SYNTHESIS, STRUCTURE, AND PROPERTIES OF THE OXYGEN-DEFICIENT BIS(3,5-DI-TERT-BUTYLCATECHOLATO)OXOMOLYBDENUM(VI) DIMER, [MOO(O2C6H2(TERT-BU)2)2]2

The reaction between Mo(CO)6 and 3,5-di-tert-butyl-l,2-benzoquinone in toluene produces a complex of empirical formula MoO(O2C6H2(t-Bu)2)2 as a toluene solvate. The results of a crystallographic molecular structure determination show that the complex is a centrosymmetric dimer with oxygen atoms of two catecholate ligands linking adjacent metal centers. Molybdenum-oxygen lengths within the bridge are quite unsymmetrical with the longest length occurring within the chelate ring to an oxygen which is trans to a strongly bound oxo ligand. The ligands have C-O lengths which are consistent with a fully reduced catecholate structure. Accordingly, the metal centers are rare examples of octahedral Mo(VI) having a single oxo ligand. The electronic spectrum of the complex is found to be nearly identical with that of a complex previously characterized as Mo(O2C6H2(t-Bu)2)3. A band in the infrared region at 990 cm-1 appears attributable to the Mo⩵O stretch and the proton NMR is consistent with the structural result. Electrochemically, the complex is not observed to undergo oxidation but does undergo two irreversible reductions, likely to Mo(V) species. © 1979, American Chemical Society. All rights reserved.