Preparation and properties of trifluoromethylated aryl derivatives of germanium, tin, and lead. High-yield syntheses of trifluoromethylbenzene

Article abstract of DOI:10.1021/om000023m

Ligand exchange reactions of Cd(CF₃)₂·glyme with a number of aryl-containing Pb, Sn, and Ge halides, acetates, and thioethers were examined in THF or CHCl₃. With an excess of trifluoromethylating agent and relatively lengthy reaction times, complete displacement of the halides or halide equivalents from the group 14 centers was observed, and the new compounds PbPh(CF₃)₃, 51%, PbPh₂(CF₃)₂, 61%, PbPh₃CF₃, 81%, SnPh₂(CF₃)₂, 55%, SnPh₃-CF₃, 80%, and GePh₃CF₃, 72%, were isolated and characterized. With shorter reaction times and/or with the trifluoromethylating agent as the limiting reactant, partial substitution predominated, and the new species PbPh₂(Cl)CF₃, 78%, PbPh₂(O₂CCH₃)CF₃, 89%, PbPh(O₂-CCH₃)₂CF₃, 63%, and PbPh(O₂CCH₃)(CF₃)₂, 64%, were separated. In addition two preliminary studies of the reactivity of aryl-group-IVA compounds were carried out. In the first, ligand exchanges of PbPh₃CF₃ with a representative main group and transition metal complex were probed; Sb(CF₃)₃, 61%, and Pd(PEt₃)₂(Cl)CF₃, 62%, were generated. In the second, the feasibility of forming aryl-CF₃ species in high yields via CuCl-mediated M-Ph cleavages was examined. In these reactions PhCF₃ was isolated from M₂Ph₆ in yields of 95% (M = Pb), 96% (M = Sn), and 58% (M = Ge).

Full text of DOI:10.1021/om000023m

Organometallics 2000, 19, 2603-2607
2603
P r ep a r a tion a n d P r op er ties of Tr iflu or om eth yla ted Ar yl
Der iva tives of Ger m a n iu m , Tin , a n d Lea d . High -Yield
Syn th eses of Tr iflu or om eth ylben zen e
J ohn K. Galiotos and J ohn A. Morrison*
Department of Chemistry (m/ c 111), The University of Illinois at Chicago,
4500 SES 845 West Taylor Street, Chicago, Illinois 60607-1607
Received J anuary 10, 2000
Ligand exchange reactions of Cd(CF3)2‚glyme with a number of aryl-containing Pb, Sn,
and Ge halides, acetates, and thioethers were examined in THF or CHCl3. With an excess
of trifluoromethylating agent and relatively lengthy reaction times, complete displacement
of the halides or halide equivalents from the group 14 centers was observed, and the new
compounds PbPh(CF3)3, 51%, PbPh2(CF3)2, 61%, PbPh3CF3, 81%, SnPh2(CF3)2, 55%, SnPh3-
CF3, 80%, and GePh3CF3, 72%, were isolated and characterized. With shorter reaction times
and/or with the trifluoromethylating agent as the limiting reactant, partial substitution
predominated, and the new species PbPh2(Cl)CF3, 78%, PbPh2(O2CCH3)CF3, 89%, PbPh(O2-
CCH3)2CF3, 63%, and PbPh(O2CCH3)(CF3)2, 64%, were separated. In addition, two prelimi-
nary studies of the reactivity of aryl-group-IVA compounds were carried out. In the first,
ligand exchanges of PbPh3CF3 with a representative main group and transition metal complex
were probed; Sb(CF3)3, 61%, and Pd(PEt3)2(Cl)CF3, 62%, were generated. In the second, the
feasibility of forming aryl-CF3 species in high yields via CuCl-mediated M-Ph cleavages
was examined. In these reactions PhCF3 was isolated from M2Ph6 in yields of 95% (M )
Pb), 96% (M ) Sn), and 58% (M ) Ge).
In tr od u ction
Although there have been many studies of alkyl group
14 species containing trifluoromethyl groups, there have
been very few reports of aryl-substituted group 14
compounds that also contain CF3 groups. This is some-
what surprising since, in general, one might expect the
aryl derivatives to be more thermally and oxidatively
stable than their alkyl counterparts. Additionally, the
arylated species should be significantly less reactive
toward nucleophilic reagents, and it seems reasonable
to expect that they will ultimately be shown to exhibit
reactivity patterns that are distinct from their alkylated
counterparts. Prior to the inception of this work, the
only trifluoromethylated group 14 aryl derivatives that
had been reported were those of carbon and silicon.7
The objectives of this study were to synthesize the
title compounds, the first series of trifluoromethylated
aryl derivatives of the lower elements of group 14, to
examine the variation in properties of these new com-
pounds, and to establish, in preliminary fashion, whether
these new compounds might have the potential to serve
as ligand exchange reagents in their own right. For the
last, a lead trifluoromethylated species was selected, in
part, because lead alkyl compounds have had a long and
rich history as alkyl sources and, in part, because the
relatively low Pb(IV)-F bond strength might serve to
discourage the difluorocarbene eliminations that have
been commonly observed in other studies of metal-CF3
reactivity. Finally, since trifluoromethylated derivatives
If one wishes to effect the substitution (or addition)
of an alkyl or aryl substituent onto a substrate, an
extremely rich and diverse array of organometallic
reagents exists with which to carry out the transforma-
tion. If it is the substitution (or addition) of a CF3 or
other perfluoroalkyl group that is desired, however, the
choice of reagents is much more restricted. Bis(tri-
fluoromethyl)cadmium‚glyme (glyme is 1,2-dimethoxy-
ethane) has been shown to be reactive toward a number
of transition metal and main group halides.1 Bis-
(trifluoromethyl)tellurium and Hg(CF3)2 have been ef-
fectively employed in main group 14, 15, and 16
transformations2 and the latter has been employed in
oxidative-additions to late transition metals.3 Trimethyl-
(trifluoromethyl)silane has been shown to be reactive,
primarily toward ketones, acyl halides, and the like;4
more recently reactions with metal fluorides have been
reported.5 The chemistry of trifluoromethyl copper has
been examined in considerable detail.6
(1) Reviews: (a) Morrison, J . A. Adv. Organomet. Chem. 1993, 35,
211. (b) Morrison, J . A. Adv. Inorg. Chem. Radiochem. 1983, 27, 293.
(2) (a) Ganja, E. A.; Morrison, J . A. Inorg. Chem. 1990, 29, 33. (b)
Ganja, E. A.; Ontiveros, C. D.; Morrison, J . A. Inorg. Chem. 1988, 27,
4535. (c) Lagow, R. J .; Eujen, R.; Gerchman, L. L.; Morrison, J . A. J .
Am. Chem. Soc. 1978, 100, 1722.
(3) Brothers, P. J .; Roper, W. R. Chem. Rev. 1988, 88, 1293.
(4) Prakash, G. K. S.; Yudin, A. K. Chem. Rev. 1997, 97, 757. (b)
Kotun, S. P.; Anderson, J . D. O.; Des Marteau, D. D. J . Org. Chem.
1992, 57, 1124.
(5) Huang, D.; Caulton, K. G. J . Am. Chem. Soc. 1997, 119, 3185.
(6) (a) Burton, D. J .; Yang, Z. Y. Tetrahedron 1992, 48, 189. (b)
Burton, F. J .; Yang, Z. Y. In Chemistry of Organic Fluorine Compounds
II; Hudlicky, M., Pavlath, A. E., Eds.; American Chemical Society:
Washington, DC, 1995; p 670.
(7) (a) Beckers, H.; Burger, H.; Bursch, P.; Ruppert, I. J . Organomet.
Chem. 1986, 316, 41. (b) Ruppert, I.; Schlich, K.; Volback, W.
Tetrahedron Lett. 1984, 25, 2195. See also: (c) Eujen, R.; Patorra, A.
J . Organomet. Chem. 1992, 438, C1; and (d) Eujen, R.; J ahn, N. J .
Fluorine Chem. 1995, 71, 75.
10.1021/om000023m CCC: $19.00 © 2000 American Chemical Society
Publication on Web 05/24/2000

2604 Organometallics, Vol. 19, No. 13, 2000
Ta ble 1. 19F a n d 207P b NMR Da ta a n d CF 3 An a lyses
CF3 analytical data
mmol compd mmol CF3H
Galiotos and Morrison
NMR dataa,b
19F, ppm 2J (M-F), Hz 207Pb, ppm 2J (207Pb-19F) Hz
mol CF3I
compd
δ
δ
taken
produced
%
produced
%
PbPh3CF3
white solid
37.8(s)
40.3(s)
41.2(s)
40.2(s)
40.6(s)
40.5(s)
39.4(s)
31.2(s)
30.1(s)
28.2(s)
324
-236.6(q)
323
440
557
0.350
0.125
0.325
0.156
0.176
0.165
0.209
0.347
99.1
0.124
0.309
0.485
99.2
99.0
98.0
PbPh2(CF3)2
white solid
PbPh(CF3)3
clear liquid
PbPh2(Cl)CF3
white solid
PbPh2(OAc)CF3
white solid
PbPh(OAc)2CF3
white solid
PbPh(OAc)(CF3)2
white solid
SnPh3CF3
white solid
SnPh2(CF3)2
white solid
440
-316.0(h)
-515.0(d)
0.643
0.528
0.206
0.186
0.271
0.469
0.265
0.480
0.342
98.9
100.0
98.5
97.9
99.6
98.9
98.9
97.9
98.0
560
301
321
0.190
0.272
0.237
349
503
285/273
427/408
0.268
0.240
0.245
0.235
0.309
97.9
98.7
GePh3CF3
white solid
0.349
0.313
a
b
M ) Ge, Sn, Pb; Ph ) C6H5, OAc ) CO2CH3. s ) singlet, h ) heptet, d ) decet. Ext. std. for 19F NMR is CF3COOH. Ext. std. for
207Pb NMR is Pb(CH3)4. 2J (M-F) ) 2J (207Pb-19F), 2J (119/117Sn-19F), as appropriate.
F or m a tion of P bP h 3CF 3. Meth od A. Triphenyllead bro-
mide (0.223 g, 0.430 mmol) was mixed with 0.297 g (0.873
mmol) of Cd(CF3)2‚glyme in a 100 mL round-bottomed flask
equipped with a 15-cm-long neck designed such that later a
coldfinger could be inserted directly into the reactor. The vessel
was attached to a standard vacuum line by means of a Teflon
valve and ground glass joint, evacuated, and cooled to -196
°C, and then 25 mL of THF was distilled onto the mixture.
The reactor contents were warmed to ambient temperature
and stirred. At the end of the reaction, all volatiles were
removed by vacuum distillation at ambient temperature and
discarded. The coldfinger was inserted into the reactor, which
was then evacuated and heated. Triphenyl(trifluoromethyl)-
lead (0.177 g, 0.349 mmol), which distilled from the solid at
131 °C, was recovered from the coldfinger of the sublimation
apparatus in 81.2% yield. The melting point of this compound
is 127.5-128 °C.
of aromatic substances are frequently desired for the
preparation of compounds of interest for medicinal or
pesticide applications, the efficacy of aryl group 14
compounds for the formation of a typical trifluoromethyl
aromatic species, trifluorotoluene, was assessed.
Exp er im en ta l Section
Gen er a l Com m en ts. The synthesis and manipulation of
air-sensitive materials were carried out in standard vacuum
lines or in glovebags. Because of the toxicity of many lead
compounds, rubber gloves and well-ventilated hoods were used
for all benchtop procedures. All reaction times were 24 h unless
otherwise noted.
Bis(trifluoromethyl)mercury8, bis(trifluoromethyl)cadmium‚
glyme,9 and PbPh3SEt10 were prepared as previously reported
Other substrates were generated by standard procedures.
Triphenyllead bromide (Alfa), PbPh2Cl2 (Alfa), PbPh2(O2-
CCH3)2 (Alfa), PbPh(O2CCH3)3 (Alfa), Sn2Ph6 (Alfa), GeO2
(Alfa), and PhI (Aldrich) were all used as received. Lead(II)
chloride (Fisher) and CuCl (Aldrich) were heated to 130 °C
under vacuum prior to use. Tetrahydrofuran was dried over
sodium benzophenone ketyl. Chloroform was dried over P2O5;
elemental iodine (Aldrich) was sublimed prior to use.
The 19F and 207Pb {1H} NMR data and the CF3 analyses are
contained in Table 1. 1H NMR: δ 7.2, 7.3, 7.4. IR: 692 (s),
995 (m), 1016 (w), 1109 (m), 1477 (s), 1572 (m), 2957 (s), 3067
cm-1 (s). MS (m/e, ion, %): 439, PbPh3+, 41.9; 431, PbPh2CF3
,
+
0.8; 381, PbPh2F+, 2.6; 362, PbPh2+, 40.0; 285, PbPh+, 51.1;
277, PbCF3+, 0.3; 227, PbF+, 8.0; 208, Pb+, 100.0; 154, Ph-
Ph+, 9.5; 77, Ph+, 25.1; 69, CF3+, 5.1. Anal. Found: C 44.42,
H 2.80. Calc: C 44.95, H 2.96.
1
The 19F (188.3 MHz), H (200.1 MHz), 13C (100.6 MHz), 31P
(181.9 MHz), and 207Pb (43.8 MHz) NMR spectra were obtained
at ambient temperature from samples that had been dissolved
in THF or CHCl3 and then sealed in 4 mm Pyrex glass tubing.
Deuterium oxide was the external lock solvent. Positive
chemical shifts are deshielded from external CF3COOH (which
is ca. +76.5 on the CFCl3 scale), Si(CH3)4, H3PO4 (80%), or Pb-
(CH3)4, as appropriate. The 70 eV mass spectra are from
quadrupole mass spectrometers. Each fragment had the cor-
rect isotopic pattern. The melting points are uncorrected. The
number of CF3 ligands in each new compound (see Table 1)
was determined by hydrolysis in 0.5 M methanolic KOH. In
selected cases, these analytical data were corroborated by
reaction with iodine at ambient temperature in THF and/or
by analyses performed by Schwarzkopf Microanalytical Labo-
ratory, Woodside, NY.
Meth od B. Triphenythioethyllead (0.254 g, 0.509 mmol)
was mixed with 0.191 g (0.561 mmol) of Cd(CF3)2‚glyme and
20 mL of THF in the apparatus described above. Triphenyl-
(trifluoromethyl)lead (0.172 g, 0.340 mmol) was recovered in
66.8% yield. The properties of this product are identical to
those reported above.
F or m a tion of P bP h 2(CF 3)2. Meth od A. White PbPh2(CF3)2
(0.077 g, 0.155 mmol) was formed in 60.8% yield from the
reaction (48 h) of PbPh2Cl2 (0.110 g, 0.255 mmol) with 0.172 g
(0.505 mmol) of Cd(CF3)2‚glyme in 25 mL of THF. This
compound, which was separated as above, melts at 46 °C and
volatilizes in vacuo at 52 °C.
The 19F and 207Pb {1H} NMR data and CF3 analyses are in
Table 1. 1H NMR: δ 7.1, 7.4, 7.5. IR: 694 (s), 725 (m), 995
(w), 1261 (m), 1655 (m), 2965 (s), 3063 cm-1 (s). MS (m/e, ion,
%): 431, PbPh2CF3+, 26.5; 381, PbPh2F+, 34.7; 285, PbPh+,
32.8; 277, PbCF3+, 0.4; 227, PbF+, 29.5; 208, Pb+, 100.0; 154,
Ph-Ph+, 7.0; 77, Ph+, 16.2; 69, CF3+, 4.7. Anal. Found: C
34.01, H 1.88. Calc: C 33.65, H 2.00.
(8) Eujen, R. Inorg. Synth. 1986, 24, 52.
(9) (a) Krause, L. J .; Morrison, J . A. J . Am. Chem. Soc. 1981, 103,
2995. (b) Ontiveros, C. D.; Morrison, J . A. Inorg. Synth. 1986, 24, 55.
(10) Henry, M. C.; Krebs, A. W. J . Org. Chem. 1963, 28, 225.

Trifluoromethylated Aryl Derivatives of Ge, Sn, Pb
Organometallics, Vol. 19, No. 13, 2000 2605
Meth od B. Diphenylbis(trifluoromethyl)lead (0.078 g, 0.157
mmol) was recovered in 50.8% yield from the reaction of
PbPh2(O2CCH3)2 (0.148 g, 0.309 mmol) with 0.298 g (0.876
mmol) of Cd(CF3)2‚glyme and 20 mL of THF. The separation
was as above.
F or m a tion of P bP h 2(Cl)CF 3. Diphenyl(trifluoromethyl)-
lead chloride (0.069 g, 0.150 mmol) was collected in 78.1% yield
from the reaction of PbPh2Cl2 (0.124 g, 0.288 mmol) with 0.065
g (0.192 mmol) of Cd(CF3)2‚glyme in 25 mL of THF. The
product was separated by briefly exposing the solution to air
(to remove any Cd-CF3 species), filtration, and then recrys-
tallizion from THF. The 19F NMR data and the CF3 analyses
are contained in Table 1. 1H NMR: δ 7.4, 7.5, 7.7. MS (m/e,
ion, %): 431, PbPh2CF3, 1.7; 397, PbPh2Cl+, 14.1; 285, PbPh+,
23.2; 277, PbCF3+, 0.3; 243, PbCl+, 45.3; 227, PbF+, 3.5; 208,
Pb+, 100.0; 154, Ph-Ph+, 1.6; 146, PhCF3+, 1.7; 77, Ph+, 18.3;
69, CF3+, 3.8.
compound, which was purified like PbPh3CF3, above, melts at
113 °C and volatilizes in vacuo at 161 °C.
The 19F NMR data and the CF3 analyses are contained in
1
Table 1. H NMR: δ 6. 5, 6.7, 6.9. IR: 769 (s), 987 (m), 1086
(m), 1261 (m), 1630 (m), 3061 cm-1 (s). MS (m/e, ion, %): 401,
SnPh3CF2+, 10.0; 351, SnPh3+, 100.0; 343, SnPh2CF3+, 3.3; 324,
SnPh2CF2+, 0.3; 274, SnPh2+, 1.2; 247, SnPhCF2+, 17.4; 197,
SnPh+, 51.8; 189, SnCF3+, 2.1; 139, SnF+, 0.4; 120, Sn+, 33.7.
F or m a tion of Sn P h 2(CF 3)2. Diphenylbis(trifluoromethyl)-
tin (0.111 g, 0.270 mmol; mp 39 °C) was recovered in 55.0%
yield from the reaction of SnPh2Cl2 (0.164 g, 0.491 mmol) with
0.201 g (0.589 mmol) of Cd(CF3)2‚glyme in 15 mL of CHCl3.
This compound was purified as described for PbPh2(Cl)CF3,
but it was recrystallized from CHCl3.
The 19F NMR data and the CF3 analyses are contained in
Table 1. 1H NMR: δ 6.4, 6.6, 6.9. IR: 439 (s), 567 (m), 733
(m), 971 (s), 1094 (s), 1259 (s), 1524 (s), 1720 (s), 3044 cm-1
(s). MS (m/e, ion, %): 343, SnPh2CF3+, 23.0; 305, SnPh2CF+,
19.6; 274, SnPh2+, 0.4; 266, SnPhCF3+, 25.9; 228, SnPhCF+,
40.3; 197, SnPh+, 10.7; 189, SnCF3+, 1.5; 154, Ph-Ph+, 100.0;
151, SnCF+, 14.8; 139, SnF+, 0.85; 120, Sn+, 23.8.
F or m a tion of P bP h 2(O2CCH3)CF 3. Diphenyl(trifluoro-
methyl)lead acetate (0.093 g, 0.191 mmol) was collected in
89.2% yield from the reaction of PbPh2(O2CCH3)2 (0.164 g,
0.343 mmol) with 0.073 g (0.214 mmol) of Cd(CF3)2‚glyme in
20 mL of THF. It was obtained as described immediately
above.
F or m a tion of GeP h 3CF 3. Triphenyl(trifluoromethyl)ger-
manium (0.141 g, 0.377 mmol) was synthesized in 71.9% yield
from the reaction of 0.178 g (0.524 mmol) of GePh3Cl with
0.285 g (0.838 mmol) of Cd(CF3)2‚glyme in 10 mL of CHCl3.
This complex, which was purified like PbPh3CF3, above, has
a melting point of 82 °C and volatilizes in vacuo at 93 °C.
The 19F NMR data and the CF3 analyses are contained in
1
Table 1. H NMR: δ 7.5, 7.6, 7.7, 2.0 (O2CCH3). MS (m/e, ion,
%): 439, PbPh2(O2CCH3)F+, 1.6; 431, PbPh2CF3+, 1.2; 421,
PbPh2(O2CCH3)+, 22.9; 413, PbPh(O2CCH3)CF3+, 2.2; 344,
PbPh(O2CCH3)+, 2.2; 285, PbPh+, 40.2; 277, PbCF3+, 0.2; 267,
PbO2CCH3+, 25.5; 227, PbF+, 5.0; 225, PbOH+, 14.2; 208, Pb+,
100.0; 154, Ph-Ph+, 1.9; 77, Ph+, 4.6; 69, CF3+, 2.0.
F or m a tion of P bP h (CF 3)3. Phenyllead triacetate (0.195
g, 0.422 mmol) was mixed with 0.699 g (2.056 mmol) of Cd-
(CF3)2‚glyme in a 25 mL flask. The vessel was attached to a
vacuum line, evacuated, and cooled to -196 °C, and 10 mL of
THF was added. After the reaction, all volatile material was
fractionated with -78 and -196 °C cold traps. Phenyltris-
(trifluoromethyl)lead (0.106 g, 0.215 mmol) was collected from
the -78 °C trap in 50.9% yield.
The 19F NMR data and the CF3 analyses are contained in
Table 1. 1H NMR: δ 6.6, 6.8, 6.9. IR: 455 (s), 696 (m), 736
(m), 1057 (m), 1295 (m), 1589 (s), 3110 cm-1 (m). MS (m/e, ion,
%): 324, GePh3F+, 8.9; 305, GePh3+, 0.5; 274, GePh2F+, 42.7;
259, GePh2CF+, 0.4; 228, GePh2+, 1.1; 201, GePhCF2+, 0.2; 170,
GePhF+, 1.4; 154, Ph-Ph+, 100; 151, GePh+, 14.9; 143, GeCF3
,
+
0.2; 93, GeF+, 30.0. Anal. Found: C 61.23, H 4.05. Calc: C
61.19, H 4.03.
In ter a ction s w ith Hg(CF 3)2. Small amounts of the above
substrates were mixed with a 2-fold excess of Hg(CF3)2 in 0.5
mL of CHCl3 or THF as appropriate. After 24 h at room
temperature, the mixtures were heated to 140 °C for 72 h and
then to 160 °C for a further 72 h. Unreacted Hg(CF3)2 was
present, but no M-CF3 (M ) Ge, Sn, Pb) linkages were
observed.
The 19F and 207Pb {1H} NMR data and CF3 analyses are in
Table 1. 1H NMR: δ 7.3, 7.4, 7.5. IR: 689 (s), 727 (m), 889
(m), 995 (s), 1231 (m), 1574 (m), 3065 cm-1 (s). MS (m/e, ion,
%): 423, PbPh(CF3)2+, 11.3; 373, PbPh(CF3)F+, 4.0; 304,
PbPhF+, 2.8; 285, PbPh+, 21.0; 277, PbCF3+, 1.6; 227, PbF+,
10.4; 208, Pb+, 100.0; 69, CF3+, 31.4.
Th er m a l Sta bilities of Ar yl(tr iflu or om eth yl) Gr ou p
IVA Com p ou n d s. In the absence of air, GePh3CF3 begins to
decompose at ca. 90 °C, SnPh3CF3 at 162 °C, and PbPh3CF3
at 170 °C. Diphenylbis(trifluoromethyl)lead thermally decom-
poses at 153 °C, whereas SnPh2(CF3)2 and PbPh(CF3)3 decom-
pose at 106 and 90 °C, respectively. At lower temperatures,
C2F4 (δ -56 ppm) is formed, but if heated above 200 °C, all of
the compounds yield hexafluorocyclopropane (δ -79 ppm).
F or m a tion of P bP h (O2CCH3)2CF . Diacetatophenyl(tri-
fluoromethyl)lead (0.1280 g, 0.272 mmol) was formed in 62.5%
yield from phenyllead triacetate (0.201 g, 0.435 mmol) and
0.135 g (0.397 mmol) of Cd(CF3)2‚glyme in 20 mL of THF. It
was purified as described for PbPh2(Cl)CF3.
1
The 19F NMR data and the CF3 analyses are in Table 1. H
NMR: δ 7.5, 7.6, 7.8, 2.1 (O2CCH3). MS (m/e, ion, %): 421,
PbPh(O2CCH3)2F+, 4.8; 413, PbPh(O2CCH3)CF3+, 11.1; 403,
PbPh(O2CCH3)2+, 7.3; 344, PbPh(O2CCH3)+, 9.7; 285, PbPh+,
P r elim in a r y St u d y of t h e R ea ct ivit y of P b P h 3CF 3.
Rea ction w ith SbI3. In a 50 mL round-bottom flask equipped
with an 18/9 ball joint and a Teflon valve, 1.359 g (2.678 mmol)
of PbPh3CF3 was mixed with 0.396 g (0.788 mmol) of SbI3. The
reaction vessel was attached to a standard vacuum line and
evacuated, and approximately 5 mL of THF was added. After
72 h at room temperature, all volatiles were fractionated with
-78, -131, and -196 °C cold traps. Tris(trifluoromethyl)-
antimony (0.158 g, 0.480 mmol) was collected in 61.0% yield
from the -131 °C trap. It was identified by 19F (δ 34.1 ppm)
11.1; 277, PbCF3+, 0.6; 267, Pb(O2CCH3)+, 90.7; 227, PbF+, 4.0;
225, PbOH+, 20.1; 208, Pb+, 100.0; 77, Ph+, 46.9; 69, CF3
22.0; 59, CO2CH3+, 2.7.
,
+
F or m a tion of P bP h (O2CCH3)(CF 3)2. Phenylbis(trifluoro-
methyl)lead acetate (0.126 g, 0.261 mmol) was collected in
63.8% yield from the reaction of PbPh(O2CCH3)3 (0.1887 g,
0.409 mmol) with 0.418 g (1.227 mmol) of Cd(CF3)2‚glyme in
20 mL of THF. This product was purified like PbPh2(Cl)CF3.
The 19F NMR data and the CF3 analysis are contained in
13
) 356 Hz) spectra.2a,b
13
19
1
and C NMR (δ 130.0 ppm, J
C-
F
Table 1. H NMR: δ 7.5, 7.6, 7.7, 2.1 (O2CCH3). MS (m/e, ion,
%): 423, PbPh(CF3)2+, 8.8; 381, PbPhCF3CH3C+, 4.3; 373,
PbPhCF3F+, 2.7; 304, PbPhF+, 1.8; 285, PbPh+, 16.0; 277,
PbCF3+, 0.9; 267, Pb(O2CCH3)+, 1.2; 227, PbF+, 8.0; 225,
PbOH+, 7.8; 208, Pb+, 32.5; 81, CF3C+, 100.0.
Rea ction w ith P d (P Et3)2Cl2. Triphenyl(trifluoromethyl)-
lead (1.091 g, 2.151 mmol) was mixed with 0.903 g (2.188
mmol) of Pd(PEt3)2Cl2. The vessel was attached to a standard
vacuum line and evacuated, and 25 mL of THF was added.
After stirring for 48 h at ambient temperature, all volatiles
were removed. Pale yellow Pd(PEt3)2(Cl)CF3 (0.595 g, 1.334
mmol), 62.0% yield, sublimed at 85 °C. The 19F NMR (CH2-
F or m a tion of Sn P h 3CF 3. Triphenyl(trifluoromethyl)tin
(0.134 g, 0.321 mmol) was prepared in 80.0% yield from the
reaction (48 h) of 0.155 g (0.403 mmol) of SnPh3Cl with 0.142
g (0.418 mmol) of Cd(CF3)2‚glyme in 30 mL of CHCl3. This
3
31
19
Cl2) is a triplet at δ 66.9 ppm
J
) 35.7 Hz. The 31P{1H}
P-
F

2606 Organometallics, Vol. 19, No. 13, 2000
Galiotos and Morrison
31
19
NMR spectrum is a quartet at δ 25 ppm J
F) ) 35 Hz. The
at temperatures up to 120 °C, no reaction between Hg-
(CF3)2 and the aryl derivatives examined here was
observed.
P-
melting point of the compound is 75 °C.11
Rea ction of P b2P h 6, Sn 2P h 6, a n d Ge2P h 6 w ith Cd (CF 3)2‚
Glym e in th e P r esen ce of Cu Cl. In a 10 mm × 10 cm
reactor, 0.0116 g (0.013 mmol) of Pb2Ph6 was mixed with
0.0135 g (0.039 mmol) of Cd(CF3)2‚glyme and 0.0078 g (0.078
mmol) of CuCl. The reactor was evacuated and cooled to -196
°C, and 5 mL of THF was added. In a second reactor 0.0108 g
(0.015 mmol) of Sn2Ph6 was combined with 0.0158 g (0.046
mmol) of Cd(CF3)2‚glyme, 0.0089 g (0.090 mmol) of CuCl, and
5 mL of THF. In a third reactor 0.0122 g (0.020 mmol) of Ge2-
Ph6 was mixed with 0.0205 g (0.060 mmol) of Cd(CF3)2‚glyme,
0.0119 g (0.120 mmol) of CuCl, and 5 mL of THF.
One advantage of the slower trifluoromethylations of
the aryl-containing group 14 substrates is that partial
substitution can be readily carried out to generate
products such as PbPh2(O2CCH3)CF3 in good yield
(89%). In the absence of electrophiles such as HCl and
CuCl (see below), the group 14-Ph bonds are unaffected
by the trifluoromethylation procedures employed. In
contrast, however, methyl substituents bonded to these
elements readily react with Hg(CF3)2 or Cd(CF3)2‚glyme
to form group 14-CF3 derivatives.13
All of the trifluoromethyl aryl compounds formed here
are colorless substances that are reasonably thermally
stable, with the stability for analogous compounds
decreasing in the order Pb > Sn > Ge. For example,
the MPh3CF3 species decompose at 170, 162, and 110
°C for M ) Pb, Sn, and Ge, respectively. Since the mean
thermochemical M-C bond enthalpies are in the op-
posite order,14 these temperatures may indeed reflect
the relative ease with which CF2 elimination occurs. The
mixed ligand species, e.g., PbPh(OAc)2CF3, however, are
much more thermally sensitive.
After 7 days at room temperature, all volatiles were removed
from the red, dark gray, and white solids and then carefully
fractionated. No compounds with M-CF3 (M ) Ge, Sn, Pb)
linkages were recovered from the solids or volatiles. Trifluo-
romethylbenzene (0.0108 g, 0.074 mmol) was recovered in 95%
yield from the lead reaction. From the tin reaction PhCF3
(0.0126 g, 0.086 mmol) was recovered in 96% yield. From the
germanium reaction PhCF3 (0.0102 g, 0.070 mmol) was
isolated in 58% yield. Trifluoromethylbenzene was character-
ized by mass spectrometry (m/e, ion, %: 146, PhCF3+, 100; 127,
PhCF2+, 94.2; 96, PhF+ 69.8) along with 19F (δ 15.7 ppm), 13C
{1H} (δ 124, 127, 129.4, 130.6, 133.6 (CF3, q)), and H NMR (δ
1
6.6, 6.9, 7.1 ppm) spectroscopy.
In ter a ction of P b2P h 6, Sn 2P h 6, a n d Ge2P h 6 w ith Hg-
(CF 3)2 in th e P r esen ce of Cu Cl. The reactivity of 20 mmol
samples of Pb2Ph6, Sn2Ph6, and Ge2Ph6 toward 60 mmol Hg-
(CF3)2 in the presence of 120 mmol CuCl and THF was
similarly monitored at ambient temperature and 100, 120, and
146 °C by 19F and 1H NMR spectroscopy. No reaction was
observed after 3 months at ambient temperature; only trace
amounts of PhCF3 were observed from the lead and tin
reactions after 72 h at 146 °C.
Upon exposure to the atmosphere, the lead com-
pounds were the least reactive, with the tin and
germanium derivatives increasingly more air sensitive.
Indeed, the compounds PbPh3CF3 and PbPh2(CF3)2 are
remarkably stable toward air; they both persist for well
over a year seemingly unaffected. The others react
within minutes or, at most, a few hours.
Ch a r a cter iza tion . The spectroscopic data are all in
accord with the formulation of the compounds as
indicated. For example, as expected, the 19F chemical
shifts for the MPh3CF3 series (δ ) 37.8, 31.2, and 28.2
ppm for M ) Pb, Sn, and Ge) become slightly more
shielded as the central element becomes located more
toward the top of the periodic table. Presumably because
of the increasing amount of s character in the Pb-CF3
Resu lts a n d Discu ssion
Syn th esis. All of the lower group IVA aryl derivatives
tested are reactive toward Cd(CF3)2‚glyme at ambient
temperature; the lead reactions were best carried out
in THF, but CHCl3 was superior for the Sn and Ge
complexes. In general, the CF3 substitutions of the lead
complexes proceed slightly faster than the reactions of
the analogous derivatives of the other elements. The
yields were good, ca. 50% to ca. 90%, and the separations
were straightforward. Because of the limited thermal
stability of the Pb(IV) halides, SC2H5 and O2CCH3
ligands were briefly examined as potentially superior
leaving groups, but no advantages were apparent. The
acetate ligand, while reactive, has the disadvantage that
two Cd-CF3 groups are required since the first forms
CH3COF, and it is only the second that appears as a
Pb-CF3 ligand.
The relatively lengthy reaction times were adopted
after preliminary experiments demonstrated that the
trifluoromethylation of aryl-substituted group IVA com-
pounds by the CdCF3 reagent is much slower than that
of the tetrahalides. For example, 48 h was needed for
the reaction of SnPh3Cl, much longer than the 1-2 h
necessary for SnBr4 or GeI4.9a Similarly, the reactions
of GeI4 and SnBr4 with Hg(CF3)2 have been shown to
generate trifluoromethyl Ge and Sn compounds,2c,12 but
bond as CF3 groups are substituted for Ph groups, 2J (207
-
Pb-19F) increases from 323 to 557 Hz for the series
PbPhn(CF3)4-n, n ) 1, 2, 3 (see Table 1), and for SnPh2-
(CF3)2 relative to SnPh3CF3 (see Table 1). Although the
1H (see Experimental Section) and 19F chemical shifts
are relatively insensitive to CF3 for Ph substitutions,
δ
207Pb is not. Here, the resonances become much more
shielded after each CF3 for Ph substitution (see Table
1). In the 207Pb{1H} NMR spectra, the PbPh3CF3 and
PbPh2(CF3)2 resonances are a quartet and a heptet as
anticipated, but only 8 of the 10 lines expected in the
207Pb{1H} NMR spectrum of PbPh(CF3)3 are unequivo-
cal. However, the calculated intensity of the outermost
two lines that would complete the expected decet is only
0.4% of the total.
As is typical for tetravalent group IVA compounds,
molecular ions were not observed in the mass spectra,
but the expected fragmentation patterns, e.g., PbPh2-
+
+
CF3 and PbPh3 ions in the PbPh3CF3 spectrum, are
evident. Each of the group IVA-containing ions had the
(13) (a) Lagow, R. J .; Eujen, R. J . Chem. Soc., Dalton Trans. 1978,
541. (b) Morrison, J . A.; Galiotos, J . K. Unpublished observations.
(14) (a) Mingos, D. M. P. Essential Trends in Inorganic Chemistry;
Oxford University Press: Oxford, U.K., 1998; p 63. (b) Huheey, J . E.;
Keiter, E. A.; Keiter, R. L. Inorganic Chemistry, 4th ed.; HarperCol-
lins: New York, 1993.
(11) (a) Nair, H. K, Ph.D. Thesis, University of Illinois at Chicago,
1987, p 57. (b) Krause, L. J .; Morrison, J . A. J . Chem Soc., Chem.
Commun. 1981, 1282.
(12) Krause, L. J .; Morrison, J . A. Inorg. Chem. 1980, 19, 604.

Trifluoromethylated Aryl Derivatives of Ge, Sn, Pb
Organometallics, Vol. 19, No. 13, 2000 2607
appropriate isotopic abundance. All of the infrared
spectra contain absorptions characteristic of monosub-
stituted phenyl rings and CF3 groups.
in the presence of CuCl, trifluorotoluene was formed in
yields that ranged from 95+% for Pb and Sn to 58% for
Ge. The mechanism of this reaction is under investiga-
tion, but the current results are not inconsistent with
transmetalation to yield CuPh followed by a radical step
involving Cd-CF3 to generate PhCF3, Cu (the red solid
observed), and Cd. Presumably, it is the more readily
oxidized Cd that intercepts any halogen released by, for
example, Pb(II).
One advantage of the reactions shown here vis-a`-vis,
for example, typical CuCF3 aryl trifluoromethylations
is that the formation of the trifluoromethyl aromatic
derivative readily proceeds at ambient temperature and
pressure rather than the elevated temperatures and
pressures that are commonly required with alternative
methodology.6,16 In addition, the less expensive aryl
bromides can be employed to form the M2Ph6 substrates
rather than the aryl iodides that have typically been
used with CuCF3. Currently the price of a mole of PhI
from one major supplier (Aldrich) is about 8 times that
of PhBr and ca. 18 times that of the chloride. The scope
of this reaction is also under further investigation.
In conclusion, we have prepared and separated a
series of trifluoromethylated derivatives of aryl-contain-
ing group 14 elements by means of reactions with Cd-
(CF3)2‚glyme and found that, once formed, the aryl-
containing trifluoromethyl compounds are reasonably
thermally and oxidatively robust. We have also shown
that one of these compounds, PbPh3CF3, is an active
trifluoromethyl transfer agent which readily forms main
group, transition metal, and aromatic derivatives.
P r elim in a r y Rea ctivity Stu d ies. One reason that
the reactivity of PbPh3CF3 was assessed is that in
contrast to SiMe3CF3 (and some of the complexes
prepared here), PbPh3CF3 is stable in air for very long
periods. Because of their extended shelf lives, PbPh3-
CF3 and PbPh2(CF3)2 might prove to be very convenient,
easily stored, and readily accessible trifluoromethylating
agents.
To begin to examine the reactivity of PbPh3CF3, its
reactions with a representative main group and transi-
tion metal halide were explored. The fully trifluoro-
methylated antimony(III) compound, Sb(CF3)3, was
easily prepared at ambient temperature in 61% yield.
Previous syntheses, which have typically required pro-
longed heating of CF3I, Hg(CF3)2, or Te(CF3)2 with Sb
or SbI3 in a bomb reactor,2ab,15 are much less convenient.
The reaction of the palladium complex Pd(PEt3)2(Cl)2
with PbPh3CF3 generated the monosubstituted Pd-
(PEt3)2(Cl)CF3, which was separated in good yield, 62%,
after 48 h at ambient temperature. These results
indicate that the monosubstituted lead compound PbPh3-
CF3 is more reactive than Hg(CF3)2 but less reactive
than Cd(CF3)2‚glyme. Presumably, the disubstituted
compound PbPh2(CF3)2 will prove to be more reactive
than PbPh3CF3. The reactions of the disubstituded
species are currently under study.
The interactions of the M2Ph6 species, M ) Pb, Sn,
and Ge, with Cd(CF3)2‚glyme were designed to examine
whether trifluoromethylated aromatic compounds could
be easily prepared in this system or if the M-M bond
would be cleaved to form, for example, GePh3CF3
instead. In the absence of CuCl or other similar reagents
no cleavage of the metal(oid)-Ph bond was found, but
Ack n ow led gm en t. The financial contributions of
the National Science Foundation are gratefully
acknowledged.
OM000023M
(16) (a) Adams, D. J .; Clark, J . H.; Hansen, L. B.; Sanders, V. C.;
Tavener, S. J . J . Fluorine Chem. 1998, 92, 123. (b) McClinton, M. A.;
McClinton, D. A. Tetrahedron 1992, 48, 6555.
(15) Dale, J . W.; Emeleus, H. J .; Haszeldine, R. N.; Moss, J . H. J .
Chem. Soc. 1957, 3708.