An unprecedented structural motif for metallaboranes is exhibited by the anion [{HFe(MeSiB10H10)}2]2− (see picture), which was isolated as the {nBu4N}2 salt in 63% yield from the reaction of deprotonated sila‐nido‐undecaborate and FeBr2.

Complexation of the silaborate ligand [MeSiB10H10]3- is described for the first time. The syntheses of the sandwich anions [(η5-C5Me5)M(MeSiB10H10)]- (M = Co, Rh, Ir) are realized by reaction of the monodeprotonated silaborate with the respective pentamethylcyclopentadienyl transition metal chloride. The reaction products are characterized by mass spectrometry, elemental analyses, and multinuclear and two-dimensional NMR spectroscopy. Because of an unresolvable disorder in the solid state structure of [NEt4][(η5-C5Me5)Rh(MeSiB10H10)], the isobutyl-substituted derivative [Ph3PMe][(η5-C5BuiMe4)Rh(MeSiB10H10)], [Ph3PMe][4], was analyzed by an X-ray structure determination. The salt [Ph3PMe][4]·THF, C37H60OPSiB10Rh, crystallizes in the triclinic space group P1̄ (No. 2) with a = 9.838(4) Å, b = 11.312(3) Å, c = 18.858(5) Å, α = 92.68(2)°, β = 90.22(3)°, γ = 96.77(3)°, and Z = 2.

Eine für Metallaborane beispiellose Struktur hat das Anion [{HFe‐(MeSiB10H10)}2]2−, das als Tetrabutylammoniumsalz in 63% Ausbeute bei der Reaktion von deprotoniertem Sila‐nido‐undecaborat mit FeBr2 erhalten wird.

The geometry of the Si B framework remains nearly unchanged when the Si-Si edge is bridged by an electron-donating amido group. This finding is clearly evident from the single-crystal X-ray structure analysis and ab initio calculations of the uprecedented adduct that is formed by the addition of Et N to o-silaborane (structure depicted bottom right).

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