Reactions and Mechanism Flashcards
The reaction of cyclooctatetraene with iron pentacarbonyl is shown below. All products A, B and C are 18-electron complexes; all of the complexes have IR bands in the region 1900 – 1980 cm-1. Clearly illustrate the structures of A, B and C (Hint: A and B belong to
the Cs point group while C belongs to C2h).
A= 3 CO’s in 3-legged piano stool. C8H8 has hapticity of 4, shape like a pringle chip
B= Remaining 2 CO and C8H* with hapticity of 6
C= two Fe with 3 CO (3-legged piano stool) bonding to same C8H8 with hapticity of 4 each.
- When Mn2(CO)10 is reacted with excess sodium-amalgam (Na/Hg) in THF, a mononuclear salt of the formula C5MnNaO5 (A) is produced; the IR spectrum of A shows a strong CO band at 1870 cm-1. In THF solution, this salt reacts with 3-chloropropene to generate a neutral monomeric complex of the formula C8H5MnO5 (B) with a CO band at 1930 cm-1. When B is heated at 80C or photolyzed at 25C, a new complex C of formula C7H5MnO4 can be isolated. Addition of PMe3 to complex C results in the formation of D having the composition C10H14MnO4P. Clearly illustrate the structures of compounds A – D and show that they all obey the 18-electron rule.
A metal M forms a carbonyl complex Mx(CO)y that contains 18.40% of carbon and in its mass spectrum exhibits a molecular ion, the isotopic pattern of which shows its most intense peak at m/z = 652. The carbonyl complex reacts with triphenylphosphine to produce two compounds; A, which has a metal-phosphorus ratio of 1:1, and B, for which the corresponding ratio is 2:1. A reacts with bromine to form a single product C, whereas B with bromine produces both C and D. D, which is identical with the sole product from the reaction of Mx(CO)y with bromine, reacts with triphenylphosphine to produce E, which is isomeric with C. C and D, but not E, have a C4 axis of symmetry. All the compounds are diamagnetic. Draw conclusions from each piece of evidence, deduce the identity of M, the values of x and y and the structures of A, B, C, D and E.
Heating [(η5-C5H5)Fe(CO)3]+ with NaH in solution affords organometallic compound A which has a room-temperature 1H NMR spectrum consisting of two singlets of relative intensity 1:5 at approximately δ = -12 ppm and δ = 5 ppm, respectively.
Compound A is thermally unstable under ambient conditions and rapidly evolves a colourless gas B and forms a purple-brown solid C having the empirical formula C7H5O2Fe. The Nujol-mull IR spectrum of solid C exhibits strong absorptions at 1961, 1942, and 1790 cm-1.
Treatment of C with an equimolar amount of iodine generates a brown solid D which is stable in air and is soluble in polar organic solvents. Its Nujol-mull IR spectrum exhibits strong absorptions at 2042 and 1992 cm-1.
Reaction of D with an equimolar amount of CH3MgI in diethyl ether affords caramel-coloured crystals of E. Compound E is unstable in air, but is soluble in common organic solvents. Its Nujol-mull IR spectrum exhibits strong absorptions at 2010 and 1965 cm-1, and its 1H NMR spectrum consists of two singlets of relative intensity 3:5 at approximately δ = 0 ppm and δ = 4 ppm.
Reaction of D with an equimolar amount of NaC5H5 produces an orange solid F with the formula C12H10O2Fe. Compound F is fairly stable in air, and its 1H NMR spectrum at 30 ºC consists of two equal intensity singlets at approximately δ = 4.5 ppm and δ = 5.7 ppm.
On heating, F evolves a colourless gas and converts to an orange solid G that is stable in air and is soluble in most organic solvents. Its 1H NMR spectrum at all temperatures consists of a single sharp resonance at approximately δ = 4 ppm.
Identify compounds A through G and sketch their molecular structures.
Identify and sketch in the frames provided the molecular structures of compounds A,
B, and C which are three different types of organometallic complexes that could
result from the reaction of (η2-H2C=CH2)Re(CO)4Cl with one equivalent of NaBH4
Name the reaction and Draw the structure of the bolded compound
Ni + 4 CO → Ni(CO)4
Adduct formation (addition reaction)
Name the reaction and Draw the structure of the bolded compound
Mn2(CO)10 + 2 Na → 2 Na[Mn(CO)5]
Reduction
Name the reaction and Draw the structure of the bolded compound
W(CO)6 refluxed in CH3CN → (CH3CN)3W(CO)3 + 3 CO
ligand substitution
Name the reaction and Draw the structure of the bolded compound
H2 + Ir(CO)(PPh3)2Cl → Ir(H)2(CO)(PPh3)2Cl
oxidative addition
Draw the molecular structures for the expected organometallic product(s) in each of the following reactions. The equations all indicate the stoichiometry
trans-Ir(PPh3)2(CO)Cl + O2 →
→
Draw the molecular structures for the expected organometallic product(s) in each of the following reactions. The equations all indicate the stoichiometry
W(CO)5[C(C6H5)(OC2H5)] + BBr3 →
Draw the molecular structures for the expected organometallic product(s) in each of the following reactions. The equations all indicate the stoichiometry
Na2[Fe(CO)4] + MeC(O)Cl →
Draw the molecular structures for the expected organometallic product(s) in each of the following reactions. The equations all indicate the stoichiometry
3 CrCl3 + 3 Al + 6 C6H6 →
Draw the molecular structures for the expected organometallic product(s) in each of the following reactions. The equations all indicate the stoichiometry
Cp*W(NO)(η3-CH2CHCHMe)(CH2CMe3) + n-hexane →
Draw the product for A-J. All obey the 18 electron rule
Draw all structures for A-I
Draw all unknown structure. Note, [] means solvent/reagent
Fe(CO)5 =[2Na in THF]=> A
A =[HCl in Et2O]=> B.
B =[Ph3SnCl in THF]=> C
A= Na2[Fe(CO)4] with the dianion having Td symmetry
B= Na[HFe(CO)4] with the monoanion having a “trigonal
bipyramidal” structure.
Neutral
C= Neutral (OC)4Fe(H)(SnPh3) having an “octahedral”
structure.
Fe(CO)5 =[reflux in C5H5]=> D
D=[2 Na in THF]=> E
E=[2CH2=CHCH2Br in THF]=> F
F =[hv, -CO in pentane]=> G
D= [CpFe(CO)2]2 having the molecular structures
E= 2 Na[CpFe(CO)2] with the anion having a “twolegged
piano-stool” molecular structure.
F= 2 CpFe(CO)2(η1-CH2CH=CH2) having the “threelegged
piano-stool” molecular structure
G = 2 CpFe(CO)(η3-C3H5) having the “three-legged
piano-stool” molecular structure:
Fe(CO)5 =[Cl2 in CCl4]=> H
H=[2 MeMgBr in Et2O]=> I
I =[CO in pentane]=>J
J=[warm in pentane]=> K (trimetallic compound) and L (organic compound)
H= Fe(CO)4Cl2 with an
“octahedral” structure.
I= Fe(CO)4Me2 with an
“octahedral” structure.
J= Fe(CO)4[C(O)Me]Me with an
“octahedral” structure.
K is Fe3(CO)12 with the
structure as shown.
L is acetone, Me2C=O.
For each of the following sequences of reactions, identify and sketch the molecular structures of each of
the organometallic cobalt compounds A to K which all satisfy the 18-valence-electron rule. Note that
concomitant gas evolution is indicated for two of the conversions
A= TBP Co(CO)4Br
B= two-legged piano stool (η5-C5H5)Co(CO)2
C=two-legged piano stool (η5-C5H5)Co(CO)[C(=OLi)Et]
D= two-legged piano stool (η5-C5H5)Co(CO)[C(=OEt)Et], Fischer carbene complex
E = two-legged piano stool (η5-C5H5)Co(Br)[C≡Et], Fischer carbyne complex
F= two-legged piano stool (η5-C5H5)Co(CO)[=C(NHR)Et], Fischer carbene complex
G = Na[Co(CO)4] in which the anion has a tetrahedral structure
H is TBP Co(CO)4H
I is TBP Co(CO)4Et
J is TBP (OC)3Co(PPh3)[C(=O)Et]
K is bimetallic (OC)4Co-Mn(CO)5 with the geometry being TBP at Co and Oh at Mn
Complete each of the following chemical transformations and identify the reaction type
involved. Note specifically the initial and final oxidation states of any element
undergoing a redox reaction during a particular transformation. Sketch the molecular
structures of the product complexes.
Re2(CO)10 + 2 Na →
2 Na[Re(CO)5]
Reaction type: Reduction
Molecular structure: The [Re(CO)5]- anion has TBP structure
Complete each of the following chemical transformations and identify the reaction type
involved. Note specifically the initial and final oxidation states of any element
undergoing a redox reaction during a particular transformation. Sketch the molecular
structures of the product complexes.
MeMn(CO)5 + AlX3 (X = Cl or Br) →
Lewis-acid induced migratory insertion of CO into the
Mn-Me bond.
A cis-octahedral arrangement
Identify and sketch in the frames provided the molecular structures of compounds A,
B, and C which are three different types of organometallic complexes that could
result from the reaction of a THF solution of (η5-C5H5)Ru(NO)(H)Cl with one
equivalent of NaBH4.
Identify and sketch in the frames provided the molecular structures of compounds A, B,
and C which are three different types of organometallic complexes that could result
from the reaction of (η2-H2C=CH2)Mn(CO)4Cl with one equivalent of MeLi
For each of the following reactions, sketch the molecular structures of each transition-metal product in
the box provided and answer the questions associated with each reaction scheme.
What are the names of these types of reactions?
For the products indicate the:
Valence electron count: __________ __________
Metal’s oxidation state: __________ __________
d-electron configuration:
Methyl anion abstraction, deprotonantion
Valence electron count: 16; 8
M’s ox. state: Nb(V); Nb(V)
d-electron configuration: d0; d0
For each of the following reactions, sketch the molecular structures of each transition-metal product in
the box provided and answer the questions associated with each reaction scheme
What are the names of these types of reactions?
For the products indicate the:
Valence electron count: __________ __________
Metal’s oxidation state: __________ __________
d-electron configuration:
ethylene polymerization
Valence electron count: 14; 14
Metal’s oxidation state: Zr(IV), Zr(V)
d-electron configuration: d0, d0
For each of the following reactions, sketch the molecular structures of each transition-metal product in
the box provided and answer the questions associated with each reaction scheme.
What types of reactions are involved in these conversions?
For the products, indicate the:
Valence electron count: __________ __________
Metal’s oxidation state: __________ __________
d-electron configuration: __________
oxadative addition (stepwise and concerted)
Valence electron count: 18; 18
Metal’s oxidation state: Ir(III), Ir(III)
d-electron configuration: d6, d6
For each of the following reactions, sketch the molecular structures of each transition-metal product in
the box provided and answer the questions associated with each reaction scheme
What type of reaction affords the product on the right-hand side?
For the products, indicate the:
Valence electron count: __________ __________
Metal’s oxidation state: __________ __________
d-electron configuration:
C-H activation or metathesis
Valence electron count: 18, 18
Metal’s oxidation state: W(0), W(II)
d-electron configuration: d6, d4
Sketch the molecular structures of the various organometallic products in the boxes provided.
All complexes satisfy the 18-valence-electron rule
Sketch the molecular structures of the various organometallic products in the boxes provided.
All complexes satisfy the 18-valence-electron rule.
For each of the following reactions, sketch the molecular structures of each transition-metal product in
the box provided and answer the questions associated with each reaction scheme
Mo(CO)6 =[LiPh]=> A =[[Et3O]BF4]=> B =[BBr3]=> C
What kind of reaction is the transformation to form complex A?
What is the valence-electron count at the metal centre in complex C?
A: Nucleophilic attack by Ph- on a carbon atom of a carbonyl ligand
C: Eighteen.valence electrons
For each of the following reactions, sketch the molecular structures of each transition-metal product in
the box provided and answer the questions associated with each reaction scheme.
[Mn(CO)5]-Na+ =[PhCH2Cl]=> D =[heat, -CO]=> EWhat kind of reaction is the transformation to form complex D?
What is the formal oxidation state of the metal centre in complex E?
D: metathesis reaction
E: Mn(I)
For each of the following reactions, sketch the molecular structures of each transition-metal product in
the box provided and answer the questions associated with each reaction scheme
What kind of reaction is the conversion to form complex F (left side)?
What is the d-electron configuration of the metal centre in complex G (right side)?
F: oxidative addition reaction
G: d6
For each of the following reactions, sketch the molecular structures of each transition-metal product in
the box provided and answer the questions associated with each reaction scheme.
What kind of reaction is the conversion to form H (left)?
What is the formal oxidation state of the metal centre in complex I (right)?
H: An α-H abstraction reaction followed by adduct formation with PMe3.
I: W(II)
Complete the following chemical equations, identify the reaction type involved in each
transformation, and sketch the molecular structures of the various organometallic products formed.
These products are indicated by bold letters
Na[(η5-C5H5)Fe(CO)2] + ClCH2CH2SCH3 → C + warming → D
Metathesis to form C followed by migratory CO insertion to form D.
For each of the following sequences of reactions, identify and sketch the molecular structures of each of the organometallic chromium compounds A to J which all satisfy the 18-valence-electron rule.
A is octahedral fac-Cr(CO)3(CH3CN)3.
B is the three-legged piano stool, (η6-C6H5Me)Cr(CO)3.
C is the three-legged piano stool, (η6-C6H5Me)(η4-C5H6)Cr(CO).
D is Li[(OC)5Cr[C(Me)O]] in which the anion has an octahedral structure.
E is the octahedral (OC)5Cr[=C(OEt)Me], a Fischer carbene complex.
F is Na[(η5-C5H5)Cr(CO)3] in which the anion has a three-legged piano stool structure.
G is the three-legged piano stool, (η5-C5H5)Cr(CO)2(NO).
H is the four-legged piano stool, (η5-C5H5)Cr(CO)3H.
I is bimetallic (η5-C5H5)(OC)3Cr-Cr(CO)3(η5-C5H5) having a single Cr-Cr bond.
J is bimetallic (η5-C5H5)(OC)2Cr≡Cr(CO)2(η5-C5H5) having a triple Cr≡Cr bond.
The molecular structures of these complexes are shown on the following pages
Identify and sketch in the frames provided the molecular structures of compounds A,
B, and C which are three different types of organometallic complexes that could
result from the reaction of a THF solution of (η5-C5H5)Ru(NO)(H)Cl with one
equivalent of NaBH4
Predict the transition-metal-containing products of the following reactions
(η5-C5H5)Fe(CO)2(CH3) + PPh3
Predict the transition-metal-containing products of the following reactions
(B) V(CO)6 + NO
(c) [Fe(CO)4]2- + CH3I
(d) (CO)5Mn(CH3) + P(CH3)(C6H5)2
(e) [Rh(H2O)6]3+ + 3 equiv. Cl-
Predict the transition-metal-containing products of the following reactions:
Predict the transition-metal-containing products of the following reactions
Using Vaska’s complex as a starting material, predict the oxidative-addition product in each
case:
(a) Me3SiH
(b) MeI
(c) H2
(d) HCl
(e) O2
(f) C6H5SO2Cl
For the following sequence of reactions, identify the products, name the reaction type, and use
arrow-pushing diagrams to rationalize the formation of the products. What is the driving force
for this reaction?
TaCl5 + 1.5 equiv. Zn(CH2tBu)2 ==> A + side products
=[2 equiv. Li(CH2tBu)]=> B + side products
Na[(η5-C5H5)Fe(CO)2] reacts with ClCH2CH2SCH3 to give A, a monomeric and diamagnetic
substance of stoichiometry C10H12FeO2S having two strong IR bands at 1980 and 1940 cm-1.
Heating of A forms B, a monomeric , diamagnetic substance having strong IR bands at 1920 and
1630 cm-1. Identify A and B.
The reaction of molybdenum hexacarbonyl, Mo(CO)6, with excess mesitylene (1,3,5-
trimethylbenzene) at reflux generates compound A having the formula C12H12MoO3. Photolysis
of A under a N2 atmosphere generates a new compound B having the formula C11H12MoN2O2.
Compound B exhibits two infra-red absorption bands at 1970 and 1940 cm-1 and another at 2050
cm-1. The addition of trimethylsilane (Me3SiH) to B generates compound C having the formula
C14H22MoO2Si along with a colourless gas; this last compound C has C1 symmetry with CO
infrared absorptions at 1990 and 1965 cm-1. When C is allowed to stand at room temperature it
slowly isomerizes to D having Cs symmetry and the identical formula as compound C.
Draw the structures of compounds A, B, C, and D clearly and show that they are all 18-electron
species. For compound B compute the changes in the IR-stretching frequencies if the reaction
had been performed under 15N2.
Using 15N2, the heavier isotope will cause a reduction in the stretching frequency of the dinitrogen ligand, since it is inversely proportional to reduced mass. Degree of change obtained using ratio of frequencies gives (2050/1.035) cm-1 = 1980.7 cm-1
For the following sequence of reactions, sketch plausible molecular structures for each of the
organometallic compounds A to H which all satisfy the 18-electron rule.
Heating [(η5-C5H5)Fe(CO)3]+ with NaH in solution affords organometallic compound A which has a
room-temperature 1H NMR spectrum consisting of two singlets of relative intensity 1:5 at approximately
δ = -12 ppm and δ = 5 ppm, respectively.
Compound A is thermally unstable under ambient conditions and rapidly evolves a colourless gas B and
forms a purple-brown solid C having the empirical formula C7H5O2Fe. The Nujol-mull IR spectrum of
solid C exhibits strong absorptions at 1961, 1942, and 1790 cm-1.
Treatment of C with an equimolar amount of iodine generates a brown solid D which is stable in air and
is soluble in polar organic solvents. Its Nujol-mull IR spectrum exhibits strong absorptions at 2042 and
1992 cm-1.
Reaction of D with an equimolar amount of CH3MgI in diethyl ether affords caramel-coloured crystals
of E. Compound E is unstable in air, but is soluble in common organic solvents. Its Nujol-mull IR
spectrum exhibits strong absorptions at 2010 and 1965 cm-1, and its 1H NMR spectrum consists of two
singlets of relative intensity 3:5 at approximately δ = 0 ppm and δ = 4 ppm.
Reaction of D with an equimolar amount of NaC5H5 produces an orange solid F with the formula
C12H10O2Fe. Compound F is fairly stable in air, and its 1H NMR spectrum at 30 ºC consists of two
equal intensity singlets at approximately δ = 4.5 ppm and δ = 5.7 ppm.
On heating, F evolves a colourless gas and converts to an orange solid G that is stable in air and is
soluble in most organic solvents. Its 1H NMR spectrum at all temperatures consists of a single sharp
resonance at approximately δ = 4 ppm.
Identify compounds A through G and sketch their molecular structures..
