Synthesis, Crystal Structure, and DFT Study of Two New Dinuclear Copper(I) Complexes Bearing Ar-BIAN Ligands Functionalized with NO2 Groups

Article abstract of DOI:10.1002/ejic.202000423

Two new bis(aryl-imino)-acenaphthene, Ar-BIAN (Ar = 2,4,6-trimethylphenyl = mes) ligands, bearing the NO₂ group in the naphthalene moiety of the iminoacenaphthene at para- (5-NO₂) and meta- (4-NO₂) position, of formulation

Full text of DOI:10.1002/ejic.202000423

European Journal of Inorganic Chemistry
Accepted Article
Title: Synthesis, Crystal Structure and DFT Study of Two New
Dinuclear Copper(I) Complexes Bearing Ar-BIAN ligands
Funtionalized with NO2
Groups
Authors: Mani Outis, Vitor Rosa, César A. T. Laia, João Carlos Lima,
Sónia Barroso, Maria José Calhorda, Ana Luísa Carvalho,
and Maria Teresa Aviles Perea
This manuscript has been accepted after peer review and appears as an
Accepted Article online prior to editing, proofing, and formal publication
of the final Version of Record (VoR). This work is currently citable by
using the Digital Object Identifier (DOI) given below. The VoR will be
published online in Early View as soon as possible and may be different
to this Accepted Article as a result of editing. Readers should obtain
the VoR from the journal website shown below when it is published
to ensure accuracy of information. The authors are responsible for the
content of this Accepted Article.
To be cited as: Eur. J. Inorg. Chem. 10.1002/ejic.202000423
Link to VoR: https://doi.org/10.1002/ejic.202000423
0
1/2020

European Journal of Inorganic Chemistry
10.1002/ejic.202000423
Synthesis, Crystal Structure, and DFT Study of Two New Dinuclear Copper(I)
Complexes Bearing Ar-BIAN Ligands Functionalized with NO Groups
2
†
†
†
†
‡,§
Mani Outis, Vitor Rosa,* César A. T. Laia, João Carlos Lima, Sónia Barroso, Ana Luísa
‡
**
†
Carvalho, Maria José Calhorda,* and Teresa Avilés*
Dedicated to Jean-François Halet on the occasion of his 60th birthday
†
LAQV, REQUIMTE, Departamento de Química, Faculdade de Ciências e Tecnologia, Universidade Nova de
Lisboa, 2829-516 Caparica, Portugal.
‡
UCIBIO, REQUIMTE, Departamento de Química, Faculdade de Ciências e Tecnologia, Universidade Nova
de Lisboa, 2829-516 Caparica, Portugal.
§
Current address: MARE – Centro de Ciências do Mar e do Ambiente, Politécnico de Leiria, 2520-641
Peniche, Portugal.
*
*
BioISI - Biosystems & Integrative Sciences Institute, Departamento de Quımica e Bioquımica, Faculdade de
́
́
Ciências, Universidade de Lisboa, 1749-016 Lisboa, Portugal.
1
This article is protected by copyright. All rights reserved.

European Journal of Inorganic Chemistry
10.1002/ejic.202000423
Abstract
Two new bis(aryl-imino)-acenaphthene, Ar-BIAN (Ar = 2,4,6-trimethylphenyl = mes) ligands,
bearing the NO group in the naphthalene moiety of the iminoacenaphtene at para- (5-NO
and meta- (4-NO ) position, of formulations 1,2-bis(mes-imino)-5-nitroacenaphthene, 1, and
,2-bis(mes-imino)-4-nitroacenaphthene, 2, were synthesized. Their respective dinuclear
iodide bridged copper(I) complexes [Cu (μ-I) (mes-BIAN-5-NO ], 3 and [Cu (μ-I) (mes-
BIAN-4-NO 4, were obtained in good yields by treatment with an equimolar amount of
CuI. All compounds were characterized by elemental analysis, single crystal X-ray diffraction,
2
2
)
2
1
2
2
2
)
2
2
2
2
) ]
2 ,
1
13
H-NMR, C-NMR, FTIR, UV-Vis spectroscopy. DFT calculations helped to understand the
different molecular structure observed in the crystals of 3 and 4 and the determining role of
packing forces. TDDFT revealed that the absorption bands in the visible were essentially
MLCT (Metal to Ligand Charge Transfer), with some n* character (intra ligand). The shift
to the red compared to the spectrum of the Cu(I) complex analogue without the NO
Cu (μ-I) ](mes-BIAN) ], 6, could be explained by the stabilization of the ligand unoccupied
* orbitals in the presence of NO
2
group,
[
2
2
2

2
.
Introduction
The design and synthesis of copper complexes is a subject of current interest since they can be
[1]
applied in a large variety of metal-mediated transformations. Moreover, copper is a cheap,
1
0
abundant and non-toxic metal. d transition metal complexes have been extensively studied
because of their unique photophysical and photochemical properties which led to applications
[2]
for light emitting devices, sensing devices, solar cells, and artificial photosynthesis. Among
those, 3d10 copper(I) complexes were studied since the last century to explore their
photophysical properties.[3]
The well-known {Cu
form a wide variety of complexes, resulting in tetracoordination around the Cu(I) atom. Their
general formulation is [Cu (µ-X) ], in which L are mainly N or P ligands, either monodentate
L), or bidentate chelating ligands (L-L). The synthesis and photophysical properties of Cu(I)
compounds of this type, bearing chelating chiral bis(phosphines), has been reported.[5]
-Diimine ligands are well known and have been extensively used due to their ability to
2
(µ-X)
2
} core (X = halide) can coordinate to different types of ligands to
2
L
2 4
[4]
(

stabilize organometallic complexes.[6,7] Elsevier et al.[8] described the synthesis and full
characterization of a new family of rigid chelating bidentate ligands of the type Ar-BIAN
(bis(aryl)acenaphthenequinonediimine) by condensation of acenaphthenequinone with two
2
This article is protected by copyright. All rights reserved.

European Journal of Inorganic Chemistry
10.1002/ejic.202000423
equivalents of an appropriate aryl-amine. Many late transition metal complexes bearing α-
diimine ligands have been extensively employed in several catalytic reactions.[9–16] Using this
synthetic route, we can easily vary the backbone and the aryl substituents, enabling thus to tune
the steric and electronic effects at the metal centre. We have been engaged during the last
decade in the synthesis of α-diimine transition metal compounds, either for structural studies[17–
2
1]
or catalytic applications.[22–27] Furthermore, copper(I) complexes bearing Ar-BIAN ligands
have been reported by us[18,22–24,26] and other authors.[28]
The excellent redox properties, stereo and electronic tunability of the
bis(aryl)acenaphthenequinonediimine (Ar-BIAN) ligands, make them extremely useful in the
contexts of synthetic, structural, and catalytic chemistry, their photophysical properties have
been studied and are found in the literature.[29–34]
Cu(I)–BIAN complexes have been studied as photosensitizers, for potential photovoltaic
applications[35,36] and as photocatalysts.[37]
We are interested in the synthesis of new Ar-BIAN ligands and their respective binuclear
{Cu
2
(µ-I)
2
}(LL) complexes, focusing on their full characterization by extensive experimental
2
methods supported by in-depth theoretical calculations. These studies allowed us to determine
their structural and electronic properties which could enlighten their potential application as,
for example, light harvesters for Dye-Sensitized Solar Cells (DSSC)[36] or as NIR emissive
complexes.[30]
Here we report the synthesis, structural characterization and DFT studies of two novel Ar-
BIAN
ligands
bis(mes-imino-5-nitroacenaphthene),
1,
and
bis(mes-imino-4-
(µ-I)
nitroacenaphthene), 2 and their two new dimeric Cu(I) complexes 3 and 4 with a {Cu
2
2
}
core, which display a redshifted MLCT, characterized by TDDFT calculations, in comparison
with the analogous complex 6 bearing the unsubstituted bis(mes-imino-acenaphthene)
ligand.[26]
Results and Discussion
Chemical studies
The first step in the synthesis of the ligands is the functionalization of acenaphthenequinone
by the NO
conditions, at room temperature, 0 ºC and 80 ºC, using NaNO
Although the authors claimed that the nitro-acenaphthenequinone held the NO
2
group, which has been described in the literature under different experimental
or HNO
as nitration agents.[38,39]
group at the
3
3
2
para- position, our attempts to repeat the synthesis following the three described methods
3
This article is protected by copyright. All rights reserved.

European Journal of Inorganic Chemistry
10.1002/ejic.202000423
afforded in all cases a mixture of products functionalized at para- and meta- position in
roughly1:2 meta-:para- proportion, from now on we will indistinctly name para- position to
5-NO
2
and meta- position to 4-NO (Scheme 1).
2
Scheme 1. Nitration of acenaphthenequinone.
The second step is diimine formation, and there are two major synthetic strategies to obtain Ar-
BIANs: (i) the template method using ZnCl or (ii) using an organic acid as a catalyst. The
2
second method using EtOH as solvent and formic acid as catalyst revealed to be quite efficient
since it allowed us to separate the two isomers due to their different solubilities. The two
separated Ar-BIANs (Scheme 2), one with the NO
2
group at the para- position, 1, which
precipitates from ethanol in 83% yield, and another with the NO
2
group at the meta- position,
2, which remains dissolved in ethanol from which the ligand is isolated after workup in 78%
yield.
Scheme 2. Synthesis of ligands 1 and 2.
Formation of ligands can be confirmed by FTIR spectroscopy. No C=O stretching vibrations
-1
of the starting diketones, in the 1700–1800 cm region, are observed, discarding thus the
formation of monosubstituted species. Characteristic vibrations of NO group are observed for
free ligands in the range of 1524-1536 cm for symmetric stretching and in the range of 1329-
2
-1
-1
1
338 cm for the asymmetric stretching of N-O bond. The C=N stretching frequency in the
free ligands cannot be assigned unambiguously because of the presence of C=C stretching
frequencies from the naphthalene backbone in this region,[8,40] however it is reported in the
4
This article is protected by copyright. All rights reserved.

European Journal of Inorganic Chemistry
10.1002/ejic.202000423
literature[41] that two bands in the range of 1617-1675 cm can be assigned to C=N stretching
-1
of Ar-BIANs.
Both ligands 1 and 2 are asymmetric molecules regarding the functionalized naphthalene
1
moiety, H-NMR characterization of ligands 1 and 2 was performed in CDCl
3
. The main
differences between the two compounds are in the naphthalene moiety bearing the NO
substituent. In the case of ligand 1, with the para-NO , we observe two duplets, for protons at
the position 3 and 4 at 6.83 and 8.31 ppm, respectively. As for ligand 2, with the meta-NO
2
2
2
,
two singlets corresponding to protons at 3 and 5 positions, were observed with a chemical shift
of 7.39 ppm and 8.86 ppm, respectively.
When we look at the protons of the aryl moieties of both compounds, we observe that in the
case of ligand 1 they are not strongly affected by the presence of the NO group. Just one
2
singlet, integrating for four protons, at 6.99 ppm, was observed, similar to the unsubstituted
ligand 5. In the case of compound 2, we see that the protons of the aryl group spatially closer
to the NO substituent, undergo some influence from the nitro group. Two singlets, both
2
integrating for two protons at 7.04 ppm and 6.99 ppm were observed. For ligand 2, the two
para-methyl groups are not equivalent, contrary to ligands 1 and 5, showing a clear influence
of the meta-NO group.
2
1
Indications of the presence of possible (E,Z) isomers were found in the H-NMR spectra. In
1
order to confirm their presence, we performed variable temperature H-NMR experiments in
C
6
6
D .
In solution, the Ar-BIAN ligands may appear in two (E,E) and (Z,E) stereo isomeric forms,
since steric repulsion prevents (Z,Z) from existing. Ragaini et al.[42] show that the ratio of the
two isomers depends on both temperature and solvent, the complete assignment of signals
being possible to make by bidimensional NMR experiments (COSY, NOESY, Figures S1-S10
in Supporting Information, SI). While asymmetric Ar-BIAN (Ar,Ar´-BIAN) molecules appear
in both forms in solution, symmetric ones seem to occur only as the (E,E) isomer. 1 and 2,
despite holding the same Ar (2,4,6-trimethylphenyl), are asymmetrical molecules regarding the
functionalized naphthalene moiety, so they can exist as (E,E), (Z,E) and (E,Z) forms in solution
(
see computational studies). While the presence of the isomers is not visible in CDCl
the solvent was changed to C , (Figures S11 and S12 in SI) all three isomers could be
observed, particularly in the case of 1 (S11 in SI). At room temperature in C the three
3
, when
6
D
6
6
D
6
isomers coexist, while at higher temperatures the isomers rapidly change and converge to one
set of peaks (see Figure 1).
5
This article is protected by copyright. All rights reserved.

European Journal of Inorganic Chemistry
10.1002/ejic.202000423
1
Figure 1. Temperature variation study by H-NMR spectroscopy in C
(B). Bottom to top spectra: temperature raise from 297 K to 327 K.
6
D
6
of ligands 1 (A) and
2
Complexes 3 and 4 were synthesized using the same strategy adopted for complex
Cu (μ-I) (Mes-BIAN)
] 6,[25] (see scheme 3), by adding CuI to the stoichiometric amount of
ligand 1 or 2 in CH CN and refluxing the mixture for 3 h. After removal of the solvent under
[
2
2
2
3
vacuum, dark solids were isolated, washed with pentane and dried under vacuum. Suitable
crystals for single crystal X-ray structure determination were obtained by slow diffusion of
pentane in a CH
2
Cl
2
solution, yielding compound 3 and 4 in 66% and 59% respectively.
6
This article is protected by copyright. All rights reserved.

European Journal of Inorganic Chemistry
10.1002/ejic.202000423
Scheme 3. Synthesis of complexes 3 and 4, and possible isomers A and B.
Two different isomers can be formed. In one of them, the ligands are in trans conformation
isomer A) and in the other one the ligands are in cis conformation (isomer B) (see Scheme 3)
(
In the synthesis of the Cu(I) dimers with ligands 1 and 2, only isomer A could be isolated as
revealed by single crystal X-ray diffraction (see below).
Characteristic vibrations of the NO
2
group are observed for complexes 3 and 4 at 1530 and
-1
1
536 cm , respectively, for symmetric stretching, and for the asymmetric stretching of N-O
-1
-1
bond at 1331 and 1339 cm , respectively. A band at 1643 cm for complex 3 and two bands,
-1
at 1649 and 1647 cm for complex 4, can be assigned to C=N stretching.
1
13
H-NMR and C-NMR studies of complexes 3 and 4 show similar patterns to those of the
ligands, only differing on the chemical shifts (Figures S13-S24 in SI). The highest difference
is for the methyl groups in the ortho-position of the aryl moieties, that are high field shifted in
comparison to the free ligands, at 2.15 ppm for 3, 2.15 and 2.17 ppm for 4. For complex 4, not
only the two para-methyl groups of the aryl are nonequivalent, like in ligand 2, but we also
observe two peaks assigned to the four ortho-methyl groups by opposition to only one peak in
complexes 3 and 6. The para-methyl groups appear as two singlets, at 2.44 and 2.36 ppm, and
the four ortho-methyl groups appear as two singlets at 2.17 and 2.15 ppm.
7
This article is protected by copyright. All rights reserved.

European Journal of Inorganic Chemistry
10.1002/ejic.202000423
Crystallography
Crystals of 1-4 suitable for single crystal X-ray diffraction were obtained as described in the
synthetic procedures. Ligands 1 and 2 crystallize in the monoclinic system, space groups P2 /n
1
and C2/c, respectively. The molecular structures of 1 and 2 are depicted in Figure 2 and selected
structural parameters are listed in Table S1 (SI). Structural parameters of the non-substituted
2
,4,6-Me
3
C
6
H
-BIAN analogue, 5, reported in the literature,[41] are also presented in Table S1
2
for comparison. The molecular structures of 1 and 2 show that the bis(imino) fragment exhibits
the (E,Z)-configuration as some other Ar-BIAN compounds,[18,43] instead of the more common
(
E,E)-configuration.[44–47] Compound 1, with a nitro substituent in the para- position, presents
a more planar bis(imino)acenaphthene skeleton than the non-substituted 2,4,6-Me
BIAN, 5, as evidenced by the N(1)-C(29)-C(19)-N(2) and C(28)-C(29)-C(19)-C(20) torsion
angles (0.2(7)º and 0.5(4)º in 1 vs. -6.2(2)º and -4.3(2)º in 2,4,6-Me -BIAN, 5. In contrast,
3
C
6
2
H -
3
C
6
H
2
compound 2, with a nitro substituent in the meta- position, displays a larger deviation from
planarity in the bis(imino)acenaphthene moiety than the non-substituted analogue 5, (N(1)-
C(29)-C(19)-N(2) and C(28)-C(29)-C(19)-C(20) torsion angles = 19.1(4)º and 10.2(2)º in 2 vs.
-6.2(2)º and -4.3(2)º in 5). The position of the nitro substituent in the naphthenic rings seems
to influence the referred deviation from planarity, possibly due to C-HO and C-H weak
hydrogen bonds, as observed in the packing diagram (Figure S25, SI). The angle between the
two mesityl rings is about 78º in compound 1 and 92º in compound 2. The imine C=N bonds
N(1)-C(29) in 1 and N(2)-C(19) in 2 are longer than the corresponding bond lengths in 2,4,6-
Me
3
C
6
2
H -BIAN, 5, (1.280(5) Å and 1.276(3) Å vs. 1.2662(16) Å), but overall they are
comparable with those observed in other Ar-BIAN compounds.[4–7,47] The breaking of
symmetry of the NO
there is symmetry.
2
substituents seems to disfavour the (E,E) configuration observed when
8
This article is protected by copyright. All rights reserved.

European Journal of Inorganic Chemistry
10.1002/ejic.202000423
Figure 2. Molecular structures of 1 (top left) and 2 (top right) using 30% probability level
ellipsoids, and molecular structure of 2,4,6-Me -BIAN, 5.
3
C
H
6 2
The molecular structures of 3 and 4 are depicted in Figures 3 and 4, respectively, and selected
structural parameters are listed in Table S2 (SI). Structural parameters of the related {CuI(Ar-
BIAN)}
2
, 6, with non-substituted 2,4,6-Me
3
C
6
H
-BIAN ligand, 5 (Figure S26 in SI),[26]
2
previously reported by us, are also presented in Table S2 (SI) for comparison. Compound 3
crystallizes in the monoclinic system, space group C2/c, with one half molecule of 3 and one
co-crystallized molecule of CH
2
Cl
2
in the asymmetric unit. Compound 4 crystallizes in the
/n, with one molecule in the asymmetric unit. In both
monoclinic system, space group P2
1
structures the Cu(I) atoms are bridged by two iodide ions and coordinated by two imine
nitrogen atoms of the BIAN ligands presenting distorted tetrahedral geometry. The I-Cu-I
angles in compound 4 are wider (about 115º) than in compound 3 (106.7(1)º). As a result, the
CuCu distance is particularly shorter in compound 4 (2.651(1) Å vs. 3.070(1) Å in 3) and it
is also shorter than the sum of the van der Waals radii of two copper atoms (2.80 Å) suggesting a
“
cuprophilic” interaction in compound 4.[29,48] Another difference between compounds 3 and
9
This article is protected by copyright. All rights reserved.

European Journal of Inorganic Chemistry
10.1002/ejic.202000423
4
is that the CuI dimer is perfectly planar in 3 while in 4 it displays a butterfly conformation
with an angle of 160.9(2)º between the triangles formed by Cu(1)-I(1)-Cu(2) and Cu(1)-I(2)-
Cu(2) (Figure 4). This distortion of the Cu-(I) -Cu core has been reported in the literature for
2
other dimeric Cu compounds and it has been related mainly to packing forces.[49,50] The
structural differences between compounds 3 and 4 may be either due to steric constraints
caused by the nitro meta- substituent or to packing arrangement. The packing diagram of 4
shows that all the molecules are arranged in the same direction, with the naphthalene moieties
lying on parallel planes (Figure S27, SI, right). For compound 3, the crystal presents molecules
packed perpendicularly to each other (Figure S27, SI, left) similar to the packing arrangement
observed for the analogue compound 6 (with non-substituted ligand) {CuI(Ar-BIAN)}
.[26] In
2
fact, the latter compound presents two crystallographically different molecules in the
asymmetric unit (molecules a and b in Figure S26, SI) whose structural differences may only
be attributed to packing forces. In the case of compound 3, there are no structural differences
between the molecules despite the perpendicular arrangement. Interestingly, the structural
parameters of 3 are very similar to those of molecule a of {CuI(Ar-BIAN)}
while the structural parameters of 4 are very similar to those of molecule b of {CuI(Ar-BIAN)}
Figure S26, SI) as can be seen in Table S2 (SI). In light of the discussion above, it is plausible
2
(Figure S26, SI)
2
(
to attribute the structural differences between compounds 3 and 4 to packing forces rather than
to steric constraints caused by the position of the nitro substituent. For both compounds the
main short contact interactions observed are non-classical C-HO and C-Hπ weak hydrogen
bonds, as well as C-HI halogen bonds connecting the molecules of 3 and 4 in different ways
(Figure S27, SI).
Comparing the structural data of compounds 3 and 4 with those of the free ligands 1 and 2, a
slight elongation is observed on the N=C bonds (mean 1.275(11) Å in 3 and 1.281(8) Å in 4)
ascribed to the coordination to the metal. In addition, there is a slight deviation from planarity
in the bis(imino)acenaphthene skeleton upon coordination in 3 (N(1)-C(29)-C(19)-N(2) and
C(28)-C(29)-C(19)-C(20) torsion angles = 0.2(12)º and -2.0(9)º vs. 0.2(7)º and 0.5(4)º in the
free ligand) while in 4 that moiety becomes more planar than in the free ligand (N(1)-C(29)-
C(19)-N(2) and C(28)-C(29)-C(19)-C(20) torsion angles = -8.6(9)º and -3.5(6)º vs. 19.1(4)º
and 10.2(2)º in the free ligand). The Cu-N and Cu-I bond lengths are in agreement with those
observed in the two related {CuI(Ar-BIAN)}
compounds found in the literature.[26,28]
2
10
This article is protected by copyright. All rights reserved.

European Journal of Inorganic Chemistry
10.1002/ejic.202000423
Figure 3. Molecular structure of 3, using 30% probability level ellipsoids. Equivalent atoms #
are generated using the symmetry transformation –x+1/2, -y+1/2, -z+2. The inset shows the
planarity of the Cu-(I)
2
-Cu core. Selected bond lengths (Å): I(1)-Cu(1) 2.569(1), I(2)-Cu(1)
2
.574(1), Cu(1)-N(1) 2.110(7), Cu(1)-N(2) 2.140(7), Cu(1)Cu(2) 3.070(1).
Figure 4. Molecular structure of 4, using 30% probability level ellipsoids. The inset shows the
butterfly conformation of the Cu-(I) -Cu core. Selected bond lengths (Å): I(1)-Cu(1) 2.555(1),
2
11
This article is protected by copyright. All rights reserved.

European Journal of Inorganic Chemistry
10.1002/ejic.202000423
I(2)-Cu(1) 2.579(1), Cu(1)-N(1) 2.086(5), Cu(1)-N(2) 2.113(6), I(2)-Cu(2) 2.563(1), I(1)-Cu(2)
.582(1), Cu(2)-N(3) 2.121(5), Cu(2)-N(4) 2.094(5), Cu(1)Cu(2) 2.651(1).
2
Computational Studies
The geometries of the ligands and the complexes were optimized using DFT calculations as
implemented in Gaussian16,[51] with the PBE1PBE functional, a 6-31G** basis set for the light
atoms, and LANL2DZ with polarization for I and Cu, considering the solvent (chloroform)
effect and dispersion corrections (more details in Experimental).
The ligand 5 without substituents may adopt two conformations, (E,E) and (Z,E). The (E,E) is
-1
slightly more stable (G = 0.6 kcal mol ). When nitro substituents are introduced, there is
another conformation, (E,Z). The three are shown, with the more relevant distances and relative
energies, in Figure S28, SI. The two ligands have similar energies, the lowest energy form of
-1
2
(E,E) being ~2.4 kcal mol more stable than the lowest energy form of 1 (E,Z). The most
stable conformation is different for the two ligands. When they bind to a metal, they must
rearrange to the (E,E) conformation.
The optimization of the geometry of complexes 3 and 4 was more difficult and it required
taking into account dispersion corrections in order to improve the agreement of the geometry
1
0
10
of the {Cu
2
(μ-I) } core with the experimental one, since M-M interactions in d -d systems
2
are difficult to reproduce.
The optimized geometry of 3 is shown in Figure 5 (top) with relevant distances (values are
only given for non-equivalent bonds). The {Cu
2
(μ-I) } core is planar and the Cu-I and Cu-N
2
bonds are very similar to the experimental ones (Table 2), the only significant difference being
observed in the Cu-Cu distance, calculated as 2.566 Å, but determined as 3.071 Å. To check
this aspect, the Cu-Cu distance of the {Cu
.566 Å to 3.071 Å in several steps and the energy increased by 2.9 kcal mol (electronic
energies, see also below). Considering the size of the molecule and the small energy difference
very flat potential energy surface), it might possible, but resources consuming, to modify the
2
(μ-I)
2
} in the core of the complex 3, was varied from
-1
2
(
methodology to get a better agreement.
The optimized geometry of complex 4 (Figure 5, bottom) is very similar to the experimentally
determined. Even the Cu-Cu distance is very close, and the I-CuCumed-I butterfly angle was
calculated as 166.1 (experimental 166.8). CuCumed is the point in the centre of the line joining
12
This article is protected by copyright. All rights reserved.

European Journal of Inorganic Chemistry
10.1002/ejic.202000423
-1
the copper atoms. Complex 4, with NO in the meta-position, is more stable (6.5 kcal mol )
2
than complex 3 with this group in para- position, following the order of stability of the ligands.
Figure 5. Optimized geometries (isomers A of Scheme 3) of 3 (top) and 4 (bottom) showing
-1
some bond distances (Å) and relative energies (G, kcal mol ).
The two complexes exhibit different {Cu (μ-I) } cores, namely flat with a long Cu-Cu distance
2
2
as seen in 3 and puckered with a Cu-Cu bond 4. Also, the phenyl groups of the two Ar-BIAN
ligands are parallel in 3 (Figure 3) and are not parallel in 4 (Figure 4). One should be tempted
to assign the preference to the substitution pattern, since the NO group occupies para and meta
2
positions in 3 and 4, respectively. It is not that simple because the analogous complex without
substituent, 6, has been structurally characterized and both forms are also present. When the
geometry is optimized, starting from any of them, the energy minimum corresponds to the flat
{Cu
2
(μ-I) } core, though the Cu-Cu distance is too short as seen above for 3. Other distances
2
are very comparable to those in 3 and 4. Since there are no substituents, the origin must be
found elsewhere. A closer look at the two independent molecules present in the crystal structure
13
This article is protected by copyright. All rights reserved.

European Journal of Inorganic Chemistry
10.1002/ejic.202000423
of 6, emphasizing the position they occupy (Figure 6), shows on the left the flat core (Cu-Cu
distance 3.08 Å) with parallel phenyl rings, while the unit on the right is puckered with a Cu-
Cu bond and not parallel phenyl groups (not so easily seen in this view). Also, the BIAN moiety
of the right-hand side unit is sandwiched between two of the phenyl groups of the left unit. In
order to maximize the interaction, the arrangement must be planar. The packing forces the
geometry to adapt, distorting the {Cu
2
(μ-I) } core, which requires a small amount of electronic
2
-1
energy (2.9 kcal mol , see Figure S29 in SI), compensated by intermolecular interactions. The
packing arrangement of 3 and 4 is probably responsible for the molecular structures observed.
Indeed, in complex 3 a very similar - stacking with three aryl rings is observed, reinforcing
the previous interpretation.
Figure 6. Molecular structure of {CuI(Ar-BIAN)} (6), showing the two crystallographically
2
different molecules present packed in the asymmetric unit (top) and of 3 showing the same type
of motif built from identical units (bottom).
14
This article is protected by copyright. All rights reserved.

European Journal of Inorganic Chemistry
10.1002/ejic.202000423
A related question is prompted by the representation of a Cu-Cu bond in the crystal structure
of 4, but not in the structure of 3 (Figures 3 and 4). In complexes 3, 4, and 6, iodine atoms
bridge the copper ones. As distances are not reliable indicators to detect bonds, we calculated
Wiberg indices (see Computational studies), which scale as bond strength indicators. For
calibration a structure with a non-supported Cu(I)-Cu(I) was searched in the CSD[52] (see
molecular representation in Figure S30, SI). The Wiberg index (WI) is 0.189 for the
experimental structure and 0.190 for the structure optimized in the same conditions as the other
complexes. The optimized structures of 3, and 6 led to WI of 0.193, and 4 to 0.178. This would
indicate a bond as strong as the reference non-supported Cu(I)-Cu(I). However, as the
experimental geometries could not be exactly reproduced as discussed above, we calculated
WIs for them. Now, the WI for 6 is 0.090 (a) and 0.148 (b), for 3 0.09, and for 4 0.132. The
distortion produced by packing effects weakens the Cu-Cu bonds, less in 3 and 6a (~75%) and
more in 4 and 6b (~50%). Probably there is a Cu-Cu in all the complexes, though weaker in 4
and 6b.
Absorption spectra
Ligands and complexes absorb in the visible and UV regions, but the complexation leads to a
shift of the lower energy bands to longer wavelengths, especially when the NO substituents
2
are present, as shown in Figure 7 and Table S3 (SI). (See also Figure S31 in SI for
comparison purposes).
15
This article is protected by copyright. All rights reserved.

European Journal of Inorganic Chemistry
10.1002/ejic.202000423
Figure 7. UV-Vis spectra of compounds 1, 3, 2 and 4 in CHCl .
3
TDDFT calculations were used to obtain the absorption spectra of all the compounds. The
frontier orbitals of the complexes were influenced by the pattern of substitution, as can be seen
in Figure 8, where the relative energies of orbitals between HOMO-3 and LUMO+2 are shown,
with a 3D representation of the HOMO and the LUMO.
In complex 6, the HOMO is mainly localized in the {Cu
2
(μ-I) } core, being antibonding
2
between all atoms. There is a very small participation of the nitrogen lone pairs which are also
Cu-N antibonding. The LUMO, on the other hand, is localized in the right side of the BIAN
ligand. Note that the nitrogen atoms also participate in this -system. The LUMO+1, not
shown, looks the same, but is localized in the left side, and these two levels have practically
the same energy (Figure 8). The introduction of the NO
the LUMO, since the -orbitals extend to the NO groups, and this effect is more pronounced
in 3 (p-NO ). The effect on the HOMOs is not so significant and is very similar for 3 and 4.
The HOMO still consists of the  network [Cu (μ-I) ] and remains antibonding. The main
contribution of the unoccupied orbitals is from the -orbitals ranging from the nitrogen atoms
to the NO groups over the whole ligand.
2
substituents leads to a stabilization of
2
2
2
2
N
4
2
16
This article is protected by copyright. All rights reserved.

European Journal of Inorganic Chemistry
10.1002/ejic.202000423
Figure 8. Frontier orbitals of complexes 3, 4 and 6, showing the 3D representation of the
HOMO and the LUMO, as well as the relative energies.
The TDDFT calculated lower energy absorption bands for the three complexes 3, 4 and 6 are
listed in Table S4 in SI, and all the orbitals are depicted in Figures S32, S33 and S34 in SI. The
nature of the transitions is more clearly seen in the Electron Energy Difference Maps (EDDM)
which are shown in Figures 9 and 10 for complexes 3 and 4, respectively. All the transitions
are essentially metal-to-ligand-charge-transfer (MLCT) from orbitals including the {Cu
cores augmented by the nitrogen lone pairs (), represented in red in all figures, to the ligand
-orbitals, represented in light blue. The participation of the nitrogen atoms in occupied (, n)
and unoccupied (*) orbitals adds to the essentially MLCT transitions an n* character (intra
ligand, IL). The nature of the {Cu (μ-I) }  and the ligand * change with the transition. As
the energy increases, the {Cu (μ-I) }  orbitals will become more stable and less antibonding,
2
(μ-I)
2
}

2
2
2
2
the opposite being observed for the ligand * orbitals (higher energy, more antibonding) as is
shown in the molecular orbitals of the three complexes in Figures S32, S33 and S34 in SI.
17
This article is protected by copyright. All rights reserved.

European Journal of Inorganic Chemistry
10.1002/ejic.202000423
Figure 9. TDDFT simulated electronic spectrum of complex 3 (red) and experimental spectrum
black). The EDDM plots are also shown, red and blue corresponding to a decrease and increase
(
in electron density, respectively.
The EDDM plots show that the low energy transitions involve the {Cu
2
(μ-I) } cores and the
2
ligands, but as the energy increases (entries 5 and 6, Table S4) the participation of the phenyl
substituents increases, adding a * character (intra ligand, IL). The calculated spectra are
shifted relative to the experimental ones, but their outline is very comparable.
The same type of plot is shown in Figure 10 for complex 4. The EDDM plots are very similar
to those of complex 3, showing MLCT transitions, with some n* character (intra ligand,
IL) in the lower energy bands, with added * character (intra ligand, IL) in the higher
energy bands.
18
This article is protected by copyright. All rights reserved.

European Journal of Inorganic Chemistry
10.1002/ejic.202000423
Figure 10. TDDFT simulated electronic spectrum of complex 4 (red) and experimental
spectrum (black). The EDDM plots are also shown, red and blue corresponding to a decrease
and increase in electron density, respectively.
The spectra of complex 6 are shown in Figure S35 in SI and display the same features, being
mostly MLCT with added n* character. As expected, the  orbitals extension is smaller,
owing to the absence of NO substituents. On the other hand, the participation of phenyl
2
contribution to the orbitals remains very reduced compared to what was observed for 3 and 4
in similar energy range, so that IL * is practically non-existent.
In order to study the possible emission, complexes 3, 4 and 6 were excited in the lower lying
bands (620-630 nm) and also in higher lying bands (330-350 nm), but no steady state emission
was observed. All complexes appear not to be luminescent in solution neither in solid phase.
Conclusions
Two dimeric new Cu(I) complexes [Cu
2
(μ-I)
2
(LL)
2
] of two new bis(aryl-imino)-acenaphthene
group in the
(LL), Ar-BIAN (Ar = 2,4,6-trimethylphenyl = mes) ligands, bearing the NO
2
19
This article is protected by copyright. All rights reserved.

European Journal of Inorganic Chemistry
10.1002/ejic.202000423
naphthalene moiety of the iminoacenaphthene at para- (3) and meta- (4) position were
synthesized. Despite the similarities, the single crystal X-ray diffraction structures showed that
the {Cu
2
(μ-I) } cores displayed different arrangements, being planar for 3 and puckered for 4.
2
Although it was possible to reproduce the main features of the geometries of these complexes
using a DFT approach (and adding Grimme3 corrections to the functional), the fact that the
analogous complexes with unsubstituted Ar-BIAN ligands also showed the same isomerism,
led us to propose that packing effects should play a relevant role in determining the molecular
structure. Indeed, the arrangement of the Ar groups is similar between the two puckered and
the two planar complexes but differs between the two groups.
The nature of the TDDFT calculated absorption spectra in the visible is MLCT, in agreement
with the experimental behaviour, but there is a n* character, resulting from transitions
involving the N atoms lone pairs and their p orbitals present in the BIAN  orbitals. At higher
energies the  orbitals of the Ar- groups also participate in the excitations.
Experimental Section
General: All manipulations dealing with air- or moisture-sensitive materials were carried out
under an inert atmosphere using a dual vacuum/Argon line and standard Schlenk techniques.
Unless otherwise stated, all reagents were purchased from commercial suppliers and used as
received. All solvents were used under an inert atmosphere and purified prior to use.
Dichloromethane and acetonitrile were purified over calcium hydride and distilled prior to use.
Ligands Ar-BIAN (Ar =2,4,6-trimethylphenyl) (5) and complex 6 were prepared according to
the literature.[8,26]
Synthesis of Nitro-Acenaphthenequinone It was prepared following a slightly modified
reported procedure.[38] Acenaphthenequinone was dissolved in concentrated H
and after formation of a dark brown viscous solution the flask was placed in an ice-bath. The
necessary amount of grinded NaNO was then added slowly. The mixture was stirred during
h and then poured on crunched ice. The product was filtered and washed with cold water
affording a 2:1 mixture of para:meta nitro-acenaphthenequinone.
SO (95-97%)
2
4
3
3
1H-NMR (400 MHz, CDCl
, 25ºC) δ = 9.27 (s, 1H), 9.16 (d, J = 8 Hz, 2 H), 8.87 (s, 1H), 8.75
3
(d, J = 8 Hz, 2H), 8.53 (d, J = 8 Hz, 1H), 8.35-8.31 (m, 3H), 8.23 (d, J = 8 Hz, 2H), 8.16 (t, J
=
8 Hz, 2H), 8.07 (t, J = 8 Hz, 1H) ppm.
20
This article is protected by copyright. All rights reserved.

European Journal of Inorganic Chemistry
10.1002/ejic.202000423
Synthesis of Ligands 1 and 2: To a suspension of Nitro-Acenaphthenequinone (1.14 g 5.02
mmol) in Ethanol, 2 eq. of 2,4,6-methylaniline (1.44 mL, 10.04 mmol) were added together
with 0.5 mL of formic acid. The mixture was stirred at R.T. overnight. A dark red solid
precipitated, and it was separated from the solution by filtration affording 1.28 g (83% yield)
of 1. The solvent of remaining red solution was evaporated until dryness affording a red oil
which was redissolved in CH
2
Cl (15 mL) and washed with HCl 0.1 M (4x5ml) in order to
2
remove the unreacted free aniline. The organic phase was separated, and the solvent removed
under vacuum, yielding 0.60 g of a red solid, ligand 2 (78% yield). Crystals of 1 were obtained
by slow diffusion of hexane in a CH
evaporation of an Et O solution.
2
Cl solution. Crystals of 2 were obtained by slow
2
2
Characterization of Ligand 1:
Elemental analysis for C30
H
27
N
3
O
2
.1/12CH
2
Cl calculated: C, 77.10; H, 5.84; N, 8.97; found:
2
C, 77.12; H, 5.90; N, 9.22.
-1
FTIR (ATR)  = 1671 (C=N), 1638 (C=N), 1524 (N-O sym), 1329 (N-O asym) cm .
1H-NMR (400 MHz, CDCl
3
) δ = 8.76 (d, J = 8 Hz, 1H), 8.31 (d, J = 8 Hz, 1H), 7.66 (t, J = 8
Hz, 1H), 6.99 (s, 4H), 6.94 (d, J = 8 Hz, 1H), 6.83 (d, J = 8 Hz, 1H), 2.39 (s, 6H), 2.08 (s, 12H)
ppm.
1
3
1
C{ H}-NMR (100.6 MHz, CDCl ) δ = 159.74, 159.53, 146.36, 145.22, 141.36, 134.72,
3
1
33.86, 133.53, 132.05, 130.05, 129.37, 129.30, 128.29, 127.10, 126.39, 124.37, 124.25,
24.05, 121.25, 21.04, 17.81 ppm.
1
UV-Vis, λmax[nm] (ε [L/(mol.cm)]): 454(1338), 376(5773), 345(8013), 316(7200), 300(6439).
+
+
ESI-MS: m/z = 462.1(100%) [1+H] , 484.1(5%) [1+Na] .
Characterization of Ligand 2:
Elemental analysis for C30
H
27
N
3
O
2
.1/5(CH
3
CH
2
) O calculated: C, 77.65; H, 6.14; N, 8.82;
2
found: C, 77.65; H, 5.98; N, 8.94.
-1
FTIR (ATR)  = 1668 (C=N), 1635 (C=N), 1532 (N-O sym), 1338 (N-O asym) cm .
1H-NMR (400 MHz, CDCl
.39 (s, 1H), 7.04 (s, 2H), 6.99 (s, 2H), 6.95 (d, J = 8 Hz, 1H), 2.41 (s, 3H), 2.38 (s, 3H), 2.09
s, 12H) ppm.
3
) δ = 8.86 (s, 1H), 8.09 (d, J = 8 Hz, 1H), 7.57 (t, J = 8 Hz, 1H),
7
(
21
This article is protected by copyright. All rights reserved.

European Journal of Inorganic Chemistry
10.1002/ejic.202000423
1
3
1
C{ H}-NMR (100.6 MHz, CDCl
3
) δ = 159.99, 159.82, 147.76, 146.42, 146.26, 142.08,
1
34.10, 133.52, 130.85, 130.51, 130.03, 129.81, 129.45, 129.28, 128.28, 126.03, 125.36,
24.47, 124.21, 116.40, 21.04, 21.01, 17.81 ppm.
1
UV-Vis, λmax[nm] (ε [L/(mol.cm)]): 450(1251), 370(2253), 353(3617), 336(5191), 315(7840),
302(9056), 282(31128), 272(30435).
+
+
ESI-MS: m/z = 462.1(100%) [2+H] , 484.1(10%) [2+Na] .
Synthesis of complexes: To a CH
3
CN (20 mL) solution of ligand 1 (137.60mg 0.30 mmol) or
2, ((207.40mg 0.45 mmol) one equivalent of CuI was added, and the mixture was heated at
reflux for 3 h. After removal of the solvent under vacuum, the resultant dark solid was washed
with pentane (3x15 mL) and dried under vacuum. Suitable crystals for single crystal X-ray
structure determination were obtained by slow diffusion of pentane in a CH
: 66%, 4: 59% after crystallization).
2
Cl solution (yield
2
3
Characterization of Complex 3:
Elemental analyses for C60
H54Cu
2
I
2
N
6
O
4
.1/6CH
2
Cl calculated: C, 54.82; H, 4.15; N, 6.38;
2
found: C, 54.82; H, 4.20; N, 6.43.
-1
FTIR(ATR)  = 1643 (C=N), 1530 (N-O sym), 1331 (N-O asym) cm .
1H-NMR (400 MHz, CDCl
Hz, 2H), 6.95 (s, 8H), 6.74 (d, J = 8 Hz, 2H), 6.65 (d, J = 8 Hz, 2H), 2.46 (s, 12H), 2.16 (s,
3
) δ = 8.76 (d, J = 8 Hz, 2H), 8.28 (d, J = 8 Hz, 2H), 7.65 (t, J = 8
24H) ppm.
1
3
1
C{ H}-NMR (100.6 MHz, CDCl
3
) δ = 160.49, 159.85, 145.46, 144.06, 143.99, 141.88,
1
34.89, 134.62, 133.94, 132.41, 129.69, 129.64, 129.00, 127.34, 127.29, 127.12, 124.61,
23.88, 121.75, 21.29, 19.29 ppm.
1
UV-Vis, λmax[nm] (ε [L/(mol.cm)]): 820(1310), 610(8443), 380(15916), 351(19549),
18(16295).
3
+
+
+
ESI-MS: m/z = 462.1(100%) [1+H] , 985.0 (25%) [2x1+Cu] , 1174.8 (0.6%) [3-I] .
Characterization of Complex 4:
Elemental analyses for C60
H54Cu
2
I
2
N
6
O
4
.1/3C H12 calculated: C, 55.77; H, 4.44; N, 6.33;
5
found: C, 56.03; H, 4.09; N, 6.44.
22
This article is protected by copyright. All rights reserved.

European Journal of Inorganic Chemistry
10.1002/ejic.202000423
-1
FTIR(ATR)  = 1649 (C=N), 1647 (C=N), 1536 (N-O sym), 1339 (N-O asym) cm .
1H-NMR (400 MHz, CDCl
.21 (s, 2H), 6.93 (s, 4H), 6.86 (s, 4H), 6.79 (d, J = 8 Hz, 2H), 2.44 (s, 6H), 2.36 (s, 6H), 2.18
s, 12H), 2.16 (s, 12H) ppm.
3
) δ = 8.88 (s, 2H), 8.13 (d, J = 8 Hz, 2H), 7.55 (t, J = 8 Hz, 2H),
7
(
1
3
1
C{ H}-NMR (100.6 MHz, CDCl ) δ = 160.59, 160.46, 148.03, 144.05, 143.95, 142.59,
3
1
35.07, 134.54, 131.67, 130.92, 129.84, 129.71, 129.62, 129.51, 128.86, 127.33, 127.07,
26.52, 126.05, 116.83, 21.22, 19.36, 19.30 ppm.
1
UV-Vis, λmax[nm] (ε [L/(mol.cm)]): 850(819), 586(10304), 372(10931), 353(11957),
17(18401), 304(24575).
3
+
+
+
ESI-MS: m/z = 462.1(100%) [2+H] , 985.0 (25%) [2x2+Cu] , 1174.8 (0.5%) [3-I] .
Crystallographic data. Crystals of 1, 2, 3 and 4 suitable for single-crystal X-ray analysis were
grown as described in the synthetic procedures. Selected crystals were covered with Fomblin
(polyfluoroether oil) and mounted on a nylon loop. The data were collected at 110(2) K on a
Bruker D8 Venture diffractometer equipped with a Photon 100 CMOS detector and an Oxford
Cryosystems gaseous nitrogen stream Cooler, using graphite monochromated Mo-Kα radiation
( = 0.71073 Å). Data were processed using APEX2 suite software package, which includes
integration and scaling (SAINT), absorption corrections (SADABS) and space group
determination (XPREP). Structure solution and refinement were done using direct methods
with the programs SHELXS-97 and SHEXL-2014/7 inbuilt in APEX and WinGX-Version
2
014.1[53] software packages. All non-hydrogen atoms were refined anisotropically and all the
hydrogen atoms were inserted in idealized positions and allowed to refine riding on the parent
carbon atom. The crystals of 3 and 4 presented disordered solvent molecules and the
PLATON/SQUEEZE[54] routine was applied as it was not possible to obtain a good disorder
model. The crystals had poor diffracting power leading to poor quality data. The molecular
diagrams were drawn with ORTEP-3 for Windows[55] and Mercury,[56] included in the software
package. Table S5 contains crystallographic experimental data and structure refinement
parameters. CCDC 1979445-1979448 contain the supplementary crystallographic data for this
paper. The data can be obtained free of charge from The Cambridge Crystallographic Data
Centre via www.ccdc.cam.ac.uk/structures.
23
This article is protected by copyright. All rights reserved.

European Journal of Inorganic Chemistry
10.1002/ejic.202000423
Computational Studies
DFT calculations were performed with Gaussian16,[51] using the double- basis set augmented
with an f polarization function, LANL2DZ, for copper and extra p and d polarization function
for iodine, with the associated effective core potential (ECP),[57] all downloaded from the
EMSL Basis Set Library.[58,59] For the remaining elements, the standard 6-31G** basis set,
comprising polarization functions, was employed. The hybrid PBE1PBE functional (also
known as PBE0),[60] was used with a Grimme D3 dispersion correction.[61] The dispersion
correction was necessary to reproduce relatively well the experimental structures, which were
taken as starting geometry guesses. Geometry optimizations were performed without symmetry
constraints in chloroform with the PCM solvation method.[62] TDDFT calculations, as
implemented in Gaussian16, were performed to calculate the absorption spectra in chloroform.
Wiberg indices were calculated with the NBO implementation in Gaussian16.[63–66] The
reference compound with a non-supported Cu-Cu bond[67] was retrieved from the CSD.[52]
The electron density difference maps (EDDMs) were obtained from scripts in the GaussSum
package.[68] Molecular structures orbitals and electron density were drawn using Chemcraft.[69]
ASSOCIATED CONTENT
Supporting Information
The Supporting Information is available free of charge at DOI:
CCDC reference numbers 1979445-1979448. NMR spectra for all compounds (Fig. S1-S24).
Mercury packing diagrams of 1 and 2 (Fig. S25) and 3 and 4 (Fig. S27). Molecular Structure
of 6 (Fig. S26). Selected bond lengths and angles for 1, 2 and 5 (Table S1) and for 3, 4 and 6
(Table S2).Crystal data and structure refinement for 1, 2, 3 and 4 (Table S5).Optimized geometry of
ligands 1 and 2 in the three possible conformations (Fig. S28). UV-Vis spectra of 5 and 6 (Fig.
S31). Maxima and shoulders in the visible and near-UV absorption spectra of the ligands 1, 2
and 5 and complexes 3, 4, and 6 in chloroform (Table S3). DFT calculated change in energy
associated with lengthening the Cu-Cu distance from 2.566 to 3.071 Å in complex 3 (Fig. S29).
The X-ray structure of a complex with a non-supported Cu(I)-Cu(I) bond (top) and a view of
the ligand (bottom) (Fig. S30). TDDFT calculated excitation energies and oscillator strengths
(OS) in the visible absorption spectra of the complexes 3, 4, and 6 in chloroform (Table S4).
Frontier molecular orbitals of complexes 3, 4 and 6 (Fig. S32-S34). TDDFT simulated
electronic spectrum, experimental spectrum and EDDM plot of complex 6, (Figure S35).
AUTHOR INFORMATION
Corresponding Author
24
This article is protected by copyright. All rights reserved.

European Journal of Inorganic Chemistry
10.1002/ejic.202000423
*E-mail: teresa.aviles@fct.unl.pt; vitor.rosa@fct.unl.pt; mjc@fc.ul.pt
Conflicts of interest
There are no conflicts of interest to declare
ACKNOWLEDGMENTS
This work was supported by the Associate Laboratory for Green Chemistry- LAQV
financed by national funds from FCT/MCTES (UIDB/50006/2020). MJC and MO
acknowledge the Fundação para a Ciência e a Tecnologia (FCT) for support
(
UIDB/04046/2020). The authors acknowledge LabRMN at FCT-UNL and Rede Nacional de
RMN (RNRMN) for access to the facilities. The NMR spectrometers are part of The National
NMR Facility, supported by FCT (ROTEIRO/0031/2013 - PINFRA/22161/2016) (co-financed
by FEDER through COMPETE 2020, POCI, and PORL and FCT through PIDDAC). Data
Mass Spectrometry obtained by the Laboratório de Análises/LAQV REQUIMTE - Chemistry
department FCT University NOVA of Lisbon. The SCXR determinations were performed in
house (equipment financed by national funds through project RECI/BBB-BEP/0124/2012 from
FCT/MCTES). SB acknowledges project SmartBioR for financial support (CENTRO-01-
0145-FEDER-000018, Integrated Programme SR&TD co-funded by Centro 2020 program,
Portugal 2020, European Union, through the European Regional Development Fund). MO
acknowledges PhD Grant SFRH/BD/120985/2016 financed by FCT.
25
This article is protected by copyright. All rights reserved.

European Journal of Inorganic Chemistry
10.1002/ejic.202000423
References:
[1]
P. J. Pérez, M. M. Díaz-Requejo, in Compr. Organomet. Chem. III (Eds.: R.H.
Crabtree, D.M.P. Mingos), Elsevier, New York, 2007, pp. 153–195.
V. W.-W. Yam, K. K.-W. Lo, Chem. Soc. Rev. 1999, 28, 323–334.
M. W. Blaskie, D. R. McMillin, Inorg. Chem. 1980, 19, 3519–3522.
[2]
[3]
[4]
K. Tsuge, Y. Chishina, H. Hashiguchi, Y. Sasaki, M. Kato, S. Ishizaka, N. Kitamura,
Coord. Chem. Rev. 2016, 306, 636–651.
[5]
S. K. Gibbons, R. P. Hughes, D. S. Glueck, A. T. Royappa, A. L. Rheingold, R. B.
Arthur, A. D. Nicholas, H. H. Patterson, Inorg. Chem. 2017, 56, 12809–12820.
[6]
[7]
[8]
H. tom Dieck, M. Svoboda, T. Greiser, Z. Naturforsch. B 1981, 36, 823–832.
G. Van Koten, K. Vrieze, in Adv. Organomet. Chem., 1982, pp. 151–239.
R. van Asselt, C. J. Elsevier, W. J. J. Smeets, A. L. Spek, R. Benedix, Rec. Trav. Chim.
Pays-Bas 2010, 113, 88–98.
[9]
B. Rieger, L.S. Baugh, S. Kacker, S. Striegler, Late Transition Metal Polymerization
Catalysis, Wiley-VCH Verlag, Weinheim, 2006.
[
[
[
10] S. D. Ittel, L. K. Johnson, M. Brookhart, Chem. Rev. 2000, 100, 1169–1203.
11] V. C. Gibson, S. K. Spitzmesser, Chem. Rev. 2003, 103, 283–315.
12] G. J. P. Britovsek, V. C. Gibson, D. F. Wass, Angew. Chem. Int. Ed. 1999, 38, 428–
4
47.
[13] J. H. Groen, J. G. P. Delis, P. W. N. M. van Leeuwen, K. Vrieze, Organometallics
1
997, 16, 68–77.
[14] J. Durand, B. Milani, Coord. Chem. Rev. 2006, 250, 542–560.
[15] A. Scarel, M. R. Axet, F. Amoroso, F. Ragaini, C. J. Elsevier, A. Holuigue, C.
Carfagna, L. Mosca, B. Milani, Organometallics 2008, 27, 1486–1494.
[16] B. L. Small, R. Rios, E. R. Fernandez, M. J. Carney, Organometallics 2007, 26, 1744–
1
749.
[17] V. Rosa, P. J. Gonzalez, T. Avilés, P. T. Gomes, R. Welter, A. C. Rizzi, M. C. G.
26
This article is protected by copyright. All rights reserved.

European Journal of Inorganic Chemistry
10.1002/ejic.202000423
Passeggi, C. D. Brondino, Eur. J. Inorg. Chem. 2006, 2006, 4761–4769.
[
[
[
[
[
[
[
18] V. Rosa, T. Avilés, G. Aullon, B. Covelo, C. Lodeiro, Inorg. Chem. 2008, 47, 7734–
7
744.
19] V. Rosa, C. I. M. Santos, R. Welter, G. Aullón, C. Lodeiro, T. Avilés, Inorg. Chem.
010, 49, 8699–8708.
2
20] T. Kauf, V. Rosa, C. Fliedel, R. Pattacini, N. Deibel, T. Avilés, B. Sarkar, P.
Braunstein, Dalton Trans. 2015, 44, 5441–5450.
21] B. Pedras, V. Rosa, R. Welter, C. Lodeiro, T. Avilés, Inorg. Chim. Acta 2012, 381,
1
43–149.
22] V. Rosa, S. A. Carabineiro, T. Avilés, P. T. Gomes, R. Welter, J. M. Campos, M. R. R.
M.R. Ribeiro, J. Organomet. Chem. 2008, 693, 769–775.
23] C. Romain, V. Rosa, C. Fliedel, F. Bier, F. Hild, R. Welter, S. Dagorne, T. Avilés,
Dalton Trans. 2012, 41, 3377–3379.
24] C. Fliedel, V. Rosa, C. I. M. Santos, P. J. Gonzalez, R. M. Almeida, C. S. B. Gomes,
P. T. Gomes, M. A. N. D. A. Lemos, G. Aullón, R. Welter, T. Avilés, Dalton Trans.
2
014, 43, 13041–13054.
[
[
[
[
25] L. Li, P. S. Lopes, V. Rosa, C. A. Figueira, M. A. N. D. A. Lemos, M. T. Duarte, T.
Avilés, P. T. Gomes, Dalton Trans. 2012, 41, 5144–5154.
26] L. Li, P. S. Lopes, C. A. Figueira, C. S. B. Gomes, M. T. Duarte, V. Rosa, C. Fliedel,
T. Avilés, P. T. Gomes, Eur. J. Inorg. Chem. 2013, 2013, 1404–1417.
27] P. De Frémont, H. Clavier, V. Rosa, T. Avilés, P. Braunstein, Organometallics 2011,
3
0, 2241–2251.
28] T. Kern, U. Monkowius, M. Zabel, G. Knör, Eur. J. Inorg. Chem. 2010, 2010, 4148–
156.
4
[
[
[
29] T. Kern, U. Monkowius, M. Zabel, G. Knör, Inorg. Chim. Acta 2011, 374, 632–636.
30] C. J. Adams, N. Fey, J. A. Weinstein, Inorg. Chem. 2006, 45, 6105–6107.
31] C. J. Adams, N. Fey, Z. A. Harrison, I. V. Sazanovich, M. Towrie, J. A. Weinstein,
Inorg. Chem. 2008, 47, 8242–8257.
27
This article is protected by copyright. All rights reserved.

European Journal of Inorganic Chemistry
10.1002/ejic.202000423
[
[
[
[
[
[
[
32] S. K. Singh, S. K. Dubey, R. Pandey, L. Mishra, R.-Q. Zou, Q. Xu, D. S. Pandey,
Polyhedron 2008, 27, 2877–2882.
33] D. A. Evans, L. M. Lee, I. Vargas-Baca, A. H. Cowley, Dalton Trans. 2015, 44,
1
1984–11996.
34] D. A. Evans, L. M. Lee, I. Vargas-Baca, A. H. Cowley, Organometallics 2015, 34,
422–2428.
2
35] P. A. Papanikolaou, N. V. Tkachenko, Phys. Chem. Chem. Phys. 2013, 15, 13128–
3136.
1
36] J. W. Kee, Y. Y. Ng, S. A. Kulkarni, S. K. Muduli, K. Xu, R. Ganguly, Y. Lu, H.
Hirao, H. S. Soo, Inorg. Chem. Front. 2016, 3, 651–662.
37] Y. Y. Ng, L. J. Tan, S. M. Ng, Y. T. Chai, R. Ganguly, Y. Du, E. K. L. Yeow, H. Sen
Soo, ACS Catal. 2018, 8, 11277–11286.
38] L. Wang, X. Wang, J. Cui, W. Ren, N. Meng, J. Wang, X. Qian, Tetrahedron:
Asymmetry 2010, 21, 825–830.
[39] Y. Xiao, X. Qian, Tetrahedron Lett. 2003, 44, 2087–2091.
[40] H. A. Jenkins, C. L. Dumaresque, D. Vidovic, J. A. C. Clyburne, Can. J. Chem. 2002,
8
0, 1398–1403.
[
41] U. El-Ayaan, F. Murata, S. El-Derby, Y. Fukuda, J. Mol. Struct. 2004, 692, 209–216.
42] M. Gasperini, F. Ragaini, E. Gazzola, A. Caselli, P. Macchi, Dalton Trans. 2004,
[
3
376–3382.
[43] J. A. Moore, K. Vasudevan, N. J. Hill, G. Reeske, A. H. Cowley, Chem. Comm. 2006,
2
913–2915.
[44] U. El-Ayaan, A. Paulovicova, Y. Fukuda, J. Mol. Struct. 2003, 645, 205–212.
[45] D. N. Coventry, A. S. Batsanov, A. E. Goeta, J. A. K. Howard, T. B. Marder,
Polyhedron 2004, 23, 2789–2795.
[46] L. Li, C. S. B. Gomes, P. T. Gomes, M. T. Duarte, Z. Fan, Dalton Trans. 2011, 40,
3
365–3380.
[47] H. D. De Ahna, H. D. Hardt, Z. Anorg. Allg. Chem. 1972, 387, 61–71.
28
This article is protected by copyright. All rights reserved.

European Journal of Inorganic Chemistry
10.1002/ejic.202000423
[48] J. K. Cheng, Y. G. Yao, J. Zhang, Z. J. Li, Z. W. Cai, X. Y. Zhang, Z. N. Chen, Y. B.
Chen, Y. Kang, Y. Y. Qin, et al., J. Am. Chem. Soc. 2004, 126, 7796–7797.
[49] P. C. Healy, C. Pakawatchai, A. H. White, J. Chem. Soc. Dalton Trans. 1985, 2531–
2
539.
[50] C. Näther, I. Jeß, N. Lehnert, D. Hinz-Hübner, Solid State Sci. 2003, 5, 1343–1357.
[51] M. J. Frisch, G. W. Trucks, H. B. Schlegel, G. E. Scuseria, M. A. Robb, J. R.
Cheeseman, G. Scalmani, V. Barone, B. Mennucci, G. A. Petersson, et al., Gaussian16
(Revision C.01) 2016.
[52] C. R. Groom, I. J. Bruno, M. P. Lightfoot, S. C. Ward, Acta Crystallogr. Sect. B Struct.
Sci. Cryst. Eng. Mater. 2016, 72, 171–179.
[
[
[
[
53] L. J. Farrugia, J. Appl. Crystallogr. 2012, 45, 849–854.
54] A. L. Spek, Acta Crystallogr. Sect. C Struct. Chem. 2015, 71, 9–18.
55] L. J. Farrugia, J. Appl. Crystallogr. 1997, 30, 565.
56] C. F. Macrae, P. R. Edgington, P. McCabe, E. Pidcock, G. P. Shields, R. Taylor, M.
Towler, J. Van De Streek, J. Appl. Crystallogr. 2006, 39, 453–457.
[
[
[
57] L. E. Roy, P. J. Hay, R. L. Martin, J. Chem. Theory Comput. 2008, 4, 1029–1031.
58] D. Feller, J. Comput. Chem. 1996, 17, 1571–1586.
59] K. L. Schuchardt, B. T. Didier, T. Elsethagen, L. Sun, V. Gurumoorthi, J. Chase, J. Li,
T. L. Windus, J. Chem. Inf. Model. 2007, 47, 1045–1052.
[
[
[
[
[
[
[
60] C. Adamo, V. Barone, J. Chem. Phys. 1999, 110, 6158–6170.
61] S. Grimme, J. Comput. Chem. 2004, 25, 1463–1473.
62] A. V. Marenich, C. J. Cramer, D. G. Truhlar, J. Phys. Chem. B 2009, 113, 6378–6396.
63] A. E. Reed, R. B. Weinstock, F. Weinhold, J. Chem. Phys. 1985, 83, 735–746.
64] J. P. Foster, F. Weinhold, J. Am. Chem. Soc. 1980, 102, 7211–7218.
65] A. E. Reed, L. A. Curtiss, F. Weinhold, Chem. Rev. 1988, 88, 899–926.
66] F. Weinhold, J. E. Carpenter, in The Structure of Small Molecules and Ions, (Eds.: R.
Naaman, Z. Vager), Plenum, 1988, pp. 227–236.
29
This article is protected by copyright. All rights reserved.