Enantioselective synthesis of a conformationally rigid, sterically encumbered, 2-arsino-7-phosphanorbornene

Article abstract of DOI:10.1016/S0022-328X(01)01209-8

Convenient access to the enantionerically pure, conformationally rigid, ligand has been established by intramolecular [4 + 2]-Diels-Alder cycloaddition between dicyclohexylvinylarsine and 3,4-dimethyl-1-phenylphosphole using chiral organopalladium(II) complexes containing orthometallated (S)-1-α-(dimethylamino)ethylnaphthalene or (R)-2-α-(dimethylamino)ethylnaphthalene as the reaction templates. The ligand was displaced from the palladium complex with cyanide and reacted with [η⁶-arene)RuCl₂]₂ and NH₄PF₆ to form diastereomeric [η⁶-arene)Ru(P-As)Cl]PF₆ complexes, chiral at ruthenium. New complexes have been characterized by elemental analyses, electrochemistry, and electronic, circular dichroism, ¹H-, ¹H{³¹P}-, ¹³C{¹H}- and ³¹P{¹H}-NMR spectroscopies, and in several cases, by X-ray crystallography.

Full text of DOI:10.1016/S0022-328X(01)01209-8

Journal of Organometallic Chemistry 643–644 (2002) 136–153
www.elsevier.com/locate/jorganchem
Enantioselective synthesis of a conformationally rigid, sterically
encumbered, 2-arsino-7-phosphanorbornene
Paul A. Gugger a, Anthony C. Willis a, S. Bruce Wild a,*, Graham A. Heath a,
Richard D. Webster a, John H. Nelson b,*
a Research School of Chemistry, Institute of Ad6anced Studies, Australian National Uni6ersity, Canberra, ACT 0200, Australia
b Department of Chemistry, Uni6ersity of Ne6ada, Reno, NV89557-0020, USA
Received 21 June 2001; accepted 31 August 2001
Dedicated to Professor Franc¸ois Mathey on the occasion of his 60th birthday
Abstract
Convenient access to the enantiomerically pure, conformationally rigid, ligand [5-(dicyclohexylarsino)-2,3-dimethyl-7-phenyl-7-
phosphabicyclo[2.2.1]hept-2-ene has been established by intramolecular [4+2]-Diels–Alder cycloaddition between dicyclo-
hexylvinylarsine and 3,4-dimethyl-1-phenylphosphole using chiral organopalladium(II) complexes containing orthometallated
(S)-1-a-(dimethylamino)ethylnaphthalene or (R)-2-a-(dimethylamino)ethylnaphthalene as the reaction templates. The ligand was
displaced from the palladium complex with cyanide and reacted with [(h6-arene)RuCl2]2 and NH4PF6 to form diastereomeric
[(h6-arene)Ru(PꢀAs)Cl]PF6 complexes, chiral at ruthenium. New complexes have been characterized by elemental analyses,
electrochemistry, and electronic, circular dichroism, 1H-, 1H{31P}-, 13C{1H}- and 31P{1H}-NMR spectroscopies, and in several
cases, by X-ray crystallography. © 2002 Published by Elsevier Science B.V.
Keywords: Phosphole; Vinylarsine; [4+2]-Diels–Alder cycloaddition; Palladium; Ruthenium, X-ray crystallography
organopalladium complexes containing enantiomeri-
cally pure forms of orthopalladated 1-a-(dimethy-
lamino)ethylnaphthalene [16] and 2-a-(dimethyl-
amino)ethylnaphthalene [17] have been used as chiral
templates for the asymmetric modification of Diels–
Alder cycloadditions with several dieneophilic ligands.
Diels–Alder cycloaddition is very sensitive to steric
effects, with sterically bulky substituents on either the
diene or dieneophile generally suppressing the reaction
[18].
1. Introduction
Through studies of the coordination modes of phosp-
holes [1–8], it was discovered that coordination of a
phosphole to a transition metal greatly increased the
dienic reactivity of the phosphole compared with that
of the free ligand [9–13]. This is because coordination
to a transition metal reduces the modest degree of
cyclic delocalization in the free phosphole [14]. Similar
effects accrue by placing strongly electron withdrawing
substituents on the phosphole phosphorus atom [13].
Simultaneous coordination of a phosphole and a di-
eneophilic ligand to a transition metal, in mutually cis
positions, activates both ligands and promotes facile
intramolecular [4+2]-Diels–Alder cycloadditions be-
tween the two coordinated ligands [15]. Recently,
Ruthenium(II) complexes of the type (9)-[(h6-
arene)Ru(AB)X]+X−, where AB is an enantiomerically
pure bidentate ligand and X is a halide, are efficient
catalysts for the asymmetric transfer hydrogenation of
ketones [19], alkenes [20], and imines [21]. The catalytic
activity of a ruthenium complex often increases with
increased steric bulk of associated ligands [22]. Com-
plexes of the type (9)-{(h6-arene)Ru(AB) X]+X− can
be prepared with high diastereoselectivity by in-
tramolecular [4+2] Diels–Alder cycloadditions be-
tween coordinated 3,4-dimethyl-1-phenylphosphole
* Corresponding authors. Tel.: +61-2-61254236; fax: +61-2-
61250750 (SBW). Tel.: +1-775-7846588; fax: +1-775-7846804
(JHN).
E-mail addresses: sbw@rsc.anu.edu.au (S.B. Wild), jhnelson@
equinox.unr.edu (J.H. Nelson).
0022-328X/02/$ - see front matter © 2002 Published by Elsevier Science B.V.
PII: S0022-328X(01)01209-8

P.A. Gugger et al. / Journal of Organometallic Chemistry 643–644 (2002) 136–153
137
(DMPP) and a variety of dieneophilic ligands [15k].
The diastereoselectivity of these reactions increases with
increasing interligand steric interactions. Within these
complexes, ruthenium is a configurationally stable
stereocenter. There is considerable current interest in
the influence of ligands on the configurational stability
of ruthenium stereocenters [23].
Herein, we describe the enantioselective synthesis of
an optically pure, conformationally rigid, sterically en-
cumbered 2-arsino-7-phosphanorbornene and two chi-
ral ruthenium derivatives.
described previously [27]. Optical rotations were mea-
sured on a Perkin–Elmer model 241 polarimeter under
the specified conditions.
Solutions of 9b+ for EPR and circular dichroism
(CD) experiments were prepared by one-electron elec-
trochemical oxidation of 9b in a divided controlled
potential electrolysis cell separated with a porosity no. 5
(1.0–1.7 mm) sintered glass frit. The working and auxil-
iary electrodes were identically sized Pt mesh plates
symmetrically arranged with respect to each other with
an Ag wire reference electrode (isolated by a salt
bridge) positioned to within 5 mm of the surface of the
working electrode. The electrolysis cell was jacketed in
a glass sleeve and cooled to 233 K using the Lauda
cryostat methanol circulating bath. The volumes of
both the working and auxiliary electrode compartments
were ca. 25 mL each and were continually purged with
argon during the electrolysis. The number of electrons
transferred during the bulk oxidation process was cal-
culated from
2. Experimental
2.1. Reagents and physical measurements
All chemicals were reagent grade and were used as
received from commercial sources or synthesized as
described below. DMPP [24], the chiral palladium chlo-
ride bridged dimers [17,25], and the [(h6-arene)RuCl2]2
complexes [26] were synthesized by literature methods.
Solvents were dried by standard procedures. All reac-
tions involving DMPP were conducted under a purified
nitrogen atmosphere by standard Schlenk techniques.
Elemental analyses were performed by staff within the
Research School of Chemistry. Melting points were
determined on a Reichert hot-stage apparatus and are
uncorrected. NMR spectra were recorded on CDCl3
solutions with a Varian Inova-500 FT spectrometer
N=Q/nF
(1)
where N is number of moles of starting compound, Q is
the charge (coulombs), n is number of electrons and F
is the Faraday constant (96 485 C mol−1). In order to
ensure that oxygen was not introduced and to minimize
temperature fluctuations during the transfer process,
the bottom of the working electrode compartment was
connected via glass tubing to an evacuated 2 mm
diameter cylindrical quartz EPR tube suspended in a
dry ice–EtOH bath maintained at 203 K. Opening the
tap on the bottom of the electrolysis cell at the comple-
tion of the electrolysis allowed the solution to flow
rapidly into the EPR tube which was sealed with a
Young’s tap before being further cooled in liquid nitro-
gen. The EPR cell was then transferred to a Bruker
ESP 300e spectrometer employing a rectangular TE102
cavity with the modulation frequency set at 100 kHz. A
similar procedure was used to obtain a solution of 9b+
for the CD experiments using a Jobin Yvon CD6
spectropolarimeter and ensuring the temperature of the
solution was at all times 5 −40 °C.
1
operating at 500 MHz for H, 202 MHz for 31P, and
125 MHz for 13C nuclei. Proton and carbon chemical
shifts were referenced to residual CHCl3 and phospho-
rus chemical shifts were referenced to an external 85%
aqueous solution of H3PO4. All shifts to low field, high
frequency, are positive. Electrochemical measurements
were recorded using a PAR model 170 or 273A system,
controlled by a Macintosh LC 630 computer and
MacLab 4e interface running MACLAB E CHEM software
(AD Instruments). Scan rates were typically 100 mV
s−1 for cyclic voltammetry (CV). Electrochemical solu-
tions contained 0.5 mol dm−3 [NBu4n][PF6] and ca.
10−3 mol dm−3 complex in CH2Cl2. The solutions
were purged and maintained under an atmosphere of
N2. The jacketed cryostatic cell (10 cm3) contained a
platinum disc (1.0 mm diameter) working electrode,
platinum wire auxiliary electrode, and Ag–AgCl refer-
ence electrode (containing 0.45 M [Bun4N][PF6] and 0.05
M [Bun4N][Cl]) (against which the ferrocene/ferrocenium
couple is found at 0.55 V). Measurements were
recorded at low temperature using a Lauda model RL6
cryostat bath to circulate dry CH3OH through the cell
jacket. In situ UV–vis–NIR spectra were measured on
a Varian Cary SE spectrophotometer at −40 °C by
use of an optically transparent thin layer electrochemi-
cal (OTTLE) cell placed in the spectrophotometer, as
2.2. Synthesis
2.2.1. Dicyclohexyl6inylarsine (Cy2AsVy) (1)
To a solution containing 38.0 g (0.137 mol) Cy2AsCl
[28] in 400 mL of dry diethyl ether was slowly added
100 mL of 1.6 M (0.16 mol) CH2CHMgBr (Aldrich) at
ambient temperature. The reaction mixture was stirred

138
P.A. Gugger et al. / Journal of Organometallic Chemistry 643–644 (2002) 136–153
3
4
vigorously for 2 h at ambient temperature and then
heated under reflux for 5 h. After cooling to ambient
temperature, the mixture was filtered through Celite,
concentrated to half volume under vacuum, and
washed with 50 mL of saturated aqueous NH4Cl. The
ether layer was separated, dried over anhydrous
Na2SO4, filtered, and the ether was removed from the
filtrate under vacuum. The residue was distilled to
obtain the product as a colorless viscous oil; b.p. 122–
128 °C (1.5–2.5 mmHg) 11.05 g (30%). Anal. Calc. for
C14H25As: C, 62.73; H, 9.33. Found: C, 62.56; H,
9.19%. 1H-NMR: l 6.47 (dd, 3J(HaHb)=18.6 Hz,
1H, Ha), 3.82 (dq, J(HH)=6.5 Hz, J(PH)=4.5 Hz,
4
1H, CH), 2.83 (d, J(PH)=2.0 Hz, 3H, NCH3), 2.69
(d, 4J(PH)=2.0 Hz, 3H, NCH3), 2.06 (apparent t,
4J(PH)=4J(HH)=1.5 Hz, 3H, DMPPꢀCH3), 2.05 (ap-
parent t, J(PH)=4J(HH)=1.5 Hz, 3H, DMPPꢀCH3),
4
1.58 (d, J(HH)=6.5 Hz, 3H, CCH3). 13C{1H}-NMR:
3
3
2
l 154.47 (d, J(PC)=1.9 Hz, C6), 152.32 (d, J(PC)=
10.9 Hz, Cb), 151.17 (d, J(PC)=10.6 Hz, Cb), 148.28
2
2
3
(d, J(PC)=2.8 Hz, C1), 136.73 (d, J(PC)=12.6 Hz,
C2), 133.66 (d, 2J(PC)=13.2 Hz, Co), 130.73 (d,
4J(PC)=2.5 Hz, Cb), 128.47 (d, J(PC)=10.9 Hz, Cm),
3
1
1
126.61 (d, J(PC)=52.4 Hz, Ca), 126.23 (d, J(PC)=
46.3 Hz, Ci), 125.50 (d, J(PC)=51.6 Hz, Ca), 125.43
(d, J(PC)=5.9 Hz, C5), 124.08 (s, C3), 123.02 (s, C4),
74.33 (d, J(PC)=3.0 Hz, CH), 49.70 (d, J(PC)=2.6
3
1
3J(HaHc)=11.4 Hz, 1H, Ha), 5.95 (dd, J(HaHc)=11.4
2
3
3
Hz. J(HbHc)=2.4 Hz, 1H, Hc), 5.68 (dd, J(HaHb)=
2
3
3
18.6 Hz, J(HbHc)=2.4 Hz, 1H, Hb), 1.73 (m, 12H,
Cy), 1.25 (m, 10H, Cy). 13C{1H} l 137.68 (C% ), 130.34
Hz, N CH3), 45.17 (d, J(PC)=2.1 Hz, N CH3), 20.03
3
a
3
(C% ), 34.21 (Ca), 31.63, 30.81 (Cb), 29.95, 27.61 (Cg),
(s, CCH3), 17.52 (d, J(PC)=12.8 Hz, DMPPꢀCH3).
b
26.54 (Cd).
31P{1H}-NMR: l 37.8.
2.2.3. (S)-(+)-[(1TMNA)PdCl(DMPP)] (3)
2.2.2. (S)-(+)-[(TMBA)PdCl(DMPP)] (2)
To
a suspension of 5.0 g (5.8 mmol) [(S)-
(1TMNA)PdCl]2 [25a] in 50 mL CH2Cl2 was added 2.8
g (14.7 mmol) DMPP. The clear yellow solution was
stirred at ambient temperature for 2 h, filtered through
Celite, and the solvent removed from the filtrate by
rotary evaporation. The resulting foamy solid was
washed with n-hexane and diethyl ether and vacuum
dried to yield 7.34 g (94.5%) of pale yellow microcrys-
tals m.p. 128–130 °C [h]D+334.9° (c, 0.2, CH2Cl2).
CD (molecular elipticity [q]l (deg cm2 d mol−1) for
c=1×10−4 M in CH2Cl2 at 25 °C) [q]332= +928,
[q]290= +5572, [q]258= +6704, [q]250=0, [q]247= −
1138, [q]243=0. Anal. Calc. for C26H29ClNPPd: C,
59.13; H, 5.49; Cl, 6.71. Found: C, 58.92; H, 5.62; Cl,
6.57%. 1H-NMR: l 7.94 (m, 2H, Ho), 7.71 (dd,
To a solution containing 10.0 g (0.017 mol) [(S)-
(TMBA)PdCl]2 [25b] in 250 mL of CH2Cl2 was added
6.6 g (0.035 mol) DMPP [24]. The resulting deep yellow
solution was stirred at ambient temperature for 1 h, the
solution volume reduced to 25 mL on a rotary evapora-
tor, and n-hexane added. The almost colorless crystals
that separated were isolated by filtration, washed with
n-hexane and diethyl ether and vacuum dried. Yield
15.2 g (92.1%) m.p. 144–146 °C. [h]D+87.0° (c, 0.2,
CH2Cl2). CD (molecular elipticity [q]l (deg cm2
mol−1) for c=1.04×10−4 M in CH2Cl2 at 25 °C)
[q]431= +5686, [q]341= +6446, [q]317= −416,
d
[q]299= +2415, [q]288=0, [q]278= −13 579, [q]263=0,
[q]240= +22 494. Anal. Calc. for C22H27ClNPPd: C,
55.27; H, 5.65; Cl, 7.42. Found: C, 55.11; H, 5.80; Cl,
4
3J(H3H4)=8.5 Hz, J(H3H5)=1.5 Hz, 1H, H3), 7.69
3
(d, J(H5H6)=8.0 Hz, 1H, H6), 7.39 (m, 4H, 2Hm, Hp,
1
3
3
7.26%. H-NMR: l 7.88 (m, 2H, Ho), 7.38 (m, 1H, Hp),
H4), 7.34 (ddd, J(H5H6)=8.0 Hz, J(H4H5)=7.0 Hz,
7.33 (m, 2H, Hm), 6.99 (dd, 3J(H3H4)=7.5 Hz,
4J(H2H4)=1.0 Hz, 1H, H4), 6.96 (apparent td,
4J(H3H5)=1.5 Hz, 1H, H5), 7.31 (d, 3J(H1H2)=8.0
Hz, 1H, H2) 7.14 (dd, J(H1H2)=8.0 Hz, J(PH)=5.8
3
4
4
2
3J(H2H3)=3J(H3H4)=7.5 Hz, J(H1H3)=1.0 Hz, 1H,
Hz, 1H, H1), 6.94 (apparent d quin, J(PH)=32. Hz,
H3), 6.91 (apparent td, J(H1H2)=3J(H2H3)=7.5 Hz,
4J(HaHa%)=4J(HH)=1.5 Hz, 1H, Ha), 6.46 (apparent
3
4J(H2H4)=1.0 Hz, 1H, H2), 6.80 (apparent td,
d quin, J(PH)=32 Hz, J(HaHa%)=4J (HH)=1.5 Hz,
2
4
3J(H1H2)=4J(PH)=7.5 Hz, 4J(H1H3)=1.0 Hz, 1H,
1H, Ha%), 4.32 (apparent quin, J(HH)=4J(PH)=6.5
3
4
H1), 6.74 (apparent
d
quin, 2J(PH)=32.0 Hz,
Hz, 1H, CH), 2.91 (d, J(PH)=3.0 Hz, 3H, N CH3),
4J(HH)=4J(HH)=1.5 Hz, 1H, Ha), 6.60 (apparent d
quin, 2J(PH)=32.5 Hz, 4J(HH)=4J(HH)=1.5 Hz,
2.76 (d, 4J(PH)=1.0 Hz, 3H, N CH3), 2.08 (apparent t,
4J(HH)=4J(PH)=1.5 Hz, 3H, DMPP–CH3), 2.04

P.A. Gugger et al. / Journal of Organometallic Chemistry 643–644 (2002) 136–153
139
4
(apparent t, J(HH)=4J(PH)=1.5 Hz, 3H, DMPP–
3J(HH)=6.5 Hz, 3H, CCH3). 13C{1H}-NMR: l 152.77
CH3), 1.86 (d, J(HH)=6.5 Hz, 3H, CCH3). 13C{1H}-
(d, J(PC)=1.8 Hz, C1), 152.42 (d, J(PC)=11.1 Hz,
Cb), 151.57 (d, 2J(PC)=11.7 Hz, Cb), 146.88 (d,
3J(PC)=2.8 Hz, C10), 135.43 (d, 2J(PC)=12.9 Hz, C2),
3
2
2
2
NMR: l 153.77 (d, J(PC)=11.2 Hz, Cb), 150.17 (d,
2J(PC)=10.2 Hz, Cb), 149.61 (d, J(PC)=1.6 Hz, C1),
2
3
3
2
4
147.04 (d, J(PC)=2.1 Hz, C10), 135.21 (d, J(PC)=
13.0 Hz, C2), 133.75 (d, J(PC)=13.1 Hz, Co), 131.05
(s, C9), 130.86 (d, J(PC)=2.4 Hz, Cp), 129.04 (s, C4),
128.62 (d, J(PC)=11.1 Hz, Cm), 127.67 (d, J(PC)=
133.85 (d, J(PC)=12.8 Hz, Co), 132.11 (d, J(PC)=
2
4
6.2 Hz, C3), 131.15 (s, C8), 130.96 (d, J(PC)=2.5 Hz,
4
3
Cp), 128.73 (d, J(PC)=11.1 Hz, Cm), 127.13 (s, C4),
3
1
1
126.71 (d, J(PC)=46.9 Hz, Ci), 126.67 (s, C7), 126.61
1
1
1
52.9 Hz, Ca), 126.34 (d, J(PC)=46.0 Hz, Ci), 125.79
(d, J(PC)=52.7 Hz, Ca), 125.74 (d, J(PC)=52.2 Hz,
(s, C7), 124.99 (d, 4J(PC)=5.8 Hz, C3), 124.35 (d,
1J(PC)=50.4 Hz, Ca%), 124.11 (s, C6), 123.06 (s, C8),
Ca), 125.17 (s, C6), 124.69 (s, C5), 120.96 (s, C9), 74.12
3
3
(d, J(PC)=3.1 Hz, CH), 49.82 (d, J(PC)=2.9 Hz, N
3
3
3
72.67 (d, J(PC)=2.9 Hz, CH), 51.03 (d, J(PC)=2.6
Hz, N CH3), 47.59 (d, J(PC)=1.8 Hz, N CH3), 23.33
CH3), 45.23 (d, J(PC)=2.3 Hz, N CH3), 19.52 (s, C
3
3
CH3), 17.75 (d, J(PC)=2.6 Hz, DMPP–CH3), 17.65
3
3
(s, C CH3), 17.64 (d, J(PC)=9.7 Hz, DMPP–CH3),
(d, J(PC)=2.6 Hz, DMPP–CH3). 31P{1H}-NMR: l
17.54 (d, 3J(PC)=10.1 Hz, DMPP–CH3). 31P{1H}-
NMR: l 37.3.
37.3.
2.2.5. {(S)-(TMBA)Pd(DMPP)(Cy2AsVy)[4+2]}ClO4
(5)
2.2.4. (R)-(−)-[(2TMNA)PdCl(DMPP)] (4)
To a solution containing 1.78 g (3.7 mmol) of [(S)-
(TMBA)PdCl(DMPP)] (2), in 25 mL CH2Cl2 was
added a solution containing 0.77 g (3.7 mmol) of
AgClO4 in 1 mL H2O and 5 mL of acetone. The
resulting mixture was stirred in the dark at ambient
temperature for 2 h, and then filtered through Celite to
remove AgCl. To the filtrate was added 1 g (3.7 mmol)
of Cy2AsVy and the mixture was stirred at ambient
temperature for one week. Evaporation to dryness,
followed by crystallization from CH2Cl2–diethyl ether,
afforded 2.6 g (86.7%) of a yellow–brown gum. This
material could not be purified by fractional crystalliza-
tion or column chromatography on silica with a variety
of solvents. It was characterized only by 31P{1H}-NMR
spectroscopy: l 120.13:119.58:119.34:118.42: with a
1:2:6:8 ratio (four diastereomeric Diels–Alder adducts).
To
a suspension of 5.0 g (5.8 mmol) [(R)-
(2TMNA)PdCl]2 [25b] in 50 mL CH2Cl2 was added 2.8
g (14.7 mmol) DMPP. The clear, light orange, solution
was stirred at ambient temperature for 10 h, reduced in
volume to ca. 10 mL, and n-hexane was added to
produce a pale yellow solid. The solid was isolated by
filtration, washed with n-hexane and diethyl ether and
recrystallized from CH2Cl2–n-hexane/diethyl ether to
yield 7.33 g (94.5%) of the product as pale yellow
prisms m.p. 186–188 °C; [h]D= −52.0 (C, 0.2,
CH2Cl2). CD (molecular elipticity [q]l (deg cm2
d
mol−1) for c=1.23×10−4 M in CH2Cl2 at 25 °C)
[q]404=0, [q]338= −7120, [q]302= −5900, [q]290=0,
[q]272= +13800, [q]247= +13400, [q]239=0, [q]233
=
−17900. Anal. Calc. for C26H29ClNPPd: C, 59.13; H,
2.2.6. {(S)-(1TMNA)Pd(DMPP)(Cy2AsVy)-
[4+2]}C1O4 (6)
5.49; Cl, 6.71. Found: C, 59.21; H, 5.30; Cl, 6.56%.
3
1H-NMR: l 7.97 (m, 2H, Ho), 7.68 (dd, J(H2H3)=8.0
4
Hz, J(H2H4)=1.5 Hz, 1H, H2), 7.45 (s, H6), 7.42 (m,
3
4
3H, Hmp), 7.41 (dd, J(H4H5)=8.0 Hz, J(H3H5)=1.5
Hz, 1H, H5), 7.33 (ddd, 3J(H2H3)=8.0 Hz, 3J(H3H4)=
4
4
7.0 Hz, J(H3H5)=1.5 Hz, 1H, H3), 7.33 (d, J(PH)=
6.5 Hz, 1H, H1), 7.30 (ddd, 3J(H4H5)=8.0 Hz,
4
3J(H3H4)=7.0 Hz, J(H2H4)=1.5 Hz, 1H, H4), 6.78
2
2
(d, J(PH)=32.0 Hz, 1H, Ha), 6.68 (d, J(PH)=32.5
Hz, 1H, Ha) 4.01 (q d, J(HH)=6.5 Hz, J(PH)=2.0
3
4
4
Hz, 1H, CH), 2.87 (d, J(PH)=2.0 Hz, 3H, N CH3),
2.72 (d, 4J(PH)=3.0 Hz, 3H, N CH3), 2.09 (s, 3H,
DMPP–CH3), 2.08 (s, 3H, DMPP–CH3), 1.71 (d,

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P.A. Gugger et al. / Journal of Organometallic Chemistry 643–644 (2002) 136–153
To a solution of 3.14 g (5.9 mmol) of [(S)-
3J(PC)=3.4 Hz, C2), 135.73 (d, 2J(PC)=3.1 Hz, C6% or
C5%), 132.26 (d, 2J(PC)=10.4 Hz, Co), 131.83 (C9),
(1TMNA)PdCl(DMPP)] (3), in 50 mL CH2Cl2 was
added a solution of 1.23 g (6 mmol) AgClO4 in 2 mL
H2O and 10 mL acetone. The resulting mixture was
stirred in the dark at ambient temperature for 2 h, and
then filtered through celite to remove AgCl. To the
filtrate was added 1.6 g (6 mmol) Cy2AsVy and the
mixture was stirred at ambient temperature for one
week. Evaporation to dryness followed by crystalliza-
tion from CH2Cl2–diethyl ether afforded 4.95 g (96%)
of colorless crystals that were shown by 31P{1H}-NMR
spectroscopy to be a 1:14 mixture of the derived
diastereomers l 119.22, 118.02. Recrystallization of the
mixture from CH2Cl2–diethyl ether afforded 4.34 g
(84%) of the major diastereomer as almost colorless
crystals having m.p. 194–196 °C; [h]D= +101.0° (c
0.2, CH2Cl2). CD (molecular elipticity [q]l (deg cm2 d
mol−1) for c=2.39×10−4 M in CH2Cl2 at 25 °C)
[q]519= −6173, [q]390=0, [q]343= +3675, [q]329=0,
[q]321= −111, [q]317=0, [q]308= +4189, [q]259= +
77786. Anal. Calc. for C40H54AsClNO4PPd: C, 55.79;
H, 6.27; Cl, 4.02. Found: C, 55.58; H, 6.40; Cl, 4.01%.
4
1
131.23 (d, J(PC)=1.5 Hz, Cp), 131.23 (d, J(PC)=
3
52.3 Hz, Ci), 129.23 (d, J(PC)=8.9 Hz, Cm), 129.21
(d, 3J(PC)=6.2 Hz, C10), 128.73 (C4), 128.24 (C5),
126.30 (C6), 125.90 (d, 4J(PC)=7.9 Hz, C3), 124.90
3
(C7), 123.60 (C8), 75.83 (d, J(PC)=4.4 Hz, CH), 55.37
(d, 1J(PC)=28.5 Hz, C1%), 51.84 (N CH3), 47.26 (d,
1J(PC)=19.6 Hz, C4%), 39.49 (N CH3), 38.64 (Ca),
34.27 (Ca), 32.38 (Cb), 32.12 (Cb), 31.79 (Cb), 31.43 (d,
2J(PC)=18.7 Hz, C3%), 29.52 (d, 2J(PC)=38.9 Hz, C2%),
28.24 (Cg), 27.99 (Cg) 27.60 (Cg), 27.59 (Cg), 25.80 (Cd),
3
25.55 (Cd), 25.03 (C CH3), 14.56 (d, J(PC)=2.5 Hz,
CꢁC CH3), 13.48 (d, 3J(PC)=2.0 Hz, CꢁC CH3).
31P{1H}-NMR: l 118.08.
2.2.7. {(R)-(2TMNA)Pd(DMPP)(Cy2AsVy)-
[4+2]}ClO4 (7)
3
4
1H-NMR: l 7.79 (dd, J(H3H4)=7.0 Hz, J(H3H5)=
1.5 Hz, 1H, H3), 7.68 (dd, 3J(H5H6)=7.0 Hz,
4J(H4H6)=1.0 Hz, 1H, H6), 7.50 (m, 6H, H2, Ho,m,p),
7.42 (apparent td, 3J(H4H5)=3J(H5H6)=7.0 Hz,
4J(H3H5)=1.5 Hz, 1H, H5), 7.39 (apparent td,
4
3J(H3H4)=3J(H4H5)=7.0 Hz, J(H4H6)=1.0 Hz, 1H,
3
4
H4), 7.21 (dd, J(H1H2)=8.5 Hz, J(PH)=6.5 Hz, 1H,
3
H1), 4,32 (q, J(HH)=6.5 Hz, 1H, CH), 3.65 (s, 1H,
To a solution of 5.28 g (10−2 mol) of [(R)-
(2TMNA)PdCl(DMPP)] (4), in 100 mL CH2Cl2 was
added a solution of 2.07 g (10−2 mol) AgClO4 in 5 mL
H2O and 15 mL acetone. The resulting mixture was
stirred in the dark at ambient temperature for 2 h, and
then filtered through celite to remove AgCl. To the
filtrate was added 2.68 g (10−2 mol) Cy2AsVy and the
mixture was stirred at ambient temperature for 4 days.
Evaporation of the solution to dryness on a rotary
evaporator, followed by crystallization of the residue
from CH3OH–diethyl ether–n-hexane afforded 9.91 g
(92%) of white microcrystals that were shown by
31P{1H}-NMR spectroscopy to be a 1:6 mixture of the
diastereomeric product. l 31P=119.86, 118.74 ppm.
Recrystallization of the mixture from CH2Cl2–
CH3OH–diethyl ether afforded 4.8 g (55.8%) of the
major diastereomer as colorless needles having m.p.
210–212 °C (dec.): [h]D= −11.0° (c 0.2, CH2Cl2). CD
(molecular elipticity [q]l (deg cm2 d mol−1) for c=
1.4×10−3 M in CH2Cl2 at 25 °C) [q]229= +49800,
[q]280 sh= +22800, [q]270=0, [q]255= −76800,
[q]231= −212000. Anal. Calc. For C40H54AsClO4PPd:
C, 55.79; H, 6.27; Cl, 4.02. Found: C, 55.58; H, 6.31;
3
H5), 3.01 (d, J(H1%H5%)=1.5 Hz, 1H, H1%), 2.84 (appar-
ent ddt, 3J(PH)=39.5 Hz, 3J(H2%H4%)=9.3 Hz,
3J(H1%H2%)=3J(H2%H4%)=1.5 Hz, 1H, H2%), 2.74 (appar-
ent tt, 3J(HH)=3J(HH)=12.5 Hz, 3J(HH)=
3J(HH)=2.5 Hz, 1H, Ha), 2.54 (apparent tt,
3J(HH)=3J(HH)=13.0 Hz, 3J(HH)=3J(HH)=3.0
4
Hz, 1H, Haa), 2.52 (d, J(PH)=4.5 Hz, 3H, N CH3),
2.52 (dd, J(H3%H4%)=13.5 Hz, J(H2%H3%)=1.5 Hz, 1H,
2
3
2
H3%), 2.41 (s, 3H, N CH3), 2.26 (dd, J(HH)=12.0 Hz,
3J(HH)=3.0 Hz, 2H, Hbe), 2.14 (dd, 2J(HH)=13.5
3
3
Hz, J(HH)=3.0 Hz, 2H, Hbe), 2.08 (ddd, J(PH)=
24.5 Hz, J(H3%H4%)=13.5 Hz, J(H2%H4%)=9.3 Hz, 1H,
2
3
H4%), 1.98 (m, 2H, Hba), 1.84 (m, 2H, Hba), 1.82 (d,
4
3J(HH)=6.5 Hz, 3H, CHCH3), 1.78 (d, J(PH)=1.0
Hz, 3H, CꢁC CH3), 1.69 (apparent q d, 2J(HH)=
3J(HH)=3J(HH)=13.0 Hz, 3J(HH)=3.0 Hz, 2H,
Hg), 1.59 (m, 2H, Hg), 1.54 (s, 3H, CꢁC CH3), 1.42
2
(apparent q t, J(HH)=3J(HH)=3J(HH)=12.5 Hz,
3J(HH)=3J(HH)=3.5 Hz, 1H, Hd), 1.35 (apparent q
t, 2J(HH)=3J(HH)=3J(HH)=12.5 Hz, 3J(HH)=
3J(HH)=3.5 Hz, 1H, Hd), 1.11 (apparent
q
t,
2J(HH)=3J(HH)=3J(HH)=12.5 Hz, 3J(HH)=
3J(HH)=3.0 Hz, 1H, Hd), 1.04 (apparent
q
t,
Cl, 3.79%. H-NMR: l 7.70 (dd, J(H2H3)=8.0 Hz,
1
3
2J(HH)=3J(HH)=3J(HH)=12.5 Hz, 3J(HH)=
3J(HH)=3.0 Hz, 1H, Hd). 13C{1H}-NMR: 156.59 (d,
2J(PC)=113 Hz, C1), 151.29 (C5% or C6%), 136.22 (d,
4J(H2H4)=1.5 Hz, 1H, H2), 7.68 (dd, J(H4H5)=8.0
Hz, J(H3H5)=1.5 Hz, 1H, H5), 7.56 (d, J(PH)=2.0
3
4
4
Hz, 1H, H1), 7.50 (s, 1H, H6), 7.48 (m, 5H, Ho, m.p.),

P.A. Gugger et al. / Journal of Organometallic Chemistry 643–644 (2002) 136–153
141
7.41 (ddd, 3J(H2H3)=8.0 Hz, 3J(H3H4)=7.0 Hz,
1.68 (m, 2H, Hg), 1.58 (m, 4H, Hg), 1.48 (m, 2H, Hg),
3
4J(H3H5)=1.5 Hz, 1H, H3), 7.37 (ddd, J(H4H5)=8.0
1.38 (apparent qt, 2J(HH)=3J(HH)=3J(HH)=13.5
Hz, 3J(H3H4)=7.0 Hz, 4J(H2H4)=1.5 Hz, 1H, H4),
Hz, J(HH)=3J(HH)=3.0 Hz, 1H, Hd), 1.35 (appar-
3
3
3.64 (apparent t, J(H3%H5%)=4J(H1%H5%)=1.5 Hz, 1H,
ent
qt,
2J(HH)=3J(HH)=3J(HH)=13.5
Hz,
3
H5%), 3.59 (q, J(HH)=6.5 Hz, 1H, CH), 3.01 (appar-
3J(HH)=3J(HH)=3.0 Hz, 1H, Hd), 1.10 (apparent qt,
2J(HH)=3J(HH)=3J(HH)=13.5 Hz, 3J(HH)=
3J(HH)=3.0 Hz, 1H, Hd), 1.06 (apparent qt,
2J(HH)=3J(HH)=3J(HH)=13.5 Hz, 3J(HH)=
3J(HH)=3.0 Hz, 1H, Hd). 13C{1H}-NMR: l 155.23 (d,
2J(PC)=113 Hz, C1), 154.0 (C5% or C6%), 137.21 (d,
3
ent q, J(H1%H2%)=3J(H1%H5%)=2J(PH) =1.5 Hz, 1H,
H1%), 2.87 (apparent ddt, 3J(PH)=41.5 Hz,
3J(H2%H4%)=9.0 Hz, 3J(H2%H3%)=3J(H1%H2%)=1.5 Hz,
1H, H2%), 2.8 (tt, 3J(HH)=3J(HH)=12.5 Hz,
3J(HH)=3J(HH)=3.0 Hz, 1H, Haa), 2.61 (tt,
3J(HH)=3J(HH)=12.5 Hz, 3J(HH)=3J(HH)=3.0
3
4J(PC)=2.5 Hz, C9), 135.39 (d, J(PC)=3.1 Hz, C10),
2
2
4
Hz, 1H, Haa), 2.52 (apparent dt, J(H3%H4%)=13.0 Hz,
132.09 (d, J(PC)=10.3 Hz, Co), 131.99 (d, J(PC)=
8.8 Hz, C3), 131.74 (s, C8), 131.08 (s, Cp), 129.20 (d,
3J(PC)=8.8 Hz, Cm), 128.26 (C5% or C6%), 127.59 (d,
1J(PC)=23.0 Hz, Ci), 127.18 (s, C4), 127.10 (s, C7),
3J(H2%H3%)=3J(H3%H5%)=1.5 Hz, 1H, H3%), 2.45 (d,
4J(PH)=2.0 Hz, 3H, N CH3), 2.32 (s, 3H, N CH3),
2.26 (dd, 2J(HH)=12.0 Hz, 3J(HH)=3.0 Hz, 2H,
Hbe), 2.18 (dd, 2J(HH)=12.5 Hz, 3J(HH)=3.0 Hz,
2H, Hbe), 2.08 (ddd, 3J(PH)=25.0 Hz, 2J(H3%H4%)=
3
125.40 (s, C5), 125.14 (s, C6), 120.48 (d, J(PC)=5.3
Hz, C2), 78.12 (d, 4J(PC)=3.3 Hz, CH), 55.18 (d,
1J(PC)=28.9 Hz, C1%), 51.22 (s, N CH3), 50.18 (d,
3
13.0 Hz, J(H2%H4%)=9.0 Hz, 1H, H4%), 2.00 (m, 2H,
4
1
Hba), 1.80 (m, 2H, Hba), 1.76 (d, J(PH)=1.0 Hz, 3H,
3J(PC)=4.9 Hz, N CH3), 47.13 (d, J(PC)=19.9 Hz,
CꢁC CH3), 1.74 (d, 3J(HH)=6.5 Hz, 3H, CHCH3),
C4%), 39.20 (Ca), 38.51 (Ca), 34.00 (Cb), 32.34 (Cb), 32.01
Table 1
Crystallographic data for complexes 3, 6b, 7b, 8b, 9b and 11
3
6b
7b
8b
9b
11
Chemical
formula
Formula weight 591.68
Crystal size
(mm)
C26H29ClNPPdCl·0.333 C40H54AsNPPd
(C7H8)·0.273 (CHCl3) (ClO4)·0.225(CH2Cl2) 0.6 CH2Cl2·0.4CH3OH CH2Cl2
C40H54AsNPPd(ClO4)· C26H38AsCl2PPd· C33H46AsClPRu C16H20Cl3Ru2
+PF6−·CH2Cl2 +PF6 −
915.04 665.80
0.30×0.16×0.03 0.20×0.20×0.20 0.26×0.14×0.03
879.73
924.40
0.33×0.20×0.15
718.72
0.23×0.20×0.10
0.30×0.06×0.04
(
Space group
Unit cell
R3
P212121
P212121
P212121
P212121
P21/a
dimensions
,
a (A)
25.9655(3)
25.9655(3)
10.87620(10)
90
90
120
6350.40(12)
9
1.392
0.903
70695
10.3395(1)
13.7179(2)
30.5848(4)
90
90
90
4338.03(8)
4
1.347
1.348
60057
10.6280(1)
13.9690(1)
29.6497(2)
90
90
90
4401.87(5)
4
1.395
1.377
210055
10.1853(1)
11.7903(1)
25.3267(3)
90
90
90
3041.43(5)
4
1.569
2.109
74129
12.1679(1)
14.5174(1)
21.4051(2)
90
90
90
3781.13(5)
4
1.607
1.634
78750
10.6399(1)
18.4496(2)
10.9676(2)
90
94.5036(5)
90
2146.31(4)
4
2.060
,
b (A)
,
c (A)
h (°)
i (°)
k (°)
V (A )
3
,
Z
Dcalc (g cm−3
)
m (mm−1
)
1.906
64180
Reflections
Collected
Unique
8292
7617
12834
7438
11072
4110
reflections
Max/min
0.926/0.812
0.950/0.811
0.876/0.735
0.939/0.586
0.779/0.753
0.946/0.667
transmission
factors
Data/restraints/pa8046/0/297
rameters
6287/0/455
9823/0/468
7438/0/317
8685/0/424
4110/0/253
Goodness-of-fit 1.59
Flack parameter 0.00(2)
1.407
0.001(1)
0.036/0.0385
1.966
0.001(1)
0.0437/0.0481
1.389
0.001(1)
0.0351/0.0368
1.610
0.001(1)
0.0388/0.0415
1.957
–
0.0505/0.0732
R1/wR2
0.031/0.041
(I\2s(I)) a
2
a R1=ꢀꢁꢁFoꢁ−ꢁFcꢁꢁ/ꢀFo, wR2={ꢀ[w(ꢁFoꢁ−ꢁFcꢁ)2]/ꢀw(Fo)2}0.5, w=1/[s2(Fo)+aꢁFoꢁ ], (3) a=0.004, (6b–9b) a=0.00022.

142
P.A. Gugger et al. / Journal of Organometallic Chemistry 643–644 (2002) 136–153
2.2.8. (−)-{PdCl2(DMPP)(Cy2AsVy)[4+2]} (8b)
To a solution containing 3.5 g (4.1 mmol) of 6b in 50
mL CH2Cl2 was added 10 mL of 12 M HCl and 50 mL
acetone. This mixture was stirred at ambient tempera-
ture for 2 days, the CH2Cl2 layer was separated and the
solvent was removed on a rotary evaporator. The pale
yellow solid that remained was washed with H2O,
ethanol and diethyl ether and recrystallized from
CH2Cl2–n-hexane to afford 2.4 g (93%) of pale yellow
crystals having m.p. 240–242 °C. [h]D= −35.5° (c 0.2,
CH2Cl2). CD (molecular elipticity [q]l (deg cm2
d
mol−1) for c=3.15×10−3 M in CH2Cl2 at 25 °C)
[q]384= +2100, [q]370=0, [q]322= −16,600, [q]300=0,
[q]292 sh= +12,500, [q]262= +45400. Anal. Calc. for
C26H38AsCl2PPd·CH2Cl2: C, 45.14; H, 5.57; Cl, 19.74.
Scheme 1.
1
Found: C, 45.01; H, 5.26; Cl, 19.66%. H-NMR: l 7.51
(m, 2H, Ho), 7.45 (m, 1H, Hp), 7.40 (m, 2H, Hm), 3.30
4
3
(dd, J(H1H5)=2.0 Hz, J(H3H5)=1.5 Hz, 1H, H5),
3.06 (apparent t, J(PH)=4J(H1H5)=2.0 Hz, 1H, H1),
2
2.89 (apparent tt, 3J(HH)=3J(HH)=13.0 Hz,
3J(HH)=3J(HH)=3.0 Hz, 1H, Haa), 2.62 (dd,
Fig. 1. Expansion of the 500 MHz COSY spectrum of 3 in the low
field region.
2
(Cb), 31.95 (Cb), 31.30 (d, J(PC)=18.2 Hz, C3%), 29.6
2
(d, J(PC)=39.1 Hz, C2%), 28.22 (Cg), 27.95 (Cg), 27.45
(Cg), 25.83 C CH3), 25.70 (Cd), 25.45 (Cd), 14.44 (d,
3
3J(PC)=2.4 Hz, CꢁC CH3), 13.35 (d, J(PC)=1.6 Hz,
Fig. 2. Expansion of the 125 MHz HETCOR spectrum of 3 in the
low field region.
CꢁC CH3). 31P{1H}-NMR: l 118.74.

P.A. Gugger et al. / Journal of Organometallic Chemistry 643–644 (2002) 136–153
143
3J(PH)=31.0 Hz, 3J(H2H4)=9.3 Hz, 1H, H2), 2.60
(dd, 2J(HH)=12.0 Hz, 3J(HH)=3.0 Hz, 1H, Hbe),
2.57 (apparent tt, J(HH)=13.0 Hz, J(HH)=3.0 Hz,
from CH2Cl2–n-hexane afforded 0.42 g (36.2%) of the
major diastereomer, m.p. \300 °C dec.
3
3
[h]D= −126.8° (c 0.2, CH2Cl2). CD (molecular
elipticity [q]l (deg cm2 d mol−1) for c=1× 10−3 M in
CH2Cl2 at 25 °C) [q]640=0, [q]516= −22200,
[q]455= −25627, [q]328= −15291, [q]251= −104460.
Anal. Calc. for C33H46AsClF6P2Ru: C, 47.77; H, 5.54;
Cl, 4.27. Found: C, 47.63; H, 5.29; Cl, 4.14%.
1H-NMR: l 7.90 (m, 1H, HoPh), 7.57 (m, 1H, HoPh),
2
3
1H, Haa), 2.49 (dd, J(H3H4)=13.0 Hz, J(H3H5)=1.5
2
3
Hz, 1H, H3), 2.43 (dd, J(HH)=13.0 Hz, J(HH)=3.0
Hz, 1H, Hbe), 2.36 (dd, 2J(HH)=13.0 Hz,
3J(HH)=3.0 Hz, 1H, Hbe), 2.27 (dd, 2J(HH)=13.0
Hz, 3J(HH)=3.0 Hz, 1H, Hbe), 1.94 (ddd,
2
3
3J(PH)=24.0 Hz, J(H3H4)=13.0 Hz, J(H2H4)=9.3
3
Hz, 1H, H4), 1.84 (m, 8H, 2 Hb, 4 Hg, 2 Hd), 1.64
7.49 (m, 3H, HmpPh), 5.96 (d, J(HH)=6.0 Hz, 1H,
2
(apparent q d, J(HH)=3J(HH)=3J(HH)=13.0 Hz,
Ho), 5.74 (t, 3J(HH)=6.0 Hz, 1H, Hm), 5.02 (d,
3J(HH)=3.0 Hz, 1H, Hba), 1.58 (apparent q d,
2J(HH)=3J(HH)=3J(HH) =13.0 Hz, 3J(HH)=3.0
Hz, 1H, Hba), 1.58 (s, 3H, CH3), 1.52 (s, 3H, CH3), 1.38
3J(HH)=6.0 Hz, 1H, Ho%), 5.02 (t, J(HH)=6.0 Hz,
3
3
1H, Hp), 4.81 (td, J(HH)=6.0 Hz, J(PH)=1.5 Hz,
3
1H, Hp), 3.13 (b s, 1H, H1), 3.11 (d, J(H3H5)=3.0 Hz,
(m, 4H, Hg), 1.29 (apparent
q
t, 2J(HH)=
1H, H5), 2.87 (apparent tt, 3J(HH)=3J(HH)=12.5
Hz, 3J(HH)=3J(HH)=2.5 Hz, 1H, Haa), 2.74 (dd,
3J(HH)=3J(HH)=13.0 Hz, 3J(HH)=3.0 Hz, 1H,
2
3
Hd), 1.24 (apparent q t, J(HH)=3J(HH)=3J(HH)=
2J(H3H4)=13.0 Hz, J(H3H5)=3.0 Hz, 1H, H3), 2.61
13.0 Hz, 1H, Hd). 13C{1H}-NMR: l 135.78 (C5), 132.50
(dd, 3J(PH)=40.5 Hz, 3J(H2H4)=9.3 Hz, 1H, H2),
2.59 (apparent tt, 3J(HH)=3J(HH)=13.0 Hz,
3J(HH)=3J(HH)=2.5 Hz, 1H, Haa), 2.08 (s, 3H, tol
CH3), 2.06−1.69 (m, 16H, 8 Hb 8 Hg), 1.64 (s, 3H,
CH3), 2.10 (ddd, 3J(PH)=21.0 Hz, 2J(H3H4)=13.0
Hz, 3J(H2H4)=9.3 Hz, 1H, H4), 1.40 (s, 3H, CH3),
1.30 (m, 4H, Hd). 13C {1H}-NMR: l 137.86 (CꢁC),
132.83 (d, 1J(PC)=44.3 Hz, Ci), 131.44 (s, CꢁC),
2
4
(d, J(PC)=9.3 Hz, Co), 131.22 (d, J(PC)=2.4 Hz,
Cp), 129.00 (d, 2J(PC)=1.9 Hz, C6), 128.16 (d,
3J(PC)=11.1 Hz, Cm), 125.69 (d, 1J(PC)=47.8 Hz,
Ci), 55.57 (d, 1J(PC)=35.0 Hz, C1), 47.48 (d,
1J(PC)=29.3 Hz, C4), 40.46 (Ca), 39.53 (Ca), 32.23
2
(Cb), 32.19 (Cb), 31.58 (Cb), 31.09 (d, J(PC)=16.6 Hz,
C3), 30.84 (Cb), 28.01 (Cg), 27.79 (Cg), 27.66 (Cg), 27.39
2
2
4
(Cg), 26.71 (d, J(PC)=40.1 Hz, C2), 25.86 (Cd), 25.68
131.21 (d, J(PC)=5.3 Hz, Co), 130.79 (d, J(PC)=2.0
(Cd), 14.95 (d, 3J(PC)=2.6 Hz, CH3), 13.62 (d,
3J(PC)=3.0 Hz, CH3). 31P{1H}-NMR: l 130.87.
Hz, Cp), 129.90 (d, J(PC)=12.1 Hz, Cm), 129.21 (d,
3
2J(PC)=7.7 Hz, Co), 128.55 (d, J(PC)=9.8 Hz Cm),
3
112.50 (d, J(PC)=2.9 Hz, arene Ci), 98.21 (s, arene
Co%), 95.85 (d, J(PC)=7.4 Hz, arene Co), 90.53 (s, arene
Cm%), 86.31 (d, J(PC)=2.3 Hz, arene Cm), 71.72 (s,
2.2.9. {(p6-H3CC6H5)Ru[(DMPP)(Cy2AsCVy)-
[4+2]Cl}PF6 (9)
1
arene Cp), 54.89 (d, J(PC)=37.0 Hz, C1), 48.26 (d,
1J(PC)=30.4 Hz, C4), 41.88 (Ca), 36.34 (Ca), 31.28
(Cb), 31.00 (Cb), 30.56 (Cb), 29.80 (Cb), 28.19 (d,
2J(PC)=11.3 Hz, C3), 27.98 (Cg), 27.78 (Cg), 26.73
(Cg), 26.41 (Cg), 26.14 (Cd), 25.91 (Cd), 25.14 (d,
2J(PC)=39.0 Hz, C2), 18.43 (tol CH3), 14.88 (d,
3
3J(PC)=2.3 Hz, CꢁC CH3), 13.72 (d, J(PC)=2.3 Hz,
CꢁC CH3). 31P{1H}-NMR: l 147.46 (s, 1P, P7),
−143.131 sept, 1J(PF)=713 Hz, 1 P, PF6−). The
minor diastereomer could not be separated from the
major diastereomer; NMR data for it were obtained
from the mixture. 1H-NMR: l 7.70 (m, 1H, HoPh), 7.59
(m, 1H, HoPh), 7.42 (m, 1H,HpPh) 7.35 (m, 2H, HmPh)
5.29 (d, 3J(HH)=5.5 Hz, 1H, Ho), 5.81 (t,
To a solution containing 1 g (1.4 mmol) of 8b in 100
mL CH2Cl2 was added a solution containing 9 g (0.18
mol) NaCN in 100 mL H2O. The mixture was stirred
vigorously for 4 h. The CH2Cl2 layer was separated,
dried over anhydrous Na2SO4, and 0.367 g (0.7 mmol)
[(h6-H3CC6H5)RuCl2]2 and 0.23 g (1.4 mmol) NH4PF6
were added. The mixture was stirred at ambient
temperature for 16 h. The solvents were removed by
rotary evaporation and the residue was crystallized
from acetone–diethyl ether to yield 0.98 g (84.5%) of
the yellow microcrystalline product that was shown by
31P{1H}-NMR spectroscopy to be a 1.67:1 ratio of
diastereomers: l 147.92 (1.67 P), 143.50 (1P), −143.13
3
3J(HH)=5.5 Hz, 1H, Hm), 5.60 (dd, J(HH)=6.0 Hz,
3
3J(HH)=5.5 Hz, 1H, Hp), 5.24 (t, J(HH)=6.0 Hz,
3
1H, Hm%), 5.04 (d, J(HH)=6.0 Hz, 1H, Ho%), 3.44 (d,
3J(PH)=42.0 Hz, 1H, H2), 3.31 (bs, 1H, H5), 2.96 (bs,
1H, H1), 2.91 (tt, 3J(HH)=3J(HH)=12.5 Hz,
3J(HH)=3J(HH)=3.0 Hz, 1H, Ha), 2.88 (tt,
3J(HH)=3J(HH)=12.5 Hz, 3J(HH)=3J(HH)=3.0
Hz, 1H, Ha), 2.38 (dd, 3J(PH)=27.0 Hz,
2
2J(H3H4)=12.0 Hz, 1H, H4), 1.82 (d, J(H3H4)=12.0
Hz, 1H, H3), 1.79 (s, 3H, Tol CH3), 1.48 (s, 3H, CꢁC
CH3), 1.47 (s, 3H, CꢁC CH3). (The remaining cyclo-
1
(sept, J(PF)=713 Hz, 2.67P, PF−6 ). Recrystallization

144
P.A. Gugger et al. / Journal of Organometallic Chemistry 643–644 (2002) 136–153
(1.4 mmol) of NH4PF6. After removal of solvents, the
residue was crystallized from acetone–diethyl ether. The
yellow–brown residue was shown by 1H-, 13C{1H}- and
31P{1H}-NMR spectroscopy to be a mixture of two
diastereomers of 10 (2.4:1) (l 31P, 145.61 and 143.84,
respectively)
and
[{(h6-p-H3CC6H4CH3)Ru}2m-
(Cl)3]PF6 (11), Compound 11 was isolated by fractional
crystallization from CH2Cl2–n-hexane and recrystal-
lized from acetone–diethyl ether to afford 0.12 g of
brownish-yellow plates m.p. 208–212 °C, (dec.). Anal.
Calc. for C16H20Cl3F6PRu2: C, 28.87; H, 3.00; Cl, 15.98.
1
Found: C, 28.69; H, 3.07; Cl, 15.75%. H-NMR (ace-
tone-d6) l 5.84 (s, 8H, arene CH), 2.20 (s, 12H, CH3).
13C{1H}-NMR: l 95.32 (arene Ci), 80.59 (arene CH),
18.72 (CH3). 31P{1H}-NMR:
l
−144.30 (sept,
Fig. 3. Structural drawing of 3 showing the atom numbering scheme
(30% probability ellipsoids). The hydrogen atom on C(11) has an
arbitrary radius.
1J(PF)=706 Hz, PF6−).
2.3. X-ray data collection and processing
Table 2
,
Selected bond distances (A) and angles (°) for 3 and 4
Crystals of the compounds were obtained from
CH2Cl2–n-hexane (6b, 7b, 8b, 9b, 11) or toluene–
CHCl3–n-hexane (3) mixtures, mounted on glass fibers
and placed on a Nonius Kappa CCD diffractometer.
Intensity data were taken in the ƒ and ꢀ modes with
Mo–Ka graphite monochromated radiation (u=0.7107
a
Compound
3
4
Bond distances
Pd(1)ꢀC(1)/C(2)
Pd(1)ꢀC1(1)
Pd(1)ꢀN(1)
2.007(4)
2.4123(10)
2.134(6)
2.08(2)
2.372(7)
2.20(2)
2.219(6)
,
A) at 200 K. The data were corrected for Lorentz,
Pd(1)ꢀP(1)
2.250(14)
polarization effects, and absorption by integration using
the Gaussian method [29]. Scattering factors and correc-
tions for anomalous dispersion were taken from a
standard source [30]. Calculations were performed with
the TEXSAN (MSC 1992–1997) software package Ver-
sion 1.8 on the Silicon Graphics Power Challenge com-
puter of the Australian National University’s
supercomputer facility. The structures were solved by
Patterson methods. Anisotropic thermal parameters
were assigned to all non-hydrogen atoms. Hydrogen
atoms were included at calculated positions in which the
Bond angles
N(1)ꢀPd(1)ꢀC(1)/C(2)
P(1)ꢀPd(1)ꢀC(1)/C(2)
N(1)ꢀPd(1)ꢀP(1)
Cl(1)ꢀPd(1)ꢀC(1)/C(2)
N(1)ꢀPd(1)ꢀCl(1)
P(1)ꢀPd(1)ꢀCl(1)
81.20(18)
92.02(5)
173.47(9)
172.06(13)
93.92(9)
82.8(8)
92.2(6)
175.0(6)
172.5(5)
92.6(6)
92.4(3)
93.18(16)
a Ref. [17].
hexyl proton resonances could not be distinguished
from those of the major diastereomer). 13C{1H}-NMR:
2
,
l 138.06 (CꢁC), 132.16 (CꢁC), 129.70 (d, J(PC)=5.5
C–H vector was fixed at 0.95 A but not refined.
3
Hz, Co), 129.45 (s, Cp), 128.70 (d, J(PC)=12.5 Hz,
Compounds 6b, 7b, 8b, and 9b crystallized as solvates.
The absolute configurations of the complexes were de-
termined by refinement of the Flack parameters [31],
and were consistent with the known configurations of
the carbon stereocenters in the amine components of the
compounds. Crystallographic data are given in Table 1.
Cm), 128.45 (d, 2J(PC)=8.9 Hz, Co), 128.12 (d,
3J(PC)=9.9 Hz, Cm), 124.40 (d, J(PC)=46.4 Hz, Ci),
1
111.00 (d, J(PC)=2.4 Hz, arene Ci), 94.52 (d, J(PC)=
7.0 Hz, arene Co), 93.01 (s, arene Co%), 90.16 (s, arene
Cm%), 86.54 (s, arene Cp), 51.33 (d, J(PC)=39.0 Hz,
C1), 48.16 (d, J(PC)=30.1 Hz, C4), 42.24 (Ca), 36.55
1
1
(Ca), 31.06 (Cb), 30.69 (Cb), 30.50 (Cb), 29.48 (Cb), 27.93
2
(d, J(PC)=12.3 Hz, C3), 27.23 (Cg), 26.50 (Cg), 26.20
3. Results and discussion
2
(Cg), 26.22 (d, J(PC)=30.6 Hz, C2), 25.88 (Cg), 25.65
(Cd), 24.98 (Cd), 17.87 (tol CH3), 14.48 (d, J(PC)=2.9
Hz, CꢁC CH3, 13.40 (d, J(PC)=2.3 Hz, CꢁC CH3.
3
As indicated in Scheme 1, like many other ligands
[16,17,32], DMPP readily cleaves the chloride bridges of
dimeric orthopalladated amine complexes in a regiose-
lective manner to form complexes 2–4. The regioselec-
tivity of the ligand substitution reactions was readily
established by NMR spectroscopy. Complete assign-
ments of all proton and carbon chemical shifts were
made with the aid of APT, COSY, and HETCOR
3
2.2.10. Attempted synthesis of {(p-H3CC6H4CH3)-
Ru(DMPP)(Cy2AsVy)[4+2]Cl}PF6 (10)
As for 9, the arsinophosphine was displaced by cya-
nide from 1 g (1.4 mmol) of 8 and reacted with 0.39 g
(1.4 mmol) of [(h6-p-H3CC6H4CH3)RuCl2]2 and 0.23 g

P.A. Gugger et al. / Journal of Organometallic Chemistry 643–644 (2002) 136–153
145
1
spectra. Typical COSY and HETCOR spectra are
shown in Figs. 1 and 2, respectively. Because the com-
plexes are devoid of symmetry, the CH3 and aCH
groups of the phosphole are each diastereotopic. The
two proton resonances for the phosphole CH3 groups
were readily distinguished from those of the NCH3 and
CHCH3 groups by observation of 4J(HH) couplings
between the aCH protons and the phosphole methyl
protons. The resonances due to the CHCH3 moiety
were readily assigned by the observation of 3J(HH)
coupling between the two proton types. The phosphole
aCH resonances were assigned by the observation of
large 2J(PH) couplings, together with the smaller
plings. The remaining H resonances in the low-field
region divide into separate tightly coupled spin sets
comprising the P-phenyl protons and the naphthyl pro-
tons. These spin sets were distinguished, one from
another, by their mutual couplings and their PH cou-
plings. The P–H coupling interactions were affirmed by
1H{31P} experiments. Once the proton NMR spectra
were fully assigned, the 13C{1H}-NMR spectra could
then be assigned from the APT and HETCOR spectra
(Fig. 2). The 31P{1H}-NMR spectrum of each complex
contains one singlet resonance (l 37.8, 2, l 37.3, 3 or 4)
the chemical shift of which is, within experimental
1
error, unaffected by the structure of the amine. The H-
4J(HH) allylic coupling and their mutual J(HH) cou-
and 13C{1H}-NCH3 resonances all exhibit J(PH) and
4
4
Scheme 2.

146
P.A. Gugger et al. / Journal of Organometallic Chemistry 643–644 (2002) 136–153
The crystal structure of 4 has previously been re-
ported [17] and that of 3 is shown in Fig. 3. Selected
bond distances and angles are given in Table 2. In both
complexes the phosphole is trans to nitrogen, consistent
with the NMR data. The palladium coordination ge-
ometry deviates slightly from planarity, having a small
tetrahedral distortion. This is reflected in the non-zero
dihedral angle between the P(1)ꢀPd(1)ꢀCl(1) and
C(2)ꢀPd(1)ꢀN(1) planes in 3 of 7.0(1)°. For both struc-
tures, the five-membered chelate ring is puckered. The
PdꢀC and PdꢀN distances in 3 are slightly shorter than
in 4 and the PdꢀCl and PdꢀP distances are shorter in 4
than in 3, but overall the two structures are similar.
Complexes 2–4 react with AgClO4 and Cy2AsVy (1)
to give Diels–Alder [4+2] cycloaddition products in
good chemical yields. As illustrated in Scheme 2, the
reaction of 2 produces four diastereomeric Diels–Alder
cycloadducts, whereas the reactions of 3 and 4 each
produce two diastereomers. The major diastereomer
formed from 3, 6b, and that formed from 4, 7b, were
separated from the minor diastereomers and were fully
characterized. The crystal structures of 6b and 7b are
shown in Figs. 4 and 5, respectively. Clearly, the con-
versions of 3 into 6b and 4 into 7b involve ligand
substitutions because arsenic is trans to nitrogen in 6b
and 7b, whereas phosphorus is trans to nitrogen in 3
and 4. It is likely that the ligand substitution precedes
the cycloaddition for the following reasons. Diels–
Alder cycloadditions of DMPP seldom occur with the
free ligand [13,15] and when they do, there is no
diastereoselectivity in contrast to that observed in the
reactions described here. Moreover, several pairs of
racemic diastereomers would be expected, (syn–endo,
syn–exo, anti–endo and anti–exo) not the single syn–
exo diastereomer that is produced by intramolecular
cycloaddition within the coordination sphere of the
chiral palladium template [15–17].
Fig. 4. Structural drawing of the cation of 6b showing the atom
numbering scheme (30% probability ellipsoids). The cyclohexyl ring
carbon atoms have been removed for clarity. The hydrogen atom on
,
C(11) has an arbitrary radius. Selected bond lengths (A): Pd(1)ꢀAs(1),
2.3584(5); Pd(1)ꢀP(1), 2.339(1); Pd(1)ꢀN(1), 2.145(4); Pd(1)ꢀC(1),
2.055(4); C(12)ꢀC(21), 1.333(6) and angles (°): P(1)ꢀPd(1)ꢀAs(1),
82.39(3); As(1)ꢀPd(1)ꢀC(1), 95.3(1); N(1)ꢀPd(1)ꢀC(1), 80.8(2);
P(1)ꢀPd(1)ꢀN(1), 101.6(1).
The 31P{1H}-NMR chemical shift for 6b (l 118.02
ppm) is almost identical to that reported [16b] for the
diphenylarsino analog 6c (l 118.1 ppm). Because the
31P-NMR chemical shifts of 2 to 4 are so similar, we
assign the structure of the major diastereomer formed
from 2, 5b, to be the (SCSC) diastereomer (l 31P=
118.42 ppm) shown in Scheme 2. The minor
diastereomer formed from 3, 6a, (l 31P=119.22 ppm)
is the(SCRC) diastereomer. By extension, the other
diastereomers formed from 2 are the (SCSC), 5d, and
(SCRC), 5c, diastereomers having phosphorus trans to
nitrogen, as shown in Scheme 2. Compounds 7b and 7a
are the (RCRC) and (RCSC) diastereomers (Scheme 2).
The ratio of diastereomers formed from 3 (14:1) and
4 (6:1) correspond to 87 and 71% diastereomeric ex-
cesses (d.e. values), respectively (%de=%major−
%minor). The diastereoselectivity in the reaction of 2 is
much lower (8:6:2:1). Consistent with the X-ray struc-
tures of 6b and 7b, neither the benzylic CH proton nor
Fig. 5. Structural drawing of the cation of 7b showing the atom
numbering scheme (30% probability ellipsoids). The cyclohexyl ring
carbon atoms have been removed for clarity. The hydrogen atom on
,
C(11) has an arbitrary radius. Selected bond lengths (A): Pd(1)ꢀAs(1),
2.3553(5); Pd(1)ꢀP(1), 2.325(1); Pd(1)ꢀN(1), 2.147(3); Pd(1)ꢀC(1),
2.062(4); C(19)ꢀC(21), 1.349(5) and angles (°): P(1)ꢀPd(1)ꢀAs(1),
82.70(3); As(1)ꢀPd(1)ꢀC(1), 94.5(1); N(1)ꢀPd(1)ꢀC(1), 80.9(1);
P(1)ꢀPd(1)ꢀN(1), 101.0(1).
3J(PC) couplings of 2–5 Hz. The CH nuclei of the
stereogenic carbon moiety are similarly coupled to
phosphorus. The NMR data indicate that the phosp-
hole is trans to nitrogen in all three complexes.

P.A. Gugger et al. / Journal of Organometallic Chemistry 643–644 (2002) 136–153
147
Scheme 3.
both of the NCH3 carbon nuclei are coupled to phos-
phorus as is usually observed when phosphorus is trans
to nitrogen in complexes of this type.
was separated from 9a by fractional crystallization
from CH2Cl2–n-hexane mixtures and fully character-
ized. The crystal structure of 9b is shown in Fig. 8. The
major diastereomer has the (SRuSC) absolute configura-
The amine can be removed from 6b,c by protonation
with HCl (Scheme 3). The crystal structures of 8c [16b]
and 8b (Fig. 6) have been determined. Selected dis-
tances and angles in the two compounds are listed in
Table 3. The absolute configurations of the stereocen-
ters in both ligands are the same: R at P, C(1) and C(4)
and S at C(2). Both complexes are distorted slightly
from planarity with the angles at palladium ranging
from 83.1(1) to 95.07(3). The smallest angle in both
cases is the ligand bite angle, which differs little be-
tween the two compounds (83.61(2), 8b; 83.1(1), 8c).
The PdꢀP and PdꢀAs bond lengths are also very similar
in the two structures and are unexceptional. In both
structures, the PdꢀCl bond trans to phosphorus is
slightly longer than that trans to arsenic, reflecting the
greater trans influence of the phosphorus donor atom.
The proton and carbon chemical shifts of 8b have
been fully assigned and are given in the experimental
1
section. COSY, APT, H{31P} and HETCOR (Fig. 7)
spectra were used to make these assignments. From
these spectra it was concluded that the cyclohexyl rings
in the complex are locked in chair conformations with
the arsenic atom in an equatorial position as found in
the solid state structure. The 31P{1H} chemical shifts of
8c (l 129.4 ppm) and 8b (l 130.87 ppm) are very
similar, indicating that the arsenic substituents have
only a small effect on the 31P chemical shift for ligands
of this type (however, see Ref. [15k]).
Fig. 6. Structural drawing of 8b showing the atom numbering scheme
(30% probability ellipsoids). The cyclohexyl ring carbon atoms have
been removed for clarity.
Table 3
,
Selected bond distances (A) and angles (°) 8c and 8b
a
Compound
8c
8b
Treatment of a dichloromethane solution of 8b with
aqueous sodium cyanide liberates the enantiomerically
pure, very air-sensitive, arsinophosphine. Because of the
extreme ease of oxidation of the free ligand it has not
been isolated and characterized. This ligand reacts with
[(h6-arene)RuCl2]2 (arene=H3CC6H5, p-H3CC6H4-
CH3), in the presence of NH4PF6, to form diastereo-
meric [(h6-arene)Ru(PꢀAs)Cl]PF6 complexes in which
the ruthenium atom is a chiral stereocenter (Scheme 4).
The diastereoselectivity of these reactions is rather low
(9a:9b=1:1.67, and 10a:10b=1:2.4). Diastereomer 9b
Bond distances
Pd(1)ꢀCl1)
Pd(1)ꢀC1(2)
Pd(1)ꢀAs(1)
Pd(1)ꢀP(1)
2.345(2)
2.360(2)
2.349(1)
2.218(2)
2.3564(8)
2.3702(9)
2.3584(9)
2.2228(9)
Bond angles
Cl(1)ꢀPd(1)ꢀCl(2)
Cl(1)ꢀPd(1)ꢀP(1)
P(1)ꢀPd(1)ꢀAs(1)
As(1)ꢀPd(1)ꢀCl(2)
94.78(9)
89.1(1)
83.1(1)
93.6(1)
95.07(3)
88.72(3)
83.61(2)
92.53(2)
a Ref. [16b].

148
P.A. Gugger et al. / Journal of Organometallic Chemistry 643–644 (2002) 136–153
Fig. 8. Structural drawing of the cation of 9b showing the atom
numbering scheme (30% probability ellipsoids). Selected bond lengths
,
(A): Ru(1)ꢀAs(1), 2.4486(4); Ru(1)ꢀCl(1), 2.4074(9); Ru(1)ꢀP(1),
2.2902(9); Ruꢀarene (average), 2.244(4) and angles (°):
As(1)ꢀRu(1)ꢀCl(1),
88.73(2);
As(1)ꢀRu(1)ꢀP(1),
79.79;
Cl(1)ꢀRu(1)ꢀP(1), 90.30(3).
tion, which is usually found for complexes of this type
[16k]. It crystallizes as discrete cations and anions with
no unusual interionic contacts.
Diastereomers 10a and 10b could not be isolated in
pure form, although the by-product 11 was separated
Fig. 7. Expansions of the 125 MHz HETCOR spectrum of 8b. (a)
Aliphatic region; (b) further expansion of the aliphatic region.
Scheme 4.

P.A. Gugger et al. / Journal of Organometallic Chemistry 643–644 (2002) 136–153
149
Fig. 10. Cyclic and rotating disc voltammograms of 9b in CH2Cl2 at
−50 °C.
There is considerable current interest in the configu-
rational stability of chiral ruthenium(II) complexes [23]
which bears directly on their application as asymmetric
homogeneous catalysts. Ruthenium(III) species are be-
lieved to be involved as intermediates in catalytic CꢀH
bond activation processes [37]. For these reasons we
have studied, in some detail, the spectroelectrochemical
behavior of enantiomerically pure 9b. Similar to
racemic analogs, 9b undergoes a chemically reversible
one-electron oxidation [E1/2(II)/(III)=1.02 V, DE=
EPcꢀEPa=60 mV versus the ferrocene–ferrocenium
couple] and a chemically irreversible two-electron re-
duction [EPc(II)/(0)= −1.98 V]. As can be seen in Fig.
10, the peak currents for these two electrochemical
events have a two-to-one ratio consistent with their
assignment as two- and one-electron processes, respec-
tively. The stability of 9b+ over time was confirmed by
bulk electrolysis experiments (at −40 °C) which al-
Fig. 9. Two views of the cation of 11 showing the atom numbering
scheme (30% probability ellipsoids).
from them by fractional crystallization and character-
ized. The crystal structure of 11 is shown in Fig. 9 and
its metrical parameters are compared with those of
analogous species in Table 4. The compound crystal-
lizes as discrete cations and anions with no unusual
interionic contacts. The cation has near D2h symmetry
with the two h6-p-H3CC6H4CH3 planes parallel (dihe-
dral angle 2.67) and eclipsed as was observed for the
C6H6 [33,34] and C6(CH3)6 [36] analogs. As is clear
from the data presented in Table 4, the structure of the
Ru2Cl3 core is almost identical in all of these complexes
and there are only minor differences in the average
RuꢀC distances among the series of complexes.
Table 4
Structural data for [{(h6-arene)Ru}2m-(Cl)3]X complexes
, , ,
RuꢀRu (A) RuꢀCl (average A) RuꢀC (average A) ClꢀRuꢀCl (average °) RuꢀClꢀRu (average °) Reference
Arene
X
C6H6
C6H6
AsF6 3.2754(4)
BF4 3.285(1)
BF4 3.275(1)
PF6 3.2798(6)
2.423
2.432
2.432
2.440
2.443
2.442
2.160
2.163
2.168
2.167
2.154
2.178
79.33
NR a
NR
79.75
79.47
79.77
85.04
84.99
84.66
84.49
84.85
84.32
[33]
[34]
[34]
This work
[35]
H3CC6H5
p-H3CC6H4CH3
p-H3CC6H4CH(CH3)2 BPh4 3.282(3)
C6(CH3)6
PF6 3.278(3)
[36]
a NR, not reported.

150
P.A. Gugger et al. / Journal of Organometallic Chemistry 643–644 (2002) 136–153
Fig. 11. Electronic spectra recorded during the one-electron oxidation of 9b in CH2Cl2 at −50 °C. (---) First scan=9b. (=) Final scan=9b+
.
lowed the starting material to be quantitatively regener-
ated from the oxidized species over a period of several
hours. Nevertheless, in order to ensure that 9b+ re-
mained stable, the temperature needed to be maintained
at 5 −40 °C. Electrochemical and spectroscopic ex-
periments showed that 9b+ decomposed within 2–3
min of warming to room temperature. Cyclic voltam-
metry experiments (Fig. 10) indicated that the two-elec-
tron reduced species was chemically unstable even over
short voltammetric timescales (since no reverse oxida-
tive peak was evident during cyclic voltammetry experi-
ments), hence was unlikely to survive for enough time
to allow spectroscopic characterization. The chemical
reversibility of the Ru(II)/(III) process was confirmed
by optical spectroelectrochemical measurements on
chilled solutions of 9b in CH2Cl2. The spectrum of
theruthenium(II) complex, 9b, exhibits absorptions sim-
ilar in energy and intensity to those that we have
reported for other three-legged piano stool rutheniu-
m(II) complexes [38]. Upon progressive oxidation of 9b
to 9b+ in CH2Cl2 at −55 °C, and a constant applied
potential of 1.2 V, a series of new bands appear and
grow to their limiting intensities (Fig. 11). These new
absorptions occur at 8.1 k Kaysers (kK) (m=3×10−3
l mol−1 cm−1), 11.1 kK (m=7×103 l mol−1 cm−1),
18.1 kK (m=7×103 lN mol−1 cm−1), 20.6 kK (m=
1.3×104 l mol−1 cm−1) and 25.9 kK (m=3.3×104 l
mol−1 cm−1). Oxidation creates a low-lying hole on
the metal center. A d-orbital splitting diagram, based
upon descent in symmetry from an octahedral parent-
age, is shown in Fig. 12. As illustrated in this diagram,
eight fully allowed dꢀd transitions could arise for this
complex cation. However, the formally dxy“dxz and
dyz“dxz transitions would be expected to occur near 3
kK and are thus too low in energy to appear in the
region investigated. The new low-energy absorptions
for this rather electropositive Ru(III) complex are in the
region anticipated for ligand-to-metal charge transfer
(LMCT) rich in As/P“Ru(III) character (8.1 and 11.1
kK). Both LMCT, especially Cl“Ru(III) and dꢀd
excitations are anticipated to occur in the visible/near
UV region (viz. 18.1, 20.6 and 25.9 kK) (see Fig. 12),
with extensive mixing and/or intensity stealing in this
low symmetry complex. The most intense band (36.5
kK) is probably dominated by a ligand based p/p*
Fig. 12. Splitting diagram (d-orbital) for 9b based upon descent in
symmetry from an octahedral parent. The eight possible d–d elec-
tronic transitions are indicated by arrows on the diagram.

P.A. Gugger et al. / Journal of Organometallic Chemistry 643–644 (2002) 136–153
151
cation. Few EPR spectra of ruthenium(III) complexes
exhibit this much detail [39].
The configurational stability of the ruthenium stere-
ocenter in 9b during redox cycling was probed by
circular dichroism spectroscopy. Figs. 14 and 15 show
the circular dichroism spectra of 9b and of 9b+ formed
by exhaustive oxidation at 1.2 V. Comparison of Figs.
11 and 15 affirms the location of transitions observed
only as shoulders in the electronic spectrum (Fig. 11),
and reveals long-wavelength features that are too weak
to be resolved in the optical spectra of d6 9b. Several of
the transitions in Fig. 15 are metal centered and
demonstrate that the Ru(III) ion in 9b+ still has a
single absolute configuration. Epimerization does not
occur upon oxidation at low temperature. A difference
spectrum is also shown in Fig. 14. This trace represents
the difference between the spectrum of pristine 9b and
a solution of 9b after exhaustive electrolytic oxidation
and reduction, all at low temperature. The spectrum
Fig. 13. First derivative EPR spectrum obtained on a 1.2 mM CH2Cl2
solution of 9b at 5 K that had been exhaustively oxidized at 1.2 V.
The inset shows an expanded second derivative in the gz region.
Modulation amplitude=2G, microwave power=0.2 mW.
Fig. 14. Circular dichroism spectrum of 9b in CH2Cl2 (solid line),
baseline (dotted line), and difference spectrum (dashed line).
transition since a similar band is present in the spectra
of divalent 9b and the corresponding palladium com-
plex, 8b.
In order to better establish that a low-spin rutheniu-
m(III) cation is indeed the product of one-electron
oxidation of 9b, the compound was exhaustively oxi-
dized at 1.2 V and the EPR spectrum shown in Fig. 13
was obtained. The EPR spectrum (rhombic) may be
interpreted [39] to indicate that the unpaired electron is
principally localized on ruthenium in an unsymmetrical
environment. This interpretation is supported by the
observation of three g values, and the observation of
hyperfine coupling to 99Ru (I=5/2, 12.72% natural
abundance and 101Ru (I=5/2, 17.07%) natural abun-
dance on gy of 30 gauss. The observation of equivalent
superhyperfine coupling to 75As (I=3/2) and 31P (I=1/
2), both 100% natural abundance, on gz of 25 gauss
shows that the RuꢀP and RuꢀAs bonds remain intact
on the EPR time scale and confirms the importance of
spin delocalization onto the ligands in this tervalent 4d5
Fig. 15. (a) Circular dichroism spectrum of 9b plus NBun4PF6 in
CH2Cl2 (−40 °C) after exhaustive oxidation at 1.2 V. [q]914
=
−5000, [q]620=0, [q]455= −8000, [q]408=0, [q]390= +5000,
[q]378=0, [q]350= −5000, [q]329=0, [q]318= +12,000, [q]280=0,
[q]251= −42000, [q]230=0. (b) UV–vis–NIR spectrum.

152
P.A. Gugger et al. / Journal of Organometallic Chemistry 643–644 (2002) 136–153
References
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stable at low temperature. At room temperature the
ruthenium(II) complex is indefinitely inert to epimeriza-
tion but the oxidized complex, 9b+, decomposes to
unidentified species at temperatures above −20 °C.
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The chiral palladium templates in 2–4 provide fair to
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Diels–Alder cycloadditions between 3,4-dimethyl-1-
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