Organomet1998_2C_2046.pdf (79.87 kB)
Synthesis and decomposition behavior of pallada(IV)cyclopentane complexes
journal contribution
posted on 2023-05-16, 11:14 authored by Allan CantyAllan Canty, Hoare, JL, Noel DaviesNoel Davies, Traill, PRThe 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 CDCls 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 PdIICH2CH2CH2CH2R species which undergo β-elimination to form alkenes (48% of detected organic products), Pd(0), and HX, with subsequent protonation Of PdIICH2CH2CH2CH2R 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.
History
Publication title
OrganometallicsVolume
17Issue
10Pagination
2046-2051ISSN
0276-7333Department/School
School of Natural SciencesPublisher
American Chemical SocietyPlace of publication
USARepository Status
- Restricted