Synthesis, spectroscopy, structure and photophysical properties of dinaphthylmethylarsine complexes of palladium(II) and platinum(II)

Article abstract of DOI:10.1016/j.ica.2005.03.026

Dinaphthylmethylarsine complexes of palladium(II) and platinum(II) with the formulae [MX₂L₂] (M = Pd, Pt; L = di(1-naphthyl) methylarsine = Nap₂AsMe and X = Cl, Br, I), [M₂Cl ₂(μ-Cl)₂L₂], [PdCl(S₂CNEt ₂)L], [Pd₂Cl₂(μ-OAc)₂L ₂] and [MCl₂(PR₃)L] (PR₃ = PEt ₃, PPr₃, PBu₃, PMePh₂) have been prepared. These complexes have been characterized by elemental analyses, IR, Raman, NMR (¹H, ¹³C, ³¹P) and UV-vis spectroscopy. The stereochemistry of the complexes has been deduced from the spectroscopic data. The crystal structures of trans-[PdCl₂(PEt ₃)(Nap₂AsMe)] and of [Pd(S₂CNEt ₂)₂], a follow-up product, were determined. The UV-vis spectra of [MX₂L₂] complexes show a red shift on going from X = Cl to X = I. The complexes [PdX₂L₂] and [PtX ₂L₂] are strongly luminescent in fluid solution and in the solid at ambient temperature.

Full text of DOI:10.1016/j.ica.2005.03.026

Inorganica Chimica Acta 358 (2005) 2609–2617
www.elsevier.com/locate/ica
Synthesis, spectroscopy, structure and photophysical properties of
dinaphthylmethylarsine complexes of palladium(II) and platinum(II)
a
a,
b
b,
b
, Thilo Schurr , Axel Klein *, Falk Lissner ,
*
Prasad P. Phadnis , Vimal K. Jain
Thomas Schleid , Wolfgang Kaim
b
b
a
Novel Materials and Structural Chemistry Division, Bhabha Atomic Research Centre, Mumbai 400 085, India
b
Institut fu¨r Anorganische Chemie, Universita¨t Stuttgart, Pfaffenwaldring 55, D-70550 Stuttgart, Germany
Received 12 August 2004; accepted 6 March 2005
Available online 20 April 2005
Abstract
Dinaphthylmethylarsine complexes of palladium(II) and platinum(II) with the formulae [MX2L2] (M = Pd, Pt; L = di(1-naph-
thyl)methylarsine = Nap2AsMe and X = Cl, Br, I), [M2Cl2(l-Cl)2L2], [PdCl(S2CNEt2)L], [Pd2Cl2(l-OAc)2L2] and [MCl2(PR3)L]
(PR3 = PEt3, PPr3, PBu3, PMePh2) have been prepared. These complexes have been characterized by elemental analyses, IR,
Raman, NMR (1H, 13C, 31P) and UV–vis spectroscopy. The stereochemistry of the complexes has been deduced from the spectro-
scopic data. The crystal structures of trans-[PdCl2(PEt3)(Nap2AsMe)] and of [Pd(S2CNEt2)2], a follow-up product, were determined.
The UV–vis spectra of [MX2L2] complexes show a red shift on going from X = Cl to X = I. The complexes [PdX2L2] and [PtX2L2]
are strongly luminescent in fluid solution and in the solid at ambient temperature.
Ó 2005 Elsevier B.V. All rights reserved.
Keywords: Organoarsenic compounds; Palladium complexes; Platinum complexes; Crystal structures; Photoluminescence
1. Introduction
organoarsines, we have now examined the chemistry of
di(1-naphthyl)methylarsine (Nap2AsMe = L) with palla-
dium(II) and platinum(II).
During the last decade, the chemistry of organoarse-
nic compounds has witnessed extensive growth due to
the development of new ligands and due to the search
for molecular precursors for CVD [1–4]. Arsines con-
taining a 1-naphthyl group could be of interest because
the facile cleavage of the M–C(naphthyl) linkage should
render them as ideal components for molecular precur-
sors. Besides, coordinated naphthylarsines in metal
complexes may cause steric crowding, thus facilitating,
e.g., the ortho metallation of the aromatic carbon atom
[5,6]. In view of this and in pursuance of our work on
2. Experimental
2.1. General procedures
The compounds Na2PdCl4, [PdCl2(MeCN)2] and
[PtCl2(PhCN)2] were prepared according to the litera-
ture procedures [7]. All reactions were carried out under
a nitrogen atmosphere in dry and distilled analytical
grade solvents. Microanalyses were carried out in the
Analytical Chemistry Division, BARC. The 1H,
13C{1H} and 31P{1H}NMR spectra were recorded on
a Bruker DPX-300 spectrometer operating at 300,
75.47 and 121.49 MHz, respectively. Chemical shifts
are relative to internal chloroform peak [d = 7.26 ppm
*
Corresponding authors. Present address: Institute for Inorganic
Chemistry, University of Cologne, Greinstrasse 6, D-50939 Cologne,
Germany. Tel.: +49 221 470 4006; fax: +49 221 470 4899.
E-mail addresses: jainvk@apsara.barc.ernet.in (V.K. Jain), aklein
@iac.uni-stuttgart.de, axel.klein@uni-koeln.de (A. Klein).
0020-1693/$ - see front matter Ó 2005 Elsevier B.V. All rights reserved.
doi:10.1016/j.ica.2005.03.026

2610
P.P. Phadnis et al. / Inorganica Chimica Acta 358 (2005) 2609–2617
for 1H; d = 77.0 ppm for 13C] and external H3PO4 (85%)
for 31P{1H} NMR. IR spectra were recorded as Nujol
mulls using CsI plates on a Bomen-102 FT IR spectro-
meter in the range 200–4000 cmꢀ1. UV–vis absorption
spectra were recorded on a JASCO V-530 spectropho-
tometer. The fluorescence spectra were recorded on Hit-
achi F-4014 Fluorescence spectrophotometer. Raman
spectra were recorded on Labram I (ISA make) Raman
spectrometer using an excitation wavelength of 488 nm
(Ar+) with a resolution of 2 cmꢀ1. Thermogravimetric
analyses were carried on a Setaram 92–16.18 instrument
(calibrated with CaC2O4 Æ 2H2O) under an N2 atmo-
sphere at a heating rate of 10 °C/min.
with n-hexane and dried in vacuo (948 mg; 93%).
Pertinent data are given in Table 1. Attempts to recrys-
tallize the title complex from pyridine gave yellow
[PdCl2(pyridine)2].
2.3.3. [PdBr2L2]
To a stirred acetone solution of [PdCl2L2] (130 mg,
0.15 mmol), an excess of KBr (683 mg, 5.7 mmol) was
added. The mixture was stirred for 48 h and the solvent
was dried in vacuo. The product was extracted with ben-
zene and filtered. The filtrate was evaporated in vacuo to
yield the title compound (110 mg; 77%).
Similarly, [PdI2L2] was prepared in 73% yield (69 mg)
as orange-red crystals from [PdCl2L2] (80 mg, 0.09
mmol) and an excess of KI (650 mg, 3.9 mmol).
2.2. Crystallography
Suitable crystals of [PdCl2(PEt3)(Nap2AsMe)] and
[Pd(S2CNEt2)2] were obtained from saturated solutions
in CH2Cl2. Data collection was performed at
T = 293(2) ([PdCl2(PEt3)(Nap2AsMe)]) or 100(2) K
([Pd(S2CNEt2)2]) on a KappaCCD device (Mo Ka:
2.3.4. [Pd2Cl2(l-Cl)2L2]
To a stirred benzene (60 cm3) solution of [PdCl2L2]
(410 mg, 0.47 mmol) [PdCl2(MeCN)2] (130 mg; 0.49
mmol) was added. The mixture was stirred with reflux-
ing for 3 h. The orange precipitate thus formed was fil-
tered through a G-3 glass filter, washed with n-hexane
and dried in vacuo to give an orange powder (450 mg;
92%). Attempts to recrystallize the product from pyri-
dine gave [PdCl2(pyridine)2]. Calc. for [PdCl2(pyri-
dine)2]: C, 35.8; H, 3.0; N, 8.3. Found: C, 35.5; H, 3.2;
N, 8.3%. 1H NMR in CDCl3 d: 7.31–7.38 (m, 2H);
7.77–7.82 (m, 1H); 8.83–8.87 (m, 2H).
˚
k = 0.71073 A; horizontally mounted graphite crystal;
95mm CCD camera on j-goniostat) using Collect (Non-
ius BV, 1997–2000) software. All structures were solved
by direct methods using the SHELXTL package [8] and
refinement was carried out with SHELXL-97 [9], employ-
ing full-matrix least-squares methods on F2 with
F 2o P 2rðF 2oÞ with the results shown in Table 2. All
non-hydrogen atoms were treated anisotropically,
hydrogen atoms were included by using appropriate rid-
ing models.
2.3.5. [PdCl(S2CNEt2)L]
To a stirred CH2Cl2 solution of [Pd2Cl2(l-Cl)2L2] (89
mg, 0.085 mmol), NaS2CNEt2 Æ 3H2O (40 mg, 0.18
mmol) was added and the reactants were stirred for 3
h. This mixture was filtered through a Florisil column
and dried in vacuo to yield an orange compound which
was rapidly recrystallized from CH2Cl2–hexane (90 mg;
87%). When the complex is left in solution for a few days
or reaction is carried out with an excess of NaS2CNEt2
Æ 3H2O, yellow orange single crystals of [Pd(S2CNEt2)2]
were separated. m.p. 221°C. Calc. for [Pd(S2CNEt2)2]:
C, 29.8; H, 5.0; N, 7.0. Found: C, 29.7; H, 4.9; N,
2.3. Syntheses
2.3.1. Di(1-naphthyl)methylarsine (Nap2AsMe or L)
To an ice cold ethereal solution of 1-naph-
thylmagnesiumbromide (9.3 g, 40.3 mmol), freshly dis-
tilled (88 °C/4 mmHg) MeAsI2 (6.51 g, 18.9 mmol) [10]
in diethyl ether (200 cm3) was added slowly with vigorous
stirring. The reactants were brought to room temperature
and then refluxed for 2 h. After cooling to 0 °C, the mix-
ture was treated with an aqueous NH4Cl solution (300
cm3). The diethyl ether layer was separated through a
canula. The ethereal extract was dried over sodium sul-
fate, filtered, and the filtrate was concentrated to dryness.
The residue was washed with n-hexane (40 cm3) and dried
to yield a white crystalline solid (2.8 g; 43%). A previously
reported synthetic procedure involved the reaction of
Nap2AsCl with RMgX in diethyl ether [11].
1
6.9%. H NMR in CDCl3 d: 1.27 (t, 7.1 Hz, NCH2Me);
3.71 (q, 7.1 Hz, NCH2). kmax: 300 (86815), 344 (11195)
nm (e in Mꢀ1cmꢀ1).
2.3.6. [PdCl2(PEt3)L]
To
a
stirred CH2Cl2 solution of [Pd2Cl2(l-
Cl)2(PEt3)2] (41 mg, 0.069 mmol), a solution of
L = Nap2AsMe (48 mg, 0.14 mmol) was added. The col-
our changed instantaneously from orange red to yellow.
The mixture was stirred for 2 h and the solvent was
evaporated in vacuo. The product was recrystallized
from an acetone–hexane mixture (56 mg; 67%).
Similarly, [PdCl2(PMePh2)L] and [PtCl2(PR3)L]
(R = Pr, Bu) were prepared from [M2Cl2(l-Cl)2(PR3)2]
(M = Pd or Pt) and Nap2AsMe (Table 1).
2.3.2. [PdCl2L2]
To a stirred acetone solution of [PdCl2(MeCN)2] (303
mg, 1.17 mmol), a solution of Nap2AsMe (810 mg, 2.34
mmol) was added with stirring whereupon a yellow
precipitate formed. The mixture was stirred for 3 h.
The precipitate was separated using a G-3 filter, washed

Table 1
Physical, analytical and 1H NMR data of dinaphthylmethylarsine complexes of palladium and platinum
Complex
Solvents of recrystallization
(% yield) (colour)
m.p. (°C)
Analyses % found (calc.)
1H NMR data in CDCl3 (d in ppm)
C
H
Nap2AsMe (=L)a
[PdCl2L2]
diethyl ether (43) (colourless)
acetone–hexane (93) (yellow)
146–148
162
72.2 (73.3)
4.7 (5.0)
1.64 (s, AsMe); 8.42–8.45 (m, H-2/or H-4); 7.82–7.89 (m, H-5, 8 + H-4 or 2); 7.36–7.53
(m, H-6, 7, H-3)
57.7 (58.3)
4.1 (4.0)
2.16 (small), 2.22 (large) (each s) (AsMe); 7.32 (td, 8.1 Hz (t), 0.9 (d)); 7.40 (td, 8.0 Hz,
1.4 (d)); 7.54 (td, 8.0 Hz (t), 1.0 (d)); 7.75 (dd, 7.1 Hz, 1.0 Hz); 7.93 (t, 7.5 Hz) (2
protons); 8.58 (d, 8.4 Hz)
[PdBr2L2]
[PdI2L2]b
CHCl3–hexane (77) (orange)
255
53.0 (52.8)
48.6 (48.1)
3.7 (3.6)
3.7 (3.3)
2.33, 2.43 (each s, AsMe 1:2 ratio); 7.31 (t, 7.3 Hz); 7.43 (t, 7.8 Hz); 7.54 (t, 7.4 Hz);
7.75 (d, 7.0 Hz); 7.92 (d, 7.7 Hz); 8.57 (d, 8.0 Hz)
CHCl3–hexane (73) (orange-red)
165–167 (deco)
2.76 (s, AsMe); 7.34 (t, 7.5 Hz); 7.48 (t, 8.1); 7.57 (t, 7.0 Hz); 7.77 (d, 6.5 Hz); 7.94 (dd,
7.6, 4.8 Hz); 8.52 (d, 8.3 Hz)
[Pd2Cl2(l-Cl)2L2]c
benzene–hexane (92) (orange)
CH2Cl2–hexane (87) (orange)
chars 225–230
212 (deco)
48.5 (48.4)
48.8 (49.2)
3.4 (3.3)
4.2 (4.3)
2.49 (s, AsMe); 7.48 (t, 8.4 Hz); 7.62 (br,); 8.09 (d, d); 8.60 (br)
[PdCl(S2CNEt2)L]d
1.08 (t, 7.1 Hz), 1.24 (t, 7.1 Hz) (Et); 2.34 (s, AsMe); 3.43 (q, 7.1 Hz), 3.65 (q, 7.1 Hz)
(CH2); 7.42–7.55 (m); 7.90–7.98 (m); 8.38, d, 7.9 Hz
[PdCl2(PEt3)L]e
acetone–hexane (67) (yellow)
119
50.3 (50.7)
5.2 (5.0)
1.21 (dt, 17 (d), 7.5 (t) Hz, PCH2CH3); 1.96 (m, PCH2); 2.15 (s, AsMe); 7.39 (t, 7.3
Hz); 7.53 (m); 7.67 (d, 7.1 Hz); 7.90–7.95 (m); 8.64 (d, 8.4 Hz)
[PdCl2(PMePh2)L]f
[PtCl2(PPr3)L]g
acetone–hexane (82) (yellow)
113
153
56.0 (56.6)
46.8 (46.5)
4.4 (4.2)
5.2 (5.0)
2.08 (d, 11.5 Hz); 2.21 (s, AsMe); 2.25 (s, small signal); 7.34–7.97 (m,); 8.65 (d, 8.6 Hz)
CH2Cl2–hexane (58) (colourless)
1.06 (t, 7.2 Hz); 1.62–1.75 (m); 1.86–1.95 (m); 2.19 (s, AsMe); 7.40 (t, 7.3 Hz); 7.49–
7.57 (m); 7.76 (d, 7.1 Hz); 7.93 (t, Hz); 8.69 (d, 8.4 Hz)
[PtCl2(PBu3)L]h
[Pd2Cl2(l-OAc)2L2]
[PtCl2L2]
CH2Cl2–hexane (62) (colourless)
CHCl3–hexane (73) (orange)
CH2Cl2–hexane (91) (cream)
153
130
253
50.7 (48.8)
51.2 (50.7)
52.7 (52.8)
5.6 (5.5)
3.8 (3.7)
3.7 (3.6)
0.71 (t, 7 Hz); 1.00–1.18 (m, PCH2CH2H2); 1.39–1.48 (m, PCH2); 2.64 (s, AsMe,
3J(Pt–H) = 19 Hz); 7.41–7.64 (m); 7.96–8.08 (m); 8.20 (d, 6.8 Hz); 8.36 (d, 8.0 Hz)
2.17 (s, AsMe); 2.25 (s, OAc); 6.93 (d, 6.8 Hz); 7.01 (d, 6.8 Hz); 7.15 (t, 7.7 Hz); 7.29 (t,
7.2 Hz); 7.53 (m); 7.74 (d, 8.3 Hz); 7.80 (8 Hz); 8.46 (8 Hz)
2.22 (small, s, AsMe), 2.24 (large, s, AsMe, 3J(Pt–H) = 12 Hz); large: 7.33 (t, 7.4 Hz);
7.43 (t, 7.1 Hz); 7.54 (t, 7 Hz); 7.83 (dd, 7.1, 0.9 Hz); 7.93 (t, 7 Hz); 8.67 (d, 8.4 Hz)
small: 7.05 (t, 7.5 Hz); 7.39 (d, 7.3 Hz); 7.74 (t, 7.3 Hz); 8.28 (d, 7.9 Hz)
[PtBr2L2]
acetone–hexane (57) (orange)
CHCl3–hexane (60) (orange)
225
265
49.9 (48.3)
43.2 (44.3)
4.1 (3.3)
3.2 (3.0)
2.31 (very small AsMe); 2.39 (s, AsMe, 3J(Pt–H) = 15 Hz); 7.33 (t, 8 Hz); 7.45 (t, 8.0
Hz); 7.55 (t, 7 Hz); 7.85 (d, 7 Hz); 7.93 (d, 8 Hz); 8.63 (d, 8.5 Hz)
[PtI2L2]i
2.71 (s, AsMe, 3J(Pt–H) = 21 Hz); 7.34 (t, 7.9 Hz); 7.47 (t, 8 Hz); 7.56 (t, 7 Hz); 7.86
(7.1 Hz); 7.92 (dd, 8, 3.4 Hz); 8.55 (d, 8.3 Hz)
a
13C{1H} NMR in CDCl3 d: 10.0 (s, AsMe); 125.7 (C-3,7); 126.1 (C-2); 126.9 (C-6); 128.9 (C-5,8); 130.5 (C-4); 133.8 (C-9); 136.1 (C-10); 139.7 (As–C).
13C{1H} NMR in CDCl3 d: 19.9 (s, AsMe); 124.8, 126.1, 126.4, 128.5, 129.3, 131.4, 133.6, 133.7, 134.2.
1H NMR in DMSO-d6.
b
c
d
e
f
% N: 1.9 (2.2); 13C{1H} NMR in CDCl3 d: 10.4 (s, NCH2Me); 12.2 (s, AsMe); 43.7 (s, NCH2); 125.2, 126.2, 126.7, 127.1, 129.0, 130.5, 131.3, 133.2, 133.7, 134.2, 206.9 (s, N–CS2).
31P{1H} in CDCl3: 29.7 ppm, 13C{1H} NMR in CDCl3 d: 8.1 (s, PCH2CH3); 9.2 (s, AsMe); 15.2 (d, J(P–C) = 28 Hz, PCH2); 125.3, 126.2, 126.4, 128.2, 128.9, 130.9, 132.9, 134.3, 134.4.
31P{1H} in CDCl3: 11.2 ppm.
g
h
i
31P{1H} in CDCl3: 3.4 ppm, 1J(Pt–P) = 3013 Hz.
31P{1H} in CDCl3: ꢀ4.5 ppm, 1J(Pt–P) = 3362 Hz.
13C{1H} NMR in CDCl3 d: 17.5 (s, AsMe); 124.7, 126.0, 126.3, 128.3, 129.2, 131.0, 131.4, 131.7, 132.6, 133.6, 134.3, 134.7.

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P.P. Phadnis et al. / Inorganica Chimica Acta 358 (2005) 2609–2617
2.3.7. [Pd2Cl2(l-OAc)2L2]
3000
To a stirred CH2Cl2 solution of [Pd2Cl2(l-Cl)2L2]
(100 mg, 0.1 mmol), 36 mg of AgOAc (0.21 mmol)
was added and the mixture was stirred for 3 h. Filtering
through a Florisil column and drying of the residue in
vacuo yielded an orange solid which was recrystallized
from CHCl3–hexane (80 mg; 73%).
2000
1000
0
2.3.8. [PtCl2L2]
To a stirred CH2Cl2 solution of [PtCl2(PhCN)2] (217
mg, 0.46 mmol), 320 mg of Nap2AsMe (0.93 mmol) was
added. The reactants were stirred for 3 h whereupon a
white precipitate formed which was filtered and washed
with CH2Cl2–hexane (1:2 v/v) and dried in vacuo (400
mg; 91%).
250
500
750
Wavenumbers (cm-1)
Fig. 1. Raman spectrum of [PdCl2(Nap2AsMe)2].
1000 1250 1500 1750
Similarly, [PtBr2L2] and [PtI2L2] were prepared from
[PtCl2L2] and excess KBr and KI, respectively
(see Table 1).
to recrystallize [Pd2Cl2(l-Cl)2L2] and [PdCl2L2] from
pyridine result in bridge cleavage and ligand substitution
with the formation of yellow [PdCl2(pyridine)2]. The IR
and Raman spectra of the complexes [MCl2L2] display
strong single absorptions at 304 (Fig. 1) or 316 cmꢀ1
for M = Pd or Pt, respectively, assigned to M–X stretch-
ing modes (m(M–X)). Similarly, the Raman spectrum of
[PdBr2L2] shows a resonance at 200 cmꢀ1. The presence
of a single absorption due to m(M–X) suggests that these
complexes adopt a trans configuration in the solid state.
The IR spectrum of [Pd2Cl2(l-Cl)2L2] exhibits three
absorptions at 360, 325 and 305 cmꢀ1, attributable to
m(Pd–Cl(terminal)), m(Pd–Cl(bridging, trans to Cl)) and
m(Pd–Cl(bridging, trans to arsine)) [1,12]. 1H NMR spec-
tra of these complexes display AsMe proton resonances
3. Results and discussion
3.1. Synthesis and spectroscopic analyses
Treatment of [MCl2(RCN)2] (M = Pd or Pt; R = Me
or Ph) with two equivalents of di(1-naphthyl)methylar-
sine (L) readily gave [MCl2L2] (Scheme 1). The chloride
ligands in the latter can be substituted with Br or I by
the reaction of [MCl2L2] with an excess of KBr or KI
in acetone. The reaction of [PdCl2L2] with
[PdCl2(MeCN)2] in refluxing benzene afforded sparingly
soluble binuclear complexes [Pd2Cl2(l-Cl)2L2]. Attempts
2 [MCl2(PR3)(Nap2AsMe)]
[M2Cl2(µ-Cl)2(PR3)2]
2 MeAsI2 + 4 NapMgBr
[MBr2(Nap2AsMe)2][
2 Nap2AsMe
- 4M gBrI
[MCl2(RCN)2]
KI excess
KBr excess
for M = Pd
[MCl2(Nap2AsMe)2]
MI2(Nap2AsMe)2]
[PdCl2(PhCN)2]
[Pd2Cl2(µ-Cl)2(Nap2AsMe)2]
2 AgOAc
.
2 NaS2CNEt2 3H2O
2 [PdCl(S2CNEt2)(Nap2AsMe)]
[Pd2Cl2(µ-OAc)2(Nap2AsMe)2]
(M = Pd or Pt; R = Me or Ph; PR3 = PEt3, PMePh2, PPr3, PBu3)
Scheme 1. Preparation of Nap2AsMe complexes.

P.P. Phadnis et al. / Inorganica Chimica Acta 358 (2005) 2609–2617
2613
which are considerably deshielded from the correspond-
ing signals for free Nap2AsMe. The naphthyl protons,
which are also deshielded, appear as multiplets (Table
1). For the complexes [MX2L2] (X = Cl or Br) two sing-
lets, attributable to the AsMe protons, were found pre-
sumably due to the occurrence of trans and cis isomers
in solution. For [PdI2L2], we found only one resonance
at 2.76 ppm after dissolving the complex. When leaving
the solution for a longer time we observed two singlets
at d 2.16 and 2.76 ppm (in a 3:2 ratio). Assuming a trans
conformation for the solid material (see IR spectros-
copy), we can assign the low field signal to the trans iso-
mer and the upcoming high field signal to the cis form.
In an analogous way (low-field = trans, high-field = cis),
we can conclude for the whole series of complexes that
in fluid solution slow trans/cis isomerization occurs with
trans being the initial isomer from the preparation pro-
cedures. This is remarkable in view of the recently re-
at ꢁ270 °C. The transition from first step to second
stage is poorly resolved.
The bridging chlorides in [Pd2Cl2(l-Cl)2L2] are read-
ily substituted by bridging acetate ligands through treat-
ment with AgOAc. The acetato-bridged complex
[Pd2Cl2(l-OAc)2L2] shows a m(C@O) resonance at 1570
cmꢀ1. This is comparable to other reported values for
acetato bridged palladium or platinum complexes
[13,14].
Reaction of [Pd2Cl2(l-Cl)2L2] with two equivalents of
NaS2CNEt2 Æ 3H2O yielded orange [PdCl(S2CNEt2)L].
The ethyl groups in the complex are anisochronous,
two separate triplets and quartets are observed for the
1
methyl and methylene protons in H NMR spectros-
copy. Such behaviour of the diethyldithiocarbamate li-
gand is not uncommon [15]. If the complex is left in
solution for a few days or if the dimer [Pd2Cl2(l-
Cl)2L2] is treated with an excess of NaS2CNEt2 Æ 3H2O,
yellow orange crystals of [Pd(S2CNEt2)2] were separated
which could be characterized by analytical, spectro-
scopic and structural analysis (see later).
ported
benzyldimethylarsine
complexes
[MX2
(BzAsMe2)2] (M = Pd or Pt) [2] which have been found
exclusively in cis conformation for X = Cl and in trans
conformation for X = Br or I and also in view of the re-
ported triallylarsine complexes [MX2(allyl3As)2]
(M = Pd or Pt) [3] where only for M = Pd and X = Cl
both trans and cis conformers were obtained after prep-
aration. However, the cis form quickly isomerizes to the
trans form, which is found exclusively for all other com-
plexes in this series. The reason for this peculiarity can
be found in the high lability of the di(1-naphthyl)methy-
larsine ligand. Ligand lability is a prerequisite for the
isomerization and was found to be much higher for the
Nap2AsMe ligand than for related BzAsMe2 or allyl3As
ligands (see, e.g., the formation of [Pd(S2CNEt2)2]).
The thermal behaviour of [PdCl2(Nap2AsMe)2] was
studied by thermogravimetric analysis. The TGA curve
(Fig. 2) shows two steps of decomposition. These steps
can be characterized by arsine loss, leaving behind PdCl2
Bridge cleavage of [M2Cl2(l-Cl)2(PR3)2] with
Nap2AsMe in dichloromethane gave the mixed ligand
complexes [MCl2(L)(PR3)]. The complexes display sin-
1
gle sets of resonances in the H and 31P NMR spectra,
indicating the formation of only one isomer. The magni-
1
tude of J(Pt–P) suggests a trans configuration which is
confirmed by X-ray structural analysis (see later).
3.2. Photophysical studies
Despite the isomerization reaction described above,
we can assume that all the compounds [PdX2L2] exhibit
initially a trans configuration. This is important for the
photophysical properties discussed here. The compounds
exhibit colours that range from colourless to red in the so-
lid as well as in solution. The electronic spectra (Table 2)
reveal that the long-wavelength absorption maxima are
lower in energy for the palladium derivatives as com-
pared to the platinum analogues. Furthermore, the en-
ergy decreases along the series Cl > Br > I. In view of
recent results on related benzyldimethylarsine complexes
[MX2(BzAsMe2)2] [2] and triallylarsine complexes
[MX2(allyl3As)2] [3], we tentatively assign the long-wave-
length absorptions to mixed ligand(pX)-to-ligand
(s/p*As)/metal(d)-to-ligand (s/p*As) charge transfer
(L0LCT/MLCT) transitions. Strong evidence for this
assignment comes from the clear separation of the long-
wavelength absorption into two bands for the iodide
derivatives (see Fig. 3). Iodide is the best donor in this re-
spect and should provide the highest contribution to the
starting orbital (HOMO) of the electronic transition.
Further support for the role of arsine in providing the
acceptor orbitals comes from recent investigations on re-
lated complexes of the type [MCl(TeCH2CH2NMe2)
(PR3)] (M = Pt or Pd; R = alkyl or aryl) where the
Fig. 2. TGA curve of [PdCl2(Nap2AsMe)2].

2614
P.P. Phadnis et al. / Inorganica Chimica Acta 358 (2005) 2609–2617
Table 2
Photophysical data of the dinaphthylmethylarsine complexes of Pd(II) and Pt(II)a
Compound
k
max/nm (e/Mꢀ1 cmꢀ1 a
)
Emission maxima kmax
Db
Naphthalene
[Nap2AsMe] (=L)
[PdCl2L2]
248 (2180), 257 (3700), 266 (3128), 275 (6044), 286 (3993)
291 (15322)
321, 334c
345, 370
7340
4340
3590
5000d
285 (37083), 368 (20025)
286 (48551), 380 (19745)
287 (45669), 364 (14619), 434 (6036)
286 (19086), 398(br)
415(sh), 438, 463(sh)
417(sh), 440, 461(sh)
445
[PdBr2L2]
[PdI2L2]
[Pd2Cl2(l-Cl)2L2]
[Pd2Cl2(l-OAc)2L2]
[PdCl(S2CNEt2)L]
[PdCl2(PEt3)L]
[PdCl2(PMePh2)L]
[PtCl2(PPr3)L]
[PtCl2(PBu3)L]
[PtCl2L2]
234 (28571), 292 (13966), 333(sh)
282 (24431), 368 (3611)
288 (13710), 340 (13042)
284 (16359), 350 (13312)
290 (24144)
289 (23900)
298 (28257)
349
359
405
4900
4510
3640
[PtBr2L2]
[PtI2L2]
292 (19335), 309 (16277)
290 (22738), 353 (3658)
a
As measured in CH2Cl2 solution.
D = Stokes shift = m(abs,max) ꢀ m(em,max) in wavenumbers (cmꢀ1).
b
c
Measured in cyclohexane, emission originating from the singlet 1IL state = fluorescence.
d
D was calculated from the second maximum at 364 nm. Taking the lowest maximum, D calculates to 570 cmꢀ1
.
5
4.5
emission
absorption
4.0
3.5
3.0
2.5
2.0
1.5
1.0
0.5
0.0
4
3
2
1
0
X = Cl
X = Br
X = I
300
350
400
450
500
550
Wavelength (nm)
Fig. 3. UV–vis spectra of [PdX2(Nap2AsMe)2] in CH2Cl2.
250
300
350
400
450
500
Wavelength (nm)
Fig. 4. Absorption and emission spectrum of Nap2AsMe in CH2Cl2.
long-wavelength absorptions were assigned to
ligand(Te)-to-ligand(P) charge transfer transitions, based
on spectroscopic and theoretical evidence [16].
are better acceptors compared to phosphine ligands,
which has been conclusively shown for related palla-
dium complexes with ER3 ligands (E = P, As or Sb)
where the lowest absorption maxima show a red-shift
when going from E = P to E = Sb [17]. The bands
around 290 nm are also present here albeit with mark-
edly lower intensity when compared to the [MX2(L)2]
derivatives, which is in excellent agreement to the IL
assignment outlined above.
The complexes [MX2L2] (M = Pd or Pt; X = Cl, Br, I)
have been found to exhibit bright luminescence in fluid
solution (Fig. 5) as well as in the solid. The highest max-
ima of the partly structured bands shift to lower energy
with decreasing electronegativity of the halide or substi-
tuting platinum by palladium (Table 2). The values for
the bromide and chloride derivatives differ only slightly
in this respect, the iodide analogues deviate much
stronger, connected to an obvious loss of the partial
Compared to the above cited benzyl- or (methyl)allyl
complexes, the dinaphthyl derivatives carry the addi-
tional naphthyl chromophore for relatively long-wave-
length absorptions and, even more importantly, strong
emissions (see later). Therefore, we assign the partially
structured bands around 290 nm to intra-ligand p–
p*(naphthyl) (IL) transitions for the complexes
[MX2(Nap2AsMe)2], they occur in the free ligand
Nap2AsMe as well as in naphthalene (Table 2, Fig. 4).
For the Pt(II) complexes, these bands partly overlap
with the long-wavelength CT bands.
The absorption spectra of the complexes
[PdCl2(L)(PR3)] are very similar to the ones described
above. The long-wavelength bands (L0LCT/MLCT)
are shifted to somewhat higher energies and are lower
in intensity. This supports our assignment since arsines

P.P. Phadnis et al. / Inorganica Chimica Acta 358 (2005) 2609–2617
2615
Table 3
Crystallographic and refinement data for [PdCl2(PEt3)(Nap2AsMe)]
and [Pd(S2CNEt2)2]
60
50
40
30
20
10
0
X = I
Compound
[PdCl2(PEt3)
(Nap2AsMe)]
[Pd(S2CNEt2)2]
X = Br
Empirical formula
Formula weight
T (K)
C27H32AsCl2PPd
639.72
293(2)
C10H20N2PdS4
402.92
100(2)
X = Cl
˚
Wavelength (A)
0.71073
monoclinic
P21/c
0.71073
tetragonal
P42/n
Crystal system
Space group
˚
a (A)
13.2660(2)
14.3565(2)
14.8659(2)
109.8824(9)
2662.50(7)
4
16.2435(3)
16.2435(3)
6.1746(2)
90.0
˚
b (A)
˚
c (A)
400
450
500
550
600
b (°)
3
˚
Wavelength (nm)
V (A )
1629.18(7)
4
1.643
Z
qcalc (g cmꢀ3
)
1.596
2.205
Fig. 5. Emission spectra of [PdX2(Nap2AsMe)2] in CH2Cl2.
l (mmꢀ1
F(000)
)
1.634
816
1859/0/120
1288
6082/0/305
structuring (Fig. 5) and a mismatch of the Stokes shifts
D calculated from the difference between the long-wave-
length absorption maxima and the main maxima of the
emission bands. Both naphthalene [18] and Nap2AsMe
(Fig. 4) are emissive in fluid solution, however, their
emission maxima do not coincide with those of the com-
plexes (Table 2). The broad emission of the free ligand
Nap2AsMe (Fig. 4) is assumed to originate from a p–
p* IL excited state. Presumably, the transition has trip-
let character (3IL) due to the heavy element influence of
arsenic, with its relatively high spin–orbit coupling. Sim-
ilarly, the emissions of the complexes [MX2(L)2] are as-
sumed to originate from corresponding 3CT states
(L0LCT/MLCT). The Stokes shifts D support the differ-
ent character of the emission. The complexes all exhibit
D values of about 3000–5000 cmꢀ1 which are typical for
CT states in platinum(II) complexes, whereas D is much
higher for the ligand indicating an IL state [19]. Com-
paring the iodide with the bromide or chloride ana-
logues, the emission behaviour suggests a marked
change for the excited state which we tentatively ascribe
to a shift from mainly MLCT for X = Cl or Br to mainly
L0LCT for X = I. In view of the fact that the naphthylar-
sine complexes exhibit much stronger luminescence than
the above-mentioned benzyldimethyl- or (methyl)ally-
larsine analogues, we suspect that the naphthyl chromo-
phore not only provides the high energy IL states but
may also contribute to the lowest transitions and the
corresponding excited states. Detailed spectroscopic
experiments (time-resolved experiments, quantum yield
determination, resonance Raman spectroscopy) com-
bined with theoretical calculations could help to gain a
better insight.
Data/restraints/
parameters
Final R indices
R1 = 0.0267;
wR2 = 0.0587
R1 = 0.0316;
wR2 = 0.0606
1.091
R1 = 0.0235;
wR2 = 0.0554
R1 = 0.0270;
wR2 = 0.0577
1.103
[I > 2r(I)]
R indices (all data)
Goodness-of-fit on F2
Largest difference in
˚
peak and hole (e A
0.567 and ꢀ0.661
0.607 and
ꢀ0.636
ꢀ3
)
troscopy. From the series of [MX2(PR3)(Nap2AsMe)]
complexes, a representative example could be examined
(Table 3). The structure of [PdCl2(PEt3)(Nap2AsMe)]
shows that the palladium atom is in a distorted square
planar environment with the neutral donors (P and
As) in a trans arrangement (Fig. 6). The two Pd–Cl dis-
tances (which are very similar), the Pd–P, Pd–As and the
As–C bond lengths (Table 4) are in agreement with the
literature values for related complexes [1,20–23]. At
3.3. Crystal structures
Unfortunately, the complexes [MX2(Nap2AsMe)2]
failed to give reasonable crystals for an XRD analysis
to confirm the isomers observed by IR and NMR spec-
Fig. 6. Molecular structure of trans-[PdCl2(PEt3)(Nap2AsMe)] in the
crystal, showing 30% thermal ellipsoids.

2616
P.P. Phadnis et al. / Inorganica Chimica Acta 358 (2005) 2609–2617
Table 4
for [Pd(SMe)(S2CNEt2)(PEt3)] [25], in contrast to
dithiophosphate ligands of analogous complexes which
show asymmetrical chelate binding, e.g., in [Pd(2-Spy)-
{S2P(OiPr)2}(PPh3)] [26] or [PdCl{S2P(OEt)2}(PPh3)]
[27]. The four Pd–S distances are essentially identical
˚
Selected bond lengths (A) and bond angles (°) of palladium(II)
complexes
[PdCl2(PEt3)(Nap2AsMe)]
[Pd(S2CNEt2)2]
˚
Bond lengths (A)
Pd–P
2.2863(6)
Pd–S(2)
2.3214(4)
2.3214(4)
2.3263(4)
2.3263(4)
1.7257(18)
1.7267(19)
1.317(2)
˚
and are in agreement with the values (2.2–2.5 A) re-
Pd–Cl(1)
Pd–Cl(2)
Pd–As
2.2970(5)
2.3055(5)
2.4560(3)
1.946(2)
1.947(2)
1.952(2)
Pd–S(2)#1
Pd–S(1)#1
Pd–S(1)
ported for a variety of palladium complexes containing
dithio ligands [25–28]. The strain imposed by the four
membered PdS2C chelate ring is reflected by a compres-
sion in those S–Pd–S angles (ꢁ75.7°), while the adjacent
angles S–Pd–S(#) have opened to 104.3°. The mutually
trans sulfur atoms exhibit an S–Pd–S angle of 180°.
The N–C(1) distance (Table 4) is significantly reduced
compared to a single N–C bond length, reflecting partial
double bond character. The S–C distances lie between
the values reported for single or double bonds, e.g.,
[RAs(S2CNEt2)2] (R = Me: C–S = 1.769(9), 1.675(9);
As–C(1)
As–C(8)
As–C(18)
S(1)–C(1)
S(2)–C(1)
N–C(1)
N–C(2)
N–C(4)
1.474(2)
1.476(2)
Bond angles (°)
P–Pd–Cl(1)
P–Pd–Cl(2)
86.34(2)
94.59(2)
S(2)–Pd–S(2)#1
S(2)–Pd–S(1)#1
S(2)#1–Pd–S(1)#1
S(2)–Pd–S(1)
180.00(2)
104.325(15)
75.675(15)
75.675(16)
104.325(15)
180.00(2)
Cl(1)–Pd–Cl(2)
P–Pd–As
178.81(2)
176.218(16)
90.585(16)
88.451(15)
101.60(10)
101.57(10)
101.94(9)
112.60(8)
121.60(6)
114.89(6)
˚
Cl(1)–Pd–As
Cl(2)–Pd–As
C(1)–As–C(8)
C(1)–As–C(18)
C(8)–As–C(18)
C(1)–As–Pd
C(8)–As–Pd
C(18)–As–Pd
S(2)#1–Pd–S(1)
S(1)#1–Pd–S(1)
C(1)–S(1)–Pd
C(1)–S(2)–Pd
N–C(1)–S(1)
R = Ph: C–S = 1.745(7), 1.691(7) A) [29]. The observed
N–C (1) and S–C distances indicate an effective delocal-
ization in the S2–C–N core. The ethyl groups of the
NEt2 moiety lie above and below the central
NCS2PdS2CN plane.
86.42 (6)
86.55 (6)
124.50 (14)
124.15 (14)
111.35 (10)
N–C(1)–S(2)
S(1)–C(1)–S(2)
Acknowledgements
˚
2.4560(3) A, the Pd–As distance is, however, longer than
i
˚
One of the authors (P.P.P.) is grateful to DAE for the
award of a Senior Research Fellowship. The authors
thank Drs. T. Mukherjee and S.K. Kulshreshtha for
encouragement of this work. The facilities provided by
Analytical Chemistry Division, BARC for microanaly-
ses are gratefully acknowledged. Support from the bilat-
eral Indo-german program from the BMBF (Project No.
IND 99/060) is gratefully acknowledged.
that reported for [Pd2Me2(l-Cl)2(As Pr3)2] (2.3495(7) A)
˚
[1] or [PdCl2{PhAs(CH2CH2CH2CH2CH2)}2] (2.3999(6) A)
[24]. The coordination around arsenic shows a typical
trigonal pyramidal AsC3 skeleton with C–As–C angles
of ꢁ101.6°, which do not differ significantly from those
reported for other coordinated arsines. The individual
naphthyl rings are planar and point away from the coor-
dination plane of the palladium atom.
The structure (Fig. 7) of the product [Pd(S2CNEt2)2]
from the reaction involving [PdCl(S2CNEt2)L] shows
discrete molecules with the palladium atom in distorted
square planar geometry defined by the two symmetri-
cally chelated dithio ligands. Similar symmetrical bind-
ing of that dithiocarbamate ligand had been reported
Appendix A. Supplementary data
Crystallographic data for the structural analyses have
been deposited with the Cambridge Crystallographic
Fig. 7. Molecular structure of [Pd(S2CNEt2)2] in the crystal, showing 30% thermal ellipsoids.

P.P. Phadnis et al. / Inorganica Chimica Acta 358 (2005) 2609–2617
2617
[10] I.T. Millar, H. Heaney, D.M. Heinekey, W. Conard Fernelius,
Inorg. Synth. 6 (1960) 113.
Data Centre, CCDC Nos. 247069 ([PdCl2(PEt3)(Na-
p2AsMe)]), 247070 ([Pd(S2CNEt2)2]). Copies of this
information may be obtained free of charge from: The
Director, CCDC, 12 Union Road, Cambridge CB2
1EZ, UK [fax: (int. code) +44 1223 336 033; e-mail: de-
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ac.uk]. Supplementary data associated with this article
can be found, in the online version, at doi:10.1016/
j.ica.2005.03.026.
Four figures illustrating the crystal structures (unit
cell and intermolecular interactions) and perspective
views as well as full structural data of both complexes
are available from the author on request.
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