A novel dimanganese complex linked by an unusually strong hydrogen bond. X-ray structure of the hydrogen-bonded complex and ab initio calculations

Article abstract of DOI:10.1016/S0022-328X(01)00829-4

In an attempt to prepare the fluoro complex (CO)₃(dppe)MnF (3) by treating a CH₂Cl₂ solution of the aqua complex [(CO)₃(dppe)Mn(OH₂)]BF₄ (1) with NaF_(aq), we isolated instead, the dimanganese complex, [(CO)₃(dppe)Mn(OH₂)FMn(dppe)(CO)₃]BF ₄ (2). The two moieties, 1 and 3, are held together by an unusually strong O-HF hydrogen bond (OF=2.458(3) ?, HF=1.52 ?) between the aqua ligand on one manganese and the fluoro atom on the other manganese. Using as a simple model the interaction between ⁺Li(H₂O) and FLi, the hydrogen bonding distance O-HF was calculated to be; OF=2.443 ?. Authentic 3 was prepared in a homogeneous system using CH₂Cl₂-soluble [Et₄N]F.

Full text of DOI:10.1016/S0022-328X(01)00829-4

Journal of Organometallic Chemistry 629 (2001) 165–170
www.elsevier.com/locate/jorganchem
A novel dimanganese complex linked by an unusually strong
hydrogen bond. X-ray structure of the hydrogen-bonded complex
and ab initio calculations
Thomas M. Becker a, Jeanette A. Krause Bauer a, Janet E. Del Bene b,
Milton Orchin a,*
a Department of Chemistry, Uni6ersity of Cincinnati, PO Box 210172, Cincinnati, OH 45211-0172, USA
b Department of Chemistry, Youngstown State Uni6ersity, Youngstown, OH 44555, USA
Received 23 January 2001; received in revised form 3 April 2001; accepted 8 April 2001
Abstract
In an attempt to prepare the fluoro complex (CO)3(dppe)MnF (3) by treating a CH2Cl2 solution of the aqua complex
[(CO)3(dppe)Mn(OH2)]BF4 (1) with NaF(aq), we isolated instead, the dimanganese complex, [(CO)3(dppe)Mn(OH2)···FMn-
(dppe)(CO)3]BF4 (2). The two moieties, 1 and 3, are held together by an unusually strong O–H···F hydrogen bond (O···F=
,
,
2.458(3) A, H···F=1.52 A) between the aqua ligand on one manganese and the fluoro atom on the other manganese. Using as
a simple model the interaction between +Li(H2O) and FLi, the hydrogen bonding distance O–H···F was calculated to be;
,
O···F=2.443 A. Authentic 3 was prepared in a homogeneous system using CH2Cl2-soluble [Et4N]F. © 2001 Elsevier Science B.V.
All rights reserved.
Keywords: Dimanganese complexes; Strong hydrogen bonds; X-ray structures; ab initio
1. Introduction
The readily
tempt to prepare the fluoro complex, we isolated a
crystalline compound whose unexpected structure
proved to be that shown in Fig. 1.
available
Mn–aqua
complex,
[(CO)3(dppe)Mn(OH2)]BF4 (1), has proven extremely
useful for the preparation of a great variety of func-
tional groups sigma bonded to the Mn center [1,2]. The
utility of this complex relies on the lability of the aqua
ligand and its ease of replacement by either neutral or
anionic ligands. Anionic ligands that have been used
include OMe, OC(O)OMe, O(Tf), NO3, Cl, Br, CN and
N3. The usual procedure for the reaction involves dis-
solving the aqua complex in CH2Cl2 and adding an
excess of a concentrated aqueous solution of the
sodium salt of the desired anion, separating the phases,
and isolation of the desired complex from the CH2Cl2
solution. When this procedure was followed in an at-
2. Experimental
All reactions were carried out under an argon atmo-
sphere unless otherwise noted. Solvents were used as
received. 1,2-Bis(diphenylphosphino)ethane (dppe) was
purchased from Pressure Chemicals. The aqua complex
[ fac-Mn(CO)3(dppe)(OH2)]BF4 (1) was prepared ac-
cording to the literature method [1]. Tetraethylammo-
nium fluoride hydrate was purchased from Aldrich. IR
spectra were recorded on a P-E Spectrum One FT-IR
1
employing 1.0 mm NaCl liquid cells. H-NMR spectra
were obtained on CDCl3 solutions using a Bruker
AC-250 spectrometer with chemical shifts recorded rel-
ative to Me4Si. Q-Tof hybrid quadrupole time of flight
* Corresponding author. Tel.: +1-513-5569200; fax: +1-513-
5569239.
E-mail address: orchinm@email.uc.edu (M. Orchin).
0022-328X/01/$ - see front matter © 2001 Elsevier Science B.V. All rights reserved.
PII: S0022-328X(01)00829-4

166
T.M. Becker et al. / Journal of Organometallic Chemistry 629 (2001) 165–170
bottomed flask. Excess [NEt4]F·xH2O (0.277 g) was
added and the one phase system was stirred for 25 min.
The CH2Cl2 solution was washed with water (4×10
ml) and the CH2Cl2 was removed by rotary evapora-
tion. The yellow residue was dissolved in benzene and
filtered to remove remaining [NEt4]F. The benzene was
removed via rotary evaporation leaving the yellow solid
3. The IR spectrum of 3 in CH2Cl2 must be taken
immediately after the solution is placed in the IR cell to
avoid reaction with the NaCl cell (see section 2.7).
The one-phase system using CH2Cl2-soluble [NEt4]F
as the fluoride source in the reaction with 1 is the
preferred procedure for preparing the fluoro complex 3.
The use of a two-phase system involving a CH2Cl2
solution of the aqua complex and NaF in an attempt to
synthesize 3 instead leads to 2 as described in Section
2.1. Reversing the order of addition by slowly dripping
1 into NaF(aq) did not change the result.
Data 3: mp 146–150°C. IR (cm−1, CH2Cl2): w(CO)
2024s, 1948s, 1907s. 1H-NMR (l, CDCl3) 7.75–7.25
(m, Ph, 20H), 2.79–2.73 (m, CH2, 4H). High Res. MS
(m/z) 537.0558 Mn(dppe)(CO)+3 (Calc. 537.0581),
472.0743 Mn(dppe)F+ (Calc. 472.0718), 453.0739
Mn(dppe)+ (Calc. 453.0734).
Fig. 1. ORTEP diagram of [(CO)3(dppe)Mn(OH2)···FMn(dppe)-
(CO)3]BF4 (2) indicating labeling scheme and 50% thermal ellipsoids.
The BF4 counterion and the external H2O, which crystallizes in the
lattice, are not shown.
mass spectrometer (Micromas UK Ltd.) fitted with an
electrospray ionization (ESI) was used for the analysis
of the compounds. Melting points were determined
using a Mel-Temp apparatus and they are uncorrected.
Chemisar Laboratories performed elemental analyses.
2.2.2. From [(CO)3(dppe)Mn(OH2)···FMn(dppe)-
(CO)3]BF4 (2)
A solution of the hydrogen-bonded dimanganese
complex 2 (23 mg, 0.019 mmol) in ca. 15 ml of CH2Cl2.
was placed in
a round bottomed flask. Excess
2.1. Preparation of [(CO)3(dppe)Mn(OH2)···FMn-
(dppe)(CO)3]BF4 (2)
[NEt4]F·xH2O (35 mg) was added and the homoge-
neous system was stirred for 3 h. The CH2Cl2 solution
was separated, washed with water (2×10 ml) and then
concentrated. Hexane was added and the solution was
cooled. The precipitated yellow fluoro complex
(CO)3(dppe)MnF (3) was then collected.
A solution of the aqua complex 1 (0.107 g, 0.167
mmol) in ca. 25 ml of CH2Cl2, was placed in a round
bottomed flask. Excess NaF(aq) (0.080 g, 1.91 mmol, in
1 ml of H2O) was added and the two-phase reaction
mixture was stirred for 2.5 h. The CH2Cl2 solution was
separated, then washed with water (2×5 ml). After
concentration, hexane was added and after cooling in
the refrigerator, yellow X-ray quality crystals of 2 were
isolated.
2.3. Reaction of [(CO)3(dppe)Mn(OH2)···FMn(dppe)-
(CO)3]BF4 (2) with CO
A small quantity of the hydrogen-bonded diman-
ganese complex 2 (ꢀ20 mg) was added to a round
bottomed flask and dissolved in ca. 15 ml of CH2Cl2.
CO was bubbled into the solution for 1 min, the flask
was stoppered and the solution was stirred for 3 h. The
TLC and the IR spectrum of the solution taken quickly
indicated the presence of a mixture of the known
tetracarbonyl complex [(CO)4Mn(dppe)]BF4 [3] and the
fluoro complex 3.
Data 2: m.p. 171–174°C. IR (cm−1, CH2Cl2):
w(OH)anti 3682.1, w(OH)sym 3602.9, w(CO) 2037 s, 2025
1
s, 1964 s, 1950 s, 1938 s, 1916 s. H-NMR (l, CDCl3)
7.67–7.04 (m, Ph, 40H), 3.0–2.0 (m, CH2, H2O, 10H).
MS (m/z) 537 Mn(dppe)(CO)+3 , 453 Mn(dppe)+. Anal.
Calc. for C58H52BF5Mn2O8P4: C, 57.26; H, 4.30.
Found: C, 56.97; H 3.82%.
2.2. Preparation of (CO)3(dppe)MnF (3)
2.4. Reaction of (CO)3(dppe)MnF (3) with NaCl
2.2.1. From [fac-Mn(CO)3(dppe)(OH2)]BF4 (1)
A solution of the aqua complex 1 (0.297 g, 0.463
mmol) in ca. 25 ml of CH2Cl2 was placed in a round
When a CH2Cl2 solution of 3 is placed in the NaCl
IR cell, the carbonyl stretching bands, originally ob-
served, shift during ca. 5 min, to give final frequencies

T.M. Becker et al. / Journal of Organometallic Chemistry 629 (2001) 165–170
167
Table 1
data were collected at 150 K on a SMART 1 K CCD
diffractometer [5], graphite-monochromated Mo–Ka
,
Selected bond lengths (A) and bond angles (°) for
[(CO)3(dppe)Mn(OH2)···FMn(dppe)(CO)3]BF4 (2)
,
radiation, u=0.71073 A, detector distance of 5.083 cm,
q range 2.41–28.21° with limiting indices of −13B
hB14, −20BkB20, −23BlB23; 29 577 reflections
collected of which 13 475 are independent reflections
(Rint=0.0950). Data corrections were applied using
SADABS [6].
Details in6ol6ing the F···H–O hydrogen-bonded interaction
O(7)–H(1)
O(7)–H(2)
O(7)···F(1)
H(1)–O(7)–H(2)
0.91
0.95
2.458(3)
110
Mn(1)···O(7)
H(1)···F(1)
O(7)–H(1)···F(1)
H(2)–O(7)–Mn(2)
3.930
1.52
166
126
Mn(1)–F(1)–H(1) 127
Mn(1)–F(1)···O(7) 122
The structure was solved by direct methods using
SHELXTL v5.03 [7] and refined by full-matrix least-
squares on F2. Non-hydrogen atoms were refined with
anisotropic displacement parameters. O–H hydrogens
were held fixed where located, all other hydrogens were
treated with a riding model, isotropic temperature fac-
tors were defined as aꢀUeq of the adjacent atom (a=1.5
for OH and 1.2 for all others). Final R1=0.0619,
wR2=0.1035 for 7038 reflections [I\2|(I)] and 703
parameters (R1=0.1501, wR2=0.1308 for all data). A
General bonding details
Mn(1)–C(2)
Mn(1)–C(1)
Mn(1)–P(2)
O(1)–C(1)
1.783(4)
1.843(4)
2.3400(12) Mn(1)–P(1)
1.144(5)
1.146(5)
1.820(5)
2.072(3)
Mn(1)–C(3)
Mn(1)–F(1)
1.842(5)
2.028(2)
2.3482(12)
1.160(5)
1.784(4)
1.837(5)
2.3434(12)
1.148(5)
1.157(4)
O(2)–C(2)
O(3)–C(3)
Mn(2)–C(32)
Mn(2)–C(30)
Mn(2)–P(4)
Mn(2)–C(31)
Mn(2)–O(7)
Mn(2)–P(3)
O(5)–C(31)
2.3511(12) O(4)–C(30)
1.146(5)
O(6)–C(32)
Bond angles
final difference Fourier map was featureless, with the
C(2)–Mn(1)–C(3)
C(3)–Mn(1)–C(1)
C(3)–Mn(1)–F(1)
C(2)–Mn(1)–P(2)
C(1)–Mn(1)–P(2)
C(2)–Mn(1)–P(1)
C(1)–Mn(1)–P(1)
P(2)–Mn(1)–P(1)
89.7(2)
92.3(2)
93.5(2)
C(2)–Mn(1)–C(1)
C(2)–Mn(1)–F(1)
C(1)–Mn(1)–F(1)
91.0(2)
−3
,
highest residual electron density peak of 0.568 e A
.
174.26(14)
93.61(14)
93.42(14)
82.78(7)
176.18(14)
83.59(7)
,
Selected bond lengths (A) and angles (°) for
[(CO)3(dppe)Mn(OH2)···FMn(dppe)(CO)3]BF4 (2) are
shown in Table 1.
92.29(12) C(3)–Mn(1)–P(2)
173.41(13) F(1)–Mn(1)–P(2)
92.99(13) C(3)–Mn(1)–P(1)
90.35(13) F(1)–Mn(1)–P(1)
2.6. Hydrogen-bonding model and ab initio calculations
83.79(4)
C(32)–Mn(2)–C(31) 84.5(2)
C(31)–Mn(2)–C(30) 88.8(2)
C(31)–Mn(2)–O(7)
C(32)–Mn(2)–C(30) 93.7(2)
C(32)–Mn(2)–O(7) 174.2(2)
We have used the hydrogen-bonded cationic complex
Li+(H2O):FLi as a model for that part of the structure
of 2 which exhibits an Mn+(H2O):FMn hydrogen
bond. The structures of this model complex and the
corresponding monomers Li+(H2O) and FLi were ge-
ometry optimized with electron correlation effects in-
cluded at second-order Møller–Plesset perturbation
theory [MBPT(2)=MP2] [8–11] with the 6-31+G(d,p)
basis set [12–15], a valence double-split basis with
polarization functions on all atoms and diffuse func-
tions on all non-hydrogen atoms. This level of theory
has been shown to yield structures of hydrogen-bonded
complexes in agreement with experimental structures
[16]. Harmonic vibrational frequencies were computed
to confirm that the complex and monomers are equi-
librium structures on their respective potential surfaces,
and to evaluate zero-point vibrational energy contribu-
tions to the binding enthalpy at 0 K (DH°). The
electronic binding energy (DEe) has been computed as
the energy for the reaction:
96.08(14)
C(30)–Mn(2)–O(7) 92.13(14) C(32)–Mn(2)–P(4)
C(31)–Mn(2)–P(4) 172.53(13) C(30)–Mn(2)–P(4)
88.49(13)
94.27(14)
92.34(13)
O(7)–Mn(2)–P(4)
C(31)–Mn(2)–P(3)
O(7)–Mn(2)–P(3)
90.60(8)
C(32)–Mn(2)–P(3)
93.74(14) C(30)–Mn(2)–P(3) 173.64(13)
81.82(8) P(4)–Mn(2)–P(3) 83.87(4)
consistent with the previously reported chloro complex
(CO)3(dppe)MnCl (4) [4]. To verify that the fluoride in
3 converts to chloride 4 while in the IR cell, a small
quantity of 3 (ꢀ20 mg) was dissolved in a minimal
amount of CH2Cl2 and excess NaCl(aq) was added. The
mixture was stirred overnight. An IR spectrum taken
immediately after the solution was placed in the cell
and monitored over the course of about 5 min, indi-
cated that the fluoro complex 3 (2024, 1948, 1907
w(CO) cm−1) was completely converted into the chloro
complex 4 (2025, 1955, 1914 w(CO) cm−1).
Li+(H2O)+FLi“Li+(H2O):FLi
(1)
2.5. X-ray structure of 2
For improved energetics, these calculations were carried
out at MP2 with the Dunning correlation-consistent
polarized valence triple-split basis set augmented with
diffuse functions on non-hydrogen atoms (aug%-cc-
pVTZ) [17–19]. For all calculations electrons below the
valence shells were frozen in the Hartree–Fock 1s
orbitals. These calculations were carried out using
GAUSSIAN-98 [20] on the SGI-Origin computer at the
Ohio Supercomputer Center.
Single crystals of 2, [C58H50FO7P4Mn2]BF4.H2O,
were obtained as pale yellow blocks from CH2Cl2/hex-
ane. Crystal data: M=1216.57, triclinic, a=10.655(2),
,
b=15.714(3), c=17.745(2) A, h=74.620(6), i=
3
,
80.021(8), k=84.205(8)°, V=2816.6(7) A , space group
P1, Z=2, Dcalc=1.434 Mg m−3, v=0.532 mm−1. A
(
crystal with dimensions of 0.10×0.10×0.10 mm was
mounted on a glass fiber with epoxy resin, intensity

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T.M. Becker et al. / Journal of Organometallic Chemistry 629 (2001) 165–170
3. Results and discussion
formed (IR) along with the fluoro complex 3. This
indicates cleavage of complex 2 during the reaction.
The reaction was not further investigated.
The aqua complex fac-[(CO)3(dppe)Mn(OH2)]BF4 (1)
is a relatively thermodynamically stable complex but it
reacts rapidly with almost any anionic species to form
neutral complexes in which the site originally occupied
by the aqua ligand is taken up by the anion. We first
became aware of this fact when we discovered that
during the time required to take the infrared spectrum
of a CH2Cl2 solution of this complex in a NaCl cell,
rapid conversion to the corresponding chloro complex,
fac-(CO)3(dppe)MnCl (4) occurred [1]. The small quan-
tity of adventitious water present in the solvent appar-
ently dissolved sufficient NaCl to cause the reaction.
We subsequently prepared authentic chloride by treat-
ing a CH2Cl2 solution of the aqua complex with an
aqueous solution of NaCl [4]. In applying a similar
procedure for the preparation of the fluoro complex,
(CO)3(dppe)MnF (3), we isolated instead, as detailed in
Section 2.1, the rather unusual hydrogen-bonded di-
manganese complex (2) possessing the structure shown
in Fig. 1.
3.3. Molecular structure of
[(CO)3(dppe)Mn(OH2)···FMn(dppe)(CO)3]BF4 (2)
Complex 2 consists of (CO)3(dppe)Mn(OH2) and
(CO)3(dppe)MnF moieties held together by an O–H···F
hydrogen-bond. Although the crystal structure of 2 also
contains a BF4 counterion and an external H2O
molecule, these are not shown in Fig. 1. The
(CO)3(dppe)MnF moiety is structurally similar to the
chloro complexes, (CO)3(P–P)MnCl (P–P=dppe, 4
[22], depe [23] and dppp [24]) in that the Mn is octahe-
drally coordinated with the F, three carbonyls, and the
diphosphine occupying the six bonding sites. The Mn–
,
F distance of 2.028(2) A in 2 is longer than that
commonly observed for M–F bonds [25], however, a
similar lengthening of the M–F bond is observed for
the M–FHF unit in trans-Ru(dmpe)2(H)(FHF), 2.284
,
,
A [26] and Mo(PMe3)4(F)(FHF), 2.124 A [27].
The geometry about the Mn atom in the
(CO)3(dppe)Mn(OH2) moiety is octahedral with an
OH2 molecule occupying one of the coordination sites
3.1. Reactions of [(CO)3(dppe)Mn(OH2)···FMn(dppe)-
(CO)3]BF4 (2) and (CO)3(dppe)MnF (3) with Cl− of
the NaCl infrared cell
,
on the metal. The Mn–O distance, 2.072(3) A, is con-
sistent with the bond distance reported for the triclinic
,
form of 1 [28], 2.075(2) A, the monoclinic form of 1 [1],
In attempting to determine the IR spectrum of 2 in
CH2Cl2 solution, using a NaCl cell, we observed a
change in spectrum with time, quite similar to the same
phenomenon encountered while taking the spectrum of
the aqua complex 1 as discussed above. If the aqua
ligand in the hydrogen-bonded complex 2 were dis-
placed by chloride (provided by the infrared cell) with
concurrent splitting of 2, one might expect a mixture of
the resulting chloro and fluoro complexes. If, in addi-
tion, the fluoro ligand in the fluoro complex were very
labile then this complex might also be converted to the
chloro complex. In fact this turns out to be the case.
When a CH2Cl2 solution of authentic 3 was placed in
the NaCl cell, the change in spectrum demonstrated
that the fluoro complex was completely transformed to
the corresponding chloro complex in about 5 min (see
section Section 2.4). It is indeed surprising that such
fluoride–chloride exchange is so facile. It may be that
F− removal is facilitated by traces of H2O.
,
2.102(3) A, and for [(depe)(CO)3Mn(OH2)]BF4 [1],
,
2.115(2) A. The triclinic structure of 1 crystallizes with
one external molecule of H2O.
The most striking structural feature of 2 is the very
short O–H···F hydrogen-bond distance observed for
the cation, O(7)···F(1)=2.458(3) A, H(1)···F(1)=1.52
A and O(7)–H(1)···F(1)=166°. In contrast, the O–
H···F interaction between the BF4 counterion and the
external H2O is substantially longer (O(8)···F(4)=
2.864(4) A, H(3)···F(4)=1.93 A, 172° and
O(8)···F(3)=3.018(5) A, H(4)···F(3)=2.17 A, 149°).
,
,
,
,
,
,
,
Long O–H···F interactions (O···F=2.68–3.66 A,
H···F=1.80–2.67 A and angles at H of 104–174°) were
,
also observed in monoclinic 1 [1] and triclinic 1 [28]
between the aqua ligand and the BF4 counterion and
also between the BF4 and the external H2O in triclinic
1. In a recent review by Steiner [29], hydrogen-bond
distances to halide ions for organic and organometallic
structures were found to have mean O···F− and H···F−
,
distances of 2.68 and 1.71 A (angles at H\140°) for
3.2. Reaction of [(CO)3(dppe)Mn(OH2)···FMn(dppe)-
(CO)3]BF4 (2) with CO
We have shown previously [21] that when the aqua
complex 1 is treated with CO, the aqua ligand is readily
replaced to give the tetracarbonyl complex [(CO)4-
(dppe)Mn]BF4. When the hydrogen-bonded complex 2
is treated similarly, the same tetracarbonyl complex is
H–O–H donors, this represents the weakest interac-
tion. Hydrogen-bond interactions with donors (D) such
as C–O–H are stronger (mean D···F− and H···F−=
,
2.57, 1.58 A) and the strongest are O–H donors (mean
D···F− and H···F =2.47, 1.50 A) which are bonded to
−
,
the atoms N, P and As.

T.M. Becker et al. / Journal of Organometallic Chemistry 629 (2001) 165–170
169
from The Director, CCDC, 12 Union Road, Cam-
bridge CB2 1EZ, UK (fax: +44-1233-336-033; e-mail:
deposit@ccdc.cam.ac.uk or www: http://www.ccdc.cam.
ac.uk). Structure factors are available upon request
from the authors.
Acknowledgements
CCD data was collected through the Ohio Crystallo-
graphic Consortium, funded by the Ohio Board of
Regents 1995 Investment Fund (CAP-075) located at
the University of Toledo, Instrumentation Center in
A&S, Toledo, OH 43606.
Fig. 2. Calculated bond angles and bond distance for Li+(H2O): FLi.
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To gain further insight of this rather unusual bond-
ing motif, we have examined the model complex Li+
(H2O):FLi, in which Mn(1) (Fig. 1) has been replaced
by Li, and Mn(2) (Fig. 1) by Li+. The optimized
structure of this model complex (see Fig. 2) has features
that are quite similar to those observed experimentally
for 2. When Li+ is bonded to one H2O molecule, the
hydrated ion Li+:H2O has C26 symmetry, with Li+
positioned at the negative end of the water dipole
moment vector. Thus, this species is stabilized by strong
electrostatic attractions. In the model complex Li+
(H2O):FLi, Li+ is similarly bonded to the oxygen.
Because the proton-donor in the model complex is a
cationic species, the O···F distance is very short, at
,
2.443 A, and the O–H···F hydrogen bond is essentially
linear. In addition, the O–F–Li angle is very large at
168°. This orientation does not provide the best orien-
tation for a directed lone pair on F participating in the
hydrogen bond. Rather, in small cationic complexes the
orientation of the proton acceptor molecule tends to
favor a head-to-tail alignment of the bond dipole mo-
ment of the proton donor ion with the dipole moment
of the proton acceptor molecule. In the model complex,
the hydrogen bonded O–H bond of water is lengthened
+
,
,
considerably, from 0.968A in Li (H2O) to 1.028 A in
Li+(H2O):FLi. All of these structural characteristics are
consistent with the presence of a very strong O–H···F
hydrogen bond, which has a computed MP2/aug’-cc-
pVTZ binding energy (DEe) of −38.7 kcal mol−1, and
a binding enthalpy (DH°) of −37.6 kcal mol−1
.
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Raghavachari, J.B. Foresman, J. Cioslowski, J.V. Ortiz, A.G.
4. Supplementary material
Crystallographic data (excluding structure factors)
for the structural analysis have been deposited with the
Cambridge Crystallographic Data Centre, CCDC no.
156936. Copies of this information may be obtained

170
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involved in a bridging motif bonds lengths of 2.00–2.30D are
observed.
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