Lanthanide(III) amidinates with six- and seven-coordinate metal atoms

Article abstract of DOI:10.1002/zaac.200400035

The crystalline lithium N,N′-diorganoamidinates Li[PhC(NR) ₂] (1: R = c-C₆H₁₁, 2: R = iPr) and Li[(CF ₃)₃C₆H₂C-(N-c-C₆H ₁₁)₂] (3) have been obtai

Full text of DOI:10.1002/zaac.200400035

Lanthanide(III) Amidinates with Six- and Seven-Coordinate Metal Atoms
Joachim Richtera, Jürgen Feilinga, Hans-Georg Schmidta, Mathias Noltemeyera, Wolfgang Brüserb, and Frank
T. Edelmannb,*
a Göttingen, Institut für Anorganische Chemie der Georg-August-Universität
b Magdeburg, Chemisches Institut der Otto-von-Guericke-Universität
Received February 10th, 2004.
Dedicated to Professor Uwe Klingebiel on the Occasion of his 60th Birthday
Abstract. The crystalline lithium N,NЈ-diorganoamidinates
Li[PhC(NR)2] (1: R ϭ c-C6H11, 2: R ϭ iPr) and Li[(CF3)3C6H2C-
(N-c-C6H11)2] (3) have been obtained by the reaction of phenyl-
lithium or 2,4,6-tris(trifluoromethyl)phenyllithium, resp., with
diorganocarbodiimides R-NϭCϭN-R (R ϭ c-C6H11, iPr). These
amidinates have been used for the synthesis of the homoleptic lan-
thanide(III) amidinates [PhC(N-c-C6H11)2]3Ln (4؊6: Ln ϭ Pr, Nd,
Sm) and [PhC(NiPr)2]3Pr (7). Seven-coordinate Lewis-base adducts
of the type [PhC(NSiMe3)2]3Ln(NCPh) (8,9: Ln ϭ Sm, Eu) have
been prepared by addition of benzonitrile to the homoleptic precur-
sors [PhC(NSiMe3)2]3Ln. The compounds 2 (as its THF adduct),
4, 6, 8 and 9 have been structurally characterized by single crystal
X-ray analyses.
Keywords: Lanthanides; Aminidates; Europium; Neodymium;
Praseodymium; Samarium
Lanthanoid(III)-amidinate mit sechs- und siebenfach koordinierten Metallatomen
Inhaltsübersicht. Die kristallinen Lithium N,NЈ-diorganoamidinate
Li[PhC(NR)2] (1: R ϭ c-C6H11, 2: R ϭ iPr) und Li[(CF3)3C6H2C-
(N-c-C6H11)2] (3) wurden durch Reaktion von Phenyllithium bzw.
2,4,6-Tris(trifluormethyl)phenyllithium mit den Diorganocarbo-
diimiden R-NϭCϭN-R (R ϭ c-C6H11, iPr) erhalten. Diese
Nd, Sm) und [PhC(NiPr)2]3Pr (7) verwendet. Siebenfach koordi-
nierte Lewis-Basenaddukte des Typs [PhC(NSiMe3)2]3Ln(NCPh)
(8,9: Ln ϭ Sm, Eu) wurden durch Addition von Benzonitril an
die homoleptischen Vorstufen [PhC(NSiMe3)2]3Ln dargestellt. Die
Verbindungen 2 (als THF-Addukt), 4, 6, 8 und 9 wurden durch
Einkristall-Röntgenstrukturanalysen strukturell charakterisiert.
Amidinate
wurden
zur
Synthese
der
homoleptischen
Lanthanoid(III)amidinate [PhC(N-c-C6H11)2]3Ln (4؊6: Ln ϭ Pr,
Introduction
of several crystalline lithium diorganoamidinates and their
use as precursors for the synthesis of homoleptic lantha-
nide(III) amidinates with six-coordinate metal atoms. In ad-
dition, novel seven-coordinate benzonitrile adducts of the
type [PhC(NSiMe3)2]3Ln(NCPh) are described.
The discovery of Brookhart et al. that late transition metal
complexes containing diimine ligands can catalyze ethylene
polymerization while suppressing β-hydride elimination has
enormously stimulated the use of chelating nitrogen-con-
taining ancillary ligands in main group, transition metal
and f-element chemistry [1, 2]. Typical examples of such
ligands besides diimines include amidinates [3Ϫ8], guanidi-
nates [9, 10] and β-diketiminates [11Ϫ17]. For the lantha-
nide elements, several homoleptic [18, 19] and heteroleptic
[20Ϫ26] amidinates, guanidinates [27] and β-diketiminates
[28] have been reported. Most recently, it has been disco-
vered, that homoleptic lanthanide amidinates and their
THF adducts exhibit extremely high activity for the ring-
opening polymerization of ε-caprolactone at room tempera-
ture [29]. As part of our ongoing studies in this field, we
report here the preparation and structural characterization
Results and Discussion
Syntheses and spectroscopic data
The synthesis of lithium-N,NЈ-bis(trimethylsilyl)benzamidin-
ate, Li[PhC(NSiMe3)2], from benzonitrile and LiN(SiMe3)2
has been reported as early as 1973 by Sanger et al. [30].
Subsequently several p-substituted derivatives have become
available as pure crystalline solids by adopting the same
synthetic route [31]. In contrast, 2,4,6-trisubstituted anions
of the type [R3C6H2C(NSiMe3)2]Ϫ were prepared by re-
acting either mesityllithium or 2,4,6-tris(trifluoromethyl)-
phenyllithium with N,NЈ-bis(trimethylsilyl)carbodiimide.
N-Alkylated lithium benzamidinates are also accessible via
metallation of the NH functional group in benzamidines
[32Ϫ34] or addition of lithium amides to benzonitrile [32].
We chose the carbodiimide route to make several lithium
benzamidinates readily available in large amounts and in
* Prof. Dr. F. T. Edelmann
Chemisches Institut der Otto-von-Guericke-Universität Magdeburg
Universitätsplatz 2, D-39106 Magdeburg, Germany
Telefax: Int. ϩ49-391-6712933
e-mail: frank.edelmann@vst.uni-magdeburg.de
Z. Anorg. Allg. Chem. 2004, 630, 1269Ϫ1275
DOI: 10.1002/zaac.200400035
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J. Richter, J. Feiling, H.-G. Schmidt, M. Noltemeyer, W. Brüser, F. T. Edelmann
the form of pure, crystalline materials. The reagents dicyclo-
hexylcarbodiimide (DCC) and diisopropylcarbodiimide are
both commercially available because of their wide appli-
cation in peptide syntheses. Scheme 1 depicts the prep-
aration of the lithium salts 1؊3:
Scheme 2 Preparation of the homoleptic lanthanide(III) amidina-
tes 4؊7.
The products were isolated by crystallization from n-hex-
ane. All four lanthanide(III) benzamidinates are highly
moisture-sensitive, but can be briefly handled in dry air.
The two praseodymium derivatives are light green, while the
Nd complex 5 forms light blue crystals and the samarium
compound 6 is dark blue. They are all freely soluble in di-
ethylether, toluene and n-hexane. It should be noted that a
bis-THF adduct of 5 has recently been reported by Shen et
al. [29]. Mass spectra of 4؊6 show the molecular ions of
the homoleptic lanthanide(III) benzamidinate molecules.
1H NMR spectra could be obtained in all four cases. They
exhibit the typical paramagnetic shift of the signals due to
the fact that the lanthanide ions act as “intramolecular shift
reagents“. For example, the signals of the phenyl protons in
the spectra of 4, 6 and 7 are shifted to higher field and
appear in a range of δ 9.22Ϫ13.63. Notable in all spectra is
the pronounced separation of the peaks corresponding to
the ortho-, meta- and para-phenyl protons as well as the
tertiary cyclohexyl protons.
As mentioned above, several homoleptic lanthanide(III)
amidinate complexes have been isolated in the form of their
THF adducts. Typical examples include the compounds
[PhC(N-c-C6H11)2]3Ln(THF)2 (Ln ϭ Y, Nd, Yb) [29].
However, none of these adducts involving coordination
numbers higher than 6 have been structurally characterized
until now. We found, that 1:1 adducts are also readily
formed with nitriles such as acetonitrile or benzonitrile.
Due to the presence of six trimethylsilyl substituents, lan-
thanide benzamidinates of the type [PhC(NSiMe3)2]3Ln
[18, 19] are highly soluble in non-polar organic solvents
such as toluene or even n-pentane and n-hexane. Somewhat
surprisingly, the solubility in MeCN was found to be much
lower. Thus acetonitrile is the most suitable solvents for
recrystallization of these complexes. Obviously, this remark-
able difference in solubility is associated with adduct forma-
tion in the presence of acetonitrile. However, thus far no
well-defined MeCN adducts could be isolated, because the
coordinated acetonitrile is easily lost upon drying of the
adducts. In order to obtain crystalline nitrile adducts we
investigated the reaction of [PhC(NSiMe3)2]3Ln complexes
with benzonitrile. In this case it is not necessary to isolate
the homoleptic lanthanide(III) benamidinates. 1:1 adducts
Scheme 1 Preparation of lithiumamidinates 1؊3.
All three reactions can be carried out on a large scale
and afford the pure unsolvated lithium salts 1؊3 as well-
defined, crystalline solids. While the yields are moderate in
the case of 1 and 2, the low yield of 3 is due to severe losses
of material during the necessary recrystallization from
n-hexane. An analogous reaction of 2,4,6-tris(trifluoromethyl)-
phenyllithium with diisopropylcarbodiimide in diethylether
failed to produce a crystalline reaction product. All three
lithium salts are highly moisture-sensitive and freely soluble
in diethylether, THF and toluene. Solubility in n-hexane is
poor for 1 and 2, but quite high in the case of 3. Character-
istic IR bands of medium intensity at ca. 1637, 1596 and
1635 cmϪ1 can be attributed to the antisymmetric valence
vibrations of the NCN units in the benzamidinate anions.
A strong band at 1151 cmϪ1 in the spectrum of 3 is caused
by the CϪF stretching vibration. The EI mass spectrum of
2 gave an indication of a dimeric solid state structure in
the unsolvated lithium benzamidinates. The peak at m/z 420
corresponds to the dimeric unit [{C6H5C(NC3H7)2}Li]2. A
fragment at m/z 377 results from abstraction of an isopropyl
group from this dimer. The dimeric structure is in fact a
common feature in this class of compounds [35] and was
later verified by the crystal structure determination of the
THF adduct of 2 (vide infra).
The lithium benzamidinate precursors 1؊3 have sub-
sequently been used to prepare a series of homoleptic lan-
thanide(III) benzamidinates. Such compounds containing
N-silylated benzamidinate ligands have been reported
several years ago [18], while related species with three N-
alkylated amidinate have only recently been described by
Shen et al. [29]. The compounds 4؊7 were prepared accord-
ing to Scheme 2:
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Lanthanide(III) Amidinates
with PhCN are easily accessible directly by reacting an-
hydrous lanthanide trichlorides with three equivalents of
Li[PhC(NSiMe3)2] in the presence of one equivalent of
PhCN according to Scheme 3:
buted to the chelating NCN units. The Raman spectrum of
2 exhibits no emission at 1663 amϪ1 but an intensive line at
1408 cmϪ1. EI mass spectra indicate a relatively weak bond-
ing of the benzonitrile ligand as they show only the parent
1
[PhC(NSiMe3)]3Ln]ϩ ions as the highest peaks. H NMR
data and elemental analyses confirm the composition of the
two compounds.
The results described here once again demonstrate that
especially in f-element chemistry almost any cyclopen-
tadienyl complex can be duplicated by replacing Cp or Cp*
with bulky heteroallylic ligands as “steric cyclopentadienyl
equivalents” [4]. Although this is most important for the
design of novel catalytically active species, the successful
preparation of Lewis-base adducts of [PhC(NSiMe3)2]3Ln
complexes also deserves special attention. The benzonitrile
adducts 8 and 9 can be regarded as benzamidinate ana-
logues of the well known Lewis-base adducts of the tris-
(cyclopentadienyl)lanthanides(III), (C5H5)3LnL (L ϭ do-
nor ligand) [38].
Scheme 3 Preparation of the benzonitrile adducts 8 and 9.
When this reaction is carried out in n-hexane, the prod-
ucts can be crystallized directly from the filtered reaction
mixtures. The samarium derivative 8 forms colorless crys-
tals, while the Eu complex 9 is bright yellow. The IR spectra
of 8 and 9 are almost superimposable and confirm the pro-
posed composition. For example, in the spectrum of 2 the
monosubstituted phenyl rings give rise to four overtone and
combination bands in the range of 1945Ϫ1783 cmϪ1, ring
valence vibrations at 1600 and 1578 cmϪ1, the four CH
rocking vibrations at 1177, 1165, 1073 and 1028 cmϪ1, as
well as the CH wagging vibration at 756 cmϪ1 and the in-
plane ring deformation band at 682 cmϪ1 [36]. The band at
2249 cmϪ1 can be attributed to the coordinated nitrile
group. The SiMe3 groups absorb at 2959 (νas CH3), 2898
(νs CH3), 1430 (δas CH3), 1246 (δs CH3), 834 (CH3 rocking),
700 (νas SiC3) [37], and 635 cmϪ1 (νs SiC3, intensive Raman
emission). Bands at 1663, 1490, and 1395 cmϪ1 can be attri-
Crystal structures
Single crystal X-ray diffraction studies have been carried
out on the compounds 2 (as its THF adduct), 4, 6, 8 and
9. Figures 1Ϫ3 show the molecular structures of 2, 6 and
9. Crystal and structure refinement data for all five com-
pounds are listed in Table 1. Important bond lengths and
angles are listed in Table 2.
The lithium benzamidinate 2 crystallizes from THF/tolu-
ene as a dimer containing two molecules of coordinated
THF. The dimer adopts a ladder-like structure which is
typical for alkali metal alkoxysilylamides [39, 40] and alkali
metal diiminosulfinates [41, 42] as well as the N-silylated
Table 1 Crystal data and details of structure determination for 2, 4, 6, 8 and 9
2
4
6
8
9
Empirical formula
Mr / gmolϪ1
C34H54Li2N4O2
564.69
colorless blocks
monoclinic
P21/c
9.4370(10)
17.086(3)
11.191(2)
90
101.980(10)
90
C63H93N6O1.50Pr
1099.34
light green prisms
rhombohedral
R-3
14.722(2)
14.722(2)
50.886(10)
90
90
120
9551(3)
6; 3504
C63H93N6O1.50Sm
1108.78
dark blue prisms
rhombohedral
R-3
14.757(2)
14.757(2)
50.961(10)
90
90
120
9611(3)
6; 3522
C49H81N7Si6Sm
1087.10
colorless blocks
monoclinic
P21/n
15.3370(10)
16.471(2)
23.438(4)
90
92.220(10)
90
C49H81EuN7Si6
1088.71
yellow blocks
monoclinic
P21/n
15.330(3)
16.466(2)
23.419(4)
90
92.182(10)
90
Crystal habit, color
Crystal system
Space group
˚
a / A
˚
b / A
˚
c / A
α / °
β / °
γ / °
3
˚
V / A
1765.1(5)
2; 616
1.062
5916.4(13)
4; 2280
1.220
5908(2)
4; 2284
1.224
Z; F(000)
ρ(calc.) /gcmϪ3
1.147
1.149
Crystal size / mm
Temperature / K
Absorption coeff. µ / mmϪ1
2θ range / °
1.00 ϫ 0.60 ϫ 0.50
153(2)
0.065
3.51 Ϫ 24.98
5797
0.40 ϫ 0.30 ϫ 0.20
153(2)
0.807
3.02 Ϫ 22.50
6027
0.50 ϫ 0.50 ϫ 0.50
153(2)
0.958
3.57 Ϫ 22.49
4380
0.50 ϫ 0.40 ϫ 0.40
153(2)
1.150
3.60 Ϫ 22.53
13455
0.50 ϫ 0.50 ϫ 0.20
153(2)
1.220
3.60 Ϫ 22.54
7750
Measured reflexes
Independent reflexes, (Rint
Refined parameters
Final R indices [I>2σ(I)] R1, wR2
R indices (all Data) R1, wR2
Goodness-of-fit on F2
)
3087, (0.0507)
194
0.0769, 0.1852
0.1212, 0.2376
1.040
2761, (0.0324)
215
0.0444, 01107
0.0580, 01295
1.124
2791, (0.0546)
215
0.0352, 0.0927
0.0368, 0.0943
1.096
7740, (0.0422)
568
0.0318, 0.0699
0.0428, 0.0777
1.008
7726, (0.1367)
568
0.0403, 0.0929
0.0530, 0.1080
1.040
Ϫ3
˚
Largest difference peak and hole / eA
0.450 / Ϫ0.273
1.509 / Ϫ0.781
1.431 / Ϫ0.635
0.463 / Ϫ0.415
1.031 / Ϫ1.455
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J. Richter, J. Feiling, H.-G. Schmidt, M. Noltemeyer, W. Brüser, F. T. Edelmann
Table 2 Selected bond lengths and bond angles for 2, 4, 6, 8 and 9
Bond lengths (pm) and -angles (°)
2
4
6
8
9
MϪN
203.0(7), 217.6(7)
131.9(4)Ϫ134.2(4)
Ϫ
Ϫ
117.2(2)
121.7(3)
246.0(4)Ϫ246.8(4)
132.9(7)Ϫ133.2(7)
Ϫ
Ϫ
117.0(5)
54.8(2)
242.4(3)Ϫ243.1(3)
133.0(5)Ϫ133.4(5)
Ϫ
Ϫ
116.7(3)
55.69(10)
244.9(3)Ϫ253.9(3)
133.1(5)Ϫ134.0(5)
263.3(4)
115.3(3)
118.7(3)Ϫ119.3(3)
54.91(10)Ϫ55.08(10)
242.3(4)Ϫ252.8(4)
132.6(7)Ϫ134.2(7)
261.3(5)
114.6(7)
118.6(5)
NϪC(amidinate)
MϪN(benzonitrile)
CϪN(benzonitrile)
NϪCϪN(amidinate)
NϪMϪN
55.04(14)Ϫ55.33(14)
Figure 1 Molecular structure of 2 in the crystal.
Figure 3 Molecular structure of 9 in the crystal.
ordinated in a distorted tetrahedral fashion by two N atoms
of one NCN chelating unit, one nitrogen of an opposite
benzamidinate ligand and one THF oxygen. The LiϪN dis-
tances are in the range of 203.0Ϫ217.6 pm and are thus in
good agreement with those typical for four-coordinate lith-
ium (204Ϫ211 pm) [43]. A characteristic structural feature
of all N-silylated metal benzamidinates is the large torsion
angle between the phenyl ring and the NCN chelating unit,
which in the case of 2 is 77°.
X-ray quality crystals of 5 and 6 were grown by slow
cooling of hot saturated solutions in THF/n-hexane mix-
tures to room temperature. As the two compounds are iso-
structural, only the molecular structure of the samarium
derivative 6 is depicted in Figure 2. The central Sm atom is
coordinated be three chelating benzamidinate ligands in a
distorted octahedral fashion. The three four-membered
SmNCN rings are planar within 7 pm and are twisted by
77.2° with respect to each other. This arrangement mini-
mizes steric repulsion between opposite cyclohexyl rings.
The average SmϪN bond length is 242.8 pm. With 79.4°
the torsion angle torsion angle between the phenyl ring and
the NCN chelating unit is even larger than in 2. This pre-
cludes any electronic conjugation between the two π-sys-
tems.
Figure 2 Molecular structure of 6 in the crystal.
lithium benzamidinate [{MeC6H4C(NSiMe3)2}Li(THF)]2
[35]. In the central unit two four-membered CN2Li rings
enclose angles of 99.1° with the central four-membered
Li2N2 ring system. The central Li2N2 ring is planar, in con-
trast to the structure of [{MeC6H4C(NSiMe3)2}Li(THF)]2
where the Li2N2 ring is folded by 26.3° along the LiϪLi
axis. This structural difference can be traced back to the
lower steric demand of the isopropyl groups as compared
to the bulkier trimethylsilyl groups. Each lithium ion is co-
The two benzonitrile adducts 8 and 9 have also been
structurally characterized by X-ray diffraction. As both
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Lanthanide(III) Amidinates
Lithium-N,NЈ-diisopropylbenzamidinate, Li[PhC(NiPr)2] (2)
compounds are isostructural, only the molecular structure
of the Eu derivative is shown in Figure 3. Lewis-base ad-
ducts of homoleptic lanthanide tris[N,NЈ-bis(trimethylsilyl)-
benzamidinates] are formally seven-coordinate, highly
crowded molecules, in which the central lanthanide ion is
bonded only to nitrogen atoms. Considered the high steric
demand of the heteroallylic ligand (intermediate between
Cp and Cp*) it is evident that only “slim” ligands such as
nitriles or isonitriles can successfully enter the coordination
sphere of the lanthanide metal to form stable 1:1 adducts.
The four-membered LnNCN chelate rings are essentially
planar. In both compounds 8 and 9 the average NϪLnϪN
angle is 55°. The average LnϪN bond lengths are 248.7 pm
(1) and 247.2 pm (2), respectively. These values can be fav-
orably compared with those found in other crystallograph-
ically characterized lanthanide benzamidinates [18Ϫ20, 22,
23]. As indicated by the mass spectrometric investigation
the bonding of the benzonitrile ligand is fairly weak (1:
SmϪN 261.3, 2: EuϪN 261.3 pm). This reflects the severe
steric crowding in these molecules.
In a similar manner, phenyllithium (30.26 g, 0.36 mol), dissolved in
200 ml of a diethylether/cyclohexane mixture (7/3), was slowly ad-
ded to
a solution of N,NЈ-diisopropylcarbodiimide (45.43 g,
0.36 mol) in diethylether (300 ml). Stirring at room temperature
was continued for 12 h, the reaction mixture was concentrated to
a total volume of 150 ml, diluted with toluene (80 ml) and cooled
to 0 °C for 24 h. The resulting crystals were isolated by filtration,
washed with n-hexane (150 ml) and dried in vacuo (12 h) to give
62.78 g (83 %) 2 in the form of colorless, moisture-sensitive crystals.
M.p. 108 °C.
Analyses: Calcd.: C 74.3, H 9.1, N 13.3 % for C13H19LiN2 (210.25)
(found: C 73.8, H 8.9, N 12.8 %).
1H NMR (25 °C, THF-d8): δ 7.30 (m, 2H, C6H5), 7.21 (m, 1H, C6H5), 7.07
(m, 3H, C6H5), 3.00 [sept, 2H, CH(CH3)2, 3J ϭ 6.2 Hz], 0.95 [d, 12H,
CH(CH3)2, 3J ϭ 6.2 Hz]. 7Li NMR (25 °C, C6D6): δ 1.64. 13C NMR (25 °C,
THF-d8): δ 174.1 [C6H5C(NC3H7)2]; 141.5 (C6H5, Cipso); 129.0, 128.4, 127.8,
127.7, 126.7 (C6H5); 48.4 [CH(CH3)2]; 27.3 [CH(CH3)2]. MS (EI, 70 eV): m/z
420 [{[C6H5C(NC3H7)2Li}2
ϭ M, 20 %], 377 [MϪC3H7, 10 %], 217
[{C6H5C(NC3H7)2}Li2, 94 %], 203 [C6H5C(NC3H7)2, 20 %], 132
[C6H5C(NC2H5)2, 15 %], 104 (C6H5CNH, 10 %), 77 (C6H5, 18 %), 58
(HNC3H7, 44 %). IR (KBr) cmϪ1: 3058(s), 2615(m), 156(m), 1410(vs),
1342(vs), 1167(s), 1127(s), 1073(m), 1043(m), 996(m), 941(w), 911(w),
821(w), 783(s), 734(m), 703(vs), 675(m), 625(w), 511(m), 488(m), 438(m).
Lithium-N,NЈ-dicyclohexyl-2,4,6-tris(trifluoromethyl)benzamidinate,
Li[(CF3)3C6H2C(N-c-C6H11)2] (3)
Experimental
A solution of n-butyllithium (6.81 g, 106.3 mmol) in n-hexane
(98.4 ml) was added dropwise to a solution of 1,3,5-tris(trifluoro-
methyl)benzene (30.00 g, 106.3 mmol) in diethylether (200 ml) at
such a rate that the ether kept gently refluxing. After stirring at
room temperature the mixture was transferred into a dropping
funnel and added slowly to a solution of N,NЈ-dicyclohexylcarbodi-
imide (21.94 g, 106.3 mmol) in diethylether (200 ml). Stirring at
room temperature was continued for 24 h. Evaporation of the sol-
vent mixture under reduced pressure left a red, oily residue, which
was recrystallized from boiling n-hexane to afford 5.53 g (11 %) 3
in the form of yellow-orange crystals. M.p. 115 °C (dec.).
General Comments. The reactions were carried out in an inert at-
mosphere of dry nitrogen using standard dry box and Schlenk tech-
niques. IR spectra were recorded on a Bio-Rad FTS 7 spectrometer.
NMR spectra were recorded on a Bruker AM 400 NMR spec-
trometer. Elemental analyses were performed at the Department of
Inorganic Chemistry of the University of Göttingen. Melting and
decomposition points were determined on a Büchi 510 apparatus.
The starting materials LnCl3 (anhydrous) [44], Li[PhC(NSiMe3)2]
[30, 31] and (CF3)3C6H2Li [45, 46] and were synthesized according
to the literature procedures. The compounds R-NϭCϭN-R (R ϭ
c-C6H11, iPr) and phenyllithium were purchased from Aldrich and
used as received.
Analyses: Calcd.: C 53.5, H 4.9, N 5.7 % for C22H24F9LiN2
(494.37) (found: C 51.3, H 4.3, N 5.3 %).
1H NMR (25 °C, THF-d8): δ 8.20 [s, 2H, C6H2(CF3)3], 2.20 (m, 2H,
CHC5H10), 0.85Ϫ1.80 (m, 20H, CHC5H10). 19F NMR (25 °C, THF-d8): δ
Ϫ57.0 (s, 6F, o-CF3), Ϫ62.7 (s, 3F, p-CF3). MS (EI, 70 eV): m/z 488
[(CF3)3C6H2C(NC6H11)2H, 5 %], 419 [(CF3)2C6H2C(NC6H11)2, 84 %], 325
[(CF3)3C6H2C(NH2)2, 87 %], 104 (C6H5CNH, 100 %), 83 (C6H11, 36 %). IR
(KBr) cmϪ1: 1653(m), 1522(m), 1369(m), 1303(m), 1281(s), 1202(s), 1151(s),
1109(m), 1057(m), 1029(m), 985(w), 915(m), 890(w), 845(w), 806(m), 685(m),
660(w), 602(w), 560(w), 429(w).
Lithium-N,NЈ-dicyclohexylbenzamidinate, Li[PhC(N-c-C6H11)2] (1)
Phenyllithium (84.05 g, 1 mol), dissolved in 550 ml of a diethyl-
ether/cyclohexane mixture (7/3), was added to a solution of N,NЈ-
dicyclohexylcarbodiimide (206.33 g, 1 mol) in diethylether
(700 ml). Stirring at room temperature was continued for 12 h,
whereby the product partially precipitated. The solvent mixture was
distilled off under reduced pressure, and the crude product was
recrystallized from diethylether/toluene (2:1). After cooling to 0 °C
for 12 the crystals were separated by filtration, washed with n-hex-
ane (250 ml) and dried in vacuo (12 h) to give 123.77 g (44 %) of
unsolvated 1 as a colorless, crystalline solid, which melts at 108 °C
under decomposition.
Preparation of the homoleptic lanthanide(III)amidinates 4؊7
(General Procedure)
A solution of the lithium amidinate in THF (100 ml) was added
dropwise to a suspension of the given amount of anhydrous lantha-
nide trichloride in THF (80 ml), and the mixture was stirred at room
temperature for 12 h. After evaporation to dryness, the residue was
extracted with boiling n-hexane (3 x 100 ml). Concentration of the
combined extracts to a total volume of ca. 100 ml and cooling to
Ϫ20 °C afforded the crystalline product, which was isolation by
filtration and drying.
Analyses: Calcd.: C 78.6, H 9.4, N 9.7 % for C29H27LiN2 (290.38)
(found: C 77.4, H 8.9, N 9.3 %).
1H NMR (25 °C, C6D6): δ 7.27 (m, 5H, C6H5), 3.11 (m, 1H, CHC5H10), 2.95
(m, 1H, CHC5H10), 0.92Ϫ2.28 (m, 20H, CHC5H10). 7Li NMR (25 °C, C6D6):
δ 1.75. 13C NMR (25 °C, THF-d8): δ 171.4 [C6H5C(NC6H11)2]; 142.8 (C6H5,
Cipso); 131.1, 129.7, 128.9, 127.9, 126.9 (C6H5); 59.6 (CHC5H10); 39.1, 27.1,
26.7 (CHC5H10). MS (EI, 70 eV): m/z 284 (MϪLi, 14 %), 201
[C6H5CNH(NC6H11), 14 %], 121 [C6H5C(NH2)2, 14 %], 104 (C6H5CNH,
20 %], 83 (C6H11, 54 %), 55 (C4H7, 100 %). IR (KBr) cmϪ1: 3060(m),
2114(vs), 1637(m), 1344(s), 1144(m), 1071(s), 985(m), 946(w), 919(w),
888(m), 838(w), 778(s), 706(s), 660(w), 641(w).
Tris(N,NЈ-dicyclohexylbenzamidinato)praseodymium(III) (4)
From 3.00 g (12.1 mmol) PrCl3 and 10.64 g (36.4 mmol) 1 4.63 g
(39 %) light green crystals of 4 were isolated. M.p. 195 °C.
Analyses: Calcd.: C 69.9, H 8.2, N 8.5 % for C57H81N6Pr (991.23)
(found: C 68.8, H 7.9, N 8.2 %).
Z. Anorg. Allg. Chem. 2004, 630, 1269Ϫ1275
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1273

J. Richter, J. Feiling, H.-G. Schmidt, M. Noltemeyer, W. Brüser, F. T. Edelmann
1H NMR (25 °C, C6D6): δ 10.11 (m, 9H, C6H5), 9.23 (m, 6H, C6H5), 2.83
(t, 2H, m-C6H5CN), Ϫ1.23 [s, 54H, Si(CH3)3]. MS (EI, 70 eV): m/z 943
(MϪC6H5CN, 8 %), 679 [{C6H5C(NSiMe3)2}2Sm, 100 %], 415 [C6H5C(NSi-
Me3)2Sm, 32 %], 263 [C6H5C(NSiMe3)2, 13 %], 176 (C6H5CNSiMe3, 22 %),
146 [Si2(CH3)6, 22 %], 73 [Si(CH3)3, 48 %]. IR (Nujol/KBr) cmϪ1: 3062(w),
2249(w), 1664(w), 1246(vs), 1073(w), 1027(w), 977(vs), 918(m), 829(vs),
755(s), 683(s), 603(m), 554(m), 471(s), 310(s).
(m, 2H, CHC5H10), 1.90 (m, 2H, CHC5H10), 1.78 (m, 2H, CHC5H10),
0.82Ϫ1.70 (m, 60H, CHC5H10). MS (EI, 70 eV): m/z 991 (M, 26 %), 908
(MϪC6H11
,
26 %),
708
[MϪC6H5C(NC6H11)2,
100 %],
283
[C6H5C(NC6H11)2, 100 %], 201 [C6H5CNH(NC6H11), 84 %], 121
[C6H5C(NH2)2, 63 %], 104 (C6H5CNH, 100 %), 98 (HNC6H11, 46 %). IR
(KBr) cmϪ1
: 3437(w), 3059(m), 2668(m), 1642(m), 1577(m), 1345(vs),
1312(s), 1244(m), 1201(s), 1153(m), 1071(s), 1026(m), 967(s), 914(m), 889(m),
842(w), 775(s), 754(m), 701(vs), 661(m), 500(w), 483(1), 424(m), 364(m),
322(vs).
Benzonitrile-tris[N,NЈ-bis(trimethylsilyl)benzamidinato]europium(III)
(9)
Similar to the preparation of 8, the europium complex 9 was made
from EuCl3 (1.50 g, 8.8 mmol), Li[PhC(NSiMe3)2] (4.71 g,
17.4 mmol) and PhCN (0.60 g, 5.8 mmol). 2.89 g (48 %) of 9 were
isolated as large, bright yellow crystals.
Analyses: Calcd.: C 52.8, H 7.1, N 9.4 % for C46H74EuN7Si6
(1045.38) (found: C 53.6, H 7.4, N 8.8 %).
Tris(N,NЈ-dicyclohexylbenzamidinato)neodymium(III) (5)
3.00 g (12.0 mmol) NdCl3 and 10.50 g (36.2 mmol) 1 gave 4.49 g
(40 %) light blue crystals of 5. M.p. 163 °C.
Analyses: Calcd.: C 68.8, H 8.2, N 8.5 % for C57H81N6Nd (994.56)
(found: C 68.2, H 7.8, N 8.3 %).
1H NMR (25 °C, C6D6): δ 7.05Ϫ7.45 (m, 15H, C6H5), 3.85 (m, 2H,
CHC5H10), 2.85 (m, 2H, CHC5H10), 2.65 (m, 2H, CHC5H10), 0.85Ϫ2.15 (m,
60H, CHC5H10). MS (EI, 70 eV): m/z 994 (M, 25 %), 911 (MϪC6H11, 17 %),
711 [MϪC6H5C(NC6H11)2, 100 %], 283 [C6H5C(NC6H11)2, 100 %], 201
[C6H5CNH(NC6H11), 87 %], 121 [C6H5C(NH2)2, 65 %], 104 (C6H5CNH,
100 %), 98 (HNC6H11, 48 %). IR (KBr) cmϪ1: 3436(w), 3080(m), 1641(s),
1601(w), 1345 (vs), 1312(s), 1200(m), 1152(m), 1071(m), 1027(m), 987(m),
914(w), 888(w), 776(m), 701(vs), 661(w), 544(w), 484(w), 423(w).
MS (EI, 70 eV): m/z 944 (MϪC6H5CN, 8 %), 680 [{C6H5C(NSiMe3)2}2Eu,
100 %], 416 [C6H5C(NSiMe3)2Eu, 36 %], 263 [C6H5C(NSiMe3)2, 23 %], 176
(C6H5CNSiMe3, 18 %), 146 [Si2(CH3)6, 28 %], 73 [Si(CH3)3, 53 %]. IR (Nu-
jol/KBr) cmϪ1: 3421(w), 3080(w), 3062(w), 3032(w), 3022(w), 2959(m),
2898(m), 2249(m), 1945(w), 1896(w), 1809(w), 1763(w), 1663(s), 1600(w),
1578(w), 1490(m), 1456(s), 1430(s), 1395(vs), 1291(w), 1246(vs), 1177(w),
1165(w), 1144(w), 1095(w), 1073(w), 1028(w), 1001(m), 978(s), 934(m),
918(m), 870(vs), 834(vs), 783(s), 756(vs), 724(s), 699(s), 682(s), 634(w),
616(w), 603(w), 554(w), 515(w), 472(s), 434(w).
Tris(N,NЈ-dicyclohexylbenzamidinato)samarium(III) (6)
The reaction of 3.00 g (11.7 mmol) SmCl3 and 10.25 g (35.3 mmol)
1 afforded 1.62 g (14 %) dark blue crystals of 6. M.p. 208 °C.
Analyses: Calcd.: C 68.4, H 8.2, N 8.4 % for C57H81N6Sm (1000.68)
(found: C 68.6, H 7.9, N 7.8 %).
1H NMR (25 °C, C6D6): δ 9.42 (d, 6H, o-C6H5), 8.21 (t, 6H, m-C6H5), 8.02
(t, 3H, p-C6H5), 1.97 (m, 6H, CHC5H10), 0.82Ϫ1.91 (m, 60H, CHC5H10).
MS (EI, 70 eV): m/z 1001 (M, 3 %), 718 [MϪC6H5C(NC6H11)2, 50 %], 434
[C6H5C(NC6H11)2Sm, 9 %], 283 [C6H5C(NC6H11)2, 100 %], 201
[C6H5CNH(NC6H11), 79 %], 121 [C6H5C(NH2)2, 51 %], 104 (C6H5CNH,
85 %). IR (KBr) cmϪ1: 3437(w), 3060(m), 2667(m), 2120(m), 1641(m),
1577(m), 1544(s), 1362(vs), 1345(vs), 1311(s), 1245(m), 1204(s), 1163(m),
1153(s), 1071(s), 1026(m), 987(s), 914(s), 889(s), 842(m), 775(vs), 755(m),
701(vs), 662(vs), 516(m), 500(m), 483(m), 424(s), 366(s).
Crystal structure determination [47]
Suitable single crystals of the THF adduct of 2 were grown by
sequential recrystallization of 2 from THF and toluene. Well-
formed single crystals of 4 and 6 were obtained upon slow cooling
of hot saturated solutions of the compounds in n-hexane/THF mix-
tures to room temperature. Single crystals of 8 and 9 were grown
by slow cooling of saturated hexane solutions to Ϫ25 °C.
All crystals were measured on a Stoe-Siemens-AED four-circle dif-
fractometer with graphite-monochromated X-radiation (Mo-Kα,
˚
λ ϭ 0.71073 A). The structures were solved by direct methods [47]
and refined by full-matrix least-squares methods, with all non-
hydrogen atoms anisotropic. The hydrogen atoms were located by
difference Fourier synthesis and refined using a riding model. In
the structure determinations, a weighting scheme with wϪ1 ϭ σ2(F)
ϩ 3F2 was used.
Tris(N,NЈ-diisopropylbenzamidinato)praseodymium(III) (7)
Treatment of 1.30 g (6.1 mmol) PrCl3 with 3.83 g (18.2 mmol) 2
gave 0.55 g (14 %) 7 as light green crystals. M.p. 125 °C.
Analyses: Calcd.: C 62.4, H 7.7, N 11.2 % for C39H57N6Pr (750.84)
(found: C 61.5, H 7.5, N 10.8 %).
Acknowledgements. This work has been generously supported by
the Otto-von-Guericke-Universität Magdeburg, the Fonds der
Chemischen Industrie and the Deutsche Forschungsgemeinschaft.
1H NMR (25 °C, C6D6): δ 13.63 (d, 6H, o-C6H5), 9.98 (t, 6H, m-C6H5), 9.22
(t, 3H, p-C6H5), Ϫ0.38 [m, 6H, CH(CH3)2], Ϫ3.98 [m, 36H, CH(CH3)2]. MS
(EI, 70 eV): m/z 750 (M, 6 %), 707 (MϪC3H7, 10 %), 547
[MϪC6H5C(NC3H7)2, 29 %], 203 [C6H5C(NC3H7)2, 27 %], 132
[C6H5C(NC2H5)2, 38 %], 104 (C6H5CNH, 100 %), 58 (HNC3H7, 53 %). IR
Supporting Information. Further details of the crystal structure in-
vestigations may be obtained from the Fachinformationszentrum
Karlsruhe, D-76344 Eggenstein-Leopoldshafen, Germany) (fax:
(ϩ49) 7247-808-666; e-mail: crysdata@fiz-karlsruhe.de) on quoting
number CSD-59285.
(KBr) cmϪ1
: 3060(m), 2611(m), 1642(s), 1602(m), 1577(m), 1337(vs),
1275(m), 1208(s), 1166(s), 1135(s), 1073(m), 1007(vs), 975(m), 947(m),
911(m), 844(w), 820(w), 780(s), 722(s), 702(vs), 582(w), 541(w), 503(w),
469(w).
Benzonitrile-tris[N,NЈ-bis(trimethylsilyl)benzamidinato]samarium(III)
(8)
References
A
mixture of anhydrous SmCl3 (3.00 g, 11.7 mmol),
Li[PhC(NSiMe3)2] (9.49 g, 35.1 mmol) and PhCN (1.21 g,
11.7 mmol) in n-hexane (100 ml) was stirred for 24 h at room tem-
perature. The precipitated LiCl was removed by filtration, the clear
filtrate was concentrated to a total volume of ca. 50 ml and cooled
to Ϫ25 °C (24 h). 8.57 g (70 %) of 8 were isolated as colorless,
moisture-sensitive crystals. M.p. 116 °C.
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1275