Chiral spiro Cu(I) complexes. Supramolecular stereocontrol and isomerisation dynamics by the use of TRISPHAT anions

Article abstract of DOI:10.1039/b515540a

Association of enantiopure TRISPHAT anion (1) with chiral spiro [Cu(LL′)₂] complexes (LL′ = 2-R-phen, 2, 6-R-bpy, 3, and 2-iminopyridine, 4) leads to an efficient NMR enantiodifferentiation. Variable temperature ¹H NMR spectroscopy has been used to determine the isomerisation kinetics of these pseudo-tetrahedral complexes and to evaluate their configurational stability; the latter depending on the structure of the diimine ligands. In the case of the 2-anthracenyl-phen derivative, a decent level of supramolecular stereocontrol was noted (d.e. up to 45%); the configuration of the complex being determined by electronic circular dichroism (ECD). The Royal Society of Chemistry 2006.

Full text of DOI:10.1039/b515540a

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PAPER
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Chiral spiro Cu(I) complexes. Supramolecular stereocontrol and isomerisation
dynamics by the use of TRISPHAT anions†
Virginie Hebbe-Viton,a Vale´rie Desvergnes,a Jonathan J. Jodry,a Christiane Dietrich-Buchecker,b
Jean-Pierre Sauvageb and Je´roˆme Lacour*a
Received 2nd November 2005, Accepted 22nd December 2005
First published as an Advance Article on the web 20th January 2006
DOI: 10.1039/b515540a
Association of enantiopure TRISPHAT anion (1) with chiral spiro [Cu(LLꢀ)2] complexes (LLꢀ =
2-R-phen, 2, 6-R-bpy, 3, and 2-iminopyridine, 4) leads to an efficient NMR enantiodifferentiation.
Variable temperature 1H NMR spectroscopy has been used to determine the isomerisation kinetics of
these pseudo-tetrahedral complexes and to evaluate their configurational stability; the latter depending
on the structure of the diimine ligands. In the case of the 2-anthracenyl-phen derivative, a decent level
of supramolecular stereocontrol was noted (d.e. up to 45%); the configuration of the complex being
determined by electronic circular dichroism (ECD).
In pseudo-tetrahedral geometry, the formation of a coordina-
tion complex with two identical symmetrical bidentate ligands
Introduction
Copper(I) complexes of heteroaromatic chelating bidentate lig-
leads invariably to an achiral D2d symmetric structure. However
ands of general 1,4-diimine type form an important class of co-
the complexation of a central Cu(I) atom with two identical
ordination compounds. They possess interesting physicochemical
unsymmetrical bidentate ligands results in the formation of chiral
properties,1 and also play a large role in the field of asymmetric
catalysis.2 From a topological perspective, these complexes can
intervene in the construction of sophisticated molecular architec-
tures such as catenates, knots, rotaxanes, etc.3
Copper(I) complexes prefer adopting a pseudo-tetrahedral
geometry. They are often sensitive to oxidation and their stability
is closely related to the nature of the ligands attached to the
metal centre. In the absence of restricting steric effects from the
ligands, these complexes are often oxidized to the more stable
square-planar Cu(II) species. For example, CuL2 complexes of
2,2ꢀ-bipyridines (bpy) and 1,10-phenanthrolines (phen) tend to
be oxidized by O2.4
cationic adducts of type [Cu(LLꢀ)2]+.7 The pseudo-tetrahedral
mononuclear complex formed in this way has a chirality centred
around the metal which occupies the centre of the tetrahedron.
Chiral spiro entities are formed, whose configuration can be
assigned using either S/R or D/K descriptors (Scheme 1).8,9 Many
such bis(diimine)copper(I) complexes with unsymmetrical 2-R-
phen, 6-R-bpy and 2-iminopyridines have been synthesised and
studied as racemates.10,11,12
To avoid the geometric reorganization that occurs upon ox-
idation and ensure air stability, bulky substituents are usually
introduced in ligand positions adjacent to the N-coordinating
atoms. These substituents sterically impede the complex’s abil-
ity to become planar and thus increase the Cu(I) to Cu(II)
interconversion barrier sufficiently to allow the air stability of
Cu(I) species. In 1961, the stabilisation of Cu(I) complexes by
this approach was demonstrated by James and Williams who
determined stability constants and redox potentials for a series
of Cu(I)/Cu(II) complexes bearing different alkyl-substituted
phenanthroline and bipyridine ligands.5 Even though alkyl groups
tend to be electron donating, their presence increases the Cu2+/Cu+
reduction potential.6
Scheme
configuration.
1
Chiral spiro Cu(LLꢀ)2 complexes of (D,S) or (K,R)
These pseudo-tetrahedral Cu(I) complexes are chemically and
configurationally labile, with an equilibrium between the enan-
tiomers occurring rapidly in solution (Scheme 2). It can be slowed
down to some extent by incorporating bulky substituents ortho to
aDepartment of Organic Chemistry, University of Geneva, Quai Ernest
Ansermet 30, CH-1211, Geneva 4, Switzerland. E-mail: jerome.lacour@
chiorg.unige.ch; Fax: +41 22 328 7396
bLaboratoire de Chimie Organo-Mine´rale, UMR CNRS n◦ 7513, Faculte´
de Chimie, Institut Le Bel, Universite´ Louis Pasteur, 4 rue Blaise-Pascal,
67070, Strasbourg-Cedex, France
† Electronic supplementary information (ESI) available: 1H NMR spectra
(Figs. S1–S14) and activation parameters (Figs. S15–S17, Graphs S15–S17
and Tables S15–S17) for the complexes. See DOI: 10.1039/b515540a
Scheme 2 Configurational lability of chiral Cu(I) complexes exemplified
with a 2-R-phen derivative.
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the ligand’s imine nitrogen.12b,13 While the flexibility of the diimine
scaffold14 has been shown to favor isomerization,15 interligand p-
stacking interactions may stabilize the [Cu(LL)2]+ structure.10a,c
The configurational lability of such Cu(I) complexes can be
precisely evaluated by NMR using ligands which present magnet-
ically non-equivalent signals after complexation. Van Koten et al.
reported a dynamic study on complexes made of 2-iminopyridine
moieties.12a Free energies of activation (DG=) around 58 kJ mol−1
were measured in CDCl3 using, for instance, the diastereotopic
methyl groups of isopropyl substituents as NMR probes. Recently,
faster kinetics of racemization were measured in MeOH-d4 on
complexes of anionic taurine-derived 2-iminopyridine ligands
(DG= 46 kJ mol−1).16 Thummel et al. used VT-NMR to study
the racemisation’s kinetics and the rates of ligand exchange
using phenanthroline ligands bearing enantiotopic geminal methyl
groups and 2,2ꢀ-bipyrimidines with substituents at the 4,4ꢀ and 6,6ꢀ
positions that become inequivalent when two ligands are bound to
a single metal in a tetrahedral fashion.13 Dynamics were found to
be fast at ambient temperature and low temperature measurements
were necessary for the determination of the energy barriers
by 1H NMR. Free energy of activation values around 61.4–
63.5 kJ mol−1 were measured in CDCl3 for 1,10-phenanthroline
and 2,2ꢀ-bipyrimidine derivatives. The lower values measured in
CD3CN solutions (around 56.5–58.5 kJ mol−1) were attributed to
solvent participation in the exchange process.
Fig. 1 The D enantiomer of TRISPHAT anion 1.
anion, namely the bis[(R)-1,1ꢀ-bis-2-naphtholato]borate, was used
by Arndtsen to distinguish effectively individual enantiomers of
chiral Cu(I) complexes.25
Herein, we present a full report on the use of chiral TRISPHAT
counterion as the source of NMR differentiation for isomerization
dynamics and stereoselective induction studies on chiral Cu(I)
complexes. Simple bpy, phen and iminopyridine ligands were used
and the configurational stability of the resulting chiral complexes
compared.
Results and discussion
Ligand and complex synthesis
Chiral ligands can also be used to induce an NMR
differentiation.17 However, as a high diastereoselectivity is often
observed upon complex formation, only the signals of the major
diastereomer appear prohibiting the determination of epimer-
ization kinetics. Indeed, this occurred when enantiopure ligands
derived from (1S)-(−)-b-pinene and (1R)-(+)-b-pinene were used
from which the corresponding bis(diimine) complexes were ob-
tained with high selectivity (d.e. > 96%).18 Circular dichroism (CD)
spectra of these complexes exhibited equal and opposite Cotton
effects in the region of MLCT absorption which were assigned to
K and D configurations respectively. Recently, Pianet and Vincent
used chiral racemic atropisomer diimine ligands to study the
exchange processes in pseudo-tetrahedral [CuL2]+ complexes by
using two-dimensional exchange NMR spectroscopy.19
Although highly efficient, these methods for the evaluation
of the isomerisation kinetics cannot be applied—by definition—
to complexes made of achiral ligands deprived of enantiotopic
substituents. For these substrates we hypothesized that a chiral
counterion could be a source of NMR differentiation.20 The asso-
ciation of chiral cationic [Cu(LLꢀ)2]+ complexes with enantiopure
anions form diastereoisomeric salts and distinct NMR signals
could thus result from the asymmetric ion pairing. Furthermore,
as the complexes are configurationally labile, the possibility of a
supramolecular stereocontrol was considered. We envisioned that
stereoselective discriminating interactions might occur between
the chiral ions and favor one diastereomeric salt over the other
(Pfeiffer effect).20,21
Our goal was thus to associate TRISPHAT anions (1) with a
large variety of complexes made from structurally different ligands
(2 to 4, Fig. 2). Care was taken to choose diimine moieties
derived from phen and bpy backbones as the differences in the
skeletons (rigidity/flexibility, planar/nonplanar) could influence
the selectivity and the configurational stability of the resulting
Cu(I) complexes. Several monosubstituted 1,10-phenanthroline
and 2,2ꢀ-bipyridine ligands were prepared following conditions
previously reported by Sauvage et al.,26 i.e. a nucleophilic addition
of alkyl- or aryl-lithium reagents to the parent phen and bpy
followed by the rearomatisation in the presence of an excess
of manganese dioxide. The aromatic lithium compounds were
obtained by reaction of the corresponding bromo-arene with
metallic lithium. This synthesis afforded the ligands 2-R-phen
(2a–c and 2e–h) and 6-R-bpy (3a–c and 3e–f) in low to good
yields (16–95%; R = Me (a); n-Bu (b); t-Bu (c); i-Pr (d); Ph (e);
4-CH3–Ph (f); 4-OMe–Ph (g); anthracenyl (h); Fig. 2).
Previously, the synthesis of tris(tetrachlorobenzenediolato)-
phosphate(V) anions 1 has been reported.22 This chiral anion,
named TRISPHAT (D and Kenantiomers, Fig. 1), can be resolved
by association with an enantiopure ammonium ion. The overall
efficiency of TRISPHAT to behave as an NMR chiral solvating
and asymmetry-inducing agent for chiral cationic derivatives20,23
led us to its use for the proposed study.24 Recently, another chiral
Fig. 2 2-R-phen (2), 6-R-bpy (3) and 2-iminopyridine (4).
The synthesis of the 2-imino-pyridine ligands 4c and 4d was also
realised following a literature procedure,12c via an easy conden-
sation between pyridine-2-carbaldehyde and the corresponding
amines.
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Table 1 Relevant data for the stereodynamics among diastereomeric [Cu(LLꢀ)2][D-1] salts
DG=/
Dm/Hz kJ mol−1b
DH=/
DS=/
DG=/
Entry
Ligand
R
Yield
d.e. (Temp./K)
Dd/ppma
Tc/K
kJ mol−1c
J K−1 mol−1d
kJ mol−1e
1
2
3
4
5
6
7
8
9
10
11
12
13i
14i
2a
2b
2c
2e
2f
2g
2h
3a
3b
3c
3e
3f
Me
85
78
82
79
97
90
80
84
90
88
86
79
80
79
0 (295 K)
10 (295 K)
8 (273 K)
4 (295 K)
6 (295 K)
4 (295 K)
45 (253 K)
8 (233 K)
4 (243 K)
7 (253 K)
0 (253 K)
0 (263 K)
9 (243 K)
9 (253 K)
0.10f
0.16f
0.03f
0.07
0.06
0.08
0.06
0.04f
0.04f
0.05g
0.08
0.07
0.03
0.02j
>328
>323
>328
>328
>328
>328
>328
303
313
263
—
—
45.2
62.4
11.4
28.4
25.2
34.0
26.0
16.8
17.2
19.6
—
>68.0
>66.0
>71.8
>69.3
>69.7
>68.8
>69.6
65.2
67.3
55.9
—
—
—
—
—
—
—
—
—
92.2
—
64.8
—
—
76.5
75.1
—
—
—
—
—
—
—
87.1
—
44.3
—
—
51.1
65.6
—
—
—
—
—
—
—
66.2
—
51.6
—
—
61.3
55.6
n-Bu
t-Bu
Ph
p-Tol
p-anisyl
anthracenyl
Me
h
n-Bu
t-Bu
Ph
p-Tol
—
9.35
10.35
4c
4d
t-Bu
285
267
62.5
58.1
i-Pr
a The precision of the measurement is about 0.01 ppm. b DG= = RTc(22.96 + Ln(Tc/Dm)). c DH= = Ea–RT. d DS= = R [ln(hA/kBT) − 1]. e DG= = DH=
TDS=; calculated at T = 298 K. f Ha. g H(t-Bu). h Not applicable. i In CD2Cl2. j H(imine).
−
Formation of the corresponding [Cu(LLꢀ)2][PF6] salts was per-
formed by reacting the different ligands with [Cu(CH3CN)4][PF6]
in acetonitrile. Association of these complexes with anion D-1
was performed by ion pairing metathesis; salts [Cu(2a–c)2][D-1],
[Cu(2e–h)2][D-1], [Cu(3a–c)2][D-1], [Cu(3e–f)2][D-1] and [Cu(4c–
d)2][D-1] being isolated by chromatography as the first eluted
fractions (SiO2, CH2Cl2, Rf = ∼ 0.6–0.9, 78–97%, Table 1).20,27
nation of the asymmetry induction by integration of the respective
signals (diastereomeric excess d.e., Table 1, entries 1–7).
In view of the results gathered in Table 1, it is apparent that the
nature of the a-substituent has a direct influence on the observed
asymmetry inductions. Two types of a-substituent, aliphatic and
aromatic groups, were used. For the former the best asymmetric
excess was obtained with the complex bearing a monosubstituted
n-butyl ligand (d.e. = 10%, Table 1, entry 2). Amongst aromatic
groups of various sizes, the results were generally low (d.e. 4–6%
at 295 K, entries 4–6, Table 1). Only in the case of the complex
made with a phen ligand bearing an a-anthracenyl group (2h) was
a decent diastereomeric excess measured at room temperature (d.e.
30% at 298 K, Fig. 4). An increase of this excess from 30 to 45%
(233 K) was obtained by lowering the temperature (see Fig. 4).
Phen complexes
The effect of anion 1 as an NMR chiral solvating reagent was
investigated. Solutions of [Cu(2a–c)2][D-1] and [Cu(2e–h)2][D-
1] salts were prepared in CDCl3 and analysed by 1H NMR
spectroscopy at room temperature.28 Due to the presence of
TRISPHAT anion, an enantio-differentiation was observed in
the spectra of the diastereomeric [(R)–Cu(2)2][D-1] and [(S)–
Cu(2)2][D-1] complexes showing partial or complete separation
of the signals (Fig. 3). Of all the split signals, those of the
higher frequency H9 protons were particularly easy to monitor. In
[Cu(2c)2][D-1], the H8 proton was better split than H9; this most
probably indicates that the steric bulk of the tert-butyl groups
hinders the approach of the TRISPHAT anion along the C2 axis
of the complex.
Fig. 4 VT-NMR analysis (1H, 400 MHz, CDCl3) of salt [Cu(2h)2][D-1]
and resulting diastereoselectivity: (a) 298 K, 30%, (b) 283 K, 40%,
(c) 273 K, 42%, (d) 263 K, 44%, (e) 253 K, 45%, (f) 243 K, 45%.
The assignment of the configuration of the metal complex
was realized by a CD analysis (Fig. 5). The salt [Cu(2h)2][K-1]
was prepared in addition to [Cu(2h)2][D-1] and opposite Cotton
effects were observed in the region of p–p* and MLCT bands
(for MLCT, De396 = + 6.3 and −6.4 M−1 cm−1, De377 = + 4.8
Fig. 3 1H NMR analyses (CDCl3, 400 MHz, 298 K) of salts (a)
[Cu(2b)2][PF6] and (b) [Cu(2b)2][D-1], with a diastereomeric excess of 10%.
Such large differences in chemical shifts (DDdmax = ∼ 0.16 ppm,
and −4.8 M−1 cm−1, in CHCl3 with c = 7.44 and 6.86 × 10−5
M
253 K) observed for analogous protons allowed a ready determi-
respectively). By comparison with the work of Thummel et al.,18
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obtained previously,10 that dynamic processes were occurring and
that the spectra were recorded around or above the coalescence
temperatures.
1H VT-NMR experiments on [Cu(3a–c)2][D-1] were therefore
performed (253–328 K) in CDCl3. For bpy-derived [Cu(3a–b)2][D-
1] salts, dynamic configurational isomerism was detected, with a
separation of the NMR signals occurring at lower temperature (co-
alescence temperature for H6ꢀ protons, Tc = ∼ 303–313 K, Fig. 6,
Table 1, entries 8–9). Racemization barriers were determined from
Tc and Dm values (DG= = ∼ 65.2–67.3 kJ mol−1 in CDCl3) and were
similar to those obtained by Thummel et al.13 For the [Cu(3c)2][D-
1] salt, faster stereodynamics (DG= = ∼ 55.9 kJ mol−1) were
monitored as lower coalescence temperatures were measured for
the H6ꢀ and t-butyl protons (Tc = ∼ 263 K, Table 1, entry 10).
Inversion barriers were also determined by line-shape analysis
(WinDNMR) of the broadened exchange signals from which rate
constants (k) were obtained. Representative experimental and
calculated line shapes are depicted in Fig. 7. The inversion barriers
were determined at different temperatures and the activation pa-
rameters (DH=, DS= and DG=) of the D(S)/K(R) interconversion
were calculated by using an Arrhenius plot (ln k vs 1/T) and
Eyring equation (see Table 1 and ESI†). Precise results were thus
obtained which are in good agreement with those obtained by the
coalescence method.
Fig. 5 CD (top) and absorption (bottom) spectra of (a) [K-Cu(2h)2][K-1]
and (b) [D-Cu(2h)2][D-1] in CHCl3 (298 K, c = 7.44 and 6.86 × 10−5
M
respectively).
these two CD spectra can be assigned to D and Kconfigurations for
the Cu(I) cationic complexes associated with D-1 and K-1 anions
respectively. It indicates that a homochiral association between the
ions is favored over a heterochiral association.
Moreover, 1H NMR analyses at higher temperatures were
performed (up to 328 K) to determine the racemization barrier
of these complexes. However, only small differences in chemical
shifts (DDd) were observed for the split signals of H9 or H8 protons
demonstrating the high configurational stability of these deriva-
tives as compared to the NMR time scale. Should stereodynamic
phenomena occur, they will appear at temperatures higher than
328 K.
The activation energy value (DG=), which quantifies the R/S
or K/D inversion barrier, is thus unknown and can only be
estimated by the “coalescence” method considering Dm values
at lower temperature and Tc ≥ 328 K (Table 1, entries 1–7).
For [(Cu(2c)2][D–1], a DG= value higher than 71.8 kJ mol−1 was
determined (Dm = 11.4 Hz).
Fig. 7 Experimental (left, 1H NMR, 400 MHz, CDCl3, 233–263 K) and
best fit calculated (right, WinDNMR, k kinetic constant (s−1)) spectra
Bpy complexes
A similar study of Cu(I) complexes bearing 6-R-bipyridine ligands
3a–c was undertaken. However, room temperature 1H NMR
analyses of these bpy-derived [Cu(3a–c)2][D-1] salts revealed broad
resonances or lack of signal separation (see Fig. 6 and ESI†).
Rather than consider a lack of NMR enantio-differentiation
from the TRISPHAT anion, we reasoned, in view of the results
of [Cu(3c)2Cu][D-1] (imine proton, d 8.63–8.44 ppm): (a) 263 K, 160 s−1
;
(b) 253 K, 50 s−1; (c) 243 K, 30 s−1; (d) 233 K, 12 s−1; (e) 223 K, 0.2 s−1
.
Low asymmetry induction was also observed with monosub-
stituted 2,2ꢀ-bipyridine ligands (maximum diastereomeric excess
8% with R = Me, Table 1, entry 8) showing a poor efficiency of
TRISPHAT anion to behave as a supramolecular chiral auxiliary
for such ligands. Moreover, as an NMR chiral solvating agent,
anion 1 is less efficient with bpy than phen derivatives, at least for
ꢀ
Ha protons: DDdmax = ∼ 0.04 ppm in bpy series (R = n-Bu) vs
DDdmax = ∼ 0.16 ppm in phen series (R = n-Bu).
Iminopyridine complexes
Copper(I) complexes of unsymmetrical pyridine imine ligands
(4) were similarly analyzed. Compound [Cu(4d)2][PF6] had been
previously studied,12 and a racemization barrier measured (DG= =
∼ 58.2 kJ mol−1 in CD2Cl2) using diastereotopic methyl groups
of the i-propyl substituents as an NMR probe. For the analogous
TRISPHAT salt, [Cu(4d)2][D-1], broadened signals were observed
at room temperature, similar to bpy-derived complexes.
Fig. 6 Variable temperature 1H NMR (CDCl3, 400 MHz, d 8.75–
8.10 ppm) of [Cu(3a)2][D-1]: (a) 323 K, (b) 313 K, (c) 303 K, (d) 293 K,
(e) 283 K, (f) 273 K, (g) 263 K.
However, a decrease of temperature revealed well separated
signals for most of the protons. The racemization barrier was
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determined using the signals of the imine hydrogen atoms, and
the obtained value (DG= = ∼ 58.1 kJ mol−1 in CD2Cl2, Table 1,
entry 14) was in complete agreement with the results previously
reported for [Cu(4d)2][PF6].12 This result demonstrates without
ambiguity that TRISPHAT anion does not influence the kinetics
of racemization of the Cu(I) complex. A slightly higher barrier
was measured for complex [Cu(4c)2][D-1] using the split t-butyl
signals (DG= = ∼ 62.5 kJ mol−1, Table 1, entry 13). As for the
bpy derivatives, a careful line shape analysis was performed for
the VT-NMR behaviour of the TRISPHAT salts of complexes 4c
and 4d (DH= ∼ 75–76 kJ mol−1 and DS= = 51 and 66 J K−1 mol−1,
respectively). Although a decent NMR enantio-differentiation was
observed at low temperature, the measured diastereomeric excess
remained low (d.e. = ∼ 9%).
phy (silica gel 60, 40 lm or Fluka basic alumina type 5016A) was
performed in air.
NMR data were obtained on Bruker 400 MHz spectrometer,
IR and mass spectra were recorded. NMR spectra were recorded
on a Bruker AMX-400 spectrometer at room temperature unless
otherwise stated. 1H NMR chemical shifts are given in ppm
relative to Me4Si with the solvent resonance used as the internal
standard. 31P NMR (162 MHz) chemical shifts were reported in
ppm relative to H3PO4. 13C NMR (100 MHz) chemical shifts were
given in ppm relative to Me4Si, with the solvent resonance used as
the internal standard (CDCl3 d 77.0 ppm, CD2Cl2 d 53.8 ppm).
Assignments may have been achieved using COSY, HETCOR
and/or NOESY experiments. IR spectra were recorded with a
Perkin–Elmer 1650 FTIR spectrometer using a diamond ATR
Golden Gate sampling. Melting points (mp) were measured in
open capillary tubes on a Stuart Scientific SMP3 melting point
apparatus and were uncorrected. Electrospray mass spectra (ES-
MS) were obtained on a Finnigan SSQ 7000 spectrometer and EI-
MS spectra were obtained on a Varian CH4 or SM1 spectrometer
(ionizing voltage 70 eV; m/z (intensity in %)) by the Department
of Mass Spectroscopy of the University of Geneva. UV spectra
were recorded on a CARY-1E spectrometer in a 1.0 cm quartz
cell; kmax are given in nm and molar adsorption coefficient e
in cm−1 dm3 mol−1. CD spectra were recorded on a JASCO J-
715 polarimeter in a 1.0 cm quartz cell; k are given in nm and
molar circular dichroic absorptions (De) in cm2 mmol−1. Optical
rotations were measured on a Perkin-Elmer 241 polarimeter in a
Conclusion
The TRISPHAT anion 1 is an efficient NMR chiral solvating agent
for chiral pseudo-tetrahedral Cu(I) complexes. Diastereomeric
ion pairs [(D/S)–Cu(LLꢀ)2][D-1] and [(K/R)–Cu(LLꢀ)2][D-1] can
indeed be distinguished by 1H NMR. Low asymmetry inductions
were measured, although these were not negligible in the case of
a 2R-phenanthroline ligand bearing an anthracenyl a-substituent
(d.e. up to 45%), with the absolute configuration of the metal
complex being determined by ECD.
The observed NMR enantio-differentiation can be used to
measure the kinetics of racemization of these chiral configura-
tionally labile Cu(I) complexes. This method, based on the use
of a chiral anion, does not require the use of ligands bearing
enantiotopic groups. Moreover it is simple to implement and very
efficient. VT-NMR experiments on these salts were performed
and revealed rather different results depending upon the nature of
the a-substituent and the diimine backbone. Amongst the studied
Cu(I) complexes the following stability order was determined:
[Cu(2-R-phen)2] > [Cu(2-R-bpy)2] ≥ [Cu(2-R-iminopyridine)2].
VT-NMR experiments also allowed us to determine the ac-
tivation parameters for the D/K interconversion of a pseudo-
tetrahedral Cu(I) complexes made of bpy and 2-iminopyridine
ligands. The dynamic process requires positive activation enthalpy
(DH= from 65–92 kJ mol−1) and shows rather strong and positive
entropy values (DS= from 52–66 J K−1 mol−1). It is unfortunate that
no data exists—to our knowledge—on the dissociation energy of
Cu–N bonds as a comparison of these and DH= values would have
shed light on the nature of the exchange mechanism.
◦
thermostated (20 C) 10.0 cm long microcell with high pressure
lamps of sodium or mercury and are reported as follows: [a]20 (c
k
(g per 100 mL), solvent).
[Cu(diimine)2][PF6] complexes, general procedure
In a 10 mL flask under an inert argon atmosphere, 10 mg (Acros,
2.6 10−5 mol, 1 equiv.) of [Cu(CH3CN)4PF6] salt and 2.0 equiv.
(5.2 10−5 mol) of the desired ligand were dissolved in acetonitrile
(SDS) and stirred at room temperature for 10–30 min. Concen-
tration in vacuo then afforded the desired products as orange and
brown solids. No further purification was required.
[Cu(diimine)2][TRISPHAT] complexes, general procedure
In a 10 mL conical flask under an argon atmosphere, the
[Cu(I)bis(diimine)][PF6] salt (2.5 10−5 mol, 1 equiv.) and the
source of the desired anion [cinchonidinium][D-1] (1 equiv.) were
dissolved in CH2Cl2–acetone (SDS, 50 : 50, 5 mL). After 30 min of
stirring, the solution was evaporated to dryness and the product
was purified by chromatography (silica gel) using CH2Cl2 as the
eluent. A and Aꢀ represent the major and minor diastereomers,
respectively.
Experimental
General
All reactions were conducted under dry N2 or Ar by means
of an inert gas/vacuum double manifold line with magnetic
stirring. CHCl3, CH2Cl2, CDCl3 and CD2Cl2 (SDS) were filtered
on basic alumina. Analytical thin layer chromatography (TLC)
was performed with Merck SIL G/UV254 plates or Fluka 0.25 mm
basic alumina (pH = 9.9) plates. Visualization of the developed
chromatogram was performed by UV/Vis detection. Organic
solutions were concentrated under reduced pressure on a Buchi
rotary evaporator. Unless otherwise noted, column chromatogra-
[Cu(2a)2][D-1]. This compound was prepared following the
general procedure and isolated after column chromatography (Rf
1
0.89 (SiO2, CH2Cl2)) in 62% yield. H NMR (CDCl3, 400 MHz,
3
3
293 K): d 8.90 (dd, J = 1.5 Hz, J = 4.5 Hz, 1H, A), 8.84 (dd,
3
3J = 1.5 Hz, J = 4.5 Hz, 1H, Aꢀ), 8.50 (m, 2H, A and Aꢀ), 8.42
3
(d, J = 8.3 Hz, 2H, A and Aꢀ), 7.98 (m, 4H, A and Aꢀ), 7.79
(m, 2H, A and Aꢀ), 7.70 (m, 2H, A and Aꢀ), 2.43 (s, 3H, Aꢀ), 2.38
(s, 3H, A). 31P NMR (CDCl3, 162 MHz): d −77.9. IR (cm−1): m
2921w, 2846w, 1618w, 1587w, 1564w, 1509w, 1491w, 1449s, 1389m,
2062 | Dalton Trans., 2006, 2058–2065
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©

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1302m, 1236m, 1146w, 992s, 848m, 818s, 719s, 670s, 619s, 582m.
104), 241.0 (8.4 × 104), 289.0 (5.8 × 104). MS (ES): (+) 575.2
([Cu(L)2]+), 320.2 ([Cu(L)]+); (−) 768.6 ([1]−).
[a]20 = − 313, [a]20 = − 339, [a]20 = − 366, [a]22 = − 562,
D
578
546
436
[a]22 = − 1255 (c = 0.00765, CHCl3). UV/Vis (CHCl3, 3.03 ×
365
10−5 M) kmax (e) 452 (6.0 × 103), 273 (4.6 × 104), 241 (5.0 × 104),
227 (2.8 × 104), 214 (2.3 × 104), 202 (1.9 × 104). MS (ES): (+)
451.3 ([Cu(L)2]+), 257.2 ([Cu(L)]+); (−) 768.5 ([1]−).
[Cu(2f)2][D-1]. This compound was prepared following the
general procedure and isolated after column chromatography (Rf
0.7 (SiO2, CH2Cl2)) in 97% yield. Mp = 175 ◦C (decomposes). 1H
NMR (CDCl3, 400 MHz, d.e. = 9%): d 9.19 (d, 3J = 4.8 Hz, 2H,
3
3
Aꢀ), 9.10 (d, J = 4.8 Hz, 2H, A), 8.54 (d, J = 7.8 Hz, 2H, Aꢀ),
8.47 (d, 3J = 7.8 Hz, 2H, A), 8.35 (d, 3J = 8.3 Hz, 2H, A), 8.31 (d,
3J = 8.3 Hz, 2H, Aꢀ), 8.0–7.9 (m, 6H), 7.79 (dd, 3J = 8.1 Hz, 3J =
4.8 Hz, 2H, A), 7.73 (d, 3J = 8.1 Hz, 2H, A), 7.72 (d, 3J = 8.1 Hz,
2H, Aꢀ), 7.03 (d, 3J = 8.1 Hz, 4H, Aꢀ), 6.95 (d, 3J = 8.1 Hz, 4H,
[Cu(2b)2][D-1]. This compound was prepared following the
general procedure and isolated after column chromatography (Rf
1
0.86 (SiO2, CH2Cl2)) in 50% yield. H NMR (CDCl3, 400 MHz,
3
3
d.e. = 10%): d 9.08 (dd, J = 1.5 Hz, J = 4.8 Hz, 1H, A), 8.95
(dd, 3J = 1.5 Hz, 3J = 4.8 Hz, 1H, Aꢀ), 8.54 (dd, 3J = 1.5 Hz, 3J =
8.1 Hz, 1H, Aꢀ), 8.48 (dd, 3J = 1.5 Hz, 3J = 8.1 Hz, 1H, A), 8.44 (d,
3J = 8.3, 1H, Aꢀ), 8.43 (d, 3J = 8.3, 1H, A), 7.98 (m, 4H, A and Aꢀ),
7.86 (dd, 3J = 4.5 Hz, 3J = 8.1 Hz, 1H, Aꢀ), 7.82 (dd, 3J = 4.5 Hz,
3J = 8.1 Hz, 1H, A), 7.71 (d, 3J = 8.3 Hz, 1H, Aꢀ), 7.67 (d, 3J =
8.3 Hz, 1H, A), 2.64 (m, 2H, Aꢀ), 2.52 (m, 2H, A), 1.29 (m, 4H, A
and Aꢀ), 0.55 (m, 2H, Aꢀ), 0.50 (m, 2H, A), 0.22 (t, 3J = 7.6 Hz, 3H,
3
3
A), 6.08 (d, J = 7.6 Hz, 4H, Aꢀ), 6.05 (d, J = 8.1 Hz, 4H, A),
1.83 (s, 6H, A and Aꢀ). 31P NMR (CDCl3, 162 MHz): d − 79.7.
IR (cm−1): m 3456m, 2964w, 1586w, 1450s, 1387m, 1301m, 1262m,
1236m, 992s, 824s, 719m, 673s, 620w. UV/Vis (CHCl3, 2.39 × 10−5
M): kmax (e) 246.0 (8.3 × 104), 291.0 (6.9 × 104), 439.0 (5.6 × 103).
CD (CHCl3, 2.39 10−5 M, 20 ◦C): k (De) 250.0 (−35), 290.0 (−19).
[a]20D = − 415, [a]20578 = − 430, [a]20546 = − 459, (c = 0.014, CHCl3).
MS (ES): (+) 603.4 ([Cu(L)2]+); 332.5 ([Cu(L)]+); (−) 768.9 ([1]−).
3
Aꢀ), 0.22 (t, J = 7.6 Hz, 3H, A). 31P NMR (CDCl3, 162 MHz):
d − 79.6. IR (cm−1): m 2960w, 2924w, 2854w, 1618w, 1587w, 1566w,
1494w, 1445s, 1389m, 1301m, 1235m, 1223m, 1147w, 1098w, 990s,
850m, 818s, 718s, 668s, 619s, 564m. [a]20D = − 313, [a]20578 = − 339,
[a]20 = − 366, [a]20 = − 562, [a]20 = − 1255 (c = 0.00765,
[Cu(2g)2][D-1]. This compound was prepared following the
general procedure and isolated after column chromatography (Rf
546
436
365
1
CHCl3). UV/Vis (CHCl3, 5.86 × 10−5 M): kmax (e) 458 (6.3 × 103),
274 (5.0 × 104), 243 (5.2 × 104), 233 (2.5 × 104), 231 (2.4 × 104),
229 (2.4 × 104), 226 (2.3 × 104), 224 (2.2 × 104), 221 (2.2 × 104);
MS (ES): (+) 535.3 ([Cu(L)2]+), 300.1 ([Cu(L)]+); (−) 768.6 ([1]−).
0.67 (SiO2, CH2Cl2)) in 88% yield. H NMR (CDCl3, 400 MHz,
d.e. = 7%): d 9.19 (d, 3J = 4.4 Hz, 2H, A), 9.10 (d, 3J = 4.4 Hz, 2H,
Aꢀ), 8.52 (d, 3J = 8.4 Hz, 2H, Aꢀ), 8.46 (d, 3J = 7.9 Hz, 2H, A), 8.33
(d, 3J = 7.9 Hz, 2H, A), 8.28(d, 3J = 8.4 Hz, 2H, Aꢀ), 8.0–7.85 (m,
6H), 7.79 (dd, 3J = 7.9 Hz, 3J = 4.9 Hz, 2H, A), 7.73 (m, 2H, A
and Aꢀ), 7.13 (d, 3J = 8.4 Hz, 4H, Aꢀ), 7.08 (d, 3J = 8.4 Hz, 4H, A),
5.81 (4H, A and Aꢀ), 3.38 (s, 6H, A and Aꢀ). 31P NMR (CDCl3, 162
MHz): d − 80.6. IR (cm−1): m 3422m, 2934w, 1653w, 1559w, 1498w,
1450s, 1388w, 1252m, 992s, 825s, 719w, 673m. UV/Vis (CHCl3,
c = 5.05 × 10−5 M): kmax (e) 205.0 (1.9 × 104), 216.0 (2.2 × 104),
228.0 (2.5 × 104), 242.0 (4.7 × 104), 300.0 (2.8 × 104), 437.0 (2.2 ×
103). MS (ES): (+) 635.1 ([Cu(L)2]+), 349.2 ([Cu(L)]+); (−) 768.7
([1]−).
[Cu(2c)2][D-1]. This compound was prepared following the
general procedure and isolated after column chromatography (Rf
1
0.76 (SiO2, CH2Cl2)) in 66% yield. H NMR (CDCl3, 400 MHz,
d.e. = 0%). d 8.88 (td, 2H, 3J = 4.5 Hz, A and Aꢀ), 8.55 (dd, 4J =
1.3 Hz, 3J = 8.1 Hz, 1H, A), 8.48 (dd, 4J = 1.3 Hz, 3J = 8.1 Hz,
3
3
1H, Aꢀ), 8.47 (d, J = 8.5 Hz, 1H, A), 8.45 (d, J = 8.5 Hz, 1H,
Aꢀ), 8.02 (d, J = 3 Hz, 1H, Aꢀ), 7.99 (d, J = 2.8 Hz, 1H, A),
7.97–7.94 (m, 4H, A and Aꢀ), 7.83 (dd, 3J = 4.8 Hz, 3J = 8.1 Hz,
3
3
1H, Aꢀ), 7.77 (dd, J = 4.8 Hz, J = 8.1 Hz, 1H, A), 1.25 (s,
9H, A), 1.22 (s, 9H, Aꢀ). 31P NMR (CDCl3, 162MHz): d − 79.6.
IR (neat) (cm−1): m 2964w, 2924w, 2857w, 1626w, 1589w, 1564w,
1510w, 1491m, 1446s, 1384m, 1301m, 1235m, 1136w, 1088w, 990s,
851m, 817s, 717s, 669s, 619s, 583m. UV/Vis (CHCl3, 9.6 × 10−6
M): kmax (e) 202.0 (2.7 × 104), 212.0 (2.9 × 104), 222.0 (3.1 × 104),
227.0 (3.3 × 104), 231.0 (3.4 × 104), 240.0 (6.0 × 104), 274.0 (5.9 ×
3
3
[Cu(2h)2][D-1]. This compound was prepared following the
general procedure and isolated after column chromatography (Rf
1
0.6 (SiO2, CH2Cl2)) in 80% yield. H NMR (CDCl3, 400 MHz,
3
3
d.e. = 30%): d 8.29 (d, J = 8.1 Hz, 1H, H4, A), 8.25 (d, J =
8.1 Hz, 1H, H4, Aꢀ), 8.12 (d, J = 8.3 Hz, 1H, H7, Aꢀ), 8.04 (d,
3
3J = 8.3 Hz, 1H, H7, A), 7.83 (d, J = 8.8 Hz, 1H, A), 7.77 (d,
3
3J = 8.8 Hz, 1H, Aꢀ), 7.74–7.65 (m, 9H), 7.58 (d, 3J = 4.0 Hz, 1H,
104). [a]20 = − 133, [a]20 = − 244, [a]20 = − 281, [a]20
=
D
578
546
365
H9, A), 7.50 (d, J = 8.5 Hz, 1H, Aꢀ), 7.45 (d, J = 8.5 Hz, 1H,
A), 7.39–7.31 (m, 4H), 7.23 (m, 2H), 7.11–6.98 (m, 4H), 6.89–6.83
(m, 3H), 6.72 (dd, 3J = 4.8 Hz, 3J = 8.3 Hz, 1H, H8, A). 31P NMR
(CDCl3, 162 MHz): d − 80.6. IR (cm−1): m 2923w, 2852w, 1730w,
1623w, 1586w, 1490w, 1446s, 1387m, 1302m, 1235m, 990s, 818s,
717w, 662m. UV/Vis (CHCl3, c = 7.44 × 10−5 M): kmax (e) 228.0
(18.7 × 103), 247.0 (21.3 × 103), 300.0 (3.7 × 103), 373.0 (1.7 ×
103), 396.0 (1.5 × 103), 473.0 (0.5 × 103). CD (CHCl3, c = 7.44 ×
10−5 M, 20 ◦C): k (De) 396.0 (−6.4), 377 (−4.9), 326.5 (+2.5),
301 (−2.9), 280.5 (+25.7). MS (ES): (+) 775.2 ([Cu(L)2]+); 419.3
([Cu(L)]+); (−) 768.7 ([1]−).
3
3
− 1111 (c = 0.0135, CHCl3). MS (ES): (+) 535.2 ([Cu(L)2]+), 299.2
([Cu(L)]+); (−) 768.7 ([1]−).
[Cu(2e)2][D-1]. This compound was prepared following the
general procedure and isolated after column chromatography (Rf
0.91 (SiO2, CH2Cl2)). Mp = 200 ◦C (decomposes). 1H NMR
3
(CDCl3, 400 MHz, d.e. 4%): d 9.11 (d, J = 3.8 Hz, 1H, Aꢀ),
9.04 (d, 3J = 3.8 Hz, 1H, A), 8.52 (d, 3J = 8.1 Hz, 1H, Aꢀ), 8.45
3
3
(d, J = 7.8 Hz, 1H, A), 8.36 (d, J = 8.1 Hz, 1H, Aꢀ), 8.32 (d,
3J = 8.3 Hz, 1H, Aꢀ), 7.98–7.90 (m, 5H), 7.80–7.74 (m, 3H), 7.16
3
3
(d, J = 7.3 Hz, 2H, Aꢀ), 7.11 (d, J = 7.3 Hz, 2H, A), 6.58 (m,
2H, A and Aꢀ), 6.30 (m, 4H, A and Aꢀ). 31P NMR (CDCl3, 162
MHz): d − 80.8. IR (cm−1): m 3051w, 1620w, 1586w, 1559w, 1489w,
1444s, 1386m, 1301m, 1235m, 1142w, 1110w, 989s, 853m, 817s,
717s, 667s, 619s, 580m. UV/Vis (CHCl3, 1.9 × 10−5 M): kmax (e)
202.0 (2.7 × 104), 212.0 (3.5 × 104), 228.0 (3.9 × 104), 230.0 (4.0 ×
[Cu(2h)2][K-1]. This compound was prepared following the
general procedure using [Bu3NH][K-1] as a source of TRISPHAT
anion and isolated after column chromatography in 82%
1
yield. H NMR (CDCl3, 400 MHz, d.e. = 30%). CD (CHCl3,
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c = 6.86 × 10−5 M, 20 ◦C): k (De) 395.5 (+6.3), 377 (+4.8), 326.0
(−1.8), 301 (+2.7), 278.0 (−27.3).
(1.8 × 105), 225.0 (1.8 × 105), 234.0 (2.2 × 105), 242.0 (4.0 × 105),
302.0 (2.2 × 105). [a]20D = − 221, [a]20578 = − 182, [a]20546 = − 221,
[a]20436 = − 441 and [a]20365 = − 909 (c = 0.0077, CHCl3). MS (ES):
(+) 527.4 ([Cu(L)2]+), 295.1 ([Cu(L)]+); (−) 769.0 ([1]−).
[Cu(3a)2][D-1]. This compound was prepared following the
general procedure and isolated after column chromatography (Rf
1
[Cu(3f)2][D-1]. This compound was prepared following the
0.82 (SiO2, CH2Cl2)) in 84% yield. H NMR (CDCl3, 400 MHz,
3
3
ꢀ
general procedure and isolated after column chromatography in
243 K, d.e. = 7%): d 8.56 (d, J = 4.5 Hz, 1H, H6 , A), 8.53 (d, J =
1
ꢀ
3
ꢀ
ꢀ
91% yield. H NMR (400 MHz, CDCl3, 253 K, d.e. = 0%): d
4.8 Hz, 1H, H6 , A ), 8.20 (d, J = 8.3 Hz, 1H, H3 , A), 8.15 (d,
3
3
3
ꢀ
3
ꢀ
ꢀ
ꢀ
ꢀ
8.50 (d, J = 4.8 Hz, 1H, H6 ), 8.44 (d, J = 4.6 Hz, 1H, H6 ),
J = 8.3 Hz, 1H, H3 , A ), 8.02 (d, J = 2.8 Hz, 1H, H3, A ), 8.00
3
3
ꢀ
ꢀ
8.08 (d, J = 8.1 Hz, 1H, H3 ), 8.01–7.95 (m, 3H), 7.85–7.81
(d, J = 2.5 Hz, 1H, H3, A), 7.94–7.77 (m, 4H, H4 and H4 , A and
3
3
ꢀ
ꢀ
3
ꢀ
(m, 4H), 7.72 (t, J = 7.5 Hz, 1H), 7.45 (t, J = 5.5 Hz, 1H,
A ), 7.48–7.42 (m, 2H, H5 , A and A ), 7.34 (d, 2H, J = 7.6 Hz, H5,
A and Aꢀ), 2.17 (s, 3H, CH3, Aꢀ), 2.14 (m, 3H, CH3, A). 31P NMR
(CDCl3, 162 MHz): d − 80.8. IR (cm−1): m 2956w, 2928w, 2851w,
1595w, 1571w, 1445s, 1389m, 1301m, 1236m, 1159w, 1100w, 990s,
905m, 814s, 770s, 717s, 668s, 619m. MS (ES): (+) 403.3 ([Cu(2-
methylbipy)2]+), 233.4 ([CuL]+); (−) 768.8 ([1]−).
3
3
ꢀ
ꢀ
H5 ), 7.44 (t, J = 5.5 Hz, 1H, H5 ), 7.40 (d, J = 7.5 Hz, 2H,
3
H5), 7.16 (t, J = 8.3 Hz, 4H), 6.53–6.50 (m, 4H), 2.07 (s, 6H,
CH3). IR (cm−1): m 2959w, 2922w, 2851w, 1594m, 1559w, 1445s,
1388m, 1301m, 1235m, 1180w, 1159w, 1091w, 989s, 817s, 770m,
717m, 668m, 619m, 551m. MS (ES): (+) 555.3 ([Cu(L)2]+), 309.3
([Cu(L)]+); (−) 768.8 ([1]−).
[Cu(3b)2][D-1]. This compound was prepared following the
general procedure and isolated after column chromatography (Rf
0.87 (SiO2, CH2Cl2)) in 65–95% yield. 1H NMR (CDCl3, 400 MHz,
[Cu(4c)2][D-1]. This compound was prepared following the
general procedure and isolated after column chromatography (Rf
0.64 (SiO2, CH2Cl2)) in 79% yield. 1H NMR (400 MHz, CD2Cl2,
295 K): d 8.57 (s, 1H, H7), 8.49 (d, 3J = 3.8 Hz, 1H, H6), 8.01 (t,
3J = 7.6 Hz, 1H, H4), 7.76 (d, 3J = 7.6 Hz, 1H, H3), 7.61 (t, 3J =
5.6 Hz, 1H, H5), 1.35 (s, 9H, H9). 13C NMR (100 MHz, CD2Cl2,
295K): d 156.3 (C7), 151.1 (C2), 148.7 (C6), 141.7 (d,3J(C,P) =
3
3
ꢀ
243 K, e.d. = 4%): d 8.66 (d, J = 4.5 Hz, 1H, H6 , A), 8.61 (d, J =
3
ꢀ
3
ꢀ
ꢀ
4.8 Hz, 1H, H6 , A), 8.25 (d, J = 8.1 Hz, 1H, H3 , A ), 8.19 (d, J =
ꢀ
ꢀ
8.3 Hz, 1H, H3 , A), 8.14–8.06 (m, 4H, H3, A and A ), 7.99–7.82 (m,
ꢀ
3
ꢀ
ꢀ
ꢀ
H4 and H4, 4H, A and A ), 7.54 (t, J = 5.8 Hz, 1H, H5 , A ), 7.46
3
3
ꢀ
ꢀ
(t, J = 5.8 Hz, 1H, H5 , A), 7.38 (d, 2H, J = 7.8 Hz, H5, A and A ),
2.39 (m, 4H, CH2, A and Aꢀ), 1.17 (m, 4H, CH2, A and Aꢀ), 0.66
(m, 4H, CH2, A and Aꢀ), 0.37 (m, 6H, CH3, A and Aꢀ). 31P NMR
(CDCl3, 162 MHz): d − 80.8. IR (cm−1): m 2956w, 2928w, 2811w,
1595m, 1571w, 1445s, 1389m, 1301m, 1236m, 1159w, 1104w, 990s,
905m, 818s, 771m, 718m, 668s, 619m. UV/Vis (CHCl3, 9.65 ×
10−5 M): kmax (e) 202.0 (7.1 × 103), 205.0 (6.9 × 103), 209.0 (6.9 ×
103), 211.0 (7.6 × 103), 216.0 (7.9 × 103), 218.0 (8.3 × 103), 222.0
(8.6 × 103), 225.0 (9.9 × 103), 244.0 (3.4 × 105), 263.0 (2.3 × 105),
ꢀ
6.4 Hz, 6C, C1 ), 138.1 (C4), 127.9 (C5), 126.9 (C3), 122.4 (6C,
C3 ), 113.7 (d, J(C,P) = 19.1 Hz, 6C, C2 ), 60.0 (C8), 30.1 (C9). 31P
NMR (162 MHz, CD2Cl2, 295K): d − 79.9 (s). IR (cm−1): m 2970w,
2920w, 2870w, 1623w, 1446s, 1389m, 1301m, 1236m, 990s, 817s,
718s, 668s. UV/Vis (CHCl3, 4.67 × 10−5 M): kmax (e) 231 (24 ×
103), 242 (53 × 103), 281 (21 × 103), 289 (21 × 103), 300 (15.8 ×
3
ꢀ
ꢀ
103), 479 (9.7 × 103). [a]20 = − 296; [a]20 = − 278; [a]20
=
D
578
546
− 333; [a]20 = − 1000; [a]20 = − 1889 (c = 0.0054, CHCl3).
436
365
MS (ES): (−) 768.8 ([1]−); (+) 387.3 [CuL2]+), 225.3 ([CuL]+).
300.0 (3.2 × 105), 452.0 (4.9 × 103). [a]20 = − 272, [a]20
=
D
578
− 255, [a]20 = − 337, [a]20 = − 1267 (c = 0.012, CHCl3). MS
546
365
[Cu(4d)2][D-1]. This compound was prepared following the
general procedure and isolated after column chromatography (Rf
(ES): (+) 487.3 ([CuL2]+); 275.2 ([CuL]+); (−) 768.6 ([1]−).
1
0.7 (SiO2, CH2Cl2)) in 80% yield. H NMR (400 MHz, CD2Cl2,
[Cu(3c)2][D-1]. This compound was prepared following the
general procedure and isolated after column chromatography (Rf
3
295 K): d 8.61 (s, 1H, H7), 8.48 (d, J = 4.8 Hz, 1H, H6), 8.02
(td,3J = 7.6 Hz, 3J = 1.5 Hz, 1H, H4), 7.75 (d, 3J = 7.8 Hz, 1H,
H3), 7.61 (ddd, 3J = 5.1 Hz, 3J = 4.8 Hz, 3J = 1.3 Hz, 1H, H55),
1
0.79 (SiO2, CH2Cl2)) in 74% yield. H NMR (CDCl3, 400 MHz,
3
ꢀ
ꢀ
233 K, d.e. = 8%): d 8.56 (d, J = 4.5 Hz, 1H, H6 , A ), 8.51 (d,
3
4.03 (septet, J = 6.3 Hz, 1H, H8), 1.22 (br, 6H, H9). 13C NMR
3
ꢀ
J = 4.5 Hz, 1H, H6 , A), 8.21–8.13 (m, 3H), 8.04–7.84 (m, 6H),
7.60–7.47 (m, 4H), 1.09 (s, 18H, A and Aꢀ). 31P NMR (CDCl3, 162
MHz): d − 80.8. IR (cm−1): m 2956w, 2925w, 2845w, 1594w, 1573w,
1445s, 1389m, 1302m, 1236m, 1182w, 1164w, 1143w, 1106w, 990s,
818s, 775m, 718m, 668s, 619m, 551m. UV/Vis (CHCl3, 3.10 × 10−5
M): kmax (e) 209.0 (1.9 × 104), 218.0 (2.2 × 104), 224.0 (2.3 × 104),
241.0 (4.9 × 104), 299.0 (3.4 × 104). MS (ES): (+) 487.3 ([CuL2]+);
(+) 275.1 ([CuL]+); (−) 768.8 ([1]−).
(100 MHz, CD2Cl2, 295K): d 158.3 (C7), 150.6 (C2), 148.9 (C6),
3
ꢀ
141.8 (d, J(C,P) = 6.4 Hz, 6C, C1 ), 138.1 (C4), 127.9 (C5), 126.6
3
ꢀ
ꢀ
(C3), 122.4 (6C, C3 ), 113.7 (d, J(C,P) = 19.8 Hz, 6C, C2 ), 60.6
(C8), 24.3 (C9). 31P NMR (162 MHz, CD2Cl2, 295K): d − 79.7 (s).
IR (cm−1): m 2969w, 2921w, 2862w, 1618w, 1592w, 1446s, 1387m,
1300m, 1235m, 1154w, 990s, 817s, 718m, 668s. UV/Vis (CHCl3,
4.25 × 10−5 M): kmax (e) 228 (20 × 103), 241 (47 × 103), 280 (18 ×
103), 289 (17.8 × 103), 301 (13.5 × 103), 476 (8.3 × 103). [a]20
− 250; [a]20 = − 229; [a]20 = − 292; [a]20 = − 833; [a]20
=
=
D
[Cu(3e)2][D-1]. This compound was prepared following the
general procedure and isolated after column chromatography (Rf
0.97 (SiO2, CH2Cl2)). 1H NMR (CDCl3, 400 MHz, 253 K, d.e. =
578
546
436
365
− 1500 (c = 0.0048, CHCl3). MS (ES): (−) 768.8 ([1]−); (+) 359.3
([CuL2]+), 211.4 ([CuL]+).
3
3
ꢀ
ꢀ
0%): d 8.60 (d, J = 4.8 Hz, 1H, H6 ), 8.52 (d, J = 4.8 Hz, 1H, H6 ),
8.09–7.98 (m, 3H), 7.91–7.22 (m, 5H), 7.56 (t, 3J = 6.0 Hz, 1H),
7.46–7.14 (m, 3H), 7.24 (d, 3J = 5.8 Hz, 4H), 6.98 (t, 3J = 7.3 Hz,
2H), 6.75 (t, 3J = 7.5 Hz, 4H). 31P NMR (CDCl3, 162 MHz): d −
80.83. IR (cm−1): m 3024w, 2927w, 2851w, 1593m, 1564w, 1444s,
1388m, 1301m, 1235m, 1177w, 1159w, 1075w, 989s, 817s, 780m,
757m, 717m, 696m, 619m. UV/Vis (CHCl3, 5.94 × 10−5 M): kmax
(e) 207.0 (1.5 × 104), 213.0 (1.6 × 104), 216.0 (1.6 × 104), 222.0
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2064 | Dalton Trans., 2006, 2058–2065
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