Catalytic addition of amine N-H bonds to carbodiimides by half-sandwich rare-earth metal complexes: Efficient synthesis of substituted guanidines through amine protonolysis of rare-earth metal guanidinates

Article abstract of DOI:10.1002/chem.200601383

Reaction of [Ln(CH₂SiMe₃)₃(thf) ₂] (Ln = Y, Yb, and Lu) with one equivalent of Me ₂Si(C₅Me₄H)NHR′ (R′ = Ph, 2,4,6-Me₃C₆H₂) affords straightforwardly the corresponding half-sandwich rare-earth metal alkyl complexes [{Me ₂Si(C₅Me₄)(NR′)}Ln(CH ₂SiMe₃)(thf)_u] (1: Ln = Y, R′ = Ph. n = 2: 2: Ln = Y, R′ = C₆H₂Me₃2,4,6, n = 1; 3: Ln = Y, R′ = tBu, n = 1: 4: Ln = Yb. R′ = Ph, n = 2: 5: Ln = Lu, R′ = Ph, n = 2) in high yields. These complexes, especially the yttrium complexes 1-3. serve as excellent catalyst precursors for the catalytic addition of various primary and secondary amines to carbodiimides, efficiently yielding a scries of guanidinc derivatives with a wide range of substituents on the nitrogen atoms. Functional groups such as C≡N, C≡CH. and aromatic C-X (X: F, Cl, Br, I) bonds can survive the catalytic reaction conditions. A primary amino group can be distinguished from a secondary one by the catalyst system, and therefore, the reaction of 1,2,3,4-tetrahydro-5-aminoisoquinoline with iPrN=C=NiPr can be achieved stepwise first at the primary amino group to selectively give the monoguanidine 38, and then at the cyclic secondary amino unit to give the biguanidine 39. Some key reaction intermediates or true catalyst species, such as the amido complexes [{Me₂Si(C ₅Me₄)(NPh)}Y(NEt₂)(thf)₂] (40) and [{Me₂Si(C₅Me₄)(NPh))Y(NHC₆H ₄Br4)(thf)₂] (42), and the guanidinate complexes [{Me ₂Si(C₅Me₄)(NPh)}Y{iPrNC(NEt₂)(NiPr)) (thf)] (41) and [{Me₂Si(C₅Me₄)(NPh)}Y(iPrN) C(NC₆H₄Br-4)(NH_iPr))(thf)] (44) have been isolated and structurally characterized. Reactivity studies on these complexes suggest that the present catalytic formation of a guanidine compound proceeds mechanistically through nucleophilic addition of an amido species, formed hy acid-base reaction between a rareearth metal alkyl bond and an amine N-H bond, to a carbodiimide, followed by amine protonolysis of the resultant guanidinate species.

Full text of DOI:10.1002/chem.200601383

FULL PAPER
DOI: 10.1002/chem.200601383
À
Catalytic Addition of Amine N H Bonds to Carbodiimides by Half-
Sandwich Rare-Earth Metal Complexes: Efficient Synthesis of Substituted
Guanidines through Amine Protonolysis of Rare-Earth Metal Guanidinates
Wen-Xiong Zhang, Masayoshi Nishiura, and Zhaomin Hou*[a]
ꢀ
ꢀ
Abstract: Reaction of [Ln
(thf)2] (Ln=Y, Yb, and Lu) with one
equivalent of Me2Si(C5Me4H)NHR’
(R’=Ph, 2,4,6-Me3C6H2, tBu) affords
straightforwardlythe corresponding
half-sandwich rare-earth metal alkyl
(CH2SiMe3)3-
groups such as C N, C CH, and aro-
as the amido complexes [{Me2Si-
(C5Me4)(NPh)}Y(NEt2)(thf)2] (40) and
[{Me2Si(C5Me4)(NPh)}Y(NHC6H4Br-
4)(thf)2] (42), and the guanidinate com-
plexes [{Me2Si(C5Me4)(NPh)}Y{iPrNC-
(NEt2)(NiPr)}(thf)] (41) and [{Me2Si-
(C5Me4)(NPh)}Y{iPrN}C(NC6H4Br-4)-
(NHiPr)}(thf)] (44) have been isolated
and structurallycharacterized. Reactiv-
itystudies on these complexes suggest
that the present catalytic formation of
a guanidine compound proceeds mech-
anisticallythrough nucleophilic addi-
tion of an amido species, formed by
À
E
matic C X (X: F, Cl, Br, I) bonds can
U
N
G
ACHTREUNG
G
survive the catalytic reaction condi-
tions. A primaryamino group can be
distinguished from a secondaryone by
the catalyst system, and therefore, the
reaction of 1,2,3,4-tetrahydro-5-amino-
isoquinoline with iPrN=C=NiPr can be
achieved stepwise first at the primary
amino group to selectivelygive the mo-
noguanidine 38, and then at the cyclic
secondaryamino unit to give the bigua-
nidine 39. Some keyreaction inter-
mediates or true catalyst species, such
N
ACHTREUNG
ACHTREUNG
N
A
ACHTREUNG
G
ACHTREUNG
complexes
[{Me2Si
(C5Me4)
G
A
N
ACHTREUNG
Ph, n=2; 2: Ln = Y, R’ = C6H2Me3-
2,4,6, n=1; 3: Ln = Y, R’ = tBu, n=
1; 4: Ln = Yb, R’ = Ph, n=2; 5: Ln
= Lu, R’ = Ph, n=2) in high yields.
These complexes, especiallythe yttrium
complexes 1–3, serve as excellent cata-
lyst precursors for the catalytic addi-
tion of various primaryand secondary
amines to carbodiimides, efficiently
yielding a series of guanidine deriva-
tives with a wide range of substituents
on the nitrogen atoms. Functional
acid–base reaction between
a rare-
earth metal alkyl bond and an amine
Keywords: amines · carbodiimides ·
guanidinates · guanidines · homoge-
neous catalysis · rare-earth metals
À
N H bond, to a carbodiimide, followed
byamine protonolysis of the resultant
guanidinate species.
Introduction
nidines employthe reaction of an amine compound with a
suitable electrophilic guanylating reagent[3] or functionaliza-
tion of a pre-existing guanidine core.[4] Although addition of
Multi-substituted guanidines, RN=C(NR’R’’)NHR, are an
A
À
important class of ’CN3’-core-containing compounds, which
can serve as building blocks for manybiologicallyrelevant
compounds,[1] and also as base catalysts in organic synthe-
sis.[2] Typical methods for the preparation of substituted gua-
amine N H bonds to carbodiimides (RN=C=NR) could, in
principle, provide a straightforward and atom-economical
route to guanidines, such catalytic reactions have been much
less extensivelyexplored. Primaryaliphatic amines were
known to undergo direct guanylation with carbodiimides to
yield N,N’,N’’-trialkylguanidines under rather forcing condi-
tions.[5a] However, except for some activated carbodi-
imides,[6] less nucleophilic aromatic amines or secondary
amines hardlyreact with carbodiimides under the same or
harsher conditions.[5] Tetrabutylammonium fluoride was re-
ported to promote the nucleophilic addition of some aro-
matic amines to carbodiimides.[7] Recently, titanium and va-
nadium imido complexes were reported to catalyze the addi-
tion of primaryaromatic amines to carbodiimides to afford
the corresponding guanidines,[5] but secondaryamines could
[a] Dr. W.-X. Zhang, Dr. M. Nishiura, Prof. Dr. Z. Hou
Organometallic ChemistryLaboratory
RIKEN (The Institute of Physical and Chemical Research)
Hirosawa 2–1, Wako, Saitama 351–0198 (Japan)
and
PRESTO, Japan Science and TechnologyAgency(JST) (Japan)
Fax : (+81)48-462-4665
E-mail: houz@riken.jp
Supporting information for this article is available on the WWW
under http://www.chemeurj.org/ or from the author.
Chem. Eur. J. 2007, 13, 4037 – 4051
ꢀ 2007 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
4037

not be used in these reactions, because the formation of a
“M=N” imido moietyis required for the catalytic process.
On the other hand, nucleophilic addition of metal amido
reagents “
ACHTREUNG
sponding guanidinate species “
A
ACHTREUNG
well-established process.[8–11] The monoanionic guanidinate
units are well known as stabilization ligands for various
metal complexes, including those of lanthanide and early
transition metals, because theycan form strong chelating
bonds with metal ions.[8–11] Catalytic transformation of a
metal guanidinate species is rare and has remained unknown
Scheme 1. Synthesis of half-sandwich yttrium, ytterbium, and lutetium
alkyl complexes.
[12,13]
until veryrecently.
We have recentlyfound that half-sandwich rare-earth
metal amidinates can be catalytically protonated by terminal
alkynes under appropriate conditions, which led to the cata-
lytic addition of terminal alkynes to carbodiimides to give a
series of propiolamidine compounds previouslyunavailable
with other means.[14] We report here that catalytic addition
Table 1. Selected bond lengths [Š] and angles [8] for 1, 4, and 5.
1
4
5
Ln
Y
Yb
Lu
À
Ln N
À
Ln O
2.327(5)
2.382(3)
2.382(3)
2.481(6)
2.336(6)
2.628
96.8(2)
98.1(3)
102.7(2)
138.0(2)
2.285(4)
2.361(2)
2.361(2)
2.423(5)
2.310(5)
2.607
97.8(2)
97.8(2)
102.7(2)
137.6(1)
2.283(5)
2.349(3)
2.349(3)
2.423(7)
2.296(7)
2.595
98.3(2)
97.9(3)
102.6(3)
138.0(2)
À
of amine N H bonds to carbodiimides can be achieved anal-
À
Ln O*
À
Ln C
A
ogouslybythe use of half-sandwich rare-earth metal alkyl
complexes as catalyst precursors, yielding a new family of
guanidines with various substituents. The corresponding
rare-earth metal guanidinate complexes have been con-
firmed to be true catalyst species in this process. A portion
À
Ln Cp
U
À
Ln Cp(av)
N-Ln-Cp
N-Si-C(Cp)
Si-N-Ln
O-Ln-O*
[12]
of this work has been communicated previously.
Results and Discussion
Synthesis of silylene-linked cyclopentadienyl-amido rare-
earth metal alkyl complexes: The yttrium alkyl complex
bearing the silylene-linked cyclopentadienyl-tert-butylamido
ligand, [{Me2Si
been reported previously. The analogous cyclopentadien-
yl-arylamido rare-earth metal complexes [{Me2Si-
(C5Me4)(NR)}Ln(CH2SiMe3)(thf)n] (1: Ln = Y, R = Ph,
A
G
G
G
[15]
A
N
ACHTREUNG
n=2; 2: Ln = Y, R = C6H2Me3-2,4,6, n=1; 4: Ln = Yb, R
= Ph, n=2; 5: Ln = Lu, R = Ph, n=2) were prepared
similarlyin high yields bythe acid–base reactions between
the rare-earth metal tris
N
N
ACHTREUNG
(C5Me4H)SiMe2NHR’ (Scheme 1).[17,18] X-rayanalsyes re-
vealed that complexes 1, 4, and 5 are isostructural and iso-
morphous. Their selected bond lengths and angles are sum-
marized in Table 1, and onlythe ORTEP drawing of 1 is
shown in Figure 1. It is noteworthythat the complex pos-
sesses a crystallographic mirror plane in the solid state, in
which the whole phenyl ring, N1, Si2, C4, Y1, C1, Si1, and
Figure 1. ORTEP drawing of 1 with 30% probabilitythermal ellipsoids.
Hydrogen atoms are omitted for clarity.
the phenyl amido ligand compared to that of the alkyl
À
amido ligand. The bond lengths of the Y1 C1 (2.481(6) Š),
À
À
À
C2 are located. The C6 C6* bond of the Cp ring and the
Y1 Cp (centroid) (2.336(6) Š), and Y1 O1 (2.382(3) Š)
whole molecule are thus bisected bythe mirror plane. The
bonds in 1 are comparable with those found in [{Me2Si-
À
bond length of the Y1 N1 bond in the phenyl amido com-
plex 1 (2.327(5) Š) is significantlylonger than that in the
C
G
G
A
[15a]
analogous
alkyl
amido
complex
[{Me2Si(C5Me4)-
A
A
G
A
Catalytic addition of primary aromatic amines to carbodi-
the difference in coordination number between the metal
centers of these two complexes is taken into account.[19] This
is probablydue to the weaker electron-donating power of
C
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Chem. Eur. J. 2007, 13, 4037 – 4051

Amine Protonolysis of Rare-Earth Metal Guanidinates
FULL PAPER
Table 3. Catalytic addition of various primary anilines to carbodiimides.[a]
was heated with aniline in C6D6 at 808C or in C6D5Cl at
1408C, but no reaction was observed in 24 h (Table 2, en-
tries 1 and 2). In contrast, addition of a small amount (1–2
Table 2. Catalytic addition of an aniline to a N,N’-diisopropylcarbodi-
imide.[a]
EntryArNH
1
RN=C=NR
Product (Yield[%][b]
)
2
iPrN=C=NiPr
EntryCataslyt (mol%)
Solvent
C6D6
Temp
[8C]
Time
[h]
Yield
[%][b]
2
3
4
iPrN=C=NiPr
iPrN=C=NiPr
CyN=C=NCy
1
2
3
4
5
6
7
8
0
0
80
140
80
80
80
80
80
80
24
24
0
0
C6D5Cl
C6D6
C6D6
C6D6
C6D6
C6D6
1 (2)
2 (2)
3 (2)
4 (2)
5 (2)
0.5
0.5
0.5
0.5
0.5
0.5
83
83
82
75
57
32
A
U
(2)
9
10
11
12
13
14
15
16
17
18
1 (2)
1 (2)
1 (1)
1 (1)
1 (0.5)
1 (0.5)
1 (1)
1 (1)
1 (1)
1 (1)
[D8]THF
[D8]toluene 80
80
0.5
0.5
0.5
1
1
3
1
24
1
81
82
62
>99
60
96
11
62
33
92
C6D6
C6D6
C6D6
C6D6
C6D6
C6D6
C6D6
C6D6
80
80
80
5
iPrN=C=NiPr
80
RT
RT
50
6
7
8
9
iPrN=C=NiPr
iPrN=C=NiPr
iPrN=C=NiPr
iPrN=C=NiPr
50
24
[a] Conditions:
aniline,
0.51 mmol;
N,N’-diisopropylcarbodiimide,
0.50 mmol. [b] Yields were determined by 1H NMR spectroscopyby
using 1,3,5-trimethylbenzene as an internal standard.
mol%) of the half-sandwich yttrium alkyl complex 1 at
808C led to rapid addition of aniline to iPrN=C=NiPr to
give the N,N’,N’’-trisubstituted guanidine 6 in high yields
(see Table 2, entries 3 and 12). Other complexes (2–5) were
also effective for this catalytic reaction, although the activity
of the Yb (4) and Lu (5) complexes was slightlylower than
that of the Y analogue 1 (Table 2, entries 3–7). The R sub-
stituents on the amido unit in the Y complexes 1–3 did not
show a significant influence on the catalytic activity in the
present reaction (Table 2, entries 3–5). However, the
10
11
CyN=C=NCy
EtN=C=NtBu
bis(pentamethylcyclopentadienyl)yttrium
[(C5Me5)2YCH(SiMe3)2] (Table 2, entry8) showed much
complex
ACHTREUNG
lower activitythan those of the half-sandwich Y analogues
1–3.
[a] Conditions: amines, 2.02 mmol; carbodiimides, 2.00 mmol; catalyst 1,
0.02 mmol; benzene, 5 mL. [b] Yield of isolated product.
The yttrium complex 1 was then chosen as a catalyst for
the addition reaction of various aromatic primaryamines
with carbodiimides. Representative results are summarized
in Tables 3 and 4. As shown in Table 3, a wide range of sub-
stituted anilines could be used for this reaction. The reaction
was not influenced byeither electron-withdrawing or elec-
tron-donating substituents or the position of the substituents
À
entry1), and C I (Table 3, entries 2 and 8) bonds survived
in the present reactions. In the case of p-aminophenylacety-
lene, the reaction took place selectivelyat the amino group,
but the terminal alkyne unit remained unchanged (Table 3,
entry 5), although amino-free phenylacetylene can undergo
À
at the phenyl ring (Table 3, entries 1–11). Aromatic C F
À
À
(Table 3, entry7), C Cl (Table 3, entry6), C Br (Table 3,
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4039

Z. Hou et al.
Table 4. Catalytic addition of heterocyclic primary amines to carbodiimi-
des.[a]
catalytic addition to carbodiimides under the similar condi-
tions.[14]
A varietyof heterocyclic primaryamines such as amino-
substituted isoxazoles, pyrazoles, imidazoles, thiazoles, and
pyridine could also be used for this reaction, as shown in
Table 4. THF seemed to be a better solvent than benzene or
toluene in this case, probablydue to the better solubilityof
the heterocyclic amine compounds in THF. In the presence
of 0.5 mol% of 1, the reaction of 5-methylisoxazol-3-amine
with iPrN=C=NiPr was completed within one hour at room
temperature in THF, yielding quantitatively the correspond-
ing guanidine compound 18 (Table 4, entry1). In the case of
the bulkier 1-tert-butyl-3-ethylcarbodiimide, the reaction
with 5-methylisoxazol-3-amine required a higher tempera-
ture (808C) for completion in one hour (Table 4, entry3).
Consistent with this observation, the reaction between 5-
methylisoxazol-3-amine and the further bulkier N,N’-di-tert-
butylcarbodiimide did not occur under the same conditions,
probablydue to steric hindrance.
EntryRNH
RN=C=NR
Temp Product
[8C] )
(Yield[%][b]
2
G
1
iPrN=C=NiPr RT
CyN=C=NCyRT
EtN=C=NtBu 80
2
3
1
The H and 13C NMR spectra of the guanidine products
7–16, 18, 19, and 22–26, formed bythe reactions of aromatic
primaryamines with the symmetric carbodiimides iPrN=C=
NiPr or CyN=C=NCy(Cy =cyclohexyl), all showed one set
of signals for the iPr or Cygroups, suggesting that the two
iPr or Cygroups in each guanidine product should be in a
similar environment. An X-raystructure analysis of 10 re-
vealed that both cyclohexylamino groups in 10 bear a
proton on their nitrogen atoms, whereas the aromatic sub-
stituent C6H4CN-p is bonded to the imino-nitrogen atom
(C=N) (Figure 2 and Table 3, entry4). This is in agreement
4
5
EtN=C=NtBu RT
iPrN=C=NiPr RT
with the H and 13C NMR spectra in solution. The H and
13C NMR spectra of the guanidine products 17, 20, and 21,
which resulted from the reactions with the unsymmetrical
carbodiimide EtN=C=NtBu, also suggested the presence of
onlyone isomer in solution. An X-raystructure analysis of
21 revealed that 21 adopts the E configuration, in which the
bulkier NtBu group is placed trans to the aromatic substitu-
ent around the C=N double bond (Figure 3 and Table 4,
entry4).
Diamines and triamines can also be applied in this catalyt-
ic reaction. In the presence of 1 mol% of 1, the reaction of
1,3-diaminobenzene with two equivalents of iPrN=C=NiPr
gave quantitativelythe corresponding biguanidine com-
pound 27 (Scheme 2). Similarly, the reaction of 2,4,6-triami-
nopyrimidine with three equivalents of iPrN=C=NiPr yield-
ed the triguanidine compound 28 in high yield. These multi-
guanidine-functionalized compounds could serve as useful
templates (or ligands) for the construction of further larger
molecules.
1
1
6
7
8
9
iPrN=C=NiPr 80
iPrN=C=NiPr 50
iPrN=C=NiPr 80
iPrN=C=NiPr 80
[a] Conditions: amines, 2.02 mmol; carbodiimides, 2.00 mmol; catalyst 1,
0.01 mmol; THF, 5 mL, unless otherwise noted. [b] Yield of isolated
product. [c] Conditions: Amine, 2.02 mmol; carbodiimide, 2.00 mmol;
catalyst 1, 0.02 mmol; benzene, 5 mL.
Catalytic addition of secondary amines to carbodiimides:
Secondaryamines are generallyless reactive than primary
amines toward carbodiimides. However, in the presence of
3 mol% of 1, various acyclic and cyclic secondary amines
could be added to iPrN=C=NiPr or CyN=C=NCyat 80 8C
or
a
higher temperature, to give the corresponding
tive yields (Table 5). When a diamine such as piperazine
N,N’,N’’,N’’-tetrasubstituted guanidines in almost quantita-
was used to react with two equivalents of iPrN=C=NiPr, the
4040
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Chem. Eur. J. 2007, 13, 4037 – 4051

Amine Protonolysis of Rare-Earth Metal Guanidinates
FULL PAPER
Table 5. Catalytic addition of secondary amines to carbodiimides.[a]
Figure 2. ORTEP drawing of 10 with 30% probabilitythermal ellipsoids.
Hydrogen atoms, except those on the nitrogen atoms, are omitted for
À
À
clarity. Selected bond lengths [Š] and angles [8]: N1 C1 1.324(3), N2 C1
EntryAmine
1
R
Temp[ 8C]
(Time[h])
Product (Yield[%][b]
)
À
À
1.352(3), N3 C1 1.366(3), N4 C8 1.131(3); N1-C1-N2 119.9(2), N1-C1-
N3 125.8(2), N2-C1-N3 114.3(2).
iPr 80 (3)
2
3
4
iPr 80 (3)
iPr 80 (3)
iPr 80 (0.5)
Figure 3. ORTEP drawing of 21 with 30% probabilitythermal ellipsoids.
Hydrogen atoms, except those on the nitrogen atoms, are omitted for
5
iPr 110 (5)
À
À
clarity. Selected bond lengths [Š] and angles [8]: N3 C1 1.3110(19), N4
À
C1 1.348(2), N5 C1 1.369(2), N3-C1-N4 120.5(1), N3-C1-N5 125.9(2),
N4-C1-N5 113.6(1), C1-N3-C(8) 119.7(1).
6
7
Cy80 (1)
Cy80 (0.5)
8
9
iPr 80 (1)
iPr 80 (3)
[a] Conditions: amines, 2.00 mmol; carbodiimides, 2.00 mmol; catalyst 1,
0.06 mmol; benzene, 5 mL. [b] Yield of isolated product.
Scheme 2. Catalytic addition of di- and triamines to a carbodiimide.
37) in the present reactions suggested that onlyone isomer
is present for each compound in solution. An X-raystruc-
ture analysis of 35 revealed that it is Eanti in the solid state
(Figure 4 and Table 5, entry7).
In the presence of 3 mol% of 1, the reaction of 1,2,3,4-tet-
rahydro-5-aminoisoquinoline with one equivalent of iPrN=
corresponding biguanidine 37 was formed in 99% yield by a
double catalytic addition reaction (Table 5, entry 9).
Although tetrasubstituted guanidines could, in principle,
[20]
1
have four possible isomers Eanti, Esyn, Zanti, Zsyn
,
the H and
13C NMR spectra of the resulting guanidine compounds (29–
Chem. Eur. J. 2007, 13, 4037 – 4051
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4041

Z. Hou et al.
Mechanistic studies:
a) Reaction of secondary amines: To gain information on
the true catalyst species, the stoichiometric reaction of 1
with diethylamine was first carried out in benzene, which
gave instantlythe corresponding amido complex [{Me 2Si-
A
(NPh)}Y
G
N
temperature (Scheme 4). Nucleophilic addition of 40 to
Figure 4. ORTEP drawing of 35 with 30% probabilitythermal ellipsoids.
Hydrogen atoms, except that of the nitrogen atom N2, are omitted for
À
À
clarity. Selected bond lengths [Š] and angles [8]: N1 C1 1.394(3), N2 C1
À
1.394(3), N3 C1 1.289(3); N1-C1-N2 113.0(2), N3-C1-N1 119.4(2), N3-
C1-N2 127.6(2), C1-N3-C17 120.3(2).
C=NiPr at 808C took place selectivelyat the primaryamino
group to give the monoguanidine compound 38 (Scheme 3),
Scheme 4. Formation of an yttrium guanidinate complex and its reaction
with diethylamine.
À
but no reaction was observed at the cyclic secondary N H
iPrN=C=NiPr took place rapidlyto give the guanidinate
complex [{Me2Si
A
(NPh)}Y
U
(NEt2)
N
N
(41) in 92% yield. The reaction between the chelating Cp-
À
anilido Y N bond and iPrN=C=NiPr was not observed even
in the presence of an excess amount of iPrN=C=NiPr. Both
40 and 41 have been structurallycharacterized byX-ray
structure analyses (Figures 5 and 6).
Scheme 3. Stepwise catalytic addition of 1,2,3,4-tetrahydro-5-aminoiso-
quinoline to N,N’-diisopropylcarbodiimide.
bond, showing that a primaryamino group can be distin-
guished from a secondaryone under the present catalytic
conditions. Heating the reaction mixture with another equiv-
alent of iPrN=C=NiPr at 1108C for three hours afforded the
biguanidine 39 almost quantitatively. The biguanidine 39
could also be obtained alternativelybyreaction of 1,2,3,4-
tetrahydro-5-aminoisoquinoline with two equivalents of
iPrN=C=NiPr at 1108C (Scheme 3).
Figure 5. ORTEP drawing of 40 with 30% probabilitythermal ellipsoids.
Hydrogen atoms are omitted for clarity. Selected bond lengths [Š] and
À
À
À
À
angles [8]: Y1 N1 2.324(2), Y1 N2 2.199(3), Y1 O1 2.399(2), Y1 O2
À
À
À
À
2.398(2), Y1 C1 2.567(3), Y1 C2 2.635(3), Y1 C3 2.709(3), Y1 C4
À
À
2.693(3), Y1 C5 2.625(3), Y1 Cp
(centroid) 96.2(1), N2-Y1-Cp(centroid) 142.9(1), N2-Y1-N1 142.94(10),
O2-Y1-O1 142.10(7), N1-Si1-C1 99.12(14).
(centroid) 2.358(3); N1-Y1-Cp-
N
ACHTREUNG
4042
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ꢀ 2007 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Chem. Eur. J. 2007, 13, 4037 – 4051

Amine Protonolysis of Rare-Earth Metal Guanidinates
FULL PAPER
would afford directlythe guanidinate species B. Protonation
of B byanother molecule of amine would regenerate the
amido complex A and release the guanidine C. Rearrange-
À
ment of C through C N bond rotation to D and the subse-
quent 1,3-hydrogen shift would take place to give the more
stable E isomer E. The isolation of the guanidinate 41 and
its reaction with diethylamine to give guanidine 29 and the
amido 41 (see Scheme 4) stronglysupport this mechanism.
b) Reaction of primary amines: The reaction of 1 with one
equivalent of 4-bromoaniline at room temperature took
place rapidlyto afford the corresponding structurallychar-
acterizable amido complex 42 (Scheme 6 and Figure 7). The
Figure 6. ORTEP drawing of 41 with 30% probabilitythermal ellipsoids.
Hydrogen atoms are omitted for clarity. Selected bond lengths [Š] and
À
À
À
À
angles [8]: Y1 N1 2.282(2), Y1 N3 2.462(2), Y1 N4 2.304(2), Y1 O1
À
À
À
À
2.4145(19), Y1 C12 2.573(3), Y1 C13 2.629(3), Y1 C14 2.743(3), Y1
À
À
À
C15 2.778(3), Y1 C16 2.673(3), Y1 Cp
ACHTREUNG
À
À
AHCTREUNG
A
ACHTREUNG
97.92(8), N1-Y1-N3 140.21(8), N4-Y1-N3 56.48(7), C1-N4-Y1 95.4(2),
N3-C1-N4 115.1(3), N3-C1-N2 124.1(3), N4-C1-N2 120.8(3), N1-Si1-C12
96.6(1).
At room temperature, no reaction was observed between
the guanidinate complex 41 and diethylamine. However,
when a 1:1 mixture of 41 and diethylamine was heated to
808C, the corresponding guanidine compound iPrN=C-
A
almost quantitatively(Scheme 4). When excess diethylamine
and iPrN=C=NiPr (1:1) were added to 41 in C6D6 at 808C,
catalytic formation of 29 was achieved.
On the basis of the above observations, a possible catalyt-
ic cycle for the addition of secondary amines to carbodi-
imides could be proposed as shown in Scheme 5. The acid–
base reaction between the yttrium alkyl complex 1 and an
amine should simplyyield an amido species such as A. Nu-
cleophilic addition of the amido species to a carbodiimide
Scheme 6. Formation of yttrium guanidinates and their reactions with 4-
bromoaniline.
reaction of 42 with one equivalent of iPrN=C=NiPr in C6D6
below 108C gave the corresponding addition product 43 in
96% yield in two hours. The guanidinate complex 43 was
not stable at room temperature in solution, and gradually
changed to 44 through intramolecular proton transfer from
the aryl amino nitrogen atom to an isopropyl amido nitro-
gen atom, followed bydissociation of the resultant isopropyl
amino group from the metal center and formation of an aryl
À
amido Y bond (Scheme 6). This isomerization reaction
probablyoccurs because the aryl amine proton in 43 is more
acidic than the isopropylamine proton in 44. The transfor-
mation of 43 to 44 took place more rapidlyat higher tem-
peratures. If the reaction of 42 with iPrN=C=NiPr was car-
ried out at 808C, onlythe formation of 44 was observed,
Scheme 5. A possible mechanism of catalytic addition of secondary
amines to carbodiimides.
Chem. Eur. J. 2007, 13, 4037 – 4051
ꢀ 2007 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemeurj.org
4043

Z. Hou et al.
At room temperature, a reaction between 44 (or 43) and
4-bromoaniline did not take place. However, when a 1:1
mixture of 44 (or 43) and 4-bromoaniline was heated to
808C in C6D6, 4-BrC6H4N=C(NHiPr)2 (7) and 42 were
A
formed almost quantitatively(Scheme 6). Rapid cataltyic
formation of 7 was achieved when excess 4-bromoaniline
and iPrN=C=NiPr (1:1) were added to 44 (or 43) at 808C.
A possible catalytic cycle for the addition reaction of pri-
maryaromatic amines to carbodiimides is shown in
Scheme 7. The acid–base reaction between a half-sandwich
Figure 7. ORTEP drawing of 42 with 30% probabilitythermal ellipsoids.
Hydrogen atoms, except that on the nitrogen atom N1, are omitted for
À
À
clarity. Selected bond lengths [Š] and angles [8]: Y1 N1 2.297(4), Y1 N2
À
À
À
À
2.337(4), Y1 O1 2.367(3), Y1 O2 2.383(4), Y1 C7 2.523(5), Y1 C8
À
À
À
À
2.597(5), Y1 C9 2.683(5), Y1 C10 2.688(5), Y1 C11 2.598(5), Y1 Cp-
(centroid) 2.321(5); N1-Y1-Cp(centroid) 107.6(2), N2-Y1-Cp(centroid)
C
G
ACHTREUNG
97.1(2), O1-Y1-O2 132.1(1), N1-Y1-N2 155.3(2), N2-Si1-C7 97.9(2).
whereas the reaction at room temperature gave a mixture of
43 and 44 at the earlystage. A reaction between the chelat-
À
ing Cp-anilido Y N bond and iPrN=C=NiPr was not ob-
served even in the presence of an excess of iPrN=C=NiPr,
as in the case of 41. Complex 44 was structurallycharacter-
ized byan X-rayanalysis (Figure 8). The bond length of the
À
N2 C18 bond (1.307(8) Š) is significantlyshorter than that
À
of the N1 C18 (1.376(8) Š) bond in the guanidinate unit,
À
and the latter is the same as that of the N3 C18 bond
(1.376(7) Š), suggesting that the C=N double bond of the
guanidinate unit in 44 is highlylocalized between the N2
and C18 atoms.
Scheme 7. A possible mechanism of catalytic addition of primary aromat-
ic amines to carbodiimides.
rare-earth metal alkyl and a primary amine yields an amido
species such as F. Nucleophilic addition of the amido species
to a carbodiimide would first afford the symmetrical guani-
dinate species G, which could then quicklybe rearranged to
the unsymmetrical guanidinate species H at high tempera-
ture through the intramolecular 1,3-hydrogen shift (path a).
Protonolysis of H byanother molecule of primayamine
would regenerate the amido F and release the guanidine I.
An intramolecular 1,3-hydrogen shift in I could give the
more stable final product J. Formation of I through proto-
nolysis of G (path b) could also be possible (see also
Scheme 6).
Figure 8. ORTEP drawing of 44 with 30% probabilitythermal ellipsoids.
Hydrogen atoms, except that on the nitrogen atom N3, are omitted for
Conclusion
À
À
clarity. Selected bond lengths [Š] and angles [8]: Y1 N1 2.370(5), Y1 N2
À
À
À
À
2.326(6), Y1 N4 2.283(5), Y1 O1 2.323(4), Y1 C1 2.527(7), Y1 C2
Rare-earth metal alkyl complexes bearing the silylene-
linked cyclopentadienyl-amido ligands such as 1–5, which
can be easilyprepared bythe reactions of the rare-earth
À
À
À
À
2.628(7), Y1 C3 2.733(7), Y1 C(4) 2.720(7), Y1 C5 2.581(6), Y1 Cp-
À
À
À
ACHTREUNG
G
ACHTREUNG
ACHTREUNG
metal tris
A
G
A
Y1-N1 57.0(2), C18-N1-Y1 92.8(4), C18-N2-Y1 96.7(5), C18-N3-C19
124.6(6), N2-C18-N3 124.3(7), N2-C18-N1 113.4(7), N3-C18-N1 122.4(6),
N4-Si1-C1 97.5(3).
corresponding neutral ligands (C5Me4H)SiMe2NHR’, can
serve as excellent catalyst precursors for the catalytic addi-
4044
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ꢀ 2007 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Chem. Eur. J. 2007, 13, 4037 – 4051

Amine Protonolysis of Rare-Earth Metal Guanidinates
FULL PAPER
À
2,4,6)NH2 in THF was added to a solution of (C5Me4H)SiMe2Cl (1 g,
4.66 mmol) in THF (30 mL). The reaction mixture was stirred at room
temperature for 12 h. After removal of the solvent under reduced pres-
sure, the residue was extracted with hexane. Evaporation of hexane gave
tion of various amine N H bonds to carbodiimides, leading
to efficient formation of a series of guanidine derivatives
with a wide range of substituents on the nitrogen atoms.
ꢀ
ꢀ
À
Functional groups such as C N, C CH, and aromatic C X
(X=F, Cl, Br, I) bonds can survive the catalytic reaction
conditions. A primaryamino group can be distinguished
from a secondary one by the catalyst system under appropri-
ate conditions, and therefore, the reaction of 1,2,3,4-tetrahy-
dro-5-aminoisoquinoline with iPrN=C=NiPr can be achieved
stepwise first at the primaryamino group to selectivelygive
the monoguanidine 38, and then at the cyclic secondary
amino unit to give the biguanidine 39. The isolation and re-
activityinvestigation of the amido (e.g., 40 and 42) and gua-
nidinate intermediates (e.g., 41 and 44) suggest that the cat-
alytic formation of a guanidine compound proceeds through
nucleophilic addition of an amido species, formed byacid–
base reaction between a rare-earth metal alkyl bond and an
(C5Me4H)SiMe2NH(C6H2Me3-2,4,6) as
a light yellow oil (1.4 g, 96%
based on (C5Me4H)SiMe2Cl). 1H NMR (300 MHz, CDCl3): d=0.28 (s,
6H; SiMe2), 1.98 (s, 6H; C5Me4), 2.15 (s, 6H; C5Me4), 2.27 (s, 6H; o-
C6H2
A
ACHTREUNG
1H; NH), 6.88 ppm (s, 2H; C6H2
AHCTREUNG
258C): d=0.3, 11.4, 14.6, 19.7, 20.6, 56.7, 128.8, 130.0, 130.5, 133.0, 136.9,
140.2 ppm.
A
SiMe2), 0.45 (brs, 1H; NH), 1.12 (s, 9H; C(CH3)3), 1.79 (s, 6H; C5Me4),
A
1.95 (s, 6H; C5Me4), 2.81 ppm (s, 1H; C5Me4H); 13C NMR (75 MHz,
CDCl3, 258C): d=0.9, 11.1, 14.7, 33.7, 49.3, 56.9, 133.3, 135.3 ppm.
A
(C5Me4)
U
G
(thf)2]
(1):
A
solution
of
A
ACHTREUNG
at room temperature. Immediate formation of a white precipitate was ob-
served. After the mixture was stirred for 2 h, the precipitate was collected
bydecanting the solution and was washed with hexane to give 1 (1.2 g,
95%). Single crystals of 1·0.5hexane could be grown from a concentrated
solution in hexane for one dayat room temperature. 1H NMR (300 MHz,
C6D6): d=À0.99 (d, J(Y,H) =2.5 Hz, 2H; CH2), 0.27 (s, 9H; SiMe3), 0.86 (s,
6H; SiMe2), 1.22 (s, 8H; b-CH2, THF), 2.08 (s, 6H; C5Me4), 2.11 (s, 6H;
C5Me4), 3.68 (s, 8H; a-CH2, THF), 6.70 (t, J=8.2 Hz, 1H; p-C6H5), 6.72
(d, J=8.2 Hz, 2H; o-C6H5), 7.25 ppm (t, J=8.3 Hz, 2H; m-C6H5);
À
amine N H bond, to a carbodiimide, followed byamine
protonolysis of the resultant guanidinate species. These re-
sults have demonstrated that a guanidinate unit, though
being often used as a supporting ligand for various metal
complexes, does not always behave as a “spectator” ligand,
and can itself participate in a reaction in a catalytic fashion
under appropriate conditions.
13C NMR (75 MHz, [D8]THF): d=4.8, 4.9, 11.8, 14.3, 23.1 (d, J(Y,C)
=
38.6 Hz), 26.4, 68.2, 106.2, 114.8, 120.5, 126.4, 127.6, 129.3, 157.2 ppm; ele-
mental analysis calcd (%) for C29H50NO2Si2Y: C 59.06, H 8.54, N 2.37;
found: C 59.66, H 8.62, N 2.37.
A
N
G
N
A
ACHTREUNG
Experimental Section
white powder (985 mg, 88% yield) in a manner analogous to that de-
scribed for the synthesis of 1. 1H NMR (300 MHz, C6D6): d=À0.88 (d,
All reactions were carried out under a dryand oxygen-free argon atmos-
phere byusing Schlenk techniques or under a nitrogen atmosphere in an
MBRAUN glovebox. The argon was purified bypassing it through a
Dryclean column (4Š molecular sieves, Nikka Seiko Co.) and a Gasclean
GC-XR column (Nikka Seiko Co.). The nitrogen in the glovebox was
constantlycirculated through a copper/molecular sieve catalyst unit. The
oxygen and moisture concentrations in the glovebox atmosphere were
monitored byan O 2/H2O Combi-Analyzer (MBRAUN) to ensure both
were always below 1 ppm. Solvents were distilled from sodium/benzophe-
none ketyl, degassed by the freeze-pump-thaw method (three times), and
dried over fresh Na chips in the glovebox. [D6]Benzene, [D8]toluene, and
[D8]THF (all 99+ atom% D) were obtained from Acros and were dried
over fresh Na chips in the glovebox for NMR reactions. All organic start-
ing materials were purchased from TCI or Aldrich and were dried over
J
(Y,H) =2.5 Hz, 2H; CH2), 0.28 (s, 9H; SiMe3), 0.86 (s, 6H; SiMe2), 1.25 (s,
4H; b-CH2, THF), 2.07 (s, 6H; C5Me4), 2.12 (s, 6H; C5Me4), 2.38 (s, 6H;
o-C6H2(CH3)3), 2.54 (s, 3H; p-C6H2(CH3)3), 3.32 (s, 4H; a-CH2, THF),
6.92 ppm (s, 2H; C6H2
(CH3)3); 13C NMR (75 MHz, C6D6): d=4.7, 5.8,
6.4, 11.0, 11.7, 14.5, 14.6, 20.8, 21.1, 23.1 (d, J(Y,C) =38.6 Hz), 25.3, 71.0,
106.4, 110.5, 120.5, 126.4, 127.6, 129.3, 150.3 ppm; elemental analysis
calcd (%) for C28H48NO2Si2Y: C 60.08, H 8.64, N 2.50; found: C 59.70, H
8.52, N 2.39.
G
ACHTREUNG
AHCTREUNG
A
U
(NPh)}Yb
G
U
G
ACHTREUNG
powder (124 mg, 90% yield) in a manner analogous to that described for
the synthesis of 1. Single crystals of 4·0.5hexane could be grown from a
concentrated solution in hexane for one dayat room temperature. Ele-
mental analysis calcd (%) for C29H50NO2Si2Yb: C 51.68, H 7.48, N 2.08;
found: C 51.99, H 7.59, N 1.82.
˚
molecular sieves (4A) for two days, and when appropriate, were distilled
prior to use. The ligands (C5Me4H)SiMe2NHR’ (R’: Ph, tBu) were pre-
pared bythe reaction of (C 5Me4H)SiMe2Cl with R’NHLi (generated in
situ from nBuLi with one equivalent of R’NH2 in THF) as described pre-
E
N
(NPh)}Lu
U
G
E
ACHTREUNG
[17]
viously. (C5Me4H)SiMe2NH(C6H2Me3-2,4,6) was prepared analogously.
powder (582 mg, 92% yield) in a manner analogous to that described for
the synthesis of 1. Single crystals of 5·0.5hexane could be grown from a
concentrated hexane solution for one dayat room temperature. 1H NMR
(300 MHz, C6D6): d=À0.86 (d, 2H; CH2), 0.25 (s, 9H; SiMe3), 0.84 (s,
6H; SiMe2), 1.17 (s, 8H; b-CH2, THF), 2.06 (s, 6H; C5Me4), 2.15 (s, 6H;
C5Me4), 3.56 (s, 8H; a-CH2, THF), 6.74 (t, J=7.5 Hz, 1H; p-C6H5), 6.90
(d, J=7.6 Hz, 2H; o-C6H5), 7.25 ppm (t, J=7.6 Hz, 2H; m-C6H5);
13C NMR (75 MHz, [D8]THF): d=4.5, 5.0, 11.8, 14.2, 26.3, 27.8, 68.2,
105.2, 114.7, 120.6, 126.1, 127.4, 129.2, 157.3 ppm; elemental analysis
calcd (%) for C29H50NO2Si2Lu: C 51.54, H 7.46, N 2.07; found: C 52.06,
H 7.63, N 1.98.
[{Me2Si
A
(NtBu)}Y
N
N
ACHTREUNG
IR spectra were obtained on a Shimadzu IRPrestige-21 spectrophotome-
ter byusing Nujol mulls between KBr disks. HRMS were recorded on a
JEOL JMS-700 instrument operated in EF-FAB+ mode. Organometallic
samples for NMR spectroscopic measurements were prepared in the glo-
vebox byuse of J. Young valve NMR tubes (Wilmad 528-JY). 1H and
13C NMR spectra were recorded on a JEOL JNM-AL400 spectrometer
(FT, 400 MHz for 1H; 100 MHz for 13C) or a JEOL JNM-AL300 spec-
trometer (FT, 300 MHz for 1H; 75 MHz for 13C) at room temperature,
unless otherwise noted. Micro elemental analyses were performed on a
MICRO CORDER JM10 apparatus (J-Science Lab. Co.).
Typical procedures for the catalytic reaction of primary aromatic amines
to carbodiimides: i) NMR tube reaction: In the glovebox, a J. Young
valve NMR tube was charged with 1 (3 mg, 0.005 mmol), C6D6 (0.5 mL),
aniline (48 mg, 0.51 mmol), N,N’-diisopropylcarbodiimide (63 mg,
0.50 mmol). The tube was taken outside the glovebox and heated at 808C
Preparation of (C5Me4H)SiMe2NH(C6H2Me3-2,4,6):
(C6H2Me3-2,4,6)NHLi (711 mg, 5.04 mmol) in THF (20 mL), which was
prepared byreaction of nBuLi with one equivalent of (C6H2Me3-
A
solution of
Chem. Eur. J. 2007, 13, 4037 – 4051
ꢀ 2007 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemeurj.org
4045

Z. Hou et al.
in an oil bath. Formation of 6 was easilymonitored by 1H NMR spectros-
copy. The reaction was quantitative and finished within 1 h.
1265, 1125, 1070, 889, 775, 687 cmÀ1; HRMS: m/z calcd for C13H21ClN3:
254.1424 [M+H]+; found: 254.1411.
ii) Preparative scale reaction: In the glovebox, a solution of aniline
(188 mg, 2.02 mmol) in benzene (3 mL) was added to a solution of 1
(12 mg, 0.02 mmol) in benzene (2 mL) in a Schlenk tube. N,N’-Diisopro-
pylcarbodiimide (252 mg, 2.00 mmol) was then added to the above reac-
tion mixture. The Schlenk tube was taken outside the glovebox, and the
mixture was stirred at 808C for 1 h. After the solvent was removed under
reduced pressure, the residue was extracted with ether and filtered to
give a clean solution. After removing the solvent under vacuum, the resi-
due was recrystallized in ether to provide a colorless solid 6 in >99%
yield.
2-(2-Fluorophenyl)-1,3-diisopropylguanidine (13): Colorless solid, yield
>99%; 1H NMR (400 MHz, C6D6): d=0.90 (d, J=6.4 Hz, 12H; CH3),
3.40 (br, 2H; NH), 3.61–3.70 (m, 2H; CH), 6.67–6.73 (m, 1H; C6H4),
6.90–6.94 (m, 1H; C6H4), 6.99–7.04 (m, 1H; C6H4), 7.11–7.15 ppm (m,
1H; C6H4); 13C NMR (100 MHz, C6D6): d=23.3, 43.5, 116.3 (d, J(C,CF)
20.6 Hz), 122.0 (d, J(C,CCF) =7.4 Hz), 124.9 (d, J(C,CCF) =3.3 Hz), 126.3 (d,
(C,CCF) =3.3 Hz), 139.1 (d, J(C,CF) =13.2 Hz), 150.2, 156.1 ppm (d, J(C,F)
243.2 Hz); IR (Nujol): n˜ =3254, 2953, 2924, 2853, 1638, 1603, 1512, 1460,
1377, 1263, 1125, 864, 723 cmÀ1
HRMS: m/z calcd for C13H21FN3:
238.1720 [M+H]+; found: 238.1713.
=
J
=
;
1,3-Diisopropyl-2-phenylguanidine (6): Colorless solid, yield >99%;
1H NMR (400 MHz, C6D6): d=0.91 (d, J=6.4 Hz, 12H; CH3), 3.52 (br,
2H; NH), 3.64–3.69 (m, 2H; CH), 6.90 (t, J=7.6 Hz, 1H; p-C6H5), 7.10
(d, J=7.6 Hz, 2H; o-C6H5), 7.25 ppm (t, J=7.6 Hz, 2H; m-C6H5);
13C NMR (100 MHz, C6D6): d=23.4, 43.4, 121.3, 123.7, 129.6, 149.7,
151.6 ppm; IR (Nujol): n˜ =3300, 2956, 2924, 2854, 1648, 1617, 1591, 1462,
1378, 1262, 1124, 1019, 800, 694 cmÀ1; HRMS: m/z calcd for C13H22N3:
220.1814 [M+H]+; found: 220.1795.
2-(2-Iodophenyl)-1,3-diisopropylguanidine (14): Colorless solid, yield
97%; H NMR (400 MHz, C6D6): d=0.93 (d, J=6.8 Hz, 12H; CH3), 3.32
1
(br, 2H; NH), 3.59–3.68 (m, 2H; CH), 6.41–6.45 (m, 1H; C6H4), 6.94–
6.96 (m, 1H; C6H4), 7.03–7.07 (m, 1H; C6H4), 7.84–7.87 ppm (m, 1H;
C6H4); 13C NMR (100 MHz, C6D6): d=23.7, 43.5, 97.3, 122.9, 123.1, 129.3,
139.6, 149.3, 152.6 ppm; IR (Nujol): n˜ =3292, 2953, 2924, 2853, 1602,
1572, 1535, 1458, 1377, 1271, 1015, 810, 762, 729 cmÀ1; HRMS: m/z calcd
for C13H21N3I: 346.0780 [M+H]+; found: 346.0748.
2-(4-Bromophenyl)-1,3-diisopropylguanidine (7): Colorless solid, yield
>99%; 1H NMR (400 MHz, C6D6): d=0.86 (d, J=6.4 Hz, 12H; CH3),
3.37 (br, 2H; NH), 3.55–3.60 (m, 2H; CH), 6.69 (d, J=8.8 Hz, 2H; o-
C6H4), 7.30 ppm (d, J=8.8 Hz, 2H; m-C6H4); 13C NMR (100 MHz, C6D6):
d=23.3, 43.4, 113.7, 125.4, 132.5, 149.6, 150.7 ppm; IR (Nujol): n˜ =3292,
2953, 2924, 2853, 1632, 1605, 1578, 1535, 1462, 1377, 1263, 1072, 859, 806,
723 cmÀ1; HRMS: m/z calcd for C13H21BrN3: 298.0919 [M+H]+; found:
298.0916.
1,3-Diisopropyl-2-(2-methoxyphenyl)guanidine (15): Colorless solid, yield
>99%; 1H NMR (400 MHz, C6D6): d=0.95 (d, J=6.4 Hz, 12H; CH3),
3.48 (s, 3H; OCH3), 3.55 (br, 2H; NH), 3.69–3.76 (m, 2H; CH), 6.77 (d,
J=8.0 Hz, 1H; C6H4), 6.87–6.96 (m, 2H; C6H4), 7.10 ppm (d, J=7.6 Hz,
1H; C6H4); 13C NMR (100 MHz, C6D6): d=23.5, 43.5, 55.7, 113.2, 122.0,
122.1, 125.0, 140.8, 149.9, 152.7 ppm; IR (Nujol): n˜ =3312, 3254, 2955,
2924, 2853, 1649, 1618, 1551, 1462, 1379, 1260, 1229, 1117, 1032, 741 cmÀ1
;
HRMS: m/z calcd for C14H24N3O: 250.1919 [M+H]+; found: 250.1887.
2-(4-Iodophenyl)-1,3-diisopropylguanidine (8): Colorless solid, yield
>99%; 1H NMR (400 MHz, C6D6): d=0.86 (d, J=6.8 Hz, 12H; CH3),
3.40 (br, 2H; NH), 3.53–3.60 (m, 2H; CH), 6.68 (d, J=8.8 Hz, 2H; o-
C6H4), 7.47 ppm (d, J=8.8 Hz, 2H; m-C6H4); 13C NMR (100 MHz, C6D6):
d=23.4, 43.4, 83.8, 126.0, 138.5, 149.7, 151.3 ppm; IR (Nujol): n˜ =3304,
2-(2-Biphenyl)-1,3-dicyclohexylguanidine (16): Colorless solid, yield
98%; 1H NMR (400 MHz, C6D6): d=0.70–1.78 (m, 20H; Cy), 3.31 (br,
2H; NH), 3.45–3.47 (m, 2H; CH), 6.99–7.03 (m, 1H; C12H9), 7.12–7.18
(m, 2H; C12H9), 7.21–7.30 (m, 3H; C12H9), 7.45–7.47 (m, 1H; C12H9),
7.74–7.77 ppm (m, 2H; C12H9); 13C NMR (100 MHz, C6D6): d=25.4, 26.1,
34.1, 50.4, 122.1, 124.5, 126.4, 127.8, 128.7, 129.8, 131.1, 135.7, 142.0,
148.2, 148.8 ppm; IR (Nujol): n˜ =3374, 3271, 2953, 2924, 2853, 1612, 1587,
1547, 1452, 1377, 889, 732, 698 cmÀ1; HRMS: m/z calcd for C25H34N3:
376.2753 [M+H]+; found: 376.2740.
2953, 2924, 2853, 1605, 1574, 1537, 1462, 1377, 1250, 1061, 841, 719 cmÀ1
;
HRMS: m/z calcd for C13H21N3I: 346.0780 [M+H]+; found: 346.0799.
2-(4-tert-Butylphenyl)-1,3-diisopropylguanidine (9): Colorless solid, yield
>99%; 1H NMR (400 MHz, C6D6): d=0.90 (d, J=5.6 Hz, 12H; CH3),
1.27 (s, 9H; C
G
tert-Butyl-3-ethyl-2-(naphthalen-1-yl)guanidine (17): Colorless solid,
yield 96%; 1H NMR (400 MHz, C6D6): d=0.62 (t, J=7.2 Hz, 3H;
8.0 Hz, 2H; o-C6H4), 7.33 ppm (d, J=8.0 Hz, 2H; m-C6H4); 13C NMR
(100 MHz, C6D6): d=23.4, 31.9, 34.4, 43.4, 123.2, 126.4, 143.5, 148.9,
149.7 ppm; IR (Nujol): n˜ =3312, 2955, 2924, 2853, 1638, 1597, 1560, 1508,
1460, 1377, 1269, 742 cmÀ1; HRMS: m/z calcd for C17H30N3: 276.2440
[M+H]+; found: 276.2431.
CH2CH3), 1.36 (s, 9H; C(CH3)3), 2.57–2.64 (m, 2H; CH2CH3), 3.52 (br,
N
2H; NH), 7.06 (d, J=7.2 Hz, 1H; C10H7), 7.31–7.40 (m, 3H; C10H7), 7.45
(d, J=8.4 Hz, 1H; C10H7), 7.74 (d, J=7.6 Hz, 1H; C10H7), 8.50 ppm (d,
J=8.4 Hz, 1H; C10H7); 13C NMR (100 MHz, C6D6): d=15.2, 30.1, 37.3,
50.9, 117.4, 121.3, 124.9, 125.2, 126.1, 126.9, 128.2, 130.3, 135.6, 148.1,
149.9 ppm; IR (Nujol): n˜ =3449, 3412, 2953, 2924, 2853, 1634, 1570, 1521,
1458, 1379, 1211, 775 cmÀ1; HRMS: m/z calcd for C17H24N3: 270.1970
[M+H]+; found: 270.1979.
2-(4-Cyanophenyl)-1,3-dicyclohexylguanidine (10): Colorless single crys-
tals suitable for X-rayanalysis were grown in ether/hexane at room tem-
perature overnight, yield 96%; 1H NMR (400 MHz, C6D6): d=0.75–1.82
(m, 20H; Cy), 3.31–3.38 (m, 2H; CH), 3.53 (d, 2H; NH), 6.82 (d, J=
8.4 Hz, 2H; o-C6H4), 7.16 ppm (d, J=8.4 Hz, 2H; m-C6H4); 13C NMR
(100 MHz, C6D6): d=25.4, 26.0, 33.9, 50.6, 103.6, 120.2, 123.9, 133.6,
149.7, 156.2 ppm; IR (Nujol): n˜ =3387, 3290, 2953, 2924, 2853, 2216, 1585,
1570, 1551, 1460, 1377, 1165, 862, 719 cmÀ1; HRMS: calcd for C20H29N4:
325.2392 [M+H]+; found: 325.2380.
Typical procedures for the catalytic reaction of heterocyclic primary
amines to carbodiimides: In the glovebox, a solution of 5-methylisoxazol-
3-amine (197 mg, 2.01 mmol) in THF (3 mL) was added to a solution of 1
(6 mg, 0.01 mmol) in THF (2 mL) in a Schlenk tube. N,N’-Diisopropylcar-
bodiimide (252 mg, 2.00 mmol) was then added to the above reaction
mixture. The Schlenk tube was taken outside the glovebox and the mix-
ture was stirred at room temperature for 1 h. After the solvent was re-
moved under reduced pressure, the residue was extracted with ether and
filtered to give a clean solution. After removing the solvent under
vacuum, the residue was recrystallized in diethyl ether to provide color-
less solid 18 (445 mg, 99% yield).
2-(4-Ethynylphenyl)-1,3-diisopropylguanidine (11): Colorless solid, yield
>99%; 1H NMR (300 MHz, C6D6): d=0.88 (d, J=6.3 Hz, 12H; CH3),
ꢀ
2.83 (s, 1H; C CH), 3.48 (br, 2H; NH), 3.52–3.63 (m, 2H; CH), 6.92 (d,
J=8.4 Hz, 2H; o-C6H4), 7.48 ppm (d, J=8.4 Hz, 2H; m-C6H4); 13C NMR
(75 MHz, C6D6): d=23.1, 43.2, 76.2, 85.0, 114.6, 123.6, 133.7, 149.7,
152.5 ppm; IR (Nujol): n˜ =3319, 2955, 2924, 2853, 2106, 1630, 1589, 1500,
1458, 1377, 1267, 1167, 1125, 862, 723 cmÀ1
The 1H NMR signals for the NH protons in 18–20 and 23–26 were not
observed probablydue to broadening.
C15H22N3: 244.1814 [M+H]+; found: 244.1817.
2-(3-Chlorophenyl)-1,3-diisopropylguanidine (12): Colorless solid, yield
>99%; 1H NMR (300 MHz, C6D6): d=0.78 (d, J=6.3 Hz, 12H; CH3),
3.33 (br, 2H; NH), 3.46–3.52 (m, 2H; CH), 6.78–6.91 (m, 3H; C6H4),
7.08–7.11 ppm (m, 1H; C6H4); 13C NMR (75 MHz, C6D6): d=23.3, 43.4,
121.1, 121.9, 123.7, 130.5, 135.0, 149.8, 153.3 ppm; IR (Nujol): n˜ =3343,
3231, 2955, 2924, 2853, 1636, 1609, 1580, 1547, 1499, 1464, 1383, 1366,
1,3-Diisopropyl-2-(5-methylisoxazol-3-yl)guanidine (18): Colorless solid,
yield >99%; 1H NMR (400 MHz, CDCl3): d=1.23 (d, J=6.4 Hz, 12H;
CH
R
C
1H; CH(isoxazolyl)); 13C NMR (100 MHz, CDCl3): d=12.2, 23.3, 43.0,
100.7, 153.1, 166.3, 168.1 ppm; IR (Nujol): n˜ =3382, 3299, 3188, 2955,
2923, 2854, 1608, 1540, 1482, 1466, 1410, 1376, 1344, 1257, 1174, 1128,
4046
www.chemeurj.org
ꢀ 2007 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Chem. Eur. J. 2007, 13, 4037 – 4051

Amine Protonolysis of Rare-Earth Metal Guanidinates
FULL PAPER
1018, 811, 792 cmÀ1; HRMS: m/z calcd for C11H21N4O: 225.1715 [M+H]+;
found: 225.1712.
C5H4N), 8.18 ppm (m, 1H; C5H4N); 13C NMR (100 MHz, C6D6): d=23.7,
42.7, 114.1, 121.3, 136.7, 145.4, 153.8, 164.6 ppm; IR (Nujol): n˜ =3454,
3422, 2953, 2924, 2853, 1622, 1589, 1547, 1464, 1433, 1377, 1172, 785,
725 cmÀ1; HRMS: m/z calcd for C12H21N4: 221.1766 [M+H]+; found:
221.1762.
1,3-Dicyclohexyl-2-(5-methylisoxazol-3-yl)guanidine (19): Colorless solid,
yield >99%; 1H NMR (400 MHz, C6D6): d=1.00–1.96 (m, 23H; Cyand
CH3), 3.55–3.59 (m, 2H; CH(Cy)), 5.82 ppm (s, 1H; CH(isoxazolyl));
13C NMR (100 MHz, C6D6): d=12.1, 25.1, 26.1, 33.8, 50.1, 101.6, 153.5,
166.4, 169.1 ppm; IR (Nujol): n˜ =3409, 3300, 2954, 2925, 2854, 1604, 1536,
1478, 1463, 1410, 1376, 1259, 1152, 1120, 890, 799 cmÀ1; HRMS: m/z calcd
for C17H29N4O: 305.2341 [M+H]+; found: 305.2344.
A
G
N
of diamine (218 mg, 2.02 mmol) in benzene (3 mL) was added to a solu-
tion of 1 (12 mg, 0.02 mmol) in benzene (2 mL) in a Schlenk tube. Then
N,N’-diisopropylcarbodiimide (505 mg, 4.00 mmol) was added to the
above reaction mixture. The Schlenk tube was taken outside the glove-
box and the mixture was stirred at 808C for 1 h. After the solvent was re-
moved under reduced pressure, the residue was extracted with diethyl
ether and filtered to give a clean solution. After removing the solvent
under vacuum, the residue was recrystallized in ether to provide a color-
less solid 27. Isolated yield >99%; 1H NMR (400 MHz, CDCl3): d=1.14
(d, J=6.4 Hz, 24H; CH3), 3.54 (br, 4H; NH), 3.70–3.76 (m, 4H; CH),
6.38 (s, 1H; C6H4), 6.44 (d, J=7.6 Hz, 2H; C6H4), 7.12 ppm (t, J=7.6 Hz,
1H; C6H4); 13C NMR (100 MHz, CDCl3): d=23.3, 43.2, 117.0, 118.5,
129.7, 149.7, 151.1 ppm; IR (Nujol): n˜ =3378, 2955, 2923, 2854, 1610,
1582, 1560, 1459, 1438, 1384, 1261, 1126, 801 cmÀ1; HRMS: m/z calcd for
C20H37N6: 361.3080 [M+H]+; found: 361.3062.
(E)-tert-Butyl-3-ethyl-2-(5-methylisoxazol-3-yl)guanidine (20): Colorless
solid, yield >99%; 1H NMR (400 MHz, CDCl3): d=1.20 (t, J=7.2 Hz,
3H; CH2CH3), 1.39 (s, 9H; C(CH3)3), 2.25 (s, 3H; CH3), 3.17–3.23 (m,
G
2H; CH2CH3), 5.62 ppm (s, 1H; CH(isoxazolyl)); 13C NMR (100 MHz,
CDCl3): d=12.3, 14.9, 29.9, 36.5, 51.0, 100.9, 153.7, 166.3, 167.9 ppm; IR
(Nujol): n˜ =3441, 3298, 3189, 2962, 2923, 2854, 1603, 1555, 1475, 1410,
1376, 1354, 1331, 1256, 1238, 1217, 882, 791, 735 cmÀ1; HRMS: m/z calcd
for C11H21N4O: 225.1715 [M+H]+; found: 225.1714.
(E)-tert-Butyl-3-ethyl-2-(3-methyl-1-phenyl-1H-pyrazol-5-yl)guanidine
(21): Colorless crystals, yield >99%. Single crystals suitable for X-ray
analysis were grown in diethyl ether/hexane at room temperature for
one day. 1H NMR (400 MHz, CDCl3): d=1.16 (t, J=7.2 Hz, 3H;
A
CH2CH3), 1.32 (s, 9H; C(CH3)3), 2.28 (s, 3H; CH3), 3.12–3.19 (m, 2H;
A
mine (253 mg, 2.02 mmol) in benzene (3 mL) was added to a solution of
1 (12 mg, 0.02 mmol) in benzene (2 mL) in a Schlenk tube. Then N,N’-dii-
sopropylcarbodiimide (757 mg, 6.00 mmol) was added to the above reac-
tion mixture. The Schlenk tube was taken outside the glovebox and the
mixture was stirred at 1108C for 3 h. The isolation and purification pro-
cesses were similar to those for 27. Colorless solid, yield 97%; 1H NMR
(400 MHz, CDCl3): d=1.18–1.22 (m, 36H; CH3), 3.49 (br, 6H; NH),
3.82–3.93 (m, 6H; CH), 5.82 ppm (s, 1H; C4HN2); 13C NMR (100 MHz,
CDCl3): d=23.4, 23.5, 42.6, 42.7, 100.1, 153.3, 153.8, 163.3, 168.3 ppm; IR
(Nujol): n˜ =3355, 2955, 2924, 2854, 1617, 1507, 1462, 1378, 1170, 1126,
1019, 801, 721 cmÀ1; HRMS: m/z calcd for C25H50N11: 504.4251 [M+H]+;
found: 504.4278.
CH2CH3), 4.14 (br, 1H; NH), 4.38 (br, 1H; NH), 5.55 (s, 1H; CH(pyra-
zolyl)), 7.16 (t, J=7.6 Hz, 1H; p-C6H5), 7.33 (t, J=7.6 Hz, 2H; m-C6H5),
7.73 ppm (d, J=7.6 Hz, 2H; o-C6H5); 13C NMR (100 MHz, CDCl3): d=
14.4, 15.0, 30.0, 36.7, 51.0, 94.1, 123.4, 125.1, 128.0, 140.2, 148.6, 148.7,
151.7 ppm; IR (Nujol): n˜ =3321, 3099, 2955, 2924, 2854, 1617, 1597, 1570,
1542, 1499, 1454, 1378, 1365, 1298, 1184, 1014, 906, 762, 693 cmÀ1
;
HRMS: m/z calcd for C17H26N5: 300.2188 [M+H]+; found: 300.2181.
1,3-Diisopropyl-2-(3-methyl-1-phenyl-1H-pyrazol-5-yl)guanidine
Colorless solid, yield >99%; 1H NMR (400 MHz, CDCl3): d=1.13 (d,
J=6.4 Hz, 12H; CH(CH3)2), 2.28 (s, 3H; CH3), 3.72–3.80 (m, 2H; CH-
(CH3)2), 4.19 (br, 2H; NH), 5.55 (s, 1H; CH(pyrazolyl)), 7.15 (t, J=
(22):
ACHTREUNG
ACHTREUNG
7.6 Hz, 1H; p-C6H5), 7.32 (dd, J=7.6, 8.0 Hz, 2H; m-C6H5), 7.77 ppm (d,
J=8.0 Hz, 2H; o-C6H5); 13C NMR (100 MHz, CDCl3): d=14.3, 23.3,
43.0, 94.3, 122.9, 124.8, 127.8, 140.1, 148.5, 148.6, 150.9 ppm; IR (Nujol):
n˜ =3363, 3315, 2952, 2924, 2854, 1598, 1556, 1534, 1500, 1462, 1378, 1360,
1128, 1029, 907, 762, 719, 694 cmÀ1; HRMS: m/z calcd for C17H26N5:
300.2188 [M+H]+; found: 300.2180.
Typical procedures for catalytic addition of secondary amines to carbodi-
imides: i) NMR tube reaction: In the glovebox, a J. Young valve NMR
tube was charged with 1 (12 mg, 0.02 mmol), C6D6 (0.5 mL), diethylamine
(50 mg, 0.67 mmol), N,N’-diisopropylcarbodiimide (85 mg, 0.67 mmol).
The tube was taken outside the glovebox and heated at 808C in an oil
bath. Formation of 29 was easilymonitored by 1H NMR spectroscopy
and 1,3,5-trimethylbenzene used as an internal standard. The reaction
was completed in 3 h. No other coupling products were observed.
1,3-Diisopropyl-2-(1-methyl-1H-benzo[d]imidazol-2-yl)guanidine
Colorless solid, yield >99%; 1H NMR (300 MHz, C6D6): d=1.16 (d, J=
6.3 Hz, 12H; CH(CH3)2), 3.32 (m, 3H; CH3), 3.55 (br, 2H; CH(CH3)2),
(23):
A
ACHTREUNG
ii) Preparative-scale reaction: In the glovebox, a solution of diethylamine
(150 mg, 2.06 mmol) in benzene (3 mL) was added to a solution of 1
(36 mg, 0.06 mmol) in benzene (2 mL) in a Schlenk tube. Then N,N’-dii-
sopropylcarbodiimide (252 mg, 2.00 mmol) was added to the above reac-
tion mixture. The Schlenk tube was taken outside the glovebox and the
mixture was stirred at 808C for 3 h. After the solvent was removed under
reduced pressure, the residue was extracted with hexane and filtered to
give a clean solution. The solution volume was reduced under vacuum to
about 2 mL, and cooled to À308C for two days. A colorless oil 29 of ana-
lytical purity was obtained after filtration and removing the solvent
under vacuum. The guanidines 30 and 31 were purified analogously. Gua-
nidines 32–37 were purified byrecrystallization in hexane to provide a
colorless solid.
6.99 (d, J=7.8 Hz, 1H; C6H4), 7.14–7.27 (m, 2H; C6H4), 7.86 ppm (d, J=
8.4 Hz, 1H; C6H4); 13C NMR (75 MHz, C6D6): d=23.1, 27.7, 42.9, 107.7,
116.7, 119.8, 121.0, 134.4, 142.6, 154.6, 158.3 ppm; IR (Nujol): n˜ =3435,
3230, 2956, 2924, 2854, 1623, 1610, 1510, 1466, 1383, 1317, 1286, 1120,
1009, 748 cmÀ1; HRMS: m/z calcd for C15H24N5: 274.2032 [M+H]+;
found: 274.2039.
1,3-Diisopropyl-2-(4-methylthiazol-2-yl)guanidine (24): Colorless solid,
yield >99%; 1H NMR (400 MHz, CDCl3): d=1.23 (d, J=6.4 Hz, 12H;
CH
N
N
1H; CH(thiazolyl)); 13C NMR (100 MHz, CDCl3): d=17.6, 23.2, 42.6,
102.5, 146.9, 152.4, 175.1 ppm; IR (Nujol): n˜ =3423, 3232, 3103, 2955,
2924, 2854, 1606, 1560, 1465, 1408, 1384, 1340, 1261, 1176, 1126, 1058,
1013, 855, 800, 727 cmÀ1; HRMS: m/z calcd for C11H21N4S: 241.1487
[M+H]+; found: 241.1480.
(E)-Diethyl-2,3-diisopropylguanidine (29): Colorless oil, yield 95%;
1H NMR (400 MHz, C6D6): d=0.92 (d, J=6.4 Hz, 6H; NCH
ACHTREUNG
2-(6-Chlorobenzo[d]thiazol-2-yl)-1,3-diisopropylguanidine (25): Colorless
solid, yield >99%; 1H NMR (300 MHz, CDCl3): d=1.26 (d, J=6.6 Hz,
12H; CH3), 3.91 (br, 2H; CH), 7.18 (d, J=8.4 Hz, 1H; C6H3), 7.38 (d,
J=8.4 Hz, 1H; C6H3), 7.53 ppm (s, 1H; C6H3)); 13C NMR (75 MHz,
CDCl3): d=23.1, 43.0, 119.3, 120.2, 125.3, 126.7, 132.6, 150.6, 153.7,
174.6 ppm; IR (Nujol): n˜ =3456, 3236, 2953, 2924, 2854, 1606, 1555, 1488,
1445, 1378, 1330, 1273, 1174, 1126, 1100, 1048, 810, 731 cmÀ1; HRMS: m/z
calcd for C14H20ClN4S: 311.1097 [M+H]+; found: 311.1117.
(t, J=6.8 Hz, 6H; CH2CH3), 1.22 (d, J=6.4 Hz, 6H; NHCH
ACHTREUNG
(br, 1H; NH), 3.14 (q, J=6.8 Hz, 4H; CH2CH3), 3.30–3.43 ppm (m, 2H;
CH); 13C NMR (100 MHz, C6D6): d=13.2, 24.0, 25.7, 43.4, 46.3, 47.9,
153.1 ppm; IR (Nujol): n˜ =3396, 2963, 2925, 2855, 1637, 1466, 1376, 1166,
1124, 1050, 800 cmÀ1; HRMS: m/z calcd for C11H26N3: 200.2127 [M+H]+;
found: 200.2119.
(E)-Isobutyl-2,3-diisopropyl
ACHTREUNG
1
ACHTREUNG
1,3-Diisopropyl-2-(pyridin-2-yl)guanidine (26): Colorless solid, yield
>99%; 1H NMR (400 MHz, C6D6): d=1.03 (d, J=6.4 Hz, 12H; CH3),
3.80 (br, 2H; CH), 6.40–6.44 (m, 1H; C5H4N), 7.18–7.20 (m, 2H;
AHCTREUNG
A
ACHTREUNG
Chem. Eur. J. 2007, 13, 4037 – 4051
ꢀ 2007 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemeurj.org
4047

Z. Hou et al.
13C NMR (100 MHz, C6D6): d=20.8, 23.8, 25.8, 27.3, 37.9, 46.3, 47.9, 59.0,
154.9 ppm; IR (Nujol): n˜ =3397, 2957, 2924, 2853, 1636, 1460, 1377, 1165,
1125, 1034, 953 cmÀ1; HRMS: m/z calcd for C12H28N3: 214.2283 [M+H]+;
found: 214.2282.
1099, 1005, 930, 721 cmÀ1; HRMS: m/z calcd for C18H39N6: 339.3236
[M+H]+; found: 339.3230.
Preparation of guanidines 38 and 39: In the glovebox, a solution of
1,2,3,4-tetrahydro-5-aminoisoquinodine (305 mg, 2.06 mmol) in benzene
(3 mL) was added to a solution of 1 (36 mg, 0.06 mmol) in benzene
(2 mL) in a Schlenk tube. Then N,N’-diisopropylcarbodiimide (252 mg,
2.00 mmol) was added to the above reaction mixture. The Schlenk tube
was taken outside the glovebox and the mixture was stirred at 808C for
1 h. After the solvent was removed under reduced pressure, the residue
was extracted with ether and filtered to give a clean solution. After re-
moving the solvent under vacuum, the residue was recrystallized in dieth-
yl ether to provide colorless solid 38. If two equivalents of N,N’-diisopro-
pylcarbodiimide (504 mg, 4.00 mmol) were added and the reaction was
carried out at 1108C for 3 h, the biguanidine 39 was obtained.
(E)-Diallyl-2,3-diisopropylguanidine (31): Colorless oil, yield 93%;
1H NMR (400 MHz, C6D6): d=0.88 (d, J=6.4 Hz, 6H; NCH
ACHTREUNG
(d, J=6.4 Hz, 6H; NHCH
ACHTREUNG
À
CH), 3.83 (d, J=6.0 Hz, 4H; CH2), 5.04–5.18 (m, 4H; CH=CH2), 5.91–
6.01 ppm (m, 2H; CH=CH2); 13C NMR (100 MHz, C6D6): d=23.8, 25.7,
À
46.3, 47.9, 51.3, 116.1, 136.2, 153.3 ppm; IR (Nujol): n˜ =3397, 2959, 2924,
2855, 1632, 1452, 1383, 1273, 1260, 1165, 1125, 916 cmÀ1; HRMS: m/z
calcd for C13H26N3: 224.2127 [M+H]+; found: 224.2134.
(E)-N,N’-Diisopropylisoindoline-2-carboxamidine (32): Colorless solid,
yield >99%; 1H NMR (400 MHz, C6D6): d=0.95 (d, J=6.4 Hz, 6H;
NCH
A
G
2-(1,2,3,4-Tetrahydroisoquinolin-5-yl)-1,3-diisopropylguanidine (38): Col-
orless solid, yield 99%; 1H NMR (400 MHz, C6D6): d=0.90 (d, J=
6.0 Hz, 12H; CH3), 2.81 (t, J=6.0 Hz, 2H; CH2NCH2CH2), 2.92–2.96 (m,
2H; CH2NCH2CH2), 3.36 (d, 2H; CH2NCH2CH2), 3.64 (br, 3H; NH),
3.86–3.87 (m, 2H; CH), 6.65 (d, J=7.6 Hz, 1H; C6H3), 6.91 (d, J=8.0 Hz,
1H; C6H3), 7.13 ppm (dd, J=7.6, 8.0 Hz, 1H; C6H3); 13C NMR
(100 MHz, C6D6): d=23.6, 26.7, 43.5, 45.1, 49.6, 119.8, 120.1, 126.4, 129.4,
138.0, 148.6, 149.6 ppm; IR (Nujol): n˜ =3327, 3296, 2957, 2924, 2853,
1612, 1576, 1524, 1454, 1377, 1263, 1123, 1062, 808, 743 cmÀ1;HRMS: m/z
calcd for C16H27N4: 275.2236 [M+H]+; found: 275.2225.
3.30–3.36 (m, 1H; CH), 3.39–3.45 (m, 1H; CH), 4.69 (s, 4H; CH2), 6.95–
6.97 (m, 2H; C6H4), 7.02–7.05 ppm (m, 2H; C6H4); 13C NMR (100 MHz,
C6D6): d=24.2, 26.2, 46.6, 47.9, 54.5, 122.6, 126.9, 138.9, 152.3 ppm; IR
(Nujol): n˜ =3387, 2957, 2924, 2853, 1632, 1462, 1384, 1346, 1163, 1124,
1089, 741 cmÀ1; HRMS: m/z calcd for C15H24N3: 246.1970 [M+H]+;
found: 246.1969.
(E)-N,N’-Diisopropyl-2-((pyrrolidin-1-yl)methyl)pyrrolidine-1-carboxami-
dine (33): Colorless solid, yield 90%; H NMR (400 MHz, C6D6): d=0.96
(d, J=6.0 Hz, 3H; CH
(d, J=6.0 Hz, 3H; CH(CH3)2), 1.31 (d, J=6.0 Hz, 3H; CH
3.17 (m, 16H; CH2), 3.31–3.43 (m, 3H; NH and CH(CH3)2), 4.46–
1
G
N
G
ACHTREUNG
2-((E)-2-Amidino-1,2,3,4-tetrahydroisoquinolin-5-yl)-1,3-diisopropylgua-
nidine (39): Colorless solid, yield 96%; 1H NMR (400 MHz, CDCl3): d=
1.10 (d, J=6.8 Hz, 6H; CH3), 1.12 (d, J=6.4 Hz, 6H; CH3), 1.17 (d, J=
6.4 Hz, 12H; CH3), 2.68 (t, J=5.6 Hz, 2H; CH2NCH2CH2), 3.34–3.38 (m,
3H; CH2NCH2CH2 and CH), 3.43–3.50 (m, 1H; CH), 3.73–3.80 (m, 2H;
CH), 4.26 (s, 2H; CH2NCH2CH2), 6.62 (d, J=7.6 Hz, 1H; C6H3), 6.75 (d,
J=7.6 Hz, 1H; C6H3), 7.04 ppm (t, J=7.6 Hz, 1H; C6H3); 13C NMR
(100 MHz, C6D6): d=23.4, 23.7, 25.0, 26.1, 43.1, 46.1, 46.3, 47.3, 49.9,
119.8, 119.9, 125.9, 128.7, 136.2, 147.8, 148.6, 154.9 ppm; IR (Nujol): n˜ =
3314, 3275, 2953, 2924, 2853, 1643, 1605, 1578, 1535, 1454, 1377, 1258,
1165, 1126, 1043, 721 cmÀ1; HRMS: m/z calcd for C23H41N6: 401.3393
AHCTREUNG
4.52 ppm (m, 1H; CH); 13C NMR (100 MHz, C6D6): d=23.6, 24.3, 24.7,
25.1, 25.7, 26.4, 31.1, 46.0, 47.8, 50.2, 55.1, 56.4, 61.4, 152.2 ppm; IR
(Nujol): n˜ =3394, 3233, 2960, 2925, 2854, 1630, 1460, 1377, 1342, 1262,
1164, 1084, 1019, 950, 889, 800 cmÀ1; HRMS: m/z calcd for C16H33N4:
281.2705 [M+H]+; found: 281.2725.
(E)-N,N’-Dicyclohexyl-4-(pyrrolidin-1-yl)piperidine-1-carboxamidine
(34): Colorless solid, yield 95%; H NMR (400 MHz, C6D6): d=0.83–2.00
1
(m, 24H; CH2(Cy) and CH2(pyrrolidine ring)), 2.38 (br, 4H;
CH2(piperidine ring)), 2.75–2.80 (m, 4H; CH2 (pyrrolidine ring)), 3.07–
3.15 (m, 3H; CH), 3.24 (br, 1H; NH), 3.75–3.48 ppm (d, 4H; CH2 (piper-
idine ring)); 13C NMR (100 MHz, C6D6): d=24.0, 25.6, 26.0, 26.2, 26.8,
32.2, 35.0, 36.1, 47.5, 51.6, 54.0, 56.2, 62.6, 154.4 ppm; IR (Nujol): n˜ =
3397, 2953, 2924, 2853, 1630, 1454, 1377, 1260, 1231, 1020, 889, 802,
721 cmÀ1; HRMS: m/z calcd for C22H41N4: 361.3331 [M+H]+; found:
361.3359.
1
[M+H]+; found: 401.3385. The H NMR signals for the NH protons in 39
were not observed probablydue to broadening.
Isolation of the amido complex [{Me2Si
A
(NPh)}Y
G
N
(40): In the glovebox, a solution of diethylamine (36 mg, 0.485 mmol) in
benzene (3 mL) was added to a solution of 1 (286 mg, 0.485 mmol) in
benzene (2 mL) in a flask. After 10 min, the solvent was removed under
reduced pressure. The residue was extracted with THF and filtered to
give a clean solution. The solution volume was reduced under vacuum to
precipitate 40 as colorless crystalline powder (265 mg, 0.461 mmol, 95%
yield). Single crystals of 40 suitable for X-rayanalysis were grown in
THF at À308C for 3 d. 1H NMR (400 MHz, C6D6): d=0.92 (s, 6H;
SiMe2), 1.16 (t, J=6.8 Hz, 6H; CH2CH3), 1.32 (br, 8H; b-CH2, THF),
2.14 (s, 6H; C5Me4), 2.16 (s, 6H; C5Me4), 3.15 (q, J=6.8 Hz, 4H;
CH2CH3), 3.61 (br, 8H; a-CH2, THF), 6.68 (t, J=7.6 Hz, 1H; p-C6H5),
6.76 (d, J=7.6 Hz, 2H; o-C6H5), 7.25 ppm (t, J=7.6 Hz, 2H; m-C6H5);
13C NMR (100 MHz, C6D6): d=5.1, 11.7, 14.3, 16.4, 25.8, 44.3, 69.3, 106.1,
114.3, 120.0, 121.6, 126.5 (d, J(Y,C) =2.5 Hz), 129.7, 157.0 ppm; IR (Nujol):
n˜ =2954, 2923, 2854, 1587, 1479, 1460, 1377, 1293, 1251, 1178, 1076, 1026,
918, 829, 800, 759, 691 cmÀ1; elemental analysis calcd for C29H49N2O2SiY:
C 60.61, H 8.59, N 4.87; found: C 60.22, H8.37, N 5.19.
(E)-N,N’-Dicyclohexyl-3,4-dihydroisoquinoline-2(1H)-carboxamidine
(35): Colorless single crystals suitable for X-ray analysis were grown in
ether/hexane at room temperature for one day, yield >99%; 1H NMR
(400 MHz, C6D6): d=0.84–1.90 (m, 20H; CH2(Cy)), 2.77 (t, J=6.0 Hz,
2H; CH2), 3.06–3.19 (m, 2H; CH), 3.31 (br, 1H; NH), 3.41 (t, J=6.0 Hz,
2H; CH2), 4.50 (s, 2H; CH2), 6.91–7.02 ppm (m, 4H; C6H4); 13C NMR
(100 MHz, C6D6): d=25.6, 25.9, 26.1, 26.8, 29.9, 35.0, 36.1, 46.9, 50.8,
53.9, 56.3, 126.0, 126.1, 126.9, 129.0, 135.2, 135.9, 154.0 ppm; IR (Nujol):
n˜ =3387, 2951, 2924, 2853, 1624, 1466, 1377, 1274, 1240, 1141, 1105, 1033,
887, 731 cmÀ1; HRMS: m/z calcd for C22H34N3: 340.2753 [M+H]+; found:
340.2779.
(E)-N,N’-Diisopropyl-4-(pyridin-2-yl)piperazine-1-carboxamidine
Colorless solid, yield >99%; 1H NMR (400 MHz, C6D6): d=0.91 (d, J=
6.4 Hz, 6H; NCH(CH3)2), 1.21 (d, J=6.4 Hz, 6H; NHCH(CH3)2), 3.00
A
ACHTREUNG
(br, 1H; NH), 3.24 (t, J=5.2 Hz, 4H; CH2), 3.27–3.40 (m, 2H; CH), 3.47
(t, J=5.2 Hz, 4H; CH2), 6.27 (d, J=8.8 Hz, 1H; C5H4N), 6.37–6.40 (m,
1H; C5H4N), 7.11–7.15 (m, 1H; C5H4N), 8.27–8.29 ppm (m, 1H; C5H4N);
13C NMR (100 MHz, C6D6): d=23.9, 25.6, 45.5, 46.4, 47.6, 48.5, 107.1,
113.2, 137.0, 148.3, 154.2, 160.0 ppm; IR (Nujol): n˜ =3399, 2957, 2924,
2853, 1638, 1593, 1460, 1377, 1242, 1161, 775 cmÀ1; HRMS: m/z calcd for
C16H28N5: 290.2345 [M+H]+; found: 290.2351.
Isolation of the guanidinate complex [{Me2Si
A
G
G
A
N
ACHTREUNG
(31 mg, 0.429 mmol) in benzene (3 mL) was added to a solution of 1
(253 mg, 0.429 mmol) in benzene (2 mL) in a flask. Then N,N’-diisopro-
pylcarbodiimide (54 mg, 0.429 mmol) was added to the above reaction
mixture. After 0.5 h, the solvent was removed under reduced pressure.
The residue was extracted with hexane and filtered to give a clean solu-
tion. The solution volume was reduced under vacuum to precipitate 41 as
colorless crystalline powder (248 mg, 0.395 mmol, 92% yield). Single
crystals of 41 suitable for X-rayanalysis were grown in THF/hexane at
ACHTREUNG
A
ACHTREUNG
1
2.96 (br, 2H; NH), 3.25 (s, 8H; CH2), 3.27–3.41 ppm (m, 4H; CH);
13C NMR (100 MHz, C6D6): d=23.9, 25.7, 46.4, 47.5, 49.0, 154.6 ppm; IR
(Nujol): n˜ =3372, 2955, 2924, 2853, 1636, 1609, 1456, 1381, 1254, 1163,
À308C for one week. H NMR (400 MHz, C6D6): d=0.96 (s, 6H; SiMe2),
0.99 (t, J=7.2 Hz, 6H; CH2CH3), 1.07 (d, J=6.4 Hz, 12H; CH(CH3)2),
N
1.16 (br, 4H; b-CH2, THF), 2.11 (s, 6H; C5Me4), 2.38 (s, 6H; C5Me4),
4048
www.chemeurj.org
ꢀ 2007 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Chem. Eur. J. 2007, 13, 4037 – 4051

Amine Protonolysis of Rare-Earth Metal Guanidinates
FULL PAPER
2.88 (q, J=7.2 Hz, 4H; CH2CH3), 3.47–3.54 (m, 2H; CH
A
5.13 (s, 1H; NH), 6.55 (d, J=8.8 Hz, 2H; C6H4), 6.71 (t, J=7.2 Hz, 1H;
C6H5), 6.80 (d, J=8.4 Hz, 2H; C6H5), 7.20 (dd, J=7.2, 8.4 Hz, 2H;
C6H5), 7.26 ppm (d, J=8.8 Hz, 2H; C6H4); 13C NMR (100 MHz, C6D6,
68C): d=5.2, 12.4, 15.3, 25.3, 25.6, 46.8, 69.7, 108.1, 113.4, 115.4, 118.6,
120.7, 122.9, 127.0 (d, J(Y,C) =1.6 Hz), 129.2, 132.4, 142.2, 156.5, 163.2 ppm
(d, J(Y,C) =1.7 Hz); 1H NMR (400 MHz, [D8]THF, 08C): d=0.61 (s, 6H;
(br, 4H; a-CH2, THF), 6.68 (t, J=7.6 Hz, 1H; p-C6H5), 6.74 (d, J=
7.6 Hz, 2H; o-C6H5), 7.18 ppm (t, J=7.6 Hz, 2H; m-C6H5); 13C NMR
(100 MHz, C6D6): d=5.1, 12.2, 14.0, 15.7, 25.3, 26.2, 44.7, 47.1, 71.2,
107.4, 115.3, 121.0, 122.2, 127.2 (d, J(Y,C) =1.7 Hz), 129.0, 156.4, 172.6 ppm
(d, J(Y,C) =1.6 Hz); IR (Nujol): n˜ =2956, 2923, 2854, 1587, 1491, 1457,
1410, 1377, 1291, 1179, 1017, 921, 831, 801, 760 cmÀ1; elemental analysis
calcd for C32H55N4OSiY: C 61.12, H 8.82, N 8.91; found: C 60.75, H 8.44,
N 9.09.
SiMe2), 0.98 (d, J=6.4 Hz, 12H; NCH
ACHTREUNG
(s, 6H; C5Me4), 3.36–3.43 (m, 2H; NCH
AHCTREUNG
(t, J=7.2 Hz, 1H; C6H5), 6.48 (d, J=8.4 Hz, 2H; C6H5), 6.79 (d, J=
9.2 Hz, 2H; C6H4), 6.84–6.90 (m, 2H; C6H5), 7.31 ppm (d, J=9.2 Hz, 2H;
C6H4); 13C NMR (100 MHz, [D8]THF, 08C): d=4.8, 12.2, 14.4, 25.3, 26.3,
47.0, 68.1, 107.8, 111.7, 114.9, 118.0, 120.8, 122.8, 126.6 (d, J(Y,C) =2.4 Hz),
128.7, 132.3, 143.7, 156.6, 164.3 ppm (d, J(Y,C) =1.6 Hz); IR (Nujol): n˜ =
3417, 2956, 2924, 2854, 1587, 1530, 1488, 1462, 1378, 1285, 1177, 1017,
992, 918, 803, 760 cmÀ1; elemental analysis calcd for C34H50BrN4OSiY: C
56.12, H 6.93, N 7.70; found: C 55.65, H 6.70, N 7.32.
Isolation of the amido complex [{Me2Si
N
N
A
a
0.485 mmol) in benzene (3 mL) was added to a solution of 1 (286 mg,
0.485 mmol) in benzene (2 mL) in a flask. After 10 min, the solvent was
removed under reduced pressure. The residue was extracted with ben-
zene/hexane (1:1) mixed solvent and filtered to give a clean solution. The
solution volume was reduced under vacuum to precipitate 42 as colorless
crystalline powder (314 mg, 0.466 mmol, 96% yield). Single crystals of
42·0.5THF suitable for X-rayanalsyis were grown in THF/hexane at
room temperature for three days. 1H NMR (400 MHz, C6D6): d=0.91 (s,
6H; SiMe2), 1.14 (br, 8H; b-CH2, THF), 2.05 (s, 6H; C5Me4), 2.06 (s, 6H;
C5Me4), 3.57 (br, 8H; a-CH2, THF), 4.06 (s, 1H; NH), 6.17 (d, J=8.8 Hz,
2H; C6H5), 6.69–6.75 (m, 3H; C6H5 and C6H4), 7.24–7.28 ppm (m, 4H;
C6H5 and C6H4); 13C NMR (100 MHz, C6D6): d=5.0, 11.4, 14.0, 25.5,
70.4, 103.0, 107.5, 115.1, 116.5, 120.0, 123.0, 126.8 (d, J(Y,C) =1.6 Hz),
129.9, 132.5, 156.6, 157.9 ppm; IR (Nujol): n˜ =3420, 2953, 2922, 2853,
1584, 1476, 1462, 1377, 1288, 1246, 1177, 1015, 910, 810, 752, 692 cmÀ1; el-
emental analysis calcd for C31H44BrN2O2SiY: C 55.28, H 6.58, N 4.16;
found: C 54.79, H 6.21, N 4.36.
Isolation of the guanidiate complex [{Me2Si
A
G
N
C(NC6H4Br-4)(NHiPr)}(thf)] (44): In the glovebox, a solution of 4-bro-
A
ACHTREUNG
moaniline (61 mg, 0.354 mmol) in benzene (3 mL) was added to a solu-
tion of 1 (209 mg, 0.354 mmol) in benzene (2 mL) in a Schlenk tube.
Then N,N’-diisopropylcarbodiimide (45 mg, 0.354 mmol) was added to
the above reaction mixture. The Schlenk tube was taken outside the glo-
vebox and the mixture was stirred at 808C for 0.5 h. After the solvent
was removed under reduced pressure, the residue was extracted with
hexane and filtered to give a clean solution. The solution volume was re-
duced under vacuum to precipitate 44 as colorless crystalline powder
(239 mg, 0.329 mmol, 93% yield). Single crystals of 44·THF suitable for
X-rayanalysis were grown in THF at room temperature for one week.
1H NMR (400 MHz, C6D6): d=0.73 (d, J=6.4 Hz, 6H; NCH
(s, 6H; SiMe2), 1.08 (d, J=6.4 Hz, 6H; NHCH(CH3)2), 1.19 (br, 4H; b-
CH2, THF), 2.01 (s, 6H; C5Me4), 2.24 (s, 6H; C5Me4), 3.04–3.11 (m, 1H;
NCH(CH3)2), 3.20–3.25 (m, 1H; NHCH(CH3)2), 3.51 (br, 4H; a-CH2,
THF), 3.55 (s, 1H; NH), 6.68–6.81 (m, 5H; C6H5 and C6H4), 7.16–
7.22 ppm (m, 4H; C6H5 and C6H4); 1H NMR (400 MHz, [D8]THF): d=
A
Isolation of the guanidiate complex [{Me2Si
G
R
AHCTREUNG
A
N
ACHTREUNG
bromoaniline (69 mg, 0.40 mmol) in THF (3 mL) was added to a solution
of 1 (236 mg, 0.40 mmol) in THF (2 mL) in a flask at À308C. Then N,N’-
diisopropylcarbodiimide (50 mg, 0.40 mmol) was added to the above re-
action mixture. The reaction mixture was stirred at À308C for 2 h. After
the solvent was removed under reduced pressure, the residue was extract-
ed with cold hexane and filtered to give a clean solution. The solution
volume was reduced under vacuum to precipitate 43 as colorless crystal-
line powder (279 mg, 0.384 mmol, 96% yield). The guanidinate com-
pound 43 was stable at low temperature in solid state. At room tempera-
ture, it graduallychanged to 44 in 15 h in C6D6. 1H NMR (400 MHz,
C6D6, 68C): d=0.98 (s, 6H; SiMe2), 0.99 (d, J=6.4 Hz, 12H; NCH-
E
ACHTREUNG
0.56 (s, 6H; SiMe2), 0.98 (d, J=6.4 Hz, 6H; NCH
6.4 Hz, 6H; NHCH(CH3)2), 1.88 (s, 6H; C5Me4), 2.03 (s, 6H; C5Me4),
3.30–3.40 (m, 2H; CH(CH3)2), 4.33 (br, 1H; NH), 6.29 (t, J=7.2 Hz, 1H;
(CH3)2), 1.07 (d, J=
AHCTREUNG
AHCTREUNG
C6H5), 6.48 (d, J=8.0 Hz, 2H; C6H5), 6.72 (d, J=8.8 Hz, 2H; C6H4), 6.82
(t, J=8.0 Hz, 2H; C6H5), 7.13 ppm (d, J=8.8 Hz, 2H; C6H4); 13C NMR
(100 MHz, THF-d8): d=5.2, 11.8, 14.8, 23.4, 25.0, 26.6, 45.7, 46.4, 68.4,
107.8, 111.1, 115.2, 120.7, 123.5, 123.8, 126.9 (d, J(Y,C) =1.7 Hz), 129.1,
132.1, 151.2, 156.9, 165.3 ppm (d, J(Y,C) =2.5 Hz); IR (Nujol): n˜ =3387,
2953, 2922, 2853, 1585, 1531, 1479, 1462, 1377, 1280, 1179, 1150, 991, 916,
ACHTREUNG
AHCTREUNG
Table 6. Crystallographic data and structure refinement details for 1, 4, 5, and 40.
1·0.5hexane
4·0.5hexane
5·0.5hexane
40
formula
Mw
C32H57NO2Si2Y
632.88
C32H57NO2Si2Yb
717.01
C32H57LuNO2Si2
718.94
C29H49N2O2SiY
574.70
crystal system
space group
a[Š]
b[Š]
c[Š]
orthorhombic
Ibam
19.770(3)
22.883(4)
15.523(2)
90
7022.4(19)
8
1.197
orthorhombic
Ibam
19.703(2)
22.817(3)
15.5323(19)
90
6982.7(15)
8
1.364
orthorhombic
Ibam
19.720(3)
22.839(3)
15.5108(19)
90
6986.0(15)
8
1.367
orthorhombic
Pbca
19.274(3)
15.952(2)
19.581(3)
90
6020.4(14)
8
1.268
b[8]
V[Š3]
Z
1calcd [gcmÀ3
]
m
A
]
1.755
2.773
2.921
2.004
F
A
2712
2960
2968
2448
q range [8]
1.36–25.06
19356
3239
191
1.036
1.37–25.56
20235
3415
191
1.011
1.36–25.57
20098
3418
193
0.965
1.96–25.07
29247
5325
323
1.027
no of reflns collected
no of indep reflns
no of variables
GOF
R [I>2s(I)]
Rw
0.0433
0.0888
0.0248
0.0592
0.0278
0.0614
0.0372
0.0753
Chem. Eur. J. 2007, 13, 4037 – 4051
ꢀ 2007 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemeurj.org
4049

Z. Hou et al.
Table 7. Crystallographic data and structure refinement details for 41, 42, and 44.
41
42·0.5THF
44·THF
formula
Mw
crystal system
space group
a[Š]
C32H55N4OSiY
626.80
C66H96Br2N4O5Si2Y2
1419.29
monoclinic
C2/c
37.755(7)
9.2298(17)
19.745(4)
96.211(2)
6840(2)
4
1.378
2.940
2944
2.08–25.04
16027
C38H58BrN4O2SiY
799.79
monoclinic
P2(1)/c
9.0094(14)
21.103(3)
17.645(3)
90.151(3)
3354.8(9)
4
1.245
1.803
1344
1.50–26.02
18822
monoclinic
P2(1)/c
17.800(5)
9.853(3)
22.577(6)
96.444(4)
3934.6(19)
4
1.350
2.565
1672
1.82–25.01
16355
b[Š]
c[Š]
b[8]
V [Š3]
Z
1calcd [gcmÀ3
]
m [mmÀ1
(000)
q range [8]
]
F
A
no of reflns collected
no of indep reflns
no of variables
GOF
6587
364
1.005
5991
359
0.959
6688
409
1.009
R [I>2s(I)]
Rw
0.0392
0.0558
0.0492
0.1159
0.0621
0.1018
827, 754 cmÀ1; elemental analysis calcd for C34H50BrN4OSiY: C 56.12, H
6.93, N 7.70; found: C 55.72, H 6.91, N 7.22.
A. Lowenthal), Plenum Press, New York, 1987; c) R. G. S. Berlinck,
M. H. Kossuga, Nat. Prod. Rep. 2005, 22, 516–550; d) R. G. S. Ber-
linck, Nat. Prod. Rep. 2002, 19, 617–649.
X-ray crystallographic studies: Crystals for X-ray analyses of 1, 4, 5, 10,
21, 35, 40, 41, 42, and 44 were obtained as described in the preparations.
The crystals were manipulated in the glovebox and were sealed in thin-
walled glass capillaries. Data collections were performed at À1008C on a
Bruker CCD APEX diffractometer with a CCD area detector, byusing
graphite-monochromated MoKa radiation (l=0.71069 Š). The determina-
tion of crystal class and unit cell parameters was carried out by the
SMART program package. The raw frame data were processed byusing
SAINT and SADABS to yield the reflection data file. The structures
were solved bythe use of the SHELXTL program. Refinement was per-
formed on F2 anisotropicallyfor all the non-hydrogen atoms bythe full-
matrix least-squares method. The hydrogen atoms were placed at the cal-
culated positions and were included in the structure calculation without
further refinement of the parameters. Crystal data, data collection, and
processing parameters for the rare-earth metal complexes 1, 4, 5, 40–42,
and 44 are summarized in Tables 6 and 7, whereas those for organic com-
pounds 10, 21, and 35 were given onlyin the Supporting Information.
CCDC-622021 (1·0.5hexane), CCDC-622022 (4·0.5hexane), CCDC-
622023 (5·0.5hexane), CCDC-622024 (10), CCDC-622025 (21), CCDC-
622026 (35), CCDC-622027 (40), CCDC-610669 (41), CCDC-622028
(42·0.5THF), and CCDC-622029 (44·THF) contains the supplementary
crystallographic data for this paper. Copies of these data can be obtained
free of charge from The Cambridge Crystallographic Data Centre via
www.ccdc.cam.ac.uk/data_request/cif.
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Acknowledgements
This work was partlysupported bya Grant-in-Aid for Scientific Research
on PriorityAreas (No. 14078224, “Reaction Control of Dynamic Com-
plexes”) from the Ministryof Education, Culture, Sports, Science, and
Technologyof Japan and bythe National Natural Science Foundation of
China (No. 20328201).
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Received: September 27, 2006
Published online: March 9, 2007
Chem. Eur. J. 2007, 13, 4037 – 4051
ꢀ 2007 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemeurj.org
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