Reversible Pt(II)–CH(3) deuteration without methane loss: metal–ligand cooperation vs. ligand-assisted Pt(II)-protonation

Di(2-pyridyl)ketone dimethylplatinum(ii), (dpk)Pt(II)(CH(3))(2), reacts with CD(3)OD at 25 °C to undergo complete deuteration of Pt–CH(3) fragments in ∼5 h without loss of methane to form (dpk)Pt(II)(CD(3))(2) in virtually quantitative yield. The deuteration can be reversed by dissolution in CH(3)OH or CD(3)OH. Kinetic analysis and isotope effects, together with support from density functional theory calculations indicate a metal–ligand cooperative mechanism wherein DPK enables Pt–CH(3) deuteration by allowing non-rate-limiting protonation of Pt(II) by CD(3)OD. In contrast, other model di(2-pyridyl) ligands enable rate-limiting protonation of Pt(II), resulting in non-rate-limiting C–H(D) reductive coupling. Owing to its electron-poor nature, following complete deuteration, DPK can be dissociated from the Pt(II)-centre, furnishing [(CD(3))(2)Pt(II)(μ-SMe(2))](2) as the perdeutero analogue of [(CH(3))(2)Pt(II)(μ-SMe(2))](2), a commonly used Pt(II)-precursor.