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. All H atoms were positioned geometrically (C—H = 0.93/1.00 Å) and allowed to ride with Uiso(H)= 1.2/1.5Ueq(C). Methyl ones were allowed to rotate around the corresponding C—C.A C2H4 is disordered and was refined in three parts with their site occupation factors adding up to one. As a consequence of this disorder, the two protons on the adjacent N atom are disordered and also were calculated is three idealized positioned and were treated riding on their parent atom. SADI and RIGU were applied to the disorder geometry to maintain equivalent bond lengths of corresponding bonds.Proton H3 were obtained from a Difference Fourier map and refined freely.