Tri(allyl)- and tri(methylallyl)arsine complexes of palladium(II) and platinum(II): Synthesis, spectroscopy, photochemistry and structures

Article abstract of DOI:10.1039/b303990k

Tri(allyl)- and tri(methylallyl)arsine complexes of palladium(II) and platinum(II) with the formulae [MX₂L₂] (M = Pd, Pt and X = Cl, Br, I): [Pd₂Cl₂(μ-Cl)₂L₂], [PdCl(S₂CNEt₂)L] and [Pd₂Cl₂(μ- dmpz)₂L₂] [L = As(CH₂CH=CH₂) ₃ (L′), As(CH₂CMe=CH₂)₃ (L″), dmpz = 3,5-dimethylpyrazolate] have been prepared. All the complexes have been characterized by elemental analyses and by IR and NMR ( ¹H, ¹³C, ¹⁹⁵Pt) spectroscopy. The stereochemistry of the complexes has been deduced from the spectroscopic data. The molecular structures of complexes [MX₂{As(CH₂CH= CH₂)₃}₂] (M = Pd, X = Cl or Br), [MX ₂{As(CH₂CMe =CH₂)₃}₂] (M = Pd, X = Cl or Br; M = Pt, X = Cl) and [Pd₂Cl₂(μ-Cl) ₂{As(CH₂CMe=CH₂)₃}₂] have been established by single crystal X-ray diffraction analyses. The mononuclear complexes exclusively adopt the trans configuration with the exception of [PdCl₂L″₂], which could be isolated as cis and trans isomers. In the binuclear derivative the arsine ligands are attached to an envelope-shaped Pd-(μ-Cl)₂-Pd rectangle with a trans (anti) orientation towards each other. The mononuclear complexes are slightly photoreactive upon irradiation in their long-wavelength absorption band.

Full text of DOI:10.1039/b303990k

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Tri(allyl)- and tri(methylallyl)arsine complexes of palladium(II) and
platinum(II): synthesis, spectroscopy, photochemistry and structures
Prasad P. Phadnis,a Vimal K. Jain,*a Axel Klein,*b Thilo Schurrb and Wolfgang Kaimb
a
Novel Materials and Structural Chemistry Division, Bhabha Atomic Research Centre,
Mumbai 400 085, India. E-mail: jainvk@apsara.barc.ernet.in
Institut fu¨r Anorganische Chemie, Universita¨t Stuttgart, Pfaffenwaldring 55, D-70550,
b
Stuttgart, Germany. E-mail: aklein@iac.uni-stuttgart.de; Fax: +49-7116854165;
Tel: +49-7116854235
Received (in Montpellier, France) 9th April 2003, Accepted 23rd June 2003
First published as an Advance Article on the web 3rd September 2003
Tri(allyl)- and tri(methylallyl)arsine complexes of palladium(II) and platinum(II) with the formulae [MX2L2]
(M ¼ Pd, Pt and X ¼ Cl, Br, I): [Pd2Cl2(m-Cl)2L2], [PdCl(S2CNEt2)L] and [Pd2Cl2(m-dmpz)2L2]
0
00
=
=
[L ¼ As(CH2CH CH2)3 (L ), As(CH2CMe CH2)3 (L ), dmpz ¼ 3,5-dimethylpyrazolate] have been prepared.
All the complexes have been characterized by elemental analyses and by IR and NMR (1H, 13C, 195Pt)
spectroscopy. The stereochemistry of the complexes has been deduced from the spectroscopic data. The
=
molecular structures of complexes [MX2{As(CH2CH CH2)3}2] (M ¼ Pd, X ¼ Cl or Br), [MX2{As(CH2CMe
=
=
CH2)3}2] (M ¼ Pd, X ¼ Cl or Br; M ¼ Pt, X ¼ Cl) and [Pd2Cl2(m-Cl)2{As(CH2CMe CH2)3}2] have been
established by single crystal X-ray diffraction analyses. The mononuclear complexes exclusively adopt the trans
configuration with the exception of [PdCl2L002], which could be isolated as cis and trans isomers. In the
binuclear derivative the arsine ligands are attached to an envelope-shaped Pd–(m-Cl)2–Pd rectangle with a
trans (anti) orientation towards each other. The mononuclear complexes are slightly photoreactive upon
irradiation in their long-wavelength absorption band.
=
have examined the chemistry of E(CH2CR CH2)3 (E ¼ As
or Sb; R ¼ H or Me) complexes of palladium and platinum.
In this paper we will report the preparation and thorough
characterization of some tri(allyl)arsine and tri(methylallyl)-
arsine complexes of Pt or Pd by multiple spectroscopies and
single crystal X-ray diffraction. Furthermore, we report the
first trials to prepare the corresponding antimony derivatives.
Introduction
Organoarsenic and -antimony compounds have attracted
considerable attention in recent years due to their relevance
as molecular precursors in the deposition of III–V semiconduc-
tor materials for microelectronic technologies.1–4 In view to
replace the EH3 source (E ¼ As or Sb; AsH3 being an extre-
mely toxic gas difficult to purify and SbH3 unstable at room
temperature) and to develop low-decomposition-temperature
precursors, several trialkyl derivatives have been evaluated.
For instance, triisopropylstibine has been successfully used
for the preparation of antimonide materials.5 The growth tem-
perature for SbR3 compounds has been reported to decrease
with decreasing bond strength of the Sb–R bond, which lies
in the following order: Sb–methyl (439.9 kJ molꢀ1) > Sb–
isopropyl (398.1 kJ molꢀ1) > Sb–allyl (361.2 kJ molꢀ1).6 Thus,
triallyl derivatives may prove to be precursors of choice.
Although metal complexes containing unsaturated
Experimental
Materials and methods
The compounds Na2PdCl4 , [PdCl2(MeCN)2],14 As(CH2CH
15,16
0
ꢁ
=
=
CH2)3 (L ; b.p. 52–53 C/2.5 mm),
As(CH2CMe CH2)3
16
(L00; b.p. 53–55 ꢁC/2.5 mm), Sb(CH2CH CH2)3 (b.p. 70–
=
73 ꢁC/2.5 mm)6,17,18 and Sb(CH2CMe CH2)3 (b.p. 73–74 C/
ꢁ
=
2.5 mm)17 were prepared according to literature methods.
Allylarsines and -stibines were purified by distillation under
vacuum. All reactions were carried out under a nitrogen atmo-
sphere in dry and distilled analytical grade solvents. Microana-
lyses were carried out in the Analytical Chemistry Division,
=
phosphines, such as Ph2P(CH CH2), PhP(CH CH2)2 and
=
Ph2P(CH2CH CH2)
=
7–12
have been investigated, only a few
allylarsine complexes have been reported for comparative
study.8,12 The structures of some allylic phosphines and arsines
have been studied by ab initio quantum chemical methods and
photoelectron spectroscopy.13 The C–E bond (E ¼ P or As)
has been shown to be out-of-plane of the allyl system and is
stabilized by negative hyperconjugation between the p orbital
and the s* orbital of the C–E bond (b effect). Consequently,
the electron pair of E interacts strongly with the p system. This
geometrical arrangement of allylphosphines and -arsines may
give complexes having structures and chemical reactivities dif-
ferent from their alkyl or aryl counter parts. In light of the
above and in pursuance of our work on the design and devel-
opment of organometallic precursors of group V elements, we
B.A.R.C. The H, 13C{1H} and 195Pt{1H} NMR spectra were
1
recorded on a Bruker DPX-300 spectrometer operating at 300
(1H), 75.47 (13C) or 64.52 (195Pt) MHz. Chemical shifts are
relative to the internal chloroform peak (d ¼ 7.26 ppm for
1H and d ¼ 77.0 ppm for 13C) and external Na2PtCl6 in D2O
for 195Pt. IR spectra were recorded as Nujol mulls using CsI
plates on a Bomen-102 FT IR spectrometer in the range
200–4000 cmꢀ1. NMR and IR data for all the compounds
are given in Tables 1 and 2. UV/Vis absorption spectra were
recorded on a Bruins Instruments Omega 10 or a JASCO
V-530 spectrophotometer. Emission and excitation spectra
were recorded on a Perkin Elmer LS5B spectrophotometer.
1584
New J. Chem., 2003, 27, 1584–1591
DOI: 10.1039/b303990k
This journal is # The Royal Society of Chemistry and the Centre National de la Recherche Scientifique 2003

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Table 1 1H, 13C{1H} NMR (in CDCl3) and IR spectral data of triallylarsine complexes of palladium and platinum
Complex
As(CH2CH CH2)3 ¼ L0
1H NMR d
13C{1H} NMR d
IR data/cmꢀ1
=
2.27 (d, 7.9 Hz, AsCH2);
4.95 (t, 1 Hz, CH2 , cis-H);
4.99 (d, 7 Hz, CH2 , trans-H);
28.2 (s, AsCH2);
=
115.2 (s, CH2 );
=
134.6 (s, CH
)
=
5.78–5.90 (m, CH
)
2.79 (d, 7.9 Hz, AsCH2);
[PdCl2L02]
25.7 (s, AsCH2);
=
118.9 (s, CH2 );
1633 nC C,
=
5.18 (d, 1 Hz, CH2 , cis-H);
5.23 (d, 1 Hz, 7 Hz, CH2 , trans-H);
354 nPd–Cl
=
131.3 (s, CH
)
=
5.89–6.00 (m, CH
2.90 (d, 7.9 Hz, AsCH2);
)
[PdBr2L02]
27.0 (s, AsCH2);
=
118.9 (s, CH2 );
1633 nC
C
C
=
5.21 (d, 1 Hz, CH2 , cis-H);
5.24 (d, 1 Hz, 7 Hz, CH2 , trans-H);
=
131.5 (s, CH
)
=
5.90–6.00 (m, CH
3.11 (d, 7.9 Hz, AsCH2);
)
[PdI2L02]
30.5 (s, AsCH2);
=
118.9 (s, CH2 );
1631 nC
=
=
5.21 (d, 1 Hz, CH2 , cis-H);
5.24 (d, 1 Hz, 7 Hz, CH2 , trans-H);
=
131.9 (s, CH
)
=
5.88–5.97 (m, CH
)
[Pd2Cl2(m-Cl)2L02]
[Pd2Cl2(m-dmpz)2L02]
2.85 (d, 7.7 Hz, AsCH2);
5.28 (d, 8.0 Hz, CH2 , trans-H);
5.36 (s, CH2 , cis-H);
27.8 (s, AsCH2);
=
120.8 (s, CH2 );
1633 nC C,
351 nPd–Cl
=
129.4 (s, CH
)
=
5.87–6.04 (m, CH
2.20, 2.35 (each s, Me, dmpz);
)
=
13.5, 14.7 (s, Me dmpz);
27.1 (s, AsCH2);
104.7 (s, CH-dmpz);
1632 nC C,
2.72 (doublet of AB pattern, AsCH2);
5.16 (d, d, 1 Hz, 7 Hz, CH2 , trans-H);
5.20 (d, 0.7 Hz, CH2 , cis-H);
364 nPd–Cl
=
119.3 (s, CH2 );
=
=
131.1 (s, CH );
147.4, 149.6 (s, C–Me dmpz)
5.84–5.93 (m, CH
)
[PdCl(S2CNEt2)L0]
1.25 (t, 7 Hz, NCH2Me);
2.72 (d, 8 Hz, AsCH2);
3.67 (dq, 7 Hz, NCH2);
=
5.16–5.22 (m, CH2 );
=
5.89–6.00 (m. CH
)
The photoreactions were performed in 1 cm quarz cuvettes by
irradiation of solutions in de-aereated MeCN (dilute solutions
Other bromo and iodo complexes were prepared similarly.
[PdI2L2]: anal. found: C, 28.5; H, 4.0%; calcd for
C18H30As2I2Pd (756.49): C, 28.6; H, 4.0%. [PdBr2L002]: Anal.
found: C, 38.4; H, 5.7%; calcd for C24H42As2Br2Pd (746.67):
C, 38.6; H, 5.7%. [PdI2L002]: Anal. found: C, 34.0; H, 5.1%;
calcd for C24H42As2I2Pd (840.67): C, 34.3; H, 5.0%.
[PtBr2L002]: Anal. found: C, 34.3; H, 5.4%; calcd for
C24H42As2Br2Pt (835.32): C, 34.5; H, 5.0%. [PtI2L002]: Anal.
found: C, 30.9; H, 4.8%; calcd for C24H42As2I2Pt (929.32):
C, 31.0; H, 4.6%.
1
for UV/Vis absorption) or MeCN-d3 (conc. solutions for H
NMR spectroscopy) using a Spindler&Hoyer HBO 50 W/AC
medium pressure Hg lamp and Schott cut-off filters.
Preparations and reactions
=
[PdCl2{As(CH2CH CH2)3}2]. To a stirred benzene solution
(50 cm3) of [PdCl2(MeCN)2] (510 mg, 1.97 mmol),
=
As(CH2CH CH2)3 (800 mg, 4.04 mmol) was added under a
=
[Pd2Cl2(l-Cl)2{As(CH2CH CH2)3}2]. To a stirred benzene
nitrogen atmosphere. The reactants were stirred for 3 h. The
solvent was evaporated in vacuo and the residue was recrystal-
lized from hexane as yellowish-orange crystals (930 mg, 82%).
Anal. found: C, 37.3; H, 5.5%; calcd for C18H30As2Cl2Pd
(573.59): C, 37.7; H 5.3%.
3
solution (50 cm ) of [PdCl2{As(CH2CH CH2)3}2] (975 mg,
=
1.70 mmol), [PdCl2(MeCN)2] (443 mg, 1.71 mmol) was added.
The reactants were stirred under reflux for 3 h. The solvent was
evaporated in vacuo and the residue was recrystallized from
CH2Cl2–hexane as deep red cubic crystals (925 mg, 72%).
Anal. found: C, 28.5; H, 4.3%; calcd for C18H30As2Cl4Pd2
(750.91): C, 28.8; H, 4.0%.
=
Similarly, [MCl2{As(CH2CMe CH2)3}2] (M ¼ Pd or Pt)
were prepared. For the platinum complex K2PtCl4 was
employed. Anal. found: C, 38.2; H, 5.8%; calcd for
C24H42As2Cl2Pt (746.42): C, 38.6; H, 5.7%. The palladium
=
Similarly, [Pd2Cl2(m-Cl)2{As(CH2CMe CH2)3}2] was pre-
pared. Anal. found: C, 34.2; H, 5.2%; calcd for
C24H42As2Cl4Pd2 (835.09): C, 34.5; H, 5.1%.
=
complex, [PdCl2{As(CH2CMe CH2)3}2], was isolated in
orange and yellow forms. Both analyze identically. Anal.
found: C, 43.6; H, 6.4%; calcd for C24H42As2Cl2Pd (657.77):
C, 43.8; H, 6.4%.
=
[Pd2Cl2(l-dmpz)2{As(CH2CH CH2)3}2] (dmpz ¼ 3,5-dimethyl-
pyrazolate). To a CH2Cl2 solution (30 cm3) of [Pd2Cl2-
=
[PdBr2{As(CH2CH CH2)3}2]. To a stirred acetone solution
=
(m-Cl)2{As(CH2CH CH2)3}2](82mg, 0.11mmol), amethanolic
3
(30 cm ) of [PdCl2{As(CH2CH CH2)3}2] (97 mg, 0.17 mmol),
=
solution of dmpzH (23.2 mg, 0.24 mmol) containing
aqueous NaOH (0.5 cm3, 0.49 N, 0.245 mmol) was added
under a nitrogen atmosphere. The mixture was stirred for
5 h at room temperature and then filtered. The filtrate was
dried in vacuo and the residue was recrystallized from
CH2Cl2–hexane as a pale yellow crystalline compound (46
mg, 48%). Anal. found: C, 38.8; H, 5.3; N, 6.8%; calcd for
C28H44N4As2Cl2Pd2 (870.25): C, 38.6; H, 5.1; N, 6.4%.
excess KBr (450 mg, 3.77 mmol) was added. The reactants
were stirred at room temperature for 48 h. The solvent was
evaporated in vacuo and the residue was extracted with CH2Cl2
and filtered. The filtrate was concentrated under reduced pres-
sure and the residue was recrystallized from acetone–hexane as
orange crystals (73 mg, 65%). Anal. found: C, 32.7; H, 4.8%;
calcd for C18H30As2Br2Pd (662.49): C, 32.6; H, 4.6%.
New J. Chem., 2003, 27, 1584–1591
1585

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Table 2 1H, 13C{1H} NMR (in CDCl3) and IR spectral data of tri(methylallyl)arsine complexes of palladium and platinum
Complex
1H NMR d
13C{1H} NMR d
IR data/cmꢀ1
00
=
As(CH2CMe CH2)3
=
L
1.78 (s, Me); 2.28 (s, AsCH2);
=
23.6 (s, Me); 37.0 (AsCH2);
=
110.5 (CH2 ); 143.3 (s, C
24.7 (s, Me); 30.5 (AsCH2);
=
=
=
=
=
=
4.68 (s, CH2
1.95 (s, Me); 2.82 (s, AsCH2);
)
)
)
)
)
)
)
trans-[PdCl2L00
]
1643 nC C, 344 nPd–Cl
=
2
=
=
115.4 (CH2 ); 139.8 (s, C
23.8 (s, Me); 40.8 (AsCH2);
=
117.1 (CH2 ); 135.3 (s, C
24.9 (s, Me); 31.8 (AsCH2);
=
115.6 (CH2 ); 140.0 (s, C
25.2 (s, Me); 35.4 (AsCH2);
=
115.9 (CH2 ); 140.4 (s, C
4.95 (s, CH2
1.92 (s, Me); 2.97 (s, AsCH2);
)
cis-[PdCl2L00
]
1640 nC C;
=
2
=
4.95 (s, CH2 ); 5.02 (m, CH2
=
)
354, 316 nPd–Cl
[PdBr2L00
]
1.93 (s, Me); 2.95 (s, AsCH2);
=
2
4.95 (br, s, CH2 )
1.90 (s, Me); 3.19 (s, AsCH2);
[PdI2L00
]
2
1798, 1640 nC
=
C
=
)
4.95 (s, CH2
1.96 (s, Me);
a
[PtCl2L00
[PtBr2L00
]
24.6 (s, Me); 29.0 (AsCH2);
=
115.4 (CH2 ); 139.7 (s, C
1780, 1638 nC C,
333 nPt–Cl
=
2
2.83 (s, AsCH2 ; 3J (Pt–H) ¼ 13.5 Hz);
=
)
4.93, 4.94 (each s, CH2
1.94 (s, Me);
=
C
]
24.8 (s, Me); 29.8 (AsCH2);
=
115.6 (CH2 ); 139.8 (s, C
1898, 1639 nC
2
2.94 (s, AsCH2 ; 3J (Pt–H) ¼ 14 Hz);
=
)
=
)
=
)
=
)
4.94, 4.97 (each s, CH2
1.92 (s, Me);
[PtI2L00
]
25.0 (s, Me); 33.0 (AsCH2);
=
115.9 (CH2 ); 140.0 (s, C
2
3.16 (s, AsCH2 ; 3J (Pt–H) ¼ 15.5 Hz);
=
)
4.95, 4.98 (each s, CH2
2.11 (s, Me);
[Pd2Cl2(m-Cl)2L00
]
2
24.7 (s, Me); 32.6 (AsCH2);
=
117.3 (CH2 ); 138.2 (s, C
1798, 1640 nC C,
352 nPd–Cl
=
2.88 (s, AsCH2);
5.05, 5.09 (each s, CH
1.98 (s, Me);
=
)
[Pd2Cl2(m-dmpz)2L00
]
2
2.21, 2.36 (each s, Me-dmpz);
2.73 (AB pattern, AsCH2);
4.93, 4.94, 4.95, 4.95 (1:2:2:1 CH2);
5.57 (s, CH-dmpz)
[PdCl(S2CNEt2)L00]
1.25 (t, d, 7 Hz, NCH2Me);
2.03 (s, Me); 2.75 (s, AsCH2);
3.67 (qd, 7 Hz, NCH2); 4.93 (br, CH2
12.4 (s, NCH2Me); 24.7 (s, Me);
31.7 (AsCH2); 43.5, 44.0 (s, NCH2);
1638 nC C, 304 nPd–Cl
=
=
)
= =
115.3(CH2 ); 139.7 (s, C ); 207.6 (s, S2C)
a
195Pt{1H} in CDCl3 d ¼ ꢀ3732 ppm
=
Similarly, [Pd2Cl2(m-dmpz)2{As(CH2CMe CH2)3}2] was
prepared. Anal. found: C, 42.2; H, 6.1; N, 5.5%; calcd for
C34H56N4As2Cl2Pd2 (954.43): C, 42.8; H, 5.9; N, 5.9%.
was added under a nitrogen atmosphere. The mixture was
stirred for 3 h and filtered. Along with an insoluble residue,
a CH2Cl2-soluble compound was obtained (m.p. 153 ꢁC
decomp.). Anal. found: C, 24.9; H, 4.0%; calcd for [Pd2-
(m-Cl)2(Z3-C3H4Me)2] (C8H14Cl2Pd2): C, 24.4; H, 3.6%. 1H
NMR (CDCl3): d 2.14 (s, Me); 2.88 (s, CH2); 3.85 (s, CH2).
=
[PdCl(S2CNEt2){As(CH2CH CH2)3}]. To a stirred acetone
solution (30 cm ) of [Pd2Cl2(m-Cl)2{As(CH2CH CH2)3}2] (94
3
=
A
similar reaction of [PdCl2(PhCN)2] with Sb(CH2-
mg, 0.125 mmol), NaS2CNEt2ꢂ3H2O (61 mg, 0.272 mmol)
was added. The reactants were stirred for 3 h and the solvent
was evaporated in vacuo. The residue was extracted with
CH2Cl2 and recrystallized from acetone–hexane as orange
cubic crystals (96 mg, 83%). Anal. found: C, 32.9; H, 5.0; N,
2.7%; calcd for C14H25NS2AsClPd (488.27): C, 34.4; H, 5.1;
N, 2.9%.
3
=
CH CH2)3 gave [Pd2(m-Cl)2(Z -C3H5)2]. Anal. found: C, 18.9;
H, 2.8%; calcd for [Pd2(m-Cl)2(Z3-C3H5)2] (C6H10Cl2Pd2): C,
19.7; H, 2.7%. IR (Nujol mull) 252 nPd–Cl, 401 nPd–allyl/
cmꢀ1 19 1H NMR (CDCl3): d 3.03 (d, 12.2 Hz, CH2); 4.10
.
(d, 6.7 Hz, CH2); 5.41–5.50 (m, CH).
=
[PdCl(S2CNEt2){As(CH2CMe CH2)3}] was prepared in a
Crystallography
similar manner. Anal. found: C, 38.6; H, 5.7; N, 2.5%; calcd
for C17H31NS2AsClPd (530.41): C, 38.5; H, 5.9; N, 2.6%.
For the complexes [PdCl2L2], [PdCl2L02], [PdBr2L002],
[PtCl2L002], and [Pd2Cl2(m-Cl)2L002] data collection was per-
formed at T ¼ 173(2) K on a Siemens P4 diffractometer with
=
Reaction between [Pd2Cl2(l-Cl)2{As(CH2CMe CH2)3}2] and
Pb(SePh)2. To a stirred CH2Cl2 solution (25 cm3) of [Pd2Cl2-
(m-Cl)2{As(CH2CMe CH2)3}2] (98 mg, 0.12 mmol), Pb(SePh)2
(67 mg, 0.13 mmol) was added and the mixture stirred for
3 h, then filtered and the solvent evaporated in vacuo. The
reaction yields an insoluble compound (41 mg, 58%).
[PdCl(SePh)]n : Anal. found: C, 24.5; H, 2.2%; calcd for
C6H5SeClPd (297.92): C, 24.2; H, 1.7%.
˚
Mo-Ka radiation (l ¼ 0.71073 A) employing the o–2y scan
=
technique. The data for [PdBr2L02] were collected at T ¼
˚
293(2) K on a KappaCCD device (Mo-Ka: l ¼ 0.71073 A;
horizontally mounted graphite crystal; 95 mm CCD camera
on a k-goniostat) using Collect (Nonius BV, 1997-2000) soft-
ware. All structures were solved using the SHELXTL pack-
age20 and refinement was carried out with SHELXL9721
employing full-matrix least-squares methods on F2 with
=
Similar reactions of [Pd2Cl2(m-Cl)2{As(CH2CH CH2)3}2]
with Pb(SPh)2 or Pb(SePh)2 gave [PdCl(EPh)]n (E ¼ S or
Se). Anal. found for E ¼ S: C, 29.5; H, 2.1%; calcd for
C6H5SClPd (251.02): C, 28.7; H, 2.0%. Anal. found for
E ¼ Se: C, 25.5; H, 2.4%.
2
2
F0 ꢃ 2s(F0 ) with the results shown in Table 3. All non-hydro-
gen atoms were treated anisotropically except for the dis-
ordered allyl C atoms in [PdBr2L02]. Hydrogen atoms were
included by using appropriate riding models.y
=
Reaction between [PdCl2(PhCN)2] and Sb(CH2CMe CH2)3.
y CCDC reference numbers 214025–214030. See http://www.rsc.org/
suppdata/nj/b3/b303990k/ for crystallographic data in .cif or other
electronic format.
To a stirred benzene solution (30 cm3) of PdCl2(PhCN)2(103
=
mg, 0.267 mmol), Sb(CH2CMe CH2)3(160 mg, 0.56 mmol)
1586
New J. Chem., 2003, 27, 1584–1591

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Table 3 Crystal data and structure refinement for six of the complexes
Compound
[PdCl2L02]
[PdBr2L02]
[PdCl2L00
]
[PdBr2L00
]
[PtCl2L00
]
[Pd2Cl2(m-Cl)2L00
]
2
2
2
2
Chemical formula
MW/g molꢀ1
T/K
C
18H30As2Cl2Pd
C18H30As2Br2Pd
662.49
293(2)
C24H42As2Cl2Pd
657.72
173(2)
C24H42As2Br2Pd
746.64
173(2)
C24H42As2Cl2Pt
746.41
173(2)
C24H42As2Cl4Pd2
835.09
173(2)
573.59
173(2)
Monoclinic
P21/n
8.0698(19)
8.102(2)
18.278(3)
90
Crystal system
Space group
Orthorhombic
Pbca
Triclinic
¯
P1
Triclinic
¯
P1
Triclinic
¯
P1
Triclinic
¯
P1
˚
a/A
8.21980(10)
18.41340(10)
49.8803(5)
90
7.9820(9)
9.366(2)
10.1692(9)
68.166(12)
82.138(9)
77.166(11)
686.81(18)
1
8.8295(17)
9.4059(14)
9.5258(19)
108.471(13)
103.331(14)
96.937(12)
713.9(2)
1
8.6461(16)
9.4107(17)
9.532(3)
108.190(17)
102.878(18)
97.604(14)
701.0(3)
1
7.7802(15)
10.0937(16)
20.620(3)
94.326(12)
98.760(13)
100.107(14)
1566.9(5)
2
˚
b/A
˚
c/A
a/ꢁ
b/ꢁ
g/ꢁ
98.426(14)
90
90
90
3
˚
U/A
1182.1(5)
2
3.787
7549.6(1)
12
6.521
Z
Abs.coeff./mmꢀ1
Total reflect.
Indep. reflect.
Rint
3.270
3471
5.758
3581
7.546
3522
3.596
7514
2749
2568
33 313
5797
3237
0.0221
3366
0.0332
3307
0.0317
3013
7514
0.0381
5602
0.0381
1744
0.0633
4184
Obs. reflect.
Abs. correction
Final R1 [I > 2s(I)]
2675
2744
Psi scans
0.0465
Numerical
0.0539
0.1183
XABS234
0.0365
0.0937
XABS234
0.0360
0.0835
Psi scans
0.0293
0.0700
Psi scans
0.0490
0.1162
Final wR [I > 2s(I)] 0.0980
R1 (all data)
wR2 (all data)
0.0902
0.1142
0.0841
0.1270
0.0485
0.0992
0.0520
0.0895
0.0349
0.0728
0.0747
0.1270
complexes depends on the halogen ligands. It increases with
increasing size of the halogen atom, which can be explained
by an increasing degree of M ! L charge transfer (see later,
Results and discussion
Synthesis and spectroscopic analyses
absorption spectra). For [PtX2L002] and [Pd2Cl2(m-Cl)2L00
]
2
The syntheses of palladium(II) and platinum(II) complexes with
triallylarsine and trimethylallylarsine are depicted in Scheme 1;
their spectroscopic data for characterization are given in
Tables 1 and 2. The reactions of [MCl2(RCN)2] with 2 equiva-
two closely spaced signals for the CH2 protons were observed
as expected; however, spectra of [PdX2L002] display only one
singlet with one exception. The orange form of [PdCl2L00
]
2
exhibits the same singlet as the other derivatives; however,
the yellow form shows two signals: a singlet at 4.95 ppm and
a multiplet at 5.02 ppm. Additionally, the shift of the AsCH2
signal is not the same in the two forms (see Table 2) and we
therefore conclude that the orange and yellow forms are the
trans and cis isomers. The 13C NMR spectra of free arsine
and their complexes show single resonances each for chemi-
cally equivalent carbon atoms. The AsCH2 carbon resonances
=
=
lents of AsR3 (R ¼ CH2CH CH2 , CH2CMe CH2) readily
gave [MCl2L2]. For [PdCl2L002] yellow microcrystals were
obtained from careful recrystallization in the cold. Upon heat-
ing the recrystallization procedure gave orange crystals. For all
the other compounds we had no evidence for more than one
form. The chloride in the latter was substituted with Br or I
by treating it with an excess of KBr or KI in acetone.
The allyl- and methylallylarsine proton resonances in the 1H
NMR spectra (Tables 1 and 2) are shifted downfield in the pal-
ladium and platinum complexes with respect to the corre-
sponding signals in the free ligands. This is in accordance
with the coordination of arsenic to the metal centers. Deshield-
ing is more pronounced for the AsCH2 protons (D ¼ 0.5–0.9
ppm) than those of the allyl group [(CH/CMe: D ꢄ 0.1 ppm;
CH2 : D ꢄ 0.25 ppm). Furthermore, we found that the degree
of deshielding of the AsCH2 proton resonance in MX2L2
=
for [MX2L2], except for [MI2{As(CH2CH CH2)3}2], appear at
higher field than those of the corresponding free allylarsines.
The AsCH2 signal moves to higher frequency with increasing
mass of the halogen atom in the series [MX2L2] (M ¼ Pd or
Pt). Upon coordination of the allylarsines, the 13C NMR che-
mical shifts of the allyl carbons are also affected by shielding
for CH/C(Me) and deshielding for CH2 carbons relative to
the corresponding signals for the free arsines. The195Pt{1H}
=
NMR spectrum of [PtCl2{As(CH2CMe CH2)3}2] displays a
singlet at ꢀ3732 ppm, indicating the formation of only one
isomeric form.
The IR spectra of these complexes exhibit an absorption at
around 1630 cmꢀ1 attributable to nC C. This indicates that
=
the allylic double bonds are not coordinated to the metal
atoms.10,11 The spectra of [MX2L2] display a band at around
345 cmꢀ1 due to M–Cl stretches.14 The presence of only one
band for M–Cl suggests that these complexes have a trans con-
figuration. However, the yellow form of [PdCl2{As(CH2ꢀC1-
=
Me CH2)3}2] shows two such bands at 316 and 354 cm
,
indicative of a cis geometry. The IR spectrum of [Pd2Cl2-
(m-Cl)2(L2)] displays four nPd–Cl attributable to terminal and
bridging Pd–Cl stretches as is usually observed for [M2Cl2-
(m-Cl)2L2] complexes.22,23
The allylarsine complexes described here are stable in solu-
tion for several days in the dark. They did not undergo olefin
isomerization as has been reported for the corresponding
Scheme 1 Preparation of the compounds [M ¼ Pd, Pt; R ¼ Me, Ph;
0
00
=
=
=
rhodium complexes derived from Ph2PCH2CH CH2 , which
L ¼ As(CH2CH CH2)3 , L ¼ As(CH2CMe CH2)3].
New J. Chem., 2003, 27, 1584–1591
1587

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Table 4 Long-wavelength absorption maxima for some of the tri-
(allyl)- and tri(methylallyl)arsine complexes of Pd(II) and Pt(II)
measured in CH2Cl2 solution.
undergo isomerization to the Z-propenyl isomers, Ph2PCH
=
11
CHMe. Nor did they show any sign of a cyclometallation
reaction as reported for R2P(allyl) (R ¼ But, c-Hx) with
max/nm (e/Mꢀ1 cmꢀ1
)
[IrCl(COT)]2 (COT ¼ cyclooctene) in the presence of
Complex
l
=
g-picoline, yielding [IrHCl(R2PCH2CH CH)(R2PCH2CH
9
[PdCl2L02]
[PdBr2L02]
[PdI2L02]
353 (24 935)
=
CH2)(g-picoline)].
When
a
methanolic solution of
[PdCl2L002] was refluxed for 3 h, unchanged parent complex
was recovered. Assuming that agostic M–H interactions are
a pre-requisite for such metallation reactions we can conclude
that in the present complexes such interactions do not occur.
This will be further substantiated in the crystal structure
section.
376 (16 385), 258 (15 791)
432 (7253), 357 (5293), 312 (13 977),
256 (23 667)
[Pd2Cl2(m-Cl)2L02]
396 (4125), 304 (19 593)
357 (19 070), 320sh (2950), 282 (2030)
362 (1230), 314 (920),
trans-[PdCl2L00
]
2
cis-[PdCl2L00
]
2
298sh (1860), 280 (3050)27
382 (12 117), 256 (10 445)
436 (8930), 319 (17 130), 279 (17 753),
253 (19 312)
Treatment of [Pd2Cl2(m-Cl)2(L2)] with 2 equiv. of dmpzH in
the presence of NaOH yields the bis-pyrazolato bridged com-
plexes [Pd2Cl2(m-dmpz)2(L2)]. The presence of only one singlet
[PdBr2 L00
]
2
[PdI2L00
]
2
1
for the CH-4 proton of the dmpz group in the H NMR spec-
tra indicates a trans configuration for these complexes. The
AsCH2 resonances appear as an AB pattern, which in the case
[PtCl2L00
[PtBr2L00
]
287 (21 609), 248 (12 249)
309 (13 113), 248sh (10 040)
354 (6619), 314sh (3327)
403 (4780), 310 (20 360), 239 (30 250)
2
2
]
[PtI2L00
]
2
=
=
of As(CH2CH CH2)3 further shows coupling with the CH
proton. Reaction of [Pd2Cl2(m-Cl)2(L2)] with NaS2CNEt2ꢂ
3H2O gave [PdCl(S2CNEt2)(L)]. The NMR spectra show
characteristic resonances for the arsine and dithio ligands.
Reaction of [Pd2Cl2(m-Cl)2(L2)] with Pb(SPh)2and Pb(Se-
Ph)2 yields a disproportionation product [PdCl(EPh)]n charac-
terized by elemental analysis.24 [PdCl(EPh)]n appears to be
formed by disproportionation of [Pd2Cl2(m-EPh)2(L2)]. The
instability of the latter indicates a poorer ligation of the
allylarsines as compared to alkyl-/arylarsines (AsR3 : R ¼ Ph,
[Pd2Cl2(m-Cl)2L00
]
2
long-wavelength absorptions of the binuclear complex
[Pd2Cl2(m-Cl)2L002] are also shown in Fig. 1. The maxima and
relative intensities follow the pattern of the mononuclear cis
derivative; however, the bands are generally much stronger.
Probably it is the steric strain of the central Pd–(m-Cl)2–Pd unit
that leads to the altered transition probabilities.
n
iPr, Pr).22
Furthermore, we found that the cis derivative is the only
compound among those listed in Table 4 that shows emission
at room temperature in fluid solution. Irradiation into the
long-wavelength band at 330–380 nm led to a very weak broad
emission with a maximum at 411 nm (Stokes shift: 3290 cmꢀ1).
The excitation spectrum shows several maxima (main at 330
nm), which do not fully coincide with the absorption bands.
This calls for further investigation of the emission properties
(quantum yield, lifetimes) but also for a detailed look at the
character of the excited states by quantum chemical calcula-
tions. So far we can tentatively assign the long-wavelength
absorptions to mixed metal(dM)-to-ligand(s/p*As)/ligand(pX)-
to-ligand(s/p*As) (MLCT/L0LCT) charge transfer transitions.
This is in line with the assignment for a series of related
benzyldimethylarsine complexes [MX2(BzAsMe2)2] (M ¼ Pt
or Pd, X ¼ Cl, Br or I)28 and is further supported by recent
investigations on related complexes of the type [MCl(Te-
CH2CH2NMe2)(PR3)] (M ¼ Pt or Pd; R ¼ alkyl or aryl)
where the long-wavelength absorptions were assigned to
ligand(Te)-to-ligand(P) charge transfer (L0LCT) transitions.29
This detailed study has shown that the acceptor orbitals are
composed by metal d orbitals and the anti-bonding component
The reaction of [PdCl2(PhCN)2] or [PdCl2(MeCN)2] with
triallyl- or trimethylallylstibine afforded [Pd2(m-Cl)2(Z3-allyl)2]
(allyl ¼ C3H5 or C4H7) together with white insoluble and
uncharacterized products [eqn. (1)].
½PdCl2ðPhCNÞ2ꢅ þ 2SbðCH2CR
B
CH2Þ3
1
!
½Pd2ðm-ClÞ2ðZ3-C3H4RÞ2ꢅ ðR ¼ H or MeÞ
2
þ other products ð1Þ
It is noteworthy that reactions with trialkylstibines yield
[PdX2(SbR3)2] (R ¼ Me, Et, iPr, nPr).4,25 Although trans-
metallation reactions to prepare allylpalladium complexes
have been reported,26 transfer of an allyl group from stibine
to a metal center is unprecedented. The cleavage of the allyl–
0
=
Sb bond of RR SbCH2CH CH2 with FeCpCl(CO)2 has been
reported to result in the formation of unstable [{FeCp-
(CO)2}2SbPh2]Cl, allyl chloride and trans 1-chloro-1-propene.8
=
However, similar reactions with Ph2E(CH2CH CH2) (E ¼ P
+ 8
or As) yield [CpFe(CO)2(Ph2E(CH2CH CH2)] . The facile
=
cleavage of the Sb–allyl bond can be exploited in organic
synthesis involving allyl groups.
Absorption spectroscopy and photochemistry
The compounds exhibit colours that range from pale yellow to
deep red in the solid state as well as in solution.
An investigation of the absorption spectra (Table 4) revealed
that the long-wavelength absorption maxima are lower in
energy for the palladium derivatives when compared to the
platinum analogues. Furthermore, the energy decreases along
the series Cl > Br > I. Fig. 1 reveals that the different colour
of the two forms of [PdCl2L002] is not caused by different
long-wavelength absorption maxima but by a dramatically
enhanced intensity of the long-wavelength band at around
360 nm for the trans derivative. We assume that in both
derivatives the same type of transitions occur with different
probabilities. The same has been observed for related benzyldi-
methylarsine complexes [MX2(BzAsMe2)2] (M ¼ Pt or Pd,
X ¼ Cl, Br or I).28 Without detailed quantum chemical calcu-
lations we cannot provide any reasonable explanation for this
behaviour. Such calculations are ongoing at the moment. The
Fig. 1 Absorption spectra of cis-[PdCl2L002] (solid line),27 trans-
[PdCl2L002] (dotted line) and [Pd2Cl2(m-Cl)2L002] (dashed line) in MeCN.
1588
New J. Chem., 2003, 27, 1584–1591

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ꢁ
˚
Table 5 Selected bond lengths (A) and angles ( ) in the mononuclear
complexes
M–As(1)
M–As(2)
M–X(1)
M–X(2)
[PdCl2L02
]
2.4020(7)
2.3962(9)
2.4012(5)
2.4143(5)
2.3895(5)
2.4020(7)
2.3970(9)
2.4012(5)
2.4143(5)
2.3895(5)
2.2993(15)
2.4140(8)
2.2968(10)
2.4397(6)
2.3063(11)
2.2993(15)
2.4177(8)
2.2968(10)
2.4397(6)
2.3063(11)
[PdBr2L02
[PdCl2L00
]
]
2
[PdBr2L00
[PtCl2L00
]
2
]
2
X(1)–M–As(1) X(2)–M–As(2) X(1)–M–As(2) X(2)–M–As(1)
[PdCl2L02
]
87.51(5)
87.38(3)
87.65(3)
87.98(2)
87.94(3)
92.49(5)
92.69(3)
92.35(3)
92.02(2)
92.06(3)
92.49(5)
92.86(3)
92.35(3)
92.02(2)
92.06(3)
87.51(5)
87.06(3)
87.65(3)
87.98(2)
87.94(3)
[PdBr2L02
[PdCl2L00
]
]
]
2
[PdBr2L00
[PtCl2L00
2
]
2
0
00
Fig. 2 Absorption spectra during photolysis of cis-[PdCl2L0002] in
MeCN. The traces are taken after every 40 min of irradiation using
a 390 nm cut-off filter.
=
=
L ¼ As(CH2CH CH2)3 , L ¼ As(CH2CMe CH2)3
0
˚
structure of [PdBr2L 2] shows Hꢂ ꢂ ꢂBr contacts of 2.848(8) A
ꢁ
˚
[Cꢂ ꢂ ꢂBr: 3.727(4) A, C–H–Br: 151.5(2) ] between As–CH2–
groups and bromine, which lead to the formation of layers
along the ab plane. In the [Pd2Cl2(m-Cl)2L002] dimer such con-
of the lone pair (s/p*P).30 Further support comes from the
comparison with related palladium complexes where in the
series of ER3 ligands (E ¼ P, As, or Sb) the lowest absorption
˚
tacts were also found [Hꢂ ꢂ ꢂCl: 2.850(9) A; Cꢂ ꢂ ꢂCl: 3.659(7)
maxima show
a red-shift when going along the series
ꢁ
˚
A; C–H–Cl: 169.9(3) ] for both bridging and terminal Cl
ligands. Additionally, this structure shows Hꢂ ꢂ ꢂCl contacts
between peripheral CH3 groups and terminal Cl liganꢁds
P < As < Sb.31 Ligand-to-metal charge transfer (LMCT)
transitions have been recently assigned for the lowest transi-
tions occurring in arsine ruthenium complexes [(Z6-tol)-
Ru(PAs)Cl]2+ (PAs ¼ 2-arsino-7-phosphanorbornene) from
˚
˚
[Hꢂ ꢂ ꢂCl: 2.884(9) A; Cꢂ ꢂ ꢂCl: 3.842(7) A; C–H–Cl: 165.7(3) ].
The Hꢂ ꢂ ꢂX interaction can be qualified as weak H bridges from
their distances and angles.32
spectroelectrochemical experiments.11b
. Since this system
contains a formal Ru(III) (d5) we expect that in our Pd(II)
(d8) complexes such LMCT transitions are shifted to much
higher energy.
Regardless of the differences in the crystal structures the
metal in all solved structures adopts a square planar environ-
ment having the two arsine ligands mutually trans (Fig. 3).
The yellow form of [PdCl2L002] gave only crystals of very poor
quality. The structure solution, which was best in the P2(1)/n
space group, could not be refined sufficiently but clearly
showed a cis configuration.
We also explored the photochemistry of these compounds.
Irradiation into the long-wavelength absorption bands led,
for cis and trans [PdCl2L00], [PdI2L002] and [Pd2Cl2(m-Cl)2L002],
to bleaching of nearly all long-wavelength bands as depicted
in Fig. 2. Parallel studies using 1H NMR spectroscopy showed
that the photoreaction comprises ligand-exchange reactions
yielding species like [PdCl2(MeCN)L00]. However, at high
concentrations, as necessary for the NMR measurements, the
decomposition rates are dramatically decreased, which allowed
us to observe only very small quantities of such species and
thus prevented unequivocal assignments. We assign this effect
to the equilibrium character of [PdCl2(MeCN)L00].
The M–As distances in the complexes lie in the expected
range around 2.4 A,28,31 as shown in Table 5, and do not vary
˚
greatly in the series of mononuclear compounds. In the binuc-
lear compound [Pd2Cl2(m-Cl)2L002] the Pd–As distances are sig-
˚
nificantly smaller (ca. 2.34 A; Table 6), which is expected since
the arsine ligands are located trans to the bridging chlorine
atoms. The M–X distances in this compound exhibit shorter
values for the terminal ligands than for the bridging chlorine
atoms, which is also in line with the argumentation that the
arsine ligands have a stonger trans influence than chlorine
ligands. Comparing the bond lengths in the palladium and pla-
tinum derivatives it can be stated that the platinum atom
appears to be smaller compared to palladium. This has also
been found in related studies28,29,33 and is attributed to the
lanthanide contraction and relativistic effects.33 Other bond
MeCN
½PdCl2L020ꢅꢆ )
½PdCl2ðMeCNÞL ꢅ þ L
00
00
00
*
MeCN
*
)
½PdCl2ðMeCNÞ2ꢅ þ 2L
ð2Þ
The labilization of the arsine ligand in the excited state sup-
ports our assignment for an MLCT/L0LCT transition [big
contribution from the anti-bonding component of the lone pair
(s/p*As) to the accepting orbital]. The trans-[PdCl2L002] com-
plex additionally undergoes partial isomerization to the cis
derivative, which has been monitored by absorption and 1H
NMR spectroscopy. The quantum yields are, however, very
low (estimated lower than 10ꢀ6), even in diluted solutions,
which prevents application of these reactions.
ꢁ
˚
Table 6 Selected bond lengths (A) and angles ( ) in [Pd2Cl2(m-
Cl)2L00
]
2
Terminal bonds
Pd(1)–As(1)
Pd(2)–As(2)
Pd(1)–Cl(1)
Pd(2)–Cl(2)
Angles
Bridging bonds
Pd(1)–Cl(3)
Pd(1)–Cl(4)
2.3439(8)
2.3341(8)
2.3236(15)
2.4329(16)
2.4498(16)
2.3218(15)
2.2686(16) Pd(2)–Cl(3)
2.2835(16) Pd(2)–Cl(4)
Crystal structures
Cl(1)–Pd(1)–Cl(3) 178.13(6)
Cl(1)–Pd(1)–Cl(4) 91.55(6)
Cl(2)–Pd(2)–Cl(4) 176.82(6)
Cl(1)–Pd(1)–As(1)
Cl(2)–Pd(2)–As(2)
91.50(5)
91.38(5)
The crystal and molecular structures of selected complexes
have been obtained by single crystal X-ray diffraction; selected
parameters are given in Tables 3, 5 and 6. All complexes of
the methylallylarsine ligand L00 are found to crystallize in the
Cl(2)–Pd(2)–Cl(3)
Cl(3)–Pd(1)–Cl(4)
Cl(4)–Pd(2)–Cl(3)
Pd(1)–Cl(3)–Pd(2)
Pd(2)–Cl(4)–Pd(1)
94.03(6)
86.60(5)
86.24(5)
88.54(5)
88.99(5)
Cl(3)–Pd(1)–As(1)
Cl(4)–Pd(2)–As(2)
90..35(4)
88.31(4)
¯
triclinic P1 space group whereas the allylarsine complexes
[PdCl2L02] (monoclinic, P21/n) and [PdBr2L02] (orthorhombic,
Pbca) adopt higher symmetric structures. There are only two
structures that exhibit intermolecular interactions. The crystal
As(1)–Pd(1)–Cl(4) 176.93(4)
As(2)–Pd(2)–Cl(3) 174.53(4)
New J. Chem., 2003, 27, 1584–1591
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benzyldimethylarsine complexes [MX2(BzAsMe2)2] of the
same type28 where the chlorine derivatives are exclusively
found in the cis configuration whereas bromine and iodine
adopt the trans conformation in the solid state (single crystals)
as well as in fluid solution. The latter findings implicate a steri-
cally driven selection enabling the thermodynamically
favoured cis conformation only for the smallest ligands. We
therefore suppose that the allyl- and methylallyl substituents
on the arsine ligands are more sterically demanding than two
methyl and one benzyl group, thus energetically labilizing the
cis conformers. Having both conformers for [PdCl2L002] in
hand we could establish some remarkable spectroscopic differ-
ences (NMR, UV/Vis). Although olefinic and agostic M–H
interactions are frequent in the organometallic chemistry of
platinum(II) and palladium(II), such interactions, either
through the olefinic group of the allyl moiety or with
AsCH2(agostic), are absent in the present case, which supports
the above discussion based on the reactivity and spectroscopy
of the compounds. The preliminary assignments for the long-
wavelength absorption bands as mixed MLCT/L0LCT transi-
tions were supported by the observed photoreactivity. Further
detailed investigations focusing on the character of the excited
states is warranted.
Acknowledgements
One of the authors (PPP) is grateful to DAE for the award of a
Senior Research Fellowship. The authors thank Drs. J. P.
Mittal and S. K. Kulshreshtha for the encouragement of this
work. The facilities provided by the Analytical Chemistry
Division, BARC, for microanalyses are gratefully acknowl-
edged. Support for this work under the Indo-German Bilateral
Agreement from BMBF (Project No. 99/060) is similarly
acknowledged. A. K. wants to thank the crystal structures
referee for the instructive comments.
Fig. 3 Molecular structures of trans-[MCl2L002] [M ¼ Pd (top) or Pt
(bottom)]. Atoms are represented by 30% ellipsoids. Hydrogen atoms
were omitted for clarity.
lengths in the compounds are in the expected range, that is
˚
˚
1.95–1.97 A for As–C(1) bonds, 1.49–1.51 A for C(1)–C(2),
˚
˚
=
1.30–1.37 A for the olefinic C(2) C(3) bond and 1.47–1.51 A
for the terminal C(2)–CH3 bond. The binuclear compound
[Pd2Cl2(m-Cl)2L002] does not deviate in that sense although
the allylarsine ligands are trans to Cl. As stated above the pal-
ladium or platinum atoms all lie in an almost perfect square
planar surrounding; the X–M–As angles (Tables 5 and 6) devi-
ate only by ꢇ2.5ꢁ from the ideal 90ꢁ. The binuclear [Pd2Cl2(m-
Cl)2L002] adopts an envelope shape for the Pd–(m-Cl)2–Pd cen-
tral unit with the terminal arsine ligands (and the terminal Cl
ligands) in anti positions as shown in Fig. 4.
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