A crystalline molecular complex derived from phenyl nitronyl nitroxide (1) and phenyl boronic acid (2) exhibits a ferromagnetic spin interaction (J = +0.65 K) below 30 K : An X-ray analysis revealed the crystal structure constituted of one-dimensional array of two component molecules linked alternately by the NO-HOB hydrogen bonds. The NO-HO-B-OH-ON linkage was suggested to act as a path for ferromagnetic spin coupling. An unusual formation of nitrosonium salt (3) was found in the reaction of 1 and BF3. Its molecular and crystal structures were determined.