The new zirconium phosphonate compound (NH4)Zr[F-2][H-3{O3PCH2NH(CH2CO2)(2)}(2)]. 3H(2)O . NH4Cl was obtained from the reaction of zirconyl chloride with N-(phosphonomethyl)iminodiacetic acid in the presence of HF. It crystallizes in the triclinic space group (No. 2) with a = 10.743(2) Angstrom, b = 11.483(2) Angstrom, c = 5.330(1) Angstrom, alpha = 90.63(2)degrees, beta = 96.65(2)degrees, gamma = 97.68(2)degrees, and Z = 1. The structure consists of linear chains of zirconium atoms linked together by phosphonate oxygens. The zirconium atom is six-coordinated by four phosphonate oxygens and two fluoride ions. The compound represents the first example of a linear chain structure in the zirconium phosphate or phosphonate systems. The formation of such linear chains as opposed to the layered structure normally observed for zirconium phosphonates is attributed to the bulkinesss of the phosphonic acid.