Issue contents
Download PDF of article
Download CIF
3D view
Navigation
Highlighting
Dictionary of Crystallography reference
IUPAC Gold Book reference
more ...
Download citation
FormatBIBTeX
EndNote
RefMan
Refer
Medline
CIF
SGML
Plain Text
share
Previous article
Next article
Previous article
Issue contents
Download PDF of article
Download CIF
3D view
Navigation
Highlighting
Dictionary of Crystallography reference
IUPAC Gold Book reference
more ...
Download citation
FormatBIBTeX
EndNote
RefMan
Refer
Medline
CIF
SGML
Plain Text
share
Next article

metal-organic compounds\(\def\hfill{\hskip 5em}\def\hfil{\hskip 3em}\def\eqno#1{\hfil {#1}}\)

Journal logoCRYSTALLOGRAPHIC
COMMUNICATIONS
ISSN: 2056-9890
Volume 68| Part 11| November 2012| Page m1338
doi:10.1107/S1600536812040913

Poly[(μ-1,3-thio­cyanato-κN,S)(iso­nicotin­ato-κN,O)(ethanol-κO)cadmium(II)]

Tristan Neumann,a Julia Werner,a Inke Jessa and Christian Näthera*

aInstitut für Anorganische Chemie, Christian-Albrechts-Universität Kiel, Max-Eyth-Strasse 2, 24118 Kiel, Germany
*Correspondence e-mail: cnaether@ac.uni-kiel.de

(Received 12 September 2012; accepted 28 September 2012; online 6 October 2012)

In the crystal structure of the title compound, [Cd(NCS)(C6H4NO2)(C2H5OH)]n, the Cd2+ cation is coordinated by one N and two O atoms of two symmetry-related isonicotinate anions, one ethanol mol­ecule and two μ-1,3-bridging thio­cyanate anions in a distorted octa­hedral N2O3S geometry. The metal cations are μ-1,3-bridged via thio­cyanate anions into chains that are further connected into layers parallel to the ab plane by bridging isonicotinate anions. The layers are stacked along the c axis. The crystal structure is stabilized by O—H⋯O hydrogen bonds.

Related literature

For general background information, including details of thermal decomposition reactions and magnetic properties, see: Näther & Greve (2003[Näther, C. & Greve, J. (2003). J. Solid State Chem., 176, 259-265.]); Boeckmann & Näther (2010[Boeckmann, J. & Näther, C. (2010). Dalton Trans. 39, 11019-11026.], 2011[Boeckmann, J. & Näther, C. (2011). Chem. Commun. 47, 7104-7106.]); Wöhlert et al. (2011[Wöhlert, S., Boeckmann, J., Wriedt, M. & Näther, C. (2011). Angew. Chem. Int. Ed. 50, 6920-6923.]). For related structures, see: Yang et al. (2001[Yang, G., Zhu, H. G., Liang, B.-H. & Chen, X. M. (2001). Dalton Trans. pp. 580-585.]). For a description of the Cambridge Structural Database, see: Allen (2002[Allen, F. H. (2002). Acta Cryst. B58, 380-388.]).

[Scheme 1]

Experimental

Crystal data

  • [Cd(NCS)(C6H4NO2)(C2H6O)]

  • Mr = 338.65

  • Monoclinic, P 21 /c

  • a = 5.7778 (2) Å

  • b = 16.1804 (6) Å

  • c = 13.0855 (6) Å

  • β = 94.685 (3)°

  • V = 1219.24 (8) Å3

  • Z = 4

  • Mo Kα radiation

  • μ = 1.96 mm−1

  • T = 293 K

  • 0.28 × 0.10 × 0.04 mm
Data collection

  • Stoe IPDS-1 diffractometer

  • Absorption correction: numerical (X-SHAPE and X-RED32; Stoe, 2008[Stoe (2008). X-AREA, X-RED32 and X-SHAPE. Stoe & Cie, Darmstadt, Germany.]) Tmin = 0.803, Tmax = 0.931

  • 17537 measured reflections

  • 2920 independent reflections

  • 2545 reflections with I > 2σ(I)

  • Rint = 0.032
Refinement

  • R[F2 > 2σ(F2)] = 0.026

  • wR(F2) = 0.061

  • S = 1.06

  • 2920 reflections

  • 145 parameters

  • H-atom parameters constrained

  • Δρmax = 0.38 e Å−3

  • Δρmin = −0.44 e Å−3

Table 1
Hydrogen-bond geometry (Å, °)

D—H⋯A D—H H⋯A D⋯A D—H⋯A
O21—H1O1⋯O12i 0.82 1.89 2.703 (3) 172
Symmetry code: (i) x-1, y, z.

Data collection: X-AREA (Stoe, 2008[Stoe (2008). X-AREA, X-RED32 and X-SHAPE. Stoe & Cie, Darmstadt, Germany.]); cell refinement: X-AREA; data reduction: X-AREA; program(s) used to solve structure: SHELXS97 (Sheldrick, 2008[Sheldrick, G. M. (2008). Acta Cryst. A64, 112-122.]); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008[Sheldrick, G. M. (2008). Acta Cryst. A64, 112-122.]); molecular graphics: XP in SHELXTL (Sheldrick, 2008[Sheldrick, G. M. (2008). Acta Cryst. A64, 112-122.]) and DIAMOND (Brandenburg, 2011[Brandenburg, K. (2011). DIAMOND. Crystal Impact GbR, Bonn, Germany.]); software used to prepare material for publication: publCIF (Westrip, 2010[Westrip, S. P. (2010). J. Appl. Cryst. 43, 920-925.]).

Supporting information

Crystal structure: contains datablocks I, global. DOI: 10.1107/S1600536812040913/bt6838sup1.cif

Structure factors: contains datablock I. DOI: 10.1107/S1600536812040913/bt6838Isup2.hkl

checkCIF report


Comment top

The structure of the title compound was prepared within a project on the synthesis of transition metal thiocyanato coordination polymers in which the metal cations are µ-1,3 bridged by the anionic ligands (Näther & Greve, 2003; Boeckmann & Näther, 2010, 2011; Wöhlert et al., 2011). In the course of our investigations crystals of the title compound were obtained and characterized by single-crystal X-ray diffraction.

In the crystal structure the cadmium(II) cations are coordinated by one N and two O atoms of two µ-1,3,6 bridging isonicotinato anions which are related by symmetry, one N and one S atom of two symmetry-related µ-1,3 bridging thiocyanato anions and one O atom of an ethanol molecule (Fig. 1). The coordination polyhedron of the cadmium cations can be described as a slightly distorted octahedron (Table 1).

The Cd2+ cations are µ-1,3 bridged by thiocyanato anions into chains, which elongate in the direction of the crystallographic a axis. These chains are bridged by µ-1,3,6 bridging isonicotinato anions into layers in the direction of the crystallographic b axis and the layers are stacked along the crystallographic c axis (Fig. 2).

The shortest Cd···Cd distances within the layers amounts to 5.7778 (3) Å and to 9.2393 (4) Å. It must be noted that according to research in the CCDC database (ConQuest Ver.1.14; Allen, 2002) one coordination compound based on Cd(NCS)2, isonicotinato anions and thiocyanato anions is known, in which ethanol is exchanged by water. The overall coordination topology is similar but this compound is not isotypic to the title compound (Yang et al., 2001).

The crystal structure is stabilized by an O—H···O hydrogen bond.

Related literature top

For general background information, including details of thermal decomposition reactions and magnetic properties, see: Näther & Greve (2003); Boeckmann & Näther (2010, 2011); Wöhlert et al. (2011). For related structures, see: Yang et al. (2001). For a description of the Cambridge Structural Database, see: Allen (2002).

Experimental top

Potassium thiocyanate and isonicotinic acid were purchased from Alfa Aesar, Cd(SO4)2.4H2O was obtained from Merck. The Cd(NCS)2 was prepared by stirring Ba(NCS)2.3H2O (3.076 g, 10 mmol) and CdSO4.8/3H2O (2.566 g, 10 mmol) in water (100 ml). The white precipitate of BaSO4 was filtered off and the water was removed from the filtrate by heating. The final product was dried at 80°C. The homogeneity of the product was investigated by X-ray powder diffraction. The title compound was prepared by the reaction of 34.3 mg Cd(NCS)2(0.15 mmol) and 36.9 mg isonicotinic acid (0.30 mmol) in 2 ml ethanol at 80°C in a closed 10 ml glass culture tube. After several days colourless needles of the title compound were obtained.

Refinement top

The C—H H atoms were positioned with idealized geometry (methyl H atoms allowed to rotate but not to tip) and were refined isotropically with Uiso(H) = 1.2Ueq(C) for aromatic H atoms (1.5 for methyl H atoms) using a riding model with C—H = 0.93 Å (aromatic H atoms) and with C—H = 0.96 Å (methyl H atoms). The O—H H atom was located in difference map, its bond length set to ideal value of 0.82 Å and finally it was refined using a riding model with Uiso(H) = 1.2Ueq(O).

Computing details top

Data collection: X-AREA (Stoe, 2008); cell refinement: X-AREA (Stoe, 2008); data reduction: X-AREA (Stoe, 2008); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: XP in SHELXTL (Sheldrick, 2008) and DIAMOND (Brandenburg, 2011); software used to prepare material for publication: publCIF (Westrip, 2010).

Figures top
[Figure 1] Fig. 1. Crystal structure of the title compound with labelling and displacement ellipsoids drawn at the 50% probability level. Symmetry code: i = -x + 1, y + 1/2, -z + 3/2.
[Figure 2] Fig. 2. Crystal structure of the title compound with view in the direction of the crystallographic c axis.
Poly[(µ-1,3-thiocyanato-κN,S)(isonicotinato- κN,O)(ethanol-κO)cadmium(II)] top
Crystal data top
[Cd(NCS)(C6H4NO2)(C2H6O)]F(000) = 664
Mr = 338.65Dx = 1.845 Mg m−3
Monoclinic, P21/cMo Kα radiation, λ = 0.71073 Å
a = 5.7778 (2) ÅCell parameters from 17537 reflections
b = 16.1804 (6) Åθ = 2.0–28.0°
c = 13.0855 (6) ŵ = 1.96 mm−1
β = 94.685 (3)°T = 293 K
V = 1219.24 (8) Å3Needle, colourless
Z = 40.28 × 0.10 × 0.04 mm
Data collection top
Stoe IPDS-1
diffractometer		2920 independent reflections
Radiation source: fine-focus sealed tube2545 reflections with I > 2σ(I)
Graphite monochromatorRint = 0.032
ϕ scansθmax = 28.0°, θmin = 2.0°
Absorption correction: numerical
(X-SHAPE and X-RED32; Stoe, 2008)		h = −7→7
Tmin = 0.803, Tmax = 0.931k = −21→21
17537 measured reflectionsl = −17→17
Refinement top
Refinement on F2Primary atom site location: structure-invariant direct methods
Least-squares matrix: fullSecondary atom site location: difference Fourier map
R[F2 > 2σ(F2)] = 0.026Hydrogen site location: inferred from neighbouring sites
wR(F2) = 0.061H-atom parameters constrained
S = 1.06 w = 1/[σ2(Fo2) + (0.0288P)2 + 0.6822P]
where P = (Fo2 + 2Fc2)/3
2920 reflections(Δ/σ)max = 0.001
145 parametersΔρmax = 0.38 e Å−3
0 restraintsΔρmin = −0.44 e Å−3
Crystal data top
[Cd(NCS)(C6H4NO2)(C2H6O)]V = 1219.24 (8) Å3
Mr = 338.65Z = 4
Monoclinic, P21/cMo Kα radiation
a = 5.7778 (2) ŵ = 1.96 mm−1
b = 16.1804 (6) ÅT = 293 K
c = 13.0855 (6) Å0.28 × 0.10 × 0.04 mm
β = 94.685 (3)°
Data collection top
Stoe IPDS-1
diffractometer		2920 independent reflections
Absorption correction: numerical
(X-SHAPE and X-RED32; Stoe, 2008)		2545 reflections with I > 2σ(I)
Tmin = 0.803, Tmax = 0.931Rint = 0.032
17537 measured reflections
Refinement top
R[F2 > 2σ(F2)] = 0.0260 restraints
wR(F2) = 0.061H-atom parameters constrained
S = 1.06Δρmax = 0.38 e Å−3
2920 reflectionsΔρmin = −0.44 e Å−3
145 parameters
Special details top

Geometry. All esds (except the esd in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell esds are taken into account individually in the estimation of esds in distances, angles and torsion angles; correlations between esds in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell esds is used for estimating esds 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 > 2sigma(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 (Å2) top
xyzUiso*/Ueq
Cd10.14587 (3)0.856111 (10)0.668028 (15)0.04089 (7)
N1−0.1966 (4)0.8771 (2)0.5822 (2)0.0667 (8)
C1−0.3839 (5)0.87582 (19)0.5463 (2)0.0492 (6)
S1−0.65079 (13)0.87510 (7)0.49397 (6)0.0662 (2)
N110.7272 (4)0.48256 (13)0.77586 (18)0.0432 (5)
C110.5200 (6)0.49095 (17)0.7245 (3)0.0578 (8)
H110.44170.44370.70050.069*
C120.4168 (5)0.56691 (17)0.7052 (2)0.0540 (7)
H120.27220.57020.66870.065*
C130.5275 (4)0.63720 (15)0.7401 (2)0.0396 (5)
C140.7445 (5)0.62913 (15)0.7913 (2)0.0480 (6)
H140.82750.67570.81450.058*
C150.8372 (5)0.55133 (16)0.8077 (2)0.0490 (6)
H150.98340.54660.84260.059*
C160.4083 (5)0.71974 (15)0.7252 (2)0.0426 (5)
O110.2091 (4)0.71926 (12)0.67857 (18)0.0592 (5)
O120.5052 (3)0.78408 (11)0.75867 (17)0.0510 (5)
O21−0.0682 (4)0.84635 (14)0.81279 (16)0.0572 (5)
H1O1−0.20250.83100.79960.086*
C210.0069 (7)0.8386 (3)0.9186 (3)0.0778 (11)
H21A0.14540.87200.93270.093*
H21B0.04970.78150.93240.093*
C22−0.1619 (11)0.8630 (4)0.9880 (4)0.129 (2)
H22A−0.09820.85521.05740.193*
H22B−0.29900.82980.97570.193*
H22C−0.20100.92010.97710.193*
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
Cd10.03291 (10)0.03170 (10)0.05680 (12)−0.00051 (7)−0.00408 (7)0.00070 (8)
N10.0336 (12)0.098 (2)0.0675 (16)0.0051 (13)−0.0028 (11)0.0164 (15)
C10.0382 (14)0.0617 (17)0.0476 (14)0.0037 (12)0.0028 (11)0.0077 (12)
S10.0357 (3)0.1101 (7)0.0514 (4)−0.0010 (4)−0.0046 (3)0.0062 (4)
N110.0401 (11)0.0317 (10)0.0569 (13)0.0011 (8)−0.0020 (10)−0.0014 (9)
C110.0541 (17)0.0349 (13)0.080 (2)−0.0018 (12)−0.0226 (16)−0.0042 (13)
C120.0452 (15)0.0390 (13)0.0739 (19)0.0016 (12)−0.0192 (14)0.0019 (13)
C130.0386 (12)0.0341 (11)0.0466 (13)0.0009 (10)0.0053 (10)0.0031 (10)
C140.0381 (13)0.0320 (12)0.0724 (18)−0.0039 (10)−0.0043 (12)−0.0003 (11)
C150.0381 (13)0.0376 (13)0.0692 (18)0.0013 (10)−0.0074 (13)−0.0007 (12)
C160.0408 (13)0.0357 (12)0.0517 (14)0.0007 (10)0.0052 (11)0.0057 (11)
O110.0486 (11)0.0379 (10)0.0880 (15)0.0055 (9)−0.0130 (11)0.0024 (10)
O120.0483 (11)0.0317 (9)0.0721 (13)0.0001 (8)−0.0004 (9)0.0024 (8)
O210.0479 (11)0.0665 (14)0.0564 (12)−0.0085 (10)−0.0011 (9)0.0004 (10)
C210.072 (2)0.092 (3)0.066 (2)0.011 (2)−0.0128 (18)0.0078 (19)
C220.125 (5)0.201 (7)0.059 (2)0.049 (4)−0.002 (3)0.000 (3)
Geometric parameters (Å, º) top
Cd1—N12.220 (3)C12—H120.9300
Cd1—O112.247 (2)C13—C141.379 (4)
Cd1—N11i2.275 (2)C13—C161.508 (3)
Cd1—O212.351 (2)C14—C151.378 (4)
Cd1—O122.583 (2)C14—H140.9300
Cd1—S1ii2.6644 (9)C15—H150.9300
Cd1—C162.746 (3)C16—O121.245 (3)
N1—C11.144 (4)C16—O111.258 (3)
C1—S11.635 (3)O21—C211.422 (4)
S1—Cd1iii2.6644 (9)O21—H1O10.8199
N11—C111.331 (4)C21—C221.441 (7)
N11—C151.331 (3)C21—H21A0.9700
N11—Cd1iv2.275 (2)C21—H21B0.9700
C11—C121.380 (4)C22—H22A0.9600
C11—H110.9300C22—H22B0.9600
C12—C131.365 (4)C22—H22C0.9600
N1—Cd1—O11108.39 (10)C12—C13—C14117.8 (2)
N1—Cd1—N11i106.05 (11)C12—C13—C16119.9 (2)
O11—Cd1—N11i145.09 (8)C14—C13—C16122.3 (2)
N1—Cd1—O2184.95 (9)C15—C14—C13119.2 (2)
O11—Cd1—O2188.73 (8)C15—C14—H14120.4
N11i—Cd1—O2188.70 (8)C13—C14—H14120.4
N1—Cd1—O12161.97 (10)N11—C15—C14123.0 (2)
O11—Cd1—O1253.60 (7)N11—C15—H15118.5
N11i—Cd1—O1291.82 (7)C14—C15—H15118.5
O21—Cd1—O1293.19 (7)O12—C16—O11122.9 (2)
N1—Cd1—S1ii89.26 (8)O12—C16—C13120.5 (2)
O11—Cd1—S1ii94.89 (7)O11—C16—C13116.6 (2)
N11i—Cd1—S1ii91.09 (6)O12—C16—Cd169.29 (14)
O21—Cd1—S1ii173.91 (6)O11—C16—Cd153.83 (13)
O12—Cd1—S1ii92.90 (5)C13—C16—Cd1169.39 (19)
N1—Cd1—C16135.24 (11)C16—O11—Cd199.30 (16)
O11—Cd1—C1626.87 (8)C16—O12—Cd183.93 (15)
N11i—Cd1—C16118.58 (8)C21—O21—Cd1130.7 (2)
O21—Cd1—C1692.37 (8)C21—O21—H1O1112.8
O12—Cd1—C1626.78 (7)Cd1—O21—H1O1113.7
S1ii—Cd1—C1693.06 (6)O21—C21—C22114.9 (3)
C1—N1—Cd1168.3 (3)O21—C21—H21A108.5
N1—C1—S1179.2 (3)C22—C21—H21A108.5
C1—S1—Cd1iii96.29 (10)O21—C21—H21B108.5
C11—N11—C15117.4 (2)C22—C21—H21B108.5
C11—N11—Cd1iv120.52 (17)H21A—C21—H21B107.5
C15—N11—Cd1iv121.17 (18)C21—C22—H22A109.5
N11—C11—C12122.7 (3)C21—C22—H22B109.5
N11—C11—H11118.7H22A—C22—H22B109.5
C12—C11—H11118.7C21—C22—H22C109.5
C13—C12—C11119.8 (3)H22A—C22—H22C109.5
C13—C12—H12120.1H22B—C22—H22C109.5
C11—C12—H12120.1
Symmetry codes: (i) −x+1, y+1/2, −z+3/2; (ii) x+1, y, z; (iii) x−1, y, z; (iv) −x+1, y−1/2, −z+3/2.
Hydrogen-bond geometry (Å, º) top
D—H···AD—HH···AD···AD—H···A
O21—H1O1···O12iii0.821.892.703 (3)172
Symmetry code: (iii) x−1, y, z.

Experimental details

Crystal data
Chemical formula[Cd(NCS)(C6H4NO2)(C2H6O)]
Mr338.65
Crystal system, space groupMonoclinic, P21/c
Temperature (K)293
a, b, c (Å)5.7778 (2), 16.1804 (6), 13.0855 (6)
β (°) 94.685 (3)
V (Å3)1219.24 (8)
Z4
Radiation typeMo Kα
µ (mm−1)1.96
Crystal size (mm)0.28 × 0.10 × 0.04
Data collection
DiffractometerStoe IPDS1
diffractometer
Absorption correctionNumerical
(X-SHAPE and X-RED32; Stoe, 2008)
Tmin, Tmax0.803, 0.931
No. of measured, independent and
observed [I > 2σ(I)] reflections		17537, 2920, 2545
Rint0.032
(sin θ/λ)max (Å−1)0.660
Refinement
R[F2 > 2σ(F2)], wR(F2), S 0.026, 0.061, 1.06
No. of reflections2920
No. of parameters145
H-atom treatmentH-atom parameters constrained
Δρmax, Δρmin (e Å−3)0.38, −0.44

Computer programs: X-AREA (Stoe, 2008), SHELXS97 (Sheldrick, 2008), SHELXL97 (Sheldrick, 2008), XP in SHELXTL (Sheldrick, 2008) and DIAMOND (Brandenburg, 2011), publCIF (Westrip, 2010).

Hydrogen-bond geometry (Å, º) top
D—H···AD—HH···AD···AD—H···A
O21—H1O1···O12i0.82001.89002.703 (3)172.00
Symmetry code: (i) x−1, y, z.
 

Acknowledgements

The authors gratefully acknowledge financial support from the DFG (project No. NA720/3-1) and the State of Schleswig–Holstein. We thank Professor Dr Wolfgang Bensch for access to his experimental facilities.

References

First citationAllen, F. H. (2002). Acta Cryst. B58, 380–388.  Web of Science CrossRef CAS IUCr Journals Google Scholar
 First citationBoeckmann, J. & Näther, C. (2010). Dalton Trans. 39, 11019–11026.  Web of Science CSD CrossRef CAS PubMed Google Scholar
 First citationBoeckmann, J. & Näther, C. (2011). Chem. Commun. 47, 7104–7106.  Web of Science CSD CrossRef CAS Google Scholar
 First citationBrandenburg, K. (2011). DIAMOND. Crystal Impact GbR, Bonn, Germany.  Google Scholar
 First citationNäther, C. & Greve, J. (2003). J. Solid State Chem., 176, 259–265.  Google Scholar
 First citationSheldrick, G. M. (2008). Acta Cryst. A64, 112–122.  Web of Science CrossRef CAS IUCr Journals Google Scholar
 First citationStoe (2008). X-AREA, X-RED32 and X-SHAPE. Stoe & Cie, Darmstadt, Germany.  Google Scholar
 First citationWestrip, S. P. (2010). J. Appl. Cryst. 43, 920–925.  Web of Science CrossRef CAS IUCr Journals Google Scholar
 First citationWöhlert, S., Boeckmann, J., Wriedt, M. & Näther, C. (2011). Angew. Chem. Int. Ed. 50, 6920–6923.  Google Scholar
 First citationYang, G., Zhu, H. G., Liang, B.-H. & Chen, X. M. (2001). Dalton Trans. pp. 580–585.  CrossRef CAS Google Scholar

This is an open-access article distributed under the terms of the Creative Commons Attribution (CC-BY) Licence, which permits unrestricted use, distribution, and reproduction in any medium, provided the original authors and source are cited.

Journal logoCRYSTALLOGRAPHIC
COMMUNICATIONS
ISSN: 2056-9890
Volume 68| Part 11| November 2012| Page m1338
doi:10.1107/S1600536812040913
Follow Acta Cryst. E
Sign up for e-alerts
E-alerts
Follow Acta Cryst. on Twitter
Twitter
Follow us on facebook
Facebook
Sign up for RSS feeds
RSS