Crystal structures of 6-cyclopropyl-1,3-diphenylfulvene and 6-(2,3-dimethoxynaphthyl)-1,3-diphenylfulvene

The title compounds were prepared from 1,3-diphenylcyclopentadiene, pyrrolidine, and the corresponding aldehydes in an ethanolic solution. Each compound crystallizes with one molecule per asymmetric unit and exhibits the alternating short and long bond lengths typical of fulvenes. A network of C—H⋯C ring interactions as well as C—H⋯O interactions is observed, resulting in the compact packing found in each structure.


Supramolecular features
Fulvene 1 packs side by side along the a-axis direction with molecules oriented in such a way that the 6-cyclopropyl groups are sandwiched between the 1-Ph and 3-Ph rings of adjacent fulvene molecules. The closest contacts caused by this stacking sequence in the a-axis direction are between the 1-Ph ring atom H9 and the exocyclic C6 atom of an adjacent fulvene (C-HÁ Á ÁC = 2.90 Å ). Other C-HÁ Á ÁC contacts (C12Á Á ÁH19 = 2.83, C2Á Á ÁH10 = 2.85, C14Á Á ÁH20B = 2.85, C11Á Á ÁH19 = 2.86 Å ) lead to the formation of a network that results in sets of zigzag chains running perpendicular to the a-axis direction and that extend in the direction parallel to the bc plane (Fig. 3).
Fulvene 2 packs so that the 1-Ph groups are oriented towards the space between the 2,3-dimethoxynaphthyl groups and the 3-Ph rings of adjacent fulvene molecules along the baxis direction. A view down the a axis ( Fig. 4) reveals layers of interlaced 2,3-dimethoxynaphthyl groups (H, head) oriented H-H and separated from layers of interlaced 1,3-diphenylfulvene groups (T, tail) oriented T-T, with the layers running perpendicular to the c-axis direction and producing a layer sequence of H-H-T-T along the c-axis direction. In the H-H layers, short intermolecular contacts of the C-HÁ Á ÁO type (O1Á Á ÁH22 = 2.50 and O2Á Á ÁH24 = 2.53 Å ; Table 2) occur between adjacent 2,3-dimethoxynaphthyl groups running along the b-axis direction (Fig. 4). The methoxy groups apparently prevent the naphthyl rings from forming anystacking interactions, with the angle between the mean planes of the 2,3-dimethoxynaphthyl groups oriented at 124.37 (5) at least partially enforced by the C-HÁ Á ÁO interactions. The molecular structure of 2. Displacement ellipsoids are shown at the 50% probability level. Table 1 Selected bond distances and angles (Å ) for fulvenes 1 and 2.

Figure 1
The molecular structure of 1. Displacement ellipsoids are shown at the 50% probability level.

Database survey
A survey of the December 2019 release of the Cambridge Structural Database, with updates through November 2019, was made using the program Conquest (Groom et al., 2016). A search for 1,3-diphenyl-6-substituted fulvenes yielded 88 results. The bond lengths and angles in 1 and 2 are consistent with those in the previously reported literature.

Refinement
Crystal data, data collection and structure refinement details are summarized in Table 3. H atoms were placed in calculated positions (0.95-1.00 Å ) and refined as riding with U iso (H) = 1.2U eq (C) or 1.5U eq (C-methyl).  Table 2 Hydrogen-bond geometry (Å , ) for 2.

5-(Cyclopropylmethylidene)-1,3-diphenylcyclopenta-1,3-diene (1)
Crystal data Special details 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.