In a previous review it was predicted that "the reactivity of five-coordinate complexes would certainly be different than that of the four-coordinate derivatives". Structurally and spectroscopically, there is very little difference in the higher-coordinate compounds when compared to the four-coordinate derivatives. However, the prediction was remarkably accurate, if not a bit understated, for the reactivity of these compounds. There appears to be a tremendous potential in catalysis and synthesis for the five-coordinate derivatives, far more possibilities than exist for the lower-coordinate derivatives. Furthermore, the higher-coordinate derivatives are rarely air or moisture sensitive and, thus, may be handled under a wider range of conditions. Although reactions such as oxirane and lactide polymerizations are fairly well-known now with five- and six-coordinate aluminum compounds, the potential of these compounds has only begun to be developed. It is easy to imagine that these types of compounds will see wider use than the related transition-metal compounds.
Two η3‐allyl ligands in an anti configuration are present in the title compound (structure depicted). Even though the Ca−C bonds are about the length expected for cyclopentadienyl complexes, the bis(trimethylsilyl)allyl anion displays hydrogen‐atom distortions similar to those found in other main group and transition metal π‐allyl complexes.
Unsolvated 1,2,4-tris(trimethylsilyl)cyclopentadienyl potassium (K[Cp 3Si ]) crystallizes as a base-free "super-sandwich" of alternating potassium ions and CpЈ rings. The polymeric chains in the structure are not connected as in other unsolvated KCpЈ structures, but uniquely consist of independent columns. This type of structure has previously been observed in base-free lithium cyclopentadienyl complexes; however, K[Cp 3Si ] is the first base-free potassium cyclopentadienyl complex that crystallizes without interactions between neighboring chains.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.