N-heterocycle chelated oxomolybdenum(VI and V) complexes with bidentate citrate

Abstract

A 1,10-phenanthroline (phen) chelated molybdenum(VI) citrate, [(MoO₂)₂O(H₂cit)(phen)(H₂O)₂]·H₂O (1) (H₄cit = citric acid), is isolated from the reaction of citric acid, ammonium molybdate and phen in acidic media (pH 0.5–1.0). A citrato oxomolybdenum(V) complex, [(MoO)₂O(H₂cit)₂(bpy)₂]·4H₂O (2), is synthesized by the reduction of citrato molybdate with hydrazine hydrochloride in the presence of 2,2′-bipyridine (bpy), and a monomeric molybdenum(VI) citrate [MoO₂(H₂cit)(bpy)]·H₂O (6) is also isolated and characterized structurally. The citrate ligand in the three neutral compounds uses the α-alkoxy and α-carboxy groups to chelate as a bidentate leaving the two β-carboxylic acid groups free, that is different from the tridentate chelated mode in the citrato molybdate(VI and V) complexes. 1 and 2 in solution show obvious dissociation based on ¹³C NMR studies.