Ligand addition or hydride elimination or elimination

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ligand addition or -hydride elimination (or elimination)
5. (15 pts) Consider the following reaction sequence: Ir Br Me 3 P CD 3 PMe 3 C PMe 3 H H Ir Br Me 3 P PMe 3 H 2 C PMe 3 CD 3 Br Br Ir Br Me 3 P PMe 3 H 2 C PMe 3 CD 3 Br Ir Br Me 3 P PMe 3 D 2 C PMe 3 CH 2 D Br + migratory insertion A B C1 C2 The deuterated methyl group in the complex A does a migratory insertion with the carbene ligand to form the ethyl group in B . Migratory insertion is the reaction of an anionic ligand with a neutral ligand to produce a new anionic ligand (examples: M-carbene + M-CD 3 M-CH 2 CD 3 ; M-ethylene + M-H M-Et). The product C2 , however, shows that one can get some scrambling of the deuterium labels from the original CD 3 methyl group. Clearly explain and show the properly labeled reaction steps that convert B to C2 . Don’t worry about bromide coordination till the last step Ir Br Me 3 P PMe 3 H 2 C PMe 3 CD 3 Br B Ir Br Me 3 P PMe 3 D 2 C PMe 3 CH 2 D C2 Ir Br Me 3 P PMe 3 PMe 3 Br D C C D H H D Ir Br Me 3 P PMe 3 PMe 3 Br D C C D H H D Br migr atory inser tion -hydrid e elimination ethylene r otati on bromide ligand addition 16e- 18e- 18e- 16e- 18e- 2 .
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10 6. (20 pts) Consider the following reaction: Sketch out a detailed proposed mechanism based on the fundamental reaction types discussed in class. Clearly draw your structures and label each step below. Explain if it is necessary that the order of reactions occurs in a specific order. Me 3 P Ni N C CH 3 Me 3 P Ni N C CH 3 CH 3 + CH 4 Me 3 P Ni N C CH 3 CH 3 NCCH 3 Me 3 P Ni CH 3 Ni Me 3 P H 3 C H CH 4 Me 3 P Ni Me 3 P Ni N C CH 3 + NCCH 3 ligand dissociation C-H oxidative addition CH 3 -H reductive elimination ligand addition
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