Supramolecular Catalysis of Orthoformate Hydrolysis in Basic Solution: An Enzyme-Like Mechanism Page: 3 of 51
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a low-spin (LS) state is stabilized by about 0.5 kcal mol-1 11-14 The low-spin isomer (2E2g in D5h
symmetry) has a doubly degenerate ground state and behaves as a dynamic Jahn-Teller molecule. The
nature of the potential energy surface of the dynamic Jahn-Teller distortion depends upon the
substituents on the Cp-ring and the host metallocene, which has lead to the study of various ring
substituted compounds. The only other manganocene whose electronic structure has been studied
extensively is (Me5C5)2Mn. -1 The magnetic moment in the solid state (5-100 K) shows it to be low-
spin and its EPR spectrum in frozen glasses and solid solutions of (Me5C5)2Fe show that the ground
state is 2E2g, consistent with the gas phase PES data. The room temperature solid-state X-ray crystal
structure of (Me5C5)2Mn with the Mn-C(ave) distances of 2.11 A show it is low-spin but there are
several distortions, which have been ascribed to a static Jahn-Teller distortion. 6 Herein, we report the
synthesis, molecular structure and electronic properties of a series of trimethylsilyl and tert-butyl
Results and Discussion
Synthesis. The synthesis of the manganocenes described in this paper (Table 1), generally uses the
corresponding magnesocenes and either MnBr2 or MnI2(thf)2 in tetrahydrofuran except for Me5C5, C5H5,
MeC5H4, (Me3Si)C5H4, (Me3Si)3C5H2 and (Me3C)3C5H2. In these examples the transfer reagent is either
the corresponding potassium or sodium salts of the substituted cyclopentadiene, since the magnesocene
reagent did not react cleanly under a variety of conditions investigated with the forementioned
cyclopentadienyl derivatives. The manganocenes are soluble in pentane and they are readily purified by
crystallization from that solvent. They all sublime from 50-80 C depending on the substituent under
dynamic diffusion pump vacuum, except (Me3Si)C5H4 which is a liquid that distils at 92-93 0C in
diffusion pump vacuum, and they all give molecular ions in their El mass spectra. The melting behavior
is rather interesting since the melting points increase in the order (Me3E)C5H4 < (Me3E)2C5H3 <<
(Me3E)3C5H2, where E= Si or C. Curiously the melting point of [(Me3C)(Me3Si)C5H3]2Mn is close to
the arithmetic mean of [(Me3C)2C5H3]2Mn and [(Me3Si)2C5H3]2Mn. The colors of the manganocenes are
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Pluth, Michael D.; Bergman, Robert G. & Raymond, Kenneth N. Supramolecular Catalysis of Orthoformate Hydrolysis in Basic Solution: An Enzyme-Like Mechanism, article, April 17, 2008; Berkeley, California. (digital.library.unt.edu/ark:/67531/metadc933976/m1/3/: accessed November 19, 2018), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.