Lithium and zinc complexes of C- and N-functionalized (2-pyridylmethyl) amines

Article abstract of DOI:10.1002/ejic.200701168

The addition reaction of benzophenone with lithium (2-pyridylmethyl)(tert- butyldimethylsilyl)amide yields dimeric 1-lithoxy-1,1-diphenyl-2-(2-pyridyl)-2- (trialkylsilylamino)ethane (1) with formation of a C-C bond. C-Functionalized 2-(pyridylmethyl)amines are accessible via the reaction of N-(2- pyridylmethylidene)phenylamine with diethylmalonate giving 2,2- bis(ethoxycarbonyl)-1-(phenylamino)-1-(2-pyridyl) ethane (2) which eliminates aniline upon heating yielding diethyl 2-(2-pyridylmethylidene)malonate (3). The addition of piperidine leads to the formation of the Michael type adduct 2,2-bis(ethoxycarbonyl)-1-piperidyl-1-(2-pyridyl)-ethane (4) which can be deprotonated with metal-organic reagents such as Zn[N(SiMe₃) ₂]₂, Zn[CH(SiMe₃)₂]₂, LiN-(SiMe₃)₂, and NaN(SiMe3)2 leading to 2,2-bis(ethoxycarbonyl)-1-piperidyl-1-(2-pyridyl)ethane-2-yl complexes of zinc (5 and 6), lithium (7), and sodium (8). N-Functionalization can be achieved via the reaction of (2-pyridylmethyl)(trialkylsilyl) amine with benzoyl chloride giving N-(2-pyridylmethyl) benzoylamine (9). Lithiation and subsequent salt metathesis reaction with another equivalent of benzoyl chloride yields N-(2-pyridylmethyl)dibenzoylamine (10). The addition reaction of ZnCl ₂ with N-(2-pyridylmethyl)(diphenylmethylidene) amine (11) forms colorless crystalline [(Py-CH₂N=CPh₂)ZnCl₂] (12). The addition of benzoyl chloride leads to N-(diphenylchloromethyl)-N-(2- pyridylmethyl)benzoylamine (13). Addition of ZnCl₂ leads to the formation of solvent-separated [(2-pyridylmethyl)(benzoylamino) diphenylcarbonium] [(tetrahydrofuran)trichlorozincate] (14). The X-ray crystal structures of 1, 4 to 7, 9, 12, and 14 are discussed. Wiley-VCH Verlag GmbH & Co. KGaA, 2008.

Full text of DOI:10.1002/ejic.200701168

FULL PAPER
DOI: 10.1002/ejic.200701168
Lithium and Zinc Complexes of C- and N-Functionalized (2-Pyridylmethyl)amines
Christian Koch,[a] Marcel Kahnes,[a] Martin Schulz,[a] Helmar Görls,[a] and
Matthias Westerhausen*[a]
Keywords: Lithium / Zinc / Amines / Diketonates
The addition reaction of benzophenone with lithium (2-pyr-
tion can be achieved via the reaction of (2-pyridylmethyl)(tri-
idylmethyl)(tert-butyldimethylsilyl)amide yields dimeric alkylsilyl)amine with benzoyl chloride giving N-(2-pyr-
1-lithoxy-1,1-diphenyl-2-(2-pyridyl)-2-(trialkylsilylamino)eth- idylmethyl)benzoylamine (9). Lithiation and subsequent salt
ane (1) with formation of a C–C bond. C-Functionalized 2-
(pyridylmethyl)amines are accessible via the reaction of N-
(2-pyridylmethylidene)phenylamine with diethylmalonate
metathesis reaction with another equivalent of benzoyl chlo-
ride yields N-(2-pyridylmethyl)dibenzoylamine (10). The ad-
dition reaction of ZnCl2 with N-(2-pyridylmethyl)(diphenyl-
giving
2,2-bis(ethoxycarbonyl)-1-(phenylamino)-1-(2-pyr- methylidene)amine (11) forms colorless crystalline [(Py–
idyl)ethane (2) which eliminates aniline upon heating yield-
ing diethyl 2-(2-pyridylmethylidene)malonate (3). The ad-
dition of piperidine leads to the formation of the Michael type
CH2N=CPh2)ZnCl2] (12). The addition of benzoyl chloride
leads to N-(diphenylchloromethyl)-N-(2-pyridylmethyl)ben-
zoylamine (13). Addition of ZnCl2 leads to the formation of
solvent-separated [(2-pyridylmethyl)(benzoylamino)diphen-
ylcarbonium] [(tetrahydrofuran)trichlorozincate] (14). The X-
ray crystal structures of 1, 4 to 7, 9, 12, and 14 are discussed.
adduct
2,2-bis(ethoxycarbonyl)-1-piperidyl-1-(2-pyridyl)-
ethane (4) which can be deprotonated with metal-organic
reagents such as Zn[N(SiMe3)2]2, Zn[CH(SiMe3)2]2, LiN-
(SiMe3)2, and NaN(SiMe3)2 leading to 2,2-bis(ethoxycar-
bonyl)-1-piperidyl-1-(2-pyridyl)ethane-2-yl complexes of
zinc (5 and 6), lithium (7), and sodium (8). N-Functionaliza-
(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim,
Germany, 2008)
Introduction
(2-Pyridylmethyl)amine and the substitution products
represent a ligand of great interest due to the enormous
biomimetic potential.[1,2] Therefore, the coordination be-
haviour of neutral (2-pyridylmethyl)amine towards zinc was
extensively explored. This amino base acts as a bidentate
ligand at zinc(II) cations, counterions being halide or pseu-
dohalide anions.[3–9] Dialkylzinc deprotonates Py–CH2–
NH2 at room temperature once and alkylzinc (2-pyr-
idylmethyl)amide is formed quantitatively.[10] At elevated
temperatures a second metallation step occurs and unintel-
ligible reaction steps and degradation reactions follow.
Therefore the amino group has to be protected which can
easily be done by substitution of one H atom by a trialkyl-
silyl group according to Equation (1). Zincation of these
(2-pyridylmethyl)(trialkylsilyl)amines yields the corres-
ponding dimeric alkylzinc (2-pyridylmethyl)(trialkylsilyl)-
amides.[11,12] Alkylation of (2-pyridylmethyl)amides yields
C-alkylated picolylamines A which may also contain minor
amounts of N-alkylation products B whereas phosphanyl-
ation occurs again only at the nitrogen atom [Equation
(1)].[13]
(1)
Prolonged heating of alkylzinc (2-pyridylmethyl)(trialkyl-
silyl)amides in the presence of dialkylzinc leads to an oxi-
dative C–C coupling of the picolylamides according to
Equation (2).[11,12] van Koten and co-workers[14–17] pre-
pared the di(tert-butyl)-protected 1,2-di(2-pyridyl)-1,2-di-
amidoethanes.These bis(alkylzinc) derivatives C dissociated
in solution into radicals D via a homolytic C–C bond cleav-
age as shown in Equation (2). In the solid state only the
dimer C was observed, however, the C–C bond length of
the ethane backbone was extremely large. Protolysis of C
(R as trialkylsilyl) with acetamide yields 1,2-dipyridyl-1,2-
diaminoethane E[18] which can be again metallated with or-
ganometallic compounds.
[a] Institut für Anorganische und Analytische Chemie, Friedrich-
Schiller-Universität Jena,
August-Bebel-Str. 2, 07743 Jena, Germany
Fax: +49-03641-9-48102
E-mail: m.we@uni-jena.de
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C. Koch, M. Kahnes, M. Schulz, H. Görls, M. Westerhausen
FULL PAPER
Results and Discussion
Synthesis
In order to obtain multi-dentate bases with an unsym-
metric coordination sphere other reaction cascades were ex-
plored. C-Substitution of (2-pyridylmethyl)amine can be
achieved by reaction of (2-pyridylmethyl)(trialkylsilyl)-
amine with n-butyllithium giving [lithium (2-pyridylmeth-
yl)(trialkylsilyl)amide][21] and thereafter with benzophenone
yielding dimeric 1-lithoxy-1,1-diphenyl-2-(2-pyridyl)-2-(tri-
alkylsilylamino)ethane (1) according to Equation (5). This
compound is also accessible by reaction of doubly lithiated
(2-pyridylmethyl)(trialkylsilyl)amine[21] with benzophenone
and subsequent partial hydrolysis.[22] The solid-state struc-
ture of 1 was determined in order to clarify the coordina-
tion behaviour of this tridentate ligand.
(2)
This oxidative C–C coupling of N-(trialkylsilyl)-pro-
tected picolylamines leads to C2-symmetric complexes C.
Another pathway offers the reductive C–C coupling of im-
ines with metals (such as Zn/Me3SiCl, Mg/Me3SiCl, Al or
Bi) to the 1,2-diaminoethanes F according to Equation (3),
however, also minor amounts of reduction products, amines
G, are formed occasionally.[19,20]
(5)
The base-catalyzed (e.g. piperidine) reaction of (2-pyr-
idylmethylidene)(phenyl)amine with diethyl malonate yields
2,2-bis(ethoxycarbonyl)-1-(phenylamino)-1-(2-pyridyl)-
ethane (2) according to a known procedure.[23] Compound
2 eliminates aniline upon heating to give the deamination
product diethyl 2-(2-pyridylmethylidene)malonate (3). The
use of N-(2-pyridylmethylidene)methylamine in this reac-
tion leads to the formation of 3 without the observation of
intermediate 2. Very recently, 3 was also obtained in 1-bu-
tyl-3-methylimidazolium hydroxide [bmim]OH which func-
tions as a solvent as well as a catalyst for the Knoevenagel
condensation.[24] Bromomalonic esters also proved to be
suitable starting materials in order to prepare 3.[25,26] The
addition of piperidine to compound 3 yields the Michael
type adduct 2,2-bis(ethoxycarbonyl)-1-piperidyl-1-(2-pyr-
idyl)ethane (4). This reaction sequence is shown in Equa-
tion (6). Similar procedures, namely the addition of dieth-
ylamine to diethyl [(3-nitro-2-pyridyl)methylidene]malon-
ate[27] as well as of piperidine to diethyl 2-(2-nitrobenzyl-
idene)malonate,[28] were reported by Kinastowski, Wnuk
and others. Compound 4 is also accessible via the reaction
of pyridine-2-carbaldehyde with diethyl malonate in the
presence of a stoichiometric amount of piperidine.
(3)
Metal complexes C with 1,2-dipyridyl-1,2-diamido li-
gands contain a folded M2N2 ring which leads to very small
M···M contacts giving rise to an unusual chemistry as dis-
played in Equation (4). Whereas acetamide yields the proto-
lysis product E, aniline gives rise to substitution product
H.[18] Experiments with [15N]aniline show that proton-
transfer reactions lead to this unusual reaction behaviour
and that not only the trialkylsilyl groups are replaced by
phenyl substituents but the NSiR3 units against NPh moie-
ties.
Compound 4 shows no keto-enol tautomerism in the
NMR experiments [Equation (7)]. Furthermore, no H/D
exchange is observed after addition of [D4]methanol to
solutions of 4. Nevertheless, this derivative is easily depro-
tonated. The metallation of 4 with zinc bis[bis(trimethyl-
(4)
The oxidative C–C coupling of 2-pyridylmethylamines silyl)amide] gives the monomeric complex 5 with a triden-
with organometallic compounds such as dimethylzinc or tate ligand, which binds with both nitrogen atoms and one
[11,12]
Sn[N(SiMe3)2]2
as well as the reductive C–C coupling oxygen base to the cation. Alkali metal bis(trimethylsilyl)-
of imines[19,20] yield C2-symmetric chelate Lewis bases. In amides are also suitable metallation reagents. Sodium deriv-
order to develop unsymmetric tetradentate ligands which ative 8 is only sparingly soluble in common organic solvents
are able to form polynuclear complexes, other synthetic which can be understood in the sense of a mainly ionic salt-
strategies have to be applied.
like complex.
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Lithium and Zinc Amine Complexes
(6)
(7)
(8)
Table 1. Comparison of the 13C{1H} NMR shifts (δ values, ppm)
of compounds 9–14. The numbering scheme is given in Scheme 1.
N-Functionalization of (2-pyridylmethyl)amines with
moieties which contain Lewis bases with oxygen-donor
atoms is known for acylation reactions. N-acyl(2-pyr-
idylmethyl)amines are valuable ligands which were recently
investigated e.g. by Houser and co-workers.[29] The reaction
of (2-pyridylmethyl)(trialkylsilyl)amines with benzoyl chlo-
rides quantitatively yields N-(2-pyridylmethyl)benzoylamine
(9). In order to obtain a tetradentate base, a second reaction
cascade consisting of lithiation and subsequent salt metath-
esis reaction with benzoyl chloride according to Equation
(8) was applied to give N-(2-pyridylmethyl)dibenzoylamine
(10) in poor yield. This oily compound always contained
traces of 9. In order to further investigate the N-acylation
another protecting group was chosen and N-(2-pyridyl-
methyl)(diphenylmethylidene)amine (11)[30] was employed
as starting material. The coordination behaviour of this
bidentate base is comparable to (2-pyridylmethyl)amine
and addition of ZnCl2 yields colorless crystalline [(Py–
CH2N=CPh2)ZnCl2] (12). However, addition of benzoyl
chloride leads to compound 13a with the benzoyl moiety
bound again to the amine functionality according to Equa-
tion (8). Addition of ZnCl2 leads to the formation of sol-
vent-separated 14 with the [(thf)ZnCl3]– anion. The similar-
ity of the NMR spectroscopic data suggests that 13b also
might be an ion pair as displayed in Equation (8).
9
10
11
12
13
14
C1 44.7
C2 156.3
C3 122.0
C4 136.7
C5 122.3
C6 148.8
C7 167.3
C8 134.2
C9 127.0
C10 125.4
C11 131.3
C12 –
51.1
156.2
121.5
136.4
121.9
148.9
170.8/173.9
136.1
127.8/128.1
129.2/129.8
131.4/133.2
–
–
–
–
–
44.1
153.4
124.1
138.8
124.6
150.0
–
–
–
–
–
196.7
138.5
130.6
129.2
133.4
56.5
155.2
123.2
141.1
125.2
148.1
–
–
53.5
52.3
151.8
126.0
147.7
127.1
138.0
150.5
128.4
147.0
127.2
138.3
168.0
168.0
[a]
[a]
[a]
[a]
[a]
[a]
[a]
[a]
–
–
–
181.6
97.4
96.8
[a]
[a]
C13 –
C14 –
C15 –
C16 –
135.8/138.5
127.6/130.0
129.2/129.8
131.1/133.1
[a]
[a]
[a]
[a]
[a]
[a]
[a] Assignment was not possible.
The 13C{1H} NMR spectroscopic data of N-(2-pyridyl-
methyl)(diphenylmethylidene)amine and of the acylation
products are listed in Table 1. A general numbering scheme
of these compounds is shown in Scheme 1.
Scheme 1. Numbering scheme for the assignment of the NMR pa-
rameters of compounds 9–14.
Eur. J. Inorg. Chem. 2008, 1067–1077
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C. Koch, M. Kahnes, M. Schulz, H. Görls, M. Westerhausen
FULL PAPER
Molecular Structures
The molecular structure of 1-lithoxy-1,1-diphenyl-2-(2-
pyridyl)-2-(trialkylsilylamino)ethane (1) is shown in Fig-
ure 1. Atoms generated by inversion symmetry (–x + 1,
–y + 2, –z) are marked with an “A”. The atom N2 is chiral,
however, due to the inversion symmetry a racemate is ob-
tained. All three Lewis bases coordinate to the lithium atom
giving a tridentate ligand. This complex dimerizes via a
Li2O2 ring yielding a strongly distorted tetrahedral environ-
ment of the lithium atoms. Dimerization of lithium deriva-
tives via formation of Li2O2 rings is a common behaviour
for alcoholates and related compounds (e.g. ref.[31,32]). The
proton binds to the silylated amino group at N2 and shows
no involvement in any hydrogen bridges. The N2–Si bond
of 175.0(3) pm is rather long due to the tetracoordinated
nitrogen atom which prevents an effective hyperconjugation
and backdonation of charge to the trialkylsilyl group.
Figure 2. Molecular structure and numbering scheme of 1-(2-pyr-
idyl)-1-piperidyl-2,2-bis(ethoxycarbonyl)ethane (4). The ellipsoids
represent a probability of 40%, H atoms are shown with arbitrary
radii.
Figure 1. Molecular structure and numbering scheme of dimeric 1-
lithoxy-1,1-diphenyl-2-(2-pyridyl)-2-(trialkylsilylamino)ethane (1).
The ellipsoids represent a probability of 40%. Hydrogen atoms
with the exception of the NH fragment are omitted for clarity
reasons.
Figure 3. Molecular structure and numbering scheme of bis(tri-
methylsilyl)amidozinc
2,2-bis(ethoxycarbonyl)-1-piperidyl-1-(2-
pyridyl)ethan-2-ide (5). The ellipsoids represent a probability of
40%, hydrogen atoms are neglected for the sake of clarity.
The ligand shows an extremely large C6–C13 bond
Several features result from a comparison of neutral 4
length of 158.4(4) pm. Similar values were also observed for and its metallated derivatives 5, 6 and 7: (i) The bond
metallated 1,2-diamino-1,2-dipyridylethanes.[11,12] This ob- lengths of the pyridyl unit are not affected by the coordina-
servation can be explained by electrostatic repulsion be- tion to lithium (7) and zinc (5 and 6). (ii) The coordination
tween carbon atoms with a similar charge due to compar- of the piperidyl group to the metal atoms leads to an elong-
able inductive and mesomeric effects of the substituents at ation of the bonds to N2. However, in all molecules a chair
C6 and C13.
conformation is adopted. (iii) The shortening of the C1–C2
The molecular structures of 4, 5 and 6 are represented in bond is a consequence of the increased s-orbital participa-
Figure 2, Figure 3 and Figure 4, respectively. The number- tion at C2 (sp2 hybridization in 5, 6 and 7 vs. sp3 in 4) in
ing schemes are identical in order to allow a direct compari- the metallated derivatives. (iv) Due to the deprotonation a
son of the structural data. Compound 4 crystallizes with planar environment at C2 is realized. The anionic charge is
two symmetry independent molecules in the asymmetric delocalized throughout the O1–C13–C2–C16–O3 unit
unit distinguished by the letters “A” and “B”. In Table 2 yielding elongated C13–O1 and C16–O3 bonds and short-
selected structural parameters of these compounds are ened C2–C13 as well as C2–C16 bonds. In addition this
listed. The metallation of 4 leads to a deprotonation at C2 unit is planarily arranged whereas in 4 the planar ester
which allows the formation of a β-diketonate with a delo- functions are distorted in order to minimize steric repulsive
calized charge within the O1–C13–C2–C16–O3 moiety.
forces. The coordination of zinc to O1 enhances the nega-
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Lithium and Zinc Amine Complexes
electron diffraction, gas phase: 182(1) pm[34]]. Enhancement
of the coordination number to three in [(Me3Si)2N–Zn(µ-
OCEt3)]2 gives Zn–N bonds lengths of 186.8(3) pm.[35]
A
further enhancement of the coordination number of zinc
as, for example, in monomeric Zn{N(2,6-iPr2H3C6)–SiMe2–
[36]
[37]
NMe2}2
and Zn{N(SiMe3)CH2CH2NMe2}2
with a
tetra-coordinate metal center leads to increased Zn–N dis-
tances comparable to those of 5. Furthermore, an enhanced
electrostatic repulsion between three anionic groups was
observed in solvent-separated zincates with [Zn{N-
(SiMe3)2}3]– anions leading to rather large Zn–N dis-
tances.[38,39] The distances of the coordinative Zn–N1 and
Zn–N2 bonds to the pyridyl and piperidyl groups are much
larger due to a reduced electrostatic attraction. Steric strain
leads to a rather large Si1–N3–Si2 angle of 125.3(1)° at a
nearly planar N3 atom (angle sum 357.8°). The dependency
of the Si–N–Si angles in bis(trimethylsilyl)amides of the Si–
N bond lengths (and hence of the electronegativity of the
metal) was discussed by Hanusa and co-workers.[40]
The lithium derivative 7 crystallizes as a tetramer as
shown in Figure 5. The four monomers are distinguished
by the letters “A” to “D”. The large gaps between these
molecules contain solvent molecules (toluene, pentane)
which are heavily disordered thus hampering the quality of
the structure determination. However, the framework
formed by compound 7 shows no thermal motion and,
hence, rather small e.s.d. values. The smallest unit can be
interpreted as a lithium β-diketonate derivative with the
lithium atom in a bridging position between the oxygen
atoms O1 and O3. In Table 3 the bond lengths of the four
units are listed. The organic anions show very similar struc-
tural parameters. However, strong differences are observed
for the LiX–O2(X+1) bonds. The LiB–O2C distance exhib-
its a value of 256.2(6) pm and is much larger than the corre-
sponding values of the other lithium atoms. The C–O single
Figure 4. Molecular structure and numbering scheme of bis(tri-
methylsilyl)methylzinc
2,2-bis(ethoxycarbonyl)-1-piperidyl-1-(2-
pyridyl)ethan-2-ide (6). The ellipsoids represent a probability of
40%. H atoms are omitted for clarity reasons with the exception
of the zinc-bound methyl group.
Table 2. Comparison of the structural parameters of 4 (molecules
A and B), 5, 6, and 7. For 7 average values are given; selected
structural parameters are listed in Table 2.
4A
4B
5
6
7[a]
C1–C2
C1–C3
C1–N2
N2–C8
N2–C12
C3–C4
C4–C5
C5–C6
C6–C7
N1–C3
N1–C7
C2–C13
C13–O1
O2–C13
O2–C14
C2–C16
C16–O3
O4–C16
O4–C17
M–N1
153.0(3) 153.4(3) 151.8(4) 151.9(3) 150.7
152.5(4) 151.3(3) 151.3(4) 151.1(3) 151.7
147.8(3) 148.2(3) 150.8(3) 150.6(3) 150.3
146.6(3) 146.3(3) 149.4(3) 149.2(3) 148.0
147.5(3) 146.5(3) 148.4(3) 148.6(3) 147.2
138.7(4) 139.3(4) 139.7(4) 139.6(3) 138.9
138.4(4) 138.7(4) 137.3(4) 137.3(4) 138.0
138.4(4) 137.7(4) 137.6(5) 139.0(4) 137.9
137.7(4) 138.0(4) 138.3(4) 137.7(3) 137.3
134.2(3) 134.4(3) 134.6(3) 134.7(3) 133.7
134.0(4) 134.0(4) 133.9(3) 134.2(3) 133.7
152.1(4) 151.9(4) 139.7(4) 139.6(3) 141.6
120.5(3) 120.8(3) 127.2(3) 127.0(3) 123.4
132.2(3) 132.4(3) 134.3(3) 134.3(3) 137.2
146.6(4) 145.8(4) 144.3(3) 144.0(3) 143.8
152.3(3) 152.6(3) 144.5(4) 144.5(3) 141.9
119.2(3) 119.2(3) 123.1(3) 122.4(3) 123.7
133.5(3) 133.4(3) 134.7(3) 134.7(3) 136.6
146.8(3) 146.1(3) 143.5(3) 144.0(3) 144.0
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
206.4(2) 207.6(2) 213.6
211.4(2) 213.9(2) 217.7
199.8(2) 200.7(2) 195.3
M–N2
M–O1
M–O2
M–O3
M–N3/C19
N3/C19–Si1
N3/C19–Si2
–
–
–
–
233.0
194.5
–
–
–
189.3(2) 198.0(2)
171.5(2) 185.2(2)
171.6(2) 185.1(2)
[a] Average values.
tive charge and the coordination number of this oxygen
atom yielding larger C13–O1 distances than C16–O3 values.
The Zn–N3 bond length to the bis(trimethylsilyl)amido
group shows a value of 189.3(2) pm which is larger than
observed for homoleptic Zn[N(SiMe3)2]2 with a two-coordi-
Figure 5. Molecular structure and numbering scheme of tetrameric
lithium 2,2-bis(ethoxycarbonyl)-1-piperidyl-1-(2-pyridyl)ethan-2-
ide (7). The ellipsoids represent a probability of 40%; H atoms are
nate zinc atom [X-ray diffraction, solid state: 183(1) pm;[33] neglected for clarity reasons.
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C. Koch, M. Kahnes, M. Schulz, H. Görls, M. Westerhausen
FULL PAPER
bonds of 7 are rather small compared to standard values. gated. Yang and Houser[29c] showed that only the pyridyl
This fact can be attributed to an additional electrostatic at- base of 9 acts as a coordination site towards copper(I). The
traction as a consequence of a highly positive carbon atom. crystal structures of copper(I) complexes with N-(2-pyr-
Similar observations are discussed in detail by Becker et idylmethyl)acetylamine are also influenced by intermo-
al.[41] for sesqui(1,2-dimethoxyethane)lithium bis(methoxy- lecular hydrogen bridges of the NH···O type, whereas the
carbonyl)phosphanide.
chloride counterions bridge two copper cations.
The molecular structure of 12 is shown in Figure 7. The
zinc atom is in a distorted tetrahedral environment. Mole-
cules with an 2-[(alkylideneamino)methyl]pyridine ligand at
zinc are already well-known.[9,42] The small bite of the li-
gand leads to a small N1–Zn–N2 bond angle of 81.53(7)°,
the Zn–N bond lengths lying in a characteristic range.[9]
This small angle allows a Cl1–Zn–Cl2 angle of 117.39(3)°.
Table 3. Selected structural parameters of tetrameric 7. The four
molecules are distinguished by the letters X = A, B, C, and D. The
letter (X + 1) shows that this coordination is carried out to the
neighbouring molecule (A + 1 = B, B + 1 = C, C + 1 = D, D + 1
= A). Selected structural parameters are listed in Table 4.
X
A
B
C
D
LiX–O1X
LiX–O3X
LiX–O2(X + 1) 224.0(6)
LiX–N1(X + 1) 212.0(6)
LiX–N2(X + 1) 219.9(6)
O1X–C13X
C2X–C13X
C2X–C16X
O3X–C16X
C1X–C2X
O2X–C13X
O2X–C14X
O4X–C16X
O4X–C17X
195.9(5)
197.0(6)
193.9(6)
196.4(6)
256.2(6)
209.1(6)
218.0(6)
123.6(4)
141.5(4)
142.0(4)
123.6(4)
151.7(4)
137.5(4)
144.1(4)
136.1(4)
143.5(4)
195.8(7)
193.0(6)
223.7(7)
213.8(7)
216.4(6)
124.0(4)
141.4(4)
141.6(5)
123.7(4)
150.3(4)
136.2(4)
143.6(4)
136.6(4)
142.6(5)
195.6(6)
191.3(6)
227.2(6)
213.3(6)
217.8(6)
122.4(4)
141.7(4)
142.1(5)
123.4(4)
149.8(5)
138.2(4)
144.7(4)
136.2(4)
144.0(5)
123.6(3)
141.0(4)
141.7(4)
123.6(4)
151.3(4)
137.7(4)
143.1(4)
137.9(4)
144.0(5)
The molecular structure of N-(2-pyridylmethyl)benzoyl-
amine (9) is shown in Figure 6. The two crystallographically
independent molecules are distinguished by the letters “A”
and “B”. The hydrogen atoms were located and the amine
nitrogen N2 is in a planar environment (angle sums 359.6°
and 359.9°). Weak N–H···O hydrogen bridges lead to a
strand formation in the solid state. The C7–O1 bond
lengths of 123.7(2) and 124.1(2) pm are slightly elongated
in comparison to isolated C=O double bonds. The values
of the N2–C7 bond lengths of 133.9(2) and 133.5(2) pm
show the formation of allylic O1–C7–N2 systems (3-center
4-electron π-system) and are very similar to the N1–C1
[133.9(3) and 133.5(3) pm] and N1–C5 [133.9(2) and
134.5(2) pm] distances of the pyridyl group. A further delo-
calization of charge from this allylic system into the phenyl
fragment does not occur and can be deduced from charac-
teristic C7–C8 single bonds of 149.8(2) and 149.6(2) pm.
Figure 7. Molecular structure and numbering scheme of [(diphenyl-
methylidene)(2-pyridylmethyl)amino]zinc(II) chloride (12). The el-
lipsoids represent a probability of 40%. The H atoms are drawn
with arbitrary radii.
Compound 14 crystallizes as a solvent-separated ion
pair, shown in Figure 8. The anion [(thf)ZnCl3]– with the
metal center in a distorted tetrahedral environment is al-
ready well-known and a common counterion in many com-
plexes.[43] The Zn–Cl bond lengths are only slightly larger
than observed for 12 which might be the consequence of
intramolecular electrostatic repulsion between the chlorine
anions.
The organic cation consists of the (benzoyl)(2-pyr-
idylmethyl)amino unit with a diphenylmethyl cation at N2
which also binds to the pyridyl base N1. Both nitrogen
bases are in nearly planar environments. The N2–C1 and
N2–C2 bond lengths adopt characteristic values for N–C
single bonds whereas the N2–C8 distance is approximately
10 pm smaller. This fact supports the formation of an allylic
π-system as described for N-(2-pyridylmethyl)benzoylamine
(9). Due to ring strain the bonding between the di-
phenylmethyl cation and the pyridyl base [N1–C1 151.9(4)]
is slightly larger than the other bond lengths. However, this
Figure 6. Molecular structure and numbering scheme of N-(2-pyr-
idylmethyl)benzoylamine (9). The ellipsoids represent a probability
of 40%; H atoms are shown with arbitrary radii.
The coordination behaviour of N-(2-pyridylmethyl)ben- bond does not affect the delocalization within the pyridyl
zoylamine (9) to copper(I) chloride was already investi- fragment.
1072
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© 2008 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Inorg. Chem. 2008, 1067–1077

Lithium and Zinc Amine Complexes
Experimental Section
General: All manipulations were carried out in an argon atmo-
sphere under anaerobic conditions. Prior to use, all solvents were
thoroughly dried and distilled in an argon atmosphere. Most of
the compounds are moisture sensitive. Starting 11 was prepared in
analogy to a published procedure.[45] 1H and 13C NMR spectra
were recorded at ambient temperature on a Bruker AC 200 or a
Bruker AC 400 spectrometer. DEI-mass spectra were obtained on
a Finnigan MAT SSQ 710 system, IR measurements were carried
out on a Perkin–Elmer System 2000 FT-IR. Melting points were
measured with a Reichert–Jung apparatus Type 302102 and are
uncorrected.
2-(tert-Butyldimethylsilylamino)-1-lithoxy-1,1-diphenyl-2-(2-pyridyl)-
ethane (1): A 1.6  solution of n-butyllithium in hexane (1.6 ,
5.1 mL, 8.2 mmol) was dropped at –78 °C to a solution of 1.83 g of
(tert-butyldimethylsilyl)(2-pyridylmethyl)amine (8.2 mmol) in 5 mL
of toluene. Thereafter, 1.49 g of benzophenone (8.2 mmol) in 5 mL
of toluene were added dropwise at –78 °C. After complete addition,
the reaction mixture was warmed to room temp. and stirred for
additional 50 h. Then all volatile components were removed at
room temp. under vacuum and the residue was redissolved in
7.5 mL of toluene and tempered at 75 °C for 4 h. After removal
of all solids, storage at r.t. afforded 0.9 g of colorless crystalline 1
(2.2 mmol, 27%). 1H NMR (CDCl3): δ = 8.31 (s, 1 H, br, Py1),
7.6–6.8 (13 H, Ph2–Ph4, Py2–Py4), 4.70 (d, 3J = 5 Hz, 1 H, C6,
Figure 8. Molecular structure andnumbering scheme of zincate 14.
The ellipsoids represent a probability of 40%, H atoms are omitted
for clarity reasons.
Conclusions
We are interested in multidentate Lewis bases containing
the (2-pyridylmethyl)amino unit. Two compound classes
fulfil these conditions, namely the derivatives of diethyl ma-
lonate (E = C–) with the negative charge delocalized within
the 1,3-diketonate fragment as well as N-benzoyl-substi-
tuted (2-pyridylmethyl)amines (E = N).
3
CH), 1.80 (d, J = 5.6 Hz, 1 H, C–NH–Si),0.58 (s, 9 H, Si–CMe3),
–0.33 and –0.350 (6 H, Si–CH3) ppm. 13C{1H} NMR (CDCl3): δ
= 148.4 (Py1), 147.1 (Ph, Cq), 145.7 (Ph, Cq), 136.5 (Py3), 132.4–
126.2 (Ph), δ = 123.6 (Py4), 121.5 (Py2), 81.8 (C7), 61.8 (C6, CH),
26.0 [Si–C(CH3)3], 17.7 (Si–CMe3), –4.8 (SiMe2) ppm. IR (Nujol,
cm–1): ν = 3362 (m), 3058 (w), 1597 (s), 1571 (m), 1377 (vs), 1335
˜
(w), 1256 (m), 1248 (m), 1186 (w), 1162 (w), 1130 (m), 1078 (s),
1063 (w), 1048 (w), 967 (w), 945 (m), 905 (w), 862 (m), 856 (m),
836 (s), 830 (s), 812 (w), 774 (s), 751 (s), 706 (vs), 701 (vs), 662 (w),
644 (w), 636 (w), 609 (w), 571 (w), 531 (w), 487 (w) cm–1. MS: m/z
(%) = 821 (19) [M+ of dimer], 639 (6) [C37H50Li2N4OSi2], 410 (9)
[monomer], 387 (54) [C25H31N2Si], 221 (99) [C12H21N2Si + H], 182
(98) [C13H10O], 164 (98) [C8H12N2Si + H], 105 (86) [C6H5N2], 77
(70) [C6H5], 73 (41) [C2H7NSi + H], 57 (25) [Bu]. C25H31Li2N2OSi
(416.49): calcd. C 72.10, H 7.26, N 6.73; found C 72.55, H 7.29, N
6.20.
The deprotonation of 4 yields the corresponding zinc (5
and 6), lithium (7) and sodium (8) derivatives. This ligand
binds to zinc in a tridentate manner via both the nitrogen
bases and one keto group whereas the lithium cation is
bound to the β-diketonate moiety; an intermolecular coor-
dination to the nitrogen bases of the neighbouring molecule
leads to the formation of cyclic tetramers. This fact can be
explained with the Pearson concept of hard/soft acids and
bases.[44] Whereas the soft 3d-element zinc binds to the
softer nitrogen bases, the hard lithium cation prefers the
negatively charged β-diketonate moiety. The sodium deriva-
tive is only sparingly soluble in common organic solvents
and therefore, recrystallization fails. However, the insolubil-
ity supports the assumption that a polymeric strand struc-
ture is formed.
The N-(2-pyridylmethyl)dibenzoylamines are formed via
an acylation of (2-pyridylmethyl)amine. Despite a protec-
tion of the amine function with the diphenylmethylidene
fragment, benzoyl chloride attacks the imino nitrogen base
and binds to both of the nitrogen atoms, thus forming a
five-membered heterocycle. Products of C-acylation reac-
tions were not observed. Zinc(II) chloride reacts as a Lewis
acid and hence, addition of zinc(II) chloride yields a sol-
vent-separated ion pair with the already well-known [(thf)-
ZnCl3]– anion.
2,2-Bis(ethoxycarbonyl)-1-phenylamino-1-(2-pyridyl)ethane (2):
A
mixture of 1.03 g of 2-(phenyliminomethyl)pyridine (5.56 mmol),
1.36 g of diethyl malonate (8.48 mmol) and 0.2 mL of piperidine
were stirred for 6 days at room temp. After removal of piperidine
a waxy dark brown oil remained and 15 mL of heptane were added.
Thereupon, 1.34 g of a colorless solid of 2 (3.91 mmol, 70%)
formed, which was collected, washed with a small amount of hep-
tane and dried in vacuo; m.p. 72.5 °C. 1H NMR (CDCl3): δ = 8.51
3
3
5
[d, J(H,H) = 4.8 Hz, 1 H, Pyr1], 7.55 [dt, J(H,H) = 7.6, J(H,H)
= 1.6 Hz, 1 H, Pyr3], 7.36 [d, 3J(H,H) = 7.6 Hz, 1 H, Pyr4], 7.11
(m, 3 H, Pyr2, Ph3/3Ј), 6.67 (m, 3 H, Ph2/2Ј,4), 5.32 (m, 1 H,
3
3
CHN), 5.16 [d, J(H,H) = 10.0 Hz, 1 H, NH], 4.37 [d, J(H,H) =
6.0 Hz, 1 H, CH(COOEt)2], 4.08 (m, 4 H, OCH2), 1.13 (m, 6 H,
CH3) ppm. 13C{1H} NMR (CDCl3): δ = 168.4 (C=O), δ = 167.8
(C=O), 159.5 (Pyr5), δ = 149.2 (Pyr1), 146.9 (Ph1), 136.5 (Pyr3),
129.2 (Ph3/3Ј), 122.3 (Pyr2), 122.0 (Pyr4), 118.1 (Ph4), 113.5 (Ph2/
2Ј), 61.6 (OCH2), 61.4 (OЈCH2), 58.3 (CHN), 56.3 [CH(COOEt)2],
13.9 (CH ) ppm. IR (Nujol, cm–1): ν = 3283 (s), 3064 (m), 2925
˜
3
(vs), 2854 (vs), 1753 (vs), 1604 (s), 1593 (s), 1570 (m), 1527 (m),
1501 (s), 1462 (vs), 1369 (s), 1311 (vs), 1287 (s), 1271 (vs), 1216
(m), 1192 (m), 1178 (s), 1133 (vs), 1094 (m), 1028 (s), 997 (m), 887
Eur. J. Inorg. Chem. 2008, 1067–1077
© 2008 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjic.org
1073

C. Koch, M. Kahnes, M. Schulz, H. Görls, M. Westerhausen
FULL PAPER
(m), 790 (m), 757 (s), 694 (s), 621 (w), 605 (m), 561 (w), 519 (w) [C11H10NO3]+, 146 (98) [HNSi2(CH3)5]+, 130 (95) [NSi2(CH3)4]+,
cm–1. C19H22N2O4 (342.38): calcd. C 66.66, H 6.46, N 8.03; found 73 (22) [Si(CH3)3]+. C24H43N3O4Si2Zn (559.20): calcd. C 51.55, H
C 66.65, H 6.48, N 8.18.
7.75, N 7.51; found C 50.56, H 7.44, N 7.39.
2,2-Bis(ethoxycarbonyl)-1-piperidyl-1-(2-pyridyl)ethane (4): A mix-
ture of 1.07 g of pyridine-2-carbaldehyde (10.0 mmol), 1.92 g of di-
ethyl malonate (12.0 mmol) and 1.02 g of piperidine (12.0 mmol)
was dissolved in 20 mL of anhydrous ethanol and heated under
Bis(trimethylsilyl)methylzinc(II) 1-Ethoxy-2-(ethoxycarbonyl)-3-(1-
piperidyl)-3-(2-pyridyl)-1-propen-1-olate (6): A solution of 335 mg
of
2,2-bis(ethoxycarbonyl)-1-(1-piperidyl)-1-(2-pyridyl)ethane
(1.0 mmol) in 2 mL of toluene was cooled to –78 °C. A 1.0  solu-
reflux for 3 h. After removal of the solvent at room temp. in vacuo, tion of [bis{bis(trimethylsilyl)methyl}zinc] (1.0 mL, 1.0 mmol) in
the dark-brown oil was dissolved in 5 mL of ethyl acetate and
25 mL of hexane. The volume was reduced to half of the original
volume. From this solution 1.98 g of colorless prisms of 4
(5.92 mmol, 59%) precipitated and were collected, washed with
pentane and dried under vacuum; m.p. 68.5 °C. 1H NMR (CDCl3):
toluene was added dropwise. Thereafter the reaction mixture was
warmed to room temp. and then the volume was reduced to approx.
30%. From this clear solution, 490 mg of colorless prisms of 6
(0.88 mmol, 88%) crystallized at –20 °C and were washed with pen-
1
tane and dried under vacuum; m.p. 185 °C (dec.). H NMR ([D6]-
3
3
δ = 8.50 [d, J(H,H) = 4.4 Hz, 1 H, Pyr1], 7.61 [dt, J(H,H) = 7.6,
5J(H,H) = 1.6 Hz, 1 H, Pyr3], 7.14 [d, 3J(H,H) = 7.6 Hz, 1 H,
Pyr4], 7.12 (m, 1 H, Pyr2), 4.66 [d, 3J(H,H) = 11.6 Hz, 1 H,
benzene): δ = 8.04 [d, 3J(H,H) = 5.2 Hz, 1 H, Pyr1], 7.50 [d,
3
4
3J(H,H) = 7.6 Hz, 1 H, Pyr4], 6.83 [dt, J(H,H) = 7.6, J(H,H) =
1.6 Hz, 1 H, Pyr3], 6.30 (m, 1 H, Pyr2), 5.44 (s, 1 H, CHN), 4.45
(m, 2 H, OЈCH2), 4.17 (m, 1 H, OCHaH), δ = 4.05 (m, 1 H,
OCHHb), 3.31 [d, 2J(Hax,Heq) = 11.6 Hz, 1 H, Pip2Јeq], 2.41 [d,
3
CH(COOEt)2], 4.40 [d, J(H,H) = 11.6 Hz, 1 H, CHN], 4.24 (m, 2
H, OCH2), 3.98 (m, 2 H, OЈCH2), 2.61 (m, 2 H, Pip2), 2.11 (m, 2
3
H, Pip2Ј), 1.43 (m, 4 H, Pip3/3Ј), 1.32 [t, J(H,H) = 7.2 Hz, 3 H, 2J(Hax,Heq) = 11.6 Hz, 1 H, Pip2eq], 2.13 (m, 1 H, Pip2Јax), 1.64
3
3
CH3], 1.13 (m, 2 H, Pip4), 1.13 [t, J(H,H) = 7.2 Hz, 3 H, ЈCH3] (m, 1 H, Pip2ax), 1.59–1.38 (m, 3 H, Pip3a/3Јa/b), 1.30 [t, J(H,H)
ppm. 13C{1H} NMR (CDCl3): δ = 168.7 (C=O), 168.0 (ЈC=O), = 7.2 Hz, 4 H, OЈCH2CH3, Pip4a], 1.17 (m, 1 H, Pip3b), 1.13 [t,
155.5 (Pyr5), 148.6 (Pyr1), 135.6 (Pyr3), 124.2 (Pyr4), 122.1 (Pyr2),
3J(H,H) = 7.2 Hz, 3 H, OCH2CH3], 0.87 (m, 1 H, Pip4b), 0.42 [s,
69.1 (CHN), 61.1 (OCH2), 60.9 (OЈCH2), 53.7 [CH(COOEt)2], 50.9 9 H, ЈSi(CH3)3], 0.31 [s, 9 H, Si(CH3)3], –0.84 [s, 1 H, CH(Si-
(Pip2/2Ј), 26.6 (Pip3/3Ј), 24.5 (Pip4), 14.3 (CH3), 13.8 (ЈCH3) ppm.
(CH3)3)2] ppm. 13C{1H} NMR ([D6]benzene): δ = 170.0 (C=O),
169.8 (ЈC=O), 162.0 (Pyr5), 145.1 (Pyr1), 139.5 (Pyr3), 123.9
(Pyr4), 122.4 (Pyr2), 74.5 [C(COOEt)2], 70.4 (CHN), 59.8 (OCH2),
IR (Nujol, cm–1): ν = 3444 (m), 2921 (vs), 2854 (vs), 2729 (m), 1741
˜
(vs), 1721 (s), 1590 (m), 1568 (m), 1463 (vs), 1376 (s), 1300 (s), 1267
(s), 1241 (m), 1227 (m), 1181 (m), 1157 (s), 1112 (m), 1095 (m), 58.9 (OЈCH2), 55.1 (Pip2), 50.9 (Pip2Ј), 25.0 (Pip3Ј), 24.3 (Pip3),
1035 (s), 1020 (s), 995 (m), 888 (m), 813 (m), 756 (m), 722 (m), 621 23.9 (Pip4), 15.2 (ЈOCH2CH3), 14.9 (OCH2CH3), 4.9 [Si(CH3)3],
(w), 551 (w) cm–1. MS (DEI): m/z (%) = 335 (13) [MH]+, 251 (100)
[MH+ – C5H10N], 178 (90) [(C10H12NO2)+], 132 (84) [C8H6NO]+,
4.3 [ЈSi(CH ) ], 0.5 {CHSi[(CH ) ] } ppm. IR (Nujol): ν = 3067
˜
3 3 3 3 2
(w), 2925 (vs), 2854 (vs), 1620 (vs), 1605 (s), 1565 (m), 1519 (vs),
84 (55) [C5H10N]+, 78 (14) [C5H4N]+. C18H26N2O4 (334.41): calcd. 1471 (s), 1414 (s), 1383 (s), 1337 (s), 1300 (m), 1267 (m), 1244 (s),
C 64.65, H 7.48, N 8.59; found C 64.83, H 8.05, N 8.39.
1209 (m), 1169 (s), 1150 (m), 1114 (s), 1101 (m), 1070 (m), 1060
(m), 1029 (m), 960 (m), 897 (s), 868 (s), 850 (vs), 781 (m), 745 (w),
670 (m), 647 (w), 615 (w), 492 (w), 496 (w) cm–1. MS (DEI): m/z
(%) = 556 (20) [M(64Zn)]+, 541 (16) [M(64Zn) – CH3]+, 472 (77)
[M(64Zn) – C5H10N]+, 204 (97) [C11H10NO3]+, 174 (100), 129 (46)
[HCSi2(CH3)4]+, 84 (15) [C5H10N]+, 73 (11) [Si(CH3)3]+.
C25H44N2O4Si2Zn (558.19): calcd. C 53.79, H 7.95, N 5.02; found
C 53.67, H 8.05, N 5.06.
[3-(2-Pyridyl)-3-(1-piperidyl)-1-ethoxy-2-ethoxycarbonyl-1-propen-
1-olato]zinc(II) Bis(trimethylsilyl)amide (5): A solution of 335 mg
of
1-(2-pyridyl)-1-piperidyl-2,2-bis(ethoxycarbonyl)ethane (4)
(335 mg, 1.0 mmol) in 3 mL of anhydrous toluene was cooled to
–78 °C and 386 mg of Zn[N(SiMe3)2]2 (1.0 mmol) were added drop-
wise. After complete addition the solution was warmed to room
temp. and the volume reduced to half of the original volume. At
–20 °C, 380 mg of colorless prisms of 5 (0.68 mmol, 68%) crys-
tallized and were isolated, washed with a small amount of pentane
1-Ethoxy-2-(ethoxycarbonyl)-1-lithoxy-3-(1-piperidyl)-3-(2-pyridyl)-
1-propene (7): A solution of 240 mg of 2,2-bis(ethoxycarbonyl)-1-
(1-piperidyl)-1-(2-pyridyl)ethane (0.72 mmol) in 2 mL of toluene
was cooled to –78 °C. A solution of 120 mg of LiN(SiMe3)2 in
1
and dried in vacuo; m.p. 172 °C (dec.). H NMR ([D6]benzene): δ
= 7.87 [d, 3J(H,H) = 5.2 Hz, 1 H, Pyr1], 7.45 [d, 3J(H,H) = 7.6 Hz,
3
5
1 H, Pyr4], 6.78 [dt, J(H,H) = 7.6, J(H,H) = 1.6 Hz, 1 H, Pyr3], 2 mL of toluene was added dropwise. Thereafter the reaction mix-
6.25 (m, 1 H, Pyr2), 5.40 (s, 1 H, CHN), 4.44 (m, 2 H, OЈCH2), ture was warmed to room temp. and the volume reduced to 1 mL.
4.18 (m, 1 H, OCHHa), 4.05 (m, 1 H, OCHbH), 3.70 [d, 2J(Hax,Heq)
Then 3 mL of pentane were added and all solids removed by fil-
= 11.6 Hz, 1 H, Pip2Јeq], 2.44 [d, 2J(Hax,Heq) = 11.6 Hz, 1 H, tration. At 20 °C, 210 mg of colorless needles of 7 (0.62 mmol;
Pip2eq], 2.06 [dt, 2J(Hax,Heq) ≈ 3J(Hax,Hax) = 11.6, 3J(H,H) = 85.7%) precipitated and were dried under reduced pressure; m.p.
2.4 Hz, 1 H, Pip2Јax], 1.71 (m, 1 H, Pip3Јax), 1.64 (m, 2 H, Pip2ax/ 160 °C (dec.). 1H NMR ([D6]benzene): δ = 8.64 (m, 1 H, Pyr1),
3ax), 1.38 (m, 2 H, Pip3Јeq/4eq), 1.30 [t, 3J(H,H) = 7.2 Hz, 3 H,
7.30 (m, 1 H, Pyr4), 6.96 (m, 1 H, Pyr3), 6.61 (m, 1 H, Pyr2), 5.35
ЈCH3], 1.16 (m, 1 H, Pip3eq), 1.10 [t, 3J(H,H) = 7.2 Hz, 3 H, CH3], (m, 1 H, CHN), 4.42–3.59 (m, 4 H, OCH2), 3.67 (m, 1 H, Pip2Јeq),
0.84 (m, 1 H, Pip4ax), 0.41 [s, 18 H, Si(CH3)3] ppm. 13C{1H} NMR 3.26 (m, 1 H, Pip2eq), 2.37–0.76 (m, 14 H, Pip2ax/2Јax, Pip3/3Ј/4,
([D6]benzene): δ = 170.1 (C=O), 169.8 (ЈC=O), 161.2 (Pyr5), 145.2
(Pyr1), 139.7 (Pyr3), 123.8 (Pyr4), 122.5 (Pyr2), 74.6 [C(COOEt)2], 167.0 (Pyr5), 147.0 (Pyr1), 136.2 (Pyr3), 123.7 (Pyr4), 120.2 (Pyr2),
70.6 (CHN), 61.0 (OCH2), 59.0 (OЈCH2), 55.6 (Pip2), 51.3 (Pip2Ј), 76.3 [C(COOEt)2], 68.8 (CHN), 58.0–56.9 (OCH2), 56.3 (Pip2),
25.4 (Pip3Ј), 25.0 (Pip3), 23.8 (Pip4), 15.2 (ЈCH3), 14.9 (CH3), 6.1 51.2 (Pip2Ј), 26.1 (Pip3/3Ј/4), 15.7–14.9 (CH3) ppm. 7Li{1H} NMR
[Si(CH ) ] ppm. IR (Nujol, cm–1): ν = 3067 (w), 2925 (vs), 2854
([D ]benzene): δ = 2.07 ppm. IR (Nujol): ν = 2924 (vs), 2854 (vs),
CH3) ppm. 13C{1H} NMR ([D6]benzene): δ = 171.8–169.7 (C=O),
˜
˜
3 3
6
(vs), 1620 (vs), 1605 (s), 1567 (m), 1521 (vs), 1454 (s), 1415 (s), 2809 (m), 1673 (vs), 1596 (m), 1570 (m), 1524 (s), 1464 (s), 1407
1383 (s), 1337 (s), 1300 (m), 1253 (s), 1208 (m), 1169 (s), 1148 (m), (s), 1377 (s), 1350 (m), 1294 (s), 1259 (s), 1214 (m), 1164 (m), 1093
1113 (s), 1099 (s), 1059 (m), 1027 (m), 983 (vs), 883 (s), 833 (s), 791 (s), 1064 (vs), 1007 (m), 977 (s), 854 (m), 791 (m), 751 (m), 729
(m), 751 (w), 670 (m), 613 (w) cm–1. MS (DEI): m/z (%) = 558 (20) (w), 686 (w), 637 (w) cm–1. MS (FAB): m/z (%) = 505 (23) [M +
[M(64Zn)H]+, 542 (38) [M(64Zn) – CH3]+, 473 (100) [M(64Zn)
C7H10O4Li]+, 347 (8) [M + Li]+, 335 (9) [M + 2H+ – Li]+, 256
–
64ZnN(Si2(CH3)5]+, 204 (91) (55) [M – C5H10N]+, 250 (50) [M + H – LiC5H10N]+, 204 (100)
–
C5H10N]+, 349 (87) [MH
1074
www.eurjic.org
© 2008 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Inorg. Chem. 2008, 1067–1077

Lithium and Zinc Amine Complexes
[C11H10NO3]+. C18H25LiN2O4 (340.34): calcd. C 63.52, H 7.40, N
8.23; found C 62.04, H 7.14, N 7.77.
(Pyr3), 136.1 (Ph8), 133.2 (Ph11), 131.4 (Ph11), 129.8 (Ph10), 129.2
(Ph10), 128.1 (Ph9), 127.8 (Ph9), 121.9 (Pyr2), 121.5 (Pyr4), 51.1
(2J, CH ) ppm. IR (Nujol): ν = 2923 (vs), 2854 (vs), 1722 (w), 1656
˜
2
Sodium 1-Ethoxy-2-(ethoxycarbonyl)-3-(1-piperidyl)-3-(2-pyridyl)-1-
propen-1-olate (8): A solution of 502 mg of 2,2-bis(ethoxycar-
bonyl)-1-(1-piperidyl)-1-(2-pyridyl)ethane (1.5 mmol) in 3 mL of
1,2-dimethoxyethane (DME) was dropped to a suspension of
36 mg of NaH (1.5 mmol) in 2 mL of DME. This mixture was
stirred at room temp. till no gas evolution was observed (approxi-
mately 12 h). The precipitating slightly orange solid (500 mg,
1.4 mmol, 94%) was collected, washed with DME and dried in
vacuo; m.p. 205 °C (dec.). 1H NMR ([D6]DMSO): δ = 8.24 [d,
3J(H,H) = 4.4 Hz, 1 H, Pyr1], 7.51 (m, 2 H, Pyr3/4), 6.94 [dd,
(vs), 1582 (m), 1489 (m), 1468 (m), 1409 (m), 1332 (s), 1287 (s),
1237 (s), 1173 (m), 1136 (m), 1041 (m), 1017 (s), 996 (s), 803 (w),
775 (m), 714 (s), 508 (vw) cm–1. MS (DEI): m/z (%) = 315 (6) [M –
1], 211 (28) [M C7H5O], 107 (93) [C6H7N2]+, 92 (22) [C6H6N]+, 77
(100) [C6H5].
Synthesis of (Diphenylmethylidene)(2-pyridylmethyl)amine (11): A
mixture of 3.97 g of (2-pyridylmethyl)amine (0.037 mol), 6.69 g of
benzophenone (0.037 mol) and 10 mg of p-toluenesulfonic acid in
50 mL of anhydrous toluene was stirred for 14 hours under reflux.
During the reaction the color changed from light to dark yellow.
At the end of the reaction the mixture was cooled to room temp.
Then it was washed with 10 mL of a 10% aqueous sodium carbon-
ate solution, three times with 10 mL of 2% aqueous sodium hy-
droxide solution and then three times with 10 mL of water. The
organic layer was separated and dried with sodium sulfate. After
removal of the drying agent most of the toluene was removed in
vacuo. Bulb-to-bulb distillation at 150 °C and 8ϫ10–3 mbar af-
forded 6.0 g of a yellow oil (yield 49%). However, 11 still contained
traces of benzophenone. The substance can be used for complex-
ation reactions without further purification or transferred into its
hydrochloride. For this purpose, 6.8 g of impure 11 was dissolved
in 50 mL of anhydrous diethyl ether at 0 °C. Now 3 mL of a solu-
tion of 4.7% HCl in anhydrous diethyl ether were added slowly and
under vigorous stirring in an argon atmosphere yielding a white
hygroscopic precipitate. The precipitate 11·HCl was isolated,
washed three times with anhydrous diethyl ether and dried in
vacuo. Overall yield 46%. 1H NMR (CD2Cl2): δ = 4.78 (s, 2 H,
CH2), 7.81 (ddd, J = 1.6, J = 6.4 Hz, 1 H, Pyr5), 7.94 (t, J = 7.6 Hz,
4 H, Ph15), 8.01 (d, J = 8.0 Hz, 1 H, Pyr3), 8.06 (ddd, J = 1.2, J
= 6.4 Hz, 2 H, Ph16), 8.17 (d, J = 8.4 Hz, 4 H, Ph14), 8.30 (ddd,
J = Pyr4, 1.6 Hz, 1 H, 7.6 Hz), 9.01 (d, J = 4.8 Hz, 1 H, Pyr6)
ppm. 13C{1H} NMR (CD2Cl2): δ = 44.1 (CH2), 124.1 (Pyr3), 124.6
(Pyr5), 129.2 (Ph15, Ph), 130.6 (Ph14), 133.4 (Ph16), 138. 5 (Ph13),
138.8 (Pyr4), 150.0 (Pyr6), 153.4 (Pyr2), 196.7 (C=N) ppm. IR
3
3J(H,H) = 8.8, J(H,H) = 4.4 Hz, 1 H, Pyr2], 4.82 (s, 1 H, CHN),
3.72 (m, 4 H, OCH2), 2.50 (m, 2 H, Pip2), 2.29 (m, 2 H, Pip2Ј),
1.50 (m, 4 H, Pip3/3Ј), 1.34 (m, 2 H, Pip4), 0.92 (m, 6 H, CH3)
ppm. 13C{1H} NMR ([D6]DMSO): δ = 169.3 (C=O), 167.4 (Pyr5),
146.9 (Pyr1), 134.3 (Pyr3), 122.3 (Pyr4), 119.1 (Pyr2), 73.8
[C(COOEt)2], 68.7 (CHN), 55.6 (OCH2), 51.9 (Pip2/2Ј), 26.2 (Pip3/
3Ј), 24.8 (Pip4), 14.9 (CH ) ppm. IR (Nujol, cm–1): ν = 2924 (vs),
˜
3
2854 (vs), 2809 (m), 1677 (vs), 1595 (m), 1566 (m), 1527 (s), 1463
(s), 1401 (m), 1378 (s), 1337 (m), 1288 (s), 1248 (m), 1212 (m), 1155
(m), 1108 (m), 1067 (s), 1055 (vs), 1004 (w), 983 (s), 852 (m), 788
(m), 756 (m), 731 (w), 684 (w), 633 (w) cm–1. MS (Micro-ESI pos.
in ethanol): m/z (%) = 357 ([MH]+, 18), 335 ([MH2]+ – Na+, 100),
250 ([MH – NaC5H10N]+, 38). C18H25N2NaO4 (356.40): calcd. C
60.66, H 7.07, N 7.86; found C 58.84, H 7.18, N 7.51.
Synthesis of N-(2-Pyridylmethyl)benzoylamine (9): Benzoyl chloride
(3.83 g, 27.3 mmol) was added at 0 °C to a solution of 6.06 g of (2-
pyridylmethyl)(tert-butyldimethylsilyl)amine (27.3 mmol) in 25 mL
of toluene. The solution turned yellow and a colorless precipitate
formed. All solids were removed and cooling of the filtrate to
–20 °C yielded 5.34 g of yellow crystalline 8 (25.2 mmol, 92%); m.p.
1
3
66 °C. H NMR (CDCl3): δ = 8.48 [d, J(H1,H2) = 4.8 Hz, 1 H,
3
Pyr1], 7.83 [d, J(H9,H10) = 5.2 Hz, 1 H, Ph9], 7.78 (s, 1 H, NH),
5
3
7.61 [dt, J(H3,H1) = 1.6, J(H3,H2/4) = 6 Hz, 1 H, Pyr3], 7.44 [t,
3J(H11,H10) = 3.6 Hz, 1 H, Ph11], 7.36 [t, 3J(H10,H9/11) = 6.4 Hz,
1 H, Ph10], 7.26 [d, 3J(H4,H3) = 7.6 Hz, 1 H, Pyr4], 7.14 [t,
3J(H1,H3) = 9.2 Hz, 1 H, Pyr2], 4.69 [d, 3J(H6,NH) = 4.8 Hz, 2
H, CH2] ppm. 13C{1H} NMR (CDCl3): δ = 167.3 (C=O), 156.3
(Pyr5), 148.8 (Pyr1), 136.7 (Pyr3), 134.2 (Ph8), 131.3 (Ph11), 128.4
(Ph10), 127.0 (Ph9), 122.3 (Pyr2), 122.0 (Pyr4), 44.7 (2J, CH2) ppm.
(Nujol): ν = 2616 (st, N–H–N), 2404 (st, N–H–N), 2085 (w), 1989
˜
(w), 1666 (w), 1630 (st), 1597 (m), 1348 (m), 1313 (m), 1277 (m),
1150 (w), 1025 (w), 940 (w), 777 (st), 701 (st), 639 (w), 610 (w), 565
(w) cm–1. MS (ESI): m/z (%) = 273 (100) [M – Cl]+, 198 (20), 167
(1), 109 (2).
IR (Nujol, cm–1): ν = 3288 (vs), 2923 (vs), 2854 (vs), 2550 (s), 2058
˜
[(Diphenylmethylidene)(2-pyridylmethyl)amino]zinc(II)
Chloride
(w), 1981 (w), 1646 (vs), 1580 (m), 1539 (vs), 1490 (s), 1466 (s),
1397 (m), 1328 (m), 1311 (s), 1283 (s), 1249 (w), 1171 (w), 1077
(w), 1036 (m), 1001 (w), 961 (w), 931 (vw), 839 (w), 772 (s), 714
(s), 691 (m), 627 (m), 594 (w), 506 (vw) cm–1. MS (DEI): m/z (%)
= 212 (76) [M+], 135 (14) [M+ – C6H5], 107 (91) [C6H7N2]+, 92 (34)
[C6H6N]+, 77 (100) [C6H5+]. C13H12N2O (212.25): calcd. C 73.57,
H 5.70, N 13.20; found C 72.64, H 5.55, N 13.39.
(12): solution of 1.36 g of (diphenylmethylidene)(2-pyr-
A
idylmethyl)amine (5 mmol) in 5 mL of THF was dropped at room
temp. into a solution of 0.68 g of anhydrous zinc dichloride
(5 mmol) in 5 mL of THF. Stirring at room temperature for one
hour yielded 1.22 g of a colorless crystalline precipitate of 12
(3.0 mmol, 60%) which was collected and recrystallized from THF
solution at –20 °C. 1H NMR (CH2Cl2): δ = 5.00 (s, 2 H, CH2),
7.30–7.32 (m, 2 H, Ph14), 7.34 (d, J = 8.0 Hz, 1 H, Pyr3), 7.50 (t,
Synthesis of N-(2-Pyridylmethyl)dibenzoylamine (10): A solution of
141 mg of N-(2-pyridylmethyl)benzoylamin (9) (0.66 mmol) in J = 8.0 Hz, 2 H, Ph15a), 7.54–7.62 (m, 5 H, Pyr5, Ph15, Ph16,
5 mL of toluene was cooled to 0 °C. Then 1.2 mL of a 1.6  butyl-
lithium solution in hexane was added dropwise. This red reaction
mixture was stirred for 10 min and thereafter, 0.31 g of benzoyl
chloride was added slowly. The color of the solution turned green
and LiCl precipitated. After filtration, a separation via column
chromatography gave 40 mg of green oily 10 (0.13 mmol, 19%). 1H
Ph16a), 7.80 (d, J = 8.0 Hz, 2 H, Ph14a), 7.98 (ddd, J = 1.2, J =
8.0 Hz, 1 H, Pyr4), 8.65 (d, J = 8.0 Hz, 1 H, Pyr6) ppm. 13C{1H}
NMR (CH2Cl2): δ = 56.5 (CH2), 123.2 (Pyr3), 125.2 (Pyr5), 127.6
(Ph14), 129.2 (Ph15a), 129.8 (Ph15), 130.0 (Ph14a), 131.1 (Ph16),
133.1 (Ph16a), 135.8 (Ph13), 138.5 (Ph13a), 141.1 (Pyr4), 148.1
(Pyr6), 155.2 (Pyr2), 181.6 (C=N) ppm. MS (DEI): m/z (%) = 373
NMR (CDCl3): δ = 8.53 (d, 1 H, Pyr1), 8.08 (d, 1 H, Ph9), 7.66 (19) [M – Cl]+, 272 180 (100) (98), 193 (50), 165 (42), 91 (51), 77
[dt, 5J(H3,H1) = 2.0, 3J(H3,H2/4) = 7.8 Hz, 1 H, Pyr3], 7.60 (m, 4
H, Ph11/Ph10), 7,47–7.36 (m, 3 H, Ph10/Pyr4), 7,26–7.11 (m, 4 H,
(30), 65 (25), 51 (19). IR (Nujol): ν = 3091 (w), 3061 (w), 1622 (st,
˜
C=N), 1606 (st), 1573 (m), 1486 (st), 1442 (st), 1411 (st), 1361 (m),
Ph11/Ph9/Pyr2), 5.36 (s, 2 H, CH2) ppm. 13C{1H} NMR (CDCl3): 1325 (m), 1301 (m), 1282 (m), 1232 (w), 1214 (w), 1156 (m), 1079
δ = 173.9 (C=O), 170.8 (C=O), 156.2 (Pyr5), 148.9 (Pyr1), 136.4
(w), 1046 (st), 1030 (st), 999 (w), 972 (w), 927 (w), 844 (w), 785
Eur. J. Inorg. Chem. 2008, 1067–1077
© 2008 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjic.org
1075

C. Koch, M. Kahnes, M. Schulz, H. Görls, M. Westerhausen
FULL PAPER
Table 4. Crystal data and refinement details for the X-ray structure determinations of the isotypic compounds 1 to 5 as well as 5·1/2
toluene and 6.
Compound
Formula
1
4
5
6
7
9
12
14
C50H62Li2N4O2Si2 C18H26N2O4
C24H43N3O4Si2Zn C25H44N2O4Si2Zn C72H100Li4N8O16 C13H12N2O C19H16Cl2N2Zn [C26H21N2O]+
[C4H8Cl3OZn]–
621.27
–90(2)
monoclinic
P21/n
16.7901(5)
9.0266(4)
19.3853(9)
90.00
104.958(3)
90.00
2838.4(2)
4
1.454
11.78
Fw (gmol–1
T/°C
)
821.10
–90(2)
triclinic
334.41
–90(2)
orthorhombic triclinic
Pca21
8.7613(3)
23.9270(6)
17.4661(7)
90.00
90.00
90.00
3661.4(2)
8
1.213
0.86
21481
6051
559.16
–90(2)
558.17
–90(2)
triclinic
1361.36
–90(2)
triclinic
212.25
–90(2)
monoclinic monoclinic
P21/c
11.1667(5)
20.6651(9)
9.6913(3)
90.00
90.258(2)
90.00
2236.35(16) 1813.78(11)
8
1.261
0.82
14861
3423
408.61
–90(2)
Crystal system
Space group
a/Å
b/Å
c/Å
¯
¯
¯
¯
P1
P1
P1
P1
P21/c
9.3163(10)
11.1849(13)
12.6410(16)
112.229(7)
102.238(6)
90.334(6)
1186.2(2)
1
1.149
1.16
8007
2864
8.6564(3)
9.6259(3)
19.6991(9)
101.171(3)
93.557(3)
112.797(2)
1467.39(10)
2
1.266
9.5
9809
5031
8.7050(3)
9.6937(3)
19.9190(7)
101.234(2)
93.247(2)
113.217(2)
1498.43(9)
2
1.237
9.3
11062
5252
14.6163(5)
15.7628(6)
20.3099(8)
83.186(2)
86.557(2)
85.903(2)
4628.1(3)
2
0.977
0.68
31386
10613
10.0416(4)
11.3596(4)
16.1273(5)
90.00
99.615(2)
90.00
α/°
β/°
γ/°
V/Å3
Z
4
ρ/gcm–3
µ/cm–1
Measured data
Data with
IϾ2σ(I)
1.496
16.5
12005
3090
18748
3638
Unique data/Rint 5215/0.0572
wR2 (all data, on 0.2238
F2)[a]
7936/0.0682
0.1504
6448/0.0381
0.1155
6789/0.0304
0.0950
20216/0.0379
0.2936
5094/0.0512 4127/0.0468
6464/0.0874
0.1091
0.1440
0.0810
R1 [IϾ2σ(I)][a]
0.0769
0.0574
1.027
0.0447
1.043
0.0391
1.013
0.0923
1.039
0.0553
1.031
0.0338
0.982
0.0460
0.944
s[b]
1.039
Resid. electron
dens./eÅ–3
Abs. method
Abs. corr.,
transm.min/max
CCDC
0.343/–0.407
0.293/–0.203
0.471/–0.527
0.291/–0.412
0.484/–0.348
0.178/–
0.194
multi-scan
0.9632/
0.9991
664408
0.335/–0.409
0.368/–0.438
multi-scan
0.9610/1.0249
multi-scan
0.9549/0.9856 0.8717/0.9243
multi-scan
multi-scan
0.7924/0.9430
multi-scan
0.9638/1.0101
multi-scan
0.7775/0.8505
multi-scan
0.8549/0.8856
664403
664404 664405
664406
664407
664409
664410
number[46]
2 2
2
[a] Definition of the R indices: R1 = (Σ||Fo| – |Fc||)/Σ|Fo| wR2 = {Σ[w(Fo2 – Fc ) ]/Σ[w(Fo2)2]}1/2 with w–1 = σ2(Fo2) + (aP)2. [b] s = {Σ[w(Fo
–
2 2
Fc ) ]/(No – Np)}1/2
.
(m), 776 (m), 760 (st), 740 (w), 721 (m), 711 (st), 702 (st), 663 (w), H, Pyr2], 7.30–7.48 (m, 15 H, Ph), 5.58 (s, 2 H, CH2) ppm.
650 (w), 633 (w), 581 (w), 472 (w) cm–1. C19H16Cl2N2Zn (408.658): 13C{1H}NMR (CDCl3): δ = 168.0 (C=O), 150,5 (Pyr5), 147.0
calcd. C 55.84, H 3.95, N 6.85, Cl 17.35; found C 54.55, H 3.77,
N 6.54, Cl 17.88.
(Pyr3), 138.3 (Pyr1), 127.2 (Pyr 2), 123.6 (Pyr4), 134,3–125,8; 96.8
[C(Ph)2], 67.0 (THF), 52.3 (CH2), 24.6 (THF) ppm. IR (Nujol,
cm–1): ν = 3087 (w), 2924 (vs), 2854 (vs), 1663 (vs), 1629 (m), 1579
˜
N-(Diphenylchloromethyl)-N-(2-pyridylmethyl)benzoylamine (13): A
solution of 0.92 g of (diphenylmethylidene)(2-pyridylmethyl)amine
(3.4 mmol) in 10 mL of toluene was cooled to 0 °C. Then 0.4 mL
of benzoyl chloride (3.4 mmol) was added slowly. The yellow pre-
cipitate of 13 (0.81 g, 1. 96 mmol, 58%) was collected and dried in
(w), 1499 (s), 1453 (s), 1378 (vs), 1293 (vw), 1224 (w), 1137 (w),
1099 (w), 1031 (vw), 1001 (vw), 969 (vw), 921 (vw), 854 (w), 777
(m), 748 (s), 725 (s), 716 (s), 701 (s), 672 (w), 638 (m), 606 (vw)
cm–1. MS (DEI): m/z (%) = 377 (14) [C26H21N2O], 272 (92)
[C19H16N2]+, 180 (90) [C13H10N]+, 166 (54) [C13H10]+, 105 (100)
[C6H5O]+, 77 (10) [C6H5], 72 (54) [THF], 39 (62) [Cl–], 37 (46) [Cl–].
1
3
vacuo. H NMR (CDCl3): δ = 8.98 [d, J(H1,H2) = 8.0 Hz, 1 H,
3
3
Pyr1], 8.75 [t, J(H2,H4) = 7.6 Hz, 1 H, Pyr3], 8.36 [d, J(H4,H3)
= 6.0 Hz, 1 H, Pyr4], 8.21 [t, 3J(H1,H3) = 6.6 Hz, 1 H, Pyr2], 8.00–
7.14 (m, 15 H, Ph), 5.91 (s, 2 H, CH2) ppm. 13C{1H} NMR
(CDCl3): δ = 168.0 (C=O), 151.8 (Pyr5), 147.7 (Pyr3), 138.0 (Pyr1),
X-ray Structure Determination of 1, 4, 5, 6, 7, 9, 12 and 14:[46] Inten-
sity data were collected on a Nonius Kappa CCD diffractometer
using graphite-monochromated Mo-Kα radiation. Data were cor-
127.1 (Pyr 2), 132,8–126.5 (Ph), 126.0 (Pyr4), 97.4 [C(Ph)2], 53.5 rected for Lorentz polarization and for absorption effects.[47–49]
(CH ) ppm. IR (Nujol): ν = 2924 (vs), 2854 (vs), 1783 (vw), 1741 Crystallographic data as well as structure solution and refinement
˜
2
(vw), 1662 (s), 1626 (m), 1599 (m), 1578 (w), 1495 (m), 1448 (s),
1378 (vs), 1318 (w), 1278 (m), 1216 (m), 1174 (w), 1137 (w), 1099
(w), 999 (w), 921 (vw), 850 (vw), 750 (m), 700 (s), 672 (w), 638 (w),
629 (w), 616 (vw) cm–1. MS (DEI): m/z (%) = 377 (42) [M – Cl],
details are summarized in Table 4.
The structures were solved by direct methods (SHELXS[50]) and
refined by full-matrix least-squares techniques against Fo
2
(SHELXL-97[51]). For the amino groups of 1 and 9, for the whole
compound 12 and for the methine group C19 of 6 the hydrogen
atoms were located by difference Fourier synthesis and refined iso-
tropically. The other hydrogen atoms were included at calculated
positions with fixed thermal parameters. All non-disordered, non-
hydrogen atoms were refined anisotropically.[51] The quality of
structure determination of 7 is rather poor due to thermal motion
and disordering as a consequence of the large gaps between the
272 (34) [M+
–
C7H5OCl], 180 (28) [C13H10N]+, 166 (22)
[C13H10]+, 105 (76) [C6H5O]+, 78 (10) [C6H5 + H+].
Zincate 14: A solution of 0.1 g of ZnCl2 (0.75 mmol) in 5 mL of
THF was dropped into a solution of 0.31 g of 13 in 10 mL of THF
and 1 mL of chloroform. Cooling of this yellow reaction mixture
to –20 °C afforded 0.38 g of colorless crystals of 14 (0.61 mmol,
82%), m.p. 157 °C. 1H NMR (CDCl3): δ = 8.66 [d, 3J(H1,H2) =
3
6.4 Hz, 1 H, Pyr1], 8.57 [t, J(H2,H4) = 7.2 Hz, 1 H, Pyr3], 8.18 tetramers. XP (SIEMENS Analytical X-ray Instruments, Inc.) and
3
3
[d, J(H4,H3) = 8.0 Hz, 1 H, Pyr4], 7.94 [t, J(H1,H3) = 7.2 Hz, 1
POVRAY were used for structure representations.
1076
www.eurjic.org
© 2008 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Inorg. Chem. 2008, 1067–1077

Lithium and Zinc Amine Complexes
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Acknowledgments
This work was supported in the collaborative research initiative of
the Deutsche Forschungsgemeinschaft (DFG) (SFB 436) and we
are grateful to DFG for generous funding. We also acknowledge
the generous support by the Fonds der Chemischen Industrie.
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Received: October 30, 2007
Published Online: January 7, 2008
Eur. J. Inorg. Chem. 2008, 1067–1077
© 2008 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjic.org
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