Trigonal bipyramid pentanuclear complexes

Similar complexes have been prepared with nitrogen as a central hereroatom but to date only the tetranuclear and pentanuclear derivatives have been achieved from the reaction of ammonia with the oxonium complexes (Figure 1.37), with a tetrahedral or trigonal bipyramidal geometry, respectively [232]. Auration of polyamines or related... 

Last but not least, mention should be made of the use of redox active organometallic clusters for the formation of CT complex. An early example was reported by Eisenberg, Miller and co-workers who exploited the trinuclear niobium cluster [Nb3(/i-Cl)6(>7 -C6Me6)3] and prepared the [TCNQ] salt, upon oxidation to the dicationic form. This material was found to be paramagnetic and to display a relatively modest conductivity (urt = 0.001 Scm , semiconductor) [75]. Finally, the pentanuclear trigonal bipyramidal vanadium cluster [(MeCp)5V5(/r -S)6] was shown to undergo CT complex formation with TCNQ affording [(MeCp)5V5(/i -S)6] [(TCNQ)2] [76]. This material, which was structurally characterized, is an n-type semiconductor with a band gap of 0.25 eV. 

As already mentioned the tervalent melal isopropoxides were shown to be pentanuclear oxo-isopropoxides [M5(/Li5-0)(/r3-OPr )4(OPr )5] with the square pyramidal structure for the M5O14 core (Fig. 5.5). Structures have been reported for M = Y, Pr, Yb, and In, and also for the heterometallic compound in which the two metals were distributed randomly over the five sites [Y4PrO(OPr )i3]. Although single crystals of [Er5(/u,5-0)(/r3-OPr )4(/u,-OPr )4(OPr )5] could not be obtained, the X-ray powder diffraction data showed that it was isomorphous and isostructural with Pr, Yb, and In compounds which are all monoclinic P2i/n (cf. the yttrium compound which is orthorhombic). Interestingly neodymium formed the pentanuclear complex [Nd5(/i5-0)(/r,3-OPr )2(/i-OPr )6(OPr )5(I OH)2] in which the fi5-oxo ligand is at the centre of a trigonal bipyramid of Nd atoms. ... 

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