603
Acta Chim. Slov. 2024, 71, 603–608
Goreshnik and Panteleieva:   Investigation of the Composition Space Diagram CuCl–   ...
DOI: 10.17344/acsi.2024.9005
Scientific paper
Investigation of the Composition Space Diagram  
CuCl–Allylamine–dabco. A New Mixed Ligand Compound 
of (H
2
dabco)
2
[Cu
4
Cl
9
(allNH
3
)] Composition with Unique 
Cu
4
Cl
9
5–
 Cupro(I)-chloride Fragment
Evgeny Goreshnik
1
  , Olha Panteleieva
1,2
  
 
1
 Department of Inorganic Chemistry and Technology, Jožef Stefan Institute, Jamova 39, 1000 Ljubljana, Slovenia.
2 
Department of Chemistry and Chemical Engineering, University of Technology, av. Dmytra Yavornitskogo 19, 49005 Dnipro, 
Ukraine.
* Corresponding author: E-mail: evgeny.goreshnik@ijs.si
Received: 09-30-2024
Abstract
The ternary system CuCl–allylamine–dabco (dabco = 1,4-diazabicyclo[2.2.2]octane) with an excess of HCl was explored. 
Starting from an ethanol solution of CuCl
2
·2H
2
O, allylamine and dabco titrated with HCl, copper(I) salts were generated 
by means of electrochemical alternating current synthesis. In addition to the already known (H
2
dabco)[CuCl
3
], two 
modifications of the (allNH
3
)
2
[Cu
2
Cl
4
] compound and some Cu(II) by-products, a new mixed ligand compound of the 
composition (H
2
dabco)
2
[Cu
4
Cl
9
(allNH
3
)] was synthesized and structurally investigated. Its structure contains unique 
Cu
4
Cl
9
5–
 inorganic moiety bound via a η
2
-interaction allylammonium moiety and discrete (H
2
dabco)
2+
 cations. The 
structure is stabilized by the system of N–H···Cl hydrogen bonds.
Keywords: copper, chloride, 1,4-diazabicyclo[2.2.2]octane, coordination polymers
1. Introduction
Copper(I) chloride coordination compounds amaze 
with a variety of inorganic fragments. Starting from the 
simplest neutral CuCl monomers,
1,2
 discrete Cu
2
Cl
2
 di-
mers,
3
 bicyclic Cu
3
Cl
3
 trimers,
4
 tetramers of cubane
5
 and 
stepped cubane types,
6
 prismane-like hexamers
7
 and many 
others were observed. An even broader spectrum of ani-
onic moieties from CuCl
2
–
 dimers to infinite chains, layers 
and 3D frameworks were reported.
8,9
 A comprehensive 
review of the structural diversity of copper(I) halide aggre-
gates was published nearly a decade ago.
10
The carbon-carbon double bond successfully com-
petes with the halide ions for the place in the coordination 
sphere of the Cu(I) ion. On the other hand, protonated or-
ganic amines form N–H···Hal hydrogen bonds with halide 
ions, thereby limiting the bridging ability of the halide ions 
to the metal centers. We hypothesized that the use of bulky 
organic amines and amino derivatives of unsaturated hy-
drocarbons in acidic media could promote the formation 
of previously unknown copper-halide aggregates. In order 
to perform a complete study of such a system, we decided 
to investigate the entire CuCl–allylamine–dabco ternary 
system in acidic (HCl) medium using the Gibbs diagram.
The electrochemical technique has proven to be an 
effective tool for the synthesis of copper(I) derivatives.
11,12
 
The absence of by-products and the possibility to grow 
high-quality single crystals in one step are the main advan-
tages of such an approach.
It is worth noting that the CCDC contains only 26 
entries for 20 compounds containing copper ions and 
diprotonated H
2
dabco cations.
13
 Moreover, only six of the 
above compounds appear to be polymeric, and also six 
contain monovalent copper ions. On the other hand, only 
three cupro(I)chloride derivatives of allyl ammonium 
were found in the CCDC, four other entries contain 
mixed-anion derivatives.
The phase diagram of CuCl–allylamine–dabco in 
acidic media was investigated by means of electrochemical 
synthesis and by varying the ratios of the starting reagents. 

604
Acta Chim. Slov. 2024, 71, 603–608
Goreshnik and Panteleieva:   Investigation of the Composition Space Diagram CuCl–   ...
A new (H
2
dabco)
2
[Cu
4
Cl
9
(allNH
3
)] salt with a unique  
Cu
4
Cl
9
5–
 anion was found and characterized by sin-
gle-crystal X-ray diffraction and Raman spectroscopy. The 
results are presented in this article.
2. Experimental Section
All chemicals were of commercial origin: CuCl
2 
· 2H
2
O from Zorka Šabac, p.a., hydrochloric acid from 
Sigma-Aldrich, ACS reagent, 37%, allylamine from Alfa 
Aesar, 98+%, 1,4-diazabicyclo[2.2.2]octane (Alfa Aesar, 
98%); ethanol (Carlo Erba, p.a) were used without further 
purification.
2. 1. Syntheses
All experiments were carried out by electrochemical 
alternating current synthesis in ethanol. 5 mL of ethanol 
solution containing calculated amounts of CuCl
2
·2H
2
O, 
dabco, allylamine and 1 mL of 37% aqueous HCl were 
placed in a small test tube. The technical details of the syn-
thetic procedures were described earlier.
10,11
 An alternat-
ing current of 50 Hz and a voltage of 0.4 V was used. In 
case of discoloration of the solution and absence of crys-
tals, the test tube was cooled in the refrigerator or the syn-
thesis was repeated with larger amount of reagents.
2. 2. X-ray Structure Determination
All crystals obtained were examined using the sin-
gle-crystal X-ray technique. Single-crystal X-ray data for 
compound 1 were collected on a Gemini A diffractometer 
with an Atlas CCD detector, using graphite monochro-
mated Mo-Kα radiation. The data were processed using 
the CrysAlisPro program package.
14
 An analytical absorp-
tion correction was applied to the data set. The structure 
was solved using the dual-space algorithm of the program 
SHELXT
15
 and the structure refinement was performed 
using the software SHELXL-2014,
16
 both of which are im-
plemented in the crystallographic software Olex.
17
 Hydro-
gen atoms bound to carbons were set to calculated posi-
tions (AFIX commands), their thermal parameters were 
set to 1.2U
eq
 of the corresponding C atoms. The positions 
of the hydrogen atoms bound to the nitrogen atoms were 
found on difference Fourier maps and refined freely. In 
some cases, the N–H bond lengths were constrained using 
the DFIX command. A summary of the crystallograph-
ic data and the structure refinement is given in Table 1. 
CCDC 2387343 (1) contains the supplementary crystal-
lographic data for this paper. These data can be obtained 
free of charge from the Cambridge Crystallographic Data 
Centre via www.ccdc.cam.ac.uk/data_request/cif.
3. Results and Discussion
3. 1.  Influence of Synthetic Conditions on  
a Formation of Definite Products
The preparation of the starting mixture CuCl
2 
·  
2H
2
O–allylamine–dabco–HCl usually resulted in a multi-
colored – from yellow to brown – solid.
Two series of experiments were carried out in 
the three-component system CuCl
2 
· 2H
2
O– ally-
lamine–dabco (Fig. 1) in an acidic (HCl) environ-
ment. First, five points were selected on a ternary di-
agram and electrochemical syntheses were carried 
out. As expected, in dabco-reach region of ternary di-
agram the formation of H
2
dabco salt, namely (H
2
dab-
co)[CuCl
3
] was observed.
18
 In contrast, an excess 
of allylamine led to the formation of the (allNH
3
)
2 
[Cu
2
Cl
4
] salt.
19
 The most remarkable result was achieved 
in a synthesis with 40 mol. % CuCl
2
, 15 mol. % allylamine 
and 45 mol. % dabco, in which the formation of earli-
er unknown yellow-orange crystals of the composition  
(H
2
dabco)
2
[Cu
4
Cl
9
(allNH
3
)] was observed. Using the 
ratio of 40 mol. % CuCl
2
, 45 mol. % allylamine and 
15 mol. % dabco resulted in a mixture of (H
2
dabco)
2  
[Cu
4
Cl
9
(allNH
3
)] and (allNH
3
)
2
[Cu
2
Cl
4
] crystals. Fur-
ther experiments were performed in steps of 10% for 
each component. In this way, 36 points of definite com-
position were determined on a Gibbs triangle, and the 
corresponding ratios of starting materials were used 
for subsequent syntheses (Table S1). No other mixed 
Table 1. Crystallographic data, details of data collection and struc-
ture refinement parameters
 1
Compound (H
2
dabco)
2
[Cu
4
Cl
9
(allNH
3
)]
Formula C
15
H
36
Cl
9
Cu
4
N
5
M [g mol
−1
] 859.70
T [K] 150
Crystal system Triclinic
Space group P
ˉ
1
a [Å] 9.3468(4)
b [Å] 12.1301(6)
c [Å] 13.6361(5)
α [°] 112.695(4)
β [°] 91.951(3)
γ [°] 98.337(4)
V [Å
3
] 1404.37(11)
Z 2
F(000) 860
ρ
calcd
 [g cm
−3
] 2.033
Radiation, λ [Å] MoKα, 0.71073
μ [mm
−1
] 3.862
Goodness–of–fit on F
2 
1.072
Final R
1
 [I > 2σ(I)] 0.0296
Final R
1
 (all data) 0.0375
wR
2
 [I > 2σ(I)] 0.0663
wR
2
 (all data) 0.0720
Largest diff. peak and hole (e Å
–3
) 0.603, –0.635

605
Acta Chim. Slov. 2024, 71, 603–608
Goreshnik and Panteleieva:   Investigation of the Composition Space Diagram CuCl–   ...
cation salts were found during this detailed investi-
gation. Crystals of another modification of the com-
pound (allNH
3
)
2
[Cu
2
Cl
4
]
20
 and undesired (H
2
dabco)
2 
[Cu
II
Cl
3
(H
2
O)
2
]Cl
3 
· H
2
O
21
 (copper(II) salt as a result of 
incomplete electrochemical reduction) were observed.
3. 2. Crystal Structure of 1
The compound (H
2
dabco)
2
[Cu
4
Cl
9
(allNH
3
)] (1) 
crystallizes in the triclinic space group P
ˉ
1. Three metal 
cations and three chloride anions form a six-membered 
ring with Cu···Cu distances of 2.9252(12)–2.9999(12) Å 
(Fig. 2). Each pair of copper ions is bound by a μ
2
 chlo-
ride bridge with Cu–μ
2
Cl distances of 2.302(2)–2.352(1) 
Å. The copper triangle is capped by a μ
3
Cl6 center with 
significantly elongated Cu–Cl bonds with lengths of 
2.632(2)–2.705(2) Å. The coordination of each copper 
center is completed to tetrahedral by another chloride ion: 
terminal chloride anions for Cu3 and Cu4 and a μ
2
 bridge 
for Cu2. In the last case, the Cl2 bridge connects a Cu
3
Cl
7
 
core with an (allNH
3
)CuCl
2
 fragment involving a π-coor-
dinated Cu1 atom.
All three Cu ions in the Cu
3
Cl
7
 core are tetra-co-
ordinated. τ
4 
parameter values of 0.81, 0.89 and 0.86 for 
Figure 1. Ternary diagram of CuCl–allylammonium–H
2
dabco. Square: region of formation (allNH
3
)
2
[Cu
2
Cl
4
], circle – (H
2
dabco)
2
[Cu
4
Cl
9
(all-
NH
3
)],
 
cross – (H
2
dabco)
2
[Cu
4
Cl
9
(allNH
3
)] and (allNH
3
)
2
[Cu
2
Cl
4
], star and triangles – (H
2
dabco)[CuCl
3
].
Figure 2. Asymmetric unit of structure 1. Thermal ellipoids are 
drawn with 50% probability.  Al

606
Acta Chim. Slov. 2024, 71, 603–608
Goreshnik and Panteleieva:   Investigation of the Composition Space Diagram CuCl–   ...
Cu2, Cu3 and Cu4 respectively indicate a slightly distorted 
tetrahedral surrounding in all cases (the value 1.00 corre-
sponds to a perfect tetrahedral geometry, the value 0 to a 
perfect square planar geometry).
22
The Dewar-Chatt-Duncanson concept states that 
an effective Cu–(C=C) interaction leads to a transfor-
mation of the Cu coordination polyhedron from tet-
rahedral to trigonal pyramidal, with the olefin group 
Figure 3. Hydrogen bonds around each organic cation in structure 1.
Figure 4. Hydrogen bonds around cupro(I) chloride fragment in structure 1.

607
Acta Chim. Slov. 2024, 71, 603–608
Goreshnik and Panteleieva:   Investigation of the Composition Space Diagram CuCl–   ...
located in the basal plane, and to an increase in the dis-
tance between the metal ion and the axial ligand.
23,24
 
π-coordinated Cu1 center possess well-pronounced 
trigonal-pyramidal surrounding. The Cu1 ion in struc-
ture 1 lies practically in the basal plane (formed by Cl1, 
Cl2, C2 and C3 atoms) of the coordination polyhedron 
(distance metal–plane is 0.4 Å), the distance to the Cl3 
atom in the apical position is much longer than the 
length of the Cu1–Cl1 and Cu1–Cl2 bonds (2.4906(6) 
Å versus 2.2905(7) and 2.3204(7) Å respectively). The 
C2=C3 bond coordinated to the metal center is tilted 
by about 2 degrees with respect to the basal plane of the 
coordination polyhedron. Despite this proper orienta-
tion and the relatively short distance Cu–m (m is the 
center of the C2=C3 double bond) of 1.97 Å, the coor-
dinated C=C-bond is very weakly elongated to 1.344(4) 
Å. For comparison, the mean length of the coordinated 
to copper(I) ion C=C bond of 1.360(17) Å was deter-
mined with the Mercury software
25
 based on 44 records 
in CCDC
13
 containing a C=C + 3Cl environment of 
the Cu
+
 center (four records with a C=C bond length 
shorter than 1.3 Å or longer than 1.4 Å were excluded 
as equivocal from the analysis).
Protonated amino-groups of allylammonium and 
H
2
dabco cations form a complex system of N–H···Cl hy-
drogen bonds (Figs. 3 and 4). Two H-atoms of the ally-
lammonium group are bound to two different Cu
4
Cl
9 
fragments, and the third H-atom forms an intramolecular 
N1–H1c···Cl3 bond. Both N4H4 and N5H5 groups from 
one H
2
dabco
2+
 cation form effective H-bonds and connect 
two chlorocuprate anions. Contrary, the N2H2 and N3H3 
groups belong to another H
2
dabco unit and form bifur-
cated hydrogen bonds. This organic cation acts also as a 
bridge between two Cu
4
Cl
9 
units.
3. 3. Raman Spectrum
A group of peaks observed in the Raman spectrum 
of 1 partially match those in the spectra of pure ally-
lamine
26
 and dabco
27
 (Table 2).
Peaks arising from allylamine were found in 1 at 
1207 cm
−1
 (1209, –CH
2
 twisting), 1253 cm
−1
 (1283, =CH 
bending), 1399 cm
−1
 (1423) =CH
2
 deformation (the values 
in parentheses correspond to the frequencies found in the 
spectrum of solid allylamine). υ
s
 and υ
as
 modes for =CH
2
 
were found in I in the range between 2909 and 3090 cm
−1
An important feature of the Raman spectra of 1 is 
that the υ
s 
mode of the C=C-bond is strongly shifted to 
1565 cm
−1
 compared to 1636 cm
−1 
in solid allylamine due 
to the Cu–(C=C) interaction. A similar shift to lower wav-
enumbers was observed in a number of copper(I) p-com-
plexes.
28
The broadened peak centered at 246 cm
−1
 in spec-
trum 1 could be assigned to the υ
s
 mode of Cu–Cl bonds 
in (Cu
4
Cl
9
)
5–
 
anion. The corresponding peak was observed 
at 255 cm
−1 
in [H
2
dabco][CuCl
3
].
4. Concusions
An idea for the synthesis of compound(s) with 
mixed organic cations and cupro(I) chloride anions was 
realized by the complete investigation of the CuCl–ally-
lamine–dabco system in acidic media. A new compound 
of (H
2
dabco)
2
[Cu
4
Cl
9
(allNH
3
)]
 
composition was obtained 
and characterized by single crystal X-ray diffraction and 
Raman spectroscopy. This new compound contains earlier 
unknown Cu
4
Cl
9
5–
 cupro(I)-chloride fragment. The for-
mation of this compound was observed in a rather narrow 
region of the ternary diagram.
Supplementary Materials
Detailed list of all explored reagents compositions, 
expanded composition diagram and Raman spectrum of 
compound 1 are placed as Supplementary Materials.
Acknowledgements
Authors gratefully acknowledge the Slovenian Re-
search Agency (ARRS) for the financial support of the 
present study within the research program P1-0045 Inor-
ganic Chemistry and Technology. O.P. acknowledges the 
financial support from Erasmus+ program.
Table 2. Originated from the organic part peaks observed in Raman spectra of 1, pure dabco and (H
2
dabco)[CuCl
3
] salt. 
 in-δ out-ν
a
 in-ν
s
 in-ν
s
 ν
a 
ν
s 
in-ν
a
 in-γ
s
 (C–N–C) (NC
3
) (NC
3
) (NC
3
), (C–C), (C–C), (NC
3
), (CH
2
)
    ν
s 
in-γ
t 
in-ν
s 
ν
a
    (C–C) (CH
2
) (NC
3
), in-δ
s 
(C–C),
      
(NC
3
) in-γ
t
       (CH
2
) 
dabco 430 579 598 807 894 972 1061 1459
(H
2
dabco)[CuCl
3
] 406 560 601 803 893 977 1056 1461
1 404 557 606 804 887 979 1056 1456

608
Acta Chim. Slov. 2024, 71, 603–608
Goreshnik and Panteleieva:   Investigation of the Composition Space Diagram CuCl–   ...
5. References
1.  A. Vakulka, E. Goreshnik, J. Coord. Chem. 2018, 71, 2426–
2440.   DOI:10.1080/00958972.2018.1481210
2.  D. Rasale, K. Patil, B. Sauter, S. Geigle, S. Zhanybekova, D. 
Gillingham, Chem. Comm. 2018, 54, 9174–9177.
 DOI:10.1039/C8CC04476G
3.  A. Szadkowska, R. Pawłowski, E. Zaorska, S. Staszko, D. Trzy-
biński, K. Woźniak, Appl. Organomet. Chem. 2019, 33 , e4983.   
DOI:10.1002/aoc.4983
4.  L. R. Collins, J. P. Lowe, M. F. Mahon, R. C. Poulten, M. K. 
Whittlesey, Inorg. Chem. 2014, 53, 2699–2707.
 DOI:10.1021/ic4031014
5.  A. N. Paesch, A. K. Kreyenschmidt; R. Herbst-Irmer, D. Stal-
ke, Inorg. Chem. 2019, 58, 7000–7009.
 DOI:10.1021/acs.inorgchem.9b00629
6.  M. Munakata, T. Kuroda-Sowa, M. Maekawa, A. Honda, 
S. Kitagawa, J. Chem. Soc. Dalton Trans. 1994, 2771–2775, 
DOI:10.1039/DT9940002771
7.  E. A. Goreshnik, L. Z. Ciunik, Yu. K. Gorelenko, M. G. 
Mys’kiv, Z. Anorg. Allg. Chem. 2004, 630, 2743–2748.
 DOI:10.1002/zaac.200400218
8.  Y u. Slyvka, E. Goreshnik, O. Pavlyuk, M. Mys’kiv, Cent. Eur. J. 
Chem. 2013, 11, 1875–1901.
 DOI:10.2478/s11532-013-0323-3
9.  J. R. D. DeBord, Y . Lu, C. J. W arren, R. C. Haushalter, J. Zubie-
ta, Chem. Comm. 1997, 1365–1366.   DOI:10.1039/a702053h
10.  R. Peng, M Li, D. Li. Coord. Chem. Rev. 2010, 254, 1–18.
 DOI:10.1016/j.ccr.2009.10.003
11.  Yu.I. Slyvka, O.V. Pavlyuk, M. Yu. Luk’yanov, M.G. Mys’kiv 
Ukraine Patent UA 118819, 2017, Bull. No. 16, August 28.
12.  Z. N Gafurov, A. O. Kantyukov, A. A. Kagilev, O. G. Sinyash-
in, D.G. Y akhvarov, Coord. Chem. Rev. 2021, 442, 213986.
 DOI:10.1016/j.ccr.2021.213986
13.  C. R. Groom, I. J. Bruno, M. P . Lightfoot, S. C. W ard, Acta Cryst. 
2016, B72, 171–179.   DOI:10.1107/S2052520616003954
14.  CrysAlisPro, Agilent Technologies, Version 1.171.37.31 (re-
lease 14-01–2014 CrysAlis171 .NET).
15.  G. M. Sheldrick, Acta Cryst. 2015, A71, 3–8.
 DOI:10.1107/S2053273314026370
16.  G. M. Sheldrick, Acta Cryst. 2015, C71, 3–8.
 DOI:10.1107/S2053229614024218
17.  O. V . Dolomanov, L. J. Bourhis, R. J. Gildea, J. A. K. Howard, 
H. Puschmann, J. Appl. Cryst. 2009, 42, 339–341.
 DOI:10.1107/S0021889808042726
18.  E. G o r es hni k, J. Coord. Chem. 2017, 5, 859–870.
 DOI:10.1080/00958972.2017.1285400
19.  M. G.Mys'kiv, Kh. Fayad, V. E. Zavodnik. Metalloorg. Khim. 
(Russ.) (Organomet. Chem. (USSR)) 1991, 4, 415–419.
20.  V. V. Olijnik, M. G. Mys'kiv. Koord. Khim. (Russ.)(Coord. 
Chem.) 1996, 22, 876–879.
21.  M. Wei, R. D. Willett, Inorg. Chem. 1996, 35, 6381–6385.
 DOI:10.1021/ic9602862
22.  L. Yang, D. R. Powell; R. P . Houser, Dalton Trans. 2007, 955–
964.   DOI:10.1039/B617136B
23.  M. J. S. Dewar. Bull. Soc. Chim. Fr. 1951, 18, C71.
24.  J. Chatt, L. A. Duncanson. J. Chem. Soc. 1953, 2939–2947.
 DOI:10.1039/jr9530002939
25.  C. F. Macrae, I. Sovago, S. J. Cottrell, P. T. A. Galek, P. Mc-
Cabe, E. Pidcock, M. Platings, G. P . Shields, J. S. Stevens, M. 
Towler, P . A. Wood, J. Appl. Cryst. 2020, 53, 226–235.
 DOI:10.1107/S1600576719014092
26.  J. R. Durig, J. F. Sullivan, C. M. Whang, Spectrochim. Acta, 
1985, 41, 129–154.   DOI:10.1016/0584-8539(85)80092-1
27.  V . I. Kovalenko, A. A. Akhmadiyarov, A. E. Vandyukov, A. R. 
Khamatgalimov, J. Mol. Struct. 2012, 1028, 134–140.
 DOI:10.1016/j.molstruc.2012.06.045
28.  H. Masuda, M. Munakata, S. Kitagawa, J. Organomet. Chem. 
1990, 391, 131–137.   DOI:10.1016/0022-328X(90)80162-S
Except when otherwise noted, articles in this journal are published under the terms and conditions of the  
Creative Commons Attribution 4.0 International License
Povzetek
Raziskovali smo ternarni sistem CuCl–alilamin–dabco (dabco = 1,4-diazabiciklo[2.2.2]oktan) s presežkom HCl. Iz 
etanolne raztopine CuCl
2
·2H
2
O, alilamina in dabco titriranega s HCl, so bile s pomočjo elektrokemijske sinteze z upo-
rabo izmeničnega toka generirane bakrove(I) soli. Poleg že znanih (H
2
dabco)[CuCl
3
], dveh modifikacij spojine (allN-
H
3
)
2
[Cu
2
Cl
4
] in nekaterih Cu(II) stranskih produktov, smo sintetizirali novo spojino (H
2
dabco)
2
[Cu
4
Cl
9
(allNH
3
)] in jo 
strukturno analizirali. Njena struktura vsebuje prej neznan anorganski del Cu
4
Cl
9
5–
, ki je vezan preko η
2
-interakcije z 
alilamonijem, in diskretnega kationa (H
2
dabco)
2+
. Strukturo stabilizira sistem vodikovih vezi N–H···Cl.