Migratory Insertion Reactions at (dppp)Pd(II) Center
J. Am. Chem. Soc., Vol. 122, No. 27, 2000 6355
Elemental analyses were obtained from Oneida Research Services
Inc., Whitesboro, NY, and Atlantic Microlabs Inc., Norcross GA.
H(OEt2)2BAr′4,24 (dppp)Pd(Me)(Cl), and (TMEDA)Pd(Me)2 (TME-
DA ) N,N,N′,N′-tetramethylethylenediamine),25 were synthesized using
published methods. 1,3-Bis-(diphenylphosphino)propane (dppp) (>98%
purity) and AgSbF6 were purchased from Aldrich and used as received.
The 1H and 13C NMR data attributed to the counterion BAr′4- (Ar′
) 3,5(CF3)2C6H3) are consistent for all cationic complexes examined
and are not included in each compound characterized below. Full
spectral details have been previously reported.26
CO atmosphere at -30 °C. The solution was then purged with CO for
5 min to ensure complete reaction followed by hexane (5 mL) to
produce a yellow oil. To the oil was added CH2Cl2 (10 mL). The
resulting yellow solution was filtered through Celite to remove some
Pd(0). The filtrate was kept at -30 °C, and hexanes (50 mL) were
layered slowly onto the CH2Cl2 solution under a CO atmosphere. The
mixture was then stored at -30 °C until a large number of yellow
crystals had formed. These crystals were filtered, washed with hexanes
(2 × 10 mL), and dried in vacuo. Yellow crystals of 10 (0.17 g, 34%)
were isolated. 1H NMR (300 MHz, CD2Cl2, -70 °C) δ 7.37-7.55 (m,
20H, (C6H5)2PCH2CH2CH2P(C6H5)2), 2.74 (br m, 2H, PCH2CH2CH2P),
2.55 (br m, 2H, PCH2CH2CH2P), 1.97 (br m, 2H, PCH2CH2CH2P),
1.85 (s, 3H, Pd-COCH3). 13C{1H} NMR (75 MHz, CD2Cl2, -70 °C)
(dppp)Pd(Me)2,27 4. The following method was adapted from van
Koten’s synthesis of (dmpe)PdMe2with only minor variations.25
A
solution of dppp, (2.00 g, 4.80 mmol) in acetone (15 mL) was added
to a solution of (TMEDA)PdMe2, (1.00 g, 3.96 mmol) in acetone (5
mL) and stirred for 18 h. The solvent was removed in vacuo at 0 °C
to yield a white precipitate. The crude product was recrystallized from
acetone at -30 °C. Repeated crystallizations from acetone yielded 1.7
2
2
2
δ 232.0 (dd, JCP ) 85, JCP ) 8.5, Pd-COCH3), 175.7 (dd, JCP
)
2
83, JCP ) 20, Pd-CO), see Supporting Information for aryl data
((C6H5)2PCH2CH2CH2P(C6H5)2), 42.1 (dd, 3JCP ) 25, 3JCP ) 24, Pd-
COCH3), 24.9 (br, PCH2CH2CH2P), 24.8 (br, PCH2CH2CH2P), 17.9
(br m, PCH2CH2CH2P). 31P{1H} NMR (121 MHz, CD2Cl2, -70 °C) δ
1
g, 77% of 4 as colorless crystals. H NMR (300 MHz, CD2Cl2, -20
2.2 (d, 2JPP ) 84), -8.0 (d, 2JPP ) 84). IR (CH2Cl2) νCO ) 2130 cm-1
,
°C) δ 7.33-7.51 (m, 20H, (C6H5)2PCH2CH2CH2P(C6H5)2), 2.42 (m,
νacyl ) 1715 cm -1. Anal. (C62H41BF24O2P2Pd) calcd C, 51.25; H, 2.84;
4H, PCH2CH2CH2P), 1.73 (m, 2H, PCH2CH2CH2P), -0.12 (d, 3JHP
)
2, 6H, Pd-(CH3)2). 13C{1H,31P} NMR (75 MHz, CD2Cl2, -20 °C) δ
132.9, 133.0, 127.9, 129.4 ((C6H5)2PCH2CH2CH2P(C6H5)2), 27.5 (PCH2-
CH2CH2P), 19.3 (PCH2CH2CH2P), 5.84 (Pd-(CH3)2). 31P{1H} NMR
(121 MHz, CD2Cl2, -20 °C) δ 7.2. Anal. (C29H32P2Pd) calcd C, 63.45;
H, 5.88; found C, 63.69; H, 5.71. An additional recrystallization in
Et2O/CH2Cl2 was often necessary to remove residual acetone.
found C, 51.64; H, 2.53).
(dppp)Pd(COMe)(Cl), 15. dpppPd(CH3)(Cl) (0.765 g, 1.34 mmol)
was dissolved in CH2Cl2 (20 mL) at room temperature with stirring. A
stream of CO was purged through the solution for 30 min and stirring
was continued for another 2 h. The solution was filtered through Celite
to remove traces of Pd black that had formed. The solvent was removed
in vacuo to yield a glassy residue. The residue was washed with pentane
(5 × 5 mL) to yield 15, as a cream colored powder (0.55 g, 69%). The
product was characterized by 1H, 13C, and 31P NMR spectroscopy and
agreed with data previously reported.5 Anal. (C29H29OP2Pd) calcd C,
58.31; H, 4.89; found C, 58.37; H, 5.00).
(dppp)PdMe(OEt2)+(BAr′4)-, 5. The dimethyl complex, 4, (0.256
g; 0.467 mmol) and H(OEt2)2BAr′4 (0.505 g, 0.499 mmol) were
suspended in ether (0.5 mL) and CH2Cl2 (1.5 mL) at -30 °C. The
reaction mixture was stirred for 2 h followed by brief warming to 25
°C to dissolve all solids. The resulting light yellow solution was brought
to 0 °C, cooled slowly, and ultimately stored overnight at -78 °C.
The resulting crystals were filtered and washed with pentane (2 × 3
mL) to afforded clear, crystalline 5 (0.521 g; 76%) which was dried in
(dppp)Pd(CH2CH2COCH3)+(BAr′4)-, 14[BAr′4]. (dppp)PdMe-
(OEt2)+(BAr′4)-, 5, (0.237 g, 0.161 mmol) was dissolved in CH2Cl2
(7.0 mL) and diethyl ether (1.0 mL) at -78 °C. A gentle stream of CO
was purged through the solution for 2-3 min followed by an argon
purge for 30 min. C2H4 (20 mL, ∼0.8 mmol) was added via syringe,
and the solution was warmed to -30 °C. The solvent was removed in
vacuo to give a yellow foam. This yellow foam was redissolved in
diethyl ether (0.5 mL) and CH2Cl2 and stored at -78 °C overnight to
give a white precipitate. This precipitate was filtered, rinsed with
hexanes (2 × 2 mL), and dried in vacuo to give 14[BAr′4] as a white
powder. 1H NMR (300 MHz, CD2Cl2, -80 °C) δ 7.34-7.48 (m, 20H,
(C6H5)2PCH2CH2CH2P(C6H5)2), 3.13(m, 2H, Pd-CH2CH2COCH3),
2.55, (m, 2H, PCH2CH2CH2P), 2.47 (m, 2H, PCH2CH2CH2P), 2.32(s,
3H, Pd-CH2CH2COCH3), 1.84 (m, 2H, Pd-CH2CH2COCH3), 1.32 (br
m, 2H, PCH2CH2CH2P). 13C{1H} NMR (75 MHz, CD2Cl2, -80 °C) δ
238.3 (d, 3JCP ) 12, Pd-CH2CH2COCH3), see Supporting Information
1
vacuo. H NMR (300 MHz, CD2Cl2, -60 °C) δ 7.27-7.51 (m, 20H,
(C6H5)2PCH2CH2CH2P(C6H5)2), 3.25 (br, 4H, O(CH2CH3)2), 2.47 (m,
4H, PCH2CH2CH2P), 1.67 (m, 2H, PCH2CH2CH2P), 1.08 (br, 6H,
3
O(CH2CH3)2), 0.44 (d, JHP ) 4.2, 3H, Pd-CH3). 13C{1H} NMR (75
MHz, CD2Cl2, -60 °C) δ see Supporting Information for aryl data
((C6H5)2PCH2CH2CH2P(C6H5)2), 68.7 (s, O(CH2CH3)2), 27.3 (br d, 1JCP
) 32, (PCH2CH2CH2P)), 26.5 (br d, 1JCP ) 23, PCH2CH2CH2P), 16.9
2
(br s, PCH2CH2CH2P), 15.3 (s, O(CH2CH3)2), 15.0 (d, JCP ) 86.4,
Pd-CH3). 31P{1H} NMR (121 MHz, CD2Cl2, -60 °C) δ 30.3 (d, 2JPP
) 51), -0.21 (d, 2JPP ) 51). Anal. (C64H51BF24OP2Pd) calcd C, 52.25;
H, 3.49; found C, 52.10; H, 3.51.
(dppp)Pd(Me)(CO)+(BAr′4)-, 8. The ether adduct, 5, was produced
in situ by the reaction of dpppPdMe2, 4, (0.256 g, 0.466 mmol) and
H(OEt2)2BAr′4 (0.479 g, 0.473 mmol) in CH2Cl2 (7 mL) at -30 °C.
CO was precooled by passing the gas through approximately 3 m of
nalgene tubing immersed in a -90 °C bath. The flask was cooled to
-90 °C and vigorously purged with CO for 5 min. The solution was
then purged with argon for 30 min. Hexane was added to precipitate 8
3
for aryl data ((C6H5)2PCH2CH2CH2P(C6H5)2), 51.2 (d, JCP ) 6, Pd-
2
CH2CH2COCH3), 35.8 (d, JCP ) 89, Pd-CH2CH2COCH3), 28.2 (s,
Pd-CH2CH2COCH3), 26.9 (dd, 1JCP ) 34, 3JCP ) 8, PCH2CH2CH2P),
1
25.5 (d, JCP ) 23, PCH2CH2CH2P), 17.9 (br, PCH2CH2CH2P). 31P-
2
{1H} NMR (121 MHz, CD2Cl2, -80 °C) δ 28.2 (d, JPP ) 55), -6.0
1
(0.612 g, 92%) as a light yellow powder. H NMR (300 MHz, CD2-
(d, 2JPP ) 55). Anal. (C63H46BF24OP2Pd) calcd C 52.07; H, 3.12; found
Cl2, -70 °C) δ 7.24-7.53 (m, 20H, (C6H5)2PCH2CH2CH2P(C6H5)2),
2.47 (br m, 4H, PCH2CH2CH2P), 1.71 (br m, 2H, PCH2CH2CH2P),
C, 52.34; H, 3.17).
3
3
0.48 (dd, JHP ) 6.0, JHP ) 6.0, 3H, Pd-CH3). 13C{1H} NMR (75
MHz, CD2Cl2, -70 °C) δ 180.1 (dd, 2JCP ) 118, 2JCP ) 14, Pd-CO),
see Supporting Information for aryl data ((C6H5)2PCH2CH2CH2P-
(C6H5)2), 24.5 (br d, 1JCP ) 17, PCH2CH2CH2P), 24.3 (br d, 1JCP ) 22,
II. Kinetics. â-Methyl Migratory Insertion Reaction of (dppp)-
Pd(CH3)(C2H4)+(BAr′4)-, 6. (a) Spectroscopic Characterization of
6: NMR data: 1H NMR (300 MHz, CD2Cl2, -80 °C) δ 7.28-7.51
(m, 20H, (C6H5)2PCH2CH2CH2P(C6H5)2), 5.19 (br, 4H, Pd-η2-C2H4),
2.60 (m, 4H, PCH2CH2CH2P), 1.83 (m, 2H, PCH2CH2CH2P), 0.32 (dd,
2
PCH2CH2CH2P), 17.5 (br, PCH2CH2CH2P), 4.8 (d, JCP ) 70, Pd-
3
3
3H, JPH ) 7, JPH ) 4, Pd-CH3). 13C{1H} NMR (75 MHz, CD2Cl2,
2
CH3). 31P{1H} NMR (121 MHz, CD2Cl2, -70 °C) δ 16.6 (d, JPP
)
60), -7.9 (d, 2JPP ) 60). IR (CH2Cl2) νCO ) 2132 cm-1. Anal. (C61H41-
BF24OP2Pd) calcd C, 51.41; H, 2.90; found C, 51.53; H, 2.90.
(dppp)Pd(CO)(COMe)+(BAr′4)-, 10. The methyl ether complex,
5, (0.521 g, 0.354 mmol) was dissolved in CH2Cl2 (3.5 mL) under a
-70 °C) δ see Supporting Information for aryl data ((C6H5)2PCH2-
CH2CH2P(C6H5)2), 108.6 (br d, JCP ) 5, Pd-η2-C2H4), 25.5 (br d,
2
1JCP ) 38, PCH2CH2CH2P), 25.2 (br d, JCP ) 23, PCH2CH2CH2P),
1
2
2
17.4 (br s, PCH2CH2CH2P), 17.3 (dd, JCP ) 91, JCP ) 7, Pd-CH3).
31P{1H} NMR (121 MHz, CD2Cl2, -70 °C) δ 17.3 (d, JPP ) 56),
2
2
(24) Brookhart, M.; Grant, B.; Volpe, A. F., Jr. Organometallics 1992,
11, 3920.
(25) de Graff, W.; Boersma, J.; Smeets, W. J. J.; Spek, A. L.; van Koten,
G. Organometallics 1989, 8, 2907.
(26) LaPointe, A.; Brookhart, M. Organometallics 1998, 17, 1530.
(27) Ozawa, F.; Yamamoto, A. Nippon Kagaku Kaishi 1987, 5, 773.
-2.0 (d, JPP ) 56).
(b) Kinetic Measurements. The ether adduct, 5 (10 mg, ∼6.8 µmol)
was dissolved in CD2Cl2 (0.7 mL) at -78 °C. The addition of C2H4
(4.25 mL, ∼170 µmol, ∼25 equiv) by gastight syringe afforded 6. The
sample was placed in a precooled NMR probe and the decrease in