K2[O(HgSO3)3], a new sulfito-mercurate with an [OHg3] core

Article abstract of DOI:10.1107/S0108270108005179

The structure of dipotassium 3-oxido-tris[sulfitomercur-ate(II)], K2[O(HgSO3)3], is characterized by segregation of the K⁺ cations and complex [O(HgSO3)3]^2- anions into layers parallel to (010). The anion has m symmetry and is a new example of a 3-oxido-trimercurate complex with a central [OHg3] core. This unit adopts the shape of a flat, almost trigonal, pyramid (mean O - Hg = 2.072 A and mean Hg - O - Hg = 110.8°). The two independent Hg - S bonds have nearly the same length (mean Hg - S = 2.335 A). Due to inter-molecular O...Hg donor-acceptor inter-actions greater than 2.65 A, the O - Hg - S fragments are slightly bent. The [KO9] coordination polyhedron of the K⁺ cation approaches a distorted tricapped trigonal prism with a [6+1+2] coordination.

Full text of DOI:10.1107/S0108270108005179

inorganic compounds
Acta Crystallographica Section C
Crystal Structure
Communications
ISSN 0108-2701
K2[O(HgSO3)3], a new sulfito-
mercurate with an [OHg3] core
Matthias Weil,a* Stefan Baumannb and Dietrich K.
Breitingerc
aInstitute for Chemical Technologies and Analytics, Division of Structural Chemistry,
Vienna University of Technology, Getreidemarkt 9/164-SC, A-1060 Vienna, Austria,
bInstitute for Materials Chemistry, Vienna University of Technology, Getreidemarkt
9/165, A-1060 Vienna, Austria, and cInstitute of Inorganic Chemistry, University of
Figure 1
The crystal structure of K2[O(HgSO3)3] in projection along [100],
showing the layered character of the cations and anions.
(K+) and anions {[O(HgSO3)3]2ꢀ} into layers is a characteristic
feature of the structure, here with a stacking of the layers
parallel to (010) (Fig. 1). The cationic and anionic layers
adopt the symmetries (a:c).21:ꢁ-p1121/a and (a:c).m.21-p21ma,
respectively (Shubnikov & Koptsik, 1974). The [O(Hg-
SO3)3]2ꢀ complex anion has site symmetry m, with the mirror
plane running through atoms O5/Hg2/S2/O6 (Fig. 2). The
anion is related to the [O(HgCl)3]+ and [O(HgI)2(HgOH)]+
cationic complexes which are present in the structures of
2HgCl2ꢂHgO {or, as a more detailed formula, [O(HgCl)3]Cl}
Erlangen-Nurnberg, Egerlandstrasse 1, D-91058 Erlangen, Germany
¨
Correspondence e-mail: mweil@mail.zserv.tuwien.ac.at
Received 19 January 2008
Accepted 23 February 2008
Online 15 March 2008
The structure of dipotassium ꢀ3-oxido-tris[sulfitomercur-
ate(II)], K2[O(HgSO3)3], is characterized by segregation of
the K+ cations and complex [O(HgSO3)3]2ꢀ anions into layers
parallel to (010). The anion has m symmetry and is a new
example of a ꢀ3-oxido-trimercurate complex with a central
[OHg3] core. This unit adopts the shape of a flat, almost
¨
(Aurivillius, 1964) and [O(HgI)2(HgOH)]ClO4 (Kohler et al.,
1974, 1975). Both the anionic and the two cationic complexes
contain flat nearly trigonal–pyramidal [OHg3] cores, i.e. they
are all ꢀ3-oxido-trimercurate complexes which are repre-
sentatives of metallo-complexes, and thus they exhibit similar
bonding parameters. In the anionic complex, the average O—
˚
trigonal, pyramid (mean O—Hg = 2.072 A and mean Hg—
O—Hg = 110.8ꢁ). The two independent Hg—S bonds have
˚
nearly the same length (mean Hg—S = 2.335 A). Due to
intermolecular Oꢂ ꢂ ꢂHg donor–acceptor interactions greater
˚
than 2.65 A, the O—Hg—S fragments are slightly bent. The
˚
Hg bond length is 2.07 A (Table 1), compared with 2.04 and
[KO9] coordination polyhedron of the K+ cation approaches a
distorted tricapped trigonal prism with a [6+1+2] coordina-
tion.
˚
2.05 A, respectively, in the cationic complexes. The slight
difference may be due to the strong trans influence of the
sulfite ligands and to the different charges, which is also
mirrored in the different average Hg—O—Hg bond angles of
110.8ꢁ for the anionic complex and of 118.9 and 119.8ꢁ for the
cationic complexes.
Comment
In a recent project, we have studied the formation conditions
and crystal structures of (NH4)[HgCl(SO3)] and (NH4)2[Hg-
(SO3)2] (Weil et al., 2007). Continuing our work on sulfite
complexes of mercury, we have also investigated in some
detail the systems K2SO3–HgX2 (X = Cl or Br) in aqueous
solution and in the solid phases formed therein. Depending on
the molar ratios of the components and on the conditions,
several phases with the general formula xK[XHgSO3]ꢂyHgX2ꢂ-
zKX were obtained. A characteristic of all the phases studied
structurally so far is the segregation of the K+ cations and of
the anions and HgX2 molecules into layers (Weil et al., 2008).
On heating solid HgO in an aqueous K2SO3 solution, a related
phase was obtained, viz. a formally basic salt of composition
K2SO3ꢂ2HgSO3ꢂHgO, or, with respect to the crystal structure
determination presented here, K2[O(HgSO3)3].
In the title compound, the average Hg—S bond length is
˚
2.335 A (Table 1), and the O—Hg—S structural fragments are
slightly bent with only a minor deviation from linearity (mean
O—Hg—S angle = 174.7ꢁ), due to the intermolecular donor–
˚
acceptor interactions with S—Oꢂ ꢂ ꢂHg > 2.65 A. These inter-
actions cause linking of the anions to the above-mentioned
layers and the remote O atoms expand the coordination
spheres of the Hg2+ cations to five- and six-coordination if
˚
Hg—O distances > 3.0 A are neglected. The average Hg—S
bond length is similar to the average Hg—Cl distance of
˚
2.31 A in [O(HgCl)3]Cl and in good agreement with the
Hg—S bond lengths in the sulfitomercurates (NH4)-
[HgCl(SO3)] and (NH4)2[Hg(SO3)2] (Weil et al., 2007), and
Na2[Hg(SO3)2]ꢂH2O (Nyberg & Cynkier, 1972), with average
˚
values of 2.394, 2.364 and 2.406 A, respectively. In contrast
The asymmetric unit of the title compound contains one K,
two Hg, two S and six O sites. As in the above-mentioned
xK[XHgSO3]ꢂyHgX2ꢂzKX structures, a segregation of cations
with K2[O(HgSO3)3], in the latter structures, Cl—Hg—SO3
and O3S—Hg—SO3 moieties are present. Nevertheless, in
agreement with the preference of mercury for linear coordi-
Acta Cryst. (2008). C64, i35–i37
doi:10.1107/S0108270108005179
# 2008 International Union of Crystallography i35

inorganic compounds
Table 1
Selected geometric parameters (A, ).
ꢁ
˚
Hg1—O5
Hg1—S1
Hg1—O6i
Hg1—O1ii
Hg1—O4iii
Hg1—O3
Hg2—O5
Hg2—S2
Hg2—O6iv
Hg2—O4v
Hg2—O4iii
Hg2—O1vi
K—O4
2.084 (3)
2.3395 (15)
2.688 (4)
2.837 (5)
2.941 (4)
3.074 (4)
2.049 (5)
2.325 (2)
2.654 (5)
2.913 (4)
2.913 (4)
2.932 (5)
2.801 (4)
2.821 (5)
K—O2vii
K—O3viii
K—O3ix
K—O1x
K—O2ix
K—O2iv
K—O1ii
S1—O2
S1—O3
S1—O1
S2—O6
S2—O4
S2—O4xi
2.824 (4)
2.845 (4)
2.852 (5)
2.895 (4)
3.021 (5)
3.253 (5)
3.276 (5)
1.453 (4)
1.455 (4)
1.472 (4)
1.472 (5)
1.473 (4)
1.473 (4)
Figure 2
K—O3ii
The [O(HgSO3)3]2ꢀ anion with the atom-labelling scheme. Displacement
ellipsoids are drawn at the 90% probability level. [Symmetry code: (i) x,
O5—Hg1—S1
O5—Hg2—S2
O2—S1—O3
O2—S1—O1
O3—S1—O1
O2—S1—Hg1
O3—S1—Hg1
O1—S1—Hg1
O6—S2—O4
172.45 (14)
179.14 (14)
112.5 (3)
112.5 (3)
111.2 (3)
107.4 (2)
105.82 (17)
106.98 (18)
110.7 (2)
O6—S2—O4xi
O4—S2—O4xi
O6—S2—Hg2
O4—S2—Hg2
O4xi—S2—Hg2
Hg2—O5—Hg1xi
Hg2—O5—Hg1
Hg1xi—O5—Hg1
110.7 (2)
111.0 (3)
105.9 (2)
109.22 (18)
109.22 (18)
114.25 (16)
114.25 (16)
103.9 (2)
1
2
ꢀy + , z.]
nation, the Cl—Hg—S and S—Hg—S angles are close to 180ꢁ,
viz. 165.5, 174.4 and 172.8ꢁ, respectively.
The S—O bond lengths of the two independent SO3 groups
in K2[O(HgSO3)3] differ slightly (mean S—O = 1.460 and
˚
1.473 A) because of their different roles in the linking within
and between the cationic and anionic layers. Not all of the O
atoms of the sulfite groups are involved in donor–acceptor
interactions within the anionic layers, and only some of the O
atoms are coordinated to the K+ cation, and thus contribute to
the linking of the cationic and anionic layers. The K+ cation
has nine O-atom neighbours with a [6+1+2] coordination and
with K—O distances ranging from 2.801 (4) to 3.276 (5) A
(Table 1). The resulting coordination polyhedron may be
described as a distorted tricapped trigonal prism.
1
2
1
3
1
2
1
2
1
Symmetry codes: (i) x; y; z þ 1; (ii) x ꢀ ; y; ꢀz þ ; (iii) x þ ; y; ꢀz þ ; (iv) x ꢀ ; y,
2
2
1
2
1
2
1
2
1
2
1
3
2
1
2
1
ꢀz þ ; (v) x þ ; ꢀy þ ; ꢀz þ ; (vi) x ꢀ ; ꢀy þ ; ꢀz þ ; (vii) ꢀx þ ; ꢀy; z ꢀ ; (viii)
2
2
2
1
2
x; y; z ꢀ 1; (ix) ꢀx; ꢀy; ꢀz þ 1; (x) x ꢀ 1; y; z ꢀ 1; (xi) x; ꢀy þ ; z.
cooling to ambient temperature, aggregated yellow crystals up to
2 mm in length with a lancet-like habit were formed within 2 d. The
crystals were not stable over a long period and decomposed within a
few days under formation of elemental mercury and SO2. However,
when the crystals were embedded in perfluorinated ether, collection
of a complete data set with high redundancy was possible without
difficulty.
˚
Results from bond-valence-sum calculations (Brown, 2002),
using the parameters of Brese & O’Keeffe (1991), are in good
agreement with the expected values for K, Hg and O (1, 2 and
Crystal data
˚
3
2, respectively): Hg1/Hg2 (including all distances < 3.0 A) 1.99
˚
K2[Hg3O(SO3)3]
Mr = 936.15
Orthorhombic, Pnma
a = 7.352 (4) A
b = 20.734 (11) A
˚
c = 7.780 (4) A
V = 1185.9 (11) A
Z = 4
Mo Kꢁ radiation
ꢀ = 40.01 mmꢀ1
T = 298 (2) K
and 2.10; K 1.07; O1 [coordination number (CN) = 5; 1 S, 2 Hg,
2 K] 1.94, O2 (CN = 4; 1 S, 3 K) 1.97, O3 (CN = 4; 1 S, 3 K)
2.11, O4 (CN = 4; 1 S, 1 Hg, 2 K) 1.90, O5 (CN = 3; 3 Hg) 2.29,
and O6 (CN = 4; 1 S, 3 Hg) 2.04. Following this concept, the S
atoms are considerably ‘overbonded’, with valence units of
5.87 for S1 and 5.75 for S2. This behaviour is attributed to the
additional metal–sulfur coordination via the lone-pair elec-
trons of the S atoms, which leads to enhanced S—O ꢂ-bonding
as a consequence (Cruickshank, 1961), and thus to shorter S—
O bond lengths. So, in comparison with other sulfates(IV) of
the formula type MSIVO3 (M is a divalent metal) where the S
atom is not coordinated to the metal centres, the overall S—O
˚
˚
0.12 ꢃ 0.11 ꢃ 0.04 mm
Data collection
Bruker SMART APEX CCD area-
detector diffractometer
Absorption correction: numerical
(HABITUS; Herrendorf, 1997)
Tmin = 0.086, Tmax = 0.327
12066 measured reflections
1763 independent reflections
1612 reflections with I > 2ꢃ(I)
Rint = 0.046
Refinement
R[F2 > 2ꢃ(F2)] = 0.023
wR(F2) = 0.055
S = 1.06
89 parameters
Áꢄmax = 1.56 e A
Áꢄmin = ꢀ1.27 e A
˚
ꢀ3
˚
distance is significantly shorter here (1.47 versus 1.54 A).
˚
ꢀ3
Nevertheless, the bonding situation in the title compound is in
agreement with the HSAB (hard and soft acids and bases)
concept (Pearson, 1997), where the soft acid Hg2+ prefers
bonding to the soft base SIV with its lone-pair electrons.
1763 reflections
The highest remaining peak in the final difference Fourier map was
˚
˚
0.76 A from atom Hg2 and the deepest hole 0.90 A from Hg1.
Data collection: SMART (Bruker, 2003); cell refinement: SAINT
(Bruker, 2003); data reduction: SAINT; program(s) used to solve
structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine
structure: SHELXL97 (Sheldrick, 2008); molecular graphics:
ATOMS (Dowty, 2006); software used to prepare material for
publication: SHELXL97.
Experimental
All chemicals used were of analytical grade (Merck) and employed
without further purification. The title compound was obtained on
dissolution of freshly precipitated HgO (25 mg, 0.115 mmol) in a
boiling aqueous solution of K2SO3 (50 ml, 180 mg, 1.1 mmol). After
ꢄ
i36 Weil et al. K2[Hg3O(SO3)3]
Acta Cryst. (2008). C64, i35–i37

inorganic compounds
Dowty, E. (2006). ATOMS for Windows. Version 6.3. Shape Software,
Kingsport, Tennessee, USA.
Herrendorf, W. (1997). HABITUS. University of Gießen, Germany.
Ko¨hler, K., Thiele, G. & Breitinger, D. K. (1974). Angew. Chem. 86, 589.
Supplementary data for this paper are available from the IUCr electronic
archives (Reference: IZ3045). Services for accessing these data are
described at the back of the journal.
¨
Kohler, K., Thiele, G. & Breitinger, D. K. (1975). Z. Anorg. Allg. Chem. 418,
79–87.
Nyberg, B. & Cynkier, I. (1972). Acta Chem. Scand. 26, 4175–4176.
Pearson, R. G. (1997). In Chemical Hardness – Applications From Molecules to
Solids. Weinheim: Wiley-VCH.
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Acta Cryst. (2008). C64, i35–i37
Weil et al. K2[Hg3O(SO3)3] i37