Oxidative Addition of Water and Aliphatic Alcohols by IrCl(trialkylphosphine)₃

Abstract

Oxidative addition of aliphatic alcohols to (C(8)H(14))IrCl(PMe(3))(3) in benzene yields the cis-hydrido-alkoxo products mer-cis-HIr(OR)Cl(PMe(3))(3) (R = Me, Et, 1-pentyl, 2-propyl). The analogous hydroxo complex is prepared by oxidative addition of water in THF. The addition rate depends on the nature of the alcohol (methanol > 1-pentanol >> 2-propanol and methanol > water). The reaction is retarded in polar media but accelerated by protic cosolvents. Anionic ligand redistribution involving chloride and alkoxide (or hydroxide) competes with the oxidative addition reaction. A detailed kinetic study suggests that the 16-electron IrCl(PMe(3))(3) is the species undergoing the oxidative addition, and mer-cis-HIr(OR)Cl(PMe(3))(3) is the kinetic product. The reaction proceeds by a single-step nucleophilic attack of the metal on the O-H proton. Pi-donation by chloride stabilizes the transition state and governs the stereochemical course of the reaction. Protic solvent aggregation in the transition state in an apolar medium is suggested. mer-cis-HIr(OH)Cl(PEt(3))(3), obtained by water addition to IrCl(PEt(3))(3), was crystallographically characterized, showing an unusual hydrophobic cage around the hydride ligand.

Iridium‐Catalyzed Dehydrogenative Decarbonylation of Primary Alcohols with the Liberation of Syngas

“…This oxidative addition has been thoroughly studied with similar iridium(I) phosphine complexes and is known to be favored by nonpolar solvents such as benzene. [27,28] The addition is reversible and is not affected by the addition of lithium chloride. [27] The oxidative addition of water to iridium(I) complexes can also occur, but this reaction does not seem to be faster than the addition of alcohols.…”

“…[27,28] The addition is reversible and is not affected by the addition of lithium chloride. [27] The oxidative addition of water to iridium(I) complexes can also occur, but this reaction does not seem to be faster than the addition of alcohols. [27] Furthermore, rapid exchange between alcohols and the alkoxide ligands has been observed in these iridium complexes [27] and a similar exchange between a hydroxide ligand and an alcohol should be possible.…”

“…This fast dissociation of the aldehyde has been observed in a number of similar iridium-dihydride complexes. [27] As the release of hydrogen from iridium increases the entropy of the reaction, it is a matter of heat to reductively eliminate hydrogen gas.…”

Benchmarking of ONIOM method for the study of NH3 dissociation at open ends of BNNTs

“…The N-H bond cleavage is a challenging problem not only toward the transformation of NH 3 into a useful amino compound but also toward the starting of many catalytic reactions [11][12][13]. Since only methodological aspects of the ONIOM method have been studied in the present work, no discussion was addressed with respect to either experimental data or absolute accuracy of the chosen levels of calculations.…”

Chemisorption of NH3 at the open ends of boron nitride nanotubes: a DFT study

“…On the other hand, the N-H bond cleavage is a challenging problem not only toward the transformation of NH 3 into a useful amino compound but also toward the beginning of many catalytic reactions [18][19][20]. Until now, several methods for N-H cleavage have been presented in the base of transition metal complexes [20].…”