o-Alkyl-substituted aromatic phosphanes for hydroformylation studies: synthesis, spectroscopic characterization and ab initio investigations

Mono and dinuclear palladium complexes of o-alkyl substituted arylphosphane ligands: Solvent-dependent syntheses, NMR-spectroscopic characterization and X-ray crystallographic studies

“…As previous results have shown, the individual signals of the phosphanes in the 31 P-{ 1 H} NMR spectra tend to move to a lower field when a phosphane is coordinated to a metal center [11,21,22]. As expected, complexes 6, 9, 10, 11, 14 and 15 showed one sharp signal initially.…”

“…The 1 H NMR signals were almost identical to those of the free phosphane ligands, the chemical shifts had shifted downfield only slightly [11,21].…”

“…The previously characterized o-alkyl substituted phosphane ligands 1-5 were prepared according to a modified literature method [11,21] at 0°C from brominated organic reagents by lithiation with n-butyl lithium and an overnight reaction with halogenated arylphosphanes. The ligands were recrystallized from ethanol or a 1:1 mixture of ethanol and hexane, and if necessary, purified by column chromatography using silica gel and hexane-dichloromethane 2:1 mixture.…”

“…Replacing the PPh 3 promising results in various alkene hydroformylation reactions. We recently observed that the o-alkyl substituents have significant effects on the activity and selectivity in the rhodium and ruthenium catalyzed hydroformylation of propene [11,12]. However, the Rh and Ru complexes of these ligands could not be crystallized and sometimes were found to be unstable in solution.…”

“…The following dinuclear palladium complexes were prepared: di-l-chlorodichlorobis(o-methylphenyldiphenylphosphane)di-palladium (6), di-l-chlorodichlorobis(o-ethylphenyldiphenylphosphane)dipalladium (7), di-l-chlorodichlorobis(o-isopropylphenyldiphenylphosphane)di-palladium (8), di-l-chlorodichlorobis-(o-cyclohexylphenyldiphenylphosphane)di-palladium (9) and di-l-chlorodichlorobis(o-phenylphenyldiphenylphosphane)di-palladium (10). We also prepared the following mononuclear complexes: dichlorobis(o-methylphenyldiphenylphosphane) palladium (11), dichlorobis(o-ethylphenyldiphenylphosphane) palladium (12), dichlorobis(o-isopropylphenyldiphenylphosphane) palladium (13), dichlorobis(ocyclohexylphenyldiphenylphosphane) palladium (14) and dichlorobis(o-phenylphenyldiphenylphosphane) palladium (15). The X-ray structures of 6, 8-12 and 14 were also obtained.…”