| Article ID | Journal | Published Year | Pages | File Type |
|---|---|---|---|---|
| 1322086 | Journal of Organometallic Chemistry | 2015 | 6 Pages |
•Rollover cycloplatinated(II) and (IV) complexes are prepared.•The Pt(II) complexes are highly reactive to oxidative addition.•The mechanistic pathway for the oxidative addition of MeI is studied.
New rollover cyclometalated platinum(II) complex [PtMe(bpy-H) (PPh2Me)] (bpy-H = κ2N,C-2,2′-bipyridine) was synthesized by the reaction of [PtMe(bpy-H)(DMSO)] with 1 equiv. of methyldiphenylphosphine. The reaction of the rollover cyclometalated Pt(II) complex with MeI gave the rollover cyclometalated Pt(IV) complex [PtMe2(bpy-H) (PPh2Me)I]. The rollover cycloplatinated(II) complexes [PtMe(bpy-H) (L)] (L = PPh3 and PPh2Me) have a metal-to-ligand charge-transfer (MLCT) band, which were used to easily follow the kinetics of their reactions with MeI. On the basis of the kinetic data, the classical SN2 mechanism was suggested. The rates of the reactions at different temperatures were measured and consistent with the proposed mechanism, large negative ΔS‡ values were found. The PPh3 complex [PtMe(bpy-H) (PPh3)] reacted almost 4 or 5 times slower with MeI as compared to that of the PPh2Me complex [PtMe(bpy-H) (PPh2Me)] in CHCl3. This was attributed to the stronger donor ability and the less steric hindrance of the PPh2Me group as compared with those of the PPh3 group. The rate of MeI oxidative addition reactions of rollover cyclometalated platinum(II) complexes, [PtMe(bpy-H) (L)], were compared to classical cyclometalated complexes [PtMe(ppy) (L)] (ppy = 2-phenylpyridinate) and found to be lower than those reported for ppy analog. This was attributed to the existence of extra electronegative nitrogen atom in bpy-H ligand compared to ppy, which makes the bpy-H ligand slightly weaker donors, thus decreasing the reaction rates for [PtMe(bpy-H) (L)] (compared to [PtMe(ppy) (L)]).
Graphical abstractThe kinetics and mechanism of oxiative addition of MeI to rollover cyclometalated platinum(II) complexes, [PtMe(bpy-H) (L)] (bpy-H = κ2N,C˗2,2′-bipyridine, L = PPh3 or PPh2Me), are investigated.Figure optionsDownload full-size imageDownload as PowerPoint slide
