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

Abstract Treatment of rhodium(III) halides with the N-heterocycles (LH), 1,3-bis(benzimidazolyl)benzene (bBzlH 2 bzH; Ia ) and its N-methyl derivative (bBzlMe 2 bzH; Ib ) in methanol gave halobridged binuclear cyclometallated products of the composition [RhX 2 L] 2 (X=Cl, Br or I). The chloro complex undergoes halobridge cleavage reactions to yield several new mononuclear complexes of the types RhCl 2 (bBzlH 2 bz)(AsPh 3 ), RhCl(bBzlH 2 bz)(OClO 3 )(L′/N-N) (L′=AsPh 3 ; N-N=2,2′-bipyridine or 1,10-phenanthroline) and the heterocycle bridged binuclear complexes of the composition [RhCl 2 (bBzlH 2 bz)] 2 ( μ -N-N) (N-N=pyrazine or 4,4′-bipyridine). Passage of CO through [RhCl 2 (bBzlH 2 bz)] 2 in DMF yielded mononuclear carbonyl complex RhCl 2 (CO)(bBzlH 2 bz)·2H 2 O. Treatment of carbonylated solution of rhodium trichloride with Ia produced non-cyclometallated mononuclear complex of the type [Rh(CO) 2 (bBzlH 2 bzH)]Cl. The complexes are characterised by 1 H, 13 C NMR, IR, Far-IR, electronic and FAB-mass spectral studies.