Direct reaction of iodine-activated lanthanoid metals with 2,6-diisopropylphenol

Article abstract of DOI:10.1039/c2dt11752e

Rare earth metals activated with ca. 2% iodine react directly with 2,6-diisopropylphenol (HOdip) in tetrahydrofuran (thf), 1,2-dimethoxyethane (dme), and dig-dme (dig = di(2-methoxyethyl) ether) to give solvated phenolate complexes [Ln(Odip)₃(thf)_n] (Ln = La, Nd, n = 3; Ln = Sm, Dy, Y, Yb, n = 2), [Eu(Odip)(μ-Odip)(thf)₂]₂, [Ln(Odip)₃(dme)₂] (Ln = La, Yb) and [La(Odip) ₃(dig)] in good yield for Ln = La, Nd, Eu but modest yield for smaller Ln metals under comparable conditions. However, increasing the excess of metal greatly increased the yield for Ln = Y. The synthetic method has general potential, at least for lanthanoid phenolates. Comparison redox transmetallation/protolysis (RTP) reactions between Ln metals, Hg(C ₆F₅)₂ and the phenol gave higher yields in shorter time and, for Eu, gave [Eu(Odip)₃(thf)₃] in contrast to an Eu^II complex from Eu(I₂). New [Ln(Odip)₃(thf)₃] complexes have fac-octahedral structures and [Ln(Odip)₃(thf)₂] monomeric five coordinate distorted trigonal bipyramidal structures with apical thf ligands. [Eu(Odip)(μ-Odip) (thf)₂]₂ is an unsymmetrical dimer with two bridging Odip ligands. One five coordinate Eu atom has distorted trigonal bipyramidal stereochemistry and the other is distorted square pyramidal. Whilst [La(Odip)₃(dme)₂] has irregular seven coordination with mer-Odip and chelating dme ligands, [Ln(Odip)₃(dme)₂] (Ln = Dy, Y (prepared by ligand exchange), Yb) are monomeric six coordinate with one chelating and one unidentate dme. A six coordinate fac-octahedral arrangement is observed in [La(Odip)₃(dig)]. The Royal Society of Chemistry 2012.

Full text of DOI:10.1039/c2dt11752e

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PAPER
Direct reaction of iodine-activated lanthanoid metals with
2,6-diisopropylphenol†
Shima Hamidi, Glen B. Deacon, Peter C. Junk* and Paul Neumann
Received 15th September 2011, Accepted 9th December 2011
DOI: 10.1039/c2dt11752e
Rare earth metals activated with ca. 2% iodine react directly with 2,6-diisopropylphenol (HOdip) in
tetrahydrofuran (thf), 1,2-dimethoxyethane (dme), and dig–dme (dig = di(2-methoxyethyl) ether) to give
solvated phenolate complexes [Ln(Odip)3(thf)n] (Ln = La, Nd, n = 3; Ln = Sm, Dy, Y, Yb, n = 2),
[Eu(Odip)(μ-Odip)(thf)2]2, [Ln(Odip)3(dme)2] (Ln = La, Yb) and [La(Odip)3(dig)] in good yield for Ln =
La, Nd, Eu but modest yield for smaller Ln metals under comparable conditions. However, increasing the
excess of metal greatly increased the yield for Ln = Y. The synthetic method has general potential, at least
for lanthanoid phenolates. Comparison redox transmetallation/protolysis (RTP) reactions between Ln
metals, Hg(C6F5)2 and the phenol gave higher yields in shorter time and, for Eu, gave [Eu(Odip)3(thf)3]
in contrast to an EuII complex from Eu(I2). New [Ln(Odip)3(thf)3] complexes have fac-octahedral
structures and [Ln(Odip)3(thf)2] monomeric five coordinate distorted trigonal bipyramidal structures with
apical thf ligands. [Eu(Odip)(μ-Odip)(thf)2]2 is an unsymmetrical dimer with two bridging Odip ligands.
One five coordinate Eu atom has distorted trigonal bipyramidal stereochemistry and the other is distorted
square pyramidal. Whilst [La(Odip)3(dme)2] has irregular seven coordination with mer-Odip and
chelating dme ligands, [Ln(Odip)3(dme)2] (Ln = Dy, Y (prepared by ligand exchange), Yb) are
monomeric six coordinate with one chelating and one unidentate dme. A six coordinate fac-octahedral
arrangement is observed in [La(Odip)3(dig)].
Ln þ nLH ! ½LnðLÞnꢀ þ n=2H2
ð3Þ
ð4Þ
Introduction
(iv) pseudo Grignard formation (reaction (4)).30–34
Syntheses of rare earth organometallics, organoamides and aryl-
oxides/alkoxides from the elemental metals provide an alterna-
tive strategy to the more commonly used salt metathesis and
protolysis reactions.1–5 Free metal-based preparations include (i)
redox transmetallation using diarylmercurials,6–13 thallium cyclo-
pentadienyls,4,13 pyrazolates,14,15 and aryloxides,16,17 tin(II)18
and organotin(IV)19,20 complexes or triphenylbismuth10–12
(reaction (1)).
Ln þ RI ! }RLnI}
and (v) metal atom reactions.35–38
Such reactions (excluding (iv) and (v)) often require activation
of the metal surface, although in (1) (MRn = HgR2) and (2), the
generated mercury metal performs this role.21,23 Of the activation
methods, addition of mercury either directly or through addition
of mercuric chloride6,7,23,39,40 is the most common, but raises
environmental concerns.41–42 Alternative methods include acti-
vation by ammonia18,43–49 (much less adopted than in alkaline
earth chemistry),50–52 naphthalene, with ytterbium naphthalenide
serving as pseudo-Yb0,11 addition of preformed LnI2 or
LnI3,10,53 and addition of iodine, either stoichiometric, yielding
[SmIII(η8-C8H8)(hmpa)3]I or catalytic, providing [Sm(η8-C8H8)
(hmpa)3][SmIII(η8-C8H8)2]54 (emulating activation of Grignard
reagent formation).55–57 The last method, used for synthesis of
lanthanum 3,5-diphenylpyrazolate [La(Ph2pz)3(dme)2] by redox
transmetallation from [SnMe2(Ph2pz)2] in 1,2-dimethoxy-
ethane,19 offers a convenient approach to LnI3 activation since
Ln metal powders react with iodine in tetrahydrofuran (thf) to
give [LnI3(thf)n] (n = 3.5, 4).58 We now report a detailed assess-
ment of the value of activation by iodine in the reaction of rare
earth metals with 2,6-diisopropylphenol in tetrahydrofuran,1,2-
dimethoxyethane and diglyme. In some cases, a comparison has
mLn þ n MRm ! m ½LnRnꢀ þ nM
ð1Þ
n ¼ 2;3
(ii) redox transmetallation/protolysis (RTP) (reaction
(2)).9,17,21–26
2Ln þ nHgR2 þ 2nLH ! 2½LnLnꢀ þ nHg þ 2nRH
ð2Þ
(iii) direct reaction of lanthanoid metals with protic agents,
often at elevated temperatures (reaction (3)).9,27–29
School of Chemistry, Box 23, Monash University, Clayton, Victoria
3800, Australia. E-mail: peter.junk@monash.edu; Fax: +61 (3) 9905
4597; Tel: +61 (3) 9905 4570
†Electronic supplementary information (ESI) available. CCDC reference
numbers 845097–845108 and 853842–853843. For ESI and crystallo-
graphic data in CIF or other electronic format see DOI: 10.1039/
c2dt11752e
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Table 1 Yields of [Ln(Odip)3(solv)n] complexes from I2 activation and
RTP reaction
been made of the method with redox transmetallation/protolysis
(reaction(2)) using the normally highly effective oxidant
Hg(C6F5)2.17,21–26 The reactant phenol was initially chosen
because a range of structurally characterized lanthanoid 2,6-di-
isopropylphenolate complexes with thf are known.2,3,59–63 In the
event, a number of new complexes have been crystallographi-
cally characterized, including a dimeric EuII species and deriva-
tives with a relatively rare unidentate 1,2-dimethoxyethane
ligand.20,25,64–67
Yield (%)
Compounds
I2 activation method
RTP method
[La(Odip)3(thf)3](1)
64
52
—
—
70
[Nd(Odip)3(thf)3]·2thf (2)
[Eu(Odip)3(thf)3]·2thf (3)
[Nd(Odip)3(thf)2] (4)
[Sm(Odip)3(thf)2] (5)
[Dy(Odip)3(thf)2] (6)
[Y(Odip)3(thf)2] (7)
[Yb(Odip)3(thf)2] (8)
[Eu(Odip)(μ-Odip)(thf)2]2 (9)
[La(Odip)3(dme)2] (10)
[Dy(Odip)3(dme)2] (11)
[Y(Odip)3(dme)2] (12)
[Yb(Odip)3(dme)2] (13)
—
60a
25
72
59
59
68
—
—
—
—
—
26
25 (75)b
26
62
Results and discussion
67
73c
68c
30
Syntheses
69c
68
Rare earth metals activated by iodine (1.7–2.5%) were found to
react directly with 2,6-diisopropylphenyl (HOdip) on ultrasoni-
cation in tetrahydrofuran (thf) and 1,2-dimethoxyethane.
[La(Odip)3(dig)2]·0.5dme (15)
82
a From recrystallization of 2 from dme. b Large excess of Y metal used
(Experimental) c From recrystallization of [Ln(Odip)3(thf)2] 6–8 from
dme
solv=I2
2Lnþ6HOdip
2½LnðOdipÞ ðsolvÞ ꢀ þ 3H
ƒƒƒƒ!
2
3
n
ÞÞÞÞ
Ln¼ La; Nd; Sm; Dy; Y; Yb;solv¼thf ; n¼3ðLa; NdÞorn¼2
Ln¼La; Yb; solv¼dme;n¼ 2
the present case, the amount formed was extremely low, since no
methanol could be detected by 1H NMR spectroscopy on
hydrolysis of the bulk product. There was no evidence of solvent
cleavage in the corresponding reaction with lanthanum. Pure
[Yb(Odip)3(dme)2] was prepared by crystallization of [Yb
(Odip)3(thf)2] from dme, and the Y and Dy analogues were simi-
larly obtained. Surprisingly, crystallization of dried [Nd(Odip)3
(thf)3] from dme yielded [Nd(Odip)3(thf)2] with a similar
outcome from crystallization from toluene, but crystallization of
the crude product from another synthesis from toluene gave
single crystals of [Nd(Odip)3(thf)3]·PhMe (2b).
ð5Þ
Hydrogen was detected by 1H NMR spectroscopy from a
representative reaction. A corresponding reaction with europium
metal yielded a europium(II) complex [Eu(Odip)(μ-dip)(thf)2]2.
thf
!
2Eu þ 4 HO dip
½EuðOdipÞðμ ꢁ OdipÞðthfÞ ꢀ þ 2 H ð6Þ
2
2 2
An analogous synthesis with La metal and HOdip in dme–dig
(dig = di(2-methoxyethyl) ether) yielded [La(Odip)3(dig)].
For reaction (5) in thf with a twofold excess of Ln metal,
yields were over 50% for Ln = La, Nd (and for Ln = Eu in (6))
but ca 25% for Sm–Yb (Y) (Table 1). However, this smaller
metal defect can be overcome since a reaction employing a
much larger excess of yttrium gave a 75% yield (metal residues
can be recycled). A similar pattern of yields was also observed
for reactions in dme, viz. high for Ln = La and smaller for Ln =
Yb. A contributing factor to lower yields for Sm → Yb may be
the need to wash the product with an excess of hexane to remove
adhering unreacted 2,6-diisopropylphenol leading to some dis-
solution in HOdip–hexane. No reaction was observed between
Ln metals and HOdip in the absence of activation by I2, and the
amount used is the minimum required for effective reaction.
However, europium has been observed to react slowly with
HOdip in the more polar solvents N-methylimidazole and aceto-
nitrile.68 Using a much larger amount of iodine led to isolation
of [YbI2(thf)4], for Ln = Yb.
For comparison of methods, a number of the [Ln(Odip)3
(thf)2] (Ln = Sm, Dy, Y, Yb) complexes were prepared by the
RTP route from Hg(C6F5)2 (reaction (8), n = 2), all of which
gave higher yields in shorter times (Table 1).
2 Ln þ 3 HgðC6F5Þ2 þ 6 HOdip
! ½LnðOdipÞ3ðthfÞnꢀ þ 3 Hg þ 6 C6F5H
ð8Þ
The EuIII complex [Eu(Odip)3(thf)3] which was not obtained
from reaction (5) (cf. reaction (6)) was prepared by this method
(reaction (8), Ln = Eu, n = 3). Overall, iodine activation of Ln
metals provides a greener metal-based synthesis of Ln(Odip)3
complexes, but RTP reactions are faster and higher yielding with
smaller Ln metals.
From the reaction of ytterbium with HOdip in dme, a crystal
of the known [Yb(Odip)2(μ-OMe)]2 was isolated, presumably
formed from metal-induced cleavage of dme (reaction (7)),
Characterisation
In most cases the complexes were initially isolated as single
crystals, and were characterised by X-ray crystal structures in the
case of new compounds or known compounds59–63 not hitherto
examined crystallographically. Previously reported compounds
of known structure2,3,59–63 were characterised by unit cells, or,
where the synchrotron was used, by a structure re-determination.
Bulk samples were washed with hexane to remove adhering
2Yb þ 4 HOdip þ ðMeOCH2Þ2
! ½YbðOdipÞ2ðOMeÞꢀ2 þ 2 H2 þ C2H4
ð7Þ
since a similar cleavage has been observed in the RTP reacion
between Yb metal, HgPh2, and HOdip in dme.69 However, in
3542 | Dalton Trans., 2012, 41, 3541–3552
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Structural determinations
unreacted liquid 2,6-diisopropylphenol. This led to loss of crys-
tallinity and characterisation was performed on the resulting bulk
powder. Where compounds were of a known stoichiometric/
The complexes [Ln(Odip)3(thf)3]·2thf (Ln = Nd (2), Eu (3)) are
isotypic, and have monomeric fac octahedral structures (Fig. 1
(a)), as reported for [Ce(Odip)3(thf)3]·PhMe.60 The neodymium
complex was also crystallized as [Nd(Odip)3(thf)3]·PhMe (2a),
which is isotypic with the cerium complex.60 A precise structure
could not be obtained for [La(Odip)3(thf)3] (1), but the connec-
tivity is the same and it has similar unit cell dimensions (Exper-
imental section) to 2a and [Ce(Odip)3(thf)3]·PhMe.60 Selected
bond lengths and angles of 2 and 3 are listed in Table 2 and
those of 2a (similar to 2) in the Supplementary Data.† Bond
lengths are unexceptional compared with literature data for ana-
logous aryloxides2,3 but two Ln–O(thf) bonds shorten by
0.064–0.070 Å from 2 to 3, nearly twice that expected from
ionic radii differences.76 The isotypic complexes [Ln(Odip)3
(thf)2] (Ln = Nd (4), Y (7), Yb (8)) are five coordinate with dis-
torted trigonal bipyramidal stereochemistry, the aryloxide
ligands being equatorial and the thf ligands axial (Fig. 1(b)) with
O(thf)–Ln–O(thf) angles 156.69(4)–157.5(3)°. Previous isotypic
1
structural class, bulk characterization was by IR and H NMR
spectroscopy (of hydrolysed samples where paramagnetism pro-
duced unsatisfactory spectra) and lanthanoid metal analysis
(employing a much larger hence more representative sample
than microanalysis). For new compound classes, microanalyses
were carried out for representative examples. For [Ln(Odip)3
(thf)2]2·2thf complexes and [Ln(Odip)3(dme)2] species with
highly disordered dme of solvation in the single crystals (Ln =
1
Dy, Y), no solvent additional to that ligated was detected by H
NMR spectroscopy and analyses were consistent with absence of
solvent of crystallization. When bulk [Eu(Odip)2(thf)2]2, was
first isolated, the Eu analysis was in agreement with that for
single crystal composition. However, a microanalysis following
overseas transfer to New Zealand was indicative of loss of vir-
1
tually all thf, and the H NMR spectrum of a similarly stored
sample showed 0.2 thf per dimer unit. There was no evidence of
loss of coordinated thf, dme, or dig from trivalent complexes,
and in the case of [La(Odip)3(dig)]·0.25dme (15), the dme of
solvation was retained in the bulk sample.
The role of iodine
After treatment of lanthanum with a small amount of iodine in
tetrahydrofuran, both the residual metal and the resulting sol-
ution were tested for ability to promote reaction with 2,6-diiso-
propylphenol. When the latter was treated with La metal and
HOdip, a good yield of [La(Odip)3(thf)3] was obtained. In
addition, the residual metal, which gave a different SEM image
from fresh La filings (Supplementary data†), reacted with HOdip
in tetrahydrofuran to give a modest yield of [La(Odip)3(thf)3].
Thus there appears to be a dual activation role. Further exper-
iments to determine the distribution of La and iodine following
treatment of the metal with a small amount of I2 in thf showed
that much of the iodine remained in solution though some was
retained by the metal, and only a small percentage of La dis-
solved. Analysis of the solution showed an La : I ratio of 1 : 3.
Although the mechanism of activation is not known, it may
involve a reactive and unstable low oxidation state species, e.g.
for Ln = La, Nd, Dy (Scheme 1).
In recent years, molecular divalent compounds of Ln
elements,70,73 not normally forming LnII derivatives, have been
characterised,53,54,70–73 greatly expanding the horizons of lantha-
noid chemistry, with the high reactivity of DyI2 and TmI2 being
well established.54,73–75
Scheme 1 A possible explanation of activation by iodine for elements
Fig. 1 Molecular structures of (a) [Eu(Odip)3(thf)3]·2thf (3) and (b)
[Nd(Odip)3(thf)2] (4). Hydrogen atoms omitted for clarity.
not normally forming stable LnII species.
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Table 2 Selected bond lengths (Å) and angles (°) of [Ln(Odip)
(thf)n]·xthf
Table 3 Selected bond lengths [Å] and angles (°) for complex 9
Bond lengths
Bond angles
Nd (2)
n = 3
Eu(3)
n = 3
Nd(4)
n = 2
Y(7)
Yb(8)
Eu(1)–O(1)
Eu(1)–O(2)
Eu(1)–O(4)
Eu(1)–O(5)
Eu(2)–O(1)
Eu(2)–O(2)
Eu(2)–O(3)
Eu(2)–O(7)
Eu(2)–O(8)
Eu(1)–Eu(2)
2.440(3)
2.454(3)
2.285(3)
2.528(3)
2.416(3)
2.500(3)
2.271(3)
2.487(4)
2.605(4)
3.8924(14)
O(1)–Eu(1)–O(2)
O(1)–Eu(2)–O(3)
O(1)–Eu(1)–O(4)
O(1)–Eu(1)–O(5)
O(2)–Eu(1)–O(4)
O(1)–Eu(1)–O(6)
O(2)–Eu(1)–O(5)
O(5)–Eu(1)–O(6)
O(1)–Eu(2)–O(2)
O(1)–Eu(2)–O(7)
O(1)–Eu(2)–O(8)
O(2)–Eu(2)–O(3)
O(2)–Eu(2)–O(7)
O(7)–Eu(2)–O(8)
75.01(10)
111.52(11)
110.53(11)
96.00(11)
121.54(12)
159.23(11)
132.59(11)
88.52(12)
74.59(10)
90.33(13)
163.28(11)
166.44(10)
100.39(12)
84.65(15)
Bond lengths
Ln(1)–O(1)
n = 2
n = 2
2.049(3)
2.189(3) 2.161(3) 2.170(2) 2.065
(7)
Ln(1)–O(2)
Ln(1)–O(3)
2.183(3) 2.158(3) 2.171(2) 2.068
2.055(3)
2.037(3)
2.322(3)
2.327(3)
—
(7)
2.189(3) 2.157(3) 2.167(2) 2.086
(7)
Ln(1)–O(4)
(thf)
Ln(1)–O(5)
(thf)
Ln(1)–O(6)
(thf)
Bond angles
O(1)–Ln–O(2)
2.550(3) 2.515(3) 2.469(3) 2.321
(8)
2.545(3) 2.481(3) 2.457(3) 2.352
(8)
2.572(3) 2.502(3)
—
—
Eu(1)–O(2)–Eu(2)
Eu(1)–O(1)–Eu(2)
103.56(11)
106.55(11)
103.03
(11)
102.46
(11)
113.21
(10)
113.8
(3)
113.97
(13)
O(2)–Ln–O(3)
O(1)–Ln–O(3)
101.76
(12)
102.27
(12)
102.45
(11)
103.35
(11)
133.87
(10)
112.83
(10)
133.7
(3)
112.5
(3)
133.74
(13)
112.28
(14)
distorted square pyramidal with O(7) apical, whereas it is dis-
torted trigonal bipyramidal at Eu(1) with O(1,6) axial. Despite
the difference in ionic radii between Eu2+ and Ca2+,76 9 is iso-
typic with the corresponding calcium complex.80 Although
dimers bridged by two aryloxide ligands are common in LnIII
chemistry,2,3 they are less so for LnII complexes2,3 and especially
EuII derivatives. In [Eu2(Odip)4)(NCMe)5],68 there is an unusual
μ-κ1:κ1 bridging acetonitrile in addition to ligands with a con-
nectivity analogous to 9. Europium(II) also forms unsymmetrical
dimeric arrays with one terminal and three bridging aryloxides,
as seen in N-methylimidazole,68 dme,47 and unsolvated81 [Eu2
(OAr)4(solv)n] complexes. In the case of YbII, the double OAr
bridges are observed in three unsolvated derivatives81,82 and a
dme solvated silyloxide is known.49 Considerable variation is
seen in the Eu–O(thf) bond lengths of 9 from similar to those of
3 to 0.1 Å longer. The two longer bonds, Eu–O(6,8), are trans to
bridging Odip ligands (Table 3) hence their trans influence is
invoked.
O(4) (thf)–Ln–
O(5) (thf)
O(5) (thf)–Ln–
O(6) (thf)
O(6) (thf)–Ln–
O(4) (thf)
O(1)–Ln–O(5)
(thf)
O(3)–Ln–O(6)
(thf)
O(2)–Ln–O(4)
(thf)
77.04
(12)
80.77
(12)
77.30
(10)
161.81
(12)
161.51
(11)
162.84
(11)
81.15
(11)
77.14
(12)
77.75
(10)
161.73
(12)
162.52
(11)
161.65
(11)
157.06
(10)
—
157.5
(3)
—
156.69
(14)
—
—
—
—
100.41
(10)
—
101.0
(3)
—
101.93
(12)
—
85.73(9) 85.2
(3)
85.20
(12)
structures are known for Ln = La,61 Pr, Gd, Er, Lu,63 Sm,62
Dy.59 Again, the bond lengths (Table 2) show few surprising fea-
tures, but the decrease in Ln–O(thf) from 4 to 8 (0.13–0.15 Å)
exceeds that (0.11 Å)76 for the difference in ionic radii. For the
light lanthanoids La–Eu, the isolation of either a six or five co-
ordinate complex depends on crystallization conditions rather
than ion size. Thus, both have been isolated for the largest rare
earth, La, and for Nd, whereas so far only a six coordinate
complex has been observed for Ce and a five coordinate for Pr.
Furthermore, both five (4) and six coordinate (2a) Nd complexes
have been crystallized from toluene. The sum of the ligand steric
coordination numbers77 for the six coordinate complexes 2 and 3
is very high (8.73) inferring instability whereas, for the five co-
ordinate 4, 7, 8, it is 7.52, in a stable range.
In the case of the [Ln(Odip)3(dme)2] complexes, there is a
change from seven coordination with two chelating dme ligands
for Ln = La (10) to six coordination with one chelating and one
unidentate dme for Ln = Dy(11), Y(12) and Yb(13) (Fig. 3(a),
Comparing the bond lengths of the six and five coordinate Nd
complexes 2 and 4, the change in Nd–O(thf) is much larger
(0.10 Å) than expected (0.05 Å).76 In 2, all the thf ligands are
trans to aryloxide groups, which exert a strong trans influence78
(for other groups with a strong trans influence in Ln com-
pounds79), lengthening the Nd–O(thf) bonds of 2.
The divalent europium complex [Eu(Odip)(μ-Odip)(thf)2]2 (9)
is an unsymmetrical aryloxide bridged dimer with one Odip and
two cis thf terminal ligands on each five coordinate europium
atom (Fig. 2). One terminal Odip ligand O(3) is trans to a brid-
ging aryloxide O(2) and cis to the other O(1), whereas terminal
ligand O(4) is cisoid to both bridging Odip ligands (Table 3),
illustrating the asymmetry. The stereochemistry at Eu(2) is
Fig. 2 Molecular structure of [Eu(Odip)(μ-Odip)(thf)2]2 (9). Hydrogen
atoms omitted for clarity.
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Table 4 Selected bond lengths [Å] and angles (°) for complexes 10–13
Bond lengths
La(10)
Dy(11)
Y(12)
Yb(13)
Ln(1)–O(1)
Ln(1)–O(2)
Ln(1)–O(3)
Ln(1)–O(4)
2.2635(17)
2.2924(15)
2.3052(16)
2.656(2)
2.111(2)
2.116(2)
2.123(2)
2.533(2)
4.533a
2.106(2)
2.107(2)
2.098(2)
2.523(2)
4.536a
2.111(6)
2.063(6)
2.049(6)
2.447(5)
5.051a
Ln(1)–O(5)
2.638(2)
Ln(1)–O(6)
Ln(1)–O(7)
2.660(18)
2.657(18)
2.467(2)
2.464(2)
2.438(2)
2.445(2)
2.401(6)
2.386(6)
Bond angles
O(1)–Ln(1)–O(2)
O(1)–Ln(1)–O(3)
O(2)–Ln(1)–O(3)
O(2)–Ln(1)–O(4)
108.19(6)
105.07(6)
146.60(6)
75.26(6)
99.01(9)
102.93(8)
107.53(8)
99.57(8)
104.4(2)
109.1(2)
101.5(2)
162.1(2)
107.86(9)
102.63(9)
163.00(9)
162.60(8)
a Calculated for bonding distances.
Fig. 4 Molecular structure of ([La(Odip)3(dig)2]·0.25dme (15). Hydro-
gen atoms and dme of crystallization omitted for clarity. Selected bond
lengths [Å] and angles (°) in compound 15: La–O(1) 2.234(3), La–O(2)
2.242(3), La–O(3) 2.252(3), La–O(4) 2.627(3), La–O(5) 2.641(3), La–
O(6) 2.712(3); O(1)–La–O(2) 114.11(13), O(1)–La–O(3) 98.87(13),
O(2)–La–O(3) 86.57(13), O(3)–La–O(6) 174.39(11).
Fig. 3 Molecular structures of (a) [La(Odip)3(dme)2] (10) and (b)
[Dy(Odip)3(dme)2] (11). Hydrogen atoms omitted for clarity.
(b), Table 4), a lanthanoid ionic radius76 effect. Although 10 is
seven coordinate compared with six coordination for [Ln
(Odip)3(thf)3] (1–3), the steric crowding is comparable in both
with the sum of the ligand steric coordination numbers77 being
8.66 for 10 compared with 8.73 for 1–3. As 8.66 represents con-
siderable crowding, a coordination number change occurs with
smaller lanthanoids giving a value of ca. 7.7.77 Compound 10
has irregular stereochemistry with the Odip ligands approaching
a mer array, whereas 11–13 are fac octahedral (Table 4). The
combination of a chelating and an unidentate dme has previously
been observed in several nine coordinate lanthanoid 3,5-diphe-
nylpyrazolates.20,65,66 Unidentate dme though quite rare is well-
established.64–67 In [Ln(Ph2pz)3(dme)2] complexes, Ln–O (κ1-
dme) is either the shortest Ln–O bond length or between the
values for chelating dme, whereas Ln–O(4) (κ1-dme) of 11–13 is
clearly the longest Ln–O(dme) bond. This can be attributed to
the trans influence of the O(2) aryloxide ligand, which is trans
to O(4). In the series (10), (11), (12), (13), the decrease in Ln–O
bond length corresponds well with ionic radius expectations.76
The complex [La(Odip)3(dig)] (15) is six coordinate with dis-
torted octahedral stereochemistry and fac dip ligands (Fig. 4). It
contrasts [La(Odpp)3(dig)]83 (Odpp = 2,6-diphenylphenolate)
which has a mer array. Nevertheless the bond lengths in the two
complexes are comparable. La–O(6) is clearly the longer La–
O(ether) bond length and this can be attributable to the trans
influence of a trans Odip-ligand.
Conclusions
A small amount of iodine can be used to activate Ln metals to
enable direct reaction with 2,6-diisopropylphenol to occur in thf,
dme, or dig–dme. Higher yields are obtained for the larger, more
electropositive Ln metals under comparable conditions.
However, use of a larger excess of Ln metal enables the small
metal deficiency to be overcome. This procedure is a greener
metal-based synthesis than RTP reactions using Hg(C6F5)2,
which give higher yields in shorter reaction times. A range
of new structures have been obtained for [Ln(Odip)3(thf)n]
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[La(Odip)3(thf)3] (1)
(n = 2,3), [Eu(Odip)(μ-Odip)(thf)2]2, [Ln(Odip)3(dme)2], and
[Ln (Odip)3(dig)] complexes with the thf and dme series
showing a decrease of coordination number in response to the
lanthanoid contraction. The iodine activation method has the
potential to become a general metal-based synthesis at least for
rare earth phenolates, especially since HOdip is a bulky phenol
with unfavourable electron donor substituents. There are poten-
tial extensions to alkoxides, amides, amidinate, pyrazolates etc.,
but considerable further development is needed and is in pro-
gress. Disappointingly, only a low yield of [Tb(ttfpz)3(thf)3]
(ttfpz = 3-(2′-thienyl)-5-trifluoromethylpyrazolate) has recently
been obtained from iodine activated Tb metal and Httfpz.84
The resulting colourless crystals from the standard iodine acti-
vation method sonicating for 2 days, gave poor quality X-ray
data only providing connectivity information. Bulk dried powder
(0.85 g, 64%); dec. temp. 144–146 °C; found: La, 15.97%.
C48H75O6La (887.01 g mol−1) requires: La 15.66%; IR (Nujol,
cm−1): 1587 m, 1428 s, 1357 m, 1327 s, 1264 s, 1206 s, 1141 w,
1108 m, 1094 m, 1056 m, 1042 s, 1022 s, 953 w, 934 m, 917 w,
886 s, 854 s, 803 m, 797 w, 755 s, 722 w, 685 s, 616 w, 570s;
1H NMR of dried sample (300 MHz, C6D6): 7.18 (d, 6H, m-
H(OAr)), 6.93 (m, 3 H, p-H(OAr)), 3.69 (m, 12H, thf), 3.47 (m,
6H, CHMe2), 1.34 (d, 36H, CHMe2), 1.18 (m, 12H, thf). (1H
NMR chemical shifts are similar to those of [La(Odip)3(thf)2]62).
Unit cell dimensions isotypic with [Ce(Odip)3(thf)3],59 monocli-
nic, a = 11.4044(15) Å, b = 35.747(5), c = 13.3608(18),Å;
β = 97.540(5)°, volume = 5399.8(12) Å3.
Experimental
General: All the lanthanoid metals and lanthanoid(II) and (III)
products are highly air- and moisture-sensitive, hence operations
were carried out under purified nitrogen using standard Schlenk
line and glovebox techniques. 2,6-Diisopropylphenol (Aldrich)
was degassed before use. Hg(C6F5)2 was prepared by the litera-
ture method.13 All solvents were dried and deoxygenated by
refluxing over and distillation from sodium–benzophenone.
Elemental analyses (C, H) were performed by the Campbell
Microanalytical Laboratory, University of Otago, Dunedin, New
Zealand. Metal analyses were performed by EDTA titrations
with Xylenol Orange as the indicator, following acid digestion
(HCl or H2SO4–HNO3) and buffering with hexamine. Infrared
spectra (4000–650 cm−1) were obtained using Nujol mulls
between NaCl plates with a Perkin–Elmer 1600 FTIR spec-
trometer. Room temperature (30 °C) NMR spectra were recorded
on a Bruker DPX 300 instrument with dry degassed perdeutero-
benzene (C6D6) as the solvent, and resonances were referenced
to residual hydrogen from the solvent.
[Nd(Odip)3(thf)3]·2thf (2)
(See crystal data discussion). The standard iodine activation
method and sonicating for 4 days gave blue crystals suitable for
X-ray crystallography. Bulk dried powder (0.69 g, 52%); dec.
temp. 140–142 °C; Found: Nd, 16.31%. C56H91O8Nd
(1036.56 g mol−1) requires: Nd, 14.48%; C48H75O6Nd (loss of 2
lattice thf, 892.34 g mol−1) requires 16.16%; IR (Nujol, cm−1):
1587 m, 1428 s, 1356 m, 1328 m, 1265 s, 1204 s, 1109 m,
1096 m, 1053 w, 1042 m, 1020 s, 934 w, 916 w, 885 m, 857 s,
803 s, 796 w, 753 m, 722 w, 687 m, 616 w, 561 m, 547 w;
1H NMR (300 MHz, C6D6): δ 17.45 (br, 6H, CHMe2), 14.80 (s,
6H, m-H(OAr)), 11.60 (s, 3H, p-H(OAr)), 3.74 (br s, 36H,
CHMe2), −6.29 (br s, 12 thf), −11.43 (br s, 12 thf). After a
similar preparation, the crude product (yield 48%) was not
washed with hexane, but was crystallized from toluene, single
crystals of [Nd(Odip)3(thf)3]·PhMe (2b) being deposited on
cooling to −4 °C.
General procedure
[Nd(Odip)3(thf)2] (4)
To a slurry of freshly prepared Ln filings (0.26 g–0.52 g,
3.0 mmol) (except for compound 9) in thf (30 mL) was added
small amounts of iodine (0.013 g, 0.051 mmol) and the mixture
was allowed to stir for an hour. 2,6-Diisopropylphenol (0.84 mL,
4.5 mmol) was added to the mixture and the flask was placed in
an ultrasound bath for 2–5 days. After filtering, the volume of
filtrate was reduced under vacuum to 5 mL and the flask was
cooled at −6 °C. After 5 days the crystals were collected and
generally examined by X-ray crystallography. The crystals were
then washed with hexane to remove unreacted liquid ligand and
left under vacuum for an hour and further characterisation was
performed on the resulting bulk powder. Where the redox trans-
metallation/protolysis (RTP) method was employed Ln filings
(2.0 mmol), Hg(C6F5)2 (1.60 g, 3.0 mmol), Hg (2 drops) and
2,6-diisopropylphenol (1.12 mL, 6.0 mmol) in thf (30 mL) were
sonicated overnight. The resulting mixture was filtered to remove
the precipitated Hg and evaporated under vacuum to 5 mL and
the flask was cooled at −6 °C for 5 days. The crystals were
washed with hexane to remove the adhering solution giving the
pure powder which was dried under vacuum for further
characterisation.
[Nd(Odip3)3(thf)3]·2thf (0.20 g, 0.20 mmol) was placed under
vacuum for 3 h and 50 mL dme was added to the compound and
stirred for 3 days at room temperature. After evaporating to 5 mL
and cooling at −6 °C for 5 days, blue crystals suitable for X-ray
crystallography were collected. Bulk dried powder (0.11 g,
1
60%); H NMR (300 MHz, C6D6): δ 17.80 (br, 6H, CHMe2),
14.51 (s, 6H, m-H(OAr)), 11.70 (s, 3H, p-H(OAr)), 3.80 (br s,
36H, CHMe2), −15.36 (br s, 8H, thf), −27.57 (br s, 8H, thf)
(concordant with previous literature).63 Similarly crystallisation
of 2 from hot toluene gave compound 4 (IR and 1H NMR
identification).
[Eu(Odip)3(thf)3]·2thf (3)
The standard RTP method gave orange crystals suitable for X-
ray crystallography. Bulk dried powder (0.85 g, 70%); dec.
temp. 146–148 °C; Found: Eu, 16.98%. C56H91O8Eu (1044.28 g
mol−1) requires: Eu, 14.55%; C48H75O6Eu (loss of 2 lattice thf,
900.07 g mol−1) requires 16.88%; IR (Nujol, cm−1): 1586 m,
3546 | Dalton Trans., 2012, 41, 3541–3552
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1428 s, 1341 m, 1330 m, 1262 s, 1207 m, 1155w, 1094 m,
1041 m, 1018 s, 934 w, 918 w, 886 m, 860 s, 800 s, 752 m, 722
s, 688 w, 660 w, 616 w, 563 w; H NMR (300 MHz, C6D6):
C6D6): 7.20 (d, 6H, m-H(OAr)), 6.92 (3H, p-H(OAr)), 3.79 (m,
8H, thf), 3.51 (m, 6H, CHMe2), 1.33 (d, 36H, CHMe2), 1.10 (m,
8H, thf). The reaction was repeated using a greater excess of Y
powder (1.30 g, 15 mmol), iodine (0.060 g, 0.24 mmol) and
2,6-diisopropylphenol (0.84 mL, 4.5 mmol) and gave colourless
1
48.88 (br s, 12H, thf), 23.24 (br s, 12H, thf), 2.88 (t, 3H, p-
H(OAr)), −2.54 (d, 6H, m-H(OAr)), −3.77 (br, 36H, CHMe2),
1
1
−20.44 (br m, 6H, CHMe2). H NMR of an hydrolysed sample
crystals. Bulk dried powder (0.86 g, 75%); (IR and H NMR
(400 MHz, C6D6, CF3CO2H 1 drop): 7.02 (d, 6H, m-H(OAr)),
6.85 (t, 3H, p-H(OAr)), 3.50 (t, 12H, thf), 2.09 (m, 6H,
CHMe2), 1.45 (t, 12H, thf), 1.22 (d, 36H, CHMe2). Both
1H NMR spectra indicated loss of thf of crystallization.
identification). The standard RTP method gave colourless
powder (0.676 g, 59%); (IR and 1H NMR identification).
[Yb(Odip)3(thf)2] (8). The standard iodine activation method
and sonicating for 5 days gave yellow crystals suitable for X-ray
crystallography. Bulk dried powder (0.33 g, 26%); dec.
temp. 156–162 °C; found: Yb, 20.31%. Calc for C44H67O5Yb
(849.04 g mol−1): Yb 20.38%; IR (Nujol, cm−1): 1587 m, 1433
s, 1357 m, 1332 s, 1274 s, 1209 s, 1172 w, 1157 w, 1109 w,
1095 w, 1041 m, 1016 m, 934 w, 888 s, 863 s, 804 m, 796 w,
756 s, 752 s, 692 m, 572 m; 1H NMR (300 MHz, C6D6): 152.24
(br m, 8H, thf), 76.23 (br m, 8H, thf), 9.77 (s, 3H, m-H(OAr)),
−12.65 (s, 6H, m-H(OAr)), −14.87 (br s, 36H, CHMe2), −15.78
(br m, 6H, CHMe2) (concordant with previous literature 63). The
standard RTP method gave yellow powder (0.86 g, 68%); (IR
and 1H NMR identification).
[Sm(Odip)3(thf)2] (5)
The standard iodine activation method and sonicating for 4 days
gave very small pale yellow crystals suitable for X-ray crystallo-
graphy. The unit cell of a complete Synchrotron structure deter-
mination (monoclinic, space group P21, a = 9.772(2), b =
19.313(3), c = 12.08(2) Å, β = 109.566(3)°, α = γ = 90°, V =
2148.17 Å3) is in reasonable agreement with the literature.62
Bulk dried powder (0.309 g, 25%); dec. temp.: 144–148 °C; IR
(Nujol, cm−1): 1586 m, 1430 s, 1357 w, 1329 s, 1262 s, 1208 m,
1157 w, 1095 m, 1041 m, 1019 s, 933 w, 886 m, 860 s, 801 m,
754 m, 721 w, 688 w. (concordant with previous literature.)62 1
H
NMR (300 MHz, C6D6): 7.80 (d, 6H, m-H(OAr)), 7.56 (t, 3H,
p-H(OAr)), 5.20 (m, 6H, CHMe2), 1.69 (br s, 36H, CHMe2),
−0.01(br s, 8H, thf), −0.84 (br s, 8H, thf). The standard RTP
[Eu(Odip)(μ-Odip)(thf)2]2 (9)
The standard synthesis from Eu powder (0.32 g, 2.1 mmol) in
thf (30 mL), iodine (0.013 g, 0.051 mmol) and addition of 2,6-
diisopropylphenol (0.065 mL, 3.5 mmol) gave considerable
number of orange crystals suitable for X-ray crystallography.
Bulk dried powder (0.91 g, 62%); dec. temp. 144 °C; found
(freshly isolated): Eu, 23.04%. C64H100O8Eu2 (1301.40 g
mol−1) requires Eu, 23.35%. Microanalysis (after transportation)
found: C, 56.35%; H, 7.01%. C48.8H69.6O4.2Eu2 (loss of 3.8 thf,
1027.40 g mol−1) requires: C, 57.04%; H, 6.82%; IR (Nujol,
cm−1): 1587 m, 1428 s, 1407 s, 1357 m, 1331 s, 1210 m, 1206
s, 1199 s, 1154 w, 1139 w, 1105 m, 1037 s, 1016 s, 953 w,
934 m, 917 w, 883 s, 852 s, 836 s, 801 m, 797 w, 745 s, 722 w,
1
method gave yellow powder (0.89 g, 72%); (IR and H NMR
identification).
[Dy(Odip)3(thf)2] (6)
The standard iodine activation method and sonicating for 4 days
gave small pale yellow crystals suitable for X-ray crystallography
and the unit cell (monoclinic, a = 9.29(8), b = 18.86(16), c =
12.16(12) Å, β = 111.4(2)°, V = 1984(8) Å3) is in reasonable
agreement with the literature.59 Bulk dried powder (0.327 g,
26%); dec. temp.: 140–145 °C; found: Dy, 18.47%. Calc for
C44H67O5Dy (838.5 g mol−1): Dy 19.38%; IR (Nujol, cm−1):
1586 m, 1434 s, 1357 m, 1331 s, 1271 s, 1210 s, 1170 w, 1095
w, 1042 m, 1017 m, 888 s, 863 s, 753 s, 691 m, 564 m in agree-
1
680 m, 616 w, 570 m; H NMR spectrum could not be assigned
due to paramagnetic broadening. 1H NMR of a stored hydrolysed
sample (300 MHz, CD3CN, CF3CO2H 1drop): 7.02 (d, 8H, m-
H(OAr)), 6.82 (t, 4H, p-H(OAr)), 3.60 (t, 0.8H, thf), 3.22 (m,
8H, CHMe2), 1.78 (t, 0.8H, thf), 1.18 (d, 48H, CHMe2), indica-
tive of 0.2 thf per [Eu2(Odip)4].
1
ment with that expected.59 The H NMR spectrum could not be
1
confidently assigned due to paramagnetic broadening. H NMR
of an hydrolysed sample (400 MHz, C6D6, CF3CO2H 1drop):
7.01 (d, 6H, m-H(OAr)), 6.84 (t, 3H, p-H(OAr)), 3.20 (t, 8H,
thf), 2.89 (m, 6H, CHMe2), 1.30 (t, 8H, thf), 1.08 (d, 36H,
CHMe2). The standard RTP method gave yellow powder (0.74 g,
59%); (IR and 1H NMR of an hydrolysed sample identification).
[La(Odip)3(dme)2] (10)
La powder (0.42 g, 3.0 mmol), iodine (0.013 g, 0.051 mmol)
and 2,6-diisopropylphenol (0.84 mL, 4.5 mmol) in dme (30 mL)
ultrasonicated for 2 days gave colourless crystals suitable for X-
ray crystallography. Bulk dried powder (0.86 g, 67%); dec.
temp. 104–106 °C; found: La, 16.52%. C44H71O7La (850.94 g
mol−1) requires: La, 16.32%; IR (Nujol, cm−1): 1586 m, 1431 s,
1358 m, 1326 s, 1272 s, 1259 s, 1200 m, 1156 w, 1141 m,
1111 m, 1088 m, 1066 s, 1045 m, 983 m, 933 w, 881 m, 846 s,
800 m, 762 m, 746 s, 687 m, 570 w, 550m; 1H NMR (300 MHz,
C6D6): 7.18 (d, 6H, m-H(OAr)), 6.91(t, 3H, p-H(OAr)), 3.53 (m,
6H, CHMe2), 3.11 (br, 8H, dme-CH2), 3.06 (br, 12H, dme-Me),
1.31 (br, 36H, CHMe2).
[Y(Odip)3(thf)2] (7)
The standard iodine activation method and sonicating for 5 days
gave colourless crystals suitable for X-ray crystallography. Bulk
dried powder (0.29 g, 25%); dec. temp. 140–143 °C; found: Y,
11.33%. C44H67O5Y (764.89 g mol−1) requires: Y 11.62%; IR
(Nujol, cm−1): 1587 m, 1428 s, 1407 s, 1357 m, 1331 s,
1210 m, 1206 s, 1172 w, 1157 w, 1141 w, 1108 m, 1095 m,
1042 s, 1016 s, 953 w, 934 m, 917 w, 887 s, 863 s, 803 m, 797
w, 755 s, 722 w, 691 s, 616 w, 570m; 1H NMR (300 MHz,
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1
[Dy(Odip)3(dme)2]
(11). [Dy(Odip)3(thf)2]
(0.50
g,
654 w. The H NMR spectrum could not be assigned due to
paramagnetic broadening.
0.59 mmol) was placed under vacuum for 3 h and 50 mL. Dme
was added to the compound and yielded colourless crystals suit-
able for X-ray crystallography after 5 days at −6 °C. Bulk dried
powder (0.38 g, 73%); dec. temp. 160–164 °C; Found: Dy,
18.06%. C44H71O7Dy (874.53g mol−1) requires: Dy, 18.58%; IR
(Nujol, cm−1): 1586 m, 1431 m, 1357 m, 1260 s, 1210 m, 1097
s, 1018 s, 935 w, 888 m, 862 s, 803 m, 799 s, 691 m, 567 w,
[La(Odip)3(dig)]·0.25dme (15)
La powder (0.42 g, 3.0 mmol) in a mixture of diglyme and dme
(30 mL), iodine (0.013 g, 0.051 mmol) and 2,6-diisopropylphe-
nol (0.84 mL, 4.5 mmol) with a sonication for 2 days gave col-
ourless crystals suitable for X-ray crystallography after 5 days at
−6 °C. Bulk dried powder (0.85 g, 68%); dec.
temp. 176–178 °C; Found: C, 62.75%; H, 8.33%; La, 16.52%.
C43H67.5O6.5La (827.39 g mol−1) requires: C, 62.41%; H,
8.22%; La, 16.78%; IR (Nujol, cm−1): 1585 m, 1533 m,
1338 m, 1326 s, 1261 s, 1201 m, 1113 s, 1078 m, 1043 m,
1
550 m; H NMR spectrum could not be assigned due to para-
magnetic broadening. 1H NMR of an hydrolysed sample
(300 MHz, C6D6, CF3CO2H 1 drop): 7.04 (d, 6H, m-H(OAr)),
6.88 (t, 3H, p-H(OAr)), 3.62 (br, 8 H, dme-CH2), 3.28 (br, 12 H,
dme-Me), 3.08 (m, 6H, CHMe2), 1.24 (d, 36H, CHMe2).
1
1006 m, 937 m, 886 m, 851 s, 804 m, 747 s, 722 w, 687 w; H
[Y(Odip)3(dme)2] (12)
NMR (300 MHz, C6D6): 7.17 (d, 6H, m-H(OAr)), 6.89 (t, 3H,
p-H(OAr)), 3.57 (d, 6H, CHMe2), 3.33 (s, 1H, dme–CH2), 3.13
(s br, 1.5H, dme–Me), 3.11 (s br, 6H, dig–Me), 2.89 (t, 8H, dig–
CH2), 1.31 (d, 36H, CHMe2). The standard RTP method in a
mixture of diglyme and dme (30 mL), gave colourless powder
(1.02 g, 61%); (IR and 1H NMR identification).
[Y(Odip)3(thf)2] (0.50 g, 0.65 mmol) was similarly treated and
yielded colourless crystals suitable for X-ray crystallography.
Bulk dried powder (0.36 g, 68%); dec. temp. 158–160 °C.;
found: C, 65.85%; H, 8.77%; Y, 11.32%. C44H71O7Y (800.93 g
mol−1) requires: C, 65.98%; H, 8.93%; Y, 11.10%; IR (Nujol,
cm−1): 1588 m, 1431 s, 1357 m, 1338 s, 1272 s, 1262 s,
1210 m, 1189w, 1110 m, 1084 m, 1057 s, 1043 m, 963 w,
1
Experiments to establish the need for and the role of I2
888 m, 859 s, 803 m,755 s, 694 m, 570 w, 550 m; H NMR
(300 MHz, C6D6): 7.17 (d, 6H, m-H(OAr)), 6.91(t, 3H, p-
H(OAr)), 3.51 (m, 6H, CHMe2), 3.18 (br, 20H, dme), 1.29 (d,
36H, CHMe2). H NMR of an hydrolysed sample (300 MHz,
C6D6, CF3CO2H 1 drop): 7.17 (d, 6H, m-H(OAr)), 6.91 (t, 3H,
p-H(OAr)), 3.96 (br, 8 H, dme–CH2), 3.44 (br, 12 H, dme–Me),
3.24 (m, 6H CHMe2), 1.23 (d, 36H, CHMe2).
(i) Yb powder (0.52 g, 3.0 mmol), iodine (0.507 g, 2.0 mmol)
and 2,6- diisopropylphenol (0.84 mL, 4.5 mmol) in thf (30 mL)
and sonication for 5 days gave a yellow solution. After filtering,
the volume of filtrate was reduced under vacuum to 5 mL and
the flask was cooled at −6 °C. After 5 days, crystals of
[YbI2(thf)4] were collected and were identified by the crystal
structure.
1
(ii) 2,6-Diisopropylphenol (0.84 mL, 4.5 mmol) was added to
La powder (0.041 g, 3.0 mmol) in thf (30 mL) and placed in an
ultrasound bath for 3 days. No colour change was observed in
the solution. Filtering and evaporating the solvent under vacuum
yielded only 2,6-diisopropylphenol. The same process was
repeated with Yb (0.521 g, 3.0 mmol) instead of La and the
result was similar.
(iii) 2,6-Diisopropylphenol (0.84 mL, 4.5 mmol) was added to
Nd powder (0.43 g, 3.0 mmol) in thf (30 mL) and placed in an
ultrasound bath for 3 days. No colour change was observed in
the solution. However, after addition of iodine (0.013 g,
0.051 mmol) the colourless reaction mixture developed a bright
blue colour indicative of NdIII after 2 days of ultrasound
treatment.
[Yb(Odip)3(dme)2] (13)
Yb powder (0.52 g, 3.0 mmol), iodine (0.013 g, 0.051 mmol)
and 2,6-diisopropylphenol (0.84 mL, 4.5 mmol) in dme (30 mL)
after sonication for 5 days gave yellow crystals of both [Yb
(Odip)3(dme)2] (13) and known [Yb(Odip)2(μ-Ome)(dme)]2
(14)69 identified by hand picking and comparison of the unit
cells (13: crystal system: monoclinic, a = 22.10(3), b = 18.98(3),
c = 23.42(3) Å, β = 115(3)°, V = 8900 Å3, in agreement with
values from a full structure determination on the product from
the 2nd preparation 14: crystal system: monoclinic, a = 11.235
(9), b = 12.967(10), c = 20.168(15) Å, β = 104.462(12)°, V =
2845 Å3, concordant with repeated values69). The percentage of
1
14 is very low as methanol was not observed in the H NMR
spectrum of an hydrolysed sample. 1H NMR (300 MHz,
CD3CN, CF3CO2H 1 drop): 7.00 (d, 6H, m-H(OAr)), 6.81 (t,
3H, p-H(OAr)), 3.43 (s br, 8H, dme–CH2), 3.25 (s br, 12H,
dme–Me), 2.45 (m, 6H, CHMe2), 1.14 (d, 36H, CHMe2). Bulk
dried powder (0.40 g, ca. 30%); dec. temp.: 150–158 °C. 2ndpre-
paration: [Yb(Odip3)3(thf)2] (7) (0.50 g, 0.58 mmol) was placed
under vacuum for 3 h and dme 50 mL was added. The solution
yielded yellow crystals suitable for X-ray crystallography after 5
days at −6 °C. (0.36 g, 69%); dec. temp.: 150–152 °C; found: C,
(iv) Evidence for the formation of H2: La powder (0.034 g,
0.025 mmol) in d8-thf (2 mL), iodine (0.001 g, 0.004 mmol) and
2,6-diisopropylphenol (0.007 mL, 0.037 mmol) were added to
an NMR tube and left it in the sonic bath for 2 days. After the
precipitate had settled, a clear solution was obtained.1H NMR
(300 MHz, d8-thf) displays a peak at 4.55 ppm which is indica-
tive of dihydrogen.85
(v) To a slurry of La powder (0.66 g, 4.75 mmol) in thf
(30 mL) was added iodine (0.086 g, 0.338 mmol) and the
mixture was allowed to stir for an hour. The total solution was
transferred to a second Schlenk flask already charged with La
powder (0.66 g, 4.75 mmol). The metal in the first Schlenk flask
was washed with thf which was transferred to the second
58.61%; H, 8.00%; Yb, 19.10%. C44H71O7Yb (885.50 g mol−1
)
requires: C, 59.68%; H, 8.08%; Yb, 19.54%; IR (Nujol, cm−1):
1588 m, 1431 s, 1331 s, 1267 s, 1210 m, 1171 w, 1096 s, 1042
s, 1018 w, 936 w, 888 m, 863 s, 803 m, 755 s, 694 m,
3548 | Dalton Trans., 2012, 41, 3541–3552
This journal is © The Royal Society of Chemistry 2012

View Article Online
Schlenk flask. 2,6-Diisopropylphenol (0.84 mL, 4.5 mmol) was
added to each Schlenk flask and they were placed in an ultra-
sound bath for 2 days. In each case, the clear filtrate obtained
after filtering was evaporated under vacuum. After washing the
residue with hexane, the H NMR of the product in both flasks
was the same and concordant with 1 (1st Schlenk flask: 0.45 g,
33%; 2nd Schlenk flask 0.72 g, 54%).
performed with anisotropic thermal parameters for non-hydrogen
atoms with hydrogen atoms constrained in calculated positions
with a riding model. Structure solutions and refinements were
performed using the programs SHELXS- 9792a and
SHELXL-9792b through the graphical interface X-Seed,93 which
was also used to generate the figures. All CIF files were checked
at http://www.iucr.org/.
1
(vi) To a slurry of La powder (0.66 g, 4.75 mmol) in thf
(30 mL) was added iodine (0.086 g, 0.336 mmol) and the
mixture was allowed to stir for an hour and then filtered into a
second Schlenk flask. The metal in the first Schlenk flask was
washed with thf then filtered and the thf washings were trans-
ferred to the second Schlenk flask. The contents of the first
Schlenk flask were dried under vacuum and digested by HCl
(2.0 M) and metal residue was dissolved. The solution in the
second Schlenk flask was evaporated to dryness under vacuum
and the residue digested by HCl (2.0 M). Analysis for metal and
iodine by iodometry86 was performed on both digests and the
percentages of initial La and iodine were determined for both
solutions (metal residue: La: 88%, I2 5%, Decanted solution: La:
5%, I2 94%). The composition of the residue from the second
Schlenk flask was I : La = 3 : 1.
CCDC 845097–845108 and 853842–853843 contain the sup-
plementary crystallographic data for this paper. These data
(excluding structure factors) can be obtained free of charge from
The Cambridge Crystallographic Data Centre via www.ccdc.
cam.ac.uk/data_request/cif.
General variata
Some compounds exhibit a relatively large ratio of ADP max/
min for carbon atoms. Ellipsoids of Pri (Me) C atoms are rela-
tively large and elongated suggesting thermal motion and dis-
order in contrast to the rigid C atoms of the aromatic rings
(compounds 4, 7, 8, 9, 12 and 15). To convey the true nature of
the ellipsoids of these atoms they have been refined anisotropi-
cally with no restraints. In extreme cases, disorder has been mod-
elled as best as possible. Specific variata for compounds are
mentioned below.
X-Ray structure determinations
Intensity data were collected using a Bruker X8 Apex II CCD (2,
7, 9 and 13), an Enraf-Nonius KAPPA CCD (8) or Oxford
Gemini Ultra (3 and 10) at 123 or 173 K with Mo-Kα radiation
(λ = 0.71073 Å). Suitable crystals were immersed in viscous
hydrocarbon oil and mounted on a glass fiber which was
mounted on the diffractometer and immediately placed under a
cold N2 vapor stream. Using phi and omega scans, Nt (total)
reflections were measured, which were reduced to N unique
reflections, with I > 2σ(I) being considered observed. Data were
initially processed and corrected for absorption using the Bruker
Apex II program suite87 or the programs DENZO88 and
SORTAV89 For compounds 4, 11, 12 and 15, the crystals on
which data were collected were microcrystalline and insufficient
in size to collect data on a conventional CCD X-ray diffracto-
meter. We therefore collected data on samples that were too
small to accurately determine the size of the crystals using a Syn-
chrotron source at the Australian Synchrotron, and therefore do
not provide sizes of these samples. For these compounds, data
were collected using the MX1 beamline at the Australian Syn-
chrotron, Victoria, Australia. A very small crystal was mounted
on a cryoloop and then flash cooled to 100 K. The crystal dimen-
sions could not be measured due to the small size. Data were col-
lected using a single wavelength (λ = 0.712 Å). The MX1 end
station comprised a phi goniostat and ADSC Quantum 210r
210 × 210 mm large area detector. Due to hardware constraints
(fixed detector angle), the maximum available data resolution on
MX1 was limited to approximately 0.80 Å at the detector edges.
For synchrotron structures, data were collected using the Blue
Ice90 GUI and processed with the XDS91 software package.
Structures were solved using direct methods that yielded the
heavy atoms, along with a number of the lighter atoms, and sub-
sequent Fourier synthesis yielded the remaining light-atom pos-
itions. Final least squares refinement cycles on F2, were
Crystal data for [Nd(Odip)3(thf)3]·2thf (2)
C56H91NdO8, M = 1036.53, blue block, 0.14 × 0.12 ×
0.04 mm3, orthorhombic, space group Pbcn (No. 60), a =
25.234(2), b = 22.3796(15), c = 20.0280(17) Å, V = 11310.4
(15) Å3, Z = 8, Dc = 1.217 g cm−3, F000 = 4408, T = 123(2)K,
2θmax = 55.0°, 171 113 reflections collected, 12 783 unique (Rint
= 0.0714). Final GooF = 1.114, R1 = 0.0568, wR2 = 0.1640, R
indices based on 8737 reflections with I > 2σ(I), 498 parameters,
0 restraints, μ = 0.966 mm−1. Variata: it was necessary to model
electron density associated with disordered solvent molecules in
the lattice voids using the PLATON program SQUEEZE.94
A
calculated electron count of 135.9 e−/asymmetric unit indicates
the presence of 3.4 thf molecules per molecule of the complex.
However, this compound is isotypic with compound 3 with
exactly two thf molecules in the lattice and they were modelled.
Crystal data for [Nd(Odip)3(thf)3]·C7H8 (2b)
C55H83NdO6, M = 984.45, 0.15 × 0.10 × 0.05 mm3, monoclinic,
space group P21/n (No. 14), a = 10.9370(4), b = 35.5722(15), c
= 13.3069(6) Å, β = 95.671(2)°, V = 5151.8(4) Å3, Z = 4, Dc =
1.269 g cm−3, F000 = 2084, Bruker X8 Apex II CCD, Mo-Kα
radiation, λ = 0.71073 Å, T = 123(1)K, 2θmax = 53.2°, 31 755
reflections collected, 10 651 unique (Rint = 0.0753). Final GooF
= 1.037, R1 = 0.0542, wR2 = 0.0819, R indices based on 7359
reflections with I > 2σ(I) (refinement on F2), 572 parameters, 0
restraints. Lp and absorption corrections applied,
μ =
1.054 mm−1. Variata: Carbon atom 39 has slightly higher
thermal motion than its neighbours. This may be expected for a
carbon on a THF molecule.
This journal is © The Royal Society of Chemistry 2012
Dalton Trans., 2012, 41, 3541–3552 | 3549

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Crystal data for [Nd(Odip)3(thf)2] (4)
Crystal data for [Eu(Odip)(μ-Odip)(thf)2]2 (9)
C44H67NdO5, M = 820.22, blue block, monoclinic, space group
P21 (No. 4), a = 9.790(2), b = 19.391(2), c = 12.139(3) Å, β =
C64H100Eu2O8, M = 1301.36, yellow block, 0.12 × 0.10 ×
0.02 mm3, monoclinic, space group P21/c (No. 14), a = 20.135
(10), b = 14.588(7), c = 22.125(12) Å, β = 100.403(11)°, V =
6392(5) Å3, Z = 4, Dc = 1.352 g cm−3, F000 = 2696, T = 123(2)
K, 2θmax = 55.0°, 55115 reflections collected, 14641 unique
(Rint = 0.0666). Final GooF = 0.978, R1 = 0.0462, wR2 =
0.0895, R indices based on 9461 reflections with I > 2σ(I), 692
parameters, 0 restraints, μ = 1.994 mm−1. Variata: Thermal par-
ameters on a number of carbons (C(43) and C(46)) were large
due to high thermal motion. One thf was modelled as disordered
with C atom position C(57), C(58), C(59) and C(60) (refined
occupancy 0.17 : 0.83). ISOR restraints applied for C(58) and
C(59). EXYZ and EADP commands were applied on C(57) and
C(57A) as well as C(60) and C(60A).
110.018(11)°, V = 2165.2(7) Å3, Z = 2, Dc = 1.258 g cm−3
,
F000 = 862, λ = 0.712 Å, T = 100(2)K, 2θmax = 54.2°, 15584
reflections collected, 8416 unique (Rint = 0.0367). Final GooF =
1.081, R1 = 0.0289, wR2 = 0.0718, R indices based on 8121
reflections with I > 2σ(I), 468 parameters, 7 restraints, μ =
1.239 mm−1. Absolute structure parameter = 0.051(11)95
Variata: ISOR restraint was applied on C(38). One thf was mod-
elled as disordered with C atom position C(38) (refined occu-
pancy 0.74 : 0.26).
Crystal data for [Eu(Odip)3(thf)3]·2thf (3)
C56H91EuO8, M = 1044.25, orange block, 0.25 × 0.25 ×
0.25 mm3, orthorhombic, space group Pbcn (No. 60), a =
25.0773(4), b = 22.1250(3), c = 19.9043(3) Å, V = 11043.6(3)
Å3, Z = 8, Dc = 1.256 g cm−3, F000 = 4432, T = 123(2)K, 2θmax
Crystal data [La(Odip)3(dme)2] (10)
= 55.0°, 59568 reflections collected, 12690 unique (Rint
=
C44H71LaO7, M = 850.92, colourless plate, 0.20 × 0.10 ×
0.08 mm3, orthorhombic, space group P212121 (No. 19), a =
13.1036(2), b = 13.4935(3), c = 25.6718(4) Å, V = 4539.12(14)
Å3, Z = 4, Dc = 1.245 g cm−3, F000 = 1792, T = 123(2)K, 2θmax
0.0308). Final GooF = 1.146, R1 = 0.0479, wR2 = 0.1138, R
indices based on 9806 reflections with I > 2σ(I), 566 parameters,
15 restraints. μ = 1.185 mm−1. Variata: Two thf molecules in the
lattice were modelled as disordered with C atom position (C(71),
C(77) and C(78)) and O atom O(7). (Refined occupancy
0.55 : 0.45).
= 64.6°, 44155 reflections collected, 10427 unique (Rint
=
0.0523). Final GooF = 1.004, R1 = 0.0298, wR2 = 0.0571, R
indices based on 9653 reflections with with I > 2σ(I), 485 par-
ameters, 0 restraints. Lp and absorption corrections applied, μ =
0.985 mm−1. Absolute structure parameter = 0.009(9)95
Crystal data for [Y(Odip)3(thf)2] (7)
C44H67O5Y, M = 764.89, colourless block, 0.12 × 0.10 ×
0.03 mm3, monoclinic, space group P21 (No. 4), a = 9.6897(14),
b = 19.343(3), c = 12.182(2) Å, β = 109.559(9)°, V = 2151.4(6)
Crystal data [Dy(Odip)3(dme)2] (11)
Å3, Z = 2, Dc = 1.181 g cm−3, F000 = 820, T = 123(2)K, 2θmax
=
C44H71DyO7, M = 874.51, colourless block, monoclinic, space
group P21/n (No. 14), a = 14.366(3), b = 19.188(1), c = 16.638
(2) Å, β = 90.624(7)°, V = 4586.1(11) Å3, Z = 4, Dc = 1.267 g
cm−3, F000 = 1828, λ = 0.712 Å, T = 100(2)K, 2θmax = 54.2°,
33363 reflections collected, 9554 unique (Rint = 0.0361). Final
GooF = 1.056, R1 = 0.0366, wR2 = 0.0988, R indices based on
8554 reflections with I > 2σ(I), 485 parameters, 0 restraints, μ =
1.673 mm−1. Variata: There are voids of 111 Å3 in the unit cell
presumably belonging to disordered dme molecules in the lattice
but these molecules could not be modelled.
50.0°, 11351 reflections collected, 6783 unique (Rint = 0.1898).
Final GooF = 0.777, R1 = 0.0775, wR2 = 0.1644, R indices
based on 3233 reflections with I > 2σ(I), 473 parameters, 55
restraints. Lp and absorption corrections applied,
μ =
1.395 mm−1. Absolute structure parameter = 0.012(13).95
Variata: This is isostructural with compound 4 and 8. One thf
(O(4)) was modelled as disordered with C atom position C(37)
and C(38) (refined occupancy 45 : 55); SIMU restraints were
applied on this molecule on C(29), C(37A), C(38A), C(39) and
C(40). ISOR restraints were applied on C(1), C(13), C(17) and
C(29). EXYZ and EADP commands were applied on C(37) and
C(37A).
Crystal data [Y(Odip)3(dme)2] (12)
Crystal data for [Yb(Odip)3(thf)2] (8)
C44H71O7Y, M = 800.92, colourless block, monoclinic, space
group P21/n (No. 14), a = 14.373(2), b = 19.227(2), c = 16.652
(2) Å, β = 90.782(9)°, V = 4601.3(10) Å3, Z = 4, Dc = 1.156 g
cm−3, F000 = 1720, λ = 0.712 Å, T = 100(2)K, 2θmax = 54.2°,
33768 reflections collected, 9679 unique (Rint = 0.0421). Final
GooF = 1.068, R1 = 0.0547, wR2 = 0.1405, R indices based on
8420 reflections with I > 2σ(I), 485 parameters, 0 restraints, μ =
1.311 mm−1. Variata: There are voids of 115 Å3 in the unit cell
presumably belonging to disordered dme molecules in the lattice
but these molecules could not be modelled.
C44H67O5Yb, M = 849.02, yellow block, 0.12 × 0.11 ×
0.03 mm3, monoclinic, space group P21 (No. 4), a = 9.7148(16),
b = 19.483(3), c = 12.344(2) Å, β = 110.053(11)°, V = 2194.7(7)
Å3, Z = 2, Dc = 1.285 g cm−3, F000 = 882, T = 173(2)K, 2θmax
=
50.0°, 10375 reflections collected, 6228 unique (Rint = 0.0223).
Final GooF = 0.999, R1 = 0.0219, wR2 = 0.0491, R indices
based on 5732 reflections with I > 2σ(I), 463 parameters, 1
restraint, μ = 2.170 mm−1. Absolute structure parameter = 0.015
(8).95
3550 | Dalton Trans., 2012, 41, 3541–3552
This journal is © The Royal Society of Chemistry 2012

View Article Online
Crystal data [Yb(Odip)3(dme)2] (13)
Acknowledgements
C44H71O7Yb, M = 885.50, yellow block, 0.12 × 0.10 ×
0.03 mm3, monoclinic, space group P21/c (No. 14), a = 22.0514
(5), b = 18.9710(4), c = 23.2542(5) Å, β = 115.2020(10)°, V =
8802.1(3) Å3, Z = 8, Dc = 1.336 g cm−3, F000 = 3688, T = 123
(2)K, 2θmax = 55.0°, 74 411 reflections collected, 19 092 unique
(Rint = 0.2136). Final GooF = 0.948, R1 = 0.0692, wR2 =
0.1224, R indices based on 9137 reflections with I > 2σ(I), 969
parameters, 42 restraints. Lp and absorption corrections applied,
μ = 2.170 mm−1. Variata: This compound is structurally similar
to compound 11 and 12. Two discrete molecules were observed
in the asymmetric unit. ISOR restraints applied for C(1), C(2),
C(3), C(4), C(41), C(48) and C(60).
This work was performed with the support of ARC grant
DP0984775. Shima Hamidi is grateful for a scholarship under
this grant, and a Dean’s award for fees. Thanks to Dr
C. M. Forsyth for assistance with X-ray crystallography. Part of
this research was undertaken on MX1 beamline at the Australian
Synchrotron, Victoria, Australia. The authors acknowledge use
of the facilities and the assistance of Dr Shery Chang at the
Monash Centre for Electron Microscopy. We also acknowledge
support from DAAD under the ISAP scheme, enabling Paul
Neumann, University of Leipzig, to study at Monash University.
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Å, α = 89.63(3), β = 79.38(3), γ = 69.75(3)°, V = 4402.5(14) Å3,
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0.0479, wR2 = 0.1203, R indices based on 15 669 reflections
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C16H32I2O4Yb, M = 715.3, yellow prism, 0.12 × 0.11 ×
3
ˉ
0.03 mm , triclinic, space group P1 (No. 2), a = 8.4437(7), b =
9.8103(8), c = 13.6182(12) Å, α = 79.672(5), β = 87.987(5), γ =
87.362(4)°, V = 1108.20(16) Å3, Z = 2, Dc = 2.143 g cm−3, F000
= 672, λ = 0.71073 Å, T = 123(1)K, 2θmax = 50.0°, 19 862
reflections collected, 3817 unique (Rint = 0.0526). Final GooF =
1.074, R1 = 0.0806, wR2 = 0.2472, R indices based on 9137
reflections with I > 2σ(I), 211 parameters, 6 restraints. Lp and
absorption corrections applied, μ = 7.019 mm−1. Variata: The
data indicates the molecule is either a different polymorph from
the known literature structure45 or twin. The asymmetric unit has
two half molecules, with the Yb atoms lying on independent
inversion centres.
This journal is © The Royal Society of Chemistry 2012
Dalton Trans., 2012, 41, 3541–3552 | 3551

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3552 | Dalton Trans., 2012, 41, 3541–3552
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