Abstract: The crystal and molecular structures of 2,3-dihydro-5,6-dipenylpyrazine (C_(16)H_(14)N_2) and its complex with silver nitrate AgNO_3(C_(16)H_(14)N_2)_2 were determined by CAD4 single crystal diffractometer, using graphite monochromated Mo-Kα radiation. The crystallographic data are: (1) C_(16)H_(14)N_2, monoclinic, P2_1/n, α=0.5685(3), b=0.7928(1), c=2.7261(8) nm, β=95.02(6)°, V=1.2287 nm, z=4. (2) AgNO_3 (C_(16)H_(14)N_2)_2, monoclinic, A_2, α=0.5655(3), b=0.7791(2), c=3.0502(5) nm, β=94.90(2)°, V=1.3355 nm, z=2.
The structure of (1) was solved by direct method and (2) by heavy atom method. The full matrix least squares refinement for (1) with isotripic thermal parameters for H atoms and anisotropic for the others was converged at R=0.031, and R_W=0.033, the refinement for (2), excluding H atoms, at R=0.033 and R_W=0.028. In the structure of C_(16)H_(14)N_2, bond lengths and angles are not unexpected, and dihedral angles between pyrazine ring plane and each plane of the two phenyls are 151.9° and 136.7° respectively. In the structure of AgNO_3 (C_(16)H_(14)N_2)_2, the Ag atom is positioned on a 2-fold axis, and coordinated by two N and four O atons to form a severely distorted octahedron, the distance Ag(1)—O(1) is 2.828, Ag(1)—O(2) 2.520, and Ag(1)—N(31) 0.2399 nm. The conformation of the C_(16)H_(14)N_2 molecule in the complex was compared with that of the free ligand.