Bis[1-(3,5-di-tert-butyl-2-hydroxybenzyl)-3-isopropylimidazolium] pentachlorido(tetrahydrofuran)samarate(III)–tetrahydrofuran–toluene (1/1/1)

The title compound, (C21H33N2O)2[SmCl5(C4H8O)]·C7H8·C4H8O, has a layered structure in which each distorted octahedral [SmCl5(THF)]2− unit (THF is tetrahydrofuran) is capped by two cations. The central metal SmIII atom of the [SmCl5(THF)]2− anionic unit is coordinated by five Cl atoms and one THF O atom, forming a distorted octahedral geometry. The crystal structure displays C—H⋯Cl and O—H⋯Cl hydrogen bonding. The structure exhibits disorder of the solvent.

The title compound, (C 21

Comment
Recently, the anionic functionalized N-heterocyclic carbenes( NHCs), such as amino-or phenoxo(alkoxo)-NHCs, have attracted much more attention particularly in the field of rare earth metals as the anionic tether can be used as anchor to enhance the bond of NHC to these electropositive metals (Arnold et al.,2006;Liddle et al., 2007). A series of anionic functionalized NHCs have been synthesized and structurally characterized (Arnold et al., 2009;Wang et al., 2006a ). However, the reaction of ligands with cerium triiodide (Arnold et al.,2005) or ytterbium trichloride (Wang et al., 2006a) in the presence of organic base gives no desired product. Especially noteworthy is the cleavage reaction of the ligand that occurs during the reaction process ( Wang et al., 2006b ). For a better understanding of the reason, the complex [NdCl 5 (THF)] 2-[HO-3,5-dit Bu-C 6 H 2 -2-CH 2 {CH(NCHCHN i Pr)] 2+ (Yao et al., 2007) has been studied. In order to further study these compounds, the title complex has been synthesized. Although the ion-pair structure has recently been reported for LnI 3 in sulfonium-based ionic liquids (Babai et al.,2005), its structural feature is different from that of the title complex. In [SEt 3 ] 3 [NdI 6 ], SEt 3 is a triethylsulfonium cation; an octahedron [NdI 6 ] 3is capped by triethylsulfonium cations (SEt 3 ) via the coordination of Nd 3+ to SEt 3 . The X-ray crystal analysis of the title complex indicates that the bis- [(3,5-ditertbutyl-2-hydroxybenzyl

Refinement
H atoms were positioned geometrically (C-H = 0.95-1.00 A\%) and included in the refinement in the riding-model approximation, with Uiso(H) = 1.2 or 1.5 times Ueq(C). The highest electron-density peak is 0.97 A \% from atom H24. The program SQUEEZE was used to handle the disordered THF and toluene molecules. Fig. 1. The molecular structure of the title compound showing 30% probability displacement ellipsoids and atom-numbering scheme.

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 > σ(F 2 ) is used only for calculating Rfactors(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.