Guanidinate derivatives of rare-earth metals. the synthesis, properties, and molecular structures of the complexes {(Me3Si) 2NC(NPri)2}3Nd, {Me3Si) 2NC(NCy)2}3Lu, and

Article abstract of DOI:10.1007/s11172-009-0146-8

The reactions of anhydrous LnCl₃ (Ln = Nd or Lu) with three equivalents of {(Me₃Si)₂NC(NR)₂}Li (R = Pri or Cy; Cy is cyclohexyl) in THF afforded the corresponding tris(guanidinate) derivatives of lanthanides {(M

Full text of DOI:10.1007/s11172-009-0146-8

Russian Chemical Bulletin, International Edition, Vol. 58, No. 6, pp. 1126—1131, June, 2009
1126
Guanidinate derivatives of rareꢀearth metals. The synthesis, properties,
and molecular structures of the complexes
{(Me3Si)2NC(NPri)2}3Nd, {(Me3Si)2NC(NCy)2}3Lu,
and {(Me3Si)2NC(NPri)2}2{HC(NPri)2}Nd*
G. G. Skvortsov, D. M. Lyubov, M. V. Yakovenko, G. K. Fukin, A. V. Cherkasov, and A. A. Trifonov
G. A. Razuvaev Institute of Organometallic Chemistry, Russian Academy of Sciences,
49 ul. Tropinina, 603950 Nizhnii Novgorod, Russian Federation.
Fax: +7 (0831) 462 7497. Еꢀmail: trif@iomc.ras.ru
The reactions of anhydrous LnCl3 (Ln = Nd or Lu) with three equivalents of
{(Me3Si)2NC(NR)2}Li (R = Pri or Cy; Cy is cyclohexyl) in THF afforded the corresponding
tris(guanidinate) derivatives of lanthanides {(Me3Si)2NC(NR)2}3Ln (Ln = Nd, R = Pri, (1);
Ln = Lu, R = Cy (2)), which were isolated after the recrystallization from hexane in 82 and
88% yields, respectively. The complex {(Me3Si)2NC(NCy)2}2{HC(NCy)2}Nd (3) containing
two guanidinate ligands and one formamidinate ligand was isolated in attempting to synthesize
the bis(guanidinate) borohydride derivative by the reaction of {(Me3Si)2NC(N—Cy)2}Na with
Nd(BH4)3(THF)2 (in a molar ratio of 2 : 1) in THF. This complex is apparently formed as a
result of the fragmentation and redistribution of the guanidinate ligands. The Xꢀray diffraction
study showed that in the crystalline state compounds 1—3 are mononuclear complexes conꢀ
taining no coordinated Lewis bases.
Key words: rareꢀearth metals, complexes, guanidinate ligand, N,Nꢀligand, synthesis,
structure.
In recent years, the search for new nonꢀcyclopentaꢀ
dienyl ligand systems has attracted attention because these
compounds can be used in the synthesis of kinetically
stable rareꢀearth metal complexes.1—3 The aim of these
investigations is not only to increase the stability (with the
retention of high reactivity) but also to extend the scope
of the design and control of the geometry of the coordinaꢀ
tion sphere about metal atoms in the complexes. Since
monoanionic N,Nꢀchelate guanidinate ligands are charꢀ
acterized by the variable and labile coordination to metal
atoms,4 they are of obvious interest from this point of
view. The guanidinate ligand can bind to the metal center
in several coordination modes (Fig. 1), which, in turn,
can reduce steric hindrance, thus allowing the synthesis
of complexes adopting the most favorable configuration.
In addition, the electronic and steric properties of the
guanidinate ligand can easily be modified by replacing
the hydrocarbon substituents at the nitrogen atoms of the
central NCN group. Recent studies have shown the
considerable synthetic potential of guanidinate ligands in
lanthanide chemistry because the use of these ligands made
it possible to prepare and isolate different classes of lanꢀ
Fig. 1. Coordination modes of the guanidinate anion to the
metal cation.
thanide derivatives,5—7 including compounds holding
promise from the catalytic point of view.8,9 Tris(guanidiꢀ
nate) complexes, whose synthesis and catalytic activity
have been documented in recent publications,10,11 are
interesting for studying the influence of the steric bulk
of the guanidinate ligands on the mode of coordination to
lanthanide atoms. To investigate the coordination ability
of the guanidinate ligand and the influence of the degree
of steric saturation of the coordination sphere about lanꢀ
thanide atoms (which can be varied by changing both the
steric bulk of the guanidinate ligand and the ionic radius
of the central atom) on the coordination mode, tris(guaniꢀ
dinate) complexes containing substituents of different
bulkiness at the nitrogen atoms of the NCN fragments
* Dedicated to Academician O. N. Chupakhin on the occasion
of his 75th birthday.
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 6, pp. 1098—1103, June, 2009.
1066ꢀ5285/09/5806ꢀ1126 © 2009 Springer Science+Business Media, Inc.

Guanidinate derivatives of rareꢀearth metals
Russ.Chem.Bull., Int.Ed., Vol. 58, No. 6, June, 2009
1127
were synthesized. In the present study, we report the synꢀ
thesis and structures of new guanidinate derivatives of
lanthanides {(Me3Si)2NC(NR)2}3Ln (Ln = Nd, R = Pri,
(1); Ln = Lu, R = Cy (2)) and {(Me3Si)2NC(NCy)2}2ꢀ
{HC(NCy)2}Nd (3) (Cy is cyclohexyl).
Si(6)
Si(5)
N(9)
C(27)
Results and Discussion
N(8)
N(7)
It was found that the reactions of anhydrous LnCl3
(Ln = Nd or Lu) with three equivalents of {(Me3Si)2NCꢀ
(NR)2}Li (R = Pri or Cy), which was prepared in situ from
[(Me3Si)2NLi(Et2O)] and the corresponding carbodiimide
(in a molar ratio of 1 : 1) in THF (20 °C), afforded the
tris(guanidinate) complexes {(Me3Si)2NC(NR)2}3Ln
(1 and 2). Complexes 1 and 2 were isolated from the
reaction mixture after the extraction with toluene and
recrystallization from hexane in 82 and 88% yields,
respectively (Scheme 1).
Nd(1)
N(5)
N(2)
C(1)
Si(4)
N(6)
Si(1)
N(3)
N(4)
C(14)
Si(3)
N(1)
Si(2)
Complexes 1 and 2 are bluishꢀbrown and colorless
crystalline compounds, respectively. They are sensitive to
atmospheric oxygen and moisture. Both compounds are
readily soluble in all organic solvents, which complicates
the isolation. The IR spectra of compounds 1 and 2 show
sets of bands characteristic of C—N and Si—C stretching
vibrations of the guanidinate ligands (1640, 1254, and
840 cm–1), which is indicative of the absence of coordiꢀ
nated solvent molecules. In the 1H NMR spectrum of
diamagnetic complex 2 (C6D6, 20 °C), the guanidinate
ligands appear as the following signals: two singlets
(δH 0.22 and 0.33) corresponding to the methyl protons
of the N(SiMe3)2 fragment and a multiplet at δ 1.25—2.02
assigned to the methylene protons of the cyclohexyl
groups. The methine protons of the cyclohexyl substituꢀ
ents appear as a broadened multiplet at δH 3.61.
Fig. 2. Molecular structure of complex 1 (the isopropyl substituꢀ
ents in the guanidinate ligands are not shown).
given in Table 1. Homoleptic complexes 1 and 2 were
found to exist as mononuclear species in the crystals. The
coordination number of the metal atom is 6 as a result of
the coordination by the nitrogen atoms of three bidentate
guanidinate ligands. In complex 1, the Nd—N distances
are in the range of 2.460(2)—2.529(2) Å and are comparꢀ
able to the corresponding distances in the complex
{Pri2NC(N—Pri)2}3Nd (2.444(3)—2.496(3) Å).11 The
C—N bond lengths in the NCN fragments (1.326(2)—
1.334(2) Å) of complex 1 are indicative of the electron
density delocalization in the central groups of the ligands.
The N—Nd—N bond angles in 1 are 53.53(5), 53.87(5),
and 53.75(5)° and are virtually equal to the correspondꢀ
ing angles in the guanidinate derivatives of neodyꢀ
mium [{(Me3Si)2NC(NPri)2}2Nd(μꢀH)]2 (54.67(8) and
54.19(8)°)12 and {Pri2NC(NPri)2}3Nd (54.68(8), 53.86(9),
and 54.42(8)°).11
Crystals of complexes 1 and 2 suitable for Xꢀray
diffraction were obtained by the slow evaporation of their
hexane solutions at room temperature. The molecular
structures of complexes 1 and 2 are shown in Figs 2 and 3,
respectively. Selected bond lengths and bond angles are
Scheme 1
Ln = Nd, R = Pri (1),
Ln = Lu, R = Cy (2)

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Russ.Chem.Bull., Int.Ed., Vol. 58, No. 6, June, 2009
Skvortsov et al.
Table 1. Selected bond lengths (d) and bond angles (ω) in
complexes 1—3
Parameter
1
2a
3
N(6)
Si(4)
Si(3)
N(4)
Bond
d/Å
Ln—N
2.529(2)
2.502(2)
2.493(2)
2.460(2)
2.503(2)
2.492(2)
1.334(2)
1.333(2)
1.330(2)
1.327(2)
1.332(2)
1.326(2)
2.385(1)
2.375(1)
2.365(1)
2.397(1)
2.367(1)
2.390(1)
1.336(2)
1.336(2)
1.332(2)
1.338(2)
1.333(2)
1.335(2)
2.466(1)
2.458(1)
2.438(1)
2.508(1)
2.569(2)
2.455(1)
1.331(2)
1.328(2)
1.335(2)
1.326(2)
1.314(2)
1.324(2)
C(20)
N(5)
Lu(1)
N(8)
N(1)
N—Cb
Si(2) C(1)
C(39)
Si(5)
N(9)
N(2)
N(3)
Si(1)
N(7)
Si(6)
Angle
ω/deg
N—Ln—N
53.53(5)
53.87(5)
53.75(5)
116.39(2)
115.21(2)
116.29(2)
56.38(4)
56.44(4)
56.35(4)
114.58(1)
114.95(2)
114.66(1)
54.34(5)
54.08(4)
54.72(5)
115.52(2)
115.39(2)
122.31(2)
Fig. 3. Molecular structure of complex 2 (the cyclohexyl subꢀ
stituents at the nitrogen atoms are not shown).
N—C—N
There are two independent molecules of complex 2
per asymmetric unit of the crystal (occupying one general
position and one special position). Since the geometric
characteristics of the molecules are similar to each other,
the bond lengths and bond angles for the molecule in the
general position are discussed hereinafter. Unlike comꢀ
plex 1, complex 2 crystallizes as the solvate {(Me3Si)2NCꢀ
(NCy)2}3Lu•(11/3) C6H14.
The Lu—N distances in complex 2 are in the range
of 2.365(1)—2.397(1) Å and characterize the asymꢀ
metric coordination of these ligands. In turn, the nitroꢀ
gen—carbon bond lengths in the NCN fragment have
similar values (1.332(2)—1.338(2) Å) and are indicative
of the electron density delocalization within the guaniꢀ
dinate ligand. It should be noted that the asymmetric
coordination of the guanidinate ligands is typical and has
a The geometric characteristics of the molecule in the general
position are given.
b The endocyclic bond lengths in the LnNCN fragments.
been observed previously in dinuclear bis(guanidinate)
hydride complexes of lutetium.12,13
The unusual neodymium complex {(Me3Si)2Nꢀ
C(NCy)2}2{HC(NCy)2}Nd (3) containing two guanidinate
ligands and one formamidinate ligand was obtained in
attempting to synthesize the bis(guanidinate) borohydride
derivative by the metathesis of {(Me3Si)2NC(NCy)2}Na
with Nd(BH4)3(THF)2 (the molar ratio was 2 : 1) and
was, apparently, formed as a result of the fragmentation
and redistribution of the guanidinate ligands (Scheme 2).
Although the fragmentation of guanidinate ligands in
Scheme 2

Guanidinate derivatives of rareꢀearth metals
C(39)
Russ.Chem.Bull., Int.Ed., Vol. 58, No. 6, June, 2009
1129
90.9(2) (91.7(2)), and 84.5(2)% for complexes 1—3, reꢀ
spectively. The higher degree of shielding of the Lu cation
(for the coordination number 6, the radius is 1.001 Å)15
in 2 compared to that of the Nd cation (for the coordinaꢀ
tion number 6, the radius is 1.123 Å)15 in 3 is essentially
attributed to the smaller radius of Lu. For an absolute
comparison of the steric bulk of the ligands, it is conveꢀ
nient to use the degree of shielding of the central metal
cation calculated for the same metal—ligand distance (for
example, 2.28 Å; the parameter G2.28). In complex 2, the
degree of shielding of the metal atom in (Me3Si)2NCꢀ
(N—Cy)2 by the ligands at a distance of 2.28 Å is in the
range of 30.8(2)—31.6(2)%, whereas the analogous value
for (Me3Si)2NC(NPri)2 in complex 1 is 30.3(2)—31.0(2)%.
N(7)
N(8)
Nd(1)
N(5)
N(1)
C(1)
Si(3)
C(20)
Si(1)
N(2)
N(6)
N(3)
Si(2)
N(4)
Si(4)
Therefore, these values show that the isopropylꢀ (GuPri
)
Fig. 4. Molecular structure of complex 3 (the cyclohexyl subꢀ
and cyclohexylꢀsubstituted (GuCy) guanidinate ligands are
comparable in terms of the shielding of the central metal
atom in complexes 1 and 2. The G parameter in complex
3 (84.5(2)%) is smaller than that in complex 1 (86.2(2)%),
which is directly associated with the smaller steric bulk of
the formamidinate ligand (G2.28 = 25.1(2)%) both comꢀ
pared to the parameter G2.28 for the GuPri ligand (30.3(2)—
31.0(2)%) in 1 and the parameters G2.28 for the GuCy
ligands in 2 (30.8(2)—31.6(2)%) and 3 (32.0(2), 32.7(2)%).
It should be noted that the parameters G2.28 for the GuCy
ligands in 3 are somewhat larger than the corresponding
parameters for the GuPri ligands in 1. Evidently, this is
associated with somewhat weaker nonꢀcovalent interacꢀ
tions in the coordination sphere of the Nd cation in 3
compared to 1, which is reflected by the G parameters in
these complexes. As a result, the GuCy ligands in 3 are
somewhat closer to the Nd cation compared to those in
complex 1. This is most clearly evidenced by the systemꢀ
atically larger NNdN angles (54.08(4) and 54.34(5)°) in
the GuCy ligands in 3 compared to the corresponding
angles in 1 (53.53(5)—53.75(5)°).
stituents at the nitrogen atoms are not shown).
alkali metal and rareꢀearth metal complexes has been
described previously, this type of the transformation was
observed for the first time.
Unfortunately, we failed to isolate complex 3 in the
individual state. Apparently, the lilac crystals, which were
formed in the reaction and were isolated by the recrystalꢀ
lization from hexane, are a mixture of complex 3 and
mixed guanidinate borohydride derivatives, as evidenced
by the fact that the IR spectrum shows intense absorption
bands assigned to stretching vibrations of the BH4 group
(2161, 2215, 2336, and 2427 cm–1).
The molecular structure of complex 3 is presented in
Fig. 4. Selected bond lengths and bond angles are given
in Table 1. The Xꢀray diffraction data showed that comꢀ
plex 3 exists as a mononuclear species in the crystal strucꢀ
ture. The coordination sphere of the neodymium atom,
like that in complex 1, is formed by six nitrogen atoms
of three chelate N,Nꢀligands. A substantial difference of
complex 3 is that it contains two different types of ligands
(two guanidinate ligands and one formamidinate ligand).
It should be noted that, unlike the guanidinate ligands
(Nd—N, 2.458(1) and 2.466(1) Å; 2.438(1) and 2.508(1) Å),
the Nd—N bond lengths within the metallacycle NdNCN
that is formed upon the coordination of the formamidinate
ligand to the metal atom are substantially different
(2.455(1) and 2.569(2) Å). By contrast, the C—N bond
lengths within the NCN fragments of all three ligands
have similar values (1.324(2) and 1.314(2) Å; 1.326(2)
and 1.335(2) Å; 1.328(2) and 1.331(2) Å), which is inꢀ
dicative of the negative charge delocalization. The NCN
bond angles in two guanidinate ligands are 115.52(2) and
115.39(2)°, respectively, and substantially differ from
the NCN angle in the formamidinate ligand (122.31(2)°).
To estimate the steric situation in complexes 1—3, we
performed calculations for the shielding of the central
Ln atom by the ligands using a procedure described previꢀ
ously.14 According to the calculations, the degree of shieldꢀ
ing (the G parameter) of the central Ln atom is 86.2(2),
Previously, we have shown16,17 that the degree of satuꢀ
ration of the coordination sphere (86(3)%) is a good
evidence that the guanidinate complexes of lanthanides
are mononuclear, i.e., there are no intermolecular metal—
ligand interactions, which are responsible for the assoꢀ
ciation of the mononuclear units, in the crystals. The
calculated degrees of shielding of the central Ln atom
(84.5(2)—91.7(2)%) in complexes 1—3 confirm the
conclusions drawn previously.
Therefore, the metathesis reactions of anhydrous rareꢀ
earth metal halides with lithium guanidinate in a molar
ratio of 1 : 3 produce the corresponding tris(guanidinate)
complexes {(Me3Si)2NC(NR)2}3Ln (Ln = Nd, R = Pri;
Ln = Lu, R = Cy) in good yields. The resulting comꢀ
pounds have similar molecular structures and do not
contain coordinated Lewis bases, which is attributed to
the high degree of saturation of the coordination sphere
about the lanthanide atoms (84.5(2)—91.7(2)%). The
formation of the heteroleptic bis(guanidinate) formamidiꢀ

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Russ.Chem.Bull., Int.Ed., Vol. 58, No. 6, June, 2009
Skvortsov et al.
The toluene extract was filtered, and the toluene was removed
in vacuo at room temperature. Bluishꢀbrown crystals of 1 were
obtained after recrystallization of the residue from hexane in a
yield of 0.99 g (82%). Found (%): C, 47.06; H, 9.83; Nd, 14.49.
C39H96N9Si6Nd. Calculated (%): C, 46.66; H, 9.64; Nd, 14.37.
IR (Nujol), ν/cm–1: 1640, 1315, 1254, 1167, 1068, 952, 841.
Tris[N,N´ꢀdicyclohexylꢀN″ꢀbis(trimethylsilyl)guanidinate]ꢀ
lutetium(III), {(Me3Si)2NC(NCy)2}3Lu (2). Lutetium chloride
LuCl3 (0.42 g, 1.49 mmol) was added to a solution of
lithium guanidinate, which was prepared by the reaction
of (Me3Si)2NLi(Et2O) (1.06 g, 4.40 mmol) with N,N´ꢀdicycloꢀ
hexylcarbodiimide (0.92 g, 4.47 mmol) in THF (50 mL), and
the reaction mixture was stirred at 20 °C for 4 h. Tetrahydroꢀ
furan was removed by condensation in vacuo, and the solid
residue was extracted with toluene to separate LiCl that formed.
The toluene extract was filtered, and the toluene was removed
in vacuo at room temperature. Colorless crystals of 2 were
obtained after recrystallization of the residue from hexane in a
yield of 1.80 g (88%). Found (%): C, 53.20; H, 10.00; Lu, 13.33.
C57H120N9Si6Lu. Calculated (%): C, 53.69; H, 9.48; Lu, 13.72.
IR (Nujol), ν/cm–1: 1639, 1611, 1303, 1254, 1072, 954,
840. 1H NMR (20 °C, benzeneꢀd6), δ: 0.22, 0.33 (s, 54 H,
N(Si(CH3)3)2); 1.25—2.02 (m, 60 H, CH2, Cy); 3.61 (br.m,
6 H, CH, Cy). 13C NMR (20 °C, benzeneꢀd6), δ: 1.2, 2.8
(N(Si(CH3)3)2); 33.2, 36.7, 38.5 (CH2, Cy); 55.0 (CH, Cy);
170.3 (CN3).
nate complex {(Me3Si)2NC(NCy)2}2{HC(NCy)2}Nd was
observed in the reaction of {(Me3Si)2NC(NCy)2}Na with
Nd(BH4)3(THF)2 in a molar ratio of 2 : 1 and is, apparꢀ
ently, the result of the fragmentation and redistribution of
the guanidinate ligands.
Experimental
The synthesis was carried out using the standard Schlenk
techniques to exclude atmospheric oxygen and moisture.
Hexane, THF, and toluene were dried over sodium benzopheꢀ
none ketyl, thoroughly degassed, and condensed in vacuo into
reaction tubes immediately before use. The IR spectra were
recorded on a Specord M80 instrument. Samples were prepared
as Nujol mulls. The 1H and 13C NMR spectra were measured
on a Bruker DPX 200 instrument. The chemical shifts are
given in ppm with respect to the known signals of the
residual protons of the deuterated solvents. Anhydrous LnCl3,18
Nd(BH4)3(THF)n,19 and (Me3Si)2NLi(Et2O) (see Ref. 20) were
synthesized according to known procedures. N,N´ꢀDiisopropylꢀ
carbodiimide and N,N´ꢀdicyclohexylcarbodiimide were comꢀ
mercial products (Acros). N,N´ꢀDiisopropylcarbodiimide was
used after drying with molecular sieves А4 and condensation
in vacuo. N,N´ꢀDicyclohexylcarbodiimide was used without
additional purification.
Tris[N,N´ꢀdicyclohexylꢀN″ꢀbis(trimethylsilyl)guanidinate]ꢀ
neodymium(III), {(Me3Si)2NC(NPri)2}3Nd (1). Neodymium
chloride NdCl3 (0.30 g, 1.20 mmol) was added to a solution
of lithium guanidinate, which was prepared by the reaction of
(Me3Si)2NLi(Et2O) (0.86 g, 3.60 mmol) with N,N´ꢀdiisopropylꢀ
carbodiimide (0.45 g, 3.60 mmol) in THF (40 mL), and the
reaction mixture was stirred at room temperature for 24 h. Tetraꢀ
hydrofuran was removed by condensation in vacuo, and the solid
residue was extracted with toluene to separate LiCl that formed.
Reaction of {(Me3Si)2NC(NCy)2}Na with Nd(BH4)3(THF)2
(molar ratio was 2 : 1). The neodymium compound Nd(BH4)3ꢀ
(THF)2 (0.41 g, 1.24 mmol) was added to a solution of sodium
guanidinate, which was prepared by the reaction of (Me3Si)2NNa
(0.47 g, 2.60 mmol) with N,N´ꢀdicyclohexylcarbodiimide
(0.50 g, 2.48 mmol) in THF (50 mL). The reaction mixture was
stirred at 20 °C for 14 h. Tetrahydrofuran was removed by
condensation in vacuo, and the solid residue was extracted with
hexane to separate NaBH4 that formed. The recrystallization
of the residue from hexane afforded blue crystals in a yield of
Table 2. Crystallographic characteristics and the Xꢀray data collection and refinement statistics for complexes 1—3
Parameter
1
2
3
Molecular formula
Molecular weight
Space group
a/Å
b/Å
C39H96N9Si6Nd
1004.03
P2(1)/n
14.4932(5)
22.9448(7)
17.1224(6)
90
C65H138.67N9Si6Lu
1390.03
C2/c
C51H103N8Si4Nd
1085.01
P2(1)/c
12.5862(3)
22.3376(6)
21.8508(6)
90
47.850(2)
14.6850(6)
39.776(2)
90
123.677(1)
90
23259.(2)
12
1.191
c/Å
α/deg
β/deg
γ/deg
V/Å3
Z
97.174(1)
90
5649.4(3)
4
1.180
1.079
105.940(1)
90
5907.0(3)
4
1.220
0.999
ρ
calc/g cm–3
μ/mm–1
1.407
θ/ωꢀScan range
1.67—26.00
47906
11080 (Rint = 0.0221)
515
1.71—26.00
68746
22787 (Rint = 0.0236)
1829
2.49—26.00
50579
11607 (Rint = 0.0274)
617
Number of measured reflections
Number of reflections with I > 2σ
Number of refined parameters
R1 (I > 2σ(I))
0.0289
0.0299
0.0314
wR2 (I > 2σ(I))
0.0752
0.0680
0.0749

Guanidinate derivatives of rareꢀearth metals
Russ.Chem.Bull., Int.Ed., Vol. 58, No. 6, June, 2009
1131
0.429 g. IR (Nujol), ν/cm–1: 2427, 2336, 2215, 2161, 1640,
1580, 1315, 1257, 1191, 1121, 865, 780.
7. Z. Lu, G. P. A. Yapp, D. S. Richeson, Organometallics,
2001, 20, 706.
Xꢀray diffraction studies were carried out on an automated
Smart APEX diffractometer (graphite monochromator, MoKα
radiation, ω—φꢀscanning technique, exposure time was 10 s per
frame) at 100 К. Principal crystallographic characteristics and
the Xꢀray data collection and refinement statistics are given in
Table 2. All structures were solved by direct methods and refined
8. Y. Luo, Y. Yao, Q. Shen, K. Yu, L. Weng, Eur. J. Inorg.
Chem., 2003, 318.
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Dalton Trans., 2001, 923.
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23, 3303.
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Skorodumova, G. K. Fukin, E. V. Baranov, V. N. Glushakova,
Chem. Eur. J., 2006, 12, 5320.
13. А. A. Trifonov, E. A. Fedorova, G. K. Fukin, M. N.
Bochkarev, Eur. J. Inorg. Chem., 2004, 4396.
14. I. A. Guzei, M. Wendt, Dalton Trans., 2006, 3991.
15. R. D. Shannon, Acta Crystallogr., Sect. A, 1976, 32, 751.
16. G. K. Fukin, I. A. Guzei, E. V. Baranov, J. Coord. Chem.,
2007, 60, No. 9, 937.
by the leastꢀsquares method based on F2 with anisotropic
hkl
displacement parameters for all nonhydrogen atoms. The H
atoms in complexes 1 and 3 were positioned geometrically and
refined using a riding model. The H atoms in the structure of 2
were located in difference electron density maps (except for the
hydrogen atoms in the hexane solvent molecules, which were
refined analogously to the H atoms in 1 and 3) and refined
isotropically. All calculations were carried out with the use of
the SHELXTL v. 6.12 program package.21 Absorption corꢀ
rections were applied using the SADABS program.22
The spectroscopic and Xꢀray diffraction studies were
carried out in the Analytical Center of the G. A. Razuvaev
Institute of Organometallic Chemistry of the Russian
Academy of Sciences. This study was financially supꢀ
ported by the Russian Foundation for Basic Research
(Project Nos 08ꢀ03ꢀ00391ꢀa and 06ꢀ03ꢀ32728a).
17. G. K. Fukin, I. A. Guzei, E. V. Baranov, J. Coord. Chem.,
2007, 60, 937.
18. M. D. Taylor, C. P. Carter, J. Inorg. Nucl. Chem., 1962,
24, 387.
19. U. Mirsaidov, I. B. Shaimuradov, M. Khikmatov, Zh. Neorg.
Khim., 1986, 31, 1321 [J. Inorg. Chem. USSR (Engl. Transl.),
1986, 31].
20. L. E. Manzer, Inorg. Chem., 1978, 17, 1552.
21. G. M. Sheldrick, SHELXTL, v. 6.12, Structure Determination
Software Suite, Bruker AXS, Madison, Wisconsin, USA,
2000.
22. G. M. Sheldrick, SADABS, v. 2.01, Bruker/Siemens Area
Detector Absorption Correction Program, Bruker AXS,
Madison, Wisconsin, USA, 1998.
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in revised form March 4, 2009
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