Computational study of bridge splitting, aryl halide oxidative addition to PtII, and reductive elimination from PtIV: route to pincer-PtII reagents with chemical and biological applications

<p>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-<i>N</i>). 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-<i>N,Br</i>) and reductive elimination from Pt^IV intermediates gives <i>mer</i>-Pt^II(L-<i>N,C,N</i>)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, <i>fac</i>-Pt^IVMe₂{2,6-(pzCH₂)₂C₆H₃-<i>N,C,N</i>)Br is predicted, as reported experimentally, acting as a model for undetected and unstable Pt^IVTol₂{L-<i>N,C,N</i>}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.</p>