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Soluble and polymer-bound palladium and platinum complexes of ferrocene derivatives

University of British Columbia

The preparation, characterization, and catalytic properties of some soluble and polymer-bound palladium and platinum complexes of ferrocene derivatives are described. Special emphasis has been placed on studies of the mixed "hard-soft" ligands such as PPFA and ISOPFA. [Formula Omitted] The soluble complexes (L-L)MC1₂ (L-L = BPPF, PPFA, ISOPFA, BPPFA; M = Pd, Pt) and [(L-L)PdS₂][C10₄]₂ (L-L = BPPF, PPFA; S = DMF, py) have been characterized by microanalyses, NMR and IR spectroscopic techniques. The cationic palladium(II) complex [(L-L)PdS₂][C10₄]₂ (L-L = PPFA, S = DMF) is an effective catalyst precursor for the hydrogenation of simple olefins at 30°C and 1 atm pressure. The rate of styrene hydrogenation depends on the substrate concentration, catalyst concentration and the solvent. The results are consistent with a homogeneous catalytic system. Platinum(II) complexes (L-L)PtCl₂ (L-L = (S,R)-PPFA, (S,R)-ISOPFA) are effective catalyst precursors for the hydrosilylation of aromatic ketones with Ph₂SiH₂. The complexes with mixed "hard-soft" ligands are better catalyst precursors than those with di(tertiary phosphine) ligands. Under the same conditions the hydrosilylation of ferrocenyl ketones results in further reduction and affords mainly the alkylferrocene products. The stable carbonium ion FcC⁺HCH₃ (Fc = Fe-(C₅H₅)(C₅H₄)-) is reduced by Ph₂SiH₂ to FcCH₂CH₃ in a thermal reaction which is catalyzed by the complex (PPFA)PtCl₂. The reaction of Ph₂SiH₂ with (L-L)PtCl₂ (L-L = PPFA, ISOPFA) yields a stable platinum(IV) hydride, which eliminates Ph₂SiHCl in solution to afford (L-L)PtHCl. The mechanistic implications of these observations are discussed. Polymers functionalized with ferrocene and ferrocene derivatives have been prepared. Mossbauer spectroscopic techniques and microanalyses are used to characterize these polymers and their palladium and platinum complexes. In a number of cases these results are confirmed by the cross-polarization/magic-angle spinning ¹³C NMR spectroscopic technique. The palladium(II) and platinum(II) derivatives of the ferrocenyl-amine and -phosphine containing polymers are effective catalysts for the hydrogenation and hydrosilylation of olefins. All the catalysts can be easily separated from the reaction mixture and can be recycled with no loss of activity. The pronounced effect of the attached ligand in the palladium based polymers indicates that free metal is not involved. However, in the case of platinum based catalysts, it is likely that reduction to platinum metal takes place.

Text

2010-08-13

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http://hdl.handle.net/2429/27312

Chemistry

University of British Columbia

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