Ferrous citrate, also known as iron(II) citrate or iron(2+) citrate, describes coordination complexes containing citrate anions with Fe2+ formed in aqueous solution. Although a number of complexes are possible (or even likely), only one complex has been crystallized. That complex is the coordination polymer with the formula [Fe(H2O)6]2+{[Fe(C6H5O7)(H2O)]−}2.2H2O, where C6H5O73- is HOC(CH2CO2−)2(CO2−, i.e., the triple conjugate base of citric acid wherein the three carboxylic acid groups are ionized.[3] Ferrous citrates are all paramagnetic, reflecting the weak crystal field of the carboxylate ligands.[4]
^ abStrouse, Jane; Layten, Steven W.; Strouse, Charles E. (1977). "Structural Studies of transition metal complexes of triionized and tetraionized citrate. Models for the coordination of the citrate ion to transition metal ions in solution and at the active site of aconitase". Journal of the American Chemical Society. 99 (2): 562–572. doi:10.1021/ja00444a041. PMID830693.