Synthesis and X-ray crystal structure of (OsO3F 2)2·2XeOF4 and the raman spectra of (OsO3F2)∞, (OsO3F 2)2, and (OsO3F2) 2·2XeOF4

Article abstract of DOI:10.1021/ic900242m

The adduct, (OsO₃F₂).2XeOF₄, was synthesized by dissolution of the infinite chain polymer, (OsO₃F ₂), in XeOF₄ solvent at room temperature followed by removal of excess XeOF₄under dynamic vacuum at 0 °C. Continued pumping at 0°C resulted in removal of associated XeOF4, yielding (Os0 ₃F₂)₂, a new low-temperature phase of OsO3F2. Upon standing at 25 °C for 1/2 h, (Oso₃F₂)₂ underwent a phase transition to the known monoclinic phase, (OsO ₃F₂). The title compounds, (OsO₃F ₂)∞ (OsO₃F₂)₂, and (OsO ₃F₂)₂.2XeOF₄ have been characterized by low-temperature (-150 °C) Raman spectroscopy. Crystallization of (OsO₃F₂)₂.2XeOF₄ from XeOF ₄ solution at O °C yielded crystals suitable for X-ray structure determination. The structural unit contains the (OsO₃F ₂)₂ dimer in which the OsO3F3 units are joined by two Os-F-Os bridges having fluorine bridge atoms that are equidistant from the osmium centers (2.117(5) and 2.107(4) A). The dimer coordinates to two XeOF₄molecules through OsF... Xe bridges in which the Xe... F distances (2.757(5) A) are significantly less than the sum of the Xe and F van der Waals radii (3.63 A). The (OsO₃F₂) ₂ dimer has C_i symmetry in which each pseudo-octahedral OsO₃F₃ unit has a facial arrangement of oxygen ligands with XeOF₄ molecules that are only slightly distorted from their gasphase C_4v, symmetry. Quantum-chemical calculations using SVWN and B3LYP methods were employed to calculate the gas-phase geometries, natural bond orbital analyses, and vibrational frequencies of (OsO₃F ₂)₂, (OsO₃F₂)₂.2XeOF ₄, XeOF₄, OsO₂F₄, and (w-FOs0 ₃F₂)₂OsO₃F~ to aid in the assignment of the experimental vibrational frequencies of (OsO₃F ₂)₂, (OsO₃F₂)₂.2XeOF ₄, and (OsO₃F₂)∞ The vibrational modes of the low-temperature polymeric phase, (OsO₃F₂)∞ have been assigned by comparison with the calculated frequencies of (w-FOsO ₃F₂)₂OsO₃F-, providing more complete and reliable assignments than were previously available.

Full text of DOI:10.1021/ic900242m

Inorg. Chem. 2009, 48, 4478-4490
Synthesis and X-ray Crystal Structure of (OsO3F2)2·2XeOF4 and the
Raman Spectra of (OsO3F2)∞, (OsO3F2)2, and (OsO3F2)2·2XeOF4
Michael J. Hughes, He´le`ne P. A. Mercier, and Gary J. Schrobilgen*
Department of Chemistry, McMaster UniVersity, Hamilton, Ontario, L8S 4M1, Canada
Received February 5, 2009
The adduct, (OsO3F2)2·2XeOF4, was synthesized by dissolution of the infinite chain polymer, (OsO3F2)∞, in XeOF4
solvent at room temperature followed by removal of excess XeOF4 under dynamic vacuum at 0 °C. Continued
pumping at 0 °C resulted in removal of associated XeOF4, yielding (OsO3F2)2, a new low-temperature phase of
OsO3F2. Upon standing at 25 °C for 11/2 h, (OsO3F2)2 underwent a phase transition to the known monoclinic
phase, (OsO3F2)∞. The title compounds, (OsO3F2)∞, (OsO3F2)2, and (OsO3F2)2·2XeOF4 have been characterized by
low-temperature (-150 °C) Raman spectroscopy. Crystallization of (OsO3F2)2·2XeOF4 from XeOF4 solution at 0
°C yielded crystals suitable for X-ray structure determination. The structural unit contains the (OsO3F2)2 dimer in
which the OsO3F3 units are joined by two Os---F---Os bridges having fluorine bridge atoms that are equidistant
from the osmium centers (2.117(5) and 2.107(4) Å). The dimer coordinates to two XeOF4 molecules through Os-
F · · · Xe bridges in which the Xe · · · F distances (2.757(5) Å) are significantly less than the sum of the Xe and F
van der Waals radii (3.63 Å). The (OsO3F2)2 dimer has Ci symmetry in which each pseudo-octahedral OsO3F3 unit
has a facial arrangement of oxygen ligands with XeOF4 molecules that are only slightly distorted from their gas-
phase C4v symmetry. Quantum-chemical calculations using SVWN and B3LYP methods were employed to calculate
the gas-phase geometries, natural bond orbital analyses, and vibrational frequencies of (OsO3F2)2, (OsO3F2)2·2XeOF4,
XeOF4, OsO2F4, and (µ-FOsO3F2)2OsO3F- to aid in the assignment of the experimental vibrational frequencies of
(OsO3F2)2, (OsO3F2)2·2XeOF4, and (OsO3F2)∞. The vibrational modes of the low-temperature polymeric phase,
(OsO3F2)∞, have been assigned by comparison with the calculated frequencies of (µ-FOsO3F2)2OsO3F-, providing
more complete and reliable assignments than were previously available.
Introduction
phase (space group P21/c).3 The structure consists of an
infinite chain in which the pseudo-octahedral Os(VIII) atoms
are bridged by fluorine atoms that are trans to oxygen atoms
and the three oxygen atoms are in a facial arrangement.
The vibrational characterization of OsO3F2 has also been
carried out for both the matrix-isolated monomer and (OsO3F2)∞.
The infrared4,5 and Raman5 spectra of monomeric OsO3F2,
obtained in both argon and nitrogen matrices at 12 K, are
consistent with a trigonal bipyramidal geometry (D3h symmetry)
in which the three oxygen atoms lie in the equatorial plane and
the fluorine atoms are in axial positions. Although incompletely
assigned, the Raman spectra2,6,7 of solid OsO3F2 are consistent
Polymeric (OsO3F2)∞ was first synthesized in 1957 by
reaction of OsO4 with BrF3.1 Only the melting point and
elemental analyses were, however, reported. Three distinct
phases of (OsO3F2)∞ were subsequently identified by X-ray
powder diffraction: a low-temperature (<90 °C) R-phase
(monoclinic), a ꢀ-phase (orthorhombic) at intermediate
temperatures (90-130 °C), and a γ-phase (orthorhombic)
at high temperatures (>130 °C).2 Single crystals of OsO3F2
were obtained by sublimation under static vacuum at 130
°C in a sapphire tube, which resulted in the X-ray crystal
structure determination of the low-temperature monoclinic
*
To whom correspondence should be addressed. E-mail:
(3) Bougon, R.; Buu, B.; Seppelt, K. Chem. Ber. 1993, 126, 1331–1336.
(4) Hope, E. G.; Levason, W.; Ogden, J. S. J. Chem. Soc., Dalton Trans.
1988, 61–65.
(5) Beattie, I. R.; Blayden, H. E.; Crocombe, R. A.; Jones, P. J.; Ogden,
J. S. J. Raman Spectrosc. 1976, 4, 313–322.
schrobil@mcmaster.ca.
(1) Hepworth, M. A.; Robinson, P. L. J. Inorg. Nucl. Chem. 1957, 4,
24–29.
(2) Nghi, N.; Bartlett, N. C. R. Acad. Sci. 1969, 269, 756–759.
4478 Inorganic Chemistry, Vol. 48, No. 10, 2009
10.1021/ic900242m CCC: $40.75  2009 American Chemical Society
Published on Web 04/14/2009

Synthesis and X-ray Crystal Structure of (OsO3F2)2·2XeOF4
Table 1. Summary of Crystal Data and Refinement Results for
(OsO3F2)2·2XeOF4
with the low-temperature fluorine-bridged polymeric structure
obtained from the single-crystal X-ray structure.3
chem formula
space group
a (Å)
b (Å)
c (Å)
Os2O8F12Xe2
P1 (2)
The present paper details the syntheses and structural
characterizations by Raman spectroscopy of a new low-
temperature phase of OsO3F2, namely (OsO3F2)2, and its
XeOF4 adduct, (OsO3F2)2·2XeOF4, which has also been
characterized by single-crystal X-ray diffraction. The Raman
spectrum of the low-temperature monoclinic R-phase,
(OsO3F2)∞, and its assignments are also reported.
j
5.0808(6)
7.7446(9)
9.2133(11)
80.012(4)
83.659(4)
89.217(4)
354.8(1)
1
R (deg)
ꢀ (deg)
γ (deg)
V (Å3)
molecules/unit cell
mol wt (g mol-1
)
999.00
Results and Discussion
calcd density (g cm-3
)
24.675
T (°C)
-173
Syntheses of (OsO3F2)2·2XeOF4 and (OsO3F2)2. Poly-
meric OsO3F2 slowly dissolved in XeOF4 at room temper-
ature forming a deep orange solution. The 19F NMR spectrum
µ (mm-1
)
22.76
a
R1
0.0408
0.0988
b
wR2
a R1 is defined as ∑||Fo| - |Fc||/∑|Fo| for I > 2σ(I). b wR2 is defined as
at 30 °C consisted of an exchange-broadened XeOF4 solvent
2
2
½
{∑[w(Fo - Fc2)2]/∑w(Fo )2} for I > 2σ(I).
19
1
line [δ( F) ) 96.0 ppm, ∆ν /2 ) 1800 Hz] and trace amounts
of cis-OsO2F4 [δ(19F) ) 68.8 ppm (t) and 18.5 ppm(t),
(OsO3F2)2 · 2XeOF4 vac 8 (OsO3F2)2 + 2XeOF4 (4)
2J(19F-19F) ) 138 Hz)] and XeO2F2 [δ(19F) ) 107.2 ppm,
0 °C
1
∆ν / ) 521 Hz]. Fluorine-19 exchange between OsO3F2 and
2
XeOF4 solvent not only resulted in broadening of the XeOF4
spectroscopy (Table S1). Raman spectroscopy established
that the dimer was stable indefinitely at 0 °C, but transformed
over a period of 2 h at 25 °C to an orange powder
corresponding to the monoclinic polymeric phase, (OsO3F2)∞
(eq 5).2
solvent line but also prevented observation of the fluorine-
on-osmium environments of the solute and the 129Xe satellites
of the solvent and of XeO2F2. The formation of trace amounts
of cis-OsO2F4 and XeO2F2 resulted from oxygen/fluo-
rine metathesis between (OsO3F2)∞ and XeOF4 solvent
(eq 1).
∞(OsO3F2)2 25 °C8 2(OsO3F2)∞
(5)
XeOF4
1
(OsO3F2)∞ + XeOF4
8 OsO2F4 + XeO2F2 (1)
∞
30 °C
X-ray Crystal Structure of (OsO3F2)2·2XeOF4. Details
of data collection parameters and other crystallographic
information are provided in Table 1. Bond lengths and bond
angles are listed in Table 2.
The sample composition was also monitored at intervals
by Raman spectroscopy as XeOF4 was removed under
dynamic vacuum at 0 °C (Table S1). The Raman spectrum
of the initial frozen solution was comprised of bands that
arose from a mixture of XeOF4 and (OsO3F2)2·2XeOF4.
Removal of excess XeOF4 at 0 °C yielded an orange solid
corresponding to (OsO3F2)2·2XeOF4 (eq 2).
The structure consists of (OsO3F2)2·2XeOF4 units that are
stacked along the a-axis but alternate along the b- and c-axes
so that the XeOF4 and OsO3F2 molecules face one another
in adjacent columns parallel to these axes (Figure S1). The
resulting intermolecular contacts are long and are near the
sums of the van der Waals radii.8,9 The OsO3F2 molecules
are bridged to one another through two fluorine atoms, F(1)
and F(1A), that are formally contributed by each OsO3F2
molecule. The remaining fluorine ligand of each OsO3F2 unit
bridges through xenon to a XeOF4 molecule (Figure 1a). The
primary coordination spheres of the osmium atoms consist
of three oxygen and three fluorine atoms in a facial
arrangement, providing a distorted octahedral environment
around osmium (Figure 1b). The preference for the fac-trioxo
structure has been previously discussed for other d0 transition
metal trioxo species such as (OsO3F2)∞,3 OsO3F3-,10 [OsO3F]-
XeOF4
2
(OsO3F2)∞ + 2XeOF4
8 (OsO3F2)2 · 2XeOF4 (2)
∞
25 °C
Slow cooling of a solution of (OsO3F2)2·2XeOF4 in XeOF4
from 25 to 0 °C resulted in light orange needle-shaped
crystals of (OsO3F2)2·2XeOF4 which were characterized by
single-crystal X-ray diffraction (vide infra) and which had a
Raman spectrum identical to that of the bulk compound. The
(OsO3F2)2·2XeOF4 adduct was stable at 25 °C for up to 5 h,
after which time dissociation to (OsO3F2)∞ and XeOF4 (eq
3) was detectable by Raman spectroscopy. Upon further
25 °C
2
(OsO3F2)2 · 2XeOF4
8 (OsO3F2)∞ + 2XeOF4 (3)
∞
(8) Bondi, A. J. Phys. Chem. 1964, 68, 441–451.
(9) The ranges of long contacts in (OsO3F2)2·2XeOF4 are F(6) · · ·F(5A)
(2.903(8) Å) to F(1) · · ·F(5B) (3.135(7) Å); F(6) · · ·O(3C) (2.810(8)
Å) to F(6) · · ·O(4D) (3.155(8) Å); O(2) · · ·O(4E) (2.954(9) Å) to
O(2)· · ·O(3A)(3.168(8)Å);Xe(1)· · ·F(4F)(3.545(6)Å)toXe(1)· · ·F(5A)
(3.684(5) Å); and Xe(1) · · ·O(3C) (3.715(6) Å) to Xe(1) · · ·O(2F)
(3.720(6) Å). The corresponding sums of the van der Waals radii (taken
from ref 8) are F · · ·F (2.94 Å), F · · ·O (2.99 Å), O · · ·O (3.04 Å),
Xe· · ·F (3.63 Å) and Xe · · ·O (3.68 Å).
pumping under dynamic vacuum at 0 °C, (OsO3F2)2·2XeOF4
slowly lost XeOF4 to give a yellow powder correspond-
ing to (OsO3F2)2(eq 4), which was confirmed by Raman
(6) Falconer, W. E.; Disalvo, F. J.; Griffiths, J. E.; Stevie, F. A.; Sunder,
W. A.; Vasile, M. J. J. Fluorine Chem. 1975, 6, 499–520.
(7) Beattie, I. R.; Livingston, K. M. S.; Reynolds, D. J.; Ozin, G. A.
J. Chem. Soc. A 1970, 1210–1216.
(10) Gerken, M.; Dixon, D. A.; Schrobilgen, G. J. Inorg. Chem. 2000, 39,
4244–4255.
Inorganic Chemistry, Vol. 48, No. 10, 2009 4479

Hughes et al.
Table 2. Experimental and Calculated Geometrical Parameters for (OsO3F2)2·2XeOF4 and Calculated Geometrical Parameters for (OsO3F2)2, XeOF4,
and (OsO3F2)2·2XeOF4
(OsO3F2)2·2XeOF4
(OsO3F2)2
XeOF4
calcd (Ci)b
calcd (C2h)
calcd (C4V)
exptla
SVWNc
B3LYPd
SVWNc
B3LYPd
SVWNc
B3LYPe
Bond Lengths (Å)
Os(1)-O(1)
Os(1)-O(2)
Os(1)-O(3)
Os(1)---F(1)
Os(1)-F(2)
Os(1)---F(1A)
Xe(1)· · ·F(2)
Xe(1)-O(4)
Xe(1)-F(3)
Xe(1)-F(4)
Xe(1)-F(5)
Xe(1)-F(6)
Xe(1)· · ·O(1A)
1.703(6)
Os-O1
Os-O2
Os-O3
Os---F1
Os-F2
Os---F1′
Xe · · ·F2
Xe-O4
Xe-F3
Xe-F4
Xe-F5
Xe-F6
Xe · · ·O1′
1.721
1.703
1.704
2.146
1.915
2.093
2.735
1.750
1.953
1.971
1.949
1.976
2.872
1.688
1.683
1.683
2.147
1.921
2.143
2.968
1.742
1.953
1.953
1.952
1.956
3.829
1.715
1.709
1.709
2.114
1.892
2.114
1.689
1.686
1.686
2.152
1.892
2.152
1.684(6)
1.685(6)
2.117(5)
1.927(5)
2.107(4)
2.757(5)
1.709(6)
1.907(5)
1.918(5)
1.912(5)
1.913(5)
3.983(6)
1.749
1.951
1.951
1.951
1.951
1.742
1.949
1.949
1.949
1.949
Bond Angles (deg)
O(1)-Os(1)-O(2)
O(1)-Os(1)-O(3)
O(1)-Os(1)---F(1)
O(1)-Os(1)-F(2)
O(1)-Os(1)---F(1A)
O(2)-Os(1)-O(3)
O(2)-Os(1)---F(1)
O(2)-Os(1)-F(2)
O(2)-Os(1)---F(1A)
O(3)-Os(1)---F(1)
O(3)-Os(1)-F(2)
O(3)-Os(1)---F(1A)
F(1)---Os(1)-F(2)
F(1)---Os(1)---F(1A)
F(2)-Os(1)---F(1A)
Os(1)---F(1)---Os(1A)
F(2)· · ·Xe(1)· · ·O(1A)
F(2)· · ·Xe(1)-F(3)
F(2)· · ·Xe(1)-F(4)
F(2)· · ·Xe(1)-F(5)
F(2)· · ·Xe(1)-F(6)
F(2)· · ·Xe(1)-O(4)
O(4)-Xe(1)-F(3)
O(4)-Xe(1)-F(4)
O(4)-Xe(1)-F(5)
O(4)-Xe(1)-F(6)
O(4)-Xe(1)· · ·O(1A)
F(3)-Xe(1)-F(4)
F(3)-Xe(1)-F(5)
F(3)-Xe(1)-F(6)
F(3)-Xe(1)· · ·O(1A)
F(4)-Xe(1)-F(5)
F(4)-Xe(1)-F(6)
F(4)-Xe(1)· · ·O(1A)
F(5)-Xe(1)-F(6)
F(5)-Xe(1)· · ·O(1A)
F(6)-Xe(1)· · ·O(1A)
Xe(1)· · ·F(2)-Os(1)
Xe(1)· · ·O(1A)-Os(1)
102.0(3)
102.1(3)
85.3(2)
157.4(3)
85.3(2)
105.1(3)
159.8(2)
91.8(3)
91.5(2)
91.5(3)
91.2(3)
159.8(2)
76.1(2)
70.2(2)
76.5(2)
109(1)
43.2(1)
82.2(2)
96.4(2)
93.8(2)
83.8(2)
171.6(2)
90.8(3)
90.6(3)
90.8(3)
91.5(3)
128.5(2)
178.6(2)
90.0(2)
89.0(2)
55.6(2)
90.1(2)
90.9(2)
123.3(2)
177.5(2)
122.7(2)
54.9(2)
163.2(2)
142.6(3)
O1-Os-O2
O1-Os-O3
O1-Os---F1
O1-Os-F2
O1-Os---F1′
O2-Os-O3
O2-Os---F1
O2-Os-F2
O2-Os---F1′
O3-Os---F1
O3-Os-F2
O3-Os---F1′
F1-Os-F2
F1-Os---F1′
F2-Os---F1′
Os---F1---Os′
F2 · · ·Xe· · ·O1′
F2 · · ·Xe-F3
F2 · · ·Xe-F4
F2 · · ·Xe-F5
F2 · · ·Xe-F6
F2 · · ·Xe-O4
O4-Xe-F3
O4-Xe-F4
O4-Xe-F5
O4-Xe-F6
O4-Xe· · ·O1′
F3-Xe-F4
F3-Xe-F5
F3-Xe-F6
F3-Xe· · ·O1′
F4-Xe-F5
F4-Xe-F6
F4-Xe· · ·O1′
F5-Xe-F6
F5-Xe· · ·O1′
F6-Xe· · ·O1′
Xe · · ·F2-Os
Xe · · ·O1′-Os′
102.7
102.7
82.2
152.9
83.8
105.6
162.6
94.5
93.7
89.3
92.4
157.4
75.6
70.0
74.2
110.0
55.4
105.7
69.9
102.5
102.4
83.8
155.1
83.8
105.3
159.8
92.5
92.2
91.8
92.5
159.4
75.8
69.2
75.7
110.8
45.4
97.2
78.3
85.3
90.1
170.3
92.2
102.4
102.4
82.9
152.8
82.9
105.3
160.7
93.9
91.4
91.4
93.9
160.7
75.0
102.2
102.2
83.0
154.2
83.0
105.2
160.3
93.4
92.1
92.1
93.4
160.3
75.8
70.7
75.0
109.3
69.5
75.8
110.5
70.4
105.6
154.6
92.5
91.8
92.7
92.6
92.6
92.6
92.6
92.6
92.3
92.4
92.3
142.7
175.5
90.0
90.1
65.6
92.6
92.6
92.6
91.9
149.9
175.6
89.3
89.5
68.3
89.3
91.6
108.2
175.3
109.3
66.0
123.2
121.0
180
89.9
89.9
174.8
89.9
89.9
89.9
89.7
89.9
89.9
89.9
89.9
110.5
175.4
116.0
60.0
158.6
146.1
180
174.8
a For the atom labeling scheme, see Figure 1a. b For the atom labeling scheme, see Figure 6b. c SDDall basis set augmented for F, O, and Xe with two
d-type polarization functions by Huzinaga.40 d Stuttgart basis set for Os augmented with one f-type polarization functional.42 aug-cc-pVTZ basis sets for all
other atoms. e aug-cc-pVTZ basis set.
16
[HF][SbF6],11 ReO3F,12 and ReO3F(CH3CN)2·CH3CN.13 The
polymeric MO2F3·SbF5 (M ) Tc, Re),15 µ-F(TcOF4)2 , µ-
+
17
13
13
-
occurrence of the bridging fluorine atoms trans to oxygen
F(ReOF4)2+, µ-F(cis-ReO2F3)2-, Re3O6F10
,
(WOF4)4,18
3
atoms is also observed in (OsO3F2)∞ and other transition
and (MoOF4)∞.19 The trans-position of the bridging fluorine
ligand is attributed to the trans-influence of the doubly
bonded oxygen ligand which results from the inability of
the fluorine ligand to compete as effectively as an oxygen
14
+
metal oxide fluorides, for example, µ-F(cis-OsO2F3)2 ,
(11) Gerken, M.; Dixon, D. A.; Schrobilgen, G. J. Inorg. Chem. 2002, 41,
259–277.
(12) Supel, J.; Marx, R.; Seppelt, K. Z. Anorg. Allg. Chem. 2005, 631,
2979–2986.
ligand for the d orbitals of osmium.20
t2g
(13) Casteel, W. J.; Dixon, D. A.; LeBlond, N.; Lock, P. E.; Mercier,
H. P. A.; Schrobilgen, G. J. Inorg. Chem. 1999, 38, 2340–2358.
(14) Casteel, W. J.; Dixon, D. A.; Mercier, H. P. A.; Schrobilgen, G. J.
Inorg. Chem. 1996, 35, 4310–4322.
(15) LeBlond, N.; Dixon, D. A.; Schrobilgen, G. J. Inorg. Chem. 2000,
39, 2473–2487.
(16) LeBlond, N.; Mercier, H. P. A.; Dixon, D. A.; Schrobilgen, G. J. Inorg.
Chem. 2000, 39, 4494–4509.
4480 Inorganic Chemistry, Vol. 48, No. 10, 2009

Synthesis and X-ray Crystal Structure of (OsO3F2)2·2XeOF4
bond domain toward the less repulsive Os(1)---F(1,1A)
bridge bonds. The F(1), F(1A), O(2), and O(3) atoms are
coplanar within (0.0001 Å, with the osmium atom lying
0.161 Å out of this plane, and displaced toward O(1). The
O(2)-Os(1)-O(3) angle (105.1(3)°) is considerably more
open as a result of greater repulsion between the Os-O
double bond domains, whereas the F(1)---Os(1)---F(1A)
angle (70.2(2)°) is considerably more closed because of
weaker repulsions between the longer and more polar
Os---F bridge bond domains. The F(1A), F(2), O(1), O(3)
[F(1), F(2), O(1), O(2)] atoms are coplanar within (0.02
[(0.02] Å, and the osmium atom is displaced 0.262
[0.265] Å out of this plane toward O(2) [O(3)]. The
displacement of the osmium atom occurs along the pseudo
3-fold axis toward the facial oxygen ligands, which is
consistent with the metal atom displacements observed
22
10
-
for (OsO3F2)∞,3 ReCl3O3
,
and OsO3F3
and for the
2-
cis-dioxo species cis-OsO2F4,23 µ-F(cis-OsO2F3)2
,
14 cis-
+
13
20
-
-
ReO2F4
,
and cis-TcO2F4
.
In the latter cases, the
central metal atom (M) is displaced toward the cis-oxy-
gen ligands along the axis bisecting the O-M-O an-
gle.
Figure 1. (a) Structural unit in the X-ray crystal structure of
(OsO3F2)2·2XeOF4 with thermal ellipsoids drawn at the 70% probability
level. (b) Visualization of the octahedron formed by the light atoms of the
OsO3F3 unit.
The XeOF4 molecule has been structurally well character-
ized by 19F NMR,24 photoelectron,25 Raman,26 and gas-phase
microwave spectroscopy,27-29 and by single-crystal X-ray
diffraction.30 Xenon oxide tetrafluoride has been shown to
have a square pyramidal geometry based on a AX4YE
VSEPR arrangement, with an axial oxygen atom, four
coplanar fluorine atoms in equatorial positions, and an axial
valence electron lone pair. The long F(2) · · · Xe(1) contact
in the present structure has no perceptible effect on the
geometry of XeOF4 which retains its square-based pyramidal
geometry, providing geometric parameters (Table 2) that are
in good agreement with those reported previously.28-30 The
only other crystal structure containing the XeOF4 molecule
is [XeF5][SbF6]·XeOF4.30 The xenon atom of the XeOF4
molecule in this structure has a short Xe · · · F contact with a
The Os-O bonds are equal to within (3σ and only the
Os(1)-O(2,3) bond lengths (1.685(6) Å) are within (3σ of
those of the polymeric phase (1.688(1) and 1.678(1) Å),
whereas the Os(1)-O(1) bond (1.703(6) Å) is significantly
shorter than the terminal bond of (OsO3F2)∞ (1.727(1) Å).
The fluorine bridges have bond lengths that are equal within
(3σ (Os(1)---F(1), 2.117(5) Å and Os(1)---F(1A), 2.107(4)
Å) and are very similar to those observed for (OsO3F2)∞
(2.126(1) and 2.108(1) Å).3 The remaining fluorine ligand,
F(2), coordinates to Xe(1), forming a Os(1)-F(2)· · · Xe(1)
bridge in which the Xe(1) · · · F(2) contact (2.757(5) Å) is
significantly less than the sum of the van der Waals radii
for F and Xe (3.63 Å).8 The Os(1)-F(2) bond length
(1.927(5) Å) is longer than the terminal Os-F bond in the
polymeric phase (1.879(1) Å)3 but is significantly shorter
than the Os---F bridge bonds in (OsO3F2)2. The Os(1)-F(2)
bond length is, in fact, similar to those of the more polar
-
fluorine atom of the SbF6 anion but has no contacts with
the XeF5+ cation. This fluorine bridge interaction also does
not significantly distort the square-pyramidal geometry of
the XeOF4 molecule nor does it result in significant elonga-
tion of the Sb-F bridge bond. In the present structure, the
Os-F bonds in the OsO3F3 anion (1.97(1)-1.91(1) Å),10
-
(21) The interatomic distances for the light atoms forming the coordination
spheres of the Os atoms in (OsO3F2)2·2XeOF4 are O(1)· · ·O(2,3)
2.634(9), 2.634(9) Å; O(1) · · ·F(1,1A) 2.606(8), 2.600(7) Å; O(2) · · ·O(3)
2.674(8) Å; O(2)· · ·F(1A,2) 2.731(7), 2.599(9) Å; O(3) · · ·F(1,2)
2.740(8), 2.587(8) Å; and F(1A) · · ·F(1,2) 2.428 (9), 2.501(7) Å.
(22) Lis, T. Acta Crystallogr. 1983, C39, 961–962.
(23) Christe, K. O.; Dixon, D. A.; Mack, H. G.; Oberhammer, H.; Pagelot,
A.; Sanders, J. C. P.; Schrobilgen, G. J. J. Am. Chem. Soc. 1993, 115,
11279–11284.
(24) Brown, T. H.; Whipple, E. B.; Verdier, P. H. J. Chem. Phys. 1963,
38, 3029–3030.
(25) Brundle, C. R.; Jones, G. R. J. Electron Spectrosc. Relat. Phenom.
1973, 1, 403–407.
and is rendered more basic by the trans influence of the
Os(1)-O(1) bond.
The light atoms of (OsO3F2)2 form a distorted octahedral
coordination sphere about each osmium atom. Although
there is significant variation in the bond lengths around
the osmium atoms, the light atom octahedra are relatively
undistorted (Figure 1b), as shown by the nearest neighbor-
ligand atom contacts.21 The O(1)-Os(1)-F(2) angle
(157.4(3)°) is bent away from the Os(1)-O(2,3) double
(26) Tsao, P.; Cobb, C. C.; Claassen, H. H. J. Chem. Phys. 1971, 54, 5247.
(27) Martins, J.; Wilson, E. B., Jr. J. Chem. Phys. 1964, 41, 570–571.
(28) Martins, J. F.; Wilson, E. B., Jr. J. Mol. Spectrosc. 1968, 26, 410–
417.
(17) Schrobilgen, G. J.; Holloway, J. H.; Russell, D. R. J. Chem. Soc.,
Dalton Trans. 1984, 1411–1415.
(18) Edwards, A. J.; Jones, G. R. J. Chem. Soc. A 1968, 2074–2078.
(19) Edwards, A. J.; Steventon, B. R. J. Chem. Soc. A 1968, 2503–2510.
(20) Casteel, W. J.; Dixon, D. A.; LeBlond, N.; Mercier, H. P. A.;
Schrobilgen, G. J. Inorg. Chem. 1998, 37, 340–353.
(29) Jacob, E. J.; Thompson, H. B.; Bartell, L. S. J. Mol. Struct. 1971, 8,
383–394.
(30) Pointner, B. E.; Suontamo, R. J.; Schrobilgen, G. J. Inorg. Chem. 2006,
45, 1517–1534.
Inorganic Chemistry, Vol. 48, No. 10, 2009 4481

Hughes et al.
Figure 4. Raman spectrum of (OsO3F2)2 recorded at -150 °C using 1064-
nm excitation; the symbols denote FEP sample tube lines (*) and an
instrumental artifact (†).
Figure 2. Raman spectrum of (OsO3F2)∞ recorded at -150 °C using 1064-
nm excitation; the symbols denote FEP sample tube lines (*) and an
instrumental artifact (†).
Figure 3. Calculated B3LYP gas-phase geometry for (µ-FOsO3F2)2OsO3F-
(C1).
Figure 5. Raman spectrum of (OsO3F2)2·2XeOF4 recorded at -150 °C
using 1064-nm excitation; the symbols denote FEP sample tube lines (*)
and an instrumental artifact (†).
primary Xe-F bond lengths range between 1.907(5) and
1.918(5) Å and are equal within (3σ. The O-Xe-F bond
angles are in the range 90.6(3) to 91.5(3)° and are equal
within (3σ, indicating that the repulsive effect of the oxygen
double bond domain is comparable to that of the electron
lone pair. This is consistent with the crystal structure of
[XeF5][SbF6]·XeOF4,30 as well as with gas-phase microwave
and electron diffraction studies of XeOF4.29
Raman Spectroscopy. The low-temperature, solid-state
Raman spectra of (OsO3F2)∞, (OsO3F2)2, and (OsO3F2)2·
2XeOF4 are shown in Figures 2, 4, and 5, respectively. The
observed and calculated frequencies and assignments for
(OsO3F2)∞ and for (OsO3F2)2 and (OsO3F2)2·2XeOF4 are listed
in Tables 3 and 4, respectively, where the atom numbering
schemes are given in Figures 3, 6a, and 6b, respectively. Spectral
assignments for (OsO3F2)2 and (OsO3F2)2·2XeOF4 were made
by comparison with the calculated frequencies and Raman
intensities (Table 4) for the energy-minimized gas-phase
geometries of (OsO3F2)2, XeOF4, and (OsO3F2)2·2XeOF4 and
by comparison with the experimental frequencies of XeOF426
(Table S2). The vibrational assignments for (OsO3F2)∞ were
made by comparison with the calculated frequencies and
assignments of the presently unknown (µ-FOsO3F2)2OsO3F-
anion (Table 3 and Table S3). The central OsO3F3 group of
(µ-FOsO3F2)2OsO3F- is comprised of two cis-bridged fluorine
atoms, one terminal fluorine atom, and a fac-OsO3 moiety,
Figure 6. Calculated B3LYP gas-phase geometries for (a) (OsO3F2)2 (C2h)
and (b) (OsO3F2)2·2XeOF4 (Ci).
providing a good approximation of the repeat unit in the
fluorine-bridged polymer. Moreover, the formal charge of the
4482 Inorganic Chemistry, Vol. 48, No. 10, 2009

Synthesis and X-ray Crystal Structure of (OsO3F2)2·2XeOF4
Table 3. Raman Frequencies, Intensities, and Assignments for (OsO3F2)∞, and Calculated Vibrational Frequencies and Intensities for
(µ-FOsO3F2)2OsO3F-
a From ref 6. b From ref 7. The abbreviations denote very strong (vs), medium (m), medium weak (mw), and weak (w) intensities. c The Raman spectrum
was recorded on a microcrystalline sample in a FEP tube at -150 °C using 1064-nm excitation. The experimental Raman intensities given in parentheses
are relative intensities with the most intense band given as 100. The abbreviation, n.o., denotes not observed. d SVWN/SDDall. B3LYP/Stuttgart cc-pVTZ.
Values in parentheses denote calculated Raman intensities (amu Å-4) and values in square brackets denote calculated infrared intensities (km mol-1).
e Assignments are for the energy-minimized geometry calculated at the B3LYP level; only the mode assignments that involve the central OsbOtOt1Ot2FtFb1Fb2
unit are provided. See Table S3 for a complete set of assignments. See Figure 3 for the atom labeling scheme. The abbreviations denote stretch (ν), bend
(δ), umbrella (δumb), twist (Ft), wag (Fw), and rock (Fr).
Inorganic Chemistry, Vol. 48, No. 10, 2009 4483

Hughes et al.
4484 Inorganic Chemistry, Vol. 48, No. 10, 2009

Synthesis and X-ray Crystal Structure of (OsO3F2)2·2XeOF4
Inorganic Chemistry, Vol. 48, No. 10, 2009 4485

Hughes et al.
anion is evenly dispersed over the light atoms (Table S4) and
is not expected to have a significant effect on the vibrational
frequencies of the central OsO3F3 group.
does not have significant contributions from terminal groups,
the highly coupled bending modes of the central OsO3F3 and
terminal OsO3F2 units in (µ-FOsO3F2)2OsO3F- are inap-
propriate models for the bending modes in (OsO3F2)∞.
(a) (OsO3F2)∞. The infrared and Raman spectra of matrix-
isolated OsO3F2 monomer4,5 and the Raman spectrum of the
low-temperature polymeric phase, (OsO3F2)∞,6,7 have been
previously reported.The vibrational bands of matrix-isolated
OsO3F2 were fully assigned under D3h symmetry and the
16O/18O isotopic shifts for the Os16O3F2, Os16O218OF2,
Os16O18O2F2, and Os18O3F2 isotopomers were used to
calculate the principal and the interaction force constants
(b) (OsO3F2)2 and (OsO3F2)2·2XeOF4. Under C1 sym-
metry, all vibrational modes (30 A for (OsO3F2)2 and 66 A
for (OsO3F2)2·2XeOF4) are predicted to be both infrared- and
Raman-active. Although correlation of the gas-phase adduct
symmetry (Ci) to the crystal site symmetry (C1) results in
no additional band splittings, correlation of the site symmetry
to the centrosymmetric unit cell symmetry (Ci with Z ) 1)
results in equal apportioning of the vibrational modes
between Ag and Au symmetries (Table S6). Thus, 33 of the
66 A modes of (OsO3F2)2·2XeOF4 are Raman-active Ag
modes and 33 are infrared-active Au modes under the unit
cell symmetry. In accord with the factor-group analysis, 37
vibrational bands were observed in the Raman spectrum. The
calculated frequencies at the SVWN and B3LYP levels are
in good agreement with each other. The degree of coupling
between the (OsO3F2)2 and XeOF4 modes varies with the
level of theory, with stronger coupling occurring at the
SVWN level. The predominant components in the mode
descriptions, however, are the same at both levels and
are therefore used as the basis for discussion. The differences
arise because the Xe atom of the XeOF4 molecule is
coordinated to F(2)/F2 of (OsO3F2)2 in both the experimental
and B3LYP geometries, while the Xe atom is coordinated
to both F(2)/F2 and O(1A)/O1′ of (OsO3F2)2 in the SVWN
geometry (see Calculated Geometries). Because the B3LYP
geometry better reproduces the experimental geometry, the
B3LYP frequencies and corresponding mode descriptions are
referred to in the following discussion.
The Os-O stretching frequencies of (OsO3F2)2 and
(OsO3F2)2·2XeOF4 (Table 4) are comparable to those of
(OsO3F2)∞. The Os-O stretching modes of (OsO3F2)2·
2XeOF4 are not coupled to any of the XeOF4 modes and
are only slightly shifted to higher frequency relative to those
of (OsO3F2)2.
The Os-F(2,2′) and Xe-F(2,2′) stretching modes of the
fluorine bridge are coupled, giving rise to two modes,
([ν(OsF2) - ν(Os′F2′)] + [ν(Xe′F2′) - ν(XeF2)]) and
([ν(OsF2) + ν(Os′F2′)] - [ν(Xe′F2′) + ν(XeF2)]). Only the
latter mode is observed at 572 cm-1 as a strong band, which
is in good agreement with the calculated frequency (571
cm-1) and strong intensity. The frequency of this mode is
shifted to lower frequency when compared with that of the
[ν(OsF2) + ν(Os′F2′)] mode in (OsO3F2)2, observed at 604
cm-1 as a broad, low-intensity band. The experimental
frequency difference upon going from the dimer to the adduct
(32 cm-1) is in reasonable agreement with the calculated shift
(45 cm-1). A similar shift (38 cm-1) was calculated for the
modes involving [ν(OsF2) - ν(Os′F2′)].
and to confirm the vibrational assignments.5 Two prior
6,7
vibrational studies of (OsO3F2)∞
are at considerable
variance with each other and with the present study (Table
3). The Raman spectrum of (OsO3F2)∞ has been re-
examined in the present study, providing frequencies and
intensities that were reproducible over multiple prepara-
tions of (OsO3F2)∞ using different synthetic procedures
(see ref 3 and eqs 3 and 5). In addition, more precise
descriptions and assignments of the vibrational modes,
based on the calculated vibrational frequencies and atomic
displacements for (µ-FOsO3F2)2OsO3F-, are also reported.
The SVWN and B3LYP frequencies (Table 3) agree well
with each other and for the purpose of this discussion,
the B3LYP frequencies are explicitly referred to in the
subsequent discussion.
Four well-resolved bands occur at 945, 949, 952, and 957
cm-1 in the (OsO3F2)∞ spectrum that are assigned to coupled
Osb-O stretching modes. The calculated frequencies associ-
ated with the central OsO3F3 unit of the (µ-FOsO3F2)2OsO3F-
anion (977, 992, 994, and 1014 cm-1) are overestimated with
respect to those of (OsO3F2)∞ but well reproduce the
experimental trend. The Os-O stretching frequencies are
overestimated by similar amounts for the benchmark, cis-
OsO2F4 (Table S5).
The infinite chain OsO3F2 polymer contains two fluorine
environments, a terminal (Ft) and a bridging (Fb) environ-
ment. The Osb-Ft stretching bands (596 and 610 cm-1) are
weak and are in good agreement with the coupled Osb-Ft
stretching modes calculated for (µ-FOsO3F2)2OsO3F- (598
and 614 cm-1). The stretching bands involving Osb-Fb(1,2)
(404 and 413 cm-1) are also weak, but their frequencies are
not modeled as well by (µ-FOsO3F2)2OsO3F-, with the
predicted values occurring at much higher frequencies (443
and 471 cm-1, respectively). As anticipated, the Osb-Ft
stretching modes occur at higher frequencies than those
involving Osb-Fb(1,2), in accord with the shorter bond length
of Osb-Ft (1.879(1) Å) relative to that of Osb-Fb (2.126(1)
Å).3
A limited number of the calculated bending modes (146,
214, 234, 398, 401, and 405 cm-1) are exclusively associated
with the central OsO3F3 unit and have been explicitly
assigned, that is, the bands at 389, 394, and 398 cm-1 can
be reliably associated with O-Osb-O bending modes.
Detailed descriptions were not attempted for the remaining
bending modes because the central OsO3F3 and terminal
OsO3F2 units are extensively coupled. Because (OsO3F2)∞
In contrast, and as expected, all stretching mode descrip-
tions and frequencies that involve Os-F(1,1′) are nearly
identical for both (OsO3F2)2 and (OsO3F2)2·2XeOF4. The in-
phase mode, [ν(OsF1) + ν(Os′F1) + ν(Os′F1′) + ν(OsF1′)],
appears as a weak band at 453 and 450 cm-1, respectively.
4486 Inorganic Chemistry, Vol. 48, No. 10, 2009

Synthesis and X-ray Crystal Structure of (OsO3F2)2·2XeOF4
The out-of-phase mode, [ν(OsF1) + ν(Os′F1′)] - [ν(Os′F1)
+ ν(OsF1′)], is significantly coupled with bending modes,
giving rise to bands at 376 and 409 cm-1 for the dimer and
at 379 and 409 cm-1 for the adduct. The frequency at 409
cm-1 is in very good agreement with the Osb-Fb frequencies
of (OsO3F2)∞ (404, 413 cm-1).
Most of the O-Os-O, F-Os-O, and F-Os-F bending
modes are not coupled or are very weakly coupled to the
F-Xe-F and F-Xe-O bending modes of the
(OsO3F2)2·2XeOF4 adduct and are generally in very good
agreement with the calculated values, as well as with the
experimental and calculated values for (OsO3F2)2 and
(OsO3F2)∞.
The XeOF4 molecules adducted to (OsO3F2)2 are rendered
non-equivalent because the Ci site symmetry of the adduct
results in lowering of the free molecule symmetry from C4V
to local C1 symmetry and removal of the degeneracies of
the E vibrational modes. In addition, all XeOF4 vibrational
modes are coupled to each other but, for the most part, do
not exhibit significant coupling with the (OsO3F2)2 modes,
except in the case noted above.
to have a minimal effect on the geometrical parameters and
vibrational frequencies associated with the OsO3F3 group.
(a) Calculated Geometries. (i) (OsO3F2)2 and
(OsO3F2)2·2XeOF4. The energy-minimized geometries cal-
culated at the SVWN/SDDall (Figure S2) and B3LYP/
Stuttgart(Os) aug-cc-pVTZ (Xe, O, F) levels (Figure 6b) for
(OsO3F2)2·2XeOF4 only differ by the relative positions of
the XeOF4 molecules in relation to the (OsO3F2)2 dimer, with
the B3LYP geometry more closely reproducing the experi-
mental interaction between (OsO3F2)2 and XeOF4. The
experimental (2.757(5) Å) and SVWN (2.735 Å) Xe · · ·F2
bond lengths are in close agreement, whereas the B3LYP
bond length is slightly longer (2.968 Å). In contrast, the
B3LYP (3.829 Å) and SVWN (2.872 Å) Xe · · · O1′ contact
distances are both shorter than the experimental distance
(3.983(6) Å). The Xe atom of the XeOF4 molecule is nearly
equidistant from O1′ and F2 at the SVWN level, whereas it
is much closer to F(2)/F2 for the experimental and B3LYP
geometries. The Xe · · · F(2)/F2-Os bond angles for the
experimental (163.2(2)°), B3LYP (158.6°), and SVWN
(123.2°) geometries also reflect the shorter Xe · · ·F(2)/F2
distance.
The calculated (OsO3F2)2 and (OsO3F2)2·2XeOF4 geom-
etries are in good agreement with the experimental geometry
of the dimer unit in (OsO3F2)2·2XeOF4, although the Os-O
bond lengths are slightly overestimated in the calculated
structures. Both calculated structures provide good estimates
for the Os---F1 bond lengths whereas the calculated Os-F2
bond length of (OsO3F2)2 is underestimated when compared
with the experimental and calculated values for
(OsO3F2)2·2XeOF4. This is likely attributable to the signifi-
cant interaction that occurs between F2 and Xe in
(OsO3F2)2·2XeOF4. The Os-O1 and Os′-O1′ bond lengths
of (OsO3F2)2·2XeOF4 calculated at the SVWN level (1.721
Å) are longer than the B3LYP (1.688 Å) and experimental
(1.703(6) Å) values because of the much shorter O1,1′· · ·Xe(′)
contacts in the SVWN geometry. The absence of an
interaction between O1 and Xe in the experimental structure
is also consistent with the similar calculated and experimental
Os-O1 bond lengths found for (OsO3F2)2.
In both the calculated and experimental structures of
(OsO3F2)2 and (OsO3F2)2·2XeOF4, the light atoms of the
(OsO3F2)2 dimer lie in two dihedral planes; one composed
of atoms O2,O3,Os,F1,F1′,Os′,O2′,O3′, and the other composed
of atoms F2,Os,O1,O1′,Os′,F2′. In the case of the O1-Os-F2
and O1′-Os′-F2′ bond angles, both are bent toward the
fluorine bridge atoms, F1 and F1′ (Figure 6).
The shorter O1,1′ · · · Xe(′) bond length obtained for the
SVWN geometry results in a O4-Xe · · · F2 bond angle that
is more closed than in the B3LYP and experimental
geometries (154.6, 170.3, and 171.6(2)°, respectively). In
both the SVWN and B3LYP geometries, the O4-Xe · · ·O1′
bond angle is calculated to be larger than in the experimental
structure (149.9, 142.7, and 128.5(2)°, respectively), with
the difference likely due to crystal packing. In the geometry
calculated at the SVWN level, the Xe atom is essentially
equidistant from the F2 atom and the O1′ atom, while in the
Both the symmetric (921 cm-1) and asymmetric (911
cm-1) Xe-O stretching modes of (OsO3F2)2·2XeOF4 occur
at higher frequencies than the calculated values (890 and
890 cm-1, respectively, Table 4). The Xe-O stretching
modes are shifted to lower frequency than that of the
experimental and calculated gas-phase XeOF4 molecule26
(927 and 928 cm-1, respectively, Table S2), in accordance
with coordination of the Lewis acidic XeOF4 molecule.
Computational Results. The geometries of (OsO3F2)2 and
(OsO3F2)2·2XeOF4 (Figure 6) optimized under C2h and Ci
symmetries, respectively, and resulted in stationary points
with all frequencies real. The starting geometries for both
energy minimizations were the crystallographic geometries.
Although (OsO3F2)2 optimized to C2h symmetry, the geom-
etry is very close to Ci symmetry, which is reflected in the
atom labeling scheme used in Figure 6a. The energy-
minimized geometries and vibrational frequencies of the
benchmarks, XeOF4 (C4V) and cis-OsO2F4 (C2V) (Tables S2
and S5, respectively) were also calculated. The geometry of
the XeOF4 molecule has been energy minimized using the
SVWN/SDDall and B3LYP/aug-cc-pVTZ methods and
provides geometrical parameters and frequencies that are
26
similar to the experimental values of XeOF4 and
(OsO3F2)2·2XeOF4.
The energy-minimized geometry of the presently unknown
(µ-FOsO3F2)2OsO3F- anion was obtained for C1 symmetry
(Table S7), resulting in a stationary point with all frequencies
real. Descriptions of the vibrational modes are provided in
Table S3. The vibrational modes and frequencies of the (µ-
FOsO3F2)2OsO3F- anion were used to aid the vibrational
assignments of the infinite-chain polymer, (OsO3F2)∞. The
central OsO3F3 group of the anion provided a satisfactory
model for the OsO3F3 group of the polymer. Moreover, the
formal negative charge of the anion is essentially equally
distributed among all of the electronegative light atoms (see
Table S4) so that the formal negative charge may be expected
Inorganic Chemistry, Vol. 48, No. 10, 2009 4487

Hughes et al.
B3LYP geometry, the Xe atom lies along a line coincident
with the Os-F2 bond that has no significant interaction with
O1′, in agreement with the crystal structure. In both calculated
structures, the Xe-F and Xe-O bond lengths of the XeOF4
molecule are slightly overestimated and the angle formed
between O4 and the plane defined by the F3, F4, F5, F6 atoms
is also slightly overestimated.
(ii) (µ-FOsO3F2)2OsO3F-. The structure of the (µ-
FOsO3F2)2OsO3F- anion, optimized at the B3LYP (Figure
3) and SVWN (values in square brackets) levels (Table S7),
has both terminal OsO3F2 units orientated so that the
Os1-Fb1-Osb-Fb2-Os2 backbone forms a shallow W-
shaped arrangement. The Os1---Fb1---Osb (144.7 [129.8]) and
Os2---Fb2---Osb (144.4° [128.8]) bridge bond angles are bent
away from each other, as a result, ∠Os1OsbOs2 is signifi-
cantly greater than 90° (106.5° [116.4]).
The Os1---Fb1 and Os2---Fb2 bridge bond lengths of the
terminal OsO3F3 units (av., 2.194 Å) are elongated with
respect to the terminal Os(1,2)-F bond lengths (av., 1.922
Å). The bridging Osb---Fb1 and Osb---Fb2 bond lengths (av.,
2.072 Å) and the terminal Osb-Ft bond (1.904 Å) are shorter
than the respective bridging Os1,2---Fb and terminal
Os1,2-F1,2,4,5 bond lengths. In contrast with the experimental
Os-O bond lengths of (OsO3F2)∞ (1.727(1), 1.688(1), and
1.678(1) Å),3 the calculated Osb-O(t,t1,t2) bond lengths of (µ-
FOsO3F2)2OsO3F- are nearly equal and are not significantly
influenced by the trans-fluorine ligands. It is noteworthy that
the trans-influence on the Os-O bond lengths is observed
for the experimental structure of (OsO3F2)2·2XeOF4 but was
not apparent in the calculated structures of (OsO3F2)2 and
(OsO3F2)2·2XeOF4.
bond (0.43, 0.40) for both (OsO3F2)2 and (OsO3F2)2·2XeOF4,
respectively, which is consistent with equivalent bonding of
the F1 bridging fluorine atom to both osmium atoms.
With the exception of F2, the Os-O and Os-F bond
orders of (OsO3F2)2 and (OsO3F2)2·2XeOF4 are comparable.
The Os-F2 bond order for (OsO3F2)2·2XeOF4 (0.40) is
slightly lower when compared with that of (OsO3F2)2 (0.43)
and is attributable to coordination of F2 to the Xe atom of
XeOF4. The Xe · · ·F2 bond order corresponding to this weak
fluorine bridge interaction is only 0.04.
Conclusions
The (OsO3F2)2·2XeOF4 adduct has been synthesized by
reaction of (OsO3F2)∞ with XeOF4 solvent and is composed
of the doubly fluorine bridged (OsO3F2)2 dimer and two
XeOF4 molecules which interact with the terminal fluorine
ligands of the dimer by means of fluorine bridges between
the Xe(VI) and Os(VIII) atoms. The XeOF4 molecule retains
its square pyramidal geometry, and the primary coordination
spheres of the osmium atoms are fac-OsO3F3 arrangements
in which the oxygen ligands are cis to one another and the
bridging fluorine atoms are trans to an oxygen ligand. The
adduct is stable at room temperature for up to 5 h, slowly
dissociating to (OsO3F2)∞ and XeOF4. The (OsO3F2)2 dimer
has been isolated by removal of XeOF4 from (OsO3F2)2·
2XeOF4 under dynamic vacuum and represents a new low-
temperature phase of OsO3F2. Upon standing at 25 °C, the
dimer undergoes an irreversible phase transition to the R-
phase of (OsO3F2)∞, a polymeric chain structure. The
vibrational modes and the Raman spectrum of (OsO3F2)∞
have been assigned in detail with the aid of quantum-
chemical calculations of the presently unknown trinuclear
(µ-FOsO3F2)2OsO3F- anion. Because the negative formal
charge was found to be essentially uniformly dispersed over
all the light atoms, the vibrational modes of the central
OsO3F3 moiety of this anion proved to be a good model for
the assignment of the vibrational modes of the OsO3F3
moieties in the infinite chain polymer, (OsO3F2)∞.
(b) Charges, Valencies, and Bond Orders. The Natural
Bond Orbital (NBO)31-34 analyses were carried out for the
SVWN- and B3LYP-optimized gas-phase geometries of
(OsO3F2)2 and (OsO3F2)2·2XeOF4 and are similar (Table S8).
Because the B3LYP geometry better reproduces the experi-
mental geometry than the SVWN geometry (see Calculated
Geometries), only the B3LYP results are referred to in the
ensuing discussion.
Experimental Section
The NBO analyses give natural charges of 2.19 and 2.18
for Os in (OsO3F2)2 and (OsO3F2)2·2XeOF4, respectively, and
3.13 for Xe in (OsO3F2)2·2XeOF4. The natural charge of the
Xe atom is approximately half of its formal oxidation
number, and the oxygen and fluorine atoms are also close
to half of their respective formal oxidation numbers, indicat-
ing that the bonding in (OsO3F2)2 and (OsO3F2)2·2XeOF4 is,
as expected, polar covalent. The Os---F1 bridge bond order
(0.23, 0.23) is approximately half that of the terminal Os-F2
Apparatus and Materials. Manipulations involving air-sensitive
materials were carried out under anhydrous conditions as previously
described.14 All preparative work was carried out in fluoroplastic
vessels fabricated from 1/4-in. o.d. lengths of FEP tubing. The tubing
was heat-sealed at one end and connected through a 45° SAE flare
to a Kel-F valve. Reaction vessels were dried on a glass vacuum
line and then transferred to a metal vacuum line where they were
passivated with F2 for several hours, refilled with dry N2, and stored
in a drybox until used. Vessels were connected to vacuum lines
through 1/4-in. 316 stainless steel Swagelok Ultratorr unions fitted
with Viton O-rings. Xenon oxide tetrafluoride was synthesized by
hydrolysis of XeF6 as previously described35 and (OsO3F2)∞ was
synthesized by reaction of OsO4 (Koch-Light, 99.9%) with ClF3
as previously described.3
(31) Glendening, E. D.; Reed, A. E.; Carpenter, J. E.; Weinhold, F. NBO,
Version 3.1; Gaussian Inc.: Pittsburgh, PA, 1990.
(32) Reed, A. E.; Curtiss, L. A.; Weinhold, F. Chem. ReV 1998, 88, 899–
926.
(33) Reed, A. E.; Weinstock, R. B.; Weinhold, F. J. Chem. Phys. 1985,
83, 735–746.
(34) Glendening, E. D.; Badenhoop, J. K.; Reed, A. E.; Carpenter, J. E.;
Bohmann, C. M.; Morales, C. M.; Weinhold, F. NBO Version 5.0;
Theoretical Chemical Institute, University of Wisconsin: Madison, WI,
2001.
Syntheses of (OsO3F2)2·2XeOF4 and (OsO3F2)2. Inside a
nitrogen-filled drybox, a fluorine passivated FEP reaction vessel
(35) Schumacher, G. A.; Schrobilgen, G. J. Inorg. Chem. 1984, 23, 2923–
2929.
4488 Inorganic Chemistry, Vol. 48, No. 10, 2009

Synthesis and X-ray Crystal Structure of (OsO3F2)2·2XeOF4
was loaded with 0.02803 g (0.1015 mmol) of orange (OsO3F2)∞.
The reaction vessel was then transferred to a metal vacuum line
and about 1.0 g (4.5 mmol) of XeOF4 was distilled into it. Upon
warming to room temperature, an orange suspension formed which
slowly dissolved, with agitation, over a period of several hours to
form a deep orange solution. The reaction vessel was attached to
a metal vacuum line through a FEP U-trap cooled to -196 °C and
excess XeOF4 was removed under dynamic vacuum at 0 °C.
Pumping for about 21/2 min yielded an orange solid that was
identified as (OsO3F2)2·2XeOF4 (0.04931 g, 0.04936 mmol) by
Raman spectroscopy. Associated XeOF4 was removed from the
adduct by further pumping on the solid at 0 °C for 3 h, producing
a yellow powder identified as (OsO3F2)2 (0.02720 g, 0.04924 mmol)
by Raman spectroscopy. The dimer underwent a phase transition
to (OsO3F2)∞ when warmed to and maintained at room temperature
for 11/2 h, whereas the Raman spectrum of the XeOF4 adduct
showed no change when the sample was held at room temperature
for up to 5 h. Slow dissociation of XeOF4 and rearrangement of
(OsO3F2)2 to (OsO3F2)∞ was, however, detected upon further
standing at room temperature and was complete after 21 days.
Raman Spectroscopy. The low-temperature Raman spectra of
(OsO3F2)∞, (OsO3F2)2·2XeOF4, XeOF4, and (OsO3F2)2 (-150 °C)
were recorded on a Bruker RFS 100 FT Raman spectrometer
using 1064-nm excitation and a resolution of 1 cm-1 as pre-
viously described.10 The spectrum was recorded using a laser
power of 300 mW and a total of 1200 scans for (OsO3F2)∞,
(OsO3F2)2·2XeOF4, and XeOF4 and 2400 scans for (OsO3F2)2.
Nuclear Magnetic Resonance Spectroscopy. (a) NMR
Sample Preparation. In a typical synthesis, a sample of
(OsO3F2)2·2XeOF4 was prepared in a 4-mm o.d. FEP tube fitted
with a Kel-F valve that had been loaded with (OsO3F2)∞ (23.24
mg, 0.08314 mmol) inside a drybox. The NMR tube was connected
to a FEP vacuum submanifold that was, in turn, connected to a
XeOF4 storage vessel. The FEP submanifold was connected to a
metal vacuum line, and about 0.5 mL of XeOF4 was statically
distilled onto (OsO3F2)∞ at -196 °C. The NMR sample was then
heat sealed under dynamic vacuum and stored at -196 °C until its
19F NMR spectrum could be recorded. Samples were dissolved at
room temperature just prior to data acquisition. When obtaining
spectra, the 4-mm FEP tubes were inserted into a 5-mm o.d. thin-
wall precision glass NMR tube (Wilmad).
in a 1/4-in. o.d. FEP T-shaped reactor. The sample vessel was placed
in a near-horizontal position, distributing the XeOF4 solution along
the length of the reaction vessel. Slow cooling of the solution to 0
°C over 3 h resulted in the growth of light orange needles while
the supernatant remained deep orange in color. Crystals were
isolated by decanting the solvent at -5 °C under dry nitrogen into
the side arm of the FEP vessel, which was immersed in liquid
nitrogen, followed by drying of the crystalline product under
dynamic vacuum at -20 °C before the side arm containing the
supernatant was removed by heat sealing off this portion of the
reaction vessel under dynamic vacuum at -196 °C.
(b) Collection and Reduction of X-ray Data. A crystal of
(OsO3F2)2·2XeOF4 having the dimensions 0.17 × 0.04 × 0.03 mm3
was selected at -105 ( 3 °C for low-temperature X-ray structure
determination and was mounted in a cold stream (-173 °C) on a
goniometer head as previously described.10
The crystal was centered on a Bruker SMART APEX II
diffractometer, equipped with an APEX II 4K CCD area detector
and a triple-axis goniometer, controlled by the APEX2 Graphical
User Interface (GUI) software,36 and a sealed source emitting
graphite-monochromated Mo KR radiation (λ ) 0.71073 Å).
Diffraction data collection at -173 °C consisted of a full ꢁ rotation
at a fixed ꢂ ) 54.74° with 0.36° (1010) frames, followed by a series
of short (250 frames) ω scans at various ꢁ settings to fill the gaps.
The crystal-to-detector distance was 4.953 cm and the data
collection was carried out in a 512 × 512 pixel mode using 2 × 2
pixel binning. Processing of the raw data was completed by using
the APEX2 GUI software,36 which applied Lorentz and polarization
corrections to three-dimensionally integrated diffraction spots. The
program SADABS37 was used for the scaling of diffraction data,
the application of a decay correction, and an empirical absorption
correction on the basis of the intensity ratios of redundant
reflections.
(c) Solution and Refinement of the Structure. The XPREP
program was used to confirm the unit cell dimensions and the crystal
lattice. The solution was obtained by direct methods which located
the positions of the atoms defining the (OsO3F2)2 dimer and the
XeOF4 molecules. The final refinement was obtained by introducing
anisotropic thermal parameters and the recommended weightings
for all of the atoms. The maximum electron densities in the final
difference Fourier map were located near the heavy atoms. All
calculations were performed using the SHELXTL-plus package for
the structure determination and solution refinement and for the
molecular graphics.38 Further confirmation of the choice of space
group was obtained by use of PLATON with the WinGX software
package.39
(b) NMR Instrumentation and Spectral Acquisitions. Fluorine-
19 NMR spectra were recorded unlocked (field drift <0.1 Hz h-1
)
on a Bruker DRX-500 spectrometer equipped with an 11.744 T
1
cryomagnet using a 5 mm combination H/19F probe operating at
470.592 MHz. The NMR probe was cooled using a nitrogen flow
and variable-temperature controller (BVT 3000).
Computational Methods. The optimized geometries and fre-
quencies of OsO3F2, cis-OsO2F4, XeOF4, (OsO3F2)2, (OsO3F2)2·
2XeOF4, and (µ-FOsO3F2)2OsO3F- were calculated at the density
functional theory (DFT) level by use of SVWN and B3LYP40
methods. The Stuttgart semirelativistic large core and effective core
pseudopotential basis sets (SDDall) augmented for F, O, and Xe
with two d-type polarization functions by Huzinaga41 was used for
The 19F NMR spectra were acquired in 32 K memories with
spectral width settings of 37.5 kHz and acquisition times of 0.87 s,
and were zero-filled to 64 K, yielding data point resolutions of 0.57
Hz/data point. Relaxation delays of 0.1 s were applied and 2500
transients were accumulated. The pulse width, corresponding to a
bulk magnetization tip angle of approximately 90°, was 8.5 µs. Line
broadenings of 0.1 Hz were used in the exponential multiplications
of the free induction decays prior to Fourier transformation. The
19F spectra were referenced externally at 30 °C to samples of neat
CFCl3. The chemical shift convention used is that a positive
(negative) sign indicates a chemical shift to high (low) frequency
of the reference compound.
(36) APEX2, Release 2.0-2; Bruker AXS Inc.: Madison, WI, 2005.
(37) Sheldrick, G. M. SADABS (Siemens Area Detector Absorption
Corrections), version 2.10; Siemens Analytical X-ray Instruments Inc:
Madison, WI, 2004.
(38) Sheldrick, G. M., SHELXTL-Plus, release 6.14, Siemens Analytical
X-ray Instruments, Inc; Madison, WI, 2000-2003.
(39) Farrugia, L. J. J. Appl. Crystallogr. 1999, 32, 837–838.
(40) Frisch, M. J. et al. Gaussian 03, revision B.04; Gaussian, Inc.:
Pittsburgh, PA, 2003.
X-ray Crystal Structure Determination of (OsO3F2)2·2XeOF4.
(a) Crystal Growth. Crystals of (OsO3F2)2·2XeOF4 were obtained
from a sample composed of 0.0502 g (0.182 mmol) of OsO3F2
dissolved in excess XeOF4 (ca. 0.500 g, 2.24 mmol) and contained
(41) Huzinaga, S.; Andzelm, J.; Kolobukowski, M.; Radzio-Andzelm, E.;
Sakai, Y.; Tatewaki, H. Gaussian Basis Sets for Molecular Calcula-
tions; Physical Science Data 16; Elsevier: Amsterdam, 1984.
Inorganic Chemistry, Vol. 48, No. 10, 2009 4489

Hughes et al.
the SVWN method and the Stuttgart basis set augmented by one
f-type polarization function (Rf Os 0.886)42 for osmium and aug-
cc-pVTZ basis sets for xenon, oxygen, and fluorine was used for
the B3LYP method.
of a Discovery Grant (G.J.S.); and SHARCNet (Shared
Hierarchical Academic Research Computing Network;
www.sharcnet.ca) for computational resources.
Pseudopotentials were used with the appropriate basis sets for
both osmium and xenon. Quantum-chemical calculations were
carried out using the programs Gaussian 98 and Gaussian 03.43
The levels and basis sets were benchmarked by calculating cis-
OsO2F4 and XeOF4 and comparing with the experimental geometries
and vibrational frequencies.23,29,30 The geometries were fully
optimized using analytical gradient methods. After optimization at
one level of theory, the geometries were calculated at the other
level of theory to ensure an equivalent energy-minimized geometry
had been achieved. The vibrational frequencies were calculated at
the SVWN and B3LYP levels using the appropriate minimized
structure, and the vibrational mode descriptions were assigned with
the aid of Gaussview.44
Supporting Information Available: Raman spectra used to
monitor the formation/dissociation of (OsO3F2)·2XeOF4 from/to
(OsO3F2)∞ and XeOF4, and the transition of (OsO3F2)2 to (OsO3F2)∞
(Table S1); view of the (OsO3F2)2·2XeOF4 crystallographic unit cell
along the a-axis. (Figure S1); experimental Raman frequencies,
intensities, and assignments for gas-phase XeOF4, and the calculated
vibrational frequencies and intensities for XeOF4 (Table S2);
calculated vibrational frequencies, Raman and infrared intensities
and assignments for (µ-FOsO3F2)2OsO3F- (Table S3); natural bond
orbital (NBO) charges, valencies, and bond orders for (µ-
FOsO3F2)2OsO3F- (Table S4); experimental and calculated frequen-
cies, intensities and assignments for cis-OsO2F4 (Table S5); factor-
group analysis for (OsO3F2)2·2XeOF4 (Table S6); calculated
geometrical parameters for (µ-FOsO3F2)2OsO3F- (Table S7);
calculated gas-phase geometry for (OsO3F2)2·2XeOF4 (C1, SVWN/
SDDall) (Figure S2); natural bond orbital (NBO) charges, valencies,
and bond orders for (OsO3F2)2 and (OsO3F2)2·2XeOF4 (Table S8);
complete references 40 and 43; and a X-ray crystallographic file
in CIF format for the structure determination of (OsO3F2)2·2XeOF4.
This material is available free of charge via the Internet at
http://pubs.acs.org.
Acknowledgment. We thank the Natural Sciences and
Engineering Research Council of Canada for the award of a
postgraduate scholarship (M.J.H.) and for support in the form
(42) Ehlers, A. W.; Bohme, M.; Dapprich, S.; Gobbi, A.; Hollwarth, A.;
Jonas, V.; Kohler, K. F.; Stegmann, R.; Veldkamp, A.; Frenking, G.
Chem. Phys. Lett. 1993, 208, 111–114.
(43) Frisch, M. J. et al. Gaussian 98, Revision A.11; Gaussian, Inc.:
Pittsburgh, PA, 2003.
(44) GaussView, release 3.0; Gaussian Inc.: Pittsburgh, PA, 2003.
IC900242M
4490 Inorganic Chemistry, Vol. 48, No. 10, 2009