The synthesis, structures and polymorphism of the dimeric trivalent rare-earth 3,5-dimethylpyrazolate complexes [Ln(Me2pz) 3(thf)]2

Article abstract of DOI:10.1002/ejic.201400099

A variety of rare-earth 3,5-dimethylpyrazolate (Me₂pz) complexes have been synthesised by (i) the direct reaction of Hg-activated metal with Me₂pzH as a pro-ligand at elevated temperatures, (ii) by redox transmetalation/protolysis with the lanthanoid element, Hg(C₆F ₅)₂, and Me₂pzH, and (iii) by protolysis of tris[bis(trimethylsilyl)amido]cerium(III) with Me₂pzH. Each product, upon crystallisation from tetrahydrofuran (thf), formed a dimeric complex, [Ln(Me₂pz)₃(thf)]₂ (Ln = La, Ce, Pr, Nd, Ho, Yb, or Lu). Despite the common formulation, two completely different structures were observed in two distinct crystallographic domains of existence , together presumptively spanning the gamut of Ln and Y. For the larger rare-earth ions (La-Pr), there are two terminal η²-Me ₂pz ligands and one thf donor on each Ln atom, with the metal atoms being linked by a pair of bridging pyrazolate ligands of an uncommon type (η²:η⁵), resulting in formal ten-coordination. A Me₂pzH complex [Ce(Me₂pz)₃(Me₂pzH)], although not isomorphous, has a similar structure. For the smaller rare-earth elements (Nd-Lu), the bridging is entirely different, with two μ-κ¹(N):κ¹(N) pyrazolate and two unusual bridging thf ligands. Each Ln atom also has two chelating Me₂pz ligands, resulting in formal eight-coordination. Crystallisation of [Nd(Me ₂pz)₃(thf)]₂ from pyridine yields monomeric, nine-coordinate [Nd(Me₂pz)₃(pyridine)₃] with only chelating Me₂pz ligands. Contrasting structures and bridging Me₂pz groups for Ln = La-Pr and Ln = Nd-Lu are described. Copyright

Full text of DOI:10.1002/ejic.201400099

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DOI:10.1002/ejic.201400099
The Synthesis, Structures and Polymorphism of the
Dimeric Trivalent Rare-Earth 3,5-Dimethylpyrazolate
Complexes [Ln(Me pz) (thf)]
2
3
2
[
a]
[a]
[b]
Glen B. Deacon,* Rita Harika, Peter C. Junk,*
Brian W. Skelton,[
c][‡]
Daniel Werner, and Allan H. White
[a]
[c]
Keywords: Lanthanides / Rare earths / N ligands / Bridging ligands / Structure elucidation / Chelates
2
A variety of rare-earth 3,5-dimethylpyrazolate (Me
plexes have been synthesised by (i) the direct reaction of Hg-
activated metal with Me pzH as a pro-ligand at elevated
temperatures, (ii) by redox transmetalation/protolysis with
the lanthanoid element, Hg(C , and Me pzH, and (iii) by
protolysis of tris[bis(trimethylsilyl)amido]cerium(III) with
Me pzH. Each product, upon crystallisation from tetra-
hydrofuran (thf), formed a dimeric complex, [Ln(Me pz)
thf)] (Ln = La, Ce, Pr, Nd, Ho, Yb, or Lu). Despite the com-
mon formulation, two completely different structures were
observed in two distinct crystallographic “domains of exis-
tence”, together presumptively spanning the gamut of Ln
and Y. For the larger rare-earth ions (La–Pr), there are two
2
pz) com-
terminal η -Me
2
pz ligands and one thf donor on each Ln
atom, with the metal atoms being linked by a pair of bridging
2
5
2
pyrazolate ligands of an uncommon type (η :η ), resulting in
formal ten-coordination. A Me pzH complex [Ce(Me pz)
(Me pzH)], although not isomorphous, has a similar struc-
ture. For the smaller rare-earth elements (Nd–Lu), the bridg-
ing is entirely different, with two μ-κ (N):κ (N) pyrazolate
and two unusual bridging thf ligands. Each Ln atom also has
two chelating Me
coordination. Crystallisation of [Nd(Me
idine yields monomeric, nine-coordinate [Nd(Me
(pyridine) ] with only chelating Me pz ligands.
2
2
6
F
5
)
2
2
3
2
1
1
2
2
3
-
(
2
2
pz ligands, resulting in formal eight-
pz) (thf)] from pyr-
3
pz) -
2
3
2
2
3
2
Introduction
with unsymmetrically 3,5-disubstituted pyrazolate li-
gands. The moderately bulky, commercially available (as
[
7]
In the last fifteen years, the coordination chemistry of
pyrazolate (“pyrazolide”) ligands has been transformed and
enriched by the discovery of many new binding modes
the pyrazole), 3,5-dimethylpyrazolate ligand (Me pz) has
2
had a prominent role in the development of transition metal
[
1]
[1a,1c,1d]
and main group complexes
as well as in cyclopen-
2
[2]
and by the extension of η -coordination from f-block to
[8]
tadienyllanthanoid pyrazolates, and the oxygen-centred
Na-Ln bimetallic 3,5-dimethylpyrazolate cages were the
[
3]
[4]
transition metal and main group elements. Many of the
new binding modes were initially observed in the trivalent
lanthanoid pyrazolates,[ for which the chemistry has been
dominated by complexes of the bulky 3,5-di-tert-butylpyr-
azolate (tBu pz) and 3,5-diphenyl-pyrazolate (Ph pz) li-
[2c]
first structurally characterised lanthanoid pyrazolates.
5]
However, tris(3,5-dimethylpyrazolato)lanthanoid complexes
[
Ln(Me pz) (L) ] (L = neutral donor) with crystallographi-
2 3 n
2
2
cally defined structures are few in number, and are restric-
[
2e–2g,2k,5a–5d]
gands.
However, there have been recent devel-
ted to monomeric [Er(Me pz) (tBupy) ] (tBu py = 4-tert-
2
3
2
2
opments in the synthesis and structures of lanthanoid un-
substituted pyrazolate complexes,
[2i]
butylpyridine) (which has been used as an MOCVD dop-
[5e,6]
and in complexes
[9]
ant source ), dimeric [Ln (Me pz) (μ-Me pz) (μ-thf) ] (Ln
2
2
4
2
2
2
[
2d]
[10]
=
Nd,
Y
), and the first complex with monodentate
pyrazolate-N-Ln coordination [{Nd(η -Me pz) {κ -(N)-
The structurally uncharacterised
Ln(Me pz) (thf)] (Ln = La, Er)
[
[
a] School of Chemistry, Monash University,
Clayton, Victoria 3800, Australia
2
1
2
2
[
5b]
E-mail: Glen.Deacon@monash.edu
Me pz}}(Me pzH)].
2
2
http://monash.edu/science/about/schools/chemistry/staff/dea-
con.html
[2h]
[
and [Nd(Me pz) -
2
3
2 3
[
5b]
b] School of Pharmacy and Molecular Sciences, James Cook
University,
(py)]
(py = pyridine) are also known.
We now report the synthesis of a range of lanthanoid(III)
tris(3,5-dimethylpyrazolate) complexes by a variety of pre-
Townsville, Queensland 4811, Australia
http://www.jcu.edu.au/phms/chemistry/staff/JCU_106241.html
[
[
c] School of Chemistry and Biochemistry M310, The University parative routes and the structural characterisation of repre-
sentative complexes, thereby defining structures that span
‡] Current address: Centre for Microscopy, Characterisation and the whole La–Lu (Y) array. These differ markedly from
of Western Australia,
Crawley 6009, Australia
Microanalysis M310, The University of Western Australia,
those of the corresponding Ph pz and tBu pz complex-
2
2
Crawley 6009, Australia
[
2e–2g,2k]
5
es.
Of particular interest is the observation of μ-
η :η coordination in complexes of the larger lanthanoids.
Supporting information for this article is available on the
WWW under http://dx.doi.org/10.1002/ejic.201400099.
2
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This binding mode is quite uncommon, but has been ob- were obtained in good yields (1–5 and 7; 50–77%), with the
served for lanthanoid complexes with bulkier pyrazolate exception of Ln = Yb. Monitoring the synthesis of both
[
5a]
19
substituents, such as [Eu(tBu pz) ] , [Ln (Ph pz) ] (Ln = the Ln = La (1) and Ln = Lu (7) complexes by F NMR
2
2 4
3
2
9
[
5d]
La, Nd),
and [K(PhMe)Ln(tBu pz) ] (Ln = La, Sm, Tb, spectroscopy indicated the complete consumption of
2 4
5
2
[5c]
Yb) {η (K):η (Ln)}, and has also been observed in some Hg(C F ) , with corresponding formation of C F H, so
alkaline earth pyrazolate complexes.
noted that η -pz-Nd binding has been observed in [Nd (pz) - solely a result of loss on isolation. The synthesis of [Yb-
pzH) ] as part of a unique μ -η :η :η binding mode,
6
5 2
6 5
[4c,4d,11]
It should be that reduction in yield from quantitative appears to be
5
3
9
5
1
1
[5e]
(
(Me pz) (thf)] (6) was problematic by the RTP route and
2 3 2
2
3
5
and there is η -binding of pyrazole ligand (pzH) in [Eu(pz) - required isolation of the complex within minutes of synthe-
2
[
5e,6c]
(
pzH) ] .
The mixed sandwich compounds [Ru(C
and [Os(C Me )(η -tBu pz)]
special examples of standalone η -pyrazolate binding.
sis, otherwise an insoluble grey material formed. Even more
remain unsuccessful was the corresponding reaction with 3,5-di-
phenylpyrazole, for which decomposition was observed
2
ϱ
5
5-
[12]
5
[13]
Me )(η -Me pz)]
5
2
5
5
2
5
[
2j]
from the outset. By contrast, the reaction of ytterbium
with Hg(C F ) and 3,5-di-tert-butylpyrazole gave [Yb-
6
5 2
[
2f]
Results and Discussion
(tBu pz) (thf) ] in good yield. Furthermore, complex 6
2 3 2
soon lost thf on workup, forming a yellow powder that was
insoluble in thf, toluene or pyridine. The lutetium analogue
(7), once separated from the metal residue, was sparingly
soluble in cold thf, but crystallisation from hot thf solution
produced crystals of [Lu(Me pz) (thf)] (7). Complex 2a
Synthesis and Characterisation of Rare-Earth 3,5-
Dimethylpyrazolate Complexes
The lanthanoid pyrazolate complexes [Ln(Me pz) (thf)]
2
2
3
2
3
2
(
1–7) {Ln = La (1), Ce (2a), Pr (3), Nd (4), Ho (5), Yb (6),
Lu (7)}, have been synthesised by three methods, namely:
i) direct reaction of activated Ln metal with the pro-ligand
was also synthesised by protolysis of [Ce{N{Si(CH ) } } ]
3
3 2 3
with Me pzH. Although the synthesis was rapid, purifica-
2
(
tion required separation of 2a from a small amount of a
Me pzH substituted complex, [Ce(Me pz) (Me pzH)] (2b),
Me pzH at elevated temperatures followed by extraction
2
2
2
3
2
2
with thf (1); (ii) redox transmetalation/protolysis (RTP)
with Hg(C F ) , Ln metals and Me pzH (1–7), and
resulting from the use of a small excess of Me pzH in the
2
6
5 2
2
synthesis. Crystallisation of complex 4 from pyridine gave
the mononuclear complex [Nd(Me pz) (py) ] (8) (py = pyr-
(iii) protolysis of [Ce{N(SiMe ) } ] with Me pzH (2a)
3 2 3 2
2
3
3
(Scheme 1).
idine) in high yield, contrasting with the formation of [Er-
[
2i]
(
Me pz) (tBupy) ]
with a rather smaller lanthanoid
2
3
2
metal.
Bulk samples of 1, 5 and 7 gave microanalyses that were
consistent with the compositions of their single crystals (see
below), and diamagnetic 7 had a satisfactory 1H NMR
spectrum. When C D was added to 1, a white, insoluble
6
6
1
precipitate formed and the H NMR spectrum of the super-
natant solution showed a ratio of thf to pyrazolate of 2:3.
Upon D O addition, the spectrum indicated a correspond-
2
ing ratio of 1:3, consistent with the analytical composition.
This observation highlights the labile nature of the coordi-
nating thf in [La(Me pz) (thf)] , and implies that the insolu-
2
3
2
Scheme 1. Synthesis of lanthanoid pyrazolate complexes by (i) the ble precipitate was unsolvated and presumably polymeric
direct method at elevated temperature; (ii) redox transmetalation/
protolysis (RTP); (iii) the protolysis reaction of [Ce{N{Si-
[
La(Me pz) ]. This is consistent with the inability to extract
2 3
unsolvated [La(Me pz) ] with nonpolar solvents following
the synthesis by method (i) (Scheme 1). It is less likely that
the product of the reaction shown in Scheme 1 (i) is
2
3
(
CH
3 3 2 3 2 3 2
) } } ], also giving [Ce(Me pz) (Me pzH)] (2b) in low yield;
(iv) ligand exchange between thf and pyridine (py).
In an attempt to synthesise an unsolvated lanthanoid(III) [La(Me pz) (Me pzH)] because the cerium analogue 2b is
2
3
2
3
,5-dimethylpyrazolate complex, [La(Me pz) ], lanthanum soluble in toluene. Metal analyses for freshly prepared 6
2 3
1
metal and 3,5-dimethylpyrazole (Me pzH) were heated to and 8, and the H NMR spectrum of the latter were as
2
300 °C. Although the synthesis was successful, extraction of expected for a mono-thf and a tris-py complex, respectively,
unsolvated [La(Me pz) ] was difficult due to its insolubility but subsequent microanalyses indicated complete loss of thf
2
3
in noncoordinating solvents. Addition of thf allowed sepa- from the former and 0.5 py/Nd from the latter. The ready
ration from the metal residue and isolation of 1 in 58% loss of pyridine from 8 indicates that this compound may be
yield, which is higher than from a previously reported syn- the precursor of structurally uncharacterised [Nd(Me pz) -
2
3
thesis by metathesis (yield 35%[ ). This elevated tempera- (py)], the bulk product of an RTP reaction between Nd
2h]
[5a]
[5d]
ture synthesis also succeeds with tBu pzH,
Ph pzH
metal, Hg(C F ) , and Me pzH in pyridine, followed by
and thus can now be considered a general work up with nonpolar solvents (hexane and toluene).
2
2
6 5 2 2
[
5e,6b]
[5b]
and pzH
method for unsolvated rare-earth pyrazolates. The Microanalysis of 2a was indicative of the loss of one thf
1
[
Ln(Me pz) (thf)] species synthesised by the RTP method molecule per two cerium atoms, although H NMR analysis
2 3
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of a hydrolysed sample was consistent with the single-crys- in two forms “α” and “β”, which putatively span the entire
tal composition. The infrared spectra of complexes 1, 2a gamut of the lanthanoid series, inclusive also of the Ln =
[
10]
and 3–8 showed no ν(N–H) absorptions, indicating that the Y complex.
Interestingly, for Ln = Ce, replacement of
Me pzH was completely deprotonated. Isomorphous 1 and the thf ligand of 2a by Me pzH is possible (compound 2b)
2
2
2
a (see below) showed ν(C–O) bands ascribable to coordi- without profoundly disturbing the coordination sphere of
–
1
nated thf at ca 880 cm , whereas for isomorphous 4, 5 and the complex. Both forms (α and β) are binuclear
7
8
(see below), the corresponding absorptions were at ca. [Ln(Me pz) (thf)] , with form α crystallising in monoclinic
2 3 2
–
1
¯
40 cm . On the other hand, no such band was observed P2 /n, and form β in triclinic P1, the dimer in each being
1
for 6, indicating loss of thf (consistent with the microanaly- disposed about a crystallographic inversion centre so that,
sis).
in each case, one half of the binuclear formula unit com-
prises the asymmetric unit. Figure 1 and Table S1 present
data for the domain of the α-form, which encompasses Ln
Structures of the Complexes
=
La (1) (regrettably no single crystal data), Ln = Ce (2a)
The structural characterization of [Ln(Me pz) (thf)] for (the largest atom extremal of the detailed geometrical data
2
3
Ln = Pr, Lu, together with the unit cell determination of available at present) to Ln = Pr (3); also included are the
the Ln = La adduct (regrettably unavailable in suitable form counterpart data for [Ce(Me pz) (Me pzH)] (2b) – the pyr-
2
3
2
2
for a single-crystal structural determination) and data avail- azole analogue. Table S2 presents data for the Ln = Nd
[
2d]
able in the literature for Ln = Nd defines these complexes (4), Lu (7) extrema of the β domain, together with values
Figure 1. Molecular projections of (a) [Ce(Me
2
pz)
3
(thf)]
2
(2a) and (b) [Ce(Me
2
pz)
3
(Me
2 2
pzH)] (2b), together with simplified schematics
(c,d) of the bridging coordination, as representative structures for 1–3. In 2b, the Me
2
pzH H(12) is included to show the intramolecular
hydrogen-bond. Selected bond lengths [Å] for 2a: Ce(1)–N(21) 2.580(3), Ce(1)–N(21)* 2.753(3), Ce(1)–N(22) 2.561(3), Ce(1)–N(22)*
2
3
.739(3), Ce(1)–N(31) 2.473(3), Ce(1)–N(32) 2.485(3), Ce(1)–N(41) 2.463(3), Ce(1)–N(42) 2.489(3). Ce(1)–C(23)* 2.953(3), Ce(1)–C(24)*
.080(3), Ce(1)–C(25)* 2.969(3), Ce(1)–O(1) 2.514(2). Selected bond lengths [Å] for 2b: Ce(1)–N(11) 2.6039(15), Ce(1)–N(21) 2.5950(15),
Ce(1)–N(21)* 2.7367(15), Ce(1)–N(22) 2.5813(15), Ce(1)–N(22)* 2.7451(15), Ce(1)–N(31) 2.5074(16), Ce(1)–N(32) 2.4701(15), Ce(1)–
N(41) 2.4621(15), Ce(1)–N(42) 2.4591(16), Ce(1)–C(23)* 2.990(2), Ce(1)–C(24)* 3.113(2), Ce(1)–C(25)* 2.973(18).
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for Ln = Y[10] and Ho (5). As expected for isogeometric coordinate [Ln{OC H (iPr)-2,6-μ-(O,η -Ar)-O-C H (iPr)-
6
6
3
6
3
ions, the bond lengths and angles are similar for 5 and the 2,6}] {Ln = La 2.978(10)–3.164(9) Å; Ln = Nd 2.898(12)–
2
[
17]
3+
3+ [16]
Y species.
3.183(1) Å } (Nd 0.04 Å smaller than Ce ), and the
La–C distances in nine-coordinate [La(η -ArH)(AlCl ) ]
Ar-H = C Me or PhMe) [2.927(7)–3.035(7) Å].
dition, they are similar to the Nd–C distances of the η (pz)-
Nd interaction of [Nd (pz) (pzH) ] [2.882(3)–3.030(3) Å],
and to the Ce–C bond lengths of the η -Ar–Ce coordina-
6
4
3
[
18]
(
In ad-
6
6
5
2
5
Complexes of the Larger Lanthanoids with μ-η :η -
[
5e]
3
9
2
Pyrazolate Bonding {[Ln(Me pz) (thf)] } {ЈαЈ-form; Ln =
2
3
2
6
Ce (2a), Pr (3)}
tion in seven-coordinate [Ce(OC H Ph -2,6) ] [2.975(3)–
6
3
2
3
Because 1, 2a and 3 have very similar unit cells and IR 3.167(3) Å].[19]
spectra (see Exp. Section), it can be inferred that they have
In [Ce(Me pz) (Me pzH)] {2b; Figure 1 (b)}, the thf sol-
2 3 2 2
similar structures, but only 2a and 3 allowed full structure vent donor of 2a is replaced by a molecule of Me pzH,
2
determinations. The dimer of 2a, together with its pyrazole retaining the binuclear α-form and the novel bridging pair
2
5
analogue 2b, and a schematic of the bonding are presented of μ-η :η -Me pz ligands, both cerium atoms of 2b remain-
2
in Figure 1 together with key bond lengths. The lanthanoid ing ten-coordinate with a coordinating pyrazole in place of
2
atoms are each ligated by a pair of terminal η -Me pz the thf of 2a. Such replacement of thf by Me pzH is known
2
2
anions and one thf molecule in a trans disposition across for oxygen-centred Na/Ln 3,5-dimethylpyrazolate cages.[
the dimer; two further μ-η :η ligands associated with each In the pyrazole-coordinated analogue of 2a, the pairs of
2c]
2
5
lanthanoid are also present, so that the lanthanoid atom is nitrogen donor atoms are slightly more symmetrically coor-
ten-coordinate. For ligand N(21,22), the C(24)–N(2n)(cen- dinated than in 2a, but the Me pz, Ce–N and Ce–C bond
2
2
troid)–Ln(1) angle (ca. 177°) is indicative of η (σ)-bonding lengths are very similar in both compounds (Figure 1 and
to the lanthanoid, whereas the C(24)-(ring centroid)–Ln(1Ј) Table S1). However, the Ce–N(11) bond of the mono-
5
angle (ca. 99°) is consistent with η (π)-bonding (the Ln–C dentate Me pzH ligand in 2b is ca. 0.1 Å longer than the
2
5
bond lengths of the η -bound ligand are discussed below). Ce–O (thf) bond that it replaces (in 2a), with some quite
Such a symmetrical η :η -pyrazolate-bridged dimeric struc- significant changes in the associated angular geometries be-
2
5
ture has not previously been observed in lanthanoid chem- ing evident (Table S1). The nitrogen-bound hydrogen atom
[
1,14]
istry,
having only previously been observed among [H(12)] interacts with the nitrogen-atom of an adjacent ter-
[
4b,4c]
Group 2 complexes.
Indeed, it is surprising that a com- minal pyrazolate ligand at a distance of 2.33(Å), with a
plex with this bridging array can be crystallised from thf N(12)–N(31) distance of 3.042(2) Å. Such a distance is
without cleavage of the bridge. Previous examples of this longer than the reported hydrogen-bonding distances in
coordination found in rare-earth chemistry[
5c,5d]
come from [Nd(η -Me pz) {κ (N)-Me pz}(Me pzH) (py)],
2
1
which
2
2
2
2
2
solventless syntheses or from the use of nonpolar solvents.
shows two, much closer N···H interactions at 1.96(3) and
2
[5b]
In 2a and 3, the terminal (ter) and bridging (br) η - 1.97(2) Å. This is ascribed to the presence of the uncoor-
2
5
1
Me pz (of the μ-η :η donor) chelate symmetrically to the dinated nitrogen of the η -Me pz ligand, permitting less
2
2
5
lanthanoid atom and the two Ln–N distances of the η - hindered access for hydrogen-bonding. However, the Ce–
Me pz–Ln interaction are similar. The Ln–N bond lengths N(11)–N(12)/C(15) angles are very unsymmetrical
2
5
2
2
2
5
decrease in the series η -Me pz Ͼ η
-Me pz Ͼ η (ter)- [117.41(11), 135.82(12)°]. The η :η bridging coordination
2
(br)
2
Me pz (Figure 1). A search of the Cambridge Structural motif displayed in both complexes 2a and 2b contrasts with
2
Database suggests that 2a (and 2b) are the first structurally that of the tetranuclear europium(II) 3,5-di-tert-butylpyr-
[
15]
2
5
characterised monometallic pyrazolatocerium complexes.
azolate complex [Eu (μ-η :η -tBu pz) (tBu pz) ] , in which
2 2 2 2 2 2
2
5
5
In the absence of precedents, the observed Ce–N(pz) bond pairs of bridging η :η pyrazolate ligands bind η to the
lengths (Table S1) can be compared with those of appropri- same europium atom, with Eu–C(tBu pz) distances of
2
[
5a]
ate lanthanum pyrazolates, because the ionic radii of ten- 3.019(4)–3.178(5) Å.
In the bimetallic systems, [K(tol-
3
+
3+
3+
[16]
coordinate La and Ce (or nine-coordinate Pr and uene)Ln(tBu pz) ] (Ln = La, Sm, Tb, Yb, Lu), the pyr-
2
4
3
+
2
5
nine-coordinate Ce ) differ by less than 0.02 Å.
for example, the terminal Ce–N bond lengths are similar to sium.
the terminal La–N bond length of the ten-coordinate cen-
Thus, azolate ligands bridge η to the rare-earth and η to potas-
[
5c]
[5d]
tral lanthanum atom of [La (Ph pz) ]
as well as to the
3
2
9
corresponding values for the nine-coordinate outer La
1
1
Complexes of the Smaller Lanthanoids with μ-κ (N):κ (N)-
[
5d]
5
atoms.
Likewise, the Ce–N bonds of the η -Me pz-Ce
2
Pyrazolate Bonding and Bridging O(thf) {[Ln(Me pz) -
thf)] } {ЈβЈ-form, Ln = Nd (4) [Ho (5)]–Lu (7), Y}
2
3
interactions are similar to the corresponding data for
(
2
[
5d]
2
[
La (Ph pz) ].
However, because the η -binding of the
3
2
9
2
5
2
μ-η :η -Ph pz ligands of this trinuclear complex is highly Dimeric complexes 4, 5 and 7 have two terminal η -pyr-
unsymmetrical, a comparison with the symmetrical μ-η - azolate ligands (the only common feature with the α-form),
2
2
1
1
Me pz-Ce interactions of 2a is less appropriate, although two μ-κ (N):κ (N)-Me pz ligands (the most common pyr-
2
2
5
[1,14]
the bonding appears stronger in 2a. For the η -Me pz-Ce azolate ligation,
although not for rare-earths), and two
2
ligation, the observed Ce–C bond lengths [2.953(3)– bridging thf donors (a very uncommon thf binding mode
3
.080(3) Å] correspond well with the Ln–C distances in six- in non-alkali metal chemistry[2d,10,15,20]) (Figure 2). The X-
Eur. J. Inorg. Chem. 0000, 0–0
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FULL PAPER
Figure 2. (Left) Molecular projection of [Lu(Me
Right) A schematic of the bridging mode. Selected bond lengths [Å] for 7: Lu(1)–N(21) 2.3508(15), Lu(1)–N(22)* 2.351(2), Lu(1)–N(31)
.290(2), Lu(1)–N(32) 2.281(2), Lu(1)–N(41) 2.279(2), Lu(1)–N(42) 2.269(2), Lu(1)–O(11) 2.6076(13), Lu(1)–O(11Ј) 2.6644(14).
2 3 2
pz) (thf)] (7), a representative structure for the Ln = Nd–Lu domain of the β-form;
(
2
ray crystal structures of [Ho(Me pz) (thf)] (5) and [Lu-
2
3
2
(
Me pz) (thf)] (7) are isomorphous with those of the pre-
2 3 2
[2d]
viously reported [Nd(Me pz) (thf)] (4) and [Y(Me pz) -
2
3
2
2
3
[
10]
(
thf)]2
shows that the decrease in Ln–N/O bond lengths from 4 to
is Ն 0.13 Å (Table S2), and is consistent with the decrease
analogues. Examination of average bond lengths
7
3
+
3+ [16]
in ionic radii from Nd to Lu , indicating that there is
3
+
no steric stress associated with the small Lu ion. Given
that complexes 4, 5 and 7 (together with the Ln = Y ana-
logue) all crystallise with the same coordination environ-
ment, it is likely that the other rare-earth elements included
in the progression from Nd to Lu crystallise in the same
manner, including 6, for which single crystals could not be
obtained.
Figure 3. Asymmetric unit of 8 showing the two molecules of
Nd(Me pz) (py) ] (8) (presented as disposed in the unit cell). Se-
lected bond lengths for molecule 1: Nd(1)–N(11) 2.451(4), Nd(1)–
[
2
3
3
Thus, there is a size-based structural break for these bi-
nuclear rare-earth 3,5-dimethylpyrazolate complexes, sug- N(12) 2.473(4), Nd(1)–N(21) 2.508(4), Nd(1)–N(22) 2.464(4),
Nd(1)–N(31) 2.475(4), Nd(1)–N(32) 2.469(4), Nd(1)–N(41)
gesting domains of existence are bounded by Ln = La, Pr
2.704(4), Nd(1)–N(51) 2.656(4), Nd(1)–N(61) 2.693(4).
for the former and Ln = Nd, Lu (Y) for the latter metals.
What is noteworthy is the considerable difference in the
bridging binding between the two structural classes, and the
crystallisation of both from thf without cleavage of the
bridging bonding, not even of the μ-(O)thf mode of 4, 5
and 7.
The Nd–N(Me pz) distances (av. 2.47 Å) exceed Nd–N
2
ter
of 4 (av. 2.41 Å, see Figure 3), concomitant with an increase
[16]
in coordination number of one, and are similar to those
found in the nine-coordinate neodymium pyrazolate com-
[2g]
plex [Nd(Ph pz) (thf) ]·thf (av. 2.46 Å),
which has mer
2
3
3
thf ligands. Similarly, the Nd–N(py) bond lengths (av.
2
2
.63 Å) are longer than that of eight-coordinate [Nd(η -
The Structure of Monomeric [Nd(Me pz) (py) ]
1
2
3
3
Me pz) {κ -(N)-Me pz}(Me pzH) (py)], by the expected
amount. The trans-influences for some ligands have been
2
2
2
2
2
[
16]
Contrasting with the stability of the dimeric complexes
[
21]
noted in rare-earth chemistry
for the Ph pz ligand in [Nd(Ph pz) (thf) ],
and have been proposed
1, 2a, 3, 4, 5 and 7 towards thf, crystallisation of
[
2g]
but there is
[
Nd(Me pz) (thf)] from pyridine gives the mononuclear
2
2
3
3
2
3
2
little evidence for any such effect in the present complex.
However, the longer Nd–N(py) bonds could account for the
relatively facile loss of py from complex 8 (see above).
complex [Nd(Me pz) (py) ] (8). Complex 8 crystallises with
two similar discrete [Nd(Me pz) (py) ] neutral molecules
within the asymmetric unit (Figure 3). The neodymium
atoms are nine-coordinate with three η -pyrazolate ligands
and three pyridine molecules (Figure 3, Table S3), with the
pyridine donors adopting a meridional quasioctahedral dis-
position.
2
3
3
2
3
3
2
Conclusions
Solvated lanthanoid pyrazolate complexes of the compo-
sition [Ln(Me pz) (thf)] (Ln = La, Ce, Pr, Nd, Ho, Yb,
2
3
2
Eur. J. Inorg. Chem. 0000, 0–0
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FULL PAPER
and Lu) have been prepared by three different synthetic by 19F NMR spectroscopy, which indicated complete consumption
of Hg(C
from the metal residue by filtration and dried under vacuum to
give [La(Me pz) (thf)] (1) as a white powder, yield 0.51 g (76%).
H NMR (300 MHz, C , 303.2 K): δ = 1.38 [m, 16 H, β-
CH (thf)], 2.11 (br. s, 36 H, Me), 3.53 [m, 16 H, α-CH (thf)], 5.96
br. s, 6 H, H4-pz) ppm; a precipitate formed on attempted dissol-
6 5 2 6 5
F ) and formation of C F H. The solution was separated
routes, with redox transmetalation protolysis (RTP) using
Hg(C F ) being an effective and high-yielding general
6
5 2
2
3
2
method. Despite the common formula, there is a substan-
tial structural break between the domains of the larger rare-
1
6
D
6
3
+
3+
3+
3+
2
2
earth ions (La , Ce , Pr ) and the smaller ions (Nd –
(
3
+
Lu ), with a striking change in the bridging bonding from
the unusual η :η -pyrazolate coordination for La and Ce to
1
ution in C
6
D
6
. H NMR (300 MHz, C
6 6 2
D + D O, 303.2 K): δ =
2
5
1
.42 [m, 8 H, β-CH
2
(thf)], 1.82 (br. s, 18 H, Me), 2.25 (br. s, 18
1
1
the completely different μ-κ (N):κ (N)-Me pz and μ-(O)thf H, Me), 3.56 [m, 8 H, α-CH (thf)], 5.68 (s, 6 H, H4) ppm.
2
2
bridging for Nd–Lu. Although the bridging bonding resists
C
38
H58La
2
N
12
O
2
(992.77): calcd. C 45.97, H 5.89, N 16.93; found
cleavage by thf, cleavage by pyridine gave nine-coordinate, C 45.84, H 5.71, N 16.82. Complex 1 was crystallised from a thf/
hexane mixture at room temperature and found to be monoclinic
monomeric [Nd(Me pz) (py) ]. Overall, reduction of the
bulk of the 3,5-disubstituted pyrazolate ligand substituents
2
3
3
P, a = 11.87(2), b = 14.04(3), c = 12.77(2) Å, β = 96.49(3)°; V =
3
2
114 Å ; T = 123 K, on a small single specimen.
pz) (thf)] (2a) and [Ce(Me pz) (Me pzH)]
Cerium filings (0.18 g, 1.3 mmol), 3,5-dimethylpyrazole (0.37 g,
.9 mmol) and Hg(C (1.02 g, 1.9 mmol) were added to a
from tBu pz and Ph pz to Me pz transforms the structures
2
2
2
of thf-solvated tris(pyrazolato)lanthanoid(III) complexes [Ce(Me
2
3
2
2
3
2
2
(2b): Method a:
from eight- or nine-coordinate [Ln(tBu pz or Ph pz) (thf) ]
2
2
3
n
3
6 5 2
F )
(
n = 2,3) monomers to [Ln(Me pz) (thf)] dimers with un-
2 3 2
Schlenk flask and dissolved in thf (10 mL). After stirring (1 d) the
solution was separated from the metal residue and the solvents
usual bridging features.
2 3 2
were evaporated to dryness, to give [Ce(Me pz) (thf)] (2) as a white
powder (0.37 g, 58%). The ligand to solvent ratio was determined
by NMR analysis of a hydrolysed sample. H NMR (300 MHz,
Experimental Section
1
C
6
D
6
+ D
2
O, 303.2 K): δ = 1.42 [m, 8 H, β-CH
2
(thf)], 2.03 (br. s,
General Considerations: All products were air-sensitive and re-
quired manipulation in an inert atmosphere and hence the use of
a glovebox, Schlenk flask and vacuum-line techniques. All solvents
were predried with sodium metal and then further dried by distil-
lation over sodium or sodium/benzophenone. The lanthanoid met-
als used were purchased from either Rhône–Poulenc or Santoku
either as fine powders or as metal ingots, which were manually filed
into metal filings in an inert atmosphere for use in the reactions.
36 H, Me-pzH), 3.58 [m, 8 H, α-CH
2
(thf)], 5.69 [s, 6 H, H4
(
(
pzH)] ppm. IR (Nujol): ν˜ = 3327 (w), 3089 (vw), 1573 (m), 1514
vs), 1422 (s), 1314 (m), 1261 (m), 1095 (m), 1075 (m), 1034 (m),
1
7
008 (vs), 962 (m), 917 (vw), 881 (m), 813 (m), 789 (m), 772 (m),
30 (m) cm .
–
1
Method b: In a glove box, [Ce{N{Si(CH ) } } ] (0.16 g, 0.25 mmol)
was added to a sample vial charged with Me PzH (0.070 g,
3
2 2 3
2
3
,5-Dimethylpyrazole (Me
2
pzH) (Aldrich) was purified by sublima-
] was synthesised by a modified
entailing treatment of [CeCl (thf) ] with
three equivalents of [K{N{Si(CH }] in hexane, and was purified
0.73 mmol) in thf (3 mL). The reaction mixture was stirred for 18 h
tion before use. [Ce{N{Si(CH
literature procedure,
3
)
2
}
2
}
3
then dried under vacuum. After washing with hexane, a thf/hexane
mixture (2 mL/5 mL) was added to dissolve the products and the
sample was allowed to evaporate slowly, forming large clear needles
of [Ce(Me Pz) (thf)] (2a; 0.06 g, 48%), and small clear blocks of
[
22]
3
2
3 2 2
) }
by filtration, evaporation to dryness and crystallisation from fresh
hexane.
2
3
2
[Ce(Me pz) (Me pzH)] (2b; 0.02 g, 15%). Small needles of 2a were
2
3
2
2
handpicked and dried under vacuum. C34
thf, 923.07) calcd. C 44.23, H 5.45, N 18.20; found. C 44.57, H
.45, N 17.51. Insufficient 2b for additional characterisation re-
2
H50Ce N12O (loss of one
Microanalyses were performed at the Campbell Microanalytical
Laboratory of the University of Otago (New Zealand) (an excep-
tion was 2a, which was analysed with an “elementar vario MICRO
cube” by Mr. Stephen Boch of Tübingen University). Metal analy-
ses were performed by a literature method.[ IR data were ob-
tained from Nujol mulls for the region 4000–650 cm with a Per-
kin–Elmer 1600 FTIR spectrometer. 1H NMR spectra were re-
corded with a Bruker DRX400 (400 MHz) spectrometer, and with
a Bruker DRX300 for the hydrolysed sample of complex 2a. No
interpretable NMR spectra were obtained for paramagnetic com-
plexes 2a, 2b, 3, 4, 5 and 6.
5
mained after the X-ray study.
2j]
[Nd(Me pz) (thf)] (4) and [Nd(Me pz) (py) ] (8): Neodymium fil-
2
3
2
2
3
3
–1
ings (0.91 g, 6.31 mmol), 3,5-dimethylpyrazole (1.01 g, 10.5 mmol)
and bis(pentafluorophenyl)mercury (2.78 g, 5.20 mmol) were
stirred for 6 d in thf (40 mL). The mixture was then heated for 5 h
at 60 °C. The blue solution obtained on filtration of the solids was
evaporated, hexane was added, and the solution was left to crystal-
lise at room temperature. Blue single crystals of [Nd(Me pz) -
2
3
(
thf)]
nation: C38
10.780(2), c = 11.200(2) Å, α = 77.65(3), β = 68.72(3), γ = 61.17(3)°;
2
(4) were obtained and characterized by a unit cell determi-
[
6
La(Me
2 3 2
pz) (thf)] (1): Method a: Lanthanum filings (0.97 g,
58 2 2
H N12Nd O
; M = 1003.45; a = 10.720(2), b =
.98 mmol), 3,5-dimethylpyrazole (1.00 g, 10.4 mmol) and two
–3
drops of mercury were sealed under vacuum (ca. 10 Torr) in a
Carius tube and heated to 300 °C for 4 d. The white product was
extracted with thf to give colourless microcrystals of the title com-
plex. The H NMR spectrum displayed chemical shifts concordant
with those reported.
3
V = 1055.4(4) Å ; Temp = 123 K. The blue crystals of [Nd(Me
thf)] (4) were then crystallised from pyridine to give blue crystals
of 8.
2 3
pz) -
(
2
1
[
2h]
Yield: 1.02 g (59%). IR (Nujol): ν˜ = 3311
2 3 2
[Nd(Me pz) (thf)] (4): Yield: 1.35 g (77%). IR(Nujol): ν˜ =
(w), 3200 (w), 3100 (w), 1574 (w), 1513 (vs), 1413 (s), 1366 m (sh),
1574(m), 1518 (s), 1414 (s), 1314 (m), 1171 (w), 1090 (w), 1062 (w),
1
306 (w), 1260 (w), 1152 (w), 1099 (w), 1047 (m), 1029 (m), 1008 1029 (m), 1008 (m), 956 (m), 931 (w), 842 (w), 814 (m), 794 (m),
–1
–1
(
vs), 962 (m), 877 (m), 806 (m), 775 (m), 740 cm .
Method b: Lanthanum filings (0.32 g, 2.3 mmol), Hg(C
1.06 g, 2.0 mmol) and Me PzH (0.39 g, 4.0 mmol) were added to
768 (m), 742 (w), 726 (m), 654 (w) cm (in agreement with reported
data).[
2d]
6 5 2
F )
1
(
2
[Nd(Me
2
pz)
3
(py)
3
] (8): Yield: 0.33 g (61%). H NMR (C
6
D
6
): δ =
a Schlenk flask and dissolved in thf (5 mL) with stirring at room
temperature. After 16 h, a small amount of solution was analysed
–0.15 [s, 6 H, H 2,6 (py)], 3.77 [s, 6 H, H 3,5 (py)], 4.45 [s, 3 H, H4
(py)], 6.60 (s, 18 H, Me), 15.38 [s (br), 3 H, H4 (pz)] ppm. IR
Eur. J. Inorg. Chem. 0000, 0–0
6
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/KAP1
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FULL PAPER
(
Nujol): ν˜ = 1589 (s), 1577 (s), 1517 (vs), 1412 (vs), 1312 (vs), 1242
dissolved in thf (5 mL) with stirring at room temperature. After
14 h, a small amount of solution was analysed by F NMR spec-
–
1
19
(
s), 1152 (s), 1008 (s), 770 (s), 721 (s), 701 (s), 668 (s) cm . Metal
Nd (666.92): calcd. 21.63%; found
1.55%. Elemental analysis (after transport to New Zealand)
8.5Nd (627.36 – loss of 0.5 pyridine): calcd. C 52.65, H
.38, N 18.98; found C 52.36, H 5.56, N 18.41.
Ho(Me pz) (thf)] (5): Holmium filings (1.04 g, 6.31 mmol), 3,5-
analysis (fresh sample) C30
2
C
5
H
36
N
9
troscopy, which indicating complete consumption of Hg(C
6 5 2
F )
and formation of C H. The reaction mixture was filtered and the
6 5
F
27.5
H
33.5
N
filtrate was evaporated under vacuum to give a white powder. The
powder was dissolved in hot thf (5 mL) and slowly cooled to pro-
1
duce small clear hexagonal crystals of 7, yield 0.30 g (53%).
NMR (300 MHz, C , 333.2 K): δ = 1.45 [m, 8 H, β-CH
.95 (s, 36 H, Me), 3.57 [m, 8 H, α-CH (thf)], 5.77 (s, 6 H,
H4) ppm. IR (Nujol): ν˜ = 3108 (w), 1655 (vw), 1578 (m), 1522 (m),
417 (vs), 1377 (s), 1326 (vs), 1261 (w), 1173 (vw), 1093 (m), 1073
m), 1037 (s), 1011 (s), 980 (s), 934 (w), 915 (vw), 840 (w), 813 (s),
H
[
2
3
2
6
D
6
2
(thf)],
dimethylpyrazole (1.04 g, 10.8 mmol) and bis(pentafluorophenyl)-
mercury (2.78 g, 5.20 mmol) in thf (40 mL) were heated to 60 °C
with stirring for 2 h and then the reaction mixture was stirred for
1
2
1
1
0 d at room temperature. The mixture was then filtered, and the
(
7
orange filtrate was concentrated under vacuum and crystallised
from thf/hexane to give 5, yield 1.17 g (63%). IR (Nujol): ν˜ = 1577
(
–
1
92 (s), 772 (s), 725 (m) cm . C38
2 12 2
H58Lu N O (1064.90): calcd. C
42.86, H 5.49, N 15.78; found C 42.84, H 5.54, N 15.68.
m), 1520 (vs), 1417 (vs), 1324 (s), 1301 (sh), 1175 (m), 1089 (w),
1
8
C
3
068 (m), 1056 (w), 1034 (m), 1010 (m), 997 (m), 959 (m), 933 (w),
Structure Determination: Full spheres of CCD area-detector dif-
39 (w), 812 (m), 793 (m), 769 (m), 743 (w), 726 (m), 652 (m) cm . fractometer data were measured (ω-scans, monochromatic Mo-K
(1044.82): calcd. C 44.02, H 4.86, N 16.21, Ho radiation, λ = 0.7107 Å), yielding Nt(otal) reflections, merging to N
1.82; found C 43.20, H 5.99, N 16.59, Ho 31.38. unique reflections after empirical/multiscan absorption correction
Yb(Me pz) (thf)] (6): Ytterbium filings (1.09 g, 6.30 mmol), 3,5-
–
1
α
38
H58Ho
2
N
12
O
2
3
(R
int cited) using either the Apex II program suite,[ or SOR-
23]
[
2
3
2
[24]
TAV,
with these data being used in the full-matrix least square
dimethylpyrazole (1.04 g, 10.8 mmol) and bis(pentafluorophenyl)-
mercury (2.78 g, 5.20 mmol) in thf (40 mL), were stirred for 15 min
at room temperature and then filtered, resulting in a bright-orange
solution. A peach-coloured, powdery solid precipitated from the
filtrate on cooling that was not soluble in thf, thf/hexane, toluene,
or pyridine, yield 0.70 g (33%). Metal analysis calculated for 6 (im-
2
refinements on F , refining anisotropic displacement parameter
forms for the non-hydrogen atoms, hydrogen atom treatment fol-
lowing a riding model. N
o
reflections with IϾ2σ(I) may be consid-
2
2
2
–1
ered “observed”; reflection weights were [σ (F
o
) + (aP) (+bP)]
2
2
[25]
[
P = (F
o
+ 2F
c
)/3], computation using SHELX software
with
[26]
the Olex 2 graphical interface. Pertinent results are presented in
the Tables and Figures, with the latter showing the non-hydrogen
atoms with 50% probability amplitude displacement envelopes.
mediately on isolation) C38
H
58
N
12
O
2
2
Yb (1061.02) calcd. Yb
32.62; found Yb 32.46. After extended drying of the sample: IR: ν˜
=
1575 (w), 1526 (vs), 1406 (vs), 1342 (w), 1303 (vs), 1147 (w), 1066
–1
(s), 1026 (vs), 981 (m), 778 (s), 736 (s), 721 (m) cm . Microanalysis CCDC-981984 (for 2a), -981985 (for 2b), -981986 (for 3), -959093
calculated for [Yb(Me
2
pz)
3
], C15
H
21
N
6
Yb (458.41, loss of thf): C
(for 5), -981988 (for 7), and -981989 (for 8) (Table 1) contain the
supplementary crystallographic data for this paper. These data can
be obtained free of charge from The Cambridge Crystallographic
Data Centre via www.ccdc.cam.ac.uk/data_request/cif.
39.30, H 4.62, N 18.33; found C 39.51, H 4.55, N 17.91. Note:
When the reaction mixture was stirred for Ͼ 15 min, the mixture
darkened and a dark-grey solution was obtained on filtration.
[
Lu(Me
2
pz)
3
(thf)]
2
(7): Lutetium metal fillings (0.32 g, 1.8 mmol),
pzH (0.31 g, 3.2 mmol) were
Supporting Information (see footnote on the first page of this arti-
cle): Further crystallographic data..
Hg(C
6
F
5
)
2
(0.86 g, 1.6 mmol) and Me
2
Table 1. Crystal/refinement data.[a]
b (Ce)[b]
2
2a (Ce)[c]
3 (Pr)[c]
5 (Ho)[c]
7 (Lu)[c]
8 (Nd)[d]
M
r
[Da]
1043.3
995.2
monoclinic
1044.8
1064.9
666.9
Crystal system
Space group
a [Å]
b [Å]
c [Å]
α [°]
β [°]
triclinic
triclinic
triclinic
triclinic
¯
¯
¯
¯
P1 (#2)
P2
1
/n (#14)
P1 (#2)
P1 (#2)
P1 (#2)
9.1695(2)
12.1187(3)
12.5199(3)
113.863(1)
93.963(1)
111.751(1)
1141.76(5)
11.9695(2)
14.1574(3)
12.8426(2)
10.6592(6)
10.7415(6)
11.1470(6)
77.732(1)
69.029(1)
60.267(1)
1033.9(2)
10.6049(2)
10.6509(2)
11.0844(2)
81.831(1)
69.233(1)
60.403(1)
1017.07(3)
10.789(2)
17.481(4)
19.773(4)
70.81(3)
64.29(3)
89.07(3)
3138(2)
97.184(1)
γ [°] 3
V [Å ]
2159.18(7)
–
3
D
c
[gcm ] (Z)
1.51
2.0
7
(2)
1.53
2.1
1
(2)
(2)
1.67
3.9
8
(1)
1.73
4.9
9
(1)
2
1.41 (4)
–
1
μMo [mm ]
1.69
0.25, 0.18, 0.13
0.74
3
Specimen [mm ]
ЈTЈmin./max.
0.3, 0.3, 0.2
0.94
0.4, 0.1, 0.1
0.71
0.25, 0.22, 0.18
0.77
0.2, 0.1, 0.1
0.88
2
N
θ
t
max (deg.)
58
59
50
72
61
50
49552
6115 (0.025)
5706
19508
5803 (0.029)
5075
16421
3766 (0.062)
3136
20979
9640 (0.018)
9201
16671
5962 (0.015)
5719
38934
11011 (0.067)
9003
N (Rint
N [IϾ2σ(I)]
o
)
R1 [IϾ2σ(I)]
wR2 (all data)
a(, b)
0.019
0.052
0.030, 0.78
1.09
1.4
0.032
0.072
0.007, 7.6
1.18
1.3
0.057
0.14
0.042, 22
1.20
3.3
0.015
0.040
0.022, 0.45
1.06
1.3
0.013
0.047
0.026, 0.03
1.24
0.65
0.043
0.12
0.071, 4.7
1.03
3.7
S
–3
|Δρmax| [eÅ ]
T [K]
100
100
100
153
123
123
10]
¯
[
6
a] For the Ln = Y analogue,[ triclinic P1(#2) the recorded dimensions are 10.798(1), 10.808(1), 11.313(1) Å, 76.914(2), 68.940(2),
3
0.510(2)°, V = 1071.5(2) Å (T not specified). [b] C40
H58Ce
2
N16. [c] C38
H58Ln
2
N
12
O
2
. [d] C30
36 9
H N Nd.
Eur. J. Inorg. Chem. 0000, 0–0
7
© 0000 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

Job/Unit: I40099
/KAP1
Date: 03-04-14 17:46:42
Pages: 9
www.eurjic.org
FULL PAPER
2
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The authors gratefully acknowledge support from the Australian
Research Council (ARC Discovery, grant number DP 130100152)
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Published Online: ᭿
Eur. J. Inorg. Chem. 0000, 0–0
8
© 0000 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

Job/Unit: I40099
/KAP1
Date: 03-04-14 17:46:42
Pages: 9
www.eurjic.org
FULL PAPER
Rare-Earth Complexes
G. B. Deacon,* R. Harika, P. C. Junk,*
B. W. Skelton, D. Werner,
A. H. White ...................................... 1–9
The Synthesis, Structures and Poly-
morphism of the Dimeric Trivalent Rare-
Earth 3,5-Dimethylpyrazolate Complexes
2 3 2
[Ln(Me pz) (thf)]
Keywords: Lanthanides / Rare earths / N
ligands / Bridging ligands / Structure eluci-
dation / Chelates
Contrasting structures and bridging Me pz groups for Ln = La–Pr and Ln = Nd–Lu are
described.
2
Eur. J. Inorg. Chem. 0000, 0–0
9
© 0000 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim