42 Questions
What type of intermediate can undergo concerted reductive elimination of ethane if the Iā concentration is low?
The reactive five-coordinate intermediate
What is the shape of the intermediate formed after ligand dissociation from M(R)(X)L2?
Three-coordinate M(R)(X)L
What is required for reductive elimination to occur in trans-M(R)(X)L2 complexes?
Initial trans to cis isomerization to bring R and H close together
What type of complexes show a variety of RE mechanisms?
Square planar d8 complexes
What type of bonds can be formed through reductive elimination in octahedral d6 species?
CāC and CāHal bonds
What is the reverse of the mechanism for reductive elimination in octahedral d6 species?
The mechanism for oxidative addition of nonpolar (CāC) and polar (MeāI) bonds to square planar d8 species
What type of pathways exist for the reductive elimination of ArāN{tolyl}2 in trans-[PdAr(N{tolyl}2)(PPh3)2]?
Competing dissociative and nondissociative pathways
Who has analyzed the kinetics for reductive elimination in certain complexes?
Hartwig
What is the typical order of the reactions shown in Equation 6.7?
Second order
What is the approximate entropy of activation (ĪSā”) for the reactions in Equation 6.7?
ā20 eu
How do electron-releasing ligands affect the reactions in Equation 6.7?
They accelerate the reactions.
What is the orientation of the CāH bond as it approaches the metal?
The H atom points toward the metal.
What is the consequence of the OA mechanism on the stereochemistry at carbon?
Retention of stereochemistry
Why do HāH and hydrocarbon CāH bonds readily oxidatively add to metals?
Due to the high MāH and MāC bond strengths in the product.
What drives the reaction in Equation 6.8?
Ring strain and the high trans effect of the biphenyl
What favors the OA of the CāC bond in Equation 6.9?
Formation of a strong MāCN bond
What is the effect of wide ligand bite angles on the reaction mechanism in chelates?
Favors RE
What determines whether OA or RE will dominate in a reaction?
Thermodynamics
What is the typical outcome of the reaction in Eq. 6.22 when X = alkyl or aryl and Y = H?
The reaction goes to the right
What is the configurations of carbon center in radical binuclear HHal?
Racemized
What is the role of polar solvents in OA reactions?
Favors SN2
What is the characteristic feature of reductive elimination (RE) products?
A and B are trans
What is the notable feature of reactions involving H in OA?
Particularly fast kinetics
What is the possible intermediate in some OA reactions?
Radical intermediates
What is the common characteristic of first row metals that prefer binuclear oxidative addition?
They prefer to change their oxidation state by one rather than two units.
What is the significance of Eq. 6.24 and Eq. 6.25 in the context of binuclear reductive elimination?
They show the importance of binuclear OA for first row metals that prefer to change their oxidation state by one rather than two units.
Why do reductive eliminations of CāF, āO, and āN have a higher kinetic barrier than those of CāH or CāC?
The Ļ donor X group (F, OR, NR2) prefers to locate at the base of the Y in the Y-shaped intermediate, remote from the RE partner.
What is the significance of the Buchwald-Hartwig coupling procedure in the context of reductive elimination?
It forms CāX bonds through reductive elimination.
What is the alternate route that apparent OA/RE sequences can take?
Ļ-bond metathesis or Ļ-bond complex-assisted metathesis.
Why is OA forbidden in d0 early metal complexes?
The product would have to be d-2, which is not possible.
What is the reaction equation that demonstrates the Ļ-bond metathesis mechanism?
Eq. 3.32: the reaction of a d0 complex with H2.
What is the significance of path b or c in Fig. 6.3?
They represent the Ļ-bond metathesis mechanism, which takes over when OA is forbidden.
What is the primary difference between the reactivity of complex A and complex B with respect to MeOSO2Me and i-PrI?
Complex A undergoes oxidative addition with MeOSO2Me, but not with i-PrI, while complex B reacts with i-PrI but not with MeOSO2Me.
Which complex would be more likely to react with MeI and why?
Complex A would be more likely to react with MeI, as it reacts with MeOSO2Me, which is similar to MeI.
What further tests could be applied to confirm the mechanism of oxidative addition for complex A and complex B?
Tests such as spectroscopic analysis, kinetic studies, or exchange reactions could be used to confirm the mechanisms.
What is the significance of the difference in reactivity between complex A and complex B with respect to MeOSO2Me and i-PrI?
The difference in reactivity suggests that the mechanisms of oxidative addition for complex A and complex B are different.
How do the reactivities of complex A and complex B with MeOSO2Me and i-PrI relate to the general principles of oxidative addition?
The reactivities of complex A and complex B demonstrate the importance of steric and electronic factors in oxidative addition.
What would be the expected outcome of reacting complex A with i-PrI, and why?
No reaction would be expected, as complex A does not react with i-PrI.
What is the significance of the reactivity of complex B with i-PrI, but not with MeOSO2Me?
This suggests that complex B has a different mechanism of oxidative addition than complex A.
How do the mechanisms of oxidative addition for complex A and complex B relate to the general principles of organometallic chemistry?
The mechanisms of oxidative addition for complex A and complex B demonstrate the importance of steric and electronic factors in organometallic chemistry.
What would be the expected outcome of reacting complex B with MeOSO2Me, and why?
No reaction would be expected, as complex B does not react with MeOSO2Me.
What is the importance of understanding the mechanisms of oxidative addition for complex A and complex B?
Understanding the mechanisms of oxidative addition is important for understanding the reactivity of organometallic complexes and designing new reactions.
Learn about the mechanisms of organometallic reactions, including the ordered transition state and the role of electron-releasing ligands. Understand the concept of agostic complexes and their relation to OA pathways.
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