[Ga18(SitBu3)8] and [Ga22(SitBu3)8]—Syntheses and Structural Characterization of Novel Gallium Cluster Compounds

Amelunxen

et al. 2001

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The reduction of black‐blue tris(supersilyl)digallanyl [R*2Ga−GaR*]· (R* = SitBu3 = supersilyl) in organic solvents with Na, NaC10H8, or NaR* leads to deep‐red sodium tris(supersilyl)digallanide−THF(1/3) NaGa2R*3×3THF = [R*2Ga−GaR*Na(THF)3], which transforms in the presence of 18‐crown‐6 into deep‐blue sodium tetrakis(supersilyl)trigallanide−18‐crown‐6(1/1)−THF(1/2) [Na(18‐C‐6)(THF)2]+[R*2Ga−GaR*−GaR*]−.The oxidation of the latter anion with R*Br or TCNE as well as the reaction of the digallanyl R*3Ga2· with R*Br leads to deep‐green tetra(supersilyl)cyclotrigallanyl [···R*Ga−GaR*2−GaR*···]·. The latter radical thermolizes at 100 °C to dark‐violet tetrakis(supersilyl)‐tetrahedro‐tetragallane R*4Ga4 besides the digallanyl R*3Ga2·. This is also prepared from NaR* and GaCl3 or R*2GaCl, as well as by oxidation of R*3Ga2−, and itself thermolizes with formation of the tetrahedrane R*4Ga4. According to X‐ray structure analyses of the mentioned compounds, the Ga−Ga bond of the digallanide NaGa2R*3×3THF (NMR spectroscopically observed) is comparably short (2.380 Å), approaching a bond order of 2. In fact, it is distinctly shorter than the Ga−Ga bond (2.420 Å) in the digallanyl R*3Ga2· (EPR spectroscopically observed). The Ga atoms of the trigallanyl R*4Ga3· (EPR spectroscopically observed) are located at the corners of a triangle with two shorter R*2Ga−GaR* sides (2.527 Å) and a comparably longer R*Ga−GaR* basis (2.879 Å). The mean value of the two Ga−Ga bonds in the trigallanide R*4Ga3− (NMR spectroscopically observed) is as long (2.53 Å) as the short Ga−Ga bonds in R*4Ga3·. The anion shows an intramolecular CH3···Ga contact (C−Ga 2.10 Å) between one peripheral methyl group of the R*2Ga entity and the anionic Ga atom in [R*2Ga−GaR*−GaR*]−.

Section: Methodsmentioning

confidence: 87%

Section: Discussionmentioning

confidence: 99%

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confidence: 94%

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confidence: 99%

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On the Gallanyls R3Ga2· and R4Ga3· As Well As Gallanides R3Ga2− and R4Ga3− (R* = SitBu3) − Syntheses, Characterization, Structures

Amelunxen

et al. 2001

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“…In fact, numerous clusters of Ga -the subject of this publication -have been isolated within the last few years (for more than 30 gallium cluster compounds see ref. [1] ).…”

Section: Introductionmentioning

confidence: 99%

Octagallane (tBu3Si)6Ga8 and Its Reduction to (tBu3Si)6Ga82− − On the Existence of Isomeric Gallium Clusters

Nöth

et al. 2002

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Thermolysis of the trigallanyl radical R*4Ga3· in heptane at 60 °C leads to the dark blue octagallane R*6Ga8 (R* = supersilyl SitBu3), as well as the digallanyl radical R*3Ga2· and the tetrahedro‐tetragallane R*4Ga4. In addition, supersilyl radicals R*· are formed which stabilize themselves either by dimerization or by addition of hydrogen atoms. R*6Ga8 can be reduced in THF with NaC10H8 to the dark‐red octagallanediide Na2Ga8R*6·2THF. According to an X‐ray structure analysis of R*6Ga8 and R*6Ga82− one finds that the Ga atoms of four R*Ga moieties, together with two “naked” Ga atoms, occupy the corners of a distorted octahedron; the “naked” Ga atoms themselves are located, along with Ga atoms of two further R*Ga moieties, at the corners of a distorted square. The reduction of R*6Ga8 leads only to a negligible shortening of the Ga−Ga distances from 2.64 to 2.61 Å (mean values) in R*6Ga82−. Both the octagallanes possess Ga8 frameworks previously unknown for group 13 clusters. They are isomeric to the recently described Ga8 framework of the octagallane Tsi6Ga8 [Tsi = trisyl C(SiMe3)3]. Hence, not only boron but also the heavier group 13 atoms form isomeric clusters.

Ditrielanes (R3Si)2E−E(SiR3)2 and Heterocubanes (R3Si)4E4Y4 (R3Si =tBu3Si,tBu2PhSi; E = Al, Ga, In, Tl; Y = O, Se)

Amelunxen

et al. 2002

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3 SiCl. According to X-ray structure analyses, the ditrielanes contain two planar groups R 2 EE which are orthogonal to each other (R = R*; angle REER ca. 90°) or nearly orthogonal (R = RЈ; angle REER ca. 80°). All compounds are deeply colored. The λ max value of the visible absorption shifts with increasing atomic number of E and with the increasing angle between the R 2 EE planes to longer wavelengths (ruby R− besides the mentioned ditrielanes − are presented.In fact, except for the compounds dealt with in this publication, only three other examples of silyl-ditrielanes, namely [(Me 3 Si) 3 Si] 4 E 2 with E ϭ Ga, [9] In, [10] Tl [11] have been published to date. On the other hand, some organyland aminyl-ditrielanes R 4 E 2 are known with R ϭ