Direct syntheses and structural novelty of lanthanoid aryloxides with flexible radial arms

Article abstract of DOI:10.1002/ejic.200500530

Direct treatment of excess lanthanum, europium or ytterbium metal with 2,6-dibenzylphenol (HOdbp) at 150°C afforded [La₂(Odbp) ₆], [Eu₂(Odbp)₄] and [Yb(Odbp) ₂]_n, respectively, in high yiel

Full text of DOI:10.1002/ejic.200500530

FULL PAPER
Direct Syntheses and Structural Novelty of Lanthanoid Aryloxides with
Flexible Radial Arms
Marcus L. Cole,[a][‡] Glen B. Deacon,[a] Peter C. Junk,*[a,b] Kathryn M. Proctor,[b]
Janet L. Scott,[b] and Christopher R. Strauss[b]
Keywords: Lanthanoids / Aryloxides / Benzyl group / π-Donors / Phenolates / X-ray crystal structures
Direct treatment of excess lanthanum, europium or ytterbium
metal with 2,6-dibenzylphenol (HOdbp) at 150 °C afforded
[La2(Odbp)6], [Eu2(Odbp)4] and [Yb(Odbp)2]n, respectively,
in high yields. Alternatively, treatment of Yb metal with ex-
cess HOdbp gave an ytterbium(III) species [Yb2(Odbp)6], sim-
ilar to the lanthanum analogue. X-ray crystal structures were
obtained for [La2(Odbp)6], [Eu2(Odbp)4] and [Yb2(Odbp)6].
[La2(Odbp)6] and [Yb2(Odbp)6] are pseudo-centrosymmetric
dimers with two terminal and four bridging Odbp– ligands
and [Eu2(Odbp)4] crystallizes as a centrosymmetric dimer
with further organization in a polymeric form through supra-
molecular interactions. All three structurally characterized
compounds achieve coordination saturation by Ln–π-arene
interactions.
(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim,
Germany, 2005)
ties for optimal π-arene–Ln coordination geometry pro-
vided that the interaction is strong enough to overcome the
capacity of the aryl group to rotate away. We now report
novel lanthanoid complexes obtained from the direct reac-
tions of La, Eu or Yb metal with 2,6-dibenzylphenol
(HOdbp) and find extensive π-arene–Ln interactions in the
solid state. These are the first lanthanoid benzylphenolates
to show such interactions, which do not appear to be exhib-
ited by related calixarenes.[11]
Introduction
Lanthanoid aryloxides are accessible by a wide array of
synthetic routes and exhibit an enormous structural vari-
ety.[1] Use of bulky aryloxides has provided a range of excit-
ing low-coordinate complexes for both LnII and LnIII oxi-
dation states.[1] Whilst most of these have additional neutral
ligands, e.g. [Ln(OAr)3(THF)n] (n = 1–3), (where OAr =
2,6-diphenylphenolate,[2] 2,6-diisopropylphenolate,[3] 3,5-di-
methyl-2,6-diphenylphenolate,[4a]
3,5-di-tert-butyl-2,6-di-
phenylphenolate[4a] and 3,5-di-tert-butylphenolate[4b]), there
has been increasing interest in homoleptic complexes, both
neutral [Ln(OAr)n] (n = 2 or 3, where OAr = 2,6-diphenyl-
phenolate[5] and 2,6-di-tert-butylphenolates[6]) and anionic
[Ln(OAr)4]– (where OAr = 2,6-diphenylphenolate[5a,7] 2,6-
diisopropylphenolate,[8,9] 2,6-di-tert-butyl-4-methylphenol-
ate[10]). Homoleptic complexes of the bulkiest aryloxides
(OAr = OC6H2tBu2-2,6-X-4, where X = H, Me) are nor-
mally coordinatively and sterically saturated with solely
oxygen donors. However, less bulky phenolates, e.g. OAr =
OC6H3Ph2-2,6,[5,7] OC6H3iPr2-2,6,[8,9] give rise to ad-
ditional π-arene–Ln interactions ranging from η1 to η6.
These can involve either the pendant groups as with
OC6H3Ph2-2,6[5,7] or the central arene as with OC6H3iPr2-
2,6.[8,9] Use of more flexible side arms presents opportuni-
Results and Discussion
Direct treatment of excess lanthanum, europium or ytter-
bium metal with 2,6-dibenzylphenol (HOdbp), in an evacu-
ated Carius tube at 170 °C for 4 d, afforded crystalline ma-
terial comprising [Ln(Odbp)n]2 [Ln = La, n = 3 (1); Ln =
Eu, n = 2 (2)] or [Yb(Odbp)2]n (3) [Equations (1) and (2)].
Initially, several drops of mercury were added to the reac-
tion mixture to form a reactive lanthanoid amalgam. In
previous related syntheses,[4,5] this was found to be essential
for complete reaction. However, subsequently, it was found
that the reactions occurred cleanly and in significant but
lower yield without mercury for 1 and 2, but not for 3 or
4. In all cases crystals were obtained directly from the reac-
tion tube. Low solubility in non-coordinating solvents (e.g.
hexane and toluene) necessitated separation of crystalline
products from excess metal by hand-picking under a micro-
scope. In an attempt to improve the method of isolation,
experiments were performed in the presence of excess ligand
(rather than metal), followed by sublimation or washing out
of the residual ligand from the product. In the cases of com-
pounds 1 and 2, this presented no apparent problems, but
[a] School of Chemistry, Box 23, Monash University,
Clayton, Victoria 3800, Australia
Fax: +61-3-9905-4597
[b] Special Research Centre for Green Chemistry, Monash Univer-
sity,
Clayton, Victoria 3800, Australia
E-mail: peter.junk@sci.monash.edu.au
[‡] Current address: Department of Chemistry, University of Ade-
laide,
South Australia 5005, Australia
4138
© 2005 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
DOI: 10.1002/ejic.200500530
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Lanthanoid Aryloxides with Flexible Radial Arms
FULL PAPER
for Ln = Yb, a YbIII species, [Yb2(Odbp)6] (4), was ob- rules out any metal–metal interactions, being well in excess
tained rather than the YbII compound 3. This is not sur- of the sum of the ionic radii of two four-coordinate La3+
prising since previously we have found that excess lan- ions.[13] Compared with monomeric [La(OC6H3Ph2-2,6)3],[5b]
thanoid metal in redox transmetallation reactions,[12] as the presence of the methylene linker in compound 1 allows
well as in direct Ln metal/phenol reactions,[5a] aids in for- for increased steric freedom about the metal center owing
mation of the lower oxidation state product. Excess metal to the rotational ability about the Ph–CH2 bond as well as
acts as a reductant if any LnIII species is formed for Ln = the ability of the Ph group to swing away from the metal
Yb. The formation of compound 4 rather than 3 contrasts centres about the CH2 linker. This creates more space about
with the chemistry of compound 2, where the EuII species the La centers resulting in dimerisation, and a higher O-
is obtained when either excess metal or ligand is used. The donor coordination number.
results are consistent with Eu having the most stable di-
valent state of the lanthanoids.
To compensate for the coordinatively unsaturated four-
coordinate La center in compound 1, the metal atom is also
involved in La···π-arene interactions. This mode of interac-
tion has been a common feature of other lanthanoid arylox-
ide chemistry that we have presented previously,[2,5,7] and
the possibility arises due to the synthesis being performed
in a donor-solvent-free manner. Thus, each La center inter-
acts with an adjacent aromatic ring of an O-bridged ligand
in an η6-fashion through carbon atoms C(28) to C(33) for
La(1) and C(8) to C(13) for La(2) (see Figure 1a). There-
fore, the four-coordination about La (O only) expands to a
formal coordination number of seven. If the centroid of the
(1)
(2)
The infrared spectra of all compounds showed the ab- η6-attachment is regarded as a coordination site, then the
sence of an OH stretching band at around 3560 cm–1 estab- geometry about La is a distorted square pyramid with the
lishing complete deprotonation of the phenol. Furthermore, arene ring seated at the apex (see Figure 1a). The La···C
1
in the H NMR spectrum (C6D6) of compounds 1 and 3, distances [for La(1) 3.057(8) to 3.277(8), for La(2) 3.043(8)
there was no appreciable resonance at δ Ϸ 4.6 ppm for the to 3.300(8) Å] are all within the parameters defined for [La-
OH protons (however, products consistently showed small (OC6H3Ph2-2,6)3][5b] (Ͼ3.5 Å is considered non-bonding for
amounts of phenol detectable in the IR and NMR spectra this compound) and similar to those in [La2(OC6H3iPr-
perhaps arising from slight decomposition during measure- 2,6)6][3b] (av. La···C 3.06 Å) where there are η6-π-arene
ment). Unfortunately, compounds 2 and 4 were too insolu- bridges. Thus, given there is only a small spread in La···C(π-
1
ble in C6D6 to afford reasonable H NMR spectroscopic arene) interactions for this compound, and there is no obvi-
data. The low solubility of all compounds in the same sol- ous cut-off in La···C distances, the interactions can only be
vent precluded recording of 13C NMR spectra. The 1H regarded as η6-binding. The π-arene bridges are from O-
NMR spectra of compounds 1 and 3 had reasonably sharp bridging ligands which thus bind in a µ-η6:η1:η1-manner
peaks. The methylene resonances were slightly shifted in and contrast the arrangement in La(OC6H3Ph2-2,6)3 where
both compounds, from δ = 4.0 ppm in the parent phenol, to an arene arm from one terminal ligand binds in an η6-fash-
δ = 3.78 and 3.72 ppm in compounds 1 and 3, respectively. ion whilst a Ph from another binds η3 to the metal atom.
Compounds 1–4 were all analytically pure based on lan-
Compound 4 is structurally similar to compound 1 in
thanoid analyses as determined by complexometric ti- that it is also a dimer with Yb–π-arene interactions. Unfor-
trations. For compounds 1, 2 and 4, crystals suitable for X- tunately, all attempts to determine a high-precision X-ray
ray crystal structure determination were obtained directly crystal structure were thwarted by consistent twinning of
from the reaction tube, however, for compound 3 no such crystals. However, the low-precision structure leaves no
crystals resulted; nor could crystals be grown from non- doubt as to the connectivity of the compound, and the
coordinating solvents such as toluene or hexane due to in- structure is similar to that of its La analogue 1. One perti-
solubility. The aggregation of compound 3 is therefore un- nent and clear feature of the structure is a reduction in co-
known.
ordination number about the metal center through reduced
¯
Compound 1 crystallizes in the triclinic space group P1 π-arene connectivity. In compound 3, Yb(1) is bound in an
with one whole dimer comprising the asymmetric unit. η3-manner, while Yb(2) is η2-bound (Figure 2), lowered
Aside from La–π-arene interactions (see below) each La from η6:η6 in 1. For Yb(1) there are three Yb···Carene dis-
center is four-coordinate, being bound by two terminal and tances of 2.719(13), 2.997(12) and 3.174(13) Å, while there
two bridging phenolate ligands. The La–O(bridging) distances is a drastic increase (well outside error limits) to the next
range from 2.402(4) to 2.565(5) Å, while the La–O(terminal) closest carbon atom on the same aromatic ring [Yb(1)–
distances [range 2.172(6)–2.227(5) Å] are expectedly shorter C(33) 3.610(12) Å], and for Yb(2) there are two Yb···Carene
than the former and comparable with those of mononuclear distances of 2.837(12) and 2.894(12) Å, and the next closest
[La(OC6H3Ph2-2,6)3],[5b] which exhibits solely terminal approach is Yb(2)–C(10), 3.358(12) Å, thus defining a cut-
OC6H3Ph2-2,6 ligands (though there are additional π-ar- off for potential bonding. These “bonding” distances com-
ene–Ln interactions). The La···La distance of 4.031(4) Å pare well with previously established YbIII···C bond lengths
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M. L. Cole, G. B. Deacon, P. C. Junk, K. M. Proctor, J. L. Scott, C. R. Strauss
FULL PAPER
above the Ln center but is rather much more angled. Thus,
in compound 1 the La–centroid–Cipso angles are 85.0° and
84.3° for La(1) and La(2), while in compound 4 the corre-
sponding angles are much more acute, at 72° and 69° for
Yb(1) and Yb(2), respectively. The Yb–O(bridging) dis-
tances are asymmetric with two short [Yb(1)–O(1) 2.198(7)
and Yb(2)–O(1) 2.209(8) Å] and two long [Yb(1)–O(2)
2.317(8) and Yb(2)–O(1) 2.378(7) Å] interactions, as is ob-
served in compound 1. In each case, the longer Ln–O bond
is cisoid to a bonding phenyl group.
Figure 2. Molecular structure of [{Yb(µ-Odbp)(Odbp)2}2] (4)
showing η3-coordination to Yb(1) and η2-coordination to Yb(2);
all hydrogen atoms omitted for clarity. Selected bond lengths [Å]
and angles [°]: Yb(1)–O(1) 2.198(7), Yb(1)–O(2) 2.317(8), Yb(1)–
O(5) 2.031(9), Yb(1)–O(6) 2.055(10), Yb(2)–O(1) 2.378(7), Yb(2)–
O(2) 2.209(8), Yb(2)–O(3) 2.056(8), Yb(2)–O(4)2.049(10), Yb(1)–
C(28) 2.997(12), Yb(1)–C(29) 2.719(13), Yb(1)–C(30)3.174(13),
Yb(2)–C(8) 2.894(12), Yb(2)–C(9) 2.837(12); O(1)–Yb(1)–O(2)
73.1(3), O(1)–Yb(1)–O(5) 121.3(3), O(1)–Yb(1)–O(6) 92.4(3), O(2)–
Yb(1)–O(5) 89.2(3), O(2)–Yb(1)–O(6) 163.0(4), O(5)–Yb(1)–O(6)
106.2(4), O(1)–Yb(2)–O(2) 71.7(3), O(1)–Yb(2)–O(3) 90.5(3), O(1)–
Yb(2)–O(4) 168.0(3), O(2)–Yb(2)–O(3) 120.6(3), O(2)–Yb(2)–O(4)
Figure 1. Molecular structure of [{La(µ-Odbp)(Odbp)2}2] (1) (40%
thermal ellipsoids): all hydrogen atoms omitted for clarity and non-
coordinating hydrocarbon groups depicted as wireframes. a) Nor-
mal to La2O2 fragment and b) along the La···La vector. Selected
bond lengths [Å] and angles [°]: La(1)–O(1) 2.402(4), La(1)–O(2)
2.565(5), La(1)–O(3) 2.172(6), La(1)–O(4) 2.218(5), La(1)···C(28)
3.057(8), La(1)···C(29) 3.058(8), La(1)···C(30) 3.182(8), La(1)
99.3(3), O(3)–Yb(2)–O(4) 101.0(4), Yb(1)–O(1)–Yb(2) 105.4(3),
Yb(1)–O(2)–Yb(2) 107.1(3).
¯
Compound 2 crystallizes in the triclinic space group P1
with two unique half dimers in the asymmetric unit. Each
unique europium() center is bound by oxygen atoms of a
···C(31) 3.277(8), La(1)···C(32) 3.258(9), La(1)···C(33) 3.127(9), terminal and two bridging phenolate groups, thereby giving
an oxygen donor coordination number about EuII of three.
La(2)–O(1) 2.549(5), La(2)–O(2) 2.417(4), La(2)–O(5) 2.189(6),
La(2)–O(6) 2.227(5), La(2)···C(8) 3.043(8), La(2)···C(9) 3.080(8),
The Eu–O bond lengths (av. 2.46 Å for bridging and av.
La(2)···C(10) 3.216(8), La(2)···C(11) 3.300(8), La(2)···C(12)
2.29 Å for terminal) are unexceptional, being similar to Eu–
3.236(7), La(2)···C(13) 3.100(7); O1–La1–O2 69.90(16), O(1)–
O bridging and terminal distances of 2.48 (av.) and
2.361(3) Å, respectively, in [Eu(OC6H3Ph2-2,6)2]2 where
there are only one terminal and three bridging ligands.[5a]
The longer Eu–Oterminal distance in [Eu(OC6H3Ph2-2,6)2]2
is consistent with a lower coordination number in com-
pound 2. Each dimer is structurally similar but with some
La(1)–O(3) 114.37(19), O(1)–La(1)–O(4) 95.18(17), O(2)–La(1)–
O(3) 84.36(18), O(2)–La(1)–O(4) 165.07(16), O(3)–La(1)–O(4)
103.1(2), O(1)–La(2)–O(2) 69.94(16), O(1)–La(2)–O(5) 87.17(18),
O(1)–La(2)–O(6) 174.38(16), O(2)–La(2)–O(5) 120.47(17), O(2)–
La(2)–O(6) 104.52(17), O(5)–La(2)–O(6) 96.72(19).
in [Yb(OC6H3Ph2-2,6)3] and are consistent (after allowance significant differences, one being a discrete dimer and the
for ionic radius differences) with the more extensive data other a polymer of dimers, involving extended nuclearity
for YbII···arene interactions.[2,5a,14] A consequence of this through inter- and intramolecular Eu–π-arene interactions
binding is that the capping aromatic ring does not sit flatly (see below) that increase the coordination number of Eu
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Lanthanoid Aryloxides with Flexible Radial Arms
FULL PAPER
Figure 3. Molecular structure of [{Eu(µ-Odbp)(Odbp)}2]/[{Eu(µ-Odbp)(Odbp)}2]ϱ (2) (40% thermal ellipsoids); all hydrogen atoms omitted
for clarity and non-coordinating hydrocarbon groups depicted as wireframes. a) [{Eu(µ-Odbp)(Odbp)}2] normal to Eu2O2 metallacycle; b)
[{Eu(µ-Odbp)(Odbp)}2]ϱ (i) side-on and (ii) along Eu···Eu vector. Selected bond lengths [Å] and angles [°]: Eu(1)–O(2) 2.287(10), Eu(1)–
O(1) 2.463(11), Eu(1)–O(1)#1 2.491(12), Eu(1)–C(8) 3.130(16), Eu(1)–C(9) 3.150(17), Eu(1)–C(13) 3.187(16), Eu(1)–C(28) 3.171(16), Eu(1)–
C(29) 3.153(19), Eu(2)–O(3) 2.446(10), Eu(2)–O(3)#2 2.461(11), Eu(2)–O(4) 2.294(10), Eu(2)–C(49) 3.196(16), Eu(2)–C(48) 3.197(15), Eu(2)–
C(64)#3 3.136(16); O(1)–Eu(1)–O(2) 90.5(4), O(1)–Eu(1)–O(1)#1 71.7(4), O(2)–Eu(1)–O(1)#1 117.4(4), O(3)–Eu(2)–O(3)#2 69.6(4), O(3)–
Eu(2)–O(4) 97.3(4), O(4)–Eu(2)–O(3)#2 119.0(4), Eu(1)–O(1)–Eu(1)#1 108.3(4), Eu(2)–O(3)–Eu(2)#2 110.4(4). Symmetry transformations
used to generate equivalent atoms: #1: –x + 1, –y + 1, –z; #2: –x + 1,–y + 2, –z + 1; #3: –x, –y + 2,–z + 1.
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M. L. Cole, G. B. Deacon, P. C. Junk, K. M. Proctor, J. L. Scott, C. R. Strauss
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removed by sublimation. Crystals suitable for XRD analysis were
obtained. Yield: 0.58 g (82%). M.p. 184–187 °C. C60H51LaO3
(958.92): calcd. La 14.48; found La 14.30. 1H NMR (C6D6): δ =
3.78 (s, 12 H, CH2), 6.67–6.70 (m, 3 H, ArH), 6.73–6.87 (m, 6 H,
significantly. In the true dinuclear molecule the Eu centers
are capped on two sides by an η2- and an η3-bound arene
ring arising from one terminal and one bridging ligand
(Figure 3a). In the other molecule, each Eu has one η2-
bound π-arene interaction with an arene group from only
the bridging group of the dimer while an arene from the
terminal groups (involved in π-interactions in the true di-
mer) swings away from the Eu atom with a closest Eu···C
distance of 4.72(1) Å. This leaves a vacancy in the coordina-
tion sphere of Eu(2) which allows a further π-arene interac-
tion between Eu(2) and (symmetry-generated) C(64)#1 of
3.136(16) Å [C(64) is the p-C atom of the central (phenol-
ate) group of a terminal ligand rather than a radial group].
This forms a single-stranded polymer, where “dimers” are
linked by Eu(2)···C(64)(arene) interactions (Figure 3b). This
structure is drastically different from the stoichiometrically
related [Eu2(OC6H3Ph2-2,6)4] which possesses a remarkable
three bridging phenolate groups and one terminal phenol-
ate ligand.
ArH), 6.88–7.12 (m, 30 H, ArH) ppm. IR (Nujol, cm–1): ν =
˜
1589 m, 1452 s, 1262 s, 1191 m, 1081 s, 1029 m, 937 w, 859 m,
819 w, 754 s, 697 s, 559 w, 515 w.
[La(Odbp)3]2. Method
B (Without Mercury): HOdbp (0.25 g,
0.91 mmol) was treated with excess lanthanum metal (0.10 g,
0.72 mmol) in an evacuated sealed glass Carius tube. The reaction
mixture was heated at 250 °C for 5 d, forming a clear glassy solid
upon cooling. Unreacted ligand was removed by a hexane wash.
The product was identical to the compound 1 synthesised in the
presence of mercury. Yield: 0.12 g (41%). M.p.183–187 °C. IR (Nu-
jol, cm–1): ν = 1601 m, 1453 s, 1260 s, 1202 m, 1074 s, 1029 m,
˜
950 w, 869 m, 820 w, 755 s, 698 s, 601 w, 515 w.
[La(Odbp)3]2. Method
C (Excess Ligand): HOdbp (0.60 g,
2.18 mmol) and lanthanum metal (0.08 g, 0.55 mmol) were sealed
under vacuum in the presence of 2 drops of mercury in a glass
Carius tube. A white oil formed after heating at 210 °C for 2 d and
all of the lanthanum metal was consumed. The remaining (excess)
ligand was sublimed to one end of the tube (HOdbp sublimes at
240 °C). The product was identical with that obtained in Methods
A and B above. Yield: 0.35 g (66%). M.p. 184–186 °C. IR (Nujol,
Conclusion
cm–1): ν = 1594 m, 1456 s, 1259 s, 1200 m, 1072 s, 1029 m, 950 w,
The direct reaction of lanthanoid metals (Ln = La, Eu,
Yb) with 2,6-dibenzylphenol at 170oC provides the corre-
sponding homoleptic lanthanoid phenolates in good yield.
For Ln = Yb, use of either excess metal or excess phenol
gives YbII or YbIII complexes. All structures feature oxy-
gen-bridged dimeric units with coordination saturation ef-
fected by intra- or intermolecular π-phenyl···Ln coordina-
tion.
˜
865 m, 819 w, 755 s, 699 s, 600 w, 510 w.
[Eu2(Odbp)4] (2). Method A: 2,6-Dibenzylphenol (0.53 g,
1.93 mmol) was treated directly with europium metal (0.15 g,
0.97 mmol) in the presence of 2 drops of mercury in an evacuated
Carius tube. After 4 d of heating at 170 °C, an orange molten/crys-
talline material formed upon cooling. Unreacted excess ligand was
removed by sublimation. Crystals suitable for XRD analysis were
obtained. Yield: 0.56 g (83%). M.p. 198–200 °C. C40H34EuO2
(698.63): calcd. Eu 22.81; found Eu 22.58. IR (Nujol, cm–1): ν =
˜
1587 m, 1458 s, 1310 m, 1286 m, 1258 m, 1231 s, 1200 m, 1157 m,
1081 m, 1028 m, 933 w, 885 w, 854 m/w, 815 w, 748 s, 698 s, 601 w.
Experimental Section
General: 2,6-Dibenzylphenol (HOdbp) was prepared by a literature
method.[15] The lanthanoid metals used were purchased either from
Strem chemicals, Tianjiao (Baotou, China), Rhône–Poulenc or
Santoku, either as fine powders or as metal ingots, which were
manually filed under an inert gas into metal powder for use in
reactions. Toluene and hexane were dried with sodium/benzophe-
none and freeze-thaw-degassed prior to use. All manipulations were
performed using conventional Schlenk or glovebox techniques un-
der high-purity argon or dinitrogen in flame-dried glassware. Infra-
red spectra were recorded as Nujol mulls using sodium chloride
plates with a Nicolet Nexus FTIR spectrophotometer. 1H NMR
spectra were recorded at 300.13 MHz using a Bruker BZH 300/52
spectrometer and chemical shifts were referenced to the residual 1H
resonances of the deuteriobenzene solvent employed. NMR and IR
spectra of compounds 1 and 3 showed slight impurities of phenol
due to decomposition of the rare earth phenolate compounds in
the process of measurement. Compounds 2 and 4 had insufficient
solubility in common non-coordinating solvents to obtain NMR
spectra. Melting points were determined in sealed glass capillaries
under dinitrogen. The metal analyses were adapted from the
method described in a previous paper.[16]
[Eu(Odbp)2]2 (2). Method B (Without Mercury): HOdbp (0.30 g,
1.09 mmol) was treated with excess europium metal (0.11 g,
0.72 mmol) in an evacuated glass Carius tube. The reaction was
heated for 5 d at 250 °C, forming a glassy orange solid upon cool-
ing. The residue was washed with hexane to remove any unreacted
ligand. The product was identical to compound 2 from Method A.
Yield: 0.19 g (49%). M.p. 197–200 °C. IR (Nujol, cm–1): ν =
˜
1586 m, 1458 s, 1305 m, 1281 m, 1252 m, 1230 s, 1155 m, 1078 m,
1026 m, 971 w, 888 w, 850 m/w, 754 s, 696 s, 595 w.
[Eu(Odbp)2]2 (2). Method C (Excess Ligand): HOdbp (0.50 g,
1.82 mmol) and europium metal (0.09 g, 0.61 mmol) were sealed
under vacuum in the presence of 2 drops of mercury in a glass
Carius tube. An orange oil formed after heating at 210 °C over-
night. All of the europium metal had reacted; the remaining excess
ligand was sublimed to one end of the tube (HOdbp sublimes at
240°). The product was identical with that obtained from Methods
A and B above. Yield: 0.32 g (77%). M.p. 197–200 °C. IR (Nujol):
ν = 1600 m, 1453 s, 1347 m, 1286 m, 1231 m, 1200 m, 1150 m,
˜
1075 m, 1026 m, 934 w, 885 w, 852 m/w, 755 s, 698 s, 590 w.
[Yb(Odbp)2] (3): 2,6-Dibenzylphenol (0.60 g, 2.19 mmol) was
[La2(Odbp)6] (1). Method A: 2,6-Dibenzylphenol (0.60 g, treated directly with excess ytterbium metal (0.40 g, 2.30 mmol) in
2.19 mmol) was treated directly with lanthanum metal (0.10 g,
0.73 mmol) in the presence of 2 drops of mercury and sealed under
vacuum in a Carius tube. After 4 d of heating at 170 °C, a white
crystalline material formed upon cooling. Unreacted ligand was
the presence of 2 drops of mercury in a sealed, evacuated Carius
tube. After 4 d of heating at 170 °C, a red glassy material formed
upon cooling. Yield: 0.53 g (67%). M.p. 125–128 °C. C40H34O2Yb
1
(719.75): calcd. Yb 23.99; found Yb 23.80. H NMR (C6D6): δ =
4142
© 2005 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjic.org
Eur. J. Inorg. Chem. 2005, 4138–4144

Lanthanoid Aryloxides with Flexible Radial Arms
FULL PAPER
3.72 (s, 8 H, CH2), 6.72–6.77 (m, 2 H, ArH), 6.82–6.87 (m, 4 H, obtained free of charge from The Cambridge Crystallographic
ArH), 6.89–7.13 (m, 20 H, ArH) ppm. IR (Nujol, cm–1): ν = Data Centre via www.ccdc.cam.ac.uk/data_request/cif.
˜
1601 m, 1456 s, 1363 s, 1230 s, 1074 w, 1028 w, 1006 w, 950 m,
923 m, 889 w, 830 w, 820 w, 794 w, 755 s, 698 s. Attempts to form
this compound in the absence of mercury with heating up to 250 °C
Acknowledgments
(2,6-dibenzylphenol slowly decomposes above 260 °C, so was not
The authors acknowledge the ARC Special Research Centre for
Green Chemistry at Monash University for financial support and
postgraduate scholarship (K. M. P.), and CSIRO for supporting C.
R. S. on secondment.
heated any further) resulted in the isolation of unreacted starting
material.
[Yb2(Odbp)6] (4): 2,6-Dibenzylphenol (0.30 g, 1.09 mmol) was
treated directly with ytterbium metal (0.04 g, 0.23 mmol) in the
presence of 2 drops of mercury. The reactants were sealed under
vacuum in a glass Carius tube. After 2 d of heating at 150 °C, deep
orange/red crystals were grown upon cooling. Unreacted ligand
was removed by a hexane wash and the remaining material charac-
terised. Yield: 0.18 g (78%). M.p. 78–80 °C. C60H51O3Yb (993.05):
[1] D. C. Bradley, R. C. Mehrotra, I. P. Rothwell, A. Singh, Alkoxo
and Aryloxo Derivatives of Metals, Academic Press, San Diego,
2001.
[2] G. B. Deacon, S. Nickel, P. MacKinnon, E. R. T. Tiekink, Aust.
J. Chem. 1990, 43, 1245–1257.
calcd. Yb 17.42; found 18.11. IR (Nujol, cm–1): ν = 1601 m, 1459 s,
˜
[3] a) D. M. Barnhart, D. L. Clark, J. C. Gordon, J. C. Huffman,
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van den Hende, P. B. Hitchcock, S. A. Holmes, M. F. Lappert,
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White, J. Chem. Soc. Dalton Trans. 1997, 1181–1186; b) G. B.
Deacon, A. Gitlits, P. C. Junk, B. W. Skelton, A. H. White, Z.
Anorg. Allg. Chem. 2005, 631, 861–865.
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31, 1554–1556.
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A. H. White, J. Chem. Soc., Chem. Commun. 1996, 1729–1730.
[10] L.-L. Zhang, Y.-M. Yao, Y.-J. Luo, Q. Shen, J. Sun, Polyhedron
2000, 19, 2243–2247.
[11] P. Thuery, M. Nierlich, J. Harrowfield, M. Ogden, Phenoxide
Complexes of f-Elements, in: Calixarenes (Eds.: Z. Asfari, V.
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ers, Netherlands, 2001, p. 561–582.
1365 s, 1230 s, 1074 w, 1029 w, 950 m, 923 m, 889 w, 829 w, 820 w,
794 w, 755 s, 698 s. Attempts to form this compound in the absence
of mercury with heating up to 250 °C (2,6-dibenzylphenol slowly
decomposes above 260 °C, so was not heated any further) resulted
in the isolation of unreacted starting material.
X-ray Crystallography: Crystalline samples of compounds 1, 2 and
4 were mounted on glass fibres in viscous paraffin oil at –150 °C
(123 K). Crystal data were obtained using an Enraf–Nonius Kappa
CCD. An empirical absorption correction (SORTAV)[17] was ap-
plied to all data. Structural solution and refinement were carried
out using SHELXL-97[18] and SHELXS-97[19] utilising the graphi-
cal interface X-Seed.[20] Crystal data and refinement parameters for
all complexes are compiled below.
[La2(Odbp)6]
(1):
C120H102La2O6,
M
=
1917.84,
¯
0.25×0.20×0.20 mm, triclinic, space group P1 (No. 2), a =
13.4374(5), b = 13.9358(5), c = 26.7937(12) Å, α = 98.976(1), β =
95.312(2), γ = 108.065(4)°, V = 4658.3(3) Å3, Z = 2, Dc = 1.367 g/
cm3, F000 = 1968, Nonius Kappa CCD, Mo-Kα radiation, λ =
0.71073 Å, T = 123(2) K, 2θmax = 56.5°, 53379 reflections collected,
21478 unique (Rint = 0.2204). Final GooF = 0.872, R1 = 0.0748,
wR2 = 0.1217, R indices based on 7518 reflections with I Ͼ 2σ(I)
(refinement on F2), 1147 parameters, 0 restraints. Lp and absorp-
tion corrections applied, µ = 0.963 mm–1.
[Eu2(Odbp)4]
(2):
C80H68Eu2O4,
M
=
1397.26,
¯
0.10×0.10×0.10 mm, triclinic, space group P1 (No. 2), a =
10.0458(12), b = 13.136(2), c = 23.773(3) Å, α = 103.448(11), β =
94.188(9), γ = 94.379(7)°, V = 3028.9(8) Å3, Z = 2, Dc = 1.532 g/
cm3, F000 = 1412, Nonius Kappa CCD, Mo-Kα radiation, λ =
0.71073 Å, T = 123(2) K, 2θmax = 55.9°, 19023 reflections collected,
10992 unique (Rint = 0.1653). Final GooF = 0.930, R1 = 0.0993,
wR2 = 0.2022, R indices based on 4255 reflections with I Ͼ 2σ(I)
(refinement on F2), 775 parameters, 66 restraints. Lp and absorp-
tion corrections applied, µ = 2.106 mm–1.
[Yb2(Odbp)6] (4): C120H102O6Yb2, M = 1986.10, orange, rectangu-
¯
lar, 0.20×0.10×0.10 mm, triclinic, space group P1 (No. 2), a =
13.364(3), b = 13.475(3), c = 26.927(5) Å, α = 98.44(3), β =
97.42(3), γ = 104.68(3)°, V = 4569.2(16) Å3, Z = 2, Dc = 1.444 g/
cm3, F000 = 2020, Nonius Kappa CCD, Mo-Kα radiation, λ =
0.71073 Å, T = 123(2) K, 2θmax = 56.5°, 57274 reflections collected,
21355 unique (Rint = 0.0743). Final GooF = 1.108, R1 = 0.0993,
wR2 = 0.2751, R indices based on 16207 reflections with I Ͼ 2σ(I)
(refinement on F2), 1153 parameters, 42 restraints. Lp and absorp-
tion corrections applied, µ = 2.094 mm–1.
[12] G. B. Deacon, C. M. Forsyth, S. Nickel, J. Organomet. Chem.
2002, 647, 50–60.
[13] R. D. Shannon, Acta Crystallogr., Sect. A 1976, 32, 751–767.
[14] a) M. Niemeyer, Eur. J. Inorg. Chem. 2001, 1969–1981; b) G. B.
Deacon, C. M. Forsyth, P. C. Junk, Eur. J. Inorg. Chem. 2005,
817–821.
[15] a) E. C. Horning, J. Org. Chem. 1945, 10, 263–266; b) M. L.
Cole, L. T. Higham, P. C. Junk, K. M. Proctor, J. L. Scott,
C. R. Strauss, Inorg. Chim. Acta, in press.
[16] J. E. Cosgriff, G. B. Deacon, B. M. Gatehouse, Aust. J. Chem.
1993, 46, 1881–1896.
CCDC-274466 (1), -274467 (2) and -274468 (3) contain the supple-
mentary crystallographic data for this paper. These data can be
Eur. J. Inorg. Chem. 2005, 4138–4144
www.eurjic.org
© 2005 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
4143

M. L. Cole, G. B. Deacon, P. C. Junk, K. M. Proctor, J. L. Scott, C. R. Strauss
FULL PAPER
[17] R. H. Blessing, Acta Crystallogr., Sect. A 1995, 51, 33–37.
[18] G. M. Sheldrick, SHELXL-97, University of Göttingen, Ger-
many, 1997.
[20] L. J. Barbour, J. Supramol. Chem. 2001, 1, 189–191.
Received: June 15, 2005
Published Online: September 9, 2005
[19] G. M. Sheldrick, SHELXS-97, University of Göttingen, Ger-
many, 1997.
4144
© 2005 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjic.org
Eur. J. Inorg. Chem. 2005, 4138–4144