New studies on the apparent allyl rotation in scorpion-like palladium complexes. The influence of non-directly bonded groups. X-ray molecular structures of [Pd(η3-2-Me-C3H4)L]TfO, L = bpzmArOMe and bpz*mCy

Article abstract of DOI:10.1016/S0022-328X(02)01253-6

New cationic 2-Me-allylpalladium complexes were prepared with the N,N-donor chelate ligands bis(pyrazol-l-yl)(R)methane (R = anisol-2-yl, bpzmArOMe; 2-hydroxyphenyl, bpzmArOH) and bis(3,5-dimethylpyrazol-l-yl)(R)methane (R = anisol-2-yl, bpz*mArOMe: cyclohexyl, bpz*mCy and ferrocenyl, bpz*mFc). The bpz′mR ligands adopt a rigid boat conformation after coordination to the Pd center and the R group is in the axial position of the metallacycle. The new complexes exhibit two isomeric forms in solution that differ in the relative orientation of the 2-Me-allyl group with respect to the bpz′mRPd fragment. The fluxional behavior of the new complexes, mainly in the context of the isomerization process, has been analyzed. Conclusions concerning the influence on this isomerization of the R group and the pyrazole substituents in positions 3 and 5 are discussed. The isomerization process was found to be affected by the presence of coordinating anions (Cl) or by a change in the complex concentration. The molecular structures of the complexes [Pd(η³-2-Me-C₃H₄)(bpzmArMe)]TfO and [Pd(η³-2-Me-C₃H₄)(bpz*mCy)]TfO have been determined by X-ray diffraction studies.

Full text of DOI:10.1016/S0022-328X(02)01253-6

Journal of Organometallic Chemistry 650 (2002) 210Á222
/
www.elsevier.com/locate/jorganchem
New studies on the apparent allyl rotation in scorpion-like palladium
complexes. The influence of non-directly bonded groups. X-ray
molecular structures of [Pd(h3-2-Me-C3H4)L]TfO, Lꢀ
and bpz*mCy
/
bpzmArOMe
M. Carmen Carrio´n a, Alberto D´ıaz a, Ana Guerrero a, Fe´lix A. Jalo´n a,*, Blanca
R. Manzano a, Ana Rodr´ıguez b, Rowena L. Paul c, John C. Jeffery c
a Dpt. de Quim. Inorg., Org. y Bioquim, Facultad de Qu´ımicas, Universidad de Castilla-La Mancha, Avda. Camilo J. Cela, 10, E-13071 Ciudad Real,
Spain
b Escuela Te´cnica Superior de Ingenier´ıa Industrial, Universidad de Castilla La Mancha, Avda. Camilo J. Cela, 3, E-13071 Ciudad Real, Spain
c The School of Chemistry, Cantock’s Close, The University of Bristol, Bristol BS8 1TS, UK
Received 1 December 2001; received in revised form 22 January 2002; accepted 22 January 2002
Abstract
New cationic 2-Me-allylpalladium complexes were prepared with the N,N-donor chelate ligands bis(pyrazol-1-yl)(R)methane
(Rꢀ
/
anisol-2-yl, bpzmArOMe; 2-hydroxyphenyl, bpzmArOH) and bis(3,5-dimethylpyrazol-1-yl)(R)methane (Rꢀanisol-2-yl,
/
bpz*mArOMe; cyclohexyl, bpz*mCy and ferrocenyl, bpz*mFc). The bpz?mR ligands adopt a rigid boat conformation after
coordination to the Pd center and the R group is in the axial position of the metallacycle. The new complexes exhibit two isomeric
forms in solution that differ in the relative orientation of the 2-Me-allyl group with respect to the bpz?mRPd fragment. The fluxional
behavior of the new complexes, mainly in the context of the isomerization process, has been analyzed. Conclusions concerning the
influence on this isomerization of the R group and the pyrazole substituents in positions 3 and 5 are discussed. The isomerization
process was found to be affected by the presence of coordinating anions (Clꢁ) or by a change in the complex concentration. The
molecular structures of the complexes [Pd(h3-2-Me-C3H4)(bpzmArOMe)]TfO and [Pd(h3-2-Me-C3H4)(bpz*mCy)]TfO have been
determined by X-ray diffraction studies. # 2002 Elsevier Science B.V. All rights reserved.
Keywords: Palladium; Allyl; Bis(pyrazolyl); Rotation
1. Introduction
syn and anti protons, an interchange that is normally
associated with a h3Áh1Áh3 dynamic process. In several
/
/
(h3-Allyl)palladium complexes bearing N-donor li-
gands are very widely studied because they can act as
precursors or intermediates in different catalytic pro-
cesses [1]. Another aspect that has attracted a lot of
interest in recent years is the study of the fluxional
behavior in these systems, either directly related with the
allyl group or with the ancillary ligands coordinated to
the metal center [2]. For instance, in halophosphine [3],
aminophosphine [4] and other Pd(II) derivatives [5] the
allyl group frequently undergoes a mutual exchange of
cases it has been demonstrated that this process is
assisted by added base, the solvent, the counteranion [6]
or a donor atom of an ancillary ligand [7]. The s-donor
character of phosphines or other donor ligands [5g]
promotes easy access to the h1-form of the coordinated
allyl ligand, although steric effects have been shown to be
important [5f]. In complexes bearing ligands with less s-
donor character a second dynamic process is more
frequently observed, namely the apparent rotation of
the allyl group [1k,8Á
symmetry, this dynamic process is observed to occur via a
syn Ásyn, anti Áanti exchange or an isomerization pro-
/10]. Depending on the molecular
/
/
cess. One type of N,N-donor ligand that has been widely
used in palladium chemistry is bis(pyrazol-1-yl)methane
* Corresponding author. Fax: ꢂ
E-mail address: felix.jalon@uclm.es (F.A. Jalo´n).
/
34-926-295318.
0022-328X/02/$ - see front matter # 2002 Elsevier Science B.V. All rights reserved.
PII: S 0 0 2 2 - 3 2 8 X ( 0 2 ) 0 1 2 5 3 - 6

M.C. Carrio´n et al. / Journal of Organometallic Chemistry 650 (2002) 210Á
/
222
211
and its derivatives. This type of chelating ligand
coordinates with the metal to form a six-membered
metallacycle that adopts a boat conformation [11]. When
hydrogen or methyl substituents [8a,12] are present in the
spacer group situated between the pyrazole rings, the
boat-to-boat interconversion usually takes place. It has
been shown that the presence of two very different
substituents in this spacer group makes the two boat
conformations energetically very different [8g,13] and we
have proposed that, as a consequence, the boat-to-boat
interconversion is not present [8g,13a]. When methyl
groups are present in the 3- and/or 5-positions of the
pyrazole rings an enhancement of the rigidity of the boat
conformation is also observed [8a]. In the work described
here, which is mainly focused on the study of the
apparent allyl rotation, we synthesized a number of
new 2-Me-allyl palladium complexes with bis(pyrazol-
2. Results and discussion
2.1. Synthesis of ligands and complexes
The ligands bis(pyrazol-1-yl)(R)methane (Rꢀ
2-yl, bpzmArOMe; 2-hydroxyphenyl, bpzmArOH) and
/
anisol-
bis(3,5-dimethylpyrazol-1-yl)(R)methane (Rꢀanisol-2-
/
yl, bpz*mArOMe; cyclohexyl, bpz*mCy and ferrocenyl,
bpz*mFc) were prepared by the reaction of 1,1?-carbo-
nyldipyrazole (or the 3,5-dimethylpyrazole derivative)
with the corresponding aldehyde in accordance with a
previously described procedure (see Scheme 1) [14].
These ligands are soluble in organic solvents such as
diethyl ether or more polar solvents. The Me-allylPd
complexes were prepared by treatment of the dimer
[Pd(h3-2-Me-C3H4)(m-Cl)]2 with AgCF3SO3 (AgTfO) in
solution in THF. The AgCl formed in the reaction was
filtered off and the corresponding bpz?mR ligand was
subsequently added. The reaction is represented in eq. 1.
1-yl)methane
and
bis(3,5-dimethylpyrazol-1-yl)-
methane ligands. We chose N,N-ligands with only one
bulky group in the spacer carbon (CHR) (see
Scheme 1) for several reasons, (i) this would preclude
the boat-to-boat interconversion process and, conse-
quently, could simplify the study of the allyl rotation.
(ii) As a consequence of the ligand rigidity, the two
isomers generated in a situation of restricted allyl
rotation would have very different chemical environ-
ments. (iii) The introduction of different R groups (and
also methyl substituents in the pyrazole rings) would
allow us to rationalize the effect that such groups have
on the apparent allyl rotation and provide new data
about the mechanism by which this process occurs.
1=2[Pd(h3-C4H7)(m-Cl)]2 ꢂAgTfO
bpz?mR
0 [Pd(h3-C4H7)(S)2]TfO 0 [Pd(h3-C4H7)
 (bpz?mR)]TfO
pz?ꢀpz, Rꢀ2-OH-C6H4 (1), 2-OMe-C6H4 (2). pz?ꢀ
3,5-Me2pzꢀpz*, Rꢀ2-OH-C6H4 (3), 2-OMe-C6H4
(4), Cy (5), Fc (6).
Complexes 2 and 4Á
(1)
/
/
/
/
/
/6 are soluble in acetone, THF
and more polar organic solvents. Complexes 1 and 3 are
sparingly soluble in these solvents.
Scheme 1.

212
M.C. Carrio´n et al. / Journal of Organometallic Chemistry 650 (2002) 210Á222
/
2.2. Characterization of the new complexes
Complexes 1Á6 were characterized by NMR and IR
of the allyl group. For each complex the corresponding
diastereomers are in solution in a ratio that depends on
the solvent, reflecting the fact that the two isomers are in
equilibrium. By considering the data of different NOE
experiments it was possible to elucidate the structure of
each specific isomer. For the exo isomers the most
informative interaction was the NOE observed between
the allylic methyl group and protons of the R group or
that between the Hanti and the Me3 of the pyrazole ring
(see Scheme 2). A noticeable characteristic of the spectra
is the shielding produced on the Me-allyl groups in the
exo isomers when the R group contains an aromatic
ring, a situation probably induced by the electron
current anisotropy. This effect has also been observed
for the complex [2-Me-allylPd(bpz*mPh)]TfO, 7 [8g].
We found that the major isomer corresponds to the exo
form. The only exception occurs for complex 2, whose
isomers are ca. in a 1:1 ratio in chloroform-d. However,
in other solvents, such as acetone-d6 or 1,1?,2,2?-tetra-
chloroethane-d2, the exo form is the major component
of the mixture.
/
spectroscopy and elemental analysis. The IR spectra
show the characteristic vibration bands of the 2-Me-allyl
group, the pyrazole groups, the counter anion
(CF3SO3ꢁ) and also those of the R substituents (see
Section 4).
The 1H and 13C-NMR data of complexes 1Á
6 are
/
compiled in Tables 1 and 2, respectively. Assignment of
the different resonances was made by considering the
chemical shifts and coupling constants expected for the
different atoms and the information obtained from
1HÁ1
H COSY experiments. NOE studies, which will
/
be discussed later, were of significant value in terms of
complementary assignment information.
Evidence for complexation of the bpz?mR ligands in
the final compounds is provided by the observation of
positive coordination-induced shifts (CIS) for the pyr-
azolyl atoms, the interpyrazolic CHa fragment and
several protons of the R groups when compared with
those of the free ligands. Some NOEs observed (H3? or
Me3 with Hsyn or Hanti; phenylic H3 in 1Á
/
4 or H2 in 6
2.3. Rotation and most stable conformation of the R
group
with Ha) also reflected the coordination of the ligands
and/or supported the signal assignments. For the whole
set of complexes an NOE between H5? (or Me5) and Ha
was observed but such an interaction was not observed
for protons of the R group (see Scheme 2). From these
data it is possible to conclude that the R group is in an
axial position (form A, Scheme 2) and form B is
unpopulated. The positioning of the relatively bulky
fragment R (when compared with H) in an equatorial
position must cause steric repulsion with Me5 and even
with the H5? pyrazolic groups. Other authors have also
suggested the axial position of the R group in similar
systems [8g,13]. A low temperature spectrum (213 K)
was recorded for some complexes (4 and 5) and, in these
cases, splitting of the signals was not observed. Conse-
quently, as we have observed previously for other
bis(pyrazolyl)methane complexes with R substituents
in the spacer group [8g,13a], the boat-to-boat intercon-
version does not occur and the ligand is a rigid system
after coordination. The axial orientation of the R group
on the CHa fragment confers on the PdbpzmR moiety a
characteristic aspect of a trapped metal in the claws of a
tailed ligand, a situation that inspired us to term these
ligands ‘scorpion-like’ in a similar way to Trofimenko’s
scorpionates [15].
As we have previously observed in other related
scorpion-like complexes with aromatic R groups, e.g.
complex 7 [8g], the phenylic H3 (1Á
4) or the ferrocenyl
/
H2 (6) protons show a negative CIS when compared
with the free ligands. This CIS can be explained by the
fact that, although the R groups can rotate around the
RꢀCa bond, there are preferred conformations that
/
result in an overall shielding effect due to the electron
current anisotropy of the pyrazole rings. The conforma-
tions shown in Scheme 4 are those found in different X-
ray structures of complexes containing these ligands
[8g,13a] (see below for the X-ray structures of complexes
2 and 5) and are in accordance with the observed
shielding (AÁC in Scheme 4). In contrast, a positive CIS
/
is observed for the Hipso proton of the Cy fragment in 5.
This proton shows a 3JHH coupling constant with Ha of
11 Hz, which is characteristic of a mutual axial Á
disposition of the two protons. Both of these facts point
Hipso bond
/
axial
to a preferred conformation in which the Cꢀ
/
is contained in the mirror plane of the complex (see
Scheme 4(D)).
VT NMR experiments were carried out in 1,1?,2,2?-
tetrachloroethane-d2 for the major isomers of complexes
All the complexes showed the presence of two
diastereomers in solution at room temperature and these
differ in the relative orientation of the allyl group with
respect to the PdNN fragment (endo and exo isomers)
(see Scheme 3). Comparable behavior has been observed
in similar complexes [8a,8g,16]. We propose that in our
case the separate observation of these isomeric forms is
possible (discussed below) due to the restricted rotation
2, 4Á
and the coalescence temperature of the corresponding
rotamers (320Á373 K). A measure of the evolution of
/
6 and 7 (previously reported [8g]) between 293 K
/
the chemical shift with temperature of the protons
assigned that could be affected by the pyrazolic electron
current anisotropy (H3 and OMe for the anisole
derivatives 2 and 4, ortho-protons for 7, H2ꢀ
/
Fc for 5
and Hipso
ꢀ
/
Cy for 6) was undertaken. These resonances

Table 1
1H-NMR data for complexes 1Á
/6 at room temperature
Complex
Pyrazole
H4?
Ha
R group
AllylÁPd
/
H3? or Me3
H5? or Me5
Hsyn Hanti Me
4.13 3.33 1.98
1M (73%) 6.67(t) 8.11 (d,J34
ꢀ
/2.2)
8.52 (dd,J45
ꢀ
/
2.6, J35
ꢀ/0.73)
8.59
6.95(d, H6, J56
ꢀ
/
8.1, 7.03(t,H4, J45
ꢀ
8.0), 7.27(t, H5), 7.27
/
(d, H3, J34
6.92(d), 7.31(t)
ꢀ8.3), 9.30(s, OH)
/
a
b
b
1m 6.65(t)
2M (57%) 6.43(t) 7.70(bs)
8.64
8.54
4.32 2.94 2.27
3.88 3.10 2.17
8.49(d) J45
ꢀ
/
2.7
6.84(d, H6, J56
ꢀ
/
8.3), 6.79(t,H4, J45
ꢀ
7.6), 7.31(t, H5),
/
6.62 (d, H3, J34
ꢀ
/
7.6), 3.71(s, OMe)
b
b
b
b
b
2m
3M (66%) 6.06
3m 6.06
4M (65%) 6.14
4.06 2.92 1.85
3.87 2.95 1.51
4.00 2.41 2.19
3.90 3.05 1.54
2.28
2.20
2.32
2.49
2.51
2.55
7.36
7.48
7.46
6.25(bd, H6), 7.20 (m, H4), 7.20(m, H5), 6.66 (bs, H3), 9.05(s, OH)
6.56(bd, H6), 7.20 (m, H4), 7.20(m, H5), 6.66 (bs, H3), 9.05(s, OH)
6.91(d, H6, J56
(d, H3, J34
ꢀ
8.1), 6.90 (m, H4), 7.38(t, H5), 6.48
7.3), 3.70(s, OMe)
/
ꢀ/
4m
5M
6.12
6.03
2.22
2.31
2.28
2.19
2.60
2.51
2.65
2.68
7.63
6.12 (d, JHH
7.74
3.71(s, OMe)
3.4(qt, CHipso
4.04 2.16 2.19
4.16 3.18 2.22
3.85 3.02 1.65
4.01 2.26 2.16
c
ꢀ/11.0)
)
6M (66%) 6.16
6m 6.13
4.25(Cp), 3.90(H2, H2’), 4.19(H3, H3’)
4.31(Cp), 4.02(H2, H2’), 4.22(H3, H3’)
7.74
See Scheme 1 for numbering. Chemical shifts in ppm and coupling constants in Hz. All resonances are singlets if not specified. The percentage of the major isomer is indicated between parenthesis.
d, doublet, t, triplet, m, multiplet, bs, broad singlet, q, quartet. M and m, major and minor isomers, respectively. Solvent is chloroform-d if not specified.
a
In acetone-d6.
Resonances non observed.
Signals for 5m are not clearly observed.
b
c

214
M.C. Carrio´n et al. / Journal of Organometallic Chemistry 650 (2002) 210Á222
/
Table 2
13C{1H}-NMR data for complexes 1Á
/6 at room temperature
Complex Pyrazole
Ca R group
AllylÁ/Pd
C4?
C3?
C5?
Me3 and Me5
CH2ꢁ
/
ꢁ
/
Cꢀ
/
Me
a
1M
1m
2M
2m
4M
4m
5M
6M
6m
107.61 146.27 136.08
107.61 146.75 136.14
106.76 144.38 135.97
106.76 144.85 136.10
155.65, 122.35, 116.77, 120.03, 131.93, 127.64
116.95, 120.03, 132.28, 127.85
72.98
73.24
59.53
59.55
a
Á
Á/
/
71.75 157.10, 123.09, 111.44, 119.53, 131.21, 126.54, 55.55(OMe)
72.07 157.30, 122.85, 111.60, 119.53, 131.61, 126.88, 55.57(OMe)
66.56 122.87, 128.11, 121.15, 132.04, 112.27, 59.79(OMe)
67.03 128.83, 119.92, 132.69, 112.40, 60.21 (OMe)
71.65 44.31, 25.12, 27.46, 25.12
68.46 69.65(Cp), 68.85, 67.45, 82.65(C1)
67.80 69.52(Cp), 68.75, 67.60, 82.32(C1)
133.61 23.02
133.75 23.53
107.89 153.05 143.89 15.48 12.05
107.53 152.33 144.22 15.81 12.05
107.21 152.09 143.67 15.04 11.55
107.75 152.80 142.16 14.97 11.61
107.40 152.25 142.53 15.29 11.61
56.3(bs) 132.47 23.16
56.3(bs)
60.04
59.10
23.42
131.10 23.85
132.00 23.30
130.50 23.00
60.06
See Scheme 1 for numbering. Chemical shifts in ppm. All signals are singlets. bs, broad singlet. M and m, major and minor isomers, respectively.
Solvent is chloroform-d if not specified.
a
In acetone-d6.
did not change significantly in the phenylic compounds
whereas a clear decrease in the absolute value of the
corresponding CIS with increasing temperature was
observed for complexes bearing Cy (5) or Fc (6) groups.
Considering the rigidity and structural analogy of this
set of complexes, the comparable region of studied
temperatures and the identical solvent, we propose that
this evolution of chemical shifts for complexes 5 and 6 is
related to an increase in the population of the excited
rotational states of the R groups. In accordance with
these observations, the fundamental state (more popu-
lated rotamer at r.t) for 5 and 6 must correspond to the
less sterically demanding disposition of the R groups
2.4. Isomer interconversion. Apparent allyl rotation
As we have previously stated, two isomers (see
Scheme 3) were observed for complexes 1Á6 (and also
/
for 7) that differ in the relative orientation of the allyl
group with respect to the Pd-NN ligand backbone. The
NOE experiments carried out at r.t. indicate that the
isomer interconversion does take place. For instance,
when the allyl Me group of one isomer is irradiated,
high magnetization transfer is observed on the same
group of the second isomer as a consequence of the spin
relaxation. Even more informative is the fact that an
intense magnetization transfer is observed between Hsyn
(or Hanti) protons of one isomer with those of the other,
but not between Hsyn and Hanti protons. The existence of
(see Scheme 4(D and C)). In this disposition the H2ꢀ
and Hipso Cy are inside and outside, respectively, of the
/Fc
ꢀ
/
Hsyn
Á
/
Hsyn (and Hanti
change clearly indicates that the isomerization phenom-
Á
/
Hanti) and not Hsyn ÁHanti ex-
/
shielding electron current anisotropy of the pyrazoles.
Other conformations for the R group would be less
populated at r.t. and begin to be more populated as the
enon is related to an apparent allyl rotation and not with
a h3Á
/
h1Áh3 pathway. Given the intensity of the
/
temperature increased. As a consequence, the H2ꢀ
experiences the observed deshielding while the Hipso Cy
/Fc
magnetization transfer at room temperature, we decided
to study the isomerization process by determining the
coalescence temperatures and to analyze the influence of
the Me pyrazolic substituents and the R group of the
N,N-donor ligands. The corresponding VT 1H-NMR
studies were recorded for the more soluble complexes 2
ꢀ
/
experiences the aforementioned shielding. We can con-
clude that the rotational barrier for the more bulky
groups, Cy and Fc is higher than for R-phenyl groups.
For these last R-groups the barrier is clearly overcome
at r.t.
Scheme 2.

M.C. Carrio´n et al. / Journal of Organometallic Chemistry 650 (2002) 210Á
/
222
215
Scheme 3.
addition of chloride a decrease in the DG%c values (see
Table 3 and Fig. 2). The favorable effect on the
isomerization in Pd(II) complexes of coordinating
agents (through pentacoordinate [9] or tricoordinate
[10] intermediates) such as solvent, counteranions or
internal functional groups in the ligands is widely
reported and, consequently, the effect of the chloride
ion is not unexpected. Both experiments on complex 4
could lead to a perturbation in the counteranionÁcation
/
contact that would explain the observed behavior. The
dilution would make this contact more difficult (ion-pair
dissociation) while the addition of anions with more
coordinating ability (Clꢁ vs. TfOꢁ) would improve this
contact.
An acceleration in the process would be expected
when coordinative functional groups are present in the
R fragments of the ligands, such as OMe in 4. Complex
4, however, exhibits the highest DG%c values (Fig. 1). On
the basis of these data it is possible to conclude that the
OMe group does not participate in the stabilization of
any intermediate. This conclusion excludes the forma-
Scheme 4.
and 4Á
/
7 in 1,1?,2,2?-tetrachloroethane-d2. In order to
exclude the influence of other variables, similar molar
concentrations in the same solvent and with the same
counteranion (CF3SO3ꢁ) were used for all the com-
plexes. Coalescence temperatures were achieved in the
tion, through a Pdꢀ
/
N bond rupture, of tricoordinated
intermediates where an interaction with the OMe group
may be feasible. After considering the experimental data
as a whole, we propose that for our complexes the
range 299Á
391 K. The corresponding DG%c data are
/
compiled in Table 3 and represented in Fig. 1. The DGc%
values fit straight lines with, in general, very low slopes.
Exceptionally, for 6 the line has a clear positive slope.
Complex 4 exhibits slightly higher values than complex
2, which suggests that the Me substituents in the
pyrazole rings make the isomerization process more
difficult, although not markedly so. A more marked
influence of the R groups can be seen when values for
anionÁcation interaction is the main cause of the
/
isomerization process through a pentacoordinated inter-
mediate. The orbital perpendicular to the coordination
plane of the complex must be the direction in which this
interaction occurs. For complexes with phenylic-R
groups containing the MeO substituent (2 and 4), this
contact could be hindered by virtue of the orbital being
blocked. Such orbital blocking would be more pro-
nounced for complex 4, which also has Me substituents
in the pyrazole rings. Bulky groups such as Cy and Fc
must have a very different effect when they are oriented
away or towards the palladium centre. In accordance
with the DG%c data, the Cy group in 5 is not very effective
in blocking the palladium centre, probably due to the
different skeletal conformations that this group can
complexes 4Á7 are compared. Cy and Ph groups in
/
complexes 5 and 7, respectively, induce similar energetic
barriers. However, the introduction of a methoxy group
in complex 4 gives rise to a remarkable increase in this
barrier.
The effect of the concentration and the addition of a
counteranion with coordination ability (Clꢁ) was also
analyzed in the case of 4. This study was performed by
the addition of more solvent (1,1?,2,2?-tetrachlor-
oethane-d2) and PPh4Cl, respectively, to solutions of
the complex. The dilution produced an increase and the
adopt*
/
even in a regime of free rotation that would
Pd moiety. In
move this group away from the allylÁ
/
contrast, the Fc group in 6 is rigid and there will be
orientations of this group that will severely hinder the

216
M.C. Carrio´n et al. / Journal of Organometallic Chemistry 650 (2002) 210Á222
/
Table 3
Free energies of activation at the coalescence temperatures for the isomerization process in complexes 2, 4Á/7 in 1,1?,2,2?-tetrachloroethane-d2
Complex
Exchanging group
DG%c/kJ molꢁ1 (T/K)
Complex
Exchanging group
DG%c/kJ molꢁ1 (T/K)
7
7
7
7
7
5
5
5
5
5
5
6
6
6
6
6
Me5
Me3
Hsyn
Horto
Meallyl
Me5
Me3
Hsyn
Ha
66.2 (305)
67.0 (315)
66.6 (323)
66.8 (325)
66.2 (343)
66.5 (299)
67.8 (315)
67.1 (321)
67.2 (321)
67.6 (327)
67.2 (339)
74.8 (325)
76.1 (333)
77.2 (345)
80.5 (375)
81.0 (385)
2
OMe
Hsyn
76.8 (337)
77.4 (353)
77.3 (363)
77.6 (385)
81.1 (361)
81.0 (369)
81.8 (383)
81.7 (391)
86.0 (391)
87.1 (407)
71.4 (327)
72.0 (339)
72.6 (349)
72.8 (363)
2
2
H3anisole
Meallyl
Me5
2
4
4
Me3
4
Hsyn
H3anisole
Me5
4
4 dilution
4 dilution
Hanti
Hipso
Ha
Me3
4ꢂ
4ꢂ
4ꢂ
4ꢂ
/
PPh4Cl
PPh4Cl
PPh4Cl
PPh4Cl
Me5
/
Me3
Hsyn
Me5
H4?
/
/
H3anisole
Me3
Hsyn
Values are represented vs. temperature in Figs. 1 and 2. Values have been calculated in accordance with the Shanan-Atidi and Bar-Eli [21] method
for the exchange of the minor to the major isomers.
cationÁ
/
anion interaction. As stated previously, as the
The molecular structures consist of a mononuclear Pd
cation and a triflate counteranion. ORTEP plots of the
cations are shown in Figs. 3 and 4. The crystallographic
data and a list of selected bond distances and angles are
given in Tables 4 and 5, respectively. In complex 5, the
cation lies on a crystallographic mirror plane containing
Pd(1), C(12), C(13) and C(7). In both compounds the
geometry around the Pd(1) atom is ca. square-planar
with two coordinated pyrazole rings and the h3-bonded
temperature is increased the populations of the rota-
tional states that cause greater steric hindrance, which
could also hinder the cationÁanion contact, are also
/
increased. In accordance with this hypothesis the DGc%
values for 6 quickly increase with temperature.
2.5. X-ray structures of complexes 2 and 5
allyl ligand. The distances of the Pd(1)ꢀ
/
N coordination
Crystals of 2 and 5 belong to the monoclinic (C2/c)
and orthorhombic (Pnma) space groups, respectively.
bonds are comparable to those of other bispyrazolyl-
Fig. 1. Linear plot of DGc% (kJ molꢁ1) vs. Tc for the isomerization process of [Pd(h3-C4H7)(bpz?mR)]TfO complexes in 1,1?,2,2?-tetrachloroethane-d2
(see Table 3 for values): (m) 7 (m) 5 (r) 2 (j) 4 (I) 6.

M.C. Carrio´n et al. / Journal of Organometallic Chemistry 650 (2002) 210Á
/
222
217
Fig. 2. Linear plot of DGc% (kJ molꢁ1) vs. Tc for the isomerization process of complex 4 in 1,1?,2,2?-tetrachloroethane-d2: (j) 1.6ꢃ
/
10ꢁ2 mol lꢁ1 (m)
0.8ꢃ
/
10ꢁ2 mol lꢁ1 (r) Addition of 5.14 mg of PPh4Cl (1.37ꢃ10ꢁ2 mmol) to 0.50 ml of the 1.6ꢃ10ꢁ2 mol lꢁ1 solution of complex 4.
/
/
methane [8g,12b,17] complexes. The coordination of the
bpz?mR ligand gives rise to a boat-like metallacycle,
PdNNCNN, with the anisole (2) or cyclohexyl (5) group
attached to the carbon atom in an axial orientation. This
situation is in agreement with the data obtained for the
complexes in solution. In complex 2 the anisole plane is
twisted (62.608) with respect to the plane defined by the
ancillary ligands bonded to Pd promotes several distor-
tions [17a]. In our case, comparing complexes 2 and 5,
we have found that the methyl groups in this position
induce the following distortions in the boat metallacycle,
(i) The dihedral angle PdNN/NNNN is smaller in 5
(153.598) than in 2 (157.78) which reduces the steric
hindrance. (ii) As a consequence, the dihedral angle
between the two pyrazole rings is smaller for 5 (124.188)
than for 2 (128.38). (iii) The same steric repulsion
influences the NPdN bite angle, which is slightly less
open in 5 [87.4(1)8] than in 2 [88.4(8)8].
Pd(1)ꢀ
/
C(11)ꢀ/C(12) atoms. The OMe group lies practi-
cally in the anisole plane and points away from the
molecule. On the contrary, the cyclohexyl group in 5 is
bisected by the previously mentioned crystallographic
plane. It has been described that the steric hindrance
between the C3 substituents of the pyrazole and the
In complex 5 the isomer found in the solid state is the
exo form and this corresponds with the major isomer
Fig. 3. ORTEP view with atomic numbering of the cation of the two isomers (exo, A and endo, B) of 2 (40% probability ellipsoids). Proton atoms
have been omitted for clarity.

218
M.C. Carrio´n et al. / Journal of Organometallic Chemistry 650 (2002) 210Á
/
222
Table 5
˚
Selected bond lengths (A) and angles (8) for 2 and 5
2
Bond lengths
Bond angles
2.100(2) N(6)ꢀPd(1)ꢀ
2.085(2) C(21A)ꢀPd(1)ꢀ
2.195(2) C(24B)ꢀPd(1)ꢀC(25B)
2.112(2) C(21A)ꢀPd(1)ꢀ
2.125(2) C(25B)ꢀPd(1)ꢀ
Pd(1)ꢀ
Pd(1)ꢀ
C(23A) 1.454(10) C(21A)ꢀ
Pd(1)ꢀ
Pd(1)ꢀ
Pd(1)ꢀ
Pd(1)ꢀ
Pd(1)ꢀ
/
N(1)
/
/
N(1)
C(22A)
88.4(8)
67.4(8)
67.9(8)
98.3(8)
102.3(8)
103.2(8)
100.0(8)
/
N(6)
/
/
/
C(21A)
C(22A)
C(20A)
/
/
/
/
/N(1)
/
/
/
N(1)
C(20A)ꢀ
C(20A)ꢀ
C(20A)ꢀ
/
C(21A) 1.430(10) C(22A)ꢀ
/
/N(6)
/
C(22A) 1.425(9) C(24B)ꢀ
/
/
N(6)
/
/
C(20A)ꢀ
C(20B)ꢀC(24B)
C(11)ꢀN(7)
2.159(2) C(17)ꢀO(18)ꢀC(19)
/C(22A) 113.6(7)
Pd(1)ꢀ
Pd(1)ꢀ
Pd(1)ꢀ
/
C(20B)
C(24B)
C(25B)
2.092(2) C(25B)ꢀ
/
/
112.9(7)
109.0(2)
117.8(3)
/
2.166(2) N(2)ꢀ
/
/
/
/
/
C(20B)ꢀ
C(20B)ꢀ
C(20B)ꢀ
N(1)ꢀ
N(6)ꢀ
N(2)ꢀ
N(7)ꢀ
/
C(24B) 1.426(10)
/
C(25B) 1.435(10)
C(26B) 1.450(10)
/
/
ꢀ
/
N(2)
1.361(3)
1.357(3)
1.463(3)
1.463(3)
1.520(4)
1.366(3)
1.434(3)
/
N(7)
/
C(11)
/
C(11)
C(11)ꢀC(12)
/
O(18)ꢀ
O(18)ꢀ
/
C(17)
C(19)
Fig. 4. ORTEP view with atomic numbering of the cation of 5 (30%
probability ellipsoids). Proton atoms have been omitted for clarity.
/
5
Bond lengths
Bond angles
2.110(2) N(1)ꢀPd(1)ꢀ
2.109(3) C(11)ꢀPd(1)ꢀ
2.119(4) C(11)ꢀPd(1)ꢀ
1.458(3) C(11)ꢀC(12)ꢀ
1.527(5) N(2)ꢀC(6)ꢀN(2)
1.371(3) N(2)ꢀN(1)ꢀPd(1)
1.407(5) N(1)ꢀN(2)ꢀC(6)
1.489(8)
Pd(1)ꢀ
Pd(1)ꢀ
Pd(1)ꢀ
/
N(1)
C(11)
C(12)
/
/
N(1)
87.36(13)
68.3(2)
/
/
/C(11)
/
/
/N(1)
170.34(12)
114.6(5)
C(6)ꢀ
C(6)ꢀ
N(1)ꢀ
C(12)ꢀ
C(12)ꢀ
/
N(2)
/
/C(11)
/C(7)
/
/
109.4(3)
Table 4
Crystal data and structure refinement for 2 and 5
/N(2)
/
/
120.04(17)
119.9(2)
/
C(11)
/
/
2
5
/
C(13)
Empirical formula
C19H21F3N4O4PdS
C11H16.5F1.5N2-
O1.5Pd0.5S0.5
298.49
found in solution. If we define a plane containing the Pd
and the two coordinated nitrogen atoms, then the
˚
terminal allylic carbons are situated 0.064 A below this
Formula weight
Temperature (K)
˚
Wavelength (A)
564.86
173(3)
293(2)
0.71070
0.71073
Monoclinic
C2/c
˚
plane and the central allylic carbon is 0.644 A above it.
Crystal system
Space group
Orthorhombic
Pnma
The plane of the allyl group defines an angle of 111.18
with the coordination plane in such a way that the
˚
a (A)
17.295(2)
11.1775(13)
23.205(3)
4454.1(9)
8
16.276(5)
10.441(3)
15.420(2)
2620.4(12)
8
˚
b (A)
C(central) to ꢀ
/CH3 vector is pointing away from the
˚
c (A)
3
Volume (A )
metal.
˚
Interestingly, both isomers of complex 2 are present in
the crystal. The allyl ligand was disordered over the two
orientations in an approximate 50:50 ratio. In one part
of the disorder (A in Fig. 3) the terminal allyl C atoms
are atoms C21A and C22A, and the methyl group is
C23A, while the central pivotal allylic carbon atom is
labeled C20A; in the other part (B in Fig. 3) these atoms
become C24B, C25B, C26B and C20B, respectively.
Z
Dcalc (g cmꢁ3
)
1.685
0.985
1.513
0.839
Absorption coefficient
(cmꢁ1
F(000)
)
2272
1224
Crystal size (mm)
Limiting indices
0.3ꢃ
225
95k 5
295l 5
/
0.3ꢃ
h 5
14,
29
/
0.3
0.4ꢃ
05h 5
05k 5
05l 520
/
0.3ꢃ
21,
13,
/
0.2
ꢁ
/
/
/
22,
/
/
ꢁ
/
/
/
/
/
ꢁ/
/
/
/
/
Data/restraints/
parameters
Goodness-of-fit on F2
Final R indices
5101/13/328
3332/0/184
1.033
0.988
3. Conclusions
R1ꢀ
wR2ꢀ
R1ꢀ0.0514,
wR2ꢀ0.0906
0.745 and ꢁ2.145
/0.0353,
R1ꢀ
wR2ꢀ
R1ꢀ0.0584,
wR2ꢀ0.1070
0.821 and ꢁ0.560
/0.0355,
[I ꢀ
/
2s(I)]
/0.0844
/
0.0896
R indices (all data)
/
/
New 2-Me-allylpalladium derivatives with bis(pyra-
/
/
zol-1-yl)methane
yl)methane ligands bearing a substituent in the methy-
or
bis(3,5-dimethylpyrazol-1-
Largest difference peak
ꢁ3
/
/
˚
and hole (e A
)
lenic spacer group, R, have been prepared and char-

M.C. Carrio´n et al. / Journal of Organometallic Chemistry 650 (2002) 210Á
/
222
219
acterized. These complexes have two isomeric forms in
solution (endo and exo) that differ in the orientation of
the allyl ligand. NOE experiments have shown that the
N,N-donor ligands exist in a rigid boat conformation in
solution with the R group in an axial position with
respect to the PdNNCNN metallacycle. VT NMR
analysis has demonstrated that, in the temperature
range studied, the R group is in a free rotation regime
when R is a phenylic group whereas it has a restricted
rotation when the R group is Cy or Fc. The isomers are
in equilibrium and their interconversion by an apparent
allyl rotation has been studied on the NMR time scale.
On the basis of the DG%c values obtained, the mechanism
proposed for this isomerization implies the occurrence
(extrapolated at the coalescence temperature) according
with the ShananÁAtidi and BarÁEli [21] method with
the formula DG%c ꢀ
aT[10.319ꢂlog (T/k)], aꢀ1.914ꢃ
10ꢁ2. The estimated error in the calculated free energies
of activation is 9
1.0 kJ molꢁ1. M and m refers to the
/
/
/
/
/
/
/
major or minor isomers, respectively.
4.1.2. X-ray structural determination of 2 and 5
2. A suitable crystal of 2 was mounted under a stream
of cold N2 on a Siemens SMART diffractometer fitted
with a CCD-type area detector. A hemisphere of data
was collected at low temperature using graphite mono-
chromated MoÁKa radiation. A detailed experimental
/
description of the methods used for data collection and
integration using the SMART system has been pub-
lished [22]. Empirical absorption corrections were ap-
plied using SADABS [23], and structure solution and
refinement was performed with the SHELX suite of
programs [24]. The crystal of 2 was stable and diffracted
well and the structure was solved by direct methods.
5. A suitable crystal was selected and mounted on fine
glass fibbers with epoxy cement. Accurate unit-cell
parameters were derived from the least-squares fit of
the angular setting of 25 high-order reflections. The data
collection was performed on a Nonius-Mach3 diffract-
of a counteranionÁcation contact through pentacoordi-
/
nate intermediates. These contacts are more difficult to
achieve when bulky groups (R or pyrazole substituents)
are present. In accordance with this mechanism, dilution
or addition of Clꢁ to a solution of one of the complexes
produced the expected increase or decrease, respectively,
in the DG%c values.
4. Experimental
4.1. Starting materials and general conditions
ometer equipped with a graphite monochromated MoÁ
/
˚
Ka radiation (lꢀ
/
0.71070 A) using a v Á2u scan
/
4.1.1. General comments
technique to a u maximum value of 288. The compound
crystallizes in the orthorhombic group Pnma with half
All manipulations were carried out under an atmo-
sphere of dry oxygen-free nitrogen using standard
Schlenk techniques. Solvents were distilled from the
appropriate drying agents and degassed before use.
AgTfO was used as purchased from Aldrich. The
preparation of the ligands bpzmArOH and
bpz*mArOH has been previously reported [18]. The
preparation of the rest of the ligands has been recently
described by us [13a]. [Pd2(h3-2-Me-C3H4)2(m-Cl)2] was
prepared as described in the literature [19]. Elemental
analyses were performed with a Thermo Quest FlashEA
1112 microanalyzer. IR spectra were recorded as KBr
molecule of 5 per asymmetric unit, Zꢀ4. Parameters
/
for the collection and refinement of diffraction data are
contained in Table 4. Intensities were corrected for
Lorentz and polarization effects and absorption correc-
tion was not necessary.
The structure was solved using direct methods [25]
and refined first isotropically by full-matrix least-
squares using SHELXL-97 [26] program and then aniso-
tropically by blocked full-matrix least-squares for all the
non-hydrogen atoms. The hydrogen atoms were in-
cluded in calculated positions and were refined isotro-
pically.
pellets with a PerkinÁ
Elmer PE 883 IR spectrometer. 1H
/
and 13C spectra were recorded on a VARIAN UNITY
300 spectrometer. Chemical shifts (ppm) are given
relative to Me4Si. COSY spectra: standard pulse se-
quence with an acquisition time of 0.214 s, pulse width
10 ms, relaxation delay 1 s, number of scans 16, number
of increments 512. The NOE difference spectra were
recorded with the following acquisition parameters:
spectral width 5000 Hz, acquisition time 3.27 s, pulse
4.2. Preparations
4.2.1. [Pd(h3-C4H7)(bpzmArOH)]TfO (1)
To a solution of [Pd(h3-C4H7)(m-Cl)]2 (100 mg, 0.25
mmol) in 20 ml of acetone, AgTfO (128 mg, 0.5 mmol)
was added. The solution was stirred at r.t. for 1 h and
the resulting suspension was filtered off. Then
bpzmArOH (120 mg, 0.5 mmol) was added to the
filtrate. After stirring for 1 h, the solution thus formed
was evaporated to dryness. The resulting white solid was
width 18 ms, relaxation delay 4 s, irradiation power 5Á
10 dB, number of scans 240. For variable temperature
spectra the probe temperature (91 K) was controlled by
/
/
a standard unit calibrated with a methanol reference.
Free energies of activation (kJ molꢁ1) were calculated
[20] from the coalescence temperature (Tc) and the
frequency difference between the coalescing signals
washed with diethyl ether (2ꢃ
were obtained after a recrystallization from acetoneÁ
diethyl ether. Yield: 55%. C18H19F3N4O4PdS (550.79):
Calc. C, 39.25; H, 3.48; N, 10.17; S, 5.82. Found: C,
/
20 ml). White crystals
/

220
M.C. Carrio´n et al. / Journal of Organometallic Chemistry 650 (2002) 210Á222
/
38.99; H, 3.70; N, 9.94; S, 5.94%. IR (cmꢁ1, KBr): 1519
Npz); 3266 (n OH); 1314, 1034, 795, 639 (CF3SO3),
1385, 832 (2-Me-C3H4).
4.2.7. NMR determination of Tc
0.5 ml of a solution of known concentration (1.3Á
1.9ꢃ 7 in 1,1?,2,2?-
10ꢁ2 mol lꢁ1) of complexes 2 or 4Á
tetrachloroethane-d2 was introduced into a 5 mm NMR
tube. The temperature of the probe was decreased to ꢁ
20 8C (253 K). NMR spectra were recorded as the
temperature was increased at intervals of 5 8C, with a
stabilization time of 10 min between each measurement.
The spectra were acquired at intervals of only 1 or 28
near the coalescence temperature. For complex 4 the
(Cꢁ
/
/
/
/
/
4.2.2. [Pd(h3-C4H7)(bpzmArOMe)]TfO (2)
A similar procedure to that used for 1 was followed
for 2. The amount of ligand bpzmArOMe added was
127 mg (0.5 mmol). Yield: 50%. C19H21F3N4O4PdS
(564.87): Calc. C, 40.40; H, 3.75; N, 9.92; S, 5.68.
Found: C, 39.98; H, 3.76; N, 9.64; S, 5.67%. IR (cmꢁ1
C); 1302, 1018,
784, 635 (CF3SO3), 1374, 837 (2-Me-C3H4).
,
coalescence temperatures were calculated on a 1.6ꢃ
/
KBr): 1585 (Cꢁ
/
Npz); 1143 (nas Cꢀ
/
Oꢀ
/
10ꢁ2 mol lꢁ1 solution (0.5 ml, 0.8ꢃ10ꢁ2 mmol).
/
Additional deuterated solvent (0.25 ml) was added to
0.25 ml of the above solution in order to obtain the
diluted sample. Another solution was prepared by
4.2.3. [Pd(h3-C4H7)(bpz*mArOH)]TfO (3)
adding 5.14 mg of PPh4Cl (1.37ꢃ
ml of a 1.6ꢃ
10Á2 mol lꢁ1 solution of complex 4 in
1,1?,2,2?-tetrachloroethane-d2 (ratio Clꢁ/4ꢀ
1.7). In all
/
10ꢁ2 mmol) to 0.50
A similar procedure to that used for 1 was followed
for 3. The amount of ligand bpz*mArOH added was 148
mg (0.5 mmol). Yield: 55%. C22H27F3N4O4PdS (606.95):
Calc. C, 43.54; H, 4.48; N, 9.23; S, 5.28. Found: C,
43.87; H, 4.61; N, 8.94; S, 4.98%. IR (cmꢁ1, KBr): 1557
/
/
the solutions the coalescence temperatures were then
measured by the standard method.
(Cꢁ
/
Npz); 3255 (n OH); 1047, 803, 638 (CF3SO3); 1374,
842 (2-Me-C3H4).
5. Supplementary material
4.2.4. [Pd(h3-C4H7)(bpz*mArOMe)]TfO×
(4)
A similar procedure to that used for 1 was followed
for 4. The amount of ligand bpz*mArOMe added was
155 mg (0.5 mmol). The recrystallization was made from
/1/2C3H6O
Crystallographic data for the structural analysis have
been deposited at the Cambridge Crystallographic Data
Centre, and allocated the deposition numbers CCDC
no. 174713 for 2 and 174714 for 5. Copies of this
information may be obtained free of charge from The
Director, CCDC, 12 Union Road, Cambridge CB2 1EZ,
acetoneÁ
/
diethyl ether. Yield: 80%. C23H29F3N4O4PdS×
/
1/2C3H6O (621.93): Calc. C, 44.48; H, 4.71; N, 9.02; S,
5.16. Found: C, 44.23; H, 4.49; N, 8.88; S, 4.70%. IR
UK (Fax: ꢂ44-1223-336033; or e-mail: deposit@ccdc.a-
c.uk or http://www.ccdc.cam.ac.uk).
/
(cmꢁ1, KBr): 1557 (Cꢁ
1048, 789, 636 (CF3SO3); 1390, 842 (2-Me-C3H4).
/
Npz); 1143 (nas Cꢀ
/
Oꢀ/C); 1321,
Acknowledgements
4.2.5. [Pd(h3-C4H7)(bpz*mCy)]TfO (5)
A similar procedure to that used for 1 was followed
for 5. The amount of ligand bpz*mCy added was 143
mg (0.5 mmol). The recrystallization was made from
We gratefully acknowledge financial support from the
Direccio´n General de Investigacio´n Cient´ıfica y Te´cnica
(DGICyT) (Grant no. PB98-0315) of Spain and the
‘‘Junta de Comunidades de Castilla-La Mancha’’ for a
grant (to A.G.).
1,2-dichloroetaneÁpentane. Suitable white crystals for
/
X-ray diffraction were obtained. Yield: 92%.
C22H33F3N4O3PdS (698.86): Calc. C, 44.26; H, 5.57;
N, 9.38; S, 5.37. Found: C, 44.09; H, 5.48; N, 9.68; S,
5.29%. IR (cmꢁ1, KBr): 1559 (Cꢁ
(CF3SO3); 1392, 837 (2-Me-C3H4).
/Npz); 1269, 1144, 637
References
[1] (a) J. Tsuji, Palladium Reagents and Catalysts, Innovation in
Organic Synthesis, Wiley, Chichester, 1996;
4.2.6. [Pd(h3-C4H7) (bpz*mFc)]TfO (6)
A similar procedure to that used for 1 was followed
for 6. The amount of ligand bpz*mFc added was 194 mg
(0.5 mmol). The recrystallization was made from
(b) B.M. Trost, Pure Appl. Chem. 68 (1996) 779;
(c) C. Bolm, D. Kaufmann, M. Zehnder, M. Neuburger,
Tetrahedron Lett. 37 (1996) 3985;
˚
(d) J.D. Oslob, B. .Akermark, P. Helquist, P.O. Norrby,
Organometallics 16 (1997) 3015;
(e) C. Larksarp, H. Alper, J. Am. Chem. Soc. 119 (1997) 3709;
˚
(f) H. Hagelin, B. .Akermark, P.-O. Norrby, Organometallics 18
(1999) 2884;
acetoneÁdiethyl ether, giving yellow crystals. Yield:
/
74%. C26H31F3FeN4O3PdS (698.86): Calc. C, 44.69; H,
4.47; N, 8.02; S, 4.59. Found: C, 44.86; H, 4.54; N, 8.06;
(g) J.C. Anderson, R.J. Cubbon, J.D. Harling, Tetrahedron
Asymmetry 10 (1999) 2829;
(h) E. Adams, J.C. Anderson, R. Cubbon, D.S. James, J.P.
S, 4.47%. IR (cmꢁ1) (KBr): 1559 (Cꢁ
Fc); 1263, 1148, 636 (CF3SO3); 1392, 837 (2-Me-C3H4).
/
Npz); 819 (p CH,

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