Complexation of aldehydes and ketones by trimeric perfluoro-ortho-phenylene mercury, a tridentate Lewis acid

Article abstract of DOI:10.1021/om020276a

A series of adducts formed by the interaction of trimeric perfluoro-ortho-phenylene mercury (2) with various organic carbonyls including acetaldehyde, acetone, acetophenone, and benzophenone have been characterized. The crystal structures of [2·μ₃acetaldehyde] (3) and [2·μ₃-benzophenone] (7), respectively, reveal the formation of 1:1 complexes in which one molecule of the organic carbonyl is concomitantly coordinated to the three mercury centers of 2 via the oxygen atom. In the benzophenone adduct 7, one of the phenyl rings of the coordinated benzophenone molecule engages in an intramolecular arene - fluoroarene interaction with a tetrafluorophenylene ring of 2 (intercentroid distance: 3.687 A?). When 2 is combined with acetone and acetophenone, adducts [2-(acetone)(μ₃-acetone)₂] (4) and [2·(μ₃-acetophenone)2] (6) are obtained. In both cases, two molecules of the ketone are positioned on each side of the planar trifunctional Lewis acid and are complexed via their respective oxygen atom to the three mercury centers of 2. In 4, a third molecule of acetone acts as a terminal ligand and forms a relatively long bond with one of the mercury atoms. In 3, 4, 6, and 7 the Hg-O bonds formed by the triply bridging carbonyl substrate range from 2.813(6) to 3.056(14) and are within the sum of the van der Waals radii of oxygen and mercury. In all cases, the carbonyl stretching vibration of the carbonyl substrate is shifted to a lower wavenumber, which suggests a weakening of the C=O bond.

Full text of DOI:10.1021/om020276a

Organometallics 2002, 21, 4201-4205
4201
Com p lexa tion of Ald eh yd es a n d Keton es by Tr im er ic
P er flu or o-or th o-p h en ylen e Mer cu r y, a Tr id en ta te Lew is
Acid
J ulie Beckwith King, Mitsukimi Tsunoda, and Franc¸ois P. Gabba¨ı*
Chemistry Department, Texas A&M University, 3255 TAMU, College Station, Texas 77843
Received April 5, 2002
A series of adducts formed by the interaction of trimeric perfluoro-ortho-phenylene mercury
(2) with various organic carbonyls including acetaldehyde, acetone, acetophenone, and
benzophenone have been characterized. The crystal structures of [2‚µ3-acetaldehyde] (3) and
[2‚µ3-benzophenone] (7), respectively, reveal the formation of 1:1 complexes in which one
molecule of the organic carbonyl is concomitantly coordinated to the three mercury centers
of 2 via the oxygen atom. In the benzophenone adduct 7, one of the phenyl rings of the
coordinated benzophenone molecule engages in an intramolecular arene-fluoroarene
interaction with a tetrafluorophenylene ring of 2 (intercentroid distance: 3.687 Å). When 2
is combined with acetone and acetophenone, adducts [2‚(acetone)(µ3-acetone)2] (4) and [2‚
(µ3-acetophenone)2] (6) are obtained. In both cases, two molecules of the ketone are positioned
on each side of the planar trifunctional Lewis acid and are complexed via their respective
oxygen atom to the three mercury centers of 2. In 4, a third molecule of acetone acts as a
terminal ligand and forms a relatively long bond with one of the mercury atoms. In 3, 4, 6,
and 7 the Hg-O bonds formed by the triply bridging carbonyl substrate range from 2.813(6)
to 3.056(14) and are within the sum of the van der Waals radii of oxygen and mercury. In
all cases, the carbonyl stretching vibration of the carbonyl substrate is shifted to a lower
wavenumber, which suggests a weakening of the CdO bond.
In tr od u ction
tional organomercurials is readily observed and is
apparently facilitated by the relatively high basicity of
these carbonyl substrates.9 Ketones and aldehydes,
however, are much less basic and,9 as a result, less
prone to multiple coordination.10 In fact, while NMR
studies have suggested the chelation of ketones,11 only
on one occasion has a bimolecular complex featuring a
chelated ketone been isolated and characterized by
X-ray diffraction methods.12,15 This complex, [1‚µ2-
acetone], involves the bidentate Lewis acid 1,2-bis-
(chloromercurio)tetrafluorobenzene (1), whose acceptor
properties are enhanced by the presence of an electron-
withdrawing backbone. Interestingly, attempts to iso-
late such complexes with aldehydes have led only to the
isolation of adducts in which the carbonyl substrate
adopts a terminal rather than bridging position.16 In
this paper, we report on the multiple coordination of
The multiple activation of organic carbonyls by poly-
dentate Lewis acids is an emerging paradigm in organic
catalysis. Indeed, a series of investigations have shown
that polyfunctional Lewis acids are valuable catalysts
for reactions involving organic carbonyls such as alde-
hydes and ketones.1-3 It has been proposed that the high
catalytic activity observed in these reactions results
from the ability of the polydentate Lewis acid to chelate
the carbonyl oxygen atom. On a few occasions, related
phenomena have been discovered in reactions involving
thioketones and thionoesters as substrates.4-6 Although
kinetic studies suggest the multiple activation of ke-
tones and aldehydes, structural data supporting this
phenomenon are extremely scarce. As shown by Wuest,7,8
the multiple coordination of formamides by polyfunc-
* To whom inquiries should be addressed.
(1) Ooi, T.; Takahashi, M.; Maruoka, K. J . Am. Chem. Soc. 1996,
118, 11307-11308.
(9) Lamsabhi, A. M.; Bouab, W.; Esseffar, M.; Alcami, M.; Yanez,
M.; Abboud, J . M. New J . Chem. 2001, 25, 509-517.
(10) Koehler, K.; Piers, W. E. Can. J . Chem. 1998, 76, 1249-1255.
(11) Reilly, M.; Oh, T. Tetrahedron Lett. 1995, 36, 217-220.
(12) Tschinkl, M.; Schier, A.; Riede, J .; Gabba¨ı, F. P. Organometallics
1999, 18, 1747-1753.
(2) Ooi, T.; Tayama, E.; Takahashi, M.; Maruoka, K. Tetrahedron
Lett. 1997, 38, 7403-7406.
(3) Maruoka, K. Organomet. News 1995, 2, 29-33.
(4) Wuest, J . D.; Zacharie, B. J . Am. Chem. Soc. 1985, 107, 6121-
6123.
(5) Lee, H.; Diaz, M.; Hawthorne, M. F. Tetrahedron Lett. 1999, 40,
7651-7655.
(6) For the double coordination of thioamides, see: Lopez, P.; Oh,
T. Tetrahedron Lett. 2000, 41, 2313-2317.
(7) Wuest, J . D. Acc. Chem. Res. 1999, 32, 81-89.
(8) Vaugeois, J .; Wuest, J . D. J . Am. Chem. Soc. 1998, 120, 13016-
13022.
(13) For an intramolecular version of such complexes, see: Sharma,
V.; Simard, M.; Wuest, J . D. J . Am. Chem. Soc. 1992, 114, 7931-
7933.
(14) Reilly, M.; Oh, T. Tetrahedron Lett. 1995, 36, 221-224.
(15) Cottone, A., III; Scott, M. J . Organometallics 2000, 19, 5254-
5256.
(16) Beckwith, J . D.; Tschinkl, M.; Picot, A.; Tsunoda, M; Gabbai,
F. P. Organometallics 2001, 20, 3169-3174.
10.1021/om020276a CCC: $22.00 © 2002 American Chemical Society
Publication on Web 08/28/2002

4202 Organometallics, Vol. 21, No. 20, 2002
Ta ble 1. Cr ysta l Da ta , Da ta Collection , a n d Str u ctu r e Refin em en t for 3, 4, 6, a n d 7
King et al.
3
4
6
7
Crystal Data
formula
Mr
C
20H4F12Hg3O
C27H18F12Hg3O3
1220.18
0.26 × 0.26 × 0.17
triclinic
P1h
9.3365(19)
10.684(2)
15.466(3)
79.47(3)
83.04(3)
84.57(3)
1501.4(5)
2
C34H16F12Hg3O2
1286.24
0.21 × 0.04 × 0.04
monoclinic
P21/n
11.098(2)
17.058(3)
17.319(4)
C31H10F12Hg3O
1228.16
0.39 × 0.15 × 0.14
monoclinic
P21/n
9.9401(7)
19.6770(15)
14.3063(10)
90
91.4750(10)
90
2797.3(4)
4
1090.00
0.46 × 0.27 × 0.17
monoclinic
P21/m
6.9082(17)
15.665(4)
9.727(2)
90
100.265(7)
90
1035.7(4)
2
cryst size (mm3)
cryst syst
space group
a (Å)
b (Å)
c (Å)
â (deg)
92.30(3)
V (Å3)
3276.2(11)
4
2.608
14.124
2336
Z
F
calc (gcm-3
)
3.495
22.300
960
2.699
15.404
1104
2.916
16.532
2208
µ(Mo KR) (mm-1
F(000) (e)
)
Data Collection
T (K)
110(0)
110(0)
110(0)
110(0)
scan mode
hkl range
ω
ω
ω
ω
-3f6, -18f15,
-11f7
-10f10, -12f12,
-17f17
13 508
-10f13, -19f20,
-20f20
16 891
-11f11, -20f21,
-12f15
12 280
no. of reflns measd
4949
no. of unique reflns, [Rint
no. of reflns used for refinement
abs corr
]
1506 [0.0469]
1506
empirical
0.2716/0.7389
4714 [0.0276]
4714
SADABS
0.4164/1
5747 [0.0587]
5747
SADABS
0.4031/1
3987 [0.0576]
3987
empirical
0.4233/0.9417
T
min/ Tmax
Refinement
no. of params refined
169
406
460
424
R1, wR2 [I>2σ(I)]
0.0417, 0.1070
4.354, -2.673
0.0353, 0.0955
3.183, -1.999
0.0705, 0.1500
2.645, -3.122
0.0292, 0.0738
1.738, -1.275
Ffin (max/min) (e Å-3
)
R1 ) ∑(Fo - Fc)/∑Fo. bwR2 ) {[∑w(Fo - Fc2)2]/[∑w(Fo2)2]}1/2; w ) 1/[σ2(Fo2) + (ap)2 + bp]; p ) (Fo + 2Fc2)/3; a ) 0.0838 (3), 0.0732
(4), 0.0289 (6); 0.0508 (7); b ) 11.2989 (3), 2.93 (4), 200 (6), 0.4977 (7).
a
2
2
Ta ble 2. Hg-O Dista n ces (Å) in th e Str u ctu r e of 3,
acetaldehyde, acetone, acetophenone, and benzophenone
4, 6, a n d 7
by trimeric perfluoro-ortho-phenylene mercury (2).17,18
Compound 3
Hg(1)-O(1) ) 2.912(13)
Hg(2)-O(1) ) 2.965(8)
Compound 4
Hg(1)-O(1) ) 2.978(6)
Hg(2)-O(1) ) 2.813(6)
Hg(3)-O(1) ) 2.899(6)
Hg(1)-O(2) ) 3.088(8)
Hg(1)-O(3) ) 2.905(6)
Hg(2)-O(3) ) 2.858(6)
Hg(3)-O(3) ) 2.814(6)
Compound 6
Hg(1)-O(1) ) 2.910(14)
Hg(2)-O(1) ) 2.873(16)
Hg(3)-O(1) ) 2.883(14)
Hg(1)-O(2) ) 2.841(13)
Hg(2)-O(2) ) 3.056(14)
Hg(3)-O(2) ) 2.956(15)
Compound 7
Hg(1)-O(1) ) 2.953(5)
Hg(2)-O(1) ) 2.888(5)
Hg(3)-O(1) ) 3.047(5)
Resu lts
distances fall within the narrow range 2.912(13)-
2.965(8) Å (Table 2, Figure 1). As a result, the oxygen
atom is essentially equidistant from the three Lewis
acidic sites and sits 2.086 Å from the plane defined by
the three mercury atoms. The linear carbonyl function-
ality is not perpendicular to the plane of the trinuclear
complex with which it forms an angle of 66.4°. The
carbonyl stretching frequency of the coordinated acet-
aldehyde (νCO ) 1706 cm-1) is substantially shifted to
a lower wavenumber when compared to that of the pure
acetaldehyde (νCO ) 1726 cm-1). Crystals of 3 are stable
for several weeks at room temperature. Thermal gravi-
metric analysis (TGA) shows that acetaldehyde loss
occurs in one step at 120 °C, which further substantiates
the stability of this 1:1 adduct. Altogether, these results
contrast with the previous observation that acetalde-
hyde does not coordinate to bifunctional 1.16
In ter a ction of 2 w ith Aceta ld eh yd e. Compound 2
dissolves spontaneously in excess acetaldehyde. Slow
concentration of the resulting solution yields large
crystals of [2‚µ3-acetaldehyde] (3), whose elemental
analysis corresponds to that expected for a 1:1 complex.
Compound 3 crystallizes in the monoclinic space group
P21/m with two molecules in the unit cell (Table 1).
Examination of the atomic connectivity confirms the
simultaneous coordination of the carbonyl oxygen atom
to the mercury centers of 2. The resulting Hg-O
(17) Sartori, P.; Golloch, A. Chem. Ber. 1968, 101, 2004-2009.
(18) (a) Chistyakov, A. L.; Stankevich, I. V.; Gambaryan, N. P.;
Struchkov, Y. T.; Yanovsky, A. I.; Tikhonova, I. A.; Shur, V. B. J .
Organomet. Chem. 1997, 536, 413-424. (b) Shubina, E. S.; Tikhonova,
I. A.; Bakhmutova, E. V.; Dolgushin, F. M.; Antipin, M. Y.; Bakhmutov,
V. I.; Sivaev, I. B.; Teplitskaya, L. N.; Chizhevsky I. T.; Pisareva I. V.;
Bregadze V. I.; Epstein L. M.; Shur V. B. Chem. Eur. J . 2001, 7, 3783-
3790.

Perfluoro-ortho-phenylene Mercury
Organometallics, Vol. 21, No. 20, 2002 4203
F igu r e 3. Solid-state structure of 6. ORTEP drawing
(50%). Hydrogen and fluorine atoms have been omitted for
clarity. Selected bond lengths [Å] and angles [deg]: O(2)-
C(09) 1.23(2), O(1)-C(01) 1.24(2); O(2)-Hg(1)-O(1) 91.9(4),
O(1)-Hg(2)-O(2) 88.3(4), O(1)-Hg(3)-O(2) 90.1(4), C(09)-
O(2)-Hg(1) 115.1(12), C(09)-O(2)-Hg(3) 128.6(14), Hg(1)-
O(2)-Hg(3) 75.9(4), C(09)-O(2)-Hg(2) 157.0(15), Hg(1)-
O(2)-Hg(2) 74.5(3), Hg(3)-O(2)-Hg(2) 73.0(3), C(01)-
O(1)-Hg(2) 126.1(18), C(01)-O(1)-Hg(3) 136.4(13), Hg(2)-
O(1)-Hg(3) 76.8(4), C(01)-O(1)-Hg(1) 139.9(15), Hg(2)-
O(1)-Hg(1) 76.4(3), Hg(3)-O(1)-Hg(1) 76.0(3), O(1)-
C(01)-C(02) 123(3), O(1)-C(01)-C(08) 118(3), O(2)-C(09)-
C(010) 122(2), O(2)-C(09)-C(016) 120(2).
F igu r e 1. Structure of 3 in the crystal. ORTEP drawing
(50%). Hydrogen atoms have been omitted for clarity.
Selected bond lengths [Å] and angles [deg]: O(1)-C(01)
1.19(2); C(1)-Hg(1)-O(1) 88.5(3), C(2)-Hg(2)-O(1) 87.5(4),
C(7)-Hg(2)-O(1) 91.6(4), C(01)-O(1)-Hg(1) 112.0(13),
C(01)-O(1)-Hg(2) 142.75(19), Hg(1)-O(1)-Hg(2) 76.2(2),
O(1)-C(01)-C(02) 129(2).
with two molecules in the unit cell. One of the acetone
molecules of the adduct is terminally ligated to Hg(1)
via a relatively long contact of 3.088(8) Å (Figure 2). The
other two acetone molecules are located above and below
the plane of the trinuclear complex and interact simul-
taneously with the three mercury atoms via formation
of Hg-O interactions that range from 2.813(6) to
2.978(6) Å (Table 2) as observed in the structure of 3.
This situation is reminiscent of that recently encoun-
tered by Shur in a bis-acetonitrile complex of 2.20 The
linear carbonyl functionalities of the triply bridging
acetone molecules are oriented almost perpendicularly
to the plane of the trinuclear complex with which they
form angles of 81.8° and 79.5°. Crystals of 4 become
quickly opaque and brittle through partial loss of
acetone when removed from the mother liquor. Elemen-
tal analysis carried out on the resulting material
indicates the loss of exactly 2 equiv of acetone. This
observation suggests the formation of a stable 1:1 adduct
2‚acetone (5). While the structure of this adduct is
unknown, infrared studies show a shift of the carbonyl
F igu r e 2. Solid-state structure of 4. ORTEP drawing
(40%). Hydrogen and fluorine atoms have been omitted for
clarity. Selected bond lengths [Å] and angles [deg]: O(1)-
C(101) 1.212(10), O(2)-C(201) 1.193(12), O(3)-C(301)
1.201(10); O(3)-Hg(1)-O(1) 85.46(17), O(3)-Hg(1)-O(2)
67.59(18), O(1)-Hg(1)-O(2) 152.98(19), O(1)-Hg(2)-O(3)
89.50(17), O(3)-Hg(3)-O(1) 88.64(17), C(101)-O(1)-Hg(2)
138.8(6), C(101)-O(1)-Hg(3) 126.0(5), Hg(2)-O(1)-Hg(3)
77.77(15), C(101)-O(1)-Hg(1) 137.1(6), Hg(2)-O(1)-Hg(1)
76.78(14), Hg(3)-O(1)-Hg(1) 75.04(14), C(201)-O(2)-
Hg(1) 125.9(7), C(301)-O(3)-Hg(3) 133.5(6), C(301)-O(3)-
Hg(2) 142.1(6), Hg(3)-O(3)-Hg(2) 78.44(15), C(301)-O(3)-
Hg(1) 123.3(6), Hg(3)-O(3)-Hg(1) 77.48(15), Hg(2)-O(3)-
Hg(1) 77.26(15), O(1)-C(101)-C(103) 121.7(9), O(1)-
C(101)-C(102) 118.4(9), O(2)-C(201)-C(202) 119.9(10),
O(2)-C(201)-C(203) 123.8(11), O(3)-C(301)-C(302)
120.4(9), O(3)-C(301)-C(303) 122.8(10).
stretching frequency to 1683 cm-1 (compared to νCO
)
1716 cm-1 for neat acetone). These results suggest that
the remaining molecule of acetone is multiply coordi-
nated to the mercury centers of 2. In support of this
view, we note that a shift of 1693 cm-1 was observed in
[1‚µ2-acetone].12
In ter a ction of 2 w ith Acetop h en on e. A crystalline
acetophenone adduct, [2‚(µ3-acetophenone)2] (6), can be
obtained upon slow concentration of a solution of 2 in
this ketone. As in the case of the acetone complex,
crystals of 6 become brittle when exposed to a dry
atmosphere. A low-temperature single-crystal X-ray
diffraction study of 6 indicates that this adduct crystal-
lizes in the monoclinic space group P21/n with four
molecules in the unit cell. Its structure is that of a 2:1
complex in which two molecules of acetophenone are
In ter a ction of 2 w ith Aceton e. The interaction of
2 with acetone has been previously studied, although
no details are available on the structure and stoichi-
ometry of the resulting complex.19 We have found that
slow concentration of an acetone solution of 2 yields [2‚
(acetone)(µ3-acetone)2] (4), in which three molecules of
acetone are bound to the trifunctional Lewis acid.
Compound 4 crystallizes in the triclinic space group P1h
(20) Tikhonova, I. A.; Dolgushin, F. M.; Yanovsky, A. I.; Starikova,
Z. A.; Petrovskii, P. V.; Furin, G. G.; Shur, V. B. J . Organomet. Chem.
2000, 613, 60-67.
(19) Ball, M. C.; Brown, D. S.; Massey, A. G.; Wickens, D. A. J .
Organomet. Chem. 1981, 206, 265-277.

4204 Organometallics, Vol. 21, No. 20, 2002
King et al.
Ta ble 3. Mer cu r y Ca r bon Dista n ces (Å) for th e
P olyh a p to-π In ter a ction s in th e Str u ctu r e of 7
Hg(2)-C(09) ) 3.626a
Hg(2)-C(010) ) 3.518a
Hg(2)-C(011) ) 3.571a
a
0.5 + x, 1.5 - y, 0.5 + z.
mercury centers of the neighboring monomer. These
Hg-C contacts range from 3.517 to 3.626 Å (Table 3).
Infrared studies show only a moderate shift of the
carbonyl stretching frequency when compared to that
of pure benzophenone (1647 vs 1650 cm-1 for the pure
ketone).
Discu ssion
The structures of 3, 4, 6, and 7 show that triple
coordination of the carbonyl oxygen atom of both alde-
hydes and ketones is a readily observable phenomenon.
The Hg-O bond distances in 3, 4, 6, and 7 are within
F igu r e 4. Solid-state structure of 7. ORTEP drawing
(50%). Hydrogen atoms have been omitted for clarity.
Selected bond lengths [Å] and angles [deg]: O(1)-C(01)
1.217(8); C(1)-Hg(1)-C(8) 176.6(3), C(1)-Hg(1)-O(1)
88.4(2), C(8)-Hg(1)-O(1) 88.6(2), C(7)-Hg(2)-O(1) 88.9(2),
C(14)-Hg(2)-O(1) 92.7(2), C(2)-Hg(3)-O(1) 85.8(2), C(13)-
Hg(3)-O(1) 91.4(2), C(01)-O(1)-Hg(2) 164.9(5), C(01)-
O(1)-Hg(1) 118.3(5), Hg(2)-O(1)-Hg(1) 75.88(11), C(01)-
O(1)-Hg(3) 102.9(4), Hg(2)-O(1)-Hg(3) 75.19(11), Hg(1)-
O(1)-Hg(3) 73.23(11), O(1)-C(01)-C(08) 118.2(7), O(1)-
C(01)-C(02) 121.0(7).
the sum of the van der Waals radii for oxygen (rvdw
)
1.54 Å)21 and mercury (rvdw ) 1.73-2.00 Å)22,23 (Table
2). They are also comparable to the value of 2.91 Å
observed by Wuest in a complex featuring a diethyl-
formamide quadruply coordinated to a cyclic tetraden-
tate mercury Lewis acid.24 These Hg-O distances are
however longer than those measured in [1‚µ2-acetone]
(av 2.73 Å), which features a carbonyl functionality
coordinated to only two mercury centers.12 Whereas the
precision of the crystallographic measurement does not
confirm a lengthening of the CdO bond in 3, 5, 6, and
7, the carbonyl stretching vibration is shifted to lower
wavenumber, which suggests a weakening of the CdO
bond. Interestingly, this effect is much more acute in
the case of the 1:1 acetaldehyde and acetone adducts 3
and 5 than in 6 and 7, which both contain aromatic
ketones.
With an intercentroid distance of 3.687 Å, the arene-
fluoroarene contact observed in the structure of 7 falls
within the range typically observed for such interac-
tions.25,26 These interactions, which result at least in
part from electrostatic forces, have often been observed
in organic arene-fluoroarene assemblies27-30 as well as
in organometallic complexes.31,32 Finally, the inter-
molecular Hg-C interactions that occur between the
triply coordinated to the mercury centers of 2. With two
triply bridging ketones on both sides of the planar
trifunctional Lewis acid, its structure resembles that of
the acetone adduct 4. The Hg-O contacts fall within
the range 2.873-3.056 Å (Table 2), and the carbonyl
functionalities are oriented at 81.1° and 63.1° from the
plane containing the three mercury atoms. Elemental
analysis carried out on a sample stored at room tem-
perature for 24 h reveals a 30% loss of the acetophenone
component. After 72 h, the loss corresponds exactly to
1 equiv of acetophenone, thus suggesting the formation
of a 1:1 adduct. IR spectroscopy carried out on a freshly
prepared sample reveals that the carbonyl stretching
vibration is only barely shifted when compared to that
of the neat ketone (1680 vs 1686 cm-1 for neat aceto-
phenone).
In ter a ction of 2 w ith Ben zop h en on e. The crystal-
line 1:1 complex [2‚µ3-benzophenone] (7) is readily
obtained upon cooling of a CH2Cl2 solution containing
a mixture of 2 and the ketone. This adduct crystallizes
in the monoclinic space group P21/n with four molecules
in the unit cell. The carbonyl oxygen is triply coordi-
nated to the mercury atoms of 2. The resulting Hg-O
distances range from 2.888(5) to 3.047(5) Å (Table 2)
and are comparable to those observed in the structures
of 3, 4, and 6. The linear carbonyl functionality is tilted
with respect to the plane containing the three mercury
atoms that it approaches at an angle of 53.6°. This
situation contrasts with those encountered in 3, 4, and
6, where the orientation of the triply coordinated
carbonyl functionalities with respect to the plane con-
taining 2 is closer to 90°. This situation possibly results
from the presence of an intramolecular arene-fluoro-
arene interaction that involves a tetrafluorophenylene
ring of 2 and one of the phenyl rings of the coordinated
molecule of benzophenone. The centroids of tetrafluoro-
phenylene and phenyl rings are separated by 3.687 Å.
Examination of the cell-packing diagram indicates that
this phenyl ring also engages in short contacts with the
(21) Nyburg, S. C.; Faerman, C. H. Acta Crystallogr. Sect. B 1985,
41, 274-279.
(22) Canty, A. J ; Deacon, G. B. Inorg. Chim. Acta 1980, 45, L225-
L227.
(23) Pyykko¨, P.; Straka, M. Phys. Chem. Chem. Phys. 2000, 2, 2489-
2493.
(24) Vaugeois, J .; Simard, M.; Wuest, J . D. Organometallics 1998,
17, 1215-1219.
(25) Williams, J . H. Acc. Chem. Res. 1993, 26, 593-598.
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Perfluoro-ortho-phenylene Mercury
Organometallics, Vol. 21, No. 20, 2002 4205
Syn th esis of [2‚µ3-Aceta ld eh yd e] (3). Slow evaporation
of a solution of 2 (50 mg, 0.048 mmol) in acetaldehyde (2 mL)
afforded a quantitative yield of 3 (52 mg, 100% yield). The
crystals were stable for weeks at room temperature. Anal.
Calcd for C20H4O1F12H3: C, 22.04; H, 0.36. Found: C, 22.08;
H, 0.30. IR: 1706, 1653, 1616, 1468, 1418,1354, 1321, 1304,
phenyl ring of the benzophenone molecule and the
mercury center of the neighboring monomer are within
the sum of the van der Waals radius of mercury
(rvdw(Hg) ) 1.73-2.00 Å)22,23 and that of carbon in
aromatic systems (rvdw(Caromatic) ) 1.7 Å)).29 They reflect
the presence of secondary polyhapto-π interactions
occurring between the electron-rich aromatic molecules
and the acidic mercury centers. Similar distances have
been previously observed in adducts involving 2 and
aromatic substrates such as benzene, naphthalene,
biphenyl, and triphenylene.34,35
1248, 1080, 1004, 815, 770 cm-1
.
Syn th esis of [2‚(Aceton e)(µ3-a ceton e)2] (4) a n d [2‚
Aceton e] (5). Compound 2 (50 mg, 0.048 mmol) was dissolved
in pure acetone (1 mL). After partial evaporation of the solvent,
crystals of 4 were collected and analyzed. These crystals are
not stable and rapidly lose two molecules of acetone, yielding
a 1:1 adduct of 2‚acetone (5) (32 mg, 60% yield). Anal. Calcd
for C21H6O1F12Hg3: C, 22.85; H, 0.58. Found: C, 23.06; H, 0.52.
IR: 2170, 1684, 1683, 1653, 1636, 1617, 1576, 1559, 1540,
1507, 1472, 1457, 1419, 1395, 1386, 1322, 1287, 1251, 1238,
Con clu sion s
The results presented herein demonstrate that tri-
meric perfluoro-ortho-phenylene mercury behaves as a
tridentate Lewis acid toward both aldehydes and ke-
tones. The resulting adducts constitute the first ex-
amples of bimolecular complexes featuring triply bridg-
ing aldehydes or ketones. Earlier investigations showed
that bidentate Lewis acids such as 1 readily chelate
acetone but not acetaldehyde or benzaldehyde.12,16 In
this regard, the isolation of 3 is especially noteworthy
and shows that weakly basic carbonyl substrates un-
dergo multiple coordination with the appropriate poly-
dentate Lewis acid. The structures of the adducts as
well as the IR stretching vibration of the carbonyl
functionality confirm the presence of a bonding interac-
tion between the mercury centers of 2 and the oxygen
atom of the carbonyl substrate. DFT calculations un-
dertaken on 2 show a positively charged electrostatic
potential surface in the center of the macrocycle.36
Hence, in addition to covalent forces, it is likely that
electrostatic forces also contribute to the stability of
these adducts.
1079, 1088, 1004, 1004, 835, 772 cm-1
.
Syn th esis of [2‚(µ3-Acetop h en on e)2] (6). Slow evapora-
tion of a solution of 2 (50 mg, 0.048 mmol) in pure acetophe-
none (1.5 mL) affords crystals of 6 (60 mg, 100% yield). At
room temperature, crystals of 6 become opaque and brittle over
a period of 8 h. Elemental analysis of a sample stored at room
temperature for a period of 24 h reveals a 30% loss of the
acetophenone component. Anal. Calcd for C34H16F12Hg3O2: C,
31.1; H, 1.10. Found: C, 28.8; H, 0.95. IR: 1680, 1599, 1583,
1470, 1417, 1362, 1272, 1248, 1181, 1003, 959, 812, 760, 689,
590 cm-1. After 72 h, the elemental analysis indicates a 50%
loss of acetophenone and suggests the formation of [2‚aceto-
phenone]. Anal. Calcd for C26H8F12Hg3O: C, 26.8; H, 0.69.
Found C, 26.94; H, 0.66.
Syn th esis of [2‚(µ3-Ben zop h en on e)] (7). In a vial, com-
pound 2 (50 mg, 0.048 mmol) was added to benzophenone (25
mg, 0.14 mmol) in CH2Cl2. Upon refrigeration of the solution,
crystals of 7 formed (32 mg, 54% yield based on 2). Anal. Calcd
for C31H10F12Hg3O: C, 30.30; H, 0.80; F, 18.56. Found: C,
30.54; H, 0.83; F, 18.52. IR: 1653, 1616, 1594, 1576, 1558,
1540, 1472, 1418, 1353, 1322, 1307, 1286, 1251, 1126, 1083,
1076, 1006, 943, 919, 815, 768, 710, 698, 636 cm-1
.
Exp er im en ta l Section
Ack n ow led gm en t. Support from the National Sci-
ence Foundation (CAREER CHE-0094264) and the
Department of Chemistry at Texas A&M University is
gratefully acknowledged. M.T. is grateful to the Uni-
versidade Federal de Sa˜o Carlos for allowing his re-
search stay at Texas A&M. The purchase of the X-ray
diffractometers was made possible by a grant from the
National Science Foundation (CHE-9807975).
Gen er a l Con sid er a tion s. All experiments were carried out
in a fume hood. Atlantic Microlab (Norcross, GA) performed
the elemental analyses. Infrared spectra were recorded as KBr
pellets on a Mattson Genesis Series FTIR. Acetaldehyde,
acetone, acetophenone, and benzophenone were purchased
from Aldrich Chemical and used as provided. Compound 2 was
prepared by the published procedure.17 Thermal gravimetric
analyses were carried out on an Instrument Specialists
Incorporated TGA 1000 analyzer.
Sin gle-Cr ysta l X-r a y An a lysis. X-ray data for 3, 4, 6, and
7 were collected on a Bruker Smart-CCD diffractometer using
graphite-monochromated Mo KR radiation ()0.71073 Å).
Specimens of suitable size and quality were selected and
mounted onto a glass fiber with Apiezon grease. The structure
was solved by direct methods, which successfully located most
of the non-hydrogen atoms. Subsequent refinement on F2 using
the SHELXTL/PC package (version 5.1) allowed location of the
remaining non-hydrogen atoms. Further crystallographic de-
tails can be found in Table 1 and in the Supporting Informa-
tion.
Note Ad d ed in P r oof: While the manuscript was
being processed, the synthesis and crystal structure of
[2‚(µ3-DMF)2] was reported by two independent research
groups.37,38 We have also been able to isolate the adduct
[2‚µ3-acetone], whose composition is identical to that of
5.39
Su p p or tin g In for m a tion Ava ila ble: Tables of structure
refinement, atomic coordinates, bond lengths and angles,
anisotropic displacement parameters, and hydrogen coordi-
nates for complexes 3, 4, 6, and 7. This material is available
free of charge via the Internet at http://pubs.acs.org.
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OM020276A
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