Tetrakis(N,N-diethylcarbamato)titanium(IV)

The mononuclear title compound, [Ti(C5H10NO2)4], is a rare example of an eight-coordinate TiIV compound in which all donor atoms are O atoms. The coordination geometry around TiIV is pseudo-dodecahedral and the O—C—O angles of the carbamate ligands are slightly compressed [range 115.3 (2)–116.7 (2)°], apparently on account of the high coordination number. One ethyl group is disordered over two positions; the site occupancy factors are 0.64 and 0.36.

The coordination environment around the Ti IV atom in the title compound consists of eight O atoms derived from the four bidentate carbamato ligands. The Ti-O bond distances are all similar, ranging between 2.0530 (15) and 2.1087 (16) Å, while the O-C-O angles of the carbamate ligands range from 115.3 (2) to 116.7 (2)°. These angles are considerably smaller than O-C-O angles in complexes having terminal η 1 or µ 1,3 -bridging carbamato ligands, which tend to be greater than 120°, and they are small even when compared to other bidentate carbamato ligands (Dell'Amico et al., 2003;McCowan et al., 2004). The compressed O-C-O angles in the title compound are attributed in part to the high coordination number about the Ti IV center, which has the effect of forcing the O atoms closer to one another.
Eight-coordinate Ti IV compounds are rare, particularly in an environment consisting solely of O donor ligands (Dell'Amico et al., 2000). The title compound has a similar core structure to tetrakis(N,N-diisopropylcarbamato)titanium(IV) (Dell'Amico et al., 2000), which together with the six-coordinate distorted octahedral compound bis(dimethylamido)bis(N,N-dimethylcarbamato)titanium(IV) (Chisholm & Extine, 1977b) are the only other crystallographically characterized mononuclear carbamato complexes of Ti IV .

Experimental
While stirring under an atmosphere of N 2 , 1.00 ml (9.12 mmol) of TiCl 4 was added to approximately 70 ml of anhydrous THF in a Schlenk flask. A yellow solid formed that dissolved within several minutes. To the resulting bright yellow solution was added 7.50 ml (72.50 mmol) of anhydrous diethylamine. The mixture turned dark blue, almost black, in color. After ten minutes the flask was evacuated of all N 2 and charged with 1 atm of anhydrous CO 2 gas which caused the reaction mixture to turn yellow/orange and precipitate solid. After stirring overnight, solid white diethylammonium chloride was removed by filtration under N 2 . Approximately 30 ml freshly distilled n-hexane was added to the clear light yellow filtrate and the volume was reduced by slow evaporation under a stream of N 2 . This gave 2.85 g (61%) of pale yellow crystals suitable for X-ray analysis.

Refinement
H atoms were positioned geometrically and allowed to ride with C-H = 0.96 Å, U iso (H) = 1.5U eq (C) for the methyl groups and C-H = 0.97 Å, U iso (H) = 1.2U eq (C) for the methylene groups. One ethyl group on the diethylcarbamate ligand supplementary materials sup-2 containing N1A is disordered. Atoms C1D-C1E represent the majority component (site occupancy factor 0.639 (4)) and C1D'-C1E' represent the minority component (site occupancy factor 0.361 (4)). The components were refined with N-C and C-C bond lengths restrained to 1.46 (1) and 1.48 (1) Å, respectively, and with anisotropic displacement parameters constrained to be identical for the atom pairs C1D/C1D' and C1E/C1E'. Data were collected at 263 K because the crystals undergo what is believed to be a destructive phase transformation somewhere in the range 173-243 K. Fig. 1. Molecular structure of the title compound with displacement ellipsoids shown at the 25% probability level. H atoms are omitted. Disorder of one ethyl group bonded to N1A is shown using C1D-C1E as the major component and C1D'-C1E' as the minor component.

Tetrakis(N,N-diethylcarbamato)titanium(IV)
Crystal data [Ti(C 5   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.