Models for Cooperative Catalysis: Oxidative Addition Reactions of Dimethylplatinum(II) Complexes with Ligands Having...

The role of NH and OH groups in the oxidative addition reactions of the complexes [PtMe₂(κ²-N,N'-L)], L = 2-C₅H₄NCH₂NH-x-C₆H₄OH [3, x = 2, L = L1; 4, x = 3, L = L2; 5, x = 4, L = L3], has been investigated. Complex 3 is the most reactive. It reacts with CH₂Cl₂ to give a mixture of isomers of [PtMe₂(CH₂Cl)(κ³-N,N',O-(L1-H)], 6, and decomposes in acetone to give [PtMe₃(κ³-N,N',O-(L1-H)], 7, both of which contain the fac tridentate deprotonated ligand. Complex 3 reacts with MeI to give complex 7, whereas 4 and 5 react to give [PtIMe₃(κ²-N,N'-L2))], 8, or [PtIMe₃(κ²-N,N'-L3)], 9, respectively. Each complex 3, 4, or 5 reacts with either dioxygen or hydrogen peroxide to give the corresponding complex [Pt(OH)₂Me₂(κ²-N,N'-L)], 10, L = L1; 11, L = L2; 12, L = L3. The ligand L3 in complexes 9 and 12 is easily oxidized to the corresponding imine ligand 2-C₅H₄NCH=N-4-C₆H₄OH, L4, in forming the complexes [PtIMe₃(κ²-N,N'-L4)], 13, and [Pt(OH)₂Me₂(κ²-N,N'-L4)], 14, respectively. The NH and OH groups play a significant role in supramolecular polymer or sheet structures of the complexes, formed through intermolecular hydrogen bonding, and these structures indicate how either intramolecular or intermolecular hydrogen bonding may assist some oxidative addition reactions.