BOND VALENCE SUMS IN COORDINATION CHEMISTRY USING OXIDATION-STATE-INDEPENDENT R-0 VALUES - A SIMPLE METHOD FOR CALCULATING THE OXIDATION-STATE OF IRON IN FE-O COMPLEXES

The use of the bond valence sum in Fe-O complexes is discussed using d ata from the Cambridge Structural Database. The oxidation state of Fe in complexes containing Fe bonded only to O can be calculated by Sigma (i) exp[(R-0-r(i))/b], where r(i) is the observed Fe-O-t bond length, R-0 is a constant = 1.745 Angstrom, and (b)over dot is taken to be 0.3 7. The R-0 value can be viewed as a bond length of unit valence. Devia tions from an integer value indicate a problem with the crystal struct ure or electron delocalization in multinuclear complexes. The oxidatio n-state-independent R-0 value of 1.745 Angstrom was calculated using 2 97 FeOn complexes with n = 3-8. An R-0 value of 1.714 Angstrom for Fe( II) was determined using 74 complexes, and a value of 1.750 Angstrom w as determined for Fe(III) using 223 complexes.