Organometallic Reactions Mechanisms
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Questions and Answers

What type of intermediate can undergo concerted reductive elimination of ethane if the I− 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?

<p>Square planar d8 complexes</p> Signup and view all the answers

What type of bonds can be formed through reductive elimination in octahedral d6 species?

<p>C–C and C–Hal bonds</p> Signup and view all the answers

What is the reverse of the mechanism for reductive elimination in octahedral d6 species?

<p>The mechanism for oxidative addition of nonpolar (C–C) and polar (Me–I) bonds to square planar d8 species</p> Signup and view all the answers

What type of pathways exist for the reductive elimination of Ar−N{tolyl}2 in trans-[PdAr(N{tolyl}2)(PPh3)2]?

<p>Competing dissociative and nondissociative pathways</p> Signup and view all the answers

Who has analyzed the kinetics for reductive elimination in certain complexes?

<p>Hartwig</p> Signup and view all the answers

What is the typical order of the reactions shown in Equation 6.7?

<p>Second order</p> Signup and view all the answers

What is the approximate entropy of activation (ΔS‡) for the reactions in Equation 6.7?

<p>−20 eu</p> Signup and view all the answers

How do electron-releasing ligands affect the reactions in Equation 6.7?

<p>They accelerate the reactions.</p> Signup and view all the answers

What is the orientation of the C–H bond as it approaches the metal?

<p>The H atom points toward the metal.</p> Signup and view all the answers

What is the consequence of the OA mechanism on the stereochemistry at carbon?

<p>Retention of stereochemistry</p> Signup and view all the answers

Why do H–H and hydrocarbon C–H bonds readily oxidatively add to metals?

<p>Due to the high M–H and M–C bond strengths in the product.</p> Signup and view all the answers

What drives the reaction in Equation 6.8?

<p>Ring strain and the high trans effect of the biphenyl</p> Signup and view all the answers

What favors the OA of the C–C bond in Equation 6.9?

<p>Formation of a strong M–CN bond</p> Signup and view all the answers

What is the effect of wide ligand bite angles on the reaction mechanism in chelates?

<p>Favors RE</p> Signup and view all the answers

What determines whether OA or RE will dominate in a reaction?

<p>Thermodynamics</p> Signup and view all the answers

What is the typical outcome of the reaction in Eq. 6.22 when X = alkyl or aryl and Y = H?

<p>The reaction goes to the right</p> Signup and view all the answers

What is the configurations of carbon center in radical binuclear HHal?

<p>Racemized</p> Signup and view all the answers

What is the role of polar solvents in OA reactions?

<p>Favors SN2</p> Signup and view all the answers

What is the characteristic feature of reductive elimination (RE) products?

<p>A and B are trans</p> Signup and view all the answers

What is the notable feature of reactions involving H in OA?

<p>Particularly fast kinetics</p> Signup and view all the answers

What is the possible intermediate in some OA reactions?

<p>Radical intermediates</p> Signup and view all the answers

What is the common characteristic of first row metals that prefer binuclear oxidative addition?

<p>They prefer to change their oxidation state by one rather than two units.</p> Signup and view all the answers

What is the significance of Eq. 6.24 and Eq. 6.25 in the context of binuclear reductive elimination?

<p>They show the importance of binuclear OA for first row metals that prefer to change their oxidation state by one rather than two units.</p> Signup and view all the answers

Why do reductive eliminations of C–F, –O, and –N have a higher kinetic barrier than those of C–H or C–C?

<p>The π 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.</p> Signup and view all the answers

What is the significance of the Buchwald-Hartwig coupling procedure in the context of reductive elimination?

<p>It forms C–X bonds through reductive elimination.</p> Signup and view all the answers

What is the alternate route that apparent OA/RE sequences can take?

<p>σ-bond metathesis or σ-bond complex-assisted metathesis.</p> Signup and view all the answers

Why is OA forbidden in d0 early metal complexes?

<p>The product would have to be d-2, which is not possible.</p> Signup and view all the answers

What is the reaction equation that demonstrates the σ-bond metathesis mechanism?

<p>Eq. 3.32: the reaction of a d0 complex with H2.</p> Signup and view all the answers

What is the significance of path b or c in Fig. 6.3?

<p>They represent the σ-bond metathesis mechanism, which takes over when OA is forbidden.</p> Signup and view all the answers

What is the primary difference between the reactivity of complex A and complex B with respect to MeOSO2Me and i-PrI?

<p>Complex A undergoes oxidative addition with MeOSO2Me, but not with i-PrI, while complex B reacts with i-PrI but not with MeOSO2Me.</p> Signup and view all the answers

Which complex would be more likely to react with MeI and why?

<p>Complex A would be more likely to react with MeI, as it reacts with MeOSO2Me, which is similar to MeI.</p> Signup and view all the answers

What further tests could be applied to confirm the mechanism of oxidative addition for complex A and complex B?

<p>Tests such as spectroscopic analysis, kinetic studies, or exchange reactions could be used to confirm the mechanisms.</p> Signup and view all the answers

What is the significance of the difference in reactivity between complex A and complex B with respect to MeOSO2Me and i-PrI?

<p>The difference in reactivity suggests that the mechanisms of oxidative addition for complex A and complex B are different.</p> Signup and view all the answers

How do the reactivities of complex A and complex B with MeOSO2Me and i-PrI relate to the general principles of oxidative addition?

<p>The reactivities of complex A and complex B demonstrate the importance of steric and electronic factors in oxidative addition.</p> Signup and view all the answers

What would be the expected outcome of reacting complex A with i-PrI, and why?

<p>No reaction would be expected, as complex A does not react with i-PrI.</p> Signup and view all the answers

What is the significance of the reactivity of complex B with i-PrI, but not with MeOSO2Me?

<p>This suggests that complex B has a different mechanism of oxidative addition than complex A.</p> Signup and view all the answers

How do the mechanisms of oxidative addition for complex A and complex B relate to the general principles of organometallic chemistry?

<p>The mechanisms of oxidative addition for complex A and complex B demonstrate the importance of steric and electronic factors in organometallic chemistry.</p> Signup and view all the answers

What would be the expected outcome of reacting complex B with MeOSO2Me, and why?

<p>No reaction would be expected, as complex B does not react with MeOSO2Me.</p> Signup and view all the answers

What is the importance of understanding the mechanisms of oxidative addition for complex A and complex B?

<p>Understanding the mechanisms of oxidative addition is important for understanding the reactivity of organometallic complexes and designing new reactions.</p> Signup and view all the answers

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