Amphiphile Phosphane für die Anwendung in neuen polaren Medien (2004)

This thesis deals with the synthesis and characterisation of phosphine ligands for the special use in polar media specially ionic liquids. The novel phosphine ligands have been functionalised with ionic or polar groups for catalyst immobilization tasks. A point of main effort were imidazol- and imidazolium-groups who have not been systematically investigated before and to which the first part of this work has been dedicated. A novel synthesis of 2-imidazolium-phosphines via deprotonation of choosen ionic liquids based on imidazolium-groups with n-BuLi and subsequent reaction with Ph2PCl has been elaborated. Additional phosphines of this type have been synthesized by metathesis reaction or by selective N-quarternisation of a corresponding neutral phosphine with Et3OPF6. The synthesis of phosphines containing peripheral 2-imidazolyl-groups seperated by a para-phenylene spacer from the P-atoms has been achieved by nucleophilic phosphination of 2-(4-fluorophenyl)-1-methylimidazol prepaired by Kosugi-Stille coupling between 2-tri-n-butyl-stannyl-1-methylimidazole and 4-fluoroiodobenzene. Selective N-protonation or N-quarternisation affords the corresponding imidazolium phosphines. Base catalyzed Anti-Markovnikov addition of PH functionalized phosphines to the exocyclic double-bond of 1-vinylimidazole allows access to a broard range of mono-, di- and triphosphan ligands with terminal 1-imidazolyl substituents. By selective N-protonation and protected group N-quarternisation novel cationic phosphines with peripheral 1-imidazolium groups are obtained. 1-Ethyl-3-vinyl-imidazolium-hexafluorophosphate has been synthesized allowing a direct synthesis of cationic ligands. Neutral and cationic derivative with extended alkyl chains are accessible by a radical initiated addition of PH-functionalized phosphines to 1-allylimidazole. The second part of this work deals with the synthesis and characterisation of novel bidentate phosphine ligands containing a rigid xanthene backbone and resonance stabilized cationic groups. The diprimary phosphine L21 has been obtained by dilithiation of 9,9-dimethylxanthene in 4,5-position and reaction of the dilithiated product with ClP(NEt2)2 to 45, followed by splitting of the P-N bond with HCl to 46 and subsequent reduction of the chlorophosphine using LiAlH4. The methods elaborated in the first part of this work have been used to synthesize xanthendiphosphine ligands with 1-imidazolyl and 1-imidazolium groups connected by flexible (CH2)2-bridges to phosphorus. Ligands with 2-imidazolyl- and 2-imidazolium-groups directly connected to the P-atoms have been obtained by reaction of 46 with 1-methyl-2-trimethylsilylimidazole and subsequent N-quarternisation or N-protonation followed by an anion exchange reaction. The guanidinium phosphines have been synthesized via Stelzer or Grignard reaction which in addition allows the synthesis of an ammoniumdiphosphine. Some novel ligands have been tested in the biphasic Rh-catalyzed hydroformylation of 1-octene employing the ionic liquid BMIM-PF6 as catalyst solvent. The last part of this thesis is tended to the steric properties and resolution of novel chiral carboxylated cyclohexylphosphines with two stereocentres, which have been synthesized by Michael addition of Ph2PH to methyl 1-cyclohexenecarboxylate. The reaction of the racemic phosphines with chlorobridged palladium complexes of ortho-metallated (R)-Alpha-phenylethyldimethylamine oder (S)-Alpha-(1-naphthyl)ethyldimethylamine gave diastereomeric palladium complexes whose (S)-Alpha-(1-naphthyl)ethyldimethylamine derivatives can be resoluted by fractionalised crystallisation. The X-ray structure determinations of these complexes gave an insight into the mechanism of the used reagents. The chiral phosphine has been obtained in 97% ee after liberation of its palladium complex. The structures of the compounds 14, 26, 45, 54, 59, (S),(R,S)-61 and (S),(S,R)-62 have been determined by X-ray structure analysis.