W. Ahlers et al., ZIRCONOCENE-(MU-ORGANYL)BORATE BETAINES DERIVED BY TREATMENT OF A (SIGMA-ALKENYL)(SIGMA-ALKYNYL)ZIRCONOCENE COMPLEX WITH TRIS(PENTAFLUOROPHENYL)BORANE, EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, (7), 1998, pp. 889-895
Hydrozirconation of propyne followed by treatment with propynyllithium
yields the (sigma-propenyl)(sigma-propynyl)zirconocene complex 11. It
s treatment with the organometallic Lewis acid B(C6F5)(3) results in t
ransfer of the sigma-propynyl group from zirconium to boron followed b
y insertion of the alkynylborate triple bond into the zirconium carbon
bond of the remaining metallaallyl cation to furnish the zirconocene(
mu-hydrocarbyl)borate betaine complex 14. This reacts with three molar
equivalents of tert-butyl isocyanide to give 16. Complex 16 contains
a five-membered carbocyclic ring, formed by carbon-carbon coupling of
the former propenyl and propynyl groups with the C=N-R reagent, to whi
ch a (eta(2)-iminoacyl)(kappa-tert-butyl isocyanide)zirconocene moiety
is attached. Complex 16 was characterized by an X-ray crystal structu
re analysis.