Synthesis and structure of tetranuclear orthometallated Pd(II) complexes derived from bis-iminophosphoranes

Article abstract of DOI:10.1039/b718108f

The reaction of Pd(OAc)₂ with bis-iminophosphoranes Ph ₃P=NCH₂CH₂CH₂N=PPh₃ (1a), [C₆H₄(C(O)N=PPh₃)₂-1,3] (1b) and [C₆H₄(C(O)N=PPh₃)₂-1,2] (1c), gives the orthopalladated tetranuclear complexes [{Pd(μ-Cl){C₆H ₄(PPh₂=NCH₂-κ-C,N)-2}}₂CH ₂]₂ (2a) [{Pd(μ-OAc){C₆H ₄(PPh₂=NC(O)-κ-C,N)-2}}₂C ₆H₄-1′,3′]₂ (2b) and [{Pd(μ-OAc){C₆H₄(PPh₂=NC(O)-κ-C,N)-2}} ₂C₆H₄-1′,2′]₂ (2c). The reaction takes place in CH₂Cl₂ for 1a, but must be performed in glacial acetic acid for 1b and 1c. The process implies in all cases the activation of a C-H bond on a Ph ring of the phosphonium group, with concomitant formation of endo complexes. This is the expected behaviour for 1a, but for 1b and 1c reverses the exo orientation observed in other ketostabilized iminophosphoranes. The influence of the solvent in the orientation of the reaction is discussed. The dinuclear acetylacetonate complexes [{Pd(acac-O,O′){C₆H₄(PPh₂=NCH ₂-κ-C,N)-2}}₂CH₂] (3a), [{Pd(acac-O,O′){C₆H₄(PPh₂=NC(O)-κ- C,N)-2}}₂C₆H₄-1′,3′] (3b) and [{Pd(acac-O,O′){C₆H₄(PPh₂=NC(O)-κ- C,N)-2}}₂C₆H₄-1′,2′] (3c) have been obtained from the halide-bridging tetranuclear derivatives. The X-ray crystal structure of [3c?4CHCl₃] is also reported. The Royal Society of Chemistry.

Full text of DOI:10.1039/b718108f

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Synthesis and structure of tetranuclear orthometallated Pd(II) complexes
derived from bis-iminophosphoranes†
Raquel Bielsa,a Rafael Navarro,a Tatiana Solerb and Esteban P. Urriolabeitia*a
Received 22nd November 2007, Accepted 10th January 2008
First published as an Advance Article on the web 20th February 2008
DOI: 10.1039/b718108f
=
=
The reaction of Pd(OAc)2 with bis-iminophosphoranes Ph3P NCH2CH2CH2N PPh3 (1a),
=
=
[C6H4(C(O)N PPh3)2-1,3] (1b) and [C6H4(C(O)N PPh3)2-1,2] (1c), gives the orthopalladated
=
tetranuclear complexes [{Pd(l-Cl){C6H4(PPh2 NCH2-j-C,N)-2}}2CH2]2 (2a) [{Pd(l-OAc)-
ꢀ
ꢀ
=
=
{C6H4(PPh2 NC(O)-j-C,N)-2}}2C6H4-1 ,3 ]2 (2b) and [{Pd(l-OAc){C6H4(PPh2 NC(O)-j-C,N)-2}}2-
C6H4-1ꢀ,2ꢀ]2 (2c). The reaction takes place in CH2Cl2 for 1a, but must be performed in glacial acetic acid
for 1b and 1c. The process implies in all cases the activation of a C–H bond on a Ph ring of the
phosphonium group, with concomitant formation of endo complexes. This is the expected behaviour for
1a, but for 1b and 1c reverses the exo orientation observed in other ketostabilized iminophosphoranes.
The influence of the solvent in the orientation of the reaction is discussed. The dinuclear
ꢀ
=
acetylacetonate complexes [{Pd(acac-O,O ){C6H4(PPh2 NCH2-j-C,N)-2}}2CH2] (3a),
ꢀ
ꢀ
ꢀ
=
[{Pd(acac-O,O ){C6H4(PPh2 NC(O)-j-C,N)-2}}2C6H4-1 ,3 ] (3b) and
ꢀ
ꢀ
ꢀ
=
[{Pd(acac-O,O ){C6H4(PPh2 NC(O)-j-C,N)-2}}2C6H4–1 ,2 ] (3c) have been obtained from the
halide-bridging tetranuclear derivatives. The X-ray crystal structure of [3c·4CHCl3] is also reported.
are the most studied, in its neutral,3 monoanionic (methanide)4
Introduction
or dianionic (carbenic) forms.2,5 Complexes derived from other
diphosphines are also known.4e,f The structure shown in Fig. 1(ii)
represents those compounds obtained from bis-amines, which are
relatively less-developed, although there are notable contributions
in coordination chemistry6 and in organic synthesis.7 The
compounds derived formally from aminophosphines [Fig. 1(iii)]
are still scarcely-represented.8
=
Bis-iminophosphoranes are species containing two formal P N
double bonds. Fig. 1 shows three structural motifs which can
represent this definition. These structures can be formally derived
from (i) bis-phosphines, (ii) bis-amines, or (iii) aminophosphines.
Due to the presence of two N atoms, these species behave as
chelating N,N-ligands towards transition metals, and show a rich
coordination chemistry.1a In addition, bis-iminophosphoranes
Following our research in C–H bond activations on P-ylides
and iminophosphoranes,9 we have now focused our attention
to bis-iminophosphoranes due to several reasons. This class of
reactions on this type of substrates is scarcely represented and
few examples have been found in the literature.5g,i,j Moreover, we
are quite useful synthons in
reactions.1b–d
a wide variety of organic
have recently reported that the orthopalladation on iminophos-
9e
=
phoranes R3P NC(O)Aryl is exo regioselective, while that of
=
R3P NCH2aryl can be oriented exo- or endo- as a function of
the substituents and reaction temperature.9g Therefore, our aim
was to expand the chemistry of bis-iminophosphoranes and their
C–H bond activation reactions, and it was also to determine if the
orientation of the palladation follows the same patterns than those
Fig. 1 Structural motifs for bis-iminophosphoranes.
=
found for iminophosphoranes containing a single P N bond. We
describe here the obtained results.
The structure shown in Fig. 1(i) represents bis-
iminophosphoranes derived from bis-phosphines, and comprises
most of the chemistry performed in this field.2–5 Amongst them,
those built from bis(diphenylphosphino)methane [Ph2PCH2PPh2]
Results and discussion
Synthesis of the bis-iminophosphoranes
The synthesis of the bis-iminophosphoranes 1a–c has been carried
out using the Staudinger method10 by reaction of the correspond-
ing azides11 with PPh3 under standard experimental conditions.
aDepartamento de Compuestos Organometa´licos, Instituto de Ciencia de
Materiales de Arago´n, Universidad de Zaragoza-C.S.I.C., Plaza San Fran-
cisco s/n, 50009, Zaragoza, Spain. E-mail: esteban@unizar.es; Fax: +34
976761187
The IR spectra of 1a–c show strong absorptions assigned to the
bServicios Te´cnicos de Investigacio´n, Facultad de Ciencias Fase II, 03690,
San Vicente de Raspeig, Alicante, Spain
−1
=
stretch of the P N bond (around 1300–1350 cm ) and, in the
case of 1b,c, additional bands due to the carbonyl group (around
† CCDC reference numbers 668605. For crystallographic data in CIF or
other electronic format see DOI: 10.1039/b718108f
1590 cm−1) are also observed. The NMR spectra of 1a–c show the
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presence of a single set of signals, meaning that each compound
is obtained as a single isomer. The pattern of peaks observed
The elemental analyses of 2a show the incorporation of two
“PdCl” units per each original ligand 1a. Due to the neutral
nature of 2a, this implies that the ligand acts as a dianionic
species. The elucidation of the bonding mode of the ligand can
be easily inferred from its spectroscopic data. The IR spectrum
of 2a suggests the N-bonding of the ligand, since the absorption
1
1
in the H and 13C{ H} NMR spectra for the (CH2)3 unit (1a)
or for the C6H4 ring (1b,c) suggests a high symmetry of the
compounds, as corresponds to the structures shown in Scheme 1.
1
The 31P{ H} NMR spectra of 1a–c show a single peak on each case,
=
centered around 11 ppm for 1a and around 20 ppm for 1b,c, being
these chemical shifts in good agreement with previous results on
related species.9e–h We have also attempted the synthesis of bis-
due to the P N stretch appears shifted to lower wavenumbers
with respect to its position in 1a [Dm = mcomplex − mfree = −53 cm−1].
1
The H NMR spectrum of 2a shows the symmetry of the two
ꢀ
iminophosphoranes derived from a,a -diazidoxylene derivatives
halves of the iminophosphorane and the presence of the palladated
Pd(C6H4) moiety. In the high field region two peaks are observed,
in a 1 : 2 molar ratio, assigned to the central and terminal
methylene protons, respectively. In the aromatic region, six peaks
(relative intensities 2 : 1 : 4 : 2 : 4 : 1) can be easily attributed
to the PPh2 (4 : 2 : 4) and Pd(C6H4) (2 : 1 : 1) groups. The
(ortho or meta) [C6H4(CH2N3)2-1,2 or -1,3]. In spite of numerous
reaction conditions tested, low yields of mixtures of mono and
bis-substituted products were found. These mixtures could not be
separated by chromatographic methods and were easily hydrolysed
to the corresponding amines and phosphine oxide. Due to these
reasons they were not subject of further investigation.
1
31P{ H} NMR spectrum of 2a shows a single peak around
40 ppm. All these facts suggest that the bis-iminophosphorane
acts as a bis-C,N-chelating dianionic ligand, through the iminic
nitrogen and orthometallated carbon atoms, giving two endo
palladacycles, and that it must be symmetric with respect to
the central methylene carbon. The presence of a Cl− ligand on
each Pd atom should give an unsaturated dinuclear species, which
completes all coordination spheres through formation of a l-Cl
bridging system and dimerization to give 2a (Scheme 1).
Additional evidence of the presence of the chloride bridging
ligands in 2a can be obtained from its reactivity. 2a reacts
with Tl(acac) (1 : 4 molar ratio) to give the dinuclear deriva-
ꢀ
=
tive [{Pd(acac-O,O ){C6H4(PPh2 NCH2-j-C,N)-2}}2CH2] (3a),
(Scheme 1). Complex 3a has been characterized following the same
key features than those described for 2a. Thus, the IR spectrum
shows strong bands assigned to the O,Oꢀ-chelating acac ligand and
=
the absorption due to the P N stretch shifted to lower energies
1
[Dm = mcomplex − mfree = −48 cm−1]. The 31P{ H} NMR spectrum
shows a peak around 40 ppm, as expected for an endo palladacycle,
and the 1H NMR spectrum reflects the presence of signals due to
the acac ligand, the PdC6H4PPh2 moiety and the terminal and
central methylene protons.
The palladation of 1a to give the endo tetranuclear complex 2a is
somewhat expected, due to the preferred metallation of the arylic
Csp2–H bonds versus the alkylic Csp3–H bonds, and since only
one type of phenyl ring is present. More interesting are the results
obtained in the metallation of 1b and 1c, derived from isophthaloyl
and terphthaloyl functional groups, respectively (Scheme 1).
We have recently reported that the palladation of stabilized
=
iminophosphoranes R3P NC(O)Aryl occurs in a regioselective
manner at the aryl ring of the benzamide unit, giving exo
palladacycles.9e If 1b is metallated with the same regioselectivity,
then mononuclear derivatives with the bis-iminophosphorane
acting as a NCN pincer should be expected, amongst other
possibilities. In the case of 1c, different stoichiometries can also be
envisaged. The results obtained show that the orientation of the
reaction is different from that expected.
Scheme 1 Ligand (1a): (i) Pd(OAc)2, CH2Cl2, D; ligands (1b) and (1c):
(i) Pd(OAc)2, AcOH, D; (ii) LiCl, MeOH, r.t.; (iii) Tl(acac), CH2Cl2.
Cyclopalladation reactions
Bis-iminophosphorane 1a reacts with Pd(OAc)2 (1 : 2 molar ratio)
in refluxing CH2Cl2 to give (after elimination of the black Pd0
formed) an orange solution which presumably contains a bridging
acetate intermediate. This intermediate reacts in MeOH with an
excess of LiCl to give a low yield of the tetranuclear chloride bridg-
The reaction of 1b with Pd(OAc)2 under the same experimental
conditions than those reported for Ph3P NC(O)Ph (refluxing
=
CH2Cl2, 2 h)9e does not afford any palladated product, and
unchanged 1b is recovered at the end of the reaction time after
usual workup. The same absence of palladation is obtained
under different experimental conditions and/or using different Pd
sources. However, the treatment of 1b with Pd(OAc)2 (1 : 2 molar
=
ing derivative [{Pd(l-Cl){C6H4(PPh2 NCH2-j-C,N)-2}}2CH2]2
(2a) as represented in Scheme 1. The yield of 2a improves slightly
if the first step of the reaction is carried out in refluxing toluene.
1788 | Dalton Trans., 2008, 1787–1794
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ratio) in glacial acetic acid at reflux temperature affords cleanly
the tetranuclear derivative [{Pd(l-OAc){C6H4(PPh2=NC(O)-j-
C,N)-2}}2C6H4-1ꢀ,3ꢀ]2 (2b) (Scheme 1). Complex 2b reacts with
an excess of anhydrous LiCl in MeOH to give, after metathesis
of the acetate by the chloride bridging ligands, a very insoluble
derivative. We were unable to characterize this solid as the corre-
sponding chloride bridging complex due to its extreme insolubility.
However, the reactivity of in situ prepared suspensions of this
solid was the expected for the chloride bridging complex. The
reaction of 2b with an excess of LiCl in MeOH, and subsequent
treatment of the suspension with Tl(acac) (1 : 4 molar ratio)
gives the acetylacetonate [{Pd(acac-O,Oꢀ){C6H4(PPh2=NC(O)-j-
C,N)-2}}2C6H4-1ꢀ,3ꢀ] (3b).
a C–H activation process would more likely to occur at the
electron-poor ring, that is, at the phenyls of the PPh3 groups.
We believe this to be the reason for the observed orientation. A
second argument can be given in favour of the obtention of endo
isomers, and is related to the endo effect.9c–f ,14–16b This effect is
based on the metalloaromaticity concept,18 and predicts a higher
thermodynamic stability for cyclometallated rings containing two
=
endocyclic conjugated double bonds (the C C double bond and
=
the iminic C N bond), with respect to metallacycles without this
electronic configuration. Clearly, the structure 2b, containing two
endo palladacycles, must show an additional stability.
The characterization of 2b has been carried out on the basis of its
analytic and spectroscopic parameters, and follows trends similar
to those described for 2a (see Experimental). The IR spectrum
suggests N-bonding, since it shows the expected shift to lower
The characterization of complex 2b shows that two metallations
have been produced at the phenyl rings of the PPh3 groups, one
palladation at each phosphine of the starting compound, and that
two endo palladacycles have been obtained. We have not observed,
in the described conditions, cyclopalladation processes at the
central arylic ring. Therefore, the orientation of the C–H bond
activation process is, in this case, the opposite to that expected.
However, we must consider that the experimental conditions of the
=
energies for the band due to the P N stretch [Dm = mcomplex
−
mfree = −77 cm−1], and to higher wavenumbers for that due to the
carbonyl group [Dm = mcomplex − mfree = +16 cm−1] in good agreement
with previous results.9e The 31P{ H} NMR spectrum shows clearly
1
the incorporation of the P atom into the metallacycle, since only
one signal is observed at about 52 ppm, typical region for endo
palladacycles.9c The 1H NMR spectrum of 2b gives definitive
proofs of the endo metallation, since signals due to the central
C6H4 unit are clearly observed at 7.31 (H5), 7.90 (H4, H6) and
10.74 (H2) ppm. The chemical shift of the H2 proton merits some
comment, since it has undergone an important downfield shift
[Dd = dcomplex − dfree = +1.41 ppm], probably due to its location
between the two carbonyl groups (Scheme 1). In fact, this shift
provides structural information, since there are two components
in this shift. One of them is the expected due to the high
electronegativity of the oxygen atom. The other component seems
palladation of 1b are not the same than those reported previously
9e
=
for Ph3P NC(O)Aryl species, and also that the nature of the
starting compound is different. A sensible explanation of the
observed behaviour can be given taking into account these two
=
facts. Our starting point is the high polarization of the P N bond,
which can be better considered as a P(+)–N(−) bond.12 Due to the
presence of a keto group bonded to the N atom, delocalization
of the charge density through the NCO system is possible, as
observed in amide functional groups. In fact, the central C6H4
aryl ring in 1b has two amide substituents and, following a
=
=
similar reasoning than that reported for Ph3P NC(O)Aryl, this
to be related to the anisotropic deshielding of the C O group for
ring should behave as electron rich (compared with other rings
in the same molecule) due to the presence of two anionic NCO
groups. Using the same argument based on charge separations,
the phenyl rings bonded to the phosphonium atom should be
electron poor, compared with the central ring, due to the formal
positive charge located at the P atom and its deactivating nature.
Now we must consider that the cyclopalladation process occurs
through an electrophilic substitution on the aromatic ring, when
solvents such as toluene, chloroform or even methanol are used as
reaction media.13 The importance of the solvent in the orientation
of the cyclopalladation is notable, as it has been reported for
imines14 and oxazolines,15 for which endo and exo isomers can be
obtained. Other examples in which a critical role of the solvent has
been reported concern the transformation between regioisomers
of cyclopalladated complexes in acetic acid.16
protons located on the same plane than the NC(=O) unit. The
latter means that the C–H2 bond (and the C6H4 core by extension)
should be more or less contained on the same plane than the
=
metallated unit [(O C)NPC6H4Pd]. Besides that, four new signals
assigned to the protons of the PdC6H4 metallated ring and peaks
attibuted to the PPh2 groups appear in the aromatic region and
confirm the structure shown in Scheme 1. The fact that two sets of
signals appear for the two phenyl rings of the PPh2 moiety means
that they are chemically inequivalent. An open-book structure,15b
in which two dinuclear units [{Pd{C6H4(PPh2=NC(O)-j-C,N)-
2}}2C6H4-1ꢀ,3ꢀ] are bridged by four acetate ligands accounts
for these facts. The same arguments can be applied for the
characterization of 3b, with additional signals due to the acac
ligand observed in the IR and 1H NMR spectra. The signal due to
1
H2 in the H NMR spectrum appears at 9.14 ppm, and that due
to the palladated C1 appears at 152.46 ppm in the 13C{ H} NMR
1
All these facts are related to the different behaviour of
Pd(OAc)2 in solvents as CHCl3 and acetic acid.13,16,17 In chloroform
Pd(OAc)2 behaves as an electrophile, promoting C–H activations
in electron rich aryl rings, while in acetic acid it behaves as a
pseudonucleophile,17a and cyclopalladations in electron poor aryl
rings are observed.16,17 In our case, substrate 1b (and, besides,
1c) contains two types of aryl rings, namely the central ring,
which should be considered as electron-rich compared with the
electron-poor phosphonium phenyl rings, (see above). Therefore,
an explanation of the observed orientation can be given. The
orthopalladation of 1b is performed in acetic acid, in which
Pd(OAc)2 behaves as a pseudonucleophile, and in this medium
spectrum.
The reactivity of 1c follows a similar behaviour to that
described for 1b. 1c reacts with Pd(OAc)2 (1 : 2 molar ra-
tio) in glacial acetic acid at reflux temperature (Scheme 1) to
give the tetranuclear [{Pd(l-OAc){C6H4(PPh2=NC(O)-j-C,N)-
2}}2C6H4-1ꢀ,2ꢀ]2 (2c). Attempts to perform the orthometallation
of 1c in other solvents failed. Subsequent treatment of 2c
with excess anhydrous LiCl and Tl(acac) in MeOH gives the
dinuclear acetylacetonate [{Pd(acac-O,Oꢀ){C6H4(PPh2=NC(O)-
j-C,N)-2}}2C6H4-1ꢀ,2ꢀ] (3c). The characterization of 2c and 3c
as endo derivatives has also been performed on the basis of their
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Table 2 Crystallographic data for complex 3c·4CHCl3
analytic and spectroscopic data, and the X-ray crystal structure of
3c has been determined.
Empirical formula
C58H50Cl12N2O6P2Pd2
Formula weight
Crystal system
Space group
1571.14
Monoclinic
P21/n
15.64371(14)
29.8167(3)
13.64503(9)
90.1952(7)
6364.60(10)
4
X-Ray structure of 3c·4CHCl3†
˚
a/A
A molecular drawing of the organometallic complex is shown in
Fig. 2. Table 1 collects selected bond distances and angles and pa-
rameters of data collection and structure solution and refinement
are given in Table 2. The structure of 3c shows a dinuclear complex,
in which two orthometallated units [(acac)PdC6H4PPh2NC(O)]
are linked to a C6H4 ring in ortho positions through the carbonyl
carbon atom. The molecule as a whole shows a notable distortion.
Three main best least square planes can be defined in this molecule:
(i) one plane containing the central aryl ring, defined by C25–
C26–C27–C28–C29–C30; (ii) the coordination plane around Pd1,
defined by Pd1–O1–O2–C6–N1; and (iii) the coordination plane
around Pd2, defined by Pd2–O5–O6–C37–N2. The dihedral angles
between planes (i) and (ii), and (i) and (iii) are 69.53(15)◦ and
64.12(14)◦, respectively, while that between the two coordination
planes (ii) and (iii) is 49.76(8)◦. Most atoms of the organometallic
fragment [(acac)PdC6H4PPh2NC(O)] around Pd1 are located at
one side of the plane (i), while the atoms of the same fragment
around Pd2 are located at the other side of the plane (i).
In consequence, the molecule shows pseudo-C2 symmetry with
˚
b/A
˚
c/A
b/◦
V/A
3
˚
Z
D
calc/Mg m−3
1.640
1.169
l/mm−1
Crystal size
0.27 × 0.17 × 0.06
Reflections collected
Independent reflections
Restraints/parameters
R1 [I >2r(I)]
wR2 [I >2r(I)]
R1 [all data]
88744
11159, Rint = 0.0405
11159/0/671
0.0543
0.1388
0.0615
0.1432
1.022
wR2 [all data]
GOF
−3
˚
Largest diffraction peak, hole/e A
Temperature/K
1.109, −0.987
100(1)
˚
Radiation (k)/A
0.71073
respect to an imaginary axis crossing the middle points of the
C25–C30 and C27–C28 bonds. This molecular arrangement is
necessary in order to minimize the intramolecular interactions
between fragments in ortho positions.
The environment around each Pd atom can be considered as
square planar, slightly distorted. Each Pd atom is surrounded
by the two oxygen atoms of the acetylacetonate ligand, by the
iminic nitrogen and the palladated carbon of the cyclometallated
=
ligand. The P N bond is endocyclic, as expected. Besides, the two
organometallic fragments are very similar, as can be deduced from
the comparison of respective bond distances and angles (Table 1).
The Pd–C and Pd–N bond distances found in 3c are identical,
within experimental error, to those found in related orthopalla-
dated iminophosphoranes,9c,d,19 and the same can be stated for
the Pd–O bond distances involving the chelating acetylacetonate
ligand.20 Other internal parameters of the ligands do not deviate
from published values.21 Finally, and as it has been noted in
keto-stabilized ylides,22 the P–O intramolecular distances [2.752(4)
Fig. 2
◦
˚
˚
Table 1 Selected bond distances [A] and angles [ ] for 3c·4CHCl3
and 2.814(4) A] are substantially shorter than the sum of the
23
˚
van der Waals radii [3.32 A], while the dihedral angles P–
N–C–O are −12.7(6)◦ and −13.5(6)◦. These values suggest that
intramolecular P · · · O contacts are also present in ketostabilized
iminophosphoranes.
Pd(1)–C(6)
Pd(1)–N(1)
Pd(1)–O(2)
Pd(1)–O(1)
N(1)–P(1)
C(11)–P(1)
N(1)–C(24)
C(24)–O(3)
1.970(5)
2.033(4)
2.005(4)
2.074(4)
1.649(4)
1.777(5)
1.370(6)
1.221(6)
1.481(7)
90.80(15)
90.91(18)
84.83(18)
93.41(15)
128.6(3)
116.8(3)
113.3(2)
122.2(4)
121.4(4)
116.0(4)
Pd(2)–C(37)
Pd(2)–N(2)
Pd(2)–O(6)
Pd(2)–O(5)
1.974(5)
2.036(4)
2.026(4)
2.071(4)
1.646(4)
1.768(5)
1.357(6)
1.226(6)
1.496(7)
90.17(15)
91.8(2)
85.15(19)
93.03(15)
129.1(3)
114.9(3)
115.6(2)
122.1(4)
119.7(4)
117.9(4)
N(2)–P(2)
P(2)–C(32)
N(2)–C(31)
C(31)–O(4)
C(31)–C(30)
O(5)–Pd(2)–O(6)
O(6)–Pd(2)–C(37)
C(37)–Pd(2)–N(2)
N(2)–Pd(2)–O(5)
C(31)–N(2)–Pd(2)
P(2)–N(2)–C(31)
Pd(2)–N(2)–P(2)
N(2)–C(31)–O(4)
O(4)–C(31)–C(30)
N(2)–C(31)–C(30)
Conclusions
C(24)–C(25)
=
The reaction of Pd(OAc)2 with bis-iminophosphoranes [Ph3P N–
O(2)–Pd(1)–O(1)
O(2)–Pd(1)–C(6)
C(6)–Pd(1)–N(1)
N(1)–Pd(1)–O(1)
C(24)–N(1)–Pd(1)
P(1)–N(1)–C(24)
Pd(1)–N(1)–P(1)
N(1)–C(24)–O(3)
O(3)–C(24)–C(25)
N(1)–C(24)–C(25)
=
linker–N PPh3] (linker = aliphatic or aromatic functional group)
gives endo palladacycles through C–H bond activation at the Ph
rings of the phosphine groups in all cases. Two palladacycles
=
=
are formed per each [Ph3P N–linker–N PPh3] ligand, and the
dinuclear moieties rearrange giving tetranuclear complexes with
acetate or chloride bridging ligands. When the linker is an
aliphatic chain, CH2Cl2 can be used; but when the linker contains
the phthaloyl functional group, acetic acid is necessary. The
1790 | Dalton Trans., 2008, 1787–1794
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palladation occurs in acetic acid with opposite orientation (endo
complexes) with respect to that expected (exo derivatives by
[{Pd(l-Cl){C6H4(PPh2=NCH2-j-C,N)-2}}2CH2]2 (2a)
To a solution of 1a (0.400 g, 0.672 mmol) in CH2Cl2 (20 mL),
Pd(OAc)2 (0.301 g, 1.344 mmol) was added, and the resulting
mixture was refluxed for 1.3 h. After the reaction is completed, the
cooled black suspension (presence of Pd0) was treated with char-
coal (15 min) and filtered through Celite giving an orange solution.
This solution, which contains the acetate bridge intermediate, was
evaporated to dryness. The orange residue was dissolved in MeOH
(10 mL) and treated with an excess of anhydrous LiCl (0.100 g,
2.38 mmol) to give 2a as a yellow solid. Yield: 0.263 g (44.7%).
Anal. calc. for C78H68Cl4N4P4Pd4 (1752.9): C, 53.40; H, 3.91; N,
3.19. Found: C, 53.21; H, 3.86; N, 3.12. IR (m, cm−1): 1257 (mPN).
=
analogy with Ph3P NC(O)aryl, already reported). This different
orientation is explained on the basis of the different behaviour of
Pd(OAc)2 in acetic acid (nucleophile) with respect to other solvents
(an electrophile).
Experimental
Safety note
CAUTION! The organic azides are highly hazardous materials
which can explode, and whose preparation and manipulation must
be carried out with◦great caution. They must be stored at low
temperature (T ≈ 0 C) and dissolved in an inert solvent.11
MS (MALDI+) [m/z, (%)]: 699 (30) [M4/2–2Cl–Pd]+. H NMR
1
(CDCl3): d = 1.76 (s, br, 1H, CH2), 3.04 (dt, 2H, 3JHH = 4.8, 3JPH
=
13.8, NCH2), 6.89–6.95 (m, 2H, C6H4), 7.18–7.23 (m, 1H, C6H4),
7.45 (m, 4H, Hm, PPh2), 7.53 (m, 2H, Hp, PPh2), 7.74 (m, 4H, Ho,
3
1
PPh2), 7.92 (d, 1H, JHH = 7.5, C6H4). 31P{ H} NMR (CDCl3):
General methods
d = 39.55.
Solvents were dried and distilled under argon using standard
procedures before use. Elemental analyses were carried out on
a Perkin-Elmer 2400-B microanalyser. Infrared spectra (4000–
200 cm−1) were recorded on a Perkin-Elmer 883 infrared spec-
trophotometer from nujol mulls between polyethylene sheets.
[{Pd(acac){C6H4(PPh2=NCH2-j-C,N)-2}}2CH2] (3a)
To a solution of 2a (0.147 g, 0.084 mmol) was added Tl(acac)
(0.102 g, 0.336 mmol). The resulting suspension was stirred at
room temperature for 30 min, and then filtered through Celite. The
clear yellow solution was evaporated to dryness and the residue
treated with cold n-hexane (10 mL). By subsequent stirring, 3a was
obtained as a pale yellow solid. Yield: 0.131 g (77.5%). Anal. calc.
for C49H48N2O4P2Pd2 (1003.7): C, 58.63; H, 4.82; N, 2.79. Found:
1
1
1
The H, 13C{ H} and 31P{ H} NMR spectra were recorded in
CDCl3, CD2Cl2 or dmso-d6 solutions at 25 ◦C (other temperatures
were specified) on Bruker ARX-300, AvanceII-300, Avance-400
and Avance-500 spectrometers (d, ppm; J, Hz); H and 13C{ H}
1
1
were referenced using the solvent signal as internal standard
while 31P{ H} was externally referenced to H3PO4 (85%). The 1H
1
C, 58.64; H, 4.65; N, 3.33. IR (m, cm−1): 1584 (mCO, acac), 1514 (mCO
,
SELNO-1D and SELRO-1D NMR experiments were performed
with optimized mixing times (D8/P15), depending of the irradi-
ated signal. ESI/APCI mass spectra were recorded using an Es-
quire 3000 ion-trap mass spectrometer (Bruker Daltonic GmbH,
Bremen, Germany) equipped with a standard ESI/APCI source.
Other MS (FAB+) were recorded from CH2Cl2 solutions on
a V. G. Autospec spectrometer. The bis-azides N3CH2CH2CH2N3,
acac), 1262 (mP=N). MS (FAB+) [m/z, (%)]: 903 (45) [M–acac]+. 1H
NMR (CDCl3): d = 1.37 (s, 3H, Me, acac), 1.61 (m, 1H, CH2), 2.02
(s, 3H, Me, acac), 2.41 (m, 2H, NCH2), 5.20 (s, 1H, CH, acac), 6.86
(t, 1H, 3JHH = 8.5, C6H4), 6.97 (m, 1H, C6H4), 7.21 (m, 1H, C6H4),
7.41 (m, 4H, Hm, PPh2), 7.53–7.63 (m, 6H, 4Ho + 2Hp, PPh2), 7.68
1
(d, 1H, 3JHH = 7.3, C6H4). 31P{ H} NMR (CDCl3): d = 39.90.
=
=
[C6H4(C(O)N PPh3)2-1,3] and [C6H4(C(O)N PPh3)2-1,2] were
=
[C6H4(C(O)N PPh3)2-1,3] (1b)
prepared according to the literature.11
Compound 1b was prepared following the Staudinger method,10
as described for 1a. Isophthaloyl bis-azide [C6H4(C(O)N3)2-1,3]
(0.844 g, 4.46 mmol) was reacted with PPh3 (2.34 g, 8.92 mmol)
in dry CH2Cl2 (40 mL) to give 1b as a white solid. Yield: 3.002 g
(100%). Anal. calc. for C44H34N2O2P2 (684.3): C, 77.16; H, 5.00;
N, 4.09. Found: C, 76.90; H, 4.92; N, 3.82. IR (m, cm−1): 1599 (mCO),
1353 (mP=N). MS (FAB+) [m/z, (%)]: 685 (20) [M + H]+. 1H NMR
=
=
[Ph3P NCH2CH2CH2N PPh3] (1a)
Staudinger method:10 To a solution of N3CH2CH2CH2N3 (0.500 g,
3.96 mmol) in freshly distilled CH2Cl2 (20 mL), a solution of
PPh3 (2.07 g, 7.92 mmol) in CH2Cl2 (20 mL) was added dropwise.
The addition was completed in 30 min, and during this time the
evolution of N2 was evident. The resulting solution was stirred
at room temperature for 16 h, until the evolution of N2 ceased.
Then, the solvent was evaporated to dryness, giving 1a as a
white solid. The compound can be used in subsequent reactions
without further purification. Yield: 1.58 g (66.9%). Anal. calc. for
C39H36N2P2 (594.7): C, 78.77; H, 6.10; N, 4.71. Found: C, 78.05; H,
6.59; N, 4.65. IR (m, cm−1): 1310 (mPN). MS (FAB+) [m/z, (%)]: 595
(100) [M + H]+. 1H NMR (CDCl3): d = 1.89 (q, 2H, 3JHH = 7.2,
CH2), 3.13 (m, 4H, NCH2), 7.36 (m, 12H, Hm, PPh3), 7.45 (m, 6H,
3
(CDCl3): d = 7.42 (t, 1H, JHH = 7.6, H5, C6H4), 7.46 (dt, 12H,
3
4JPH = 3.0, JHH = 7.5, Hm, PPh3), 7.55 (m, 6H, Hp, PPh3), 7.80
(dd, 12H, 3JPH = 12.3, 3JHH = 7.4, Ho, PPh3), 8.39 (dd, 2H, 5JPH
=
1
3
1.3, JHH = 7.6, H4, H6, C4H4), 9.33 (s, 1H, H2, C6H4). 13C{ H}
1
NMR (CDCl3): d = 127.06 (C6H4), 128.40 (d, JPC = 99.4, Ci,
3
PPh3), 128.60 (d, JPC = 12.2, Cm, PPh3), 130.65 (C6H4), 131.90
(C6H4), 132.06 (d, 4JPC = 2.5, Cp, PPh3), 133.16 (d, 2JPC = 9.9, Co,
PPh3), 138.11 (d, 3JPC = 20.5, C1, C3, C6H4), 176.47 (d, 2JPC = 8.0,
CO). 31P{ H} NMR (CDCl3): d = 20.05.
1
Hp, PPh3), 7.58 (m, 12H, Ho, PPh3). 13C{ H} NMR (CDCl3): d =
1
40.56 (CH2), 44.08 (d, 2JPC = 5.1, NCH2), 128.34 (d, 3JPC = 11.5,
[{Pd(l-OAc){C6H4(PPh2=NC(O)-j-C,N)-2}}2C6H4-1ꢀ,3ꢀ]2 (2b)
1
4
Cm, PPh3), 131.25 (d, JPC = 96.4, Ci, PPh3), 131.25 (d, JPC
=
2.4, Cp, PPh3), 132.58 (d, JPC = 9.0, Co, PPh3). 31P{ H} NMR
To a solution of Pd(OAc)2 (0.262 g, 1.160 mmol) in glacial acetic
acid (15 mL) was added compound 1b (0.400 g, 0.584 mmol) and
2
1
(CDCl3): d = 11.18.
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the resulting solution was refluxed for 1h. The resulting black
suspension was filtered through Celite (removal of Pd0) and the
orange solution was evaporated to small volume (≈ 2 mL). By
addition of Et2O (25 mL) and subsequent stirring, 2b precipitated
as a yellow solid, which was filtered, washed with additional Et2O
(40 mL) and dried in vacuo. Yield: 0.313 g (55.4%). Anal. calc.
for C96H76N4O12P4Pd4 (2026.3): C, 56.85; H, 3.78; N, 2.76. Found:
C, 56.60; H, 3.79; N, 2.99. IR (m, cm−1): 1615 (mC=O), 1580 (mC=O),
1559 (mC=O), 1276 (mP=N). MS (FAB+) [m/z, (%)]: 789 (40) [M/2-
Pd-2OAc]+. 1H NMR (CDCl3): d = 1.16 (s, 3H, OAc), 2.12 (s, 3H,
OAc), 6.92 (m, 2H, PdC6H4), 7.05 (m, 2H, PdC6H4), 7.21 (m, 2H,
PdC6H4), 7.29–7.33 (m, 3H, 2H (PdC6H4) + H5 (C6H4)), 7.41–7.48
(m, 6H, 4Hm + 2Hp, PPh2), 7.55 (m, 2H, Hp, PPh2), 7.63 (m, 4H,
3JHH = 7.1, Hp, PPh3), 7.39 (m, 2H, H4, H5, C6H4), 7.63 (m, 2H,
1
H3, H6, C6H4), 7.68 (m, 12H, Ho, PPh3). 13C{ H} NMR (CDCl3):
d = 127.98 (C3, C6, C6H4), 128.12 (C4, C5, C6H4) 128.34 (d, 3JPC
12.3, Cm, PPh3), 128.59 (d, 1JPC = 99.8, Ci, PPh3), 131.74 (d, 4JPC
2.8, Cp, PPh3), 133.44 (d, 2JPC = 9.9, Co, PPh3), 141.05 (d, 3JPC
=
=
=
2
1
20.8, C1, C2, C6H4), 180.00 (d, JPC = 8.6, CO). 31P{ H} NMR
(CDCl3): d = 18.85.
[{Pd(l-OAc){C6H4(PPh2=NC(O)-j-C,N)-2}}2C6H4-1ꢀ,2ꢀ]2 (2c)
Complex 2c was prepared following a synthetic procedure similar
to that described for 2b. Therefore Pd(OAc)2 (0.131 g, 0.583 mmol)
was reacted with 1c (0.200 g, 0.291 mmol) in glacial acetic acid
(20 mL) to give 2c as a yellow solid. Yield: 0.236 g (80.0%). Anal.
calc. for C96H76N4O12P4Pd4 (2026.3): C, 56.85; H, 3.78; N, 2.76.
Found: C, 56.99; H, 4.21; N, 2.66. IR (m, cm−1): 1614 (mC=O), 1583
(mC=O), 1558 (mC=O), 1275 (mP=N). MS (FAB+) [m/z, (%)]: 954 (30)
Hm, PPh2), 7.71 (m, 4H, Ho, PPh2), 7.90 (dd, 2H, 3JHH = 7.6, 4JHH
=
1.7, H4, H6, C6H4), 8.26 (m, 4H, Ho, PPh2), 10.74 (m, 1H, H2,
1
C6H4). 31P{ H} NMR (CDCl3): d = 52.41.
1
[M/2-OAc]+. H NMR (CDCl3): d = 1.30 (s, 3H, OAc), 2.17 (s,
[{Pd(acac){C6H4(PPh2=NC(O)-j-C,N)-2}}2C6H4-1ꢀ,3ꢀ] (3b)
3H, OAc), 6.76 (m, 2H, PdC6H4), 7.02–7.09 (m, 14H, 4Ho, 4Hm,
2Hp (PPh2) + 4H (PdC6H4)), 7.27 (m, 2H, PdC6H4), 7.32 (dd, 2H,
To a solution of 2b (0.313 g, 0.159 mmol) in MeOH (20 mL),
was added an excess of anhydrous LiCl (0.210 g, 5.0 mmol).
The resulting yellow suspension was stirred for 30 min (rt) and
then Tl(acac) (0.193 g, 0.636 mmol) was added. The suspension
changed its colour and the resulting pale yellow suspension was
stirred for 30 additional min (rt). The solvent was evaporated to
dryness and the residue was extracted with CH2Cl2 (2 × 15 mL).
The combined extracts were evaporated to dryness and the
oily residue was treated with cold n-pentane (20 mL), giving
3b as a yellow solid. Yield: 0.200 g (57.2%). Anal. calc. for
C54H46N2O6P2Pd2 (1093.7): C, 59.27; H, 4.24; N, 2.56. Found: C,
58.97; H, 4.45; N, 2.73. IR (m, cm−1): 1615 (mCO), 1583 (mCO, acac),
1514 (mCO, acac), 1299 (mP=N). MS (FAB+) [m/z, (%)]: 995 (35) [M–
acac]+. 1H NMR (CDCl3): d = 1.02 (s, 6H, Me, acac), 1.88 (m, 6H,
Me, acac), 4.95 (s, 2H, CH, acac), 6.88 (m, 2H, PdC6H4), 7.04 (m,
4
3
4
3JHH = 6.0, JHH = 3.0, C6H4), 7.39 (dd, 2H, JHH = 5.7, JHH
=
3.1, C6H4), 7.67 (m, 4H, Hm, PPh2), 7.76 (m, 2H, Hp, PPh2), 8.11
(m, 4H, Ho, PPh2). 13C{ H} NMR (CDCl3): d = 22.32 (Me, OAc),
1
24.28 (Me, OAc), 124.43 (d, JPC = 11.0, PdC6H4), 126.31 (d, 1JPC
74.0, Ci, PPh2), 126.62 (d, 1JPC = 71.1, Ci, PPh2), 128.40 (d, 3JPC
=
=
=
=
3
10.0, Cm, PPh2), 128.67 (C6H4), 128.98 (C6H4), 129.18 (d, JPC
10.0, Cm, PPh2), 130.19 (d, 4JPC = 3.0, Cp, PPh2), 131.95 (d, JPC
2
5.0, PdC6H4), 133.23 (d, JPC = 9.8, Co, PPh2) 133.41 (m, Cp,
Co, PPh2), 134.39 (d, JPC = 11.0, PdC6H4), 136.16 (d, 3JPC = 9.0,
C1, C2, C6H4), 148.13 (d, 2JPC = 16.0, C1, PdC6H4), 177.99 (CO),
181.64 (CO, OAc), 181.96 (CO, OAc). Signals due to two C atoms
of the PdC6H4 unit were not observed. 31P{ H} NMR (CDCl3):
1
d = 53.05.
2H, PdC6H4), 7.23–7.28 (m, 3H, 2H (PdC6H4) + H5 (C6H4), 7.45
[{Pd(acac){C6H4(PPh2=NC(O)-j-C,N)-2}}2C6H4-1ꢀ,2ꢀ] (3c)
3
(m, 8H, Hm, PPh2), 7.55 (m, 4H, Hp, PPh2), 7.64 (d, 2H, JHH
=
3
8.0, PdC6H4), 7.88 (m, 8H, Ho, PPh2), 8.42 (dd, 2H, JHH = 7.6,
Complex 3c was prepared following a synthetic procedure similar
to that described for 3b. Therefore 2c (0.240 g, 0.122 mmol)
was reacted with LiCl (0.210 g, 5.0 mmol) in methanol (20 mL)
and with Tl(acac) (0.148 g, 0.490 mmol) to give 3c as a yellow
solid. Yield: 0.136 g (50.7%). 3c was recrystallized from CH2Cl2–
Et2O, giving yellow crystals of 3c·0.5CH2Cl2, which were used
for analytic and spectroscopic purposes. However, they were
not useful for X-ray purposes (see below). Anal. calc. for
[C54H46N2O6P2Pd2]0.5CH2Cl2 (1136.2): C, 57.61; H, 4.17; N, 2.46.
Found: C, 57.12; H, 4.11; N, 2.52. IR (m, cm−1): 1633 (mCO), 1588
(mCO, acac), 1512 (mCO, acac), 1300 (mP=N). MS (FAB+) [m/z, (%)]:
4
4JHH = 1.7, H4, H6, C6H4), 9.14 (t, 1H, JHH = 1.4, H2, C6H4).
1
13C{ H} NMR (CDCl3): d = 26.55 (Me, acac), 27.29 (Me, acac),
99.65 (CH, acac), 124.56 (d, JPC = 13.9, PdC6H4), 125.63 (C5,
1
3
C6H4), 126.44 (d, JPC = 13.9, Ci, PPh2), 128.80 (d, JPC = 12.6,
Cm, PPh2), 129.16 (PdC6H4), 130.21 (d, JPC = 2.5, PdC6H4), 130.76
(C2, C6H4), 132.02 (C4, C6, C6H4), 132.40 (d, JPC = 14.2, PdC6H4),
132.79 (d, 4JPC = 2.5, Cp, PPh2), 133.56 (d, 2JPC = 10.9, Co, PPh2),
135.41 (d, 1JPC = 131.5, C2, PdC6H4), 136.51 (d, 3JPC = 11.9, C1,
C3, C6H4), 152.46 (d, 2JPC = 19.5, C1, PdC6H4), 178.94 (d, 2JPC
=
1
5.9, CO), 184.37 (CO, acac), 187.56 (CO, acac). 31P{ H} NMR
1
(CDCl3): d = 50.98.
995 (100) [M–acac]+. H NMR (CDCl3): d = 0.89 (s, 6H, Me,
acac), 1.89 (m, 6H, Me, acac), 4.94 (s, 2H, CH, acac), 6.89 (m, 2H,
PdC6H4), 7.04 (m, 2H, PdC6H4), 7.23–7.27 (m, 4H, 2H (PdC6H4) +
H4, H5 (C6H4)), 7.39 (m, 8H, Hm, PPh2), 7.52 (m, 4H, Hp, PPh2),
7.69 (d, 2H, 3JHH = 8.0, PdC6H4), 7.90 (s, broad, 8H, Ho, PPh2),
=
[C6H4(C(O)N PPh3)2-1,2 (1c)
Compound 1c was prepared following the Staudinger method,10 as
described for 1a. Phthaloyl bis-azide [C6H4(C(O)N3)2-1,2] (1.00 g,
4.62 mmol) was reacted with PPh3 (2.42 g, 9.25 mmol) in dry
CH2Cl2 (40 mL) to give 1c as a white solid. Yield: 2.11 g (72.5%).
Anal. calc. for C44H34N2O2P2 (684.3): C, 77.16; H, 5.00; N, 4.09.
Found: C, 77.30; H, 4.92; N, 3.82. IR (m, cm−1): 1580 (mCO), 1346
(mP=N). MS (FAB+) [m/z, (%)]: 685 (45) [M + H]+. 1H NMR
1
8.25 (dd, 2H, 3JHH = 5.6, 4JHH = 3.3, H3, H6, C6H4). 13C{ H} NMR
(CDCl3): d = 25.92 (Me, acac), 27.16 (Me, acac), 99.42 (CH, acac),
124.42 (d, 3JPC = 13.7, PdC6H4), 127.89 (C4, C5, C6H4), 128.66 (d,
3JPC = 12.7, Cm, PPh2), 129.31 (d, 2JPC = 20.4, PdC6H4), 130.14 (d,
4JPC = 2.9, PdC6H4), 132.25 (d, 3JPC = 14.3, PdC6H4), 132.43 (d,
4JPC = 2.8, Cp, PPh2), 133.56 (d, 2JPC = 10.2, Co, PPh2), 135.61 (d,
1JPC = 130.7, C2, PdC6H4), 139.82 (d, 3JPC = 12.4, C1, C2, C6H4),
5
(CDCl3): d = 7.18 (m, 12H, Hm, PPh3) 7.32 (dt, 6H, JPH = 1.2,
1792 | Dalton Trans., 2008, 1787–1794
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The Royal Society of Chemistry 2008
©

View Article Online
2
2
152.18 (d, JPC = 20.9, C1, PdC6H4), 178.94 (d, JPC = 5.7, CO),
M. Thornton-Pett, L. A. Gerrard and M. Bochmann, J. Chem. Soc.,
Dalton Trans., 2001, 822; (f) M. J. Sarsfield, M. Thornton-Pett and M.
Bochmann, J. Chem. Soc., Dalton Trans., 1999, 3329; (g) M. W. Avis,
C. J. Elsevier, N. Veldman, H. Kooijman and A. L. Spek, Inorg. Chem.,
1996, 35, 1518.
183.75 (CO, acac), 187.49 (CO, acac). Peaks of C3 and C6 were not
observed. 31P{ H} NMR (CDCl3): d = 53.59.
1
5 (a) K. L. Hull, B. C. Noll and K. W. Henderson, Organometallics,
2006, 25, 4072; (b) M. Fang, N. D. Jones, R. Lukowski, J. Tjathas, M. J.
Ferguson and R. G. Cavell, Angew. Chem., Int. Ed., 2006, 45, 3097;
(c) W. P. Leung, C. W. So, K. W. Kan, H. S. Chan and T. C. W. Mak,
Organometallics, 2005, 24, 5033; (d) Y. Smurnyy, C. Bibal, M. Pink
and K. G. Caulton, Organometallics, 2005, 24, 3849; (e) V. Cadierno, J.
Crystal structure determination of complex 3c·4CHCl3†
Crystals of adequate quality for X-ray measurements were grown
by vapour diffusion of Et2O into a CHCl3 solution of the crude
product at room temperature. A single crystal was mounted at the
end of a quartz fiber in a random orientation, covered with magic
oil and placed under the cold stream of nitrogen. Data collection
was performed at 100(1) K on an Oxford Diffraction Xcalibur2
diffractometer using graphite-monocromated Mo Ka radiation
´
Garc´ıa-Alvarez, J. Gimeno and J. Rubio-Garc´ıa, J. Organomet. Chem.,
´
2005, 690, 5856; (f) V. Cadierno, J. D´ıez, J. Garc´ıa-Alvarez and J.
Gimeno, J. Organomet. Chem., 2005, 690, 2087; (g) V. Cadierno, J. D´ıez,
´
J. Garc´ıa-Alvarez and J. Gimeno, Organometallics, 2005, 24, 2801; (h) V.
´
Cadierno, J. D´ıez, J. Garc´ıa-Alvarez, J. Gimeno, M. J. Calhorda and
˚
(k = 0.71073 A). A hemisphere of data was collected based
L. F. Veiros, Organometallics, 2004, 23, 2421; (i) G. Lin, N. D. Jones,
R. A. Gossage, R. McDonald and R. G. Cavell, Angew. Chem., Int. Ed.,
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on three x-scan and φ-scan runs. The diffraction frames were
integrated using the program CrysAlis RED24 and the integrated
intensities were corrected for absorption with SADABS.25 The
structures were solved and developed by direct methods.26 All
non-hydrogen atoms were refined with anisotropic displacement
parameters. The H atoms were placed at idealized positions and
treated as riding atoms. Each H atom was assigned an isotropic
displacement parameter equal to 1.2 times the equivalent isotropic
displacement parameter of its parent atom. The structures were
refined to F2o, and all reflections were used in the least-squares
calculations.27 3c crystallizes with four molecules of solvent per
dimeric organometallic unit. Two of the CHCl3 sites were found
to be severely disordered—so resistant to attempts to establish an
acceptable atomic model, that we decided to employ PLATON
SQUEEZE28 to remove the influence of these sites form the data.
6 (a) C. Metallinos, D. Tremblay, F. B. Barrett and N. J. Taylor,
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15, 1033; (h) Related species: S. A. Ahmed, M. S. Hill, P. B. Hitchcock,
S. M. Mansell and O. St John, Organometallics, 2007, 26, 538.
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Foces, P. Molina, M. Alajar´ın, A. Vidal, R. M. Claramunt and J.
Elguero, J. Chem. Soc., Perkin Trans. 2, 1991, 1025; (d) P. Molina and
M. J. Vilaplana, Synthesis, 1994, 1197; (e) P. Molina, C. Conesa and
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(g) M. Alajar´ın, P. Molina, P. Sa´nchez-Andrada and M. C. Foces-Foces,
J. Org. Chem., 1999, 64, 1121.
N.b., the values we report for stoichiometric quantities, Dc, F000
etc., are based on the full content of the crystal-that is, using all
four molecules of CHCl3. CCDC reference number 668605.
,
Acknowledgements
8 (a) N. L. S. Yue and D. W. Stephan, Organometallics, 2001, 20, 2303;
(b) V. V. Sushev, A. N. Kornev, Y. A. Min’ko, N. V. Belina, Y. A. Kurskiy,
O. V. Kuznetsova, G. K. Fukin, E. V. Baranov, V. K. Cherkasov and
G. A. Abakumov, J. Organomet. Chem., 2006, 691, 879.
Funding by the Ministerio de Educacio´n y Ciencia (MEC) (Spain,
Project CTQ2005-01037) is gratefully acknowledged. R. B. thanks
the MEC (BES2003-0296) for a PhD research grant.
9 (a) C. Gracia, G. Marco, R. Navarro, P. Romero, T. Soler and E. P.
Urriolabeitia, Organometallics, 2003, 22, 4910; (b) A. Lledo´s, J. J.
Carbo´, R. Navarro, E. Serrano and E. P. Urriolabeitia, Inorg. Chem.,
2004, 43, 7622; (c) R. Bielsa, A. Larrea, R. Navarro, T. Soler and
E. P. Urriolabeitia, Eur. J. Inorg. Chem., 2005, 1724; (d) E. Serrano,
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