Nonisomorphous X-Ray Structures of Tritylnitrile and Tritylisonitrile

The crystal structures of a related series of isosteric compounds, namely tritylnitrile 1, tritylisonitrile 2, and a solid solution of tritylnitrile/tritylisonitrile 3 have been determined by single crystal X-ray diffraction. The bond lengths, angles, and intermolecular interactions do not deviate significantly from previously reported nitriles and isonitriles. These isosteric compounds pack in nonisomorphous but very similar structures. Subtle differences between the packing of 1 and 2 are detailed. The solid solution of tritylnitrile/tritylisonitrile 3 is isomorphous with the structure of tritylnitrile 1. This solid solution possesses substitutional disorder involving the nitrile and isonitrile groups (Z' = 2, nitrile/isonitrile occupancy ratios 53.7/46.3 and 54.6/45.4). The structure of tritylisonitrile 2 possesses positional disorder over two sites (Z' = 2, occupancy ratio of 93.1/6.9). A comparison with previously reported nearly isosteric structures reveals that other chemically dissimilar compounds crystallize in each of the two molecular packing arrangements described in this report. Structure 1: monoclinic, P2(1)/c, a = 18.049(11) , b = 9.583(6) , c = 17.824(11) , beta = 108.680(10)A degrees, V = 2921(3) (3), Z = 8, R (1) = 0.0467, wR (2) = 0.1491. Structure 2: triclinic, P , a = 9.5877(13) , b = 10.7479(14) , c = 14.809(2) , alpha = 88.457(2)A degrees, beta = 80.303(2)A degrees, gamma = 77.128(2)A degrees, V = 1466.4(3) (3), Z = 4, R (1) = 0.0423, wR (2) = 0.1151. Structure 3: monoclinic, P2(1)/c, a = 18.03464(15) , b = 9.5739(8) , c = 17.8251(11) , beta = 108.5920(10)A degrees, V = 2917.4(4) (3), Z = 8, R (1) = 0.0587, wR (2) = 0.1734. The crystal structures of the isosteric pair tritylnitrile 1 and tritylisonitrile 2 are nonisomorphous while the structure of a solid solution of tritylnitrile/tritylisonitrile 3 is isomorphous with the structure of tritylnitrile 1.