title: Alkynylcyclohexanol chairs and twist-boats: Co(2)(CO)(6) as a conformational switch.
abstract: Treatment of 1-[axial]-(trimethylsilylethynyl)cyclohexan-1-ol with dicobalt octacarbonyl results in a conformational ring flip such that the bulky dicobalt-alkyne cluster moiety now occupies the favored equatorial site. However, when a 4-tert-butyl substituent is present, the coordinated alkynyl group retains its original axial or equatorial position. Complexation of trans-[diaxial]-1,4-bis(triphenylsilylethynyl)cyclohexane-1,4-diol brings about a chair-to-chair conformational inversion such that both cluster fragments now occupy equatorial sites. In contrast, cis-1,4-bis(triphenylsilylethynyl)cyclohexane-1,4-diol reacts with Co(2)(CO)(8) to yield the twist-boat conformer in which the two axial hydroxy substituents exhibit intra-molecular hydrogen bonding. Likewise, the corresponding reaction of cis-1,4-bis(trimethylsilylethynyl)cyclohexane-1,4-diol with Co(2)(CO)(8) leads to a twist-boat, but in this case, the molecules are linked through inter-molecular hydrogen bonds. Eight of these cobalt clusters have been characterized by X-ray crystallography, and the potential use of twist-boats in synthesis is discussed.
authors.affiliation: Department of Chemistry, McMaster University, Hamilton, Ontario, Canada L8S 4M1.
authors.forename: N M
authors.initials: NM
authors.lastname: Deschamps
authors.forename: J H
authors.initials: JH
authors.lastname: Kaldis
authors.forename: P E
authors.initials: PE
authors.lastname: Lock
authors.forename: J F
authors.initials: JF
authors.lastname: Britten
authors.forename: M J
authors.initials: MJ
authors.lastname: McGlinchey