The basicity of [tris-(trimethylphosphine)(cyclooctadiene)iridium(I)]

[Tris-(trimethylphosphine)(cyclooctadiene)iridium(I)]chloride, [Ir(COD)(PMe3)3]Cl, is very electron rich. In this report, that electron rich character is probed by examining the protonation of the complex at the metal center to form the dicationic [tris-(trimethylphosphine)(cyclooctadiene)(hydrido)iridium(III)], [HIr(COD)(PMe3)3]+2. The exact formulation of the species formed depends on the nature of the Bronsted acid's counterion. Protonation with hydrogen chloride, fluoroboric acid, and triflic acid are all described and the structure of the dication and some products from further reaction of the dication are elucidated. Simple aqueous acid/base titration of [Ir(COD)(PMe3)3]Cl is described yielding a pKa for [HIr(COD)(PMe3)3]+2 of 4.2.

Graphical abstractThe electron rich iridium complex, [Ir(COD)(PMe3)3]+ readily undergoes protonation with a number of Bronsted acids. The protonation takes place on the metal and the structure and reactivity of the dication, [Hir(COD)(PMe3)3]2+ are discussed.Figure optionsDownload full-size imageDownload as PowerPoint slideHighlights► [Ir(COD)(PMe3)3]+ is readily protonated by a variety of Bronsted acids. ► Extra equivalents of acid may be retained in the protonated product leading to further reactions. ► [HIr(COD)(PMe3)3]2+ is structurally characterized and reaction chemistry studied. ► DFT calculations show very good agreement with experiment for [HIr(COD)(PMe3)3]2+.