Bond-valence parameters of lanthanides

Abstract

Ln-O and Ln-N bond-valence parameters have been computed in coordination complexes for lanthanides (Ln) at oxidation states other than +3 (Ce(IV), Sm(II), Eu(II) and Yb(II)). Moreover, Ln-Cl, Ln-S and Ln-C(pi-bonded) bond-valence parameters are presented, as calculated for coordination compounds. In general, the bond-valence parameters decrease in the order Ln-O > Ln-C > Ln-N > Ln-Cl > Ln-S. It has been found that the values of bond-valence parameters decrease with increasing lanthanide atomic number for coordination compounds. As expected, the values of lanthanide-oxygen and lanthanide-nitrogen bond-valence parameters diminish with increasing lanthanide oxidation state. Several examples are given where the total valence of the lanthanide ion is apparently incorrectly assigned, as well as cases where bond-valence method calculations confirm the doubtful oxidation state assignment.

Crystal structure and non-stoichiometry of cerium brannerite: Ce0.975Ti2O5.95

“…In addition, the presence of significant Ce 3 þ species was ruled out based on the Ce L III edge XANES data presented in Section 3. Two recent studies re-evaluated the r 0 parameter for Ce(IV)-O bond lengths in the context of metal-organic compounds (r 0 ¼2.074 (4)Å [45]) and co-ordination compounds (r 0 ¼2.121(13)Å [46]); these parameters yield, respectively, bond valence sums of 3.56 v.u. and 4.16 v.u.…”

Data mining of iron(II) and iron(III) bond-valence parameters, and their relevance for macromolecular crystallography

“…Some notable results based on CSD data include bond-valence parameters for copper (Shields et al , 2000), lanthanides (Trzesowska et al , 2004, 2006), cadmium (Palenik, 2006), antimony (Palenik et al , 2005) and ammonium (García-Rodríguez et al , 2000). Several more metals were discussed later, as summarized and reviewed by Brown (2009).…”

Alkali metal halogenides coordination compounds with hexamethylenetetramine

“…The symmetry generated atoms indicated by dashed lines are obtained by symmetry transformations (C2A, C3A, H2AA, H2BA, H3AA, H3BA, IA1: x, -y, z; N2A: -x, y, -z; K1A: -x, -y, -z; K1B, O1A: -x, -y, -z ? 1) the formal sense R ij can be considered as a parameter equal to the idealised single-bond length between i and j atoms for given b) and b was taken as 0.37 Å [47][48][49][50]. The R Li-O , R Na-O , R Na-N , R K-N , R K-O , R K-I , R Rb-N , R Rb-O , and R Rb-I were taken as 1.466, 1.80, 1.93, 2.26, 2.13, 2.28, 2.37, 2.26 and 3.01, respectively [51].…”