title: Structural analysis of zincocenes with substituted cyclopentadienyl rings.
abstract: New zincocenes [ZnCp'(2)] (2-5) with substituted cyclopentadienyl ligands C(5)Me(4)H, C(5)Me(4)tBu, C(5)Me(4)SiMe(2)tBu and C(5)Me(4)SiMe(3), respectively, have been prepared by the reaction of ZnCl(2) with the appropriate Cp'-transfer reagent. For a comparative structural study, the known [Zn(C(5)H(4)SiMe(3))(2)] (1), has also been investigated, along with the mixed-ring zincocenes [Zn(C(5)Me(5))(C(5)Me(4)SiMe(3))] (6) and [Zn(C(5)Me(5))(C(5)H(4)SiMe(3))] (7), the last two obtained by conproportionation of [Zn(C(5)Me(5))(2)] with 5 or 1, as appropriate. All new compounds were characterised by NMR spectroscopy, and by X-ray methods, with the exception of 7, which yields a side-product (C) upon attempted crystallisation. Compounds 5 and 6 were also investigated by (13)C CPMAS NMR spectroscopy. Zincocenes 1 and 2 have infinite chain structures with bridging Cp' ligands, while 3 and 4 exhibit slipped-sandwich geometries. Compounds 5 and 6 have rigid, eta(5)/eta(1)(sigma) structures, in which the monohapto C(5)Me(4)SiMe(3) ligand is bound to zinc through the silyl-bearing carbon atom, forming a Zn--C bond of comparable strength to the Zn--Me bond in ZnMe(2). Zincocene 5 has dynamic behaviour in solution, but a rigid eta(5)/eta(1)(sigma) structure in the solid state, as revealed by (13)C CPMAS NMR studies, whereas for 6 the different nature of the Cp' ligands and of the ring substituents of the eta(1)-Cp' group (Me and SiMe(3)) have permitted observation for the first time of the rigid eta(5)/eta(1) solution structure. Iminoacyl compounds of composition [Zn(eta(5)-C(5)Me(4)R)(eta(1)-C(NXyl)C(5)Me(4)R)] resulting from the reactions of some of the above zincocenes and CNXyl (Xyl=2,6-dimethylphenylisocyanide) have also been obtained and characterised.
authors.affiliation: Instituto de Investigaciones Químicas, Departamento de Química Inorgánica, Universidad de Sevilla-Consejo Superior de Investigaciones Científicas, Avenida Américo Vespucio 49, 41092 Sevilla, Spain.
authors.forename: Rafael
authors.initials: R
authors.lastname: Fernández
authors.forename: Abdessamad
authors.initials: A
authors.lastname: Grirrane
authors.forename: Irene
authors.initials: I
authors.lastname: Resa
authors.forename: Amor
authors.initials: A
authors.lastname: Rodríguez
authors.forename: Ernesto
authors.initials: E
authors.lastname: Carmona
authors.forename: Eleuterio
authors.initials: E
authors.lastname: Alvarez
authors.forename: Enrique
authors.initials: E
authors.lastname: Gutiérrez-Puebla
authors.forename: Angeles
authors.initials: A
authors.lastname: Monge
authors.forename: Juan Miguel
authors.initials: JM
authors.lastname: López del Amo
authors.forename: Hans-Heinrich
authors.initials: HH
authors.lastname: Limbach
authors.forename: Agustí
authors.initials: A
authors.lastname: Lledós
authors.forename: Feliu
authors.initials: F
authors.lastname: Maseras
authors.forename: Diego
authors.initials: D
authors.lastname: del Río