Asymmetric fluoro-alkynyl mercurials: The synthesis and solid state structures of RHgC=CCF3 (R = Ph, Fc)

Article abstract of DOI:10.1021/om050366q

The fluoro-alkynyl mercurials RHgC=CCF₃ (R = Ph, Fc) have been prepared, from the respective organomercurihalides and LiC=GCF₃, and are the first examples of such materials to be studied crystallographically. These studies have revea

Full text of DOI:10.1021/om050366q

Organometallics 2005, 24, 5487-5490
5487
Asymmetric Fluoro-alkynyl Mercurials: The Synthesis
and Solid State Structures of RHgCtCCF (R ) Ph, Fc)
3
†
Alan K. Brisdon,* Ian R. Crossley, and Robin G. Pritchard
School of Chemistry, The University of Manchester, Manchester M60 1QD, U.K.
Received May 9, 2005
5
Summary: The fluoro-alkynyl mercurials RHgCtCCF3
R ) Ph, Fc) have been prepared, from the respective
in which we are involved, we have sought to obtain and
(
structurally characterize for the first time a series of
trifluoropropynyl-mercurials. We report herein the syn-
thesis and structural investigation of the asymmetric
mercury(II) trifluoropropynyl compounds PhHgCtCCF3
and FcHgCtCCF3.
organomercurihalides and LiCtCCF3, and are the first
examples of such materials to be studied crystallo-
graphically. These studies have revealed the presence of
appreciable mercury-centered intermolecular interac-
tions in the extended structures, including an apparent
mercurophilic interaction.
Results and Discussion
Introduction
We sought to synthesize a “family” of mercurials by
the reactions of the organomercurihalides RHgCl (R )
Me, n-Bu, t-Bu, Ph, (C5H5)Fe(C5H4-) [Fc]) with an
excess of trifluoropropynyllithium (LiCtCCF3), gener-
Despite their inherent toxicity, organomercurials are
among the most widely studied of organometallic com-
pounds, in part because of their synthetic utility as
convenient and efficient organo-transfer reagents, and
more recently for their potential to exhibit closed-shell
5
ated in situ as we have previously described. This met
with limited success; the alkyl derivatives were formed,
19
6
as evident from F NMR studies, but in admixture
with intractable byproducts, and it proved impossible
to effect complete separation due to their appreciable
thermal and photolytic sensitivity. In contrast, the
compounds PhHgCtCCF3 (1) and FcHgCtCCF3 (2)
were each obtained as crystalline solids in high yield
“
mercurophilic” interactions in the solid state.1 The
latter is also one of several factors contributing to the
recent proliferation of research into heavily fluorinated
2
organomercury compounds, which seeks to exploit the
synergy between the inherently Lewis-acidic mercury-
II) center and the potently σ-withdrawing perfluoro-
carbon moiety. There remains, however, a dearth of
compounds containing small, unsaturated organofluo-
rine fragments bound to mercury. Most significantly,
there is currently just a single example of a fluorinated
alkynyl-mercurial: Hg(CtCCF3)2. Indeed, alkynyl-mer-
(
19
1
and purity, as determined from spectroscopic ( F, H,
13
C NMR) and microanalytical data.
The properties of compounds 1 and 2 allowed for the
isolation of X-ray quality single crystals, thus enabling
a structural study to be undertaken. Compounds 1 and
2
represent the first examples of trifluoropropynyl deriv-
3
curials per se have been little explored; the structures
atives of mercury to be crystallographically character-
ized; indeed, only four structural studies of trifluoro-
propynyl compounds have previously been reported, viz.,
of only 20 such materials are recorded by Cambridge
Crystallographic Data Center (CCDC), none of which
are fluorinated.
5b
Ph3ECtCCF3 (E ) C, Si, Ge) and In(CtCCF3)3-
In view of this clear deficiency, and the recent
7
(THF)2. In common with these systems, compounds 1
renaissance in trifluoropropynyl (CtCCF3) chemistry,4
and 2 exhibit largely typical internal geometries (Fig-
ures 1 and 2), with the CtC, C-CF3, and C-F linkages
each lying within 2σ of the mean values for CsptCsp
*
To whom correspondence should be addressed. E-mail:
alan.brisdon@manchester.ac.uk.
†
3
3
8
Present address: Research School of Chemistry, Institute of
[1.183 Å], Csp-Csp [1.466 Å], and Csp -F [1.322 Å],
Advanced Studies, Australian National University, Canberra Austra-
lian Capital Territory 0200, Australia.
respectively. The ancillary R groups (Ph, Fc) are also
largely unremarkable.
1
0
10
(
1) For a general treatment of “metallophilic” d -d interactions
see for example: (a) Grohmann, A.; Schmidbaur, H. In Comprehensive
Organometallic Chemistry II; Wilkinson, G., Stone, F. G. A., Abel, E.
W., Eds.; Pergamon: Oxford, 1995. (b) Schmidbaur, H. Chem. Soc. Rev.
Potentially greater interest resides with the extended
structures of these compounds, and their apparent
influence upon the geometry about mercury. Both 1 and
1
5
995, 24, 391. (c) Mingos, D. M. P. J. Chem. Soc., Dalton Trans. 1996,
61. (d) Pyykk o¨ , P. Chem. Rev. 1997, 97, 597.
(
2) See for example: (a) Omary, M. A.; Kassab, R. M.; Haneline, M.
R.; Elbjeurami, O.; Gabbai, F. P. Inorg. Chem. 2003, 42, 2176. (b)
Tschinkl, M.; Schier, A.; Riede, J.; Gabbai, F. P. Organometallics 1999,
(5) (a) Brisdon, A. K.; Crossley, I. R. Chem. Commun. 2002, 2420.
(b) Brisdon, A. K.; Crossley, I. R.; Pritchard, R. G.; Sadiq, G.; Warren,
J. E. Organometallics 2003, 22, 5534.
1
8, 2040. (c) King, J. B.; Gabbai, F. P. Organometallics 2003, 22, 1275.
(
d) Haneline, M. R.; Tsunoda, M.; Gabbai, F. P. J. Am. Chem. Soc.
002, 124, 3737.
3) See for example: Long, N. J.; Williams, C. K. Angew. Chem.,
Int. Ed. 2003, 42, 2586.
(6) In each case the mercury-bound CtCCF group is apparent from
3
19
2
a singlet resonance in the F NMR spectrum, in the characteristic
alkynyl CF region (ca -50 ppm), exhibiting mercury-satellite coupling
(
3
1
99
(
Hg, I ) 1/2, 16.8%, 15-30 Hz). This is supported by three quartet-
13 1
(
4) (a) Yamazaki, T.; Mizutani, K.; Kitazume, T. J. Org. Chem. 1995,
0, 6046. (b) Katritzky, A. R.; Qi, M.; Wells, A. P. J. Fluorine Chem.
996, 80, 145. (c) Konno, T.; Chae, J.; Kanda, M.; Nagai, G.; Tamura,
K.; Ishihara, T.; Yamanaka, H. Tetrahedron 2003, 59, 7571. (d) Konno,
T.; Daitoh, T.; Noiri, A.; Chae, J.; Ishihara, T.; Yamanaka, H. Org.
Lett. 2004, 6, 933.
based resonances in the C{ H} NMR spectrum, in the region 145-
88 ppm.
6
1
(7) Schumann, H.; Seuss, T. D.; Just, G.; Wetmann, R.; Hemlin, H.;
G o¨ rlitz, F. J. Organomet. Chem. 1994, 479, 171.
(8) Lide, R. Handbook of Chemistry and Physics, 76th ed.; CRC
Press: New York, 1995.
1
0.1021/om050366q CCC: $30.25 © 2005 American Chemical Society
Publication on Web 09/28/2005

5488 Organometallics, Vol. 24, No. 22, 2005
Notes
concomitant reduction of the CtC bond order. The
significance of this argument has on occasion been
questioned,12 and it should be noted that while both 1
and 2 exhibit nonlinear geometry, in neither case is
there significant supporting evidence for a reduction of
the CtC bond order, i.e., from a comparison of vibra-
tional data for the CtC stretching mode in solution (νmax
-
1
-1
2
185 cm ) and the solid state (νmax 2181 cm ).
Figure 1. Representation of the molecular structure of
PhHgCtCCF (1) (30% thermal ellipsoids). Selected bond
distance (Å) and angles (deg): Hg1-C1 2.029(9), Hg1-C10
.052(9), C1-C2 1.192(13), C2-C3 1.465(13), C3-F1 1.327-
11), C3-F2 1.344(12), C3-F3 1.336(11), Hg1-C1-C2
70.2(7), C10-Hg1-C1 175.3(3), C1-C2-C3 174.2(9), C2-
C3-F1 114.7(7), C2-C3-F2 111.5(8), C2-C3-F3 112.2-
8).
2
Notwithstanding, a secondary Hg-η -C2 interaction
3
is clearly apparent in the extended structure of 2 [d(Hg‚
‚‚C1) 3.359(6) Å; d(Hg‚‚‚C2) 3.487(6) Å], the Hg‚‚‚C
distances being below the classically accepted sum of
2
(
13
1
the van der Waals radii [3.4-3.7 Å] and being com-
2d
parable to literature precedent. The analogous inter-
(
action in compound 1 is weaker and asymmetric in
nature, being localized to C2 [d(Hg‚‚‚C2) 3.582(9), d(Hg‚
‚
‚C1) 3.910(8) Å] with the Hg‚‚‚C1 distance apparently
exceeding the sum of van der Waals radii. However,
several recent reports have advocated latitude in the
1
3a,14
interpretation of the mercury radius,
with values
of up to 2.2 Å being proposed.15 Using such a value both
of the Hg‚‚‚C distances of 1 are indicative of interactions,
albeit that Hg‚‚‚C1 is very weak in nature.
Both 1 and 2 exhibit further secondary interactions
that are within the sum of the van der Waals radii, such
that the effective coordination number at each mercury
2
center is six. Thus, the noted Hg-η -C2 interactions are
each augmented by a trans π(CdC)fHg interaction
with a cyclopentadiene [2 d(Hg‚‚‚C10) 3.531(6), d(Hg‚‚
‚C14) 3.363(6) Å] or phenyl [1 C12, C13, C14; d(Hg‚‚‚C)
3.376(9)-3.517(9) Å] ring of an adjacent molecule. The
Figure 2. Representation of the molecular structure of
FcHgCtCCF
distances (Å) and angles (deg): Hg1-C1 2.050(6), Hg1-
C10 2.039(6), C1-C2 1.183(9), C2-C3 1.450(9), C3-F1
significance of these interactions may be contextualized
by comparison with the shortest examples relevant to
3
(2) (30% thermal ellipsoids). Selected bond
16
each case [3.20-3.24 Å for Hg‚‚‚Ccp; 3.24-3.36 for Hg‚
‚‚Carene17]; those in excess of 3.4 Å must thus be deemed
weak. It is noteworthy that complex 1 also exhibits a
strong secondary Hg‚‚‚F interaction [d(Hg‚‚‚F1) 3.199-
1
.335(8), C3-F2 1.344(8), C3-F3 1.341(8), Hg1-C1-C2
78.1(6), C10-Hg-C1 179.4(2), C1-C2-C3 175.9(7), C2-
1
C3-F1 112.9(6), C2-C3-F2 112.5(6), C2-C3-F3 112.7-
(
5).
(7) Å].
The structure of 2 also exhibits evidence of mercuro-
2
exhibit appreciable deviation from linearity of the
philic interactions that are strongly implicated in the
arrangement of the molecules through the crystal. When
viewed along the c direction, adjacent molecules align
in a criss-cross fashion in such a way as to form a linear
arrangement of successive Hg‚‚‚Hg interactions [d(Hg‚
alkynyl function [∠ CtC-C 174.2(9)° 1; 175.9(7)° 2],
with 1 also exhibiting a significantly “bent” geometry
about the Hg(II) center [∠ C-Hg-C 175.3(3)°, ∠ Hg-
CtC 170.2(7)°]. This latter effect is also present in 2
but is somewhat less pronounced [179.4(2)° and 178.1-
‚
‚Hg) 4.0882(3) Å], as shown in Figure 3. The signifi-
(
6)°, respectively]. Although there is only a limited range
cance of these interactions is, however, dependent upon
the chosen value of the mercury radius (vide supra).
of structurally characterized alkynyl-mercurials, such
distortions are common among them, particularly in the
cases of Hg(CtCPh)2 [∠ (Hg-CtC) 170.4(17)°; ∠ (CtC-
CPh) 174(2)°] and PhHgCtCPh [∠ Hg-CtC 171.9(15)°;
∠
13b
Thus, if a classical value of 1.73-2.00 Å is applied,
then the distance is more than twice the van der Waals
radius and therefore may be deemed largely superficial.
However, adopting a value in excess of 2.00 Å would
render the interaction much more significant. Indeed,
interactions at similar distances have previously been
9
10
(C-Hg-C) 176.6(7)°], the closest available analogue
11
of 1, although other examples have been recorded.
The origin of these effects has, however, been little
discussed, although it is believed to arise from inter-
molecular π(CtC)fHg interactions, which result in
distortion of the coordination geometry at mercury, with
(12) Weak packing forces have been suggested as the basis for these
“small” deviations from linearity, rather than intrinsic electronic
effects. But it is questionable whether such packing forces alone would
be sufficient to account for the observed (10°) distortion from linearity.
(13) (a) Pyykk o¨ , P.; Straka, M. Phys. Chem. Chem. Phys. 2000, 2,
2489. (b) Canty, A. J.; Deacon, G. B. Inorg. Chim. Acta 1980, 45, L225.
(c) Caillet, C.; Claverie, P. Acta Crystallogr. Sect. A 1975, 31, 448.
(14) (a) Casa, J. S.; Garcia-Tasende, M. S.; Sardo, J. Coord. Chem.
Rev. 1999, 195, 283. (b) Flower, K. R.; Howard, V. J.; Naguthney, S.;
Pritchard, R. G.; Warren, J. E. Inorg. Chem. 2002, 41, 1907.
(15) Batsanov, S. S. J. Chem. Soc., Dalton Trans. 1998, 1541.
(16) Haneline, M. R.; Gabbai, F. P. Angew. Chem., Int. Ed. 2004,
43, 5471.
(
9) Faville, S. J.; Henderson, W.; Mathieson, T. J.; Nicholson, B. K.
J. Organomet. Chem. 1999, 580, 363.
10) Deacon, G. B.; Field, L. D.; Forsyth, C. M.; Kay, D. L.; Masters,
A. F. Manuscript in preparation.
11) See for instance: (a) Wong, W.-Y.; Choi, K.-H.; Lu, G.-L.
(
(
Organometallics 2002, 21, 4475. (b) Hartbaum, C.; Roth, G.; Fischer,
H. Eur. J. Inorg. Chem. 1999, 191. (c) Hoskins, B. F.; Robson, R.;
Sutherland, E. E. J. Organomet. Chem. 1996, 515, 259. (d) Wong, W.-
Y.; Choi, K.-H.; Lu, G.-L.; Shi, J.-X.; Lai, P.-Y. Organometallics 2001,
2
0, 5448.
(17) Tsunoda, M.; Gabbai, F. P. J. Am. Chem. Soc. 2000, 122, 8335.

Notes
Organometallics, Vol. 24, No. 22, 2005 5489
handling such materials and their solutions. Reactions were
performed in well-ventilated fume hoods, using standard inert
atmosphere techniques. Diethyl ether was dried over sodium
wire for ca. 1 day prior to use. The compounds RHgCl (R )
Me, n-Bu, t-Bu) were prepared by metathesis between HgCl
and RLi (MeLi, 1.6 M in ether; n-BuLi, 2.5 M in hexane;
t-BuLi, 1.7 M in pentane (Across)); CF CH CF H (HFC-245fa,
Honeywell), FcHgCl and PhHgCl (Aldrich) were used as
supplied. NMR spectra (CDCl ) were recorded on Bruker
DPX200 ( F, 188.310 MHz with respect to CFCl ) or DPX400
C, Dept-135, 100.555 MHz; H 400.4 MHz, with respect to
SiMe ) spectrometers. Infrared (CHCl , KBr plates) and Ra-
2
3
2
2
3
1
9
3
1
3
1
(
4
3
man spectra were recorded on a Nicolet Nexus FTIR/Raman
spectrometer. Elemental analyses were performed by the
UMIST microanalytical service.
General Synthetic Procedure. With the exclusion of
3
light, under N
2
3
, a stirred ethereal solution (100 cm ) of HFC-
3
Figure 3. View of the packing of FcHgCtCCF
3
(2) along
245fa (0.45 cm , 4.43 mmol) was treated with n-BuLi (4.80 cm ,
12.00 mmol), at -10 °C, then after 20 min. RHgCl (3.20 mmol)
in ether (20 cm ) was added. After stirring overnight at 0 °C
the c axis. Thermal ellipsoids are set at the 30% probability
3
level, and hydrogen atoms are omitted for clarity.
the reaction was allowed to attain ambient temperature, then
3
ascribed to mercurophilicity; for example, a distance of
hexane (200 cm ) added to precipitate the inorganic salts; the
4
.077 Å is calculated for the Hg‚‚‚Hg separation in the
settled mixture was filtered through Celite and the solvent
removed in vacuo. For R ) Me, Bu see Supporting Information.
PhHgCtCCF
n-BuLi (3.25 cm , 8.13 mmol), PhHgCl (0.640 g, 2.04 mmol).
Yield: 0.634 g, 84%. Anal. Calcd for C
.4; F, 15.4. Found: C, 31.0; H, 1.2; F, 15.6. δ
18
extended structure of HgH2, while distances of 3.811-
.093 Å are reported for trimeric perfluoro ortho-
3
4
3
3
(1). From HFC-245fa (0.30 cm , 2.96 mmol),
3
d
phenylene mercury. It is an assumed fact that inter-
actions close to, or in excess of, 4 Å are weakscf. the
shortest reported example of 3.1463(6) Å in Hg-
9
H
5
F
3
Hg: C, 29.2; H,
4
1
F
-50.1 ( JHgF
1
19
26.0 Hz). δ 132.8 [q, 7.3, J
HgC 3
1458.3, CtCCF ], 111.6 [q,
(SiMe3)2 showever, given the literature precedent, and
C
3
3 3
57.2, JHgC 37.1 CF JHgC 405.5 CtCCF ],
], 90.2 [q, 50.1, 2
2
1
[
the apparent significance to the crystal packing adopted
by 2, these interactions would, in this case, seem
appropriately classified as a manifestation of mercuro-
philicity.
55.3 [s, C, JHgC 1828.9 Hz], 136.4 [s, CH, JHgC 94.5 Hz], 128.5
7.6-7.2 (m). νmax/cm- 2185 (CtC
1
s, CH, JHgC 24.7 Hz]. δ
str), 1247, 1139 (C-F str).
FcHgCtCCF
H
3
3
(2). From HFC-245fa (0.50 cm , 4.82 mmol),
3
n-BuLi (5.70 cm , 14.25 mmol), FcHgCl (1.000 g, 2.37 mmol).
Conclusion
Yield: 0.995 g, 88%. Anal. Calcd for C13
H
9
F
3
FeHg: C, 32.6;
4
H, 1.9; F, 11.9. Found: C, 32.8; H, 1.9; F, 11.6. δ
7.1 Hz). δ 136.1 [q, 6.8, CtCCF ], 111.7 [q, 257.0, CF
q, 50.2, CtCCF ], 83.7 [q, C, JCF 1.0 Hz], 74.6 [s, CH, JHgC
63.2 Hz], 71.2 [s, CH, JHgC 137.1 Hz], 68.4 [s, CH]. δ 4.4 (br
m, JHgH 20.8 Hz, 2H), 4.3 (br m, JHgH 21.1 Hz, 5H), 4.1 (br m,
HgH 39.7 Hz, 2H). νmax/cm 2185 (CtC str), 1247, 1141 (C-F
str).
X-ray Crystallography. Data were recorded on a Nonius
κ-CCD four-circle diffractometer using Mo KR radiation (λ )
.71073 Å) at 120(2) K, solved using direct methods, and
subject to full-matrix least-squares refinement on F using
SHELX-97. Absorption correction was by the multiscan
method. Non-hydrogen atoms were refined with anisotropic
thermal parameters, while hydrogen atoms were included in
idealized positions and refined isotropically. Geometric analy-
F
-50.1 ( JHgF
The first attempt to prepare asymmetric mercurials
of the type RHgCtCCF3 has revealed that, as with
many alkynyl mercurials, where R ) alkyl instability
precludes effective isolation. Where R ) Ph or Fc, the
compounds are stable and have been isolated and fully
characterized. These compounds are amenable to crys-
tallographic characterization, thus allowing the first
structural study of any RHgCtCCF3 compounds: a
significant development given the dearth of structurally
characterized alkynyl-mercurials. This has revealed
largely typical intramolecular geometries, though with
appreciable distortion of the alkynyl unit and mercury-
2
C
3
3
], 90.1
[
3
1
H
-1
J
0
2
2
0
(
II) center from linearity, attributed to intermolecular
2
Hg-η -C2 association. A network of intermolecular Hg‚
‚C and Hg‚‚‚F interactions is elucidated, including, for
‚
21
ses were performed using Platon, and figures generated with
ORTEP 3 for Windows. Data for 1: C
orthorhombic, P2 (no. 19), a ) 5.8459(1) Å, b ) 8.4130(2)
the ferrocenyl compound 2, an apparent mercurophilic
interaction. Taken together these observations offer
further experimental support for the current debate as
to the most appropriate van der Waals radius of
mercury, for which a value of at least 2.00 Å has been
suggested.
22
9 5 3
H F Hg, M ) 370.72,
1 1 1
2 2
3
c
Å, c ) 18.2492(5) Å, V ) 897.52(4) Å , z ) 4, D ) 2.744 g
cm-3, µ ) 17.141 mm-1, θ ) 3.66-27.46°, 2045 unique
reflections, 119 parameters, R ) 0.0443, wR 0.1096. Data for
FeHg, M ) 478.64, monoclinic, P2
6.0728(6) Å, b ) 9.7449(3) Å, c ) 8.1183(3) Å, â ) 100.8620-
10)°, V ) 1248.77(8) Å , z ) 4, D ) 2.546 g cm , µ ) 13.453
c
mm , θ ) 3.30-27.39°, 2840 unique reflections, 164 param-
2
2: C13H
9
F
3
1
/c (no. 14), a )
1
(
3
-3
Experimental Section
-
1
General Methods. CAUTION! Organomercurials are highly
toxic and prone to disproportionation; fluorinated derivatives
are potentially volatilesextreme care is necessary when
eters, R ) 0.0366, wR 0.0924.
2
(20) Sheldrick, G. M. SHELX-97; Institut fur Anorganische Chemie
der Universitat Gottingen: Gottingen, Germany, 1998.
(21) Spek, A. L. Acta Crystallogr. Sect. A 1990, 46, C34.
(22) ORTEP 3 for Windows: Farrugia, L. J. J. Appl. Crystallogr.
1997, 30, 565.
(
(
18) Wang, X.; Andrews, L. Inorg. Chem. 2004, 43, 7146.
19) Pickett, N. L.; Just, O.; VanDerveer, D. G.; Rees, W. S., Jr. Acta
Crystallogr. Sect. C 2000, 56, 412.

5490 Organometallics, Vol. 24, No. 22, 2005
Notes
Acknowledgment. We thank the Engineering and
Supporting Information Available: For the single-
crystal structure determinations, tables of crystal data and
structure refinement, atomic coordinates, anisotropic displace-
ment parameters, bond lengths, bond angles, and an X-ray
crystallographic file, in CIF format. Synthetic procedures and
Physical Sciences Research Council (EPSRC) and UMIST
for financial support and Honeywell Specialty Chemi-
cals for donation of HFC-245fa. We acknowledge the
EPSRC for support of the UMIST NMR (GR/L52246)
and FT/IR Raman (GR/M30135) facilities and for access
to the Chemical Database Service at Daresbury. We
thank the EPSRC National Crystallographic Service,
Department of Chemistry, University of Southampton,
for data collections for compounds 1 and 2.
spectroscopic data for RHgCtCCF (R ) Me, t-Bu, n-Bu). This
3
material is available free of charge via the Internet at
http://pubs.acs.org.
OM050366Q