Palladium(II) and platinum(II) complexes with heteroditopic 10-(Aryl)phenoxarsine (Aryl = 2-C6H4OR, R = H, Me, Pr i) ligands: Solvent-oriented crystallization of cis isomers

Article abstract of DOI:10.1021/ic7021648

The synthesis and characterization of 10-(o-alkoxyphenyl)phenoxarsines 2-ROC₆H₄As(C₆H₄)₂O (R = H, Me, and Prⁱ, As(C₆H₄)₂O = phenoxarsine) and their platinum(II) and palladium(II) complexes cis-[PtCl ₂{2-PrⁱOC₆H₄As(C₆H ₄)₂O-κAs}₂] (1), trans-[PdCl ₂{2-PrⁱOC₆H₄As(C₆H ₄)₂O-κAs}₂] (2), cis-[PtCl ₂{2-HOC₆H₄As(C₆H₄) ₂O-κAs}₂] (3), cis-[PdCl₂{2-HOC ₆H₄As(C₆H₄)₂O-κAs} ₂] (4), cis-[Ptl₂{2-MeOC₆H₄As(C ₆H₄)₂O-κAs}₂] (5), and trans-[PdCl₂{2-MeOC₆H₄As(C₆H ₄)₂O-κAs}₂] (6) are reported. The chelate complex cis-[Pt{2-OC₆H₄As(C₆H ₄)₂O-κAs,O}₂] (7) is also described. The molecular structures of 1-4 and 7 were determined. The short As?O intramolecular interaction found in complexes 1-4 in the solid state was also verified by calculations at the B3LYP/LANL2DZ level for complex 2 and for 10-(o-isopropoxyphenyl)phenoxarsine in the gas phase, and this suggests that the interaction is a characteristic of the ligand rather than a packing effect. Calculations at the B3LYP/LANL2DZ and Oniom(B3LYP/LANL2DZ:uff) levels for complexes 1-4 showed that the solvent plays a crucial role in the crystallization (through geometry constraints) of the kinetically stable cis isomers.

Full text of DOI:10.1021/ic7021648

Inorg. Chem. 2008, 47, 1524-1531
Palladium(II) and Platinum(II) Complexes with Heteroditopic
10-(Aryl)phenoxarsine (Aryl ) 2-C6H4OR, R ) H, Me, Pri) Ligands:
Solvent-Oriented Crystallization of cis Isomers
Natalia Moldovan,†,‡ Peter Lönnecke,‡ Ioan Silaghi-Dumitrescu,† Luminita Silaghi-Dumitrescu,*,†
and Evamarie Hey-Hawkins*,‡
Department of Chemistry, Babes-Bolyai UniVersity, Kogalniceanu 1, RO-400084, Cluj-Napoca,
Romania and UniVersität Leipzig, Institut für Anorganische Chemie, Johannisallee 29,
D-04103, Leipzig, Germany
Received November 2, 2007
The synthesis and characterization of 10-(o-alkoxyphenyl)phenoxarsines 2-ROC6H4As(C6H4)2O (R ) H, Me, and
Pri, As(C6H4)2O ) phenoxarsine) and their platinum(II) and palladium(II) complexes cis-[PtCl2{2-PriOC6H4As(C6H4)2O-
κAs}2] (1), trans-[PdCl2{2-PriOC6H4As(C6H4)2O-κAs}2] (2), cis-[PtCl2{2-HOC6H4As(C6H4)2O-κAs}2] (3), cis-[PdCl2{2-
HOC6H4As(C6H4)2O-κAs}2] (4), cis-[PtI2{2-MeOC6H4As(C6H4)2O-κAs}2] (5), and trans-[PdCl2{2-MeOC6H4As(C6H4)2O-
κAs}2] (6) are reported. The chelate complex cis-[Pt{2-OC6H4As(C6H4)2O-κAs,O}2] (7) is also described. The molecular
structures of 1–4 and 7 were determined. The short As···O intramolecular interaction found in complexes 1–4 in
the solid state was also verified by calculations at the B3LYP/LANL2DZ level for complex 2 and for
10-(o-isopropoxyphenyl)phenoxarsine in the gas phase, and this suggests that the interaction is a characteristic of
the ligand rather than a packing effect. Calculations at the B3LYP/LANL2DZ and Oniom(B3LYP/LANL2DZ:uff)
levels for complexes 1–4 showed that the solvent plays a crucial role in the crystallization (through geometry
constraints) of the kinetically stable cis isomers.
Introduction
a limited number of 10-(aryl)phenoxarsines have been
reported (aryl ) RC6H4, with R ) 2-MeO10 and 2-, 3-, or
4-PhO11), which were obtained from 10-chlorophenoxarsine
and the corresponding Grignard reagent. The 10-(phe-
noxyaryl)phenoxarsines are useful as fungicides, herbicides,
and insecticides.11
We now report the synthesis and characterization of
ligands with the general formula 2-ROC6H5As(C6H4)2O,
where R ) H, Me, or Pri, and their platinum(II) and
Organoarsenic compounds are mainly known as ligands
in transition metal complexes, some of which are used in
catalytic reactions, and as biologically active compounds.
Tertiary arsines have been reported as more efficient ligands
than their phosphorus analogues in a number of transition-
metal-catalyzed reactions, for example, Stille1–3 and Suzuki-
Miyaura coupling reactions,4 the hydroformylation of ter-
minal alkenes,5,6 Heck olefination,7 carbonylation,8and the
copolymerization of olefins and CO.9
(4) Bedford, R. B.; Cazin, C. S. J.; Coles, S. J.; Gelbrich, T.; Hursthouse,
M. B.; Scordia, V. J. M. Dalton Trans. 2003, 3350–3356.
(5) van der Veen, L. A.; Keeven, P. K.; Kamer, P. C. J.; van Leeuwen,
P. W. N. M. Chem. Commun. 2000, 333–334.
Heteroditopic ligands containing oxygen as a potential
donor along with arsenic may be good candidates to prepare
catalytically active transition metal complexes. So far, only
(6) van der Veen, L. A.; Keeven, P. K.; Kamer, P. C. J.; van Leeuwen,
P. W. N. M. Dalton Trans. 2000, 2105–2112.
(7) Baber, R. A.; Collard, S.; Hooper, M.; Orpen, A. G.; Pringle, P. G.;
Wilkinson, M. J.; Wingad, R. L. Dalton Trans. 2005, 1491–1498.
(8) Ceccarelli, S.; Piarulli, U.; Gennari, C. J. Org. Chem. 2000, 65, 6254–
6256.
* Authors to whom correspondence should be addressed. E-mail:
hey@rz.uni-leipzig.de (E. H.-H.).
†
Babes-Bolyai University.
Universität Leipzig.
‡
(9) Wang, C.-Y.; Tan, D.-M.; Chan, K. S.; Liu, Y.-H.; Peng, S.-M.; Liu,
S.-T. J. Organomet. Chem. 2005, 690, 4920–4925.
(1) Farina, V. K.; Krishnan, B. J. Am. Chem. Soc. 1991, 113, 9585–9595.
(2) Amatore, C.; Bucaille, A.; Fuxa, A.; Jutand, A.; Meyer, G.; Ntepe,
A. N. Chem.sEur. J. 2001, 7, 2134–2142.
(10) Gavrilov, V. I.; Gavrilova, G. R.; Khlebnikov, V. N.; Chernokal’skii,
B. D. IzV. Vyssh. Uchebn. ZaVed., Khim. Khim. Tekhnol. 1973, 16,
1602–1604.
(3) Amatore, C.; Bahsoun, A. A.; Jutand, A.; Meyer, G.; Ntepe, A. N.;
Ricard, L J. Am. Chem. Soc. 2003, 125, 4212–4222.
(11) Wang, C.-S.; McGee, T. W. U.S. Patent 3547967, 1970.
1524 Inorganic Chemistry, Vol. 47, No. 5, 2008
10.1021/ic7021648 CCC: $40.75
2008 American Chemical Society
Published on Web 02/07/2008

Pd(II) and Pt(II) Complexes with Heteroditopic Ligands
Table 1. Crystal Data and Refinement Details for cis-[PtCl2{2-PriOC6H4As(C6H4)2O-κAs}2] (1), trans-[PdCl2{2-PriOC6H4As(C6H4)2O-κAs}2] (2),
cis-[PtCl2{2-HOC6H4As(C6H4)2O-κAs}2] (3), cis-[PdCl2{2-HOC6H4As(C6H4)2O-κAs}2] (4), and cis-[Pt{2-OC6H4As(C6H4)2O-κAs,O}2] (7)
1
2
3
4
7
empirical formula
fw
temp. (K)
cryst syst
space group
unit cell
C42H38As2Cl2O4Pt
1022.55
210(2)
monoclinic
P21/n
C42H38As2Cl2O4Pd
933.86
210(2)
monoclinic
P21/n
C36H26As2Cl2O4Pt·CH2Cl2 C36H26As2Cl2O4Pd·CH2Cl2 C36H24As2O4Pt
1023.32
297(2)
934.63
297(2)
865.48
213(2)
monoclinic
C2/c
monoclinic
C2/c
monoclinic
P21/c
a (Å)
b (Å)
c (Å)
9.953(6)
20.800(12)
18.408(11)
90
97.238(12)
90
3780(4)
1.797
5.632
10.865(2)
12.586(3)
14.840(3)
90
109.956(4)
90
1907.5(7)
1.626
2.390
16.388(1)
14.964(1)
14.960(1)
90
93.258(1)
90
3662.8(5)
1.856
5.954
16.331(1)
14.988(1)
14.933(1)
90
93.405(1)
90
3648.6(4)
1.701
2.640
10.287(1)
19.241(1)
14.867(1)
90
96.458(1)
90
2923.9(3)
1.966
7.086
R (deg)
ꢀ (deg)
γ (deg)
vol (Å3)
density (calcd) (Mg/m3)
abs coeff (mm-1
F(000)
)
2000
936
1976
1848
1664
cryst size (mm3)
θ range (deg)
index ranges
0.30 × 0.10 × 0.10 0.40 × 0.20 × 0.20 0.47 × 0.34 × 0.26
0.40 × 0.20 × 0.19
1.85–26.37
-20 e h e +20
-18 e k e +18
-18 e l e +18
14449
0.60 × 0.60 × 0.30
1.99–28.40
-13 e h e +13
-25 e k e +23
-19 e l e +17
20178
1.96–28.31
2.18–29.07
1.84–26.37
-9 e h e +13
-27 e k e +25
-24 e l e +10
18053
-14 e h e +9
-16 e k e +14
-18 e l e +19
11761
-20 e h e +20
-18 e k e +18
-18 e l e +18
14435
reflns collected
independent (Rint
data/restraints/parameters 8973/ 0/464
final R indices
)
8973 (0.0639)
4684 (0.0247)
4684/0/234
3744 (0.0323)
3744/0/224
3728 (0.0305)
3728/0/219
R1 ) 0.0458
wR2 ) 0.1007
R1 ) 0.0502
wR2 ) 0.1029
1.163
6740 (0.0438)
6740/0/388
R1 ) 0.0392
wR2 ) 0.0968
R1 ) 0.0470
wR2 ) 0.1009
1.063
R1 ) 0.0438
wR2 ) 0.0717
R1 ) 0.0897
wR2 ) 0.0852
0.938
R1 ) 0.0317
wR2 ) 0.0722
R1 ) 0.0483
wR2 ) 0.0760
1.051
R1 ) 0.0382
wR2 ) 0.0891
R1 ) 0.0412
wR2 ) 0.0905
1.146
R indices (all data)
goodness-of-fit on F2
largest difference peak
and hole (e Å-3
)
2.156 and -1.162
0.656 and -0.550
1.903 and -0.873
0.748 and -0.839
3.097 and -1.515
The mass spectra were recorded on a Ltd. ZAB-HSQ-VG Analytical
Manchester Spectrometer (FAB mass spectra) and on a FT-ICR-
MS Bruker-Daltonics ESI mass spectrometer. The elemental
analyses were recorded on a VARIO EL (Heraeus).
palladium(II) halide complexes cis- or trans-[MX2{2-
ROC6H4As(C6H4)2O-κAs}2]. The chelate complex cis-[Pt{2-
OC6H4As(C6H4)2O-κAs,O}2] (7) was obtained by the elimi-
nation of HCl from cis-[PtCl2{2-HOC6H4As(C6H4)2O-
κAs}2] (3).
Data for X-ray structures were collected on a Siemens CCD
diffractometer (SMART) using Mo KR radiation (λ ) 0.71073 Å)
and ω-scan rotation. Data reduction was performed using SAINT,
including the program SADABS for empirical absorption correction.
The structures were solved by direct methods, and the refinement
of all non-hydrogen atoms was performed with SHELX97. H atoms
were mainly calculated on idealized positions (Table 1). Structure
figures were generated with ORTEP and DIAMOND-3.15 The
Cambridge Crystallographic Data Centre, under CCDC 665586 (1),
665587 (2), 665588 (3), 665589 (4), and 665590 (7), contains the
supplementary crystallographic data for this paper. These data can
be obtained free of charge from the Cambridge Crystallographic
Data Centre via the Internet at www.ccdc.cam.ac.uk/data_request/
cif. Also, CIF files for compounds 1-4 and 7 are available as
Supporting Information.
Experimental Section
Materials. All reactions were carried out under a dry nitrogen
atmosphere using standard Schlenk or vacuum line techniques. The
solvents were purified (THF, toluene: refluxed over Na/benzophe-
none; CH2Cl2, n-hexane, MeOH: refluxed over powdered CaH2)
and distilled under nitrogen. All chemicals were of reagent grade
and were used as received: phenol, anisole, isopropyl bromide,
Ph2O, n-BuLi and t-BuLi, TMEDA (N,N,N′,N′-tetramethylethyl-
enediamine), THP (tetrahydropyran), and AsCl3 were purchased
from Merck; PdCl2 and H2[PtCl6]·6H2O were generously donated
by Umicore. [PtCl2(COD)],12 [PdCl2(COD)],12 isopropyl phenyl
ether,13 and 10-chlorophenoxarsine were prepared according to
published procedures (COD ) 1,5-cyclo-octadiene).14
Instrumentation. The IR spectra were recorded on a Perkin-
Elmer System 2000 FT-IR spectrometer scanning between 400 and
4000 cm-1 by using KBr disks, and between 200 and 400 cm-1 by
using CsI plates. The 1H, 13C, and APT NMR spectra of the ligands
were recorded on an AVANCE DRX 400 spectrometer (Bruker)
and those of the transition metal complexes 1-7 on an AVANCE
300 spectrometer (Bruker) with tetramethylsilane as the standard.
Preparation of Ligands. (2-Isopropoxyphenyl)phenoxarsine
and (2-Methoxyphenyl)phenoxarsine10. A round-bottomed three-
neck flask was charged with 0.725 mol of phenyl ether (isopropyl-
phenyl ether or anisole) and 0.725 mol of TMEDA. A total of 0.725
mol of n-BuLi (1.95 M, in n-hexane) was added dropwise under a
(15) (a) SMART: Area-Detector Software Package; Siemens Industrial
Automation, I.M.: Madison, WI, 1993. (b) SAINT: Area-Detector
Integration Software, version 6.01; Siemens Industrial Automation,
Inc.: Madison, WI, 1999. (c) Sheldrick, G. M. SADABS, Program for
Scaling and Correction of Area-detector Data, University of Göttingen:
Göttingen, Germany, 1997. (d) Sheldrick, G. M. SHELX97, Programs
for Crystal Structure Analysis, release 97–2; University of Göttingen:
Göttingen, Germany, 1997; includes SHELXS97 and SHELXL97. (e)
ORTEP3 for Windows: Farrugia, L. J. J. Appl. Crystallogr. 1997, 30,
565. (f) Brandenburg, K. DIAMOND 3; Crystal Impact GbR: Bonn,
Germany..
(12) Drew, D.; Doyle, J. R. Inorg. Synth. 1990, 28, 346–349.
(13) Becker, H.; Berger, W.; Domschke, G.; Fanghänel, E.; Faust, J.;
Fischer, M.; Gentz, F.; Gewald, K.; Gluch, R.; Mayer, R.; Müller,
K.; Pavel, D.; Schmidt, H.; Schollberg, K.; Schwetlick, K.; Seiler, E.;
Zeppenfeld, G. Organicum; VEB Deutscher Verlag der Wissen-
schaften: Berlin, 1978.
(14) Wag, C.-S.; Chang, K. Y. U.S. Patent 3,532,727, 1970.
Inorganic Chemistry, Vol. 47, No. 5, 2008 1525

Moldovan et al.
nitrogen stream with continuous stirring. After all of the n-BuLi
was added, the solution was stirred for 20 h at room temperature.
The cloudy reaction mixture was then cooled to 0 °C, and
10-chlorophenoxarsine, dissolved in THF, was added to this solution
(1:1 molar ratio). The reaction mixture was refluxed for 2 h, then
cooled to 0 °C and neutralized with degassed water. The organic
layer was separated.
(2-Isopropoxyphenyl)phenoxarsine. The solvent was evapo-
rated and the residue distilled. The compound was isolated as a
pale yellow oil (0.4 mbar, bp 160 °C), which started to crystallize
after storage at low temperatures in a refrigerator. Yield: 1.83 g
(41%). mp ) 91 °C. Anal. calcd (found) for C21H19O2As: C, 66.66
(66.60); H, 5.02 (4.93). EI-MS: m/z 379 [M + H]+.
C18H13O2As: C, 64.28 (64.60); H, 3.86 (4.22); O, 9.54 (9.46). EI-
1
MS: m/z 336 [M]+. H NMR (CDCl3): δ 6.47 (dd, 1H, H6, JH6-H5
) 7.33 Hz, JH6-H4 ) 2 Hz), 6.58 (m, 1H, H4), 6.63 (d, 1H, H3,
JH3-H4 ) 7.33 Hz), 7.03 (m, 3H, H5, H10), 7.11 (dd, 2H, H11,
JH11-H10 ) 8.31 Hz, JH11-H9 ) 1.46 Hz), 7.25 (m, 2H, H9), 7.57
(dd, 2H, H8, JH8-H9 ) 7.33 Hz, JH8-H10 ) 1.46 Hz), OH not observed.
13C NMR (CDCl3): δ 114.0 (C6), 117.6 (C10), 119.3 (C4), 119.9
(C7), 123.1 (C11), 126.8 (C2), 129.2 (C3), 130.2 (C9), 131.6 (C5),
135.3 (C8), 155.6 (C12), 158.8 (C1). IR (cm-1, KBr disks): 435,
763, 1018–1074, 1223, 1265, 1597, 3059, 3403 ν(O-H).
Preparation of Complexes. A total of 2 equiv of the arsine
ligand dissolved in toluene was added very slowly to a solution of
1 equiv of [MCl2(COD)] (M ) Pt, Pd) dissolved in dichloromethane
so as to form two layers. The complexes which contain arsine
ligands with a 2-methoxyphenyl moiety were prepared by treating
the ligand with [MX2(COD)] (M ) Pt, Pd; X ) I, Cl) in
dichloromethane at a molar ratio of 2:1.
The numbering scheme used to assign the NMR spectra is
presented below for (2-isopropoxyphenyl)phenoxarsine, and it is
valid for the aromatic atoms in all of the compounds reported:
cis-[PtCl2{2-PriOC6H4As(C6H4)2O-KAs}2] (1). A yellow crys-
talline product was obtained. Yield: 0.066 g (56%). mp ) 294 °C
(decomp. without melting). Anal. calcd (found) for C42H38O4As2-
1
PtCl2: C, 49.33 (49.20); H, 3.75 (3.66); Cl, 6.93 (6.81). H NMR
(CDCl3): δ 1.33 (d, 12H, CH3, J ) 6.04 Hz), 4.57 (m, 2H, CH),
6.70 (d, 2H, H6, JH6-H5 ) 7.74 Hz), 6.85 (d, 2H, H3, JH3-H4 ) 8.30
Hz), 6.91 (m, 2H, H4), 7.20–7.37 (m, 14H, H5, H9, H10, H11),
7.72 (m, 4H, H8). IR (cm-1, CsI plates): 311, 324 ν(Pt-Cl). IR
(cm-1, KBr disks): 462, 750, 1030–1132, 1263, 882, 1383, 1461,
1580, 2976, 3062.
1H NMR (CDCl3): δ 1.35 (d, 6H, CH3, J ) 5.86 Hz), 4.57 (m,
1H, CH), 6.55 (dd, 1H, H6, JH6-H5 ) 7.33 Hz, JH6-H4 ) 1.46 Hz),
6.66 (m, 1H, H4), 6.72 (d, 1H, H3, JH3-H4 ) 8.31 Hz), 7.11 (m,
trans-[PdCl2{2-PriOC6H4As(C6H4)2O-KAs}2] (2). Orange crys-
tals were obtained. Yield: 0.068 g (60%). mp ) 222–225 °C
(decomp. without melting). Anal. calcd (found) for C42H38O4As2-
3H, H5, H10), 7.19 (dd, 2H, H11, JH11-H10 ) 8.31 Hz, JH11-H9
)
1.95 Hz), 7.33 (m, 2H, H9), 7.65 (dd, 2H, H8, JH8-H9 ) 7.33 Hz,
JH8-H10 ) 1.46 Hz). 13C NMR (CDCl3): δ 21.9 (CH3), 69.7 (CH),
111.7 (C6), 118.2 (C10), 120.3 (C7), 120.5 (C4), 123.3 (C11), 129.5
(C2), 129.6 (C3), 130.4 (C9), 132.2 (C5), 135.7 (C8), 156.0 (C12),
158.9 (C1). IR (cm-1, KBr disks): 461, 753, 1029–1124, 881, 1059,
1262, 1382, 1461, 1580.
1
PdCl2: C, 54.01 (53.82); H, 4.10 (3.97); Cl, 7.59 (7.43). H NMR
(CDCl3): δ 1.32 (d, 12H, CH3, J ) 6.04 Hz), 4.57 (m, 2H, CH),
6.74 (d, 2H, H6, JH6-H5 ) 8.30 Hz), 6.86 (d, 2H, H3, JH3-H4 ) 8.30
Hz), 6.93–7.37 (m, 16H, H4, H5, H9, H10, H11), 8.15 (m, 4H,
H8). IR (cm-1, CsI plates): 362 δ(Pd-Cl); 278 ν(Pd-As). IR
(cm-1, KBr disks): 459, 751, 1031–1127, 884, 1265, 1384, 1464,
1580, 2971, 3064.
(2-Methoxyphenyl)phenoxarsine. After the solvent was re-
moved, the compound was obtained as a pale yellow powder, which
was recrystallized from n-hexane. Yield: 2.95 g (52%). mp ) 115
°C. Anal. calcd (found) for C19H15O2As: C, 65.14 (64.60); H, 4.28
1
cis-[PtCl2{2-HOC6H4As(C6H4)2O-KAs}2] (3). Pale yellow crys-
tals were obtained. Yield: 0.022 g (45%). mp ) 268–272 °C
(decomp. without melting). Anal. calcd (found) for C36H26O4As2-
(4.39). EI-MS: m/z 350 [M]+. H NMR (CDCl3): δ 3.82 (s, 3H,
CH3), 6.55 (dd, 1H, H6, JH6-H5 ) 7.33 Hz, JH6-H4 ) 1.46 Hz), 6.70
(m, 1H, H4), 6.74 (d, 1H, H3, JH3-H4 ) 7.82 Hz), 7.12 (m, 3H, H5,
H10), 7.20 (dd, 2H, H11, JH11-H10 ) 8.31 Hz, JH11-H9 ) 1.46 Hz),
1
PtCl2: C, 46.08 (45.50); H, 2.79 (2.52); Cl, 7.56 (7.39). H NMR
(CDCl3): δ 6.85 (dd, 2H, H6, JH6-H5 ) 8.30 Hz, JH6-H4 ) 0.94 Hz),
6.91–7.22 (m, 14H, H3, H4, H5, H10, H11), 7.35 (m, 4H, H9),
7.45 (dd, 4H, H8, JH8-H9 ) 7.74 Hz, JH8-H10 ) 1.70 Hz), OH not
observed. IR (cm-1, CsI plates): 311, 325 ν(Pt-Cl). IR (cm-1, KBr
disks): 460, 752, 1225, 1267, 1583, 3073, 3374 ν(O-H).
7.34 (m, 2H, H9), 7.62 (dd, 2H, H8, JH8-H9 ) 7.33 Hz, JH8-H10
)
1.46 Hz). 13C NMR (CDCl3): δ 55.5 (CH3), 110.2 (C6), 118.3
(C10), 119.8 (C7), 121.2 (C4), 123.4 (C11), 129.2 (C2), 129.8 (C3),
130.6 (C9), 132.1 (C5), 135.6 (C8), 155.9 (C12), 160.8 (C1). IR
(cm-1, KBr disks): 460, 753, 1021–1122, 1021–1057, 1241–1261,
1580, 1392, 1428, 2954, 2929, 3059.
cis-[PdCl2{2-HOC6H4As(C6H4)2O-KAs}2] (4). Reddish-orange
crystals were obtained. Yield: 0.017 g (58%). mp ) 190–200 °C
(decomp. without melting). Anal. calcd (found) for C36H26O4As2-
(2-Hydroxyphenyl)phenoxarsine. ortho-Dilithiated phenol was
prepared by adding dropwise 2.8 equiv of t-BuLi in n-pentane to
1.0 equiv of phenol dissolved in 4.2 equiv of THP at 25 °C
(exothermic reaction). The reaction mixture was stirred for 5 h after
the addition of t-BuLi was completed. The reaction mixture was
cooled to 0 °C; 2 equiv of 10-chlorophenoxarsine dissolved in THF
was added, and the solution was stirred at room temperature
overnight. The reaction mixture was cooled to 0 °C and treated
with an aqueous solution of NH4Cl (3%). Two liquid layers and a
precipitate at the interface of these layers were formed. The product
was isolated from the organic layer, combined with the precipitate,
and purified by column chromatography on silica with MeOH/
toluene (1:5) as the eluent. A white crystalline powder was obtained.
Yield: 1.85 g (37%). mp ) 106 °C. Anal. calcd (found) for
1
PdCl2: C, 50.88 (49.94); H, 3.08 (2.95); Cl, 8.34 (8.02). H NMR
(CDCl3): δ 6.84–7.21 (m, 16H), 7.35–7.46 (m, 8H), OH not
observed. IR (cm-1, CsI plates): 300, 326 ν(Pd-Cl). IR (cm-1
KBr disks): 459, 751, 1225, 1267, 1582, 3070, 3347 ν(O-H).
,
cis-[PtI2{2-MeOC6H4As(C6H4)2O-KAs}2] (5). An orange powder
was obtained. Yield: 0.103 g (45%). mp ) 266–272 °C (decomp.
without melting). Anal. calcd (found) for C38H30O4As2PtI2: C, 39.71
(39.58); H, 2.63 (2.41); I, 22.08 (21.89). 1H NMR (CDCl3): δ 3.93
(s, 6H, CH3), 6.64 (dd, 2H, H6, JH6-H5 ) 7.36 Hz, JH6-H4 ) 1.32
Hz), 6.71–6.83 (m, 10H, H3, H4, H5, H10), 7.24 (dd, 4H, H11,
JH11-H10 ) 7.17 Hz, JH11-H9 ) 1.32 Hz), 7.46 (m, 4H, H9), 8.12
1526 Inorganic Chemistry, Vol. 47, No. 5, 2008

Pd(II) and Pt(II) Complexes with Heteroditopic Ligands
(dd, 4H, H8, JH8-H9 ) 7.55 Hz, JH8-H10 ) 1.70 Hz). IR (cm-1, CsI
plates): 310, 322 ν(Pt-I). IR (cm-1, KBr disks): 459, 799, 1262,
1580, 2963, 3060.
2 × 2-ROC6H4AsC12H8O + [MX2(COD)] f
R ) Pri, Me, H
M ) Pt, Pd; X ) Cl, I
COD ) 1,5-cyclo-octadiene
[MX2{2-ROC6H4As(C6H4)2O-κAs}2] (3)
trans-[PdCl2{2-MeOC6H4As(C6H4)2O-KAs}2] (6). An orange
powder was obtained. Yield: 0.130 g (60%). mp ) 167–175 °C
(decomp. without melting). Anal. calcd (found) for C38H30O4As2-
(1-6)
The complex cis-[Pt{2-OC6H4As(C6H4)2O-κAs,O}2] (7)
was obtained upon heating 3 with sodium acetate in ethanol
for several minutes (eq 4).
1
PdCl2: C, 51.99 (50.97); H, 3.44 (3.12); Cl, 8.08 (7.93). H NMR
(CDCl3): δ 3.95 (s, 6H, CH3), 6.57 (dd, 2H, H6, JH6-H5 ) 7.55 Hz,
JH6-H4 ) 1.70 Hz), 6.79–6.86 (m, 10H, H3, H4, H5, H10), 7.22
(dd, 4H, H11, JH11-H10 ) 7.36 Hz, JH11-H9 ) 1.32 Hz), 7.39 (m, 4H,
H9), 8.22 (dd, 4H, H8, JH8-H9 ) 7.54 Hz, JH8-H10 ) 1.51 Hz). IR
(cm-1, CsI plates): 368 ν(Pd-Cl). IR (cm-1, KBr disks): 459, 798,
1262, 1579, 2963, 3061.
cis-[PtCl2{2-HOC6H4As(C6H4)2O-κAs}2] NaOAc, ∆8
(3)
cis-[Pt{2-OC6H4As(C6H4)2O-κ2As,O}2] (4)
(7)
cis-[Pt{2-OC6H4As(C6H4)2O-KAs,O}2] (7). A mixture of cis-
[PtCl2{2-HOC6H4As(C6H4)2O-κAs}2] (3) (0.02 g, 0.026 mmol) and
sodium acetate (0.008 g, 0.104 mmol) in ethanol (5 mL) was
refluxed for several minutes until a white suspension formed. The
white precipitate was filtered off and washed with water to give
the product as a white powder. Yield: 0.01 g (47%). The complex
was recrystallized from dichloromethane and n-hexane to give
colorless crystals. mp ) 262 °C (decomp. without melting). Anal.
calcd (found) for C36H24O4As2Pt: C, 49.96 (49.54); H, 2.79 (2.32).
1H NMR (CDCl3): δ 6.46 (m, 2H, H4), 6.81–6.95 (m, 12H),
7.13–7.27 (m, 10H). IR (cm-1, KBr disks): 613 ν(Pt-O); 467, 1224,
1263, 1578, 751, 3070.
The new platinum(II) and palladium(II) complexes cis-
[PtCl2{2-PriOC6H4As(C6H4)2O-κAs}2] (1), trans-[PdCl2{2-
PrOC6H4As(C6H4)2O-κAs}2](2), cis-[PtCl2{2-HOC6H4As(C6H4)2O-
κAs}2] (3), cis-[PdCl2{2-HOC6H4As(C6H4)2O-κAs}2] (4), cis-
[PtI2{2-MeOC6H4As(C6H4)2O-κAs}2] (5), trans-[PdCl2{2-
MeOC6H4As(C6H4)2O-κAs}2] (6), and 7 were characterized
by IR and 1H NMR spectroscopy and 1–4, 7 also by single-
crystal X-ray diffraction. The stereochemistry around the
central atom (cis or trans geometry) was assigned on the
basis of the IR spectra.
i
The IR spectra of compounds 1, 3, and 4 exhibit two bands
which can be assigned to symmetric and antisymmetric
Pt-Cl vibrations: 311 and 324 cm-1 (1), 311 and 325 cm-1
(3), and 300 and 326 cm-1 (4), supporting a cis arrangement
of the ligands, while in the spectra of compounds 2 and 6,
the presence of only one band [362 cm-1 (2) and 368 cm-1
(6)] can be attributed to a trans orientation of the two chlorine
atoms.19 In the case of the chelate complex, 7, only one
absorption band at 613 cm-1 due to ν(Pt-O) is observed.
No O-H vibrational bands are present in the spectrum due
Discussion
Heteroditopic ligands 2-ROC6H5As(C6H4)2O, where R )
Me and Pri, were prepared by ortho-lithiation of the corre-
sponding alkyl aryl ethers, followed by transmetalation with
10-chlorophenoxarsine according to the methods presented
in the literature for phosphorus and arsenic analogues (eq
1).16,17
1
to deprotonation of the ligand. The H NMR spectra of
complexes 1–7 show the characteristic signals of the orga-
noarsenic ligands with the appropriate coupling constants (see
the Experimental Section).
X-ray structure determinations were carried out on com-
pounds 1-4 and 7. The molecular structures of the platinum-
(II) and palladium(II) complexes with (2-isopropoxy-
phenyl)phenoxarsine (1 and 2) are presented in Figure 1,
those with (2-hydoxyphenyl)phenoxarsine (3 and 4) in Figure
2, and the structure of the chelate complex cis-[Pt{2-
OC6H4As(C6H4)2O-κAs,O}2] (7) is shown in Figure 3.
Selected structural parameters for complexes 1-4 and 7 are
summarized in Table 2.
(1)
The free hydroxyphenyl ligand was prepared via dilithiated
phenol18 followed by transmetalation with 10-chlorophe-
noxarsine (eq 2).
Although all complexes have a square-planar geometry,
1, 3, and 4 have the two arsine ligands in a cis orientation,
while the ligands are coordinated in trans positions in the
palladium complex 2 (Figures 1 and 2). In 3 and 4, the metal
atom is located on a crystallographic C2 axis, and in 2, it is
on an inversion center.
(16) Horner, L.; Simons, G. Phosphorus Sulfur Relat. Elem. 1983, 14, 189–
(2)
209.
(17) Horner, L.; Simons, G. Phosphorus Sulfur Relat. Elem. 1983, 14, 253–
260.
Platinum(II) and palladium(II) complexes containing the
arylphenoxarsine ligands were synthesized by reaction of the
organoarsenic ligands with [MCl2(COD)] (M ) Pt, Pd; COD
) 1,5-cyclo-octadiene) in a molar ratio of 2:1 (eq 3).
(18) Posner, G. H.; Canella, K. A. J. Am. Chem. Soc. 1985, 107, 2571–
2573.
(19) Nakamoto, K. Infrared and Raman Spectra of Inorganic and Coor-
dination Compounds, 5th ed.; Wiley: New York, 1997; Chapter I.10.
Inorganic Chemistry, Vol. 47, No. 5, 2008 1527

Moldovan et al.
Figure 1. ORTEP drawings of cis-[PtCl2{2-PriOC6H4As(C6H4)2O-κAs}2] (1) (left) and trans-[PdCl2{2-PriOC6H4As(C6H4)2O-κAs}2] (2) (right). 50% ellipsoids
are shown. Hydrogen atoms are omitted for clarity.
literature for related compounds; that is, for cis-
[PtCl2(AsBzMe2)2], the values are 2.337(1) and 2.334(1) Å
(Pt-As) and 2.340(3) and 3.355(3) Å (Pt-Cl),20 and in cis-
dichloro[(S)-2-(2-(diphenylarsino)phenyl)-4-(isopropyl)-ox-
azoline-κAs,N]platinum(II), they are 2.3048(9) Å (Pt-As)
and 2.350(3) and 2.285(3) Å (Pt-Cl).21
The Pd-As bond length of 2.4042(5) Å in 2 is slightly
longer than the values reported for trans-[PdCl2(AsBzMe2)2]
(2.3524(9) and 2.3586(9) Å),20 while in 4, the distance is
similar (2.3558(5) Å). The Pd-Cl bond lengths are 2.2904(7)
Å in 2 and 2.334(1) Å in 4, and the former is significantly
shorter than those in trans-[PdCl2(AsBzMe2)2] (2.370(2) and
2.359(2) Å)20 but close to the values reported for
[PdCl2(PEt3){AsMe(Nap)2}] (Nap ) 1-naphthyl).22
The molecular structure of cis-[Pt{2-OC6H4As(C6H4)2O-
Figure 2. ORTEP drawing of cis-[PdCl2{2-HOC6H4As(C6H4)2O-κAs}2]
κAs,O}2] (7) (Figure 3) has the chelate ligands in a cis
(4). 50% ellipsoids are shown (disordered solvent molecules and hydrogen
arrangement. The Pt-As bond lengths of 2.2962(5) and
2.3024(6) Å are shorter than those in 1-4 (Table 2).
atomsotherthanOHareomittedforclarity).cis-[PtCl2{2-HOC6H4As(C6H4)2O-
κAs}2] (3) is isostructural and isotypical.
The As-M-As angles in the cis complexes 1, 3, and 4
range from 95.28(2)° in 4 to 97.77(4)° in 1, and the
Cl-M-Cl angles range from 88.82(8)° to 91.78(6)° (cf.
As-M-As ) 100.74(5)° and Cl-M-Cl ) 90.1(1)° in cis-
[PtCl2(AsBzMe2)2]).20 The trans complex 2 is located on a
crystallographic inversion center with both As-Pd-As and
Cl-Pd-Cl angles being 180.00°. The arsenic atoms are in
a distorted tetrahedral environment in all of the complexes,
with angles in the range of 97.1(3)-116.8(5)° (As1) and
97.1(3)-121.9(2)° (As2) in 1, 97.2(1)-122.03(9)° in 2,
97.8(3)-121.0(2)° in 3, 98.1(2)-121.7(1)° in 4, and
96.8(2)-122.6(2)° (As1) and 96.3(2)-121.2(2)° (As2) in
chelate complex 7. Arsenic-carbon bonds in the phenox-
arsine units in 1-4 (range 1.902(6)-1.919(4) Å) are slightly
shorter than the arsenic-carbonsubstituted-phenyl bonds (As(1)-C(1)
) 1.928(5) and As(2)-C(22) ) 1.924(6) Å in 1, As(1)-C(1)
Figure 3. Molecular structure of cis-[Pt{2-OC6H4As(C6H4)2O-κ2As,O}2]
(7). 50% ellipsoids are shown (hydrogen atoms are omitted for clarity).
The arsine ligands are coordinated to the metal center only
(20) Phadnis, P. P.; Jain, V. K.; Klein, A.; Weber, M.; Kaim, W. Inorg.
through the arsenic atom. The Pt-As bond lengths of
2.346(1) and 2.351(1) Å in 1 and 2.3425(5) Å in 3, and the
Pt-Cl bond lengths of 2.308(2) and 2.329(2) Å in 1 and
2.338(2) Å in 3, are close to the values reported in the
Chim. Acta 2003, 346, 119–128.
(21) Kwong, F. Y.; Lai, C. W.; Yu, M.; Tan, D.-M.; Lam, F. L.; Chan,
A. S. C.; Chan, K. S. Organometallics 2005, 24, 4170–4178.
(22) Phadnis, P. P.; Jain, V. K.; Schurr, T.; Klein, A.; Lissner, F.; Schleid,
T.; Kaim, W. Inorg. Chim. Acta 2005, 358, 2609–2617.
1528 Inorganic Chemistry, Vol. 47, No. 5, 2008

Pd(II) and Pt(II) Complexes with Heteroditopic Ligands
Table 2. Selected Bond Lengths (Å) and Angles (deg) in cis-[PtCl2{2-PriOC6H4As(C6H4)2O-κAs}2] (1), trans-[PdCl2{2-PriOC6H4As(C6H4)2O-κAs}2]
(2), cis-[PtCl2{2-HOC6H4As(C6H4)2O-κAs}2] (3), cis-[PdCl2{2-HOC6H4As(C6H4)2O-κAs}2] (4), and cis-[Pt{2-OC6H4As(C6H4)2O-κ2As,O}2] (7)
1
2
3
4
7
M(1)-As(1)
2.346(1)
2.351(1)
2.308(2)
2.329(2)
2.4042(5)
2.3425(5)
2.3558(5)
2.2962(5)
2.3024(6)
M(1)-As(2)
M(1)-Cl(1)
2.2904(7)
2.338(2)
2.334(1)
M(1)-Cl(2)
M(1)-O(1)
2.043(4)
2.035(4)
M(1)-O(2)
As(1)-M(1)-As(2)
As(1)-M(1)-Cl(2)
As(1)-M(1)-Cl(1)
As(2)-M(1)-Cl(2)
As(2)-M(1)-Cl(1)
Cl(2)-M(1)-Cl(1)
O(1)-M(1)-O(2)
O(1)-M(1)-As(1)
O(2)-M(1)-As(1)
O(2)-M(1)-As(2)
O(1)-M(1)-As(2)
As(1)-M(1)-As(2)
97.77(4)
173.20(5)
86.87(6)
85.85(5)
174.43(5)
89.86(7)
180.00a
87.81(3)
92.19(3)
96.29(3)a
87.48(4)
175.81(4)
95.28(2)a
86.50(3)
117.52(3)
87.81(3)
180.00b
87.48(4)
86.50(3)
88.82(8)b
91.78(6)b
88.2(2)
85.5(1)
173.3(1)
85.3(1)
173.3(1)
101.06(2)
a
b
As1-M(1)-As(1′). Cl(1)-M(1)-Cl(1′).
Figure 4. Calculated molecular structures of 2 and 10-(o-isopropoxyphenyl)phenoxarsine 2-PriOC6H4As(C6H4)2O.
reported so far lie in the range of 150-180°. In
O(C6H4)2AsS(S)PR2 (R ) Me, Et), this angle is 176.1 and
173.1°,23 and the known bis(phenoxarsine) compounds
O(C6H4)2As-E-As(C6H4)2O (E ) S,24 Se25) also contain
two nearly planar phenoxarsine moieties (dihedral angles:
175.2 and 175.8° for E ) S, and 173.9 and 176.0° for E )
Se). In contrast, the phenoxarsine moieties in 1–4 exhibit a
folded (butterfly) arrangement with dihedral angles of 151.20
and 150.07° in 1, 153.70° in 2, 162.96° in 3, and 163.40° in
4, close to the values reported for O(C6H4)2AsCl (156.3°),26
O(C6H4)2AsS2CN(CH2CH2)2 (155.2°),27 the phenoxarsin-10-
yl derivative of 2-aminocyclopent-1-ene-1-carbodithioic acid
O(C6H4)2AsS(S)CC5H6NH2-2 (150.3°),28 O(C6H4)2AsS2PPh2
Figure 5. HOMO-8 of 10-(o-isopropoxyphenyl)phenoxarsine.
(23) Cea-Olivares, R.; Alvarado-Rodriguez, J. G.; Espinosa-Perez, G.;
Hernandez-Ortega, S. Inorg. Chim. Acta 1997, 255, 319–323.
(24) Grindstaff, W. K.; Cordes, A. W.; Fair, C. K.; Perry, R. W.; Handy,
L. B. Inorg. Chem. 1972, 11, 1852–1855.
) 1.940(3) Å in 2, As(1)-C(13) ) 1.931(5) Å in 3, and
As(1)-C(13) ) 1.931(5) Å in 4). No significant differences
are observed for arsenic-carbon bonds in 7. Unusually large
C-Oether-C angles were found: 119.4(5) and 118.1(5)° in 1
and 120.0(2)° in 2. Short As···O contacts found in 1-4 (2.940
and 2.952 Å in 1, 2.895 Å in 2, 3.005 Å in 3, and 2.986 Å
in 4; sum of the van der Waals radii: 3.37 Å) are related to
the C-Oether-C angles.
(25) Meyers, E. A.; Applegate, C. A.; Zingaro, R. A. Phosphorus Sulfur
Relat. Elem. 1987, 29, 317–327.
(26) Holliday, R. J.; Broach, R. W.; Handy, L. B.; Cordes, A. W.; Thomas,
L. Inorg. Chem. 1972, 11, 1849–1851.
(27) Cea-Olivares, R.; Toscano, R.-A.; Silvestru, C.; Garcia-Garcia, P.;
Lopez-Cardoso, M.; Blass-Amador, G.; Noeth, H. J. Organomet.
Chem. 1995, 493, 61–67.
(28) Cea-Olivares, R.; Toscano, R.-A.; Estrada, M.; Silvestru, C.; Garcia,
P. G.; Lopez-Cardoso, M.; Blass-Amador, G. Appl. Organomet. Chem.
1995, 9, 133–140.
The phenoxarsine group is very flexible and can adopt
either a planar or a folded geometry; the dihedral angles
Inorganic Chemistry, Vol. 47, No. 5, 2008 1529

Moldovan et al.
Table 3. DFT Total (au)/Relative (kcal/mol) Energies for the
Optimized Structures of 1-4
B3LYP/LANL2DZ
Oniom(B3LYP/lnl2dz:uff)
1
-2805.3747389
+2.29
-164.666774
+10.60
1_trans
2_cis
2
-2805.3783977
0.0
-164.683671
0.0
-2092.9514997
-172.2470994
+4.81
+5.66
-2092.9591704
0.0
-172.2561179
0.0
3
-1849.5432723
-164.7033719
+2.36
+2.15
3_trans
4
-1849.5470302
0.0
-164.7068015
0.0
-1857.1185657
-172.2744279
0.0
+10.18
4_trans
-1857.1181863
+0.24
-172.2906444
0.0
contacts in the gas phase and, in case the interaction is
present, to gain insight into the molecular orbitals involved
(see Figure 4). Short arsenic-oxygen contacts and O-C-C
and C-C-As angles smaller than 120° were calculated both
for 2 and for the respective ligand; that is, these values are
determined neither by solid-state packing nor by the presence
of the metal and are thus rather a characteristic of the ligand.
The HOMO-8 of 10-(o-isopropoxyphenyl)phenoxarsine,
drawn at the isodensity value of 0.032 e/Å3 as calculated at
the B3LYP/6-31G(d) level within Spartan’04,34 shows that
direct p-p interaction between arsenic and oxygen is
responsible for the shortening of the As···O distance (Figure
5). This As···O interaction explains the stability of both the
ligand and the complexes reported here toward dealkylation.
Noteworthy for 2 is the steric effect of the two isopropyl
groups of the ligand, located below and above the
PdAs2Cl2plane. B3LYP/LANL2DZ calculations reproduce
this arrangement.
Figure 6. (a) View perpendicular to the two-dimensional sheets in trans-
[PdCl2{2-PriOC6H4As(C6H4)2O-κAs}2] (2). (b) View along a two-dimen-
sional sheet.
Weak intermolecular interactions (C···H and H···H) due to
packing effects can be observed in 1-4 and 7. Short
intermolecular Cl···H(C) interactions of 2.762 Å in the crystal
structure of trans-[PdCl2{2-PriOC6H4As(C6H4)2O-κAs }2] (2)
result in the formation of sheets (Figure 6a). These sheets
consist of a polar part with the nonpolar aryl groups located
above and below this plane (Figure 6b).
In contrast, the crystal structures of the isotypical com-
pounds cis-[PtCl2{2-HOC6H4As(C6H4)2O-κAs}2] (3) and cis-
[PdCl2{2-HOC6H4As(C6H4)2O-κAs}2] (4) consist of chains
parallel to the c axis connected in a 3D structure through
short intermolecular (Pt)Cl···H(O) interactions of 2.500 and
2.577 Å in 3 and 2.489 Å in 4 (sum of the van der Waals
radii: 2.95 Å). Weak H···Cl interactions of the solvent
molecules (CH2Cl2) with the PtCl2 unit are also observed
(Figure 7).
Figure 7. (Pt)Cl···H(O) and (Pt)Cl···H(C) interactions in cis-[PtCl2{2-
HOC6H4As(C6H4)2O-κAs}2] (3).
(154.4°),29 and O(C6H4)2AsOAs(C6H4)2O (157.6 and
176.0°),25 or in the adduct of SbCl5 with 10-chlorophenox-
arsine oxide {O(C6H4)2AsClOSbCl5} (167.7°).26 Smaller
values (145.24 and 146.64°) are observed in cis-[Pt{2-
OC6H4As(C6H4)2O-κ2As,O}2] (7).
The formation of the different isomers of PdX2 and PtX2
arsine complexes seems to be determined by several factors,
as supported by recently reported examples. The benzyldi-
Calculations were performed at the B3LYP/LANL2DZ
level30–33 for complex 2 to check for arsenic-oxygen
(29) Cea-Olivares, R.; Alvarado, J.-G.; Espinosa-Perez, G.; Silvestru, C.;
Haiduc, I. J. Chem. Soc., Dalton Trans. 1994, 2191–2195.
(30) Becke, A. D. J. Chem. Phys. 1993, 98, 5648–5652.
(31) Lee, C.; Yang, W. Y.; Parr, R. G. Phys. ReV. B: Condens. Matter
Mater. Phys. 1988, 37, 785–789.
(32) Vosko, S. H.; Wilk, L.; Nusair, M. Can. J. Phys. 1980, 58, 1200–
1211.
(33) Stephens, P. J.; Devlin, F. J.; Chabalowski, C. F.; Frisch, M. J. J.
Phys. Chem. 1994, 98, 11623–11627.
(34) SPARTAN ‘04; Wavefunction Inc.: Irvine, CA.
1530 Inorganic Chemistry, Vol. 47, No. 5, 2008

Pd(II) and Pt(II) Complexes with Heteroditopic Ligands
Figure 8. Hydrogen bonds formed by the solvent favor the cis isomer of 3 (left) and 4 (right).
methylarsine complexes [MX2(AsBzMe2)2] (M ) Pd or Pt;
X ) Cl, Br, or I)20 have been found exclusively in the cis
conformation for X ) Cl and in the trans conformation for
both PdII and PtII with X ) Br or I. For the triallylarsine
complexes [MX2{As(allyl)3}2] (M ) Pd or Pt),35 both trans
and cis conformers were obtained after preparation for M )
Pd and X ) Cl, while only the trans conformation is adopted
in the solid state by mononuclear complexes of platinum and
palladium in which X ) Cl or Br. For the complexes
[MX2{AsMe(Nap)2}2], it was shown by spectroscopic meth-
ods22 that both cis and trans isomers were observed in
solution, even when only the trans isomer was obtained in
the solid state. The high lability of the bis(1-naphthyl)-
methylarsine ligand was considered by these authors to be a
prerequisite for isomerization, as this was found to be much
more important for the AsMe(Nap)2 ligand than for related
AsBzMe2 or As(allyl)3 ligands.
molecule might be important in the preference for one or
the other of the isomers, combined quantum mechanics/
molecular mechanics Oniom(B3LYP/LANL2DZ:uff)37–39
optimizations were performed on the same compounds, with
the expectation that the molecular mechanics treatment would
better describe the possible intramolecular dispersion interac-
tions.40 The calculated data (Table 3) show that in each case
the trans isomer is lower in energy and is the thermodynami-
cally favored product. The formation of the cis isomers of
1, 3, and 4 is thus kinetically controlled. In the cases of 3
and 4, crystallization is driven by the presence of the solvent
(dichloromethane), which forms H···Cl hydrogen bonds with
the two cis-positioned chlorine atoms, and Cl···H hydrogen
bonds with two of the cis phenoxarsine ligands (Figure 8).
Thus, the role of the solvent here is more than just to
occupy the empty volume in the solid network, but also to
orient (through geometry constraints) crystallization of the
kinetically stable cis isomers.
To rationalize the observed experimental geometries,
B3LYP/LANL2DZ full-geometry optimizations were per-
formed on 1-4 with the aid of the Gaussian 98 package.36
Since dispersive forces between remote parts of the same
Acknowledgment. We thank Umicore for a generous
donation of PdCl2 and H2[PtCl6]·6H2O.
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Supporting Information Available: Provided are cif files of
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