2,2′-Bipyridine or 1,10-phenanthroline chelated oxomolybdenum(V) complexes with glycolate, lactate and malate in acidic media

A series of dimeric oxomolybdenum(V) 2,2′-bipyridine or 1,10-phenanthroline α-hydroxycarboxylates trans-[(MoO)2O(glyc)2(bpy)2]·3H2O (1), trans-[(MoO)2O(lact)2(bpy)2]·3H2O (2), trans-[(MoO)2O(Hmal)2(bpy)2] (3), trans-[(MoO)2O(lact)2(phen)2]·4H2O (4) and trans-[(MoO)2O(Hmal)2(phen)2]·4H2O (5) have been synthesized in acidic media for comparisons, where glycolate, lactate and malate in 1–5 chelate to molybdenum(V) with bidentate α-alkoxy and α-carboxy groups respectively. Unlike the molybdenum(IV) lactate in low valence [1] , no protonation was observed for α-alkoxy groups even under acidic condition. The two molybdenum atoms in 1 and 3 are paramagnetic independently as examples by EPR spectroscopies. Solid state 13C NMR spectra of 1 and 3 show large downfield shifts for the coordinated glycolate and malate (δα-alkoxy 75.4, 82.8 ppm, Δδ 13.4 ppm). Moreover, a monomeric mixed ligand oxomolybdenum(VI) complex MoO2(glyc)(bpy) (6) was isolated.