the anion [ la2 ( edta ) 2 ( h2o ) 4 ] 2- turns out to be a dimer , in which each of the two edta4- ions is coordinated to a la3+ ion with five of its six coordinating sites and the remaining sixth one -- the oxygen atom of carboxylis bridged to two la3+ ions , thus forming a parallelogrammic four-membered ring la2o2 .
C0003075
anion
C0022023
ions