Crystal structures of strontium and barium ethylenediaminetetraacetato cobaltates(III), Sr[CoEdta]{sub 2}.9H{sub 2}O and Ba[CoEdta]{sub 2}.8H{sub 2}O: Comparison of the structures of complexes in the series M'[CoEdta]{sub 2}.nH{sub 2}O (M' = Mg, Ca, Sr, Ba; n = 7-10)
- Russian Academy of Sciences, Kurnakov Institute of General and Inorganic Chemistry (Russian Federation)
- Moscow State University (Russian Federation)
- National Academy of Sciences of Belarus, Institute of Molecular and Atomic Physics (Belarus)
Cobalt(III) complexes, namely, Sr[CoEdta]{sub 2}.9H{sub 2}O (I) and Ba[CoEdta]{sub 2}.8H{sub 2}O (II) (where Edta{sup 4-} is the ethylenediaminetetraacetate ion), are synthesized. The crystal structures of these compounds are determined using X-ray diffraction. Crystals of compound I are triclinic, a = 6.514(1) A, b = 11.410(2) A, c = 12.317(2) A, {alpha} = 67.87(1) deg., {beta} = 88.73(2) deg., {gamma} = 84.22(2) deg., V = 843.63(3) A{sup 3}, Z = 1, space group P1, and R = 0.0295 for 4130 reflections with I > 2{sigma}(I). Crystals of compound II are monoclinic, a = 6.543(2) A, b = 12.895(3) A, c = 19.489(4) A, {beta} = 95.24(3) deg., V = 1637.5(5) A{sup 3}, Z = 2, space group P2{sub 1}, and R = 0.050 for 3016 reflections with vertical bar F vertical bar > 3{sigma}( vertical bar F vertical bar ). The structures of compounds I and II are compared with those of the previously studied complexes Mg[CoEdta]{sub 2}.10H{sub 2}O (III) and Ca[CoEdta]{sub 2}.7H{sub 2}O (IV). The crystal structure of the cobalt(III) complex with the strontium cation (I) is topologically similar to the crystal structure of cobalt(III) complex with the calcium cation (IV). The former structure is built up of the two symmetrically independent homochiral anionic complexes [CoEdta]{sup -} (A{sub I} and B{sub I}), the aqua cations [Sr(H{sub 2}O){sub 8}]{sup 2+}, and the molecules of crystalization water w{sub cr}. The structure of compound II involves two independent anions [CoEdta]{sup -} (A{sub II} and B{sub II}) with different chiralities (i.e., they are kryptoracemates). The A{sub II} anions are linked via the barium cations into {l_brace}Ba(H{sub 2}O){sub 7}[CoEdta]{r_brace}{sub 1{infinity}}{sup +} chain agglomerates due to the incorporation of two terminal oxygen atoms O{sub u} of the anions neighboring in the chain into the coordination sphere of the barium atom. All four structures (I-IV) contain stacks composed of the [CoEdta]{sup -} homochiral anions forming layers aligned parallel to the (001) plane. The aqua cations [Sr(H{sub 2}O){sub 8}]{sup 2+}, [Mg(H{sub 2}O){sub 6}]{sup 2+}, and [Ca(H{sub 2}O){sub 7}]{sup 2+} or the partially hydrated barium cations [Ba(H{sub 2}O){sub 7}(O{sub u}){sub 2}]{sup 2+} (in structure II), as well as water molecules w{sub cr}, are located between the anion layers. The octahedral environment of the cobalt(III) atoms consists of donor atoms (2N and 4O) of the Edta{sup 4-} ligand. The Co-N bonds in the A{sub I}, B{sub I}, A{sub II}, and B{sub II} anions [the mean bond lengths are 1.927(4), 1.921(4), 1.910(6), and 1.921(6) A, respectively] are considerably longer than the Co-O bonds [the mean bond lengths are 1.908(5), 1.902(5), 1.904(6), and 1.908(6) A, respectively]. The mean distances Sr-O{sub w} and Ba-O{sub w} in the strontium and barium polyhedra are 2.609(4) and 2.834(8) A, respectively. The mean distance Ba-O{sub u} is 2.814(7) A.
- OSTI ID:
- 21091478
- Journal Information:
- Crystallography Reports, Vol. 51, Issue 3; Other Information: DOI: 10.1134/S1063774506030138; Copyright (c) 2006 Nauka/Interperiodica; Article Copyright (c) 2006 Pleiades Publishing, Inc; Country of input: International Atomic Energy Agency (IAEA); ISSN 1063-7745
- Country of Publication:
- United States
- Language:
- English
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