Changing the chemical and physical properties of high valent heterobimetallic bis-(μ-oxido) Cu-Ni complexes by ligand effects

Article abstract of DOI:10.1039/c6dt02391f

Two new heterobimetallic [LNiO₂Cu(RPY2)]⁺ (RPY2 = N-substituted bis 2-pyridyl(ethylamine) ligands with R = indane, 3a or R = Me, 3b) complexes have been spectroscopically trapped at low temperatures. They were prepared by reacting the mononuclear side-on LNi^II superoxo precursor bearing a β-diketiminate ligand (L = [HC-(CMeNC₆H₃(iPr)₂)₂]) with the Cu(i) complexes. In contrast to the oxo groups in known high-valent [M₂(μ-O)₂]ⁿ⁺ (M = Fe, Co, Ni, Cu) cores that display electrophilic reactivities, 3a and 3b display rather nucleophilic oxo cores active in aldehyde deformylation reactions. However, the spectroscopic and reactivity properties of 3a/3b are found to be distinct relative to that of the previously reported [LNiO₂Cu(MeAN)]⁺ complex containing a more basic (nucleophilic) N,N,N′,N′,N′-pentamethyl-dipropylenetriamine (MeAN) ligand at the copper centre. The geometry and electronic properties of the copper ligands affect the electron density of the oxygen atoms of the heterodinuclear {Ni(μ-O)₂} core and 3a/3b undergo slower nucleophilic and faster electrophilic reactions than the previously reported [LNiO₂Cu(MeAN)]⁺ intermediate. The present study therefore demonstrates the tuning of the electrophilicity/nucleophilicity of the oxygen atoms of the heterobimetallic [Ni(μ-O)₂Cu]²⁺ cores by controlling the electron donation from the ancillary ligands, and underlines the significance of subtle electronic changes in the physical and chemical properties of the biologically relevant heterobimetallic metal-dioxygen intermediates.

Full text of DOI:10.1039/c6dt02391f

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Changing the chemical and physical properties of high valent
heterobimetallic bis-(µ-oxido) Cu-Ni complexes by ligand effects
Received 00th January 20xx,
Accepted 00th January 20xx
a
a
a
b
b
Maria-Chrysanthi Kafentzi, Maylis Orio, Marius Réglier, Shegnlai Yao, Uwe Kuhlmann, Peter
b
b
a
c
Hildebrandt, Matthias Driess,* A. Jalila Simaan* and Kallol Ray*
DOI: 10.1039/x0xx00000x
+
Two new heterobimetallic [LNiO
2
Cu(RPY2)] (RPY2 = N-substituted bis 2-pyridyl(ethylamine) ligands with R= Indane, 3a or
www.rsc.org/
R=Me; 3b) complexes have been spectroscopically trapped at low temperatures. They were prepared by reacting the
II
mononuclear side-on LNi superoxo precursor bearing a β-diketiminate ligand (L= [HC-(CMeNC
6
H
3
(iPr)
2
2
) ]) with the Cu(I)
n+
]
complexes. In contrast to the oxo groups in known high-valent [M
2
(ꢀ−O)
2
(M= Fe, Co, Ni, Cu) cores that display
electrophilic reactivities, 3a and 3b display rather nucleophilic oxo cores active in aldehyde deformylation reactions.
However, the spectroscopic and reactivity properties of 3a/3b are found to be distinct relative to that of the previously
+
reported [LNiO
2
Cu(MeAN)] complex containing
a
more basic (nucleophilic) N,N,N′,N′,N′- pentamethyl-
dipropylenetriamine (MeAN) ligand at the copper centre. The geometry and electronic properties of the copper ligands
affect the electron density of the oxygen atoms of the heterodinuclear {Ni((ꢀ−O)
nucleophilic and faster electrophilic reactions than the previously reported [LNiO
2
} core and 3a/3b undergo slower
+
2
Cu(MeAN)] intermediate. The present
study therefore demonstrates the tuning of the electrophilicity/nucleophilicity of the oxygen atoms of the heterobimetallic
2
+
[
2
Ni(μ-O) Cu] cores by controlling the electron donation from the ancillary ligands, and underlines the significance of
subtle electronic changes on the physical and chemical properties of the biologically relevant heterobimetallic metal–
dioxygen intermediates.
7
hydroxylation by tyrosinase , as well as in methane oxidation
8
by particulate methane monooxygenase .
Introduction
In contrast to the homobimetallic systems, the properties
The synthesis and characterisation of metal-oxygen
intermediates are very important for understanding the
mechanisms of transition metal mediated dioxygen activation
reactions taking place in chemical and biological systems. In
of mixed-metal dioxygen species have been less explored.
These types of intermediates are probably involved in various
catalytic processes in metalloenzymes; for example, in
I
cytochrome c oxidase, where a Cu ion cooperates with an
II
Fe (heme) to activate dioxygen or in Cu-Zn superoxide
this context homobimetallic bis(µ-oxido) complexes with
n+
[
M
2
(µ-O)
2
]
cores have attracted much attention and they
2
1
have been extensively studied for systems involving Cu, Mn,
dismutase, in which the superoxido ligand disproportionation
is mediated through a mixed Cu-Zn metal site. The generation
and the study of such mixed metal species are therefore of
significant interest due to the unique properties obtained by
the combination of two different metal ions. The synthesis of
heterodinuclear complexes, however, presents a special
challenge because of the possibility of disproportionation and
selectivity problems resulting in the formation of mixtures of
homo- and heterodinuclear complexes, as well as metal-site
isomers. In order to overcome these problems two main
3
4
5
6
Ni, Co , Fe, and Pt centres. In particular, homobimetallic
copper dioxygen cores have been the subject of extensive
investigations due to their possible involvement in biological
oxidation reactions as key intermediates in phenol
9
strategies were previously used in the literature (Figure 1).
The first one involves the synthesis of ligands providing
different coordination environments that are specific for each
of the two metal ions. An alternative route is the reaction of a
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fleeting [LNiO
2
ML] (M= Fe, Zn) could not be isolated, in a
+
Cu(MeAN)] species was
subsequent study a related [LNiO
2
II
2
stabilized at low temperature by reacting the [LNi O ]
+
precursor with a copper triamine [Cu(MeAN)] reductant
Scheme 1A). Interestingly, the presence of Cu in the second
(
metal binding site was shown to result in nucleophilic oxo
groups in the high-valent bis-µ-oxido Ni-Cu species, and it was
able to react towards aldehyde substrates, in contrast to the
reported electrophilic properties of the homobimetallic
1
7
2 2 2
NiO Ni, CuO Cu and heterobimetallic NiO Fe counterparts. In
Fig. 1: Two main strategies for the development of heterobimetallic metal-
the present manuscript we now try to systematically explore
how the nature of the ancillary ligand can modulate the
formation, structure, electronic properties and reactivity of
such high-valent heterobimetallic dioxygen species. For this
purpose, we report on the synthesis, spectroscopy, DFT
derived description, and reactivity studies of two new bis-µ-
oxido CuNi intermediates, where the triamine MeAN ligand at
Cu is replaced by relatively weaker bases/nucleophiles in the
dioxygen complexes.
bis 2-pyridyl(ethylamine) (RPY ; R = Methyl or Indane) ligand
2
systems. Notably, the RPY -type ligands have been previously
2
II
utilised in the formation of binuclear Cu -peroxido complexes,
2
which were shown to exist in equilibrium with the isomeric
III
1a
Cu (µ-oxido) species depending on the reaction conditions .
2
The side-on peroxido dicopper(II) intermediates exhibited
electrophilic character towards C-H bond oxygenation of
1
f,h,i
substrates.
For example, using an "indane" substrate
covalently attached to the ligand (IndanePY , Scheme 2), an
2
intramolecular oxygen atom transfer was shown to take place
in a highly regio- and stereo-selective manner leading to the
1
8
cis-hydroxylated diastereoisomers of the ligand.
The
+
successful generation of the [LNiO Cu(RPY )] complexes now
2
2
offers the opportunity to compare and contrast the reactivity
of the present complexes with that of the previously reported
+
III
III
+
2
Scheme 1: A: Generation of the [LNi O Cu (MeAN)] complex which is already
heterodinuclear [LNiO Cu(MeAN)]
2
and homodinuclear
17
III
III
+
reported. B: Generation of [LNi O
2
Cu (RPY
2
)] species 3a (3b) upon mixing a
2+
{Cu(RPY )} O ] complexes.
[
II
I
2 2 2
solution of the LNi superoxo complex 2 with the (RPY
2
)Cu complexes 1a (or 1b).
well-defined dioxygen metal subunit L M-O with a low-valent
n
2
metal complex fragment L’ M’. This last strategy has been
m
Results and discussion
successfully used to generate heterobimetallic oxygen-
11
1
0
12
13
containing species with PdMo, CuNi, CuGe, PtCu and Synthesis and UV-Vis spectroscopy
1
3
CuPd
combinations, starting from well-defined metal-
The complexes 1a and 2b were prepared by mixing one molar
I
eq of Cu (CH
dioxygen precursors. Our contribution in the field involves the
3
CN)
4
(OTf) with one molar eq of ligand in
synthesis of a novel family of NiO M complexes generated by
2
II
using a mononuclear side-on LNi superoxo precursor bearing
dichloromethane.
Equimolar
amounts
I
)Cu (OTf)} and
of
1a
I
)Cu (OTf)} or 1b {(CH PY
{
(IndanePY
2
3
2
2
were then
a β-diketiminate (Nacnac) ligand (L= [HC-(CMeNC H (iPr) ) ])
6
o
mixed at -90 C in dry dichloromethane leading to the
3
2 2
1
4
system. Notably, this precursor is remarkably stable and can
be handled at room temperature, which made it a suitable
precursor for the synthesis of heterobimetallic metal-dioxygen
immediate formation of the brownish intermediates 3a
{
(
(
(IndanePY
CH PY )Cu(O
Scheme 1Β). The generation of these species was monitored
2
)Cu(O
2
)Ni(C-(CMeNC
6
H
3
(iPr)
2
)
2
(OTf)}
and
3b
3
2
2
)Ni(C-(CMeNC
6
H
3
(iPr)
2 2
)
(OTf),
respectively
complexes. Interestingly, in our previous studies, the
n+
electronic structure of the [NiO M] core in such complexes
2
by UV-Vis spectroscopy following the appearance of a
were found to be dependent on the nature of the second
n+
characteristic absorption band centred at 885 nm for 3a and
metal ion, M; whereas a peroxido species [Ni(µ-O )K] was
2
8
9
70 nm for 3b (Figure 2). The intermediates are stable at -
o
0 C, but they are thermally sensitive, as indicated by
stabilized in presence of potassium, replacement of the
+
+
monovalent potassium ion by LZn (L= Nacnac) or Fe ions
initiated peroxido O-O bond scission and subsequent H-atom
abstraction to generate the heterobimetallic bis(μ-hydroxo)
Ni–Zn or alkoxo hydroxido Ni–Fe species. Although, the
bleaching of their UV-Vis absorption features upon warming to
higher temperatures (see ESI) with t1/2 = 2000 s at -60 C.
o
2
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DFT calculations were performed on 3a and 3b in an effort to
understand their structural and electronic properties as well as
1
8
the origin of the additional O sensitive band in the rRaman
spectra. DFT-optimised structures revealed a four-coordinate
distorted square-planar geometry around the nickel centre.
Two conformations around the copper ion were computed for
each system (conformers A and B). In all cases, the copper site
is in a five-coordinate square pyramidal geometry but with
either the amine group (conformer A) or one pyridine group
EPR spectroscopy
(conformer B) weakly bonded to the metal ion in axial position.
Energetic analysis conducted on both 3a and 3b showed that
the minimum free energy is obtained for the conformers (A)
which make these structures the most favoured one (see Table
S3; ESI). The computed structures for 3a and 3b (conformers A
and B) are presented on Figures 4, S11, and S12.
Both spin density plots and Singly Occupied Molecular
Orbitals (SOMO) reveal that 3a and 3b bear one unpaired
electron located at the nickel centre (see Figures S13-S14; ESI).
III
These results confirm the presence of one low-spin Ni (S =
7
/2, 3d ) and one low-spin Cu (S = 0, 3d ) centres in both 3a
III
8
1
I
II
Fig. 2: Absorption spectra of Cu complex (solid trace) 1a, Ni superoxo complex 2
III
III
+
and 3b. This assignment is further confirmed by the computed
EPR parameters, which are in fair agreement with the
experimental data (see Table S4; ESI). Frequency calculations
were conducted on the DFT-optimised structures of the two
species and Raman spectra were calculated. Vibration modes
(
dotted trace) and the 0.15mM [Ni (µ-O
2
)Cu ] species 3a (dashed trace) in
o
dichloromethane at -90 C. Inset: X-band EPR spectrum of 3a in dichloromethane at 77K
2 2
The EPR spectra were recorded on frozen CH Cl solutions (77
K) for 3a and 3b and are very similar for both complexes. The
EPR spectrum obtained in the case of 3a is presented in Figure
-1
involving the oxygen ligands were predicted at 596 cm and
-
1
6
21 cm for 3a and 3b (Figures S15-S16; Table S5),
respectively, in agreement with the assignment previously
2
. The spectra are composed of typical S = 1/2 rhombic signals
with g = 2.39, g = 2.13, g = 2.005 for 3a and g =2.39, g = 2.13,
= 2.006 for 3b. These EPR signals are very similar to the one
1
2
3
1
2
1
proposed for the MeAN-based Cu-Ni analog . A second mode
17 was calculated to be at 553 cm and 528 cm for 3a and 3b
,
7
g
3
-1
-1
+
reported previously for the [LNiO
2
Cu(MeAN)] complex.
respectively, originating from the coupling of the Ni(µ-O )Cu
2
Notably, no interaction of electron spin with nuclear spin of
III
3b, consistent with their Ni (µ-
core and the Ni-coordinated β-diketiminate ligand coordinates
(see Figures S17-S18; ESI). Both sets of calculated results are in
good agreement with the observed rRaman bands for each
complex (Table S5; ESI). The five-coordination geometry at the
copper is observed for both 3a
/
III
Cu assignment, in agreement with the data previously
O)
2
1
7
reported in the literature for the Cu-Ni analog.
Cu ions obtained in the case of RPY -type ligands is affecting
2
the coordination sphere of the Ni ion in 3a and 3b and the
geometry around the Ni ion appears to be significantly
distorted from planarity (dihedral angle of 11.2 and 16.2°,
respectively) while it is perfectly planar in the
Resonance Raman Spectroscopy
The Resonance Raman (rRaman) spectra of 3a and 3b were
recorded using a 413-nm laser excitation. rRaman bands are
-1
-1
detected at 605 cm and 612 cm for 3a and 3b, respectively
1
Figure 3, ESI), which are sensitive to O substitution
8
(
1
8
(
2
performed by using Ni O as a starting reagent) and
1
8
-1
-1
downshift (
ꢁ O) by 31 cm and 29 cm , respectively. Notably,
these bands are shifted to lower energies relative to the tetra-
+
2
atomic vibrational mode of the [LNi(µ-O )Cu(MeAN)] complex
-1 17
observed at 625 cm . Furthermore, as previously observed,
-
the absence of any isotope sensitive bands in the 700-1200 cm
1
region, excludes the possibility of the presence of peroxo or
18
superoxo units in 3a or 3b. Interestingly, a second O sensitive
-1
18
-1
-
band is also detected at 556 cm (
ꢁ
O =-21 cm ) and 579 cm
O =-19 cm ) for 3a and 3b respectively, which was not
observed in the previously reported spectrum of the
1
18
-1
(
ꢁ
+
[
2
LNiO Cu(MeAN)] complex.
DFT calculations
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16
Fig 3. Raman shifts obtained using a 413 excitation laser for 3a involving O (top) and
6
0°C was treated with an excess of the above-mentioned
18
O (bottom) atoms. Bands originated from the solvent are marked by asterisks.
substrates under a pseudo first-order condition.
o
Fig.5: Spectral changes of 3a in the presence of 50 mM CCA at -60 C. Inset: Time trace
of the decay at 885nm band upon addition of the substrate (black trace) and the first-
order fit (inset: red trace).
Fig.6: Pseudo first-order rate constants as a function of substrate concentration the
reaction of 3a with cyclohexane carboxaldehyde (left) and 2,4 di-tert-butylphenol
(
2 2
right) in CH Cl .
The disappearance of the characteristic band at 885 nm in the
UV-Vis absorption spectrum was then monitored over time
(
2 2
Figure 5 for reaction of 3a with CCA). Rate constants in CH Cl
o
o
at -60 C or at -90 C were obtained from the pseudo-first order
fit of the time trace of the decay of the 885 nm band (Figure
Fig. 4. Optimized molecular structures for 3a; Conformer A (top) and B (bottom)
5
). Second-order rate constants were then determined from
MeAN-based complex (dihedral angle of 2.3°). This explains the dependence of the first-order rate constants on substrate
the appearance of a new vibration in the rR spectra of 3a/3b
concentration (Figure 6). Second-order rate constants derived
The spectroscopic data thus support the DFT- calculated from those studies are listed in Table 1 and compared with
.
structure and validate the formation of both 3a and 3b
.
that of the results obtained for the previously reported
+
[
LNiO
2
Cu(MeAN)] intermediate. Notably, complex 3b reacts
with CCA and benzaldehyde at rates significantly slower than
Reactivity studies
+
[
LNiO
In contrast, in presence of DHA, CHD, 2,4-DTBP, or 2,6-
DTBP, complex 3b is found to be a better oxidant than
2
Cu(MeAN)] .
The reactivity of the complexes 3a and 3b have been
investigated in a number of nucleophilic and electrophilic
reactions. The nucleophilicity of 3a and 3b has been studied in
reactions with benzaldehyde, and cyclohexane carboxaldehyde
+
[
LNiO Cu(MeAN)] . These studies point to the presence of less
2
+
nucleophilic oxygen atoms in 3b relative to [LNiO Cu(MeAN)] .
2
(CCA). The ability of 3a (3b) to undergo electrophilic Hydrogen
Notably, replacement of the methyl group of the MePy ligand
2
Atom Transfer (HAT) reactions were also evaluated in
reactions with 9,10 dihydroantracene (DHA) and 1,3
cyclohexadiene (CHD) for C-H bonds and with 2,4-di-tert-
butylphenol (2,4-DTBP) and 2,6- di-tert-butylphenol (2,6-DTBP)
for O-H bonds. In a typical reaction preformed 3a and 3b at -
in 3b with a bulkier indane group in 3a did not lead to any
significant change in the rate constants for the reactions with
DHA and benzaldehyde. However, for reactions with bulkier
substrates like 2,6-DTBP, 2,4-DTBP, or CCA, a significantly
reduced rate constant is observed for 3a relative to 3b. This
4
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may be attributed to the sterically induced hindered access of
the substrates in presence of the covalently attached indane
Table 1 : Second order rate constants determined for different substrates by kinetic studies by UV-Vis spectroscopy
Benzaldehyde
o
o
o
o
o
Substrates
o
CCA(-60 C)
DHA(-60 C)
CHD(-60 C)
2,4 DTBP(-90 C)
2,6 DTBP(-60 C)
(-60 C)
3
a
0
.021
0.088
0.015
0.053
0.014
4.60
0.0065
-
1
-1
-1
k
k
2
/ M
s
s
3
b
0
.0178
0.557
0.015
Too
Too fast
0.0985
-1
2
/ M
III
III
+
LNi (µ-oxo)Cu (MeAN)]
o
Too fast
o
o
o
-1
-1
0.11 (-50 C)
o
o
0.0005 (-70 C )
2.44 (-90 C)
0.0001 (-80 C)
k
2
/ M
s
(-90 C )
slow (-70 C )
2
basic/nucleophilic RPY ligands in 3a/3b led to slower
group of the IndanePY
2
ligand in 3a. Analysis of the resultant nucleophilic and faster electrophilic reactions in the later.
solution after reactions of 3a or 3b with various substrates Based on the DFT calculations, the difference in reactivity has
showed the formation of the oxidised products in 45-70 % been attributed to the presence of a five coordinate copper
yields (Table ESI). Interestingly, for reactions with 3a no centre and a significant distortion of the nickel centre from
evidence of the hydroxylation of the indane moiety was planarity in 3a/3b. These result in the development of lower
observed, which is in contrast to the previous report of the negative charges at the oxygen atoms of 3a/3b relative to the
+
)Cu(MeAN)] complex, where a four coordinate
intramolecular indane hydroxylation reaction mediated by the [LNi(µ-O
1
2
8
homodinuclear copper-oxygen intermediate.
square planar structure has been reported to be prevalent at
Additional DFT calculations were performed in order to both the Cu and Ni centres. Furthermore, for reactions with 3a
further characterize the reactivity differences. Natural no hydroxylation of the indane moiety occurred, in contrast to
population analysis were performed for 3a
were compared to those obtained for [LNi O
see SI). The natural negative charges found at the O atoms are py
smaller (by -7 % to -8%) in 3a and 3b with respect to those of initiation of novel reactivity properties in heterodinucler
/3b and the results the previous report of the intramolecular indane hydroxylation
III
III
+
2
Cu (MeAN)]
reaction mediated by the homodinuclear {(indane-
)CuO Cu(indane-py )} complex. This again emphasizes the
(
2
2
2
III
III
+
the corresponding atoms in [LNi O
2
Cu (MeAN)] . These data systems relative to their homobimetallic counterparts. The
indicate that the oxido cores in 3a and 3b are less electron-rich present results therefore underline the significance of subtle
+
III
compared to the one of [LNi O
III
2
Cu (MeAN)] . It thus geometric and electronic changes on the physical and chemical
correlates with the decreased nucleophilicity presently properties of this important class of biologically relevant
observed.
metal–dioxygen intermediates.
Conclusions
Experimental
Examples of heterobimetallic dioxygen intermediates are All chemicals used in this study except the ligands and the
extremely rare in the literature and hence, very little is known complexes were commercial products of the highest available
about their reactivity. This is unfortunate, as metal dioxygen purity. Commercial starting materials were used without
cores involving non-equivalent metal-sites have been further purification, except for 2-vinylpyridine which was
proposed as the active species in a number of biological and distilled prior to use. Preparation and handling of air sensitive
chemical oxidation processes, and a detailed knowledge about materials were performed in a N glove box OMNI-Lab 2 (VAC)
2
1
their reactivity can provide vital mechanistic insights. In our with O and moisture concentration less than 2 ppm. H NMR
2
continuous effort to uncover structure-reactivity relationships spectra were recorded on a Bruker Avance III 300MHz NMR
of unprecedented dinuclear metal-dioxygen intermediates we spectrometer. UV-Vis spectra were recorded by Agilent 8453
now investigate the role of ancillary ligands in controlling the diode array spectrophotometer from 300-1100 nm with
spectroscopic and reactivity properties of a heterobimetallic samples in 1.0 path length quartz cuvette, connected with a
+
Ni(μ-O) Cu] core. The first (and only example before this cryostat from Unisoku Scientific Instruments, Japan.
[
2
study of such a core) has been spectroscopically identified in
our groups and previously shown to possess nucleophilic oxo Synthetic procedures
group that led to the deformylation of aldehydes. We now
General procedure of synthesis of ligands
CH PY2.The ligand has been synthesized in slightly different
1g
show that the nucleophilicity of the oxo groups can be tuned
by varying the electron donation of the ancillary ligand at the
3
way from the already reported procedure. To absolute
MeOH (80mL) were added 2-vinylpyridine (11g, 0.210 mol), 2-
copper center. Thus replacement of the MeAN ligand in the
+
previously reported [LNi(µ-O )Cu(MeAN)] complex by less
2
(
2-methylaminoethyl) pyridine (4.2g, 0.030 mol), and glacial
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Journal Name
acetic acid (1.8g, 0.060 mol). After refluxing for 5 days under single-point calculations using the same combination of
Argon, MeOH was evaporated and 15% NaOH was added. The functional and basis sets. They were computed from the gas-
product was extracted with CH
organic layers were dried over Na
under reduced pressure left the crude product. Flash solvation. g-tensors
chromatography (neutral alumina, ethylacetate/MeOH, 98:2) point calculations using the B3LYP functional. Scalar relativistic
2
Cl
2
(x3) and the combined phase optimized structures as a sum of electronic energy,
2
SO
4
. Evaporation of CH Cl thermal corrections to free energy, and free energy of
2
2
29-32
were evaluated from additional single
afforded the ligand as a yellow product (yield: 40%).
effects were included with ZORA paired using the SARC def2-
3
3,34
TZVP(-f) basis sets
and the decontracted def2-TZVP/J
IndanePY2 The ligand has been synthesized according to the
8a
already reported procedure.
Coulomb fitting basis sets for all atoms. Increased integration
grids (Grid4 and GridX4 in ORCA convention) and tight SCF
convergence criteria were used. Picture change effects were
applied and the integration grids were increased to an
integration accuracy of 11 (ORCA convention) for the metal
centre. Natural charges were obtained from additional single-
point calculations using the Natural Population Analysis (NPA)
1
General procedure of the synthesis of complexes
The complexes 1a and 1b has been synthesized in situ by the
I
dropwise addition of solution of 1 eq Cu (CH
3
CN)
4
OTf in
anhydrous dichloromethane in a solution of 1eq dissolved
ligand in the same solvent
3
5
and the B3LYP functional together with the TZV/P basis set.
Molecular orbitals, spin density plots and vibrational normal
.
3
6
III
III
modes were visualized with Chemcraft software.
General procedure for the synthesis of [LNi (O
2
)Cu (RPY2)]
Cl (2.5 mL; 0.15
mM) was cooled to -90 C. Then 1 equivalent of 1a 1b) in
anhydrous CH Cl (0.1mL) was added, to yield deep brown
The greenish solution of in anhydrous CH
2
2
2
o
Reactivity studies
(
2
2
Exogenous substrate oxidation
intermediate 3a (3b). The generation of the deep brown
species 3a (3b) was monitored by the growth of 885 nm band
In a typical experiment, 0.15mM to 0.2mM of 3a
(
3b) was
o
generated at -90 C, as discussed previously. The reactivity
1
8
in the UV/vis spectrum. O Labelled samples for rRaman
experiments were prepared using the same procedure but
o
(3b) were performed at -60 C under inert
studies of 3a
1
using starting from O labelled Ni precursor 2.
8
atmosphere, by injecting the CH Cl solution of substrate
2
2
(varying from 1mM to 60mM). Spectral changes at 885 nm
band were monitored by a UV-Vis spectrum every 1 second.
The pseudo-first order oxidation rate was then extracted and
EPR spectroscopy
EPR measurements were performed on a Bruker ESP 300 X-
band EPR spectrometer equipped with a fused quartz Dewar
for measurements at liquid nitrogen temperature.
compared to the self decay of 3a (3b) in the absence of
substrate. If the rate of oxidation in the presence of substrate
was higher than that in the absence of substrate, it was
concluded that 3a (3b) reacted with that substrate. The
pseudo-first order fitting of the decay curves yielded the rate
constants (kobs), which follow linear dependence with the
concentration of the substrate. The slope of the rate constant
Resonance Raman
2 2
rRaman spectra were measured in CH Cl at -92°C (Bruker
cryostat) using 413 nm excitation with by a Horiba Jobin-Yvon
LabRAM HR800 confocal Raman spectrometer. The
concentrations of samples were from 3 mM to 8 mM.
(kobs) versus substrate concentration fitting plot provided the
2
second order rate constants (k ).
DFT Calculations
Intramolecular ligand oxidation
All theoretical calculations were performed with the ORCA
The brownish solution of 3a warmed up at room temperature.
The solution was treated with ammonia solution 35% and after
extractions with dichloromethane (x2) and the organic phases
were washed with brine (x2), the organic phases were
1
9
program package. Full geometry optimizations were carried
2
0-22
out for all complexes using the GGA functional BP86
2
in
3
combination with the TZV/P basis set for all atoms and by
taking advantage of the resolution of the identity (RI)
2
approximation in the Split-RI-J variant with the appropriate
4
collected, dried over MgSO and the solvent removed under
4
1
vacuum. The resulting solid was analysed by H NMR
spectroscopy and mass spectrometry which showed the
absence of hydroxylated product.
2
5
Coulomb fitting sets. Increased integration grids (Grid4 in
ORCA convention) and tight SCF convergence criteria were
used. Solvent effects were accounted within the framework of
the conductor like screening (COSMO) dielectric continuum
2
6
approach. Vibrational frequency calculations were performed
to ensure that each geometry optimization converged to a real
minimum. IR and rRaman spectra were obtained from
numerical frequency calculations performed on optimized
Acknowledgements
This work has been carried out in the framework of COST
action CM1305 (ECOSTBio) including two STSMs (STSM-
CM1305-28897 and STSM-CM1305-32182). Financial supports
by the French Research Agency (COMEBAC / ANR-13-BSO7-
2
7,28
structures using the B3LYP
functional together with the
2
TZV/P basis set. The relative energies were obtained from
3
6
| J. Name., 2012, 00, 1-3
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Ple Da s ae l tdo onn To rt aa nd sj ua s ct t mi o an r sg ins
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Journal Name
ARTICLE
0
018) as well as from the DFG (Cluster of Excellence “Unifying 17 S. Kundu, F. F Pfaff, E. Miceli, I. Zaharieva, C. Herwig, S. Yao,
Concepts in Catalysis”; EXC 314-2) are gratefully
acknowledged. K.R. also thanks the Heisenberg-Program of
DFG for financial support.
E. R. Farquhar, U. Kuhlmann, E. Bill, P. Hildebrandt, H. Dau,
M. Driess, C. Limberg, K. Ray, Angew. Chem. Int. Ed., 2013,
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This journal is © The Royal Society of Chemistry 20xx
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DOI: 10.1039/C6DT02391F
Supporting information for
Changing the chemical and physical properties of high
valent heterobimetallic bis-(µ-oxido) Cu-Ni complexes by
ligand effects
Maria-Chrysanthi Kafentzi, Maylis Orio, Marius Réglier, Shegnlai Yao, Uwe Kuhlmann, Peter
Hildebrandt, Matthias Driess, A. Jalila Simaan and Kallol Ray
I. Additional spectroscopic data for 3a and 3b ....................................................................... 2
II. Kinetic plots of 3a vs. substrate concentration................................................................... 4
III. Kinetic plots of 3b vs. substrate concentration ................................................................. 5
IV. Products obtained after reaction of 3b with electrophilic and nucleophilic substrates..... 7
V. DFT Calculations on 3a and 3b ......................................................................................... 8
Metrical parameters and Gibbs free energies......................................................................... 9
Spin densities and SOMOs................................................................................................... 10
Spectroscopic parameters..................................................................................................... 11
Total density and individual Natural Charges...................................................................... 14

Dalton Transactions
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Kafentzi et al. Supporting information
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DOI: 10.1039/C6DT02391F
I. Additional spectroscopic data for 3b
4
.5
.0
.5
.0
.5
.0
.5
.0
.5
.0
4
3
3
2
2
1
1
0
0
400
600
800
1000
Wavelength (nm)
o
o
Figure S 1. Absorption spectra of 3a at -90 C (red) and at -30 C (black) in dichloromethane (0.15 mM).
4
3
2
1
0
400
600
800
1000
Wavelength (nm)
o
Figure S 2. Absorption spectrum of 3b at -90 C in dichloromethane (0.1 mM).
2

Page 11 of 23
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Kafentzi et al. Supporting information
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DOI: 10.1039/C6DT02391F
g=2.13
g=2.39
g=2.006
260
280
300
320
340
360
380
B-Field (mT)
Figure S 3. X-band EPR spectrum of 3b in dichloromethane at 77K
16
18
Figure S 4. Raman shifts obtained using a 413 nm laser excitation for 3b with O
2
(top), and O
2
(
bottom). Bands originating from the solvent are marked by asterisks.
3

Dalton Transactions
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Kafentzi et al. Supporting information
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DOI: 10.1039/C6DT02391F
II. Kinetic plots of 3a vs. substrate concentration
0
.0014
.0012
.0010
.0008
.0006
.0004
.0002
.0000
0.0011
0.0010
0.0009
0.0008
0.0007
0.0006
0.0005
0.0004
O
O
0
0
H
H
0
0
0
0
0
0.00
0.01
0.02
0.03
0.04
0.05
0.06
0.000 0.001 0.002 0.003 0.004 0.005 0.006
[CCA] (M)
[benzaldehyde] (M)
o
-1 -1
o
-1 -1
k2(-60 C)=0.021 M s
k2(-60 C)=0.088M s
Figure S 5. Pseudo first-order rate constants as a function of substrate concentration the reaction of
3
a with benzaldehyde (left) and CCA at -60°C in CH
2
Cl
2
0.0018
0.0030
0.0016
0.0025
0.0014
0.0020
0.0012
0.0015
0.0010
0.0010
0.0008
0
.0005
0.00
0.01
0.02
0.03
DHA] (M)
0.04
0.05
0.06
0.00
0.01
0.02
0.03
0.04
[
[CHD] (M)
o
-1 -1
o
-1 -1
k2(-60 C)=0.015 M s
k2(-60 C)=0.053 M s
Figure S 6. Pseudo first-order rate constants as a function of substrate concentration the reaction of
a with dihydroanthracene (left) and 1,3 cyclohexadiene (right) at -60°C in CH Cl
3
2
2
.
4

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DOI: 10.1039/C6DT02391F
0
.030
.025
.020
.015
.010
.005
.000
0
.00105
.00100
.00095
.00090
.00085
.00080
0.00075
0.00
OH
0
0
tBu
0
0
OH
0
0
tBu
tBu
0
tBu
0
0
0
0
0.000 0.001 0.002 0.003 0.004 0.005 0.006
0.01
0.02
0.03
0.04
0.05
[2,4-di-tert-butylphenol] (M)
[2,6-di-tert-butylphenol] (M)
o
-1 -1
o
-1 -1
k2(-90 C)=0.006 M s
k2(-90 C)=4.60 M s
Figure S 7. Pseudo first-order rate constants as a function of substrate concentration the reaction of
a with 2,4-di-tert-butylphenol (left) and 2,6-di-tert-butylphenol (right) at -90°C in CH Cl
3
2
2
.
III. Kinetic plots of 3b vs. substrate concentration
0.0014
O
O
0.0025
0.0012
H
H
0.0020
0.0010
0.0015
0.0008
0.0010
0.0006
0
.0005
0.00
0.01
0.02
0.03
0.04
0.000
0.001
0.002
[CCA] (M)
0.003
[
benzaldehyde] (M)
o
-1 -1
o
-1 -1
k2(-60 C)=0.0178 M s
k2(-60 C)=0.557 M s
Figure S 8. Pseudo first-order rate constants as a function of substrate concentration the reaction of
b with benzaldehyde (left) and cyclohexane carboxaldehyde (right) at -60°C in CH Cl
3
2
2
.
5

Dalton Transactions
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DOI: 10.1039/C6DT02391F
0
.0008
.0007
.0006
0.0005
.0004
.0003
0.0014
0
0.0012
0
0.0010
0
0.0008
0
0.0006
0
.0002
0.00
0.01
0.02
0.03
DHA] (M)
0.04
0.05
0.06
0.000 0.005 0.010 0.015 0.020 0.025 0.030
[
[CHD] (M)
o
-1 -1
o
-1 -1
k2(-60 C)=0.0148 M s
k2(-60 C)=0.015 M s
Figure S 9. Pseudo first-order rate constants as a function of substrate concentration the reaction of
b dihydroanthracene (left) and 1,3 cyclohexadiene (right) at -60°C in CH Cl
3
2
2
.
0.0025
0.0020
0.0015
0.0010
0.0005
0.000
0.005
0.010
0.015
0.020
[2,6-di-tert-butylphenol] (M)
o
-1 -1
k2(-60 C)=0.098 M s
Figure S 10. Pseudo first-order rate constants as a function of substrate concentration the reaction of
b 2,6-di-tert-butylphenol (right) at -60°C in CH Cl
3
2
2
.
6

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DOI: 10.1039/C6DT02391F
IV. Products obtained after reaction of 3b with electrophilic and
nucleophilic substrates
Table S1: Reaction of 3b with various electrophilic and nucleophilic substrates
Substrate
Products
DHA
CHD
Anthracene (45%)
Benzene (49%)
2
2
,2’,4,4’-tetra-tert-butyl-6,6’-biphenol
2
2
,4-DTBP
(
82%)
,2’,6,6’-tetra-tert-butyl-4,4’-biphenol
85%)
cyclohexene (62%) + Formate
,6-DTBP
CCA
(
7

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DOI: 10.1039/C6DT02391F
V. DFT Calculations on 3a and 3b
Figure S 11 Optimized molecular structures for 3b; Conformer A (left) and B (right).
Figure S 12 Optimized molecular structure for MEAN.
8

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Metrical parameters and Gibbs free energies
Table S 2. Calculated metrical parameters for the 3a and 3b conformers and the previously reported
III
III
+
[
LNi O Cu (MeAN)] complex.
2
Species
3a
3b
MEAN
Parameter
(A)
(B)
(A)
(B)
Cu-Ni
Cu-O1
2.758
2.857
2.769
2.750
2.792
1.772
1.788
2.036
2.047
-
1.781
1.802
1.980
1.966
2.514
1.815
1.764
1.861
1.895
79.1
1.944
1.817
2.077
2.095
2.072
1.817
1.751
1.854
1.887
74.6
1.782
1.799
1.992
1.992
2.408
1.814
1.771
1.855
1.884
78.8
1.784
1.798
2.006
2.032
2.373
1.765
1.819
1.879
1.852
79.7
Cu-O2
Cu-N1
Cu-N2
Cu-N3
Ni-O1
1.817
1.785
1.855
1.887
77.9
98.2
90.6
93.3
-
Ni-O2
Ni-N4
Ni-N5
O1-Cu-O2
N1-Cu-N2
O1-Cu-N1
O2-Cu-N2
O1-Cu-N3
O2-Cu-N3
O1-Ni-O2
N4-Ni-N5
95.1
136.9
111.1
92.6
96.5
90.0
90.6
89.5
93.5
91.5
91.7
93.3
104.7
106.0
79.2
99.3
107.5
101.3
78.7
101.0
107.0
79.6
173.7
79.5
-
76.8
95.3
95.4
95.3
95.4
95.4
O1-Ni-N4
O2-Ni-N5
93.0
92.5
93.6
93.8
93.3
94.7
4.5
93.4
11.2
92.8
3.7
94.4
16.2
92.7
14.3
O1-N4-N5-O2
9

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Table S 3. Calculated Gibbs free energies for the 3a and 3b conformers
Stability
kcal/mol)
Conformer
Energy (Eh)
Favored species
(
(
A)
B)
A)
B)
-5121.457043
-5121.372839
0
3
a
Conformer (A)
Conformer (A)
(
52.8
(
-4813.04405014
-4813.02925132
0
3
b
(
9.30
Spin densities and SOMOs
3
a
3b
Figure S 13. Spin density plots of 3a and 3b conformer (A)
1
0

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DOI: 10.1039/C6DT02391F
3
a
3b
Figure S 13. Singly Occupied Molecular Orbitals of 3a and 3b (conformer A)
Spectroscopic parameters
Table S 4. Comparison between calculated and experimental EPR parameters for 3a and 3b
conformer (A)
g
1
; g
2
; g
3
; (gav
)
3a
3b
Expt.
2.006; 2.140; 2.410 (2.185)
2.006; 2.130; 2.390 (2.175)
Calc.
2.067; 2.129; 2.282 (2.160)
2.061; 2.124; 2.280 (2.155)
Table S 5. Comparison between calculated and experimental Raman shifts for 3a and 3b conformer (A)
1
8
]) (cm-1)
ν (Δ[ Ο
2
3a
3b
Expt.
Calc.
605 (-31)
596 (-22)
556 (-21)
553 (-7)
612 (-29)
621 (-21)
579 (-19)
528 (-6)
1
1

Dalton Transactions
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Figure S 14. Computed Raman spectrum for 3a in the presence of 16-O .
2
Figure S 15. Computed Raman spectrum for 3b in the presence of 16-O .
2
1
2

Page 21 of 23
Dalton Transactions
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-
1
-1
Figure S 16. Normal modes relevant to the 596 cm (left) and 553 cm (right) Raman shifts of 3a
-
1
-1
Figure S 17. Normal modes relevant to the 621 cm (left) and 528 cm (right) Raman shifts of 3b
1
3

Dalton Transactions
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Total density and individual Natural Charges
Figure S 18. Total density and individual natural charges for 3a.
Figure S 19. Total density and individual natural charges for 3b.
1
4

Page 23 of 23
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III
III
+
Figure S 20. Total density and individual natural charges for [LNi O
2
Cu (MeAN)] .
1
5