Crystal structure of a racemic geijerene–silver nitrate adduct, 1,2-di-hapto: 7,8,11,12-tetrahapto-3-isopropenyl-4-methyl-4-vinylcyclohexenedisilver nitrate

Abstract

The crystal structure of a racemic geijerene–silver nitrate adduct, 1,2-dihapto: 7,8,11,12-tetrahapto-3-isopropenyl-4-methyl-4-vinylcyclohexenedisilver nitrate, C₁₂H₁₈(AgNO₃)₂, has been determined by use of three-dimensional equi-inclination Weissenberg X-ray diffraction data with 1188 visually estimated reflections. The monoclinic unit cell, space group P2₁/n, has dimensions, a= 12·17(2), b= 19·34(2), c= 6·55(2)Å, β= 93·0(3)°, with Z= 4. The structure was refined by least-squares calculations to R 0·19. The cyclohexene ring shows a half-chair conformation, with one carbon on each side of the planar, four-carbon (–CHR·CH:CH·CH₂–) segment. The isopropenyl group is not planar. The isopropenyl and vinyl groups are trans to one another, and are both associated with the same silver atom (Ag–C, 2·39, 2·59, 2·54, and 2·54 Å). This atom completes its tetrahedral co-ordination by association with the oxygen from two bridging nitrate groups (Ag–O, 2·42 and 2·49 Å). The other silver atom is trigonally co-ordinated with two bridging nitrate groups (Ag–O, 2·31 and 2·48 Å), and with the double bond in the cyclohexene ring (Ag–C, 2·30 and 2·33 Å).