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Metallocarboranes polyhedral expansion

Polyhedral contraction is not so general a method of preparing metallocarboranes as is polyhedral expansion since some metallocarboranes degrade completely under these conditions. [Pg.190]

Similar polyhedral expansion reactions have been used to synthesize metallocarboranes containing 3 metal atoms, e.g., the icosahedral (CsHsColsCaByHj (80), or containing two different metals (71,175), e.g., the bicapped square-antiprismatic CsHsCoCByHgNiCsHs (175). [Pg.27]

Although a number of different metallocarboranes have been synthesized in high yield by this reaction (18, 24), the actual chemistry is frequently much more complex than implied by Eqs. (5) and (6). For example, products containing greater and fewer numbers of boron atoms than present in the carborane starting materials have been isolated from polyhedral expansion reactions. [Pg.152]

The polyhedral expansion reaction appears to be a general synthetic method for metallocarboranes all the known doso-carboranes have been found to produce metal-containing compounds when subjected to the re-duction-complexation operations of this synthetic scheme. Moreover, metallocarboranes containing more than one transition metal may be prepared by the polyhedral expansion of monometallocarboranes. Examples of this synthetic route will be described in following sections. [Pg.152]

It should be noted that in the polyhedral expansion process, as idealized in Eqs. (5) and (6), the product mctallocarborane has one more vertex than was present in the carborane starting material—hence the origin of the descriptive phrase polyhedral expansion. By contrast, wThen metallocarboranes are prepared by reaction with O2B9H112- ions, which are prepared from the icosahedral C2B10H12 carboranes, twelve-vertex metallocarboranes result. [Pg.152]

Only one trimetallic twelve-vertex metallocarborane has been reported. This species, (C5H5)3Co3C2B7H9, arose as a side product during the polyhedral expansion of 2-C5H6-2-Co-l,6-C2B7H9 with Co(II) and C6H5 (25, 28). The isolation of this trimetallic complex suggests that the polyhedral expansion reaction may be extended to bimetallic substrates to produce novel metal-rich polyhedra. [Pg.167]

The nido eleven-vertex complex, C5H5C0C2B8H12, has been prepared, and spectral data indicate the presence of B—H—B and B—H—Co bridges (67). The commo eleven-vertex metallocarborane, (C2B8Hio)2Co-, prepared by polyhedral expansion of 1,6-C2B8Hio with Co(II) in the absence of cyclopentadienide ion, has carbon atoms in positions identical to the sites in the C5H5C0C2B8H10 isomer prepared by polyhedral expansion in the presence of C5H5-, i.e., at low-coordinate vertices (26). [Pg.172]

Reactions of monometallic eleven-vertex metallocarboranes have been discussed in previous sections and may be summarized briefly as (a) polyhedral expansion to bimetallic twelve-vertex complexes and (6) thermal metal transfer to bimetallic twelve-vertex compounds. Polyhedral contraction to ten-vertex monometallocarboranes is discussed in Section VII. [Pg.173]

Ten-vertex metallocarboranes containing both cobalt and nickel in the same polyhedron have been synthesized from the nine-vertex anionic species C5H5C0CB7HS- (Section VIII) by polyhedral expansion (87). The resulting neutral complexes, of formula (C5Hs)2CoNiCB7H8 and con-... [Pg.177]

There are now at least a dozen synthetic routes to metallocarboranes including (i) coordination using nido-carborane anions as ligands, (ii) polyhedral expansion reactions, (iii) polyhedral contraction reactions, (iv) polyhedral subrogation and (v) thermal metal transfer reactions. These first five routes were all devised by... [Pg.189]


See other pages where Metallocarboranes polyhedral expansion is mentioned: [Pg.189]    [Pg.191]    [Pg.732]    [Pg.27]    [Pg.49]    [Pg.153]    [Pg.171]    [Pg.177]    [Pg.191]   
See also in sourсe #XX -- [ Pg.169 ]




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