Crystal structures and raman spectra of imidazolium poly[perfluorotitanate(IV)] salts containing the [TiF6]2-, ([Ti2F9]-)∞, and [Ti 2F11]3- and the New [Ti4F 20]4- and [Ti5F23]3- anions

Article abstract of DOI:10.1021/ic302468j

Reactions between imidazole (Im, C₃H₄N₂) and TiF₄ in anhydrous hydrogen fluoride (aHF) in different molar ratios have yielded [ImH]₂[TiF₆]·2HF, [ImH] ₃[Ti₂F₁₁], [ImH]₄[Ti ₄F₂₀], [ImH]₃[Ti₅F₂₃], and [ImH][Ti₂F₉] upon crystallization. All five structures were characterized by low-temperature single-crystal X-ray diffraction. The single-crystal Raman spectra of [ImH]₄[Ti₄F₂₀], [ImH]₃[Ti₅F₂₃], and [ImH][Ti₂F ₉] were also recorded and assigned. In the crystal structure of [ImH]₂[TiF₆]·2HF, two HF molecules are coordinated to each [TiF₆]^2- anion by means of strong F-H···F hydrogen bonds. The [Ti₂F ₁₁]^3- anion of [ImH]₃[Ti₂F ₁₁] results from association of two TiF₆ octahedra through a common fluorine vertex. Three crystallographically independent [Ti ₂F₁₁]^3- anions, which have distinct geometries and orientations, are hydrogen-bonded to the [ImH]⁺ cations. The [ImH]₄[Ti₄F₂₀] salt crystallized in two crystal modifications at low (α-phase, 200 K) and ambient (β-phase, 298 K) temperatures. The tetrameric [Ti₄F₂₀]^4- anion of [ImH]₄[Ti₄F₂₀] consists of rings of four TiF₆ octahedra, which each share two cis-fluorine vertices, whereas the pentameric [Ti₅F₂₃]^3- anion of [ImH] ₃[Ti₅F₂₃] results from association of five TiF₆ units, where four of the TiF₆ octahedra share two cis-vertices, forming a tetrameric ring as in [Ti₄F ₂₀]^4-, and the fifth TiF₆ unit shares three fluorine vertices with three TiF₆ units of the tetrameric ring. The [ImH][Ti₂F₉] salt also crystallizes in two crystal modifications at low (α-phase, 200 K) and high (β-phase, 298 K) temperatures and contains polymeric ([Ti₂F₉] ^-)_∞ anions, which appear as two parallel infinite zigzag chains comprised of TiF₆ units, where each TiF₆ unit of one chain is connected to a TiF₆ unit of the second chain through a shared fluorine vertex. Quantum-chemical calculations at the B3LYP/SDDALL level of theory were used to arrive at the gas-phase geometries and vibrational frequencies of the [Ti₄F₂₀]^4- and [Ti₅F₂₃]^3- anions, which aided in the assignment of the experimental vibrational frequencies of the anion series.

Full text of DOI:10.1021/ic302468j

Article
pubs.acs.org/IC
Crystal Structures and Raman Spectra of Imidazolium
2
−
−
Poly[perfluorotitanate(IV)] Salts Containing the [TiF ] , ([Ti F ] ) ,
6
2 9
∞
3
−
4−
3−
and [Ti F ] and the New [Ti F ] and [Ti F ] Anions
2
11
4 20
5 23
†
†
‡
,‡
Igor M. Shlyapnikov, Hel
́
en
̀
e P. A. Mercier, Evgeny A. Goreshnik, Gary J. Schrobilgen,*
,†
and Zoran Mazej*
†
Department of Inorganic Chemistry and Technology, Joze
̌
f Stefan Institute, Jamova 39, SI-1000 Ljubljana, Slovenia
Department of Chemistry, McMaster University, Hamilton, Ontario L8S 4M1, Canada
S Supporting Information
‡
*
ABSTRACT: Reactions between imidazole (Im, C H N ) and TiF in anhydrous hydrogen
3
4
2
4
fluoride (aHF) in different molar ratios have yielded [ImH] [TiF ]·2HF, [ImH] [Ti F ],
2
6
3
2 11
[
ImH] [Ti F ], [ImH] [Ti F ], and [ImH][Ti F ] upon crystallization. All five structures
4 4 20 3 5 23 2 9
were characterized by low-temperature single-crystal X-ray diffraction. The single-crystal
Raman spectra of [ImH] [Ti F ], [ImH] [Ti F ], and [ImH][Ti F ] were also recorded and
4
4
20
3
5
23
2 9
assigned. In the crystal structure of [ImH] [TiF ]·2HF, two HF molecules are coordinated to
2
6
each [TiF6]2 anion by means of strong F−H···F hydrogen bonds. The [Ti F ] anion of
−
3−
2
11
[
ImH] [Ti F ] results from association of two TiF octahedra through a common fluorine
3 2 11 6
3
−
vertex. Three crystallographically independent [Ti F ] anions, which have distinct
geometries and orientations, are hydrogen-bonded to the [ImH] cations. The [ImH] [Ti F ]
2
11
+
4
4 20
salt crystallized in two crystal modifications at low (α-phase, 200 K) and ambient (β-phase, 298
4
−
K) temperatures. The tetrameric [Ti F ] anion of [ImH] [Ti F ] consists of rings of four
4
20
4
4 20
3
−
TiF octahedra, which each share two cis-fluorine vertices, whereas the pentameric [Ti F ]
6
5 23
anion of [ImH] [Ti F ] results from association of five TiF units, where four of the TiF octahedra share two cis-vertices,
3
5
23
6
6
4
−
forming a tetrameric ring as in [Ti F ] , and the fifth TiF unit shares three fluorine vertices with three TiF units of the
4
20
6
6
tetrameric ring. The [ImH][Ti F ] salt also crystallizes in two crystal modifications at low (α-phase, 200 K) and high (β-phase,
2
9
−
2
98 K) temperatures and contains polymeric ([Ti F ] ) anions, which appear as two parallel infinite zigzag chains comprised of
2 9 ∞
TiF units, where each TiF unit of one chain is connected to a TiF unit of the second chain through a shared fluorine vertex.
6
6
6
Quantum-chemical calculations at the B3LYP/SDDALL level of theory were used to arrive at the gas-phase geometries and
4−
3−
vibrational frequencies of the [Ti F ] and [Ti F ] anions, which aided in the assignment of the experimental vibrational
4
20
5 23
frequencies of the anion series.
1
8
3−
1
. INTRODUCTION
[[H O] [TiF ]]·[NH ][F]. The [Ti F ]
anion was
2
4
6
4
4 19
19
recently isolated for the first time as the [XeF ] [Ti F ] salt.
In the present paper, crystallizations of imidazole (Im,
C H N ) and TiF have been carried out in anhydrous
hydrogen fluoride (aHF) and have yielded five imidazolium
salts containing the [TiF ] , [Ti F ] , [Ti F ] , [Ti F ] ,
and ([Ti F ] ) anions. The salts have been isolated, and their
crystal structures were determined and are described in the
present paper. Although [TiF ] salts are well-known, salts
containing ([Ti F ] ) and [Ti F ]
Ti F ] anion represents a new example of a tetrameric
anion comprised of four vertex-sharing octahedral TiF units,
whereas the [Ti F ] anion is comprised of five vertex-sharing
TiF octahedra, providing a novel example of a pentameric
poly[perfluorotitanate] anion. Quantum-chemical calculations
have been used to compare the experimental geometries of
5
3
4 19
Complex poly[perfluorotitanate(IV)] compounds are of
interest because they are used as stereoselective catalysts in
organic synthesis and in reactions leading to olefin polymer-
ization. Two types of main-group titanium fluoride complexes
exist: organometallic complexes with chemical bonds between
titanium and organic molecules and coordination complexes in
which the fluorotitanate anions are coordinated to their cations
through fluorine atoms.
1
3
4
2
4
2
2−
3−
4−
3−
6
2
11
4
20
5 23
−
3
2
9
∞
2−
6
4
−
3−
4
,9
are rare.
The
2
9
∞
2 11
4−
Among the many possible poly[perfluorotitanate(IV)]
[
4
20
y−
anions, [TixF
4x+y
]
(x, y ≥ 1), several have been synthesized,
6
2
−
5,6
2− 7,8
3−
9
2− 4,10
3−
namely, [TiF ] , [Ti F ] , [Ti F ] , [Ti F ] ,
6
2
10
11
2
11
4
18
5 23
−
−
4
(
(
(
[TiF ] ) (single chains), ([Ti F ] ) (double chains),
[Ti F ] ) (columns), ([Ti F ] ) (columns), and
[Ti F ] ) (layers). Salts of the [TiF7] anion are
5
∞
2
9
∞
6
−
12
2−
13
3
13
∞
7
30
∞
−
14
3−
8
33
∞
4
−
3−
presently unknown. Salts that have been formulated as
Cs [TiF ] and [NH ][Cu][TiF ]·4H O are actually
comprised of isolated [TiF6] anions and a fluoride ion and
are correctly formulated as Cs [TiF ]·Cs[F]
[Ti
4
F
20
]
and [Ti
5
F
23
]
with their calculated gas-phase
1
5
16
3
7
4
7
2
2
−
Received: November 12, 2012
Published: July 9, 2013
15,17
and [Cu]-
2
6
©
2013 American Chemical Society
8315
dx.doi.org/10.1021/ic302468j | Inorg. Chem. 2013, 52, 8315−8326

Inorganic Chemistry
Article
Table 1. Crystal Data and Refinement Results for Imidazolium Poly[perfluorotitanate(IV)] Salts Arising from Im−TiF −aHF
4
Systems
a
a
a
a
[
ImH] [TiF ]·2HF [ImH] [Ti F ] β-[ImH] [Ti F ]
α-[ImH] [Ti F ]
[ImH] [Ti F ] β-[ImH][Ti F ]
α-[ImH][Ti F ]
2 9
2
6
3
512.07
C2/m
2
11
4
847.96
C2/m
4
20
4
4
20
3
5
23
2
9
fw (g/mol)
space group
a (Å)
340.07
C2/c
847.96
883.78
Pna21
335.89
335.89
P1
̅
Pnma
P2 /a
1
14.437(8)
7.436(4)
13.261(8)
90.00
13.5371(2)
25.7451(4)
10.4139(2)
90.00
13.2139(4)
15.2096(7)
8.9514(3)
90.00
8.791(3)
22.0259(4)
10.2622(2)
12.3180(2)
90.00
5.3978(2)
12.2169(6)
15.2345(7)
90.00
5.3914(3)
b (Å)
9.971(4)
15.4836(10)
11.9543(8)
90.00
c (Å)
10.126(4)
118.808(8)
92.366(3)
113.595(8)
681.8(5)
1
α (deg)
β (deg)
γ (deg)
V (Å3)
115.77(2)
90.00
100.980(1)
90.00
129.690(1)
90.00
90.00
90.00
90.977(4)
90.00
90.00
90.00
1282.1(13)
4
3562.95(10)
8
1384.35(10)
2
2784.29(9)
4
1004.63(8)
4
997.78(11)
4
Z
Dcalc (g/cm3)
1.762
1.909
2.034
2.065
2.108
2.221
2.236
T (K)
200
200
298
200
200
298
200
b
R1
0.0882
0.2181
0.0481
0.1416
0.0518
0.1561
0.0466
0.0317
0.0898
0.0490
0.1523
0.0655
c
wR2
0.1181
0.1576
a
b
The symbols α and β correspond to the low- and high-temperature modifications, respectively, of [ImH] [Ti F ] and [ImH][Ti F ]. R is defined
4
4
20
2
9
1
c
2
2
2
2 2 1/2
as ∑||F | − |F ||/∑|F | for I > 2σ(I). wR is defined as [∑[w(F −F ) ]/∑w(F ) ] for I > 2σ(I).
o
c
o
2
o
c
o
geometries. Their Raman spectra were assigned with the aid of
the calculated frequencies and vibrational-mode descriptions.
2. RESULTS AND DISCUSSION
Crystal Structures of [ImH] [TiF ]·2HF, [ImH] [Ti F ],
2
6
3
2 11
[
ImH] [Ti F ], [ImH] [Ti F ], and [ImH][Ti F ]. The title
4 4 20 3 5 23 2 9
salts were crystallized from aHF, providing single crystals from
which their X-ray crystal structures were determined. The
corresponding crystal data and refinement results are
summarized in Table 1, geometrical parameters are summarized
in Tables 2−4 and S1−S3 (Supporting Information), and
packing diagrams are shown in Figures S1−S7 (Supporting
Information) for [ImH] [TiF ]·2HF, [ImH] [Ti F ], [Im-
2
6
3
2 11
H] [Ti F ], [ImH] [Ti F ], and [ImH][Ti F ].
4
4
20
3
5
23
2 9
(
a) [ImH] [TiF ]·2HF. The crystal structure of [Im-
2 6
2
−
H] [TiF ]·2HF consists of [TiF ] anions and two HF
2
6
6
solvent molecules that are coordinated to the F2 ligands of
−
Figure 1. Crystal structure of [ImH]
[TiF ]·2HF showing coordina-
2 6
[
TiF6]2 by means of F−H···F hydrogen bonds, whereas the F3
tion of the hydrogen atoms of the HF molecules to the fluorine atoms
2−
and F1 ligands of [TiF ] are more weakly hydrogen-bonded
2−
of the [TiF6]
6
anion. Thermal ellipsoids are drawn at the 50%
probability level. Only one of the two orientations of the disordered
+
+
to [ImH] cations (Figure 1). The [ImH] cations are 2-fold-
disordered. The Ti−F2 bonds are longer [1.908(4) Å] than the
Ti−F3 [1.811(4) Å] and Ti−F1 [1.837(3) Å] bonds. The
F4(H)···F2(−Ti) distance [2.374(6) Å] is shorter, i.e., the HF
molecules are more strongly hydrogen-bonded than in
+
[
ImH] cations is depicted.
equal to 1.9805(6) and 1.796(4)−1.857(2) Å, respectively, and
a Ti1−F −Ti1 angle of 180°. The equatorial TiF planes of the
20
2−
K CrF ·2HF [F(−H)···F(−Cr), 2.455 Å]. Each [TiF6] +
2
6
b
4
+
3−
anion is coordinated to six [ImH] cations, and the [ImH]
TiF octahedra of [Ti F ] are eclipsed. The Ti F unit
6 2 11 2 11
cations are each coordinated to three TiF units through N−
containing Ti2 is likewise comprised of two symmetry-related
6
H···F and C−H···F hydrogen bonds.
octahedra, but their TiF planes have a gauche conformation
4
(
b) [ImH] [Ti F ]. The crystal structure of [ImH] [Ti F ]
with a dihedral angle of 8.50(6)° (Figure S8 in the Supporting
3
2
11
3
2 11
3
−
consists of discrete [Ti F ] anions in which two TiF6
octahedra of [Ti F ] share a common vertex (Figure 2).
Information). The Ti2−F bond [1.9683(5) Å] is longer than
2
11
b
3
−
the Ti2−F bonds [1.792(2)−1.862(2) Å] and shorter than the
2
11
t
The Ti−F bond lengths range from 1.768(3) to 1.908(2) Å
corresponding Ti1−F bond, with a Ti2−F −Ti2 angle that is
t
b
b
and from 1.9683(5) to 1.9805(6) Å for the Ti−F bond lengths
slightly bent [174.28(18)°]. The Ti F unit containing Ti3 has
2 11
b
(
Table 2 and Figure 3) and are comparable to the
a Ti3−F bond length [1.9778(8) Å] that is very similar to the
b
corresponding bond lengths in [C H N] [H O][Ti F ] [Ti−
F , 1.776(2)−1.880(2) Å; Ti−F , 1.9732(10) Å].
Ti1−F bond length [1.9805(6) Å] with a linear Ti3−F −Ti3
5
6
2
3
2
11
b
b
9
angle and eclipsed TiF planes.
The coordination spheres formed by the [ImH] cations of
the three crystallographically independent [Ti F ] anions
t
b
4
+
In contrast with [C H N] [H O][Ti F ], where only one
5
6
2
3
2 11
9
3−
Ti2F11 unit is defined, there are three crystallographically
2
11
independent Ti2F11 units in [ImH] [Ti F ] which have
differ with respect to their hydrogen-bonded contacts (Table
3
2 11
3
−
different conformations and coordination spheres (Figures 2
and 3). The Ti2F11 unit containing Ti1 is comprised of two
symmetry-related octahedra with Ti1−F and Ti1−F bonds
S4 in the Supporting Information). The [Ti1 F ] anions are
2 11
+
hydrogen-bonded to eight [ImH] cations containing the non-
disordered N3 and N4 atoms and the disordered N5/N5A and
b
t
8
316
dx.doi.org/10.1021/ic302468j | Inorg. Chem. 2013, 52, 8315−8326

Inorganic Chemistry
Article
+
Figure 2. Crystal structure of [ImH] [Ti F ] showing coordination between the hydrogen atoms of the [ImH] cations and the fluorine atoms of
3
2 11
3
−
+
the [Ti F ] anion. Thermal ellipsoids are drawn at the 50% probability level. Only one of the two orientations of the disordered [ImH] cations is
2
11
depicted.
3
−
Table 2. Experimental Geometrical Parameters of the Three Crystallographically Independent [Ti F ] Anions in the Crystal
2
11
a
Structure of [ImH] [Ti F ]
3
2 11
Bond Lengths (Å)
1.792(2)
Ti1−F3
Ti1−F2
Ti1−F4
Ti1−F5
Ti1−F5A
Ti1−F1
1.796(3)
1.849(3)
1.824(2)
1.857(2)
1.857(2)
1.9805(6)
Ti2−F9
Ti2−F8
Ti2−F11
Ti2−F10
Ti2−F7
Ti2−F6
Ti3−F14
Ti3−F13
Ti3−F15
Ti3−F16
Ti3−F16B
Ti3−F12
1.768(3)
1.908(2)
1.798(3)
1.847(2)
1.847(2)
1.9770(8)
1.862(2)
1.841(2)
1.834(2)
1.837(2)
1.9683(5)
Bond Angles (deg)
F3−Ti1−F2
F3−Ti1−F4
F3−Ti1−F5
F3−Ti1−F5A
F3−Ti1−F1
F2−Ti1−F4
F2−Ti1−F5
F2−Ti1−F5A
F2−Ti1−F1
F4−Ti1−F5
F4−Ti1−F5A
F4−Ti1−F1
F5−Ti1−F5A
F5−Ti1−F1
F5A−Ti1−F1
Ti1−F1−Ti1A
93.55(15)
93.63(14)
93.00(6)
93.00(6)
179.38(11)
172.82(12)
89.52(5)
89.52(5)
85.83(10)
90.10(5)
90.10(5)
86.99(9)
173.97(12)
87.00(6)
87.00(6)
180.0
F9−Ti2−F8
F9−Ti2−F11
F9−Ti2−F10
F9−Ti2−F7
F9−Ti2−F6
F8−Ti2−F11
F8−Ti2−F10
F8−Ti2−F7
F8−Ti2−F6
F11−Ti2−F10
F11−Ti2−F7
F11−Ti2−F6
F10−Ti2−F7
F10−Ti2−F6
F7−Ti2−F6
Ti2−F6−Ti2A
93.73(9)
93.36(9)
94.11(10)
92.35(9)
179.01(11)
172.92(8)
88.62(7)
89.26(7)
86.78(6)
90.95(7)
90.37(7)
86.13(6)
173.32(9)
86.75(11)
86.81(11)
174.28(18)
F14−Ti3−F13
F14−Ti3−F15
F14−Ti3−F16
F14−Ti3−F16B
F14−Ti3−F12
F13−Ti3−F15
F13−Ti3−F16
F13−Ti3−F16B
F13−Ti3−F12
F15−Ti3−F16
F15−Ti3−F16B
F15−Ti3−F12
F16−Ti3−F16B
F16−Ti3−F12
F16B−Ti3−F12
Ti3−F12−Ti3A
89.55(13)
96.56(16)
94.90(7)
94.90(7)
176.17(12)
173.89(14)
86.92(6)
86.92(6)
86.61(8)
92.54(5)
92.54(5)
87.28(12)
168.37(14)
84.90(7)
84.90(7)
180.0
a
The atom-labeling schemes correspond to those used in Figure 3.
4
−
N6/N6A atoms [N3···F5, 2.813(3) Å; N5A···F2, 2.925(9) Å;
where the [Ti F ] anion has been structurally characterized
4 20
3−
C8···F5, 2.957(10) Å; C11···F4, 3.017(3) Å]. The [Ti2 F ]
for the first time. Examples of tetrameric metal fluoride species
are rare. The first evidence for a tetramer comprised of four
MF octahedra sharing four vertices was provided by the Sn
and F NMR spectra of “N SnF ” in a HF solution, which
yielded the gross geometry of the [Sn F ] anion. Two
tetrameric perfluorotitanate salts, [Ti F ]
[Ti F ] , and two tetrameric non-titanium compounds,
2
11
+
anions are hydrogen-bonded to six [ImH] cations containing
the N1 and N2 atoms and the disordered N5/N5A and N6/
N6A atoms [N2···F11, 2.793(3) Å; N6···F8, 2.866(3) Å;
1
19
6
1
9
5
5
3
−
4−
21
C8A···F10, 2.868(4) Å]. Each [Ti3 F ] anion is hydrogen-
2
11
4 20
+
2− 4,10
bonded to eight non-disordered [ImH] cations containing the
and
4
18
3−
19
N1 and N2 atoms and the N3 and N4 atoms [N4···F16,
4
19
2
2
23
2
.743(3) Å; N1···F13, 2.749(2) Å; C1···F16, 2.996(4) Å]. The
[C N H ] [V O F ]·3H O and [CN H ] [Zr F ]·4H O,
6
4
21 2
4
4
14
2
4
8 4
4
24
6−
2
3−
three Ti2F11 units are pairwise coordinated so that [Ti1 F ]
is bridged to [Ti2 F ] through [ImH] cations containing
N5/N5A and N6/N6A and to [Ti3 F ] through cations
containing N3 and N4, whereas [Ti2 F ] is bridged to
have been described in the literature. The [V O F ] anion is
comprised of four VOF octahedra sharing two vertices and two
edges, whereas the [Zr F ] anion is comprised of four ZrF8
square antiprisms sharing four edges.
2
11
4
4 14
3−
+
2
11
5
3−
8−
2
11
4 24
3
−
2
11
3−
[
Ti3 F ] through cations containing N1 and N2.
The α- and β-phases of [ImH] [Ti F ] (the crystal
2
11
4
4 20
(
c) [ImH] [Ti F ]. The crystalline phase corresponding to
structures were determined at 200 and 298 K, respectively)
4
4 20
4−
+
an Im:TiF molar ratio of 1:1 is formulated as [ImH] [Ti F ],
consist of tetrameric [Ti F ] anions and [ImH] cations that
4
4
4
20
4
20
8
317
dx.doi.org/10.1021/ic302468j | Inorg. Chem. 2013, 52, 8315−8326

Inorganic Chemistry
Article
3
−
Figure 3. Experimental geometries of the [Ti F ] anions in the crystal structure of [ImH] [Ti F ]. Thermal ellipsoids are drawn at the 50%
2
11
3
2 11
probability level.
+
interact through hydrogen bonds. The two [ImH] cations
85.8(2)°]. Each titanium atom is coordinated to two bridging
4−
defined in the β-phase are 2-fold disordered. The [Ti F ]
anion is comprised of four TiF octahedra sharing two cis
vertices (Figures 4 and 5). All titanium atoms in β-
and four terminal fluorine atoms. The Ti−F bond lengths
4
20
t
6
range from 1.776(3) to 1.824(4) Å and are significantly shorter
than the Ti−F bonds, i.e., Ti1−F , 1.956(2) Å; Ti2−F ,
b
b
b
1
.978(2) Å (Table 3).
Each [Ti F ] anion is hydrogen-bonded to 12 [ImH]+
4
−
4
20
cations, with N−H···F and C−H···F distances of 2.872(7)−
3
.093(22) and 2.836(13)−3.153(12) Å, respectively (Table S4
in the Supporting Information).
The Ti···Ti distances and Ti−F and Ti−F bond lengths in
t
b
α-[ImH] [Ti F ] (Figure 5) are comparable to those in the β-
4
4 20
modification [Ti···Ti, 3.854(1)−3.902(1) Å; Ti−F , 1.790(2)−
t
4
−
1
.840(2) Å; Ti−F , 1.965(2)−1.989(2) Å]. Each [Ti F ]
b
4 20
+
+
anion is hydrogen-bonded to 14 [ImH] cations. Eight [ImH]
cations containing N1 and N2 atoms are hydrogen-bonded to
different anions through one C−H···F [C1···F10, 2.990(4) Å]
and four N−H···F [N2···F5, 2.847(4) Å; N2···F8, 2.936(4) Å;
N1···F4, 2.839(3) Å; N1···F9, 2.977(4) Å] hydrogen bonds.
Figure 4. Crystal structure of β-[ImH] [Ti F ], determined at 298 K,
+
4
4 20
+
The remaining six [ImH] cations containing N3, N4, and C4
are coordinated to two [Ti F ] anions through two N−H···F
showing coordination between the hydrogen atoms of the [ImH]
cations and the fluorine atoms of the [Ti F ] anion. Thermal
4−
4
−
4 20
4
20
[
N4···F6, 2.811(4) Å; N3···F9, 3.003(4) Å] hydrogen bonds
and to two other anions through two N−H···F [N3···F4,
.906(4) Å; N4···F7, 2.961(5) Å] and through one C−H···F
C4···F7, 2.935(5) Å] hydrogen bonds (Table S4 in the
Supporting Information).
d) [ImH] [Ti F ]. The [ImH] [Ti F ] salt was obtained
ellipsoids are drawn at the 50% probability level. Only one of the two
+
orientations of the disordered [ImH] cations is depicted.
2
[
(
3
5
23
3
5 23
from a starting molar ratio of Im:TiF = 1:1.67 (3:5). To the
4
authors’ knowledge, no pentameric units consisting of MX (X
n
=
F or F/O, n = 4−8) polyhedra have been reported thus far
24
3−
for organically templated metal fluorides. The [Ti F ]
5
23
anion, which is comprised of five TiF octahedra, represents a
6
unique geometry among known pentameric polyanions
comprised of octahedra. Each of four TiF octahedra share
6
two cis vertices with adjacent TiF units, forming a tetrameric
6
ring (Figure 6 and Table 4). The fifth TiF unit shares three
6
vertices with three octahedra of the tetrameric ring. All titanium
atoms are crystallographically independent. Four of them (Ti2,
Ti3, Ti4, and Ti5) are coordinated to three bridging and three
terminal fluorine atoms. The unique Ti1 atom is coordinated to
Figure 5. Crystal structure of α-[ImH] [Ti F ] determined at 200 K
4
4 20
+
showing coordination between the hydrogen atoms of the [ImH]
4
−
cations and the fluorine atoms of the [Ti F ] anion. Thermal
two cis-bridged and to four terminal fluorine atoms. The Ti−F
4
20
t
ellipsoids are drawn at the 50% probability level.
and Ti−F bond length ranges are 1.757(3)−1.848(3) and
b
3−
1
.942(2)−2.014(2) Å, respectively. The [Ti F ] anion is
5
23
+
[
ImH] [Ti F ] are situated in the same plane with four
coordinated to six [ImH] cations (three are crystallo-
graphically unique) through eight N−H···F [N···F, 2.805(4)−
2.999(4) Å] and two C−H···F [C···F, 2.989(4)−2.995(4) Å]
4
4 20
equal Ti···Ti distances [3.897(1) Å] and Ti···Ti···Ti angles
close to 90° [Ti2···Ti1···Ti2, 94.2(2)°; Ti2···Ti1···Ti2,
8
318
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Inorganic Chemistry
Table 3. Experimental and Calculated Geometrical Parameters for the [Ti F ] Anion
a,b
Article
4
−
4
20
exptl
4−
4−
b,c
β-[Ti F ]
α-[Ti F ]
calcd (D2d)
4
20
4 20
Bond Lengths (Å)
Ti1−F1
Ti1−F1
Ti1−F1A
Ti1−F2
Ti1−F3
Ti1−F3A
Ti1−F7
Ti2−F1
Ti2−F1B
Ti2−F4
Ti2−F4B
Ti2−F6
Ti2−F6B
1.956(2)
1.956(2)
1.807(4)
1.793(3)
1.793(3)
1.824(4)
1.978(2)
1.978(2)
1.803(3)
1.803(3)
1.776(3)
1.776(3)
1.965(2)
1.970(2)
1.807(2)
1.817(2)
1.793(2)
1.840(2)
1.989(2)
1.826(2)
1.790(2)
1.800(2)
1.800(2)
1.989(2)
Ti1−F1
Ti1−F2
Ti1−F3
Ti1−F4
Ti1−F5
Ti1−F6
Ti2−F1
Ti2−F7
Ti2−F8
Ti2−F9
Ti2−F10
Ti2−F11
2.007
Ti1−F2
Ti1−F3
Ti1−F4
Ti1−F5
Ti1−F6
Ti2−F1
Ti2−F7
Ti2−F8
Ti2−F9
Ti2−F10
Ti2−F2A
2.007
1.839
1.842
1.842
1.839
2.007
1.839
1.842
1.842
1.839
2.007
Bond Angles (deg)
F1−Ti1−F1A
F1−Ti1−F2
F1−Ti1−F3A
F1−Ti1−F3
89.18(18)
86.35(14)
178.06(15)
89.20(13)
86.92(13)
86.35(14)
89.20(13)
178.06(15)
86.92(13)
92.49(13)
92.49(13)
170.54(19)
92.41(20)
94.05(13)
94.05(13)
82.93(17)
86.23(14)
90.60(14)
173.46(16)
87.78(14)
87.78(14)
173.46(16)
90.60(14)
87.78(14)
92.74(16)
92.62(15)
172.00(20)
95.88(24)
92.62(15)
92.74(16)
164.40(19)
164.40(19)
F1−Ti1−F2
F1−Ti1−F3
F1−Ti1−F4
F1−Ti1−F5
F1−Ti1−F6
F2−Ti1−F3
F2−Ti1−F4
F2−Ti1−F5
F2−Ti1−F6
F3−Ti1−F4
F3−Ti1−F5
F3−Ti1−F6
F4−Ti1−F5
F4−Ti1−F6
F5−Ti1−F6
F1−Ti2−F2A
F1−Ti2−F7
F1−Ti2−F8
F1−Ti2−F9
F1−Ti2−F10
F2A−Ti2−F7
F2A−Ti2−F8
F2A−Ti2−F9
F2A−Ti2−F10
F7−Ti2−F8
F7−Ti2−F9
F7−Ti2−F10
F8−Ti2−F9
F8−Ti2−F10
F9−Ti1−F10
Ti1−F1−Ti2
Ti1−F2−Ti2A
89.46(9)
F1−Ti1−F2
F1−Ti1−F3
F1−Ti1−F4
F1−Ti1−F5
F1−Ti1−F6
F2−Ti1−F3
F2−Ti1−F4
F2−Ti1−F5
F2−Ti1−F6
F3−Ti1−F4
F3−Ti1−F5
F3−Ti1−F6
F4−Ti1−F5
F4−Ti1−F6
F5−Ti1−F6
F1−Ti2−F11
F1−Ti2−F7
F1−Ti2−F8
F1−Ti2−F9
F1−Ti2−F10
F11−Ti2−F7
F11−Ti2−F8
F11−Ti2−F9
F11−Ti2−F10
F7−Ti2−F8
F7−Ti2−F9
F7−Ti2−F16
F8−Ti2−F9
F8−Ti2−F10
F9−Ti2−F10
Ti1−F1−Ti2
Ti1−F2−Ti1A
86.9
88.9
177.5
90.6
88.9
88.9
90.6
177.5
88.9
91.1
91.1
176.9
91.9
91.1
91.1
86.9
88.9
90.6
177.5
88.9
88.9
88.9
90.6
88.9
91.1
91.1
176.9
91.9
91.1
91.1
176.9
176.9
86.47(10)
177.75(10)
89.71(10)
87.09(9)
F1−Ti1−F7
F1A−Ti1−F2
F1A−Ti1−F3A
F1A−Ti1−F3
F1A−Ti1−F7
F2−Ti1−F3A
F2−Ti1−F3
86.22(9)
88.43(10)
179.14(9)
86.07(9)
92.37(10)
93.95(10)
170.14(10)
92.40(10)
93.55(9)
F2−Ti1−F7
F3A−Ti1−F3
F3A−Ti1−F7
F3−Ti1−F7
F1−Ti2−F1B
F1−Ti2−F4
93.67(10)
82.51(9)
86.15(10)
90.58(10)
172.74(10)
88.11(10)
86.74(10)
173.08(10)
90.41(10)
86.17(10)
92.43(11)
91.85(10)
171.41(10)
96.48(11)
94.02(11)
93.06(11)
154.16(13)
160.53(12)
F1−Ti2−F6
F1−Ti2−F6B
F1−Ti2−F4B
F1B−Ti2−F4
F1B−Ti2−F6
F1B−Ti2−F6B
F1B−Ti2−F4B
F4−Ti2−F6
F4−Ti2−F6B
F4−Ti2−F4B
F6−Ti2−F6B
F6−Ti2−F4B
F6B−Ti2−F4B
Ti1−F1−Ti2
Ti1−F1A−Ti2A
a
b
Experimental geometrical parameters correspond to α- and β-[ImH] [Ti F ]. The atom-labeling schemes correspond to those used in Figure 10.
4
4
20
c
The SDDALL basis set was used.
hydrogen bonds (Table S4 in the Supporting Information).
There is only one crystallographically independent titanium
−
Each of the six cations is coordinated to two anions.
atom in the β-phase. The [Ti F ] anion is an infinite dimeric
2 9
+
(
e) [ImH][Ti F ]. The smallest proportion of [ImH] cations
zigzag chain comprised of TiF octahedra sharing vertices
2
9
6
(
Im:TiF = 1:2) is observed in [ImH][Ti F ], which crystal-
(Figure 7). Each TiF octahedron shares three of its vertices
4
2
9
6
lized in two modifications (Figures 7 and 8). A high-
temperature β-phase (structure determined at 298 K) crystal-
lized in an orthorhombic unit cell, and a low-temperature α-
phase (structure determined at 200 K) crystallized in a+
monoclinic unit cell. The crystallographically unique [ImH]
cation of the β-phase is 2-fold-disordered.
with three other TiF units so that each titanium atom is
6
coordinated to three bridging [Ti−F , two within a chain,
b
1.9669(8) and 1.973(2) Å, and one between two polymeric
chains, 1.979(2) Å] and three terminal [Ti−F , 1.763(2)−
t
1.772(3) Å] fluorine atoms. Nearest-neighbor pairs of TiF
6
octahedra, belonging to different chains, coordinate to a single
8
319
dx.doi.org/10.1021/ic302468j | Inorg. Chem. 2013, 52, 8315−8326

Inorganic Chemistry
Article
the Supporting Information) of [TiF ]2 were also calculated
−
6
(
Ti−F, 1.893 Å) and served as a benchmark; the calculated Ti−
F bond lengths are shown to be overestimated by 0.03 Å,
whereas the Ti−F stretching frequencies are underestimated by
−
1
ca. 40 cm .
4
−
3−
The calculated geometries of [Ti F ] and [Ti F ] are in
4
20
5 23
good agreement with the experimental geometries, although all
bond lengths are slightly overestimated, as observed for the
[
TiF6]2 anion.
−
4
−
(
a) [Ti F ] . All calculated terminal Ti−F bonds trans to
4
20
terminal (Ti−F ) and bridging (Ti−F ) bonds are similar
tt
tb
(
[
1.839 and 1.842 Å, respectively), as observed experimentally
β, 1.803(3)−1.824(4) and 1.776(3)−1.793(3) Å; α,
Figure 6. Crystal structure of [ImH] [Ti F ] showing coordination
3
5
23
1.800(2)−1.840(2) and 1.790(2)−1.817(2) Å, respectively;
+
between the hydrogen atoms of the [ImH] cations and the fluorine
Table 3]. The Ti−F bonds are significantly longer (2.007 Å),
b
3
−
atoms of the [Ti F ] anion. Thermal ellipsoids are drawn at the
5
23
in accordance with the experimental structure [β, 1.956(2)−
50% probability level.
1
.978(2) Å; α, 1.965(2)−1.989(2) Å].
3−
(
b) [Ti F ] . The major features of the experimental
5 23
3
−
bridging [ImH]+ cation through two crystallographically
[
Ti F ] anion structure are well reproduced, i.e., five TiF6
5 23
units form a four-membered ring, with three of the TiF units
equivalent N−H···F (or C−H···F) hydrogen bonds
6
connected to a fifth TiF unit through three F atoms. The
[
N1A···F2, 2.907(7) Å (or C2···F2, 2.992(7) Å); Table S4 in
6
b
terminal Ti−F bond lengths that are trans to another terminal
the Supporting Information].
tt
Ti−F bond are longer than the terminal Ti−F bond lengths
The α-phase (Figure 8) is comprised of infinite dimeric
chains consisting of crystallographically independent TiF6
tt
tb
that are trans to Ti−F bridge bonds, in accordance with the
b
experimental bond lengths (Table 4). The bridging Ti−F
octahedra that coordinate to nearest-neighbor TiF units in a
b
6
bonds range from 1.930 to 2.054 Å [exptl, 1.946(2)−2.014(2)
Å]. The Ti−F and Ti−F bonds are shorter than the
manner similar to that observed in the β-phase. The Ti−F
t
[
1.768(2)−1.787(2) Å] and Ti−F [1.963(1)−1.991(1) Å]
tt
tb
b
4
−
analogous bonds in [Ti F ] . Experimentally, this trend is
bond lengths are similar to the corresponding Ti−F bond
4 20
only apparent for the Ti−F bonds. Among the F −Ti−F
lengths in Cs[Ti F ] at 200 K [Ti−F , 1.758(7)−1.790(7) Å;
tb
b
b
2
9
t
angles of the four-membered ring, the F2−Ti5−F18 angle
81.6°) is the smallest and is unique because F2 and F18 are
not F-bridged to the triply F-bridged TiF unit. The other F −
Ti−F , 1.955(3)−1.988(7) Å] and [H O][Ti F ] at 100 K
b
3
2 9
(
[
Ti−F , 1.754(2)−1.803(3) Å; Ti−F , 1.966(3)−2.004(2)
t
b
4
Å]. Nearest-neighbor pairs of TiF octahedra, belonging to
different chains, coordinate to two different [ImH] cations
6
b
6
+
Ti−F
comparable to the F
(av. 86.9°). The Ftt−Ti−Ftt angle is smaller (168.3°) in
angles within the four-membered ring (av. 85.9°) are
b
4
−
through two crystallographically inequivalent N1−H···F6
b
−Ti−F
b
angles of the [Ti
F
4
20
]
anion
[
N···F, 2.810(3) Å] and N2−H···F8 [N···F, 2.929(3) Å]
3−
4−
hydrogen bonds (Table S4 in the Supporting Information); no
[Ti
F
5
23
]
than that in [Ti
F
4
20
]
(176.9°). The calculated
+
[
ImH] bridging occurs between the octahedra of neighboring
angles are in good agreement with the experiment.
Raman Spectroscopy of β-[ImH][Ti
[Ti 20], and [ImH] [Ti 23]. The Raman spectra of β-
[ImH][Ti ] (Figure 11), β-[ImH] [Ti 20], and [Im-
H] [Ti 23] (Figures 12 and S9 and S10 in the Supporting
chains.
F ], β-[Im-
2 9
The Ti−F −Ti angles within the individual zigzag chains of
H]
4
F
4
3
F
5
b
the dimers are crystallographically equivalent in β-[ImH]-
2
F
9
4
F
4
[
[
Ti F ] [152.1(1)°], whereas these angles are comparable in α-
3
F
5
2
9
ImH][Ti F ] [149.54(8)° and 151.21(9)°]. The correspond-
Information) were acquired on randomly oriented single
crystals. It was not possible to acquire usable spectra for the
2
9
ing angles in [H O][Ti F ] and Cs[Ti F ] are more open
3
2
9
2 9
+
+
4
3−
2−
25
[
[
[H O] , 166.4(2)°; Cs , 156.3(4)°]. The Ti−F −Ti angles in
[Ti
F
2
11
]
and [TiF
6
]
salts. As previously reported, the
3
b
ImH][Ti F ], where the titanium atoms belong to two
frequency of the most intense Raman band can be used to
identify complex titanium fluoride anions. This band
corresponds to the symmetric in-phase terminal Ti−F
stretching mode and has been shown to increase in frequency
2
9
neighboring chains, are the same, within ±3σ for the α-phase
[
1
salts.
162.27(8)°] and β-phase [163.1(2)°]. These angles are
+
+
43.7(2)° and 149.3(6)°, respectively, in the H O and Cs
3
4
with increasing TiF
experimental Raman frequencies and intensities for the [ImH]
cation (Table S6 in the Supporting Information) compare well
content and decreasing anion charge. The+
4
In the case of Cs[Ti F ], the TiF octahedra within one chain
2
9
6
of the dimer are slightly rotated relative to those in the other
chain (Figure 9a), with a dihedral angle of 22°. The
corresponding dihedral angle (17°) of α-[ImH][Ti F ] (Figure
26
with previously published values and are not discussed.
−
2−
(a) [Ti F ] . In contrast to the well-known [TiF ] anion,
4
2
9
2
9
6
−
4
9
c) results in ([Ti F ] ) chains of lower symmetry. In
and as previously observed for [H O][Ti F ] and Cs[Ti F ],
2
9
∞
3 2 9 2 9
−
contrast, the TiF octahedra of one chain eclipse those of the
the Raman spectra of polymeric [Ti F ] anions are more
2 9
complex (Figure 11) because the ([Ti F ] ) anions consist of
6
−
second chain in β-[ImH][Ti F ] (Figure 9d) and in [H O]-
2
9
3
2 9 n
[
Ti F ] (Figure 9b).
infinite double chains of TiF octahedra that share cis-vertices
2
9
6
Computational Results. The gas-phase geometries of
within each chain and because the component chains are joined
by means of neighboring octahedra sharing a common vertex
(Figure 7). The Raman spectrum of Cs[Ti F ] is the most
4
−
3−
[
Ti F ] and [Ti F ] were energy-minimized starting from
4
20
5 23
the crystallographic coordinates and resulted in stationary
points with all frequencies real. The B3LYP/SDDALL results
are reported in Tables 3 and 4 and Figure 10. The energy-
minimized geometry and vibrational frequencies (Table S5 in
2
9
complex, presumably because of the twisted orientation of the
TiF octahedra in one chain relative to those of the other chain.
6
The twist results in symmetry lowering (i.e., the center of
8
320
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Inorganic Chemistry
Table 4. Experimental and Calculated Geometrical Parameters for the [Ti F ] Anion
Article
3
−
5
23
a,
b
b,
c
c
c
exptl
calcd (C1)
exptl
calcd (C1)
Bond Lengths (Å)
Ti1−F4
Ti1−F15
Ti1−F14
Ti1−F9
Ti1−F8
Ti1−F1
Ti2−F3
Ti2−F1
Ti2−F7
Ti2−F11
Ti2−F22
Ti2−F17
Ti3−F21
Ti3−F2
Ti3−F4
1.985(2)
1.770(2)
1.942(2)
1.769(2)
1.785(2)
1.971(2)
1.982(2)
2.007(2)
1.946(2)
1.784(2)
1.761(2)
1.772(2)
1.769(4)
1.961(2)
1.980(2)
1.974
1.793
1.975
1.799
1.799
1.997
1.974
1.995
1.977
1.799
1.792
1.799
1.795
1.930
2.010
Ti3−F3
1.983(2)
1.770(2)
1.771(2)
1.956(2)
1.757(3)
1.758(3)
1.776(3)
1.999(2)
1.991(2)
1.783(2)
1.814(3)
1.782(2)
1.995(2)
1.848(3)
2.014(2)
2.010
1.803
1.795
1.932
1.796
1.795
1.803
2.007
2.011
1.812
1.826
1.812
2.054
1.826
2.051
Ti3−F19
Ti3−F10
Ti4−F18
Ti4−F20
Ti4−F13
Ti4−F23
Ti4−F7
Ti4−F14
Ti5−F12
Ti5−F16
Ti5−F6
Ti5−F18
Ti5−F5
Ti5−F2
Bond Angles (deg)
F15−Ti1−F4
F14−Ti1−F4
F9−Ti1−F4
F1−Ti1−F4
F8−Ti1−F4
F15−Ti1−F14
F9−Ti1−F15
F15−Ti1−F1
F15−Ti1−F8
F9−Ti1−F14
F14−Ti1−F1
F8−Ti1−F14
F9−Ti1−F1
F9−Ti1−F8
F8−Ti1−F1
F3−Ti2−F1
F7−Ti2−F3
F11−Ti2−F3
F22−Ti2−F3
F17−Ti2−F3
F7−Ti2−F1
F11−Ti2−F1
F22−Ti2−F1
F17−Ti2−F1
F22−Ti2−F7
F11−Ti2−F7
F17−Ti2−F7
F22−Ti2−F11
F17−Ti2−F11
F22−Ti2−F17
F21−Ti3−F2
F21−Ti3−F4
F21−Ti3−F3
F19−Ti3−F21
F10−Ti3−F21
F2−Ti3−F4
F2−Ti3−F3
F19−Ti3−F2
89.01(11)
86.84(11)
172.05(12)
82.09(9)
90.7
85.5
172.4
83.2
90.1
91.0
95.5
171.6
95.7
90.0
82.9
172.1
90.2
93.7
90.0
83.2
85.6
172.3
90.8
90.1
82.9
90.0
171.7
90.1
90.0
90.8
172.2
95.6
93.5
95.7
91.2
90.7
171.8
93.8
97.1
85.9
86.0
172.6
F10−Ti3−F2
F3−Ti3−F4
89.45(11)
83.35(9)
91.2
81.4
88.5
171.8
88.3
90.7
93.6
91.9
91.2
172.8
86.3
85.8
97.0
93.5
172.0
90.7
93.7
90.6
171.8
93.7
88.5
81.6
93.9
96.1
172.7
93.9
91.2
93.9
85.6
168.3
85.6
91.2
93.9
172.7
85.6
81.5
85.5
F19−Ti3−F4
F10−Ti3−F4
F19−Ti3−F3
F10−Ti3−F3
F19−Ti3−F10
F20−Ti4−F18
F13−Ti4−F18
F23−Ti4−F18
F18−Ti4−F7
F18−Ti4−F14
F20−Ti4−F13
F20−Ti4−F23
F20−Ti4−F7
F20−Ti4−F14
F13−Ti4−F23
F13−Ti4−F7
F13−Ti4−F14
F23−Ti4−F7
F23−Ti4−F14
F14−Ti4−F7
F12−Ti5−F16
F6−Ti5−F12
F12−Ti5−F18
F6−Ti5−F5
90.10(12)
168.89(11)
88.53(11)
88.45(11)
97.21(12)
90.17(12)
90.11(12)
169.52(12)
84.27(10)
82.47(10)
98.40(13)
95.99(14)
171.01(12)
91.22(12)
97.33(13)
88.70(12)
167.89(12)
88.52(12)
88.92(12)
81.07(10)
96.13(12)
96.43(12)
172.33(11)
90.76(11)
89.60(10)
96.43(12)
86.25(11)
169.57(11)
85.68(11)
90.55(12)
90.53(11)
173.35(11)
86.13(11)
83.30(10)
86.37(10)
87.69(11)
89.33(10)
98.20(11)
168.75(11)
95.50(11)
89.87(11)
83.36(9)
172.64(11)
90.35(10)
94.92(12)
91.01(10)
82.23(9)
83.49(10)
169.75(12)
89.71(11)
89.52(11)
83.94(10)
88.64(11)
170.90(11)
87.38(10)
90.99(12)
90.95(11)
169.51(11)
99.02(13)
94.72(11)
96.81(12)
90.26(11)
91.90(11)
173.84(11)
95.41(13)
95.73(12)
82.42(10)
85.26(10)
170.77(11)
F12−Ti5−F2
F6−Ti5−F16
F16−Ti5−F18
F16−Ti5−F5
F16−Ti5−F2
F12−Ti5−F5
F6−Ti5−F18
F6−Ti5−F2
F5−Ti5−F18
F18−Ti5−F2
F5−Ti5−F2
a
b
c
Experimental geometrical parameters correspond to [ImH] [Ti F ]. The atom-labeling schemes correspond to those used in Figure 10. The
3
5 23
SDDALL basis set was used.
4
−
3−
symmetry of Ti F is removed), and as a consequence, a larger
number of vibrational bands is observed (Table 5).
(b) [Ti F ] and [Ti F ] . The observed and calculated
4 20 5 23
2
9
4−
frequencies and detailed mode descriptions for [Ti F ] and
4
20
8
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Inorganic Chemistry
Article
ing schemes correspond to those given in Figure 10. Spectral
4
−
3−
assignments for [Ti F ] and [Ti F ] were made by
4
20
5 23
comparison with the calculated frequencies and Raman
intensities of the energy-minimized gas-phase geometries,
which are in good agreement with the experimental values at
the B3LYP level of theory.
4
−
4−
(
i) [Ti F ] . The vibrational spectrum of [Ti F ] was
4 20 4 20
assigned under D2d symmetry. A total of 66 fundamental
vibrational modes belonging to the irreducible representations
1
0A + 7B + 16E + 7A + 10B are expected, where the E and
1 1 2 2
B modes are both Raman- and IR-active, the A and B modes
2
1
1
are Raman-active, and the A modes are both Raman- and IR-
2
−1
inactive. The most intense band at 695 cm is assigned to the
totally symmetric Ti−F stretch (F , fluorine atom trans to a
tb
tb
bridging fluorine atom), in good agreement with the calculated
−1
value (659 cm ), which is also predicted to be the most
intense band in the Raman spectrum (Table 6). The bands at
5
60 and 624 cm− are assigned to the Ti−F and Ti−F (F ,
1
tt
tb
tt
Figure 7. Crystal structure of β-[ImH][Ti F ] showing coordination
2
9
+
fluorine atom trans to a terminal fluorine atom) symmetric and
between the hydrogen atoms of the [ImH] cations and the fluorine
−
asymmetric stretching modes, respectively, and also compare
atoms of the [Ti F ] anion chains. Thermal ellipsoids are drawn at
2
9
−1
the 50% probability level. Only one of the two orientations of the
well with the calculated values (547 and 604 cm ). The Ti−F
b
+
−1
disordered [ImH] cations is depicted.
stretches are predicted at ca. 450 cm and are expected to be
very weak in the Raman spectrum and are therefore unlikely to
be observed. The remaining experimental bands at 189, 241,
71, 295, and 350 cm− are assigned to deformations that occur
1
2
in the calculated frequency ranges.
3−
3−
(
ii) [Ti F ] . The vibrational spectrum of [Ti F ] was
5 23 5 23
assigned under C symmetry. A total of 78 fundamental Raman
1
(
IR) vibrational modes and bands are predicted. All bands that
were calculated to be intense, were observed in the Raman
spectrum. The most intense band at 741 cm− is assigned to the
1
totally symmetric in-phase Ti−F stretches, which is in very
tb
−1
good agreement with the calculated frequency (732 cm ) and
is also predicted to be the most intense band in the Raman
spectrum (Table 7). The band at 717 cm− is assigned to the
out-of-phase coupled Ti−F and Ti−F stretches, in good
1
tb
tt
−1
agreement with the predicted values at 700 and 710 cm . The
bands at 678 and 694 cm− are assigned to out-of-phase
1
coupled Ti−F stretches that are predicted to occur at 648,
tt
−1
6
78, and 681 cm . The broad bands appearing at 476 and 562
−1
cm also involve Ti−F and Ti−F out-of-phase and in-phase
Figure 8. Crystal structure of α-[ImH][Ti F ] showing coordination
b
tb
2
9
+
−1
between the hydrogen atoms of the [ImH] cations and the fluorine
stretches, respectively. The medium-intensity band at 373 cm
is assigned to the δ(F −Ti−F ) deformation, which is well
−
atoms of the [Ti F ] anion. Thermal ellipsoids are drawn at the 50%
2
9
b
b
−1
probability level. The Ti2 octahedra are eclipsed by the Ti1 octahedra
and therefore are not labeled.
reproduced by the calculation (366 cm ).
3
. CONCLUSIONS
Although [TiF ]2 salts are well-known, structural reports of
−
6
poly[perfluorotitanate(IV)] anions were limited to
−
11
12
−
4
2− 7,8
3−
9
(
(
[TiF ] ) ,
([Ti F ] ) , [Ti F ] ,
[Ti F ] ,
5
∞
2
9
∞
2
10
3− 19
2
11
−
2− 4,10
2−
13
[Ti F ] ) , [Ti F ] ,
[Ti F ] , ([Ti F ] ) ,
3
13
∞
4
18
4
19
7
30
∞
−
14
and ([Ti F ] ) . Investigations of the Im−TiF system in
8
33
∞
4
aHF solvent have afforded five new salts, [ImH] [TiF ]·2HF,
2
6
[
[
ImH] [Ti F ], [ImH] [Ti F ], [ImH] [Ti F ], and [ImH]-
3 2 11 4 4 20 3 5 23
Ti F ], where two of them have provided examples of new
2
9
4
−
poly[perfluorotitanate] anions, namely, [Ti F ]
and
4
20
3−
[Ti F ] .
−
5 23
Figure 9. Infinite ([Ti F ] ) dimeric chains in the crystal structures
2
9
∞
Quantum-chemical calculations using the B3LYP method
of (a) Cs[Ti F ], (b) [H O][Ti F ], (c) α-[ImH][Ti F ], and (d) β-
2
9
3
2
9
2 9
have been used to obtain energy-minimized gas-phase geo-
[
ImH][Ti F ].
2
9
2
−
4−
3−
metries for the [TiF ] , [Ti F ] , and [Ti F ] anions. The
6
4
20
5 23
4
−
3−
Raman spectra of the [Ti F ] and [Ti F ] anions have
4
20
5 23
3
−
[
Ti F ] are provided in Tables 6 and 7 and S6 and S7 in the
been assigned based on the calculated vibrational frequencies
and vibrational displacements of their respective modes.
5
23
Supporting Information, respectively, where the atom number-
8
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Inorganic Chemistry
Article
4
−
3−
Figure 10. Experimental (left column) and calculated (right column; B3LYP/SDDALL) geometries of the [Ti F ] and [Ti F ] anions. The
4
20
5 23
geometrical parameters are provided in Tables 3 and 4. Thermal ellipsoids are drawn at the 50% probability level.
Figure 12. Raman spectra of [ImH] [Ti F ] and β-[ImH] [Ti F ]
recorded at room temperature on randomly oriented single crystals
sealed in quartz capillaries using 632.8-nm excitation.
3
5
23
4
4 20
Figure 11. Raman spectrum of β-[ImH][Ti F ] recorded at room
temperature on a randomly oriented single crystal sealed in a quartz
capillary using 632.8-nm excitation.
2
9
tube. Before use, the above-mentioned reaction/crystallization vessel
assemblies were dried under dynamic vacuum and passivated with
elemental fluorine at 1.1 bar for 2 h. Anhydrous HF (Linde, 99.995%)
4
. EXPERIMENTAL SECTION
Reagents. Fluorine (Solvay Fluor and Derivate GmbH, Hannover,
Germany), aHF (Linde AG, Puliach, Germany), and imidazole
Aldrich, 99%) were used. Titanium tetrafluoride was synthesized by
was treated with K NiF6 (Advance Research Chemicals, Inc.) for
2
(
several hours prior to use.
the reaction of TiCl3 (Sigma-Aldrich, 99.999%) with elemental
Crystal Growth of Imidazolium Poly[perfluorotitanates(IV)].
fluorine F in aHF. The purity of TiF was confirmed by Raman
Stoichiometric amounts of imidazole and TiF (totaling ca. 200 mg)
2
4
4
spectroscopy and chemical analysis.
Synthetic Apparatus. All manipulations were carried out under
anhydrous conditions. Volatile compounds, such as aHF and F , were
handled on a vacuum line constructed from nickel/Teflon, and
were loaded into the 19-mm o.d. arm of the crystallization vessel inside
a drybox (Table 8). The reagent mixture was then transferred to a
metal/Teflon manifold, where aHF (5−7 mL) was condensed onto
the starting material at −196 °C. The crystallization mixture was
warmed to ambient temperature, and the resulting clear, colorless
solution was decanted into the 6-mm o.d. side arm. Evaporation of the
solvent from this solution was carried out by maintaining a
temperature gradient of ca. 10−20 °C between the 6-mm o.d. (22−
32 °C) and 19-mm o.d. (ca. 12 °C) tubes for several weeks. When the
HF level in the smaller-diameter vessel ceased to further decrease, it
was necessary to increase the temperature gradient. This was
accomplished by slowly cooling the larger vessel in a cryostat from
2
nonvolatile materials were handled in a drybox (M. Braun) in an argon
atmosphere (<0.5 pmm H O). Single crystals of imidazolium
2
poly[perfluorotitanates(IV)] were grown in T-shaped crystallization
vessels comprised of two tetrafluoroethylene−hexafluoropropylene
block copolymer (FEP; Polytetra GmbH, Germany) tubes (one 16-
mm i.d. × 19-mm. o.d. and the other 4-mm i.d. × 6-mm. o.d.); each
tube was heat-sealed on one end and joined at 90° through a Teflon T-
connector. A Teflon valve was connected at 180° to the 19-mm-o.d.
8
323
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Inorganic Chemistry
Article
Table 5. Experimental Raman Frequencies and Intensities
Table 7. Experimental and Calculated Vibrational
a b
3−
for β-[ImH][Ti F ] Compared with Those of Cs[Ti F ] and
Frequencies and Intensities for the [Ti F ] Anion in
5 23
2
9
2
9
a
[
H O][Ti F ]
[ImH] [Ti F ]
3
2
9
3 5 23
b
c
c
β-[ImH][Ti F ]
[H O][Ti F ]
Cs[Ti F ]
2 9
2
9
3
2
9
751(10)
756(10)
751(10)
7
7
6
6
21(0.7)
02(0.7)
67(0.5)
35(0.5)
3
2
96(1)
91(1)
397(1)
293(1)
397(1.5)
294(0.9)
2
53(2)
2
2
41(3)
245(1.2)
229(1)
241(1.9)
229(1.6)
17(0.5)
2
11(0.7)
198(0.1)
198 (sh)
1
70(0.5)
147(0.2)
a
−1
b
c
Frequencies are given in cm . This work. From ref 4.
+
12 to −20 °C and then to −55 °C for [ImH] [TiF ]·2HF. Several
2
6
days to several weeks were required to induce crystallization. Slow
distillation of aHF from the 6-mm o.d. tube into the 19-mm o.d. tube
resulted in crystal growth inside the 6-mm o.d. tube. Selected single
crystals were transferred to 0.3-mm quartz capillaries inside the
drybox, and their Raman spectra were recorded at several random
positions.
a
−1
Frequencies are given in cm . The full set of calculated frequencies is
b
reported in Table S8 (Supporting Information). Values in
parentheses denote relative Raman intensities. The abbreviation sh
denotes a shoulder. Modes associated with the cation were also
observed at 928(2), 912(5), and 876(2) cm . The Raman spectrum
was recorded at ambient temperature on a randomly oriented single
Raman Spectroscopy. Raman spectra with a resolution of 0.5
−1
c
−1
cm were recorded at room temperature on a Horiba Jobin Yvon
LabRam-HR spectrometer equipped with an Olympus BXFM-ILHS
microscope. Samples were excited by the 632.8-nm emission line of a
He−Ne laser with regulated power in the range 20−0.0020 mW,
which gives 17−0.0017 mW focused on a 1 μm spot through a 50×
microscope objective on the top surface of the sample.
d
crystal sealed in a quartz capillary using 632.81-nm excitation. The
B3LYP/SDDALL method was used. Values in parentheses denote
4
−1
Raman intensities (Å u ). Values in square brackets denote IR
−1
e
intensities (km mol ). Vibrational assignments were based on modes
calculated at the B3LYP level of theory. The abbreviations denote in-
phase (ip), out-of-phase (oop), stretch (ν), bend (δ), rock (ρrock),
Single crystals were mounted in the drybox in previously vacuum-
dried quartz capillaries, which were initially sealed with Halocarbon
torsion (ρ ), a fluorine atom that is trans to a terminal fluorine atom
t
2
5-5S grease (Halocarbon Corp.) inside the drybox and later heat-
(
F ), a fluorine atom that is trans to a bridging fluorine atom (F ), and
tt
tb
sealed in an oxygen−hydrogen flame outside the drybox. Raman
spectra of [ImH][Ti F ], [ImH] [Ti F ], and [ImH] [Ti F ] were
f
a bridging fluorine atom (F ). This band was visible for some crystals
b
2
9
3
5
23
4
4 20
at specific orientations (Figure S10, Supporting Information).
recorded at 17 mW with a 5 s exposure time for each scan. For
[
ImH] [Ti F ] and [ImH] [Ti F ], five scans, and for [ImH][Ti F ],
3
5
23
4
4
20
2 9
three scans were accumulated.
under a microscope, and mounted on the goniometer head of the
diffractometer in a cold nitrogen stream. Although up to 15 crystals of
consistent crystal habit were screened for each phase (Table 8), the
X-ray Crystal Structure Determinations. Crystals were
immersed in perfluorodecalin (ABCR, 98%) inside a drybox, selected
a
b
4−
Table 6. Experimental and Calculated Vibrational Frequencies and Intensities for the [Ti F ] Anion in β-[ImH] [Ti F ]
4
20
4
4 20
c
d
e
exptl
calcd
assgmnt (D )
2d
6
6
5
3
2
2
2
1
95(100)
24(12)
60(30)
659(70)[0]
604(7)[0]
A1
B1
A1
A1
E
ν (Ti−F )
s tb
ν (Ti−F )
as
tb
547(22)[0]
341(6)[0]
ν (Ti−F )
s tt
f
50sh
δ(F −Ti−F )/δ(F −Ti−F )/δ(F −Ti−F )
tt tt tb tb b b
95(30)
71(15)
41(65)
89(25)
299(2)[<0.1]
277(4)[<0.1]
233(5)[<1]
170(3)[<0.1]
δ(TiF2tbF )
2b umb
B2
E
δ(F −Ti−F )/δ(F −Ti−F )
tt tt tb tb
δ(F −Ti−F )/δ(F −Ti−F )/ρ (F −Ti−F )
tt
tb
tt
b
t
tb
b
B2
ρ (F −Ti−F )/δ(F −Ti−F )
w tt tt tb tb
a
−1
b
Frequencies are given in cm . The full set of calculated frequencies is reported in Table S7 (Supporting Information). Values in parentheses
4
−1
−1
c
denote Raman intensities (Å u ). Values in square brackets denote IR intensities (km mol ). The Raman spectrum was recorded at ambient
temperature on a randomly oriented single crystal sealed in a quartz capillary using 632.81-nm excitation. Values in parentheses denote relative
Raman intensities. The abbreviation sh denotes a shoulder. Bands associated with the cation were also observed at 926(5), 908(10), and 882(5)
−1
d
e
cm . The B3LYP/SDDALL method was used. Vibrational assignments were based on modes calculated at the B3LYP level of theory. The
abbreviations denote symmetric (s), asymmetric (as), stretch (ν), bend (δ), wag (ρ ), a fluorine atom that is trans to a terminal fluorine atom (F ), a
w
tt
f
fluorine atom that is trans to a bridging fluorine atom (F ), and a bridging fluorine atom (F ). This band was visible for some crystals at specific
tb
b
orientations (Figure S9 in the Supporting Information).
8
324
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Inorganic Chemistry
Article
and effective-core pseudopotential basis sets (SDDall) augmented for
fluorine, oxygen, and titanium atoms with two d-type polarization
functions by Huzinaga et al. were used.
Table 8. Stoichiometries Used To Crystallize Imidazolium
Poly[perfluorotitanates(IV)] and Phases Observed after
3
5
Crystallization of Imidazole (Im) and TiF in aHF
4
Quantum-chemical calculations were carried out using the program
3
4
starting n(Im):n(TiF4)
Gaussian 03. The levels and basis sets were benchmarked by
calculating [TiF6]2 (Table S5 in the Supporting Information). The
geometries were fully optimized using analytical gradient methods.
The vibrational frequencies were calculated at the B3LYP level using
the appropriate minimized structure, and the vibrational mode
−
molar ratios
phases observed after crystallization
2
1
1
1
1
1
:1
[ImH] [TiF ]·2HF, [ImH] [Ti F ]
a
2
6
3
2 11
.5:1
:1
[ImH] [Ti F ], [ImH] [Ti F ]
4
4
20
3
5
23
36
descriptions were arrived at with the aid of GaussView.
:1.5
:1.67
:2
[ImH] [Ti F ], [ImH] [Ti F ], [ImH][Ti F ]
4 4 20 3 5 23 2 9
[ImH] [Ti F ], [ImH][Ti F ]
3
5
23
2 9
ASSOCIATED CONTENT
[ImH][Ti F ]
■
2
9
a
*
S
Supporting Information
The nature of this phase is unknown because the single crystals that
were grown were too small for an X-ray structure determination. In
addition, Raman spectra could not be obtained because of an intense
fluorescence background.
List of geometrical parameters for [ImH] [TiF ]·2HF (Table
2
6
S1) and α- and β-[ImH][Ti F ] (Tables S2 and S3), unit cells
2
9
of [ImH] [TiF ]·2HF (Figure S1), [ImH] [Ti F ] (Figure
2
6
3
2 11
S2), β-[ImH] [Ti F ] (Figure S3), α-[ImH] [Ti F ] (Figure
4
4
20
4
4 20
presence of other crystal phase(s) cannot be definitively ruled out.
Data were collected at 200 or 298 K on a Rigaku AFC7 diffractometer
equipped with a Mercury CCD area detector using graphite-
monochromated Mo Kα radiation (λ = 0.71069 Å).
S4), [ImH] [Ti F ] (Figure S5), β-[ImH][Ti F ] (Figure S6),
3 5 23 2 9
and α-[ImH][Ti F ] (Figure S7), hydrogen-bonding geo-
2
9
metries in α- and β-[ImH][Ti F ], [ImH] [Ti F ], α- and β-
2
9
3
2 11
[
[
ImH] [Ti F ], and [ImH] [Ti F ] (Table S4), geometries of
4 4 20 3 5 23
Processing of the raw data sets of [ImH] [TiF ]·2HF, α-
2
6
3−
2−
Ti F ] anions (Figure S8), vibrational data for [TiF6]
2
11
[
ImH] [Ti F ], and α-[ImH][Ti F ] were completed using the
4 4 20 2 9
27
(Table S5), Raman spectra of β-[ImH] [Ti F ] and
TEXSAN package. Processing of the raw data sets of [Im-
4 4 20
[
ImH] [Ti F ] (Figures S9 and S10), experimental vibrational
H] [Ti F ], β-[ImH] [Ti F ], [ImH] [Ti F ], and β-[ImH][Ti F ]
3 5 23
3
2
11
4
4
20
3
5
23
2 9
28
were completed by using APEX2 GUI software, which applied
Lorentz and polarization corrections to three-dimensionally integrated
diffraction spots. This was done after converting the data format from
the Rigaku AFC7 to the Bruker APEX2 format. The program
SADABS was used for the scaling of diffraction data, the application
of decay corrections, and empirical absorption corrections on the basis
of the intensity ratios of redundant reflections. Although the data for
frequencies for imidazolium cations in β-[ImH][Ti
F ], β-
2 9
[ImH] [Ti F ], and [ImH] [Ti F ] (Table S6); complete list
4
4
20
3
5 23
of experimental and calculated vibrational frequencies for the
4−
3−
[
Ti F ] and [Ti F ] anions (Tables S7 and S8), complete
4 20 5 23
29
ref 34, and X-ray crystallographic files in CIF format for the
structure determinations of [ImH] [TiF ]·2HF, α- and β-
2
6
[
[
ImH][Ti F ], [ImH] [Ti F ], α- and β-[ImH] [Ti F ], and
2 9 3 2 11 4 4 20
[
ImH] [TiF ]·2HF are not of good quality (see the CIF files in the
2 6
ImH] [Ti F ]. This material is available free of charge via the
Supporting Information), the authors are convinced that the structure
solution is correct and have therefore integrated this result into the
manuscript to provide a more comprehensive account.
3
5 23
Internet at http://pubs.acs.org.
In the case of [ImH] [TiF ]·2HF, α-[ImH] [Ti F ], and α-
AUTHOR INFORMATION
2
6
4
4 20
27
■
[
ImH][Ti F ], the TEXSAN program was used to confirm the unit
2 9
Corresponding Author
*E-mail: schrobil@mcmaster.ca (G.J.S.), zoran.mazej@ijs.si
(Z.M.).
cell dimensions and the crystal lattices. In the case of [ImH] [Ti F ],
3
2 11
3
0
β-[ImH] [Ti F ], [ImH] [Ti F ], and β-[ImH][Ti F ], the XPREP
4
4
20
3
5
23
2 9
program was used to confirm the unit cell dimensions and crystal
lattices. The solutions were obtained by direct methods using the SIR-
Notes
3
1
9
2 (as implemented in the program package WinGX) or the
30,32
The authors declare no competing financial interest.
SHELXTL-plus
programs, which located the positions of the
titanium and fluorine atoms. All further solution refinements were
30
ACKNOWLEDGMENTS
performed using the SHELXTL-plus program. The positions of the
remaining carbon and nitrogen atoms were revealed in successive
difference Fourier syntheses. In the case of [ImH] [TiF ]·2HF,
■
I.M.S., E.A.G., and Z.M. gratefully acknowledge the Slovenian
Research Agency (ARRS), and G.J.S. acknowledges the Natural
Sciences and Engineering Research Council of Canada for a
Discovery Grant for financial support of the present work.
Calculations were carried out using facilities provided by the
Shared Hierarchical Academic Research Computing Network
(SHARCNET: www.Sharcnet.ca). The authors acknowledge
Dr. James Britten of the McMaster University X-ray Facility for
helping to convert Rigaku-formatted data to Bruker-formatted
data.
2
6
[
ImH] [Ti F ], β-[ImH] [Ti F ], and β-[ImH][Ti F ], 2-fold
3 2 11 4 4 20 2 9
disorders had to be taken into account when refining some or all of
+
the [ImH] cations. Hydrogen atoms were included on idealized
positions and allowed to ride on the atoms they were bonded to. The
final refinements were obtained by introducing anisotropic thermal
parameters and the recommended weightings for all atoms except the
hydrogen atoms. The maximum electron densities in the final
difference Fourier maps were located near the heavy atoms. The
choices of space group were confirmed by PLATON from the WinGX
3
1
software package. Figures were prepared using the program
33
DIAMOND 3.1.
CCDC 907014 ([ImH] [TiF ]·2HF), 907015 ([ImH] [Ti F ]),
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