Abstract: Based on the crystal structure data of the lanthanide complexes, lanthanide contraction of the single valance bond length R0 for Ln－O bond is confirmed. The R0 values with B=0.037 nm were re-determined systematically as described by the linear equation R0 (nm)=0.2879－0.00132N, where N is the atomic number of lanthanide. Using the parameters suggested by Brown-O′Keeffe and the present authors, the bond valance sums for Ln(III) in some organometallic compounds were calculated and discussed in detail. Prospects for the further studies in the line of bond valence parameters were briefly presented.

Key words: Bond valance parameter, Lanthanide contraction, Bond valance sum