Poly[([mu]₂-aqua-[kappa]²O:O)([mu]₃-azido-[kappa]³N¹:N¹:N³)([mu]₂-isonicotinato-[kappa]²O:O')­lead(II)]

In the title compound, [Pb(C₆H₄NO₂)(N₃)(H₂O)]_n, the Pb ion is seven-coordinated by three N atoms from three azide ligands, two O atoms from two isonicotinate (inic) ligands and two O atoms from two coordinated water mol­ecules, forming a distorted monocapped triangular prismatic coordination geometry. Each azide ligand bridges three Pb^II ions in a [mu]_1,1,3 coordination mode to form a two-dimensional three-connected 6³ topology network extending in the bc plane. The carboxyl­ate group of the inic unit and the aqua ligand act as coligands to bridge Pb^II ions. Adjacent two-dimensional layers are connected by hydrogen-bonding inter­actions between the isonicotinate N atom and the water mol­ecule, resulting in an extended three-dimensional network. The title complex is the first reported coordination polymer involving a p-block metal, an azide and a carboxyl­ate.

S1. Comment

In recent years, azide has attracted much attention not only for its versatile coordination mode as a bridging ligand, but also for its inherent advantages in the construction of materials with magnetic properties and potential applications (Yue et al., 2008; Ray et al., 2008; Liu et al., 2007; Zeng et al., 2006, 2005; Liu et al., 2006; Chen et al., 2001). The synthetic strategy of choosing a different second ligand for propagating new motifs has been used to produce a large number of azide-bridged complexes (Cheng et al., 2007; Liu et al., 2006, 2005; Chen et al., 2001). So far, most of the second ligands selected to coligate with the azide have been neutral (Escuer et al., 2000; Gao et al., 2003; Meyer et al., 2003; Lewis et al., 2004; Koner et al., 2004). Anionic coligands have not been widely studied because of the added complication of having two different negative ligands that must coexist and compete in the same molecule (Cheng et al., 2007; Liu et al., 2006, 2005; Chen et al., 2001). Isonicotinic acid (Hinic), as a good source of a negative carboxylate ligand, has been applied in transition-metal–azide systems to construct metal-organic frameworks and a few such complexes have been synthesized (Zeng et al., 2006; Liu et al., 2006, 2005). However, the combination of azide with the negative carboxylate coligands has been applied with p-block metals only rarely, with just one discrete compound reported (Fischer et al., 1999). So far, coordination polymers of p-block metals with azide and carboxylate coligands have not been reported. In this context, we carried out the reaction of Pb₃(OH)₂(CO₃)₂ with NaN₃ and Hinic under hydrothermal conditions and isolated a novel Pb^II complex, [Pb(inic)(N₃)(H₂O)]_n (I). We report the crystal stucture here. To the best of our knowledge, (I) is the first reported p-block metal–azide–carboxylate coordination polymer.

Compound (I) crystallizes in the monoclinic space group P2₁/c and the asymmetric unit contains one Pb^II ion, one isonicotinate anion, one azide anion and one water molecule. The Pb^II center is seven-coordinated by three N atoms from three azide ligands, two O atoms from two Hinic ligands and two O atoms from two coodinated water molecules, forming a distorted monocaped triangular prismatic coordination geometry (Fig. 1). Each azide anion ligates three equivalent Pb^II ions in the µ_1,1,3 coordination mode to form a honeycomb-like two-dimensional layer structure (Fig. 2). The Pb—N bond lengths (Table 1) are similar to reported values (Marandi, Mirtamizdoust, Soudi & Fun, 2007; Marandi, Mirtamizdoust, Chantrapromma & Fun, 2007; Fischer et al., 1999). The deprotonated carboxylate group and the aqua ligand act as coligands in a syn–anti carboxylate and a µ²-aqua bridging mode, respectively, to link the Pb^II ions. The inic and aqua coligands are distributed on both sides of the two-dimensional layer. To emphasize the nature of the Pb-atom net bridged by azide, inic or aqua ligands, each Pb atom can be regarded as a three-connected node bridged to three nearest neighbor Pb atoms by a pair of `double-bridge' ligands [with Pb···Pb separations of 4.480–4.514 Å and Pb···Pb···Pb angles of 89.26–166.73° (are s.u. values available?)]. By defining each seven-coordinated Pb atom as a three-connected node, the two-dimensional network in (I) can be described as a two-dimensional three-connected topology with short and long Schläfli vertical symbols of 6³ and 6.6.6 (Smith, 1978; O'Keeffe & Hyde, 1996, 1997). Within the two-dimensional layer, one hydrogen-bonding interaction is formed bewteen an aqua ligand and a carboxylate O atom (Table 2). Adjacent two-dimensional layers are further interlinked by hydrogen-bonding interactions between the water molecule and the isonicotinate N atom into a three-dimensional supramolecular framework (Fig. 3).

Compared with the reported lead azide complexes [Pb(phen)(N₃)₂]_n and [Pb(deta)(N₃).(N₃)]_n (phen and deta are 1,10-phenanthroline and diethylentriamine, respectively; Marandi, Mirtamizdoust, Soudi & Fun, 2007), the difference in the charge of the coligand [negative carboxylate in (I) versus neutral phen or deta] leads to a different ratio of Pb and N₃ [1:1 for (I) versus 1:2 for the reported complexes]. As a result, the three-dimensional framework of (I) is constructed from genuinely two-dimensional layers formed completely via the bridging ligand. By contrast, in the reported [Pb(phen)(N₃)₂]_n and [Pb(deta)(N₃).(N₃)]_n complexes, the three-dimensional supramolecular frameworks were constructed from quasitwo-dimensional layers, which were formed by the weak Pb—N interaction and lone pair activity between the adjacent one-dimensional chains.

Related literature

For related literature, see: Chen et al. (2001); Cheng et al. (2007); Escuer et al. (2000); Fischer et al. (1999); Gao et al. (2003); Koner et al. (2004); Lewis et al. (2004); Liu et al. (2005, 2006, 2007); Marandi, Mirtamizdoust, Chantrapromma & Fun (2007); Marandi, Mirtamizdoust, Soudi & Fun (2007); Meyer et al. (2003); O'Keeffe & Hyde (1997); Ray et al. (2008); Smith (1978); Yue et al. (2008); Zeng et al. (2005, 2006).

S2. Experimental

A mixture of Pb₃(OH)₂(CO₃)₂ (0.25 mmol, 0.1939 g), NaN₃ (0.5 mmol, 0.0325 g), isonicotinic acid (0.3 mmol, 0.0330 g) and distilled water (8 ml) was sealed in a 25 ml Teflon-lined stainless steel autoclave and heated to 393 K for 3 d. After cooling to room temperature at a rate of 10 K h^-1, colourless crystals of the title compound suitable for X-ray analysis were isolated from the solution by filtration. Caution: Azide complexes are potentially explosive. Only a small amount of the materials should be prepared and handled with care.

S3. Refinement

Carbon-bound H atoms were positioned geometrically and were included in the refinement in the riding-model approximation, with C–H = 0.93 Å and U_iso(H) = 1.2*Ueq(C). Water H atoms were located in a difference Fourier map and were refined with a distance restraint of O—H = 0.84 (1) Å.

Computing details

Data collection: CrystalClear (Rigaku, 2002); cell refinement: CrystalClear (Rigaku, 2002); data reduction: CrystalClear (Rigaku, 2002); program(s) used to solve structure: SHELXTL (Sheldrick, 2008); program(s) used to refine structure: SHELXTL (Sheldrick, 2008); molecular graphics: SHELXTL (Sheldrick, 2008); software used to prepare material for publication: SHELXTL (Sheldrick, 2008).

Figures

	Fig. 1. A view of (I), showing the atom-labelling scheme. Displacement ellipsoids are drawn at the 30% probability level and H atoms have been omitted for clarity. [Symmetry codes: (i) x, -y + 3/2, z - 1/2; (ii) -x + 1, -y + 2, -z + 1; (iii) x, -y + 3/2, z + 1/2; (iv) -x + 1, y + 1/2, -z + 1/2.] iv doesn't match table 2
	Fig. 2. The two-dimensional coordination polymer formed by Pb^II and N3^- in (I). The view is onto the bc plane. The inic and aqua ligands have been omitted for clarity.
	Fig. 3. A packing diagram of (I), showing the N···H–Owater hydrogen-bond network in the adjacent two-dimensional layers (dashed lines). H atoms not involved in hydrogen bonding have been omitted.

Poly[(µ₂-aqua-κ²O:O)(µ₃-azido- κ³N¹:N³:N³)(µ₂-isonicotinato- κ²O:O')lead(II)]

Crystal data

[Pb(C6H4NO2)(N3)(H2O)]	F(000) = 704
Mr = 389.34	Dx = 3.016 Mg m^−3
Monoclinic, P21/c	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: -P 2ybc	Cell parameters from 25 reflections
a = 10.815 (2) Å	θ = 12–18°
b = 12.963 (3) Å	µ = 19.66 mm^−1
c = 6.3422 (13) Å	T = 298 K
β = 105.33 (3)°	Prism, colourless
V = 857.5 (3) Å^3	0.18 × 0.15 × 0.10 mm
Z = 4

Data collection

Rigaku Mercury CCD area-detector diffractometer	1720 independent reflections
Radiation source: fine-focus sealed tube	1660 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.055
ω scans	θmax = 26.4°, θmin = 3.1°
Absorption correction: multi-scan (RAPID-AUTO; Rigaku, 1998)	h = −13→13
Tmin = 0.038, Tmax = 0.135	k = −16→16
5684 measured reflections	l = −7→7

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)] = 0.045	Hydrogen site location: inferred from neighbouring sites
wR(F^2) = 0.127	H atoms treated by a mixture of independent and constrained refinement
S = 1.09	w = 1/[σ^2(Fo^2) + (0.0915P)^2 + 2.9191P] where P = (Fo^2 + 2Fc^2)/3
1720 reflections	(Δ/σ)max = 0.002
133 parameters	Δρmax = 3.03 e Å^−3
3 restraints	Δρmin = −3.02 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
Pb1	0.45204 (2)	0.873907 (19)	0.25014 (4)	0.0209 (2)
O1	0.2276 (5)	0.8183 (4)	0.2412 (10)	0.0319 (13)
O2	0.3297 (5)	0.6678 (5)	0.3288 (9)	0.0277 (12)
OW1	0.3715 (5)	0.9836 (4)	0.5429 (8)	0.0199 (10)
N1	0.5753 (6)	0.7009 (5)	0.1560 (11)	0.0248 (14)
N2	0.5977 (7)	0.6366 (5)	0.2967 (13)	0.0215 (15)
N3	0.6192 (8)	0.5729 (6)	0.4349 (11)	0.0344 (17)
N4	−0.1425 (6)	0.5770 (6)	0.1266 (11)	0.0260 (14)
C1	0.2296 (6)	0.7213 (6)	0.2652 (11)	0.0188 (14)
C2	0.0998 (7)	0.6687 (6)	0.2134 (13)	0.0203 (15)
C3	−0.0124 (7)	0.7240 (6)	0.1069 (12)	0.0201 (14)
H3	−0.0073	0.7924	0.0660	0.024*
C4	−0.1300 (8)	0.6743 (6)	0.0646 (14)	0.0258 (17)
H4	−0.2031	0.7101	−0.0098	0.031*
C5	−0.0366 (7)	0.5251 (7)	0.2264 (13)	0.0256 (18)
H5	−0.0452	0.4570	0.2659	0.031*
C6	0.0878 (8)	0.5679 (6)	0.2756 (12)	0.0216 (15)
H6	0.1592	0.5296	0.3474	0.026*
H1WA	0.304 (5)	1.008 (6)	0.463 (11)	0.026*
H1WB	0.354 (7)	0.948 (6)	0.642 (10)	0.026*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
Pb1	0.0205 (3)	0.0169 (3)	0.0235 (3)	−0.00103 (8)	0.00258 (18)	−0.00351 (8)
O1	0.032 (3)	0.022 (3)	0.042 (3)	−0.013 (2)	0.011 (3)	−0.004 (2)
O2	0.012 (2)	0.043 (4)	0.025 (3)	−0.002 (2)	0.000 (2)	−0.008 (3)
OW1	0.016 (2)	0.019 (3)	0.024 (3)	0.0021 (19)	0.004 (2)	0.002 (2)
N1	0.023 (3)	0.023 (3)	0.030 (4)	−0.001 (3)	0.010 (3)	−0.003 (3)
N2	0.021 (4)	0.015 (3)	0.028 (4)	0.000 (2)	0.004 (3)	−0.003 (3)
N3	0.046 (4)	0.027 (4)	0.024 (4)	0.001 (3)	−0.001 (3)	0.007 (3)
N4	0.021 (3)	0.030 (4)	0.024 (3)	−0.008 (3)	0.002 (3)	−0.004 (3)
C1	0.017 (3)	0.024 (4)	0.016 (3)	−0.001 (3)	0.006 (3)	−0.002 (3)
C2	0.020 (3)	0.018 (4)	0.025 (4)	0.000 (3)	0.010 (3)	−0.002 (3)
C3	0.023 (4)	0.017 (3)	0.020 (4)	0.001 (3)	0.005 (3)	0.005 (3)
C4	0.022 (4)	0.021 (4)	0.034 (5)	0.001 (3)	0.006 (3)	0.002 (3)
C5	0.031 (5)	0.022 (4)	0.024 (4)	−0.009 (3)	0.008 (4)	−0.001 (3)
C6	0.020 (4)	0.023 (4)	0.019 (4)	0.000 (3)	0.000 (3)	−0.003 (3)

Geometric parameters (Å, º)

Pb1—O1	2.518 (5)	N1—Pb1^i	2.744 (7)
Pb1—OW1	2.662 (5)	N2—N3	1.181 (10)
Pb1—O2^i	2.704 (6)	N4—C5	1.334 (10)
Pb1—OW1^ii	2.729 (5)	N4—C4	1.339 (12)
Pb1—N1^iii	2.744 (7)	C1—C2	1.516 (10)
Pb1—N1	2.754 (7)	C2—C6	1.381 (12)
O1—C1	1.266 (9)	C2—C3	1.417 (10)
O2—C1	1.259 (9)	C3—C4	1.387 (10)
O2—Pb1^iii	2.704 (6)	C3—H3	0.9300
OW1—Pb1^ii	2.729 (5)	C4—H4	0.9300
OW1—H1WA	0.84 (7)	C5—C6	1.412 (11)
OW1—H1WB	0.84 (7)	C5—H5	0.9300
N1—N2	1.198 (10)	C6—H6	0.9300
O1—Pb1—OW1	71.18 (17)	N2—N1—Pb1^i	113.9 (5)
O1—Pb1—O2^i	72.76 (18)	N2—N1—Pb1	114.8 (5)
OW1—Pb1—O2^i	129.16 (16)	Pb1^i—N1—Pb1	110.4 (2)
O1—Pb1—OW1^ii	138.72 (17)	N3—N2—N1	179.7 (10)
OW1—Pb1—OW1^ii	67.60 (17)	C5—N4—C4	118.3 (6)
O2^i—Pb1—OW1^ii	135.05 (17)	O2—C1—O1	124.8 (7)
O1—Pb1—N1^iii	98.4 (2)	O2—C1—C2	119.4 (7)
OW1—Pb1—N1^iii	72.65 (17)	O1—C1—C2	115.8 (6)
O2^i—Pb1—N1^iii	147.74 (19)	C6—C2—C3	118.7 (7)
OW1^ii—Pb1—N1^iii	71.54 (18)	C6—C2—C1	121.0 (7)
O1—Pb1—N1	106.33 (19)	C3—C2—C1	120.2 (7)
OW1—Pb1—N1	148.52 (18)	C4—C3—C2	118.9 (7)
O2^i—Pb1—N1	76.2 (2)	C4—C3—H3	120.5
OW1^ii—Pb1—N1	109.77 (17)	C2—C3—H3	120.5
N1^iii—Pb1—N1	76.86 (14)	N4—C4—C3	122.6 (7)
C1—O1—Pb1	107.2 (5)	N4—C4—H4	118.7
C1—O2—Pb1^iii	125.6 (5)	C3—C4—H4	118.7
Pb1—OW1—Pb1^ii	112.40 (17)	N4—C5—C6	123.7 (8)
Pb1—OW1—H1WA	100 (6)	N4—C5—H5	118.1
Pb1^ii—OW1—H1WA	115 (6)	C6—C5—H5	118.1
Pb1—OW1—H1WB	114 (6)	C2—C6—C5	117.7 (7)
Pb1^ii—OW1—H1WB	106 (6)	C2—C6—H6	121.2
H1WA—OW1—H1WB	109 (5)	C5—C6—H6	121.2

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

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
OW1—H1WA···N4^iv	0.84 (7)	1.91 (4)	2.711 (8)	160 (8)
OW1—H1WB···O2^iii	0.84 (7)	1.98 (4)	2.790 (8)	164 (9)

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