Two heterocyclic cyclopentadienyl analogs with a CB₂N₂ skeleton, 4-methyl-1,2,3,5-tetraphenyl-1,2-diaza-3,5-diborolidine and 4-methyl-3,5-dimethylamino-1,2-diphenyl-1,2-diaza-3,5-diborolidine were prepared through cyclocondensation of the corresponding 1,1-bis(organochloroboryl)ethane with 1,2-diphenylhydrazine. The former diazadiborolidine featured a cyclopentadiene-like structure with short B–N bonds and a planar ring framework, while in the latter the B–N bonds were noticeably longer and the ring framework was considerably folded as a result of the interaction between boron and the electron donating NMe₂ groups. The dimethylamino substituted diazadiborolidine could not be deprotonated due to the reduced acidity of the ring proton, however, the B-phenylated analog was easily deprotonated and the lithium, sodium and potassium 1,2-diaza-3,5-diborolyls were isolated and structurally characterized. The solid state structures of the lithium and sodium salts were similar, with an η¹-coordinated π ligand and three THF molecules completing the coordination sphere of the metal. The potassium salt featured a highly unusual mono-dimensional polymeric structure with the metal π-coordinated by the CB₂N₂ ligand and two of the phenyl groups on boron and nitrogen, and σ-coordinated by one THF molecule.