Cover Picture (Angew. Chem. Int. Ed. Engl. 12/1986)

The cover shows the sandwich structure, determined by X‐ray analysis, of the dimeric 1,3‐diboratacyclobutadiene Li 2 [( t BuB) 2 (Me 3 SiC) 2 ] (H atoms omitted). Noteworthy is the Li, layer between the two four‐membered rings. Thus, this interesting organoboron compound is, at the same time, an example of a new type of organolithium compound. A detailed discussion of the structure, the charge distribution in the cyclic dianion based on NMR spectroscopy, and the reactions of the diboratacyclobutadiene are presented in the communication by A. Berndt et al. on p. 1111 f.