title: Synthesis and structure of a new heptaborate oxoanion isomer: B7O9(OH)5(2-).
abstract: The nonmetal borate [H3N(CH2)7NH3][B7O9(OH)5].H2O (1) was prepared via a neat reaction of 1,7-diaminoheptane with excess boric acid under mild nonhydrothermal conditions. Single-crystal X-ray characterization of 1 revealed a new isomer of the heptaborate anion, B7O9(OH)5(2-). The heptaborate anion in 1 is comprised of four fused (BO)3 rings sharing three four-coordinate boron atoms and a single three-coordinate oxygen atom. This anion is a structural isomer of another recently described heptaborate anion, consisting of a chain of three (BO)3 rings. Compound 1 crystallized in the triclinic space group P1 with a=9.3266(17) A, b=10.1222(19) A, c=10.847(2) A, alpha=89.422(2) degrees, beta=82.349(2) degrees, gamma=75.158(2) degrees, V=980.7(3) A3, and Z=2.
authors.affiliation: U.S. Borax Inc., Rio Tinto Minerals, Greenwood Village, CO 80111, USA. dave.schubert@riotinto.com
authors.forename: David M
authors.initials: DM
authors.lastname: Schubert
authors.forename: Mandana Z
authors.initials: MZ
authors.lastname: Visi
authors.forename: Saeed
authors.initials: S
authors.lastname: Khan
authors.forename: Carolyn B
authors.initials: CB
authors.lastname: Knobler