Synthesis and Reactivity of [(C2F5)2MeP]2Pt(Me)X (X = Me, O2CCF3, OTf, OSO2F): A Reactivity Comparison with Chelate Acceptor Analogues

Abstract

A comparative study of new platinum methyl complexes cis-(dfmp)2Pt(Me)2 and trans-(dfmp)2Pt(Me)X (dfmp = (C2F5)2MeP; X = O2CCF3, OTf, OSO2F) with previously reported acceptor chelate analogues (dfepe)Pt(Me)X (dfepe = (C2F5)2PCH2CH2P(C2F5)2; X = Me, O2CCF3, OTf, OSO2F) is presented. In contrast to (dfepe)Pt(Me)2, which is inert to both H2 and CO addition, cis-(dfmp)2Pt(Me)2 reacts readily to form (dfmp)4Pt and cis-(dfmp)(CO)Pt(Me)2, respectively. Similarly, whereas (dfepe)Pt(Me)2 is stable up to 180 °C, thermolysis of cis-(dfmp)2Pt(Me)2 in benzene-d6 at 80 °C leads to ethane reductive elimination and production of (dfmp)4Pt. Dissolving cis-(dfmp)2Pt(Me)2 in neat trifluoroacetic, triflic, or fluorosulfonic acid at ambient temperature cleanly produces the corresponding trans-(dfmp)2Pt(Me)(X) complexes. Attempted isolation of trans-(dfmp)2Pt(Me)(O2CCF3) resulted in dfmp loss and reversible formation of the crystallographically characterized dimer, [(dfmp)Pt(Me)(μ-O2CCF3)]2. Monitoring the thermolysis of trans-(dfmp)2Pt(Me)(X) complexes by 31P NMR in their respective neat acids reveals a kinetic protolytic stability that is dependent on the nature of the trans X ligand: whereas trans-(dfmp)2Pt(Me)(O2CCF3) is less stable than the corresponding (dfepe)Pt(Me)(O2CCF3) complex, trans-(dfmp)2Pt(Me)(OTf) and trans-(dfmp)2Pt(Me)(OSO2F) are significantly more resistant to protolytic cleavage than the chelating analogues. Thermolysis in CF3CO2D or DOTf resulted in deuteration of the methyl ligand prior to methane loss, indicating the reversible formation of a methane adduct intermediate.