[{Na + (thf) 2 } 4 (rubrene 4− )]: Crystallization and Structure Determination of a Contact‐Ion Quintuple for the First π‐Hydrocarbon Tetraanion

Four negative charges in a π‐hydro‐carbon are generated by the reduction of rubrene, a tetraphenyl tetracene, at a sodium metal mirror. The black crystals of the contaction quintuple [{Na + (thf) 2 } 4 (rubrene 4− )] (see structure; the thf molecules have been omitted) contain the first hydrocarbon tetraanion ever isolated. Its structure determination confirms the severe skeletal distortions: the tetracene plane, for instance, is bent up and down by 43°.