(β-Alanine)dibromolead(II)

The structure of the title compound, [PbBr₂(C₃H₇NO₂)], contains Pb²⁺ ions, Br⁻ ions and β-alanine mol­ecules in their zwitterion form. Each lead(II) ion has a seven-coordinate geometry, with four sites occupied by Br⁻ ions, two by a bidentate carboxyl­ate group and the last by a single O atom. The singly-bridging Br⁻ ions link the Pb^II ions into layers that are further aggregated into a three dimensional array by the formation of Pb—O bonds and hydrogen bonds involving the —NH₃⁺ groups.

Key indicators

• Single-crystal X-ray study
• T = 82 K
• Mean [sigma](C-C) = 0.008 Å
• R factor = 0.018
• wR factor = 0.042
• Data-to-parameter ratio = 16.9

checkCIF results

No syntax errors found

ADDSYM reports no extra symmetry

---

S1. Comment

The sevenfold local coordination for the lead(II) ion is shown in Fig. 1, and can conveniently be viewed as a severely distorted octahedron in which one site of the octahedron is occupied by the bidentate carboxylate group. The four Pb—Br bonds range from 2.9918 (6) to 3.1731 (5) Å. The carboxylate group in the zwitterion form of the β-alanine molecule coordinates in one octahedral site in a bidentate fashion, while the sixth site is occupied by an O atom from a β-alanine molecule of an adjacent octahedron. The Pb—O distances are 2.533 (3) and 2.600 (4) Å for the O atoms in the bidentate group, and 2.754 (4) Å for the bridging O atom. As anticipated, the angular distortions imposed by the presence of the bidentate group are significant. As is also seen in Fig. 1, the backbone of the β-alanine molecule assumes a gauche conformation. As discussed below, this allows the formation of an intramolecular hydrogen bond as well as several other interactions.

Corner-sharing through the bromide ions on adjacent octahedra lead to the formation of a two-dimensional structure, as shown in Fig. 2. This layer structure may be viewed as an (110) section of the parent cubic AMX₃ structure. This is a single metal halide layer of the type in the multiple layer (NH₂CINH₂)₂(CH₃NH₃)_n-1Sn_nI_3n+1 (110) sections reported by Mitzi et al. (1995). This is in contrast to the typical [001] section formed by the (RNH₃)₂MX₄ layer perovskite compounds such as in the (β-alaninium)₂CuX₄ salts (X = Cl⁻ and Br⁻) (Willett, et al., 1981, 1983).

These metal halide layers are linked together via bibridged Pb—O—Pb bonds (dashed lines, Fig. 3), as well as N—H···O and N—H···Br hydrogen bonds (dashed lines, inset, Fig. 3). These Pb—O bonds are 0.15 Å longer than those in the bidentate linkage. The bridging Pb—O—Pb angle is 109.0 (1)°. The –NH₃⁺ group forms one asymmetric bifurcated hydrogen bond (to two different Br2, see Table 1) and two normal hydrogen bonds (to Br1 and O1). The intramolecular N—H···Br hydrogen bond is nearly 0.2 Å longer than the one between layers, presumably because of steric constraints on the conformation of the β-alanine molecule·In addition, there is an electrostatic interaction of the –NH₃⁺ group with an O2 atom from the adjacent layer, in which the C—N···O angle is close to linear.

S2. Experimental

Crystals of the title compound were prepared by slow evaporation of a solution obtained by dissolving 0.9282 g PbBr₂ (0.002 mmol) and 0.4550 g β-alanine (0.005 mmol) in 80 ml deionized water that had been acidified with 5 drops of concentrated HBr.

S3. Refinement

H atoms were positioned geometrically and refined using a riding model, with U_iso for the methylene C—H groups constrained to be 1.2U_eq of the carrier atom, while those of the N—H protons were set at 1.5U_eq. There is a large residual of 1.19 e Å ⁻³ ca 0.92 Å from Pb1.

Computing details

Data collection: SMART (Bruker, 2002); cell refinement: SAINT-Plus (Bruker, 2001); data reduction: SAINT-Plus; program(s) used to solve structure: SHELXTL (Bruker, 2000); program(s) used to refine structure: SHELXTL; molecular graphics: SHELXTL; software used to prepare material for publication: SHELXTL.

Figures

	Fig. 1. Illustration of the lead(II) ion coordination. Ellipsoids are drawn at the 70% probability level.
	Fig. 2. Illustration of the [110] PbBr2 layer.
	Fig. 3. Illustration of the interconnection of the PbBr2 layers, as viewed down the a direction. The b axis is horizontal. The bridging Pb—O bonds are shown as dotted lines. The inset shows the hydrogen-bonding contacts.

Lead(II) bromide β-alanine

Crystal data

[PbBr2(C3H7NO2)]	F(000) = 800
Mr = 456.11	Dx = 3.737 Mg m^−3
Monoclinic, P21/c	Mo Kα radiation, λ = 0.71073 Å
a = 6.0073 (4) Å	θ = 2.5–28.3°
b = 16.5286 (10) Å	µ = 30.60 mm^−1
c = 8.3057 (5) Å	T = 82 K
β = 100.56 (1)°	Rhomboid, colorless
V = 810.71 (9) Å^3	0.11 × 0.08 × 0.06 mm
Z = 4

Data collection

Bruker–Siemens SMART APEX diffractometer	1423 independent reflections
Radiation source: normal-focus sealed tube	1366 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.034
Detector resolution: 8.3 pixels mm^-1	θmax = 25.0°, θmin = 2.5°
ω scans	h = −7→7
Absorption correction: multi-scan (SADABS; Bruker, 2001)	k = −19→19
Tmin = 0.066, Tmax = 0.159	l = −9→9
7447 measured reflections

Refinement

Refinement on F^2	Secondary atom site location: difference Fourier map
Least-squares matrix: full	Hydrogen site location: inferred from neighbouring sites
R[F^2 > 2σ(F^2)] = 0.018	H-atom parameters constrained
wR(F^2) = 0.042	w = 1/[σ^2(Fo^2) + 2.9938P] where P = (Fo^2 + 2Fc^2)/3
S = 1.20	(Δ/σ)max = 0.001
1423 reflections	Δρmax = 1.11 e Å^−3
84 parameters	Δρmin = −0.68 e Å^−3
48 restraints	Extinction correction: SHELXL97, Fc^*=kFc[1+0.001xFc^2λ^3/sin(2θ)]^-1/4
Primary atom site location: structure-invariant direct methods	Extinction coefficient: 0.00191 (12)

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
Pb1	0.04516 (3)	0.383518 (12)	0.12507 (2)	0.00242 (10)
Br1	0.10815 (9)	0.25372 (3)	0.37005 (6)	0.00587 (14)
Br2	−0.45035 (8)	0.40113 (3)	0.12565 (6)	0.00672 (13)
O1	0.1708 (6)	0.4607 (2)	0.3896 (4)	0.0067 (8)
O2	0.0661 (6)	0.5390 (2)	0.1725 (4)	0.0078 (8)
N1	0.6250 (8)	0.6014 (3)	0.2990 (5)	0.0075 (10)
H1A	0.6951	0.5812	0.3972	0.011*
H1B	0.7233	0.6333	0.2564	0.011*
H1C	0.5789	0.5598	0.2290	0.011*
C4	0.1616 (8)	0.5292 (3)	0.3197 (6)	0.0019 (10)
C2	0.4228 (9)	0.6506 (3)	0.3225 (6)	0.0062 (11)
H2A	0.3358	0.6669	0.2143	0.007*
H2B	0.4745	0.7004	0.3845	0.007*
C3	0.2715 (10)	0.6027 (3)	0.4143 (6)	0.0057 (11)
H3A	0.1509	0.6388	0.4396	0.007*
H3B	0.3622	0.5842	0.5195	0.007*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
Pb1	0.00103 (14)	0.00296 (13)	0.00330 (13)	−0.00016 (7)	0.00051 (7)	−0.00020 (7)
Br1	0.0075 (3)	0.0043 (3)	0.0058 (3)	0.0003 (2)	0.00138 (19)	0.0015 (2)
Br2	0.0019 (3)	0.0115 (3)	0.0069 (3)	−0.0003 (2)	0.0013 (2)	−0.0006 (2)
O1	0.006 (2)	0.009 (2)	0.0037 (18)	0.0021 (16)	−0.0003 (15)	−0.0016 (15)
O2	0.009 (2)	0.007 (2)	0.0062 (18)	0.0014 (16)	−0.0018 (15)	−0.0002 (15)
N1	0.007 (3)	0.011 (3)	0.004 (2)	−0.0008 (19)	0.0015 (18)	0.0005 (18)
C4	0.0015 (13)	0.0024 (13)	0.0021 (13)	0.0006 (9)	0.0011 (9)	0.0002 (9)
C2	0.0061 (14)	0.0058 (14)	0.0063 (13)	0.0005 (9)	0.0000 (9)	−0.0005 (9)
C3	0.0055 (14)	0.0056 (14)	0.0057 (13)	0.0003 (9)	0.0008 (9)	−0.0012 (9)

Geometric parameters (Å, º)

Pb1—O1	2.533 (3)	O2—Pb1^i	2.755 (4)
Pb1—O2	2.600 (4)	N1—C2	1.505 (7)
Pb1—O2^i	2.755 (4)	N1—H1A	0.9100
Pb1—Br1	2.9333 (5)	N1—H1B	0.9100
Pb1—Br2	2.9918 (6)	N1—H1C	0.9100
Pb1—Br2^ii	3.0437 (6)	C4—C3	1.530 (7)
Pb1—Br1^iii	3.1731 (5)	C2—C3	1.513 (7)
Br1—Pb1^iv	3.1731 (5)	C2—H2A	0.9900
Br2—Pb1^v	3.0437 (6)	C2—H2B	0.9900
O1—C4	1.270 (6)	C3—H3A	0.9900
O2—C4	1.262 (6)	C3—H3B	0.9900
O1—Pb1—O2	51.12 (11)	C4—O2—Pb1	91.2 (3)
O1—Pb1—O2^i	121.93 (12)	C4—O2—Pb1^i	157.1 (3)
O2—Pb1—O2^i	70.95 (12)	Pb1—O2—Pb1^i	109.05 (12)
O1—Pb1—Br1	77.67 (8)	C2—N1—H1A	109.5
O2—Pb1—Br1	128.41 (8)	C2—N1—H1B	109.5
O2^i—Pb1—Br1	160.31 (8)	H1A—N1—H1B	109.5
O1—Pb1—Br2	95.04 (8)	C2—N1—H1C	109.5
O2—Pb1—Br2	85.64 (8)	H1A—N1—H1C	109.5
O2^i—Pb1—Br2	83.02 (8)	H1B—N1—H1C	109.5
Br1—Pb1—Br2	94.121 (16)	O2—C4—O1	122.1 (5)
O1—Pb1—Br2^ii	79.18 (9)	O2—C4—C3	118.2 (4)
O2—Pb1—Br2^ii	83.38 (8)	O1—C4—C3	119.7 (4)
O2^i—Pb1—Br2^ii	91.98 (8)	N1—C2—C3	110.9 (4)
Br1—Pb1—Br2^ii	93.848 (16)	N1—C2—H2A	109.5
Br2—Pb1—Br2^ii	168.93 (2)	C3—C2—H2A	109.5
O1—Pb1—Br1^iii	152.37 (8)	N1—C2—H2B	109.5
O2—Pb1—Br1^iii	143.09 (8)	C3—C2—H2B	109.5
O2^i—Pb1—Br1^iii	76.84 (8)	H2A—C2—H2B	108.1
Br1—Pb1—Br1^iii	85.652 (7)	C2—C3—C4	113.6 (4)
Br2—Pb1—Br1^iii	108.126 (15)	C2—C3—H3A	108.9
Br2^ii—Pb1—Br1^iii	80.144 (15)	C4—C3—H3A	108.9
Pb1—Br1—Pb1^iv	165.91 (2)	C2—C3—H3B	108.9
Pb1—Br2—Pb1^v	168.93 (2)	C4—C3—H3B	108.9
C4—O1—Pb1	94.1 (3)	H3A—C3—H3B	107.7
O1—Pb1—Br1—Pb1^iv	99.92 (12)	Br1—Pb1—O2—C4	15.0 (3)
O2—Pb1—Br1—Pb1^iv	93.36 (13)	Br2—Pb1—O2—C4	106.8 (3)
O2^i—Pb1—Br1—Pb1^iv	−75.1 (2)	Br2^ii—Pb1—O2—C4	−74.7 (3)
Br2—Pb1—Br1—Pb1^iv	5.66 (8)	Br1^iii—Pb1—O2—C4	−138.5 (3)
Br2^ii—Pb1—Br1—Pb1^iv	177.96 (8)	O1—Pb1—O2—Pb1^i	175.8 (2)
Br1^iii—Pb1—Br1—Pb1^iv	−102.24 (8)	O2^i—Pb1—O2—Pb1^i	0.0
O1—Pb1—Br2—Pb1^v	−122.03 (13)	Br1—Pb1—O2—Pb1^i	−175.92 (5)
O2—Pb1—Br2—Pb1^v	−172.33 (13)	Br2—Pb1—O2—Pb1^i	−84.11 (11)
O2^i—Pb1—Br2—Pb1^v	116.36 (13)	Br2^ii—Pb1—O2—Pb1^i	94.41 (11)
Br1—Pb1—Br2—Pb1^v	−44.07 (10)	Br1^iii—Pb1—O2—Pb1^i	30.6 (2)
Br2^ii—Pb1—Br2—Pb1^v	180.0	Pb1—O2—C4—O1	−12.5 (5)
Br1^iii—Pb1—Br2—Pb1^v	42.70 (10)	Pb1^i—O2—C4—O1	−165.1 (6)
O2—Pb1—O1—C4	−6.7 (3)	Pb1—O2—C4—C3	166.8 (4)
O2^i—Pb1—O1—C4	−2.1 (3)	Pb1^i—O2—C4—C3	14.1 (11)
Br1—Pb1—O1—C4	179.9 (3)	Pb1—O1—C4—O2	12.8 (5)
Br2—Pb1—O1—C4	−87.0 (3)	Pb1—O1—C4—C3	−166.4 (4)
Br2^ii—Pb1—O1—C4	83.5 (3)	N1—C2—C3—C4	−65.4 (6)
Br1^iii—Pb1—O1—C4	125.7 (3)	O2—C4—C3—C2	−48.5 (7)
O1—Pb1—O2—C4	6.8 (3)	O1—C4—C3—C2	130.8 (5)
O2^i—Pb1—O2—C4	−169.1 (4)

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

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
N1—H1A···O1^vi	0.91	1.93	2.843 (6)	177
N1—H1B···Br1^vii	0.91	2.55	3.422 (5)	162
N1—H1C···Br2^ii	0.91	2.75	3.604 (5)	156
N1—H1C···Br2^i	0.91	2.98	3.490 (4)	118

Symmetry codes: (i) −x, −y+1, −z; (ii) x+1, y, z; (vi) −x+1, −y+1, −z+1; (vii) −x+1, y+1/2, −z+1/2.