Abstract
Single-crystals X-ray structure analysis of very thermally labile and moisture sensitive ammoniate crystals of [K0.28Rb7.72Si9Ni(CO)2]2·16NH3 show the presence of the very rarely observed nickel-silicide complex [{Ni(CO)2}2(µ-Si9)2]8−, which was up to now only known in the 18-crown-6 involving solid [Rb@18-crown-6)]2[K@18-crown-6)]2Rb4[{Ni(CO)2}2(µ-Si9)2]·22NH3. This shows that, like already known for the heavier homologues, the presence of 18-crown-6 (1,4,7,10,13,16-hexaoxacyclooctadecane) is no precondition for the stabilization of the silicide cluster anion in solid state and the absence of the alkali metal ligand even allows for the crystallization in the higher symmetric monoclinic space group C2/c compared to the triclinic space group P-1 when 18-crown-6 is present.
Highlights
Homoatomic polyanions of group 14 elements represent naked, anionic elemental building blocks and are an intriguing field of main group chemistry due to their versatile reaction possibilities
[(MesCu)2Si4]4− [16] (Mes = mesitylene = C6H2(CH3)3)) (Figure 1a,b), where organometallic precursors have been used during synthesis, we previously could show that the Si94− cluster anions act as ligands in a simple ligand-exchange reaction of triphenylphosphine in the transition metal complex Ni(CO)2(PPh3)2 (PPh3 = triphenylphosphine = P(C6H5)3) yielding the new complex
The reaction of the ternary Zintl material K6Rb6Si17 and Ni(CO)2(PPh3)2 in the presence of 18-crown-6 resulted in the first chelate free crystal structure of the silicide transition metal complex
Summary
Homoatomic polyanions of group 14 elements represent naked, anionic elemental building blocks and are an intriguing field of main group chemistry due to their versatile reaction possibilities. They can be used as promising starting materials for the synthesis of new compounds, and especially the monocapped square antiprismatic shaped nine atom cluster anions E94− show a wide synthetic potential [1,2,3,4]. [(MesCu)2Si4]4− [16]; (c) [{Ni(CO)2}2(μ-Si9)2]8− [17]
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