Models for Cooperative Catalysis: Oxidative Addition Reactions of Dimethylplatinum(II) Complexes with Ligands Having Both NH and OH Functionality

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.