Seven coordinate molybdenum

In seven-coordinate molybdenum peroxo complexes of the type Mo(0)(02)2L2, there is the problem of dissociation of the complex in the case of monodentate ligands like pyridine, HMPA, DMF or H2O. Bidentate hgands like 2,2 -bipyridine, on the other hand, tend to give insoluble complexes. A solution to this problem was presented by Thiel in 1997 and 1998 . His group utilized the Mo-diperoxo complex 160 bearing a pyrazolylpyridine ligand. 

Heating seven-coordinate molybdenum reagents with internal alkynes in hexane has yielded CpMo(CO)(RC=CR)X products in selected cases [Eq. (12)]. The CpMo(CO)3Cl reagent was more reactive than the bromo... 

Thus far, the reactions of the diiodo-complexes [MI2(CO)3(NCMe)2] with alkynes have been described. In this section the reactions of other seven-coordinate molybdenum(II) and tungsten(II) halocarbonyls with alkynes are described. 

HgX)(CO)2Cp] (X = Cl, Br, I, SCN, N3) to give the seven-coordinate molybdenum and tungsten complexes [CpFe(CO)2HgMX(CO)3(N"N)], with Fe-Hg-M-X arrays. Riera et have described the reactions... 

A. Hroch, G. Gemmecker, W. R. Thiel, Metal-catalyzed oxidations, 10 New insights into the mechanism of hydroperoxide activation by investigation of dynamic processes in the coordination sphere of seven-coordinated molybdenum peroxo complexes, Eur. J. Inorg. Chem. (2000) 1107. 

Tin - A crystallographic study on [Rh(COD)(Ti -dppp)(SnCl3)] reveals two molecules in the asymmetric unit with trigonal bipyramidal and square-based pyramidal geometry about rhodium, while addition of tin dichloride to arene complexes [(T -arene)RuCI(ri -S2CPR3)] results in insertion into the ruthenium-chloride bond giving further tin trichloride complexes. A number of seven-coordinate molybdenum complexes [Mo(CX))2(PR3)Cl(r -phen)(SnRCl2)] ,... 

Divalent molybdenum compounds occur in mononuclear, dinuclear, and hexanuclear forms. Selected examples are shown in Figure 6. The mononuclear compounds are mostiy in the realm of organometaUic chemistry (30—32). Seven-coordinate complexes are common and include MoX2(CO)2(PR3)2, where X = Cl, Br, and I, and R = alkyl MoCl2(P(CH3)3)4, heptakis(isonitrile) complexes of the form Mo(CNR) 2 (Fig. 6d), and their chloro-substituted derivatives, eg, Mo(CNR)3CR. The latter undergo reductive coupling to form C—C bonds in the molybdenum coordination sphere (33). 

Seven and eight coordinate molybdenum complexes and related molybaenum(IV) oxo complexes with cyanide and isocyanide ligands. S. J. Lippard, Prog. Inorg. Chem., 1976, 21, 91-103 (44). 

Seven coordination in molybdenum chemistry analysis of oligonuclear structures. M. Melnik and P. Sharrock, Coord. Chem. Rev., 1985, 65, 49 (91). 

A number of attempts have been made over the years to develop reproducible synthetic routes to six- and seven-coordinate isocyanide complexes of molybdenum and tungsten. Two of the older methods, namely, the reaction of the hexacarbonyls with halogens in the presence of an isocyanide (775,116) or reactions of the salt Ag4Mo(CN)8 with isocyanides (74), have given six- and seven-coordinate products. Recently, however, the discovery of the reductive or nonreductive cleavage of multiple metal - metal bonds in dinuclear group VIA compounds by isocyanides has provided a facile route to the synthesis of a variety of homoleptic and related isocyanide complexes of these metals in reasonable yields. 

The most recent x-ray and EXAFS studies of dmso reductase (R. sphaero-ides) used enzyme crystals grown in the presence of excess dimethylsulfide [126], The reduced molybdenum site is apparently seven-coordinate with a bound dmso (Figure 12). The Mo=0 bond length is 1.7 A (1.6 A x-ray) the Mo—0 bond distances of the dmso and serine are each = 2.0 A. The Mo—S bond distances were 2.4-2.5 A. 

Lippard, Stephen J., Seven and Eight Coordinate Molybdenum Complexes and Related Molybdenum (IV) Oxo Complexes, with Cyanide and Isocyanide... 

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