Composés organométalliques à cycle moyen. VII. Structure cristalline et moléculaire de la diméthyl-6,6 germa-6 cycloundécanone à –40°C

Abstract

The structure of 6,6-dimethyl-6-germacycloundecanone has been determined by single-crystal X-ray techniques at -40°C. The compound crystallizes in space group P2Jn with Z=4, a= 9.662 (2), b = 15.602 (2), c = 9.768 (2) A, fl = 117.65 (2) °. The structure was solved by the Patterson method from diffractometer data. The least-squares refinement yielded an R of 3.2%. There is a tetrahedral coordination around the Ge atom with two methyl groups and a bidentate chain (CH2)4-CO-(CH2)5 giving rise to a ring [GeCl01.Les compos6s cycliques de taille moyenne (8 /t 13 chainons) sont caract6ris6s par une structure compacte. La g~ne st6rique importante qui en r6sulte conduit la mol6cule /l adopter des conformations particuli6res. Aueune d&ermination structurale par rayons X n'a &6 r6alis6e fi notre connaissance dans la s6rie des cyclanones de taille moyenne. Une approche structurale de ces c&ones par &ude en chromatographie en phase vapeur (Ledaal, 1967) et par effet de solvant en RMN

Structure of tetraspiro[1,3,5,7-tetraoxa-2,4,6,8-tetragermacyclooctane-2,1':4,1'':6,1''':8,1''''-tetrakisgerminane]

“…The C---Ge bond lengths [1.929 (5)-1.942 (7) A] are within the range of C(sp3)--Ge bond lengths [1.933 (6)-1.967 (3)A] previously reported for germacyclanes (Faucher, Mazerolles, Jaud & Galy, 1978;Preut, Krcher & Neumann, 1985;Sommese, Cremer, Campbell & Thompson, 1990). All the C---C--C angles (2) (Takeuchi, Shimoda, Tanaka, Tomoda, Ogawa & Suzuki, 1988), except for the bond angle Cring-----Gc ¢-~ for "~ring, which the calculation gave a significantly smaller value (101.9°).…”