Molybdenum , crystal structure

A number of substances such as graphite, talc, and molybdenum disulfide have sheetlike crystal structures, and it might be supposed that the shear strength along such layers would be small and hence the coefficient of friction. It is true... 

The crystal structures observed during the oxidation of molybdenum consist of stable molybdenum dioxide in contact with the metal throughout the range 300-700°C. As the film thickens in the low-temperature range, the trioxide predominates on the surface. At 400°C, molybdenum trioxide is no longer observed and molybdenum dioxide is the only oxide observed. 

M03S7X4 (X = Cl, Br), monoclinic (P2i/c). Figure 24 shows the asymmetrical unit of the crystal structure. The three, independent molybdenum atoms form an almost equilateral triangle. Six of the seven sulfur atoms occur in three S2 groups, each one bridging one Mo-Mo... 

However, when the X-ray crystal structure of the MoFe protein was examined, it was clear that homocitrate could not directly hydrogen bond to the histidine, since the carboxylate group and imidazole are stacked parallel to each other in the crystal. Nevertheless, as noted in the previous section, studies on model complexes have suggested that homocitrate can become monodentate during nitrogenase turnover, with the molybdenum carboxylate bond breaking to open up a vacant site at molybdenum suitable for binding N2. 

Kiessling, R. The Crystal Structures of Molybdenum and Tungsten Borides. 

Binary Systems and Related Compounds.—Halides. The thermodynamics of gas-phase equilibria in the W-F2 and W-F2-H2 systems at high temperatures have been described.The Raman spectrum of solid MoF exhibits Mo—F stretching bands at 746, 722, and 690 cm These results suggest that the compound has a similar structure to NbF4, with each molybdenum co-ordinated to six fluorine atoms.The Raman spectrum of crystalline M0F5 has also been reported and interpreted in terms of the crystal structure.The electronic spectrum of liquid M0F5 has been determined and shown to be consistent with a trigonal-bipyramidal molecular unit. ... 

Phosphides. The crystal structure of MogPj has been shown to involve trigonal prisms of molybdenum atoms each enclosing a central phosphorus atom. M0P4 has been prepared by reaction of the elements at 15—65 kbar and shown to be isostructural with CrP, and therefore to involve the metal atom surrounded by six phosphorus atoms in a distorted octahedral manner. ... 

Molybdenum and Tungsten Bronzes.—The results of the majority of studies of studies of new bronze phases are summarized in Table 9. Sno.2W03 and Sno.3 WO3 have been prepared and their crystal structures determined. Whether they are bronzes is debatable since they do not involve a host lattice of WO ... 

A potentiometric study of polymeric anions of molybdenum in nitrate melts has resolved apparent contradictions in earlier work and confirmed that [Mo207] ", rather than [Mo30,o] , is the polymeric anion in equilibrium with [MoOj ] The crystal structure of K2[Mo,07] has been shown to involve chains of M0O4 tetrahedra and MoO octahedra " and the dissociation of molten Na2[W207] to Na and a mixture of anions including [W04], [W207] , and has been confirmed. " The results of other... 

N-Donor Ligands. The full account of the crystal structure of [Mo02(8-hydroxyquinolate)2] has been published. The dimensions of the M0O2 unit are O—Klo—O = 104.C and Mo—O = 171(2) pm. The electrochemistries of this and the related molybdenum(v) complex. [ MoO(8-hydroxyquino-late)2 2 0], have been investigated as simple models of molybdenum-fluoro-protein enzymes (p. 146). Reduction of the molybdenum(vi) complex occurs in two one-electron steps with solvent attack of the reduced intermediates and displacement of the 8-hydroxyquinolato-groups. ... 

The formation of a monomeric amidino complex has been reported for the reaction of rhenium pentachloride with di-isopropylcarbodiimid. A composition of [ReCl4(prop 2N2CCI)] was derived from elemental analysis, spectroscopic data and the crystal structure of the molybdenum analogue. " ... 

The possibility of this binding mode was shown recently with the synthesis and structural analysis of the dumbbell-shaped bis-fullerene complexes of molybdenum and timgsten. The X-ray crystal structure proves the (71 -0 0)21 1 binding mode (Figure 7.9) [87]. 

Metalloenzymes, 33 40, see also Enzymes crystal structure, 44 230-258 DNA repair, 45 251 inhibitors, 36 40-42 molybdenum, 45 2, 53, 60-63 nuleic acid hydrolysis, 45 251-252 superoxide dismustases and, 45 130 zinc-containing, hard and soft acid-base behavior, 42 103-109 Metalloids... 

MoOCl2(02)(OPR3)2, 10, one of the few examples of mono-peroxo molybdenum derivatives, has been isolated and characterized in the solid state . These derivatives are fairly unstable and the crystal structures obtained derive from a mixture with their reduction products Mo02(Cl2)(OPR3)2. 

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