title: Chiral bora[1]ferrocenophanes: syntheses, mechanistic insights, and ring-opening polymerizations.
abstract: A series of new boron-bridged [1]ferrocenophanes ([1]FCPs) was prepared by salt-metathesis reactions between enantiomerically pure dilithioferrocenes and amino(dichloro)boranes (Et2 NBCl2 , iPr2 NBCl2 , or tBu(Me3 Si)NBCl2 ). The dilithioferrocenes were prepared in situ by lithium-bromine exchange from the respective planar-chiral dibromides (Sp ,Sp )-[1-Br-2-(HR2 C)H3 C5 ]2 Fe (R=Me or Et). In most of the cases, mixtures of the targeted [1]FCPs 4 and the unwanted 1,1'-bis(boryl)ferrocenes 5 were formed. The product ratio depends on the bulkiness of the amino group, the speed of addition of the amino(dichloro)borane, the alkyl group on Cp rings, and in particular on the reaction temperature. The formation of strained [1]FCPs is strongly favored by increased reaction temperatures. Secondly, CHEt2 groups at Cp rings favored the formation of the targeted [1]FCPs stronger than CHMe2 groups. These discoveries open up new possibilities to further suppress the formation of unwanted byproducts by a careful choice of the reaction temperature and through tailoring the bulkiness of CHR2 groups on ferrocene. Thermal ring-opening polymerizations of selected boron-bridged [1]FCPs gave metallopolymers with a Mw of 10 kDa (GPC).
authors.affiliation: Department of Chemistry, University of Saskatchewan, 110 Science Place, Saskatoon, Saskatchewan S7N 5C9 (Canada), Fax: (+1) 306 966 4730.
authors.forename: Saeid
authors.initials: S
authors.lastname: Sadeh
authors.forename: Hridaynath
authors.initials: H
authors.lastname: Bhattacharjee
authors.forename: Elaheh
authors.initials: E
authors.lastname: Khozeimeh Sarbisheh
authors.forename: J Wilson
authors.initials: JW
authors.lastname: Quail
authors.forename: Jens
authors.initials: J
authors.lastname: Müller
keywords: boron; chiral ferrocenes; ferrocenophanes; metallocenes; ring-opening polymerization