Geometry. All esds (except the esd in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell esds are taken into account individually in the estimation of esds in distances, angles and torsion angles; correlations between esds in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell esds is used for estimating esds involving l.s. planes.

Refinement. The H atoms on the carbons were positioned geometrically and constrained to ride on their parent atoms. C—H bond distances were constrained to 0.93 Å for aromatic and alkene C—H moieties, and to 0.98, 0.91 and 0.96 Å for aliphatic C—H, CH2 and CH3 moieties, respectively. Methyl CH3 H atoms were allowed to rotate but not to tip to best fit the experimental electron density. Uiso(H) values were set to a multiple of Ueq(C) with 1.5 for CH3, and 1.2 for C—H and CH2 units, respectively.