Bond Valence Sums in Coordination Chemistry. The Calculation of the Oxidation State of Cerium in Complexes Containing Cerium Bonded Only to Oxygen

Abstract

A total of 119 CeO(n)fragments with n = 3-12 were analyzed by using the bond valence sum, or BVS, method to yield new R(0) values for Ce(III)-O of 2.121(13) A and for Ce(IV)-O of 2.068(12) A. These R(0) values can be used to calculate the oxidation state of Ce in complexes where Ce is bonded only to O ligands. Furthermore, the average R(0) value of 2.094 A gives a good indication of whether the oxidation state of the Ce ion is +3 or +4 from the observed distances without any assumptions. The fact that complexes with coordination numbers of 10-12 are in agreement is significant since this study is the first example which indicates that high coordination numbers also follow BVS rules. The Ce-O distances used in deriving the R(0) values for the +3 and +4 complexes are tabulated as a function of coordination number and have a wide range of values, but the average Ce-O distance reflects the requirement that the BVS must equal the oxidation state. Several examples are given where the oxidation state of the Ce ion is apparently incorrectly assigned, as well as cases where problems with the X-ray structure determinations are indicated by a disagreement between the postulated and calculated oxidation state.

A novel three-dimensional open framework constructed from infinite chains of edge-sharing CeO8(H2O) polyhedron: [Ce2(ad)3(H2O)2]n

“…1). The Ce1-O distance ranges from 2.470(2) to 2.633 (2) A and the average bond length is 2.545 (2) A; similarly, Ce2-O bond lengths are from 2.456(2) to 2.635 (2) A and the average value is 2.531 (2) A, which is consistent with the average distances of nine-coordinated Ce(III)-O [16].…”

“…The oxidation state of cerium in compound 1 is considered as +3 based on the structural analysis and the charge balance, which is consistent with the result of BVS calculation (Ce1, 2.87; Ce2, 3.02) according to the formula s ij ¼ exp½ðR 0 À R ij Þ=bðR 0 ¼ 2:131 A, b ¼ 0:37Þ [16]. In addition, the existence of Ce(III) is also confirmed by the XPS measurement of compound 1, which shows peak at 884.7 eV (Ce3d 5=2 ) and no sign of Ce(IV).…”

The first pentanuclear heterobimetallic coordination cation with CeIII, CeIV and MnII

“…A very similar motif, namely Ce IV (dipic) 3 , is found also within the pentanuclear coordination cation [MnCe 4 (dipic) 6 [20][21][22][23]. The search through CCD [24] shows that only one Ce/Mn coordination species reveals Ce in two oxidation states [Ce 4 Mn 10 O 10 (OCH 3 ) 6 ] 18+ [25].…”

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.…”