Bond valence sum analysis of Tl(I) and Tl(III) complexes with O and N donors

The influence of the lone pair of electrons in thallium complexes is analyzed using the bond valence sum method. Bond length data for metal-organic Tl complexes were obtained from the Cambridge Structural Database (CSD), and problems with searching the CSD file for Tl complexes are discussed. The recommended R(0) values for Tl(I)-O of 2.162 angstrom, Tl(III)-O of 2.016 angstrom, Tl(I)-N of 2.286 angstrom, and for Tl(III)-N of 2.014 angstrom used with b = 0.37 were derived from analyses of homoleptic Tl-O, Tl-N, and heteroleptic Tl-O and -N metal organic complexes. These R(0) values can be used to assign correctly the oxidation state of Tl in complexes containing any combination of Tl-O or Tl-N bonds. Examples of questionable oxidation states for Tl complexes are given. The R(0) value for Tl(III)-Cl of 2.300 angstrom was also determined.