Synthesis and chemistry of diphenyl-2-pyridyIphosphine complexes of palladium(o). X-Ray characterisation of Pd(Ph2Ppy)2-(η2-DMAD) and fra/w-Pd(Ph2Ppy)2(PhC=CH2)(CF 3CO2)

Article abstract of DOI:10.1039/a908050c

The zerovalent complexes Pd(Ph₂Ppy)₃1 and Pd(Ph₂Ppy)₂(dba) 2, where Ph₂Ppy is diphenyI-2-pyridylphosphine and dba = /;ww, /ra-dibenzylideneacetone, have been synthesized and characterised. Reactions of 1 with alkynes have been studied and the dimethyl acetylenedicarboxylate complex Pd(Ph₂Ppy)₂(η²-DMAD) 3, where DMAD is dimethyl acetylenedicarboxylate, isolated and structurally characterised. The complexes /ra;w-Pd(Ph₂Ppy)₂(PhO=CH₂)X, X = CF₃CO₂^- 4 or Cl^- 5, and //w;s-Pd(Ph₂Ppy)₂{CO(CH₃)C=CH₂}Cl 6 result from oxidative addition of phenylacetylene/CF₃CO₂H, phenylacetylene/Et₃NHCl and methacryloyl chloride respectively to 1, and the crystal structure of 4 is presented. The alkenyl ligand is bound to palladium through the a carbon in 4. Insertions into the M-C bond of the vinyl complexes have been studied. No isolable insertion product is obtained with carbon monoxide although the complex is active for the catalytic alkoxycarbonylation of phenylacetylene to 2-phenylpropenoate. Propadiene inserts into the Pd-C bond in 4 to give the cationic rc-allyl complex [Pd(Ph₂Ppy)₂{η³-C₃H ₄C(Ph)=CH₂}][CF₃CO₂] 7. The complex Pd(Ph₂Ppy)₃ is found to catalyse the vinylation of Ph2Ppy to the corresponding 2-propenylphosphonium trifluoromethanesulfonate. The Royal Society of Chemistry 2000.

Full text of DOI:10.1039/a908050c

View Article Online / Journal Homepage / Table of Contents for this issue
Synthesis and chemistry of diphenyl-2-pyridylphosphine complexes
of palladium(0). X-Ray characterisation of Pd(Ph2Ppy)2-
(ꢀ2-DMAD) and trans-Pd(Ph Ppy) (PhC᎐CH )(CF CO )
᎐
2
2
2
3
2
Athanasia Dervisi,a Peter G. Edwards,*a Paul D. Newmana and Robert P. Toozeb
a Department of Chemistry, Cardiff University, PO Box 912, Cardiff, UK CF10 3TB.
E-mail: edwardspg@cardiff.ac.uk
b INEOS Acrylics, PO Box 90, Wilton Centre, Middlesbrough, Cleveland, UK TS90 8JE
Received 6th October 1999, Accepted 17th December 1999
The zerovalent complexes Pd(Ph2Ppy)3 1 and Pd(Ph2Ppy)2(dba) 2, where Ph2Ppy is diphenyl-2-pyridylphosphine and
dba = trans,trans-dibenzylideneacetone, have been synthesized and characterised. Reactions of 1 with alkynes have
been studied and the dimethyl acetylenedicarboxylate complex Pd(Ph2Ppy)2(η2-DMAD) 3, where DMAD is dimethyl
acetylenedicarboxylate, isolated and structurally characterised. The complexes trans-Pd(Ph Ppy) (PhC᎐CH )X,
᎐
2
2
2
X = CF3CO2Ϫ 4 or ClϪ 5, and trans-Pd(Ph Ppy) {CO(CH )C᎐CH }Cl 6 result from oxidative addition of phenyl-
᎐
2
2
3
2
acetylene/CF3CO2H, phenylacetylene/Et3NHCl and methacryloyl chloride respectively to 1, and the crystal structure
of 4 is presented. The alkenyl ligand is bound to palladium through the α carbon in 4. Insertions into the M–C bond
of the vinyl complexes have been studied. No isolable insertion product is obtained with carbon monoxide although
the complex is active for the catalytic alkoxycarbonylation of phenylacetylene to 2-phenylpropenoate. Propadiene
inserts into the Pd–C bond in 4 to give the cationic π-allyl complex [Pd(Ph Ppy) {η3-C H C(Ph)᎐CH }][CF CO ] 7.
᎐
2
2
3
4
2
3
2
The complex Pd(Ph2Ppy)3 is found to catalyse the vinylation of Ph2Ppy to the corresponding 2-propenyl-
phosphonium trifluoromethanesulfonate.
The complex Pd(Ph2Ppy)3, 1, is obtained by a number of
synthetic methods as outlined in Scheme 1. In our hands, the
Introduction
The insertion of unsaturated molecules like CO, alkenes,
alkynes and allenes into metal–carbon bonds is a very import-
ant step in many transition metal-catalysed processes.1
A
recently developed example, in which a palladium-based
catalyst is used, is the alkoxycarbonylation of alkynes.2 We and
others have recently prepared alkoxycarbonyl complexes and
commented on their likely role as intermediates in such catalytic
reactions where insertion of an unsaturated hydrocarbon into
the M–C(O)OR bond and subsequent protonolysis give a vinyl
ester.3 An alternative pathway involves the oxidative addition of
HX to a palladium(0) complex to give a metal hydride which
inserts the alkyne to produce a palladium alkenyl intermedi-
ate. Subsequent insertion of carbon monoxide generates a
palladium acyl species which is released by alcohol to give the
desired ester. The validity of this mechanism is further demon-
strated by the isolation of novel vinylic palladium complexes
from mixtures of Pd(Ph2Ppy)3 (Ph2Ppy = diphenyl-2-pyridyl-
phosphine), protic acids and phenylacetylene as presented in
this paper. The reactivity of these complexes towards insertion
of CO and propadiene has also been studied. A 2-propenyl
palladium intermediate was too unstable to be isolated,
although 2-propenylphosphonium salts have been character-
ised from these reactions as decomposition products.
Scheme 1
synthesis from K2PdCl4 proved to be the most convenient.6
When K2PdCl4 was treated with 3.5 equivalents of Ph2Ppy in
basic ethanol 1 was obtained as a yellow solid which is moder-
ately stable in air. In addition, Pd(Ph2Ppy)3 was obtained from
Pd2(η3-CH2CMeCH2)2Cl2 and a six-fold excess of ligand follow-
ing a modified literature procedure for the preparation of
Pd(PCy3)2,7 or from palladium acetate and an excess of Ph2Ppy.
In all cases, an excess of ligand was required in order to isolate
the desired complex in good yield. Unlike the smaller nickel(0)
centre8 and the related Pd(PPh3)4, no tetrakis complex, Pd(Ph2-
Ppy)4, was detected by NMR even when Ph2Ppy:Pd ratios of
>4:1 were employed. Although published spectroscopic data
for 1 are absent, its crystal structure has been reported
recently.9
Results and discussion
Zerovalent palladium complexes
The observation of a singlet (δ 21.7) in the 31P-{1H} NMR
spectrum of Pd(Ph2Ppy)3 over the temperature range Ϫ80 to
ϩ27 ЊC suggests that either no ligand dissociation occurs or
that it takes place rapidly even at low temperature. The complex
Pd(PPh3)4 has been shown to dissociate readily to the tris com-
plex, and there has been much debate as to whether there is
further dissociation to the bis(phosphine)palladium(0) com-
plex; Pd(L)2 species are well established for very bulky, electron
rich phosphines, e.g. Pd(PtBu3)2.10 The extent of ligand dissoci-
A common synthetic route to zerovalent platinum and pal-
ladium complexes with tertiary aromatic phosphines is by
reduction of a metal() phosphine species with hydrazine, alco-
holic KOH or an excess of phosphine. The zerovalent com-
plexes are, in general, less readily obtained as the σ basicity of
the phosphine increases.4 Syntheses using preformed metal(0)
species have since proved to be more versatile.5
DOI 10.1039/a908050c
J. Chem. Soc., Dalton Trans., 2000, 523–528
This journal is © The Royal Society of Chemistry 2000
523

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Fig. 1 Structure of Pd(Ph2Ppy)2(η2-DMAD) 3.
Table 1 Selected bond lengths (Å) and angles (Њ) in Pd(Ph2Ppy)2-
ation is believed to be dependent on the steric bulk and basicity
(η2-DMAD), 3
of the co-ordinated phosphine. The cone angle of Ph2Ppy is
very similar to that of PPh3 and, on a purely steric basis, a
tetrakis complex would be expected. Since Pd(Ph2Ppy)4 is not
detected, it appears that inherent electronic differences and/or
transient chelate formation through the ancillary nitrogen
donor(s) may stabilise the sixteen-electron tris complex to the
extent that no tetrakis species is observed. Some authors have
attributed the stability of co-ordinatively unsaturated species
such as 1 to the formation of stronger π bonds in trigonal or
linear metal complexes than in corresponding tetrahedral
forms.11
Pd(1)–P(1)
Pd(1)–P(2)
Pd(1)–C(1)
Pd(1)–C(4)
C(1)–C(4)
C(1)–C(2)
C(2)–O(1)
2.333(1)
2.305(1)
2.072(5)
2.023(5)
1.263(6)
1.462(7)
1.331(6)
C(2)–O(2)
O(1)–C(3)
C(4)–C(5)
C(5)–O(3)
C(5)–O(4)
O(3)–C(6)
1.221(5)
1.444(6)
1.440(6)
1.348(5)
1.220(6)
1.450(6)
P(2)–Pd(1)–P(1)
C(4)–Pd(1)–C(1)
103.98(5)
35.9(2)
C(2)–C(1)–C(4)
C(1)–C(4)–C(5)
146.5(5)
146.7(5)
The complex Pd(Ph2Ppy)2(dba), 2, is prepared by treating
Pd(dba)2 (dba = dibenzylideneacetone) with two equivalents of
Ph2Ppy. Replacement of one Ph2Ppy ligand in Pd(Ph2Ppy)3 by
dimethyl acetylenedicarboxylate (DMAD) gives the complex
Pd(Ph2Ppy)2(η2-DMAD), 3. Attempts to isolate Pd(Ph2Ppy)3-
(CO) or Pd(Ph2Ppy)2(η2-C2H4) by procedures known to be
successful for the PPh3 analogues failed, Pd(Ph2Ppy)3 being
recovered intact.
away from the metal so as to resemble the shape of the excited
state of free alkyne. This mode of alkyne co-ordination has
been rationalised in terms of electronic arguments where a
redistribution of the valence electrons occurs upon bonding to
the metal.12 Both these characteristics are evident in the crystal
structure of Pd(Ph2Ppy)2(η2-DMAD) as shown in Fig. 1. The
complex has monodentate phosphorus bonded Ph2Ppy ligands
and a propeller-like conformation of aromatic rings as does the
triphenylphosphine analogue.13 The M–C bond distances of
2.072(5) and 2.023(5) Å (Table 1) are similar to those reported
for the PPh3 complex. As expected, the shorter Pd–C(4) bond is
trans to the longer Pd–P(1) bond and vice versa. The methoxy-
Both methoxycarbonyl groups are equivalent in the 1H NMR
spectrum of Pd(Ph2Ppy)2(η2-DMAD) 3 giving rise to a singlet
at δ 3.21. The infrared spectrum shows a strong band at 1848
cmϪ1 assignable to ν(C᎐C). This value is very close to that
᎐
᎐
reported for Pd(PPh3)2(η2-DMAD) (1845, 1830 cmϪ1 shoulder),
and is only slightly higher than the typical value for an unco-
ordinated double bond indicating a bonding mode intermediate
between that of an alkyne and an alkene. Complexes M(PR3)2-
(RCCR) are stabilised by metals in low oxidation states bearing
electron donating ligands especially when the alkynes have
electron withdrawing substituents; such is the case in 3. Only
starting material is recovered in similar reactions with the
electron rich alkynes butyne, propyne and phenylacetylene.
Available crystallographic data for d10 metal complexes of the
type M(PR3)2(RCCR) show two common characteristics: (i) the
co-ordination around the metal is planar and (ii) the substitu-
ents on the alkyne ligand adopt a cis orientation projecting
carbonyl groups are mutually cis and point away from the metal
᎐
(C–C᎐C bond angles of 146Њ). The alkyne C–C bond length of
᎐
1.263(6) Å lies between the typical values for unco-ordinated
alkynes and alkenes, and is comparable with data reported for
other alkyne complexes which range from 1.279(2) to 1.32(9)
Å.14,15 The co-ordination around the metal is distorted square
planar with a P(1)–Pd(1)–P(2) bond angle of 103.98(5)Њ and a
C(1)–Pd–C(4) angle of 35.9(2)Њ. The dihedral angle between the
planes P(1)–Pd(1)–P(2) and C(1)–Pd–C(4) is smaller at 2.9(1)Њ
than that for the PPh3 analogue (9.7Њ). The planes of the
carboxylates are approximately 33Њ from collinearity with the
alkynic carbons with the plane of the methoxycarbonyl sub-
524
J. Chem. Soc., Dalton Trans., 2000, 523–528

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Table
2
Selected bond lengths (Å) and angles (Њ) for trans-
stituent on C(1) being nearly normal to the C(1)–Pd–C(4) plane
whereas that on C(4) is not; the two dihedral angles are 86.9(8)
and 64.2(2)Њ respectively. For the triphenylphosphine analogue,
Pd(PPh3)2(η2-DMAD), the corresponding values are 89.5(3)
and 41.6(3)Њ. As expected on the basis of the rationale proposed
by McGinetty,13 the shorter Pd–C bond is to the carbon of
the alkyne [C(1)] that has its substituent carboxylate plane
perpendicular to the co-ordination plane.
Pd(Ph2Ppy)2(PhC᎐CH2)(CF3CO2), 4
᎐
Pd(1)–P(1)
Pd(1)–C(20)
C(2)–C(21)
P(1)–C(6)
2.334(2)
1.998(6)
1.328(8)
1.824(8)
1.837(7)
1.820(7)
1.432(8)
1.360(9)
Pd(1)–P(2)
Pd(1)–O(1)
C(20)–C(22)
P(1)–C(12)
P(2)–C(34)
P(2)–C(28)
N(1)–C(1)
N(2)–C(35)
2.346(2)
2.136(5)
1.488(9)
1.829(7)
1.820(8)
1.825(7)
1.437(9)
1.39(1)
P(1)–C(1)
P(2)–C(39)
N(1)–C(5)
N(2)–C(34)
Oxidative additions to Pd(Ph2Ppy)3
Although no stable hydride complexes could be isolated from
the reactions of Pd(Ph2Ppy)3 with protic acids, σ-vinyl-
palladium derivatives were obtained from the reaction of
phenylacetylene with Pd(Ph2Ppy)3 in the presence of a proton
source (Scheme 2). When 1 was treated with equimolar
C(20)–Pd(1)–O(1)
O(1)–Pd(1)–P(1)
O(1)–Pd(1)–P(2)
C(21)–C(20)–Pd(1)
171.2(3)
92.3(2)
96.9(2)
121.8(6)
C(20)–Pd(1)–P(1)
C(20)–Pd(1)–P(2)
P(1)–Pd(1)–P(2)
86.8(2)
85.9(2)
164.56(8)
C(22)–C(20)–Pd(1)
115.4(5)
palladium atom couples with the two trans phosphorus atoms
to give a triplet, whereas the cis vinylic proton appears as a
singlet. The δ values differ appreciably from those reported for
the putative palladium alkenyl complex of Scrivanti et al.17 who
saw no 4JPH coupling even at low temperature. In the IR spectra
of 4 and 5 the carbon–carbon bond stretch is not observed. The
antisymmetric ν(CO) stretch of the carboxylate ligand in 4
appears at 1684.4 cmϪ1.
Scheme 2
Colourless crystals of complex 4 suitable for structural
determination were obtained by slow diffusion of light petrol-
eum into a solution of it in toluene. The molecular structure of
4 with the adopted numbering scheme is shown in Fig. 2.
Selected bond lengths and angles are summarised in Table 2.
Although a few σ-alkenyl palladium complexes have been struc-
turally characterised, 4 is a rare example containing a vinyl
group; a similarly co-ordinated vinylamine derivative has been
reported recently.18 In the complex each Ph2Ppy is co-ordinated
to the metal through the phosphorus atom and mutually trans.
The M–C distance of 1.998(6) Å is close to those of 2.051(2)
amounts of phenylacetylene and trifluoroacetic acid trans-
Pd(Ph Ppy) (PhC᎐CH )(CF CO ), 4, was isolated. Replacing
᎐
2
2
2
3
2
CF CO H with Et NHCl gave trans-Pd(Ph Ppy) (PhC᎐CH )-
᎐
3
2
3
2
2
2
Cl, 5. Possible polymerisation and/or phosphonium salt form-
ation were suppressed by adding the acid slowly at 0 ЊC. Hydro-
chloric acid was less suitable for the synthesis of 5 as a mixture
of products was obtained. No σ-vinyl complex was isolated
with propyne, the main product in this case being the phos-
phonium salt [Ph pyP{(CH )C᎐CH }][CF CO ]. Similarly,
᎐
2
3
2
3
2
efforts to form such palladium() vinyl species from the oxid-
ative addition of vinyl triflate to 1 or 2 gave [Ph2pyP{(CH3)-
and 2.004(12) Å reported for Pd(PMe ) [(CO CH )C᎐CH(CO -
᎐
3 2 2 3 2
CH3)][CCPh]19 and Pd(PMe ) [(tBuCC)C᎐C(tBu)(CCtBu)]Br,20
᎐
3
2
C᎐CH }][CF SO ] as the only isolable product. In the absence
respectively. The average M–P distance is typical for pal-
ladium() complexes (2.340(2) Å). The phosphine ligands are
compressed towards the vinyl group with P–Pd–C angles of
86.8(2) and 85.9(2)Њ respectively, the O–Pd–P angles being
92.3(2) and 96.9(2)Њ. The alkenyl group in square planar com-
plexes is generally perpendicular to the co-ordination plane
of the molecule; there is no exception in 4 where the dihedral
angle between the planes defined by the vinyl group and the
᎐
2
3
3
of a palladium species, no reaction is observed between Ph2Ppy
and vinyl triflate. It was found that the triflate salt is formed in
the presence of catalytic amounts of 1 or 2. The above observ-
ations suggest formation of an unstable palladium() vinyl tri-
flate that reductively eliminates to generate the phosphonium
triflate and a palladium(0) complex. A similar palladium cata-
lysed formation of [Ph P{(CH )C᎐CH }]ϩ has been reported by
᎐
3
3
2
Stang and co-workers.15 Although stable palladium 2-propenyl
complexes have not been isolated so far from addition of pro-
penyl triflate to a palladium(0) species, the analogous reaction
has been reported for Pt(PPh3)4 to give the more kinetically
robust platinum() propenyl complex.16
co-ordination plane is 85.99(19)Њ. The C᎐C bond lengths are
᎐
somewhat shorter than in the more conjugated derivatives
above.
The oxidative addition of methacryloyl chloride ClCO(CH3)-
C᎐CH to complex 1 gave a compound tentatively assigned
᎐
2
Literature examples of monosubstituted vinyl ligands
σ-bound to palladium through the α carbon (i.e. both vinylic
protons are on the unco-ordinated β carbon) are rare. Very
recently, Scrivanti et al.17 observed σ-alkenyl complexes of
this type by solution NMR of Pd(OAc)2–Ph2Ppy–CH3SO3H
(1:3:3) and phenylacetylene in C6D6 containing methanol.
However, they were unable to isolate and characterise fully any
‘stable’ σ-vinyl complexes. Intimate details of the mechanism of
formation of 4 and 5 remain obscure, although displacement of
one Ph2Ppy ligand by phenylacetylene prior to oxidative addi-
tion of HX seems unlikely as 1 has been shown to be unreactive
toward the alkyne alone.
as trans-Pd(Ph Ppy) {CO(CH )C᎐CH }Cl, 6. The complex
᎐
2 2 3 2
showed two vinylic resonances at δ 6.79 (broad) and 6.44 (t,
5JH,P = 5.5 Hz) in the 1H NMR with the methyl singlet at δ 1.93.
The antisymmetric ν(CO) stretch was observed at 1643.5 cmϪ1
in the infrared spectrum. However, reproducible analytical data
for the complex could not be obtained as it decomposed prior
to combustion, presumably by loss of the acyl ligand.
Although attempts to isolate an acyl complex by treating
Pd(Ph Ppy)(PhC᎐CH )(CF CO ) 4 with carbon monoxide
᎐
2
2
3
2
failed, the reactivity of the vinyl group towards CO suggested
the complex may be useful in catalytic applications. Therefore
methanol and phenylacetylene were introduced in order to test
whether complex 4 would catalyse the alkoxycarbonylation of
terminal alkynes in the presence of carbon monoxide. Complex
4, methanol and phenylacetylene in a 1:10:6 ratio were com-
bined in a glass pressure vessel and carbon monoxide intro-
Sharp singlets at δ 17.1 and 16.5 are observed in the 31P-{1H}
NMR spectra of complexes 4 and 5, respectively. The 13C
spectra show pertinent Ph2Ppy resonances (ipso carbons) to be
split into triplets, thus a trans conformation is assigned, in
accord with the crystal structure of 4 (see below). The α vinylic
carbon appears at δ 153.6 for complex 4 (δ 159.9, 5) and the
β carbon at δ 117.2 (116.5, 5); neither vinylic carbon is coupled
1
duced at 30 psi and the mixture left for one day. A H NMR
spectrum of the solution showed complete conversion of
phenylacetylene into methyl 2-phenylpropenoate, as evidenced
by signals at δ 5.65 (s), 6.35 (s) and 3.45 (s) (C6D6). In the
1
to phosphorus. In the H NMR the vinylic proton trans to the
J. Chem. Soc., Dalton Trans., 2000, 523–528
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Fig. 2 Structure of trans-Pd(Ph2Ppy)2(PhC᎐CH2)(CF3CO2) 4.
᎐
31P-{1H} spectrum two main signals were observed at δ 17.6 and
1H NMR spectrum the syn and anti protons (with respect to the
0.5 assignable to oxidised ligand Ph2P(O)py and a palladium()
Ph2Ppy dimer.21 An orange solid was precipitated from the
reaction solution on addition of light petroleum. GC-MS
and NMR analysis of the supernatant solution confirmed for-
mation of methyl 2-phenylpropenoate (m/z 162) and phosphine
oxide (m/z 280). The isolated solid gave two broad vinylic
resonances at δ 6.45 and 5.67 in the 1H NMR spectrum, shifted
downfield in comparison with the vinylic resonances of
complex 4 {δ 5.11 (t, 5.5 Hz), δ 4.74 (s)}, indicating introduction
of an electron withdrawing group. Acquisition of further
spectroscopic data for the complex was not possible since
decomposition occurred during its purification.
palladium centre) give two broad signals and the vinylic protons
two separate singlets. The NMR data compare well with
those of the structurally characterised analogue [Pd(Ph2Ppy)2-
{η3-C H C(CH )᎐CH }][CF CO ] (ref. 3) confirming the
᎐
3
4
3
2
3
2
assignment of 7.
Conclusion
The zerovalent palladium complex Pd(Ph2Ppy)3 has been
shown to undergo oxidative addition of phenylacetylene–HX
mixtures to give stable σ-vinyl complexes of the type trans-
Pd(Ph Ppy) (PhC᎐CH )X where the alkenyl ligand is bound
᎐
2
2
2
through the α-carbon. This chemistry does not extend to
propyne–HX mixtures where only phosphonium salts of the
Insertions into the palladium–carbon bond of the vinyl
complexes were further investigated by treating complex 4
with propadiene. The cationic π-allyl complex [Pd(Ph2Ppy)2{η3-
type [Ph Ppy{(CH )C᎐CH }]X are isolated. The Pd–vinyl bond
᎐
2
3
2
is not stable to CO, but simple insertion (acyl) products are not
isolated from these reactions only ill characterised decom-
position products. Oxidative addition of methacryloyl chloride
C H C(Ph)᎐CH }][CF CO ], 7, was formed from insertion of
᎐
3
4
2
3
2
allene into the metal–carbon bond. In accord with similar
reported reactions, insertion takes place via migration of the R
group to the central most electrophilic carbon atom of allene22
(Scheme 3). Known reactions of this type involve insertion of
to trans-Pd(Ph Ppy) (PhC᎐CH )X does give a thermally un-
᎐
2
2
2
stable acyl species. The Pd-vinyl complexes act as catalysts for
the selective formation of methyl 2-phenylpropenoate from
methanol and phenylacetylene.
Experimental
All reactions were performed under a nitrogen atmosphere
using standard Schlenk techniques. Solvents were freshly dis-
tilled from sodium–benzophenone under nitrogen, except for
toluene (sodium), methanol (calcium hydride) and dichloro-
methane (calcium hydride). Light petroleum had bp 40–60 ЊC.
All other chemicals were used as supplied (Aldrich) without
further purification. The 1H and 13C NMR spectra were
recorded on a Bruker DPX400 spectrometer operating at
400.13 and 100 MHz, respectively, 31P NMR spectra using
a JEOL FX90Q spectrometer at 36.2 MHz and referenced to
Scheme 3
allene into a metal–halide, –alkyl or –acyl bond. This is the first
example of insertion into a palladium–vinylic bond. The 31P
spectrum of 7 reveals a singlet at ambient temperature. In the
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J. Chem. Soc., Dalton Trans., 2000, 523–528

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85% H3PO4 (δ 0). Infrared spectra were recorded as KBr
discs on a Nicolet 510 FT-IR spectrophotometer. Micro-
analyses were obtained within the department. The compounds
[Pd(η3-CH2CMeCH2)Cl]2,23 Pd2(dba)3,24 2-propenyl triflate 25
and propadiene26 were prepared by literature procedures.
1131.2s, ν(Ph2Ppy) 1437.5, 693.8, 521.9. 31P-{1H} NMR
(CDCl3): δ 17.1. H NMR (C6D6): δ 8.25 (d, 2 H, py), 7.74
1
(br, 8 H), 7.43 (d, 2 H, py), 7.21 (d, 2 H, py), 6.88 (m, 12 H), 6.58
4
(m, 3 H), 6.50 (t, 2 H), 5.11 (t, JH,P = 5.5 Hz, H C᎐CPh) and
᎐
2
4.74 (s, H C᎐CPh). 13C-{1H} NMR (C6D6–CD3CN): δ 153.6
᎐
2
(s, Cα) and 117.2 (s, Cβ).
Preparations
trans-Pd(Ph Ppy) (PhC᎐CH )Cl 5. To a solution of Pd(Ph -
᎐
2
2
2
2
Pd(Ph2Ppy)3 1. To a suspension of [Pd(η3-CH2CMeCH2)Cl]2
(0.2 g, 0.51 mmol) in methanol (8 ml) at Ϫ5 ЊC was added a
cooled solution of Ph2Ppy (0.8 g, 3.04 mmol) in methanol (7
ml) over 2 min. A bright yellow solid was formed quickly after
completion of the addition. The mixture was stirred for two
hours and Et2O (15 ml) added to complete the precipitation.
The yellow solid was washed twice with diethyl ether and dried
in vacuo. Yield = 0.75 g (82%). Calc. for C51H42N3P3Pd: C, 68.4;
H, 4.7; N, 4.7. Found: C, 68.3; H, 4.9; N, 4.8%. 31P-{1H} NMR
Ppy)3 (0.4 g, 0.45 mmol) and phenylacetylene (0.1 ml, 0.90
mmol) in toluene (45 ml) was added a solution of triethyl-
ammonium chloride (0.06 g, 0.45 mmol) in methanol (8 ml)
over 5 min. An immediate change from yellow to red occurred
on addition of the Et3NHCl. After stirring (3 h) the solvent was
evaporated to afford a yellow solid. Yield = 0.22 g (64%). Calc.
for C42H35ClN2P2Pd: C, 65.4; H, 4.6; N, 3.6. Found: C, 64.9;
1
H, 4.6; N, 3.3%. 31P-{1H} NMR (CDCl3): δ 16.5. H NMR
(CDCl3): δ 8.57 (d, 2 H, py), 7.84 (d, 2 H, py), 7.63 (br, 8 H, Ph),
7.45 (t, 2 H, py), 7.2–6.9 (m, 10 H, Ph), 6.73 (m, 2 H, PhCCH2),
1
(C6D6): δ 21.7. H NMR (C6D6): δ (d, py), 7.60 (dd, py), 6.88
(t, py), 7.75 (m, 4 H, Ph), 7.10 (m, 6 H, Ph), 6.55 (dd, py).
13C-{1H} NMR (C6D6): δ 164.68 (d, J 26, py, ipso-C), 149.60
(d, J 11, C), 138.65 (d, J 14, CH), 134.71 (d, J 18, CH), 134.01
(d, J 18, CH), 132.22 (d, J 9, CH), 131.30 (s, CH), 128.90 (d,
J 24 Hz, CH) and 125.40 (s, CH). The complex was also pre-
pared by adapting the known procedure for the formation of
Pt(Ph2Ppy)3.
6.68 (m, 3 H, PhCCH2), 5.06 (t, 4JH,P = 6.1 Hz, trans-HC᎐CPh)
᎐
and 4.72 (s, cis-HC᎐CPh); (C D ) 5.59 (t, 4JH,P = 5.9 Hz, trans-
᎐
6
6
HC᎐CPh) and 5.32 (s, cis-HC᎐CPh). 13C-{1H} NMR (CDCl3):
᎐
᎐
δ 159.9 (s, Cα) and 116.5 (s, Cβ).
[Ph pyP{(CH )C᎐CH }][CF CO ]. To a cooled solution of
᎐
2
3
2
3
2
Pd(Ph2Ppy)3 (0.33 g, 0.37 mmol) in THF (30 ml) was added
slowly CF3CO2H (0.25 ml, 0.33 mmol). Propyne (≈1 g) was
then bubbled through the solution. The resultant red solution
was allowed to warm slowly to room temperature and stirred
for five hours. The solvent was removed in vacuo to afford an
oily residue that was triturated with Et2O to give a yellow
solid. Yield = 0.10 g (72%). Calc. for C22H19F3NO2P: C, 63.3;
H, 4.6; N, 3.4. Found: C, 63.2; H, 4.7; N, 3.3%. 31P-{1H}
Pd(Ph2Ppy)2(dba) 2. To a solution of Pd(dba)2 (0.5 g, 0.54
mmol) in toluene (40 ml) was added, over 3 min, a solution of
Ph2Ppy (0.57 g, 2.16 mmol) in toluene (20 ml). After stirring
(3 h) the dark solution was filtered through Celite and reduced
to half volume. Light petroleum (60 ml) was added to precipi-
tate the compound as a yellow solid. The product was recrystal-
lised by diffusion of light petroleum into a solution of 2 in
toluene. Yield 0.8 g (85%). Calc. for C51H42N2OP2Pd: C, 70.6;
H, 4.9; N, 3.2. Found: C, 70.2; H, 4.8; N, 3.6%. 31P-{1H} NMR
(C6D6): δ 24.7. 1H NMR (C6D6): δ 8.36 (m, 2 H, py), 7.75–7.50
(br, 10 H, dba), 7.25–7.04 (m, 20 H, Ph), 6.88 (t, 4 H, py) and
6.49 (m, 2 H, py).
1
NMR (CDCl3): δ 15.2. H NMR (CDCl3): δ 8.93 (d, 1 H,
py), 8.13 (m, 1 H, py), 7.88 (t, 1 H, py), 7.8–7.6 (m, 11 H),
3
3
6.59 (d, JH,P = 47.7, CH C᎐CH ), 5.84 (d, JH,P = 22.5,
᎐
3
2
3
CH C᎐CH ) and 2.12 (d, JH,P = 13.9 Hz, CH C᎐CH ).
᎐
᎐
3
2
3
2
Attempts to isolate a σ-vinyl palladium() species from the
oxidative addition of Cl(CH )C᎐CH to either complex 1 or 2
᎐
3
2
failed.
Pd(Ph2Ppy)2(ꢀ2-DMAD) 3. Dimethyl acetylenedicarboxylate
(0.2 ml) in Et2O (1:10 v/v) was added dropwise to a suspension
of Pd(Ph2Ppy)3 (0.2 g, 0.22 mmol) in Et2O (40 ml) to give an
immediate white precipitate. After a few minutes of stirring the
supernatant was decanted and the compound dried under a
stream of nitrogen. Yield 0.13 g (76%). Calc. for C40H34N2O4-
P2Pd: C, 62.0; H, 4.4; N, 3.6. Found: C, 61.7; H, 4.6; N, 3.4%.
[Ph pyP{(CH )C᎐CH }][CF SO ]. To a solution of Ph Ppy
᎐
2
3
2
3
3
2
(1.03 g, 3.91 mmol) in Et2O (60 ml) was added vinyl triflate
(0.70 g, 3.66 mmol) and Pd(Ph2Ppy)2(dba) (0.33 g, 0.37 mmol).
The resultant red solution was stirred overnight. The precipi-
tated white solid was collected and recrystallised from THF–
light petroleum. Yield = 1.16 g (70%). Calc. for C21H19F3NO3-
PS: C, 52.0; H, 4.0; N, 2.9. Found: C, 51.8; H, 4.1; N, 2.9%.
31P-{1H} NMR (CDCl3): δ 17.1. 1H NMR (CDCl3): δ 6.65 (dd,
Ϫ1
᎐
IR (KBr disks, cm ): ν(DMAD) ν(C᎐C) 1848.0s, 1728.7s,
᎐
νasym(CO) 1689.0vs, 1218.4vs, 1040.35s, ν(Ph2Ppy) 1571.3s,
1434.6vs, 1097.5s, 747.76s, 695.3vs and 514.05vs. 31P-{1H}
NMR (C6D6): δ 29.6. 1H NMR (C6D6): δ 8.28 (d, 2 H, py), 7.83
(m, 4 H, Ph), 7.76 (t, 2 H, py), 7.04 (m, 6 H, Ph), 6.90 (dt, 2 H,
py), 6.46 (dt, 2 H, py) and 3.21 (s, 3 H, DMAD). 13C-{1H}
NMR (C6D6): δ 187.0 (s, CO2CH3), 162.78 (t, J 49 Hz, py,
ipso-C), 148.27 (t, J 25, C), 134.38 (d, J 24, CH), 133.38 (d, J 31,
3JH,P = 47.7, JH,H = 1.2, CH C᎐CH ), 5.89 (d, JH,P = 22.5,
2
3
᎐
3
2
3
CH C᎐CH ) and 2.17 (d, J = 13.9 Hz, CH C᎐CH ). This
᎐
᎐
3
2
H,P
3
2
reaction can also be performed catalytically with complex 1
(10%) to give 70% yield.
trans-Pd(Ph Ppy) {CO(CH )C᎐CH }Cl 6. The complex
᎐
2
2
3
2
2
᎐
CH), 124.27 (s, CH), 111.9 (d, JC,P = 263.3 Hz, C᎐C), 49.92
Pd(Ph2Ppy)3 (0.20 g, 0.22 mmol) was dissolved in toluene (25
ml) and a solution of methacryloyl chloride (30 µl, 0.4 mmol)
in toluene (2 ml) added via syringe. The flask was sealed and
the yellow solution left to stir overnight with heating at 75 ЊC.
The precipitation of a white solid that occurred during the
reaction was completed by addition of light petroleum (25 ml).
Recrystallisation from CH2Cl2–toluene–light petroleum gave
110 mg (67%) of 6 as yellow microcrystals. No microanalysis
was possible as the complex decomposed prior to combustion.
IR (KBr disks, cmϪ1): ν(CO) 1643.5m, 1200.0s, ν(Ph2Ppy)
᎐
(s, CO2CH3).
trans-Pd(Ph Ppy) (PhC᎐CH )(CF CO ) 4. The complex
᎐
2
2
2
3
2
Pd(Ph2Ppy)3 (0.14 g, 0.16 mmol) was dissolved in toluene (25
ml) and CF3CO2H (0.3 ml) added causing an immediate change
from yellow to red. Phenylacetylene (0.1 ml) was introduced
and the solution stirred for 3 h, then filtered through Celite and
the solvent removed to afford a red oil. Addition of CH2Cl2 (6
ml) gave a red solution and white precipitate. The precipitate
was collected and washed with light petroleum (20 ml). The
product was obtained as colourless crystals by diffusion of light
petroleum into a solution of the complex in a 1:1 mixture of
toluene and acetonitrile. Yield 0.11 g (85%). Calc. for C44H35-
F3N2O2P2Pd: C, 63.3; H ,4.0; N 3.2. Found: C, 62.9; H, 4.0;
N, 3.2%. IR (KBr disks, cmϪ1): ν(CF3CO2) 1684.4vs, 1200.0,
1435.1, 693.4, 521.2. 31P-{1H} NMR (CDCl3): δ 19.2. 1H NMR
(CDCl ): δ 6.79 (br, C᎐CH ), 6.44 (t, J = 5.5 Hz, H C᎐C)
and 1.93 (s, C᎐CCH ). It is noteworthy that no acyl complexes
could be isolated from CO insertion reactions into the Pd–vinyl
bond; only decomposition to unidentified species was observed
when such reactions were attempted.
5
᎐
᎐
2
3
2
H,P
᎐
3
J. Chem. Soc., Dalton Trans., 2000, 523–528
527

View Article Online
Table 3 Crystal data for Pd(Ph2Ppy)2(η2-DMAD) 3 and trans-
See http://www.rsc.org/suppdata/dt/a9/a908050c/ for crystal-
lographic files in .cif format.
Pd(Ph2Ppy)2(PhC᎐CH2)(CF3CO2) 4
᎐
3
4
Acknowledgements
Empirical formula
Formula weight
T/K
Crystal system
C40H34N2O4P2Pd
777.05
150(2)
Monoclinic
P21/n
C44H35F3N2O2P2Pd
849.08
293(2)
We thank ICI Acrylics for funding (A. D., P. D. N.) and the
Departmental Crystallography Service, Dr D. E. Hibbs, Dr
S. J. Coles and Professor M. B. Hursthouse, for the crystallo-
graphic data.
Triclinic
¯
Space group
P1
a/Å
b/Å
c/Å
α/Њ
12.8446(6)
14.596(4)
18.6187(14)
11.837(2)
13.342(7)
13.729(3)
95.32(7)
103.28(2)
110.28(3)
1943.8(12)
2
References
1 A. Yamamoto, Organotransition Metal Chemistry, Wiley, New
York, 1986; J. P. Collman, L. S. Hegedus and R. G. Finke, Principles
and Applications of Organotransition Metal Chemistry, University
Science Books, Mill Valley, CA, 1987; B. Cazes, Pure Appl. Chem.,
1990, 62, 1867.
β/Њ
97.777(13)
γ/Њ
V/Å3
3458.5(11)
4
0.674
Z
µ/mmϪ1
0.614
2 E. Drent, P. Arnoldy and P. Budzelaar, J. Organomet. Chem., 1993,
455, 247.
3 A. Dervisi, P. G. Edwards, P. D. Newman, R. P. Tooze, S. J. Coles
and M. B. Hursthouse, J. Chem. Soc., Dalton Trans., 1999, 1113 and
refs. therein.
Reflections collected
Independent reflections
Rint
Final R1, wR2 [I > 2σ(I)]
(all data)
12630
5163
0.0906
0.0413, 0.0814
0.0726, 0.1071
7136
5014
0.0827
0.0397, 0.0587
0.0740, 0.1120
4 R. Ugo, Coord. Chem. Rev., 1968, 3, 319.
5 A. Scrivanti, A. Berton, L. Toniolo and C. Bottechi, J. Organomet.
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6 F. R. Hartley, Chem. Rev., Sect. A, 1976, 6, 119.
7 W. Kuran and A. Musco, Inorg. Chim. Acta, 1975, 12, 187.
8 I. R. Baird, M. B. Smith and B. R. James, Inorg. Chim. Acta, 1995,
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9 C. H. Su and M. Y. Chiang, J. Chin. Chem. Soc., 1997, 44, 539.
10 B. E. Mann and A. Musco, J. Chem. Soc., Dalton Trans., 1975, 1673.
11 L. Malatesta, R. Ugo and F Cariati, Adv. Chem. Ser., 1966, 62, 318
and refs. therein.
12 E. O. Greaves, C. J. L. Lock and P. M. Maitlis, Can. J. Chem., 1968,
46, 3879.
13 J. A. McGinetty, J. Chem. Soc., Dalton Trans., 1974, 1038.
14 R. S. Dickson and J. A. Ibers, J. Organomet. Chem., 1972, 36, 191
and refs. therein.
15 R. J. Hinkle, P. J. Stang and M. H. Kowalski, J. Org. Chem., 1990,
55, 5033.
16 M. H. Kowalski and P. J. Stang, Organometallics, 1986, 5, 2392.
17 A. Scrivanti, V. Beghetto, E. Campagna, M. Zanato and U.
Matteoli, Organometallics, 1998, 17, 630.
18 J. G. P. Delis, P. G. Aubel, K. Vrieze, P. W. N. M. van Leeuwen,
N. Veldman and A. L. Spek, Organometallics, 1997, 16, 4150.
19 T. Yasuda, Y. Kai, N. Tasuoka and N. Kasai, Bull. Chem. Soc. Jpn.,
1977, 50, 2888.
[Pd(Ph Ppy) {ꢀ3-C H C(Ph)᎐CH }][CF CO ] 7. The com-
᎐
2
2
3
4
2
3
2
plex Pd(Ph Ppy) (PhC᎐CH )(CF CO ) (0.2 g, 0.24 mmol) was
᎐
2
2
2
3
2
dissolved in toluene (30 ml) and propadiene (0.5 g, 12.5 mmol)
passed through the solution. After 18 h the solvent was evapor-
ated and the red solid washed with hexane. Yield = 0.17 g
(68%). Calc. for C47H38F3N2O2P2Pd: C, 63.5; H, 4.3; N, 3.2.
Found: C, 63.6; H, 4.3; N, 3.3%. 31P-{1H} NMR (CDCl3):
δ 22.8. 1H NMR (CDCl ): δ 5.39 (br s, 1 H, C᎐CH ), 5.32 (br s,
᎐
3
2
1 H, C᎐CH ), 3.83 (br s, 2 H, allyl Hsyn) and 3.45 (br s, 2 H, allyl
᎐
2
Hanti).
Methoxycarbonylation of phenylacetylene
The complex Pd(Ph Ppy) (PhC᎐CH )(CF CO ) (30 mg, 0.03
᎐
2
2
2
3
2
mmol), methanol (12 µl, 0.3 mmol) and phenylacetylene (20 µl,
0.2 mmol) were combined in C6D6 (2 ml) and 30 psi of CO
1
pressure applied. The solution was stirred for one day and H
and 31P-{1H} NMR spectra recorded. Light petroleum was
added for precipitation of solid products and a sample from the
supernatant solution was analysed by GC-MS (m/z 162, methyl
2-phenylpropenoate) and NMR; the 1H and 13C spectra were in
agreement with those reported.27
20 H. F. Klein, B. Zettel, U. Florke and H. J. Haupt, Chem. Ber., 1992,
125, 9.
21 A. Dervisi, P. G. Edwards, P. D. Newman, R. P. Tooze, S. J. Coles
and M. B. Hursthouse, J. Chem. Soc., Dalton Trans., 1998, 3771 and
refs. therein.
Crystallography
22 J. H. Groen, C. J. Elsevier, K. Vrieze, W. J. J. Smeets and A. L. Spek,
Organometallics, 1996, 15, 3445 and refs. therein.
23 W. T. Dent, R. Long and A. J. Wilkinson, J. Chem. Soc., 1964, 1585.
24 M. F. Rettig and P. M. Maitlis, Inorg. Synth., 1977, 17, 134.
25 P. J. Stang, M. Hanack and L. R. Subramanian, Synthesis, 1982, 85.
26 H. N. Cripps and E. F. Kiefer, Org. Synth., 1962, 42, 12.
27 D. Haigh, L. J. Jefcott, K. Magee and H. McNab, J. Chem. Soc.,
Perkin Trans. 1, 1996, 2895; C. A. Busacca, J. Swestock, R. E.
Johnson, T. R. Bailey, L. Muszla and C. A. Rodger, J. Org. Chem.,
1994, 59, 7553.
28 J. W. Pflugrath and A. Messerschmidt. MADNES, version 11,
September 1989, Delft Instruments, Delft, 1989.
29 S. R. Drake, M. B. Hursthouse, K. M. A. Malik and S. A. S. Miller,
Inorg. Chem., 1993, 32, 4653.
30 ABSMAD, Program for FAST data processing, A. I. Karaulov,
University of Wales, Cardiff, 1992.
31 G. M. Sheldrick, Acta Crystallogr., Sect. A, 1990, 46, 467.
32 G. M. Sheldrick, University of Gottingen, 1993.
33 N. P. C. Walker and D. Stuart, Acta Crystallogr., Sect. A, 1983, 39,
158; adapted for FAST geometry by A. Karaulov, University of
Wales, Cardiff, 1991.
Single crystals of complexes 3 and 4 suitable for X-ray diffrac-
tion analysis were mounted on glass fibres and data were
recorded on a Delft Instruments FAST TV area detector at the
window of a rotating anode generator with a molybdenum
target [λ(Mo-Kα) = 0.71069 Å], driven by MADNES28 soft-
ware using a procedure previously described.29 Data reduction
was performed using the program ABSMAD.30
The structures were solved by heavy atom methods
(SHELXS)31 and then subjected to full-matrix least squares
2
refinement based on Fo (SHELXL 93).32 Non-hydrogen
atoms were refined anisotropically with all hydrogens fixed in
idealised positions and isotropic thermal parameters tied to
the value of the parent atom. The nitrogen atoms in the pyr-
idyl rings were distinguished from the carbons by inspection of
peak heights in the difference map, bond lengths and consider-
ation of thermal ellipsoids. Data were corrected for absorption
effects using the program DIFABS.33 Diagrams were drawn
with SNOOPI.34 The crystal data are summarised in Table 3.
CCDC reference number 186/1776.
34 K. Davies and K. C. Prout, University of Oxford, 1993.
Paper a908050c
528
J. Chem. Soc., Dalton Trans., 2000, 523–528