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Acta Cryst. (2008). E64, m20    [ doi:10.1107/S1600536807062022 ]

Di-[mu]-chlorido-bis[dichlorido(N,N-diethylacetamidinato)(N,N-diethylacetamidine)titanium(IV)] acetonitrile disolvate

N. A. Straessler, M. T. Caudle and T. L. Groy

Abstract top

In the centrosymmetric title compound [Ti2Cl6(C6H13N2)2(C6H14N2)2]·2C2H3N, an inversion center relates the two Ti atoms which display a distorted octahedral coordination geometry. There are two uncoordinated acetonitrile solvent molecules per molecule of title compound in the crystal structure.

Comment top

The structure of title compound, (I) was solved as part of an investigation into the effects of nitriles on N,N-dialkylamido titanium(IV) complexes. Compound (I) is a dimeric molecule in which two symmetrically equivalent titanium atoms are each coordinated by one anionic diethylacetamidino group (N1), one neutral diethylacetamidine ligand (N3), two terminal chlorides (Cl2 and Cl3), and two equivalent bridging chlorides (Cl1). This gives a pseudo–octahedral configuration about each titanium center. The acetamidine and acetamidino ligands are oriented in cis coordination positions.

The Ti2Cl2 unit of (I) is distorted such that the Ti1—Cl1 bond that is trans to the diethylacetamidino ligand is significantly longer than the Ti—Cl1 bond that is trans to Cl3 (2.7002 (8) Å versus. 2.4557 (8) Å). This is consistent with the greater sigma-electron donating ability of the acetamidino ligand relative to the Cl-. The Ti—Cl1—Ti bond angle is 102.96 (3)°, similar to that of other dichloro-bridged Ti4+ compounds (Nielson et al., 2001). The terminal titanium–chloride bond lengths (Ti—Cl2 = 2.3882 (8) Å and Ti—Cl3 = 2.3511 (9) Å) are shorter than the bridging Ti—Cl1 bonds, and are within the normal range for such linkages.

In general, the ligands in (I) bend away from the diethylacetamidino group resulting in bond angles greater than the ideal 90° for octahedral complexes {N1—Ti—Cl3 = 101.24 (9)°, N1—Ti—Cl1 = 95.57 (9)°, N1—Ti—Cl2 = 95.51 (8)°, N1—Ti—N3 = 94.42 (10)°}. This can be attributed to electrostatic repulsion caused by substantial pi–electron donation from the diethylacetamidino nitrogen to the empty 3 d orbitals on Ti4+. The approximately linear Ti—N1—C1 bond angle (165.7 (2)°) and the short Ti—N1 bond length (1.751 (2) Å) indicate significant Ti—N1 multiple–bond character analogous to those observed in titanium(IV) imides (Guiducci et al., 2001; Lewkebandara et al., 1994; Dunn et al., 1994). The Ti—N3 acetamidine bond length is 2.130 (2) Å, which is 0.379 Å longer than the Ti—N1 acetamidino bond length at 1.751 (2) Å, clearly supporting multiple–bond character in the Ti—N1 bond.

Formation of metal–amidine complexes has been shown to occur by two different mechanisms: (1) acetonitrile insertion into metal–amide bonds (Bradley & Ganorkar, 1968; Chandra et al., 1970); (2) nucleophilic attack by free amine on coordinated nitriles in the presence of metal ions (Forsberg et al., 1987; Rouschias & Wilkinson, 1968; Maresca et al., 1986). However, secondary amines such as diethylamine do not react with nitriles in the absence of metal ions. The addition of TiCl4 to acetonitrile results in a yellow solvate formed by coordination of CH3CN to the titanium atom. We speculate that (I) then most likely forms via mechanism 2 because the metal-nitrogen linkage to the nitrile is established before addition of diethylamine. Furthermore, direct insertion of CH3CN has been reported to only occur slowly (Bradley & Ganorkar, 1968), whereas we observe reaction of diethylamine with the TiCl4–acetonitrile solvate to occur immediately.

Related literature top

For the structure, see: Dunn et al. (1994); Guiducci et al. (2001); Lewkebandara et al. (1994); Nielson et al. (2001). For the reaction mechanism, see: Bradley & Ganorkar (1968); Chandra et al. (1970); Forsberg et al. (1987); Maresca et al. (1986); Rouschias & Wilkinson (1968).

Experimental top

While stirring under an atmosphere of nitrogen, 2 ml (18.24 mmol) of TiCl4 were added to approximately 50 ml of anhydrous acetonitrile in a Schlenk flask. To the resulting bright yellow solution was added 5.66 ml (54.71 mmol) of diethylamine. The exothermic reaction turned dark orange and white solid began to precipitate immediately. After twelve hours of stirring, solid white diethylammonium chloride was removed by filtration under nitrogen, and the filtrate was concentrated by intermittent evaporation with a stream of nitrogen over a period of four days. Removal of almost half of the solvent yielded X-ray quality crystals of I.

Refinement top

Hydrogen atoms were positioned geometrically and allowed to ride on their bonding partners with C—H distances = 0.96Å and Uiso(H) = 1.5Ueq(C) for the methyl H atoms, C—H distances = 0.97Å and Uiso(H) = 1.2Ueq(C) for the methylene H atoms, and N—H distance = 0.86Å and Uiso(H) = 1.2Ueq(N) for the amino hydrogen.

Computing details top

Data collection: SMART (Bruker, 2003); cell refinement: SAINT (Bruker, 2003); data reduction: SAIN(Bruker, 2003); program(s) used to solve structure: SHELXS97 (Sheldrick, 1997); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: SHELXTL (Sheldrick, 2003b); software used to prepare material for publication: SHELXTL (Sheldrick, 2003b).

Figures top
[Figure 1] Fig. 1. Thermal ellipsoid plot of centrosymmetric title compund shown at the 30% probability level. Solvent molecules and hydrogen atoms omitted for clarity. Only unique atoms are labeled.
Di-µ-chlorido-bis[dichlorido(N,N-diethylacetamidinato)(N,N- diethylacetamidine)titanium(IV)] acetonitrile disolvate top
Crystal data top
[Ti2Cl6(C6H13N2)2(C6H14N2)2]·2C2H3NZ = 1
Mr = 845.36F000 = 444
Triclinic, P1Dx = 1.282 Mg m−3
Hall symbol: -P 1Mo Kα radiation
λ = 0.71073 Å
a = 9.6217 (6) ÅCell parameters from 5597 reflections
b = 11.1812 (7) Åθ = 4.7–55.0º
c = 11.2298 (8) ŵ = 0.76 mm−1
α = 95.680 (1)ºT = 298 (2) K
β = 105.192 (1)ºBlock, orange
γ = 106.938 (1)º0.30 × 0.15 × 0.15 mm
V = 1095.03 (12) Å3
Data collection top
Bruker SMART APEX
diffractometer		3871 independent reflections
Radiation source: fine-focus sealed tube2999 reflections with I > 2σ(I)
Monochromator: graphiteRint = 0.045
T = 298(2) Kθmax = 25.0º
ω scanθmin = 1.9º
Absorption correction: multi-scan
(SADABS; Sheldrick, 2003a)		h = −11→11
Tmin = 0.870, Tmax = 0.890k = −13→13
8928 measured reflectionsl = −13→13
Refinement top
Refinement on F2Secondary atom site location: difference Fourier map
Least-squares matrix: fullHydrogen site location: inferred from neighbouring sites
R[F2 > 2σ(F2)] = 0.045H-atom parameters constrained
wR(F2) = 0.134  w = 1/[σ2(Fo2) + (0.0851P)2]
where P = (Fo2 + 2Fc2)/3
S = 1.02(Δ/σ)max < 0.001
3871 reflectionsΔρmax = 0.82 e Å−3
215 parametersΔρmin = −0.28 e Å−3
Primary atom site location: structure-invariant direct methodsExtinction correction: none
Crystal data top
[Ti2Cl6(C6H13N2)2(C6H14N2)2]·2C2H3Nγ = 106.938 (1)º
Mr = 845.36V = 1095.03 (12) Å3
Triclinic, P1Z = 1
a = 9.6217 (6) ÅMo Kα
b = 11.1812 (7) ŵ = 0.76 mm−1
c = 11.2298 (8) ÅT = 298 (2) K
α = 95.680 (1)º0.30 × 0.15 × 0.15 mm
β = 105.192 (1)º
Data collection top
Bruker SMART APEX
diffractometer		3871 independent reflections
Absorption correction: multi-scan
(SADABS; Sheldrick, 2003a)		2999 reflections with I > 2σ(I)
Tmin = 0.870, Tmax = 0.890Rint = 0.045
8928 measured reflections
Refinement top
R[F2 > 2σ(F2)] = 0.045215 parameters
wR(F2) = 0.134H-atom parameters constrained
S = 1.02Δρmax = 0.82 e Å−3
3871 reflectionsΔρmin = −0.28 e Å−3
Special details top

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 F2 against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F2, conventional R-factors R are based on F, with F set to zero for negative F2. The threshold expression of F2 > σ(F2) is used only for calculating R-factors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F2 are statistically about twice as large as those based on F, and R- factors based on ALL data will be even larger.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å2) top
xyzUiso*/Ueq
Ti0.68333 (5)0.53749 (4)0.65286 (4)0.04665 (18)
Cl10.62466 (7)0.54169 (6)0.42723 (6)0.0509 (2)
Cl20.65097 (9)0.31620 (6)0.60603 (8)0.0697 (3)
Cl30.66161 (11)0.52732 (8)0.85562 (7)0.0787 (3)
N10.8818 (3)0.5903 (2)0.6847 (2)0.0596 (6)
C11.0294 (5)0.6394 (3)0.6804 (3)0.0803 (10)
C21.0542 (5)0.7145 (5)0.5730 (5)0.135 (2)
H2A1.12190.68770.53580.203*
H2B1.09790.80410.60730.203*
H2C0.95790.69780.51010.203*
N21.1381 (3)0.6309 (3)0.7609 (3)0.0836 (9)
C31.1039 (5)0.5546 (4)0.8621 (4)0.0909 (12)
H3A1.19160.58540.93710.109*
H3B1.01840.56970.88370.109*
C41.0682 (6)0.4183 (5)0.8236 (5)0.136 (2)
H4A1.08270.37990.89670.204*
H4B1.13450.40340.77740.204*
H4C0.96410.38150.77140.204*
C51.2977 (4)0.6763 (4)0.7612 (4)0.0981 (14)
H5A1.30020.68150.67600.118*
H5B1.34660.61530.78970.118*
C61.3848 (5)0.8030 (5)0.8434 (5)0.132 (2)
H6A1.48550.83190.83530.198*
H6B1.39170.79640.92920.198*
H6C1.33340.86260.81890.198*
N30.6676 (3)0.72414 (19)0.66808 (19)0.0484 (5)
H3C0.58730.72820.61480.058*
C70.7531 (3)0.8339 (2)0.7406 (2)0.0480 (6)
C80.8672 (3)0.8363 (3)0.8616 (3)0.0621 (8)
H8A0.85640.75070.87380.093*
H8B0.84990.88230.93000.093*
H8C0.96840.87760.85840.093*
N40.7431 (3)0.9462 (2)0.7128 (2)0.0579 (6)
C90.8370 (4)1.0706 (3)0.7955 (3)0.0731 (9)
H9A0.86731.13230.74430.088*
H9B0.92891.06240.85010.088*
C100.7545 (5)1.1182 (4)0.8737 (4)0.1025 (14)
H10A0.81751.20110.92220.154*
H10B0.73121.06080.92930.154*
H10C0.66151.12370.82030.154*
C110.6473 (4)0.9544 (3)0.5929 (3)0.0742 (10)
H11A0.62731.03460.60060.089*
H11B0.55030.88620.57050.089*
C120.7191 (6)0.9456 (5)0.4896 (4)0.1124 (16)
H12A0.65900.96370.41530.169*
H12B0.72360.86120.47210.169*
H12C0.82041.00610.51570.169*
N50.7942 (7)0.9547 (5)0.1738 (6)0.175 (2)
C130.7192 (6)0.8570 (5)0.1685 (5)0.1060 (14)
C140.6195 (7)0.7345 (5)0.1617 (6)0.1335 (18)
H14A0.52410.74020.16830.200*
H14B0.66390.69770.22930.200*
H14C0.60250.68190.08280.200*
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
Ti0.0470 (3)0.0384 (3)0.0445 (3)0.0127 (2)−0.0004 (2)0.0059 (2)
Cl10.0511 (4)0.0509 (4)0.0447 (4)0.0153 (3)0.0081 (3)0.0041 (3)
Cl20.0661 (5)0.0421 (4)0.0841 (6)0.0206 (4)−0.0059 (4)0.0067 (4)
Cl30.0915 (6)0.0739 (5)0.0456 (4)0.0040 (5)0.0037 (4)0.0171 (4)
N10.0457 (14)0.0528 (14)0.0677 (15)0.0153 (11)0.0003 (11)0.0041 (11)
C10.076 (2)0.073 (2)0.081 (2)0.032 (2)0.008 (2)−0.0126 (18)
C20.079 (3)0.152 (5)0.187 (5)0.022 (3)0.055 (3)0.099 (4)
N20.0541 (17)0.082 (2)0.097 (2)0.0180 (15)0.0127 (16)−0.0198 (17)
C30.083 (3)0.103 (3)0.084 (3)0.041 (2)0.006 (2)0.027 (2)
C40.126 (4)0.097 (4)0.134 (4)0.023 (3)−0.022 (3)0.010 (3)
C50.051 (2)0.118 (3)0.113 (3)0.027 (2)0.022 (2)−0.027 (3)
C60.058 (2)0.137 (4)0.159 (5)−0.001 (3)0.030 (3)−0.046 (4)
N30.0502 (13)0.0409 (12)0.0443 (12)0.0163 (10)−0.0014 (9)0.0029 (9)
C70.0476 (15)0.0463 (15)0.0444 (14)0.0132 (12)0.0093 (12)0.0026 (11)
C80.0627 (19)0.0536 (17)0.0512 (17)0.0114 (15)−0.0018 (13)0.0011 (13)
N40.0654 (16)0.0363 (12)0.0557 (14)0.0118 (11)0.0013 (11)−0.0024 (10)
C90.083 (2)0.0399 (16)0.072 (2)0.0089 (16)0.0028 (17)−0.0060 (14)
C100.134 (4)0.077 (3)0.090 (3)0.044 (3)0.022 (3)−0.013 (2)
C110.093 (2)0.0432 (16)0.070 (2)0.0233 (16)−0.0030 (18)0.0061 (14)
C120.150 (4)0.106 (3)0.071 (3)0.026 (3)0.029 (3)0.032 (2)
N50.170 (5)0.122 (4)0.249 (6)0.012 (3)0.132 (5)0.038 (4)
C130.102 (3)0.101 (3)0.132 (4)0.028 (3)0.069 (3)0.031 (3)
C140.144 (5)0.101 (4)0.162 (5)0.029 (3)0.065 (4)0.041 (3)
Geometric parameters (Å, °) top
Ti—N11.751 (2)N3—C71.307 (3)
Ti—N32.130 (2)N3—H3C0.8600
Ti—Cl32.3511 (9)C7—N41.348 (3)
Ti—Cl22.3882 (8)C7—C81.498 (4)
Ti—Cl12.4557 (8)C8—H8A0.9600
Ti—Cl1i2.7002 (8)C8—H8B0.9600
Cl1—Tii2.7002 (8)C8—H8C0.9600
N1—C11.381 (4)N4—C111.447 (4)
C1—N21.225 (4)N4—C91.478 (3)
C1—C21.566 (6)C9—C101.484 (5)
C2—H2A0.9600C9—H9A0.9700
C2—H2B0.9600C9—H9B0.9700
C2—H2C0.9600C10—H10A0.9600
N2—C51.469 (4)C10—H10B0.9600
N2—C31.534 (5)C10—H10C0.9600
C3—C41.454 (6)C11—C121.506 (5)
C3—H3A0.9700C11—H11A0.9700
C3—H3B0.9700C11—H11B0.9700
C4—H4A0.9600C12—H12A0.9600
C4—H4B0.9600C12—H12B0.9600
C4—H4C0.9600C12—H12C0.9600
C5—C61.485 (6)N5—C131.106 (6)
C5—H5A0.9700C13—C141.406 (7)
C5—H5B0.9700C14—H14A0.9600
C6—H6A0.9600C14—H14B0.9600
C6—H6B0.9600C14—H14C0.9600
C6—H6C0.9600
N1—Ti—N394.42 (10)C5—C6—H6C109.5
N1—Ti—Cl3101.24 (9)H6A—C6—H6C109.5
N3—Ti—Cl390.72 (6)H6B—C6—H6C109.5
N1—Ti—Cl295.51 (8)C7—N3—Ti134.05 (18)
N3—Ti—Cl2168.45 (6)C7—N3—H3C113.0
Cl3—Ti—Cl293.10 (3)Ti—N3—H3C113.0
N1—Ti—Cl195.57 (9)N3—C7—N4123.2 (2)
N3—Ti—Cl184.04 (6)N3—C7—C8119.0 (2)
Cl3—Ti—Cl1162.74 (4)N4—C7—C8117.8 (2)
Cl2—Ti—Cl189.15 (3)C7—C8—H8A109.5
N1—Ti—Cl1i172.61 (9)C7—C8—H8B109.5
N3—Ti—Cl1i84.93 (6)H8A—C8—H8B109.5
Cl3—Ti—Cl1i86.13 (3)C7—C8—H8C109.5
Cl2—Ti—Cl1i84.46 (3)H8A—C8—H8C109.5
Cl1—Ti—Cl1i77.04 (3)H8B—C8—H8C109.5
Ti—Cl1—Tii102.96 (3)C7—N4—C11121.7 (2)
C1—N1—Ti165.7 (2)C7—N4—C9123.6 (2)
N2—C1—N1121.7 (4)C11—N4—C9114.5 (2)
N2—C1—C2120.8 (4)N4—C9—C10112.4 (3)
N1—C1—C2117.4 (3)N4—C9—H9A109.1
C1—C2—H2A109.5C10—C9—H9A109.1
C1—C2—H2B109.5N4—C9—H9B109.1
H2A—C2—H2B109.5C10—C9—H9B109.1
C1—C2—H2C109.5H9A—C9—H9B107.9
H2A—C2—H2C109.5C9—C10—H10A109.5
H2B—C2—H2C109.5C9—C10—H10B109.5
C1—N2—C5125.3 (4)H10A—C10—H10B109.5
C1—N2—C3117.5 (3)C9—C10—H10C109.5
C5—N2—C3116.9 (3)H10A—C10—H10C109.5
C4—C3—N2113.5 (4)H10B—C10—H10C109.5
C4—C3—H3A108.9N4—C11—C12112.4 (3)
N2—C3—H3A108.9N4—C11—H11A109.1
C4—C3—H3B108.9C12—C11—H11A109.1
N2—C3—H3B108.9N4—C11—H11B109.1
H3A—C3—H3B107.7C12—C11—H11B109.1
C3—C4—H4A109.5H11A—C11—H11B107.9
C3—C4—H4B109.5C11—C12—H12A109.5
H4A—C4—H4B109.5C11—C12—H12B109.5
C3—C4—H4C109.5H12A—C12—H12B109.5
H4A—C4—H4C109.5C11—C12—H12C109.5
H4B—C4—H4C109.5H12A—C12—H12C109.5
N2—C5—C6112.4 (3)H12B—C12—H12C109.5
N2—C5—H5A109.1N5—C13—C14178.0 (6)
C6—C5—H5A109.1C13—C14—H14A109.5
N2—C5—H5B109.1C13—C14—H14B109.5
C6—C5—H5B109.1H14A—C14—H14B109.5
H5A—C5—H5B107.9C13—C14—H14C109.5
C5—C6—H6A109.5H14A—C14—H14C109.5
C5—C6—H6B109.5H14B—C14—H14C109.5
H6A—C6—H6B109.5
Symmetry codes: (i) −x+1, −y+1, −z+1.
Acknowledgements top

We express our gratitude to the National Science Foundation for their contribution toward the purchase of the single-crystal instrumentation used in this study through Award #CHE-9808440.

references
References top

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