title: Palladium complexes derived from N,N-bidentate NH-iminophosphorane ligands: synthesis and use as catalysts in the Sonogashira reaction.
abstract: The addition of primary amines to the C=C bond of diphenylalkenyl iminophosphoranes yielded a new subtype of N,N-bidentate ligands bearing N=P(V)-C-C-NH backbones. These donor ligands reacted with PdCl(2)(COD) to give the corresponding σN,σN-palladium complexes containing secondary amino groups, bearing an intrinsically chiral nitrogen atom, and iminophosphorane units. These new complexes have been fully characterized by the use of spectroscopic techniques and X-ray crystallography. The comparison of the data extracted from their solution NMR spectra with their solid state structures demonstrated the conformational stability of their six-membered chelate ring and also the configurational stability of the chiral nitrogen atom, thus ruling out an arm-off racemization process. The addition of the chiral, racemic α-methylbenzylamine to the prochiral P-alkenyl iminophosphoranes yielded mixtures of the two expected diasteroisomeric ligands in low diastereoisomeric ratios. One of these mixtures was resolved into their components, each one in turn giving rise to a pair of diasteromeric palladium complexes epimeric at the amino nitrogen atom. One selected example of the new complexes efficiently catalyzes the copper- and amine-free Sonogashira reaction of aryl halides with acetylenes.
authors.affiliation: Departamento de Química Orgánica, Facultad de Química, Regional Campus of International Excellence Campus Mare Nostrum, Universidad de Murcia, E-30100 Murcia, Spain. alajarin@um.es
authors.forename: Mateo
authors.initials: M
authors.lastname: Alajarin
authors.forename: Carmen
authors.initials: C
authors.lastname: Lopez-Leonardo
authors.forename: Pilar
authors.initials: P
authors.lastname: Llamas-Lorente
authors.forename: Rosalia
authors.initials: R
authors.lastname: Raja
authors.forename: Delia
authors.initials: D
authors.lastname: Bautista
authors.forename: Raul-Angel
authors.initials: RA
authors.lastname: Orenes