Homogenous catalysis II

Question 1

Possible steps

Answer 1

Ligand substitution, oxidative addition/reductive elimination, migratory insertion, β-H transfer and external nucleophilic attack

Question 2

Wilkinson’s catalyst

Answer 2

Selective hydrogenation, RhCl(PPh3)3, bulky PPh3 promotes dissociation to active 14e- species, rate slowed by added PPh3 so dissociation important in the cycle

Question 3

Metal hydride catalysts

Answer 3

Can have side reactions involving alkene isomerism from terminal to the more stable internal alkene

Question 4

Hydroformylation

Answer 4

Conversion alkenes to aldehydes, addition of H-CHO over C=C bond which is supplied vie CO2 and H2 substrates

Question 5

Stille coupling reactions

Answer 5

Forms C-C bonds, Re-X + R3Sn-Rn and palladium catalyst gives Re-Rn and R3Sn-X

Question 6

Heck reaction

Answer 6

C-C bond formation between electrophilic organic halides and alkenes

Question 7

Conditions for Re in Stille and Heck

Answer 7

Must not have β-hydrogens