A High Yield Synthesis of an Octastannacubane and a Bis(silyl) Stannylene via Reductive Elimination of a Silane

Abstract

Thermolysis of tris(silyl) tin hydride 2 at 70 °C for 3 hours results in elimination of tBu2MeSiH and generation of bis(silyl) stannylene 3 which dimerizes instantaneously yielding distannene 4. Compound 3 can be trapped by NHCMe yielding stannylene‐NHCMe complex 5. Upon heating (70 °C, 24 h) 4 yields stannyl radical 8 along with pentastannatricyclo[2.1.0.02, 5]pentane 10 (ca. 30 %) and traces (ca. 5 %) of the novel octastannacubane 9. Remarkably, octastannacubane 9 is produced in 70 % yield by mild heating (50 °C) of 1,1,2,2‐tetrasilyldistannane 11, along with tBu2MeSiH. Octastannacubane 9 was characterized by X‐ray crystallography, NMR and UV/Vis spectroscopy. Based on DFT quantum‐mechanical calculations the 11 → 9 transformation occurs via reductive elimination of two tBu2MeSiH molecules from 11 yielding a distannyne, (or its bis‐stannylene isomer), followed by its tetramerization.

Facile Synthesis of an Octagermacubane with Two Three‐Coordinate Germanium(0) Atoms and its Unique Radical Anion

“…Moreover, density functional theory (DFT) [9] calculations [10] predict that elimination of tBu 2 MeSiH from (tBu 2 MeSi) 3 GeH ( 9 ) is energetically feasible. Thus, the calculated Δ G °=19.2 kcal mol −1 is only by 6.4 kcal mol −1 more endergonic than tBu 2 MeSiH elimination from (tBu 2 MeSi) 3 SnH ( 7 ) (Δ G °=12.8 kcal mol −1 ), realized experimentally, [3i] and the calculated activation free energy (Δ G ° ≠ =30.4 kcal mol −1 ) is in the experimentally accessible range (see Supporting Information for details) [11] . Indeed, by analogy to stannane 7 , [3i] also germane 9 undergoes elimination of tBu 2 MeSiH (at 100 °C, slightly higher temp.…”

“…Thus, the calculated Δ G °=19.2 kcal mol −1 is only by 6.4 kcal mol −1 more endergonic than tBu 2 MeSiH elimination from (tBu 2 MeSi) 3 SnH ( 7 ) (Δ G °=12.8 kcal mol −1 ), realized experimentally, [3i] and the calculated activation free energy (Δ G ° ≠ =30.4 kcal mol −1 ) is in the experimentally accessible range (see Supporting Information for details) [11] . Indeed, by analogy to stannane 7 , [3i] also germane 9 undergoes elimination of tBu 2 MeSiH (at 100 °C, slightly higher temp. than for 7 ), generating the corresponding bis(silyl)germylene 10 (Scheme 2, step a).…”

“…Recently, we reported a high yield synthesis of a bis(silyl)stannylene, (tBu 2 MeSi) 2 Sn: ( 5 ) and of an octastannacubane, (tBu 2 MeSi) 8 Sn 8 ( 6 ) by the reductive elimination of a silane from the corresponding tris(silyl)stannane, (tBu 2 MeSi) 3 SnH ( 7 ) (producing 5 ), and tetra(silyl)distannane, (tBu 2 MeSi) 2 (H)Sn−Sn(H)(SiMetBu 2 ) 2 ( 8 ), producing 6 [3i] . This discovery prompted us to study the reductive elimination of silane from the analogous (tBu 2 MeSi) 3 GeH ( 9 ), which interestingly has a nearly planar central Ge atom (Σ∡Ge=356.4°) [8] .…”

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

“…The syntheses of the first polyhedral clusters of the heavier group 14 elements date back to the 1980s. There were reports on hexagerma- and hexasilaprismanes, 1,2 octastanna-, 3,4 octasila- 5–8 and octagermacubanes 6,9 (see Fig. 1) and even a decastannaprismane.…”

“…Another way is the reductive coupling of tri-or tetracyclic precursors, as well as thermolysis of these precursors. 4,10 The general formula of these polyhedranes is M n R n ( n = 6, 8, 10), therefore, the oxidation state is + i for all germanium atoms in these compounds. Later there were reports on the new class of polyhedral metalloid germanium cluster compounds, which feature also so called “naked” germanium atoms, bearing no substituent and therefore exhibiting an oxidation state of zero.…”