Crystal structure of tribenzylbis(tetrahydrofuran-κO)lutetium(III)

In the compound [Lu(C7H7)3(C4H8O)2], the Lu ion is coordinated by three benzyl and two tetrahydrofuran ligands. Two of the benzyl groups are bonded in a classical η1-fashion through the methylene via the ipso-carbon atom of the benzyl ligand in addition to bonding through the methylene C atom, resulting in a modified trigonal–bipyramidal coordination geometry about the Lu center.

The mixed modes of benzyl coordination in the title compound are in contrast to the structure of the related hexacoordinate tris-THF compound, [Lu(CH 2 Ph) 3 (THF) 3 ], in which all of the benzyl ligands are 1 -coordinated (Meyer et al., 2008(Meyer et al., , 2013. The structural results provide yet another example of the importance of the metal size in the series of homologous [RE(CH 2 Ph) 3 (THF) 2 ] (RE = Sc, Er, Lu) compounds: the complex featuring the small scandium center shows all three benzyl ligands adopting the 1 -bonding mode (Meyer et al., 2008), whereas the larger lutetium can allow one of the three benzyl ligands to adopt the more stericallydemanding 2 -bonding mode; indeed, the Lu compound is isomorphous with the similarly-sized erbium complex, [Er( 2 -CH 2 Ph)( 1 -CH 2 Ph) 2 (THF) 2 ] (Huang et al., 2013), with metrical parameters reflecting the small decrease in ionic radius from erbium to lutetium (Shannon, 1976).

Supramolecular features
The closest intermolecular contacts are between benzyl carbons C11 and C12 and the THF methylene-group hydrogen H1B (at x À 1, y, z), at 2.80 and 2.89 Å , respectively, and between the benzyl carbon C16 and the phenyl-group hydrogen H22 (at Àx, Ày, 1 À z), at 2.86 Å . These interactions connect the complexes in a supramolecular ribbon running along the a-axis direction
X-ray quality crystals of compound 1 were obtained by cooling a dilute toluene solution of the compound to 243 K for several days. Molecular structure of 1 in the crystal. Displacement ellipsoids are shown at the 50% probability level. Hydrogen atoms are shown with arbitrarily small displacement parameters.

Refinement
Crystal data, data collection and structure refinement details are summarized in Table 1. Hydrogen atoms were generated in idealized positions according to the sp 2 or sp 3 geometries of their attached carbon atoms, and given isotropic displacement parameters U iso (H) = 1.2U eq (parent atom). C-H distances in the CH 2 groups were constrained to 0.99 Å and those in phenyl-ring C-H groups to 0.95 Å .

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.