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Synthesis and characterization of bis(cyclopentadienyl)bis(hexafluoroantimonato) titanium(IV)
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Polyhedron Vol. I, No. 13, pp. 12214223.1988 Printed in Great Britain
COMMUNICATION SYNTHESIS AND CHARACTERIZATION OF BIS(CYCLOPENTADIENYL)BIS(HEXAFLU~ROANTIMONATO) TITANIUM(IV)* TH. KLAPOTKE Institut fur Anorganische und Analytische Chemie, Technische Universitat Berlin, D-1000 Berlin 12, F.R.G. (Received 14 March 1988 ; accepted 23 March 1988) Abstract-Reaction of titanocene dichloride with two equivalents of silver hexafluoroantimonate in sulphur dioxide quantitatively yields CpzTi(SbF& (Cp = $-C,H,) and AgCl. The titanocene bishexafluoroantimonate was recrystallized from SO* and characterized by chemical analysis, ‘H NMR, IR and mass spectroscopy.
Transition metal halides have been reported to possess Lewis base qualities and it has been assumed that the metal-halide bond is not broken in the complexes formed. ’ Adduct formation between Cp,TiF,,and Lewis acids (e.g. BF3 and PFS) has been investigated. However, by these reactions and by treatment of Cp,TiClz with two equivalents of AgBF4 (or AgPFJ only oils could be obtained.’ The isolation of Cp,TiF* has been reported from reactions involving fluorine-containing reagents such as the silver salts of CF3S-,3 BF;, PF;, SbF; and AsF; ;4 but in these cases no complex of the type Cp,Ti(MF&t was either isolated or identified. Titanocene derivatives containing MF; groups, directly coordinated to the Cp,Ti centre, have not previously been described, so this was the reason to study this particular problem in organometallic chemistry. The synthesis of a compound like Cp,Ti(MF& seemed to be of interest in terms of the Cp,Ti-MF6 bond situation (ionic or Ti-F bond interaction with reduced MF, symmetry: Oh + C4J, its stability (decomposition routes and mechanism), and last but not least the possibility that (Cp,Ti(NR,):+(SbF&) (known as a stable
* Organo-transition metal chemistry of highly fluorinated ligand systems (Organo-fjhergangsmetall-Chemie hochlluorierter Ligand-Systeme) : first communication. t (M = pnictogen).
complex’) may be the only preparation of (Cp,Ti (SO&+(SbF;),). The first results on this project are reported in this paper. Reaction of Cp,TiCll with two equivalents of AgSbFQ (Alfa) in SO1 at -20°C quantitatively yielded the precipitation of AgCl and led to the formation of Cp,Ti(SbF& (1) according to eq. (1). Cp,TiClz+2AgSbF, “‘(‘) rCp,Ti(SbF,),+2AgClJ. - 20°C
(1)
(1)
1, which is highly soluble in SO2 (deep red solution), was separated from AgCl by filtration (D4) and recrystallized from the same solvent at room temperature (yield, 94%). The chemical analysis (C1,,H10F12Sb2Ti, M = 649,55 gmol-‘. Found: C, 18.3; H, 1.35. Calc. for CloH,,,FlzSbzTi: C, 18.5; H, 1.55%) of the deep red microcrystalline air- and moisture-sensitive solid is in very good agreement with the composition CpaTi(SbF& and there is no evidence for coordinated S02. While the ‘H NMR spectrum of CpzTiF, consists of a triplet in the Cp region3s6 in the ‘H NMR spectrum of 1 (SO2 solution, relative to TMS) only one very sharp singlet appears in the Cp range at 6 = 7.25 ppm (6, Cp,TiClz = 6.65 ppm). This value and the low-field shift, compared with Cp,TiClz, indicate a partial dissociation of 1 in solution
1221
1222
Communication
3100
1400
1000 vlcm
600
-‘I
Fig. 1. IR spectrum of solid Cp,Ti(SbF& in the regions 1600-200 cm-’ (Perkin-Elmer 457).
according
to eq. (2) (cf. ref. 4). 1 so2o)b(Cp*Ti(S~~)~+(SbF~~*).
(2)
The mass spectrum of 1 (electron-impact, 70 eV, 60°C) does not show a peak due to the molecular ion but to one corresponding to CpTiF3. This fact and also the appearance of SbFz indicate that a fluorine transfer from the SbF6 group to the transition metal occurs as a decomposition reaction at low temperature. The base peak is given by Cp’. Figure 1 shows the IR spectrum of 1, obtained with the pure powdered compound. IR values and assignments are given in Table 1. All bands due to the Cp,Ti fragment are quite strong and nearly unchanged compared with those of CpzTiFz. In the spectrum of Cp,TiFz, bands at 564 and 539 cm- ’ have been assigned to the Ti-F
Table 1. IR frequencies of Cp,Ti(SbF& Frequency (cm- ‘) 3110s 1435 s 1025 m,sh 1015 s 845 vs 665 vs 640 vs 535 s so5 s 287 vs 275 vs
Assignment V-CH W-CC s-CH &CH y-CH v,,-SbF, v, 2 v,,-SbF 1 v,-TiF v,,-TiF a-SbF4 ,,,z &SbF, t
260 and 3200-3000 cm- ’
symmetric and asymmetric stretching modes, respectively.’ However, in 1 these bands are shifted to 535 and 505 cm-‘. This indicates weaker Ti-F bonds in 1 compared with Cp,TiFz. This is in agreement with a fluorine bridged structure where a “divalent” fluorine is coordinated to both the Cp,Ti group and a “SbF,” unit. The lower symmetry (C,,) of the SbF6 system (0, in SbF;) with five short (strong) and one long (weak) Sb-F bonds leads as expected to a splitting of the v3 and v4 bands at 650 and 285 cm’ ‘, respectively.8-10 While Cp2Ti(PF& seems to be unstable in the solid state, the antimony analogue is described as the first stable and well characterized titanocene MF6 (M = pnictogen) compound in the present paper. Our interest will now be extended to the AsF, compounds, as the fluorine affmity of AsFJ is significantly higher than that of PFS” and therefore the preparation of Cp,Ti(AsF,), seems to be very likely. AcknowZe&ement.+Thanks
are given to P. Gowik (TU Berlin) for cooperation in the experimental work and to A. Stijckel (TV Berlin) for carrying out the mass spectroscopy. I also thank M. Schriver for the ‘H NMR spectra and helpful discussions. REFERENCES M. Pankowski, B. Demerseman, G. Bouquet and M. Bigorgne, J. Organomet. Chem. 1972,35, 155 ; T. J. Marks, J. Kristoff, A. Alich and D. F. Shriver, J. ~rganomet. Chem. 1971,33, C35. H. C. Clark and A. Shaver, J. Coord. Chem. 1975, 4,243. R. B. King and N. Welcman, Inorg. Chem. 1969,8,
2540.
Communication G. Doyle and R. S. Tobias, Zrzorg. Chem. 196’7, 6, 1111. K. Berhalter and U. Thewalt, J. Organomet. Chem. 1987,332,123. A. N. Nesmeyanov, 0. V. Nogina, E. I. Fedin, V. A. ~~~ts~i, B. A. Kvasov and P. V. Petrovskii, Dokl. Adad. Nauk. S.S.S.R. 1972,205,857. P. M. Druci, B. M. Kingston, M. F. Lappert, R. C. Srivastava, M. J. Frazer and W. E. Newton, J. Chem. Sot. A 1969,2814.
1223
8. S. Buffagni, L. M. Vallarino and J. V. Quagliano, Znorg. Chem. 1964,3,671. 9. H. C. Clark and R. J. O’Brien, Znorg. Chem. 1963, 2, 1020. 10. K. Seppelt, 2. Anorg. A&. Chem. 1978,899,87. 11. T. E. Mallouk, G. L. Rosenthal, G. Miiller, R. Brusasco and N. Bartlett, fnorg. Chem. 1984,23,3167. 12. T. Birchall, P. A. W. Dean and R. J. Gillespie, J. Chem. Sot. A 1971, 1777.
Polyhedron Vol. I, No. 13, pp. 12214223.1988 Printed in Great Britain
COMMUNICATION SYNTHESIS AND CHARACTERIZATION OF BIS(CYCLOPENTADIENYL)BIS(HEXAFLU~ROANTIMONATO) TITANIUM(IV)* TH. KLAPOTKE Institut fur Anorganische und Analytische Chemie, Technische Universitat Berlin, D-1000 Berlin 12, F.R.G. (Received 14 March 1988 ; accepted 23 March 1988) Abstract-Reaction of titanocene dichloride with two equivalents of silver hexafluoroantimonate in sulphur dioxide quantitatively yields CpzTi(SbF& (Cp = $-C,H,) and AgCl. The titanocene bishexafluoroantimonate was recrystallized from SO* and characterized by chemical analysis, ‘H NMR, IR and mass spectroscopy.
Transition metal halides have been reported to possess Lewis base qualities and it has been assumed that the metal-halide bond is not broken in the complexes formed. ’ Adduct formation between Cp,TiF,,and Lewis acids (e.g. BF3 and PFS) has been investigated. However, by these reactions and by treatment of Cp,TiClz with two equivalents of AgBF4 (or AgPFJ only oils could be obtained.’ The isolation of Cp,TiF* has been reported from reactions involving fluorine-containing reagents such as the silver salts of CF3S-,3 BF;, PF;, SbF; and AsF; ;4 but in these cases no complex of the type Cp,Ti(MF&t was either isolated or identified. Titanocene derivatives containing MF; groups, directly coordinated to the Cp,Ti centre, have not previously been described, so this was the reason to study this particular problem in organometallic chemistry. The synthesis of a compound like Cp,Ti(MF& seemed to be of interest in terms of the Cp,Ti-MF6 bond situation (ionic or Ti-F bond interaction with reduced MF, symmetry: Oh + C4J, its stability (decomposition routes and mechanism), and last but not least the possibility that (Cp,Ti(NR,):+(SbF&) (known as a stable
* Organo-transition metal chemistry of highly fluorinated ligand systems (Organo-fjhergangsmetall-Chemie hochlluorierter Ligand-Systeme) : first communication. t (M = pnictogen).
complex’) may be the only preparation of (Cp,Ti (SO&+(SbF;),). The first results on this project are reported in this paper. Reaction of Cp,TiCll with two equivalents of AgSbFQ (Alfa) in SO1 at -20°C quantitatively yielded the precipitation of AgCl and led to the formation of Cp,Ti(SbF& (1) according to eq. (1). Cp,TiClz+2AgSbF, “‘(‘) rCp,Ti(SbF,),+2AgClJ. - 20°C
(1)
(1)
1, which is highly soluble in SO2 (deep red solution), was separated from AgCl by filtration (D4) and recrystallized from the same solvent at room temperature (yield, 94%). The chemical analysis (C1,,H10F12Sb2Ti, M = 649,55 gmol-‘. Found: C, 18.3; H, 1.35. Calc. for CloH,,,FlzSbzTi: C, 18.5; H, 1.55%) of the deep red microcrystalline air- and moisture-sensitive solid is in very good agreement with the composition CpaTi(SbF& and there is no evidence for coordinated S02. While the ‘H NMR spectrum of CpzTiF, consists of a triplet in the Cp region3s6 in the ‘H NMR spectrum of 1 (SO2 solution, relative to TMS) only one very sharp singlet appears in the Cp range at 6 = 7.25 ppm (6, Cp,TiClz = 6.65 ppm). This value and the low-field shift, compared with Cp,TiClz, indicate a partial dissociation of 1 in solution
1221
1222
Communication
3100
1400
1000 vlcm
600
-‘I
Fig. 1. IR spectrum of solid Cp,Ti(SbF& in the regions 1600-200 cm-’ (Perkin-Elmer 457).
according
to eq. (2) (cf. ref. 4). 1 so2o)b(Cp*Ti(S~~)~+(SbF~~*).
(2)
The mass spectrum of 1 (electron-impact, 70 eV, 60°C) does not show a peak due to the molecular ion but to one corresponding to CpTiF3. This fact and also the appearance of SbFz indicate that a fluorine transfer from the SbF6 group to the transition metal occurs as a decomposition reaction at low temperature. The base peak is given by Cp’. Figure 1 shows the IR spectrum of 1, obtained with the pure powdered compound. IR values and assignments are given in Table 1. All bands due to the Cp,Ti fragment are quite strong and nearly unchanged compared with those of CpzTiFz. In the spectrum of Cp,TiFz, bands at 564 and 539 cm- ’ have been assigned to the Ti-F
Table 1. IR frequencies of Cp,Ti(SbF& Frequency (cm- ‘) 3110s 1435 s 1025 m,sh 1015 s 845 vs 665 vs 640 vs 535 s so5 s 287 vs 275 vs
Assignment V-CH W-CC s-CH &CH y-CH v,,-SbF, v, 2 v,,-SbF 1 v,-TiF v,,-TiF a-SbF4 ,,,z &SbF, t
260 and 3200-3000 cm- ’
symmetric and asymmetric stretching modes, respectively.’ However, in 1 these bands are shifted to 535 and 505 cm-‘. This indicates weaker Ti-F bonds in 1 compared with Cp,TiFz. This is in agreement with a fluorine bridged structure where a “divalent” fluorine is coordinated to both the Cp,Ti group and a “SbF,” unit. The lower symmetry (C,,) of the SbF6 system (0, in SbF;) with five short (strong) and one long (weak) Sb-F bonds leads as expected to a splitting of the v3 and v4 bands at 650 and 285 cm’ ‘, respectively.8-10 While Cp2Ti(PF& seems to be unstable in the solid state, the antimony analogue is described as the first stable and well characterized titanocene MF6 (M = pnictogen) compound in the present paper. Our interest will now be extended to the AsF, compounds, as the fluorine affmity of AsFJ is significantly higher than that of PFS” and therefore the preparation of Cp,Ti(AsF,), seems to be very likely. AcknowZe&ement.+Thanks
are given to P. Gowik (TU Berlin) for cooperation in the experimental work and to A. Stijckel (TV Berlin) for carrying out the mass spectroscopy. I also thank M. Schriver for the ‘H NMR spectra and helpful discussions. REFERENCES M. Pankowski, B. Demerseman, G. Bouquet and M. Bigorgne, J. Organomet. Chem. 1972,35, 155 ; T. J. Marks, J. Kristoff, A. Alich and D. F. Shriver, J. ~rganomet. Chem. 1971,33, C35. H. C. Clark and A. Shaver, J. Coord. Chem. 1975, 4,243. R. B. King and N. Welcman, Inorg. Chem. 1969,8,
2540.
Communication G. Doyle and R. S. Tobias, Zrzorg. Chem. 196’7, 6, 1111. K. Berhalter and U. Thewalt, J. Organomet. Chem. 1987,332,123. A. N. Nesmeyanov, 0. V. Nogina, E. I. Fedin, V. A. ~~~ts~i, B. A. Kvasov and P. V. Petrovskii, Dokl. Adad. Nauk. S.S.S.R. 1972,205,857. P. M. Druci, B. M. Kingston, M. F. Lappert, R. C. Srivastava, M. J. Frazer and W. E. Newton, J. Chem. Sot. A 1969,2814.
1223
8. S. Buffagni, L. M. Vallarino and J. V. Quagliano, Znorg. Chem. 1964,3,671. 9. H. C. Clark and R. J. O’Brien, Znorg. Chem. 1963, 2, 1020. 10. K. Seppelt, 2. Anorg. A&. Chem. 1978,899,87. 11. T. E. Mallouk, G. L. Rosenthal, G. Miiller, R. Brusasco and N. Bartlett, fnorg. Chem. 1984,23,3167. 12. T. Birchall, P. A. W. Dean and R. J. Gillespie, J. Chem. Sot. A 1971, 1777.