Mononuclear molybdenum systems

Molybdenum, 819-820 Molybdenum deficiency, 819-820 Monocytes, atherosclerosb and, 359 Monoglycerides, 93 Mononuclear phagocytic system, 752 Memosaccharides, chemical stTveture, 10-12 Monosodium glutamate, 461 Monouruiaturated fatty acids, 361, 366... 

The lower nuclearity clusters [Mo5Cl13]2 were isolated from MoCls in AlCl3/KCl/BiCl3/Bi melts that led to the hexanuclear species (17). This is the only intermediate isolated from reaction mixture that produces the Mo6C18 4+ core. Solution chemistry has yielded Mo2, Mo3, and Mo4 halide species from mononuclear molybdenum complexes, suggesting that a nucleation process similar to that proposed for the tungsten systems may take place during the formation of hexanuclear molybdenum clusters (18-22). 

Ni(CN)3(NO)] - + iOa + HaO—[Ni(CN)3(NO)]2- + 20H-The importance of the redox nature of molybdenum centres in biological systems has been recognized in several studies. Model systems for nitrogenase, involving molybdate, catalytic amounts of iron(ii), and cysteine, effect the reduction of aliphatic nitriles to alkanes and ammonia in the presence of sodium borohydride. The reaction is accelerated by substrate concentrations of ATP, the active species being considered to be mononuclear molybdenum-thiol complexes. The dinuclear molybdenum complex (7) formed by... 

The most extensive group of molybdenum hydride complexes are those which contain phosphine ligands, and mononuclear systems with one to six hydride ligands have been identified. 

Tables I and II summarize the structural studies of mononuclear and binuclear vinylidene complexes, and Table III those of propadienylidene complexes which had been reported to mid-1982. As can be seen, the C=C bond lengths range from 1.29 to 1.38 A, and the M-C bond (1.7-2.0 A) is considerably shorter than those found in alkyl or simple carbene complexes. Both observations are consistent with the theoretical picture outlined above, and in particular, the short M-C bonds confirm the efficient transfer of electron density to the n orbitals. In mononuclear complexes, the M—C=C system ranges from strictly linear to appreciably bent, e.g., 167° in MoCl[C=C(CN)2][P(OMe3)2]2(fj-C5H5) these variations have been attributed to electronic rather than steric factors. In the molybdenum complex cited, the vinylidene ligand bends towards the cyclopentadienyl ring (111).

There is very little information concerning one-electron reactions at oxo-molybdenum centers because of the tendency for oxo-molybdenum complexes to form dinuclear systems (37 and 38). To our knowledge, (L-N3)MoO,jX3, j complexes constitute the only family of mononuclear... 

Molybdenum iw)and Tungsteriw). The discussion about the nature of molybdenum(iv) in solution continues, evidence being presented for both mononuclear and dinuclear species. Mononuclear oxomolybdate(ii) complex anions have been demonstrated as models for the reduction of CN and N2 by molybdothiol catalyst systems. ... 

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