The First Chelate-Free Crystal Structure of a Silicide Transition Metal Complex [K0.28Rb7.72Si9Ni(CO)2]2•16NH3

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-crown6)]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.