Hydrogen bonding in substitutionally disordered di-μ-hydroxido-bis­{aqua­tri[bromido/chlorido(1/2)]tin(IV)} acetone disolvate

The structure of the title compound, [Sn₂Br_1.97Cl_4.03(OH)₂(H₂O)₂]·2C₃H₆O, contains two hexa­coordinated Sn atoms bridged symmetrically by two hydroxide groups, with an inversion center in the middle of the planar Sn₂O₂ ring, half of the mol­ecule being generated by inversion symmetry. The other sites of the distorted octa­hedral coordination geometry are occupied by halide atoms and water mol­ecules. The structure exhibits substitutional disorder of the halide atoms bonded to the Sn atom, with 0.672 (4) occupancy for Cl and 0.328 (4) for Br for each halide position. The compound crystallizes with two acetone mol­ecules, which are involved in intra- and inter­molecular O—H...O contacts. The water mol­ecules coordinated to the Sn atoms are also involved in O—H...O and O—H...X contacts, leading to a polymeric array along the a axis.

Key indicators

• Single-crystal X-ray study
• T = 297 K
• Mean [sigma](C-C) = 0.012 Å
• Disorder in main residue
• R factor = 0.040
• wR factor = 0.102
• Data-to-parameter ratio = 17.8

checkCIF/PLATON results

No syntax errors found



Alert level B
PLAT420_ALERT_2_B D-H Without Acceptor       O2     -   H3     ...          ?

Alert level C
            Value of measurement temperature given =   297.000
            Value of melting point given =     0.000
PLAT222_ALERT_3_C Large Non-Solvent    H     Ueq(max)/Ueq(min) ...       3.75 Ratio
PLAT242_ALERT_2_C Check Low       Ueq as Compared to Neighbors for        Sn1
PLAT242_ALERT_2_C Check Low       Ueq as Compared to Neighbors for         C1
PLAT301_ALERT_3_C Main Residue  Disorder .........................      21.00 Perc.
PLAT342_ALERT_3_C Low Bond Precision on C-C Bonds (x 1000) Ang ...         12
PLAT068_ALERT_1_C Reported F000 Differs from Calcd (or Missing)...          ?
PLAT077_ALERT_4_C Unitcell contains non-integer number of atoms ..          ?
PLAT716_ALERT_1_C H...A   Unknown or Inconsistent Label ..........         X3
                    H3     X3
PLAT716_ALERT_1_C H...A   Unknown or Inconsistent Label ..........         X1
                    H3     X1
PLAT717_ALERT_1_C D...A   Unknown or Inconsistent Label ..........         X3
                    O2     X3
PLAT717_ALERT_1_C D...A   Unknown or Inconsistent Label ..........         X1
                    O2     X1
PLAT718_ALERT_1_C D-H..A  Unknown or Inconsistent Label ..........         X3
                    O2     H3     X3
PLAT718_ALERT_1_C D-H..A  Unknown or Inconsistent Label ..........         X1
                    O2     H3     X1

Alert level G
PLAT860_ALERT_3_G Note: Number of Least-Squares Restraints .......          2

   0 ALERT level A = In general: serious problem
   1 ALERT level B = Potentially serious problem
  13 ALERT level C = Check and explain
   1 ALERT level G = General alerts; check

   7 ALERT type 1 CIF construction/syntax error, inconsistent or missing data
   3 ALERT type 2 Indicator that the structure model may be wrong or deficient
   4 ALERT type 3 Indicator that the structure quality may be low
   1 ALERT type 4 Improvement, methodology, query or suggestion
   0 ALERT type 5 Informative message, check

---

S1. Comment

The title compound forms a dimeric structure with two aquatrihalidotin(IV) fragments bridged symmetrically by two hydroxo groups (Figure 1). Half of the molecule is generated by symmetry due to the presence of the inversion center in the middle of the Sn₂O₂ ring. This ring is planar and describes a rhomb with the endocyclic angles at O larger than those at the Sn atoms [Sn1—O1—Sn1ⁱ = 109.2 (2)°, O1—Sn1—O1ⁱ = 70.8 (2)°; symmetry code: (i) = -x + 1, -y + 1, -z + 1]. The tin atoms are hexacoordinated with the two hydroxo, three halides and one water molecule occupying the distorted octahedral positions around the metal centre. The tin atoms are out of the best plane described by O1/O1ⁱ/X1/X2 (X = Cl/Br) with 0.174 Å towards X3.

The compound exhibits substitutional disorder of the halide atoms bonded to the Sn with 0.672 occupancy for Cl and 0.328 for Br for each halide position.

The compound crystallizes with two acetone molecules, which establish two strong hydrogen bonds, one with the hydroxo group and one with the water from a neighboring dimer (Table 1). The water molecules are also involved in hydrogen bond type interactions with halide atoms, a strong one inside the dimeric unit and one intermolecular with a halide from another dimer (Table 1). The intramolecular interactions strengthen the dimeric unit and the intermolecular ones give rise to a polymer-like supramolecular arrangement along the a axis (Figure 2), with no further interactions between different chains (Figure 3).

Related literature

For related tin(IV) compounds, see: Barnes et al. (1980); Bokii & Struchkov (1971).

S2. Experimental

The title compound was obtained as a by-product after the work up of the crude reaction mixture obtained by reacting [2,6-(Me)₂C₆H₃]MgBr and SnCl₄.

S3. Refinement

The hydrogen atoms of the methyl groups were placed in calculated positions and were allowed to rotate but not to tip, with C—H = 0.96 Å and with U_iso(H) = 1.5U_eq(C). The three halide atoms were refined as substitutional disorder between chlorine and bromine, with 0.672 occupancy for Cl and 0.328 occupancy for Br for each position. Hydrogen atoms from the water molecule and hydroxyl group were found from a difference map and refined with a restrained O—H distance of 0.88 (5) Å,0.89 (9) Å and 0.79 (7) Å, with U_iso(H) = (1.5, 3.0, and 1.2)U_eq(O), respectively.

Computing details

Data collection: SMART (Bruker, 2000); cell refinement: SAINT-Plus (Bruker, 2001); data reduction: SAINT-Plus (Bruker, 2001); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: DIAMOND (Brandenburg & Putz, 2006); software used to prepare material for publication: publCIF (Westrip, 2009).

Figures

	Fig. 1. : View of the title compound showing the atom-numbering scheme at 30% probability thermal ellipsoids [symmetry code: (i) = -x + 1, -y + 1, -z + 1].
	Fig. 2. : Intra- and intermolecular interactions in the title compound (dashed lines; only H atoms involved in interactions are shown). Symmetry codes as in Table 1.
	Fig. 3. : Crystal packing of the title compound showing the supramolecular arrangement.

di-µ-hydroxido-bis{aquatri[bromido/chlorido(2/1)]tin(IV)} acetone solvate

Crystal data

[Sn2Br1.97Cl4.03(OH)2(H2O)2]·2C3H6O	F(000) = 680
Mr = 723.80	Dx = 2.240 Mg m^−3
Monoclinic, P21/c	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: -P 2ybc	Cell parameters from 1714 reflections
a = 6.9057 (13) Å	θ = 2.3–24.6°
b = 14.029 (3) Å	µ = 6.55 mm^−1
c = 11.400 (2) Å	T = 297 K
β = 103.195 (4)°	Block, colourless
V = 1075.3 (4) Å^3	0.21 × 0.20 × 0.17 mm
Z = 2

Data collection

Bruker SMART APEX CCD area-detector diffractometer	1891 independent reflections
Radiation source: fine-focus sealed tube	1641 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.032
ϕ and ω scans	θmax = 25.0°, θmin = 2.3°
Absorption correction: multi-scan (SADABS; Bruker, 2000)	h = −7→8
Tmin = 0.278, Tmax = 0.329	k = −16→13
5535 measured reflections	l = −13→13

Refinement

Refinement on F^2	Primary atom site location: structure-invariant direct methods
Least-squares matrix: full	Secondary atom site location: difference Fourier map
R[F^2 > 2σ(F^2)] = 0.040	Hydrogen site location: inferred from neighbouring sites
wR(F^2) = 0.102	H atoms treated by a mixture of independent and constrained refinement
S = 1.08	w = 1/[σ^2(Fo^2) + (0.049P)^2 + 2.7199P] where P = (Fo^2 + 2Fc^2)/3
1891 reflections	(Δ/σ)max < 0.001
106 parameters	Δρmax = 0.92 e Å^−3
2 restraints	Δρmin = −0.75 e Å^−3

Special details

Geometry. All e.s.d.'s (except the e.s.d. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell e.s.d.'s are taken into account individually in the estimation of e.s.d.'s in distances, angles and torsion angles; correlations between e.s.d.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell e.s.d.'s is used for estimating e.s.d.'s involving l.s. planes.

Refinement. Refinement of F² against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F², conventional R-factors R are based on F, with F set to zero for negative F². The threshold expression of F² > σ(F²) is used only for calculating R-factors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F² are statistically about twice as large as those based on F, and R- factors based on ALL data will be even larger.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Ų)

	x	y	z	Uiso*/Ueq	Occ. (<1)
O2	0.2519 (8)	0.6291 (4)	0.5292 (5)	0.0490 (12)
Sn1	0.34131 (6)	0.55296 (3)	0.38433 (4)	0.03550 (19)
O1	0.3796 (6)	0.4390 (3)	0.5018 (4)	0.0370 (11)
O3	0.1078 (7)	0.2974 (3)	0.4886 (5)	0.0535 (13)
C1	0.1355 (11)	0.2115 (5)	0.4779 (6)	0.0475 (17)
C2	0.3092 (13)	0.1783 (7)	0.4365 (9)	0.080 (3)
H2A	0.2750	0.1715	0.3504	0.120*
H2B	0.3517	0.1179	0.4729	0.120*
H2C	0.4150	0.2239	0.4589	0.120*
C3	−0.0070 (14)	0.1438 (6)	0.5094 (8)	0.073 (3)
H3A	−0.0928	0.1768	0.5512	0.109*
H3B	0.0640	0.0947	0.5603	0.109*
H3C	−0.0852	0.1157	0.4372	0.109*
Br2	0.3538 (2)	0.70915 (9)	0.29307 (11)	0.0567 (4)	0.328 (4)
Br3	0.4654 (2)	0.46498 (12)	0.23225 (13)	0.0661 (5)	0.328 (4)
Br1	−0.0046 (2)	0.51539 (12)	0.30386 (13)	0.0642 (5)	0.328 (4)
Cl2	0.3538 (2)	0.70915 (9)	0.29307 (11)	0.0567 (4)	0.672 (4)
Cl3	0.4654 (2)	0.46498 (12)	0.23225 (13)	0.0661 (5)	0.672 (4)
Cl1	−0.0046 (2)	0.51539 (12)	0.30386 (13)	0.0642 (5)	0.672 (4)
H2	0.128 (5)	0.647 (6)	0.520 (7)	0.07 (3)*
H1	0.307 (11)	0.396 (5)	0.506 (6)	0.04 (2)*
H3	0.282 (19)	0.587 (7)	0.589 (8)	0.15 (5)*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
O2	0.041 (3)	0.052 (3)	0.055 (3)	0.016 (2)	0.013 (2)	0.008 (3)
Sn1	0.0296 (3)	0.0384 (3)	0.0370 (3)	−0.00171 (19)	0.00458 (19)	0.00437 (19)
O1	0.026 (2)	0.034 (3)	0.048 (3)	−0.008 (2)	0.003 (2)	0.010 (2)
O3	0.042 (3)	0.033 (3)	0.086 (4)	0.000 (2)	0.015 (3)	0.001 (3)
C1	0.046 (4)	0.046 (5)	0.045 (4)	0.001 (3)	−0.002 (3)	−0.003 (3)
C2	0.070 (6)	0.073 (6)	0.103 (7)	0.003 (5)	0.030 (6)	−0.034 (6)
C3	0.092 (7)	0.045 (5)	0.077 (6)	−0.013 (5)	0.011 (5)	0.004 (4)
Br2	0.0705 (9)	0.0447 (8)	0.0525 (7)	−0.0056 (6)	0.0091 (6)	0.0170 (6)
Br3	0.0596 (9)	0.0805 (11)	0.0572 (8)	0.0018 (7)	0.0112 (7)	−0.0109 (7)
Br1	0.0400 (8)	0.0857 (11)	0.0624 (8)	−0.0056 (7)	0.0025 (6)	0.0144 (8)
Cl2	0.0705 (9)	0.0447 (8)	0.0525 (7)	−0.0056 (6)	0.0091 (6)	0.0170 (6)
Cl3	0.0596 (9)	0.0805 (11)	0.0572 (8)	0.0018 (7)	0.0112 (7)	−0.0109 (7)
Cl1	0.0400 (8)	0.0857 (11)	0.0624 (8)	−0.0056 (7)	0.0025 (6)	0.0144 (8)

Geometric parameters (Å, º)

O2—Sn1	2.171 (5)	O3—C1	1.230 (8)
O2—H2	0.88 (5)	C1—C2	1.462 (11)
O2—H3	0.89 (9)	C1—C3	1.470 (11)
Sn1—O1	2.064 (4)	C2—H2A	0.9600
Sn1—O1^i	2.066 (4)	C2—H2B	0.9600
Sn1—Br1	2.4138 (14)	C2—H2C	0.9600
Sn1—Br2	2.4357 (13)	C3—H3A	0.9600
Sn1—Br3	2.4376 (16)	C3—H3B	0.9600
O1—Sn1^i	2.066 (4)	C3—H3C	0.9600
O1—H1	0.79 (7)
Sn1—O2—H2	119 (6)	Sn1—O1—Sn1^i	109.2 (2)
Sn1—O2—H3	102 (9)	Sn1—O1—H1	130 (5)
H2—O2—H3	110 (10)	Sn1^i—O1—H1	121 (5)
O1—Sn1—O1^i	70.8 (2)	O3—C1—C2	120.0 (7)
O1—Sn1—O2	84.5 (2)	O3—C1—C3	118.8 (7)
O1^i—Sn1—O2	83.21 (19)	C2—C1—C3	121.2 (8)
O1—Sn1—Br1	92.67 (13)	C1—C2—H2A	109.5
O1^i—Sn1—Br1	162.00 (13)	C1—C2—H2B	109.5
O2—Sn1—Br1	88.16 (15)	H2A—C2—H2B	109.5
O1—Sn1—Br2	164.26 (14)	C1—C2—H2C	109.5
O1^i—Sn1—Br2	95.74 (13)	H2A—C2—H2C	109.5
O2—Sn1—Br2	85.79 (15)	H2B—C2—H2C	109.5
Br1—Sn1—Br2	99.36 (5)	C1—C3—H3A	109.5
O1—Sn1—Br3	93.18 (14)	C1—C3—H3B	109.5
O1^i—Sn1—Br3	92.62 (14)	H3A—C3—H3B	109.5
O2—Sn1—Br3	175.70 (14)	C1—C3—H3C	109.5
Br1—Sn1—Br3	95.57 (6)	H3A—C3—H3C	109.5
Br2—Sn1—Br3	95.70 (5)	H3B—C3—H3C	109.5
O1^i—Sn1—O1—Sn1^i	0.0	Br2—Sn1—O1—Sn1^i	−32.6 (6)
O2—Sn1—O1—Sn1^i	−84.7 (2)	Br3—Sn1—O1—Sn1^i	91.67 (19)
Br1—Sn1—O1—Sn1^i	−172.60 (19)

Symmetry code: (i) −x+1, −y+1, −z+1.

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
O1—H1···O3	0.79 (7)	1.93 (7)	2.714 (6)	170 (7)
O2—H3···X3^i	0.89 (9)	2.47 (10)	3.244 (5)	146 (8)
O2—H3···X1^ii	0.89 (9)	2.88 (12)	3.483 (6)	127 (8)
O2—H2···O3^ii	0.88 (5)	1.79 (5)	2.654 (7)	170 (4)

Symmetry codes: (i) −x+1, −y+1, −z+1; (ii) −x, −y+1, −z+1.