title: 3-(Triphenylphosphoranylidene)pentane-2,4-dione and diethyl 2-(triphenylphosphoranylidene)malonate.
abstract: The title ylides, 3-(triphenylphosphoranylidene)pentane-2,4-dione, C23H21O2P, (I), and diethyl 2-(triphenylphosphoranylidene)malonate, C25H25O4P, (II), differ in the conformations adopted by their extended ylide moieties. In (I), one carbonyl O atom is syn and the other is anti with respect to the P atom, the ylide group is nearly planar, with a maximum P-C-(C=O) angle of 18.2 (2)degrees, and the P-C, C-C and C=O bond lengths are consistent with electronic delocalization involving the O atoms. In (II), both carbonyl O atoms are anti and the ester groups are twisted out of the plane of the near trigonal ylide C atom, reducing delocalization, the largest P-C-(C=O) angle being 30.2 (2)degrees.
authors.affiliation: Departamento de Química Orgánica y Fisicoquímica, Facultad de Ciencias, Químicas y Farmacéuticas, Universidad de Chile, Casilla 233, Santiago, Chile. fcastane@ciq.uchile.cl
authors.forename: Fernando
authors.initials: F
authors.lastname: Castañeda
authors.forename: Christian
authors.initials: C
authors.lastname: Aliaga
authors.forename: Clifford A
authors.initials: CA
authors.lastname: Bunton
authors.forename: María Teresa
authors.initials: MT
authors.lastname: Garland
authors.forename: Ricardo
authors.initials: R
authors.lastname: Baggio