Reactions of a Platinum(II) Agostic Complex: Decyclometalation, Dicyclometalation, and Solvent-Switchable Formation of a Rollover Complex

Good donor ligands react with an sp² cyclometalated complex of platinum containing an agostic interaction, initially causing displacement of the agostic interaction and decyclometalation. Eventually, these complexes rearrange to give sterically less congested complexes containing an sp³ cyclometalated group. The same end products are observed even with poor donor ligands that do not displace the agostic interaction, and this, together with other results, suggests to us that the route to the end products goes via a different agostic species. These sp³ cyclometalated complexes can be made to dicyclometalate via the simple expedient of adding water/base. Finally, dissolution of the agostic complex in DMSO results in a reversible “rollover” reaction, giving a C^∧C chelated ligand.