Reaction of [Cp ∗2W 2O 5] with mercaptocarboxylic acids: Addition rather than reduction. Isolation and characterization of Cp ∗WO 2(SCH 2CH 2COOH)

Abstract

The reaction of Cp ∗ 2W 2O 5 with HS(CH 2) nCOOH (n = 1, 2) in MeOH or in CH 2Cl 2 solutions at room temperature proceeds in slightly different ways depending on the value of n. For n = 2, it selectively yields compound Cp ∗WO 2(SCH 2CH 2CO 2H), which has been isolated and characterized by elemental analysis, NMR and single crystal X-ray diffraction. The reaction is equilibrated, being shifted to the product by absorption of water by anhydrous Na 2SO 4 in CH 2Cl 2, and to the reactants by addition of water. Contrary to the Mo analogue, no products resulting from metal reduction are obtained. The corresponding reaction for n = 1 occurs similarly at low substrate/W ratios (<0.5), but proceeds further to several uncharacterized products for greater substrate amounts. The primary product could not be isolated, but its 1H NMR spectrum suggests a different, asymmetric structure.