Diazidobis(η-cyclopentadienyl)titanium

Gil, E. Rodulfo de; Burguera, M. de; Rivera, A. V.; Maxfield, Perry L.

doi:10.1107/s0567740877004142

“…Likewise, for the new structure 12 presented in this work, the Ti–Cl bond length (2.335(2) Å) in complex 12 is slightly contracted when compared to other Ti–Cl bond distances (2.346–2.379 Å) in similar titanocene chloride complexes . A comparison of the Ti–N distances in the titanium azide complex 15 versus the known bis(azide) complex, Cp 2 Ti(N 3 ) 2 ( 17 ), also shows that the Ti–N distance (1.991(1) Å) in 15 is smaller than the Ti–N distance (2.03(1) Å) reported for 17 . This consistent bond shortening across the series of Ti–X complexes (where X is the α-heteroatom F ( 1 ), O ( 2 ), Cl ( 12 ), or N ( 15 )) is likely due to the electron-withdrawing effect of the CF 3 ligand, which increases the electrophilicity of the Ti center.…”

Section: Resultssupporting

confidence: 52%

Titanium(IV) Trifluoromethyl Complexes: New Perspectives on Bonding from Organometallic Fluorocarbon Chemistry

Taw

¹

,

Clark

²

,

Mueller

³

et al. 2012

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Trifluoromethyltrimethylsilane, (CH 3 ) 3 SiCF 3 , in the presence of CsF serves as an excellent CF 3 group-transfer reagent, and reaction with Cp 2 TiF 2 in THF gives the titanocene trifluoromethyl fluoride complex Cp 2 Ti(CF 3 )(F) (1; Cp = C 5 H 5 ) in 60% isolated yield. Reaction of complex 1 with the trimethylsilyl reagents, (CH 3 ) 3 SiX (X = OTf = OSO 2 CF 3 , Cl, Br, I, N 3 , and OSO 2 Ph), in a tetrahydrofuran or toluene solution affords the corresponding Ti−CF 3 derivatives Cp 2 Ti(CF 3 )(X) (X = OTf (2), Cl (12), Br (13), I (14), N 3 (15), and OSO 2 Ph ( 16)) in good isolated yields of 67−84%. These compounds have been characterized by a combination of reactivity studies, IR and 1 H/ 13 C{ 1 H}/ 19 F NMR spectroscopies, and single-crystal X-ray diffraction. The Ti−CF 3 linkage in these complexes is remarkably robust, and although the α-C−F bonds are elongated, there is no evidence of an α-fluoride (Ti•••F−CF 2 ) between the electrophilic Ti(IV) metal center and any of the C−F bonds in the trifluoromethyl group in the solid-state or in solution. In the solid-state, these complexes are shock-sensitive; energetic decomposition of Cp 2 Ti(CF 3 )(F) (1) produces uniform spherical nanoparticles ranging from ∼70 to 120 nm in size and porous fluorinated oligomers and polymers containing both −(CF 2 −CF 2 )− and −(CF 2 −CFH)− units, as determined by a combination of SEM, XRD, XRF, XPS, and 19 F MAS NMR. Density functional theory results show good agreement with experimental structural data obtained for Cp 2 Ti(CF 3 )(X) (X = F (1), OTf (2), Cl (12), N 3 (15)) and accurately predicts longer Ti−CF 3 distances than for each specific CH 3 analogue, and the trend extends to structurally related Zr and Hf analogues. Simpler model compounds from groups 4 and 8 (M(CH 3 ) 4 , M(CH 3 ) 3 (CF 3 ), M(CH 3 ) 3 (CCl 3 ), and M(CH 3 ) 3 (CF 2 CF 2 CF 2 CF 3 ); M = Ti, Zr, Hf, Fe, Ru, Os)) were also examined and show that, for group 4 complexes, π-bonding is a significant factor in shortening the strongly ionic M−CH 3 relative to M−CF 3 , whereas for the predominantly covalent group 8 analogues, π-back-bonding helps to shorten the predominantly covalent M−CF 3 relative to M−CH 3 . The bonding analysis suggests that the significant elongation of C−F bonds α to metals is mainly a consequence of the electropositivity of the group 4 metal centers, with minor, if any, contributions from π-effects; the bond-lengthening effect is most pronounced at the α-position and decays rapidly on moving away from the metal.

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The Binary Group 4 Azides [Ti(N₃)₄], [P(C₆H₅)₄][Ti(N₃)₅], and [P(C₆H₅)₄]₂[Ti(N₃)₆] and on Linear TiNNN Coordination

Haiges

¹

,

Boatz

²

,

Schneider

³

et al. 2004

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Whereas numerous partially azide-substituted titanium compounds had been reported, [1][2][3][4][5][6][7] no binary Group 4 azides were known. In a recent theoretical study, the Group 4 metal tetrazides [M(N 3 ) 4 ] (M = Ti, Zr, Hf, Th) were predicted [8] to be vibrationally stable, exhibiting tetrahedral structures with unique linear M À N À NN bond angles (see Figure 1). All the characterized covalent binary azide species possess bent MÀ NÀNN angles.[9] Herein, we report the synthesis, isolation, and characterization of the first binary Group 4 azide species Removal of the volatile products (CH 3 CN, (CH 3 ) 3 SiF, and excess (CH 3 ) 3 SiN 3 ) at ambient temperature results in the isolation of [Ti(N 3 ) 4 ] as an amorphous orange solid. All attempts to obtain single crystals by recrystallization or sublimation were unsuccessful.As expected for a highly endothermic, covalent polyazide species, [Ti(N 3 ) 4 ] is very shock sensitive and can explode violently when touched with a metal spatula or when exposed to a rapid change in temperature (e.g. freezing with liquid nitrogen). Its identity was established by the observed material balance, and vibrational and NMR spectroscopy. The presence of covalent azido ligands [10][11][12][13][14][15] is confirmed by the observed 14 N NMR shifts of d = À134 ppm (N b , Dñ1 = 2 = 26 Hz), À195 ppm (N g , Dñ1 = 2 = 39 Hz) and À255 ppm (N a , extremely broad) in DMSO solution at 25 8C.The observed Raman and IR spectra of solid [Ti(N 3 ) 4 ] are shown in Figure 2, and the frequencies and intensities are listed in the Experimental Section. The experimental vibrational spectra deviate significantly from those calculated for free [Ti(N 3 ) 4 ] at the B3LYP level of theory, [8,16] and resemble those of higher-coordinated compounds with bent MÀNÀNN bonds. Therefore, the predicted [8] tetrahedral structure with linear TiÀNÀNN bonds could not be confirmed. The discrepancy between the calculated and observed spectra arises from solid-state effects. The Ti atoms in [Ti(N 3 ) 4 ] are coordinatively unsaturated seeking higher coordination numbers by the formation of nitrogen bridges, and crystal-structure data will be required for a reliable determination of the precise arrangement of the azido ligands in solid [Ti(N 3 ) 4 ]. The growing of single crystals for such a study will be difficult because the compound is hard to recrystallize and does not sublime without decomposition. The structure determination of free monomeric [Ti(N 3 ) 4 ] and proof for its predicted tetrahedral structure with linear TiÀNÀNN bonds will be even more difficult.

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The Binary Group 4 Azides [Ti(N₃)₄], [P(C₆H₅)₄][Ti(N₃)₅], and [P(C₆H₅)₄]₂[Ti(N₃)₆] and on Linear TiNNN Coordination

Haiges

¹

,

Boatz

²

,

Schneider

³

et al. 2004

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Whereas numerous partially azide-substituted titanium compounds had been reported, [1][2][3][4][5][6][7] no binary Group 4 azides were known. In a recent theoretical study, the Group 4 metal tetrazides [M(N 3 ) 4 ] (M = Ti, Zr, Hf, Th) were predicted [8] to be vibrationally stable, exhibiting tetrahedral structures with unique linear M À N À NN bond angles (see Figure 1). All the characterized covalent binary azide species possess bent MÀ NÀNN angles.[9] Herein, we report the synthesis, isolation, and characterization of the first binary Group 4 azide species Removal of the volatile products (CH 3 CN, (CH 3 ) 3 SiF, and excess (CH 3 ) 3 SiN 3 ) at ambient temperature results in the isolation of [Ti(N 3 ) 4 ] as an amorphous orange solid. All attempts to obtain single crystals by recrystallization or sublimation were unsuccessful.As expected for a highly endothermic, covalent polyazide species, [Ti(N 3 ) 4 ] is very shock sensitive and can explode violently when touched with a metal spatula or when exposed to a rapid change in temperature (e.g. freezing with liquid nitrogen). Its identity was established by the observed material balance, and vibrational and NMR spectroscopy. The presence of covalent azido ligands [10][11][12][13][14][15] is confirmed by the observed 14 N NMR shifts of d = À134 ppm (N b , Dñ1 = 2 = 26 Hz), À195 ppm (N g , Dñ1 = 2 = 39 Hz) and À255 ppm (N a , extremely broad) in DMSO solution at 25 8C.The observed Raman and IR spectra of solid [Ti(N 3 ) 4 ] are shown in Figure 2, and the frequencies and intensities are listed in the Experimental Section. The experimental vibrational spectra deviate significantly from those calculated for free [Ti(N 3 ) 4 ] at the B3LYP level of theory, [8,16] and resemble those of higher-coordinated compounds with bent MÀNÀNN bonds. Therefore, the predicted [8] tetrahedral structure with linear TiÀNÀNN bonds could not be confirmed. The discrepancy between the calculated and observed spectra arises from solid-state effects. The Ti atoms in [Ti(N 3 ) 4 ] are coordinatively unsaturated seeking higher coordination numbers by the formation of nitrogen bridges, and crystal-structure data will be required for a reliable determination of the precise arrangement of the azido ligands in solid [Ti(N 3 ) 4 ]. The growing of single crystals for such a study will be difficult because the compound is hard to recrystallize and does not sublime without decomposition. The structure determination of free monomeric [Ti(N 3 ) 4 ] and proof for its predicted tetrahedral structure with linear TiÀNÀNN bonds will be even more difficult.

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Diazidobis(η-cyclopentadienyl)titanium

Cited by 33 publications

References 3 publications

Titanium(IV) Trifluoromethyl Complexes: New Perspectives on Bonding from Organometallic Fluorocarbon Chemistry

Titanium(IV) Trifluoromethyl Complexes: New Perspectives on Bonding from Organometallic Fluorocarbon Chemistry

The Binary Group 4 Azides [Ti(N₃)₄], [P(C₆H₅)₄][Ti(N₃)₅], and [P(C₆H₅)₄]₂[Ti(N₃)₆] and on Linear TiNNN Coordination

The Binary Group 4 Azides [Ti(N₃)₄], [P(C₆H₅)₄][Ti(N₃)₅], and [P(C₆H₅)₄]₂[Ti(N₃)₆] and on Linear TiNNN Coordination

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Diazidobis(η-cyclopentadienyl)titanium

Cited by 33 publications

References 3 publications

Titanium(IV) Trifluoromethyl Complexes: New Perspectives on Bonding from Organometallic Fluorocarbon Chemistry

Titanium(IV) Trifluoromethyl Complexes: New Perspectives on Bonding from Organometallic Fluorocarbon Chemistry

The Binary Group 4 Azides [Ti(N3)4], [P(C6H5)4][Ti(N3)5], and [P(C6H5)4]2[Ti(N3)6] and on Linear TiNNN Coordination

The Binary Group 4 Azides [Ti(N3)4], [P(C6H5)4][Ti(N3)5], and [P(C6H5)4]2[Ti(N3)6] and on Linear TiNNN Coordination

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The Binary Group 4 Azides [Ti(N₃)₄], [P(C₆H₅)₄][Ti(N₃)₅], and [P(C₆H₅)₄]₂[Ti(N₃)₆] and on Linear TiNNN Coordination

The Binary Group 4 Azides [Ti(N₃)₄], [P(C₆H₅)₄][Ti(N₃)₅], and [P(C₆H₅)₄]₂[Ti(N₃)₆] and on Linear TiNNN Coordination