Synthesis and reactivity studies of palladium(II) complexes containing the N-phosphorylated iminophosphorane-phosphine ligands Ph2PCH 2P{=NP(=O)(OR)2}Ph2 (R = Et, Ph): Application to the catalytic synthesis of 2,3-dimethylfuran

Article abstract of DOI:10.1039/b609359k

Reactions of [PdCl₂(COD)] with 1 equiv. of the iminophosphorane-phosphine ligands Ph₂PCH₂P{=NP(=O)(OR) ₂}Ph₂ (R = Et 1, Ph 2) lead to the novel Pd(ii) derivatives cis-[PdCl₂(κ²-(P,N)-Ph ₂PCH₂P{=NP(=O)(OR)₂}Ph₂)] (R = Et 3, Ph 4). Pd-N bond cleavage readily takes place upon treatment of these species with a variety of two-electron donor ligands. By this way, complexes cis-[PdCl₂(κ¹-(P)-Ph₂PCH ₂P{=NP(=O)(OR)₂}Ph₂)(L)] (R = Et, L = CN ^tBu 5a, CN-2,6-C₆H₃Me₂ 5b, py 5c, P(OMe)₃ 5d, P(OEt)₃ 5e; R = Ph, L = CN^tBu 6a, CN-2,6-C₆H₃Me₂ 6b, py 6c, P(OMe)₃ 6d, P(OEt)₃ 6e) have been synthesized in high yields. The addition of two equivalents of ligands 1/2 to dichloromethane solutions of [PdCl ₂(COD)] results in the formation of complexes trans-[PdCl ₂(κ¹-(P)-Ph₂PCH₂P{=NP(=O)(OR) ₂}Ph₂)₂] (R = Et 7, Ph 8), which can be converted into the dicationic species [Pd(Ph₂PCH₂P{=NP(=O) (OR)₂}Ph₂)₂][SbF₆]₂ (R = Et 9, Ph 10) by treatment with AgSbF₆. Complex 10 also reacts with CN^tBu to afford trans-[Pd(κ¹(P)-Ph ₂PCH₂P{=NP(=O)(OPh)₂}Ph₂) ₂(CN^tBu)₂][SbF₆]₂ 11. The structures of 4, 5b, 7 and 9 have been determined by single-crystal X-ray diffraction methods. In addition, the ability of these Pd(ii) complexes to promote the catalytic cycloisomerization of (Z)-3-methylpent-2-en-4-yn-1-ol into 2,3-dimethylfuran has also been studied. The Royal Society of Chemistry 2006.

Full text of DOI:10.1039/b609359k

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PAPER
www.rsc.org/dalton | Dalton Transactions
Synthesis and reactivity studies of palladium(II) complexes containing
the N-phosphorylated iminophosphorane-phosphine ligands
=
=
Ph2PCH2P{ NP( O)(OR)2}Ph2 (R = Et, Ph): application to the
catalytic synthesis of 2,3-dimethylfuran
´
Victorio Cadierno,* Josefina D´ıez, Joaqu´ın Garc´ıa-Alvarez, Jose´ Gimeno,* Noel Nebra and Javier Rubio-Garc´ıa
Received 3rd July 2006, Accepted 2nd October 2006
First published as an Advance Article on the web 10th October 2006
DOI: 10.1039/b609359k
Reactions of [PdCl2(COD)] with 1 equiv. of the iminophosphorane-phosphine ligands
2
=
=
Ph2PCH2P{ NP( O)(OR)2}Ph2 (R = Et 1, Ph 2) lead to the novel Pd(II) derivatives cis-[PdCl2(j -
=
=
(P,N)-Ph2PCH2P{ NP( O)(OR)2}Ph2)] (R = Et 3, Ph 4). Pd–N bond cleavage readily takes place
upon treatment of these species with a variety of two-electron donor ligands. By this way, complexes
1
t
=
=
cis-[PdCl2(j -(P)-Ph2PCH2P{ NP( O)(OR)2}Ph2)(L)] (R = Et, L = CN Bu 5a, CN-2,6-C6H3Me2 5b,
py 5c, P(OMe)3 5d, P(OEt)3 5e; R = Ph, L = CNtBu 6a, CN-2,6-C6H3Me2 6b, py 6c, P(OMe)3 6d,
P(OEt)3 6e) have been synthesized in high yields. The addition of two equivalents of ligands 1/2 to
dichloromethane solutions of [PdCl2(COD)] results in the formation of complexes trans-[PdCl2(j1-
=
=
(P)-Ph2PCH2P{ NP( O)(OR)2}Ph2)2] (R = Et 7, Ph 8), which can be converted into the dicationic
=
=
species [Pd(Ph2PCH2P{ NP( O)(OR)2}Ph2)2][SbF6]2 (R = Et 9, Ph 10) by treatment with AgSbF6.
t
1
=
=
Complex 10 also reacts with CN Bu to afford trans-[Pd(j (P)-Ph2PCH2P{ NP( O)(OPh)2}Ph2)2-
(CNtBu)2][SbF6]2 11. The structures of 4, 5b, 7 and 9 have been determined by single-crystal X-ray
diffraction methods. In addition, the ability of these Pd(II) complexes to promote the catalytic
cycloisomerization of (Z)-3-methylpent-2-en-4-yn-1-ol into 2,3-dimethylfuran has also been
studied.
diphosphine dppm (bis(diphenylphosphino)methane) via classical
Introduction
Staudinger4,5 or Kirsanov6,7 reactions (see Chart 1).
The coordination chemistry of heterodifunctional P,N- and P,O-
donor ligands has received considerable attention during the last
decades, the continuous efforts in the design of new ligands
being justified by their potential application in homogeneous
catalysis.1 In addition to their well-known hemilabile properties,
allowing the generation of open coordination sites on the metal
for substrate binding,2 they can also control the reactivity of
the metal sites owing to the different steric and electronic
properties of the donor groups. Thus, taking advantage of
these properties, new highly efficient catalytic transformations
have been recently developed using heteroditopic P,N- and
P,O-ligands.1,2 Diphosphine-monoxides R2P–X–P( O)R2 (X =
=
divalent bridging group) clearly illustrate this situation, its rich
chemistry and catalytic applications being recently reviewed.1h
In contrast, despite its great potential and anticipated diver-
Chart 1 The Staudinger and Kirsanov reactions of dppm.
sity, the coordination and catalytic chemistry of closely related
ꢀ
=
iminophosphorane-phosphine ligands R2P–X–P( NR )R2 still
Concerning the chemistry of palladium, it is interesting to note
that, although several complexes containing j2-(P,N)-coordinated
iminophosphorane-phosphine ligands have been described in
the literature (most of them of general composition [PdCl2(P–
N)]),5b,d–f ,7a,8 their catalytic applications are almost unexplored.
Thus, as far as we are aware, the only catalytic transformations
reported to date for this type of complexes are: (i) the Sonogashira
coupling of aryl halides with terminal alkynes,8h (ii) the cross-
coupling of amines with aryl halides,5d and (iii) the allylic
alkylation of 1,3-diphenylallyl acetate with dimethyl malonate.8i,9
3
=
remains scarcely explored. Compounds Ph2PCH2P( NR)Ph2 are
probably the most popular iminophosphorane-phosphine ligands
known, being readily accessible from the commercially available
Departamento de Qu´ımica Orga´nica e Inorga´nica, Instituto Universitario
de Qu´ımica Organometa´lica “Enrique Moles” (Unidad Asociada al
CSIC), Facultad de Qu´ımica, Universidad de Oviedo, E-33071, Oviedo,
Spain. E-mail: vcm@uniovi.es, jgh@uniovi.es; Fax: +34 985103446;
Tel: +34 985102985
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As part of our ongoing work dealing with the synthe-
sis, reactivity and catalytic activity of transition-metal com-
plexes containing iminophosphorane ligands,10 we have recently
described the preparation of the heterotrifunctional systems
The characterization of complexes 3/4 was achieved by means
1
1
of elemental analyses and multinuclear (1H, 31P{ H} and 13C{ H})
NMR spectroscopy (details are given in the Experimental section).
In particular, the j2-(P,N)-coordination of the ligands is fully
1
Ph2PCH2P{ NP( O)(OR)2}Ph2 (R = Et 1, Ph 2), via single-
supported by the 31P{ H} NMR data. Thus, the spectra show
=
=
stage oxidation of dppm with the corresponding phosphorylated
the expected presence of three well separated signals with equal
10c
=
=
azide (RO)2P( O)N3. The attachment of these functionalities
relative intensities in the ranges dP 43.27–45.04 (dd, Ph2P N),
=
at one of the phosphorus atoms of dppm generates a new class
of versatile polydentate ligands with ability to adopt j1-(P)-(I),
j2-(P,N)-(II), j2-(P,O)-(III) and j3-(P,N,O)-coordination modes
(IV), as assessed by studying their behaviour towards Ru(II)
and Ru(IV) fragments (see Chart 2). Moreover, the resulting
ruthenium complexes were found to be active catalysts in transfer
hydrogenation of ketones.10c
13.12–13.74 (d, Ph2P) and −3.15–6.16 (d, (RO)2P( O)), the
chemical shifts of the iminophosphorane and diphenylphosphino
groups being comparable to those reported in the literature
2
=
for related cis-[PdCl2{j -(P,N)-Ph2PCH2P( NR)Ph2}] (R = H,
SiMe3, aryl or alkyl groups) complexes.5b,d–f ,7a,8a The 1H and
13C{ H} NMR spectra also exhibit signals in accordance with the
1
proposed formulations, the most significant features being those
concerning the methylenic PCH2P group of the ligands, i.e. doublet
2
of doublet signals at ca. dH 4 ppm (2J(HPIII) = J(HPV) = 11.1–
1
11.5 Hz) and dC 31 ppm (1J(CPV) = 71.1–72.5 Hz, J(CPIII) =
19.1–19.5 Hz), respectively. In addition, the formation of a five-
membered chelate ring was unambiguously confirmed by means of
a X-ray diffraction analysis on complex 4. X-Ray quality crystals
were obtained by slow diffusion of diethyl ether into a saturated
dichloromethane solution of the complex. The ORTEP view of
the molecule, along with selected structural parameters, is shown
in Fig. 1.
Chart 2 Coordination modes of iminophosphorane-phosphine ligands
=
=
Ph2PCH2P{ NP( O)(OR)2}Ph2 in ruthenium fragments.
Continuing with these studies aimed at exploiting the utility
=
=
of compounds Ph2PCH2P{ NP( O)(OR)2}Ph2 (R = Et 1, Ph 2),
herein we describe the synthesis of the first palladium(II) complexes
containing these ligands, as well as their application in the catalytic
synthesis of 2,3-dimethylfuran via cycloisomerization of (Z)-3-
methylpent-2-en-4-yn-1-ol.
Results and discussion
Synthesis and reactivity of palladium(II) complexes cis-
2
=
=
[PdCl2(j -(P,N)-Ph2PCH2P{ NP( O)(OR)2}Ph2)] (R = Et, Ph)
Fig. 1 ORTEP-type view of the structure of complex 4 showing the
crystallographic labeling scheme. Hydrogen atoms have been omitted for
clarity. Thermal ellipsoids are drawn at 10% probability level. Selected
Treatment of the Pd(II) precursor [PdCl2(COD)] (COD =
1,5-cyclooctadiene)11 with an stoichiometric amount of the
iminophosphorane-phosphine ligands 1/2,10c in dichloro-
methane at room temperature, leads to the selective for-
mation of the mononuclear complexes cis-[PdCl2(j2-(P,N)-
˚
bond lengths (A): Pd(1)–Cl(1) 2.2895(11); Pd(1)–Cl(2) 2.3700(12);
Pd(1)–P(1) 2.2362(13); Pd(1)–N(1) 2.131(4); P(1)–C(1) 1.848(5);
C(1)–P(2) 1.805(5); P(2)–N(1) 1.621(4); N(1)–P(3) 1.638(4); P(3)–O(1)
1.473(4); P(3)–O(2) 1.593(4); P(3)–O(3) 1.581(4). Selected bond angles (◦):
Cl(1)–Pd(1)–Cl(2) 92.41(4); Cl(1)–Pd(1)–P(1) 87.95(4); Cl(1)–Pd(1)–N(1)
176.85(11); P(1)–Pd(1)–N(1) 88.95(11); P(1)–Pd(1)–Cl(2) 176.75(5);
N(1)–Pd(1)–Cl(2) 90.72(11); P(1)–C(1)–P(2) 103.9(2); C(1)–P(2)–N(1)
=
=
Ph2PCH2P{ NP( O)(OR)2}Ph2)] (R = Et 3, Ph 4) (Scheme 1).
These compounds, which result from the expected exchange of
the labile COD ligand, were isolated as air-stable yellow solids in
excellent yields (90–94%).
105.2(2);
P(2)–N(1)–P(3)
124.5(2);
N(1)–P(3)–O(1)
114.9(2);
N(1)–P(3)–O(2) 107.8(2); N(1)–P(3)–O(3) 108.27(19); O(1)–P(3)–O(2)
113.7(2); O(1)–P(3)–O(3) 115.4(2); O(2)–P(3)–O(3) 94.77(19).
The geometry around the Pd atom is almost ideal square
˚
planar, with the metal displaced for only 0.0546 A from the
plane defined by the Cl(1), Cl(2), P(1) and N(1) atoms. The Pd-
coordination is characterized by metal-centered angles between
87.95(4) and 92.41(4)◦, with the two chloride ligands mutually
Scheme 1 Synthesis of the neutral Pd(II) complexes 3/4.
5594 | Dalton Trans., 2006, 5593–5604
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2
˚
=
Table 1 Comparative bond lengths (A) for complexes cis-[PdCl2{j -(P,N)-Ph2PCH2P( NR)Ph2}]
=
R
Pd–PA
Pd–N
PA–C
PB–C
PB
N
Ref.
Ph
2.2135(6)
2.2425(6)
2.224(2)
2.2259(11)
2.2248(9)
2.2362(13)
2.076(2)
2.094(2)
2.021(6)
2.062(3)
2.0798(24)
2.131(4)
1.842(2)
1.834(2)
1.842(7)
1.845(3)
1.834(3)
1.848(5)
1.800(2)
1.805(3)
1.805(7)
1.818(4)
1.795(3)
1.805(5)
1.619(2)
1.601(2)
1.599(6)
1.628(2)
1.6029(24)
1.621(4)
7a
a-(+)-CHMePh
H
C(CO2Et) C(H)Fc
7a
5b
a
=
5e
=
4-C6F4C( O)NH2
5f
=
P( O)(OPh)2 4
This work
a Fc = Ferrocenyl.
cis disposed. The larger Pd(1)–Cl(2) vs Pd(1)–Cl(1) bond length
(2.3700(12) vs 2.2895(11) A) is consistent with the stronger trans
influence of phosphorus compared to nitrogen. Remarkably, with
Thus, as depicted in Scheme 2, we have found that compounds
1
˚
=
=
cis-[PdCl2(j -(P)-Ph2PCH2P{ NP( O)(OR)2}Ph2)(L)] 5/6a–e
are irreversibly formed upon treatment of complexes 3/4 with an
equimolar amount of tert-butyl isocyanide (5/6a), 2,6-dimethyl-
phenyl isocyanide (5/6b), pyridine (5/6c), trimethylphosphite
(5/6d) or triethylphosphite (5/6e), the chelate ring opening
process proceeding in all cases at room temperature.15 Remarkably,
all attempts to promote a similar ring opening reaction with
acetone or nitriles have failed recovering the starting complexes
3/4 unchanged even when a large excess of these ligands or
˚
the exception of the Pd(1)–N(1) bond length (2.131(4) A) which is
slightly longer, distances within the five-membered metallacycle
are comparable to those previously reported for related cis-
2
=
[PdCl2{j -(P,N)-Ph2PCH2P( NR)Ph2}] complexes (see Table 1).
The longer Pd–N bond distance observed for 4 can be explained
on the basis of the strong p-acceptor nature of the phosphoryl
=
(PhO)2P( O) group which imposes some electronic delocalization
of the nitrogen lone pair along this unit. In accord with this, the
higher temperatures are used. These results, which evidence the
2
=
bond length value found for the formally single N(1)–P(3) bond
lack of hemilability of the P N unit in the Pd(II) complexes 3/4,
˚
=
(1.638(4) A) borders the range usually observed for P N double
contrast with the behaviour previously observed for the dicationic
ruthenium derivative [Ru(g -p-cymene)(j3-(P,N,O)-Ph2PCH2P-
12
6
˚
bonds (1.45–1.62 A).
Remarkably, the selective j2-(P,N)-coordination of the N-
phosphorylated iminophosphorane-phosphines 1/2 in complexes
3/4 is in sharp contrast with the marked preference for the biden-
tate j2-(P,O)-coordination (III in Chart 2) previously observed for
{ NP( O)(OEt)2}Ph2)][SbF6]2 (IV in Chart 2) which reversibly
=
=
6
generates the solvated species [Ru(g -p-cymene)(Me2CO)(j2-
=
=
(P,O)-Ph2PCH2P{ NP( O)(OEt)2}Ph2)][SbF6]2 in acetone at
room temperature.10c
6
these ligands in the ruthenium fragments [RuCl(g -p-cymene)]+
3
3
and [RuCl(g :g -C10H16)]+ (C10H16 = 2,7-dimethylocta-2,6-diene-
1,8-diyl).10c Formation of seven-membered ruthenacycles III,
which is in disagreement with the well-known fact establishing that
an increase in the size of a chelate ring usually leads to a drop in
complex stability,13 was explained on the basis of the higher steric
hindrance between the phosphoryl group substituents and the
6
3
3
g -p-cymene or g :g -octadienediyl ligands in the five-membered
chelates II (Chart 2). Following this reasoning, the smaller steric
6
requirements of the palladium(II) fragment [PdCl2] vs [RuCl(g -
3
3
p-cymene)]+ and [RuCl(g :g -C10H16)]+ can be proposed as the
driving force responsible for the selective j2-(P,N)-coordination
of the phosphorylated ligands 1/2 in complexes 3/4.
Scheme 2 Reactivity of complexes 3/4 towards 2e− donor ligands.
It is now well-established the weaker coordinating ability
Complexes 5/6a–e, isolated as pale yellow solids in 66–87%
yield, have been characterized by means of standard spectroscopic
techniques (IR and multinuclear NMR) as well as elemental
analyses, being all data fully consistent with the proposed
formulations (details are given in the Experimental section).
In particular, an unequivocal proof of the monodentate j1-
(P)-coordination of the iminophosphorane-phosphine ligands is
ꢀ
=
of iminophosphoranes R3P NR as compared to that of con-
ventional two-electron donor ligands. For instance, they are
easily exchanged by phosphines, arsines, amines, nitriles, iso-
cyanides or carbon monoxide under mild conditions.9b,d,10,14
However, as far as we are aware, no studies on the reactivity
of iminophosphorane-phosphine Pd(II) complexes cis-[PdCl2{j2-
1
(P,N)-Ph2PCH2P( NR)Ph2}] have been reported to date. With
provided by their 31P{ H} NMR spectra in which a remarkable
=
=
these precedents in mind, we decided to evaluate the strength of
shielding is observed for the Ph2P N group resonances (dP 10.50–
the j2-(P,N)-chelate ring in our N-phosphorylated complexes cis-
12.96 ppm) with respect to the parent compounds 3/4 (dP 43.27–
2
[PdCl2(j -(P,N)-Ph2PCH2P{ NP( O)(OR)2}Ph2)] (R = Et 3, Ph
45.04 ppm). Moreover, the structure of complex cis-[PdCl2(j1-(P)-
=
=
=
=
4) by studying their reactivity towards neutral ligands.
Ph2PCH2P{ NP( O)(OEt)2}Ph2)(CN-2,6-C6H3Me2)] 5b could
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be unambiguously confirmed by means of a single-crystal X-ray
diffraction study. Suitable crystals were obtained by diffusion of
n-pentane into a saturated solution of the complex in CH2Cl2. An
ORTEP-type view of the molecule is shown in Fig. 2; selected bond
distances and angles are listed in the caption. The palladium atom
is in the expected square planar environment (maximum deviation
from the ideal angles 2◦) with the two chloride ligands oriented
mutually cis. The isocyanide ligand is bound to palladium in a
nearly linear fashion (Pd(1)–C(30)–N(2) 177.7(3)◦; C(30)–N(2)–
C(31) 177.1(4)◦) with metal-carbon (Pd(1)–C(30)) and carbon-
which the functionalized phosphine ligands adopt a monodentate
coordination through the PPh2 group, were isolated as air-stable
yellow solids in 88–91% yield (see Scheme 3).
˚
nitrogen (C(30)–N(2)) bond distances of 1.931(4) and 1.143(4) A,
respectively. These bonding parameters fit well with those reported
in the literature for other isocyanide-palladium(II) complexes.16
Concerning the iminophosphorane-phosphine ligand backbone,
the expected electronic delocalization of the nitrogen lone pair
=
=
along the –Ph2P N–P( O)(OEt)2 unit is clearly reflected on the
˚
very similar PN bond distances, i.e. P(2)–N(1) 1.564(3) A and
17
˚
N(1)–P(3) 1.590(3) A.
Scheme 3 Synthesis and reactivity of the neutral Pd(II) complexes 7–8.
Characterization of these compounds was straightforward
by following their analytical and spectroscopic data (details
are given in the Experimental section). Key spectroscopic fea-
1
tures are: (i) (31P{ H} NMR) the presence of three well-
separated signals (second order spectra) at dP 10.86–12.66 (m,
2
=
Ph2P N), 11.37–11.47 (m, Ph2P) and −8.47−2.81 (d, J(PP) =
=
28.7–32.1 Hz, (RO)2P( O)), the chemical shifts observed for
the Ph2P N and (RO)2P( O) groups being comparable with
those found in the spectra of complexes cis-[PdCl2(j1-(P)-
=
=
=
=
Ph2PCH2P{ NP( O)(OR)2}Ph2)(L)] (5/6a–e; Scheme 2) also
=
=
containing uncoordinated –Ph2P NP( O)(OR)2 frameworks.
And (ii) (1H and 13C{ H} NMR) the presence of characteristic
1
Fig. 2 ORTEP-type view of the structure of complex 5b showing the
crystallographic labeling scheme. Hydrogen atoms have been omitted for
clarity. Thermal ellipsoids are drawn at 20% probability level. Selected
resonances for the methylenic PCH2P group of the ligands whose
protons resonate as an unresolved multiplet at ca. dH 4 ppm, and
its carbon as a doublet of doublets (1J(CPV) ≈ 70 Hz, 1J(CPIII) ≈
10 Hz) at ca. dC 24 ppm.
˚
bond lengths (A): Pd(1)–Cl(1) 2.3102(8); Pd(1)–Cl(2) 2.3554(9);
Pd(1)–P(1) 2.2579(8); Pd(1)–C(30) 1.931(4); C(30)–N(2) 1.143(4); N(2)–
C(31) 1.403(5); P(1)–C(1) 1.832(3); C(1)–P(2) 1.813(3); P(2)–N(1)
1.564(3); N(1)–P(3) 1.590(3); P(3)–O(1) 1.462(3); P(3)–O(2) 1.592(3);
P(3)–O(3) 1.581(3). Selected bond angles (◦): Cl(1)–Pd(1)–Cl(2)
92.35(3); Cl(1)–Pd(1)–P(1) 90.53(3); Cl(1)–Pd(1)–C(30) 178.80(10);
P(1)–Pd(1)–C(30) 90.64(10); P(1)–Pd(1)–Cl(2) 171.68(4); C(30)–Pd(1)–
Cl(2) 86.45(10); P(1)–C(1)–P(2) 115.25(16); C(1)–P(2)–N(1) 108.75(15);
P(2)–N(1)–P(3) 134.9(2); N(1)–P(3)–O(1) 120.23(17); N(1)–P(3)–O(2)
105.14(17); N(1)–P(3)–O(3) 106.03(16); O(1)–P(3)–O(2) 112.4(2);
O(1)–P(3)–O(3) 107.32(17); O(2)–P(3)–O(3) 104.5(2); Pd(1)–C(30)–N(2)
177.7(3); C(30)–N(2)–C(31) 177.1(4).
The trans stereochemistry of compounds 7/8, which undoubt-
edly leads to a less sterically encumbered structure when compared
to the corresponding cis isomer, was confirmed by means of a X-
ray diffraction study on complex 7 after appropriate crystallization
by slow evaporation of a saturated dichloromethane solution. An
ORTEP-type view of the centrosymmetric molecule, along with
selected structural parameters, is shown in Fig. 3. Remarkably,
with the exception of the Pd(1)–P(1) bond length which is ca.
˚
0.1 A longer due to the higher trans effect of the phosphine vs.
=
=
chloride ligands, bond distances along the Pd–P–C–P N–P O
˚
skeleton are almost identical (ca. 0.02 A) to those found in the
structure of the isocyanide complex 5b (Fig. 2).
Synthesis and reactivity of palladium(II) complexes trans-
Chelation of the iminophosphorane-phosphine ligands 1/2
in complexes 7/8 has been achieved by abstraction of the
chloride ligands upon treatment with two equivalents of
AgSbF6. Thus, following this approach, the dicationic species
1
=
=
[PdCl2(j -(P)-Ph2PCH2P{ NP( O)(OR)2}Ph2)2] (R = Et, Ph)
Incorporation of two molecules of the iminophosphorane-
=
=
phosphine ligands Ph2PCH2P{ NP( O)(OR)2}Ph2 (R = Et 1, Ph
2) in the coordination sphere of palladium could be easily achieved
by treatment, at room temperature, of a dichloromethane solution
of [PdCl2(COD)] (COD = 1,5-cyclooctadiene) with a two-fold
excess of 1/2. By this way, the neutral complexes trans-[PdCl2(j1-
=
=
[Pd(Ph2PCH2P{ NP( O)(OR)2}Ph2)2][SbF6]2 (R = Et 9, Ph
10) were isolated as air-stable white solids in 83–85% yield
(see Scheme 3). Conductance measurements in acetone con-
firm that compounds 9–10 are 2 : 1 electrolytes (KM = 195–
198 X−1 cm2 mol−1). The structure of complex 9 in the solid
=
=
(P)-Ph2PCH2P{ NP( O)(OR)2}Ph2)2] (R = Et 7, Ph 8), in
5596 | Dalton Trans., 2006, 5593–5604
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Fig. 3 ORTEP-type view of the structure of complex 7 showing the
crystallographic labeling scheme. Atoms labeled with an “a” are related
to those indicated by a crystallographic center of symmetry. Hydrogen
atoms have been omitted for clarity. Thermal ellipsoids are drawn at
Fig. 4 ORTEP-type view of the structure of complex 9 showing the
crystallographic labeling scheme. Phenyl groups, SbF6 anions and
hydrogen atoms have been omitted for clarity. Thermal ellipsoids are
−
˚
drawn at 10% probability level. Selected bond lengths (A): Pd(1)–N(1)
˚
20% probability level. Selected bond lengths (A): Pd(1)–Cl(1) 2.2969(8);
2.148(6); Pd(1)–P(1) 2.2397(19); P(1)–C(1) 1.840(7); C(1)–P(2) 1.813(7);
P(2)–N(1) 1.622(7); N(1)–P(3) 1.640(7); P(3)–O(1) 1.464(7); P(3)–O(2)
1.581(6); P(3)–O(3) 1.565(8); Pd(1)–O(1ꢀ) 2.100(5); Pd(1)–P(1ꢀ) 2.2637(18);
P(1ꢀ)–C(1ꢀ) 1.832(8); C(1ꢀ)–P(2ꢀ) 1.826(7); P(2ꢀ)–N(1ꢀ) 1.590(7); N(1ꢀ)–P(3ꢀ)
1.578(7); P(3ꢀ)–O(1ꢀ) 1.502(5); P(3ꢀ)–O(2ꢀ) 1.573(5); P(3ꢀ)–O(3ꢀ) 1.566(6).
Selected bond angles (◦): P(1)–Pd(1)–N(1) 81.02(18); P(1)–Pd(1)–P(1ꢀ)
97.44(7); P(1)–Pd(1)–O(1ꢀ) 170.13(15); P(1ꢀ)–Pd(1)–N(1) 171.61(18);
P(1ꢀ)–Pd(1)–O(1ꢀ) 90.95(15); N(1)–Pd(1)–O(1ꢀ) 91.4(2); Pd(1)–P(1)–
C(1) 102.3(2); P(1)–C(1)–P(2) 109.6(4); C(1)–P(2)–N(1) 104.7(3);
P(2)–N(1)–P(3) 127.4(4); P(2)–N(1)–Pd(1) 115.7(3); Pd(1)–N(1)–P(3)
116.8(3); N(1)–P(3)–O(1) 116.3(4); N(1)–P(3)–O(2) 101.1(3); N(1)–P(3)–
O(3) 105.4(4); Pd(1)–P(1ꢀ)–C(1ꢀ) 111.7(3); P(1ꢀ)–C(1ꢀ)–P(2ꢀ) 117.9(4);
C(1ꢀ)–P(2ꢀ)–N(1ꢀ) 113.2(3); P(2ꢀ)–N(1ꢀ)–P(3ꢀ) 125.3(4); N(1ꢀ)–P(3ꢀ)–O(1ꢀ)
117.4(3); N(1ꢀ)–P(3ꢀ)–O(2ꢀ) 108.3(3); N(1ꢀ)–P(3ꢀ)–O(3ꢀ) 107.1(3);
P(3ꢀ)–O(1ꢀ)–Pd(1) 117.6(3).
Pd(1)–P(1) 2.3446(8); P(1)–C(1) 1.836(3); C(1)–P(2) 1.829(3); P(2)–N(1)
1.567(3); N(1)–P(3) 1.602(3); P(3)–O(1) 1.477(3); P(3)–O(2) 1.579(3);
P(3)–O(3) 1.585(3). Selected bond angles (◦): Cl(1)–Pd(1)–P(1) 90.41(3);
Cl(1)–Pd(1)–Cl(1a) 180.00(4); Cl(1)–Pd–P(1a) 89.59(3); Pd(1)–P(1)–C(1)
116.98(11); P(1)–C(1)–P(2) 121.90(18); C(1)–P(2)–N(1) 113.54(15);
P(2)–N(1)–P(3) 130.61(19); N(1)–P(3)–O(1) 116.63(15); N(1)–P(3)–O(2)
105.42(16); N(1)–P(3)–O(3) 108.71(16); O(1)–P(3)–O(2) 114.49(16);
O(1)–P(3)–O(3) 112.37(16); O(2)–P(3)–O(3) 97.32(15).
state was determined by a single-crystal X-ray diffraction study.
An ORTEP-type drawing of the molecule showing the expected
square-planar geometry around the palladium atom is depicted in
Fig. 4; selected bond distances and angles are listed in the caption.
The coordination sphere around the palladium atom consists
of two molecules of the iminophosphorane-phosphine ligand
1, one of them adopting a j2-(P,N)-coordination mode, and
the second one forming a seven-membered metallacycle via j2-
(P,O)-coordination. Remarkably, bond distances within the five-
membered j2-(P,N)-chelate ring in the dicationic complex 9 are
coordination ability of the N-phosphorylated iminophosphorane-
=
=
phosphine ligands Ph2PCH2P{ NP( O)(OR)2}Ph2 (R = Et 1,
Ph 2).
It is interesting to note that the room temperature 31P{ H}
1
˚
almost identical (ca. 0.01 A) to those found in the neutral
NMR spectrum of complex 9 shows the presence of only three
2
=
=
=
complex cis-[PdCl2(j -(P,N)-Ph2PCH2P{ NP( O)(OPh)2}Ph2)]
4 (see Fig. 1 and Table 1), reflecting that, once j2-(P,N)-
coordinated, the structure of these ligands is non-sensitive to
the palladium environment. Concerning the second molecule of
the ligand, that j2-(P,O)-coordinated to Pd, the phosphorus-
nitrogen and phosphorus-oxygen bond distances observed for
broad signals at dP 30.60 (Ph2P), 28.33 (Ph2P N) and 7.68
=
((EtO)2P( O)) ppm, indicating that both iminophosphorane-
phosphine ligands are formally equivalent. The same pattern is
also observed in the 31P{ H} NMR spectrum of complex 10 (see
1
the Experimental section). However, according to the X-ray struc-
ture (Fig. 4), the spectra should show a more complicated pattern
as a consequence of the presence of six non-equivalent phosphorus
atoms. The formal equivalence of the two ligands in these com-
pounds seems to indicate the existence of a dynamic equilibrium in
solution probably involving j2-(P,N)/j2-(P,O) isomerizations.20
Such a fluxional behaviour, previously observed in ruthenium
complexes,10c evidences the hemilability of iminophosphorane-
phosphines 1/2 in the dicationic Pd(II) complexes 9/10. This fact
ꢀ
ꢀ
˚
=
=
the –Ph2P N–P( O)(OEt)2 unit, i.e. P(2 )–N(1 ) 1.590(7) A,
N(1 )–P(3 ) 1.578(7) A and P(3 )–O(1 ) 1.502(5) A, are very
ꢀ
ꢀ
ꢀ
ꢀ
˚
˚
˚
similar (ca.
0.04 A) to those found in the structures
of the cationic ruthenium complexes [RuCl(g -p-cymene)(j2-
6
3
3
=
=
(P,O)-Ph2PCH2P{ NP( O)(OPh)2}Ph2)][PF6] and [RuCl(g :g -
2
=
=
C10H16)(j -(P,O)-Ph2PCH2P{ NP( O)(OEt)2}Ph2)][BF4] previ-
ously reported by us.10c The Pd(1)–O(1ꢀ) bond length (2.100(5)
˚
A) also compares well with those found in the structure of
contrasts with the behaviour shown by the neutral complexes cis-
2
the related dicationic phosphine-phosphonate complex [Pd{j2-
[PdCl2(j -(P,N)-Ph2PCH2P{ NP( O)(OR)2}Ph2)] (R = Et 3, Ph
4) pointing out that the hemilabile properties of ligands 1/2 are
strongly dependent on the metal environment.
=
=
=
(P,O)-Ph2PCH(Ph)P( O)(OEt)2}2][BF4]2 (2.109(3) and 2.113(3)
18,19
˚
A), recently reported by P. Braunstein and co-workers.
The
=
unprecedented coexistence of both bidentate coordination modes
of 1 within the same molecule is a clear example of the versatile
In accord with the lability of the coordinated Ph2P N and
=
(RO)2P( O) units in 9/10, we have found that the dicationic
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Table 2 Cycloisomerization of (Z)-3-methylpent-2-en-4-yn-1-ol into 2,3-dimethylfurana
Entry
Catalyst
[catalyst]
t/h
Yieldb (%)
TOFc/h−1
2
=
=
1
2
3
4
5
cis-[PdCl2(j -(P,N)-Ph2PCH2P{ NP( O)(OEt)2}Ph2)] 3
0.2 mol%
0.2 mol%
0.2 mol%
0.2 mol%
0.2 mol%
0.2 mol%
0.2 mol%
0.1 mol%
0.1 mol%
0.1 mol%
0.1 mol%
5
5
>99
>99
>99 (70)
98 (68)
93 (56)
>99
92
>99
96
91
99
99
21 (70)
20 (68)
52 (56)
2
=
=
cis-[PdCl2(j -(P,N)-Ph2PCH2P{ NP( O)(OPh)2}Ph2)] 4
1
=
=
trans-[PdCl2(j -(P)-Ph2PCH2P{ NP( O)(OEt)2}Ph2)2] 7
24 (5)
24 (5)
9 (5)
4
18
1
24
24
6
1
=
=
trans-[PdCl2(j -(P)-Ph2PCH2P{ NP( O)(OPh)2}Ph2)2] 8
= =
[Pd(Ph2PCH2P{ NP( O)(OEt)2}Ph2)2][SbF6]2 9
=
=
6
[Pd(Ph2PCH2P{ NP( O)(OPh)2}Ph2)2][SbF6]2 10
124
7d
8e
9
K2[PdI4]
26
990
40
38
165
AuCl3
2
=
=
cis-[PdCl2(j -(P,N)-Ph2PCH2P{ NP( O)(OEt)2}Ph2)] 3
2
=
=
10
11
cis-[PdCl2(j -(P,N)-Ph2PCH2P{ NP( O)(OPh)2}Ph2)] 4
=
=
[Pd(Ph2PCH2P{ NP( O)(OPh)2}Ph2)2][SbF6]2 10
>99
a Conditions: reactions were carried out without solvent at room temperature using 5 mmol of (Z)-3-methylpent-2-en-4-yn-1-ol. b Yield of 2,3-dimethylfuran
determined by GC. c Turnover frequencies [(mol product/mol catalyst)/time] were calculated at the indicated time in each case. d Data taken from ref.
24c. e Data taken from ref. 27a.
complex 10 readily reacts with two equivalents of tert-butyl
1-ol into 2,3-dimethylfuran was used as a model reaction (see
Scheme 4). In a typical experiment, the palladium catalyst precur-
sor (0.01 mmol) was added under inert atmosphere to 5 mmol of
(Z)-3-methylpent-2-en-4-yn-1-ol and the mixture stirred at room
temperature, the course of the reaction being monitored by gas
chromatography. Selected results are collected in Table 2.
isocyanide, in dichloromethane at r.t., to afford trans-[Pd(j1(P)-
t
=
=
Ph2PCH2P{ NP( O)(OPh)2}Ph2)2(CN Bu)2][SbF6]2 11 via open-
ing of the two chelate rings (see Scheme 3). Compound 11, isolated
as an air-stable white solid in 78% yield, has been characterized by
means of standard spectroscopic techniques (IR and 31P{ H}, 1H,
1
and 13C{ H} NMR), conductance measurements (2 : 1 electrolyte;
1
KM = 189 X−1 cm2 mol−1) as well as elemental analysis, with all data
fully consistent with the proposed formulation (details are given in
the Experimental Section). In particular, its trans stereochemistry
is supported by the appearance of only one absorption band for
the isocyanide ligands in the IR spectrum (m(CN) = 2227 cm−1).
Scheme
4
Palladium-catalyzed cycloisomerization of (Z)-3-methyl-
pent-2-en-4-yn-1-ol into 2,3-dimethylfuran.
Catalytic studies
All the complexes studied have proven to be active and efficient
catalysts for this particular transformation leading to nearly
quantitative conversions of (Z)-3-methylpent-2-en-4-yn-1-ol into
The synthesis of furans is of particular interest since they can be
found in many naturally occurring compounds, being also key
structural units in several important pharmaceuticals as well as in
flavor and fragrance compounds.21 Furthermore, furans are useful
and versatile building blocks in synthetic organic chemistry.22
Apart from classical synthetic approaches, the cycloisomeriza-
tion of unsaturated acyclic precursors into furans catalyzed
by transition-metal complexes has attracted great attention in
recent years.21 These atom economical methodologies, which
usually proceed under mild conditions, allow the access to furans
with the desired substitution pattern in a one-step procedure.
Among the different acyclic precursors used in furan syntheses, i.e.
alkyne and allene-containing compounds, readily available (Z)-2-
en-4-yn-1-ols are probably the most appealing. In this context,
several rhodium-,23 iridium-,23b palladium-,24 copper-,25 silver-,26
gold-,27 and especially ruthenium-based catalysts23b,24a,28 have been
successfully used to promote the cycloisomerization of (Z)-2-en-
4-yn-1-ols into the corresponding furans. Among them, K2[PdI4]
2,3-dimethylfuran within 5–24 h, with the chelate complexes cis-
2
=
=
[PdCl2(j -P,N-Ph2PCH2P{ NP( O)(OR)2}Ph2)] (R = Et 3, Ph
=
=
4) and [Pd(Ph2PCH2P{ NP( O)(OR)2}Ph2)2][SbF6]2 (R = Et
9, Ph 10) showing the best performances (TOF = 52–124 h−1;
entries 1, 2, 5 and 6). In particular, the dicationic complex
=
=
[Pd(Ph2PCH2P{ NP( O)(OPh)2}Ph2)2][SbF6]2 10 was found to
be the most active yielding 2,3-dimethylfuran quantitatively in
only 4 h (TOF = 124 h−1; entry 6).29 It is now well-established
that this metal-catalyzed cycloisomerization reaction proceeds
via initial p-coordination of the C≡C of the enynol on the
metal and subsequent intramolecular nucleophilic attack of
the pendant OH group on the coordinated alkyne unit (see
Scheme 5).24 Therefore, the higher catalytic activities shown by
all the chelate complexes when compared to trans-[PdCl2(j1-(P)-
=
=
Ph2PCH2P{ NP( O)(OR)2}Ph2)2] (R = Et 7, Ph 8; entries 3 and
27
(formed in situ from PdI2 + 2 equiv. of KI)24b–d and AuCl3 show
the best performances under mild reaction conditions (r.t.).
With these precedents in mind, we decided to explore the
catalytic activity of the novel Pd(II) complexes cis-[PdCl2(j2-
=
=
P,N-Ph2PCH2P{ NP( O)(OR)2}Ph2)] (R = Et 3, Ph 4), trans-
1
=
=
[PdCl2(j -P-Ph2PCH2P{ NP( O)(OR)2}Ph2)2] (R = Et 7, Ph
=
=
8) and [Pd(Ph2PCH2P{ NP( O)(OR)2}Ph2)2][SbF6]2 (R = Et
9, Ph 10) in such a cyclization process. The cycloisomerization
of the commercially available enynol (Z)-3-methylpent-2-en-4-yn-
Scheme 5 Mechanism of the Pd-catalyzed cycloisomerization process.
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4) seem to indicate that the generation of a vacant coordination
site by chelate ring opening vs. chloride dissociation is much more
effective.
in dichloromethane (15 cm3) was stirred at room temperature for
6 h. After concentration to a small volume (ca. 5 cm3), diethyl
ether (40 cm3) was slowly added yielding a yellow solid precipitate,
which was washed with diethyl ether (2 × 5 cm3) and vacuum-
dried. 3: Yield: 0.670 g, 94% (Found: C, 48.51; H, 4.71; N,
Remarkably, compounds 3/4 and 9/10 were found to be much
more active than K2[PdI4] (entries 1/2 and 5/6 vs entry 7), which
is at present the most efficient palladium-based catalyst for this
particular transformation.24c,d It is also important to note that the
catalytic activity of our complexes is retained at lower catalyst
loadings (0.1 mol%; entries 9–11). Nevertheless, they still remain
less efficient than AuCl3 (entry 8) which is the best catalyst reported
to date for this cycloisomerization reaction.27
1.73. C29H32O3P3Cl2NPd requires C, 48.86; H, 4.52; N, 1.96%);
2
mmax/cm−1 (P O) 1241 m (KBr); dP (CD2Cl2) 6.16 (d, J(PP) =
=
2
=
11.9 Hz, (EtO)2P( O)), 13.74 (d, J(PP) = 21.4 Hz, Ph2P), 43.27
2
=
(dd, J(PP) = 21.4 and 11.9 Hz, Ph2P N); dH (CD2Cl2) 1.10 (t,
3
2
6H, J(HH) = 6.9 Hz, OCH2CH3), 3.84 (dd, 2H, J(HP) = 11.5
and 11.5 Hz, PCH2P), 4.14 (m, 4H, OCH2), 7.41–7.89 (m, 20H,
3
Ph); dC (CD2Cl2) 16.58 (d, J(CP) = 7.2 Hz, OCH2CH3), 31.15
1
2
(dd, J(CP) = 71.1 and 19.5 Hz, PCH2P), 64.39 (d, J(CP) =
Conclusions
3
4.9 Hz, OCH2), 129.63 (d, J(CP) = 12.1 Hz, m-Ph), 129.94 (d,
3J(CP) = 13.2 Hz, m-Ph), 131.05 (d, J(CP) = 70.1 Hz, i-Ph),
1
In summary, in the present work we have described the high-
yield synthesis of a series of palladium(II) complexes contain-
ing the N-phosphorylated iminophosphorane-phosphine ligands
1
132.20 (d, J(CP) = 107.2 Hz, i-Ph), 132.75 and 134.94 (s, p-
2
2
Ph), 133.78 (d, J(CP) = 10.0 Hz, o-Ph), 134.42 (d, J(CP) =
=
=
Ph2PCH2P{ NP( O)(OR)2}Ph2 (R = Et 1, Ph 2) in which
these heterotrifunctional ligands adopt j1-(P)-, j2-(P,N)- and j2-
(P,O)-coordination modes, confirming their versatile coordination
ability and hemilabile properties. The utility of these complexes as
efficient catalysts for the cycloisomerization of (Z)-3-methylpent-
2-en-4-yn-1-ol into 2,3-dimethylfuran is also reported. In fact,
some of them have found to be the most active Pd-based catalysts
reported to date in the literature for this particular transfor-
mation. Therefore, it is shown that the search of appropriate
metallic complexes containing heteroditopic iminophosphorane-
phosphine ligands is a matter of synthetic interest to be applied in
homogeneous catalysis.
11.5 Hz, o-Ph). 4: Yield: 0.728 g, 90% (Found: C, 54.59; H, 3.87;
N, 1.90. C37H32O3P3Cl2NPd requires C, 54.94; H, 3.99; N, 1.73%);
2
mmax/cm−1 (P O) 1258m (KBr); dP (CD2Cl2) −3.15 (d, J(PP) =
=
2
=
10.2 Hz, (PhO)2P( O)), 13.12 (d, J(PP) = 20.9 Hz, Ph2P), 45.04
2
=
(dd, J(PP) = 20.9 and 10.2 Hz, Ph2P N); dH (CD2Cl2) 3.65 (dd,
2H, 2J(HP) = 11.1 and 11.1 Hz, PCH2P), 7.07–7.28 (m, 14H, Ph),
7.42–7.66 (m, 16H, Ph); dC (CD2Cl2) 31.50 (dd, 1J(CP) = 72.5 and
19.1 Hz, PCH2P), 121.49 (d, 3J(CP) = 4.9 Hz, o-OPh), 125.15 (s,
p-OPh), 127.91 (d, 1J(CP) = 65.8 Hz, i-Ph), 129.24 (d, 3J(CP) =
3
11.1 Hz, m-Ph), 129.53 (d, J(CP) = 12.9 Hz, m-Ph), 129.71 (s,
m-OPh), 130.40 (d, 1J(CP) = 103.5 Hz, i-Ph), 132.38 and 134.63
(s, p-Ph), 133.31 (d, 2J(CP) = 10.8 Hz, o-Ph), 134.01 (d, 2J(CP) =
11.1 Hz, o-Ph), 151.19 (d, 2J(CP) = 7.2 Hz, i-OPh).
Experimental
1
=
=
cis-[PdCl2(j (P)-Ph2PCH2P{ NP( O)(OR)2}Ph2)(L)] (R =
Et, L = CNtBu 5a, CN-2,6-C6H3Me2 5b, py 5c, P(OMe)3 5d,
P(OEt)3 5e; R = Ph, L = CNtBu 6a, CN-2,6-C6H3Me2 6b, py 6c,
P(OMe)3 6d, P(OEt)3 6e). To a solution of the corresponding
complex 3/4 (0.2 mmol) in dichloromethane (10 cm3) was added
at room temperature the appropriate two-electron donor ligand L
(0.22 mmol). The mixture was stirred at room temperature for
30 min and then evaporated to dryness. The resulting solid residue
was washed with hexanes (3 × 10 cm3) to give compounds 5/6a–e
as pale yellow solids. 5a: Yield: 0.105 g, 66% (Found: C, 51.59; H,
5.30; N, 3.37. C34H41O3P3Cl2N2Pd requires C, 51.31; H, 5.19; N,
General comments
All manipulations were performed under an atmosphere of dry
nitrogen using vacuum-line and standard Schlenk techniques. Sol-
vents were dried by standard methods and distilled under nitrogen
before use. All reagents were obtained from commercial suppliers
and used without further purification with the exception of com-
pounds [PdCl2(COD)]11 and Ph2PCH2P{ NP( O)(OR)2}Ph2
(R = Et 1, Ph 2)10c which were prepared by following the methods
described in the literature, and (Z)-3-methylpent-2-en-4-yn-1-ol
which was used freshly distilled in the catalytic reactions. Infrared
spectra were recorded on a Perkin-Elmer 1720-XFT or a Perkin-
Elmer 599 spectrometer. The conductivities were measured at
room temperature, in ca. 10−3 mol dm−3 acetone solutions, with
a Jenway PCM3 conductimeter. The C, H and N analyses were
carried out with a Perkin-Elmer 2400 microanalyzer. NMR spectra
were recorded on a Bruker DPX300 instrument at 300 MHz (1H),
121.5 MHz (31P) or 75.4 MHz (13C) using SiMe4 or 85% H3PO4
as standards. DEPT experiments have been carried out for all the
compounds reported in this paper. GC measurements were made
on a Hewlett-Packard HP6890 equipment (Supelco Beta-DexTM
120 column; 30 m, 250 lm).
=
=
3.52%); mmax/cm−1 (P O) 1263m, (CN) 2223s (KBr); dP (CD2Cl2)
=
2
2
=
3.32 (d, J(PP) = 29.5 Hz, (EtO)2P( O)), 10.50 (dd, J(PP) =
2
=
29.5 and 14.3 Hz, Ph2P N), 22.13 (d, J(PP) = 14.3 Hz, Ph2P);
dH (CD2Cl2) 1.06 (s, 9H, C(CH3)3), 1.12 (t, 6H, 3J(HH) = 7.0 Hz,
OCH2CH3), 3.80 (m, 4H, OCH2), 4.56 (dd, 2H, 2J(HP) = 13.9 and
13.9 Hz, PCH2P), 7.27–7.50 (m, 12H, Ph), 7.73–8.00 (m, 8H, Ph);
3
dC (CD2Cl2) 18.64 (d, J(CP) = 8.2 Hz, OCH2CH3), 29.49 (dd,
1J(CP) = 61.6 and 25.4 Hz, PCH2P), 31.67 (s, C(CH3)3), 61.57 (s,
C(CH3)3), 63.84 (d, 2J(CP) = 6.3 Hz, OCH2), 123.04 (br, Pd–CN),
131.08 (d, 3J(CP) = 12.2 Hz, m-Ph), 131.17 (dd, 1J(CP) = 64.1 Hz,
3J(CP) = 3.5 Hz, i-Ph), 131.37 (d, 3J(CP) = 13.3 Hz, m-Ph), 132.56
(d, 1J(CP) = 109.8 Hz, i-Ph), 134.28 (d, 4J(CP) = 3.2 Hz, p-Ph),
4
134.42 (d, 2J(CP) = 11.5 Hz, o-Ph), 134.83 (d, J(CP) = 2.5 Hz,
Preparations
p-Ph), 136.48 (d, 2J(CP) = 11.4 Hz, o-Ph). 5b: Yield: 0.131 g, 78%
2
=
=
cis-[PdCl2(j (P,N)-Ph2PCH2P{ NP( O)(OR)2}Ph2)] (R = Et
3, Ph 4). A solution of [PdCl2(COD)] (0.285 g, 1 mmol) and the
corresponding iminophosphorane-phosphine ligand 1/2 (1 mmol)
(Found: C, 53.89; H, 5.07; N, 3.20. C38H41O3P3Cl2N2Pd requires
C, 54.08; H, 4.90; N, 3.32%); mmax/cm−1 (P O) 1266m, (CN) 2201s
=
2
=
(KBr); dP (CDCl3) 3.46 (d, J(PP) = 29.3 Hz, (EtO)2P( O)), 10.59
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The Royal Society of Chemistry 2006
Dalton Trans., 2006, 5593–5604 | 5599
©

View Article Online
2
2
2
2
=
(dd, J(PP) = 29.3 and 12.2 Hz, Ph2P N), 22.28 (d, J(PP) =
12.2 Hz, Ph2P); dH (CDCl3) 1.13 (t, 6H, 3J(HH) = 7.1 Hz,
OCH2CH3), 1.95 (s, 6H, C6H3Me2), 3.78 (m, 4H, OCH2), 4.69 (dd,
2H, 2J(HP) = 14.1 and 14.1 Hz, PCH2P), 7.12–8.07 (m, 23H, Ph
and C6H3Me2); dC (CDCl3) 16.08 (d, 3J(CP) = 7.6 Hz, OCH2CH3),
18.06 (s, C6H3Me2), 27.03 (ddd, 1J(CP) = 61.0 and 26.2 Hz,
Ph), 132.28 (d, J(CP) = 10.9 Hz, o-Ph), 134.20 (d, J(CP) =
11.9 Hz, o-Ph). 6a: Yield: 0.155 g, 87% (Found: C, 56.37; H, 4.81;
N 3.06. C42H41O3P3Cl2N2Pd requires C, 56.55; H, 4.63; N, 3.14%);
mmax/cm−1 (P O) 1245m, (CN) 2224s (KBr); dP (CD2Cl2) −7.59
=
2
2
=
(d, J(PP) = 32.5 Hz, (PhO)2P( O)), 12.69 (dd, J(PP) = 32.5 and
2
=
18.5 Hz, Ph2P N), 21.31 (d, J(PP) = 18.5 Hz, Ph2P); dH (CD2Cl2)
3J(CP) = 3.2 Hz, PCH2P), 61.31 (d, J(CP) = 6.5 Hz, OCH2),
1.07 (s, 9H, C(CH3)3), 4.46 (dd, 2H, 2J(HP) = 13.0 and 13.0 Hz,
PCH2P), 7.00–7.30 (m, 8H, Ph), 7.41–7.53 (m, 12H, Ph), 7.68–7.74
(m, 10H, Ph); dC (CD2Cl2) 27.25 (ddd, 1J(CP) = 66.8 and 25.4 Hz,
3J(CP) = 3.8 Hz, PCH2P), 29.46 (s, C(CH3)3), 59.81 (s, C(CH3)3),
120.75 (d, 3J(CP) = 5.1 Hz, o-OPh), 124.15 (s, p-OPh), 125.20 (br,
2
125.13 (br, Pd–CN), 127.65 and 130.23 (s, CH of C6H3Me2),
1
3
128.03 (dd, J(CP) = 59.7 Hz, J(CP) = 3.2 Hz, i-Ph), 128.60
3
3
(d, J(CP) = 12.0 Hz, m-Ph), 128.91 (d, J(CP) = 13.1 Hz, m-
1
Ph), 129.13 and 135.74 (s, C of C6H3Me2), 129.60 (d, J(CP) =
2
1
3
106.1 Hz, i-Ph), 131.80 (d, J(CP) = 10.4 Hz, o-Ph), 131.92 (d,
Pd–CN), 128.59 (dd, J(CP) = 60.3 Hz, J(CP) = 3.0 Hz, i-Ph),
4J(CP) = 3.3 Hz, p-Ph), 132.37 (d, 4J(CP) = 2.2 Hz, p-Ph), 133.99
129.13 (d, 3J(CP) = 12.1 Hz, m-Ph), 129.41 (d, 3J(CP) = 13.2 Hz,
2
1
(d, J(CP) = 12.0 Hz, o-Ph). 5c: Yield: 0.127 g, 80% (Found: C,
m-Ph), 129.68 (s, m-OPh), 130.15 (d, J(CP) = 108.1 Hz, i-Ph),
2
51.42; H, 4.65; N, 3.70. C34H37O3P3Cl2N2Pd requires C, 51.57; H,
132.25 (d, J(CP) = 10.9 Hz, o-Ph), 132.53 and 133.09 (s, p-Ph),
4.71; N, 3.54%); mmax/cm−1 (P O) 1263m (KBr); dP (CD2Cl2) 2.86
134.39 (d, 2J(CP) = 11.5 Hz, o-Ph), 152.54 (d, J(CP) = 7.0 Hz,
2
=
2
2
=
(d, J(PP) = 29.5 Hz, (EtO)2P( O)), 11.09 (dd, J(PP) = 29.5
i-OPh). 6b: Yield: 0.141 g, 75% (Found: C, 58.49; H, 4.29; N,
2
=
and 11.0 Hz, Ph2P N), 16.53 (d, J(PP) = 11.0 Hz, Ph2P); dH
2.79. C46H41O3P3Cl2N2Pd requires C, 58.77; H, 4.40; N, 2.98%);
(CD2Cl2) 1.08 (t, 6H, 3J(HH) = 6.8 Hz, OCH2CH3), 3.84 (m, 4H,
OCH2), 4.20 (dd, 2H, 2J(HP) = 13.4 and 13.4 Hz, PCH2P), 7.29–
7.84 (m, 23H, Ph and C5H5N), 8.89 (m, 2H, C5H5N); dC (CD2Cl2)
mmax/cm−1 (P O) 1254m, (CN) 2198s (KBr); dP (CD2Cl2) −7.44
=
2
2
=
(d, J(PP) = 32.9 Hz, (PhO)2P( O)), 12.71 (dd, J(PP) = 32.9 and
2
=
17.7 Hz, Ph2P N), 21.69 (d, J(PP) = 17.7 Hz, Ph2P); dH (CD2Cl2)
3
1
16.51 (d, J(CP) = 7.9 Hz, OCH2CH3), 27.71 (ddd, J(CP) =
62.5 and 27.3 Hz, 3J(CP) = 5.9 Hz, PCH2P), 61.70 (d, 2J(CP) =
5.8 Hz, OCH2), 125.14, 138.98 and 151.99 (s, C5H5N), 128.42
(d, 3J(CP) = 11.6 Hz, m-Ph), 128.45 (d, 1J(CP) = 64.7 Hz, i-Ph),
128.90 (d, 3J(CP) = 12.8 Hz, m-Ph), 131.28 (d, 1J(CP) = 101.3 Hz,
1.90 (s, 6H, C6H3Me2), 4.54 (dd, 2H, 2J(HP) = 13.2 and 13.2 Hz,
PCH2P), 6.96–7.82 (m, 33H, Ph and C6H3Me2); dC (CD2Cl2) 18.41
1
3
(s, C6H3Me2), 27.28 (ddd, J(CP) = 65.7 and 25.7 Hz, J(CP) =
4.5 Hz, PCH2P), 120.72 (d, 3J(CP) = 5.3 Hz, o-OPh), 124.12 (s, p-
OPh), 125.55 (br, Pd–CN), 128.14 (dd, 1J(CP) = 55.9 Hz, 3J(CP) =
3.0 Hz, i-Ph), 128.35 and 130.73 (s, CH of C6H3Me2), 129.19 (d,
2
i-Ph), 131.77 and 132.44 (s, p-Ph), 132.36 (d, J(CP) = 11.6 Hz,
o-Ph), 134.59 (d, 2J(CP) = 10.5 Hz, o-Ph). 5d: Yield: 0.132 g, 79%
3J(CP) = 12.3 Hz, m-Ph), 129.52 (d, J(CP) = 12.8 Hz, m-Ph),
3
(Found: C, 45.67; H, 4.81; N, 1.80. C32H41O6P4Cl2NPd requires
129.63 (s, m-OPh), 129.67 and 136.37 (s, C of C6H3Me2), 129.71
(d, 1J(CP) = 107.3 Hz, i-Ph), 132.25 (d, 2J(CP) = 11.3 Hz, o-Ph),
C, 45.92; H, 4.94; N, 1.67%); mmax/cm−1 (P O) 1260m (KBr); dP
=
2
4
4
=
(CD2Cl2) 3.14 (d, J(PP) = 27.1 Hz, (EtO)2P( O)), 11.92 (dd,
132.67 (d, J(CP) = 3.0 Hz, p-Ph), 133.13 (d, J(CP) = 2.7 Hz,
2
2
2
2
=
J(PP) = 27.1 and 14.5 Hz, Ph2P N), 24.07 (dd, J(PP) = 33.4
p-Ph), 134.40 (d, J(CP) = 12.1 Hz, o-Ph), 152.48 (d, J(CP) =
7.6 Hz, i-OPh). 6c: Yield: 0.145 g, 82% (Found: C, 56.55; H, 4.09;
2
and 14.5 Hz, Ph2P), 93.37 (d, J(PP) = 33.4 Hz, P(OMe)3); dH
(CD2Cl2) 1.15 (t, 6H, 3J(HH) = 6.9 Hz, OCH2CH3), 3.52 (d, 9H,
3J(HP) = 12.7 Hz, P(OCH3)3), 3.84 (m, 4H, OCH2), 4.55 (dd, 2H,
2J(HP) = 13.1 and 13.1 Hz, PCH2P), 7.34–7.51 (m, 12H, Ph),
N, 3.30. C42H37O3P3Cl2N2Pd requires C, 56.81; H, 4.20; N, 3.15%);
mmax/cm−1 (P O) 1248m (KBr); dP (CD2Cl2) −7.97 (d, J(PP) =
2
=
2
=
34.3 Hz, (PhO)2P( O)), 12.41 (dd, J(PP) = 34.3 and 11.7 Hz,
3
2
=
7.74–7.86 (m, 8H, Ph); dC (CD2Cl2) 16.49 (d, J(CP) = 8.2 Hz,
Ph2P N), 16.40 (d, J(PP) = 11.7 Hz, Ph2P); dH (CD2Cl2) 4.30
1
3
OCH2CH3), 30.22 (ddd, J(CP) = 71.9 and 28.5 Hz, J(CP) =
(dd, 2H, 2J(HP) = 13.0 and 13.0 Hz, PCH2P), 7.11–7.91 (m, 33H,
Ph and C5H5N), 8.95 (m, 2H, C5H5N); dC (CD2Cl2) 27.95 (ddd,
2
6.2 Hz, PCH2P), 54.45 (d, J(CP) = 4.6 Hz, P(OCH3)3), 61.70
2
3
3
(d, J(CP) = 6.1 Hz, OCH2), 128.67 (d, J(CP) = 11.8 Hz, m-
1J(CP) = 73.3 and 26.3 Hz, J(CP) = 6.6 Hz, PCH2P), 120.96
1
3
3
Ph), 128.83 (d, J(CP) = 72.3 Hz, i-Ph), 128.96 (d, J(CP) =
12.7 Hz, m-Ph), 131.50 (d, 1J(CP) = 101.7 Hz, i-Ph), 131.84 and
(d, J(CP) = 5.4 Hz, o-OPh), 124.08 (s, p-OPh), 125.02, 138.80
1
3
and 152.01 (s, C5H5N), 128.18 (dd, J(CP) = 63.9 Hz, J(CP) =
2
3
132.41 (s, p-Ph), 132.26 (d, J(CP) = 11.0 Hz, o-Ph), 134.09 (d,
4.2 Hz, i-Ph), 128.50 (d, J(CP) = 11.3 Hz, m-Ph), 129.05 (d,
2J(CP) = 11.4 Hz, o-Ph). 5e: Yield: 0.128 g, 73% (Found: C, 48.20;
3J(CP) = 13.2 Hz, m-Ph), 129.65 (s, m-OPh), 130.20 (d, 1J(CP) =
102.3 Hz, i-Ph), 131.86 and 132.77 (s, p-Ph), 132.33 (d, 2J(CP) =
H, 5.12; N, 1.70. C35H47O6P4Cl2NPd requires C, 47.83; H, 5.39;
N, 1.59%); mmax/cm−1 (P O) 1262m (KBr); dP (CD2Cl2) 3.00 (d,
10.7 Hz, o-Ph), 134.54 (d, J(CP) = 10.8 Hz, o-Ph), 152.79 (d,
2
=
2
2
2J(CP) = 7.2 Hz, i-OPh). 6d: Yield: 0.142 g, 76% (Found: C,
=
J(PP) = 28.0 Hz, (EtO)2P( O)), 11.65 (dd, J(PP) = 28.0 and
2
=
15.3 Hz, Ph2P N), 23.61 (dd, J(PP) = 33.4 and 15.3 Hz, Ph2P),
51.34; H, 4.60; N, 1.41. C40H41O6P4Cl2NPd requires C, 51.49; H,
2
4.43; N, 1.50%); mmax/cm−1 (P O) 1251m (KBr); dP (CD2Cl2) −7.75
=
88.15 (d, J(PP) = 33.4 Hz, P(OEt)3); dH (CD2Cl2) 0.99 (t, 9H,
3J(HH) = 7.1 Hz, P(OCH2CH3)3), 1.14 (t, 6H, 3J(HH) = 6.3 Hz,
OCH2CH3), 3.80 (m, 4H, OCH2), 3.94 (m, 6H, P(OCH2CH3)3),
4.59 (dd, 2H, 2J(HP) = 13.4 and 13.4 Hz, PCH2P), 7.29–7.53 (m,
12H, Ph), 7.77–7.84 (m, 8H, Ph); dC (CD2Cl2) 15.78 (d, 3J(CP) =
(d, J(PP) = 32.5 Hz, (PhO)2P( O)), 12.96 (dd, J(PP) = 32.5
2
2
=
2
=
and 19.0 Hz, Ph2P N), 24.02 (dd, J(PP) = 31.6 and 19.0 Hz,
2
Ph2P), 92.46 (d, J(PP) = 31.6 Hz, P(OMe)3); dH (CD2Cl2) 3.49
3
2
(d, 9H, J(HP) = 12.7 Hz, P(OCH3)3), 4.68 (dd, 2H, J(HP) =
3
7.0 Hz, P(OCH2CH3)3), 16.47 (d, J(CP) = 8.3 Hz, OCH2CH3),
12.8 and 12.8 Hz, PCH2P), 7.04–7.46 (m, 22H, Ph), 7.76–7.83 (m,
30.21 (ddd, 1J(CP) = 70.8 and 32.4 Hz, 3J(CP) = 6.1 Hz, PCH2P),
8H, Ph); dC (CD2Cl2) 29.78 (ddd, J(CP) = 66.5 and 26.7 Hz,
1
2
2
61.71 (d, J(CP) = 6.1 Hz, OCH2), 64.55 (d, J(CP) = 4.8 Hz,
3J(CP) = 5.1 Hz, PCH2P), 54.41 (d, 2J(CP) = 5.1 Hz, P(OCH3)3),
120.81 (d, 3J(CP) = 5.0 Hz, o-OPh), 124.04 (s, p-OPh), 128.76 (d,
3
P(OCH2CH3)3), 128.60 (d, J(CP) = 11.4 Hz, m-Ph), 128.79 (d,
1J(CP) = 65.9 Hz, i-Ph), 128.93 (d, J(CP) = 13.1 Hz, m-Ph),
3J(CP) = 12.0 Hz, m-Ph), 129.19 (d, J(CP) = 13.2 Hz, m-Ph),
3
3
1
1
130.98 (d, J(CP) = 103.4 Hz, i-Ph), 131.80 and 132.20 (s, p-
129.33 (d, J(CP) = 64.4 Hz, i-Ph), 129.58 (s, m-OPh), 131.96
5600 | Dalton Trans., 2006, 5593–5604
This journal is
The Royal Society of Chemistry 2006
©

View Article Online
2
=
=
and 132.72 (s, p-Ph), 132.21 (d, J(CP) = 11.4 Hz, o-Ph), 132.
(br, (EtO)2P( O)), 28.33 (br, Ph2P N), 30.60 (br, Ph2P); dH
(CD2Cl2) 1.24 (t, 12H, 3J(HH) = 7.6 Hz, OCH2CH3), 4.05 (m, 8H,
OCH2), 4.67 (dd, 4H, 2J(HP) = 12.6 and 12.6 Hz, PCH2P), 7.24–
7.81 (m, 40H, Ph); This compound was not soluble enough to be
1
2
31 (d, J(CP) = 100.7 Hz, i-Ph), 134.14 (d, J(CP) = 12.0 Hz,
o-Ph), 152.55 (d, 2J(CP) = 7.7 Hz, i-OPh). 6e: Yield: 0.138 g, 71%
(Found: C, 52.69; H, 4.72; N, 1.60. C43H47O6P4Cl2NPd requires
C, 52.97; H, 4.86; N, 1.44%); mmax/cm−1 (P O) 1257m (KBr); dP
characterized by 13C{ H} NMR spectroscopy. 10: Yield: 0.313 g,
1
=
2
=
(CD2Cl2) −7.76 (d, J(PP) = 33.4 Hz, (PhO)2P( O)), 12.80 (dd,
85% (Found: C, 48.06; H, 3.61; N, 1.73. C74H64F12O6P6N2Sb2Pd
requires C, 48.28; H, 3.50; N, 1.52%); conductivity (acetone, 20 ◦C)
2
2
=
J(PP) = 33.4 and 18.1 Hz, Ph2P N), 23.70 (dd, J(PP) = 32.5 and
18.1 Hz, Ph2P), 87.44 (d, 2J(PP) = 32.5 Hz, P(OEt)3); dH (CD2Cl2)
1.01 (t, 9H, 3J(HH) = 7.1 Hz, P(OCH2CH3)3), 3.96 (m, 6H,
P(OCH2CH3)3), 4.72 (dd, 2H, 2J(HP) = 13.0 and13.0 Hz, PCH2P),
7.07–7.47 (m, 22H, Ph), 7.77–7.85 (m, 8H, Ph); dC (CD2Cl2) 15.81
195 X−1 cm2 mol−1; mmax/cm−1 (SbF6 ) 656s, (P O) 1197m and
−
=
=
1260m (KBr); dP (CD2Cl2) −1.92 (br, (PhO)2P( O)), 28.27 (br,
2
=
Ph2P N), 29.09 (br, Ph2P); dH (CD2Cl2) 4.18 (dd, 4H, J(HP) =
12.4 and 12.4 Hz, PCH2P), 6.97–7.62 (m, 60H, Ph); dC (CD2Cl2)
33.54 (dd, 1J(CP) = 61.2 and 24.6 Hz, PCH2P), 120.60 (d, 3J(CP) =
4.7 Hz, o-OPh), 125.72 (s, p-OPh), 129.85 (m, m-Ph and m-OPh),
132.15 and 132.31 (s, p-Ph), 134.33 (m, o-Ph), 150.97 (d, 2J(CP) =
8.1 Hz, i-OPh), i-Ph signals not observed.
3
1
(d, J(CP) = 6.6 Hz, P(OCH2CH3)3), 29.81 (ddd, J(CP) = 66.0
and 25.7 Hz, 3J(CP) = 3.6Hz, PCH2P), 64.58 (d, 2J(CP) = 4.4 Hz,
3
P(OCH2CH3)3), 120.82 (d, J(CP) = 4.8 Hz, o-OPh), 124.03 (s,
p-OPh), 128.73 (d, 3J(CP) = 12.0 Hz, m-Ph), 128.82 (d, 1J(CP) =
3
66.0 Hz, i-Ph), 129.16 (d, J(CP) = 13.2 Hz, m-Ph), 129.59 (s,
1
t
m-OPh), 130.83 (d, 1J(CP) = 102.8 Hz, i-Ph), 131.97 and 132.70
(s, p-Ph), 132.24 (d, 2J(CP) = 11.3 Hz, o-Ph), 134.21 (d, 2J(CP) =
11.9 Hz, o-Ph), 152.59 (d, 2J(CP) = 7.2 Hz, i-OPh).
=
=
trans-[Pd(j (P)-Ph2PCH2P{ NP( O)(OPh)2}Ph2)2(CN Bu)2]-
[SbF6]2 11. To a solution of complex 10 (0.184 g, 0.1 mmol)
in dichloromethane (20 cm3) was added at room temperature
tert-butyl isocyanide (24 lL, 0.21 mmol). The mixture was stirred
at room temperature for 30 min and then evaporated to dryness.
The resulting solid residue was washed with diethyl ether (3 ×
10 cm3) to give compound 11 as a white solid. Yield: 0.157 g,
78% (Found: C, 50.02; H, 4.31; N, 2.90. C84H82F12O6P6N4Sb2Pd
requires C, 50.26; H, 4.12; N, 2.79%); conductivity (acetone,
1
=
=
trans-[PdCl2(j (P)-Ph2PCH2P{ NP( O)(OR)2}Ph2)2] (R =
Et 7, Ph 8). A solution of [PdCl2(COD)] (0.143 g, 0.5 mmol)
and the corresponding iminophosphorane-phosphine ligand 1/2
(1.1 mmol) in dichloromethane (15 cm3) was stirred at room
temperature for 6 h. After concentration to a small volume (ca.
5 cm3), diethyl ether (40 cm3) was slowly added yielding a yellow
solid precipitate which was washed with diethyl ether (3 × 5 cm3)
and vacuum-dried. 7: Yield: 0.568 g, 91% (Found: C, 55.67; H,
5.01; N, 2.43. C58H64O6P6Cl2N2Pd requires C, 55.81; H, 5.17;
◦
−
20 C) 189 X−1 cm2 mol−1; mmax/cm−1 (SbF6 ) 656s, (P O) 1301m,
=
2
(CN) 2227s (KBr); dP (CD2Cl2) −10.68 (d, J(PP) = 32.9 Hz,
=
=
(PhO)2P( O)), 12.93 (m, Ph2P), 15.44 (m, Ph2P N); dH (CD2Cl2)
0.79 (s, 18H, C(CH3)3), 4.43 (m, 4H, PCH2P), 6.97–7.61 (m, 60H,
Ph); dC (CD2Cl2) 30.86 (s, C(CH3)3), 31.98 (dd, 1J(CP) = 59.2 and
27.1 Hz, PCH2P), 63.62 (s, C(CH3)3), 122.31 (d, 3J(CP) = 5.7 Hz,
o-OPh), 127.95 (s, p-OPh), 128.30 (br, Pd–CN), 131.79 (m, m-Ph),
132.39 (s, m-OPh), 133.82 and 133.97 (s, p-Ph), 135.49 (m, o-Ph),
153.16 (d, 2J(CP) = 8.7 Hz, i-OPh), i-Ph signals not observed.
N, 2.24%); mmax/cm−1 (P O) 1259m (KBr); dP (CD2Cl2) 2.81 (d,
=
2
=
=
J(PP) = 28.7 Hz, (EtO)2P( O)), 10.82 (m, Ph2P N), 11.47 (m,
3
Ph2P); dH (CD2Cl2) 1.06 (t, 12H, J(HH) = 7.1 Hz, OCH2CH3),
3.68 (m, 8H, OCH2), 4.31 (m, 4H, PCH2P), 7.24–7.73 (m, 40H,
Ph); dC (CD2Cl2) 16.51 (d, 3J(CP) = 8.2 Hz, OCH2CH3), 23.30 (dd,
1J(CP) = 70.5 and 10.0 Hz, PCH2P), 61.50 (d, 2J(CP) = 5.8 Hz,
3
OCH2), 128.36 (m, m-Ph), 128.83 (d, J(CP) = 12.8 Hz, m-Ph),
2
General procedure for the catalytic cycloisomerization of
(Z)-3-methylpent-2-en-4-yn-1-ol into 2,3-dimethylfuran
131.28 and 132.27 (s, p-Ph), 132.05 (d, J(CP) = 10.1 Hz, o-Ph),
135.12 (m, o-Ph), i-Ph signals not observed. 8: Yield: 0.634 g, 88%
(Found: C, 61.59; H, 4.61; N, 1.88. C74H64O6P6Cl2N2Pd requires
The corresponding palladium catalyst (0.01 mmol) was added,
under N2 atmosphere, to neat (Z)-3-methylpent-2-en-4-yn-1-ol
(549 lL, 5 mmol), and the resulting mixture stirred at room
temperature for the indicated time (see Table 2). The course of the
reaction was monitored by regular sampling and analysis by gas
chromatography. The identity of the resulting 2,3-dimethylfuran
was assessed by comparison with a commercially available pure
sample.
C, 61.70; H, 4.48; N, 1.94%); mmax/cm−1 (P O) 1244m (KBr); dP
=
2
=
(CD2Cl2) −8.47 (d, J(PP) = 32.1 Hz, (PhO)2P( O)), 11.37 (m,
=
Ph2P), 12.66 (m, Ph2P N); dH (CD2Cl2) 4.26 (m, 4H, PCH2P),
1
6.96–7.70 (m, 60H, Ph); dC (CD2Cl2) 24.03 (dd, J(CP) = 69.9
and 9.7 Hz, PCH2P), 120.77 (d, 3J(CP) = 5.2 Hz, o-OPh), 124.01
3
(s, p-OPh), 128.34 (m, m-Ph), 128.89 (d, J(CP) = 13.3 Hz, m-
Ph), 129.58 (s, m-OPh), 131.30 and 132.42 (s, p-Ph), 132.00 (d,
2J(CP) = 11.1 Hz, o-Ph), 134.95 (m, o-Ph), 152.63 (d, J(CP) =
2
7.6 Hz, i-OPh), i-Ph signals not observed.
X-Ray crystal structure determination of complexes 4, 5b, 7 and 9
=
=
[Pd(Ph2PCH2P{ NP( O)(OR)2}Ph2)2][SbF6]2 (R = Et 9, Ph
10). A solution of the corresponding neutral complex 7/8
(0.2 mmol) in dichloromethane (20 cm3) was treated, at room
temperature and in the absence of light, with AgSbF6 (0.141 g,
0.41 mmol) for 2 h. After the AgCl formed was filtered off
(Kieselguhr), the solution was evaporated to dryness and the
resulting white solid residue washed with diethyl ether (3 × 10 cm3)
and dried in vacuo. 9: Yield: 0.274 g, 83% (Found: C, 42.11; H,
4.13; N, 1.82. C58H64F12O6P6N2Sb2Pd requires C, 42.25; H, 3.91; N,
The most relevant crystal and refinement data are collected in
Table 3. Diffraction data for complexes 5b and 7 were recorded
on a Nonius Kappa CCD single-crystal diffractometer, using Cu-
˚
Ka radiation (k = 1.5418 A). The data were collected using the
oscillation method, with 2◦ oscillation and 40 s exposure time per
frame, and with a crystal-to-detector distance of 29 mm. The data-
collection strategy was calculated with the program Collect.30 Data
reduction and cell refinement were performed using the programs
HKL Denzo and Scalepack.31 Absorption correction was applied
by means of XABS232 (for 5b) or SORTAV33 (for 7).
1.70%); conductivity(acetone, 20 ◦C) 198 X−1 cm2 mol−1; mmax/cm−1
−
=
(SbF6 ) 658s, (P O) 1189m and 1262m (KBr); dP (CD2Cl2) 7.68
This journal is
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Dalton Trans., 2006, 5593–5604 | 5601
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Table 3 Crystal data and structure refinement for compounds 4, 5b, 7 and 9
4
5b
7
9
Empirical formula
C37H32O3P3Cl2NPd
808.85
100(2)
1.54180
Orthorhombic
P212121
10.6582(2)
15.0716(4)
21.1627(4)(1)
90
C38H41O3P3Cl2N2Pd
843.94
293(2)
1.54180
Monoclinic
P21/c
13.6438(1)
14.8151(2)
23.1199(2)
90
122.635(5)
90
4
3935.51(7)
1.424
6.507
C58H64O6P6Cl2N2Pd
1248.23
200(2)
1.54180
Triclinic
¯
P1
9.5971(2)
9.9089(2)
17.5208(4)
102.3320(10)
98.4270(10)
109.9560(10)
1
1485.66(5)
1.395
5.276
C58H64F12O6P6N2Sb2Pd·2CH2Cl2
Mr
1818.68
100(2)
T/K
˚
k/A
1.54180
Triclinic
¯
P1
Crystal system
Space group
˚
a/A
12.5698(4)
13.6979(4)
21.3980(7)
82.941(2)
86.073(2)
75.890(2)
2
3543.22(19)
1.705
11.403
˚
b/A
˚
c/A
a/◦
b/◦
c /◦
Z
90
90
4
3
˚
V/A
3399.49(13)
1.580
7.501
Dc/g cm−3
l/mm−1
F(000)
1640
1728
644
1808
Crystal size/mm
0.30 × 0.06 × 0.06
3.60–70.37
14111
5932
0.0497
95.0
424/0
0.996
0.0572, 0
0.0375
0.40 × 0.22 × 0.10
3.75–68.46
57429
7224
0.099
99.7
446/0
1.053
0.0936, 0.7660
0.0474
0.1286
0.0526
0.1348
0.673, −0.894
0.25 × 0.07 × 0.07
2.66–70.02
9981
5470
0.0461
96.9
342/0
1.105
0.0899, 1.2057
0.0374
0.1072
0.0451
0.1376
0.780, −0.834
0.20 × 0.12 × 0.06
2.08–70.03
26848
11585
0.0426
86.1
818/0
1.047
0.1023, 16.5267
0.0631
0.1667
0.0805
0.1800
3.170, −2.479
h Range/◦
No. reflns. collected
No. unique reflns.
Rint (%)
Completeness to hmax (%)
No. of parameters/restraints
Goodness-of-fit on F2
Weight functions (a, b)
R1 [I > 2r(I)]a
wR2 [I > 2r(I)]a
R1 (all data)
0.0914
0.0419
0.0936
wR2 (all data)
Dqmax, min/e A
−3
˚
1.186, −0.616
ꢀ
ꢀ
ꢀ
ꢀ
a R1 = (|Fo| − |Fc|)/ |Fo|; wR2 = { [w(Fo − Fc2)2]/ [w(Fo2)2]}
.
2
1/2
Diffraction data for complexes 4 and 9 were recorded on a
Bruker Smart 6k CCD area-detector three-circle diffractometer
Acknowledgements
This work was supported by the Ministerio de Ciencia y Tec-
nolog´ıa (MCyT) of Spain (Project BQU2003-00255) and the
Gobierno del Principado de Asturias (Projects PR-01-GE-6 and
IB05-035). V. C. thanks the MCyT and the European Social Fund
for the award of a “Ramo´n y Cajal” contract.
˚
(Cu-Ka radiation, k = 1.5418 A). The data were collected using
0.3◦-wide x scans with a crystal-to-detector distance of 40 mm.
The diffraction frames were integrated using the SAINT package34
and corrected for absorption with SADABS.35
The software package WINGX was used in all cases for space
group determination, structure solution and refinement.36 The
structures were solved by Patterson interpretation and phase
expansion using DIRDIF.37 Isotropic least-squares refinement on
F2 using SHELXL97 was performed.38 For all the complexes,
during the final stages all non-hydrogen atoms were refined
with anisotropic displacement parameters. The H atoms were
geometrically located and their coordinates refined riding on their
parent atoms. The maximum residual electron density is located
near to the disordered CH2Cl2 molecules for 9 and near to heavier
atoms for the rest of structures reported. The function minimized
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=
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=
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◦
1
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5604 | Dalton Trans., 2006, 5593–5604
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