Rafael Aguado

Addition compounds of dichlorodioxomolybdenum(VI) with sulfoxides. Molecular structure of [MoO2Cl2(Me2SO)2]

Abstract MoO2Cl2L2 (L=dimethyl sulfoxide (Me2SO), deuterated dimethyl sulfoxide (Me2SO-d6), di-n-buthyl sulfoxide (Bu2SO), tetramethylene sulfoxide (C4H8SO), dibenzyl sulfoxide (Bz2SO), diphenyl sulfoxide (Ph2SO), di-p-tolyl sulfoxide (p-Tol2SO), di-p-chloro-phenyl sulfoxide (p-Cl-Ph2SO) and methyl phenyl sulfoxide (MePhSO)) have been prepared by reacting a solution of MoO2Cl2(H2O)2 in diethyl ether with the respective ligand. The molecular structure of MoO2Cl2(Me2SO)2 has been established by X-ray diffraction analysis. The ability of representative complexes to work as oxotransfer catalysts has been tested.

Synthesis, characterization and catalytic activity of addition compounds of dioxomolybdenum(VI) pyridine-2,6-dicarboxylate. Crystal structure of MoO2(dipic)(L) (L=DMF, DMSO, OPPh3)

Abstract MoO 2 (dipic)(L) (dipic=pyridine 2,6-dicarboxylate (dipicolinate); L=dimethyl formamide (DMF), dimethyl sulfoxide (DMSO), hexamethyl phosphorotriamide (HMPA), triphenylphosphine oxide (OPPh 3 ), triethylamine, tripropylamine, tributylamine, pyridine, 2-methylpyridine, 3-methylpyridine, 4-methylpyridine) have been prepared by reacting equimolar amounts of MoO 2 Cl 2 (L) 2 (L=DMF, DMSO) with Na 2 dipic, followed by addition of the appropriate ligand to the resulting solutions. The molecular structures of the DMF, DMSO and HMPA derivatives have been established by X-ray diffraction analysis. The ability of MoO 2 (dipic)(L) (L=DMF, DMSO, HMPA, OPPh 3 ) to work as oxotransfer catalysts has been examined and compared with that of the prototypical MoO 2 (Et 2 dtc) 2 (Et 2 dtc=diethyl dithiocarbamate). Dipicolinate complexes proved to be more efficient catalysts than dithiocarbamate for the deoxygenation of azoxybenzene with triphenylphosphine in boiling toluene.

Dioxomolybdenum(VI) halides as oxotransfer catalysts

Abstract The catalytic activity of [MoO2X2(DMSO)2] (X = F, Cl, Br; DMSO = dimethylsulphoxide) in both the oxidation of triphenylphosphine (PPh3) by DMSO and the deoxygenation of azoxybenzene by PPh3 has been examined. While [MoO2F2(DMSO)2] was nearly inactive, [MoO2Cl2(DMSO)2] proved to be an excellent catalyst. The oxotransfer reactions from [MoO2Cl2(DMF)2] (DMF = dimethylformamide) to PPh3, and from DMSO to [MoOCl2(DMF)2], in DMF at 25°C, follow a second-order kinetic law with rate constants k = (4.3 ± 0.1) × 10−2 and k = (8.7 ± 0.2) × 10−2 M−1 s−1, respectively.

Addition compounds of dichlorodioxomolybdenum(VI) from hydrochloric acid solutions of molybdenum trioxide. Crystal structure of dichlorodioxodiaquamolybdenum(VI) bis(2,5,8-trioxanonane)

Abstract The behaviour of hydrochloric acid solutions of MoO3 with some common solvents has been explored. MoO2Cl2(H2O)2 separates from solution stabilized as polyether solvates. The crystal structure of [MoO2Cl2(H2O)2(2,5,8-trioxanonane)2] presents octahedral MoO2Cl2(H2O)2 units linked to the polyether chains through hydrogen bonds involving the water molecules. The polyether molecules show a cis-cis conformation.

Addition compounds of MoO2Br2 from MoO2Br2(H2O)2. Molecular structure of MoO2Br2{OP[N(CH3)2]3}2 and MoO2Br2{CH2[P(O)(C6H5)2]2}

Abstract MoO2Br2L2 (L=dimethyl formamide (DMF), N-methyl pirrolidone (NMP), dimethyl sulfoxide (DMSO), methyl phenyl sulfoxide (MePhSO), diphenyl sulfoxide (Ph2SO), hexamethyl phosphorotriamide (HMPA), triphenyl phosphine oxide (OPPh3), tributhyl phosphine oxide (OPBu3), triocthyl phosphine oxide (OPOct3), methyl diphenyl phosphine oxide (OPMePh2), and 1/2 methylene bis(diphenyl phosphine) dioxide (dppmO2)) have been prepared by reacting a solution of MoO2Br2(H2O)2 in diethyl ether with the corresponding ligand. The molecular structures of MoO2Br2(HMPA)2 and MoO2Br2(dppmO2) have been established by X-ray diffraction analysis. The ability of MoO2Br2L2 to oxidize (CH3)3CSH to (CH3)3CSSC(CH3)3 has been determined by 1H NMR spectroscopy.

Outer-sphere addition compounds of MoO2Br2(H2O)2 with ethers. Molecular structure of MoO2Br2(H2O)2·L (L=2,5,8-trioxanonane; 2,5,8,11,14-pentaoxapentadecane)

Abstract Outer-sphere addition compounds of MoO2Br2(H2O)2 with diethyl ether, dioxane, glyme, diglyme, triglyme and tetraglyme have been readily prepared by crystallizing diethyl ether extracts of a solution of sodium molybdate in concentrated hydrobromic acid in the presence of the corresponding ether. The molecular structures of MoO2Br2(H2O)2·L (L=2,5,8-trioxanonane; 2,5,8,11,14-pentaoxapentadecane) have been established by X-ray diffraction analysis.

Uranyl polyhalides. Molecular structure of [UO2(OAsPh3)4](Br3)2 and [UO2(OPPh3)4](I3)2

Abstract Uranyl trihalides of general formula [UO2L4](X3)2 (L=hexamethylphosphoramide (HMPA), triphenylphosphine oxide (OPPh3), triphenylarsine oxide (OAsPh3); X=Br, I), along with some other higher polyiodides, have been prepared by reacting UO2X2·nH2O with X2 and L in methanol or acetonitrile. The molecular structures of [UO2(OAsPh3)4](Br3)2 and [UO2(OPPh3)4](I3)2 have been established by X-ray diffraction analysis. 31P NMR spectra are consistent with the existence of conformational isomers in solution for cations bearing HMPA and OPPh3.

Synthesis and molecular structure of the all-trans- and the trans–cis-[UO2Br2(OAsPh3)2] isomers

Abstract The all-trans and the trans–cis isomers of [UO2Br2(OAsPh3)2] have been prepared by reacting UO2Br2·xH2O with OAsPh3. The molecular structures for both isomers have been established by X-ray diffraction analysis. The all-trans isomer is singular as the two UOAsPh3 bonds are very different.

Microscale thermite reactions

The reaction of aluminum with the oxides of a variety of elements (aluminothermy, or the Goldschmidt process) illustrates exothermic reactions that require a high activation energy. It is also an appropriate experiment with regard to the discussion of Ellingham diagrams. Because it is spectacular, this reaction is a favorite for demonstrations. When drama is not the main objective, conducting these reactions at microscale level offers numerous advantages over the usual scale.