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Synthesis and Decomposition Behavior of Pallada(IV)cyclopentane Complexes

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Canty, AJ and Hoare, JL and Davies, NW and Traill, PR (1998) Synthesis and Decomposition Behavior of Pallada(IV)cyclopentane Complexes. Organometallics, 17 (10). pp. 2046-2051. ISSN 0276-7333

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Abstract

The octahedral pallada(IV)cyclopentane complexes PdX(C4H8)R(bpy) [RX = MeI (1), EtI (2), PhCH2Br (3), CH2=CHCH2Br (4); bpy = 2,2'-bipyridine] may be isolated on oxidative addition of organohalides to the palladium(II) complex Pd(C4H8)(bpy) in acetone at -20 °C. The complex PdBr(C4H8)(CF3)(bpy) (5) has been generated in solution but was too unstable to permit isolation as a solid. Complex 1 occurs as a mixture of isomers in a 4:1 ratio, where the dominant isomer has the methyl group trans to bpy and the minor isomer has 2-fold symmetry with the methyl group trans to the iodo ligand. Complexes 2-5 adopt only the configuration with R trans to X. The complexes exhibit low stability, allowing studies of decomposition in solution under mild conditions in CDCl3 or CD2Cl2. Formation of the major products from PdI(C4H8)Me(bpy) (1) and PdI(C4H8)Et(bpy) (2) is assumed to result from C4H8...R coupling at Pd(IV) to give undetected Pd(II)ICH2CH2CH2CH2R species which undergo alpha-elimination to form alkenes (48% of detected organic products), Pd(0), and HX, with subsequent protonation of Pd(II)CH2CH2CH2CH2R to give alkanes (39%). Complexes 1 and 2 also give iodopentane (~12% from 1) and iodohexane (~9% from 2). The complex PdBr(C4H8)(CH2Ph)(bpy) (3) gives phenylpentane (15%), phenylpentenes (66%), toluene (10%), and butenes (8%); PdBr(C4H8)(CH2CH=CH2)(bpy) (4) and PdI(C4H8)(CF3)(bpy) (5) give predominantly cyclobutane, together with minor amounts of butenes (4, 5) and propene (4). Deuteration studies implicate the occurrence of intermolecular hydrogen atom transfer for elimination of alkenes and alkanes, except for cyclobutane.

Item Type: Article
Journal or Publication Title: Organometallics
Page Range: pp. 2046-2051
ISSN: 0276-7333
Identification Number - DOI: 10.1021/om980005t
Date Deposited: 16 Jan 2008 22:05
Last Modified: 18 Nov 2014 03:27
URI: http://eprints.utas.edu.au/id/eprint/2883
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