Tetraphenylgermole dianion

Tetraphenylgermole dianions have been studied by Hong and Boudjouk. Sonication of C4Ph4GeCl2 with excess of lithium in THF gives [C4Ph4Ge]2 (Li+)2 (139) as the major product197 (equation 82). 

The X-ray structure of the dilithium salt of the tetraphenylgermole dianion 139 was recently reported198.139 crystallizes from dioxane in two structurally distinct forms, 139a and 139b, depending upon the crystallization temperature. 

The dilithium salt of the tetraphenylgermole dianion has the very interesting property of crystallizing from dioxane in two structurally distinct forms (a and b) depending upon the crystallization temperature. The crystals obtained from dioxane at — 20 °C have a reverse sandwich structure (a), while crystals obtained at 25 °C have one lithium atom / -coordinated to the ring atoms and the other rj1 -coordinated to the germanium atom (b)35 (Figure 8). 

The synthesis of alkali salts of the sterically encumbered germole 98 (Equations (159) and (160)),18 as well as the dilithio salt of tetraphenylgermole 99 (Equation (161)),19 have been reported. The latter species crystallized in two isomorphic forms (99a and 99b, Figure 6) and the dianion was shown to be aromatic. 

Fig. 3. Molecular stnictures of the tj, t dilithio complexes of the tetraphenylgermole and tctraphenylsilole dianions (4b, 4c],...

These considerations led to the preparation of the ti -coordinated complexes of siloles and germoles (94PAC1431). A number of facts in support of this view were obtained by X-ray determination of the structures of the organometallic derivatives of nontransition metals. Thus, the dianion of tetraphenylgermole forms a sandwich (Ulithium salt264 in dioxane at —20°C [96AG(E)1002]. At 25°C, however, the salt with a mixed coordination mode 265 results. Columnar structure is observed... 

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