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Issue 1, 2001
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A new class of anionic phosphinooxazoline ligands in palladium and ruthenium complexes: catalytic properties for the transfer hydrogenation of acetophenone

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Abstract

The synthesis of the cationic Pd complex [Pd(dmba)(PCH2-oxazoline)]Cl [PCH2-oxazoline = 2-oxazoline-2-ylmethyl)diphenylphosphine] (2) has allowed for the first time the observation of hemilabile behaviour for a phosphinooxazoline ligand. This molecular dynamics is stopped upon removal of the chloride anion, by reaction with either NH4PF6, which retains the cationic nature of the complex, or ButOK. The latter reaction leads to the formation of the first example of a Pd complex bearing an anionic phosphinooxazoline ligand, [[upper bond 1 start]Pd(dmba){Ph2PCH[horiz bar, triple dot above][lower bond 1 start]C([horiz bar, triple dot above]N[upper bond 1 end])CH2CH2O[lower bond 1 end]}], abreviated [Pd(dmba)(PCH-oxazoline)] (7), the anionic charge resulting from the monodeprotonation of the PCH2 group. Following this methodology, the Ru complex [[upper bond 1 start]RuCl(p-cymene){Ph2PCH[horiz bar, triple dot above][lower bond 1 start]C([horiz bar, triple dot above]N)CH2CH2O[lower bond 1 end]}], abreviated [RuCl(η6-p-cymene)(PCH-oxazoline)] (8) and containing this four-electron chelating anionic ligand, was prepared and shown to be more reactive for the catalytic transfer hydrogenation of acetophenone in propan-2-ol than the analogous complex bearing the neutral phosphinooxazoline ligand PCH2-oxazoline. The crystal structure of cis-[[upper bond 1 start]Pd{Ph2PCH[horiz bar, triple dot above][lower bond 1 start]C([horiz bar, triple dot above]N[upper bond 1 end])CH2CH2O[lower bond 1 end]}2], abbreviated cis-[Pd(PCH-oxazoline)2] (6), was determined by X-ray diffraction.

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Publication details

The article was received on 13 Jun 2001, accepted on 12 Jul 2001, published on 12 Dec 2000 and first published online on 12 Dec 2000


Article type: Paper
DOI: 10.1039/B004786O
Citation: New J. Chem., 2001,25, 32-39
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    A new class of anionic phosphinooxazoline ligands in palladium and ruthenium complexes: catalytic properties for the transfer hydrogenation of acetophenone

    P. Braunstein, F. Naud and S. J. Rettig, New J. Chem., 2001, 25, 32
    DOI: 10.1039/B004786O

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