Abstract Oxomolybdenum (V) complexes of the type (LH)2-[MoOCl5], (LH)2 [MoOCl4.OH], (LH)MOOCI4.F2O], [Mo2O4cl-(L - H)L′ (H2O)2-].nH2O, (where L = benzimidazole, 2 - α-hydroxymethyl benzimidazole, 2 - α - hydroxyethyl benzimidazole and 2 - α- hydroxybenzyl benzimidazole, L″ = EtOH or H2O and n = O, 1 or 2); [MoOCl3(L)2]H2O, (L = benzimidazole); [MoOCl2(L - H)H2O].H2O, (where L=2−α — hydroxymethyl benzimidazole) and [Mo2O4Cl2L2″]. 2H2.O (where L″ = 2-acetyl benzimidazole, 2 - benzoyl benzimidazole and 2 -{o - aminophenyl} benzimidazole)have been isolated and characterised. All monomeric complexes show absorptions in the visible region (∼ 710 nm and ∼ 440 nm) characteristic of octahedral Mo(V) complexes. The dimeric complexes do not absorb in the visible region, possibly due to the presence of the Mo2O4 2+ core. All complexes show an IR absorption band in the region 950 - 1000 cm−1 characteristic of terminal Mo =O Thermal stabilities of some of the complexes are reported.