Mixed Noble-Gas Compounds of Krypton(II) and Xenon(VI); [F5Xe(FKrF)AsF6] and [F5Xe(FKrF)2AsF6]

Article abstract of DOI:10.1002/anie.202014682

The coordination chemistry of KrF₂ has been limited in contrast with that of XeF₂, which exhibits a far richer coordination chemistry with main-group and transition-metal cations. In the present work, reactions of [XeF₅][AsF₆] with KrF₂ in anhydrous HF solvent afforded [F₅Xe(FKrF)AsF₆] and [F₅Xe(FKrF)₂AsF₆], the first mixed krypton/xenon compounds. X-ray crystal structures and Raman spectra show the KrF₂ ligands and [AsF₆]^? anions are F-coordinated to the xenon atoms of the [XeF₅]⁺ cations. Quantum-chemical calculations are consistent with essentially noncovalent ligand?xenon bonds that may be described in terms of σ-hole bonding. These complexes significantly extend the XeF₂–KrF₂ analogy and the limited chemistry of krypton by introducing a new class of coordination compound in which KrF₂ functions as a ligand that coordinates to xenon(VI). The HF solvates, [F₅Xe(FH)AsF₆] and [F₅Xe(FH)SbF₆], are also characterized in this study and they provide rare examples of HF coordinated to xenon(VI).

Full text of DOI:10.1002/anie.202014682

A Journal of the Gesellschaft Deutscher Chemiker
Angewandte
International Edition Chemie
www.angewandte.org
Accepted Article
Title: Mixed Noble-gas Compounds of Krypton(II) and Xenon(VI);
[F5Xe(FKrF)AsF6] and [F5Xe(FKrF)2AsF6]
Authors: Matic Lozinšek, Hélène P. A. Mercier, and Gary J.
Schrobilgen
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To be cited as: Angew. Chem. Int. Ed. 10.1002/anie.202014682
Link to VoR: https://doi.org/10.1002/anie.202014682

Angewandte Chemie International Edition
10.1002/anie.202014682
RESEARCH ARTICLE
Mixed Noble-Gas Compounds of Krypton(II) and Xenon(VI);
F Xe(FKrF)AsF ] and [F Xe(FKrF) AsF ]
[
5
6
5
2
6
[
a,b]
[a]
[a]
Matic Lozinšek,*
Hélène P. A. Mercier,* and Gary J. Schrobilgen*
th
Dedicated to Professor Boris Žemva on the occasion of his 80 birthday
[
[
a]
b]
Dr. M. Lozinšek, Dr. H. P. A. Mercier, Prof. G. J. Schrobilgen
Department of Chemistry
McMaster University
Hamilton, ON L8S 4M1 (Canada)
E-mail: matic.lozinsek@ijs.si, mercierhpa@live.com, schrobil@mcmaster.ca
Asst. Prof. M. Lozinšek (present address)
Department of Inorganic Chemistry and Technology
Jožef Stefan Institute
Jamova 39, 1000 Ljubljana (Slovenia)
Supporting information for this article is given via a link at the end of the document.
[
8]
Abstract: The coordination chemistry of KrF
contrast with that of XeF , which exhibits a far richer coordination
chemistry with main-group and transition-metal cations. In the
present work, reactions of [XeF ][AsF ] with KrF in anhydrous HF
solvent afforded [F Xe(FKrF)AsF ] and [F Xe(FKrF) AsF ], the first
mixed krypton/xenon compounds. X-ray crystal structures and
2
has been limited, in
[F
2 2 6
OBr(FKrF) AsF ], a neutral covalent transition-metal Hg(II)
[
9]
2+
2
compound, Hg(OTeF
5
)
2
·1.5KrF
2
,
a transition-metal cation, Hg ,
[
11]
2+
[Hg(KrF
[Mg(FKrF)
weak fluoride-ion acceptor, CrOF
2
)
8
][AsF
6
]
2
,
and a main-group metal cation, Mg ,
[
10]
5
6
2
4
(AsF
6
)
2
].
Most recently, the KrF
2
adducts of the
5
6
5
2
6
4
, have been reported and
[
12]
structurally characterized for KrF
2
·nCrOF
4
(n = 1, 2).
OBr(FXeF) AsF
The
−
[13]
Raman spectra show the KrF
2
ligands and [AsF
6
]
anions are F-
xenon
analogues,
[F
(n
2
2
[12]
6
],
+
[9]
coordinated to the xenon atoms of the [XeF
5
]
cations. Quantum-
Hg(OTeF
5
)
2
·1.5XeF
2
14]
,
XeF
2
·nCrOF
4
=
1, 2),
and
[
chemical calculations are consistent with essentially noncovalent
[Mg(FXeF)
structurally characterized by SCXRD and Raman spectroscopy.
The linear, centrosymmetric (D∞h NgF (Ng Kr, Xe)
molecules distort upon coordination to a fluoride-ion acceptor
(A) to form a Ng−F ---A bridge in which the Ng−F bond is
elongated and the terminal Ng−F bond is contracted relative to
free NgF . The extent to which distortion and polarization of the
NgF ligand occurs, and thus the extent to which the positive
charge on Ng is enhanced, depends on the Lewis acidity of the
4
(AsF
6
)
2
]
have also been synthesized and
ligand-xenon bonds that may be described in terms of σ-hole
bonding. These complexes significantly extend the XeF
analogy and the limited chemistry of krypton by introducing a new
class of coordination compound in which KrF functions as a ligand
that coordinates to xenon(VI). The HF solvates, [F Xe(FH)AsF ] and
Xe(FH)SbF ], are also characterized in this study, and provide
2
-KrF
2
)
2
=
[
15]
2
b
b
5
6
t
[
F
5
6
2
rare examples of HF coordinated to Xe(VI).
2
[
5,6,16]
fluoride-ion acceptor.
Interactions with the strongly Lewis
, result in the formation of
acidic pnictogen pentafluorides, PnF
5
Introduction
[6,15]
+
strongly ion-paired [NgF][PnF
6
]
salts in which the [NgF]
anions interact by means of Ng---F −Pn
bridges. The electrophilicities of [NgF] and coordinated NgF
ligands relative to free NgF are manifested by marked
increases in their oxidative fluorinating abilities. In the case of
−
cations and [PnF
6
]
b
[
1]
Krypton reactivity was discovered soon after the landmark
+
2
[
2]
synthesis of the first true noble-gas compound, Xe[PtF
Although the precise formulation of Xe[PtF ] remains unproven,
it is likely a salt or a mixture of salts of the [XeF] cation.
6
].
2
[5]
6
+
[3,4]
KrF
KrF
2
, the number of suitable Lewis acids that can coordinate to
and withstand its extraordinary oxidative fluorinating
Although the discoveries of xenon and krypton chemical
reactivities occurred nearly 60 years ago and within a year of
one another, their chemistries never became entwined to form a
single compound that contains both chemically bound noble
gases. In contrast with xenon, which exhibits formal oxidation
states in its isolated compounds of 0, +½, +2, +4, +6, and +8,
krypton only exhibits the +2 oxidation state and a far more
limited chemistry. The only binary krypton fluoride that can be
synthesized in macroscopic and synthetically useful amounts is
2
strength is very limited.
Two criteria must therefore be met for the formation of a
mixed xenon/krypton adduct: (1) The fluorobasicity of KrF
closely balance the Lewis acidity of the xenon substrate, i.e., a
Lewis acid that is too weak will be unable to coordinate KrF
2
must
2
,
−
whereas a Lewis acid that is too strong will abstract F to form a
+
more electrophilic and strongly oxidizing [KrF] salt. (2) The
fluoride-ion acceptor must be sufficiently resistant to attack by
[
5-7]
KrF
derived.
Prior studies have explored the ligating properties of KrF
and have provided several KrF adducts that were structurally
2
,
from which all other krypton compounds have been
+
2 5
the potent oxidative fluorinator, KrF . The Lewis acidic [XeF ]
[
5-12]
cation meets the latter criterion by virtue of its net positive
2
charge and the high formal oxidation state of xenon (+6).
+
2
The coordination behavior of the [XeF
is well documented for Xe---F
cations and their counteranions. Examples in which [XeF
coordinated to XeF ligand are known,
5
] cation in its salts
characterized by low-temperature (LT) single-crystal X-ray
diffraction (SCXRD) and Raman spectroscopy. The latter include
+
b
5
interactions between the [XeF ]
[17]
+
5
] is
for
complexes with
a
main-group Br(V) oxyfluoride cation,
a
2
1
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Angewandte Chemie International Edition
10.1002/anie.202014682
RESEARCH ARTICLE
[
[
F
F
5
5
Xe(FXeF)XeF
Xe(FXeF) AsF
5
(AsF
6
)
2
],
[F
5
Xe(FXeF)AsF
6
],
and
Table 1.
Summary of X-ray crystal data and refinement results for
[
18,19]
2
6
],
which were characterized by SCXRD
5
[F Xe(FKrF)AsF ] (1), [F Xe(FKrF) AsF ] (2) [F Xe(FH)AsF ] (3), and
6
5
2
6
5
6
[
20]
and Raman spectroscopy, and [F
5
Xe(FXeF)RuF
6
], which was
5
[F Xe(FH)SbF ] (4)
6
characterized by Raman spectroscopy. In contrast, the cocrystal,
Compound
Space group
a (Å)
1
2
3
4
[
21]
+
[
XeF
and XeOF
XeOF
5
][SbF
6
]·XeOF
4
,
exhibits no interactions between [XeF
5
]
P2 /n
P2 /c
P2/c
P2 /c
1
1
1
4
, in accordance with the low relative fluorobasicity of
9.03170(10)
9.7065(2)
12.1261(2)
106.8920(10)
1017.18(3)
4
9.3142(5)
8.0482(4)
16.1545(8)
95.942(3)
1204.48(11)
4
12.2989(4)
6.4853(2)
10.6717(3)
106.317(2)
816.91(4)
4
6.3279(2)
15.2663(4)
4
.
b (Å)
c (Å)
8.8234(2)
92.6730(10)
851.45(4)
4
o
β ( )
3
Results and Discussion
V (Å )
Z
–
1
Syntheses
M
W
(g mol
)
3
537.02
658.82
435.23
3.539
482.06
3.761
–
D
calcd (g cm
o
)
3.507
3.633
+
5
In the present work, the Lewis acidity of the [XeF ] cation and
T ( C)
–173
–173
–173
–173
the fluorobasic character of KrF
2
have been exploited for the
−1
µ (mm
)
11.101
13.062
8.411
7.319
syntheses of the first mixed noble-gas Kr/Xe compounds that
are isolable in macroscopic quantities. The products obtained
[a]
R
1
0.0288
0.0306
0.0228
0.0452
0.0195
0.0415
[b]
wR
2
0.0561
0.0568
from the LT reactions of [XeF
aHF) solvent and subsequent crystallizations at LT depended
on the initial KrF :[XeF ][AsF molar ratio. The complex,
Xe(FKrF)AsF ] (1), was obtained by use of a 1.5:1 molar ratio
of reactants, whereas a stoichiometric excess of KrF (3.5:1 or
.1:1) resulted in [F Xe(FKrF) AsF ] (2). In an attempt to prepare
the KrF analogue of [F Xe(FXeF)XeF
ratio of reactants was used, which resulted in crystallization of 1
and [F Xe(FH)AsF ] (3). Compound 3 was also isolated from an
aHF solution of [XeF ][AsF ] upon removal of HF at LT. The
synthesis of the antimony analogue [F Xe(FH)SbF ] (4) is
5
][AsF
6
] and KrF
2
in anhydrous HF
2
2
2
2
2
) )]
1/2
[
a] R
1
= Σ||F
o
| – |F
c
||/Σ|F
o
|. [b] wR
2
= [Σ(w(F
o
– F
c
) )/Σ(w(F
o
.
(
2
5
6
]
[
F
5
6
2
(
Figure 1b and Figures S3 and S4 in the Supporting Information).
2
5
2
6
+
[
19]
The coordination spheres of the [XeF
5
] cations in 1 and 2 are
2
5
5 6 2
(AsF ) ], a 1:1.9 molar
[
19]
similar to their known xenon analogues, [F
5
Xe(FXeF)AsF
In the latter cases, the longer Xe---
As secondary bonds (1:1, 2.59, 3.03, and 3.15 Å; 1:2, 2.95 and
.57 Å) are shorter than or equal to the sum of the Xe and F van
6
],
[
19]
5 2 6
and [F Xe(FXeF) AsF ].
5
6
F
5
6
3
5
6
[
23]
[24]
der Waals radii (3.63 , 3.52 Å). Although the crystal structure
of [F Xe(FKrF)AsF is isotypic with its xenon analogue,
Xe(FKrF) AsF ] is not.
The trajectories of the four Xe---F secondary bonds in 1
and 2 avoid the Xe−Feq bond pair and valence electron lone pair
described in the Supporting Information. The syntheses of 1–3
are in accordance with the proposed Equilibria (1–4), which are
supported by LT SCXRD structure determinations of the adduct-
5
6
]
[
F
5
2
6
cation salts, [F
5
Xe(FKrF)AsF
6
] and [F
5 2 6
Xe(FKrF) AsF ], and the
intermediate solvate, [F
5
Xe(FH)AsF
6
], as well as by LT Raman
+
(
VELP) domains of the square-pyramidal [XeF
5
]
cation, where
-axis and is trans to the Fax
] anions of 1 are mer-coordinated to
cations by means of asymmetric
spectroscopy. Vibrational frequency assignments were aided by
calculated frequencies and intensities obtained from DFT
the lone pair lies on the pseudo C
4
+
−
atom of [XeF
5
] . The [AsF
6
calculations (vide infra). It is apparent that HF also behaves as a
+
+
5
three different [XeF ]
weak ligand towards [XeF
5
]
in aHF solution and that KrF
2
, a
[
22]
secondary Xe---FAs bonds, where the cis-Xe---FAs bond is
notably shorter (2.5944(10) Å) than the trans-Xe---FAs bonds
somewhat less fluorobasic ligand than XeF
2
,
is sufficiently
6
] [Eq.(3)].
fluorobasic to displace HF to form [F Xe(FKrF)AsF
5
(
2.9147(10), 3.0572(11) Å). The three Xe---FAs secondary bonds
[
XeF
5
][AsF
6
] + HF ⇌ [F
5
Xe(FH)AsF
6
]
(1)
(2)
result in the layered structure depicted in Figure S1b. The
–
[
[
6
AsF ] anions of 2 are asymmetrically trans-coordinated to two
[
XeF
5
][AsF
6
] + KrF ⇌ [F
2
5
Xe(FKrF)AsF
6
]
+
XeF
5
]
cations (Xe---FAs, 2.812(2), 3.124(2) Å), which form
and/or
chains that run parallel to the b-axis of the unit cell (Figures S3b
+
and S4). The KrF
secondary Xe---F
2.550(2), 2.576(2) Å) than the secondary Xe---FAs bonds of the
2
ligands coordinate to [XeF
5
] by means of
[
F
5
Xe(FH)AsF
6
] + KrF
2
⇌ [F
5
Xe(FKrF)AsF
6
] + HF
(3)
(4)
b
bonds that are shorter ((1) 2.5139(9) Å; (2)
[
F
5
Xe(FKrF)AsF
6
] + KrF
2
⇌ [F
5
Xe(FKrF) AsF ]
2
6
−
coordinated [AsF
6
] anions (Table 2 and Tables S1 and S2 in the
and Kr−F bond asymmetry
X-ray Crystallography
Supporting Information). The Kr−F
t
b
is somewhat more pronounced in 1 (1.8393(12), 1.9367(9) Å)
than in 2 (1.845(2), 1.927(2) Å and 1.851(2), 1.917(2) Å), which
Details of X-ray data collection and crystallographic information
pertaining to [F Xe(FKrF)AsF (1), [F Xe(FKrF) AsF (2),
Xe(FH)AsF ] (3), and [F Xe(FH)SbF
Table 1.
5
6
]
5
2
6
]
is attributed to stronger and shorter Xe---F
in 2. Similar Kr−F and Kr−F bond length asymmetries are
observed in the crystal structures of [FO Br(FKrF) AsF
1.840(5) and 1.847(4) Å, 1.943(4) and 1.933(4) Å),
b
interactions in 1 than
[
F
5
6
5
6
] (4) are summarized in
t
b
2
2
6
]
[
8]
+
(
[
F
5
Xe(FKrF)AsF
cations are coordinated to four
coordination numbers, CNXe = 5 + 4: one secondary bond from a
6 5 2 6 5
] (1) and [F Xe(FKrF) AsF ] (2). The [XeF ]
[
Mg(KrF
2
)
4
(AsF
[Hg(KrF
and KrF
6
)
2
]
(1.817(2)–1.821(2) Å, 1.965(1)–1.979(1)
F
atoms to give xenon
[
10]
2+
Å),
Å),
2
)
8
]
(1.822(1)–1.852(1) Å, 1.933(1)–1.957(1)
[
11]
[12]
−
·CrOF
4
(1.8489(9) and 1.9279(9) Å).
KrF
Xe(FKrF)AsF
Supporting Information),
Xe(FKrF) AsF ] (2), two secondary bonds are from two KrF
ligands and two are from two [AsF
2
ligand and three from three [AsF
] (1) (Figure 1a and Figures S1 and S2 in the
whereas in the case of
6
]
anions in
2
Regardless of their Kr−F bond asymmetries, the average Kr−Ft/b
bond lengths ((1) 1.888(2) Å; (2) 1.886(2) and 1.884(2) Å) are
[
F
5
6
[
15]
comparable to the Kr−F bond length of α-KrF
2
(1.894(5) Å)
[
F
5
2
6
2
[
12]
−
and symmetrically bridged KrF in KrF ·2CrOF4 (1.8881(6) Å).
2
2
6
] anions
2
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Angewandte Chemie International Edition
10.1002/anie.202014682
RESEARCH ARTICLE
The F−Kr−F bond angles are essentially linear ((1) 178.49(6)°;
fluorine atoms are slightly elongated (1.719(2), 1.727(2),
1.749(2) Å) with respect to the two non-interacting axial As−F
bonds (1.701(2), 1.705(2) Å). The secondary Xe---FAs and Xe---
(
2) 178.47(8) and 179.40(7)°), whereas the Kr−F
b
---Xe angles
are bent ((1) 133.24(5)°; (2) 137.40(8) and 141.80(7)°), as
[
8–12]
observed in all other KrF
and are similar to the Kr−F
Br(FKrF) AsF (132.1(2) and 139.9(2)°)
intermediate with respect to the range of Kr−F
2
adducts.
The Kr−F
b
---Xe angles of
H
F bonds result in layers that are parallel to the ac-plane and are
1
2
b
---Br angles of
stacked along the b-axis of the unit cell.
[
8]
[
FO
2
2
6
]
and are
---Mg angles
b
Table 2. Selected experimental bond lengths for [F Xe(FKrF)AsF ] (1) and
5
6
[
10]
[
a]
observed for [Mg(KrF
2
)
4
(AsF
6
)
2
] (121.84(7)–144.43(8)°).
5 2 6
[F Xe(FKrF) AsF ] (2); and calculated bond lengths and Wiberg bond
2
−
−
indices (WBI) for [F
5
Xe(FKrF)(AsF
6
)
3
]
(1') and [F
5
Xe(FKrF)
2
(AsF
6 2
) ] (2')
1
1'
1'
2
2'
2'
a
Bond lengths (Å)
WBI
Bond lengths (Å)
WBI
Xe−Fax
Xe−Feq
1.8067(11)
1.919
0.550
1.8125(15)
1.911
0.566
1.8394(12)
1.910
0.596
0.595
0.601
0.600
1.8371(14)
1.8418(14)
1.8449(14)
1.8482(14)
1.912
1.903
1.909
1.925
0.595
0.607
0.598
0.597
1
1
1
.8404(12)
.8455(13)
.8462(12)
1.910
1.909
1.910
2
2
.550(2)
.576(2)
2.784
2.626
0.037
0.069
Xe---F
b
2.5139(9)
2.500
0.102
2
.5944(10)
2.9147(10)
.0572(11)
2.468
2.802
2.828
0.098
0.031
0.028
2
3
.812(2)
.124(2)
2.480
2.563
0.096
0.068
Xe---FAs
3
1
1
1
1
.845(2)
.851(2)
.917(2)
.927(2)
1.862
1.874
1.909
1.930
0.603
0.576
0.502
0.464
Kr−F
Kr−F
t
1.8393(12)
1.9367(9)
1.860
1.939
0.610
0.450
b
b
[
a] APFD/aVDZ(-PP)(Kr, Xe, As)/aVDZ(F).
The Xe---F
H
secondary bonds of [F
5
Xe(FH)PnF
6
] (As,
2
.656(2) Å; Sb, 2.6501(10) Å) are similar, but are significantly
[
25]
greater than those of [F
3
Xe(FH)Sb
2
F
11] (2.462(2) Å)
and
[
26]
[
FXe(FH)Sb
Lewis acidity of [XeF
brief description of the crystal structure of the
2
F11] (2.359(4) Å),
in accordance with the lower
+
+
+ [10,13,19]
5
3
] relative to [XeF ] and [XeF] .
A
nonisotypic antimony analogue (4) is provided in the Supporting
Information along with associated X-ray data (Figures S7 and S8
Figure 1. The X-ray crystal structure of a) [F
Xe(FKrF) AsF ] (2) where the coordination environments of the Xe atom are
is expanded to include symmetry-generated atoms (symmetry codes: (1) (i)
−x, y−½, ½−z; (ii) 1−x, 1−y, 1−z; (2) (i) x, y+1, z). Thermal ellipsoids are
drawn at the 50% probability level.
5
Xe(FKrF)AsF
6
] (1) and b)
and Table S3). The LT Raman spectrum of [F
was also acquired and is reported in the Supporting Information
Figure S9 and Table S4).
5 6
Xe(FH)AsF ] (3)
[
F
5
2
6
(
½
[
F
5
Xe(FH)AsF
6
] (3). The asymmetric unit in the crystal structure
+
of 3 is comprised of two [XeF
5
]
cations located on special
−
positions, and an [AsF
6
] anion and an HF molecule located on
general positions (Figure 2 and Figures S5 and S6 in the
Supporting Information). The Xe(VI) atoms have CNXe = 5 + 4,
+
where one [XeF
5
]
cation has four Xe---FAs secondary bonds
originating from the coordination of two pairs of symmetry-
−
6
related [AsF ] anions (2.647(2), 3.058(2) Å) whereas the other
+
−
[
5 6
XeF ] cation interacts with two symmetry-related [AsF ] anions
through two secondary Xe---FAs bonds (2.929(2) Å) and with two
symmetry-related HF ligands through two short secondary Xe---
H
F bonds (2.656(2) Å) (Table S3). Each HF molecule is also H-
−
bonded to two neighboring [AsF
6
] anions with F
H
···FAs distances
5 6
Figure 2. The crystal structure of [F Xe(FH)AsF ] (3). The coordination
of 2.545(2) Å, where the As−F bond of the H–bonded F ligand
environment of Xe1 is expanded to include symmetry-generated atoms
(symmetry codes: (i) −x, y, ½−z). Thermal ellipsoids are drawn at the 50%
probability level. The coordination environment of Xe2 is shown in Figure S5a.
−
(
1.746(2) Å) is the longest As−F bond of the [AsF
6
+
] anion. Each
−
[
AsF ] anion also coordinates to three [XeF ] cations in a
6 5
mer-arrangement where the As−F bonds of the interacting
3
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Angewandte Chemie International Edition
10.1002/anie.202014682
RESEARCH ARTICLE
[
10]
Raman Spectroscopy
[Mg(FKrF)
4
(AsF
6
)
2
].
The experimental and calculated
frequencies, their detailed assignments, and mode descriptions
5 6
The LT solid-state Raman spectra of [F Xe(FKrF)AsF ] (1) and
for 1 and 2 are provided in Tables S5 and S6, respectively. The
5 2 6
[F Xe(FKrF) AsF ] (2) are depicted in Figure 3. Vibrational
vibrational frequencies and intensities of the gas-phase KrF
2
assignments for 1 were initially made by comparison with the
molecule were also calculated (Table S7 in the Supporting
Information) in order to estimate the degree to which the
calculated frequencies and assignments of gas-phase
5 6
[F Xe(FKrF)AsF ] (1") (Table S5 in the Supporting Information).
calculated frequencies of coordinated KrF
2
are over- or
Although this model accounts for the majority of experimental
frequencies and intensities, several differences occur for modes
underestimated in 1', 1", and 2'. The experimental vibrational
frequencies and their trends are well reproduced by the
calculated frequencies, with the exception of their ν(Kr−F)
stretching frequencies, which are overestimated.
[
F
5
Xe(FKrF)AsF
coordination of a fluorine atom of KrF
the appearance of two distinct stretching bands in the Raman
spectrum that are assigned to ν(Kr−F ) and ν(Kr−F ). The
calculated vibrational displacements of 1, show no significant
intraligand coupling between the Kr−F and Kr−F stretching
modes of coordinated KrF ligands (Table S5). This contrasts
with the KrF ligands of KrF
coupling between the ν(Kr−F
The most intense band in the Raman spectrum of 1 at 454
6
] (1). Loss of the center of symmetry upon
+
2
5
to Xe of [XeF ] results in
b
t
b
t
2
[
12]
2
2
·CrOF
4
,
which exhibit intraligand
) modes.
b
) and ν(Kr−F
t
−
1
−1
cm (calcd, 491 cm ) is assigned to the ν(Kr−F
mode. As predicted, the ν(Kr−F ) stretching band corresponding
to the shorter Kr−F bond occurs at higher frequency, 533 cm
calcd, 585 cm ). The experimental frequencies of ν(Kr−F ) and
(464 cm ), and are
OBr(FKrF) AsF (443/472 and
33/549 cm ). The observed frequencies are in accordance
with the experimental Kr−F bond length trend (Tables 2 and S1),
with a similar trend observed for [F Xe(FXeF)AsF ] (433 and 559
b
) stretching
t
−
1
t
−
1
(
b
−
1
t 2
ν(Kr−F ) bracket that of free KrF
comparable to those of [F
2
2
6
]
−
1
[8]
5
5
6
−
1
[19]
cm ).
The degeneracy of the ν
removed upon coordination, which results in Raman-active
δ(F KrF KrF o.o.p. modes that bend in-plane and out-
of-plane with respect to the XeF KrF -plane. The calculated out-
of-plane bend couples with the two ρ (FeqXeFeq) wagging modes
] , whereas the in-plane bend is not coupled. Both bands
are predicted to have low relative Raman intensities and were
2
u 2
(Π ) bending mode of free KrF is
t
b
)
i.p. and δ(F
t
b
)
b
t
w
+
of [XeF
5
−
1
observed as weak bands at 294 and 255 cm (calcd, 289 and
−
1
Figure 3.
The Raman spectra of a) [F
AsF ] (2) recorded at −144 and −161 C, respectively, using
064-nm excitation. The spectrum of (2) also shows bands due to (1), which
5
Xe(FKrF)AsF
6
]
(1) and b)
264 cm ), respectively. Both bands are shifted to higher
o
−1 [31]
[
F
5
Xe(FKrF)
2
6
frequency relative to ν
2 u 2
(Π ) of free KrF (232.6 cm ), but have
1
frequencies that are comparable to the corresponding modes of
are indicated by bullets (•) (see Table S6, footnote c). Symbols denote FEP
sample tube bands (*) and an instrumental artifact (†).
−
1
[8]
[
F
2
OBr(FKrF)
2
AsF
6
]
(301 and 254/266 cm ).
The bands
assigned to the ρ
r
(F
t
KrF ) rocking and ρ (F KrF ) torsional modes
b
t
t
b
−
that mainly involve [AsF
6
]
anion displacements. This is
−1
are predicted at 152 and 136 cm and were observed at 143
+
expected because the coordination sphere of [XeF
5
] in the gas-
−1
and 130 cm , respectively. Interestingly, and similar to the
phase [F Xe(FKrF)AsF ] model (1", CNXe = 5 + 3, Figure S10 in
5
6
δ(F
(F
of the cation, whereas the in-plane rocking mode, ρ
does not couple. The δ(XeF Kr) and δ(XeFAsAs) bends are
t
KrF
b
)
bending modes, the out-of-plane torsional mode,
o.o.p., also couples with the ρ (FeqXeFeq) wagging modes
(F KrF
the Supporting Information) differs from that of the solid-state
ρ
t
t
KrF
b
)
w
structure 1 (CNXe = 5 + 4). An alternative gas-phase model,
r
t
b i.p.
) ,
2
−
[
F
5
Xe(FKrF)(AsF
6
)
3
]
(1', CNXe = 5 + 4, Figure 4a), addresses
b
these differences and better reproduces the xenon coordination
−1
predicted at very low frequencies, 60 and 71/74 cm ,
respectively, but could not be observed.
+
−
environment of [XeF
anions to the
Xe(FKrF)
5
] by coordination of two additional [AsF
6
]
+
[XeF
5
]
cation.
The
gas-phase
[
F
5
Xe(FKrF)
2
AsF
results in additional splittings on the Kr−F stretching
bands of the KrF ligands that are due to intra- and interligand
6 2
]. Coordination of a second KrF ligand to
−
[
F
5
2
(AsF
6
)
2
]
model (2', Figure 4b), which well
+
[
5
XeF ]
+
reproduces the coordination environment of the [XeF
5
] cation in
2
2
2
, was used to aid in the assignment of the Raman spectrum of
−1
couplings. The bands at 543 and 564/567 cm (calcd, 585, 598
+
−
. The vibrational assignments of [XeF
5
] and [AsF
6
] in 1 and 2
−1
cm ) are respectively assigned to modes that are predominantly
[
27]
were also aided by comparisons with those of [XeF
5
][AsF
6
],
],
coupled ν(Kr−F
t
) stretching modes, {[ν(Kr
−F13) – ν(Kr and {[ν(Kr
−F13) + ν(Kr −F15)]small} (see Table S6). Similar couplings,
1
−F12) – ν(Kr
2
−F14)] –
[
28]
[29]
[29]
[
[
[
XeF
XeF
5
][BF
[Cr
4
],
[XeF
5
][fac-OsO
[XeF ][Xe
Mo, W),
3
F
3
],
[XeF
]·2CrOF
OBr(FKrF) AsF
5
][µ-F(OsO
3
F
2
)
2
[
[
ν(Kr
ν(Kr
1
2
−F15)]small
}
1
−F12) + ν(Kr
2
−F14)] –
[
30]
[30]
5
]
2
2
O
2
F
8
],
5
2
F
11][CrOF
5
4
,
5
[XeF ]
1
2
[
17]
[8]
M
2
O
2
F
9
]
(M
=
[F
2
2
6
],
and
which are exclusively interligand couplings, also occur in other
4
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Angewandte Chemie International Edition
10.1002/anie.202014682
RESEARCH ARTICLE
[
8-11]
KrF
2
adducts that contain more than one NgF
2
ligand.
The
The calculated Xe---F
b
contact distances (2.500, 2.468,
−
1
−1
bands at 466 and 472/474 cm (calcd, 507, 517 cm ) are
2.802, and 2.828 Å) are underestimated relative to their
experimental values (2.5139(9), 2.5944(10), 2.9147(10), and
3.0572(11) Å), but reproduce the alternation of their long and
short Xe---F secondary bonds in 1. The shorter calculated
assigned to modes that are predominantly coupled ν(Kr−F
stretching modes, [ν(Kr −F13) + ν(Kr
ν(Kr small], respectively. Interestingly, and unlike adducts
which contain more than one NgF
interligand couplings among the ν(Kr−F
b
)
1
1 2
−F12)small] and [ν(Kr −F15) +
2
−F14)
2
ligand, there are no
) stretching modes. The
contact distances are accompanied by large F
angles (142.1 and 141.1º) whereas long contact distances are
accompanied by smaller F −Xe---F contact angles (128.9 and
1 b
−Xe---F contact
b
room-temperature Raman spectrum of the xenon analogue,
Xe(FXeF) AsF ], also displays split ν(Xe−F ) (420/438, 479
cm ) and ν(Xe−F ) (542, 550 cm ) bands which are likely due to
vibrational mode coupling.
Vibrational coupling between the KrF
two out-of-plane, δ(F KrF o.o.p. (calcd, 246, 247 cm ), and two
in-plane, δ(F KrF i.p. (calcd, 275, 280 cm ), bends which occur
at 251 (o.o.p.) and 273/278 (i.p.) cm . The bands at 145 and
1
b
[
F
5
2
6
b
128.5º), in very good agreement with the corresponding angles
−
1
−1
t
in 1 (143.54(6) and 146.48(6)º; 129.90(6) and 124.67(6)º).
[
19]
2
ligands results in
−
1
t
b
)
−
1
t
b
)
−
1
−
1
1
10 cm , are assigned to the in-plane ρ
r
(F
t
KrF
b
) rocking mode
−
1
(
(
calcd, 136 cm ) and the out-of-plane ρ
t
t
(F KrF
b
) torsional mode
−
1
calcd, 119 cm ), respectively.
Computational Results
The gas-phase geometries of [F
5
Xe(FKrF)AsF
6
] (1") (Figure
2
−
S10), the hypothetical model anions, [F
5
Xe(FKrF)(AsF
6
)
3
]
(1')
−
and [F
5 2 6 2
Xe(FKrF) (AsF ) ] (2') (Figure 4 and Figure S11 in the
+
Supporting Information), KrF
2
5 5
, [XeF ] , and IF were optimized
with all frequencies real at the APFD/aVDZ(-PP)(Xe, As,
Kr)/aVDZ(F) level of theory (Tables S1, S2, S5–S8). The
crystallographic coordinates were used as the starting
geometries for the geometry optimizations. A common limitation
of the gas-phase structural models used for 1' and 2' is the
isolated nature of the ion-pairs, which contrast with the extended
(
layer and chain) structures observed in the crystal structures of
and 2. However, both models reproduce the coordination
1
environment of xenon and therefore proved useful for the
assignment of the Raman spectra and provided insights into the
+
secondary bonding interactions among [XeF
5
] and coordinated
–
KrF
2 6
and [AsF ] .
Calculated Geometries
2
−
[
F
5
Xe(FKrF)AsF
Xe(FKrF)AsF
resulted in twisting of the [AsF
in a bidentate fashion through two cis-fluorine ligands to the Xe
6
] (1") and [F
5
Xe(FKrF)(AsF
6
)
3
]
(1'). The
[
F
5
6
] (1") ion-pair was initially calculated, but
–
Figure 4. Calculated geometries [APFD/aVDZ(-PP)(Kr, Xe, As)/aVDZ(F)] for
6
] anion such that it coordinated
2−
−
a) [F
5
Xe(FKrF)(AsF
6
)
3
]
5 2 6 2
(1') and b) [F Xe(FKrF) (AsF ) ] (2').
2
−
atom to give CNXe = 5 + 3. In contrast, the [F
model (1') reproduced the experimental Xe coordination sphere
CNXe = 5 + 4) and better reproduced the Xe---F interactions
5 6 3
Xe(FKrF)(AsF ) ]
−
[
F
5
Xe(FKrF)
2
(AsF
6
)
2
]
(2'). The calculated geometrical
(
b
parameters of the KrF
2
ligands reproduce the experimental
and their avoidance of the Xe VELP and Xe−Feq bond pair
values and trends in 2, i.e., the shorter Kr−F
Å; exptl, 1.8445(15) Å) is accompanied by a longer Kr−F
calcd, 1.930 Å; exptl, 1.9267(15) Å) for one KrF ligand, and a
longer Kr−F bond (calcd, 1.874 Å; exptl, 1.8505(15) Å) is
accompanied by a shorter Kr−F bond (calcd, 1.909 Å; exptl,
1.9167(15) Å) for the other KrF ligand. The near-linear F −Kr−F
angles (178.47(8) and 179.40(7)º) of 2 are also reproduced
177.60 and 176.98º), but the Xe---F −Kr angles (137.40(8) and
41.80(7)º) are significantly underestimated (123.99 and
24.71º). The difference is likely attributable to the absence of a
t
bond (calcd, 1.862
domains.
b
bond
The calculated Kr−F
t
bond lengths (1.860 Å) are shorter
(
2
than the Kr−F bond lengths (1.939 Å), as observed in the
b
t
crystal structure (1.8393(12) and 1.9367(9) Å), and the average
b
calculated Kr−F bond length (1.900 Å) is very similar to the
[
15]
2
t
b
calculated (1.889 Å) and experimental (1.894(5) Å)
lengths of free KrF . The calculated F −Kr−F bond angle
176.7º) is in good agreement with the experimental value
178.49(6)º), whereas the Kr−F ---Xe bond angle (121.2º) is
bond
2
t
b
(
b
(
(
1
1
b
significantly smaller than the experimental value (133.24(5)º).
The difference between the calculated and experimental Kr−F --
Xe angles is likely due to crystal packing and the deformability
secondary Xe---FAs bond in 2' that is trans to the bridging As−F
bond in 2. This results in bridging As–F (1.7285(14) and
1.7433(14) Å) and Xe---FAs (2.8117(15) and 3.124(2) Å) bond
b
-
−
1
b
of this angle (δ(XeF Kr), 60 cm ).
5
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Angewandte Chemie International Edition
10.1002/anie.202014682
RESEARCH ARTICLE
lengths that are overestimated (1.834 and 1.847 Å) and
with the polar-covalent characters of their bonds. The toroidal
shapes of the Kr valence basins result from the combination of
the three valence electron lone-pair (VELP) domains of Kr, with
the atomic core electron basin (C(Kr)) lying at the center of the
torus. The perturbations of the toroidal V(Kr) basin of
underestimated (2.480 and 2.563 Å), respectively, and F
As angles (126.57(6) and 132.26(6)º) that are overestimated
139.81 and 140.53º). The Xe---F bond lengths (2.550(2) and
.5760(15) Å) are overestimated (2.784 and 2.626 Å) and the
−Xe---F angles (139.59(7) and 140.35(7)º) are
underestimated (128.26 and 130.55º). As observed in 2, there
are two groups of alternating short and long calculated Xe---F
1
−Xe---
F
(
b
2
2
−
F
1
b
[F
[F
5
Xe(FKrF)(AsF
6
)
3
]
and one of the torodial V(Kr) basins of
arise from accommodation of the V(Kr)
−
5
Xe(FKrF) (AsF
2
6
)
2
]
b
basins to their immediate environments (Figure 5). In both
instances, the krypton valence basin torus of a KrF ligand is
flattened parallel to the KrF molecular axis because the ligand is
sandwiched between the fluorine valence basins of neighboring
secondary bonds whose domains avoid the Xe VELP and
2
Xe−Feq bond pair domains.
2
−
Natural Bond Orbital (NBO) Analyses
[AsF
Xe(FKrF)
V(Kr) basin that is essentially unperturbed, closely
resembling the toroidal V(Kr) valence basin of free KrF (Figure
S12). Small perturbations of the toroidal V(Ng) basins (Ng = Kr,
6
]
ions (Figure 5). In contrast, the second KrF
2
ligand of
−
[
F
5
2 6 2
(AsF ) ] is less sterically congested which results
2
−
The NBO analyses for [F
5
Xe(FKrF)(AsF
6
)
3
]
(1') and
in
a
−
[
F
5
Xe(FKrF)
charges on the [XeF
notably less than the net positive charge of the uncoordinated
2 6 2
(AsF ) ]
(2') (Table S9) show the total positive
2
+
5
] cations of 1' (0.776) and 2' (0.771) are
Xe) of NgF
attributed
2
·CrOF
4
and NgF
2
·2CrOF
4
have also been noted and
of their immediate
+
[
XeF
KrF
', −1.864). Charge transfer mainly affects the Fax atoms of 1'
−0.490) and 2' (−0.475), which are significantly more negative
5
] cation, and are consistent with charge transfer from the
to
[12]
the asymmetries
−
2
ligand (1', 0.092 and 2', 0.092) and [AsF
6
] (1', −2.871 and
environments.
2
(
+
relative to Fax of free [XeF
5
] (−0.384). In contrast the average
NPA cahrges of the Feq atoms of 1' (−0.483) and 2' (−0.486) are
+
much closer to the Feq charges of free [XeF
and F charges of KrF in 1' (−0.513, F and −0.453, F
−0.526, F and −0.456, F ; −0.514, F and −0.475, F ) bracket
that of free KrF (−0.492). The charge distribution is consistent
with an axially distorted KrF ligand in which partial removal of
the bridging fluorine atom by the Lewis acidic [XeF
5
] (−0.447). The F
b
t
2
b
t
) and 2'
(
b
t
b
t
2
2
+
5
]
cation
results in more KrF character and correspondingly shorter Kr−F
and longer Kr−F bonds (Tables S1 and S2). The Kr−F and
Kr−F Wiberg bond indices of 1' (Kr−F , 0.610 and Kr−F , 0.450)
and 2' (Kr−F , 0.603 and Kr−F , 0.464; Kr−F , 0.576 and Kr−F
.502) bracket those of KrF (0.551). The small Xe−F bond
indices of 1' (0.102) and 2' (0.069 and 0.037), and the low
+
t
b
t
b
t
b
t
b
t
b
,
0
2
b
+
degree of charge transfer from KrF
with predominantly electrostatic secondary bonding interactions
between the Xe and the F atom(s) of the KrF ligand(s) and the
long experimental and calculated Xe---F bonds observed in 1, 2,
', and 2' (Tables S1 and S2). The NBO analyses of [AsF
2 5
to [XeF ] are consistent
b
2
Figure 5. ELF isosurface plots [APFD/aVDZ(-PP)(Kr, Xe, As)/aVDZ(F)], η(r) =
+ 2− −
0
5 5 6 3 5 2 6 2
.55) for a) [XeF ] , b) [F Xe(FKrF)(AsF ) ] , and c) [F Xe(FKrF) (AsF ) ] .
b
−
Color code: red = core basin; C(Xe), C(As), C(Kr); blue = monosynaptic
valence basin; V(F), V(Ng).
1
6
] in 1'
and 2' show that the larger Xe---FAs bond indices of 1' (0.098)
and 2' (0.096) correspond to smaller As−F bond indices of 1'
(
-
0.386) and 2' (0.382). This is in accordance with the shorter Xe-
-FAs bonds (calcd, 1': 2.468 Å; 2': 2.480 Å; exptl, 1: 2.5944(10)
The valence basins, V(Xe) and V(I) of Xe and I in the
+
isoelectronic [XeF
5
]
cation and IF
5
, correspond to stereoactive
Å; 2: 2.8117(15) Å) and correspondingly longer As−F bridge
bonds (calcd, 1': 1.844 Å; 2': 1.847 Å; exptl, 1: 1.7559(10) Å; 2:
+
3
lone-pairs, where the [XeF
5
]
VELP (2.14 Å ) is significantly
3
contracted relative to that of IF
5
(3.08 Å ), in accordance with the
1
.7433(14) Å).
+
higher charge on Xe (3.17) of [XeF
IF (also see MEPS analyses).
Notable differences occur between the Xe VELP
5
] relative to that of I (2.90) in
5
Electron Localization Function (ELF) Analyses
[
32,33]
The Electron Localization Function analyses
were carried
distributions of the adduct-cations, where the VELP volumes and
2
−
−
out for [F
5
Xe(FKrF)(AsF
] , and isoelectronic IF
discussion denote electron localization function (η(r)); core basin
C(Ng), C(As)); monosynaptic valence basins (V(F) and V(Ng));
6
)
3
] , [F
5
Xe(FKrF)
2
(AsF
6
)
2
] , KrF
2
,
shapes accomodate to the spaces provided by the neighboring
+
−
[
XeF
5
5
. The abbreviations in the ensuing
V(F) basins of the KrF
2
2
ligands and [AsF
6
] ions. The Xe VELPs
−
−
of [F
5
Xe(FKrF)(AsF
6
)
3
]
5 2 6 2
and [F Xe(FKrF) (AsF ) ] are sterically
(
more congested in their nine-coordinate Xe environments,
where the Xe VELPs are notably flattened and their volumes
and f, a localization domain that is bounded by the isosurface,
η(r) = f. The ELF isosurface plots for the aforementioned species
at η(r) = 0.55 are depicted in Figure 5 and Figure S12 in the
Supporting Information.
3
(0.44 and 0.46 Å , respectively) are significantly reduced with
+
respect to those of [XeF
5
]
and IF
5
(vide supra). Similar steric
influences on the Xe(VI) VELP volume have been noted for the
2
−
[34]
The
ELF
(AsF
analyses
of
[F
5
Xe(FKrF)(AsF
6
)
3
] ,
6 6 3 6 3 2
series, XeF (C3v), F XeNCCH , and F Xe(NCCH ) .
−
+
[
F
5
Xe(FKrF)
2
6
)
2
] , KrF
2
,
[XeF
5
] , and IF
5
display only
monosynaptic Xe, Kr, As, F, and I valence basins in accordance
6
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Angewandte Chemie International Edition
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RESEARCH ARTICLE
Molecular Electrostatic Potential Surface (MEPS) Analyses
+
The MEPS isosurfaces of [XeF
5
]
5
and isoelectronic IF are
depicted in Figure 6. Their isosurfaces have regions of high EP
−
1
−1
(
Xe, 773 kJ mol and I, 228 kJ mol ), which are located trans to
their ax atoms. The xenon atom is significantly more
electrophilic than the iodine atom, and the MEPS maxima of the
F
+
fluorine ligand isosurfaces of [XeF
5
]
are significantly more
positive than those of IF which have small negative values, in
5
accordance with their NPA charges (Table S9).
Examination of the top 5% of the positive EP ranges in
+
[
XeF
5
]
5
and IF (Figure 6) allowed the visualization of four
regions of higher EP on the xenon and iodine MEPS isosurfaces
−
1
−1
(
Xe, 798 kJ mol and I, 236 kJ mol ) that are located at the
intersections of the Feq isosurfaces. Similar regions have been
[
35]
reported for IF
5
and XeF
4
.
These regions are symmetrically
disposed with respect to the xenon and iodine VELPs, which are
+
trans to Fax atoms of IF
calculated trajectories of the secondary Xe---F
bonds in 1 (Figure S1), 2 (Figure S3), 1' and 2' (Figure S11) are
5
and [XeF
5
] . The experimental and
b
and Xe---FAs
+
staggered with respect to the Feq atoms of [XeF
xenon VELP, in accordance with the calculated positions of the
four EP maxima on xenon. The crystal structure of XeF ·IF
exhibits similar features, i.e., four I---F secondary bonds whose
trajectories are staggered with respect to the I−Feq bond
5
] and avoid the
2
5
b
[
36]
domains of IF
electrostatic nature of the secondary Xe---F
supported by the Wiberg bond indices obtained for 1' and 2'
Table S9), and may be ascribed to σ-hole bonding. The MEPS
of XeO (C3v) also show discrete regions of higher EP on the
xenon MEPS isosurface, which were visualized by examination
5
and avoid the VELP domain of iodine.
The
b
bonds is also
(
3
[
37]
of the top 20% of the xenon MEPS isosurface. In contrast with
Figure 6. The molecular electrostatic potential surface (MEPS) contours
+
–3
+
[
XeF
5
] and IF
5
, three regions of higher EP of XeO
3
are located
5 5
calculated at the 0.001 e·bohr isosurfaces of [XeF ] and IF and the top 5%
of the positive electrostatic potential range (bottom left). The extrema of
selected electrostatic potentials are indicated by arrows. The optimized
geometries and MEPS were calculated at the APFD/aVDZ(-PP)(Xe, I)/
aVDZ(F) level of theory.
trans to the highly electronegative oxygen atoms of the primary
[
38]
Xe–O bonds, a characteristic of σ-hole bonding,
and have
contact trajectories that are staggered with respect to these
bonds.
Experimental Section
Conclusion
Cautionary statements relating to the safe handling of XeF
6
, KrF
2
, and
+
The present study provides the first instances where both
chemically bound krypton and xenon are present in the same
[XeF ] salts are provided in the Supporting Information. Details relating
5
to the apparatus, starting materials, syntheses, low-temperature crystal
mounting, X-ray data collection and refinement, Raman spectroscopy,
and computational details are provided in the Supporting Information.
Details of the crystal structure investigations may be obtained from the
joint CCDC/FIZ Karlsruhe online deposition service by quoting the
deposition numbers CSD-2000547 (3), 2000548 (2), 2000549 (4), and
compound. The [F
5
Xe(FKrF)AsF
6
]
5 2 6
and [F Xe(FKrF) AsF ]
complexes have been isolated in macroscopic quantities and
structurally characterized by X-ray crystallography and Raman
spectroscopy. Their syntheses, which significantly extend the
limited chemistry of krypton and the XeF
2 2
–KrF analogy, provide
2
000550 (1).
a new class of coordination complex in which KrF
2
+
coordinates
through a fluorine atom to Xe(VI) of the [XeF ] cation. The
5
stabilities of these complexes are reliant on the Lewis acidity of
Acknowledgements
+
[
XeF
fluorinator, KrF
that the bonding interactions between the fluorine bridge atom of
KrF and the Lewis acidic xenon atom are essentially
noncovalent and may be ascribed to σ-hole bonding. The HF
solvates, [F Xe(FH)PnF ] (Pn = As, Sb), also characterized in
this study, provide rare examples of HF coordinated to Xe(VI).
5
]
and its resistance to oxidation by the potent oxidative
2
. NBO, ELF, and MEPS analyses demonstrate
Support from the Marie Curie International Outgoing Fellowship
th
(
M.L.) within the
7
European Community Framework
2
Programme; the Natural Sciences and Engineering Research
Council of Canada, in the form of a Discovery Grant (G.J.S.);
and the Slovenian Research Agency, in the form of the
Research Programme P1-0045 (M.L.), are gratefully
acknowledged. We also thank SHARCNet (Shared Hierarchical
Academic Research Computing Network; www.sharcnet.ca) and
Compute Canada (www.computecanada.ca) for providing
5
6
7
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Angewandte Chemie International Edition
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RESEARCH ARTICLE
computational resources. We are grateful to Mark R. Bortolus for
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Keywords: fluorine chemistry hyper-valent compounds
•
•
krypton and xenon compounds • Raman spectroscopy • X-ray
crystallography
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8
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RESEARCH ARTICLE
Entry for the Table of Contents
KrF
2
and [XeF
5
][AsF
6
] react in anhydrous HF to form [F
5
Xe(FKrF)AsF
6
] and [F
5
Xe(FKrF)
2
AsF
6
]. The complexes were structurally
2
characterized by low-temperature single-crystal X-ray diffraction and Raman spectroscopy. The KrF ligands interact with xenon(VI)
through Xe----FKrF secondary bonds that are shown by computational studies to be noncovalent, electrostatic, σ-hole interactions.
The complexes provide unique examples of mixed noble-gas compounds.
9
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