Tetrels

Quaternary Rare-earth Metal Chalcotrielates and Tetrelates... 

We have developed a systematic study of quaternary chalco-gallates, indates (trielates) and chalco-silicates, and germinates (tetrelates) of the rare-earth metals. We have demonstrated that a series of new compounds could be formed in these families of materials [1, 3, 9, 10, 14, 81, 82]. There have been reports in the literature of a few examples of these types of materials, but there is sufficient evidence to support the fact that this area is wide open for exploring the likelihood for new rare-earth metal-based materials [83-90]. Our studies have focused on the gallium, indium, germanium and sihcon sulfides, selenides, and teUurides. 

Scharfe S, Eassler TP (2010) Polyhedral nine-atom clusters of tetrel elements and intermetalloid derivatives. Phil Trans Royal Soc A Math Phys Eng Sci 368 1265-1284... 

Relationships Between Soluble Zintl Anions, Ligand-Stabilized Cage Compounds, and Intermetalloid Clusters of Tetrel (Si-Pb) and Pentel (P-Bi) Elements... 

Keywords Cage compound Cluster Intermetalloid Pentel Structure Tetrel Zintl anion... 

Zintl Phases Containing Deltahedral Tetrel Clusters and Pentel Cage Anions.94... 

Smaller tetrel element clusters like the tetrahedral [E4] ions were observed for the first time in the alloy NaPb [38] and are present in AE phases for E = Si to Pb and A = Na-Cs. Although these phases are not soluble, ammoniates of [Pb4]" have been obtained from liquid ammonia solutions of the binary phase RbPb [39]. The Zintl phases Ai2Sii7 (A = K, Rb, Cs) and KgRb6Sii7, which in the solid state contain [Si4]" and [Sig]" anions in the ratio 2 1, readily dissolve in liquid ammonia, and recently it has been shown that both cluster anions [Si4]" [37] and [Sig]" [40] are retained in solution. Corresponding pentel element clusters in bulk solids are [Pn7] and [Pnn] (Table 1). 

Soluble Zintl ions can also be obtained by electrochemical methods using the respective element as cathode material [34, 60, 61], or through the reaction of the various modifications of the tetrel (Sn and Pb) and pentel (P, As, Sb) elements with dissolved or finely dispersed alkali or alkaline-eatth metals in solution [62] as well as in molten crown-ethers [63]. 

Beside the most frequent soluble tetrel and pentel element clusters listed in Table 1, other homoatomic polyanions have been isolated from solution. An overview is given in Figs. 2 and 3 for group 14 and 15 elements, respectively, and in Table 2. The smaller tetrel clusters [Es] and [Eio] have been isolated as A-crypt salts (Fig. 2b, e, respectively), and most probably they are formed upon... 

Table 1 Polyanions of tetrel and pentel elements of soluble Zintl phases ...

Table 2 Structurally characterized homoatomic tetrel and pentel element cluster anions obtained from solutions...

Soluble heptapnicanortricyclane anions [Pny] (Fig. 3a) and trishomocubane-shaped (ufosane-like) anions [Pnn] (Fig. 3d) are very common and known as in the binary solids for Pn = P, As, Sb (Table 2). Oxidative coupling of these monomers leads to the dimers [Pny-Pny]" and [Pnn-Pnn]" for Pn = P and As (Fig. 3b, e), which - as observed for the tetrel element clusters - have an external homoatomic bond, but in this case the structures of the monomeric units are fully retained upon dimerization. A trimeric oxidative coupling product of [Py] is the... 

B. Tetrylenes with Higher-coordinate Tetrel Atoms. 304... 

C. Other Systems with Multiple Bonds between Heavier Tetrel Atoms. . 334... 

Some of the novel systems are known only with silyl, germyl or other inorganometallic substituents, but not with simple organyl substituents. Since no principal differences from the related organyl derivatives are expected, these compounds are also included in the present discussions. Excluded are compounds in which the tetrel exclusively bears halido, amido and alkoxo substituents or other hetero-element atoms with lone-pairs. 

II. TETRYLENES (TETRELANEDIYLS) R2E AND THEIR DERIVATIVES A. Tetrylenes with Two-coordinate Tetrel Atom... 

In this chapter the focus is laid on species comprising two E—C bonds, including however those rare examples where two different organyl groups are bonded to the two-coordinate tetrel atom (Table 1) and which are not homoleptic within a stricter definition. 

TABLE 1. Parameters (bond length in pm, angle in deg) of germylenesR1R2Ge with two-coordinate tetrel atom... 

Heteroleptic carbene homologues with two-coordinate tetrel atoms still bearing one organyl group are relatively rare, since in most cases the second substituent is an amido, alkoxy or halido group which possesses one or more free electron pairs and thus tend to... 

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