Stoichiometric and catalytic H/D incorporation by cationic iridium complexes: a common monohydrido-iridium intermediate.
A mechanistic study of the stoichiometric and catalytic H/D exchange reactions involving cationic iridium complexes is presented. Strong evidence suggests that both stoichiometric and catalytic reactions proceed via a monohydrido-iridium species. Stoichiometric deuterium incorporation reactions introduce multiple deuterium atoms into the organic products when aryliridium compounds CpPMe(3)Ir(C(6)H(4)X)(OTf) (X = H, o-CH(3), m-CH(3), p-CH(3)) react with D(2). Multiple deuteration occurs at the unhindered positions (para and meta) of toluene, when X = CH(3). The multiple-deuteration pathway is suppressed in the presence of an excess of the coordinating ligand, CH(3)CN. The compound CpPMe(3)IrH(OTf) (1-OTf) is observed in low-temperature, stoichiometric experiments to support a monohydrido-iridium intermediate that is responsible for catalyzing multiple deuteration in the stoichiometric system. When paired with acetone-d(6)(), [CpPMe(3)IrH(3)][OTf] (4) catalytically deuterates a wide range of substrates with a variety of functional groups. Catalyst 4 decomposes to [CpPMe(3)Ir(eta(3)-CH(2)C(OH)CH(2))][OTf] (19) in acetone and to [CpPMe(3)IrH(CO)][OTf] (1-CO) in CH(3)OH. The catalytic H/D exchange reaction is not catalyzed by simple H(+) transfer, but instead proceeds by a reversible C-H bond activation mechanism.
Contribution from Pfizer Global Research and Development, Pfizer Inc., 301 Henrietta Street, Kalamazoo, MI 49007, USA.
Cathleen M
CM
Yung
Marc B
MB
Skaddan
Robert G
RG
Bergman
D000438:Alcohols / Q000737:chemistry; D000588:Amines / Q000737:chemistry; D002264:Carboxylic Acids / Q000737:chemistry; D003903:Deuterium / Q000737:chemistry*; D006859:Hydrogen / Q000737:chemistry*; D007495:Iridium / Q000737:chemistry*; D007553:Isotope Labeling / Q000379:methods*; D009942:Organometallic Compounds / Q000737:chemistry
D000438:Alcohols; D000588:Amines; D002264:Carboxylic Acids; D009942:Organometallic Compounds; D007495:Iridium; D006859:Hydrogen; D003903:Deuterium