[(2R,3S)-Butane-1,2,3,4-tetraol-κ3 O 1,O 2,O 3](ethanol-κO)tris(nitrato-κ2 O,O′)samarium(III)

The title SmIII–erythritol complex, [Sm(NO3)3(C2H6O)(C4H10O4)], is isotypic with its Nd, Eu, Y, Gd, Tb and Ho analogues. The SmIII cation exhibits a coordination number of ten and is chelated by a tridentate erythritol ligand and three bidentate nitrate anions. It is additionally coordinated by an O atom of an ethanol molecule, completing an irregular coordination sphere. The Sm—O bond lengths range from 2.416 (2) to 2.611 (2) Å. In the crystal, extensive O—H⋯O hydrogen bonding involving all hydroxy groups and some of the nitrate O atoms links the molecules into a three-dimensional network.

The title Sm [Sm(NO 3 ) 3 (C 2 H 6 O)-(C 4 H 10 O 4 )], is isotypic with its Nd, Eu, Y, Gd, Tb and Ho analogues. The Sm III cation exhibits a coordination number of ten and is chelated by a tridentate erythritol ligand and three bidentate nitrate anions. It is additionally coordinated by an O atom of an ethanol molecule, completing an irregular coordination sphere. The Sm-O bond lengths range from 2.416 (2) to 2.611 (2) Å . In the crystal, extensive O-HÁ Á ÁO hydrogen bonding involving all hydroxy groups and some of the nitrate O atoms links the molecules into a threedimensional network.
Here the sugar alcohol erythritol was chosen as a model compound to study the coordination behavior of hydroxyl groups to f-block metal ions.
The molecular structure of the title complex, [Sm(C 4 H 10 O 4 )(C 2 H 5 OH)(NO 3 ) 3 ], denoted as SmEN, where E stands for erythritol, N stands for nitrate, is shown in Fig. 1. In the title compound the Sm III cation is 10-fold coordinated by three hydroxyl groups (O1, O2 and O3) from one erythritol molecule, by one hydroxyl group from ethanol (O5), and by three bidentate nitrate ions through O6, O7; O9, O10; O12, O13. The structure of SmEN is isotypic with its Nd, Eu, Y, Gd, Tb (Yang et al., 2003(Yang et al., , 2004(Yang et al., , 2012 and Ho (Hua et al., 2013) analogues. The Sm-O distances range from 2.416 (2) to 2.611 (2) Å, the average Sm-O distance being 2.499 Å. The C-C-C and the O-C-C bond angles of the central backbone in the free centrosymmetric erythritol molecule are 113° and 107°, respectively (Bekoe & Powell, 1959). After The coordinating O2 hydroxyl group forms a bifurcated hydrogen bonds with two oxygen atoms from a nitrate ion (O7, O8). The coordinating hydroxyl group O3 forms a hydrogen bond with an oxygen atom from another nitrate ion (O12).
The non-coordinating hydroxyl group O4 is a donor of a bifurcated hydrogen bond to O8 and O6 from one nitrate ion.
The ethanol hydroxy group (O5) forms a hydrogen bond with an oxygen atom from a nitrate ion (O11). Details of the hydrogen bonding are given in Table 1 and Fig. 2.

Experimental
Sm(NO 3 ) 3 . 6H 2 O (3 mmol) and erythritol (3 mmol) were dissolved in 6 ml water and 6 ml ethanol. The solution was put on a water bath, and the temperature was raised to 353 K. Small aliquots of EtOH were periodically added to the solution during the heating process to prolong the reaction time. The resulting mixture was filtered and left for crystallization at room temperature. Suitable crystals for X-ray diffraction measuraments were obtained in the course of two weeks.

Refinement
C-bound H-atoms were placed in calculated positions and were included in the refinement in the riding model approximation, U iso (H) = 1.5U eq (C) for methyl group carbon atoms, U iso (H) = 1. bound H atoms were located in a difference Fourier map and were refined with distance constraints of O-H = 0.84 Å, U iso (H) = 1.2U eq (O). The two highest peaks in the difference map are 1.33 and 0.97 eper Å 3 , respectively. The corresponding distances to the nearest atom, Sm1, are 0.866 and 0.864 Å.

Figure 1
The molecular structure of the title complex with displacement ellipsoids drawn at the 30% probability level. Hydrogen atoms have been omitted for clarity.  The packing of the title complex, showing hydrogen bond interactions as dashed lines.

[(2R,3S)-Butane-1,2,3,4-tetraol-κ 3 O 1 ,O 2 ,O 3 ](ethanol-κO)tris(nitrato-κ 2 O,O′)samarium(III)
Crystal data [Sm(NO 3  where P = (F o 2 + 2F c 2 )/3 (Δ/σ) max = 0.001 Δρ max = 1.33 e Å −3 Δρ min = −0.72 e Å −3 Special details 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 F 2 against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F 2 , conventional R-factors R are based on F, with F set to zero for negative F 2 . The threshold expression of F 2 > 2sigma(F 2 ) is used only for calculating R-factors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F 2 are statistically about twice as large as those based on F, and R-factors based on ALL data will be even larger.