Pd(II) complexes with N-substituted pyrazoles as ligands. The influence of the R group [OMe versus NMe2] of [1-{Re(CH2)2-}-3,5-Ph2-(C3HN2)] on their cytotoxic activity on breast cancer cell lines

The study of the reactivity of the novel pyrazole derivative [1-{MeOe(CH2)(2)-}-3,5-PH2-(C3HN2)] (1) with Na-2[PdCl4] or Pd(OAc)(2) under different experimental conditions has allowed us to isolate and characterize the trans-isomers of [Pd{[1-{MeOe(CH2)(2)-}-3,5-PH2-(C3HN2)]}(2)(X)(2)] [X = Cl (2) or OAc (3)] and the di-m-ligand bridged cyclopalladated complexes [Pd{kappa(2),C,N[1-{MeOe(CH2)(2)-}-3-(C6H4), 5-Ph-(C3HN2)]}(mu-X)](2) [X = OAc (4) or Cl (5)]. Further treatment of compounds 4 or 5 with PPh3 in CH2Cl2 produced the bridge splitting and the formation of [Pd{kappa(2),C,N[1-{MeOe(CH2)(2)-}-3-(C6H4), 5-Ph-(C3HN2)]}X(PPh3)] [X = OAc (6) or Cl (7)]. The cytotoxic assessment of the free ligand (1) and the Pd(II) complexes on the two breast cancer cell lines MCF7 and MDA-MB231 reveals that: a) compound 1 is less active than its analogue [1-{Me2N-(CH2)(2)-}-3,5-Ph(2)e(C3HN2)] (Ic) and b) palladacycles 4-7 showed a remarkable cytotoxic activity in the MDA-MB231 cell line (with IC50 values in the range 9.1-14.4 mu M). (C) 2014 Elsevier B. V. All rights reserved.