THE MOLECULAR-STRUCTURE OF BICYCLO[3.3.1]NONA-2,6-DIENE)DICHLOROPALLADIUM(II)

The molecular structure of (C9H12)PdCl2 in solution has been studied b y two-dimensional n.m.r. spectroscopy, and the crystal structure has b een determined. The spectroscopic results support earlier conclusions that in solution the Pd-diene interactions involve non-equivalent carb on atoms at each of the equivalent ethenic centres. The crystals are d isordered with respect to the atoms of the eight-membered ring. The mo lecule has point symmetry 2 and is chiral. However, in the crystal str ucture, the molecules are in the special position with symmetry m(2)m in the ortborhombic space group Cmcm. Thus right- and left-handed mole cules randomly occupy the same site. Full-matrix least-squares refinem ent with all 485 reflections (d(min) = 0.85 Angstrom, Mo K alpha radia tion) measured at ambient temperature gave R(F) = 0.047 and R(w)(F) = 0.038 for 430 reflections with F-2 > 2 sigma. The distance Pd-C1 is 2. 300(3) Angstrom. The short Pd-C2 and Pd-C3 distances (2.223 and 2.245 Angstrom, respectively) differ by only 1.2 sigma. However, the ethenic carbon atoms are non-equivalent since C2 is considerably closer to th e PdCl2 plane than C3 (0.43 v. 0.99 Angstrom). The shortest distance b etween disordered sites for superposed molecules is 0.61 Angstrom. The corresponding platinum(II) complex is isomorphous and is disordered i n the same way.