Computational Study of Bridge Splitting, Aryl Halide Oxidative Addition to Pt^II, and Reductive Elimination from Pt^IV: Route to Pincer-Pt^II Reagents with Chemical and Biological Applications

Density functional theory computation indicates that bridge splitting of [Pt^IIR₂(μ-SEt₂)]₂ proceeds by partial dissociation to form R₂Pt^a(μ-SEt₂)Pt^bR₂(SEt₂), followed by coordination of N-donor bromoarenes (L-Br) at Pt^a leading to release of Pt^bR₂(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)₂C₆H₃Br (pz=pyrazol-1-yl) and 2,6-(Me₂NCH₂)₂C₆H₃Br, subsequent oxidative addition assisted by intramolecular N-donor coordination via Pt^IITol₂(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)₂C₆H₃Br, a stable Pt^IV product, fac-Pt^IVMe₂{2,6-(pzCH₂)₂C₆H₃-N,C,N)Br is predicted, as reported experimentally, acting as a model for undetected and unstable Pt^IVTol₂{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.