The carbenoid, CCl3Li, eschews tetrahedral structures

Abstract

7147collapses to one identical with that calculated for initial attack perpendicular to the plane.The orbital situation outlined above is by no means uncommon, so that Skell's suggestion' that there may be more cases of excited-state radical generation is almost certainly correct. The search for further examples can, however, be greatly facilitated by preliminary screening of likely precursors by molecular orbital theory. Schleyer for support and encouragement and Dr. J. Chandrasekhar and Dr. P. Hofmann for helpful discussions. This work was facilitated by the cooperation of the staff of the Regionales Rechenzentrum Erlangen. Supplementary Material Available: Summaries of M N D O resultsfor NCS and the two succinimidoyl radicals ( 3 pages). Ordering information is given on any current masthead page. References and Notes(1) See Skell, P. S.; Day, J. C. Acc. Chem. Res. 1978, 7 7, 381, and references therein.(2) INDO calculations (Koenig, T.; Wielesek, A. Tetrahedron Lett. 1975Lett. , 2007 suggest that the uo radical may also be low in energy. We have been unable to calculate this species directly," but the reaction paths give only the s and ON radicals. (3) Dewar, M. J. S.; Thiel, W. J. Am. Chem. Soc. 1977, 99, 4899, 4907. Dewar, M. J. S.; McKee, M. L.; Rzepa, H. S. /bid. 1978, 700, 3607. (4) All radical calculations employed the half-electron method: Dewar, M. J. S.; Hashmall, J. A,; Vernier, C. G. J. Am. Chem. SOC. 1968, 90, 1953. Dewar, M. J. S.; Trinajstic, N. J. Chem. SOC. A 1971, 1220. (5) The MNDO geometry for NCS is in good agreement with the X-ray structure: Brown, R. N. Acta Crystallogr. 1961, 74, 711. (6) Howard, P. B.; Skinner, H. A. J. Chem. SOC. A. 1966, 1536.

Isomers of SiCl3Li

“…Isomer 3 is found to have a C 3v structure in which the lithium is situated on the "wrong side" of the molecule, which will be named the "anti-C 3v " structure later. This result is similar to that of CCl 3 Li at the HF/4-31G, HF/STO-3G, HF/MIDI-4, and HF/MIDI-4 * levels of theory [8,9] (however, our calculation shows that in higher level of theory the lowest energy structure of CCl 3 Li is a C s one [10]). The Si-Cl bond length of isomer 3 (2.244 Å) is 0.045 Å longer than that of SiCl − 3 , while the ClSiCl (91.0 • ) of 3 is 7.0 • smaller that of SiCl − 3 , which may be the result of the attraction of the electopositive Li atom to the three Cl atoms.…”

Theory of complex molecular interactions: computer graphics, distance geometry, molecular mechanics, and quantum mechanics

“…The recent studies by Cram et al50 and Trueblood et al50 on spherand 1 have also proven to be very fertile ground for theoretical study. In simulating spherands 1-3, we61 did not use any X-ray coordinates as input, constructing the spherands and their alkali cation (Li+, Na+, K+) complexes by using a template-driven distance-geometry program and then energy refining them with molecular mechanics.…”

“…Figure1. Stereo view of model of tetrahedral intermediate for JV-acetyl-L-tryptophanamide catalysis by a-chymotrypsin.…”

Structures and Bonding in Silane Derivatives with One Alkali Atom

“…These geometries resemble an inverted umbrella-like shape with the bond between carbon (or silicon) and the alkali atom as the stick of the umbrella. For methane derivatives, CCl 3 Li , displays this inverted structure as the lowest lying conformer of the minima on its potential energy surface. In the case of one-silicon derivatives, silyl-lithium, SiH 3 Li, , has been more thoroughly studied than any other silanes presenting these anomalous structures.…”