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Strukturen und Moleküleigenschaften sterisch überfüllter Moleküle, 37. Hexakis(trimethylsilylmethyl)benzol C 6 [CH 2 Si(CH 3 ) 3 ] 6
Author(s) -
Bock Hans,
Meuret Jochen,
Ruppert Klaus
Publication year - 1993
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.19931261011
Subject(s) - chemistry , steric effects , intramolecular force , trimethylsilyl , crystallography , molecule , substituent , spectroscopy , methylene , van der waals force , stereochemistry , ring (chemistry) , crystal structure , molecular orbital , medicinal chemistry , physics , organic chemistry , quantum mechanics
Structures and Molecular Properties of Sterically Overcrowded Molecules, 37 [1] . — Hexakis(trimethylsilylmethyl)benzene C 6 [CH 2 Si(CH 3 ) 3 ] 6 Both the low first vertical ionization energy of only 7.40 eV, determined by PE spectroscopy for C 6 [CH 2 Si(CH 3 ) 3 ] 6 , and the blocked substituent rotation in its radical cation as proven by ESR/ENDOR spectroscopy suggest considerable steric over‐crowdedness. To further substantiate this interpretation of the molecular properties, the crystal structure (hexagonal R 3, Z = 2) has been determined at 100 K. Accordingly, the bulky trimethylsilyl groups are arranged alternatingly above or below the C 6 ‐ring plane, out of which the methylene C centers are twisted by ±9°. Due to the angles CCSi widened to 115°, however, the intramolecular distances C(H)(H)C between non‐neighboured methyl groups of 443 and 452 pm even slightly exceed their van der Waals radii sum of 400 pm and thus avoid severe spatial congestion.