Preparation and properties of trans-Pd(Ar) (C≡CPh) (PEt3)2. Intermolecular alkynyl ligand transfer between copper(I) and palladium(II) complexes relevant to palladium complex catalyzed cross-coupling of terminal alkyne with haloarene in the presence of CuI cocatalyst

Article abstract of DOI:10.1021/om970266n

trans-Pd(C₆H₄Me-p)(I)(PEt₃)₂ (2a) reacts with [Cu(C≡CPh)(PPh₃)]₄ (Pd:Cu = 1:1) at room temperature to give the cross-coupling product PhC≡CC₆H₄Me-P (3a) in 74% yield. Reactions of 2a with [Cu(C≡CPh)(PPh₃)I₄ at -30 °C as well as of trans-Pd(C₆H₄X-P)(I)(PEt₃)₂ (2a, X = Me; 2b, X = OMe; 2c, X = F) with the alkynylcopper complex and additional PPh₃ (2 mol/ mol of Cu) at room temperature give mixtures of PhC≡CC₆H₄X-P (3a, X = Me; 3b, X = OMe; 3c, X = F) and trans-Pd(C₆H₄X-P)(C≡CPh)(PEt₃) ₂ (4a, X = Me; 4b, X = OMe; 4c, X = F). Complexes 4a,b have been isolated from the latter reaction mixtures and fully characterized. Pd-C(alkynyl) and Pd-C(aryl) bond distances in 4a are 2.016(8) and 2.062(7) A, respectively. Addition of Cul to a solution of 4a at room temperature causes complete conversion of 4a into 2a and 3a in 1 h. The relative molar ratio between 2a and 4a after reaction for 2 h varies, depending on the amount of added PPh₃. Reactions of trans-Pt(C₆H₄X-p)(I)(PEt₃)₂ (5b, X = OMe; 5c, X = F) with [Cu(C≡CPh)(PPh₃)]₄ at room temperature afford trans-Pt(C₆H₄X-p)(C≡CPh)(PEt₃) ₂ (6b, X = OMe; 6c, X = F), respectively. Heating an equimolar mixture of 4a and 5b at 35-50 °C leads to inter-metal exchange of the alkynyl and iodo ligands, giving 2a and 6b quantitatively. The reaction follows the kinetics that is first order in concentration of 4a and in that of 5b. The kinetic parameters are obtained as ΔH? = 110 kJ mol^-1, ΔS? = -58 J mol^-1 deg^-1, and ΔG? = 127 kJ mol^-1 at 298 K. The alkynyl ligand migration from Pd(II) to Pt(II) is enhanced by addition of a catalytic amount of CuI.

Full text of DOI:10.1021/om970266n

5354
Organometallics 1997, 16, 5354-5364
P r ep a r a tion a n d P r op er ties of
tr a n s-P d (Ar )(CtCP h )(P Et3)2. In ter m olecu la r Alk yn yl
Liga n d Tr a n sfer betw een Cop p er (I) a n d P a lla d iu m (II)
Com p lexes Releva n t to P a lla d iu m Com p lex Ca ta lyzed
Cr oss-Cou p lin g of Ter m in a l Alk yn e w ith Ha loa r en e in
th e P r esen ce of Cu I Coca ta lyst
Kohtaro Osakada,* Reiko Sakata, and Takakazu Yamamoto*
Research Laboratory of Resources Utilization, Tokyo Institute of Technology, 4259 Nagatsuta,
Midori-ku, Yokohama 226, J apan
Received March 31, 1997X
trans-Pd(C6H4Me-p)(I)(PEt3)2 (2a ) reacts with [Cu(CtCPh)(PPh3)]4 (Pd:Cu ) 1:1) at room
temperature to give the cross-coupling product PhCtCC6H4Me-p (3a ) in 74% yield. Reactions
of 2a with [Cu(CtCPh)(PPh3)]4 at -30 °C as well as of trans-Pd(C6H4X-p)(I)(PEt3)2 (2a , X )
Me; 2b, X ) OMe; 2c, X ) F) with the alkynylcopper complex and additional PPh3 (2 mol/
mol of Cu) at room temperature give mixtures of PhCtCC6H4X-p (3a , X ) Me; 3b, X )
OMe; 3c, X ) F) and trans-Pd(C6H4X-p)(CtCPh)(PEt3)2 (4a , X ) Me; 4b, X ) OMe; 4c, X )
F). Complexes 4a ,b have been isolated from the latter reaction mixtures and fully
characterized. Pd-C(alkynyl) and Pd-C(aryl) bond distances in 4a are 2.016(8) and 2.062(7)
Å, respectively. Addition of CuI to a solution of 4a at room temperature causes complete
conversion of 4a into 2a and 3a in 1 h. The relative molar ratio between 2a and 4a after
reaction for 2 h varies, depending on the amount of added PPh3. Reactions of trans-Pt(C6H4X-
p)(I)(PEt3)2 (5b, X ) OMe; 5c, X ) F) with [Cu(CtCPh)(PPh3)]4 at room temperature afford
trans-Pt(C6H4X-p)(CtCPh)(PEt3)2 (6b, X ) OMe; 6c, X ) F), respectively. Heating an
equimolar mixture of 4a and 5b at 35-50 °C leads to inter-metal exchange of the alkynyl
and iodo ligands, giving 2a and 6b quantitatively. The reaction follows the kinetics that is
first order in concentration of 4a and in that of 5b. The kinetic parameters are obtained as
∆Hq ) 110 kJ mol-1, ∆Sq ) -58 J mol-1 deg-1, and ∆Gq ) 127 kJ mol-1 at 298 K. The
alkynyl ligand migration from Pd(II) to Pt(II) is enhanced by addition of a catalytic amount
of CuI.
Sch em e 1. P ossible Mech a n ism of th e
In tr od u ction
Cr oss-Cou p lin g of 1-Alk yn e a n d Ar yl Ha lid e
Palladium complex catalyzed cross-coupling of a
terminal alkyne with bromoarene or with bromoalkene
gives arylacetylene or enynes selectively under mild
conditions and has been applied to the synthesis of
various organic molecules as well as π-conjugated
polymers.1-3 Scheme 1 depicts a possible mechanism
of the reaction. According to the pathway, Cu(CtCR),
generated in situ from a mixture of CuI, terminal
alkyne, and amine, undergoes alkynyl ligand transfer
to Pd(Ar)(X)(L)n (X ) halide), giving Pd(Ar)(CtCR)(L)n,
X Abstract published in Advance ACS Abstracts, November 1, 1997.
(1) Review articles: (a) Carruthers W. In Comprehensive Organo-
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Pergamon: Oxford, U.K., 1982; Vol. 7, pp 722-724. (b) Lipshutz, B.
H. In Organometallics in Synthesis: A Manual; Schlosser, M., Ed.;
Wiley: Chichester, U.K., 1994; pp 300-302, and references therein.
(c) Heck, R. F. Palladium Reagents in Organic Synthesis; Academic
Press: London, 1985; p 299. (d) Sonogashira, K.; Takahashi, S. Yuki
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Org. Chem. 1983, 48, 5135. (d) Havens, S. J .; Hergenrother, P. M. J .
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Chem. Soc. 1988, 110, 631. (f) Mascarenas, J . L.; Sarandeses, L. A.;
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L.; Okamura, W. H. J . Am. Chem. Soc. 1991, 113, 6958. (h) Lin, J . T.;
Wu, J . J .; Li, C.-S.; Wen, Y. S.; Lin, K.-J . Organometallics 1996, 15,
5028.
which is responsible for reductive elimination of the
coupling product.2a
Although the Pd complex bearing both aryl and
alkynyl ligands is believed to play an important role in
(3) (a) Sanechika, K.; Yamamoto, T.; Yamamoto, A. Polym. Prepr.
J pn. 1981, 30, 160. (b) Sanechika, K.; Yamamoto, T.; Yamamoto, A.
Bull. Chem. Soc. J pn. 1984, 57, 752. (c) Yamamoto, T.; Takagi, M.;
Kizu, K.; Maruyama, T.; Kubota, K.; Kanbara, H.; Kurihara, T.; Kaino,
T. J . Chem. Soc., Chem. Commun. 1993, 797. (d) Takagi, M.; Kizu, K.;
Miyazaki, Y.; Maruyama, T.; Kubota, K.; Yamamoto, T. Chem. Lett.
1993, 913. (e) Yamamoto, T.; Yamada, W.; Takagi, M.; Kizu, K.;
Maruyama, T.; Ooba, N.; Tomaru, S.; Kurihara, T.; Kaino, T.; Kubota,
K. Macromolecules 1994, 27, 6620. (f) Wautelet, P.; Moroni, M.; Oswald,
L.; Moigne, J . L.; Pham, A.; Bigot, J .-Y.; Luzzati, S. Macromolecules
1996, 29, 446. (g) Weder, C.; Wrighton, M. S. Macromolecules 1996,
29, 5157.
S0276-7333(97)00266-5 CCC: $14.00 © 1997 American Chemical Society

trans-Pd(Ar)(CtCPh)(PEt3)2
Organometallics, Vol. 16, No. 24, 1997 5355
Sch em e 2
the above catalytic reaction, there have been only a few
reports on Pd(Ar)(CtCR)(L)n type complexes with a
highly electron withdrawing Ar group (C6F5).4
On the other hand, alkynylcopper compounds, [Cu-
(CtCR)]n, isolated or generated in situ from the reaction
of CuI, base, and alkyne, have been reported to react
readily with group 5-10 transition-metal complexes to
give σ-alkynyl complexes of these metals (Scheme
2(i))5-8 or bimetallic complexes containing an alkynyl
ligand that is π-bonded to the Cu(I) center and σ-bonded
to other transition metals such as Re, Fe, Ru, Ir, and
Pt (Scheme 2(ii)).9-14 The intermolecular transfer of the
alkynyl ligand from Cu(I) to Pd(II) and to Pt(II) in the
former reactions is utilized for synthesis of alkynyl
complexes (e.g., Pd(CtCR)2Ln) of group 10 metals.
Similar alkynyl ligand transfer from an alkynylcopper(I)
complex to arylpalladium halide complexes would give
Pd(Ar)(CtCR)Ln type complexes, whose chemical prop-
erties are of interest with regard to the mechanism of
the above cross-coupling reaction.
F igu r e 1. ORTEP drawings of (a) Pd(C6H4Me-p)(I)(tmeda)
(1a ) at the 50% ellipsoid level and (b) Pd(C6H4OMe-
p)(I)(tmeda) (1b) at the 30% ellipsoid level.
type complexes. The isolated trans-PdAr(CtCPh)(PEt3)2
complexes show interesting reactivity. For example,
they react with CuI to cause a reverse type of alkynyl
ligand transfer from Pd(II) to Cu(I) as well as liberation
of ArCtCPh as the coupling product. Similar alkynyl
ligand transfer also takes place from Pd(II) to Pt(II),
and such chemical reactivity of the trans-PdAr(CtCPh)-
(PEt3)2 type complexes will be presented in this paper.
Part of this work has been reported in a preliminary
form.15
In this paper, we report the preparation of trans-
PdAr(CtCPh)(PEt3)2 complexes via such alkynyl ligand
transfer from an alkynylcopper(I) complex to PdAr(I)Ln
(4) Preparation and characterization of trans- and cis-Pd(C6F5)-
(CtCR)(PR3)2 have been reported. Even the cis complexes do not
undergo coupling of the alkynyl and aryl ligands, probably due to the
very stable Pd-C6F5 bond. See: Espinet, P.; Fornie´s, J .; Mart´ınez, F.;
Sotes, M.; Lalinde, E.; Moreno, M. T.; Ruiz, A.; Welch, A. J . J .
Organomet. Chem. 1991, 403, 253.
Resu lts
(5) Abu Salah, O. M.; Bruce, M. I. Aust. J . Chem. 1976, 29, 73.
(6) (a) Sonogashira, K.; Fujikura, Y.; Yatake, T.; Toyoshima, N.;
Takahashi, S.; Hagihara, N. J . Organomet. Chem. 1978, 145, 101. (b)
Fujikura, Y.; Sonogashira, K.; Hagihara, N. Chem. Lett. 1975, 1067.
(c) Sonogashira, K.; Yatake, T.; Tohda, Y.; Takahashi, S.; Hagihara,
N. J . Chem. Soc., Chem. Commun. 1977, 291. (d) Ogawa, H.; J oh, T.;
Takahashi, S.; Sonogashira, K. J . Chem. Soc., Chem. Commun. 1988,
561. (e) Ohshiro, N.; Takei, F.; Onitsuka, K.; Takahashi, S. Chem. Lett.
1996, 871.
(7) Cross, R. J .: Davidson, M. F. J . Chem. Soc., Dalton Trans. 1986,
1987.
(8) Osakada, K.; Takizawa, T.; Yamamoto, T. Organometallics 1995,
14, 3531.
(9) (a) Bruce, M. I.; Clark, R.; Howard, J .; Woodward, P. J .
Organomet. Chem. 1972, 42, C107. (b) Abu Salah, O. M.; Bruce, M. I.;
Redhouse, A. D. J . Chem. Soc., Chem. Commun. 1974, 855. (c) Abu
Salah, O. M.; Bruce, M. I. J . Chem. Soc., Dalton Trans. 1974, 2302.
(d) Bruce, M. I.; Abu Salah, O. M.; Davis, R. E.; Reghavan, N. V. J .
Organomet. Chem. 1974, 64, C48. (e) Abu Salah, O. M.; Bruce, M. I.
J . Chem. Soc., Dalton Trans. 1975, 2311.
(10) (a) Abu Salah, O. M.; Bruce, M. I.; Churchill, M. R.; Bezman,
S. A. J . Chem. Soc., Chem. Commun. 1972, 858. (b) Churchill, M. R.;
Bezman, S. A. Inorg. Chem. 1974, 13, 1418.
P r ep a r a t ion a n d Ch a r a ct er iza t ion of tr a n s-
P d (C6H 4X-p )(I)(P R3)2 (X ) Me, OMe, F ; R ) E t ,
Me, P h ). Organopalladium complexes with a tmeda
(N,N,N′N′-tetramethylethylenediamine) ligand serve as
convenient precursors of the complexes with phosphine
ligands because their labile Pd-N bonds undergo facile
substitution by the more π-acidic P ligands.16 Pd(C6H4X-
p)(I)(tmeda) (1a , X ) Me; 1b, X ) OMe; 1c, X ) F) have
been prepared according to a procedure already reported
and characterized by NMR spectra as well as X-ray
crystallography. Figure 1 shows the molecular struc-
tures of 1a and 1b to have a slightly distorted square
planar coordination around the Pd center. Selected
bond distances and angles are summarized in Table 1.
The difference between the two Pd-N bond distances
in each molecule (Pd-N1 ) 2.143(5) Å and Pd-N2 )
2.203(5) Å in 1a and Pd-N1 ) 2.130(7) Å and Pd-N2
(11) Clark, R.; Howard, J .; Woodward, P. J . Chem. Soc., Dalton
Trans. 1974, 2027.
(12) (a) Yamazaki, S.; Deeming, A. J . J . Chem. Soc., Dalton Trans.
1993, 3051. (b) Yamazaki, S.; Deeming, A. J .; Hursthouse, M. B.; Malik,
K. M. A. Inorg. Chim. Acta 1995, 235, 147.
(13) Tanaka, S.; Yoshida, T.; Adachi, T.; Yoshida, T.; Onitsuka, K.;
Sonogashira, K. Chem. Lett. 1994, 877.
(14) Alkynylsilver(I) and -mercury(II) compounds also undergo
similar ligand transfer to result in the formation of alkynylplatinum
complexes. See: Espinet, P.; Fornie´s, J .; Martinez, F.; Toma´s, M.;
Lalinde, E.; Moreno, M. T.; Ruiz, A.; Welch, A. J . J . Chem. Soc., Dalton
Trans. 1990, 791.
(15) Osakada, K.; Sakata, R.; Yamamoto, T. J . Chem. Soc., Dalton
Trans. 1997, 1265.
(16) (a) de Graaf, W.; Boersma, J .; Smeets, W. J . J .; Spek, A. L.;
van Koten, G. Organometallics 1989, 8, 2907. (b) de Graaf, W.; van
Wegen, J .; Boersma, J .; Spek, A. L.; van Koten, G. Recl. Trav. Chim.
Pays-Bas 1989, 108, 275. (c) Alsters, P. L.; Boersma, J .; van Koten, G.
Organometallics 1993, 12, 1629. (d) Markies, B. A.; Canty, A. J .; de
Graaf, W.; Boersma, J .; J anssen, M. D.; Hogerheide, M. P.; Smeets,
W. J . J .; Spek, A. L.; van Koten, G. J . Organomet. Chem. 1994, 482,
191.

5356 Organometallics, Vol. 16, No. 24, 1997
Osakada et al.
Ta ble 1. Selected Bon d Dista n ces (Å) a n d An gles
(d eg) of 1a ,b, 4a , a n d 6c
1a
1b
4a
6c
Pd-I
2.584(3) 2.596(5)
Pd-C1
C1-C2
Pd-C9
Pd-N1
Pd-N2
Pd-P1
1.988(6) 1.956(9) 2.016(8) 1.99(1) (Pt-C1)
1.196(9) 1.21(1) (C1-C2)
2.062(7) 2.02(1) (Pt-C9)
2.143(5) 2.130(7)
2.203(5) 2.195(7)
2.300(2) 2.313(3) (Pt-P1)
2.292(2) 2.282(3) (Pt-P2)
89.1(2) 89.8(2)
176.8(1) 177.2(2)
95.1(1) 95.3(2)
Pd-P2
I-Pd-C1
I-Pd-N1
I-Pd-N2
C1-Pd-N1 92.2(2) 91.6(3)
C1-Pd-N2 175.4(2) 174.8(3)
N1-Pd-N2 83.4(2) 83.3(3)
C1-Pd-P1
87.4(2)
92.3(2)
91.2(2)
89.1(2)
86.2(3) (C1-Pt-P1)
91.5(3) (C1-Pt-P2)
91.2(3) (C9-Pt-P1)
90.5(3) (C9-Pt-P2)
C1-Pd-P2
C9-Pd-P1
C9-Pd-P2
C1-Pd-C9
176.7(3) 172.7(7) (C1-Pt-C9)
176.81(8) 174.8(1) (P1-Pt-P2)
174.6(7) 175(1) (Pt-C1-C2)
179.0(7) 176(1) (C1-C2-C3)
P1-Pd-P2
F igu r e 2. ORTEP drawing of trans-Pd(C6H4Me-p)(CtC-
Ph)(PEt3)2 (4a ) at the 30% ellipsoid level.
Pd-C1-C2
C1-C2-C3
) 2.195(7) Å in 1b) is ascribed to a larger trans influence
of the aryl than of the iodo ligand. Complexes 1a -c
readily react with 2 equiv of PEt3 to give the corre-
sponding aryliodopalladium complexes trans-Pd(C6H4X-
p)(I)(PEt3)2 (2a , X ) Me; 2b, X ) OMe; 2c, X ) F), as
shown in eq 1. Similar reactions of 1a with PMe3 and
Cu ) 1:1) at -30 °C does not give the coupling product
3a but gives
a
mixture of trans-Pd(C6H4Me-
p)(CtCPh)(PEt3)2 (4a ) (65%) and 2a (35%).
Addition of PPh3 ligand to the reaction mixture of 2a
and [Cu(CtCPh)(PPh3)]4 at room temperature makes
isolation of the inorganic products possible, as shown
below. The hexane-insoluble fraction of the product is
a mixture of PPh3-coordinated Cu complexes from which
CuI(PPh3)3 is isolated in 51% yield. The hexane extract
from the reaction mixture contains 2a (21%), 3a (36%),
and 4a (42%), as revealed by the 1H NMR spectrum.
Aryl(alkynyl)palladium complex 4a is isolated as color-
less crystals by repeated recrystallization of the hexane-
soluble fraction of the product from acetone. The low
isolated yield (3%) is mainly due to the solubility of the
complex being similar to that of 2a . Figure 2 shows the
molecular structure of 4a , as determined by X-ray
crystallography. The molecule has a trans configuration
around the Pd center. The fact that the Pd-C(alkynyl)
bond (2.016(8) Å) is shorter than the Pd-C(aryl) bond
(2.062(7) Å), despite a larger trans influence for aryl
over alkynyl ligands,17 is due to the partial contribution
of a vinylidene structure (Pd-dCdC+sPh) in the coor-
dination of the phenylethynyl group to the Pd center.18
The 13C{1H} NMR spectrum shows signals due to R- and
â-alkynyl carbons at δ 119.8 and 111.3 as a triplet
with PPh3 give trans-Pd(C6H4Me-p)(I)(PR3)2 (2d , R )
Me; 2e, R ) Ph). The NMR spectra of the complexes
are consistent with the trans structure.
Rea ction of 2a -c w ith [Cu (CtCP h )(P P h 3)]4 To
Ca u se Alk yn yl Liga n d Tr a n sfer . Table 2 sum-
marizes the results of the reactions of 2a -c with the
alkynylcopper(I) complex causing alkynyl ligand trans-
fer from Cu to Pd and/or coupling of the alkynyl and
aryl groups depending on the conditions. Complex 2a
reacts with [Cu(CtCPh)(PPh3)]4 (Pd:Cu ) 1:1) at room
temperature to give the coupling product PhCtCC6H4-
Me-p (3a ; 74%). The NMR spectrum of the reaction
mixture showed the presence of starting complex 2a
(26%) also. Although Cu-containing products in this
reaction have not been fully characterized, [Cu(CtCPh)-
(PPh3)]4 seems to be converted to the corresponding
iodocopper complexes during the reaction. A 1:2 reac-
tion of the complexes causes complete conversion of 2a
to 3a . Reaction of 2a with [Cu(CtCPh)(PPh3)]4 (Pd:
(17) Manna, J .; J ohn, K. D.; Hopkins, M. D. Adv. Organomet. Chem.
1995, 38, 79 and references therein.
(18) (a) Bruce, M. I. Chem. Rev. 1991, 91, 197. (b) Bruce, M. I. J .
Organomet. Chem. 1990, 400, 321. (c) Doherty, S.; Corrigan, J . F.;
Carty, J . A.; Sappa, E. Adv. Organomet. Chem. 1995, 37, 39.

trans-Pd(Ar)(CtCPh)(PEt3)2
Organometallics, Vol. 16, No. 24, 1997 5357
Ta ble 2. Rea ction of 2a -c w ith [Cu (CtCP h )(P P h 3)]4
products (yield %)b,c
reacn conditionsa
Pd complex
2a (26)
run no.
Pd complex
additived
temp/°C
time/min
PhCtCC6H4X-p
1
2e
3
4
5
6
7
8
9
2a
2a
2a
2a
2b
2c
2d
2e
1a
room temp
room temp
-30 °C
60
60
20
210
60
60
240
60
20
3a (74)
3a (100)
2a (35)
2a (21)
2b (41)
2c (23)
2d (46)
4a (65)
4a (42)
4b (42)
4c (64)
PPh3
PPh3
PPh3
room temp
room temp
room temp
room temp
-30 °C
3a (36)
3b (17)
3c (13)f
3a (54)
3a (>95)
3a (78)
room temp
a
b
Reactions were performed in toluene, except for runs 3 and 8, which were carried out in CH2Cl2. Yields by NMR. c CuI(PPh3)3 was
isolated in 45% (run 4) and 49% (run 5) yields. [PPh3]/[Pd] ) 2.0. e Pd/Cu ratio is 1:2. f Formation of 2c, 3c, and 4c was confirmed by
d
the 1H NMR spectrum of the reaction mixture, but separation of the products was not plausible.
(J (CP) ) 20 Hz) and a singlet, respectively. A similar
reaction of 2b with [Cu(CtCPh)(PPh3)]4 in the presence
of PPh3 gives a mixture of 2b, PhCtCC6H4OMe-p (3b),
and trans-Pd(C6H4OMe-p)(CtCPh)(PEt3)2 (4b), in a
ratio of 41:17:42. Complex 4b is isolated from the reac-
tion mixture by fractional recrystallization and has been
characterized by NMR spectroscopy.19 The reaction
mixture of 2c and [Cu(CtCPh)(PPh3)]4 in the presence
of PPh3 also contains 2c, 3c, and trans-Pd(C6H4F-
p)(CtCPh)(PEt3)2 (4c) in a ratio of 23:13:64, although
with and without PPh3 addition. The reaction without
PPh3 (Figure 3a) causes consumption of 4a in 1 h
accompanied by formation of 2a and 3a . Addition of
PPh3 to the reaction mixture changed the profile,
depending on the molar ratio of the Pd complex and
PPh3, as shown in parts b-d of Figure 3. Reactions of
1, 3, and 5 equiv of added PPh3 with 4a result in
formation of 2a , 3a , and 4a in the ratios of 36:35:29,
29:22:49, and 28:14:59, respectively, after 2 h. In each
reaction, the decrease in the amount of 4a and the
increase of 2a almost cease after 2 h, although concomi-
tant formation of coupling product 3a results in a slow
decrease of both complexes throughout the measure-
ment. Complexes 2a and 4a seem to be in equilibrium
under these conditions during the reaction. The molar
ratio between 4a and 2a after the reaction for 2 h
increases with an increase in the PPh3/Pd ratio.
isolation of 4c from the mixture has not been successful.
Complexes 4a and 4b, once isolated, are stable and do
not undergo reductive elimination of 3a and 3b in the
solution at room temperature.
NMR measurement of the reaction mixture of 2a and
[Cu(CtCPh)(PPh3)]4 at low temperature has provided
detailed information on the initial product of reaction
2. The 1H and 31P{1H} NMR spectra of a toluene-d8
solution of 2a and [Cu(CtCPh)(PPh3)]4 (Pd:Cu ) 1:1)
soon after dissolution of the complexes in CD2Cl2 at -30
°C show the presence of 2a and 4a in a 36:64 ratio.
Raising the temperature of the solution to -10 °C for 3
min results in a change of the relative ratio of the
complexes to 49:51, although liberation of 3a is negli-
gible at this stage. Partial conversion of 4a to 2a due
to the temperature change can be attributed to a shift
of equilibrium between the complexes under these
conditions:
P r ep a r a tion of tr a n s-P t(C6H4OMe-p)(I)(P Et3)2
a n d Its Rea ction s w ith [Cu (CtCP h )(P P h 3)]4 a n d
w ith 4a . Aryliodoplatinum(II) complexes trans-Pt-
(C6H4X-p)(I)(PEt3)2 (5b, X ) OMe; 5c, X ) F) are
prepared by oxidative addition of IC6H4OMe-p and of
IC6H4F-p, respectively, to Pt(PEt3)4. The 1H and 31P
NMR spectra agree well with the trans structure of the
complexes. Reactions of 5b,c with [Cu(CtCPh)(PPh3)]4
(Pt:Cu ) 1:1) convert the Pt complex into trans-
Pt(C6H4X-p)(CtCPh)(PEt3)2 (6b, X ) OMe; 6c, X ) F)
immediately. Coupling products 3b,c are not formed
in the reaction mixtures at all, due to the high stability
of 6b,c. Complex 6b does not react with CuI at room
temperature. The 13C{1H} NMR spectrum of 6b shows
signals due to the R- and â-alkynyl carbons at δ 114.3
2a + 1/4[Cu(CtCPh)(PPh3)]4 a
4a + (1/n)[Cu(I)(PPh3)]n (3)
Further raising of the reaction temperature to 25 °C
causes conversion of 4a into 2a and the coupling product
3a .
Alk yn yl Liga n d Tr a n sfer fr om 4a to Cu I. As
shown above, the alkynyl ligand migration from [Cu-
(CtCPh)(PPh3)]4 to trans-Pd(C6H4X-p)(I)(PEt3)2 appears
to be reversible. More direct evidence for reversibility
of the alkynyl ligand transfer is obtained from an NMR
study on the reaction of 4a with CuI. Reactions of 4a
with CuI at 25 °C in the presence and absence of added
PPh3 give a mixture of 2a and 3a , as shown in eq 4. A
similar reaction with addition of PEt3 (3 mol/mol of CuI)
does not cause alkynyl ligand transfer from Pd(II) to
Cu(I) at all, presumably due to blocking of the reaction
site. Figure 3 summarizes the profiles of the reactions
1
and 109.9, respectively. The J (CPt) value observed for
the former signal (890 Hz) is larger than that observed
in the ipso carbon signal of the aryl ligand (673 Hz).
Appearance of the alkynyl carbon signals as well as
some aryl carbon signals as triplets due to P-C coupling
indicates the trans structure of 6b unambiguously. The
trans structure of 6c has been confirmed by X-ray
crystallography, as shown in Figure 4. The fact that
(19) Preliminary results of the X-ray crystallography of 4b show the
trans structure of the complex.

5358 Organometallics, Vol. 16, No. 24, 1997
Osakada et al.
F igu r e 3. Reaction profiles of 4a with CuI: (a) without addition of PPh3; (b) with addition of PPh3 (1 mol/mol of 4a ); (c)
with addition of PPh3 (3 mol/mol of 4a ); (d) with addition of PPh3 (5 mol/mol of 4a ). The molar fractions of the compounds
are determined from 1H NMR peaks (C6H4CH3 region); the temperature was 25 °C.
time-yield curves of the complexes shown in eq 6 for a
the Pt-C(alkynyl) bond (1.99(1) Å) is shorter than the
1:1 reaction of 4a and 5b. Sufficient linearity of the
Pt-C(aryl) bond (2.02(1) Å) of 6c and the above differ-
plots of [4a ]0/[4a ]t suggests that the reaction obeys first-
order kinetics with respect to both [4a ] and [5b]. The
1
ence between the two J (CPt) values of 6b suggest a
partial contribution of the vinylidene structure to the
presence of a large excess amount of 5b gives a pseudo-
Pt-alkynyl bond of the complexes.
first-order kinetic condition, and the first-order plots of
Heating a toluene solution of an equimolar mixture
[4a ] show good linearity, as shown in Figure 7. The
of 4a and 5b at 50 °C causes intermolecular alkynyl
temperature dependence of the rate constants of the
ligand transfer from the former complex to the latter,
giving a mixture of 2a and 6b. The reaction proceeds
irreversibly and is almost completed within 9 h. Figure
reactions under pseudo-first-order conditions gives the
kinetic parameters ∆Hq ) 110 kJ mol-1, and ∆Sq ) -58
J mol-1 deg-1, and ∆Gq ) 127 kJ mol-1 at 298 K.
5 shows the 31P{1H} NMR spectrum of the reaction
mixture containing the complexes 2a , 4a , 5b, and 6b.
The 31P{1H} and 1H NMR spectra taken during the
reaction do not show any peaks due to compounds other
than the above four complexes, indicating that the aryl
groups behave as spectator ligands and do not undergo
migration between the metal centers. Figure 6 shows
Addition of CuI (2.09 µM, [Cu]/[Pd] ) 0.10) to the
reaction mixture causes consumption of more than 90%
of the starting materials within 5 min at 50 °C, while
the reaction without the additive requires ca. 3 h to
obtain conversion of 50% of the starting materials at
the same temperature. Enhancement of the reaction

trans-Pd(Ar)(CtCPh)(PEt3)2
Organometallics, Vol. 16, No. 24, 1997 5359
F igu r e 6. Time-yield curves and second-order plots of an
equimolar reaction of 4a and 5b to give 2a and 6b. [4a ]0 )
[5b]0 ) 0.055 M.
F igu r e 4. ORTEP drawing of trans-Pt(C6H4F-p)(CtC-
Ph)(PEt3)2 (5c) at the 30% ellipsoid level.
F igu r e 5. 31P{1H} NMR spectrum of the reaction mixture
of 4a and 5b at 50 °C. The peaks with arrows and with
asterisks are due to the satellite peaks of 5b and 6b,
respectively.
F igu r e 7. Pseudo-first-order plots of reaction 6 at 30-50
°C. An Arrhenius plots of the kinetic data is shown in the
inset.
by CuI suggests a pathway for alkynyl ligand transfer
from Pd and Pt assisted by the Cu compound.
Sch em e 3
Equimolar reaction of 4a and trans-Pd(C6H4OMe-
p)I(PMe3)2 (7b) at -30 °C even in the absence of CuI
results in alkynyl ligand exchange between the com-
plexes to give a mixture of 2a , trans-Pd(C6H4OMe-
p)(CtCPh)(PMe3)2 (8b), and the above two complexes.20
Discu ssion
Many dinuclear transition-metal complexes with bridg-
ing alkynyl ligands bonded to the metal centers in a σ-π
manner undergo rapid switching of µ-η1:η2 to µ-η2:η1
coordination, as shown in Scheme 3(i). The reaction
proceeds through concerted cleavage and formation of
the σ- and π-bonds between the alkynyl carbons and two
metal centers,21 except for diiron complexes with bridg-
ing ethynyl ligands, which undergo similar changes of
the coordination mode induced by a 1,2-shift of the
ethynyl hydrogen.22 The intermolecular transfer of the
The results indicate that the alkynyl ligand transfer
between the Pd centers proceeds much more readily
than the alkynyl ligand transfer from Pd to Pt com-
plexes.
(20) The NMR spectra of the reaction mixture after 1 h at -30 °C
showed conversion of ca. 10% of 4a and 7b into 2a and 8b, while raising
the temperature caused formation of many Pd complexes, probably
due to accompanying exchange of the phosphine ligands among the
complexes.

5360 Organometallics, Vol. 16, No. 24, 1997
Osakada et al.
Sch em e 4
complexes with several structures, such as those shown
in Scheme 4. These complexes, formulated as [Cu(I)-
(PR3)m]n and [Cu(CtCPh)(PR3)m]n, could have versatile
multinuclear structures with bridging coordination of
iodo and alkynyl ligands.23 The complexes A (R ) Ph,
SiMe3) have been obtained and characterized by X-ray
crystallography.8,23e B and C show the most reasonable
structures for the formulas, [Cu(CtCPh)(PR3)2]n and
[Cu(CtCPh)(PR3)3]n, respectively. Each of the com-
plexes is obtained by using a PPh3 ligand in the present
study (see Experimental Section). These complexes in
solution are considered to be in rapid equilibrium
involving dissociation and ligation of the phosphine
ligands due to the labile d10 metal center. The presence
of added PEt3 or excess amounts of PPh3 in the reaction
mixture tends to destabilize alkynylcopper species (or
stabilize iodocopper species) and shift the equilibrium
in Scheme 4. The obtained results here can be rational-
ized by assuming that ligation of phosphine ligands
destabilizes σ-donation in the alkynyl-copper bonding24
and cleaves the bridging coordination of the alkynyl
ligand to form less stable mononuclear alkynylcopper
species such as [Cu(CtCR)(PR′3)3].
The alkynyl ligand transfer between Cu and Pd
complexes is accompanied by coupling of the aryl and
phenylethynyl groups to give ArCtCPh. Formation of
the coupling product in the reaction of 2e, having PPh3
ligands, with [Cu(CtCPh)(PPh3)]4 at -30 °C is ac-
counted for by assuming initial alkynyl ligand transfer
to give cis- or trans-Pd(C6H4Me-p)(CtCPh)(PPh3)2. The
cis complex would liberate arylphenylacetylene by direct
reductive elimination, while the trans isomer would
undergo reductive elimination through dissociation of
the PPh3 ligand, which is less basic and more bulky than
PEt3, or trans-cis isomerization involving dissociation
of PPh3 followed by reductive elimination. Reactions
of 2a -c with [Cu(CtCPh)(PPh3)]4 and of 4a with CuI
also give the coupling product ArCtCPh. The aryl(al-
kynyl)palladium complexes with a trans structure 4a ,b
do not undergo spontaneous reductive elimination of the
two organic ligands at room temperature due to their
rigid trans coordination with compact and highly basic
PEt3 ligands, preventing isomerization of the trans to
the cis structure that is suited for reductive elimination
of the product. Coexistence of CuI in solution with 2a
causes coupling of the aryl and alkynyl ligands at room
temperature.
alkynyl ligand among Cu, Pd, and Pt in the present
study as well as in the previous studies seems to proceed
through formation of bimetallic intermediates and their
rapid structural change, as depicted in Scheme 3(ii).
The present study on the reactions of Pd(Ar)(I)(PEt3)2
with [Cu(CtCPh)]n and of Pd(Ar)(CtCPh)(PEt3)2 with
CuI has disclosed reversible alkynyl ligand transfer
between the Cu and Pd complexes. On the other hand,
the reactions of [Cu(CtCPh)]n and of Pd(Ar)(CtCPh)-
(PEt3)2 with Pt(Ar)(I)(PEt3)2 give PtAr(CtCPh)(PEt3)2
quantitatively without any sign of reverse alkynyl
ligand transfer from alkynylplatinum complexes already
produced to the iodo complexes of Cu or Pd. The highly
stable Pt-C(alkynyl) bond compared with the corre-
sponding Cu-C(alkynyl) and Pd-C(alkynyl) bonds is
attributed to significant back-donation of the alkynyl
group to the Pt center.
Reactions of 4a with CuI give various reaction pro-
files, depending on the presence of tertiary phosphine
added to the reaction mixture. The reaction with added
PEt3 (3 mol/mol of 4a ) does not cause alkynyl ligand
transfer from Pd to Cu at all, while the reaction without
phosphine addition leads to complete conversion of 4a
into a mixture of 3a and 2a . Addition of PPh3 causes
partial conversion of 4a , suggesting an equilibrium
between 4a and 2a under these conditions. The total
reaction and the structures of related copper complexes
are shown in Scheme 4. Alkynylcopper and iodocopper
species in the reaction are composed of mixtures of
There seem to be two plausible mechanisms for the
coupling of the aryl and phenylethynyl groups in the
presence of CuI. One involves CuI-induced removal of
a PEt3 ligand of the Pd complex to cause dissociative
(23) Structure of alkynylcopper complexes: (a) Corfield, P. W. R.;
Shearer, H. M. M. Acta Crystallogr. 1966, 21, 957. (b) ten Hoedt, R.
W. M.; Noltes, J . G.; van Koten, G.; Spek, A. L. J . Chem. Soc., Dalton
Trans. 1978, 1800. (c) Knotter, D. M.; Spek, A. L.; Grove, D. M.; van
Koten, G. Organometallics 1992, 11, 4083. (d) Knotter, D. M.; Grove,
D. M.; Smeets, W. J . J .; Spek, A. L.; van Koten, G. J . Am. Chem. Soc.
1992, 114, 3400. (e) Naldini, L.; Demartin, F.; Manassero, M.; Sansoni,
M.; Rassu, G.; Zoroddu, M. A. J . Organomet. Chem. 1985, 279, C42.
(f) Gamasa, M. P.; Gimeno, J .; Lastra, E.; Solans, X. J . Organomet.
Chem. 1988, 346, 277. (g) Diez, J .; Gamasa, M. P.; Gimeno, J .; Lastra,
E.; Aguirre, A.; Garc´ıa-Granda, S. Organometallics 1993, 12, 2213. (h)
Edwards, A. J .; Paver, M. A.; Raithby, P. R.; Rennie, M.-A.; Russell,
C. A.; Wright, D. S. Organometallics 1994, 13, 4967. (i) Mason, R.;
Mingos, D. M. P. J . Organomet. Chem. 1973, 50, 53.
(21) (a) Nubel, P. O.; Brown, T. L. Organometallics 1984, 3, 29. (b)
Deraniyagala, S. P.; Grundy, K. R. Organometallics 1985, 4, 424. (c)
Hutton, A. T.; Langrick, C. R.; McEwan, D. M.; Pringle, P. G.; Shaw,
B. L. J . Chem. Soc., Dalton Trans. 1985, 2121. (d) Cherkas, A. A.;
Randall, L. H.; MacLaughlin, S. A.; Mott, G. N.; Taylor, N. J .; Carty,
A. J . Organometallics 1988, 7, 969. (e) Koridze, A. A.; Kizas, O. A.;
Petrovskii, P. V.; Kolobova, N. E.; Struchkov, Y. T.; Yanovsky, A. I. J .
Organomet. Chem. 1988, 338, 81. (f) Seyferth, D.; Hoke, J . B.; Wheeler,
D. R. J . Organomet. Chem. 1988, 341, 421. (g) Fornie´s, J .; Go´mez-
Saso, M. A.; Lalinde, E.; Mart´ınez, F.; Moreno, M. T. Organometallics
1992, 11, 2873. (h) Esteruelas, M. A.; Lahuerta, O.; Modrego, J .;
Nu¨rnberg, O.; Oro, L. A.; Rodr´ıguez, L.; Sola, E.; Werner, H. Organo-
metallics 1993, 12, 266. (i) Lotz, S.; van Rooyen, P. H.; Meyer, R. Adv.
Organomet. Chem. 1995, 37, 219.
(24) (a) van Koten, G.; Noltes, J . G. In Comprehensive Organome-
tallic Chemistry; Wilkinson, G., Stone, F. G. A., Abel, E. W., Eds.;
Pergamon: Oxford, U.K., 1982; Vol. 2, pp 714-716. (b) Ibid., Vol. 2,
pp 737-739, and references therein. (c) van Koten, G. J . Organomet.
Chem. 1990, 400, 283 and references therein.
(22) (a) Akita, M.; Terada, M.; Oyama, S.; Moro-oka, Y. Organome-
tallics 1990, 9, 816. (b) Akita, M.; Ishii, N.; Takabuchi, A.; Tanaka,
M.; Moro-oka, Y. Organometallics 1994, 13, 258.

trans-Pd(Ar)(CtCPh)(PEt3)2
Organometallics, Vol. 16, No. 24, 1997 5361
Sch em e 5
reductive elimination of the aryl and alkynyl ligands
from Pd(Ar)(CtCPh)(PEt3) through trans to cis isomer-
ization in the three-coordinate species.25 Another pos-
sible mechanism is shown in Scheme 5. According to
the mechanism, alkynyl ligand transfer between Pd and
Cu gives a mixture of trans- and cis-PdAr(CtCPh)(PEt3)2.
The cis complex formed seems to undergo rapid reduc-
tive elimination of the product, since the cis isomer is
almost negligible in the NMR spectra of the reaction
mixture. Our experimental results are not sufficient to
compare the probability of cationic or neutral interme-
diates in the reaction and also in the catalytic cross-
coupling of alkyne and haloarene. The pathway of
trans-cis isomerization of the aryl(alkynyl)palladium
complex given in Scheme 5 resembles CuI- or HgI2-
induced cis- to trans-Pt(CtCPh)2(PPh2Me)2 isomeriza-
tion involving reversible alkynyl transfer between the
metal centers.7,26 Similar structural changes of square-
planar diorganopalladium complexes in the presence of
organomagnesium compounds also proceed through
reversible alkyl ligand transfer between Pd and Mg
centers.27
or cause reductive elimination of biaryls.30 The alkynyl
ligand transfer seems to be kinetically favored, because
the bimetallic intermediate with an unsymmetrically
bridging alkynyl ligand undergoes rapid σ-π structural
change, as shown in Scheme 3(i).
Alkynyl group transfer from PdAr(CtCPh)(PEt3)2 to
PtAr(I)(PEt3)2 occurs with gentle heating. The kinetic
results indicate that the reaction proceeds through a
bimetallic transition state probably containing a µ-η1:
η1-alkynyl ligand bonded both to Pd and to Pt centers.31
Enhancement of the reaction by addition of CuI is
rationalized by assuming two independent reaction
pathways in the presence of CuI. Scheme 6 depicts
pathway i, involving direct ligand exchange through a
transition state with bridging alkynyl ligands, and
pathway ii, in which the alkynyl ligand transfer from
Pd to Pt is assisted by more rapid alkynyl ligand
transfer between Cu and Pd. The latter pathway
contributes significantly in the presence of a catalytic
amount of CuI because of the large effect of addition of
a catalytic amount of CuI. Amounts of the coupling
products (ArCtCPh) are almost negligible in this reac-
tion mixture. This suggests that transfer of the alkynyl
ligand of the once formed alkynylcopper to the arylpal-
ladium iodo complex in pathway ii to generate cis-
PdAr(CtCPh)L2 is slower than the alkynyl ligand
transfer reaction from the alkynylcopper species to Pt,
giving a Pt alkynyl product.
In general, the aryl-metal bond is thermodynamically
less stable than the corresponding alkynyl-metal bond28
and several aryl-nickel and -palladium complexes
have been reported to undergo intermolecular transfer
of the aryl ligands.29 The alkynyl transfer reactions in
the present study always occur prior to aryl ligand
migration that would give diarylpalladium complexes
(29) (a) Ozawa, F.; Fujimori, M.; Yamamoto, T.; Yamamoto, A.
Organometallics 1986, 5, 2144. (b) Yamamoto, T.; Wakabayashi, S.;
Osakada, K. J . Organomet. Chem. 1992, 428, 223. (c) Osakada, K.;
Sato, R.; Yamamoto, T. Organometallics 1994, 13, 4645. See also: van
Koten, G.; Noltes, J . G. J . Organomet. Chem. 1975, 84, 129.
(30) (a) Braterman, P. S.; Cross, R. J .; Young, G. B. J . Chem. Soc.,
Dalton Trans. 1977, 1892. (b) Komiya, S.; Abe, Y.; Yamamoto, A.;
Yamamoto, T. Organometallics 1983, 2, 1466.
(31) Blagg, A.; Hutton, A. T.; Pringle, P. G.; Shaw, B. L. J . Chem.
Soc., Dalton Trans. 1984, 1815. See also: J anssen, M. D.; Ko¨hler, K.;
Herres, M.; Dedieu, A.; Smeets, W. J . J .; Spek, A. L.; Grove, D. M.;
Lang, H.; van Koten, G. J . Am. Chem. Soc. 1996, 118, 4817.
(25) Pd(0) species, once formed through reductive elimination of the
coupling product, may also abstract PEt3 coordinated to the Pd complex
to enhance the formation of the three-coordinate species.
(26) (a) Cross, R. J .; Gemmill, J . J . Chem. Soc., Dalton Trans. 1984,
199, 205. (b) Cross, R. J .; Davidson, M. F. Inorg. Chim. Acta 1985, 97,
L35. (c) Anderson, G. K.; Cross, R. J . Chem. Soc. Rev. 1980, 9, 185.
(27) (a) Ozawa, F.; Ito, T.; Nakamura, Y.; Yamamoto, A. Bull. Chem.
Soc. J pn. 1981, 54, 1868. (b) Ozawa, F.; Kurihara, K.; Yamamoto, T.;
Yamamoto, A. J . Organomet. Chem. 1985, 279, 233.
(28) Bryndza, H. E.; Fong, L. K.; Paciello, R. A.; Tam, W.; Bercaw,
J . E. J . Am. Chem. Soc. 1987, 109, 1444.

5362 Organometallics, Vol. 16, No. 24, 1997
Osakada et al.
Complex 1a , prepared according to the already reported
procedure, showed NMR peaks identical with the literature
data.16 Similar reactions of 4-iodoanisole and of 4-fluoroiodo-
benzene with Pd2(dba)3 in the presence of tmeda gave 1b (79%)
and 1c (79%), respectively. Data for 1b: 1H NMR (C6D6) δ
1.49 (t, 2H, CH2, J ) 4 Hz), 1.60 (t, 2H, CH2, J ) 4 Hz), 1.68
(s, 6H, NCH3), 2.26 (s, 6H, NCH3), 3.43 (s, 3H, OCH3), 6.80 (d,
2H, C6H2H2, J ) 9 Hz), 7.36 (d, 2H, C6H2H2, J ) 9 Hz). Anal.
Calcd for C13H23ION2Pd: C, 34.19; H, 5.08; N, 6.13. Found:
C, 34.09; H, 5.11; N, 6.18. Data for 1c: 1H NMR (C6D6) δ 1.41
(t, 2H, CH2, J ) 5 Hz), 1.51 (t, 2H, CH2, J ) 5 Hz), 1.54 (s,
6H, NCH3), 2.21 (s, 6H, NCH3), 6.85 (d, 2H, C6H2H2, J ) 9
Hz), 7.29 (dd, 2H, C6H2H2, J (HH) ) 9 Hz, J (HF) ) 6 Hz). Anal.
Calcd for C12H20FIN2Pd: C, 32.41; H, 4.53; N, 6.30. Found:
Sch em e 6
C, 32.35; H, 4.61; N, 6.39.
8,23e
[Cu(CtCPh)(PPh3)]4
was prepared by the reaction of
[Cu(CtCPh)]n with PPh3 as shown below. A mixture of
[Cu(CtCPh)]n (2.56 g, 16 mmol) and PPh3 (12.1 g, 46 mmol)
was dissolved in THF (40 mL) containing HNEt2 (5.5 mL) with
gentle heating. The initial yellow dispersion gradually turned
into a greenish brown solution. After the mixture was stirred
for an additional 18 h at room temperature, the solvent was
evaporated to dryness. The product was extracted with
toluene (50 mL) at room temperature. A slightly green solid
obtained from washing the toluene-insoluble fraction with
Et2O gave [Cu(CtCPh)(PPh3)]4 (3.00 g, 45%). IR (KBr)
ν(CtC): 2018 cm-1 (lit.23e 2014 cm-1). Anal. Calcd for C104
80P4Cu4: C, 73.14; H, 4.72. Found: C, 73.05; H, 4.91. The
-
H
toluene-soluble fraction was washed with Et2O to give
[Cu(CtCPh)(PPh3)2]2 (2.23 g, 21%) as a colorless solid. Anal.
Calcd for C88H70P4Cu2: C, 75.83; H, 5.30. Found: C, 76.12;
Con clu sion
H, 5.43. IR(KBr) ν(CtC): 2040 cm-1
.
Intermolecular transfer of an alkynyl ligand bonded
to Cu(I) to arylpalladium halo complexes occurs under
mild conditions to give the corresponding arylpalladium
alkynyl complexes, which are isolated and characterized
by use of the PEt3 ligand. The alkynyl ligand transfer
sometimes proceeds reversibly to give an equilibrated
mixture of the Cu- and Pd-alkynyl complexes, al-
though the reaction is accompanied by irreversible
coupling of the aryl and alkynyl groups of the complexes.
Alkynyl ligand transfer from arylpalldium to arylplati-
num complexes requires more severe conditions but is
facilitated by addition of CuI, which seems to transport
the alkynyl group from Pd to Pt complexes. The present
study has disclosed alkynyl ligand transfer among Cu(I),
Pd(II), and Pt(II) complexes and the role of intermo-
lecular organic ligand transfer in selective cross-
coupling reactions catalyzed by Pd(II) complexes in the
presence of CuI. CuI in the catalytic process serves to
make cross-coupling efficient by promoting selective and
reversible transfer of the alkynyl ligand between the
metal centers.
A similar reaction of [Cu(CtCPh)]n (0.30 g, 1.8 mmol) and
PPh3 (2.33 g, 8.9 mmol) gave a mixture of [Cu(CtCPh)(PPh3)]4
and Cu(CtCPh)(PPh3)3, the latter of which was isolated from
the toluene-soluble fraction (5 mL) of the product. IR (KBr)
ν(CtC): 2042 cm-1. Anal. Calcd for C62H50P3Cu: C, 78.25;
H, 5.30. Found: C, 78.26; H, 5.56.
P r ep a r a tion of 2a -c. To 1a (1.80 g, 4.1 mmol) dispersed
in Et2O (65 mL) was added PEt3 (1.13 g, 9.6 mmol) dropwise
at 0 °C. After the cooling bath was removed, the reaction
mixture was stirred at room temperature for 20 min to cause
separation of a yellow solid from the yellow-orange solution.
The resulting solid was collected by filtration and recrystallized
1
from Et2O to give 2a as pale yellow crystals (1.90 g, 83%). H
NMR (C6D6): δ 0.89 (m, 18H, P(CH2CH3)3), 1.56 (m, 12H,
P(CH2CH3)3), 2.18 (s, 3H, CH3), 6.90 (d, 2H, C6H2H2, J ) 7
Hz), 7.21 (d, 2H, C6H2H2, J ) 7 Hz). 31P{1H} NMR: 25 °C in
C6D6, δ 10.3 (s); (-30 °C in CD2Cl2, δ 11.0 (s). Anal. Calcd
for C19H37IP2Pd: C, 40.70; H, 6.65. Found: C, 40.48; H, 6.75.
Similar reactions of 1b and of 1c gave trans-Pd(C6H4X-
p)(I)(PEt3)2 (2b, X ) OMe, 11%; 2c, X ) F, 87%). Data for 2b:
1H NMR (C6D6) δ 0.89 (m, 18H, P(CH2CH3)3), 1.59 (m, 12H,
P(CH2CH3)3), 3.40 (s, 3H, CH3), 6.79 (d, 2H, C6H2H2, J ) 9
Hz), 7.14 (d, 2H, C6H2H2, J ) 9 Hz); 31P{1H} NMR (25 °C in
C6D6) δ 10.7 (s). Anal. Calcd for C19H37IOP2Pd: C, 39.57; H,
6.47. Found: C, 39.16; H, 6.52. Data for 2c: 1H NMR (C6D6)
δ 0.83 (m, 18H, P(CH2CH3)3), 1.52 (m, 12H, P(CH2CH3)3), 6.82
(t, 2H, C6H2H2, J (HH) ) 9 Hz, J (HF) ) 9 Hz), 7.14 (dd, 2H,
C6H2H2, J (HH) ) 9 Hz, J (HF) ) 6 Hz); 31P{1H} NMR (25 °C
in C6D6) δ 10.6 (s). Anal. Calcd for C18H34FIP2Pd: C, 38.28;
H, 5.58. Found: C, 38.19; H, 5.96.
Rea ction of 2a -c w ith [Cu (CtCP h )(P P h 3)]4. 1. Rea c-
tion a t Room Tem p er a tu r e. Addition of a toluene (2 mL)
solution of 2a (123 mg, 0.22 mmol) to [Cu(CtCPh)(PPh3)]4 (102
mg, 0.24 mmol of Cu) at room temperature caused an immedi-
ate color change of the solution from yellow to black. After
further stirring for 5 h at room temperature, the solvent was
evaporated to dryness. 1H NMR spectrum measurement of
the product using diphenylmethane as an internal standard
showed the presence of 2a (26% yield) and 3a (74% yield) in
the product.
Exp er im en ta l Section
Gen er a l Con sid er a tion s, Mea su r em en t, a n d Ma ter ia ls.
Manipulations of the metal complexes were carried out under
nitrogen or argon using standard Schlenk techniques. Pd2-
32
33
(dba)3 and Pt(PEt3)4 were prepared according to the litera-
ture. IR and NMR spectra (1H, 13C, and 31P) were recorded
on a J ASCO 810 spectrophotometer and on a J EOL EX-400
spectrometer, respectively. 31P{1H} NMR peak positions were
referenced to external 85% H3PO4. Elemental analyses were
carried out with a Yanagimoto Type MT-2 CHN autocorder.
(32) Ukai, T.; Kawazura, H.; Ishii, Y. J . Organomet. Chem. 1974,
65, 253.
(33) (a) Otsuka, S.; Yohida, T.; Matsumoto, M.; Nakatsu, K. J . Am.
Chem. Soc. 1976, 98, 5850. (b) Yoshida, T.; Matsuda, T.; Otsuka, S.
Inorg. Synth. 1979, 19, 110.

trans-Pd(Ar)(CtCPh)(PEt3)2
Organometallics, Vol. 16, No. 24, 1997 5363
2. Rea ction a t -30 °C. To [Cu(CtCPh)(PPh3)]4 (88 mg,
0.21 mmol of Cu) was added a CH2Cl2 (1 mL) solution of 2a
(110 mg, 0.20 mmol) cooled to -30 °C. Stirring of the reaction
mixture was continued at -30 °C with occasional warming of
the flask at room temperature over a short period. Soon after
complete dissolution of the starting materials the solvent was
evaporated to dryness. The Pd-containing products were
extracted with hexane (5 mL) to remove Cu complexes by
filtration. The 1H and 31P{1H} NMR spectra of the hexane
extract showed the presence of 2a (35%) and 4a (65%) and
the absence of 3a .
A mixture of 2d (50 mg, 0.10 mmol) and [Cu(CtCPh)(PPh3)]4
(43 mg, 0.10 mmol of Cu) was dissolved in toluene (2 mL) at
room temperature to cause an immediate color change of the
solution to black. After the reaction mixture was stirred for
4 h at room temperature, the solvent was evaporated to
dryness. The 1H NMR spectrum of the resulting black solid
showed the presence of 2d (46%) and 3a (54%).
P r ep a r a tion of 2e a n d Its Rea ction w ith [Cu (CtCP h )-
(P P h 3)]4. A mixture of 1a (152 mg, 0.34 mmol) and PPh3 (182
mg, 0.69 mmol) was dispersed in Et2O (10 mL) at room
temperature. Stirring the pale pink mixture for 2 h caused a
color change of the solid to pale yellow. The solid product was
collected by filtration and dried in vacuo to give 2e as a pale
yellow solid (253 mg, 87%). 1H NMR (C6D6): δ 1.93 (s, 3H,
CH3), 6.15 (d, 2H, C6H2H2, J ) 7 Hz), 6.69 (d, 2H, C6H2H2, J
) 7 Hz), 6.98 (br, 18H, P(C6H3H2)3), 7.73 (br, 12H, P(C6H3H2)3).
31P{1H} NMR (C6D6): δ 22.5 (s). Anal. Calcd for C43H37IP2Pd:
C, 60.83; H, 4.39. Found: C, 60.92; H, 4.57.
3. Rea ction a t Room Tem p er a tu r e w ith P P h 3 Ad d i-
tion . To a toluene (3 mL) solution of [Cu(CtCPh)(PPh3)]4 (408
mg, 0.96 mmol of Cu) and PPh3 (502 mg, 1.9 mmol) was added
a toluene (4 mL) solution of 2a (521 mg, 0.93 mmol) at room
temperature. Stirring the mixture caused dissolution of the
initial pale green suspension to give a yellow-orange solution.
After reaction for 4 h the solvent was evaporated to dryness.
At this stage the 1H NMR measurement of the reaction
mixture showed the presence of 2a (21%), 3a (36%), and 4a
(42%). Extraction of the product with hexane (5 mL) followed
by repeated recrystallization from acetone gave 4a as colorless
A mixture of 2e (135 mg, 0.16 mmol) and [Cu(CtCPh)-
(PPh
3)]4 (70 mg, 0.16 mmol of Cu) was dissolved in CH2Cl2 (3
mL) at -30 °C. Stirring the pale green reaction mixture at
-30 °C caused deposition of a black solid. After 1 h the 1H
NMR spectrum of the reaction mixture showed formation of
phenyl(4-methylphenyl)acetylene (95%).
Rea ction of 1a w ith [Cu (CtCP h )(P P h 3)]4. A mixture
of 1a (113 mg, 0.25 mmol) and [Cu(CtCPh)(PPh3)]4 (103 mg,
0.24 mmol) was dissolved in THF (2 mL) with stirring at room
temperature. The initial orange solution soon turned into a
yellow solution, from which a black solid began to precipitate.
After the mixture was stirred for 20 min at room temperature,
the 1H NMR analysis of the product showed formation of 3a
(78%).
Rea ction of 4a w ith Cu I. A typical experiment was
carried out as follows. An NMR tube containing 4a (5.70 mg,
1.07 × 10-2 mmol), CuI (2.20 mg, 1.16 × 10-2 mmol), PPh3
(3.32 mg, 1.26 × 10-2 mmol), and anisole (2 µL, internal
standard) was connected to a vacuum line. Benzene-d6 (ca.
0.5 mL) was introduced by trap-to-trap distillation. After the
sample tube was sealed, changes in the peaks in the region of
the tolyl methyl hydrogens were monitored by comparison with
the peak of the internal standard.
crystals (13.4 mg, 3%). IR (KBr) ν(CtC): 2092 cm-1 1H NMR
.
(C6D6): δ 0.98 (m, 18H, P(CH2CH3)3), 1.57 (m, 12H, P(CH2-
CH3)3), 2.29 (s, 3H, CH3), 7.00 (t, 1H, C6H4H, J ) 7 Hz), 7.08
(d, 2H, C6H2H2, J ) 7 Hz), 7.16 (t, 2H, C6H3H2, J ) 7 Hz),
7.46 (d, 2H, C6H2H2, J ) 7 Hz), 7.62 (d, 2H, C6H3H2, J ) 7
Hz). 31P{1H} NMR: 25 °C, C6D6, δ 14.5 (s); -30 °C, CD2Cl2, δ
14.8 (s). 13C{1H} NMR (25 °C in CD2Cl2): δ 8.4 (P(CH2CH3)3),
16.2 (apparent triplet due to virtual coupling, P(CH2CH3)3),
21.0 (CH3), 111.3 (CtC), 119.8 (t, PdCtC, J (CP) ) 20 Hz),
124.8, 127.9, 128.2, 129.7, 130.7, 131.0, 138.2, 157.2. Anal.
Calcd for C27H42P2Pd: C, 60.62; H, 7.91. Found: C, 60.23; H,
8.12. The hexane-insoluble solid in the product was washed
with Et2O to give CuI(PPh3)3 as a pale green solid (459 mg,
51%). Anal. Calcd for
Found: C, 66.37; H, 4.69.
C54H45IP3Cu: C, 66.36; H, 4.64.
A similar reaction of 2b with [Cu(CtCPh)(PPh3)]4 in the
presence of PPh3 gave 4b, which was isolated by recrystalli-
zation of the hexane-soluble fraction of the product (5%). IR
(KBr) ν(CtC): 2092 cm-1 1H NMR (C6D6): δ 0.98 (m, 18H,
.
P(CH2CH3)3), 1.56 (m, 12H, P(CH2CH3)3), 3.48 (s, 3H, OCH3),
6.95 (t, 1H, C6H4H, J ) 7 Hz), 7.01 (d, 2H, C6H2H2, J ) 7 Hz),
7.18 (t, 2H, C6H3H2, J ) 7 Hz), 7.39 (d, 2H, C6H2H2, J ) 7
Hz), 7.63 (d, 2H, C6H3H2, J ) 7 Hz). 31P{1H} NMR (25 °C,
C6D6): δ 14.8 (s). 13C{1H} NMR (25 °C, CD2Cl2): δ 8.4
(P(CH2CH3)3), 16.2 (apparent triplet due to virtual coupling,
P(CH2CH3)3), 54.3 (OCH3), 111.2 (CtC), 113.3 (ortho carbon
of 4-methoxyphenyl ligand), 119.7 (t, PdCtC), 124.9 (CH, para
carbon of the CtCC6H5 group), 128.3, 129.7 (CCtC), 131.0,
138.3, 150.0 (t, J (CP) ) 7 Hz), 156.1 (COMe). Anal. Calcd
for C27H42OP2Pd: C, 58.86; H, 7.68. Found: C, 58.95; H, 7.98.
Reaction of 2c with [Cu(CtCPh)(PPh3)]4 in the presence of
PPh3 gave 4c, which was characterized by 1H NMR in a
mixture with 2c and 3c. Isolation of the complex was not
feasible due to the low crystallinity. 1H NMR of 4c (C6D6): δ
0.93 (m, 18H, P(CH2CH3)3), 1.49 (m, 12H, P(CH2CH3)3), 6.97
(t, 1H, C6H4H, J ) 7 Hz), 7.38 (d, 2H, C6H2H2, J ) 7 Hz), 7.59
(d, 2H, C6H3H2, J ) 7 Hz). Other peaks were overlapped with
those of 2c and 3c. 31P{1H} NMR (25 °C, C6D6): δ 14.7 (s).
P r ep a r a tion of 2d a n d Its Rea ction w ith [Cu (CtCP h )-
(P P h 3)]4. To a THF (40 mL) solution of 1a (993 mg, 2.3 mmol)
was added PMe3 (350 mg, 4.6 mmol) in one portion at 0 °C.
Stirring the reaction mixture at room temperature resulted
in formation of a red solution, which was evaporated to
dryness. The product was recrystallized from Et2O to give 2d
as yellow crystals (160 mg, 15%). 1H NMR (400 MHz at 25
°C in C6D6): δ 0.98 (apparent triplet due to virtual coupling,
18H, CH3), 2.17 (s, 3H, CH3), 6.89 (d, 2H, C6H2H2, J ) 8 Hz),
7.05 (d, 2H, C6H2H2, J ) 8 Hz). 31P{1H} NMR (160 MHz, 25
°C, C6D6): δ -21.3 (s). Anal. Calcd for C13H25IP2Pd: C, 32.76;
H, 5.29. Found: C, 32.67; H, 5.19.
P r ep a r a tion of 5b,c. A mixture of Pt(PEt3)4 (1.32 g, 2.0
mmol) and 4-iodoanisole (1.21 g, 5.2 mmol) was dissolved in
toluene (17 mL) with heating under reflux for 1 h. The initial
yellow solution turned colorless, accompanied by deposition
of a small amount of colorless solid. Evaporating the solvent
to dryness followed by washing the product with hexane gave
5b as a colorless solid (1.0 g, 75%). 1H NMR (in C6D6): δ 0.87
(m, 18H, P(CH2CH3)3), 1.71 (m, 12H, PCH2), 3.43 (s, 3H,
OCH3), 6.77 (d, 2H, C6H2H2, J ) 8 Hz), 7.32 (d, 2H, C6H2H2,
J (HH) ) 8 Hz, J (HPt) ) 65 Hz). 31P{1H} NMR (C6D6): δ 8.9
(s, J (PPt) ) 2727 Hz)). Anal. Calcd for C19H37IOP2Pt: C,
34.29; H, 5.60. Found: C, 33.99; H, 6.09.
A similar reaction of Pt(PEt3)4 with 4-fluoroiodobenzene
gave 5c (77%). 1H NMR (400 MHz, C6D6): δ 0.82 (m, 18H,
P(CH2CH3)3), 1.67 (m, 12H, P(CH2CH3)3), 6.80 (dd, 2H, C6H2H2,
J (HH) ) 7 Hz, J (HF)) 9 Hz), 7.23 (d, 2H, C6H2H2, J (HH) )
7 Hz, J (HPt) ) 68 Hz). 31P{1H} NMR (160 MHz, C6D6): δ 8.4
(s, J (PPt) ) 2696 Hz)). Anal. Calcd for C18H34FIP2Pt: C,
33.09; H, 5.25. Found: C, 33.18; H, 5.10.
Rea ction s of 5b,c w ith [Cu (CtCP h )(P P h 3)]4. P r ep a r a -
tion of 6b,c. A toluene (2 mL) dispersion of 5b (170 mg, 0.26
mmol), [Cu(CtCPh)(PPh3)]4 (109 mg, 0.26 mmol of Cu), and
PPh3 (134 mg, 0.51 mmol) was stirred at room temperature.
The pale green solid gradually dissolved to give slightly brown
solution from which a colorless solid separated. After 1 h of
stirring the solvent was evaporated to dryness. The product
was extracted with hexane (12 mL) at room temperature and
then recrystallized from acetone to give 6b as colorless crystals
(31 mg, 20%). IR (KBr) ν(CtC): 2098 cm-1
.
1H NMR (400
MHz, C6D6): δ 0.96 (m, 18H, CH3), 1.66 (m, 12H, PCH2), 3.50
(s, 3H, OCH3), 6.96 (d, 2H, C6H2H2, J ) 7 Hz), 7.02 (t, 1H,

5364 Organometallics, Vol. 16, No. 24, 1997
Ta ble 3. Cr ysta llogr a p h ic Da ta a n d Deta ils of Refin em en t for 1a ,b, 4a , a n d 6c
Osakada et al.
1a
1b
4a
6c
chem formula
fw
C13H23IN2Pd
440.64
C13H23IN2OPd
456.64
C27H42P2Pd
534.98
C26H39FP2Pt
627.63
cryst syst
space group
a, Å
b, Å
c, Å
monoclinic
C2/c (No. 15)
13.176(8)
9.530(9)
25.922(10)
95.29(4)
3240
monoclinic
C2/c (No. 15)
13.311(10)
9.524(8)
26.42(2)
94.60(7)
3337
monoclinic
P21/a (No. 14)
13.902(10)
12.187(4)
17.988(9)
111.22(6)
2841
monoclinic
P21 (No. 4)
9.087(4)
11.907(4)
13.378(6)
107.64(3)
1379
â, deg
V, Å3
Z
8
8
4
7.66
1120
250
2
µ, cm-1
F(000)
30.02
1712
1.806
29.22
1776
1.818
52.71
624
1.512
D
calcd, g cm-3
cryst size, mm × mm × mm
0.2 × 0.2 × 0.2
3.0-50.0
0 e h e 15
-30 e k e 30
0 e l e 11
3049
2300
154
0.032
0.033
0.4 × 0.6 × 0.6
3.0-55.0
0 e h e 17
0 e k e 12
-34 e l e 34
4090
2992
163
0.055
0.052
0.2 × 0.4 × 0.4
3.0-52.8
0 e h e 16
0 e k e 14
-21 e l e 19
5274
3844
271
0.066
0.069
0.2 × 0.4 × 0.4
3.0-55.0
0 e h e 11
0 e k e 15
-16 e l e 16
3336
2564
270
0.036
0.029
2θ range, deg
hkl ranges
no. of unique rflns
no. of rflns used (I g 3σ(I))
no. of variables
R(Fo)a
Rw(Fo)a
a
2
2
R ) ∑||Fo| - |Fc||/∑|Fo|; Rw ) [∑w|Fo - Fc| /∑w|Fo| ]1/2; weighting scheme w ) [{σ(Fo)}2]-1
.
C6H4H, J ) 7 Hz), 7.17 (t, 2H, C6H3H2, J ) 7 Hz), 7.48 (d, 2H,
C6H2H2, J ) 7 Hz), 7.61 (d, 2H, C6H2H2, J ) 7 Hz). 31P{1H}
NMR (160 MHz in C6D6): δ 10.2 (s, J (PPt) ) 2641 Hz).
13C{1H} NMR (100 MHz in CD2Cl2): δ 8.1 (s, P(CH2CH3)3,
J (CPt) ) 26 Hz), 16.2 (apparent triplet, P(CH2CH3)3, J (CPt)
) 35 Hz), 55.1 (OCH3), 109.9 (tCC, J (CPt) ) 22 Hz), 113.7
(CHCPt, J (CPt) ) 50 Hz), 114.3 (PtCt, t, J (PC) ) 15 Hz,
J (CPt) ) 890 Hz), 124.8 (para carbon of the CtCC6H5 ligand),
128.2, 130.0 (tCC, J (CPt) ) 22 Hz), 131.0, 139.1, 145.0
(PtC(ipso), t, J (PC) ) 10 Hz, J (CPt) ) 673 Hz), 155.5 (OC).
Anal. Calcd for C27H42OP2Pt: C, 50.72; H, 7.57. Found: C,
50.18; H, 6.50.
3.68 (s, 3H, OCH3), 6.63 and 7.13 (d, 4H, C6H4, J ) 8 Hz),
7.18 (t, 1H, C6H4H, J ) 7 Hz), 7.34 (d, 2H, C6H3H2, J ) 7 Hz),
7.54 (t, 2H, C6H3H2, J ) 7 Hz); 31P{1H} NMR (160 MHz, -30
°C, CD2Cl2) -17.3 ppm (s). Complexes 4a (5.20 mg, 0.98 ×
10-2 mmol) and 7b (4.80 mg, 0.97 × 10 -2 mmol) were dissolved
in CD2Cl2 (ca. 0.6 mL) at -60 °C. The solution was transferred
into an NMR tube through a Teflon tube at that temperature.
1
Measurement of the H and 31P{1H} NMR spectra at -30 °C
has revealed partial formation of 3a and 8b.
Cr ysta l Str u ctu r e Deter m in a tion . Crystals of 1a and
1b suitable for crystallography were obtained by recrystalli-
zation from THF, while 4a and 6c were recrystallized from
acetone. Crystals were mounted in glass capillary tubes under
argon. The unit cell parameters were obtained by least-
squares refinement of 2θ values of 25 reflections with 25° e
2θ e 35°. Intensities were collected on a Rigaku AFC-5R
automated four-cycle diffractometer by using graphite-mono-
chromated Mo KR radiation (λ ) 0.710 69 Å) and the ω-2θ
method. Empirical absorption correction (ψ-scan method) of
the collected data was applied. Table 3 summarizes crystal
data and details of the data refinement.
A similar reaction of 5c with [Cu(CtCPh)(PPh3)]4 gave 6c
(90%). IR (KBr) ν(CtC): 2094 cm-1
.
1H NMR (400 MHz,
C6D6): δ 0.91 (m, 18H, P(CH2CH3)3), 1.60 (m, 12H, P(CH2CH3)3),
6.99 (d, 2H, C6H2H2, J ) 8 Hz), 7.03 (t, 1H, C6H4H, J ) 7 Hz),
7.17 (t, 2H, C6H3H2, J ) 7 Hz), 7.41 (d, 2H, C6H2H2, J (HH) )
7 Hz, J (HPt) ) 39 Hz), 7.61 (d, 2H, C6H2H2, J ) 8 Hz). 31P{1H}
NMR (160 MHz, C6D6): δ 9.8 (s, J (PPt) ) 2621 Hz). Anal.
Calcd for C26H39FP2Pt: C, 49.78; H, 6.22. Found: C, 49.87;
H, 6.43.
Kin etic Mea su r em en ts. A typical experimental procedure
is as follows. Complexes 4a (1.85 mg, 3.46 × 10-5 mmol) and
5b (22.6 mg, 3.40 × 10-4 mmol) as well as diphenylmethane
(internal standard) were dissolved in C6D6 (0.586 mL). The
resulting solution was transferred through a silicon rubber
tube into an NMR sample tube fitted with a glass stopcock.
After the solution was degassed, the sample tube was sealed
with a flame. The peak areas of the 1H NMR peaks due to
Me hydrogens of C6H4Me-p and of C6H4OMe-p groups of the
complexes compared with the peak of the internal standard
were monitored in an NMR apparatus whose probe was
maintained at 50 °C. The second-order rate constants were
obtained as follows: 1.33 × 10-3 L mol-1 s-1 (303 K), 4.31 ×
10-3 L mol-1 s-1 (313 K), 6.08 × 10-3 L mol-1 s-1 (318 K), and
1.13 × 10-2 L mol-1 s-1 (323 K).
Calculations were carried out by using the program package
teXsan on a VAX-II computer. Atomic scattering factors were
taken from the literature.34 A full-matrix least-squares refine-
ment was used for non-hydrogen atoms with anisotropic
thermal parameters. Hydrogen atoms were located by assum-
ing ideal positions and were included in the structure calcula-
tion without further refinement of the parameters.
Ack n ow led gm en t. This work was financially sup-
ported by a Grant-in-Aid for Scientific Research from
the Ministry of Education, Science, Sports, and Culture
of J apan. We are grateful to Mr. Take-aki Koizumi of
our laboratory for X-ray crystallography.
Su p p or tin g In for m a tion Ava ila ble: Tables giving crys-
tallographic data for 1a , 2b, 4a , and 6c (20 pages). Ordering
information is given on any current masthead page.
Rea ction of 4a a n d 7b. Complexes 7b and 8b were
prepared similarly to the PEt3-coordinated complexes. 7b: 1H
NMR (400 MHz, -30 °C, CD2Cl2) δ 1.19 (apparent triplet due
to virtual coupling, 18H, CH3), 3.683 (s, 3H, OCH3), 6.67 and
7.05 (d, 4H, C6H4, J ) 8 Hz); 31P{1H} NMR (160 MHz, 25 °C,
C6D6) -21.0 ppm (s). 8b: 1H NMR (400 MHz, -30 °C, CD2Cl2)
δ 1.19 (apparent triplet due to virtual coupling, 18H, CH3),
OM970266N
(34) International Tables for X-ray Crystallography; Kynoch: Bir-
mingham, U.K., 1974; Vol. IV.