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Titanium tetraperchlorate and chromyl perchlorate
J inorg, nucl. Chem., Supplement1976. PergamonPress. Printedin GreatBritain
TITANIUM TETRAPERCHLORATE AND CHROMYL PERCHLORATE CARL J. SCHACK, DONALD PILIPOVICH and KARL O. CHRISTE Rocketdyne,A Divisionof RockwellInternational,CanogaPark, 91304,U.S.A. (Received 11 March 1974)
Abstract--Synthesesof titaniumtetraperchlorateand chromylperchlorateare reported usingchlorineperchlorateand the respective metal chlorides. These anhydrous metal perchlorates were found to contain bidentate perchlorato ligands. STUDIES of anhydrous metal perchlorates have been restricted mainly to metals from Groups I and II[1]. Limited studies of transition metal perchlorates have also been reported [2] as well as some work on NO2+ and NH4+ complex perchlorates[3]. Only more recently have the halogen perchlorates C1OC103 [4] and BrOCIOs [5] become available and been shown to be excellent sources of perchlorates[6], I(OClO3)s and Cs+I(OC103)4-, and the novel fluorocarbon perchlorate[7], CFsOCIOs. As a continuation of the investigation of the chemistry of chlorine perchlorate, its reactions with transition metal chlorides have been examined. We now report that the action of chlorine perchlorate on titanium tetrachloride and chromyl chloride produced titanium tetraperchlorate and chromyl perchlorate, respectively. The observed stoichiometry for the titanium system was: TiCI4 + 4C1OC10~--*Ti(CIO,)4 + C12. The reaction was carried out at or below -25 °, in either Teflon FEP or stainless steel vessels, and without a solvent. Yields of Ti(CIO4)4 were always 95 per cent or better based on the limiting reagent, TiCL. The identification of the Ti(CIO4)4 was based on the overall excellent material balance obtained for the synthesis, elemental analysis, and the i.r. and Raman spectra of the solid. A patent reported[8] the preparation of Ti(C104)4 which involved the reaction of TIC14 and at least 8-fold amounts of anhydrous perchloric acid. From the data presented, i.e.m.p., analysis and stability, it appears that the Ti(CIO4)4 described[8] may have been less pure than our samples. For example, it was stated that long term storage required refrigeration to avoid decomposition. Our samples have not degraded during 3 months at ambient temperature. The C104 content reported, 86.4 per cent, significantly differs from the theoretical value of 89.25 per cent. In addition, the reported[8] m.p. of 90-94° is appreciably lower than our value of 101-20, nor did we note any of the polycrystalline forms that were reported. Thus, it is likely that the present synthesis produces an anhydrous material of higher purity. The vibrational spectra of Ti(CIO4)4 were particularly revealing with respect to the nature of the bonding between the titanium central atom and the C104 ligands.
The i.r. spectrum in the range 4000-300 cm -~ contained bands at 1300, 1160, 910, 870, 850, 660, 575, 535 and 375 cm -1, all of strong to very strong intensity. These bands are not typical of either an ionic[9] or covalent monodentate [10,11] perchlorate. Instead, they indicate the presence of bidentate perchlorato groups in an approximately tetrahedral arrangement around the titanium. Typical bidentate perchlorate spectra[11] show two pairs of strong i.r. bands at about 1310 and 1170, and 880 and 660 cm-1. These pairs are due to the antisymmetric and symmetric stretching vibrations of the terminal CT/~O~oand the bridging C ( r' ~e s pgroups, ectively.,,,
They
are obviously dominant in the Ti(C104)4 spectrum. Four C104 groups surrounding Ti lead to a monomeric, coordination number wise saturated configuration which accounts for its observed volatility, i.e. low temperature sublimation. The thermal stability of Ti(C104)4 was examined in closed bomb tests. After one hour at 115°, the decomposition was incomplete as evidenced by the recovery of less than the theoretical amount of oxygen in the form of O: and C1207. After 4 hr at 115°, approximately half the oxygen content of the Ti(C10,)4 was converted to O: and half to C1207. The latter was decomposed at 190° in 1.5 hr. Quantitative overall results were obtained for the reaction sequence shown: bidentate
Ti(CIO4)4 a ~TiO2 + 2C1:O7 ~ ) 2C12+ 70:. The observed O2:C12 ratio of 3.54:1-00 compared favorably with the theoretical ratio of 3.50:1.00. The solid product was identified as titanium dioxide by comparison of its Raman spectrum with that of an authentic sample. Chromyl perchlorate has been synthesized previously from the reaction of chromyl chloride and chlorine hexoxide[2]. With C1204, the observed reaction was: 2C1204 + CrO:CI: ~ CrO:(C104): + 2C1:. Chromyl perchlorate is a dark red liquid with less than 1 mm vapor pressure at room temperature. Its high reactivity and low stability precluded successful transfers 207
C . J . SCHACK et al.
208
in the vacuum line. Although AgC1 windows were attacked, it was possible to obtain i.r. spectra of the liquid using rapid scanning. Bands were observed at 1305 s, 1240 vs, 1180 s, 1030 s, 980 s, 875 m, 850 m, 735 s, 685 s, 660 s, 580 m, 545 m, 510 w, 435 w and 380 m cm -1. These bands indicate the presence of covalent bidentate perchlorato ligands and of a bent chromyl group. As expected, CrO2(CIO4)2 decomposed on heating according to the equation: CRO2(C104)2
a > CrO3 + C12 + 3.502.
The observed O2:C12 ratio was 3.35:1.00 while the CrO3 was identified by its i.r. spectrum and m.p. Additional studies of metal halides with halogen perchlorates are in progress and will be reported later. EXPERIMENTAL Titanium tetrachloride (1.22 mmole) and ClOCIO3 (6.01 mmole) were combined at -196 ° in a 75 ml stainless steel cylinder and then gradually warmed to -25 °. After several days, recooling to -196 ° showed no noncondensable gases were present. The contents of the reactor were separated by fractional condensation in a series of U-traps cooled to -78, -112 and -196 °. Nothing was trapped at -78 ° while the -112 ° fraction consisted solely of unreacted C1204 (1.17 mmole), and the -196 ° fraction was C12 (4.88 mmole). The pale yellow solid residue left in the reactor weighed 0.525 g. The weight calculated for 1.22 mmole of Ti(ClO4)4 was 0.544 g and therefore the yield of Ti(CIO,), was 97 per cent. Vacuum sublimation of the Ti(CIO,h was carried out in a Pyrex apparatus at 50-600 using a -78 ° cold finger. The sublimed material was nearly colorless and had a m.p. with dec. of 101-102 °. Almost no residue remained unsublimed (Anal. Calcd. for Ti(ClO4),:Ti, 10.75; CIO4, 89.25. Found: Ti, 10.8; CIO4, 87-9%). A sample of Ti(CIO4), (0.242 mmole) was heated in a stainless steel cylinder for 4 hr at 115° followed by 1.5 hr at 190°. This produced O2 (1.705
mmole), Cl2 (0.481 mmole) and a white solid residue of TiO: (0.241 mmole). Chromyl chloride (1.41 mmole) and CIOCIO3 (3.16 mmole) were reacted at -450 for several days in a stainless steel cylinder. After separation and identification, the volatile products found were CrO2F2 (0.18 mmole), C12 (2.59 mmole) and C1~O4 (0.66 mmole). The CrO~ (CIO,)2 (1.23 mmole) remained in the cylinder. The CrO2F2 probably arose through reaction of CrO2C12 with the CIF3 passivated metal surfaces in the reactor and/or vacuum line during transfers (Anal. Calcd. for CrO2 (C104)~:CIO,, 70.3 Found: CIO,, 69.6%). A sample of CrO2 (C104)2 (0.65 mmole) was pyrolyzed for 15 hr at 110° producing C12 (0.66 mmole), O5 (2.21 mmole) and CrO3 (0.65 mmole), m.p. 195-7°, lit. 196°.
Acknowledgements--We are most grateful to the Ofiice of Naval Research, Power Branch, for support of this work. Also, we thank Dr. L. R. Grant for helpful discussions. REFERENCES 1. J. C. Schumacher, Perchlorates. ACS Monograph Series No. 146, Reinhold, New York (1960). 2. M. Schmeisser and K. Brandle, Adv. Inorg. Chem. Radiochem. 5, 64 (1963). 3. E. W. Lawless and I. C. Smith, Inorganic High Energy Oxidizers, pp. 183-187. Dekker, New York (1968). 4. C.J. Schack and D. Pilipovich, Inorg. Chem. 9, 1387 (1970). 5. C. J. Schack, K. O. Christe, D. Pilipovich and R. D. Wilson, Inorg. Chem. 10, 1078 (1971). 6. K. O. Christe and C. J. Schack, lnorg. Chem. 11, 1682 (1972). 7. C. J. Schack, D. Pilipovich and K. O. Christe, Inorg. Nucl. Chem. Lett. 10, 449 (1974). 8. R. J. Laran, U.S. Pat. 3,157,464 (Nov. 1964).
9. K. Nakamoto, In[rared Spectra o[ Inorganic and Coordination Compounds. Wiley, New York (1970). 10. K. O. Christe, C. J. Schack and E. C. Curtis, Inorg. Chem. 10, 1589 (1971). 11. K. O. Christe and C. J. Schack, Inorg. Chem. 13, May (1974).
TITANIUM TETRAPERCHLORATE AND CHROMYL PERCHLORATE CARL J. SCHACK, DONALD PILIPOVICH and KARL O. CHRISTE Rocketdyne,A Divisionof RockwellInternational,CanogaPark, 91304,U.S.A. (Received 11 March 1974)
Abstract--Synthesesof titaniumtetraperchlorateand chromylperchlorateare reported usingchlorineperchlorateand the respective metal chlorides. These anhydrous metal perchlorates were found to contain bidentate perchlorato ligands. STUDIES of anhydrous metal perchlorates have been restricted mainly to metals from Groups I and II[1]. Limited studies of transition metal perchlorates have also been reported [2] as well as some work on NO2+ and NH4+ complex perchlorates[3]. Only more recently have the halogen perchlorates C1OC103 [4] and BrOCIOs [5] become available and been shown to be excellent sources of perchlorates[6], I(OClO3)s and Cs+I(OC103)4-, and the novel fluorocarbon perchlorate[7], CFsOCIOs. As a continuation of the investigation of the chemistry of chlorine perchlorate, its reactions with transition metal chlorides have been examined. We now report that the action of chlorine perchlorate on titanium tetrachloride and chromyl chloride produced titanium tetraperchlorate and chromyl perchlorate, respectively. The observed stoichiometry for the titanium system was: TiCI4 + 4C1OC10~--*Ti(CIO,)4 + C12. The reaction was carried out at or below -25 °, in either Teflon FEP or stainless steel vessels, and without a solvent. Yields of Ti(CIO4)4 were always 95 per cent or better based on the limiting reagent, TiCL. The identification of the Ti(CIO4)4 was based on the overall excellent material balance obtained for the synthesis, elemental analysis, and the i.r. and Raman spectra of the solid. A patent reported[8] the preparation of Ti(C104)4 which involved the reaction of TIC14 and at least 8-fold amounts of anhydrous perchloric acid. From the data presented, i.e.m.p., analysis and stability, it appears that the Ti(CIO4)4 described[8] may have been less pure than our samples. For example, it was stated that long term storage required refrigeration to avoid decomposition. Our samples have not degraded during 3 months at ambient temperature. The C104 content reported, 86.4 per cent, significantly differs from the theoretical value of 89.25 per cent. In addition, the reported[8] m.p. of 90-94° is appreciably lower than our value of 101-20, nor did we note any of the polycrystalline forms that were reported. Thus, it is likely that the present synthesis produces an anhydrous material of higher purity. The vibrational spectra of Ti(CIO4)4 were particularly revealing with respect to the nature of the bonding between the titanium central atom and the C104 ligands.
The i.r. spectrum in the range 4000-300 cm -~ contained bands at 1300, 1160, 910, 870, 850, 660, 575, 535 and 375 cm -1, all of strong to very strong intensity. These bands are not typical of either an ionic[9] or covalent monodentate [10,11] perchlorate. Instead, they indicate the presence of bidentate perchlorato groups in an approximately tetrahedral arrangement around the titanium. Typical bidentate perchlorate spectra[11] show two pairs of strong i.r. bands at about 1310 and 1170, and 880 and 660 cm-1. These pairs are due to the antisymmetric and symmetric stretching vibrations of the terminal CT/~O~oand the bridging C ( r' ~e s pgroups, ectively.,,,
They
are obviously dominant in the Ti(C104)4 spectrum. Four C104 groups surrounding Ti lead to a monomeric, coordination number wise saturated configuration which accounts for its observed volatility, i.e. low temperature sublimation. The thermal stability of Ti(C104)4 was examined in closed bomb tests. After one hour at 115°, the decomposition was incomplete as evidenced by the recovery of less than the theoretical amount of oxygen in the form of O: and C1207. After 4 hr at 115°, approximately half the oxygen content of the Ti(C10,)4 was converted to O: and half to C1207. The latter was decomposed at 190° in 1.5 hr. Quantitative overall results were obtained for the reaction sequence shown: bidentate
Ti(CIO4)4 a ~TiO2 + 2C1:O7 ~ ) 2C12+ 70:. The observed O2:C12 ratio of 3.54:1-00 compared favorably with the theoretical ratio of 3.50:1.00. The solid product was identified as titanium dioxide by comparison of its Raman spectrum with that of an authentic sample. Chromyl perchlorate has been synthesized previously from the reaction of chromyl chloride and chlorine hexoxide[2]. With C1204, the observed reaction was: 2C1204 + CrO:CI: ~ CrO:(C104): + 2C1:. Chromyl perchlorate is a dark red liquid with less than 1 mm vapor pressure at room temperature. Its high reactivity and low stability precluded successful transfers 207
C . J . SCHACK et al.
208
in the vacuum line. Although AgC1 windows were attacked, it was possible to obtain i.r. spectra of the liquid using rapid scanning. Bands were observed at 1305 s, 1240 vs, 1180 s, 1030 s, 980 s, 875 m, 850 m, 735 s, 685 s, 660 s, 580 m, 545 m, 510 w, 435 w and 380 m cm -1. These bands indicate the presence of covalent bidentate perchlorato ligands and of a bent chromyl group. As expected, CrO2(CIO4)2 decomposed on heating according to the equation: CRO2(C104)2
a > CrO3 + C12 + 3.502.
The observed O2:C12 ratio was 3.35:1.00 while the CrO3 was identified by its i.r. spectrum and m.p. Additional studies of metal halides with halogen perchlorates are in progress and will be reported later. EXPERIMENTAL Titanium tetrachloride (1.22 mmole) and ClOCIO3 (6.01 mmole) were combined at -196 ° in a 75 ml stainless steel cylinder and then gradually warmed to -25 °. After several days, recooling to -196 ° showed no noncondensable gases were present. The contents of the reactor were separated by fractional condensation in a series of U-traps cooled to -78, -112 and -196 °. Nothing was trapped at -78 ° while the -112 ° fraction consisted solely of unreacted C1204 (1.17 mmole), and the -196 ° fraction was C12 (4.88 mmole). The pale yellow solid residue left in the reactor weighed 0.525 g. The weight calculated for 1.22 mmole of Ti(ClO4)4 was 0.544 g and therefore the yield of Ti(CIO,), was 97 per cent. Vacuum sublimation of the Ti(CIO,h was carried out in a Pyrex apparatus at 50-600 using a -78 ° cold finger. The sublimed material was nearly colorless and had a m.p. with dec. of 101-102 °. Almost no residue remained unsublimed (Anal. Calcd. for Ti(ClO4),:Ti, 10.75; CIO4, 89.25. Found: Ti, 10.8; CIO4, 87-9%). A sample of Ti(CIO4), (0.242 mmole) was heated in a stainless steel cylinder for 4 hr at 115° followed by 1.5 hr at 190°. This produced O2 (1.705
mmole), Cl2 (0.481 mmole) and a white solid residue of TiO: (0.241 mmole). Chromyl chloride (1.41 mmole) and CIOCIO3 (3.16 mmole) were reacted at -450 for several days in a stainless steel cylinder. After separation and identification, the volatile products found were CrO2F2 (0.18 mmole), C12 (2.59 mmole) and C1~O4 (0.66 mmole). The CrO~ (CIO,)2 (1.23 mmole) remained in the cylinder. The CrO2F2 probably arose through reaction of CrO2C12 with the CIF3 passivated metal surfaces in the reactor and/or vacuum line during transfers (Anal. Calcd. for CrO2 (C104)~:CIO,, 70.3 Found: CIO,, 69.6%). A sample of CrO2 (C104)2 (0.65 mmole) was pyrolyzed for 15 hr at 110° producing C12 (0.66 mmole), O5 (2.21 mmole) and CrO3 (0.65 mmole), m.p. 195-7°, lit. 196°.
Acknowledgements--We are most grateful to the Ofiice of Naval Research, Power Branch, for support of this work. Also, we thank Dr. L. R. Grant for helpful discussions. REFERENCES 1. J. C. Schumacher, Perchlorates. ACS Monograph Series No. 146, Reinhold, New York (1960). 2. M. Schmeisser and K. Brandle, Adv. Inorg. Chem. Radiochem. 5, 64 (1963). 3. E. W. Lawless and I. C. Smith, Inorganic High Energy Oxidizers, pp. 183-187. Dekker, New York (1968). 4. C.J. Schack and D. Pilipovich, Inorg. Chem. 9, 1387 (1970). 5. C. J. Schack, K. O. Christe, D. Pilipovich and R. D. Wilson, Inorg. Chem. 10, 1078 (1971). 6. K. O. Christe and C. J. Schack, lnorg. Chem. 11, 1682 (1972). 7. C. J. Schack, D. Pilipovich and K. O. Christe, Inorg. Nucl. Chem. Lett. 10, 449 (1974). 8. R. J. Laran, U.S. Pat. 3,157,464 (Nov. 1964).
9. K. Nakamoto, In[rared Spectra o[ Inorganic and Coordination Compounds. Wiley, New York (1970). 10. K. O. Christe, C. J. Schack and E. C. Curtis, Inorg. Chem. 10, 1589 (1971). 11. K. O. Christe and C. J. Schack, Inorg. Chem. 13, May (1974).