Reductive Elimination from Platinum(IV) Aminotroponiminate Dimethyl Complexes Promoted by Sterically Hindered Lewis Bases

A series of PtII and PtIV aminotroponimate (ATI = N-tolyl-aminotroponiminate) complexes has been prepared. The PtII complex (ATI)­Pt­(CH3)­(SMe2) (1a) is synthesized from the reaction of [Li]­[ATI] with (Me)­(Cl)­Pt­(SMe2)2. Addition of either ethylene or carbon monoxide to 1a results in the formation of (ATI)­Pt­(CH3)­(η2-C2H4) (1b) or (ATI)­Pt­(CH3)­(CO) (1c), respectively. Oxidative addition of MeOTf or MeI to 1a results in formation of the PtIV complex [(ATI)­Pt­(CH3)2(X)­(SMe2)] (X = OTf (3), I (2)). Complex 3 reacts with isocyanides, which replace the triflate ligand to form [(ATI)­Pt­(CH3)2(CNR)­(SMe2)]­[OTf] (4). Complex 3 also undergoes ligand substitution reactions with azide or cyanide to form (ATI)­Pt­(CH3)2(N3)­(SMe2) (5a) or (ATI)­Pt­(CH3)2(CN)­(SMe2) (5b). Addition of PR3 results in the substitution product [(ATI)­Pt­(CH3)2(PR3)­(SMe2)]­[OTf] for phosphines with cone angles ≤136° (P­(OMe)3, PMe3, PMe2Ph). The PtIV complex [(ATI)­Pt­(CH3)2(PPh2Me)­(SMe2)]­[OTf] (6c) reductively eliminates [PMe2Ph2]­[OTf] or [SMe3]­[OTf] to form the PtII complex (ATI)­Pt­(CH3)­(PPh2Me) (7a) in solution at room temperature. Addition of 1 equiv of PPh3, which has a cone angle of 145°, results in the formation of 50% of PtII(ATI)­Pt­(CH3)­(PR3) and [MePPh3]­[OTf]. Reaction of 3 with PCy3, which has a cone angle of 170°, yields complete and immediate conversion to (ATI)­Pt­(CH3)­(SMe2) and [MePCy3]­[OTf].