Insertion reactions of SO2 into Pd-OR bonds: Preparation of alkyl sulfito complexes of palladium(II)

Article abstract of DOI:10.1039/b316697j

Mononuclear palladium-hydroxo complexes of the type [Pd(N-N)(C ₆F₅)(OH)] [(N-N = 2,2′-bipyridine (bipy), 4,4′-dimethyl-2,2′-bipyridine (Me₂bipy), or N,N,N′, N′-tetramethylethylenediamine (tmeda) react with SO₂ (

Full text of DOI:10.1039/b316697j

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Insertion reactions of SO2 into Pd–OR bonds:
preparation of alkyl sulfito complexes of palladium(II)†
José Ruiz,*a M. Teresa Martínez,a Félix Florenciano,a Venancio Rodríguez,a Gregorio López,*a
José Pérez,b Penny A. Chalonerc and Peter B. Hitchcockc
a Departamento de Química Inorgánica, Facultad de Química, Universidad de Murcia,
30071 Murcia, Spain. E-mail: jruiz@um.es; gll@um.es; Fax: (ϩ34) 968 36 41 48
b Departamento de Ingeniería Minera, Geológica y Cartográfica (Area de Química Inorgánica),
Universidad Politécnica de Cartagena, 30203 Cartagena, Spain
c Chemistry Department, School of Life Sciences, University of Sussex, Brighton, UK BN1 9QJ
Received 22nd December 2003, Accepted 28th January 2004
First published as an Advance Article on the web 10th February 2004
Mononuclear palladium–hydroxo complexes of the type [Pd(N–N)(C6F5)(OH)] [(N–N = 2,2Ј-bipyridine (bipy),
4,4Ј-dimethyl-2,2Ј-bipyridine (Me2bipy), or N,N,NЈ,NЈ-tetramethylethylenediamine (tmeda) react with SO2 (1 atm) at
room temperature in alcohol (methanol, ethanol, propanol or isopropanol) to yield alkyl sulfito palladium complexes
[Pd(N–N)(C6F5)(SO2OR)] (R = Me, Et, Pr or iPr). Similar alkyl sulfito complexes [Pd(N–N)(C6F5)(SO2OR)] (N–N =
bis(3,5-dimethylpyrazol-1-yl)methane); R = Me or Et) are obtained when [Pd(N–N)(C6F5)Cl] is treated with KOH in
the corresponding alcohol ROH and SO2 is bubbled through the solution. The reaction of [Pd(bipy)(C6F5)(OH)] with
SO2 in tetrahydrofuran gives [Pd(N–N)(C6F5)(SO2OH)]. The X-ray diffraction study of [Pd(tmeda)(C6F5)(SO2OPr)]
has established the sulfur coordination of the propyl sulfito ligand.
(C6F5)(OH)] (N–N = bipy, Me2bipy or tmeda) in alcohol
(methanol, ethanol, propanol or isopropanol) for 10 min the
corresponding alkyl sulfito complexes 1–9 are obtained
Introduction
The reactions of CO (in alcohol, ROH) and CO2 (in tetrahydro-
furan) with [(N–N)(C6F5)Pd(OH)]-type complexes have been
(Scheme 1) in 68–90% yields. The structures were assigned on
recently studied,1 the reaction products being the result of
the basis of microanalytical, IR, and 1H and 19F NMR data.
insertion of CO into the Pd–OR bond or of insertion of CO2
into the Pd–OH bond to give [(N–N)(C6F5)Pd(COOR)] or
[(N–N)(C6F5)Pd(CO2OH)], respectively. By analogy with the
observed formation of the methoxy carbonyl ligand, –C(O)OR,
by nucleophilic attack of alkoxide on ligated CO and the hydro-
gen carbonate, –OC(O)OH, by nucleophilic attack of hydroxide
on ligated CO2, the presumed behavior of SO2 toward [(N–N)-
(C6F5)Pd(OH)] should be the formation of hydrogen sulfito
or alkyl sulfito complexes depending on the experimental
conditions used.
Examples of transition-metal alkyl sulfito complexes are
known for Mn,2 Fe,2 Co,3 Ru,4,5 Rh,6 Ir,7 Ni,3 Pd8–10 and Pt.9–13
Although no general synthetic routes to such compounds have
Scheme 1 Reagents and conditions: (i) SO2, ROH, 10 min, room temp.
been developed, the insertion of SO2 into M–OR has been
widely used. In the case of the group 10 metals, metal–sulfur
bonding was established in [Ni(SO2OEt)(np3)]BF4ؒ0.5EtOHؒ
0.5H2O3 (np3 = tris(2-(diphenylphosphino)ethyl)amine) and
[Pt(PPh3)2(SO2OMe)2]13 by X-ray crystallography, but no crys-
tal structure has been reported for alkyl sulfite–palladium com-
plexes [3D Search using the Cambridge Structural Database,
July 2003 release].
We have now examined the reactions of the monomeric
hydroxo complexes [Pd(N–N)(OH)(C6F5)] in alcoholic solvents
with SO2 to yield complexes of the type [Pd(N–N)(C6F5)-
(SO2OR)]. We also report the first crystal structure of an alkyl
sulfito–palladium complex. The synthetic method described
herein may be of general use in the preparation of alkyl sulfite
and hydrogen sulfite complexes of the Group 10 elements.
Complexes 1–9 are all air-stable solids and thermal analysis
shows that they decompose above 190 ЊC in a dynamic N2
atmosphere. The IR spectra show the characteristic absorptions
of the C6F5 group14 at 1630, 1490, 1450, 1050, 950, and a single
band at ca. 800 cmϪ1 derived from the so-called X-sensitive
mode15 in C6F5X (X = halogen) molecules, which is character-
istic of the presence of only one C6F5 group in the coordination
sphere of the palladium atom and behaves like a ν(M–C)
band.16 The strong absorptions in the IR spectra at ca. 1230 and
1095 cmϪ1 (Experimental section) can be safely attributed to
the alkyl sulfito group SO2(OR) and may be assigned3 to the
νas(SO2) and νs(SO2) stretching vibrations, respectively, suggest-
ing a sulfur-coordinated alkyl sulfite.7 The sulfur-coordination
of alkyl sulfite to palladium has been confirmed by an X-ray
diffraction study of complex 8 (vide infra). Metal–sulfur bond-
ing was established in [Ni{SO2(OC2H5)}(np3)]BF4ؒ0.5C2H5OHؒ
0.5H2O (np3 = tris(2-diphenylphosphino)ethyl)amine) by X-ray
crystallography,3 though an oxygen-coordinated methyl sulfito
ligand in Ir(CO)[OS(O)OMe](SO2)(PPh3)2 has been described.17
The characteristic resonances of the neutral ligands are
observed in the 1H NMR spectra.1,18–21 The signals corre-
sponding to the alkyl group of the alkyl sulfite ligands are also
observed (for example, at ca. 3.50 ppm due to the SO3Me
Results and discussion
Alkyl sulfito complexes [Pd(N–N)(C6F5)(SO3R)]
When SO2 is bubbled at room temperature through a solution
of the monomeric hydroxo palladium complex [Pd(N–N)-
1
† Electronic supplementary information (ESI) available: Table S1: H
and 19F NMR data. See http://www.rsc.org/suppdata/dt/b3/b316697j/
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 , 9 2 9 – 9 3 2
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protons in complexes 1, 4 and 6). The 19F NMR spectra of
complexes 1–9 reveal the presence of a freely rotating penta-
fluorophenyl ring which gives the expected three resonances
(in the ratio 2 : 1 : 2) for the o-, p- and m-fluorine atoms,
respectively.
When SO2 is bubbled through an alcoholic (methanol or
ethanol) solution of [Pd(N–N)(C6F5)(OH)] [N–N = bis(3,5-di-
methylpyrazol-1-yl)methane], generated in situ by the addition
of KOH to the complexes [Pd(N–N)(C6F5)Cl], the correspond-
ing bis(pyrazol-1-yl)methane complexes [Pd(N–N)(C6F5)-
(SO3R)] [R = Me (10) or Et (11)] are obtained (Scheme 2).
Scheme 3
H2O. To a CDCl3 (0.6 mL) solution of [(bipy)(C6F5)Pd(OH)]
(30 mg) was added 1, 2, 4, 10 and 30 equiv. of methanol and the
19F NMR spectra of the solutions indicated that the equi-
librium mixture of [(bipy)(C6F5)Pd(OH)] [δ Ϫ117.8 (2Fo),
Ϫ158.7 (1Fp), Ϫ162.0 (2Fm)] and [(bipy)(C6F5)Pd(OMe)]
[δ Ϫ118.9 (2Fo), Ϫ159.9 (1Fp), Ϫ162.3 (2Fm)] was present in
every case with a methoxo complex : hydroxo complex ratio
of 0.3, 0.4, 0.6, 0.75 and 1, respectively. The chemical shifts
given above for both complexes refer to the solution to which
30 equiv. of MeOH were added; the figures are slightly different
depending on the amount of MeOH added.
Hydrogen sulfito complex [Pd(bipy)(C6F5)(SO2OH)]
The reaction of [Pd(bipy)(C6F5)(OH)] with SO2 in tetrahydro-
furan gives the hydrogen sulfite complex 12 (Scheme 4), which
can be viewed as the insertion product of SO2 into the Pd–OH
bond. Complexes containing the –SO3H ligand are known but
are less common than those with alkyl sulfito ligands. The
related ruthenium complexes [Ru(C5Me5)(CO)2(SO2OH)] and
[Ru(bipy)2(py)(SO2OH)] have been characterized by X-ray
crystallography.24,25 On studying the insertion of SO2 into the
Pt–OH bonds of [Pt(Ph PCH᎐CHPPh )(CH CN)(OH)] and
᎐
2
2
2
[Pt(Ph PCH᎐CHPPh )(CF )(OH)] the incipient formation of
᎐
2
2
3
Pt–SO2OH complexes was presumed but the experimental data
did not support definite formulations.12
Scheme 2 Reagents and conditions: (i) KOH, SO2, ROH, 10 min, room
temp.
The IR spectra of complexes 10 and 11 show two bands at
ca. 1230 and 1100 cmϪ1 which are attributed to the alkyl
sulfito group SO2(OR) and a single band located at 795 cmϪ1 is
indicative of the presence of only one C6F5 group in the co-
ordination sphere of the palladium atom. Two sets of 1H reson-
ances are observed for the C3HMe2N2 rings corresponding to
one pyrazolate ligand trans to SO3R and one pyrazolate ligand
trans to C6F5; the lower field set is assigned to the pyrazolate
ligand trans to C6F5. The proton resonances of the bridging
methylene of the bis(pyrazol-1-yl)methane ligand in com-
plexes 10 and 11 show that the boat-to-boat inversion usually
observed in this type of complexes1 is frozen at room temper-
ature; the methylene protons are magnetically non-equivalent
Scheme 4 Reagents and conditions: (i) SO2, thf, 10 min, room temp.
The elemental analysis data are consistent with the proposed
formula for 12. The IR spectrum shows two absorptions at 1185
(νas(SO2)) and 1070 (νs(SO2)) cmϪ1 as well as the characteristic
single band at 790 cmϪ1 corresponding to the Pd–C6F5 bond.
Because of the insolubility of 12 in chloroform or acetone, the
1H and 19F NMR spectra of 12 were recorded from (CD3)2SO
solution and the resonance signals are not well resolved due to
proton exchange on the SO3H group. Unlike [Pd(bipy)(C6F5)-
(CO3H)],1 the hydrogen sulfito complex does not react with the
precursor [Pd(bipy)(C6F5)(OH)] to give the corresponding
µ-sulfito complex [(bipy)(C6F5)Pd{OS(O)O}Pd(bipy)(C6F5)].
This different result may be taken as indirect evidence of the
S-coordination of SO3OH in complex 12.
and give the NMR pattern corresponding to two diastereotopic
2
protons: two doublets at δ 7.17 and 6.34 with JH = 15 Hz.
AHB
The signals corresponding to the alkyl sulfite ligands are
observed at δ 3.42 (SO2OMe) and δ 3.85 and 0.97 (SO2OEt),
respectively. The 19F NMR spectra of complexes 10 and 11 at
room temperature show hindered rotation of the C6F5 ring
around the Pd–C bond and two separate signals are observed
for the o- and m-fluorine atoms but only one for the p-fluorine
atom.
The formation of complexes 1–11 is formally the insertion of
SO2 into the Pd–OR bond. By analogy with the carbonylation
reactions of M–OMe complexes (M = group 10 metal), which
are best described as inner-sphere migratory insertions involv-
ing precoordination of CO to the metal center,22,23 the mechan-
ism shown in Scheme 3 may be proposed. Although no alkoxo
complex has been isolated, it is formed in the alcoholic solution
Crystal structure of 8
Colourless crystals suitable for X-ray diffraction studies were
obtained by slow diffusion of hexane into a benzene solution of
8. The crystal structure of complex 8 is shown in Fig. 1, together
with some selected bond lengths and bond angles.
The coordination around Pd is distorted square-planar. The
different Pd–N (Pd–N(1), 2.155(2) Å; Pd–N(2), 2.126(2) Å) dis-
tances are in agreement with the higher trans influence of the
via the Brønsted acid–base reaction M–OH ϩ ROH
M–OR ϩ
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Experimental
Instrumental measurements
The 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 ЊC minϪ1 and the solid samples under nitrogen flow
(100 mL minϪ1). The NMR spectra were recorded on a Bruker
AC 200E or Varian Unity 300 spectrometer, using SiMe4 and
CFCl3 as standards, respectively. IR spectra were recorded on a
Perkin-Elmer 1430 spectrophotometer using Nujol mulls
between polyethylene sheets. Solvents were dried by the usual
methods.
Fig. 1 Crystal structure of complex 8. Selected bond lengths (Å):
Pd–N(1) 2.155(2), Pd–N(2) 2.126(2), Pd–C(1) 2.017(2), Pd–S 2.2487(7),
S–O(1) 1.451(2), S–O(2) 1.443(2), S–O(3) 1.619(2). Selected bond
angles (Њ): N(1)–Pd–N(2) 83.78(8), C(1)–Pd–N(1) 173.77(8), N(2)–Pd–S
171.98(6), C(1)–Pd–S 91.82(7), O(1)–S–O(2) 115.60(14), O(1)–S–O(3)
105.48(11), O(2)–S–O(3) 101.70(11).
Materials
The starting complexes [(N–N)Pd(C6F5)(OH)] (N–N = bipy,
Me2bipy and tmeda) and [(N–N)Pd(C6F5)Cl] (N–N = bis(3,5-
dimethylpyrazol-1-yl)methane) were prepared by procedures
described elsewhere.1
C6F5 group compared to SO3Pr. The Pd–S bond distance
of 2.2487(7) Å is shorter than the sum of the covalent radii
of palladium and sulfur (2.33 Å) suggesting a percentage of
double bond character (in the aryl thiolate complex [Pd-
(C6F5)(SC6H5)(o-Ph2PC6H4CHNiPr)] Pd–S is 2.357(2) Å).26 The
S–O bond distances of the terminal oxygen atoms are, as
expected, significantly shorter than the S–OPr bond length
(1.447(2) average vs. 1.619(2) Å). Also the O–S–O angles reflect
the non-equivalence of the three oxygen atoms; such distortions
can be accounted for by the larger bond order of the terminal
S–O bond compared to that of S–OR in terms of electron pair
repulsions. The Pd–C6F5 bond length (2.017(2) Å) is in the
range found in the literature for pentafluorophenyl–palladium
complexes.21 The chelate angle N(1)–Pd–N(2) (83.78(8)Њ) is
similar to that found in [Pd(tmeda)(C6F5)(CO2Me)].1
Preparation of complexes [Pd(N–N)(C6F5)(SO2OR)]
(N–N ؍ bipy, R ؍ Me 1, Et 2 or Pr 3; N–N ؍ Me2bipy,
R ؍ Me 4 or Et 5)
Through an alcohol (methanol, ethanol, or propanol) solution
(15 mL) of the hydroxo palladium complex [Pd(N–N)-
(C6F5)(OH)] (N–N = bipy or Me2bipy) (0.134 mmol) at room
temperature was passed SO2 for 10 min. The solvent was par-
tially evaporated under vacuum and a suspension was obtained
from which a white solid was collected by filtration and air-
dried. 1: Yield: 90% (Found: C, 39.0; H, 2.0; N, 5.3; S, 6.3.
C17H11N2F5O3PdS requires C, 38.9; H, 2.1; N, 5.3; S, 6.1%).
Mp: 229 ЊC (decomp.). IR (Nujol, cmϪ1) νas(SO2) 1250, νs(SO2)
1105, ν(Pd–C6F5), 775. 1H NMR (CDCl3) δ 3.59 (s, 3 H,
SO2OCH3). 2: Yield 77% (Found: C, 39.8; H, 2.3; N, 5.1; S,
6.0. C18H13N2F5O3PdS requires C, 40.1; H, 2.4; N, 5.2; S,
6.0%). Mp: 227 ЊC (decomp.). IR (Nujol, cmϪ1) νas(SO2) 1230,
νs(SO2) 1100, ν(Pd–C6F5) 770. 1H NMR (CDCl3) δ 4.03 (q,
2 H, SO2OCH2CH3, J 7.2 Hz), 1.13 (t, 3 H, SO2OCH2CH3,
J 7.2 Hz). 3: Yield 75% (Found: C, 41.2; H, 2.7; N, 5.0; S, 5.6.
C19H15N2F5O3PdS requires C, 41.3; H, 2.7; N, 5.1; S, 5.8%).
Mp: 203 ЊC (decomp.). IR (Nujol, cmϪ1) νas(SO2) 1240, νs(SO2)
1095, ν(Pd–C6F5) 765. 1H NMR (CDCl3) δ 3.93 (t, 2 H,
SO2OCH2CH2CH3, J 6.7 Hz), 1.49 (m, 2 H, SO2OCH2CH2-
CH3), 1.13 (t, 3 H, SO2OCH2CH2CH3, J 7.3 Hz). 4: Yield 78%
(Found: C, 41.2; H, 2.8; N, 5.0; S, 5.6. C19H15N2F5O3PdS
requires C, 41.3; H, 2.7; N, 5.1; S, 5.8%). Mp: 227 ЊC (decomp.).
IR (Nujol, cmϪ1) νas(SO2) 1284, νs(SO2) 1104, ν(Pd–C6F5) 796.
1H NMR (CDCl3) δ 3.51 (s, 3H, SO2OCH3). 5: Yield 70%
(Found: C, 42.0; H, 3.1; N, 5.0; S, 5.6. C20H17N2F5O3PdS
requires C, 42.4; H, 3.0; N, 4.9; S, 5.7%). Mp: 215 ЊC (decomp.).
IR (Nujol, cmϪ1): νas(SO2) 1235, νs(SO2) 1095, ν(Pd–C6F5) 795.
1H NMR (CDCl3) δ 4.03 (q, 2 H, SO2OCH2CH3, J 6.8 Hz), 1.03
(t, 3 H, SO2OCH2CH3, J 6.8 Hz).
Conclusion
S-Bound alkyl sulfite–palladium complexes are readily
obtained when SO2 is bubbled through an alcoholic solution of
the mononuclear hydroxo complexes [Pd(N–N)(C6F5)(OH)].
The reaction products are the result of the insertion of SO2 into
the Pd–OR bond of alkoxy–palladium intermediates formed
from the acid–base reaction between the hydroxo complex and
the corresponding alcohol (Pd–OH ϩ ROH = Pd–OR ϩ H2O).
Although the presence of the Pd–OR complex is demonstrated
by NMR spectroscopy, attempts made to isolate pure samples
of the alkoxy complex were fruitless. This result is consistent
with the previous one that the σ-ligand metathesis reaction
Pt–OH ϩ MeO–H = Pt–OMe ϩ H–OH is reversible and nearly
thermoneutral.27 Obviously, the subsequent reaction of added
SO2 with the alkoxy complex forces the equilibrium system
in the direction of the Pd–OR complex. So alcoholic solutions
of the hydroxo complex are convenient reagents for the pre-
paration of alkyl sulfite–palladium complexes. The method
parallels the recently reported syntheses of methoxy carbonyl–
palladium complexes by reaction of carbon monoxide with
alcoholic solutions of hydroxo–palladium complexes. In the
absence of alcohol the reaction of SO2 with the hydroxo com-
plex leads to the insertion of SO2 into the Pd–OH bond and the
hydrogen sulfite complex (Pd–SO2OH) is formed. When this
result is compared with that obtained from the reaction of CO2
with Pd–OH1 some discrepancy is found. In latter case the
hydrogen carbonate complex reacts with the starting hydroxo
complex to finally give the carbonate-bridged binuclear com-
plex Pd{OC(O)O}Pd with the concomitant formation of water.
The non-acidic behaviour of coordinated alkyl sulfite towards
the hydroxo–palladium complex may be a consequence of the
S-coordination of the SO2OR ligand.
Preparation of complexes [Pd(N–N)(C6F5)(SO2OR)]
(N–N ؍ tmeda, R ؍ Me 6, Et 7, Pr 8, or iPr 9)
Through an alcohol (methanol, ethanol, propanol or iso-
propanol) solution (15 mL) of the hydroxo palladium complex
[Pd(tmeda)(C6F5)(OH)] (55 mg, 0.135 mmol) at room temper-
ature was passed SO2 for 10 min. After evaporation of the
solvent under reduced pressure, the residue was treated with
ether–hexane and a white solid was collected by filtration and
air-dried. 6: Yield 45 mg, 68% (Found: C, 31.9; H, 4.0; N, 6.0; S,
6.4. C13H19N2F5O3PdS requires C, 32.2; H, 4.0; N, 5.8; S, 6.6%).
Mp: 208 ЊC (decomp.). IR (Nujol, cmϪ1) νas(SO2) 1235, νs(SO2)
1095, ν(Pd–C6F5) 770. 1H NMR (CDCl3) δ 3.42 (s, 3H,
SO2OCH3). 7: Yield 73% (Found: C, 33.9; H, 4.3; N, 5.5; S, 6.3.
C14H21N2F5O3PdS requires C, 33.7; H, 4.2; N, 5.6; S, 6.4%).
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Mp: 200 ЊC (decomp.). IR (Nujol, cmϪ1) νas(SO2) 1240, νs(SO2)
1095, ν(Pd–C6F5) 770. 1H NMR (CDCl3) δ 3.90 (q, 2 H,
SO2OCH2CH3, J 7.0 Hz), 1.07 (t, 3 H, SO2OCH2CH3,
J 7.0 Hz). 8: Yield 78% (Found: C, 34.9; H, 4.5; N, 5.4; S, 6.1.
C15H23N2F5O3PdS requires C, 35.1; H, 4.5; N, 5.5; S, 6.3%).
Mp: 197 ЊC (decomp.). IR (Nujol, cmϪ1) νas(SO2) 1230, νs(SO2)
1090, ν(Pd–C6F5) 775. 1H NMR (CDCl3) δ 3.72 (t, 2 H,
SO2OCH2CH2CH3, J 6.7 Hz), 1.40 (m, 2 H, SO2OCH2CH2-
CH3), 0.75 (t, 3 H, SO2OCH2CH2CH3, J 7.0 Hz). 9: Yield 87%
(Found: C, 34.9; H, 4.5; N, 5.6; S, 6.4. C15H23N2F5O3PdS
requires C, 35.1; H, 4.5; N, 5.5; S, 6.3%). Mp: 229 ЊC (decomp.).
IR (Nujol, cmϪ1) νas(SO2) 1240, νs(SO2) 1090, ν(Pd–C6F5) 770.
1H NMR (CDCl3) δ 4.64 (sept, 1H, SO2OCH(CH3)2, J 6.3 Hz),
1.03 (d, 6H, SO2OCH(CH3)2, J 6.3 Hz).
by full matrix least squares Enraf-Nonius MolEN programs.29
Hydrogen atoms were included using a riding model.
Crystal data. Formula: C15H23F5N2O3PdS. Mr = 512.8, tri-
¯
clinic, space group P1 (no. 2), a = 8.141(2), b = 8.6250(10),
c = 15.837(2) Å, α = 96.830(10), β = 98.26(2), γ = 112.930(10),
V = 994.7(3) Å3, Z = 2. T = 293 K, µ = 1.10 mmϪ1. Number
of reflections measured: 5776. Final R indices [I > 2σ(I )]:
R1 = 0.028; R indices (all data): R1 = 0.034.
CCDC reference number 227318.
See http://www.rsc.org/suppdata/dt/b3/b316697j/ for crystal-
lographic data in CIF or other electronic format.
Acknowledgements
Preparation of complexes [Pd(N–N)(C6F5)(SO2OR)]
(N–N ؍ bis(3,5-dimethylpyrazol-1-yl)methane,
CH2(C3HMe2N2)2; R ؍ Me 10, Et 11)
This work was supported by the Dirección General de Investi-
gación 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), Spain.
To a solution of [Pd(N–N)(C6F5)Cl] (100 mg, 0.19 mmol) in
acetone (15 ml) was added AgClO4 (40 mg, 0.19 mmol). The
suspension was stirred at room temperature for 30 min pro-
tected from light. The white AgCl was then filtered off. The
resulting solution was concentrated to dryness under vacuum.
The residue was redissolved in the corresponding alcohol ROH
(R = Me or Et) (10 ml) and KOH (aq) (11 mg, 0.19 mmol) was
added. A SO2 stream was then passed through the resulting
mixture for 10 min. Then the solution was concentrated under
vacuum. The addition of water caused the precipitation of a
white solid which was collected by filtration, washed with water
and air-dried. 10: Yield 76% (Found: C, 37.8; H, 3.4; N, 9.6; S,
5.4. C18H19N4F5O3PdS requires C, 37.7; H, 3.3; N, 9.8; S, 5.6%).
Mp: 211 ЊC (decomp.). IR (Nujol, cmϪ1) νas(SO2) 1228, νs(SO2)
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14 D. A. Long and D. Steel, Spectrochim. Acta, 1963, 19, 1955.
15 E. Maslowski, Vibrational Spectra of Organometallic Compounds,
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20 G. D. Smith, B. E. Hanson, J. S. Merola and F. J. Waller,
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21 J. Forniés, F. Martínez, R. Navarro and E. P. Urriolabeitia,
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1
1106, ν(Pd–C6F5) 798. H NMR (CDCl3) δ 7.17 (d, 1H, CH,
Jab 14.9 Hz), 6.34 (d, 1H, CH, Jab 14.9 Hz), 5.88 (s, 1H, H4Ј),
5.75 (s, 1 H, H4), 3.42 (s, 3H, SO2OCH3), 2.50 (s, 3H, Me3Ј),
2.31 (s, 6H, Me5 and Me5Ј), 1.72 (s, 3 H, Me3). 19F NMR
(CDCl3) δ Ϫ119.8 (m, 1Fo), Ϫ120.1 (m, 1Fo), Ϫ159.8 (t, 1Fp,
J(FmFp) 20.3 Hz), Ϫ162.9 (m, 1Fm), Ϫ163.8 (m, 1Fm). 11: Yield
82% (Found: C, 38.6; H, 3.6; N, 9.8; S, 5.3. C19H21N4F5O3PdS
requires C, 38.9; H, 3.6; N, 9.6; S, 5.5%). Mp: 252 ЊC (decomp.).
IR (Nujol, cmϪ1) νas(SO2) 1244, νs(SO2) 1096, ν(Pd–C6F5) 794.
1H NMR (CDCl3) δ 7.17 (d, 1H, CH, Jab 15.0 Hz), 6.34 (d, 1H,
CH, Jab 15.0 Hz), 5.88 (s, 1H, H4Ј), 5.74 (s, 1 H, H4), 3.85 (q,
2H, SO2OCH2CH3, J 7.1 Hz), 2.51 (s, 3H, Me3Ј), 2.32 (s, 3H,
Me5), 2.30 (s, 3H, Me5Ј), 1.72 (s, 3H, Me3), 0.97 (t, 3H,
SO2OCH2CH3, J 7.1 Hz). 19F NMR (CDCl3) δ Ϫ119.9 (m, 2Fo),
Ϫ159.9 (t, 1Fp, J(FmFp) 20.3 Hz), Ϫ162.9 (m, 1Fm), Ϫ164.1 (m,
1Fm).
Preparation of the complex [Pd(N–N)(C6F5)(SO2OH)]
(N–N ؍ bipy 12)
Through a tetrahydrofuran solution (15 mL) of the hydroxo
palladium complex [Pd(bipy)(C6F5)(OH)] (60 mg, 0.134 mmol)
at room temperature was passed SO2 for 10 min. The solvent
was partially evaporated under vacuum and a suspension was
obtained from which a white solid was collected by filtration
and dried in the oven. Yield 90% (Found: C, 37.3; H, 2.0; N, 5.3;
S, 6.3. C16H9N2F5O3PdS requires C, 37.6; H, 1.8; N, 5.5; S,
6.3%). Mp: 236 ЊC (decomp.). IR (Nujol, cmϪ1) νas(SO2) 1185,
νs(SO2) 1070, ν(Pd–C6F5) 790
22 H. E. Bryndza and W. Tam, Chem. Rev., 1988, 88, 1163, and
references therein.
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1988, 27, 3880.
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G. López, P. A. Chaloner and P. B. Hitchcock, Polyhedron, 2001, 20,
571.
X-Ray structure determination
27 H. E. Bryndza, S. A. Kretchmar and T. H. Tulip, J. Chem. Soc.,
Chem. Commun., 1985, 977.
28 Program for Crystal Structure Solution: G. M. Sheldrick, Institüt
für Anorganische Chemie der Universität, Tammanstrasse 4,
D-3400 Göttingen, Germany, 1986.
Suitable crystals of 8 were grown from benzene–hexane. The
crystal was mounted onto the tip of a glass fiber, and the data
collection was performed with a Enraf-Nonius CAD4 diffract-
ometer. The scan mode was θ–2θ. The structure was solved by
heavy atom methods (SHELXS-86).28 The structure was refined
29 MolEN, CAD4 Software, Version 5.0, Enraf-Nonius, Delft, 1989.
D a l t o n T r a n s . , 2 0 0 4 , 9 2 9 – 9 3 2
932