Bond-length distributions for ions bonded to oxygen: results for the transition metals and quantification of the factors underlying bond-length variation in inorganic solids
Bond-length distributions are examined for 63 transition metal ions bonded to O 2− in 147 configurations, for 7522 coordination polyhedra and 41 488 bond distances, providing baseline statistical knowledge of bond lengths for transition metals bonded to O 2− . A priori bond valences are calculated f...
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| Vydáno v: | IUCrJ Ročník 7; číslo 4; s. 581 - 629 |
|---|---|
| Hlavní autoři: | , |
| Médium: | Journal Article |
| Jazyk: | angličtina |
| Vydáno: |
England
International Union of Crystallography
01.07.2020
|
| Témata: | |
| ISSN: | 2052-2525, 2052-2525 |
| On-line přístup: | Získat plný text |
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| Shrnutí: | Bond-length distributions are examined for 63 transition metal ions bonded to O
2−
in 147 configurations, for 7522 coordination polyhedra and 41 488 bond distances, providing baseline statistical knowledge of bond lengths for transition metals bonded to O
2−
.
A priori
bond valences are calculated for 140 crystal structures containing 266 coordination polyhedra for 85 transition metal ion configurations with anomalous bond-length distributions. Two new indices, Δ
topol
and Δ
cryst
, are proposed to quantify bond-length variation arising from bond-topological and crystallographic effects in extended solids. Bond-topological mechanisms of bond-length variation are (1) non-local bond-topological asymmetry and (2) multiple-bond formation; crystallographic mechanisms are (3) electronic effects (with an inherent focus on coupled electronic vibrational degeneracy in this work) and (4) crystal-structure effects. The indices Δ
topol
and Δ
cryst
allow one to determine the primary cause(s) of bond-length variation for individual coordination polyhedra and ion configurations, quantify the distorting power of cations via electronic effects (by subtracting the bond-topological contribution to bond-length variation), set expectation limits regarding the extent to which functional properties linked to bond-length variation may be optimized in a given crystal structure (and inform how optimization may be achieved) and more. These indices further provide an equal footing for comparing bond-length variation and the distorting power of ions across ligand types, including resolution for heteroligand polyhedra. The observation of multiple bonds is found to be primarily driven by the bond-topological requirements of crystal structures in solids. However, sometimes multiple bonds are observed to form as a result of electronic effects (
e.g.
the pseudo Jahn–Teller effect, PJTE); resolution of the origins of multiple-bond formation follows calculation of the Δ
topol
and Δ
cryst
indices on a structure-by-structure basis. Non-local bond-topological asymmetry is the most common cause of bond-length variation in transition metal oxides and oxysalts, followed closely by the PJTE. Non-local bond-topological asymmetry is further suggested to be the most widespread cause of bond-length variation in the solid state, with no
a priori
limitations with regard to ion identity. Overall, bond-length variations resulting from the PJTE are slightly larger than those resulting from non-local bond-topological asymmetry, comparable with those resulting from the strong JTE, and less than those induced by π-bond formation. From a comparison of
a priori
and observed bond valences for ∼150 coordination polyhedra in which the strong JTE or the PJTE is the main reason underlying bond-length variation, the JTE is found
not
to have a cooperative relation with the bond-topological requirements of crystal structures. The magnitude of bond-length variation caused by the PJTE decreases in the following order for octahedrally coordinated
d
0
transition metal oxyanions: Os
8+
> Mo
6+
> W
6+
>> V
5+
> Nb
5+
> Ti
4+
> Ta
5+
> Hf
4+
> Zr
4+
> Re
7+
>> Y
3+
> Sc
3+
. Such ranking varies by coordination number; for [4] it is Re
7+
> Ti
4+
> V
5+
> W
6+
> Mo
6+
> Cr
6+
> Os
8+
>> Mn
7+
; for [5] it is Os
8+
> Re
7+
> Mo
6+
> Ti
4+
> W
6+
> V
5+
> Nb
5+
. It is concluded that non-octahedral coordinations of
d
0
ion configurations are likely to occur with bond-length variations that are similar in magnitude to their octahedral counterparts. However, smaller bond-length variations are expected from the PJTE for non-
d
0
transition metal oxyanions. |
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| Bibliografie: | ObjectType-Article-1 SourceType-Scholarly Journals-1 ObjectType-Feature-2 content type line 14 ObjectType-Review-3 content type line 23 |
| ISSN: | 2052-2525 2052-2525 |
| DOI: | 10.1107/S2052252520005928 |