Pt(II) and Pt(IV) Amido, Aryloxide, and Hydrocarbyl Complexes: Synthesis, Characterization, and Reaction with Dihydrogen and Substrates that Possess C−H Bonds

The Pt(II) amido and phenoxide complexes (tbpy)Pt(Me)(X), (tbpy)Pt(X)2, and [(tbpy)Pt(X)(py)][BAr′4] (X = NHPh, OPh; py = pyridine) have been synthesized and characterized. To test the feasibility of accessing Pt(IV) complexes by oxidizing their Pt(II) precursors, the previously reported (tbpy)Pt(R)2 (R = Me and Ph) systems were oxidized with I2 to yield (tbpy)Pt(R)2(I)2. The analogous reaction with (tbpy)Pt(Me)(NHPh) and MeI yields the corresponding (tbpy)Pt(Me)2(NHPh)(I) complex. Reaction of (tbpy)Pt(Me)(NHPh) and phenylacetylene at 80 °C results in the formation of the Pt(II) phenylacetylide complex (tbpy)Pt(Me)(CCPh). Kinetic studies indicate that the reaction of (tbpy)Pt(Me)(NHPh) and phenylacetylene occurs via a pathway that involves [(tbpy)Pt(Me)(NH2Ph)][TFA] as a catalyst. The reaction of H2 with (tbpy)Pt(Me)(NHPh) ultimately produces aniline, methane, tbpy, and elemental Pt. For this reaction, mechanistic studies reveal that 1,2-addition of dihydrogen across the Pt−NHPh bond to initially produce (tbpy)Pt(Me)(H) and free aniline is catalyzed by elemental Pt. Heating the cationic complexes [(tbpy)Pt(NHPh)(py)][BAr′4] and [(tbpy)Pt(OPh)(py)][BAr′4] in C6D6 does not result in the production of aniline and phenol, respectively. Attempted synthesis of a cationic system analogous to [(tbpy)Pt(NHPh)(py)][BAr′4] with ligands that are more labile than pyridine (e.g., NC5F5) results in the formation of the dimer [(tbpy)Pt(μ-NHPh)]2[BAr′4]2. Solid-state X-ray diffraction studies of the complexes (tbpy)Pt(Me)(NHPh), [(tbpy)Pt(NH2Ph)2][OTf]2, (tbpy)Pt(NHPh)2, (tbpy)Pt(OPh)2, (tbpy)Pt(Me)2(I)2, and (tbpy)Pt(Ph)2(I)2 are reported.