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Organometallic Compounds

Building Bridges to Knowledge

Photo of Old Faithful (Yellowstone National Park)

Organometallic compounds contain an alkyl or aryl component in combination with a metal. These compounds are named as derivatives of the metal. The metal is the parent and the alkyl or aryl groups are substituent prefixes. For example, compound I, is called cyclohexyl magnesium bromide

2

Compound I

Compound II is phenyl magnesium iodide:

Compound II

When the compound does not contain a halogen, simply name the compound using the akyl or aryl group followed by the name of the metal with no space between the alkyl or aryl group and the metal. For example, compound III would be called dicyclopentylmagnesium.

Compound III

Compound IV would be p-methoxyphenyllithium.

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Compound IV

Compound V would be 1-butyn-1-ylsodium.

Compound V

Another name for 1-butyn-1-ylsodium is sodium 1-butyn-1-yl.

The metal is less electronegative than carbon in organometallic compounds; therefore, the carbon has a partial negative charge, and the metal has a partial positive charge.

This arrangement gives the organometallic compounds its ability to exhibit its reactive behavior.

Preparation of organometallic compounds

Lithium and sodium organometallic compounds can be prepared by reacting primary, secondary or tertiary alkyl halides with lithium or sodium in an anhydrous solvent. As you know, water will react with the metal to form hydrogen gas and the metal hydroxide. For example, sodium reacts violently with water to form sodium

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hydroxide and hydrogen gas, Na + 2 H2O (l) → 2 NaOH(aq + H2 (g). Therefore, solvents used for preparing organometallic compounds cannot have protons attached to electronegative atoms; otherwise, reactions producing hydrogen gas similar to the one above will occur, e.g., 2 RCH2OH + 2 Li → 2 RCH2O- Li + H2. These solvents are aprotic solvents, i.e., they cannot have protons attached to electronegative atoms; therefore, they cannot be alcohols, water, primary or secondary amines, or mercaptans (RSH).

Trace amounts of water, alcohols, ammonia, primary or secondary amines, hydrogen sulfide or mercaptans would destroy the organometallic reagent, because small quantities of alcohols (primary, secondary or tertiary) will react with lithium or sodium to produce lithium or sodium alkoxides and the organolithium or organosodium compound would be converted to a hydrocarbon, and the resulting lithium or sodium alkoxides would coat the surface of remaining lithium or sodium metal to prevent it from reacting with the remaining alkyl halide molecules.

If water, ammonia, primary or secondary amines, hydrogen sulfide or mercaptans are present in the reaction vessel, they would react with organolithium or organosodium compounds to produce a hydrocarbon.

Therefore, aprotic solvents, solvents without hydrogen atoms attached to an electronegative atom, such as hydrocarbon solvents

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and ethers are effective solvent systems for producing organolithium or organosodium compounds from lithium or sodium and alkyl halides.

Alkyl iodides react with lithium and sodium faster than alkyl bromides, and alkyl bromides react faster than alkyl chlorides, and alkyl fluorides do not react with lithium or sodium metal.

Even though vinyl halides, H2C=CHX, and aryl halides, C6H5X, will not undergo nucleophilic substitution reactions and elimination reactions, they will react with lithium and sodium in the following manner:

The preferred solvent for reactions involving alkyl halides, vinyl halides and aryl halides is diethyl ether, CH3CH2OCH2CH33

or tetrahydrofuran.

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In tetrahydrofuran

In diethyl ether

CH3CH2OCH2CH3

In diethyl ether

CH3CH2OCH2CH3

In diethyl ether

CH3CH2OCH2CH3

The mechanism (the series of elementary steps that rationalize the

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formation of the compound) for the synthesis of organolithium and organosodium compounds is based on the easy ability of sodium to lose an electron. The first step would involve the transfer of an electron to the alkyl group to form a radical anion.

(1) The first step in the mechanism is the transfer of an electron from the metal to the alkyl halide to form the unstable radical anion intermediate.

The structure of the radical anion would have an electron in an antibonding molecular orbital of the carbon atom.

(2) The second step is that the resulting radical anion, with the extra electron in an antibonding molecular orbital of carbon, quickly dissociates to an alkyl radical and a halogen anion.

(3) The final step is the alkyl radical reacting with another sodium atom to form the alkyl anion molecule and sodium cation.

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Adding equations 1-3 would gives the overall reaction

RBr + 2 Na → R:- Na+ + Na+ Br-

Hydroboration-Oxidation

Probably the most revolutionary and most important organometallic compounds are the alkylboranes. As indicated in the paper titled “Alkenes Building Bridges to Knowledge,” Dr. Herbert C. Brown (05/22/1912-12/19/2004) pioneered the organoborane exploration at Purdue University. He received the 1979 Nobel Prize in chemistry for his revolutionary work on the syntheses of organoborane from alkenes. Organoboranes can be used to synthesize leading medicinals including antidepressants and cholesterol-lowering drugs.

In review, diborane adds to carbon-carbon double bonds followed by treatment with hydrogen peroxide to form alcohols that have an apparent anti-Markovnikov’s arrangement. These reactions are referred to as hydroboration-oxidation reactions.

Following is a general equation that represents the addition of diborane to alkenes to form alkylboranes.

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Once the alkylborane has been formed, it can be oxidized with hydrogen peroxide in basic media to produce an alcohol where the OH group resides on the lesser alkylated carbon atom of the precursor alkene. A general equation for this reaction can be represented by the following chemical equation.

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Following is an illustration of H. C. Brown’s hydroboration-oxidation reaction for the synthesis of 2-methylcyclohexanol from 1-methylcyclohexene.

F

1-methylcyclohexene

2-methylcyclohexanol

The product, 2-methylcyclohexanol, has the OH group on the carbon atom with the fewer number of carbon atoms.

The following mechanism represents a pathway that explains hydroboration-oxidation reactions.

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(1) HOOH + -OH → HOO- + HOH

(2)

12

(3)

(4)

(5)

HOOH + -OH → HOO- + HOH

13

(6)

(7)

14

(8)

(9)

HOOH + -OH → HOO- + HOH

(10)

15

(11)

(12)

The sum of elementary steps (1) -(12) gives the reactants and products with their stoichiometric quantities. Hydroxide, -OH, is the catalyst for the reaction; therefore, it does not appear as a reactant or a product.

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Grignard Reagents

Grignard reagents are very important compounds used as precursors for the syntheses of multiple compounds. Professor Victor Grignard, the recipient of the 1912 Nobel Prize in Chemistry, reported that alkyl halides react with magnesium to produce organomagnesium halides, and these halides can be used to synthesize primary, secondary and tertiary alcohols.

“R” can be a primary alkyl group, a secondary alkyl group, a tertiary alkyl group, cycloalkyl group, alkenyl groups, or aryl groups. Following is an example of this process where the aprotic solvent used is tetrahydrofuran.

The reactivity of organohalide compounds with Mg is: RI > RBr > RCl

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> RF; and alkyl halides are more reactive than aryl and vinyl halides. The solvent of preference for vinyl and aryl halides is tetrahydrofiran (THF) because tetrahydrofuran has a higher boiling point (339 K) than ether (bp 291 K).

The mechanism for the formation of the Grignard reagent is analogous to the mechanism for formation of organolithium and organosodium compounds with the formation of a radical anion intermediate.

(1) Formation of the unstable radical anion intermediate.

(2) The rapid disintegration of the radical anion produces the alkyl radical.

(3) The alkyl radical can react with magnesium radical cation produced in step (1) to produce Grignard reagent.

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In a like manner that was described earlier, water; alcohols (primary, secondary or tertiary); ammonia; primary or secondary amines; hydrogen sulfide or mercaptans (R-SH) convert Grignard reagents to hydrocarbons.

Grignard reagents can react with the acidic protons of terminal alkynes to form alkyne magnesium halides.

Grignard reagents can be used to synthesize primary alcohols, secondary alcohols, and tertiary alcohols. Primary alcohols are

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synthesized from Grignard reagents and formaldehyde; secondary alcohols are synthesized from Grignard reagents and aldehydes; and tertiary alcohols are synthesized from Grignard reagents and ketones.

Grignard reagents react with formaldehyde to form intermediate alkoxymagnesium halides, and then the alkoxymagnesium halides are hydrolyzed by mineral acids in water to primary alcohols. The following examples illustrate this reaction.

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Secondary alcohols are synthesized from Grignard reagents and aldehydes in diethyl ether, and the alkoxymagnesium halides are hydrolyzed by mineral acids in water to produce the desired secondary alcohols. The following examples are illustrations of this process.

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Tertiary alcohols are synthesized from Grignard reagents and

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ketones in diethyl ether. The alkoxymagnesium halides are hydrolyzed by mineral acids in water to produce the desired tertiary alcohols. The following examples are illustrations of this process.

Organolithium compounds are more reactive toward formaldehyde,

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aldehydes and ketones than Grignard reagents. The products, i.e., primary, secondary and tertiary alcohols, are analogous to the products produced by the Grignard reagents with formaldehyde, aldehydes and ketones.

Acetylenic alcohols can be made using the following chemical

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processes.

Acetylenic Grignard reagents are prepared by reacting terminal acetylenes with alkyl Grignard reagents.

Acetylenic Grignard reagents react with formaldehyde, aldehydes and ketones to form primary, secondary and tertiary alkynols.

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For example, let’s look at one possible pathway for the synthesis of 4-cylcohexyl-2-butyn-1-ol (II). The synthesis can be accomplished by treating 3-cyclohexyl-1-propynmagnesium bromide (I) with formaldehyde in dry ether, followed by the acid hydrolysis.

I

II

A similar synthesis could be used for the preparation of 6-cyclohexyl-4-hexyn-3-ol (III); however, the acetylenic Grignard reagent would be treated with propionaldehyde (propanal) instead of formaldehyde.

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III

Analogously, the process could also be used to synthesize 6-cyclohexyl-3-methyl-4-hexyn-3-ol (IV); however, the acetylenic Grignard reagent would be treated with a ketone, 2-propanone.

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IV

Let’s design a synthesis for 2-phenyl-2-butanol. The process is easier if worked backwards. Working backwards is referred to as a retrosynthesis.

2-phenyl-2-butanol

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There are three (3) pathways that could lead to the synthesis of 2-phenyl-2-butanol.

(1) From bromobenzene

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(2) From methyl bromide

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(3) From ethylmagnesium bromide

Tertiary Alcohols can also be synthesized from esters. If two moles of the Grignard reagent react with a designated ester, after acid hydrolysis, the resulting compound would be a tertiary alcohol.

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The synthesis of 3-cyclohexyl-3-pentanol illustrates the process where two moles of a Grignard reagent lead to the formation of a tertiary alcohol.

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3-cyclohexyl-3-pentanol

Following is the mechanism that explains this reaction.

(1)

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(2)

(3)

Acid Hydrolysis:

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Syntheses of Alkanes from Grignard reagents

Alkanes result from the hydrolysis of Grignard reagents.

Following are illustrations of the hydrolysis of Grignard reagents resulting in the formation of alkanes.

Methane is formed from the hydrolysis of methyl magnesium bromide.

2-Methylpropane is formed from the hydrolysis of t-butyl magnesium bromide.

Propane is formed from the hydrolysis of n-propyl magnesium iodide.

1-Deuteropropane is formed from treating n-propyl magnesium

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iodide with deuterium oxide, D2O. Deuterium is an isotope of hydrogen. A hydrogen atom has one proton in its nucleus, and deuterium has one proton and one neutron in its nucleus.

As mentioned in paper titled “Alkanes, Building Bridges to Knowledge,” the hydrolysis of methyl magnesium halide can be used to quantitatively determine the amount of water in some inert compounds. This is due to the stoichiometry of the reaction. There is a clear relationship between the number of moles of methane and the number of moles of water present in the sample, because the moles of methane formed from the hydrolysis is equivalent to the moles of water present in the sample.

The Corey-House Reaction Revisited

As indicated in the paper titled “Alkanes, Building Bridges to Knowledge,” the Corey-House reaction involves the coupling of an alkyl halide with an organometallic compound, a lithium diakylcuprate (the Gilman reagent) to produce an alkane. The reaction occurs between a primary or secondary alkyl halide (works best for a primary alkyl halide) and a lithium dialkylcuprate reagent,

.

The overall reaction can be represented by the following equation.

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The reaction is used to prepare unsymmetrical alkanes. The preparation of R2CuLi is from the corresponding alkyl halide.

R’X + 2 Li → R’Li + LiX

This is not a simple coupling reaction, and the mechanism is not well understood. The alkyl group in the lithium dialkylcuprate reagent can be primary, secondary, or tertiary; however, as indicated previously, the reagent reacts best with a primary alkyl halide. The lithium diaklycuprate reagent will work fairly well on an unhindered secondary alkyl halide.

For example, the synthesis of 2-methylpentane is an example of the Corey-House reaction.

RX + R2' CuLi → RR' + RCu + LiX

2 R'Li + CuX → R2' CuLi + LiX

C

CH3

CH3

H

I

+ Li2

H

CH3

CH3

C

Li

+ LiI

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Lithium dialkylcuprates react best with primary alkyl iodides.

Even though the mechanism is not clear, organocuprates work best with methyl and primary alkyl halides where the order of reactivity with halogens is I >Br > Cl >F. Alkyl p-toluenesulfonates are more reactive than alkyl halides. The reaction works best with primary alkyl halides and Gilman reagents, which are primary dialkycuprates.

CH

CH3

CH3

+LiCu2

H

CH3

CH3

C

Li

+LiI

CuI

2

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Even though vinyl halides and aryl halides are not reactive toward SN2 mechanisms, they react in Corey-House reactions.

Formation of Cyclopropane from Organozinc Reagents, the Simmons-Smith Reaction Revisited

Zinc is more electronegative than lithium or magnesium (Chart 1.1 on page 51 of the paper titled “Basic Principles for Introduction to Organic Chemistry Building Bridges to Knowledge”) .

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Metal Electronegativity

Zn 1.7 Mg 1.3 Li 1.0

Therefore, the C-Zn bond would be less polar than C-Li or C-Mg bond.

Organozinc reagents are less reactive toward aldehydes and ketones.

A special organozinc reagent, iodomethylzinc iodide (ICH2ZnI), plays

a role in organic synthesis. Iodomethylzinc iodide is prepared by reacting iodomethane and zinc with its surface activated with Cu in diethyl ether as a solvent.

Iodomethylzinc iodide reacts with alkenes to form cyclopropane derivatives.

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The above reaction is referred to as the Simmons-Smith reaction, and the reaction is stereospecific, i.e., cis alkenes will give rise to cis substituted cyclopropane, and trans alkenes will give rise to trans substituted cyclopropane:

Following is the mechanism (series of elementary steps) for the Simmons-Smith reaction.

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(1)

(2)

The reaction, in reality, is essentially a one step process that proceeds through the formation of a non-isolatable activated complex at the transition stage of the reaction. The reaction is represented as a two-step mechanism, because of the formation of the activated complex. The reaction would follow a second order kinetic process.

Additional information about the Simmons-Smith reaction can be found at http://www.organic-

C

C

H3C H

CH3H

+ C

I

H

Zn

I

H

H CH3

HH3C

C

CCH2

I

ZnI

C

H3C H

CH3H

+

H CH3

HH3C

C

CCH2

I

ZnI

CCH2 ZnI2

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chemistry.org/namedreactions/simmons-smith-reaction.shtm

The Wurtz Reaction

The Wurtz reaction is one of the oldest coupling reactions in organic chemistry. The Wurtz product is a dimer formed from two equivalent alkyl halides.

2 R-X + 2 Na → R-R + 2 NaX

For example, n-octane can be synthesized from 1-bromobutane via the Wurtz Reaction.

By products of the Wurtz Reaction could be alkanes and alkenes.

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The Mechanism of the Wurtz Reaction could be as simple as a transfer of an electron to an antibonding orbital on a carbon atom to form a radical

(1) The initial step takes place twice

(2) This step also takes place twice

CH3CH2CH2

C

H

H

Br+ Na .

Br

H

HCH3CH2CH2

: :....-

C.

+ Na+

CH3CH2CH2

C

H

H

Br+ Na .

Br

H

HCH3CH2CH2

: :....-

C.

+ Na+

Br

H

HCH3CH2CH2

: :....-

C..

C-

..

..::

CH3CH2CH2 H

H

Br

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(3)

The Wurtz reaction can be used to synthezise strained ring compounds like bicyclo[1.1.0]butane.

Carbenes and Carbenoids

Iodomethylzinc iodide is a carbenoid, i.e., it acts like a carbene.

Carbenes have the formula R2C:. If the R groups are hydrogen, H2C:, the species is referred to as methylene. As expected, carbenes are very reactive chemical species. Carbenes will add to double bonds to produce cyclopropanes. Reactions one and two are examples of carbene insertion reactions.

Br

H

HCH3CH2CH2

: :....-

C..

C-

..

..::

CH3CH2CH2 H

H

Br

+

H

HCH3CH2CH2

C. .

CCH3CH2CH2 H

H

HH

HH

CH3CH2CH2C C

CH2CH2CH3

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Theoretically, the cyclopropane product, bicyclo[4.1.0]heptanes, in equation 2 can assume both a cis and trans form, but the reaction product is always cis. Therefore the reaction is stereospecific.

For obvious reasons, the cis isomer dominates.

Carbenes are also of the type X2C:, where X represents Cl, I or Br.

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Carbenes are highly reactive; therefore, they are generated in situ in the presence of the alkene. The following reactions are examples of a couple of common carbene generators.

1. RHCI2 + Zn-Cu → [IRCHZnI] → ZnI + :CHR

2. K+ -OC(CH3)3 + CHX3 → X2C: + KX + HOC(CH3)3

In reaction 1, the diiodoalkane reacts with ZnCu alloy to give the unstable IRCHZnI which decomposes to the carbene.

Reaction 2 uses the powerful base potassium tert-butoxide to generate the carbene from trihalomethanes.

(CH3)3CO- K+ + H:CCl3 → K+ - :CCl3

K+ - :CCl3 → KCl + :CCl2

Cyclopropanes can also be prepared via 1,3-dihalopropane.

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Carbenes can also be prepared from diazomethanes and ketenes:

The carbenes generated can be inserted into alkenes to form cyclopropanes.

C

H

H

UV lightCH2: + COOC

ketene

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The carbenes generated from diazomethanes and ketenes can have either a singlet state or a triplet state. The singlet state carbene has an unshared pair of electrons, i.e., electrons with opposite spins:

The C-H bond length is 1.12Ǻ

The pairing of the electrons can be

Therefore, the term singlet is applied to this carbene.

The triplet state carbene has unshared electrons which are not paired, i.e., electrons with or without opposite spins.

Therefore, the possible spin arrangements for the two electrons could be:

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1:2:1 hence the term triplet is applied to this carbene system.

In the triplet state, the C-H bond length is 1.12 Ǻ.

The singlet state carbenes add to alkenes stereospecifically to form cyclopropanes.

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Carbenes in the triplet state add to alkenes in a nonstereospecific manner to form cyclopropane.

Diazomethane generates the triplet carbene, and ketene generates a triplet carbene.

Transition-Metal Organometallic Compounds

Diiron nonacarbonyl can be used in the synthesis of cubane. The synthesis of cubane was discussed in the paper titled “Cycloalkanes, Building Bridges to Knowledge.” This section is a review of the synthesis of cubane, and an explanation of the structure of diiron nonacarbonyl, a neutral molecules with the formula Fe2(CO)99

. Diiron

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nonacarbonyl is an orange solid that is prepared by the photolysis of an acetic acid solution of iron pentacarbonyl, Fe2(CO)55

.

The two iron atoms in diiron nonacarbonyl have zero oxidation states, and the carbonyl molecules attached are referred to as ligands. As in many transition-metal organometallic compounds, the bonds between Fe and CO are coordinate covalent bonds. However in diiron nonacarbonyl, each iron atom has four coordinate covalent bonds and two single covalent bonds.

The ylide, carbon monoxide,

,

is a Lewis base. The Fe, a transition metal, is a Lewis acid.

Four carbon monoxide molecules form coordinate covalent bonds with each iron atom. The two iron atoms share a carbon monoxide molecule via two single covalent bonds. Finally, the iron atoms form a single covalent with each other. The lone pair of electrons on the carbon of the carbonyl group (a carbon monoxide molecule) forms a coordinate covalent bond with an empty 4sp3d2 hybridized atomic orbital of Fe.

The electron configuration for Fe is 1s22s23s2 3p63d64s2. The iron has eight valence electron (six electrons in the 3d atomic orbitals and 2 electrons in the 4s atomic orbital). There are two iron atoms in the diiron nonocarbonyl. Each iron has four carbonyl groups covalently bonded to it and one carbon atom that is covalently bonded to it.

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The two iron atoms are formed by a single covalent bond; therefore, the total number of electrons provided by the carbon atoms is 10. The number of valence electrons on each iron atom is eight. The eight valence electrons and the 10 electrons provided by the carbonyl carbon atoms equal 18. Consequently, the transition-metal complex obeys the rule of 18. The rule of 18 for transition-metal complexes is that the number of electrons provided by the ligands and the valence electrons of the transition metal equal 18.

First, let’s explain the hybridization in each Fe atom.

The iron electrons in the 4s atomic orbital and 4p and 4d low lying atomic orbitals of iron can be arrange in the following manner:

One of the electrons in the 4s atomic orbital can be promoted to the 4p orbital:

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The 4s atomic orbital, the three 4p atomic orbitals, and two of the 4d atomic orbitals hybridize to form six degenerate 4sp3d2 atomic orbitals:

These data suggest that the structure of diiron noncarbonyl is:

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or it may be written as

Diiron nonacarbonyl reacts with 3,4-dichlorocyclobutene to produce cyclobutadiene tricarbonyliron. This compound obeys the 18-rule where four electrons are contributed by the cyclobutadiene, six from the carbonyl and eight valence iron electrons.

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The cyclobutadienetricarbonyiron is a precursor for the synthesis of cubane via the following reaction schema:

Fe(CO)3

Ce4+

+

+

O

O

Br

Br

O

O

hνO

O

Br

Br

Br

Br

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Metallocenes

Metallocenes are organometallic compounds with the aromatic carbanion, cyclopentadenide, sandwiching a metal cation. Cyclopentadenide can form a metallocene called ferrocene. The cyclopentadenide functions as a ligand in ferrocene where two cyclopentadenide entities sandwich a ferrous ion.

O

O

Br

Br

aq KOH100oC

C

C

O

O

OH

OH

(2)

(1)

H3O+

(1)

(2)

SOCl2

(CH3)3COOH

C

C

O

O

OO-Bu-t

OO=Bu-t

Δ

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Ferrocene has the following structure.

Many metallocenes are known (http://en.wikipedia.org/wiki/Metallocene), and some have industrial use.

The Ziegler Natta Catayst

The Ziegler-Natta catalyst named after Karl Ziegler and Giulio Natta is used in the preparation of isotactic, i.e., the “R” groups are in the cis position in the polymer.

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Several decades ago, Karl Ziegler first published his studies on organoaluminum compounds as catalyst for the polymerization of ethylene. Natta discovered that the Ziegler’s catalyst produced polymers in which the side chains have the same direction, i.e., isotactic polymers. An effective catalyst for the isotactic polymerization of α alkenes is the Ziegler-Natta catalyst.

The Ziegler-Natta catalyst can be used with three platforms, one platform uses metallocenes and zirconium; however, a variety of metal catalysts (e.g., Ti, Zr, and Hf) are used in this process. Karl Ziegler and Giulio Natta received the Nobel in 1963 for their pioneering work.

The details of the mechanism are not well understood, because the reaction takes place on the surface of insoluble materials, and it is difficult to conduct kinetic experiments in the solid phase. Therefore, the series of elementary steps to rationalize the isotactic product are based on experimental evidence and scientific intuition. A popular Ziegler-Natta metal catalytic used for the isotactic polymerization of alpha substituted alkenes is Titanium with aluminum as a co-catalyst. The mechanism of the reaction could proceed via the following series of elementary steps.

C C

RH

H H

Ziegler-Natter

Catalystn

n

R R RR

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Step 1 involves the formation of a titanium-aluminum complex by reacting titanium tetrachloride with trimethylaluminum. Trimethyl aluminum is a dimer made by treating aluminum with methyl chloride in the presence of sodium.

Step 2 involves the reaction of the titanium-aluminum complex with the desired alkene.

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Step 3 involves the rearrangement of the titanium-aluminum-alkene complex where a methyl group is moved to the alkene, and the methylene of the alkene replaces the methyl that is complex with aluminum and titanium.

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Step 4 involves multiple attachments of the alkene in such a manner that the alkyl groups are isotactic.

Step 5, the final step, releases the polymer and generates the titanium-aluminum complex formed in step 3.

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Problems

Organometalilc Compounds

1. Using benzene, methanol, and any other necessary inorganic materials suggest syntheses for the following compounds.

(a)

(b)

(c)

(d)

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2. Suggest syntheses for the following

(a) 3-methyl-1-pentyn-3-ol from 2-butanone and any other necessary organic or inorganic material

(b)

and any other necessary organic and inorganic compounds

(c)

and any other necessary organic and inorganic compounds

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3. Suggest products for the following reactions.

(a)

(b)

(c)

(d)

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(e)

4. Suggest the major product for the reaction of t-butylmagnesium bromide with compound A followed by acid hydrolysis. What is the IUPAC name for this compound?

Compound A

5. Predict the major product expected from reacting compound B with excess phenylmagnesium iodide followed by acid hydrolysis.

Compound B

6. Compound I, C3H5Br, reacts with magnesium in dry ether to form C3H5MgBr. Treating C3H5MgBr with formaldehyde followed by acidic hydrolysis produces C4H8O, compound II. When three

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moles of C4H8O are treated with phosphorous tribromide, three moles of C4H7Br, compound III, are formed. Treating C4H7Br with magnesium in dry ether, followed by treatment with p-ethoxybenzaldehyde, resulted in the production of C13H17OMgBr. Acid hydrolysis of C13H17OMgBr produces C13H17OH, compound IV.

Suggest structures for compounds I, II, III, and IV.

7. Ferrocene is readily oxidized to ferrocenium ion by hydroxyl radicals or other kinds of free radicals. Consequently, ferrocene may serve as a therapeutic agent for treating cancer. The reaction for ferrocene as a chemical to treat cancer may be described by the following equation.

Suggest a synthesis for ferrocene from cyclopentadiene.

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8. Suggest the product (with the appropriate stereochemistry) produced when (2S)-2-bromobutane reacts with lithium n-propylcuprate.

9. Suggest the major product expected for the following reaction.

Give a rational for your answer.

10. Suggest a synthesis for compound B from compound A.

compound B

compound A

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11. Suggest syntheses that would lead to the major products for the following compounds from any necessary organic or inorganic reagents.

(a) 1-deuteriobutane from butane

(b) 2-deuteriobutane from butane

(c) 2-deuterio-2-methylpropane from isobutane

(d) 1-deuterio--2-methylpropane from isobutane

12. The name of the following compound

is pentacyclo[4.2.0.02.5 03,8.04,7]octane.

Suggest an IUPAC name for the following compound:

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13. Suggest structures for the product or products obtained in the following sequence of reactions.

14. Consider the following reaction schemas:

(a)

(b)

(c)

Suggest structures for A, B, C8H14O, the product of (b) and C8H14, the product of (c)

+ MgBr A + B

+AO H3O

+C8H14O

C8H14O + 2 Na + 2 NH3 → C8H14 + NaOH + NaNH2 + NH3