title: New chiral P-N ligands for the regio- and stereoselective Pd-catalyzed dimerization of styrene.
abstract: Two new chiral, enantiomerically pure, hybrid P-N ligands, namely (2R,5S)-2-phenyl-3-(2-pyridyl)-1,3-diaza-2-phosphanicyclo[3,3,0]octan-4-one (1) and (2R,5S)-2-phenyl-3-(2-pyridyl)-1,3-diaza-2-phosphanicyclo[3,3,0]octane (2), have been synthesized starting from L-proline. The two ligands differ in the presence or not of a carbonyl group in the diazaphosphane ring. Their coordination chemistry towards Pd(II) was studied by reacting them with [Pd(CH₃)Cl(cod)]. A different behaviour was observed: ligand 2 shows the expected bidentate chelating behaviour leading to the mononuclear Pd-complex, while ligand 1 acts as a terdentate ligand giving a dinuclear species. The corresponding cationic derivatives were obtained from the palladium neutral complexes, both as mono- and dinuclear derivatives, and tested as precatalysts for styrene dimerization, yielding E-1,3-diphenyl-1-butene regio- and stereoselectively as the sole product. A detailed analysis of the catalytic behaviour is reported.
authors.affiliation: Dipartimento di Scienze Chimiche e Farmaceutiche, Università di Trieste, Via Licio Giorgieri 1, 34127 Trieste, Italy.
authors.forename: Lidia
authors.initials: L
authors.lastname: Fanfoni
authors.forename: Angelo
authors.initials: A
authors.lastname: Meduri
authors.forename: Ennio
authors.initials: E
authors.lastname: Zangrando
authors.forename: Sergio
authors.initials: S
authors.lastname: Castillon
authors.forename: Fulvia
authors.initials: F
authors.lastname: Felluga
authors.forename: Barbara
authors.initials: B
authors.lastname: Milani
mesh_terms: D002384:Catalysis; D002412:Cations / Q000737:chemistry; D019281:Dimerization; D008024:Ligands; D009682:Magnetic Resonance Spectroscopy; D015394:Molecular Structure; D010165:Palladium / Q000737:chemistry*; D013237:Stereoisomerism; D020058:Styrene / Q000737:chemistry*; D013696:Temperature
chemical_list: D002412:Cations; D008024:Ligands; D020058:Styrene; D010165:Palladium