Novel Double Layer Salts of Copper(I) Bromide with N-Substituted Ethylenediammonium Cations

Article abstract of DOI:10.1021/ic030260s

The structures of three hybrid organic/inorganic halometalate salts are reported, and the layer structures developed are contrasted. Crystal structures of the isostructural N-methylethylenediammonium (MEDA²⁺) and N-ethylethylenediammonium (EEDA²⁺) salts of copper(I) bromide are both triclinic, space group P1, with lattice constants a = 6.284(7), b = 7.842(6), and c = 12.03(1) A, α = 84.84(3), β = 83.08(2), and γ = 88.00(3)°, and V = 586(1) A³ with Z = 2 for (MEDA)Cu₂Br₄ while (EEDA)Cu₂Br₄ has lattice constants a = 6.27(2), b = 7.78(2), and c = 13.12(3) A, α = 84.69(4), β = 78.18(3), and γ = 88.17(7)°, and V = 623(3) A³ with Z = 2. The dominant inorganic feature in both salts is anionic (CuBr₂)_n^n- chains of edge-shared CuBr₄ tetrahedra. The diammonium cations hydrogen bond these chains together into a unique double layer structure. For comparison purposes, the crystal structure of (CHA)PbBr₃ (CHA⁺ = cyclohexylammonium) is reported (monoclinic, space group P2₁/n, a = 8.088(2) A, b = 7.912(2) A, and c = 19.572(4) A, β = 96.98(4)°, and V = 1243.2(4) A³ with Z = 4). This contains (PbBr₃)_n^n- halometalate chains, this time of face-shared PbBr₆ octahedra. However, here the organic cations tie the chains together into the more common single layer structure.

Full text of DOI:10.1021/ic030260s

Inorg. Chem. 2004, 43, 954−957
Novel Double Layer Salts of Copper(I) Bromide with N-Substituted
Ethylenediammonium Cations
Roger D. Willett*
Department of Chemistry, Washington State UniVersity, Pullman, Washington 99164
Brendan Twamley
UniVersity Research Office, UniVersity of Idaho, Moscow, Idaho 83844
Received August 18, 2003
The structures of three hybrid organic/inorganic halometalate salts are reported, and the layer structures developed
2+
are contrasted. Crystal structures of the isostructural N-methylethylenediammonium (MEDA ) and N-ethylethyl-
2+
enediammonium (EEDA ) salts of copper(I) bromide are both triclinic, space group P1h, with lattice constants a )
6.284(7), b ) 7.842(6), and c ) 12.03(1) Å, R ) 84.84(3), â ) 83.08(2), and γ ) 88.00(3)°, and V ) 586(1)
3
Å with Z ) 2 for (MEDA)Cu2Br4 while (EEDA)Cu2Br4 has lattice constants a ) 6.27(2), b ) 7.78(2), and c )
3
13.12(3) Å, R ) 84.69(4), â ) 78.18(3), and γ ) 88.17(7)°, and V ) 623(3) Å with Z ) 2. The dominant
inorganic feature in both salts is anionic (CuBr2)nn- chains of edge-shared CuBr4 tetrahedra. The diammonium
cations hydrogen bond these chains together into a unique double layer structure. For comparison purposes, the
+
crystal structure of (CHA)PbBr3 (CHA ) cyclohexylammonium) is reported (monoclinic, space group P21/n, a )
3
8.088(2) Å, b ) 7.912(2) Å, and c ) 19.572(4) Å, â ) 96.98(4)°, and V ) 1243.2(4) Å with Z ) 4). This
contains (PbBr3)nn- halometalate chains, this time of face-shared PbBr6 octahedra. However, here the organic
cations tie the chains together into the more common single layer structure.
Chart 1
Introduction
The crystal chemistry of hybrid organic/inorganic halo-
metalates is an important area of investigation, since such
systems yield novel magnetic, conductive, thermo- and/or
piezochromic, NLO, etc., materials. Much of the focus in
this area has been on the intrinsic inorganic linkages that
produce the desired physical effects. Many of these materials
crystallize in well-defined low dimensional structures, e.g.,
layers or chains.1 However, understanding the final crystalline
structure of these materials depends as much, if not more,
on the understanding of the secondary interactions, such as
hydrogen bonding, π-π stacking, etc., present in the system.
Thus, compounds with halometalate chains counterbalanced
by non-hydrogen-bonding cations typically form hexagonal
or pseudohexagonal structures in which each chain is
surrounded by columns of six cations.2 In contrast, com-
pounds that contain primary or secondary ammonium cations
typically form layered structures in which the organic cations
hydrogen bond the chains together into sheets, effectively
forming bilayer structures, as illustrated diagrammatically
in Chart 1.3 In this type of structure, the ionic components
(2) (a) Morosin, B.; Graeber, E. J. Acta Crystallogr. 1967, 23, 766. (b)
Morosin, B. Acta Crystallogr. 1972, B28, 2303. (c) Stucky, G. D.
Acta Crystallogr. 1968, B24, 330. (d) Clay, R. M.; Murray-Rust, P.;
Murray-Rust, J. J. Chem. Soc., Dalton Trans. 1973, 595. (e) Fujii,
Y.; Wang, Z.; Willett, R. D.; Zhang, W.; Landee, C. P. Inorg. Chem.
1995, 34, 2870.
* To whom correspondence should be addressed. E-mail: rdw@
mail.wsu.edu.
(1) (a) Mitzi, D. B. Prog. Inorg. Chem. 1999, 48, 1. (b) Bloomquist, D.
R.; Willett, R. D. Coord. Chem. ReV. 1982, 47, 125. (c) Willett, R. D.
NATO ASI Ser., Ser. C 1985, No. 140, 389.
(3) (a) Groenendijk, H. A.; Blo¨te, H. W. J.; van Duyneveldt, A. J.; Gaura,
R. M.; Landee, C. P.; Willett, R. D. Phys. B+C (Amsterdam) 1981,
106B+C, 47. (b) Caputo, R.; Willett, R. D. Phys. ReV. B 1976, 13,
3956. (c) Roberts, S. A.; Bloomquist, D. R.; Willett, R. D.; Dodgen,
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954 Inorganic Chemistry, Vol. 43, No. 3, 2004
10.1021/ic030260s CCC: $27.50 © 2004 American Chemical Society
Published on Web 01/15/2004

Double Layer Salts of Copper(I) Bromide
are concentrated in the central portions of each layer and
the organic portions form hydrophilic layers that sandwich
the ionic portions.
One area of hybrid organic/inorganic chemistry that
continues to provide a fertile area for structural research is
that of the cuprous halide salts, due to the diverse coordina-
tion chemistry of the Cu(I) ion as well as the multiple
bridging capabilities of the halide ions.4 A wide variety of
oligomeric and polymeric species have been observed, based
primarily on corner or edge sharing of planar CuX3 or
tetrahedral CuX4 (regular or distorted) species.5-7 With a few
exceptions, extended structures observed to date have been
one-dimensional in nature,6 with only a couple of two-
dimensional examples reported.7 The most common one-
dimensional systems have contained single or double chains
of edge-shared tetrahedral species, although many other,
much more complex, structures have been observed. Most
of the initial studies in this area have focused on counter-
cations without hydrogen-bonding capabilities. It is clear that
when hydrogen bonding is present, new constraints are placed
on the system, and new and unusual structures can be
obtained. Examples of this include the two layer structures
recently obtained.7 It should be noted in passing that, in our
laboratory, these species have most frequently been obtained
serendipitously via autoreduction of Cu(II) halides in non-
aqueous solvents or at elevated temperatures.7b,8
Figure 1. Illustration of the (CuBr2)nn- chain in (EEDA)Cu2Br4. Thermal
ellipsoids are shown at 50%. Selected bond distances (Å) and angles (deg)
are as follows. (MEDA)Cu2Br4: Cu1-Br1, 2.445(2); Cu1-Br3, 2.469(2);
Cu1-Br4, 2.483(2); Cu1-Br2, 2.572(2); Cu2-Br3, 2.434(2); Cu2-Br2a,
2.500(2); Cu2-Br1a, 2.503(2); Cu2-Br, 2.524(2); Cu1-Br1-Cu2a,
80.18(9); Cu1-Br2-Cu2a, 77.86(9); Cu2-Br3-Cu1, 78.65(10); Cu2-
Br4-Cu1, 76.73(10)°. (EEDA)Cu2Br4: Cu1-Br1, 2.430(4); Cu1-Br3,
2.431(4); Cu1-Br4, 2.478(5); Cu1-Br2, 2.560(4); Cu2-Br3, 2.406(4);
Cu2-Br2a 2.485(4); Cu2-Br1a 2.494(4); Cu2-Br4, 2.499(4); Cu1-Br1-
Cu2a, 80.32(19); Cu1-Br2-Cu2a, 78.03(18); Cu2-Br3-Cu1, 79.77(19);
Cu2-Br4-Cu1, 77.12(19).
two hydrogen-bonding moieties in the organic cation leads
to a unique double layer structure. For comparison purposes,
we report on a lead(II) halide structure that contains the more
traditional single layer substructure.
Discussion
The structures of both (MEDA)Cu2Br4 and (EEDA)Cu2-
Br4 consist of tightly packed double layers of the diammo-
n-
nium cations and the (CuBr2)n chains. The cations in the
MEDA and EEDA structures (not illustrated) assume all-
n-
trans conformations. The (CuBr2)n chains in both com-
pounds consist of edge-shared tetrahedra, as illustrated in
Figure 1 for the (CuBr2)nn- chain in EEDA structure. These
tetrahedra show considerable variations, both in bond lengths
and angles. The range of bond lengths is somewhat greater
in the EEDA salt (2.406-2.560 Å) than in the MEDA
structure (2.434-2.572 Å). The edge-shared structure causes
the Cu-Br-Cu angles to be rather acute (76.7-80.3°) with
Cu-Cu distances lying between 3.1 and 3.2 Å. These type
of chains are not unique, with other systems containing
(CuBr2)nn- chains having been reported in several instances.9
Nevertheless, there are subtle differences between the chains
in the various compounds, probably attributable to the
hydrogen-bonding capabilities (or lack thereof) of the coun-
terions. Thus, in the paraquat salt, where no hydrogen
bonding is present, the bridging Cu-Br-Cu angles are
substantially smaller (67.9-72.5°), leading to shorter Cu-
Cu distances than observed in these two structures.6g In the
substituted pyrazinium salt, an alternation of Cu-Br-Cu
angles (and thus Cu-Cu) distances occurs.9b
In this article, we report on the structures of two such
copper(I) bromide compounds obtained in our synthetic
efforts in the preparation of copper(II) halide salts of
N-substituted ethylenediammonium cations. The presence of
(4) Subramanian, L.; Hoffmann, R. Inorg. Chem. 1992, 31, 1021.
(5) (a) Asplund, M.; Jagner, S.; Nilsson, M. Acta Chem. Scand. A 1983,
37, 57. (b) Healy, P. C.; Engelhardt, L. M.; Patrick, V. A.; White, A.
H. J. Chem. Soc., Dalton Trans. 1985, 2541. (c) Pallenberg, A. J.;
Koenig, K. S. Barnhart, D. M. Inorg. Chem. 1995, 34, 2833. (d) Levy,
A. T.; Olmstead, M. M.; Patten, T. E. Inorg. Chem. 2000, 39, 1628.
(e) Andersson, S.; Jagner, S. Acta Chem. Scand. A 1987, 41, 230. (f)
Asplund, M.; Jagner, S. Acta Chem. Scand. A 1984, 38, 135. (g)
Andersson, S.; Jagner, S. Acta Chem. Scand. A 1985, 39, 423. (h)
Andersson, S.; Jagner, S. Acta Crystallogr., Sect. C 1987, 31, 1089.
(i) Asplund, M.; Jagner, S. Acta Chem. Scand. A 1985, 39, 47. (j)
Hartl, H.; Bru¨dgam, I.; Hahdjour-Hassan-Abadi, F. Z. Naturforsch.
1985, 40b, 1032. (k) Hoyer, M.; Hartl, H. Z. Anorg. Allg. Chem. 1990,
587, 23. (l) Hu, G.; Holt, E. M. Acta Crystallogr. 1994, C50, 1578.
(m) Asplund, M.; Jagner, S. Acta Chem. Scand. A 1984, 38, 725. (n)
Andersson, S.; Jagner, S. Acta Chem. Scand. A 1986, 40, 210. (o)
Hartl, H.; Mahdjour-Hassan-Abadi, F. Angew. Chem., Int. Ed. Engl.
1984, 23, 378. (p) Andersson, S.; Jagner, S. Acta Chem. Scand. A
1989, 43, 39. (q) Hartl, H.; Mahdjour-Hassan-Abadi, F.; Fuchs, J.
Angew. Chem., Int. Ed. Engl. 1984, 23, 514.
(6) (a) Hu, G.; Holt, E. M. Acta Crystallogr. 1994, C50, 1578. (b)
Andersson, S.; Jagner, S. Acta Chem. Scand. A 1985, 39, 181. (c)
Andersson, S.; Jagner, S. Acta Chem. Scand. A 1986, 40, 177. (d)
Andersson, S.; Jagner, S.; Nilsson, M. Acta Chem. Scand. A 1985,
39, 447. (e) Asplund, M.; Jagner, S. Acta Chem. Scand. A 1984, 38,
129. (f) Batsanov, A. S.; Struchkov, Yu T.; Ukhin L. Yu; Dolgopolova,
N. A. Inorg. Chim. Acta 1982, 63, 17. (g) Scott, B. L.; Willett, R. D.;
Sacconi, A.; Sandrolini, F.; Ramakrishna, B. L. Inorg. Chim. Acta
1996, 248, 73. (h) Place, H.; Scott, B.; Willett, R. D. Inorg. Chim.
Acta 2001, 319, 403.
As illustrated in Figure 2 for (EEDA)Cu2Br4, the double
layers lie parallel to the ab planes in the crystal lattice. Each
half of a double layer consists of alternating columns of the
anionic chains and of the diammonium cations. In both
structures, the diammonium cations are in all-trans confor-
+
mations. The cations are oriented such that the -NH3
headgroups penetrate into the layers and the -R tails protrude
out from the surface of the layers. In this manner, each
diammonium cation hydrogen bonds to the bromide ions in
three separate (CuBr2)nn- chains, utilizing a “bidentate bite”
to hydrogen bond to two adjacent chains in half of the double
(7) (a) Place, H.; Scott, B.; Long, G.; Willett, R. D. Inorg. Chim. Acta
1998, 279, 1. (b) Willett, R. D. Inorg. Chem. 2001, 40, 966.
(8) (a) Willett, R. D. Inorg. Chem. 1987, 26, 3423. (b) Place, H.; Willett,
R. D. Acta Cryst. 1988, C43, 34. (c) Willett, R. D. Acta Crystallogr.
1988, C43, 450. (d) Willett, R. D.; West, D. X. Acta Crystallogr. 1987,
C42, 2300. (e) Willett, R. D.; Jeitler, J. R.; Twamley, B. Inorg. Chem.
2001, 40, 6502. (f) Haddad, S.; Willett, R. D.; Twamley, B. Acta
Crystallogr. 2000, C56, e437.
(9) (a) Sertuka, J.; Luque, A.; Lloret, F.; Roman, P. Polyhedron 1999,
17, 3875. (b) Scott, B.; Willett, R. D.; Porter, L.; Williams, J. Inorg.
Chem. 1992, 31, 2483.
Inorganic Chemistry, Vol. 43, No. 3, 2004 955

Willett and Twamley
Figure 5. Space-filling illustration of the single layer structure in (CHA)-
PbBr3.
Figure 2. Illustration of the double layer structure in (EEDA)Cu2Br4 as
viewed parallel to the a axis.
Figure 6. Space-filling illustration of the double layer structure in
(MEDA)Cu2Br4.
n-
Figure 3. Illustration of the (PbBr3)n chain in (CHA)PbBr3. Thermal
Chart 2
ellipsoids are shown at 50%. Selected bond distances (Å): Pb1-Br1,
3.068(1); Pb1-Br1A, 3.005(1); Pb1-Br2, 3.148(1); Pb1-Br2A, 2.936(1);
Pb1-Br3A, 3.313(1) Å.
To compare the layer structures in the two systems,
representations of the two types of layers are given in Charts
1 and 2 for the single and double layers respectively, while
space-filling representations are shown in Figures 5 and 6
for (CHA)PbBr3 and (MEDA)Cu2Br4, respectively. In the
Figure 4. Illustration of the layer structure in (CHA)PbBr3 as viewed
parallel to the b axis.
+
single layer structure, the -NH3 group only penetrates
partway into the halometalate layer. In contrast, the “biden-
tate” hydrogen-bonding bite of the diammonium cation
allows the cation to penetrate through the halometalate layer
so that the -NH3+ group is also able to hydrogen bond to a
second layer, forming the double layer.
layer with the -NH3+ headgroup spanning across to a chain
in the other half. In both compounds, the -NH3 groups
+
form two nearly linear N-H‚‚‚Br hydrogen bonds and one
+-
asymmetric bifurcated hydrogen bond, while each -NH2
group forms a single linear hydrogen bond and one asym-
metric bifurcated hydrogen bond.
Experimental Section
It is of interest to compare these two (REDA)Cu2Br4
structures with the structures attained by monoammonium
salts containing halometalate chains.3 For this purpose, we
examine the structure of (CHA)PbBr3, where CPA+ is the
cyclohexylammonium cation. This contains a prototypical
hybrid organoammonium halometalate chain structure ob-
served when the cation is a primary or secondary ammonium
The copper(I) compounds were obtained as colorless flat
crystalline platelets in the crystallization of solutions contain-
ing a 1:2 (REDA)Br2:CuBr2 ratio (R ) Me or Et) in ethanol/
hydrobromic acid mixtures evaporated on a hot plate with
temperatures held at 50-60 °C. The solutions were partially
covered during this process so that reduction of the volume
occurred slowly. Similarly, the lead(II) salt was crystallized
from a solution containing a 1.5:1 ratio of cyclohexyl-
ammonium bromide and lead(II) bromide dissolved in 1 M
HBr.
X-ray Studies. Crystals were attached to a glass fiber
using glue. Datasets were collected at 297(2) K using a
Bruker/Siemens SMART 1K instrument (Mo KR radiation,
λ ) 0.710 73 Å). Data were measured using ω scans of 0.3°/
n-
ion. Figure 3 shows a portion of the (PbBr3)n chains of
face-shared PbBr6 octahedra that are found in this structure,
while Figure 4 shows the hydrogen bonding with the cations
that ties the chains together into layers. The cyclohexyl ring
of the CPA+ cation is in a boat conformation. The organic
tails of the cations protrude well out from the ionic core of
the layer, and these interdigitate to form the final crystal
structure.
956 Inorganic Chemistry, Vol. 43, No. 3, 2004

Double Layer Salts of Copper(I) Bromide
Table 1. Crystal Data and Structure Refinement Parameters
Table 3. Atomic Coordinates (×104) and Equivalent Isotropic
Displacement Parameters (Å2 × 103) for (EEDA)Cu2Br4
empirical formula
fw
T (K)
C3H12Br4Cu2N2 C4H14Br4Cu2N2 C6H14Br3PbN
522.87
303(2)
0.710 73
triclinic
P1h
6.284(7)
7.842(7)
12.026(13)
84.84(3)
83.08(2)
88.00(3)
585.8(10)
2
536.89
303(2)
0.710 73
triclinic
P1h
6.268(15)
7.775(17)
13.12(3)
84.69(4)
78.18(3)
88.17(7)
623(3)
2
547.10
301(2)
0.710 73
monoclinic
P21/n
8.088(2)
7.912(2)
19.572(4)
90
96.98(4)
90
1243.2(4)
4
x
y
z
U(eq)a
Cu1
Cu2
Br1
Br2
Br3
Br4
N1
C1
N2
C2
C3
4652(1)
-303(1)
7086(1)
7418(1)
1667(1)
2727(1)
1390(9)
2664(11)
3213(8)
1817(10)
2584(12)
4146(14)
7668(1)
7447(1)
9944(1)
5210(1)
6813(1)
7128(1)
7182(1)
7304(1)
6708(1)
8568(1)
5653(1)
5617(4)
6337(5)
8106(4)
7404(5)
9177(5)
9809(6)
49(1)
47(1)
38(1)
35(1)
38(1)
35(1)
38(1)
34(2)
28(1)
30(1)
43(2)
65(2)
λ (Å)
cryst system
space group
a (Å)
b (Å)
c (Å)
R (deg)
â (deg)
γ (deg)
V (Å3)
8165(1)
12365(7)
13013(8)
12761(6)
12264(7)
11954(9)
12470(11)
Z
F
C4
calc (Mg/m3)
2.964
2.861
2.923
µ (mm-1
)
17.222
2004
16.193
2536
23.164
3431
Table 4. Atomic Coordinates (×104) and Equivalent Isotropic
indpndt reflcns
R(int)
Displacement Parameters (Å2 × 103) for (CPA)PbBr3
0.0059
0.0541
0.0584
atom
x
y
z
U(eq)a
T (max, min.)
0.7245, 0.1966 0.8548, 0.2468 0.249, 0.047
goodness-of-fit on F2 0.910
0.910
0.980
Pb1
Br1
Br2
Br3
C2
C3
C4
C5
C6
2530(1)
4998(1)
2641(1)
5157(1)
7302(9)
7842(12)
7175(14)
7603(13)
7023(16)
7747(13)
8053(8)
5112(1)
2407(1)
8051(1)
7097(1)
2893(8)
1097(9)
244(10)
1178(12)
2962(12)
3846(10)
3746(7)
2420(1)
2058(1)
1343(1)
3119(1)
3906(4)
3970(4)
4567(5)
5223(4)
5145(5)
4562(4)
3339(3)
38(1)
43(1)
43(1)
44(1)
41(2)
59(2)
74(3)
74(3)
85(3)
64(3)
49(2)
R1
wR2
0.0420
0.0644
0.0371
0.0762
0.0408
0.0697
Table 2. Atomic Coordinates (×104) and Equivalent Isotropic
Displacement Parameters (Å2 × 103) for (MEDA)Cu2Br4
atom
x
y
z
U(eq)a
Cu1
Cu2
Br1
Br2
Br3
Br4
N1
N2
C1
C2
C3
4997(2)
54(2)
7674(1)
7450(1)
9931(1)
5212(1)
6783(1)
7310(1)
7379(1)
7545(1)
6871(1)
8893(1)
5716(1)
5665(6)
8415(5)
6450(6)
7631(7)
9576(7)
51(1)
48(1)
38(1)
36(1)
39(1)
36(1)
39(2)
36(2)
33(2)
34(2)
50(2)
C7
N1
7452(1)
7692(1)
2275(1)
2816(1)
1521(9)
3653(9)
2913(11)
2191(11)
3085(14)
package.13 No decomposition was observed during data
collection. Structure refinements were straightforward in all
three cases, and no disorder was observed. Data collection
parameters are given in Table 1, and positional parameters
are given in Tables 2-4. Further details are provided in the
Supporting Information.
8183(1)
12379(8)
12746(8)
13009(9)
12240(9)
11943(11)
a U(eq) is defined as one-third of the trace of the orthogonalized Uij
tensor.
Acknowledgment. The assistance of Mr. Jason Jellison
and Ms. Kathleen Reynolds in the syntheses is gratefully
acknowledged. This work was supported in part by American
Chemical Society PRF Grant 34779-AC5. The Bruker
(Siemens) SMART CCD diffraction facility was established
at the University of Idaho with the assistance of the NSF-
EPSCoR program and the M. J. Murdock Charitable Trust,
Vancouver, WA.
frame for 30 s, and a half sphere of data was collected. The
first 50 frames were recollected at the end of data collection
to monitor for decay. Cell parameters were retrieved using
SMART10 software and refined using SAINTPlus11 on all
observed reflections. Data reduction and correction for Lp
and decay were performed using the SAINTPlus software.
Absorption corrections were applied using SADABS.12 The
structures were solved by direct methods and refined by least-
squares methods on F2 using the SHELXTL program
Supporting Information Available: Crystallographic data in
CIF format. This material is available free of charge via the Internet
at http://pubs.acs.org.
(10) SMART: Bruker Molecular Analysis Research Tool, V.5.059; Bruker
AXS: Madison, WI, 1997-98.
(11) SAINTPlus: Data Reduction and Correction Program; Bruker AXS:
Madison, WI, 1999.
IC030260S
(12) Sheldrick, G. M. SADABS V.2.01: an empirical absorption correction
(13) Sheldrick, G. M. SHELXTL: Version 5.10, Structure Determination
Software Suite; Bruker AXS Inc.: Madison, WI, 1998.
program; Bruker AXS Inc.: Madison, WI, 1999.
Inorganic Chemistry, Vol. 43, No. 3, 2004 957