It is of interest for producing soluble imides and imines without introducing a chiral center. Amidrazones can exists in two tautomeric forms&colon; hydrazide imides (RC(=NH)NHNH) and amide hydrazones (RC(NH)=NNH). These phosphazenes are also known as iminophosphoranes and phosphine imides. Treatment of imides with halogens and base gives the "N"-halo derivatives. The phosphine imides were first prepared in the laboratory of Nobelist Hermann Staudinger. These ligands include fluoride (F), oxide (O), nitride (N), alkoxides (RO), and imides (RN). Heterogenous ammonolyses of triphosphorus pentanitride gives imides such as HPN and HPN. In the Einhorn-Brunner reaction hydrazines react with imides to give triazoles. Certain imides can also be prepared in the isoimide-to-imide Mumm rearrangement. The compounds are structurally related to acid anhydrides, although imides are more resistant toward hydrolysis. Being highly polar, imides exhibit good solubility in polar media.