Polymeric complexes from molybdenum trioxide, with notes on derivatives and related compounds

Abstract

Molybdenum trioxide dissolves in dimethyl sulphoxide (dmso) to give a solution from which the polymeric complex [{MoO₃(dmso)_1.33}_n](1a) may be crystallised. It also reacts with pyridine N-oxide (pyo), triphenylarsine oxide, and pyridine (py) to give insoluble polymeric complexes [{MoO₃(pyo)}_n](2), [{MoO₃(AsPh₃O)_0.5}_n](3), and [{MoO₃(py)}_n](4). The solubility of (1a) enables its conversion to (2), (3), or (4). Another compound, [{MoO₃(AsPh₃O)}_n](5) has been obtained from the Mo^VI acetylacetonate complex [MoO₂(acac)₂]. Evidence on the constitution of the insoluble compounds comes from i.r. spectra and X-ray diffractograms, with the ‘white’ and ‘yellow’ molybdic acids, [{MoO₃(OH₂)}_n] and [{MoO₃(OH₂)}_n]·nH₂O respectively, providing reference structures. The molybdenum co-ordination environment comprises the ligand opposite a single terminal oxygen, along with four bridging atoms, as in the yellow form of the acid. The formation of these compounds is considered in relation to the simpler Mo–O–Mo bridge-cleavage reaction shown by the ‘digol’ compound [{MoO₂(deg)}_n](H₂deg = diethylene glycol), to give complexes of the type [MoO₂(deg)L]. Solutions of (1a) react with hydroxylic compounds in the presence of triethoxymethane as condensing agent. Products obtained from 2-amino-2-methylpropane-1,3-diol and 2-hydroxymethy1-2-methylpropane-1,3-diol are reported.