Binary Polyazides of Cerium and Gadolinium

Article abstract of DOI:10.1002/ejic.201701408

Herein, we report on the preparation and full characterization (melting point, ATR-IR/Raman, elemental analysis, ¹⁴N NMR) of binary gadolinium(III) azide as DMSO solvate Gd(N₃)₃·⁸/₃DMSO (DMSO = dimethylsulfoxide), along with the partially hydroxide substituted species Gd₄(OH)₂(N₃)₁₀·nDMSO (n = 8, 10). Moreover, the isolation and comprehensive characterization of hexaazido lanthanate(III) anions [Ln(N₃)₆]^3– (Ln = Ce, Gd) in a series of [Ph₄P]⁺ and [EtPh₃P]⁺ salts is presented. Single-crystal structures of all compounds were determined, and the magnetic susceptibility in solution (NMR, Evans Method), as well as in the solid state (VSM), was investigated.

Full text of DOI:10.1002/ejic.201701408

A Journal of
Accepted Article
Title: Binary Polyazides Of Cerium And Gadolinium
Authors: Kati Rosenstengel, Axel Schulz, Oliver Niehaus, Oliver Janka,
Rainer Pöttgen, and Alexander Villinger
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To be cited as: Eur. J. Inorg. Chem. 10.1002/ejic.201701408
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10.1002/ejic.201701408
European Journal of Inorganic Chemistry
FULL PAPER
Binary Polyazides Of Cerium And Gadolinium
Kati Rosenstengel,[a] Axel Schulz,[a,b] Oliver Niehaus,[c] Oliver Janka,[c] Rainer Pöttgen,[c] and Alexander
Villinger*[a]
Abstract: Herein, we report on the preparation and full
characterization (m.p., ATR-IR/Raman, elemental analysis, 14N
NMR) of binary gadolinium(III) azide as DMSO solvate
Gd(N3)3 · 8/3 DMSO (DMSO = dimethylsulfoxide), along with the
partially hydroxide substituted species Gd4(OH)2(N3)10 · n DMSO (n
= 8, 10). Moreover, the isolation and comprehensive characterization
of hexaazido lanthanate(III) anions [Ln(N3)6]3– (Ln = Ce, Gd) in a
series of [Ph4P]+ and [EtPh3P]+ salts is presented. Single crystal
structures of all compounds were determined, and the magnetic
susceptibility in solution (NMR, Evans Method), as well as in the
solid state (VSM), was investigated.
Darapsky,[4] Rosenwasser et al. reported on the reaction of rare
earth sesquioxides Ln2O3 (Ln = La, Nd, Sm - Er, Yb, Y) or Pr6O11
in aqueous hydrazoic acid, which in contrary yielded basic
lanthanide azides of the empiric formula Ln(OH)2N3 · n H2O (n =
½, Ln = La – Dy; n = 1, Ln = Ho, Er, Y, Yb) while no reaction
was observed for CeO2, Tb4O7, Lu2O3 and Sc2O3 (Scheme 1).[7]
Moreover, Abdel-Aziz and coworker succeeded in isolating rare
earth hydroxide azides in yet another composition,
Ln(OH)2N3 · H2O (Ln = Pr – Yb, except Pm). The latter were
obtained by addition of sodium azide to the corresponding
lanthanide perchlorates Ln(ClO4)3 in aqueous perchloric acid
(Scheme 1).[8] While numerous elemental analyses,[4,7a,8b-d] DTA
measurements (DTA
=
differential thermal analysis),[7b] IR
spectra,[7a,8d] susceptibility measurements,[8b,d] electron-beam
sensitivities,[ 9 ] as well as spectrophotometric and radiometric
measurements (143Pr) of complex stability constants[8a-c] were
reported in the last decades, the exact constitution of basic
lanthanide azides remains still unclear, since no structural data
is available to date.
Introduction
Binary polyazides of transition-metal and main-group elements
form a class of highly endothermic compounds, which often tend
to decompose explosively.[ 1] Nevertheless, the synthesis and
isolation of these nitrogen-rich species has attracted much
attention in the last decades.[ 2 , 3 ] However, the chemistry of
binary azides of the rare earth elements in specific has scarcely
been investigated, and only few reports on structural and
spectroscopic properties are available, to date.
The first attempted preparation of rare earth azides in
aqueous medium was carried out by Curtius and Darapsky as
early as 1900.[4] However, according to elemental analyses, the
reactions of lanthanum, cerium and didymium hydroxides
(didymium = Pr/Nd)[5] with concentrated hydrazoic acid in water
yielded only basic lanthanide azides instead of the expected
binary azides (Scheme 1). In agreement with these findings,
Ant-Wuorinen could demonstrate that basic lanthanide azides
can selectively be precipitated from an aqueous mixture of
lanthanide nitrates by addition of sodium azide.[ 6 ] While the
constitution of these rare earth hydroxide azides was formulated
as Ln(OH)(N3)2 · 11/2 H2O (Ln = La, Ce, Dy) by Curtius and
Scheme 1. Reported syntheses of rare earth hydroxide azides.
Already in 1966, the formation of binary praseodymium
and neodymium polyazides in anhydrous DMSO or TMP (TMP =
trimethylphosphate, (MeO)3PO) was observed by Gutmann et
10
]
al.[
The reactions of the corresponding lanthanide(III)
perchlorate solvates Ln(ClO4)3 · n solvent (Ln = Pr, Nd; solvent
= DMSO (n = 10), TMP (n = 8)) with azide ions were studied by
spectrophotometric, conductometric and potentiometric methods,
which indicated the formation of species such as
Ln(N3)3 · n solvent or [Ln(N3)4(solvent)n]–, however, without any
further characterization. Only recently, Schnick, Kraus and
coworkers successfully synthesized binary europium(II) azide,
obtained from the reaction of silver azide and elemental
europium in liquid ammonia at −40 °C (Scheme 2).[11] Thereby,
thermal treatment of the initially formed ammonia solvate
Eu(N3)2 · n NH3 (n = unknown) resulted in the formation of
binary europium(II) azide, Eu(N3)2, as deduced from elemental
analyses and vibrational spectra (IR, Raman). While structural
data could not be recorded due to the amorphous nature of
Eu(N3)2, it was possible to isolate the corresponding holmium(III)
[a]
M.Sc. K. Rosenstengel, Prof. Dr. A. Schulz, Dr. A. Villinger
Institut für Chemie, Universität Rostock
Albert-Einstein-Strasse 3a, 18059 Rostock (Germany)
E-mail: alexander.villinger@uni-rostock.de
http://www.chemie.uni-rostock.de/
[b]
[c]
Prof. Dr. A. Schulz
Abteilung Materialdesign
Leibniz-Institut für Katalyse e.V. an der Universität Rostock
Albert-Einstein-Strasse 29a, 18059 Rostock (Germany)
Dr. O. Niehaus, Dr. O. Janka, Prof. Dr. R. Pöttgen
Institut für Anorganische und Analytische Chemie, Universität
Münster
Corrensstrasse 30
48149 Münster (Germany)
Supporting information for this article is given via a link at the end of
the document.
amide
azide
as
ammonia
solvate,
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10.1002/ejic.201701408
European Journal of Inorganic Chemistry
FULL PAPER
[Ho2(NH2)3(NH3)10][N3]3 · 11/4 NH3. Furthermore, the latter could Results and Discussion
be characterized by single crystal structure determination and IR
Gd(N3)3 · 8/3 DMSO
and
spectroscopy, which however implied, that this species is better
Synthesis
of
described as dinuclear holmium amide ammonia solvate
displaying no metal-azide bonds.
Gd4(OH)2(N3)10 · n DMSO (n = 8, 10)
Following our interest in element nitrogen compounds with
a high nitrogen content, we envisaged the preparation of binary
lanthanide(III) azides by means of a halide/azide exchange
reaction, starting from the trihalides according to Scheme 3. Two
routes seemed feasible: i) Reaction of lanthanide trifluorides
LnF3 with excess trimethylsilyl azide Me3SiN3 and ii) treatment of
lanthanide triiodides LnI3 with silver azide in
anhydrous solvent.
a suitable,
Scheme 2. Preparation of Eu(N3)2, Cs3[La(N3)6], Cs2[Nd(N3)5], Cs4[Nd(N3)7],
Cs5[Eu(N3)8], Cs3[Nd2(N3)9(H2O)2] and [enH2][Nd2(N3)8] (en = ethylendiamine).
Pioneering work in the field of polyazido lanthanates was
carried out by Mautner, Fritzer and coworkers.[12a-d] In the year
1982 they reported on the reaction of lanthanide sesquioxides
Ln2O3 (Ln = La, Nd) with a mixture of CsN3 and KN3 (6:1) in
concentrated aqueous hydrazoic acid, resulting in the formation
of crystalline Cs3[La(N3)6], Cs2[Nd(N3)5] and Cs4[Nd(N3)7],
respectively (Scheme 2).[12a] Similarly, the synthesis of
Cs5[Eu(N3)8] was achieved starting from Eu2O3, CsN3 and
hydrazoic acid in water (Scheme 2).[12c] Besides elemental
analyses,[12] all compounds were characterized by IR
spectroscopy (IR/Raman),[12a] susceptibility measurements,[12a,
Scheme 3. Preparation of Ln(N3)3 · n solvent and Gd4(OH)2(N3)10 · n DMSO (n
= 8, 10).
Indeed, the reactions of cerium(III)- and gadolinium(III)
iodide with stoichiometric amounts of silver azide in DMSO
proceeded well within a few minutes at ambient temperature.
Separation of silver iodide by filtration resulted in a deep red
solution in case of cerium, and a yellow solution for gadolinium,
13 b]
diffuse reflectance spectroscopy,[12a] and optical spectra
(electronic absorption, luminescence and laser excitation).[13c]
Later, Starynowicz et al. isolated polyazido neodymate salts
Cs3[Nd2(N3)9(H2O)2] and [enH2][Nd2(N3)8] (en = ethylendiamine,
C2H4(NH2)2) by vapor diffusion of gaseous hydrazoic acid into an
aqueous solution of Nd(OH)3 and Cs2CO3 or ethylendiamine,
16
]
respectively (Scheme 3).[
An iodide/azide exchange in
acetonitrile was also observed, but co-precipitation of all
products rendered these conditions unsuitable in a preparative
sense. However, careful layering of the DMSO solution of
gadolinium(III) azide with MeCN, followed by further vapor
diffusion of MeCN, allowed to selectively crystallize silver iodide
as large hexagonal crystals. Subsequently, Gd(N3)3 · 8/3 DMSO
(= [Gd(N3)3]3 · 8 DMSO) was obtained as yellow needle-like
crystals (Figure 1).[16] Interestingly, after the separation of silver
azide the partially hydroxide substituted gadolinium(III) azide
Gd4(OH)2(N3)10 · 10 DMSO was reproducibly obtained, when
both solvents were solely dried by distillation from CaH2. The
formation of this formal basic gadolinium(III) azide could be
completely prevented when the solvents were stored over
molecular sieves (4 Å) prior to use (Scheme 3, Figure 2).[16] On
]
respectively (Scheme 2).[ 14 Single-crystal structures were
determined, with exception of Cs4[Nd(N3)7], which decomposed
when exposed to X-ray radiation.[12,14] For the latter, a model for
the micro symmetry was refined to fit the optical spectra,
indicating a six-fold coordination environment for the Nd(III)
atoms[13a] while the coordination numbers in the other polyazido
lanthanate anions range from eight in Cs5[Eu(N3)8],
Cs3[Nd2(N3)9(H2O)2] and Cs2[Nd(N3)5], to nine in Cs3[La(N3)6]
and [enH2][Nd2(N3)8].[12,13,14] In 2005, Crawford et al. succeeded
in the isolation and structural characterization of the heavy
analog actinide salt [Bu4N]3[U(N3)7], which displays the
heptaazido uranate(III) anions in
bipyramidal ligand sphere.[15]
a distorted pentagonal-
the
other
hand,
large
colorless
crystals
of
Gd4(OH)2(N3)10 · 10 DMSO could be prepared in bulk, when a
DMSO solution of Gd(N3)3 was directly layered by moist MeCN
(Figure 2). Thereby, Gd4(OH)2(N3)10 · 10 DMSO crystallizes as
mixture of
a monoclinic phase (P21/c, denoted as β-
Gd4(OH)2(N3)10 · 10 DMSO) as major component, besides small
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10.1002/ejic.201701408
European Journal of Inorganic Chemistry
FULL PAPER
̅
amounts
of
a
triclinic
modification
(P
1
,
α-
temperature, according to X-ray structure determination (Figure
2). In case of cerium, the same procedure (ii) resulted in bright
red, oily residues, which could thus far not be separated or
isolated. Nevertheless, the presence of cerium(III) azides
Ce(N3)3 · n DMSO in solution can be assumed, since further
treatment with excess [M]N3 ([M]+ = [Ph4P]+, [EtPh3P]+) led to the
formation of hexaazido cerate salts [M]3[Ce(N3)6] · n MeCN ([M]+
= [Ph4P]+ (n = 2), [EtPh3P]+ (n = 0); vide infra).
Gd4(OH)2(N3)10 · 10 DMSO), which could not be separated for
analytical purposes. Nevertheless, some crystals could be
manually separated, which allowed for the determination of both
single crystal X-ray structures (Figure 2).[16] Moreover, slow
conversion into colorless, crystalline Gd4(OH)2(N3)10 · 8 DMSO
was observed upon storage of Gd4(OH)2(N3)10 · 10 DMSO in a
mixture of DMSO/MeCN for several weeks at ambient
Figure 1. Left: ORTEP drawing of Gd(N3)3 · 8/3 DMSO in the solid state. Displacement ellipsoids with 50 % probability at 173 K. Disorder not displayed. Right
(top): Perspective view of Gd(N3)3 · 8/3 DMSO (ball-and-stick representation); Right (bottom): ORTEP drawings of the square anti-prismatic coordination spheres
of Gd(N3)3 · 8/3 DMSO in the crystal. Selected bond lengths (Å): Gd1–O2 2.381(3), Gd1–N10 2.386(4), Gd1–O1A 2.404(3), Gd1–N7 2.408(4), Gd1–N13 2.453(4),
Gd1–N25 2.472(4), Gd1–N4 2.603(4), Gd1–N1 2.649(4), Gd2–O4A 2.330(5), Gd2–O3 2.339(3), Gd2–O5A 2.355(4), Gd2–N16 2.423(4), Gd2–N13 2.455(4),
Gd2–N19 2.473(4), Gd2–N1 2.641(4), Gd2–N4 2.666(4), Gd3 O8 2.330(3), Gd3–O6 2.332(3), Gd3–O7 2.365(3), Gd3–N22 2.443(4), Gd3–N19 2.455(4), Gd3–
N25 2.491(4), Gd3–N4 2.586(4), Gd3–N1 2.622(4).
Astonishingly, the fluoride/azide exchange reaction by treatment
of lanthanide(III) fluorides with excess Me3SiN3 in MeCN or
DMSO was not successful.[16] Even after thermal treatment at
120 °C for several days, no conversion of LnF3 (Ln = La, Pr, Gd)
was observed, as indicated by the almost quantitative recovery
of starting materials in all attempted reactions (Scheme 3).
Similarly, the formation of lanthanide azides by means of a OTf–
Synthesis of [M]3[Ln(N3)6] · n MeCN ([M]+ = [Ph4P]+ (n = 2),
[EtPh3P]+ (n = 0)) and [Ph4P]4[Gd(N3)6][Ag(N3)2]
For the synthesis of polyazido lanthanate(III) salts
[M]3[Ln(N3)6] with the bulky [Ph4P]+ and [EtPh3P]+ counterions,
we intended a one-pot procedure in acetonitrile starting from
lanthanide triiodides LnI3 (Ln = Ce, Gd) or GdCl3 · 2 MeCN,
respectively, and the corresponding phosphonium iodides [M]I,
followed by addition of AgN3 in the required stoichiometry
(Scheme 4).[16] The reaction of cerium(III) iodide as well as
gadolinium(III) halides with six equivalents of AgN3 and three
equivalents of the required [M]I was complete within half an hour
at ambient temperature, and after filtration and concentration of
–
/N3 (OTf– = triflate, trifluoromethyl sulfonyl) exchange failed in
the solvothermal reaction of Gd(OTf)3 and Me3SiN3 in various
solvents (MeCN, fluorobenzene, Me3SiN3, [BMIm][OTf] ([BMIm]+
= N,N-butyl-methyl imidazolium)).[16] Likewise, no reaction could
be observed upon treatment of elemental cerium with hydrazoic
acid HN3 in fluorobenzene.[16]
the
reaction
solution,
all
hexaazido
lanthanates
[M]3[Ln(N3)6] · n MeCN were obtained as colorless crystals
(Figure 3). Salts containing the [EtPh3P]+ cation crystallized free
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10.1002/ejic.201701408
European Journal of Inorganic Chemistry
FULL PAPER
Scheme 4. Preparation of [M]3[Ln(N3)6] n MeCN and [Ph4P]4[Gd(N3)6][Ag(N3)2].
of solvent (n = 0), whereas both tetraphenylphosphonium
derivatives
were
isolated
as
acetonitrile
di-solvates
[Ph4P]3[Ln(N3)6] · 2 MeCN (cf. Vion: [Ph4P]+ 464 vs. [EtPh3P]+ 409
Å3).[16,17]
[Ph4P]3[Ce(N3)6] · 2 MeCN was isolated as a crystalline
mixture of two different triclinic modifications (denoted as α- and
β-[Ph4P]3[Ce(N3)6] · 2 MeCN), evident from single crystal X-ray
structure analyses. Interestingly, the same iodide/azide
exchange procedure was not successful when CeI3 · 4 THF was
used as a starting material instead of neat CeI3. Besides
colorless crystals of [Ph4P]N3, which could be separated and
identified by means of a single crystal X-ray determination, only
intense colored decomposition products were obtained in the
course of the reaction.[16] The formation of polyiodo cerates in
the reaction of CeI3 · 4 THF with [Ph4P]I in MeCN was also not
observed. After workup, a crystalline mixture of [Ph4P]I and
[Ph4P]I3 was isolated, which clearly indicated that cerium(III)
iodides tend to decompose in the presence of THF.[16]
Figure 2. Left (top): ORTEP drawing of β-Gd4(OH)2(N3)10 · 10 DMSO (1) in the solid state. Displacement ellipsoids with 50 % probability at 173 K. Disorder not
displayed. Selected bond lengths (Å): Gd1–O3A 2.261(9), Gd1–O1 2.364(4), Gd1–O4 2.377(4), Gd1–N1 2.435(6), Gd1–N4 2.450(5), Gd1–N28 2.510(5), Gd1–
N10 2.522(5), Gd1–N7 2.545(5), Gd2–O5 2.346(4), Gd2–O2 2.351(4), Gd2–O7 2.362(4), Gd2–O6 2.384(4), Gd2–O1 2.389(4), Gd2–N7 2.500(5), Gd2–N13
2.508(5), Gd2–N10 2.597(5), Gd3–O9 2.374(4), Gd3–O8A 2.379(6), Gd3–O2 2.388(4), Gd3–N19 2.421(6), Gd3–N16 2.444(6), Gd3–N13 2.489(5), Gd3–N22
2.545(5), Gd3–N25 2.549(5), Gd4–O12 2.349(4), Gd4–O10 2.360(4), Gd4–O2 2.380(4), Gd4–O11 2.387(4), Gd4–O1 2.388(4), Gd4–N28 2.484(5), Gd4–N22
2.495(5), Gd4–N25 2.569(5). Right: Perspective view (ball-and-stick representation) of β-Gd4(OH)2(N3)10 · 10 DMSO (top), and α-Gd4(OH)2(N3)10 · 10 DMSO
(bottom). Remark: The α- and β-phase differ in the orientation of two DMSO ligands. Left (bottom): Perspective view of the chains of Gd4(OH)2(N3)10 · 8 DMSO in
the crystal (ball-and-stick representation, view along [001]).
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10.1002/ejic.201701408
European Journal of Inorganic Chemistry
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Additionally, the iodide/azide exchange in GdI3 was carried out
with four eqivalents of AgN3/[M]I (Scheme 4), which, however,
resulted in the unintended isolation of the double salt
[Ph4P]4[Gd(N3)6][Ag(N3)2] (Figure 4), instead of possible
polyazido gadolinate(III) salts [Ph4P]n[Gd(N3)3+n] with an higher
degree of azide substitution (n > 3; vide supra). Like in the
previous case, the formation and co-crystallization of an
argentate(I) anion was also observed in the partially azide
substituted species [Ph4P]4[GdCl2(N3)4][AgCl2] (Scheme 4),
which was obtained in the reaction of Gdl3 with four equivalents
of AgN3 and [M]Cl (Figure 4).[16] The same species,
[Ph4P]4[GdCl2(N3)4][AgCl2], was also formed as preferred product
in the reaction of GdCl3 · 2 MeCN and three equivalents of AgN3
and [M]I. It is interesting to note, that in both reactions involving
less than six equivalents of AgN3, the co-crystallization of small
amounts of the mixed chlorido/iodo diargentate(I) salt
[Ph4P][Ag2Cl2I] as tiny, needle-like crystals was observed.[16]
[Ph4P]4[Gd(N3)6][N3(daa)] · acetone (daa = diacetone alcohol),
which could be obtained in small amounts in the attempted re-
crystallization of [Ph4P]3[Gd(N3)6] · 2 MeCN from acetone (Figure
4). According to X-ray structure determination, the co-
crystallized azide anion is coordinated by the hydroxyl group of
the diacetone alcohol. Presumably, the latter was formed as
product of the aldol reaction of acetone upon longer standing
(vide infra).[16,18]
It is interesting to note, that a complete halide/azide
exchange in GdX3 (X = Cl, I) was observed for all reactions,
irrespective of the applied trihalide. The double-salt
[Ph4P]4[Gd(N3)6][Ag(N3)2] is an exception which was found to be
slightly contaminated by chloride. According to X-ray structure
determination, the latter contained about 8 % of the dichlorido
argentate(I)
anion
[AgCl2]−
as
impurity
(=
[Ph4P]4[Gd(N3)6][AgCl0.16(N3)1.84]) when GdCl3 · 2 MeCN was
used instead of GdI3 (Table S4).[16]
Figure 4. ORTEP drawings of the molecular structure of the [GdCl2(N3)4]3–
anion (top, left), the [Ag(N3)2]− anion (bottom, left), the [N3(daa)]− anion (top,
right) and the [AgCl2]− anion (bottom, right) in the solid state. Disorder of the
[GdCl2(N3)4]3– and [N3(daa)]− anions not displayed. Displacement ellipsoids
with 50 % probability at 173 K. Selected bond lengths (Å):
[Ph4P]4[GdCl2(N3)4][AgCl2] (1) (symmetry codes: (i) −x, −y, 1−z; (ii) 1−x, 1−y,
−z): Gd1–N4 2.326(7), Gd1–N4i 2.326(7), Gd1–N1 2.345(2), Gd1–N1i
2.3449(19), Gd1–N7 2.35(3), Gd1–N7i 2.35(3), Gd1–Cl1 2.7107(9), Gd1–Cl1i
2.7107(9), Ag1–Cl3 2.3440(6), Ag1–Cl3ii 2.3440(6); [Ph4P]4[Gd(N3)6][Ag(N3)2]
(symmetry code: (ii) 1−x, 1−y, −z): Ag1–N10 2.0882(19), Ag1–N10 2.0882(19),
N10–N11 1.194(3), N11–N12 1.156(3); [Ph4P]4[Gd(N3)6][N3(daa)] · acetone:
N10–N11 1.195(5), N11–N12 1.174(5), C49a–C51a 1.495(8), C49a–C50a
1.502(11), C51a–C52a 1.551(7), C52a–C53a 1.523(9), C52a–C54a 1.524(8),
O1a–C49a 1.212(8), O2a–C52a 1.431(7).
Figure 3. ORTEP drawings of the molecular structure of the [Ln(N3)6]3– anions
in the solid state (top: [Ph4P]+, bottom: [EtPh3P]+ salts). For
[Ph4P]3[Ln(N3)6] · 2 MeCN salts, only one of four independent anions in the
asymmetric unit are displayed. [Ph4P]3[Ce(N3)6] · 2 MeCN exists in two
modifications,
only
the
α-modification
is
displayed.
For
α-
[Ph4P]3[Ce(N3)6] · 2 MeCN, only one of two independent anions in the
asymmetric unit is shown. Displacement ellipsoids with 50 % probability at 173
K. Selected bond lengths (Å): [Ph4P]3[Ce(N3)6] · 2 MeCN: Ce1–N10 2.435(4),
Ce1–N4 2.436(4), Ce1–N7 2.445(3), Ce1–N13 2.446(3), Ce1–N1 2.452(3),
Ce1–N16 2.457(3); [Ph4P]3[Gd(N3)6] · 2 MeCN: Gd1–N4 2.331(3), Gd1–N13
2.338(3), Gd1–N1 2.342(4), Gd1–N10 2.345(4), Gd1–N7 2.354(3), Gd1–N16
2.371(3); [EtPh3P]3[Ce(N3)6] (symmetry codes:(i) −x+y+1, −x+1, z; (ii) −y+1,
x−y, z): Ce1–N1 2.458(8), Ce1–N1i 2.458(8), Ce1–N1ii 2.458(8), Ce1–N4
2.411(8), Ce1–N4i 2.411(8) Ce1–N4ii 2.411(8); [EtPh3P]3[Gd(N3)6] (symmetry
codes:(i) −x+y+1, −x+1, z; (ii) −y+1, x−y, z): Gd1–N1 2.357(5), Gd1–N1i
2.357(5), Gd1–N1ii 2.357(5), Gd1–N4 2.344(5), Gd1–N4i 2.344(5), Gd1–N4ii
2.344(5).
Physical and spectroscopic data
All considered azide compounds could be fully characterized by
14N NMR, ATR-IR and Raman spectroscopy, elemental analysis,
DSC and single-crystal structure elucidation.[16] The magnetic
properties in solution as well as in solid state were examined by
19
]
1H NMR (Evans Method),[
and magnetic susceptibility
measurements carried out in a PPMS (PPMS = physical
The preferred formation of double salts was further indicated by
the
unintended
isolation
of
crystalline
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10.1002/ejic.201701408
European Journal of Inorganic Chemistry
FULL PAPER
property
measurement
system),
respectively.[16]
The
157 and 173 °C, respectively, which was accompanied by a
characterization data of all isolated compounds is summarized in
Table 1.
color change to black (cf. Cd(N3)2 · 3/2 DMSO 120 °C (m.p.),
Bi(N3)3 · DMSO 200 °C (detonation)).[
In contrast, all
20 a,b]
Neither gadolinium(III) azide Gd(N3)3 · 8/3 DMSO and its
hydroxide analogs Gd4(OH)2(N3)10 · n DMSO (n = 8, 10), nor the
hexaazido lanthanate salts [M]3[Ln(N3)6] · n MeCN (Ln = Ce, Gd;
[M]+ = [Ph4P]+ (n = 2), [EtPh3P]+ (n = 0)) were sensitive to friction
or shock, and notably did not explode upon burning in a flame.
All compounds were found to be highly hygroscopic and slowly
decomposed in air, but were stable for several months under
argon atmosphere in crystalline state. Moreover, all compounds
were found to be slightly sensitive to light and should therefore
be stored in the dark.
hexaazido lanthanate salts [M]3[Ln(N3)6] · n MeCN showed
sharp melting points and were stable in the molten state.
Thereby, the [EtPh3P]+ salts of both different lanthanides
showed similar melting points (Ce: 213, Gd: 229 °C), while the
[Ph4P]+ derivatives, which additionally contained acetonitrile as
solvate, melted at slightly lower temperatures (Ce: 187 °, Gd
216 °C). Likewise, the double salts [Ph4P]4[Gd(N3)6][Ag(N3)2] as
well as [Ph4P]4[GdCl2(N3)4][AgCl2] displayed melting points in a
similar range with 222 and 229 °C, respectively (cf. 235 °C for
[Ph4P]N3).[20a]
Gd(N3)3 · 8/3 DMSO
decomposed on gentle heating (heating-rate 5–20 °C/min) at
and
Gd4(OH)2(N3)10 · 10 DMSO
Table 1. Selected analytical data (melting points, 14N NMR data, magnetic susceptibility data, IR and Raman data of as(N3)).[a]
μeff(soln.)[b] μeff(solid)
Gd
M.p.[°C] 14N NMR [ppm][a]
IR as(N3) [cm−1 [c]
]
Raman as(N3) [cm−1 [d]
]
NMR [μB]
7.71(1)
PPMS [μB]
8.03(1)
Gd(N3)3 · 8/3 DMSO
157[e]
−284(824)
2126(s), 2084(s),2046(s)
2123(0.9), 2088(0.9),
2080(0.8), 2075(0.7)
2109(0.7), 2073(0.4)
Gd4(OH)2(N3)10 · 10 DMSO[f]
Gd4(OH)2(N3)10 · 8 DMSO
173[e]
−283(991)
7.30(1)
8.33(1)
2092(m), 2066(s), 2047(s)
[g]
[g]
[g]
[g]
[g]
-
-
2104(1.0), 2062(1.0)
-
-
-
Ce
M.p.
213
14N NMR[a]
IR as(N3)[c]
Raman as(N3)[d]
–
–
[EtPh3P]3[Ce(N3)6]
−126(100),
−232(394)
−126(101),
−228(434)
2.14(1)
2.21(1)
2105(w), 2044(s)
2149(0.6), 2140(0.5),
2095(0.6), 2037(0.5)
2153(4.4), 2098(4.7),
2043(4.2),
[Ph4P]3[Ce(N3)6] · 2 MeCN[f]
187
2101(w), 2040(s)
Gd
M.p.
229
14N NMR[a]
IR as(N3)[c]
Raman as(N3)[d]
8.04(1)
[EtPh3P]3[Gd(N3)6]
−243(634)
7.70(1)
2110(w), 2052(s)
2111(0.1), 2057(0.1),
2050(0.1)
2110(1.8), 2054(1.6)
−240(750)[h]
−214(557)
−252(830)
7.74(1)
7.77(1)
2111(w), 2052(s)
2111(w), 2058(s)[i]
7.87(1)
8.20(1)
[Ph4P]3[Gd(N3)6] · 2 MeCN
[Ph4P]4[Gd(N3)6][Ag(N3)2]
[Ph4P]4[GdCl2(N3)4][AgCl2]
216
222
229
2112(1.6), 2052(1.6)
[g]
[g]
-
-
2102(w), 2067 (m), 2053 (s)
2113(0.1), 2105(0.1),
2097(0.1), 2056(0.1)
[g]
[g]
[g]
[g]
[g]
2110(w), 2092(sh, w), 2060(m)[j]
-
-
-
[Ph4P]4[Gd(N3)6][N3(daa)] · acetone
-
-
[a] Values from [D6]DMSO, in parenthesis ν1/2 values in Hz. [b] Measured values were corrected for the diamagnetic contribution of DMSO (χmol,퐷푀푆푂
=
−0.5549 · 10−9 m3 · mol−1). [c] Relative IR intensities denoted as weak (w), medium (m), strong (s), shoulder (sh). [d] Relative Raman intensities scaled to 10. [e]
Decomposition. [f] Mixture of α- and β-phase. [g] Measurement not performed. [h] acetonitrile: 14N δ = –136(190). [i] [Ag(N3)2]−: as(N3) 2035(s) (IR). [j] [N3(daa)]−:

as(N3) 2007(m) (IR).
The
vibrational
spectra
(ATR-IR/Raman)
of
and 3581 cm–1 (IR) was found in the spectra of
Gd4(OH)2(N3)10 · 10 DMSO, while the X-Ln-X stretching modes
(νi.p./o.p.(X-Ln-X), X = N, O) could not be identified due to overlap
with vibrations caused by the DMSO molecules. While the
vibrational modes of the azide units in Gd(N3)3 · 8/3 DMSO and
Gd4(OH)2(N3)10 · n DMSO (n = 8, 10) lay in a similar range, the
Gd(N3)3 · 8/3 DMSO as well as the mixed azide/hydroxide
derivate Gd4(OH)2(N3)10 · n DMSO (n = 8, 10) confirmed the
presence of azido ligands as shown by the antisymmetric
stretching mode (νas(N3)) in the range 2126–2046 cm–1, the
symmetric stretching mode (νs(N3)) at 1367–1227 cm–1, and the
deformation mode (γ/δ(N3)) at 659–613 cm–1 (Table 1, Scheme
S5 – S20).[16] In addition, the combination mode of antisymmetric
and symmetric vibration (νas+νs(N3)) in the range 3390–3326 cm–
vibrational
[M]3[Gd(N3)6] · n MeCN, double salts [Ph4P]4[Gd(N3)6][Ag(N3)2],
[Ph4P]4[GdCl2(N3)4][AgCl2], and
spectra
of
hexaazido
gadolinate
salts
1
was found in the IR spectra (cf. νas(N3): 2103–2036, νs(N3):
[Ph4P]4[Gd(N3)6][N3(daa)] · acetone differed considerably, which
may be attributed to the more ionic bonding situation in the
latter. Thereby, the antisymmetric stretching modes (νas(N3)) in
the range 2113–2050 cm–1 were shifted to slightly lower
wavenumbers (cf. [N3(daa)]− (νas(N3) 2007 cm–1), while the
symmetric stretching modes (νs(N3)) at 1378–1350 cm–1 as well
1401–1220 and γ/δ(N3); 632–545 cm–1 for binary Eu(N3)2).[11] In
good accordance with theoretical data, the existence of more
than one azido ligand resulted in in-phase (i.p.) and out-of-phase
(o.p.) coupling of vibrational modes (Table 1).[16] Moreover, the
characteristic O–H stretching mode (ν(O-H)) at 3583 (Raman)
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10.1002/ejic.201701408
European Journal of Inorganic Chemistry
FULL PAPER
as combination modes of antisymmetric and symmetric vibration
(νas+νs(N3)) were observed at higher wavenumbers in the range
3475–3386 cm–1. Furthermore, the deformation modes (γ/δ(N3))
at 628–623 cm–1, which lie in a similar range, were visible in the
ATR-IR and Raman spectra, respectively.
[Ph4P]4[GdCl2(N3)4][AgCl2] was considerably shifted to higher
frequency (δ = –252 (Δν1/2 = 830 Hz)). Again, no resonances for
the Nβ atoms were visible in the double-salts.[16] Between spectra
of the hexaazido lanthanates for both different counter ions
[EtPh3P]+ and [Ph4P]+, respectively (Table 1), only negligible
differences were found indicating only weak cation–anion
interactions in solution.
Moreover,
the
diazido
argentate(I)
anion
in
[Ph4P]4[Gd(N3)6][Ag(N3)2] (νas(N3): 2035, νs(N3): 1330–1329 and
γ/δ(N3); 640 cm–1) were identified in the ATR-IR and Raman
spectra, in good agreement with the values found by Klapötke et
al. (cf. νas(N3): 2036–1993 (IR), νs(N3): 1328 cm–1 (Raman) in
[Ph4P][Ag(N3)2]).[21]On the other hand, the vibrational spectra of
hexaazido cerate salts [M]3[Ce(N3)6] · n MeCN displayed the
azide units in a slightly more ionic bonding situation (cf. rion(Ce3+)
1.23 vs. rion(Gd3+) 1.19 Å, (Ce) = 1.12 vs. (Gd) = 1.2).[ 22 ]
Compared to the analogous gadolinium compounds, the
antisymmetric stretching modes (νas(N3)) in the range 2105–
2037 cm–1 were shifted to slightly lower wavenumbers, while the
symmetric stretching modes (νs(N3)) at 1378–1345 cm–1, were
observed in a similar range. Consequently, the combination
modes of antisymmetric and symmetric vibration (νas+νs(N3)) at
3453–3375 cm–1 were also slightly shifted to lower frequency, in
accord with the expectations.
The 14N NMR spectra of Gd(N3)3 · 8/3 DMSO, as well as the
mixed azide/hydroxide derivate Gd4(OH)2(N3)10 · 10 DMSO
showed almost identical resonances at δ = –284 (Δν1/2 = 824 Hz)
and δ = –283 (Δν1/2 = 991 Hz), both considerably shifted to lower
frequency compared to the hexaazido gadolinate salts
[M]3[Gd(N3)6] · n MeCN (cf. Bi(N3)3 δ = –137 (Nβ, Δν1/2 = 71 Hz),
–260 (Nα/γ, Δν1/2 = 632 Hz)).[16,23]
As displayed in Table 1, the 14N NMR resonances of all
considered cerium and gadolinium azides measured in
[D6]DMSO at 300 K were strongly influenced by the
paramagnetic moments of the corresponding lanthanide(III)
nuclei (Ce3+: [Xe]4ƒ1, 2F5/2; Gd3+: [Xe]4ƒ7, 8S7/2). In the spectra of
the hexaazido cerates [M]3[Ce(N3)6] · n MeCN two well-resolved
resonances, a medium-sharp signal for the Nβ atoms ([M]+
=
[EtPh3P]+ –126 (Δν1/2 = 100 Hz); [Ph4P]+ –126 (Δν1/2 = 101 Hz))
and a remarkably broadened Nα/γ-resonance ([M]+ = [EtPh3P]+ –
232 (Δν1/2 = 394 Hz); [Ph4P]+ –228 (Δν1/2 = 434 Hz)) were
observed (Table 1).[16] In comparison to previously reported
diamagnetic hexaazido bismuthates [M]3[Bi(N3)6] ([M]+
[EtPh3P]+, [Ph4P]+), these values were reasonably shifted to
lower field ([M]+ = [EtPh3P]+ –134 (Nβ; Δν1/2 = 72 Hz); –260 (Nα/γ
=
;
,
Δν1/2 = 547 Hz); [Ph4P]+: –132 (Nβ, Δν1/2 = 42 Hz), –258 (Nα/γ
Δν1/2 = 390 Hz).[ 23 ] Analogous to known binary azides, the
observation of only one set of azide signals, along with the
absence of a separate Nα resonance indicate a rapid ligand
exchange relative to the NMR timescale.[24]
Figure 5. Magnetic properties of Gd4(OH)2(N3)10 · 10 DMSO: (top)
temperature dependence of the magnetic susceptibility (χ and χ–1 data)
measured at 10 kOe; (bottom) zero-field-cooled / field cooled (ZFC/FC)
measurements at 100 Oe; (bottom inset) magnetization isotherms at 3, 10 and
50 K.
In contrast, the 14N NMR spectra of the corresponding
hexaazido gadolinate salts [M]3[Gd(N3)6] · n MeCN displayed
only the resonance for the Nα/γ atoms ([M]+ = [EtPh3P]+: –243
(Δν1/2 = 634 Hz); [Ph4P]+: –240 (Δν1/2 = 700 Hz), while the Nβ-
resonance was completely absent due to the strong magnetic
field of Gd3+ cations.[16] As a result, the 14N NMR resonance for
the N atom of acetonitrile in [Ph4P]3[Gd(N3)6] · 2 MeCN became
visible at –136 (Δν1/2 = 190 Hz), while no 14N NMR resonance for
The paramagnetic susceptibilities of all presented
compounds in solution were determined by the Evans method
(Table 1).[16] In a slight variation of the original procedure, a
MeCN
could
be
detected
in
the
spectrum
of
NMR sample tube containing
a
dilute solution of the
[Ph4P]3[Ce(N3)6] · 2 MeCN, due to strong overlap with the Nβ
resonance of the azide groups (Table 1). Interestingly, also only
one signal for the Nα/γ atoms of the azide units in
[Ph4P]4[Gd(N3)6][Ag(N3)2] at very low frequency (δ = –214 (Δν1/2
= 557 Hz)) could be detected, indicating a fast ligand exchange
corresponding paramagnetic compound in [D8]DMSO/DMSO
and HMDS (HMDS = hexamethyldisiloxane, (Me3Si)2O) as inert
probe molecule, as well as a sealed capillary containing solely a
solution of the probe (HMDS in [D8]DMSO/DMSO) was used.
Given a known concentration of lanthanide(III) ions cLn3+,
the molar magnetic susceptibility χmolof the sample solution is
proportional to the shift difference ∆δ between the 1H NMR
between gadolinium(III) and silver(I) ions. In contrast, the Nα/γ
-
resonance of the azide units in the chloride substituted species
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10.1002/ejic.201701408
European Journal of Inorganic Chemistry
FULL PAPER
resonance of the HMDS methyl protons of the metal-free
solution and the solution containing the paramagnetic sample
(Eq. 1).[16]
determined from single crystal X-ray data. The crystallographic
data is summarized in the supporting materials (Tables S3 –
S25).[16] CCDC 1575812 – 1575830 contain the supplementary
crystallographic data for this paper. These data can be obtained
free of charge from The Cambridge Crystallographic Data
Centre.
3Δδ
χmol
=
(1)
3+
푐Ln
As depicted in Figures 3 and 4, all examined azido
lanthanate(III) salts display the [LnX6]3− anions (X = N3, Cl) in a
slightly distorted octahedral ligand sphere, with X–Ln–X angles
averaging to the ideal values of 90 and 180 °, respectively (Gd:
83.8–96.2 °, 174.3–180.0 °; Ce: 83.2–97.6 °, 173.5–178.3 °;
Table 2). Within these structures, well separated lanthanate
anions [LnX6]3− with metal-metal distances in the range 11.077–
13.404 Å (Gd) and 11.128–11.709 Å (Ce) were found, which lie
in a similar range for both, the homologous cerate, as well as
gadolinate salts (cf. [EtPh3P]3[Ln(N3)6]: 11.135 (Gd) vs. 11.128 Å
(Ce); [Ph4P]3[Ln(N3)6] · 2 MeCN: 11.560 (Gd), vs. 11.675–
11.709 Å (Ce)). The Gd···Ag, as well as Ag···Ag distances in
The molar susceptibility χmol is connected to the effective
magnetic moment μeff by equation 2, which gives a measure for
the sample magnetism in terms of the Bohr magneton number
μB.
3푘푇χ
mol
2
휇e2ff
=
(2)
휇
0
푁
휇
퐴
퐵
For metal ions with a small spin-orbit coupling constant, the pure
spin magnetism can be described by the spin-only formula,
which neglects all spin-orbit contributions to μeff (Eq. 3):
2
both
mixed
gadolinate/argentate
double
salts
(
)
휇eff = 4푆 푆 + 1
(3)
[Ph4P]4[Gd(N3)6][Ag(N3)2]
and [Ph4P]4[GdCl2(N3)4][AgCl2],
For Gd3+ ions with seven un-paired spins in high-spin ƒ7
configuration (S = 7/2, L = 0), the effective magnetic moment
μeff(spin-only) amounts to 7.94 μB, which is in good agreement
with the experimental values (cf. 7.30–7.77 μB, Table 1). In
contrast, considerably large spin-orbit coupling constants may
be expected for cerium(III) ions (S = 1/2, L = 3). In this case,
orbital contributions have to be included in the calculation of μeff
using equation 4:
covered a comparable range ([Ph4P]4[Gd(N3)6][Ag(N3)2]: Gd···Ag
9.352, Ag···Ag 11.077 Å; [Ph4P]4[GdCl2(N3)4][AgCl2]: 9.156,
12.804 Å).[16]
In all investigated lanthanate salts, only weak N···H
interactions between the anions and cations ([M] + = [EtPh3P]+
2.424 (Ce), 2.439 Å (Gd); [Ph4P]+ 2.335 Å), within the sum of the
van der Waals radii of rvdW(N–H) 3.00 Å were observed in the
solid state.[22] The closest intramolecular N···H contacts were
found between the hydroxyl group of the diacetone alcohol
molecule
and
the
adjacent
azide
a
anion
donor–acceptor
in
(
)
휇eff = 푔퐽√퐽 퐽 + 1
(4)
[Ph4P]4[Gd(N3)6][N3(daa)] · acetone, with
distance (D–H···A) of 2.776 Å (cf. rvdW (N–O) 3.10 Å,[22] Figure
4).
(
)
(
)
where
푔퐽 = 1 + 푆 푆+1 −퐿 퐿+1 +퐽(퐽+1)
2퐽(퐽+1)
In contrast, the structures of gadolinium(III) azide DMSO
solvate Gd(N3)3 · 8/3 DMSO as well as the mixed azide/hydroxide
derivates Gd4(OH)2(N3)10 · n DMSO (n = 8, 10) were composed
of eight-coordinated gadolinium atoms, resembling slightly
distorted square anti-prismatic coordination polyhedra (Figures 1
and 2). Thereby, all angles A-M-B, A-M-C and A-M-D as defined
in Scheme 5, lay within the expected range, and averaged to the
ideal values of 82.06, 70.53 and 109.47 ° (Gd(N3)3 · 8/3 DMSO
The calculated value of 2.54 μB for a Ce3+ ion compares well with
the measured effective magnetic moments of 2.14 and 2.21 μB
for
[EtPh3P]3[Ce(N3)6]
and
[Ph4P]3[Ce(N3)6] · n MeCN,
respectively (cf. μeff(spin-only) 1.73 μB).
In Figure 5, the magnetic properties of solid
Gd4(OH)2(N3)10 · 10 DMSO are depicted. The sample shows
paramagnetism over the whole temperature range (Fig. 5, top)
and no magnetic coupling down to 2.5 K (Fig. 5, bottom).[16] The
effective magnetic moment was calculated to 8.33(1) μB, which
is slightly higher compared to the calculated moment of 7.94 μB.
The magnetization isotherm (Fig. 5, bottom inset) at 3 K shows
saturation at 7.00(1) μB above 40 kOe, in line with the calculated
saturation magnetization of 7 μB according to gJ × J. The other
gadolinium compounds all exhibit magnetic moments close to
the theoretical one, in line with the solution data. Additional
information on the magnetic properties of the other investigated
compounds are summarized in Table 1 and in the Supporting
Information (Table S2, Figures S1 – S4).[16]
59.4–96.2,
68.1–85.8,
92.9–136.0 °;
α-
Gd4(OH)2(N3)10 · 10 DMSO 64.4–85.4, 65.7–82.0, 97.6–131.3 °;
β-Gd4(OH)2(N3)10 · 10 DMSO 64.3–85.7, 65.3–82.5, 96.5–
132.0 °; Gd4(OH)2(N3)10 · 8 DMSO 66.5–87.7, 66.0–83.3, 99.0–
131.0 °).[16] The structural units within these compounds were
associated in the solid state, forming aggregates or chains,
respectively (Figures 1 and 2). Accordingly, short Gd···Gd
distances were observed (Gd(N3)3 · 8/3 DMSO 3.934–3.950 Å, α-
and
β-Gd4(OH)2(N3)10 · 10 DMSO
3.748–6.794 Å,
Gd4(OH)2(N3)10 · 8 DMSO 3.729–6.676 Å), which lie only slightly
above the sum of the van der Waals radii (rvdW(Gd–Gd) =
3.57 Å).[22] The square anti-prismatic GdX8 coordination
polyhedra within these structures are either connected by μ2(1,1)-,
μ2(1,3) or μ3(1,1,1)-bridging azide ligands, as well as μ3(1,1,1)-bridging
hydroxide groups (Figures 1 and 2), leading either to common
X-ray crystallography
Single crystal X-ray structures of all synthesized lanthanide(III)
azides, as well as the structures of the starting materials
CeI3 · 4 THF, GdCl3 · 2 MeCN and Gd(OTf)3 · 3 MeCN were
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10.1002/ejic.201701408
European Journal of Inorganic Chemistry
FULL PAPER
corner-sharing, edge-sharing or face-sharing between two or
three polyhedra, respectively.
Table 2. Selected structural data from single crystal X-ray determinations. Distances in Å, angles in °.
X–Gd–X (X = N,
Gd
Gd···Gd[a]
Gd–X[c] (X = O, Cl)
Gd–N
Nα–Nβ
Nβ–Nγ
Nα–Nβ–Nγ
O)[b]
3.934–3.950
59.4–96.2,
68.1–85.8,
92.9–136.0
2.355
2.415
2.467 μ2(1,1)
2.628 μ3(1,1,1)
1.167
1.153
177.9
[d]
Gd(N3)3 · 8/3 DMSO
1.197
1.211
1.152
1.149
178.6
179.5
64.4–85.4,
65.7–82.0,
97.6–131.3
64.3–85.7,
65.3–82.5,
96.5–132.0
66.5–87.7,
66.0–83.3,
99.0–131.0
3.748–6.789
2.376 (OH)
2.361 (ODMSO
2.435
2.522 μ2(1,1)
1.158
1.191
1.147
1.145
177.4
178.6
α-Gd4(OH)2(N3)10 · 10 DMSO
β-Gd4(OH)2(N3)10 · 10 DMSO
Gd4(OH)2(N3)10 · 8 DMSO
)
3.748–6.794
3.729–6.676
2.377 (OH)
2.358 (ODMSO
2.438
2.526 μ2(1,1)
1.167
1.190
1.156
1.151
178.0
178.4
)
)
2.372 (OH)
2.367 (ODMSO
2.382
2.502 μ2(1,1)
2.487 μ2(1,3)
1.180
1.205
1.164
1.160
1.140
1.167
178.4
178.3
178.6
[EtPh3P]3[Gd(N3)6]
11.135
11.560
11.077[e]
12.804[f]
13.404
Ce···Ce[a]
11.128
11.709
11.675
84.5–92.6, 174.3
87.9–93.8, 178.7
88.5–91.6, 180.0
83.8–96.2, 180.0
87.9–92.1, 180.0
N–Ce–N[b]
-
2.351
2.346
2.343
2.337
2.243
Nα–Nβ
1.189
1.177
1.177
1.179
1.170
1.179
1.181
1.163
1.158
1.158
1.156
1.156
1.145
177.8
178.5
179.2
179.1
178.9
Nα–Nβ–Nγ
178.0
178.9
178.8
[Ph4P]3[Gd(N3)6] · 2 MeCN
[Ph4P]4[Gd(N3)6][Ag(N3)2]
[Ph4P]4[GdCl2(N3)4][AgCl2]
[Ph4P]4[Gd(N3)6][N3(daa)] · acetone
Ce
-
-
2.711
-
Ce–N
2.435
2.443
2.435
Nβ–Nγ
[EtPh3P]3[Ce(N3)6]
83.2–93.6, 173.5
86.1–97.6, 174.2
86.9–92.2, 178.3
1.158
1.158
1.156
α-[Ph4P]3[Ce(N3)6] · 2 MeCN
β-[Ph4P]3[Ce(N3)6] · 2 MeCN
[a] Closest Ln···Ln distances. [b] For a square anti-prismatic coordination sphere, the angles are listed in the order: range A–M–B, range A–M–C and range A–M–
D according to Scheme 5; for an octahedral coordination sphere, the angles are listed in the order: range of Xcis–Ln–Xcis and average of Xtrans–Ln–Xtrans. [c] If there
are more than one azide, tetrazolate or DMSO ligand, the average value is given. In case of disorder, only geometrical parameters of the major part were used. [d]
μn(k,l,m) denotes the bridging mode of the N3 unit. [e] Closest Gd···Ag/Ag···Ag distances: 9.352/11.077 Å. [f] Closest Gd···Ag/Ag···Ag distances: 9.156/12.804 Å.
In the structure of Gd(N3)3 · 8/3 DMSO, only face-sharing
interactions were observed, leading to the formation of a
molecular, cyclic assembly of three GdX8 polyhedra (Figure 1).
Thereby, each gadolinium cation is connected to both adjacent
Gd atoms by two μ2(1,1)- as well as two μ3(1,1,1)-bridging azide
units, while all DMSO ligands are bound in terminal positions.
Between the molecular units, only weak N···HDMSO distances in
the range 2.485–2.794 Å are found, all within the sum of the van
der Waals radii (rvdW(N–H) 3.00 Å).[22]
bicyclic
arrangement
as
discussed
for
Gd4(OH)2(N3)10 · 10 DMSO, except that two terminal DMSO
ligands are replaced by azide groups of the adjacent
Gd4(OH)2(N3)10 · 8 DMSO units (Figure 2). These μ2(1,3)-bridging
interactions resulted in the condensation of molecular units and
the formation of a chain-like structure along [1 −1 0]. Between
these polymeric units, only weak N···HDMSO interactions can be
found, with N···H distances in the range 2.2566–3.1612 Å, all
within the sum of the van der Waals radii (rvdW(N–H) 3.00 Å).[22]
Likewise, face-sharing square anti-prismatic Gd units were
found in α- and β-Gd4(OH)2(N3)10 · 10 DMSO, each connected to
one adjacent GdX8 polyhedron by two μ2(1,1)-bridging azide
ligands as well as one μ3(1,1,1)-bridging hydroxide group (Figure
2). Further edge-sharing interactions via one μ2(1,1)-bridging
azide ligand and one μ3(1,1,1)-bridging hydroxide ligand results in
the aggregation of four GdX8 polyhedra, forming a bicyclic, tetra-
nuclear structure. As shown in Figure 2, the molecular units in α-
and β-Gd4(OH)2(N3)10 · 10 DMSO differ only with respect to the
orientation of two adjacent DMSO ligands. While the structural
units in α-Gd4(OH)2(N3)10 · 10 DMSO resemble local Ci
3
̅
symmetry (P1, d = 2.01 g/cm ), the rotation of both DMSO
Scheme 5. Ideal square-antiprismatic ligand sphere (left: top-view, right: side-
view).
molecules led to
a
distortion to C1-symmetry in β-
Gd4(OH)2(N3)10 · 10 DMSO (P21/c, d = 2.00 g/cm3), along with a
slightly lower density in the crystal (cf. d(N···H) α-
As illustrated in Table 2, the Ln–N and N–N distances varied
strongly dependent on the coordination mode of the azide units.
Accordingly, the shortest Ln–N distances are found for the single
Gd4(OH)2(N3)10 · 10 DMSO:
Gd4(OH)2(N3)10 · 10 DMSO: 2.588 Å). In the structure of
Gd4(OH)2(N3)10 · 8 DMSO the GdX8 polyhedra adopt the same
2.493 Å;
β-
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10.1002/ejic.201701408
European Journal of Inorganic Chemistry
FULL PAPER
bonded, terminal azide groups in the octahedrally coordinated Conclusions
hexaazido gadolinate anions [Gd(N3)6]3−, with averaged Gd–N
series of [Ph4P]+ and [EtPh3P]+ salts of hexaazido
bond lengths in the range 2.243–2.351 Å, within the sum of the
A
lanthanate(III) anions [M]3[Ln(N3)6] · n MeCN (Ln = Ce, Gd; [M]+
= [Ph4P]+ (n = 2), [EtPh3P]+ (n = 0)), along with the double-salts
[Ph4P]4[Gd(N3)6][Ag(N3)2] and [Ph4P]4[GdCl2(N3)4][AgCl2] was
synthesized and comprehensively characterized. All salts were
easily accessible by means of an iodide/azide exchange starting
from the corresponding lanthanide(III) iodide LnI3, AgN3, and the
desired [M]I in acetonitrile or DMSO. Likewise, gadolinium(III)
azide as DMSO solvate Gd(N3)3 · 8/3 DMSO, as well as the
mixed azide/hydroxide derivates Gd4(OH)2(N3)10 · n DMSO (n =
8, 10) were synthesized by the reaction of GdI3 and AgN3 in
DMSO. In the solid state, only slightly distorted, octahedral
coordinated lanthanide(III) atoms are observed in the [Ln(N3)6]3−
anions, while the structures of Gd(N3)3 · 8/3 DMSO and
Gd4(OH)2(N3)10 · n DMSO (n = 8, 10) display the Gd3+ cations in
a distorted square anti-prismatic coordination environment.
ion radii (rion(Gd–N) = 2.40 Å) for an octahedral coordination
sphere (cf. Ce-N 2.435–2.443 Å in [M]3[Ce(N3)6] · n MeCN,
rion(Ce–N) = 2.47 Å).[22,25] Slightly longer Ln–N distances with
average Gd–N bond lengths in the range 2.382–2.377 Å were
observed in the square anti-prismatic GdX8 coordination
polyhedra
in
Gd(N3)3 · 8/3 DMSO
as
well
as
Gd4(OH)2(N3)10 · n DMSO (n = 8, 10), which lay also well within
the sum of the ion radii for an eight-coordinated Gd3+ ion
(rion(Gd–N) = 2.51 Å). The azide units adopt a typical trans-bent
structure with short averaged Nα–Nβ (1.158–1.181 Å) and Nβ–Nγ
distances (1.145–1.160 Å), as well as Nα–Nβ–Nγ angles in the
range 177.4–179.2 °, which deviated considerably from linearity
(cf. [M]3[Ce(N3)6] · n MeCN Nα–Nβ 1.177–1.189 Å, Nβ–Nγ 1.156–
1.158 Å, Nα–Nβ–Nγ 178.0–178.9 °).
On the other hand, the Gd–N distances to the μ2(1,1)-, μ2(1,3)
-
or μ3(1,1,1)-bridging azide ligands in the square anti-prismatic
coordination sphere of the Gd atoms in Gd(N3)3 · 8/3 DMSO and
Gd4(OH)2(N3)10 · n DMSO (n
= 8, 10) were considerably
Experimental Section
elongated (μ2(1,1) 2.467–2.526 Å, μ2(1,3) 2.487 Å, μ3(1,1,1) 2.628 Å),
in good agreement with the sum of the ionic radii (rion(Gd–N) =
2.51 Å) This, together with the slightly longer Nα–Nβ distances
(Nα–Nβ 1.190–1.211 Å, Nβ–Nγ 1.140–1.167), and flat angles in
the range 178.3–179.5° indicated a higher degree of ionic
bonding (Table 2).
Caution! Covalent azides are potentially hazardous and can decompose
explosively under various conditions! Especially dry, crystalline AgN3 is
extremely sensitive to shock and friction and can explode violently upon
the slightest provocation. Appropriate safety precautions (safety shields,
face shields, leather gloves, protective clothing) should be taken.
The Gd–ODMSO bond lengths in the range 2.355–2.367 Å
were slightly longer than the sum of the covalent radii rcov(Gd–
O) = 2.32 Å,[25] but within with the sum of ionic radii rion(Gd–O)
Gd(N3)3 · 8/3 DMSO: To a solution of gadolinium(III) iodide GdI3 (0.261 g,
0.49 mmol) in DMSO (5 mL) silver azide AgN3 (0.222 g, 1.46 mmol) was
added. After stirring for 40 minutes, the resulting yellow precipitate was filtered
off and the resulting clear, orange filtrate was concentrated to 2 mL by
evaporation of the solvent. Dried acetonitrile was added by gas diffusion over
a period of several days. The formed AgI crystals were removed by filtration,
and the filtrate was concentrated to 1 mL and layered with 2 mL of dried
acetonitrile. Over the course of a few days yellow, needle-like crystals were
deposited. The supernatant was removed by decantation and the crystals of
Gd(N3)3 · 8/3 DMSO were dried in vacuum (yield: 60–70 %). M.p. 157 °C
of 2.40 Å for
a
square anti-prismatic coordination
environment.[22] In accord with a higher coordination number of
the oxygen atom in the μ3(1,1,1)-bridging hydroxide group, the Gd–
OOH bonds were slightly elongated in the range 2.372–2.377 Å.
As depicted in Figure 4, well separated argentate(I) [AgX2]–
anions (X
= N3, Cl) were found in the double salts
[Ph4P]4[Gd(N3)6][Ag(N3)2] and [Ph4P]4[GdCl2(N3)4][AgCl2] with
closest intramolecular N···H contacts of 2.489 and 2.591 Å (cf.
rvdW(N–H) 3.00 Å).[22] In both structures, the [AgX2]– anions
(decomp.), 14N NMR (300 K, [D6]DMSO, 36.1 MHz): δ = -284 ppm (Nα/γ, Δν1/2
=
824 Hz). IR (ATR, 32 scans): 휈̃ = 3390 (w), 3326 (w), 3001 (w), 2917 (w), 2664
(w), 2586 (w), 2126 (s), 2084 (s), 2046 (s), 1411 (m), 1402 (m), 1351 (m),
1325 (m), 1314 (m), 1297 (m), 1288 (sh, m), 1257 (m), 1231 (w), 999 (s), 958
(s), 911 (m), 714 (m), 681 (w), 656 (m), 643 (m), 616 cm-1 (m); Raman
(633 nm, 6 mW, 25 °C, 40 s, 8 acc.): 휈̃ = 3002 (2.0), 2916 (5.1), 2123 (0.9),
2088 (0.9), 2080 (0.8), 2075 (0.7), 1413 (1.5), 1352 (4.0), 1332 (1.3), 1295
(0.8), 1259 (0.7), 1008 (1.1), 958 (1.0), 942 (sh, 0.8), 712 (3.2), 680 (5.4), 654
(1.2), 638 (1.1), 405 (1.5), 380 (1.5), 341 (2.3), 312 (2.9), 254 (3.6), 172 (4.1),
97 cm-1 (10); elemental analysis calcd (%) for C16H48N27Gd3O8S8: C 13.03, H
3.28, N 25.64, S 17.39; found C 13.40, H 3. 29, N 25.21, S 17.02.
were linearly coordinated (X–Ag–X 180 °) and obey ideal D∞h
-
([AgCl2]–) ([Ag(N3)2]–),
and C2h-symmetry respectively.
Accordingly, both Ag–N bond lengths in the diazido argentate(I)
anion were equal and amount to 2.088 Å, which lies only slightly
above the sum of the covalent radii for a silver nitrogen single
bond (rcov(Ag–N) = 1.99 Å), but within the sum of the ion radii
for a linearly coordinated Ag+ ion (rion(Ag–N) = 2.13 Å).[25,22]
Only recently, the structures of two diazido argentate(I) salts
[M][Ag(N3)2] ([M]+ =[Ph3S], [Ph4P]) could be determined by
Klapötke et al., which, however, displayed the silver cations in a
distorted tetrahedral or distorted trigonal-planar coordination
sphere, resulting in considerably elongated Ag–N bond lengths
Gd4(N3)10(OH)2 · 10 DMSO and Gd4(N3)10(OH)2 · 8 DMSO: To a solution of
gadolinium(III) iodide GdI3 (0.133 g, 0.25 mmol) in DMSO (3 mL) silver azide
AgN3 (0.112 g, 0.75 mmol) was added. After stirring for 30 minutes, the
resulting yellow precipitate was removed by filtration and the clear, orange
filtrate was concentrated by evaporation of the solvent. Moist, degassed
acetonitrile was added by slow gas diffusion into the DMSO solution. The
formation of crystalline silver iodide AgI was observed which was separated by
decantation from the supernatant. The solution was concentrated and layered
with moist, degassed acetonitrile. Storage at ambient temperature for several
days resulted in the deposition of colorless, block-like crystals of
Gd4(N3)10(OH)2 · 10 DMSO. According to X-ray structure determinations,
([M]+
=
[Ph3S]+ Ag–N 2.291–2.331 Å; [Ph4P]+Ag–N 2.139–
2.485 Å).[21] To the best of our knowledge, the present structure
represents the only example for an isolated, linearly coordinated
diazido argentate(I) anion in the literature.
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10.1002/ejic.201701408
European Journal of Inorganic Chemistry
FULL PAPER
Gd4(N3)10(OH)2 · 10 DMSO was found to be a mixture of a triclinic (α) and a
[Ph4P]3[Gd(N3)6] · 2 MeCN were washed with acetonitrile. Drying in vacuum
led to non-stoichiometric loss of solvent (yield: 20–30 %). M.p. 216 °C; 1H
NMR (300 K, [D6]DMSO, 500.13 MHz): δ = 2.17 (s, CH3CN, Δν1/2 = 240 Hz),
7.88 ppm (s, 20 H; Aryl, Δν1/2 = 340 Hz); 13C NMR (300 K, [D6]DMSO,
̅
monoclinic (β) modification (space groups P 1 and P21/c) in varying
compositions
(yield:
20–30 %).
Storage
of
crystalline
Gd4(N3)10(OH)2 · 10 DMSO in DMSO/acetonitrile (excess MeCN) solution for
several months resulted in the slow transformation into crystals of
Gd4(N3)10(OH)2 · 8 DMSO as confirmed by single crystal X-ray diffraction.
125.8 MHz):
δ = 135.79 (s, para), 134.97 (s, ortho), 130.89 (s, meta),
118.10 ppm (d, 1J(13C - 31P) = 87 Hz, PC); 31P NMR (300 K, [D6]DMSO,
202.5 MHz): δ = 22.34 ppm (s); 14N NMR (300 K, [D6]DMSO, 36.1 MHz): δ = -
136 (MeCN, Δν1/2 = 190 Hz), -240 ppm (Nα/γ, Δν1/2 = 750 Hz); IR (ATR,
32 scans): 휈̃ = 3468 (w), 3392 (w), 3168 (w), 3079 (w), 3058 (w), 3022 (w),
2993 (w), 2963 (w), 2690 (w), 2581 (w), 2111 (w), 2052 (s), 1828 (w), 1790
(w), 1585 (m), 1483 (m), 1434 (m), 1357 (m), 1316 (m), 1222 (w), 1186 (w),
1163 (w), 1105 (s), 1079 (sh, m), 1027 (w), 995 (m), 937 (w), 850 (w), 754 (m),
719 (s), 686 (s), 665 (sh, m), 615 cm-1 (m); Raman (473 nm, 0.36 mW, 25 °C,
40 s, 12 acc.): 휈̃ = 3168 (3.4), 3144 (3.4), 3061 (10), 3025 (3.0), 3010 (3.0),
2993 (3.0), 2959 (2.9), 2931 (3.3), 2248 (2.2), 2110 (1.8), 2054 (1.6), 1585
(6.3), 1482 (1.0), 1438 (1.2), 1364 (4.8), 1340 (sh, 1.1), 1274 (0.8), 1223 (0.7),
1188 (1.1), 1163 (1.0), 1106 (sh, 1.9), 1096 (3.2), 1076 (0.7), 1026 (4.1), 999
(7.5), 935 (0.6), 854 (0.4), 749 (0.4), 724 (0.5), 677 (1.5), 614 (1.1), 533 (0.2),
454 (0.2), 394 (0.1), 376 (0.1), 283 (0.6), 254 (1.3), 196 (0.9), 154 cm-1 (1.6);
elemental analysis calcd (%) for C76H66N20GdP3: C 60.47, H 4.41, N 18.56;
found C 58.81, H 4.65, N 17.54.
Gd4(N3)10(OH)2 · 10 DMSO (Mixture of α- and β-phase): M.p. 173 °C
(decomp.); 14N NMR (300 K, [D6]DMSO, 36.1 MHz): δ = -283 ppm (Nα/γ, Δν1/2
=
991 Hz). IR (ATR, 32 scans): 휈̃ = 3581 (w), 3390 (w), 3343 (w), 2997 (w), 2916
(w), 2653 (w), 2092 (m), 2066 (s), 2047 (s), 1413 (m), 1404 (sh, m), 1350 (m),
1315 (m), 1298 (m), 1290 (m), 1233 (w), 1227 (w), 1007 (s), 964 (s), 942 (m),
911 (m), 712 (m), 679 (m), 657 (m), 650 (m), 613 cm-1 (m); Raman (633 nm,
5 mW, 25 °C, 20 s, 10 acc.): 휈̃ = 3583 (0.5), 3002 (1.6), 2918 (4.0), 2109 (0.7),
2073 (0.4), 1416 (0.9), 1357 (3.8), 1320 (0.2), 1299 (0.3), 1291 (0.4), 1030
(0.5), 1013 (0.4), 968 (0.4), 946 (0.1), 717 (2.0), 684 (5.2), 659 (0.3), 615 (0.2),
404 (0.4), 342 (1.0), 318 (1.5), 293 (1.3), 223 (2.3), 174 (2.3), 87 cm-1 (10);
elemental analysis calcd (%) for C20H62N30Gd4O12S10: C 12.88, H 3.35, N
22.54, S 17.20; found C 13.21, H 2.80, N 19.28, S 15.45.
Gd4(N3)10(OH)2 · 8 DMSO: Raman (633 nm, 5 mW, 25 °C, 20 s, 10 acc.): 휈̃ =
2998 (3.3), 2912 (8.6), 2104 (1.0), 2062 (1.0), 1409 (1.1), 1367 (3.4), 1354
(2.3), 1304 (0.8), 1294 (0.9), 1233 (0.4), 1027 (0.5), 1006 (0.6), 970 (0.2), 954
(0.3), 799 (2.6), 739 (1.7), 710 (1.7), 675 (4.6), 635 (0.4), 527 (0.5), 402 (0.5),
328 (2.2), 296 (3.0), 217 (3.1), 203 (3.0), 175 (4.2), 71 cm-1 (10).
[EtPh3P]3[Ce(N3)6]: To
a solution of cerium(III) iodide CeI3 (0.130 g,
0.25 mmol) and silver azide AgN3 (0.114 g, 0.76mmol) in acetonitrile (4 mL), a
suspension of ethyltriphenylphosphonium iodide [EtPh3P]I (0.313 g,
0.75 mmol) and AgN3 (0.114 g, 0.76 mmol) in acetonitrile (4 mL) was added.
After stirring for 30 minutes, the resulting black-brownish solution was
separated from the yellow precipitate by filtration (F4) and concentrated to
about 3 mL in vacuum. Storage at ambient temperature for several hours
resulted in the deposition of colorless crystals of [EtPh3P]3[Ce(N3)6] besides
small amounts of a brownish, amorphous precipitate, which was removed by
washing with acetonitrile (yield: 10–20 %). M.p. 213 °C; 1H NMR (300 K,
[D6]DMSO, 500.13 MHz): δ = 7.73 - 7.90 (m, 15 H, Aryl), 3.61 (dquartett, 2 H,
J(1H - 1H) = 7.4 Hz, J(1H - 31P) = 13.6 Hz, CH2CH3), 1.22 (dtriplett, 3 H, J(1H - 1H)
= 7.4 Hz, 53 J(1H - 31P) = 20.2 Hz, CH2CH3); 13C NMR (300 K, [D6]DMSO,
125.8 MHz): δ = 134.91 (d, 4J(13C - 31P) = 2.8 Hz, para), 133.52 (d, 2J(13C -
31P) = 10.1 Hz, ortho), 130.28 (d, 3J(13C - 31P) = 12.8 Hz, meta), 118.33 (d,
1J(13C - 31P) = 85.2 Hz, PC), 14.41 (d, 1J(13C - 31P) = 51.5 Hz, CH2), 6.27 (d,
2J(13C - 31P) = 5.5 Hz, CH3); 31P NMR (300 K, [D6]DMSO, 202.5 MHz): δ =
26.01 (s, 1J(13C - 31P) = 85.2 Hz); 14N NMR (300 K, [D6]DMSO, 36.1 MHz): δ =
-126 (Nβ, Δ휈1/2 = 100 Hz), -232 (Nα/γ, Δ휈1/2 = 394 Hz); IR (ATR, 32 scans): 휈̃ =
3446 (w), 3376 (w), 3082 (w), 3064 (w), 3053 (w), 2993 (w), 2983 (w), 2936
(w), 2902 (w), 2877 (w), 2648 (w), 2105 (w), 2044 (s), 1824 (w), 1781 (w),
1585 (m), 1573 (w), 1483 (m), 1450 (w), 1434 (m), 1402 (m), 1383 (w), 1347
(m), 1315 (m), 1293 (w), 1279 (w), 1238 (w), 1225 (w), 1186 (w), 1160 (m),
1111 (s), 1073 (m), 1037 (m), 1028 (m), 1013 (w), 996 (m), 978 (w), 929 (w),
848 (w), 770 (sh, w), 746 (m), 737 (s), 721 (s), 690 (s), 665 (m), 617 (m), 530
cm-1 (s). Raman (633 nm, 6 mW, 25 °C, 30 s, 12 acc.): 휈̃ = 3166 (0.7), 3139
(0.7), 3062 (2.5), 3051 (2.1), 3004 (0.7), 2980 (0.7), 2933 (1.3), 2900 (1.0),
2874 (0.8), 2245 (0.6), 2149 (0.6), 2140 (0.5), 2095 (0.6), 2037 (0.5), 1581
(3.3), 1569 (0.9), 1480 (0.4), 1447 (0.4), 1434 (0.4), 1399 (0.4), 1379 (0.4),
1351 (2.1), 1345 (sh, 1.0), 1312 (0.3), 1185 (0.6), 1159 (0.7), 1099 (2.1), 1069
(0.3) 1022 (2.8), 994 (5.5), 922 (0.2), 849 (0.1), 765 (0.1), 733 (0.1), 717 (0.1),
704 (0.1), 686 (0.1), 660 (2.0), 617 (sh, 0.3), 610 (0.8), 524 (0.1), 482 (0.1),
462 (0.1), 449 (0.1), 430 (0.1), 391 (0.1), 374 (0.3), 304 (0.4), 293 (0.2), 275
(0.6), 248 (1.9), 210 (0.9), 196 (0.9), 82 cm-1 (10); elemental analysis calcd
(%) for C60H60N18CeP3: C 56.91, H 4.71, N 19.91; found C 54.72, H 5.00, N
19.46.
[Ph4P]3[Ce(N3)6] · 2 MeCN: To a solution of cerium(III) iodide CeI3 (0.130 g,
0.25 mmol) and tetraphenylphosphonium azide [Ph4P]N3 (0.286 g, 0.75 mmol)
in acetonitrile (7 mL) silver azide AgN3 (0.113 g, 0.75 mmol) was added and
stirred for 45 minutes. After filtration the clear, black-brown solution was slowly
concentrated by evaporation, resulting in the deposition of colorless crystals.
The supernatant was removed by decantation and the colorless crystals of
[Ph4P]3[Ce(N3)6] · 2 MeCN were washed with acetonitrile. According to X-ray
structure determinations, [Ph4P]3[Ce(N3)6] · 2 MeCN was found to be a mixture
̅
of two triclinic modifications (denoted as (α) and (β), space group P1) in
varying compositions. Drying in vacuum led to the non-stoichiometric loss of
solvent (yield: 10–20 %). M.p. 187 °C (heating rate 20 °C/min); 1H NMR
(300 K, [D6]DMSO, 500.13 MHz): δ = 7.95 (m, 4 H, para), 7.81 (m, 8 H, meta),
7.75 (m, 8 H, ortho), 2.04 ppm (s, CH3CN); 13C NMR (300 K, [D6]DMSO,
125.8 MHz): δ = 135.39 (d, 4J(13C - 31P) = 2.75 Hz, para), 134.58 (d, 2J(13C -
31P) = 10.08 Hz, ortho), 130.50 (d, 3J(13C - 31P) = 12.83 Hz, meta), 117.73 ppm
(d, 1J(13C - 31P) = 88.89 Hz, PC); 31P NMR (300 K, [D6]DMSO, 202.5 MHz): δ =
C - =
22.29 ppm (s, 1J(13 31P) 88.89 Hz); 14N NMR (300 K, [D6]DMSO,
36.1 MHz): δ = -126 (Nβ; Δν1/2 = 101 Hz), -228 ppm (Nα/γ, Δν1/2 = 434 Hz); IR
(ATR, 32 scans): 휈̃ = 3453 (w), 3375 (w), 3163 (w), 3079 (w), 3058 (w), 3022
(w), 2993 (w), 2931 (w), 2692 (w), 2584 (w), 2247 (w), 2101 (w), 2040 (s),
1834 (w), 1788 (w), 1585 (m), 1483 (m), 1435 (s), 1350 (m), 1316 (m), 1277
(w), 1226 (w), 1187 (m), 1162 (w), 1105 (s), 1076 (sh, w), 1026 (m), 995 (m),
939 (w), 848 (w), 755 (m), 719 (s), 686 (s), 665 (m), 616 cm-1 (m); Raman
(473 nm, 2 mW, 25 °C, 15 s, 10 acc.): 휈̃ = 3171 (6.0), 3146 (6.0), 3062 (10),
3012 (5.4), 2963 (5.3), 2938 (5.5), 2251 (4.0), 2153 (4.4), 2098 (4.7), 2043
(4.2), 1587 (5.5), 1485 (2.6), 1442 (2.6), 1362 (4.1), 1355 (sh, 3.2), 1347 (sh,
2.7), 1187 (2.2), 1168 (2.2), 1110 (2.6), 1099 (3.8), 1028 (4.1), 1001 (6.8), 932
(1.6), 725 (1.4), 679 (2.2), 615 (2.0), 548 (1.4), 383 (0.9), 288 (1.1), 260 (1.5),
249 (1.6), 198 (1.4), 156 cm-1(1.7); elemental analysis calcd (%) for
C76H66N20CeP3: C 61.16, H 4.46, N 18.77; found C 58.91, H 5.08, N 17.62.
[Ph4P]3[Gd(N3)6] · 2 MeCN: Gadolinium(III) chloride GdCl3 · 2 MeCN (0.086 g,
0.25 mmol) and tetraphenylphosphonium iodide [Ph4P]I (0.351 g, 0,75 mmol)
were dissolved in acetonitrile (10 mL) and silver azide AgN3 (0.229 g,
1.53 mmol) was added. After stirring for one hour, the yellow precipitate was
removed by filtration. Evaporation of the solvent resulted in the deposition of
colorless crystals. For purification the product was recrystallized from
[EtPh3P]3[Gd(N3)6]: To a solution of gadolinium(III) chloride GdCl3 · 2 MeCN
(0.086 g, 0.25 mmol) in acetonitrile (10 mL), ethyltriphenylphosphonium iodide
(0.318 g, 0.76 mmol) followed by silver azide AgN3 (0.225 g, 1.50 mmol) were
added. After stirring for 90 minutes, the resulting yellow precipitate was
removed by filtration (F4). Evaporation of the solvent in vacuum led to the
acetonitrile. After
decantation of supernatant, the crystals
of
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10.1002/ejic.201701408
European Journal of Inorganic Chemistry
FULL PAPER
deposition of [EtPh3P]3[Gd(N3)6] as colorless, needle-like crystals (yield: 20–
30 %). M.p. 229 °C; 1H NMR (300 K, [D6]DMSO, 500.13 MHz): δ = 7.86 (s, 15
H, Aryl, Δν1/2 = 341 Hz), 3.67 (s, 2 H, CH2CH3, Δν1/2 = 302 Hz), 1.26 ppm (s, 3
H, CH2CH3, Δν1/2 = 322 Hz); 13C NMR (300 K, [D6]DMSO, 125.8 MHz): δ =
135.36 (s, para), 134.03 (s, ortho), 130.70 (s, meta), 118.75 (d; 1J(13C - 31P) =
84 Hz, PC), 14.80 (s, CH2), 6.68 ppm (s, CH3); 31P NMR (300 K, [D6]DMSO,
202.5 MHz): δ = 26.3 ppm (s); 14N NMR (300 K, [D6]DMSO, 36.1 MHz): δ = -
243 ppm (Nα/γ, Δν1/2 = 634 Hz); IR (ATR, 32 scans): 휈̃ = 3463 (w), 3387 (w),
3081 (w), 3063 (w), 3052 (w), 3024 (w), 3010 (w), 2994 (w), 2983 (w), 2935
(w), 2901 (w), 2879 (sh, w), 2110 (w), 2052 (s), 1826 (w), 1779 (w), 1585 (m),
1573 (w), 1483 (m), 1451 (w), 1434 (m), 1402 (m), 1383 (w), 1352 (m), 1315
(m), 1279 (w), 1239 (w), 1187 (w), 1159 (m), 1111 (s), 1073 (m), 1037 (m),
1027 (w), 1013 (m), 996 (m), 980 (m), 935 (w), 928 (w), 847 (w), 770 (w), 760
(w), 746 (s), 737 (s), 721 (s), 690 (s), 665 (m), 617 cm-1 (m); Raman (785 nm,
10 mW, 25 °C, 20 s, 12 acc.): 3065 (0.1), 3055 (0.1), 2983 (0.1), 2939 (0.1),
2904 (0.1), 2111 (0.1), 2057 (0.1), 2050 (0.1), 1586 (0.6), 1574 (0.2), 1485
(0.1), 1454 (0.2), 1436 (0.2), 1404 (0.2), 1384 (0.2), 1363 (0.7), 1355 (0.4),
1318 (0.2), 1275 (0.2), 1242 (0.2), 1193 (0.3), 1162 (0.4), 1113 (sh, 0.4), 1105
(0.7), 1074 (0.2), 1028 (1.1), 1000 (2.2), 929 (0.3), 855 (0.3), 848 (0.3), 771
(0.3), 752 (0.3), 739 (0.4), 722 (0.4), 710 (0.4), 690 (0.4), 665 (1.2), 623 (sh,
0.4), 615 (0.8), 531 (0.4), 526 (sh, 0.4), 505 (0.4), 489 (0.5), 452 (0.4), 436
(0.4), 380 (0.7), 310 (0.9), 301 (0.7), 280 (0.9), 260 (sh, 1.4), 253 (1.7), 220
(1.2), 202 (1.1), 141 (3.5), 94 (10), 72 cm-1 (8.4); elemental analysis calcd (%)
for C60H60N18GdP3: C 56.15, H 4.71, N 19.64; found C 55.80, H 4.43, N 19.3.
deposition of large, block-like crystals. Removal of supernatant, washing with
acetonitrile (0.2 mL) and drying in vacuum yielded [Ph4P]4[Gd(N3)4Cl2][AgCl2]
as colorless, crystalline solid. The mother liquor was further concentrated,
which yielded a second crop of crystals (combined yield: 50–60%). M.p: 227 -
229 °C; 1H NMR (300 K, [D6]DMSO, 500.13 MHz): δ = 7.83 ppm (s, 20 H; Aryl,
Δν1/2 = 270 Hz); 13C NMR (300 K, [D6]DMSO, 125.8 MHz): δ = 135.66 (s,
para), 134.83 (s, ortho), 130.80 (s, meta), 117.96 ppm (d, 1J(13C - 31P) =
88 Hz, PC); 14N NMR (300 K, [D6]DMSO, 36.1 MHz): δ = -252 ppm (Nα/γ, Δν1/2
= 830 Hz); IR (ATR, 32 scans): 휈̃ = 3459 (sh, w), 3413 (w), 3386 (w), 3167
(w), 3090 (w), 3057 (w), 3021 (w), 2993 (w), 2683 (w), 2579 (w), 2102 (w),
2067 (m), 2053 (s), 1830 (w), 1784 (w), 1682 (w), 1614 (w), 1584 (w), 1575
(sh, m), 1481 (m), 1432 (m), 1412 (sh, m), 1369 (m), 1350 (m), 1340 (sh, m),
1316 (m), 1232 (w), 1223 (m), 1186 (w), 1163 (m), 1158 (w), 1104 (s), 1073
(m), 1025 (w), 995 (m), 936 (w), 851 (w), 759 (m), 752 (m), 719 (s), 687 (s),
625 (w), 615 cm-1 (m); Raman (633 nm, 3.0 mW, 25 °C, 20 s, 10 acc.): 휈̃ =
3168 (0.2), 3141 (0.2), 3092 (0.3),3064 (1.8), 3025 (0.1), 3008 (0.1), 2991
(0.1), 2959 (0.1), 2113 (0.1), 2105 (0.1), 2097 (0.1), 2056 (0.1), 1585 (2.6),
1573 (0.5), 1484 (0.2), 1439 (0.2), 1433 (0.2), 1372 (3.8), 1354 (0.2), 1340
(0.1), 1315 (0.2), 1223 (0.2), 1187 (0.7), 1166 (0.6), 1159 (0.7), 1105 (0.4),
1096 (1.7), 1073 (1.9),1026 (2.1), 1000 (6.6), 986 (0.4), 978 (0.2), 964 (0.1),
940 (0.1), 933 (0.1), 856 (0.1), 848 (0.1), 806 (broad, 0.1), 761 (sh, 0.1), 750
(0.1), 728 (0.2), 725 (0.2), 696 (0.1), 678 (1.4), 615 (0.7), 533 (0.1), 525 (0.1),
470 (sh, 0.1), 464 (0.1), 456 (0.1), 440 (0.1), 432 (0.1), 406 (sh, 0.1), 395
(0.1), 284 (0.3), 274 (0.5), 256 (sh, 1.6), 250 (1.8), 205 (1.5), 197 (sh, 1.0),
158 (sh, 1.4), 112 (7.8), 85 cm-1 (10); elemental analysis calcd (%) for
C96H80N12AgCl4GdP4: C 59.66, H 4.17, N 8.70; found C 59.40, H 3.70, N 8.73.
[Ph4P]4[Gd(N3)6][Ag(N3)2]: Gadolinium(III) iodide GdI3 (0.081 g, 0.15 mmol)
and tetraphenylphosphonium azide (0.227 g, 0.59 mmol) were mixed and
suspended in acetonitrile (7 mL). Silver azide AgN3 (0.090 g, 0.60 mmol) was
added, and after stirring for one hour at ambient temperature, the resulting
yellow precipitate was removed by filtration. The filtrate was slowly evaporated
in vacuum, resulting in the deposition of colorless crystals. Washing with
acetonitrile and drying in vacuum yielded [Ph4P]4[Gd(N3)6][Ag(N3)2] as
colorless, crystalline solid (yield: 20–30 %). M.p. 222 °C; 1H NMR (300 K,
[D6]DMSO, 500.13 MHz): δ = 7.80 ppm (s, 20 H; Aryl, Δν1/2 = 294 Hz); 13C
NMR (300 K, [D6]DMSO, 125.8 MHz): δ = 135.74 (s, para), 134.92 (s, ortho),
130.84 (s, meta), 118.05 ppm (d, 1J(13C - 31P) = 86 Hz, PC); 31P NMR (300 K,
[D6]DMSO, 202.5 MHz): δ = 22.36 ppm (s); 14N NMR (300 K, [D6]DMSO,
36.1 MHz): δ = -214 ppm (Nα/γ, Δν1/2 = 557 Hz); IR (ATR, 32 scans): 휈̃ = 3469
(w), 3411 (w), 3393 (w), 3168 (w), 3146 (w), 3085 (w), 3061 (w), 3022 (w),
2994 (w), 2692 (w), 2579 (w), 2111 (w), 2058 (s), 2035 (s), 1828 (w), 1789
(w), 1586 (m), 1575 (w), 1483 (m), 1435 (m), 1368 (m), 1358 (m), 1340 (m),
1316 (m), 1223 (m), 1185 (m), 1164 (m), 1107 (s), 1074 (m), 1027 (w), 997
(m), 984 (sh, m), 935 (w), 853 (w), 754 (m), 722 (s), 689 (s), 666 (m), 640 (m),
616 cm-1 (m); Raman (633 nm, 6 mW, 25 °C, 15 s, 20 acc.): 휈̃ = 3170 (2.3),
3145 (2.4), 3088 (2.7), 3063 (4.1), 2112 (1.6), 2052 (1.6), 1587 (2.9), 1576
(1.3), 1483 (0.7), 1439 (0.7), 1372 (1.6), 1363 (1.5), 1330 (1.0), 1314 (sh, 0.6),
1279 (0.1), 1188 (0.7), 1169 (0.8), 1111 (0.7), 1100 (1.6), 1078 (0.1), 1028
(2.0), 1002 (4.3), 990 (0.3), 939 (0.2), 853 (0.1), 756 (0.1), 728 (0.2), 682 (1.2),
617 (0.7), 537 (0.1), 530 (0.1), 460 (0.1), 453 (0.1), 312 (0.1), 286 (0.5), 274
(0.4), 256 (1.6), 200 (1), 159 (1.8), 91 cm-1 (10.0); elemental analysis calcd
(%) for C96H80N24AgGdP4: C 58.86, H 4.12, N 17.16; found C 58.86, H 3.87, N
17.12.
[Ph4P]4[Gd(N3)6][N3(daa)] · acetone
(daa
=
diacetonealcohol):
Gadolinium(III) chloride GdCl3 · 2 MeCN (0.086 g, 0.25 mmol) and
tetraphenylphosphonium iodide [Ph4P]I (0.351 g, 0,75 mmol) were dissolved in
acetonitrile (10 mL). Silver azide AgN3 (0.229 g, 1.53 mmol) was added, and
after stirring for one hour, the yellow precipitate was removed by filtration. The
clear, colorless solution was evaporated in vacuum and the resulting solid was
re-crystallized
from
acetone,
yielding
small
amounts
of
[Ph4P]4[Gd(N3)6][N3(daa)] · acetone (daa
=
diacetonealcohol) as colorless,
crystals. IR (ATR, 32 scans): 휈̃ = 3475 (w), 3400 (w), 3305 (w), 3273 (w), 3064
(w), 3023 (w), 2991 (w), 2971 (w), 2917 (w), 2686 (w), 2580 (w), 2110 (w),
2092 (sh, w), 2060 (m), 2007 (m), 1830 (w), 1788 (w), 1755 (w), 1710 (m),
1691 (m), 1615 (w), 1587 (m), 1577 (sh, w), 1485 (m), 1436 (m), 1417 (m),
1360 (m), 1314 (m), 1238 (m), 1223 (m), 1187 (m), 1164 (m), 1129 (w), 1107
(s), 1076 (w), 1061 (m), 1027 (m), 1014 (w), 999 (m), 985 (m), 949 (m), 905
(w), 856 (w), 811 (w), 756 (m), 721 (s), 689 (s), 654 (sh, m), 644 (m), 630 (m),
617 cm-1 (m).
Magnetic Properties: Samples of [EtPh3P]3[Gd(N3)6], [Ph4P]3[Gd(N3)6] · 2
MeCN, [Ph4P]4[Gd(N3)6][Ag(N3)2], Gd(N3)3 · 8/3 DMSO and Gd4(OH)2(N3)10
10 DMSO were packed into polyethylene (PE) capsules in an argon filled
drybox and attached to the sample holder rod of Vibrating Sample
Magnetometer unit (VSM) for measuring the magnetization M(T,H) in
Quantum Design Physical Property Measurement System (PPMS). The
·
a
a
samples were investigated in the temperature range of 2.5-300
magnetic flux densities up to 80 kOe.[16]
K with
[Ph4P]4[Gd(N3)4Cl2][AgCl2]: Gadolinium(III) iodide GdI3 (0.134 g, 0.25 mmol)
and tetraphenylphosphonium chloride [Ph4P]Cl (0.375 g, 1.00 mmol) were
combined and dissolved in acetonitrile (10 mL). To the colorless solution,
silver azide AgN3 (0.150 g, 1.00 mmol) was added in one portion. After stirring
for 30 minutes, the off-white precipitate was filtered off. The clear, colorless
solution was slowly evaporated to half volume in vacuum. Storage at ambient
temperature for 18 hours resulted in the deposition of tiny amounts of
colorless, needle-like crystals, which could be identified as [Ph4P][Ag2Cl2I] by
single crystal X-ray diffraction. The crystals were removed by
decantation/filtration, and the resulting solution was concentrated to a volume
of about 1 mL. Storage at ambient temperature for 12 hours resulted in the
Acknowledgements
Dr. Philipp Thiele (University Rostock), Dr. Dirk Michalik
(University Rostock) and Dr. Astrid Lehmann (Leibniz Institute
for Catalysis) are acknowledged for helpful advice. We thank the
University of Rostock and the Leibniz Institute for Catalysis for
financial support.
This article is protected by copyright. All rights reserved.

10.1002/ejic.201701408
European Journal of Inorganic Chemistry
FULL PAPER
[14] a) P. Starynowicz, Acta Crystallogr. 1992, C48, 4–5; b) P. Starynowicz,
K. Bukietyńska, W. Ryba-Romanowski in The Second International
School On Excited States Of Transition Elements, World Scientific
Publishing Co. Pte. Ltd. 1992 pp. 418–420; c) P. Starynowicz, K.
Bukietyńska, W. Ryba-Romanowski, G. Dominiak-Dzik, St. Gołąb,
Polyhedron 1994, 13, 1069–75.
Keywords: cerium • gadolinium • nitrogen • azide • magnetic
susceptibility
[1]
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1082.
[15] M.-J. Crawford, A. Ellern, P. Mayer, Angew. Chem. 2005, 117, 8086–
8090; Angew. Chem. Int. Ed. 2005, 44, 7874–7878.
[3]
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P. Portius, M. Davis, Coord. Chem. Rev. 2013, 257, 1011–1025.
T. Curtius, A. Darapsky, J. Prakt. Chem. 1900, 61(2), 408–422.
C. Auer v. Welsbach, Monatsh. Chem. 1885, 6(1), 477–491.
a) J. Ant-Wuorinen, Teknillinen Aikakauslehti, 1931, 7–8, 365–369; b) J.
Ant-Wuorinen, Suomen Kemistilehti, 1940, B30, 1–3.
[16] Full set of experimental and theoretical data for all considered species
can be found in the Supporting Information.
[17] D. W. M. Hofmann, Acta Crystallogr. 2002, B58, 489–493.
[18] J. Clayden, N. Greeves, S. Warren, P. Wothers in Organic Chemistry,
1st ed., Oxford University Press, Oxford, 2001, pp. 690–691.
[19] a) D. F. Evans, J. Chem. Soc. 1959, 2003; b) D. M. Corsi, C. Platas-
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723; c) R. E. Hoffman, J. Magn. Reson. 2006, 178, 237; d) X. Kästele,
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6126.
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a) A. M. El-Atrash, H. K. El-Shamy, I. E. Abdel-Aziz, J. Radioanal.
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[22] Holleman Wiberg, Lehrbuch der Anorganischen Chemie, 102. Aufl.,
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313–18; b) F. A. Mautner, H. Krischner, H. P. Fritzer, C. Kratky, J. Mol.
Struct. 1989, 213, 169–174. c) F. A. Mautner, H. Krischner, Monatsh.
Chem. 1990, 121, 781–786; d) F. A. Mautner, H. Krischner, H. P.
Fritzer, C. Kratky, Z. Kristallogr. 1989, 188, 279–86.
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[13] a) K. Gatterer, P. Day, H. P. Fritzer, G. Sperka, J. Mol. Struct. 1988,
174, 429–34; b) K. Gatterer, H. P. Fritzer, J. Phys.: Condens. Matter
1992, 4, 4667–4673; c) K. Gatterer, C. D. Flint, H. P. Fritzer, F. A.
Mautner, J. Phys.: Condens. Matter 1992, 4, 2087–2096;
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10.1002/ejic.201701408
European Journal of Inorganic Chemistry
FULL PAPER
Entry for the Table of Contents (Please choose one layout)
Layout 2:
FULL PAPER
Kati Rosenstengel, Axel Schulz, Oliver
Niehaus, Oliver Janka, Rainer Pöttgen,
and Alexander Villinger*
Page No. – Page No.
Binary Polyazides of Cerium and
Gadolinium
Gadolinium(III) azide Gd(N3)3 · 8/3 DMSO, the mixed azide/hydroxide derivates
Gd4(OH)2(N3)10 · n DMSO (n = 8, 10), and a series of hexaazido lanthanate(III) salts
[M]3[Ln(N3)6] · n MeCN (Ln = Ce, Gd; [M]+ = [Ph4P]+ (n = 2), [EtPh3P]+ (n = 0)) were
synthesized and comprehensively characterized. The magnetic susceptibilities in
solution as well as in the solid state were investigated.
1 I. C. Tornieporth-Oetting, T. M. Klapötke, Angew. Chem. 1995, 107, 559–568; Angew. Chem. Int. Ed. 1995, 34, 511–520.
2 W. P. Fehlhammer, W. Beck, Z. Anorg. Allg. Chem. 2013, 639, 1053–1082.
3 P. Portius, M. Davis, Coord. Chem. Rev. 2013, 257, 1011–1025.
4 T. Curtius, A. Darapsky, J. Prakt. Chem. 1900, 61(2), 408-422.
5C. Auer v. Welsbach, Monatsh. Chem. 1885, 6(1), 477–491.
6 a) J. Ant-Wuorinen, Teknillinen Aikakauslehti, 1931, 7–8, 365–369; b) J. Ant-Wuorinen, Suomen Kemistilehti, 1940, B30, 1–3.
7 a) H. Rosenwasser, J. I. Bryant, Proc. Conf. Rare Earth Res., 3rd, Clearwater, Florida 1964, 1963, 75–86; b) H. Rosenwasser, Kezer, O. F., Proc. Conf. Rare
Earth Res., 4th, Phoenix, Ariz. 1965, 545–60.
8 a) A. M. El-Atrash, H. K. El-Shamy, I. E. Abdel-Aziz, J. Radioanal. Chem. 1974, 23, 83-88; b) M. S. El-Ezaby, I. E. Abdel-Aziz, J. Inorg. Nucl. Chem. 1975, 37,
2013–16; c) I. E. Abdel-Aziz, Ind. J. Chem. 1978, 16A, 218–220; d) I. E. Abdel-Aziz, Ind. J. Chem. 1979, 18A, 79–80.
9 P. J. Herley, W. Jones, Mater. Res. Soc. Symp. Proc. 1993, 296, 87-92.
10 V. Gutmann, O. Leitmann, R. Schuetz, Inorg. Nucl. Chem. Lett. 1966, 2, 133–135.
11 T. G. Müller, F. Karau, W. Schnick, F. Kraus, Angew. Chem. 2014, 126, 13913–13915; Angew. Chem. Int. Ed. 2014, 53, 13695–13697.
12 a) A. Popitsch, F. A. Mautner, H. P. Fritzer, J. Mol. Struct. 1982, 79, 313–18; b) F. A. Mautner, H. Krischner, H. P. Fritzer, C. Kratky, J. Mol. Struct. 1989, 213,
169– 174. c) F. A. Mautner, H. Krischner, Monatsh. Chem. 1990, 121, 781–786; d) F. A. Mautner, H. Krischner, H. P. Fritzer, C. Kratky, Z. Kristallogr. 1989, 188,
279– 86.
13 a) K. Gatterer, P. Day, H. P. Fritzer, G. Sperka, J. Mol. Struct. 1988, 174, 429–34; b) K. Gatterer, H. P. Fritzer, J. Phys.: Condens. Matter 1992, 4, 4667–4673;
c) K. Gatterer, C. D. Flint, H. P. Fritzer, F. A. Mautner, J. Phys.: Condens. Matter 1992, 4, 2087–2096;
14 a) P. Starynowicz, Acta Crystallogr. 1992, C48, 4–5; b) P. Starynowicz, K. Bukietyńska, W. Ryba-Romanowski in The Second International School On Excited
States Of Transition Elements, World Scientific Publishing Co. Pte. Ltd. 1992 pp. 418–420; c) P. Starynowicz, K. Bukietyńska, W. Ryba-Romanowski, G.
Dominiak-Dzik, St. Gołąb, Polyhedron 1994, 13, 1069–75.
15 M.-J. Crawford, A. Ellern, P. Mayer, Angew. Chem. 2005, 117, 8086–8090; Angew. Chem. Int. Ed. 2005, 44, 7874–7878.
16 Full set of experimental and theoretical data for all considered species can be found in the Supporting Information.
17 D. W. M. Hofmann, Acta Crystallogr. 2002, B58, 489–493.
18 J. Clayden, N. Greeves, S. Warren, P. Wothers in Organic Chemistry, 1st ed., Oxford University Press, Oxford, 2001, pp. 690–691.
19 a) D. F. Evans, J. Chem. Soc. 1959, 2003; b) D. M. Corsi, C. Platas-Iglesias, H. van Bekkum, J. A. Peters, Magn. Reson. Chem. 2001, 39, 723; c) R. E.
Hoffman, J. Magn. Reson. 2006, 178, 237; d) X. Kästele, C. Sturm, P. Klüfers, Eur. J. Pharm. Biopharm. 2014, 86, 469–477.
20 a) A. Schulz, A. Villinger, Chem. Eur. J. 2015, 21, 3649–3663; b) K. Rosenstengel, A. Schulz, A. Villinger, Inorg. Chem. 2013, 52, 6110–6126.
21 T. M. Klapötke, B. Krumm, M. Scherr, J. Am. Chem. Soc. 2009, 131, 72–74.
22 Holleman Wiberg, Lehrbuch der Anorganischen Chemie, 102. Aufl., Walter de Gruyter, Berlin, 2007, Anhang IV.
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