J Am Chem Soc. 2008 Aug 13;130(32):10612-24. doi: 10.1021/ja8012903. Epub 2008 Jul 16.

Pd(I) phosphine carbonyl and hydride complexes implicated in the palladium-catalyzed oxo process.

Journal of the American Chemical Society

Miguel Baya, Jennifer Houghton, Denes Konya, Yohan Champouret, Jean-Claude Daran, Karina Q Almeida Leñero, Lodewijk Schoon, Wilhelmus P Mul, A Bart van Oort, Nicolaas Meijboom, Eite Drent, A Guy Orpen, Rinaldo Poli

PMID: 18630871 DOI: 10.1021/ja8012903

Abstract

Reduction of compound "Pd(bcope)(OTf)2" [bcope = (c-C8H14-1,5)PCH2CH2P(c-C8H14-1,5); OTf = O3SCF3] with H2/CO yields a mixture of Pd(I) compounds [Pd2(bcope)2(CO)2](OTf)2 (1) and [Pd2(bcope)2(mu-CO)(mu-H)](OTf) (2), whereas reduction with H2 or Ph3SiH in the absence of CO leads to [Pd3(bcope)3(mu3-H)2](OTf)2 (3). Exposure of 3 to CO leads to 1 and 2. The structures of 1 and 3 have been determined by X-ray diffraction. Complex [Pd2(bcope)2(CO)2](2+) displays a metal-metal bonded structure with a square planar environment for the Pd atoms and terminally bonded CO ligands and is fluxional in solution. DFT calculations aid the interpretation of this fluxional behavior as resulting from an intramolecular exchange of the two inequivalent P atom positions via a symmetric bis-CO-bridged intermediate. A cyclic voltammetric investigation reveals a very complex redox behavior for the "Pd(bcope)(OTf)2"/CO system and suggests possible pathways leading to the formation of the various observed products, as well as their relationship with the active species of the PdL2(2+)/CO/H2-catalyzed oxo processes (L2 = diphosphine ligands).

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• Journal Article