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

Density functional theory computation indicates that bridge splitting of [(PtR2)-R-II(mu-SEt2)](2) proceeds by partial dissociation to form R2Pta(mu-SEt2)(PtR2)-R-b(SEt2), followed by coordination of N-donor bromoarenes (L-Br) at Pt-a leading to release of (PtR2)-R-b(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-(pzCH(2))(2)C6H3Br (pz=pyrazol-1-yl) and 2,6-(Me2NCH2)(2)C6H3Br, subsequent oxidative addition assisted by intramolecular N-donor coordination via Pt(II)Tol(2)(L-N,Br) and reductive elimination from Pt-IV intermediates gives mer-Pt-II(L-N,C,N)Br and Tol(2). The strong sigma-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-(pzCH(2))(2)C6H3Br, a stable Pt-IV product, fac-(PtMe2)-Me-IV{2,6-(pzCH(2))(2)C6H3-N,C,N)Br is predicted, as reported experimentally, acting as a model for undetected and unstable Pt(IV)Tol(2){L-N,C,N}Br undergoing facile Tol(2) reductive elimination. The mechanisms reported herein enable the synthesis of Pt-II pincer reagents with applications in materials and bio-organometallic chemistry.

Automated summary

Density functional theory calculations elucidate the mechanism of bridge splitting of [(PtR2)-R-II(mu-SEt2)](2) and reveal differences in reaction pathways with different substituents and N-donor bromoarenes. This provides theoretical support for the synthesis of Pt-II pincer reagents.