Dr. Donna S. Amenta
Professor of Chemistry and Head
office: Physics/Chemistry 1186
the past several years our attention has centered on the synthesis of
crown ether-containing transition metal complexes in which catalytic
activity and/or product selectivity is "switched" on or off
through binding of simple cations by crown ether units.1,2
One project addresses our hypothesis that the migratory insertion
reaction depicted in Scheme 1 for a transition metal carbonyl complex
can be accelerated by the addition of added cation when R is a crown
is precedent in the literature to support this hypothesis.
The presence of Lewis acids has been shown to activate the carbon
of metal carbonyl complexes toward nucleophilic attack. 3
Included among the reports are increased reactivity induced by
cations held in proximity to metal-bonded CO's by crown ether and crown
ether-like ligand.4-9 Preliminary
studies1,2 performed in our laboratory, suggest that the
number of intervening methylene groups between the metal site and the
benzo-crown ether are critical in providing the correct
conformation for interaction between a CO and the cation trapped
within the crown. CPKTM
molecular models and Sybyl molecular modeling program indicate that a
three methylene group spacer provides the flexibility required to place
the crown ether in a favorable conformation for complexation with a
terminal carbonyl group. It
is therefore proposed that the migratory insertion reaction of a crown
ether substituted transition metal carbonyl complexes with a three
methylene group space between the metal and the crown ether, Complex 1
(Scheme 1, x = 3) be investigated both in the presence and absence of
added cation. The rates of
these reactions will be determined using variable temperature nuclear
magnetic resonance spectroscopy (NMR).
Prior to beginning the kinetic studies, complex 1 will be
synthesized. The proposed
method for synthesis is a modification of several literature procedures.4
A similar study of a crown ether prototype of complex 1 is well
K.E. Norton, A.E. Morton, Donna S. Amenta and J.W.
Gilje, "Study of Migratory Insertion Reaction of a Molybdenum
Complex," presented at the Chemical and
Biological Sciences Research Symposium, October 23, 1999, at the University of Maryland, Baltimore, Baltimore, MD.
Aimee D. Morton, Donna S. Amenta and John W. Gilje,
"Crown Ether Functionalized Alkyl Molybdenum Complexes,"
South East Regional Meeting of the American
Chemical Society, Research Triangle Park, NC, November,
Richards, T.P., Hamilton, A.D., "p-Acceptor Macrocycles: New Crown Ethers Containing
Isocyanide Groups," J. Chem.
Soc. Chem. Commun., 1198 (1985).
Collman, J.P., R.G. Fink, J.N. Cawse, J.I. Brauman,
"Lewis Acid Catalyzed [Rfe(CO)4]- ALKY Migration
J. Chem. Soc. Chem., Commun., 100, 4766
Benn, Taarit, Y., J.L. Bilhour, M. LeComte, J.M.
Basset, "31P Nuclear Magnetic Resonance and Infrared
Evidence for Co-ordinatively Unsaturated Zerovalent
Tungsten by Interaction of W(CO)5L with AlBr3," J.
Chem. Soc., Chem. Commun., 38 (1978).
S.P., R.L. de la Vega, C.D. Hoff, "Thermochemical
Study of the Lewis Acid Promoted Carbonyl Insertion Reaction," J. Am. Chem. Soc.,
108, 7852 (1988), and references therein.
King, R.B., in
Organometallic Synthesis, J.J. Eisch, R.B. King, Eds., "Transition Metal
New York, 1965.
Can, M., J. Campo,
"Organometallic Chemistry of Systems with Mo_Hg Bonds," J. Chem. Ed.,
70, 948 (1993).
E.M., B.L. Shaw, I., Shepher, "Comp[lexes
of Platinum Metals Crown Ethers Containing Tertiary Phosphino-
Substituted Benzo Groups," J. Chem. Soc.,
Dalton Trans., 1696 (1978).