Dodecahedral clusters

Two completely separated P2 ligands originating from P4 activation are present in the previously mentioned complexes [ CpxM 2(/j, 1 1P2)2] (M=Co, Rh, Ir). Orthogonally arranged P2 ligands similar to a diphosphido dumbbell were found in the dodecahedral cluster [ Cp Fe 4(/j, 1 2 2 1-P2)] which is generated via high temperature cothermolysis of [ Cp Fe(CO)2 2] with P4 [80]. 

Figure 2 The distribution of different types of H-bonds in dodecahedral cluster for optimal configurations according to SWB model. A local geometry optimization performed using T1P4P and TIP5P potentials (a, b) - 21 strong H-bonds, (c, d) - 20 strong H-bonds (a, c) - Energy values of H-bonds, as such (b, d) - Effective energy values of H-bonds.

Fig. 19.3. Two canonical forms of a hydrogen-bonded rhombic dodecahedral cluster of (H20)i4. Circles represent oxygen atoms arrows represent hydrogen atoms. The oxygen atoms which are bonded to the four hydrogen atoms not used in the formation of the cluster are indicated by the dots. (Donohue, 1969.)...

Ab initio studies of (H20)2oH+ and (H20)2 H prisnuc, fused cubic and dodecahedral clusters can H30 ion remain in cage cavity ... 

Boron carbide is often represented as B4C, but this is only a rough empirical formula. The compound is thought to consist of dodecahedral clusters of 12 boron atoms associated with linear rods of 3 carbon atoms, but the stoichiometry is highly variable and can range from BeCs to B4C. Boron carbide is extremely hard (9.3 on the Mohs scale) and is used as an abrasive. 

Fig. 13.13 The family of B X (X = Cl, Br, I) molecules possess cluster structures, (a) B4CI4 has a tetrahedral core, (b) BgClg possesses a dodecahedral cluster core and (c) B9Br9 has a tricapped trigonal prismatic core. Colour code B, blue Cl, green Br, gold.

McDonald, S., Ojamaee, L., Singer, S. J. (1998). Graph theoretical generation and analysis of hydrogen-bonded structures with applications to the neutral and protonated water cube and dodecahedral clusters. Journal of Physical Chemistry A, 102,2824-2832. 

B8C18 has a dodecahedral Bg c/o.vo-skclclon with 2n = 16 electrons. In this case, the Wade rule neither can be applied, nor can it be interpreted as an electron precise cluster nor as a cluster with 3c2e bonds. B4(BF2)6 has a tetrahedral B4 skeleton with a radially bonded BF2 ligand at each vertex, but it has two more BF2 groups bonded to two tetrahedron edges. In such cases the simple electron counting rules fail. 

In other related studies,186 we determined the structures of mixed water-methanol clusters the intensity distributions of (H20)n(CH30H)JBH+ showed magic numbers at n + m = 21, 0 < m 8 due to the enhanced stabilities of the dodecahedral cage structures in the mixed clusters. Studies of the metastable dissociation of (H20)B(CH30H)mH+ (n + m < 40) provided evidence that the dissociation channels... 

The dianionic Ga8 cluster [Ga8(flu)8]2 453 (flu = fluorenyl) has been synthesized by salt metathesis reaction between a metastable Ga Br solution and fluorenyllithium.344 The eight Ga atoms form a square antiprismatic core. This is rather unexpected because 453, which is a z/oro-cluster according to the Wade-Mingos rules, was expected to adopt the dodecahedral structure as was observed for the corresponding boron clusters. However, computational calculations demonstrated that in the case of eight Ga atoms, the formation of a square antiprismatic structure is energetically favored (Figure 33). 

In this section we discuss another family of high-symmetrical strained clusters in which the icosahedral aluminum "subcluster" AI12 with diameter 5.2 A and with a "dopant" atoms L or isoelectronic ions in the center (L = B-, C, N+, Al-, and Si), is inserted into the dodecahedral cage Al2o03o with diameter 9.5 A (Figure 8). All calculations were performed at the B3LYP/6-31G level [61]. 

The isolated doped aluminum clusters L Ali2 with various dopants L have been systematically calculated earlier [62]. In [35] it was predicted that the dodecahedral isomer AUoCbo (4) is a high-lying intermediate which is, by 1 30-150 kcal/mol, less favorable as compared with the more compact... 

Table 15 Geometrical parameters and vibrational frequencies of the icosahedral L A1i2 guest and the dodecahedral AI20O30 cage in the isolated state (A) and in the matreshka-like L A112 A12oC>3 clusters...

Water clusters containing simple ions are another area of current experimental and theoretical interest. Accordingly, they are also the subject of EA studies. Chaudhury et al. [113] have used EA methods on empirical potentials to obtain optimized structures of halide ions in water clusters, which they then subjected to AMI calculations for simulation of spectra. EA applications to alkali cations in TIP4P water clusters [114,115] have led to explanations of experimental mass-spectroscopic signatures of these systems, in particular the lack of magic numbers for the sodium case and some of the typical magic numbers of the potassium and cesium cases, and the role of dodecahedral clathrate structures in these species. 

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