Supplementary information for

{Sn10Si(SiMe3)2[Si(SiMe3)3]4}2-: Cluster enlargement via dismantling of labile ligands

Claudio Schrenk and Andreas Schnepf

1.) Quantum Chemical Calculations on {Sn10Si(SiMe3)2[Si(SiMe3)3]4}2- 5

All quantum chemical calculations on the metalloid cluster {Sn10Si(SiMe3)2[Si(SiMe3)3]4}2- 5 were carried out with the RI-DFT version of the TURBOMOLE program package (Eichkorn et al., 1995; Treutler and Ahlrichs, 1995) by using the Becke-Perdew-86 functional (Perdew, 1986; Becke, 1988). The basis sets were of SVP quality (Schäfer et al., 1992). To get further insight into the electronic structure of the cluster core, an Ahlrichs-Heinzmann population analysis (Davidson, 1967; Roby, 1974; Heinzmann and Ahlrichs, 1976; Ehrhardt and Ahlrichs, 1985) based on occupation numbers is performed. The received shared electron numbers (SENs) are thereby a reliable measure of the bond strength. For example, the SEN for the Sn – Sn single bond in the model compound R3Sn-SnR3 (R = H, CH3, SiH3) is 1.27(H), 1.07(CH3) and 1.11(SiH3) respectively. On this way it is also possible to get insight into three- or four-centre bonding systems applying the three- or four centre SENs, respectively. Two centre SENs of 5 are illustrated in figure S1 and three centre SENs in figure S2.

Figure S1 Calculated 2c SENs in the cluster core of {Sn10Si(SiMe3)2[Si(SiMe3)3]4}2- 5. The numbers are given for every topological line within the cluster core.

Figure S2 All calculated three centre SENs in the cluster core of {Sn10Si(SiMe3)2[Si(SiMe3)3]4}2- 5. The numbers are given for the highlighted triangles in der cluster core.

2. NMR investigation of {Sn10Si(SiMe3)2[Si(SiMe3)3]4}2- 5

Crystals of {Sn10Si(SiMe3)2[Si(SiMe3)3]4}2- 5 were transferred into a NMR tube and treated with deuterated thf. The NMR tube was flame sealed and the proton NMR spectra was recorded within 30 minutes. As a result, instead of clear signals a broad wall in the range of 0.0 to 0.4 is observed for the SiMe3 groups in the proton NMR spectra. Beside this, a singlet at 3.6 ppm is clearly identified and corresponds to the protons of the crown ether molecule 12-crown-4. Furthermore the thf solution of 5 seemed to be unstable; i.e. the colour of the solution changes from black to light yellow and a grey solid precipitates. Applying other deuterated solvents like benzene failed due to an insolubility of 5 within these solvents.

Figure S3 Measured 1H-NMR-spectra of the cluster 5 in THF-d8 directly after preparation.

References

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