catena-Poly[bis­(tert-butyl­ammonium) [plumbate(II)-tri-μ-iodo] iodide dihydrate]

The title compound, {(C₄H₁₂N)₂[PbI₃]I·2H₂O}_n, crystallizes as an organic–inorganic hybrid. The six-coordinate Pb atom lies on a centre of inversion and all the I atoms lie on mirror planes; the two independent cations both lie across mirror planes. The structure contains anionic chains along [100] of fused [PbI₃]⁻ units forming face-sharing octa­hedra. Four cations enclose channels occupied by isolated iodide ions and water mol­ecules of hydration.

S1. Comment

In recent years, a significant number of organic–inorganic hybrid materials based on metal halide units have been prepared and studied. For reviews see Papavassiliou (1997) and Mitzi (1999). Haloplumbates in particular have demonstrated a propensity for forming a great variety of crystalline structures by self-assembling from suitable solution mixtures. It has been shown that their structures can vary considerably, ranging from systems based on isolated molecules to systems containing extended chains as in [Me₄N][PbI₃] (Contreras et al., 1983) and right up to two- or three-dimensional networks (Mitzi, 1999). For systems containing extended chains, the extended chains may be formed by one, two or three bridging halides. A search of the Cambridge Structural Database (Version 5.27, November 2005 release; Allen 2002) indicated that most crystal structures with tertiary butylammonium groups have isolated octahedra, as in SnCl₆ (Ghozlen et al., 1991), TeCl₆ (Ishida & Kashino, 1992) and TeBr₆ (Baker et al., 1995), or isolated SnCl₄ tetrahedra (Ishida & Kashino, 1993). To the best of our knowledgwe, only two structures have a one-dimensional system, viz. (C₄H₁₂N)₂Sb₂Cl₈, which has edge-sharing chains of square–pyramidal SbCl₅ (Belz et al., 1992) and [(t-C₄H₁₂N)CdBr₃]₂·H₂O, which has edge-sharing chains of trigonal–bipyramidal CdBr₅ (Ishihara et al., 1999).

The title compound has a one-dimensional arrangement in which chains of face-sharing PbI₆ octahedra run along the unit cell (see Fig. 1). The channels in between the chains are occupied by t-butylammonium molecules, an isolated I atom on a mirror plane at y = 1/4 (I4), and water moleucles of hydration. In the direction perpendicular to the chains, the crystal cohesion is achieved by N—H···I, N—H···O and O—H···I hydrogen bridges. In the direction parallel to the chains, the cohesion is archieved by strong ionic bonds between the I and Pb atoms.

The inorganic motif is built up from characteristic face-sharing PbI₆ octahedra, which form infinite chains along the b axis. One unique inorganic chain runs through the centre of the unit cell. The asymmetric unit consists of a Pb atom on a centre of inversion and three I atoms, all on special positions, with I1 and I3 lying on the mirror plane at y = 0.75 and I2 on the mirror plane at y = 0.25. Within the chains, the shared face consists of these three halides. The octahedra are somewhat distorted, with all three unique Pb—I distances different (Table 1), while the bond angles between cis ligands range from 83.346 (16) to 96.654 (16)°.

There are two unique t-butylammonium cations in the asymmetric unit, labeled cat1 (containing atom N1) and cat2 (containing atom N2). In cat1, atoms N1, C1 and C3 lie on the mirror plane at y = 3/4; atom C2 occupies a general position. In cat2, atoms N2, C5 and C6 lie on the mirror plane at y = 1/4, with atom C4 in a general position.

The two unique cations in the asymmetric unit interact with the inorganic chains via long N—H···I3 hydrogen bridges; the distances are 3.21 Å and 3.25 Å, respectively, for cat1 and cat2 (Table 2). The last two H atoms on the ammonium head groups bridge to the O atom of the water molecule of hydration. The N—H···O distances range from 2.05 to 2.48 Å. Lastly, the H atoms on the water molecule bridge towards the isolated I atom to form a symmetrical ring with graph-set notation R₂²(8), with donor–acceptor distances of 2.73 and 2.78 Å.

S2. Experimental

PbI₂ (0.126 g, 0.273 mmol) was dissolved in 47% HI (2 ml) in a sample vial. Thereafter, C(CH₃)₃NH₂ (0.050 g, 0.684 mmol) was added and the precipitate was dissolved by refluxing for 12 h at 363 K. The solution was slowly cooled at 2 K h⁻¹ to room temperature. A yellow single-crystal suitable for X-ray diffraction analysis was selected and studied. Analysis calculated for C₈H₂₈I₄N₂O₂Pb: C 10.7, H 3.1, N 3.1%; found: C 10.8, H 3.3, N 3.2%

S3. Refinement

All H were found in a difference map. For the H atoms bonded to O atoms, restraints were used to obtain reasonable details of O—H distances and H—O—H angles. Finally these H atoms were refined using a riding model, with U_iso(H) = 1.2U_iso(O). H atoms bonded to C and N atoms were refined in idealized positions in the riding-model approximation, with C—H = 0.98 Å and N—H = 0.91 Å, and with U_iso(H) = 1.5U_eq(C,N). The highest residual peak is 0.83 Å from atom Pb1.

Computing details

Data collection: SMART-NT (Bruker, 1998); cell refinement: SAINT-Plus (Bruker, 1999); data reduction: SAINT-Plus; program(s) used to solve structure: SHELXS97 (Sheldrick, 1997); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: ORTEP-3 for Windows (Farrugia, 1997) and DIAMOND (Brandenburg, 1999); software used to prepare material for publication: WinGX (Farrugia, 1999) and PLATON (Spek, 2003).

Figures

	Fig. 1. The asymmetric unit of (I), showing the atomic numbering scheme. Displacement ellipsoids are shown at the 50% probability level. [Symmetry codes: (i) 1 − x, 1 − y, 1 − z; (ii) x, −y + 3/2, z.]
	Fig. 2. The packing of (I), viewed along the b axis.
	Fig. 3. Magnified view of the face-sharing [Pb6] octahedra and hydrogen-bonding scheme. Atoms labelled with an ampersand (&), a percentage sign (%), a hash (#), an asterisk (*) and an at sign (@) are at the symmetry positions (-x, 3/4, -z), (1 − x, 1/2 + y, 1 − z), (1 − x, 1 − y, 1 − z), (x, 3/2 − y, z) and (−x, 1 − y, −z), respectively.

catena-Poly[bis(tert-butylammonium) [plumbate(II)-tri-µ-iodo] iodide dihydrate]

Crystal data

(C4H12N)2[PbI3]I·2H2O	F(000) = 800
Mr = 899.11	Dx = 2.673 Mg m^−3
Monoclinic, P21/m	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: -P 2yb	Cell parameters from 927 reflections
a = 9.7917 (10) Å	θ = 4.0–28.1°
b = 7.9649 (8) Å	µ = 13.08 mm^−1
c = 15.0594 (16) Å	T = 173 K
β = 107.985 (3)°	Needle, white
V = 1117.1 (2) Å^3	0.28 × 0.1 × 0.09 mm
Z = 2

Data collection

Bruker SMART CCD area-detector diffractometer	2416 reflections with I > 2σ(I)
ϕ and ω scans	Rint = 0.074
Absorption correction: integration (XPREP; Bruker, 1999)	θmax = 28°, θmin = 1.4°
Tmin = 0.174, Tmax = 0.388	h = −12→12
5842 measured reflections	k = −10→10
2878 independent reflections	l = −19→12

Refinement

Refinement on F^2	2 restraints
Least-squares matrix: full	H-atom parameters constrained
R[F^2 > 2σ(F^2)] = 0.039	w = 1/[σ^2(Fo^2) + (0.0497P)^2 + 0.2377P] where P = (Fo^2 + 2Fc^2)/3
wR(F^2) = 0.101	(Δ/σ)max = 0.001
S = 1.07	Δρmax = 2.67 e Å^−3
2878 reflections	Δρmin = −2.32 e Å^−3
96 parameters

Special details

Experimental. Numerical integration absorption corrections based on indexed crystal faces were applied using the XPREP routine (Bruker, 1999)

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.

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

	x	y	z	Uiso*/Ueq	Occ. (<1)
Pb1	0.5	0.5	0.5	0.02074 (12)
I1	0.23893 (7)	0.75	0.39913 (5)	0.02601 (18)
I2	0.45960 (7)	0.25	0.32440 (5)	0.02323 (17)
I3	0.70541 (7)	0.75	0.43448 (5)	0.02369 (17)
I4	0.15583 (8)	0.25	−0.02974 (6)	0.0324 (2)
N1	0.3639 (11)	0.75	0.2031 (7)	0.029 (2)
H1A	0.421	0.7908	0.2586	0.044*	0.5
H1B	0.3367	0.6433	0.2112	0.044*	0.5
H1C	0.2846	0.8159	0.1818	0.044*	0.5
N2	0.9123 (9)	0.75	0.7016 (7)	0.026 (2)
H2A	0.9082	0.7123	0.7577	0.04*	0.5
H2B	0.8592	0.6814	0.6554	0.04*	0.5
H2C	0.8766	0.8562	0.6917	0.04*	0.5
O1	0.1355 (6)	0.4963 (7)	0.1640 (4)	0.0310 (13)
H2	0.1381	0.4198	0.1239	0.037*
H1	0.0874	0.5843	0.1395	0.037*
C1	0.4482 (11)	0.75	0.1311 (7)	0.021 (2)
C2	0.5367 (9)	0.5936 (11)	0.1486 (6)	0.0331 (19)
H2D	0.4735	0.4955	0.1327	0.05*
H2E	0.5938	0.5883	0.2147	0.05*
H2F	0.601	0.5944	0.11	0.05*
C3	0.3394 (13)	0.75	0.0346 (8)	0.036 (3)
H3A	0.3892	0.7382	−0.0124	0.053*	0.5
H3B	0.2857	0.8558	0.0245	0.053*	0.5
H3C	0.2727	0.656	0.0291	0.053*	0.5
C4	1.0871 (9)	0.5933 (12)	0.6483 (7)	0.038 (2)
H4A	1.0754	0.4932	0.6831	0.057*
H4B	1.1833	0.5933	0.6413	0.057*
H4C	1.0148	0.5925	0.5865	0.057*
C5	1.0681 (11)	0.75	0.7013 (8)	0.028 (3)
C6	1.1670 (13)	0.75	0.8006 (9)	0.035 (3)
H6A	1.1593	0.8578	0.8301	0.053*	0.5
H6B	1.2662	0.7332	0.8007	0.053*	0.5
H6C	1.1396	0.659	0.8355	0.053*	0.5

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
Pb1	0.0247 (2)	0.0156 (2)	0.0211 (2)	−0.00140 (15)	0.00596 (15)	0.00049 (16)
I1	0.0222 (3)	0.0296 (4)	0.0243 (4)	0	0.0045 (3)	0
I2	0.0241 (3)	0.0261 (4)	0.0195 (3)	0	0.0069 (3)	0
I3	0.0253 (3)	0.0214 (4)	0.0278 (4)	0	0.0134 (3)	0
I4	0.0335 (4)	0.0302 (4)	0.0357 (4)	0	0.0141 (3)	0
N1	0.037 (5)	0.023 (5)	0.032 (5)	0	0.016 (4)	0
N2	0.021 (5)	0.032 (6)	0.029 (5)	0	0.011 (4)	0
O1	0.040 (3)	0.026 (3)	0.030 (3)	0.003 (2)	0.015 (3)	0.003 (3)
C1	0.025 (5)	0.021 (6)	0.015 (5)	0	0.003 (4)	0
C2	0.038 (4)	0.032 (5)	0.031 (4)	0.008 (4)	0.014 (4)	0.011 (4)
C3	0.039 (7)	0.048 (8)	0.019 (6)	0	0.007 (5)	0
C4	0.029 (4)	0.032 (5)	0.052 (6)	−0.001 (4)	0.012 (4)	−0.015 (5)
C5	0.014 (5)	0.041 (7)	0.030 (6)	0	0.008 (4)	0
C6	0.030 (6)	0.042 (8)	0.028 (6)	0	0.002 (5)	0

Geometric parameters (Å, º)

Pb1—I3	3.1953 (5)	C1—C2^iv	1.494 (10)
Pb1—I3^i	3.1953 (5)	C1—C2	1.494 (10)
Pb1—I1^i	3.2263 (6)	C1—C3	1.513 (15)
Pb1—I1	3.2263 (6)	C2—H2D	0.98
Pb1—I2^i	3.2355 (6)	C2—H2E	0.98
Pb1—I2	3.2355 (6)	C2—H2F	0.98
I1—Pb1^ii	3.2263 (6)	C3—H3A	0.98
I2—Pb1^iii	3.2355 (6)	C3—H3B	0.98
I3—Pb1^ii	3.1953 (5)	C3—H3C	0.98
N1—C1	1.553 (13)	C4—C5	1.523 (10)
N1—H1A	0.91	C4—H4A	0.98
N1—H1B	0.91	C4—H4B	0.98
N1—H1C	0.91	C4—H4C	0.98
N2—C5	1.527 (12)	C5—C6	1.510 (16)
N2—H2A	0.91	C5—C4^iv	1.523 (10)
N2—H2B	0.91	C6—H6A	0.98
N2—H2C	0.91	C6—H6B	0.98
O1—H2	0.8633	C6—H6C	0.98
O1—H1	0.8616
I1^i—Pb1—I1	180	C1—C2—H2D	109.5
I2^i—Pb1—I2	180	C1—C2—H2E	109.5
I3—Pb1—I3^i	180	H2D—C2—H2E	109.5
I3—Pb1—I1^i	92.706 (16)	C1—C2—H2F	109.5
I3—Pb1—I1	87.294 (16)	H2D—C2—H2F	109.5
I3—Pb1—I2^i	86.509 (15)	H2E—C2—H2F	109.5
I3—Pb1—I2	93.491 (15)	C1—C3—H3A	109.5
I1—Pb1—I2	96.654 (16)	C1—C3—H3B	109.5
I1—Pb1—I2^i	83.346 (16)	H3A—C3—H3B	109.5
Pb1^ii—I1—Pb1	76.221 (17)	C1—C3—H3C	109.5
Pb1—I2—Pb1^iii	75.966 (17)	H3A—C3—H3C	109.5
Pb1—I3—Pb1^ii	77.097 (16)	H3B—C3—H3C	109.5
C1—N1—H1A	109.5	C5—C4—H4A	109.5
C1—N1—H1B	109.5	C5—C4—H4B	109.5
H1A—N1—H1B	109.5	H4A—C4—H4B	109.5
C1—N1—H1C	109.5	C5—C4—H4C	109.5
H1A—N1—H1C	109.5	H4A—C4—H4C	109.5
H1B—N1—H1C	109.5	H4B—C4—H4C	109.5
C5—N2—H2A	109.5	C6—C5—C4	112.0 (6)
C5—N2—H2B	109.5	C6—C5—C4^iv	112.0 (6)
H2A—N2—H2B	109.5	C4—C5—C4^iv	110.1 (10)
C5—N2—H2C	109.5	C6—C5—N2	109.5 (9)
H2A—N2—H2C	109.5	C4—C5—N2	106.6 (6)
H2B—N2—H2C	109.5	C4^iv—C5—N2	106.6 (6)
H2—O1—H1	113.9	C5—C6—H6A	109.5
C2^iv—C1—C2	113.0 (10)	C5—C6—H6B	109.5
C2^iv—C1—C3	111.6 (6)	H6A—C6—H6B	109.5
C2—C1—C3	111.6 (6)	C5—C6—H6C	109.5
C2^iv—C1—N1	106.3 (6)	H6A—C6—H6C	109.5
C2—C1—N1	106.3 (6)	H6B—C6—H6C	109.5
C3—C1—N1	107.6 (9)
I3—Pb1—I1—Pb1^ii	−40.902 (15)	I1^i—Pb1—I2—Pb1^iii	45.793 (14)
I3^i—Pb1—I1—Pb1^ii	139.098 (15)	I1—Pb1—I2—Pb1^iii	−134.207 (14)
I2^i—Pb1—I1—Pb1^ii	45.896 (13)	I1^i—Pb1—I3—Pb1^ii	−138.796 (16)
I2—Pb1—I1—Pb1^ii	−134.104 (13)	I1—Pb1—I3—Pb1^ii	41.204 (16)
I3—Pb1—I2—Pb1^iii	138.114 (14)	I2^i—Pb1—I3—Pb1^ii	−42.289 (14)
I3^i—Pb1—I2—Pb1^iii	−41.886 (14)	I2—Pb1—I3—Pb1^ii	137.711 (14)

Symmetry codes: (i) −x+1, −y+1, −z+1; (ii) −x+1, y+1/2, −z+1; (iii) −x+1, y−1/2, −z+1; (iv) x, −y+3/2, z.

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
N1—H1A···I3	0.91	3.21	4.016 (10)	148
N1—H1B···O1	0.91	2.21	2.936 (9)	136
N1—H1C···O1^iv	0.91	2.05	2.936 (9)	164
N2—H2A···O1^i	0.91	2.16	2.958 (9)	147
N2—H2B···I3	0.91	3.25	3.905 (10)	131
N2—H2C···O1^ii	0.91	2.48	2.958 (9)	113
O1—H2···I4	0.86	2.73	3.572 (6)	165
O1—H1···I4^v	0.86	2.78	3.570 (6)	154

Symmetry codes: (i) −x+1, −y+1, −z+1; (ii) −x+1, y+1/2, −z+1; (iv) x, −y+3/2, z; (v) −x, −y+1, −z.