139655-76-8Relevant academic research and scientific papers
Migratory insertion reactions of indenyliridium dialkyls and alkyl and aryl hydrides
Foo, Thomas,Bergman, Robert G.
, p. 1811 - 1819 (1992)
This paper reports the migratory insertion chemistry of indenyliridium complexes described in the companion paper. Complexes of general formula (η5-Ind)(PMe3)Ir(R)(R′), where R = alkyl or aryl and R′ = alkyl, aryl, or hydride (4-6) react with dative ligands L such as tert-butylisocyanide and CO. These transformations lead to η5 to η1 isomerization of the indenyl ligand, giving octahedral iridium complexes of general formula (η1-Ind)(PMe3)(L)2Ir(R)(R′) (8, 9, 11). Treatment of the methyl aryl and dimethyl η1-indenyl complexes 9a, 9d, and 9e with trimethylamine oxide removes CO, allowing the indenyl ligand to reestablish η5-coordination by inducing CO migratory insertion to give acyl complexes 10. Reaction of η1-indenyl aryl and methyl hydrides 6 (as well as the dihydride (η5-Ind)(PMe3)IrH2 (7)) with CO leads to reductive elimination of arene, methane, or H2 rather than migratory insertion, forming (η1-Ind)(CO)3(PMe3)Ir (12) as the organometallic product. In contrast, treatment of methyl and aryl hydrides 6 with alkynes leads to the methyl vinyl complexes (η5-Ind)(PMe3)Ir(Me)(CR=C(R′)(H)) (13) and reaction of 6a with ethylene gives the methyl ethyl complex (η5-Ind)(PMe3)Ir(Me)(Et) (14). Isotope labeling, stereochemical, and kinetic studies have been carried out on the insertion reaction of 6a with 3,3-dimethyl-1-butyne. The results of these experiments are most consistent with a mechanism involving initial reversible coordination of alkyne to the metal center (probably with concurrent η5-η3 isomerization of the indenyl ligand) followed by irreversible migration of the metal-bound hydrogen to the tert-butyl-substituted carbon of the alkyne and then rapid recoordination of the indenyl group.
