Structure and oxidation of octakis(tert-butyldimethylsilyl)octasilacubane

Synthesis of Phosphine-Functionalized Silicon Cubane and Its Oxidative Addition, Giving a Bis(silyl)copper Complex

A new strategy for the introduction of a second type of Si atom to silicon cubanes has been developed starting from the tricyclic hexasilane dianion [Ar₆Si₆]^2- (Ar = 2,4,6-Me₃C₆H₂). Treatment of the dianion with Ar'SiCl₃, followed by KC₈, gave new types of octasilacubanes Ar₆Ar'₂Si₈ [Ar' = 2,4,6-iPr₂C₆H₂ (3a), 2-Ph₂PC₆H₄ (3b)] in high yields. Remarkably, treatment of cubane 3b bearing with two phosphine groups with 2 equiv of CuCl in CH₂Cl₂ yielded the bis(silyl)copper complex via the selective oxidative addition of the newly formed Si-Si bond to Cu ion. Single-crystal X-ray analysis indicated the unique square-planar, four-coordinate Cu cation paired with the [CuCl₂]^- counteranion.

{Ge8[Fe(CO)4]8}7-: an anionic cubic germanium-iron-cluster featuring an unpaired electron

Within the reaction of a metastable Ge(I)Cl solution and Na₂Fe₂(CO)₈ the anionic cubic cluster compound {(thf)₁₄Na₆Ge₈[Fe(CO)₄]₈}^- (3) is obtained. The open shell character of 3 is proven by EPR spectroscopy. Quantum chemical calculations furthermore show that also the closed shell systems should be stable, but could not be isolated so far. Additionally, 3 can be seen as an intermediate cluster compound on the formation of metalloid clusters.

Transformative Si8R8 Siliconoids

Molecular silicon clusters with unsubstituted silicon vertices (siliconoids) have received attention as unsaturated silicon clusters and potential intermediates in the gas-phase deposition of elemental silicon. Investigation of behaviors of the siliconoids could contribute to the greater understanding of the transformation of silicon clusters as found in the chemical vapor deposition of elemental silicon. Herein we reported drastic transformation of a Si8R8 siliconoid to three novel silicon clusters under mild thermal conditions. Molecular structures of the obtained new clusters were determined by XRD analyses. Two clusters are siliconoids that have unsaturated silicon vertices adopting unusual geometries, and another one is a bis(disilene) which has two silicon–silicon double bonds interacted to each other through the central polyhedral silicon skeleton. The observed drastic transformation of silicon frameworks suggests that unsaturated molecular silicon clusters have a great potential to provide various molecular silicon clusters bearing unprecedented structures and properties.

Facile synthesis and bridgehead-functionalization of bicyclo[3.3.3]pentasiloxanes

Various bicyclo[3.3.3]pentasiloxanes (BPSO) were successfully synthesized via regioselective functionalization at the bridgehead positions.

Two pentasilahousanes fused together

The organosilicon cluster 1 with two pentasilahousanes fused together was synthesized by the reduction of 1,1,3-trichlorocyclotetrasilane. This reaction involves dimerization and rearrangement of the silicon skeleton. The structure and properties of 1 were studied by X-ray crystallographic and spectroscopic analyses.

Stereoisomers of 1,3,5,7-Tetrahydroxy-1,3,5,7-tetraisopropylcyclotetrasiloxane: Synthesis and Structures in the Crystal

The first synthesis of all four stereoisomers of 1,3,5,7-tetrahydroxy-1,3,5,7-tetraisopropylcyclotetrasiloxane, [i-PrSiO(OH)]4 (all-trans-, cis-cis-trans-, cis-trans-cis-, and all-cis-1), is presented. The starting compounds, all-trans-, cis-cis-trans-, cis-trans-cis-, and all-cis-1,3,5,7-tetraaryl-1,3,5,7-tetraisopropylcyclotetrasiloxanes, were prepared by the hydrolysis of the corresponding arylisopropyldichlorosilanes, i-PrArSiCl2 (Ar = Ph, p-tolyl), and subsequent separation of isomers. A combination of dephenylchlorination of tetraarylcyclotetrasiloxanes and the following hydrolysis proved to be an efficient method for the stereospecific transformation of aryl-substituted cyclotetrasiloxanes into (i-PrSiO(OH))4. For example, treatment of cis-trans-cis-1,3,5,7-tetraphenyl-1,3,5,7-tetraisopropylcyclotetrasilane with HCl and AlCl3, followed by hydrolysis in the presence of pyridine, resulted in the exclusive formation of cis-trans-cis-1 in 92% yield. The structures of cis-cis-trans-1, cis-trans-cis-1, and all-cis-1 were determined by X-ray crystallography. All isomers were found to construct unique packing structures by intermolecular hydrogen bonding; cis-trans-cis-1 composed an infinite antiladder structure, and cis-cis-trans-1 formed a sheetlike structure.