Carbene and carbonyl transfer from [W(CO)5(carbene)] to palladium, affording palladium(II) carbene acyl complexes

Article abstract of DOI:10.1021/om800358f

The reaction of [W(CO)₅{C(NEt₂)Ph}] (3) with [PdClR(SMe₂)]₂ (R = Me, Ph) occurs with transfer of carbene and carbonyl groups to give [PdCl{C(O)R} {C(NEt₂)Ph}] ₂ (R = Me, 4; R = Ph, 5). When

Full text of DOI:10.1021/om800358f

Organometallics 2008, 27, 4193–4198
4193
Carbene and Carbonyl Transfer from [W(CO)5(carbene)] to
Palladium, Affording Palladium(II) Carbene Acyl Complexes
Isabel Meana, Ana C. Albe´niz,* and Pablo Espinet*
IU CINQUIMA/Qu´ımica Inorga´nica, UniVersidad de Valladolid, 47071-Valladolid, Spain
ReceiVed April 22, 2008
The reaction of [W(CO)5{C(NEt2)Ph}] (3) with [PdClR(SMe2)]2 (R ) Me, Ph) occurs with transfer of
carbene and carbonyl groups to give [PdCl{C(O)R}{C(NEt2)Ph}]2 (R ) Me, 4; R ) Ph, 5). When the
reaction is monitored for R ) Me, only [PdCl(COMe)(SMe2)]2 and the final carbene 4 are observed,
suggesting that the transfer and insertion of the carbonyl group are faster than the carbene transmetalation.
Although CO insertion into M-X bonds is thermodynamically excluded in many systems (e.g., in
M-halogen and M-C6F5 bonds), this study warns of the fact that CO is easily available when
[M(CO)5(carbene)] complexes are used as carbene sources, whether for stoichiometric or for catalytic
reactions. This CO could react with the intermediates or the products in these reactions.
synthesize NHC metal carbenes,9 to prepare palladium monoam-
ino carbenes,10,11 and to generate unstable Pd alkoxycarbenes.10,12
Thus, [M(CO)5(carbene)] complexes (M ) group 6) have been
used by Sierra et al. in Pd-catalyzed reactions8,13 and by
Barluenga and Aumann in Ni-,14 Rh-,15 and Cu-catalyzed15b,16
cyclizations.
Introduction
Over many years metal carbene complexes have been used
in many selective processes.1 Most reactions use stable group
6 metal complexes containing alkoxycarbenes (C(OR1)R2);2
others (e.g., for cyclopropanation reactions) use in situ generated
metal carbene complexes of nonstabilized carbenes (CR1R2).1,3
In the past decade, metal complexes of stable N,N-heterocyclic
carbenes (NHCs) have become extremely popular in catalysis.4
Metal carbene complexes are accessible by a number of
methods, including coordination of stable carbenes4,5 and
others.6 The use of diazo derivatives and transmetalation from
other easily prepared metal carbenes7,8 can be applied to
generate carbenes in catalytic cycles. In this context the carbene
complexes derived from group 6 carbonyls have been used to
In the course of our studies of the migratory insertion reaction
in palladium carbenes,10,11 we attempted to prepare some
[PdRX{C(NR1 )R2}L] (R ) Me, Ph) complexes by carbene
2
transmetalation from [W(CO)5{C(NR1 )R2}] and we have found
2
out that carbene transfer occurs concurrently with carbonyl
insertion into the Pd-R bond. The increasing use of [M(CO)5-
(7) The first reported carbene transmetalation involved a molybdenum
methoxycarbene to form an iron and, presumably, a Ni carbene Fischer,
E. O.; Beck, H.-J. Angew. Chem., Int. Ed. Engl. 1970, 9, 72–73.
(8) Go´mez-Gallego, M.; Manchen˜o, M. J.; Sierra, M. A. Acc. Chem.
Res. 2005, 38, 44–53.
* To whom correspondence should be addressed. E-mail: albeniz@qi.uva.es
(A.C.A.); espinet@qi.uva.es.
(1) Zaragoza-Do¨rwald, F. Metal Carbenes in Organic Synthesis; Wiley-
VCH: Weinheim, Germany, 1999.
(9) (a) Liu, S.-T.; Reddy, K. R. Chem. Soc. ReV. 1999, 28, 315–322.
(b) Ku, R.-Z.; Huang, J.-C.; Cho, J.-Y.; Kiang, F.-M.; Reddy, K. R.; Chen,
Y.-C.; Lee, K.-J.; Lee, J.-H.; Lee, G.-H.; Peng, S.-M.; Liu, S.-T. Organo-
metallics 1999, 18, 2145–2154. (c) Wang, H. M. J.; Lin, I. J. B.
Organometallics 1998, 17, 972–975. (d) Liu, S.-T.; Hsieh, T.-Y.; Lee, G.-
H.; Peng, S.-M. Organometallics 1998, 17, 993–995.
(10) (a) Albe´niz, A. C.; Espinet, P.; Manrique, R.; Pe´rez-Mateo, A.
Chem. Eur. J. 2005, 11, 1565–1573. (b) Albe´niz, A. C.; Espinet, P.;
Manrique, R.; Pe´rez-Mateo, A. Angew. Chem., Int. Ed. 2002, 41, 2363–
2366.
(11) Albe´niz, A. C.; Espinet, P.; Pe´rez-Mateo, A.; Nova, A.; Ujaque,
G. Organometallics 2006, 25, 1293–1297.
(12) A ligand-stabilized Pd alkoxycarbene has been recently isolated
using transmetalation: Lo´pez-Alberca, M. P.; Manchen˜o, M. J.; Ferna´ndez,
I.; Go´mez-Gallego, M.; Sierra, M. A.; Torres, R. Org. Lett. 2007, 9, 1757–
1759.
(2) (a) Barluenga, J.; Santamar´ıa, J.; Toma´s, M. Chem. ReV. 2004, 104,
2259–2283. (b) De Meijere, A.; Schirmer, H.; Duetsch, M. Angew. Chem.,
Int. Ed. 2000, 39, 3964–4002. (c) Wulff, W. D. Organometallics 1998, 17,
3116–3134. (d) Schwindt, M. A.; Miller, J. R.; Hegedus, L. S. J. Organomet.
Chem. 1991, 413, 143–153. (e) Do¨tz, K. H. Angew. Chem., Int. Ed. Engl.
1984, 23, 587–608.
(3) (a) D´ıaz-Requejo, M. M.; Pe´rez, P. J. J. Organomet. Chem. 2005,
690, 5441–5450. (b) Miki, K.; Nishino, F.; Ohe, K.; Uemura, S. J. Am.
Chem. Soc. 2002, 124, 5260–5261. (c) Straub, B. F. J. Am. Chem. Soc.
2002, 124, 14195–14201. (d) Rodr´ıguez-Garc´ıa, C.; Oliva, A.; Ortun˜o,
R. M.; Branchadell, V. J. Am. Chem. Soc. 2001, 123, 6157–6163.
(4) (a) Kantchev, E. A. B.; O’Brien, C. J.; Organ, M. G. Angew. Chem.,
Int. Ed. 2007, 46, 2768–2813. (b) Herrmann, W. A. Angew. Chem., Int.
Ed. 2002, 41, 1290–1309.
(5) (a) Enders, E.; Gielen, H. J. Organomet. Chem. 2001, 617-618,
70–80. (b) Weskamp, T.; Bo¨hm, V. P. W.; Herrmann, W. A. J. Organomet.
Chem. 2000, 600, 12–22.
(13) (a) Del Amo, J. C.; Manchen˜o, M. J.; Go´mez-Gallego, M.; Sierra,
M. A. Organometallics 2004, 23, 5021–5029. (b) Sierra, M. A.; Del Amo,
J. C.; Manchen˜o, M. J.; Go´mez-Gallego, M. J. Am. Chem. Soc. 2001, 123,
851–861.
(6) Some examples are as follows. (i) Oxidative addition: (a) Fu¨rstner,
A.; Seidel, G.; Kremzow, D.; Lehmann, C. W. Organometallics 2003, 22,
907–909. (b) Gu¨ndemann, S.; Albrech, M.; Kovacevic, A.; Faller, J. W.;
Crabtree, R. H. Dalton Trans. 2002, 2163–2167(ii) Nucleophilic attack on
coordinated isonitriles: (c) Uso´n, R.; Fornie´s, J.; Espinet, P.; Navarro, R.;
Lalinde, E. Transition Met. Chem. 1984, 9, 277–279. (d) Butler, W. M.;
Enemark, J. H.; Parks, J.; Balch, A. L. Inorg. Chem. 1973, 12, 451–457.
(e) Busetto, L.; Palazzi, A.; Crociani, B.; Belluco, U.; Badley, E. M.; Kilby,
B. J. L.; Richards, R. L. J. Chem. Soc., Dalton Trans. 1972, 1800–1805(iii)
Reaction of electron-rich olefins: (f) Cetinkaya, B.; Dixneuf, P.; Lappert,
M. F. J. Chem. Soc., Dalton Trans. 1974, 1827–1833(iv) Other methods: (g)
Matsumura, N.; Kawano, J.; Fukunishi, N.; Inoue, H. J. Am. Chem. Soc.
1995, 117, 3623–3624.
(14) (a) Barluenga, J.; Vicente, R.; Barrio, P.; Lo´pez, L. A.; Toma´s, M.
J. Am. Chem. Soc. 2004, 126, 5974–5975. (b) Barluenga, J.; Barrio, P.;
´
Lo´pez, L. A.; Toma´s, M.; Garc´ıa-Granda, S.; Alvarez-Ru´a, C. Angew.
Chem., Int. Ed. 2003, 42, 3008–3011.
(15) (a) Aumann, R.; Go¨ttker-Schnetmann, I.; Fro¨hlich, R.; Meyer, O.
Eur. J. Org. Chem. 1999, 2545–2561. (b) Go¨ttker-Schnetmann, I.; Aumann,
R.; Bergander, K. Organometallics 2001, 20, 3574–3581. (c) Barluenga,
´
J.; Vicente, R.; Lo´pez, L. A.; Rubio, E.; Toma´s, M.; Alvarez-Ru´a, C. J. Am.
Chem. Soc. 2004, 126, 470–471.
(16) Barluenga, J.; Lo´pez, L. A.; Lo¨bet, O.; Toma´s, Garc´ıa-Granda, S.;
´
M.; Alvarez-Ru´a, C.; Borge, J. Angew. Chem., Int. Ed. 2001, 40, 3392–
3394.
10.1021/om800358f CCC: $40.75
2008 American Chemical Society
Publication on Web 07/30/2008

4194 Organometallics, Vol. 27, No. 16, 2008
Meana et al.
Scheme 1. Synthesis of Complexes 4-7
Table 1. Selected Distances (Å) and Angles (deg) for Complexes 4,
5, and 7
phino derivatives (245.9 ppm, 6; 245.6 ppm, 7). The latter show
high values for the JP-C coupling constant (102 and 104 Hz)
2
4a
5
7
consistent with the trans PPh3-carbene arrangement found in
the solid. The acyl groups show characteristic 13C NMR
resonances in the range 242-236 ppm and ν(CdO) IR bands
Pd-Ccarbene
Pd-Cacyl
Pd-Cl
2.00(3)
2.02(4)
2.455(11)
1.976(12)
1.978(14)
2.406(3)
2.048(8)
1.969(9)
2.438(2)
2.352(2)
1.311(10)
1.231(10)
in the range 1670-1630 cm-1
.
Pd-P
The 1H NMR spectral patterns of these complexes in solution
are interesting. The monomeric complexes 6 and 7 show,
whether at room or at low temperature, just one isomer with
diastereotopic methylene hydrogens (one AB system for each
of the two inequivalent ethyl groups), consistent with fast
rotation of the acyl group and slow rotation of the carbene
moiety (fast rotation of both groups should produce equivalence
within each methylene group). Similar slow rotation of the
carbene ligand has been observed before in [PdBr(C6F5)-
{C(NEt2)Ph}(PPh3)].10 For the dimeric complex 4 at room
temperature, the 1H NMR spectrum shows just one species, with
equivalent methylene hydrogen atoms within each ethyl group,
indicating that, in contrast with the monomeric 6, the rotation
of the carbene moiety is also fast in the dimer.17 At low
temperature, when rotation of the carbene becomes slow, 4 gives
rise to two isomeric forms, syn and anti (Scheme 2), depending
on whether the carbene substituents are on the same or opposite
sides of the Pd coordination plane in the dimer (keep in mind
that the acyl group is still rotating quickly). Similar rotation
rates are observed for 5, although in this case a mixture of trans
(major) and cis (minor) isomers in the dimer is additionally
present at 243 K (cis:trans ) 1:10).
Ccarbene-N
Cacyl-O
1.30(4)
1.16(5)
1.298(15)
1.211(16)
Ccarbene-Pd-Cacyl
Ccarbene-Pd-Cl
85.6(13)
94.8(9)
88.9(5)
93.7(3)
84.8(3)
91.2(2)
a Average values of both data in the dimer are given.
(carbene)] complexes (M ) group 6 metal) in carbene trans-
metalations, for either stoichiometric or catalytic syntheses,
makes it necessary to take this potential complication into
account.
Results and Discussion
Reactions of the Me-Pd and Ph-Pd derivatives 1 and 2 with
the tungsten carbene complex 3 leads to the dimeric carbene
acyl complexes 4 and 5, respectively (Scheme 1). In addition
to the transmetalation of the carbene from W to Pd, an insertion
of CO into the Pd-R bond has occurred, so that the initially
expected [Pd2(µ-Cl)2Me2{C(NEt2)Ph}2] compound is not ob-
tained. In solution and in the solid state, complex 4 is obtained
as a trans isomer, regarding the arrangement of the carbene
groups on both sides of the dimer (see below); in solution,
complex 5 is a mixture of cis (minor) and trans (major) isomers
whose signals partially overlap at room temperature but can be
distinguished at 243 K (cis:trans ) 1:10). Compounds 4 and 5
can be easily transformed into 6 and 7 by bridge cleavage with
PPh3. The substitution of the bridging chloride occurs trans to
the carbene, the ligand with the highest trans effect, as observed
before for analogous palladium carbene complexes.10
Some reactions were monitored by NMR to follow the
competition of CO transfer/insertion (insertion is apparently very
fast, and carbonyl intermediates of Pd were never detected) and
carbene transfer. Figure 2 shows the evolution of the reaction
of 1 with an excess of the tungsten carbene 3 (1:3 ) 1:6),
monitored by 1H NMR at 263 K in CD3CN.18 The disappearance
of 1 is accompanied by the appearance of the palladium acyl
carbene complex 4 and the palladium acyl complex [Pd2(µ-
Cl)2(COMe)2(SMe2)2] (8), along with [W(CO)5(SMe2)]. Com-
plex 8 is the result of CO transfer and insertion into the Pd-Me
bond of 1; in fact, it was independently synthesized by bubbling
CO in a solution of 1.19 Complex 4 could be the result of carbene
transfer to 8 or the formation of a putative [Pd2(µ-Cl)2-
Me2{C(NEt2)Ph}2] complex (which was never detected),20
The single crystal X-ray structures of 4, 5, and 7 were
determined. Table 1 gives a selection of distances and angles,
and Figure 1 shows the corresponding ORTEP drawings.
Complexes 4 and 5 exhibit a planar structure for the double
bridge and a trans arrangement of the two carbene (and the two
acyl) ligands in the dimer. In all the complexes the C(O)R
moiety lies perpendicular to the palladium coordination plane.
The carbene group (defined by the NCcarbeneCPh plane) also lies
perpendicular to the palladium coordination plane, with bond
lengths consistent with a Pd-Ccarbene single bond (1.976-2.048
Å) and a CdN double bond (1.298-1.311 Å). The double-
bond character of the latter is also consistent with an ν(CdN)
IR band at ca. 1570 cm-1. Hence, as for other palladium
monoamino carbenes synthesized before,10,11 a bond representa-
tion as depicted in Scheme 1 is chosen for the molecule
throughout this paper.
(17) The different rates of carbene rotation in the monomeric and the
dimeric complexes could be due to the different geometrical constraints in
both complexes. However, it looks more likely that the rotation of the
carbene in the dimers requires cleavage of at least one of the chloro bridges.
(18) Complex 1 shows a fluxional behavior in CD3CN solutions. A
mixture of three species, but no free SMe2, was found when 1 was dissolved
in CD3CN and cooled to 233 K. Thus, these species can be tentatively
assigned to the three isomers of [PdClMe(SMe2)(NCCD3)] (Pd-Me, δ 0.68,
0.53, 0.36). These complexes undergo fast exchange upon warming to give,
at 263 K, the average Pd-Me signal shown in Figure 2 and broad SMe2
resonances around 2.3 ppm. This is not observed for the acyl derivative 8,
which at 233 K in CD3CN shows only one species with coordinated SMe2.
(19) 8 was prepared by following the method described for the analogous
[Pd2(µ-Cl)2(COMe)2L2] (L ) PR3): Hayashi, Y.; Isobe, K.; Nakamura, Y.;
Okeya, S. J. Organomet. Chem. 1986, 310, 127–134.
The 13C NMR chemical shifts in solution for the carbene
carbon are similar to those found for other monoamino carbene
complexes of palladium: 230.7 (4), and 227.2 (5) ppm for the
dimeric complexes and somewhat higher values for the phos-

Carbene and CO Transfer from W to Pd
Organometallics, Vol. 27, No. 16, 2008 4195
Figure 1. ORTEP drawings for complexes 4, 5, and 7 (40% probability ellipsoids). Hydrogen atoms are omitted for clarity.
Scheme 2. Isomers Associated with Slow Carbene Rotation
8 with SMe2 signals (Figure 2). However, Figure 3 shows the
quantitative results obtained, by H NMR at 273 K, for the
1
about the Pd-C Bond
reaction of the acyl complex 8 and an excess of [W(CO)5-
{C(NEt2)Ph}] (3) (8:3 ) 1:6, Figure 3a), compared with the
reaction of an equimolar mixture of the methyl complex 1 and
the acyl derivative 8 with the tungsten carbene (1:8:3 ) 1:1:6,
Figure 3b). The profile of the reaction of 8 with 3, which
corresponds only to carbene transmetalation, shows a steady
variation where the decay in the rate of formation of 4 with
time is faster than that expected from a first-order dependence
on [4]. This suggests that part of the SMe2 liberated in the
reaction is not trapped by the W(CO)5 byproduct in the form
of [W(CO)5(SMe2)] (some [W(CO)5(NCCD3)] is also formed,
and some decomposition is observed), and is competing with
the carbene for the coordination site on Pd, progressively
slowing the transmetalation down. For comparison, Figure 3b
shows that complex 1 (50% of the starting mixture of Pd
compounds, starting at 100 in the graphics) undergoes a fast
reaction to give the palladium acyl 8. This happens with a rate
that is faster than the carbene transmetalation to 8 to give 4,
and consequently, an increase in concentration of 8 over the
initial value of 100 is observed. The CO transfer/insertion to 1
is fairly fast. When it is complete (t ≈ 200 min), an amount of
8 equivalent to the initial amount is still unreacted. This, along
with the absence of any methylcarbene intermediate and the
accumulation of 8 observed in the reaction monitored in Figure
2, support that the CO transfer/insertion is noticeably faster than
carbene transmetalation.21
which should then undergo fast CO transfer and insertion into
the Pd-Me bond as soon as it is formed.
The evolution of the reaction of 1 and 3 could not be
quantified, due to severe overlap of the C(O)Me resonance of
A couple of examples of the transfer of a carbene and a CO
group that leads to a rhodium15c or platinum carbonyl complex
have been reported.9b,d As far as we know, there is only one
report on the formation of palladium acyls by CO transfer from
(20) Reaction mixtures were cooled to 233 K, at different times and
conversions, to slow down the exchange process that affects 1, in order to
facilitate the observation of a possible palladium methyl carbene complex.
Cooling led to better resolved spectra, but no complex of this type was
detected.
(21) We have checked the CO transfer ability of these types of tungsten
complexes. [W(CO)5(NCMe)] reacts with 1 to give 8, demonstrating that
not only 3 but also the reaction byproducts can be the source of CO in the
carbonylation. In other words, the carbonylating agent is not necessarily
consumed (although its nature changes) as the carbonylation proceeds, this
helping to keep the carbonylation rate high.
Figure 2. 1H NMR spectra of the evolution of a mixture of 1 and
3 (1:6) in CD3CN at 263 K. Signals for unreacted [W(CO)5-
{C(NEt2)Ph}], used in excess, and broad signals corresponding to
SMe2 are also seen.

4196 Organometallics, Vol. 27, No. 16, 2008
Meana et al.
presence of a Pd-R group (R ) Me, Ph) leads to a fast CO
insertion reaction that alters the nature of the organometallic
moiety formed. This complication cannot happen when a Pd-R
group is absent (e.g., halide complexes with Pd-X bonds) or
when the insertion of CO into the Pd-R bond is thermodynami-
cally disfavored (this is the case for electronegative R groups:
e.g., C6F5 in our former work, acyls, etc.).10,11,24 Although in
those cases CO transfer may be irrelevant or negligible, the
results reported here indicate that, in the transmetalation of
carbene moieties from [W(CO)5(carbene)] complexes, CO is
always present as a potential reagent, which can induce
unexpected transformations. This should be taken into account
when planning stoichiometric or catalytic processes that use this
type of carbene source.8
Experimental Section
General Considerations. 1H, 13C{1H}, 19F, and 31P{1H} NMR
spectra were recorded on Bruker AC-300 and ARX-300 spectrom-
eters. Chemical shifts (in δ units, ppm) were referenced to Me4Si
(1H and 13C), CFCl3 (19F), and 85% H3PO4 (31P). The spectral
data were recorded at 293 K unless otherwise noted. IR spectra
were recorded on a Perkin-Elmer IR 883 and Perkin-Elmer FT-IR
1720X spectrophotometer. C, H, and N elemental analyses were
performed on a Perkin-Elmer 2400 CHN microanalyzer.
All the reactions described were carried out under a nitrogen
atmosphere using standard Schlenk techniques. Solvents were dried
over and distilled from appropriate drying agents under nitrogen,
prior to use. Complexes 1,25 3,26 trans-[PdCl2(SMe2)2],27 and
[W(CO)5(MeCN)]28 were prepared according to literature methods.
[Pd(µ-Cl)Ph(SMe)2]2 (2). To a solution of trans-[PdCl2(SMe2)2]
(1.5000 g, 4.973 mmol) in THF (225 mL) at -80 °C under nitrogen
was added dropwise over a period of 45 min a solution of ZnPhCl
in THF (25 mL), previously prepared from LiPh (1.73 M in Bu2O,
7.460 mmol) and ZnCl2 (0.64 M in THF, 6.848 mmol) at -80 °C.
The orange solution obtained was warmed to -15 °C over a period
of 5 h, giving a yellow solution. It was evaporated to dryness at 0
°C, and the residue was extracted with CH2Cl2 (25 mL). The filtered
CH2Cl2 solution was evaporated to dryness at 0 °C, and addition
of Et2O (25 mL) to the residue yielded a white solid, which was
filtered, washed with Et2O (2 × 5 mL), and vacuum-dried. Yield:
0.5315 g (38%). Anal. Calcd for C16H22Cl2Pd2S2: C, 34.18; H, 3.95.
Found: C, 33.85; H, 3.68. IR (Nujol mull, cm-1): ν(Pd-S) 334
(w); ν(Pd-Cl) 287 (m), 249 (w). 1H NMR (300 MHz, δ, CDCl3):
7.15 (m, 2H; Hortho Ph), 7.00-6.85 (m, 3H; Hpara, Hmeta Ph), 2.18
(s, 6H; SMe2). 13C{1H} NMR (74.5 MHz, δ, CDCl3, 253 K): 142.9
(s, Cipso Ph), 133.8 (Cmeta Ph), 128.1 (Cpara Ph), 124.40 (Cortho Ph),
23.2 (s, SMe2).
Figure 3. Plots representing the percentage of Pd complexes vs
time for the following reactions: (a) 8 and 3 (8:3 ) 1:6); (b) a
mixture of 1 and 8 with an excess of 3 (1:8:3 ) 1:1:6). Note that
for (a) the maximum production of 4 is 100, whereas that for (b)
is 200.
metal carbonyl complexes in the literature.22 On the basis of
theoretical studies on the reaction with cobalt carbonyl com-
plexes, a mechanism was proposed that involves transmetalation
of the methyl group from Pd to Co, insertion of CO into the
new Co-Me bond, and transmetalation of the acyl group from
Co back to Pd. In the reactions reported here, there is no
evidence of the formation of a any tungsten acyl in the reactions
monitored, starting either from 3 or from [W(CO)5(NCMe)],
and we suggest that simple CO dissociation from 3, a usual
step in most tungsten carbonyl substitution reactions,23 followed
by coordination to Pd and insertion into the Pd-R bond can
explain the observed results.
trans-[Pd(µ-Cl)(COMe){C(NEt2)Ph}]2 (4). Complex 3 (0.6100
g, 1.257 mmol) was added to a solution of 1 (0.2914 g, 0.629 mmol)
in CH3CN (12 mL) at room temperature. The mixture was stirred
for 2 h. The dark solution was filtered through activated carbon
and Celite and then concentrated to ca. 6 mL. Et2O (10 mL) was
added to the residue, and the solution was kept at -20 °C for 1 h.
(24) (a) Yamamoto, A. Organotransition Metal Chemistry: Fundamental
Concepts and Applications; Wiley-Interscience: New York, 1986; p 251.
(b) Mukhadkar, A. J.; Green, M.; Stone, F. G. A. J. Chem. Soc. A 1969,
3023.
(25) Byers, P. K.; Canty, A. J.; Engelhardt, L. M.; White, A. H. J. Chem.
Soc., Dalton Trans. 1986, 1731–1734.
In conclusion, the transfer of CO is a noticeable feature of
the transmetalation of carbene described in this work, since the
(22) Komine, N.; Tsutsuminai, S.; Hoh, H.; Yasuda, T.; Hirano, M.;
Komiya, S. Inorg. Chim. Acta 2006, 359, 3699–3708.
(26) Fischer, E. O.; Kreissl, F. R. In Synthetic Methods of Organometallic
and Inorganic Chemistry; Herrmann, W. A., Ed.; Thieme Verlag: New York,
1997; Vol. 7, pp 129-131.
(23) (a) Kirtley, S. W. In ComprehensiVe Organometallic Chemistry;
Wilkinson, G., Stone, F. G. A., Abel, E. W., Eds.; Pergamon: Oxford, U.K.,
1982; Vol. 3, Chapter 26.1, p 804. (b) Collman, J. P.; Hegedus, L. S.; Norton,
J. R.; Finke, R. G. Principles and Aplications of Organotransition Metal
Chemistry; University Science Books: Mill Valley, CA, 1987; pp 249-
253.
(27) A synthetic procedure analogous to that for the complex
[PdCl2(tht)2] was used: Uso´n, R.; Fornie´s, J.; Mart´ınez, F.; Toma´s, M.
J. Chem. Soc., Dalton Trans. 1980, 888–893.
(28) (a) Buchner, W.; Schenk, W. A. Inorg. Chem. 1984, 23, 132–137.
(b) Schenk, W. A. J. Organomet. Chem. 1979, 179, 253–261.

Carbene and CO Transfer from W to Pd
Organometallics, Vol. 27, No. 16, 2008 4197
Table 2. Crystallographic Data for Complexes 4, 5, and 7
4
5
7
formula
mol wt
C26H36Cl2N2O2Pd2
692.27
C36H40Cl2N2O2Pd2
816.40
C36H35ClNOPPd
670.47
cryst color and habit
cryst size (mm)
T (K)
yellow prism
0.11 × 0.07 × 0.02
298(2)
yellow prism
0.12 × 0.1 × 0.04
298(2)
yellow prism
0.18 × 0.09 × 0.04
298(2)
wavelength (Mo KR) (Å)
cryst syst
space group
a (Å)
b (Å)
c (Å)
0.710 73
triclinic
P1
8.109(2)
0.710 73
orthorhombic
Pbca
15.724(4)
13.236(3)
16.927(4)
90
0.710 73
monoclinic
P21/n
10.082(2)
33.052(8)
10.983(3)
90
116.573(4)
90
3273.3(14)
4
1.361
0.725
32993
8.126(2)
12.537(4)
102.591(5)
101.595(5)
109.386(5)
726.3(4)
R (deg)
ꢀ (deg)
90
90
γ (deg)
V (Å3)
3523.0(15)
4
1.539
1.206
30475
2.34 e θ e 26.39
3608 (0.2266)
1675
Z
1
Dcalcd (g cm-3
)
1.583
1.446
6926
1.74 e θ e 28.34
3539 (0.0618)
2684
µ (mm-1
)
no. of collected rflns
scan range (θ) (deg)
no. of unique rflns (Rint
no. of rflns (I > 2σ(I))
no. of params
1.23 e θ e 24.71
5687 (0.1568)
3074
)
308
201
372
final R indicesa (I > 2σ(I))
R indicesa (all data)
R1 ) 0.0735
wR2 ) 0.1971
R1 ) 0.0958
wR2 ) 0.2138
1.501, -1.049
R1 ) 0.0852
wR2 ) 0.1811
R1 ) 0.1976
wR2 ) 0.2492
1.438, -1.129
R1 ) 0.0595
wR2 ) 0.1345
R1 ) 0.1407
wR2 ) 0.1905
0.745, -1.048
largest diff peak, hole (e Å-3
)
2
2 2
a R1 ) ∑(||Fo| - |Fc||)/∑|Fo|); wR2 ) [∑[w(Fo - Fc ) /∑[w(Fo2)2]]1/2
.
A grayish solid was obtained, which was filtered, washed with
n-hexane (2 × 5 mL), and air-dried. Yield: 0.2436 g (65%).
Recrystallization of a small portion of this solid from a CH2Cl2/
Et2O solution at -20 °C, previous disolution of the solid in CH2Cl2,
and filtration through activated carbon and Celite yielded yellow
crystals suitable for X-ray diffraction studies and elemental analyses.
Anal. Calcd for C26H36Cl2N2O2Pd2: C, 45.10; H, 5.25; N, 4.04.
Found: C, 44.81; H, 4.88; N, 4.08. IR (Nujol mull, cm-1): ν(CdO)
cis + trans), 226.0 (s, Pd-Ccarbene, cis + trans), 143.0 (s, Cipso Ph,
cis + trans), 138.8 (s, Cipso C(O)Ph, cis + trans), 131.1 (s, Cpara
C(O)Ph, cis + trans), 130.3 (s, Cortho C(O)Ph, cis + trans), 128.2
(s, Cmeta Ph, cis + trans), 127.6 (s, Cmeta C(O)Ph, cis + trans), 126.8
(s, Cpara Ph, cis + trans), 121.5 (s, Cortho Ph, cis + trans), 55.9 (s,
CH2, trans), 55.7 (s, CH2, cis), 47.2 (s, C′H2, cis/trans), 14.0 (s,
CH3, C′H3, cis + trans).
[PdCl(COMe){C(NEt2)Ph}(PPh3)] (6). PPh3 (0.0907 g, 0.346
mmol) was added to a solution of 4 (0.1100 g, 0.158 mmol) in
CH2Cl2 (15 mL) at room temperature. The dark greenish solution
was stirred for 30 min and evaporated to dryness. Et2O (10 mL)
was added to the residue, and the solution was kept at -20 °C for
1 h. A grayish solid was obtained, which was filtered, washed with
Et2O (2 × 5 mL), and air-dried. Yield: 0.1678 g (87%). Recrys-
tallization of a small portion of this solid from CH2Cl2/Et2O solution
at -20 °C, previous disolution of the solid in CH2Cl2, and filtration
through activated carbon and Celite yielded yellow crystals suitable
for elemental analyses.
1674 (m), 1652 (m); ν(CdN) 1596 (w), 1570 (m); ν(Pd-Clbridging
)
1
275 (w). H NMR (300 MHz, δ, CDCl3): 7.39 (m, 2H; Hmeta Ph),
7.28 (m, 1H; Hpara Ph), 6.95 (m, 2H; Hortho Ph), 4.90 (m, 2H; CH2),
3.41 (m, J ) 14.5, 7.0 Hz, 2H; CH′2), 2.23 (s, 3H; C(O)Me), 1.69
(t, J ) 7.0 Hz, 3H; CH3), 1.11 (t, J ) 7.0 Hz, 3H; CH′3). 13C{1H}
NMR (74.5 MHz, δ, CDCl3): 241.5 (s, C(O)Me), 228.4 (s,
Pd-Ccarbene), 143.0 (s, Cipso Ph), 128.4 (s, Cmeta Ph), 127.0 (s, Cpara
Ph), 121.3 (s, Cortho Ph), 56.1 (s, CH2), 47.0 (s, C′H2), 37.5 (s,
C(O)Me), 13.9 (s, CH3, C′H3).
[Pd(µ-Cl)(COPh){C(NEt2)Ph}]2 (5). To a solution of 3 (0.2130
g, 0.439 mmol) in CH3CN (20 mL) was added 2 (0.1234 g, 0.219
mmol) at room temperature. The mixture was stirred for 5 h. The
dark solution was filtered through activated carbon and Celite and
then evaporated to dryness. EtOH (20 mL) was added to the residue,
and the solution was kept at -20 °C for 30 min. A dark greenish
solid was obtained, which was filtered, washed with Et2O (2 × 5
mL), and air-dried. Yield: 0.1056 g (59%). Recrystallization of this
solid from CH2Cl2/Et2O solution at -20 °C, previous dissolution
of the solid in CH2Cl2, and filtration through activated carbon and
Celite yielded yellow crystals suitable for X-ray diffraction studies
and elemental analyses. 5 is a mixture of trans and cis isomers at
293 K (see text). Anal. Calcd for C36H40Cl2N2O2Pd2: C, 52.95; H,
4.95; N, 3.43. Found: C, 52.51; H, 4.86; N, 3.46. IR (Nujol mull,
cm-1): ν(CdO) 1644 (m); ν(CdN) 1588 (w), 1576 (m), 1562 (m);
ν(Pd-Cl) 272 (w). 1H NMR (300 MHz, δ, CDCl3): 8.06 (bm, 2H;
Anal. Calcd for C31H33ClNOPPd: C, 61.19; H, 5.48; N, 2.30.
Found: C, 60.92; H, 5.24; N, 2.46. IR (Nujol mull, cm-1): ν(CdO)
1662 (m), 1647 (m); ν(CdN) 1597 (w), 1578 (m), 1571 (m);
1
ν(Pd-Cl) 331 (w). H NMR (300 MHz, δ, CDCl3): 7.65 (m, 6H;
PPh3), 7.50-7.29 (m, 14H; PPh3, Ph), 5.00, 4.78 (AB system, J )
12.7, 7.2 Hz, 2H; CH2), 3.59, 3.44 (AB system, J ) 12.3, 7.2 Hz,
2H; CH′2), 1.76 (t, J ) 7.2 Hz, 3H; CH3), 1.48 (s, 3H; C(O)Me),
1.18 (t, J ) 7.2 Hz, 3H; CH′3). 31P{1H} NMR (121.4 MHz, δ,
CDCl3): 20.3 (s). 13C{1H} NMR (74.5 MHz, δ, CDCl3, 243 K):
2
245.9 (d, JC,P )102 Hz, Pd-Ccarbene), 242.2 (s, C(O)Me), 142.9
2
1
(s, Cipso Ph), 134.5 (d, JC,P ) 12 Hz, Cortho PPh3), 131.5 (d, JC,P
) 40 Hz, Cipso PPh3), 130.4 (s, Cpara PPh3), 128.7 (s, Cmeta Ph),
3
128.5 (d, JC,P ) 9 Hz, Cmeta PPh3), 127.3 (s, Cpara Ph), 122.4 (s,
4
Cortho Ph), 55.8 (s, CH2), 47.1 (d, JC,P ) 4.6 Hz, C′H2), 39.5 (d,
3JC,P ) 11 Hz, C(O)Me), 14.4 (s, CH3), 13.6 (s, C′H3).
H
H
H
ortho C(O)Ph, cis + trans), 7.55 (bm, Hpara C(O)Ph, cis), 7.32 (bm,
para C(O)Ph, trans), 7.28-7.05 (ma, 5H; Hmeta C(O)Ph, Hmeta Ph,
para Ph, cis + trans), 6.69 (bm, Hortho Ph, cis), 6.63 (bm, Hortho Ph,
[PdCl(COPh){C(NEt2)Ph}(PPh3)] (7). PPh3 (0.0744 g, 0.284
mmol) was added to a solution of 5 (0.1079 g, 0.132 mmol) in
CH2Cl2 (15 mL) at room temperature. The greenish solution was
stirred for 1 h 30 min and evaporated to dryness. n-Hexane (10
mL) was added to the residue, and the solution was stirred for 1 h
while being kept at -20 °C. A grayish solid was obtained, which
trans), 5.02 (bm, 2H; CH2, cis + trans), 3.31(bm, 2H; CH′2, cis +
trans), 1.70 (bm, 3H; CH3, cis + trans), 0.99 (t, 3H; CH′3 cis +
trans). 13C{1H} NMR (74.5 MHz, δ, CDCl3): 240.8 (s, C(O)Ph,

4198 Organometallics, Vol. 27, No. 16, 2008
Meana et al.
was filtered, washed with cold n-hexane (2 × 5 mL), and air-dried.
Yield: 0.1433 g (81%). Recrystallization of this solid from CH2Cl2/
Et2O solution at -20 °C, previous dissolution of the solid in CH2Cl2,
and filtration through activated carbon and Celite yielded yellow
crystals suitable for X-ray diffraction studies and elemental analyses.
Anal. Calcd for C36H35ClNOPPd: C, 64.48; H, 5.27; N, 2.09.
Found: C, 64.38; H, 4.91; N, 2.00. IR (Nujol mull, cm-1): ν(CdO)
1630 (m); ν(CdN) 1591 (w), 1577 (m), 1571 (m); ν(Pd-Cl) 333
(w). 1H NMR (300 MHz, δ, CDCl3): 7.50 (m, 6H; PPh3), 7.10-7.40
(17H; PPh3, C(O)Ph, Ph), 6.85 (m, 2H; Hortho C(O)Ph), 5.17, 4.80
(AB system, J ) 12.7, 7.2 Hz, 2H; CH2), 3.50, 3.38 (AB system,
J ) 12.7, 7.2 Hz, 2H; CH′2), 1.77 (t, 3H; CH3), 1.12 (t, J ) 7.2
Hz, 3H; CH′3). 31P{1H} NMR (121.4 MHz, δ, CDCl3): 19.7 (s).
13C{1H} NMR (74.5 MHz, δ, CDCl3, 243 K): 245.6 (d, 2JC,P )104
Hz, Pd-Ccarbene), 236.4 (d, 2JC,P ) 4.5 Hz, C(O)Ph), 143.1 (s, Cipso
hydrogen atoms were refined anisotropically, and hydrogen atoms
were constrained to ideal geometries and refined with fixed isotropic
displacement parameters. Relevant crystallographic data are col-
lected in Table 2.
Followup of the Reactions by NMR Reaction of 1 and 3. A
5 mm NMR tube was charged with 1 (0.0020 g, 0.005 mmol), 3
(0.0133 g, 0.027 mmol), and CD3CN (0.6 mL), under nitrogen at
-30 °C. The solution was then monitored by 1H NMR spectroscopy
at 263 K. The resulting products were identified as 4, 8, and
[W(CO)5(SMe2)]. The same sample was warmed to room temper-
ature and the complete disappearance of 8, to form 4 was observed.
8: 1H NMR (300 MHz, δ, CDCl3/CD3CN) 2.48/2.41 (s, 3H; Me),
2.38/2.31 (s, 6H; SMe2).
[W(CO)5(SMe2)]: 1H NMR (300 MHz, δ, CD3CN) 2.65 (s, 6H;
SMe2).
3
3
Ph), 139.8 (d, JC,P ) 7.5 Hz, Cipso C(O)Ph), 134.4 (d, JC,P ) 12
1
The reactions of a mixture of 1 + 8 + 3 or 8 + 3, in the starting
molar ratios given in the text, were carried out by following the
same procedure, but the followup was carried out at 273 K.
Hz, Cortho PPh3), 131.3 (d, JC,P ) 41 Hz, Cipso PPh3), 130.8 (s,
C
para C(O)Ph), 130.0 (s, Cpara PPh3, Cortho C(O)Ph), 128.2 (s, Cmeta
Ph), 128.1 (d, 3JC,P ) 10.5 Hz, Cmeta PPh3), 127.1 (s, Cmeta C(O)Ph),
4
126.8 (s, Cpara Ph), 55.1 (s, CH2), 47.2 (d, JC,P ) 4.5 Hz, C′H2),
14.3 (s, CH3), 13.6 (s, C′H3).
Acknowledgment. Financial support from the Spanish
MEC (DGI, Grant CTQ2007-67411/BQU; Consolider Inge-
nio 2010, Grant INTECAT, CSD2006-0003; FPU fellowship
to I.M.) and the Junta de Castilla y Leo´n (Project VA117A06)
is gratefully acknowledged.
X-ray Crystal Structure Determinations. Crystals suitable for
X-ray analyses were obtained by slow diffusion of n-hexane (4) or
Et2O (5, 7) into a solution of the complex in CH2Cl2 at -20 °C.
Each crystal was mounted on the tip of a glass fiber. X-ray
measurements were made using a Bruker SMART CCD area-
detector diffractometer with Mo KR radiation (0.710 73 Å). The
reflections were collected, the intensities were integrated, and the
structures were solved by direct methods procedures.29 Non-
Supporting Information Available: Figures showing 1H NMR
spectra of 4 and 5, as well as NMR data at different temperatures,
and CIF files giving complete crystallographic data for complexes
4, 5, and 7. This material is available free of charge via the Internet
at http://pubs.acs.org.
(29) Data analysis and drawing were performed with the programs
SMART V5.051 (1998), SAINT V6.02 (1999), and: Sheldrick, G. M.
SHELXTL V5.1; Bruker AXS, Inc., Madison, WI, 1998.
OM800358F