A eta(2)-triflate (OTf) intermediate in the solution dynamics of PtMe3(OTf)center dot TMEDA: the 'windscreen-wiper process' revisited

The reaction of tetrameric [PtMe3(OTf)](4), (OTf = triflate = CF3SO3-) with TMEDA (N,N,N',N'-tetramethylethylene diamine) gave the monomeric compound PtMe3(OTf). TMEDA in quantitative yield. The non-planar TMEDA ligand contai ns two different sorts of methyl groups in PtMe3(OTf) . TMEDA, and thus off ers a second and independent set of NMR parameters in addition to the commo nly used signals of the Me3Pt unit. The additional information derived from these NMR data provides detailed insight into the mechanistic picture of c helating phenomena at Pt-IV. At low temperature the twisting of the ethylen e bridge of the TMEDA ligand can be observed; at room temperature an intram olecular two-step ligand exchange takes place. Evidence for an equilibrium involving a TMEDA chelate as well as a eta(2)-O3SCF3 chelate has been found . Dependent on the applied temperature, two types of ligand exchange motion s can be distinguished by dynamic NMR spectroscopy because of their differe nt activation parameters. These motions have been identified as the two ess ential steps in the so-called 'windscreen-wiper process' that has been invo ked for exchange phenomena in Me3Pt complexes previously. Moreover, the dat a indicate the crucial role of a eta(2)-triflate in this process in PtMe3(O Tf). TMEDA.