title: Nickel poly-acetylide carbonyl clusters: structural features, bonding and electrochemical behaviour.
abstract: The reactions of [NEt(4)](2)[Ni(6)(CO)(12)] with miscellaneous carbon halides (e.g. CCl(4), C(4)Cl(6)) in CH(2)Cl(2) have been extensively investigated particularly focusing on the stoichiometric ratio of the reagents and reaction temperature. This allowed the preparation of the previously known acetylide clusters [Ni(16)(C(2))(2)(CO)(23)](4-), [HNi(25)(C(2))(4)(CO)(32)](3-) and [Ni(22)(C(2))(4)(CO)(28)Cl](3-), as well as isolation and full characterisation of the closely related [Ni(17)(C(2))(2)(CO)(24)](4-) and [Ni(25)(C(2))(4)(CO)(32)](4-) tetraanions. From a structural point of view, all these clusters are based on a Ni(16) square orthobicupola which contain interstitial C(2), Ni(η(2)-C(2))(4) or Ni(2)(μ-η(2)-C(2))(4) moieties, displaying rather short C-C bonds. Electrochemical studies reveal that all these species undergo different redox processes, even if their stability is rather limited. This is corroborated by an extensive analysis of the interaction between interstitial C(2) acetylide units and the metal cluster cage by Extended Huckel Molecular Orbital (EHMO) calculations, which indicates that tightly bonded C-C units are less effective than isolated C-atoms in stabilising the cluster cage.
authors.affiliation: Dipartimento di Chimica Fisica ed Inorganica, Università di Bologna, Viale Risorgimento 4-40136 Bologna, Italy.
authors.forename: Cristina
authors.initials: C
authors.lastname: Femoni
authors.forename: Maria Carmela
authors.initials: MC
authors.lastname: Iapalucci
authors.forename: Giuliano
authors.initials: G
authors.lastname: Longoni
authors.forename: Stefano
authors.initials: S
authors.lastname: Zacchini
authors.forename: Serena
authors.initials: S
authors.lastname: Fedi
authors.forename: Fabrizia
authors.initials: F
authors.lastname: Fabrizi de Biani