The reaction between iron and implanted boron, due to the presence of defects induced by ion bombardment, at annealing temperature of 300 and 500 degree C leads to an intense process of formation of complexes of FeB type. The energy of complex formation is equal to 1. 4 plus or minus 0. 03 eV. The process of complex formation at 300 and 500 degree C increases the solubility of iron in the presence of implanted boron and reduces the electric activity of boron.