The Molecular Structure of (Bicyclo[3.3.1]nona-2,6-diene)dichloropalladium(II)

Abstract

The molecular structure of (C₉H₁₂)PdCl₂ in solution has been studied by two-dimensional n.m.r. spectroscopy, and the crystal structure has been determined. The spectroscopic results support earlier conclusions that in solution the Pd-diene interactions involve non-equivalent carbon atoms at each of the equivalent ethenic centres. The crystals are disordered with respect to the atoms of the eight-membered ring. The molecule has point symmetry 2 and is chiral. However, in the crystal structure, the molecules are in the special position with symmetry m2m in the orthorhombic space group Cmcm. Thus right- and left-handed molecules randomly occupy the same site. Full-matrix least-squares refinement with all 485 reflections (d_min = 0.85 Ǻ, Mo Kα radiation) measured at ambient temperature gave R(F) = 0.047 and R_w(F) = 0.038 for 430 reflections with F² > 2σ. The distance Pd-Cl is 2.300(3) Ǻ. The short Pd-C2 and Pd-C3 distances (2.223 and 2.245 Ǻ, respectively) differ by only 1.2σ. However, the ethenic carbon atoms are non equivalent since C2 is considerably closer to the PdCl₂ plane than C 3 (0.43 v. 0.99 A). The shortest distance between disordered sites for superposed molecules is 0.61 Ǻ. The corresponding platinum(II) complex is isomorphous and is disordered in the same way.