The syntheses and structural characterizations of some monoaza- and diaza-crown ethers

Article abstract of DOI:10.1071/CH99103

Several aza-crown ethers have been synthesized and their structures determined by X-ray crystallography. In a modified synthesis of diaza-18-crown-6 we isolated two of the intermediates, viz. the NaI salt (1) of N,N′-dibenzyldiaza-18-crown-6 and the salt-free macrocycle (2), and determined their stuctures. In compound (1) a hydrated crown-encapsulated sodium cation was revealed with both benzyl groups folded down and away from the water molecule while in compound (2) a centrosymmetric crown with the benzyl groups splayed out from the ring was found. In addition, we have determined the X-ray crystal structures of monoaza-18-crown-6 and the hydrochloride salt of monoaza-15-crown-5. In the former, the crown resides on an inversion centre showing N/O disorder, and in the latter the protonated amine hydrogen bonds with the chloride anion. CSIRO 1999.

Full text of DOI:10.1071/CH99103

C S I R O P U B L I S H I N G
Australian Journal
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Volume 52, 1999
©
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Aust. J. Chem., 1999, 52, 1109–1114
The Syntheses and Structural Characterizations
of Some Monoaza- and Diaza-crown Ethers
A
A,B
Kym R. Fewings and Peter C. Junk
A
Department of Chemistry, James Cook University, Townsville, Qld. 4811.
Author to whom correspondence should be addressed.
B
Several aza-crown ethers have been synthesized and their structures determined by X-ray crystallography. In a
modified synthesis of diaza-18-crown-6 we isolated two of the intermediates, viz. the NaI salt (1) of N,NЈ-diben-
zyldiaza-18-crown-6 and the salt-free macrocycle (2), and determined their stuctures. In compound (1) a hydrated
crown-encapsulated sodium cation was revealed with both benzyl groups folded down and away from the water
molecule while in compound (2) a centrosymmetric crown with the benzyl groups splayed out from the ring was
found. In addition, we have determined the X-ray crystal structures of monoaza-18-crown-6 and the hydrochloride
salt of monoaza-15-crown-5. In the former, the crown resides on an inversion centre showing N/O disorder, and in
the latter the protonated amine hydrogen bonds with the chloride anion.
Introduction
N analyses were thwarted by the extremely hygroscopic nature of the
material.
The crown ethers have received a large amount of atten-
1
tion since their discovery by Pedersen. This chemistry has
N,NЈ-Dibenzyl-2,2Ј-(ethylenedioxy)bis(ethylamine)
predominantly been centred on the oxygen-containing
crowns while crowns with other heteroatoms such as nitro-
1,2-Bis(2-chloroethoxy)ethane (16.83 g, 90 mmol) was added to a
stirred solution of benzylamine (21.22 g, 198 mmol) in distilled MeCN
3
2
,3
(600 cm ) over Na CO (20.99 g, 198 mmol) under an argon atmo-
2
3
gen and sulfur have been studied to a much lesser extent
sphere. The mixture was stirred and heated at reflux for 4 days, after
which time the solid was removed by filtration and the solvent removed
on a rotary evaporator. The product was a yellow oil (29.6 g, 100%),
which formed colourless crystals upon standing and was used without
further purification.
(
this refers only to the crown ethers and does not include
macrocycles such as the solely nitrogen-containing cyclic
systems such as cyclam (1,4,8,11-tetraazacyclotetradecane),
triazacyclononane and the porphyrins). There have been
extensive reviews covering the synthesis of the aza-crown
(
N,NЈ-Dibenzyl-4,13-diaza-18-crown-6)sodium Iodide (1) and N,NЈ-
4
ethers and many synthetic approaches have been pursued.
As part of our studies of metal complexes of crown ethers,
Dibenzyl-4,13-diaza-18-crown-6 (2)
5
N,NЈ-Dibenzyl-2,2Ј-(ethylenedioxy)bis(ethylamine) (28.2 g, 86
we have turned our attention to the aza-crown ethers, and, to
our surprise, we find a paucity of X-ray crystal structures for
this family of macrocyclic ligands. Indeed, for N,NЈ-dibenz-
yldiaza-18-crown-6 only one such structure has been deter-
mmol), NaI (35.02 g, 233 mmol), 1,2-bis(2-chloroethoxy)ethane (19.83
g, 106 mmol), Na
2
CO
3
(45.3 g, 427 mmol) and distilled MeCN (1.7
3
3
dm ) were placed in a 3 dm round-bottom flask under an argon atmo-
sphere. The mixture was mechanically stirred and heated at reflux for
23 h after which time the solid was removed by filtration and the solvent
removed on a rotary evaporator. The resultant red oil was dissolved in
6
mined, viz. the bis(2,4,6-trinitrophenol) solvate, while for
monoaza-18-crown-6 and monoaza-15-crown-5 several
3
a boiling 1: 1 solution of dioxan and acetone (175 cm each) and then
7
,8
metal complexes and solvates have been studied.
Our
placed in the freezer to crystallize. The colourless crystalline solid (a
mixture of NaI and the NaI complex of the product from which crystals
for the X-ray experiment were selected) was dried and dissolved in dis-
initial foray into this field involved the synthesis of the nitro-
gen-containing crown ethers and we report herein a modified
synthesis of diaza-18-crown-6. In addition we present the X-
ray crystal structures of the NaI salt (1) of N,NЈ-dibenz-
yldiaza-18-crown-6, N,NЈ-dibenzyldiaza-18-crown-6 (2),
monoaza-18-crown-6 (3) and the anhydrous hydrochloride
salt (4) of monoaza-15-crown-5.
3
tilled water (500 cm ) and the organic material was extracted with
3
3
CH
2
Cl (400 cm and 3×75 cm ). The combined organic phases were
2
dried (NaSO
4
) and the solvent was removed on a rotary evaporator. As
only a small amount (2.48 g) of product was isolated and more crystals
had formed in the mother liquor, the isolation process was repeated
several times. The product was recrystallized from boiling hexane to
1
give a total yield of 4.2 g (11%). H n.m.r. (CDCl
3
) ꢀ 2.8, t, CH N;
2
–1
Experimental
3.6, m, CH
2
O; 3.7, s, ArCH
2
N; 7.3, m, aromatics. I.r. (ꢁ, Nujol, cm )
1
293m, 1122s, 1024w, 962w, 847w, 699m.
1
All reagents were purchased from Aldrich Chemical Co. H n.m.r.
1
3
spectra were recorded at 300.138 MHz and C n.m.r. spectra were
recorded at 75.4769 MHz on a Bruker BZH 300/52 spectrometer with
a Varian console, and chemical shifts were referenced against residual
protons in deuterated solvent. Compounds (1)–(3) have been previ-
ously reported in the literature, so no microanalyses were performed on
these samples; for compound (4), repeated attempts to obtain C, H and
4
,13-Diaza-18-crown-6
N,NЈ-Dibenzyl-4,13-diaza-18-crown-6 (4 g, 9.0 mmol) (crystallized
3
from freshly distilled absolute EtOH (30 cm ) under an argon atmo-
3
sphere), absolute EtOH (60 cm ) and Pd/C catalyst (0.2 g, 10% Pd)
were shaken in a Parr hydrogenation apparatus at 60 psi H pressure and
2
Manuscript received 23 August 1999
© CSIRO 1999
10.1071/CH99103
0004-9425/99/121109

1
110
K. R. Fewings and P. C. Junk
Table 1. Crystal data and summary of data collection for complexes (1)–(4)
Data common for all compounds: radiation, Mo Kꢂ (0.71073 Å); temperature, c. 295 K
Compound (1)
Compound (2)
Compound (3)
Compound (4)
22ClNO
Mol. formula
Mol. wt
Space group
a (Å)
C
26
H
40IN
2
NaO
5
C
26
442.6
H
38
N
2
O
4
C
12
263.3
H
25NO
5
C
10
255.7
H
4
610.5
–
/a (No. 14A)
Pnam (No. 62 )
B
P42
1
c (No. 114)
C 2/c (No. 15)
19.479(2)
11.235(3)
17.038(3)
90
P2
1
21.362(1)
9.0046(8)
9.400(1)
b (Å)
21.362(1)
8.505(1)
10.416(2)
c (Å)
12.1754(8)
10.3185(8)
13.6954(7)
ꢂ (deg)
ꢃ (deg)
ꢄ (deg)
90
90
90
90
136.677(7)
90
110.210(7)
90
90
90
90
3
Volume (Å )
5556.2(5)
2558.3(9)
4
741.6(1)
1340.9(3)
Molecules/unit cell
8
2
4
–
3
D
c
(g cm )
1.460
1.149
1.179
1.267
–
1
ꢅ (cm )
12.0
0.8
0.9
2.9
Dimensions (mm)
A*min,max
0.40 by 0.35 by 0.21
0.32 by 0.42 by 0.32
1.017, 1.036
0.32 by 0.46 by 0.22
1.018, 1.031
0.52 by 0.20 by 0.30
1.057, 1.085
T
min,max
F(000)
0.6442, 0.7945
2512
960
288
552
Diffractometer
Bruker Smart 1000
2.70–46.56
25196
Enraf–Nonius CAD4
Enraf–Nonius CAD4
Enraf–Nonius CAD4
2
ꢆ range (deg)
2–50
2461
738
2–50
1494
833
2–50
1398
794
Total reflections
Observed reflections
Parameters varied
R
C
3528
477
146
83
86
0.0306 (R
1
)
0.091
0.088
0.053
0.062
0.055
0.067
R
w
0.0621 (wR )
2
A
B
C
Alternative setting for P2
1
/c.
Alternative setting for Pnma.
Number of unique reflections 4002 (Rint 0.066).
Table 2. Non-hydrogen positional and isotropic displacement parameters for compounds (1)–(4)
Compound
Atom
x
y
z
U
eq (Å2)
Compound
(2)
Atom
x
y
z
U
eq (Å2)
(1)
I(1)
0.1622(1)
0.3664(1)
0.2550(2)
0.4050(2)
0.2934(1)
0.3619(2)
0.4327(2)
0.3647(1)
0.2199(2)
0.2297(2)
0.3059(3)
0.3140(2)
0.3732(3)
0.4231(2)
0.4610(2)
0.4502(2)
0.4191(2)
0.4122(2)
0.3035(2)
0.2628(2)
0.2255(2)
0.3644(2)
0.1581(2)
0.1439(2)
0.0819(2)
0.0348(3)
0.0484(2)
0.1093(2)
0.3559(2)
0.3742(2)
0.4023(2)
0.4209(2)
0.4122(2)
0.3839(2)
0.4519(2)
0.1979(1)
0.3937(1)
0.4280(2)
0.2855(2)
0.4145(1)
0.3072(1)
0.4092(1)
0.5123(1)
0.4482(2)
0.4070(2)
0.3783(2)
0.3109(2)
0.2452(2)
0.2486(2)
0.3023(2)
0.3541(2)
0.4610(2)
0.5179(2)
0.5323(2)
0.4796(2)
0.3730(2)
0.1361(2)
0.3834(2)
0.4137(2)
0.4281(2)
0.4108(2)
0.3785(3)
0.3645(2)
0.2542(2)
0.1915(2)
0.1866(2)
0.1291(3)
0.0762(3)
0.0796(2)
0.4191(2)
0.0712(1)
0.1294(1)
0.2073(3)
0.2075(3)
–0.0235(2)
–0.0137(2)
0.2919(3)
0.2102(3)
0.1104(3)
0.0114(4)
–0.1200(4)
–0.0941(4)
0.0252(4)
0.1108(4)
0.2716(4)
0.3522(4)
0.3618(4)
0.2921(5)
0.2449(5)
0.2869(4)
0.2616(4)
0.2634(4)
0.2974(3)
0.3945(3)
0.4211(5)
0.3506(5)
0.2560(4)
0.2294(4)
0.2747(4)
0.3226(3)
0.4259(4)
0.4660(4)
0.4045(4)
0.3034(4)
0.0054(4)
0.074(1)
0.041(1)
0.036(1)
0.037(1)
0.040(1)
0.046(1)
0.048(1)
0.046(1)
0.039(1)
0.043(1)
0.044(1)
0.047(1)
0.045(1)
0.042(1)
0.046(1)
0.050(1)
0.052(1)
0.054(1)
0.050(1)
0.045(1)
0.039(1)
0.045(1)
0.036(1)
0.041(1)
0.050(1)
0.054(1)
0.053(1)
0.043(1)
0.039(1)
0.038(1)
0.046(1)
0.054(1)
0.056(1)
0.052(1)
0.053(1)
C(1)
C(2)
O(1)
C(3)
C(4)
O(2)
C(5)
C(6)
N(1)
C(7)
C(8)
C(9)
C(10)
C(11)
C(12)
C(13)
0.3702(7)
0.4051(7)
0.4088(5)
0.4341(7)
0.4428(7)
0.5335(5)
0.5383(9)
0.6325(7)
0.3711(5)
0.2785(7)
0.2882(6)
0.3629(6)
0.3734(6)
0.3064(7)
0.2296(6)
0.2199(6)
–0.1090(9)
–0.0255(9)
0.0879(5)
0.1830(9)
0.2943(9)
0.2848(7)
0.333(1)
0.3206(9)
–0.2326(6)
–0.2528(8)
–0.3665(7)
–0.3778(8)
–0.4824(8)
–0.5704(8)
–0.5622(8)
–0.4567(9)
0.3155(7)
0.2848(7)
0.3263(5)
0.2940(7)
0.3467(7)
0.4649(5)
0.5372(9)
0.6549(7)
0.2827(5)
0.1586(7)
0.1181(6)
0.1257(6)
0.0904(7)
0.0445(7)
0.0353(7)
0.0711(7)
0.11(1)
0.11(1)
0.120(8)
0.12(1)
0.12(1)
0.143(7)
0.16(2)
0.12(1)
0.092(7)
0.101(9)
0.082(8)
0.088(8)
0.103(9)
0.105(9)
0.106(9)
0.110(9)
Na(1)
N(1)
N(2)
O(1)
O(2)
O(3)
O(4)
C(1)
C(2)
C(3)
C(4)
C(5)
C(6)
C(7)
C(8)
C(9)
C(10)
C(11)
C(12)
C(13)
C(26)
C(14)
C(15)
C(16)
C(17)
C(18)
C(19)
C(20)
C(21)
C(22)
C(23)
C(24)
C(25)
O(1s)
(3)
N(1)
O(1)
O(2)
O(3)
C(1)
C(2)
C(3)
C(4)
C(5)
C(6)
0.4935(2)
0.4935(2)
0.5837(2)
0.6676(2)
0.4967(3)
0.6250(3)
0.7024(3)
0.6537(3)
0.6253(3)
0.3679(3)
0.5667(2)
0.5667(2)
0.8002(2)
0.6992(2)
0.7311(3)
0.8069(3)
0.8688(3)
0.8572(3)
0.6844(4)
0.4845(4)
0.2193(2)
0.2193(2)
0.4308(2)
0.7186(2)
0.1940(2)
0.3106(3)
0.5460(3)
0.6701(3)
0.8384(3)
0.1200(3)
0.0514(8)
0.0514(8)
0.0514(8)
0.0539(8)
0.053(1)
0.053(1)
0.054(1)
0.053(1)
0.053(1)
0.051(1)
(4)
Cl(1)
C(1)
O(1)
C(2)
C(3)
O(2)
C(4)
C(5)
N(1)
1.1202(2)
0.649(1)
0.4769(2)
0.6670(9)
0.5556(3)
0.5473(5)
0.4310(5)
0.3143(3)
0.2679(5)
0.1813(4)
0.2542(5)
1/4
0.0515(6)
0.064(4)
0.083(2)
0.059(2)
0.055(2)
0.045(1)
0.047(2)
0.045(2)
0.039(2)
0.2963(7)
0.3541(3)
0.4233(4)
0.4844(4)
0.4299(2)
0.4270(3)
0.3406(3)
1/4
0.6823(5)
0.7927(6)
0.7660(6)
0.7807(3)
0.9234(5)
0.9357(5)
0.9114(6)

Monoaza- and Diaza-crown Ethers
1111
Fig. 2. Molecular projection of N,NЈ-dibenzyl-4,13-diaza-18-crown-
6
(2).
Fig. 1. (a),(b) Two projections of the X-ray structure of (N,NЈ-diben-
zyl-4,13-diaza-18-crown-6)sodium iodide (1). Selected bond lengths
and angles: Na(1)–O(1s) 2.430(4), Na(1)–O(1) 2.469(3), Na(1)–O(2)
2
2
.541(3), Na(1)–O(3) 2.455(3), Na(1)–O(4) 2.718(3), Na(1)–N(1)
.666(4), Na(1)–N(2) 2.631(4) Å, O(1s)–Na(1)–O(1) 88.1(2),
O(1s)–Na(1)–O(2)
O(1s)–Na(1)–O(4)
76.4(1),
O(1s)–Na(1)–O(3)
O(1s)–Na(1)–N(1)
92.2(2),
91.5(1),
146.2(1),
o
O(1s)–Na(1)–N(2) 100.7(1) .
Fig. 4. Cation projection of monoaza-15-crown-5 hydrochloride (4);
this resides on a mirror plane with Cl(1) and N(1) resident on the plane.
Selected bond lengths: N(1)–H(2n) 0.9
Cl(1)···N(1) 3.043(2) Å.
9
, Cl(1)···H(2n) 2.246(2) Å,
Fig. 3. Molecular projection of monoaza-18-crown-6 (3).

1
2
112
K. R. Fewings and P. C. Junk
o
3 C for 48 h; the pressure was adjusted twice during the reaction. The
Discussion
Diaza-18-crown-6 was prepared by a variation of the
solid was removed by filtration through Celite, the solvent removed by
evaporation and the colourless solid recrystallized from hexane (1 g/35
1
2
3
1
method described in the literature. N,NЈ-Dibenzyl-2,2Ј-
(ethylenedioxy)bis(ethylamine) (Scheme 1) was prepared by
treating a dilute solution (MeCN) of triethylene glycol
dichloride with 2 equiv. of benzylamine in the presence of
cm ) under an argon atmosphere. Yield 1.81g, 76%. H n.m.r. (CDCl )
3
1
3
ꢀ
2.2, br s, NH; 2.7, t, CH
s, CH N; 66.1, 2s, CH O. I.r. (ꢁ, Nujol, cm ) 1287m, 1251m, 1210m,
128s, 1069m, 975m, 951m, 874m, 839m, 780m, 520w.
2
N; 3.5, m, CH
2
O. C n.m.r. (CDCl
3
) ꢀ 45.5,
–
1
2
2
1
Na
2
CO
3
.
Monoaza-18-crown-6 (3)
Formation of the protected azacrown ether N,NЈ-
This compound was synthesized according to the published proce-
9
dibenzyl-4,13-diaza-18-crown-6 (Scheme 2) involved
heating a dilute solution of N,NЈ-dibenzyl-2,2Ј-(ethylene-
dioxy)bis(ethylamine), in MeCN, with 1 equiv. of 1,2-bis(2-
iodoethoxy)ethane (formed in situ by treatment of
dure of Okahara et al. Crystals of suitable quality for an X-ray struc-
o
ture determination were grown by cooling a toluene solution to –30 C.
1
13
H n.m.r. (CDCl
n.m.r. (CDCl
3
) ꢀ 2.4, br s, NH; 2.7, t, CH
2
N; 3.5, m, CH
2
O.
C
3
) ꢀ 45.2, 66.0, 66.2, 66.4.
1
,2-bis(2-chloroethoxy)ethane with NaI) in the presence of
and NaI.
Monoaza-15-crown-5 Hydrochloride (4)
These crystals were obtained as a side-reaction of the reaction of
NaCO
3
+
–
[
Na ] [monoaza-15-crown-5 ] and ErCl in tetrahydrofuran. After
3
decantation by cannula of a white precipitate, an apricot-coloured solu-
o
tion remained. This was cooled to –30 C whereupon small colourless
crystals of the title complex deposited. These were suitable for the X-
ray crystallography experiment.
Structure Determinations
For compounds (2)–(4) room-temperature data sets were acquired
o
on capillary-mounted specimens (2ꢆmax 50 , 2ꢆ/ꢆ scan mode;
monochromatic Mo Kꢂ radiation, ꢇ 0.7107 Å; temperature c. 295K)
3
yielding 2461 independent reflections, 738 with I > 3ꢈ(I) being con-
sidered ‘observed’ for compound (2) (1494 and 833 respectively for
(
3), and 1398 and 794 respectively for (4)) and used in the full-matrix
least-squares refinement after Gaussian absorption correction.
Anisotropic thermal parameters were refined for the non-hydrogen
atoms; (x,y,z,Uiso
H
) were included constrained at estimated values.
w
Conventional residuals on |F|, viz. R and R (statistical weights deriva-
2
2
4
tive of ꢈ (I) = ꢈ (Idiff)+0.0004ꢈ (Idiff)), are quoted. Neutral atom
complex scattering factors were employed, computation using the
1
0
Xtal3.4 program system implemented by S. R. Hall.
For compound (1) a hemisphere of data were collected at room tem-
perature on a Bruker Smart CCD diffractometer using the ꢉ scan mode
yielding a total of 25196 reflections which reduced to 4002 unique data
During this preparation, the NaI complex of N,NЈ-diben-
zyl-4,13-diaza-18-crown-6 was isolated, and its X-ray
crystal structure determined (Fig. 1). In this complex, the
sodium ion resides within the crown cavity, perched within
the plane of the oxygen atoms, but the nitrogen atoms of the
crown are bent down from the crown forming a bowl-shaped
cavity (Figs 1a and 1b). The sodium ion is also bound to a
water molecule on the side of the crown opposite to which
(
R
int 0.066) with 3528 (F
o
> 4ꢈ(F )) being considered observed. Data
o
were corrected for absorption with the program SADABS. The structure
was solved using direct methods in SHELXS and refined using SHELXL97-
11
2
.
All non-hydrogen were located and were refined with anisotropic
thermal parameters. The hydrogen atoms were located and refined with
their own isotropic thermal parameters.
Crystal data and a summary of data collection parameters appear in
Table 1; pertinent results are shown in Table 2, and Figs 1–4, and
selected bond lengths are shown in the figure captions; material
deposited† comprises anisotropic thermal parameters, tables of com-
plete bond distances and angles, and full non-hydrogen atom geome-
tries. In Figs 1–4 thermal ellipsoids are shown at the 50% probability
level.
the nitrogen atoms splay.
There are three shorter
Na–O(crown) distances of 2.455(3), 2.469(3) and 2.541(3)
Å and one longer (Na(1)–O(4), 2.718(3) Å), and the Na–N
distances are 2.666(4) and 2.631(4) Å for N(1) and N(2)
respectively. The O(1s)–Na(1)–O(crown) angles average
o
8
7.1 , while the O(1s)–Na(1)–N(crown) angles are 100.7(1)
o
and 146.2(1) for N(2) and N(1) respectively emphasizing
the bowl-shaped conformation of the crown at the nitrogen
centres. The benzyl groups bound to the nitrogen atoms
bend down and away from the crown on the opposing side of
the crown to which the water molecule is bound. There does
not appear to be any ꢊ-stacking within the structure and the
reason as to why the benzyl groups adopt this conformation,
rather than being splayed out from the crown (as in the
uncomplexed crown (see later) and the bis(2,4,6-trinitrophe-
6
nol) solvate ), is due to the sodium binding (the lone pairs of
†
Copies are available (until 31 December 2004) on application to the Australian Journal of Chemistry, P.O. Box 1139, Collingwood, Vic. 3066.

Monoaza- and Diaza-crown Ethers
1113
the nitrogen atoms now being directed towards the centre of
the macrocyclic ring). The shortest Na···I separation is
tibility of much lanthanoid chemistry, as the hydrochloride
salt of the azacrown ether presumably formed as a result of a
fortuitous contamination by moisture.
5
.680(4) Å and the iodide ion does not appear to be involved
in any interaction with the aromatic ring (shortest I···C dis-
tance 4.200(4) Å), an effect which discounts entrapment of
the iodide as the reason for this conformation. The closest
contacts to the iodide ion are hydrogen atoms on the crown
ether rings of adjacent molecules, where there are several
distances of 3.2–3.3 Å, with a corresponding shortest I···C
distance of 3.859(4) Å. There is a precedent for I···C(arene)
interaction in calixarene chemistry, but distances of
Monoaza-15-crown-5 hydrochloride crystallizes in
orthorhombic space group Pnam with half the molecule as
the asymmetric unit, the other half being generated by a
mirror plane with Cl(1) and N(1) resident on the mirror plane
(Fig. 4). This structure represents the first example of an
anhydrous hydrochloride salt of an azacrown ether, but is
1
5,16
related to several hydrated examples.
There is a small
amount of disorder in the crown ether, but this was success-
fully modelled with C(1) and C(1a) having 50% occupancy;
C–O and C–C bond lengths are typical (average 1.42 and
1.49 Å respectively) with a C–N distance of 1.472(5) Å. The
chloride ion is involved in a hydrogen bond to the nitrogen
atom of the crown: Cl(1)···H(2n) 2.246(2) Å, Cl(1)···N(1)
3.043(2) Å. It is more distant to an adjacent nitrogen centre
at 3.64 Å and is not considered as bound.†
1
3
3
.60–3.78 Å were considered as significant.
The crystal structure of N,NЈ-dibenzyl-4,13-diaza-18-
crown-6 was also determined from a suitable crystal grown
during purification (see Fig. 2). The compound crystallizes
in space group C 2/c and resides on an inversion centre
giving half a molecule in the asymmetric unit. The oxygen
atoms reside in an endodentate fashion as is typical with
most crowns, while the nitrogen atoms flip to an exodentate
mode to incorporate binding of the benzyl groups. The C–N,
C–O and C–C bonds (averages 1.49, 1.39 and 1.46 Å) are
unexceptional. This structure is similar to that of the
Acknowledgments
We are grateful to theAustralian Research Council (ARC)
for support of this research (ARC Large Grant No.
A29801469), and to James Cook University, Bruker and the
ARC (RIEFP Grant) for funding of the Smart CCD diffrac-
tometer system.
6
bis(2,4,6-trinitrophenol) solvate, where the benzyl side
arms splay out from the crown rather than both down and
away as in the previous case for compound (1). As with com-
pound (1), there does not appear to be any ꢊ-stacking in
compound (2).
References
1
Pedersen, C. J., J. Am. Chem. Soc., 1967, 89, 2495.
The synthesis of monoaza-18-crown-6 involved treatment
of diethanolamine with tetraethylene glycol di(p-toluenesul-
fonate) in the presence of potassium t-butoxide following the
2
Fenton, D. E., ‘Alkali Metals and Group IIA Metals’ in
‘
Comprehensive Coordination Chemistry’ (Eds G. Wilkinson, R. D.
Gillard and J. A. McCleverty) Vol. 3, p. 35 (Pergamon: Oxford
9
published procedure of Okahara et al.
1
987).
3
The crystal structure of monoaza-18-crown-6 (Fig. 3) was
determined after suitable crystals were grown from toluene.
The molecule crystallizes in space group P2 /a and resides
Mertes, K. B., and Lehn, J.-M., ‘Multidenate Macrocyclic and
Macropolycyclic Ligands’ in ‘Comprehensive Coordination
Chemistry’ (Eds G. Wilkinson, R. D. Gillard and J. A. McCleverty)
Vol. 2, p. 931 (Pergamon: Oxford 1987).
1
on an inversion centre with only half a molecule as the asym-
metric unit. Therefore, to satisfy this symmetry requirement
assuming this space group and cell, the model must be disor-
dered with partial occupancy of both N(1) and O(1).
Refinement successfully converged with 50: 50 occupancy
of these atoms. The structure shows that all the heteroatoms
reside in an endodentate (pointing inwards) environment
within the macrocycle. The proton on N(1) was located in the
difference map and the N–H bond length of 1.132 Å is
4
5
For example: Krakowiak, K. E., Bradshaw, J. S., and Zamecka-
Krakowiak, D. J., Chem. Rev., 1989, 89, 929.
Hassaballa, H., Steed, J. W., and Junk, P. C., Chem. Commun., 1998,
5
1
77; Junk, P. C., Lynch, S. M., and McCool, B. J., Supramol. Chem.,
998, 9, 151; Steed, J. W., McCool, B. J., and Junk, P. C., J. Chem.
Soc., Dalton Trans., 1998, 3417; Hassaballa, H.; Steed, J. W., Junk,
P. C., and Elsegood, M. R. J., Inorg. Chem., 1998, 37, 4666; Junk, P.
C., and Steed, J. W., J. Chem. Soc., Dalton Trans., 1999, 407; Steed,
J. W., and Junk, P. C., J. Chem. Soc., Dalton Trans., 1999, 2141;
Junk, P. C., McCool, B. J., Moubaraki, B., Murray, K. S., and
Spiccia, L., Angew. Chem., Int. Ed. Engl., 1999, 38, 2224.
Saleh, M. I., Salhin, A., Saad, B., Sivakumar, K., and Fun, H. K., Z.
Kristallogr. (New Cryst. Struct.), 1997, 212, 107.
1
4
typical. C–N, C–O and C–C bond lengths (average 1.423,
6
7
1
.420 and 1.494 Å respectively) are typical.
Crystals of the hydrochloride salt of monoaza-15-crown-
Some examples of monoaza-18-crown-6: Byriel, K., Dunster, K. R.,
Gahan, L. R., Kennard, C. H. L., Latten, J. L., Swann, I. L., and
Duckworth, P. A., Polyhedron, 1992, 11, 1205; Motevalli, M.,
O’Brien, P., and Watson, I. M., Polyhedron, 1996, 15, 1865;
Atwood, J. L., Bott, S. G., Junk, P. C., and May, M. T., J. Coord.
Chem., 1996, 37, 89.
5
were inadvertently obtained from the reaction of ErCl and
3
the sodium salt of monoaza-15-crown-5. After treatment of
the sodium salt with ErCl , the colourless mother liquor was
3
decanted via cannula and the solvent removed to reveal a
small amount of colourless precipitate, which was recrystal-
lized from tetrahydrofuran to yield small colourless, rod-
shaped crystals that were very hygroscopic. An X-ray
structure determination of these crystals identified them as
the hydrochloride salt of monoaza-15-crown-5 (Fig. 4). The
formation of this compound highlights the moisture suscep-
8
Some examples of monoaza-15-crown-5: Rebiza, J., Spirlet, M. R.,
Barthelemy, P. P., and Desreux, J. F., Acta Crystallogr., Sect. C,
1
987, 43, 909; Byriel, K., Dunster, K. R., Gahan, L. R., Kennard, C.
H. L., and Latten, J. L., Inorg. Chim. Acta, 1992, 196, 35; Byriel, K.,
Dunster, K. R., Gahan, L. R., Kennard, C. H. L., Latten, J. L.,
Swann, I. L., and Duckworth, P. A., Inorg. Chim. Acta, 1993, 205,
1
91.
†
The N···Cl cutoff for significant hydrogen bonding interactions is 3.3 Å, which is the sum of the van der Waals radii of Cl and N.17

1
114
K. R. Fewings and P. C. Junk
9
13
Maeda, H., Furuyoshi, S., Nakatsuji, Y., and Okahara, M., Bull.
Holman, K. T., Halihan, M. M., Jurisson, S. S., Atwood, J. L.,
Burkhalter, R. S., Mitchell, A. R., and Steed, J. W., J. Am. Chem.
Soc., 1996, 118, 9567.
Chem. Soc. Jpn, 1983, 56, 212.
1
0
Hall, S. R., King, G. S. D., and Stewart, J. M., Xtal3.4 User’s
Manual, University of Western Australia, Lamb, Perth, 1995.
Sheldrick, G. M., SHELXL97; A Program for Crystal Structure
Refinement. Release 97-2. University of Goettingen, Germany, 1997.
Gokel, G., ‘Crown Ethers and Cryptands’ (The Royal Society of
Chemistry: Cambridge 1991); Gatto, V. J., Arnold, K. A.,
Viscariello, A. M., Miller, S. R., Morgan, C. R., and Gokel, G. W.,
J. Org. Chem., 1986, 51, 5373.
1
1
4
5
Allen, F. H., Kennard, O., Watson, D. G., Brammer, L., Orpen, G. A.,
and Taylor, R. A., J. Chem. Soc., Perkin Trans. 2, 1987, S1.
Gokel, G. W., and Garcia, B. J., Tetrahedron Lett., 1977, 4, 317.
Desiraju, G. R., Acc. Chem. Res., 1991, 24, 291.
11
1
2
16
1
7
Hamilton, W. C., and Ibers, J. A., ‘Hydrogen Bonding in Solids’ p.
16 (Benjamin: New York 1968).