THE STRUCTURE AND CONFORMATION OF [1,1'-BIPYRROLIDINE]-2,2'-DITHIONE

The molecular structure of [1,1′-bipyrrolidine]-2,2′-dithione (1) has been determined by single-crystal X-ray crystallography. The compound crystallizes in the orthorhombic system: Pbca, a = 9.314(12), b = 13.213(2), c = 16.321(3) Å, V = 2008.4 Å3, Z = 8, Dc = 1.33 g cm-3, R = 0.042 for 2583 unique reflections and 140 variable parameters. The dihedral angle between the mean planes of the rings is 104.2(7)°. The conformations of the rings themselves are presented in terms of normalized linear combinations of the primitive envelope and twist forms. Certain bond distances are rationalized in terms of the screening of nuclear repulsion. The rorational barrier about the NN bond has been calculated from variable temperature nuclear magnetic resonance (NMR) measurements in deuterated toluene as 73 kJ mol-1. All measured parameters are contrasted with those found in the literature for the 2,2′-dioxo analogue (2), for which the rotational barrier has been determined in this work as 44 kJ mol-1. © 1990.