Novel palladium (II) complexes belonging to a family of potential catalytic precursors

[摘要] ENGLISH ABSTRACT: This study comprises the preparation and characterization of various novelorganometallic complexes of palladium(ll) which contain symmetric andunsymmetric (heteroatom-containing) r..-dicarbonyl-type ligands, T]3-heteroallylligands and T]3-coordinated trimethylsilyl-containing ligands.With the ultimate objective of preparing potential catalytic precursors similar toknown catalytic precursors which exhibit hemilabile activity, the main goals ofthis study were the following: -• Investigate the coordination mode of the aforementioned ligand-types tothe palladium of the starting compound, trans-[Pd(CeHs)CI{P(CeHshhl (1),by physical measurements.• Carry out single crystal structure determinations where possible.• Investigate the influence of the properties of the ligands on the stability ofthe prepared complexes.• Investigate the existence of hemilability (if any) in the prepared complex.The deprotonated symmetric and unsymmetric f!,-dicarbonyl-type ligandsreadily bind to the palladium of the starting compound in a bidentate fashionthrough the oxygens by displacing a triphenylphosphine group and producingeasily removable sodium chloride. These complexes show that a negativecharge can be accommodated in a delocalized fashion by the -S=O and -P=O groups of these acac--type ligands in a similar manner to the carbonylgroups of acetylacetonate. However, no evidence of hemilabile activity wasfound in this series of complexes.In a similar fashion, the deprotonated T]3-heteroallyl ligands, L = [PhzPS£],[PhCOz-], [PhC{NSi(CH3hhl [(Ph)zP{NSi(CH3hh-], were linked to palladiumin the same starting complex, in T]3-fashion by triphenylphosphine substitution.No evidence of hemilabilty was evident in this series of complexes, but whenL = [PhzPSz-], an exchange of the coordinated triphenylphosphine group withthe free triphenylphosphine group was observed in the reaction mixture. Finally, the preparation, isolation and spectroscopic characterization ofseveral T\3-allyl paliadium(lI) complexes with ligands of the typeR-TeCH2CH2CQQCH3, (R = isopropyl, t-butyl ,ethyl) were attempted with thecompound bis-( T\3-allyl )-di-~ -iodo-dipalladium( II), [T\3 -( CH2CHCH2J2Pd212J,which had also now been crystallographically characterized. Chelateformation by TeAQ coordination seemed possible by halide precipitation withsilver tetrafluoroborate. Unfortunately the resulting compounds were toounstable to be isolated in the pure form for characterization.

[发布机构] Stellenbosch University