L. Zhang et al., The cis-trans isomerization of 1,2,5,6-tetrasilacycloocta-3,7-dienes: Analysis by mechanistic probes and density functional theory, J ORG CHEM, 66(16), 2001, pp. 5275-5283
A series of alkyl- and aryl-substituted derivatives of cis, cis-1,2,5,6-tet
rasilacyclooeta-3,7-diene were prepared. Isomerization of these compounds t
o the corresponding trans,trans-1,2,5,6-tetrasilacyclooeta-3,7-dienes by ex
posure 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 intermediat
es. Analysis of the low energy conformers of the various cis and trans isom
ers of 1,1,2,2,5,5,6,6-octamethyl-1,2,5,6-tetrasilacyclooeta-3,7-diene usin
g density functional theory suggested the following trend in stability: tra
ns,trans > cis,trans > cis,cis. The calculated trend in stability was consi
stent with the experimentally observed unidirectional isomerization of the
carbon-carbon double bonds from all cis to all trans and supports a cis,tra
ns isomer as a tenable intermediate.