title: The cis-trans isomerization of 1,2,5,6-tetrasilacycloocta-3,7-dienes: analysis by mechanistic probes and density functional theory.
abstract: A series of alkyl- and aryl-substituted derivatives of cis,cis-1,2,5,6-tetrasilacycloocta-3,7-diene were prepared. Isomerization of these compounds to the corresponding trans,trans-1,2,5,6-tetrasilacycloocta-3,7-dienes by exposure to Ru and Zr hydride complexes was explored. Experimental probes of the isomerization were consistent with a stepwise mechanism involving metal hydride addition/elimination rather than one involving radical intermediates. Analysis of the low energy conformers of the various cis and trans isomers of 1,1,2,2,5,5,6,6-octamethyl-1,2,5,6-tetrasilacycloocta-3,7-diene using density functional theory suggested the following trend in stability: trans,trans > cis,trans > cis,cis. The calculated trend in stability was consistent with the experimentally observed unidirectional isomerization of the carbon-carbon double bonds from all cis to all trans and supports a cis,trans isomer as a tenable intermediate.
authors.affiliation: Department of Chemistry, University of Houston, Houston, Texas 77204-5003, USA.
authors.forename: L
authors.initials: L
authors.lastname: Zhang
authors.forename: C W
authors.initials: CW
authors.lastname: Borysenko
authors.forename: T A
authors.initials: TA
authors.lastname: Albright
authors.forename: E R
authors.initials: ER
authors.lastname: Bittner
authors.forename: T R
authors.initials: TR
authors.lastname: Lee