Synthesis and reactivity of cycloplatinated rollover complexes, an experimental and theoretical approach

Cyclometalation reactions constitute one of the evergreen fields in synthetic chemistry because of the variety of applications, from substrate functionalization to catalyst production and model for C-H activation. A variation on this theme is rollover cyclometalation where a bidentate donor, such as 2,2'-bipyridine, upon C-H activation leads to a species with a free donor atom that is able to influence the properties, hence the reactivity, of the complex.We explored the similarities/differences between classical and rollover cyclometalation to check the importance of the second nitrogen donor by comparing suitably substituted 2,2'-bipyridines and 2-phenylpyridines; moreover the properties of the ligands were tuned to investigate the impact of stereoelectronic modification on the C-H activation process.The reactivity of the newly synthesized cyclometalates having formula [Pt(K2-NC)(CH3)(L)] (κ2-N,C = cyclometalated ligand, L = neutral ligand) was tested in different conditions: ligand substitutions, protonolysis, oxidative additions and reductive eliminations. A wide variety of mono and dinuclear complexes was obtained and fully characterized by NMR spectroscopy.Further insight has been sought fromin silicoexperiments using DFT calculations that led to a nice agreement with the chemistry observed.