Nitrogen in molybdenum

In animal metabolism, oxomolybdoenzymes catalyse a number of oxidation processes. These oxidases contain Mo coordinated to terminal O and S atoms, and their action appears to involve loss of an O or S atom along with reduction to Mo or Mo". It is, however, the role of molybdenum in nitrogen fixation which has received most attention. 

Fig. 6. Mechanism of recrystallization of molybdenum in nitrogen/chlorine plasma. A cross-sectional view of the sheet with the growing crystals...

Uptake and Role of Molybdenum in Nitrogen-Fixing Bacteria... 

The function of molybdenum in enzymic mechanisms has been reviewed and the role of molybdenum in nitrogen fixation examined. ... 

In many of the transition metals, such as titanium, vanadium and molybdenum, carbon, nitrogen and oxygen atoms can fit into octahedral holes, and hydrogen into the teualredral holes. The fit here is estimated by assuming the atoms all have incompressible radii, and die contact must be such tlrat tire interstitial atoms do not rattle around in the holes. 

Howarth, R.W. and J.J. Cole. 1985. Molybdenum availability, nitrogen limitation, and phytoplankton growth in natural waters. Science 229 653-655. 

Molybdenum is essential for a number of enzymes, for example xanthine oxidases in mammals and nitrogenases in nitrogen-fixing bacteria. 

Molybdenum In its pure form, without additions, it is the most efficient catalyst of all the easily obtainable and reducible substances, and it is less easily poisoned than iron. It catalyzes in another way than iron, insofar as it forms analytically easily detectable amounts of metal nitrides (about 9% nitrogen content) during its catalytic action, whereas iron does not form, under synthesis conditions, analytically detectable quantities of a nitride. In this respect, molybdenum resembles tungsten, manganese and uranium which all form nitrides during their operation, as ammonia catalysts. Molybdenum is clearly promoted by nickel, cobalt and iron, but not by oxides such as alumina. Alkali metals can act favorably on molybdenum, but oxides of the alkali metals are harmful. Efficiency, as pure molybdenum, 1.5%, promoted up to 4% ammonia. 

MgATP hydrolysis and, 47 189-191 nitrogenase complex, 47 186-189 substrates, 47 192-202 molybdenum iron proteins, 47 161, 166-174, 176-183, 191-192 structure, 47 162-164, 166-170 nitrogen fixation role, 36 78 in nitrogen fixation systems, 27 265-266 noncomplementary reactions with Sn", 10 215... 

Figure 6.5 The structure of a four-coordinate molybdenum amido/nitride [MoN(NPh2)3]. " Molybdenum and nitrogen atoms are shown as black spheres and carbon are given in white shadow. Selected bond lengths Mo-NI 1.63, Mo-N2 2.00, Mo-N3 1.99, Mo-N4 2.00A...

Figure 6.7 View of [Fe N2Mo[(Me3SiN)3N] 3f (without H atoms) showing the three-coordinate iron atom and four-coordinate molybdenum atoms. Iron, molybdenum and nitrogen atoms are shown as black spheres, silicon atoms are grey and carbon atoms are given in white shadow. Selected bond lengths Fe-NI 1.86, Fe-N3 1.84, Fe-N5 1.82, Mo1-N2 1.86, Mo2-N4 1.81, Mo3-N6 1.82A...

Compound 59 forms complexes of the type L(CuC1)2, L2CuBr2, L2PdCl2 IR spectra show coordination to be via the nitrogen lone pairs. They show a bridging tendency toward iron and molybdenum in, e.g., LFe2(CO)7 and [LMo(CO)4]2.72... 

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