| Summary: | 碩士 === 國立清華大學 === 化學系 === 103 === Abstract
The low-valent and low-coordinate quadruply-bonded dimolybdenum complex, Mo2[μ-κ2-PhB(N-2,6-iPr2C6H3)2]2(C7H8) (1), shows interesting reactivities toward organozinc, main group reagents and small molecules.
Treatment of 1 with one equiv of organozinc reagents, such as diphenylzinc, dimethylzinc, and diethylzinc, leads to the formation of dimolybdenum complex, cis-(R-Mo)2[μ-κ2-PhB(N-2,6-iPr2C6H3)2]2 (R = Ph (2), Me (3), Et (4)), which are formed via an oxidative addition of one molecular organozinc reagents to 1, and then release one zinc atom.
Treatment of 1 with S8 gives two products. One is sulfide complex (μ-S)Mo2[μ-κ2-PhB(N-2,6-iPr2C6H3)2]2 (5) and the other is persulfide complex (μ-κ2-S2)Mo2[μ-κ2-PhB(N-2,6-iPr2C6H3)2]2 (6). Subsequent introduction of KC8 to the product mixture results in the isolation of the supersulfido complex (κ2-S2Mo)2[μ-κ2-PhB(N-2,6-iPr2C6H3)2]2 (7). Moreover, complex 5 can be isolated from complex 7 by adding three equivs of triphenylphosphine. However, treatment of 1 with Se or Te only leads to (μ-E)Mo2[μ-κ2-PhB(N-2,6-iPr2C6H3)2]2 (E = Se (8), Te (9)). Besides, complex 9 is unstable in organic solvents and it slowly decomplses back to complex 1.
Furthermore, the reaction of 1 with one equiv of organic azides, such as 1-adamantyl azide and trimethylsilyl azide, extrudes one equiv of dinitrogen molecule and gives a dimolybdenum imido complex, [μ-RN]Mo2[μ-κ2-PhB(N-2,6-iPr2C6H3)2]2 (R = 1-Ad (10), TMS (11)).
Reaction of 1 with one equiv of alkyl nitriles, such as propionitrile and isobutyronitrile, respectively, affords [μ-η2-(R)CN]Mo2[μ-κ2-PhB(N-2,6-iPr2C6H3)2]2 (R = Et (12), iPr (13)).
However, treatment of 1 with two equivs of 4-bromobenzonitrile gives a [2+2+2] cycloaddition dimolybdenum adduct, [μ-η2-NC(4-BrC6H4)C(4-BrC6H4)N]Mo2[μ-κ2-PhB(N-2,6-iPr2C6H3)2]2 (14), which is formed via a C-C coupling. In contrast to the [2+2+2] dimolybdenum adducts formed from Mo-Mo quintuple bonded complexes, the central C2N2Mo2 six-membered ring of complex 14 is not planar, so it does not have aromatic property.
Treatment of 1 with one equiv of phenylacetylene leads to characterization of the [2+2] dimolybdenum cycloadduct, (μ-η1:η1-C6H5CCH)Mo2[μ-κ2-PhB(N-2,6-iPr2C6H3)2]2 (15),
Finally, the dimolybdenum complex syn-Cl2Mo2[μ-κ2-PhB(N-2,6-Et2C6H3)2]2 (16) stabilized by the less bulky ligand PhB[N-2,6-Et2C6H3]2 can be prepared. However, subsequent KC8 reduction leads to the characterization of an arene-bridged tetranuclear complex {Mo2[μ-κ2-PhB(N-2,6-Et2C6H3)2]2}2(C6D6) (17), in which two dimolybdenum units are bridged by a benzene-d6.
The bridged benzene-d6 in 7 is not planar but reather reduced to adopt a chair form and it is not labile. As a result, complex 17 is much less reactive than complex 1.
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