[6,6′-Bis(1,1-dimethylethyl)-4,4′-dimethyl-2,2′-methylenediphenolato-κ2 O,O′]dichlorido(9H-fluoren-9-ol-κO)titanium(IV)–fluorene–diethyl ether (1/0.5/1)

The title adduct, [TiCl2(C23H30O2)(C13H10O]·0.5C13H10·C4H10O, is a monomer with a trigonal–bypyramidal coordination sphere of the TiIV atom in which the ligand O atoms of the bidentate diphenolate anion are located in both apical and equatorial positions. Chloride ligands occupy the remaining two equatorial sites of the trigonal bypyramid with the fluoren-9-ol O atom occupying the other apical site. The hydroxy group H atom of this latter group is hydrogen bonded to an O atom of a non-coordinating diethyl ether molecule. The title compound also contains a further fluorene solvent molecule, which lies across a centre of symmetry and which is equally disordered over an inversion centre.

The title adduct, [TiCl 2 (C 23 H 30 O 2 )(C 13 H 10 O]Á0.5C 13 H 10 Á-C 4 H 10 O, is a monomer with a trigonal-bypyramidal coordination sphere of the Ti IV atom in which the ligand O atoms of the bidentate diphenolate anion are located in both apical and equatorial positions. Chloride ligands occupy the remaining two equatorial sites of the trigonal bypyramid with the fluoren-9-ol O atom occupying the other apical site. The hydroxy group H atom of this latter group is hydrogen bonded to an O atom of a non-coordinating diethyl ether molecule. The title compound also contains a further fluorene solvent molecule, which lies across a centre of symmetry and which is equally disordered over an inversion centre.

Experimental
Crystal data [TiCl 2 (C 23  H atoms treated by a mixture of independent and constrained refinement Á max = 0.35 e Å À3 Á min = À0.37 e Å À3 Table 1 Selected bond lengths (Å ).  product. Over the extended crystallization period a small quantity of crystals was obtained and these were found to be the The overall coordination geometry of the molecule is that of a distorted trigonal bipyramid with the oxygen atom of one side of the bidentate bis-phenolato ligand in one apical position and the oxygen atom of the fluoren-9-ol ligand in the other apical site. This positioning is similar to that of the two other 5-coordinate molecules characterized by X-ray crystallography (Okuda et al. 1995;Gielens et al.1999). The crystal structure also shows that there is also a half-weighted fluorene molecule, C 13 H 10 contained in the unit cell which is not coordinated to the metal. This lies across a centre of symmetry.

Experimental
Using normal bench-top techniques for air-sensitive compounds, n-butyl lithium (3.8 ml of a 1.6 mol/L solution, 6.02 mmol) was added dropwise to a solution of fluorene (1.00 g, 6.02 mmol) in diethyl ether (30 ml) cooled to 78°C and the mixture was warmed to room temperature and stirred for a further 2 h. The solution was added dropwise to a solution of [TiCl 2 {(OAr) 2 }] (2.83 g, 6.02 mmol) in diethyl ether (50 ml), chilled to 0°C and the mixture allowed to warm to room temperature and the stirring continued overnight. The solution was filtered, the volume reduced to ca 20 ml and the solution stood at -20° C for several months whereupon a small quantity of colourless crystals was formed. A crystal was chosen from the mass and the X-ray crystal structure obtained.

Refinement
All H atoms, except H4, were included in calculated positions and refined using a riding model [U(H) eq = 1.2UC eq for aromatic CH and U(H) = 1.5U(C) for methyl H atoms]. C-H distances of 0.96 Å and 0.93 Å were assumed for aromatic and methyl groups respectively. For H4, the atom involved in the H-bonding, the positional parameters were refined but the thermal parameter was held constant at 0.08.
The non H-bonded solvent molecule was half-weighted since it lay across the centre of symmetry and its two sixmembered rings were refined as rigid groups.

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 > σ(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.