Syntheses and reactivity studies of hydroxo-palladium(II) and amido-platinum(IV) complexes.

摘要

The research presented in this thesis involves investigations of two types of product release reactions that could be important in processes catalyzed by late-metal complexes.; We have prepared a novel PNC-type ligand by a Schiff base condensation of 2-(diphenylphosphino)benzaldehyde and 2-bromobenzylamine. Reaction of this PNC ligand with Pd₂(dba) ₃ led to the formation of (PNC)PdBr. The palladium(II)-hydroxo dimer, [(PN)Pd(μ-OH)]₂[BF₄]₂, was prepared by reaction of (PNC)PdBr with AgBF₄ in acetone followed by the addition of water. The formation of the Pd(II)-μOH dimer was shown via a labeling experiment to result from protonation by water of the benzyl arm of the tridentate PNC ligand. This is a rare example of protonation of a hydrocarbyl group from a late-metal center by water. In addition, this protonation reaction serves as a model for the final step of a process catalyzed by a late-metal center in which the organic product is released from the metal using water.; We have also prepared the first Pt(IV)-amido complexes. The fac-(dppbz)PtMe₃(HNSO₂R) (R = ptolyl, Me) complexes were synthesized by the reaction of fac-(dppbz)PtMe ₃OH with H₂NSO₂R in THF. The thermolyses of fac-(dppbz)PtMe₃(HNSO₂R) in the non-polar solvents C₆D₆ or THF-d₈ results in C-N reductive elimination to form HN(Me)SO₂R and (dppbz)PtMe ₂. C-C reductive elimination to form ethane and (dppbz)PtMe(HNSO ₂ptol) is observed as a competing reaction. Kinetic and mechanistic studies of this novel carbon-nitrogen reductive elimination from a d6 octahedral compound are presented. The data suggests that C-N coupling occurs by a mechanism involving dissociation of the HNSO ₂R− anion from the Pt(IV) center followed by nucleophilic attack of the anion on a methyl group of the cationic five-coordinated intermediate that is formed. However, in the presence of added HNSO₂R −, a competing pathway involving direct attack of a sulfonamide anion on a methyl group of the six-coordinate Pt(IV) complex may be involved. Carbon-nitrogen reductive elimination from a high valent late-metal center could be the product release step in a process catalyzed by a late-transition metal complex which involves C-N bond formation.