title: Electronic perturbation in a molecular nanowire of [IrCl5(NO)]- units.
abstract: The nitrosyl in [IrCl5(NO)]- is probably the most electrophilic known to date. This fact is reflected by its extremely high IR frequency in the solid state, electrochemical behavior, and remarkable reactivity in solution. PPh4[IrCl5(NO)] forms a crystal in which the [IrCl5(NO)]- anions are in a curious wire-like linear arrangement, in which the distance between the N--O moiety of one anion and the trans chloride of the upper one nearby is only 2.8 A. For the same complex [IrCl5(NO)]- but with a different counterion, Na[IrCl5(NO)], the anions are stacked one over the other in a side-by-side arrangement. In this case the electronic distribution can be depicted as the closed-shell electronic structure Ir III-NO+, as expected for any d(6) third-row transition metal complex. However, in PPh4[IrCl5(NO)] an unprecedented electronic perturbation takes place, probably due to NO*-Cl- acceptor-donor interactions among a large number of [IrCl5(NO)]- units, favoring a different electronic distribution, namely the open-shell electronic structure Ir IV-NO*. This conclusion is based on XANES experimental evidence, which demonstrates that the formal oxidation state for iridium in PPh4[IrCl5(NO)] is +4, as compared with +3 in K[IrCl5(NO)]. In agreement, solid-state DFT calculations show that the ground state for [IrCl5(NO)]- in the PPh4+ salt comprises an open-shell singlet with an electronic structure which encompasses half of the spin density mainly localized on a metal-centered orbital, and the other half on an NO-based orbital. The electronic perturbation could be seen as an electron promotion from a metal-chloride to a metal-NO orbital, due to the small HOMO-LUMO gap in PPh4[IrCl5(NO)]. This is probably induced by electrostatic interactions acting as a result of the closeness and wire-like spatial arrangement of the Ir metal centers, imposed by lattice forces due to pi-pi stacking interactions among the phenyl rings in PPh4+. Experimental and theoretical data indicate that in PPh4[IrCl5(NO)] the Ir-N-O moiety is partially bent and tilted.
authors.affiliation: Departamento de Química Inorgánica, Analítica y Química Física/INQUIMAE-CONICET, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Ciudad Universitaria, Pabellón II, piso 3, C1428EHA Buenos Aires, Argentina.
authors.forename: Florencia
authors.initials: F
authors.lastname: Di Salvo
authors.forename: Natalia
authors.initials: N
authors.lastname: Escola
authors.forename: Damián A
authors.initials: DA
authors.lastname: Scherlis
authors.forename: Darío A
authors.initials: DA
authors.lastname: Estrin
authors.forename: Carlos
authors.initials: C
authors.lastname: Bondía
authors.forename: Daniel
authors.initials: D
authors.lastname: Murgida
authors.forename: José M
authors.initials: JM
authors.lastname: Ramallo-López
authors.forename: Félix G
authors.initials: FG
authors.lastname: Requejo
authors.forename: Linda
authors.initials: L
authors.lastname: Shimon
authors.forename: Fabio
authors.initials: F
authors.lastname: Doctorovich
mesh_terms: D018360:Crystallography, X-Ray; D005583:Fourier Analysis; D007495:Iridium / Q000737:chemistry*; D053770:Nanowires; D010084:Oxidation-Reduction
chemical_list: D007495:Iridium