Cyclometallation of bis-benzimidazole derivatives with rhodium(III) halides

Treatment of rhodium(III) halides with the N-heterocycles (LH), 1,3-bis(ben zimidazolyl)benzene (bBzlH(2)bzH; Ia) and its N-methyl derivative (bBzlMe(2 )bzH; Ib) in methanol gave halobridged binuclear cyclometallated products o f the composition [RhX2L](2) (X = Cl, Br or I). The chloro complex undergoe s halobridge cleavage reactions to yield several new mononuclear complexes of the types RhCl2(bBzlH(2)bz)(AsPh3), RhCl(bBzlH(2)bz)(OClO3)(L'/N-N) (L' = AsPh3; N-N = 2,2'-bipyridine or 1, 10-phenanthroline) and the heterocycle bridged binuclear complexes of the composition [RhCl2(bBzlH(2)bz)](2)(mu-N -N) (N-N = pyrazine or 4,4'-bipyridine). Passage of CO through [RhCl2(bBzlH (2)bz)](2) in DMF yielded mononuclear carbonyl complex RhCl2(CO)(bBzlH(2)bz ). 2H(2)O. Treatment of carbonylated solution of rhodium trichloride with I a produced non-cyclometallated mononuclear complex of the type [Rh(CO)(2)(b BzlH(2)bzH)]Cl. The complexes are characterised by H-1, C-13 NMR, IR, Far-I R, electronic and FAB-mass spectral studies. (C) 1999 Elsevier Science Ltd. All rights reserved.