Oxo- and imido-molybdenum(VI) and -tungsten(VI) functionalities supported by diacetoneglucose

Abstract

The synthesis of novel complexes of Mo^VI and W^VI containing oxo- and imido-functionalities was undertaken using the carbohydrate derivative diacetoneglucose (1,2:5,6-di-O-isopropylidene-α-D-glucofuranose)(HL) as a ligand. Starting from the oxo chlorides MoOCl₄, WOCl₄ and MoO₂Cl₂, the complexes [MOL₄](M = Mo 1 or W 2) and [MoO₂L₂] were obtained by reaction with the previously reported lithium derivative LiL. Complexes 1 and 2 reacted with pyridine forming the adducts [MOL₄(py)]. The complex [MoO₂L₂] also acts as a Lewis acid towards 1,10-phenanthroline (phen) to yield [MoO₂L₂(phen)] and the sodium salt of dibenzoylmethane Na(dbm) affording the heterobimetallic complex [MoO₂L₂{(dbm)Na}]. Reaction of LiL with W(NC₆H₄Me-p)Cl₄ gave the imido derivative [W(NC₆H₄Me-p)L₄]. All the complexes have been characterized by means of ¹H and ¹³C NMR spectroscopy and gave correct elemental analyses. The specific rotations [α]₅₈₉²⁹⁸ have been measured and are briefly discussed. The crystal structures of [MoO₂L₂] and [MoO₂L₂(phen)] have been determined. In the former the cis-MoO₂ fragment is bonded to two bidentate L ligands. The octahedral co-ordination of molybdenum is achieved via two weak Mo ⋯ O interactions, displaced by phen in the latter complex.