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OrganometallicOrganometallic ChemistryChemistry C21J,C21J, 44 LecturesLectures MohammedMohammed Bakir,Bakir, OfficeOffice #8#8  IntroductionIntroduction  BondingBonding  ππ--acidsacids  MetalMetal CarbonylCarbonyl CompoundsCompounds  OrganometallicOrganometallic CompoundsCompounds  PreparationPreparation andand reactionsreactions ofof organometallicorganometallic compounds.compounds.  Reference:Reference: ChaptersChapters 1010  Textbook:Textbook: B.B. Douglas,Douglas, D.D. H.H. McDaniel,McDaniel, && J.J. J.J. Alexander,Alexander, ConceptsConcepts && ModelsModels ofof InorganicInorganic ,Chemistry, 22nd edition,edition, Wiley,Wiley, NewNew YorkYork WhatWhat isis Organometallic?Organometallic?  OrganometallicOrganometallic isis thethe chemistrychemistry ofof MM--CC bondbond formationformation andand reactivity.reactivity.  AlthoughAlthough ZnZn--alkylsalkyls e.g.e.g. Zn(CHZn(CH3))2 werewere preparedprepared byby FranklandFrankland inin 1827,1827, organometallicorganometallic chemistrychemistry hashas undergoneundergone aa renaissancerenaissance inin thethe lastlast 5050 yearsyears duedue toto thethe importanceimportance ofof manymany organometallicorganometallic compoundscompounds inin manymany importantimportant chemicalchemical processesprocesses thatthat includeinclude ,catalysis, sensorssensors andand others.others. MetalMetal CarbonylCarbonyl CompoundsCompounds

 ππ--acidacid .Ligands.  WhatWhat areare ππ--acidacid ligands?ligands?  LigandsLigands withwith aa pairpair ofof electronselectrons availableavailable forfor donationdonation toto thethe metalmetal centercenter andand vacantvacant orbitalorbital p,p, ππ*,*, oror dd availableavailable forfor acceptingaccepting electronelectron densitydensity fromfrom thethe .metal.  e.g.e.g. CO,CO, andand PPhPPh3 wherewhere PhPh == CC6HH5.. σ∗ π∗ 2s σ nb

2p π

σ 2s σ nb 2s σ∗ 1s 1s C 1s σ MO E-L Diagram for CO 1s O M.O. Diagram for CO σ∗ Empty π∗ LUMO σ Full nb © ΗΟΜΟ

π

σ σ nb (O)

σ∗ 1s

σ 1s Sketches of the M.O. for CO

+ - π * π * C O ( x ) or y ┴ - +

+ (π ) or π ┴ C O x y -

--C + O σ

+ C - - O + σ (σnb) ( nb) C o MetalMetal CarbonylCarbonyl CompoundsCompounds

 RequirementsRequirements  MetalMetal shouldshould bebe inin lowlow oxidationoxidation statestate 0,0, 11 oror 2;2; i.e.i.e. electronelectron rich.rich.  LigandLigand shouldshould aa ππ--acceptoracceptor ,ligand, i.e.i.e. σσ-- donordonor oror electronelectron acceptoracceptor throughthrough emptyempty p,p, ππ** oror dd orbitals.orbitals. BondingBonding

 SequenceSequence ofof bondingbonding  AA pairpair ofof electronselectrons isis donateddonated fromfrom thethe ππ-- acidacid toto thethe metalmetal centercenter  TheThe excessexcess electronelectron densitydensity aroundaround thethe metalmetal centercenter isis donateddonated backback toto thethe emptyempty orbitalsorbitals onon thethe ligand.ligand. SynergicSynergic BondingBonding

- ++ - M ++CC- OO + M + - - +

Ligand→Metal σ bonding Metal→ ligand π-back bonding (one of a mutual ┴ is shown)

The back donation to the π* orbitals should strongly affect the bond order of C≡O. IR data can be correlated C-O bond order. ππ--acidacid LigandsLigands

 ExamplesExamples ofof 22--e’se’s donorsdonors && havehave emptyempty orbitalsorbitals ofof ππ--symmetrysymmetry includeinclude isocyanidesisocyanides CNRCNR andand

carbenescarbenes :C(X)(Y):C(X)(Y) havehave emptyempty 2p2pz orbital.orbital.  ππ--acidsacids withoutwithout C,C, NONO+ (isoelectronic(isoelectronic withwith CO),CO),

::phosphines PRPR3 ,, arsinesarsines AsRAsR3,, stibenesstibenes SbRSbR3,, bipyridinebipyridine (bipy)(bipy) andand phenanthrolinephenanthroline (Phen)(Phen)  BipyBipy && phenphen possesspossess ππ** orbitalorbital ┴┴ molecularmolecular plane.plane. TheThe EffectiveEffective AtomicAtomic ## RuleRule oror thethe 18e18e-- RuleRule

 TheThe rulerule predictspredicts thethe stabilitystability ofof organometallicorganometallic compoundscompounds andand simplysimply statesstates thatthat stabilitystability isis attainedattained oror gainedgained whenwhen allall ofof thethe bondingbonding andand nonnon--bondingbonding orbitalsorbitals areare occupied.occupied.  TheThe rulerule isis usefuluseful inin predictingpredicting thethe stoichiometrystoichiometry ofof stablestable speciesspecies andand alsoalso reactivityreactivity patterns.patterns.  - σσ COCO donatesdonates 2e2e toto thethe systemsystem fromfrom thethe nb orbitalsorbitals onon C.C. MetalMetal CarbonylCarbonyl CompoundsCompounds

 MM--CC≡≡OO’’ss areare importantimportant forfor theirtheir richrich propertiesproperties andand applicationsapplications inin manymany industrialindustrial processesprocesses thatthat includeinclude catalysis,catalysis, medicalmedical diagnosticsdiagnostics andand molecularmolecular sensors.sensors.  MondMond Pprocess,Pprocess, 18901890  0 Ni(CO)Ni(CO)4 →→ NiNi ++ 4CO4CO  0 Fe(CO)Fe(CO)5 →→ FeFe ++ 5CO5CO MononuclearMononuclear MetalMetal CarbonylsCarbonyls  M(CO)xM(CO)x ––hydrophobichydrophobic (lacking(lacking affinityaffinity forfor water,water, i.e.i.e. waterwater insoluble),insoluble), volatile,volatile, solublesoluble inin nonnon--polarpolar solvents.solvents.  e.g.e.g. V(CO)V(CO)6 OOh

Cr(CO)Cr(CO)6 OOh

Mo(CO)Mo(CO)6 OOh

W(CO)W(CO)6 OOh

Fe(CO)Fe(CO)5 tbptbp

Ru(CO)Ru(CO)5 tbptbp

Ni(CO)Ni(CO)4 TTd MononuclearMononuclear MetalMetal CarbonylsCarbonyls

 StableStable homoleptichomoleptic carbonylscarbonyls ofof transitiontransition metalmetal elementselements cancan bebe predictedpredicted usingusing thethe EANEAN rule.rule.  VanadiumVanadium-- 23VV 1s1s2 2s2s22p2p6 3s3s2spsp63d3d3 4s4s2  VV0 55 ee-  6xCO6xCO 1212 ee-  1x1e1x1e- 1e1e-  TotalTotal 18e18e-

 - StableStable V(CO)V(CO)6 MetalMetal carbonylscarbonyls

 M = Cr, Mo, & W – 3d4 4s2  M0 = 6 e-  6xCO = 12 e-  Total = 18 e-  Stable M(CO)6 –stable

Mn, Tc, Re M0 7 ∴ Need 11 e- ∴ Possibilities ∴ - 1. M(CO)5 ∴ + 2. M(CO)6 ∴ 5 3. (CO)5M-M(CO) Metal metal bond donates 1e to each metal MnMn22(CO)(CO)1010

Mn - Mn

CO CoCo22(CO)(CO)88 CO CO CO All C≡O terminal

Bridging C=O) OC Co - Co CO CO C=O CO CO C=O CO OC Co - Co CO CO CO CO MetalMetal CarbonylsCarbonyls O ≡ ≡ ≡ ≡ C C=O

M M M M C C=O ≡ ≡ ≡ ≡ O

I.R. ν(C≡O) ~ 2150 -1850 cm-1 ν(C=O) -1850-1750 cm-1 ν(C-O) ~ <1600 cm-1 fac-Re(CO)3(dpk.oxime)Cl and fac-Re(CO)3(dpk)Cl

a

b

3400 3000 2600 2200 1800 1400 1000 600

Wavenumber, cm-1 MM22(CO)(CO)99

ν h , CH3COOH  Fe(CO)Fe(CO)5 FeFe2(CO)(CO)9

33--bridgingbridging CO’sCO’s (D(D3d))

hν, heptane, -40  M(CO)M(CO)5 MM2(CO)(CO)9 11--bridgingbridging CO’sCO’s M=M= Ru,Ru, OsOs MM33(CO)(CO)1212

 HigherHigher nuclearitynuclearity ∆  3M(CO)3M(CO)5 MM3(CO)(CO)12  MM == Fe,Fe, Ru,Ru, OsOs  33 MM == 2424 ee-  1212 COCO == 2424 ee-  NeedNeed 3x183x18 == 54e54e- forfor EANEAN  6e6e-- short,short, thenthen needneed 33 (M(M--M)M) bondsbonds MM44(CO)(CO)1212

M(CO)  4xM4xM == 3636 ee- 3  1212 COCO == 2424 ee- (CO) M M(CO)  TotalTotal == 6060 ee- 3 3  NeedNeed 4x184x18 == 7272 ee- M(CO)3  ∴∴ needneed 6(M6(M--M)M) bondsbonds

M(CO)3

= bridging CO (CO)2M M(CO)2

M(CO)2 RhRh66(CO)(CO)1616

 6xRh6xRh == 5454  16xCO16xCO == 3232  TotalTotal 8686

 6x186x18 == 108,108, thenthen needneed 2222 electrons,electrons, i.e.i.e. 1111 MM--MM bondsbonds PreparationPreparation ofof metalmetal carbonylcarbonyl CompoundsCompounds

 TwoTwo proceduresprocedures areare usedused  DirectDirect reactionreaction ofof aa metalmetal withwith COCO

e.g.e.g. Fe(CO)Fe(CO)5 andand Ni(CO)Ni(CO)4..

FeFe ++ xs.xs. COCO→→ Fe(CO)Fe(CO)5

NiNi ++ xs.xs. COCO →→ Ni(CO)Ni(CO)4 NoteNote onlyonly NiNi && FeFe areare preparedprepared thisthis way,way, xs.xs. ≡≡ excess.excess.  ReductiveReductive CarbonylationCarbonylation ofof metalmetal saltssalts usingusing aa reductingreducting agentagent oror COCO asas aa reducingreducing agent.agent. e.g.e.g. ReductiveReductive CarbonylationCarbonylation

 2Co(H2Co(H2O)O)4(O(O2CCHCCH3))2 ++ 88 (CH(CH3CO)CO)2OO ++ 88 COCO ++ 2H2H2 →→ CoCo2(CO)(CO)8 ++ 20CH20CH3COCO2HH

HH2 isis thethe reducingreducing agentagent  CoCOCoCO3 ++ HH2 ++ 88 COCO →→ CoCo2 (CO)(CO)8 ++ 2CO2CO2 ++ 2H2H2OO

HH2 isis thethe reducingreducing agentagent  CrClCrCl3 ++ AlAl ++ 66 COCO →→ CrCr (CO)(CO)6 AlAl isis thethe reducingreducing agentagent ∆  VClVCl3 ++ Na(xs)Na(xs) ++ COCO →→ Na[VNa[V (CO)(CO)6]]

 ReRe2OO7 ++ 1717 COCO →→ ReRe2 (CO)(CO)10 ++ 77 COCO2 COCO isis thethe reducingreducing agentagent PolynuclearPolynuclear CarbonylsCarbonyls

 HigherHigher carbonylscarbonyls cancan bebe preparedprepared fromfrom thethe thermolysisthermolysis oror photolysisphotolysis ofof lowerlower carbonylscarbonyls  3OsO3OsO4 ++ CO(xs)CO(xs) →→ OsOs3(CO)(CO)12 ++ 1212 COCO2

ν ∆  h 3Os(CO)3Os(CO)5 →→ OsOs3 (CO)(CO)12

∆  2Fe(CO)2Fe(CO)5 →→ FeFe2(CO)(CO)9 SubstitutedSubstituted CarbonylsCarbonyls && CarbonylateCarbonylate AnionsAnions

 TheThe carbonylcarbonyl groupgroup inin metalmetal carbonylscarbonyls areare labilelabile andand cancan bebe replacedreplaced withwith ofof otherother ligands.ligands.  TheThe EANEAN rolerole cancan bebe usedused toto predictpredict thethe stabilitystability ofof thethe substitutionsubstitution product.product.  e.g.e.g.  Cr(CO)Cr(CO)6 ++ CNRCNR →→ Cr(CO)Cr(CO)5(CNPh)(CNPh) ++ COCO  IrIr4(CO)(CO)12 ++ 22 PPhPPh3 →→ IrIr4(CO)(CO)10(PPh(PPh3))2 ++ 22 COCO  - - Mo(CO)Mo(CO)6 ++ BrBr →→ MoMo(CO)(CO)5BrBr ++ COCO LewisLewis BasesBases && ## ofof valencevalence e’se’s

 HH-,, XX-,, NCSNCS-,, CNCN- wherewhere XX == halidehalide == 2e2e- donordonor  + CO,CO, CNR,CNR, NONO ,, PRPR3,, P(OR)P(OR)3,, AsRAsR3,, NRNR3,, SbRSbR3,, SRSR2,, :CXY:CXY = 2 e- donor ligands  RR-,, C(O)RC(O)R-,, ArAr- == 2e2e- donordonor ligandsligands  NONO == 3e3e- donordonor LigandLigand MetalMetal CarbonylsCarbonyls ReactionsReactions 11 1. Direct Substitution  2 e- ≡≡ 1 CO  e.g.

 Cr(CO)6 + CNPh → Cr(CO)5(CNPh) + CO  Ir4(CO)12 + 2 PPh3 → Ir4(CO)10(PPh3)2 + 2 CO  - - Mo(CO)6 + Br → Mo(CO)5Br + CO

:CNR P :

Triphenylphosphine Isonitrile, R = Aryl or alkyl

PPh3 MetalMetal CarbonylCarbonyl ReactionsReactions 22

2.2. OxidationOxidation 0 I MnMn 2(CO)(CO)10 ++ ClCl2 →→ MnMn (CO)(CO)5ClCl 0 II FeFe (CO)(CO)5 ++ BrBr2 →→ FeFe (CO)(CO)4BrBr2

0 + - CoCo 2(CO)(CO)8 ++ HH2 →→ HH [[Co(CO)Co(CO)4]] SubstitutionSubstitution ReactionsReactions 33

3.3. RearrangementsRearrangements ~90º C µµ 2RhCl2RhCl3 ++ 44 COCO →→ [Rh(CO)[Rh(CO)2(( --Cl)]Cl)]2 ++ 2Cl2Cl2

OCOC Cl:Cl: COCO RhRh RhRh OCOC :Cl:Cl COCO

BridgingBridging chloridechloride inin thisthis casecase isis 33 ee- donor,donor, explain?explain? AndAnd predictpredict ifif EANEAN isis satisfied!satisfied! ReactivityReactivity ofof OrganometallicsOrganometallics

∆, -CO  2Mn(CO)2Mn(CO) ClCl WW MnMn (CO)(CO) ((µµ--BrBr )) 5 +CO, pressure 2 8 2

 µµ ReRe2(CO)(CO)10 ++ ClCl2 →→ ReRe2(CO)(CO)8(( --ClCl2))

 µµ [Rh(CO)[Rh(CO)2(( --Cl)]Cl)] ++ 22 PPhPPh3 →→

transtrans--Rh(PPhRh(PPh3))2(CO)Cl(CO)Cl ++ COCO CarbonylateCarbonylate AnionsAnions

 SynthesisSynthesis  ReactionReaction ofof metalmetal carbonylscarbonyls withwith base.base.  e.g.e.g. - - 1313MnMn2(CO)(CO)10 ++ 4040 OHOH →→ Mn(CO)Mn(CO)5 ++ 22 2+ MnMn ++ 2020 HH2OO - 2- 2- FeFe2(CO)(CO)9 ++ 44 OHOH →→ FeFe2(CO)(CO)8 ++ COCO3 ++ 2020 HH2OO I + - CoCo2(CO)(CO)8 ++ 55 RNCRNC →→ [Co[Co (CNR)(CNR)5]] [Co[Co I - (CNR)(CNR)4]] ++ 4CO4CO Reaction of Metal Carbonyls with a reducing agent

NH3(l)  FeFe(CO)(CO)5 ++ 22 NaNa →→ NaNa2Fe(CO)Fe(CO)4 ++ COCO

THF  CrCr(CO)(CO)6 ++ Na/HgNa/Hg →→ NaNa2[Cr(CO)[Cr(CO)5]] ++ COCO

NH3(l)  CrCr(CO)(CO)6 ++ NaBHNaBH4 →→ NaNa2[Cr(CO)[Cr(CO)5]] ++ COCO

THF  CoCo2(CO)(CO)8 ++ 2Li[HB(C2Li[HB(C2HH5))3]] →→

LiLi[Co(CO)[Co(CO)4]] ++ B(CB(C2HH5))3 ++ HH2 THF  MnMn2(CO)(CO)10 ++ 2KH2KH →→ KMn(CO)KMn(CO)5 ++ HH2 ReactionsReactions ofof MetalMetal CarbonylsCarbonyls withwith AnionsAnions

 - MnMn(CO)(CO)5 ++ ReRe(CO)(CO)5ClCl →→ - (CO)(CO)5ReRe--Mn(CO)Mn(CO)5 ++ ClCl

 ReRe(CO)(CO)5ClCl ++ 22 KCNKCN →→

K[Re(CO)K[Re(CO)4(CN)(CN)2]] ++ KClKCl ++ 22 COCO  ReactionsReactions withwith alky,alky, acylacyl halideshalides - - ReRe(CO)(CO)5 ++ CHCH3II →→ (CO)(CO)5ReRe--CHCH3 ++ II - MnMn(CO)(CO)5 ++ CHCH3C(=O)ClC(=O)Cl →→ - (CO)(CO)5MnMn--C(=O)CHC(=O)CH3 ++ ClCl ProtonationProtonation ofof CarbonylateCarbonylate anionsanions

 - + MnMn(CO)(CO)5 ++ HH →→ HH--Re(CO)Re(CO)5

 -- + - FeFe(CO)(CO)4 ++ HH →→ HH--Fe(CO)Fe(CO)4

 - + HH--Fe(CO)Fe(CO)4 ++ HH →→ HH2--Fe(CO)Fe(CO)4 OxidationOxidation StatesStates

 AlwaysAlways considerconsider thethe metalmetal inin itsits zerozero oxidationoxidation state.state.  e.g.e.g.  HH--Mn(CO)Mn(CO)5  BrBr--Mn(CO)Mn(CO)5  CHCH3--Mn(CO)Mn(CO)5  MnMn inin oxidationoxidation statestate ofof zero,zero,  ∴∴ - H,H, CHCH3,, BrBr allall donatedonate 11 ee .. ReactivityReactivity ofof polynuclearpolynuclear CarbonylsCarbonyls

 11 COCO ≡≡ 22 ee--;; ∴∴ ifif 11 COCO isis removedremoved thenthen youyou needneed toto replacereplace itit withwith twotwo 11 ee--

donorsdonors suchsuch asas H,H, CHCH3,, BrBr  e.g.e.g. OsOs3(CO)(CO)12 ∆  OsOs3(CO)(CO)12 ++ HH2 →→ HH2OsOs3(CO)(CO)10 W W W W

HH2OsOs3(CO)(CO)11 BondingBonding

CO

H H

H H Os H2 + CO Os3(CO)12 H2Os3(CO)10 H2Os3(CO)11 -CO BondingBonding

Cl2 Os3(CO)12 Os3(CO)10Cl2

CO

Cl Cl

Cl Cl Cl Cl Os 2 e- donor 3 e- donor BondingBonding

2 Mn(CO)5Br → Mn2(CO)8Br2 + 2 CO Br Br Mn - Mn Kinetic product

Mn = Mn Br

Br Br Mn Mn Br

Thermodymanic product Observed NitricNitric OxideOxide LigandLigand

 NONO hashas aa veryvery similarsimilar M.O.M.O. diagramdiagram toto thatthat ofof CO,CO, exceptexcept thatthat itit containscontains oneone extraextra electronelectron inin thethe ππ** orbital.orbital.

σ . 3 e- are donated M :N≡O: to the M.O. scheme of the complex by NO. In this case L-N-O bond π ~ 170 -180 º. NO is 3 e- donor; ∴NO+ is 2 e- donor ∴i.e. NO+ ≡ CO, i.e. isoelectronic CompoundsCompounds ofof NONO

 Co(CO)Co(CO)4NO;NO; Mn(CO)Mn(CO)4NO;NO; Fe(CO)Fe(CO)2(NO)(NO)2..  EANEAN ?? Check.Check.

 BentBent MM--NO,NO, withwith MM--NN--OO bondbond angleangle ofof 110110-- 120120º,º, thenthen NONO isis 11 ee- donor.donor.

.. NN≡≡OO MM BondingBonding ofof OrganicOrganic LigandsLigands toto MetalsMetals

 OlifinOlifin CompoundsCompounds  Zeises’Zeises’ SaltSalt

KK2PtClPtCl4 ++ HH2C=CHC=CH2 →→ K[PtClK[PtCl3(H(H2C=CHC=CH2)])] TheThe bondingbonding isis bestbest describeddescribed byby thethe DewerDewer--ChattChatt Mode.Mode. TheThe olefinolefin herehere isis aa totaltotal ofof 22 ee-- donordonor toto

thethe metalmetal center.center. H 2 H –CH C – 2 C=CH metallocyclopropane M M 2 2 AcetyleneAcetylene  AsAs inin thethe casecase ofof olefins,olefins, acetyleneacetylene cancan useuse oneone ofof itsits pp--bondsbonds oror bothboth toto coordinatecoordinate toto metalmetal .atoms. NoteNote eacheach ππ--bondbond isis 2e2e- donor.donor. H H 2 2 C =CH C ≡ ≡ M ≡ ≡ M CH 2 2

Note: this type of bonding is not common AcetyleneAcetylene (ac)(ac) BondingBonding  BridgingBridging acetyleneacetylene bondingbonding isis moremore commoncommon

 e.g.e.g.  ≡≡ CoCo2(CO)(CO)8 ++ HCHC CHCH →→ CoCo2(CO)(CO)6(ac)(ac) HC - CH

M - M ConjugatedConjugated OlefinOlefin SystemsSystems  FerroceneFerrocene  FeClFeCl2 ++ 22 NaCpNaCp →→ FeCpFeCp2 = Cp- - is 5e- donor

Fe η5 -Cp Pentahapto

Staggered=sandwich ReactionsReactions ofof CCpp--compoundscompounds  WithWith OrganometallicsOrganometallics

Li CO2H n Bu Li + Fe CO2/H Fe Fe ReactionsReactions ofof CCpp--compoundscompounds THF  Mo(CO)Mo(CO)6 ++ NaCNaCp →→ CpCp--Mo(CO)Mo(CO)3 +H+ +CH3I

ηη5--CpCp--MoH(CO)MoH(CO) ηη5 3 --CpCp--Mo(CHMo(CH3)(CO))(CO)3 ∆, −−ΗΗ2 ∆ ηη5 ηη5 [[ --CpCp--Mo(CO)Mo(CO)3]]2 →→ [[ --CpCp--Mo(CO)Mo(CO)2]]2 -2CO Cp Mo ≡ Mo

Cp ReactionsReactions ofof CCpp--compoundscompounds  NucleophilicNucleophilic AdditionAddition  ηη5- ηη4 - CoCpCoCp2 ++ CHCH3BrBr →→ Co(Co( Cp)(Cp)( --CC5HH5R)R) ++ BrBr

Co

H R ReactionsReactions ofof CCpp--compoundscompounds  AdditionAddition reactionsreactions [2[2 ++ 2]2] cycloadditioncycloaddition  ηη5- ηη3 NiCpNiCp2 ++ FF2C=CFC=CF2 →→ Ni(Ni( Cp)(Cp)( --CC5HH3CC2FF4))

Ni η3-

F F F F OtherOther systemssystems

 AllylsAllyls  NaMn(CO)NaMn(CO)5 ++ HH2C=CHC=CH--CHCH2BrBr →→ ηη1 Mn(CO)Mn(CO)5(( --CHCH2--CH=CHCH=CH2)) →→ ηη3 Mn(CO)4(Mn(CO)4( --CHCH2--CH=CHCH=CH2))

(CO)(CO)4

MM

Mn(CO)Mn(CO)4 OtherOther systemssystems η4- + Fe(CO)5 →

Fe(CO)3 H H H H η4-

+ Fe(CO)5 →

Fe(CO)3 ReactionsReactions H H H H η4-

+ Fe(CO)5 →

Fe(CO)3

O -CO C Cp CO ∆ η5- C FeH(CO) Fe - Fe p 2 -H2 OC C Cp O OtherOther ringring systemssystems

 CyclobutadieneCyclobutadiene η4- H Cl  + 3 CO + 2Cl FeFe2(CO)(CO)9 ++ 22 2 Cl H Fe(CO)3

CH3COCl/AlCl3

COCH3

Fe(CO)3 OtherOther ringring systemssystems

 BenzeneBenzene

Et2O/H2O  + PhMgBrPhMgBr ++ 22 CrClCrCl3 [Cr(PhH)[Cr(PhH)2 ]] + e-

η6-

Cr(CO)6 Cr Cr(CO)3