Metal complexes of biologically important ligands. CXXVI. Palladium(II) and platinum(II) complexes with the antimalarial drug mefloquine as ligand

The coordination sites of the antimalarial drug mefloquine (L) were studied . Reactions of the chloro bridged complexes (allyl)Pd(mu-Cl)(2)Pd(allyl) an d (R3P)-(Cl)M(mu-Cl)(2)M(Cl)(PR3) (M = Pd, Pt) with racemic mefloquine give the compounds (allyl)(Cl)Pd(L) (1), Cl-2(Et3P)Pt(L) (2) and Cl-2(Et3P)Pd(L ) (3) with coordination of the piperidine N atom of mefloquine. In the pres ence of NaOMe the N,O-chelate complexes Cl(Et3P)Pt(L-H+) (4) and Cl(R3P)Pd( L-H+) (5, 6, R = Et, nBu) were obtained. Protection of the piperidine N ato m of mefloquine by protonation allows the synthesis of the complexes Cl-2(E t3P)Pt(L + H+) (7) in which mefloquine is coordinated via the quinoline N a tom. The structures of 2, 3 and 4 were determined by X-ray diffraction anal ysis. In the crystal of 4 pairs of enantiomers are found which are linked b y two hydrogen bridges between the amine group and the chloro ligand.