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

Abstract

Density functional theory computation indicates that bridge-splitting of [Pt II R 2 (μ-SEt 2 )] 2 proceeds via partial dissociation to form R 2 Pt a (μ-SEt 2 )Pt b R 2 (SEt 2 ), followed by coordination of N-donor bromoarenes (L-Br) at Pt a leading to release of Pt b R 2 (SEt 2 ), which reacts with a second molecule of L-Br, providing two molecules of PtR 2 (SEt 2 )(L-Br- N ). For R = 4-tolyl (Tol), L-Br = 2,6-(pzCH 2 ) 2 C 6 H 3 Br (pz = pyrazol-1-yl) and 2,6-(Me 2 NCH 2 ) 2 C 6 H 3 Br, 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 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-(pzCH 2 ) 2 C 6 H 3 Br, a stable Pt IV product, fac -Pt IV Me 2 {2,6-(pzCH 2 ) 2 C 6 H 3 - 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.