The fac-[RuCl3(NO)(dppb)] complex I has been prepared from solution of the correspondent mer isomer in refluxing methanol (dppb = 1,4-bis(diphenylphosphino)butane). The mer-[RuCl3(NO)(diop)] (11) has been obtained from the mer-[RuCl3(diop)(H2O)] by bubbling NO for 1 h in dichloromethane (diop = 2S,3S-O-isopropylidene-2,3-dihydroxy-1,4-bis(diphenylphosphino)butane). The complexes have been characterized by microanalysis, cyclic voltammetry (CV), IR and P-31{H-1} NMR spectroscopies. The crystal and molecular structures of these two compounds have been determined from X-ray studies. The mer-[RUCl3(NO)(dppb)] isomer III was characterized in solution by NMR spectra (P-31{H-1}, H-1{P-31}, P-31-H-1 HETCORR, (COSYH)-H-1-H-1, HMQC(1)H- C-13 and (HMBCH)-H-1- C-13). (C) 2002 Elsevier B.V. Ltd. All rights reserved.