Dimerization of an organoplatinum complex triggered by oxidative addition: A model for dynamic ring-opening polymerization

• A thiophene bis(amidopyridine) ligand (NN) forms a chelate complex [PtMe2(NN)].
• Oxidative addition of MeI occurs easily to give [PtIMe3(NN)].
• [PtIMe3(NN)] spontaneously dimerizes to give [{PtIMe3(μ-NN)}2].
• The flexible ligand undergoes significant conformational change.
• A new strategy for triggering dynamic ring opening polymerization is suggested.

The bis(pyridine) ligand thiophene-2,5-dicarboxylic acid bis(N-methyl-N-4-pyridyl-amide), 1, reacts with [Pt2Me4(μ-SMe2)2], with displacement of Me2S, to give the chelate complex [PtMe2(1)], 2, which then reacts with methyl iodide to give [PtIMe3(1)], 3. Complex 3 spontaneously dimerizes to give a macrocyclic complex [{PtIMe3(μ-1)}2], 4, which exists as a mixture of anti and syn isomers 4a and 4b, as characterized by both NMR spectroscopy and X-ray structure determination. In the complex 4*, formed by oxidative addition of CD3I, the CH3 and CD3 ligands are scrambled between the axial and equatorial coordination sites at platinum(IV). The dimerization can be considered as a model for the first step in a dynamic ring-opening polymerization and occurs to give a new conformation of the flexible ligand.

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