Synthesis and properties of alkaline metal complexes with new overcrowded β-diketiminato ligands

Article abstract of DOI:10.1016/j.jorganchem.2006.08.055

Enaminoimines TbtNHC(Me)CHC(Me)NAr (5, Tbt = 2,4,6-[CH(SiMe₃)₂]₃C₆H₂) bearing a Tbt group were synthesized by the two steps condensation of acetylacetone with bulky amines. Enaminoimines 5 were treate

Full text of DOI:10.1016/j.jorganchem.2006.08.055

Journal of Organometallic Chemistry 692 (2007) 44–54
www.elsevier.com/locate/jorganchem
Synthesis and properties of alkaline metal complexes with
new overcrowded b-diketiminato ligands
Hirofumi Hamaki, Nobuhiro Takeda, Takayuki Yamasaki,
*
Takahiro Sasamori, Norihiro Tokitoh
Institute for Chemical Research, Kyoto University, Gokasho, Uji, Kyoto 611-0011, Japan
Received 28 February 2006; accepted 26 May 2006
Available online 9 September 2006
Abstract
Enaminoimines TbtNHC(Me)CHC(Me)NAr (5, Tbt = 2,4,6-[CH(SiMe3)2]3C6H2) bearing a Tbt group were synthesized by the two
steps condensation of acetylacetone with bulky amines. Enaminoimines 5 were treated with n-BuLi to give the corresponding lithium
b-diketiminates, [Li{TbtNHC(Me)CHC(Me)NAr}] (1). The X-ray structural analysis of [Li{TbtNC(Me)CHC(Me)NMes}] (1c,
Mes = mesityl) revealed that it is a monomeric, solvent-free lithium b-diketiminate. The equilibrium between free 1c plus THF and
THF-coordinated (1c Æ thf) was investigated in detail by the determination of the association constant (Ka) in C6D6 at 293 K and the
Job’s plot. The heavier alkali metal complexes, sodium and potassium b-diketiminates (6c–9c), were prepared by the two routes.
THF-coordinated [M{TbtNC(Me)CHC(Me)NMes}(thf)] (6c: M = Na. 7c: M = K) were prepared by the reaction of 5c (Ar = Mes) with
MH (M = Na, K). Solvent-free [M{TbtNC(Me)CHC(Me)NMes}] (8c: M = Na. 9c: M = K) were prepared by the reaction of 1c with
t-BuOM (M = Na, K).
ꢀ 2006 Elsevier B.V. All rights reserved.
Keywords: b-Diketiminato ligand; Alkali metals; 7Li NMR spectra; Association constant; Job’s plot; Steric protection
1. Introduction
plexes having activities as catalysts, and model complexes
for protein active sites. Most of these complexes were
derived from the corresponding alkaline metal b-di-
ketiminates, and their syntheses and properties have been
studied extensively [3–12]. In general, the alkaline metals
in these complexes are coordinated by bases, such as ethers,
amines, or nitriles, due to their extremely high Lewis
acidity. Base-free complexes exist as dimers, oligomers, or
polymers in the solid states, and there has been no example
for X-ray analysis of monomeric, base-free alkaline metal
b-diketiminates so far. Even [M{[DipNC(Me)]2CH}]
(M = Li [8,11], K [11]) bearing bulky Dip groups report-
edly exists as a dimer (M = Li), a dodecamer (M = Li),
or a polymer (M = K), in the crystalline states.
The b-diketonato ligands, such as acetylacetonate
(acacꢀ), 1,3-diphenyl-1,3-propanedionate (dbzmꢀ), etc.,
are one of the most popular chelating systems in coordina-
tion chemistry [1]. In recent years, the isoelectronic b-dike-
timinato ligands have attracted much attention as spectator
ligands, since they strongly coordinate to the metal centers
and tune the reactivities on the metal by changing the steric
and electronic properties of the substituents of the
nitrogen atoms [2]. In particular, crowded b-diketiminato
ligands having bulky substituents at the nitrogen atoms,
e.g., [{(Dip)NC(Me)}2CH]ꢀ (Dip = 2,6-diisopropylphenyl),
have been applied to the synthesis of various complexes of
main group elements and transition metals, such as low
coordinate complexes, low oxidation state complexes, com-
On the other hand, we have successfully synthesized a
variety of highly reactive species containing heavier main
group elements [13–15] and transition metals [16] by taking
advantage of 2,4,6-tris[bis(trimethylsilyl)methyl]phenyl
(Tbt) group (Chart 1) [17]. We have preliminarily reported
*
Corresponding author. Tel.: +81 774 38 3200; fax: +81 774 38 3209.
E-mail address: tokitoh@boc.kuicr.kyoto-u.ac.jp (N. Tokitoh).
0022-328X/$ - see front matter ꢀ 2006 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2006.08.055

H. Hamaki et al. / Journal of Organometallic Chemistry 692 (2007) 44–54
45
Chart 1.
the synthesis of the first monomeric lithium b-diketiminate,
[Li{TbtNC(Me)CHC(Me)NHMes}] (1c), which has no
coordination of heteroatom donors, by use of a new over-
crowded b-diketiminato ligand bearing a Tbt group (Chart
1) [18]. Very recently, we have reported the application of
1c to the synthesis of the corresponding tetravalent group
4 metal b-diketiminates [MIVCl3{TbtNC(Me)CHC(Me)-
NHMes}(thf)n] (M = Ti, Zr, Hf), which show unique reac-
tivities in the reduction with KC8 [19].
In this paper, we present the details of the synthesis and
properties of the lithium b-diketiminate 1 together with the
synthesis of sodium and potassium complexes coordinated
with the overcrowded b-diketiminato ligand.
Scheme 2. Synthesis of enaminoimine 5.
these conditions, the reaction of 4 with PhNH2 in the
presence of TiCl4 (0.6 equiv.) resulted in the almost quan-
titative formation of 5a. The synthesis of o-tolyl- and Mes-
substituted enaminoimine 5b and 5c was also achieved by
the similar method in almost quantitative yields. However,
the condensation reaction with DipNH2 scarcely proceeded
under similar conditions, and the reaction with 3 resulted
in complete recovery of the starting materials, probably
due to the severe steric hindrance.
2. Results and discussion
2.2. Structures of enaminoketone 4 and enaminoimines 5a,c
2.1. Synthesis of enaminoimines 5a,b
Enaminoketone 4 and enaminoimines 5a–c were charac-
1
terized by the H and 13C NMR spectra, high-resolution
Enaminoimine 5 bearing a Tbt group was synthesized by
successive condensation of acetylacetone with bulky
amines as shown in Scheme 2. Tbt-substituted amine 3
was prepared in a good yield by modifying the reported
method [20], i.e., the treatment of TbtLi with tosylazide fol-
lowed by the reduction of the resulting TbtN3 (2) with
LiAlH4 (Scheme 1) [21]. When Tbt-substituted amine 3
was allowed to react with excess of acetylacetone (10
equiv.) in the presence of HCl/Et2O (0.5 equiv.) in refluxing
toluene, enaminoketone 4 was quantitatively obtained via
monocondensation reaction. The exclusive formation of 4
can be explained in terms of the suppression of the nucleo-
philic attack of 3 to the carbonyl group of 4 due to the ste-
ric hindrance of the Tbt group, since the reaction using 0.5
molar amount of acetylacetone under the similar condi-
tions also gave 4 along with the starting material 3. Further
condensation with PhNH2 was investigated by using HCl/
Et2O (0.8 equiv.), BF3 Æ Et2O (0.8 equiv.), and ZnCl2 (0.6
equiv.) as acid catalysts in the presence of molecular sieves
4A to give the expected enaminoimine 5a in 18%, 41%, and
11% yields, respectively. In contrast to the low yields in
mass spectra, and elemental analysis, and the molecular
structures of these compounds were definitively determined
by X-ray structural analysis.
Figs. 1–3 show the ORTEP drawings of 4, 5a, and 5c,
respectively. Table 6 shows the crystal data and structure
refinements for 4, 5a, and 5c. The N1–C1–C2–C3–N2(O1)
moieties of all these compounds are almost planar, and
˚
˚
the C–O, C–N (1.285–1.340 A) and C–C (1.366–1.437 A)
bond lengths (Table 1) are intermediate values between
the typical single [C–OH: av. 1.432; C–N: av. 1.469; C–C:
˚
av. 1.530 A] and double [(C)2C@O: av. 1.210; C–C@N–C:
av. 1.279; (C)HCsp2 = Csp2(C)2: av. 1.326 A] bond lengths
˚
[22]. Although these observations suggest the conjugation
Fig. 1. ORTEP drawing of enaminoketone 4 (50% thermal ellipsoids).
Scheme 1. Synthesis of Tbt-substituted amine 3.
Hydrogen atoms, except for NH, are omitted for clarity.

46
H. Hamaki et al. / Journal of Organometallic Chemistry 692 (2007) 44–54
It should be noted that the pattern of the bond alterna-
tion in 5a is different from that in 5c, i.e., in 5a, the N1–C1
˚
bond [1.318(3) A] tethered with Tbt group is shorter than
˚
the N2–C3 bond [1.354(3) A] tethered with Ph group,
˚
while, in 5c, the (Tbt)N1–C1 bond [1.340(4) A] is longer
˚
than the (Mes)N2–C3 bond [1.285(4) A]. The bond alterna-
tion pattern of 5a may be explained in terms of the contri-
bution of the resonance structure shown in Chart 2. On the
other hand, the structure of 5c may be little affected by the
resonance structure, since the dihedral angles between the
C3N2 plane and Mes ring are almost orthogonal (Table
1). The longer (Tbt)N1–C1 bond of 5c is probably due to
the relaxation of the steric repulsion between Tbt group
and Me(C4) group.
Fig. 2. ORTEP drawing of enaminoimine 5a (50% thermal ellipsoids).
Hydrogen atoms, except for NH, are omitted for clarity.
2.3. Synthesis and structure of lithium b-diketiminates 1a,b
Enaminoimines 5a and 5c were treated with 1.5 molar
amount of n-BuLi in ether at 0 ꢁC, and then the reaction
mixture was warmed to room temperature to give a color-
less solution. The exchange of the solvents to dry hexane
followed by the filtration of the mixture resulted in the
isolation of lithium b-diketiminates 1a and 1c, which are
insoluble in hexane and isolated as colorless, moisture-
sensitive crystals in 81% and 85% yields, respectively
(Scheme 3).
Lithium b-diketiminates 1a,c were characterized with
1H, 13C, and 7Li NMR spectroscopy. The 1H and 13C
NMR spectra showed that no solvent such as ether coordi-
nates to the lithium atoms of 1a,c. These results are in
sharp contrast to the case of Li[{(Dip)NC(Me)}2-
CH](Et2O), which does not lose the coordinated ether even
in hydrocarbon solvents such as hexane and C6D6 [18].
This difference is probably due to the steric hindrance of
the extremely bulky substituent, Tbt group, attached to
the nitrogen atom of 1a,c.
Fig. 3. ORTEP drawing of enaminoimine 5c (50% thermal ellipsoids).
Hydrogen atoms, except for NH, are omitted for clarity.
of the p-bonds in the N1–C1–C2–C3–N2(O1) systems, the
C3NO and C3N2 structures clearly show bond alternation
(Table 1). Considering these results, the C3NO and C3N2
systems indicate the obvious localization of the double
bonds despite the partial delocalization of the p-electrons,
as well as the case of other enaminoimines, (Ar)N@
C(Me)–CH@C(Me)–NH(Ar) (Ar = Ph [23] or Dip [8]).
The X-ray structural analysis revealed the crystalline-
state structure of 1c, and the ORTEP drawings and the
crystal packing diagram of 1c are shown in Figs. 4 and 5,
respectively.
Table 1
˚
Selected bond lengths (A), bond and dihedral angles (ꢁ)
Compound
4
5a
5c
1c
˚
Bond lengths (A)
C1–C2
C2–C3
C1–N1
C3–N2
1.383(5)
1.407(5)
1.342(4)
1.426(3)
1.366(3)
1.318(3)
1.354(3)
1.372(4)
1.437(4)
1.340(4)
1.285(4)
1.424(4)
1.418(4)
1.323(4)
1.328(4)
–
Chart 2.
C3–O1
1.259(4)
–
–
–
Bond angles (ꢁ)
C1–C2–C3
N1–C1–C2
123.3(4)
120.9(4)
122.6(4)
127.4(2)
121.3(2)
120.2(2)
125.2(3)
122.6(3)
121.0(3)
130.2(3)
123.6(3)
125.1(3)
E–C3–C2
(E = N2 or O1)
Dihedral angles (ꢁ)
C3NE plane –
Tbt ring
C3N2 plane –
Ar ring
83.40(42)
–
77.96(26)
46.22(36)
86.78(37)
88.20(43)
86.76(34)
87.86(36)
Scheme 3. Synthesis of lithium b-diketiminate 1.

H. Hamaki et al. / Journal of Organometallic Chemistry 692 (2007) 44–54
47
The X-ray structural analysis of 1c showed that there is
no intermolecular contact between neighboring molecules
˚
(the shortest Liꢁ ꢁ ꢁC intermolecular distance: 3.718(6) A)
and no solvent coordinates to the lithium atom of 1c
(Fig. 5). To the best of our knowledge, this is the first
example for the structural analysis of monomeric, lithium
b-diketiminate free of heteroatom donor. It should be
noted that [Li{[DipNC(Me)]2CH}] [8], [Li{(Me3Si)-
NC(R1)CHC(R2)N(SiMe3)}] (R1 = R2 = Ph [3]; R1 = Ph,
R2 = t-Bu [7]; R1 = R2 = NMe2 [9]), and [Li{(Me3Si)-
NC(R1)C(R2)(C5H4N-2)}] (R1 = t-Bu, R2 = H; R1 = Ph,
R2 = SiMe3) [6] reportedly exist as dimers or dodecamers
in the crystalline states. This difference is most likely due
to the steric hindrance of the extremely bulky Tbt group
on the nitrogen atom in 1c.
It should be of additional interest for the newly obtained
complex 1c that it probably has two intramolecular
Liꢁ ꢁ ꢁCH3 interactions as judged by the Liꢁ ꢁ ꢁC(15) and
Liꢁ ꢁ ꢁC(29) distances. The Liꢁ ꢁ ꢁCH interaction has been
reported for some lithium amides, alkyllithiums, and ate
complexes (Fig. 4(b)) [18,24]. The C3N2Li ring of 1c is
almost planar and the two sets of Li–N, N–C and C–C dis-
tances in the C3N2Li ring are almost equivalent to each
other (Table 1). In addition, the N–C and C–C bond
lengths are intermediate values between the typical single
Fig. 4. ORTEP drawing of lithium b-diketiminate 1c (50% thermal
ellipsoids). (a) Top view, (b) side view. Hydrogen atoms are omitted for
˚
clarity. Selected bond distances (A) and angles (ꢁ): Li(1)–N(1) 1.917(6),
Li(1)–N(2) 1.915(6), Li(1)ꢁ ꢁ ꢁC(15) 2.835, Li(1)ꢁ ꢁ ꢁC(29) 2.670(6), N(2)–
Li(1)–N(1) 103.8(3), Li(1)–N(1)–C(1) 119.0(2), C(3)–N(2)–Li(1) 117.9(3).
Fig. 5. The crystal packing of lithium b-diketiminate 1c.

48
H. Hamaki et al. / Journal of Organometallic Chemistry 692 (2007) 44–54
˚
[C–N: av. 1.469; C–C: av. 1.530 A] and double [C–C@N–
dobs ¼ ð1 ꢀ aÞdfree þ adTHF-coordinated
a ¼ ðdfree ꢀ dobsÞ=ðdfree ꢀ dTHF-coordinated
ð1Þ
ð2Þ
2
2
˚
C: av. 1.279; (C)HCsp = Csp (C)2: av. 1.326 A] bonds
Þ
[22].
If the THF molecules coordinates to 1c with the ratio of
1:1 in the C6D6 solution as well as the case of (1a Æ thf) in
the crystalline state, Ka is described by Eq. (3), where
[(1c Æ thf)], [1c], and [THF] are the equilibrium concentra-
tions of THF-coordinated complex, (1c Æ thf), and THF,
respectively. Eq. (3) can be rearranged to give Eq. (4) by
introducing [(1c Æ thf)] = a[1c]0, [1c] = (1 ꢀ a)[1c]0, and
[THF] = [THF]0 ꢀ a[1c]0, where [1c]0 and [THF]0 are the
total concentrations of 1c and THF, respectively.
2.4. Complexation of lithium b-diketiminate 1c with THF
When various amounts of THF were added to the C6D6
7
solution of 1c, the Li NMR signals shifted to the upper-
field with the increase of the amount of THF (Table 2).
1
In addition, the signals assigned to THF in the H NMR
spectra moved to the lower field by the addition of a larger
amount of THF (Table 2). These results suggest the rapid
equilibrium at 298 K between free 1c plus THF and
THF-coordinated (1c Æ thf) in the time scale of NMR spec-
troscopy (Scheme 4). That is, the addition of a large
amount of THF leads to the increase of the ratio of
(1c Æ thf) compared to 1c and the ratio of free THF relative
to the coordinating THF to 1c.
Ka ¼ ½ð1c ꢁ thfÞꢂ=½1cꢂ½THFꢂ
ð3Þ
ð4Þ
ðaꢀ1 ꢀ 1Þꢀ1 ¼ Kað½THFꢂ0 ꢀ a½1cꢂ0Þ
The (aꢀ1 ꢀ 1)ꢀ1 values were plotted against the
([THF]0 ꢀ a[1c]0) values, where the a values were calcu-
lated by taking the dTHF-coordinated value as various values
between 1.50 and 1.75 ppm in Eq. (2) (Table 3), since the
dTHF-coordinated value cannot be directly determined by the
measurement [25]. The dTHF-coordinated value giving the best
correlation coefficient (R2 = 0.996) is 1.682 ppm, and the
linear plots, where the dTHF-coordinated value is taken as this
value, indicate that the association constant (Ka) is
18 1 Mꢀ1 (Fig. 6, Tables 2 and 3).
When the C6D6 solution containing 1a–c and THF was
fully evaporated, the lithium b-diketiminate coordinated by
one THF molecule (1c Æ thf) was isolated. We have succeeded
in the X-ray structural analysis of the analogously prepared
lithium complex having Tbt and Ph groups on the N-termi-
nals, [Li{TbtNC(Me)CHC(Me)NPh}(thf)] (1a Æ thf) [18].
In order to clarify the details of this equilibrium, the
determination of the association constant (Ka) between free
1c and THF in C6D6 at 298 K was performed by the mea-
Fig. 7 shows a continuous variation plot (Job’s plot) for
the complex formation between 1c and THF [26]. The plots
show a maximum at 0.50 of the 1c fraction, indicating that
1c form the complex with THF with the ratio of 1:1 in
C6D6 at 298 K (Table 4).
7
surement of the Li NMR spectra. The observed chemical
7
shifts in the Li NMR spectra (dobs) are described by Eq.
(1), where a is the mole fraction of (1c Æ thf) and dfree and
dTHF-coordinated are the 7Li NMR chemical shifts of 1c
and (1c Æ thf), respectively. Eq. (1) can be rearranged to give
an expression shown in Eq. (2).
2.5. Synthesis of sodium and potassium b-diketiminates
We now focus on the heavier alkali metal compounds of
the b-diketiminato ligand. Sodium or potassium b-diketi-
minates are sometimes better precursors for the metal com-
plexes rather than the lithium analogues, because of the
ready separation from the heavier alkali metal chlorides
Table 2
The 7Li and 1H NMR measurements of 1c in C6D6/THF
[THF]0/[1c]0 7Li NMR 1H NMR aa
[THF]0 ꢀ (aꢀ1 ꢀ 1)ꢀ1a
dobs
(ppm)
THF
a[1c]0
(ppm)
(M)a
0 (pure 1c)
0.533
1.02
2.31
4.33
6.54
7.96
9.86
2.33 (dfree
2.21
2.11
1.99
1.89
1.84
1.82
1.79
)
–
0
0
0
1.24, 3.37 0.185 0.0104
1.25, 3.39 0.343 0.0204
1.33, 3.46 0.532 0.0532
1.35, 3.49 0.674 0.110
1.37, 3.51 0.762 0.174
1.38, 3.53 0.792 0.215
1.38, 3.53 0.836 0.271
0.227
0.521
1.14
2.07
3.21
3.80
5.11
Table 3
The relation between dTHF-coordinated and the association constant (Ka)
dTHF-coordinated (ppm)
Ka (M)ꢀ1
R2
1.50
1.60
1.61
1.62
1.63
1.64
1.65
1.66
1.67
1.68
1.682
1.69
1.70
1.71
1.72
1.75
7.58
11.2
11.8
12.4
13.1
13.9
14.8
15.8
16.9
18.2
18.5
19.8
21.7
24.0
26.8
42.6
0.904
0.963
0.967
0.974
0.979
0.984
0.988
0.991
0.994
0.995
0.996
0.995
0.993
0.988
0.978
0.898
Conditions: [1c]0 = 30.0 mM, C6D6 solution, 298 K.
a
The a values were calculated by using Eq. (2), where the dTHF-coordinated
value was taken as 1.682 ppm. The chemical shifts of THF in the 1H NMR
spectra were 1.40, 3.57 ppm.
Scheme 4. Equilibrium between free 1c and THF-coordinated (1c Æ thf).

H. Hamaki et al. / Journal of Organometallic Chemistry 692 (2007) 44–54
49
Scheme 5. Reaction of enaminoimine 5c with metal hydrides.
Scheme 6. Reaction of lithium b-diketiminate 1c with metal tert-
butoxides.
Fig. 6. Plot for determining the association constant for 1c and (1c Æ thf).
The regression line is y = 18.53x, (Ka = 18 1, dTHF-coordinated
=
1.682 ppm, R2 = 0.996).
Table 5
The Reactions of 1c with t-BuOM (M = Na, K)
Entry
Reagent
Equivalent
Yield (%)a
1c
8c or 9c
1
2
3
4
a
t-BuONa
t-BuONa
t-BuONa
t-BuOK
1.5
2.0
10
38
17
9
62 (8c)
83 (8c)
91 (8c)
93 (9c)
1.5
7
Judged by 1H NMR spectrum at 298 K.
MH (M = Na, K) in THF (Scheme 5) [28]. In hydrocarbon
(benzene or toluene) or diethyl ether solvents, these reac-
tions did not occur.
Next, we examined the synthesis of the THF-free
sodium and potassium b-diketiminates. The lithium b-dik-
etiminate 1c reacted with sodium or potassium tert-butox-
ide in C6D6 at 293 K, giving in high yield the appropriate
alkali metal derivative, THF-free complex 8c or 9c, respec-
tively (Scheme 6) [11].
Fig. 7. Job’s plot showing the 1:1 stoichiometry of the complex between
1c and THF in C6D6. [1c]0 + [THF]0 = 38.8 mM.
In the case of sodium, the reaction of 1c with 1.5 molar
amount of t-BuONa gave the corresponding sodium com-
plex 8c in a moderate yield (62%) together with the starting
material 1c (38%), and the almost quantitative formation
of 8c required the use of 10 molar amounts of t-BuONa
(Scheme 6, Table 5). Meanwhile, in the case of potassium,
the reaction of 1c with 1.5 molar amount of t-BuOK
resulted in the almost quantitative formation of 9c. This
difference probably depends on the affinity of the alkali
metal with the coordinating nitrogens.
Table 4
The Job’s plot between 1c and THF in C6D6
[1c]0/([THF]0 + [1c]0)
7Li NMR
(ppm)
a
[1c]0 (mM)
[(1c Æ thf)]
(mM)
0.20
0.30
0.40
0.50
0.60
0.70
0.80
2.02
2.01
2.07
2.11
2.16
2.21
2.26
0.478
0.494
0.401
0.340
0.262
0.185
0.108
12.0
18.0
24.0
30.0
36.0
42.1
48.1
5.75
8.90
9.64
10.2
9.46
7.79
5.19
3. Conclusion
Conditions: [1c]0 + [THF]0 = 38.8 mM (constant), C6D6 solution, 298 K.
Enaminoimines TbtNHC(Me)CHC(Me)NAr (5) bear-
ing a Tbt group (Tbt = 2,4,6-[CH(SiMe3)2]3C6H2) were
synthesized by the two-step condensation of acetylacetone
with bulky amines. It should be noted that the pattern of
the bonds alternation in 5a (Ar = Ph) is different from that
in 5c [Ar = Mes (mesityl)] as judged by the crystalline state
structures.
co-products, as in the synthesis of lanthanide metal b-dik-
etiminates [27].
First, THF-coordinated sodium and potassium b-diketi-
minates (6c and 7c) were prepared by the reaction of
enaminoimine 5c with the appropriate metal hydrides

50
H. Hamaki et al. / Journal of Organometallic Chemistry 692 (2007) 44–54
Enaminoimines 5 were treated with n-BuLi, yielding the
CDCl3) d 0.03 (s, 18H, SiMe3), 0.04 (s, 36H, SiMe3), 1.32
(s, 1H, p-benzyl), 1.99 (s, 2H, o-benzyl), 6.30 (br s, 1H,
Tbt m-H), 6.39 (br s, 1H, Tbt m-H); 13C NMR (75 MHz,
CDCl3) d 0.6 (q, SiMe3), 0.7 (q, SiMe3), 23.3 (d · 2, o-ben-
zyl), 30.0 (d, p-benzyl), 122.1 (d, Tbt Cm), 126.9 (d, Tbt
Cm), 131.8 (s), 138.7 (s), 141.2 (s), a signal assignable to
ipso-13C of Tbt group was not observed. HRMS (EI) found
m/z 565.3268 ([MꢀN2]+), calcd for C27H59NSi6 ([MꢀN2]+)
649.3838. Anal. Calc. for C27H59N3Si6: C, 54.57; H, 10.01;
N, 7.07. Found: C, 54.50; H, 10.04; N, 7.13%.
lithium b-diketiminates [Li{TbtNC(Me)CHC(Me)NAr}]
(1a: Ar = Ph, 1c: Ar = Mes). The X-ray structural analysis
of [Li{TbtNC(Me)CHC(Me)NMes}] (1c) revealed that it is
a monomeric, solvent-free lithium b-diketiminate in con-
trast to the previously reported lithium b-diketiminates,
which are oligomeric, solvent-free or monomeric, solvent-
coordinated lithium b-diketiminates. The equilibrium
between free 1c plus THF and THF-coordinated (1c Æ thf)
is examined from various points of view. The association
constant (Ka) for this equilibrium was determined by the
7Li NMR spectra to be 18 1 Mꢀ1 in C6D6 at 298 K,
and the Job’s plot indicated a 1:1 stoichiometry of the com-
plex of 1c with THF.
4.3. Synthesis of TbtNH2
A solution of TbtN3 (2.97 g, 5.0 mmol) in THF (50 mL)
was added dropwise to a suspension of LiAlH4 (1.0 g,
26.3 mmol) in THF (20 mL) at 0 ꢁC. The mixture was
allowed to warm to room temperature and stirred for 1
day. An aqueous solution of NaOH (15 mL, 0.01 M) was
added very slowly, and a vigorous reaction occurred. The
mixture was warmed to room temperature, whereupon
the grey precipitates turned white. The mixture was filtered
and the organic filtrate was dried over Na2SO4. Filtration
and evaporation of the organic layer resulted in the forma-
tion of colorless crystals of TbtNH2. Yield: 2.13 g (75%).
The spectral data and elemental analysis of TbtNH2 have
been described in Ref. [20].
Enaminoimine 5c was treated with MH (M = Na, K) in
THF to afford the THF-coordinated, sodium and potassium
b-diketiminates,
[M{TbtNC(Me)CHC(Me)NMes}(thf)]
(6c: M = Na, 7c: M = K). In addition, lithium b-diketimi-
nates 1c was treated with 10 equiv. of t-BuONa or 1.5
equiv. of t-BuOK to give the THF-free, sodium and potas-
sium b-diketiminates, [M{TbtNC(Me)CHC(Me)NMes}]
(8c: M = Na, 9c: M = K), respectively.
4. Experimental
4.1. General experimental details
All solvents used were purified by the reported methods.
THF was purified by distillation from sodium diphenylketyl
before use. All reactions were carried out under an argon
atmosphere, unless otherwise noted. The 1H NMR
(300 MHz) and 13C NMR (75 MHz) spectra were measured
in CDCl3 or C6D6 with a JEOL AL-300 spectrometer using
4.4. Synthesis of TbtNHC(Me)CHC(O)Me (4)
To a mixture of TbtNH2 (886 mg, 1.56 mmol) and acet-
ylacetone (410 lL, 16 mmol) in toluene (10 mL) was added
at room temperature an ether solution of hydrogen chlo-
ride (1 M solution, 790 lL, 0.79 mmol). The reaction mix-
ture was refluxed for 8 h, and then cooled to ambient
temperature. After the addition of a saturated aqueous
solution (5 mL) of NaHCO3, the mixture was extracted
with hexane (4 mL) 4 times. The combined organic layers
were dried with Na2SO4, and the solvents were evaporated.
The residue was dissolved in a small amount of CHCl3, and
CH3CN was added to the solution to afford colorless pre-
7
CHCl3 or C6D5H as an internal standard. The Li NMR
(116 MHz) spectra were measured in C6D6 with a JEOL
AL-300 spectrometer using LiCl in D2O (1 mol Lꢀ1) as an
external standard. The infrared and electronic spectra were
recorded on JASCO FT/IR 460 Plus and JASCO V530 UV/
Vis spectrometers, respectively. Mass spectral data were
obtained on a JEOL JMS-700 spectrometer. Elemental
analyses were performed by the Microanalytical Laboratory
of the Institute for Chemical Research, Kyoto University.
1
cipitates of 4. Yield: 1.01 g (99%). M.p. 179–181 ꢁC. H
NMR (300 MHz, CDCl3) d 0.00 (s, 18H, SiMe3), 0.03 (s,
18H, SiMe3), 0.04 (s, 18H, SiMe3), 1.33 (s, 1H, p-benzyl),
1.63 (s, 3H, MeC(N)), 1.69 (s, 2H, o-benzyl), 2.06 (s, 3H,
MeC(O)), 5.11 (s, 1H, 3-CH), 6.32 (br s, 1H, Tbt m-H),
6.43 (br s, 1H, Tbt m-H), 11.57 (s, 1H, NH); 13C NMR
(75 MHz, CDCl3) d 0.3 (q, SiMe3), 0.6 (q, SiMe3), 1.4 (q,
SiMe3), 19.4 (q, MeC(NHTbt)), 22.5 (d · 2, o-benzyl),
28.9 (q, MeC(O)), 30.1 (d, p-benzyl), 94.9 (d, 3-CH),
122.1 (d, Tbt Cm), 126.8 (d, Tbt Cm), 130.0 (s, Tbt), 142.0
(s, Tbt), 142.1 (s · 2, Tbt Co), 163.1 (s, C(NHTbt)), 195.0
(s, C(O)); IR (KBr) 689, 739, 760, 839, 893, 974, 1038,
1248, 1582, 1616, 2955 cmꢀ1; UV–Vis (hexane) 222 (e
3.1 · 104), 309 nm (e 1.1 · 104 Mꢀ1 cmꢀ1); HRMS (EI)
found m/z 649.3843 (M+), calcd for C32H67NOSi6
649.3838. Anal. Calc. for C32H67NOSi6: C, 59.09; H,
10.38; N, 2.15. Found: C, 58.82; H, 10.44; N, 2.32%.
4.2. Synthesis of TbtN3
To a THF solution (10 mL) of TbtBr (0.632 g, 1.00
mmol) was added t-BuLi (2.2 M in pentane, 0.90 mL,
2.0 mmol) at ꢀ78 ꢁC. The reaction mixture was stirred at
the same temperature for 30 min. TsN3 (0.20 g, 1.0 mmol)
was added to the reaction mixture. After stirring at the
same temperature for 30 min, the reaction mixture was
allowed to warm up to room temperature. The solvent
was evaporated under reduced pressure, and hexane was
added to the residue. Insoluble inorganic salts were
removed by filtration thorough Celiteꢂ. The removal of
the solvent from the filtrate gave TbtN3. Yield: 0.412 g
1
(69%). M.p. 115.3–117.1 ꢁC (dec.). H NMR (300 MHz,

H. Hamaki et al. / Journal of Organometallic Chemistry 692 (2007) 44–54
51
4.5. Synthesis of TbtNHC(Me)CHC(Me)NPh (5a)
156.6 (s, C(N)), 164.4 (s, C(N)); HRMS (EI) found m/z
738.4461 (M+), calcd for C39H74N2Si6 738.4468. Anal.
Calc. for C39H74N2Si6: C, 63.34; H, 10.09; N, 3.79. Found:
C, 62.84; H, 10.17; N, 3.87%.
To a solution of 4 (2.00 g, 3.07 mmol) and PhNH2
(3.0 mL, 31 mmol) in toluene (20 mL) was added TiCl4
(240 lL, 2.2 mmol) at 0 ꢁC. The reaction mixture was
refluxed for 16 h, and then cooled to ambient temperature.
After the addition of a saturated aqueous solution (20 mL)
of NaHCO3, the mixture was extracted with hexane
(15 mL) 4 times. The combined organic layers were dried
with Na2SO4, and then the solvents were evaporated. The
residue was dissolved in a small amount of CHCl3, and
CH3CN was added to the solution to afford colorless pre-
cipitates of 5a. Yield: 2.12 g (95%). M.p. 199.4–200.1 ꢁC.
1H NMR (300 MHz, CDCl3) d ꢀ0.07 (s, 18H, SiMe3),
0.03 (s, 18H, SiMe3), 0.08 (s, 18H, SiMe3), 1.30 (s, 1H,
Tbt p-benzyl), 1.68 (s, 3H, MeC(N)), 1.86 (s, 2H, Tbt o-
benzyl), 1.92 (s, 3H, MeC(N)), 4.78 (s, 1H, 3-CH), 6.32
(br s, 1H, Tbt m-H), 6.40 (br s, 1H, Tbt m-H), 6.79 (d,
J = 7.4 Hz, 2H, Ph o ꢀ H), 6.95 (t, J = 7.4 Hz, 1H, Ph
p ꢀ H), 7.21 (dd, J = 7.4 Hz, J = 7.4 Hz, 2H, Ph m-H),
11.67 (s, 1H, NH); 13C NMR (75 MHz, CDCl3) d 0.4 (q,
SiMe3), 0.7 (q, SiMe3), 1.5 (q, SiMe3), 20.7 (q, MeC(N)),
21.1 (q, MeC(N)), 22.2 (d · 2, Tbt o-benzyl), 29.8 (d, Tbt
p-benzyl), 94.7 (d, 3-CH), 121.9 (d, Tbt Cm), 122.2 (d, Ph
Cp), 122.3 (d, Ph Co), 126.7 (d, Tbt Cm), 128,3 (d, Ph
Cm), 134.1 (s, Tbt), 139.9 (s, Tbt), 140.2 (s · 2, Tbt Co),
149.2 (s, Ph Cipso), 157.9 (s, C(N)), 162.7 (s, C(N)); IR
(KBr) 687, 737, 760, 837, 893, 926, 974, 1036, 1161, 1188,
1246, 1262, 1377, 1412, 1437, 1485, 1547, 1582, 1620,
2899, 2953 cmꢀ1; UV–Vis (hexane) 223 (e 5.3 · 104),
330 nm (e 1.9 · 104 Mꢀ1 cmꢀ1); HRMS (EI) found m/z
724.4300 (M+), calcd for C38H72N2Si6 724.4312. Anal.
Calc. for C38H72N2Si6: C, 62.91; H, 10.00; N, 3.86. Found:
C, 62.71; H, 10.06; N, 3.95%.
4.7. Synthesis of TbtNHC(Me)CHC(Me)NMes (5c)
TbtNHC(Me)CHC(Me)NMes (5c) was prepared by the
procedure similar to that for the synthesis of 5a from 4
(3.39 g, 5.21 mmol), MesNH2 (7.3 mL, 52 mmol), and
TiCl4 (120 mM toluene solution, 1.0 mL, 120 lmol) in tol-
1
uene (1 mL). Yield: 3.76 g (94%). M.p. 207.5–209.3 ꢁC. H
NMR (300 MHz, CDCl3) d ꢀ0.08 (s, 18H, SiMe3), 0.04 (s,
18H, SiMe3), 0.08 (s, 18H, SiMe3), 1.30 (s, 1H, Tbt p-ben-
zyl), 1.63 (s, 3H, MeC(N)), 1.67 (s, 3H, MeC(N)), 1.91 (s,
2H, Tbt o-benzyl), 2.07 (s, 6H, Mes o-Me), 2.24 (s, 3H,
Mes p-Me), 4.76 (s, 1H, 3-CH), 6.33 (br s, 1H, Tbt m-H),
6.38 (br s, 1H, Tbt m-H), 6.80 (s, 2H, Mes m-H), 11.08
(s, 1H, NH); 13C NMR (75 MHz, CDCl3) d 0.5 (q, SiMe3),
0.7 (q, SiMe3), 1.6 (q, SiMe3), 18.5 (q, Mes o-Me), 20.8 (q,
MeC(N)), 21.1 (q, MeC(N)), 21.3 (q, Mes p-Me), 22.2
(d · 2, Tbt o-benzyl), 29.7 (d, Tbt p-benzyl), 93.5 (d, 3-
CH), 122.0 (d, Tbt Cm), 126.9 (d, Tbt Cm), 128.3 (d, Mes
Cm), 130.1 (s, Mes Cp), 132.2 (s, Mes Co), 135.2 (s, Tbt),
139.3 (s, Tbt), 139.4 (s · 2, Tbt Co), 143.6 (s, Mes Cipso),
158.4 (s, C(N)), 162.9 (s, C(N)); IR (KBr) 687, 719, 760,
839, 893, 974, 1040, 1188, 1248, 1377, 1437, 1480, 1555,
1584, 1622, 2899, 2953 cmꢀ1; UV–Vis (hexane) 222 (e
7.1 · 104), 316 nm (e 2.7 · 104 Mꢀ1 cmꢀ1). HRMS (EI)
found m/z 766.4768 (M+), calcd for C41H78N2Si6
766.4781. Anal. Calc. for C41H78N2Si6: C, 64.15; H,
10.24; N, 3.65. Found: C, 63.90; H, 10.15; N, 3.64%.
4.8. Synthesis of TbtNHC(Me)CHC(Me)NDip (5d)
4.6. Synthesis of TbtNHC(Me)CHC(Me)N(o-Tol) (5b)
TbtNHC(Me)CHC(Me)NDip (5d) was prepared by the
procedure similar to that for the synthesis of 5a from 4
(130 mg, 200 lmol), DipNH2 (380 lL, 200 lmol), and
TiCl4 (430 lL, 3.6 mmol) in toluene (30 mL). The purifica-
tion was performed using GPLC (eluent: CHCl3) and wet
column chromatography (alumina, CHCl3/hexane = 1/5).
TbtNHC(Me)CHC(Me)N(o-Tol) (5b) was prepared by
the procedure similar to that for the synthesis of 5a from
4 (100 mg, 154 lmol), o-TolNH2 (170 lL, 1.54 mmol),
and TiCl4 (120 mM toluene solution, 1.28 mL, 154 lmol)
in toluene (2 mL). Yield: 109 mg (95%). M.p. 198.2–
1
Yield: 3.2 mg (2%). H NMR (300 MHz, CDCl3) d ꢀ0.10
1
199.3 ꢁC. H NMR (300 MHz, CDCl3) d ꢀ0.07 (s, 18H,
(s, 18H, SiMe3), 0.02 (s, 18H, SiMe3), 0.07 (s, 18H, SiMe3),
1.09 (d, J = 6.9 Hz, 6H, Dip Me), 1.21 (d, J = 6.9 Hz, 6H,
Dip Me), 1.30 (s, 1H, Tbt p-benzyl), 1.67 (s, 3H, MeC(N)),
1.81 (s, 3H, MeC(N)), 1.91 (s, 2H, Tbt o-benzyl), 2.84 (sept,
J = 6.9 Hz, 1H, Dip CHMe2), 3.20 (sept, J = 6.9 Hz, 1H,
Dip CHMe2), 4.80 (s, 1H, 3-CH), 6.29 (br s, 1H, Tbt m-
H), 6.39 (br s, 1H, Tbt m-H), 6.51–7.01 (m, 3H, Dip aro-
matic H), 11.1 (s, 1H, NH). MS (EI) found m/z 808
(M+), calcd for C44H83N2Si6 808.
SiMe3), 0.03 (s, 18H, SiMe3), 0.08 (s, 18H, SiMe3), 1.31
(s, 1H, Tbt p-benzyl), 1.68 (s, 3H, MeC(N)), 1.73 (s, 3H,
MeC(N)), 1.93 (s, 2H, Tbt o-benzyl), 2.11 (s, 3H, Tol o-
Me), 4.78 (s, 1H, 3-CH), 6.31 (br s, 1H, Tbt m-H), 6.40
(br s, 1H, Tbt m-H), 6.65 (dd, J = 7.4, 1.0 Hz, 1H, Tol 6-
H), 6.90 (ddd, J = 7.4, 7.4, 1.0 Hz, 1H, Tol 4-H), 7.06
(dd, J = 7.4, 7.4 Hz, 1H, Tol 5-H), 7.12 (d, J = 7.4 Hz,
1H, Tol 3-H), 11.29 (s, 1H, NH); 13C NMR (75 MHz,
CDCl3) d 0.4 (q, SiMe3), 0.7 (q, SiMe3), 1.5 (q, SiMe3),
18.1 (q, Tol Me), 20.5 (q, MeC(N)), 21.4 (q, MeC(N)),
22.3 (d · 2, Tbt o-benzyl), 29.9 (d, Tbt p-benzyl), 93.9 (d,
3-CH), 122.0 (d, Tbt Cm), 122.2 (d, Tol), 122.5 (d, Tol),
126.7 (d, Tbt Cm), 129.3 (s, Tol), 129.9 (d, Tol), 133.2 (s,
Tbt), 140.2 (s, Tbt), 140.9 (s · 2, Tbt Co), 149.3 (s, Tol),
4.9. Synthesis of [Li{TbtNC(Me)CHC(Me)NPh}] (1a)
To an ether solution (40 mL) of 5a (1.65 g, 2.28 mmol)
was added n-butyllithium (1.60 M hexane solution,
3.6 mL, 5.7 mmol) at 0 ꢁC. The reaction mixture was grad-

52
H. Hamaki et al. / Journal of Organometallic Chemistry 692 (2007) 44–54
ually warmed to 25 ꢁC, and was stirred at the same temper-
ature for 8 h. After removal of the solvents under reduced
pressure, dry hexane was added to the residue in a glove-
box. The colorless, moisture-sensitive precipitates were sep-
arated by filtration, and were washed with a small amount
of hexane to afford pure 1a. Yield: 1.35 g (81%). M.p.
Tbt o-benzyl), 2.23 (s, 3H, Mes p-Me), 2.27 (s, 6H, Mes
o-Me), 4.91 (s, 1H, 3-CH), 6.58 (br s, 2H, Tbt m-H), 6.92
(s, 2H, Mes m-H); 13C NMR (75 MHz, C6D6) d 0.1 (q,
SiMe3), 1.0 (q, SiMe3), 1.7 (q, SiMe3), 18.8 (q, Mes o-
Me), 20.9 (q, Mes p-Me), 21.5 (d, Tbt o-benzyl), 23.0 (q,
MeC(N)), 23.8 (q, MeC(N)), 29.7 (d, Tbt p-benzyl), 92.5
(d, 3-CH), 128.3 (d, Tbt Cm), 129.3 (d, Mes Cm), 130.1
(s), 131.2 (s), 135.5 (s), 136.1 (s), 145.3 (s), 148.9 (s),
164.3 (s, C(N)), 164.6 (s, C(N)); 7Li NMR (116 MHz,
C6D6) d 2.33. Anal. Calc. for C41H77N2LiSi6: C, 63.66;
H, 10.03; N, 3.62. Found: C, 63.36; H, 10.13; N, 3.77%.
1
232.3–233.1 ꢁC (dec). H NMR (300 MHz, C6D6) d 0.03
(s, 18H, SiMe3), 0.17 (s, 18H, SiMe3), 0.20 (s, 18H, SiMe3),
1.42 (s, 1H, Tbt p-benzyl), 1.91 (s, 3H, MeC(N)), 1.99 (s,
3H, MeC(N)), 2.12 (s, 2H, Tbt o-benzyl), 4.91 (s, 1H, 3-
CH), 6.57 (br s, 2H, Tbt m-H), 6.94 (t, J = 7.6 Hz, 1H,
Ph p-H), 7.01 (d, J = 7.6 Hz, 2H, Ph o-H), 7.26 (dd,
J = 7.6 Hz, J = 7.6 Hz, 2H, Ph m-H); 13C NMR
(75 MHz, C6D6) d 0.0 (q, SiMe3), 0.9 (q, SiMe3), 1.6 (q,
SiMe3), 21.5 (d, Tbt o-benzyl), 22.9 (q, MeC(N)), 23.8 (q,
MeC(N)), 29.7 (d, Tbt p-benzyl), 94.5 (d, 3-CH), 121.8
(d, Ph), 123.8 (d, Ph), 128.3 (d, Tbt Cm), 129.3 (d, Ph),
135.3 (s), 136.2 (s), 144.9 (s), 154.3 (s), 163.4 (s, C(N)),
4.11. Determination of the association constant for 1c and
(1c Æ thf)
Solutions of 1c and THF in C6D6 were prepared by mix-
ing a 96.7 mM 1c/C6D6 solution (200 lL, 19.3 lmol of 1c),
a 776 mM THF/C6D6 solution and C6D6 in a 5B NMR
tube with the amount shown in Table 7. After the NMR
7
164.6 (s, C(N)); Li NMR (116 MHz, C6D6) d 2.31. Anal.
7
1
Calc. for C38H72N2LiSi6: C, 62.31; H, 9.91; N, 3.82.
Found: C, 62.55; H, 9.99; N, 3.81%.
tube was sealed, the Li and H NMR spectra were mea-
sured at 298 K. The amount of THF was evaluated by
1
the integral of the THF peaks in the H NMR spectrum.
4.10. Synthesis of [Li{TbtNC(Me)CHC(Me)NMes}]
(1c)
4.12. Job’s plot between 1c and THF
[Li{TbtNC(Me)CHC(Me)NMes}] (1c) was prepared
from 5c (2.55 g, 3.32 mmol) and n-butyllithium (1.60 M
hexane solution, 5.2 mL, 8.3 mmol) in Et2O (40 mL) by
the procedure similar to that for the synthesis of 1a. Yield:
2.18 g (85%). M.p. 255.3–256.1 ꢁC (dec). 1H NMR
(300 MHz, C6D6) d 0.06 (s, 18H, SiMe3), 0.18 (s, 18H,
SiMe3), 0.22 (s, 18H, SiMe3), 1.43 (s, 1H, Tbt p-benzyl),
1.76 (s, 3H, MeC(N)), 1.90 (s, 3H, MeC(N)), 2.20 (s, 2H,
Solutions of 1c and THF in C6D6 were prepared by mix-
ing a 96.7 mM 1c/C6D6 solution, a 776 mM THF/C6D6
[sum of the concentrations of 1c and THF was 38.8 mM
(constant)] and C6D6 (246 lL) in a 5B NMR tube with
the ratio shown in Table 8. After the NMR tube was
7
1
sealed, the Li and H NMR spectra were measured at
298 K. The amount of THF was evaluated by the integral
1
of the THF peaks in the H NMR spectrum.
Table 6
Crystal data and structure refinements for TbtN3, 4, 5a and 5c
Compound
4
5a
5c
Empirical formula
Formula weight
Crystal system
Space group
C
769.77
Triclinic
32H65NOSi6 Æ CHCl3
C38H72N2Si6
725.52
Triclinic
C41H78N2Si6
767.59
Triclinic
ꢀ
ꢀ
ꢀ
P1 ð#2Þ
P1 ð#2Þ
P1 ð#2Þ
˚
a (A)
9.0850(7)
10.8042(13)
23.694(3)
93.432(4)
94.083(3)
99.704(3)
2280.5(4)
2
9.0221(5)
10.7273(4)
23.6488(9)
85.6337(16)
86.705(2)
99.334(4)
2246.26(17)
2
9.2635(6)
12.9228(5)
22.6743(14)
78.0296(16)
86.5819(19)
70.018(5)
2495.3(2)
2
˚
b (A)
˚
c (A)
a (ꢁ)
b (ꢁ)
c (ꢁ)
3
˚
V (A )
Z
Dcalc (Mg mꢀ3
)
1.121
0.383
1.073
0.212
1.022
0.194
l (Mo Ka) (mmꢀ1
)
Crystal size (mm)
0.30 · 0.30 · 0.10
15153
8133 (0.0510)
436
0.20 · 0.20 · 0.02
20070
8259 (0.0415)
439
0.25 · 0.15 · 0.10
15817
8303 (0.0675)
469
Reflections collected
Independent reflections (Rint
Parameters
)
R1 [I > 2r(I)]
0.0554
0.0400
0.0532
wR2 (all data)
0.1377
0.1050
0.1224
Goodness-of-fit
Largest difference in peak and hole (e A
1.002
0.542 and ꢀ0.525
1.006
0.361 and ꢀ0.264
1.006
0.299 and ꢀ0.300
ꢀ3
˚
)

H. Hamaki et al. / Journal of Organometallic Chemistry 692 (2007) 44–54
53
Table 7
4.14. [K{TbtNC(Me)CHC(Me)NMes}(thf)] (7c)
The preparation of 1c/THF/C6D6 solution for determining Ka
a
[THF]0/[1c]0
776 mM THF/C6D6
C6D6 (lL)
[K{TbtNC(Me)CHC(Me)NMes}(thf)] (7c) was pre-
pared from 5c (100 mg, 130 lmol) and KH (52.2 mg,
1.30 mmol) in Et2O (4 mL) by the procedure similar to that
for the synthesis of 6c. Yield: 98.1 mg (86%). M.p. 232.3–
233.1 ꢁC (dec.). 1H NMR (300 MHz, C6D6) d 0.12 (s,
18H, SiMe3), 0.22 (s, 18H, SiMe3), 0.27 (s, 18H, SiMe3),
1.40 (br, 4H, thf b-H), 1.41 (s, 1H, Tbt p-benzyl), 1.42 (s,
3H, Me), 1.88 (s, 3H, Me), 2.17 (s, 6H, Mes o-Me), 2.29
(s, 3H, Me), 2.30 (s, 2H, Tbt o-benzyl), 3.14 (br, 4H, thf
a-H), 4.60 (br s, 1H, 3-CH), 6.55 (br s, 2H, Tbt m-H),
6.93 (s, 2H, Mes m-H); 13C NMR (75 MHz, C6D6) d 1.1
(q, SiMe3), 1.7 (q, SiMe3), 2.0 (q, SiMe3), 18.9 (q, Mes o-
Me), 20.9 (q, Mes p-Me), 21.1 (d, Tbt o-benzyl), 23.1 (t,
thf Cb), 23.8 (q, MeC(N)), 26.4 (q, MeC(N)), 29.3 (d, Tbt
p-benzyl), 65.9 (t, thf Ca), 90.3 (d, 3-CH), 128.3 (d, Tbt
Cm), 129.0 (d, Mes Cm), 129.7 (s, Mes Co), 133.6 (s),
135.0 (s, Tbt Co), 135.5 (s), 148.1 (s), 151.7 (s), 161.8 (s,
C(N)), 162.1 (s, C(N)). Anal. Calc. for C45H85N2OKSi6:
C, 61.57; H, 9.76; N, 3.19. Found: C, 61.47; H, 9.66; N,
3.09%.
solution (lL)b
0.533
1.02
2.31
4.33
6.54
7.96
9.86
a
13
25
57
108
163
198
245
433
421
389
338
283
248
201
A 96.7 mM 1c/C6D6 solution (3.0 mL), which was prepared by dis-
solving 1c (224 mg, 290 lmol) into C6D6, was used.
A 776 mM THF/C6D6 solution (3.0 mL) was prepared by dissolving
THF (189 lL, 2.33 mmol) into C6D6.
b
Table 8
The preparation of 1c/THF/C6D6 solution for Job’s plot
Mole fractions
96.7 mM 1c/C6D6
solution (lL)a
96.7 mM THF/C6D6
solution (lL)b
of 1c
0.20
0.30
0.40
0.50
0.60
0.70
0.80
a
80
120
160
200
240
280
320
320
280
160
200
160
120
80
4.15. Reactions of 1c with t-BuONa
(1) 1.5 molar amount of sodium tert-butoxide. To a mix-
ture of 1c (39.6 mg, 51.7 lmol) and sodium tert-butoxide
(7.5 mg, 77.6 lmol) in an NMR tube was added 0.6 mL
of C6D6. After the NMR tube was sealed, the measurement
of the 1H NMR spectrum revealed the formation of a mix-
ture of 1c and 8c (1c:8c = 38:62 as judged by the integral of
A 96.7 mM 1c/C6D6 solution (2.0 mL) was prepared by dissolving 1c
(150 mg, 194 lmol) into C6D6.
A 96.7 mM THF/C6D6 solution (10.0 mL) was prepared by dissolving
THF (79 lL, 967 lmol) into C6D6.
b
1
4.13. Synthesis of [Na{TbtNC(Me)CHC(Me)NMes}-
(thf)] (6c)
the 3-CH peaks in the H NMR spectrum). (2) 2.0 molar
amount of sodium tert-butoxide. The experiment was per-
formed by the procedure similar to the case mentioned
above using the sample prepared from 1c (60.0 mg,
77.6 lmol), sodium tert-butoxide (14.9 mg, 155 lmol) and
C6D6 (0.6 mL). The 1H NMR spectrum showed the forma-
tion of a mixture of 1c and 8c (1c:8c = 17:83). (3) 10 molar
amount of sodium tert-butoxide. The experiment was per-
formed by the procedure similar to the case mentioned
above using the sample prepared from 1c (40.0 mg,
51.7 lmol), sodium tert-butoxide (49.7 mg, 517 lmol) and
C6D6 (0.6 mL). The 1H NMR spectrum showed the forma-
tion of a mixture of 1c and 8c (1c:8c = 9:91). [Na{TbtNC(-
To a THF solution (4 mL) of 4a (100 mg, 130 lmol) was
added NaH (31.3 mg, 1.30 mmol). The reaction mixture
was stirred for 3 days. After removal of the solvents under
reduced pressure, dry benzene was added to the residue in a
glovebox. Insoluble inorganic salts were removed by filtra-
tion thorough Celiteꢂ. The removal of the solvent from the
filtrate gave 6c. Yield: 90.7 mg (81%). M.p. 221.1–223.3 ꢁC
1
(dec.). H NMR (300 MHz, C6D6) d 0.14 (s, 18H, SiMe3),
0.21 (s, 18H, SiMe3), 0.27 (s, 18H, SiMe3), 1.21 (br, 4H, thf
b-H), 1.45 (s, 1H, Tbt p-benzyl), 1.79 (s, 3H, Me), 1.95 (s,
3H, Me), 2.24 (s, 3H, Me), 2.26 (s, 6H, Mes o-Me), 2.43 (s,
2H, Tbt o-benzyl), 3.14 (br, 4H, thf a-H), 4.76 (s, 1H, 3-
CH), 6.59 (br s, 2H, Tbt m-H), 6.85 (s, 2H, Mes m-H);
13C NMR (75 MHz, C6D6) d 0.9 (q, SiMe3), 1.8 (q, SiMe3),
2.0 (q, SiMe3), 18.8 (q, Mes o-Me), 20.7 (q, Mes p-Me),
21.5 (d, Tbt o-benzyl), 22.9 (q, MeC(N)), 25.3 (q, MeC(N)),
26.3 (t, thf Cb), 29.6 (d, Tbt p-benzyl), 66.0 (t, thf Ca), 91.5
(d, 3-CH), 128.2 (d, Tbt Cm), 129.1 (d, Mes Cm), 130.3 (s,
Mes Co), 133.5 (s), 135.7 (s, Tbt Co), 136.2 (s), 147.8 (s),
149.9 (s), 162.2 (s, C(N)), 162.8 (s, C(N)). Anal. Calc. for
C45H85N2ONaSi6: C, 62.72; H, 9.94; N, 3.25. Found: C,
62.99; H, 10.13; N, 3.55%.
1
Me)CHC(Me)NMes}] (8c): H NMR (300 MHz, C6D6) d
0.00 (s, 18H, SiMe3), 0.22 (s, 18H, SiMe3), 0.29 (s, 18H,
SiMe3), 1.41 (s, 1H, Tbt p-benzyl), 1.78 (s, 3H, MeC(N)),
1.90 (s, 3H, MeC(N)), 2.28 (br s, 11H, Tbt o-benzyl + Mes
Me), 4.73 (s, 1H, 3-CH), 6.52 (br s, 2H, Tbt m-H), 6.97 (s,
2H, Mes m-H).
4.16. Reactions of 1c with t-BuOK
To a mixture of 1c (40.2 mg, 51.7 lmol) and potassium
tert-butoxide (8.7 mg, 77.6 lmol) in an NMR tube was

54
H. Hamaki et al. / Journal of Organometallic Chemistry 692 (2007) 44–54
added 0.6 mL of C6D6. After the NMR tube was sealed,
the measurement of the H NMR spectrum revealed the
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This work was supported by Grants-in-Aid for COE Re-
search on Elements Science (No. 12CE2005), Creative Sci-
entific Research (17GS0207), Scientific Research on
Priority Areas (No. 14078213), Young Scientists (B) (No.
15750031), and the 21st Century COE Program on Kyoto
University Alliance for Chemistry from Ministry of Educa-
tion, Culture, Sports, Science, and Technology of Japan.