N 3,N 6,2,5,7-Pentaphenyl-2,5,7-triazabicyclo[2.2.1]heptane-3,6-diamine

In the title compound, C34H31N5, the observed molecular geometry suggests that anomeric effects are present in terms of short C—N bond lengths and reduced pyramidality of the N atoms.

In the title compound, C 34 H 31 N 5 , the observed molecular geometry suggests that anomeric effects are present in terms of short C-N bond lengths and reduced pyramidality of the N atoms.
As a part of our continuing efforts on the development of polyazapolycyclics, structural stability and synthesis of 2,5,7-triazabicyclo[2.2.1]heptan derivative (Taheri & Moosavi, 2009) via a catalytic reaction between aminoethane derivatives (Kliegman & Barnes, 1970;Taheri & Moosavi, 2008) and glyoxal were recently described another crystal system of the title compound without any solvent on the crystal packing in which geometric parameters for stability of the skeleton is scrutinized by study of anomeric interactions.
The molecular structure of I shown in Fig. 1 has racemic configuration, all S-and all R-configuration molecules and composed of a six-membered piperazine ring and an N atom bridging between the C1 and C4 situations, norbornane skeleton construction. Notwithstanding the presence of two NH groups, viz. N31 and N61, and five N atoms carrying lone-pair electrons potentially available for H-bond creation, there are not actually intra-or intermolecular N-H···N or C-H···N hydrogen bonds. As shown in the scheme, the skeleton has a good local twofold symmetry, namely through the N7 bridge and almost perpendicular to the least-squares plane of the piperazine ring. It is noteworthy that the symmetry involves not only the skeleton but also the peripheral phenyl groups, except for that attached to the bridging N7 atom.
The anomeric effect in N-C-N systems investigated extensively (Senderowitz et al., 1992), occurred between a lone pair on N and an antiperiplanar σ* orbital of the adjacent C-N bond (n N →σ* C-N ), negative hyperconjugation (Reed & Schleyer, 1988).
There are four dissimilar anomeric effects manifested by the bond distances and N-atom pyramidality on four N'-C-N" fragments or n N '→σ* C-N " systems. Within the N'-C-N" unit, the N'-C bond is shorter, than the C-N" bond. On the other hand, the pyramidality of N' (the sum of the three bond angles around N') is larger than that of N". These geometric parameters related to the anomeric effect are shown in Tabl. 1. Among them, the n N5 →σ* C4-N7 system shows a distinguished anomeric interaction and the largest bond-length difference [0.029 (2)Å], which is comparable to that reported for an other crystal system (Taheri & Mossavi, 2009). However, the pyramidality differences in the N'-C-N" units are not so indicative. The differences within the N2-C2-N7 and N7-C4-N5 systems are 16.14 (16) and 17.83 (15)°, respectively, and these are much larger, than those for the N31-C3-N2 and N61-C6-N5 groups, 2.95 and 0.21°, respectively. Furthermore, the calculated pyramidalities for atoms N31 and N61 are not accurate because they include H atoms, whose positions were determined from adifference Fourier synthesis. Thus, the anomeric effect on the pyramidality is not clear in this molecule. It could be that, the anomeric effect on the angle is buried among the steric effects caused by the crowding of the substituent groups, which would strongly affect the molecular structure.
Reflecting the local twofold symmetry, the corresponding N atoms in this symmetric skeleton (N2 and N5, N31 and N61) have nearly the same pyramidality. The pyramidality angle of N7 [330.71 (19)°] is rather small, and the attached phenyl group is inclined from the local twofold axis in the direction of atoms N2, C3 and N31. Corresponding to this inclination, the C72-C71-N7 angle [122.79 (17)°] is distorted from theideal value of 120°, which is attributable to the short contact between the voluminous phenyl ring and the skeleton. For example, the H76···H1 separation (atom C1 is the bridgehead) is only 2.281Å . The same distortion is seen in another norbornane derivative [122.5 (4)°; Watson et al., 1990] for the phenyl ring on the bridging N7 atom.
The angle at the bridging N atom, C1-N7-C4, is 94.11 (13)°. Although this bridge angle is comparable to those reported for norbornane and diazanorbornane (Davies et al., 1992), it still indicates the presence of ring strain.

Refinement
The H atoms of the NH-groups were located in the difference Fourier map and refined in rigid model with fixed U iso (H) = 1.2U eq (N) parameters. The H(C) atoms were placed in calculated positions and refined in riding model with fixed U iso (H) = 1.2U eq (C) parameters. Friedel opposites were merged supplementary materials sup-3 Figures Fig. 1. The molecular structure of I, with the atom-numbering scheme. Displacement ellipsoids are drawn at the 50% probability level. H atoms are presented as a small spheres of arbitrary radius.