Intramolecular transmetalation of arylpalladium(II) and arylplatinum(II) complexes with silanes and stannanes

Article abstract of DOI:10.1021/om980157o

The oxidative addition of o-(Me₂RSiCH₂O)C₆H₄I (R = Me, Ph, F) to palladium (0) complexes [Pd(PPh₃)], [Pd(dba)(AsPh₃)₂] (dba = dibenzylideneacetone), and [Pd(dba)(L₂)] [L₂ = 1,1′-bis(diphenylphosphino)ferrocene (dppf), 2,2′-bipyridine (bpy), o-phenanthroline (phen)] leads to the corresponding complexes o-(Me₂RCH₂O)C₆H₄Pd(L₂)I (L = PPh₃, AsPh₃; L₂ = dppf, bpy, phen). This Pd(II)/Si transmetalation, the key step in the Hiyama cross-coupling reaction, proceeds smoothly with different fluorides as the promoters. Additionally, silver and potassium carbonate promote the transmetalation by the likely formation of an intermediate with a Pd-O bond. The related Pt(II)/Sn and Pt(II)/Si transmetalation leads to the formation of stable oxaplatinacycles. In contrast with the requirement of additives for the Pd(II)/Si transmetalation, the transmetalation of Pt(II) complexes proceeds directly in the absence of additives. Additionally, [Pt(PPh₃)]₄ was shown to behave as a moderate catalyst for the cross-coupling of two aryl triflates with ethenyltributylstannane to form the corresponding styrenes.

Full text of DOI:10.1021/om980157o

Organometallics 1998, 17, 3661-3669
3661
In tr a m olecu la r Tr a n sm eta la tion of Ar ylp a lla d iu m (II)
a n d Ar ylp la tin u m (II) Com p lexes w ith Sila n es a n d
Sta n n a n es
Cristina Mateo, Carolina Ferna´ndez-Rivas, Diego J . Ca´rdenas, and
Antonio M. Echavarren*
Departamento de Quı´mica Orga´nica, Universidad Auto´noma de Madrid,
Cantoblanco, 28049 Madrid, Spain
Received March 4, 1998
The oxidative addition of o-(Me2RSiCH2O)C6H4I (R ) Me, Ph, F) to palladium(0) complexes
[Pd(PPh3)], [Pd(dba)(AsPh3)2] (dba ) dibenzylideneacetone), and [Pd(dba)(L2)] [L2 ) 1,1′-
bis(diphenylphosphino)ferrocene (dppf), 2,2′-bipyridine (bpy), o-phenanthroline (phen)] leads
to the corresponding complexes o-(Me2RCH2O)C6H4Pd(L2)I (L ) PPh3, AsPh3; L2 ) dppf,
bpy, phen). This Pd(II)/Si transmetalation, the key step in the Hiyama cross-coupling
reaction, proceeds smoothly with different fluorides as the promoters. Additionally, silver
and potassium carbonate promote the transmetalation by the likely formation of an
intermediate with a Pd-O bond. The related Pt(II)/Sn and Pt(II)/Si transmetalation leads
to the formation of stable oxaplatinacycles. In contrast with the requirement of additives
for the Pd(II)/Si transmetalation, the transmetalation of Pt(II) complexes proceeds directly
in the absence of additives. Additionally, [Pt(PPh3)]4 was shown to behave as a moderate
catalyst for the cross-coupling of two aryl triflates with ethenyltributylstannane to form the
corresponding styrenes.
Sch em e 1
In tr od u ction
Transmetalation of stannanes with organopalladium-
(II) complexes is a key step in the Stille1 cross-coupling
reaction, which allows for the efficient formation of
carbon-carbon bonds in an almost general way (Scheme
1, M ) SnR3).2 However, the toxicity of the byproducts
R3SnX is a limitation for the application of this reaction
to the large-scale preparation of valuable organic com-
pounds.3 Organosilanes, which are considerably less
toxic than organostannanes,4 also react with organic
electrophiles in the presence of a palladium catalyst
(Hiyama reaction).5 However, silanes are relatively
poor nucleophilic organometallic reagents6,7 and require
the addition of stoichiometric amounts of fluoride salts
in their reactions.5,8,9 It has been proposed that the
(1) Stille, J . K. Angew. Chem., Int. Ed. Engl. 1986, 25, 508.
(2) Farina, V.; Krishnamurthy, V.; Scott, W. J . Org. React. 1997,
50, 1.
(3) (a) Pereyre, M.; Quintard, J .-P.; Rham, A. Tin in Organic
Synthesis; Butterworth: London, 1987; pp 6-7. (b) For the efficient
removal of tin byproducts by using fluorous tin reactants: Hoshino,
M.; Degenkolb, P.; Curran, D. P. J . Org. Chem. 1997, 62, 8341.
(4) (a) Calvin, E. W. Silicon Reagents in Organic Synthesis; Aca-
demic: New York, 1988. (b) Walsh, R. In The Chemistry of Organic
Silicon Compounds; Patai, S., Rappoport, Z., Eds.; Wiley: New York,
1989.
(5) Reviews: (a) Hatanaka, Y.; Hiyama, T. Synlett 1991, 845. (b)
Hiyama, T.; Hatanaka, Y. Pure Appl. Chem. 1994, 66, 1471.
(6) Allylsilanes are several orders of magnitude less reactive than
allylstannanes toward electrophiles: Mayr, H.; Patz, M. Angew. Chem.,
Int. Ed. Engl. 1994, 33, 938.
acceleration observed in the presence of fluoride is the
result of the formation of a pentacoordinated fluorosi-
lane intermediate, more nucleophilic toward the orga-
nopalladium in the rate-determining transmetalation
step.4,5,10 Alternatively, fluoride anion may shift the
(8) (a) Takahashi, K.; Minami, T.; Ohara, Y.; Hiyama, T. Bull. Chem.
Soc. J pn. 1995, 68, 2649. (b) Gouda, K.-I.; Hagiwara, E.; Hatanaka,
Y.; Hiyama, T. J . Org. Chem. 1996, 61, 7232. (c) Hiyama, T.;
Matsuhashi, H.; Fujita, A.; Tanaka, M.; Hirabayashi, K.; Shimizu, M.;
Mori, A. Organometallics 1996, 15, 5762.
(9) For lead references on fluoride salts commonly used in organic
synthesis: Pasenock, S. V.; de Roos, M. E.; Appel, W. K. Tetrahedron
1996, 52, 9755.
(7) (a) For
a review on the transmetalation of allyl-, alkenyl-,
alkynyl-, and arylsilanes with Pd(II) salts: Akhrem, I. S.; Chistovalova,
N. M.; Vol’pin, M. E. Russ. Chem. Rev. 1983, 52, 542. (b) Weber, W.
P.; Felix, R. A.; Willard, A. K.; Koenig, K. E. Tetrahedron Lett. 1971,
4701. (c) Yamamoto, K.; Shinohara, K.; Ohuchi, T.; Kumada, M.
Tetrahedron Lett. 1974, 1153.
S0276-7333(98)00157-5 CCC: $15.00 © 1998 American Chemical Society
Publication on Web 07/30/1998

3662 Organometallics, Vol. 17, No. 17, 1998
Mateo et al.
Sch em e 2
transmetalation equilibrium by the formation of a
strong Si-F bond.4 Fluorides also enhance the reactiv-
ity of alkenyl- and arylboronic acids in the cross-
coupling with organic electrophiles (Suzuki reaction) by
the likely formation of a reactive fluoroborate.11-13
Fluoride anion can also promote the reduction of phos-
phine palladium(II) complexes to palladium(0), which
is initiated by the nucleophilic attack of fluoride on the
coordinated phosphine.14 Alternatively, AgF has been
found to yield arylpalladium fluorides.15 Recently it has
been demonstrated that NaOH, a commonly used ad-
ditive in the Suzuki reaction,11 also promotes the
Hiyama reaction.16,17
We have recently reported that derivatives I (X ) Br,
I) undergo oxidative addition to [Pd(PPh3)4] to give
intermediate complexes II, which suffered a rapid
transmetalation to form palladacycles III.18 The iso-
lated palladacycles III are stable species which do not
reductively eliminate due to the high ring strain of the
four-membered ring heterocycles IV. This truncated
intramolecular Stille coupling process was first demon-
strated with iodoarylstannanes 1a ,b, which cleanly
react with [Pd(PPh3)4] to afford the parent oxapallada-
cycle 2 (Scheme 2).18 Interestingly, arylpalladium(II)
complex 3, an intermediate of type II, could be isolated
as a stable yellow solid from the oxidative addition of
1a to the palladium(0) complex [Pd(dba)dppf].18b,19 This
aryliodopalladium(II) complex underwent smooth trans-
metalation in the presence of Ag2CO3 to form pallada-
cycle 4.18b We have recently also found that, by using
silanes instead of stannanes, the oxidative addition
intermediates can be obtained as stable compounds in
a general way, making it possible to systematically
study the transmetalation step of the synthetically
important Hiyama cross-coupling reaction, isolated from
the oxidative addition and reductive elimination steps.20
Herein we describe the use of substrates related to 1
as tools for the comparative study on the transmetala-
tion of organosilanes with Pd(II) and Pt(II) as well as
the related transmetalation of stannanes with Pt(II).21-23
Resu lts a n d Discu ssion
Tr a n sm eta la tion of Sila n es w ith P d (II). Silanes
5 and 6 were prepared by alkylation of o-iodophenol in
the presence of K2CO3 as the base with iodomethyltri-
methylsilane (92% yield) and chloromethyldimethyl-
phenylsilane (81% yield), respectively. Fluorosilane 7
was prepared by selective cleavage of the phenylsilicon
bond of 6 by reaction with HBF4 (82% yield).24 Thio-
ether 8 was prepared by reaction of o-bromothiophenol
with iodomethyltrimethylsilane in 93% yield. Similarly,
germane 9 was obtained in 73% yield by alkylation of
o-iodophenol with iodomethyltrimethylgermane.25
(10) Chuit, C.; Corriu, R. J . P.; Reye, C.; Young, J . C. Chem. Rev.
1993, 93, 1371.
(11) (a) Miyaura, N.; Suzuki, A. Chem. Rev. 1995, 95, 2457. (b)
Ridgway, B. H.; Woerpel, K. A. J . Org. Chem. 1998, 63, 458. (c) Matos,
K.; Soderquist, J . A. J . Org. Chem. 1998, 63, 461.
(12) (a) Wright, S. W.; Hageman, D. L.; McClure, L. D. J . Org. Chem.
1994, 59, 6095. (b) Laurent, D.; Srebnik, M. Tetrahedron Lett. 1996,
37, 2735. (c) Desurmont, G.; Dalton, S.; Giolando, D. M.; Srebnik, M.
J . Org. Chem. 1996, 61, 7943. (d) Darses, S.; Geneˆt, J .-P.; Brayer, J .-
L.; Demoute, J .-P. Tetrahedron Lett. 1997, 38, 4393.
Silane 5 reacted smoothly with [Pd(PPh3)4] in toluene
at 40 °C to give oxidative addition product 10 (88%). A
similar reaction of silane 7 with [Pd(PPh3)4] in THF at
23 °C gave 11 (82%). Synthesis of complexes 12-14
(13) Lead references on the coupling of other organometals. (a)
RMgX: Kumada, M. Pure Appl. Chem. 1980, 52, 669. (b) RZnX:
Negishi, E. Acc. Chem. Res. 1982, 15, 340. (c) RMnX: Riguet, E.; Alami,
M.; Cahiez, G. Tetrahedron Lett. 1997, 38, 4397.
(14) Mason, M. R.; Verkade, J . G. Organometallics 1992, 11, 2212.
(15) (a) Fraser, S. L.; Antipin, M. Y.; Khoroustalyov, V. N.; Grushin,
V. V. J . Am. Chem. Soc. 1997, 119, 4769. (b) Pilon, M. C.; Grushin, V.
V. Organometallics 1998, 17, 1774.
(16) Hagiwara, E.; Gouda, K.-I.; Hatanaka, Y.; Hiyama, T. Tetra-
hedron Lett. 1997, 38, 439.
(17) In situ-generated ethoxide also promotes the reaction of allylic
carbonates with alkenylfluorosilanes: (a) Matsuhashi, H.; Hatanaka,
Y.; Kuroboshi, M.; Hiyama, T. Tetrahedron Lett. 1995, 36, 1539. (b)
Matsuhashi, H.; Asai, S.; Hirabayashi, K.; Mori, A.; Hiyama, T. Bull.
Chem. Soc. J pn. 1997, 70, 1943.
(18) (a) Ca´rdenas, D. J .; Mateo, C.; Echavarren, A. M. Angew. Chem.,
Int. Ed. Engl. 1994, 33, 2445. (b) Mateo, C.; Ca´rdenas, D. J .;
Ferna´ndez-Rivas, C.; Echavarren, A. M. Chem. Eur. J . 1996, 2, 1596.
(19) Abbreviations: dba ) dibenzylideneacetone; dppf ) 1,1′-bis-
(diphenylphosphino)ferrocene; bpy ) 2, 2′-bipyridine; phen ) 1, 10-
phenanthroline; TASF ) tris(dimethylamino)sulfonium difluorotri-
methylsilicate; TBAF ) tetrabutylammonium fluoride.
(20) Mateo, C.; Ferna´ndez-Rivas, C.; Echavarren, A. M.; Ca´rdenas,
D. J . Organometallics 1997, 16, 1997.
(21) Transmetalation of stannanes with PtX2L2 complexes: (a)
Eaborn, C.; Kundu, K.; Pidcock, A. J . Chem. Soc., Dalton Trans. 1981,
933. (b) Weisemann, C.; Brune, H. A. J . Organomet. Chem. 1986, 312,
133. (c) Brune, H. A.; Schmidtberg, G.; Weisemann, C. J . Organomet.
Chem. 1989, 371, 121. (d) Weisemann, C.; Schmidtberg, G.; Brune, H.
A. J . Organomet. Chem. 1989, 365, 403. (e) Weisemann, C.; Schmidt-
berg, G.; Brune, H. A. J . Organomet. Chem. 1989, 362, 63. (f) Mu¨ller,
W.-D.; Brune, H. A. Chem. Ber. 1986, 119, 759.
(22) Transmetalation of hypercoordinated aryltrialkylsilanes and
-stannanes with Pd(II) and Pt(II) complexes: Steenwinkel, P.; J astr-
zebski, J . T. B. H.; Deelman, B.-J .; Grove D. M.; Kooijman, H.;
Veldman, N.; Smeets, W. J . J .; Spek, A. L.; van Koten, G. Organome-
tallics 1997, 16, 5486 and references therein.
(23) Lead references on related transmetalations of Pt(II) or Pd(II)
complexes: (a) Vicente, J .; Abad, J .-A.; Rink, B.; Herna´ndez, F.-S.;
Ram´ırez de Arellano, M. C. Organometallics 1997, 16, 6, 5269. (b)
Vicente, J .; Abad, J . A.; Teruel, F.; Garc´ıa, J . J . Organomet. Chem.
1988, 345, 233. (c) Siegmann, K.; Pregosin, P. S.; Venanzi, L. M.
Organometallics 1989, 8, 2659.
(24) (a) Fleming, I.; Henning, R.; Plaut, H. J . Chem. Soc., Chem.
Commun. 1984, 29. (b) J ones, G. R.; Landais, Y. Tetrahedron 1996,
52, 7599.
(25) Seyferth, D.; Andrews, S. B. J . Organomet. Chem. 1971, 30,
151.

Si, Sn Transmetalation of Pd(II) and Pt(II) Complexes
Organometallics, Vol. 17, No. 17, 1998 3663
Sch em e 3
Ta ble 1. Tr a n sm eta la tion of Com p lexes 10-15
with two AsPh3 ligands was carried out by reaction of
silanes 5-7 with [Pd(dba)(AsPh3)2]26 in acetone at 23
°C (59-88%) (Scheme 3). However, no reaction was
observed after treatment of 5-7 with [Pd(dba)(SbPh3)2]
or [Pd(dba)(BiPh3)2] prepared in situ from [Pd2(dba)3-
dba] and SbPh3 or BiPh3.26 On the other hand, silanes
5 and 7 reacted smoothly with [Pd(dba)(dppf)]27 in
toluene at 23 °C to afford complexes 15 (76%) and 16
(43%), respectively. Similarly, reaction of 5 with [Pd-
(dba)(bpy)] or [Pd(dba)(phen)]19,26 in THF at 23 °C gave
17 (78%) and 18 (66%), respectively. In contrast with
these results, thiosilane (8) led only to decomposition
products after treatment with [Pd(dba)(AsPh3)2]. Ger-
mane 9 also failed to give stable oxidative addition
complexes with [Pd(PPh3)4] or [Pd(dba)(AsPh3)2], lead-
ing instead to uncharacterized mixtures of products and
black palladium precipitates.28
P r om oted by F lu or id es
reaction time
(h)
yield
entry Ar-Pd-I additivea
palladacycle (%)c
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
10
10
10
12
12
12
13
13
13
14
14
14
15
15
15
TASF
TBAFb
KF
TASF
TBAF
KF
TASF
TBAF
KF
TASF
TBAF
KF
d
d
d
22
80
d
51
51
19
19
d
51
51
1
1
51
19
19
19
19
19
67
14
100
100
25
d
TASF
TBAF
KF
d
d
a
b
2 equiv of additive in MeCN at 23 °C. MeOH was used as
the solvent. c Yields were determined by integration of the 1H
The arylpalladium(II) complexes of Scheme 3 were
obtained as yellow-brown solids which were fully char-
acterized spectroscopically. Complexes 10-14, with two
mutually trans phosphines or arsines, show the CH2
d
NMR spectra. No reaction was observed after 24-48 h.
1
hydrogens at 2.5-2.7 ppm in the H NMR spectra as
singlets or doublets coupled with 19F. On the other
hand, complexes 15-18 bearing a cis bidentate ligand
show the characteristic diastereotopic CH2 hydrogens
around 2.8-3.8 ppm with 2J (1H-1H) ) 12.5-13.0 Hz.
Palladium(II) complexes 10-18 are stable compounds
which do not suffer intramolecular Pd/Si transmetala-
tion after being heated at 50 °C for 17 h (CDCl3 or CD3-
CN solutions). Furthermore, trimethylsilyl derivatives
10 and 15 failed to undergo transmetalation in the
presence of fluoride anion as the promoter (Table 1,
entries 1-3, 13-15). However, the desired transmeta-
lation could be achieved from the complexes 12-14
bearing triphenylarsine as the ligand for palladium.29
(26) This complex was prepared in situ by reaction of [Pd2(dba)3‚
dba] with 2 equiv of AsPh3. For the preparation of similar complexes:
(a) Takahashi, Y.; Ito, T.; Sakai, S.; Ishii, Y. J . Chem. Soc., Chem.
Commun. 1970, 1065. (b) Ukai, T.; Kawazura, H.; Ishii, Y.; Bonnet, J .
J .; Ibers, J . A. J . Organomet. Chem. 1974, 65, 253. (c) Amatore, C.;
J utand, A.; Khalil, F.; M’Barki, M. A.; Mottier, L. Organometallics
1993, 12, 3168.
(27) (a) Xi, Z.; Yang, R.; J in, D. Chin. Chem. Lett. 1991, 2, 331. (b)
For the synthesis of related PdL2(dba) complexes (L2 ) dppe, dppp):
Herrmann, W. A.; Thiel, W. R.; Brossmer, C.; O¨ fele, K.; Priermeier,
T.; Scherer, W. J . Organomet. Chem. 1993, 461, 51.
(28) Palladium-catalyzed coupling of germanes. (a) Coupling of
trimethylvinylgermanium with aryl tetrafluoroborates: Ikenaga, K.;
Matsumoto, S.; Kikukawa, K.; Matsuda, T. Chem. Lett. 1990, 185. (b)
Coupling with aryl bromides: Kosugi, M.; Tanji, T.; Tanaka, Y.;
Yoshida, A.; Fugami, K.; Kameyama, M.; Migita, T. J . Organomet.
Chem. 1996, 508, 255.

3664 Organometallics, Vol. 17, No. 17, 1998
Mateo et al.
Thus, addition of TASF or TBAF19 to 12 led to formation
of palladacycle 19 (entries 4 and 5). Less soluble KF
failed to promote this transmetalation (entry 6). Phen-
ylsilane 13 also reacted in the presence of TBAF or KF
(entries 8 and 9). The more favorable cleavage of the
alkyl-Si in 13 in the presence of the usually more
reactive phenyl-Si bond is another example of endocy-
clic restriction30 in the intramolecular transmetalation
reaction.18 Fluorosilyl derivative 14 was the most
reactive complex in the presence of fluorides. Thus, 14
gave 19 in almost quantitative yield after treatment
with 1 equiv of TASF or TBAF (entries 10 and 11). In
general, best results were obtained by using com-
mercially available TBAF hydrate as the fluoride source.
No attempt was made to increase the reactivity of this
fluoride by drying or by using other commercially
available sources. KF was only able to promote the
reactions of complexes 13 and 14 to give oxapalladacycle
19 in poor yields (entries 9 and 12). Similar results
were obtained with the more soluble CsF.
Ta ble 2. Tr a n sm eta la tion of Com p lexes 10-18
P r om oted by Ag(I) or K2CO3 a s Ad d itives
reaction
T
time
(h)
yield
(%)b
entry Ar-Pd-I additivea (°C)
palladacycle
1
2
3
4
5
6
7
8
9
10
11
12
13
14
10
11
11
12
12
12
13
13
14
14
15
16
17
18
Ag2CO3
Ag2CO3
K2CO3
Ag2CO3
K2CO3
Ag2O
Ag2CO3
K2CO3
Ag2CO3
K2CO3
Ag2CO3
Ag2CO3
Ag2CO3
Ag2CO3
50
23
23
50
50
50
23
50
23
23
50
23
50
50
c
94
1
2
c
24
5
6
51
44
2
19 + 20
19
19 + 20
19
19
19
19
95d
100
(100)d
(100)
(20)
90 (100)
(27)
c
100
100
100
43
1
32
32
4
21
22
a
b
2 equiv of additive in MeCN. Isolated yields. Numbers in
parentheses are for yields determined by 1H NMR. c No reaction
was observed after 24-48 h. A 1:1 mixture of 19 and 20.
d
cleaved by a trimethylsilyl electrophile. Significantly,
the presence of silver ion was not essential for these
reactions since the transmetalation of 12 to 19 could
be cleanly triggered by the addition of K2CO3 in aceto-
nitrile (Table 2, entry 5). Experiments carried out with
complex 12 in the presence of Ag2CO3 (acetonitrile, 20
°C) showed that addition of excess AsPh3 (10 equiv)
almost completely suppressed the transmetalation reac-
tion. NaOH and Na2HPO4 also promoted the trans-
metalation of 12 in acetonitrile (23 °C), albeit quite
inefficiently (e8% yields).31 Reaction of 13 with Ag2-
CO3 or K2CO3 also led to 19 (Table 2, entries 7 and 8).
As expected, fluorodimethylsilyl complexes 14 and 16
underwent smooth transmetalation in the presence of
Ag2CO3 to give oxapalladacycles 19 or 4 (Table 2, entries
9 and 12). However, trimethylsilyl derivative 15 failed
to react under these conditions (Table 2, entry 11). The
lack of reactivity of complexes 10 and 15 in the presence
of fluoride (Table 1, entries 1-3 and 13-15) or Ag2CO3
(Table 2, entries 1 and 11) is probably due to the
stronger coordination ability of PPh3 and dppf toward
Pd(II). Interestingly, trimethylsilyl derivatives 17 and
18, bearing bidentate pyridine-type ligands, reacted
smoothly in the presence of Ag2CO3 to give palladacycles
21 and 22, respectively (Table 2, entries 13 and 14).
The activation observed with the carbonates suggests
that an arylpalladium carbonato complex32,33 or a pal-
ladium oxo complex11b,c,34 is involved as the reactive
species in the transmetalation. Nevertheless, the high
reactivity of fluorosilanes 14 and 16 in their reactions
with Ag2CO3 or K2CO3 suggests that the silane is also
activated by the carbonate to form a pentacoordinated
silicon species. Formation of a reactive palladium oxo
or hydroxo intermediate is probably involved in the
activation promoted by Ag2O, NaOH, or Na2HPO4.
Interestingly, formation of complexes with a Pd-O bond
Although the above results demonstrate that the
addition of fluoride is a convenient method for the
activation of silanes toward transmetalation with Pd-
(II) compounds,5,8 we also tried to promote this reaction
by increasing the electrophilicity of the palladium center
by removal of the iodide ligand. However, all the
experiments carried out with 12 by using silver salts
such as AgOTf, AgBF4, AgOTs, Ag2SO4, and AgNO3
gave negative results, leading to extensive decomposi-
tion of 12 or recovery of the starting complex. Interest-
ingly, the use of Ag2CO3 as the additive led to the
desired transmetalation under smooth conditions. Thus,
complex 11 led readily to palladacycle 2 after being
treated with Ag2CO3 in acetonitrile solution for 1 h at
room temperature (Table 2, entry 2). Complex 12 also
reacted with Ag2CO3 in acetonitrile at 50 °C to give the
corresponding palladacycle 19. In addition, an equimo-
lar amount of silyl-substituted complex 20 was obtained
in this experiment (Table 2, entry 4). A similar result
was obtained by using Ag2O as the additive (Table 2,
entry 6). The formation of an equimolar quantity of 19
and 20 suggests that a binuclear palladium complex
with a carbonate or oxide bridge is formed which is
(31) On the other hand, Na3BO3‚4H2O, Na3PO4, NaH2PO4, and
(NaO)3PS‚12H2O failed to promote the transmetalation.
(32) For the formation of bis(triphenylphosphino)carbonatopalladium-
(II): Nyman, C. J .; Wymore, C. E.; Wilkinson, G. J . Chem. Soc. A 1968,
561.
(33) Reaction of Ag2CO3 with dichloro(diphosphine)platinum(II)
complexes leads to (diphosphine)carbonatoplatinum(II) complexes: (a)
Andrews, M. A.; Gould, G. L.; Voss, E. J . Inorg. Chem. 1996, 35, 5740.
(b) Andrews; M. A.; Gould, G. L:, Klooster, W. T.; Koenig, K. S.; Voss,
E. J . Inorg. Chem. 1996, 35, 5478 and references therein.
(29) (a) Farina, V.; Krishnan, B.; Marshall, D. R.; Roth, G. J . Org.
Chem. 1993, 58, 5434. (b) Farina, V.; Krishnan, B. J . Am. Chem. Soc.
1991, 113, 9585. (c) For
a review: Farina, V. In Comprehensive
Organometallic Chemistry II; Abel, E. W., Stone, F. G. A., Wilkinson,
G., Eds.; Pergamon: Oxford, 1995; Vol. 12, Chapter 3.4.
(30) Beak, P. Acc. Chem. Res. 1992, 25, 215.

Si, Sn Transmetalation of Pd(II) and Pt(II) Complexes
Organometallics, Vol. 17, No. 17, 1998 3665
Sch em e 4
chromatographic purifications. No reaction was ob-
served by using palladium(0) complexes such as [Pd-
(PPh3)4], [Pd(dba)AsPh3], or [Pd(dba)dppf] as the cata-
lysts. Formation of 25 reveals that this transformation
proceeds by a Pd(II)/Si transmetalation through a
complex similar to 2 and 19 in which palladium(II) is
probably coordinated with two molecules of DMF.
Tr a n sm eta la tion of Sila n es a n d Sta n n a n es w ith
P t(II). The oxidative addition of aryl iodides to plati-
num(0) is known to provide the corresponding arylplati-
num(II) complexes.37 In the event, when solutions of
iodoaryl stannanes 1b or 27 and [Pt(PPh3)4]38 were
heated at 40-70 °C in toluene, oxaplatinacycles 28 (85%
yield) and 29 (46% yield) were cleanly obtained (eq 1).
No intermediate arylplatinum(II) complex could be
observed upon performing the reactions at lower tem-
peratures and/or shorter reaction times, which demon-
strates that the Pt(II)/Sn transmetalation is faster than
the oxidative addition of the aryl iodides to platinum-
(0) coordinated to PPh3.
has been proposed to accelerate the Pd/B transmetala-
tion in the Suzuki coupling reaction.11 Indeed, prelimi-
nary results show that hydroxo complexes 23 (as a
mixture of trans and cis isomers)34c react with tribu-
tylvinylstannane in CDCl3 at room temperature to yield
styrene.
Platinacycles 28 and 29 are white solids which can
be purified by chromatography on silica gel without
decomposition. Their structures were determined by
1
NMR. Thus, the H NMR spectrum of 28 is similar to
that of 2 and shows the aryl hydrogens between 5.99
and 6.92 ppm as multiplets coupled to 31P, with the
expected satellites due to the coupling with 195Pt. The
CH2 hydrogens appeared as a dd (3J (31P-1H) ) 4.4 and
2
2.9 Hz) with J (1H-195Pt) ) 49.5 Hz. The 13C{1H} NMR
spectrum of 28 showed the CH2 carbon at δ ) 85.99 ppm
as a dd due to the coupling with two distinct phosphines
(2J (13C-13C) ) 93.8, 5.3 Hz) with the corresponding
coupling to 195Pt (1J ) 683.2 Hz). The 31P{1H} NMR
spectrum showed a resonance at δ ) 28.36 ppm as a
singlet, although the corresponding 195Pt satellites
appeared as a pair of doublets corresponding to 1J
couplings of two different 31P with 195Pt of 2146 and
1888 Hz and 2J (31P-31P) ) 14.2 Hz.39 The 31P{1H}
NMR of 29 showed an AB pattern (δ ) 27.54 and 27.02
ppm, 2J (31P-31P) ) 15.5 Hz) corresponding to different
phosphine ligands further coupled with 195Pt (1J ) 1860
and 2267 Hz). The 2J (31P-31P) of 14-15 Hz in oxa-
platinacycles 28 and 29 is smaller than that found for
the oxapalladacycles (25.6 Hz for 2).18
Recently, Dyker reported a remarkable palladium-
catalyzed synthesis of dibenzo[b,d]pyrane (24) from
o-iodoanisole (Scheme 4)35 which presumably takes
place through palladacycle intermediates such as 2 as
a result of an activation of the methoxy C-H bond by
palladium35,36 Therefore, it was of some interest to
determine if a silane such as 5 would afford the
corresponding dibenzo[b,d]pyranes 25 or 26 by a process
initiated by C-Si or C-H activation by palladium(II).
In the event, heating of 5 at 100 °C in DMF with Pd-
(OAc)2 as the catalyst in the presence of Bu4NBr and
K2CO3 led to 25, isolated in 20% yield after repeated
In analogy with what was observed in the case of
silanes, we had expected to isolate the corresponding
oxidative addition products in the reaction of silane 5
with platinum(0) complexes. However, reaction of 5
with [Pt(PPh3)4] in toluene at 70 °C led exclusively to
the slow formation of oxaplatinacycle 28 (isolated in 45%
yield) (eq 2). On the other hand, treatment of 5 with
(34) Hydroxo palladium complexes: (a) Bushnell, G. W.; Dixon, K.
R.; Hunter, R. G.; McFarland, J . J . Can. J . Chem. 1972, 50, 3694. (b)
Lo´pez, G.; Ruiz, J .; Garc´ıa, G.; Vicente, C.; Mart´ı, J . M.; Santana, M.
D. J . Organomet. Chem. 1990, 393, C53. (c) Grushin, V. V.; Alper, H.
Organometallics 1993, 12, 1890. (d) Grushin, V. V.; Bensimon, C.;
Alper, H. Organometallics 1993, 12, 2737. (e) Ruiz, J .; Rodr´ıguez, V.;
Lo´pez, G.; Chaloner, P. A.; Hitchcok, P. B. J . Organomet. Chem. 1996,
523, 23. (f) Ruiz, J .; Cutillas, N.; Sampedro, J .; Lo´pez, G.; Hermoso, J .
A.; Mart´ınez-Ripoll, M. J . Organomet. Chem. 1996, 526, 67. (g)
Grushin, V. V.; Alper, H. Organometallics 1996, 15, 5242. (h) Kuz-
netsov, V. F.; Bensimon, C.; Facey, G. A.; Grushin, V. V.; Alper, H.
Organometallics 1997, 16, 97.
(37) Manna, J .; Whiteford, J . A.; Stang, P. J .; Muddiman, D. C.;
Smith, R. D. J . Am. Chem. Soc. 1996, 118, 8731 and references therein.
(38) Ugo, R.; Cariati, F.; La Monica, G. Inorg. Synth. 1990, 28, 124.
(39) For the relation between 1J (119Pt-31P) and the Pt-P distance
in Pt(II) complexes: Mather, G. G.; Pidcock, A.; Rapsey, G. J . N. J .
Chem. Soc., Dalton Trans. 1973, 2095.
(35) (a) Dyker, G. Angew. Chem., Int. Ed. Engl. 1992, 31, 1023. (b)
Dyker, G. J . Org. Chem. 1993, 58, 6426. (c) Dyker, G. Chem. Ber. 1994,
127, 739.
(36) Dyker, G. Chem. Ber. Recl. 1997, 1567.

3666 Organometallics, Vol. 17, No. 17, 1998
Mateo et al.
[Pt(dba)(AsPh3)2], prepared in situ from [Pt(dba)2]40 and
AsPh3, in acetone or THF led only to the recovery of
the starting materials. Oxaplatinacycle 28 was the only
new platinum complex observed in the reaction of 5 with
[Pt(PPh3)4], which indicates that, in contrast with what
was observed in the Pd(II)/Si transmetalation, the
related Pt(II)/Si transmetalation is a facile process
which takes place in the absence of any additive.
The Pt(II)/Sn and Pt(II)/Si transmetalations also take
place, leading to the formation of oxaplatinacycles.
Interestingly, the Pt(II)/Si transmetalation takes place
readily in the absence of additives. A platinum ana-
logue of the Stille and related cross-coupling reactions
could be possible by using the adequate platinum(0)
complexes as catalyst.
Despite much mechanistic work on cross-coupling
reactions,1,2,42-44 some recent results indicate that these
reactions may proceed by a variety of mechanisms.
Thus, for example, coupling of an alkynylstannane with
aryl iodides with a palladium catalyst with a bidentate
ligand has been recently proposed to proceed by a
mechanism which involves an oxidative addition of the
alkynylstannane to the palladium(0) complex, followed
by reaction of an Ar-Pd-SnBu3 complex with ArI.45
Additionally, several aspects of the key transmetalation
step46 are not clearly understood. Thus, inversion47 or
retention48,49 of the configuration of alkylstannanes or
silanes has been found to depend on the presence of
additives, solvent polarity, and temperature.50 On the
other hand, alkylboranes have been recently reported
to transmetalate with retention of configuration in the
presence of hydroxide anion.11b,c Efforts directed to
study the stereochemistry of the Pd(II)/Sn or Pd(II)/Si
transmetalation step by using a system related to that
outlined in Scheme 1 are underway.
The results shown in eqs 1 and 2 suggest that
platinum(0) could catalyze the coupling of stannanes or
silanes with organic electrophiles. However, prelimi-
nary results show that the reactions are rather slow
under catalytic conditions, probably due to an inefficient
oxidative addition reaction. Thus, the coupling of aryl
triflates 30 and 31 with tributylvinylstannane could be
catalyzed by [Pt(PPh3)4] (5 mol %) in the presence of
K2CO3 to give styrenes 32 and 33 (eq 3), although the
reaction is much slower than that catalyzed by the
analogous Pd complex.41
Exp er im en ta l Section
Only the most significant IR frequencies are given. Ele-
mental analyses were performed at the SIdI (UAM). All
reactions were carried out under an atmosphere of Ar.
Solvents were purified and dried by standard methods.
Chromatographic purifications were carried out with flash
grade silica gel.
Con clu sion s
The following palladium and platinum complexes were
prepared according to the known procedures: [Pd(PPh3)4],51
[Pd2(dba)3dba],26 [Pd(dba)(o-phen)],26 [Pd(dba)(bpy)],26 [Pd-
(dba)(AsPh3)2],26 [Pd(dba)(dppf)],27 [Pt(PPh3)4],37 [Pt(dba)2],38
and palladium complexes 23.34c Stannanes 1b and 27 were
The system that we have developed for the study of
the Stille reaction18 makes it possible also to study the
effect of ligands and additives on the Pd(II)/Si trans-
metalation, isolated from the oxidative addition and
reductive elimination steps. We have found that the
intramolecular transmetalation of alkylsilanes with
arylpalladium complexes, the key step in the Hiyama
(42) Brown, J . M.; Cooley, N. A. Chem. Rev. 1988, 88, 1031.
(43) Stille, J . K. In The Chemistry of the Metal-Carbon Bond;
Hartley, F. R., Patai, S. Eds.; Wiley: Chichester, 1985; Vol. 2, Chapter
9.
2-
coupling reaction, requires the addition of F- or CO3
as promoters. Additionally, the use of AsPh3 as the
ligand for palladium(II) substantially accelerates the
Pd(II)/Si transmetalation step. Among the tested bi-
dentate ligands, best results were obtained with pyri-
dine-type ligands (bpy and phen), which allow for the
efficient transmetalation of the less reactive trimeth-
ylsilyl derivatives. On the other hand, additives which
may favor formation of cationic arylpalladium(II) com-
plexes do not promote the intramolecular transmetala-
tion. The higher reactivity of phenyl- and fluorosilanes
in the transmetalation reactions with fluorides and
carbonates as the additives suggests that the silane is
activated by formation of a more nucleophilic pentaco-
ordinated Si(IV) species. However, formation of palla-
dium(II)-oxygen bond11 by reaction of the arylpalladium-
(II) iodide with the carbonates cannot be excluded as a
key step in the Pd(II)/Si transmetalation.
(44) Lead recent references: (a) Stang, P. J .; Kowalski, M. H.;
Schiavelli, M. D.; Longford, D. J . Am. Chem. Soc. 1989, 111, 3347. (b)
Brown, J . M.; Hii, K. K. Angew. Chem., Int. Ed. Engl. 1996, 35, 657.
(c) Amatore, C.; Broeker, G.; J utand, A.; Khalil, F. J . Am. Chem. Soc.
1997, 119, 5176. (d) Casado, A. L.; Espinet, P. Organometallics 1998,
17, 954. (e) For a recent discussion of the role of phosphines on the
reductive elimination step: Vicente, J .; Arcas, A.; Bautista, D.; J ones,
P. G. Organometallics 1997, 16, 2127. (g) For a study on the mechanism
of coupling of alkynylcopper(I) complexes with palladium(II) complexes
(Sonogashira reaction): Osakada, K.; Sakata, R.; Yamamoto, T.
Organometallics 1997, 16, 5354.
(45) Shirakawa, E.; Yoshida, H.; Hiyama, T. Tetrahedron Lett. 1997,
38, 5177.
(46) (a) Louie, J .; Hartwig, J . F. J . Am. Chem. Soc. 1995, 117, 11598.
(b) Morita, D. K.; Stille, J . K.; Norton, J . R. J . Am. Chem. Soc. 1995,
117, 8576. (c) Vedejs, E.; Haight, A. R.; Moss, W. O. J . Am. Chem.
Soc. 1992, 114, 6556.
(47) Labadie, J . W.; Stille, J . K. J . Am. Chem. Soc. 1983, 105, 6129.
(48) (a) Ye, J .; Bhatt, R. K.; Falck, J . R. J . Am. Chem. Soc. 1994,
116, 1. (b) Ye, J .; Bhatt, R. K.; Falck, J . R. Tetrahedron Lett. 1993, 34,
8007.
(49) For the coupling of organostannanes with organic iodides
mediated by copper: (a) Allred, G. D.; Liebeskind, L. S. J . Am. Chem.
Soc. 1996, 118, 2748. (b) Zhang, S.; Zhang, D.; Liebeskind, L. S. J .
Org. Chem. 1997, 62, 2312. (c) Coupling mediated by Cu(I) or Mn(II):
Kang, S.-K.; Kim, J .-S.; Choi, S.-C. J . Org. Chem. 1997, 62, 4208.
(50) Hatanaka, Y.; Hiyama, T. J . Am. Chem. Soc. 1990, 112, 7793.
(51) Cotton, F. A. Inorg. Synth. 1972, 13, 121.
(40) Moseley, K.; Maitlis, P. M. J . Chem. Soc., Dalton Trans. 1974,
169.
(41) Echavarren, A. M.; Stille, J . K. J . Am. Chem. Soc. 1987, 109,
5478.

Si, Sn Transmetalation of Pd(II) and Pt(II) Complexes
Organometallics, Vol. 17, No. 17, 1998 3667
prepared according to our previously described method.18
Triflates 29 and 30 were prepared according to the described
procedure.41 (Iodomethyl)trimethylgermane was synthesized
from ICH2ZnI, GeCl4, and MeMgBr:25 1H NMR (200 MHz,
CDCl3) δ 2.08 (s, 2H), 0.27 (s, 9H).
1.42 mmol) in DMF (10 mL) was added, and the mixture was
stirred at 60 °C for 21 h. After being cooled to 23 °C, the
mixture was partitioned between water and hexane. The
organic extract was dried (Na2SO4 and MgSO4) and evapo-
rated. Chromatography (hexane) gave 9 as a colorless oil (363
mg, 73%): 1H NMR (200 MHz, CDCl3) δ 7.76 (dd, J ) 7.6, 1.6
Hz, 1H), 7.32 (td, J ) 7.3, 1.6 Hz, 1H), 6.93 (dd, J ) 8.2, 1.3
Hz, 1H), 6.69 (td, J ) 7.6, 1.5 Hz, 1 H), 3.87 (s, 2H), 0.37 (s,
9H); 13C{1H} NMR (50 MHz, CDCl3) δ 159.54, 139.17, 129.29,
122.07, 111.30, 86.53, 63.00, -3.05; EI-MS m/z (relative
intensity) 353 (M+ + 2, 4), 351 (M+, 5), 350 (M+ - 1, 2), 349
(M+ - 2, 4), 347 (M+ - 4, 2), 337 (13), 335 (10), 297 (9), 295
(8), 237 (50), 236 (20), 235 (67), 233 (54), 121 (20), 119 (100),
117 (75), 115 (56). Anal. Calcd for C10H15GeIO: C, 34.24; H,
4.31. Found: C, 33.70; H, 4.93.
(2-Iod op h en oxym eth yl)tr im eth ylsila n e (5). A mixture
of o-iodophenol (1.00 g, 4.54 mmol) and K2CO3 (850 mg, 6.16
mmol) was stirred at 23 °C in DMF (10 mL). After 30 min,
iodomethyltrimethylsilane (975 mg, 4.54 mmol) was added,
and the resulting mixture was heated at 70 °C for 17 h. After
being cooled to room temperature and undergoing extractive
workup (1:1 hexanes-Et2O), the residue was chromatographed
(hexane) to give 5 as a colorless oil (1.28 g, 92%): 1H NMR
(200 MHz, CDCl3) δ 7.81 (d, J ) 7.5 Hz, 1H), 7.37 (t, J ) 8.6
Hz, 1H), 7.0 (d, J ) 8.6 Hz, 1H), 6.75 (t, J ) 7.5 Hz, 1H), 3.69
(s, 2H), 0.29 (br s, 9H); 13C{1H} NMR (75 MHz, CDCl3; DEPT)
δ 159.60 (C), 139.08 (CH), 129.29 (CH), 121.97 (CH), 111.11
(CH), 86.55 (C), 62.20 (CH2), -3.00 (3 × CH3). Anal. Calcd
for C10H15IOSi: C, 39.22; H, 4.93. Found: C, 39.66; H, 4.87.
tr a n s-Bis(tr ip h en ylp h osp h in e)iod o[2-(tr im eth ylsilyl-
m eth oxy)p h en yl]p a lla d iu m (10). To a partial solution of
[Pd(PPh3)4] (1.03 g, 0.89 mmol) in toluene (3 mL) was added
silane 5 (300 mg, 0.98 mmol), and the mixture was stirred at
40 °C for 3 h. The resulting solid was filtered and washed
with Et2O to give 10 as a yellow solid (670 mg, 88%): 1H NMR
(200 MHz, CDCl3) δ 7.57-7.17 (m, 30H), 6.82 [dq, J (1H-1H)
) 9.7 Hz, J (1H-1H) ) J (1H-31P) ) 1.8 Hz, 1H], 6.47 [t, J (1H-
1H) ) 7.5 Hz, 1H], 6.17 [t, J (1H-1H) ) 7.2 Hz, 1H], 5.79 [dd,
J (1H-1H) ) 8.1 Hz, J (1H-1H) ) 1.2 Hz, 1H], 2.51 (s, 2H), 0.16
(s, 9H); 13C{1H} NMR (75 MHz, CDCl3; DEPT) δ 161.65 [t,
J (13C-31P) ) 2.6 Hz; C], 144.71 [t, J (13C-31P) ) 3.7 Hz; C],
Dim et h yl(2-iod op h en oxym et h yl)p h en ylsila n e (6).
A
mixture of o-iodophenol (500 mg, 2.27 mmol) and K2CO3 (471
mg, 3.41 mmol) was stirred at 23 °C in DMF (10 mL). After
30 min, chloromethyldimethylphenylsilane (382 mg, 2.06
mmol) in DMF (10 mL) was added, and the resulting mixture
was heated at 60 °C for 24 h. After being cooled to room
temperature and undergoing extractive workup (1:1 hexanes-
Et2O), the residue was chromatographed (hexane) to give 6
as a colorless oil (614 mg, 81%): 1H NMR (200 MHz, CDCl3)
δ 7.75 (dd, J ) 7.7, 1.6 Hz, 1H), 7.70-7.66 (m, 2H), 7.43-7.38
(m, 3H), 7.28 (br t, J ) 8.6 Hz, 1H), 6.90 (dd, J ) 7.9 1.0, Hz,
1H), 6.68 (br t, J ) 7.9 Hz, 1H), 3.79 (s, 2H), 0.52 (s, 6H); 13C-
{1H} NMR (50 MHz, CDCl3) δ 159.42, 139.05, 136.35, 133.98,
129.48, 129.30, 127.88, 122.07, 111.02, 86.46, 61.54, -4.40.
Anal. Calcd for C15H17IOSi: C, 48.92; H, 4.65. Found: C,
49.22; H, 4.53.
F lu or o(2-iod op h en oxym eth yl)d im eth ylsila n e (7). To
a solution of silane 6 (964 mg, 2.62 mmol) in CH2Cl2 (20 mL)
at 0 °C was added HBF4 (0.72 mL, 54% solution in Et2O, 4.9
mmol), and the resulting mixture was stirred at this temper-
ature for 24 h. After extractive workup (CH2Cl2/H2O), 7 was
obtained as a very pale yellow oil (664 mg, 82%): 1H NMR
(200 MHz, CDCl3) δ 7.76 [dd, J (1H-1H) ) 8.5, 1.5 Hz, 1H],
7.30 [td, J (1H-1H) ) 7.7, 1.5 Hz, 1H], 6.91 [(dd, J (1H-1H) )
8.0, 1.0 Hz, 1H], 6.72 [td, J (1H-1H) ) 8.5, 1.5 Hz, 1H], 3.74
[d, 3J (1H-19F) ) 3.9 Hz, 2H], 0.49 [d, 3J (1H-19F) ) 7.2 Hz,
6H]; 13C{1H} NMR (50 MHz, CDCl3) δ 158.91, 139.17, 129.41,
122.47, 111.07, 86.31, 60.16 [dd, 2J (13C-19F) ) 20.0 Hz], -2.46
[d, 2J (13C-19F) ) 14.1 Hz]. This compound suffered some
decomposition after chromatography (3:1 hexanes-EtOAc) to
give a product whose mass spectrum showed peaks corre-
sponding to the siloxane (RMe2Si)2O (R ) o-IC6H4OCH2).
2
134.96 [t, J (13C-31P) ) 6.3 Hz, PPh3; CH], 134.31 [t, J (13C-
1
31P) ) 4.1 Hz; CH], 132.23 [t, J (13C-31P) ) 23 Hz, PPh3; C],
129.56 (br s, PPh3; CH), 127.47 [t, 3J (13C-31P) ) 5.1 Hz, PPh3;
CH], 124.09 (s; CH), 119.43 (s; CH), 110.18 (s; CH), 59.47 (s;
CH2), -2.33 (s; CH3); 31P{1H} NMR (121.5 MHz, CDCl3) δ
23.06. Anal. Calcd for C46H45IOP2PdSi: C, 58.95; H, 4.83.
Found: C, 58.92; H, 4.63.
tr a n s-Bis(tr ip h en ylp h osp h in e)[2-(flu or od im eth ylsilyl-
m eth oxy)p h en yl]iod op a lla d iu m (11). A mixture of silane
7 (80 mg, 0.26 mmol) and [Pd(PPh3)4] (271 mg, 0.24 mmol) in
THF (5 mL) was stirred at 23 °C for 18 h. The solvent was
evaporated, and the residue was triturated with Et2O to give
11 as a yellow solid (181 mg, 82%): 1H NMR (200 MHz, CDCl3)
δ 7.54-7.43 (m, 12H), 7.40-7.16 (m, 18H), 6.89-6.81 (m, 1H),
6.46 (br t, J ) 7.3 Hz, 1H), 6.20 (br t, J ) 7.2 Hz, 1H), 5.58 (br
3
d, J ) 7.4 Hz, 1H), 2.57 [d, J (1H-19F) ) 6.1 Hz, 2H], 0.40 [d,
3J (1H-19F) ) 7.5 Hz, 6H]; 13C{1H} NMR (50 MHz, CDCl3) δ
160.78 (br s), 145.16 (br s), 134.88 [t, 2J (13C-31P) ) 5.3 Hz;
1
PPh3], 134.09 (br s), 132.12 [t, J (13C-31P) ) 24.2 Hz; PPh3],
129.56 (s; PPh3), 127.49 [br d, 3J (13C-31P) ) 5.2 Hz; PPh3],
124.10, 119.87, 110.46, 57.62 [d, 2J (13C-19F) ) 18.6 Hz], -2.16
2
[d, J (13C-19F) ) 14.7 Hz]; 31P{1H} NMR (CDCl3, 121.5 Hz) δ
23.09. Anal. Calcd for C45H42FIOP2PdSi: C, 57.43; H, 4.50.
Found: C, 57.78; H, 4.61.
tra ns-Bis(triphenylarsine)iodo[2-(trimethylsilylmethoxy)-
p h en yl]p a lla d iu m (12). A mixture of [Pd2(dba)3dba] (625
mg, 0.54 mmol) and AsPh3 (990 mg, 3.24 mmol) in acetone
(15 mL) was stirred at 23 °C for 3 h, yielding [Pd(dba)(AsPh3)2].
To this suspension was added silane 5 (500 mg, 1.63 mmol)
and toluene (20 mL), and the mixture was heated at 40 °C for
17 h. The resulting solution was filtered through Celite, and
the solvent was evaporated. The residue was triturated with
Et2O to give 12 as a yellow solid (720 mg, 65%): 1H NMR (200
MHz, CDCl3) δ 7.44-7.16 (m, 30H), 6.71 (dd, J ) 7.5, 1.5 Hz,
1H), 6.49 (t, J ) 7.5 Hz, 1H), 6.16 (t, J ) 7.2 Hz, 1H), 5.70 (d,
J ) 8.0 Hz, 1H), 2.48 (s, 2H), 0.06 (s, 9H); 13C{1H} NMR (75
MHz, CDCl3; DEPT) δ 162.35 (C), 136.26 (C), 135.74 (CH),
134.22 (CH; AsPh3), 134.0 (C; AsPh3), 129.31 (CH; AsPh3),
128.07 (CH; AsPh3), 124.49 (CH), 119.27 (CH), 111.42 (CH),
59.45 (CH2), -2.53 (CH3). Anal. Calcd for C46H45As2IOPdSi:
C, 53.89; H, 4.42. Found: C, 53.79; H, 4.15.
(2-Br om oth iop h en oxym eth yl)tr im eth ylsila n e (8).
A
suspension of 2-bromothiophenol (500 mg, 2.64 mmol) and K2-
CO3 (547 mg, 3.96 mmol) in DMF (10 mL) was stirred at 23
°C for 30 min. A solution of iodomethyltrimethylsilane (566
mg, 2.64 mmol) in DMF (5 mL) was then added, and the
mixture was stirred at 60 °C for 24 h. After being cooled to
23 °C, the mixture was partitioned between water and 1:1
hexanes-Et2O. The organic extract was dried (Na2SO4 and
MgSO4), and the solvent was evaporated. The residue was
chromatographed (hexane) to give 8 as a colorless oil (680 mg,
94%): 1H NMR (300 MHz, CDCl3) δ 7.51 (dd, J ) 8.0, 1.3 Hz,
1H), 7.33-7.25 (m, 2H), 6.99 (ddd, J ) 7.9, 6.8, 2.1 Hz, 1H),
2.12 (s, 2H), 0.22 (s, 3H); 13C{1H} NMR (75 MHz, CDCl3) δ
141.17, 132.28, 127.42, 125.22, 125.16, 121.09, 17.90, -1.64.
Anal. Calcd for C10H15BrSSi: C, 43.63; H, 5.49. Found: C,
43.49; H, 5.37.
(2-Iod op h en oxym eth yl)tr im eth ylger m a n e (9). A sus-
pension of 2-iodophenol (318 mg, 1.56 mmol) and K2CO3 (294
mg, 2.13 mmol) in DMF (25 mL) was stirred at 25 °C for 20
min. A solution of (iodomethyl)trimethylgermane (366 mg,
tra ns-Bis(triphenylarsine)[2-dimethylphenylsilylmethoxy)-
p h en yl]iod op a lla d iu m (13). A mixture of [Pd2(dba)3dba]
(335 mg, 0.29 mmol) and AsPh3 (375 mg, 1.22 mmol) in acetone

3668 Organometallics, Vol. 17, No. 17, 1998
Mateo et al.
(20 mL) was stirred at 23 °C for 3 h, yielding [Pd(dba)(AsPh3)2].
To this suspension was added silane 6 (322 mg, 0.87 mmol) in
acetone (5 mL), and the resulting mixture was stirred at 23
°C for 20 h. The solvent was evaporated, and the residue was
triturated with Et2O to give 13 as a brown solid (426 mg,
67%): 1H NMR (200 MHz, CDCl3) δ 7.49-7.13 (m, 35H), 6.71
(dd, J ) 7.2, 1.5 Hz, 1H), 6.49 (td, J ) 8.3, 1.4 Hz, 1H), 6.18
(td, J ) 7.4, 1.0 Hz, 1H), 5.73 (br d, J ) 8.3 Hz, 1H), 2.69 (s,
2H), 0.39 (s, 6H); 13C{1H} NMR (50 MHz, CDCl3) δ 162.41,
137.20, 136.12, 135.96, 134.20, 133.98, 133.70, 129.31, 128.61,
128.07, 127.89, 124.55, 119.41, 111.69, 58.88, -3.88. Anal.
Calcd for C51H47As2IOPdSi: C, 56.35; H, 4.36. Found: C,
55.82; H, 4.35.
Hz, 1H), 7.31 (td, J ) 5.5, 1.4 Hz, 1H), 6.99 (td, J ) 7.8, 1.4
Hz, 1H), 6.75-6.68 (m, 2H), 3.70 (part A of an AB system, J
) 12.5 Hz, 1H), 3.41 (part B of an AB system, J ) 12.5 Hz,
1H), -0.14 (s, 3H); 13C{1H} NMR (75 MHz, CDCl3; DEPT) δ
162.89 (C), 155.58 (C), 153.63 (C), 152.80 (CH), 150.09 (CH),
138.55 (CH), 138.47 (CH), 131.80 (C), 128.90 (CH), 126.57
(CH), 126.09 (CH), 124.29 (CH), 122.00 (CH), 121.62 (CH),
119.64 (CH), 110.77 (CH), 60.91 (CH2), -3.12 (CH3); EI-MS
m/z (relative intensity) 261 (7), 179 (32), 156 (100), 135 (44),
78 (26), 73 (23) [the molecular ion was not observed]. Anal.
Calcd for C20H23IN2OPdSi‚H2O: C, 40.94; H, 4.29; N, 4.77.
Found: C, 41.07; H, 3.99; N, 4.91.
tr a n s-Iodo[2-(tr im eth ylsilylm eth oxy)p h en yl](1,10-p h e-
n a n th r olin e-N1,N10)p a lla d iu m (18).
A suspension of
tra ns-Bis(triphenylarsine)[2-(fluorodimethylsilylmethoxy)-
p h en yl]iod op a lla d iu m (14). A mixture of [Pd2(dba)3dba]
(586 mg, 0.51 mmol) and triphenylarsine (655 mg, 2.14 mmol)
in acetone (20 mL) was stirred at 23 °C for 3 h, yielding [Pd-
(dba)(AsPh3)2]. To this suspension was added silane 7 (474
mg, 1.53 mmol) in acetone (5 mL), and the mixture was stirred
at 23 °C for 24 h. The solvent was evaporated, and the residue
was triturated with Et2O to give 14 as a yellow solid (622 mg,
59%): 1H NMR (200 MHz, CDCl3) δ 7.46-7.19 (m, 30 H), 6.77
(br d, J ) 7.5 Hz, 1H), 6.50 (br t, J ) 7.3 Hz, 1H), 6.21 (br t,
silane 5 (293 mg, 0.96 mmol) and [Pd(dba)(phen)] (500 mg,
0.96 mmol) in THF (25 mL) was stirred at 23 °C for 18
h. The solvent was evaporated, and the residue was
triturated with Et2O to give 18 as a brown solid (372 mg,
66%): 1H NMR (200 MHz, CDCl3) δ 9.95 (m, 1H), 9.00
(m, 1H), 8.47 (m, 1H), 7.98-7.80 (m, 1H), 7.67-7.55 (m,
2H), 7.48-7.40 (m, 2H), 7.35-7.21 (m, 2H), 6.86-6.75 (m,
2H), 3.78 (part A of an AB system, J ) 12.8 Hz, 1H),
3.45 (part B of an AB system, J ) 12.8 Hz, 1H), -0.24
(s, 3H); EI-MS m/z (relative intensity) 466 (<1), 180 (100),
154 (17), 131 (25), 77 (28) [the molecular ion was not
observed]. Anal. Calcd for C22H23IN2OPdSi: C, 44.57; H,
3.91. Found: C, 44.97; H, 4.10.
Bis(tr ip h en yla r sin e)(m eth ylen eoxy-1,2-p h en ylen e)p a l-
la d iu m (19). Meth od a . A mixture of 12 (175 mg, 0.17
mmol) and Ag2CO3 (94 mg, 0.34 mmol) in MeCN (10 mL) was
heated at 50 °C for 24 h. The solvent was evaporated, and
the residue was partially dissolved in CH2Cl2 and filtered
through Celite. The filtrate was evaporated to give a 1:1
mixture of 19 and 20 (139 mg, 95%). Repeated trituration with
Et2O, Et2O-hexane, and hexane led to 19 as the less soluble
palladacycle in Et2O and 20 as the less soluble palladacycle
in hexane.
Meth od b. A mixture of 12 (20 mg, 0.019 mmol) and K2-
CO3 (5 mg, 0.039 mmol) in MeCN (10 mL) was heated at 80
°C for 18 h. The solvent was evaporated, and the residue was
partially dissolved in CH2Cl2 and filtered through Celite. The
filtrate was evaporated, and the residue was triturated with
1:1 Et2O-hexane to give 19 as a white solid (15 mg, quantita-
tive).
Meth od c. A mixture of 14 (25 mg, 0.024 mmol) and Ag2-
CO3 (14 mg, 0.049 mmol) in MeCN (6 mL) was stirred at 23
°C for 1 h. Workup as above yielded 19 (14 mg, 70%).
Complex 19 was identical to that prepared before by ligand
exchange reaction from palladacycle 2.18
3
J ) 7.4 Hz, 1H), 5.64 (br d, J ) 8.0 Hz, 1H), 2.58 [d, J (1H-
3
19F) ) 5.5 Hz, 2H], 0.39 [d, J (1H-19F) ) 7.5 Hz, 6H];13C{1H}
NMR (50 MHz, CDCl3) δ 161.44, 136.79, 135.66, 134.09,
133.92, 129.29, 128.05, 124.50, 119.76, 110.80, 57.67 [d,
2J (13C-19F) ) 19.1 Hz], -2.34 [d, 2J (13C-19F) ) 14.4 Hz]. Anal.
Calcd for C45H42As2FIOPdSi: C, 52.52; H, 4.11. Found: C,
52.50; H, 4.14.
[1,1′-Bis(d ip h e n ylp h osp h in o)fe r r oce n e ]iod o[2-(t r i-
m eth ylsilylm eth oxy)p h en yl]p a lla d iu m (15). To a suspen-
sion of [Pd(dba)(dppf)] (70 mg, 78.2 mmol) in toluene (10 mL)
was added a solution of silane 5 (25 mg, 81.6 mmol) in toluene
(3 mL). The resulting suspension was stirred at 23 °C for 17
h. The solvent was evaporated, and the residue was triturated
with Et2O to give 15 as a red solid (60 mg, 76%): 1H NMR
(200 MHz, CDCl3) δ 8.19-7.95 (m, 6H), 7.51-7.45 (m, 6H),
7.42-7.28 (m, 2H), 7.16-7.03 (m, 3H), 6.87-6.82 (m, 2H),
6.80-6.63 (m, 2H), 6.54-6.38 (m, 2H), 6.01-5.95 (m, 1H), 5.10
(br s, 1H), 4.59 (br s, 1H), 4.30 (br s, 2H), 4.09 (br s, 2H), 3.69
2
(br s, 1H), 3.57 (br s, 1H), 3.29 [d, J (1H-1H) ) 12.9 Hz, 1H],
2.86 [d, 2J (1H-1H) ) 12.9 Hz, 1H], 0.30 (s, 9H); 31P{1H} NMR
(121.5 MHz, CDCl3) δ 26.35 [d, J (31P-31P) ) 30.8 Hz, 1P], 8.91
[d, J (31P-31P) ) 30.8 Hz, 1P]. Anal. Calcd for C44H43FeIOP2-
PdSi: C, 54.65; H, 4.48. Found: C, 54.49; H, 4.59.
[1,1′-Bis(diph en ylph osph in o)fer r ocen e][2-(dim eth ylflu -
or osilylm eth oxy)p h en yl]iod op a lla d iu m (16). A mixture
of silane 7 (76 mg, 0.22 mmol) and [Pd(dba)(dppf)] (200 mg,
0.22 mmol) in toluene (6 mL) was stirred at 23 °C for 24 h.
The solvent was evaporated, and the residue was triturated
with 20:1 hexanes-Et2O to give 16 as a yellow solid (95 mg,
43%): 1H NMR (300 MHz, CDCl3) δ 8.22-8.16 (m, 2H), 8.04-
7.93 (m, 4H), 7.56-7.39 (m, 6H), 7.33-7.28 (m, 3H), 7.18-
7.11 (m, 1H), 7.08-7.03 (m, 1H), 6.88-6.82 (m, 2H), 6.75-
6.68 (m, 2H), 6.53-6.43 (m, 2H), 5.93-5.88 (m, 1H), 5.21 (br
s, 1H), 4.61 (br s, 1H), 4.29 (br s, 2H), 4.14-4.07 (m, 2H), 3.64-
3.58 (m, 2H), 3.35 [dd, 2J (1H-1H) ) 13.0 Hz, 3J (1H-19F) ) 10.7
Hz, 1H], 3.01 [br d, 2J (1H-1H) ) 13.0 Hz, 1H], 0.64 [d, 3J (1H-
19F) ) 7.6 Hz, 3H], 0.40 [d, 3J (1H-19F) ) 7.4 Hz, 3H]; 31P NMR
(121.4 MHz, CDCl3) δ 27.05 (d, J ) 31.0 Hz, 1P), 9.22 (d, J )
31.0 Hz, 1P). Anal. Calcd for C43H40FFeIOP2PdSi: C, 53.19;
H, 4.15. Found: C, 53.26; H, 4.35.
cis-Iod o[2-(tr im eth ylsilylm eth oxy)p h en yl](2,2′-bip yr i-
d in e-N1,N1′)p a lla d iu m (17). A suspension of silane 5 (51 mg,
0.17 mmol) and [Pd(dba)(bpy)] (75 mg, 0.15 mmol) in THF (7
mL) was stirred at 23 °C for 16 h. The solvent was evaporated,
and the residue was triturated (3:1 hexanes-Et2O) to give 17
as a yellow solid (66 mg, 78%): 1H NMR (200 MHz, CDCl3) δ
9.71 (d, J ) 5.4 Hz, 1H), 8.08-7.92 (m, 4H), 7.72 (d, J ) 5.1
Hz, 1H), 7.53 (td, J ) 5.4, 1.5 Hz, 1H), 7.41 (dd, J ) 8.1, 1.7
Bis(tr ip h en yla r sin e)(m eth ylen eoxy-1,2-(6-tr im eth ylsi-
1
lyl)p h en ylen e)p a lla d iu m (20): H NMR (200 MHz, CDCl3)
δ 7.32-7.02 (m, 31H), 6.85 (t, J ) 7.3 Hz, 1H), 6.06 (t, J ) 7.3
Hz, 1H), 5.43 (s, 2H), 0.14 (s, 9H); 13C{1H} NMR (75 MHz,
CDCl3; DEPT) δ 171.86 (C), 142.68 (CH), 136.08 (C), 134.54
(C; AsPh3), 134.28 (CH; AsPh3), 133.62 (CH; AsPh3), 131.04
(CH), 129.45 (CH; AsPh3), 129.14 (CH; AsPh3), 128.46 (CH;
AsPh3), 128.30 (CH; AsPh3), 116.93 (C), 116.70 (CH), 90.13
(CH2), -0.82 (CH3) (the ipso C of one of the AsPh3 ligands was
not observed). This compound was contaminated with variable
amounts of 19.
Bis(tr iph en ylph osph in e)(m eth ylen eoxy-1,2-ph en ylen e)-
p a lla d iu m (2). A mixture of 11 (20 mg, 0.021 mmol) and Ag2-
CO3 (12 mg, 0.043 mmol) in MeCN (3 mL) was heated at 50
°C for 5 h. The solvent was evaporated, and the residue was
partially dissolved in CH2Cl2 and filtered through Celite. The
filtrate was evaporated, and the residue was triturated with
Et2O to give 2 (15 mg, 94%). Complex 2 was identical with
that prepared before by Pd/Sn transmetalation.18
[1,1′-Bis(diph en ylph osph in o)fer r ocen e](m eth ylen eoxy-
1,2-p h en ylen e)p a lla d iu m (4). A mixture of 16 (18 mg, 0.02
mmol) and Ag2CO3 (10 mg, 0.04 mmol) in MeCN (3 mL) was

Si, Sn Transmetalation of Pd(II) and Pt(II) Complexes
Organometallics, Vol. 17, No. 17, 1998 3669
stirred at 23 °C for 15 h. The solvent was evaporated, and
the residue was suspended in CH2Cl2, filtered through Celite,
and evaporated. The residue was triturated with hexane to
give 4 as an orange solid (15 mg, quantitative) identical with
the complex prepared before from the corresponding stan-
nane.18
washed with Et2O to give 28 as a white solid (56 mg, 85%).
Further purification of samples of 28 contaminated with other
Pt(II) complexes could be carried out by partial dissolution in
CH2Cl2, followed by filtration and evaporation of the solvent.
Meth od b. A suspension of 5 (31 mg, 0.10 mmol) and [Pt-
(PPh3)4] (127 mg, 0.10 mmol) in toluene (4 mL) was heated at
70 °C for 54 h. After being cooled to room temperature, the
mixture was filtered off, and the solid was washed with Et2O
to give 28 (38 mg, 45%): 1H NMR (300 MHz, CDCl3) δ 7.54-
7.35 (m, 14H), 7.32-7.21 (m, 2H), 7.20-7.14 (m, 8H), 7.08-
7.02 (m, 6H), 6.84-6.80 (m, 3H, satellites of 195Pt as multiplets
at 6.92-6.87 and 6.79-6.71), 6.06-5.99 (m, 1H), 5.14 [dd,
3J (1H-31P) ) 4.4, 2.9 Hz, 2J (1H-195Pt) ) 49.5 Hz, 2H]; 13C-
{1H} NMR (75 MHz, CDCl3) δ 174.31 [3J (13C-31P) ) 4.0 Hz,
(Meth ylen eoxy-1,2-p h en ylen e)(2,2′-bip yr id in e-N1,N1′)-
p a lla d iu m (21). A suspension of 17 (15 mg, 0.03 mmol) and
Ag2CO3 (10 mg, 0.04 mmol) in MeCN (2 mL) was stirred at 50
°C for 32 h. The solvent was evaporated, and the residue was
partially dissolved in CH2Cl2 and filtered through Celite. The
solvent was evaporated, and the residue was triturated with
Et2O to give 21 as an orange solid (10 mg, quantitative): 1H
NMR (200 MHz, CDCl3) δ 9.14 (d, J ) 5.4 Hz, 1H), 8.17 (d, J
) 5.4 Hz, 1 H), 8.06 (d, J ) 7.9 Hz, 2H), 7.94 (qd, J ) 7.5, 1.3
Hz, 2H), 7.71-7.09 (m, 4H), 6.99 (td, J ) 7.6, 1.5 Hz, 1H),
6.73 (br t, J ) 7.6 Hz, 1H), 6.00 (s, 2H); 13C{1H} NMR (75
MHz, CDCl3) δ 174.85, 154.63, 150.74, 150.45, 148.87, 140.47,
140.03, 138.35, 134.51, 126.47, 126.07, 125.72, 122.78, 122.00,
117.46, 107.93, 83.08; EI-MS m/z (relative intensity) 277 (1),
262 (<1), 156 (100), 128 (22), 78 (33) [the molecular ion was
not observed]. This complex was isolated contaminated with
traces of minor bipyridine palladium complexes, and an
analytically pure sample could not be obtained.
(Met h ylen eoxy-1,2-p h en ylen e)(1,10-p h en a n t h r olin e-
N1,N10)p a lla d iu m (22). A suspension of 18 (15 mg, 0.03
mmol) and Ag2CO3 (10 mg, 0.04 mmol) in MeCN (2 mL) was
stirred at 50 °C for 32 h. The solvent was evaporated, and
the residue was partially dissolved in CH2Cl2 and filtered
through Celite. The solvent was evaporated, and the residue
was triturated with Et2O to give 22 as a yellow solid (10 mg,
quantitative): 1H NMR (300 MHz, CDCl3) δ 9.56 (dd, J ) 5.0,
1.5 Hz, 1H), 8.63 (dd, J ) 4.9, 1.4 Hz, 1H), 8.47 (m, 2H), 7.95
(part A of an AB system, J ) 8.8 Hz, 1H), 7.93 (part B of an
AB system, J ) 8.8 Hz, 1H), 7.92 (dd, J ) 8.3, 5.0 Hz, 2H),
7.59 (dd, J ) 7.1, 1.4 Hz, 1H), 7.03 (td, J ) 7.5, 1.5 Hz, 1H),
6.79 (m, 2H), 6.25 (s, 2H); 13C{1H} NMR (75 MHz, CDCl3) δ
175.05, 150.36, 150.21, 148.54, 146.38, 146.27, 140.24, 137.36,
137.25, 134.55, 129.78, 127.28, 126.86, 125.83, 124.95, 124.88,
117.40, 108.05, 83.03; IR (KBr) ν 3040 (w), 2890 (w), 2820 (w),
1505 (m), 1465 (m), 1415 (s), 1275 (s), 960 (m), 840 (s), 750
(m), 720 (m) cm-1; MS-FAB m/z (relative intensity) 395 (30),
394 (11), 393 (36), 392 (M+, 29), 391 (19), 290 (50), 289 (58),
288 (78), 287 (38), 285 (90), 284 (70), 181 (100). Anal. Calcd
for C19H14N2OPd‚0.5H2O: C, 56.81; H, 3.76; N, 6.97. Found:
C, 56.96; H, 3.51; N, 6.96.
2
2J (13C-195Pt) ) 78.5 Hz], 142.63 [dd, J (13C-31P) ) 101.2, 4.8
Hz], 140.95 [t, 3J (13C-31P) ) 4.7 Hz, 2J (13C-195Pt) ) 48.1 Hz],
135.56-135.19 (m, PPh3), 134.55-134.28 (m, PPh3), 134.10 [d,
1J (13C-31P) ) 53.7 Hz, PPh3], 131.90 [d, 1J (13C-31P) ) 48.2
Hz, PPh3], 129.94 (PPh3), 129.59 (PPh3), 127.79 [d, 3J (13C-
3
31P) ) 9.9 Hz, PPh3], 127.48 [d, J (13C-31P) ) 9.5 Hz, PPh3],
4
3
125.50, 116.53 [t, J (13C-31P) ) 4.9 Hz, J (13C-195Pt) ) 47.9
Hz], 108.05 [4J (13C-195Pt) ) 23.1 Hz], 85.99 [dd, J (13C-31P)
2
) 93.8, 5.3 Hz, 1J (13C-195Pt) ) 683.2 Hz]; 31P NMR (121.4
MHz, CDCl3) δ 28.36 [s, J (31P-195Pt) ) 2146, J (31P-31P) )
13.9 Hz, 1J (31P-195Pt) ) 1888, 2J (31P-31P) ) 14.6 Hz, 2P]; EI-
MS m/z (relative intensity) 826 (M+, <1), 277 (2), 262 (100),
261 (13), 184 (15), 183 (69), 108 (32); EI-HRMS calcd for
1
2
C
C
4.70.
43H36PP2195Pt (obsd), 825.1889 (825.1903). Anal. Calcd for
43H36OP2Pd‚H2O: C, 61.21; H, 4.54. Found: C, 61.04; H,
[(3,5-Dich lor o-1,2-p h en ylen )oxym eth ylen ]bis(tr ip h en -
ylp h osp h in e)p la tin u m (29). A suspension of 27 (190 mg,
0.32 mmol) and [Pt(PPh3)4] (400 mg, 0.32 mmol) in toluene (7
mL) was heated at 40 °C for 67 h. After being cooled to room
temperature, the mixture was filtered off, and the solid was
washed with Et2O to give 29 as a white solid (132 mg, 46%):
1H NMR (300 MHz, CDCl3) δ 7.48-7.00 (m, 30H), 6.84 (d, J
) 2.3 Hz, 1H), 6.52 [dt, 4J (1H-1H) ) 2.3 Hz, 4J (1H-31P) ) 2.3,
7.1 Hz, 3J (1H-195Pt) ) 48.9 Hz, 1H], 5.23 [dd, 3J (1H-31P) )
4.6, 3.5 Hz, 2J (1H-195Pt) ) 46.3 Hz, 2H]; 31P NMR (121.4 MHz,
CDCl3) δ 27.54 [d, 2J (31P-31P) ) 15.5 Hz, 1J (31P-195Pt) ) 1860
Hz, 1P], 27.02 [d, 2J (31P-31P) ) 15.5 Hz, 1J (31P-195Pt) ) 2267
Hz, 1P]; EI-MS m/z (relative intensity) 729 (<1), 262 (100),
183 (73), 152 (11), 108 (34), 107 (2) [the molecular ion was not
observed]. An analytically pure sample could not be obtained.
P la tin u m Ca ta lyzed Cou p lin g of Ar yl Tr ifla tes. To a
suspension of [Pt(PPh3)4] (23 mg, 0.018 mmol) and K2CO3 (105
mg, 0.74 mmol) in 1,4-dioxane (4 mL) was added triflate 30
or 31 (0.37 mmol) and ethenyltributylstannane (177 mg, 0.56
mmol). The mixture was stirred at 90 °C for 48 h. After being
cooled to room temperature, the mixture was partitioned
between water and Et2O. The organic extract was washed
with 10% aqueous HCl and water, dried (MgSO4), and evapo-
rated. Chromatography (50:1 hexanes-EtOAc) gave styrenes
32 (20 mg, 37%) or 33 (15 mg, 30%), identical with compounds
prepared before.41
[10-Tr im eth ylsilylm eth oxy-4-(2-tr im eth ylsilylm eth ox-
y)p h en yl]-6H-d iben zo[b,d ]p yr a n (25). A mixture of silane
5 (612 mg, 2 mmol), Pd(OAc)2 (18 mg, 0.08 mmol), K2CO3 (1.10
g, 8 mmol), and Bu4NBr (645 mg, 2 mmol) in DMF (10 mL)
was stirred at 100 °C for 3 d. After being cooled to room
temperature, the mixture was partitioned between water and
Et2O. The organic extract was filtered through silica gel and
evaporated, and the residue was chromatographed (50:1
hexanes-EtOAc) to give 25 as a colorless oil (63 mg, 20%):
1H NMR (200 MHz, CDCl3) δ 8.50 (dd, J ) 8.1, 1.6 Hz, 1H),
7.44-7.07 (m, 8H), 6.85 (d, J ) 7.5 Hz, 1H), 5.01 (s, 2H), 3.81
(s, 2H), 3.66 (s, 2H); 13C{1H} NMR (75 MHz, CDCl3; DEPT) δ
158.81 (C), 158.40 (C), 152.80 (C), 134.67 (C), 131.03 (CH),
130.78 (CH), 128.48 (CH), 128.14 (CH), 128.04 (CH), 127.93
(C), 127.12 (C), 121.99 (C), 120.02 (CH), 119.82 (CH), 119.46
(C), 116,70 (CH), 111.58 (CH), 111.40 (CH), 68.91 (CH2), 61.98
(CH2), 61.46 (CH2), -2.91 (CH3), -3.36 (CH3); EI-MS m/z
(relative intensity) 462 (M+, 100), 375 (5), 307 (12), 154 (59),
136 (51), 107 (16), 73 (76), 59 (65); EI-HRMS calcd for
Ack n ow led gm en t. This work was supported by the
DGICYT (project PB94-0163). C.M. and C.F.-R acknowl-
edge the receipt of predoctoral fellowships by the
Ministerio de Educacio´n y Ciencia. We acknowledge
J ohnson Matthey PLC for a generous loan of palladium
dichloride. We thank a reviewer for suggesting a
rationalization for the formation of equimolar quantities
of 19 and 20.
C
27H34O3Si2 (obsd), 462.2046 (462.2050).
(Meth ylen eoxy-1,2-ph en ylen e)bis(tr iph en ylph osph in e)-
Su p p or tin g In for m a tion Ava ila ble: NMR spectra for 7,
9, 20, 21, 25, and 29 (6 pages). See any current masthead
page for ordering and Internet access instructions.
p la tin u m (28). Meth od a . A suspension of 1b (462 mg, 0.88
mmol) and [Pt(PPh3)4] (1.000 g, 0.80 mmol) in toluene (25 mL)
was heated at 70 °C for 48 h. After being cooled to room
temperature, the mixture was filtered off, and the solid was
OM980157O