Molybdenocene

Catalytic Ionic Hydrogenation of Ketones by Molybdenocene Complexes... 

Hydride transfer reactions from [Cp2MoH2] were discussed above in studies by Ito et al. [38], where this molybdenum dihydride was used in conjunction with acids for stoichiometric ionic hydrogenations of ketones. Tyler and coworkers have extensively developed the chemistry of related molybdenocene complexes in aqueous solution [52-54]. The dimeric bis-hydroxide bridged dication dissolves in water to produce the monomeric complex shown in Eq. (32) [53]. In D20 solution at 80 °C, this bimetallic complex catalyzes the H/D exchange of the a-protons of alcohols such as benzyl alcohol and ethanol [52, 54]. 

Further evidence for initial generation of molybdenocene (see Reaction 10) comes from trapping experiments. Irradiation under a carbon monoxide or an acetylene purge, for example, leads to near quantitative formation of the previously characterized [Mo -CsHs CO] (42) and [Mo(r/5-C5H5)2(C2H2)] adducts (43). These can be separated and purified by fractional sublimation and identified by their ir, NMR, and mass spectra. 

The phosphine complexes provide a thermal route to other molybdenocene adducts since the molybdenum-phosphorus bond appears to be labile. When solutions of [Mo(7 5-C5H5)2PEt3] react with CO or diphenylacetylene, formation of the corresponding adduct results (see Reaction 11). 

The quantum yield for H2 elimination from [Mo( y5-C5H5)2H2], measured at 366 nm in hexane solution in a degassed and sealed spectrophotometer cell, is 0.10. This value should be treated as a lower limit since reverse reaction of H2 with photogenerated molybdenocene was not prevented. This compares with a value of 0.01 that we obtained for H2 elimination from [ W(r75-CsH5)2H2] under similar photolysis conditions. 

Indenyl-fluorenyl systems, propylene polymerization, 4, 1068 Indenylidenes, in ROMP initiation, 11, 633 7]5-Indenyl ligand, in molybdenocene dihalides, 5, 573 Indenyl ligands, in cobalt(III) complexes, 7, 20 7]5-Indenyl ligands, in rhodium alkene complexes, 7, 197 2-(Indenyl)—phenoxo complexes, with mono-Cp Ti(IV),... 

Molecular recognition, in Rh Cp complexes, 7, 155 Molecular weight, in alkene living polymerizations, 11, 715 Moller-Plesset calculations, as perturbation method, 1, 646 Molten salts, and ionic liquids, 1, 848 Molybdacarboranes, synthesis, 3, 216 Molybdenocene dichloride, bioorganometallic chemistry,... 

Molybdenocene dihalides, associated chemistry, 5, 573 Molybdenocene dihydrides monomeric complexes, 5, 568 multimetallic complexes, 5, 570 protonation studies, 5, 570 Molybdenocenes... 

Multimetallic complexes, molybdenocene dihydrides, 5, 570 Multimetallic nickel-alkynes, synthesis and reactivity, 8, 145 Multinuclear chromium(II) complexes, with halides, alkyls,... 

Unsubstituted [( j5-C5H5)Mo(CO)2(>j3-C5H7)] has been prepared by different routes, photochemically (13) or by reduction of molybdenocene derivatives (122,123). 

Molybdenocene, jt-bound Organic Ligand-bridged Dimers... 

In addition to monocyclopentadienyl dimers, various molybdenocene derivatives can form dimers, as shown in equation (33). This is one example of a vast range of organic ligands that bridge metal-metal bonded complexes. Another example is one of the several products obtained by reaction of diphenylacetylene and molybdenum carbonyl (equation 34). 

The molybdenum analog of chromocene see Metallocene Complexes) [CP2M0] (molybdenocene) is not stable and has only been isolated using matrix isolation techniques see Matrix Isolation). The IR, magnetic circular dichroism spectra of the matrix isolated [CP2M0] were interpreted in terms of a paramagnetic metallocene, with parallel rings. 

Molybdenocene is not as reactive as tungstenocene and does not insert into C—H bonds, but it adds CO, CjHj, PEtj, and PPhj (=L) to give (h -CjHPjMoL derivatives ... 

Neutral molybdenocene derivatives coordinated with tertiary phosphines, Cp2Mo(PR3) (R = Ph, Et, cj c/o-QHii, -Bu, OEt) have been prepared from CP2M0H2 by the reaction steps shown below (eq. (7)- 9)) [29]. 

Compared to molybdenocene dichloride, the thiol derivatives are stable in water at physiological pH, and in tests on V79 Chinese hamster lung, human breast MCF7, and ovarian 2008 cell lines, they are not cycotoxic. The... 

Figure 6 Examples of molybdenocene dichloride thiol derivatives of biological relevance prepared in water under facile conditions.

Very related to the titanium chemistry described above are experiments with resembling molybdenocene complexes. If the molybdenum-diphenyl-acetylene complex Cp2Mo(PhC=CPh) is used as starting material, no C-C linkage reaction takes place with carbon dioxide. Instead, a crystalline solid was isolated whose x-ray proved the formation of a molybdenum-carbon dioxide complex [85] (Equation 15). 

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