Neutral thioether and selenoether macrocyclic coordination to Group 1 cations (Li-Cs)-synthesis, spectroscopic and structural properties

Article abstract of DOI:10.1039/c5dt02583d

The complexes [M(L)][BAr^F] (BAr^F = tetrakis{3,5-bis(trifluoromethyl)-phenyl}borate), L = [18]aneO₄S₂ (1,4,10,13-tetraoxa-7,16-dithiacyclooctadecane): M = Li-Cs; L = [18]aneO₂S₄ (1,10-dioxa-4,7,13,16-tetrathiacyclooctadecane): M = Li, Na, K; L = [18]aneO₄Se₂ (1,4,10,13-tetraoxa-7,16-diselenacyclooctadecane): M = Na, K, as well as [Na(18-crown-6)][BAr^F], are obtained in good yield as crystalline solids by reaction of M[BAr^F] with the appropriate macrocycle in dry CH₂Cl₂. X-ray crystallographic analyses of [Li([18]aneO₄S₂)][BAr^F] and [Li([18]aneO₂S₄)][BAr^F] show discrete distorted octahedral cations with hexadentate coordination to the macrocycle. The heavier alkali metal complexes all contain hexadentate coordination of the heterocrown, supplemented by M...F interactions via the anions, producing extended structures with higher coordination numbers; Na: CN = 7 or 8; K: CN = 8; Rb: CN = 9; Cs: CN = 8 or 10. Notably, all of the structures exhibit significant M-S/Se coordination. The crystal structures of the potassium and rubidium complexes show two distinct [M(heterocrown)]⁺ cations, one with M...F interactions to two mutually cis [BAr^F]^- anions, and the other with mutually trans [BAr^F]^- anions, giving 1D chain polymers. Solution multinuclear (¹H, ¹³C, ⁷Li, ²³Na, ¹³³Cs) NMR data show that the macrocyclic coordination is retained in CH₂Cl₂ solution.

Full text of DOI:10.1039/c5dt02583d

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Neutral thioether and selenoether macrocyclic
coordination to Group 1 cations (Li–Cs) –
Cite this: DOI: 10.1039/c5dt02583d
synthesis, spectroscopic and structural properties†
Martin J. D. Champion, William Levason, David Pugh and Gillian Reid*
The complexes [M(L)][BArF] (BArF = tetrakis{3,5-bis(trifluoromethyl)-phenyl}borate), L = [18]aneO4S2
(1,4,10,13-tetraoxa-7,16-dithiacyclooctadecane): M = Li–Cs; L = [18]aneO2S4 (1,10-dioxa-4,7,13,16-tetra-
thiacyclooctadecane): M = Li, Na, K; L = [18]aneO4Se2 (1,4,10,13-tetraoxa-7,16-diselenacyclooctadecane):
M = Na, K, as well as [Na(18-crown-6)][BArF], are obtained in good yield as crystalline solids by reaction of
M[BArF] with the appropriate macrocycle in dry CH2Cl2. X-ray crystallographic analyses of [Li([18]-
aneO4S2)][BArF] and [Li([18]aneO2S4)][BArF] show discrete distorted octahedral cations with hexadentate
coordination to the macrocycle. The heavier alkali metal complexes all contain hexadentate coordination
of the heterocrown, supplemented by M⋯F interactions via the anions, producing extended structures
with higher coordination numbers; Na: CN = 7 or 8; K: CN = 8; Rb: CN = 9; Cs: CN = 8 or 10. Notably, all
of the structures exhibit significant M–S/Se coordination. The crystal structures of the potassium and rubi-
dium complexes show two distinct [M(heterocrown)]+ cations, one with M⋯F interactions to two mutually
cis [BArF]− anions, and the other with mutually trans [BArF]− anions, giving 1D chain polymers. Solution
multinuclear (1H, 13C, 7Li, 23Na, 133Cs) NMR data show that the macrocyclic coordination is retained in
CH2Cl2 solution.
Received 8th July 2015,
Accepted 14th August 2015
DOI: 10.1039/c5dt02583d
www.rsc.org/dalton
include [CaI2([18]aneO2S4)] and [MI2([18]aneO4E2)] (M = Ca, Sr;
E = S, Se; [18]aneO2S4 = 1,10-dioxa-4,7,13,16-tetrathiacycloocta-
Introduction
Thioethers and selenoethers are soft, moderate σ-donor decane, [18]aneO4S2 = 1,4,10,13-tetraoxa-7,16-dithiacycloocta-
ligands with a high affinity for medium and low oxidation decane; [18]aneO4Se2 1,4,10,13-tetraoxa-7,16-
=
state transition metal ions in particular, whilst a significant diselenacyclooctadecane), all of which are eight-coordinate
body of work concerning high oxidation state early transition with the macrocycle hexadentate (d(Ca–S/Se) ∼ 3.0 Å) and the
metals, f- and p-block acceptors has emerged over the last iodides mutually cis. The lower lattice energies of the alkaline
decade or so.1 In contrast, examples showing thioether or sele- earth diiodides (MI2) compared to MCl2 or M(CF3SO3)2, etc.,
noether coordination towards the oxophilic s-block cations are leads to MI2 being suitable metal sources for this chemistry
much rarer.2–4 Within Group 2, while there are no complexes due to their higher solubilities in non-competitive solvents.3
with neutral acyclic thio- or seleno-ether coordination, a small
The lower charge : radius ratio of the Group 1 cations is
number of examples containing Ca–S/Se and Sr–S/Se coordi- expected to lead to considerably lower affinity of these cations
nation, based upon 15- and 18-membered oxa-thia and oxa- for soft thio- or seleno-ether coordination. This is supported
selena macrocycles, have been reported recently.2,3 These by early data on binding constants for alkali metal cations
towards the oxa-thia analogues of 18-crown-6. Thus, the stabi-
lity constant for K+/[18]aneO5S (1,4,7,10,13-pentaoxa-16-thiacy-
clooctadecane) and K+/[18]aneO4S2 are more than 102 and 106
School of Chemistry, University of Southampton, Southampton SO17 1BJ, UK.
E-mail: G.Reid@soton.ac.uk
†Additional Data Available: Original NMR spectra for all complexes are available
times lower than for K+/18-crown-6, respectively, in methanol.5
Unsurprisingly therefore, well-characterised complexes of the
(DOI: 10.5258/SOTON/380541) and can be downloaded via <http://dx.doi.org/
10.5258/SOTON/380541>. CCDC 1410981 ([Na(18-crown-6-][BArF]), 1410982
([Li([18]aneO4S2)][BArF]), 1410983 ([Na([18]aneO4S2)][BArF]), 1410984 ([K([18]aneO4S2)]-
[BArF]), 1410985 ([Rb([18]aneO4S2)][BArF]), 1410986 ([Cs([18]aneO4S2)][BArF]),
1410987 ([Li([18]aneO2S4)][BArF]), 1410988 ([Na([18]aneO2S4)][BArF]), 1410989
([K([18]aneO2S4)][BArF]), 1410990 ([Na([18]aneO4Se2)][BArF]) and 1410991 ([K([18]-
aneO4Se2)][BArF]). For crystallographic data in CIF or other electronic format see
DOI: 10.1039/c5dt02583d
Group 1 metals with similar soft donor ligands are extremely
rare. There are no complexes with simple neutral acyclic
thioethers, and only two prior examples with oxa-thia macro-
cycles, the K+ and Na+ cations with [18]aneO4S2 are structurally
characterised. These are based upon lamellar halo-cuprate
species, in which the K⋯S distances are 3.322(5)–3.496(4) Å
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and Na⋯S = 3.11(1) Å, although the presence of Cu–S coordi- 18-Crown-6 was purchased from Sigma and dried using SOCl2.
nation in these structures clearly has a significant influence.4 CH2Cl2 was dried by distillation from CaH2 and n-hexane dis-
We have exploited the high solubility of alkali metal salts with tilled from Na/K alloy. 1H and 13C{1H} NMR spectra were
diffuse, weakly coordinating anions in weakly coordinating recorded in CD2Cl2 solution at 295 K using a Bruker AV II-400
(non-competitive) solvents, as a source of ‘naked’ alkali metal spectrometer and are referenced to the residual CH2Cl2 reson-
cations, as a synthetic entry to promote their coordination ance. 7Li, 23Na and 133Cs NMR spectra were obtained in
towards soft, neutral donor ligands. Even so, it was surprising CH2Cl2 solution on a Bruker AV II-400 spectrometer at 298 K
to us to find that this can lead to homoleptic octathia coordi- (unless otherwise stated) and referenced to a 0.1 mol dm−3
nation to Na+ in the macrocyclic complex [Na([24]aneS8)][BArF] solution of LiCl, NaCl or CsNO3 in D2O, respectively. NMR pro-
([24]aneS8 = 1,4,7,10,13,16,19,22-octathiacyclotetracosane; BArF perties: 7Li: I = 3/2, N = 92.6%, Rc = 1.54 × 103, Q = −3.7 × 10−30
= tetrakis{3,5-bis(trifluoromethyl)-phenyl}borate), containing m2, Ξ = 38.87 MHz; 23Na: I = 3/2, N = 100%, Rc = 5.24 × 102, Q =
distorted dodecahedral S8-coordination at the sodium centre, 0.10 × 10−28, Ξ = 26.43; 39K: I = 3/2, N = 93.3%, Rc = 2.69, Q =
with d(Na–S) = 2.9561(15)–3.0524(15) Å.6 DFT calculations 5.5 × 10−30, Ξ = 4.67; 85Rb: I = 5/2, N = 72.1%, Rc = 43.4, Q =
suggested that the pre-organisation of the [24]aneS8 macro- 0.25 × 10−28, Ξ = 9.69; 133Cs: I = 7/2, N = 100%, Rc = 2.75 × 102,
cycle contributed to the successful isolation of this unique Q = −0.3 × 10−30, Ξ = 13.21.12 Microanalyses were undertaken
cation. Subsequently, using a similar approach we have also at London Metropolitan University.
found that using even softer, neutral diphosphines leads to
X-ray crystallography
homoleptic Li+ and Na+ hexaphosphine cations in [Li(L–L)3]-
[Al{OC(CF3)3}4] and [Na(L–L)3][BArF] (L–L = Me2PCH2CH2PMe2 Crystals were obtained as described below. Details of the crys-
or o-C6H4(PMe2)2).7 Further interest in caesium–sulfur coordi- tallographic data collection and refinement are in Table 1.
nation comes from the important role of Cs2CO3 in the for- Diffractometer: Rigaku AFC12 goniometer equipped with an
mation of thioether macrocycles via high dilution cyclisation enhanced sensitivity (HG) Saturn724+ detector mounted at the
reactions in dmf solution.8 The key role in the cyclisation reac- window of an FR-E+ SuperBright molybdenum rotating anode
tion is the formation of a Cs+–thiolate ion pair, however, despite generator (λ1 = 0.71073 Å) with VHF Varimax optics (70 or
the widespread application of this procedure for thioether 110 µm focus). Cell determination and data collection: Crystal-
macrocycle formation, evidence of caesium–thioether coordi- Clear-SM Expert 3.1 b27, data reduction, cell refinement, and
nation, i.e. following ring-closure, has remained elusive.
absorption correction: CrystalClear-SM Expert 2.1 b29.13 Struc-
We report here the results of a systematic study of the ture solution and refinement were carried out using Olex2 or
preparation, spectroscopic and structural features of a series of WinGX and software packages within.14 Disorder in the CF3
complexes of the Group 1 cations with hexadentate, 18-mem- groups of the [BArF]− anions was present in all of the struc-
bered ring macrocycles containing both hard (O) and soft tures, which is often observed in compounds containing
(S, Se) donor functions, which demonstrate that coordination [BArF]−,15 and this was satisfactorily modelled using DFIX,
of neutral thioether functions to alkali metal cations is not DANG, DELU and SIMU restraints. Positional disorder was
limited to just sodium and potassium, but extends to examples also present in the macrocycle ligands in one of the crystallo-
with all five cations from Li+ to Cs+. We also report the first graphically independent cations in each of [Na(L)][BArF] com-
examples of neutral selenoether coordination to a Group 1 plexes (L = [18]aneO4S2, [18]aneO4Se2 and [18]aneO2S4) and was
cation, including structural authentication for [M([18]- modelled similarly. H-atoms were placed in geometrically-
aneO4Se2)][BArF], M = Na and K.
assigned positions with C–H distances of 0.95 Å (CH) or 0.98 Å
(CH2) and refined using a riding model with Uiso(H) = 1.2Ueq(C).
enCIFer was used to prepare material for publication.16
Experimental
Preparations
All preparations were carried out under a dry dinitrogen atmos-
General method. M[BArF] was suspended in CH2Cl2 (10 mL)
phere using standard Schlenk and glove box techniques. and a solution of the macrocycle in CH2Cl2 (5 mL) was added.
[Li(thf)4][BArF] and Na[BArF]·2thf were synthesised using a Complete dissolution occurred and the reaction was stirred for
slight modification of the literature procedure.9 The lithium 16 h. After this time the solution was filtered, concentrated to
salt was isolated as [Li(OH2)4][BArF], which was converted to ∼3 mL and layered with n-hexane (20 mL) to form crystals. These
the thf adduct by stirring in thf for 16 h over 4 Å molecular were isolated by decanting away the supernatant and drying
sieves. Filtration and removal of solvents afforded the thf in vacuo. Specific details for individual complexes are below.
adduct. Crude Na[BArF] was recrystallised from thf/n-hexane to
[Na(18-crown-6)][BArF]. Na[BArF]·2thf (50 mg, 0.05 mmol)
remove the last traces of coloured impurity, resulting in the and 18-crown-6 (13 mg, 0.1 mmol). Yield: 40 mg, 70%.
isolation of Na[BArF]·2thf. K[BArF], Rb[BArF] and Cs[BArF] were Required for C44H36BF24NaO6 (1150.53): C, 45.93; H, 3.15.
synthesised via cation exchange of Na[BArF]·2thf in water at Found: C, 45.82; H, 2.97%. 1H NMR (CD2Cl2): δ = 7.72 ([8H], br
95 °C with excess (5 mol equiv.) KNO3, RbNO3 or CsNO3, s, H2/6), 7.57 ([4H], s, H4), 3.64 ([24H], s, OCH2). 13C{1H} NMR
respectively.10 The macrocycles [18]aneO4S2, [18]aneO2S4 and (CD2Cl2): δ = 162.36 (C, q, JC–B = 49.9 Hz, BArF C1), 135.40
2
[18]aneO4Se2 were prepared using literature procedures.11 (CH, BArF C2/6), 129.49 (C, qq, JC–F = 31.6, 2.9 Hz, BArF C3/5),
Dalton Trans.
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Table 1 Crystallographic parametersa
Compound
Formula
[Li([18]aneO4S2)][BArF]
44H36O4BF24LiS2
1166.60
Monoclinic
Pc (7)
12.753(3)
22.349(5)
17.450(4)
90
95.618(4)
90
[Na([18]aneO4S2)][BArF]
[K([18]aneO4S2)][BArF]
C88H72O8B2F48K2S4
2397.51
Monoclinic
P21/c (14)
16.9189(12)
13.6483(10)
44.153(3)
90
97.6620(10)
90
10 104.4(13)
4
[Rb([18]aneO4S2)][BArF]
C44H36O4BF24RbS2
1245.13
C
C44H36O4BF24NaS2
1182.65
Monoclinic
Pc (7)
12.682(3)
22.573(5)
17.452(4)
90
97.460(3)
90
4954(2)
4
M/g mol−1
Crystal system
Space group (no.)
a/Å
Triclinic
ˉ
P1 (2)
13.923(3)
16.765(3)
22.402(5)
97.029(4)
105.185(5)
90.376(3)
5005(2)
4
b/Å
c/Å
α/°
β/°
γ/°
U/Å3
4950(2)
4
0.240
Z
μ(Mo-Kα)/mm−1
F(000)
0.249
2384
0.318
4832
1.204
2488
2352
Total reflections
Unique reflections
Rint
65 730
21 600
0.064
1.022
0.069
0.103
0.165
0.188
37 772
16 023
0.038
1.015
0.042
0.051
0.096
0.102
79 011
17 773
0.102
0.961
0.077
0.126
0.194
0.229
58 188
17 632
0.071
1.023
0.055
0.083
0.132
0.146
Goodness-of-fit on F2
R1b [Io > 2σ(Io)]
R1 (all data)
wR2b [Io > 2σ(Io)]
wR2 (all data)
Compound
Formula
[Cs([18]aneO4S2)][BArF]
[Li([18]aneO2S4)][BArF]
C44H36BF24LiO2S4
1198.72
Monoclinic
P21 (4)
16.596(4)
19.366(5)
23.794(6)
90
[Na([18]aneO4Se2)][BArF]
[Na([18]aneO2S4)][BArF]
C44H36BF24NaO2S4
1214.77
Monoclinic
C2/c (15)
22.415(5)
8.9368(17)
25.072(5)
90
C44H36O4BCsF24S2
1292.57
Orthorhombic
Pbca (61)
17.974(5)
19.582(5)
28.567(7)
90
C44H36BF24O4NaSe2
1276.45
Monoclinic
Cc (9)
12.7830(12)
67.748(7)
17.4535(18)
90
M/g mol−1
Crystal system
Space group (no.)
a/Å
b/Å
c/Å
α/°
β/°
90
90
10 055(5)
8
0.950
93.056(5)
90
7637(3)
6
0.312
3624
96.603(3)
90
15 015(3)
12
1.617
7584
99.731(4)
90
4950.2(17)
4
0.330
2448
γ/°
U/Å3
Z
μ(Mo-Kα)/mm−1
F(000)
5120
Total reflections
Unique reflections
Rint
68 140
11 507
0.097
1.016
0.060
0.118
0.127
0.155
42 404
28 887
0.063
1.024
0.086
0.145
0.191
0.234
70 507
26 208
0.065
0.984
0.065
0.079
0.155
0.167
13 830
5638
0.047
0.988
0.038
0.056
0.090
0.096
Goodness-of-fit on F2
R1b [Io > 2σ(Io)]
R1 (all data)
wR2b [Io > 2σ(Io)]
wR2 (all data)
Compound
Formula
[Na(18-crown-6)][BArF]
C44H36BF24NaO6
1150.53
[K([18]aneO2S4)][BArF]
[K([18]aneO4Se2)][BArF]
C88H72B2F48K2O8Se4
2585.11
Monoclinic
P21/c (14)
16.622(3)
13.876(2)
44.516(8)
90
98.567(2)
90
10 153(3)
4
C44H36BF24KO2S4
1230.88
Monoclinic
Cc (15)
22.558(4)
8.9230(14)
25.072(4)
90
99.950(2)
90
4970.8(14)
4
M/g mol−1
Crystal system
Space group (No.)
a/Å
Triclinic
ˉ
P1 (2)
10.495(2)
11.085(2)
21.361(4)
83.314(10)
77.451(8)
79.135(10)
2374.7(8)
2
b/Å
c/Å
α/°
β/°
γ/°
U/Å3
Z
μ(Mo-Kα)/mm−1
F(000)
0.175
1160
0.403
2480
1.668
5120
Total reflections
Unique reflections
Rint
27 127
8375
0.068
1.064
0.099
0.149
0.260
0.303
15 982
5069
0.039
1.043
0.050
0.061
0.123
0.131
58 673
17 383
0.043
1.023
0.065
0.104
0.163
0.193
Goodness-of-fit on F2
R1b [Io > 2σ(Io)]
R1 (all data)
wR2b [Io > 2σ(Io)]
wR2 (all data)
2 1/2
a Common items: T = 100 K; wavelength (Mo-Kα) = 0.71073 Å; θ(max) = 27.5°. b R1 = ∑||Fo| − |Fc||/∑|Fo|; wR2 = [∑w(Fo2 − Fc2)2/∑wFo
]
.
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125.20 (C, q, JC–F = 272 Hz, CF3), 118.08 (CH, septet, 3JC–F = 4.0 white solid, 63%. Required for C44H36BF24LiO2S4 (1198.72): C,
1
Hz, BArF C4), 69.19 (OCH2). 23Na NMR (298 K, CH2Cl2) δ = 44.09; H, 3.03. Found: C, 44.00; H, 2.98%. H NMR (CD2Cl2):
−14.4.
δ = 7.72 ([8H], s, H2/6), 7.57 ([4H], s, H4), 3.70 ([8H], t, J = 5.5
[Li([18]aneO4S2)][BArF]. [Li(thf)4][BArF] (116 mg, 0.1 mmol) Hz, OCH2), 2.90 ([8H], s, SCH2), 2.82 ([8H], t, J = 5.5 Hz, SCH2).
and [18]aneO4S2 (31 mg, 0.1 mmol). Yield: 75 mg of an off- 13C{1H} NMR (CD2Cl2): δ = 162.35 (C, q, JC–B = 49.9 Hz, BArF
white solid, 61%. Required for C44H36BF24LiO4S2 (1166.60): C, C1), 135.39 (CH, BArF C2/6), 129.47 (C, qq, JC–F = 31.6, 2.9 Hz,
2
45.30; H, 3.11. Found: C, 45.26; H, 3.13%. H NMR (CD2Cl2) δ = BArF C3/5), 125.20 (C, q, JC–F = 272 Hz, CF3), 118.07 (CH,
1
7.73 ([8H], s, H2/6), 7.57 ([4H], s, H4), 3.68–3.72 ([16H], m, septet, JC–F = 4.0 Hz, BArF C4), 69.06 (OCH2), 31.54, 31.03
3
OCH2), 2.83 ([8H], t, J = 5.7 Hz, SCH2). 13C{1H} NMR (CD2Cl2): δ = (SCH2). 7Li NMR (298 K, CH2Cl2): δ = +1.85.
162.34 (C, q, JC–B = 49.9 Hz, BArF C1), 135.39 (CH, BArF C2/6),
[Na([18]aneO2S4)][BArF]. Na[BArF]·2thf (100 mg, 0.1 mmol)
and [18]aneO2S4 (33 mg, 0.1 mmol). Yield: 86 mg, 65%.
129.49 (C, qq, 2JC–F = 31.6, 2.9 Hz, BArF C3/5), 125.21 (C, q, JC–F
=
272 Hz, CF3), 118.08 (CH, septet, JC–F = 4.0 Hz, BArF C4), 68.07, Required for C44H36BF24NaO2S4 (1214.76): C, 43.51; H, 2.99.
3
68.04 (OCH2), 32.19 (SCH2). 7Li NMR (298 K, CH2Cl2): δ = +0.07.
Found: C, 43.57; H, 2.87%. 1H NMR (CD2Cl2): δ = 7.72 ([8H], br
[Na([18]aneO4S2)][BArF]. Na[BArF]·2(thf) (100 mg, 0.1 mmol) s, H2/6), 7.57 ([4H], s, H4), 3.74 ([8H], t, J = 6.0 Hz, OCH2), 2.89
and [18]aneO4S2 (31 mg, 0.1 mmol). Yield: 55 mg, 44%. ([8H], s, SCH2), 2.80 ([8H], t, J = 6.0 Hz, SCH2). 13C{1H} NMR
Required for C44H36BF24NaO4S2 (1182.64): C, 44.69; H, 3.07. (CD2Cl2): δ = 162.34 (C, q, JC–B = 49.9 Hz, BArF C1), 135.40 (CH,
Found: C, 44.55; H, 3.01%. 1H NMR (CD2Cl2): δ = 7.72 ([8H], br BArF C2/6), 129.46 (C, qq, JC–F = 31.6, 2.9 Hz, BArF C3/5),
2
3
s, H2/6), 7.57 ([4H], s, H4), 3.68 (m, [16 H], OCH2), 2.84 ([8H], 125.21 (C, q, JC–F = 272 Hz, CF3), 118.07 (CH, septet, JC–F
=
t, J = 5.0 Hz, SCH2). 13C{1H} NMR (CD2Cl2): δ = 162.34 (C, q, JC–B
=
4.0 Hz, BArF C4), 68.87 (OCH2), 31.58, 30.61 (SCH2). 23Na NMR
49.9 Hz, BArF C1), 135.40 (CH, BArF C2/6), 129.48 (C, qq, JC–F (298 K, CH2Cl2): δ = +2.4.
2
= 31.6, 2.9 Hz, BArF C3/5), 125.20 (C, q, JC–F = 272 Hz, CF3),
[K([18]aneO2S4)][BArF]. K[BArF] (45 mg, 0.05 mmol) and
118.08 (CH, septet, JC–F = 4.0 Hz, BArF C4), 69.54, 68.20 [18]aneO4S2 (16 mg, 0.05 mmol). Yield: 41 mg of an off-white
3
(OCH2), 31.75 (SCH2). 23Na NMR (298 K, CH2Cl2): δ = −1.9.
solid, 67%. Required for C44H36BF24KO2S4 (1230.87): C, 42.94;
[K([18]aneO4S2)][BArF]. K[BArF] (45 mg, 0.05 mmol) and H, 2.95. Found: C, 42.86; H, 2.89%. H NMR (CD2Cl2): δ = 7.72
[18]aneO4S2 (15 mg, 0.05 mmol). Yield: 25 mg, 38%. Required ([8H], s, H2/6), 7.57 ([4H], s, H4), 3.72 ([8H], t, J = 5.1 Hz,
for C44H36BF24KO4S2 (1198.75): C, 44.09; H, 3.03. Found: C, OCH2), 2.89 ([8H], s, SCH2), 2.84 ([8H], t, J = 5.1 Hz, SCH2).
1
43.90; H, 3.12%. H NMR (CD2Cl2): δ = 7.72 ([8H], br s, H2/6), 13C{1H} NMR (CD2Cl2): δ = 162.34 (C, q, JC–B = 49.9 Hz, BArF
1
7.57 ([4H], s, H4), 3.65 ([16H], m, OCH2), 2.83, 2.80 (each [4H], C1), 135.41 (CH, BArF C2/6), 129.46 (C, qq, JC–F = 31.6, 2.9 Hz,
2
t, J = 7.0 Hz, SCH2). 13C{1H} NMR (CD2Cl2): δ = 162.34 (C, q, BArF C3/5), 125.20 (C, q, JC–F = 272 Hz, CF3), 118.08 (CH, septet,
JC–B = 49.9 Hz, BArF C1), 135.39 (CH, BArF C2/6), 129.47 (C, qq, 3JC–F = 4.0 Hz, BArF C4), 69.69 (OCH2), 32.94, 32.07 (SCH2).
2JC–F = 31.6, 2.9 Hz, BArF C3/5), 125.20 (C, q, JC–F = 272 Hz,
[Na([18]aneO4Se2)][BArF]. Na[BArF]·2thf (100 mg, 0.1 mmol)
CF3), 118.08 (CH, septet, JC–F = 4.0 Hz, BArF C4), 70.84, 68.93 and [18]aneO4Se2 (38 mg, 0.1 mmol). Yield: 71 mg, 56%.
3
(OCH2), 32.29 (SCH2).
Required for C44H36BF24NaO4Se2 (1276.44): C, 41.40; H, 2.84.
[Rb([18]aneO4S2)][BArF]. Rb[BArF] (95 mg, 0.1 mmol) and Found: C, 41.29; H, 2.74%. 1H NMR (CD2Cl2): δ = 7.72 ([8H], br
[18]aneO4S2 (31 mg, 0.1 mmol). Yield: 97 mg of an off-white s, H2/6), 7.57 ([4H], s, H4), 3.70 ([16H], m, OCH2), 2.86 ([8H], t,
solid, 74%. Required for C44H36BF24O4RbS2 (1245.12): C, J = 6.0 Hz, SeCH2). 13C{1H} NMR (CD2Cl2): δ = 162.35 (C, q, JC–B
42.44; H, 2.91. Found: C, 42.34; H, 2.99%. H NMR (CD2Cl2): = 49.9 Hz, BArF C1), 135.41 (CH, BArF C2/6), 129.49 (C, qq,
1
δ = 7.73 ([8H], s, H2/6), 7.57 ([4H], s, H4), 3.61–3.68 ([16H], m, 2JC–F = 31.6, 2.9 Hz, BArF C3/5), 125.20 (C, q, JC–F = 272 Hz,
OCH2), 2.81 ([8H], t, J = 5.1 Hz, SCH2). 13C{1H} NMR (CD2Cl2): CF3), 118.08 (CH, septet, JC–F = 4.0 Hz, BArF C4), 69.48, 68.54
3
δ = 162.35 (C, q, JC–B = 49.9 Hz, BArF C1), 135.41 (CH, BArF (OCH2), 24.45 (SeCH2). 23Na NMR (298 K, CH2Cl2): δ = +2.3.
C2/6), 129.48 (C, qq, JC–F = 31.6, 2.9 Hz, BArF C3/5), 125.21
[K([18]aneO4Se2)][BArF]. K[BArF] (45 mg, 0.05 mmol) and
2
3
(C, q, JC–F = 272 Hz, CF3), 118.08 (CH, septet, JC–F = 4.0 Hz, [18]aneO4Se2 (19 mg, 0.05 mmol). Yield: 47 mg, 79%. Required
BArF C4), 70.56, 69.33 (OCH2), 32.91 (SCH2).
for C44H36BF24KO4Se2 (1292.55): C, 40.89; H, 2.81. Found: C,
[Cs([18]aneO4S2)][BArF]. Cs[BArF] (100 mg, 0.1 mmol) and 40.93; H, 2.69%. H NMR (CD2Cl2) δ = 7.72 ([8H], br s, H2/6),
[18]aneO4S2 (31 mg, 0.1 mmol). Yield: 91 mg of an off-white 7.57 ([4H], s, H4), 3.74 ([8H], t, J = 6 Hz, OCH2), 2.89 ([8H], s,
solid, 67%. Required for C44H36BCsF24O4S2 (1292.56): C, 40.89; OCH2), 2.80 ([8H], t, J = 6 Hz, SeCH2). 13C{1H} NMR (CD2Cl2):
1
H, 2.81. Found: C, 40.72; H, 2.91%. H NMR (CD2Cl2): δ = 7.72 δ = 162.33 (C, q, JC–B = 49.9 Hz, BArF C1), 135.39 (CH, BArF
1
([8H], s, H2/6), 7.57 ([4H], s, H4), 3.65 ([8H], t, J = 5.1 Hz, C2/6), 129.46 (C, qq, JC–F = 31.6, 2.9 Hz, BArF C3/5), 125.20 (C,
2
OCH2), 3.62 ([8H], s, OCH2), 2.81 ([8H], t, J = 5.1 Hz, SCH2). q, JC–F = 272 Hz, CF3), 118.07 (CH, septet, JC–F = 4.0 Hz, BArF
3
13C{1H} NMR (CD2Cl2): δ = 162.32 (C, q, JC–B = 49.9 Hz, BArF C4), 70.80, 69.89 (OCH2), 24.76 (SeCH2).
C1), 135.36 (CH, BArF C2/6), 129.42 (C, qq, JC–F = 31.6, 2.9 Hz,
2
BArF C3/5), 125.16 (C, q, JC–F = 272 Hz, CF3), 118.05 (CH,
3
septet, JC–F = 4.0 Hz, BArF C4), 69.79, 69.30 (OCH2), 33.03
Results and discussion
(SCH2). 133Cs NMR (298 K, CH2Cl2): δ = +45.2.
[Li([18]aneO2S4)][BArF]. [Li(thf)4][BArF] (116 mg, 0.1 mmol) Coordination of the Group 1 cations to a range of 18-mem-
and [18]aneO2S4 (33 mg, 0.1 mmol). Yield: 75 mg of an off- bered oxa-thia and oxa-selena macrocyclic ligands was
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achieved by the direct reaction of M[BArF] with the appropriate C6H4(PMe2)2}3]+,7 whereas δ23Na for solutions of NaBPh4 with
macrocycle in anhydrous CH2Cl2 solution (Scheme 1). The iso- 15-crown-5 in a variety of O-donor solvents are reported to be
lated complexes are highly soluble in CH2Cl2 and were to low frequency of the reference irrespective of the concen-
obtained in good yield as white powders or colourless crystals. tration of the crown ether.18 The quadrupole moment (Q) for
Their formulations were confirmed by microanalysis, solution the 133Cs nucleus is small, hence NMR spectra are readily
1H, 13C{1H}, 7Li, 23Na and 133Cs NMR spectroscopic data as observed. The 133Cs NMR spectrum recorded for [Cs([18]-
appropriate, and by single crystal X-ray structure analysis. No aneO4S2)][BArF] (CH2Cl2) is a singlet at +45.2 ppm, signifi-
solvent incorporation was evident in any of the products. The cantly to high frequency of the chemical shifts observed for
1H and 13C{1H} NMR spectra confirm a 1 : 1 ratio of the macro- [Cs(crown)]+ (crown = 12-crown-4, 15-crown-5, 18-crown-6) in
cycle and the [BArF]− anion in each case, but were otherwise various solvents,19 whilst [Cs(Me6[18]aneN6)]+ shows a singlet
not very informative.
Lithium-7 NMR spectra recorded for [Li([18]aneO4S2)]+ and in fast relaxation in these low-symmetry environments and no
[Li([18]aneO2S4)]+ each contain
singlet, at +0.07 and resonances were seen. Overall, the spectroscopic data for the
+54 ppm at 298 K.20 The large Q values for 39K and 85Rb result
a
+1.85 ppm respectively, i.e. very small differences from LiCl in complexes reported herein are consistent with coordination of
water (δ = 0). This is not unexpected given the small chemical the macrocycles to the alkali metal cations, the complexes
shift range observed for 7Li (typically ca. 15 ppm).12 For the being dynamic in solution, most likely through ‘ring-whizzing’
sodium complexes, 23Na NMR spectra (CH2Cl2) show a shift of within the complex cations (it is unlikely that the [BArF]−
the resonance to higher frequency as the S/Se donor atoms are coordination is retained in solution). However, these measure-
introduced to the macrocycle (18-crown-6: −14.4 ppm; ments do not provide unequivocal evidence for coordination
[18]aneO4S2: −1.9 ppm; [18]aneO4Se2: +2.3 ppm; [18]aneO2S4: of the soft S or Se donor atoms.
+2.4 ppm). These chemical shifts compare with those for [Na-
([24]aneS8)][BArF] (S8 donor set, δ23Na = +4.0),6 [Na(thf)x][BArF]
X-ray structures and comparisons
(δ23Na = −4.8),16 [Na(Me3tacn)2][BArF] (δ23Na = +6.2; Me3tacn =
The paucity of complexes with thio- or seleno-ether coordi-
nation to a Group 1 cation in the literature means that struc-
tural authentication of the new complexes was essential to
establish their identities. Furthermore, it is difficult to draw
comparisons with other structures, and determining the sig-
nificance of particular metal–ligand interactions is somewhat
uncertain. Table 2 provides the sums of the relevant radii, on
one hand the sum of the ionic radii of the cations and the
covalent radii of the donor atoms (O, S, Se and F) and on the
other the sum of the van der Waals radii for the relevant
metal-donor atom combinations. Distances close to the former
are considered to be ‘normal’ coordinate bonds, while in iden-
tifying weak interactions, for example, between the metal
cation and the CF3 groups from [BArF]− anions, we have
chosen to include any M⋯X distances at least 0.5 Å below the
sum of the van der Waals radii. Although the precise cut-off is
somewhat arbitrary, it seems to be a reasonable basis on
which to describe the overall coordination in these complexes.
It is also pertinent to note that due to the disorder present in
1,4,7-trimethyl-1,4,7-triazacyclononane) and [Na(Me4cyclam)-
(thf)][BArF] (δ23Na = +11.4; Me4cyclem = 1,4,7,10-tetramethyl-
1,4,7,10-tetraazacyclododecane).17 Small positive chemical
shifts were also seen for [Na{Me2P(CH2)2PMe2}3]+ and [Na{o-
Scheme 1 Synthesis of the complexes reported in this work.
Table 2 Sum of the M–X radii for Group 1 cations with various relevant donor atoms
X = O
X = S
X = Se
X = F
∑(ionic +
∑(ionic +
∑(ionic +
∑(ionic +
M–X
cov radii)a
∑(vdW radii)b
cov radii)a
∑(vdW radii)b
cov radii)a
∑(vdW radii)b
cov radii)a
∑(vdW radii)b
M = Lic
M = Nad
M = Kd
1.56
1.98
2.31
2.41
2.54
3.62
4.00
4.23
4.71
4.98
1.95
2.37
2.70
2.80
2.93
4.01
4.39
4.54
5.10
5.37
2.10
2.52
2.85
2.95
3.08
3.94
4.32
4.55
5.03
5.30
1.47
1.89
2.22
2.32
2.45
2.58
3.96
4.19
4.67
4.94
M = Rbd
M = Csd
a Ionic radii of Group 1 cations taken from ref. 21 and covalent radii for ligand donor atoms taken from ref. 22. b van der Waals radii taken from
ref. 23. c Based upon CN = 6. d Based upon CN = 8.
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Fig. 1 The structure of the Li1-centred cation in [Li([18]aneO4S2)][BArF]
with ellipsoids drawn at the 50% probability level. Hydrogen atoms are
omitted for clarity. The Li2 cation adopts a similar geometry, with some
variation in the bond distances and angles. Selected bond lengths (Å)
and angles (°): Li1–O4 = 2.055(12), Li1–O2 = 2.094(12), Li1–O3 =
2.150(13), Li1–O1 = 2.349(13), Li1–S1 = 2.745(12), Li1–S2 = 2.761(11),
O4–Li1–O3 = 78.5(5), O2–Li1–O1 = 75.4(4), O4–Li1–S1 = 81.2(4), O1–
Li1–S1 = 71.7(3), O2–Li1–S2 = 77.7(4), O3–Li1–S2 = 75.2(4), S1–Li1–S2 =
106.2(4).
Fig. 2 The structure of the Li1-centred cation in [Li([18]aneO2S4)][BArF]
with ellipsoids drawn at the 50% probability level. Hydrogen atoms are
omitted for clarity. Selected bond lengths (Å) and angles (°): Li1–O2 =
2.082(18), Li1–O1 = 2.118(18), Li1–S3 = 2.539(16), Li1–S1 = 2.573(16),
Li1–S2 = 2.593(16), Li1–S4 = 2.604(15), O2–Li1–S3 = 80.9(6), O1–Li1–
S1 = 82.1(6), O2–Li1–S2 = 84.2(6), S1–Li1–S2 = 81.5(4), O1–Li1–S4 =
79.9(5), S3–Li1–S4 = 85.6(5).
the CF3 groups of the [BArF]− anions in the structures, while
the gross coordination at the metal and the ligand confor-
mations are secure, care should be exercised in any detailed
analyses of bond lengths and angles.
The crystals of [Na([18]aneO4S2)][BArF] are isomorphous,
but not isostructural, with their direct Li analogue, again with
two crystallographically independent cations (the Na1-centred
one of which is partly disordered, hence the structural descrip-
tion below is concerned with the Na2-centred cation) and two
The crystal structure of [Li([18]aneO4S2)][BArF] comprises
discrete cations (Fig. 1) and anions, with two of each in the
asymmetric unit. Each Li cation is six-coordinate with the
hexadentate macrocycle, leading to a severely distorted octa-
hedral geometry. The Li–O and Li–S bond distances show a
range of values, with d(Li–O) = 2.055(12) to 2.349(13) Å and
d(Li–S) = 2.724(11) to 2.788(11) Å. The angles, S1–Li1–S2 =
106.2(4)° and S3–Li2–S4 = 111.3(4)°, whilst the angles involved
in the five-membered chelate rings all vary between ∼70–80°,
indicating a significant degree of distortion from a regular
octahedron. The irregularity of the coordination may in part
reflect the poor size match of the 18-membered ring for the
small Li+ centre, coupled with the packing of the large [BArF]−
anions around the cations in the crystal lattice.
Substituting two further S donor atoms into the macrocyclic
ring, as in [Li([18]aneO2S4)][BArF], also leads to a structure
comprising of discrete cations and anions, with three crystallo-
graphically independent, but structurally similar, variants of
each in the asymmetric unit. Each Li is six-coordinate, encap-
sulated by the macrocycle which is folded to accommodate a
distorted octahedral geometry at lithium (Fig. 2). The distor-
tion from ideal octahedral is significantly less than in the
[18]aneO4S2 analogue above, and the conformation of the co-
ordinated macrocycle has the –S(CH2)2O(CH2)2S– linkages
occupying meridional coordination sites, placing the CCOC
torsion angles anti. The Li–O and Li–S distances vary between
the different cations, and are ∼2.1 Å and ∼2.6 Å, respectively.
The latter appear to be slightly shorter than those in [Li([18]-
aneO4S2)]+ above.
Fig. 3 The structure of the Na2-centred cation in [Na([18]aneO4S2)]-
[BArF] showing the interaction to a fluoride from the anion, with ellip-
soids drawn at the 50% probability level. Hydrogen atoms are omitted
for clarity. Selected bond lengths (Å) and angles (°): Na2–O5 = 2.389(4),
Na2–O6
= 2.355(4), Na2–O7 = 2.394(4), Na2–O8 = 2.395(4),
Na2⋯F26i = 3.306(3), Na2–S3 = 2.849(2), Na2–S4 = 2.890(2), O6–Na2–
O5 = 71.64(12), O7–Na2–O8 = 71.55(12), O5–Na2–S3 = 72.14(10), O8–
Na2–S3 = 73.73(10), O6–Na2–S4 = 73.64(10), O7–Na2–S4 = 70.74(9),
S3–Na2–S4 129.77(8). Symmetry operation: (i) −1 + x, −1 + y, z.
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anions in the asymmetric unit. In this case, the Na-macrocycle
coordination is quite similar to that in the Li analogue, with
d(Na–O) in the range 2.355(4)–2.395(4)
Å and d(Na2–S)
(2.849(2) and 2.890(2) Å) all somewhat elongated. This is a con-
sequence of the larger ionic radius of the Na+ centre, hence
the ligand is less puckered, and the angles involved in the five-
membered chelate rings span a narrower range (∼71–74°),
with <S3–Na2–S4 = 129.77(8)°. Notably in this species there is
an additional weak interaction to one F atom derived from a
CF3 group in the anion, Na2⋯F26i = 3.306(3) Å (Fig. 3), leading
to overall seven-coordination at the sodium centre through
weakly associated ion pairs.
[Na([18]aneO4Se2)][BArF] crystallises with three crystallogra-
phically distinct cations (the Na3-centred cation shows some
disorder and is therefore excluded from the structural descrip-
tion) and three [BArF]− anions in the asymmetric unit. The
Na1 centre is seven-coordinate through a puckered hexaden-
tate macrocycle and one long, weak Na⋯F interaction (this is
of borderline significance based on our criteria stated above;
however the corresponding distances in the Na2 and Na3-
centred cations are slightly shorter) (Fig. 4), with a near planar
O3Se donor set and the remaining donor atoms above and
below that plane. Similar coordination environments are
Fig. 4 The structure of the Na1-centred cation in [Na([18]aneO4Se2)]-
[BArF] showing the interaction to fluoride from the anion, with ellipsoids
drawn at the 50% probability level. Hydrogen atoms are omitted for
clarity. Selected bond lengths (Å) and angles (°): Na1–O3 = 2.332(7),
Na1–O1 = 2.380(7), Na1–O4 = 2.393(6), Na1–O2 = 2.396(7), Na1–Se1 =
2.942(3), Na1–Se2
= 2.967(3), Na1⋯F5 = 3.501(6), O3–Na1–O4 =
72.3(2), O1–Na1–O2 = 71.9(2), O1–Na1–Se1 = 74.90(18), O4–Na1–Se1 =
73.16(17), O3–Na1–Se2 = 74.54(17), O2–Na1–Se2 = 71.74(16), Se1–Na1–
Se(2) = 121.13(13).
Fig. 5 (a) The structure of the centrosymmetric Na1-centred cation in [Na([18]aneO2S4)][BArF] showing the interactions to fluorides from the
anions, with ellipsoids drawn at the 50% probability level. The other crystallographically independent cation adopts a similar structure. Hydrogen
atoms are omitted for clarity. Selected bond lengths (Å) and angles (°): Na1⋯F1 = 2.8766(13), Na1–O1 = 2.5526(13), Na1–S1 = 2.8823(6), Na1–S2 =
3.0718(7), O1–Na1–S1 = 67.26(3), O1–Na1–S2 = 66.22(3), S1i–Na1–S2 = 69.427(14), S1–Na1–S2i = 69.426(14). Symmetry operation: (i) 0.5 − x, 0.5 −
y, 1 − z. (b) View of a portion of the polymeric chain with the [BArF]− anions greyed out for clarity. Colour key: gold = Na, yellow = S, red = O, green
= F, black = C.
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present in the other cations, although there is a spread of bond There are two 50% occupancy (centrosymmetric) Na environ-
distances, d(Na–O) = 2.315(7)–2.479(7), d(Na–Se) = 2.942(2)– ments in the asymmetric unit, one of which (Na2-centred
2.986(4) Å. The latter are in line with the increased covalent cation) shows severe rotational disorder of the macrocycle,
radius of Se over S; otherwise the Na coordination environments while the other refines much better and is therefore the focus
are very similar to [Na([18]aneO4S2)][BArF] above.
of the structural description and illustrated in Fig. 6a and b.
The structure of [Na([18]aneO2S4)][BArF] is markedly The crown ether provides hexagonal planar coordination at
different from its Li analogue above. It crystallises as a 1D Na, with irregular Na–O bond distances spanning >0.3 Å, and
chain polymer, with the Na in an eight-coordinate environ- with a slightly puckered conformation as expected (<O–Na–O
ment (Fig. 5a), and only one centrosymmetric cation and one ∼ 62–65°), with two axial Na⋯F interactions (2.435(4) Å),
anion (with crystallographic 2-fold symmetry) in the asym- similar motifs are evident in other salts containing the
metric unit. The macrocycle adopts a chair conformation with sodium-18-crown-6 cation.1 The Na⋯F distances are very
all four S atoms coordinated and the S4 donor set planar, much shorter than in the mixed donor macrocyclic cations
d(Na–S) = 2.8823(6), 3.0718(7) Å, with the two oxygen atoms described above.
above and below that plane, d(Na–O) = 2.5526(13) Å. Two weak
[K([18]aneO2S4)][BArF] is isostructural and isomorphous
Na⋯F interactions (2.8766(13) Å) from bridging [BArF]− anions with [Na([18]aneO2S4)][BArF] described above, hence also
on opposite sides of the macrocycle give a distorted dodeca- forming a chain polymer with the K+ in an eight-coordinate
hedral geometry overall at sodium, and give rise to the poly- environment via the O2S4 donor set from the hexadentate
meric chain structure (Fig. 5b).
macrocycle (endocyclic) and weak axial interactions to CF3
To provide a benchmark comparison for the mixed donor groups from the bridging [BArF]− anions (Fig. 7). All of the
macrocyclic complexes in this work, we also prepared and bond distances at K1 are elongated by ca. 0.1 Å compared to
determined the structure of [Na(18-crown-6)][BArF]. The struc- the Na analogue. This is less than expected based purely on
ture also shows a 1D chain polymer with eight-coordinate Na. the difference in the ionic radii of the metal ions (0.33 Å for
Fig. 6 (a) View of the structure around Na1 of the centrosymmetric [Na(18-crown-6)][BArF], with ellipsoids drawn at the 50% probability level. The
second crystallographically independent cation in the asymmetric unit contains a disordered 18-crown-6, but is otherwise similar. Hydrogen atoms
are omitted for clarity. Selected bond lengths (Å) and angles (°): Na1–O1 = 2.804(4), Na1–O2 = 2.489(4), Na1–O3 = 2.605(4), Na1⋯F1 = 2.435(4).
Symmetry operation: (i) 2 − x, 2 − y, −z. (b) View of a portion of the polymeric chain formed through the bridging [BArF]− anions with the [BArF]−
anions greyed out for clarity. Colour key: gold = Na, red = O, green = F, black = C.
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CN = 8), possibly reflecting a better size match between K+ and
the [18]aneO2S4 binding cavity (although caution is required to
avoid over-interpretation of such differences given that there is
some disorder in the anion).
The structure of [K([18]aneO4S2)][BArF] is formed of a 1D
chain polymer with three crystallographically independent
cations in the asymmetric unit (as well as three [BArF]−
anions). The K centres are eight-coordinate, through hexaden-
tate endocyclic coordination of the macrocycle, with d(K–O) ∼
2.7 Å and d(K–S) ∼ 3.2 Å, with two quite short K–F interactions
(each ∼2.7 Å) completing the coordination environment (Fig. 8).
The centrosymmetric K1- and K3-centred cations have signifi-
cant K⋯F interactions on opposite sides of the macrocycle,
while in the K2-centred cation the K⋯F interactions lie mutually
cis, and <S3–K2–S2 = 154.90(6)°. Some puckering of the rings is
evident from the angles subtended at K, which are all ∼64°.
[K([18]aneO4Se2)][BArF] (Fig. 9) is isomorphous and iso-
structural with the tetraoxa-dithia analogue, and presents the
first known complex containing potassium–selenoether coordi-
nation, d(K–Se) ca. 3.3 Å.
Fig. 7 View of the structure of the K1-centred cation in [K([18]-
aneO2S4)][BArF] showing the interactions to fluoride from the anions,
with ellipsoids drawn at the 50% probability level. Hydrogen atoms are
omitted for clarity. Selected bond lengths (Å) and angles (°): K1–O1 =
2.6253(18), K1⋯F7 = 2.9589(19), K1–S1 = 3.0445(8), K1–S2 = 3.1399(8),
O1–K1–S1 = 65.74(4), O1–K1–S2 = 65.98(4), S1i–K1–S2 = 68.880(19).
Symmetry operation: (i) −0.5 − x, 0.5 − y, −z.
Fig. 8 The structures of (a) the K1-centred cation and (b) the K2-centred cation in the asymmetric unit of [K([18]aneO4S2)][BArF], showing the inter-
action to fluoride from the anions, with ellipsoids drawn at the 50% probability level. The K3-centred cation is very similar to the K1-centred cation.
Hydrogen atoms are omitted for clarity. The macrocycle around K1 is disordered positionally (up/down) around O2 with an occupancy split of
roughly 3 : 2; the major component is shown. Selected bond lengths (Å) and angles (°): K1–F1 = 2.744(3), K1–S1 = 3.2161(12), K1–O1 = 2.703(3), K1–
O2A = 2.706(7), K2–F7 = 2.690(6), K2–F25 = 2.733(3), K2–S2 = 3.2119(15), K2–S3 = 3.2075(16), K2–O5 = 2.709(3), K2–O3 = 2.731(3), K2–O4 =
2.744(3), K2–O6 = 2.750(3), S3–K2–S2 = 154.90(6). Symmetry operation: (i) 1 − x, 1 − y, −z. (c) View of a portion of the polymer chain with the
[BArF]− anions greyed out for clarity. Colour key: blue = K, yellow = S, red = O, green = F, black = C.
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Fig. 9 The structures of the K1- and K2-centred cations in the asymmetric unit for [K([18]aneO4Se2)][BArF] showing the interactions to fluoride from
the anions, with ellipsoids drawn at the 50% probability level. The K3-centred cation is very similar to the former. Hydrogen atoms are omitted for
clarity. Selected bond lengths (Å): K1–O1 = 2.663(4), K1–O2 = 2.686(4), K1–F1 = 2.714(4), K1–Se1 = 3.3123(7), K2–O3 = 2.712(5), K2–O4 = 2.734(4),
K2–O5 = 2.642(17), K2–O6 = 2.757(5), K2⋯F7 = 3.040(9), K2–F25 = 2.674(8), K2–Se2 = 3.3065(13), K2–Se3 = 3.307(4). Symmetry code: (i) −x, −y,
1 − z.
The structure of [Rb([18]aneO4S2)][BArF] is also a 1D both 8-coordinate. The macrocycle donor set is closer to
chain polymer, very similar to the K analogue, with the planar than in the K analogue.
macrocycle hexadentate in each form of the cation, d(Rb–S)
Finally, the structure of [Cs([18]aneO4S2)][BArF] (Fig. 11)
∼ 3.3 Å (Fig. 10), although the crystal is not isomorphous. shows one cation and one anion in the asymmetric unit, and
All the Rb–F distances are comparable to the Rb–O dis- forms a 2D sheet polymer. The hexadentate macrocycle
tances, indicating significant interactions that lie well within occupies one face of the Cs+ cation (Cs–S ∼ 3.5 Å), with four
the sum of vdW radii. The geometry at Rb1 is higher than CF3 groups (each from a different [BArF]− anion) also co-
in the K analogue, as there are now three CF3 groups inter- ordinated through the other face, although the precise coordi-
acting with the Rb centre which appears to be ten-coordi- nation at Cs cannot be confirmed due to disorder of the CF3
nate.
The
Rb2
(and
Rb3:
two
half-occupancy groups. There is also one longer Cs⋯F interaction through the
centrosymmetric Rb centres in the asymmetric unit) are centre of the macrocycle of ∼4.2 Å.
Fig. 10 The structures of the two independent cations in [Rb([18]aneO4S2)][BArF] showing the interactions to fluoride from the anions, with ellip-
soids drawn at the 50% probability level. Hydrogen atoms are omitted for clarity. Selected bond lengths (Å) and angles (°): Rb1–O1 = 2.944(3), Rb1–
O2 = 3.026(3), Rb1–O3 = 2.981(3), Rb1–O4 = 3.030(7), Rb1–S1 = 3.35564(12), Rb1–S2 = 3.2897(13), Rb1⋯F7 = 2.965(3), Rb1⋯F8 = 3.269(2),
Rb1⋯F37 = 3.249(2), Rb1⋯F44 = 3.269(2), Rb2–O5 = 2.901(3), Rb2–O6 = 2.907(2), Rb2–S3 = 3.2690(12), Rb2⋯F23 = 2.818(7); O1–Rb1–O2 =
56.42(7), S2–Rb1–S1 = 146.62(3), O2–Rb1–S2 = 58.98(6), O3–Rb1–O4 = 57.34(14), O4–Rb1–S1 = 58.25(14), O1–Rb1–S1 = 57.99(6), O3–Rb1–S2 =
58.10(6), O5–Rb2–O6 = 59.10(8), O5–Rb2–S3 = 62.33(6), O6–Rb2–S3i = 61.72(6). Symmetry operation: (i) 1 − x, 1 − y, −z.
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nation numbers are observed in all of the other cations; Na:
CN = 7 or 8; K: CN = 8; Rb: CN = 9; Cs: CN = 8 or 10.
Although unexpected, these M–S/Se interactions clearly
make a favourable contribution to the stability of the cations
since other conformations of the macrocycles with O-only
coordination are possible.1
Acknowledgements
We thank the EPSRC for supporting the SCFED project
through a Programme Grant (EP/I033394/1). The SCFED
Project (http://www.scfed.net) is a multidisciplinary collabor-
ation of British universities investigating the fundamental and
applied aspects of supercritical fluids.
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Fig. 11 The structure of the cation in [Cs([18]aneO4S2)][BArF] showing
the interactions to fluoride from the anions, with ellipsoids drawn at the
50% probability level. Hydrogen atoms are omitted for clarity. Selected
bond lengths (Å) and angles (°): Cs1–O1 = 3.374(7), Cs1–O2 = 3.068(9),
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