Cs[Cl(3)F(10)]: A Propeller‐Shaped [Cl(3)F(10)](−) Anion in a Peculiar A([5])B([5]) Structure Type

Reaction of CsF with ClF(3) leads to Cs[Cl(3)F(10)]. It contains a molecular, propeller‐shaped [Cl(3)F(10)](−) anion with a central μ(3)‐F atom and three T‐shaped ClF(3) molecules coordinated to it. This anion represents the first example of a heteropolyhalide anion of higher ClF(3) content than [ClF(4)](−) and is the first Cl‐containing interhalogen species with a μ‐bridging F atom. The chemical bonds to the central μ(3)‐F atom are highly ionic and quite weak as the bond lengths within the coordinating XF(3) units (X = Cl, and also calculated for Br, I) are almost unchanged in comparison to free XF(3) molecules. Cs[Cl(3)F(10)] crystallizes in a very rarely observed A([5])B([5]) structure type, where cations and anions are each pseudohexagonally close packed, and reside, each with coordination number five, in the trigonal bipyramidal voids of the other.