Martin Minelli

Bio: Martin Minelli is an academic researcher from University of Arizona. The author has contributed to research in topics: Molybdenum & Nuclear magnetic resonance spectroscopy. The author has an hindex of 15, co-authored 39 publications receiving 564 citations.

Electrochemistry of monomeric molybdenum(V)-oxo complexes in dimethylformamide

Abstract: The electrochemistry of nine monomeric molybdenum(V)-oxo complexes in dimethylformamide has been investigated by cyclic voltammetry and controlled-potential coulometry at a platinum electrode. MoOC13L (L = o-phenanthroline, ol,a'-bipyridyl), MoOClL2 (L = 8-hydroxyquinoline, 8-mercaptoquinoline), and MoOClL (L = disalicylaldehyde ophenylenediimine, N,N'-dimethyl-N,N'-bis(2-mercaptoethyl)ethylenediamine, N,N'-bis(2-mercapto-2-methylpropyl)ethylenediamine) are facilely reduced by one-electron reductions to Mo(1V) species. (C2H5)4NMoOC12(salicylaldehyde o-hydroxyanil) is reduced in a two-electron step to an Mo(1II) species. None of the complexes are oxidizable in the voltage range used (+OS0 to -2.50 V vs. SCE) to Mo(V1) complexes. Comparison with reduction peaks for molybdenum(V1)-dioxo complexes indicates the Mo(V) monomers are not obtainable by electrochemical reduction of the Mo(V1) complexes, and are, in some cases, thermodynamically unstable to disproportionation into Mo(1V) and Mo(V1). Implications for redox states in molybdenum enzymes are discussed.

Preparation and characterization of binuclear complexes of molybdenum(III) and molybdenum(V) via oxidative decarbonylation. Reactions of LMo(CO)3 (L = 1,5,9-triazacyclododecane) and crystal structure of anti-[L2Mo2O4](ClO4)2.2H2O

Abstract: The cyclic triamine 1,5,9-triazacyclododecane (L), C/sub 9/H/sub 21/N/sub 3/, reacts with Mo(CO)/sub 6/ in Decalin at 150/sup 0/ to yield yellow, air-stable LMo(CO)/sub 3/ (1). Oxidation of 1 with bromine, nitrous acid (or NOBF/sub 4/), or hydrochloric acid in the presence of O/sub 2/ affords the monomeric complexes (LMo(CO)/sub 3/Br)(Br/sub 3/), (LMo(CO)/sub 2/NO)BF/sub 4/, and LMoCl/sub 3/, respectively. Oxidative decarbonylation of 1 in HClO/sub 4/ with O/sub 2/ gives the two isomers purple anti-(L/sub 2/Mo/sub 2/O/sub 4/)/sub 2/(ClO/sub 4/)/sub 2/ x 2H/sub 2/O and yellow syn-(L/sub 2/Mo/sub 2/O/sub 4/)(ClO/sub 4/)/sub 2/ x H/sub 2/O. Reduction of the former with zinc amalgam in aqueous solution in the presence and absence of coordinating acids (HBF/sub 4/, formic acid, acetic acid, hydrochloric acid) affords diamagnetic, green, dimeric bis(..mu..-hydroxo)-bridged species of molybdenum(III): (L/sub 2/Mo/sub 2/(..mu..-OH)/sub 2/(OH)/sub 2/)I/sub 2/ x 2H/sub 2/O, (L/sub 2/Mo/sub 2/(..mu..-OH)/sub 2/(..mu..-HCOO))I/sub 3/ x 2H/sub 2/O, (L/sub 2/Mo/sub 2/(..mu..-OH)/sub 2/(..mu..-CH/sub 3/CO/sub 2/))I/sub 3/, and (L/sub 2/Mo/sub 2/(..mu..-OH)/sub 2/Cl/sub 2/)(ClO/sub 4/)/sub 2/. Purple anti-(L/sub 2/Mo/sub 2/O/sub 4/)(ClO/sub 4/)/sub 2/ x 2H/sub 2/O crystallizes in the monoclinic space group P2/sub 1//c with a = 8.515 (8) A, b = 11.11 (2) A, c = 16.56 (3) A, ..beta.. = 92.3 (1)/sup 0/, Vmore » = 1565 (1) A/sup 3/, and d/sub calcd/ = 1.77 g/cm/sup 3/ for Z = 2 and M/sub r/ = 833.4. Least-squares refinement of the structure based on 3216 observations led to final discrepancy indices of R = 0.039 and R/sub w/ = 0.045. 21 references, 4 figures, 6 tables.« less

Direct identification of copper-molybdenum-sulfur clusters by molybdenum-95 NMR spectroscopy

Abstract: Utilisation des deplacements chimiques RMN de 95 Mo pour identifier divers ions en solution, du type [(XCu) n MoS 4 ] 2− , et determination des rapports CuX:MoS 4 pour des complexes inconnus. On montre que les clusters Cu-Mo-S ne se dissocient pas en solution car chaque complexe donne seulement une resonance de 95 Mo

The DFT route to NMR chemical shifts

Abstract: An overview is given of the recent development and use of density functional methods in nuclear magnetic resonance (NMR) chemical-shift calculations. The available density functional theory (DFT) methods are discussed, and examples for their validation and application are given. Relativistic effects are also considered, with an emphasis on spin–orbit coupling. The systems discussed range from transition-metal complexes and clusters via biological systems and fullerenes to weakly bound van der Waals molecules. DFT results not published previously comprise spin–orbit effects on 31P chemical shifts in phosphorus halides, the orientation of the 31P-shift tensor in Ru4(PPh)(CO)13, δ(95Mo) data, 13C and endohedral chemical shifts for fullerenes and for C60H36, as well as the shielding surface of the Ne2 molecule. © 1999 John Wiley & Sons, Inc. J Comput Chem 20: 91–105, 1999

Vanadyl(IV) EPR Spin Probes Inorganic and Biochemical Aspects

Abstract: Many proteins have metal ions as an integral part of their structure or require them as cofactors in enzyme catalysis. In many cases, these metal ions serve as useful spectrochemical probes of molecular structure, electron transfer, and enzyme kinetics (Vallee and Williams, 1968; Vallee and Wacker, 1970; Ochiai, 1977; Hughes, 1972; Eichhorn and Marzilli, 1979). Often the native metal (frequently zinc) can be removed and another metal ion substituted which has different and sometimes more desirable spectroscopic properties. By judicious choice of substitute metal ion to match particular technique, e.g., nuclear magnetic resonance (NMR), Mossbauer, optical absorption, or electron paramagnetic resonance (EPR) spectroscopy, much can be learned about the metal binding site and its role in the function of the protein.

Nitrido Complexes of Transition Metals

Abstract: In the past decade new syntheses and numerous structural determinations have enlivened studies in the still relatively young field of nitrido-transition-metal complexes. Aside from the terminal function of the nitrido ligand MN:, this group also occurs as linear μ2-bridging ligand in symmetric and asymmetric coordination; examples are known with almost right-angled bridge function; and, finally, it also functions as μ3-bridging ligand. Accordingly, the fresh impulses given to synthetic chemistry by nitrido complexes are also many-sided: such complexes are used, inter alia, for the preparation of phosphaniminato and thionitrosyl complexes as well as for the synthesis of metallaheterocycles of the type MN3S2 and MN3P2 with delocalized π-systems. In technetium chemistry complexes with terminal nitrido group are employed as radiopharmaceuticals, and, owing to the strong trans influence of the MN: group, nitrido complexes of molybdenum are suitable as catalysts in olefin metathesis. Finally, nitrido complexes are also of wide interest in theoretical studies.