Phosphine σ-sydnonyl complexes of Ni, Pd, and Pt

Article abstract of DOI:10.1023/A:1011338029948

3-R′-4-Bromosydnones 1 (R′ = Me) and 2 (R′ = Ph) react with complexes M(PR₃)_n (M = Ni, Pd, Pt) to form mononuclear phosphine σ-sydnonyl d⁸-complexes of trans-configuration MBr(3-R′-sydnon-4-yl)(PR₃)₂: 3, 4 (M = Ni, R′ = Ph); 5 (M = Pd, R′ = Me); 6a (M = Pd, R′ = Ph); 7 (M = Pt, R′ = Ph). In the reaction of bromosydnone 2 with Pd(PPh₃)₄, the cis-complex PdBr(3-Ph-sydnon-4-yl)(PPh₃)₂ (6b) is formed initially; 6b rearranges in solution to give trans-complex 6a. On heating in THF, complex 6a is converted into the binuclear [PdBr(3-phenylsydnon-4-yl)(PPh₃)]₂ complex (8). The reaction of 4-chloromercurio-3-phenylsydnone (10) with Ni(PEt₃)₄, Pt(PPh₃)₄, and Pt(PPh₃)₄ gives mononuclear NiCl(3-phenylsydnon-4-yl)(PEt₃)₂ complex (11), binuclear [PdCl(3-phenylsydnon-4-yl) (PPh₃)]₂ complex (14), and cis- and trans-bimetallic PtCl(3-phenylsydnon-4-ylmercurio)(PPh₃)₂ complexes 15a and 15b, respectively. UV irradiation of 15a and 15b in a benzene solution induces redox demercuration to yield the PtCl(3-phenylsydnon-4-ylcarbonyl)(PPh₃)₂ complex (16). In carbonylation of complexes 3, 6, and 7, CO insertion into the M-C bond occurred to form the corresponding acyl derivatives MBr(3-phenylsydnon-4-ylcarbonyl)(PR₃)₂ (17-19).

Full text of DOI:10.1023/A:1011338029948

Russian Chemical Bulletin, International Edition, Vol. 50, No. 3, pp. 525—530, March, 2001
525
Phosphine σ-sydnonyl complexes of Ni, Pd, and Pt
V. N. Kalinin,« F. M. She, V. N. Khandozhko, and P. V. Petrovskii
A. N. Nesmeyanov Institute of Organoelement Compounds, Russian Academy of Sciences,
28 ul. Vavilova, Moscow 117813, Russian Federation.
Fax: +7 (095) 135 5085. E-mail: vkalin@ineos.ac.ru
3-R′-4-Bromosydnones 1 (R´ = Me) and 2 (R´ = Ph) react with complexes Ì(PR3)n
(M = Ni, Pd, Pt) to form mononuclear phosphine σ-sydnonyl d8-complexes of trans-configu-
ration MBr(3-R´-sydnon-4-yl)(PR3)2: 3, 4 (Ì = Ni, R´ = Ph); 5 (M = Pd, R´ = Me); 6a
(M = Pd, R´ = Ph); 7 (M = Pt, R´ = Ph). In the reaction of bromosydnone 2 with
Pd(PPh3)4, the cis-complex PdBr(3-Ph-sydnon-4-yl)(PPh3)2 (6b) is formed initially; 6b
rearranges in solution to give trans-complex 6a. On heating in THF, complex 6a is converted
into the binuclear [PdBr(3-phenylsydnon-4-yl)(PPh3)]2 complex (8). The reaction of
4-chloromercurio-3-phenylsydnone (10) with Ni(PEt3)4, Pd(PPh3)4, and Pt(PPh3)4 gives
mononuclear NiCl(3-phenylsydnon-4-yl)(PEt3)2 complex (11), binuclear [PdCl(3-phenyl-
sydnon-4-yl) (PPh3)]2 complex (14), and cis- and trans-bimetallic PtCl(3-phenylsydnon-
4-ylmercurio)(PPh3)2 complexes 15a and 15b, respectively. UV irradiation of 15a and 15b in a
benzene solution induces redox demercuration to yield the PtCl(3-phenylsydnon-
4-ylcarbonyl)(PPh3)2 complex (16). In carbonylation of complexes 3, 6, and 7, CO insertion
into the M—C bond occurred to form the corresponding acyl derivatives MBr(3-phenylsydnon-
4-ylcarbonyl)(PR3)2 (17—19).
Key words: sydnones, nickel, palladium, platinum, σ-complexes, oxidative addition,
carbonylation, redox demercuration.
Scheme 2
RHgM(PR´3)2X
One of the methods for the preparation of heterocy-
clic derivatives with C—M σ-bonds (M is a transition
metal) is oxidative addition of heteryl halides to
zerovalent Ni, Pd, and Pt phosphine complexes.1 De-
pending on the nature of the metal, reactant ratio, and
reaction conditions, either mono- or binuclear com-
plexes are formed (Scheme 1).
M(PR´ )
n
3
RHgX
RM(PR´3)2X
X = Cl
M = Ni, Pd, Pt
can also be achived by using sterically hindered deriva-
tives, namely, duryl, mesityl, indolyl, carboranyl, and
manganese- and rheniumcyclopentadienyl(tricarbonyl)
derivatives.10,11 The absence of the above-noted factors
in the bimetallic Hg—M complexes (M = Ni, Pd, Pt)
results in redox demercuration giving rise to a monome-
tallic complex.
Scheme 1
R
M(PR´3)2Hal
Hal
M(PR´ )
n
3
RHal
(PR´3)RM
MR(PR´3)
Hal
M = Ni, Pd, Pt
In this study, using mesoionic heterocycles, sydnones,
we prepared the first representatives of mesionic com-
pounds containing a C—M σ-bond (M = Ni, Pd, Pt),
studied the behavior of these compounds toward
carbonylation, and also synthesized a stable bimetallic
sydnonyl platinum complex with a Pt—Hg σ-bond. The
tentative results of this study were reported previously.12,13
This method has been used successfully to prepare a
number of σ-complexes by reactions of Ni0 with 8-chlo-
roquinoline,2 Pd0 with 2-chloro-6-X-pyridines (X is Cl,
Br, I), 2-chlorobenzothiazole3 or 2-chloropyrazine,4 and
Pt0 with 2-chloro- or 2,6-dichloropyridine.5
Organomercury compounds can also react with
zerovalent nickel, palladium, and platinum complexes to
give either mono- or bimetallic complexes, depending
on the nature of organic radicals6,7 (Scheme 2).
Results and Discussion
Reaction of 4-bromosydnones with zerovalent
Ni, Pd, and Pt phosphine complexes
The formation of stable bimetallic complexes of these
three metals is facilitated by the strong electron-with-
drawing effect of the organic substituent R. Stabilization
of bimetallic complexes is attained due to perfluorinated
substituents.8,9 In the case of platinum, this stabilization
We investigated oxidative addition of 4-bromo-3-
methylsydnone (1) and 4-bromo-3-phenyl-sydnone (2)
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 3, pp. 503—508, March, 2001.
1066-5285/01/5003-525 $25.00 © 2001 Plenum Publishing Corporation

526
Russ.Chem.Bull., Int.Ed., Vol. 50, No. 3, March, 2001
Kalinin et al.
to zerovalent nickel, palladium, and platinum phosphine
complexes (Scheme 3).
solvent used in the reaction (1 : 6.7 in THF and 1.6 : 1
in benzene). The presence of isomers is confirmed by
the IR spectra, which exhibit bands for Pd—Br stretch-
–1
ing vibrations in two compounds, at 244 and 216 cm .
Scheme 3
At room temperature, the isomer ratio in the solution
remains virtually unchanged, and when the temperature
is raised, the amount of trans-isomer 6a gradually in-
creases.
R´
M(PR )
N
N
C Br
n
3
+
–
C O
THF, C6H6
It should be noted that oxidative addition of organic
halides in which halogen is attached to an sp2-hybridized
carbon atom to M0 complexes (M = Ni, Pd, Pt) gives
normally trans-compounds. In the case of monodentate
ligands, the formation of cis-isomers as unstable inter-
mediates rapidly rearranging into trans-isomers was pos-
tulated. Stable palladium complexes with substituted
uracil14,15 and 3,5-dichlorotrifluorophenyl16 ligands hav-
ing the cis-structure were reported as exceptions.
Palladium σ-sydnonyl complexes 5 and 6a,b are
yellow crystalline solids stable in air and in the light.
Complex 5 is readily soluble, while 6a,b are poorly
soluble in THF and benzene.
O
1: R´ = Me
2: R´ = Ph
PR3
M Br
PR3
R´
R´
N
N
C
C
M
PR3
+
+
N
+
–
–
C O
N
C O
Br
PR3
O
O
3—6a, 7
6b
Com-
pound
3
4
5
M
R´
R
n
Com-
pound
6a
M
R´
R
n
Ni
Ni
Ph
Ph
Et
Ph
Ph
4
3
4
Pd
Pd
Pt
Ph
Ph
Ph
Ph
Ph
Ph
4
4
4
6b
Refluxing of an isomer mixture of palladium com-
plexes 6a,b in THF or benzene gives rise to a binuclear
complex, trans-bis[bromo(triphenylphosphine)(3-phenyl-
sydnon-4-yl)palladium] (8) (Scheme 4).
Pd
Ìå
7
As the starting compounds, we used Ni(PEt3)4,
Ni(PPh3)3, Pd(PPh3)4, and Pt(PPh3)4. In each case,
except for the reaction of 2 with Pd(PPh3)4, the oxida-
tive addition of 4-bromosydnone occurred smoothly and
yielded only the trans-isomer MBr(3-R´-sydnon-
4-yl)(PR3)2. The reactions took place at ∼20 °C; for Ni,
they required 2 h (R = Et) and 4 h (R = Ph), for Pd, the
reaction times were 0.25 h (R´ = Ph) and 2 h (R´ = Me),
and for Pt, the duration was 0.5 h. In the oxidative
addition of 4-bromo-3-phenylsydnone 2 to Pd(PPh3)4,
the formation of rather stable cis-isomer 6b was detected
apart from the trans-isomer 6a.
σ-Sydnonyl nickel compounds 3 and 4 are mono-
nuclear complexes, whose 31P NMR spectra contain one
narrow singlet at 13.19 and 20.76 ppm, respectively,
indicating the trans-arrangement of the phosphine ligands
around the nickel atom. Nickel complexes 3 and 4 are
dark-brown crystalline compounds, stable against atmo-
spheric oxygen in the solid state and soluble in benzene.
The oxidative addition of 4-bromo-3-methylsydnone
(1) to Pd(PPh3)4 affords trans complex 5; this was
confirmed by the 31P NMR spectrum, which exhibits
one singlet at 17.53, pointing to equivalence of phos-
phine ligands. The 1Í NMR spectrum contains a singlet
at 3.17 ppm and a multiplet at about 7.5 ppm. The ratio
of the integral intensities of the 1Í NMR signals, equal
to 1 : 10, confirms the formation of a mononuclear
complex.
Scheme 4
PPh3
Ph
N
Br
Ph
N
∆
C
Pd PPh3
C
Pd Br
PPh3
THF
+
+
–
–
N
C O
N
C O
PPh3
O
O
6a
6b
PPh3
Ph
N
Ph
N
Br Pd
Pd Br
C
THF, ∆
+
O C
O
–
C
N
–PPh3
+
–
N
C O
PPh3
O
8
This reaction was studied by 31P NMR spectroscopy.
Samples for recording the spectra in THF were taken
directly during the reaction. The presence of particular
complexes in the reaction mixture was judged from the
above-mentioned signals typical of trans- (6a) and
cis-isomers (6b) and the newly formed singlet at
22.26 ppm assigned to binuclear trans-complex 8. The
ratio of these complexes in the reaction mixture was
determined from the integral intensities of the signals.
Initially, cis-isomer 6b rearranges into trans-isomer 6a;
when the remaining amount of 6b is ∼3—5%, 6a starts to
transform into binuclear complex 8, i.e., at this instant,
all three compounds are detected in the solution. Within
30 min after refluxing has started, only complexes 6a
and 8 in ∼2 : 1 ratio remain in the reaction mixture, and
2 h later, the solution contains only binuclear complex 8.
However, a mixture of trans (6a) and cis (6b) isomers
is formed in the reaction of 4-bromo-3-phenylsydnone
(2) with Pd(PPh3)4. The 31P NMR spectrum contains a
singlet at 21.50 ppm and an AB-quartet (δA = 19.20,
δB = 29.39, J = 21.5 Hz), assigned to complexes 6a and
6b. The 6a to 6b isomer ratio determined from the ratio
of the integral intensities of these signals depends on the

Phosphine σ-sydnonyl complexes of Ni, Pd, and Pt Russ.Chem.Bull., Int.Ed., Vol. 50, No. 3, March, 2001
527
Our attempts to isolate trans-isomer 6a in a pure state
failed. Binuclear complex 8 is a yellow crystalline com-
pound stable in air and, unlike complexes 6a and 6b,
readily soluble in THF and benzene.
Binuclear complex 14, similar to binuclear palladium
complex 8, was obtained in the reaction of 9 with
Pd(PPh3)4 (Scheme 6).
4-Bromo-3-phenylsydnone (2) reacts with Pt(PPh3)4
to give mononuclear complex 7. Its 31P NMR spectrum
contains a singlet at 11.60 ppm with satellites caused by
the 195Pt—31P spin-spin coupling with a constant of
3573 Hz, which implies trans-arrangement of the phos-
phine ligands. The IR spectrum displays Pt—Br stretch-
Scheme 6
Ph
Pd(PPh3)4
N
N
C
HgCl
+
–
THF
C O
O
–1
ing vibrations at 209 cm ; the absorption band for the
–1
9
sydnone carbonyl group is shifted from 1700 cm ,
typical of analogous nickel and palladium complexes, to
the region of 1500 cm , which is apparently due to
partial coordination of the exocyclic oxygen atom of
sydnone to platinum. Complex 7 is a white crystalline
solid, stable in air and in the light and poorly soluble
in THF.
Ph
N
–1
C Hg
Pd(PPh3)2Cl
+
–Hg↓
–
N
C O
O
12
PPh3
Reaction of 4-chloromercurio-3-phenylsydnone
with zerovalent Ni, Pd, Pt phosphine complexes
Ph
N
C
Pd
Cl
PPh3
–PPh3
+
–
N
C O
The 3-phenylsydnon-4-yl radical exhibits a substan-
tial electron-withdrawing effect.17 Therefore, we at-
tempted to prepare bimetallic sydnonyl complexes con-
taining a Hg—M bond (M = Ni, Pd, Pt) by the reaction
of 4-chloromercurio-3-phenylsydnone (9) with Ni0, Pd0,
and Pt0 phosphine complexes. However, the stabilizing
effect of the sydnon-4-yl substituent was found to be
insufficient for the formation of stable bimetallic com-
plexes of nickel and palladium. The reaction of 9 with
Ni(PEt3)4 gave rise to trans-chlorobis(triethylphos-
phine)(3-phenylsydnon-4-yl)nickel (11), resulting from
redox demercuration of intermediate 10 (Scheme 5).
Complex 11 is similar in properties to nickel bromo
complexes 3 and 4. The 31P NMR spectrum of complex
11 contains a singlet at 13.19 ppm.
O
13
PPh3
Pd
Ph
N
Ph
N
C
Cl
+
–
C
Pd
O C
N
Cl
O
+
–
N
C O
PPh3
O
14
Interesting results were obtained in a 31P NMR study
of this reaction. The spectrum of a sample taken from
the reaction mixture in benzene 15 min after the begin-
ning of the reaction displays a singlet at 23.47 ppm and
an AB-quartet (δA = 21.05, δB = 31.50, J = 21.3 Hz),
assigned to the trans- and cis-isomers of the bimetallic
complex 12; the ratio of the integral intensities of these
signals is 1 : 2.3. Apart from these signals, the spectrum
contains a weak singlet at 21.93 ppm, close to the singlet
in the spectrum of mononuclear palladium bromo
trans-complex 6a (21.50 ppm), which was attributed to
the mononuclear chloro complex 13. Subsequently, the
signals for complexes 12 start decreasing, while that for
13 starts increasing. After 1 h, the signals of trans- and
cis-complexes 12 disappear, while the singlet at
21.93 ppm persists. A new singlet close to the singlet in
the spectrum of binuclear bromo complex 8 (22.26 ppm)
appears at 22.96 ppm; it was assigned to binuclear chloro
trans-complex 14. Within 5 h after the beginning, only
singlet due to complex 14 is found in the spectrum.
The reaction of 9 with Pt(PPh3)4, unlike the reac-
tions with Ni(PEt3)4 and Pd(PPh3)4, gives rise to a
mixture of stable bimetallic complexes trans- (15a) and
cis-chlorobis(triethylphosphine)(3-phenylsydnon-4-yl-
mercurio)platinum (15b) (Scheme 7). The isomer ratio
Scheme 5
Ph
Ni(PEt3)4
N
N
C
HgCl
+
–
C6H6
C O
O
9
Ph
N
C Hg
Ni(PEt3)2Cl
+
–Hg↓
–
N
C O
O
10
PEt3
Ph
N
C
Ni
Cl
PEt3
+
–
N
C O
O
11

528
Russ.Chem.Bull., Int.Ed., Vol. 50, No. 3, March, 2001
Kalinin et al.
was determined from the 31P NMR spectrum. The sin-
glet at 13.93 ppm with satellites caused by the 195Pt—31P
spin-spin coupling with a constant of 3679.9 Hz was
assigned to the trans-isomer 15a. The AB-quartet
(δA = 12.56, δB = 19.42, J = 14.5 Hz) with satel-
lites due to the 195Pt—31P spin-spin coupling with
J(195Pt—31PA) = 2414.7 Hz, J(195Pt—31PB) = 2996.4 Hz,
was attributed to the nonequivalent phosphine ligands in
cis-isomer 15b. The integral intensity of the signals
indicates that the cis- to trans-isomer ratio amounts to
1 : 2.7. The 15a and 15b mixture is a white crystalline
solid poorly soluble in THF.
namely, trans-bromobis(triethylphosphine)(3-phenyl-
sydnon-4-ylcarbonyl)nickel (17) (Scheme 8).
Scheme 8
PR3
Ph
N
Ph
N
O
C
CO
C
M(PR3)2Br
C
M Br
PR3
+
+
–
–
N
C O
N
C O
O
O
3, 6a,b, 7
17: M = Ni, R = Et
18: M = Pd, R = Ph
19: M = Pt, R = Ph
Scheme 7
The isomer mixture of palladium complexes 6a, 6b
and platinum complex 7 were carbonylated in an auto-
clave under a CO pressure of 25•105 Pa at 50 °C in
THF. This also gave acyl complexes, trans-bro-
mobis(triphenylphosphine)(3-phenylsydnon-4-ylcarbo-
nyl)palladium (18) and trans-bromobis(triphenyl-
phosphine)(3-phenylsydnon-4-ylcarbonyl) platinum (19).
The nickel acyl complex 17 was isolated as a dark-
yellow crystalline solid; the attempt to recrystallize this
product failed because it was readily decarbonylated,
similarly to arylacyl complexes.23 The sydnonyl acyl
complexes of palladium 18 and platinum 19 are stable
only in solutions saturated with carbon monoxide. We
were unable to isolate these acyl complexes in a pure
state, although rather stable acyl complexes of palladium
with pyridyl and thienyl9 ligands and a platinum com-
plex with an aroyl22 ligand are known. The formation of
acyl complexes 17—19 was confirmed by the IR spectra.
In the case of nickel and palladium, the IR spectra
Ph
Pt(PPh3)4
N
N
C
HgCl
+
–
THF
C O
O
9
Ph
hν
N
N
C Hg
Pt(PPh3)2Cl
+
–Hg↓
–
C O
O
15a,b
PPh3
Pt
Ph
N
N
C
Cl
PPh3
+
–
C O
O
16
–1
exhibit an absorption band at about 1770 cm , which is
The results confirm the general trend: in the series of
Ni, Pd, and Pt complexes with the 3-phenylsydnon-4-yl
group, the bimetallic platinum complex is the most
stable, as has been also noted previously for complexes
with other organic substituents.6—8,18
Complexes 15a and 15b slowly decompose in a THF
solution. This process is markedly accelerated on expo-
sure to ultraviolet radiation. This gives a mononuclear
chloro trans-complex 16, an analog of the platinum
bromo complex 7. The 31P NMR spectrum of this
complex contains a singlet at 12.11 ppm with satellites
caused by the 195Pt—31P spin-spin coupling with a con-
stant of 3560 Hz.
missing from the spectra of starting complexes 3, 6, and
7. In the case of palladium complex, the 31P NMR
spectrum points to the formation of only trans acyl
complex 18, although the starting compound used in
carbonylation was a mixture of isomers 6a and 6b; this
confirms the previously established influence of acyl
groups promoting the predominant formation of
trans-isomers for related acyl complexes.21
In the IR spectrum of platinum acyl complex 19, the
–1
absorption band shifts from the region of 1500 cm
–1
observed for the starting complex 7 to 1715 cm ,
pointing to the absence of coordination of the exocyclic
sydnone oxygen atom to platinum. Two new absorption
–1
–1
bands appear at 1728 cm and 1780 cm ; they were
assigned to the carbonyl group of the acyl complex. The
presence of two absorption bands is, apparently, due to
the presence of conformers resulting from hindered rota-
tion around the C—C bond in α-substituted acyl com-
Carbonylation of σ-sydnonyl
complexes of Ni, Pd, and Pt
It is known that the products of oxidative addition of
nickel triad metals can be carbonylated by CO, which is
inserted into the C—M bond to give the corresponding
acyl complexes.19—22 The stability of acyl complexes
decreases in the series Ni > Pd > Pt.
plex 19; this is similar to the platinum aroyl complex 22
.
Experimental
Carbonylation of nickel σ-sydnonyl complex 3 on
passing CO through a suspension of 3 in hexane
at room temperature results in an acyl complex,
1
H and 31P NMR spectra were recorded on a Bruker
WP-200SY spectrometer (200.13 ÌHz and 81.01 ÌHz),

Phosphine σ-sydnonyl complexes of Ni, Pd, and Pt Russ.Chem.Bull., Int.Ed., Vol. 50, No. 3, March, 2001
529
IR spectra were measured on UR-20 (KBr pellets) and
Bruker IFS-113v (mineral oil) instruments. The compounds
Ni(PPh3)3,24 Ni(PEt3)4,25 Pd(PPh3)4,26 Pt(PPh3)4,27 4-bro-
mo-3-methyl-sydnone,28 4-bromo-3-phenyl-sydnone,28 and
4-chloromercurio-3-phenylsydnone29 were prepared by known
procedures. The reactions were carried out in anhydrous sol-
vents prepared by distillation from benzophenone ketyl under
argon.
trans-Bromobis(triethylphosphine)(3-phenylsydnon-4-
yl)nickel (3). A suspension of 4-bromo-3-phenylsydnone (1.25 g,
5.20 mmol) in 10 mL of benzene was added to a suspension
Ni(PEt3)4 (2.75 g, 5.17 mmol) in 20 mL of benzene. The
reaction mixture was stirred for 2 h at ∼20 °C. The solution thus
formed was concentrated to dryness and the residue was diluted
with 20 mL of ether. The orange compound that formed was
filtered off, washed with ether, and dried in vacuo to give 1.27 g
(69%) of complex 3, m.p. 129—131 °C. 31P NMR (CHCl3),
δ: 13.19 (s). IR, ν/cm–1: 1705. Found (%): N, 5.11; P, 11.30;
Br, 14.58. C20H35BrN2NiO2P2. Calculated (%): N, 5.27;
P, 11.50; Br, 14.5.
trans-Bromobis(triphenylphosphine)(3-phenylsydnon-4-
yl)nickel (4). A suspension of 4-bromo-3-phenylsydnone (0.66 g,
2.74 mmol) in 10 mL of toluene was added to a suspension of
Ni(PPh3)3 (2.97 g, 3.51 mmol) in 20 mL of toluene at –40 °C.
The reaction mixture was stirred for 4 h at ∼20 °C and concen-
trated. The resulting brown compound was filtered off, washed
with ether, and dried in vacuo to give 1.27 g (58%) of com-
pound 4, m.p. 137—135 °C. 31P NMR (CHCl3), δ: 20.76 (s).
IR, ν/cm–1: 1705. Found (%): C, 64.07; H, 4.24; N, 3.40.
C44H35BrN2NiO2P2. Calculated (%): C, 63.48; H, 4.34; N, 3.63.
trans-Bromobis(triphenylphosphine)(3-methylsydnon-4-
yl)palladium (5). At ∼20 °C, Pd(PPh3)4 (2.43 g, 2.1 mmol) was
added to a solution of 4-bromo-3-methylsydnone (0.38 g,
2.1 mmol) in 50 mL of THF. The reaction mixture was stirred
for 1 h, then the solvent was evaporated, and the yellow residue
was recrystallized from a chloroform—hexane mixture (1 : 1)
and dried in vacuo to give 1.11 g (65%) of compound 5, m.p.
168—170 °C. 1H NMR (CDCl3), δ: 3.17 (s, 3 H, Me);
7.38—7.62 (m, 30 H, Ar). 31P NMR (CDCl3), δ: 17.53 (s). IR,
ν/cm–1: 1700. Found (%): C, 57.82; N, 3.46; P, 7.66.
C39H33BrN2O2P2Pd. Calculated (%): C, 57.59; N, 3.78; P, 7.34.
trans-Bromobis(triphenylphosphine)- (6a) and cis-bromo-
bis(triphenylphosphine)(3-phenylsydnon-4-yl)palladium (6b). At
∼20 °C, Pd(PPh3)4 (2.43 g, 2.1 mmol) was added with stirring
to a solution of 4-bromo-3-phenylsydnone (0.51 g, 2.1 mmol)
in 50 mL of THF or benzene. After 20 min, the yellow
precipitate was filtered off, washed with 40 mL of THF or
benzene, and dried in vacuo to give 1.59 g (87%) of a mixture of
trans- (6a) and cis-isomers (6b). 31P NMR (CDCl3), δ: 19.20,
29.39 (both d, J = 21.5 Hz), 21.50 (s). IR, ν/cm–1: 216, 244,
1700. Found (%): C, 60.62; H, 4.18; N, 3.21; Br, 9.18.
C44H35BrN2O2P2Pd. Calculated (%): C, 60.83; H, 4.06; N, 3.07;
Br, 9.13.
precipitate completely dissolved and for an additional 1 h. The
reaction mixture was cooled to ∼20 °C and the solvent was
evaporated in vacuo. The resulting yellow precipitate was dis-
solved in chloroform, hexane was added, and the resulting
precipitate was filtered off and dried in vacuo to give 2.00 g
(78%) of compound 8, m.p. 149—151 °C. 31P NMR (THF),
δ: 22.26 (s). Found (%): N, 4.59; P, 5.09; Br, 13.12.
C52H44Br2N4O4P2Pd2. Calculated (%): N, 4.12; P, 5.19;
Br, 13.48.
trans-Chlorobis(triethylphosphine)(3-phenylsydnon-4-
yl)nickel (11). A suspension of 4-chloromercurio-3-phenyl-
sydnone (1.53 g, 3.84 mmol) in 10 mL of benzene was added to
a solution of Ni(PEt3)4 (2.04 g, 3.84 mmol) in 10 mL of
benzene. The reaction mixture was stirred for 20 h at ∼20 °C.
Then the precipitated metallic mercury was filtered off and the
filtrate was concentrated to dryness. The residue was diluted
with 20 mL of ether. The light-brown powder that crystallized
was filtered off. The filtrate was concentrated to dryness and the
residue was diluted with 10 mL of pentane. The orange crystal-
line precipitate was filtered off, washed with pentane, and dried
in vacuo to give 1.08 g (57%) of compound 11, m.p.
103—104 °C. 31P NMR (CHCl3), δ: 13.19 (s). Found (%):
C, 47.88; H, 7.02; P, 12.30. C20H35ClN2NiO2P2. Calcu-
lated (%): C, 47.51; H, 6.92; P, 12.31.
trans-Bis[chloro(triphenylphosphine)(3-phenylsydnon-4-
yl)palladium] (14). Pd(PPh3)4 (4.44 g, 3.84 mmol) was added
to a suspension of 4-chloromercurio-3-phenylsydnone (1.53 g,
3.84 mmol) in 20 mL of benzene. The reaction mixture was
stirred for 5 h at ∼20 °C. The precipitated metallic mercury was
filtered off and the filtrate was concentrated to dryness. The
residue was dissolved in chloroform and treated with hexane.
The light-yellow precipitate thus formed was filtered off and
dried in vacuo to give 4.36 g (51%) of compound 14, m.p.
149—151 °C. 31P NMR (C6H6), δ: 22.26 (s). Found (%):
N, 4.97; P, 5.51; Cl, 6.31. C52H44Cl2N4O4P2Pd2. Calcu-
lated (%): N, 4.56; P, 5.29; Cl, 6.30.
trans-Chlorobis- (15a) and cis-chlorobis(triethylphos-
phine)(3-phenylsydnon-4-ylmercurio)platinum (15b). Pt(PPh3)4
(4.78 g, 3.84 mmol) was added to a suspension of 4-chlo-
romercurio-3-phenylsydnone (1.53 g, 3.84 mmol) in 20 mL of
benzene. The reaction mixture was stirred for 2 h at ∼20 °C and
filtered. The white crystalline product formed was washed with
50 mL of ether and dried in vacuo to give 3.35 g (78%) of a
mixture of isomers 15a and 15b. 31P NMR (C6H6), δ: 12.56 (d,
J = 14.5 Hz (dd, J(195Pt—31PA) = 2414.7 Hz)); 13.93 (s,
J(195Pt—31P) = 3679.9 Hz); 19.42 (d, J = 14.5 Hz (dd,
J(195Pt—31PB) = 2996.4 Hz)). Found (%): C, 47.31; H, 3.14;
N, 4.97; P, 5.55. C44H35ClHgN2O2P2Pt. Calculated (%):
C, 47.05; H, 3.59; N, 4.56; P, 5.51.
trans-Chlorobis(triethylphosphine)(3-phenylsydnon-4-
yl)platinum (16). A stirred solution of the mixture of 15a and
15b (2.35 g, 2.1 mmol) in 50 mL of benzene was exposed to UV
radiation at ∼20 °C for 3 h. The precipitated metallic mercury
was separated and the white precipitate was filtered off, washed
with 50 mL of ether, and dried in vacuo to give 0.69 g (36%) of
compound 16, m.p. 269—271 °C. 31P NMR (CDCl3) δ: 12.11
(s, J(195Pt—31P) = 3560 Hz). Found (%): C, 57.67; H, 3.82;
Cl, 6.77. C44H35ClN2O2P2Pt. Calculated (%): C, 57.36; H, 3.76;
Cl, 6.54.
trans-Bromobis(triethylphosphine)(3-phenylsydnon-4-
ylcarbonyl)nickel (17). A flow of CO prepared by dehydration
of formic acid was passed for 2 h at ∼20 °C through a suspension
of complex 3 (0.53 g, 1 mmol) in 30 mL of hexane. The
resulting dark-yellow precipitate was filtered off, washed with
pentane, and dried in an argon flow to give compound 17 in a
yield of 0.042 g (75%). IR, ν/cm–1: 1705, 1770. Found (%):
trans-Bromobis(triphenylphosphine)(3-phenylsydnon-4-
yl)platinum (7). At ∼20 °C, Pt(PPh3)4 (2.61 g, 2.1 mmol) was
added with stirring to a solution of 4-bromo-3-phenylsydnone
(0.51 g, 2.1 mmol) in 50 mL of THF. After 30 min, the white
precipitate was filtered off, washed with 40 mL of THF or
benzene, and dried in vacuo to give 1.53 g (76%) of compound
8, m.p. 281—283 °C. 31P NMR (CDCl3), δ: 11.60 (s,
J(195Pt—31P) = 3573 Hz). IR, ν/cm–1: 209, 1705. Found (%):
C, 55.00; H, 3.65; P, 6.46. C44H35BrN2O2P2Pt. Calculated (%):
C, 55.05; H, 3.89; P, 6.51.
trans-Bis[bromî(triphenylphosphine)(3-phenylsydnon-4-
yl)palladium] (8). A suspension of an isomer mixture 6a and 6b
(1.83 g, 2.1 mmol) in THF was refluxed for 1.5 h until the

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Russ.Chem.Bull., Int.Ed., Vol. 50, No. 3, March, 2001
Kalinin et al.
C, 44.02; H, 6.13; Br, 10.80. C21H35BrN2NiO3P2. Calcu-
lated (%): C, 44.37; H, 6.15; Br, 10.55.
9. E. V. Maskaeva, V. V. Bashilov, M. V. Galakhov, and V. I.
Sokolov, Metalloorgan. Khim., 1991, 4, 910 [Organomet.
Chem., 1991, 4 (Engl. Transl.)].
trans-Bromobis(triphenylphosphine)(3-phenylsydnon-4-
ylcarbonyl)palladium (18). A suspension of a mixture of 6a and
6b (0.87 g, 1 mmol) in 30 mL of THF was placed in an
autoclave and stirred under a CO pressure of 25•105 Pa for 2 h
at 50 °C. The CO pressure was reduced to atmospheric pressure
and the temperature was decreased to ∼20 °C. A sample
for recording the spectrum was taken from the mixture.
31P NMR,(THF), δ: 21.56 (s). IR, ν/cm–1: 1700, 1770.
trans-Bromobis(triphenylphosphine)(3-phenylsydnon-4-
ylcarbonyl)platinum (19). A suspension of complex 7 (0.96 g,
1 mmol) in 30 mL of THF was placed in an autoclave and
stirred under a CO pressure of 25•105 Pa for 2 h at 50 °C. Then
the CO pressure was reduced to atmospheric pressure and the
temperature was decreased to ∼20 °C. A sample for recording
the spectrum was taken from the mixture. 31P NMR (THF),
δ: 12.35 (s, J(195Pt—31P) = 3567 Hz). IR, ν/cm–1: 1715,
1728, 1780.
10. V. V. Bashilov, V. I. Sokolov, and O. A. Reutov, Izv. Akad.
Nauk SSSR, Ser. Khim., 1982, 2069 [Bull. Acad. Sci. USSR,
Div. Chem. Sci., 1982, 31 (Engl. Transl.)].
11. L. I. Zakharkin and I. V. Pisareva, Izv. Akad. Nauk SSSR,
Ser. Khim., 1978, 252 [Bull. Acad. Sci. USSR, Div. Chem.
Sci., 1978, 27 (Engl. Transl.)].
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Kravtsov, F. M. She, and V. N. Kalinin, J. Organomet.
Chem., 1990, 381, 281.
13. V. N. Kalinin, F. M. She, and P. V. Petrovskii, J. Organomet.
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14. Urata, M. Tanaka, and T. Fuchigami, Chem. Lett., 1987, 751.
15. D. Minniti, Inorg. Chem., 1994, 33, 2631.
16. L. Casado and P. Esprinet, Organometallics, 1998, 17, 954.
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19. G. Whlig and D. Walther, Coord. Chem. Rev., 1980, 33, 31.
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Received October 12, 2000