Intramolecular and interionic structural studies of novel olefin palladium(II) and platinum(II) complexes containing poly(pyrazol-1-yl)borate and -methane ligands. X-ray structures of palladium five-coordinate complexes

Article abstract of DOI:10.1021/om010751p

Complexes [M(η¹,η²-C₈H₁₂OMe)(pz₂ -YH₂)]⁽⁺⁾ (M = Pd, Y = C, 1; M = Pt, Y = C, 2; M = Pt, Y = B, 3) and [M(η¹,η²-C₈H₁₂OMe)(pz₃ -YH)]⁽⁺⁾ (M = Pd, Y = C, 4; M = Pd, Y = B, 5; M = Pt, Y = C, 6; M = Pt, Y = B, 7) were synthesized by the reaction of the dimers [M(η¹,η²-C₈H₁₂OMe)Cl]₂ with the poly(pyrazol-1-yl)borate and -methane ligands. Complexes 1-7 were characterized in solution by multinuclear and multidimensional low-temperature NMR spectroscopy. The solid-state structures of olefinic five-coordinate Pd complexes 4 and 5 were investigated by X-ray single-crystal studies. The relative cation-anion position (interionic structure) was investigated in solution, for all cationic complexes at room and low temperature by ¹⁹F, ¹H-HOESY NMR spectroscopy, and in the solid state for 4. A remarkable specifity of the interionic contacts is observed in solution: the counterion is placed close to the peripheral protons of the pyrazolyl ligands probably due to the partial protection of the apical positions introduced by the nonplanar ligands and the delocalization of the positive charge on the pyrazolyl rings. In the case of complex 4 there is an excellent agreement between the solid state and solution results: the anion selectively interacts with the CH and five protons of the pz₃-CH ligand via an assembly of hydrogen bonds.

Full text of DOI:10.1021/om010751p

346
Organometallics 2002, 21, 346-354
In tr a m olecu la r a n d In ter ion ic Str u ctu r a l Stu d ies of
Novel Olefin P a lla d iu m (II) a n d P la tin u m (II) Com p lexes
Con ta in in g P oly(p yr a zol-1-yl)bor a te a n d -m eth a n e
Liga n d s. X-r a y Str u ctu r es of P a lla d iu m F ive-Coor d in a te
Com p lexes
Barbara Binotti, Gianfranco Bellachioma, Giuseppe Cardaci,
Alceo Macchioni,* and Cristiano Zuccaccia
Dipartimento di Chimica, Universita` di Perugia, Via Elce di Sotto, 8-06123 Perugia, Italy
Elisabetta Foresti and Piera Sabatino
Dipartimento di Chimica “G. Ciamician”, Universita` di Bologna, Via Selmi 2,
40126 Bologna, Italy
Received August 15, 2001
Complexes [M(η1,η2-C8H12OMe)(pz2-YH2)](+) (M ) Pd, Y ) C, 1; M ) Pt, Y ) C, 2; M ) Pt,
Y ) B, 3) and [M(η1,η2-C8H12OMe)(pz3-YH)](+) (M ) Pd, Y ) C, 4; M ) Pd, Y ) B, 5; M ) Pt,
Y ) C, 6; M ) Pt, Y ) B, 7) were synthesized by the reaction of the dimers [M(η1,η2-C8H12-
OMe)Cl]2 with the poly(pyrazol-1-yl)borate and -methane ligands. Complexes 1-7 were
characterized in solution by multinuclear and multidimensional low-temperature NMR
spectroscopy. The solid-state structures of olefinic five-coordinate Pd complexes 4 and 5 were
investigated by X-ray single-crystal studies. The relative cation-anion position (interionic
structure) was investigated in solution, for all cationic complexes at room and low
temperature by 19F, 1H-HOESY NMR spectroscopy, and in the solid state for 4. A remarkable
specifity of the interionic contacts is observed in solution: the counterion is placed close to
the peripheral protons of the pyrazolyl ligands probably due to the partial protection of the
apical positions introduced by the nonplanar ligands and the delocalization of the positive
charge on the pyrazolyl rings. In the case of complex 4 there is an excellent agreement
between the solid state and solution results: the anion selectively interacts with the CH
and five protons of the pz3-CH ligand via an assembly of hydrogen bonds.
In tr od u ction
the counterion. In complexes [Pd(η1,η2-C8H12OMe)-
(bipy)]+X- (where bipy ) 2,2′-bipyridine), which are
active catalysts for the CO/styrene copolymerization,3
the counterion is located in solution above or below the
bipy ligand shifted toward the pyridine ring trans to
the Pd-C σ bond. Interestingly, but not surprisingly
considering the low level of stabilization energy that
determines the average favored structure, the interionic
structure in solution is different than that observed in
the solid state. Furthermore, the least coordinating
anion is, as usual, the best for the catalytic activity of
the organometallic complex.
The importance of having direct structural informa-
tion about transition metal complex ion pairs in solution
is demonstrated daily by the increasing number of
reactions in which the noncovalent anion-cation inter-
actions play a crucial role.1
In the past few years, we have shown that detailed
information about the relative cation-anion position in
solution (interionic structure) can be gained by detecting
interionic dipolar interactions, between nuclei belonging
to the cation and others belonging to its counterion, in
the NOESY and HOESY NMR spectra.2
An increased steric hindrance above and below the
coordination plane should prevent the counterion from
After having investigated “model” compounds, we
have now started to study charged organometallic
complexes that are active homogeneous catalysts,3 or
strictly related to them,4 whose activity is a function of
(2) Bellachioma, G.; Cardaci, G.; Macchioni, A.; Reichenbach, G.;
Terenzi, S. Organometallics 1996, 15, 4349. Macchioni, A.; Bella-
chioma, G.; Cardaci, G.; Gramlich, V.; Ru¨egger, H.; Terenzi, S.;
Venanzi, L. M. Organometallics 1997, 16, 2139. Macchioni, A.; Bella-
chioma, G.; Cardaci, G.; Cruciani, G.; Foresti, E.; Sabatino, P.;
Zuccaccia, C. Organometallics 1998, 17, 5549. Bellachioma, G.; Cardaci,
G.; Gramlich, V.; Macchioni, A.; Valentini, M.; Zuccaccia, C. Organo-
metallics 1998, 17, 5025. Zuccaccia, C.; Bellachioma, G.; Cardaci, G.;
Macchioni, A. Organometallics 1999, 18, 1.
(3) Macchioni, A.; Bellachioma, G.; Cardaci, G.; Travaglia, M.;
Zuccaccia, C.; Milani, B.; Corso, G.; Zangrando, E.; Mestroni, G.;
Carfagna, C.; Formica, M. Organometallics 1999, 18, 3061.
(4) Zuccaccia, C.; Macchioni, A.; Orabona, I.; Ruffo, F. Organome-
tallics 1999, 18, 4367.
* To whom correspondence shoud be addressed. E-mail: alceo@
unipg.it.
(1) Chen, E. Y.-X.; Marks, T. J . Chem. Rev. 2000, 100, 1391, and
references therein. J ohnson, L. K.; Mecking, S.; Brookhart, M. J . Am.
Chem. Soc. 1996, 118, 267. Drent, E.; Budzelaar, P. H. M. Chem. Rev.
1996, 96, 663. Milani, B.; Vicentini, L.; Sommazzi, A.; Garbassi, F.;
Chiarparin, E.; Zangrando, E.; Mestroni, G. J . Chem Soc., Dalton
Trans. 1996, 3139. Lightfoot, A.; Schnider, O.; Pfaltz, A. Angew. Chem.,
Int. Ed. 1998, 37, 2897. Nandi, M.; J in, J .; RajanBadu, T. V. J . Am.
Chem. Soc. 1999, 121, 9899.
10.1021/om010751p CCC: $22.00 © 2002 American Chemical Society
Publication on Web 12/18/2001

Pd Five-Coordinate Complexes
Organometallics, Vol. 21, No. 2, 2002 347
Ch a r t 1
Sch em e 2
Sch em e 1
Five-coordinate complexes 4-7 are stable in both the
solid state and in solution and little sensitive to mois-
ture; as usual, the Pt compounds are more stable than
the Pd ones. Four-coordinate 16-electron complexes are
stable in the solid state and little sensitive to moisture,
while in solution they undergo decomposition processes
that may be initiated by the activation of the Y-H bond.
The stability decreases going from Pt to Pd and from Y
) C to Y ) B; as a confirmation, attempts to synthesize
the four-coordinate complex where M ) Pd and Y ) B
were unsuccessful.
occupying the apical positions. For this reason, we
decided to substitute the planar bipy ligand with
ligands, namely, the bis- and tris(pyrazol-1-yl)borate
and -methane ligands, that can cause steric hindrance
above and below the square planar coordination plane.
In this paper we report the synthesis of four-
coordinate [M(η1,η2-C8H12OMe)(pz2-YH2)](+) (1-3) and
five-coordinate [M(η1,η2-C8H12OMe)(pz3-YH)](+) (4-7)
complexes (Chart 1) and their NMR characterization at
room and low temperature. The interionic structures of
complexes 1, 2, 4, and 6 in methylene chloride deduced
by 19F, 1H-HOESY NMR spectroscopy is described.
Finally, the X-ray molecular structures of five-coordi-
nate 4 and 5 complexes is also reported.
Five-coordinate Pd and Pt olefin complexes are well
known in the literature,7 even if the palladium ones are
much less numerous. However, to our knowledge, there
are no complexes where the olefin takes part in a chelate
ring while the other ligand spans three coordination
sites. Furthermore, five-coordinate Pd olefin complexes
containing the trispyrazolylborate or -methane ligands
are not known; this makes complexes 4 and 5 quite
interesting and pushed us to thoroughly investigate
their structures in both solution and in the solid state
(see below).
Resu lts a n d Discu ssion
NMR In t r a m olecu la r Ch a r a ct er iza t ion . Com-
plexes 1-7 were characterized in CD2Cl2 by 1H, 13C, 19F,
and 31P NMR spectroscopies. All the complexes present
some dynamic processes and were, consequently, inves-
tigated by low-temperature NMR experiments. In par-
ticular, complexes 1-3 undergo exchange of the two
pyrazolyl rings and inversion of the six-membered
chelate rings. Two isomers are present in solution
(indicated with A and B in Scheme 2) and both exchange
their pyrazolyl rings. Complexes 4-7 also undergo
pyrazolyl ring exchange. At low temperature, the reso-
nances of the aromatic protons 3′, 3′′, 5′, and 5′′ of the
two isomers A and B shown in Scheme 2 are separated
(see Chart 2 for the numbering scheme8 of protons and
carbons). Despite this, the inversion of the six-mem-
Syn th esis. Organometallic complexes 1-7 were syn-
thesized according to Scheme 1. The first step of the
reaction5 involves a direct exo attack6 of MeO- on the
coordinated cyclooctadiene of [M(C8H12)Cl2] with the
formation of the dimers [M(η1,η2-C8H12OMe)Cl]2 as air-
stable, pale yellow solids. The latter react in methanol
with bis- and tris(pyrazol-1-yl)methane ligands in the
presence of NH4PF6, forming complexes (1, 2, 4, and 6)
that precipitate from solution. The reactions of the
aforementioned dimers with bis- and tris(pyrazol-1-yl)-
borate ligands afford complexes 3, 5, and 7, which
precipitate from the methanolic solution after the ad-
dition of ethylic ether. Several attempts to synthesize
the Pd complex analogous to 3 were unsuccessful. In
all cases the reaction afforded Pd metal.
1
bered ring (MNNYNN) is still fast compared to the H
(5) For the Pt dimer see: Chatt, J .; Vallarino, L. M.; Venanzi, L.
M. J . Chem. Soc. 1957, 2496. For the Pd dimer see: Chatt, J .;
Vallarino, L. M.; Venanzi, L. M. J . Chem. Soc. 1957, 3413.
(6) Hoel, G. R.; Stockland, R. A., J r.; Anderson, G. K.; Lapido, F. T.;
Braddock-Wilking, J .; Rath, N. P.; Mareque-Rivas, J . C. Organome-
tallics 1998, 17, 1155.
(7) Albano, V. G.; Natile, G.; Panunzi, A. Coord. Chem. Rev. 1994,
133, 67, and references therein.
(8) The numeration of compounds 1-3 follows the same criteria
considering that the ′′′-ring is no longer present and the ring trans to
C1 is again labeled with ′.

348 Organometallics, Vol. 21, No. 2, 2002
Binotti et al.
Ta ble 1. Selected 1H a n d 13C NMR Ch em ica l Sh ift
Va lu es (p p m ) Obta in ed in CD2Cl2
complex
1
4
5
8
3′
3′′
3′′′
1
1H
A
B
A
B
3.38 6.30 5.74 3.75 7.49 7.87
3.18 6.23 5.67 3.59 7.40 7.63
50.0 111.7 106.4 82.5 141.8 142.8
48.7 107.7 104.4 82.3 141.3 142.2
13C
2
1H
A
B
A
B
2.62 5.12 5.28 3.65 7.66 7.98
2.62 5.00 5.21 3.40 7.44 7.75
28.4 90.5 93.6 82.8 141.4 142.5
27.6 87.1 90.6 82.6 140.8 142.5
13C
3
4
5
6
7
1H
2.60 4.96 4.81 3.54 7.33 7.67
26.2 87.5 84.9 83.6 139.5 137.7
13C
1H
3.51 5.35 4.70 3.75 7.26 8.00 7.98
48.2 90.3 81.3 82.7 142.7 142.7 142.7
13C
1H
3.36 5.12 4.53 3.91 7.11 7.91 7.91
43.9 84.9 75.5 83.1 137.6 140.0 141.2
13C
1H
2.81 3.61 3.64 3.72 7.33 8.02 8.08
23.7 58.2 48.0 81.9 139.5 142.2 143.6
F igu r e 1. Section of the 1H-NOESY NMR spectrum
(400.13 MHz, 217 K) of compound 6 recorded in CD2Cl2
showing the assignment of the 3′, 3′′, and 3′′′ protons based
on the “contacts” with the protons belonging to the cy-
clooctenylmethoxy moiety.
13C
1H
2.70 3.24 3.30 3.85 7.12 7.89 7.95
20.5 52.7 42.2 82.2 135.6 139.5 141.2
13C
(see Table 1): they resonate at lower frequency going
(a) from palladium to platinum, (b) from four- to five-
coordinate complexes, and (c) from the (pyrazol-1-yl)-
borate to the -methane ligands. All these trends can be
explained assuming that the correlation between the
low-frequency shift and the extent of π-back-donation
is correct.10 It is in fact known that the π-back-donation
is smaller in Pd compounds, for four-coordinate com-
plexes, and when the ligands are less nucleophilic. In
the case of complex 1, there is no shielding effect; on
the contrary, the proton resonances have a higher
frequency than those due to the protons of free olefin.
NMR In ter ion ic Ch a r a cter iza tion . The interionic
structure of 1, 2, 4, and 6 cationic complexes was
investigated in methylene chloride-d2 at low tempera-
ture (188 K) by detecting the dipolar interactions
between F-nuclei belonging to the anion and H-nuclei
Ch a r t 2
longitudinal relaxation time, and it is not possible to
assign the resonances relative to the A and B isomers.9
The C8 was the starting point for the assignment of
the proton and carbon resonances, as its chemical shift
is known from previous studies and is well separated
from other carbon resonances. H8 was easily assigned
from the 1H, 13C HMQC spectrum. All the proton
resonances of the cyclooctenyl group were then assigned
1
of the cation in the 19F, H-HOESY spectra. The only
interionic dipolar interactions detected were those
between the fluorine atoms of the counterion and the 5
and CHn protons (n ) 2, 1 and 2; n ) 1, 4 and 6). The
resulting interionic structure is depicted in Scheme 3.
1
In Figure 2 the 19F, H-HOESY spectrum of complex 4
1
-
following the scalar connectivity in the H-COSY spec-
is reported and is clearly visible as PF6 interacts
trum. The carbon resonances of this group were again
identified from the 1H, 13C HMQC spectrum. The
assignment of the resonances relative to the pyrazolyl-
rings were carried out on the basis of intramolecular
dipolar interactions detected in the 1H-NOESY spectra.
In particular, for compounds 1-3, the 3′ proton dipolarly
interacts with the olefinic protons 4 and 5, while 3′′
shows a contact with proton 1. For complexes 4-7, the
3′ proton shows a contact with the olefinic protons 4 and
5, 3′′ interacts with 1 and 2, and 3′′′ shows contacts with
8 and OMe (see Figure 1). The other protons of the
pyrazolyl rings and of the YHn groups were assigned
strongly with 5′/5′′′ and CH protons, while it gives only
a very weak contact with 4′/4′′′ protons. No other cross-
1
peaks are present. Figure 3 shows the 19F, H-HOESY
-
spectrum of complex 1; again PF6 interacts only with
CH2, 5′/5′′, and 4′/4′′ (weakly) protons. In our previous
investigations on transition metal complex ion pairs, we
found that there can be two conditions that allow a well-
defined anion-cation relative position: (1) electron
polarizability of the complex that causes an accumula-
tion of positive charge far away from the metal; and (2)
axial steric protection of the metal. The second condition
is naturally reached in octahedral complexes11,12 where
the ion-pair structure is, consequently, determined by
point (1). In the case of square planar complexes, the
axial positions must be sterically protected in order to
prevent the anion from occupying the “natural” position
1
either from the H-COSY or -NOESY spectra. Finally,
their carbons were identified by the 1H, 13C HMQC
spectra.
It is interesting to note that the resonances of 4 and
5 olefinic protons and carbons follow well-defined trends
(10) For a more detailed dicussion about the correlation between
the low-frequency shift of olefinic protons and carbons and the extent
of π-back-donation see: Albano, V. G.; Castellari, C.; Cucciolito, M.
E.; Panunzi, A.; Vitagliano, A. Organometallics 1990, 9, 1269.
(9) Neuhaus, D.; Williamson, M. The Nuclear Overhauser Effect in
Structural and Conformational Analysis; VCH Publishers: New York,
1989.

Pd Five-Coordinate Complexes
Sch em e 3
Organometallics, Vol. 21, No. 2, 2002 349
above and below the coordination plane.4 A degree of
specificity comparable to that of complexes 1 and 2 was
observed only for complex [PtMe(dpa)(Me2SO)]X, where
dpa ) bis(2-pyridyl)amine, which contains two pyridyl
rings separated by a bridging NH group even though
the apical positions are almost free of steric hindrance.13
In such a case, the NH bridging proton has a strong
electropositive character and gives robust hydrogen-
bonding interaction with the counteranion X-. While the
interionic structure of five-coordinate 4 and 6 complexes
can be rationalized with considerations similar to those
valid for octahedral complexes, the interionic structure
of complexes 1 and 2 is not easy to explain. In such cases
the apical positions are only partially protected by the
steric hindrance introduced by the boat conformation
of the MNNYNN cycle and the anion should be able to
occupy the apical position that is not hindered by CH2.
Instead, it prefers to locate in the peripheral part of the
N,N ligand, which leads one to think that the ac-
cumulation of positive charge on the N,N ligands is
considerably higher than the “residual” positive charge
on palladium. Such accumulation could also favor the
formation of F‚‚‚H hydrogen bonds between the CH
moiety and the counteranion.
1
F igu r e 2. 19F, H-HOESY NMR spectrum (376.63 MHz,
188 K) of compound 4 recorded in CD2Cl2 showing the
remarkable specificity of interaction between PF6- and the
5′-5′′′ and 4′-4′′′ protons of the cation. The 1D-trace
-
relative to the PF6 column is reported on the right.
examples of five-coordinate Pd olefin complexes contain-
ing trispyrazolylmethane or trispyrazolylborate ligands
as well as the first examples of cyclooctenyl five-
coordinate Pd complexes. The palladium ligand bonds
are as follows: the axial positions are occupied by one
pyrazolyl nitrogen and the C sp3 atom of the cyclooctenyl
moiety [C(15)-Pd-N(2) 175.6(3)° and 173.9(2)°, Pd-
C(15) 2.048(9), 2.042(6) Å, Pd-N(2) 2.186(6) and 2.168-
(5) Å in 4 and 5, respectively]. The equatorial sites are
occupied by two pyrazolyl nitrogens [Pd-N(4) 2.343(6),
2.226(6) Å and Pd-N(6) 2.254(6), 2.322(5) Å for 4 and
5, respectively] and by the olefin double bond [Pd-C(11)
2.116(8), 2.122(7) Å, Pd-C(12) 2.128(8), 2.110(7) Å,
C(11)-C(12) 1.40 (1) and 1.38(1) Å for 4 and 5, respec-
tively]. The Pd-C interactions can be compared with
those observed in the five-coordinate Pt(II) complex [Pt-
(η1,η2-C8H12-OMe)Cl(Me2Phen)] [2.057(9) and 2.052(7),
2.075(7) Å for the Pt-C axial and the Pt-olefin interac-
tions respectively].14 Only four other examples of five-
coordinate Pt(II) complexes containing the cyclooctenyl
ligand have been found, and their relative Pt-C bond
Molecu la r Str u ctu r es of [P d (η1,η2-C8H12OMe)-
(p z3-CH)][P F 6] (4) a n d [P d (η1,η2-C8H12OMe)(p z3-
BH)] (5). X-ray structural studies of the title complexes
established the five-coordination of the metal center in
both species, instead of the more usual four-coordina-
tion. Structure models of 4 and 5 are reported in Figures
4 and 5, together with their crystallographic numbering,
while the stereogeometries are reported in Table 2.
Complex 4 consists of discrete [Pd(η1,η2-C8H12OMe)(pz3-
CH)]+ cations and PF6 counterions. Both 4 and 5
-
exhibit equivalent stereogeometries and are the first
(11) Bellachioma, G.; Cardaci, G.; D’Onofrio, F.; Macchioni, A.;
Sabatini, S.; Zuccaccia, C. Eur. J . Inorg. Chem. 2001, 1605.
(12) Macchioni, A.; Zuccaccia, C.; Clot, E.; Gruet, K.; Crabtree, R.
H. Organometallics 2001, 20, 2367.
(13) Romeo, R.; Nastasi, N.; Monsu` Scolaro, L.; Plutino, M. R.;
Albinati, A.; Macchioni, A. Inorg. Chem. 1998, 37, 5460.

350 Organometallics, Vol. 21, No. 2, 2002
Binotti et al.
F igu r e 5. Molecular structure of [Pd(η1,η2-C8H12OMe)-
(pz3-BH)] (5) showing the atomic numbering (thermal
ellipsoids at 50% probability level).
1
F igu r e 3. 19F, H-HOESY NMR spectrum (376.63 MHz,
188 K) of compound 1 recorded in CD2Cl2 showing the
-
specificity of interaction between PF6 and the 5′-5′′ and
4-4′′ protons of the cation. The 1D-trace relative to the
Ta ble 2. Releva n t Bon d Dista n ces (Å) a n d An gles
(d eg) for 4 a n d 5
-
PF6 column is reported on the right.
4
5
Pd-N(2)
2.186(6)
2.343(6)
2.254(6)
2.116(8)
2.128(8)
2.048(9)
1.454(10)
1.465(10)
1.438(10)
1.367(9)
1.366(9)
1.357(8)
83.4(2)
83.7(2)
77.5(2)
95.6(3)
98.0(3)
175.6(3)
156.7(3)
118.4(3)
92.4(3)
125.7(3)
164.1(3)
96.7(3)
2.168(5)
2.226(6)
2.322(5)
2.122(7)
2.110(7)
2.042(6)
B-N(1) 1.545(9)
B-N(3) 1.527(10)
B-N(5) 1.543(10)
1.357(7)
1.363(8)
1.343(7)
84.6(2)
85.3(2)
82.5(2)
94.0(2)
96.9(2)
173.9(2)
163.1(2)
125.4(3)
91.5(2)
114.2(2)
152.1(3)
98.8(2)
37.9(3)
88.4(3)
Pd-N(4)
Pd-N(6)
Pd-C(11)
Pd-C(12)
Pd-C(15)
C(1)-N(1)
C(1)-N(3)
C(1)-N(5)
N(1)-N(2)
N(3)-N(4)
N(5)-N(6)
N(2)-Pd-N(4)
N(2)-Pd-N(6)
N(4)-Pd-N(6)
N(2)-Pd-C(11)
N(2)-Pd-C(12)
N(2)-Pd-C(15)
N(4)-Pd-C(11)
N(4)-Pd-C(12)
N(4)-Pd-C(15)
N(6)-Pd- C(11)
N(6)-Pd-C(12)
N(6)-Pd-C(15)
C(11)-Pd-C(12)
C(11)-Pd-C(15)
C(12)-Pd-C(15)
N(1)-C(1)-N(3)
N(1)-C(1)-N(5)
N(3)-C(1)-N(5)
F igu r e 4. Molecular structure of [Pd(η1,η2-C8H12OMe)-
(pz3-CH][PF6] (4) showing the ionic pair and the atomic
numbering (thermal ellipsoids at 30% probability level);
both positions C19 and C19′ for the disordered methyl
group are shown.
38.5(3)
87.7(4)
82.8(4)
111.6(6)
112.2(6)
110.7(6)
81.6(3)
N(1)-B-N(3) 109.4(6)
N(1)-B-N(5) 108.2(6)
N(3)-B-N(5) 110.7(6)
distances, which show great variability (being influ-
enced by the nature of the other equatorial ligands), are
reported in Table 3 for comparison.
The cyclooctenyl ligand forms a five-membered and
a six-membered metallacycle, the latter bearing the
substituent -OMe. The complex molecules are intrinsi-
cally chiral because they contain four chiral centers at
C(11), C(12), C(15), and C(16). Both crystals are racemic
and contain the diastereoisomer with the following
configuration: C(11) R, C(12) S, C(15) R, and C(16) R
(with reference to Figures 4 and 5) and its enantiomer.
The η1,η2-cyclooctenyl ring has the boatlike conforma-
tion usually found for this ligand and exhibits trans-
orientation of the C(16)-O methoxy bond with respect
(14) Albano, V. G.; Castellari, C.; Morelli, G.; Vitagliano, A. Gazz.
Chim. Ital. 1989, 119, 235.

Pd Five-Coordinate Complexes
Organometallics, Vol. 21, No. 2, 2002 351
Ta ble 3. Meta l-to-Ca r bon In ter a ction s (Å) in F ive-Coor d in a te P t a n d P d Cycloocten yl Com p lexes
complex
M-C sp3
M-C sp2
equatorial
axial
[Pt(NO2C6H4)2N4)(η1,η2-C8H12PEt3)(PEt3)]24
[(CO)4Cr(µ-PPh2)(µ-CO)Pt(η1,η2-C8H12)]25
[PtCl2(η1,η2-C8H12{CH(PPh3)CO2Me})]26
[Pt(py)2(η1,η2-C8H12{CH(PPh3)CO2Me})]+ 26
[Pd(η1,η2-C8H12OMe)(pz3-CH][PF6] (4)
[Pd(η1,η2-C8H12OMe)(pz3-BH] (5)
2.079(6)
2.073(7)
2.051(9)
2.057(7)
2.048(9)
2.042(6)
2.095(6), 2.101(7)
2.275(7), 2.272(7)
2.15(1), 2.10(1)
2.140(6), 2.144(7)
2.116(8), 2.128(8)
2.122(7), 2.110(7)
to the C(15)-Pd bond. Complex 4 shows two different
orientations of the carbon atom belonging to the meth-
oxy group (see Experimental Section).
The trispyrazolylmethane or trispyrazolylborate
ligands are usually found as trihapto donors in octahe-
dral complexes,15 otherwise they behave like dihapto
donors in square planar complexes according to the
electronic requirements of the metal centers.16 In the
present complexes, the ligand trihapticity is stabilized
by the attainment of the effective atomic number of the
metal center. The Pd-N distances in 4 and 5 show that
the axial bonds are shorter than the equatorial ones. A
similar effect was observed in the platinum complex [Pt-
(C2H4)Cl(py)(Me2phen)]+.17 It is also noteworthy that the
equatorial Pd-N bonds are not equivalent [2.343(6),
2.254(6) Å in 4 and 2.322(5), 2.226(6) Å in 5], differing
from what was observed in octahedral Pd complexes
containing tridentate trispyrazolyl ligands which exhibit
very similar values [average 2.182 Å].15
In complex 4, however, the major focus of the solid-
state structure lies in the position of the anion with
respect to the cation. The formation of an ion pair is
evident with preferential interactions involving anion
fluorine atoms and trispyrazolyl ligand (Figure 4).
H-bonding interactions are established between the
highly polarized H-C(N)3 proton and fluorine lone pairs.
The strongest contacts have the following geometries:
C(1)-H(1)‚‚‚F(2) 3.16 Å, angle 165.6°; C(1)-H(1)‚‚‚F(5)
3.20 Å, angle 137.1°; C(2)-H(2)‚‚‚F(5) 3.25 Å, angle
117.4°. Weaker interactions are as follows: C(8)-H(8)‚
‚‚F(5) 3.32 Å, angle 123.5°; C(5)-H(5)‚‚‚F(2) 3.43 Å,
angle 130.6°; and C(2)-H(2)‚‚‚F(4) 3.52 Å, angle 161.1°.
The remaining three fluorine atoms are implied in
H-bonding interactions of the weaker type with three
different symmetry-related cations.
A cation-cation H-bonding interaction occurs be-
tween C(5)-H(5) and the symmetry-related O(1) atom
[x, y-1, z] with a contact 3.25 Å long and an angle of
135.6°.
The anion-cation recognition is therefore extremely
specific, analogous to what is observed in solution, and
quite strong due to the formation of an assembly of
hydrogen bonds within the ion pair, with the strongest
interactions involving the -CH group. The space-filling
representation of the ion pair (Figure 6) clearly shows
the cation pocket where the anion fits in a sort of
docking process. Actually, the cation positive charge is
mainly localized on the pyrazolyl moiety, producing a
F igu r e 6. Space-filling diagram of complex 4 with the
same orientation as in Figure 4; only C19 is shown, for
clarity.
significantly polarized C-H group. The present example
of cation-anion recognition will be compared with both
solid-state and solution structures of analogous com-
plexes containing different anions of comparable shape
and size, capable of behaving as proton acceptors.
Ca ta lytic Tests. Complexes 1 and 4 were tested as
catalysts for the CO/styrene copolymerization carried
out in methylene chloride at room temperature and at
atmospheric pressure. Complex 4 is not active at all,
while complex 1 affords oligomers but decomposes into
Pd metal within a few minutes. The analogous complex
[Pd(η1,η2-C8H12OMe)(bipy)]+PF6- is a good catalyst for
the CO/styrene copolymerization carried out under the
same conditions. The reduction of the catalytic activity
due to the substitution of the bipy ligand with the
bispyrazolyl ligand can be explained by considering that
the second is a weaker σ-donor compared to the first.18
This makes complex 1 more electrophilic than complex
[Pd(η1,η2-C8H12OMe)(bipy)]+PF6 but also less stable.
-
Con clu sion s
We have reported the synthesis of neutral and cat-
ionic four-coordinate compounds [M(η1,η2-C8H12OMe)-
(pz2-YH2)](+) (where M ) Pd and Pt; Y ) B and C).
-
(15) Byers, P. K.; Canty, A. J .; Skelton, B. W.; White, A. H.
Organometallics 1990, 9, 826. Canty, A. J .; J in, H.; Roberts, A. S.;
Skelton, B. W.; Traill, P. R.; White, A. H. Organometallics 1995, 14,
199. Canty, A. J .; J in, H.; Roberts, A. S.; Skelton, B. W.; White, A. H.
Organometallics 1996, 15, 5713.
(16) Valk, J . M.; Maassarani, F.; van der Sluiss, P.; Spek, A. L.;
Boersma, J .; van Koten, G. Organometallics 1994, 13, 2320. Akita, M.;
Miyaji, T.; Hikichi, S.; Moro-oka, Y. Chem. Commun. 1998, 1005.
(17) Albano, V. G.; Castellari, C.; Monari, M.; De Felice, V.; Panunzi,
A.; Ruffo, F. Organometallics 1992, 11, 3665.
Compound 1 (where M ) Pd, Y ) C, and having PF6
as counterion) catalyzes the CO/styrene oligomerization,
even if its efficiency is limited by its stability.
Five-coordinate compounds [M(η1,η2-C8H12OMe)-
(pz3-YH)](+) (where M ) Pd and Pt; Y ) B and C) are
(18) Tsuji, S.; Swenson, D. C.; J ordan, R. F. Organometallics 1999,
18, 4758, and references therein.

352 Organometallics, Vol. 21, No. 2, 2002
Binotti et al.
4′′B), 108.4 (s, 4′A or 4′B), 108.1 (s, 4′B or 4′A), 106.4 (s, 5A or
5B), 104.4 (s, 5B or 5A), 82.5 (s, 8A or 8B), 82.3 (s, 8B or 8A),
63.5 (s, CH2A and CH2B), 57.1 (s, OMeA and OMeB), 50.0 (s,
1A or 1B), 48.7 (s, 1B or 1A), 34.6 (s, 2A or 2B), 34.1 (s, 2B or
2A), 30.3 (s, 7A or 7B), 30.1 (s, 7B or 7A), 29.2 (s, 6A and 6B),
27.6 (s, 3A or 3B), 26.7 (s, 3B or 3A). 31P{1H} NMR (CD2Cl2,
also reported. The Pd compounds represent, to our
knowledge, the first olefin five-coordinate compounds
containing the trispyrazolyl ligands as well as the first
examples of cyclooctenyl five-coordinate Pd complexes.
The interionic structure of all the cationic compounds
was investigated in methylene chloride solution by 19F,
1H-HOESY NMR spectroscopy. There is a remarkable
specificity in the interaction between the cation and
1
200 K): δ -143.2 (sept, J PF ) 711). 19F NMR (CD2Cl2, 200
1
K): δ -72.1 (d, J FP ) 711).
P r ep a r a t ion a n d Ch a r a ct er iza t ion of Com p lex 2.
pz2-CH2 (48 mg, 0.32 mmol) was added to a suspension of [Pt-
(η1,η2-C8H12OMe)Cl]2 (100 mg, 0.14 mmol) in methanol (3 mL)
at room temperature. The suspension became a colorless
solution; NH4PF6 (88 mg, 0.54 mmol) and ethyl ether (1 mL)
were added, and the solution was put in the refrigerator at
-18 °C. After 12 h, complex 2 precipitated; it was filtered off,
washed with ethyl ether, and dried under vacuum. Yield: 66%.
1H NMR (CD2Cl2, 192 K): δ 8.23 (br, 5′′A or 5′′B), 8.21 (br,
5′′B or 5′′A), 8.07 (br, 5′A and 5′B), 7.98 (br, 3′′A or 3′′B), 7.75
(br, 3′′B or 3′′A), 7.66 (br, 3′A or 3′B), 7.44 (br, 3′B or 3′A),
anion that is incredibly higher than that observed in
-
similar compounds [Pd(η1,η2-C8H12OMe)(bipy)]+PF6
,
where the N,N ligand is planar. In fact, while in these
compounds the anion interacts preferentially with the
protons belonging to the bipy ligand but still “sees” the
protons belonging to the cyclooctenyl ligand that are
closer to the metal, in these newly reported complexes
the counterion interacts exclusively with the peripheral
protons of the pyrazolyl ligands. We believe that such
unexpected specificity must be due not only to the
partial protection of the apical position exerted by the
pyrazolyl ligands but also to a considerable delocaliza-
tion of the positive charge on the pz rings. All the
spectroscopic evidence fully agrees with the identifica-
tion of a specific ion pair in the crystalline state,
stabilized by an assembly of cation-anion hydrogen
bonds.
2
6.72 (brd, J HH ) 14.7, CH2ax), 6.63 (br, CH2ax, 4′′A and 4′′B),
2
6.56 (brd, J HH ) 13.8, CH2eq), 6.49 (br, CH2eq, 4′A and 4′B),
5.28 (br, 5A or 5B), 5.21 (br, 5B or 5A), 5.12 (br, 4A or 4B),
5.00 (br, 4B or 4A), 3.65 (br, 8A or 8B), 3.40 (br, 8B or 8A),
3.30 (br, OMeA or OMeB), 3.17 (br, OMeB or OMeA), 2.97 (br,
3A and 3B), 2.62 (br, 1A, 1B, 2A, and 2B), 2.35 (br, 6A and
6B), 2.04 (br, 6A and 6B), 1.79 (br, 7A and 7B), 1.73 (br, 7A
and 7B). 13C{1H} NMR (CD2Cl2, 192 K): δ 142.5 (s, 3′′A and
3′′B), 141.4 (s, 3′A or 3′B), 140.8 (s, 3′B or 3′A), 136.1 (s, 5′′A
or 5′′B), 135.6 (s, 5′′B or 5′′A), 134.9 (s, 5′A or 5′B), 134.1 (s,
5′B or 5′A), 109.0 (s, 4′′A and 4′′B), 108.6 (s, 4′A and 4′B), 93.9
(s, 5A or 5B), 90.6 (s, 5B or 5A), 90.5 (s, 4A or 4B), 87.1 (s, 4B
or 4A), 82.8 (s, 8A or 8B), 82.6 (s, 8B or 8A), 63.2 (s, CH2A and
CH2B), 56.6 (s, OMeA or OMeB), 56.5 (s, OMeB or OMeA),
33.2 (s, 7), 29.2 (s, 3), 28.9 (s, 2 and 6), 28.7 (s, 2), 28.4 (s, 1A
or 1B), 27.6 (s, 1B or 1A). 31P{1H} NMR (CD2Cl2, 302 K): δ
Exp er im en ta l Section
One- and two-dimensional 1H, 13C, 31P, and 19F NMR spectra
were measured on Bruker DPX 200 and DRX 400 spectrom-
eters. Referencing is relative to TMS (1H and 13C) and CCl3F
(19F). NMR samples were prepared dissolving about 20 mg of
1
compound in 0.5 mL of CD2Cl2. Two-dimensional H-NOESY
1
-143.1 (sept, J PF ) 711). 19F NMR (CD2Cl2, 192 K): δ -71.9
and 19F, 1H-HOESY spectra were recorded with a mixing time
1
(d, J FP ) 711).
of 500-800 ms. Complexes M(C8H12)Cl2 (M ) Pd19 and Pt20
)
P r ep a r a t ion a n d Ch a r a ct er iza t ion of Com p lex 3.
pz2-BH2 (60 mg, 0.32 mmol) was added to a suspension of [Pt-
(η1,η2-C8H12OMe)Cl]2 (100 mg, 0.14 mmol) in methanol (3 mL)
at 0 °C. The suspension became a yellow solution; it was put
in the refrigerator at -18 °C. After 12 h, complex 3 precipi-
tated; it was filtered off, washed with cold methanol, and dried
and [M(η1,η2-C8H12OMe)Cl]25 were prepared as reported in the
literature.
P r ep a r a t ion a n d Ch a r a ct er iza t ion of Com p lex 1.
pz2-CH2 (79 mg, 0.53 mmol) was added to a suspension of [Pd-
(η1,η2-C8H12OMe)Cl]2 (100 mg, 0.18 mmol) in methanol (5 mL)
at room temperature. The suspension became a yellow solu-
tion; NH4PF6 (232 mg, 1.42 mmol) was added, and the solution
was put in the refrigerator at -18 °C. After 12 h, complex 1
precipitated; it was filtered off, washed with ethyl ether, and
dried under vacuum. Yield: 60%. 1H NMR (CD2Cl2, 195 K): δ
8.11 (d,3J HH ) 2.5, 5′′A and 5′′B), 7.98 (br, 5′A or 5′B), 7.96
1
under vacuum. Yield: 56%. H NMR (CD2Cl2, 230 K): δ 7.67
(d, 3J HH ) 2.3, 3′′ and 5′′), 7.56 (dd, 3J HH ) 2.2, 4J HH ) 0.5, 5′),
3
3
7.33 (br, 3′), 6.35 (t, J HH ) 2.3, 4′′), 6.23 (t, J HH ) 2.1, 4′),
4.96 (td, 3J HH ) 8.6, 3J HH ) 3.0, 4), 4.81 (br, 5), 3.54 (brd, 3J HH
) 10.4, 8), 3.24 (s, OMe), 2.88 (brd, J HH ) 17.6, 6), 2.60 (m, 1
2
and 6), 2.33 (m, 3), 1.96 (m, 3), 1.89 (m, 2), 1.85 (m, 2), 1.76
(m, 7). 13C{1H} NMR (CD2Cl2, 230 K): δ 139.5 (s, 3′), 137.7 (s,
3′′), 137.2 (s, 5′), 136.1 (s, 5′′), 105.7 (s, 4′′), 105.5 (s, 4′), 87.4
(s, 4), 84.9 (s, 5), 83.6 (s, 8), 56.0 (s, OMe), 33.4 (s, 7), 29.4 (s,
2), 29.1 (s, 6), 28.6 (s, 3), 26.2 (s, 1).
(br, 5′B or 5′A), 7.87 (br, 3′′A or 3′′B), 7.63 (br, 3′′B or 3′′A),
2
7.49 (br, 3′A or 3′B), 7.40 (br, 3′B or 3′A), 6.66 (brd, J HH
)
14.1, CH2eqA and CH2eqB),21 6.55 (t, 3J HH ) 2.5, 4′′A and 4′′B),
6.54 (brd buried under 4′′, CH2axA or CH2axB), 6.42 (brd, J HH
2
) 14.1, CH2axB or CH2axA), 6.39 (br, 4′A and 4′B), 6.30 (br, 4A
or 4B), 6.23 (br, 4B or 4A), 5.74 (br, 5A or 5B), 5.67 (br, 5B or
5A), 3.75 (br, 8A or 8B), 3.59 (br, 8B or 8A), 3.38 (br, 1A or
1B), 3.35 (s, OMeA or OMeB), 3.20 (s, OMeB or OMeA), 3.18
(br, 1B or 1A), 2.76 (br, 6A and 6B), 2.38 (br, 3A, 3B, 2A or
2B), 2.03 (br, 7A and 7B), 1.67 (br, 2B or 2A). 13C{1H} NMR
(CD2Cl2, 195 K): δ 142.8 (s, 3′′A or 3′′B), 142.2 (s, 3′′B or 3′′A),
141.8 (s, 3′A or 3′B), 141.3 (s, 3′B or 3′A), 135.3 (s, 5′′A or 5′′B),
135.0 (s, 5′′B or 5′′A), 134.4 (s, 5′A or 5′B), 133.7 (s, 5′B or
5′A), 111.7 (s, 4A or 4B), 109.7 (s, 4B or 4A), 108.6 (s, 4′′A and
P r ep a r a t ion a n d Ch a r a ct er iza t ion of Com p lex 4.
pz3-CH (92 mg, 0.43 mmol) was added to a suspension of [Pd-
(η1,η2-C8H12OMe)Cl]2 (100 mg, 0.18 mmol) in methanol (5 mL)
at room temperature. The suspension became a pale yellow
solution; NH4PF6 (117 mg, 0.72 mmol) was added and after
10 min, complex 4 started to precipitate; it was filtered off,
washed with ethyl ether, and dried under vacuum. Yield: 65%.
1H NMR (CD2Cl2, 188 K): δ 8.74 (s, CH), 8.16 (br, 5′′ and 5′′′),
8.11 (br, 5′), 8.00 (br, 3′′ or 3′′′), 7.98 (br, 3′′′ or 3′′), 7.26 (br,
3′) 6.49 (br, 4′′ and 4′′′), 6.35 (br, 4′), 5.35 (br, 4), 4.70 (brd,2J HH
) 8.2, 5), 3.75 (br, 8), 3.51 (br, 1), 3.18 (s, OMe), 2.54 (br, 6),
2.34 (br, 2 and 3), 2.14 (br, 3), 1.99 (br, 7), 1.62 (br, 2). 13C-
{1H} NMR (CD2Cl2, 217 K): δ 142.7 (br, 3′, 3′′, and 3′′′), 133.5
(s, 5′, 5′′, and 5′′′), 108.1 (s, 4′, 4′′, and 4′′′), 90.3 (s, 4), 82.7 (s,
8), 81.3 (s, 5), 76.6 (s, CH), 57.0 (s, OMe), 48.2 (s, 1), 35.2 (s,
2), 30.5 (s, 7), 28.2 (s, 6), 27.3 (s, 3). 31P{1H} NMR (CD2Cl2,
(19) Scultz, R. J . Organomet. Chem. 1966, 6, 435.
(20) Clark, H. C.; Manzer, L. E. J . Organomet. Chem. 1973, 59, 411.
(21) CH2eq and CH2ax indicate the CH2 protons of the A and B
structures reported in Scheme 2 that can be considered pseudoequa-
torial and pseudoaxial with respect to the coordination plane. The
distinction between CH2eq and CH2ax was made by considering that
equatorial protons belonging to A and B conformational isomers
(Scheme 2) are less magnetically different and should show chemical
shift values that are more similar than the axial ones.
1
302 K): δ -142.6 (sept, J PF ) 711). 19F NMR (CD2Cl2, 188
1
K): δ -70.9 (d, J FP ) 711).

Pd Five-Coordinate Complexes
Organometallics, Vol. 21, No. 2, 2002 353
Ta ble 4. Cr ysta l Da ta a n d Deta ils of Str u ctu r e Refin em en t for Com p lexes 4 a n d 5
4
5
empirical formula
fw
C
19H25F6N6OPPd
C18H25BN6OPd
458.65
604.82
temp (K)
223
293
wavelength (Å)
cryst syst
space group
unit cell dimens
0.71069
monoclinic
C2/c
a ) 23.249(5), b ) 10.530(5),
c ) 20.646(5) Å; â ) 109.53°
4764(3)
8
1.687
2432
0.71069
monoclinic
P21/c
a ) 12.280(2), b ) 12.702(3), c ) 13.751(2) Å;
â ) 113.63°
1965(1)
volume (Å3)
Z
density (Mg/m3)
F(000)
4
1.550
936
cryst size (mm)
θ range for data collection
index range
0.3 × 0.3 × 0.5
0.3 × 0.2 × 0.4
2-25°
2-25°
-25 e h e 25, 0 e k e 12,
0 e l e 24
-14 e h e 13, 0 e k e 15,
0 e l e 16
no. of reflns collected
4271
3598
no. of data/restraints/params
4143/10/300
1.009
3441/0/164
1.033
goodness-of-fit on F2
2
2
final R indices [I > 2σ(I)]
R indices (all data)
largest diff peak and hole (e Å-3
R ) 0.0540, Rw ) 0.159
R ) 0.040, Rw ) 0.109
R ) 0.109, Rw2) 0.189
1.58 and -0.859
R ) 0.114, Rw2 ) 0.133
1.21 and -0.68
)
P r ep a r a t ion a n d Ch a r a ct er iza t ion of Com p lex 5.
pz3-BH (88 mg, 0.37 mmol) was added to a suspension of [Pd-
(η1,η2-C8H12OMe)Cl]2 (100 mg, 0.18 mmol) in methanol (3 mL)
at room temperature. The suspension became a colorless
solution; after 30 min, complex 5 started to precipitate; after
2 h it was filtered off, washed with cold methanol, and dried
(br, 3′), 6.34 (br, 4′′ and 4′′′), 6.22 (br, 4′), 4.52 (vbr, BH), 3.85
3
3
(brd, J HH ) 10.0, 8), 3.30 (m, 5), 3.24 (t, J HH ) 8.2, 4), 3.20
3
(s, OMe), 2.70 (brd, J HH ) 6.6, 1), 2.33 (m, 6), 2.19 (m, 3),
2.08 (m, 2), 1.83 (m, 7), 1.66 (m, 2), 1.53 (m, 3). 13C{1H} NMR
(CD2Cl2, 217 K): δ 141.2 (s, 2J CPt ) 33.1, 3′′′), 139.5 (s, 2J CPt
)
42.0, 3′′), 136.3 (s, 5′), 136.0 (s, 5′′′), 135.9 (s, 5′′), 135.6 (s, 3′),
1
1
under vacuum. Yield: 68%. H NMR (CD2Cl2, 217 K): δ 7.91
(br, 3′′ and 3′′′), 7.76 (br, 5′′ and 5′′′), 7.68 (br, 5′), 7.11 (br, 3′),
105.9 (s, 4′), 105.8 (s, 4′′′), 105. 8 (s, 4′′), 82.2 (s, J CPt ) 11.2,
8), 56.2 (s, OMe), 52.7 (s, 1J CPt ) 375.4, 4), 42.2 (s, 2J CPt ) 369.6,
3
3
2
2
6.32 (br, 4′′ and 4′′′), 6.18 (br, 4′), 5.12 (td, J HH ) 8.7, J HH
)
5), 35.3 (s, J CPt ) 47.0, 2), 29.7 (s, J CPt ) 18.9, 7), 29.5 (s, 3),
2 1
2.9, 4), 4.51 (vbr, BH), 4.53 (d, 3J HH ) 7.8, 5), 3.91 (m, 8), 3.36
27.3 (s, J CPt ) 34.2, 6), 20.5 (s, J CPt ) 626.4, 1).
3
(d, J HH ) 4.5, 1), 3.22 (s, OMe), 2.54 (m, 6), 2.46 (m, 2), 2.38
X-r a y Cr ysta llogr a p h y. Crystals of 4 and 5 suitable for
X-ray single-crystal studies were precipitated from dichlo-
romethane/ethanol. Diffraction intensities were collected at
room temperature on an Enraf-Nonius CAD-4 diffractometer
using graphite-monochromated Mo KR radiation. The data
were collected using an ω/2θ scanning technique and corrected
for absorption empirically. Crystal data and details of structure
refinement are reported in Table 4. Five independent data
collections were performed for 4 on crystals from different
crystallization batches both at room temperature and at 223
K, trying to overcome the disorder problems inherent to the
cation structure. Finally, the set of data at 223 K, with the
highest number of observed reflections, revealed the most
ordered cation model and was therefore used for structure
solving and refinement. Both structures were solved by direct
methods and refined on F2 by full matrix least squares
calculations using the SHELXTL/PC package.22 Thermal
vibrations were treated anisotropically except for the OMe
fragment of 4; H atoms were geometrically positioned [C-H
0.96 Å ] and refined “riding” on their corresponding carbon
atoms. For 4, the carbon atom of the OMe appendage was
found affected by positional disorder over two orientations.
Refinement of the relative contribution to each orientation
converged to an occupancy factor ratio of 50:50 (Figure 4). That
accounts for the apparent very short C-C contact for C(19)
with its symmetry equivalent to 1-x, y, 1.5-z, where the
carbon atom has a different position at C(19′). The first
neighbor of each molecule is the one with the opposite
orientation at the -OMe group, and the contact does not occur
in the crystal lattice. Taking this disorder into account as well
as the greater flexibility of the cyclooctenyl ring in 4, it can be
concluded that the packing of 4, despite the presence of the
ionic pair, seems to be looser than the packing of 5. Refinement
2
3
(m, 3), 2.13 (m, 3), 1.99 (m, 7), 1.70 (dd, J HH ) 14.1, J HH
)
7.8, 2). 13C{1H} NMR (CD2Cl2, 217 K): δ 141.2 (s, 3′′ or 3′′′),
140.0 (s, 3′′′ or 3′′), 137.6 (s, 3′), 136.0 (s, 5′′ and 5′′′), 135.6 (s,
5′), 105.5 (s, 4′), 105.3 (s, 4′′ and 4′′′), 84.9 (s, 4), 83.1 (s, 8),
75.5 (s, 5), 56.6 (s, OMe), 43.9 (s, 1), 34.8 (s, 2), 30.6 (s, 7),
28.3 (s, 6), 27.8 (s, 3).
P r ep a r a t ion a n d Ch a r a ct er iza t ion of Com p lex 6.
pz3-CH (70 mg, 0.32 mmol) was added to a suspension of [Pt-
(η1,η2-C8H12OMe)Cl]2 (100 mg, 0.14 mmol) in methanol (5 mL)
at room temperature. The suspension became a pale yellow
solution; NH4PF6 (88 mg, 0.54 mmol) was added and after 10
min, complex 6 started to precipitate; it was filtered off,
washed with ethyl ether, and dried under vacuum. Yield: 59%.
1H NMR (CD2Cl2, 217 K): δ 8.96 (s, CH), 8.32 (d,3J HH ) 2.7,
3
3
5′′ and 5′′′), 8.30 (d, J HH ) 2.7, 5′), 8.08 (d, J HH ) 2.0, 3′′′),
3
3
3
8.02 (d, J HH ) 2.0, 3′′), 7.33 (d, J HH ) 2.0, 3′), 6.59 (t, J HH
)
3
3
2.3, 4′′), 6.58 (t, J HH ) 2.3, 4′′′), 6.48 (t, J HH ) 2.3, 4′), 3.72
3
3
(dd, J HH ) 8.11, J HH ) 3.3, 8), 3.64 (m, 5), 3.61 (m, 4), 3.21
3
3
(s, OMe), 2.81 (brd, J HH ) 6.45, 1), 2.34 (brd, J HH ) 7.05, 6),
2.21 (m, 3), 2.04 (m, 2), 1.86 (br, 7), 1.80 (dd, 2J HH ) 11.5, 3J HH
2
3
2
) 7.94, 7), 1.67 (dd, J HH ) 14.0, J HH ) 6.2, 2), 1.59 (dd, J HH
) 14.0, 3J HH ) 8.2, 3). 13C{1H} NMR (CD2Cl2, 217 K): δ 143.6
(s, 3′′′), 142.2 (s, 3′′), 139.5 (s, 3′), 134.1 (s, 5′), 133.7 (s, 5′′ or
5′′′), 133.4 (s, 5′′′ or 5′′), 108.7 (s, 4′), 108.6 (s, 4′′ and 4′′′), 81.9
(s, 8), 77.3 (s, CH), 58.2 (s, 4), 56.5 (s, OMe), 48.0 (s, 5), 35.3
(s, 2), 29.4 (s, 7), 28.9 (s, 3), 27.2 (s, 6), 23.7 (s, 1). 31P{1H}
NMR (CD2Cl2, 217 K): δ -142.8 (sept, J PF ) 711). 19F NMR
(CD2Cl2, 217 K): δ -70.9 (d, J FP ) 711).
1
1
P r ep a r a t ion a n d Ch a r a ct er iza t ion of Com p lex 7.
pz3-BH (77 mg, 0.32 mmol) was added to a suspension of [Pt-
(η1,η2-C8H12OMe)Cl]2 (100 mg, 0.14 mmol) in methanol (3 mL)
at room temperature. Complex 7 immediately precipitated
from solution. After 30 min, it was filtered off, washed with
cold methanol, and dried under vacuum. Yield: 69%. 1H NMR
(22) SHELXTLplus Version 5.1 (Windows NT version) Structure
Determination Package; Siemens Analytical X-ray Instruments Inc.:
Madison, WI, 1998.
3
(CD2Cl2, 217 K): δ 7.95 (br, 3′′′), 7.89 (br, 3′′), 7.83 (d, J HH
)
3
3
1.9, 5′′′), 7.81 (d, J HH ) 1.9, 5′′), 7.75 (d, J HH ) 1.9, 5′), 7.12

354 Organometallics, Vol. 21, No. 2, 2002
Binotti et al.
2
converged at a final R ) 0.054, Rw ) 0.16, S ) 1.01 for 4, R
and Prof. Vincenzo G. Albano for useful discussions.
This work was supported by grants from the Ministero
dell’Universita` e della Ricerca Scientifica e Tecnologica
(MURST, Rome, Italy), Programma di Rilevante Inter-
esse Nazionale, Cofinanziamento 2000-1.
2
) 0.040, Rw ) 0.11, S ) 1.03 for 5.
Molecular graphics were prepared using ORTEP3 for Win-
dowsNT.23
Ack n ow led gm en t. The authors wish to thank Dr.
Barbara Milani for catalytic tests of complexes 1 and 4
Su p p or tin g In for m a tion Ava ila ble: A listing of atomic
coordinates, bond lengths and angles, and anisotropic thermal
parameters. Crystallographic files for both complexes 4 and
5. This material is available free of charge via the Internet at
http://pubs.acs.org.
(23) Farrugia, L. J . J . Appl. Crystallogr. 1997, 565.
(24) Overbosch, P.; van Koten, G.; Grove, D. M.; Spek, A. L.;
Duisenberg, A. J . M. Inorg. Chem. 1982, 21, 3254.
(25) Powell, J .; Gregg, M. R.; Sawyer, J . F. Inorg. Chem. 1989, 28,
4451.
(26) Vicente, J .; Chicote, M. T.; MacBeath, C.; Baez, J . F.; Bautista,
D. Organometallics 1999, 18, 2677.
OM010751P