Heterocubane structure

Like 215, cyclopentadienylmagnesium ethoxide exists in the solid state as tetrameric [CpMgOEt]4 (216) with a heterocubane structure (Figure. In 216 the cyclopenta-dienyl groups are /j -bonded to the magnesium atoms. 

Compounds 22-26 possess heterocubane structures in which four metal atoms are linked via bridges of the OR or OSiMe3 groups, forming the Met404 skeleton. 

The imide [(MeInNC6F5)4] 5" was synthesized by a similar method. The tetrameric cubanes [In4X4(p-NBu )4] (where X Cl, Br or I) formed from the corresponding indium trihalide, InXa and LiHNBu have In4N4 heterocubane structures that are similar to their aluminium and gallium counterparts. The chloride [In4Cl4(NBu )4] is shown in Figure 8.11. 

The reaction of InX3 (X = C1, Br, I) with two equivalents of LiN(H)(t-Bu) led to imido derivatives [In4X4(t-BuN)4] (10) with 104X4 heterocubane structures. The reaction involving InBr3 also produced a minor by-product [In3Br4(t-BuN)(t-BuNH)3] (11). ... 

RbN=PPh3)6 (45) can be characterized as double cube, whereas (CsN=PPh3)4 (46) possesses a heterocubane structure. "... 

For alkali metal t-butoxides and trimethylsilanolates the heterocubane structure is found for the heavier alkali metals potassiiun, rubidium, and cesium. For sodium a related heterocubane derivative can also be obtained with a suitable phenolate ligand providing additional donor sites. One example is tetrameric [Na OC6H2-(CH2NMe2)2-2,6-Me-4 ]4, 172 [136], which contains tridentate pincer phenolate ligands and pentacoordinate sodium ions. 

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