Zinc complexes with the chelating amido-imino ligand [1-n-butyl-2-(2,6- diisopropylphenyl)iminoacenaphthen-1-yl]-2,6-diisopropylphenylamide (l): Synthesis, molecular structure and reactivity of [(L)ZnCl]2, (L)Zn-nBu and (L)ZnN(SiMe3)

Article abstract of DOI:10.1002/ejic.200700796

Dimeric [(L)ZnCl]₂ (4) {L = [1-n-butyl-2-(2,6-diisopropylphenyl) iminoacenaphthen-1-yl]-2,6-diisopropylphenylamide} was prepared by treatment of the lithium salt of the ligand (LLi) with equimolar amounts of anhydrous ZnCl₂. Treatmen

Full text of DOI:10.1002/ejic.200700796

FULL PAPER
DOI: 10.1002/ejic.200700796
Zinc Complexes with the Chelating Amido-Imino Ligand [1-n-Butyl-2-(2,6-
diisopropylphenyl)iminoacenaphthen-1-yl]-2,6-diisopropylphenylamide (L):
Synthesis, Molecular Structure and Reactivity of [(L)ZnCl]2, (L)Zn-nBu and
(L)ZnN(SiMe3)2
Igor L. Fedushkin,*[a] Alexandra N. Tishkina,[a] Georgii K. Fukin,[a] Markus Hummert,[b]
and Herbert Schumann[b]
Keywords: Zinc / N ligands / Structure elucidation
Dimeric [(L)ZnCl]2 (4) {L = [1-n-butyl-2-(2,6-diisopropyl-
phenyl)iminoacenaphthen-1-yl]-2,6-diisopropylphenyl-
amide} was prepared by treatment of the lithium salt of the
ligand (LLi) with equimolar amounts of anhydrous ZnCl2.
Treatment of 4 with KN(SiMe3)2 affords the bis(trimethyl-
silyl)amido compound (L)ZnN(SiMe3)2 (5). The alkylzinc
complex (L)Zn-nBu (6) is the product of the reaction between
the adduct LLi·nBuLi (3) and ZnCl2. Compounds 4–6 were
X-ray analysis. In the solid state, the molecules of 4 exist as
centrosymmetric, heterochiral dimers bridged by chlorine
atoms, while compound 6 consists of monomeric molecules
with three-coordinate zinc atoms. The reactions of 6 with
tert-butanol, adamanthanol, 2,5-di-tert-butylaniline and di-
phenylacetonitrile do not proceed with alkane elimination
but with protonation of the ligand affording the amino-imine
LH (7).
1
characterized by H NMR and IR spectroscopy. The molecu-
lar structures of 4 and 6 were determined by single-crystal
(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim,
Germany, 2008)
Introduction
With regard to their chemical behaviour, organozinc
compounds resemble organomagnesium and organolithium
compounds, but in their addition reactions they are less re-
active.[1] Their lower reactivity towards several functional
groups of the respective organic reactants allows the prepa-
ration of organozinc compounds that are successfully used
in Pd-catalyzed organic cross-coupling reactions.[2,3] A fur-
ther synthetic application of zinc organyls is the Noyori ad-
dition of R2Zn compounds to aldehydes mediated by chiral
organozinc alcoholates, for example by (DAIB)ZnR. This
approach provides a highly enantioselective synthesis of
chiral secondary alcohols.[4]
zinc catalysts used for the polymerization of lactides are
achiral. With regard to this it is worth noting that so far no
chiral organozinc derivative has been employed for hydro-
amination reactions.
Recently we reported that the reaction between nBuLi
and 1,2-bis[(2,6-diisopropylphenyl)imino]acenaphthene (1,
dpp-bian) in diethyl ether produces the lithium salt of the
asymmetrically chelating, chiral amido-imino ligand 2.
When the reaction is conducted with the twofold molar
amount of nBuLi and in the noncoordinating solvent
hexane the 1:1 adduct (3) of 2 and nBuLi is formed
(Scheme 1).[7]
Over the last few years, monoalkylzinc compounds sup-
ported by bi- and tri-dentate N ligands have also been
shown to be effective as catalysts for the intramolecular hy-
droamination of amino olefins[5] and as syntons for the
ring-opening polymerization of lactides.[6] Except for [(Ϯ)-
[6g]
trans-Cy(NHSiMe3)(NSiMe3)]2Zn2Et2
all other organo-
Compound 2 also reacts with GeCl2 affording the mono-
meric, three-coordinate germanium(II) compound (L)-
GeCl.[7] As with nBuLi, the Grignard reagent EtMgBr adds
to the C=N bond of 1 producing the corresponding C-eth-
ylated magnesium product.[8]
Van Koten and coworkers have shown that the reactions
of (2,6-iPr2C6H3)N=CH-CH=N(2,6-iPr2C6H3) (DAB) with
dialkylzinc compounds ZnR2 containing primary or sec-
[a] G. A. Razuvaev Institute of Organometallic Chemistry of Rus-
sian Academy of Sciences,
Tropinina 49, 603950 Nizhny Novgorod, GSP-445, Russia
Fax: +7-831-4627497
E-mail: igorfed@iomc.ras.ru
[b] Institut für Chemie der Technischen Universität Berlin,
Straße des 17. Juni 135, 10623 Berlin, Germany
Fax: +49-30-31422168
E-mail: schumann@chem.tu-berlin.de
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FULL PAPER
Scheme 1.
Scheme 3.
ondary alkyl groups (R = nPr, nBu, Np, Bn, sBu) give C-
alkylated products that are formed from the initial addition
product by a subsequent hydrogen shift from the alkylated
carbon to the neighbouring imine carbon atom (Scheme 2).
This hydrogen transfer is combined with the loss of chirality
of the amido-imino chelating ligand.[9]
Treatment of 4 with KN(SiMe3)2 gives the monomeric
bis(trimethylsilyl)amidozinc complex 5, which can be iso-
lated from hexane as brown crystals in 53% yield. Despite
the poor quality of the X-ray data obtained for 5, the ar-
rangement of the atoms within the molecule could be deter-
mined. It corresponds with the picture shown in Scheme 3.
The alkylzinc derivative (L)Zn-nBu (6) is the product of
the salt elimination reaction between adduct 3 and anhy-
drous zinc dichloride in diethyl ether (Scheme 4). The ad-
duct 3 precipitates when dpp-bian is reacted with a twofold
molar amount of nBuLi in hexane. The subsequent dissol-
ution of the decanted 3 in diethyl ether may probably cause
its splitting into 2 and nBuLi, but, in any case, an exact
stoichiometry of the reactants is ensured. Compound 6
crystallizes from hexane as red-orange crystalline needles in
61% yield.
Scheme 2.
In contrast to the alkylated DAB ligands, the ligand sys-
tems formed by the addition of nBuLi or EtMgBr to 1 are
far less labile due firstly to the absence of hydrogen at the
respective imino-carbon atom and secondly to the fact that
this imino-carbon atom is part of the conformationally ri-
gid cyclic-carbon skeleton.
The reason for our investigations on zinc compounds
supported by chelating amido-imino ligands was the
suggestion that these compounds might be promising cata-
lysts for both olefin hydroamination and lactide polymeri-
zation. In this paper we report on the synthesis, the spectro- Scheme 4.
scopic and chemical properties, and the molecular structure
of zinc complexes supported by the amido-imino ligand L.
Molecular Structures of Compounds 4 and 6
The molecular structures of 4 and 6 are depicted in Fig-
ures 1 and 2, respectively. Each of the two butyl groups in
6 is disordered with regard to two positions. Since there are
no significant differences in the geometry of these groups
only one orientation of each alkyl chain is shown in Fig-
ure 2. The crystal data and structure refinement details for
Results and Discussion
Synthesis of [(L)ZnCl]2 (4), (L)ZnN(SiMe3)2 (5) and
(L)Zn-nBu (6) {L = [1-n-Butyl-2-(2,6-diisopropylphenyl)-
iminoacenaphthen-1-yl]-2,6-diisopropylphenylamide}
Dimeric [(L)ZnCl]2 (4) is formed by lithium chloride eli- 4 and 6 are given in Table 1, selective bond lengths and
mination from an equimolar mixture of anhydrous zinc di- angles are listed in Table 2.
chloride and the lithium derivative 2 formed by the addition
The molecular structure of 4 shows centrosymmetric,
of nBuLi to dpp-bian (1) in diethyl ether. Crystallization heterochiral, dimeric molecules (Z = 2) formed by two
from toluene affords red, prismatic crystals of 4 in 70% bridging chlorine atoms. Recently, we published the molec-
yield (Scheme 3).
ular structure of the corresponding heterochiral magnesium
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Zinc Complexes with Chelating Amido-Imino Ligand
Figure 1. Molecular structure of 4. The hydrogen atoms are omitted for clarity. Thermal ellipsoids are drawn at the 50% probability
level.
flects the coordinative character of the Zn(1)–Cl(1a) bond.
In contrast to compound 4, molecule 6 represents a three-
coordinate monomeric alkylzinc derivative. Although the
bond angles N(1)–Zn(1)–N(2) [83.3(1)°], N(2)–Zn(1)–C(41)
[119.4(3)°] and N(1)–Zn(1)–C(41) [153.9(3)°] in 6 vary sig-
nificantly, the sum of the angles (357°) indicates a trigonal-
planar environment of the zinc atom. The length of the Zn–
C(nBu) bond [2.006(10) Å] compares well with those in
[nBuZnP(SiMe3)2]3 [2.035(13), 2.022(16) Å].[12]
The amido-imino character of the chelating N,N-ligand
in 4 and 6 becomes apparent from the bond length within
the fragments N(1)–C(1)–C(2)–N(2) as well as from the
zinc–nitrogen bond lengths. The C(1)–N(1) bond lengths in
4 [1.458(1) Å] and 6 [1.472(5) Å] correspond well with the
value of carbon–nitrogen single bonds [1.472(5) Å][13] and
are significantly longer than the respective C(2)–N(2) bond
lengths [4: 1.283(1); 6: 1.286(4) Å], which are in the range
of the lengths of the C=N double bonds in 1 [both
1.282(4) Å].[14] Because of the different functionality of the
nitrogen atoms of the N,N-ligand, the distances of N(1)–
Figure 2. Molecular structure of 6. The hydrogen atoms are omit-
Zn(1) [4: 1.897(1); 6: 1.875(3) Å] are much shorter than
ted for clarity. Thermal ellipsoids are drawn at the 30% probability
those of N(2)–Zn(1) [4: 2.107(1); 6: 2.179(3) Å].
level.
Up to now, only three alkylzinc derivatives supported by
amido-imino ligands have been characterized by X-ray crys-
tallography: A,[15] B[5a] and C.[16]
dimer [(LЈ)MgCl]2 {LЈ = [1-(4-trimethylsiloxybutyl)-2-(2,6-
diisopropylphenyl)iminoacenaphthen-1-yl]-2,6-diisopropyl-
phenylamide} also containing a C-alkylated dpp-bian li-
gand.[10] The formation and stability of homo- and hetero-
chiral dimers of methylzinc alkoxides has been studied in
detail by Noyori and coworkers.[11] They found that in solu-
tion as well as in the solid state, the heterochiral dimers are
more stable than the homochiral isomers. The zinc atoms in
4 show a distorted tetrahedral coordination. The significant
difference in the length of the metal–halide distances
The structural parameters of 6 can be compared with
[Zn(1)–Cl(1) 2.2880(4) and Zn(1)–Cl(1a) 2.4012(4) Å] re- those of the three-coordinate Zn species A and B. In the
Eur. J. Inorg. Chem. 2008, 483–489
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485

I. L. Fedushkin et al.
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Table 1. Crystal data and structure refinement details for 4 and 6.
4
6
Empirical formula
Mr [gmol–1]
Temperature [K]
Wavelength [Å]
Crystal system
Space group
a [Å]
b [Å]
c [Å]
α [°]
β [°]
C40H49ClN2Zn·C7H8
750.77
100(2)
C44H58N2Zn
680.29
150(2)
0.71073
0.71073
triclinic
triclinic
¯
¯
P1
P1
10.170(5)
12.554(6)
16.892(8)
85.800(10)
81.687(10)
74.426(10)
2054.3(17)
2
10.200(5)
11.766(5)
17.028 (5)
85.709(5)
73.545(5)
79.197(5)
1924.6(14)
2
γ [°]
Volume [Å3]
Z
ρcalcd [gcm–3]
1.214
0.696
1.174
0.669
µ [mm–1]
F(000)
Crystal size [mm]
θmin/θmax
800
732
0.25ϫ0.22ϫ0.14
1.69 to 30.07
–13ՅhՅ12
–13ՅkՅ17
–23ՅlՅ23
15564
0.21ϫ0.15ϫ0.10
2.98 to 27.49
–12ՅhՅ12
–13ՅkՅ15
–22ՅlՅ19
14390
Index ranges
Reflections collected
Independent reflections
Rint
10897
0.0146
7342
0.0350
Absorption correction
Max./min. transmission
Refinement method
Data/restraints/parameters
GOF on F2
Final R indices [IϾ2σ(I)]
R indices (all data)
Largest diff. peak/hole [eÅ–3]
empirical
empirical
0.9361/0.8722
0.9088/0.8451
full-matrix least-squares on F2
10897/0/656
1.033
R1 = 0.0372, wR2 = 0.0946
R1 = 0.0450, wR2 = 0.0995
0.851 and –0.297
full-matrix least-squares on F2
7342/20/510
1.158
R1 = 0.0594, wR2 = 0.1534
R1 = 0.1032, wR2 = 0.1716
0.509 and –0.714
Table 2. Selected bond lengths [Å] and angles [°] for 4 and 6.
both N atoms. Although the difference between the Zn–
N distances in the pyrrolylaldimine derivative A is larger
[1.996(5) and 2.089(7) Å] than it is in B, it is less pro-
nounced than in 6 [1.875(3) and 2.179(3) Å]. To sum up it
can be established that with the increase in the average
value of the Zn–N bond lengths on going from B (1.967 Å)
to A (2.043 Å) and 6 (2.027 Å) the Zn–C(alkyl) bond
lengths increase in the same order [B 1.941(5), A 1.990(6),
6 2.006(10) Å].
4
6
C(1)–N(1)
C(2)–N(2)
C(1)–C(2)
C(1)–C(37)
1.4583(18)
1.2833(18)
1.5470(19)
1.562(2)
1.472(5)
1.286(4)
1.536(5)
1.63(3)
Zn(1)–N(1)
Zn(1)–N(2)
Zn(1)–C(41)
1.8969(12)
2.1070(12)
1.875(3)
2.179(3)
2.006(10)
Zn(1)–Cl(1)
Zn(1)–Cl(1a)
2.2880(4)
2.4012(4)
106.76(11)
118.87(12)
112.00(11)
108.39(12)
109.37(9)
107.09(9)
84.63(5)
N(1)–C(1)–C(2)
N(2)–C(2)–C(1)
N(1)–C(1)–C(37)
C(2)–C(1)–C(37)
C(1)–N(1)–Zn(1)
C(2)–N(2)–Zn(1)
N(1)–Zn(1)–N(2)
N(1)–Zn(1)–C(41)
N(2)–Zn(1)–C(41)
N(1)–Zn(1)–Cl(1)
N(1)–Zn(1)–Cl(1a)
N(2)–Zn(1)–Cl(1)
N(2)–Zn(1)–Cl(1a)
Cl(1)–Zn(1)–Cl(1a)
108.0(3)
118.3(3)
104.5(12)
110.6(13)
113.9(2)
107.6(2)
83.33(13)
153.9(3)
119.4(3)
1H NMR Spectroscopy of 4–6
1
Selected H NMR spectroscopic data of the compounds
4, 5 and 6 are presented in Table 3. The asymmetry of the
amido-imino ligand of compounds 4–6 causes nonequiva-
lence of all aromatic protons as well as of the four methine
protons and the eight methyl groups of the iPr substituents.
In the spectrum of each compound, the methyl groups
give rise to the appearance of eight doublets in the range δ
= 2 to 0 ppm and the methine protons give rise to four
septets in the range δ = 4.8 to 2.6 ppm. The methine proton
region in the spectrum of 6 is shown in Figure 3.
127.30(4)
125.91(4)
122.92(3)
106.08(4)
91.385(14)
The presence of the chiral atom C(1) (see Figures 1 and
troponiminate derivative B the Zn–N bond lengths are al- 2) next to the α-CH2 group of the ligand-bonded butyl sub-
most equal [1.980(4) and 1.955(4) Å] due to the delocaliza- stituent causes the nonequivalence of these two methylene
tion of the π electrons over the seven-membered ring and protons and the appearance of two triplets of doublets in
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Zinc Complexes with Chelating Amido-Imino Ligand
1
Figure 3. Part of the H NMR spectrum of 6 ([D8]THF, 200 MHz, 20 °C).
1
Table 3. Selected H NMR chemical shifts (δ values, ppm) for 4–6
Conclusions
([D8]THF, 200 MHz).
The complexes 4–6 are the first zinc chelates containing
a chiral amido-imino ligand. They are prepared by simple
salt elimination reactions from the lithium salt of the li-
gand, which in turn can be generated in situ from 1,2-
bis[(2,6-diisopropylphenyl)imino]acenaphthene (1: dpp-
bian) and nBuLi. Unexpectedly, the nucleophilicity of the
nBuZn group in the derivative 6 turned out to be lower than
that of the amido ligand. The cancellation of the steric
stress within the Zn-metallacycle may be a preliminary ex-
planation of this fact.
4
5
6
(CH3)2HC–Ar
4.77
3.38
3.13
2.68
2.48
2.34
4.58
3.25
3.16
2.66
2.79
2.25
4.60
3.30
3.04
2.79
2.57
2.15
CH3(CH2)2CH2–C*
the range δ = 3 to 2 ppm (Table 3). The shift difference of
the two diastereotopic protons increase on going from 4
containing four-coordinate zinc to 5 and 6 containing three-
coordinate zinc (28, 108, and 84 Hz, respectively). For com-
parison, in the three-coordinate germylene compound (L)-
GeCl, having the same C-alkylated amido-imino ligand,
this difference is much larger (300 Hz) and reflects the pres-
ence of not only the chiral C(1) but also the chiral Ge atom.
In the spectrum of 6 recorded in [D8]THF, the resonance
of the protons of the α-CH2(nBu) group bonded to the zinc
atom appears as a triplet at δ = 0.47 ppm, whereas the spec-
trum recorded in C6D6 shows no signal attributable to these
protons. A definite detection of this signal is very difficult
because of the overlap of numerous resonances in the range
1.8–0.8 ppm. In the 1H NMR spectrum of nBu2Zn recorded
in C6D6 the respective signal appears at δ = 0.40 ppm.[17]
Experimental Section
General Remarks: All manipulations were carried out in vacuo
using Schlenk techniques. Hexane, diethyl ether and toluene were
dried by distillation from sodium/benzophenone. The diimine 1 was
prepared by condensation of acenaphthenequinone (Aldrich) with
2,6-diisopropylphenylaniline (Aldrich) in CH3CN. The solvents
C4D8O (Aldrich) and C6D6 (Aldrich), used for the NMR spectro-
scopic experiments, were dried with sodium/benzophenone at am-
bient temperature and were, just prior to use, condensed under vac-
uum into the NMR tubes already containing the respective com-
pound. Melting points were measured in sealed capillaries. IR spec-
1
tra were recorded with an FTIR FSM-1201 spectrometer, and H
NMR spectra were obtained using a Bruker DPX-200 spectrome-
ter. Complexes 2 and 3 were prepared by literature procedures[7]
and used in situ.
Reactivity of 6 Towards Some Organic Substances
[(L)ZnCl]2 (4): A solution of nBuLi in hexane (2.74 , 0.8 mL,
2 mmol) was added to a suspension of 1 (1.00 g, 2 mmol) in Et2O
(20 mL) while stirring. The mixture instantly changed colour from
orange to blue. ZnCl2 (0.27 g, 2 mmol) was then added and the
reaction mixture was stirred at 40 °C for 30 min. Within this time
the solution turned red. Evaporation of the solvent and treatment
of the residue with toluene (15 mL) caused the precipitation of LiCl
formed in the reaction, which was filtered off. Compound 4 (0.92 g,
70%) separated as red crystals from the concentrated clear toluene
solution, m.p. 101 °C (dec.). C80H98Cl2N4Zn2·2C7H8 (1501.57):
In order to synthesize new alkoxy and amido zinc com-
plexes with the alkylated amido-imino ligand L, we treated
compound 6 with tert-butanol, adamanthanol, 2,5-di-tert-
butylaniline and diphenylacetonitrile. In contrast to our ex-
pectations, the reactions of 6 with these substrates do not
proceed with elimination of butane, but with protonation
of the ligand yielding the amino-imine LH (7) (Scheme 5).[7]
calcd. C 75.12, H 7.59; found C 74.96, H 7.35. IR (Nujol): ν =
˜
2723 (w), 1940 (w), 1630 (vs), 1590 (m), 1494 (m), 1431 (vs), 1360
(s), 1347 (w), 1316 (s), 1257 (s), 1205 (m), 1192 (m), 1176 (m), 1160
(w), 1140 (w), 1101 (m), 1081 (w), 1059 (s), 1029 (s), 1007 (w), 995
(w), 963 (w), 934 (w), 917 (m), 860 (m), 833 (m), 804 (s), 783 (vs),
755 (vs), 728 (vs), 693 (m) cm–1. 1H NMR (200 MHz, [D8]THF,
20 °C): δ = 7.96 (d, J = 8.0 Hz, 1 H, CH arom.), 7.65 (d, J =
8.3 Hz, 1 H, CH arom.), 7.43–7.06 (m, 6 H, CH arom.), 6.95 (d, J
= 7.5 Hz, 1 H, CH arom.), 6.78 (dd, J = 7.5, J = 1.5 Hz, 1 H, CH
arom.), 6.42 (d, J = 7.0 Hz, 1 H, CH arom.), 6.17 (d, J = 7.0 Hz,
1 H, CH arom.), 4.77 [sept, J = 7.0 Hz, 1 H, CH(CH3)2], 3.38 [sept,
J = 6.8 Hz, 1 H, CH(CH3)2], 3.13 [sept, J = 6.8 Hz, 1 H, CH-
Scheme 5.
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487

I. L. Fedushkin et al.
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(CH3)2], 2.55–2.27 [m, 2 H, CH2(CH2)2CH3], 2.68 [sept, J = 6.8 Hz,
1 H, CH(CH3)2], 1.46 [d, J = 7.0 Hz, 3 H, CH(CH3)CH3], 1.35 [d, J
= 7.0 Hz, 3 H, CH(CH3)CH3] ppm. 13C NMR (50 MHz, C4D8O,
20 °C): δ = 192.8, 150.9, 148.3, 148.2, 143.8, 142.8, 139.9, 138.7,
= 6.8 Hz, 3 H, CH(CH3)CH3], 1.26 [d, J = 6.8 Hz, 3 H, CH(CH3)- 131.8, 130.2, 128.8, 127.9, 127.0, 125.4, 124.5, 124.4, 124.1, 123.5,
CH3], 1.23 [d, J = 7.0 Hz, 3 H, CH(CH3)CH3], 1.15 [d, J = 6.8 Hz,
3 H, CH(CH3)CH3], 0.85 [d, J = 6.8 Hz, 3 H, CH(CH3)CH3], 0.62
[d, J = 6.8 Hz, 3 H, CH(CH3)CH3], –0.21 [d, J = 6.8 Hz, 3 H,
CH(CH3)CH3] ppm.
122.7, 79.3, 68.1, 67.7, 66.8, 52.7, 30.8, 30.3, 30.0, 29.3, 29.0, 28.8,
28.1, 26.3, 26.0, 25.6, 25.2, 24.8, 24.6, 24.4, 24.2, 23.9, 20.3, 14.1,
13.9, 8.9 ppm.
Single Crystal X-ray Structure Determination of 4 and 6: The data
of 4 were collected with a Siemens SMART CCD diffractometer
(graphite-monochromated Mo-Kα radiation, ω-scan technique, λ =
0.71073 Å) at 100 K. The data of 6 were collected using an Xcali-
bur S Sapphire diffractometer (Oxford Diffraction) at 150 K. The
structures of 4 and 6 were solved by direct methods using the
SHELXS-97[18] and SIR-2004 programs,[19] respectively, and were
[(L)ZnN(SiMe3)2] (5): A solution of nBuLi in hexane (2.74 ,
0.8 mL, 2 mmol) was added to a suspension of 1 (1.00 g, 2 mmol)
in Et2O (20 mL) while stirring. The colour of the mixture instantly
changed from orange to blue. After addition of ZnCl2 (0.27 g,
2 mmol) the mixture was stirred at 40 °C for 30 min. The precipi-
tated LiCl was then filtered off. A solution of KN(SiMe3)2 (0.4 g,
2 mmol) in Et2O (10 mL) was added to the remaining clear solution
of 4 that was formed in this reaction, and the mixture was stirred
for a few minutes. After evaporation of the solvent in vacuo and
dissolution of the residue in hexane (20 mL) the mixture was heated
for 30 min at 60 °C, and then filtered off from the precipitated KCl.
Concentration of the hexane solution causes the crystallization of
compound 5 (0.76 g, 53%) as brown crystals, m.p. 173 °C. IR (Nu-
refined on F2 by
a full-matrix least-squares method using
SHELXL-97.[20] All non-hydrogen atoms were refined anisotropi-
cally. The hydrogen atoms were placed in calculated positions using
a riding model. The program SADABS[21] was used to perform
area-detector scaling and absorption corrections.
CCDC-660725 (for 4) and -660726 (for 6) contain the supplemen-
tary crystallographic data for this paper. These data can be ob-
tained free of charge from The Cambridge Crystallographic Data
Centre via www.ccdc.cam.ac.uk/data_request/cif.
jol): ν = 1639 (s), 1615 (w), 1589 (m), 1491 (w), 1463 (s), 1428 (w),
˜
1378 (w), 1363 (s), 1347 (m), 1310 (w), 1254 (m), 1243 (w), 1198
(s), 1190 (w), 1180 (w), 1138 (w), 1109 (m), 1046 (w), 1034 (m), 985
(s), 966 (w), 925 (w), 917 (w), 883 (s), 859 (w), 849 (w), 833 (m),
818 (w), 802 (w), 782 (m), 757 (m), 670 (s), 648 (w), 614 (m) cm–1.
1H NMR (200 MHz, C6D6, 20 °C): δ = 7.36–6.90 (m, 9 H, CH
arom.), 6.73 (pst, J = 8.0 Hz, 1 H, CH arom.), 6.53 (d, J = 7.0 Hz,
1 H, CH arom.), 6.33 (d, J = 6.8 Hz 1 H, CH arom), 4.75 [sept, J
= 7.0 Hz, 1 H, CH(CH3)2], 3.33 [sept, J = 6.8 Hz, 1 H, CH-
(CH3)2], 3.31 [sept, J = 6.8 Hz, 1 H, CH(CH3)2], 2.93 [td, J = 12.5,
1 H, J = 4.8 Hz, CH2(CH2)2CH3], 2.85 [sept, J = 6.8 Hz, 1 H,
CH(CH3)2], 2.41 [td, J = 12.5, 1 H, J = 3.3 Hz, CH2(CH2)2CH3],
1.61 [d, J = 7.0 Hz, 3 H, CH(CH3)CH3], 1.55 [d, J = 7.0 Hz, 3 H,
CH(CH3)CH3], 1.37 [d, J = 6.8 Hz, 3 H, CH(CH3)CH3], 1.34 [d, J
= 6.8 Hz, 3 H, CH(CH3)CH3], 1.05 [d, J = 6.8 Hz, 3 H, CH(CH3)-
CH3], 0.99 [d, J = 6.8 Hz, 3 H, CH(CH3)CH3], 0.85 [d, J = 6.8 Hz,
3 H, CH(CH3)CH3], 0.60 [t, J = 7.4 Hz, 3 H, CH2(CH2)2CH3], 0.18
[s, 18 H, Si(CH3)3], –0.13 [d, J = 6.8 Hz, 3 H, CH(CH3)CH3] ppm.
Acknowledgments
This work was supported by the Russian Foundation for Basic Re-
search (grant no. 07-03-00545 and 06-03-32728), the Alexander von
Humboldt Foundation (to I. L. F.), the Fonds der Chemischen In-
dustrie, and the Deutsche Forschungsgemeinschaft (to H. S.).
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After evaporation of the solvent in vacuo the remaining residue
was dissolved in hot hexane (25 mL). The insoluble LiCl was fil-
tered off. Compound 6 was isolated (0.58 g, 61%) as red-orange
crystalline needles from the concentrated (7 mL) hexane solution,
m.p. 154 °C. C44H58N2Zn (680.29): calcd. C 77.61, H 8.53; found
C 77.47, H 8.30. IR (Nujol): ν = 2723 (w), 1927 (w), 1638 (s), 1588
˜
(m), 1427 (s), 1361 (m), 1364 (m), 1311 (m), 1254 (s), 1204 (m),
1190 (w), 1160 (w), 1136 (w), 1104 (w), 1059 (m), 1031 (m), 833
(s), 801 (s), 778 (vs), 757 (s), 722 (m) cm–1. 1H NMR (200 MHz,
C4D8O, 20 °C): δ = 7.97 (d, J = 8.3 Hz, 1 H, CH arom.), 7.67 (d,
J = 8.3 Hz, 1 H, CH arom.), 7.44–7.22 (m, 6 H, CH arom.), 7.08
(pst, J = 7.6 Hz, 1 H, CH arom.), 6.85 (dd., J = 7.5, J = 1.5 Hz, 1
H, CH arom.), 6.51 (d, J = 7.0 Hz, 1 H, CH arom.), 6.09 (d, J =
7.0 Hz, 1 H, CH arom.), 4.60 [sept, J = 7.0 Hz, 1 H, CH(CH3)2],
3.30 [sept, J = 7.0 Hz, 1 H, CH(CH3)2], 3.04 [sept, J = 7.0 Hz, 1
H, CH(CH3)2], 2.79 [sept, J = 7.0 Hz, 1 H, CH(CH3)2], 2.57 [td, J
= 12.8, J = 4.8 Hz, 1 H, CH2(CH2)2CH3], 2.15 [td, J = 12.8, J =
3.5 Hz, 1 H, CH2(CH2)2CH3], 1.49 [d, J = 7.0 Hz, 3 H, CH(CH3)-
CH3], 1.37 [d, J = 7.0 Hz, 3 H, CH(CH3)CH3], 1.25–1.09 [m, 9 H,
CH(CH3)CH3], 0.80 [d, J = 7.0 Hz, 3 H, CH(CH3)CH3], 0.69 [d, J
= 7.0 Hz, 3 H, CH(CH3)CH3], 0.69 [t, J = 7.3 Hz, 3 H, CH2-
(CH2)2CH3], 0.47 [t, J = 7.7 Hz, 2 H, CH2(CH2)2CH3], 0.03 [d, J
488
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© 2008 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
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Published Online: November 23, 2007
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