released(to(supply(the(energy(for(electron(pairing.(

(

( ( (20(

Strength(of(Bonds(&(the$Spectrochemical-Series" "Overview"of"the"strength"of"bonds"formed"by"ligands"based"on"donor"atom"( strongest !!!!!! > ! > ! > X! halide!ion !!!!!(weakest)(

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Spectrochemical"Series"• based(on(measurements(of(the(absorption(spectra(of(coordination(compounds.(Stronger(ligands(cause(a(larger(splitting(of(the(dMorbitals.(

• strength(of(ligand(determined(from(spectrochemical(series(correlates(with(the(strength(of(bonds(formed(by(the(ligand(with(transition(metals(

(strongFfield,ligands)(CO(>(CN!(>(en(>(NH3(>(|(H2O(>(C!O!!!(>(OH!(>(F!(>(Cl!(>((Br!(>(I!((weakFfield,ligands)(