Synthesis, structure, reactivity, and catalytic activity of C,N- and C,N,N-orthopalladated iminophosphoranes

Article abstract of DOI:10.1002/ejic.200400907

The orthopalladated complexes [Pd(μ-Cl)(C₆H ₄-2PPh₂=NPh-κ-C,N)]₂ (1) and [Pd(C ₆H₄-2-PPh₂=N-C(O)-2NC₅H ₄-κ-C,N,N)Cl] (11) have been obtained by reaction of Pd(OAc)₂ (OAc = acetate) with the iminophosphoranes Ph ₃P=NPh and Ph₃P=N-C(O)-2-NC₅H₄, respectively, in the presence of excess LiCl. Complex 11 has been characterised by X-ray diffraction methods. The orthoplatinated derivative [Pt(C ₆H₄-2-PPh₂=N-C(O)-2-NC₅H ₄-κ-C,N,N)a] (12) can be obtained by reaction of [PtCl ₂(NCPh)₂] with Ph₃P=N-C(O)-2-NC ₅H₄ in refluxing 2-methoxyethanol. Complex 1 shows the typical reactivity of C,N-orthopalladated complexes, while complex 11 shows that the C,N,N-orthometallated ligand is strongly bonded to the Pd atom and cannot be easily displaced. The catalytic activity of the complexes [Pd(μ-Cl)-(C₆H₄-2-PPh ₂=NPh-κ-C,N)]₂ (1), [Pd₆(C ₆H₄-PPh₂NPh-κ-C,N)(Cl)(py)] (4), [Pd(C₆H₄-2-PPh₂=N-C(O)-2-NC₅H ₄-κ-C,N,N)Cl] (11) and [Pd(C₆H ₄-2-PPh₂=N-C(O)-2-NC₅H ₄-κ-C,N,N)(NCMe)]ClO₄ (13) in the Mizoroki-Heck (MH) reaction between methyl acrylate and different haloarenes has been examined. All complexes behave as moderate to good catalysts, yielding turnover numbers (TON) up to 526000. Their role as catalysts or precatalysts and the formation of nanoparticles is also discussed. Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005.

Full text of DOI:10.1002/ejic.200400907

FULL PAPER
Synthesis, Structure, Reactivity, and Catalytic Activity of C,N- and C,N,N-
Orthopalladated Iminophosphoranes
Raquel Bielsa,[a] Angel Larrea,[b] Rafael Navarro,*[a] Tatiana Soler,[a] and
Esteban P. Urriolabeitia*[a]
Keywords: C–C Coupling / C–H Activation / Homogeneous catalysis / N ligands / Palladium
The
orthopalladated
complexes
[Pd(μ-Cl)(C6H4-2-
placed. The catalytic activity of the complexes [Pd(μ-Cl)-
(C6H4-2-PPh2=NPh-κ-C,N)]2 (1), [Pd(C6H4-2-PPh2=NPh-κ-
C,N)(Cl)(py)] (4), [Pd(C6H4-2-PPh2=N-C(O)-2-NC5H4-κ-
C,N,N)Cl] (11) and [Pd(C6H4-2-PPh2=N-C(O)-2-NC5H4-κ-
C,N,N)(NCMe)]ClO4 (13) in the Mizoroki–Heck (MH) reac-
tion between methyl acrylate and different haloarenes has
been examined. All complexes behave as moderate to good
catalysts, yielding turnover numbers (TON) up to 526000.
Their role as catalysts or precatalysts and the formation of
nanoparticles is also discussed.
PPh2=NPh-κ-C,N)]2 (1) and [Pd(C6H4-2-PPh2=N-C(O)-2-
NC5H4-κ-C,N,N)Cl] (11) have been obtained by reaction of
Pd(OAc)2 (OAc
= acetate) with the iminophosphoranes
Ph3P=NPh and Ph3P=N-C(O)-2-NC5H4, respectively, in the
presence of excess LiCl. Complex 11 has been characterised
by X-ray diffraction methods. The orthoplatinated derivative
[Pt(C6H4-2-PPh2=N-C(O)-2-NC5H4-κ-C,N,N)Cl] (12) can be
obtained by reaction of [PtCl2(NCPh)2] with Ph3P=N-C(O)-2-
NC5H4 in refluxing 2-methoxyethanol. Complex 1 shows the
typical reactivity of C,N-orthopalladated complexes, while
complex 11 shows that the C,N,N-orthometallated ligand is
strongly bonded to the Pd atom and cannot be easily dis-
(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim,
Germany, 2005)
tate or chelate bidentate ligands towards PdII and PtII com-
plexes using different donor atoms.[29,30]
Introduction
Iminophosphoranes (phosphane imines) are compounds
of general structure R3P=NRЈ (R, RЈ = alkyl, aryl, acyl,
etc). They show notable analogies with the phosphorus
ylides R3P=CRЈ(RЈЈ),[1] and also have numerous applica-
tions in organic chemistry (e.g. the aza-Wittig reaction),
either as neutral or as anionic reagents.[1–3] In addition, the
bonding properties of these compounds as ligands towards
transition metals are still attracting the interest of chem-
ists,[4–28] for several reasons: their ability to form and to
stabilize carbene complexes,[5,8] the easy modulation of the
electronic and steric properties of different types of catalysts
(for instance, in oligo- and polymerisation of ethylene,[4,6,23]
hydrogen-transfer processes,[9,10] etc.), their applications in
enantioselective synthesis and catalysis (allylic substitu-
tion),[25,26] the synthesis of alkaline earth organometallic
complexes,[7] and, in general, due to their versatility. In this
context, we have recently reported some aspects of the
chemistry of the α-stabilized iminophosphoranes
Ph3P=NCN, Ph3P=NC(O)CH2Cl and Ph3P=NC(O)-2-
NC5H4, which can behave as monodentate, bridging biden-
However, the synthesis of orthometallated aryl com-
plexes derived from iminophosphoranes is still scarcely rep-
resented, as well as the properties of the resulting complexes
(reactivity, catalytic performance),[31–36] although very re-
cently relevant contributions have appeared in the litera-
ture.[37,38]
With the aim of expanding the scope of this type of or-
thometallated derivatives, and also to gain more insight into
their chemical behaviour, we have studied the reactivity of
several iminophosphoranes towards PdII and PtII metallat-
ing reagents. In addition, we have also studied the reactivity
of the resulting orthopalladated complexes towards dif-
ferent neutral and anionic ligands. We also report their be-
haviour as catalysts in specific C–C couplings such as the
MH reaction, a field in which the application of orthopalla-
dated complexes is in continuous growth.[39–44]
Results and Discussion
Synthesis of Orthometallated Iminophosphorane Complexes
[a] Departamento de Química Inorgánica, Instituto de Ciencia de
Materiales de Aragón, Universidad de Zaragoza-CSIC,
50009 Zaragoza, Spain
The reactivity of different iminophosphoranes, such as
Ph3P=NPh,
Ph3P=NCN,[45]
Ph3P=NC(O)CH2Cl,
[46]
and Ph3P=N–NϵC[47] towards
E-mail: esteban@unizar.es
Ph3P=NC(O)-2-NC5H4
[b] Centro Politécnico Superior, Instituto de Ciencia de Materiales
de Aragón, Universidad de Zaragoza-CSIC,
50018 Zaragoza, Spain
some standard metallating PdII and PtII reagents has been
studied. The reaction of Pd(OAc)2 (OAc = acetate) with
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C,N- and C,N,N-Orthopalladated Iminophosphoranes
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Ph3P=NPh (1:1 molar ratio) in refluxing CH2Cl2, followed Ph3P=N-C(O)-2-NC5H4 and with LiCl, performed under
by evaporation to dryness and treatment of the residue with the same experimental conditions as those reported for 1,
excess LiCl in MeOH, gives the orthometallated dimer gives the orthometallated monomer [Pd(C6H4-2-PPh2=N-
[Pd(C6H4-2-PPh2=NPh-κ-C,N)(μ-Cl)]2 (1) in very good C(O)-2-NC5H4-κ-C,N,N)(Cl)] (11) in good yield (see
yield (see Scheme 1). It has been previously reported that Scheme 2). As described for 1, the reaction of Li2[PdCl4]
complexes related to 1, but with different aryl substituents, with Ph3P=N-C(O)-2-NC5H4 gives a mixture of 11 and the
can be obtained from the reaction of Na2[PdCl4][36] or coordination product [Cl2Pd{N(=PPh3)C(O)-2-NC5H4}],
[37]
Pd(OAc)2
and the corresponding iminophosphoranes in already described by us,[30] and from which 11 could not be
moderate to good yields (56–97%). The synthesis of 1 has cleanly separated. On the other hand, the analogous PtII
been reported very recently[38] from the reaction of [o-C6H4- complex
[Pt(C6H4-2-PPh2=N-C(O)-2-NC5H4-κ-C,N,N)-
PPh2NPh)Li]2·OEt2 with [PdCl2(COD)] (COD = 1,5-cyclo- (Cl)] (12) can be easily obtained in moderate yield by reac-
octadiene). However, this process gives a mixture of 1 and tion of [PtCl2(NCPh)2] with Ph3P=N-C(O)-2-NC5H4 (1:1
the bis-aryl derivative, from which 1 is isolated in very poor molar ratio) in refluxing 2-methoxyethanol for 8 h. It is
yield (14%). As expected, 1 can also be obtained from the worthwhile to note that the previous reactivity of the imino-
reaction of Li2[PdCl4] and Ph3P=NPh, but this reaction phosphorane Ph3P=N-C(O)-2-NC5H4 towards different
gives a mixture of 1 and the N-bonded derivative PdII and PtII precursors[30] never resulted in a metallated
[Cl2Pd{N(=PPh3)Ph}2] from which 1 could not be sepa- compound. The obvious difference in reactivity with that
rated in pure form. Thus, the preparation described here reported here comes from the reaction conditions: the pro-
seems to be the most convenient method for the synthesis cesses performed at room temperature or at a low reflux
of 1. In order to obtain the corresponding PtII derivative, temperature (CH2Cl2/acetone) give coordination com-
two different procedures were checked. The first one in- pounds,[30] while those performed in harsh conditions (re-
volves the direct orthometallation of the substrate by reac- fluxing 2-methoxyethanol) give the metallated derivatives.
tion with [PtCl2(NCPh)2] in refluxing 2-methoxyethanol, a
Attempted orthometallation reactions involving the imi-
method successfully applied in the synthesis of cycloplati- nophosphoranes Ph3P=NCϵN, Ph3P=NC(O)CH2Cl and
nated complexes derived from phosphonium salts.[48,49] The Ph3P=NNϵC using the methods described above were not
second one is the reaction of the substrate with the dimer successful. In the case of Pd, mixtures of the corresponding
[Pt(μ-Cl)(η3-2-MeC3H4)]2 in refluxing chloroform.[50] How- cis- and trans-[Cl2Pd(N-ligand)2] derivatives were ob-
ever, neither of the two methods gives the expected ortho- tained;[29,30] in the case of platinum only decomposition to
platinated dimer: in the first case, complete reduction to black Pt0 was observed. Due to the lack of reactivity of
black Pt0 was observed, while in the second case a complex these iminophosphoranes, they were not further investi-
mixture of unidentified products was obtained.
gated.
We attempted a similar reaction with the other α-stabi-
Complex 1 has been characterised previously and its
lized iminophosphoranes. The reaction of Pd(OAc)2 with structure is shown in Scheme 1.[38] Complexes 11 and 12
Scheme 1. (i) Pd(OAc)2, reflux, CH2Cl2; (ii) LiCl, room temp., MeOH; (iii) L, CH2Cl2, room temp.; (iv) Tl(acac), – TlCl, CH2Cl2, room
temp.; (v) AgClO4, – AgCl, NCMe, room temp.; (vi) AgClO4, – AgCl, L, acetone, room temp.
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Scheme 2. (i) Pd(OAc)2, reflux, CH2Cl2; (ii) LiCl, room temp., MeOH; (iii) [PtCl2(NCPh)2], 2-methoxyethanol, reflux; (iv) AgClO4,
– AgCl, L, NCMe or acetone, room temp.; v) AgClO4, – AgCl, L, acetone, room temp.
give satisfactory elemental analyses, and their mass spectra ladated derivatives in which the metallated iminophos-
show the expected molecular peaks with the correct isotopic phorane behaves as a C,N-chelating group.[37] Finally, the
distribution. The IR spectra of 11 and 12 show sharp ab- 13C{1H} NMR spectrum of 11 shows signals corresponding
sorptions due to the νCO stretch at 1644 (11) and 1646 (12) to the presence of all the expected functional groups, and
cm–1, shifted to higher frequencies with respect to the corre- confirms the structure proposed in Scheme 2. The ortho-
sponding absorption in the free ligand, and also show two metallated carbon atom C1-Pd appears at δ = 153.19 ppm.
strong bands due to the νPN stretch at 1332 (11) and 1330
In summary, the standard methods of C–H bond acti-
(12) cm–1, while in the free ligand this absorption appears vation to give orthometallated complexes of PdII and PtII
at 1366 cm–1.[46] These two facts indicate that the iminic N- can be applied successfully to iminophosphorane ligands to
1
atom is coordinated to the metal centre.[30] The H NMR afford cyclopalladated and cycloplatinated complexes. The
spectra of 11 and 12 show similar patterns, and unambigu- crystal structure of 11 has been determined by X-ray dif-
ously reveal the presence of the cyclometallated [M(C6H4- fraction methods and provides additional structural infor-
2-PPh2=N-)] unit. Thus, four different signals assigned to mation.
the protons of the C6H4 unit can be observed at δ = 7.00,
7.13, 7.28 and 8.10 ppm in complex 11 and at δ = 6.95,
7.05, 7.23 and 8.02 ppm in 12, with the signal at δ =
X-ray Structure of Complex 11
8.02 ppm showing 195Pt satellites, as well as signals corre-
sponding to the pyridine group. Moreover, the N-bonding
Crystals of 11 of adequate quality for X-ray purposes
of the pyridine ring can be inferred from the shift to low were grown by slow vapour diffusion of Et2O into a CH2Cl2
field of the resonance attributed to the Hα proton (δ = solution of the crude complex at room temperature. A
8.97 ppm in 11; δ = 9.17 ppm in 12) with respect to its posi- drawing of the organometallic complex is shown in Fig-
tion in the free ligand (δ = 8.69 ppm),[46] and from the pres- ure 1. The parameters concerning the data collection and
ence, in 12, of 195Pt satellites for the multiplet at δ = refinement are collected in Table 1, and selected bond
9.17 ppm (3JPt,H Ϸ 20 Hz). These IR and 1H NMR spectro- lengths and angles are given in Table 2.
scopic data are in good agreement with the structure pro-
The Pd atom is located in a slightly distorted square-
posed in Scheme 2 for 11 and 12, in which the orthometall- planar environment and is surrounded by the metallated
ated iminophosphorane acts as a C,N,N-terdentate ligand. carbon atom C(7), the chlorine atom Cl(1) and the two N
The 31P{1H} NMR spectra of 11 and 12 show singlet sig- atoms of the iminophosphorane ligand, the iminic N atom,
nals at δ = 51.88 ppm in both cases (the signal of 12 shows N(1), and the pyridinic N atom, N(2). Thus, the metallated
the expected 195Pt satellites), and these signals are strongly iminophosphorane behaves as a C,N,N-terdentate ligand, in
deshielded with respect to their position, not only in the good agreement with the NMR spectroscopic data, forming
free ligand (δ = 23.89 ppm) but also in the N,N-bonded two fused, five membered rings. The bite angles of the two
complexes (δ Ϸ 34 ppm).[30] The position of this resonance chelating moieties are 87.24(9)° [C(7)–Pd(1)–N(1)] and
is similar to that found in other recently described cyclopal- 79.40(8)° [N(1)–Pd(1)–N(2)], and the sum of the bond
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C,N- and C,N,N-Orthopalladated Iminophosphoranes
FULL PAPER
angles around the Pd(1) atom is 360.05(9)°. The molecule
deviates only slightly from planarity: for instance, the maxi-
mum deviations found in the best least-square planes de-
fined by [C(7)–C(12)–P(1)–N(1)–Pd(1)] and [Pd(1)–N(1)–
C(1)–C(2)–N(2)] are only 0.09 Å and 0.02 Å, respectively.
The dihedral angle between these two planes is 4.5°. The
Pd(1)–C(7) bond length [1.976(3) Å] is statistically identical
or slightly longer than those found in the related complex
[Pd{κ2-C,N-C6H4(PPh2=NC6H4Me-4Ј)-2}(μ-OAc)]2
[1.964(3) Å and 1.959(3) Å], and is shorter than that found
in [Pd{κ2-C,N-C6H4(PPh2=NC6H4Me-4Ј)-2}(tmeda)]ClO4
[2.019(3) Å] (tmeda = N,N,NЈ,NЈ-tetramethylethylenedi-
amine).[37] The Pd–N(iminic) bond length [Pd(1)–N(1) =
1.997(2) Å] is shorter than those found in the aforemen-
tioned related complexes [2.050(2), 2.051(2) and
2.055(2) Å], probably reflecting the low trans influence of
the chlorine ligand. The Pd–N(pyridine) bond length [Pd–
N(2) = 2.120(2) Å] is similar to those found in related ar-
rangements (pyridine trans to aryl carbon).[51,52] This dis-
tance is longer than those found in related PdII complexes
in which the pyridine fragment is trans to an atom with a
smaller trans influence; for instance, the Pd–N(py) bond
length in [Pd(C6H4CH2NMe2)(Ph3PNC(O)-2-NC5H4)]ClO4
is 2.056(3) Å, and in this complex the pyridine is trans to
the aminic N atom of the NMe2 group.[30]
The P(1)–N(1) bond length [1.649(2) Å] is longer than
those reported in all related complexes. The complex
[Pd{κ2-C,N-C6H4(PPh2=NC6H4Me-4Ј)-2}(μ-OAc)]2 shows
P–N bond length values of 1.605(2) Å and 1.610(2) Å, while
that found in [Pd{κ2-C,N-C6H4(PPh2=NC6H4Me-4Ј)-
2}(tmeda)]ClO4 is 1.607(3) Å.[37] This clear elongation of
the P–N bond in 11 is due to two main facts: the coordina-
tion of the N atom and the presence of the carbonyl group,
which delocalizes the charge density through the P-N-C-O
system. As a comparison, the P–N bond length in
Figure 1. Thermal ellipsoid plot of [Pd(C6H4-2-PPh2=N-C(O)-2-
NC5H4-κ-C,N,N)Cl] (11). Non-hydrogen atoms are drawn at the
50% probability level.
Table 1. Crystal data and structure refinement for complex 11.
Formula
C24H18ClN2OPPd
523.22
monoclinic
P21/n
9.9726(6)
11.4926(7)
18.6220(11)
101.033(1)
2094.8(2)
4
Formula mass
Crystal system
Space group
a [Å]
b [Å]
c [Å]
β [°]
V [Å3]
Z
Dc [Mgm–3]
1.659
1.109
μ [mm–1]
Refl. collected
Unique reflections
Data/restr./param.
R1 [I Ͼ 2σ(I)]
wR2 [I Ͼ 2σ(I)]
Goodness of fit
T [K]
18137
4791, Rint = 0.0391
4791/0/271
0.0300
0.0660
1.042
100(2)
0.71073
[Pd(C6H4CH2NMe2)(Ph3PNC(O)-2-NC5H4)]ClO4
is
1.624(4) Å,[30] and in this complex the iminophosphorane
bonds to the palladium through the pyridine N-atom and
the carbonyl oxygen, leaving the -N=P fragment uncoordi-
nated. The delocalisation of the charge density is also re-
flected in the short value of the N(1)–C(1) bond length
[1.362(3) Å], which is similar, within experimental error, to
that found in Ph3P=NC(O)Ph [1.353(5) Å].[53,54] Finally, the
environment around the P atom is tetrahedral, with P–C
bond lengths similar to those found in related com-
plexes.[30,37]
λ(Mo-Kα) [Å]
Table 2. Selected bond lengths [Å] and angles [°] for complex 11.
Pd(1)–C(7)
Pd(1)–N(2)
P(1)–N(1)
P(1)–C(13)
C(1)–O(1)
N(2)–C(6)
C(1)–C(2)
C(7)–C(12)
C(9)–C(10)
C(11)–C(12)
C(7)–Pd(1)–N(1) 87.24(9)
N(1)–Pd(1)–N(2) 79.40(8)
N(1)–Pd(1)–Cl(1) 175.83(6)
N(1)–P(1)–C(12) 100.49(11)
C(1)–N(1)–Pd(1) 118.70(17)
1.976(3)
2.120(2)
1.649(2)
1.788(3)
1.227(3)
1.335(3)
1.506(4)
1.416(3)
1.388(4)
1.395(4)
Pd(1)–N(1)
Pd(1)–Cl(1)
P(1)–C(12)
P(1)–C(19)
N(1)–C(1)
N(2)–C(2)
C(7)–C(8)
C(8)–C(9)
C(10)–C(11)
1.997(2)
2.3039(7)
1.777(3)
1.796(3)
1.362(3)
1.347(3)
1.403(3)
1.382(4)
1.383(4)
Reactivity of Orthometallated Iminophosphorane Complexes
The reactivity of complexes 1 and 11 was examined in
order to check the stability of the metallated chelating (1)
or pincer (11) ligands. The main results are resumed in
Scheme 1 and 2, respectively. Thus, the dinuclear complex
1 reacts with neutral monodentate ligands L (L = PPh3,
PPhMe2 or pyridine) to give the corresponding mononu-
clear derivatives 2, 3 and 4, respectively, as a result of the
cleavage of the chloride bridging system. The NMR spectra
C(7)–Pd(1)–N(2)
C(7)–Pd(1)–Cl(1) 96.06(8)
N(2)–Pd(1)–Cl(1) 97.35(6)
C(1)–N(1)–P(1)
P(1)–N(1)–Pd(1)
O(1)–C(1)–C(2)
166.54(9)
122.96(18)
117.10(11)
122.5(2)
O(1)–C(1)–N(1)
N(1)–C(1)–C(2)
125.2(2)
112.3(2)
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of 2 and 3 display a single set of signals in each case, which
Complex 1 reacts with AgClO4 (1:2 molar ratio) in ace-
shows that these complexes are obtained as a single isomer. tone to give, after filtration of the AgCl, solutions contain-
The 31P{1H} NMR spectrum of 2 shows the presence of ing the solvated species [Pd(C6H4-2-PPh2=NPh)(S)x]ClO4
two doublet signals (3JP,P = 4.7 Hz), which suggests the (S = solvent; x = 2). The treatment of these freshly prepared
trans location of the iminic nitrogen and the PPh3 ligand. solutions with bidentate ligands L2 (1:1 molar ratio) gives
The cis arrangement of the metallated carbon and the phos- the cationic complexes [Pd(C6H4-2-PPh2=NPh)(L2)]ClO4
phane ligand is in good agreement with the transphobia be- [L2 = Ph2PCH2PPh2 (7), Ph2PCH2CH2PPh2 (8), 1,10-phen-
tween these ligands.[37,55–57] However, the NMR spectra of anthroline (9), 2,2Ј-bipyridine (10)]. We have not observed
complex 4 show the presence of a mixture of isomers a and the displacement of the metallated unit, nor the decoordi-
b (see Scheme 1) in a molar ratio 4a:4b of 4.1:1. This fact nation of the iminic nitrogen, even if the reactions are per-
is worthy of note, since the typical reactivity of C,N-cyclo- formed in presence of an excess of incoming ligand L2.
palladated halide-bridged dimers towards neutral ligands L Compounds 7–10 show correct elemental analyses and
(L = phosphanes, pyridines, etc.) always gives a single iso- mass spectra, and their IR spectra show in all cases the
mer in which the incoming ligand is coordinated trans to presence of a strong absorption in the range 1260–
the nitrogen atom.[58–60] Moreover, the major isomer 4a has 1290 cm–1, assigned to the νPN stretch, which suggest that
been characterised as that containing the pyridine ligand cis the iminic N-atom is bonded to the metal centre. The che-
with respect to the iminic nitrogen, that is, to the NPh late coordination of the L2 ligands is clearly inferred from
group. This assignment of structures 4a and 4b has been their NMR spectra. The 31P{1H} NMR spectrum of 7
carried out by comparison of the chemical shifts of the H6 shows three signals, one at low field (δ = 48.38 ppm) attrib-
proton of the C6H4 group (ortho to the metallated position) uted to the P atom in the metallated ring, and two at high
in the two isomers. Thus, the major isomer 4a shows the field (δ = –10.60 and –34.16 ppm) characteristic of the P,PЈ-
signal corresponding to H6 at δ = 8.30 ppm, while the chelating dppm.[62] From the analysis of the 31P{1H} NMR
minor isomer 4b shows the corresponding signal at δ = spectrum of 8 the P,PЈ-bonding mode of the dppe is also
6.30 ppm. This clear upfield shift can be due to the aniso- evident since it shows three low-field signals, one corre-
tropic shielding undergone by H6, which is promoted by sponding to the iminophosphorane (δ = 45.31 ppm) and the
the cis pyridine ligand in 4b.[58] In line with this, a mutual other two to the dppe ligand (δ = 43.81 and 58.85 ppm).[63]
1
anisotropic shielding between the phenyl and pyridine rings In the case of complex 9 the H NMR spectrum shows, in
in complex 4a should be possible and, in fact, the chemical addition to the signals assigned to the NPh, PPh2 and C6H4
shifts of the ortho protons of both rings in 4a are found at protons, eight sharp peaks attributed to the phen ligand,
higher field than the corresponding ones in 4b [NPh: δ = and this fact clearly reveals the inequivalence of the two
6.79 ppm (4a) and δ = 7.13 ppm (4b), Δδ = 0.34 ppm; py: δ halves of the phen ligand due to its N,NЈ-bonding to the
= 8.52 ppm (4a) and δ = 8.90 ppm (4b), Δδ = 0.38 ppm]. metal centre. Moreover, the complete attribution of all reso-
Obviously, the free rotation of both rings − the pyridine nances of the phen ligand can be done unambiguously since
around the Pd–N bond and the phenyl around the N–C one of the ortho protons is shifted to high field (δ =
bond − gives less-effective shielding (about 0.3–0.4 ppm) 8.00 ppm) with respect to the other (δ = 9.22 ppm) due to
than in the case of the fixed orthometallated ring (2 ppm). the anisotropic shielding exerted by the NPh ring.
A similar behaviour is observed in the 13C{1H} NMR spec-
trum of the mixture 4a/4b (see Experimental Section).
In summary, the reactivity of 1 in cleavage reactions with
neutral ligands (2–4) or substitution reactions of the halide
The treatment of 1 with Tl(acac) (acac = acetylacetonate; bridging system by anionic (5) or neutral ligands (6–10)
CH2Cl2, 1:2 molar ratio) gives the O,OЈ-acac derivative shows that the five-membered orthometallated iminophos-
[Pd(C6H4-2-PPh2=NPh)(acac-O,OЈ)] (5), while the reaction phorane is quite stable, and behaves similarly to other C,N-
of 1 with AgClO4 (1:2 molar ratio) in acetonitrile gives the orthometallated complexes derived from different amines.
bis-solvate [Pd(C6H4-2-PPh2=NPh)(NCMe)2]ClO4 (6). The However, the reactivity of complex 11, which contains a
two complexes show correct elemental analyses and mass C,N,N-terdentate ligand reveals some noteworthy differ-
spectra. Key spectroscopic parameters for 5 are the pres- ences.
ence of two strong absorptions attributed to the O,OЈ-
The reaction of 11 with AgClO4 (1:1 molar ratio) in
bonded acac ligand in the IR spectrum (1582, 1515 cm–1) NCMe gives the solvate derivative [Pd(C6H4-2-PPh2=N-
1
and the presence of the typical signals in the H [δ = 1.74 C(O)-2-NC5H4-κ-C,N,N)(NCMe)]ClO4 (13). The presence
and 2.06 ppm (CH3); δ = 5.35 ppm (CH)] and 13C{1H} of bonded NCMe is inferred from the observation of an
NMR spectra [δ = 27.14 and 27.31 ppm (CH3); δ = absorption in the IR spectrum at 2328 cm–1 (νCN) and a
99.75 ppm (CH); δ = 185.42 and 187.92 ppm (CO)].[61] In signal at δ = 2.79 ppm in the H NMR spectrum. A com-
1
the same way, the observation of two absorptions at 2321 parison of the spectral parameters of 13 with those of 11
and 2291 cm–1 in the IR spectrum, and two signals at δ = suggests that the metallated iminophosphorane still behaves
1
2.26 and 2.50 ppm in the H NMR spectrum of 6 suggest as a C,N,N-terdentate ligand. The complex [Pd(C6H4-2-
the presence of bonded acetonitrile. In these two cases, the PPh2=N-C(O)-2-NC5H4-κ-C,N,N)(PPh3)]ClO4 (14) can be
presence of the cyclopalladated unit is confirmed through obtained in the same way by treatment of 11 with AgClO4
the observation of its characteristic absorptions (IR, νPN
and resonances in the NMR spectra.
)
and PPh3 (1:1:1 molar ratio) in acetone. The characterisa-
tion of 14 is straightforward from its 31P{1H} NMR spec-
1728
© 2005 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
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C,N- and C,N,N-Orthopalladated Iminophosphoranes
FULL PAPER
trum, which shows the presence of coordinated PPh3 (δ = stopped at low temperature, with P,PЈ-chelation of the dppe
1
39.34 ppm), and from its H NMR spectrum, which shows ligand.
all expected signals for the proposed stoichiometry. It is
The 1H NMR spectra of 17 and 18 are temperature inde-
noteworthy that complex 14 is also obtained when the reac- pendent from 298 to 213 K (CD2Cl2) and show some note-
tion is performed in the presence of an excess of PPh3 (1:1:2 worthy features. The first is the equivalence of the two rings
molar ratio), thus showing that the displacement of the N- of the bipy or phen ligands, inferred from the presence of a
bonded pyridine group does not take place under these con- set of only four resonances (see Experimental Section),
ditions.
which do not split on cooling. This equivalence can be ex-
In order to check the strength of the pyridine fragment plained by assuming that they are bonded to the metal cen-
(usually a ligand easily removable from the metal coordina- tre through only one nitrogen atom and that there is a rapid
tion sphere) and the stability of the terdentate bonding exchange of the N-bonded atoms, which can not be stopped
mode κ-C,N,N of the metallated iminophosphorane, we in- at low temperature. This fast exchange can be easily ration-
vestigated the reactivity of 11 towards several bidentate li- alised through either a dissociative mechanism of the Pd–
gands, which usually act as chelating ligands. Complex 11 N bond or through a fluxional process, which could be a
does not react with Tl(acac) under the usual experimental “single oscillatory motion of the potentially bidentate li-
conditions (room temperature, 1:1 molar ratio), and un- gand via a trigonal-bipyramidal transition state”. Similar
changed 11 can be recovered at the end of the reaction. proposals have been reported for related systems.[50,63]
However, the reaction of 11 with AgClO4 and Whatever the mechanism, the coordination of the N-N li-
Ph2PCH2PPh2 (dppm), Ph2PCH2CH2PPh2 (dppe), 1,10- gands seems to occur in a plane normal to the molecular
phenanthroline (phen) or 2,2Ј-bipyridine (bipy) (1:1:1 molar plane. This fact is clearly reflected in the anisotropic shield-
ratio) in acetone gives complexes of stoichiometry ing undergone not only by the H6 proton of the metallated
[Pd(C6H4-2-PPh2=N-C(O)-2-NC5H4)(L-L)]ClO4 [L-L
=
C6H4 group (ortho to the palladated position), but also by
dppm (15), dppe (16), bipy (17), phen (18)], in keeping with the ortho proton of the pyridine fragment (Hα). These two
their elemental analyses and mass spectra. The IR spectra protons appear strongly shifted to high field with respect to
of 15–18 show the absorption due to the νPN stretch in the their positions in any other derivative. For instance, H6
range 1330–1340 cm–1, thereby suggesting that the Pd–N- (C6H4) appears at δ = 6.33 (17) or 5.85 ppm (18) while in
(imine) bond is still present. The NMR spectra of 15 are 11 its chemical shift is δ = 8.10 ppm; Hα (py) appears at δ
temperature independent and show clearly that the metall- = 7.95 (17) or 7.29 ppm (18) and at δ = 8.97 ppm in 11.
ating ligand is terdentate κ-C,N,N: the 31P{1H} NMR spec-
In summary, the reactivity of 11 shows that the bonding
trum shows three well-defined signals at δ = 49.14 of the terdentate ligand [C6H4-2-PPh2=N-C(O)-2-NC5H4-
(N=PPh2), 27.05 (dppm, Pd-PPh2) and –24.75 ppm (dppm, κ-C,N,N] to the Pd atom is remarkably stable. The decoor-
free PPh2). The observation of only one signal at high field dination of the pyridine fragment is not achieved upon
(δ = –24.75 ppm) is diagnostic for the presence of mono- treatment with classical chelating ligands (dppm, phen,
dentate P-dppm.[62] The formation of a four-membered bipy) and even in the presence of strongly chelating groups
metallacycle (P,PЈ-dppm) at the expense of the loss of the (dppe) only a competitive dynamic process is observed.
more stable five-membered ring by cleavage of the Pd– These facts, together with the stability shown by the C,N-
N(py) bond is probably not an energetically favourable pro- metallated complexes 1–10, prompted us to study the plaus-
cess. In contrast to this, the NMR spectra of 16 are tem- ible applications of this type of complex in catalytic pro-
perature dependent. At room temperature, the 31P{1H} cesses.
NMR spectrum shows only a sharp singlet peak at δ =
47.28 ppm, assigned to the metallated C6H4-2-PPh2=N
Catalityc Activity of Orthometallated Complexes: Their
unit. On cooling (CDCl3, 233 K) two new signals appear
Role as Precatalysts and the Formation of Nanoparticles in
and an AMX spin system is observed. At this temperature,
Mizoroki–Heck Processes
the chemical shift of the iminophosphorane appears at vir-
tually the same position (δ = 47.84 ppm), as a doublet of
Four different complexes were selected in order to check
doublets, and the signals attributed to the dppe ligand ap- the catalytic activity of orthopalladated iminophos-
pear at δ = 41.38 (dd) and 58.21 ppm (d), clearly showing phoranes. Complexes 1 and 4 are representative of com-
its P,PЈ-chelating mode.[50,63] The cleavage of the Pd–N(py) plexes with the metallated Ph3P=NPh ligand, one neutral
bond at low temperature is also inferred from the position and one cationic, and both of them with available coordina-
of the ortho proton of the pyridine group, which appears in tion sites. In the same way, 11 and 13 are representative
1
the H NMR spectrum at δ = 8.72 ppm, that is, shifted to examples of complexes with the metallated Ph3P=NC(O)-
high field with respect to its position in 11. All these facts 2-py ligand, and with the same characteristics. The selected
suggest that the metallated C6H4-2-PPh2=N unit behaves catalytic process is the C–C Mizoroki–Heck (MH) coupling
statically on the NMR timescale in the range of tempera- between aryl halides and methyl acrylate, due to the excep-
tures measured, while the pyridine and dppe groups are in- tional activity shown by C,X-cyclopalladated complexes in
volved into a series of dynamic process of coordination– this type of reaction (not limited to the MH reaction, but
decoordination, with the two processes being more or less also applied to Suzuki, Stille, etc.),[39–44,50,64–69] and the
equally favourable at room temperature. This process is wide interest in C–C Heck or Heck-type couplings.[70–77]
Eur. J. Inorg. Chem. 2005, 1724–1736
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R. Bielsa, A. Larrea, R. Navarro, T. Soler, E. P. Urriolabeitia
FULL PAPER
Table 3. Catalytic results in the MH reaction performed with cata-
lysts 1, 4, 11 and 13.
En- Catalyst
try
Substrate
Solvent
Yield
[%]
TON
1
2
3
4
5
6
7
8
1 (1%)
1 (0.1%)
1 (0.001%)
1 (0.0001%) IPh
4 (1%)
4 (0.1%)
4 (0.001%)
4 (0.0001%) IPh
11 (1%)
11 (0.1%)
11 (0.0001%) IPh
13 (1%)
13 (0.1%)
13 (0.0001%) IPh
1 (1%)
4 (1%)
11 (1%)
13 (1%)
1 (1%)
4 (1%)
11 (1%)
13 (1%)
1 (1%)
4 (1%)
11 (1%)
13 (1%)
IPh
IPh
IPh
DMF
DMF
DMF
DMF
DMF
DMF
DMF
DMF
DMF
DMF
DMF
DMF
DMF
DMF
DMA
DMA
DMA
DMA
92.1
72.0
86.0
43.4
64.9
57.8
52.0
52.6
80.0
78.6
11.4
72.1
58.7
45.6
27.2
42.6
20.7
6.2
92
720
86000
434000
65
578
52000
526000
80
786
114000
72
587
456000
27
43
21
6
9
47
14
15
5
IPh
IPh
IPh
9
IPh
IPh
10
11
12
13
14
15
16
17
18
19
20
21
22
23
IPh
IPh
IPh
IPh
IPh
IPh
All selected complexes behave as moderate to good cata-
lysts (see Experimental Section and Table 3) in the arylation
of methyl acrylate to give methyl (E)-cinnamate in refluxing
DMF (entries 1–14) when phenyl iodide is employed. The
best yields are obtained when the amount of catalyst is 10–2
p-BrC6H4CHO DMF
p-BrC6H4CHO DMF
p-BrC6H4CHO DMF
p-BrC6H4CHO DMF
p-BrC6H4CN
p-BrC6H4CN
p-BrC6H4CN
p-BrC6H4CN
8.9
47.0
14.4
15
5.0
23.0
4.1
DMF
DMF
DMF
DMF
(mmol catalyst per mmol aryl halide; entries 1, 5, 9 and 12) 24
23
4
11
but this amount can be as low as 10–6 (entries 4, 8, 11 and
25
26
11.5
14) and still give reasonable yields of isolated products and
very high turnover numbers. However, as is evident from
Table 3, the yield of isolated cinnamates drops when the
concentration of catalyst decreases. The best reaction sol- metallated unit is lost during the catalytic cycle. Interest-
vent for this type of process was found to be DMF. In spite ingly, the resulting dark red solutions obtained at the end
of its similarity, very poor yields were obtained when N,N- of the catalysis are still catalytically active and, after the
dimethylacetamide (DMA) was used (entries 1–4 vs. en- addition of a second batch of reagents, the catalysis can be
tries 15–18), and the reaction was completely inhibited in reassumed without an induction period. However, the yields
NMP (N-methylpyrrolidinone). A comparison of the dif- drop from the first to the second and following runs, show-
ferent catalysts shows that complexes 1 and 4 give better ing the deactivation of the catalytically active species. For
conversions than complexes 11 or 13, and this fact could be instance, in a series of test experiments of four consecutive
related to the presence of the highly stable terdentate ligand runs under the conditions described in entry 1 (1% catalyst
[C6H4-2-PPh2=N-C(O)-2-NC5H4-κ-C,N,N] in 11 and 13 1, PhI, DMF, reflux 24 h for each run) the obtained yields
(see below). The presence of weakly bonded ligands in 4 or of methyl (E)-cinnamate were 90% (1st run), 60% (2nd run),
13 seems also to improve the yields, with respect to 1 or 20% (3rd run) and 0% in the last run.
11, at low concentrations of catalyst. On the other hand, a
The observation of an induction period in all catalytic
comparison of the different substrates shows that the reac- experiments, the evidence of the decomposition of the cata-
tivity of deactivated bromoarenes (p-BrC6H4CN or p- lyst by NMR spectroscopy, the obvious impossibility to re-
BrC6H4CHO) is substantially lower for all catalysts than cover the catalyst after the end of the first run, and the
that described for PhI (entries 19–26). Due to these low confirmation that the catalysis can be reassumed after the
conversions, no reactions were attempted with activated first run strongly suggest that the organometallic derivatives
bromoarenes or with chloroarenes.
1, 4, 11 or 13 are not the true catalysts, but only the precata-
As general trends, we have observed that all reactions lysts. What, therefore, is the nature of the true catalytic spe-
start after an induction period of approx. 30 min. During cies? Recent studies in this area show that, in many cases,
this time, the initial yellow or pale-yellow solution becomes the orthopalladated derivatives behave only as palladium
dark red but without evidence of formation of palladium reservoirs which, depending on the nature of the metallated
black. After the reaction, we attempted the recovery of the unit, produces either low-coordinate Pd0 species (cyclo-
catalyst during the workup, but all these attempts were un- metallated phosphanes) or palladium nanoparticles (for in-
successful. Moreover, the analysis of the crude of the cata- stance, C,N-cyclopalladated complexes),[39–41,50,69,78] which
lytic reaction, after removal of solvent (DMF) by distil- are the true catalysts. Since our orthometallated iminophos-
lation, by 31P{1H} NMR spectroscopy shows only peaks phoranes can be considered to be closely related to a C,N-
due to O=PPh3 and other unidentified species; signals due cyclometallated complex, we investigated the plausible for-
to the initial catalyst were not observed. That is, the ortho- mation of nanoparticles of Pd0 from our catalysts. With this
1730
© 2005 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
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Eur. J. Inorg. Chem. 2005, 1724–1736

C,N- and C,N,N-Orthopalladated Iminophosphoranes
FULL PAPER
purpose, we checked the stability of the complexes under of the nanoparticles as the catalytically active species is the
the reaction conditions (DMF, refluxing for 24 h). Thus, mercury drop test (poisoning experiments).[78,82–84] The ad-
complexes 1, 4, 11 and 13 were refluxed in DMF for 24 h, dition of an excess of Hg (with respect to the catalyst) to
and the resulting solutions were analysed by TEM, since the process described in entry 1 completely inhibits the re-
this method is one of the best for detecting nanopart- action and no product, even at trace levels, was detected at
icles.[79–81] In all studied cases, the presence of nanoparticles the end of the reaction.
(averaged diameter 10 nm) was evident. Figure 2 shows a
In summary, the complexes with orthopalladated imino-
TEM image obtained from a solution of complex 4 after phosphoranes are precatalysts for the MH arylation of
thermal treatment. It is worthy of mention that the amount methyl acrylate to give the corresponding (E)-cinnamates
of nanoparticles detected is not the same in all cases. For in moderate to good yields. The true catalytic species are
complexes 1 and 4, the amount of nanoparticles is substan- nanoparticles of elemental palladium, whose presence was
tially higher than that found in solutions of complexes 11 confirmed by TEM, generated by decomposition of the cat-
and 13, after the same thermal treatment. Thus, the simple alyst.
heating of the complexes in the reaction solvent produces
their decomposition and the formation of the nanoparticles,
Conclusions
and it is known that nanoparticles of Pd catalyze the MH
reaction.[79–81]
The orthopalladated complexes [Pd(μ-Cl)(C6H4-2-
PPh2=NPh-κ-C,N)]2 (1) and [Pd(C6H4-2-PPh2=N-C(O)-2-
NC5H4-κ-C,N,N)Cl] (11) have been obtained by reaction
of Pd(OAc)2 with the iminophosphoranes Ph3P=NPh and
Ph3P=N-C(O)-2-NC5H4, respectively, in the presence of ex-
cess LiCl. The orthoplatinated derivative [Pt(C6H4-2-
PPh2=N-C(O)-2-NC5H4-κ-C,N,N)Cl] (12) can be obtained
by reaction of [PtCl2(NCPh)2] with Ph3P=N-C(O)-2-
NC5H4 in refluxing 2-methoxyethanol. The reactivity of 1
in cleavage reactions with neutral ligands (2–4) or substitu-
tion reactions of the halide-bridging system by anionic (5)
or neutral ligands (6–10) shows that the five-membered or-
thometallated iminophosphorane is quite stable, and be-
haves similarly to other C,N-orthometallated complexes de-
rived from different amines. The reactivity of 11 shows that
the bonding of the terdentate ligand [C6H4-2-PPh2=N-
C(O)-2-NC5H4-κ-C,N,N] to the Pd atom is remarkably
stable. The decoordination of the pyridine fragment is not
achieved with classical chelating ligands (dppm, phen, bipy)
and even in the presence of strongly chelating groups (dppe)
only a competitive dynamic process is observed. The com-
plexes 1, 4, 11 and 13 are precatalysts for the MH arylation
of methyl acrylate to give the corresponding (E)-cinnamates
in moderate to good yields. The true catalytic species are
nanoparticles of elemental palladium, whose presence is
confirmed by TEM, generated by decomposition of the cat-
alyst.
Figure 2. TEM image taken from a solution of complex 4 after 24 h
in refluxing DMF.
We then compared the catalytic process described in en-
try 1 with that performed under the same experimental con-
1
ditions but using nanoparticles. Monitoring by H NMR
spectroscopy showed that in the reaction carried out with
nanoparticles, generated from 1 as described above, the
presence of the reaction product can be detected only
10 min after the start of the reaction (time required to reach
reflux temperature), that is, without an induction period,
while in the process performed with catalyst 1 (entry 1) the
presence of the products of the reaction is not detected until
30 min of additional refluxing. This additional time
matches very well with the induction period (change of col-
our of the solution) observed in all catalytic reactions per-
formed with complexes 1, 4, 11 and 13. The yields obtained
in these two processes are very similar (92% with catalyst 1
Experimental Section
CAUTION: Perchlorate salts of metal complexes with organic li-
gands are potentially explosive. Only small amounts of these materi-
als should be prepared and handled with great care.[85]
General Methods: Solvents were dried and distilled under argon
using standard procedures. Elemental analyses were performed on
a Perkin–Elmer 2400-B microanalyser. Infrared spectra (4000–
400 cm–1) were recorded on a Perkin–Elmer Spectrum One FT-IR
spectrophotometer from nujol mulls between polyethylene sheets.
Mass spectra (positive ion FAB) were recorded from CH2Cl2 solu-
tions on a V. G. Autospec spectrometer. H, 13C{1H} and 31P{1H}
NMR spectra were recorded in CDCl3 or CD2Cl2 solutions at
1
vs. 98% with nanoparticles). A second test to check the role room temperature (other temperatures are specified) on Bruker
Eur. J. Inorg. Chem. 2005, 1724–1736
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R. Bielsa, A. Larrea, R. Navarro, T. Soler, E. P. Urriolabeitia
FULL PAPER
ARX-300 or Avance400 spectrometers operating, respectively, at
10.4, 3JH,H = 7.6, 4JH,H = 1.6 Hz, H3, C6H4, 4a), 6.94–6.99 (m, Hm,
3
4
300.13 MHz (ARX300) and 400.13 MHz (Avance400). The 1H and py, 4a), 7.00–7.04 (m, H4, C6H4, 4a), 7.13 (dm, JH,H = 8.4, JH,H
13C{1H} NMR spectra were referenced to the residual solvent sig-
nal as internal standard and the 31P{1H} NMR spectra to external
H3PO4 (85%). The starting material Ph3P=NPh is commercially
available (Aldrich) and Ph3P=N-C(O)-2-NC5H4 was prepared fol-
lowing published methods.[46]
= 1.2 Hz, Ho, NPh, 4b), 7.22 (tt, JH,H = 7.2, JH,H
Ϸ
5JP,H
=
=
3
4
1.6 Hz, H5, C6H4, 4a), 7.31–7.35 (m, Hm, py, 4b), 7.43 (tt, JH,H
3
7.6, 4JH,H = 1.6 Hz, Hp, py, 4a), 7.48–7.55 (m, Hm, PPh2, 4a + 4b),
7.59–7.63 (m, Hp, PPh2, 4a + 4b), 7.74–7.79 (m, Ho, PPh2, 4a),
7.88–7.93 (m, Ho, PPh2, 4b), 8.30 (ddd, JH,H = 7.2, JP,H = 1.6,
3
4
4JH,H = 1.2 Hz, H6, C6H4, 4a), 8.52 (dd, JH,H = 6.4, JH,H
=
3
4
Complex 1: Pd(OAc)2 (1.000 g, 4.45 mmol) was added to a solution
of Ph3P=NPh (1.572 g, 4.45 mmol) in dry CH2Cl2 (20 mL) under
argon, and this mixture was refluxed for 1.5 h. The initial orange-
brown solution evolved slowly during the reaction time to give a
deep orange solution. After cooling, the solvent was removed to
dryness, the residue was dissolved in MeOH (20 mL), treated with
an excess of anhydrous LiCl (0.755 g, 17.8 mmol) and then stirred
at room temperature. After a few seconds complex 1 precipitated
as a deep-yellow solid, although stirring was continued for an ad-
ditional 30 min. After this time 1 was filtered off, washed with
MeOH (20 mL) and Et2O (50 mL) and air dried. Yield: 2.108 g
(95.9%). C48H38Cl2N2P2Pd2 (988.50): calcd. C 58.32, H 3.87, N
1.6 Hz, Ho, py, 4a), 8.90 (dd, JH,H = 5.2, JH,H = 1.6 Hz, Ho, py,
3
4
4b) ppm. 13C{1H} NMR (CDCl3) (not all signals for the minor
5
isomer 4b could be detected due to overlap): δ = 121.74 (d, JP,C
=
=
=
=
2.0 Hz, Cp, NPh, 4a), 123.83 (s, Cm, py, 4a), 124.04 (d, JP,C
3
14.1 Hz, C4, C6H4, 4a), 125.02 (s, Cm, py, 4b), 127.43 (d, JP,C
3
9.1 Hz, Co, NPh, 4a), 127.72 (s, Cm, NPh, 4a), 128.24 (d, JP,C
2
21.1 Hz, C3, C6H4, 4a), 128.61 (d, 1JP,C = 86.5 Hz, Cipso, PPh2, 4a),
128.86 (d, JP,C = 11.1 Hz, Cm, PPh2, 4a), 128.90 (d, JP,C
=
3
3
4
11.1 Hz, Cm, PPh2, 4b), 130.29 (d, JP,C = 3.0 Hz, C5, C6H4, 4b),
130.38 (d, JP,C = 3.1 Hz, C5, C6H4, 4a), 132.75 (d, JP,C = 2.0 Hz,
4
4
Cp, PPh2, 4a), 133.23 (d, JP,C = 9.1 Hz, Co, PPh2, 4a), 133.50 (d,
2
2JP,C = 10.1 Hz, Co, PPh2, 4b), 134.43 (d, 3JP,C = 15.1 Hz, C6, C6H4,
2.83; found C 58.58, H 3.93, N 2.91. IR: ν = 1292, 1263 (νPN) cm–1.
˜
4b), 136.48 (s, Cp, py, 4a), 137.35 (s, Cp, py, 4b), 138.53 (d, JP,C
=
3
NMR spectroscopic data have been reported previously.[38]
1
15.1 Hz, C6, C6H4, 4a), 140.55 (d, JP,C = 139 Hz, C2, C6H4, 4a),
147.12 (d, 2JP,C = 3.0 Hz, Cipso, NPh, 4a), 147.19 (d, 2JP,C = 3.0 Hz,
Complex 2: PPh3 (0.041 g, 0.158 mmol) was added to a suspension
of 1 (0.078 g, 0.079 mmol) in 5 mL of CH2Cl2. The initial orange
suspension gradually dissolved and, after 5 min stirring at room
temperature, a pale-yellow solution was obtained. The evaporation
of this solution and treatment of the oily residue with 20 mL of
Et2O gave 2 as a white solid, which was filtered off, washed with
additional Et2O (10 mL) and air dried. Yield: 0.092 g (77%).
C42H34ClNP2Pd (756.54): calcd. C 66.68, H 4.53, N 1.85; found C
Cipso, NPh, 4b), 151.04 (s, Co, py, 4a), 152.27 (d, JP,C = 20.1 Hz,
2
C1, C6H4, 4a), 153.73 (s, Co, py, 4b), 156.39 (d, 2JP,C = 20.1 Hz, C1,
C6H4, 4b) ppm. 31P{1H} NMR (CDCl3): δ = 44.31 (4b), 48.21 (4a)
ppm.
Complex 5: Tl(acac) (0.123 g, 0.404 mmol) was added to a suspen-
sion of 1 (0.200 g, 0.202 mmol) in CH2Cl2 (10 mL). The resulting
mixture was stirred at room temperature for 1 h, then filtered
through Celite. The clear yellow solution was evaporated to dryness
and the oily residue treated with cold n-hexane (10 mL) to give 5
as a yellow solid. This solid was filtered off and dried in vacuo.
Yield: 0.184 g (81.5%). C29H26NO2PPd (557.91): calcd. C 62.43, H
66.51, H 4.47, N 1.85. IR: ν = 1289 (νPN) cm–1. MS (FAB+): m/z
˜
1
3
(%) = 720 (25) [M – Cl]+. H NMR (CDCl3): δ = 6.46 (tt, JH,H
=
4
7.8, JH,H = 1.2 Hz, 1 H, C6H4), 6.59–6.75 (m, 3 H, C6H4), 6.83–
6.98 (br. m, 5 H, NPh), 7.18–7.24 (m, 6 H, Hm, PPh3), 7.27–7.33
(m, 3 H, Hp, PPh3), 7.48–7.62 [m, 12 H, PPh3 (6 Ho) + PPh2 (4 Hm
+ 2 Hp)], 7.89–7.96 (m, 4 H, Ho, PPh2) ppm. 31P{1H} NMR
(CDCl3): δ = 33.46 (d, 3JP,P = 4.7 Hz, 1 P, Pd–PPh3), 38.69 (d, 3JP,P
= 4.7 Hz, 1 P, P=N) ppm.
4.69, N 2.51; found C 62.49, H 4.60, N 2.35. IR: ν = 1582, 1515
˜
(νCO), 1287, 1262 (νPN) cm–1. MS (FAB+): m/z (%) = 557 (30)
[M]+. 1H NMR (CD2Cl2): δ = 1.74 (s, 3 H, Me, acac), 2.06 (s, 3 H,
3
4
Me, acac), 5.35 (s, 1 H, CH, acac), 6.83 (td, JH,H = 7.8, JH,H
=
3
4
1.2 Hz, 1 H, Hp, NPh), 6.95 (dd, JH,H = 7.6, JH,H = 1.2 Hz, 1 H,
Complex 3: Complex 3 was prepared following a synthetic pro-
cedure similar to that reported for 2. Thus, 1 (0.200 g, 0.202 mmol)
in CH2Cl2 (5 mL) was treated with PPhMe2 (57.6 μL, 0.404 mmol)
to give 3 as a cream solid. Yield: 0.232 g (90.7%). C32H30ClNP2Pd
(632.4): calcd. C 60.78, H 4.78, N 2.21; found C 60.61, H 4.74, N
H3, C6H4), 6.99 (t, JH,H = 7.2 Hz, 2 H, Hm, NPh), 7.05–7.10 [m,
3
3 H, NPh (Ho) + C6H4 (H4)], 7.27 (tt, JH,H = 7.6, JH,H Ϸ JP,H
3
4
5
= 1.6 Hz, 1 H, H5, C6H4), 7.53–7.57 (m, 4 H, Hm, PPh2), 7.64–7.68
(m, 2 H, Hp, PPh2), 7.71 (dm, JH,H = 8.0 Hz, 1 H, H6, C6H4),
3
1.91. IR: ν = 1291, 1260 (νPN) cm–1. MS (FAB+): m/z (%) = 631
7.82–7.87 (m, 4 H, Ho, PPh2) ppm. 13C{1H} NMR (CD2Cl2): δ =
˜
(20) [M]+, 596 (100) [M – Cl]+. 1H NMR (CDCl3): δ = 1.68 (d,
2JP,H = 10.5 Hz, 6 H, PMe2), 6.69–6.74 (m, 1 H, C6H4), 6.78–6.95
[m, 8 H, C6H4 (3 H) + NPh], 7.30–7.38 (m, 3 H, Hm + Hp, PPh),
7.45–7.51 (m, 4 H, Hm, PPh2), 7.54–7.60 (m, 2 H, Hp, PPh2), 7.69–
7.76 (m, 2 H, Ho, PPh), 7.83–7.89 (m, 4 H, Ho, PPh2) ppm. 31P{1H}
NMR (CDCl3): δ = 8.75 (s, 1 P, Pd-PPhMe2), 34.12 (s, 1 P, P=N)
ppm.
27.14 (s, Me, acac), 27.31 (s, Me, acac), 99.75 (s, CH, acac), 121.39
3
3
(s, Cp, NPh), 124.17 (d, JP,C = 14 Hz, C4, C6H4), 126.99 (d, JP,C
2
= 10 Hz, Co, NPh), 127.47 (s, Cm, NPh), 127.73 (d, JP,C = 22 Hz,
1
3
C3, C6H4), 128.21 (d, JP,C = 85 Hz, Cipso, PPh2), 128.91 (d, JP,C
= 11 Hz, Cm, PPh2), 129.64 (d, JP,C = 3 Hz, C5, C6H4), 132.40 (d,
4
3JP,C = 14 Hz, C6, C6H4), 132.79 (d, 4JP,C = 2 Hz, Cp, PPh2), 133.22
(d, JP,C = 10 Hz, Co, PPh2), 140.75 (d, JP,C = 139 Hz, C2, C6H4),
2
1
146.49 (d, JP,C = 3 Hz, Cipso, NPh), 152.99 (d, JP,C = 20 Hz, C1,
C6H4), 185.42 (s, CO, acac), 187.92 (s, CO, acac) ppm. 31P{1H}
NMR (CD2Cl2): δ = 46.04 ppm.
2
2
Complex 4: Complex 4 was prepared following a synthetic pro-
cedure similar to that reported for 2. Thus, 1 (0.200 g, 0.202 mmol)
in CH2Cl2 (10 mL) was treated with pyridine (65.1 μL, 0.808 mmol)
to give 4 as a yellow solid. Yield: 0.198 g (85.3%). Complex 4 was
characterised spectroscopically (NMR) as a mixture of the isomers
Complex 6: AgClO4 (0.084 g, 0.405 mmol) was added to a suspen-
sion of 1 (0.200 g, 0.202 mmol) in NCMe (15 mL) and the resulting
4a/4b in a molar ratio of 4.1:1. C29H24ClN2PPd (573.35): calcd. C mixture was stirred at room temperature for 30 min with exclusion
60.75, H 4.22, N 4.89; found C 60.80, H 4.10, N 5.06. IR: ν = 1589
of light. After this time the grey suspension was filtered through
Celite and the resulting pale-yellow solution was evaporated to
small volume (approx. 1 mL). Addition of n-pentane (10 mL) and
˜
(py), 1285 (νPN) cm–1. 1H NMR (CDCl3) (not all signals for the
minor isomer 4b could be detected due to overlap): δ = 6.30 (dd,
4
3
4
3JH,H = 5.6, JH,H = 1.6 Hz, H6, 4b), 6.56 (tm, JH,H = 7.2, JH,H continuous stirring gave 6 as a pale-yellow solid, which was filtered
= 1.2 Hz, Hp, NPh, 4a), 6.65 (t, 3JH,H = 7.2 Hz, Hm, NPh, 4a), 6.79
off and dried in vacuo. Yield: 0.226 g (87.5%). C28H25ClN3O4PPd
(640.35): calcd. C 52.52, H 3.93, N 6.56; found C 52.60, H 3.93, N
(dm, JH,H = 7.2, JH,H = 1.2 Hz, Ho, NPh, 4a), 6.86 (ddd, JP,H
=
3
4
3
1732
© 2005 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjic.org
Eur. J. Inorg. Chem. 2005, 1724–1736

C,N- and C,N,N-Orthopalladated Iminophosphoranes
FULL PAPER
6.78. IR: ν = 2321, 2291 (νCN), 1287, 1260 (νPN) cm–1. MS (FAB+): 4JH,H = 1.2 Hz, 1 H, H3, C6H4), 7.33 (tdd, 3JH,H = 7.6, 4JP,H = 5.2,
˜
m/z (%) = 499 (10) [M – ClO4 – NCMe]+, 458 (25) [M – ClO4
–
4JH,H = 0.8 Hz, 1 H, H4, C6H4), 7.60–7.62 [m, 5 H, PPh2 (4 Hm) +
2NCMe]+. H NMR (CDCl3): δ = 2.26 (br. s, 3 H, NCMe), 2.50 C6H4 (H5)], 7.65 (dd, 3JH,H = 8.0, JH,H = 4.8 Hz, 1 H, HβЈ, phen),
1
3
(s, 3 H, NCMe), 6.85–6.99 [m, 6 H, NPh + C6H4 (H3)], 7.09 (ddt, 7.69–7.74 (m, 2 H, Hp, PPh2), 7.75 (br. d, 3JH,H = 8.0 Hz, 1 H, H6,
3JH,H = 7.2, 4JP,H = 4.8, 4JH,H = 1.5 Hz, 1 H, H4, C6H4), 7.16–7.26
C6H4), 7.76–7.82 (m, 4 H, Ho, PPh2), 8.00–8.03 (m, 2 H, Hβ + HαЈ,
(m, 2 H, H5 + H6, C6H4), 7.48–7.54 (m, 4 H, Hm, PPh2), 7.60–7.66
phen), 8.12 (s, 2 H, Hδ + HδЈ, phen), 8.62 (dd, JH,H = 8.0, JH,H
3
4
(m, 2 H, Hp, PPh2), 7.67–7.74 (m, 4 H, Ho, PPh2) ppm. 31P{1H} = 1.2 Hz, 1 H, HγЈ, phen), 8.75 (dd, 3JH,H = 8.4, JH,H = 1.6 Hz, 1
4
3
NMR (CDCl3): δ = 54.29 ppm.
H, Hγ, phen), 9.22 (d, JH,H = 5.2 Hz, 1 H, Hα, phen) ppm.
13C{1H} NMR (CD2Cl2): δ = 122.77 (s, Cp, NPh), 125.26 (s, CβЈ,
Complex 7: AgClO4 (0.084 g, 0.405 mmol) was added to a suspen-
sion of 1 (0.200 g, 0.202 mmol) in acetone (20 mL) and the re-
sulting mixture was stirred at room temperature for 30 min with
exclusion of light. The grey suspension was then filtered through a
Celite pad and dppm (0.155 g, 0.404 mmol) was added to the
freshly prepared solution of the solvate to give a pale-orange solu-
tion. After stirring at room temperature for 4 h, the solvent was
evaporated to dryness and the residue treated with Et2O (10 mL)
to give 7 as a pale-orange solid, which was filtered and air dried.
Yield: 0.357 g (93.7%). C49H41ClNO4P3Pd (942.65): calcd. C 62.43,
3
phen), 125.33 (d, JP,C = 14.1 Hz, C4, C6H4), 125.69 (s, Cβ, phen),
3
1
126.64 (d, JP,C = 9.1 Hz, Co, NPh), 126.68 (d, JP,C = 91 Hz, Cipso
,
PPh2), 127.40, 127.82 (2s, Cδ + CδЈ, phen), 128.95 (s, Cm, NPh),
2
3
129.34 (d, JP,C = 17.1 Hz, C3, C6H4), 129.37 (d, JP,C = 12.0 Hz,
Cm, PPh2), 130.11, 130.56 (2Cq, phen), 131.64 (d, JP,C = 3.0 Hz,
4
C5, C6H4), 133.36 (d, 2JP,C = 10.6 Hz, Co, PPh2), 133.73 (d, JP,C
=
4
2.0 Hz, Cp, PPh2), 135.17 (d, JP,C = 14.1 Hz, C6, C6H4), 139.17 (s,
3
Cγ, phen), 139.63 (s, CγЈ, phen), 144.21 (d, JP,C = 131 Hz, C2,
1
C6H4), 145.18, 147.14 (2 Cq, phen), 146.45 (d, 2JP,C = 3.0 Hz, Cipso
,
=
NPh), 150.06 (s, Cα, phen), 152.15 (s, CαЈ, phen), 160.46 (d, JP,C
2
H 4.38, N 1.48; found C 62.35, H 4.40, N 1.35. IR: ν = 1263 (ν
)
˜
18.1 Hz, C1, C6H4) ppm. 31P{1H} NMR (CD2Cl2): δ = 45.84 ppm.
PN
cm–1. MS (FAB+): m/z (%) = 842 (100) [M – ClO4]+. 1H NMR
2
2
Complex 10: Complex 10 was prepared following a synthetic pro-
cedure similar to that reported for 7. A solution of 1 (0.200 g,
0.202 mmol) in acetone (20 mL) was treated with AgClO4 (0.084 g,
0.405 mmol) and 2,2Ј-bipyridine (0.063 g, 0.404 mmol) to give 10
as a yellow solid. Yield: 0.289 g (100%). C34H27ClN3O4PPd
(714.43): calcd. C 57.16, H 3.81, N 5.88; found C 57.23, H 3.88, N
(CDCl3): δ = 4.06 (dd, JP,H = 11.1, JP,H = 7.8 Hz, 2 H, CH2),
6.52–6.59 (m, 3 H, NPh), 6.71–6.74 (m, 2 H, NPh), 6.91–6.98 (m,
2 H, C6H4), 7.03–7.12 [m, 6 H, C6H4 (2 H) + PPh2], 7.20–7.26 (m,
4 H, PPh2), 7.35–7.58 (m, 12 H, PPh2), 7.61–7.76 (m, 10 H, PPh2)
ppm. 13C{1H} NMR (CDCl3): δ = 40.97 (dd, JP,C = 28.4, JP,C
=
1
1
21.5 Hz, CH2), 122.76 (s, Cp, NPh), 125.70 (d, JP,C = 13.8 Hz, C4,
3
5.94. IR: ν = 1289, 1263 (νPN) cm–1. MS (FAB+): m/z (%) = 614
C6H4), 126.33 (d, JP,C = 30.7 Hz, Cipso, PPh2), 126.49 (d, JP,C
=
1
3
˜
1
3
(100) [M – ClO4]+. H NMR (CDCl3): δ = 6.84 (td, NPh, JH,H
=
9.5 Hz, Co, NPh), 127.96 (d, JP,C = 30.7 Hz, Cipso, PPh2), 128.01
1
7.6, JH,H = 1.5 Hz, 1 H, Hp), 6.93 (t, JH,H = 8.1 Hz, 2 H, Hm,
4
3
(d, JP,C = 30.6 Hz, Cipso, PPh2), 128.40 (s, C5, C6H4), 129.12 (s,
1
NPh), 6.95 (d, JH,H = 8.1 Hz, 2 H, Ho, NPh), 7.05 (ddd, JP,H
=
=
=
3
3
Cm, NPh), 129.19 (d, JP,C = 10.2 Hz, Cm, PPh2), 129.20 (d, JP,C
3
3
9, JH,H = 7.2, JH,H = 1.2 Hz, 1 H, C6H4, H3), 7.19 (tdd, JH,H
3
4
3
= 12.1 Hz, Cm, PPh2), 129.62 (d, 3JP,C = 11.7 Hz, Cm, PPh2), 131.37
7.0, JP,H = 5.1, JH,H = 1.5 Hz, 1 H, C6H4, H4), 7.44 (tt, JH,H
4
4
3
(d, JP,C = 1.7 Hz, Cp, PPh2), 132.60 (s, Cp, PPh2), 132.69 (d, JP,C
4
2
7.2, JP,H Ϸ JH,H = 1.5 Hz, 1 H, C6H4, H5), 7.46–7.66 [m, 15 H,
5
4
= 13.2 Hz, Co, PPh2), 133.05 (d, JP,C = 9.9 Hz, Co, PPh2), 133.39
2
PPh2 + bipy (4 H, Hβ + Hδ) + C6H4 (H6)], 8.07 (br. t, JH,H
=
3
(d, 4JP,C = 2.0 Hz, Cp, PPh2), 133.75 (d, 2JP,C = 12.8 Hz, Co, PPh2),
6.9 Hz, 1 H, Hγ, bipy), 8.22 (br. t,, JH,H = 6.6 Hz 1 H, Hγ, bipy),
3
138.86 (td, JP,C = 15.7, JP,C = 2.8 Hz, C6, C6H4), 141.92 (d, JP,C
3
3
1
8.51 (br. s, 1 H, Hα, bipy), 8.68 (br. d, JH,H = 3.9 Hz, 1 H, Hα,
3
= 97 Hz, C2, C6H4), 148.85 (s, Cipso, NPh), 160.97 (ddd, JP,Ctrans
2
bipy) ppm. 31P{1H} NMR (CDCl3): δ = 45.96 ppm.
= 135.6, 2J(N)P,C = 23.5, 2JP,Ccis = 10.7 Hz, C1, C6H4) ppm. 31P{1H}
2
3
NMR (CDCl3): δ = –34.16 (dd, JP,P = 68, JP,P = 14.5 Hz, 1 P, P
Complex 11: Ph3P=NC(O)-2-NC5H4 (0.500 g, 1.307 mmol), was
added to a solution of Pd(OAc)2 (0.293 g, 1.307 mmol) in 20 mL
of dry CH2Cl2 and the resulting solution was refluxed for 1 h. At
this point, some decomposition was evident. After cooling, the
black suspension was treated with charcoal for 30 min and then
filtered through a Celite pad. The resulting orange solution was
evaporated to dryness and the residue redissolved in MeOH
(20 mL). An excess of LiCl (0.222 g, 5.23 mmol) was added to the
methanolic solution, which was stirred vigorously at room tempera-
ture for 16 h. The yellow precipitate of 11 formed was collected by
filtration, washed with MeOH (20 mL) and Et2O (40 mL) and air
dried. Yield: 0.604 g (88.3%). C24H18ClN2OPPd (523.25): calcd. C
2
trans to N), –10.60 (d, JP,P = 68 Hz, 1 P, P trans to C), 48.38 (d,
3JP,P = 14.5 Hz, 1 P, P=N) ppm.
Complex 8: Complex 8 was prepared following a synthetic pro-
cedure similar to that reported for 7. A solution of 1 (0.200 g,
0.202 mmol) in acetone (20 mL) was treated with AgClO4 (0.084 g,
0.405 mmol) and dppe (0.161 g, 0.404 mmol) to give 8 as a pale-
orange solid. Yield: 0.347 g (90%). C50H43ClNO4P3Pd (956.67):
calcd. C 62.77, H 4.53, N 1.46; found C 62.31, H 4.57, N 1.28. IR:
ν = 1289, 1261 (νPN) cm–1. MS (FAB+): m/z (%) = 856 (100) [M –
˜
ClO4]+. 1H NMR (CDCl3): δ = 2.09, 2.16, 2.37, 2.46 (4m, 4 H,
CH2, dppe), 6.42–6.55 (m, 5 H, NPh), 6.79–6.98 (m, 4 H, C6H4),
7.14–7.66 (m, 30 H, PPh2) ppm. 31P{1H} NMR (CDCl3): δ = 43.81
55.09, H 3.47, N 5.35; found C 55.15, H 3.60, N 5.28. IR: ν = 1644
˜
(νCO), 1332 (νPN) cm–1. MS (FAB+): m/z (%) = 523 (20) [M]+, 487
3
3
3
(dd, JP,P = 26.2, JP,P = 16.0 Hz, 1 P, P trans to N), 45.31 (d, JP,P
= 16.0 Hz, 1 P, P=N), 58.85 (d, JP,P = 26.2 Hz, 1 P, P trans to C).
1
3
(100) [M – Cl]+. H NMR (CD2Cl2): δ = 7.00 (ddd, JP,H = 11.1,
3
3JH,H = 7.8, JH,H = 1.5 Hz, 1 H, H3, C6H4), 7.13 (tdd, JH,H
=
=
4
3
4
4
3
Complex 9: Complex 9 was prepared following a synthetic pro-
cedure similar to that reported for 7. A solution of 1 (0.200 g,
0.202 mmol) in acetone (20 mL) was treated with AgClO4 (0.084 g,
0.405 mmol) and 1,10-phenanthroline (0.073 g, 0.404 mmol) to give
9 as a deep-yellow solid. Yield: 0.263 g (88%). C36H27ClN3O4PPd
(738.46): calcd. C 58.55, H 3.68, N 5.69; found C 58.32, H 3.56, N
7.8, JP,H = 5.1, JH,H = 1.2 Hz, 1 H, H4, C6H4), 7.28 (tt, JH,H
4
7.8, JH,H
Ϸ
5JP,H = 1.5 Hz, 1 H, H5, C6H4), 7.55–7.64 [m, 5 H,
PPh2 (4 Hm) + py (Hβ)], 7.69–7.75 (m, 2 H, Hp, PPh2), 7.87–7.94
[m, 5 H, PPh2 (4 Ho) + py (Hδ)], 7.98 (td, JH,H = 7.5, JH,H
=
=
3
4
1.5 Hz, 1 H, Hγ, py), 8.10 (ddd, JH,H = 8.1, JP,H = 2.7, JH,H
3
4
4
1.2 Hz, 1 H, H6, C6H4), 8.97 (ddd, JH,H = 5.1, JH,H = 1.5, JH,H
= 0.6 Hz, 1 H, Hα, py) ppm. 13C{1H} NMR (CD2Cl2): δ = 124.77
(d, 1JP,C = 90 Hz, Cipso, PPh2), 125.48 (s, C3, py), 125.68 (s, C5, py),
3
4
5
5.72. IR: ν = 1290 (νPN) cm–1. MS (FAB+): m/z (%) = 638 (100)
˜
[M – ClO4]+. H NMR (CD2Cl2): δ = 6.97 (td, JH,H = 7.6, JH,H
1
3
4
= 1.2 Hz, 1 H, Hp, NPh), 7.08 (t, JH,H = 7.6 Hz, 2 H, Hm, NPh),
128.84 (s, C5, C6H4), 129.69 (d, JP,C = 12.7 Hz, Cm, PPh2), 130.60
3
3
7.18 (br. d, 2 H, Ho, NPh), 7.22 (ddd, JP,H = 9.2, JH,H = 7.2, (d, 2JP,C = 22.6 Hz, C3, C6H4), 132.09 (d, 3JP,C = 3.0 Hz, C4, C6H4),
3
3
Eur. J. Inorg. Chem. 2005, 1724–1736
www.eurjic.org
© 2005 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
1733

R. Bielsa, A. Larrea, R. Navarro, T. Soler, E. P. Urriolabeitia
FULL PAPER
133.79 (d, 2JP,C = 11.2 Hz, Co, PPh2), 134.52 (d, 4JP,C = 2.5 Hz, Cp,
(20 mL). Continuous stirring gave 14 as a white solid, which was
filtered, washed with Et2O (10 mL) and air dried. Yield: 0.321 g
1
3
PPh2), 138.48 (d, JP,C = 130 Hz, C2, C6H4), 139.11 (d, JP,C
=
14.5 Hz, C6, C6H4), 139.51 (s, C4, py), 149.18 (s, C6, py), 152.98 (s, (76.0%). Complex 14 was recrystallised from CH2Cl2/n-hexane to
2
2
C2, py), 153.19 (d, JP,C = 8.6 Hz, C1, C6H4), 172.25 (d, JP,C
=
give pale-yellow crystals of 14·2.5CH2Cl2, which were used
for analytical and spectroscopic measurements.
C42H33ClN2O5P2Pd·2.5CH2Cl2 (1061.9): calcd. C 50.33, H 3.61, N
2.64; found C 49.76, H 3.42, N 2.48. IR: ν = 1651 (νCO), 1339 (νPN
4.6 Hz, C=O) ppm. 31P{1H} NMR (CD2Cl2): δ = 51.88 ppm.
Complex 12: A suspension of [PtCl2(NCPh)2] (0.200 g, 0.424 mmol)
and Ph3P=NC(O)-2-NC5H4 (0.162 g, 0.424 mmol) in 15 mL of 2-
methoxyethanol was refluxed for 8 h. During this time the initial
suspension dissolved, and a greenish solution (presence of Pt0) was
obtained. After cooling, complex 12 precipitated from the alcoholic
medium as a green solid. This solid was filtered and washed with
Et2O (20 mL). The crude solid of 12 was further dissolved in
CH2Cl2 (40 mL), treated with charcoal and filtered through Celite
to give a yellow solution. The evaporation of the solvent to dryness
and treatment of the residue with Et2O (30 mL) gave 12 as a yellow
solid. Yield: 0.118 g (45.7%). Complex 12 was recrystallised from
CH2Cl2/OEt2 to give yellow needles of 12.CH2Cl2, which were
)
˜
cm–1. MS (FAB+): m/z (%) = 749 (55%) [M – ClO4]+. 1H NMR
(CD2Cl2): δ = 6.78 (dd, 3JH,H = 5.2, 4JH,H = 0.4 Hz, 1 H, py), 6.85–
6.87 (m, 2 H, C6H4), 7.13–7.17 [m, 3 H, C6H4 (2 H) + py (1 H)],
7.52–7.57 (m, 6 H, Hm, PPh3), 7.63–7.68 (m, 3 H, Hp, PPh3), 7.71–
7.76 (m, 4 H, Hm, PPh2), 7.84–7.91 [m, 8 H, PPh3 (6 Ho) + PPh2
(2 Hp)], 7.96–8.04 [m, 5 H, PPh2 (4 Ho) + py (1 H)], 8.07 (dm,
3JH,H = 8.0 Hz, 1 H, py) ppm. 31P{1H} NMR (CDCl3): δ = 39.34
(s, 1 P, Pd–PPh3), 49.18 (s, 1 P, P=N) ppm.
Complex 15: Complex 15 was prepared following a procedure sim-
ilar to that reported for 14. A solution of 11 (0.100 g, 0.191 mmol)
in acetone (20 mL) was treated with AgClO4 (0.040 g, 0.191 mmol)
used
for
analytical
and
spectroscopic
measurements.
C24H18ClN2OPPt·CH2Cl2 (696.87): calcd. C 43.09, H 2.89, N 4.02; and dppm (0.073 g, 0.191 mmol) to give 15 as an orange solid.
found C 42.98, H 2.84, N 4.24. IR: ν = 1646 (νCO), 1330 (νPN Yield: 0.163 g (87.8%). Complex 15 was crystallised from
cm–1. MS (FAB+): m/z (%) = 612 (95) [M]+, 576 (100) [M – Cl]+. CH2Cl2/OEt2 to give orange crystals of 15.CH2Cl2, which were
)
˜
3
4
1H NMR (CD2Cl2): δ = 6.95 (ddd, 3JP,H = 11.6, JH,H = 6.0, JH,H
used
for
analytical
and
spectroscopic
measurements.
= 1.2 Hz, 1 H, H3, C6H4), 7.05 (tdd, 3JH,H = 7.6, 4JP,H = 5.2, 4JH,H C49H40ClN2O5P3Pd·CH2Cl2 (1056.6): calcd. C 56.84, H 4.00, N
= 1.2 Hz, 1 H, H4, C6H4), 7.23 (tt, JH,H = 7.6, JH,H
Ϸ
5JP,H
=
2.65; found C 56.93, H 3.75, N 2.79. IR: ν = 1650 (νCO), 1338 (νPN)
˜
3
4
1.6 Hz, 1 H, H5, C6H4), 7.48–7.53 (m, 4 H, Hm, PPh2), 7.60 (ddd,
cm–1. MS (FAB+): m/z (%) = 871 (100) [M – ClO4]+. 1H NMR
3JH,H = 7.2, JH,H = 5.2, JH,H = 1.2 Hz, 1 H, Hβ, py), 7.62–7.67 (CDCl3): δ = 3.47 (d, 2JP,H = 11.1 Hz, 2 H, CH2, dppm), 6.84–7.97
3
4
(m, 2 H, Hp, PPh2), 7.78 (dm, JH,H = 7.6 Hz, 1 H, Hδ, py), 7.80– (m, 38 H, Ph; extensive overlap of the signals) ppm. 31P{1H} NMR
3
3
4
2
7.86 (m, 4 H, Ho, PPh2), 7.98 (td, JH,H = 7.6, JH,H = 1.6 Hz, 1 (CDCl3): δ = –24.75 (d, JP,P = 100 Hz, 1 P, free PPh2), 27.05 (d,
3
4
4
3
H, Hγ, py), 8.02 (ddd, JH,H = 7.6, JP,H = 3.2, JH,H = 1.2, JPt,H
2JP,P = 100Hz, 1 P, Pd–PPh2), 49.14 (s, 1 P, P=N) ppm.
= 30.4 Hz, 1 H, H6, C6H4), 9.17 (ddd, JH,H = 5.2, JH,H = 1.6,
3
4
Complex 16: Complex 16 was prepared following a procedure sim-
ilar to that reported for 14. A solution of 11 (0.100 g, 0.191 mmol)
in acetone (20 mL) was treated with AgClO4 (0.040 g, 0.191 mmol)
and dppe (0.076 g, 0.191 mmol) to give 16 as a cream solid. Yield:
0.157 g (83.3%). Complex 16 was recrystallised from CH2Cl2/n-
hexane to give pale yellow crystals of 16·CH2Cl2, which were
5JH,H = 0.4, JPt,H Ϸ 20 Hz, 1 H, Hα, py) ppm. 31P{1H} NMR
3
(CD2Cl2): δ = 51.88 (2JPt,P = 452 Hz) ppm.
Complex 13: AgClO4 (0.040 g, 0.191 mmol) was added to a suspen-
sion of 11 (0.100 g, 0.191 mmol) in NCMe (20 mL). The resulting
white suspension was stirred at room temperature with exclusion
of light for 30 min, then filtered through Celite. The resulting pale-
yellow solution was evaporated to small volume (approx. 1 mL).
Addition of Et2O (20 mL) and continuous stirring gave 13 as an
off-white solid, which was filtered, washed with additional Et2O
(10 mL) and air dried. Yield: 0.081 g (67.5%). Complex 13 was
recrystallised from CH2Cl2/OEt2 to give colourless microcrystals
of 13·2CH2Cl2, which were used for analytical and spectroscopic
used
for
analytical
and
spectroscopic
measurements.
C50H42ClN2O5P3Pd·CH2Cl2 (1070.6): calcd. C 57.22, H 4.14, N
2.62; found C 57.53, H 4.02, N 2.64. IR: ν = 1622 (νCO), 1329
˜
(νPN) cm–1. MS (FAB+): m/z (%) = 885 (70) [M – ClO4]+. Room
temperature NMR spectroscopic data: 1H NMR (CDCl3): δ =
2.22–2.29 (br. s, 4 H, CH2, dppe), 6.83–7.92 (m, 38 H, aromatics)
ppm. 31P{1H} NMR (CDCl3): δ = 47.28 (s, P=N) ppm. Low tem-
perature NMR spectroscopic data (233 K): 1H NMR (CDCl3): δ =
2.31, 2.42, 2.88, 3.01 (4m, 4 H, CH2, dppe), 6.60 (m, 1 H, C6H4),
measurements. C26H21ClN3O5PPd·2CH2Cl2 (798.17): calcd.
C
42.14, H 3.16, N 5.26; found C 41.56, H 3.27, N 5.10. IR: ν = 2328
˜
(νCN), 1669 (νCO), 1323, 1296 (νPN) cm–1. MS (FAB+): m/z (%) = 6.92–7.11 (3m, 3 H, C6H4), 7.17–8.12 (m, 33 H, aromatics), 8.72
487 (100) [M – NCMe – ClO4]+. H NMR (CDCl3): δ = 2.79 (s, 3
(dd, 3JH,H = 5.6, 4JH,H = 1.8 Hz, 1 H, Hα, py) ppm. 31P{1H} NMR
(CDCl3): δ = 41.38 (dd, JP,P = 27.5, JP,P = 13.0 Hz, 1 P, P trans
1
3
3
4
3
3
H, NCMe), 7.04 (ddd, JP,H = 10.6, JH,H = 7.6, JH,H = 1.1 Hz, 1
H, H3, C6H4), 7.23 (tdd, JH,H = 7.5, JP,H = 5.1, JH,H = 1.2 Hz,
to N), 47.84 (dd, JP,P = 13.0, JP,P = 3.2 Hz, 1 P, P=N), 58.21 (d,
3
4
4
3
3
1 H, H4, C6H4), 7.37 (tt, JH,H = 7.3, JH,H Ϸ 5JP,H = 1.7 Hz, 1 H,
3JP,P = 27.5 Hz, 1 P, P trans to C) ppm.
3
4
3
4
4
H5, C6H4), 7.45 (ddd, JH,H = 7.6, JP,H = 2.2, JH,H = 0.8 Hz, 1
H, H6, C6H4), 7.56–7.63 (m, 4 H, Hm, PPh2), 7.70–7.75 (m, 2 H,
Hp, PPh2), 7.84–7.91 [m, 5 H, PPh2 (4 Ho) + py (Hβ)], 7.95 (d,
3JH,H = 7.5 Hz, 1 H, Hδ, py), 8.09 (td, 3JH,H = 7.5, 4JH,H = 1.8 Hz,
Complex 17: Complex 17 was prepared following a procedure sim-
ilar to that reported for 14. A solution of 11 (0.100 g, 0.191 mmol)
in acetone (20 mL) was treated with AgClO4 (0.040 g, 0.191 mmol)
and 2,2Ј-bipyridine (0.030 g, 0.191 mmol) to give 17 as a yellow
solid. Yield: 0.110 g (77.5%). Complex 17 was crystallised from
CH2Cl2/n-hexane to give yellow crystals of 17·CH2Cl2, which were
1 H, Hγ, py), 8.97 (dd, JH,H = 5.4, JH,H = 2.2 Hz, 1 H, Hα, py)
3
4
ppm. 31P{1H} NMR (CDCl3): δ = 56.71 ppm.
Complex 14: AgClO4 (0.103 g, 0.497 mmol) was added to a suspen-
sion of 11 (0.260 g, 0.497 mmol) in acetone (20 mL). The resulting
suspension was stirred at room temperature with exclusion of light
for 20 min, then filtered through Celite. PPh3 (0.130 g, 0.497 mmol)
was added to this freshly prepared solution and stirring was contin-
ued for an additional 30 min. The pale-yellow solution was evapo-
rated to dryness and the oily residue was treated with Et2O
used
C34H26ClN4O5PPd·CH2Cl2 (807.13): calcd. C 51.71, H 3.43, N
6.94; found C 51.79, H 2.87, N 7.18. IR: ν = 1652 (νCO), 1332 (νPN
for
analytical
and
spectroscopic
measurements.
)
˜
cm–1. MS (FAB+): m/z (%) = 643 (25) [M – ClO4]+. 1H NMR
3
4
4
(CDCl3): δ = 6.33 (ddd, JH,H = 7.1, JP,H = 4.7, JH,H = 2.6 Hz, 1
H, H6, C6H4), 6.92–6.99 (m, 1 H, C6H4), 7.08–7.12 (m, 2 H, C6H4),
7.55 (ddd, 3JH,H = 7.6, 3JH,H = 5.2, 4JH,H = 1.2 Hz, 2 H, Hβ, bipy),
1734
© 2005 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjic.org
Eur. J. Inorg. Chem. 2005, 1724–1736

C,N- and C,N,N-Orthopalladated Iminophosphoranes
FULL PAPER
7.58–7.67 [m, 5 H, PPh2 (4 Hm) + py (Hβ)], 7.71–7.74 (m, 2 H, Hp, atoms. Each hydrogen atom was assigned an isotropic displacement
PPh2), 7.76–7.85 (m, 4 H, Ho, PPh2), 7.87–7.92 (m, 2 H, Hδ + Hγ,
parameter equal to 1.2-times the equivalent isotropic displacement
3
4
py), 7.95 (dd, JH,H = 4.0, JH,H = 1.5 Hz, 1 H, Hα, py), 8.02 (td, parameter of its parent atom. The structure was refined to Fo2, and
4
3
3JH,H = 7.7, JH,H = 1.6 Hz, 2 H, Hγ, bipy), 8.30 (dt, JH,H = 7.7,
all reflections were used in the least-squares calculations.[89]
4JH,H
Ϸ
5JH,H = 1 Hz, 2 H, Hδ, bipy), 8.91 (ddd, JH,H = 5.2,
3
CCDC-253369 (for 11) contains the supplementary crystallo-
graphic data for this paper. These data can be obtained free of
charge from The Cambridge Crystallographic Data Centre via
www.ccdc.cam.ac.uk/data_request/cif.
4JH,H = 1.6 Hz, 2 H, Hα, bipy) ppm. 31P{1H} NMR (CDCl3): δ =
53.96 ppm.
Complex 18: Complex 18 was prepared following a synthetic pro-
cedure similar to that reported for 14. A solution of 11 (0.100 g,
0.191 mmol) in acetone (20 mL) was treated with AgClO4 (0.040 g,
0.191 mmol) and 1,10-phenanthroline (0.034 g, 0.191 mmol) to give
18 as a yellow solid. Yield: 0.100 g (68.2%). C36H26ClN4O5PPd
(767.45): calcd. C 56.34, H 3.41, N 7.30; found C 56.15, H 3.08, N
Acknowledgments
Funding by the Diputación General de Aragón (Spain, Project
P061/2001) and Dirección General de Investigación Científica y
Técnica (DGICYT) (Spain, Projects BQU2002-0510, BQU2002-
00554 and MAT2003-1182) is gratefully acknowledged. R. B.
thanks the MECD (Spain) for a predoctoral fellowship and T. S.
thanks the MECD (Spain) for a postdoctoral fellowship.
7.09. IR: ν = 1645 (νCO), 1338 (νPN) cm–1. MS (FAB+): m/z (%) =
˜
3
667 (30) [M – ClO4]+. 1H NMR (CDCl3): δ = 5.85 (dd, JH,H
=
7.8, JH,H = 2.4 Hz, 1 H, H6, C6H4), 6.83–6.88 (m, 1 H, C6H4),
6.97–7.02 (m, 2 H, C6H4), 7.29 (dm, JH,H = 4.2, JH,H = 0.6 Hz,
4
3
4
1 H, Hα, py), 7.36 (ddd, JH,H = 7.5, JH,H = 5.1, JH,H = 1.5 Hz,
1 H, Hβ, py), 7.53–7.58 (m, 1 H, py), 7.63–7.69 (m, 4 H, Hm, PPh2),
7.75–7.80 (m, 2 H, Hp, PPh2), 7.88 (dd, 3JH,H = 8.1, 3JH,H = 4.8 Hz,
2 H, Hβ, phen), 7.94–8.01 [m, 5 H, PPh2 (4 Ho) + py (1 H)], 8.10
3
3
4
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3
4
phen), 9.36 (dd, JH,H = 4.8, JH,H = 1.8 Hz, 2 H, Hα, phen) ppm.
3
4
31P{1H} NMR (CDCl3): δ = 53.96 ppm.
Catalytic Mizoroki–Heck Arylations of Methyl Acrylate. General
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at
room
temperature.
A
crystal
of
dimensions
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Eur. J. Inorg. Chem. 2005, 1724–1736
www.eurjic.org
© 2005 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
1735

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Received: October 27, 2004
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