Geometrical optimizations and electronic structural analyses of the -O2B2- bridged hydrometal complexes (M4H3C)(2)B2O2 and (M4H3N)(2)B2O22+ (M = Ni, Mg) containing double tetracoordinate planar nonmetals (TPN) have been performed using the density functional theory at the B3LYP/6-31+G(d,p) level. Theoretical evidence of the possibility of double TPN centers coexisting in one planar molecule is presented.