A Study of Oxomolybdenum Chelate Compounds of Oxidation States (V) and (IV) When Prepared by Photochemical Reduction of Oxomolybdenum (VI) Complexes in Ethanol Under Inert Atmosphere and by Chemical Reduction
Dissertation - Open Access
Doctor of Philosophy (PhD)
Henry Gehrke, Jr.
A photolysis system was designed for meticulous exclusion of oxygen and moisture. Photolyzed ethanol solutions of dioxobis(acetylacetonato)-molybdenum(VI), Mo02 (acac)2, were studied via preparation of derivatives with several uninegative bidentate ligands (chelH, cysteine was designated cystH2) and pyridine (py). Infrared spectroscopy was a useful tool in identifying these compounds. An oxomolybdenum(IV) compound, MoO(dtc)2 was isolated from the red photolyzed solution when dtc was the N,N-diethyldithiocarbamate ion. Tropolone, 8-hydroxyquinoline, N,N-diethyldithiocarbamate, and cysteine formed products formulated as the dioxo bridged molybdenum(V) compounds, Mo204(che1)2. Acetylacetone, tropolone, 8-Hydroxyquinoline and N,N-diethyldithiocarbamate, formed derivatives formulated as the monooxo bridged molybdenum(V) compounds, Mo203 (che1)4. When pyridine was added to the photolyzed solution the product Mo204(chel)2(py)2, where chel was the acetylacetonate ion, was isolated. This product was also prepared by refluxing an ethanol-pyridine solution of dioxobis(acetylacetonato)molybdenum(VI). Both pyridine and 2,2'-bipyridine formed apparent polymeric products with the former compound formulated as Mo02 (OH)(py)0.8. The pyridine product was also obtained from the reflux of an ethanol-pyridine-MoO2(acac)2 mixture. Photolysis of an ethanol suspension of the diethyldithiocarbamate compound, MoO2(dtc)2 resulted in an unique, air stable, pressure sensitive green product with the stoichiometry 3 Mo2O3 (dtc)4•Mo2O4(dtc)2. Photolysis of an ethanol suspension of a solvated form of Na2Mo2O5(cyst)2(OH)2 where cyst is the dinegative cysteinate anion, resulted in a solvated form of the product, Na2Mo2O4(cyst)2. The type and amount of product formed from the red photolyzed solution established that the reduced molybdenum species in ethanol solution had one acetylacetonate ligand attached to each metal atom. The second acetylacetonate unit was proposed to have been oxidized in the photo-oxidation-reduction process. Various other ethanol and aqueous solution and suspension systems were investigated by the photochemical method. Only ethanol solutions resulted in conclusive photochemical reduction. Chemical methods were utilized to prepare the pyridine products Mo2O5(acac)2(py)2 and (pyH)4 (Mo8O26). The tropolonate(trop) compound MoO2 (trop)2 was synthesized and the compound Mo2O4(dtc)2 was obtained by refluxing aqueous Mo2O3 (dtc)4. The many oxygen bridged molybdenum(V) complexes, especially those containing sulfur ligands, were significant to molybdoenzyme chemistry.
Library of Congress Subject Headings
South Dakota State University
Dendinger, Richard Donald, "A Study of Oxomolybdenum Chelate Compounds of Oxidation States (V) and (IV) When Prepared by Photochemical Reduction of Oxomolybdenum (VI) Complexes in Ethanol Under Inert Atmosphere and by Chemical Reduction" (1974). Electronic Theses and Dissertations. 5520.