Journal Article

PUBDB-2023-03486

http://join2-wiki.gsi.de/foswiki/pub/Main/Artwork/join2_logo100x88.png Regioselective Derivatization of Silylated [20]Silafulleranes

Bamberg, M.Extern* ; Gasevic, T. ; Bolte, M. ; Virovets, A.Extern* ; Lerner, H.-W. ; Grimme, S. ; Bursch, M. (Corresponding author) ; Wagner, M. (Corresponding author)Extern*

2023
ACS Publications Washington, DC

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Please use a persistent id in citations: doi:10.1021/jacs.3c03270  doi:10.3204/PUBDB-2023-03486

Abstract: Silafulleranes with endohedral Cl$^−$ ions are a unique,scarcely explored class of structurally well-defined silicon clustersand host-guest complexes. Herein, we report regioselectivederivatization reactions on the siladodecahedrane [nBu$_4$N][Cl@Si$_{20}$(SiCl$_3$)$_{12}$Cl$_8$] ([nBu$_4$N][1]), which has its cluster surfacedecorated with 12 SiCl$_3$ and 8 Cl substituents in perfect T$_h$ symmetry. The room-temperature reaction of [nBu$_4$N][1] withexcess iBu$_2$AlH in ortho-difluorobenzene (oDFB) furnishesperhydrogenated [nBu$_4$N][Cl@Si$_{20}$(SiH$_3$)$_{12}$H$_8$] ([nBu$_4$N][2]) in 50% yield; the non-pyrophoric [2]$^−$ is the largest structurallyauthenticated (by X-ray diffraction) hydridosilane known to date. Asimple switch from pure oDFB to an oDFB/Et$_2$O solvent mixturesuppresses core hydrogenation and results in the formation of[nBu$_4$N][Cl@Si$_{20}$(SiH$_3$)$_{12}$Cl$_8$] ([nBu$_4$N][3]). In addition to the exhaustive Cl/H exchange at all 44 Si−Cl bonds of [1]$^−$ and theregioselective 36-fold silyl group hydrogenation, we achieved the simultaneous introduction of Me substituents at all 8 SiCl verticesalong with the conversion of all 12 SiCl$_3$ to SiH$_3$ groups by treating [nBu$_4$N][1] with Me$_2$AlH/Me$_3$Al in oDFB ([nBu$_4$N][Cl@Si$_{20}$(SiH$_3$)$_{12}$Me$_8$], [nBu$_4$N][4]; 73%). Quantum-chemical free-energy calculations find an SN$_2$-Si-type hydrogenation of theexohedral SiCl$_3$ moieties in [1]$^−$ (trigonal-bipyramidal intermediate) slightly preferred over metathesis-like SNi-Si substitutions (four-membered transition state). Cage hydrogenation likely occurs via SNi-Si processes. The experimentally demonstrated influenceof an Et$_2$O co-solvent, which drastically increases the respective reaction barriers, is attributed to the increased stability of theresulting iBu$_2$AlH-OEt$_2$ adduct and its higher steric bulk compared to free iBu$_2$AlH.

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Contributing Institute(s):

1. DOOR-User (DOOR ; HAS-User)

Research Program(s):

1. 6G3 - PETRA III (DESY) (POF4-6G3) (POF4-6G3)
2. FS-Proposal: I-20220865 (I-20220865) (I-20220865)
3. DFG project 506550642 - Siladodecahedrane: Untersuchungen zu Reaktivität, Bindungssituation und optoelektronischen Eigenschaften (506550642) (506550642)

Experiment(s):

1. PETRA Beamline P24 (PETRA III)

Appears in the scientific report 2023

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