5 Hz, 2H, C6H2F3), 6.87–6.95 (m, 6H, Ph), 7.00–7.07 (m, 4H, Ph). dP (121.5
MHz, C6D6, 85% H3PO4): 24.54 (s). dF (282.3 MHz, C6D6): 284.91 (t, J
= 5 Hz, 2F), 2114.41(d, J = 24 Hz, 2F), 2115.99 (t, J = 7 Hz, 1F),
2159.51 (t, J
=
21 Hz, 1F), 2161.00 (m, 2F). Anal. Calc. for
C
28H24F8P2Pd: C, 49.40; H, 3.55; F, 22.32. Found: C, 49.14; H, 3.75; F,
22.33%. For 9: colorless crystals, yield 47%. dH (300 MHz, C6D6): 1.46
(apparent triplet by virtual coupling, 6H, CH3), 6.15 (dd, J = 9 Hz, J = 5
Hz, 2H, C6H2F3), 6.88–6.93 (m, 12H, Ph), 7.30–7.37 (m, 8H, Ph). dP (121.5
MHz, C6D6, 85% H3PO4): 9.77 (s). dF (282.3 MHz, C6D6): 283.29 (t, J =
5 Hz, 2F), 2113.23 (d, J = 23 Hz, 2F), 2116.50 (t, J = 9 Hz, 1F), 2160.28
(t, J = 20 Hz, 1F), 2160.95 (m, 2F). Anal. Calc. for C38H28F8P2Pd: C,
56.70; H, 3.51; F, 18.88. Found: C, 56.50; H, 3.71; F, 19.24%.
‡ Crystal data. For 7: C24H32F8P2Pd, M = 640.85, monoclinic, space group
P21/n, a = 12.309(4), b = 12.207(5), c = 9.460(3) Å, b = 104.81(3)°, V
= 1374.2(8) Å3, Z = 2, T = 298 K, m(Mo–Ka) = 8.57 cm21, Rigaku
AFC7R diffractometer, 1739 measured reflections (2qmax = 55.0°). At
convergence, R1 = 0.032, wR2 = 0.037, and GOF = 2.02 for 169 variables
refined against all 1077 unique reflections. A space group C2/m is excluded
by the presence of reflections (I > 10s(I)) that do not obey the reflection
suppdata/cc/b3/b308741g/ for crystallographic data in .cif or other elec-
tronic format.
Fig. 1 An ORTEP drawing of 7 with 50% thermal ellipsoidal plotting. The
molecule has crystallographic C2 symmetry within the molecule. Atoms
with asterisks are crystallographically equivalent to those having the same
numbers without asterisks. Fluorine (F4* and F5*) with occupancies of 0.5
and hydrogen atoms were omitted for clarity. Selected interatomic distances
(Å) and angles (°): Pd1–C1 2.066(6), Pd1–P1 2.310(2), P1–Pd1–C1
88.5(2), P1–Pd1–C1* = 91.5(2).
carbon signals of the aryl ligands are observed as triplets at d 121.30
and 126.67. These NMR data are similar to those of the previously
reported trans-PdAr2(PEt3)2 and are consistent with the trans
structure in solution.
We evaluated the transmetallation rate by the reactions of
2,4,6-trifluorophenylboronic acid with trans-Pd(C6F5)I(PR3)2 (PR3
1 For reviews for cross-coupling reactions of organoboron compounds,
see: A. Suzuki, Pure Appl. Chem., 1986, 58, 629–638; A. Suzuki, J.
Organomet. Chem., 1999, 576, 147–168.
2 J. Uenishi, J.-M. Beau, R. W. Armstrong and Y. Kishi, J. Am. Chem.
Soc., 1987, 109, 4756–4758.
12
=
PEt3, PMe2Ph, PMePh2) forming trans-Pd(C6F5)(2,4,6-
C6F3H2)(PR3)2 (7: PR3 = PEt3; 8: PR3 = PMe2Ph; 9: PR3
PMePh2). The observed rates of formation of diarylpalldium(II
3 F. Ozawa, K. Kurihara, M. Fujimori, T. Hidaka, T. Toyoshima and A.
Yamamoto, Organometallics, 1989, 8, 180–188.
4 A. L. Casado, P. Espinet and A. M. Gallego, J. Am. Chem. Soc., 2000,
122, 11771–11782; A. L. Casado and P. Espinet, J. Am. Chem. Soc.,
1998, 120, 8978–8985.
5 N. Miyaura and A. Suzuki, Chem. Rev., 1995, 95, 2457–2483.
6 The vinylrhenium complex was formed by the reaction between the
vinylboronic ester and the methoxorhenium complex via a vinyl group
transfer. R. D. Simpson and R. G. Bergman, Organometallics, 1992, 11,
3980–3993.
7 A. O. Aliprantis and J. W. Canary, J. Am. Chem. Soc., 1994, 116,
6985–6986.
8 N. Mintcheva, Y. Nishihara, M. Tanabe, K. Hirabayashi, A. Mori and K.
Osakada, Organometallics, 2001, 20, 1243–1246; N. Mintcheva, Y.
Nishihara, A. Mori and K. Osakada, J. Organomet. Chem., 2001, 629,
61–67.
=
)
complexes increase in the following order, 7 (12 h) < 8 (3 h) < 9
(40 min) at room temperature. This result correlates with the order
of pKa of the phosphine ligand, e.g. PEt3 (8.65) < PMe2Ph (6.50)
< PMePh2 (4.65).13
The reaction of Ag2O with 5 (1.2 : 1.0 molar ratio) in toluene–
H2O generated trans-Pd(C6F5)(OH)(PEt3)2 (10) with concomitant
generation of AgI. The 31P{1H} NMR measurement of the above
reaction mixture in C6D6 showed that a signal of the starting
material 5 at d 16.41 decreased with apparance of a new signal at d
18.50, which is identical with that of 10, synthesized independ-
ently.14 The H NMR spectrum of 10 exhibits a resonance at d
1
22.40, diagnostic of the Pd–OH, while the 13C{1H} NMR signal of
the PCH2 carbon appears at d 14.19 as an apparent triplet due to
virtual coupling, indicating trans positions of two phosphorus
atoms. These results suggest an explanation for the role of Ag2O,
which promotes to replace the iodo ligand of 5 with a OH group of
H2O to afford 10, the intermediate of transmetallation. Further
details of the mechanism of transmetallation are still unclear.
In summary, we have successfully isolated diarylpalladium
complexes 7–9 from the reactions of arylboronic acids with
aryl(iodo)palladium(II) complexes. This methodology provides a
novel and potentially practical synthetic method for unsymmetrical
diaryl complexes of Pd, which are normally synthesized using
organolithium and organomagnesium compounds.15 Extensive
exploration of this approach using the analogous arylboronates to
illuminate more mechanistic details of the Suzuki–Miyaura cross-
coupling reaction will be reported in due course.
9 Ag2O promoted Suzuki–Miyaura reactions have been reported; see, F.
S. Ruel, M. Braun and C. R. Johnson, Org. Synth., 1997, 74, 69–77.
10 R. Uson, A. Laguna, J. Forniés and I. Valenzela, J. Organomet. Chem.,
1984, 273, 129–139; P. G. Jones, J. Organomet. Chem., 1988, 345,
405–411.
11 F. Ozawa, T. Hidaka, T. Yamamoto and A. Yamamoto, J. Organomet.
Chem., 1987, 330, 253–263.
12 G. Lopez, G. Garcia, M. D. Santana, G. Sanchez, J. Ruiz, J. A. Hermoso,
A. Vegas and M. Martinez-Ripoll, J. Chem. Soc., Dalton Trans., 1990,
1621–1626; F. Ozawa, M. Fujimori, T. Yamamoto and A. Yamamoto,
Organometallics, 1986, 5, 2144–2149; R. Uson, J. Forniés, F. Martínez,
M. Tomas and I. Reoyo, Organometallics, 1983, 2, 1386–1390; R.
Uson, J. Forniés, P. Espinet, F. Martínez and M. Tomas, J. Chem. Soc.,
Dalton Trans., 1981, 463–465; R. Ceder, J. Granell, G. Muller, O.
Rossell and J. Sales, J. Organomet. Chem., 1979, 174, 115–120; R.
Uson, J. Forniés, R. Navarro, M. P. Garcia and B. Bergareche, Inorg.
Chim. Acta, 1977, 25, 269–271; R. Uson, J. Forniés and F. Martínez, J.
Organomet. Chem., 1977, 132, 429–437; G. W. Parshall, J. Am. Chem.
Soc., 1974, 96, 2360–2366.
Notes and references
13 G. M. Kosolapoff and L. Maier, Organic phosphorus compounds,
Wiley-Interscience, New York, Vol. 1, 1972.
† Selected data. For 7: colorless crystals, yield 92%. dH (300 MHz, C6D6):
0.80 (dt, J = 16 Hz, 8 Hz, 18H, CH3), 1.02 (m, 12H, PCH2), 6.51 (dd, J =
9 Hz, 5 Hz, 2H, C6H2). dP (121.5 MHz, C6D6, 85% H3PO4): 15.88 (s). dF
(282.3 MHz, C6D6): 282.45 (s, 2F), 2112.14 (d, J = 24 Hz, 2F), 2115.92
(m, 1F), 2158.60 (t, J = 20 Hz, 1F), 2160.51 (m, 2F). Anal. Calc. for
C24H32F8P2Pd: C, 44.98; H, 5.03; F, 23.72. Found: C, 44.90; H, 4.94; F,
24.06%. For 8: colorless crystals, yield 77%. dH (300 MHz, C6D6): 0.98
(apparent triplet by virtual coupling, 12H, PCH3), 6.39 (dd, J = 9 Hz, J =
14 Complex 10 was obtained according to the preparation procedure of
trans-Pd(C6F5)(OH)(PPh3)2 and trans-PdPh(OH)(PR3)2 (R = Cy, iPr);
see, T. Yoshida, T. Okano and S. Otsuka, J. Chem. Soc., Dalton Trans.,
1976, 993–999; V. V. Grushin and H. Alper, Organometallics, 1996, 15,
5242–5245.
15 E.-I. Negishi, T. Takahashi and K. Akiyoshi, J. Organomet. Chem.,
1987, 334, 181–194.
C h e m . C o m m u n . , 2 0 0 4 , 1 9 2 – 1 9 3
193