Halogenation with molybdenum complexes

An unusual binuclear molybdenum complex has been described, for which 2.27 is a possible structure. It undergoes metathetical bridge replacement, for example with sodium methoxide the tri-/<-methoxy analogue is prepared, and the halogen bridge can be split by amines giving 7i-C3H5Mo(CO)2(aniine)2Cl [88a]. 

Furthermore, chemical oxidation of [Mo(CO)6] with organic molecules containing acidic hydrogen gives rise to molybdenum species in the +2, -i-3 and +A oxidation states. Higher oxidation states (r-5 and -i-6) have been observed when halogens directly oxidize [Mo(CO)6], A Mo tetranuclear complex has been obtained when hydrochloric acid reacts with the tri-p-hydroxy-dimolybdenum complex, as shown in Equation 9.2 ... 

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. 

Fluorocarbonyl complexes of molybdenum(II) and tungsten(II) are much less common than their other halogen counterparts. However, several examples have been reported. For example, the selective fluorination of [Mo(CO)6] with XeF, in perfluoro solvents or HF yields [MoF2(CO)3], which has been characterized by 1R, mass spectrometry, and X-ray powder diffraction analysis.195... 

The orange complex is air sensitive in the solid state. It is reasonably soluble and stable in THF but decomposes in nonpolar solvents, such as benzene, to give polymeric halogen-bridged products.9 It is paramagnetic with a magnetic moment of 3.63 BM, and its IR spectrum shows a very intense band at about 820 cm-1 due to coordinated THF. Its reactions with tertiary phosphines in THF give a series of molybdenum (III) tertiary phosphine complexes,9 and with trimethyl-silyl azide Mo(V) nitrido complexes are formed.8... 

Like all the other transition elements, molybdenum is a metal, and it is widely used as an alloying element and as a metallic coating. Some of its physical properties are listed in Table 3.2. In chemical reactions it shows little tendency to form cations, which is usuaily a characteristic of metals. In fact its sait-forming properties resembie those of non-metals, in that it has the ability to form salts (molybdates, sulphomolybdates, etc) or other complex compounds with another metal and a non-metal such as oxygen, sulphur or a halogen. The chemistry of molybdenum is very... 

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