title: Synthetic, structural, NMR and catalytic studies of phosphinic amide-phosphoryl chalcogenides (chalcogen = O, S, Se) as mixed-donor bidentate ligands in zinc chemistry.
abstract: ortho Substituted (diphenylphosphoryl)-, (diphenylphosphorothioyl)- and (diphenylphosphoroselenoyl)-phosphinic amides o-C6H4(P(X)Ph2)(P(O)N(i)Pr2) (X = O (20a), S (20b), Se (20c)) were synthesized by ortho directed lithiation of N,N-diisopropyl-P,P-diphenylphosphinic amide (Ph2P(O)N(i)Pr2) followed by trapping with Ph2PCl and subsequent oxidation of the o-(diphenylphosphine)phosphinic amide (19) with H2O2, S8 and Se. The reaction of the new mixed-donor bidentate ligands with zinc dichloride afforded the corresponding complexes [ZnCl2(P(X)Ph2)o-C6H4(P(O)N(i)Pr2)] (21a-c). The new compounds were structurally characterized in solution by nuclear magnetic resonance spectroscopy and in the solid-state by X-ray diffraction analysis of the ligand (20b) and the three complexes (21a-c). The X-ray crystal structure of 20b suggests the existence of a P[double bond, length as m-dash]O→P(S)-C intramolecular nonbonded interaction. The natural bond orbital (NBO) analysis using DFT methods showed that the stabilization effect provided by a nO→σ*P-C orbital interaction was negligible. The molecular structure of the complexes consisted of seven-membered chelates formed by O,X-coordination of the ligands to the zinc cation. The metal is four-coordinated by binding to the two chlorine atoms showing a distorted tetrahedral geometry. Applications in catalysis revealed that hemilabile ligands 20a-c act as significant promoters of the addition of diethylzinc to aldehydes, with 20a showing the highest activity. Chelation of Et2Zn with 20a was evidenced by NMR spectroscopy.
authors.affiliation: Área de Química Orgánica, Universidad de Almería, Carretera de Sacramento s/n, 04120 Almería, Spain. flortiz@ual.es.
authors.forename: Miguel A
authors.initials: MA
authors.lastname: del Águila-Sánchez
authors.forename: Neidemar M
authors.initials: NM
authors.lastname: Santos-Bastos
authors.forename: Maria C
authors.initials: MC
authors.lastname: Ramalho-Freitas
authors.forename: Jesús
authors.initials: J
authors.lastname: García López
authors.forename: Marcos
authors.initials: M
authors.lastname: Costa de Souza
authors.forename: Jackson A L
authors.initials: JA
authors.lastname: Camargos-Resende
authors.forename: María
authors.initials: M
authors.lastname: Casimiro
authors.forename: Gilberto
authors.initials: G
authors.lastname: Alves-Romeiro
authors.forename: María José
authors.initials: MJ
authors.lastname: Iglesias
authors.forename: Fernando
authors.initials: F
authors.lastname: López Ortiz