Targeted attachment of functional groups at Ge₉ clusters: Via silylation reactions

Molecules with low-valent Ge atoms are generally synthesized from organohalogen germanes as precursors. The Zintl phase K₄Ge₉ provides reactive building blocks for a targeted synthesis of germanium-rich molecules. The silylation of Ge9 clusters with chlorosilanes ClSiR₂R′, that carry unsaturated olefin groups R′ leads to the introduction of olefinic side chains of variable lengths allowing for further reactions. The compounds K[Ge₉{Si(SiMe₃)₃}₂(SiPh₂R′)] (R′ = -CHCH₂ (1); -(CH₂)₃CHCH₂ (2)) carry one such functionality, whereas K[Ge₉(SiPh₂R′)₃] (3 and 4) offer the possibility for an interconnection of clusters due to three functional groups on the Ge₉ core. XPS measurements show that the silylated clusters are much more air-stable than the unsubstituted, bare cluster units.