SOLVENT-INDUCED REACTION OF RHODIUM(III)HALIDE WITH N-HETEROCYCLIC LIGANDS - CRYSTAL-STRUCTURE OF NS-DICHLOROTETRAKIS(N-METHYLIMIDAZOLE)RHODIUM(III) CHLORIDE DIHYDRATE

The synthesis of complexes of the type trans-[RhL4X2](+) {L = N-alkyli midazoles (N-RIm) [R = methyl (Me), ethyl (Et), n-propyl (Pr-n) n-buty l (Bu-n)], 4(6)-hydroxypyrimidine (4(6)-hydPm); X = Cl- or Br-} is ach ieved by the general catalytic method involving the use of ethanol. Th e formation of complexes with L = N-MeIm was reexamined and a new proc edure has been established. The distribution of the trans-[RhL4X2](+) and [RhL5X](2+) ions as reaction products strongly depends on the natu re of the solvent and the structure of the ligand. We proposed that th e initial product trans-[RhL4X(sol)](2+) produced by catalytic action of ethanol, undergoes nucleophilic substitution reactions either by ha logenide anions X- or by ligand molecules L, thus giving rise to the f ormation of trans-[RhL4X2](+) or [RhL5X](2+) complexes. The direction of the nucleophilic substitution is determined by the concentration of ethanol, the L ligand and the X- halogen. IR, Raman, electronic absor ption and H-1 NMR spectra were used to characterize the complexes. The prepared complexes show significant antifungal activity. The crystall ographic structure of trans-[Rh(N-MeIm)(4)Cl-2] Cl . 2H(2)O has been d etermined. The octahedron is slightly distorted since it has, in a squ are plane, four nitrogen ligands and two Cl atoms at the two apical si tes. The octahedral bond angles are very close to the ideal values and are in the range of 88.1(1)-89.6(1)degrees. The Ph atom is located on the two-fold rotation axis which relates two pairs of N-methylimidazo le molecules and Cl atoms. (C) 1998 Elsevier Science S.A. All rights r eserved.