Synthesis and insertion reactions of the cyclometalated palladium-alkyl complexes Pd(CH2CME2-o-C6H4)L2. Observation of a pentacoordinated intermediate in the insertion of SO2

Article abstract of DOI:10.1021/ic010114r

Palladacycles of the type Pd(CH₂CMe₂-o-C₆H₄)L₂, 2, have been synthesized by treatment of the corresponding chloroalkylcomplexes Pd(CH₂CMe₂C₆H₅)ClL₂ (L₂ = (PMe₃)₂, 2a, or 1,5-cyclooctadiene (cod), 2b) with suitable bases, or by simple ligand exchange reactions from the cyclooctadiene derivative 2b. The metallacycles 2 react with activated alkynes and with sulfur dioxide, giving rise to different insertion products.

Full text of DOI:10.1021/ic010114r

4116
Inorg. Chem. 2001, 40, 4116-4126
Synthesis and Insertion Reactions of the Cyclometalated Palladium-Alkyl Complexes
Pd(CH2CMe2-o-C6H4)L2. Observation of a Pentacoordinated Intermediate in the Insertion
of SO2
J. Ca´mpora,* J. A. Lo´pez, P. Palma,* D. del Rio, and E. Carmona
Departamento de Qu´ımica Inorga´nica-Instituto de Investigaciones Qu´ımicas, Universidad de
Sevilla-Consejo Superior de Investigaciones Cient´ıficas, c/Americo Vespucio s/n, Isla de la Cartuja,
41092 Sevilla, Spain
P. Valerga
Departamento de Ciencia de Materiales, Ingenieria Metalu´rgica y Qu´ımica Inorga´nica, Facultad de
Ciencias, Universidad de Ca´diz, Apdo 40, 11510 Puerto Real, Ca´diz, Spain
C. Graiff and A. Tiripicchio
Dipartimento di Chimica Generale ed Inorganica, Chimica Analitica, Chimica Fisica, Universita` di
Parma, Centro di Studio per la Strutturistica Diffrattometrica del CNR, Viale delle Scienze,
I-43100 Parma, Italy
ReceiVed January 29, 2001
Palladacycles of the type Pd(CH2CMe2-o-C6H4)L2, 2, have been synthesized by treatment of the corresponding
chloroalkylcomplexes Pd(CH2CMe2C6H5)ClL2 (L2 ) (PMe3)2, 2a, or 1,5-cyclooctadiene (cod), 2b) with suitable
bases, or by simple ligand exchange reactions from the cyclooctadiene derivative 2b. The metallacycles 2 react
with activated alkynes and with sulfur dioxide, giving rise to different insertion products.
Introduction
compound Ni(CH2CMe2-o-C6H4)(PMe3)2 has been exploited in
The chemistry of group 10 metallacycles has experienced an
important development in the past years due to the involvement
of these compounds as intermediates in different types of
catalytic reactions and to their numerous applications in organic
synthetically useful transformations, and its study has provided
a good model for metallacyclic reactivity.2 In addition, the
mechanism of the formation of the corresponding platinum
complexes is now well understood, on the basis of the detailed
studies carried out by Young and co-workers.3 Therefore, it is
somewhat surprising that, despite the well-known ability of
palladium complexes to undergo cyclometalation processes,4 the
synthesis.1 Benzannelated complexes of the type M(CH2CMe2-
o-C6H4)L2 (M ) Ni,2a,b Pt3) stand among the best studied
metallacycles of this group, due in part to their ready synthesis
by thermal decomposition of the bis(neophyl) derivatives
M(CH2CMe2C6H5)2L2. The rich insertion chemistry of the nickel
corresponding palladium metallacycles Pd(CH2CMe2-o-C6H4)-
L2 have been reported only recently in preliminary form.5 In
this paper we provide full details for the synthesis of this type
(1) (a) Ca´mpora, J.; Palma, P.; Carmona, E. Coord. Chem. ReV. 1999,
193-195, 207-205. (b) Smith, A. K. In ComprehensiVe Organome-
tallic Chemistry II; Abel, E. W., Stone, F. G. A., Wilkinson, G., Eds.;
Puddephatt, R. J., Vol. Ed.; Pergamon: Oxford, 1995; Vol. 9, p 29.
(c) Canty, A. J. In ComprehensiVe Organometallic Chemistry II; Abel,
E. W., Stone, F. G. A., Wilkinson, G., Eds.; Puddephatt, R. J., Vol.
Ed.; Pergamon: Oxford, 1995; Vol. 9, p 225. (d) Anderson, G. K. In
ComprehensiVe Organometallic Chemistry II; Abel, E. W., Stone, F.
G. A., Wilkinson, G., Eds.; Puddephatt, R. J., Vol. Ed.; Pergamon:
Oxford, 1995; Vol. 9, p 431.
of metallacycle, including the cyclooctadiene derivative Pd(CH2-
CMe2-o-C6H4)(cod), 2b, which is a useful starting material, that
allows the introduction of a variety of co-ligands. Additionally,
we describe their reactivity toward unsaturated molecules such
as alkynes and SO2.
Results and Discussion
(2) (a) Carmona, E.; Palma, P.; Paneque, M.; Poveda, M. L.; Gutie´rrez-
Puebla, E.; Ruiz, C. J. Am. Chem. Soc. 1986, 108, 6424. (b) Carmona,
E.; Palma, P.; Paneque, M.; Poveda, M. L.; Gutie´rrez-Puebla, E.;
Monge, A. Polyhedron 1989, 8, 1069. (c) Ca´mpora, J.; Llebar´ıa, A.;
Moreto´, J. M.; Poveda, M. L.; Carmona, E. Organometallics 1993,
12, 4032. (d) Ca´mpora, J.; Palma, P.; Gutie´rrez, E.; Poveda, M. L.;
Ruiz, C.; Carmona, E. Organometallics 1994, 13, 1728.
(3) (a) Griffiths, D. C.; Young, G. B. Polyhedron 1983, 2, 1095. (b)
Griffiths, D. C.; Young, G. B. Organometallics 1989, 8, 875. (c)
Ankaniec, B. C.; Hardy, D. T.; Thomson, S. K.; Watkins, W. N.;
Young, G. B. Organometallics 1992, 11, 2591.
Synthesis of the Palladacycles Pd(CH2CMe2-o-C6H4)L2.
The nickel and platinum bis(neophyl) complexes M(CH2-
(4) (a) Ryabov, A. D. Chem. ReV. 1990, 90, 403. (b) Newkome, G. R.;
Puckett, W. E.; Gupta, V. K. Chem. ReV. 1986, 86, 451. (c) Kiefer,
G. E. Chem. ReV. 1986, 86, 151. (d) Catellani, M.; Chiusoli, G. P.
Gazz. Chim. Ital. 1993, 123, 1.
(5) Ca´mpora, J.; Lo´pez, J. A.; Palma, P.; Valerga, P.; Spillner, E.;
Carmona, E. Angew. Chem., Int. Ed. 1999, 38, 147.
10.1021/ic010114r CCC: $20.00 © 2001 American Chemical Society
Published on Web 07/12/2001

Cyclometalated Palladium-Alkyl Complexes
Inorganic Chemistry, Vol. 40, No. 17, 2001 4117
Scheme 1
Scheme 2
2a,b,3
CMe2C6H5)2(PR3)2
experience a thermal, intramolecular
cyclometalation that allows the efficient synthesis of the
corresponding metallacycles M(CH2CMe2-o-C6H4)(PMe3)2. For
palladium, however, this procedure is thwarted by the ready
decomposition of the corresponding dialkyls.6a For example, the
which, although stable at room temperature, eliminates revers-
ibly 2,5-dimethylpyrrole when heated at 50 °C in CD2Cl2,
leading to an equilibrium mixture of 2a and 3 (Keq ≈ 0.52 at
this temperature). The same equilibrium mixture can be reached
if solutions that contain equimolar amounts of 2a and 2,5-
dimethylpyrrole are heated at 50 °C. These observations suggest
that the cyclometalation of 1a is induced more effectively by
bases with a low capacity to coordinate to the Pd center. It is
worth noting that at variance with the above results, the reaction
of the nickel analogue of 1a with sodium hydroxide or 2,5-
dimethylpyrrolylsodium leads to stable hydroxo and pyrrolyl
complexes that do not undergo the cyclometalation reaction.9
6b,c
trimethylphosphine derivative Pd(CH2CMe2C6H5)2(PMe3)2
undergoes clean reductive elimination of 2,4-dimethyl-2,4-
diphenylhexane (bineophyl) when heated in solution at 50 °C
(see Experimental Section). Since closely related palladium
metallacycles of composition Pd(CH2X-o-C6H4)L2 (X ) O, NR;
L ) P- or N-donor) are stable species, readily synthesized by
an intramolecular transmetalation reaction,7 it appears likely that
our target compound Pd(CH2CMe2-o-C6H4)(PMe3)2, 2a, could
form under the appropriate experimental conditions. Early work
by Catellani and Chiusoli,8a-c subsequently followed by others,8d
has demonstrated that (halo)alkyl complexes of palladium that
possess a â-phenyl group can be cyclometalated by bases, much
in the same fashion as the well-known cyclopalladation of
aromatic amines, imines, and other nitrogen ligands.4 Using a
similar approach, we have prepared the desired metallacycle,
2a, by treatment of the chloroneophyl complex 1a with suitable
bases (Scheme 1).5
The results described above show that the conditions required
to effect the cyclometalation of a neophyl ligand in Pd
complexes differ significantly from those needed for the similar
Ni or Pt derivatives. For the latter metals the cyclometalation
is accomplished by electron-rich bis(neophyl)complexes, whereas
in the Pd system, the activation of the C-H bond appears to
involve a cationic intermediate,5 thereby suggesting an elec-
trophilic attack of the Pd atom on the aromatic ring.
The selection of the base is important to achieve a clean
conversion of 1a to 2a. Sodium bis(trimethylsilyl)amide has
proved to be particularly efficient, but other reagents such as
sodium hydroxide, or alkali metal alkoxides and amides, can
also effect the cyclometalation (albeit in lower yields or less
cleanly). The sensitivity of this process to the nature of the basic
reagent might be due to the ability of the latter to displace the
chloro ligand from 1a, giving rise to intermediate complexes
that cyclometalate slowly or incompletely, or find other
decomposition pathways in competition with the cyclometala-
tion. For instance, the reaction of 1a with 2,5-dimethylpir-
rolylsodium leads to the substitution product 3 (Scheme 1),
With the purpose of improving the synthesis of palladium
metallacycles of type 2, we have studied the cyclometalation
of the neophyl complex 1b, containing the 1,5-cyclooctadiene
ligand (cod). This compound is the synthetic precursor of 1a
and is readily available from PdCl2(cod). Moreover, since cod
is much poorer a donor than PMe3, the enhanced electrophilicity
of the Pd center in 1a should facilitate the cyclometalation
process. In accord with these expectations 2b is readily formed
when a solution of 1b in moist THF or CH2Cl2 is treated with
grounded sodium hydroxide (Scheme 2). Further elaboration
of this synthetic methodology allows the direct preparation of
2b (without isolation of 1b) in 70-80% yield, based on
PdCl2(cod) (see Experimental Section), as well as the generation
of the related palladacycles 2a-2g (vide infra).
(6) (a) Gillie, A.; Stille, J. K. J. Am. Chem. Soc. 1980, 102, 4933. (b)
Trooze, R.; Chiu, K. W.; Wilkinson, G. Polyhedron 1984, 3, 1025.
(c) Gutie´rrez, E.; Nicasio, M. C.; Paneque, M.; Ruiz, C.; Salazar, V.
J. Organomet. Chem. 1997, 549, 167.
(7) (a) Ca´rdenas, D. J.; Mateo, C.; Echevarren, A. M. Angew. Chem., Int.
Ed. Engl. 1994, 33, 2445. (b) Mateo, C.; Ca´rdenas, D. J.; Ferna´ndez-
Rivas, C.; Echevarren, A. M. Chem. Eur. J. 1996, 2, 1996. (c) Mateo,
C.; Ca´rdenas, D. J.; Echevarren, A. M. Organometallics 1998, 17,
3661.
(8) (a) Catellani, M.; Chiusoli, G. P. J. Organomet. Chem. 1988, 346,
C27. (b) Catellani, M.; Chiusoli, G. P. J. Organomet. Chem. 1992,
437, 369. (c) Catellani, M.; Chiusoli, G. P. J. Organomet. Chem. 1992,
425, 151. (d) Liu, C. H.; Li, C. S.; Cheng, C. H. Organometallics
1994, 13, 18.
Compounds 2a and 2b are very stable and can be handled in
air without apparent decomposition. Their structures, first
established on the basis of spectroscopic and analytical data,
have been confirmed by X-ray diffraction studies (see Figures
1 and 2) to be discussed in a later section.
Alkylpalladium complexes with labile co-ligands are of
interest because they permit tuning the electronic or the steric
(9) Carmona, E.; Mar´ın, J. M.; Palma, P.; Paneque, M.; Poveda, M. L.
Inorg. Chem. 1989, 28, 1895.

4118 Inorganic Chemistry, Vol. 40, No. 17, 2001
Ca´mpora et al.
Scheme 3
selective broadening of only one of the two signals at low
concentrations of the added trimethylphosphine (0.02 M, Figure
3b). At higher PMe3 concentrations (0.26 M, Figure 3c), both
coordinated ligands exchange rapidly so that only a broad
resonance is observed for the free and the coordinated phos-
phine. The signals corresponding to the methylene group and
the Pd-bound aromatic carbon of 2a appear as doublets of
doublets due to their coupling with the trans and cis phosphorus
nuclei. On addition of PMe3, the signal due to the methylene
group collapses into a broad singlet (Figure 1c), while the
quaternary aromatic resonance remains a broad doublet, with a
typically high trans-JCP constant of 123 Hz. This indicates that
the ligand located in trans to the methylene group exchanges
faster, doubtless due to the stronger trans effect of the latter, as
compared to the aryl fragment. Values of ∆Gq (at 298 K) for
the exchange of the PMe3 ligands cis and trans to the CH2 group
of 13.3(8) and 12.1(4) kcal/mol, respectively, have been
determined by line-shape simulation of the 31P{1H} spectrum
of a 0.1 M solution of 2a in CD2Cl2 containing added PMe3
(0.15 M); spectra were recorded at ten different temperatures
between 227 and 326 K (see Supporting Information).
Figure 1. X-ray structure of complex 2b.
Figure 2. X-ray structure of complex 2a.
The higher trans effect of the methylene group becomes also
apparent in the selective substitution of the trans PMe3 ligand
by tert-butyl isocyanide, to give the mono(isocyanide) complex
2h (Scheme 3). The thermodynamic preference for this substitu-
tion pattern is demonstrated by the formation of the same isomer
in the reaction of the bis(isocyanide) derivative 2e with PMe3.
The same trend was also observed in the analogous nickel
system, where the PMe3 ligand trans to the methylene group
can be selectively displaced by pyridine2a or t-BuNC.2c As
already noted, this substitution pattern governs the regioselec-
tivity of the insertion reactions of these metallacycles.2c,d
environment of the metal center by simple ligand exchange
reactions.10 As already mentioned, the ready availability of 2b
and its easy manipulation makes this complex an excellent
starting material for the preparation of a wide range of palladium
metallacyclic derivatives (Scheme 2). Thus, on a preparative
scale, 2a is best obtained by treating 2b with 2 equiv of PMe3.
Similar exchange reactions occur with t-butylisocyanide, 1,2-
bis(dimethyphosphino)ethane (dmpe), or 2,2′-bipyridyl. Deriva-
tives of pyridine (2f) and even of the less basic ligand
4-cyanopyridine (2g) can also be generated, but the bulkier R,R′-
lutidine fails to displace the cyclooctadiene from 2b.
Insertion Reactions. The insertion of small molecules into
the M-C bonds of metallacycles often leads to the formation
of carbo- or heterocyclic compounds that may be difficult to
prepare by other methods. We have studied the reactivity of
the palladacycles 2 toward several molecules amenable to
participate in such insertion reactions and have found that these
compounds are much less prone to undergo migratory insertion
reactions than the related nickel compounds. Thus, in contrast
NMR spectra of analytically pure samples of the pyridine
(2f) and 4-cyanopyridyne complexes (2g) display sharp reso-
nances, which nevertheless broaden readily in the presence of
trace amounts of the free ligand or other impurities, indicating
the occurrence of fast, associative ligand exchange processes.
Similarly, the NMR spectra of 2a reveal ligand exchange in
the presence of added PMe3. Figure 3 shows the effect of added
PMe3 on the room temperature 13C{1H} spectrum of 2a (0.24
M in CD2Cl2). As can be seen, the exchange rate of the two
PMe3 ligands is appreciably different, this being evinced by the
with the ready carbonylation of Ni(CH2CMe2-o-C6H4)(PMe3)2,
neither 2a or 2b react with CO under rather forcing conditions
(80 °C, 20 atm). Similarly, no reaction was observed when these
complexes were brought into contact with CO2, CS2, or other
heterocumulenes known to insert readily into the Ni-C bonds
of the analogous Ni metallacycles.2d In fact, the metallacycle
2b constitutes a rare example of stable Pd-aryl-alkene complex.
Few compounds of this kind are known, migratory insertion of
(10) (a) Byers, P. K.; Canty, A. J. Organometallics 1990, 9, 210. (b) Graaf,
W.; Boersma, J.; Smeets, W.; Spek, A. L.; van Koten, G. Organo-
metallics 1989, 8, 2907. (c) Pan, Y.; Young, G. B. J. Organomet.
Chem. 1999, 577, 257.

Cyclometalated Palladium-Alkyl Complexes
Inorganic Chemistry, Vol. 40, No. 17, 2001 4119
Figure 3. Selected zones of the 100 MHz 13C{1H} NMR spectrum of 2a. (a) 0.24 M solution in CD2Cl2. (b) and (c) the same spectrum recorded
in the presence of free PMe3, 0.02 and 0.26 M, respectively.
Scheme 4
the olefin into Pd-aryl bonds is a very favorable rearrangement,
even for Pd-cyclooctadiene complexes with relatively inert
perfluoroaryl groups.11 The stability of 2b is probably due to
the difficulty experienced by the rigid metallacycle and the
cyclooctadiene ligand to attain the geometry of the insertion
transition state.
It has been reported that nickel and palladium metallacar-
bocycles insert acetylenes leading to different organic pro-
ducts.2c,7,8b,c,12 Once more, in contrast with the high reactivity
of the nickel analogue of 2a, the palladacycles 2a, 2b, and 2f
react only with alkynes that bear electron-withdrawing substit-
uents. Dimethyl acetylenedicarboxylate (dmad) gives rise to the
2,3-dihydronaphthalene derivative 4 (Scheme 4), which by
analogy with the related Ni chemistry, can be assumed to form
by insertion of the alkyne into the Pd-aryl bond, followed by
reductive elimination.2b The final fate of the palladium atom
depends on the co-ligand present in the metallacycle. Thus, the
reduced thermal stability. However, its identity was authenti-
cated by comparison of its spectroscopic data with those of a
cod and pyridine complexes, 2b and 2f, give rise, respectively,
to the known palladacyclopentadienes 513b and 6.13c These
sample prepared independently from Pd(η5-C5H5)(η3-C3H5),
products have been reported to form in the reaction of Pd(0)
PMe3 and dmad.
species with dmad.13 In contrast, the PMe3 derivative 2a leads
Catellani8a has shown that palladium metallacycles that
to the unstable Pd(0) alkyne complex 7, which could not be
contain methyl isonicotinate as a coligand can react with alkynes
isolated in a pure state, owing to its low melting point and its
less activated than dmad. In a similar fashion, the 4-cyano-
pyridine complex 2g reacts with methyl propiolate to afford a
(11) (a) Albe´niz, A. C.; Espinet, P.; Jeanin, Y.; Philoches-Levisalles, M.;
5:1 mixture of the dihydronaphthalene isomers 8 and 8′
Mann, B. E. J. Am. Chem. Soc. 1990, 112, 6594. (b) Espinet, P.;
(eq 1). Neither palladacyclopentadiene nor Pd(0)-alkyne com-
plexes were detected in this reaction. The regioselectivity
displayed is in line with that of the nickel analogue of 2a, and
also with Catellani’s results, and favors the organic product in
which the more electronegative substituent of the alkyne ends
up in the position adjacent to the methylene group. This analogy
gives some additional support to the mechanistic proposal of
Scheme 4.
Mart´ınez-Ilarduya, J. M.; Pe´rez-Briso, C.; Casado, A. L.; Alonso, M.
A. J. Organomet. Chem. 1998, 551, 9.
(12) (a) Bennett, M. A.; Hockless, D. C. R.; Wenger, E. Organometallics
1995, 14, 2091. (b) Bennett, M. A.; Glewis, M.; Hockless, D. C. R.;
Wenger, E. J. Chem. Soc., Dalton Trans. 1996, 5536.
(13) (a) Moseley, K.; Maitlis, P. J. Chem. Soc., Dalton Trans. 1974, 169.
(b) Ito, T. S.; Hasegawa, S.; Takahashi, Y.; Ishii, Y. J. Chem. Soc.
Chem. Commun. 1972, 629. (c) Suzuki, H.; Itoh, K.; Ishii, Y.; Simon,
K.; Ibers, J. A. J. Am. Chem. Soc. 1976, 98, 8494. (d) tom Dieck, H.;
Munz, C.; Mu¨ller, C. J. J. Organomet. Chem. 1990, 384, 283.

4120 Inorganic Chemistry, Vol. 40, No. 17, 2001
Ca´mpora et al.
Many transition metal alkyls undergo facile insertion reactions
with SO2.14 This reaction leads to sulfinate complexes and can
be exploited for the preparation of sulfinic acids.15a-c Addition-
ally, it has been suggested that Pd complexes may catalyze the
formation of polysulfones by alternating insertion of ethylene
and SO2, much in the same way as the well-known copolym-
erization of CO and olefins.14a, 15d,e
On exposure to 1 equiv of SO2 at 0 °C, solutions of 2a
inmediately develop an intense orange coloration which gradu-
ally fades into a pale yellow color. This reaction leads to the
formation of two products, 10 and 11 (Scheme 5), with a
remarkable solvent dependence, to the point that compound 11
is formed selectively in solvents such as CH2Cl2, MeCN, or
Me2CO, whereas the use or diethyl ether or toluene leads to
mixtures of 10 an 11. It is worth pointing out that whereas 11
is always the major product, the two compounds form in a
poorly reproducible ratio, albeit in nearly quantitative combined
yield. The analytical and spectroscopic data indicate that they
are isomeric S-sulfinate complexes, arising from the insertion
of one molecule of SO2 into a Pd-C bond. Thus, they display
two strong infrared absorptions in the 1000-1200 cm-1 range,
Figure 4. Crystal structure of complex 10.
Scheme 5
characteristic of the sulfinate functionality (10, 1146, 1064 cm-1
;
11, 1155, 1036 cm-1). The 13C{1H} NMR spectra of 10 and 11
show that these compounds differ in the site of insertion of the
molecule of SO2. Thus, the typically large trans-13C-31P
coupling (>90 Hz) is missing in the methylene signal of 10, as
well as in the initially Pd-bound aromatic quaternary resonance
of 11, which leads to the conclusion that they result from the
insertion of SO2 into the Pd-CH2 and the Pd-C(aryl) bonds
of 2a, respectively (see Scheme 5). The proposed structure of
10 has been confirmed by single-crystal, X-ray methods
(Figure 4).
Compound 11 is rapidly generated by addition of PMe3 to a
suspension of 12 in methanol. Obviously, the low solubility of
the latter complex favors its formation, but this requires
dissociation of PMe3, which becomes subsequently oxidized by
adventitious oxygen. Accordingly, large crystals of 12 can be
readily obtained upon exposure of methanolic solutions of 11
to air for 1-2 days (eq 2).
Even though attempts to grow suitable crystals of 11 did not
meet with success, upon leaving a methanol solution of this
complex to stand for 15 days at -20 °C in a septum-capped
Schlenk tube, crystals of a fairly insoluble compound, 12, were
formed. Its X-ray structure (Figure 5) shows that 12 is a dimer,
resulting from the loss of the PMe3 ligand trans to the methylene
group of 11. Compound 12 is sparingly soluble in CD2Cl2,
where its NMR spectra can be recorded. These are in full accord
with its solid-state structure, and show the presence of a single
PMe3 ligand cis to the methylene group.
(14) (a) Gates, D. P.; White, P. S.; Brookhart, M. J. Chem. Soc. Chem.
Commun. 2000, 47. (b) Morton, M. S.; Lachicotte, R. J.; Vicic, D.
A.; Jones, W. D. Organometallics 1999, 18, 227. (c) Rashidi, M.;
Shahabadi, N.; Esmaeilbeig, A. R.; Joshaghani, M.; Puddephatt, R. J.
J. Organomet. Chem. 1994, 484, 53. (d) Diversi, P.; Ingrosso, G.;
Lucherini, A.; Murtas, S. J. Chem. Soc., Dalton Trans. 1980, 1633.
(e) Diversi, P.; Ingrosso, G.; Lucherini, A.; Lumini, T.; Marchetti, F.;
Merlino, S.; Adovasio, V.; Nardelli, M. J. Chem. Soc., Dalton Trans.
1988, 461. (f) Muller, G.; Panyella, D.; Rocamora, M.; Sales, J.; Font-
Bard´ıa, M.; Solans, X. J. Chem. Soc., Dalton Trans. 1993, 2959. (g)
Hu, Y. R.; Wojcicki, A.; Calligaris, M.; Nardin, G. Organometallics
1987, 6, 1561.
(15) (a) Pelzer, G.; Keim, W. J. Mol. Catal. A 1999, 139, 235. (b) Herwig,
J.; Keim, W. Inorg. Chim. Acta 1994, 122, 381. (c) Keim, W.; Herwig,
J. J. Chem. Soc., Chem. Commun. 1993, 1592. (d) Jurgen, J. Thesis,
Rheinish-Westfalischen Tecnische Hohschule Aachen, 1995. (e) Klein,
H. S. J. Chem. Soc., Chem. Commun. 1968, 377.
Single and double insertions of SO2 into the M-C bonds of
group 10 dialkyl or metallacyclic complexes are known.14 In
our case, subjecting solutions of 10 and 11 to 3 atm of SO2
(100 °C, 12 h) does not result in further insertion chemistry.
Additionally, in the absence of SO2, toluene solutions of 10 or
11 do not isomerize or extrude sulfur dioxide. Hence it can be
assumed that under these conditions the formation of the two
compounds is irreversible.
Although the analogies in the bonding of CO and SO2 to
metal in their complexes16 suggest that the insertion of these
molecules might follow similar pathways (i.e., migratory
insertion), in most cases the insertion of SO2 is thought to
proceed by a direct electrophilic attack at the metal-bound

Cyclometalated Palladium-Alkyl Complexes
Inorganic Chemistry, Vol. 40, No. 17, 2001 4121
insertion leads selectively to 11 in CD2Cl2 and acetone-d6 and
to a mixture of 10 and 11 in toluene-d8. The reaction is
noticeable above -60 °C in the former solvents, and slower in
toluene, where the insertion takes place at around -20 °C. No
significant changes can be detected in the shape or the chemical
shifts of the 1H and 31P{1H} signals of 9 up to 0 °C (Figure 6).
This suggests that SO2 insertion takes place directly from the
pentacoordinated species 9. In agreement with this observation,
the metallacycle 2c, bearing the chelating diphosphine dmpe
as a coligand, also reacts readily with SO2, affording selectively
complex 13 (eq 3), i.e., the product of insertion into the Pd-
aryl bond.
Figure 5. Crystal structure of compound 12.
Crystal Structures of 2a, 2b, 10, and 12. Figures 1 and 2
show the crystal structures of the metallacycles 2a and 2b, which
differ only in the nature of the ancillary ligand. In both
complexes, the central Pd atom is in a square planar environment
distorted by the chelating organic ligand that imposes acute
CH2-Pd-aryl bond angles of 77.4(5)° and 79.08°(13), respec-
tively. Both rings are appreciably puckered (puckering angle:
47.90(2)°, 2a; 37.0(2)°, 2b), with the methylenic carbon placed
well above the mean plane formed by the remaining atoms in
the metallacycle. In 2a, the steric repulsion between the aryl
ring and the adjacent PMe3 ligand induces a slight tetrahedral
distortion which was also observed in the Ni analogue.2a This
distortion is not apparent in 2b, where such steric interactions
are absent. Thus, the planes defined by the Pd, C1 and C6 and
Pd, P1 and P2 in 2a form an angle of 10.21(2)°, while the
analogous measurement for 2b, considering the geometric
centers of the olefinic bonds as the attachment points of the
cod ligand, amounts only to 1.3(4)°. Although the reactivity
and thermal stability of 2a does not differ significantly from
that of 2b, it has been shown that related palladium metallacycles
can be destabilized by the introduction of substituents in the
aromatic ring position next to the metal center.8a
The two Pd-P bond lengths in 2a are 2.310(4) and 2.341(3)
Å, with the longer distance corresponding to the phosphorus
atom trans to the methylene group. A similar trend was also
found in 2b, where the distance from the Pd atom to the
geometric centers of the cyclooctadiene double bonds are 2.231-
(4) (trans to CH2) and 2.193(4) Å (trans to the aromatic ring).
The dissimilarity of the metal-ligand distances is a clear
reflection of the larger trans influence of the alkyl functionality.
Figures 4 and 5 contain ORTEP views for compounds 10
and 12, respectively. Both molecules display the S-sulfinate
functionality that arises from SO2 insertion19 but differ in the
site of the insertion. Compound 12 consists of two identical
metallacyclic fragments. The coordination of an oxygen atom
from each sulfinyl group to the palladium center of the
neighboring fragment gives rise to a boat-shaped six-membered
ring. This configuration brings the coordination planes of the
palladium atoms face to face, but the Pd-Pd distance (3.586
Å) is too long to allow any bonding interaction.
carbon atom. However, Brookhart has recently reported that the
insertion of sulfur dioxide into the Pd-Me bond of the cationic
complex [PdMe(Et2O)(dppe)]+ is preceded by the displacement
of the coordinated molecule of Et2O by SO2,14a suggesting an
intramolecular insertion mechanism. Apart from this example,
we are not aware of other cases of intramolecular insertion of
a coordinated molecule of SO2. Interestingly, the observation
of a transient orange coloration during the reaction of 2a with
SO2 suggests the existence of a detectable intermediate,17 and
this prompted us to undertake a low-temperature NMR study.
1
The H, 31P{1H}, and 13C{1H} NMR spectra of samples of 2a
dissolved in CD2Cl2, acetone-d6, and toluene-d8 were recorded
at -80 °C before and after treatment with ca. 1.7 equiv of SO2.
In all the experiments, the NMR spectra showed the conversion
of 2a into a single new species, 9. Although the spectra of 9
and 2a are similar, their signals are significantly displaced (see
Experimental Section). For example, in CD2Cl2 and acetone-
d6, the resonances due to the methylene group of 9 are shifted
1
to low field by ca. 0.64 ppm in the H and 10 ppm in the
13C{1H} NMR spectra. The shifts are less pronounced in
toluene-d8 (0.3 and 6.7 ppm, respectively), but the variation upon
conversion of 2a into 9 is also evident in this solvent. The fact
that 9 is a SO2 complex18 and not an insertion product is revealed
by the 13C resonances due to the palladium bound carbon atoms,
which appear splitted into doublets of doublets by coupling with
the phosphorus nuclei, displaying characteristic trans-2JCP values
higher than 80 Hz. These coupling constants are indicative of
a square pyramidal geometry in which both the Pd-bound carbon
atoms and the phosphine ligands preserve their relative positions
as in 2a. The methyl substituents of the metallacyclic fragment
give rise to a broad resonance in the 13C spectra, possibly due
to intermolecular exchange of the coordinated SO2.
As the temperature of the samples of 9 rises, insertion of
SO2 to give the final products proceeds without any other
intermediate being observed. As previously discussed, the SO2
(16) (a) Mingos, D. M. P. Trans. Met. Chem. 1978, 3, 1. (b) Kubas, G. J.
Acc. Chem. Res. 1994, 27, 183. (c) Wojcicki, A. AdV. Organomet.
Chem. 1973, 11, 18. (d) Wojcicki, A. AdV. Organomet. Chem. 1974,
12, 32.
(17) Somewhat similar color changes have been noted in an analogous
reaction involving SO2 and Pt compounds. See: ref 17a and 17b.
(18) (a) Albrecht, M.; Gossage, R. A.; Spek, A. L.; van Koten, G. J. Chem.
Soc., Chem. Commun. 1998, 1003. (b) Albrecht, M.; Lutz, M.; Spek,
A. L.; van Koten, G. Nature 2000, 406, 970. (c) Livingstone, S. L. In
ComprehensiVe Coordination Chemistry; Wilkinson, G., Gillard, R.
G., McCleverty, J. A., Eds.; Pergamon: Oxford, 1987; Vol. 2, p 634.
(d) Hill, A. F. AdV. Organomet. Chem. 1994, 36, 159.
The preferred conformation of the metallacyclic rings of 10
and 12 depends markedly on the position of the SO2 unit. Thus,
(19) For further examples of X-ray characterized palladium S-sulfinates,
see: Tuntulani, T.; Musie, G.; Reibenspies J. H.; Darensbourg, M. Y.
Inorg. Chem. 1995, 34, 6279.

4122 Inorganic Chemistry, Vol. 40, No. 17, 2001
Ca´mpora et al.
Figure 6. 1H NMR monitoring of the transformation 2a f 9 f 11 in CD2Cl2.
The spectroscopic instruments used were Perkin-Elmer Models 684
and 883 and Bruker Model Vector 22 for IR spectra, and Bruker AMX-
300, DRX-400, AMX-500, and DRX-500 for NMR spectroscopy. The
13C resonance of the solvent was used as an internal standard, but
chemical shifts are reported with respect to SiMe4. The 13C{1H} NMR
assignments were helped in most cases with the use of gate-decoupling
techniques. 31P{1H} NMR shifts are referenced to external 85% H3-
PO4. Gas chromatography was performed in a Thermoquest trace GC
Cromatograph, equipped with an Automass Multi Mass Spectrometer.
All preparations and other operations were carried out under oxygen-
free nitrogen by conventional Schlenk techniques. Solvents were dried
and degassed before use. The petroleum ether used had a boiling point
of 40-60 °C. The compounds PdCl2(cod)2 (cod ) 1,5-cyclooctadiene),20
Pd(CH2CMe2C6H5)Cl(cod),6c Pd(CH2CMe2C6H5)Cl(PMe3)2,6c [PdCl(η3-
C3H5)]2,21 phosphine PMe3,22 and the isonitrile, ButNC,23 were prepared
according to literature methods. Na(2,5-Me2C4H2N) and NaCp were
obtained by reacting NaH with 2,5-Me2C4H2NH and freshly cracked
dicyclopentadiene, respectively.
complex 10 adopts a boat conformation while each metallacyclic
half of 12 is found as a half-chair, with the methylene group
markedly departing from the nearly planar unit formed by the
Pd, S, C2, C5, and C10 atoms.
The larger size of the metallacycle rings in 10 and 12, as
compared to 2a and 2b, allow S-Pd-C bond angles close to
the ideal 90° values (85.9(2)° and 87.6(2)° respectively).
However, and similarly to 2a, the phosphine and the aryl ligands
of 10 also cause a slight tetrahedral distortion of the palladium
environment of this compound.
Conclusions
The cyclometalation of Ni, Pd, and Pt neophyl complexes
provides access to a family of metallacyclic derivatives that
illustrate important differences in the chemistry of these metals.
The striking difference in the conditions required for the
synthesis of the palladium derivatives with respect to those
previously found for the Ni and Pt analogues suggests the
formation of these metallacycles may involve different C-H
activation mechanisms. The comparison of the structural and
chemical properties of the Ni and Pd metallacycles evidences a
number of closely related features, in particular with regards to
the ligand substitution pattern, controlled by the different
labilizing effects exerted by the methylene and the aryl groups.
Although these effects seem to influence the regioselectivity
of the insertion reactions in the same direction for both metals
(Ni and Pd), the cyclometalated Pd-neophyl complexes show
much lower tendency to undergo migratory insertion reactions
than the Ni analogues. Pd metallacycles have nevertheless found
to display an interesting reactivity toward strong electrophilic
reagents such as SO2, whose intimate aspects are far from being
understood. Further studies on the mechanism of the cyclo-
metalation of the neophyl complexes of group 8 and the
reactivity of the resulting metallacycles are currently under way
in our laboratories.
Thermolysis of Pd(CH2CMe2Ph)2(PMe3)2. A solution containing
0.4 g (0.08 mmol) of the title compound in 10 mL of Et2O was heated
at 55 °C for 3h. The resulting black suspension was evaporated under
vacuum, the residue extracted with 2 × 0.5 mL of C6D6, and the solution
1
filtered through a small pad of silica. The H NMR spectrum of this
solution showed the presence of a pure compound identified as 2,4-
dimethyl-2,4-diphenylhexane (bineophyl) by comparison with published
NMR data.24 This compound was isolated in nearly quantitative yield
by evaporation of the solvent.
The same reaction was also carried out in an NMR tube, using C6D6
as a solvent, and monitored by 1H NMR and 31P{1H} NMR. Bineophyl
was formed cleanly, along with free PMe3 and a black precipitate of
palladium. CI MS: 266 (M+). 1H NMR (C6D6, 20 °C) δ 1.12 (s, 12H,
CMe2), 1.14 (s, 4H, CH2), 7.07 (m, 1 H, CHar), 7.15 (m, 4H, CHar);
13C{1H} (C6D6, 20 °C) δ 29.2 (s, CMe2), 37.5 (s, CMe2), 39.2 (s, CH2),
125.7, 126.2, 128.3 (CarH), 149.3 (Car).
(20) Drew, D.; Doyle, J. R. Inorg. Synth. 1972, 13, 47.
(21) Tatsuno, Y.; Yoshida, T.; Otsika, S. Inorg. Synth. 1990, 28, 343.
(22) Luetkens, M. L., Jr., Sattelberger, A. P.; Murray, H. H.; Basil, J. D.;
Fackler, J. P., Jr. Inorg. Synth. 1990, 28, 305.
(23) Gokel, G. W.; Widera, R. P.; Weber, W. P. Org. Synth. 1976, 55, 96.
(24) Whitesides, G. M.; Panek, E. J.; Steronsky, E. R. J. Am. Chem. Soc.
1972, 94, 232.
Experimental Section
Microanalyses were performed by the Analytical Service of the
University of Seville and the Instituto de Investigaciones Qu´ımicas.

Cyclometalated Palladium-Alkyl Complexes
Inorganic Chemistry, Vol. 40, No. 17, 2001 4123
NMR (C6D6, 20 °C) δ 0.80-0.90 (m, 4 H, P-CH2), 0.88 (d, 6 H,
Synthesis of Pd(CH2CMe2-o-C6H4)(PMe3)2, 2a. Method A. To a
cooled (-30 °C) suspension of 2b (0.34 g, 1 mmol) in 30 mL of Et2O
was added 2 mL of a 1 M solution of PMe3 (2 mmol) in THF. After
removing the cold bath, the mixture was stirred at room temperature
for 1 h. The solvent was evaporated under reduced pressure and the
oily residue extracted with 15 mL of Et2O. Filtration, partial concentra-
tion of the solvent and addition of some petroleum ether, provided,
upon cooling to -30 °C white crystals of 2a in quantitative yield.
Method B. A solution of the complex Pd(CH2CMe2C6H5)Cl(PMe3)2,
1a (0.21 g, 0.5 mmol) in 30 mL of Et2O was cooled at -50 °C and
treated with NaN(SiMe3)2 (0.5 mmol, 0.85 mL of a 0.6 M solution in
toluene). The mixture was allowed to reach room temperature and then
stirred at 50 °C for 5 h, during which time the color of the solution
turned dark gray. The reaction mixture was taken to dryness and the
residue extracted with 30 mL of Et2O. Afterwards, filtration and
concentration of the solution to ca. 5-10 mL, addition of some
petroleum ether, and cooling to -30 °C, gave white crystals of 2a in
65% yield.
2
2JHP ) 6.9 Hz, PMe2), 0.95 (d, 6 H, JHP ) 6.9 Hz, PMe2), 1.77 (s, 6
H, CMe2), 2.43 (t, 2 H, 3JHP ) 7.0 Hz, CH2), 7.35 (m, 3 H, CHar), 7.78
(tm, 1 H, CHar); 31P{1H} NMR (C6D6, 20 °C) AX spin system, δΑ
)
11.7, δX ) 18.4, JAX ) 7 Hz; 13C{1H} NMR (C6D6, 20 °C) δ 12.5 (d,
1
1JCP ) 14 Hz, PMe2), 13.0 (d, JCP ) 18 Hz, PMe2), 27.0-29.0 (m,
4
2
P-CH2), 36.0 (d, JCP ) 6 Hz, CMe2), 46.1 (dd, JCP ) 7 and 96 Hz,
CH2), 50.8 (t, 3JCP ) 6 Hz, CMe2), 122.8 (d, JCP ) 3 Hz, CarH), 123.4
(s, CarH), 124.0 (d, JCP ) 10 Hz, CarH), 139.8 (dd, JCP ) 5 and 13 Hz,
2
CarH), 168.5 (sa, Car), 169.2 (dd, JCP ) 10 and 125 Hz, Car).
Synthesis of Pd(CH2CMe2-o-C6H4)(bipy), 2d. To a suspension of
compound 2b (0.34 g, 1 mmol) in Et2O (20 mL) cooled at -50 °C
was added a solution of bipy (0.16 g, 1 mmol) in Et2O (10 mL). The
cooling bath was removed with continued stirring; when the mixture
developed a yellow coloration, some microcrystalline solid precipitated.
After further stirring for 1 h at room temperature the suspension was
filtered and the solid washed with petroleum ether and dried. Recrys-
tallization from CH2Cl2-petroleum ether gave yellow crystals in 90%
yield. Anal. Calcd for C20H20N2Pd: C, 60.8; H, 5.1; N, 7.1. Found: C,
61.1; H, 5.2; N, 7.1. 1H NMR (CD2Cl2, 20 °C) δ 1.39 (s, 6 H, CMe2),
2.37 (s, 2 H, CH2), 6.80 (m, 1 H, CHar), 6.93 (m, 2 H, CHar), 7.49 (m,
1 H, CHar), 7.58 (m, 2 H, CHar), 8.00 (m, 2 H, CHar), 8.12 (m, 2 H,
CHar), 8.75 (d, 1 H, JHH ) 4.4 Hz, CHar), 9.17 (d, 1 H, JHH ) 4.4 Hz,
CHar); 13C{1H} NMR (CD2Cl2, 20 °C) δ 35.7 (s, CMe2), 47.1 (s, CH2),
49.4 (s, CMe2), 123.7, 124.0, 124.9, 126.0, 127.6, 127.8, 136.8, 139.8,
151.2, 152.1 (s, CHar), 156.4, 156.7, 162.1, 171.1 (s, Car).
The use of NaOH or NaButO, as the base provides complex 2a in
60% or 45% yield, respectively.
Anal. Calcd for C16H30P2Pd: C, 49.2; H, 7.7. Found: C, 49.2; H,
1
2
7.6. H NMR (C6D6, 20 °C) δ 0.85 (d, 9 H, JHP ) 6.7 Hz, PMe3),
2
0.90 (d, 9 H, JHP ) 6.7 Hz, PMe3), 1.77 (s, 6 H, CMe2), 2.20 (dd, 2
3
H, JHP ) 5.7 and 8.8 Hz, CH2), 7.27 (m, 3 H, CHar), 7.63 (tm, 1 H,
CHar); 31P{1H} NMR (C6D6, 20 °C) AX spin system, δΑ ) -27.9,
δX ) -22.9, JAX ) 23 Hz; 13C{1H} NMR (C6D6, 20 °C) δ 16.3 (d,
1JCP ) 19 Hz, PMe3), 17.7 (dd, JCP ) 3, JCP ) 17 Hz, PMe3), 35.5
2
1
Synthesis of Pd(CH2CMe2-o-C6H4)(ButNC)2, 2e. A total of 2 mL
of a 1 M solution of ButNC (2 mmol) in Et2O was added to a suspension
of complex 2b (0.34 g, 1 mmol) in 30 mL of Et2O cooled at -30 °C.
The mixture was stirred at room temperature for 1 h. The solvent was
stripped off and the residue extracted with Et2O, and filtered. After
partial evaporation of the solvent, cooling to -30 °C provided
compound 2e as white crystals in 90% yield. Anal. Calcd for C20H30N2-
Pd: C, 59.3; H, 7.4; N, 6.9. Found: C, 59.4; H, 7.1; N, 6.8. IR (Nujol
mull): 2188, 2166 cm-1 (υ(CN)). 1H NMR (C6D6, 20 °C) δ 0.83 (s, 9
H, But), 0.90 (s, 9 H, But), 1.73 (s, 6 H, CMe2), 2.65 (s, 2 H, CH2),
7.23 (m, 3 H, CHar), 7.97 (m, 1 H, CHar); 13C{1H} NMR (C6D6, 20
°C) δ 29.4, 29.5 (s, Me3C), 35.3 (s, CMe2), 44.3 (s, CH2), 50.7 (s,
CMe2), 55.9 (s, Me3C), 122.7, 123.7, 124.0, 139.6 (s, CarH), 144.3 (ta,
(d, 4JCP ) 9 Hz, CMe2), 50.9 (t, 3JCP ) 6 Hz, CMe2), 52.5 (dd, 2JCP
)
9 and 95 Hz, CH2), 122.1 (d, JCP ) 3 Hz, CarH), 123.2 (s, CarH), 123.7
(d, JCP ) 10 Hz, CarH), 138.0 (dd, JCP ) 5 and 11 Hz, CarH), 167.0 (s,
2
Car), 169.2 (dd, JCP ) 14 and 123 Hz, Car).
In an additional, NMR-monitored study, 0.011 g (0.023 mmol) of
compound 3 (vide infra) was dissolved in 0.6 mL of CD2Cl2 and placed
in an NMR tube. The NMR probe was heated at 50 °C and spectra
were adquired every 30 min during 10 h. After this time, an equilibrium
mixture of compounds 3, 2a, and pyrrole was attained.
Synthesis of Pd(CH2CMe2-o-C6H4)(cod), 2b. Method A. To a
solution of Pd(CH2CMe2C6H5)Cl(cod), 1b (0.38 g, 1 mmol) in THF
(30 mL), NaOH (0.12 g, 3 mmol), and H2O (0.3 mL) were added. The
mixture was stirred at room temperature for 2-3 h and then taken to
dryness. The residue was extracted with Et2O and filtered. The filtrate
was concentrated and some petroleum ether added. Cooling to -30
°C furnished complex 2a as white crystals in 65% yield.
1
ButNC), 145.2 (t, JCN ) 7 Hz, ButNC), 164.7, 167.7 (s, Car).
Synthesis of Pd(CH2CMe2-o-C6H4)(py)2, 2f. To a suspension of
compound 2b (0.34 g, 1 mmol) in Et2O (30 mL) cooled to -30 °C,
0.16 mL (2 mmol) of pyridine was added. The mixture was stirred at
room temperature for 1 h and a white solid precipitated. The solvent
was removed under vacuum and the solid washed with petroleum ether
and dried. It was recrystallized from CH2Cl2 and obtained as white
crystals in 90% yield. Anal. Calcd for C20H22N2Pd: C, 60.5; H, 5.5;
Method B. 10 mL of a 1 M solution of Mg(CH2CMe2C6H5)Cl (10
mmol) in Et2O was added to a cooled (-70 °C) solution of PdCl2(cod)
(2.85 g, 10 mmol) in 120 mL of Et2O. The mixture was warmed to
room temperature and stirred overnight. The solvent was removed under
vacuum and the residue extracted with 150 mL of CH2Cl2 and
centrifuged. The solution of the alkyl Pd(CH2CMe2C6H5)Cl(cod) formed
was treated with an excess of NaOH (1.2 g, 30 mmol) and 0.5 mL of
water, and the resulting suspension stirred at room temperature for 2 h
and filtered through silica. The filtrate was partially evaporated under
reduced pressure and some petroleum ether added. After cooling to
-30 °C, compound 2a was obtained as white crystals in 70% yield.
Anal. Calcd for C18H24Pd: C, 62.3; H, 6.9. Found: C, 62.4; H, 7.0.
1H NMR (C6D6, 20 °C) δ 1.80-2.00 (m, 8 H, CH2 cod), 1.57 (s, 6 H,
CMe2), 2.54 (s, 2 H, CH2), 5.16 (s, 2 H, CH cod), 5.67 (s, 2 H, CH
cod), 7.15 (tm, 2 H, CHar), 7.22 (tm, 1 H, CHar), 7.27 (dm, 1 H, CHar);
13C{1H} NMR (C6D6, 20 °C) δ 28.2, 28.9 (s, CH2 cod), 34.0 (s, CMe2),
49.7 (s, CMe2), 53.4 (s, CH2), 109.9, 113.2 (s, CH cod), 123.1, 124.5,
124.8, 134.6 (s, CarH), 162.5, 167.5 (s, Car).
1
N, 7.0. Found: C, 60.4; H, 5.6; N, 7.0. H NMR (CD2Cl2, 20 °C) δ
1.33 (sa, 6 H, CMe2), 2.02 (sa, 2 H, CH2), 6.42 (da, 1 H, JHH ) 6.3
Hz, CHar), 6.60 (ta, 1 H, JHH ) 7.0 Hz, CHar), 6.73 (da, 1 H, JHH ) 7.3
Hz, CHar), 6.81 (ta, 1 H, JHH ) 7.3 Hz, CHar), 7.28 (sa, 2 H, py), 7.36
(sa, 2 H, py), 7.73 (sa, 1 H, py), 7.79 (sa, 1 H, py), 8.47 (sa, 2 H, py),
8.79 (sa, 2 H, py); 13C{1H} NMR (CD2Cl2, 20 °C) δ 35.8 (s, CMe2),
44.0 (s, CH2), 49.5 (s, CMe2), 123.6, 124.3, 125.4 (s, CarH), 126.7 (s,
4 CarH py), 137.4 (s, CarH), 138.8 (s, 2 CarH py), 152.8 (s, 2 CarH py),
153.2 (s, 2 CarH py), 161.0, 170.8 (s, Car).
Synthesis of Pd(CH2CMe2-o-C6H4)(4-CNpy)2, 2g. A cooled (-30
°C) suspension of complex 2b (0.17 g, 0.5 mmol) in Et2O (30 mL)
was treated with a solution of 4-CNpy (0.1 g, 1 mmol) in 10 mL of
Et2O. When the mixture was warming to room-temperature some yellow
solid precipitated, the stirring was continued for 1 h. The suspension
was taken to dryness and the solid washed with petroleum ether. It
can be crystallized from CH2Cl2 and isolated as yellow crystals in
quantitative yield. Anal. Calcd for C22H20N4Pd: C, 59.1; H, 4.5; N,
12.5. Found: C, 59.2; H, 4.7; N, 12.8. IR (Nujol mull): 2232 cm-1
(υ(CN)). 1H NMR (DMSO-d6, 20 °C) δ 1.25 (s, 6 H, CMe2), 1.96 (sa,
2 H, CH2), 6.40 (sa, 1 H, CHar), 6.57 (t, 1 H, JHH ) 3.2 Hz, CHar),
6.65 (d, 1 H, JHH ) 6.4 Hz, CHar), 6.77 (ta, 1 H, JHH ) 6.1 Hz, CHar),
Synthesis of Pd(CH2CMe2-o-C6H4)(dmpe), 2c. To a cooled (-30
°C) suspension of complex 2b (0.34 g, 1 mmol) in 30 mL of Et2O,
was added dmpe (1 mmol, 1 mL of a 1 M solution in THF). The cooling
bath was removed and the mixture stirred at room temperature for 1 h,
and then taken to dryness. The residue was extracted with a mixture
of CH2Cl2-petroleum ether and the solution cooled to -30 °C.
Compound 2c was obtained as white crystals in quantitative yield. Anal.
1
Calcd for C16H28P2Pd: C, 49.4; H, 7.2. Found: C, 49.2; H, 7.2. H

4124 Inorganic Chemistry, Vol. 40, No. 17, 2001
Ca´mpora et al.
7.93 (d, 4 H, JHH ) 5.9 Hz, 4-CNpy), 8.91 (d, 4 H, JHH ) 5.1 Hz,
4-CNPy); 13C{1H} NMR (DMSO-d6, 20 °C) δ 33.8 (s, CMe2), 43.2 (s,
CH2), 47.9 (s, CMe2), 116.4, 119.9 (s, Car, 4CNpy), 121.4, 123.0, 123.5
(s, CarH), 126.3 (s, 4 CarH, 4-CNpy), 134.3 (s, CarH), 151.5 (s, 4 CarH,
4-CNpy), 160.5, 166.8 (s, Car).
mmol) of a 1 M solution of PMe3 in THF. The resulting mixture was
stirred at this temperature for 1 h and then taken to dryness. The red
oily residue was identified as complex 7 by NMR.
1H NMR (C6D6, 20 °C) δ 1.06 (d, 18 H, 2JHP ) 7.2 Hz, PMe3), 3.51
(s, 6 H, CO2Me); 31P {1H} NMR (C6D6, 20 °C) δ -21.4 (s, PMe3);
13C {1H} NMR (C6D6, 20 °C) δ 18.5 (d, 1JCP ) 22 Hz, PMe3), 51.0 (s,
Synthesis of Pd(CH2CMe2-o-C6H4)(ButNC)(PMe3), 2h. ButNC (1
mmol, 1 mL of a 1 M solution in Et2O) was added to a solution of
compound 2a (0.39 g, 1 mmol) in Et2O (30 mL) cooled at -30 °C.
The mixture was stirred at room temperature for 1 h, the solvent
evaporated under reduced pressure, and the residue extracted with Et2O.
After partial concentration of the solution, cooling to -30 °C furnished
white crystals of compound 2h in quantitative yield.
2
3
CO2Me), 137.0 (t, JCP ) 45 Hz, -CtC-), 165.3 (t, JCP ) 16 Hz,
CO2Me).
Reaction of Metallacycle 2g with HC≡CO2Me (dmad). Synthesis
of 8 and 8′. To a solution of complex 2g (0.33 g, 0.75 mmol) in 40
mL of CH2Cl2, methyl propiolate (209 µL, 2.25 mmol) was added, the
color of the mixture changed from yellow to dark red. It was stirred
3.5 h at room temperature and then the solvent evaporated under reduced
pressure. The dark red oily residue was extracted with petroleum ether
and filtered. From the filtrate, compounds 8 and 8′ were isolated by
spinning band chromatography, using petroleum ether, with 2% Et2O,
as eluant.
Isomer 8: Spectroscopy data for this isomer has been reported
previously2c. EI-HRMS: m/z 216.1142, M+ (exact mass calculated for
C14H16O2 216.1150) Isomer 8′: 1H NMR (C6D6, 20 °C) δ 1.10 (s, 6 H,
CMe2), 2.44 (d, 2 H, 3JHH ) 1.9 Hz, CH2), 3.56 (s, 3 H, CO2Me), 6.10
(t, 1 H, 3JHH ) 1.8 Hz, CH), 7.00-7.30 (m, 4 H, CHar); 13C{1H} NMR
(C6D6, 20 °C) δ 29.3 (s, CMe2), 41.0 (CMe2), 48.6 (CH2), 52.5 (CO2-
Me), 110.8, 122.0, 127.3, 129.8, 131.4 (s, CarH, CH). EI-HRMS: m/z
216.1150, M+ (exact mass calculated for C14H16O2 216.1150).
This complex can be similarly prepared in similar yield by treating
complex 2e with the stoichiometric amount of PMe3. Anal. Calcd for
C18H30NPPd: C, 54.3; H, 7.5; N, 3.5. Found: C, 54.7; H, 7.7; N, 3.5.
1
IR (Nujol mull): 2160 cm-1 (υ(CN)). H NMR (C6D6, 20 °C) δ 0.86
(s, 9 H, But), 0.96 (d, 9 H, 2JHP ) 7.2 Hz, PMe3), 1.76 (s, 6 H, CMe2),
2.21 (d, 2 H, 3JHP ) 8.7 Hz, CH2), 7.37 (m, 3 H, CHar), 8.10 (m, 1 H,
CHar); 31P{1H} NMR (C6D6, 20 °C) δ -22.5 (s, PMe3); 13C{1H} NMR
(C6D6, 20 °C) δ 15.5 (d, 1JCP ) 20 Hz, PMe3), 29.6 (s, Me3C), 35.5 (s,
CMe2), 46.7 (d, 2JCP ) 9 Hz, CH2), 50.9 (d, 3JCP ) 8 Hz, CMe2), 55.7
(s, Me3C), 122.6 (d, JCP ) 3 Hz, CarH), 123.5 (s, CarH), 124.1 (d,
JCP ) 9 Hz, CarH), 139.2 (s, CarH), 146.4 (sa, ButNC), 167.5 (s, Car),
2
167.9 (d, JCP ) 124 Hz, Car).
Synthesis of Pd(CH2CMe2C6H5)(2,5-Me2C4H2N)(PMe3)2, 3. To a
cooled (-70 °C) solution of Pd(CH2CMe3C6H5)Cl(PMe3)2 (0.42 g, 1
mmol) in 40 mL of THF, 0.37 mL (1 mmol) of a 2.7 M solution of
Na(2,5-Me2C4H2N) in THF was added. The cooling bath was removed
and the mixture stirred at room temperature for 3 h. The solvent was
removed under vacuum and the residue extracted with Et2O (30 mL).
After centrifugation, partial concentration of the solvent and cooling
to -30 °C, compound 3 was isolated as orange crystals in 65% yield.
Anal. Calcd for C22H39NP2Pd: C, 54.4; H, 8.1; N, 2.9. Found: C, 54.5;
H, 8.1; N, 2.9. 1H NMR (CD2Cl2, 20 °C) δ 0.73 (t, 18 H, J(app)HP ) 3.2
Synthesis of Pd[S(O2)CH2CMe2-o-C6H4)(PMe3)2, 10. To a cooled
(0 °C) solution of complex 2a (0.18 g, 0.45 mmol) in 20 mL of toluene,
12 mL (0.45 mmol) of SO2(g) was added. The mixture was stirred at
room temperature for 2 h and a white solid precipitated. The suspension
was filtered and the solid, identified as compound 10, dried under
vacuum. The spectroscopic analysis of the mother liquor revealed the
presence of a mixture of complexes 10 and 11. Yield: 60%. Compound
10 can be purified by recrystallization from a mixture toluene:petrol
ether (2:1).
3
Hz, PMe3), 1.50 (s, 6 H, CMe2), 1.67 (t, 2 H, JHP ) 9.2 Hz, CH2),
Anal. Calcd for C16H30O2P2SPd: C, 42.2; H, 6.6. Found: C, 42.5;
1
H, 6.7. IR (Nujol mull): 1146, 1064 cm-1 (υ (SO)). H NMR (CD2-
2.57 (s, 6 H, Me2C4H2N), 6.50 (s, 2 H, Me2C4H2N), 7.0-8.0 (m, 5 H,
CHar); 31P{1H} NMR (CD2Cl2, 20 °C) δ -16.2 (s, PMe3); 13C{1H}
NMR (CD2Cl2, 20 °C) δ 15.0 (t, J(app)CP ) 14 Hz, PMe3), 17.8 (s, CMe2),
25.2 (s, CH2), 34.2 (s, Me2C4H2N), 41.8 (s, CMe2), 105.4 (s, CHar pirr),
120.0, 126.7, 127.0 (s, CarH), 132.2 (s, Car pirr), 155.5 (s, Car).
Reaction of Metallacycles 2b and 2f with MeO2C≡CO2Me
(dmad). Synthesis of 4, 5 and 6. To a solution of complex 2b (0.4 g,
1.16 mmol) in 30 mL of CH2Cl2 was added 0.34 mL (3.48 mmol) of
dmad. Upon stirring for 3.5 h at room temperature the reaction mixture
developed a dark red color. The solvent was stripped off and the residue
extracted with petroleum ether and filtered. The remaining solid was
identified as the crude palladacycle 5. The filtrate was passed through
a short silica column and concentrated to ca. 1 mL. The dihydronaph-
thalene 4 was isolated by spinning band chromatography, using a
petroleum ether/Et2O mixture (9:1) as eluant. Yield: 88%. The known
palladacycle 5 was purified by recrystallization from a mixture CH2-
Cl2/petroleum ether (3:1) and obtained as yellow crystals in 83% yield.
The reaction of complex 2f with dmad follows a similar course and
gives the dihydronaphthalene 4 and complex 6, isolated in 60% and
72% yield, respectively.
Reaction of Metallacycle 2a with MeO2C≡CO2Me (dmad).
Synthesis of 4 and 7. Method A. A total of 0.37 mL (3 mmol) of
dmad was added to a cooled (0 °C) solution of complex 2a (0.39 g, 1
mmol) in 30 mL of Et2O. The mixture was stirred at this temperature
for 1 h, and then taken to dryness. The dark red oily residue was
dissolved in Et2O and the solution passed through a silica column,
providing the organic compound 4 in 93% yield. The presence of
complex 7 was ascertained by NMR spectroscopy (31P{1H} and 1H) of
the crude reaction mixture, by comparison with spectra of an authentic
sample prepared by Method B.
Cl2, 20 °C) δ 1.15 (d, 9 H, 2JHP ) 9.0 Hz, PMe3), 1.43 (s, 3 H, CMe2),
1.55 (d, 9 H, 2JHP ) 8.3 Hz, PMe3), 1.93 (s, 3 H, CMe2), 2.35 (d, 1 H,
3
3JHH ) 12.1 Hz, CH2), 2.73 (d, 1 H, JHH ) 12.1 Hz, CH2), 6.90 (m,
1 H, CHar), 7.04 (m, 1 H, CHar), 7.26 (m, 1 H, CHar), 7.49 (m, 1 H,
CHar); 31P{1H} NMR (CD2Cl2, 20 °C) AX spin system, δΑ ) -22.8,
δX ) -18.7, JAX ) 40.5 Hz; 13C{1H} NMR (CD2Cl2, 20 °C) δ 15.9
(d, 1JCP ) 25 Hz, PMe3), 16.1 (d, 1JCP ) 21 Hz, PMe3), 28.8 (s, CMe2),
4
3
30.6 (s, CMe2), 39.3 (d, JCP ) 5 Hz, CMe2), 76.1 (d, JCP ) 11 Hz,
CH2), 123.8 (d, JCP ) 7 Hz, CarH), 124.4 (s, CarH), 124.8 (t, JCP ) 4
3
Hz, CarH), 135.0 (d, JCP ) 13 Hz, CarH), 148.5 (d, JCP ) 3 Hz, Car),
154.7 (dd, JCP ) 6 and 103 Hz, Car).
2
Synthesis of Pd[CH2CMe2C6H4-o-S(O2)](PMe3)2, 11. A total of
0.16 mL (0.65 mmol) of SO2(g) was added to a cooled (0 °C) solution
of complex 2a (0.28 g, 0.65 mmol) in 40 mL of CH2Cl2. The solution
turned yellow-orange and, after some minutes, colorless again. The
mixture was stirred at this temperature for 4 h. The solvent was reduced
under vacuum and the residue extracted with 20 mL of toluene. After
filtration, partial evaporation of the solvent, addition of some petroleum
ether, and cooling to -30 °C, compound 11 was isolated as white
crystals in 92% yield. Anal. Calcd for C16H30O2P2SPd: C, 42.2; H,
6.6. Found: C, 42.3; H, 6.8. IR (Nujol mull): 1155, 1036 cm-1 (υ
(SO)). 1H NMR (CD2Cl2, 20 °C) δ 1.47 (d, 9 H, 2JHP ) 8.6 Hz, PMe3),
2
1.52 (s, 6 H, CMe2), 1.54 (d, 9 H, JHP ) 8.1 Hz, PMe3), 1.88 (dd, 2
3
H, JHP ) 5.7 and 10.7 Hz, CH2), 7.29 (m, 2 H, CHar), 7.39 (m, 1 H,
CHar), 7.95 (m, 1 H, CHar); 31P{1H} NMR (CD2Cl2, 20 °C) AX spin
system, δΑ ) -24.3, δX ) -16.1, JAX ) 39.7 Hz; 13C{1H} NMR (CD2-
1
1
Cl2, 20 °C) δ 15.6 (d, JCP ) 25 Hz, PMe3), 16.9 (d, JCP ) 21 Hz,
4
2
PMe3), 34.8 (d, JCP ) 8 Hz, CMe2), 36.9 (d, JCP ) 118 Hz, CH2),
38.7 (s, CMe2), 123.0, 125.2, 126.4, 129.2 (s, CarH), 147.6 (s, Car),
148.9 (d, JCP ) 16 Hz, Car).
Method B. To a solution of 0.35 g (0.9 mmol) of [(η3-C3H5)PdCl]2
in THF (25 mL) cooled at -20 °C, CpNa (1.8 mmol, 4.6 mL of a 0.39
M solution in THF) was added. The mixture was stirred at this
temperature for 1 h, at 20 °C for 30 min and then cooled again to -10
°C and treated with 0.22 mL (1.8 mmol) of dmad and 3.6 mL (3.6
3
Synthesis of Pd{CH2CMe2C6H4-o-S(O2)}(PMe3)]2, 12. Large
colorless crystals of compound 12 were isolated after leaving a solution
of complex 11 (0.26 g, 0.5 mmol) in MeOH (3 mL) exposed to air at

Cyclometalated Palladium-Alkyl Complexes
Inorganic Chemistry, Vol. 40, No. 17, 2001 4125
Table 1. Crystal and Refinement Data for Compounds 2a and 10 and 12
2a
10
12
formula
mol wt
crystal system
space group
cell dimensions
a, Å
C16H30P2Pd
390.76
monoclinic
P21/c (No. 14)
C16H30O2P2PdS
454.82
monoclinic
P21/c (No. 14)
C13H21O2PPdS
378.74
monoclinic
P2/c (No. 15)
9.331(3)
16.349(1)
12.628(3)
93.90(2)
4
1922(1)
1.350
8.244(4)
17.519(3)
13.854(4)
94.59(3)
4
1994(1)
1.515
13.490(6)
11.841(5)
19.602(6)
103.79(3)
8
3040(3)
1.654
b, Å
c, Å
â, deg
Z
V, Å3
D
calcd, g cm-3
F(000)
temp, K
808
290
936
290
1536
290
diffractometer
radiation, λ Å
µ, cm-1
crystal size, mm
scan technique
decay, %
transmision factors
scan speed (ω), deg min-1
measured reflections
observed reflections, I > 3σ(I)
parameters
Rigaku AFC6S
Cu KR, 1.5418
9.476
Rigaku AFC6S
Mo KR, 0.7107
1.181
Rigaku AFC6S
Mo KR, 0.7107
1.432
0.30 × 0.28 × 0.24
0.35 × 0.30 × 0.15
0.14 × 0.14 × 0.10
ω/2θ
ω/2θ
ω/2θ
-10.00
0.788-1.000
4
-2.20
-0.93
0.949-1.000
4
0.923-1.000
4
2978
1663
172
3932
2234
199
2961
1649
163
refln/parameter ratio
9.69
0.0716
0.0864
2.704
11.23
0.0391
0.0452
1.367
10.12
0.0356
0.0445
1.530
Ra
-2
b
Rw (w ) σF
)
GOF
maximum ∆/σ in final cycle
0.2521
+0.73, -0.91
0.0004
+1.39, -0.61
0.1291
+0.93, -0.77
resd density (e Å-3
)
2
a R ) ∑(|Fo| - |Fc|)/∑|Fo|. b Rw ) (∑w (|Fo| - |Fc|)2/∑w|Fo| )1/2
.
1
room temperature for 2 days. Anal. Calcd for C26H42O4P2S2Pd2: C,
13 and 122 Hz, Car). 9, H NMR δ 1.16 (bs, 6 H, CMe2), 2.32 (bt, 2
H, Japp ) 4.3 Hz, CH2); 31P{1H} NMR AX spin system, δΑ ) -25.4,
δX ) -16.6, JAX ) 31 Hz; 13C{1H} NMR δ 34.4 (bs, CMe2), 61.7 (dd,
41.3; H, 5.5. Found: C, 41.4; H, 5.4. IR (Nujol mull): 1131 (υ
1
(SO)terminal), 1056 cm-1 (υ (SO)bridging). H NMR (CD2Cl2, 20 °C) δ
2
3
1.30 (d, 18 H, JHP ) 9.6 Hz, PMe3), 1.57 (s, 12 H, CMe2), 1.99 (dd,
2JCP ) 7 and 89 Hz, CH2), 169.5 (dd, JCP ) 12 and 117 Hz, Car).
3
1
4 H, JHP ) 8.7 Hz, CH2), 7.35 (m, 4 H, CHar), 7.44 (m, 2 H, CHar),
(Toluene-d8): 2a, H NMR δ 1.87 (s, 6 H, CMe2), 2.18 (bt, 2 H,
7.91 (m, 2 H, CHar); 31P{1H} NMR (CD2Cl2, 20 °C) δ -12.2 (s, PMe3);
Japp ) 6.5 Hz, CH2); 31P{1H} NMR AX spin system, δΑ ) -26.1,
δX ) -21.5, JAX ) 24 Hz; 13C{1H} NMR δ 35.9 (s, CMe2), 52.7 (d,
1
13C{1H} NMR (CD2Cl2, 20 °C) δ 13.1 (d, JCP ) 27 Hz, PMe3), 29.6
2JCP ) 87 Hz, CH2), 169.7 (dd, JCP ) 14 and 122 Hz, Car). 9, H
NMR δ 1.46 (bs, 6 H, CMe2), 2.51 (bs, 2 H, CH2); 31P{1H} NMR AX
spin system, δΑ ) -26.7, δX ) -18.6, JAX ) 30 Hz; 13C{1H} NMR
2
1
(s, CH2), 34.9 (s, CMe2), 37.7 (s, CMe2), 123.0, 126.8, 130.4 (s, CarH),
146.2, 147.6 (s, Car).
Reaction of Complex 11 with PMe3. A suspension of complex 11
(0.40 g, 0.5 mmol) in 20 mL of MeOH was treated with 1 mL (1 mmol)
of a 1 M solution of PMe3 in THF. The mixture was stirred at room
temperature for 2 h. The solvent was evaporated under reduced pressure
and the solid residue dissolved in 10 mL of toluene. After partial
concentration, addition of some petroleum ether and cooling to -30
°C provided compound 10 in quantitative yield.
2
3
δ 34.4 (bs, CMe2), 59.4 (d, JCP ) 84 Hz, CH2), 167.8 (dd, JCP ) 12
and 117 Hz, Car).
Synthesis of Pd[CH2CMe2C6H4-o-S(O2)](dmpe), 13. To a solution
of 0.24 g (0.7 mmol) of complex 2c in 30 mL of toluene, cooled at 0
°C, 17 mL of SO2(g) (0.7 mmol) was added. The solution was stirred at
this temperature for 3 h. During this time the color of the solution
turned yellow and some white solid precipitated. The suspension was
filtered, and the solid residue washed with Et2O (2 × 5 mL) and dried.
Complex 12 was crystallized from a mixture of toluene/petroleum ether
(2:1) and isolated as white crystals in 72% yield. Anal. Calcd for
C16H28O2P2SPd: C, 42.4; H, 6.2. Found: C, 42.0; H, 6.1. IR (Nujol
NMR Study of the Reaction of the Metallacycle 2a with SO2 at
Low Temperature. Compound 2a (0.022 g, 0.06 mmol) was dissolved
in 0.6 mL of CD2Cl2 and NMR spectra were recorded at -80 °C (1H,
31P{1H}, and 13C{1H}). SO2(g) (2.5 mL, 0.1 mmol) was added afterward
at -90 °C and the initial colorless solution turned bright orange, NMR
spectra were recorded again, starting at -80 °C and raising every 20
°C (-60 °C, -40 °C, -20 °C, 0 °C and 20 °C).
mull): 1146, 1022 cm-1 (υ (SO)). H NMR (CD2Cl2, 20 °C) δ 1.50
1
2
(d, 6 H, JHP ) 10.0 Hz, PMe2), 1.52 (s, 6 H, CMe2), 1.61 (d, 6 H,
The same experiment was carried out in acetone-d6 and toluene-d8.
2JHP ) 10.0 Hz, PMe2), 1.69-2.07 (m, 4 H, P-CH2), 1.75 (dd, 2 H,
3JHP ) 6.0 and 9.0 Hz, CH2), 7.29 (m, 2 H, CHar), 7.43 (m, 1 H, CHar),
7.99 (m, 1 H, CHar); 31P{1H} NMR (CD2Cl2, 20 °C) AX spin system,
δΑ ) 22.6, δX ) 24.0, JAX ) 24.7 Hz; 13C{1H} NMR (CD2Cl2, 20 °C)
1
Selected NMR Data, -80 °C. (CD2Cl2): 2a, H NMR δ 1.22 (s,
3
6 H, CMe2), 1.69 (dd, 2 H, JHP ) 5.6 and 8.3 Hz, CH2); 31P{1H}
NMR AX spin system, δΑ ) -24.8, δX ) -19.6, JAX ) 26 Hz;
13C{1H} NMR δ 35.2 (s, CMe2), 52.1 (dd, 2JCP ) 8 and 94 Hz, CH2),
1
1
2
1
δ 11.3 (d, JCP ) 26 Hz, PMe2), 12.3 (d, JCP ) 21 Hz, PMe2), 25.9
169.6 (dd, JCP ) 13 and 121 Hz, Car). 9, H NMR δ 1.19 (bs, 6 H,
CMe2), 2.32 (dd, 2 H, 3JHP ) 4.2 and 8.3 Hz, CH2); 31P{1H} NMR AX
spin system, δΑ ) -25.8, δX ) -16.8, JAX ) 31 Hz; 13C{1H} NMR
1
2
1
(dd, JCP ) 28 Hz, JCP ) 13 Hz, P-CH2), 28.9 (dd, JCP ) 31 Hz,
2JCP ) 20 Hz, P-CH2), 34.3 (d, JCP ) 85 Hz, CH2), 35.7 (d, JCP
)
2
4
2
3
8 Hz, CMe2), 36.5 (s, CMe2), 123.0, 126.0, 126.2, 129.2 (s, CarH), 147.9
(s, Car), 149.1 (d, JCP ) 17 Hz, Car).
X-ray Structure Determination of Compounds 2a, 10, and 12.
Crystals of the appropriate size were mounted on a glass fiber and
transferred to an AFC6S-Rigaku automatic diffractometer. Accurate
unit cell parameters and an orientation matrix were determined in each
δ 34.0 (bs, CMe2), 62.2 (d, JCP ) 83 Hz, CH2), 169.1 (dd, JCP ) 12
and 117 Hz, Car).
3
1
(Acetone-d6): 2a, H NMR δ 1.20 (s, 6 H, CMe2), 1.66 (dd, 2 H,
3JHP ) 5.9 and 8.1 Hz, CH2); 31P{1H} NMR AX spin system, δΑ
)
)
)
-24.5, δX ) -20.2, JAX ) 26 Hz; 13C{1H} NMR δ 35.8 (d, JCP
4
6.4 Hz, CMe2), 52.4 (dd, 2JCP ) 8 and 95 Hz, CH2), 170.4 (dd, 2JCP

4126 Inorganic Chemistry, Vol. 40, No. 17, 2001
Ca´mpora et al.
Table 2. Crystal and Refinement Data for Compound 2b
Table 4. Selected Bond Distances and Angles for Compound 10
2b
Bond Distances (Å)
Pd-S
2.298(2)
2.317(2)
2.367(2)
2.053(6)
1.474(5)
S-O2
1.457(6)
1.809(7)
1.53(1)
1.554(9)
1.399(8)
formula
mol wt
C18H24Pd
346.77
Pd-P1
Pd-P2
Pd-C(10)
S-O1
S-C1
C(1)-C(2)
C(2)-C(5)
C(5)-C(10)
crystal system
space group
cell dimensions, a, Å
b, Å
orthorhombic
P bca
19.908(5)
10.311(4)
14.735(5)
90
8
3025(2)
1.523
1424
Bond Angles (deg)
c, Å
S-Pd-P2
89.80(7)
85.9(2)
O1-S-O2
114.0(4)
119.4(4)
107.3(5)
119.6(6)
126.4(5)
R ) â ) γ (deg)
S-Pd-C10
P1-Pd-P2
P1-Pd-C10
Pd-S-C1
S-C1-C2
Z
96.91(7)
88.7(2)
C1-C2-C5
C2-C5-C10
Pd-C10-C5
V, Å3
D
calcd, g cm-3
108.6(2)
F(000)
Temp, K
293
Siemens AED
0.71073
12.12
Table 5. Selected Bond Distances and Angles for compound 12
diffractometer
radiation, λ Å
Bond Distances (Å)
µ, cm-1
Pd1-S
Pd1-P1
Pd1-O2
Pd1-C1
S-O1
2.281(2)
2.296(2)
2.175(5)
2.033(8)
1.462(5)
S-O2
1.499(5)
1.800(7)
1.53(1)
1.54(1)
1.39(1)
S-C10
C1-C2
C2-C5
C5-C10
crystal size, mm
scan technique
measured reflections
observed reflections
parameters
0.21 × 0.32 × 0.28
ω/2θ
4458
2982
179
Bond Angles (deg)
extinction coefficient
final R indices, [I > 2σ(I)]
R indices (all data)
0.0019(4)
S-Pd1-O2
S-Pd1-C1
P1-Pd1-O2
P1-Pd1-C1
Pd1-S-O2
Pd1-S-C10
89.4(1)
87.6(2)
93.6(1)
89.2(2)
111.4(2)
114.8(2)
O1-S-O2
110.7(3)
124.4(3)
116.9(5)
113.0(6)
123.4(6)
125.2(5)
R1a ) 0.0423, wR2b ) 0.1214
Pd1-O2-S
Pd1-C1-C2
C1-C2-C5
C2-C5-C10
S-C10-C5
R1a ) 0.0613, wR2b ) 0.1303
a R1 ) ∑|Fo - Fc|/∑(Fo). b wR2 ) [∑[w(Fo2 - Fc2)2]/∑[w(Fo )2]]2.
2
Table 3. Selected Bond Distances and Angles for Compound 2a
Bond Distances (Å)
Table 6. Selected Bond Distances and Angles for Compound 2b
Pd-P1
Pd-P2
Pd-C1
Pd-C6
2.310(4)
2.341(3)
2.08(1)
2.04(1)
C1-C2
C2-C5
C5-C6
1.54(2)
1.51(2)
1.39(2)
Bond Distances (Å)
Pd1-C1
2.023(3)
2.030(3)
2.342(4)
2.319(4)
2.311(3)
2.276(4)
C1-C6
1.405(4)
1.500(4)
1.528(5)
1.348(6)
1.344(5)
Pd1-C10
Pd1-C11
Pd1-C12
Pd1-C15
Pd1-C16
C6-C7
C7-C10
C11-C12
C15-C16
Bond Angles (deg)
P1-Pd-P2
P1-Pd-C1
P2-Pd-C6
C1-Pd-C6
98.3(1)
90.4(3)
94.6(4)
77.4(5)
Pd-C1-C2
C1-C2-C5
C2-C5-C6
Pd-C6-C5
108.0(8)
103.0(1)
116.0(1)
115.1(8)
Bond Angles (deg)
C1-Pd1-C10
C10-Pd1-C16
C10-Pd1-C15
C16-Pd1-C15
C1-Pd1-C12
C1-Pd1-C11
79.08(13)
95.39(14)
96.86(14)
34.07(13)
99.30(13)
102.24(13)
C12-Pd1-C11
C6-C1-Pd1
C1-C6-C7
C6-C7-C10
C7-C10-Pd1
33.63(14)
115.7(2)
115.4(3)
104.7(3)
112.0(2)
case by least-squares fitting from the settings of 25 high-angle
reflections. Crystal data and details on data collection and refinements
are given in Table 1. Data were collected by the ω/2θ scan method.
Lorentz and polarization corrections were applied. Decay was monitored
by measuring three standard reflections every 200 measurements. Decay
and semiempirical absorption corrections (ψ method) were also applied.
The structure was solved in each case by Patterson methods and
subsequent expansion of the model using DIRDIF.25 Reflections having
I > 3σ(I) were used for structure refinement. All non-hydrogen atoms
were anisotropically refined by full-matrix least. The hydrogen atoms
were localized in difference electron density maps or included at
idealized positions with fixed isotropic displacements parameters 1.2
times the value of their parent atom. All calculations for data reduction,
structure solution, and refinement were carried out on a VAX 3520
computer at the Servicio Central de Ciencia y Tecnolog´ıa de la
Universidad de Ca´diz, using the TEXSAN26 software system and
ORTEP27 for plotting.
X-ray Structure Determination of Compound 2b. The intensity
data of 2b were collected at room temperature on a Siemens AED
single-crystal diffractometer using a graphite monochromated Mo KR
radiation and the ω/2θ scan technique. Crystallographic and experi-
mental details for the structures are summarized in Table 2.
A correction for absorption was made (maximum and minimum
values for the transmission coefficient were 1.000 and 0.436).28
The structures were solved by Patterson and Fourier methods and
97)29 first with isotropic thermal parameters and then with anisotropic
thermal parameters in the last cycles of refinement for all the non-
hydrogen atoms.
The hydrogen atoms were introduced into the geometrically calcu-
lated positions and refined riding on the corresponding parent atoms.
In the final cycles of refinement, a weighting scheme for 2b was w )
1/[σ2Fo + (0.0887 P)2], where P ) (Fo +2Fc2)/3 was used.
2
2
Acknowledgment. Financial support from the Direccio´n
General de Ensen˜anza Superior e Investigacio´n Cient´ıfica
(Research grant to D.R.D-J. and Project 1FD97-019-C02-01)
and Junta de Andaluc´ıa is gratefully acknowledged. J.A.L.
thanks the CONACYT and the University of Guanajuato
(Mexico) for a studentship. We also thank the University of
Sevilla for the use of its analytical and NMR facilities.
Supporting Information Available: Tables of atomic coordinates,
thermal parameters, and bond lengths and angles for 2a, 2b, 10, and
12. This material is available free of charge via the Internet at
http://pubs.acs.org.
2
refined by full-matrix least-squares procedures (based on Fo ) (SHELX-
IC010114R
(25) Beursken, P. T. DIRDIF; Crystallography Laboratory: Toernooiveld,
1984; Technical Report 1984/1.
(26) TEXSAN, Single-Crystal Structure Analysis Software, version 5.0;
Molecular Structure Corporation: Houston, TX, 1989.
(27) Johnson, C. K. ORTEP, A Thermal Ellipsoid Plotting Program; Oak
Ridge National Laboratory: Oak Ridge, TN, 1965.
(28) Walker, N.; Stuart, D. Acta Crystallogr., Sect. A 1983, 39, 158.
Ugozzoli, F.; Comput. Chem. 1987, 11, 109.
(29) Sheldrick, G. M. SHELXS-97, Program for the solution and the
refinement of crystal structures; University of Go¨ttingen: Go¨ttingen,
Germany, 1997.