Synthesis and structures of lithium N-trimethylsilyl- and -neopentyl-anilides and their Et2O and tmen adducts; Crystal structures of [(Li{μ-N(Ph)R}-trans)2(μ-tmen)]∞ (R = SiMe3 1 or CH2But 2) and [Li{μ-N(Ph)CH2But}(OEt2)]2

Article abstract of DOI:10.1039/b009724l

The synthesis and structures of lithium N-trimethylsilyl- and -neopentyl-anilides and their Et₂O and tmen adducts were studied by using nuclear magnetic resonance (NMR) spectroscopy. The treatment of N-trimethylsilyl- or -neopentyl-aniline successively with n-butyllithium and tmen in hexane yielded the crystalline polymeric lithium amides. The results showed that the reactivity of lithium amides was related to their degree of aggregation because the high polarity of the Li-N bond caused it to associate in the absence of a neutral donor.

Full text of DOI:10.1039/b009724l

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Synthesis and structures of lithium N-trimethylsilyl- and
neopentyl-anilides and their Et O and tmen adducts; crystal
-
2
structures of [(Li{ꢀ-N(Ph)R}-trans) (ꢀ-tmen)] (R ؍ SiMe
2
∞
3
t
t
1
or CH Bu 2) and [Li{ꢀ-N(Ph)CH Bu }(OEt )] †
2
2
2
2
Jean Philippe Bezombes, Peter B. Hitchcock, Michael F. Lappert* and Philippe G. Merle
The Chemistry Laboratory, University of Sussex, Brighton, UK BN1 9QJ.
E-mail: m.f.lappert@sussex.ac.uk
Received 5th December 2000, Accepted 5th February 2001
First published as an Advance Article on the web
Treatment of N-trimethylsilyl- or -neopentyl-aniline successively with n-butyllithium and tmen in hexane yielded
t
the crystalline polymeric lithium amides [(Li{µ-N(Ph)R}-trans) (µ-tmen)] (R = SiMe 1 or CH Bu 2), which contain
2
∞
3
2
the rare bridging, rather than chelating, tmen ligands. Details are also provided of: (i) the preparation of crystalline
t
[
(
Li{N(Ph)SiMe }] , hydrocarbon-insoluble [Li{N(Ph)CH Bu }] , and diethyl ether adducts [Li{µ-N(Ph)R-trans}-
3
4
2
n
t
OEt )] (R = SiMe or CH Bu ); (ii) variable temperature multinuclear NMR spectra in toluene-d and (iii) three
2
2
3
2
8
crystal structures.
Introduction
Bulky amides of lithium are important reagents, both in
coordination and organic chemistry. As for the former, they are
valuable ligand transfer reagents, often giving rise to unusual
1
low coordination number metal amides. Regarding the latter,
they are powerful proton abstractors, particularly from acidic
hydrocarbons, and are useful in the formation of carbon–
2
carbon bonds; homochiral lithium amides even have a useful
3
role in asymmetric synthesis. The reactivity of lithium amides
is related to their degree of aggregation, since the high polarity
of the Li–N bond causes them to associate in the absence of
4
a neutral donor. In the presence of O- or N-centred neutral
ligands, dimeric, or more rarely monomeric, molecular com-4
plexes usually predominate, at any rate in the crystalline state.
Monomers or dimers are generally the most reactive.
A much favoured neutral ligand is Me NCH CH NMe
2
2
2
2
(
tmen), which generally functions as a chelating bidentate
5
ligand, as in the crystalline [Li{µ-N(Ph)Me}(tmen)]2, [Li-
µ-N(Ph)C H -1}(tmen)] [a loosely held dimer, by virtue
{
1
0
7
2
2
5
6
of (Li ؒ ؒ ؒ η -Ph) contacts], [Li{N(SiMe ) }(tmen)] , and
2
t
3
2
2
7
[
Li{N(H)C H Bu -2,4,6}(tmen)] . Whereas the literature is
6
2
3
2
replete with numerous tmen-chelating LiX complexes, those
4
having bidentate bridging tmen ligands are rare. As far as we
are aware, there are to date just four such crystalline lithium
8
9
10
11
amides A, B, C and D. Other examples of tmen as a bridg-
ing ligand in crystalline (LiX) (tmen) compounds include (i)
n
m
n
[
(LiBu )(µ-tmen)] , in which only two of the four lithium atoms
∞
12
in each tetranuclear unit are implicated with the tmen ligand;
NMR spectra) that tmen had been totally dissociated yielding
i
(
ii) [{Li(OC H OMe)} (µ-tmen)], having two tetranuclear
[Li(µ-NPr )] ; and addition of thf or excess of tmen led to
6
4
8
2
2
13
i
i
9
clusters joined by the tmen bridge; (iii) [{Li(tmen)} -
(
case of LiNPr (LDA) is particularly well studied. The crystal-
line complex B was obtained by crystallising LDA from
a tmen–C H mixture. However, when the hexane poorly
soluble LDA was treated with tmen (2 mol) the crystalline
product had the composition Li(NPr ){N(H)Pr }1/10(tmen)1/40
but X-ray diffraction revealed it to be the helical tmen-free
[Li(µ-NPr )(thf) ] and [Li(µ-NPr )(tmen)] respectively.
3
2 2 2 2 2
14
15
µ-Cl) Li] (µ-tmen) and (iv) {Li(SiMe )} (µ-tmen). The
We now present data on the synthesis and structures of the
4
2
3
2
i
2
crystalline complexes [{Li[N(Ph)R]} (µ-tmen)] (R = SiMe 1
2
∞
3
t
or CH Bu 2). Additionally, we provide details on the synthesis
2
9
6
14
and NMR solution spectra of the corresponding tmen-free
lithium amides and their diethyl ether adducts, as well as the
molecular structure of the crystalline complex [Li{µ-N(Ph)-
i
2
i
2
t
CH Bu }(OEt )] .
2
2
2
i
16
13
[
Li(µ-NPr )] . A toluene-d8 solution of B showed ( C
2 ∞
Results and discussion
†
In memoriam Ron Snaith, a valued friend and scientist.
The chosen precursors to the target compounds 1 and 2 were
8
16
J. Chem. Soc., Dalton Trans., 2001, 816–821
This journal is © The Royal Society of Chemistry 2001
DOI: 10.1039/b009724l

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t
the secondary amines HN(Ph)R (R = SiMe 3 or CH Bu 4).
Table 1 Selected bond lengths (Å) and angles (Њ) for compounds 1
and 2
3
2
n
The amine 3 was prepared from aniline and successively LiBu
and ClSiMe , as described by Schumann et al. Compound 4
was likewise obtained from aniline, as shown in eqn. (1). It had
17
3
1
2
Li ؒ ؒ ؒ LiЈ
Li–N(1)
Li–N(1Ј)
Li–N(2)
N(1)–C(1)
N(1)–C(ꢀ)
2.391(10)
2.030(10)
2.088(10)
2.065(10)
1.422(6)
—
2.4ꢀ1(4)
1.999(4)
2.0ꢀꢀ(4)
2.121(4)
1.386(3)
1.4ꢀ1(3)
(
1)
previously been isolated either by Na[BH ] reduction of
4
N(1)–Li–N(1Ј)
Li–N(1)–LiЈ
N(1)–Li–N(2)
N(2)–Li–N(1Ј)
C(1)–N(1)–Li
C(1)–N(1)–LiЈ
109.0(4)
ꢀ1.0(4)
125.2(5)
122.4(5)
11ꢀ.1(4)
90.1(4)
105.38(1ꢀ)
ꢀ4.62(1ꢀ)
128.5(2)
124.29(19)
10ꢀ.56(1ꢀ)
112.93(18)
t
18a
Bu CH᎐NPh, or by treatment of HN(Ph)CH SPh succes-
2
t
18b
sively with LiBu and water. The crystalline, tmen-bridged
binuclear lithium amide polymers 1 and 2 were obtained as
shown in eqn. (2).
(
2)
The crystalline, neutral, ligand-free [Li{N(Ph)SiMe }] 5 had
3
4
n
16
previously been made from the amine 3 and LiBu in pentane.
The molecular structure, determined by single crystal X-ray dif-
fraction, revealed its unusual tetranuclear arrangement, shown
1
9
t
schematically in 5Ј. The ether-free amide [Li{N(Ph)CH Bu }]
6
2
n
Fig. 1 Molecular structure and atom labelling for compound 1.
was insoluble even in hot toluene or xylene and is presumed
to be a polymer. Treatment of 5 with diethyl ether afforded
19
crystals of [Li{µ-N(Ph)SiMe }(OEt )] 7 (see also ref. 20). The
3
2
2
crystalline neopentyl analogue 8 has now been prepared by a
procedure similar to that of eqn. (2) except that diethyl ether
was used in place of tmen–C H , and, like 1 and 2, has been
6
14
crystallographically characterised, see below.
Fig. 2 Molecular structure and atom labelling for compound 2.
Suitable single crystals of compounds 1 and 2 were obtained
from hot hexane (1) or a toluene–hexane (2) mixture. Their
structures are broadly similar, each comprising an infinite chain
along the a axis direction, linked via inversion centres which are
the centroids of the bridging tmen ligands and the centres of
the Li N rings. A dinuclear unit of each is shown in Figs. 1 (1)
2
2
and 2 (2) and some comparative geometric data are assembled
in Table 1. The central N(1)LiN(1Ј)LiЈ ring is essentially planar.
The endocyclic angles are wider at the lithium (1 ӷ 2) than at
the nitrogen (2 ӷ 1) atoms. The two Li–N bond lengths in each
unit are unequal and the mean values are slightly longer in 1
(
2.059 Å) than in 2 (2.038 Å), whereas the exocyclic Li–N bonds
are longer in 2 [2.121(4) Å] than in 1 [2.065(10) Å]. There is a
trans arrangement of the substituents at the endocyclic nitrogen
atoms and the N–C(Ph-ipso) bonds are significantly longer in 1
[
1.422(6) Å] than in 2 [1.386(3) Å]. The aromatic C–C bond
Fig. 3 Molecular structure and atom labelling for compound 8.
The structure of the crystalline dinuclear complex trans-
lengths are very slightly shorter (by an av. 0.01 Å) in 1 than in 2.
The (ipso-Ph)C–N–Li (or LiЈ) bond angles are rather similar
and close to tetrahedral in 2 [109.2 ± 2.ꢀЊ], whereas in 1 they
differ widely [103.6 ± 13.5Њ]. The lithium atoms are in a dis-
torted trigonal and nearly planar environment, the sum of
the angles at the Li atoms being 356.6Њ in 1 and 358.2 in 2.
t
[Li{µ-N(Ph)CH Bu }(OEt )] 8 is illustrated in Fig. 3. Selected
2
2
2
geometric data are in Table 2. There are no surprises, as
may be judged by comparing some core data for 8 with those
21
2
22
for [Li{µ-N(SiMe ) }(OEt )]
and [Li(µ-NPh )(OEt )] ,
3
2
2
2 2 2
J. Chem. Soc., Dalton Trans., 2001, 816–821
817

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Table 2 Selected geometric parameters (lengths in Å, angles in Њ) for compound 8, [Li{µ-N(SiMe ) }(OEt )] and [Li{µ-N(Ph) }(OEt )]
2
3
2
2
2
2
2
t
21
22
[
Li{µ-N(Ph)CH Bu }(OEt )] 8
[Li{µ-N(SiMe ) }(OEt )]
[Li{µ-N(Ph) }(OEt )]
2 2 2
2
2
2
3
2
2
2
Li ؒ ؒ ؒ LiЈ
Li–N
Li–O
N–C(Ph)
N–C(Np)
2.505a
2.038
2.492
2.055(5)
1.943(6)
—
2.501
2.02
1.882a
1.406
—
a
a
a
1.965a
1.3ꢀ3a
1.462
—
a
a
N–Li–NЈ
Li–N–LiЈ
O–Li–N
104.2a
104.9(3)
ꢀ5.1(2)
12ꢀ.5(1)
103.45a
ꢀ6.31
ꢀ5.8
116.3, 135.5
129.13, 128.42 and 120.3ꢀ, 134.4ꢀ
a
Np = Neopentyl. Mean value.
1
Table 3 Variable temperature selected H NMR spectroscopic chemical shifts (δ) at 300.1 MHz for compounds 1, 2 and tmen in toluene-d
8
δ (tmen)
a
NCH3
CH N
δ (R)
2
b
b
T/K
1
2
1
2
Si(CH ) (1)
C(CH ) (2)
3 3
3
3
1
2
2
2
3
3
93
23
53
93
23
ꢀ3
1.81, 1.ꢀꢀ
—
1.64
1.66
1.ꢀ1, 1.68
1.80
—
2.04
2.05
2.0ꢀ
2.09
—
1.52, 1.36
—
1.49
1.53
1.63, 1.59
1.ꢀꢀ
—
2.28
2.28
2.30
2.30
—
0.53, 0.38
—
0.39
0.30
0.25
—
1.66
1.ꢀ3
1.ꢀꢀ
—
1.66
1.66
1.ꢀ3
—
0.ꢀ8, 1.21
0.ꢀ8, 1.1ꢀ
0.ꢀ8, 1.09
—
1.91
—
1.95
—
0.19
0.85
a
t
b
Refers to [Li{µ-N(Ph)R}] (µ-tmen)] (R = SiMe or CH Bu ). Values for tmen.
2
3
2
indicated in Table 2. Several other examples of related crystal-
23
line dimeric lithium amide diethyl etherates are known.
While the NMR spectra of the diethyl ether complexes
t
[
Li{µ-N(Ph)R}(OEt ) ] (R = SiMe 7 or CH Bu 8) in C D CD
2
2
3
2
6
5
3
or C D6 at ambient temperature are unexceptional (for
6
assignments, see Experimental section), those of the crystalline
t
amides [Li{µ-N(Ph)R}] (µ-tmen) (R = SiMe 1 or CH Bu 2)
2
3
2
and [Li{N(Ph)SiMe }] 5 require further comment. It had pre-
3
4
7
viously been noted briefly that the Li NMR spectrum of 5 in
toluene-d at 163 K was consistent with the tetranuclear struc-
8
ture 5Ј of the crystalline 5 being preserved, whereas at higher
19
temperatures fluxional processes became operative; these data
and conclusions are now presented in greater detail.
The bonding in crystalline compound 5 (cf. 5Ј) may be
described as comprising a central LiNLiN core with each of
these Li atoms acting as a Lewis acid site for binding by a
terminal lithium amide, as indicated by the Li–N bond lengths
in 5Љ.
The case of the neutral donor-free lithium amide 5 is first
t
considered. Unlike its neopentyl analogue [Li{N(Ph)CH Bu }]
6
2
n
7
, it was soluble in aromatic hydrocarbons. The Li-{H} NMR
spectroscopic data are particularly informative. At 163 K two
signals of equal intensity at δ 0.9 and Ϫ4.6 were observed. The
relatively low frequency of the latter is consistent with it being
assigned to the terminal lithium nuclei of structure 5Ј experi-
encing the ring current of the adjacent phenyl rings. The δ 0.89
signal is attributed to the core lithium atoms (these assignments
are shown in parentheses in 5Љ). At 183 K the spectrum showed
7
Fig. 4 2-D Li EXSY spectrum of compound 5 at 183 K.
(
3)
7
four signals at δ 0.9, Ϫ0.1, Ϫ1.4 and Ϫ4.6. The 2-D Li EXSY
spectrum at this temperature (Fig. 4) demonstrates that the
signals at δ 0.9 and Ϫ4.6 exchanged more rapidly with one
another than either did with the intense signal at δ Ϫ1.4; hence
an intramolecular exchange of the ligands is the fastest. At
2
98 K there was just one signal at δ Ϫ0.4, which presumably is
the time-averaged value. These data are interpreted in terms of
the equilibrium (3), involving not only 5Ј but also 9 and 10. The
latter two are suggested to arise by successive thermal dissoci-
ation of each of the terminal lithium amides from 5Ј (the Li
assignments are shown in parentheses for each of 9 and 10),
each monomer rapidly dimerising to afford 10. At ambient
7
temperature the δ Ϫ0.4 signal is attributed to arising from a fast
exchange process between 9 and 10. (It is possible that 10 is
a cyclooligomer rather than the cyclodimer shown.) The H
1
8
18
J. Chem. Soc., Dalton Trans., 2001, 816–821

View Article Online
3
NMR spectrum of 5 at 183 K in toluene-d is consistent with
cm ). The resulting thick white suspension was stirred for ca. 3 h
then filtered. The filtrate was concentrated in vacuo, and the
residue crystallised from diethyl ether, to give colourless needles
of N-pivaloylaniline (34.2 g, 90%) (Found: C, ꢀ4.6; H, 8.56; N,
ꢀ.91. C H NO requires C, ꢀ4.5; H, 8.53; N, ꢀ.90%), mp 129–
8
the data of eqn. (3), but at 298 K the spectrum simplified into
only one set of signals (see Experimental section). It is possible
7
that if the Li NMR spectra were to be recorded at higher
dilution the intensities of the signals attributed to 9 and 10
1
1
15
1
3
might increase.
130 ЊC. H NMR (CDCl ): δ ꢀ.58 (d, 2 H, J = 8.ꢀ, m-H), ꢀ.53
3 HH
3
1
The H NMR spectra of each of compounds 1 and 2 in
(br s, 1 H, NH), ꢀ.34 (t, 2 H, J = 8.ꢀ, o-H), ꢀ.13 (t, 1 H,
HH
3
13
toluene-d were shown to be temperature-dependent, as sum-
JHH = ꢀ.5 Hz, p-H) and 1.35 (s, 9 H, CH ). C NMR (CDCl ):
8
3
3
marised in Table 3; for the tmen and E(CH ) (E = Si or C)
δ 1ꢀꢀ.1 (CO), 138.4, 129.2, 120.5 and 119.4 (Ph), 39.3 (CCH )
3
3
3
ϩ
chemical shifts comparative data for free tmen are also listed.
and 2ꢀ.9 (CH ). EI-MS (m/z, %): 1ꢀꢀ {ꢀ8, [M] } and 5ꢀ {100,
3
7
t ϩ
From Li-{H} NMR spectroscopic data and reference to
[Bu ] }.
those for compound 5 in eqn. (3), there is no evidence of dis-
sociation of 1 into tmen and 5. Thus, at 193 K, two Li signals
were observed at δ 1.06 and Ϫ0.11 in a 2 : 1 relative intensity
ratio, respectively. At 233 and 323 K these gave way to single
signals at δ 0.85 and Ϫ0.9ꢀ, respectively, indicative of the
presence of fast exchange processes.
A solution of N-pivaloylaniline (34.1 g, 192 mmol) in thf
7
3
(200 cm ) was added dropwise to a cooled (0 ЊC) suspension of
3
Li[AlH ] (14.0 g, 368 mmol) in thf (300 cm ). After 2 d at ca.
4
25 ЊC and 12 h at reflux the grey suspension was carefully hydro-
lysed at 0 ЊC by a mixture of water and thf. After filtration,
concentration of the filtrate and distillation of the residue
under reduced pressure, compound 4 was obtained as a colour-
less oil (2ꢀ.9 g, 89%) (Found: C, 81.0; H, 10.65; N, 8.49.
The absence of free tmen at various temperatures in solutions
of compound 1 or 2 in toluene-d is borne out by noting the
8
1
relative values of the H chemical shifts for the CH and the
C H N requires C, 80.9; H, 10.49; N, 8.58%), bp 85–8ꢀ ЊC/5
2
11 17
1
CH protons, which invariably were found at higher frequency
Torr. H NMR (CDCl ): δ 6.ꢀ5–ꢀ.34 (m, 5 H, Ph), 3.03 (s, 2 H,
3
3
13
for the latter, whereas for free tmen this order is reversed (see
NCH ), 3.ꢀ5 (br s, 1 H, NH) and 1.14 (s, 9 H, CH ). C NMR
2
3
Table 3). For example, for [Li{N(SiMe ) }(tmen)], the tmen
(CDCl ): δ 149.5, 129.ꢀ, 11ꢀ.3 and 113.1 (Ph), 56.2 (NCH ),
3 2
ϩ
3
2
7
24a
protons are δ(CH ) 1.63 and δ(CH ) 1.81, with δ( Li) 0.41;
32.3 (CCH ) and 28.1 (CH ). EI-MS (m/z, %): 163 {60, [M] }
3 3
t ϩ
2
3
while for [Li{N(Ph)Me}(tmen)], δ(CH ) 1.ꢀ2 and δ(CH ) 1.80,
and 106 {100, [M Ϫ Bu ] }.
2
3
7
24b
with δ( Li) Ϫ1.60.
1
3
At 193 K the H NMR spectrum of compound 1 (see Table 3)
[Li{N(Ph)SiMe }] 5. n-Butyllithium (12 cm of a 1.6 mol
3
4
Ϫ3
showed (i) two SiMe signals in relative intensity 2 : 1, (ii) broad
dm solution in hexane, 19.2 mmol) was added dropwise dur-
3
and not fully resolved Ph signals and (iii) two sets (rel. intensity
ing ca. 15 min to a cooled (0 ЊC) solution of trimethyl-
silylaminobenzene (3.00 g, 18.2 mmol) in hexane (50 cm ).
3
1
: 1) of tmen signals. Upon warming this solution the tmen
appeared as singlets and the SiMe and Ph signals, although
broad at 298 K, became sharp at 323 K.
After ca. 30 min at 0 ЊC and then ca. 2 h at ca. 25 ЊC the mixture
was filtered, the white precipitate washed with hexane and dried
in vacuo yielding compound 5 (3.15 g, 98%) as a white powder.
Crystallisation from hot toluene gave colourless crystals of 5
(2.20 g, ꢀ0%) (Found: C, 62.6; H, 8.05; N, 8.33. C H LiNSi
3
Observations on the behaviour of crystalline [Li{N(Ph)-
t
CH Bu }] (µ-tmen) 2 in toluene-d solutions were rather differ-
2
2
8
7
ent in detail. Thus, the Li NMR spectra revealed only single
signals at both 223 (δ 1.02) and 3ꢀ3 K (0.90). The H NMR
9
14
1
requires C, 63.1; H, 8.24; N, 8.18%), mp 1ꢀ5–1ꢀꢀ ЊC. It was
1
spectrum at 293 K of a dilute solution of 2 showed broad
sparingly soluble in toluene at low temperature. H NMR:
t
3
3
signals centred at δ 0.ꢀ8 and 1.09 for the Bu protons (which
δ ꢀ.13 (t, 2 H, J = ꢀ, m-H), 6.ꢀ0 (t, 1 H, J = ꢀ, p-H), 6.56
HH HH
3 13
coalesced in a concentrated solution); this situation remained
unchanged down to 223 K, but appeared as a sharp singlet at
(d, 2 H, J = ꢀ Hz, o-H) and 0.09 (s, 9 H, SiMe ). C NMR:
δ 116.4, 123.4, 130.2, 159.2 (ipso-C) and 2.2 (SiMe ). Si NMR
(benzene-d ): δ Ϫ8.1. Li NMR: δ Ϫ0.4. EI-MS (m/z, %) 349
25, [(PhNSiMe ) Li ] }, 342 {20, [(PhNSiMe ) Li ] }, 32ꢀ
3 2 3 3 2 2
ϩ ϩ
10, [(PhNSiMe ) Li Ϫ Me] }, 1ꢀ8 {100, [(PhNSiMe )Li ] },
65 {45, [PhNHSiMe ] } and 150 {95, [PhNHSiMe ] }.
HH
3
29
3
7
3
ꢀ3 K.
6
ϩ
ϩ
{
{
1
3
2
2
3
2
Experimental
ϩ
ϩ
3
2
General procedures
[
{Li[N(Ph)SiMe ]} (ꢀ-tmen)] 1. To a suspension of the
3 2 ∞
All manipulations were performed under argon using standard
Schlenk techniques. Toluene and diethyl ether were dried using
sodium. Pentane and hexane were dried using sodium–
potassium alloy; thf was first dried over CaH then sodium.
tmen (Aldrich) was distilled from CaH prior to use. The NMR
lithium amide 5 (0.88 g, 5.13 mmol [based on monomer]) in
hexane (50 cm ) tmen (0.ꢀ5 g, 6.45 mmol) was added. The mix-
3
ture was heated to reflux, whereupon the solid dissolved. Con-
centration of the solution in vacuo yielded white crystals of
compound 1 (1.08 g, 90%) (Found: C, 60.9; H, 9.22; N, 12.01.
C H LiN Si requires C, 62.8; H, 9.6ꢀ; N, 12.21%), mp 105–
2
2
1
13
7
spectra were recorded on a Bruker DPX 300 ( H, C and Li)
29
7
12 22
2
or AMX 500 ( Si, 2-D Li EXSY as well as low temperature
1
1
06 ЊC. H NMR (toluene-d ): δ ꢀ.18–6.62 (m, 10 H, Ph), 1.66
s, 12 H, NCH ), 1.53 (s, 4 H, CH N) and 0.30 (s, 18 H, SiMe ).
C NMR (toluene-d ): δ 160.ꢀ (ipso-C), 129.ꢀ (m-C), 121.5
1
13
29
8
H and C) instruments and referenced externally ( Si, using
(
3
2
3
SiMe ) or internally to the residual solvent resonances (chem-
4
13
8
ical shift data in δ). Unless otherwise stated, all NMR spectra
were measured at 298 K in C D and other than H were
(
o-C), 113.0 ( p-C), 56.0 (CH N), 44.ꢀ (NCH ) and 2.6 (SiMe ).
2 3 3
29
1
6
6
7
Li NMR (toluene-d ): δ 1.0. Si NMR (toluene-d ): δ Ϫ6.85.
8
8
ϩ
proton-decoupled. Electron impact mass spectra were taken
from solid samples using a Kratos MS 80 RF instrument.
Melting points were taken in sealed capillaries and are un-
corrected. Elemental analyses (empirical formulae shown) were
determined by Medac Ltd., Brunel University.
EI-MS (m/z, %): (L = N(Ph)SiMe ) 349 (50, [L Li ] ), 342 (35,
3
2
3
ϩ
ϩ
ϩ
[
(
[
L Li ] ), 32ꢀ (25, [L Li Ϫ Me] ), 222 (10, [L Ϫ PhN] ), 1ꢀ8
2 2 2 2 2
ϩ ϩ ϩ
100, [LLi ] ), 165 (65, [L] ), 150 (95, [L Ϫ Me] ) and ꢀ3 (35,
2
ϩ
SiMe ] ).
3
3
[
Li{N(Ph)SiMe }(OEt )] 7. n-Butyllithium (18.0 cm of a 1.6
3 2 2
Ϫ3
Preparations
mol dm solution in hexane, 28.8 mmol) was added dropwise
during ca. 15 min to a cooled (0 ЊC) solution of trimethyl-
silylaminobenzene (4.64 g, 28.1 mmol) in diethyl ether
t
HN(Ph)R (R ؍ SiMe 3 or CH Bu 4). The amine 3 was pre-
3
2
17
pared from aniline, as described in the literature. The known
amine 4 was obtained as follows. A solution of trimethyl-
acetyl chloride (26.4 g, 219 mmol) in thf (100 cm ) was added
18
3
(100 cm ). The resulting colourless solution was set aside for
3
ca. 20 min at 0 ЊC, then 2 h at ca. 25 ЊC and concentrated
in vacuo yielding colourless crystals of compound 7 (4.21 g,
60%) (Found: C, 63.6; H, 9.85; N, 6.30. C H LiNOSi requires
dropwise at room temperature to a solution of aniline (20.0 g,
2
15 mmol) and triethylamine (21.8 g, 216 mmol) in thf (400
13
24
J. Chem. Soc., Dalton Trans., 2001, 816–821
819

View Article Online
Table 4 Crystal data and refinement for compounds 1, 2 and 8
1
2
8
Formula
M
Crystal system
C H Li N Si
434.34
Monoclinic
C H LiN
22ꢀ.29
Monoclinic
C H Li N O
2
486.62
Monoclinic
2
4
44
2
4
2
14 24
2
30 52
2
2
Space group
P2 /c (no. 14)
P2 /c (no. 14)
P2 /n (no. 14)
1
1
1
a/Å
b/Å
c/Å
β/Њ
9.259(1)
18.225(2)
9.3338(ꢀ)
118.61ꢀ(6)
1382.6(2)
2
8.0808(6)
19.835(2)
9.481ꢀ(6)
106.504(5)
145ꢀ.2(2)
4
9.9810(2)
16.1914(4)
19.2524(4)
95.ꢀ96(1)
3095.4(1)
4
3
U/Å
Z
Ϫ1
µ(Mo-Kα)/mm
T/K
0.15
1ꢀ3(2)
0.06
1ꢀ3(2)
0.06
1ꢀ3(2)
Total reflections
11ꢀ9ꢀ
1900, 0.113
1469
6ꢀ59
2536, 0.042
2005
25409
ꢀ25ꢀ, 0.050
5366
Independent reflections, Rint
Reflections with I > 2σ(I )
R1 [I > 2σ(I )]
0.082
0.0ꢀ0
0.061
wR2 (all data)
0.200
0.195
0.180
1
13
C, 63.4; H, 9.86; N, 5.ꢀ1%), mp 115–116 ЊC. H NMR: δ ꢀ.23
12 H, CH CH ). C NMR: δ 162.2 (ipso-C), 130.4 (m-C), 112.ꢀ
2
3
3
3
(
1
(
t, 2 H, J = ꢀ, 2 H, m-H), 6.89 (d, 2 H, J = ꢀ, o-H), 6.ꢀ0 (t,
H, J = ꢀ, p-H), 3.0ꢀ (q, 4 H, J = ꢀ.2, OCH CH ), 0.ꢀ8
t, 6 H, J = ꢀ.2 Hz, OCH CH ) and 0.40 (s, 9 H, SiMe ).
(o-C), 110.4 (p-C), 65.3 (CH CH ) 59.8 (NCH ), 35.8 (CCH ),
2 3 2 3
7
HH
HH
3
3
29.2 (CCH ) and 14.2 (CH CH ). Li NMR: δ 1.1. MS: only
3 2 3
HH
3
HH
2
3
13
C
signals corresponding to the parent amine (m/z = 163) were
HH
2
3
3
NMR: δ 159.4 (ipso-C), 129.ꢀ (m-C), 123.0 (o-C), 115.3 ( p-C),
observed.
2
9
6
4.9 (OCH CH ), 2.8 (SiMe ) and 14.4 (OCH CH ). Si NMR:
2 3 3 2 3
7
δ Ϫ8.8. Li NMR: δ 1.0. EI-MS (m/z, %), 349 {55, [(PhN-
SiMe ) Li ] }, 342 {50, [(PhNSiMe ) Li ] }, 32ꢀ {20, [(PhN-
SiMe ) Li Ϫ Me] }, 252 [10], 1ꢀ8 {100, [(PhNSiMe )Li ] }, 165
Crystal data and refinement details for compounds 1, 2 and 8
ϩ
ϩ
3
2
3
3
2
2
ϩ
ϩ
Diffraction data were collected on an Enraf-Nonius Kappa-
CCD diffractometer using monochromated Mo-Kα radiation,
λ 0.ꢀ10ꢀ3 Å. Crystals were directly mounted on the diffract-
ometer under a stream of cold nitrogen gas. Those of com-
pound 1 were extremely thin plates; the diffraction data were
limited and weak. The structures were refined on all F using
SHELXL 9ꢀ. Further details are in Table 4.
CCDC reference numbers 1541ꢀ2–1541ꢀ4.
3
2
2
3
2
ϩ
ϩ
{
60, [PhNSiMe ] }, 150 {80, [PhNSiMe ] }, 134 [20], 123 [25],
3
2
ϩ
ꢀ
3 {35, [SiMe ] } and 58 [65].
3
t
3
[
Li{N(Ph)CH Bu }] 6. n-Butyllithium (4.0 cm of a 1.6 mol
2
n
2
Ϫ3
dm solution in hexane, 6.4 mmol) was added dropwise during
25
ca. 15 min to a cooled (0 ЊC) solution of neopentylamino-
3
benzene (1.0 g, 6.12 mmol) in pentane (10 cm ). The resulting
See http://www.rsc.org/suppdata/dt/b0/b009ꢀ24l/ for crystal-
lographic data in CIF or other electronic format.
beige suspension was stirred for ca. 20 min at ca. 25 ЊC, then
filtered. The precipitate was washed with pentane and dried
in vacuo yielding compound 6 as a white solid (1.03 g, 99%)
(
Found: C, ꢀ6.4; H, 9.52; N, 8.45. C H LiN requires C, ꢀ8.1;
11 16
Acknowledgements
H, 9.53; N, 8.28%), mp > 250 ЊC.
We thank the European Commission for the award of a Marie
Curie fellowship for P. G. M., the Leverhulme Trust for a
fellowship for J. P. B. and for other support, Dr A. G. Avent
for some variable temperature NMR spectra and the 2-D Li
EXSY data, and Professor R. E. Mulvey for kindly providing
t
[
{Li[N(Ph)CH Bu ]} (ꢀ-tmen)] 2. To a suspension of lithium
2
2
∞
amide 6 (3.94 g, 23.3 mmol [based on monomer]) in a mixture
3
3
7
of hexane (ꢀ0 cm ) and toluene (30 cm ) was added tmen (0.ꢀ5
g, 6.45 mmol). The mixture was heated to reflux, whereupon the
solid dissolved. Cooling the solution to ca. 25 ЊC yielded pale
pink crystals of compound 2 (4.12 g, ꢀ8%) (Found: C, ꢀ3.0;
H, 10.58; N, 12.40. C H LiN requires C, ꢀ4.0; H, 10.64; N,
the data of ref. 24(b).
14
24
2
1
References
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6
2.32%), mp 109 ЊC (decomp.). H NMR (toluene-d ): δ ꢀ.14–
8
t
.40 (m, 10 H, Ph), 2.90 (br s, 4 H, Bu CH ), 1.ꢀꢀ (s, 12 H,
2
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3
2
13
3
8
t
1
(
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7
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(
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[
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(
ꢀ
15
26
1
4.0; H, 10.ꢀꢀ; N, 5.ꢀ6%), mp ca. 240 ЊC (decomp.). H NMR:
2
3
3
δ ꢀ.25 (t, J = ꢀ, 4 H, m-H), 6.ꢀ0 (t, J = ꢀ, 4 H, o-H), 6.4ꢀ
HH
HH
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3
3
(
8
t, J = ꢀ, 2 H, p-H), 3.32 (s, 4 H, NCH ), 3.05 (q, J = ꢀ,
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HH
2
HH
5 D. Barr, W. Clegg, R. E. Mulvey, R. Snaith and D. S. Wright,
3
2
3
3
HH
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20
J. Chem. Soc., Dalton Trans., 2001, 816–821

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821