Some binuclear molybdenum(VI) complexes obtained from condensation reactions: their crystal and molecular structures

Abstract

Molybdenum(VI) complexes of three new structural types have been obtained from ethanol solution through use of triethoxymethane as condensing agent. The complex MoO₃(dmso)_1.33(dmso = dimethyl sulphoxide) alone yields [{MoO₂(OEt)₂(dmso)}₂](1), MoO₃(dmso)_1.33 with 2-amino-1,3-dihydroxy-2-methylpropane (H₂amp) gives [{MoO₂(amp)}₂]·2dmso (2), and two isomeric compounds [{MoO(hmmp)(OEt)}₂], (3a) and (3b), are obtained from [MoO₂(Hhmmp)](H₃hmmp = 1,3-dihydroxy-2-hydroxymethyl-2-methylpropane). The crystal structures of these compounds have been determined and show that all four contain coplanar di-µ-O_Ib bridges (O_Ib= deprotonated ligand-bridging O). The molecules of (1), (2), and (3b) have C_i symmetry, while (3a) has C₂ symmetry. The O_Ib–Mo–O_Ib angles are 69–72°, the low values being imposed by the bridging ligands. For [{MoO₂(amp)}₂] there is the unusual feature that each bridging atom belongs to a five-membered ring, and there is evidence of consequent ligand strain.