Xenon(IV)-carbon bond of [C6F5XeF2]+; Structural characterization and bonding of [C6F5XeF2][BF4], [C6F5XeF2][BF4]·2HF, and [C6F5XeF2][BF4]· n NCCH 3 (n = 1, 2); And the fluorinating properties of [C6F5XeF2][BF4]

Article abstract of DOI:10.1021/ic501831j

The [C₆F₅XeF₂]⁺ cation is the only example of a Xe^IV-C bond, which had only been previously characterized as its [BF₄]^- salt in solution by multi-NMR spectroscopy. The [BF₄]^- salt and its new CH₃CN and HF solvates, [C₆F₅XeF₂][BF₄]·1.5CH₃CN and [C₆F₅XeF₂][BF₄]·2HF, have now been synthesized and fully characterized in the solid state by lowerature, single-crystal X-ray diffraction and Raman spectroscopy. Crystalline [C₆F₅XeF₂][BF₄] and [C₆F₅XeF₂][BF₄]·1.5CH₃CN were obtained from CH₃CN/CH₂Cl₂ solvent mixtures, and [C₆F₅XeF₂][BF₄]·2HF was obtained from anhydrous HF (aHF), where [C₆F₅XeF₂][BF₄]·1.5CH₃CN is comprised of an equimolar mixture of [C₆F₅XeF₂][BF₄]·CH₃CN and [C₆F₅XeF₂][BF₄]·2CH₃CN. The crystal structures show that the [C₆F₅XeF₂]⁺ cation has two short contacts with the F atoms of [BF₄]^- or with the F or N atoms of the solvent molecules, HF and CH₃CN. The lowerature solid-state Raman spectra of [C₆F₅XeF₂][BF₄] and C₆F₅IF₂ were assigned with the aid of quantum-chemical calculations. The bonding in [C₆F₅XeF₂]⁺, C₆F₅IF₂, [C₆F₅XeF₂][BF₄], [C₆F₅XeF₂][BF₄]·CH₃CN, [C₆F₅XeF₂][BF₄]·2CH₃CN, and [C₆F₅XeF₂][BF₄]·2HF was assessed with the aid of natural bond orbital analyses and molecular orbital calculations. The ¹²⁹Xe, ¹⁹F, and ¹¹B NMR spectra of [C₆F₅XeF₂][BF₄] in aHF are reported and compared with the ¹⁹F NMR spectrum of C₆F₅IF₂, and all previously unreported J(¹²⁹Xe-¹⁹F) and J(¹⁹F-¹⁹F) couplings were determined. The long-term solution stabilities of [C₆F₅XeF₂][BF₄] were investigated by ¹⁹F NMR spectroscopy and the oxidative fluorinating properties of [C₆F₅XeF₂][BF₄] were demonstrated by studies of its reactivity with K[C₆F₅BF₃], Pn(C₆F₅)₃ (Pn = P, As, or Bi), and C₆F₅X (X = Br or I).

Full text of DOI:10.1021/ic501831j

Article
pubs.acs.org/IC
Xenon(IV)−Carbon Bond of [C6F5XeF2]+; Structural Characterization
and Bonding of [C6F5XeF2][BF4], [C6F5XeF2][BF4]·2HF, and
[C6F5XeF2][BF4]·nNCCH 3 (n = 1, 2); and the Fluorinating Properties of
[C6F5XeF2][BF4]
Karsten Koppe,†,‡,§,⊥ Jamie Haner,‡,⊥ Helene P. A. Mercier,‡ Hermann-J. Frohn,*,†
́
̀
and Gary J. Schrobilgen*,‡
†Inorganic Chemistry, Universitat Duisburg-Essen, Lotharstraße 1, D-47048 Duisburg, Germany
̈
‡Department of Chemistry, McMaster University, Hamilton, Ontario L8S 4M1, Canada
S
* Supporting Information
ABSTRACT: The [C6F5XeF2]+ cation is the only example of a
XeIV−C bond, which had only been previously characterized as its
[BF4]− salt in solution by multi-NMR spectroscopy. The [BF4]−
salt and its new CH3CN and HF solvates, [C6F5XeF2][BF4]·
1.5CH3CN and [C6F5XeF2][BF4]·2HF, have now been synthe-
sized and fully characterized in the solid state by low-temperature,
single-crystal X-ray diffraction and Raman spectroscopy. Crystal-
line [C6F5XeF2][BF4] and [C6F5XeF2][BF4]·1.5CH3CN were
obtained from CH3CN/CH2Cl2 solvent mixtures, and
[C6F5XeF2][BF4]·2HF was obtained from anhydrous HF (aHF),
where [C6F5XeF2][BF4]·1.5CH3CN is comprised of an equimolar
mixture of [C6F5XeF2][BF4]·CH3CN and [C6F5XeF2][BF4]·2CH3CN. The crystal structures show that the [C6F5XeF2]+ cation
has two short contacts with the F atoms of [BF4]− or with the F or N atoms of the solvent molecules, HF and CH3CN. The low-
temperature solid-state Raman spectra of [C6F5XeF2][BF4] and C6F5IF2 were assigned with the aid of quantum-chemical
calculations. The bonding in [C6F5XeF2]+, C6F5IF2, [C6F5XeF2][BF4], [C6F5XeF2][BF4]·CH3CN, [C6F5XeF2][BF4]·2CH3CN,
and [C6F5XeF2][BF4]·2HF was assessed with the aid of natural bond orbital analyses and molecular orbital calculations. The
129Xe, 19F, and 11B NMR spectra of [C6F5XeF2][BF4] in aHF are reported and compared with the 19F NMR spectrum of
C6F5IF2, and all previously unreported J(129Xe−19F) and J(19F−19F) couplings were determined. The long-term solution
stabilities of [C6F5XeF2][BF4] were investigated by 19F NMR spectroscopy and the oxidative fluorinating properties of
[C6F5XeF2][BF4] were demonstrated by studies of its reactivity with K[C6F5BF3], Pn(C6F5)3 (Pn = P, As, or Bi), and C6F5X (X
= Br or I).
7
(VSEPR) arrangements, [XeF5]− and [XeOF3]−;12 the missing
INTRODUCTION
■
oxide of Xe(IV), XeO2;13 and the only example of HF
coordinated to Xe(IV), which was observed in the crystal
structure of [XeF3][Sb2F11]·HF.20
The majority of the known Xe(IV) compounds are stabilized
by oxidatively resistant F or O atoms, or by polyatomic, highly
electronegative O-bonded groups. These are exemplified by
XeF4,1−3 [XeF3]+,4−6 [XeF5]−,7 XeOF2,8−11 [XeOF3]−,11,12
XeO2,13 Xe(OTeF5)4,14,15 Xe(OTeF5)4−xFx (x = 1−3),2
[FxXe(OTeF5)3−x]+ (x = 0−2),16 F3XeOIOF4,17 and the XeF4
coordination compound [Mg(XeF2)(XeF4)][AsF6]2.18 Xenon-
(IV) chemistry has experienced a resurgence in the areas of
oxide and oxide fluoride compounds in recent years.8,12,13,19,20
Most recently, the mixed oxidation state Xe(IV)/Xe(II) oxide
fluoride cations [(XeOF2)nXeF]+ (n = 1, 2),20 and the first
Xe(IV) hydroxy derivatives, namely, [HOXeF2]+ and
[HOXeF2OXeF2]+, have been described.20 The aforementioned
studies have also led to the discovery of a number of new
bonding modalities such as the first XeIV−N bond in the
donor−acceptor adduct XeOF2·CH3CN;8 the first examples of
AX5E2 and AX3YE2 valence shell electron pair repulsion
An impressive variety of XeII−C-bonded compounds are now
known, which include not only xenonium salts having the
formulations [RXe][A] (R = aryl,21−23 alkenyl,24−26 and
alkynyl,27−29 A = anion) but also neutral XeAr2 and ArXeZ
(Ar = aryl, Z = F or Cl) species, which are exemplified by
Xe(C6F5)2,30−33 C6F5XeCl,34 and C6F5XeF.35 More recently,
the syntheses of the dicationic salt, [XeC6F4Xe][BF4]2, and the
zwitterionic compound, XeC6F4BF3, along with their solution
characterizations by 13C, 19F, and 129Xe NMR spectroscopy,
were reported.36
Received: July 29, 2014
© XXXX American Chemical Society
A
dx.doi.org/10.1021/ic501831j | Inorg. Chem. XXXX, XXX, XXX−XXX

Inorganic Chemistry
Article
The oxidative strength of the parent Xe(IV) fluoride, XeF4, is
much greater than that of XeF2, and the fluoride ion donor
strength of XeF4 is less than that of XeF2 or XeF6.37
Consequently, a suitable organic ligand and corresponding
ligand transfer reagent for the formation of a XeIV−C bond
must be oxidatively robust.
The synthesis and characterization by low-temperature
solution 11B, 13C, 19F, and 129Xe NMR spectroscopy of the
first compound to contain a XeIV−C bond, [C6F5XeF2][BF4],
was reported in a prior communication.38 The substitution of a
fluorine atom of XeF4 by an organic ligand was achieved by
reaction of XeF4 with C6F5BF2 in CH2Cl2 at −55 °C (Scheme
1).38 The ensuing xenodeborylation reaction likely occurs by
Pn(C6F5)3 (Pn = As, Bi) in CH3CN and to fluorinations of
the fluoroaryl halides, C6F5X (X = Br or I) in CH3CN and aHF.
RESULTS AND DISCUSSION
■
Syntheses and Stabilities of [C6F5XeF2]+ Salts. (a)
[C6F5XeF2][BF4] and [C6F5XeF2][BF4]·2HF. In the previous38 and
present work, [C6F5XeF2][BF4] was obtained by reaction of
C6F5BF2 and XeF4 in CH2Cl2 at −55 °C (eq 1).
CH2Cl2
C6F5BF + XeF ⎯⎯⎯⎯⎯⎯→⎯ [C6F5XeF ][BF ]
2
4
2
4
(1)
−55 °C
The present work shows that the synthesis of high-purity
[C6F5XeF2][BF4] in high yield is limited to a narrow
concentration range. Unlike the syntheses of organoxenon(II)
salts,21−23 more dilute solutions must be used to obtain
optimum yields because of the low solubility of XeF4 in CH2Cl2
at −55 °C (∼20 μmol mL−1) and the voluminous nature of the
precipitated product, which tends to partially occlude solid
XeF4 and likely inhibits its reaction with C6F5BF2. In a typical
reaction, XeF4 (∼1 mmol) was partially dissolved, with
vigorous stirring, in cold CH2Cl2 (−78 °C, 20 mL). A freshly
prepared solution of C6F5BF2 in CH2Cl2 (∼7 mL) was added
to the XeF4 suspension at −78 °C. The reaction rate was
negligible at this temperature, but accelerated at ca. −60 °C,
whereupon [C6F5XeF2][BF4] rapidly precipitated as a volumi-
nous light yellow solid, resulting in complete reaction after 1 h
at −55 °C. Although it was not possible to weigh the product
because of its thermal instability, the reaction appears to be
nearly quantitative based on the consumption of XeF4 and
Raman and NMR spectroscopic analyses. Syntheses employing
smaller quantities of solvent (1−5 mL) resulted in reduced
yields (<50%) even with longer reaction times (3 h). In these
instances, the separated and washed solids consisted of
mixtures containing up to 50 mol% XeF4. In addition to high
dilution, the use of equimolar amounts of XeF4 and C6F5BF2 is
essential because excess XeF4 cannot be effectively removed by
multiple washings of [C6F5XeF2][BF4]/XeF4 mixtures with
cold CH2Cl2 (−55 °C). The use of a stoichiometric excess of
C6F5BF2 also resulted in reduced yields. A probable explanation
is provided in the Supporting Information (Electrophilic
Fluorination Properties of [C6F5XeF2][BF4]).
The solution stability of [C6F5XeF2][BF4] depends on the
nature of the solvent and on the temperature. The [C6F5XeF2]-
[BF4] salt is insoluble in the weakly coordinating solvents
CH2Cl2, SO2ClF, and 1,1,1,3,3-pentafluorobutane (PFB),
which is consistent with strongly ion-paired [C6F5XeF2]+
cations and [BF4]− anions. Although [C6F5XeF2][BF4] is a
strong oxidant, it is stable as a suspension in CH2Cl2 at low
temperatures with oxidation taking place at temperatures
exceeding −40 °C. Warming of these suspensions to room
temperature resulted in rapid gas evolution and formation of a
black suspension that contained a mixture of C6F5H, C6F6, and
C6F5Cl in a 6:3:1 molar ratio and the fluorination products of
CH2Cl2, namely, CH2F2, CH2ClF, CHF3, and HF, in a
78:33:7:75 molar ratio.
Scheme 1. Proposed Xenodeborylation21,22 Mechanism for
the Formation of [C6F5XeF2][BF4]
polarization of an Xe−F bond by the Lewis acid C6F5BF2
without complete fluoride ion abstraction. As a result of this
acid−base interaction, the C6F5 group acquires more
nucleophilic character and migrates to the electrophilic Xe(IV)
center.21,22 In a final step, fluoride abstraction from the XeF3
group of C6F5XeF3 by BF3 yields [C6F5XeF2][BF4] (Scheme
1).
Although the 11B, 13C, 19F, and 129Xe NMR spectra of
[C6F5XeF2][BF4] in CH3CN/CD3CN at −40 °C were
reported in a preliminary communication,38 the J(19F−19F)
coupling constants of the C6F5 group, the J(19F−129Xe)
couplings involving aryl fluorine nuclei, and the J(13C−129Xe)
couplings were not reported. The ability of [C6F5XeF2]+ to
oxidatively fluorinate P(C6F5)3, C6F5I, and I2 in CH3CN
solutions to P(C6F5)3F2, C6F5IF2, and IF5, respectively, was
demonstrated in the preliminary work.38
Since its discovery, the [C6F5XeF2]+ cation had not been
structurally characterized in the solid state by single-crystal X-
ray diffraction or by vibrational spectroscopy, and no
computational studies leading to a detailed description of its
bonding have been forthcoming. The present paper provides an
improved synthesis of [C6F5XeF2][BF4] in high purity and
yield as well as the detailed characterization of this salt and its
solvates, namely, [C6F5XeF2][BF4]·1.5CH3CN and
[C6F5XeF2][BF4]·2HF, by low-temperature single-crystal X-
ray diffraction and Raman spectroscopy. Quantum-chemical
calculations were employed to arrive at detailed assignments of
the Raman spectra of the [C6F5XeF2]+ cation and of
isoelectronic C6F5IF2 and to assess and compare the bonding
in both species. Improved 129Xe, 19F, and 11B NMR spectra of
[C6F5XeF2][BF4] in CH3CN and anhydrous HF (aHF) are
reported, and the complex 19F NMR spectra of [C6F5XeF2]-
[BF4] and C6F5IF2 were simulated to determine all J(19F−19F)
and J(19F−129Xe) couplings. The long-term decomposition
profiles of [C6F5XeF2][BF4] solutions in CH3CN and aHF
were assessed, and studies of its fluorinating abilities were
extended to its reactions with K[C6F5BF3] in CH3CN,
The bright yellow-orange crystalline HF solvate, [C6F5XeF2]-
[BF4]·2HF, was formed by pumping aHF solutions of
[C6F5XeF2][BF4] to dryness under dynamic vacuum at ca.
−76 °C, enabling its X-ray crystal structure to be determined
(see X-ray Crystal Structures). The color of crystalline
[C6F5XeF2][BF4]·2HF contrasts with that of [C6F5XeF2][BF4],
which is pale yellow. Conversion of the HF solvate to its parent
[C6F5XeF2][BF4] salt was achieved by dissolution of the solid
B
dx.doi.org/10.1021/ic501831j | Inorg. Chem. XXXX, XXX, XXX−XXX

Inorganic Chemistry
Article
in CH3CN followed by removal of CH3CN/HF at ca. −40 °C
under dynamic vacuum.
significantly faster than it does in the case of [C6F5Xe][BF4],
which is stable in aHF at room temperature for 12 h and
decomposed (eq 4) by only 1.5 and 15% to form C6F6 and Xe0
after 2 and 54 d, respectively.40
(b) Stability of [C6F5XeF2][BF4] in aHF. Solutions of
[C6F5XeF2][BF4] are more stable in aHF than in the basic
solvent, CH3CN, and can be stored at −78 °C for up to 18 d
with negligible decomposition. Complete decomposition
occurred within 88 d in aHF at −40 °C, within 4 d at −30
°C, and was very rapid with vigorous gas evolution at room
temperature (reaction product distributions are given in
Scheme 2). Solutions of [C6F5XeF2][BF4] in aHF that were
In conclusion, Xe(IV) in [C6F5XeF2]+ is more strongly
electron-withdrawing than Xe(II) in [C6F5Xe]+, enabling
heterolysis of the strongly polarized XeIV−C bond in BF3-
acidified aHF. In both cases, heterolytic cleavage of the Xe−C
bonds in [C6F5Xe]+ and [C6F5XeF2]+ in aHF leads to Xe0 and
XeF2 formation, respectively.
(c) Stability of [C6F5XeF2][BF4] in CH3CN and the Synthesis
of [C6F5XeF2][BF4]·1.5NCCH3. The decomposition of
[C6F5XeF2][BF4] in CH3CN solution proceeds slowly at −40
°C. After 58 d, the salt had completely decomposed and was
converted to mainly [C6F5Xe]+, with smaller amounts of C6F6,
c-C6F8-1,4, XeF2, and HF (Scheme 3). The decomposition was
Scheme 2. Decomposition Product Distribution of
[C6F5XeF2][BF4] in aHF
a
Scheme 3. Product Distribution for the Decomposition of
[C6F5XeF2][BF4] in CH3CN (cf. Scheme 2)
a
The total weighted 19F NMR intensities of the C6F5 groups and their
derivatives is set equal to 100 mol%.
attributed to reduction of R−XeIV to R−XeII by the organic
solvent. Single crystals of [C6F5XeF2][BF4] were grown from
CH3CN by slow removal of the solvent under dynamic vacuum
at ca. −40 °C.
The [C6F5XeF2][BF4]·1.5CH3CN adduct is only stable at
low temperatures (−78 °C). As noted above, pumping on
solutions of [C6F5XeF2][BF4] in CH3CN above the freezing
point of the solvent (ca. −40 °C) does not result in CH3CN
coordination to the electrophilic Xe(IV) center of [C6F5XeF2]-
[BF4] in the solid state. When solutions of [C6F5XeF2][BF4] in
CH2Cl2/CH3CN mixtures were cooled to and allowed to stand
at −78 °C for several days, the more strongly coordinating
cosolvent, CH3CN, slowly crystallized along with yellow
crystals of [C6F5XeF2][BF4]·1.5CH3CN.
allowed to decompose at −40 °C contained XeF2, C6F6, c-C6F8-
1,4, and c-C6F10. The formation of XeF2 and C6F6 (eq 2) may
arise from the formal heterolysis of the Xe−C bond of the
[C6F5XeF2]+ cation and fluoride addition to the ipso-carbon
atom of the carbenium ion (Balz−Schiemann-type reaction, eqs
3 and 4).39 Alternatively, nonionic reductive elimination of the
Xe(IV) center in [C6F5XeF2][BF4] to Xe(II), accompanied by
C−F bond formation, could occur.
aHF
[C6F5XeF ][BF ] ⎯⎯⎯⎯⎯⎯⎯⎯→ C6F6 + XeF + BF
2
4
2
3
(2)
(3)
≥−40 °C
[ArN2][BF ] → ArF + N2 + BF
4
3
Electrophilic Fluorination Properties of [C6F5XeF2]-
[BF4]. (a) Reactivity of [C6F5XeF2][BF4] with K[C6F5BF3]. It is
possible that excess C6F5BF2 used in the preparation of
[C6F5XeF2][BF4] could further react to form [C6F5XeF2]-
[C6F5BF3], which is presumed to be less stable than
[C6F5XeF2][BF4]. The reactivity of [C6F5XeF2]+ toward
[C6F5BF3]− was studied by reacting [C6F5XeF2][BF4] with
suspensions of K[C6F5BF3] in CH3CN at −40 °C. The main
soluble product was [C6F5Xe]+ (86) along with C6F6 (6),
[C6F7BF3]− (8), XeF2 (27), and HF (15) (Scheme 4). The
products, [C6F5Xe]+ and HF, were also detected in the
decomposition of [C6F5XeF2][BF4] in CH3CN in the absence
of K[C6F5BF3]. The more rapid reduction of the [C6F5XeF2]+
aHF
[C6F5Xe][BF ] ⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯→⎯ C6F6 + Xe0 + BF
4
3
(4)
20 °C, 54 d
The cyclic olefins, c-C6F8-1,4 and c-C6F10, likely result from the
fluorination of C6F6 by XeF2 and, to a lesser extent, by
[C6F5XeF2][BF4].
Samples that had decomposed at −30 °C contained c-C6F8-
1,4 and the [BF4]− salts of [C6F5Xe]+ and [c-C6F7Xe]+
(Scheme 2). The formation of c-C6F8-1,4 and [c-C6F7Xe]+
can be attributed to fluorination of C6F6 and the [C6F5Xe]+
cation, respectively. No fluorine addition to [C6F5Xe]+
occurred with XeF2 in aHF below −10 °C in the absence of
a Lewis acid.24 However, the oxidative strength of the aHF
solution is expected to increase with the formation of the Lewis
acid BF3 as [C6F5XeF2][BF4] decomposition proceeds (eq 2).
Boron trifluoride serves to activate the fluoro-oxidizers XeF2
and [C6F5XeF2]+, enabling the formation of [c-C6F7Xe]+. The
salt, [C6F5XeF2][BF4], decomposes spontaneously at room
temperature in aHF to yield c-C6F8-1,4 as the major product
and small amounts of [C6F5Xe][BF4] and C6F6. Overall, c-
C6F8-1,4 formation is the dominant reaction channel at all
temperatures that were studied (24, −30, and −40 °C).
Heterolytic cleavage of [C6F5XeF2][BF4] by HF proceeds
Scheme 4. Product Distribution Resulting from the Reaction
of [C6F5XeF2][BF4] with a Suspension of K[C6F5BF3] in
CH3CN at −40 °C
C
dx.doi.org/10.1021/ic501831j | Inorg. Chem. XXXX, XXX, XXX−XXX

Inorganic Chemistry
Article
Figure 1. (a) The 19F NMR spectrum (282.40 MHz) (FXe, o-, p-, and m-F) and (b) the 129Xe NMR spectrum (83.02 MHz) of the [C6F5XeF2]+
cation in [C6F5XeF2][BF4] (aHF, −40 °C). The experimental spectra, resolution-enhanced by Gaussian multiplication (left), and the simulated
spectra (right) are shown.
cation to [C6F5Xe]+ in the presence of [C6F5BF3]− is
attributable to fluorination and cleavage of the B−C bond of
[C6F5BF3]− to give C6F6 and [BF4]− and fluorine addition to
the C6F5 group of [C6F5BF3]− to give [C6F7BF3]−. The rate of
[C6F5XeF2]+ consumption in CH3CN at −40 °C was ca. 10
times faster when a suspension of [C6F5BF3]− was present. For
a more detailed discussion of this topic, see Supporting
Information.
(b) Reactivity of [C6F5XeF2][BF4] with Pn(C6F5)3 (Pn = P, As,
or Bi) and C6F5X (X = Br or I). A preliminary communication
provided a report of the fluorination of P(C6F5)3, C6F5I, and I2
to P(C6F5)3F2, C6F5IF2, and IF5 by [C6F5XeF2][BF4] in
CH3CN.38 The reactivities of [C6F5XeF2][BF4] with Pn(C6F5)3
(Pn = P, As, or Bi) and C6F5X in both CH3CN and aHF were
studied in the present work.
The triarylpnictogens, Pn(C6F5)3 (Pn = P, As, or Bi), were
fluorinated to Pn(C6F5)3F2 by [C6F5XeF2][BF4] in CH3CN at
−40 °C over a period of 15 min, but no reaction occurred in
aHF. The iodine atom of C6F5I was oxidatively fluorinated to
C6F5IF2 by [C6F5XeF2][BF4] in CH3CN and aHF (−40 °C
within 15 min), but C6F5Br was unreactive under these
conditions. Solutions of [C6F5XeF2][BF4] in aHF at −20 °C
also did not oxidize the bromine substituent but fluorinated the
C6F5 group instead, providing a product mixture comprised of
D
dx.doi.org/10.1021/ic501831j | Inorg. Chem. XXXX, XXX, XXX−XXX

Inorganic Chemistry
Article
Figure 2. 19F NMR spectra (282.40 MHz) of the o-, p-, and m-F 19F environments in C6F5IF2 (aHF, −80 °C). The experimental spectrum(left),
resolution-enhanced by Gaussian multiplication (left), and the simulated spectrum (right) are shown.
Table 1. Coupling Constants (Hz) Derived from the Simulated 19F NMR Spectra of [C6F5XeF2]+, C6F5IF2, [C6F5Xe]+, and C6F5I
a
b
cd
,
de
,
[C6F5XeF2]+
C6F5IF2
[C6F5Xe]+
C6F5I
1J(19FXe−129Xe)
3902
19.05
21.61
8.23
3J(19Fo−129Xe)
67.7
8.8
4J(19Fm−129Xe)
5J(19Fp−129Xe)
3.7
3J(19Fo−19Fm) = J23
4J(19Fo−19Fp) = J24
5J(19Fo−19Fm′) = J25
4J(19Fo−19Fo′) = J26
3J(19Fm−19Fp) = J34
4J(19Fm−19Fm′) = J35
4J(19FXe−19Fo) = J12
5J(19FXe−19Fm) = J13
−17.24
10.38
−2.71
−17.01
−19.39
2.50
−20.64 [−22.65]
7.33 [5.61]
6.03 [6.30]
−11.21 [−9.51]
−19.09 [−20.32]
0.85 [0.31]
3.16
−20.2
8.24
6.50
−9.9
−19.5
0.83
−22.7
2.1
7.2
−4.9
−19.5
−1.2
3.27
2.30
−1.48
4.74
6J(19FXe−19Fp) = J14
7.50
a
b
c
d
e
aHF (−40 °C). aHF (−80 °C) [CH2Cl2 (24 °C)]. CH3CN (−40 °C). Reference 40. CD3CN (24 °C).
[C6F5XeF2]+ (3), [C6F5Xe]+ (9), C6F5Br (26), c-C6F7Br (8), c-
C6F9Br (8), c-C6F8-1,4 (11), c-C6F10 (1), C6F5Y (14) (where Y
is unknown) C6F6 (21), and XeF2 (6). The presence of
[C6F5Xe]+, C6F6, and c-C6F8-1,4 in the product mixture is
consistent with the decomposition of the [C6F5XeF2]+ cation.
For a more detailed discussion of this topic, see Supporting
Information (Electrophilic Fluorination Properties of
[C6F5XeF2][BF4]).
Characterization of [C6F5XeF2][BF4] by 11B, 13C, 19F,
and 129Xe NMR Spectroscopy. The 11B, 13C, 19F, and 129Xe
NMR spectra of [C6F5XeF2][BF4] (CH3CN/CD3CN, −40 °C)
have been previously reported.38 Only the chemical shifts,
1J(19F−129Xe), and several 1J(13C−19F) coupling constants were
reported for [C6F5XeF2]+, but neither the J(19F−19F) couplings
nor the J(19F−129Xe) couplings involving the C6F5 group could
be resolved.38 The present work provides a 11B, 19F, and 129Xe
E
dx.doi.org/10.1021/ic501831j | Inorg. Chem. XXXX, XXX, XXX−XXX

Inorganic Chemistry
Article
NMR study of [C6F5XeF2][BF4] in aHF solvent at −40 °C
(Figure 1 and Supporting Information, Figure S1) and −80 °C
(Supporting Information, Figure S2). The NMR parameters are
listed in Supporting Information, Table S1 and a detailed
discussion of the 19F NMR spectrum of the [BF4]− anion (−40
°C, aHF, Supporting Information, Figure S1) is provided. The
19F NMR spectrum of isoelectronic C6F5IF2 had also been
previously reported in numerous solvents including CH3CN
(24 °C)41 and aHF (−40 °C),42 but the 19F resonance of the
IF2 group could not be observed in aHF at −40 °C.42 The
present study also reports the 19F NMR spectrum of C6F5IF2 at
−80 °C in aHF (Figure 2).
couplings with Fo and Fm of the C6F5 group (3J(19Fo−129Xe) ≈
4J(19Fm−129Xe) ≈ 20 Hz), which appears as a pseudoquintet.
Complete sets of J(19F−19F) and J(19F−129Xe) couplings
have now been obtained for the 19F NMR spectra of
[C6F5XeF2]+ (−40 °C, aHF), and complete sets of
J(19F−19F) couplings have also been obtained for C6F5IF2
(−80 °C, aHF), which afforded the best-resolved spectra for
simulation (Figures 1 and 2). The 19F spectra were simulated
using the multi-NMR simulation programs gNMR43 and
ISOTOPOMER.44 The well-resolved multiplet fine structures
observed for the Fp resonances of [C6F5XeF2]+ and C6F5IF2, a
triplet of triplets of triplets, provided preliminary values for
3J(19Fp−19Fm), 4J(19Fp−19Fo), and 6J(19Fp−19FXe). The Fo and Fm
fluorine resonances exhibited partially resolved multiplet
structures, which prevented direct extraction of the remaining
The 19F NMR spectrum of [C6F5XeF2]+ in aHF is comprised
of four multiplets (Figure 1a) having chemical shifts that are in
good agreement with the published values.38 The most
deshielded 19F environment is that of the XeF2 group (−32.5
ppm, −40 °C and −33.2 ppm, −80 °C) which is a partially
resolved multiplet flanked by satellite multiplets attributed to
1J(19F−129Xe) (3902 Hz, −40 °C and 3889 Hz, −80 °C). The
magnitude is in good agreement with that observed for
[C6F5XeF2]+ in CH3CN (3896 Hz, −40 °C) (Supporting
Information, Table S1). In contrast, the fluorine resonance of
the IF2 group of C6F5IF2 was not observed in aHF at −40 °C
because its fluorine ligands are sufficiently fluoro-basic to
undergo rapid 19F chemical exchange with HF. The rate of 19F
1
J(19F−19F) couplings. Moreover, the 129Xe satellites (I = /2,
26.44% natural abundance) associated with the 19F resonances
of the C6F5 group could not be fully resolved. Initial estimates
of the missing J(19F−19F) coupling constants were arrived at by
using empirical relationships between the 19Fp chemical shifts
and their 19F−19F coupling constants as previously described
for [C6F5Xe]+ and C6F5I.40 The observed chemical shifts and
resulting estimated coupling constants were imported into
gNMR, and the 19F spectra of [C6F5XeF2]+ and C6F5IF2 were
simulated in manual and iterative modes. The couplings and
their relative signs were then systematically varied to achieve
the best fits with the experimental spectra. In the case of the
C6F5IF2 spectrum, which was better resolved than the
[C6F5XeF2]+ spectrum, it proved possible to iterate the
spectrum in the automatic iterative mode. The optimized
coupling constants obtained from gNMR43 were then imported,
without further iteration, into the multi-NMR simulation
program ISOTOPOMER,44 which provided graphical represen-
tations that better reproduced all spectral features (Figures 1
and 2 and Supporting Information, Figure S3).
chemical exchange was sufficiently slow in aHF at −80 °C to
1
allow its observation as a broad singlet at −177.2 ppm (Δν /
=
2
615 Hz). All J(19F−19F) couplings involving the axial fluorine
ligands of C6F5IF2 were observed in CH2Cl2 (24 °C) (Table 1
and Supporting Information, Figure S3), but were absent in the
spectra recorded in aHF (−40 and −80 °C) due to 19F
chemical exchange with HF solvent. The assignments of the
J(19F−19F) couplings involving the axial fluorine atoms of
C6F5IF2 (CH2Cl2, 24 °C) and [C6F5XeF2]+ (aHF, −40 °C)
(Table 1) are confirmed by the excellent agreement between
the experimental and simulated spectra (Figure S3, Supporting
Information, and Figure 1, respectively). The absence of
significant exchange broadening of the XeF2 group resonance of
[C6F5XeF2]+ at −40 °C in aHF is attributed to the lower ionic
characters of the axial Xe−F bonds of [C6F5XeF2]+ relative to
the I−F bonds of C6F5IF2 (see Natural Bond Orbital (NBO)
Analyses). Consequently, the fluorine atoms of the XeF2 group
are also considerably less shielded than those of the IF2 group.
The o-, m-, and p-F environments of [C6F5XeF2]+ and
C6F5IF2 are more shielded in CH3CN than in aHF (Supporting
Information, Table S1). Their enhanced shieldings are
attributed to CH3CN coordination to Xe(IV)/I(III), which
results in negative charge transfer to the aryl group (see Natural
Bond Orbital (NBO) Analysis). Dissolution of [C6F5XeF2]+
and C6F5IF2 in aHF may be promoted by hydrogen bonding
with their basic Xe(IV)- and I(III)-bonded fluorine atoms, and
may also contribute to their 19F deshielding in aHF.
The signs of 3J(19Fo−19Fm), 3J(19Fm−19Fp), and 4J(19Fo−19Fo′)
4
for [C6F5XeF2]+ are likely negative, and J(19Fo−19Fp) is likely
positive based on comparisons with C6F5IF2, [C65F5Xe]+, C6F5I
(Table 1), and other C6F5-compounds.45 The J(19Fo−19Fm′)
coupling is assigned a negative sign because substitution of a
positive sign greatly altered the appearance of the calculated
spectrum. The remaining J(19F−19F) ring couplings were either
too small or lacked relevant literature values for comparison to
confidently assign their relative signs. All trends in the relative
magnitudes and signs of the J-values are in good agreement
with those obtained from the spectral simulation of C6F5IF2
(Table 1). Similar trends are observed when the J(19F−19F)
couplings of [C6F5Xe+] and C6F5I are compared (Table 1).40,45
X-ray Crystal Structures of [C6F5XeF2][BF4] (1),
[C6F5XeF2][BF4]·2HF (2), and [C6F5XeF2][BF4]·1.5CH3CN
(3a,b). A summary of the refinement results and other
crystallographic information is provided in Table 2. Selected
bond lengths and bond angles involving the xenon centers in
[C6F5XeF2][BF4] (Figure 3 and Supporting Information,
Figure S4), [C6F5XeF2][BF4]·2HF (Figure 4), and [C6F5XeF2]-
[BF4]·1.5CH3CN (Figure 5) are listed in Table 3, and a full list
of geometrical parameters that include the remaining geo-
metrical parameters associated with xenon as well as the
structural parameters of the [BF4]− anions, C6F5 groups, and
the coordinated CH3CN and HF molecules are given in
Supporting Information, Table S2. The latter parameters are in
good agreement with previously published values8,20,46−48 and
do not require further comment.
The 129Xe NMR spectrum of [C6F5XeF2]+ (Figure 1;
δ(129Xe) = −1765.9 ppm, aHF, −40 °C) is a 1:2:1 triplet
arising from 1J(19F−129Xe) = 3902 Hz. The 1J(19F−129Xe)
coupling constant and 129Xe chemical shift show little in the
way of temperature or solvent dependencies in aHF (δ(129Xe)
1
= −1756.2 ppm, J(19F−129Xe) = 3889 Hz, −80 °C) and
1
CH3CN (δ(129Xe) = −1702.7 ppm, J(19F−129Xe) = 3896 Hz,
−40 °C) (Supporting Information, Table S1). Each branch of
the triplet can be resolved into an overlapping triplet of triplets
(Figure 1b, inset). The latter multiplet arises from similar 129Xe
F
dx.doi.org/10.1021/ic501831j | Inorg. Chem. XXXX, XXX, XXX−XXX

Inorganic Chemistry
Article
Table 2. Crystallographic Data for [C6F5XeF2][BF4] (1),
[C6F5XeF2][BF4]·2HF (2), and [C6F5XeF2][BF4]·1.5NCCH3
(3)
1
2
3
chem formula
space group
a (Å)
C6F11BXe
P21/n
C6H2F13BXe
P21/n
C9H4.5F11BN1.5Xe
C2/c
7.4707(2)
19.0245(5)
7.7595(2)
109.873(1)
1037.15(5)
4
7.1022(2)
19.5471(5)
9.0812(2)
109.966(1)
1184.94(5)
4
12.752(5)
23.520(5)
19.398(5)
103.213(5)
5664(3)
4
b (Å)
c (Å)
β (deg)
V (Å3)
molecules/unit cell
mol wt (g mol−1
)
423.17
463.19
1939.00
2.274
calcd density (g cm−3
)
2.710
2.596
T (°C)
−173
3.464
−173
3.067
−173
2.56
μ (mm−1
)
a
R1
0.0459
0.0417
0.0332
b
wR2
0.0887
0.0885
0.0897
a
b
R1 is defined as Σ∥F0| − |Fc∥/Σ|F0| for I > 2σ (I). wR2 is defined as
[Σ[w(F0 − Fc2)2]/Σw(F0 )2]1/2 for I > 2σ(I).
2
2
Figure 4. Structural unit in the crystal structure of [C6F5XeF2][BF4]·
2HF (a) showing the contacts, Xe---F(19,18)H, FB---H, and Xe---FB.
(b) A side-on view showing the Xe---FH and Xe---FB contacts viewed
along the crystallographic b-axis and their avoidance of the trigonal
plane containing C(11), Xe(1), and the two valence electron lone pairs
of xenon. Thermal ellipsoids are shown at the 50% probability level.
The present study represents the only crystallographic
characterization of XeIV−C bonds. The X-ray crystal structures
of the isoelectronic C6F5IF2 molecule42 and its N-base adducts
of 1,10-phenanthroline (C12H8N2), 2,2′-bypyridine (C10H8N2),
and quinoline (C9H7N)41 have been previously reported and
are compared.
The XeIV−C bonds (1, 2.058(2); 2, 2.058(3); 3a, 2.067(4);
3b, 2.066(5), 2.083(5) Å) are slightly shorter than the XeII−C
bonds of [C6F5Xe]+ salts (2.100(6)−2.104(5) Å)46 and are not
significantly affected by differences in contacts to xenon or by
the higher positive charge on the Xe(IV) atom (see Natural
Bond Orbital Analyses). The Xe−F bonds (1: 1.925(2),
1.948(2); 2: 1.935(2), 1.941(2); 3a: 1.930(2), 1.939(2); and
3b: 1.940(2) Å) are significantly longer than the Xe−Fax bonds
of [XeF3]+ (1.894(2) and 1.901(2) Å in the [SbF6]− salt;48
1.908(4) and 1.883(4) in the [Sb2F11]− salt6), but are only
marginally shorter than the Xe−F bonds of XeF4 (1.953(2)
Å).3 Electron transfer from the C6F5 group results in more
polar Xe−F bonds than in the parent cations. The Xe−F bonds
of [C6F5XeF2]+ are, in turn, significantly shorter and less polar
than the I−F bonds of C6F5IF2 (1.959(2)−2.025(2) Å) as a
consequence of the higher positive charge and the electro-
negativity of Xe(IV).
The ligand arrangements around xenon and iodine in
42
[C6F5XeF2]+ and C6F5IF2 are T-shaped, in accordance with
the AX2YE2 VSEPR arrangement of three bonding electron
pairs and two electron lone pairs in the xenon/iodine valence
shell. The more electronegative fluorine atoms occupy the axial
positions, and the less electronegative C6F5 group and the two
xenon/iodine valence electron lone pairs occupy the equatorial
plane. In all three Xe(IV) crystal structures, the C(11), Xe(1),
F(17), and F(18) atoms are coplanar within 3σ. The electron
lone pair domains cause the F−Xe(I)−F angles to bend toward
the C6F5 group producing nonlinear F−Xe(I)−F angles (1,
170.22(7); 2, 168.7(1); 3a, 170.5(1); and 3b, 165.5(2) and
167.3(1)°). Similar bent F−I−F angles are observed for
Figure 3. Structural unit in the crystal structure of [C6F5XeF2][BF4]
(a) showing the Xe---FB cation−anion contacts. (b) A side-on view
showing the Xe---FB contacts and their avoidance of the trigonal plane
containing C(11), Xe(1), and the two valence electron lone pairs of
xenon. (c) A view showing the [C6F5XeF2]2 dimer units in
[C6F5XeF2][BF4]. Thermal ellipsoids are shown at the 50% probability
level.
G
dx.doi.org/10.1021/ic501831j | Inorg. Chem. XXXX, XXX, XXX−XXX

Inorganic Chemistry
Article
of the plane orthogonal to the C6F5 plane in the crystal
structures of [C6F5XeF2]+, with F−Xe−Cipso−C2,6 dihedral
angles of 1, 67.5(2); 2, 68.3(3); 3a, 62.5(3); 3b, 75.2(2), and
79.4(2)°. The calculated geometries of [C6F5XeF2][BF4],
[C6F5XeF2][BF4]·2HF, [C6F5XeF2]+·CH3CN, and
[C6F5XeF2]+·2CH3CN show that the Xe---F and Xe---N
contacts significantly influence the above angles (see Computa-
tional Results). Comparable dihedral angles occur for the two
crystallographically distinct C6F5IF2 molecules in the crystallo-
graphic unit cell of C6F5IF2 (74.40(3), 74.7(3)°)42 and the N-
base adducts of C6F5IF2 (59.0(2), 59.1(2)° (C12H8N2);
68.9(2), 71.5(2)°, (C10H8N2); 63.8(3), 68.3(3)° (C9H7N)).41
The xenon atom of [C6F5XeF2][BF4] shows two short
contacts, Xe(1)---F(1), 2.686(2) Å and Xe(1)---F(4), 2.833(2)
Å, with two fluorine atoms of the same [BF4]− anion. The Xe---
F contacts are significantly less than the sum of the van der
Waals radii of Xe and F (3.63 Å)49 and are significantly shorter
than the Xe---F contact in [C6F5Xe][B(CF3)4] (2.913(4) Å),46
indicating that the [BF4]− anion is more strongly coordinated
to the [C6F5XeF2]+ cation than [B(CF3)4]− is to the [C6F5Xe]+
cation, which is consistent with the greater anticipated Lewis
acidity of [C6F5XeF2]+ and lower fluorobasicity of [B(CF3)4]−.
Unfortunately, the structural parameters of [C6F5Xe][BF4]
cannot be compared because its crystal structure has not been
determined. As expected, the B−FB bonds, where the FB atoms
are involved in Xe---FB contacts (B(1)−F(1), 1.406(3) Å and
B(1)−F(4), 1.407(4) Å), are slightly elongated relative to the
terminal B−F bonds (B(1)−F(2), 1.369(3) Å and B(1)−F(3),
1.386(4) Å). When the coordination sphere is enlarged to 3.5
Å, two additional long contacts with two different [BF4]−
anions, Xe(1)---F(2A) and Xe(1)---F(3B), are found at
2.937(2) and 3.073(2) Å, respectively. As depicted in Figure
3, the Xe---FB contacts avoid the trigonal plane containing
C(11), Xe(1) and the two valence electron lone pairs of xenon.
The two shorter contacts approach from above and below the
trigonal plane, whereas the two longer contacts approach from
below the trigonal plane. These fluorine contacts approach
xenon from opposite sides of the Xe(1),C(11),F(17),F(18)-
plane, which is orthogonal to the trigonal plane. A third, long
intermolecular Xe(1)---FXe contact (3.137(2) Å) occurs with a
second [C6F5XeF2]+ cation in [C6F5XeF2][BF4] (Figure 3).
The long contacts result in weakly bonded four-membered
(XeF)2 dimer rings between adjacent [C6F5XeF2]+ cations,
which pack along the c-axis (Supporting Information, Figure
S4). The [C6F5XeF2]+ dimers form zigzag chains along the b-
axis that are separated by alternating layers of [BF4]− anions
(Supporting Information, Figure S4). The (XeF)2 rings are
similar to the (IF)2 rings found in the X-ray crystal structures of
C6F5IF2 and C6F5IF2·C9H7N.41 Unlike the (XeF)2 rings of
42
Figure 5. The two solvated cations in the crystal structure of
[C6F5XeF2][BF4]·1.5CH3CN: (a) [C6F5XeF2]·CH3CN solvate and its
Xe---FB contacts with two adjacent [BF4]− anions and (b) one of two
crystallographically nonequivalent [C6F5XeF2]·2CH3CN solvates and
its Xe---FB contacts with two adjacent [BF4]− anions. (c, d) The side-
on views of the Xe---N and Xe---FB contacts, shown along the
crystallographic b-axes, depict their avoidance of the trigonal planes
containing C(11/12), Xe(1/2) and the two valence electron lone pairs
of xenon. Thermal ellipsoids are shown at the 50% probability level.
[C6F5XeF2][BF4], the (IF)2 rings of C6F5IF2 are part of an
infinite chain structure. The smallest angle around Xe is the
cation−anion contact angle F(1)---Xe(1)---F(4) (47.90(5)o),
which is constrained by the near-tetrahedral F(1)−B(1)−F(4)
angle as well as by the Xe(1)---F(1,4) contact distances.
The xenon atom of [C6F5XeF2][BF4]·2HF shows two short
contacts, Xe(1)---F(19) (2.855(2) Å) and Xe(1)---F(20)
(2.800(3) Å), with the fluorine atoms of two crystallo-
graphically distinct HF molecules. The Xe---F contacts are
significantly shorter than the sum of the van der Waals radii of
Xe and F (3.63 Å)49 and are comparable to the Xe---F contacts
observed in [C6F5XeF2][BF4] (vide supra).46 Each HF
molecule interacts with two fluorine atoms of the same
[BF4]− anion (F(19)---F(1), 2.543(4) Å and F(20)---F(4),
isoelectronic C6F5IF2 and its nitrogen base adducts (C6F5IF2:
170.46(10) and 171.59(9)o;42 C6F5IF2 adducts: 161.07(7)
(C12H8N2),41 158.63(8) (C10H8N2),41 165.86(8) and
172.59(8)o (C9H7N)41). The XeF2 moieties are twisted out
H
dx.doi.org/10.1021/ic501831j | Inorg. Chem. XXXX, XXX, XXX−XXX

Inorganic Chemistry
Article
Table 3. Selected Experimental Geometrical Parameters of [C6F5XeF2][BF4], [C6F5XeF2][BF4]·2HF, and [C6F5XeF2][BF4]·
a
1.5NCCH3
a
b
The labeling schemes correspond to those used in Figures 3, 4, and 5, respectively. A full list of geometrical parameters is given in Supporting
Information, Table S2.
2.550(4) Å). As observed for [C6F5XeF2][BF4], the B−FB
bonds, where the FB ligands are hydrogen-bonded to HF or
coordinated to xenon, are elongated (Figure 4). When the
xenon coordination sphere is enlarged to 3.5 Å, two additional
long contacts with two different [BF4]− anions, Xe(1)---F(2A)
and Xe(1)---F(3B), are found at 3.040(3) and 3.110(3) Å,
respectively. The Xe---F contacts avoid the trigonal plane
containing C(11), Xe(1), and the two valence electron lone
pairs of xenon and are directed away from the C6F5 group in a
manner similar to that observed in [C6F5XeF2][BF4]. The local
geometry around the xenon atom is similar to that observed in
the [C6F5XeF2][BF4] ion pair except for the F(17)−Xe(1)---
F(19) (64.1(1)o) and F(18)−Xe(1)---F(20) (65.9(1)o) angles,
which are more closed, and the F(19)---Xe(1)---F(20) angle,
which is more open (65.29(9)o).
The crystal structure of [C6F5XeF2][BF4]·1.5CH3CN
contains three types of solvates, two crystallographically
nonequivalent [C6F5XeF2][BF4]·2CH3CN and one
[C6F5XeF2][BF4]·CH3CN salt formulations (Figure 5). The
asymmetric units of [C6F5XeF2][BF4]·2CH3CN are on C2-axes,
whereas the [C6F5XeF2][BF4]·CH3CN structural unit is on a
general position, giving rise to the same number of
[C6F5XeF2][BF4]·2CH3CN and [C6F5XeF2][BF4]·CH3CN
units in the unit cell and the average formulation [C6F5XeF2]-
[BF4]·1.5CH3CN.
[C6F5XeF2][BF4]·2CH3CN has two Xe---N contacts with two
symmetry-related CH3CN molecules in which the CH3CN
geometries are not noticeably affected by coordination. The
Xe---N contact distances, 2.816(4) and 2.868(4) Å, are
comparable to the Xe---F contact distances in [C6F5XeF2][BF4]
and [C6F5XeF2][BF4]·2HF, but are longer than the Xe---N
contact distances in [C6F5Xe]+·CH3CN (2.613(15) and
2.637(7) Å).46 The angles subtended at the xenon atoms are
similar to those of [C6F5XeF2][BF4] except for the N---Xe---N
angles (63.6(1) and 64.6(1)o), which are comparable to the
corresponding F---Xe---F angle in [C6F5XeF2][BF4]·2HF
(65.29(9)o). The [C6F5XeF2]+ cation of the [C6F5XeF2]-
[BF4]·CH3CN unit has one Xe---N contact with the CH3CN
molecule (2.742(4) Å). The next shortest contacts are Xe---F
contacts with the fluorine atoms of the [BF4]− anions (3a:
2.959(3), 3.041(3), and 3.049(3) Å; 3b: 2 × 3.028(3) and 2 ×
3.036(3) Å), which are comparable to those in [C6F5XeF2]-
[BF4] and [C6F5XeF2][BF4]·2HF. Again, the Xe---F contacts
avoid the trigonal plane containing C(11), Xe(1), and the two
valence electron lone pairs of xenon (Figures 3 and 4). The
C−Xe---N angles of [C6F5XeF2]+·2CH3CN (148.20(8)° and
147.71(8)°) and [C6F5XeF2]+·CH3CN (159.4(1)°) deviate
more from linearity than the C−Xe---N and C−Xe---F angles in
[C6F5Xe][B(CF3)4] (174.8(2)°),46 [C6F5Xe·CH3CN][B-
(C6F5)2F2]·CH3CN (174.5(3)°),50 [C6F5Xe·CH3CN][B-
(C6F5)4] (177.1 (4)°),46 and C6F5Xe---NCB(CN)3
(175.9(1)°).46
The xenon atom coordination spheres in [C6F5XeF2][BF4]·
1.5CH3CN are comprised of contacts with CH3CN and
[BF4]−, which are geometrically similar to those of [C6F5XeF2]-
[BF4] and [C6F5XeF2][BF4]·2HF. The [C6F5XeF2]+ cation of
Raman Spectroscopy. The low-temperature, solid-state
Raman spectra of the [C6F5XeF2][BF4] (1) ion pair and the
I
dx.doi.org/10.1021/ic501831j | Inorg. Chem. XXXX, XXX, XXX−XXX

Inorganic Chemistry
Article
[C6F5XeF2][BF4]·2HF (2) HF-solvated ion pair (Figures 6 and
7 and Supporting Information, Figures S5 and S6) were
The majority of the vibrational frequencies and their
descriptions for the C6F5 groups of [C6F5XeF2][BF4],
[C6F5XeF2][BF4]·2HF, and C6F5IF2 are very similar to those
of [C6F5Xe]+,46 C6F5I,53−55 and related C6F5 derivatives,51,52
and therefore do not require further commentary.
Factor-group analyses57 of (1) and (2) were carried out by
correlating their calculated gas-phase geometries (C1) to their
crystal site symmetries (C1) and, in turn, to their unit cell
symmetries (C2h) (Supporting Information, Tables S3 and S4).
The analyses reveal that vibrational coupling within the
crystallographic unit cell leads to splitting of each vibrational
band of (1) into four components, two Raman-active Ag and Bg
components, and two infrared-active Au and Bu components. In
the experimental spectra (Table 4), many of the Raman bands
of (1) are split, but no band splittings were resolved for (2),
indicating that vibrational coupling within the unit cell of (2) is
weak.
(a) [C6F5XeF2][BF4] (1) and [C6F5XeF2][BF4]·2HF (2). The
bands at 789 (1) and 786 (2) cm−1 are assigned to the
extensively coupled ν(Xe(1)−C(1)) − [ν(C(3)−C(4)) +
ν(C(5)−C(4))] − [ν(C(3)−F(3)) + ν(C(5)−F(5))] mode.
The experimental frequencies are in good agreement with the
calculated values ((1), 788 [811]; (2), 787 [812] cm−1; Table
4) and are in accordance with the observed Xe−Cipso, C3,5−C4,
and C3,5−F3,5 bond lengths, which are equal in both salts
(Table 3). This mode is shifted to higher frequency relative to
that of the isolated [C6F5XeF2]+ cation. The calculations show
that the Xe−C stretch also contributes to a low-frequency
mode, which is strongly coupled to the δ(XeF2)i.p deformation
mode ((1), 251 [260] cm−1; (2), 245 [271] cm−1). The
δ(XeF2)i.p. mode is also coupled to ν(Xe---FB) of (1) (197
[203] cm−1) and ν(Xe---FH) of (2) (190 [195] cm−1). As
predicted, the majority of these low-frequency modes
correspond to weak to very weak bands in the Raman spectra
((1), 213 and 188 cm−1; (2), 248 and 186 cm−1), except for the
band at 188 cm−1, which has medium intensity. The
contribution of ν(Xe−C) to both a high- and a low-frequency
mode has also been observed for the [C6F5Xe]+ cation.46
The νs(XeF2) bands of [C6F5XeF2]+ in (1) and (2) are
calculated at 507 [536] and 524 [551] cm−1, respectively, and
correspond to the most intense Raman bands in their
experimental Raman spectra (530/535 (1) and 524 (2)
cm−1). The splittings in the Raman spectrum of [C6F5XeF2]-
[BF4] (1) arise from vibrational coupling within the crystallo-
graphic unit cell (vide supra, Supporting Information, Table
S3). The calculated νas(XeF2) frequencies are 565 [589] cm−1
(1) and 587 [609] cm−1 (2) and are predicted to be very weak
because of the near-centrosymmetric local geometry of the
XeF2 group. Consequently, these modes were observed in the
experimental Raman spectra as very weak bands (608/609 (1)
and 606 (2) cm−1). Both frequencies are comparable to
νas(XeF2ax) (619 cm−1) and νs(XeF2ax) (583 cm−1) in
[XeF3][Sb2F11],58 but occur at higher frequencies relative to
XeF4, i.e., νas(XeF4) (solid, 502 cm−1;59 gas, 524 cm−160) and
νs(XeF4) (solid, 543 cm−1;59 gas: 554 cm−160). The calculated
frequencies of the νs(XeF2) and νas(XeF2) modes of
[C6F5XeF2][BF4]·2HF (2) (νs, 524 [551] cm−1; νas, 587
[609] cm−1) are in good agreement with those predicted for
gas-phase [C6F5XeF2]+ (νs, 524 [556] cm−1; νas, 600 [634]
cm−1), but are shifted to lower frequencies in (1) (νs, 507
[536] cm−1; νas, 565 [589] cm−1). In contrast with the
δ(XeF2)i.p. deformation modes of (1) and (2), which were
shown to be coupled to ν(Xe−C) (vide supra), the out-of-
Figure 6. Raman spectrum of [C6F5XeF2][BF4] recorded in a Pyrex
glass NMR tube at −155 °C using 1064-nm excitation. The symbol
(†) denotes an instrumental artifact. Bands that occur in the 835−
1835 cm−1 region of the spectrum are given in Table 4 and are shown
in Supporting Information, Figure S5.
Figure 7. Raman spectrum of [C6F5XeF2][BF4]·2HF recorded in a
FEP sample tube at −155 °C using 1064-nm excitation. The symbols
denote bands arising from an instrumental artifact (†) and the FEP
sample tube (*). Bands that occur in the 835−1835 cm−1 region of the
spectrum are listed in Table 4 and are shown in Supporting
Information, Figure S6.
assigned under C1 symmetry based on their experimental and
calculated geometries and are provided in Table 4. A total of 51
(1) and 63 (2) Raman- and infrared-active bands are predicted.
The frequency assignments were aided by the calculated
frequencies and Raman intensities of [C6F5XeF2][BF4] and
[C6F5XeF2][BF4]·2HF and by previous vibrational assignments
for [C6F5Xe]+,46 the C6F5 group,51−55 and [BF4]−.56 The
calculations were carried out using the B3LYP and PBE1PBE
(values given in square brackets) functionals and aug-cc-
pVTZ(-PP) basis sets. The experimental Raman and infrared
frequencies of C6F5IF2 have been reported, but were not
assigned.42 Complete assignments of the Raman and infrared
spectra of C6F5IF2 are provided in the ensuing discussion,
allowing a comparison of the vibrational frequencies of C6F5IF2
with those of the isoelectronic [C6F5XeF2]+ cation (Table 5).
Overall, there is good agreement between the calculated and
observed frequencies of both species.
J
dx.doi.org/10.1021/ic501831j | Inorg. Chem. XXXX, XXX, XXX−XXX

Inorganic Chemistry
Article
Table 4. Experimental Raman Frequencies and Intensities for [C6F5XeF2][BF4] and [C6F5XeF2][BF4]·2HF and Calculated
Vibrational Frequencies, Intensities, and Assignments for [C6F5XeF2][BF4] and [C6F5XeF2][BF4]·2HF
a
b
Frequencies are given in cm−1. The abbreviations denote a shoulder (sh) and broad (br). The Raman spectrum was recorded at −150 °C in 4-mm
c
d
o.d. Pyrex glass sample tube. Values in parentheses denote relative Raman intensities. The aug-cc-pVTZ(-PP) basis set was used. Values in
e
parentheses denote calculated Raman intensities (Å4 amu−1), and values in square brackets denote calculated infrared intensities (km mol−1). The
f
1
Raman spectrum was recorded at −150 °C in a /4-in. o.d. FEP sample tube. The deformation modes of the C6F5 ring are denoted by δ and are
K
dx.doi.org/10.1021/ic501831j | Inorg. Chem. XXXX, XXX, XXX−XXX

Inorganic Chemistry
Article
Table 4. continued
relative to the plane of the C6F5 ring; i.p. and o.o.p. denote in-plane and out-of-plane, respectively. The deformation modes of the XeF2 group are
relative to a plane passing through the XeF2 group and the C(1) atom, i.e., δ(XeF2)i.p. denotes a bend within the CXeF2 plane, and δ(XeF2)o.o.p.
g
denotes bending out of this plane. The symbols ν, ρr, and ρt denote a stretch, a rock, and a twist. The detailed description is ν(Xe(1)−C(1)) −
[ν(C(3)−C(4)) + ν(C(5)−C(4))] − [ν(C(3)−F(3)) + ν(C(5)−F(5))].
Table 5. Experimental Vibrational Frequencies and Intensities for [C6F5XeF2]+ in [C6F5XeF2][BF4] and for C6F5IF2, and
Calculated Vibrational Frequencies, Intensities, and Assignments for [C6F5XeF2]+ and C6F5IF2
a
b
1
Frequencies are given in cm−1. The abbreviation denotes a shoulder (sh). The Raman spectrum was recorded at −150 °C in a /4-in. o.d. FEP
sample tube. Values in parentheses denote relative Raman intensities. Bands at 765(10), 367(10), 361(6), and 353(1) cm−1 were assigned to [BF4]−
c
by comparison with previous assignments given in ref 56 and by comparison with the assignments reported for [C6F5XeF2][BF4] in Table 4. The
aug-cc-pVTZ(-PP) basis set was used. Values in parentheses denote calculated Raman intensities (Å4 amu−1), and values in square brackets denote
d
e
calculated infrared intensities (km mol−1). Raman frequencies and relative Raman intensities are from ref 42. Infrared frequencies and intensities
f
are from ref 42. The abbreviations denote weak (w), medium (m), strong (s), and very strong (vs). The C6F5 ring deformation modes are denoted
by δ and are relative to the plane containing the C6F5 ring; i.p. and o.o.p. denote in-plane and out-of-plane, respectively. The deformation modes of
the XF2 group are described relative to a plane passing through the XF2 group and the C(1) atom, i.e., δ(XF2)i.p. denotes a bend within the CXF2
g
plane, and δ(XF2)o.o.p. denotes bending out of this plane. The symbols ν, ρr, and ρt denote a stretch, a rock, and a twist. The detailed description is
h
ν(X(1)−C(1)) − [ν(C(3)−C(4)) + ν(C(5)−C(4))] − [ν(C(3)−F(3)) + ν(C(5)−F(5))]. In the xenon case, there is also a small contribution
i
from δ(CCC)o.o.p. at both levels of theory. In the xenon case, there is also a small contribution from νas(XeF2) at both levels of theory.
plane counterparts, δ(XeF2)o.o.p., are not significantly coupled to
any other modes. The δ(XeF2)o.o.p. modes are predicted to
occur as very weak Raman bands at 216 [224] (1) and 232
[239] cm−1 (2), respectively, and correspond to weak bands at
203 and 205 cm−1 in the experimental spectrum of
[C6F5XeF2][BF4]. In contrast, the ρr(XeF2) deformation
modes are predicted to couple with δ(CCF)o.o.p. to give three
weak Raman bands at 152, 182, 241 [156, 186, 247] cm−1 (1)
and 148, 178, 238 [162, 188, 251] cm−1 (2); however, only two
weak bands were observed for (1) (156 and 236 cm−1), and
L
dx.doi.org/10.1021/ic501831j | Inorg. Chem. XXXX, XXX, XXX−XXX

Inorganic Chemistry
Article
a
Table 6. Selected Calculated Geometrical Parameters for [C6F5XeF2][BF4], [C6F5XeF2][BF4]·2HF, [C6F5XeF2]+·2NCCH3,
[C6F5XeF2]+, and C6F5IF2
a
b
The aug-cc-pVTZ(-PP) basis set was used. The labeling schemes correspond to those used in Figure 8.
only one weak band was observed for (2) (252 cm−1). A broad
band at 2590 cm−1 (not shown in Supporting Information,
Figure S6) was assigned to the HF stretching bands (Table 4).
(b) C6F5IF2 and Its Comparison with [C6F5XeF2]+. The
Raman band at 812 cm−1 is assigned to the coupled mode,
ν(I(1)−C(1)) − [ν(C(3)−C(4)) + ν(C(5)−C(4))] −
[ν(C(3)−F(3)) + ν(C(5)−F(5))] (Table 5). The experimen-
tal frequency shifts 23/26 cm−1 to higher frequency when going
from [C6F5XeF2][BF4] (789 cm−1) and [C6F5XeF2][BF4]·2HF
(786 cm−1) to C6F5IF2 (812 cm−1) and by 20/21 [18/17] cm−1
for their calculated values (Xe, 788/787 [811/812]; I, 808
[829] cm−1). A similar pattern was found for the corresponding
stretching modes of [C6F5Xe][BF4] and C6F5I (experimental:
Xe, 795 and I, 808 cm−1; calculated: Xe, 760 [782] and I, 807
[826] cm−1).46 The I−C stretching mode of C6F5IF2 also
contributes to a low-frequency mode (224 [230]), and is
strongly coupled to the δ(IF2)i.p. deformation mode. This mode
appears as a medium-intensity band at 241 cm−1. The XeIV−C
and IIII−C stretching frequencies of [C6F5XeF2]+ and [C6F5IF2]
occur at higher frequencies than the XeII−C and II−C
stretching frequencies of [C6F5Xe]+ and C6F5I owing to the
greater electronegativities of I(III) and Xe(IV) and consequent
greater covalent characters of their IIII−C and XeIV−C bonds.
The νs(IF2) frequency of C6F5IF2 is calculated to be only 20
[19] cm−1 lower than that of νas(IF2). Both values are
intermediate with respect to the corresponding calculated
frequencies of [C6F5XeF2]+, which differ by 76 [78] cm−1. The
symmetric IF2 stretch of C6F5IF2 (533 cm−1) was observed as
the most intense band in its Raman spectrum.42 The
asymmetric stretch, νas(IF2), was not observed in the Raman
spectrum in contrast with [C6F5XeF2]+ where it was observed
as a weak, split band (vide supra); however, νas(IF2) was
observed as a very intense band in the infrared spectrum (541
cm−1).42 The corresponding νs(IF2ax) and νas(IF2ax) modes of
IF3 occur at similar frequencies (48861 and 48062 cm−1,
respectively), but the frequency order is reversed in C6F5IF2.
The δ(IF2)o.o.p. deformation mode is predicted to occur as a
very weak Raman band at 200 [205] cm−1, but was not
observed. In contrast, and as noted above, the δ(IF2)i.p.
deformation mode is coupled to ν(I−C). For comparison,
the δ(IF2ax) mode of IF3 occurs at 217 cm−1.61
Computational Results. The electronic structures of
[C6F5XeF2][BF4], [C6F5XeF2][BF4]·2HF, [C6F5XeF2]+,
C6F5IF2, and [C6F5XeF2]+·2CH3CN were calculated using the
M
dx.doi.org/10.1021/ic501831j | Inorg. Chem. XXXX, XXX, XXX−XXX

Inorganic Chemistry
Article
Figure 8. Energy-minimized gas-phase geometries of (a) [C6F5XeF2][BF4], (b) [C6F5XeF2][BF4]·2HF, (c) [C6F5XeF2]+·2NCCH3, (d)
[C6F5XeF2]+, and (e) C6F5IF2 (B3LYP/aug-cc-pVTZ(-PP)).
B3LYP and PBE1PBE (values given in square brackets)
functionals and the aug-cc-pVTZ(-PP) basis sets starting from
the crystallographic coordinates (C1 symmetry). The gas-phase
structure of [C6F5XeF2]+·CH3CN was also calculated to study
the effect of coordinating a single CH3CN ligand to
[C6F5XeF2]+. All calculations resulted in stationary points
with all frequencies real. The electronic structures of C6F5I,
C6F5IF2, [C6F5Xe]+, [C6F5Xe]+·CH3CN, C6F6, [XeF3]+, IF3,
[XeF]+, IF, [BF4]−, HF, and CH3CN were also calculated at the
same levels of theory to allow comparisons of their respective
charges, valencies, and bond orders. Molecular orbitals and
NBO analyses for all species were carried out with NBO 6.063
at the same levels of theory. The electronic structure of C6F5IF2
was calculated to compare its geometrical and vibrational
frequencies with those of [C6F5XeF2]+. The basis sets
employed semirelativistic effective core potentials (RLC
ECP); consequently, the present calculated values for C6F5IF2
were improved when compared with the previously reported
values obtained at the RHF/LANL2DZ level.42 Calculated
vibrational frequencies, intensities, and geometrical parameters
are reported in Tables 4−6 and Supporting Information, Tables
S5−S12, and energy-minimized structures are shown in Figure
8 and Supporting Information, Figures S7 and S8.
(a) Geometries. The calculated geometrical parameters of
the C6F5 rings in [C6F5XeF2]+ and C6F5IF2 are in good
agreement with the experimental values and remain essentially
unchanged upon coordination of [C6F5XeF2]+ to HF or
CH3CN and ion pairing with [BF4]−. Therefore, these
geometric parameters are not further commented on in the
ensuing discussion but are listed in Supporting Information,
Table S5.
N
dx.doi.org/10.1021/ic501831j | Inorg. Chem. XXXX, XXX, XXX−XXX

Inorganic Chemistry
Article
(i) [C6F5XeF2][BF4] (1) and [C6F5XeF2][BF4]·2HF (2). The
calculations reveal that both the ion pair (1) and the HF-
solvated ion pair (2) are stable entities whose solid-state
geometries are well-reproduced by the gas-phase calculations.
As observed experimentally, the calculated Xe−C (2.116
[2.085] Å) and Xe−F (1.982 [1.957] Å) bond lengths of (1)
are in good agreement with those of (2) (Xe−C, 2.102 [2.078]
Å; Xe−F, 1.969 [1.947] and 1.978 [1.948] Å). When compared
with their experimental values ((1): Xe−C, 2.058(2) Å; Xe−F,
1.925(2) and 1.948(2) Å; (2): Xe−C, 2.058(3) Å; Xe−F,
1.935(2) and 1.941(2) Å), the calculated Xe−C and Xe−F
bond lengths are slightly elongated for (1) and (2). The Xe---
FB bond lengths of (1) (2.481 [2.451] and 2.481 [2.452] Å)
and the Xe---FH (2.558 [2.556] and 2.605 [2.538] Å), and the
FB---FH (2.364 [2.357] and 2.390 [2.350] Å) bond lengths of
(2) are underestimated compared to their experimental values
((1): Xe---FB, 2.686(2) and 2.833(2) Å; (2): Xe---FH, 2.800(3)
and 2.855(2) Å, FB---FH, 2.543(4) and 2.550(4) Å). As
expected, upon ion pairing or coordination to HF, the two B−
FB bonds of the [BF4]− anions are elongated ((1) 1.470 [1.462]
Å; (2) 1.464 [1.462] and 1.466 [1.457] Å) relative to the
terminal B−F bonds ((1) 1.357 [1.353] Å; (2) 1.356 [1.352]
and 1.365 [1.356] Å). The F(11)−Xe(1)−F(12) angles are
comparable in (2) (166.6 [164.2]o) and (1) (161.8 [161.7]o),
but are smaller than those of the isolated [C6F5XeF2]+ cation
(178.3 [177.8]o) showing the sensitivity of this angle to
coordination. This sensitivity is also apparent in the crystal
structures of the [C6F5XeF2]+ salts (see X-ray Crystal
Structures) and the N-base adducts of C6F5IF2.41 The
calculated F(11)−Xe(1)−F(12) angles are slightly under-
estimated when compared with the experimental angles. The
calculations show that the F−Xe−Ci−C2,6 dihedral angle is also
sensitive to coordination. In the calculated and experimental
structures of (2), the F−Xe−Cipso−C2,6 dihedral angles deviate
from 90° (calcd, 79.6 [65.5]o; exptl, 68.3(3)o). The calculated
dihedral angle of (1) (90.0 [90.0]o) is significantly larger than
in the experimental structure (67.5(2)o), where the dihedral
angle is most likely affected by dimer formation between
adjacent [C6F5XeF2]+ cations (Figure 3). It is also noteworthy
that the relative orientations of the cation and the anion in the
calculated [C6F5XeF2][BF4] ion pair are such that avoidance of
the xenon valence electron lone pairs is maximized; that is, the
C(1), Xe(1), F(11), F(12)- and the F(13), B(1), F(14)-planes
are coplanar (Figure 8a). The observed trends among the
angles subtended at xenon are well-reproduced; in particular,
F(13)---Xe(1)---F(14) in (1) (54.1 [54.6]o) is less than
F(17)---Xe(1)---F(18) in (2) (69.7 [70.4]o).
higher positive Xe(IV) charge compared to that of I(III) (see
Natural Bond Orbital Analyses). Although the calculated F−I−
F angle (172.2 [171.3]o) compares well with the experimental
value (171.59(9)o), the calculated F−Xe−F angle (178.3
[177.8]o) is significantly more open than in the crystal
structures of [C6F5XeF2][BF4] (170.22(7)o), [C6F5XeF2]-
[BF4]·2HF (168.7(1)o), and [C6F5XeF2]+·2NCCH3
(165.5(2)−170.5(1)o). Compressions of the F−Xe−F angles
in the crystal structures likely occur to accommodate base
([BF4]−, CH3CN, and [BF4]−·2HF) coordination to xenon and
to provide better access to the σ Xe−F* antibonding orbitals
(see Natural Bond Orbital (NBO) Analyses). The calculated
F−Xe−Cipso−C2,6 and F−I−Cipso−C2,6 dihedral angles vary
depending on the level of the calculation and on the basis set
used. Although the [C6F5XeF2]+ cation could be optimized
using C2v symmetry with the XeF2 group orientated
perpendicular to the C6F5 group, C6F5IF2 gave an energy-
minimized geometry having C2 symmetry and a F−I−Cipso−C2,6
dihedral angle of 92.8 [103.9]o (Table 6). Similar behavior was
observed at the LANL2DZ/RHF level.42 It is difficult to
account for some differences between calculated and observed
geometrical parameters. Although all crystal structures reveal
several interionic/intermolecular contacts to xenon (see X-ray
Crystal Structures) or iodine,42 their numbers and strengths
vary, likely influencing the local geometries at xenon and iodine.
(iii) [C6F5XeF2]+·CH3CN (3a) and [C6F5XeF2]+·2CH3CN (3b).
The calculated Xe−C bond lengths remain essentially
unchanged upon coordination of one CH3CN molecule, but
elongate slightly for two coordinated CH3CN molecules (calcd:
[C6F5XeF2]+, 2.090 [2.056] Å; (3a), 2.088 [2.058] Å; (3b),
2.106 [2.073] Å; exptl: (3a), 2.067(4) Å; (3b), 2.066(5) and
2.083(5) Å). The calculated Xe−F bond lengths elongate
slightly upon coordination to one or two CH3CN molecules
([C6F5XeF2]+, 1.963 [1.938] Å; (3a), 1.975 [1.949] Å; (3b),
1.978 [1.953] Å), reproducing the observed behavior ((3a),
1.930(2) and 1.939(2) Å; (3b), 1.940(2) and 1.940(2) Å). The
calculated Xe---N contact distances also increase with the
number of CH3CN molecules ((3a), 2.691 [2.673] Å; (3b),
2.795 [2.764] Å), in agreement with the experimental trends
((3a), 2.742(4) Å; (3b), 2.816(4) and 2.868(4) Å). The
calculated Xe−C and Xe−F bond lengths of [C6F5XeF2]+·
2CH3CN are slightly overestimated when compared with the
experimental values of [C6F5XeF2][BF4]·2CH3CN, whereas the
calculated Xe---N contact distances are slightly underestimated.
The F−Xe−F angles decrease as the xenon coordination
number increases, with calculated F−Xe−F values for one
CH3CN (177.1 [176.4]o) and two CH3CN molecules (164.5
[165.1]o) that are close to those in the crystal structures ((3a),
170.5(1)o; (3b), 165.5(2), 167.3(1)o). The calculated F−Xe−
Cipso−C2,6 dihedral angles vary only slightly with the number of
coordinated CH3CN molecules (90.2 [90.0]o for one CH3CN
molecule; 88.6 [82.3]o for two CH3CN molecules). The
calculated N---Xe---N and C−Xe---N angles in [C6F5XeF2]+·
2CH3CN are 66.4 [66.7]o and 146.8 [146.7]o, respectively, in
good agreement with experiment (63.6(1) and 64.6(1)o;
148.20(8) and 147.71(8)o, respectively). The Xe---N−C angles
are close to linear in [C6F5XeF2]+·CH3CN (179.8 [180.0]o),
but are significantly bent in [C6F5XeF2]+·2CH3CN (169.1
[169.9]o and 169.0 [169.9]o). The differences between
calculated and experimental values ((3a), 161.1(4)o; (3b),
153.1(4), 142.7(3)o) most likely result from crystal packing.
(b) Natural Bond Orbital (NBO) Analyses; Charges,
Valencies, and Bond Orders. The NBO63 analyses of
(ii) [C6F5XeF2]+ and C6F5IF2. The calculated Xe−C and I−C
bond lengths are essentially equal (Xe, 2.090 [2.056] Å; I, 2.090
[2.067] Å), in agreement with the observed average bond
lengths (Xe, 2.058(2)−2.058(3) Å; I, 2.068(3), 2.068(4) Å).
Although both the Xe−F and I−F bond lengths are slightly
overestimated, the experimental trend, Xe−F < I−F, is
reproduced (calcd: Xe, 1.963 [1.938] Å and I, 2.009 [1.986]
Å; exptl: Xe, 1.925(2)−1.948(2) Å and I, 1.950(3)−2.032(2)
Å). The calculations also reproduce the experimental F−Xe−F
angles ((1): 170.22(7); (2): 168.7(1); (3a): 170.5(1); (3b):
165.5(2) and 167.3(1)°) and F−I−F angles (170.46(10) and
171.59(9)o), which are bent toward the C6F5 groups. The
calculated F−I−F angle (172.2 [171.3]o) is less than the
calculated F−Xe−F angle (178.3 [177.8]o. The larger calculated
F−Xe−F angle is consistent with the more contracted xenon
lone pair domains in [C6F5XeF2]+, which are attributable to the
O
dx.doi.org/10.1021/ic501831j | Inorg. Chem. XXXX, XXX, XXX−XXX

Inorganic Chemistry
Article
Figure 9. Energies and molecular orbitals of [C6F5XeF2]+ ranging from LUMO +1 to HOMO −7 and selected orbitals having >5% Xe−C/F or Xe
lone pair character (B3LYP/aug-cc-pVTZ).
[C6F5XeF2]+, [C6F5XeF2]+·CH3CN, [C6F5XeF2]+·2CH3CN,
C6F5IF2, and the ion pairs, [C6F5XeF2][BF4] and [C6F5XeF2]-
[BF4]·2HF, were carried out for the optimized gas-phase
structures and are compared with those of [XeF3]+, IF3
[C6F5Xe]+, [C6F5Xe]+·CH3CN, C6F5I, [XeF]+, C6F6, HF, and
CH3CN at the B3LYP and PBE1PBE/aug-cc-pVTZ(-PP) levels
of theory (Supporting Information, Tables S13 and S14). Only
the B3LYP values are referred to in the ensuing discussion.
The positive charges on Xe/I decrease with decreasing
formal oxidation state within their respective C6F5- and fluoro-
analogue series (Supporting Information, Table S13), that is,
[XeF3]+ (2.311) and IF3 (1.776); [C6F5XeF2]+ (1.934) and
C6F5IF2 (1.490); [XeF]+ (1.338) and IF (0.531); [C6F5Xe]+
(0.885) and C6F5I (0.249). The ipso-carbon atoms of the
Xe(IV) (−0.183 to −0.335), Xe(II) (−0.215 and −0.251),
I(III) (−0.269), and I(I) (−0.234) derivatives bear substantial
negative charges. The ipso-carbon charges of [C6F5Xe]+ and
[C6F5XeF2]+ are less negative than those of their less
electrophilic neutral isoelectronic I(I) and I(III) analogues.
The negatively charged ipso-carbons are indicative of ring
charge migration in both the xenon and iodine derivatives. The
charges on C2,6, C3,5, and C4 are positive for Xe(IV) (0.421−
0.283), Xe(II) (0.312−0.352), I(III) (0.288−0.326), and I(I)
(0.287−0.305), reflecting the greater inductive effects of xenon
on the C6F5-ring. Overall, the charges on the carbon atoms of
[C6F5XeF2]+, C6F5IF2, [C6F5Xe]+, and C6F5I alternate as
follows; Cipso < C3,5 < C2,6 < C4. These charge distributions
are significantly influenced by the C6F5 group, which favors
higher positive charges on the C2,6 and C4 atoms. The
[C6F5XeF2]+ and [C6F5Xe]+ cations show nearly identical
charges on the C3,5 atoms (0.317 and 0.319), but the C2,6
(0.345 and 0.322) and C4 (0.377 and 0.352) atoms are more
positively charged in [C6F5XeF2]+ than in [C6F5Xe]+. Similarly,
the C3,5 atoms in C6F5IF2 and C6F5I show charges of 0.288 and
0.287, but the C2,6 (0.292 and 0.318) and C4 (0.305 and 0.326)
atoms are more positively charged in C6F5IF2 than in C6F5I.
The Cipso atom is more negatively charged in [C6F5XeF2]+
(−0.255) than in [C6F5Xe]+ (−0.215), and this trend also
applies to C6F5IF2 (−0.269) and C6F5I (−0.234). The total
C6F5 group charges are positive for [C6F5XeF2]+ (0.171),
[C6F5Xe]+ (0.122), [C6F5XeF2]+·CH3CN (0.083), and
[C6F5XeF2]+·2CH3CN (0.045), whereas the C6F5 group
charges of [C6F5XeF2][BF4] (−0.056), [C6F5XeF2][BF4]·2HF
(−0.009), [C6F5Xe]+·CH3CN (−0.001), C6F5IF2 (−0.183),
and C6F5I (−0.249) are negative or close to zero. The C6F5
group charges of the xenon derivatives are not only influenced
by the oxidation state of xenon but also significantly reduced by
electron-pair donors coordinated to xenon. The negative C6F5
group charges of the neutral iodine analogues also reflect the
formal oxidation state of the iodine atom.
The XeIV−C (0.633−0.740) and IIII−C (0.706) Mayer bond
orders are approximately twice those of the more ionic Xe−F
(0.360) and I−F (0.345) bonds of the XeF2/IF2 groups. The
XeII−C bond orders of [C6F5Xe]+ (0.714) and [C6F5Xe]+·
CH3CN (0.676) and the II−C bond order of C6F5I (0.746) also
display the same trend, I(I) > Xe(II) and I(III) > Xe(IV),
reflecting the greater ionic characters of the Xe−C bonds for
both pairs of isoelectronic species. The Xe−C bond order of
[C6F5XeF2]+ (0.740) is only slightly higher than that of
[C6F5Xe]+ (0.714). As expected, the Xe−C bond order
P
dx.doi.org/10.1021/ic501831j | Inorg. Chem. XXXX, XXX, XXX−XXX

Inorganic Chemistry
Article
decreases slightly upon complexation ([C6F5XeF2]+ 0.740;
[C6F5XeF2]+·2CH3CN 0.690; [C6F5XeF2]+·CH3CN 0.667;
[C6F5XeF2][BF4] 0.633; [C6F5XeF2][BF4]·2HF 0.657). The
small Xe---N bond orders of [C6F5XeF2]+·CH3CN (0.101),
[C6F5XeF2]+·2CH3CN (0.078), and [C6F5Xe]+·CH3CN
(0.085) are in accordance with the small calculated ν(CN)
complexation shifts (Supporting Information, Table S7). The
xenon valency is very similar for [C6F5XeF2]+ (1.472) and
[C6F5XeF2]+·CH3CN (1.467) but is significantly greater for
[C6F5XeF2]+·2CH3CN (1.560). The added valency contribu-
tion to xenon resulting from CH3CN coordination is
compensated for by decreases in the respective Cipso atom
valency and FXe atom valencies of [C6F5XeF2]+·CH3CN (2.640
and 0.322) and [C6F5XeF2]+·2CH3CN (2.818 and 0.314)
compared to those of [C6F5XeF2]+ (2.914 and 0.338).
contributes 8, 29, 8, 14, 7, and 17% to HOMO −5, −18, −21,
−24, −28, and −32, respectively (Figure 9). The bonding and
lone pair NBOs of C6F5IF2 are very similar in character to those
of [C6F5XeF2]+, but their MO mixings are significantly different
as a consequence of the different orbital energies.
The LUMO and LUMO +1 of the [C6F5XeF2]+ cation
represent its electrophilic behavior and are mainly σ Xe−C*
(−0.334 au) and σ Xe−F* (−0.329 au) in character,
respectively (Figure 9). The HOMO (−0.457 au) and
HOMO −1 (−0.474 au) are nearly degenerate and mainly
consist of π orbitals centered on the carbon and fluorine atoms
of the C6F5 group. The frontier orbitals of C6F5IF2 are similar
to those of [C6F5XeF2]+ but are higher in energy and include a
HOMO −1 comprised of I and F lone-pair density (Supporting
Information, Figure S9). In comparison, the [XeF3]+ cation
contains HOMO and LUMO orbitals with energies (−0.625
and −0.464 au, respectively) that are substantially lower than
those of the [C6F5XeF2]+ cation. Higher orbital energies of
[C6F5XeF2]+ are anticipated because of the lower electron-
withdrawing strength of the C6F5 group relative to that of
fluorine. The HOMO/LUMO energy gap of [C6F5XeF2]+
(0.123 au) is less than those of [XeF3]+ (0.161 au) and its
isoelectronic iodine analogue, C6F5IF2 (0.197 au).
The CH3CN molecules coordinated to [C6F5Xe]+ and
[C6F5XeF2]+ show significant nitrogen and carbon atom charge
polarizations for their CN groups relative to those of free
CH3CN, with nitrogen becoming more negative and carbon
becoming more positive by about the same amounts upon
coordination. The CH3 group charges are little affected by
coordination. The positive charges born by Xe(II) and Xe(IV)
in the [C6F5Xe]+ and [C6F5XeF2]+ adducts slightly increase
upon coordination, and their corresponding C6F5 ring charges
become more negative. The mutual polarizations of the xenon
cations and their coordinated base molecules (HF and
CH3CN) and anions ([BF4]− and [BF4]−·2HF) are reflected
in their respective cation and CH3CN ligand or [BF4]−/[BF4]−·
2HF anion charges: [C6F5Xe]+·CH3CN (0.934, 0.064),
[C6F5XeF2]+·CH3CN (0.939, 0.064), [C6F5XeF2]+·2CH3CN
(0.913, 0.090), [C6F5XeF2][BF4]·2HF (0.899, −0.899), and
[C6F5XeF2][BF4] (0.822, −0.829) and correspond to negative
charge transfers from the base to the [C6F5XeF2]+ cation of
−0.064, −0.064, −0.090, −0.101, and −0.171, respectively. The
Xe---N and Xe---F donor−acceptor interactions display small
Xe---N bond orders for the CH3CN complexes with
[C6F5XeF2]+ (0.078−0.101) and [C6F5Xe]+ (0.085) and similar
Xe---F bridge bond orders for the [C6F5XeF2]+ ion pairs with
[BF4]− (0.084) and [BF4]−·2HF (0.069, 0.061).
The crystal structure of [C6F5XeF2][BF4]·1.5CH3CN shows
two coordination behaviors for [C6F5XeF2]+, the nearly linear
C−Xe−N arrangement in [C6F5XeF2]+·CH3CN and a distorted
pentagonal planar arrangement of Cipso, 2F, and 2N atoms
around Xe in [C6F5XeF2]+·2CH3CN. Neglecting Xe---F
interactions involving the [BF4]− anions, the Xe−N donor−
acceptor interactions of the gas-phase [C6F5XeF2]+·CH3CN
and [C6F5XeF2]+·2CH3CN cations were investigated. The
nitrogen lone pair of the adduct cation, [C6F5XeF2]+·CH3CN,
overlaps with the σ Xe−C* orbital to provide a stabilization of
32.1 kJ mol−1, but does not interact with the orthogonal σ Xe−
F* orbitals (Figure 10a). The nitrogen atom lone pairs of
(c) Bonding. The bonding of the T-shaped CXF2 group (X =
Xe(IV), I(III)) in [C6F5XeF2]+ and C6F5IF2 can be described in
terms of a 3c−4e bond for the nearly linear trans-axial F−X−F
group and a 2c−2e bond for the equatorial C−X bond. The
3c−4e bond can be viewed as a linear combination of a filled
pure Xe/I 5p orbital that overlaps with two half-filled 2p
orbitals of the axial fluorine ligands. The occupied nonbonding
molecular orbital has mainly ligand character, which accounts
for the high electron densities on the fluorine atoms of the
XeF2/IF2 groups. The Xe−F bonding is mixed into five orbitals
corresponding to HOMO −6, −7, −23, −33, and −34 (Figure
9). The bonding is essentially p in character for Xe (ca. 97% p)
and F (6% s and 93% p). The charges on the axial fluorine
ligands bonded to Xe(IV) in [C6F5XeF2]+ and its various base
complexes fall into a narrow range (−0.554 to −0.573) and are
less negative than those of C6F5IF2 (−0.653).
The Xe−C σ bond results from the interaction of a Xe p-
orbital (13% s, 86% p) and a C p-orbital (20% s, 77% p), with a
slightly higher polarization coefficient for Xe that corresponds
to its higher electronegativity relative to that of carbon. The σ
I−C bond of C6F5IF2 has very similar hybridizations for I (12%
s, 87% p) and C (23% s, 76% p), but the more electronegative
carbon atom has a higher polarization coefficient than iodine.
The Xe−C bonding NBO is distributed over six orbitals and
Figure 10. Selected prenormalized NBOs for (a) the [C6F5XeF2]+·
CH3CN and (b, c) [C6F5XeF2]+·2CH3CN cations which have
significant N−Xe bonding interactions (B3LYP/aug-cc-pVTZ).
[C6F5XeF2]+·2CH3CN are orientated such that each nitrogen
atom donates density into the σ Xe−C* orbital as well as into
both σ Xe−F1* and σ Xe−F2* orbitals, providing 14.1, 4.4, and
1.1 kJ mol−1 of stabilization (Figure 10b,c; the least stable N:→
Xe−F* NBO is not shown). The natural linear molecular
orbital (NLMO) analysis of these adducts shows 1−2% mixing
of the Xe and C orbitals with the N valence electron lone pairs.
Similar geometries and donor−acceptor behaviors were
observed for [C6F5XeF2][BF4] and [C6F5XeF2][BF4]·2HF
Q
dx.doi.org/10.1021/ic501831j | Inorg. Chem. XXXX, XXX, XXX−XXX

Inorganic Chemistry
Article
glass vessel to minimize water diffusion through the FEP walls and
PTFE stoppers. Samples were shielded from light and were
periodically agitated. Reaction progress was monitored by 19F and
129Xe NMR spectroscopy at −40 or −78 °C. The total fluorine-atom-
weighted integrated 19F intensities of the C6F5 groups and their
derivatives were set equal to 100 mol%. The mole percentages of non-
C6F5 derivatives are reported relative to those of C6F5 compounds.
In the reactivity and long-term stability studies, [C6F5XeF2][BF4]
(100−150 mg; 0.48−0.72 mmol) was dissolved in the desired solvent
(CH3CN or aHF 400−1000 μL) at −40 or −78 °C, respectively. The
solution was then split into two to four equal portions. One portion
was initially checked for impurities and to establish the initial solution
composition by recording its 11B, 19F, and 129Xe NMR spectra at −40
°C.
and in the crystal structures of C6F5IF2 with adducted nitrogen
bases.41
Two lone-pair NBOs are present on the Xe atom of
[C6F5XeF2]+, where one lone pair NBO is ca. 87% s and 13% p
character, and the other is >99% p character. The lone pair of
greater p-character is approximately perpendicular to the Xe−C
and Xe−F bonds and is a contributor to HOMO −2 (55%) and
HOMO −15 (36%) along with the lone pairs of the axial
fluorine atoms. The lone pair having mainly s character is
oriented at ca. 180° with respect to the Xe−C bond and mixes
with six orbitals. This lone pair contributes 6, 6, 7, 19, 32, and
11% to HOMO −5, −18, −29, −31, −32, and −34,
respectively.
Caution! Anhydrous HF must be handled using appropriate protective
gear with immediate access to proper treatment procedures75−77 in the
event of contact with liquid HF, HF vapor, or HF-containing solutions. The
pure, light yellow solid, [C6F5XeF2][BF4], is shock sensitive. Explosions of
the solid have occurred at −78 °C without leaving a residue when samples
were impacted by an FEP rod (ca. 3 g) dropped from a height of ca. 6 cm
or by rapid pressurization of the evacuated reaction tube with dry argon
gas to ca. 1 atm. Solvent-free [C6F5XeF2][BF4] decomposes explosively
when mechanically shocked at temperatures as low as −140 °C. Although
samples of [C6F5XeF2][BF4] containing unreacted XeF4 did not decompose
explosively at −40 °C, even when the solid was pulverized by striking the
outside of the FEP storage vessel with a wooden dowel, extreme care must
nevertheless be taken when handling [C6F5XeF2][BF4] and mixtures
containing this compound.
EXPERIMENTAL SECTION
■
General. (a) Apparatus. Manipulations involving air-sensitive
materials were carried out under anhydrous conditions on glass and
metal high-vacuum lines as previously described.64 Solid, low-volatility,
and moisture-sensitive materials were handled inside a drybox
(Vacuum Atmospheres Model DLX, nitrogen atmosphere or Braun
equipped with a MB 100G gas purification unit, argon atmosphere).
Reaction vessels were constructed from 23-, 8.0-, and 3.5-mm i.d.
tetrafluoroethylenehexafluoropropylene block copolymer (FEP) tub-
ing and were dried under dynamic vacuum for several hours prior to
use. Vessels used for low-temperature crystallization were constructed
1
from /4-in. o.d. (1/16-in. wall thickness) lengths of FEP tubing. The
tubing was heat-sealed at one end, heat flared at the other end, and
connected through a 45° SAE flare nut to the conical end of a
chlorotrifluoroethylene polymer (Kel-F) valve to form a compression
seal. Prior to use, the vacuum-dried reaction vessels were passivated for
at least 8 h with 1 atm of F2 gas. Vacuum line connections were made
Synthesis of [C6F5XeF2][BF4]. In a typical synthesis, XeF4 (0.2132
g; 1.03 mmol) was suspended in cold (−78 °C) CH2Cl2 (20 mL) in a
23-mm i.d. FEP reaction vessel. A freshly prepared, cold (−78 °C)
C6F5BF2 solution (1950 μL; 1.03 mmol) was added to a vigorously
stirred XeF4 suspension at −78 °C and stirred for a further 15 min.
The temperature was then raised to −55 °C, whereupon a voluminous
yellow solid precipitated. After 1 h of additional stirring at −55 °C, the
suspension was centrifuged at −78 °C, and the CH2Cl2 supernatant
was removed under dry argon through a cannula as previously
described.40 The pale yellow solid was dried under dynamic vacuum
(ca. 10−3 to 10−4 mbar) at temperatures below −55 °C, yielding pale
yellow microcrystalline [C6F5XeF2][BF4]. The salt, [C6F5XeF2][BF4],
is very soluble in CH3CN (−40 °C) or aHF (−78 °C). Such solutions
contained ca. 6 mol% of by-products (mostly C6F6), which were
present immediately after dissolution.
1
using /4-in. 316 stainless steel Swagelok Ultratorr unions fitted with
Viton O-rings.
(b) Materials. Acetonitrile65 (Caledon, HPLC grade), CH2Cl2
40
(Caledon, reagent grade), and SO2ClF66 (Allied Chemical, Baker and
Adams Division) were purified by the literature methods and stored
over 3 Å molecular sieves. 1,1,1,3,3-Pentafluorobutane (Solvay,
>99.5%) was refluxed over P4O10 and stored over 3 Å molecular
sieves. Anhydrous HF (Harshaw Chemicals Co.) was purified in a
nickel vessel by exposure to F2 gas at room temperature as previously
described.67 Anhydrous HF was then vacuum-distilled into a dry Kel-F
storage vessel equipped with a Kel-F valve and stored at room
temperature until used. Anhydrous HF was dispensed by vacuum
distillation into FEP reaction vessels or NMR sample tubes.
Alternatively, aHF was purified in an electrochemical cell equipped
with Ni anodes using a voltage of 4.5−5.5 V and a current density of
0.20−0.35 A dm−3 for 50 to 130 h before being transferred to a high-
density polyethylene, FEP, or poly(tetrafluoroethylene) (PTFE)
storage vessel and stored inside a freezer at −18 °C.68 Portions of
aHF were transferred from the storage vessel to reaction vessels
through PTFE cannulas using a low pressure of dry argon.40 The
reagents C6F5Br (Institute of Organic Chemistry, Novosibirsk, 99%)
and C6F5I (Bristol Organics Ltd.) were dried over 3 Å molecular sieves
(Bayer AG, 3 Å). Xenon tetrafluoride was prepared according to the
literature method.69 Small amounts of XeF6 contaminant were flash
distilled from the bulk sample at room temperature. The purity of
XeF4 was assessed by low-temperature Raman spectroscopy, which
showed that XeF2 and XeF6 were absent. The compounds C6F5IF2,42
P(C6F5)3,70,71 As(C6F5)3,71 Bi(C6F5)3,72,73 K[C6F5BF3],74 and
19F NMR (282.40 MHz, aHF, −80 °C): −33.1 (s with 129Xe-
satellites: 1J(19F−129Xe) = 3891 Hz, RXeF2, 2F), −123.6 (mult, o-C6F5,
2F), −129.3 (tt, 3J(19F−19F) = 18 Hz, 4J(19F−19F) = 9 Hz, p-C6F5, 1F),
−148.3 (quar., 1J(11B−19F) = 12 Hz, 4F), −150.4 ppm (mult., m-C6F5,
2F). 11B NMR (96.29 MHz): −1.3 ppm (quin, 1J(11B−19F) = 11 Hz).
1
129Xe NMR (83.02 MHz): −1765.9 ppm (t, J(19F−129Xe) = 3894
Hz).
19F NMR (282.40 MHz, CH3CN, −40 °C): −27.7 ppm (s with
129Xe-satellites: J(19F−129Xe) = 3910 Hz, 2F), −124.1 ppm (mult, o-
1
C6F5, 2F), −133.9 ppm (t, J(19F−19F) = 20 Hz, p-C6F5, 1F), −147.1
3
ppm (s, Δν / = 4 Hz, 11BF4, 4F), −154.3 ppm (mult, m-C6F5, 2F). 11
B
1
2
NMR (96.29 MHz): −0.6 ppm (quin, J(11B−19F) = 11 Hz). 129Xe
1
NMR (83.02 MHz): −1701.3 ppm (t, J(129Xe−19F) = 3881 Hz).
1
Stabilities of [C6F5XeF2][BF4] in aHF or CH3CN Solutions.
Long-term stability studies were carried out on solutions of
[C6F5XeF2][BF4] (0.10−0.35 mmol) in aHF or CH3CN (400−600
μL) contained in a 3.5-mm i.d. FEP reaction vessels that also served as
NMR sample tubes when inserted into 5-mm o.d. Pyrex glass NMR
tubes. The initial solution compositions were established by 11B, 19F,
and 129Xe NMR spectroscopy at −78 °C (aHF) or −40 °C (CH3CN).
The solution was subsequently allowed to warm to the desired
temperature (−40, −30 °C, or room temperature). The samples were
monitored by 19F NMR spectroscopy at −78 or −40 °C. For low-
temperature studies, the samples contained in a glass trap filled with
dry argon gas, were placed in a cryostat set to the desired temperature.
74
C6F5BF2 were prepared as previously described.
The salt, [C6F5XeF2][BF4] (vide infra), was transferred as a solid in
a drybox equipped with a cryowell at ca. −140 °C using a precooled
solid syringe, or under argon as a suspension in CH2Cl2, or as
solutions in CH3CN or aHF (−40 to −78 °C) through 1.5-mm o.d.
PTFE cannulas as previously described.40 The solid syringe consisted
of a length of 2.0-mm o.d. FEP tubing and a 1.5 mm o.d. nickel rod,
which served as the piston. Samples for long-term studies were stored
in PTFE-stoppered FEP tubes inside a rigorously dried, argon-flushed
R
dx.doi.org/10.1021/ic501831j | Inorg. Chem. XXXX, XXX, XXX−XXX

Inorganic Chemistry
Article
Reactions of [C6F5XeF2][BF4] with the Pnictogen(III) Com-
pounds, Pn(C6F5)3 (Pn = P, As, and Bi) in CH3CN. In a 3.5-mm i.d.
FEP reaction vessel, Pn(C6F5)3 (Bi, 95.89 mg, 0.142 mmol; As, 143.46
mg, 0.251 mmol; P, 133.49 mg, 0.25 mmol), was dissolved or, in the
cases of the arsenic and phosphorus compounds, suspended in
CH3CN (1000 μL) and then cooled to −78 °C. Quantities of cold
(−40 °C) CH3CN solutions of [C6F5XeF2][BF4] (ca. 50 mg, 0.25
mmol) were added to the CH3CN solutions/suspensions of
Pn(C6F5)3 and allowed to warm to −40 °C. Yellow suspensions of
P(C6F5)3 and As(C6F5)3 turned white after 40 min at −40 °C. The
progress of each reaction was monitored by 19F NMR spectroscopy at
−40 °C. The resulting white suspensions were dissolved at room
temperature and analyzed by 19F NMR spectroscopy (24 °C) to
determine the reaction product distributions.
annular space, or internally as dry solvents in precision glass NMR
tubes. Ambient (24 °C) and low-temperature NMR spectra were
recorded in the deuterium-locked mode on a Bruker Avance 300
spectrometer equipped with a 7.0463 T cryomagnet. For low-
temperature work, the NMR probe was cooled using a nitrogen flow
and a variable-temperature controller (BVT 3000).
The 19F NMR spectra were acquired using a 5-mm combination
1H/19F probe operating at 282.40 MHz. The 11B and 129Xe NMR
spectra were obtained using a 5-mm broad-band inverse probe
operating at 96.29 and 83.02 MHz. Pulse widths, corresponding to
bulk magnetization tip angles of ca. 90°, were 9.3 (11B), 14.6 (19F), and
8.5 (129Xe) μs. Line-broadening parameters used in exponential
multiplication of the free induction decays were set equal to or less
than their respective data-point resolutions or the natural line widths
of the resonances. All line-shape functions were Lorentzian unless
specified otherwise. In some cases, the free induction decays were
multiplied by Gaussian functions for resolution enhancement upon
Fourier transformation. Spectra were recorded using optimal memory
sizes, acquisition times, and relaxation delays (0.5−2 s).
P(C6F5)3F2 (282.40 MHz, CH3CN, −40 °C). 19F NMR: −2.0 ppm (d,
1J(19F−35P) = 681 Hz, 2F), −132.6 ppm (mult, o-C6F5, 6F), −145.3
ppm (t, 3J(19F−19F) = 20 Hz, p-C6F5, 3F), −158.1 ppm (mult, m-C6F5,
6F)
As(C6F5)3F2 (282.40 MHz, CH3CN, −40 °C). 19F NMR: −23.6 ppm
(mult, 2F), −132.6 ppm (mult, o-C6F5, 6F), −145.3 ppm (t,
3J(19F−19F) = 20 Hz, p-C6F5, 3F), −158.1 ppm (mult, m-C6F5, 6F)
Bi(C6F5)3F2 (282.40 MHz, CH3CN, −40 °C). 19F NMR: −60.5 ppm
All chemical shifts were referenced with respect to their respective
standards at 24 °C. The 19F NMR spectra were referenced to CCl3F
using either the internal standards C6F6 (−162.9 ppm) or C6H5CF3
(−63.9 ppm) or externally to neat CCl3F. The 129Xe NMR spectra
were referenced externally to liquid XeOF4 or indirectly by use of the
secondary external reference XeF2/CD3CN extrapolated to zero
concentration, yielding an XeF2 chemical shift of −1813.3 ppm
relative to external liquid XeOF4.78 The 11B NMR spectra were
referenced to external BF3·Et2O (neat) or to an external BF3·Et2O/
CD3Cl solution (15% v/v). A positive (negative) sign denotes a
chemical shift to high (low) frequency of the reference compound.
(b) Simulation of NMR Spectra. The 19F and 129Xe NMR spectra of
the [C6F5XeF2]+ cation and of the isoelectronic C6F5IF2 molecule
were simulated using the programs gNMR43 and ISOTOPOMER.44
The programs provided heteronuclear simulations that took into
account the natural abundance of 129Xe (I = 1/2, 26.44%). The
J(19F−131Xe) couplings were assumed to be quadrupole collapsed
131Xe (I = 3/2, 21.23%) due to the asymmetry of the electric field at the
xenon nucleus.
1
(s, Δν / = 49 Hz, BiF2, 2F), −126.3 ppm (mult, o-C6F5, 6F), −142.6
2
ppm (t, 3J(19F−19F) = 21 Hz, p-C6F5, 3F), −154.4 ppm (mult, m-C6F5,
6F)
Reactions of [C6F5XeF2][BF4] with C6F5X (X = Br or I) in
CH3CN and aHF. In a 3.5-mm i.d. FEP reaction vessel, C6F5Br (20
μL, 0.16 mmol) was dissolved in CH3CN (100 μL) and cooled (−40
°C). A cold (−40 °C) CH3CN (800 μL) solution of [C6F5XeF2][BF4]
(ca. 50 mg, 0.25 mmol) was added to the C6F5Br solution at −40 °C.
The reaction mixture was maintained for ca. 18 h at −40 to −54 °C.
No reaction was evident when the 19F NMR spectrum was periodically
monitored at −40 °C.
The salt, [C6F5XeF2][BF4], (ca. 25 mg, 0.12 mmol) was dissolved in
cold (−78 °C) aHF (500 μL) and initially checked by 19F NMR
spectroscopy at −80 °C to establish its purity. Approximately an
equimolar amount of C6F5Br (mp −31 °C; 15 μL, 0.12 mmol) was
added to the aHF solution of [C6F5XeF2][BF4] at −40 °C, and the
mixture was maintained for 2 h at this temperature. Although C6F5Br
is practically insoluble in aHF and frozen at −40 °C, it was detected in
the aHF supernatant. The sample was stored for 4 d under argon
inside a glass tube at −78 °C, but no reaction between [C6F5XeF2]-
[BF4] and C6F5Br ensued. Iodopentafluorobenzene, C6F5I (20 μL;
0.15 mmol), was added to the sample at −40 °C. The compound,
C6F5I, has a melting point of −29 °C and a very low solubility in aHF.
During the course of the reaction, the sample was maintained at −40
°C for 30 min. C6F5IF2 (282.40 MHz, aHF, −80 °C): 19F NMR:
−119.6 ppm (mult, o-C6F5, 2F), −138.3 ppm (tt, 3J(19F−19F) = 19 Hz,
4J(19F−19F) = 8 Hz, p-C6F5, 1F), −154.9 ppm (mult, m-C6F5, 2F),
Raman Spectroscopy. (a) Raman Sample Preparation. The
Raman spectrum of the pale yellow solid, [C6F5XeF2][BF4], was
measured in a precision Pyrex glass NMR tube (Wilmad 507) fused to
1
a /4-in. o.d. length of Pyrex glass tubing that was, in turn, connected
to a J. Young stopcock by means of a 1/4-in. 316 stainless steel
Swagelok Ultratorr union outfitted with Viton O-rings. The assembly
was opened inside the drybox, and the compound was loaded into the
sample tube (ca. −140 °C) by use of a solid syringe (vide supra). To
avoid temperature shock and sample detonation, the bottom portion
of the syringe was precooled to −140 °C immediately prior to
insertion into the bulk sample, filled, and rapidly transferred into the
cold (−140 °C) NMR tube. The J. Young valve assembly was
reconnected to the sample tube and removed cold from the drybox.
The sample was cooled to −196 °C, evacuated, heat sealed, and stored
at −196 °C until its Raman spectrum could be recorded. The Raman
spectrum of bright yellow, solid [C6F5XeF2][BF4]·2HF was measured
directly in the 1/4-in. o.d. FEP reaction tube and Kel-F valve assembly
that was used for its synthesis.
1
−177.4 ppm (s, Δν / = 723 Hz, 2F).
2
Reactivity of [C6F5XeF2][BF4] with [C6F5BF3]−. The salt,
K[C6F5BF3] (100 mg; 0.36 mmol), was suspended in cold (−80
°C) aHF (400 μL) inside a 3.5-mm i.d. FEP reaction tube. A cold
(−40 °C) aHF solution of [C6F5XeF2][BF4] (ca. 50 mg, 0.25 mmol)
was added to the suspension. The reaction mixture was maintained at
−40 °C for 30 min and was monitored by 19F NMR spectroscopy
(−40 °C).
(b) Raman Instrumentation and Spectral Acquisition. The low-
temperature (−150 °C) Raman spectrum was recorded on a Bruker
RFS 100 FT Raman spectrometer using 1064-nm excitation at 350
mW and a resolution of 1 cm−1 as previously described.79 A total of
2000−2400 scans were recorded.
The salt K[C6F5BF3] (25.00 mg; 0.09 mmol) was suspended in
CH3CN (300 μL) inside a 3.5 mm i.d. FEP reaction tube and cooled
to −40 °C. A cold (−40 °C) CH3CN solution of [C6F5XeF2][BF4]
(ca. 50 mg, 0.25 mmol) was added to the K[C6F5BF3] suspension in
CH3CN. The sample was maintained at −40 °C for 140 h and was
monitored by 19F NMR spectroscopy (−40 °C).
NMR Spectroscopy. (a) Instrumentation and Spectral Acqui-
sition Parameters. NMR spectra were measured in 18.5-cm lengths of
4.1-mm o.d. × 3.5-mm i.d. FEP tubing that were sealed at one end,
closed with PTFE plugs at the other end, and placed inside a thin-
walled precision Pyrex glass NMR tubes (Wilmad 537 PPT), which
contained CD2Cl2 or CD3CN as the deuterium-lock substance in the
X-ray Crystallography. Each crystallization commenced from a
suspension of [C6F5XeF2][BF4] in CH2Cl2, which was transferred
under argon at −78 °C by means of an FEP cannula into a dry 1/4-in.
o.d. T-shaped FEP vessel and connected to a Kel-F valve. Following
crystal growth, suitable crystals were selected in a dry nitrogen cold
stream at −110 3 °C and were mounted on a goniometer head in a
nitrogen cold stream (−173 °C) as previously described.79
(a) Crystal Growth. (i) [C6F5XeF2][BF4] (1). On a glass vacuum line,
CH3CN (0.8 mL) was condensed at −196 °C onto a suspension of
S
dx.doi.org/10.1021/ic501831j | Inorg. Chem. XXXX, XXX, XXX−XXX

Inorganic Chemistry
Article
[C6F5XeF2][BF4] (ca. 100 mg, 0.24 mmol) in CH2Cl2 (0.5 mL) to
give a partially soluble yellow suspension at −40 °C. The reaction
vessel was pumped under dynamic vacuum at −55 °C until enough
CH2Cl2 was removed to completely dissolve all of the [C6F5XeF2]-
[BF4] (final volume, ca. 0.8 mL). The reactor was then pumped to
dryness under dynamic vacuum at −40 °C over a period of 18 h to
yield yellow plates. The crystal that was mounted had the dimensions
of 0.27 × 0.14 × 0.08 mm3.
(ii) [C6F5XeF2][BF4]·2HF (2). Methylene chloride was removed from
a suspension of [C6F5XeF2][BF4] (∼0.05 g, ∼0.1 mmol) in CH2Cl2
(0.4 mL) under dynamic vacuum at −55 to −45 °C and redissolved in
aHF (0.16 mL) at −78 °C. The solution was pumped to dryness at
−76 °C over a period of 10 h to yield [C6F5XeF2][BF4]·2HF as bright
yellow, rhombohedral crystals. The crystal that was mounted had the
dimensions of 0.22 × 0.49 × 0.13 mm3.
(iii) [C6F5XeF2][BF4]·1.5NCCH3 (3). On a glass vacuum line, CH3CN
(ca. 1 mL) was condensed at −196 °C onto a suspension of
[C6F5XeF2][BF4] (ca. 100 mg, 0.24 mmol) in CH2Cl2 (0.6 mL) to
give a yellow solution at −60 °C. The reactor was then slowly cooled
to −78 °C over a period of 6 h and placed in a −78 °C bath for 48 h.
During this time period, CH3CN crystallized, and small yellow crystals
of [C6F5XeF2][BF4]·1.5NCCH3 were formed within the crystalline
CH3CN mass. The remaining supernatant was removed through a 1.5
mm o.d. PTFE cannula as previously described.40 Crystals of
[C6F5XeF2][BF4]·1.5NCCH3 were selected from the bulk solid
mixture under a flow of dry, cold nitrogen. The crystal that was
mounted had the dimensions 0.17 × 0.15 × 0.06 mm3.
H atoms of the HF molecules were placed at locations derived from a
difference map, and no restrictions were applied to the H−F bonds. In
both cases, the H atoms were included as riding contributions with
isotropic displacement parameters that were 1.2 times those of the
attached atoms. In all three cases, the maximum electron densities in
the final difference Fourier maps were located near the heavy atoms.
The PLATON program86 could not suggest additional or alternative
symmetries. All calculations were performed using the SHELXTL-plus
package85 for the structure determinations, solution refinements, and
molecular graphics.
Calculations. The optimized geometries and vibrational frequen-
cies of [C6F5XeF2]+, [C6F5XeF2]+·NCCH3, [C6F5XeF2]+·2NCCH3,
[C6F5XeF2][BF4], C6F5IF2, [C6F5Xe]+, [C6F5Xe]+·NCCH3, C6F5I,
C6F6, [XeF3]+, IF3, [XeF]+, IF, [BF4]−, and CH3CN were calculated at
the B3LYP and PBE1PBE levels of theory using aug-cc-pVTZ for H, B,
C, N, and F, and aug-cc-pVTZ-(PP) for the I and Xe basis sets.87
Quantum-chemical calculations were carried out using the program
Gaussian 0988 for geometry optimizations and vibrational frequencies
and intensities. The program GaussView89 was used to visualize the
vibrational displacements that form the basis for the vibrational mode
descriptions given in Tables 4 and 5 and Supporting Information,
Tables S7, S9, and S10. Natural bond orbital analyses were performed
using B3LYP and PBE1PBE densities with the NBO program (version
6.0).63
ASSOCIATED CONTENT
■
S
* Supporting Information
(b) Crystal Mounting and X-ray Data Collection. The mounted
crystal was centered on a SMART APEX II diffractometer, equipped
with an APEX II 4K charge-coupled device (CCD) and a triple-axis
goniometer, controlled by the APEX2 Graphical User Interface (GUI)
software.80 A Bruker Triumph curved crystal monochromator with a
Mo Kα source (λ = 0.710 73 Å) was used. The diffraction data
collections consisted of: (1) ω scans (6204 frames) collected at 0.5°
intervals at fixed χ = 54.7361°, (2) ω scans (9712 frames) and ϕ scans
(1440) all collected at 0.5° intervals at fixed χ = 54.7361°, and (3) ω
scans (3340 frames) collected at 0.5° intervals at fixed χ = 54.7361°.
The crystal-to-detector distances were 4.954 cm for [C6F5XeF2][BF4],
[C6F5XeF2][BF4]·2HF, and [C6F5XeF2][BF4]·1.5CH3CN, and the
data collections were carried out in a 512 × 512 pixel mode using 2 ×
2 pixel binning. All diffraction data were processed by use of the
APEX2 GUI software,80 which applied Lorentz and polarization
corrections to three-dimensionally integrated diffraction spots. For
[C6F5XeF2][BF4]·2HF and [C6F5XeF2][BF4]·1.5CH3CN, the process-
ing of the raw data was straightforward and was completed using
SAINT+,81 which applied Lorentz and polarization corrections to
three-dimensionally integrated diffraction spots. The program
SADABS82 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. For [C6F5XeF2][BF4], a
preliminary solution was obtained (vide infra), but gave rise to a wR2
value that was too high (∼20%). The analysis of 1678 reflections with
CELL_NOW83 revealed the existence of two domains (∼1323/332
reflections), the second domain being rotated with respect to the first
domain by 178.6° about the reciprocal axis, 0.034, 1.000, 0.015. The
raw data were processed using the multicomponent version of
SAINT81 under control of the two-component orientation file
generated by CELL_NOW. The program TWINABS84 was then
used to generate different hkl files; the best Rint was obtained by fitting
the first and largest domain separately as well as composite reflections
that contained at least one contribution from the first domain.
(c) Solution and Refinement of the Structure. The XPREP85
program was used to confirm the unit cell dimensions and the crystal
lattices. The solutions were obtained by direct methods, which located
the positions of the heavy atoms. The final refinement was obtained by
introducing anisotropic thermal parameters and the recommended
weightings for all of the atoms except the hydrogen atoms. In the case
of [C6F5XeF2][BF4]·1.5CH3CN, the H atoms bonded to the carbon
atoms of the CH3CN molecules were placed in calculated positions
(C−H = 0.980 Å), whereas in the case of [C6F5XeF2][BF4]·2HF, the
Complementary discussion of the electrophilic fluorination
properties of [C6F5XeF2][BF4]; the 19F NMR spectrum of the
[BF4]− anion in [C6F5XeF2][BF4] (aHF, −40 °C) (Figure S1);
the 19F and 129Xe NMR spectra of [C6F5XeF2][BF4] (aHF, −80
°C) (Figure S2); the experimental and calculated 19F NMR
spectra of C6F5IF2 (CH2Cl2, 24 °C) (Figure S3); a comparison
of NMR parameters for [C6F5XeF2][BF4], C6F5IF2, and
[C6F5Xe][BF4] (Table S1); discussion of the 19F NMR
spectrum of [BF4]− in [C6F5XeF2][BF4] (−40 °C, aHF);
complete list of experimental geometrical parameters for
[C6F5XeF2][BF4], [C6F5XeF2][BF4]·2HF, and [C6F5XeF2]-
[BF4]·1.5CH3CN (Table S2); the unit cell of [C6F5XeF2][BF4]
showing the crystal packing viewed along the a-axis (Figure
S4); complete Raman spectra of [C6F5XeF2][BF4] (Figure S5)
and [C6F5XeF2][BF4]·2HF (Figure S6); factor-group analyses
for [C6F5XeF2][BF4] (Table S3) and [C6F5XeF2][BF4]·2HF
(Table S4); complete list of calculated geometrical parameters
for [C6F5XeF2][BF4], [C6F5XeF2][BF4]·2HF, [C6F5XeF2]+·
2CH3CN, [C6F5XeF2]+, and C6F5IF2 (Table S5); calculated
geometrical parameters for [C6F5XeF2]+·CH3CN (Table S6);
calculated geometry of [C6F5XeF2]+·CH3CN (Figure S7);
calculated vibrational frequencies for [C6F5XeF2]+·CH3CN,
[C6F5XeF2]+·2CH3CN, and CH3CN (Table S7); calculated
geometrical parameters for [C6F5Xe]+ and C6F5I (Table S8);
calculated geometries of [C6F5Xe]+ and C6F5I (Figure S8);
calculated vibrational frequencies and intensities for [C6F5Xe]+
and C6F5I (Table S9); calculated geometrical parameters and
the vibrational frequencies and intensities for [XeF3]+ and IF3
(Table S10), [XeF]+ and IF (Table S11) and [BF4]− (Table
S12); calculated natural atomic charges, Mayer bond orders,
and Mayer natural atomic orbital valencies for [C6F5XeF2]+,
[C6F5XeF2]+·CH3CN, [C6F5XeF2]+·2CH3CN, [C6F5XeF2]-
[BF4], [C6F5XeF2][BF4]·2HF, C6F5IF2, [C6F5Xe]+,
[C6F5Xe]+·CH3CN, C6F5I, C6F6, [XeF3]+, IF3, [XeF]+, IF,
CH3CN, [BF4]−, and HF (Tables S13 and S14); energies and
molecular orbitals of C6F5IF2 (Figure S9). The X-ray
crystallographic files in CIF format for the structure
determinations of [C6F5XeF2][BF4], [C6F5XeF2][BF4]·2HF,
T
dx.doi.org/10.1021/ic501831j | Inorg. Chem. XXXX, XXX, XXX−XXX

Inorganic Chemistry
Article
̌
(19) Brock, D. S.; Schrobilgen, G. J.; Zemva, B. Noble-Gas
Chemistry. In Comprehensive Inorganic Chemistry II; Reedijk, J.,
Poepplemeier, K., Eds.; Elsevier: Oxford, U.K., 2013; Vol. 1, Chapter
1.25, pp 755−822.
and [C6F5XeF2][BF4]·1.5CH3CN. This material is available
free of charge via the Internet at http://pubs.acs.org.
AUTHOR INFORMATION
■
(20) Brock, D. S.; Mercier, H. P. A.; Schrobilgen, G. J. J. Am. Chem.
Soc. 2013, 135, 5089−5104.
(21) Frohn, H.-J.; Bardin, V. V. Organometallics 2001, 20, 4750−
4762.
Corresponding Authors
*E-mail: schrobil@mcmaster.ca (G.J.S.).
*E-mail: h.j.frohn@gmx.de (H.-J.F.).
(22) Frohn, H.-J.; Bardin, V. V. Organoxenonium Salts: Synthesis by
Xenodeborylation, Reactivities, and NMR Spectroscopic Properties. In
Recent Developments in Carbocation and Onium Ion Chemistry; Laali, K.
K., Ed.; ACS Symposium Series 965; American Chemical Society:
Washington, DC., 2007; pp 428−457.
Present Address
§Department of Inorganic and Structural Chemistry, Heinrich-
Heine-Universitat Dusseldorf, Universitatsstraße 1, 40225
̈
̈
̈
Dusseldorf, Germany.
̈
Author Contributions
(23) Tyrra, W.; Naumann, D. Organoxenon Compounds. In
Inorganic Chemistry Highlights; Meyer, G., Naumann, D., Wesemann,
L., Eds.; Wiley−VCH: Weinheim, Germany, 2002; pp 297−316.
(24) Frohn, H.-J.; Bardin, V. V. J. Chem. Soc., Chem. Commun. 1993,
1072−1074.
⊥These authors contributed equally to the manuscript.
Notes
The authors declare no competing financial interest.
(25) Frohn, H.-J.; Bardin, V. V. Z. Anorg. Allg. Chem. 2003, 629,
2465−2469.
ACKNOWLEDGMENTS
This paper is dedicated to Prof. Dr. Boris Zemva on the
■
̌
(26) Frohn, H.-J.; Adonin, N. Y.; Bardin, V. V. Z. Anorg. Allg. Chem.
2003, 629, 2499−2508.
occasion of his 75th birthday (June 8, 2015). We thank the
Natural Sciences and Engineering Research Council of Canada
for support in the form of a Discovery Grant (G.J.S.), the
Deutsche Forschungsgemeinschaft and the Fonds der Chem-
ischen Industrie for support in the form of research grants (H.-
J.F.), the Ontario Ministry of Training, Colleges, and
Universities for graduate scholarships (J.H.), and SHARCNet
(Shared Hierarchical Academic Research Computing Network;
www.sharcnet.ca) for computational resources.
(27) Frohn, H.-J.; Bardin, V. V. Chem. Commun. 2003, 2352−2353.
(28) Frohn, H.-J.; Bardin, V. V. Eur. J. Inorg. Chem. 2006, 3948−
3953.
(29) Zhdankin, V. V.; Stang, P. J.; Zefirov, N. S. J. Chem. Soc., Chem.
Commun. 1992, 578−579.
(30) Frohn, H.-J.; Theißen, M. Angew. Chem., Int. Ed. 2000, 39,
4591−4593.
(31) Frohn, H.-J.; Theißen, M. J. Fluorine Chem. 2004, 125, 981−988.
(32) Maggiarosa, N.; Naumann, D.; Tyrra, W. Angew. Chem., Int. Ed.
2000, 39, 4588−4591.
REFERENCES
(33) Bock, H.; Hinz-Hubner, D.; Ruschewitz, U.; Naumann, D.
̈
■
Angew. Chem., Int. Ed. 2002, 41, 448−450.
(34) Frohn, H.-J.; Schroer, T.; Henkel, G. Angew. Chem., Int. Ed.
1999, 38, 2554−2556.
(1) Claassen, H. H.; Chernick, C. L.; Malm, J. G. J. Am. Chem. Soc.
1963, 85, 1927−1928.
(2) Schumacher, G. A.; Schrobilgen, G. J. Inorg. Chem. 1984, 23,
2923−2929.
(35) Bilir, V.; Frohn, H.-J. Acta Chim. Slov. 2013, 51, 505−512.
(36) Frohn, H.-J.; Bilir, V.; Westphal, U. Inorg. Chem. 2012, 51,
11251−11258.
(3) Levy, H. A.; Burns, J. H.; Agron, P. A. Science 1963, 139, 1208−
1209.
(37) Bartlett, N.; Sladky, F. O. J. Am. Chem. Soc. 1968, 90, 5316−
5317.
(4) Gillespie, R. J.; Landa, B.; Schrobilgen, G. J. Chem. Commun.
1971, 1543−1542.
̌
(38) Frohn, H.-J.; LeBlond, N.; Lutar, K.; Zemva, B. Angew. Chem.,
(5) Boldrini, P.; Gillespie, R. J.; Ireland, P. R.; Schrobilgen, G. J. Inorg.
Chem. 1974, 13, 1690−1694.
Int. Ed. 2000, 39, 391−393.
(39) Zollinger, H. Diazo Chemistry I; Aromatic and Heteroatomic
Compounds; VCH Verlagsgesellshaft mbH: Weinheim, Germany,
1994.
(6) McKee, D. E.; Zalkin, A.; Bartlett, N. Inorg. Chem. 1973, 12,
1713−1717.
(7) Christe, K. O.; Curtis, E. C.; Dixon, D. A.; Mercier, H. P.;
Sanders, J. C. P.; Schrobilgen, G. J. J. Am. Chem. Soc. 1991, 113, 3351−
3361.
(40) Koppe, K.; Bilir, V.; Frohn, H.-J.; Mercier, H. P. A.; Schrobilgen,
G. J. Inorg. Chem. 2007, 46, 9425−9437.
(41) Frohn, H.-J.; Hirschberg, M. E.; Westphal, U.; Florke, U.; Boese,
̈
(8) Brock, D. S.; Bilir, V.; Mercier, H. P. A.; Schrobilgen, G. J. J. Am.
Chem. Soc. 2007, 129, 3598−3611.
R.; Blaser, D. Z. Anorg. Allg. Chem. 2009, 635, 2249−2257.
̈
(42) Bailly, F.; Barthen, P.; Breuer, W.; Frohn, H.-J.; Giesen, M.;
Helber, J.; Henkel, G.; Priwitzer, A. Z. Anorg. Allg. Chem. 2000, 626,
2249−2257.
(9) Ogden, J. S.; Turner, J. J. Chem. Commun. 1966, 19, 693−694.
(10) Jacob, E.; Opferkuch, R. Angew. Chem., Int. Ed. Engl. 1976, 15,
158−159.
(43) Budzelaar, P. H. M. gNMR, 5.0.5; Adept Scientific plc: Oxford,
U.K., 1999.
(11) Gillespie, R. J.; Schrobilgen, G. J. Chem. Commun. 1977, 595−
597.
(44) Santry, D. P.; Mercier, H. P. A.; Schrobilgen, G. J.
ISOTOPOMER, A Multi-NMR Simulation Program, version 3.02NTF;
Snowbird Software, Inc.: Hamilton, Ontario, Canada, 2000.
(45) Pushkina, L. N.; Stepanov, A. P.; Zhukov, V. S.; Naumov, A. D.
Org. Magn. Reson. 1972, 4, 607−623.
(12) Brock, D. S.; Mercier, H. P. A.; Schrobilgen, G. J. J. Am. Chem.
Soc. 2010, 132, 10935−10943.
(13) Brock, D. S.; Schrobilgen, G. J. J. Am. Chem. Soc. 2011, 133,
6265−6269.
(14) Jacob, E.; Lentz, D.; Seppelt, K.; Simon, A. Z. Anorg. Allg. Chem.
1981, 472, 7−25.
(15) Turowsky, L.; Seppelt, K. Z. Anorg. Allg. Chem. 1992, 609, 153−
156.
(46) Koppe, K.; Frohn, H.-J.; Mercier, H. P. A.; Schrobilgen, G. J.
Inorg. Chem. 2008, 47, 3205−3217.
(47) Brunton, G. Acta. Crystallogr., Sect. B 1969, 25, 2161−2162.
(48) Boldrini, P.; Gillespie, R. J.; Ireland, P. R.; Schrobilgen, G. J.
Inorg. Chem. 1974, 13, 1690−1694.
(16) Syvret, R. G.; Mitchell, K. M.; Sanders, J. C. P.; Schrobilgen, G.
J. Inorg. Chem. 1992, 31, 3381−3385.
(49) Bondi, A. J. Phys. Chem. 1964, 68, 441−451.
(50) Frohn, H.-J.; Jakobs, S.; Henkel, G. Angew. Chem., Int. Ed. Engl.
1989, 28, 1506−1507.
(17) Syvret, R. G.; Schrobilgen, G. J. J. Chem. Soc. Chem. Commun.
1985, 1529−1530.
̌
̌
r, G.; Zemva, B. Angew. Chem., Int. Ed. 2009, 48, 1432−
(18) Tavca
1434.
(51) Steele, D.; Whiffen, D. H. Spectrochim. Acta 1960, 17, 368−375.
U
dx.doi.org/10.1021/ic501831j | Inorg. Chem. XXXX, XXX, XXX−XXX

Inorganic Chemistry
Article
(52) Steele, D.; Whiffen, D. H. Trans. Faraday Soc. 1959, 55, 369−
376.
(53) Long, D. A.; Steele, D. Spectrochim. Acta 1963, 19, 1947−1954.
(54) Long, D. A.; Steele, D. Spectrochim. Acta 1963, 19, 1955−1961.
(55) Hyams, I. J.; Lippincott, E. R. Spectrochim. Acta 1966, 22, 695−
702.
P.; Izmaylov, A. F.; Bloino, J.; Zheng, G.; Sonnenberg, J. L.; Hada, M.;
Ehara, M.; Toyota, K.; Fukuda, R.; Hasegawa, J.; Ishida, M.; Nakajima,
T.; Honda, Y.; Kitao, O.; Nakai, H.; Vreven, T.; Montgomery, J. A., Jr.;
Peralta, J. E.; Ogliaro, F.; Bearpark, M.; Heyd, J. J.; Brothers, E.; Kudin,
K. N.; Staroverov, V. N.; Kobayashi, R.; Normand, J.; Raghavachari, K.;
Rendell, A.; Burant, J. C.; Iyengar, S. S.; Tomasi, J.; Cossi, M.; Rega,
N.; Millam, N. J.; Klene, M.; Knox, J. E.; Cross, J. B.; Bakken, V.;
Adamo, C.; Jaramillo, J.; Gomperts, R.; Stratmann, R. E.; Yazyev, O.;
Austin, A. J.; Cammi, R.; Pomelli, C.; Ochterski, J. W.; Martin, R. L.;
Morokuma, K.; Zakrzewski, V. G.; Voth, G. A.; Salvador, P.;
(56) Bates, J. B.; Quist, A. S. Spectrochim. Acta 1975, 31, 1317−1327.
(57) Carter, R. L. J. Chem. Educ. 1971, 48, 297−303.
(58) Gillespie, R. J.; Landa, B.; Schrobilgen, G. J. Inorg. Chem. 1976,
15, 1256−1263.
̈
Dannenberg, J. J.; Dapprich, S.; Daniels, A. D.; Farkas, O.;
Foresman, J. B.; Ortiz, J. V.; Cioslowski, J.; Fox, D. J. Gaussian 09,
Revision D.01; Gaussian, Inc: Wallingford, CT, 2009.
(59) Claassen, H. H.; Chernick, C. L.; Malm, J. G. J. Am. Chem. Soc.
1963, 85, 1927−1928.
(60) Tsao, P.; Cobb, C. C.; Claassen, H. H. J. Chem. Phys. 1971, 54,
5247−5253.
(89) GaussView, release 3.0; Gaussian, Inc; Pittsburgh, PA, 2003.
(61) Naumann, D.; Rank, E.; Lehmann, E. J. Fluorine Chem. 1977, 10,
395−403.
(62) Schmeisser, M.; Naumann, D.; Lehmann, E. J. Fluorine Chem.
1973, 3, 441−444.
(63) Glendening, E. D.; Badenhoop, J. K.; Reed, A. E.; Carpenter, J.
E.; Bohmann, J. A.; Morales, C. M.; Landis, C. R.; Weinhold, F. NBO
6.0, Theoretical Chemistry Institute; University of Wisconsin: Madison,
WI, 2013.
(64) Casteel, W. J., Jr.; Dixon, D. A.; Mercier, H. P. A.; Schrobilgen,
G. J. Inorg. Chem. 1996, 35, 4310−4322.
(65) Winfield, J. M. J. Fluorine Chem. 1984, 25, 91−98.
(66) Schrobilgen, G. J.; Holloway, J. H.; Granger, P.; Brevard, C.
Inorg. Chem. 1978, 17, 980.
(67) Emara, A. A. A.; Schrobilgen, G. J. Inorg. Chem. 1992, 31, 1323−
1332.
(68) Ignat’ev, N.; Sartori, P. J. Fluorine Chem. 2000, 103, 57−61.
(69) Chernick, C. L.; Malm, J. G. Inorg. Synth. 1966, 8, 254−258.
(70) Wall, L. A.; Donadio, R. E.; Pummer, W. J. J. Am. Chem. Soc.
1960, 82, 4846−4848.
(71) Fild, M.; Glemser, O.; Christoph, G. Angew. Chem. 1964, 76,
953.
(72) Royo, P.; Uson, R. Rev. Acad. Cienc. Zaragoza (2) 1969, 24,
119−122.
(73) Schmuck, A.; Seppelt, K. Chem. Ber. 1989, 122, 803−808.
(74) Frohn, H.-J.; Franke, H.; Fritzen, P.; Bardin, V. V. J. Organomet.
Chem. 2000, 598, 127−135.
(75) Bertolini, J. C. J. Emerg. Med. 1992, 10, 163−168.
(76) Peters, D.; Miethchen, R. J. Fluorine Chem. 1996, 79, 161−165.
(77) Segal, E. B. Chem. Health Saf. 2000, 7, 18−23.
(78) Gerken, M.; Schrobilgen, G. J. Coord. Chem. Rev. 2000, 197,
335−395.
(79) Gerken, M.; Dixon, D. A.; Schrobilgen, G. J. Inorg. Chem. 2000,
39, 4244−4255.
(80) APEX2, release v2011.6−1; Bruker AXS, Inc.: Madison, WI,
1995.
(81) SAINT+, Version 6.02; Siemens Energy and Automation, Inc.:
Madison, WI, 1999.
(82) Sheldrick, G. M. Siemens Area Detector Absorption Corrections
(SADABS), Version 2.03; Bruker AXS, Inc.: Madison, WI, 1999.
(83) Sheldrick, G. M. CELL-NOW, University of Gottingen:
̈
Germany, 2008.
(84) Sheldrick, G. M. TWINABS, University of Gottingen: Germany,
̈
2008.
(85) Sheldrick, G. M. SHELXTL-Plus, release 5.1; Siemens Analytical
X-ray Instruments, Inc.; Madison, WI, 1998.
(86) Spek, A. L. J. Appl. Crystallogr. 2003, 36, 7−13.
(87) Basis sets and pseudopotentials were obtained from the
Extensible Computational Chemistry Environment Basis set Database,
version 2/25/04, as developed and distributed by the Molecular
Science Computing Facility, Environmental and Molecular Science
Laboratory, which is part of the Pacific Northwest Laboratory, P.O.
Box 999, Richland, WA 99352.
(88) Frisch, M. J.; Trucks, G. W.; Schlegel, H. B.; Scuseria, G. E.;
Robb, M. A.; Cheeseman, J. R.; Scalmani, G.; Barone, V.; Mennucci,
B.; Petersson, G. A.; Nakatsuji, H.; Caricato, M.; Li, X.; Hratchian, H.
V
dx.doi.org/10.1021/ic501831j | Inorg. Chem. XXXX, XXX, XXX−XXX