Divalent europium and ytterbium complexes supported by a bulky 2-pyridyl amido ligand: Synthesis, structure and reactivity studies

Article abstract of DOI:10.1039/c2dt30333g

Metallation of the N-arylated 2-pyridyl amine [HN(C₆H ₃Prⁱ₂-2,6)(2-C₅H₃N-6-Me)] (1) with potassium hydride in Et₂O and THF yielded potassium amides [{KL(OEt₂)}₂] [L = N(C₆H₃Pr ⁱ₂-2,6)(2-C₅H₃N-6-Me)] (2) and KL(THF)₂ (3), respectively. Treatment of LnI₂(THF) ₂ (Ln = Eu, Yb) with 2 afforded the corresponding Ln(ii) amido complexes [EuL(μ-L)₂K(THF)] (4) and [YbL₂(THF) ₂] (5). In contrast, an analogous reaction of SmI₂(THF) ₂ with 2 only led to the isolation of homoleptic Sm(iii) triamide [SmL₃] (6). The reaction chemistry of divalent complexes 4 and 5 was examined. Oxidation of the Eu(ii) amido complex 4 by iodine yielded the trivalent [EuL₃] (7), whereas addition of Yb(ii) diamide 5 to iodine led to the isolation of the bis(amido) Yb(iii) iodide complex [YbL ₂(i)(THF)] (8). Complex 8 could also be prepared by the reaction of 5 with copper(i) iodide. A subsequent reaction of 8 with KOBu^t gave, unexpectedly, the Yb(iii) triamide [YbL₃] (9). Reactions of complex 5 with diphenyl dichalcogenides PhEEPh (E = S, Se, Te) also gave [YbL ₃] (9) as the only isolable product. The solid-state structures of complexes 2 and 4-9 were elucidated by X-ray diffraction analysis.

Full text of DOI:10.1039/c2dt30333g

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Divalent europium and ytterbium complexes
supported by a bulky 2-pyridyl amido ligand: synthesis,
Cite this: Dalton Trans., 2013, 42, 2841
structure and reactivity studies†
Ka Wai Ku, Chi Wai Au, Hoi-Shan Chan and Hung Kay Lee*
Metallation of the N-arylated 2-pyridyl amine [HN(C6H3Pri2-2,6)(2-C5H3N-6-Me)] (1) with potassium
hydride in Et2O and THF yielded potassium amides [{KL(OEt2)}2] [L = N(C6H3Pri2-2,6)(2-C5H3N-6-Me)] (2)
and KL(THF)2 (3), respectively. Treatment of LnI2(THF)2 (Ln = Eu, Yb) with 2 afforded the corresponding
Ln(II) amido complexes [EuL(μ-L)2K(THF)] (4) and [YbL2(THF)2] (5). In contrast, an analogous reaction of
SmI2(THF)2 with 2 only led to the isolation of homoleptic Sm(III) triamide [SmL3] (6). The reaction chem-
istry of divalent complexes 4 and 5 was examined. Oxidation of the Eu(II) amido complex 4 by iodine
yielded the trivalent [EuL3] (7), whereas addition of Yb(II) diamide 5 to iodine led to the isolation of the
bis(amido) Yb(III) iodide complex [YbL2(I)(THF)] (8). Complex 8 could also be prepared by the reaction of 5
with copper(I) iodide. A subsequent reaction of 8 with KOBut gave, unexpectedly, the Yb(III) triamide
[YbL3] (9). Reactions of complex 5 with diphenyl dichalcogenides PhEEPh (E = S, Se, Te) also gave [YbL3]
(9) as the only isolable product. The solid-state structures of complexes 2 and 4–9 were elucidated by
X-ray diffraction analysis.
Received 28th September 2012,
Accepted 20th November 2012
DOI: 10.1039/c2dt30333g
www.rsc.org/dalton
behaviour. They can be bound to metal ions in a monodentate,
N,N′-chelating or N,N′-bridging fashion (Chart 1). Additionally,
Introduction
Over the past few decades, there has been a growing interest in their steric and electronic properties can be readily modified
the chemistry of organolanthanide complexes supported by by introduction of various substituents at the amido nitrogen
various non-cyclopentadienyl ligands.1–3 Amido anions [NR2]− atom or on the pyridyl ring. Accordingly, a number of main-
(R = H, alkyl, aryl or silyl) have proven to be useful ancillary group, transition-metal and f-element complexes with interest-
ligands in organolanthanide(II) chemistry.3b,4 Amido com- ing coordination geometry as well as different degrees of
plexes of Sm(II), Eu(II) and Yb(II) derived from the bulky association have been reported.9–20 In recent years, Kempe and
[N(SiMe3)2]− ligand, and the related [N(Ph)(SiMe3)]− and co-workers have reported on the synthesis of Sm(II), Eu(II) and
[NPh2]− anions have been reported.5–7 Besides these three tra- Yb(II) complexes supported by several sterically very crowded
ditional lanthanide(II) ions, it has also been shown that a reac- pyridine-functionalized amido ligands, such as [N(C6H3Pri2-
tion system containing the [N(SiMe3)2]− ligand and the more 2,6){2-C5H3N-6-(C6H2Pri3-2,4,6)}]−
(Ap*),
[N(C6H3Pri2-2,6)-
reducing Tm(II), Dy(II) or Nd(II) ions has led to a facile {2-C5H3N-6-(C6H3Me2-2,6)}]− (Ap′), and [N(C6H2Me3-2,4,6)-
reduction of dinitrogen and the isolation of the corresponding {2-C5H3N-6-(C6H2Me3-2,4,6)}]− (ApMe).20 It was also reported
(N2)2− complexes.8
that a slight modification in the steric bulkiness of these
2-Pyridyl amides, with a general formula [N(R)(2-Py)]− (R = amido ligands could crucially affect the structures of the corre-
H, alkyl, aryl or silyl), are pyridine-functionalized amido sponding lanthanide(II) complexes.
ligands which have attracted considerable research interest in
the last few decades.9 One remarkable property of this class of
ligands is their ability to exhibit a flexible coordination
Department of Chemistry, The Chinese University of Hong Kong, Shatin, New
Territories, Hong Kong. E-mail: hklee@cuhk.edu.hk
†Electronic supplementary information (ESI) available: Crystallographic infor-
mation files (CIF), selected bond distances (Å) and angles (°) for complexes 2
and 4–9, 1H NMR spectrum of 9, and 1H NMR spectra showing the reactions of
complex 5 with PhEEPh (E = S and Se). CCDC 866987–866993. For ESI and
crystallographic data in CIF or other electronic format see DOI: 10.1039/c2dt30333g
Chart 1 Three common coordination modes of 2-pyridyl amido ligands.
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We are interested in the coordination chemistry and reactiv- Diisopropylaniline was allowed to react with 2-bromo-6-pico-
ity of metal complexes supported by anionic nitrogen-based line, in the presence of tris(dibenzylideneacetone)dipalladium(0)
ligands, such as amides19,21,22 and amidinates.23 Earlier, we (Pd2(dba)3) as the catalyst together with 1,3-bis(diphenyl-phos-
have studied the coordination behaviour of 2-pyridyl amides phanyl)propane (DPPP) and NaOBut, in toluene at 95 °C for
with transition-metal19a,b and trivalent lanthanide ions.19c two days. Work-up of the product mixture afforded compound
Recently, we have reported on the preparation and reaction 1 as a pale yellow solid in 80% yield. Subsequent metallation
chemistry of divalent samarium, europium and ytterbium of compound 1 with potassium hydride in diethyl ether and
complexes derived from the bulky amidinate ligand [PhC- THF solutions yielded potassium amides [{KL(OEt2)}2] (2) and
(NSiMe3)(NC6H3Pri2-2,6)]−.23b The 2-pyridyl amide and amidi- KL(THF)2 (3), respectively (Scheme 1). Alternatively, the THF-
nate systems have one structural similarity: both ligand adduct 3 could also be prepared by a transmetallation reaction
systems possess an NCN ligand backbone. This leads to the of lithium amide LiL with KOBut in THF. The formulation of
formation of highly strained four-membered MNCN metalla- complexes 2 and 3 was confirmed by NMR spectroscopy and
1
cycle rings when these ligands are bonded to the metals in a elemental analysis. The H and 13C NMR spectra of both com-
bidentate manner. In order to compare the coordination prop- plexes showed one set of resonance signals assignable to
erties of these two types of monoanionic N-donor ligands with ligand L as well as the respective donor solvent molecules (i.e.
divalent lanthanide ions, we have prepared a new 2-pyridyl 1 : 1 L/Et2O for 2 and 1 : 2 L/THF for 3). It is noted that the iso-
amido ligand, [N(C6H3Pri2-2,6)(2-C5H3N-6-Me)]− (L), which has propyl methyl groups of the L ligands on both complexes are
a steric requirement comparable to that of the amidinate anion diastereotopic and occur as two doublets (at 0.93 and
[PhC(NSiMe3)(NC6H3Pri2-2,6)]− recently reported by us.23b 1.18 ppm for 2, and 1.00 and 1.23 ppm for 3) in their respect-
Herein, we report on the synthesis and structural charac- ive 1H NMR spectra.25,26
terization of Eu(II) and Yb(II) complexes derived from amido
The solid-state structure of Et2O-adduct 2 was determined
ligand L. The reductive chemistry of these lanthanide(II) amides by single-crystal X-ray diffraction analysis. The molecular struc-
is also described. To our knowledge, studies on the reducing ture of complex 2 is illustrated in Fig. 1. Selected bond dis-
properties of lanthanide(II) complexes derived from 2-pyridyl tances and angles of the complex are provided in Table S1 in
ˉ
amido ligands have been rarely reported in the literature.
ESI.† Complex 2 crystallizes in the triclinic space group P1.
The crystal structure of 2 consists of two potassium ions
bridged by a pair of μ–η2, η2-bound L ligands. The K–N(amido)
distances measure 2.772(1) Å [K(1)–N(1)] and 3.006(1) Å [K(1)–
N(1)#1], whereas the corresponding K–N(pyridyl) distances are
2.836(2) Å [K(1)–N(2)] and 2.853(2) Å [K(1)–N(2)#1]. The
observed K(1)⋯K(1)#1 distance is 3.346(1) Å. Each potassium
ion is further coordinated by one Et2O solvent molecule, with
K(1)–O(1) being 2.704(1) Å.
Results and discussion
Ligand synthesis
The ligand precursor [HN(C6H3Pri2-2,6)(2-C5H3N-6-Me)] (1) was
prepared by a palladium-catalyzed aryl amination method as
developed
by
Buchwald
and
co-workers.24
2,6-
Scheme 1 Synthesis of complexes 2 and 3.
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Synthesis of Eu(II) and Yb(II) amido complexes
product from toluene led to the solvated complex [YbL2(THF)2]·
0.25C7H8 (5·0.25C7H8). Complexes 4 and 5·0.25C7H8 were iso-
lated as extremely air-sensitive orange and purple crystals,
respectively. The Eu(II) complex is readily soluble in THF and
hexane, whereas the Yb(II) complex is soluble in THF and
toluene but only sparingly soluble in diethyl ether and hexane.
Results of elemental analysis are in good agreement with the
Divalent europium and ytterbium complexes of the L ligand
were prepared by metathesis reactions of the appropriate
lanthanide(II) diiodide with potassium amide [{KL(OEt2)}2] (2)
(Scheme 2). Treatment of EuI2(THF)2 with two molar equi-
valents of 2 in THF at ambient temperature afforded the Eu(II)
amido complex [EuL(μ-L)2K(THF)] (4), whereas an analogous
reaction of YbI2(THF)2 with 2 followed by crystallization of the
1
formulation of both complexes. The H and 13C NMR spectra
of the diamagnetic 5·0.25C7H8 are consistent with the struc-
ture of the complex as shown in Scheme 2. The isopropyl
methyl groups of the L ligand are diastereotopic as evidenced
by two doublets observed at 1.11 and 1.27 ppm, respectively.
Single crystals of complexes 4 and 5·0.25C7H8 suitable for
X-ray diffraction were obtained from hexane and toluene,
respectively. Both complexes crystallize in the triclinic space
27
ˉ
group P1. Fig. 2 shows the molecular structure of complex 4.
The Eu(II) ion has a six-coordinate ligand environment formed
by three L ligands. One of these L ligands is bound to the
Eu(II) centre in an N,N′-chelating manner (η2-bound), whilst
the other two are μ–η2, η2-bound to the Eu(II) ion and a potass-
ium ion [K(1)]. The potassium ion is further bonded to one
THF molecule. The N,N′-chelating L ligand forms a highly
strained, four-membered metallacycle ring with the Eu(II) ion,
resulting in an acute N(1)–Eu(1)–N(2) bite angle of 52.1(1)°.
The amido nitrogen atom N(1) adopts a nearly trigonal planar
geometry (sum of bond angles = 359.1°). The Eu(1)–N(1) bond
length of 2.563(3) Å is slightly shorter than the corresponding
Eu(II)–N(pyridyl) distance [Eu(1)–N(2)] of 2.605(3) Å. Compared
with other Eu(II) amido complexes reported in the literature,
the Eu(1)–N(1) bond length in 4 is longer than the terminal
Eu(II)–N(amido) distance in the heterobimetallic [Eu{N-
(SiMe3)2}{μ-N(SiMe3)2}2Na] [2.448(4) Å],5b and slightly longer
Fig. 1 Molecular structure of [{KL(OEt2)}]2 (2) (30% thermal ellipsoids) with
atom labelling.
Scheme 2 Synthesis of divalent amido complexes 4 and 5.
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Fig. 2 Molecular structure of [EuL(μ-L)2K(THF)] (4) (30% thermal ellipsoids)
with atom labelling. One of the coordinated THF molecules is 2-fold disordered
and only one of the two possible orientations is shown for clarity.
Fig. 3 Molecular structure of [YbL2(THF)2]·0.25C7H8 (5·0.25C7H8) (30%
thermal ellipsoids) with atom labelling. The two coordinated THF molecules are
2-fold disordered and only one of the two possible orientations is shown for
clarity. The toluene solvate molecule is also omitted for clarity.
than the corresponding distances reported for the binuclear
[{Eu(Ap*)(I)(THF)2}2] [2.481(3) Å] and the mononuclear
[Eu(Ap*)2(THF)2] [2.526(6) and 2.547(6) Å] [Ap* = [N(C6H3Pri2-
2,6){2-C5H3N-6-(2,4,6-Pri2C6H2)}]−].20d
The
Eu(II)–nitrogen
YbNCN metallacycle ring with the Yb(II) ion. The N(1)–Yb(1)–
N(2) and N(3)–Yb(1)–N(4) bite angles are acute, namely
55.5(1)° and 54.8(1)°. The amido nitrogen atoms N(1) and N(3)
have an almost trigonal planar geometry (sum of bond angles
around N(1) and N(3) are 359.8° and 359.4°, respectively). The
Yb(II)–N(amido) distances in complex 5 are 2.431(4) Å [Yb(1)–
N(1)] and 2.427(4) Å [Yb(1)–N(3)], whereas the corresponding
Yb(II)–N(pyridyl) distances are slightly longer, namely 2.453(4)
Å [Yb(1)–N(2)] and 2.501(4) Å [Yb(1)–N(4)]. The observed Yb(II)–
N(amido) distances in 5 are slightly longer than the terminal
Yb(II)–N(amido) bond lengths reported for [Yb{N(SiMe3)2}-
{μ-N(SiMe3)2}2Na] [2.38(2) Å]5c and [Yb{NPh(SiMe3)}2(THF)]2
[2.326(4) and 2.353(4) Å].7 Compared with other Yb(II) com-
plexes supported by sterically hindered pyridine-functionalized
amido ligands, the Yb(II)–N(amido) distances in 5 are margin-
ally longer than the corresponding distances reported for the
four-coordinate [Yb(Ap′)2] [2.371(1) and 2.404(1) Å],20b the five-
coordinate [Yb(Ap′)2(THF)] [2.380(4) and 2.384(3) Å]20b and the
six-coordinate [Yb(ApMe)2(THF)2] [2.396(5) Å],20b and similar to
those reported for [Yb(Ap*)2(THF)2] [2.431(6) and 2.464(7) Å].20d
Attempts to prepare a Sm(II) complex of the L ligand have
not been successful. Addition of two molar equivalents of pot-
assium amide 2 to SmI2(THF)2 in THF resulted in a dark
brown suspension. After work-up, a yellow crystalline product
was isolated from the solution (Scheme 3). Both X-ray diffrac-
tion data and elemental analysis indicated that the product
was the homoleptic Sm(III) triamide [SmL3] (6). In order to
explore other plausible synthetic routes for the desired Sm(II)
derivative of L, we also examined the transamination reaction
of [Sm{N(SiMe3)2}2(THF)2] with free 2-pyridyl amine 1. The
latter reaction also afforded a brown suspension from which
complex 6 was isolated as the only product from the solution.
bonds formed by the two μ–η2, η2-bound L ligands in complex
4 fall within the range of 2.582(3)–2.717(3) Å. They are slightly
longer than the bridging Eu(II)–N(amido) distances reported
for [Eu{N(SiMe3)2}{μ-N(SiMe3)2}2Na] [2.539(4) and 2.554(4)
Å].5b The longer Eu(II)–nitrogen bond distances in 4 may be
attributed to a sterically more crowded ligand environment
generated by L as compared with that of the [N(SiMe3)2]−
ligand.
The chemistry of a series of heterobimetallic alkali-metal–
lanthanide complexes of the general formula M3[Ln(binol)3]
(Ln = lanthanide, M = alkali metal, binol = binaphtholates) has
been studied in detail by two research groups led indepen-
dently by Shibasaki28 and Aspinall.29 These complexes were
shown to be multifunctional catalysts, which possess a unique
combined Lewis acid–BrØnsted base property.28 They can cata-
lyze a wide range of enantioselective transformations. Using a
sulfur-bridged binaphtholate ligand (LSN), Arnold and co-
workers have reported on the preparation of heterobimetallic
tris-ligand complexes of the type [Li(THF)3][Ln(LSN)3] (Ln =
Sm, Eu, Y).30 The latter complexes were prepared by metathesis
reactions of the corresponding lanthanide(III) triamide com-
plexes [Ln{N(SiMe3)2}3] with a lithium salt of the LSN ligand,
irrespective of ligand-to-metal stoichiometry. Results of these
studies on the heterobimetallic alkali-metal–lanthanide
binaphtholate complexes can provide us insights on our future
reactivity studies involving the heterometallic Eu(II) complex 4.
The solid-state structure of the solvated Yb(II) diamide
5·0.25C7H8 is depicted in Fig. 3.27 The Yb(II) centre exhibits
a hexacoordinate geometry, with its coordination sphere con-
sisting of two η2-bound L ligands and two THF molecules.
Each
L ligand forms a highly strained, four-membered
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Scheme 3
Me)]−. The corresponding Sm(III) derivative, [Sm{N(SiButMe2)-
(2-C5H3N-6-Me)}3], was also prepared in our laboratory by
using a similar procedure.31 The structural parameters of
complex 6 are comparable to those observed in the [Sm-
{N(SiButMe2)(2-C5H3N-6-Me)}3] complex.
Reaction chemistry of [EuL(μ-L)2K(THF)] (4) and
[YbL2(THF)2] (5)
One interesting feature of organolanthanide(II) compounds is
their highly reducing reactivity.32 The redox chemistry of
lanthanide(II) metallocene complexes has been studied in
detail.33–36 On the other hand, there were only a few reports on
the redox chemistry of lanthanide(II) complexes supported by
non-cyclopentadienyl systems.37,38 An interesting issue in
organolanthanide(II) chemistry is to understand the effects of
steric and electronic properties of different ligands on the redox
reactivity of lanthanide(II) complexes. Recently, we have reported
on the reactions of a few lanthanide(II) amidinate complexes
with iodine, diphenyl dichalcogenides PhEEPh (E = Se, Te) and
N,N′-dicyclohexylcarbodiimide.23b In order to compare the redox
reactivity of lanthanide(II) complexes supported by amido and
amidinato ligands, we have carried out an initial study on the
reduction chemistry of complexes 4 and 5 in this work.
Fig. 4 Molecular structure of [SmL3] (6) (30% thermal ellipsoids) with atom
labelling. Only one of the two independent molecules in the asymmetric unit is
shown.
1. Reactions of complexes 4 and 5 with iodine. Oxidation
of the Eu(II) complex 4 with iodine led to the isolation of
purple, crystalline Eu(III) triamide [EuL3] (7) (Scheme 4). Appar-
ently, the presence of three L ligands in the coordination
sphere of the Eu(II) ion in 4 favours the formation of the homo-
leptic triamide 7, instead of a mixed amide-iodide species
“EuL2(I)”. The molecular structure of complex 7 was deter-
mined by X-ray crystallography (Fig. 5).27 Complex 7 crystallizes
Apparently, L may not be a good supporting ligand for the
more reducing Sm(II) ion.
The molecular structure of [SmL3] (6) is depicted in Fig. 4.27
Complex 6 crystallizes in the hexagonal crystal system with
ˉ
space group P3. The Sm(III) ion is coordinated by three N,N′-
chelating L ligands, and the complex conforms closely to a C3
symmetry. The Sm(III)–N(amido) distances [Sm(1)–N(1)
2.363(3) Å and Sm(1)–N(1)#1 2.362(3) Å] are shorter than the
corresponding Sm(III)–N(pyridyl) distances [Sm(1)–N(2)
2.503(3) Å]. The amido nitrogen atoms exhibit a trigonal
planar geometry (sum of bond angles around N(1) = 360°). The
N(1)–Sm(1)–N(2) bite angle of 55.5(1)° is acute. Earlier, we have
reported on the use of the N-silylated [N(SiButMe2)(2-C5H3N-6-
Me)]− ligand in the preparation of homoleptic Ce(III) and
Nd(III) triamides.19c The latter complexes were prepared by the
reactions of anhydrous LnCl3 (Ln = Ce, Nd) with three molar
equivalents of a potassium salt of [N(SiButMe2)(2-C5H3N-6-
ˉ
in the hexagonal crystal system with space group P3, and is iso-
structural to the Sm(III) triamide 6. Each L ligand is bonded to
the Eu(III) ion in an N,N′-chelating manner, with an acute
N(1)–Eu(1)–N(2) bite angle of 55.68(6)°. The amido nitrogen
atom N(1) displays a nearly trigonal planar geometry (sum of
bond angles around N(1) = 360°). The observed Eu(III)–
N(amido) distance in 7 is 2.350(1) Å [Eu(1)–N(1)], whereas the
corresponding Eu(III)–N(pyridyl) distances are slightly longer
[Eu(1)–N(2) 2.492(1) Å]. The europium–nitrogen bond dis-
tances in 7 are shorter than the corresponding bond lengths
observed in the Eu(II) amido complex 4. These differences may
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Scheme 4
2. Treatment of [YbL2(I)(THF)] (8) with KOBut. It is noted
that the presence of an iodide ligand in complex 8 may allow
further metathesis reactions of the complex with other anionic
ligands. Accordingly, we attempted to prepare a mixed-ligand
Yb(III) diamide-alkoxide complex by treatment of 8 with KOBut.
Addition of 8 to a slurry of KOBut in THF resulted in a yellow
suspension from which the homoleptic Yb(III) triamide [YbL3]
(9) was isolated as the only product in our hands (Scheme 6).
Elemental analysis and NMR spectroscopic data agree with the
1
formulation of complex 9. The H NMR spectrum of 9 showed
one set of isotropically shifted signals, which were assignable
to the L ligand. The solid-state structure of complex 9 was elu-
cidated by single-crystal X-ray crystallography (Fig. 7).27
Complex 9 crystallizes in the triclinic crystal system with space
ˉ
group P3, and is isostructural to the Sm(III) and Eu(III) counter-
parts 6 and 7. The Yb(III) centre in 9 is six-coordinated by three
η2-bound L ligands. The N(1)–Yb(1)–N(2) bite angle of 58.1° is
acute. The amido nitrogen atoms in 9 also adopt a trigonal
planar geometry (sum of bond angles around N(1) = 360°). The
Yb(III)–N(amido) distance of 2.270(6) Å [Yb(1)–N(1)] is some-
what shorter than the corresponding Yb(III)–N(pyridyl) dis-
tance of 2.388(5) [Yb(1)–N(2)]. Compared to other homoleptic
Yb(III) triamide complexes derived from pyridine-functiona-
lized amido ligands, the Yb(1)–N(1) distance in 9 is close to
the corresponding distances reported for [Yb(ApMe)3]20b
[2.263(7)–2.299(7) Å] and [Yb{N(SiButMe2)(2-C5H3N-6-Me)}3]
Fig. 5 Molecular structure of [EuL3] (7) (30% thermal ellipsoids) with atom lab-
elling. Only one of the two independent molecules in the asymmetric unit is
shown.
be attributed to a smaller ionic radius of Eu(III) as compared to [2.257(4)–2.300(4) Å].31 The Yb(1)–N(2) bond length in our
that of Eu(II).
current complex is also comparable to the Yb(III)–N(pyridyl)
distances observed in [Yb(ApMe)3]20b [2.357(8)–2.543(7) Å] and
Treatment of Yb(II) diamide 5 with iodine afforded the
mononuclear Yb(III) complex [YbL2(I)(THF)] (8) in 45% yield [Yb{N(SiButMe2)(2-C5H3N-6-Me)}3] [2.349(4)–2.375(4) Å].31
(Scheme 5). Alternatively, complex 8 could also be prepared by
the reaction of 5 with copper(I) iodide in 60% isolated yield.
The factors that give rise to the ligand redistribution and
the formation of the Yb(III) triamide 9 remain unclear to us at
Fig. 6 shows the X-ray structure of complex 8.27 The Yb(III) this stage of our study. One plausible reason may be attributed
centre is coordinated by two η2-bound L ligands, one iodide to the steric bulkiness of the alkoxide ligand. Accordingly,
ligand and one THF molecule. The coordination geometry
complex [YbL2(I)(THF)] (8) was allowed to react with the steri-
around the Yb(III) ion can be described as distorted octahedral. cally less demanding NaOMe under similar reaction con-
The Yb(III)–N(amido) bond lengths [Yb(1)–N(1) 2.241(2) Å and ditions.39 Unfortunately, only an intractable oil was obtained
Yb(1)–N(3) 2.265(2) Å] in 8 are shorter than the corresponding
Yb(III)–N(pyridyl) distances [Yb(1)–N(2) 2.363(3) Å and Yb(1)– terised by H NMR spectroscopy, which revealed the presence
N(4) 2.366(2) Å]. The bite angles subtended by each of the two of complex [YbL3] (9) as the major product in the mixture
after the reaction. The crude product mixture was charac-
1
L ligands, 58.50(9)° [N(1)–Yb(1)–N(2)] and 58.42(8)° [N(3)–
Yb(1)–N(4)], are acute. The Yb(1)–I(1) and Yb(1)–O(1) distances ently, the size of the alkoxide ligands did not play a key role in
together with some unidentified paramagnetic species. Appar-
are 2.9205(3) Å and 2.362(2) Å, respectively.
the ligand redistribution reaction.
2846 | Dalton Trans., 2013, 42, 2841–2852
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Scheme 5 Reactions of complex 5 with I2 and CuI.
towards Eu(II), Yb(II) and Sm(II) ions were studied in this work.
Divalent amido complexes [EuL(μ-L)2K(THF)] (4) and
[YbL2(THF)2] (5) were successfully prepared by the reactions of
the appropriate LnI2(THF)2 (Ln = Eu, Yb) with potassium
amide [{KL(OEt2)}2] (2). The difference in the structures of 4
and 5 (i.e. an ate-complex versus a neutral mononuclear
complex) may be attributed to the different ionic size of Eu2+
(0.947 Å) and Yb3+ (0.868 Å).41 Unfortunately, attempts to
prepare a Sm(II) complex of L have been unsuccessful. In our
hands, only the homoleptic Sm(III) triamide [SmL3] (6) was iso-
lated. An initial study on the reduction chemistry of complexes
4 and 5 was also carried out in this work. Complexes 4 and 5
reacted readily with iodine to yield trivalent complexes [EuL3]
(7) and [YbL2(I)(THF)] (8), respectively. Unexpectedly, addition
of 5 to diphenyl dichalcogenides, and a further reaction of 8
with KOBut gave the homoleptic [YbL3] (9) as the only isolable
product. These results were contrasted to those we obtained
earlier with divalent lanthanide complexes of the amidinate
anion [PhC(NSiMe3)(NC6H3Pri2-2,6)]−.23b Although both ligand
L and the latter amidinate are monoanionic bridging ligands
with similar steric properties, they showed different coordi-
nation behaviour towards divalent lanthanide ions, particu-
larly the Sm(II) ion. Additionally, based on the results of our
initial reactivity studies, the 2-pyridyl amido ligand L may have
a higher tendency to form homoleptic lanthanide(III) tri-
amides, probably due to its intrinsic steric and electronic
properties.
Fig. 6 Molecular structure of [YbL2(I)(THF)] (8) (30% thermal ellipsoids) with
atom labelling. The coordinated THF molecule is 2-fold disordered and only one
of the two possible orientations is shown for clarity.
3. Reactions of complex 5 with PhEEPh (E = S, Se, Te).
Besides iodine, we have also examined the redox chemistry of
Yb(II) diamide 5 with diphenyl dichalcogenides PhEEPh (E = S,
Se, Te). Addition of PhEEPh to a solution of 5 in THF afforded a
yellow solution from which the homoleptic [YbL3] (9) was isolated
as the only product, though the product yields were modest
(Scheme 7). Recently, we have reported on the reactions of Ln(II)
(Ln = Sm, Eu, Yb) bis(amidinate) complexes with PhEEPh (E = Se,
Te), which yielded the respective Ln(III) amidinate–chalcogenolate
complexes. Unfortunately, the expected Yb(III) bisamide–chalco-
genolate complexes have not been isolated in this work.40
Experimental
General procedures
All manipulations were carried out using standard Schlenk
techniques or in a Braun MB 150-M dry box under an atmos-
phere of purified nitrogen. Solvents were dried over a sodium
wire and distilled under nitrogen from sodium benzophenone
(diethyl ether and THF), Na/K alloy (toluene) or calcium
hydride (hexane), and degassed twice by freeze–thaw cycles
before use. 2,6-Diisopropylaniline was distilled over KOH
before use. All other reagents were used as received.
LnI2(THF)2 (Ln = Sm, Eu, Yb)42–44 and [Sm{N(SiMe3)2}2(THF)2]6
Summary
The coordination properties of the bulky, monoanionic were prepared according to literature procedures. 1H and 13C
2-pyridyl amido ligand [N(C6H3Pri2-2,6)(2-C5H3N-6-Me)]− (L) NMR spectra were recorded on a Bruker DPX300 NMR
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Scheme 6 Reaction of complex 8 with KOBut.
30 cm3). The combined organic layer was washed with satu-
rated sodium chloride solution and dried over magnesium sul-
phate. All the volatiles were then removed under reduced
pressure to give a brown solid. The crude product was purified
by column chromatography (CH2Cl2) to give compound 1 as a
pale yellow solid. Yield: 5.64 g, 21.1 mmol (80%). 1H NMR
(300.13 MHz, CDCl3): δ 7.32 (dd, J = 6.6, 8.6 Hz, 1H, p-ArH),
7.26–7.20 (m, 3H, m-ArH and PyH), 6.48 (d, J = 7.3 Hz, 1H,
PyH), 6.05 (br, 1H, NH), 5.74 (d, J = 8.3 Hz, 1H, PyH), 3.21
(sept, J = 6.9 Hz, 2H, CHMe2), 2.43 (s, 3H, PyMe), 1.13 (d, J =
6.9 Hz, 12H, CHMe2). 13C NMR (75.47 MHz, CDCl3): δ 159.0,
157.2, 148.1, 138.2, 133.7, 128.1, 124.1, 112.9, 102.6, 28.4, 24.4,
24.0. MS (E.I. 70 eV): m/z (%) [M]+ 268 (17), [M − CH3]+ 253
(11), [M − Pri]+ 225 (100). HRMS (LSI): m/z calc. for C18H24N2
[M + H]+ 268.1934, found: 268.1940.
Synthesis of [{KL(OEt2)}2] (2). A solution of compound 1
(5.48 g, 20.5 mmol) in diethyl ether (15 cm3) was added to a
slurry of KH (0.99 g, 24.8 mmol) in the same solvent (10 cm3)
at 0 °C. The reaction mixture was stirred at room temperature
for 1 day, filtered, and the filtrate was concentrated in vacuo to
ca. 10 cm3. The title compound was obtained as colourless
crystals at room temperature. Yield: 6.21 g, 16.3 mmol (80%).
Fig. 7 Molecular structure of [YbL3] (9) (30% thermal ellipsoids) with atom
labelling.
1
M.p. = 261–266 °C. H NMR (400.13 MHz, C6D6): δ 7.22–7.11
(m, 6H, ArH), 6.93 (dd, J = 6.7, 8.6 Hz, 2H, PyH), 5.93 (d, J = 6.7
Hz, 2H, PyH), 5.64 (d, J = 8.6 Hz, 2H, PyH), 3.25 (q, J = 7.0 Hz,
8H, OCH2CH3), 2.92 (sept, J = 6.9 Hz, 4H, CHMe2), 2.25 (s, 6H,
PyMe), 1.18 (br, 12H, CHMe2), 1.11 (t, J = 7.0 Hz, 12H,
OCH2CH3), 0.93 (br, 12H, CHMe2). 13C NMR (100.61 MHz,
C6D6): δ 166.8, 155.8, 150.1, 141.7, 137.3, 123.8, 121.4, 105.4,
102.8, 65.9, 28.1, 25.9, 24.1, 15.5. Anal. calc. for C44H66K2N4O2:
C, 69.43; H, 8.74; N, 7.36%. Found: C, 69.02; H, 8.97; N,
7.88%.
Synthesis of KL(THF)2 (3). Method A: Compound 3 was pre-
pared by a procedure similar to that of 2 described above,
except that THF was used as the solvent. Reagents used: [HL]
(1), 3.77 g, 14.1 mmol; KH, 0.64 g, 16.0 mmol. The product
was obtained as a colourless crystalline solid. Yield: 4.62 g,
10.3 mmol (73%). M.p.: 261–266 °C. 1H NMR (400.13 MHz,
C6D6): δ 7.25 (d, J = 7.6 Hz, 2H, m-ArH), 7.14 (m, 1H, p-ArH),
6.92 (dd, J = 6.7, 8.6 Hz, 1H, PyH), 5.88(d, J = 6.7 Hz, 1H, PyH),
5.67 (d, J = 8.6 Hz, 1H, PyH), 3.48 (m, 8H, THF), 3.03 (sept, J =
6.9 Hz, 2H, CHMe2), 2.21 (s, 3H, PyMe), 1.38 (m, 8H, THF),
spectrometer (at 300.13 and 75.47 MHz) or a Bruker Advance
III 400 NMR spectrometer (at 400.13 and 100.61 MHz). Chemi-
cal shifts were referenced to residue protons of CDCl3 and
C6D6 at 7.26 and 7.16 ppm (in 1H NMR), and 77.16 and
128.06 ppm (in 13C NMR), respectively. Melting-points were
recorded on an Electrothermal melting-point apparatus and
were uncorrected. Mass spectra were obtained on a Thermo-
Finnigan MAT 95 XP Mass Spectrometer (E.I. 70 eV). Elemental
analyses (C, H, N) were performed by MEDAC Ltd., Brunel Uni-
versity, U.K.
Synthesis of [HN(C6H3Pri2-2,6)(2-C5H3N-6-Me)] (HL) (1). To
a mixture of sodium tert-butoxide (2.56 g, 26.64 mmol), tris-
(dibenzylideneacetone)dipalladium(0) (0.25 g, 0.27 mmol) and
1,3-bis(diphenylphosphanyl)propane (0.34 g, 0.81 mmol) in
toluene (20 cm3) was added a solution of 2,6-Pri2C6H3NH2
(4.78 g, 27.0 mmol) and 2-BrC5H3N-6-Me (4.53 g, 26.3 mmol)
in the same solvent (20 cm3). The reaction mixture was stirred
at 95 °C for 3 days, and then quenched with water (10 cm3).
The resulting mixture was extracted with diethyl ether (2 ×
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Scheme 7 Reactions of complex 5 with PhEEPh.
1.23 (br, 6H, CHMe2), 1.00 (br, 6H, CHMe2). 13C NMR (s, 6H, PyMe), 2.11 (s, 0.75H, PhMe), 1.27 (d, J = 6.8 Hz, 12H,
(100.62 MHz, C6D6): δ 166.8, 156.0, 150.3, 141.8, 137.3, 123.8, CHMe2), 1.22 (br, 8H, THF), 1.11 (d, J = 6.8 Hz, 12H, CHMe2).
121.4, 105.4, 102.7, 67.8, 28.2, 25.8, 25.7, 24.3, 24.1. Anal. calc. 13C NMR (100.62 MHz, C6D6): δ 168.7, 153.8, 147.9, 143.5,
for C26H39KN2O2: C, 69.29; H, 8.72; N, 6.21%. Found: C, 69.03; 138.0, 123.6, 122.8, 105.2, 104.1, 68.7, 28.1, 25.4, 25.2, 24.3,
H, 8.64; N, 6.55%.
Method B: A solution of LiBun (1.6 M in hexanes, 8.93 cm3, 7.47; N, 5.93%. Found: C, 64.42; H, 7.61; N, 6.19%.
14.3 mmol) was added to a solution of compound 1 (3.80 g, Reaction of SmI2(THF)2 with [{KL(Et2O)}2] (2). A solution of
23.9, 21.4. Anal. calc. for C44H62N4O2Yb·C7H8: C, 64.88; H,
14.2 mmol) in THF (15 cm3) at 0 °C. The reaction mixture was [{KL(Et2O)}2] (2) (1.95 g, 5.12 mmol) in THF (15 cm3) was
stirred at room temperature for 4 h and then added directly to slowly added to a solution of SmI2(THF)2 (1.56 g, 2.84 mmol)
a slurry of KOBut (1.59 g, 14.2 mmol) in THF (10 cm3) at 0 °C. in the same solvent (15 cm3). The reaction mixture was stirred
The resultant mixture was stirred at room temperature for at room temperature for 1 day, whereupon its colour changed
another period of 12 h. All the volatiles were then removed gradually from dark blue to dark brown. The solution was
in vacuo to give a yellow solid. It was washed with hexane pumped to dryness and the residue was extracted with hexane.
(30 cm3) and re-dissolved in THF (30 cm3). After filtration, the Concentration of the solution yielded complex [SmL3] (6) as
solution was concentrated under reduced pressure to ca. 10 cm3. yellow crystals. Yield: 0.72 g, 0.76 mmol (30%). M.p.: decom-
Standing the solution at room temperature for 1 day gave posed at 357–359 °C without melting. 1H NMR (400.13 MHz,
complex 3 as colourless crystals. Yield: 3.96 g, 8.81 mmol (62%).
C6D6): δ 12.55 (br, 3H, CHMe2), 9.02 (d, J = 8.6 Hz, 3H, PyH),
Synthesis of [EuL(μ-L)2K(THF)] (4). A solution of [{KL- 8.19 (dd, J = 7.2, 8.6 Hz, 3H, PyH), 8.04 (dd, J = 1.3, 7.7 Hz, 3H,
(OEt2)}2] (2) (1.67 g, 4.38 mmol) in THF (15 cm3) was added to m-ArH), 7.18–7.14 (m, 3H, p-ArH), 5.59 (dd, J = 1.3, 7.7 Hz, 3H,
a solution of EuI2(THF)2 (1.21 g, 2.20 mmol) in the same m-ArH), 5.47 (d, J = 7.2 Hz, 3H, PyH), 3.86 (d, J = 6.5 Hz, 9H,
solvent (15 cm3). The reaction mixture was stirred at room CHMe2), 3.11 (d, J = 6.5 Hz, 9H, CHMe2), 1.16 (d, J = 6.3 Hz,
temperature for 1 day to give an orange-red suspension. The 9H, CHMe2), 0.7 (br, 3H, CHMe2), −3.9 (s, 9H, PyMe), −6.5 (d,
solution was pumped to dryness and the residue was extracted J = 6.3 Hz, 9H CHMe2). 13C NMR (100.62 MHz, C6D6): δ 151.0,
with hexane. The hexane extract was concentrated under 146.9, 144.9, 141.8, 140.5, 125.6, 123.5, 111.3, 104.5, 34.5, 27.8,
reduced pressure to give complex 4 as orange crystals. Yield: 27.1, 26.3, 24.0, 19.3, 17.0. Anal. calc. for C54H69N6Sm: C,
0.90 g, 0.85 mmol (39%). M.p.: 190–193 °C. Anal. calc. for 68.09; H, 7.30; N, 8.82%. Found: C, 67.55; H, 7.36; N, 9.59%.
C58H77EuKN6O: C, 65.39; H, 7.28; N, 7.88%. Found: C, 64.79;
H, 7.98; N, 8.45%.
Reaction of [Sm{N(SiMe3)2}2(THF)2] with [HN(C6H3Pri2-2,6)-
(2-C5H3N-6-Me)] (1). Compound 1 (1.34 g, 5.03 mmol) was
Synthesis of [YbL2(THF)2]·0.25C7H8 (5·0.25C7H8). To a solu- added to a purple solution of [Sm{N(SiMe3)2}2(THF)2] (1.54 g,
tion of YbI2(THF)2 (2.21 g, 3.86 mmol) in THF (15 cm3) was 2.51 mmol) in hexane (30 cm3) at 0 °C. The reaction mixture
added a solution of [{KL(OEt2)}2] (2) (2.30 g, 3.02 mmol) in the was stirred at room temperature for 8 h, whereupon a dark
same solvent (15 cm3) at room temperature. The reaction brown suspension was obtained. The brown suspension was
mixture was stirred at room temperature for 1 day. All the vola- filtered and the filtrate was evaporated to dryness under
tiles were removed under reduced pressure to give a dark reduced pressure. The resulting dark brown residue was
purple solid residue. The residue was extracted with toluene extracted with toluene. Concentration of the solution under
and filtered. Concentration of the resulting solution yielded reduced pressure yielded complex 6 as a yellow crystalline
the title compound as deep purple block-shaped crystals. solid. Yield: 0.44 g, 0.46 mmol (18%).
Yield: 1.98 g, 2.33 mmol (77%). M.p.: 216–219 °C. 1H NMR
Reaction of [EuL(μ-L)2K(THF)] (4) with I2. To a solution of
(400.13 MHz, C6D6): δ 7.28 (d, J = 7.5 Hz, 4H, m-ArH), complex 4 (1.96 g, 1.84 mmol) in THF (20 cm3) at 0 °C was
7.21–7.12 (m, 1.25H, PhMe), 7.03 (t, J = 7.5 Hz, 2H, p-ArH), 6.89 slowly added a solution of I2 (0.23 g, 0.89 mmol) in THF
(dd, J = 6.9, 8.6 Hz, 2H, PyH), 5.86 (d, J = 6.9 Hz, 2H, PyH), 5.66 (10 cm3). The reaction mixture was stirred at room temperature
(d, J = 8.6 Hz, 2H, PyH), 3.49 (br, 12H, THF and CHMe2), 2.18 for 1 day. All the volatiles were removed in vacuo and the solid
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residue was extracted with hexane. Concentration of the solu-
Reaction of [YbL2(THF)2] (5) with CuI. A solution of
tion gave complex [EuL3] (7) as purple crystals. Yield: 1.12 g, complex 5 (1.41 g, 1.65 mmol) in THF (20 cm3) was slowly
1.17 mmol (64%). M.p.: 378–380 °C (dec.). Anal. calc. for added to a slurry of CuI (0.32 g, 1.7 mmol) in the same solvent
C54H69EuN6: C, 67.98; H, 7.29; N, 8.80%. Found: C, 67.55; H, (10 cm3). The reaction mixture was stirred at room temperature
7.58; N, 8.92%.
for 1 day, whereupon its colour changed from dark purple to
Reaction of [YbL2(THF)2] (5) with I2. To a solution of orange-red. The resulting solution was filtered and concen-
complex 5 (1.64 g, 1.92 mmol) in THF (20 cm3) at 0 °C was trated under reduced pressure to give [YbL2(I)(THF)] (8) as
slowly added a solution of I2 (0.25 g, 0.97 mmol) in the same orange-red crystals. Yield: 0.83 g, 0.92 mmol (56%).
solvent (10 cm3). The reaction mixture was allowed to warm to
Reaction of [YbL2(I)(THF)] (8) with KOBut. A solution of
room temperature and stirring was continued for 1 day, after [YbL2(I)(THF)] (8) (0.12 g, 1.1 mmol) in THF (20 cm3) at 0 °C
which the solution was filtered and concentrated under was slowly added to a slurry of KOBut (0.83 g, 0.92 mmol) in
reduced pressure to give [YbL2(I)(THF)] (8) as orange-red crys- THF (10 cm3). The resulting mixture was stirred at room temp-
tals. Yield: 0.78 g, 0.86 mmol (45%). M.p.: 241–243 °C (dec.). erature for 1 day, after which all the volatiles were removed
Anal. calc. for C40H54N4OIYb: C, 52.98; H, 6.00; N, 6.18%. in vacuo. The solid residue obtained was extracted with
Found: C, 52.69; H, 6.15; N, 6.29%.
toluene. Filtration followed by concentration of the solution
Table 1 Selected crystallographic dataa for complexes 2, 4–6 and 7–9
2
4
5·0.25C7H8
6
Molecular formula
C44H66K2N4O2
761.20
0.50 × 0.40 × 0.30
Triclinic
ˉ
P1
10.2513(9)
11.0830(9)
11.6691(10)
62.1870(10)
89.257(2)
C58H77EuKN6O
1065.32
0.50 × 0.40 × 0.30
Triclinic
ˉ
P1
11.870(2)
13.542(2)
22.292(4)
98.072(3)
C44H62N4O2Yb·0.25C7H8
875.05
0.40 × 0.30 × 0.20
Triclinic
ˉ
P1
10.4629(17)
12.0079(19)
20.892(3)
92.854(3)
90.430(3)
C54H69N6Sm
952.50
0.40 × 0.30 × 0.20
Hexagonal
ˉ
P3
12.673(2)
12.673(2)
18.424(3)
90
Molecular weight
Crystal size (mm3)
Crystal system
Space group
a (Å)
b (Å)
c (Å)
α (°)
β (°)
99.164(3)
90
γ (°)
77.994(2)
1
1141.54(17)
1.107
0.244
112.940(3)
2
3175.8(9)
1.114
110.628(2)
2
2452.6(7)
1.185
1.942
120
2
2562.7(8)
1.234
Z
V (Å3)
Density (g cm−3
)
Abs coeff. (mm−1
)
1.090
1.185
Temperature (K)
173(2)
12 915
4021 (Rint = 0.0774)
3107
R1 = 0.0520, wR2 = 0.1368
R1 = 0.0722, wR2 = 0.1517
293(2)
17 254
11 114 (Rint = 0.0354)
8868
R1 = 0.0434, wR2 = 0.0990
R1 = 0.0582, wR2 = 0.1051
293(2)
13 360
8588 (Rint = 0.0340)
7243
R1 = 0.0448, wR2 = 0.1180
R1 = 0.0554, wR2 = 0.1240
293(2)
14 233
3112 (Rint = 0.0520)
2677
R1 = 0.0336, wR2 = 0.0846
R1 = 0.0451, wR2 = 0.1025
Reflections collected
Independent reflections
Obs. data with I ≥ 2σ(I)
Final R indices [I ≥ 2σ(I)]b
R indices (all data)b
7
8
9
Molecular formula
C54H69EuN6
954.11
0.40 × 0.30 × 0.30
Hexagonal
ˉ
P3
C40H54IN4OYb
906.81
0.40 × 0.30 × 0.20
Monoclinic
P21/c
C54H69N6Yb
975.19
0.50 × 0.40 × 0.30
Hexagonal
ˉ
P3
Molecular weight
Crystal size (mm3)
Crystal system
Space group
a (Å)
12.6538(8)
19.2421(5)
12.576(2)
b (Å)
c (Å)
12.6538(8)
18.4222(12)
12.6237(3)
17.8425(4)
12.576(2)
18.465(3)
α (°)
β (°)
90
90
90
90
90
100.4080(10)
γ (°)
120
2
2554.5(3)
1.240
90
4
120
2
2529.1(8)
1.281
Z
V (Å3)
4262.75(18)
1.413
2.950
Density (g cm−3
)
Abs coeff. (mm−1
)
1.267
1.889
Temperature (K)
293(2)
21 005
3103 (Rint = 0.0412)
2783
R1 = 0.0221, wR2 = 0.0569
R1 = 0.0275, wR2 = 0.0591
296(2)
39 618
7711 (Rint = 0.0376)
6816
R1 = 0.0253, wR2 = 0.0629
R1 = 0.0300, wR2 = 0.0647
296(2)
22 027
3059 (Rint = 0.0701)
2699
R1 = 0.0584, wR2 = 0.1525
R1 = 0.0670, wR2 = 0.1577
Reflections collected
Independent reflections
Obs. data with I ≥ 2σ(I)
Final R indices [I ≥ 2σ(I)]b
R indices (all data)b
a Data collected on a Bruker SMART CCD diffractometer or a Bruker KAPPA APEX II diffractometer with graphite-monochromatized Mo Kα
radiation (λ = 0.71073 Å) using ω scan. b R1 = ∑||Fo| − |Fc||/∑|Fo|; wR2 = {∑[w(Fo2 − Fc2)2]/∑[w(Fo2)2]}1/2
.
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gave [YbL3] (9) as yellow crystals. Yield: 0.20 g, 0.20 mmol
(22%). M.p.: 219–220 °C (dec.). H NMR (400.13 MHz, C6D6): δ
Notes and references
1
67.00 (s, 9H, Me), 61.84 (s, 9H, Me), 43.49 (br, 3H, CHMe2),
19.07 (s, 3H, ArH or PyH), 8.60 (s, 3H, ArH or PyH), 6.60 (s, 3H,
ArH or PyH), −1.27 (s, 9H, Me), −2.85 (s, 3H, ArH or PyH),
−8.76 (s, 3H, ArH or PyH), −20.11 (s, 9H, Me), −34.19 (s, 3H,
ArH or PyH), −98.47 (br, 3H, CHMe2). Anal. calc. for
C54H69N6Yb: C, 66.51; H, 7.31; N, 8.61%. Found: C, 65.81; H,
7.59; N, 8.93%.
Reaction of [YbL2(THF)2] (5) with PhSSPh. To a solution of
PhSSPh (0.12 g, 0.54 mmol) in THF (10 cm3) at 0 °C was added
dropwise a solution of [YbL2(THF)2] (5) (0.87 g, 1.0 mmol) in
the same solvent (20 cm3). After stirring at room temperature
for 1 day, all the volatiles were removed in vacuo. The solid
residue was extracted with toluene and then filtered. Concen-
tration of the filtrate afforded the yellow crystalline Yb(III) tri-
amide [YbL3] (9). Yield: 0.16 g, 0.16 mmol (16%).
Reaction of [YbL2(THF)2] (5) with PhSeSePh. Complex 5 was
reacted with PhSeSePh according to a similar procedure as
described above, yielding complex 9 as the only isolable
product. Reagents used: [YbL2(THF)2] (5), 1.59 g, 1.87 mmol;
PhSeSePh, 0.29 g, 0.92 mmol. Yield: 0.21 g, 0.22 mmol (23%).
Reaction of [YbL2(THF)2] (5) with PhTeTePh. Complex 5 was
reacted with PhTeTePh according to a similar procedure as
described above, yielding complex 9 as the only isolable
product. Reagents used: [YbL2(THF)2] (5), 1.59 g, 1.87 mmol;
PhTeTePh, 0.38 g, 0.94 mmol. Yield: 0.12 g, 0.12 mmol (13%).
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Acknowledgements
This work was supported by the Research Grants Council of
The Hong Kong Special Administrative Region, China (Project 12 (a) L. M. Engelhardt, G. E. Jacobsen, P. C. Junk,
No. CUHK 401405). We are indebted to Professor Thomas
C. W. Mak for helpful discussions on the X-ray structural ana-
lyses. We also thank The Chinese University of Hong Kong for
a postgraduate studentship to K.W.K. and C.W.A.
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This journal is © The Royal Society of Chemistry 2013
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2852 | Dalton Trans., 2013, 42, 2841–2852
This journal is © The Royal Society of Chemistry 2013