Isolation of enantiomers of a range of tris(bidentate)ruthenium(II) species using chromatographic resolution and stereoretentive synthetic methods

Article abstract of DOI:10.1002/(SICI)1099-0682(199811)1998:11<1677::AID-EJIC1677>3.0.CO;2-S

A range of chiral building blocks of the type Δ- or Λ-[Ru(PP)₂(CO)₂]²⁺ {pp = bidentate ligands bpy (2,2′-bipyridine), phen (1,10-phenanthroline) and Me₂bpy (4,4′-dimethyl-2,2′-bipyridine)} have been synthesized, and their enantiomeric purity and absolute configurations determined by CD and NMR studies. Decarbonylation using trimethylamine oxide in the presence of the respective pp ligand at room temperature produced the corresponding tris-(bidentate) species [Ru(pp)₃]²⁺ with retention of configuration at the ruthenium(II) centre. A general chromatographic technique for resolution of tris-homoleptic complexes of the type [Ru(pp)₃]²⁺ was investigated, with the absolute configurations of the resolved complexes confirmed by CD studies, and the X-ray structural analyses of Δ-(-)-[Ru(Me₂bpy) ₃]{(-)-O,O′-dibenzoyl-l-tartrate} and Λ-(+)-[Ru(phen)₃]{(+)-O,O′-di-4-toluoyl-d-tartrate}. Resolution is also reported for the analogous species containing three potential bridging ligands, [Ru(bpm)₃]²⁺ and [Ru(HAT)₃]²⁺ (bpm = 2,2′-bipyrimidine; HAT = 1,4,5,8,9,12-hexaazatriphenylene). The versatihty of the chromatographic procedure was demonstrated by the resolution of a series of bis-heteroleptic complexes [Ru(Pp)₂(PP′)]²⁺ (pp′ = dpq (dipyrido[3,2-d:2,3′-f]quinoxaline), dpqc (dipyrido[3,2-a:2,3-d]-6,7,8,9-tetrahydrophenazine), and dppz {dipyrido[3,2-a:2,3′-d]phenazine)}.

Full text of DOI:10.1002/(SICI)1099-0682(199811)1998:11<1677::AID-EJIC1677>3.0.CO;2-S

FULL PAPER
Isolation of Enantiomers of a Range of Tris(bidentate)ruthenium(II) Species
Using Chromatographic Resolution and Stereoretentive Synthetic Methods
Todd J. Rutherforda, Paul A. Pellegrinib, Janice Aldrich-Wrightb, Peter C. Junka, and F. Richard Keene*a
School of Biomedical and Molecular Sciences, James Cook University,a
Townsville, Queensland 4811, Australia
Fax: (internat.) ϩ 61-7/47814600
E-mail: Richard.Keene@jcu.edu.au
Faculty of Business & Technology, University of Western Sydneyb
Macarthur, N. S. W. 2560, Australia
Received March 19, 1998
Keywords: Chirality / Ruthenium / Chiral resolution / Nitrogen heterocycles / Carbonyl complexes
A range of chiral building blocks of the type ∆- or Λ-
[Ru(pp)2(CO)2]2+ {pp
bidentate ligands bpy (2,2Ј-bi-
by CD studies, and the X-ray structural analyses of ∆-(–)-
[Ru(Me2bpy)3]{(–)-O,OЈ-dibenzoyl- -tartrate} and Λ-(+)-
[Ru(phen)3]{(+)-O,OЈ-di-4-toluoyl- -tartrate}. Resolution is
also reported for the analogous species containing three
potential bridging ligands, [Ru(bpm)3]2+ and [Ru(HAT)3]2+
=
l
pyridine), phen (1,10-phenanthroline) and Me2bpy (4,4Ј-
dimethyl-2,2Ј-bipyridine)} have been synthesized, and their
enantiomeric purity and absolute configurations determined
by CD and NMR studies. Decarbonylation using trimeth-
ylamine oxide in the presence of the respective pp ligand at
room temperature produced the corresponding tris-
d
(bpm
= 2,2Ј-bipyrimidine; HAT = 1,4,5,8,9,12-hexaaza-
triphenylene). The versatility of the chromatographic
procedure was demonstrated by the resolution of a series of
bis-heteroleptic complexes [Ru(pp)2(ppЈ)]2+ {ppЈ
= dpq
(bidentate)
species
[Ru(pp)3]2+
with
retention
of
configuration at the ruthenium(II) centre.
A
general
(dipyrido[3,2-d:2,3Ј-f]quinoxaline), dpqc (dipyrido[3,2-a:2,3-
d]-6,7,8,9-tetrahydrophenazine), and dppz {dipyrido[3,2-
a:2,3Ј-d]phenazine)}.
chromatographic technique for resolution of tris-homoleptic
complexes of the type [Ru(pp)3]2+ was investigated, with the
absolute configurations of the resolved complexes confirmed
Introduction
interactions, it is required that they be available in optically
pure form and have known absolute configurations. Gener-
ally, the chiral resolutions of bis(bidentate)- and tris(biden-
tate)ruthenium(II) complexes of polypyridyl ligands have
been achieved by diastereoisomeric salt forma-
tion,[8][10][15][19][20][21][22][23][24] or chromatographic tech-
niques.[15][16][25][26][27][28][29][30][31] The absolute configura-
tion of a number of these enantiomeric forms have been
assigned by exciton analysis of their circular dichroism
(CD) spectra,[19][32][31][32][33][34][35][36] although more re-
cently X-ray analyses have unambiguously confirmed the
absolute configurations of Λ-[Ru(bpy)2(py)2]2ϩ[37] and Λ-
Ruthenium(II) complexes of polypyridyl ligands have re-
ceived considerable attention as potential chromophoric
components in photochemical molecular devices,[1] largely
as a consequence of their synthetic versatility, and favour-
able photophysical and redox properties.[2][3][4]
For polynuclear assemblies based on such octahedral me-
tal centres, stereoisomerism may occur by virtue of chirality
or geometrical isomerism in the individual components,
particularly when bidentate ligands are involved.[5][6][7]
Since the initial chiral resolution of [Ru(bpy)3]2ϩ (bpy ϭ
2,2Ј-bipyridine),[8][9][10] increasing attention has been drawn
to the stereochemistry of this species and its analogues as a
result of the differential interactions of the enantiomeric
forms {e.g. of ∆- and Λ-[Ru(phen)3]2ϩ (phen ϭ 1,10- of
[Ru(phen)3]2ϩ [38]
.
We recently communicated details of the chiral resolution
a
series of dicarbonyl complexes of the type
phenanthroline)} with certain biological molecules such as [Ru(pp)2(CO)2]2ϩ {where pp ϭ bpy, phen, and Me2bpy (ϭ
DNA or oligonucleotides.[11][12][13][14] Additionally, the chi- 4,4Ј-dimethyl-2,2Ј-bipyridine)} and demonstrated their po-
ral resolution of [Ru(pp)2(BL)]2ϩ [15]
(BL)]2ϩ [16]
,
[Ru(pp)(ppЈ)- tential as chiral building blocks in the stereoselective syn-
{pp ϭ bidentate polypyridyl ligand and BL ϭ thesis of oligonuclear assemblies with predetermined stereo-
,
bridging ligand}, [Ru(pp)2(X)2]nϩ {X ϭ py, CO, ClϪ, and chemistry.[15] We now report in detail the chiral resolution
CNϪ},[15][17][18][19][20] and [Ru(pp)(ppЈ)(py)2]nϩ[16] species procedures and assignment of their absolute configurations,
have also been investigated in terms of their potential use an NMR method of determining their optical purity, and
as chiral building blocks for oligonuclear assemblies with the stereochemical consequences of their decarbonylation
predetermined stereochemistry.[6][7]
reactions. Also discussed is the development of a general
In the utilization of these species as chiral building blocks chromatographic resolution technique for a variety of tris-
in stereoselective syntheses, or in the investigation of chiral (bidentate)ruthenium(II) species and the factors which in-
Eur. J. Inorg. Chem. 1998, 1677Ϫ1688
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T. J. Rutherford, P. A. Pellegrini, J. Aldrich-Wright, P. C. Junk, F. R. Keene
FULL PAPER
fluence this resolution procedure. X-ray structural analyses tions: a non-polar solvent such as [D2]dichloromethane is
of
∆-(Ϫ)-[Ru(Me2bpy)3]{(Ϫ)-O,OЈ-dibenzoyl--tartrate} preferable in such studies,[40] but for solubility reasons
and Λ-(ϩ)-[Ru(phen)3]{(ϩ)-O,OЈ-di-4-toluoyl--tartrate} [D3]acetonitrile was required for the former two complexes.
were used in combination with CD studies to confirm the For all three dicarbonyl complexes, chemical shift discrimi-
absolute configurations of the tris(bidentate) species.
nations between the enantiomeric forms were observed
upon the addition of tris[3-(trifluoromethylhydroxymethyl-
ene)-d-camphorato]europium(III), Eu(tfc)3, with the largest
and most pronounced effects occurring for [Ru(Me2bpy)2-
(CO)2]Cl2 measured in [D2]dichloromethane solution.
The effect of the sequential addition of Eu(tfc)3 on the
1H-NMR spectrum of [Ru(bpy)2(CO)2]Cl2 is shown in Fig-
ure 2, where all the protons exhibited an induced downfield
chemical shift of a magnitude influenced by their environ-
ment. The distinction between the enantiomers can be seen
most clearly by comparison of the H3Ј and H5Ј proton res-
onances in Figures 2d and 2e (the racemate and a sample
enriched in the Λ-(ϩ) form, respectively, under similar con-
ditions).
Results and Discussion
Dicarbonyl Species
Stereochemistry
Chiral resolutions of the cations [Ru(bpy)2(CO)2]2ϩ
,
[Ru(phen)2(CO)2]2ϩ
,
and [Ru(Me2bpy)2(CO)2]2ϩ were
achieved by conventional diastereoisomeric salt formation
as the antimonyl-(ϩ)- or -(Ϫ)-tartrate salts. The CD spectra
of the Λ-(ϩ)- and ∆-(Ϫ)-[Ru(phen)2(CO)2](PF6)2 and Λ-
(ϩ)- and ∆-(Ϫ)-[Ru(bpy)2(CO)2](PF6)2 are shown in Figure
1; assignments of the absolute configurations of the three
cations are discussed below.
Figure 1. CD spectra of the enantiomeric forms of
[Ru(bpy)2(CO)2]2ϩ; ∆ (ᎏ᎐) and Λ (······), and [Ru(phen)2(CO)2]2ϩ
∆ (------) and Λ (-··-··-··)
;
The complexes [Ru(phen)2(CO)2]Cl2 and [Ru(Me2bpy)2-
(CO)2]Cl2 also showed an induced downfield chemical shift
and chiral descrimination. Intersection of initial and final
slopes in plots of the induced perturbation in chemical shift
as a function of added [Eu(tfc)3] for [Ru(phen)2(CO)2]Cl2
and [Ru(bpy)2(CO)2]Cl2 indicated a ca. 1:1 adduct with the
shift reagent. For the complex [Ru(Me2bpy)2(CO)2]Cl2, the
ratio of shift reagent to complex exceeded unity.
Figure 2. The effect of [Eu(tfc)3] on the 1H-NMR (300 MHz;
Cation-exchange chromatography utilizing a chiral eluent
CD3CN) spectrum of [Ru(bpy)2(CO)2]Cl2; {a ϭ no Eu(tfc)3; b ϭ
{e.g. sodium (Ϫ)-O,OЈ-dibenzoyl--tartrate}[15] was at- 0.25 equiv.; c ϭ 0.6 equiv.; d ϭ 1 equiv.; e ഠ 1 equiv.; sample
1
enriched in Λ isomer}; H labelling scheme shown in text}
tempted as a resolution procedure but was found to be ex-
perimentally difficult due to the colourless character of
these dicarbonyl complexes.
Chiral Lanthanide-Shift Reagent Studies
1H-NMR techniques have provided an accurate and de-
finitive method for the determination of enantiomeric pu-
rity of a variety of ruthenium(II) complexes of polypyridyl
ligands. Such studies involve the addition to the complex of
a chiral lanthanide-induced shift reagent[15][20][39][40][41][42]
or tartrate derivative,[28] which causes a discrimination in
the chemical shifts between the two enantiomeric forms. In
the present work, the lanthanide-shift reagent studies of
[Ru(pp)2(CO)2]Cl2 (pp ϭ bpy, phen, and Me2bpy) were per-
formed in [D3]acetonitrile or [D2]dichloromethane solu-
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Eur. J. Inorg. Chem. 1998, 1677Ϫ1688

Isolation of Enantiomers of a Range of Tris(bidentate)ruthenium(II) Species
FULL PAPER
Stereochemical Consequences of the Decarbonylation Reac- idyl ligands occurred at 25°C, but isomerization took place
tion
at elevated temperatures.[44]
The stereochemical consequences of the decarbonylation
reaction with trimethylamine N-oxide (TMNO) were inves-
tigated by treating the enantiomerically pure Λ-(ϩ)-
Absolute Configuration Determinations
Assignment of the absolute configurations of (ϩ)- and
[Ru(phen)2(CO)2]2ϩ, ∆-(Ϫ)-[Ru(bpy)2(CO)2]2ϩ and Λ-(ϩ)- (Ϫ)-[Ru(phen)2(CO)2]2ϩ and (ϩ)- and (Ϫ)-[Ru(bpy)2-
[Ru(Me2bpy)2(CO)2]2ϩ species (see below for absolute con- (CO)2]2ϩ was achieved by their reaction with a third biden-
figuration assignments) with the ligands phen, bpy, and tate ligand to yield a tris(bidentate) product of known chir-
Me2bpy under a variety of conditions, as given in Table 1. ality. To ensure the decarbonylation reactions occurred with
The [Ru(pp)3]2ϩ products from the reactions were isolated complete retention of configuration, the reactions were per-
and the corresponding [α]D values compared with those of formed at room temperature and in subdued light (see
the independently fully resolved products, allowing an as- above). The decarbonylation of (Ϫ)-[Ru(bpy)2(CO)2]2ϩ with
sessment of the enantiomeric excess (ee) of the products TMNO in 2-methoxyethanol in the presence of a 10-fold
1
formed under the various decarbonylation conditions. H- excess of bpy yielded the product ∆-(Ϫ)-[Ru(bpy)3]2ϩ[36]
NMR techniques utilizing the chiral shift reagent [Eu(tfc)3] with [α]D ϭ Ϫ816 (compared with the literature value of
were also used to confirm these ee determinations.
Ϫ819[9]). This observation established a ∆ configuration for
Previous studies[15][43] of the decarbonylation reactions of (Ϫ)-[Ru(bpy)2(CO)2]2ϩ and confirmed complete retention
enantiomerically-enriched [Ru(bpy)2(CO)2]2ϩ indicated that of configuration under those decarbonylation reaction con-
the three parameters which most significantly influenced ditions.
the degree of stereoretention were temperature, solvent and
The absolute configuration of Λ-(ϩ)-[Ru(phen)3]2ϩ has
ligand concentration. In order to maintain chiral integrity been assigned by CD [36] and X-ray crystallographic stud-
during the decarbonylation process, reaction conditions in- ies[38] and confirmed in the present work. It was formed by
volved use of the solvent 2-methoxyethanol, ligand concen- decarbonylation of (ϩ)-[Ru(phen)2(CO)2]2ϩ in the presence
trations of ca. 10-fold or higher excess and low reaction of phen, but otherwise under identical conditions to those
temperatures. Photoracemization was not observed, but described above for the formation of ∆-(Ϫ)-[Ru(bpy)3]2ϩ
light was excluded in this study as a precaution.[15][43]
thus indicating the Λ configuration for (ϩ)-[Ru(phen)2-
,
Table 1. Stereochemical consequences of the decarbonylation reactions of ∆- or Λ-[Ru(pp)2(CO)2]2ϩ {where pp ϭ phen, bpy, or Me2bpy}
[Ru(pp)2(CO)2]2ϩ
precursor
Reaction
[Ru(pp)3]2ϩ
product [α]D
Column resolution
[α]D
Literature[b]
[α]D
Enantiomeric
excess (ee)
conditions[a]
Λ-(ϩ)-[pp ϭ phen]
25°C
45°C
ϩ1395
ϩ1330
ϩ1134
ϩ980
ϩ1400
ϩ1340
> 0.99
0.95
60°C
0.82
120°C
200°C[c]
25°C
0.74
0.70
ϩ938
∆-(Ϫ)-[pp ϭ bpy]
Ϫ816
Ϫ823
Ϫ819
> 0.99
0.50
120°C
120°C[d]
25°C
Ϫ254
Ϫ300
0.53
Λ-(ϩ)-[pp ϭ Me2bpy]
ϩ1000[e]
ϩ920[e]
ϩ1045[e]
0.96
120°C
0.88
[a] All reactions were performed in subdued light using 2-methoxyethanol as solvent, with 10-fold excess of pp and 3-fold excess of TMNO
[b]
[c]
unless otherwise specified. Ϫ
Optical rotations measured in water as ClϪ or IϪ salt for phen and bpy, respectively. Ϫ
Reaction
conditions of ethylene glycol as solvent and heating under microwave conditions. Ϫ [d] Reaction conditions of 30-fold excess of bpy, 20-
fold excess of TMNO and 2-methoxyethanol as solvent. Ϫ
[e]
Ϫ
Optical rotations measured as PF6 salts in CH3CN as solvent at λ ϭ
546 nm.
All reactions were observed to proceed with complete or (CO)2]2ϩ (see above). The product showed [α]D ϭ ϩ1395
near-complete retention of configuration at room tempera- compared with the literature value of ϩ1340.[10]
ture, whereas racemization occurred to varying degrees for
The decarbonylation of (ϩ)-[Ru(Me2bpy)2(CO)2]2ϩ un-
all complexes at elevated temperatures. The most likely der the same conditions described above but in the presence
stage at which racemization might occur is subsequent to of Me2bpy yielded the Λ-(ϩ)-[Ru(Me2bpy)3]2ϩ product
the removal of one carbonyl group, when competition for (configuration determined by X-ray structural determi-
the “free” (or solvated) coordination site may occur be- nation, Figure 4). The synthesized Λ-(ϩ)-[Ru(Me2bpy)3]2ϩ
tween the uncoordinated nitrogen of an incoming mono- showed [α]546 ϭ ϩ1000 compared to the independently re-
dentate pp ligand and a rearrangement involving one of the solved (ϩ)-[Ru(Me2bpy)3]2ϩ complex (see below) where
coordinated bidentate pp ligands. The extent of racemiz- [α]546 ϭ ϩ1045, which may suggest that minor racemization
ation during the decarbonylation reaction agrees with work (< 4%) occurs under the above reaction conditions.
previously completed by the authors, which demonstrated
The electronic spectrum of [Ru(phen)2(CO)2]2ϩ exhibited
that retention of geometric integrity of an analogous dicar- a strong absorption band at ca. 275 nm which is assigned
bonyl complex incorporating two non-symmetrical polypyr- to an intraligand πǞπ* transition, while the weak bands at
Eur. J. Inorg. Chem. 1998, 1677Ϫ1688
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T. J. Rutherford, P. A. Pellegrini, J. Aldrich-Wright, P. C. Junk, F. R. Keene
FULL PAPER
340 and 350 nm are most likely to be dπǞπ* tran- termination of the absolute configuration of ∆-(Ϫ)-
sitions.[45][46] The intense circular dichroism band at ca. 280 [Ru(Me2bpy)3]2ϩ is discussed below). The Cotton effects of
nm (phen long-axis polarization transition) for (ϩ)- the three complexes [Ru(pp)3]2ϩ (pp ϭ bpy, Me2bpy, and
[Ru(phen)2(CO)2]2ϩ is strongly positive and the circular Me4bpy) were near identical, as expected because of their
dichroism band at higher energy (ca. 260 nm) negative (Fig- electronic and structural similarity.
ure 1), confirming the (ϩ) isomer as having the Λ abso-
Figure 3. CD spectra of the enantiomeric forms of
lute configuration.[33]
[Ru(Me2bpy)3]2ϩ; ∆ (······) and Λ (ᎏ᎐), and [Ru(Me4bpy)3]2ϩ
∆ (-··-··-··) and Λ (------)
;
The electronic spectrum of [Ru(bpy)2(CO)2]2ϩ was domi-
nated by πǞπ* transitions in the region of ca. 200Ϫ300
nm.[45][46] The long-axis polarized transitions of bpy occur
at ca. 300 nm:[33] the CD band at 315 nm for the (ϩ)-en-
antiomer is strongly positive and the high energy band at
300 nm is negative (Figure 1), confirming the assignment
as Λ-(ϩ)-[Ru(bpy)2(CO)2]2ϩ
. For the complexes [Ru-
(bpy)2(CO)2]2ϩ and [Ru(phen)2(CO)2]2ϩ, the lower energy
long-axis polarized transitions were red-shifted relative to
those reported for the [Ru(pp)2(py)2]2ϩ analogues,[19][33]
presumably due to the electron-withdrawing carbonyl li-
gands. Accordingly, the two methods used to determine the
absolute configurations of the chirally resolved dicarbonyl
complexes (i.e. stereoselective syntheses and CD studies)
were in agreement.
Tris(bidentate) Complexes
Chromatographic Resolutions of Tris-homoleptic
Tris( bidentate) Species
Stereochemistry
During the course of this study, a chromatographic tech-
In the chromatographic resolutions, large variations in ef-
nique was developed for the resolution of tris(bidentate)ru- ficiencies were observed between the different eluents for
thenium(II) complexes. The technique is based on a cation- the same complex and between different complexes for the
exchange mechanism (SP Sephadex C-25 support) with the same eluent {where a decreased distance for column resolu-
mode of resolution significantly influenced by the differen- tion (“effective column length”, ECL) indicates a more ef-
1
tial association of the chiral anions of the eluent with the ficient resolution}, as shown in Table 2. H-NMR studies
enantiomeric forms of the complex.[30][31] As Sephadex has have suggested that there is a differential association be-
a dextran base and is itself chiral, it believed to significantly tween the above complexes and the anions in the eluent
influence the resolution procedure, as demonstrated by the solutions which involves π-stacking and hydrophobic inter-
chiral resolution of [{Ru(Me2bpy)2}2(µ-bpm)]4ϩ[30] and actions.[30][31] This is further supported by the X-ray
[Ru(bpq)3]2ϩ {bpq ϭ 2,3-bis(2-pyridyl)quinoxaline} with structure of Λ-[Ru(bpy)2(py)2]{(ϩ)-O,OЈ-dibenzoyl--tart-
the achiral eluent sodium toluene-4-sulfonate.[47]
rate}[37] ∆-[Ru(Me2bpy)3]{(Ϫ)-O,OЈ-dibenzoyl--tartrate}
The resolutions of a number of ruthenium(II) complexes and Λ-(ϩ)-[Ru(phen)3]{(ϩ)-O,OЈ-di-4-toluoyl--tartrate};
involving α,αЈ-diimine ligands have recently been reported the latter two are reported herein. The associations leading
using CM and SP Sephadex C-25 and (ϩ or Ϫ)-SbOtart to the chromatographic resolution are believed to involve
salts as eluents.[25][27][28] Generally, these resolution pro- three-way interaction between the complex, the chiral elu-
cedures have required the collection of a series of fractions ent and the Sephadex support.[31]
to obtain the resolved complex. The procedure reported be-
Chromatographic resolution using aqueous sodium (Ϫ)-
low resulted in the clear separation into two bands (i.e. the O,OЈ-dibenzoyl--tartrate as the eluent is significantly more
two enantiomeric forms) of every mononuclear complex efficient in complexes containing methyl-substituted ligands
examined.
The study was based primarily on the resolution of the 30 cm)
{[Ru(bpy)3]2ϩ (ECL ϭ 55 cm) > [Ru(Me2bpy)3]2ϩ (ECL ϭ
>
[Ru(Me4bpy)3]2ϩ (ECL
ϭ
20 cm) or
four tris-homoleptic tris(bidentate) complexes [Ru(pp)3]2ϩ [Ru(Me4bpy)2(bpm)]2ϩ (ECL ϭ 25 cm) > [Ru(Me4bpy)3]2ϩ
(pp ϭ bpy, phen, Me2bpy, and Me4bpy), although a num- (ECL ϭ 20 cm)}. For these complexes in which there is an
ber bis-heteroleptic complexes [Ru(pp)2(ppЈ)]2ϩ were exam- increase in resolution efficiency, it is also noted that there
ined to demonstrate the generality of the resolution pro- is an enhanced rate-of-travel down the column.
cedure. The CD spectra of ∆- and Λ-[Ru(bpy)3]2ϩ and ∆-
While sodium (Ϫ)-O,OЈ-di-4-toluoyl--tartrate is more
and Λ-[Ru(phen)3]2ϩ resolved by the technique were in ex- efficient than sodium (ϩ)-O,OЈ-di-4-toluoyl--tartrate solu-
cellent agreement with the spectra reported previously.[35] tion as an eluent in the resolution of [Ru(bpy)3]2ϩ (ECL ϭ
The CD spectra of ∆-(Ϫ)- and Λ-(ϩ)-[Ru(Me2bpy)3]2ϩ and 30 cm and 55 cm, respectively), the opposite is true for
∆- and Λ-[Ru(Me4bpy)3]2ϩ are shown in Figure 3 (the de- [Ru(Me2bpy)3]2ϩ (ECL ϭ 80 cm and 30 cm, respectively)
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Eur. J. Inorg. Chem. 1998, 1677Ϫ1688

Isolation of Enantiomers of a Range of Tris(bidentate)ruthenium(II) Species
FULL PAPER
Table 2. Chromatographic resolution efficiency for a range of polypyridyl complexes of ruthenium(II)
Effective column length (ECL)[a]
Complex
sodium (Ϫ)-O,OЈ-di-
benzoyl--tartrate[b]
sodium (ϩ)-O,OЈ-di-
benzoyl--tartrate[b]
sodium (Ϫ)-O,OЈ-di-
p-toluoyl--tartrate[b]
sodium (ϩ)-O,OЈ-di-
p-toluoyl--tartrate[b]
[Ru(bpy)3]2ϩ
55
30
120
65
[Ru(bpy)2(Me2bpy)]2ϩ
[Ru(Me2bpy)2(bpy)]2ϩ
[Ru(Me2bpy)3]2ϩ
70
30
70
20
25
60
45
50
> 120
24
80
80
40
22
25
> 120
[Ru(phen)3]2ϩ
[Ru(Me4bpy)3]2ϩ
[Ru(Me4bpy)2(bpm)]2ϩ[15]
[Ru(bpm)3]2ϩ
[Ru(Me4bpy)(phen)(bpm)]2ϩ[16]
[Ru(HAT)3]2ϩ
[Ru(bpy)2(HAT)]2ϩ[48]
[Ru(phen)2(HAT)]2ϩ[48]
> 400
ca. 300
200
[a] ECL given in cm; error ± 2.5 cm. Ϫ [b] Eluent concentrations at 0.075 .
and [Ru(Me4bpy)3]2ϩ (ECL ϭ 40 cm and 20 cm, respec- dent of the eluent or its chirality. This is presumably a result
tively). The apparent anomaly may arise from increased of the increased hydrophobic interactions between the Se-
steric interactions between the toluoyl substituent in the phadex support and the methyl-substituted ligands, leading
anion and the methyl substituents on the ligands, which to the chirality of the Sephadex dominating the elution or-
diminish the association between the eluent anion and the der of the enantiomeric forms. For the elution order of the
substrate cation and thus reduce the degree of chiral dis- enantiomers of [Ru(bpy)3]2ϩ and [Ru(phen)3]2ϩ to be de-
crimination.
pendent on the chirality of the eluent, the interaction be-
Chromatographic resolution using sodium (ϩ)-O,OЈ-di- tween the complex and the eluent must be significantly
4-toluoyl--tartrate solution as the eluent is also more ef- greater than the interaction of the enantiomeric forms with
ficient for resolution of complexes with increased numbers the Sephadex support. The involvement of the support in
of methyl-substituted ligands, although not with the same the chromatographic resolution of dinuclear complexes has
predicability as in the case above {e.g. [Ru(bpy)3]2ϩ (ECL ϭ also been reported previously.[30] These simultaneous inter-
120 cm) > [Ru(bpy)2(Me2bpy)]2ϩ (ECL ϭ 65 cm) ഠ actions of the target cation with the support itself and the
[Ru(bpy)(Me2bpy)2]2ϩ (ECL ϭ 70 cm) compared with chiral anion of the eluent may be cooperative or in oppo-
[Ru(Me4bpy)3]2ϩ (ECL > 120 cm)}. The apparent anomaly sition, with the consequence that the two enantiomeric
in the resolution efficiency of [Ru(Me4bpy)3]2ϩ may also forms of the eluent have unequal efficiencies in achieving
have its origins in competing steric interactions, as de- the resolution of a particular substrate.
scribed above.
The study demonstrates the effectiveness of the technique
The degree of aromaticity of the polypyridyl ligand also for the chiral resolution of tris(bidentate) polypyridyl com-
has a significant influence in the resolution efficiency. For plexes of ruthenium, and provides an appreciation of the
example, the resolution of [Ru(phen)3]2ϩ was significantly factors involved for efficient chiral resolution in terms of
more efficient than [Ru(bpy)3]2ϩ using both the (ϩ)-tartrate the nature of the interactions between the complex, Se-
salts as eluents.
phadex support and the chiral eluent.
The order of elution of the two enantiomeric forms was
also observed to be significantly influenced by the chirality
of the eluent. For example, elution of the complex
X-ray Structural Studies
The X-ray crystal structures of (Ϫ)-[Ru(Me2bpy)3]{(Ϫ)-
[Ru(bpy)3]2ϩ with sodium (Ϫ)-O,OЈ-di-4-toluoyl--tartrate O,OЈ-dibenzoyl--tartrate}·6 H2O (1; Figure 4) and (ϩ)-
solution or sodium (Ϫ)-O,OЈ-dibenzoyl--tartrate solutions [Ru(phen)3]{(ϩ)-O,OЈ-di-4-toluoyl--tartrate}·8 H2O (2;
resulted in resolution with the first eluted band (Band 1) as Figure 5) are reported. The incorporation of an anion of
the ∆-(Ϫ) enantiomer and the second eluted band (Band 2) known chirality allowed ready and unambiguous assign-
as Λ-(ϩ) enantiomer. This elution order is reversed when ment of the absolute configuration of the respective cations
eluting with aqueous sodium (ϩ)-O,OЈ-di-4-toluoyl--tar- as ∆ and Λ. Such assignments are significant: while there
trate and sodium (ϩ)-O,OЈ-dibenzoyl--tartrate (Table 3). have been a number of structural determinations of tris(bid-
This observation suggests the ∆ enantiomer of the complex entate)ruthenium(II) complexes containing polypyridyl li-
has a higher degree of association with the (Ϫ) forms of the gands, a vast majority have involved racemic samples. There
two anions, reducing its effective charge (relative to the Λ are in fact very few structural confirmations of chirality
enantiomer), and thus leading to the resolution.
within complexes of this genre, and in view of recent inter-
However, this “band switching” was not observed in the est in the control of the stereochemistry of polymetallic as-
complexes containing ligands with one or more methyl-sub- semblies incorporating such centres as components,[6][7][49]
stituents (e.g. [Ru(bpy)2(Me2bpy)]2ϩ and [Ru(Me2bpy)3]2ϩ); such confirmations are timely. In this case, the determi-
in those cases the (Ϫ)-enantiomer was eluted first indepen- nation of the chirality of the (ϩ)-[Ru(phen)3]2ϩ cation as Λ
Eur. J. Inorg. Chem. 1998, 1677Ϫ1688
1681

T. J. Rutherford, P. A. Pellegrini, J. Aldrich-Wright, P. C. Junk, F. R. Keene
FULL PAPER
Table 3. Chromatographic elution order for the enantiomeric forms of [Ru(pp)2(ppЈ)]2ϩ and [Ru(pp)3]2ϩ with various resolving agents as
eluents
Elution order of the enatiomeric forms
Complex
Elution band
(Band 1 eluted
first)
sodium (Ϫ)-O,OЈ-
dibenzoyl--
tartrate[a]
sodium (ϩ)-O,OЈ-
dibenzoyl--
tartrate[a]
sodium (Ϫ)-O,O-
di-p-toluoyl--
tartrate[a]
sodium (ϩ)-O,O-
di-p-toluoyl--
tartrate[a]
[Ru(bpy)3]2ϩ
Band 1
Band 2
Band 1
Band 2
Band 1
Band 2
Band 1
Band 2
Band 1
Band 2
Band 1
Band 2
∆-(Ϫ)
Λ-(ϩ)
∆-(Ϫ)
Λ-(ϩ)
Λ-(ϩ)
∆-(Ϫ)
∆-(Ϫ)
Λ-(ϩ)
∆-(Ϫ)
Λ-(ϩ)
∆-(Ϫ)
Λ-(ϩ)
Λ-(ϩ)
∆-(Ϫ)
∆-(Ϫ)
Λ-(ϩ)
[Ru(bpy)2(Me2bpy)]2ϩ
[Ru(Me2bpy)2(bpy)]2ϩ
[Ru(Me2bpy)3]2ϩ
[Ru(phen)3]2ϩ
∆-(Ϫ)
Λ-(ϩ)
∆-(Ϫ)
Λ-(ϩ)
∆-(Ϫ)
Λ-(ϩ)
∆-(Ϫ)
Λ-(ϩ)
Λ-(ϩ)
∆-(Ϫ)
∆-(Ϫ)
Λ-(ϩ)
∆-(Ϫ)
Λ-(ϩ)
∆-(Ϫ)
Λ-(ϩ)
[Ru(Me4bpy)3]2ϩ
[a] Eluent concentration 0.075 .
confirms earlier CD analyses based on exciton the- Figure 5. X-ray structure of the Λ-(ϩ)-[Ru(phen)3]2ϩ cation in
ory,[32][33][34][35][36] and the recent structural determination
by Maloney and MacDonnell,[38] which utilised the tech-
complex Λ-(ϩ)-[Ru(phen)3]{(ϩ)-O,OЈ-di-4-toluoyl--tartrate}·8
H2O (2); hydrogen atoms have been omitted for clarity
nique of fractal analysis in the assignment. Bond lengths
and angles are typical for such complexes.[38][50][51][52][53]
Figure 4. X-ray structure of one of the unique ∆-(Ϫ)-
[Ru(Me2bpy)3]2ϩ cations in compound (Ϫ)-[Ru(Me2bpy)3]{(Ϫ)-
O,OЈ-dibenzoyl--tartrate} (1) which resides on a two-fold rotation
axis; hydrogen atoms have been omitted for clarity
˚
line rings varies in the range 3.4Ϫ3.9 A, which is consistent
˚
with π-stacking, for which a spacing of ca. 3.5 A is con-
sidered normal.[54] While this present observation is made
in the solid state, the interaction supports our proposal for
the mode of association of anions with such complexes in
1
solution (based on H-NMR evidence),[30][31] which we as-
The packing diagram for the structure of 2 is shown in
sert is a major contributing factor to the mechanism of sep-
aration of complexes (and their stereoisomers) in cation-
exchange chromatographic techniques involving the organic
counter-anions in the eluents.
Figure 6, and attention is draw to a particular feature. The
[Ru(phen)3]2ϩ cations form layers which alternate with lay-
ers containing water molecules. The (ϩ)-O,OЈ-di-4-toluoyl-
-tartrate anions are positioned such that the tartrate back-
bone (containing the two carboxylate functionalities) reside
in the water layer (hydrophilic), while the toluoyl rings pen-
etrate into a virtually hydrophobic region in the complex
Chiral Resolutions of Heteroleptic Tris( bidentate) Species
To demonstrate the versatility of the chromatographic
cations where they essentially π-stack with the phenanthro- techniques and stereoretentive synthetic procedures, a range
line rings. The distance between the toluoyl and phenantho- of bis-heteroleptic complexes [Ru(pp)2(ppЈ)]2ϩ were also re-
1682
Eur. J. Inorg. Chem. 1998, 1677Ϫ1688

Isolation of Enantiomers of a Range of Tris(bidentate)ruthenium(II) Species
FULL PAPER
Figure 6. Packing diagram for Λ-(ϩ)-[Ru(phen)3]{(ϩ)-O,OЈ-di-4- at the assessment of their potential as photoprobes in sequ-
encing and in cleavage reactions of DNA.[12][13][14]
Analogous bis-heteroleptic complexes [Ru(Me2bpy)2-
(bpy)]2ϩ, [Ru(Me2bpy)(bpy)2]2ϩ, [Ru(Me2bpy)2(phen)]2ϩ
toluoyl--tartrate}·8 H2O (2) showing penetration of the toluoyl
residues of the anion into the hydrophobic cationic layer; the carbo-
xylate groups reside in the hydrophilic layer; water molecules have
been omitted for clarity
,
and [Ru(bpy)(phen)2]2ϩ were also resolved chromatograph-
ically {aqueous sodium (ϩ)-O,OЈ-dibenzoyl--tartrate solu-
tion eluent}. It is also noted that we have previously re-
ported the chromatographic resolution of a tris-heteroleptic
species, [Ru(phen)(Me4bpy)(bpm)]2ϩ, using aqueous so-
dium (Ϫ)-O,OЈ-dibenzoyl--tartrate solution as eluent.[16]
The incorporation of potential bridging ligands such as
2,2Ј-bipyrimidine (bpm) or 1,4,5,8,9,12-hexaazatripheny-
lene (HAT) in such chiral tris(bidentate) metal centres pro-
vides the potential basis of stereochemical control in the
construction of polymetallic ligand-bridged assemblies.[6][7]
In such a context, we also chromatographically resolved the
tris-homoleptic complexes [Ru(bpm)3]2ϩ and [Ru(HAT)3]2ϩ
by these techniques using 0.1  sodium (Ϫ)-O,OЈ-diben-
zoyl--tartrate solution as eluent.
Summary
The chiral building blocks ∆- and Λ-[Ru(pp)2(CO)2]2ϩ
(where pp ϭ bpy, phen, and Me2bpy) were obtained by dia-
stereoisomeric salt formation, and their enantiomeric purity
1
established by H-NMR spectroscopy using the chiral lan-
solved. Each of the complexes [Ru(bpy)2(ppЈ)]2ϩ and
[Ru(Me2bpy)2(ppЈ)]2ϩ {ppЈ ϭ phen (1,10-phenanthroline),
dpq (dipyrido[3,2-d:2,3Ј-f]quinoxaline), dpqc (dipyrido[3,2-
a:2,3-d]-6,7,8,9-tetrahydrophenazine), and dppz {dipy-
rido[3,2-a:2,3Ј-d]phenazine)}, and [Ru(phen)2(ppЈЈ)]2ϩ
(ppЈЈ ϭ dpq, dpqc, and dppz) were resolved by the cation-
exchange chromatographic procedure on SP Sephadex C-25
support using sodium (Ϫ)-O,OЈ-dibenzoyl--tartrate solu-
tion as eluent. Aqueous K (ϩ)-SbOtart solution was also
used as eluent for the resolution of [Ru(phen)2(dpqc)]2ϩ
and [Ru(phen)2(dppz)]2ϩ. Additionally, [Ru(bpy)2(dpqc)]2ϩ
and [Ru(bpy)2(dppz)]2ϩ were also obtained in specific en-
antiomeric forms by the reaction of the respective ligands
thanide-shift reagent [Eu(tfc)3]. These species were demon-
strated to undergo decarbonylation to form tris(bidentate)
complexes with retention of stereochemical integrity under
certain reaction conditions. Their absolute configurations
were established by comparison of the configuration of the
products with the the X-ray crystal structure determi-
nations
of
the
diastereoisomeric
salts
∆-(Ϫ)-
[Ru(Me2bpy)3]{(Ϫ)-O,OЈ-dibenzoyl--tartrate} and Λ-(ϩ)-
[Ru(phen)3]{(ϩ)-O,OЈ-di-4-toluoyl--tartrate}, and com-
parison of CD spectra with compounds whose configura-
tion has previously assigned by exciton analysis.
The development of a cation-exchange chromatographic
resolution procedure provided an efficient means of ob-
taining a wide range of enantiomerically-pure tris(biden-
tate)ruthenium(II) complexes containing polypyridyl li-
gands, which have application as chiral building blocks for
oligomeric assemblies, or as chiral probes for biological
molecules (e.g. polynucleotides, DNA).
with resolved [Ru(bpy)2(py)2]2ϩ [19]
.
This work was supported by the Australian Research Council,
and Research Grants Schemes with both James Cook University
and the University of Western Sydney. We thank Professor R. S.
Vagg for access to the CD facilities at Macquarie University, and
Ms. Sue Butler for measurement of the CD spectra at the Univer-
sity of Wollongong. We are grateful to Dr. Nick Fletcher and Dr.
Brett Yeomans for useful comments on the manuscript.
Experimental Section
Materials, Instrumentation, and Techniques: The following chemi-
cals were used without further purification: 2,2Ј-bipyridine (bpy,
99ϩ%; Aldrich), 1,10-phenanthroline (phen, 99ϩ% anhydrous; Al-
This general method for chiral resolution is significant as
there have been a number of studies of the nature of the
interaction of such complexes with polynucleotides, aimed drich), 4,4Ј-dimethyl-2,2Ј-bipyridine (Me2bpy, 99%; Aldrich),
Eur. J. Inorg. Chem. 1998, 1677Ϫ1688 1683

T. J. Rutherford, P. A. Pellegrini, J. Aldrich-Wright, P. C. Junk, F. R. Keene
FULL PAPER
tris[3-(trifluoromethylhydroxymethylene)-d-camphorato]europium-
X-Ray Crystal Structure Determinations: Crystals of (Ϫ)-
(III) {Eu(tfc)3, 97%; Fluka}, ruthenium(III) chloride hydrate [Ru(Me2bpy)3]{(Ϫ)-O,OЈ-dibenzoyl--tartrate} (1) and (ϩ)-
(RuCl3, 99.9%; Strem), potassium hexafluorophoshate (KPF6,
98%; Aldrich), 2,3-bis(2-pyridyl)pyrazine (dpp, 98%; Aldrich),
[Ru(phen)3]{(ϩ)-O,OЈ-di-4-toluoyl--tartrate} (2) were grown by
slow concentration of aqueous solutions of the respective salts. Un-
2,2Ј-bipyrimidine (bpm, 98ϩ%; Lancaster), sodium hydroxide ique room-temperature diffractometer data sets (T ഠ 295 K; mono-
˚
(BDH), sodium chloride (BDH), sodium toluene-4-sulfonate (95%; chromatic Mo-Kα radiation, λ ϭ 0.71073 A; 2θ/θ scan mode;
Aldrich), potassium antimonyl (ϩ)-tartrate hydrate {K(ϩ)-SbOt-
2Ϫ50°) were measured on an Enraf-Nonius CAD4 diffractometer,
art, 99ϩ%, [α]D ϭ ϩ141; Aldrich}, (Ϫ)-O,OЈ-di-4-toluoyl--tar- yielding No independent reflections, No with I > 3σ(I) being con-
taric acid (98ϩ%, [α]D ϭ Ϫ139; Fluka), (ϩ)-O,OЈ-di-4-toluoyl--
tartaric acid (97%, [α]D ϭ ϩ139; Aldrich), (ϩ)-O,OЈ-dibenzoyl--
tartaric acid (99%, [α]D ϭ ϩ117; Fluka), (Ϫ)-O,OЈ-dibenzoyl--
tartaric acid (99ϩ%, [α]D ϭ Ϫ117; Fluka), tetra-n-butylammonium
bromide (TBABr, 99%; Aldrich), tetra-n-butylammonium iodide
(TBAI, 98ϩ%; BDH) and tetraethylammonium chloride (TEACl,
> 98%; Fluka).
sidered “observed” and used in the large-block least-squares refine-
ments.
For both compounds, anisotropic thermal parameters were re-
fined for all non-hydrogen atoms, except the oxygen atoms of the
hydration water molecules (due to high thermal motion and dis-
order, see below). Hydrogen atoms were placed in calculated posi-
tions and were not refined. Two oxygen atoms in compound 1 were
disordered and were successfully modelled with half occupancies
{O(5w), O(6w), O(7w) and O(8w)}. Likewise in compound 2 two
water molecules were also disordered and were modelled with half
occupancies {O(1w), O(4w), O(5w) and O(7w)}. Conventional re-
siduals R, Rw on F are quoted, statistical weights derivatives of
σ2(I) ϭ σ2(Idiff) ϩ 0.0004σ4(Idiff) being used. Neutral atom complex
scattering factors were employed, and computation was by the
XTAL 3.4 program system, implemented by S. R. Hall.[67] A sum-
mary of crystal data and data collection is compiled in Table 4
and structures are shown in Figures 4 and 5; material deposited
comprises all atomic coordinates and thermal parameters, complete
bond lengths and angles and full non-hydrogen atom geometries.
The ligands dpq,[55] dpqc,[56] and dppz[57] were prepared as re-
ported previously.
[Ru(pp)2Cl2],[58] [Ru(CO)2Cl2]n, [Ru(pp)(CO)2Cl2], and [Ru(pp)2-
(CO)2](PF6)2 pp ϭ Me2bpy, phen, and bpy),[59] [Ru(OH2)6](tol-
uene-4-sulfonate)2,[60] and [Ru(DMSO)4Cl2] (DMSO ϭ dimethyl
sulfoxide)[61] were prepared as reported previously. [Ru(b-
py)3](PF6)2, [Ru(Me2bpy)3](PF6)2, [Ru(bpy)2(Me2bpy)](PF6)2 [Ru(-
Me2bpy)2(bpy)](PF6)2, [Ru(Me4bpy)3](PF6)2 and [Ru(phen)3](PF6)2
were synthesized in a manner similar to the literature methods,[62]
Ϫ
except that they were isolated as the PF6 salts by addition of
KPF6. Their 1H-NMR and electronic spectra were in agreement
with those reported previously.[4][63][64] ∆- and Λ-[Ru(bpy)2(py)2]2ϩ
were obtained by diastereoisomeric salt fomation with the chiral
anion O,OЈ-dibenzoyltartrate, as described previously.[18][19]
Synthetic and Stereochemical Studies
Homoleptic Dicarbonyl Ruthenium( II) Complexes: The [Ru-
(phen)2(CO)2](PF6)2 species was converted to the bromide salt by
metathesis with TBABr in acetone. For 1H-NMR, UV/Vis, and
ORD measurements, the bromide salt was converted to the chloride
by anion-exchange chromatography. [Ru(Me2bpy)2(CO)2](PF6)2
and [Ru(bpy)2(CO)2](PF6)2 were converted to the respective bro-
mide salts by metathesis with TBABr in 2-butanone. The chloride
salts were obtained as described above.
Trifluoromethanesulfonic acid (3 ) was distilled under vacuum
prior to use. Trimethylamine N-oxide hydrate (TMNO, Aldrich)
was sublimed under vacuum at 120°C and stored under argon.
4,4Ј,5,5Ј-Tetramethyl-2,2Ј-bipyridine (Me4bpy) was kindly supplied
by Michael Quagliotto and was prepared according to a literature
method.[16][65] Silver antimonyl (Ϫ)-tartrate {Ag (Ϫ)-SbOtart} and
silver antimonyl (ϩ)-tartrate {Ag (ϩ)-SbOtart} were prepared ac-
cording to a literature method.[66]
1H NMR ([D3]acetonitrile): [ Ru( phen) 2( CO) 2] Cl2: δ ϭ 7.63 [m,
4 H], 8.25 [d, 2 H, J ϭ 9 Hz], 8.29 [dd, 2 H, J ϭ 5.5, 8 Hz], 8.36
[d, 2 H, J ϭ 9 Hz], 8.71 [dd, 2 H, J ϭ 5.5, 1.5 Hz], 9.10 [d, 2 H,
J ϭ 8 Hz], 9.60 [d, 2 H, J ϭ 5 Hz]. [ Ru( bpy) 2(CO)2]Cl2: δ ϭ 7.42
[d, 2 H, J ϭ 5 Hz], 7.51 [ddd, 2 H, J ϭ 8, 6, 1 Hz], 7.94 [ddd, 2
H, J ϭ 8, 6, 1 Hz], 8.22 [td, 2 H, J ϭ 8, 1 Hz], 8.48 [td, 2 H, J ϭ
8, 1 Hz], 8.82 [d, 2 H, J ϭ 8 Hz], 8.96 [d, 2 H, J ϭ 8 Hz], 9.14 [d,
2 H, J ϭ 5 Hz]. Ϫ 1H NMR ([D2]dichloromethane): [ Ru( Me2-
bpy) 2( CO) 2] Cl2: δ ϭ 2.57 [s, 6 H], 2.61 [s, 6 H], 7.37 [m, 4 H],
7.78 [d, 2 H, J ϭ 5.5 Hz], 9.04 [d, 2 H, J ϭ 5.5 Hz], 9.11 [s, 2 H],
9.28 [s, 2 H]. UV/Vis [λ (ε), H2O]: [ Ru( phen) 2( CO) 2] Cl2: 226 nm
(57900), 274 (52100), 305 (15000). [ Ru( bpy) 2( CO) 2] Cl2: 210 nm
(35600), 250 (26200), 306 (24800). [ Ru( Me2bpy) 2( CO) 2] Cl2: 214
nm (43800), 252 (26900), 302 (23300), 312 (22900).
Electronic spectra, elemental analyses, and optical rotations were
recorded as described previously.[48] CD (circular dichroism) spec-
tra were measured using either a Jobin Yvon Dichrograph 6 or a
JASCO-500C spectropolarimeter. Mass spectra were recorded with
a Fisons/VG Biotech Quattra (Altrinchem, U.K.) instrument which
is a tandem mass spectrometer with quadrupoles for MS1 and
MS2, each with a mass range of 4000 amu for single-charged ions,
a
hexapole collision cell and photomultiplier detectors. The
samples were dissolved in acetonitrile (50Ϫ100 pmol/µl).
Chromatographic procedures were carried out using SP Se-
phadex C-25 cation exchanger as the support and aqueous sodium
chloride, sodium toluene-4-sulfonate, sodium (Ϫ)-O,OЈ-dibenzoyl-
-tartrate, sodium (ϩ)-O,OЈ-dibenzoyl--tartrate, sodium (Ϫ)-
O,OЈ-di-4-toluoyl--tartrate or sodium (ϩ)-O,OЈ-di-4-toluoyl--
tartrate solutions as eluents. The tartrate salts were prepared by the
neutralization of the respective acids with sodium hydroxide. The
support was contained in a column approximately 100 cm long ϫ
2 cm diameter and the flow rate was controlled at ca. 1.5 ml/min.
When necessary, the column was sealed enabling the complex to be
recycled several times down its length with the aid of a peristaltic
pump: in these cases, an “effective column length” (ECL) for the
separation represents the length of support travelled by the sample
for visual band separation. All chromatography was carried out in
subdued light.
Λ-[ Ru( phen) 2( CO) 2] {( ϩ) -SbOtart}2 ·3 H2O: [Ru(phen)2-
(CO)2]Br2 (1.369 g, 2.019 mmol) was stirred in the minimum of
distilled water for dissolution, and Ag(ϩ)-SbOtart (1.589 g, 4.038
mmol) added. The mixture was stirred over glass balls for ca. 30
min in subdued light, then filtered through Celite to remove AgBr,
and the filtrate concentrated to dryness. Yield 2.00 g, 90%. Ϫ
C33H26N4O17RuSb2: calcd. C 36.2, H 2.39, N 5.1%; found: C 36.2,
H 2.25, N 5.0%.
(ϩ)-[Ru(phen)2(CO)2]{(ϩ)-SbOtart}2 was dissolved in a mini-
mum volume of hot water and methanol added dropwise until the
appearance of a faint cloudiness. The mixture was stored at 4°C
1684
Eur. J. Inorg. Chem. 1998, 1677Ϫ1688

Isolation of Enantiomers of a Range of Tris(bidentate)ruthenium(II) Species
Table 4. Crystal data and summary of data collection for complexes 1 and 2
FULL PAPER
Compound
(Ϫ)-[Ru(Me2bpy)3]{(Ϫ)-O,OЈ-dibenzoyl--
tartrate}·6 H2O (1)
(ϩ)-[Ru(phen)3]{(ϩ)-O,OЈ-di-4-toluoyl--
tartrate}·8 H2O (2)
Molecular formula
Molecular weight
Crystal system
Space group
C54H60N6O14Ru
1118.2
Monoclinic
C2 (no. 5)
2328
C56H56N6O16Ru
1170.2
Monoclinic
P21 (no. 4)
1212
F( 000)
Cell constants
˚
a [A]
16.520(5)
10.597(2)
˚
b [A]
26.279(2)
24.921(2)
˚
c [A]
15.073(3)
11.634(2)
α [deg]
β [deg]
γ [deg]
90
90
115.47(2)
99.78(1)
90
90
V [A3]
5908(4)
3028.2(8)
˚
Molecules/unit cell (Z)
4
2
Dc [g cmϪ3
]
1.257
1.265
µ [cmϪ1
]
3.3
3.3
A* min., max.
1.107, 1.138
1.125, 1.144
Crystal dimensions [mm]
σ cutoff
0.62 ϫ 0.40 ϫ 0.36
0.42 ϫ 0.42 ϫ 0.38
3σ
2σ
No. reflcections collected ( N)
No. observed reflections (No)
No. parameters varied
R
5326
4128
655
0.058
0.067
5456
3512
680
0.064
0.071
Rw
overnight, the product collected and the precipitation procedure
repeated a further two times. The precipitate was collected and
either converted to the ClϪ salt by anion exchange or precipitated
by the addition of KPF6 to yield [Ru(phen)2(CO)2]Cl2 or [Ru-
37.1, H 2.83, N 5.3; found C 37.4, H 2.72, N 5.3. Ϫ The disas-
teroisomer was recrystallized twice from methanol. The product
was stirred with boiling methanol (ca. 20 ml) and collected by fil-
tration while hot. The precipitate was washed with methanol, ether,
(phen)2(CO)2](PF6)2, respectively. Λ-(ϩ)-[Ru(phen)2(CO)2]Cl2: and air-dried. The product was then converted to the chloride and
[α]365 (water) ϭ ϩ2320, [M]365 (water) ϭ ϩ13640. Λ-(ϩ)-[Ru- hexafluorophosphate salts as described above. (ϩ)-[Ru(Me2bpy)2-
(phen)2(CO)2](PF6)2: CD [λ (∆ε), CH3CN] ϭ 211 nm (Ϫ55), 236 (CO)2]Cl2: [α]365 (water) ϭ ϩ840 and [M]365 (water) ϭ ϩ5006.
(Ϫ40), 262(Ϫ67), 278 (ϩ315), 316 (Ϫ17).
Decarbonylation Reactions of ∆- or Λ-[ Ru( pp) 2( CO) 2] 2ϩ
The enantiomeric form was obtained in an analogous manner,
Λ-( ϩ) -[ Ru( phen) 3] Cl2: (ϩ)-[Ru(phen)2(CO)2](PF6)2 (20 mg,
0.0247 mmol) was dissolved in 2-methoxyethanol (10 ml) and the
solution purged with N2 for 20 min prior to the addition of phen
(44 mg, 0.247 mmol). TMNO (12 mg, 0.116 mmol) was then added
and the reaction mixture stirred at room temperature in subdued
light for 72 h. The reaction mixture was diluted with water and the
product purified by cation exchange chromatography (SP Sephadex
C25, eluent 0.2  NaCl). The orange band was collected and pre-
using Ag(Ϫ)-SbOtart.
∆-(Ϫ)-[Ru(phen)2(CO)2]Cl2: [α]365 (water) ϭ Ϫ2330 and [M]365
(water) ϭ Ϫ13710. ∆-(Ϫ)-[Ru(phen)2(CO)2](PF6)2: CD [λ (∆ε),
CH3CN] ϭ 211 nm (ϩ54), 236(ϩ41), 262 (ϩ70), 278 (Ϫ322), 316
(ϩ19).
∆-[ Ru( bpy) 2( CO) 2] {( ϩ) -SbOtart}2 ·2 H2O: [Ru(bpy)2(CO)2]-
{(ϩ)-SbOtart}2 ·2 H2O was prepared in an identical manner to that
described above, using [Ru(bpy)2(CO)2]Br2 in place of [Ru(phen)2-
(CO)2]Br2. Ϫ C29H24N4O16RuSb2: calcd. C 33.8, H 2.35, N 5.3;
found C 33.8, H 2.31, N 5.3. Ϫ The diastereoisomer was recrys-
tallized four times from methanol, the collected product being
washed with cold methanol, ether, and air-dried. The product was
then converted to the chloride and hexafluorophosphate salts as
described above. ∆-(Ϫ)-[Ru(bpy)2(CO)2]Cl2: [α]365 (water) ϭ Ϫ1020
and [M]365 (water) ϭ Ϫ5570. ∆-(Ϫ)-[Ru(bpy)2(CO)2](PF6)2: CD [λ
(∆ε), CH3CN] ϭ 231 nm (Ϫ13), 244 (ϩ11), 258 (Ϫ46), 278 (Ϫ31),
301 (ϩ22), 319 (Ϫ47), 327 (ϩ9).
Ϫ
cipitated as the PF6 salt by the addition of a saturated solution
of KPF6, which was collected by filtration and washed with water,
ether, and air dried. Yield: 8 mg, 40%. NMR spectra were in agree-
ment with those published previously for [Ru(phen)3]2ϩ [63][68]
Λ-
.
(ϩ)-[Ru(phen)3](PF6)2: [α]546 (CH3CN) ϭ ϩ2000. The complex was
converted to the chloride salt by metathesis from acetone solution
using TEACl. [α]D (water) ϭ ϩ1385; ref.[10][35] ϩ1340.
The above reaction was repeated at a series of temperatures and
reaction times, with all other conditions remaining identical, and
[α]D values measured as the chloride salts in water: 45°C for 24 h;
yield 48%, [α]D ϭ ϩ1330; 60°C for 6 h; yield 62%, [α]D ϭ ϩ1134;
120°C for 3 h; yield 75%, [α]D ϭ ϩ980. Microwave (low power)
using ethylene glycol/10% water for 40 s; yield 78%, [α]D ϭ ϩ938.
The enantiomeric form was obtained in an analogous manner,
using Ag(Ϫ)-SbOtart. Λ-(ϩ)-[Ru(bpy)2(CO)2]Cl2: [α]365 (water) ϭ
ϩ1025 and [M]365 (water) ϭ ϩ5545. Λ-(ϩ)-[Ru(bpy)2(CO)2](PF6)2:
CD [λ (∆ε), CH3CN] ϭ 231 nm (ϩ13), 244 (Ϫ10), 258 (ϩ43), 278
(ϩ31), 301 (Ϫ18), 319 (ϩ45), 327 (Ϫ8).
∆-( -) -[ Ru( bpy) 3] I2: Bpy (30 mg, 0.197 mmol) was dissolved in
2-methoxyethanol (5 ml) and the solution purged with N2 for 20
min. (Ϫ)-[Ru(bpy)2(CO)2](PF6)2 (15 mg, 0.0197 mmol) and TMNO
( ϩ) -[ Ru( Me2bpy) 2( CO) 2] {( ϩ) -SbOtart}2 ·H2O:
[Ru-
(Me2bpy)2(CO)2]{(ϩ)-SbOtart}2 ·H2O was prepared in an identical (10 mg, 0.133 mmol) were added and the mixture stirred at room
manner to that described above using [Ru(Me2bpy)2(CO)2]Br2 in
temperature for 72 h in subdued light, and after addition of water
place of [Ru(phen)2(CO)2]Br2. Ϫ C33H30N4O15RuSb2: calcd. C
purification was achieved as described for Λ-(ϩ)-[Ru(phen)3]Cl2.
Eur. J. Inorg. Chem. 1998, 1677Ϫ1688
1685

T. J. Rutherford, P. A. Pellegrini, J. Aldrich-Wright, P. C. Junk, F. R. Keene
FULL PAPER
Yield: 9 mg, 58%. The NMR spectrum was in agreement with the ECL ഠ 120 (Band 1 positive rotation). Ϫ CD [λ (∆ε), CH3CN]: ∆-
literature.[63][68] The complex was converted to the iodide salt by (Ϫ): 240 nm (24), 257 (Ϫ12), 278 (149), 292 (Ϫ331), 323 (21), 358
metathesis with TBAI in 2-butanone solution. [α]D and [M]D
(12), 418 (23), 469 (Ϫ18); Λ-(ϩ): 240 (Ϫ23), 257 (12), 278 (Ϫ147),
292 (347), 323 (Ϫ20), 358 (Ϫ12), 418 (Ϫ22), 469 (18).
(water) ϭ Ϫ816 and Ϫ6740 respectively; ref.[9][35] [α]D and [M]D
Ϫ819and Ϫ6750, respectively.
ϭ
Λ-( ϩ) /∆-( Ϫ) -[ Ru( Me2bpy) 3] 2ϩ: Chromatographic resolution
was achieved for [Ru(Me2bpy)3]2ϩ using aqueous sodium (Ϫ)-
O,OЈ-dibenzoyl--tartrate solution at ECL ഠ 30 cm, [α]546 and
[M]546 (CH3CN; PF6Ϫ): Band 1 ϭ Ϫ1060 and Ϫ10027 respectively
and Band 2 ϭ ϩ1045 and ϩ9845, respectively; sodium (Ϫ)-O,OЈ-
di-4-toluoyl--tartrate at ECL ഠ 80 cm (Band 1 negative rotation);
and sodium (ϩ)-O,OЈ-di-4-toluoyl--tartrate at ECL ഠ 22 cm
(Band 1 negative). Ϫ CD [λ (∆ε), CH3CN]: ∆-(Ϫ): 231 (54), 260
(Ϫ7), 277 (142), 292 (Ϫ351), 328 (18), 367 (11), 424 (21), 477 (Ϫ17);
Λ-(ϩ): 231 (Ϫ55), 260 (4), 277 (Ϫ141), 292 (357), 328 (Ϫ18), 367
(Ϫ11), 424 (Ϫ21), 477 (19).
Λ-( ϩ) /∆-( Ϫ) -[ Ru( Me4bpy) 3] 2ϩ: Chromatographic resolution
was achieved for [Ru(Me4bpy)3]2ϩ using aqueous sodium (Ϫ)-
O,OЈ-dibenzoyl--tartrate solution at ECL ഠ 20 cm, [α]546 and
[M]546 (CH3CN; PF6Ϫ): Band 1 ϭ Ϫ831 and Ϫ8530 respectively
and Band 2 ϭ 839 and ϩ8631 respectively, and for sodium (Ϫ)-
O,OЈ-di-4-toluoyl--tartrate eluent at ECL ഠ 40 cm (Band 1 nega-
tive rotation), sodium(ϩ)-O,OЈ-di-4-toluoyl--tartrate eluent at
ECL > 120 cm (Band 1 negative). Ϫ CD [λ (∆ε), CH3CN]: ∆-(Ϫ):
234 nm (49), 283 (180), 299 (Ϫ361), 329 (19), 366 (12), 418 (22),
468 (Ϫ17); Λ-(ϩ): 234 (Ϫ48), 283 (Ϫ178), 299 (357), 329 (Ϫ19),
366 (Ϫ12), 418 (Ϫ22), 468 (17).
The above reaction was repeated at 120°C for 3 h with all other
conditions identical; yield 81%, [α]D ϭ Ϫ254.
The above reaction was repeated at 120°C for 3 h with a 30-fold
excess of bpy and 20-fold excess of TMNO with all other con-
ditions identical; yield 85%, [α]D ϭ Ϫ300.
Λ-( ϩ) -[ Ru( Me2bpy) 3] Cl2: (ϩ)-[Ru(Me2bpy)3]Cl2 was formed
by the decarbonylation of (ϩ)-[Ru(Me2bpy)2(CO)2](PF6)2 in the
presence of an excess of Me2bpy, but otherwise under identical con-
ditions to those described for Λ-(ϩ)-[Ru(phen)3]Cl2; yield 40%.
The NMR spectrum was in agreement with that described pre-
viously.[63] Λ-(ϩ)-[Ru(Me2bpy)3](PF6)2 [α]546 (CH3CN) ϭ ϩ972
and [M]546 ϭ ϩ9164. Chromatographically resolved Λ-(ϩ)-[Ru-
(Me2bpy)3](PF6)2 (see below): [α]546 ϭ ϩ1045 and [M]546 ϭ ϩ9845.
(See above for X-ray structural determination of absolute configu-
ration.)
The above reaction was repeated at 120°C for 3 h with all other
conditions identical; yield 84%, [α]D ϭ ϩ920.
Chromatographic Resolutions: The chromatographic resolutions
of the mononuclear complexes were all achieved by cation-ex-
change chromatography (SP Sephadex C-25) using 0.075  solu-
tions of the eluent specified in the text. The impact of the enantio-
meric identity of the eluent anion on the efficiency of the chromato-
graphic resolution procedure {quoted as ECL for the chiral resolu-
tion (cm)}, and on the order of elution of the chiral forms of the
cation (sign of optical rotation quoted at 589 nm, or the sign of ∆ε
from the CD spectra at the MLCT absorption maximum at ca. 450
nm), was investigated by separately examining the resolution of
complex {30 mg} with the eluents sodium (ϩ)- and (Ϫ)-O,OЈ-di-
benzoyltartrate and sodium (ϩ)- and (Ϫ)-O,OЈ-di-4-toluoyltartrate.
( ϩ) /( Ϫ) -[ Ru( Me2bpy) 2( bpy) ] 2ϩ and [ Ru( Me2bpy) ( bpy) 2] 2ϩ
:
Chromatographic resolution was observed for [Ru(Me2bpy)2-
(bpy)]2ϩ and [Ru(Me2bpy)(bpy)2]2ϩ using aqueous sodium (ϩ)-
O,OЈ-di-4-toluoyl--tartrate solution as eluent, where ECL ഠ 65
and 70 cm, respectively (Band 1 negative rotation).
[ Ru( pp) 2( ppЈ) ] ( PF6) 2 {pp ϭ bpy or Me2bpy; ppЈ ϭ phen, dpq,
dpqc, or dppz} and [ Ru( phen) 2( ppЈЈ) ] ( PF6) 2 {ppЈЈ ϭ dpq, dpqc, or
dppz} were synthesized by a literature procedure.[69] The respective
[Ru(pp)2Cl2] precursor in 50% aqueous ethanol was refluxed in the
presence of a slight excess of the third bidentate ligand for 2 h.
Ethanol was evaporated from the solution, which was filtered be-
fore the dropwise addition of a saturated solution of KPF6 to give
an orange precipitate which was collected by filtration, washed with
ice/water, and dried at 100°C. The complexes were purified by chro-
matography on alumina (acetonitrile eluent). the major band col-
lected and concentrated to dryness. Yields were typically in the
range 60Ϫ80%. Mass spectra m/z observed for all species were
within 0.5 amu of the values calculated for [Ru(pp)2(ppЈ)](PF6]ϩ.
1H-NMR spectra were consistent with the complex formulations.
Visible spectra [λmax (MLCT) (ε), CH3CN]: [Ru(bpy)2(phen)]2ϩ 452
(14900); [Ru(bpy)2(dpq)]2ϩ 449 (14500); [Ru(bpy)2(dpqc)]2ϩ 451
(16200); [Ru(bpy)2(dppz)]2ϩ 448 (16400); [Ru(Me2bpy)2(phen)]2ϩ
456 (14100); [Ru(Me2bpy)2(dpq)]2ϩ 439 (13900); [Ru(Me2bpy)2-
(dpqc)]2ϩ 452 (15200); [Ru(Me2bpy)2(dppz)]2ϩ 443 (16100);
[Ru(phen)2(dpq)]2ϩ 446 (17300); [Ru(phen)2(dpqc)]2ϩ 448 (14300);
[Ru(phen)2(dppz)]2ϩ 439 (16100).
∆.Λ-[ Ru( phen) 3] 2ϩ: Chromatographic resolution was achieved
using aqueous sodium (Ϫ)-O-OЈ-dibenzoyl--tartrate solution as
the eluent (ECL ഠ 60 cm). The two bands were collected and the
products isolated as the PF6Ϫ salts by addition of a saturated aque-
ous solution of KPF6. The two products were converted to the
chloride salts by anion exchange. By comparisons with the litera-
ture,[35][38] Band
1 (eluted first) was assigned as ∆-(Ϫ)-
[Ru(phen)3]2ϩ and Band 2 (eluted second) as Λ-(ϩ)-[Ru(phen)3]2ϩ
with [α]D (water) ϭ Ϫ1310 and ϩ1400 respectively (literature val-
ues of Ϫ1330 and ϩ1340).[10] Ϫ CD [λ (∆ε), CH3CN]: ∆-(Ϫ): 227
nm (Ϫ19), 234 (33), 259 (437), 268 (Ϫ602), 296 (Ϫ72), 385 (ϩ7),
419 (15), 464 (Ϫ22); Λ-(ϩ): 227 (10), 234 (Ϫ33), 259 (Ϫ430), 268
(582), 296 (87), 385 (Ϫ7), 419 (Ϫ15), 464 (23).
Elution with sodium (Ϫ)-O,OЈ-dibenzoyl--tartrate, sodium (ϩ)-
O,OЈ-dibenzoyl--tartrate, sodium (Ϫ)-O,OЈ-di-4-toluoyl--tartrate
and sodium (ϩ)-O,OЈ-di-4-toluoyl--tartrate solutions demon-
strated resolution at ECL ഠ 70 cm (Band 1 having a negative and
Band 2 a positive rotation), ECL ഠ 30 cm (Band 1 positive),
ECL ഠ 80 cm (Band 1 negative) and ECL ഠ 25 cm (Band 1 posi-
tive) respectively.
Chiral Resolution of [ Ru( pp) 2( ppЈ) ] 2ϩ Cations: All cations were
chromatographically resolved on SP Sephadex C-25 support using
as eluent aqueous 0.1  sodium (Ϫ)-O,OЈ-dibenzoyl--tartrate solu-
tion containing 5% acetone to maintain complex solubility. In all
cases, two distinct enantiomer bands were observable within
ECL ഠ 1.5Ϫ2 m, and the separated bands were collected after 3
∆.Λ-[ Ru( bpy) 3] 2ϩ: Chromatographic resolution was achieved
for [Ru(bpy)3]2ϩ using aqueous sodium (Ϫ)-O,OЈ-dibenzoyl--tar-
trate solution at ECL ഠ 55 cm {[α]546 (water; IϪ salt) Ϫ Band 1 ϭ m of passage down the column. The enantiomer with a negative
Ϫ824 and Band 2 ϭ ϩ817} (literature values of Ϫ819[9][35]), so-
dium (Ϫ)-O,OЈ-di-4-toluoyl--tartrate at ECL ഠ 30 cm (Band 1
negative rotation) and sodium (ϩ)-O,OЈ-di-4-toluoyl--tartrate at
∆ε in the CD spectrum at the absorption maximum (ca. 450 nm)
was invariably eluted first; by comparison with the CD character-
istics of similar complexes (see above), these were assigned the ∆
1686
Eur. J. Inorg. Chem. 1998, 1677Ϫ1688

Isolation of Enantiomers of a Range of Tris(bidentate)ruthenium(II) Species
FULL PAPER
absolute configuration. CD [λ (∆ε), CH3CN]: [Ru(bpy)2(phen)]2ϩ
zoyl--tartrate solution as the eluent (ECL ഠ 80 cm). The two
∆
380 nm (58), 457 (Ϫ56) and 380 (Ϫ59), 457 (55); bands were collected and precipitated by the addition of a saturated
Λ
[Ru(bpy)2(dpq)]2ϩ ∆ 400 (79), 461 (Ϫ67) and Λ 400 (Ϫ81), 461
(66); [Ru(bpy)2(dpqc)]2ϩ ∆ 412 (62), 468 (Ϫ54) and Λ 412 (Ϫ64),
468 (54); [Ru(bpy)2(dppz)]2ϩ ∆ 395 (64), 461 (Ϫ58) and Λ 395
(Ϫ70), 461 (58); [Ru(Me2bpy)2(phen)]2ϩ ∆ 400 (53), 465 (Ϫ54) and
solution of KPF6, reprecipitated twice from acetone/water solution
by the addition of KPF6, collected, washed with cold water, and
diethyl ether. Comparisons with similar compounds,[15][19][35] Λ-
(ϩ)-[Ru(HAT)3]2ϩ (Band 1) [α]546 ϭ ϩ974 and [α]589 ϭ ϩ623, CD
Λ 400 (Ϫ59), 457 (56.5); [Ru(Me2bpy)2(dpq)]2ϩ ∆ 415 (53.6), 476 [λ (∆ε), CH3CN]: 232 (ϩ8), 250 (Ϫ15), 262 (ϩ4), 282 (Ϫ6), 314
(Ϫ38.8) and Λ 415 (Ϫ54), 476 (40); [Ru(Me2bpy)2(dpqc)]2ϩ ∆ 386 (ϩ48), 406 (Ϫ13), 462 (ϩ12) and ∆-(Ϫ)-[Ru(HAT)3]2ϩ (Band 2)
(51), 464 (Ϫ46) and Λ 386 (Ϫ60), 464 (46); [Ru(Me2bpy)2(dppz)]2ϩ
390 (63), 467 (Ϫ51) and 390 (Ϫ70), 467
[α]546 ϭ Ϫ940 and [α]589 ϭ Ϫ618, CD (λ nm (∆ε), CH3CN): 232
(Ϫ8), 250 (ϩ15), 262 (Ϫ2), 282 (ϩ7), 314 (Ϫ45), 406 (ϩ14), 462
(Ϫ11).
∆
Λ
(51);[Ru(phen)2(dpq)]2ϩ ∆ 396 (30), 456 (Ϫ52) and Λ 396 (Ϫ33),
456 (51); [Ru(phen)2(dpqc)]2ϩ ∆ 407 (40), 467 (Ϫ54) and Λ 407
(Ϫ43), 467 (58); [Ru(phen)2(dppz)]2ϩ ∆ 405 (41), 458 (Ϫ49) and Λ
405 (Ϫ55), 458 (61) {incomplete separation}.
Chiral Lanthanide Shift Reagent Studies: All complexes were
converted to the ClϪ salts for the chiral-lanthanide shift reagent
(CLSR) studies, which were performed on rac- and ∆- or Λ-[Ru(b-
py)2(CO)2]Cl2, [Ru(phen)2(CO)2]Cl2, [Ru(Me2bpy)2(CO)2]Cl2 and
[Ru(Me4bpy)2(CO)2]Cl2 in [D3]acetonitrile for the former two and
[D2]dichloromethane for the latter two complexes. Mol ratios of
[Complex]/[CLSR] varied from 0 to 2, depending on solvent and
complex. Shift reagent studies were also performed on [Ru(Me2-
bpy)3]Cl2 in [D2]dichloromethane and [Ru(Me4bpy)3]Cl2 in
[D2]dichloromethane and [D3]acetonitrile. Complexes were dis-
solved in the solvent at concentrations between 3·10Ϫ2  and
3·10Ϫ3 .
The complexes [Ru(phen)2(dpqc)]2ϩ and [Ru(phen)2(dppz)]2ϩ
could also be separated using aqueous 0.1  potassium antimonyl
(ϩ)-tartrate solution (containing 10% acetone) as eluent (ECL ഠ
3 m).
The enantiomers of the complexes [Ru(bpy)2(dpqc)]2ϩ and
[Ru(bpy)2(dppz)]2ϩ were also obtained by the stereoretentive reac-
tions of ∆- or Λ-[Ru(bpy)2(py)2]2ϩ with dpqc or dppz, in an anal-
ogous manner to that described previously.[18][19]
Synthesis of [ Ru( bpm) 3] ( PF6) 2: [Ru(H2O)6](toluene-4-sulfon-
ate)2[60] (100 mg, 0.079 mmol) and bpm (62 mg, 0.394 mmol) were
added to ethylene glycol (30 ml) and heated in a microwave oven
(medium high) for 45 s. The reaction mixture was diluted with dis-
tilled water and purified by cation-exchange chromatography (SP
Sephadex C-25, 0.2  NaCl). The product was precipitated from
the orange band by addition of KPF6, collected and washed with
[1]
V. Balzani, F. Scandola, Supramolecular Photochemistry, Ellis
Horwood, Chichester, 1991.
[2]
K. Kalyanasundaram, Coord. Chem. Rev. 1982, 46, 159Ϫ244.
[3]
V. Balzani, A. Juris, M. Venturi, S. Campagna, S. Serroni,
Chem. Rev. 1996, 96, 759Ϫ833.
[4]
A. Juris, S. Barigelletti, S. Campagna, V. Balzani, P. Belser, A.
von Zelewsky, Coord. Chem. Rev. 1988, 84, 85Ϫ277.
[5]
A. von Zelewsky, Stereochemistry of Coordination Compounds,
water and diethylether. Yield
ϭ
140 mg, 62%.
Ϫ
Wiley, Chichester, 1995.
[6]
C
24H18F12N12P2Ru: calcd. C 33.3, H 2.09, N 19.4; found: C 33.2,
F. R. Keene, Coord. Chem. Rev. 1997, 166, 122Ϫ159.
[7]
H 2.08, N 19.4. Ϫ UV/Vis data was in agreement with the litera-
F. R. Keene, Chem. Soc. Rev. 1998, 27, 185Ϫ193.
[8]
1
ture.[70] Ϫ H NMR ([D3]acetonitrile): δ ϭ 9.12 (dd, 6 H, J ϭ 5, 2
F. H. Burstall, J. Chem. Soc. 1936, 173Ϫ175.
[9]
F. P. Dwyer, E. C. Gyarfas, J. Proc. Roy. Chem. Soc. N.S.W.
Hz], 8.15 (dd, 6 H, J ϭ 5, 2 Hz], 7.59 (t, 6 H, J ϭ 5.5 Hz].
1949, 83, 174Ϫ176.
[10]
Resolution of [ Ru( bpm) 3] 2ϩ: Resolution was achieved by cation-
exchange chromatography using 0.1  sodium (Ϫ)-O,OЈ-dibenzoyl-
-tartrate as the eluent (ECL ഠ 150 cm). The two bands were col-
lected and the enantiomers precipitated by the addition of a satu-
rated solution of KPF6, reprecipitated twice from acetone/water
solution by the addition of KPF6, collected, washed with cold
water and diethyl ether. Comparisons with similar com-
pounds,[15][19][35] enabled the assignment of ∆-(Ϫ)-[Ru(bpm)3]2ϩ
(Band 1) [α]546 ϭ Ϫ909 and [α]D ϭ Ϫ454, CD [λ (∆ε), CH3CN]:
235 nm (ϩ51), 254 (ϩ45), 268 (Ϫ210), 320 (Ϫ19), 411 (ϩ22), 468
F. P. Dwyer, E. C. Gyarfas, J. Proc. Roy. Chem. Soc. N.S.W.
1949, 83, 170Ϫ173.
[11]
A. Shulman, F. P. Dwyer, Chelating Agents and Metal Chelates
(Eds.: F. P. Dwyer, D. P. Mellor), Academic Press, New York,
1964, pp. 383Ϫ439.
[12]
A. M. Pyle, J. K. Barton, Prog. Inorg. Chem. 1990, 38, 413Ϫ475.
[13]
A. Kirsch-De Mesmaeker, J.-P. Lecomte, J. M. Kelly, Top. Curr.
Chem. 1996, 177, 25Ϫ76.
[14]
R. E. Holmlin, P. J. Dandliker, J. K. Barton, Angew. Chem.
1997, 109, 2830Ϫ2848; Angew. Chem. Int. Ed. Engl. 1997, 36,
2715Ϫ2730.
[15]
T. J. Rutherford, M. G. Quagliotto, F. R. Keene, Inorg. Chem.
1995, 34, 3857Ϫ3858.
(Ϫ14) and Λ-(ϩ)-[Ru(bpm)3]2ϩ (Band 2) [α]546 ϭ ϩ890 and [α]D
ϭ
[16]
B. T. Patterson, F. R. Keene, Inorg. Chem. 1998, 37, 645Ϫ650.
[17]
A. Yamagishi, K. Naing, Y. Goto, M. Taniguchi, M. Takahashi,
ϩ451, CD [λ (∆ε), CH3CN]: 235 nm (Ϫ48), 254 (Ϫ40), 268 (ϩ200),
320 (ϩ19), 411 (Ϫ21), 468 (ϩ14).
J. Chem. Soc., Dalton Trans. 1994, 2085Ϫ2089.
[18]
X. Hua, A. von Zelewsky, Inorg. Chem. 1991, 30, 3796Ϫ3798.
[19]
Synthesis of [ Ru( HAT) 3] ( PF6) 2: [Ru(HAT)3]2ϩ was synthesiszd
in a similar manner to that described by Kirsch-De Mesmaeker et
al.[71] [Ru(DMSO)4Cl2] (65 mg, 0.2 mmol) was dissolved in distilled
water (60 ml) and degassed with N2 for 20 min. HAT (233 mg, 0.99
mmol) was added and the mixture refluxed for 48 h. The reaction
mixture was allowed to cool, then filtered to remove unreacted
HAT. The orange product was purified by cation-exchange chroma-
tography (SP Sephadex C-25, 0.2  NaCl) and collected as de-
scribed above. Yield 140 mg, 64%. Ϫ UV/Vis [λ (ε), CH3CN]: 212
X. Hua, A. von Zelewsky, Inorg. Chem. 1995, 34, 5791Ϫ5797.
[20]
R. T. Watson, J. L. Jackson, J. D. Harper, K. A. Kane-Maguire,
L. A. P. Kane-Maguire, N. A. P. Kane-Maguire, Inorg. Chim.
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