Lanthanide Structures, Coordination, and Extraction Investigations of a 1,3-Bis(diethyl amide)-Substituted Calix[4]arene Ligand

Article abstract of DOI:10.1021/ic9512441

The synthesis and structure determinations of lanthanum, samarium, ytterbium, and lutetium complexes of 5,11,17,23-tetra-tert-butyl-25,27-bis((diethylcarbamoyl)methoxy)-26,28- dihydroxycalix[4]arene (L) are described. The four structures display similar characteristics with the trivalent lanthanide cation being encapsulated in an eight-coordinate oxygen environment, consisting of six oxygens from the calixarene, a water molecule, and unidentate picrate for lanthanum [La(L-2H)(picrate)(H₂O)]; and bidentate chelating picrate for the other lanthanides [Ln(L-2H)(picrate)]Ln = Sm, Yb, Lu. Under optimised experimental conditions solvent extraction investigations showed the calix[4]arene ligand L exhibited generally very high percentage extractabilities of lanthanide cations into dichloromethane, presumably on account of the ligand's unique lower rim oxygen containing coordination sphere and its lipophilic exterior.

Full text of DOI:10.1021/ic9512441

2202
Inorg. Chem. 1996, 35, 2202-2211
Lanthanide Structures, Coordination, and Extraction Investigations of a
1,3-Bis(diethyl amide)-Substituted Calix[4]arene Ligand
Paul D. Beer,*,† Michael G. B. Drew,*,‡ Mark Kan,§ Philip B. Leeson,‡ Mark I. Ogden,† and
Gareth Williams§
Inorganic Chemistry Laboratory, University of Oxford, South Parks Road, Oxford OX1 3QR, U.K.,
Department of Chemistry, University of Reading, Whiteknights, Reading RG6 2AD, U.K., and
Analytical Chemistry Branch, AWE plc, Aldermaston, Reading RG7 4PR, U.K.
ReceiVed September 26, 1995X
The synthesis and structure determinations of lanthanum, samarium, ytterbium, and lutetium complexes of
5,11,17,23-tetra-tert-butyl-25,27-bis((diethylcarbamoyl)methoxy)-26,28-dihydroxycalix[4]arene (L) are described.
The four structures display similar characteristics with the trivalent lanthanide cation being encapsulated in an
eight-coordinate oxygen environment, consisting of six oxygens from the calixarene, a water molecule, and
unidentate picrate for lanthanum [La(L-2H)(picrate)(H2O)]; and bidentate chelating picrate for the other lanthanides
[Ln(L-2H)(picrate)]Ln ) Sm, Yb, Lu. Under optimised experimental conditions solvent extraction investigations
showed the calix[4]arene ligand L exhibited generally very high percentage extractabilities of lanthanide cations
into dichloromethane, presumably on account of the ligand’s unique lower rim oxygen containing coordination
sphere and its lipophilic exterior.
Introduction
In spite of this variety of, in particular, hard donor group
substituted calix[4]arene based ligands there have been relatively
few reports detailing their potential to coordinate the trivalent
lanthanide cations. The coordination properties of the parent
calixarenes towards the lanthanides have been investigated in
detail by most notably Harrowfield and co-workers.12 Sparse
instances with modified calixarenes can be found with lower
rim tetrasubstituted calix[4]arenes containing tertiary amide
groups,13 2,2-bipyridyls,14 and mixed lower rim trisubstituted
carboxylic acids-mono amide calix[4]arenes15 which encap-
sulate and shield lanthanide ions from solvent molecules. None
of these latter reports however describe any solid state lan-
thanide-calixarene structural investigations or extraction studies.
Extraction studies of lanthanides have been reviewed re-
cently,16 and work covering a range of macrocycles is described
including calixarenes. However it is reported that while the
few results obtained so far indicate a generally high stability
for complexes with lanthanides, data are still scarce but a great
number of possible derivatives have not yet been tested.
The calix[4]arene macrocyclic structural framework1,2 has
been shown to be an attractive building block which can be
selectively functionalized both at the hydroxyl lower rim3 and
at the upper rim4 para positions of the phenol aryl moieties for
the coordination of neutral,1 cationic2 and, more recently, anionic
guest species.5 Focussing on metal cations for example,
additional donor groups such as esters,2,6 amides,2,6 carboxylic
acids,2,7 crown ethers,8 and spherands9 have been appended to
the lower rim for the complexation of alkali and alkaline earth
metal cations, whereas pendent phosphino-,10 bipyridyl-,11 and
thioether-2,3 substituted calix[4]arenes have been shown to
coordinate transition metals.
† Inorganic Chemistry Laboratory, University of Oxford.
‡ Department of Chemistry, University of Reading.
§ Analytical Chemistry Branch, Aldermaston.
X Abstract published in AdVance ACS Abstracts, March 15, 1996.
(1) (a) Gutsche, C. D. In Calixarenes, Monographs in Supramolecular
Chemistry; Stoddart, J. F. Ed.; The Royal Society of Chemistry:
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1992, 57, 4527.
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M.; Ferguson, G.; Harns, S. J. J. Chem. Soc., Perkin Trans. 1. 1991,
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Inorg. Chem. 1992, 31, 4213. (c) Loeber, C.; Matt, M.; DeCian, A.;
Fischer, J. J. Organomet. Chem. 1994, 475, 297.
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9917. (b) Regnouf de Vains, J.-B.; Lamartine, R. HelV. Chim. Acta
1994, 77, 1817. (c) Beer, P. D.; Chen, Z.; Goulden, A. J.; Grive, A.;
Hesek, D.; Szemes, F.; Wear, T. J. Chem. Soc., Chem. Commun. 1994,
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J.; Stokes, S. E. J. Chem. Soc., Chem. Commun. 1993, 229. (b) Xu,
W.; Vittal, J. J.; Puddephatt, R. J. Am. Chem. Soc. 1993, 115, 6456.
(c) Morzherin, Y.; Rudkevich, D. M.; Verboom, W.; Reinhoudt, D.
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A.; Schwing-Weill, M.-J.; Schwinte´, P. Inorg. Chem. 1993, 32, 2644.
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Leonard, R. G.; McKervey, M. A.; Owens, M.; Tabatabai, M.;
Vierengel, A.; Voyt, W. J. Chem. Soc., Perkin Trans. 2 1992, 1595.
(8) (a) Ghidini, E.; Vgozzoli, F.; Ungaro, R.; Harkenna, S.; El-Fodl, A.-
A.; Reinhoudt, D. N. J. Am. Chem. Soc. 1990, 112, 6979. (b) Brzozka,
Z.; Lammerink, B.; Reinhoudt, D. N.; Ghidini, E.; Ungaro, R. J. Chem.
Soc., Perkin Trans. 2 1993, 1037.
(12) (a) Bu¨nzli, J.-C. G.; Harrowfield, J. M. In Calixarenes, a Versatile
Class of Macrocyclic Compounds; Bo¨hmer, V., Vicens, J., Eds.;
Kluwer: Dordrecht, The Netherlands, 1991; p 211. (b) Harrowfield,
J. M.; Ogden, M. I.; Richmond, W. R.; White, A. H. J. Chem. Soc.,
Dalton Trans. 1991, 2153. (c) Bunzli, J.-C. G.; Proideraux, P.;
Harrowfield, J. M. Inorg. Chem. 1993, 32, 3306.
(13) Sabbatini, N.; Guardigli, M.; Mecati, A.; Balzani, V.; Ungaro, R.;
Ghidini, E.; Casnati, A.; Pochini, A. J. Chem. Soc., Chem. Commun.
1990, 878.
(14) Sabbatini, N.; Guardigli, M.; Mannet, I.; Ungaro, R.; Casnati, A.;
Ziessel, R.; Ulrich, G.; Asfari, Z.; Lehn, J.-M. Pure Appl. Chem. 1995,
67, 135.
(15) Rudkevich, D.; Verboom, W.; van der Tol, E.; van Staveren, C. J.;
Kaspersen, F. M.; Verhoeven, J. W.; Reinhoudt, D. N. J. Chem. Soc.,
Perkin Trans. 2 1995, 131.
(9) Dijkstra, P. J.; Brunink, J. A. J.; Bugge, K.-E.; Harkenna, S.; Ungaro,
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(16) Arnaud-Neu, F., Chem. Soc. ReV. 1994, 235 and references therein.
0020-1669/96/1335-2202$12.00/0 © 1996 American Chemical Society

Lanthanide Structures
Inorganic Chemistry, Vol. 35, No. 8, 1996 2203
Table 1. Crystal Data and Structure Refinement for 1-4
1
2
3
4
formula
[La(L-2H)(picrate)H2O)]‚
3MeCN‚CH2Cl2
C69H91Cl2N8O14La
1466.31
[Sm(L-2H)(picrate)],
EtOH
C64H84N5O14Sm
1265.14
[Yb(L-2H)(picrate)]‚
3CH2Cl2
C65H86Cl6N5O14Yb
1547.13
[Lu(L-2H)(picrate)]‚
CH2Cl2‚EtOH‚H2O
C65H90Cl2N5O15Lu
1427.27
empirical formula
fw
T (K)
293(2)
0.71070
triclinic
P1h (No. 2)
293(2) K
293(2)
0.71070
triclinic
P1h (No. 2)
293(2)
0.71070
triclinic
P1h (No. 2)
wavelength (Å)
cryst syst
space group
Unit cell dimens (Å)
a (Å)
b (Å)
c (Å)
0.71070 A
monoclinic
C2/c
12.631(8)
17.464(9)
17.881(8)
76.61(1)
85.16(1)
72.77(1)
3664.3
30.459(8)
12.702(6)
40.757(12)
(90)
112.00(1)
(90)
14620(9)
8
1.150
13.949(7)
14.876(7)
18.020(7)
87.56(1)
80.97(1)
72.16(1)
3515(3)
2
14.147(7)
15.040(7)
18.524(7)
89.08(1)
81.13(1)
72.32(1)
3708.3
R (deg)
â (deg)
γ (deg)
V (Å3)
Z
2
2
D (calcd) (Mg/m3)
1.329
0.720
1528
1.431
1.603
1546
1.276
1.464
1473
abs coeff (mm-1
F(000)
)
0.860
5416
cryst size (mm)
θ range for data
collcn (deg)
0.35 * 0.35 * 0.20
2.86-24.99
0.35 * 0.30 * 0.25
2.56-25.07
0.3 * 0.3 * 0.3
1.78-25.15
0.3 * 0.3 * 0.3
2.79-24.88
index ranges
0 e h e 14
-19 e k e 20
-20 e l e 20
9936
0 e h e 36
0 e h e 16
-16 e k e 17
-21 e l e 21
11298
0 e h e 16
-16 e k e 17
-21 e l e 21
11564
-13 e k e 13
-48 e l e 44
19109
11220/744 [R(int) )
0.0453]
no. of indep reflcns
data/params
9936/809
11298/795
11564/63/786
goodness-of-fit on F2
0.574
0.950
0.687
1.127
final R indices [I > 2σ(I)]a
R1 ) 0.0743,
wR2 ) 0.1675
R1 ) 0.1160,
wR2 ) 0.3686
1.542 and -1.287
R1 ) 0.0869,
wR2 ) 0.219
R1 ) 0.1234,
wR2 ) 0.2702
1.851 and -0.761
R1 ) 0.0849,
wR2 ) 0.2436
R1 ) 0.1406,
wR2 ) 0.3086
2.276 and -2.449
R1 ) 0.0932,
wR2 ) 0.1930
R1 ) 0.1222,
wR2 ) 0.2072
1.417 and -1.989
R indices (all data)
largest diff peak and
hole (e Å-3
)
2
2
a R1 ) ∑(|Fo| - |Fc|)/∑|Fo|], wR2 ) [∑[w(Fo - Fc2)2)/∑[w(Fo )2]1/2
.
which was filtered and left to evaporate. The product usually
precipitated as large dark brown rhombs, with occasional formation of
fine needles (presumably due to subtle changes in the reaction
conditions). Microanalytical results suggested that the composition of
the product is the same in each case, but the fine needles were not
appropriate for crystallographic studies, and hence the product was
recrystallized from dichloromethane/ethanol to form the larger crys-
tals when necessary. For X-ray diffraction studies, crystals were
kept wet with supernatant solution. Crystals collected in the labora-
tory atmosphere, washed with ethanol, and dried by vacuum desicca-
tion became opaque. Microanalyses were consistent with loss of
solvent relative to the stoichiometries implied by the structure
determinations.
We report here one such study describing the synthesis and
structure determinations of lanthanum, samarium, ytterbium, and
lutetium complexes of a 1,3-bis(diethyl amide)-substituted calix-
[4]arene ligand L and in addition this ligand’s noteworthy
lanthanide solvent extraction capabilities.
Microanalysis. (1) [La(L-2H)(picrate)(H2O)]‚H2O, (Found: C,
58.5; H, 6.28; N, 5.48. Calcd for C62H82LaN5O15: C, 58.4; H, 6.48;
N. 5.49.)
(2) [Sm(L-2H)(picrate)] (Found: C, 59.4; H, 6.33; N, 5.52. Calcd
for C62H78N5O13Sm: C, 59.5; H, 6.28; N, 5.59).
(3) [Yb(L-2H)(picrate)]‚H2O (Found: C, 57.7; H, 5.97; N, 5.24.
Calcd for C62H80N5O14Yb: C, 57.6; H, 6.24; N. 5.42).
L
Experimental Section
(4) [Lu(L-2H)(picrate) (Found: C, 58.1; H, 6.15; N, 5.51. Calcd
for C62H78LuN5O13: C, 58.3; H, 6.16; N. 5.49).
Synthesis. 5,11,17,23-Tetra-tert-butyl-25,27-bis((diethylcarbamoyl)-
methoxy)-26,28-dihydroxycalix[4]arene3 (L), and the lanthanide picrate
dodecahydrates17 were synthesised by literature methods. Lanthanide
analyses were performed on a ThermoElectron AtomScan 25 sequential
ICP-AES.
Synthesis of Ln(L-2H)(picrate)‚xH2O. A solution of Ln-
(picrate)3.12H2O (0.025 mmol) in ethanol (1.5 mL) was added to a
solution of the calixarene L (0.023 mmol) in dichloromethane (1.5 mL).
Triethylamine (0.02 mL) was then added, to give a dark brown solution,
X-ray Crystallography. Crystals were prepared as described above
and loaded in thin-walled capillaries. Crystals were found to decompose
rapidly in the absence of solvent and so the appropriate solvent was
also included within the capillaries. Crystal data are given in Table 1,
together with refinement details. Data for all four crystals [La(L-2H)-
(picrate)(H2O)]‚3MeCN. CH2Cl2 (1), [Sm(L-2H)(picrate)]‚EtOH (2),
[Yb(L-2H)(picrate)]‚3CH2Cl2‚H2O (3), [Lu(L-2H)(picrate)]‚CH2Cl2‚
EtOH‚2H2O (4) were collected with Mo KR radiation using the
MARresearch image plate system. The crystals were positioned at 75
mm from the image plate. A total of 95 frames were measured at 2°
intervals with a counting time of 2 min. Data analysis was carried out
(17) Harrowfield, J. M.; Lu, W. M.; Skelton, B. W.; White, A. H. Aust. J.
Chem. 1994, 47, 321.

2204 Inorganic Chemistry, Vol. 35, No. 8, 1996
Beer et al.
U(eq)a
Table 2. Atomic coordinates (×104) and Equivalent Isotropic Displacement Parameters (Å2 × 103) for 1a
x
y
z
U(eq)a
x
y
z
La
1447(1)
1632(14)
1954(12)
2977(16)
3787(15)
3502(15)
2455(17)
4392(13)
4535(12)
5343(14)
5512(15)
4789(16)
3988(13)
3871(12)
3224(12)
2211(11)
2286(18)
1378(15)
517(14)
2889(1)
3958(10)
3859(11)
3515(12)
3150(11)
3256(11)
3707(11)
2820(11)
1907(9)
1426(10)
555(12)
275(12)
738(12)
1577(10)
361(10)
397(8)
3463(1)
1030(9)
284(10)
124(11)
53(1)
48(4)
56(4)
66(5)
60(5)
58(4)
64(5)
57(4)
43(3)
66(5)
70(5)
67(5)
56(4)
50(4)
52(4)
45(4)
66(5)
53(4)
53(4)
55(4)
53(4)
51(4)
50(4)
63(5)
58(4)
56(4)
56(5)
55(4)
63(5)
55(3)
63(5)
66(5)
78(4)
77(5)
102(8)
142(14)
102(8)
215(24)
65(3)
54(3)
65(5)
45(4)
73(4)
63(4)
73(5)
111(10)
104(9)
C(358)
O(450)
C(100)
C(101)
C(102)
C(103)
C(200)
C(201)
C(202)
C(203)
C(300)
C(301)
C(302)
C(303)
C(400)
C(401)
C(402)
C(403)
W(1)
-2612(23)
482(10)
2528(18)
2989(7)
3445(13)
4025(16)
3703(17)
2592(15)
7(13)
5478(24)
2445(7)
141(14)
57(3)
73(5)
101(8)
91(7)
C(11)
C(12)
C(13)
C(14)
C(15)
C(16)
C(17)
C(21)
C(22)
C(23)
C(24)
C(25)
C(26)
C(27)
C(31)
C(32)
C(33)
C(34)
C(35)
C(36)
C(37)
C(41)
C(42)
C(43)
C(44)
C(45)
C(46)
C(47)
O(150)
C(151)
C(152)
O(153)
N(154)
C(155)
C(156)
C(157)
C(158)
O(250)
O(350)
C(351)
C(352)
O(353)
N(354)
C(355)
C(356)
C(357)
3397(17)
4067(23)
2355(19)
4024(24)
6430(20)
7244(25)
5883(45)
6827(56)
1592(16)
1665(32)
2600(23)
689(26)
-2209(20)
-2724(29)
-3060(29)
-1528(30)
47(14)
1850(16)
2451(21)
3516(19)
4166(20)
3911(15)
2951(18)
2316(21)
3759(21)
3079(23)
4701(28)
4654(19)
5460(19)
4469(23)
1197(27)
464(24)
1238(24)
1916(24)
2619(28)
3721(32)
7683(28)
7190(18)
6593(19)
-113(30)
-346(24)
-669(30)
2262(22)
1672(28)
1417(28)
-767(11)
-1045(15)
-1264(12)
-815(14)
1582(16)
1171(26)
849(37)
1985(28)
1568(11)
2027(15)
1072(16)
1037(24)
-48(10)
-24(18)
-255(26)
-747(17)
3519(11)
4844(9)
5345(12)
5639(12)
6079(10)
6369(11)
6182(11)
5699(12)
5381(14)
5333(16)
5097(22)
6873(15)
7092(14)
7083(16)
5513(19)
5333(35)
5606(13)
5489(17)
5861(19)
6238(23)
2933(21)
3442(12)
2851(12)
2618(21)
2417(17)
2191(21)
1118(16)
406(22)
652(10)
1410(11)
1560(10)
2044(11)
2240(8)
1836(13)
1998(12)
2544(12)
2924(10)
2751(10)
3479(10)
3049(10)
2557(11)
2095(9)
2116(11)
2614(10)
3112(11)
2584(10)
1912(10)
1253(11)
658(11)
108(9)
101(10)
171(19)
302(45)
397(66)
69(5)
132(13)
101(8)
199(25)
78(7)
125(12)
222(27)
191(22)
104(5)
107(6)
102(10)
76(6)
386(23)
18(49)
-765(25)
-636(12)
-1474(14)
-664(16)
-380(23)
3350(13)
2656(15)
4133(31)
3464(28)
4334(9)
2390(12)
2494(20)
1860(14)
1962(13)
2671(15)
3252(14)
3155(13)
1071(17)
745(14)
-84(11)
-23(9)
593(9)
369(14)
1116(10)
978(10)
1828(9)
2515(9)
2607(11)
3246(11)
3806(11)
3722(9)
3073(11)
4326(11)
3841(6)
4482(10)
4334(12)
3799(9)
4815(11)
5439(15)
6286(19)
4721(15)
4114(33)
2077(7)
1482(7)
1189(11)
1899(10)
2614(8)
1802(9)
1008(12)
863(16)
2522(14)
O(50)
C(51)
C(52)
C(53)
C(54)
C(55)
C(56)
1219(13)
-688(13)
-771(13)
-1401(14)
-1521(14)
-941(13)
-257(12)
-143(12)
421(14)
2206(10)
2644(15)
2824(16)
2571(13)
3357(15)
3806(27)
2864(33)
3486(26)
4599(36)
3060(9)
74(6)
71(6)
75(6)
84(7)
651(11)
1230(12)
1868(10)
1215(12)
2316(7)
2444(11)
3254(12)
3725(8)
3463(10)
2951(15)
2833(19)
4325(15)
4590(24)
3109(8)
3649(7)
4347(11)
4668(9)
4228(8)
5326(9)
5862(12)
6404(15)
5595(16)
N(520)
O(521)
O(522)
N(540)
O(541)
O(542)
N(560)
O(561)
O(562)
N(700)
C(701)
C(702)
C(800)
Cl(01)
Cl(02)
N(900)
C(901)
C(902)
N(903)
C(904)
C(905)
107(7)
145(8)
204(14)
104(7)
145(9)
159(10)
143(11)
340(35)
154(10)
132(9)
114(9)
163(14)
131(11)
280(9)
297(10)
172(13)
107(8)
140(12)
121(8)
122(10)
121(10)
906(17)
2755(15)
2181(16)
3365(18)
3748(17)
3635(18)
4456(15)
-819(17)
-1014(19)
-1341(25)
3949(21)
4621(14)
3502(14)
5919(24)
6570(20)
7417(22)
1721(17)
1781(20)
1776(20)
1039(9)
516(16)
-111(12)
-282(12)
-602(13)
-335(19)
551(27)
-1347(22)
-96(20)
a U(eq) is defined as one-third of the trace of the orthogonalized Uij tensor.
with the XDS program.18 The positions of the heavy atoms in 1, 2,
and 4 were determined using direct methods with the Shelx86 pro-
gram19 and the remaining atoms were located via Fourier methods. 3
(M ) Yb) was found to be isomorphous with 4 (M ) Lu), and input
coordinates were therefore taken from the refined structure of 4. All
of Reading. Atomic coordinates in the four structures are given in
Table 2-5 inclusive. Dimensions in the metal coordination spheres
are compared in Table 6. Data for three similar compounds with
different lanthanides were also measured. M ) Er, Tm were found to
be isomorphous with 3 and 4 and M ) Pr with 2 but structural details
are not reported here.25
structures exhibited features of disorder, particularly in the tert-butyl
groups at the top of the calix[4]arene cavity and in addition showed a
variety of solvent molecules. All ordered non-hydrogen atoms in the
complexes were refined with anisotropic thermal parameters. When
the tert-butyl groups were disordered, which was often, two sets of
constrained tetrahedra were refined with occupancies that added
up to 1.0. High thermal parameters were obtained for the amide ethyl
groups at the bottom of the cone and for some nitro groups. Disordered
models were tried but with few exceptions they did not give any
significantly better fits. Solvent molecules, of which there were many,
were included with isotropic thermal parameters. Hydrogen atoms were
included in geometric positions (methyls as rigid groups) with thermal
parameters equivalent to 1.2 times the atom to which they were bonded.
The structures were then refined using Shelxl.20 Neither absorption
nor extinction corrections were carried out. All calculations were
carried out on a Silicon Graphics R4000 Workstation at the University
Extraction Experiments. Standard lanthanide solutions were made
from high purity lanthanide carbonates (99.99%) dissolved in nitric
acid. Picric acid was introduced to obtain stock source phase solutions
containing 0.4 mM lanthanide and 9.6 mM picrate. The aqueous
solution was altered to the required pH with lithium hydroxide solution.
The pH was maintained at 5.8 ( 0.3 in these experiments. The
extractant solvent phase was produced by dissolving the calixarene L
in dichloromethane to a concentration of 9.6 mM. Thus, the ratio of
lanthanide:picrate:L was 1:25:25.
Equal volumes (10 mL) of each solution were mixed in a sealed
flask, and stirred rapidly for 1 h at 22 °C, after which the mixture was
transferred to a separating flask and allowed to settle for 3 h. The
aqueous layer was removed and the lanthanide concentration deter-
mined.
(18) Kabsch, W. J. Appl. Crystallogr. 1988, 21, 916.
(19) Shelx86. Sheldrick, G. M. Acta Crystallogr. 1990, A46, 467.
(20) Sheldrick, G. M. Shelxl. Package for crystal structure refinement,
University of Gottingen, 1993.

Lanthanide Structures
Inorganic Chemistry, Vol. 35, No. 8, 1996 2205
Table 3. Atomic Coordinates (×104) and Equivalent Isotropic Displacement Parameters (Å2 × 103) for 2
x
y
z
U(eq)b
x
y
z
U(eq)b
Sm(1)
C(11)
C(12)
C(13)
C(14)
C(15)
C(16)
C(17)
C(21)
C(22)
C(23)
C(24)
C(25)
C(26)
C(27)
C(31)
C(32)
C(33)
C(34)
C(35)
C(36)
C(37)
C(41)
C(42)
C(43)
C(44)
C(45)
C(46)
C(47)
C(100)
C(101)
C(102)
C(103)
C(200)
C(201)a
C(202)a
C(203)a
C(204)a
C(205)a
C(206)a
C(300)
C(301)a
C(302)a
C(303)a
C(304)a
C(305)a
C(306)a
2729(1)
2173(3)
1794(3)
1683(4)
1973(4)
2372(3)
2461(3)
2673(3)
2406(3)
2264(3)
1981(4)
1880(4)
2029(3)
2293(4)
1894(4)
1529(3)
1086(4)
741(4)
3121(1)
5129(7)
5220(7)
4454(9)
3615(8)
3493(7)
4253(7)
2505(7)
1551(7)
811(7)
-84(8)
-179(7)
554(7)
1415(7)
451(7)
1276(8)
1220(8)
1984(10)
2797(8)
2906(7)
2109(7)
3870(8)
4826(7)
5538(8)
6385(8)
6513(8)
5844(7)
4989(7)
5920(7)
4583(10)
5324(22)
3611(17)
4946(23)
-832(9)
-1164(27)
-1636(19)
-254(23)
-1924(13)
-692(22)
-966(28)
1920(11)
2851(24)
877(26)
2205(37)
1276(32)
1130(38)
2851(32)
1607(1)
743(2)
434(2)
174(2)
228(2)
533(2)
784(2)
579(2)
608(2)
345(2)
354(3)
659(2)
934(2)
37(1)
35(2)
42(2)
49(3)
46(2)
38(2)
33(2)
40(2)
36(2)
44(2)
52(3)
48(2)
41(2)
44(2)
45(2)
42(2)
51(3)
65(3)
50(2)
42(2)
38(2)
46(2)
38(2)
47(2)
47(2)
48(2)
35(2)
35(2)
37(2)
C(400)
C(401)
C(402)
C(403)
O(250)
O(450)
O(150)
C(151)
C(152)
O(153)
N(154)
C(155)
C(156)a
C(159)a
C(157)
C(158)
O(350)
C(351)
C(352)
O(353)
N(354)
C(355)
C(356)
C(357)
C(358)
C(51)
C(52)
C(53)
C(54)
C(55)
C(56)
O(50)
N(520)
O(521)
O(522)
N(540)
O(541)
O(542)
N(560)
O(561)a
O(562)a
O(563)a
O(564)a
C(500)
C(501)
O(502)
649(4)
272(7)
419(10)
773(8)
7134(10)
6917(17)
6970(29)
8190(15)
2110(5)
4327(5)
4122(4)
4621(7)
4656(8)
4380(5)
4961(8)
5063(19)
6182(23)
4020(44)
5230(11)
4323(15)
2196(5)
1816(8)
2289(9)
3008(5)
1926(8)
984(4)
1121(7)
609(6)
70(3)
164(11)
266(23)
264(22)
46(2)
38(1)
36(1)
39(2)
44(2)
45(2)
66(3)
127(7)
131(14)
190(22)
81(4)
127(7)
41(2)
46(2)
52(3)
45(2)
61(2)
94(5)
95(11)
67(3)
96(5)
85(4)
66(3)
85(4)
111(6)
108(6)
108(6)
73(2)
1076(11)
1166(2)
1492(2)
1108(1)
1141(2)
1530(3)
1744(2)
1630(3)
2003(5)
2136(11)
2133(15)
1372(4)
1275(6)
1732(2)
2068(2)
2318(2)
2216(2)
2646(2)
2892(3)
2826(6)
2771(3)
2953(4)
1748(3)
1476(3)
1303(4)
1398(5)
1675(5)
1837(5)
1881(2)
1383(3)
1474(2)
1202(3)
1209(6)
1353(5)
1008(5)
2134(5)
2374(7)
2027(7)
2381(10)
2111(18)
3022(14)
3124(13)
2904(12)
2442(2)
2196(2)
2841(2)
3259(3)
3557(3)
3375(2)
4006(3)
4290(6)
4266(15)
4432(20)
4227(5)
4462(6)
2080(2)
2131(3)
2577(4)
2779(2)
2754(3)
3194(5)
3613(8)
2541(5)
2229(6)
3224(6)
3422(5)
3473(6)
3361(7)
3201(6)
3156(7)
3130(3)
3594(4)
3490(3)
3844(5)
3407(8)
3363(7)
3584(7)
2970(8)
3174(9)
2597(10)
3225(12)
2628(20)
4039(19)
4213(17)
4165(15)
911(2)
1246(2)
1239(2)
985(3)
949(3)
867(3)
1182(3)
1443(2)
1474(2)
1669(2)
1468(2)
1342(2)
1133(2)
1052(3)
1167(2)
1377(2)
1030(2)
-160(3)
-392(5)
-375(5)
-82(5)
74(3)
-73(9)
101(7)
-263(6)
216(7)
-224(5)
-78(8)
663(4)
1303(3)
1625(3)
1417(4)
1441(3)
1065(3)
1066(4)
1465(4)
1849(3)
1833(3)
2232(3)
1247(4)
1350(8)
1118(7)
845(7)
1822(4)
2198(10)
1458(9)
1493(10)
1981(11)
1986(10)
1295(5)
252(5)
2346(15)
1873(29)
1055(10)
1458(13)
690(10)
679(9)
-203(10)
-1146(11)
-1246(12)
-331(12)
1474(6)
1634(8)
2479(6)
65(3)
210(15)
166(11)
189(13)
77(4)
103(10)
77(7)
93(9)
107(11)
86(8)
140(14)
88(5)
87(9)
99(10)
133(14)
120(12)
144(15)
122(13)
72(3)
69(2)
1607(8)
124(5)
158(7)
187(7)
192(7)
140(6)
133(9)
138(9)
188(14)
387(42)
176(21)
144(16)
214(17)
-2103(16)
-2900(16)
-2053(14)
-456(18)
-20(24)
-846(24)
-898(31)
-71(62)
5104(43)
5754(41)
6695(35)
193(12)
104(12)
-146(15)
272(14)
-23(15)
-4(15)
424(8)
521(9)
820(11)
347(10)
801(12)
547(12)
a Occupation factor of 0.50. b See footnote a in Table 2.
Results and Discussion
O(350) and two from the amide oxygen atoms O(153), O(353)
are all available for bond formation. These six oxygen atoms
can bind smaller transition metal ions and indeed the structure
of [Fe(L-2H)]+ has been determined.21 Here the metal is six-
coordinate with Fe(III)-O bonds ranging from 1.89-2.21 Å.
However the metal is in an ideal trigonal prismatic environment
with the four oxygen atoms O(150), O(250), O(350), and O(450)
forming a rectangular plane and atoms O(153) and O(353) the
remaining edge. Our molecular mechanics calculations21 show
that this donor set cannot provide an octahedral environment
as is favored by the majority of transition metals because these
four oxygen atoms at the lower rim of the substituted calix[4]-
arene {O(n50), (n ) 1,4)} are perforce nearly planar, and this
clearly prevents formation of complexes with these metals.
As shown by the present structures, it is possible to expand
the donor set to 8 and provide a suitable environment for the
larger lanthanide metals. In the case of La (1), the extra donor
atoms are a water molecule and the O- of a picrate anion but
for Sm (2), Yb (3), and Lu (4), these extra atoms are provided
The lanthanum, samarium, ytterbium, and lutetium complexes
of L were prepared via the addition of the respective lanthanide
picrate dodecahydrate17 in ethanol to a dichloromethane solution
of the calixarene L3 in the presence of triethylamine. Slow
evaporation of the solvent led to the precipitation of the
lanthanide complexes whose microanalytical results suggested
the general formulation [Ln(L-2H) (picrate)]‚xH2O. (See
Experimental Section.) Crystals suitable for X-ray structural
determinations were grown from dichloromethane/ethanol sol-
vent mixtures. The four structures all contain discrete mole-
cules of the metal complexed with calix[4]arenediamide together
with solvent molecules. The common numbering scheme is
shown in Charts 1 and 2.
The metal complexes in structures 1-4 are illustrated in
Figures 1-4 together with the common numbering system. The
structures have very similar features showing an eight-coordinate
lanthanide encapsulated within the calix[4]arenediamide which
has the cone conformation. In this conformation the six oxygen
atoms in the lower rim, two from the anionic O- moities O(250)
and O(450), two from the ethereal oxygen atoms O(150) and
(21) Beer, P. D.; Drew, M. G. B.; Leeson, P. B.; Ogden, M. I. J. Chem.
Soc., Dalton Trans. 1995, 1273.

2206 Inorganic Chemistry, Vol. 35, No. 8, 1996
Beer et al.
Table 4. Atomic Coordinates (×104) and Equivalent Isotropic Displacement Parameters (Å2 × 103) for 3
x
y
z
U(eq)b
x
y
z
U(eq)b
Yb(1)
C(11)
C(12)
C(13)
C(14)
C(15)
C(16)
C(17)
C(21)
C(22)
C(23)
C(24)
C(25)
C(26)
C(27)
C(31)
C(32)
C(33)
C(34)
C(35)
C(36)
C(37)
C(41)
C(42)
C(43)
C(44)
C(45)
C(46)
C(47)
C(100)
C(101)
C(102)
C(103)
C(200)
C(201)
C(202)
C(203)
C(300)
C(301)a
C(302)a
C(303)a
C(304)a
C(305)a
C(306)a
C(400)
C(401)a
C(402)a
C(403)a
C(404)a
C(405)a
1338(1)
-112(8)
1931(1)
559(6)
520(7)
535(8)
609(8)
617(8)
556(7)
731(8)
2643(1)
1460(6)
1253(7)
1764(7)
2501(6)
2738(6)
2216(6)
3569(7)
3859(6)
4367(7)
4678(7)
4451(7)
3964(6)
3647(6)
3760(8)
2975(7)
2799(9)
2080(9)
1529(8)
1687(8)
2383(7)
1036(7)
616(7)
39(1)
31(2)
39(2)
44(3)
44(3)
41(3)
36(2)
46(3)
42(3)
52(3)
54(3)
56(3)
46(3)
42(3)
53(3)
49(3)
59(4)
56(3)
52(3)
46(3)
41(3)
44(3)
41(3)
44(3)
49(3)
40(2)
35(2)
36(2)
36(2)
52(3)
90(6)
92(6)
115(8)
79(5)
207(19)
196(19)
321(39)
76(5)
89(11)
139(19)
119(15)
69(8)
100(12)
115(14)
54(3)
59(7)
76(9)
78(9)
91(11)
84(10)
C(406)a
O(150)
C(151)
C(152)
O(153)
N(154)
C(155)
C(156)
C(157)
C(158)
O(250)
O(350)
C(351)
C(352)
O(353)
N(354)
C(355)
C(356)
C(357)
C(358)
O(450)
C(51)
C(52)
C(53)
C(54)
C(55)
C(56)
O(50)
N(520)
O(521)
O(522)
N(540)
O(541)
O(542)
N(560)
O(561)
O(562)
C(1)
Cl(2)
Cl(3)
C(4)
Cl(5)
277(27)
876(5)
1618(8)
2625(8)
2649(5)
2124(25)
554(5)
-352(7)
-165(8)
634(5)
-1784(20)
2435(4)
2373(6)
2278(7)
2309(5)
2191(7)
2120(11)
1324(11)
2152(11)
2916(13)
1546(5)
2579(5)
2623(8)
2561(6)
2381(5)
2706(8)
2931(13)
2334(16)
2663(12)
3416(11)
3174(5)
4412(7)
4711(7)
5363(7)
5758(7)
5549(8)
4924(8)
3778(4)
4361(6)
3719(5)
4710(6)
6397(7)
6578(7)
6709(6)
4724(8)
4507(14)
4756(17)
1981(9)
2626(3)
1091(4)
617(18)
250(8)
80(9)
37(2)
38(2)
41(3)
42(2)
58(3)
77(5)
101(7)
74(5)
116(8)
45(2)
41(2)
46(3)
40(2)
46(2)
66(3)
89(6)
134(9)
83(6)
113(8)
57(2)
54(3)
51(3)
51(3)
58(3)
75(5)
63(4)
51(2)
55(3)
60(2)
75(3)
73(4)
99(4)
99(4)
78(4)
187(11)
189(11)
74(4)
-1009(8)
-1822(8)
-1747(9)
-868(9)
3450(8)
-877(7)
-1849(10)
-2149(14)
-715(11)
-661(17)
2124(5)
3606(5)
4116(7)
3419(8)
2595(5)
3665(8)
4608(11)
5101(17)
2942(12)
2412(15)
2218(6)
2389(10)
1670(9)
1757(10)
2607(11)
3259(11)
3146(10)
2403(6)
796(8)
-38(8)
3425(12)
3714(15)
4420(10)
4685(17)
1058(6)
778(6)
1462(9)
2493(9)
2614(6)
3262(8)
3183(13)
3644(20)
4253(10)
4277(18)
-86(7)
1200(10)
823(10)
145(9)
-152(11)
270(14)
952(12)
1701(7)
-845(10)
-1361(8)
-2240(10)
-2731(10)
-2259(10)
-1387(9)
-949(9)
1711(8)
1925(9)
2814(10)
3466(9)
3319(8)
2419(8)
4044(9)
4393(8)
4970(9)
5289(8)
4944(8)
4351(7)
4122(7)
3947(8)
3168(7)
3331(8)
2608(9)
1751(8)
1579(7)
2293(7)
617(7)
-890(10)
-963(10)
-1853(10)
-1968(10)
-1148(10)
-234(9)
-155(8)
587(9)
448(9)
40(10)
-101(9)
143(9)
510(8)
679(8)
-37(7)
-431(8)
-127(6)
531(6)
920(6)
865(6)
763(8)
1190(9)
1602(8)
-2775(9)
-3697(11)
-2682(13)
-2849(15)
-3717(13)
-3718(26)
-4517(16)
-3925(38)
-2958(12)
-3787(31)
-3088(48)
-2970(40)
-2836(25)
-3815(33)
-3475(38)
-514(11)
-744(23)
176(26)
436(9)
1517(8)
1975(11)
1529(13)
713(11)
5258(10)
5807(17)
4820(17)
5538(28)
1907(11)
2213(24)
2292(35)
1144(28)
1719(19)
2551(25)
1435(28)
-1178(7)
-1490(16)
-1733(19)
-1042(21)
-1410(23)
-1118(21)
708(6)
112(7)
993(13)
-615(12)
705(20)
3002(12)
3628(27)
3501(31)
2229(20)
5990(11)
5616(30)
6869(41)
6160(37)
6938(22)
6225(32)
5541(35)
2802(10)
2026(20)
3100(25)
3719(24)
3714(27)
2470(26)
1057(10)
-912(11)
-1226(11)
-1208(10)
1477(14)
1039(19)
2289(17)
-2078(13)
-3137(5)
-2321(6)
3287(25)
4089(12)
3784(12)
3551(49)
2516(17)
3497(17)
2935(30)
3350(38)
-4307(25)
2729(11)
2078(11)
3465(10)
3852(11)
4586(15)
3682(14)
2920(12)
3200(4)
3092(5)
1978(21)
992(11)
2859(11)
1327(46)
1371(16)
470(16)
1926(27)
313(36)
4480(24)
108(2)
129(2)
111(9)
192(5)
198(5)
215(23)
179(7)
189(8)
158(11)
202(17)
258(15)
Cl(6)
C(7)
586(9)
5454(37)
6268(12)
4921(14)
6108(22)
5632(29)
-135(19)
Cl(8)a
Cl(9)a
Cl(8A)a
Cl(9A)a
OW1
-1572(28)
-864(32)
-1442(28)
a Population factors 0.50. b See footnote a in Table 2.
by a picrate anion chelating in a bidentate fashion. This is also
true for the isomorphous Er, Tm, and Pr structures. It is likely
to be significant that the largest of the metals, La, has the unique
structure with a water molecule in the coordination sphere. As
a consequence the geometry of the coordination sphere is
different from the others. The structures in 2-4 are all similar
indicating that this arrangement is stable over a wide range of
metal sizes from the small Yb to the large Sm and the even
larger Pr. Taking into account the range of metals studied and
the lanthanide radii,26 it can be suggested that all lanthanides
except for La and possibly Ce will have the bidentate picrate
structure.
Dimensions of the coordination spheres in 1-4 are compared
in Table 6 and the conformations of the molecules are described
by least-squares plane calculations in Table 7. All four
structures have similar features. It is usual to describe the cone
formation of the calix[4]arene with reference to the plane of
four methylene carbon atoms C(17), C(27), C(37), and C(47).
The angles of intersection with the four phenyl rings are shown
in Table 7. In all structures, rings 1 and 3, which have the
amide groups substituted at the oxygen atoms at the bottom of
the cone, are more nearly perpendicular to the methylene plane
than rings 2 and 4 which are unsubstituted. Thus the cone
conformation has C2 symmetry rather than the C4 symmetry
often found for the unsubstituted calix[4]arene. The four oxygen
atoms at the bottom of the cone O(150), O(250), O(350), and
O(450) which are all bonded to the metal atom form a plane
that is approximately parallel to the methylene plane. The other
four donor atoms O(153), O(353), O(50), and O(521) (for
structure 1) also form a plane on the other side of the metal
which is also approximately parallel to the methylene plane and
also the other four oxygen plane. This results in an ap-
proximately square antiprismatic donor set for the metal atom.
This is apparent from Figure 4, which is a view of 2 down the
cone axis. Despite these similarities the structure of 1 is
significantly different from those of 2-4 and this is illustrated
in Figure 5(a,b). The main features of the structure are similar
but the position of the picrate is very different and this results

Lanthanide Structures
Inorganic Chemistry, Vol. 35, No. 8, 1996 2207
Table 5. Atomic Coordinates (×104) and Equivalent Isotropic Displacement Parameters (Å2 × 103) for 4
x
y
z
U(eq)
x
y
z
U(eq)
Lu(1)
C(11)
C(12)
C(13)
C(14)
C(15)
C(16)
C(17)
C(21)
C(22)
C(23)
C(24)
C(25)
C(26)
C(27)
C(31)
C(32)
C(33)
C(34)
C(35)
C(36)
C(37)
C(41)
C(42)
C(43)
C(44)
C(45)
C(46)
1355(1)
-79(7)
-976(7)
-1794(7)
-1708(8)
-843(7)
-15(7)
-827(8)
-1335(7)
-2214(8)
-2676(8)
-2210(9)
-1343(7)
-904(7)
-848(8)
-931(8)
-1836(8)
-1990(8)
-1179(8)
-261(7)
-148(7)
565(8)
1931(1)
538(6)
499(7)
489(7)
549(7)
594(6)
531(6)
707(7)
2650(1)
1487(5)
1287(6)
1782(6)
2511(6)
2754(5)
2213(5)
3558(6)
3870(6)
4372(6)
4695(6)
4491(7)
3987(6)
3671(6)
3810(6)
3039(6)
2889(7)
2199(8)
1633(7)
1759(6)
2462(6)
1110(6)
693(6)
32(1)
27(2)
33(2)
35(2)
38(2)
30(2)
27(2)
36(2)
35(2)
45(3)
48(3)
50(3)
37(2)
34(2)
45(3)
37(2)
48(3)
53(3)
45(3)
37(2)
33(2)
38(2)
32(2)
39(3)
37(2)
34(2)
27(2)
31(2)
32(2)
50(3)
89(6)
101(7)
98(6)
69(4)
102(5)
102(5)
102(5)
102(5)
102(5)
102(5)
75(4)
105(5)
105(5)
105(5)
105(5)
105(5)
105(5)
51(3)
74(3)
C(402)a
C(403)a
C(404)a
C(405)a
C(406)a
O(150)
C(151)
C(152)
O(153)
N(154)
C(155)
C(156)
C(157)
C(158)
O(350)
C(351)
C(352)
O(353)
N(354)
C(355)
C(356)
C(357)
C(358)
O(250)
O(450)
C(51)
108(16)
-1590(14)
-911(25)
201(21)
-1477(20)
895(4)
1617(7)
2624(7)
2669(5)
3448(6)
4415(9)
4616(13)
3454(8)
3751(14)
802(4)
1468(7)
2512(8)
2624(5)
3273(6)
4253(8)
4340(13)
3194(10)
3583(16)
-80(5)
3179(16)
3667(14)
3786(15)
2196(21)
2378(23)
532(4)
-362(6)
-179(7)
624(4)
-1609(11)
-884(13)
-1275(17)
-1676(13)
-981(18)
2435(4)
2385(6)
2336(6)
2344(4)
2256(6)
2266(9)
3009(11)
2198(9)
1430(12)
2614(4)
2677(7)
2598(6)
2416(4)
2748(6)
2713(9)
3414(10)
2981(10)
2424(12)
3200(4)
1594(4)
4409(7)
4713(6)
5365(6)
5764(6)
5562(8)
4925(7)
3781(4)
4356(6)
6426(6)
4719(8)
3718(5)
4684(5)
6743(6)
6622(6)
4521(10)
4820(17)
2053(10)
1172(3)
2703(3)
538(18)
479(29)
364(20)
6189(13)
4980(15)
74(3)
74(3)
74(3)
74(3)
74(3)
28(2)
32(2)
36(2)
35(2)
48(3)
64(4)
104(7)
63(4)
110(7)
32(2)
40(3)
38(2)
35(2)
50(3)
68(4)
103(6)
70(4)
108(7)
43(2)
34(2)
44(3)
43(3)
48(3)
50(3)
66(4)
49(3)
47(2)
52(3)
67(3)
77(4)
56(2)
75(3)
92(4)
99(4)
158(8)
227(14)
77(5)
134(2)
103(2)
141(11)
140(17)
91(10)
201(9)
245(11)
1688(7)
1906(9)
2783(8)
3454(8)
3281(7)
2391(7)
4033(7)
4386(7)
4976(7)
5309(7)
4959(7)
4361(7)
4135(6)
3975(7)
3190(6)
3335(7)
2638(7)
1752(7)
1568(6)
2294(6)
603(6)
-905(6)
-737(9)
-605(15)
-1876(7)
-2244(13)
3603(4)
4136(7)
3397(8)
2593(4)
3690(7)
2973(10)
2474(14)
4631(9)
5158(13)
2213(5)
2124(5)
2377(8)
1673(8)
1774(9)
2588(9)
3279(10)
3152(8)
2384(6)
757(7)
417(7)
12(8)
-162(7)
120(7)
523(6)
667(7)
759(7)
57(6)
-347(6)
1048(5)
1242(8)
849(9)
196(9)
-55(9)
-56(6)
587(5)
C(52)
C(53)
C(54)
C(55)
C(56)
O(50)
965(6)
891(6)
1538(6)
2028(9)
1604(11)
748(7)
C(47)
C(100)
C(101)
C(102)
C(103)
C(200)
C(201)a
C(202)a
C(203)a
C(204)a
C(205)a
C(206)a
C(300)
C(301)a
C(302)a
C(303)a
C(305)a
C(306)a
C(304)a
C(400)
C(401)a
-2741(8)
-3667(8)
-2702(12)
-2811(11)
-3650(10)
-3527(22)
-4072(21)
-4451(18)
-3500(29)
-4526(20)
-3815(30)
-2966(9)
-2794(23)
-3416(22)
-3777(19)
-3120(20)
-2921(20)
-3853(11)
-599(9)
-798(19)
365(8)
378(11)
1024(9)
1722(6)
1198(8)
-805(9)
1541(13)
1625(7)
1054(9)
-1059(9)
-1144(10)
1084(16)
2345(15)
-2093(11)
-2375(6)
-3110(4)
3909(26)
3501(40)
4095(28)
2612(18)
3543(22)
971(11)
-651(9)
614(14)
3003(9)
3394(21)
2187(17)
3781(18)
2208(24)
3034(32)
3915(21)
6039(9)
6909(16)
5593(21)
6199(22)
6913(12)
6320(20)
5661(18)
2822(7)
2006(13)
N(520)
N(540)
N(560)
O(521)
O(522)
O(541)
O(542)
O(561)
O(562)
C(60)
Cl(61)
Cl(62)
O(601)
C(602)
C(603)
OW1
5247(7)
5951(11)
5351(16)
4890(15)
5813(18)
4880(20)
5671(21)
2088(7)
1793(18)
1500(16)
2762(14)
2571(16)
1289(10)
2307(19)
-1054(6)
-1352(12)
2731(9)
3853(9)
676(6)
95(7)
3492(8)
2103(9)
4577(13)
3694(12)
2930(9)
3088(5)
3172(4)
2786(24)
2034(35)
978(24)
1380(16)
517(20)
OW2
a Population parameters 0.50. b See footnote a in Table 2.
in distortions elsewhere. For example in 1 the four angles
O(450)-La-O(153), O(450)-La-O(353), O(250)-La-O(153),
and O(250)-La-O(353) are 130.9(4), 84.0(4), 86.8(5) and
134.0(4)°, respectively, while in 4 they are 93.8(3), 91.9(3),
135.4(3), and 140.5(3)°, respectively (2 and 3 are similar to
(4).
However, the bond length distribution is similar in the four
structures, taking into account the differences in atomic radii.
In this discussion we will quote values for 4 (M ) Lu) although
all values are given in Table 7. Values for 3 (M ) Yb) are
very similar but slightly shorter as befits an atomic radii only
0.05 Å less. Values for M ) Sm are from 0.04 to 0.17 Å longer
and for M ) La up to 0.30 Å longer, consistent with the increase
in atomic radii. The shortest bonds are to the negatively charged
O- atoms at the bottom of the calix[4]arene rim (Lu-O(250)
2.048(7), 2.066(6) Å). A search of structures in the Cambridge
Crystallographic database indicate that these distances are among
the shortest lanthanide to oxygen bond lengths known. It is
interesting that the C(n6)-O(n50)-Lu angles are all close to
180° indicating that the excess electron density from the negative
charge is located trans to the C-O bond. The next shortest
bonds are to the two amide oxygen atoms, Lu-O(153) )
2.266(7), 2.287(7) Å. Here the C(n52)-O(n53)-Lu angles are
ca. 120°. The bonds to the ethereal oxygens at the bottom of
the calix[4]arene rim are ca. 0.1 Å longer at Lu-O(150) )
2.439(6) Å, and Lu-O(350) ) 2.399(6) Å. The coordination
sphere is completed by the picrate ion which is bonded to the
metal in a bidentate fashion via the anionic oxygen O(50) at
2.391 (8) and a nitro oxygen O(521) at 2.702 (9) Å. As
expected27 the bond to the O- ion is significantly shorter than
to the nitro oxygen atom.
The arrangement of the picrate anion in 3 (M ) Yb) and 4
(M ) Sm) is similar. However in 1, the picrate is bonded via
the anionic O- (La-O(50) ) 2.46(2) Å) and the coordina-
tion sphere is completed by a water molecule (La-W(1) )
2.636(14) Å).
The geometry of the coordination spheres of 2-4 is very
similar with all angles within 8°. The stability of this arrange-
ment is striking with similar coordination sphere pertaining

2208 Inorganic Chemistry, Vol. 35, No. 8, 1996
Beer et al.
Table 6. Bond Lengths (Å) and Angles (deg) in the Metal
Coordination Spheres
M ) La
M ) Sm M ) Yb M ) Lu
M-O(250)
M-O(450)
M-O(353)
M-O(153)
M-O(150)
M-O(350)
M-O(50)
M-O(521)
M-W(1)
O(250)-M-O(450) 97.3(5)
O(250)-M-O(153) 86.8(5)
O(450)-M-O(153) 130.9(4)
O(250)-M-O(353) 134.0(4)
O(450)-M-O(353) 84.0(4)
O(153)-M-O(353) 126.3(5)
2.247(12) 2.114(6) 2.066(8) 2.048(7)
2.220(11) 2.153(6) 1.991(9) 2.066(6)
2.585(14) 2.430(6) 2.241(7) 2.287(7)
2.560(14) 2.434(6) 2.267(8) 2.266(6)
2.631(11) 2.468(6) 2.388(7) 2.439(7)
2.600(10) 2.511(6) 2.375(7) 2.399(6)
2.46(2)
2.529(8) 2.366(7) 2.381(5)
2.697(9) 2.592(9) 2.702(8)
2.636(14)
102.0(2) 99.6(4)
129.5(3) 136.7(3) 135.4(2)
93.5(2) 90.7(3) 93.8(3)
132.8(2) 140.7(3) 140.5(3)
99.3(3)
91.0(2)
84.0(2)
81.1(3)
90.6(3)
80.4(3)
85.2(4)
91.8(3)
80.7(2)
84.5(3)
O(250)-M-O(50)
O(450)-M-O(50)
O(153)-M-O(50)
O(353)-M-O(50)
93.3(6)
151.2(5)
76.2(5)
69.5(5)
155.1(3) 154.1(3) 155.0(3)
103.5(3) 103.2(3) 100.7(3)
70.0(2)
77.3(2)
77.9(2)
Figure 1. Structure of [La(L-2H)(picrate)(H2O)] (1). Thermal ellipsoids
are shown at 45% probability. For clarity, the hydrogen atoms not
included.
70.8(3)
79.0(3)
79.2(3)
70.8(3)
79.7(2)
78.8(2)
O(250)-M-O(350) 77.2(4)
O(450)-M-O(350) 74.4(4)
O(153)-M-O(350) 134.6(4)
O(353)-M-O(350) 58.7(4)
153.1(2) 144.3(3) 144.9(2)
61.2(3)
78.8(3)
76.0(2)
77.6(2)
60.9(2)
65.7(3)
76.8(3)
76.1(3)
78.5(3)
64.9(2)
65.5(2)
77.6(3)
75.8(2)
79.1(2)
65.1(2)
O(50)-M-O(350)
81.9(5)
O(250)-M-O(150) 75.1(4)
O(450)-M-O(150) 74.3(4)
O(153)-M-O(150) 59.6(4)
O(353)-M-O(150) 146.4(4)
151.1(2) 143.2(3) 143.7(2)
126.7(2) 127.2(3) 125.5(2)
138.7(2) 143.2(3) 143.6(2)
O(50)-M-O(150)
134.5(5)
O(350)-M-O(150) 134.6(4)
O(250)-M-O(521)
O(450)-M-O(521)
O(153)-M-O(521)
O(353)-M-O(521)
O(560)-M-O(521)
O(350)-M-O(521)
O(150)-M-O(521)
76.0(3)
143.8(3) 143.5(3) 143.4(2)
64.1(2) 67.8(3) 66.0(2)
117.2(3) 113.1(3) 112.9(2)
61.2(3) 62.4(3) 61.5(3)
134.5(2) 135.1(3) 135.2(2)
66.8(2) 65.8(3) 65.0(2)
79.8(3)
78.8(3)
O(450)-M-W(1)
O(250)-M-W(1)
O(50)-M-W(1)
O(153)-M-W(1)
O(353)-M-W(1)
O(350)-M-W(1)
O(150)-M-W(1)
84.0(5)
152.8(5)
98.5(6)
72.5(6)
73.2(5)
128.6(5)
79.2(5)
Figure 2. Structure of [Sm(L-2H)(picrate)] (2). Thermal ellipsoids
are shown at 45% probability. For clarity, the hydrogen atoms are not
included.
throughout all lanthanides despite variations in atomic radii over
a range of 0.3 Å.
It is interesting that in 2-4, the bidentate picrate anion is
closely parallel to phenyl ring 2. This is apparent in Figure 5.
The angle of intersection between the planes is ca. 20°. Note
the difference in position of the atom O(250) in Figure 4 with
reference to the Lu structure compared to the La structure. The
position in the Lu structure allows the ring to be more closely
parallel in 4, and this is manifested in the least-squares planes
calculations which show that ring 2 is more closely parallel to
the methylene plane than ring 4. Rather surprisingly the chelate
ring formed by the metal and bidentate picrate is far from planar
and the angle between the M, O(50), O(521) plane and the
O(50), O(521), C(50), C(51), N(520) plane ranges between 39
and 48° in the three structures. Another feature of interest is
that the three nitro groups are all significantly twisted out of
the plane of the phenyl ring. The groups on N(520) and N(540)
are nearly planar with angles of intersection of ca. 20, and 10°
respectively but the group on N(560) is almost perpendicular
(angles of intersection 76.2, 69.4, 65.4°). It is noticeable that
the nitro group on N(540) is the most planar while that on
N(560) is the least planar presumably because it is adjacent to
the oxygen O(50) and steric effects are important. However
on chelation, the nitro group on N(520) becomes more nearly
planar than the other ortho group on N(560). The reasons for
the suitability of this system for selective extraction of the
lanthanide elements are clear. The calix[4]arenediamide pro-
vides a relatively rigid donor set of six oxygen atoms of which
two are negatively charged. This feature is suitable for
lanthanide elements, but not for transition elements (as the donor
set provides a trigonal prismatic and not an octahedral donor
set), nor for alkali metals which because of the -2 charge would
need to form a negatively charged complex. For the lanthanide
elements, the donor set is completed by a picrate anion which
provides the third negative charge to balance the Ln3+ charge.
The coordination number thus becomes 8 which is about average
for lanthanides28 but clearly is a consequence of the rigidity of
the calix[4]arene.
All four structures have some solvent in the unit cells. As is
usual in the calix[4]arene in the cone conformation, in the
majority of structures, one solvent molecule is found in the cone.
The other solvent molecules are found filling in the gaps
between the molecules in the unit cell. In 1 there are three
acetonitrile molecules and one dichloromethane. The acetoni-
trile is situated within the cavity with the methyl group furthest

Lanthanide Structures
Inorganic Chemistry, Vol. 35, No. 8, 1996 2209
Figure 3. Structure of [Lu(L-2H)(picrate)] (4). Thermal ellipsoids are
shown at 45% probability. For clarity, the hydrogen atoms are not
included.
Figure 5. Two views of the structures of 1 (left) and 4 (right) showing
the differences between the geometry of the coordination spheres.
Table 7. Least-Squares-Planes Information
plane 1
plane 2
plane 3
plane 4
plane 5
plane 6
plane 7
plane 8
plane 9
plane 10
plane 11
plane 12
plane 13
C(11), C(12), C(13), C(14), C(15), C(16)
C(21), C(22), C(23), C(24), C(25), C(26)
C(31), C(32), C(33), C(34), C(35), C(36)
C(41), C(42), C(43), C(44), C(45), C(46)
C(17), C(27), C(37), C(47)
O(150), O(250), O(350), O(450)
O(153), O(353), O(50), O(521)a
M, O(50), O(521)
O(50), O(521), C(50), C(51), N(520)
C(51), C(52), C(53), C(54), C(55), C(56)
N(520), O(521), O(522)
N(540), O(541), O(542)
N(560), O(561), O(562)
Angles between Planes
M
La
Sm
Yb
Lu
1 and 5
2 and 5
3 and 5
4 and 5
5 and 6
5 and 7
6 and 7
8 and 9
10 and 11
10 and 12
10 and 13
2 and 10
73.3
53.1
72.0
41.3
3.5
5.9
2.4
83.8
36.8
81.2
44.1
2.9
3.9
1.6
39.0
15.1
15.8
65.4
28.5
72.1
33.5
69.6
45.7
4.7
5.2
1.8
44.8
20.2
7.9
69.4
18.9
71.4
34.0
69.5
46.2
5.3
5.7
1.3
47.7
18.7
7.2
76.2
20.4
Figure 4. Structure of [Yb(L-2H)(picrate)] (3) viewed down the
calixarene axis. Thermal ellipsoids are shown at 45% probability. For
clarity, the hydrogen atoms are not included. The solvent dichlo-
romethane molecule in the cavity is also shown.
48.1
5.0
24.0
in. This arrangement is found in several calix[4]arene structures
and is thought to be due to favorable electrostatic interactions
between the hydrogen atoms of the methyl group and the phenyl
rings. In 3 and 4, which are isostructural, different solvent
molecules are found. In 4, M ) Lu, the solvent consists of
one dichloromethane, one ethanol, and two water molecules of
which the dichloromethane is found within the cavity. In 3, M
) Yb, there are three dichloromethane molecules and one water
molecule of which the dichloromethane is also found within
the cavity. In 2, only one ethanol molecule was located, but
this is found within the cavity. The solvent molecule within
the cavity is shown in all the figures but the others are excluded.
Lanthanide Extraction Studies. Using the optimised ex-
perimental conditions of the calix[4]arene ligand L dissolved
in dichloromethane (9.6 mM), solvent extractions of aqueous
lanthanoid cation solutions (0.4 mM) in the presence of excess
a In the case of 1 W(1) replaces O(521) in this plane.
picrate (9.6mM) were performed at an aqueous phase pH value
of 5.8 ( 0.3. The percentage extractabilities obtained are listed
in Table 8. Generally very high percentage extraction was
observed for most lanthanide cations, especially with lanthanum
(87%), neodymium (98%) europium (89%), and holmium
(87%). This contrasts with the percentage extractabilities of
lanthanide picrates reported for crown ethers22,23 and a bis(crown
ether)24 under similar experimental conditions where maximum
values of only 20-22% extraction were determined. At low
(22) (a) Nakagawa, K.; Okada, S.; Inoue, Y.; Tai, A.; Hakushi, T. Anal.
Chem. 1988, 60, 2527. (b) Nakagawa, K.; Inoue, Y.; Hakushi, T. J.
Chem. Res., Synop. 1992, 268; J. Chem. Res., Miniprint 1992, 2122.

2210 Inorganic Chemistry, Vol. 35, No. 8, 1996
Table 8. Solvent Extraction of Lanthanides with La
Beer et al.
La
87
Ce
82
Pr
Nd
98
Sm
75
Eu
89
Gd
63
Tb
72
Dy
71
Ho
87
Er
83
Tm
84
Yb
41
Lu
64
extractablity (%)
83
a Extraction performed as described in the text.
Chart 1. Numbering Scheme in the 1,3-Bis(diethyl amide)-Substituted Calix[4]arene Ligand
Chart 2. Numbering Scheme in the Picrate Anion
pH <2 no extraction took place suggesting deprotonation of
the 2- and 4-hydroxyl groups of the calix[4]arene ligand is
crucial to the success of the extraction process. Presumably
the dichloromethane organic phase contains solution lan-
thanide-L complex species (Ln(L-2H) picrate) with structures
similar to the those of solid state complexes discussed earlier,
in which the trivalent lanthanide cation is fully encapsulated in
a polar environment within the lipophilic exterior of the calix-
[4]arene ligand. Solvent extraction of lanthanum using in the
absence of picrate was carried out for comparison. However
no extraction was discernable indicating that neither the nitrate
or carbonate anion were participating in the extraction process,
(23) Under identical experimental extraction conditions to those used with
L, dicyclohexano-18-crown-6 gave very poor extraction of lanthanides,
<5%.
(24) Inoue, Y.; Nakagawa, K.; Hakushi, T. J. Chem. Soc., Dalton Trans.
1993, 2279.
thus establishing the crucial role of the picrate anion in the
extraction process.
(25) [Er(L-2H)(picrate)], CH2Cl2‚ EtOH‚2H2O, triclinic, space group P1h,
a ) 14.093(8) Å, b ) 15.087(9) Å, c ) 18.228(9) Å, R ) 87.72(1)°,
â ) 80.82 (1)°, γ ) 72.48(1)°, U ) 3648.4 Å3. [Tm(L-2H)-
(picrate)]‚2.5CH2Cl2‚H2O, triclinic, space group P1h, a ) 14.100(8)
Å, b ) 15.136(9) Å, c ) 18.201(9) Å, R ) 88.08(1)°, â ) 81.11(1)°,
γ ) 72.10 (1)°, U ) 3651.5 Å3. [Pr(L-H)(picrate)]‚EtOH, mono-
clinic, space group C2/c, a ) 29.853(8) Å, b ) 12.677(9) Å, c )
40.641(18) Å, â ) 110.36(1)°, U ) 14419.73 Å3.
(26) Various sources list different values for the radii of the lanthanides.
We have therefore carried out a survey of lanthanide metal complexes
in the Cambridge Crystallographic DataCentre and have calculated
the average M-O bond lengths excluding complexes with unusually
high or low coordination numbers. To ensure that the mean values
were not biased by outliers, M-O bond lengths that differed from
the mean by more than 4σ were excluded. Mean values (Å) were as
follows: La, 2.66; Ce, 2.63; Pr, 2.59; Nd, 2.62; Sm, 2.50; Eu, 2.55;
Gd, 2.49; Tb, 2.53; Ho, 2.48; Er, 2.47; Tm, 2.43; Yb, 2.33; Lu, 2.41.
(27) There are 23 examples in the Cambridge Crystallographic Database
of the picrate anion bonded in a bidentate fashion to a lanthanide metal.
All show the bond to the phenoxide oxide significantly shorter than
the bond to the nitro oxygen (mean values 2.344, 2.694 Å, respec-
tively).
Conclusions
The synthesis and structure determinations of lanthanum,
samarium, ytterbium, and lutetium complexes of a 1,3-bis-
(diethyl amide) lower rim substituted calix[4]arene ligand L
have been achieved. The structures exhibit similar features with
the lanthanide cation being fully encapsulated in an eight-
coordinate polar environment, consisting of six oxygen donor
atoms from the calix lower rim and in the case of lanthanum a
water molecule and a unidentate O--picrate, and for samarium,
ytterbium and lutetium a picrate anion chelating in a bidentate
arrangement. Solvent extraction studies revealed that under
optimised conditions the calix[4]arene ligand L displayed
generally very high percentage extractabilities of lanthanide
cations which may be attributed to the calixarene’s unique lower
rim lanthanide coordination sphere environment and lipophilic
exterior.
(28) Search of the Cambridge Crystallographic Database show coordination
numbers ranging from 3 to 12. Disregarding structures involving
organometallic La-C bonds we find that coordination numbers 8 and
9 are the most frequently observed each with over 30% of the total.
We calculate the mean coordination number as 8.12.
Acknowledgment. This work was supported by A.W.E.
(plc.). Funds for the Image Plate system were obtained from

Lanthanide Structures
Inorganic Chemistry, Vol. 35, No. 8, 1996 2211
Tables S1-S5, for [Sm(L-2H)(picrate)]EtOH (2) in Tables S6-S10,
for [Yb(L-2H)(picrate)]3CH2Cl2,H2O, (3) in Tables S11-S15 and
for [Lu(L-2H)(picrate)] CH2Cl2,EtOH,H2O (4) in Tables S16-S20
(52 pages). Ordering information is given on any current masthead
page.
the United Kingdom Science and Engineering Council and the
University of Reading.
Supporting Information Available: Text detailing the structure
solution and tables of crystal data, atomic coordinates, and molecular
dimensions, anisotropic thermal parameters, for the four structures.
Details for [La(L-2H)(picrate)H2O)]3MeCN,CH2Cl2 (1) are given in
IC9512441