Symmetrical Hydrogen Bonds in Iridium(III) Alkoxides with Relevance to Outer Sphere Hydrogen Transfer

Nathan D. Schley (1) , Stéphanie Halbert (2) , Christophe Raynaud (2) , Odile Eisenstein (2) , Robert Crabtree (1)

1 Department of Chemistry [New Haven]
2 ICGM ICMMM - Institut Charles Gerhardt Montpellier - Institut de Chimie Moléculaire et des Matériaux de Montpellier

A chelating ligand formed by deprotonation of 2-(2′-pyridyl)-2-propanol stabilizes a distorted trigonal bipyramidal geometry in a 16e- d6 5-coordinate iridium complex with the alkoxide acting as a π donor. Ambiphilic species such as AcOH bearing both nucleophilic and electrophilic functionality form adducts with the unsaturated iridium complex which contain strong intramolecular O***H***O hydrogen bonds that involve the basic alkoxide oxygen. Density functional theory (DFT) calculations on the isolated cations reproduce with high accuracy the geometrical features obtained via X-ray diffraction and corroborate the presence of very short hydrogen bonds with O***O distances of about 2.4 Å. Calculations further confirm the known trend that the hydrogen position in these bonds is sensitive to the O***O distance, with the shortest distances giving rise to symmetrical O***H***O interactions. Dihydrogen is shown to add across the Ir-O π bond in a presumed proton transfer reaction, demonstrating bifunctional behavior by the iridium alkoxide.

Domaines: Chimie inorganique; Chimie théorique et/ou physique

Nathan D. Schley, Stéphanie Halbert, Christophe Raynaud, Odile Eisenstein, Robert Crabtree. Symmetrical Hydrogen Bonds in Iridium(III) Alkoxides with Relevance to Outer Sphere Hydrogen Transfer. Inorganic Chemistry, 2012, 51, pp.12313-12323. ⟨10.1021/ic301601c⟩. ⟨hal-00755799⟩