In pursuing the development of novel catalysts for aerobic methane-to-CH3X conversion, two PtIIMe complexes supported by sulfonated CNN pincer ligands, K[(L1)PtIIMe] and K[(L2)PtIIMe], were prepared and their aerobic transformation to CH3-X products (X = OH, CF3CO2, N+PhMe2) was studied. Complex K[(L1)PtIIMe] reacts with O2 in MeOH to form (L1)PtIVMe2 as the only PtIVMe product which is barely reactive in the subsequent CH3-X reductive elimination. However, K[(L2)PtIIMe] reacts with O2 in MeOH or acetone / 2,2,2-trifluoroethanol to selectively form three out of four possible diastereomeric (L2)PtIV(Me)OH complexes with (L2)PtIVMe2 as a minor byproduct. The remaining fourth diastereomer (L2)PtIV(Me)OH was prepared using H2O2 as oxidant. These products as well as a series of complexes (L)PtIVMe(Y) (L = L1, L2; Y = I, Cl, OCH2CF3) were studied in C-C and C-X (X = O, N) reductive elimination. The results show that C-X coupling is only efficient when the Me ligand can be accommodated trans- to the sulfonate group. When such arrangement is not readily attainable, the C-C coupling is the dominant process.

Small modification of sulfonated CNN pincer ligands L changes dramatically the outcome of aerobic LPtIIMe-to-CH3X functionalization

ACS Fall 2021

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