N-Heterocycle Chelated Oxomolybdenum(Vi And V) Complexes With Bidentate Citrate

A 1,10- phenanthroline ( phen) chelated molybdenum( VI) citrate, [(MoO(2))(2)O( H(2)cit)( phen)(H(2)O)(2)] center dot H(2)O ( 1) ( H(4)cit = 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)(2)O(H(2)cit)(2)(bpy)(2)] center dot 4H(2)O (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 [MoO(2)(H(2)cit)(bpy)] center dot H(2)O (6) is also isolated and characterized structurally. The citrate ligand in the three neutral compounds uses the alpha-alkoxy and alpha-carboxy groups to chelate as a bidentate leaving the two beta-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 (13)C NMR studies.