Condensation reactions of monomeric hydroxo palladium complexes with active methyl and methylene compounds

Article abstract of DOI:10.1039/b409942g

Heating a suspension of the monomeric hydroxo palladium complex of the type [Pd(N-N)(C₆F₅)(OH)] (N-N = bipy, Me₂bipy, phen or tmeda) in methylketone (acetone or methylisobutylketone) under reflux affords the corresponding ketonyl palladium complex [Pd(N-N)(C₆F ₅)(CH₂COR)]. On the other hand, the reaction of the hydroxo palladium complexes [Pd(N-N)(C₆F₅)(OH)] (N-N = bipy, phen or tmeda) with diethylmalonate or malononitrile yields the C-bound enolate palladium complexes [Pd(N-N)(CHX₂)(C₆F ₅)] (X = CO₂Et or CN), and the reaction of [Pd(N-N)(C ₆F₅)(OH)] (N-N = bipy or phen) with nitromethane gives the nitromethyl palladium complexes [Pd(N-N)(CH₂NO₂)(C ₆F₅)]. [Pd(tmeda)(C₆F₅)(OH)] catalyses the cyclotrimerization of malononitrile. The crystal structures of [Pd(bipy)(C₆F₅)(CH₂COMe)]·1/2Me ₂CO, [Pd(tmeda)(C₆F₅){CH(CO₂Et) ₂}], [Pd(tmeda)(C₆F₅){CH(CN)₂}] and [Pd(tmeda)(C₆F₅)(CH₂NO₂)]·1/ 2CH₂Cl₂ have been established by X-ray diffraction.

Full text of DOI:10.1039/b409942g

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F U L L P A P E R
Condensation reactions of monomeric hydroxo palladium complexes
with active methyl and methylene compounds†
José Ruiz,*a M. Teresa Martínez,a Venancio Rodríguez,a Gregorio López,*a José Pérez,b
Penny A. Chalonerc and Peter B. Hitchcockc
a
Departamento de Química Inorgánica, Universidad de Murcia, E-30071 Murcia, Spain.
E-mail: jruiz@um.es; gll@um.es; Fax: +34968364148
Departamento de Ingeniería Minera, Geológica y Cartográfica. Area de Química Inorgánica,
b
Universidad Politécnica de Cartagena, E-30203 Cartagena, Spain
Chemistry Department, School of Life Sciences, University of Sussex, Brighton, UK BN1 9QJ
c
Received 30th June 2004, Accepted 15th September 2004
First published as an Advance Article on the web 29th September 2004
Heating a suspension of the monomeric hydroxo palladium complex of the type [Pd(N–N)(C6F5)(OH)]
(N–N = bipy, Me2bipy, phen or tmeda) in methylketone (acetone or methylisobutylketone) under reflux affords
the corresponding ketonyl palladium complex [Pd(N–N)(C6F5)(CH2COR)]. On the other hand, the reaction of
the hydroxo palladium complexes [Pd(N–N)(C6F5)(OH)] (N–N = bipy, phen or tmeda) with diethylmalonate or
malononitrile yields the C-bound enolate palladium complexes [Pd(N–N)(CHX2)(C6F5)] (X = CO2Et or CN),
and the reaction of [Pd(N–N)(C6F5)(OH)] (N–N = bipy or phen) with nitromethane gives the nitromethyl pal-
ladium complexes [Pd(N–N)(CH2NO2)(C6F5)]. [Pd(tmeda)(C6F5)(OH)] catalyses the cyclotrimerization of malo-
nonitrile. The crystal structures of [Pd(bipy)(C6F5)(CH2COMe)]·ꢀMe2CO, [Pd(tmeda)(C6F5){CH(CO2Et)2}],
[Pd(tmeda)(C6F5){CH(CN)2}] and [Pd(tmeda)(C6F5)(CH2NO2)]·ꢀCH2Cl2 have been established by X-ray diffraction.
Pd(l-CH2C(R)O)2Pd-type complexes with a monodentate
Introduction
ligand afforded the acetonyl complexes >Pd{CH2C(O)R}L.
Palladium has been widely used for assisting the reactivity
These acetonyl complexes should directly be formed by using
of enolate species,1–9 but the number of isolated and well-
a monohydroxo complex as precursor. Recently abstraction of
characterized complexes is rather limited. Oxygen-bound
the a-proton of a carbonyl compound by a hydroxo palladium
enolates (type A in Scheme 1) are common for early transition
complex has been reported to be a key for the synthetically use-
metals, but, as expected for a late transition metal, enolates pre-
ful enantioselective catalysis.29 We have recently described30,31
fer to coordinate to palladium either through the carbon atom
the synthesis of monomeric hydroxo palladium(II) complexes
10–18
(type B; Scheme 1)
or in the chelating g3-oxoallyl fashion
of the type [Pd(N–N)(C6F5)(OH)] (N–N = bipy, Me2bipy, phen
or tmeda) and their reactions with CO or SO2 in methanol at
room temperature to yield the corresponding methoxy carbonyl
or alkylsulfito complexes [Pd(N–N)(C6F5)(X)] (X = CO2Me or
SO3Me)]. The reactions of the monomeric hydroxo complexes
[Pd(N–N)(C6F5)(OH)] with some active methyl (CH3COR or
CH3NO2) and methylene (CH2X2) (X = CO2Et or CN) com-
pounds have now been examined and we report herein the first
crystal structure of a dicyanomethanide–palladium complex
(3D Search using the Cambridge Structural Database, CSD
version 5.25, April 2004 release), together with the crystal struc-
tures of an acetonyl–palladium complex, a nitromethyl–palla-
dium complex, and a dimethyl malonate–palladium complex.
(type C; Scheme 1).19–22 Bridging C,O–enolates have also been
isolated.11–13,23 O-bound and C-bound enolates may be alterna-
tively named as enolate and ketonyl complexes, respectively.
Results and discussion
Ketonyl palladium complexes 1–6
On heating a suspension of the hydroxo complex [Pd(N–N)-
(C6F5)(OH)] (N–N = bipy, Me2bipy or phen) in methylketone
(acetone or methylisobutylketone) under reflux the b-carbonyl-
methyl palladium complexes 1–6 are formed with the concomi-
tant release of water (Scheme 2). Complexes 1–6 are all air-stable
solids and the thermal analysis shows that they decompose
above 220 °C in a dynamic N2 atmosphere. The IR spectra
show the characteristic absorptions of the C6F5 group32 at 1630,
1490, 1450, 1050, 950 and a single band at ca. 800 cm−1 which is
derived from the so-called X-sensitive mode33 in C6F5-halogen
molecules, which is characteristic of the presence of only one
C6F5 group in the coordination sphere of the palladium atom
and behaves like a m(M–C) band.34–36 The carbonyl stretching
frequencies for these b-carbonylmethyl–palladium complexes
fall in the range 1635–1615 cm−1. These values are similar to
those found in related monomeric b-carbonylmethyl–palladium
Scheme 1
Palladium enolates can be prepared by oxidative addition
of haloketones to a Pd(0) complex13,16,17,23,24 and Pt–methyl
enolate complexes have also been prepared by reacting
acetone with hydroxo complexes.25–28 In particular, bridg-
ing C,O-enolates were prepared11 from acetone and di-l-
hydroxo complexes >Pd(l-OH)2Pd< and the reaction of the
1
† Electronic supplementary information (ESI) available: Table S1: H
and 19F NMR data. See http://www.rsc.org/suppdata/dt/b4/b409942g/
T h i s j o u r n a l i s
©
T h e R o y a l S o c i e t y o f C h e m i s t r y 2 0 0 4
D a l t o n T r a n s . , 2 0 0 4 , 3 5 2 1 – 3 5 2 7
3 5 2 1

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complexes6,10–14 and are indicative of the absence of interaction
between the carbonyl group and the palladium atom. The full
Table 1 Selected bond lengths (Å) and angles (°) for complex 1·ꢀ
Me2CO
1
list of H and 19F NMR data is given in the ESI† (Table S1)
Pd(1)–C(11)
Pd(1)–C(17)
Pd(1)–N(1)
Pd(1)–N(2)
C(18)–O(1)
C(17)–C(18)
C(18)–C(19)
2.009(2)
2.078(2)
2.097(2)
2.102(2)
1.229(3)
1.468(4)
1.517(4)
C(11)–Pd(1)–C(17)
C(11)–Pd(1)–N(1)
C(17)–Pd(1)–N(1)
C(11)–Pd(1)–N(2)
C(17)–Pd(1)–N(2)
N(1)–Pd(1)–N(2)
C(18)–C(17)–Pd(1)
87.84(10)
174.97(9)
96.85(9)
96.77(9)
173.28(9)
78.70(8)
and relevant data are found in the Experimental section. The
characteristic resonances of the neutral ligands bipy, Me2bipy,
1
phen and tmeda are observed in the H NMR spectra within
the ranges found for related compounds.30,37–39 The signals in
the range d 2.54–2.72 are assignable to the methylene protons
for complexes 1–6. Complexes 1, 3 and 5 show also a resonance
at d 1.97–1.86 for the methyl protons of the acetonyl ligand,
whereas complexes 2,4 and 6 show resonances at d 1.87 and
0.78 for the methylidene and methyl protons, respectively, of
the Bui group. The 19F NMR spectra of complexes 1–6 reveal
the presence of a freely rotating pentafluorophenyl ring which
gives three resonances (in the ratio 2:2:1) at ca. −116.0, −160.5
and −163.0 for the o-, m- and p-fluorine atoms, respectively. In
the 13C{1H} NMR spectrum of complex 1, resonances due to the
chelating ligand, together with those of the methyl (d 29.6) and
the methylene (d 25.0) of the acetonyl group were observed. No
carbonyl carbon resonance could be observed probably due to
the low solubility of this complex.
107.22(17)
Fig. 1 ORTEP of complex 1·ꢀMe2CO showing the atom numbering
scheme. Displacement ellipsoids are drawn at the 50% probability level.
Scheme 2 Reagents and conditions: (i) MeCOR/−H2O, 5–7 h, reflux.
Fig. 1 shows the X-ray structure of complex 1·ꢀMe2CO, with
selected bond lengths and bond angles listed in Table 1. Complex
1·ꢀMe2CO contains a palladium atom located in a distorted
square planar environment, formed by the two nitrogen atoms
of the chelating bipy ligand, the Cipso of the C6F5 ring and one
carbon atom of the acetonyl ligand. The Pd–N bond distances
(Pd(1)–N(1), 2.097(2) Å; Pd(1)–N(2), 2.102(2) Å) are longer
than those observed in the related complex [Pd(bipy)(C6F5)-
(OOCPh)]·CHCl3.40 The chelate angle N(1)–Pd–N(2) (78.70(8)°)
is smaller than that found in [Pd(bipy)(C6F5)(OOCPh)]·CHCl3.40
The distance Pd–C(17) (2.078(2) Å) is shorter than that found
in [Pd(AsPh3)(C6F5){CH2C(O)CH3}(tBuNC)] (2.111(4) Å)11
but longer than that in [Pd2{CH2C(O)CH3}(l-Cl)2(tetrahydro-
thiophene)2] (2.050(3) Å).12 The length of the carbon–oxygen
double bond (1.229(3) Å) is similar to that found in [Pd-
(AsPh3)(C6F5){CH2C(O)CH3}(tBuNC)] (1.230(5) Å).11 The
enolate ligand is nearly perpendicular to the mean coordination
plane (dihedral angle 71.7°); the same conformation is found
in [Pd(AsPh3)(C6F5){CH2C(O)CH3}(tBuNC)]11 or in [Pd(CH2-
COPh)Cl(PPh3)2].13 In complex 1·ꢀMe2CO there is a stack of
inversion related molecules along the b-axis direction with p–p
interactions between pyridine rings of bipyridine ligands.41 As
can be seen in Fig. 2 there is a slipped packing with a deviation
of the centre–centre line of the perpendicular of the plane of
16.4°, the interplanar distance is 3.47 Å. The are also CHO
and CHF bonds links (2.516–2.594 Å).
Fig. 2 p–p Interactions in complex 1·ꢀMe2CO. Symmetry code:
(a) 1 − x, −y, 1 − z.
which further confirms the presence of the Pd–C r-bond for-
1
mation.42,43 The H NMR spectra show the methine proton of
the malonate ligand as a singlet at ca. d 3.6–3.0. This value is
close to the d 4.0–4.4 range for related C-bonded complexes and
differs significantly from the O-bonded range (d 4.7–5.4).42 In
the 13C{1H} NMR spectra the CH resonance is observed at d
22.5 (for 7), 22.7 (for 8) or 26.4 (for 9).
Malonate–palladium complexes 7–9
The reaction of the corresponding hydroxo complex [Pd(N–N)-
(C6F5)(OH)] (N–N = bipy, phen or tmeda) with diethylmalonate
yields the malonate palladium complexes 7–9 shown in
Scheme 3. Complexes of malonate anions are likely intermedi-
ates in the recently developed palladium-catalyzed arylations
of malonates7,8 and C–C bond-forming reductive elimination
from aryl palladium(II) complexes of malonate anions has
been very recently reported.9 The IR spectra of complexes
7–9 show a very strong carbonyl absorption at ca. 1720 cm−1,
Scheme 3 Reagents: CH2X2/−H2O.
3 5 2 2
D a l t o n T r a n s . , 2 0 0 4 , 3 5 2 1 – 3 5 2 7

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Table 2 Selected bond lengths (Å) and angles (°) for complex 9 (mean
values for the two molecules in the asymmetric unit)
Table 3 Selected bond lengths (Å) and angles (°) for complex 12
Pd(1)–C(1)
Pd(1)–C(7)
Pd(1)–N(1)
Pd(1)–N(2)
2.0078(15)
2.0877(16)
2.1182(13)
2.1511(13)
C(1)–Pd(1)–C(7)
C(1)–Pd(1)–N(1)
C(7)–Pd(1)–N(1)
C(1)–Pd(1)–N(2)
C(7)–Pd(1)–N(2)
N(1)–Pd(1)–N(2)
89.20(6)
91.75(6)
179.02(6)
176.33(5)
94.40(6)
84.64(5)
Pd(1)–C(1)
Pd(1)–C(13)
Pd(1)–N(2)
Pd(1)–N(1)
2.001(4)
2.094(4)
2.145(4)
2.161(4)
C(1)–Pd(1)–C(13)
C(1)–Pd(1)–N(2)
C(13)–Pd(1)–N(2)
C(1)–Pd(1)–N(1)
C(13)–Pd(1)–N(1)
N(2)–Pd(1)–N(1)
89.4(2)
92.4(2)
177.2(2)
176.1(2)
94.0(2)
84.4(2)
The structure of 9 is shown in Fig. 3 and selected bond lengths
and bond angles are given in Table 2. There are two independent
molecules which differ in the orientation of one CO2Et group.
The coordination around Pd is distorted square planar. The
different Pd–N (Pd–N(1), 2.161(4) Å; Pd–N(2), 2.145(4) Å)
distances are in agreement with the higher trans influence of
the C6F5 group compared to the malonate ligand. The Pd–C(13)
bond distance (2.094(4) Å) is similar to that observed in the
previously reported bis(diethylmalonate-C)[2,2-bis(2-pyridyl)-
1,3-dioxolane]palladium(II) complex.42 The angles at the central
carbon atom of the malonate ligand indicate sp3-hybridization
of carbon. The Pd–C6F5 bond length (2.001(4) Å) is in the range
found in the literature for pentafluorophenyl–palladium comp-
lexes. The chelate angle N(1)–Pd–N(2) (84.4(2)°) is similar to
that found in [Pd(tmeda)(C6F5)(CO2Me)].30
Scheme 4
the central carbon atom of malononitrilate (108.9–111.0°)
indicate sp3-hybridization of carbon. The Pd–C(7) bond dis-
tance (2.0877(16) Å) is shorter than that observed in the previ-
ously reported [Pd2(C6F5)4{l-CH(CN)CN}2]2− (2.191(7) Å).51
The C(CN)2 moiety is planar with maximum deviations of
0.008(1) Å [C(8)] and 0.006(1) Å [C(7)]. Both nitrile groups
are linear, the corresponding angles C(7)–C(9)–N(4) and C(7)–
C(8)–N(3) are 178.88(19) and 178.87(18)°, respectively. The C–N
distances (1.148(2) and 1.150(2) Å) are similar to those found in
[Co(salpn){CH(CN)2}(py)] (1.16(2) and 1.14(2) Å).52
Fig. 3 ORTEP of complex 9 showing the atom numbering scheme.
Displacement ellipsoids are drawn at the 50% probability level.
Dicyanomethanide–palladium complexes 10–12
The reaction of [Pd(N–N)(C6F5)(OH)] (N–N = bipy, phen or
tmeda) with malononitrile yields the dicyanomethanide–palla-
dium complexes 10–12 (Scheme 3). The dicyanomethanide
anion, [CH(CN)2]−, resulting from the deprotonation of malo-
nitrile, may coordinate to metal centres either by the nitrogen
or the carbon atom, depending on the hard–soft character of
the metal ion, and examples of both possibilities (Scheme 4),
A (dicyanomethyl–metal linkage) and B (monocyanoketimine
structure), are found in the literature.28,44–49 A third coordina-
tion mode is as bidentate N,N-bonded ligand bridging two
metal atoms as found in [{Ni(C6F5)2(l-NCCHCN)}2]2− (C).50
The malonitrilate anion also can act as bidentate C,N–bonded
ligand as observed in [{Pd(C6F5)2(l-CH(CN)CN)}2]2− (D).51
The IR spectra of complexes 10–12 show a sharp m(CN)
band at 2210–2220 cm−1, which is similar to the value of
2225 cm−1 found in the related C-bonded28,45 complexes
[(TpMe2)(py)Pd{CH(CN)2}] and [(dppe)PtMe{CH(CN)2}],
whereas N-bonded dicyanoketeniminato complexes containing
the unit M–NCCH(CN) show44,45 a broad, intense m(CN)
band in the range 2120–2150 cm−1.
Fig. 4 ORTEP of complex 12 showing the atom numbering scheme.
Displacement ellipsoids are drawn at the 50% probability level.
In the course of our research into the chemistry of
[NBu4]2[(C6F5)2M(l-OH)2M(C6F5)2]-type complexes (M = Ni,
Pd, Pt),53 we found that the nickel and palladium complexes can
be used as efficient catalysts for the cyclotrimerization of malo-
nonitrile.50,51 Similarly, catalytic amounts of the mononuclear
hydroxo palladium complex [Pd(tmeda)(C6F5)(OH)] in wet
toluene also effect the cyclotrimerization of malononitrile, lead-
ing to 4,6-diamino-2-cyanomethyl-3,5-pyridinedicarbonitrile
(Scheme 5), the so-called trimer I of malononitrile.54 From a
1:100 molar mixture of [Pd(tmeda)(C6F5)(OH)]:malononitrile
in boiling wet toluene the cyclic trimer is isolated in 35% yield.
The relevant data are listed in the Experimental section, and are
identical with those previously reported.50,55
The structure of 12 is shown in Fig. 4 and selected bond
lengths and angles in Table 3. The different Pd–N (Pd–N(2),
2.1511(13) Å; Pd–N(1), 2.1182(13) Å) distances are in agree-
ment with the higher trans influence of the C6F5 group
compared to the dicyanomethanide ligand. The angles at
Nitromethyl palladium complexes 13 and 14
On heating a suspension of the corresponding hydroxo palla-
dium complex [Pd(N–N)(C6F5)(OH)] (N–N = bipy or phen)
D a l t o n T r a n s . , 2 0 0 4 , 3 5 2 1 – 3 5 2 7
3 5 2 3

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Table 4 Selected bond lengths (Å) and angles (°) for complex
13·ꢀCH2Cl2
Pd(1)–C(11)
Pd(1)–C(17)
Pd(1)–N(1)
Pd(1)–N(2)
2.003(3)
2.060(3)
2.102(2)
2.073(2)
C(11)–Pd(1)–C(17)
C(11)–Pd(1)–N(2)
C(17)–Pd(1)–N(2)
C(11)–Pd(1)–N(1)
C(17)–Pd(1)–N(1)
N(1)–Pd(1)–N(2)
N(3)–C(17)–Pd(1)
87.11(12)
96.22(10)
173.71(11)
173.64(10)
98.01(11)
79.05(9)
110.7(2)
Conclusion
Scheme 5 Reagents and conditions: (i) [Pd(tmeda)(C6F5)(OH)], wet
toluene, 6 h, reflux.
The acid–base reaction between [Pd(N–N)(C6F5)(OH)] and
methyl ketones is a convenient method for the preparation
of C-bonded enolate–palladium complexes. Previous results
recently reported by us11 showed that the di-l-C,O-enolate com-
plex [(N–N)(C6F5)Pd{l-CH2C(R)O}Pd(C6F5)(N–N)] is formed
when the starting hydroxo complex is [(N–N)(C6F5)Pd(l-
OH)2Pd(C6F5)(N–N)], because the vacant site at the palladium
atom is occupied by the oxygen atom of the C-bound enolate.
However, the carbophilic nature of palladium(II) is manifested
when the bridging C,O-enolate complex is treated with a donor
ligand and the Pd{(CH2C(O)R}L-type complex is formed.
Some structural data of the terminal C-bound and bridging
C,O-bound enolate are compared in Scheme 7. The shorter
C–O distance in the C-bound enolate correlates with the higher
wavenumber observed for m(CO) and the lack of electron delo-
calization on the C-bound enolate results in a high-field shift
of the CH2 proton resonance. So the carbonyl stretching band
and the methylene proton resonance may be used as criteria for
distinguishing terminal C-bound enolate from bridging C,O-
bound enolate. The nitromethyl–palladium complex is obtained
by a similar acid–base reaction between nitromethane and the
hydroxo–palladium complex. Although aqua–palladium com-
plexes have been obtained by protonation of hydroxo–palladium
complexes,58 no intermediate aqua complex has been detected in
the above reactions.
in nitromethane under reflux the nitromethyl–palladium
complexes 13 and 14 are obtained (Scheme 6). The nitromethyl
complexes show m(NO2) in the expected region26,28 of the IR
spectrum (Experimental section). The methylene proton reso-
nance is observed at d 4.9–4.726,56,57 and the 13C{1H} NMR spec-
trum of 13 shows the CH2 resonance at d 22.4.
Scheme 6 Reagents and conditions: (i) MeNO2/−H2O, 3–4 h, reflux.
Fig. 5 shows the X-ray structure of complex 13·ꢀCH2Cl2,
with selected bond lengths and bond angles listed in
Table 4. The metal atom shows a distorted square planar geo-
metry. The different Pd–N (Pd(1)–N(1), 2.102(2) Å; Pd(1)–
N(2), 2.073(2) Å) distances are in agreement with the higher
trans influence of the C6F5 group compared to the nitromethyl
ligand. The chelate angle N(1)–Pd–N(2) (79.05(9)°) is higher
than that found in complex 1·ꢀMe2CO. The CH2NO2 group is
characterized by the Pd–C(17) distance and a N(3)–C(17)–Pd
angle of 2.060(3) Å and 110.7(2)° (sp3 hybridization for the C
atom), respectively. These values are shorter than those found
in [Pd(dppp)(tmphen)(CH2NO2)]+ and higher than those of
[Pd(phen)2(CH2NO2)]+.56
Scheme 7
C-Bound dicyanomethanide– and diethylmalonate–palla-
dium complexes are readily obtained by reaction between
[Pd(N–N)(C6F5)(OH)] and malononitrile or diethylmalonate,
respectively. However, when malononitrile is reacted with a
di-l-hydroxo–palladium complex the C,N-bound malonitrilate
complex >Pd{CH(CN)CN}Pd< is formed.51 This behaviour
of malonitrile towards terminal monohydroxo and bridging
hydroxo palladium complexes is similar to that described above
for methyl ketones. The deprotonation of dialkylmalonate by the
di-l-hydroxo palladium complex leads to the formation of the
O,O-bound malonate complex >Pd{OC(OEt)CHC(OEt)O}
whereas the same reaction carried out with the monohydroxo
palladium complex affords the C-bound dialkylmalonate
complex Pd{CH(CO2Et)2}. The X-ray structural data indicate
that in the chelating O,O-bound malonate the methine
Fig. 5 ORTEP of complex 13·ꢀCH2Cl2 showing the atom numbering
scheme. Displacement ellipsoids are drawn at the 50% probability level.
3 5 2 4
D a l t o n T r a n s . , 2 0 0 4 , 3 5 2 1 – 3 5 2 7

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carbon atom is sp2-hybridized and in the C-bound malonate
it is sp3-hybridized. There is again a correlation between these
data and the corresponding IR and 1H NMR data: mCO)
1720 cm−1 and d(CH) 3.6–3.0 for C-bound malonate vs. m(CO)
1620 cm−1 and d(CH) 4.2 for chelating O,O-bound malonate.
Preparation of complexes [Pd(N–N)(C6F5){CH(CO2Et)2}]
[N–N = bipy (7) or phen (8)]
To a suspension of the corresponding hydroxo palladium
complex [(N–N)Pd(C6F5)(OH)] (N–N = bipy or phen)
(0.134 mmol) in toluene (15 mL) was added diethylmalonate
(24.4 lL, 0.161 mmol). The suspension was boiled under reflux
for 7 h to afford a solution from which solvent was partially
evaporated under reduced pressure. On addition of hexane
the white complexes 7 and 8 precipitated and were filtered
off and air-dried. 7: Yield 71% (Found: C, 46.6; H, 3.0; N
4.7. C23H19N2F5O4Pd requires C, 46.9; H, 3.3; N, 4.8%); mp
187 °C (decomp.). IR (Nujol, cm−1): m(CO) 1730, m(Pd–C6F5)
Experimental
Instrumental measurements
C,H,N analyses were performed with a Carlo Erba model
EA 1108 microanalyzer. Decomposition temperatures were
determined with a Mettler TG-50 thermobalance at a heating
rate of 5 °C min−1 and the solid sample under nitrogen flow
1
790. H NMR (CDCl3): d 3.98 (m, 4 H, CH2O), 3.52 (s, 1 H,
1
(100 mL min−1). The H and 19F NMR spectra were recorded
PdCH), 1.12 (t, 6 H, CH2CH3, J(HH) = 6.9 Hz). 19F NMR
(CDCl3): d −118.1 (d, 2Fo, J(FoFm) = 21.4 Hz), −160.3 (t, 1 Fp,
J(FmFp) = 19.8 Hz), −162.9 (m, 2 Fm). 8: Yield 69% (Found: C,
49.1; H, 2.9; N 4.7. C25H19N2F5O4Pd requires C 49.0, H 3.1, N
4.6%); mp 228 °C (decomp.). IR (Nujol, cm−1): m(CO) 1710,
m(Pd–C6F5) 790. 1H NMR (CDCl3): d 3.99 (m, 4 H, CH2O), 3.65
(s, 1 H, PdCH), 1.13 (t, 6 H, CH2CH3, J(HH) = 7.1 Hz). 19F
NMR (CDCl3): d −117.8 (d, 2Fo, J(FoFm) = 21.2 Hz), −160.3 (t,
1 Fp, J(FmFp) = 19.8 Hz), −162.6 (m, 2 Fm).
on a Bruker AC 200E or Varian Unity 300 spectrometer, using
SiMe4 or CFCl3 as standards, respectively. Infrared spectra were
recorded on a Perkin-Elmer 16F PC FT-IR spectrophotometer
using Nujol mulls between polyethylene sheets.
Materials
The compounds [Pd(N–N)(C6F5)(OH)] (N–N = bipy, Me2bipy,
phen or tmeda) were prepared as described elsewhere.30
Preparation of complexes [Pd(N–N)(C6F5)(CH2COR)] (1–6)
Preparation of [Pd(tmeda)(C6F5){CH(CO2Et)2}] (9)
A suspension of the corresponding hydroxo palladium com-
plex [(N–N)Pd(C6F5)(OH)] (N–N = bipy, Me2bipy or phen)
(0.134 mmol) in methylketone (acetone or MeCOBui) (15 mL)
was heated under reflux for 5–7 h to yield a solution and then
partially concentrated under vacuum. On addition of hexane
the white complexes 1–6 precipitated and were filtered off and
air-dried. Complex 1 was heated in the oven for 24 h at 80 °C to
remove solvated acetone. 1: Yield 90% (Found: C, 46.9; H, 2.8;
N, 5.6. C19H13N2F5OPd requires C, 46.9; H, 2.7; N, 5.8%); mp
241 °C (decomp.). IR (Nujol, cm−1): m(CO) 1635, m(Pd–C6F5) 780.
1H NMR (CDCl3): d 2.56 (s, 2 H, PdCH2), 1.88 (s, 3 H, COCH3).
19F NMR (CDCl3): d −116.3 (d, 2Fo, J(FoFm) = 22.9 Hz), −160.4
(t, 1 Fp, J(FmFp) = 19.8 Hz), −162.5 (m, 2 Fm). 2: Yield 65%
(Found: C, 50.2; H, 3.4; N, 5.4. C22H19N2F5OPd requires C,
50.0; H, 3.6; N, 5.3); mp 224 °C (decomp.). IR (Nujol, cm−1):
m(CO) 1625, m(Pd–C6F5) 785. 1H NMR (CDCl3): d 2.57 (s, 2 H,
PdCH2), 2.13 (d, 2 H, CH2CH, J(HH) = 6.9 Hz), 1.87 (m,
1 H, CH), 0.78 (d, 6 H, CHCH3, J(HH) = 6.5 Hz). 19F NMR
(CDCl3): d −116.3 (d, 2Fo, J(FoFm) = 22.9 Hz), −160.5 (t, 1 Fp,
J(FmFp) = 20.0 Hz), −162.7 (m, 2 Fm). 3: Yield 96% (Found: C,
48.8; H, 3.2; N, 5.2. C21H17N2F5OPd requires C, 49.0; H, 3.3;
N, 5.4%); mp 257 °C (decomp.). IR (Nujol, cm−1): m(CO) 1635,
m(Pd–C6F5) 780. 1H NMR (CDCl3): d 2.56 (s, 2 H, PdCH2), 2.45
(s, 3 H, Me2bipy), 2.42 (s, 3 H, Me2bipy), 1.86 (s, 3 H, COCH3).
19F NMR (CDCl3): d −116.3 (d, 2Fo, J(FoFm) = 22.9 Hz), −160.7
(t, 1 Fp, J(FmFp) = 20.0 Hz), −162.8 (m, 2 Fm). 4: Yield 60%
(Found: C, 51.6; H, 4.0; N, 4.9. C24H23N2F5OPd requires C,
51.8; H, 4.2; N, 5.0%); mp 236 °C (decomp.). IR (Nujol, cm−1):
m(CO) 1630, m(Pd–C6F5) 780. 1H NMR (CDCl3) d: 2.54 (s, 2 H,
PdCH2), 2.50 (s, 3 H, Me2bipy), 2.46 (s, 3 H, Me2bipy), 2.09 (d,
2 H, CH2CH, J(HH) = 6.9 Hz), 1.87 (m, 1 H, CH), 0.78 (d, 6 H,
CHCH3, J(HH) = 6.5 Hz). 19F NMR (CDCl3) d −116.0 (d, 2Fo,
J(FoFm) = 24.3 Hz), −160.8 (t, 1 Fp, J(FmFp) = 19.8 Hz), −162.9
(m, 2 Fm). 5: Yield 69% (Found: C, 49.1; H, 2.8; N, 5.4.
C21H13N2F5OPd requires C, 49.4; H, 2.6; N, 5.5); mp 250 °C
To a solution of the hydroxo palladium complex [Pd(tmeda)-
(C6F5)(OH)] (0.134 mmol) in toluene (15 mL) was added diethyl-
malonate (24.4 lL, 0.161 mmol). The solution was boiled under
reflux for 6 h. The solvent was evaporated-off under reduced
pressure. The residue was treated with diethyl ether to render a
white solid which was collected by filtration and air-dried. Yield
78% (Found: C, 41.8; H, 4.9; N, 4.8. C19H27N2F5O4Pd requires C,
41.6; H, 5.0; N 5.1%); mp 196 °C (decomp.). IR (Nujol, cm−1):
1
m(CO) 1685, m(Pd–C6F5) 784. H NMR (CDCl3): d 4.00 (m,
4 H, CH2O), 2.97 (s, 1 H, PdCH), 2.79 (s, 6 H, CH3), 2.72 (m,
2 H, CH2), 2.61 (m, 2 H, CH2), 2.37 (s, 6 H, CH3), 1.16 (t, 6 H,
CH2CH3, J(HH) = 7.1 Hz). 19F NMR (CDCl3): d −120.7 (d, 2Fo,
J(FoFm) = 24.5 Hz), −161.0 (t, 1 Fp, J(FmFp) = 19.8 Hz), −164.2
(m, 2 Fm).
Preparation of complexes [Pd(N–N)(C6F5){CH(CN)2}]
[N–N = bipy (10), phen (11) or tmeda (12)]
To a solution of the corresponding hydroxo palladium com-
plex [Pd(N–N)(C6F5)(OH)] (N–N = bipy, phen or tmeda)
(0.134 mmol) in methanol (12 mL) was added malononitrile.
Spontaneously the white complexes 10 and 11 precipitated.
The suspension was stirred for 30 min at room temperature.
The white solids were collected by filtration and air-dried. In
the case of the more soluble compound 12 the solvent was
evaporated-off under reduced pressure. The residue was treated
with hexane–ether to render a pale-yellow solid which was
collected by filtration and air-dried. 10: Yield 85% (Found: C,
46.1; H, 2.0; N, 11.1. C19H9N4F5Pd requires C, 46.1; H, 1.8; N,
11.3%); mp 229 °C (decomp.). IR (Nujol, cm−1): m(CN) 2215,
m(Pd–C6F5) 795. 1H NMR ([D6]DMSO): d 8.70 (m, 3 H), 8.42 (m,
1 H), 8.30 (m, 1 H), 7.96 (m, 1 H), 7.86 (br, 1 H), 7.59 (m, 1 H),
3.54 (s, 1 H, PdCH). 19F NMR ([D6]DMSO): d −117.5 (d, 2Fo,
J(FoFm) = 22.9 Hz), −159.7 (t, 1 Fp, J(FmFp) = 21.4 Hz), −161.9
(m, 2 Fm). 11: Yield 74% (Found: C, 48.4; H, 1.7; N, 10.6.
C21H9N4F5Pd requires C, 48.6; H, 1.8; N, 10.8%); mp 221 °C (de-
comp.). IR (Nujol, cm−1): m(CN) 2220, m(Pd–C6F5) 795. 1H NMR
([D6]DMSO): d 3.71 (s, 1 H, PdCH). 19F NMR ([D6]DMSO):
1
(decomp.). IR (Nujol, cm−1): m(CO) 1635, m(Pd–C6F5), 780. H
NMR (CDCl3): d 2.72 (s, 2 H, PdCH2), 1.95 (s, 3 H, COCH3).
19F NMR (CDCl3): d −116.0 (d, 2Fo, J(FoFm) = 21.4 Hz), −160.4
(t, 1 Fp, J(FmFp) = 19.8 Hz), −162.6 (m, 2 Fm). 6: Yield 72%
(Found: C, 51.8; H, 3.3; N, 5.3. C24H19N2F5OPd requires C,
52.1; H, 3.5; N, 5.1%); mp 244 °C (decomp.). IR (Nujol, cm−1):
m(CO) 1615, m(Pd–C6F5) 790. 1H NMR (CDCl3): d 2.69 (s, 2 H,
PdCH2), 2.14 (d, 2 H, CH2CH, J(HH) = 7.0 Hz), 1.88 (m, 1
H, CH), 0.77 (d, 6 H, CHCH3, J(HH) = 6.6 Hz). 19F NMR
(CDCl3): d −116.0 (d, 2Fo, J(FoFm) = 23.1 Hz), −160.5 (t, 1 Fp,
J(FmFp) = 19.8 Hz), −162.8 (m, 2 Fm).
d −116.8 (d, 2Fo, J(FoFm) = 24.3 Hz), −159.7 (t,
1 Fp,
J(FmFp) = 21.4 Hz), −161.9 (m, 2 Fm). 12: Yield 86% (Found:
C, 39.4; H, 4.0; N, 12.0. C15H17N4F5Pd requires C, 39.6; H, 3.8;
N, 12.3%); mp 187 °C (decomp.). IR (Nujol, cm−1): m(CN) 2212;
m(Pd–C6F5) 788. 1H NMR (CDCl3): d 2.81 (s, 7 H, CH3 + PdCH),
2.76 (m, 2 H, CH2), 2.66 (m, 2 H, CH2), 2.43 (s, 6 H, CH3). 19
F
NMR (CDCl3): d −119.4 (d, 2Fo, J(FoFm) = 21.4 Hz), −158.5 (t,
1 Fp, J(FmFp) = 19.8 Hz), −161.5 (m, 2 Fm).
D a l t o n T r a n s . , 2 0 0 4 , 3 5 2 1 – 3 5 2 7
3 5 2 5

View Article Online
Table 5 Crystal structure determination details
1·ꢀMe2CO
9
12
13·ꢀCH2Cl2
Formula
M
Crystal system
Space group
C19H13F5N2OPd·ꢀMe2CO
C19H27F5N2O4Pd
548.83
Triclinic
P1
C15H17F5N4Pd
454.73
Monoclinic
P21/c
C17H10ClF5N3O2Pd·ꢀCH2Cl2
515.75
Triclinic
P1
532.14
Monoclinic
P21/c
Unit cell dimensions
a/Å
b/Å
c/Å
a/°
b/°
8.2813(8)
8.7515(6)
13.4037(11)
85.610(6)
78.086(7)
84.053(7)
943.86(14)
293(2)
11.736(3)
13.911(5)
15.750(6)
104.67(3)
103.00(3)
101.02(2)
2338.3(14)
293(2)
11.5401(4)
8.4604(3)
17.1175(6)
90
90.239(1)
90
1671.23(10)
100(2)
4
13.0446(7)
10.8897(6)
13.3268(8)
90
109.280(1)
90
1786.92(17)
100(2)
4
c/°
V/Å3
T/K
Z
2
4
l/mm−1
1.049
0.859
1.168
1.260
Reflections collected
Independent reflections
Rint
6641
3321
0.0195
0.0214
8209
8209
0.0000
0.0399
18592
3873
0.0150
0.0213
0.0582
20422
4145
0.0279
0.0330
0.0740
R1 [I > 2r(I)]a
wR2 (all data)b
0.0558
0.1041
2
2
a R1 = R||Fo| − |Fc|| / R|Fo|, wR2 = [R[w(Fo2 − Fc2)2]/R w(Fo2)2]0.5. b w = 1/[r2(Fo ) + (aP)2 + bP], where P = (2Fc2 + Fo )/3 and a and b are constants set by
the program.
Catalytic conversion of malononitrile into its trimer, 4,6-
diamino-3,5-dicyano-2-cyanomethylpyridine
was performed on a Siemens P4 and a Enraf-Nonius CAD 4
diffractometer, respectively, data collection for 12 and 13 was
performed on a Bruker Smart CCD diffractometer. Details of
data collection and refinement are given in Table 5. The h/° range
were 3–25 for 1, 2–25 for 9 and 2–28 for 12 and 13. Empirical psi-
scan absorption corrections was made in 1 and 9 while SADABS
was employed in 12 and 13.
CCDC reference numbers 243409–243412.
See http://www.rsc.org/suppdata/dt/b4/b409942g/ for crystal-
lographic data in CIF or other electronic format.
[Pd(tmeda)(C6F5)(OH)] (30 mg, 0.074 mmol) was added to a
solution of malononitrile (487.3 mg, 7. 4 mmol) in wet toluene
(20 mL toluene; 2.65 lL H2O) and the mixture was boiled under
reflux for 6 h. The toluene was evaporated under vacuum and
the resulting sticky material was treated with ethanol and vigor-
ously stirred to give a beige solid, which was isolated (171 mg,
35% yield), recrystallized from dioxane, dried in the oven at
110 °C and identified as 4,6-diamino-3,5-dicyano-2-cyano-
methylpyridine (trimer I). MS: m/z 198 (M+, 100%) (Found: C,
54.2; H, 2.9; N, 42.1. C9H6N6 requires C, 54.5; H, 3.0; N, 42.4%).
IR (Nujol, cm−1): m(NH) 3400–3200, m(CN) 2210. UV-VIS (in
Acknowledgements
Financial support of this work by the Dirección General de
Investigación del Ministerio de Ciencia y Tecnología (Project
No. BQU2001-0979-C02–01), Spain, and the Fundación Séneca
de la Comunidad Autónoma de la Región de Murcia (Project
No. PI-72-00773-FS-01) is acknowledged.
1
MeOH): kmax/nm: 313, 245 (sh), 237. H NMR ([D6]DMSO): d
4.15 (s, 2 H), 7.45 (s, 2 H), 7.65 (s, 2 H).
Preparation of complexes [Pd(N–N)(C6F5)(CH2NO2)]
[N–N = bipy (13) or phen (14)]
References
A suspension of the corresponding hydroxo palladium complex
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nitromethane (15 mL) was heated for 3–4 h and then concen-
trated under vacuum until dryness. The residue was extracted in
dichloromethane. On addition of hexane the white complexes 13
and 14 precipitated and were filtered off and air-dried. 13: Yield
74% (Found: C, 41.4; H, 2.3; N, 8.9. C17H10N3F5O2Pd requires
C, 41.7; H, 2.1; N, 8.6%); mp 203 °C (decomp.). IR (Nujol, cm−1)
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C19H10N3F5O2Pd requires C, 44.4; H, 2.0; N, 8.2%); mp 263 °C
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795. 1H NMR ([D6]DMSO): d 4.92 (s, 2 H, PdCH2). 19F NMR
([D6]DMSO): d −116.3 (d, 2Fo, J(FoFm) = 22.9 Hz), −160.4 (t, 1
Fp, J(FmFp) = 20.0 Hz), −162.6 (m, 2 Fm).
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D a l t o n T r a n s . , 2 0 0 4 , 3 5 2 1 – 3 5 2 7

View Article Online
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