Synthesis and fluxional behavior, including a comparative analysis of the Pd-N bond rupture, of new chiral complexes of palladium(0) and -(II) with a rigid (aminoferrocenyl)phosphine ligand. crystal structure of the two rotamers of a palladium(0) maleic anhydride complex

Article abstract of DOI:10.1021/om980312z

The (aminoferrocenyl)phosphine ligand 1-diphenylphosphino-2,1′-(1-dimethylaminopropanediyl(ferrocene, 1, was used to synthesize new palladium(0) and -(II) complexes. The reaction of Pd₂(dba)₃?CHCl₃ with 1 in the presence of the electron-withdrawing olefins dimethylfumarate (DMFU) and maleic anhydride (MA) gave the new complexes Pd(1)(DMFU) (2) and Pd(1)(MA) (3). The allyl complex [Pd(η³-Me-C₃H₄)(1)]Tf (4) was obtained from the reaction of 1 with [Pd(η³-2-Me-C₃H₄)(Cl)]₂ in the presence of AgTf. In solution all these compounds exist as mixtures of two diastereomers, with either the alkene or the allyl group differently oriented with respect to the aminophosphine ligand. The orientation of these ligands in the major isomers has been determined by means of NOEs. Alkene rotation takes place in complexes 2 and 3 with free energies of activation ΔG₃₄₀? = 73.1 kJ mol^-1 (2) and ΔG₃₆₈? = 79.9 kJ mol^-1 (3), respectively. These barriers are compared with those of some analogous ferrocenyl aminophosphine ligands, PPFA (2-(1-dimethylaminoethyl)-1-diphenylphosphinoferrocene) and PTFA (1-diphenylphosphino-2,3-endo-(α-dimethylamino)tetramethyleneferrocene) complexes. For 3, the alkene rotation leads to isomer interconversion, while the observed isomerization of 2 must proceed via an olefin face exchange. Some experiments in relation to the nature of this process are discussed. Starting from PdRR′L′ precursors and 1 or PPFA, other Pd(II) derivatives of formulas PdRR′(1), R = Cl, R′ = Me, L′ = cod, 5; R = R′ = Me, L′ = tmeda, 6; R = R′ = C₆F₅, L′ = cod, 7, or PdClMe(PPFA), 8, were prepared. For 5 and 8, only the isomers with the methyl group trans to nitrogen were obtained. The Pd-N bond rupture in the new complexes of 1 and in similar derivatives of PPFA and PTFA has been analyzed by variable-temperature ¹H NMR studies, and in some cases a line shape analysis has been carried out. The influence of the ferrocenyl aminophosphine and ancillary ligands as well as of the oxidation state of the palladium center on this process is discussed. The molecular structures of both rotamers of 3, present in the same crystal, were determined by X-ray structure analysis.

Full text of DOI:10.1021/om980312z

4634
Organometallics 1998, 17, 4634-4644
Syn th esis a n d F lu xion a l Beh a vior , In clu d in g a
Com p a r a tive An a lysis of th e P d -N Bon d Ru p tu r e, of
New Ch ir a l Com p lexes of P a lla d iu m (0) a n d -(II) w ith a
Rigid (Am in ofer r ocen yl)p h osp h in e Liga n d . Cr ysta l
Str u ctu r e of th e Tw o Rota m er s of a P a lla d iu m (0) Ma leic
An h yd r id e Com p lex
Felipe Go´mez-de la Torre, Fe´lix A. J alo´n, Ana Lo´pez-Agenjo,
Blanca R. Manzano,*,† and Ana Rodr´ıguez
Departamento de Quı´mica Inorga´nica, Orga´nica y Bioquı´mica, Facultad de Quı´micas,
Campus Universitario, 13071 Ciudad Real, Spain
Thomas Sturm and Walter Weissensteiner*,‡
Institut fu¨r Organische Chemie, Universita¨t Wien, Wa¨hringer Straâe 38,
A-1090 Wien, Austria
Mart´ın Mart´ınez-Ripoll
Instituto Rocasolano del CSIC, Serrano,119, 28006 Madrid, Spain
Received April 23, 1998
The (aminoferrocenyl)phosphine ligand 1-diphenylphosphino-2,1′-(1-dimethylaminopro-
panediyl)ferrocene, 1, was used to synthesize new palladium(0) and -(II) complexes. The
reaction of Pd2(dba)3‚CHCl3 with 1 in the presence of the electron-withdrawing olefins
dimethylfumarate (DMFU) and maleic anhydride (MA) gave the new complexes Pd(1)(DMFU)
(2) and Pd(1)(MA) (3). The allyl complex [Pd(η3-2-Me-C3H4)(1)]Tf (4) was obtained from the
reaction of 1 with [Pd(η3-2-Me-C3H4)(Cl)]2 in the presence of AgTf. In solution all these
compounds exist as mixtures of two diastereomers, with either the alkene or the allyl group
differently oriented with respect to the aminophosphine ligand. The orientation of these
ligands in the major isomers has been determined by means of NOEs. Alkene rotation takes
q
place in complexes 2 and 3 with free energies of activation ∆G340 ) 73.1 kJ mol-1 (2) and
∆G368 ) 79.9 kJ mol-1 (3), respectively. These barriers are compared with those of some
q
analogous ferrocenyl aminophosphine ligands, PPFA (2-(1-dimethylaminoethyl)-1-diphe-
nylphosphinoferrocene) and PTFA (1-diphenylphosphino-2,3-endo-(R-dimethylamino)tet-
ramethyleneferrocene) complexes. For 3, the alkene rotation leads to isomer interconversion,
while the observed isomerization of 2 must proceed via an olefin face exchange. Some
experiments in relation to the nature of this process are discussed. Starting from PdRR′L′
precursors and 1 or PPFA, other Pd(II) derivatives of formulas PdRR′(1), R ) Cl, R′ ) Me,
L′ ) cod, 5; R ) R′ ) Me, L′ ) tmeda, 6; R ) R′ ) C6F5, L′ ) cod, 7, or PdClMe(PPFA), 8,
were prepared. For 5 and 8, only the isomers with the methyl group trans to nitrogen were
obtained. The Pd-N bond rupture in the new complexes of 1 and in similar derivatives of
1
PPFA and PTFA has been analyzed by variable-temperature H NMR studies, and in some
cases a line shape analysis has been carried out. The influence of the ferrocenyl
aminophosphine and ancillary ligands as well as of the oxidation state of the palladium
center on this process is discussed. The molecular structures of both rotamers of 3, present
in the same crystal, were determined by X-ray structure analysis.
In tr od u ction
fully as P-N coordinating ligands of a variety of
homogeneous catalysts. Catalytic reactions include
inter alia allylic alkylations, allylic aminations, hy-
droborations, and Grignard cross-coupling reactions.4 A
typical example of a Grignard cross-coupling is the
reaction of vinyl bromide and phenylethylmagnesium
chloride giving 3-phenylbutene as the final product.
Originally, with use of PdCl2(PPFA) as the catalyst
precursor, an enantioselectivity of 68% was obtained.2d
Enantiopure ferrocenyl aminophosphines1 such as
2-(1-dim et h yla m inoet hyl)-1-diphenylphosphinofer-
rocene,2 PPFA (Chart 1), as well as a number of
ferrocenyl pyrazol derivatives3 have been used success-
† Fax: 34 926 295318. E-mail: bmanzano@qino-cr.uclm.es.
‡ E-mail: Walter.Weissensteiner@univie.ac.at.
(1) Togni, A., Hayashi, T., Eds. Ferrocenes, Homogeneous Catalysis,
Organic Synthesis, Material Science; VCH: Weinheim, Germany, 1995.
S0276-7333(98)00312-4 CCC: $15.00 © 1998 American Chemical Society
Publication on Web 09/19/1998

Rotamers of a Pd(0) Maleic Anhydride Complex
Organometallics, Vol. 17, No. 21, 1998 4635
Ch a r t 1. Con figu r a tion of (S,R)-P P F A,
(R,R)-P TF A, a n d (R,R)-1
bond cleavage can be observed for PPFA-Pd(0) and
PPFA-Pd(II) complexes but not for the respective PTFA
derivatives.9d Other cases of Pd-N bond rupture have
been proposed recently in the literature.9 Since at least
for PPFA complexes the activation barriers of these
Pd-N bond rupture processes are rather low and can
be observed on the NMR time scale even for the [Pd-
(η3-2-Me-C3H4)(PPFA)]CF3SO3 complex, it is likely that
under catalysis conditions such a Pd-N bond cleavage
is a fast process not only in Grignard cross-couplings
but also in allylic alkylations, allylic amination, or
related reactions. Thus, to identify more general trends
or correlations, it was of interest to investigate in addi-
tion to PPFA and PTFA a broader range of additional
ferrocenyl P-N coordinating palladium complexes.
In this paper we describe the synthesis and the
fluxional behavior of Pd(0) complexes of ligand 1 with
maleic anhydride (MA) and dimethyl fumarate (DMFU)
as well as of a number of Pd(II) complexes PdRR′(1) (RR′
) 2-methylallyl; R ) R′ ) C6F5; R ) R′ ) Me; R′ ) Me,
R ) Cl). The set of data obtained for these complexes
is compared to those of the related PPFA and PTFA
complexes. PdClMe(PPFA) and PdCl2(PPFA)2d,e have
also been synthesized in order to make complementary
NMR studies. Trends in the activation barriers for the
different dynamic processes (P-N bond cleavage, olefin
rotations, allyl interconversions) are discussed. In
addition, the molecular structures of both rotamers of
the Pd(1)(MA) complex are reported.
We recently reported the synthesis of two new confor-
mationally less flexible ferrocenyl aminophosphines,5
1-diphenylphosphino-2,3-endo-(R-dimethylamino)tet-
ramethyleneferrocene, PTFA, and 1-diphenylphosphino-
2,1′-(1-dimethylaminopropanediyl)ferrocene, 1 (Chart 1),
which in the above Grignard cross-coupling reaction
gave the product with 79% and 63% ee, respectively.
This type of palladium-catalyzed Grignard cross-cou-
pling reaction is thought to proceed via Pd(0) and Pd-
(II) intermediates, and the enantioselective step is
assumed to be the transmetalation step in which the
phenylethyl group is transferred from the Grignard
reagent onto the palladium catalyst.6 According to a
proposal by Kumada and Hayashi,2d,7 this step involves
a Pd-N bond cleavage of the (PPFA)Pd(vinyl)Br inter-
mediate followed by a coordination of the Grignard
reagent to the uncoordinated nitrogen prior to the
transfer of the Grignard alkyl group to palladium.
Other authors have suggested that the partial dissocia-
tion of a chiral ferrocenyl P-N3a,c or P-S8 ligand may
be the origin of lower enantioselectivities in some cata-
lytic reactions. Very recently we could show by means
of NMR spectroscopy that, indeed, a palladium nitrogen
Resu lts a n d Discu ssion
Syn th esis. Palladium(0) complexes were obtained
according to eq 1. Reaction of Pd2(dba)3‚CHCl3 (dba )
dibenzylideneacetone) in toluene with 1 in the presence
of the electron-poor olefin (L) dimethyl fumarate (DMFU)
or maleic anhydride (MA) gave the new complexes Pd-
(1)(L).
(2) (a) Marquarding, D.; Klusacek, H.; Gokel, G.; Hoffmann, P.; Ugi,
I. J . Am. Chem. Soc. 1970, 92, 5389. (b) Hayashi, T.; Yamamoto, K.;
Kumada, M. Tetrahedron Lett. 1974, 4405. (c) Hayashi, T.; Mise, T.;
Fukushima, M.; Kagotani, M.; Nagashima, N.; Hamada, Y.; Matsu-
moto, A.; Kawakami, S.; Konishi, M.; Yamamoto, K.; Kumada, M. Bull.
Chem. Soc. J pn. 1980, 53, 1138. (d) Hayashi, T.; Konishi, M.;
Fukushima, M.; Mise, T.; Kagotani, M.; Tajika, M.; Kumada, M. J .
Am. Chem. Soc. 1982, 104, 180. (e) Hayashi, T.; Konishi; M.; Ito, H.;
Kumada, M. J . Am. Chem. Soc. 1982, 104, 4962. (f) van der Steen, F.
H.; Kanters, J . A. Acta Crystallogr. 1986, C42, 547.
(3) (a) Schnyder, A.; Hintermann, L.; Togni, A. Angew. Chem., Int.
Ed. Engl. 1995, 34, 931. (b) Togni, A. Chimia 1996, 50, 86. (c) Schnyder,
A.; Togni, A.; Wiesli, U. Organometallics 1997, 16, 255. (d) Burckhardt,
U.; Baumann, M.; Togni, A. Tetrahedron: Asymmetry 1997, 8, 155.
(e) Burckhart, U.; Gramlich, V.; Hofmann, P.; Nesper, R.; Pregosin, P.
S.; Salzmann, R.; Togni, A. Organometallics 1996, 15, 3496. (f) Togni,
A.; Burckhart, U.; Gramlich, V.; Pregosin, P. S.; Salzmann, R. J . Am.
Chem. Soc. 1996, 118, 1031. (g) Blo¨chl, P. E.; Togni, A. Organometallics
1996, 15, 4125.
Pd2(dba)3‚CHCl3 + 21 + 2L f 2Pd(1)(L) + 3dba (1)
2, 3
L ) DMFU, 2; MA, 3
The allyl complex [Pd(η3-2-Me-C3H4)(1)]Tf (4) was
synthesized, according to a method described in the
literature,10 by reacting [Pd(η3-2-Me-C3H4)Cl]2 with 1
in the presence of silver triflate (eq 2)
[Pd(η3-2-Me-C3H4)Cl]2 + 21 + 2AgTf f
3
+ 2AgCl (2)
2[Pd(η -2-Me-C3H4)(1)]Tf
4
(4) (a) Hayashi, T. Pure Appl. Chem. 1988, 60, 7. (b) Sawamura,
M.; Ito, Y. Chem. Rev. 1992, 92, 857. (c) Brunner, H.; Zettlmeier, W.
Handbook of Enantioselective Catalysis with Transition Metal Com-
pounds; VCH: Weinheim, Germany, 1993. (d) Ojima, I., Ed.; Catalytic
Asymmetric Synthesis; VCH: Weinheim, Germany, 1993. (e) Hayashi,
T. Asymmetric Catalysis with Chiral Ferrocenylphosphine Ligands.
in ref 1, p 105. (f) Togni, A. Angew. Chem., Int. Ed. Engl. 1996, 35,
1475.
(5) (a) J edlicka, B.; Widhalm, M.; Weissensteiner, W. J . Chem. Soc.,
Chem. Commun. 1993, 1329. (b) Mernyi, A.; Kratky, C.; Weissen-
steiner, W.; Widhalm, M. J . Organomet. Chem. 1993, 370, 397.
(6) (a) Baker, K. V.; Brown, J . M.; Cooley, N. A.; Hughes, G. D.;
Taylor, R. J . J . Organomet. Chem. 1993, 370, 397. (b) Brown, J . M.;
Cooley, N. A. Chem. Rev. 1988, 88, 1031. (c) Indolese, A.; Consiglio, G.
J . Organomet. Chem. 1993, 463, 209.
Displacement of weakly coordinated ligands from the
corresponding starting materials allows the isolation
of new palladium(II) complexes of formula PdRR′(1)
(see eq 3).
(9) (a) Albinati, A.; Kunz, R. W.; Ammann, C. J .; Pregosin, P. S.
Organometallics 1991, 10, 1800. (b) Gogoll, A.; O¨ rnebro, J .; Grennberg,
H.; Ba¨ckvall, J .-E. J . Am. Chem. Soc. 1994, 116, 3631. (c) Elguero, J .;
Fruchier, A.; de la Hoz, A.; J alo´n, F. A.; Manzano, B. R.; Otero, A.;
Go´mez-de la Torre, F. Chem. Ber. 1996, 129, 589. (d) Ferna´ndez-Gala´n,
R.; J alo´n, F. A.; Manzano, B. R.; Rodr´ıguez-de la Fuente, J .; Vrahami,
M.; J edlicka, B.; Weissensteiner, W.; J ogl, G. Organometallics 1997,
16, 3758. (e) Gogoll, A.; Grennberg, H.; Axe´n, A. Organometallics 1997,
16, 1167.
(7) Hayashi, T.; Kumada, M. Acc. Chem. Res. 1982, 15, 395.
(8) Albinati, A.; Eckert, J .; Pregosin, P.; Ru¨egger, H.; Salzmann, R.;
Sto¨ssel, C. Organometallics 1997, 16, 579.
(10) Breutel, C.; Pregosin, P. S.; Salzmann, R.; Togni, A. J . Am.
Chem. Soc. 1994, 116, 4067.

4636 Organometallics, Vol. 17, No. 21, 1998
Go´mez-de la Torre et al.
Ch a r t 2. Obser ved Dia ster eom er s of 2-4a
PdRR′(L′) + 1 f PdRR′(1) + L′
5-7
(3)
R ) Cl, R′ ) Me, L′ ) 1,5-cyclooctadiene (COD), 5; R )
R′ ) Me, L′ ) tetramethylethylenediamine (TMEDA),
6; R ) R′ ) C6F5 , L′ ) COD, 7.
Using the same method, the derivatives PdClMe-
(PPFA), 8 (from PdClMe(COD)), and PdCl2(PPFA),2d,e
9 (from PdCl2(PhCN)2), have also been prepared.
All complexes are soluble in the polar solvents acetone
or chloroform and, except 4, are also soluble in toluene
or benzene. They are highly stable in the solid state if
stored under nitrogen. In solution, the Pd(0) complexes
as well as 6 slowly decompose. In halogenated solvents,
6 evolves quickly and quantitatively to 5, which in a
slow transformation reacts further, giving PdCl2(1) as
the final product. All other complexes are stable in
solution.
NMR Ch a r a ct er iza t ion of t h e New P a lla d iu m
Com p lexes. Complexes 2-4 exist in solution always
as a mixture of two diastereomers (major, M, and minor,
m) (see Chart 2) whose ratio, which usually depends on
the solvent nature, was deduced from the 1H NMR
spectra at room temperature and is indicated in Table
1. Those isomers differ in how either the alkene or the
allyl group is oriented with respect to the amino
phosphine ligand. For related ferrocenyl phosphine
palladium derivatives, such a mixture of diastereomers
has been observed previously by us9d,11 and others.3e,f,8,12
Although in some N,P-ferrocenyl palladium complexes3e
conformational isomers involving the chelate ring have
been observed by 1H NMR at low temperature, this fact
is not frequent, and for complexes of 1, the possibility
of such conformational isomers can be ruled out. This
is due to the fact that, although two conformations are
possible5b for noncoordinated 1 (see Chart 3), only the
conformation a, which according to previous calculations
is 22 kJ mol-1 more stable than conformation b, is
suitable for a chelate coordination. In this orientation
the heteroannular chain has the central carbon pointing
toward the phosphorus atom, and as a consequence, the
NMe2 group is located above Cp1.
a
R ) CO2Me. Conformation of different isomers has been
elucidated by NOE studies (see text and Chart 4). Re and Si
refer to the olefin face coordinated to the Pd center, and endo
and exo refer to the orientation of the endocyclic oxygen of the
MA or the allyl group pointing toward or away from the
ferrocene core.
The proton resonances of the two diastereomers
mixtures of derivatives 2-4 were assigned mainly with
the use of COSY spectra. This allowed us not only to
classify the seven Cp signals of each isomer but also to
differentiate the resonances corresponding to the Cp1
and Cp2 rings. This has not been possible for 4, which
shows a quite similar ratio of isomers and too many
overlapping signals. Except for 4, the protons of the
trimethylene bridges have also been completely as-
signed, mainly on the basis of COSY experiments and
the analysis of the spin systems. In all cases, where
the coupling constants of the chain proton attached to
carbon 1c (for the numbering scheme, see Chart 3) could
be analyzed, the chain conformation with the dimethyl-
amino group pointing straight above Cp1 is found. (By
analogy, these resonances have also been assigned for
complexes 5-7.) As in the more stable conformation of
the free ligand,5b in complexes 2-4 the central chain
carbon, C(2c), is always positioned in close proximity
to the phosphorus, which is reflected in the 13C spectra,
in which C(2c) is the only chain carbon showing a 31P-
13C coupling constant.
In Tables 1-3, H and 13C NMR chemical shifts as
1
well as coupling constants are given for selected signals
of the aminophosphine and ancillary ligands of com-
plexes 2-8. For complexes 5, 6, and 8, the methyl
resonances are indicated in the Experimental Section.
The rest of the data are given as Supporting Informa-
tion. On complexation of the aminophosphine ligands,
some general trends are observed for the resonances of
all these derivatives: (i) the two equivalent amino
methyl groups of 1 or PPFA are deshielded and trans-
1
formed into two diastereotopic singlets in both H and
13C NMR spectra, (ii) as compared to 1 or PPFA, the
31P NMR resonances are shifted downfield by 27-49
ppm, and (iii) in cases of complexes with 1, the P-
coordination and the special rigidity of this ferrocenyl
ligand lead to a particular orientation of one of the
phenyl groups that shields the H(5′) proton (δ ) 2-3
ppm) of Cp2 (see Chart 3, conformation a).
The alkene protons and carbons (see Table 2) of the
MA and DMFU groups give rise to two separated signals
shifted to lower frequency with respect to the free
olefins.13 These shifts, higher for the MA derivative,
are in the range usually expected for other zerovalent
ML2(alkene) complexes of palladium and platinum.14 In
(11) J edlicka, B.; Ru¨lke, R. E.; Weissensteiner, W.; Ferna´ndez-Gala´n,
R.; J alo´n, F. A.; Manzano, B. R.; Rodr´ıguez-de la Fuente, J .; Veldman,
N.; Koijman, H.; Spek, A. L. J . Organomet. Chem. 1996, 508, 69.

Rotamers of a Pd(0) Maleic Anhydride Complex
Ta ble 1. 1H a n d 13C NMR Da ta for Liga n d 1 in Com p lexes 2-7 a n d P P F A in 8a
13C NMR
chain
Organometallics, Vol. 17, No. 21, 1998 4637
1H NMR
complex
amt,b %
H5′(Cp2)
N(CH3)2
ortho-Phup
ortho-Phdown
C1
C2
C3
N(CH3)2
2M
60
2.86(m)
D-2.81(s)
U-2.19(s)
D-2.90(s)
U-2.25(s)
D-2.73(s)
U-1.99(s)
D-2.78(s)
U-2.07)s)
D-3.29(s)
U-2.67(s)
D-3.28(s)
U-2.74(s)
D-2.98(s)
U-2.60(s)
D-2.47(s)
U-2.29(s)
D-2.23(s)
U-1.84(s)
D-3.23(s)
U-2.52(s)
7.40(pt)
J ) 7.5
7.27(pt)
8.20(ddd)
J ) 11.0, 8.1, 1.5
7.90(ddd),
J ) 10.5, 8.5, 1.5
7.90(ddd)
J ) 11.5, 6.9, 1.4
7.80(m)
69.11
42.57(d)
J ) 4.5
42.87(d)
J ) 5.0
42.18(d)
J ) 5.0
42.12(d)
J ) 5.6
42.67(d)
J ) 5.1
42.49
J ) 4.0
41.89(d)
J ) 3.0
42.16(d)
J ) 5.0
42.36(d)
24.90
c
2m
3M
3m
4a
4b
5
40
77
23
54
46
2.53(m)
3.0(m)
68.86
68.66
68.77
68.82
69.04
68.24
67.99
68.74
24.98
24.47
24.55
24.30
24.13
24.70
24.94
24.57
c
J ) 7.2
7.26(dd)
J ) 7.5, 1.5
7.29(ptd)
J ) 9.1, 2.0
7.24(m)
51.02
54.44
50.62
54.21
52.52
57.18
55.51
51.42
52.35
49.61
51.85
49.84
54.78
50.47
42.68
48.59
2.97(m)
c
8.18(m)
c
7.20(m)
7.19(m)
7.26(m)
6.84(m)
7.97(dd)
J ) 12.2, 7.6
8.11(m)
2.05(m)
2.05(m)
2.52(m)
CHMe CHMe
6
8.13(m)
7
8.1(ddd)
J ) 11.4, 8.0, 1.7
8.04(m)
8
7.35(pt)
J ) 11.0
CHMe CHMe
3.38(c) 1.04(d)
73.47 15.87
J HH ) 6.6
a
1H NMR recorded at room temperature in toluene-d8, (2, 8), benzene-d6 (3, 6, 7), chloroform-d (5), or 1,1,2,2-tetrachloroethane-d2 (4).
13C NMR recorded at room temperature in acetone-d6 (2), chloroform-d (3-5), benzene-d6 (6, 7), or toluene-d8 (8). The 1H and 13C NMR
data of the Cp groups (except the H5′ of complexes with ligand 1), the 13C NMR signals of the Ph rings and a complete assignment of the
1H NMR resonances of the trimethylene bridge protons are given as Supporting Information. pt ) pseudotriplet; M ) major isomer; m
) minor isomer; D ) down; U ) up. Up and down refer to the phenyl or Me groups oriented away from or toward the ferrocenyl unit,
b
respectively. For the adopted numbering scheme, see Chart 3. Percentage of the isomers. c Signals not clearly distinguished.
Ch a r t 3. P r efer r ed (a ) a n d Less Sta ble (b)
Con for m a tion of liga n d 1 a n d Nu m ber in g Sch em e
of 1 (a )
appear at higher frequencies according to the stronger
trans influence of this atom. A NOE has been found
from the allyl methyl to the syn protons, confirming this
assignment. As expected,11 in the case of complex 5,
according to the small coupling constant J HP and
J CP16 observed (see the Experimental Section), only the
isomer with the methyl group trans to nitrogen is
present.
The structural analysis of the two nonequivalent
pentafluorophenyl groups of 7 has been carried out by
19F NMR (see the Experimental Section). The more
relevant conclusion is that 10 unique fluorine signals
are observed, implying a restricted rotation of the
pentafluorophenyl groups around the Pd-Cipso bond,
which must be a consequence of the steric requirements
of ligand 1. This fact has been previously observed in
other cis palladium and platinum complexes,17 but
usually freely rotating groups are seen.18
Ster eoch em ica l Assign m en ts of Com p lexes 2-4.
Considering the importance of the particular arrange-
ment of the ligands around the metal center, especially
in enantioselective homogeneous catalysis, we have
undertaken several NOE studies in order to establish
the orientation of the alkene and allyl ligands of the
isomers of complexes 2-4. For the equilibrium mix-
tures of 3 (chloroform-d solution, 3M/3m ) 62:38) and
4 (acetone-d6, 4a /4b ) 27:73) spectra were recorded at
the case of the 1H NMR signals additional INDOR
experiments were carried out. Complex 4 shows four
different allyl protons and two terminal allyl carbons
for each isomer, reflecting the asymmetric environment
in its coordination sphere (see Table 3). The assignment
is based on COSY experiments and on characteristic
chemical shifts15 and coupling constants. As expected,
the proton and carbon resonances trans to phosphorus
(12) Pregosin, P. S.; Salzmann, R.; Togni, A. Organometallics 1995,
14, 842.
(13) 1H (13C) NMR data for the free alkenes in CDCl3: MA, 7.04
(137.1) ppm; DMFU, 6.86 (133.9) ppm.
(14) See, for example: (a) Cenini, S.; Ugo, R.; La Monica, G. J . Chem.
Soc. A 1971, 409. (b) Otsuka, S.; Yoshida, T.; Tatsuno, Y. J . Am. Chem.
Soc. 1971, 93, 6462. (c) Ito, T.; Hasegawa, S.; Takahashi, Y.; Ishii, Y.
J . Organomet. Chem. 1974, 73, 401. (d) Ittel, S. D. Inorg. Chem. 1977,
16, 2589. (e) Itoh, K.; Ueda, F.; Hirai, K.; Ishii, Y. Chem. Lett. 1977,
877. (f) Chicote, M. T.; Green, M.; Spencer, J . L.; Stone, F. G. A.;
Vicente, J . J . Chem. Soc., Dalton Trans. 1979, 536. (g) Cavell, K. J .;
Stufkens, D. J .; Vrieze, K. Inorg. Chim. Acta 1980, 47, 67. (h) Krause,
J .; Bonrath, W.; Po¨rschke, K. R. Organometallics 1992, 11, 1158. (i)
van Asselt, R.; Elsevier, C. J .; Smeets, W. J . J .; Spek, A. L. Inorg. Chem.
1994, 33, 1521. (j) Tschoerner, M.; Trabesinger, G.; Albinati, A.;
Pregosin, P. S. Organometallics 1997, 16, 3447.
(15) Wilkinson, G., Stone, F. G. A., Abel, E. W., Eds. Comprehensive
Organometallic Chemistry; Pergamon Press: Oxford, U.K., 1982; Vol,
6, p 409.
(16) Baker, K. V.; Brown, J . M.; Cooley, N. A.; Hughes, G. D.; Taylor,
R. J . J . Organomet. Chem. 1989, 370, 397.
(17) See, for example: (a) Casas, J . M.; Fornie´s, J .; Mart´ın, A.;
Menjo´n, B.; Toma´s, M. J . Chem. Soc., Dalton Trans. 1995, 2949. (b)
Fornie´s, J .; Mart´ınez, F.; Navarro, R.; Urriolabeitia, E.; Welch, A. J .
J . Chem. Soc., Dalton Trans. 1995, 2805. (c) Ara, I.; Delgado, E.;
Fornie´s, J .; Herna´ndez, E.; Lalinde, E.; Mansilla, N.; Moreno, M. T. J .
Chem. Soc., Dalton Trans. 1996, 3201.

4638 Organometallics, Vol. 17, No. 21, 1998
Go´mez-de la Torre et al.
Ta ble 2. 1H a n d 13C NMR Da ta for th e Alk en e Liga n d s in Com p lexes P d (1)(a lk en e) (2, 3)a
1H NMR
olef H
13C NMR
CO
olef C
CO2Me
trans P
complex
cis P
trans P
CO2Me
cis P
trans P
cis P
trans P
cis P
2M
4.89(dd)
4.11(pt)
3.57
2.86
b
b
48.22(d)
J ) 28.7
172.97(d)
J ∼ 2.3
173.122(d)
J ) 5.5
b
50.24(d)
J ) 15.6
J H-P ) 2.6
J H-H ) 9.7
4.16(ABX)
J H-P ) 2.9
J H-H ) 9.8
3.91(pt)
J H-P ) 3.7
J H-H ) 3.9
4.31(pt)
J H-P ) 9.6
J H-H ) 9.7
4.16(ABX)
J H-P ) 10.5
J H-H ) 9.8
3.45(dd)
J H-P ) 10.0
J H-H ) 3.9
3.66
2m
3M
3m
3.41
3.34
49.56(d)
J ) 29.2
174.51(d)
J ∼ 2.3
172.72(d)
J ) 5.6
b
50.33(d)
J ) 20.7
47.64(d)
J ) 2.21
48.35(d)
J ) 29.7
172.82(s)
170.90(s)
170.93(d)
J ) 5.0
47.43(s)
48.35(d)
171.35(d)
J H-P ) 3.4
J H-H ) 3.4
J ) 29.7
J ) 5.1
a
1
Spectra recorded at room temperature. H NMR in toluene-d8 (2) or benzene-d6 (3). 13C NMR in acetone-d6 (2) or chloroform-d (3). M
b
) major isomer; m ) minor isomer. Signals not clearly distinguished.
Ta ble 3. 1H a n d 13C NMR Da ta for th e Allyl Gr ou p in [P d (2-Me-C3H4)(1)]Tf (4)a
13C
1H NMR
Ha cis P
CH2
complex
Me
Hs cis P
2.89(bs)
Hs trans P
4.35(m)
Ha trans P
cis P
trans P
Me
-Cd
4a
2.25(s)
2.75(bs)
1.92(bs)
3.65(d)
J ) 9.3
3.59(d)
J ) 11.0
57.49(s)
80.32(d)
J ) 30.2
82.04(d)
J ) 28.7
22.91(s)
b
4b
1.38(s)
3.50(bs)
4.45(m)
59.02(s)
23.57(s)
b
a
1H NMR (1,1,2,2,-tetrachloroethane-d2) and 13C NMR (chloroform-d) spectra recorded at room temperature. M ) major isomer; m )
b
minor isomer. s ) syn; a ) anti. Signals not clearly distinguished; they appear in the phenylic region.
Ch a r t 4. Ma in NOEs Obser ved for Com p lexes 2M,
233 K in order to slow the isomer interconversion (see
Fluxional Behavior section). In the case of complex 2
3M, 4a , a n d 4b
(benzene-d6), a sample with only the major isomer,
obtained from crystallization of the isomer mixture, was
measured.
In all these complexes, the cyclopentadienyl protons
H(5′) (see Chart 3) are in close proximity to the phenyl
ring pointing toward Cp2 allowing the measurement of
an NOE from H(5′) to the ortho phenyl protons (ortho-
Phdown). A clear but less intense NOE is observed
between one of the amino methyl groups and one Cp1
proton. Taking into account the rigidity of 1 when
coordinated, these resonances can be assigned to the
amino methyl pointing toward the distal Cp1 side (Meup
)
and the Cp1 proton H(3), respectively. An NOE has also
been observed from this Meup to the ortho protons of
the adjacent phenyl group (Phup). These data show that
for each complex 2-4 the signals for both the Meup and
the ortho-Phup appear always at higher field than the
corresponding groups situated down (Table 1). The
corresponding signals of 5-7 have been assigned by
analogy.
In Chart 4, the observed NOEs for complexes 2M, 3M,
and both isomers of 4, which have allowed their stereo-
chemical assignment, are indicated by arrows. Several
NOEs have been found between the Meup and the ortho-
Phup hydrogens and different olefinic protons or the
allylic methyl group situated above the Pd coordination
plane (2M, 3M, and 4b). In 2M and 4a , NOEs between
the ortho-Phdown protons and the respective groups
situated below this plane are observed.
F lu xion a l Beh a vior of Com p lexes 2-8. We have
1
carried out variable-temperature H NMR studies for
complexes 2-8 (2, 3, 5-8 in toluene-d8 and 4 in 1,1,2,2-
tetrachloroethane-d2) over the full temperature range
of the solvents. The different dynamic processes ex-
pected to be present in this type of complexes can be
divided into two groups: isomer interconversion and
Pd-N bond rupture processes. According to our previ-
ous results for ferrocenyl aminophosphine palladium
complexes,9d this bond rupture is a feasible process,
while the cleavage of the stronger Pd-P bond is rather
unlikely.
(18) See for example: (a) Uso´n, R.; Fornie´s, J .; Espinet, P.; Fortun˜o,
C.; Toma´s, M. J . Chem. Soc., Dalton Trans. 1988, 3005. (b) Uso´n, R.;
Fornie´s, J .; Toma´s, M.; Menjo´n, B.; Fortun˜o, C.; Welch, A. J .; Smith,
D. E.. J . Chem. Soc., Dalton Trans. 1993, 275. (c) Casas, J . M.; Falvello,
L. R.; Fornie´s, J .; Mart´ın, A.; Toma´s, M. J . Chem. Soc., Dalton Trans.
1993, 1107. (d) Uso´n, R.; Fornie´s, J .; Uso´n, M. A.; Toma´s, M.; Iban˜ez,
M. A. J . Chem. Soc., Dalton Trans. 1994, 401. (e) Ara, I.; Fornie´s, J .;
Lalinde, E.; Moreno, M. T.; Toma´s, M.. J . Chem. Soc., Dalton Trans.
1994, 2735. (f) Falvello, L. R.; Fornie´s, J .; Navarro, R.; Sicilia, V.;
Toma´s, M. J . Chem. Soc., Dalton Trans. 1994, 3143. (g) Fornie´s, J .;
Lalinde, E.; Mart´ın, A.; Moreno, M. T.; Welch, A. J . J . Chem. Soc.,
Dalton Trans. 1995, 1333.

Rotamers of a Pd(0) Maleic Anhydride Complex
Organometallics, Vol. 17, No. 21, 1998 4639
Ta ble 4. F r ee Activa tion En er gies Rela ted w ith Alk en e Rota tion for P d F ec(MA) a n d P d F ec(DMF U) (F ec )
P P F A, P TF A, 1) Com p lexes
qa
entry no.
complex
δν (Hz)
Tc (K)
∆Gc (kJ /mol)
interchanging groups
ref
1
2
3
4
5
6
7
8
9
10
11
12
13
14
Pd(1)(DMFU), 2
2
Pd(PTFA)(DMFU), 10
10
10
10
Pd(PPFA)(DMFU), 11
Pd(1)(MA), 3
3
Pd(PTFA)(MA), 12
12
Pd(PPFA)(MA), 13
13
13
2.9
18.75
52.7
168.2
114.0
250.0
250.0
16.04
16.70
10.2
320
340
330
353
358
373
298
368
368
338
346
293
303
313
67.9
73.1
68.0
69.5
71.7
72.4
57.3
80.0 (83.7)
79.9 (83.6)
74.6 (76.5)
74.8 (76.7)
64.1 (66.5)
65.4 (67.9)
65.9 (68.5)
alkene protons (m)
alkene methyls (m)
alkene methyls (m)
alkene protons (m)
alkene methyls (M)
alkene protons (M)
alkene protons (M)
aminomethyls (up) (M+m)
aminomethyls (down) (M+m)
aminomethyls (up) (M+m)
aminomethyls (down) (M+m)
aminomethyls (up) (M+m)
aminomethyls (down) (M+m)
alkene protons (M+m)
b
b
9d
9d
9d
9d
9d
b
b
9d
9d
9d
9d
9d
18.3
11.0
16.4
32.0
a
b
See Experimental Section for the calculation method used. This paper. For complexes 3, 12, and 13, minor (m) to major (M) (major
to minor) isomer transformations are given.
Ta ble 5. F r ee Activa tion En er gies Rela ted w ith Isom er In ter con ver sion for [P d (2-Me-a llyl)F ec]Tf (F ec )
P P F A, P TF A, 1)
qa
entry
complex
δν (Hz)
Tc (K)
∆Gc (kJ /mol)
interchanging groups
ref
1
2
3
4
5
6
[Pd(2-Me-allyl)(1)]Tf, 4
4
[Pd(2-Me-allyl)(PPFA)]Tf, 14
[Pd(2-Me-allyl)(PTFA)]Tf, 15
15
15
5.5
28.5
6.6
21.5
37.4
42.4
355
385
345
351
359
361
80.3 (80.8)
82.1 (82.6)
77.4 (77.9)
75.4 (76.0)
75.6 (76.2)
75.6 (76.2)
aminomethyls (down) (M+m)
aminomethyls (up) (M+m)
nonfunctionalized Cp (M+m)
b
b
9d
9d
9d
9d
Hsyn,trans(M) T Hsyn,trans(m)
nonfunctionalized Cp (M+m)
aminomethyls (M+m)
a
See Experimental Section for the calculation method used. b This paper. Minor (m) to major (M) (major to minor) isomer transformations
are given.
Isom er In ter con ver sion for 2-4. In our studies,
recorded. To calculate the barrier of the possible
several coalescences related to olefin rotation or/and
diastereomer interconversion have been observed, and
the corresponding data of coalescence temperature and
free energy of activation at this temperature are listed
in Tables 4 and 5. In case of the olefin complex 3, a
simple rotation leads to isomer interconversion (alkene
symmetry: C2v), whereas for the DMFU derivative, 2
(alkene symmetry: C2h), the rotation gives rise only to
an interchange of the olefin substituents; however, in
order to achieve an isomer interconversion, a process
that exchanges the olefin faces must be operating (see
Chart 2). For this complex, a coalescence of the two
ester methyl resonances of the minor isomer is observed.
Also the AB system (31P-decoupled) of the alkene
protons of this isomer (2m ) transforms into an A2
system, whose singlet narrows with increasing temper-
ature. The corresponding alkene signals of 2M broaden
enormously, but the higher chemical shift difference δν
prevents the coalescence to be clearly observed up to
the maximum temperature registered (378 K). All these
observations are in agreement with an alkene rotation
process. The ∆Gq values are in accordance with values
reported in the literature for alkene rotation of differ-
ent types of complexes,19 especially for those of the
closely related Pd(L-L)(alkene), L-L ) PPFA, PTFA,9d
and diimine.14i However, some Pd(0) examples where
the olefin rotation could not be observed have been
described.14h For theoretical studies about alkene rota-
tion see, for example, ref 20. No coalescence phenom-
enon corresponding to an isomer interconversion 2M S
2m could be detected up to the maximum temperature
isomerization process 2M S 2m , we have monitored the
1
transformation of isolated 2M into 2m by H NMR in
benzene-d6 at 40 °C until an equilibrium ratio was
reached (6:4 ratio, 6 h). A barrier of ∆Gq
) 110 kJ
313
mol-1 was calculated.
With the aim of obtaining information about the
1
isomerization mechanism, several additional H NMR
experiments (in benzene-d6 at 40 °C) have been carried
out:21 (i) When a small amount of free DMFU (0.2 equiv)
is added, the barrier of the isomerization decreases to
103.5 kJ mol-1 at 40 °C. In the presence of free alkene,
this acceleration effect suggest an associative rather
than a dissociative mechanism. (ii) To demonstrate that
for 2M an inter- rather than an intramolecular olefin
interchange takes place, 1 equiv of free trans-CD3CO2-
CHdCH-CO2CD3 (DMFU-d6) was added to a solution
of 2M in benzene-d6 at 40 °C. 2M was transformed into
a mixture of 2M and 2m as well as into the deuterated
complexes. The isomerization process 2M S 2m and
the alkene substitution are observed simultaneously
with identical barriers (∆Gq
) 102.6 and 102.1 kJ
313
mol-1, respectively). Experiments i and ii have been
performed in the presence of free alkene, which may
open up the possibility of associative mechanisms. To
determine whether a spontaneous olefin dissociation
takes place in the absence of free ligand, a third
experiment has been carried out: (iii) An equimolar
mixture of 2M and Pd(PPFA)(DMFU-d6) was prepared
1
and studied by H NMR. The ester methyl signals of
Pd(PPFA)(DMFU) appeared; hence, an interchange of
the alkene ligands between the Pd(NP) fragments must
have taken place. A similar interchange has been
(19) Ref 15, Vol. 3, pp 103-109.
(20) (a) Wheebock, K. S.; Nelson, J . H.; Cusachs, L. C.; J onassen,
H. B. J . Am. Chem. Soc. 1970, 92, 5110. (b) Albright, T. A.; Hoffmann,
R.; Thibeault, J . C.; Thorn, D. L. J . Am. Chem. Soc. 1979, 101, 3801.
(21) The noncoordinating character of this solvent makes its par-
ticipation in the process less likely.

4640 Organometallics, Vol. 17, No. 21, 1998
Go´mez-de la Torre et al.
described by Elsevier14i for Pd(diimine)(alkene) com-
plexes. Simultaneously to the olefin exchange, also the
2M S 2m isomerization occurs. Both alkene cross-
interchange and isomerization show nearly identical
For complex 4, an isomer interconversion is also
indicated by the coalescence of the respective resonances
of the NMeup and the NMedown groups (see Table 5).
Although the two allylic methyl signals broaden enor-
mously, the high chemical shift difference (δν about 260
Hz) precludes the observation of the corresponding
coalescence below 413 K. In principle, several mecha-
nisms might be proposed to explain the observed
isomerization.24 An η3-η1-η3 mechanism is commonly
accepted for palladium allyl complexes with ferrocenyl
phosphine ligands containing additional P-10,12,25 or S-26-
functionalities. Recently, we have shown9d that this
mechanism is also operating in [Pd(η3-2-Me-C3H4)-
(PTFA)]Tf, a complex closely related to 4. Considering
these data, an η3-η1-η3 pathway is likely to account
for the observed isomer interconversion in 4.
free energies of activation: ∆Gq
) 107.3 and 106.0
313
kJ mol-1, respectively. This points to a common limiting
rate-determining step in both processes, with the olefin
dissociation being the most reasonable alternative.
Although the differences are not very pronounced, the
isomerization barriers found in experiment iii are
between those observed for pure 2M and 2M in the
presence of free DMFU. This may be due to the fact
that the Pd(PPFA)(DMFU) complex dissociates the
olefin more easily than 2, which parallels the observa-
tion of smaller olefin rotation barriers in PPFA com-
plexes as compared to complexes of 1. See below for a
more general discussion of rotational barriers.
The ∆Gqc values for 4 and also for the corresponding
allyl complexes with PPFA and PTFA9d are summarized
in Table 5. These values are higher than those of the
corresponding alkene rotations. In this series, the
energy increases in the order 1 > PPFA > PTFA (see
ref 27 for arguments).
1
The variable-temperature H NMR study of complex
3 shows an exchange of the two NMeup signals belonging
to unlike isomers, and the same is observed for the two
NMedown signals. This evidences unambiguously a 3M
S 3m isomer interconversion. In principle, several
processes may account for such an observation. Unfor-
tunately, the alkene resonances do not give supplemen-
tary information. The four signals of the two isomers
broaden and nearly disappear at 378 K, but a coales-
cence is not clearly reached. Nevertheless, considering
our observations for the DMFU complex, 2, and for other
related amino ferrocenyl complexes,9d we propose the
alkene rotation to be the process causing the observed
isomer interconversion.
A comparison of the activation barriers of the alkene
rotation in 2 and 3 with those of the corresponding
values of the analogous PPFA and PTFA complexes9d
(see Table 4) shows an order of these barriers of 1 >
PTFA > PPFA, both for the DMFU and MA complexes
(see ref 22 for arguments). According to these results
and from an electronic point of view, it seems that the
donor ability of the fragments (Fec)Pd (Fec ) ferrocenyl
aminophosphine ligands) follows the order 1 > PTFA
> PPFA. Although steric effects cannot be fully ex-
cluded, a severe steric hindrance of the alkene rotation
is very unlikely, as deduced from different X-ray struc-
tures of these type of complexes (see refs 9d, 11 and the
structure described below).
P d -N Bon d Ru p tu r e. According to our previous
study,9d it is possible to observe and investigate Pd-N
bond rupture processes in ferrocenyl aminophosphine
palladium derivatives on the NMR time scale. We have
now studied the influence of different factors such as
the nature of the ferrocenyl and ancillary ligands or the
oxidation state of the palladium center on the activation
parameters of the Pd-N bond cleavage. If the energy
barrier involved in the Pd-N bond rupture is low
enough, a broadening and in some cases also a coales-
cence of the two diastereotopic aminomethyl groups of
a specific complex are observed. The chemical inter-
change between these two groups requires, after the
Pd-N bond rupture and prior to the recoordination to
the unsaturated metal center, an inversion at the
nitrogen atom and a rotation of the whole dimethy-
lamino group. It is reasonable to assume that from all
these consecutive steps the Pd-N bond cleavage con-
tributes most to the measured activation barrier. In
neither case of complexes 2-7, all derivatives of ligand
1, could a signal coalescence be reached up to the
maximum temperature registered. For complex 6, a
marked broadening of the aminomethyl signals is
observed, but, due to the product decomposition which
is completed at about 353 K, a proper analysis of the
line width evolution and the detection of the coalescence
temperature were not possible. Only a slight broaden-
ing of the aminomethyl resonances was observed at high
The data of Table 4 also show that for each amino-
phosphine ligand the olefin rotation barrier is higher
in the MA complexes than in the respective DMFU
derivatives, implying a smaller withdrawing character
for the latter ligand in these type of complexes (see ref
23 for arguments). In addition, we have observed that
complex 2M is quantitatively transformed into 3 when
2M is reacted with 1 equiv of MA at 8 °C. This confirms
the higher thermodynamic stability of 3 as a conse-
quence of a stronger Pd-alkene bond.
(23) A comparison of the two complexes with ligand 1 (Table 4)
shows that although in entry 2 the δν is higher than in entry 8, the Tc
and also ∆Gq values are smaller for entry 2 (DMFU derivative). For
c
the PTFA complexes, the Tc values of entries 10 and 11 are between
those of entries 3 and 4, while the ∆Gq data are clearly higher in 10
c
and 11 (MA complex). A similar comparison can be made for the PPFA
derivatives. The Tc of entry 7 (298 K) is between the Tc values of entries
(22) To establish this order we have taken into account the ∆Gq
,
12 and 13, and the ∆Gq for the DMFU complex is notably smaller.
c
c
Tc, and δν values, considering especially that ∆Gq changes with
(24) Vrieze, K. In Dynamic Nuclear Magnetic Resonance Spectros-
copy; J ackman, L. M., Cotton, F. A., Eds.; Academic Press: NewYork,
1975.
(25) Pregosin, P. S.; Salzmann, R. Coord. Chem. Rev. 1996, 155, 35.
(26) Herrmann, J .; Pregosin, P. S.; Salzmann, R.; Albinati, A.
Organometallics 1995, 14, 3311.
c
temperature. Table 4 shows, for example, that for the DMFU deriva-
tives the Tc value (340 K) given in entry 2 lies between the two Tc
values of entries 3 and 4, but ∆Gqc is higher for the complex with ligand
1 (2), (1 > PTFA). On the other hand, in entries 6 and 7, the δν’s are
equal but the Tc and also the ∆Gq values are clearly higher for the
c
complex with PTFA (10) (PTFA > PPFA). In the case of MA complexes,
(27) The difference between PPFA and 1 is not very pronounced. A
the δν is higher in entry 11 than in 8, but the inverse order is found
comparison of entries 1 and 3 shows that the smaller δν corresponds
for the Tc and ∆Gq values (1 > PTFA). The same comparison can be
to the higher Tc and ∆Gq (complex 4). The comparison between the
c
c
made with entries 10 and 14 to compare PPFA and PTFA complexes,
PPFA and PTFA derivatives can be made with use of entries 3 and 4.
(PTFA > PPFA).
For a lower Tc, a higher ∆Gq is observed for the PPFA complex.
c

Rotamers of a Pd(0) Maleic Anhydride Complex
Organometallics, Vol. 17, No. 21, 1998 4641
Ta ble 6. F r ee Activa tion En er gies Rela ted to th e
P d -N Bon d Ru p tu r e in P P F A P a lla d iu m
Com p lexes
entry
complex
δν (Hz) Tc (K) ∆Gcq (kJ /mol)
1
2
3
4
5
6
Pd(PPFA)(DMFU), 11
11
PdClMe(PPFA), 8
8
Pd(PPFA)(MA), 13
PdCl2(PPFA), 9
368
373
368
373
368
63.5a
63.4a
68.4a
68.0a
235.3
249
71.6b
>373
>72.4b
a
q
The ∆Gc has been calculated from a band-shape analysis.
b
See Experimental Section for the calculation method used.
To compare kinetic parameters of the Pd-N bond
rupture processes in Pd(0) and Pd(II) complexes, a line
shape analysis for complex 8 has also been carried out.
The kinetic data are given in Figure 1. In this figure,
a k value for the complex Pd(PPFA)(MA), 13, was also
F igu r e 1. Eyring plot of the k values deduced from line
shape analysis of the exchanging aminomethyl groups of
added, which was calculated from ∆Gq at the coales-
c
complexes 8 (9): ∆Hq ) 96.3 kJ mol-1, ∆Sq ) 75.9 J mol-1
.
cence temperature. A complete line shape analysis for
this derivative has not been possible due to overlapping
lines and because the line width is also affected by the
alkene rotation process. For PdCl2(PPFA), 9, at 373 K
a very pronounced broadening of the aminomethyl
signals is observed, but a decomposition process pre-
vents a full variable-temperature NMR study. Hence,
only limiting data are given: at 373 K, the k value is
11M ([): ∆Hq ) 73.5 kJ mol-1, ∆Sq ) 27.17 J mol-1. For
complex 11m (s) this analysis has been carried out only
for the slow exchange region below the coalescence tem-
perature (see text) ∆Hq = 65.5 kJ mol-1. The corresponding
values calculated from the experimental ∆Gq’s at the
coalescence temperatures for complexes 11M (/), 13 (b) and
9 (2) are included.
temperature for complexes 2-5 and 7. Therefore, this
general behavior implies that the Pd-N bond rupture
in complexes of ligand 1 is a process with a considerably
high activation barrier. Similar considerations can be
made for PTFA complexes.
lower than 550 s-1, which correspond to ∆Gq > 72.4
373
kJ mol-1
.
To make proper comparisons, we have
collected in Table 6 the ∆Gqc values at 368 or 373 K for
the described PPFA complexes 8, 11, 13, and 9. Al-
though not extremely big, the differences in ∆Gq are
c
In the case of the PPFA complexes, however, a more
conclusive analysis of this process can be made. In both
Pd(0) and Pd(II) derivatives a general broadening of the
aminomethyl resonances is observed while in the case
of Pd(PPFA)(DMFU) (11),9d PdClMe(PPFA) (8), and Pd-
(PPFA)(MA) (13), the coalescence temperature is reached.
To compare the kinetic parameters of this process, a line
shape analysis of the spectra has been carried out for
complexes 11 and 8. The corresponding Eyring plot is
depicted in Figure 1, and the kinetic parameters are
given in the figure captions. In the case of complex 8
and the major isomer of 11 (11M), the analysis was
possible over the whole temperature range. However,
for 11m the overlap of lines with those of 11M has
prevented a full analysis in the fast exchange region. A
comparison of the data for the two isomers of 11 (see
Figure 1) shows some differences. In fact, in the
analyzed region, 11M has lower rate constants as well
as higher ∆Hq values for the bond rupture process. In
a previous work9d and by means of NOE studies, we
have determined the orientation of the DMFU unit in
both isomers 11M and 11m . In the major isomer the
olefin is coordinated with its Re face to the (S,R)-PPFA
palladium unit. An identical arrangement of the DMFU
ligand is seen in 2M (Chart 2), where the olefin also
coordinates with its Re side to the (R,R)-1 palladium
fragment. As compared to 11m , the steric interaction
of the CO2Me olefin fragment and the ferrocenyl NMe2
group seems to be less demanding in 11M, which might
be the origin of the higher ∆Hq observed for the Pd-N
significant. If we compare the data at 373 K for
complexes 11, 8, and 9 (entries 2, 4, and 6), it is clear
that the palladium(II) complexes exhibit higher barriers
than the palladium(0) derivatives. This may be a
consequence of the lower electronic density at the metal
in the higher oxidation state. The lower value obtained
for complex 8 as compared to 9 may be explained on
the basis of the high trans influence of the methyl group
that weakens the Pd-N bond. In the comparison of the
data at 368 K (entries 1, 3, and 5), the DMFU derivative
also shows the lowest value. The substantially higher
value of complex 13 as compared to the other palladium-
(0) derivative, 11, is likely to be due to the previously
stated higher electron withdrawing ability of MA, which
makes the metal center a better electron acceptor, thus
strengthening the Pd-N bond.
X-r a y str u ctu r e of (1)P d (MA) (3). Racemic com-
plex 3 crystallizes in the triclinic space group P1h with
two molecules in the asymmetric unit and four mol-
ecules in the unit cell. It was with surprise that the
two independent molecules of the asymmetric unit are
those that in solution were assigned to the minor 3m
and the major diastereomer 3M with the maleic anhy-
dride unit either pointing away or toward the ferrocenyl
core.
A list of selected bond lengths and bond angles is
given in Table 7, and experimental parameters for the
structure determinations are given in Table 8. An
ORTEP of the exo diastereomer is shown in Figure 2.
bond rupture process in this isomer. If the ∆Gq value
The general structural features of the ferrocenyl units
of both molecules are similar to those found for ligand
1 and its PdCl2 complex. Bond lengths and bond angles
are within the usual range, e.g., with average Fe-Car
c
for 11M at the coalescence temperature is used to
calculate the rate constant, the resulting value fits per-
fectly to the straight lines of the Eyring plot (Figure 1).

4642 Organometallics, Vol. 17, No. 21, 1998
Go´mez-de la Torre et al.
F igu r e 3. Superposition of the molecular structures of exo-
(R,R)-Pd(1)(MA) (s) and endo-(R,R)-Pd(1)(MA)(- - -).
Ta ble 8. Cr ysta l Da ta a n d Str u ctu r e Refin em en t
for 3
empirical formula
fw
C62H60Fe2N2O6P2Pd2
1315.56
temp
293(2) K
wavelength
cryst system
space group
unit cell dimensions
0.71070 Å
triclinic
P1h
a ) 9.8145(7) Å; R ) 104.040(10)°
b ) 13.827(2) Å; â ) 97.994(7)°
c ) 21.461(4) Å; γ ) 102.005(8)°
2707.9(7) Å3
volume
F igu r e 2. ORTEP drawing of the exo-(R,R)-Pd(1)(MA)
diastereomer of complex 3.
Z
2
density (calcd)
abs coeff
F(000)
crystal size
θ range for data collection
index ranges
1.613 g/cm3
12.93 cm-1
1336
Ta ble 7. Selected Bon d Len gth s (Å) a n d An gles
(d eg) for 3
0.5 × 0.3 × 0.25 mm
2.08-20.02°
Bond Distances
-9 e h e 9, -13 e k e 13,
-20 e l e 20
Pd(1)-C(51)
Pd(1)-C(54)
Pd(1)-N(7)
Pd(1)-P(3)
P(3)-C(31)
N(7)-C(55)
O(4)-C(52)
O(5)-C(52)
O(5)-C(53)
O(6)-C(53)
2.103(5)
2.128(5)
2.196(4)
2.2915(13)
1.807(5)
1.514(6)
1.196(7)
1.400(7)
1.410(8)
1.210(8)
Pd(11)-C(511)
Pd(11)-C(541)
Pd(11)-N(71)
Pd(11)-P(31)
P(31)-C(311)
N(71)-C(551)
O(41)-C(521)
O(51)-C(521)
O(51)-C(531)
O(61)-C(531)
2.102(5)
2.131(5)
2.201(4)
2.306(2)
1.804(5)
1.506(7)
1.206(6)
1.403(6)
1.403(7)
1.201(6)
no. of reflections collected
refinement method
no. of data/restraints/
parameters
10 130
full-matrix least-squares on F2
5066/0/685
goodness-of-fit on F2
final R indices [I > 2σ(I)]
R indices (all data)
1.120
R1 ) 0.0300, wR2 ) 0.0673
R1 ) 0.0385, wR2 ) 0.0736
0.677 and -0.417 e Å-3
largest diff peak and hole
Bond Angles
C(51)-Pd(1)-C(54) 39.1(2)
C(511)-Pd(11)-C(541) 39.0(2)
N(71)-Pd(11)-P(31) 96.45(12)
C(541)-Pd(11)-N(71) 109.3(2)
C(511)-Pd(11)-P(31) 115.0(2)
C(311)-P(31)-Pd(11) 110.3(2)
C(551)-N(71)-Pd(11) 111.7(3)
C(321)-C(551)-N(71) 110.6(4)
C(321)-C(551)-C(561) 113.9(5)
N(71)-C(551)-C(561) 110.3(4)
C(551)-C(561)-C(571) 115.3(5)
C(411)-C(571)-C(561) 113.8(5)
ring imposes conformational changes mostly in the
diphenyl phosphine part. One phenyl ring is positioned
in close proximity to the Cp2 protons H42 and H421
(attached to carbons C42 and C421), a fact that in the
NMR spectra is reflected by a strong high-field shift of
these particular nuclei. At the same time the phospho-
rus atoms P3 and P31 are severely forced out of plane
by 0.30 Å (3m ) and 0.26 Å (3M) above Cp1.
N(7)-Pd(1)-P(3)
95.68(11)
C(54)-Pd(1)-N(7) 111.8(2)
C(51)-Pd(1)-P(3) 113.5(2)
C(31)-P(3)-Pd(1) 111.4(2)
C(55)-N(7)-Pd(1) 113.3(3)
C(32)-C(55)-N(7) 110.9(4)
C(32)-C(55)-C(56) 113.5(4)
N(7)-C(55)-C(56) 109.9(4)
C(55)-C(56)-C(57) 114.6(4)
C(41)-C(57)-C(56) 114.1(4)
A superposition (Figure 3) of the molecular structures
of 3m and 3M shows that the ferrocenyl aminophos-
phine ligands adopt quite similar conformations in both
complexes. Major differences are only seen in the
coordination sphere of palladium and in the arrange-
ment of the maleic anhydride unit. In both cases
palladium and its coordinated atoms are found in a
slightly but differently distorted square planar arrange-
ment. The maleic anhydride ligands are attached to
palladium with the Pd-C bonds trans to P being longer
than those trans to N, reflecting the stronger trans
influence of phosphorus (Pd-C [trans P] 2.128(5) Å
(3m ), 2.130(5) Å (3M); Pd-C [trans N] 2.103(5) Å (3m ),
2.102(5) Å (3M)).
and Car-Car bond lengths of 2.032(8) and 1.42(1) Å (3m )
and 2.03(1) and 1.42(1) Å (3M). The Cp rings are
essentially planar. However, the trimethylene bridge
forces the Cp rings to be tilted by 8.8° and 10.6°,
respectively. In addition, the benzylic bridge carbons
are moved out of plane, both toward the inner bridge
carbons (C56 and C561). Carbons C55 and C551 are
displaced by 0.13 and 0.12 Å below Cp1 (Cp1 formed by
the following: 3m , C31-C35; 3M, C311-C351), while
C57 and C571 are out of the plane of Cp2 (Cp2 formed
by the following: 3m , C41-C45; 3M, C411-C451) by
0.18 and 0.12 Å, respectively. Like in the free ligand,
the trimethylene bridge adopts a conformation in which
the carbon nitrogen bonds (C55-N7 and C551-N71) are
positioned almost perpendicular to the respective Cp1
planes. A comparison with the molecular structure of
1 shows that the formation of a palladium P-N chelate
The anhydride ligands are essentially planar and
bound to the square planar unit with a dihedral angle
of 98° (3m ) and 100° (3M), respectively. In 3m the
shortest nonbonding distances of atoms of the maleic

Rotamers of a Pd(0) Maleic Anhydride Complex
Organometallics, Vol. 17, No. 21, 1998 4643
13C NMR), CClF3 (19F NMR), and 85% H3PO4 (31P NMR).
Coupling constants (J ) are in hertz. The NOE difference
spectra were recorded with 5000 Hz, acquisition time 3.27 s,
pulse width 90°, relaxation delay 4 s, irradiation power 5-10
dB. For variable-temperature spectra, the probe temperature
((1 K) was controlled by a standard unit calibrated with a
methanol reference. Free energies of activation were calcu-
lated from the coalescence temperature (Tc), and the frequency
difference between the coalescing signals (extrapolated at the
coalescence temperature) with the formula28 ∆Gqc ) aT(10.319
+ log T/k), k values were calculated according to the Shanan-
Atidi and Bar-Eli method.28 In cases of equal populated
species (for example, interchange of olefin substituents in 2
or aminomethyl interchange in complexes of Table 6), the
formula28 ∆Gqc ) aT(9.972 + log T/δν) has been used. For the
anhydride units to the ferrocenyl core are those of the
olefin protons H51 to ortho-Phdown proton H22 (2.32 Å)
and H54 to Medown protons H59A and H59B (2.89 and
2.96 Å) and of oxygens O4 to the ortho-Phup proton H12
(3.04 Å) and O6 with proton H59B (2.75 Å). In 3M the
shortest related distances are those of oxygens O41 to
ortho-Phdown H221 (2.55 Å) and O61 to Medown protons
H59D and H59F (2.82 and 3.10 Å) and of the olefinic
proton H541 to Meup H58E (3.28 Å) and to Medown H59F
(2.65 Å). A comparison of these distances in 3m and
3M shows that only in 3M is the olefinic proton H541
(trans P) close enough to the respective Meup group to
allow for NOE enhancement as described in the Ster-
eochemical Assignments section. In 3m the closest
distance of H54 (trans P) to a Meup proton is 4.30 Å,
much longer than that in 3M (H541/H59F: 2.65 Å), an
argument that has been used in the assignment of 3M
in solution. Intramolecular nonbonding H-H distances
have been derived from calculated hydrogen positions.
AB system of complex 2 (entry 1 of Table 4), ∆Gq has been
c
calculated from the following expression: ∆Gq ) aT[9.972 +
c
2
log(T/(δν2 + 6J AB
)
1/2 (a ) 1.914 × 10-2, ∆Gqc in kJ mol-1). The
estimated error in the calculated free energies of activation is
1.0-1.1 kJ mol-1. Pd2(dba)3‚CHCl3,29 [Pd(η3-2-Me-C3H4)Cl]2,30
PdClMe(COD),31 Pd(C6F5)2(COD),32 and PdMe2(TMEDA)33 were
prepared according to literature methods. DMFU-d6 was
prepared from fumaryl chloride and CD3OD.
Con clu sion s
P r ep a r a tion of P d (1)(DMF U)‚1/4P h CH3 (2‚1/4P h CH3).
To a degassed solution of Pd2(dba)3‚CHCl3 (90 mg, 0.087 mmol)
in 20 mL of toluene are added 87.0 mg (0.191 mmol) of 1 and
36.4 mg (0.252 mmol) of dimethyl fumarate. The solution is
stirred for 2 h, filtered, and evaporated to dryness. Free dba
is removed from the mixture by chromatography on a Silica
60 column (25 × 1 cm) with toluene as eluent. Complex 2 is
eluted with THF and the solution evaporated to dryness. 2‚
1/4P h CH3 is obtained as an orange solid. Crystals of pure
2M were obtained by recrystallization from toluene/diethyl
ether. Yield: 62.4 mg (0.089 mmol, 51%). Anal. Calcd for
Several new palladium(0) and -(II) derivatives of
ligand 1 and PPFA have been prepared. NMR variable-
temperature studies on these complexes have allowed
the determination of the activation barriers of different
fluxional processes such as alkene rotation, alkene face
exchange, apparent allyl rotation, and Pd-N bond
rupture. The calculated ∆Gq , together with our previ-
c
ously reported data for PPFA and PTFA complexes,
allows us to draw the following conclusions: The activa-
tion barriers for alkene rotations in the palladium(0)
complexes are in the order of 1 > PTFA > PPFA and
MA > DMFU. For the DMFU complexes the observed
isomerization must imply an alkene face exchange,
which according to our results most likely takes place
via a dissociative pathway. An apparent allyl rotation
is observed for the allyl complexes with the activation
barriers following the order 1 > PPFA > PTFA. In Pd-
(0) and Pd(II) complexes with PPFA, the Pd-N bond
rupture is a process with an activation barrier low
enough to be observable on the NMR time scale. For
derivatives with PTFA or 1, this process, although
feasible, must be of higher energy. The activation
barriers are higher in palladium(II) than in palladium-
(0) complexes, but the donor or acceptor ability of the
ancillary ligands is an important factor to be considered.
The fact that on the NMR time scale Pd-N bond
rupture in complexes with PPFA type aminophosphine
ligands is a fast process indicates that the Pd-N bond
cleavage may be involved in important steps of different
catalytic processes not only in cross-coupling reactions
but also in allylic alkylations, allylic aminations, or
other similar processes.
C
33H36FeNO4PPd‚1/4C7H8: C, 57.42; H, 5.26; N, 1.93.
Found: C, 57.59; H, 4.94; N, 1.68. IR: ν(CdO) 1676 cm-1
,
π(C-H) 882 cm-1 31P NMR (toluene-d8): 2M, 15.83, s; 2m ,
.
15.44, s.
P r ep a r a tion of P d (1)(MA) (3). The procedure is identical
to that described for 2. Amounts are as follows: Pd2(dba)3‚
CHCl3 (93.1 mg, 0.090 mmol); 1 (90.0 mg, 0.199 mmol); maleic
anhydride (25.7 mg, 0.262 mmol). 3 is obtained as an orange
solid. Yield: 40.2 mg (0.061 mmol, 34%). Orange crystals
were obtained by vapor diffusion from methylene chloride/
diethyl ether. Anal. Calcd for C31H30FeNO3PPd: C, 56.60;
H, 4.60; N, 2.12. Found: C, 56.65; H, 4.98; N, 2.09. IR: ν-
(CdO) 1786, 1717 cm-1; π(C-H) 779 cm-1
form-d): 3M, 15.89, s; 3m , 17.63, s.
.
31P NMR (chloro-
P r ep a r a tion of [P d (η3-2-Me-C3H4)(1)]Tf‚1/2Et2O (4‚1/
2Et2O). This complex is prepared in a way similar to that
described by Pregosin.10 To a degassed solution of 35.0 mg
(0.089 mmol) of [Pd(η3-2-Me-C3H4)Cl]2 and 80.8 mg of 1 (0.180
mmol) in 20 mL of acetone is added a solution of AgCF3SO3
(45.7 mg, 0.180 mmol) in 2 mL of methanol. After stirring for
3 h in the dark, the orange solution is filtered over a plug of
Celite and evaporated to dryness. The gummy residue is
triturated with hexane and diethyl ether, giving 4‚1/2Et2O as
an orange solid. Yield: 71.1 mg (0.116 mmol, 65%). Anal.
Calcd for C32H35F3FeNO3PPdS‚1/2C4H10O: C, 50.98; H, 5.03;
Exp er im en ta l Section
Gen er a l Com m en ts. All manipulations were carried out
under an atmosphere of dry oxygen-free nitrogen using
standard Schlenk techniques. Solvents were distilled from the
appropriate drying agents and degassed before use. Elemental
analyses were performed with a Perkin-Elmer 2400 microana-
lyzer. IR spectra were recorded as KBr pellets or Nujol mulls
with a Perkin-Elmer PE 883 IR spectrometer.1H, 13C, 19F, and
31P NMR spectra were recorded on a Varian Unity 300
spectrometer. Chemical shifts (ppm) are relative to TMS (1H,
(28) Sandstro¨m, J . Dynamic NMR Spectroscopy; Academic Press:
London, 1982.
(29) Ukai, T.; Kawazura, H.; Ishii, Y.; Bonnet, J . J .; Ibers, J . A. J .
Organomet. Chem. 1974, 65, 253.
(30) Dent, W. T.; Wilkinson, A. J . J . Chem. Soc. 1964, 1585.
(31) Ru¨lke, R. E.; Ernsting, J . M.; Spek, A. L.; Elsevier: C. J .; van
Leeuwen, P. W. N. M.; Vrieze, K. Inorg. Chem. 1993, 32, 5769.
(32) Espinet, P.; Mart´ınez-Ilarduya, J . M.; Pe´rez-Briso, C.; Casado
A. L.; Alonso, M. A. J . Organomet. Chem. 1998, 551, 9.
(33) de Graaf, W.; Boersma, J .; Smeets, W. J . J .; Spek, A. L.; van
Koten, G. Organometallics 1989, 8, 2907.

4644 Organometallics, Vol. 17, No. 21, 1998
Go´mez-de la Torre et al.
N,1.75. Found: C, 51.16; H, 4.57; N, 1.79. IR:34 CF3SO3 1271,
1223, 1147, and 636 cm-1; 2-Me-C3H4 1029, 1480, 1469, 1435,
residue is washed and triturated with hexane. A filtration
yields 8 as a pale orange solid. Yield: 47 mg (0.079 mmol,
58%). Anal. Calcd for C27H30ClFeNPPd: C, 54.30; H, 5.06;
N, 2.34. Found: C, 54.08; H, 4.64; N, 2.32. IR:34b ν(Pd-CH3)
829, 839 cm-1 31P NMR (1,1,2,2,-tetrachloroethane-d2): 4M,
.
16.50, s; 4m , 19.58, s.
P r ep a r a tion of P d ClMe(1) (5). A degassed solution of
35.1 mg of PdClMe(COD) (0.132 mmol) and 60 mg of 1 (0.132
mmol) in 30 mL of methylene chloride is stirred for 24 h. The
reaction mixture is evaporated to dryness, and the gummy
residue is washed and triturated with hexane. 5 is obtained
as a yellow solid. Yield: 62.0 mg (0.10 mmol, 77%). Anal.
501 cm-1, ν(Pd-Cl) 275 cm-1 1H NMR (toluene-d8): 1.12 (d),
.
J H-P ) 4.4 Hz, Me. 13C NMR (toluene-d8): 1.61 (d), J C-P
3.5 Hz, Me. 31P NMR (toluene-d8): 24.09, s.
)
X-r a y Str u ctu r a l An a lysis of Com p lex 3. A crystal of
approximate dimensions of 0.5 × 0.30 × 0.25 mm was mounted
on a glass capillary. Intensity data were collected on a
PHILIPS PW1100 diffractometer equipped with graphite Mo
KR radiation (λ ) 0.710 73 Å) using an ω/2θ scan to a
maximum value of 30°. Data were corrected for Lorentz and
polarization effects, and absorption correction was not required
because the variation in integrated Ψ scan intensities was
<10%.
Calcd for
C28H31ClFeNPPd: C, 55.11; H, 5.12; N, 2.29.
Found: C, 55.02; H, 4.61; N, 2.82. IR:34b ν(Pd-CH3) 512 cm-1
;
ν(Pd-Cl) 269 cm-1 1H NMR (chloroform-d): 0.54 (d), J H-P
. )
3.7 Hz, Me; 13C NMR (chloroform-d): 2.21 (d), J C-P ) 8.50 Hz,
Me. 31P NMR (chloroform-d): 22.97, s.
P r ep a r a tion of P d Me2(1) (6). A degassed solution of 27.9
mg of PdMe2(TMDA) (0.11 mmol) and 50 mg of 1 (0.11 mmol)
in 20 mL of toluene is stirred for 18 h. The pale yellow solution
is concentrated up to 3 mL, and 10 mL of hexane are added.
6 is obtained as pale yellow crystals after keeping the solution
in a freezer for several hours. Yield: 44.1 mg (0.075 mmol,
68%). Anal. Calcd for C29H34FeNPPd: C, 59.05; H, 5.81;
N,2.37. Found: C, 59.15; H, 5.81; N, 2.35. IR:34b ν(Pd-Me)
The structure was solved using direct methods (SIR92).37
Refinement on F2 was carried out by full-matrix least-squares
techniques (SHELXL-93).38 All non-hydrogen atoms were
refined with anisotropic thermal parameters. The hydrogen
atoms were included in calculated positions. Refinement
converged at the following reliability values: R1 ) 0.0300, wR2
) 0.0692 for reflections with I > 2σI and R1 ) 0.0385, wR2 )
0.0760 for all reflections. Goodnes-of-fit ) 1.12. Maximum
and minimum electron density in the final electron density
523, 510 cm-1 1H NMR (benzene-d6): 0.77 (d), J H-Pcis ) 6.8
.
Hz, Me cis P; 0.83 (d), J H-Ptrans ) 8.8 Hz, Me trans P. 13C NMR
(benzene-d6): 5.61 (d), J C-Pcis ) 8.50 Hz, Me cis P; 10.10 (d),
J C-Ptrans ) 114.8 Hz, Me trans P. 31P NMR (benzene-d6): 6.75,
s.
map was 0.677 (near the Pd atom) and -0.417 e Å-3
.
Ack n ow led gm en t. We gratefully acknowledge the
Direccio´n General de Investigacio´n Cient´ıfica y Te´cnica
(DGICYT, Grant PB95-0901, and Accio´n Integrada
Project HU94-009, Ciudad Real, Spain), the Fonds zur
Fo¨rderung der Wissenschaftlichen Forschung (Project
P09859-CHE), and O¨ sterreichischer Akademischer Aus-
tauschdienst (O¨ AD, Accio´n Integrada Project 29/95,
Wien, Austria).
P r ep a r a tion of P d (C6F 5)2(1)‚1/2Et2O (7‚1/2Et2O).
A
degassed solution of 80.0 mg of 1 (0.180 mmol) and 96.0 mg of
Pd(C6F5)2(COD) (0.180 mmol) in methylene chloride is refluxed
at 40 °C for 2 h. The solvent of the resulting solution is
reduced to 3 mL, and a pale yellow precipitate of 7 is formed
when diethyl ether is added. Yield: 93.3 mg (0.104 mmol,
58%). Anal. Calcd for C39H28F10FeNPPd‚1/2C4H10O: C, 52.89;
H, 3.57; N, 1.50. Found: C, 53.03; H, 3.14; N, 1.52. IR:35 C6F5
1497, 957, and 789 cm-1 31P NMR (bencene-d6): 7.99, s. 19F
.
NMR36 (benzene-d6): -114.77, -115.64, -116.46, -117.07 (m,
ortho); -163.05, -163.65, -164.14, -164.79 (m, meta); -160.91
(dd, J FF ) 21.4, 18.3 Hz, para), -162.24 (dd, J FF ) 21.4, 18.3
Hz, para).
Su p p or tin g In for m a tion Ava ila ble: Crystal data and
structure refinement. Tables of positional and atomic dis-
placement parameters for all atoms, anisotropic displacement
parameters, bond lengths and bond angles, least-squares
planes, important intermolecular contacts, and unit cell and
packing diagram of complex 3. Full 1H and 13C NMR data for
the new complexes (25 pages). Ordering information is given
on any current masthead page.
P r ep a r a tion of P d ClMe(P P F A) (8). A degassed solution
of 36.2 mg of PdClMe(COD) (0.136 mmol) and 60 mg of PPFA
(0.136 mmol) in 20 mL of toluene is stirred for 16 h at room
temperature. The solution is evaporated to dryness, and the
(34) (a) Shobatake, K.; Nakamoto, K. J . Am. Chem. Soc. 1970, 92,
2. 3339. (b) Nakamoto, K., Ed. Infrared and Raman Spectra of
Inorganic and Coordination Compounds; J . Wiley and Sons: New York,
1986.
(35) Deacon, G. B.; Green, J . H. S. Spectrochim. Acta, Part A 1968,
24, 1125.
OM980312Z
(37) Altomare, A.; Cascarano, G.; Giacovazzo, C.; Guagliardi, A.;
Burla, M. C.; Polidori, G.; Camalli, M. J . Appl. Crystallogr. 1994, 435.
(38) Sheldrick, G. M. Program for the Refinement of Structures from
Diffraction Data; University of Go¨ttingen, Go¨ttingen, Germany, 1993.
(36) Uso´n, R.; Fornie´s, J . Adv. Organomet. Chem. 1988, 28, 219.