Synthesis and functionalization of the six-vertex anionic amido-substituted silicon cluster [Si6{N(SiMe3)Ph}5].

The reaction of the six-vertex amido-substituted silicon cluster Si6{N(SiMe3)Ph}6 1 with two equiv. of KC8 results in the abstraction of K{N(SiMe3)Ph} and leads to the contact ion pair 2 including an anionic silicon cluster with two unsubstituted pyramidal vertices. Facile functionalization of 2 was achieved with MeI, SiCl4 and SiBr4 and results in neutral two-fold functionalized silicon clusters.

Unsaturated amido-substituted six-vertex mixed silicon germanium clusters.

The synthesis of mixed silicon and germanium clusters SixGe6-x{N(SiMe3)Dipp}41-3 (x = 3.7, 3.1, 2.1) with amido-substituents and two unsubstituted germanium atoms was achieved in co-reductions using the tribromosilane {N(SiMe3)Dipp}SiBr3 and the tribromogermane {N(SiMe3)Dipp}GeBr3 in three different ratios. The ratio of Si and Ge used for the synthesis of 1-3 approximately corresponds to that in the final products. All compounds were characterized by single crystal X-ray diffraction and EI mass spectrometry. In addition, 1 and 2 were characterized by solid-state 29Si{1H} CP/MAS NMR spectroscopy and multinuclear NMR spectroscopy in solution.

A strongly twisted SiSi bond with resemblance to a buckled dimer in an unexpected isomer of hexasilabenzene.

The reductive debromination of {N(SiMe3)Ph}SiBr31 with Rieke magnesium yields the six-vertex amido-substituted silicon cluster 2 with zwitterionic character that represents an unprecedented isomer of hexasilabenzene. The topology of Si1 and Si2 in 2 has bonding features of a highly twisted disilene and resembles that of a buckled dimer of Si(100)2 × 1 reconstructed surfaces. Cluster 2 forms the adducts 3 and 4 with NHCMe4 and DMAP, respectively. The NHC adduct 4 additionally coordinates to BH3 which affords the saturated cluster BH3NHCMe4Si6{N(SiMe3)Ph}6 (5). Furthermore, 2 undergoes addition with MeI and iodine to form the halogenated silicon clusters 6 and 7, respectively.

Tetracyclic silaheterocycle formed through a pericyclic reaction cascade including a two-fold intramolecular C-C bond activation.

Reductive debromination of the tribromoamidosilane 2 gave the tetracyclic silaheterocycle 3 through a unique reaction cascade involving unprecedented two-fold intramolecular cycloaddition by transient silylenes. Experimental and computational analyses of the reaction mechanism allowed the identification of the key intermediates that lead to the silaheterocycle 3 or, alternatively, to the cyclotrisilene 19.

An unsaturated amido-substituted six-vertex germanium cluster and its reactions with alkenes and alkynes.

The unsaturated metalloid germanium cluster Ge6{N(SiMe3)Dipp}42 with two ligand-free germanium atoms and only four amine substituents was obtained starting from the base-coordinated germylene {N(SiMe3)Dipp}GeCl·DMAP 1 in 50% yield (DMAP = 4-(dimethylamino)-pyridine). This cluster reacts as a masked digermyne in cycloadditions with ethylene, diphenylacetylene and 2,3-dimethyl-1,3-butadiene in toluene at 100 °C to yield 3-5.