title: Four (2,2'-bipyridyl)(ferrocenyl)boronium derivatives.
abstract: Crystal structures are reported for four (2,2'-bipyridyl)(ferrocenyl)boronium derivatives, namely (2,2'-bipyridyl)(ethenyl)(ferrocenyl)boronium hexafluoridophosphate, [Fe(C5H5)(C17H15BN2)]PF6, (Ib), (2,2'-bipyridyl)(tert-butylamino)(ferrocenyl)boronium bromide, [Fe(C5H5)(C19H22BN3)]Br, (IIa), (2,2'-bipyridyl)(ferrocenyl)(4-methoxyphenylamino)boronium hexafluoridophosphate acetonitrile hemisolvate, [Fe(C5H5)(C22H20BN3O)]PF6·0.5CH3CN, (IIIb), and 1,1'-bis[(2,2'-bipyridyl)(cyanomethyl)boronium]ferrocene bis(hexafluoridophosphate), [Fe(C17H14BN3)2](PF6)2, (IVb). The asymmetric unit of (IIIb) contains two independent cations with very similar conformations. The B atom has a distorted tetrahedral coordination in all four structures. The cyclopentadienyl rings of (Ib), (IIa) and (IIIb) are approximately eclipsed, while a bisecting conformation is found for (IVb). The N-H groups of (IIa) and (IIIb) are shielded by the ferrocenyl and tert-butyl or phenyl groups and are therefore not involved in hydrogen bonding. The B-N(amine) bond lengths are shortened by delocalization of π-electrons. In the cations with an amine substituent at boron, the B-N(bipyridyl) bonds are 0.035 (3) Å longer than in the cations with a methylene C atom bonded to boron. A similar lengthening of the B-N(bipyridyl) bonds is found in a survey of related cations with an oxy group attached to the B atom.
authors.affiliation: Institut für Organische Chemie und Chemische Biologie, Universität Frankfurt, Max-von-Laue-Strasse 7, D-60438 Frankfurt am Main, Germany.
authors.forename: Jan W
authors.initials: JW
authors.lastname: Bats
authors.affiliation: Institut für Anorganische und Analytische Chemie, Universität Frankfurt, Max-von-Laue-Strasse 7, D-60438 Frankfurt am Main, Germany.
authors.forename: Kuangbiao
authors.initials: K
authors.lastname: Ma
authors.affiliation: Institut für Anorganische und Analytische Chemie, Universität Frankfurt, Max-von-Laue-Strasse 7, D-60438 Frankfurt am Main, Germany.
authors.forename: Hans Wolfram
authors.initials: HW
authors.lastname: Lerner
keywords: (2,2′-bipyridyl)(ferrocenyl)boronium derivatives; B—N bond lengths; crystal structure; delocalization of π-electrons