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The Molecular Structure of Triasterane: An Experimental and Theoretical Study
Author(s) -
Ahlquist Bjørn,
Almenningen Arne,
Benterud Birgit,
Trætteberg Marit,
Bakken Pirkko,
Lüttke Wolfgang
Publication year - 1992
Publication title -
chemische berichte
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.667
H-Index - 136
eISSN - 1099-0682
pISSN - 0009-2940
DOI - 10.1002/cber.19921250531
Subject(s) - chemistry , methylene , nonane , ab initio , molecule , ab initio quantum chemistry methods , crystallography , computational chemistry , steric effects , torsion (gastropod) , ring strain , molecular geometry , basis set , stereochemistry , organic chemistry , medicine , surgery
The molecular structure of triasterane (tetracyclo‐[3.3.1.0 2,3 .0 2,6 ]nonane) has been investigated by using the gasphase electron‐diffraction method and by theoretical calculations. The experimental data are in accordance with the molecule having D 3h symmetry. The C–C bonds in the three‐membered rings are observed to be slightly shorter than those in the methylene bridges [ r a 1.508(5) versus 1.520(4) Å; 2s̀ in parentheses]. The C–C–C angle at the methylene bridges is observed to be 118.9(3)°, while the M–C–CH 2 angle is determined to be 123.9(2)° (C–M is bisecting the cyclopropyl ring). Theoretical force‐field, semiempirical, and ab initio calculations of the triasterane molecule have also been carried out. The semiempirical results deviate substantially from the experimentally determined parameters, while the ab initio results, using a 6–31G * basis set, are in excellent agreement with the latter. The steric strain in triasterane has its origin mainly in nonbonded repulsion between the cyclopropyl groups and in torsion at the C–C bonds involving the methylene groups.