A Tetramethylplatinum(IV) Complex with 1,1′‐Bis(diphenylphosphanyl)ferrocene Ligands: Reaction with Trifluoroacetic Acid

A new tetramethylplatinum(IV) complex [PtMe 4 (dppf)] [ 2 ; dppf = 1,1′‐bis(diphenylphosphanyl)ferrocene], as the first platinum(IV) complex to contain a chelating dppf ligand, was prepared by the reaction of the known dimeric tetramethylplatinum(IV) complex cis , cis ‐[Me 4 Pt(μ‐SMe 2 ) 2 PtMe 4 ] ( 1 ) with the biphosphane ligand dppf (2 equiv.) at room temperature by replacement of the SMe 2 ligands with the P ligating atoms of dppf. The single‐crystal X‐ray structure of complex 2 revealed that the dppf chelating ligand is arranged close to the “synperiplanar–eclipsed” conformation, with a Cp(centroid) ··· Fe ··· Cp(centroid) twist angle of 17.6° and a dppf bite angle, P1–Pt1–P2, of 95.77(3)°. This is in contrast to the usually preferred “synclinal–staggered” conformation, in which the Cp(centroid) ··· Fe ··· Cp(centroid) twist angle is close to 36° as found in Pt II complexes with chelating dppf ligands, like for example [PtMe 2 (dppf)] exhibiting a dppf bite angle close to 100°. When complex 2 was treated with the strong acid CF 3 COOH (1 equiv.) first evolution of methane was observed, followed by a C–C coupling reaction to give ethane and the methylplatinum(II) complex [PtMe(OCOCF 3 )(dppf)] ( 3 ). The reaction of complex 2 with the nucleophile HgCl 2 (1 equiv.) similarly gave MeHgCl, ethane, and the methylplatinum(II) complex [PtMeCl(dppf)] ( 11 ). The structure of complex 3 was also determined by X‐ray crystallography. The geometry around the platinum center is best described as distorted square‐planar and the dppf is arranged in the usually preferred “synclinal–staggered” conformation.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)