CYCLOMETALATION OF N-(4-METHOXYPHENYL)-ALPHA-BENZOYLBENZYLIDENEAMINE WITH PALLADIUM(II) ACETATE - EVIDENCE FOR A NEW KIND OF DIASTEREOISOMERISM

The reaction of Pd(OAc)2 with N-(4-methoxyphenyl)-alpha-benzoylbenzylideneamine yielded two different acetate-bridged ortho-palladated compounds, Pd2[4-OCH3C6H4N=C(COC6H5)C6H5]2(mu-OAc)2 (2 and 3), depending on the relative ratio of the reagents. Both diastereoisomeric complexes exhibit a nonplanar, open-book shape, differing only in the dihedral angle formed between the C6H5C=O and the C6H5C=N planes; i.e., they are atropisomers around the CO-CN bond, as could be established from X-ray diffraction data. Both complexes crystallize in the centrosymmetric triclinic space group P1BAR, with Z = 2. Unit cell parameters are as follows: compound 2, a = 14.206 (9) angstrom, b = 15.764 (5) angstrom, c = 11.149 (3) angstrom, alpha = 92.46 (2)-degrees, beta = 95.31 (4)-degrees, gamma = 116.03 (4)-degrees; compound 3, a = 11.889 (15) angstrom, b = 13.209 (23) angstrom, c = 15.436 (9) angstrom, alpha = 87.34 (1)-degrees, beta = 78.51 (7)-degrees, gamma = 87.73 (1)-degrees.