Bis(alkyl) yttrium complex containing a new tridentate amidinate ligand: Synthesis and structure

Article abstract of DOI:10.1007/s11172-013-0255-2

New potentially tridentate amidine containing the quinoline fragment in the lateral chain, viz., NC₉H₆-8-NHC(Bu^t)N-2,6- Prⁱ-₂-C₆H₃ (1), was synthesized by the reaction of chloroimine 2,6-Prⁱ ₂-C₆H ₃-N=C(Bu^t)Cl and lithium derivative of 8-aminoquinoline NC₉H₆-8-NHLi. The elimination of alkane under the action of amidine 1 on Y(CH₂SiMe₃)₂(THF)₂ in THF affords bis(alkyl) yttrium complex [NC₉H₆-8- NC(Bu^_t)N-2,6-Prⁱ ₂-C ₆H₃]Y(CH₂SiMe₃)₂(THF) (2), monomeric in the crystalline state.

Full text of DOI:10.1007/s11172-013-0255-2

Russian Chemical Bulletin, International Edition, Vol. 62, No. 8, pp. 1772—1776, August, 2013
1772
Bis(alkyl) yttrium complex containing a new tridentate
amidinate ligand: synthesis and structure*
M. V. Yakovenko, A. V. Cherkasov, G. K. Fukin, and A. A. Trifonov
G. A. Razuvaev Institute of Organometallic Chemistry, Russian Academy of Sciences,
49 ul. Tropinina, 603950 Nizhni Novgorod, Russian Federation.
Fax: +7 (0831) 462 7497. Eꢀmail: trif@iomc.ras.ru
New potentially tridentate amidine containing the quinoline fragment in the lateral chain,
viz., NC9H6ꢀ8ꢀNHC(But)Nꢀ2,6ꢀPri2ꢀC6H3 (1), was synthesized by the reaction of chloroimine
2,6ꢀPri2ꢀC6H3ꢀN=C(But)Cl and lithium derivative of 8ꢀaminoquinoline NC9H6ꢀ8ꢀNHLi. The
elimination of alkane under the action of amidine 1 on Y(CH2SiMe3)2(THF)2 in THF affords
bis(alkyl) yttrium complex [NC9H6ꢀ8ꢀNC(But)Nꢀ2,6ꢀPri2ꢀC6H3]Y(CH2SiMe3)2(THF) (2),
monomeric in the crystalline state.
Key words: rareꢀearth metals, complexes, amidinate ligand, N,N,Nꢀligand, synthesis, strucꢀ
ture, catalysis.
Alkyl derivatives of rareꢀearth metals of the monoꢀ and
bis(cyclopentadienyl) series exhibited high reactivity, reꢀ
sulting in the vigorous development of this field of chemꢀ
istry.1—4 The alkyl complexes of rareꢀearth elements turned
out to be active catalysts (or their precursors) of the polyꢀ
merization/oligomerization,4,5 hydrosilylation,6 hydroamꢀ
ination,6,7 hydroboration,8 and hydrophosphination9 of
diverse unsaturated substrates. Presently, interest of reꢀ
searchers shifted towards using nonꢀcyclopentadienyl
ligands that allow one to efficiently stabilize alkyl and
hydride complexes of rareꢀearth metals and also provide
rich possibilities for the formation of various geometries of
the coordination enviornment of the metal atom.10,11
Among them polydentate monoꢀ and dianionic Nꢀ and/or
Oꢀcontaining ligands are promising, since they are capaꢀ
ble of providing steric saturation of the coordination sphere
of the metal atom and, hence, kinetic stability of the metal
complexes without decreasing their reactivity.10—12 The
monoanionic bidentate amidinate anions [RC(NR´)2]– are
among the most interesting nitrogenꢀcontaining ligands
successfully used in the chemistry of transition and nonꢀ
transition metals.13—22 The variation of substituents at the
nitrogen and carbon atoms of the NCN fragment makes it
possible to change the electronic and spatial characterisꢀ
tics of the ligand thus creating conditions for the conꢀ
struction of the coordination sphere of the metal atom,
modification of the reactivity of the metal complex, and
achievement of control of the catalyzed processes. The
introduction of fragments with donor groups into the amidꢀ
inate ligands can result in the additional stabilization of the
complexes due to the coordination of the new basic sites
to the metal. At the same time, the coordination bond
between the metal atom and donor functional group can
be labile, under some conditions, and capable of dissociꢀ
ating to release the coordination site for the substrate in
the sphere of the metal. This property is interesting from
the viewpoint of a possible catalytic use of these complexes.
In this work, we consider the results of syntheses and
structural studies of the new potentially tridentate amiꢀ
dine NC9H6ꢀ8ꢀNHC(But)Nꢀ2,6ꢀPri2ꢀC6H3 (1) containꢀ
ing the quinoline moiety in the lateral chain and its derivꢀ
ative, viz., yttrium bis(alkyl) complex [NC9H6ꢀ8ꢀNCꢀ
(But)Nꢀ2,6ꢀPri2ꢀC6H3]Y(CH2SiMe3)2(THF) (2).
Results and Discussion
Amidine NC9H6ꢀ8ꢀNHC(But)Nꢀ2,6ꢀPri2ꢀC6H3 (1)
was synthesized by the reaction of equimolar amounts of
chlorimine 2,6ꢀPri2C6H3N=C(But)Cl (see Ref. 23) and
lithium 8ꢀaminoquinoline derivative NC9H6ꢀ8ꢀNHLi,
which was synthesized in situ from NC9H6ꢀ8ꢀNH2 and
BunLi (molar ratio 1 : 1), in an Et2O—hexane (Hex) at
0 С (Scheme 1).
Amidine 1 was isolated by recrystallization from an
Et2O—hexane mixture at room temperature as yellow crysꢀ
tals highly soluble in polar solvents, such as diethyl ether,
chloroform, and THF, and poorly soluble in hexane. The
compound was characterized by Xꢀray diffraction analyꢀ
sis, NMR and IR spectroscopy, mass spectrometry, and
1
elemental analysis. The Н NMR spectrum of amidine 1
* Dedicated to blessed memory of Mikhail Yuvenal´evich Antipin
(1951—2013).
(C6D6, 20 C) contains the broadened singlet at 9.64 ppm
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 8, pp. 1772—1776, August, 2013.
1066ꢀ5285/13/6208ꢀ1772 © 2013 Springer Science+Business Media, Inc.

Dialkyl yttrium complex with amidinate ligand
Russ.Chem.Bull., Int.Ed., Vol. 62, No. 8, August, 2013
1773
Scheme 1
Table 1. Selected bond lengths (d) and bond angles
() in amidine 1 and dialkyl complex 2
Compound
Parameter
Distance
Value
1
d/Å
N(1)—C(13)
N(2)—C(13)
1.2805(16)
1.3765(16)
Angle
N(1)—C(13)—N(1)
Distance
/deg
117.15(11)
d/Å
2
Y(1)—C(27)
Y(1)—C(31)
Y(1)—N(1)
Y(1)—N(2)
Y(1)—N(3)
Y(1)—O(1)
N(1)—C(1)
N(2)—C(1)
2.419(3)
2.435(3)
2.350(3)
2.413(3)
2.446(3)
2.456(2)
1.360(4)
1.337(4)
i. 0 C, Et2O/Hex; ii. 25 C, Et2O.
corresponding to the N—Н proton. The methine protons
of the Pri groups appear as a septet at 3.21 ppm (3JH,H
=
= 6.8 Hz). The methyl protons of the isopropyl groups
give one doublet at 1.17 ppm (3JH,H = 6.8 Hz) correꢀ
sponding by integral intensity to six protons, whereas the
signals corresponding to the remained protons are overꢀ
lapped with the signals from the tertꢀbutyl protons, resultꢀ
ing in the formation of a multiplet in the range from 1.28
to 1.30 ppm. The aromatic protons give a set of signals at
6.76—8.74 ppm. The observed shape of the spectrum can
be caused by a series of dynamic processes that occur in
molecule 1, such as proton migration between the nitroꢀ
gen atoms of the amidinate moiety, and hindered rotation
of bulky organic substituents around the C—N bonds. In
the IR spectrum of compound 1, the intense band at
3387 cm–1 corresponds to stretching vibrations of the
N—H bond and vibrations of the С=N bond appear as
a band at 1647 cm–1. The mass spectrum of the compound
contains the molecular peak with m/z 388 [M]+.
Angle
/deg
N(1)—Y(1)—N(2)
C(27)—Y(1)—C(31)
N(1)—C(1)—N(2)
54.93(9)
120.62(12)
109.1(3)
The Xꢀray diffraction study of compound 1 showed
that the quinoline and amidinate moieties of the molecule
are coplanar, whereas the planes of the NC9H6ꢀ8ꢀNHCꢀ
(But)N moiety and aromatic ring 2,6ꢀPri2ꢀC6H3 are orꢀ
thogonal. The С(13)—N(1) bond length (1.2805(16) Å)
in the NCN fragment is comparable with the values usually
observed for the С=N double bond,24 while the С(13)—N(2)
bond is substantially longer (1.371(2) Å) and its length
corresponds to the N—C ordinary bond. In amidine 1, an
intramolecular hydrogen bond is formed between the amiꢀ
dine hydrogen atom and the nitrogen atom of the quinoꢀ
line moiety, which is indicated by the short contact
N(3)—H(2) 2.13(1) Å.
The bis(alkyl) yttrium complex [NC9H6ꢀ8ꢀNC(But)Nꢀ
2,6ꢀPri2ꢀC6H3]Y(CH2SiMe3)2(THF) (2) was synthesized
by the reaction of equimolar amounts of amidine 1 and
Y(CH2SiMe3)3(THF)2 (see Ref. 25) in toluene at 0 С and
isolated by recrystallization from hexane at –10 С in 47%
yield as yellow crystals very sensitive to air moisture
and oxygen.
The compound was characterized by Xꢀray diffraction
analysis, NMR and IR spectroscopy, and elemental analꢀ
yses. The presence of alkyl groups in diamagnetic yttrium
complex 2 is confirmed by the presence of a doublet at
–0.64 ppm (2JY,H = 2.62 Hz) in the 1H NMR spectrum of
compound 2. The doublet corresponds to signals from the
protons of the methene group bound to the metal atom.
The spectrum also exhibits a singlet at –0.13 ppm attribꢀ
uted to the signals from the protons of the SiMe3 groups.
In the 13C NMR spectrum, the carbon atoms of the alkyl
Transparent crystals of amidine 1 were obtained by
slow concentrating od its solution in an Et2O—hexane
mixture at room temperature. The molecular structure of
amidine 1 is shown in Fig. 1. Selected bond lengths and
bond angles are given in Table 1.
C(15)
C(17)
C(11)
C(16)
C(14)
C(10)
H(2)
C(6)
C(13)
C(5)
C(12)
C(25)
N(3)
N(2)
C(1)
C(12)
C(7)
N(1)
C(4)
C(3)
C(8)
C(18)
C(2)
C(26)
C(22)
C(23)
C(24)
C(19)
C(9)
C(20)
C(21)
Fig. 1. Molecular structure of amidine NC9H6ꢀ8ꢀNHC(But)Nꢀ
2,6ꢀPri2ꢀC6H3(1).

1774
Russ.Chem.Bull., Int.Ed., Vol. 62, No. 8, August, 2013
Yakovenko et al.
Scheme 2
The crystallographic data for complex 2 are listed in Table 2.
The Xꢀray structural study showed that complex 2 crystalꢀ
lized in the space group of the P21/n symmetry. The comꢀ
pound is monomeric. The coordination sphere of the ytꢀ
trium atom in the complex is formed by two alkyl groups,
three nitrogen atoms of the amidinate ligand, and one
THF molecule. The amidinate ligand in complex 2 is triꢀ
dentate, which results in the coordination number of the
yttrium atom equal to six. The Y(1)N(1)C(1)N(2) metalꢀ
locycle and the NC9H6 quinoline fragment lie in one
plane. The alkyl groups are arranged above and under
the plane of the Y(1)N(1)C(1)N(2) metallocycle. The
C(27)—Y(1)—C(31) angle is 120.62(12), which is more
than a similar value in the dialkyl complex {(Me3Si)2NCꢀ
(NCy)2}Y(CH2SiMe3)2(THF)2 (112.40(7))26 and comꢀ
parable with the С—Y —C angle in the dialkyl derivaꢀ
tive
{(Me3Si)2NC(NPri)2}Y(CH2SiMe3)2(THF)2
(123.4(1)).27 The Y—C bond lengths in complex 2 are
2.419(3) Å and 2.435(3) Å and are noticeably shorter
than the corresponding bond lengths in related guanidiꢀ
nate dialkyl yttrium complexes {(Me3Si)2NC(NCy)2}Yꢀ
(CH2SiMe3)2(THF)2 (2.462(2), 2.473(2) Å)26 and
{(Me3Si)2NC(NPri)2}Y(CH2SiMe3)2(THF)2 (2.466(2) Å).27
The distances between the yttrium atom and amidꢀ
inate nitrogen atoms in complex 2 differ insignificantly
(2.350(3) Å, 2.413(3) Å), which is likely a consequence of
the coordination of the nitrogen atom of the quinoline
fragment to yttrium. The Y—N bond lengths are compaꢀ
rable with similar distances in the guanidinate dialkyl deꢀ
rivatives (2.3833(17)—2.4165(17) Å).26,27
The distance between the yttrium atom and nitrogen
atom of the quinoline moiety (2.446 (3) Å) is somewhat
longer than other Ln—N distances in the complex. The
close values of C—N bond lengths (1.337(4)—1.360(4) Å)
indicate the delocalization of the negative charge inside
the amidinate fragment.
i. (1) Tol, 0 C; (2) Hex, –10 C.
group appear as a doublet at 30.5 (2JY,C = 38.0 Hz) and a
singlet at 3.8 ppm, respectively. According to the 1H NMR
spectrum, complex 2 contains one coordinated tetraꢀ
hydrofuran molecule, whose ꢀСH2 protons appear as a broꢀ
adened singlet at 3.53 ppm, whereas the protons of the
ꢀСH2 group along with the methyl protons of the Pri and
But groups give a multiplet at 1.32—1.36 ppm. A septet at
3.44 ppm (3JH,H = 6.8 Hz) corresponds to the methine protꢀ
ons of the Pri groups. Complex 2 turned out to be a thermally
stable compound that manifests no properties of decomꢀ
position in benzeneꢀd6 at room temperature within 1 week.
The molecular structure of complex 2 is shown in Fig. 2.
Selected bond lengths and bond angles are given in Table 1.
C(34)
Bis(alklyl) yttrium derivative 2 was studied as a comꢀ
ponent of the catalytic systems of isoprene polymerꢀ
ization 2—B(C6F5)3—AlBui3, 2—[CPh3][B(C6F5)4]—
AlBui3, 2—[HNEt3][B(C6H5)4]—AlEt3, and 2—[HNEt3]ꢀ
[B(C6H5)4]—AlBui3 (molar ratio of the components
1 : 1 : 50; 25 С, 24 h). However, all studied systems are
inactive, most likely, due to instability of the cationic alkyl
complexes formed in the reactions of 2 with B(C6F5)3,
[CPh3][B(C6F5)4], and [HNEt3][B(C6H5)4].
Pri
C(32)
C(16)
But
C(17)
C(33)
Si(2)
C(8)
C(7)
N(1)
C(1)
C(15)
C(31)
C(9)
C(10)
C(11)
C(18)
C(6)
C(14)
N(2)
C(20)
C(19)
Y(1)
N(3)
Pri
THF
C(29)
Thus, new tridentate amidine 1 containing the quinoꢀ
line fragment in the lateral chain was synthesized. The
reaction of Y(CH2SiMe3)3(THF)2 with amidine 1 affords
bis(alkyl) yttrium complex 2 with intramolecular coordiꢀ
nation of the quinoline fragment to the yttrium atom.
C(12)
C(13)
C(27)
Si(1)
C(30)
C(28)
Experimental
Fig. 2. Molecular structure of complex [NC9H6ꢀ8ꢀNC(But)Nꢀ
2,6ꢀPri2ꢀC6H3]Y(CH2SiMe3)2(THF) (2). The THF molecule,
Me groups, and But and Pri groups are omitted.
The complexes were synthesized under conditions excluding
contact with air oxygen and moisture using the standard Schlenk

Dialkyl yttrium complex with amidinate ligand
Russ.Chem.Bull., Int.Ed., Vol. 62, No. 8, August, 2013
1775
technique. Diethyl ether, hexane, benzene, and toluene were
dried over sodium benzophenone ketyl. Isoprene was dried above
CaH2 and then thoroughly degassed and condensed in vacuo
into the reaction ampule prior to use. С,НꢀAnalyses were carꢀ
ried out on a PerkinꢀElmer Series II CHNS/O Analyser 2400
instrument. IR spectra were recorded on a Specord Mꢀ80 instruꢀ
ment. Samples of compounds were prepared in dry argon as
suspensions in dried and degassed Nujol. 1H, 7Li, 11B, and
13С NMR spectra were measured on Bruker DPX 200 and Brukꢀ
er DPX 400 instruments. Chemical shifts are presented in ppm
with respect to the known shifts of residual protons of the deuterꢀ
ated solvents. The mass spectrum was recorded on a Polaris
Q/Trace GC Ultra (Ion Trap analiser) instrument. Compounds
and then the solution was filtered to separate LiCl that formed;
Et2O was removed in vacuo at room temperature. Colorless crysꢀ
tals of compound 1 were obtained by the recrystallization of the
residue from an Et2O—hexane mixture in a yield of 1.54 g (75%).
Found (%): C, 80.67; H, 8.56; N, 10.79. С26Н33N3. Calculatꢀ
ed (%): C, 80.58; H, 8.58; N, 10.84. IR (Nujol), /cm–1: 3387 (m),
1647 (s), 1596 (m), 1521 (s), 1483 (m), 1429 (m), 1396 (m),
1382 (m), 1325 (m), 1258 (w), 1209 (w), 1207 (w), 1151 (w),
1130 (w), 1107 (w), 1096 (w), 1096 (w), 1059 (w), 935 (w),
891 (w), 858 (w), 819 (w), 806 (w), 789 (m), 750 (w), 650 (w),
607 (w). 1Н NMR (200 MHz, 20 С, benzeneꢀd6), : 1.17 (d, 6 H,
3
МеPr , JH,H = 6.8 Hz); 1.28—1.30 (m, 15 Н, МеPri, Ме t); 3.21
i
Bu
(sept, 2 Н, CHPri, 3JH,H = 6.8 Hz); 6.76—7.26 (m, 6 Н, Ar); 7.52
25
2,6ꢀPri2C6Н3N=C(But)Cl23 and (Me3SiСН2)3Y(THF)2 were
(dd, 1 Н, Ar, 3JH,H = 8.3 Hz); 8.53 (dd, 1 Н, Ar, 3JH,H = 4.2 Hz);
8.74 (d, 1 Н, Ar, 3JH,H= 7.3 Hz); 9.64 (br.s, 1 Н, NH). 13C NMR
(50 MHz, 20 С, benzeneꢀd6), : 22.1 (МеPri); 23.6 (МеPri); 28.6
(МеBut); 29.2 (МеPri); 115.4, 118.9, 120.8, 121.5, 122.3, 125.3,
128.2 (CHAr); 129.0 (CAr); 135.6 (CAr); 135.7 (CHAr); 137.1
(CAr); 137.5 (CAr); 139.5 (CAr); 145.2 (CAr); 147.3 (CHAr); 153.6
(CN2). m/z: 388 [M]+.
synthesized according to published procedures. 8ꢀAminoquinoꢀ
line, AlBui3, and AlEt3 are commercial reagents. 2,6ꢀDiisoproꢀ
pylaniline was applied after drying with molecular sieves А4.
8ꢀAminoquinoline was used without additional purification.
Nꢀ2,6ꢀDiisopropylphenylꢀN´ꢀ8ꢀquinolineꢀtertꢀbutylamidine
(1). Lithium salt of 8ꢀaminoquinoline in Et2O (20 mL), obtained
in situ by mixing solutions of 8ꢀaminoquinoline (0.76 g,
5.30 mmol) in Et2O (10 mL) and BunLi (5.60 mL, 5.30 mmol,
{Nꢀ2,6ꢀDiisopropylphenylꢀN´ꢀ8ꢀquinolineꢀtertꢀbutylamidꢀ
inate]ꢀdi(trimethylsilylmethyl)yttrium}tetrahydrofuranate (2).
A solution of amidine 1 (0.25 g, 0.70 mmol) in toluene (5 mL)
was added at –10 С to a solution of Y(Me3SiCH2)3(ТНF)2
(0.36 g, 0.70 mmol) in toluene (25 mL). The reaction mixture
0.94 mmol L–1
) in hexane at 0 C, was added with
2,6ꢀPri2C6H3N=C(But)Cl (1.49 g, 5.30 mmol)23 in Et2O (20 mL).
The reaction mixture was stirred at room temperature for 24 h,
Table 2. Crystallographic data and parameters of Xꢀray diffraction experiments and refinement for amidine 1
and complex 2
Parameter
1
2
Empirical formula
Molecular weight
C26H33N3
387.55
C38H62N3OSi2Y
722.00
Т/K
100(2)
100(2)
Crystal system
Space group
Monoclinic
P21/n
Monoclinic
P21/n
a/Å
b/Å
c/Å
/deg
7.8919(5)
33.907(2)
8.7070(6)
90
10.8079(3)
19.8975(5)
19.0798(5)
90
/deg
/deg
110.2700(10)
90
98.420(3)
90
V/Å
2185.6(3)
4
1.178
4058.86(18)
4
Z
/g cm–3
1.182
1.526
/mm–1
0.069
F (000)
840
1544
Crystal size/mm
Measurement range, /deg
Range indices
0.42×0.12×0.07
2.40—26.50
–9  h  9,
–42  k  28,
–10  l  9
13523
0.20×0.20×0.10
2.85—30.00
–15  h  15,
–27  k  27,
–26  l  26
80316
Number of measured reflections
Number of independent reflections
Number of observed reflections
4496
3639
11801
6387
(Rint
)
(0.0294)
(0.2031)
(I > 2(I))
Goodnessꢀofꢀfit
0.998
0.997
R1/wR2 (I > 2(I))
R1/wR2 (for all parameters)
0.0493/0.1255
0.0625/0.1323
0.0738/0.0957
0.1462/0.1120

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Russ.Chem.Bull., Int.Ed., Vol. 62, No. 8, August, 2013
Yakovenko et al.
was stirred for 1 h at 0 С, then toluene was removed, and the
residue was dissolved in hexane (30 mL). After the substance was
recrystallized from hexane at –10 С, product 2 was isolated as
yellow crystals (0.21 г, 47%). Found (%): C, 63.25; H, 8.20;
Y, 12.26. C38H62N3OSi2Y. Calculated (%): C, 63.21; H, 8.66;
Y, 12.31. IR (Nujol), /cm–1: 1651 (s), 1595 (m), 1531 (s),
1483 (m), 1423 (m), 1384 (s), 1323 (m), 1259 (w), 1246 (w),
1233 (w), 1196 (w), 1151 (w), 1132 (w), 1107 (w), 1096 (w),
1080 (w), 1059 (w), 1018 (w), 949 (w), 937 (w), 891 (w), 819 (w),
806 (w), 789 (m), 750 (w), 667 (w), 650 (w), 606 (w). 1Н NMR
Sciences and the Division of Chemistry and Materials Sciꢀ
ence of the Russian Academy of Sciences).
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(200 MHz, 20 С, benzeneꢀd6), : –0.64 (d, 4 Н, YCH2, 2JY,H
= 2.62 Hz); –0.13 (s, 18 H, Si(CH3)3); 1.32—1.36 (m, 34 H,
МеPri, Ме t, ꢀСH (THF); 3.44 (sept, 2 H, CHPr
3JH,H
=
,
i
,
=
Bu
2
= 6.8 Hz)); 3.53 (br.s, 4 H, ꢀСH2 (THF), 6.64—7.63 (m, 8 H,
СНAr), 8.95 (dd, 1 H, СНAr
,
3JH,H = 4.6 Hz). 13C NMR
(50 MHz, 20 С, benzeneꢀd6), : 3.8 (Si(CH3)3); 23.4, 23.9,
25.0, 25.3, 26.9, 27.6, 28.0, 29.2, 29.7, 30.5 (d, YCH2,
2JYC = 38.0 Hz); 68.42 (ꢀСH2 (THF)); 117.7, 118.9, 120.5,
120.6, 122.8, 123.6, 124.0 (CHAr); 125.3 (CAr); 130.0 (CAr);
138.5 (CHAr); 139.4, 140.9, 144.8, 148.3 (CAr); 149.4 (CHAr);
178.1 (CN2).
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Polymerization of isoprene (general procedure). Complex 2
(28.13 mg, 0.039 mmol) and borate (B(C6F5)3, [HNEt2]ꢀ
[B(C6H5)4], or [CPh3][B(C6F5)4] (0.039 mmol) were dissolved
in toluene (5 mL). A solution of AlR3 (R = Bui, Et) (1.1 mL,
1.76 mol L–1, 1.9 mmol) in hexane and isoprene (0.98 mL, 0.66 g,
9.7 mmol) were added to the obtained solution. After stirring for
24 h at room temperature, ethanol (10 mL) was added to the
reaction mixture, the solvent was removed, and the residue was
dried in vacuo at room temperature. The NMR analysis of the
residue showed than the substance contained no isoprene.
Xꢀray diffraction experiment. Xꢀray diffraction studied for
compounds 1 and 2 were carried out on Bruker Smart Apex
(for 1, graphite monochromator,  scan mode, МоꢀК radiaꢀ
tion,  = 0.71073 Å) and Agilent Xcalibur E (for 2, graphite
monochromator,  scan mode, МоꢀК radiation,  = 0.71073 Å)
diffractometer. The structures were solved by a direct method
and refined by least squares for F2hkl in the anisotropic approxiꢀ
mation for all nonꢀhydrogen atoms. All hydrogen atoms in comꢀ
pounds 1 (except H(2)) and 2 were placed in geometrically calꢀ
culated positions and isotropically refined in the riding model.
The Н(2) atom was found from the difference electron density
synthesis and refined isotropically. The calculations were perꢀ
formed using the SHELXTL28 (1) and CrysAlis Pro29 (2) proꢀ
gram packages. The SADABS30 (1) and ABSPACK29 (CrysAlis
Pro) (2) programs were used to apply absorption corrections.
The crystallogrpahic data and parameters of Xꢀray diffraction
experiments and refinement for the synthesized compounds are
given in Table 2.
This work was financially supported by the Russian
Foundation for Basic Research (Project Nos 11ꢀ03ꢀ00555ꢀa,
12ꢀ03ꢀ31865ꢀmolꢀa, and 14ꢀ03ꢀ31039ꢀmol_a), the Minꢀ
istry of Education and Science of the Russian Federation
(Project No. 8445), and the Russian Academy of Sciences
(Programs of the Presidium of the Russian Academy of
Received May 21, 2013;
in revised form May 29, 2013