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Crystal Structure and Electron‐Density Distribution of Two [1.1.1] Propellane Derivatives at 81 K
Author(s) -
Seiler Paul,
Belzner Johannes,
Bunz Uwe,
Szeimies Günter
Publication year - 1988
Publication title -
helvetica chimica acta
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.74
H-Index - 82
eISSN - 1522-2675
pISSN - 0018-019X
DOI - 10.1002/hlca.19880710827
Subject(s) - propellane , chemistry , crystallography , electron density , molecule , crystal structure , atom (system on chip) , crystal (programming language) , stereochemistry , electron , bicyclic molecule , physics , organic chemistry , quantum mechanics , computer science , programming language , embedded system
The molecular structure and electron‐density distribution of two [1.1.1]propellane derivatives have been determined from accurate single‐crystal X‐ray diffraction measurements at 81 K. The crystals of these highly reactive compounds (both are liquid at room temperature) were grown directly on the X‐ray diffractometer at ca. 208 and 228 K, respectively. Both compounds crystallize in the space group P 2 1 / c with one molecule in the asymmetric unit. The symmetry of the propellane C‐atom skeleton is close to D 3 h for both molecules. The distances between the two bridgehead C‐atoms are 1.587 and 1.585 Å, and the mean lengths of the propellane side bonds are 1.525 and 1.528 Å, respectively. The deformation density peaks of the propellane side bonds ( ca. 0.25 e/Å 3 ) lie somewhat outside the internuclear connection lines and so correspond to ‘bent bonds’ as expected. On the other hand, the difference electron density between the bridgehead nuclei is slightly negative in both molecules. An interesting feature, observed in these difference maps, is presence of a diffuse, positive difference density at each inverted C‐atom, outside the bridgehead bond, a probable site of electrophilic attack.