Heteroleptic copper(I) complexes prepared from phenanthroline and bis-phosphine ligands

Article abstract of DOI:10.1021/ic4020042

Preparation of [Cu(NN)(PP)]⁺ derivatives has been systematically investigated starting from two libraries of phenanthroline (NN) derivatives and bis-phosphine (PP) ligands, namely, (A) 1,10-phenanthroline (phen), neocuproine (2,9-dimethyl-1,10-phenanthroline, dmp), bathophenanthroline (4,7-diphenyl-1,10-phenanthroline, Bphen), 2,9-diphenethyl-1,10-phenanthroline (dpep), and 2,9-diphenyl-1,10-phenanthroline (dpp); (B) bis(diphenylphosphino) methane (dppm), 1,2-bis(diphenylphosphino)ethane (dppe), 1,3- bis(diphenylphosphino)propane (dppp), 1,2-bis(diphenylphosphino)benzene (dppb), 1,1′-bis(diphenylphosphino)ferrocene (dppFc), and bis[(2- diphenylphosphino)phenyl] ether (POP). Whatever the bis-phosphine ligand, stable heteroleptic [Cu(NN)(PP)]⁺ complexes are obtained from the 2,9-unsubstituted-1,10-phenanthroline ligands (phen and Bphen). By contrast, heteroleptic complexes obtained from dmp and dpep are stable in the solid state, but a dynamic ligand exchange reaction is systematically observed in solution, and the homoleptic/heteroleptic ratio is highly dependent on the bis-phosphine ligand. Detailed analysis revealed that the dynamic equilibrium resulting from ligand exchange reactions is mainly influenced by the relative thermodynamic stability of the different possible complexes. Finally, in the case of dpp, only homoleptic complexes were obtained whatever the bis-phosphine ligand. Obviously, steric effects resulting from the presence of the bulky phenyl rings on the dpp ligand destabilize the heteroleptic [Cu(NN)(PP)]⁺ complexes. In addition to the remarkable thermodynamic stability of [Cu(dpp)₂]BF₄, this negative steric effect drives the dynamic complexation scenario toward almost exclusive formation of homoleptic [Cu(NN)₂]⁺ and [Cu(PP)₂]⁺ complexes. This work provides the definitive rationalization of the stability of [Cu(NN)(PP)]⁺ complexes, marking the way for future developments in this field.

Full text of DOI:10.1021/ic4020042

Article
pubs.acs.org/IC
Heteroleptic Copper(I) Complexes Prepared from Phenanthroline
and Bis-Phosphine Ligands
Adrien Kaeser,†,‡ Meera Mohankumar,† John Mohanraj,§ Filippo Monti,§ Michel Holler,† Juan-Jose Cid,†
́
Omar Moudam,†,‡ Iwona Nierengarten,†,∥ Lydia Karmazin-Brelot,∥ Carine Duhayon,‡
Beatrice Delavaux-Nicot,*,‡ Nicola Armaroli,*,§ and Jean-Franco
̧
is Nierengarten*,†
́
†Laboratoire de Chimie des Mater
Strasbourg Cedex 2, France
́
iaux Molec
́
ulaires, Universite
́
de Strasbourg et CNRS (UMR 7509), 25 rue Becquerel, 67087
§Istituto per la Sintesi Organica e la Fotoreattivita,
̀
Consiglio Nazionale delle Ricerche, Via Gobetti 101, 40129 Bologna, Italy
∥Service de Radiocristallographie, Institut de Chimie, Universite
Cedex, France
‡Laboratoire de Chimie de Coordination du CNRS (UPR 8241), Universite
31077 Toulouse Cedex 4, France
́
de Strasbourg, 1 rue Blaise Pascal, B.P. 296/R8, 67008 Strasbourg
́
de Toulouse (UPS, INPT), 205 Route de Narbonne,
S
* Supporting Information
ABSTRACT: Preparation of [Cu(NN)(PP)]+ derivatives has
been systematically investigated starting from two libraries of
phenanthroline (NN) derivatives and bis-phosphine (PP)
ligands, namely, (A) 1,10-phenanthroline (phen), neocuproine
(2,9-dimethyl-1,10-phenanthroline, dmp), bathophenanthro-
line (4,7-diphenyl-1,10-phenanthroline, Bphen), 2,9-diphe-
nethyl-1,10-phenanthroline (dpep), and 2,9-diphenyl-1,10-
phenanthroline (dpp); (B) bis(diphenylphosphino)methane
(dppm), 1,2-bis(diphenylphosphino)ethane (dppe), 1,3-bis(diphenylphosphino)propane (dppp), 1,2-bis(diphenylphosphino)-
benzene (dppb), 1,1′-bis(diphenylphosphino)ferrocene (dppFc), and bis[(2-diphenylphosphino)phenyl] ether (POP).
Whatever the bis-phosphine ligand, stable heteroleptic [Cu(NN)(PP)]+ complexes are obtained from the 2,9-unsubstituted-
1,10-phenanthroline ligands (phen and Bphen). By contrast, heteroleptic complexes obtained from dmp and dpep are stable in
the solid state, but a dynamic ligand exchange reaction is systematically observed in solution, and the homoleptic/heteroleptic
ratio is highly dependent on the bis-phosphine ligand. Detailed analysis revealed that the dynamic equilibrium resulting from
ligand exchange reactions is mainly influenced by the relative thermodynamic stability of the different possible complexes. Finally,
in the case of dpp, only homoleptic complexes were obtained whatever the bis-phosphine ligand. Obviously, steric effects
resulting from the presence of the bulky phenyl rings on the dpp ligand destabilize the heteroleptic [Cu(NN)(PP)]+ complexes.
In addition to the remarkable thermodynamic stability of [Cu(dpp)2]BF4, this negative steric effect drives the dynamic
complexation scenario toward almost exclusive formation of homoleptic [Cu(NN)2]+ and [Cu(PP)2]+ complexes. This work
provides the definitive rationalization of the stability of [Cu(NN)(PP)]+ complexes, marking the way for future developments in
this field.
1 , 1 0 - p h e n a n t h r o l i n e d e r i v a t i v e s a n d b i s [ 2 -
(diphenylphosphino)phenyl]ether (POP).3,4 Not only is ligand
dissociation essentially suppressed for complexes prepared from
this particular chelating bis-phosphine ligand4 but also these
compounds are characterized by remarkably high emission
quantum yields from their long-lived metal-to-ligand charge
transfer (MLCT) excited state. Following this key finding,
numerous examples of related heteroleptic Cu(I) complexes
have been prepared from bis-phosphine and aromatic diimine
ligands.6−9 Their outstanding emission properties have been
exploited to produce efficient light-emitting devices, thus
showing that inexpensive and earth-abundant Cu(I) is an
INTRODUCTION
■
Cu(I) complexes prepared from phosphines and ligands such as
2,2′-bipyridine (bipy) or 1,10-phenanthroline (phen) were first
investigated in detail more than 30 years ago.1,2 Initially, such
systems generally prepared with PPh3 as the P ligands looked
promising because they exhibit long excited state lifetimes upon
light excitation both in the solid state and in frozen solution.1
They also display interesting photochemical properties in
relation to bimolecular photoinduced electron transfer.2
However, detailed studies have shown that exciplex quenching
is important even for compounds incorporating bulky
phosphines such as PPh3.1 Moreover, the speciation of these
compounds was hard to control even in noncoordinating
solvents such as CH2Cl2.1 Subsequently, McMillin and co-
workers reported mixed-ligand Cu(I) complexes prepared from
Received: August 2, 2013
© XXXX American Chemical Society
A
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attractive alternative to noble metal ions for such applica-
tions.7,8 As part of this research, our groups investigated
heteroleptic Cu(I) complexes combining various phenanthro-
line derivatives (NN) with different bis-phosphine ligands
(PP).8,10−12 During the course of these studies, it was found
that an equilibrium between the homoleptic and the
heteroleptic complexes is sometimes observed in solution.
This represents actually a major limitation for preparation of
stable [Cu(NN)(PP)]+ derivatives.13 We thus became
interested in a deeper understanding of the structural
parameters influencing the stability of these compounds and
decided to systematically investigate their preparation starting
from the libraries of phenanthroline derivatives and PP ligands
depicted in Chart 1.
The heteroleptic complexes were then isolated in a pure form
by recrystallization in CH2Cl2/Et2O. Similar results were
obtained when Bphen was used as the NN ligand; the
[Cu(Bphen)(PP)]BF4 complexes were thus prepared in
excellent isolated yields.
The [Cu(phen)(PP)]BF4 and [Cu(Bphen)(PP)]BF4 com-
plexes were characterized by 1H, 13C, and 31P NMR
spectroscopies, mass spectrometry, and elemental analysis.
1
Typical examples of H and 31P NMR spectra are shown in
Figure 1. For all compounds the 31P NMR spectrum recorded
at room temperature revealed a single resonance for the two
equivalent P atoms of the chelating PP ligand. Cooling the
samples to −60 °C did not give rise to significant changes, and
1
no additional signals could be detected. H NMR spectra were
also consistent with the proposed structures. Analysis of the
1
integration of the H NMR spectra revealed that, in all cases,
Chart 1. Libraries of NN Derivatives and PP Ligands Used
for Preparation of Heteroleptic [Cu(NN)(PP)]+ Derivatives
both PP and NN ligands are present in a 1:1 ratio. As shown in
1
Figure 1, a slight line broadening is observed for the H NMR
resonance of the phenanthroline proton H(2) of all complexes;
this effect is most likely due to the proximity of the quadrupolar
16
63/65Cu nuclei. In contrast, all other signals in the H NMR
spectra of complexes [Cu(NN)(PP)]BF4 (NN = phen or
Bphen) are well resolved and show no signs of broadening.
It can also be noted that the signal of proton H(2) is shielded
in [Cu(Bphen)(PP)]BF4 when compared to the corresponding
signal in Bphen as a result of the ring current effect of the
phenyl groups of the PP ligand on this particular proton.
Shielding ranges from 0.4 to 0.9 ppm, the most important one
being observed with dppb. Actually, since the bite angles are
different for each of the chelating PP ligands, the relative
orientation of the phenyl groups is not the same in the various
complexes; thus, the effect on the chemical shift of H(2) is
specific for each PP ligand. Importantly, the NMR spectra
indicate also that there is no significant ligand exchange in
solution leading to formation of the corresponding homoleptic
species. Finally, the structure of all complexes was confirmed by
FAB mass spectrometry. For all compounds the mass spectrum
displays a singly charged ion peak assigned to [Cu(NN)(PP)]+.
Other minor peaks corresponding to [Cu(NN)]+ and [Cu-
(PP)]+ are also systematically observed in the mass spectra.
X-ray-quality crystals of [Cu(phen)(dppb)]BF4 were ob-
tained by vapor diffusion of Et2O into a CH2Cl2 solution of the
complex. As shown in Figure 2, the copper atom is in a highly
distorted tetrahedral environment in which both the phenan-
throline and the dppb are chelating ligands. The distortion
mainly arises from the restricted chelate bite angles of both
ligands (P(1)−Cu(1)−P(2) 88.11(3)° and N(1)−Cu(1)−
N(2) 81.9(1)°). The angle between the planes P(1)−Cu(1)−
P(2) and (N1)−Cu(1)−(N2) is 85.62(7)°, and the bridging
phenyl ring of dppb is tilted by ca. 31.6° with respect to the
P(1)−Cu(1)−P(2) plane.
1
RESULTS AND DISCUSSION
■
The six selected bis-phosphine ligands (dppm, dppe, dppp,
dppb, dppFc, and POP) are all commercially available as well as
1,10-phenanthroline (phen), neocuproine (2,9-dimethyl-1,10-
phenanthroline, dmp), and bathophenanthroline (4,7-diphenyl-
1,10-phenanthroline, Bphen). 2,9-Diphenethyl-1,10-phenan-
throline14 (dpep) and 2,9-diphenyl-1,10-phenanthroline8,15
(dpp) were prepared according to reported procedures.
2,9-Unsubstituted-1,10-phenanthroline Derivatives
(phen and Bphen). Treatment of phen with an equimolar
amount of the appropriate bis-phosphine ligand (dppe, dppp,
dppb, POP, or dppFc) and Cu(CH3CN)4BF4 in CH2Cl2/
CH3CN gave the corresponding [Cu(phen)(PP)]BF4 deriva-
tives (Scheme 1). 1H NMR analysis of the crude mixtures thus
obtained indicated formation of a single complex in all cases.
Scheme 1. Preparation of Heteroleptic [Cu(NN)(PP)]+
Derivatives from phen and Bphen
Inspection of the crystal packing reveals a dimeric arrange-
ment of the [Cu(phen)(dppb)]+ cations in which the
phenanthroline ligands partially overlay one another; the
average distance between the mean planes of the two
phenanthroline ligands is ca. 3.5 Å (Figure 2). A similar
arrangement has been already reported for X-ray crystal
structures of [Cu(phen)(POP)]BF43 and [Cu(phen)(dppFc)]-
BF4.10 In all cases the components of the pair are related to one
another through a center of inversion that is located between
the planes of the phenanthroline rings. As shown in Figure 2,
two notable C−H/π intermolecular interactions are also
observed between neighboring [Cu(phen)(dppb)]+ cations.
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1
Figure 1. H (left) and 31P{1H} (right) NMR spectra of [Cu(Bphen)(PP)]+ (PP = dppb, dppe, dppp, and POP) recorded in CD2Cl2 at room
temperature.
Figure 2. Structure of [Cu(phen)(dppb)]BF4 (H atoms and counteranion are omitted for clarity; thermal ellipsoids are drawn at the 50% probability
level). (Inset) Pairwise stacking of the phenanthroline ligands of neighboring [Cu(phen)(dppb)]+ cations. Selected bond lengths (Angstroms):
Cu(1)−P(1) 2.2381(9), Cu(1)−P(2) 2.2486(9), Cu(1)−N(1) 2.040(2), Cu(1)−N(2) 2.049(2). Selected bond angles (degrees): P(1)−Cu(1)−
P(2) 88.11(3), P(1)−Cu(1)−N(1) 124.61(7), P(1)−Cu(1)−N(2) 129.37(7), P(2)−Cu(1)−N(1) 120.88(7), P(2)−Cu(1)−N(2) 116.11(8),
N(1)−Cu(1)−N(2) 81.9(1).
These interactions involve one hydrogen atom of the
phenanthroline unit and a phenyl group of the dppb ligand
belonging to the neighboring cations. These phenanthroline
hydrogen atoms are located at 2.8 Å from the center of their
neighboring phenyl ring.
In the particular case of dppm, reaction with an equimolar
amount of Cu(CH3CN)4BF4 and phen in CH2Cl2/CH3CN
gave the dinuclear complex [Cu2(phen)2(μ-dppm)2](BF4)2
(Scheme 2). Similarly, [Cu2(Bphen)2(μ-dppm)2](BF4)2 was
obtained when the reaction was performed with Bphen. Indeed,
dppm can chelate metals, but the four-membered ring in such
complexes is strained, and the ligand has a greater tendency to
act either as a monodentate ligand or as a bridging bidentate
ligand.17 Whereas a few examples of Cu(I) complexes in which
dppm is a chelate ligand have been reported,11 dinuclear Cu(I)
complexes with two bridging dppm ligands are by far more
C
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Scheme 2. Preparation of [Cu2(phen)2(μ-dppm)2](BF4)2
and [Cu2(Bphen)2(μ-dppm)2](BF4)2
common.18,19 It is also interesting to note that the chelating
tendency of the Ph2P(CH2)nPPh2 ligands observed for n = 2
and 3 in the particular case of these Cu(I) complexes decreases
when the chain length further increases. Effectively, dinuclear
complexes have been reported for 1,4-bis(diphenylphosphino)-
butane (n = 4).5
Dinuclear complexes were characterized by NMR spectros-
1
copy, mass spectrometry, and elemental analysis. H and 31P
NMR spectra of [Cu2(Bphen)2(μ-dppm)2](BF4)2 recorded in
CD2Cl2 at room temperature are depicted in Figure 3. In
addition to the signals corresponding to phenyl groups of the
Figure 4. (A) Structure of [Cu2(Bphen)2(μ-dppm)2](BF4)2·CH2Cl2
(H atoms, counteranions, and CH2Cl2 molecule are omitted for
clarity; thermal ellipsoids of the ORTEP plot are drawn at the 50%
probability level). (B) CPK representation of the [Cu2(Bphen)2(μ-
dppm)2] dication highlighting the intramolecular π−π interactions.
(C) Details of the coordination sphere around the Cu(I) cations in the
structure of [Cu2(Bphen)2(μ-dppm)2](BF4)2·CH2Cl2.
1
dppm moieties, the H NMR spectrum of [Cu2(Bphen)2(μ-
dppm)2](BF4)2 is characterized by four sets of signals in a
typical pattern for a 4,7-diphenyl-1,10-phenanthroline and a
broad singlet at δ = 3.88 ppm for the dppm ligands. 31P NMR
of this compound gave a broad singlet signal at room
temperature (δ = −6.62 ppm, Δν1/2 = 216 Hz). Cooling the
sample to 200 K did not give rise to additional peaks, and no
2
2
Et2O into a CH2Cl2 solution of the complex. Two views of the
[Cu2(Bphen)2(μ-dppm)2]2+ dication are shown in Figure 4.
Selected bond lengths and angles are summarized in Table 1.
The two dppm moieties are bridging two [Cu(Bphen)]+
cations, thus forming an eight-membered Cu2P4C2 metallacycle.
With a Cu(1)−Cu(2) distance of 4.4640(4) Å, there are no
Cu−Cu interactions in [Cu2(Bphen)2(μ-dppm)2]2+. Notable
intramolecular π−π interactions involve two phenyl rings
couplings were observed (e.g., JP−C−P or JP−Cu−P) at all
temperatures. This shows that the four P atoms are chemically
and magnetically equivalent; thus, it can be deduced that the
compound remains intact in solution.
For [Cu2(Bphen)2(μ-dppm)2](BF4)2, crystals suitable for X-
ray crystal structure analysis were obtained by slow diffusion of
Table 1. Bond Distances (Angstroms) and Bond Angles
(degrees) within the Coordination Sphere of
[Cu2(Bphen)2(μ-dppm)2](BF4)2·CH2Cl2 (see Figure 4 for
numbering)
selected bond lengths
selected bond angles
P(1)−Cu(1)−P(2)
Cu(1)−P(1)
2.2183(8)
2.2369(8)
2.091(2)
2.081(2)
2.2845(8)
2.2296(8)
2.081(2)
2.130(2)
141.34(3)
105.86(7)
108.25(7)
103.49(7)
101.25(7)
79.70(9)
134.83(3)
97.69(7)
98.25(7)
122.56(7)
108.04(7)
79.10(9)
Cu(1)−P(2)
Cu(1)−N(1)
Cu(1)−N(2)
Cu(2)−P(3)
Cu(2)−P(4)
Cu(2)−N(3)
Cu(2)−N(4)
P(1)−Cu(1)−N(1)
P(1)−Cu(1)−N(2)
P(2)−Cu(1)−N(1)
P(2)−Cu(1)−N(2)
N(1)−Cu(1)−N(2)
P(3)−Cu(2)−P(4)
P(3)−Cu(2)−N(3)
P(3)−Cu(2)−N(4)
P(4)−Cu(2)−N(3)
P(4)−Cu(2)−N(4)
N(3)−Cu(2)−N(4)
Figure 3. 1H (bottom) and 31P{1H} (top right) NMR spectra of
[Cu2(Bphen)2(μ-dppm)2](BF4)2 recorded in CD2Cl2 at room temper-
ature.
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within both of the dppm ligands. The average distance between
the mean planes of the aromatic rings is ca. 3.6 Å in both cases.
In addition, two intramolecular face-to-face π−π interactions
are also observed between both phenanthroline ligands and a
phenyl unit of one of their neighboring PPh2 moieties.
Establishment of these interactions is at the origin of the
particularly large P−Cu−P angles. As a result, the metallacycle
adopts a peculiar folded conformation and both phenanthro-
lines are no longer in a relative face-to-face orientation as
typically observed in the X-ray crystal structures of related
compounds.19
2,9-Disubstituted-1,10-phenanthroline Derivatives
(dmp, dpep, and dpp). Reaction of dmp, dpep, and dpp
with the PP ligands and Cu(CH3CN)4BF4 was systematically
investigated. A solution of the appropriate bis-phosphine ligand
(1 equiv) and Cu(CH3CN)4BF4 (1 equiv) in CH2Cl2/CH3CN
was stirred for 0.5 h; then dmp, dpep, or dpp (1 equiv) was
added. After 1 h, solvents were evaporated. Products were
1
analyzed as received by H NMR. The relative proportion of
the different possible complexes, i.e., [Cu(NN)(PP)]BF4,
[Cu(NN)2]BF4, and [Cu(PP)2]BF4, was deduced from
1
comparison with the H NMR spectrum of the corresponding
[Cu(NN)2]BF4 derivative recorded in the same solvent. The
results are summarized in Table 2, and typical 1H NMR spectra
are depicted in Figure 5.
Figure 5. Aromatic region of the 1H NMR spectra of the crude
Table 2. Proportion of Heteroleptic Complex Obtained
upon Reaction of the Various PP Ligands with
products obtained after treatment of various PP ligands with
◆
Cu(CH3CN)4BF4 and dpep: ( ) [Cu(dpep)2]BF4; (*) [Cu(dpep)-
(PP)](BF4). For comparison purposes, the 1H NMR spectrum of
[Cu(dpep)2]BF4 (top) is also represented.
Cu(CH3CN)4BF4 and dmp, dpep, or dpp as Deduced from
1
Integration of the H NMR Spectra of the Crude Product
Mixture
dmp
30%
dpep
10%
dpp
known. Values of 113.18°, 116.44°, and 117.98° have been
reported for the P−Cu−P bond angles of [Cu(dmp)(dppFc)]-
BF4,10 [Cu(dmp)(POP)]BF4,3,4 and [Cu(dpep)(POP)]BF4,8
dppm
dppe
dppp
dppb
dppFc
POP
traces
traces
traces
traces
traces
traces
80%
15%
1
respectively. H and 31P NMR analysis of the recrystallized
80%
10%
65%
5%
samples recorded in CD2Cl2 revealed that the heteroleptic
complex was the largely major species present in solution
(>99%). However, traces of [Cu(dmp)2]BF421 or [Cu(dpep)2]-
>99%
>99.5%
>99%
>99.5%
15
BF4 were always detected in the 1H NMR, thus showing that
Whereas the heteroleptic [Cu(NN)(PP)]+ complexes were
the only reaction products whatever the PP ligand when
starting from 2,9-unsubstituted-1,10-phenanthrolines, the sit-
uation became completely different when 2,9-substituted-1,10-
phenanthroline derivatives were used as starting material.
Effectively, when using dmp and dpep as reagents, a mixture of
[Cu(NN)(PP)]BF4, [Cu(NN)2]BF4, and [Cu(PP)2]BF4 was
always obtained and their relative proportion found to be highly
dependent on the bis-phosphine ligand (Table 2). In contrast,
homoleptic complexes were obtained as the only detectable
products when dpp was used as the NN ligand. Obviously,
steric effects resulting from the presence of the bulky phenyl
rings on the dpp ligand destabilize the heteroleptic [Cu(dpp)-
(PP)]+ complexes. In addition to the remarkable thermody-
namic stability of [Cu(dpp)2]BF4,20 this negative steric effect
drives the dynamic complexation scenario toward formation of
homoleptic complexes almost exclusively.
ligand exchange reactions take place to a minor extent for the
heteroleptic complexes prepared from 2,9-disubstituted-1,10-
phenanthroline and dppFc or POP.
dppm, dppe, dppp, and dppb. Some of the heteroleptic
complexes were obtained pure as crystalline solids by vapor
diffusion of Et2O into a CH2Cl2 solution of the corresponding
reaction mixture. This was the case for [Cu2(dmp)2(μ-
dppm)2](BF4)2, [Cu(dmp)(dppe)]BF4, [Cu(dmp)(dppp)]-
BF4, and [Cu(dmp)(dppb)]BF4. All attempts to obtain other
heteroleptic complexes in a pure form by recrystallization of the
crude product mixture failed. Indeed, slow diffusion of Et2O
into a CH2Cl2 solution of the mixture of complexes yielded
either only orange-red crystals of [Cu(NN)2]BF4 or a mixture
of orange-red and yellow crystals corresponding to [Cu-
(NN)2]BF4 and [Cu(NN)(PP)]BF4, respectively.
X-ray-quality crystals were obtained for both [Cu(dmp)-
(dppe)]BF4 and [Cu(dmp)(dppp)]BF4. Their X-ray crystal
structures are depicted in Figure 6. Selected bond lengths and
angles are summarized in Table 3.
dppFc and POP. [Cu(dmp)(dppFc)]BF4,10 [Cu(dmp)-
(POP)]BF4,3,4 [Cu(dpep)(dppFc)]BF4,10 and [Cu(dpep)-
8
(POP)]BF4 were obtained pure by vapor diffusion of Et2O
Structures of the [Cu(dmp)(dppe)]+ and [Cu(dmp)-
(dppp)]+ cations are similar to the one described for the X-
ray crystal structures of the corresponding PF6− salts.5 Whereas
no particular differences in bond lengths are observed for
into a CH2Cl2 solution of the corresponding reaction mixture.
The four compounds have been already reported in the
literature, and X-ray crystal structures of three of them are
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result of the P−Cu−P angles imposed by the different number
of methylene units between the two P atoms in both
complexes. It can be noted that the PPh2 groups do not
significantly interact with the dmp ligand; however, in both
cases, they are sterically close to the methyl groups which are
located in between two phenyl groups. The closest C−H (Me)
to phenyl distances ranges from 2.54 to 2.85 Å for
[Cu(dmp)(dppe)]BF4. Values ranging from 2.85 to 3.30 Å
are seen for [Cu(dmp)(dppp)]BF4. These observations explain
well the observed destabilization of heteroleptic complexes
prepared from 2,9-disubstituted-1,10-phenanthroline ligands
(vide infra).
Whereas all dmp-containing heteroleptic complexes obtained
in pure form by recrystallization were perfectly stable in the
solid state, it is important to highlight that equilibration between
the homoleptic and the heteroleptic complexes was observed as soon
as the crystals are dissolved (even in a noncoordinating solvent
such as CH2Cl2). Indeed, the heteroleptic/homoleptic ratio
deduced from the 1H NMR spectrum is exactly the same as the
one observed in the crude mixture (Table 2). These
observations show that ligand exchange reactions are taking
place in solution for all compounds. In other words, there is a
dynamic equilibrium between the heteroleptic complexes and
the corresponding homoleptic species in solution (Figure 7).
Indeed, all species present in the solutions were clearly
Figure 6. Structures of [Cu(dmp)(dppe)]BF4·Et2O (left) and
[Cu(dmp)(dppp)]BF4 (right). H atoms, solvent in the case of dppe,
and counteranion are omitted for clarity; thermal ellipsoids are drawn
at the 50% probability level.
Table 3. Bond Distances and Bond Angles within the
Coordination Sphere of [Cu(dmp)(PP)]BF4 (PP = dppe and
dppp, see Figure 6 for the numbering)
selected bond lengths (Å)
PP = dppe PP = dppp
selected bond angles (deg)
PP = dppe PP = dppp
Cu(1)−
2.267(2)
2.273(2)
2.059(6)
2.050(6)
2.268(3) P(1)−Cu(1)−
91.54(7)
132.1(2)
119.7(2)
114.5(2)
120.3(2)
82.2(2)
104.2(1)
121.9(2)
108.0(2)
120.7(2)
119.5(2)
81.3(3)
P(1)
P(2)
1
identified by H and 31P NMR spectroscopy as well as by
Cu(1)−
P(2)
2.261(3) P(1)−Cu(1)−
N(1)
FAB mass spectrometry.
Typical resonances of both [Cu(dmp)(PP)]+ and [Cu-
Cu(1)−
N(1)
2.091(8) P(1)−Cu(1)−
N(2)
1
(dmp)2]+ derivatives were clearly recognized in the H NMR
Cu(1)−
N(2)
2.090(8) P(2)−Cu(1)−
spectra of the dynamic mixtures, but typical resonances of
[Cu(PP)2]BF4 were not always easily distinguishable (Figure
8). The presence of the homoleptic complex [Cu(PP)2]BF4
was however unambiguously demonstrated by 31P NMR
spectroscopy (Figure 9). [Cu(dppm)2]BF4,11 [Cu(dppe)2]-
N(1)
P(2)−Cu(1)−
N(2)
N(1)−
Cu(1)−
N(2)
11
BF4,22 [Cu(dppp)2]BF4,22 and [Cu(dppb)2]BF4 are all
known compounds, and their 31P NMR spectra are described
in the literature. For all systems the diagnostic signals of both
homoleptic and heteroleptic complexes were clearly observed at
[Cu(dmp)(dppe)]BF4 and [Cu(dmp)(dppp)]BF4, the bond
angles around the Cu(I) cation are significantly different as a
Figure 7. Dynamic equilibrium evidenced in solution between the heteroleptic complexes and their corresponding homoleptic species.
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It can also be noted that the 31P NMR resonance of
[Cu(dppp)2]BF4 is not well resolved and appears complicated
at room temperature. Detailed variable-temperature NMR
studies have been reported for this compound22 and the
complicated 31P NMR pattern of [Cu(dppp)2](BF4) explained
by a slow conformational exchange (ring inversion) on the
NMR time scale. Indeed, at low temperature the phosphorus
atoms of [Cu(dppp)2]BF4 are nonequivalent as a result of a
frozen chair conformation of the CuP2C3 six-membered rings.
It is well known that thermodynamically stable copper(I)
complexes are also kinetically labile, and fast ligand exchange is
often observed in solution at ambient temperature.23 This is
also clearly observed for the Cu(I) complexes prepared from
bis-phosphines and phenanthroline ligands. In this particular
case, whatever the ratio of homoleptic and heteroleptic
complexes in solution, all ligands and metal binding sites are
utilized to generate coordinatively saturated complexes. There-
fore, the equilibrium between the different complexes must be
mainly governed by the relative thermodynamic stability of the
different possible complexes.24 On one hand, homoleptic
[Cu(NN)2]+ complexes prepared from 2,9-disustituted-1,10-
phenanthroline ligands are particularly stable (log β = 10−
12);20 they have thus a priori tendency to drive the equilibrium
toward formation of the homoleptic complexes. In contrast, this
is not the case for the Cu(I) complexes obtained from 2,9-
unsubstituted-1,10-phenanthrolines. The corresponding [Cu-
(NN)2]+ complexes are actually less stable and therefore unable
to significantly compete with formation of [Cu(NN)(PP)]+.
On the other hand, subtle steric effects may also contribute to
stabilize/destabilize both [Cu(PP)2]+ and [Cu(NN)(PP)]+
derivatives. Actually, the differences in behavior observed for
the various bis-phosphine ligands may be explained by the
differences in bite angles for the different chelating P ligands.
When this angle is small enough (dppe, dppp, and dppb), the
Cu(I) center can easily accommodate two ligands to form a
stable homoleptic complex.11,22 In contrast, steric factors
resulting from the wider P−Cu−P angle for the other bis-
phosphines (dppFc and POP) may substantially destabilize the
[Cu(PP)2]+ derivative. This is clearly seen in the case of
[Cu(POP)2]+ for which a X-ray crystal structure could be
obtained (Figure 10).25 The Cu(I) cation is effectively too
small to accommodate two POP ligands in a tetrahedral
coordination geometry. Only one POP ligand is chelating the
metal, while the other one is acting as a monodentate ligand. As
a result the Cu(I) cation is in a distorted trigonal coordination
geometry.
Figure 8. 1H NMR (CD2Cl2) recorded upon dissolution of
recrystallized samples of [Cu2(dmp)2(μ-dppm)2](BF4)2, [Cu(dmp)-
(dppe)]BF4, and [Cu(dmp)(dppb)]BF4. In all cases, ligand exchange
reactions take place and the typical resonances of [Cu(dmp)2]BF4 are
clearly observed. For comparison purposes, the H NMR spectrum of
[Cu(dmp)2]BF4 (top) is also represented.
1
The homoleptic Cu(I) complex prepared from dppFc has
been characterized in solution by Long and co-workers, but no
X-ray crystal structure has been published for this compound.26
We decided to prepare this compound from dppFc and
Cu(CH3CN)4BF4. As reported by Long and co-workers, the
resulting complex displays broadened 1H and 31P NMR
features at room temperature, suggesting dissociative processes
in solution. Crystals were obtained by slow diffusion of Et2O
into a CH2Cl2 solution of the crude mixture of complexes.
Surprisingly, their X-ray crystal structure analysis revealed
formation of a dinuclear Cu(I) complex (Figure 10). Each
metal center is chelated by a dppFc ligand, and the two
[Cu(dppFc)]+ subunits are connected by an additional bridging
dppFc ligand. 1H and 31P NMR spectra recorded upon
dissolution of the recrystallized sample are different when
compared to the crude mixture. This is consistent with a
different ligand to metal ratio in solution. However, as in the
Figure 9. 31P{1H} NMR (CD2Cl2) recorded upon dissolution of
recrystallized samples of [Cu(dmp)(dppb)]BF4, [Cu(dmp)(dppe)]-
BF4, [Cu2(dmp)2(μ-dppm)2](BF4)2, and [Cu(dmp)(dppe)]BF4. In all
cases, ligand exchange reactions take place and the typical resonances
of [Cu(PP)2]BF4 are clearly observed.
room temperature (Figure 9) except in the case of dppe.
Actually, the 31P NMR signal of [Cu(dppe)2]BF4 is particularly
broad at room temperature,22 preventing its observation under
these conditions. As reported in the literature, lowering the
temperature led to a significant decrease of Δν1/2, and the
characteristic signal observed at δ = +7.8 ppm confirmed the
presence of [Cu(dppe)2]BF4 in solution.
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also well the further destabilization observed for the
corresponding heteroleptic complexes prepared from dpep.
Steric hindrance may also limit the stability of the dinuclear
Cu(I) complexes obtained from dppm and 2,9-disubstituted-
1,10-phenanthrolines. For all these P ligands, steric effects are
involved in destabilization of the heteroleptic complexes and
thus contribute, at least in part, to displacing the dynamic
mixture toward the homoleptic species. In contrast, for dppFc
and POP, the P−Cu−P angle is wider (113−118°) and the
wrapping of the phenanthroline ligand is more effective in
[Cu(NN)(PP)]+. As a result, the orientation of the phenyl
groups of the two PPh2 subunits is different and negative steric
effects are limited. In addition to destabilization of the
homoleptic Cu(I) complexes of dppFc and POP (vide
supra), this limited steric hindrance drives the system toward
almost exclusive formation of the heteroleptic complexes.
CONCLUSIONS
■
The systematic investigations done with the libraries of
phenanthroline derivatives and bis-phosphine ligands shown
in Chart 1 revealed several important trends: (i) whatever the
bis-phosphine ligand, stable heteroleptic complexes are
obtained from 1,10-phenanthroline; (ii) 4,7-substituents on
the phenanthroline ligand (Bphen) have no negative influence
on formation of the heteroleptic complexes; (iii) heteroleptic
complexes obtained from dmp are stable in the solid state, but a
dynamic ligand exchange reaction is systematically observed in
solution, and the homoleptic/heteroleptic ratio is highly
dependent on the bis-phosphine ligand; (iv) by increasing the
size of the 2,9-substituents, e.g., when going from dmp to dpep,
the heteroleptic complexes are further destabilized and the
homoleptic complexes are favored except in the cases of dppFc
and POP for which the heteroleptic complexes are still almost
exclusively obtained, (v) by further increasing the size of the
2,9-substituents, e.g., when going from dpep to dpp, only
homoleptic complexes were obtained whatever the bis-
phosphine ligand as a result of steric hindrance, (vi) the
difference in behavior of the various bis-phosphine ligands has
been explained by their different chelate bite angles influencing
the stability of both [Cu(NN)(PP)]+ and [Cu(PP)2]+; the
remarkable stability of the dppFc- and POP-containing
heteroleptic derivatives results from a substantial destabilization
of both [Cu(dppFc)2]+ and [Cu(POP)2]+ species as well as
from a favorable orientation of the aromatic groups of the PPh2
moieties limiting steric hindrance effects when the phenanthro-
line ligand is substituted in its 2 and 9 positions.
Detailed analysis revealed that the dynamic equilibrium
resulting from ligand exchange reactions is mainly influenced by
the relative thermodynamic stability of the different possible
complexes. The exceptionally high thermodynamic stability of
the homoleptic [Cu(NN)2]+ complexes tends to drive the
equilibrium toward formation of the homoleptic complexes;
this is particularly the case when steric hindrance effects
destabilize the [Cu(NN)(PP)]+ derivatives prepared from 2,9-
disubstituted-1,10-phenanthroline ligands. This effect is how-
ever in part counterbalanced by a substantial destabilization of
the [Cu(PP)2]+ derivatives in the case of POP and dppFc. With
these particular chelating P ligands, stable [Cu(NN)(PP)]+
derivatives are obtained even from 1,10-phenanthroline ligands
bearing substituents of a reasonable size at the 2,9-positions.
Most of the copper(I) complexes described in the present
paper show interesting electronic properties which have been
Figure 10. (A) Structure of [Cu(POP)2]BF4. H atoms and
counteranion are omitted for clarity; thermal ellipsoids are drawn at
the 50% probability level. Selected bond lengths (Angstroms):
Cu(1)−P(1) 2.273(1), Cu(1)−P(2) 2.261(1), Cu(1)−P(3)
2.263(1). Selected bond angles (degrees): P(1)−Cu(1)−P(2)
114.03(6), P(1)−Cu(1)−P(3) 121.49(6), P(2)−Cu(1)−P(3)
121.90(6). P(4) is at a nonbonding distance from the Cu center
(3.96 Å). (B) Structure of [Cu2(dppFc)3](BF4)2·(H2O)2·CH2Cl2. H
atoms, solvent molecules, and counteranions are omitted for clarity;
thermal ellipsoids are drawn at the 50% probability level. Selected
bond lengths (Angstroms): Cu(1)−P(1) 2.264(2), Cu(1)−P(2)
2.273(1), Cu(1)−P(3) 2.248(2). Selected bond angles (degrees):
P(1)−Cu(1)−P(2) 111.72(6), P(1)−Cu(1)−P(3) 122.47(7), P(2)−
Cu(1)−P(3) 125.01(7).
case of the crude mixture, NMR data suggest the presence of
several species in solution. Being out of the scope of the present
investigation, this system was not further investigated.
X-ray crystal structure analysis of the homoleptic Cu(I)
complexes prepared from dppFc and POP revealed that the
Cu(I) cation is too small to accommodate two ligands in a
distorted tetrahedral coordination geometry. Indeed, the large
P−Cu−P angle prevents formation of a tetracoordinated
complex in both cases. As mentioned above, these homoleptic
complexes are thus destabilized, and this effect contributes to
favor formation of the [Cu(NN)(PP)]+ derivatives.
Finally, the difference in bite angle for the various chelating P
ligands may also affect the stability of [Cu(NN)(PP)]+. Indeed,
when the phenanthroline ligand is substituted in its 2 and 9
positions, negative steric effects may contribute to destabilize
the heteroleptic complex. This view is indeed supported by the
X-ray crystal structures of [Cu(dmp)(dppe)]BF4 and [Cu-
(dmp)(dppp)]BF4 in which the methyl groups of the dmp
ligand are close to the phenyl units of the PPh2 moieties. In the
case of dppb, the P−Cu−P angle is in the same range and
similar steric effects are expected. These observations explain
H
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[Cu2(phen)2(μ-dppm)2](BF4)2. This compound was thus obtained in
87% yield as a yellow crystalline solid. H NMR (CD2Cl2, 300 MHz,
293 K): 8.68 (d, J = 4 Hz, 4H), 8.24 (d, J = 8 Hz, 4H), 7.77 (m, 4H),
7.69 (s, 4H), 7.07−6.87 (m, 40H), 3.88 (m, 4H). 31P{1H} NMR
(CD2Cl2, 293 K, 162 MHz): −6.62. Anal. Calcd for
C74H60N4P4Cu2B2F8: C, 62.16; H, 4.23; N, 3.92. Found: C, 62.43;
H, 4.55; N, 3.92.
already investigated in detail. The results will be described in a
second paper.
1
EXPERIMENTAL SECTION
■
General Procedures. Reagents were purchased as reagent grade
and used without further purification. Compounds dpep,15 dpp,14
[Cu(dpep)2]BF4,15 and [Cu(dmp)2]BF421 were prepared according to
previously reported procedures. Acetonitrile (CH3CN) was distilled
over CaH2 under Ar. Dichloromethane (CH2Cl2) was distilled over
CaH2 under Ar. All reactions were performed in standard glassware
under an inert Ar atmosphere. Evaporation and concentration were
done at water aspirator pressure and drying in vacuo at 10−2 Torr.
Column chromatography: silica gel 60 (230−400 mesh, 0.040−0.063
mm) was purchased from E. Merck. Thin layer chromatography
(TLC) was performed on aluminum sheets coated with silica gel 60
F254 purchased from E. Merck. NMR spectra were recorded on a
Bruker AC 300 or AC 400 with solvent peaks as reference. Elemental
analyses were carried out on a Perkin-Elmer 2400 B analyzer at the
LCC Microanalytical Laboratory in Toulouse. Mass spectra were
[Cu(Bphen)(dppe)]BF4. This compound was thus obtained in 61%
1
yield as a yellow crystalline solid. H NMR (CD2Cl2, 300 MHz, 293
K): 8.86 (d, J = 5 Hz, 2H), 8.19 (s, 2H), 7.87 (d, J = 5 Hz, 2H), 7.68
(m, 10H), 7.53−7.41 (m, 20H), 2.83 (t, J = 6 Hz, 4H). 31P{1H} NMR
(CD2Cl2, 293 K, 162 MHz): −4.44. 13C {1H} NMR (CD2Cl2, 298 K,
75 MHz): 151.2, 150.5, 145.4 (t, JP−C = 2 Hz), 137.0, 133.0 (t, JP−C = 8
Hz), 132.9, 132.7, 131.4, 130.4, 130.3, 130.1 (t, JP−C = 5 Hz), 129.8,
128.5, 126.1, 125.9, 26.4 (t, JP−C = 19 Hz). Anal. Calcd for
C50H40N2P2CuBF4: C, 68.15; H, 4.57; N, 3.18. Found: C, 68.32; H,
4.35; N, 3.34. FAB-MS: 793 ([M − BF4]+, calcd for C50H40N2P2Cu
793.2).
[Cu(Bphen)(dppp)]BF4. This compound was thus obtained in 65%
1
yield as a yellow crystalline solid. H NMR (CD2Cl2, 300 MHz, 293
K): 8.84 (d, J = 5 Hz, 2H), 8.12 (s, 2H), 7.77 (d, J = 5 Hz, 2H), 7.63
(m, 10H), 7.41−7.29 (m, 20H), 2.77 (m, 4H), 2.38 (m, 2H). 31P{1H}
NMR (CD2Cl2, 293 K, 162 MHz): −13.03. 13C {1H} NMR (CD2Cl2,
298 K, 75 MHz): 150.9, 150.4, 145.1 (t, JP−C = 2 Hz), 137.0, 134.3 (t,
JP−C = 16 Hz), 132.8 (t, JP−C = 8 Hz), 130.9, 130.4, 130.3, 129.8, 129.7,
129.73, 129.6, 128.4, 126, 125.8, 29.5 (t, JP−C = 8 Hz), 20.6 (t, JP−C = 2
Hz). Anal. Calcd for C51H42N2P2CuBF4: C, 68.43; H, 4.73; N, 3.13.
Found: C, 68.12; H, 4.90; N, 2.99. FAB-MS: 807 ([M − BF4]+, calcd
for C51H42N2P2Cu 807.21).
obtained at the Service Commun de Spectromet
́
rie de Masse de
l’Universite Paul Sabatier et du CNRS de Toulouse. Fast atom
́
bombardment (FAB) spectra were performed on a Nermag R 10−
10H spectrometer. A 9 kV xenon atom beam was used to desorb
samples from the 3-nitrobenzyl alcohol matrix.
General Procedure for Preparation of [Cu(phen)(PP)]BF4 and
[Cu(Bphen)(PP)]BF4. A solution of the appropriate bis-phosphine
ligand (1 equiv) and Cu(CH3CN)4BF4 (1 equiv) in a 7:3 CH2Cl2/
CH3CN mixture was stirred for 0.5 h; then phen or Bphen (1 equiv)
was added. After 1 h, solvents were evaporated. Heteroleptic
complexes were then obtained pure as crystalline solids by slow
diffusion of Et2O into a CH2Cl2 solution of the crude product.
[Cu(phen)(dppe)]BF4. This compound was thus obtained in 86%
[Cu(Bphen)(dppb)]BF4. This compound was thus obtained in 90%
1
yield as a yellow crystalline solid. H NMR (CD2Cl2, 300 MHz, 293
K): 8.44 (d, J = 5 Hz, 2H), 8.11 (s, 2H), 7.76 (d, J = 5 Hz, 2H), 7.70
(m, 4H), 7.63 (m, 10H), 7.49−7.29 (m, 20H). 31P{1H} NMR
(CD2Cl2, 293 K, 162 MHz): −2.71. 13C{1H} NMR (CD2Cl2, 298 K,
75 MHz): 151.1, 150.2, 145.2 (t, JP−C = 2 Hz), 142.1 (t, JP−C = 35 Hz),
136.9, 135.7 (t, JP−C = 4 Hz), 133.5 (t, JP−C = 8 Hz), 133.2, 132.9,
132.7, 132.4, 131.1, 130.4, 130.3, 129.9, 129.92, 129.8, 129.81, 128.3,
126.0, 125.8. Anal. Calcd for C54H40N2P2CuBF4·H2O: C, 68.47; H,
4.47; N, 2.96. Found: C, 68.12; H, 4.71; N, 3.07. FAB-MS: 841 ([M −
BF4]+, calcd for C54H40N2P2Cu 841.2).
[Cu(Bphen)(dppFc)]BF4. This compound was thus obtained in 70%
yield as an orange crystalline solid. 1H NMR (CD2Cl2, 300 MHz, 293
K): 8.83 (d, J = 5 Hz, 2H), 8.09 (s, 2H), 7.67−7.58 (m, 12H), 7.33
(m, 20H), 4.59 (m, 4H), 4.45 (m, 4H). 31P{1H} NMR (CD2Cl2, 293
K, 162 MHz): −8.70. 13C{1H} NMR (CD2Cl2, 298 K, 100 MHz):
150.9, 150.4,144.8 (t, JP−C = 2 Hz), 137.0, 134.4, 134.1, 133.9, 133.8 (t,
JP−C = 8 Hz), 131, 130.4, 130.3, 129.8, 129.5 (t, JP−C = 5 Hz), 128.4,
126.0, 125.8, 75.44, 75.4 (t, JP−C = 5 Hz), 75.2, 74.9, 73.7 (t, JP−C = 2
Hz). Anal. Calcd for C58H44N2P2FeCuBF4: C, 67.17; H, 4.28; N, 2.70.
Found: C, 67.05; H, 4.44; N, 2.67. FAB-MS: 949 ([M − BF4]+, calcd
for C58H44N2P2FeCu 949.16).
1
yield as a yellow crystalline solid. H NMR (CD2Cl2, 300 MHz, 293
K): 8.76 (d, J = 4 Hz, 2H), 8.67 (d, J = 8 Hz, 2H), 8.17 (s, 2H), 7.90
(dd, J = 8 Hz, J = 4 Hz, 2H), 7.39 (m, 20H), 2.76 (t, J = 6 Hz, 4H).
31P{1H} NMR (CD2Cl2, 293 K, 162 MHz): −4.80. 13C {1H} NMR
(CD2Cl2, 298 K, 75 MHz): 150.9, 144.7, 138.6, 133.1, 132.9 (t, JP−C
=
8 Hz), 132.8, 132.6, 131.4, 130.7, 130.1 (t, JP−C = 4 Hz), 128.2, 125.9,
26.4 (t, JP−C = 19 Hz). Anal. Calcd for C38H32N2P2CuBF4: C, 62.61;
H, 4.42; N, 3.84. Found: C, 62.72; H, 4.56; N, 3.80. FAB-MS: 641.0
([M − BF4]+, calcd for C38H32N2P2Cu 641.13).
[Cu(phen)(dppp)]BF4. This compound was thus obtained in 62%
1
yield as a yellow crystalline solid. H NMR (CD2Cl2, 300 MHz, 293
K): 8.77 (d, J = 4 Hz, 2H), 8.60 (d, J = 8 Hz, 2H), 8.12 (s, 2H), 7.83
(dd, J = 8 Hz, J = 4 Hz, 2H), 7.36 (m, 4H), 7.24 (m, 16H), 2.71 (m,
4H), 2.34 (m, 2H). 31P{1H} NMR (CD2Cl2, 293 K, 162 MHz):
−13.39. 13C{1H} NMR (CD2Cl2, 298 K, 75 MHz): 150.8, 144.4,
138.3, 134.2 (t, JP−C = 16 Hz, 4C), 132.7 (t, JP−C = 8 Hz), 130.9, 130.6,
129.7 (t, JP−C = 5 Hz), 128.2, 125.8, 29.5 (t, JP−C = 8 Hz), 20.6 (t, JP−C
= 4 Hz). Anal. Calcd for C39H34N2P2CuBF4·CH2Cl2: C, 58.03; H,
4.38; N, 3.38. Found: C, 57.94; H, 4.75; N, 3.11. FAB-MS: 655 ([M −
BF4]+, calcd for C39H34N2P2Cu 655.15).
[Cu(Bphen)(POP)]BF4. This compound was thus obtained in 92%
yield as a yellow crystalline solid. Analytical data were identical to
those described in the literature.26
[Cu(phen)(dppb)]BF4. This compound was thus obtained in 93%
1
yield as a yellow crystalline solid. H NMR (CD2Cl2, 300 MHz, 293
[Cu2(Bphen)2(μ-dppm)2](BF4)2. This compound was thus obtained
in 48% yield as a yellow crystalline solid. 1H NMR (CD2Cl2, 300 MHz,
293 K): 8.75 (d, J = 5 Hz, 4H), 7.72 (m, 8H), 7.58 (m, 13H), 7.51 (m,
7H), 7.09 (m, 25H), 6.96 (m, 15H), 3.98 (m, 4H). 31P{1H} NMR
(CD2Cl2, 293 K, 162 MHz): −6.45. 13C{31P}{1H} NMR (CD2Cl2, 298
K, 75 MHz): 151.1, 150.1, 144.2, 137.3, 133.7, 133.3, 130.5, 130.4,
129.9, 129.7, 129.1, 127.5, 126.2, 124.9, 66.5, 27.3, 15.9. Anal. Calcd
for C98H76N4P4Cu2B2F8·CH2Cl2: C, 65.36; H, 4.32; N, 3.08. Found:
C, 65.20; H, 4.01; N, 3.25. FAB-MS: 1647 ([M − BF4]+, 10%, calcd
for C98H76N4P4Cu2BF4 1646.37), 780 ([M − (BF4)2]2+, 100%, calcd
for C98H76N4P4Cu2 780.18).
General Procedure for Preparation of [Cu(dmp)(PP)]BF4 and
[Cu(dpep)(PP)]BF4. A solution of the appropriate bis-phosphine
ligand (1 equiv) and Cu(CH3CN)4BF4 (1 equiv) in a 7:3 CH2Cl2/
CH3CN mixture was stirred for 0.5 h; then dmp or dpep (1 equiv) was
added. After 1 h, solvents were evaporated. Products were analyzed as
K): 8.59 (d, J = 8 Hz, 2H), 8.35 (d, J = 4 Hz, 2H), 8.09(s, 2H), 7.79
(dd, J = 8 Hz, J = 5 Hz, 2H), 7.66 (m, 4H), 7.44 (m, 4H), 7.35 (m,
8H), 7.25(m, 8H). 31P{1H} NMR (CD2Cl2, 293 K, 162 MHz):
−2.94.13C{1H} NMR (CD2Cl2, 298 K, 75 MHz): 150.7, 144.6, 142.0,
138.5, 135.7 (t, JP−C = 4 Hz), 133.5 (t, JP−C = 8 Hz), 133.1, 132.9,
132.6, 132.3, 131.1, 130.5, 129.9 (t, JP−C = 5 Hz), 128.1, 125.8. Anal.
Calcd for C42H32N2P2CuBF4: C, 59.92; H, 3.97; N, 3.25. Found: C,
60.01; H, 3.99; N, 3.01. FAB-MS: 689 ([M − BF4]+, calcd for
C42H32N2P2Cu 689.13).
[Cu(phen)(dppFc)]BF4. This compound was thus obtained in 75%
yield as an orange crystalline solid. Analytical data were identical to
those described in the literature.10
[Cu(phen)(POP)]BF4. This compound was thus obtained in 95%
yield as a yellow crystalline solid. Analytical data were identical to
those described in the literature.3,4
I
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received by 1H NMR. The relative proportion of the different possible
complexes, i.e., [Cu(NN)(PP)]BF4, [Cu(NN)2]BF4, and [Cu(NN)2]-
BF4, was deduced from comparison with the 1H NMR spectrum of the
corresponding [Cu(NN)2]BF4 derivative recorded in the same solvent.
Some of the heteroleptic complexes were obtained pure as crystalline
solids by vapor diffusion of Et2O into a CH2Cl2 solution of the
corresponding reaction mixture. This was the case for [Cu2(dmp)2(μ-
dppm)2](BF4)2, [Cu(dmp)(dppe)]BF4, [Cu(dmp)(dppp)]BF4, [Cu-
(dmp)(dppb)]BF4, [Cu(dmp)(dppFc)]BF4, [Cu(dmp)(POP)]BF4,
[Cu(dpep)(dppFc)]BF4, and [Cu(dpep)(POP)]BF4. All attempts to
obtain the other heteroleptic complexes in a pure form by
recrystallization of the crude product mixture failed. Indeed, slow
diffusion of Et2O into a CH2Cl2 solution of the mixture of complexes
yielded either only orange-red crystals of [Cu(NN)2]BF4 or a mixture
of orange-red and yellow crystals corresponding to [Cu(NN)2]BF4
and [Cu(NN)(PP)]BF4, respectively.
obtained by vapor diffusion of n-hexane into this CH2Cl2 solution.
Compound [Cu(POP)2]BF4 was thus obtained in 68% yield as
colorless crystals. 1H NMR (CD2Cl2, 300 MHz, 293 K): 6.49 (d, J = 4
Hz, 2H), 6.76−6.83 (m, 10H), 7.00 (t, J = 8 Hz, 10H), 7.18 (td, J = 8
and 2 Hz, 2H), 7.26 (t, J = 7 Hz, 4H). 31P{1H} NMR (CD2Cl2, 293 K,
121.5 MHz): −13.57. 13C{31P}{1H} NMR (CD2Cl2, 298 K, 75.5
MHz): 119.6, 125.0, 129.0, 130.5, 131.5, 132.4, 134.1, 134.7, 158.5.
Anal. Calcd for C72H56O2P4CuBF4: C, 70.45; H, 4.6. Found: C, 70.13;
H, 4.44. FAB-MS: 1139.7 (17%, [Cu(POP)2]+), 601.3 (100%,
[Cu(POP)]+).
Preparation of the Homoleptic Complex from dppFc. A
mixture of Cu(CNCH3)BF4 (0.03 g, 0.09 mmol) and DPPF (0.100 g,
0.18 mmol) in CH2Cl2 (10 mL) was stirred for 1 h at room
temperature. The resulting solution was evaporated to yield an orange
powder in quantitative yield. The product was analyzed as received. 1H
NMR (CD2Cl2, 300 MHz, 298 K): 4.01 (br, 4H), 4.27 (br, 4H), 7.26−
7.30 (m, 16H), 7.41−7.47 (m, 4H). 31P{1H} NMR (CD2Cl2, 298 K,
121.5 MHz): −9.33. Anal. Calcd for C68H56P4Fe2CuBF4·0.5CH2Cl2:
C, 63.21; H, 4.41. Found: C, 63.54; H, 3.99. As described in the
literature for the corresponding PF6 salt,26 the broad signals of the 1H
NMR spectra suggest a dynamic equilibrium between different species.
[Cu2(dmp)2(μ-dppm)2](BF4)2. This compound was thus obtained in
52% yield as a yellow crystalline solid. As soon as dissolved in CH2Cl2,
1
ligand exchange took place and analysis of the H NMR spectrum
revealed the presence of different species in solution: [Cu2(dmp)2(μ-
dppm)2](BF4)2, [Cu(dmp)2]BF4,21 and [Cu(dppm)2]BF4 in a 7:3:3
ratio.11 The presence of [Cu(dppm)2]BF4 was confirmed by its 31P
NMR resonance observed at δ = −6.03 ppm; the additional peak
observed in the 31P NMR spectrum at δ = −15.67 ppm is assigned to
[Cu2(dmp)2(μ-dppm)2](BF4)2.
1
This was confirmed by variable-temperature H and 31P NMR studies
in the case of the PF6 salt.26 Recrystallization by slow diffusion of n-
hexane into a CH2Cl2 solution of the crude product yielded dark
orange crystals (65 mg). X-ray crystal structure analysis revealed
crystallization of [Cu2(dppFc)(dppFc)2](BF4)2. 1H and 31P NMR
spectra recorded upon dissolution of these crystals in CD2Cl2 were
complex and consistent with the presence of different species in
solution. This compound was not further investigated.
[Cu(dmp)(dppe)]BF4. This compound was thus obtained in 69%
yield as a yellow crystalline solid. As soon as dissolved in CH2Cl2,
1
ligand exchange took place and analysis of the H NMR spectrum
revealed the presence of different species in solution: [Cu(dmp)-
(dppe)]BF4, [Cu(dmp)2]BF4,21 and [Cu(dppe)2]BF4 in a 4:1:1
ratio.22 The presence of [Cu(dppe)2]BF4 was confirmed by its
broad 31P NMR resonance observed at δ = 7.80 ppm (207 K); the
additional peak observed in the 31P NMR spectrum at δ = −7.53 ppm
is assigned to [Cu(dmp)(dppe)]BF4. FAB-MS: 859.8 ([Cu(dppe)2]+,
X-ray Crystal Structures. A. [Cu(phen)(dppb)]BF4. Crystals
suitable for X-ray crystal structure analysis were obtained by slow
diffusion of Et2O into a CH2Cl2 solution of [Cu(phen)(dppb)]BF4.
Data were collected at 173 K on a Nonius Kappa-CCD diffractometer
(Mo Kα radiation, λ = 0.71073 Å). The structure was solved by direct
methods (SHELXS-97) and refined against F2 using the SHELXL-97
software. Non-hydrogen atoms were refined anisotropically using
weighted full-matrix least-squares on F2. H atoms were included in
calculated positions and treated as riding atoms using SHELXL default
parameters. Crystallographic data are reported in Table S1, Supporting
Information.
B. [Cu2(Bphen)2(μ-dppm)2](BF4)2·CH2Cl2. Crystals suitable for X-ray
crystal structure analysis were obtained by slow diffusion of Et2O into
a CH2Cl2 solution of [Cu2(Bphen)2(μ-dppm)2](BF4)2. Data were
collected at 173 K on a Nonius Kappa-CCD diffractometer (Mo Kα
radiation, λ = 0.71073 Å). The structure was solved by direct methods
(SHELXS-97) and refined against F2 using the SHELXL-97 software.
Non-hydrogen atoms were refined anisotropically using weighted full-
matrix least-squares on F2. H atoms were included in calculated
positions and treated as riding atoms using SHELXL default
parameters. A semiempirical absorption correction was applied using
the MULscanABS routine in PLATON;27 transmission factors,
Tmin/Tmax = 0.69776/0.84015. The SQUEEZE instruction in
PLATON27 was applied. Residual electron density was assigned to
four molecules of dichloromethane. Crystallographic data are reported
in Table S1, Supporting Information.
+
33%), 669.7 (Cu[(dppe)(dmp)]+, 100%), 479.5 ([Cu(dmp)]2 , 40%),
461.5 ([Cu(dppe)]+, 63%), 271.4 ([Cu(dmp)]+, 3%).
[Cu(dmp)(dppp)]BF4. This compound was thus obtained in 76%
yield as a yellow crystalline solid. As soon as dissolved in CH2Cl2,
1
ligand exchange took place and analysis of the H NMR spectrum
revealed the presence of different species in solution: [Cu(dmp)-
(dppp)]BF4, [Cu(dmp)2]BF4,21 and [Cu(dppp)2]BF4 in a 4:1:1
ratio.22 The presence of [Cu(dppp)2]BF4 was confirmed by its
broad 31P NMR resonance centered at δ = −10 ppm; the additional
peak observed in the 31P NMR spectrum at δ = −17.01 ppm is
assigned to [Cu(dmp)(dppp)]BF4.
[Cu(dmp)(dppb)]BF4. This compound was thus obtained in 45%
yield as a yellow crystalline solid. As soon as dissolved in CH2Cl2,
1
ligand exchange took place and analysis of the H NMR spectrum
revealed the presence of different species in solution: [Cu(dmp)-
(dppb)]BF4, [Cu(dmp)2]BF4,21 and [Cu(dppp)2]BF4 in a 65:35:35
ratio.11 The presence of [Cu(dppb)2]BF4 was confirmed by its 31P
NMR resonance observed at δ = 8.42 ppm; the additional peak
observed in the 31P NMR spectrum at δ = −4.64 ppm is assigned to
[Cu(dmp)(dppb)]BF4.
[Cu(dmp)(dppFc)]BF4. This compound was thus obtained in 90%
yield as a yellow crystalline solid. Analytical data were identical to
those described in the literature.10
[Cu(dmp)(POP)]BF4. This compound was thus obtained in 70%
yield as a yellow crystalline solid. Analytical data were identical to
those described in the literature.3,4,10
[Cu(dpep)(dppFc)]BF4. This compound was thus obtained in 71%
yield as a yellow crystalline solid. Analytical data were identical to
those described in the literature.10
[Cu(dpep)(POP)]BF4. This compound was thus obtained in 86%
yield as a yellow crystalline solid. Analytical data were identical to
those described in the literature.8
Preparation of [Cu(POP)2]BF4. A mixture of Cu(CH3CN)BF4
(0.05 g, 0.16 mmol) and POP (0.171 g, 0.32 mmol) in CH2Cl2 (10
mL) was stirred for 1 h at room temperature. The resulting solution
was concentrated to ca. 5 mL. Crystals of [Cu(POP)2]BF4 were
C. [Cu(dmp)(dppe)]BF4·Et2O. Crystals suitable for X-ray crystal
structure analysis were obtained by slow diffusion of Et2O into a
CH2Cl2 solution of [Cu(dmp)(dppe)]BF4. Data were collected at 180
K on a Stoe IPDS diffractometer (Mo Kα radiation, λ = 0.71073 Å).
The structure was solved by direct methods (SIR92) and refined
against F using the CRYSTALS software. Non-hydrogen atoms were
−
refined anisotropically (excepting the BF4 anion and cocrystallized
solvent molecule). H atoms were refined as riding atoms constraints.
Crystallographic data are reported in Table S1, Supporting
Information.
D. [Cu(dmp)(dppp)]BF4. Crystals suitable for X-ray crystal structure
analysis were obtained by slow diffusion of Et2O into a CH2Cl2
solution of [Cu(dmp)(dppp)]BF4. Data were collected at 180 K on a
Stoe IPDS diffractometer (Mo Kα radiation, λ = 0.71073 Å). The
structure was solved by direct methods (SIR92) and refined against F
J
dx.doi.org/10.1021/ic4020042 | Inorg. Chem. XXXX, XXX, XXX−XXX

Inorganic Chemistry
Article
using the CRYSTALS software. Non-hydrogen atoms (excepting the
BF4− anion) were refined anisotropically. Constraints were applied on
the phenyl groups. H atoms were refined as riding atoms constraints.
Crystallographic data are reported in Table S1, Supporting
Information.
(2) (a) Sakaki, S.; Koga, G.; Ohkubo, K. Inorg. Chem. 1986, 25,
2330−2333. (b) Sakaki, S.; Koga, G.; Hinokuma, S.; Hashimoto, S.;
Ohkubo, K. Inorg. Chem. 1987, 26, 1817−1819.
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Walton, R. A. J. Am. Chem. Soc. 2002, 124, 6−7.
E. [Cu(POP)2]BF4. Crystals suitable for X-ray crystal structure
analysis were obtained by slow diffusion of n-hexane into a CH2Cl2
solution of [Cu(POP)2]BF4. Data were collected at 180 K on a Bruker
APEX-II CCD diffractometer (Mo Kα radiation, λ = 0.71073 Å). The
structure was solved by direct methods (SIR92) and refined against F
using the CRYSTALS software. Non-hydrogen atoms were refined
anisotropically. Thermal constraints were applied on the phenyl
(4) Kuang, S.-M.; Cuttell, D. G.; McMillin, D. R.; Fanwick, P. E.;
Walton, R. A. Inorg. Chem. 2002, 41, 3313−3322.
(5) (a) Coppens, P. Chem. Commun. 2003, 1317−1320. (b) Coppens,
P.; Vorontsov, I. I.; Graber, T.; Kovalevsky, A Y.; Chen, Y.-S.; Wu, G.;
Gembicky, M.; Novozhilova, I. V. J. Am. Chem. Soc. 2004, 126, 5980−
5981. (c) Saito, K.; Arai, T.; Takahashi, N.; Tsukuda, T.; Tsubomura,
T. Dalton Trans. 2006, 4444−4448.
−
groups and BF4 anion. H atoms were refined as riding atoms
(6) Costa, R. D.; Tordera, D.; Orti, E.; Bolink, H.; Schonle, J.;
̈
constraints. Crystallographic data are reported in Table S1, Supporting
Information.
Graber, S.; Housecroft, C. E.; Constable, E. C.; Zampese, J. A. J. Mater.
Chem. 2011, 21, 16108−16118.
F. [Cu2(μ-dppFc)(dppFc)2](BF4)2·(CH2Cl2)(H2O)2. Crystals suitable
for X-ray crystal structure analysis were obtained by slow diffusion of
n-hexane into a CH2Cl2 solution of dppFc (2 equiv) and
Cu(CH3CN)4BF4 (1 equiv). Data were collected at 180 K on an
Oxford Diffraction XCALIBUR diffractometer (Mo Kα radiation, λ =
0.71073 Å). The structure was solved by direct methods (SIR92) and
refined against F using the CRYSTALS software. Non-hydrogen atoms
were refined anisotropically. H atoms were refined with riding
constraints. Crystallographic data are reported in Table S1, Supporting
Information.
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Forde, M. M.; Collins, A.; White, F.; Robertson, N. Dalton Trans.
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ASSOCIATED CONTENT
* Supporting Information
■
(9) Yang, L.; Feng, J.-K.; Ren, A.-M.; Zhang, M.; Ma, Y.-G.; Liu, X.-D.
S
Eur. J. Inorg. Chem. 2005, 1867−1879.
Crystallographic and structure refinement data; crystallographic
(CIF) files for [Cu(phen)(dppb)]BF4, [Cu2(Bphen)2(μ-
dppm)2](BF4)2, [Cu(dmp)(dppe)]BF4·Et2O, [Cu(dmp)-
(dppp)]BF4, [Cu(POP)2]BF4, and [Cu2(μ-dppFc)(dppFc)2]-
(BF4)2·(CH2Cl2)(H2O)2. This material is available free of
charge via the Internet at http://pubs.acs.org. Final atomic
positional coordinates, with estimated standard deviations,
bond lengths, and angles, have been deposited at the
Cambridge Crystallographic Data Centre and were allocated
deposition numbers CCDC 953017, CCDC 953018, CCDC
952426, CCDC 952427, CCDC 952429, and CCDC 972428.
(10) Armaroli, N.; Accorsi, G.; Bergamini, G.; Ceroni, P.; Holler, M.;
Moudam, O.; Duhayon, C.; Delavaux-Nicot, B.; Nierengarten, J.-F.
Inorg. Chim. Acta 2007, 360, 1032−1042.
(11) Moudam, O.; Kaeser, A.; Delavaux-Nicot, B.; Duhayon, C.;
́
Holler, M.; Accorsi, G.; Armaroli, N.; Seguy, I.; Navarro, J.; Destruel,
P.; Nierengarten, J.-F. Chem. Commun. 2007, 3077−3079.
(12) Listorti, A.; Accorsi, G.; Rio, Y.; Armaroli, N.; Moudam, O.;
́
Gegout, A.; Delavaux-Nicot, B.; Holler, M.; Nierengarten, J.-F. Inorg.
Chem 2008, 47, 6254−6261.
(13) Mohankumar, M.; Holler, M.; Nierengarten, J.-F.; Sauvage, J.-P.
Chem.Eur. J. 2012, 18, 12192−12195.
(14) Dietrich-Buchecker, C. O.; Marnot, P. A.; Sauvage, J.-P.
Tetrahedron Lett. 1982, 23, 5291−5294.
AUTHOR INFORMATION
Corresponding Authors
*E-mail: beatrice.delavaux-nicot@lcc-toulouse.fr.
*E-mail: nicola.armaroli@isof.cnr.it.
*E-mail: nierengarten@unistra.fr.
(15) Gumienna-Kontecka, E.; Rio, Y.; Bourgogne, C.; Elhabiri, M.;
Louis, R.; Albrecht-Gary, A.-M.; Nierengarten, J.-F. Inorg. Chem. 2004,
43, 3200−3209.
■
(16) Gschwind, R. M. Chem. Rev. 2008, 108, 3029−3053.
(17) (a) Puddephatt, R. J. Chem. Soc. Rev. 1983, 12, 99−127.
(b) Chaudret, B.; Delavaux, B.; Poilblanc, R. Coord. Chem. Rev. 1988,
86, 191−243.
Notes
The authors declare no competing financial interest.
(18) (a) Harvey, P. D.; Drouin, M.; Zhang, T. Inorg. Chem. 1997, 36,
4998−5005. (b) Bera, J. K.; Nethaji, M.; Samuelson, A. C. Inorg. Chem.
1999, 38, 218−228. (c) Deivaraj, T. C.; Vittal, J. J. J. Chem. Soc., Dalton
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X.-Y.; Jin, D.-M. Inorg. Chim. Acta 2000, 304, 1−6. (e) Ruina, Y.;
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179−188.
ACKNOWLEDGMENTS
■
This research was supported by the CNRS, the University of
Strasbourg, the EC (contract PITN-GA-2008-215399-FINE-
LUMEN), MIUR (PRIN 2010 INFOCHEM-CX2TLM), and
the CNR (MACOL PM.P04.010 and Progetto Bandiera N-
CHEM).
(19) Wei, Y.-Q.; Wu, K.-C.; Zhuang, B.-T.; Zhou, Z.-F. J. Coord.
Chem. 2006, 59, 713−719.
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