Oxidative addition of water and aliphatic alcohols by IrCl(trialkylphosphine)3

Ofer Blum, David Milstein

Research output: Contribution to journalArticle

48 Citations (Scopus)

Abstract

Oxidative addition of aliphatic alcohols to (C8H14)IrCl(PMe3)3 in benzene yields the cis-hydridoalkoxo products mer-cis-HIr(OR)Cl(PMe3)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- (PMe3)3 is the species undergoing the oxidative addition, and mer-cis-HIr(OR)Cl(PMe3)3 is the kinetic product. The reaction proceeds by a single-step nucleophilic attack of the metal on the O-H proton. π-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(PEt3)3, obtained by water addition to IrCl(PEt3)3, was crystallographically characterized, showing an unusual hydrophobic cage around the hydride ligand.

Original languageEnglish
Pages (from-to)11456-11467
Number of pages12
JournalJournal of the American Chemical Society
Volume124
Issue number38
DOIs
Publication statusPublished - Sep 25 2002

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Alcohols
Methanol
Water
Chlorides
Ligands
Addition reactions
Kinetics
2-Propanol
Propanol
Benzene
Hydrides
Protons
Agglomeration
Metals
Electrons
Hydrogen
n-pentanol
hydroxide ion
N,N,N'-tri(beta-chloroethyl)-N'-(4-formylphenyl)-1,3-propylenediamine

ASJC Scopus subject areas

  • Chemistry(all)

Cite this

Oxidative addition of water and aliphatic alcohols by IrCl(trialkylphosphine)3 . / Blum, Ofer; Milstein, David.

In: Journal of the American Chemical Society, Vol. 124, No. 38, 25.09.2002, p. 11456-11467.

Research output: Contribution to journalArticle

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N2 - Oxidative addition of aliphatic alcohols to (C8H14)IrCl(PMe3)3 in benzene yields the cis-hydridoalkoxo products mer-cis-HIr(OR)Cl(PMe3)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- (PMe3)3 is the species undergoing the oxidative addition, and mer-cis-HIr(OR)Cl(PMe3)3 is the kinetic product. The reaction proceeds by a single-step nucleophilic attack of the metal on the O-H proton. π-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(PEt3)3, obtained by water addition to IrCl(PEt3)3, was crystallographically characterized, showing an unusual hydrophobic cage around the hydride ligand.

AB - Oxidative addition of aliphatic alcohols to (C8H14)IrCl(PMe3)3 in benzene yields the cis-hydridoalkoxo products mer-cis-HIr(OR)Cl(PMe3)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- (PMe3)3 is the species undergoing the oxidative addition, and mer-cis-HIr(OR)Cl(PMe3)3 is the kinetic product. The reaction proceeds by a single-step nucleophilic attack of the metal on the O-H proton. π-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(PEt3)3, obtained by water addition to IrCl(PEt3)3, was crystallographically characterized, showing an unusual hydrophobic cage around the hydride ligand.

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