Preparation of complexes of palladium chloride with di-tert-butylsydnonylphosphine and diphenylsydnonylphosphine and structural analysis of the sydnone ring containing phosphine and palladium complex

Article abstract of DOI:10.1016/S0022-328X(00)00321-1

Three sydnonylphosphinepalladium(II) chloride were prepared. X-ray analyses of complexes of diphenylsydnonylphosphine with palladium chloride reveals that the sydnone ring contributes electrons through phosphorus to metal resulting in decreasing substanti

Full text of DOI:10.1016/S0022-328X(00)00321-1

www.elsevier.nl/locate/jorganchem
Journal of Organometallic Chemistry 610 (2000) 1–7
Preparation of complexes of palladium chloride with
di-tert-butylsydnonylphosphine and diphenylsydnonylphosphine
and structural analysis of the sydnone ring containing phosphine
and palladium complex
Shaw-Tao Lin a,*1, Hung-Sheng Choe a, Lin-Shuh Liu b, Ju-Chun Wang b,*2
a Department of Applied Chemistry, Pro6idence Uni6ersity, Sha-Lu, Taichung Hsien 433-01 Taiwan
b Department of Chemistry, Soochow Uni6ersity, Taipei 111-01, Taiwan
Received 9 March 2000; received in revised form 19 April 2000; accepted 25 April 2000
Abstract
Three sydnonylphosphinepalladium(II) chloride were prepared. X-ray analyses of complexes of diphenylsydnonylphosphine
with palladium chloride reveals that the sydnone ring contributes electrons through phosphorus to metal resulting in decreasing
substantial bond lengths. By comparing the bond length of PꢀC(sydnone) and PꢀC(phenyl) suggests that phenyl rings are able to
contribute more electrons to phosphorus for chelation leading to short PꢀC(phenyl) bond lengths. © 2000 Elsevier Science S.A.
All rights reserved.
Keywords: Sydnonylphosphines; Crystal structures; Sydnonylphosphinepalladium chloride; Mesoionic compounds; Disubstituted sydnones
1. Introduction
a complex with a metal halide. A number of crystal
structures of sydnones have been reported [5], but none
of them containing a phosphine moiety. In this work,
we attempted to compare the variation of bond lengths
of the sydnone ring in compounds 3, 4, and 8 by means
of X-ray analyses. From the comparison of the bond
length of phosphorusꢀcarbon [PꢀC(sydnone) or
P(s)ꢀC(4), PꢀC(phenyl) or P(s)ꢀC(p)] in compounds 4
and 8 to conclude the ability of electron-donating of the
sydnone ring relating to the phenyl ring. Substantial
shorter bonds in the sydnone ring were observed after
the formation of the palladium complex is reported
(Scheme 1).
The chemical and physical properties of sydnone and
its derivatives have attracted significant interest due to
their unique electronic structure and their physical
properties. In general, the sydnone ring demonstrates
the electron-withdrawing character on N(3) and elec-
tron-donating properties on C(4) and are also confi-
rmed by various calculations [1]. This dual character of
the ring has been observed in the nitration of 3-(4-
alkylphenyl)sydnones and 3-benzylsydnones, resulting
in the formation of 3-(4-alkyl-3-nitrophenyl)sydnone
and 3-(3-nitrobenzyl)sydnone, respectively [2]. Elec-
trophilic substitution, i.e. formylation and acetylation,
takes place at the C(4) position [3]. Position C(4) can be
functionalized by various functional groups, such as
phosphino, silyl, alkyl, halide, etc. [4]. The structure of
the sydnone ring shall be influenced by the addition of
the phosphino group at C(4), and even the formation of
2. Results and discussion
Sydnones containing the phosphino group at the
4-position were prepared in 1986 [6]. However, in our
previously work, it was the first report dealing with the
preparation of the palladium complex from syd-
nonylphosphine [7]. Reaction of di-tert-butyl-4-anisyl-
sydnonylphosphine (2) with PdCl2 in the presence of
1 *Corresponding author. Fax: +1-886-46327554; e-mail:
sdlin@pu.edu.tw
2 *Corresponding author.
0022-328X/00/$ - see front matter © 2000 Elsevier Science S.A. All rights reserved.
PII: S0022-328X(00)00321-1

2
S.-T. Lin et al. / Journal of Organometallic Chemistry 610 (2000) 1–7
concentrated HCl resulting in a dimeric product 5 with
ortho-metallation at the phenyl ring [7] (Scheme 2)
Under the same condition, di-tert-butyl(phenylsyd-
nonyl)phosphine (1), diphenyl(phenylsydnonyl)phos-
phine (3), and diphenyl(2-diphenylphosphinophenylsyd-
nonyl)phosphine (4) were reacted with PdCl2, instead of
2, resulting in the complexes 6, 7, and 8, respectively,
without ortho-metallation (Scheme 3). Apparently, the
combination of the methoxyl group on the phenyl ring
and the tert-butyl group on the phosphorus is essential
for palladium to insert into the C(phenyl)ꢀH bond. The
IR absorption by the carbonyl group of the sydnone
ring in compounds 6, 7, and 8 have the same wavenum-
ber as the free state of 1, 3, and 4. The 31P-NMR of
complex 8 exhibits two doublets at l 25.95 and 12.78
with a coupling constant of 15 Hz. The small coupling
constant indicates two phosphorus atoms chelate with a
palladium atom in the cis-form. Those air-stable com-
plexes are quite stable under heating before the decom-
position point, except complex 8, which changes from
yellow to orange, to red and then melted at 125, 135,
and 232–235°C, respectively.
The C(4) of the sydnone ring has been recognized as
an electron-donating character. In this study, we would
like to investigate the structure of sydnone ring in
compounds 3, 4, and 8 by means of X-ray diffraction
analyses (Figs. 1–3). Their crystal data and experimen-
tal parameters are given in Table 1. The bond length of
Scheme 1.
Scheme 2.

S.-T. Lin et al. / Journal of Organometallic Chemistry 610 (2000) 1–7
3
paring the influence of the phosphino group at C(4).
In general, compound containing diphenylphosphino
group at C(4) as well as C%(2) leads to a slight change in
the bond length. The lengths of the N(3)ꢀC(4),
,
C(4)ꢀC(5) and C(5)ꢀO(1) [1.363(5), 1.420(4), 1.412(6) A
,
(3); 1.359(6), 1.429(7), 1.422(6) A (4)], are apparently
longer than those of the five independent molecules
with disubstituents at the 3-, 4-positions which are
,
,
,
1.350–1.358 A, [average, 1.352 A], 1.413–1.420 A, [av-
,
,
erage 1.417], 1.399–1.419 A, [average 1.408 A], respec-
tively. There are larger effects on the N(3)ꢀC(1p) and
,
N(2)ꢀN(3) bonds [1.419(3), 1.302(5) A (3), 1.420(5),
,
1.300(6) A (4)], for which the range of lengths for the
,
disubstituted compounds is 1.447–1.467 A, [average
,
,
,
1.456 A] and 1.295–1.325 A, [average 1.313 A]. The
phosphino group is able to donate the electron to the
sydnone ring to increase the bonds connected to C(4)
and to decrease the bond length of bonds connected to
N(3). In addition, the bond length of C(4)ꢀP(1s)
,
[1.807(4) A], is much shorter than that of P(1s)ꢀC(p)
[1.832(2) and 1.838(2) A]. It suggests that the phospho-
,
rus atom is bound well with C(4) of sydnone ring.
Evidently, the presence of the phosphorus moiety de-
creases the bonding ability of C(4) and C(5), and
enhances the ability of N(2) and N(3). It might indicate
more electron localization for the compounds contain-
ing the phosphine group at C(4) position.
When a ligand binds with a metal, it will donate the
electron pair to the metal for complexation. During this
process, the electron density of the ligand will be lower
Scheme 3.
the sydnone ring, the selected bond lengths, and bond
angles in compounds 3, 4, 5, and 8 along with the
average value obtained from five four-substituted 3-
arylsydnones were summarized in Table 2. The bond
length of 4-substituted sydnones was chosen for com-
Fig. 1. ORTEP drawing of 3 with thermal ellipsoids shown at the 30% probability level.

4
S.-T. Lin et al. / Journal of Organometallic Chemistry 610 (2000) 1–7
Fig. 2. ORTEP drawing of 4 with thermal ellipsoids shown at the 30% probability level.
Fig. 3. ORTEP drawing of 8 with thermal ellipsoids shown at the 30% probability level.
than in the free state. When compound 4 chelates with
PdCl2, we expect the electron of the sydnone ring to
flow to the metal via a phosphorus atom and result in
a change of the bond length of the ring. Indeed, the
bond lengths of the sydnone ring decrease substantial,
,
especially for O(1)ꢀN(2) [1.382(5) (4) vs. 1.332(16) A

S.-T. Lin et al. / Journal of Organometallic Chemistry 610 (2000) 1–7
5
,
(8)] and C(5)ꢀO(6) [1.202(6)(4) vs. 1.159(19) A (8)]. The
more electron localization in the sydnone ring. The
bond lengths of the sydnone ring are reduced by bond-
ing with metals, suggesting an electron flow during the
complexation. In comparison, the bond lengths of
PꢀC(sydnone) and PꢀC(phenyl) suggest that phenyl
rings are able to contribute more electrons to phospho-
rus for chelation, leading to smaller PꢀC(phenyl) bond
lengths.
decrease of bond lengths of the C(4)ꢀP(1s) [1.796(5) (4)
,
vs. 1.802(12) A (8)] is much less than that of P(1s)ꢀC(p)
[1.822(5), 1.835(3) (4) vs. 1.784(9), 1.789(10) A (8)]. It
suggests that the phenyl ring is a better electron dona-
tor than the sydnone ring to phosphorus. Although the
bond lengths of the sydnone ring are varied substan-
tially, the bond angles do not exhibit a significant
change.
,
By comparison with the bond lengths of P(s)ꢀPd in
,
,
compounds 5 [2.257(1) A] and 8 [2.237(3) A], the
former is longer due to the better electron-donating
nature of the tert-butyl group on the phosphorus atom
for binding with PdII. The PdꢀCl distance [2.344(4),
3. Experimental
All melting points were measured with a Yanaco
MP-J3 apparatus and are uncorrected. 1H- and 31P-
NMR spectra were recorded on a Bruker AC-250 spec-
trometer at 250 and 101.20 MHz, respectively. IR data
were obtained using a Perkin–Elmer 883 spectrophoto-
meter. FAB mass spectra were measured on a JEOL
JM5-SX/SX 102A spectrometer, using 3-nitrobenzyl al-
cohol as a solvent. Microanalyses were performed on a
Heraeus CHNꢀO rapid analyzer. Di-tert-butyl(3-
phenylsydnonyl)phosphine (1), diphenyl(3-phenylsyd-
nonyl)phosphine (3), and diphenyl[3-(2-diphenylphos-
phinophenylsydonyl)phosphine (4), were prepared as
described in the literature [4].
,
2.336(4) A] are closed to cis-PdCl2 in Calix[6]arene
,
[2.309(3), 2.317(2) A] [11]. For comparison, the bond
lengths of PdꢀCl in some recent reports are [2.3917(8),
2.4018(8) A], 2.408(1) A for Cl trans respective to aryl
[12], and the CH2SCH3 group [13], respectively, and
,
,
,
2.437(1) A in a bridging type in our previous report [7].
The trans-effect resulted in different PdꢀCl distances,
further suggesting the cis-relationship of two chlorine
atoms.
In this study, we find that the phosphino group at
C(4) possesses an electron-donating nature leading to
Table 1
Crystal data for compounds 3, 4, and 8
Compound 3
Compound 4
Compound 8
Formula
C20H15O2N2P
C32H24N2O2P2
C32H24Cl2N2O2P2Pd
Crystal size (mm)
Crystal system
Space group
0.2×0.4×0.5
Triclinic
0.3×0.4×0.5
Monoclinic
P21/n
0.3×0.4×0.5
Orthorhombic
P212121
(
P1
Formula weight
346.3
530.5
723.8
,
a (A)
9.814(2)
10.214(2)
10.273(2)
72.15(1)
78.80(1)
62.98(1)
871.3(3)
2
13.336(2)
13.524(1)
15.538(1)
10.145(2)
12.758(2)
28.174(2)
,
b (A)
,
c (A)
h (°)
i (°)
k (°)
100.28(1)
3
,
V (A )
2757.4(4)
4
1.278
Colorless
0.190
3646.6(5)
4
1.318
Yellow
0.774
Z
Dcalc (g cm−3
Crystal color
)
1.320
Yellow
0.173
v (mm−1
)
Reflections measured
Unique reflections
Observed reflections
Criterion for observation
Rint
2411
2252
1835
F\3|(F)
0.0211
190
0.0471; 0.0540
0.0002
1.66
3787
3606
2322
F\4|(F)
0.0295
283
0.0574; 0.0643
0.0006
1.34
3655
3626
2634
F\4|(F)
0.0000
320
0.0553; 0.0653
0.0005
1.44
Variables
a
R; Rw
g
Goodness-of-fit
Max. shift/|
Residual electron density (e A
0.000
0.26
0.001
0.34
0.001
0.47
−3
,
)
a R=ꢀ(ꢁFoꢁ−ꢁFcꢁ)/ꢀ(ꢁFꢁ); Rw=[ꢀ w(ꢁFoꢁ−ꢁFcꢁ)2/ꢀ wꢁFoꢁ]2]1/2. w=[|2(Fo)+gF2o]−1
.

6
S.-T. Lin et al. / Journal of Organometallic Chemistry 610 (2000) 1–7
Table 2
,
Selected interatomic distances (A) and angles (°) in compounds 3, 4, 5, and 8
Compound 3
Compound 4
Compound 8
Compound 5
Average a
[7]
Interatomic distances
O(1)ꢀN(2)
N(2)ꢀN(3)
N(3)ꢀC(4)
C(4)ꢀC(5)
C(5)ꢀO(1)
C(5)ꢀO(6)
N(3)ꢀC(1p)
C(4)ꢀP(1s)
P(1s)ꢀC(p)
P(1p)ꢀC(p)
P(1s)ꢀPd
1.378(4)
1.302(5)
1.363(5)
1.420(4)
1.412(6)
1.209(5)
1.419(3)
1.807(4)
1.382(5)
1.300(6)
1.359(6)
1.429(7)
1.422(6)
1.202(6)
1.420(5)
1.796(5)
1.332(16)
1.286(15)
1.356(16)
1.411(19)
1.403(19)
1.159(19)
1.414(12)
1.802(12)
1.784(9), 1.789(10)
1.784(10), 1.816(8), 1.857(7)
2.237(3)
2.262(3)
2.344(4)
1.363 (4)
1.306(4)
1.379(4)
1.430(4)
1.409(5)
1.207(5)
1.427(5)
1.794(3)
1.378 (1.368–1.382)
1.313 (1.295–1.325)
1.352 (1.350–1.358)
1.417 (1.413–1.420)
1.408 (1.399–1.419)
1.205 (1.196–1.217)
1.456 (1.447–1.467)
1.832(2), 1.838(2) 1.822(5), 1.835(3)
1.837(4), 1.842(4), 1.866(3)
2.257(1)
2.437(1)
P(1p)ꢀPd
PdꢀCl(1)
PdꢀCl(2)
2.336(4)
Interatomic angles
O(1)ꢀN(2)ꢀC(4) 104.3(4)
N(2)ꢀN(3)ꢀC(4) 115.8(3)
N(3)ꢀC(4)ꢀC(5) 104.6(4)
C(4)ꢀC(5)ꢀO(1)
C(5)ꢀO(1)ꢀN(2) 110.8(3)
C(4)ꢀC(5)ꢀO(6) 136.3(5)
N(2)ꢀN(3)ꢀC(1p) 115.5(3)
N(3)ꢀC(4)ꢀP(1s) 123.0(2)
P(1s)ꢀPdꢀP(2p)
103.1(3)
105.8(10)
115.1(10)
103.8(11)
104.6(12)
110.6(10)
136.1(15)
117.0(9)
122.7(9)
93.4(1)
104.8(3)
115.5(3)
103.8(3)
104.5(3)
111.2(3)
136.8(4)
116.5(3)
122.6(2)
117.7(4)
103.8(4)
104.1(4)
111.3(3)
136.2(5)
116.3(4)
121.8(3)
104.4(3)
P(1s)ꢀPdꢀCl(1)
P(2p)ꢀPdꢀCl(2)
Cl(1)ꢀPdꢀCl(2)
88.5(1)
90.4(1)
90.1(1)
102.8(1)
a Average values from five 3,4-disubstituted sydnones [4-acetyl-3-(4-toyl)sydnone [8], 4-acetyl-3-phenylsydnone oxime [8]. 4-(3-Methyl-1-buten-2-
yl)-3-phenylsydnone [9]. 4-Cyclohexenyl-3-phenylsydnone [9]. 3-Phenyl-4-(N-carbamyl-1,4,2-oxathiazolimin-3-yl)sydnone] [10].
3.1. Reaction of diphenyl(3-phenylsydnonyl)phosphine
(3) and PdCl2
crystals. M.p. (dec.) 188–200°C; IR (KBr) 1743
1
cm−1(wCꢁO); H-NMR (CDCl3) l 1.40 (s, 18H), 1.49 (s,
18H), 7.53–7.65 (m, 10H); 31P-NMR (CDCl3) l 50.53
(s); FAB-MS m/z (relative intensity) 753 (M+1−HCl,
7), 585 (M+1−306−HCl, 100), 412 (M+1−306−
HClꢀCl, 41), 354 (M+1−306−HClꢀClꢀCOꢀNO, 51);
Anal. Calc. for C32H46Cl2N4O4P2Pd: C, 48.65; H, 5.87;
N, 7.09. Found: C, 48.39; H, 5.94; N, 7.09%.
A mixture of PdCl2 (35.4 mg, 0.2 mmol) in HCl
(conc. 8.0 ml) solution and compound 3 (141.0 mg, 0.4
mmol) was heated at 80°C for 4 h. The yellow crystals
were filtered out and then crystallized from CH2Cl2
with the aid of diffusion of diethyl ether to give 149.0
mg (86% yield) of compound 7 as orange crystals. M.p.
(dec.) 226–228°C; IR (KBr) 1762 cm−1(wCꢁO); 1H-
NMR (CDCl3) l 7.35–7.58 (m, 20H), 7.70–7.83 (m,
10H); 31P-NMR (CDCl3) l 39.80 (s); FAB-MS m/z
(relative intensity) 833 (M+1−HCl, 15), 460 (M+
3.3. Reaction of diphenyl[3-(2-diphenylphosphino-
phenylsydonyl)]phosphine (4) and PdCl2
A mixture of PdCl2 (35.2 mg, 0.2 mmol) in HCl
(conc. 8.0 ml) solution and compound 4 (120 mg, 0.2
mmol) was heated at 80°C for 4 h. The yellow crystals
were filtrated out and then crystallized from CH2Cl2
with the aid of diffusion of diethyl ether to give 106.0
mg (68% yield) of compound 8 as yellow cubic crystals;
M.p. (dec.) 232–235°C; IR (KBr) 1760 cm−1(wCꢁO);
1H-NMR (CDCl3) l 7.45–7.68 (m, 24H); 31P-NMR
(CDCl3) l 25.95 (d, J=15 Hz), 12.78 (d, J=15 Hz);
FAB-MS (relative intensity) m/z 671(M+1−HCl, 80),
1−346−HClꢀCO,
100),
429
(M+1−346−
HClꢀCOꢀNO, 31); Anal. Calc. for C40H30Cl2N4O4P2Pd:
C, 55.22; H, 3.48; N, 6.44. Found: C, 55.07; H, 3.29; N,
6.45%.
3.2. Reaction of
di-tert-butyl(3-phenylsydnonyl)phosphine (1) and PdCl2
Same procedure was adapted for this preparation to
give 131.0 mg (83% yield) of compound 6 as red needle

S.-T. Lin et al. / Journal of Organometallic Chemistry 610 (2000) 1–7
7
613 (M+1−ClꢀCOꢀNO, 25), 578 (M+1−
Acknowledgements
2ClꢀCOꢀNO, 100); Anal. Calc. for C32H24Cl2N2-
O2P2Pd: C, 54.30; H, 3.42; N, 3.96. Found: C, 54.06; H,
3.55; N, 4.02%.
Financial support by the National Science Council of
the Republic of China (NSC85-2113-M-126-003 STL;
All crystals were mounted on a glass fiber for X-ray
structural analysis. Cell constants were derived from
least-square refinements of 25 high-angle reflections
having of 15B2qB25. Intensity data were collected
using a ꢀ scan mode on a Siemens P4 diffractometer
equipped with graphite monochromatized Mo–Ka radi-
NSC85-2113-M-031-004
acknowledged.
JCW)
is
gratefully
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data. Three standard reflections were measured every
300 reflections and only small (B6%) random varia-
tions were observed. Lorentz and polarization correc-
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The palladium atom was revealed on a Patterson map.
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Tables of atomic coordinates and displacement
parameters and complete lists of bond lengths and
angles have been deposited at the Cambridge Crystallo-
graphic Database Centre. The deposition numbers
CCDC 142603, 142604, and 142605 have been allocated
to the compounds 3, 8, and 4, respectively. Copies of
this information can be obtained free of charge from
The Director, CCDC, 12 Union Road, Cambridge CB2
1EZ, UK (fax: +44-1223-336033; e-mail: deposit@
ccdc.cam.ac.uk or www:http://www.ccdc.cam.ac.uk).
.