Computational Study of Bridge Splitting, Aryl Halide Oxidative Addition to Pt^II , and Reductive Elimination from Pt^IV...

Density functional theory computation indicates that bridge splitting of [Pt^II R₂ (μ-SEt₂ )]₂ proceeds by partial dissociation to form R₂ Pt^a (μ-SEt₂ )Pt^b R₂ (SEt₂ ), followed by coordination of N-donor bromoarenes (L-Br) at Pt^a leading to release of Pt^b R₂ (SEt₂ ), which reacts with a second molecule of L-Br, providing two molecules of PtR₂ (SEt₂ )(L-Br-N). For R=4-tolyl (Tol), L-Br=2,6-(pzCH₂ )₂ C₆ H₃ Br (pz=pyrazol-1-yl) and 2,6-(Me₂ NCH₂ )₂ C₆ H₃ Br, subsequent oxidative addition assisted by intramolecular N-donor coordination via Pt^II Tol₂ (L-N,Br) and reductive elimination from Pt^IV intermediates gives mer-Pt^II (L-N,C,N)Br and Tol₂ . The strong σ-donor influence of Tol groups results in subtle differences in oxidative addition mechanisms when compared with related aryl halide oxidative addition to palladium(II) centres. For R=Me and L-Br=2,6-(pzCH₂ )₂ C₆ H₃ Br, a stable Pt^IV product, fac-Pt^IV Me₂ {2,6-(pzCH₂ )₂ C₆ H₃ -N,C,N)Br is predicted, as reported experimentally, acting as a model for undetected and unstable Pt^IV Tol₂ {L-N,C,N}Br undergoing facile Tol₂ reductive elimination. The mechanisms reported herein enable the synthesis of Pt^II pincer reagents with applications in materials and bio-organometallic chemistry.