{2-[Bis(3-methyl-1H-indol-2-yl)methyl]phenolato-κO}dimethyl(tetrahydrofuran-κO)aluminium(III)

The title compound, [Al(CH3)2(C25H21N2O)(C4H8O)], was isolated as a minor component from a reaction mixture of the parent indolyl ligand and trimethylaluminum in tetrahydrofuran. The ligands adopt a distorted tetrahedral geometry around aluminium. Obvious hydrogen-bonding interactions are not present.

The title compound, [Al(CH 3 ) 2 (C 25 H 21 N 2 O)(C 4 H 8 O)], was isolated as a minor component from a reaction mixture of the parent indolyl ligand and trimethylaluminum in tetrahydrofuran. The ligands adopt a distorted tetrahedral geometry around aluminium. Obvious hydrogen-bonding interactions are not present.

Experimental
Crystal data [Al(CH 3

S1. Comment
The molecule of the title complex ( Fig. 1), has a distorted tetrahedral coordination geometry around aluminum with X-Al-X (X = C, O) angles ranging from 99.26 (5)° to 121.34 (8)°. The phenoxy(bisindolyl)methane ligand is coordinated to aluminum through a deprotonated phenol oxygen that is bent well out of the ideal sp 3 to 140.50 (8)°, consistent with significant π-donation to Al(III) from the phenoxide O. In the crystal structure ( Fig. 2), weak intramolecular N-H···N interactions may stabilize the ligand conformations while weak intermolecular N-H···N interactions may stabilize crystal packing. The distances of these contacts [2.703 (15) Å and 2.734 (14) Å, respectively] are quite long (Steiner, 2002). However, they are slightly less then the sum of the relevant Van der Waals radii.

S3. Refinement
Hydrogen atoms on carbon were added geometrically and refined using a riding model, whereas hydrogen atoms on nitrogen were located in the difference map and refined semi-freely with the help of a distance restraint. U iso values for hydrogen atoms were assigned to be 1.20 times the U eq value of the atom to which they are attached, except for hydrogen atoms on methyl carbon atoms, which were assigned a U iso of 1.50 times the U eq of the methyl carbon atom to which they are attached.  The molecular structure of (I), with atom labels and 50% probability displacement ellipsoids for non-H atoms.  The molecular structure of (I), showing the possible weak intra-and intermolecular hydrogen bonds. Only the atoms involved are labeled and non-involved H atoms are omitted for clarity. Atoms with the 'i′ superscript are related by the inversion operation (1-x,-y,-z).

{2-[Bis(3-methyl-1H-indol-2-yl)methyl]phenolato-κO}dimethyl(tetrahydrofuran-κO)aluminium(III)
Crystal data [Al(CH 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 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 > 2σ(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. An extinction parameter (EXTI in SHELXL-97) refined to zero and was removed from the refinement.