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ISSN: 2056-9890

Cs[Tf2N]: a second polymorph with a layered structure

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aMaterials Physics and Applications Division, Associate Directorate for Experimental Physical Sciences, Los Alamos National Laboratory, Los Alamos, New Mexico, 87545, USA
*Correspondence e-mail: jstritzinger@lanl.gov

Edited by M. Weil, Vienna University of Technology, Austria (Received 20 December 2017; accepted 15 March 2018; online 23 March 2018)

The structural determination of the ionic liquid, caesium bis­[(tri­fluoro­meth­yl)sulfon­yl]imide or poly[[μ4-bis­[(tri­fluoro­meth­yl)sulfon­yl]imido]caesium(I)], Cs[N(SO2CF3)2] or Cs[Tf2N], reveals a second polymorph that also crystallizes in a layer structure possessing monoclinic P21/c symmetry at 120 K instead of C2/c for the known polymorph [Xue et al. (2002[Xue, L., Padgett, C. W., DesMarteau, D. D. & Pennington, W. T. (2002). Solid State Sci. 4, 1535-1545.]). Solid State Sci. 4, 1535–1545]. The caesium ions in the cationic layers are coordinated by the sulfonyl groups of the bis­triflimide mol­ecules from anion layers while the tri­fluoro­methyl groups are oriented in the opposite direction, forming a non-polar surface separating the layers. The layer direction is (100).

1. Chemical context

Recently, ionic liquids (IL) with melting points below 373 K, known as room temperature ionic liquids (RTIL), have emerged as a novel system that can be used to replace processes utilizing haza­rdous organic solvents and provide water-free environments (Welton, 1999[Welton, T. (1999). Chem. Rev. 99, 2071-2084.]). The exclusion of water from RTIL can be challenging as their ionic nature predisposes a hygroscopic nature, and even so-called hydro­phobic ILs can be difficult to dry (Francesco et al., 2011[Francesco, F. D., Calisi, N., Creatini, M., Melai, B., Salvo, P. & Chiappe, C. (2011). Green Chem. 13, 1712-1717.]). Reducing the solubility of water is possible by exchanging constituent ions of the IL for those that are less hydro­philic, but this often results in higher melting points or increased viscosity (Francesco et al., 2011[Francesco, F. D., Calisi, N., Creatini, M., Melai, B., Salvo, P. & Chiappe, C. (2011). Green Chem. 13, 1712-1717.]). The ability to change the physicochemical characteristics of ionic liquids has lead them to be praised as `tunable solvents', but is often more of a challenging act of balancing physical properties.

The substitution of bis­(tri­fluoro­meth­yl)sulfon­yl)imide (bis­triflimide, Tf2N) as the anion in ILs offers a more hydro­phobic IL with lower melting point (Matsumoto et al., 2002[Matsumoto, H., Kageyama, H. & Miyazaki, Y. (2002). Chem. Commun. pp. 1726-1727.]; Sun et al., 1997[Sun, J., MacFarlane, D. R. & Forsyth, M. (1997). Ionics, 3, 356-362.]). In general, anions of the triflate family are weakly coordinating when in the presence of other ligands, and inter­actions with metal ions may not be observed when in the presence of water. These weak inter­actions are due to the delocalization of charge across the mol­ecule. The structure of bis­triflimide also allows for multidentate coordination motifs when binding through the oxygen atoms, and often results in coordination of multiple metal cations. When Tf2N inter­actions expand beyond a single central metal atom, the ability to diffuse charge across a structure is highlighted (DesMarteau, 1995[DesMarteau, D. D. (1995). J. Fluor. Chem. 72, 203-208.]).

Cs[Tf2N] has a desirably low melting point of 398 K which is outside the conventional definition of a RTIL; however, this melting point is in the range of many well-known ILs while still being above the boiling point of water to enable con­venient drying (Hagiwara et al., 2008[Hagiwara, R., Tamaki, K., Kubota, K., Goto, T. & Nohira, T. (2008). J. Chem. Eng. Data, 53, 355-358.]; Scheuermeyer et al., 2016[Scheuermeyer, M., Kusche, M., Agel, F., Schreiber, P., Maier, F., Steinrück, H.-P., Davis, J. H., Heym, F., Jess, A. & Wasserscheid, P. (2016). New J. Chem. 40, 7157-7161.]). Previous reports of alkali metals and Tf2N include Cs[Tf2N], which presents as either an anhydrate or a variety of hydrates (Xue et al., 2002[Xue, L., Padgett, C. W., DesMarteau, D. D. & Pennington, W. T. (2002). Solid State Sci. 4, 1535-1545.]). Some common structural similarities can be observed across the A[Tf2N]·nH2O (A = Li, Na, K, Rb, and Cs) series. The most notable feature is the formation of polar and non-polar regions that result from the coordination of multiple metal cations by the Tf2N ion. Each of the sulfonyl groups binds to a metal cation creating a polar chain that may extend to a layer, and orientates the tri­fluoro­methyl groups to create non-polar surfaces. Within the series, only the structures of Cs and K salts as anhydrates have been reported.

Our synthesis and analysis of Cs[Tf2N] has revealed a second layered polymorph set in P21/c in addition to the previously reported structure in C2/c (Xue et al., 2002[Xue, L., Padgett, C. W., DesMarteau, D. D. & Pennington, W. T. (2002). Solid State Sci. 4, 1535-1545.]).

[Scheme 1]

2. Structural commentary

The structure develops from the various ways in which six Tf2N mol­ecules coordinate the central 10-coordinate caesium cation (Fig. 1[link]). The simplest coordination mode is monodentate, where one oxygen atom on one of the sulfonyl groups of the Tf2N mol­ecule coordinates to the caesium cation. The bidentate coordination mode has two motifs. In end-on coord­ination, both oxygen atoms of a single sulfonyl group coordinate with Cs+, while in side-on coordination one oxygen on each of the sulfonyl groups within a Tf2N mol­ecule coord­inate with Cs+. Two of the six distinct Tf2N mol­ecules exhibit the side-on coordination mode, and in one of them the nitro­gen atom of the Tf2N mol­ecule may come close enough to inter­act with the caesium cation. Examining the bond lengths in the coordination environment of the caesium cation, it is comprised of nine oxygen atoms ranging from 3.060 (2)–3.539 (3) Å and one inter­action with a nitro­gen atom of 3.280 (3) Å. These three different modes of Tf2N binding join the caesium cations together in a complex sheet with layers of tri­fluoro­methyl groups above and below (Fig. 1[link]).

[Figure 1]
Figure 1
The coordination of the Cs+ cation by nine oxygen atoms and one nitro­gen atom of six different bis­triflimide anions coordinating above and three below, in a view slightly off the (100) plane. Other caesium cations are crystallographically equivalent to Cs1, and are shown to depict how the sheet extends. The displacement ellipsoids are drawn at the 50% probability function with the color scheme of caesium (purple), oxygen (red), sulfur (yellow), nitro­gen (blue), carbon (black), and fluorine (green).

As the Tf2N mol­ecule coordinates in the cis conformation, this orients the tri­fluoro­methyl groups in the opposite direction from the sulfonyl groups creating a layer of fluorine atoms. With this layer, tri­fluoro­methyl groups have an intra­molecular closest contact of 2.770 (4) Å and an inter­molecular closest contact of 2.970 (4) Å. There is a fluorine–fluorine closest contact length of 3.01 Å spanning the void between the non-polar surfaces of adjacent sheets in the layered structure. These layers are easily observed parallel to (100), Fig. 2[link]. Examining the bis­triflimide mol­ecule, the S—N—S bond angle is 127.60 (17)° resulting in an intra­molecular carbon–carbon separation of 4.18 Å.

[Figure 2]
Figure 2
Ball and stick model view along [001] showing the layer of the structure arising from the hydro­phobic surfaces formed by orientation of the tri­fluoro­methyl groups, comparing (a) the unit cell of the stucture discussed in the paper set in P21/c and (b) that of the previously reported structure set in C2/c (Xue et al., 2002[Xue, L., Padgett, C. W., DesMarteau, D. D. & Pennington, W. T. (2002). Solid State Sci. 4, 1535-1545.]). Atoms are designated as caesium (purple), oxygen (red), sulfur (yellow), nitro­gen (blue), carbon (black), and fluorine (green).

This structure of alternating layers of hydro­philic alkali metal cations bound by the sulfonyl groups and hydro­phobic layers of tri­fluoro­methyl groups closely matches the reported structures of K[Tf2N] and Cs[Tf2N] (Xue et al., 2002[Xue, L., Padgett, C. W., DesMarteau, D. D. & Pennington, W. T. (2002). Solid State Sci. 4, 1535-1545.]). The noted deviations are in the coordination environment of the Cs+ cation. For the previously reported structure of Cs[Tf2N], the caesium coordination environment is also 10; however, the oxygen inter­actions are generally longer by about 0.05 Å, with Cs—O bonds ranging from 3.04 (1) to 3.65 (1) Å. The lone Cs—N bond is 3.39 (1) Å, which is considerably longer than the 3.280 (3) Å bond length observed in the current structure. This extension of bond lengths is reflected in the bis­triflimide mol­ecule where the S—N—S bond angle is contracted to 126.38 and the intra­molecular carbon–carbon separation is shortened to 4.08 Å. As the mol­ecule shifts, so does the orientation of the tri­fluoro­methyl groups, resulting in an intra­molecular closest contact of 2.72 Å and an inter­molecular closest contact of 2.96 Å. The shift also extends to the void between the non-polar surface of adjacent sheets, where fluorine–fluorine closest contacts are observed at 2.69 Å spanning the void. While the void space between layers appears reduced, the overall structure has a calculated density of 2.58 g cm−3 (Xue et al., 2002[Xue, L., Padgett, C. W., DesMarteau, D. D. & Pennington, W. T. (2002). Solid State Sci. 4, 1535-1545.]), less dense than the calculated 2.65 g cm−3 of the more compact current structure.

The Cs[Tf2N] purity was confirmed by melting point measurements that closely match literature values, showing an onset temperature of 397 K and complete melting at 399 K (Hagiwara et al., 2008[Hagiwara, R., Tamaki, K., Kubota, K., Goto, T. & Nohira, T. (2008). J. Chem. Eng. Data, 53, 355-358.]; Scheuermeyer et al., 2016[Scheuermeyer, M., Kusche, M., Agel, F., Schreiber, P., Maier, F., Steinrück, H.-P., Davis, J. H., Heym, F., Jess, A. & Wasserscheid, P. (2016). New J. Chem. 40, 7157-7161.]). Additional Raman analysis (Fig. 3[link]), shows a number of features that closely match the reported spectra for Tf2N in water and solid-state measurements made on HTf2N, confirming the presence of the Tf2N mol­ecule (Rey et al., 1998[Rey, I., Johansson, P., Lindgren, J., Lassègues, J. C., Grondin, J. & Servant, L. (1998). J. Phys. Chem. A, 102, 3249-3258.]). To elucidate bands that signify inter­actions with metal cations, a comparison to the reported Raman spectra of La[Tf2N]3(H2O)3 (Bhatt et al., 2005[Bhatt, A. I., May, I., Volkovich, V. A., Collison, D., Helliwell, M., Polovov, I. B. & Lewin, R. G. (2005). Inorg. Chem. 44, 4934-4940.]) was made. The major bands and assignments of all compounds in the comparisons are reported in Table 1[link]. The additional bands observed at 535 and 507 cm−1 for Cs[Tf2N] suggest multiple SO2 bending modes associated with multiple coordination modes of Tf2N. In particular, the band at 507 cm−1 for Cs[Tf2N] matches with a 511 cm−1 band in La[Tf2N]3(H2O)3 suggesting a tentative assignment to a down-shift of the SO2 bending mode by the bidentate side-on coordination of the Tf2N mol­ecule, observed in both structures.

Table 1
Comparison of Raman modes in Tf2N compounds

Comparison of observed Raman shifts in cm−1 from Tf2N-containing compounds. Band wavenumbers given in bold are unassigned and in italicized are from reanalysis of reported spectra for La[Tf2N]3(H2O)3. Major band assignments are given with ν (stretching), δ (bending), ω (wagging), τ (twisting) and ρ (rocking) and planar designations are i.p. for in plane and o.p. for out of plane.

Mode Group Tf2N in H2O HTf2N La[Tf2N]3(H2O)3 Cs[Tf2N]  
      1456      
      1443      
νa i.p. SO2 1351        
νa o.p. SO2 1332 1436 1316 1322  
      1427      
δ NH   1332      
νs CF3 1239 1250 1243 1240  
νa CF3   1220      
    1203 1208 1210 1206  
νs i.p. SO2 1131 1134 1148 1145  
δs CF3 744 765 754 740  
δ SNS   634 669 659  
δa i.p. SO2 594 583      
δa CF3 567 570 573 572  
      555      
δs SO2 551   554 553  
          535  
        511 507  
γ NH   526      
      495 444    
ω SO2 407, 401     420, 412  
      380      
τ SO2 351   356 349  
    339        
ρ SO2 325 335 332 328  
    312 299 310 304  
ν MO     297?    
ρ CF3 276   288 283  
      264 241    
      210   215  
      202   173  
      185   130  
[Figure 3]
Figure 3
Raman spectra of Cs[Tf2N] with no other bands observed from 1400 cm−1 to 3200 cm−1. The additional bands at 535 and 507 cm−1 suggest the multiple SO2 bending modes associated with multiple coordination modes. Major band assignments are given with ν (stretching), δ (bending), ω (wagging), τ (twisting) and ρ (rocking) followed by the functional group. Planar designations are i.p.for in plane and o.p. for out of plane.

3. Synthesis and crystallization

All reagents were used as received without further purification. 20.281 g of caesium carbonate (Alfa Aesar, 99.9%) were dissolved in 20 ml of deionized water. 26.26 ml of 4.74 molar bis­triflimide acid (Alfa Aesar, 98.0%) were slowly added to the caesium carbonate solution, resulting in vigorous release of carbon dioxide. The solution was then placed in a sand bath at 403 K under stirring at approximately 100 rotations per minute. After four h, the temperature was reduced to 378 K. While the liquid cooled, the stirring deposited droplets of the ionic liquid on the sides of the beaker resulting in rapid crystallization. These crystals were harvested and suitable crystals were selected for diffraction. Yield was estimated at 95% based on mass.

3.1. Experimental

Raman measurements were collected using a Thermo Scientific DXRxi Raman Imaging Microscope. A 532 nm laser was focused on the sample surface through a 10x objective providing a spot size of 1 um and the collection consisted of 200 scans at 10 mW for 0.25 seconds each.

Melting point data were collected on a Büchi M-560, where two glass sample tubes were filled with 4–5mm of sample and the temperature was ramped at a rate of 0.5 K per minute.

4. Refinement

Crystal data, data collection and structure refinement details are summarized in Table 2[link].

Table 2
Experimental details

Crystal data
Chemical formula [Cs(C2F6NO4S2)]
Mr 413.06
Crystal system, space group Monoclinic, P21/c
Temperature (K) 120
a, b, c (Å) 11.431 (4), 6.918 (2), 13.469 (4)
β (°) 103.686 (4)
V3) 1035.0 (5)
Z 4
Radiation type Mo Kα
μ (mm−1) 4.07
Crystal size (mm) 0.40 × 0.35 × 0.33
 
Data collection
Diffractometer Bruker Photon 100
Absorption correction Multi-scan (SADABS; Bruker, 2014[Bruker (2014). APEX2, SAINT-Plus and SADABS. Bruker AXS Inc., Madison, Wisconsin, USA.])
Tmin, Tmax 0.507, 0.746
No. of measured, independent and observed [I > 2σ(I)] reflections 12467, 2354, 1980
Rint 0.048
(sin θ/λ)max−1) 0.650
 
Refinement
R[F2 > 2σ(F2)], wR(F2), S 0.022, 0.058, 0.99
No. of reflections 2354
No. of parameters 145
Δρmax, Δρmin (e Å−3) 0.84, −1.15
Computer programs: APEX2 (Bruker, 2014[Bruker (2014). APEX2, SAINT-Plus and SADABS. Bruker AXS Inc., Madison, Wisconsin, USA.]), SAINT-Plus (Bruker, 2014[Bruker (2014). APEX2, SAINT-Plus and SADABS. Bruker AXS Inc., Madison, Wisconsin, USA.]), SHELXT2014 (Sheldrick, 2015a[Sheldrick, G. M. (2015a). Acta Cryst. A71, 3-8.]), SHELXL2014 (Sheldrick, 2015b[Sheldrick, G. M. (2015b). Acta Cryst. C71, 3-8.]), CrystalMaker (CrystalMaker, 2013[CrystalMaker (2013). CrystalMaker. CrystalMaker Software, Oxfordshire, UK.]).

Supporting information


Computing details top

Data collection: APEX2 (Bruker, 2014); cell refinement: SAINT-Plus (Bruker, 2014); data reduction: SAINT-Plus (Bruker, 2014); program(s) used to solve structure: SHELXT2014 (Sheldrick, 2015a); program(s) used to refine structure: SHELXL2014 (Sheldrick, 2015b); molecular graphics: CrystalMaker (CrystalMaker, 2013); software used to prepare material for publication: SHELXL2014 (Sheldrick, 2015b).

Poly[[µ4-bis[(trifluoromethyl)sulfonyl]imido]caesium(I)] top
Crystal data top
[Cs(C2F6NO4S2)]Dx = 2.651 Mg m3
Mr = 413.06Melting point: 399 K
Monoclinic, P21/cMo Kα radiation, λ = 0.71073 Å
a = 11.431 (4) ÅCell parameters from 12467 reflections
b = 6.918 (2) Åθ = 3.1–27.5°
c = 13.469 (4) ŵ = 4.07 mm1
β = 103.686 (4)°T = 120 K
V = 1035.0 (5) Å3Block, colorless
Z = 40.40 × 0.35 × 0.33 mm
F(000) = 768
Data collection top
Bruker Photon 100
diffractometer
2354 independent reflections
Radiation source: sealed tube1980 reflections with I > 2σ(I)
Detector resolution: 0 pixels mm-1Rint = 0.048
0.5 wide w/exposures scansθmax = 27.5°, θmin = 3.1°
Absorption correction: multi-scan
(SADABS; Bruker, 2014)
h = 1414
Tmin = 0.507, Tmax = 0.746k = 88
12467 measured reflectionsl = 1717
Refinement top
Refinement on F2145 parameters
Least-squares matrix: full0 restraints
R[F2 > 2σ(F2)] = 0.022 w = 1/[σ2(Fo2) + (0.0256P)2 + 1.4815P]
where P = (Fo2 + 2Fc2)/3
wR(F2) = 0.058(Δ/σ)max = 0.001
S = 0.99Δρmax = 0.84 e Å3
2354 reflectionsΔρmin = 1.15 e Å3
Special details top

Experimental. Single crystal data for [Cs][Tf2N] were collected on a Bruker D8 Quest diffractometer, with CMOS detector in shutterless mode. The crystal was cooled to 100 K employing an Oxford Cryostream liquid nitrogen cryostat. The diffractometer was equipped with graphite monochromatized MoKa (λ= 0.71073 Å) radiation. A hemisphere of data was collected using omega scans and 0.5° frame widths. Data collection and initial indexing and cell refinement were handled using APEX II1 (Bruker, 2014)software. Frame integration, including Lorentz-polarization corrections, and final cell parameter calculations were carried out using SAINT+ software (Bruker, 2014). The data were corrected for absorption using redundant reflections and the SADABS (Bruker, 2014)program. Decay of reflection intensity was not observed as monitored via analysis of redundant frames. The structure was solved using Direct methods and difference Fourier techniques.

Geometry. All esds (except the esd in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell esds are taken into account individually in the estimation of esds in distances, angles and torsion angles; correlations between esds in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell esds is used for estimating esds involving l.s. planes.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å2) top
xyzUiso*/Ueq
Cs10.03866 (2)0.63206 (3)0.14267 (2)0.01618 (7)
S10.19100 (7)1.13281 (11)0.03845 (6)0.01796 (16)
S20.19461 (7)0.61691 (11)0.37165 (6)0.01711 (16)
F30.3349 (2)1.3866 (4)0.0842 (2)0.0490 (7)
O10.1407 (2)1.0987 (4)0.14485 (18)0.0335 (6)
F60.4204 (2)0.5355 (4)0.29152 (18)0.0473 (7)
F20.4023 (2)1.0936 (4)0.0776 (2)0.0523 (7)
F10.4044 (2)1.2485 (4)0.06094 (18)0.0451 (6)
F50.3425 (2)0.7475 (4)0.21036 (16)0.0419 (6)
O40.1614 (2)0.4598 (4)0.31460 (17)0.0282 (6)
F40.3890 (2)0.8228 (4)0.3522 (2)0.0512 (7)
N10.2092 (3)0.5687 (4)0.48229 (19)0.0198 (6)
O20.1390 (2)1.2826 (4)0.01035 (19)0.0301 (6)
O30.1285 (2)0.7926 (4)0.3755 (2)0.0355 (6)
C20.3470 (3)0.6835 (6)0.3026 (3)0.0286 (8)
C10.3433 (3)1.2186 (5)0.0345 (3)0.0284 (8)
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
Cs10.02257 (12)0.01463 (11)0.01149 (10)0.00018 (7)0.00432 (7)0.00054 (7)
S10.0186 (4)0.0238 (4)0.0111 (3)0.0036 (3)0.0026 (3)0.0028 (3)
S20.0171 (4)0.0168 (4)0.0171 (4)0.0003 (3)0.0035 (3)0.0026 (3)
F30.0498 (15)0.0461 (15)0.0501 (15)0.0090 (12)0.0098 (12)0.0265 (12)
O10.0318 (14)0.0543 (17)0.0119 (11)0.0032 (13)0.0004 (10)0.0044 (11)
F60.0293 (13)0.0630 (17)0.0413 (14)0.0197 (12)0.0084 (10)0.0121 (12)
F20.0309 (13)0.0638 (18)0.0702 (19)0.0044 (12)0.0278 (13)0.0039 (14)
F10.0422 (14)0.0450 (14)0.0385 (13)0.0177 (11)0.0094 (11)0.0069 (11)
F50.0439 (14)0.0521 (15)0.0249 (11)0.0025 (12)0.0017 (10)0.0189 (11)
O40.0422 (15)0.0271 (13)0.0193 (12)0.0111 (11)0.0157 (11)0.0058 (10)
F40.0458 (15)0.0580 (16)0.0496 (15)0.0322 (13)0.0103 (12)0.0048 (13)
N10.0249 (15)0.0184 (13)0.0154 (13)0.0017 (11)0.0034 (11)0.0029 (10)
O20.0414 (15)0.0269 (13)0.0266 (13)0.0148 (11)0.0170 (11)0.0097 (10)
O30.0315 (15)0.0251 (13)0.0462 (16)0.0104 (11)0.0019 (12)0.0091 (12)
C20.0229 (18)0.0355 (19)0.0259 (18)0.0031 (15)0.0029 (14)0.0092 (15)
C10.0284 (19)0.0291 (19)0.0257 (18)0.0036 (15)0.0022 (15)0.0061 (14)
Geometric parameters (Å, º) top
Cs1—O2i3.060 (2)S2—N11.574 (3)
Cs1—O3ii3.074 (3)S2—C21.829 (4)
Cs1—O1ii3.110 (2)S2—Cs1vii4.0548 (12)
Cs1—O4iii3.174 (3)F3—C11.333 (4)
Cs1—O2iv3.208 (2)F3—Cs1vi3.703 (3)
Cs1—O43.207 (2)O1—Cs1iii3.110 (2)
Cs1—N1v3.280 (3)F6—C21.310 (5)
Cs1—O13.435 (3)F2—C11.314 (5)
Cs1—O3v3.539 (3)F1—C11.326 (4)
Cs1—O33.694 (3)F5—C21.331 (4)
Cs1—F3iv3.703 (3)O4—Cs1ii3.175 (3)
Cs1—S23.9118 (12)F4—C21.326 (5)
S1—O11.432 (2)N1—S1vii1.576 (3)
S1—O21.430 (3)N1—Cs1vii3.280 (3)
S1—N1v1.576 (3)O2—Cs1i3.060 (2)
S1—C11.828 (4)O2—Cs1vi3.208 (2)
S1—Cs1vi3.9719 (12)O3—Cs1iii3.074 (3)
S2—O31.426 (3)O3—Cs1vii3.539 (3)
S2—O41.433 (2)
O2i—Cs1—O3ii65.81 (8)O3—Cs1—S221.36 (4)
O2i—Cs1—O1ii99.58 (7)F3iv—Cs1—S265.85 (4)
O3ii—Cs1—O1ii74.33 (7)O1—S1—O2117.87 (17)
O2i—Cs1—O4iii54.48 (6)O1—S1—N1v108.10 (16)
O3ii—Cs1—O4iii97.22 (8)O2—S1—N1v116.27 (14)
O1ii—Cs1—O4iii66.20 (7)O1—S1—C1103.70 (16)
O2i—Cs1—O2iv87.52 (7)O2—S1—C1104.35 (17)
O3ii—Cs1—O2iv60.48 (7)N1v—S1—C1104.86 (16)
O1ii—Cs1—O2iv126.37 (7)O1—S1—Cs1vi75.58 (12)
O4iii—Cs1—O2iv141.95 (6)O2—S1—Cs1vi48.47 (10)
O2i—Cs1—O4162.97 (7)N1v—S1—Cs1vi159.36 (11)
O3ii—Cs1—O499.20 (7)C1—S1—Cs1vi93.60 (12)
O1ii—Cs1—O467.27 (7)O1—S1—Cs157.66 (12)
O4iii—Cs1—O4123.62 (5)O2—S1—Cs1126.74 (12)
O2iv—Cs1—O491.89 (7)N1v—S1—Cs152.89 (10)
O2i—Cs1—N1v82.39 (7)C1—S1—Cs1128.83 (13)
O3ii—Cs1—N1v135.52 (7)Cs1vi—S1—Cs1120.90 (3)
O1ii—Cs1—N1v144.35 (7)O3—S2—O4117.41 (17)
O4iii—Cs1—N1v87.65 (7)O3—S2—N1108.66 (16)
O2iv—Cs1—N1v89.20 (7)O4—S2—N1116.61 (14)
O4—Cs1—N1v114.62 (7)O3—S2—C2103.71 (17)
O2i—Cs1—O195.58 (7)O4—S2—C2105.06 (17)
O3ii—Cs1—O1159.64 (7)N1—S2—C2103.49 (16)
O1ii—Cs1—O1102.31 (7)O3—S2—Cs170.70 (12)
O4iii—Cs1—O163.81 (7)O4—S2—Cs150.92 (10)
O2iv—Cs1—O1130.03 (7)N1—S2—Cs1157.27 (11)
O4—Cs1—O197.80 (6)C2—S2—Cs198.57 (12)
N1v—Cs1—O142.47 (6)O3—S2—Cs1vii59.03 (12)
O2i—Cs1—O3v56.78 (7)O4—S2—Cs1vii133.75 (11)
O3ii—Cs1—O3v93.89 (6)N1—S2—Cs1vii50.27 (10)
O1ii—Cs1—O3v156.36 (7)C2—S2—Cs1vii120.87 (13)
O4iii—Cs1—O3v95.87 (6)Cs1—S2—Cs1vii120.87 (3)
O2iv—Cs1—O3v58.95 (7)C1—F3—Cs1vi117.4 (2)
O4—Cs1—O3v135.86 (7)S1—O1—Cs1iii158.44 (17)
N1v—Cs1—O3v41.69 (6)S1—O1—Cs1101.72 (13)
O1—Cs1—O3v81.53 (6)Cs1iii—O1—Cs185.77 (6)
O2i—Cs1—O3142.43 (6)S2—O4—Cs1ii135.68 (14)
O3ii—Cs1—O3126.88 (6)S2—O4—Cs1108.79 (12)
O1ii—Cs1—O359.74 (7)Cs1ii—O4—Cs188.69 (6)
O4iii—Cs1—O387.95 (6)S2—N1—S1vii127.60 (17)
O2iv—Cs1—O3130.02 (6)S2—N1—Cs1vii108.07 (13)
O4—Cs1—O340.70 (6)S1vii—N1—Cs1vii104.58 (12)
N1v—Cs1—O397.36 (7)S1—O2—Cs1i144.39 (15)
O1—Cs1—O363.07 (6)S1—O2—Cs1vi112.04 (12)
O3v—Cs1—O3138.32 (6)Cs1i—O2—Cs1vi92.48 (7)
O2i—Cs1—F3iv131.63 (6)S2—O3—Cs1iii169.31 (18)
O3ii—Cs1—F3iv100.78 (7)S2—O3—Cs1vii100.76 (13)
O1ii—Cs1—F3iv122.16 (7)Cs1iii—O3—Cs1vii86.11 (6)
O4iii—Cs1—F3iv161.69 (6)S2—O3—Cs187.94 (13)
O2iv—Cs1—F3iv49.29 (6)Cs1iii—O3—Cs181.90 (6)
O4—Cs1—F3iv56.56 (7)Cs1vii—O3—Cs1146.66 (8)
N1v—Cs1—F3iv77.18 (7)F6—C2—F5108.6 (3)
O1—Cs1—F3iv97.90 (6)F6—C2—F4109.1 (3)
O3v—Cs1—F3iv79.67 (6)F5—C2—F4109.1 (3)
O3—Cs1—F3iv83.94 (6)F6—C2—S2111.6 (3)
O2i—Cs1—S2162.46 (5)F5—C2—S2108.4 (2)
O3ii—Cs1—S2116.76 (6)F4—C2—S2110.0 (3)
O1ii—Cs1—S266.21 (6)F2—C1—F1108.9 (3)
O4iii—Cs1—S2108.62 (4)F2—C1—F3109.5 (3)
O2iv—Cs1—S2109.03 (5)F1—C1—F3108.0 (3)
O4—Cs1—S220.30 (5)F2—C1—S1111.0 (3)
N1v—Cs1—S2103.02 (5)F1—C1—S1111.0 (3)
O1—Cs1—S278.43 (4)F3—C1—S1108.3 (3)
O3v—Cs1—S2136.79 (5)
Symmetry codes: (i) x, y+2, z; (ii) x, y1/2, z+1/2; (iii) x, y+1/2, z+1/2; (iv) x, y1, z; (v) x, y+3/2, z1/2; (vi) x, y+1, z; (vii) x, y+3/2, z+1/2.
Comparison of Raman modes in Tf2N compounds top
Comparison of observed Raman shifts in cm-1 from Tf2N-containing compounds. Band wave numbers given in bold are unassigned and in italicized are from reanalysis of reported spectra for La[Tf2N]3(H2O)3. Major band assignments are given with ν (stretching), δ (bending), ω (wagging), τ (twisting) and ρ (rocking) and planar designations are i.p. for in plane and o.p. for out of plane.
ModeGroupTf2N- in H2OHTf2NLa[Tf2N]3(H2O)3Cs[Tf2N]
1456
1443
νa i.p.SO21351
νa o.p.SO21332143613161322
1427
δNH1332
νsCF31239125012431240
νaCF31220
1203120812101206
νs i.p.SO21131113411481145
δsCF3744765754740
δSNS634669659
δa i.p.SO2594583
δaCF3567570573572
555
δsSO2551554553
535
511507
γNH526
495444
ωSO2407, 401420, 412
380
τSO2351356349
339
ρSO2325335332328
312299310304
νMO297?
ρCF3276288283
264241
210215
202173
185130
 

Funding information

Funding for this research was provided by: National Nuclear Security Administration (NA-23).

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