Electrochemical generation and reactivity of bis(tertiary phosphine)platinum(0) complexes: A comparison of the reactivity of [Pt(PPh3)2] and [Pt(PEt3)2] equivalents

Article abstract of DOI:10.1021/om00106a032

Electrochemical reduction of cis-[PtCl₂(PR₃)₂] (R = Ph, Et) in CH₃CN/C₆H₆ containing NBu₄ClO₄ at a Hg pool electrode generates [Pt(PR₃)₂] equivalents in solution. Where R = Ph, the [Pt(PR₃)₂] equivalent may be trapped by O₂, O₂/CO₂, HCl, MeI, C₆H₅COCl, and RC≡CR (R = Ph, COOMe) but not by the less reactive substrate PhCl. Where R = Et, the [Pt(PR₃)₂] equivalent reacts with the NBu₄⁺ cation to ultimately generate trans-[PtH(Cl)(PEt₃)₂]. Prolonged electrolyses cause reduction of trans-[PtH(Cl)(PEt₃)₂] leading to hydride attack on the CH₃CN solvent and ultimately forming trans-[PtH(CH₂CN)(PEt₃)₂]. In the presence of bases such as NBu₃, trans-[PtH(CH₂CN)(PEt₃)₂] is isomerized in CH₃CN solution producing trans-[PtCN(CH₃)(PEt₃)₂]. The use of electroinactive trapping agents such as PhCl or PhCN as cosolvents for the reduction of cis-[PtCl₂(PEt₃)₂] allows trapping of the [Pt(PEt₃)₂] equivalents as trans-[PtPh-(X)(PEt₃)₂] (X = Cl, CN).