Homoleptic complexes molybdenum

By way of example, we can focus on the cyano complexes. Palladium and platinum can form homoleptic complexes with two, four, or six cyanides, depending on the metal oxidation state zero, two, and four, respectively. Rhenium forms heptacyano complexes in its - -3 and -t-4 oxidation states but forms an octacyano complex in its -t-5 state. Molybdenum and tungsten also appear commonly in octacyano complexes for +4 and - -5 oxidation states, and heptacyano analogs for the - -2 and - -3 cases, with only one occurrence of [Mo(CN)6]" anions in two oxidation states (n = 3, 4). Similar situations can be found with phosphine or carbonyl complexes. For instance, the group... 

Cyanide complexes of molybdenum(II) generally appear elsewhere under other classifications, where CN- is an andlliary ligand. The homoleptic anions [Mo(CN)6]4- and [Mo(CN)7]5- (pentagonal bipyramid) have been reviewed elsewhere.10... 

In the case of the alkoxides and phenoxides of molybdenum(III) the interaction between metal atoms becomes dominant, leading to diamagnetic compounds of stoichiometry Mo2(OR)6 or Mo4(OR )i2(R/ = the less bulky Me or Et).78 These compounds are readily sublimable, (70-90 °C/ 10-3 Torr for Mo OPr1 ) and retain either their dimeric or tetrameric nature both in solution and the gas phase, as determined by cryoscopic measurements and mass spectrometry, respectively.78 An analogous tungsten(III) complex W2(OBu )6 can be obtained, but for other alkoxides the simple homoleptic compounds cannot be isolated.79,168... 

The striking advance since 1973 has been the synthesis of homoleptic isocyanides for vanadium and almost all of the post-group-VIA metals up to group IB (see Table I), and this has been helped in some respects by synthetic rationale. For example, the discovery of the simple reductive or nonreduc-tive cleavage of multiple metal-metal bonds in suitable dinuclear complexes of molybdenum and tungsten has provided a high yield route to W(CNPh)6 and [M(CNR)7]2+ (M = Mo, W) and related complexes (5-14). During these studies the series [M(CNR)7]2+ was completed with the isola-... 

There are no routes yet to homoleptic metal isocyanide anions. If one considers the interesting products obtained from methyl iodide additions to molybdenum (43) and manganese (44) carbonyl isonitrile anions, negatively charged isocyanide complexes should have some interesting chemistry. Also, now that a simple route to [CpFe(CNR)2]2 complexes has been devised (45), the synthesis of the anion [CpFe(CNR)2] could provide a route to a range of products including heterometal-metal bonded systems. 

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 homoleptic derivatives of Mo and W(VI) are rather scarcely studied. The only structurally characterized complex, W(OMe)5, possesses the molecular structure analogous to those of alkoxide halids, i.e. a dimer built up of two edge-sharing octahedra. The structure of monooxo homometallic derivatives is unknown and their individuality appears questionable. The only dioxocom-plex of molybdenum(V) isolated as pyridin solvate demonstrates the [Ti(OMe)w]-type structure (Table 12.19). 

Homoleptic germylenes, preparation and properties, 3, 773 Homoleptic lanthanide(II) alkyl compounds, properties, 4, 4 Homoleptic manganese aryl complexes, preparation, 5, 816 Homoleptic manganese isonitrilates, preparation, 5, 773—774 Homoleptic molybdenum complexes, preparation and characteristics, 5, 514... 

The nature of the complexes, synthesized from metal vapor and t-BuC=P, is highly dependent upon the nature of the metal. Thus, with iron, chromium, or vanadium atoms, pentaphosphametallocenes are obtained.51 In contrast, the phosphaalkyne and molybdenum or tungsten atoms afford homoleptic tris[i74-l,3-diphosphete] metal(O) complexes [M(tj4-P2C2- -Bu2)3] (M = Mo, W).51... 

As used here cluster refers to molecules that contain at least 3 metal atoms and electron configurations suitable for the formation of metal-metal bonds. Molybdenum readily forms strong homoleptic metal-metal bonds (see Homoleptic Compound) and so it is not surprising that molybdenum is readily incorporated into cluster stractures (see Polynuclear Organometallic Cluster Complexes). 

A unique homoleptic molybdenum thiolate, Mo(//r -dmpt)(dmpt)2 (388), is produced in the reaction of MoCl3(thf)3 with Li(2,6-dimesitylphenylthiolate) in diethyl ether at 0°C. The paramagnetic (/rB = 3.6), pseudo-tetrahedral complex features two monodentate thiolates, the third being bound through sulfur and 7r-arene interactions.893 The investigation of Mo111 and MoIV dithiocarbamates as oil additives and lubricant precursors continues. 

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