title: Effective computational modeling of constitutional isomerism and aggregation states of explicit solvates of lithiated phenylacetonitrile.
abstract: We present the first calculations which accurately account for the position of metalation and aggregation state of lithiated nitriles. Solvation is found to be a key determinant of structure. Five known solvates of lithiated phenylacetonitrile were examined computationally to determine the minimum level of theory required to reproduce the observed X-ray and multinuclear NMR structures. In all cases Hartree-Fock 3-21G energies of explicit solvates calculated at PM3 geometries correctly predict the observed N-lithiated constitutional isomer. Selected density functional theory (B3LYP/6-31+G*//PM3) energy calculations reproduce this trend. We also show that 3-21G//PM3 calculations which do not include explicit solvent molecules, or which include water as a model for diethyl ether, may lead to incorrect predictions of the preferred constitutional isomer. 3-21G//PM3 energies also adequately account for observed aggregation states of the TMEDA, diethyl ether, and THF solvates. Finally, calculations of THF-solvated monomers up to the B3LYP/6-31+G*//B3LYP/6-31+G level indicate a significant (6.8 kcal/mol) preference for N-lithiation.
authors.affiliation: Department of Chemistry, Virginia Tech, Blacksburg, VA 24060, USA. pcarlier@vt.edu
authors.forename: Paul R
authors.initials: PR
authors.lastname: Carlier
authors.forename: Jeffry D
authors.initials: JD
authors.lastname: Madura