Synthesis and structures of lithium, aluminium, gallium and lanthanide amidinates containing a γ-pendant amine functionality

Article abstract of DOI:10.1039/b005824f

Lithium, aluminium, gallium, lanthanum and cerium complexes of the new amidinato ligand ^--N(SiMe₃)C(Ph)N(CH₂)₃NMe ₂ (L^-), having a γ-pendant amine functionality, have been prepared. The dimeric lithium amidinate 1 was obtained in four steps from l-amino-3-(dimethylamino)propane. Using 1 and MCI₃ in appropriate stoichiometry led to the mononuclear M(L)C1₂ (M = A12 or Ga 3) and the dinuclear [{M(L)₂(u-Cl)}₂] (M = La 4 or Ce 5). Structures of four of these (1, 2,3 and 5) have been studied by X-ray crystallography. In crystalline 1 each amidinato ligand L^-1 is chelating with respect to one of the lithium atoms and bridging by virtue of its pendant γ-tertiary nitrogen atom to the second Li atom. In 2 and 3, by contrast, L^- behaves as a tripodal chelating ligand, whereas in crystalline 5 the seven-co-ordinate Ce atom is bound by two bidentate benzamidinato fragments and only one of the pendant amines. The Royal Society of Chemistry 2000.

Full text of DOI:10.1039/b005824f

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Synthesis and structures of lithium, aluminium, gallium and
lanthanide amidinates containing a ꢀ-pendant amine functionality
David Doyle,a Yurii K. Gun’ko,*a Peter B. Hitchcockb and Michael F. Lappert*b
a The Department of Chemistry, Trinity College Dublin, Dublin 2, Ireland
b The Chemistry Laboratory, University of Sussex, Brighton, UK BN1 9QJ
Received 19th July 2000, Accepted 18th September 2000
First published as an Advance Article on the web 27th October 2000
Lithium, aluminium, gallium, lanthanum and cerium complexes of the new amidinato ligand ϪN(SiMe3)C(Ph)-
N(CH2)3NMe2 (≡ LϪ), having a γ-pendant amine functionality, have been prepared. The dimeric lithium amidinate
1 was obtained in four steps from 1-amino-3-(dimethylamino)propane. Using 1 and MCl3 in appropriate
stoichiometry led to the mononuclear M(L)Cl2 (M = Al 2 or Ga 3) and the dinuclear [{M(L)2(µ-Cl)}2] (M = La 4
or Ce 5). Structures of four of these (1, 2, 3 and 5) have been studied by X-ray crystallography. In crystalline 1
each amidinato ligand LϪ is chelating with respect to one of the lithium atoms and bridging by virtue of its pendant
γ-tertiary nitrogen atom to the second Li atom. In 2 and 3, by contrast, LϪ behaves as a tripodal chelating ligand,
whereas in crystalline 5 the seven-co-ordinate Ce atom is bound by two bidentate benzamidinato fragments and only
one of the pendant amines.
Introduction
In recent years interest in amidines, especially N-silylated ben-
zamidines, has increased significantly. Structures and chemistry
of numerous metal benzamidinates have been reviewed.1,2
Alkali metal salts have been shown to be excellent precursors
for other main group element, as well as transition and f-metal,
complexes. Cationic aluminium complexes containing amid-
inato ligands have shown remarkable catalytic activity in the
polymerisation of olefins.3 Group 13 metal amidinates are also
promising precursors for MOCVD of III–V nitride semi-
Scheme 1 Synthesis of the lithium amidinate [Li{N(SiMe3)C(Ph)-
N(CH2)3NMe2}]2 [≡ (LiL)2] 1.
conductor materials.4 Additionally, amidinato ligands are of
fundamental interest, because their steric and electronic proper-
ties can be modified by variation of substituents on either or
both N and C atoms.
The lithium amidinate 1 was characterised by elemental
1
7
analysis, IR and H and Li-{1H} NMR spectroscopy and by
single crystal X-ray diffraction. The 1H NMR spectrum in C6D6
revealed only a single set of signals assignable to the amidinato
ligand LϪ. The 7Li-{1H} NMR spectrum showed a single sharp
signal at δ 0.19, whereas its lithium amide precursor had a
broad peak at δ 1.97. The IR spectral bands at 1645 and 1577
New types of amidinato ligands with pendant amine
(CH2CH2NMe2)5 or pyridine6 functionality have recently been
reported. Several metal complexes of such ligands have been
prepared and structurally characterised.5,6
We now report on the design of a new potentially tridentate
benzamidinato ligand ϪN(SiMe3)C(Ph)N(CH2)3NMe2 (≡ LϪ)
having an extended pendant amine function and its role in the
synthesis of its lithium (1), aluminium (2), gallium (3), lan-
thanum (4) and cerium (5) derivatives, as well as the crystal
structures of 1–3 and 5.14 An objective, not yet realised, was to
establish whether the remote amine might serve as a donor to
stabilise unusual metal complexes, such as M(L)2 (M = Al, Ga,
La or Ce).
cmϪ1 were appropriate for an amidinate; the ν(C᎐N) region at
᎐
᎐
>2100 cmϪ1 was transparent.
X-Ray quality crystals of (LiL)2 1 were prepared by recrystal-
lisation from a concentrated hexane solution at Ϫ22 ЊC. The
X-ray structure of 1 shows it to be a C2-symmetric dimer,
Fig. 1. Selected bond lengths and angles are presented in
Table 1. There is a central puckered N(2)LiN(2)ЈLiЈ ring, with
Li–N(2) and Li–N(2)Ј bond lengths of 2.015(3) and 2.232(3) Å,
respectively and the angle subtended at Li [106.1(2)Њ] wider
than that at N, 69.3(2)Њ. Each lithium atom is chelated with
respect to a benzamidinato ligand [e.g. Li with respect to N(1)Ј,
C(1)Ј and N(2)Ј] and also another N,N-centred fragment
[e.g. Li with respect to N(2) and N(3)]. The LiЈ–N(1)–C(1)–N(2)
ring is puckered, the angles subtended at C(1), N(1), N(2) and
Li being 119.0(2), 89.9(2), 79.80(13) and 65.12(11)Њ, respect-
ively; and the LiЈ–N(1), N(1)–C(1) and C(1)–N(2) bond lengths
being 1.989(3), 1.321(2) and 1.327(2) Å, respectively. The Li–
N(3) bond distance is 2.050(3) Å. Thus, each delocalised benz-
amidinato moiety of the LϪ ligand is chelating with respect to
one lithium atom and bridging via the central nitrogen atom
N(2) [or N(2)Ј] and NMe2 nitrogen atom N(3) [or N(3)Ј]. In
Results and discussion
The starting amine HN(SiMe3)(CH2)2NMe2 was prepared
in good yield from commercially available 1-amino-3-(dimethyl-
amino)propane by treatment successively with LiBun and
Me3SiCl (steps i and ii of Scheme 1). The corresponding lithium
salt LiN(SiMe3)(CH2)3NMe2 was prepared (step iii of
Scheme 1) by reaction of this amine with LiBun. The white,
crystalline lithium amidinate [Li{N(SiMe3)C(Ph)N(CH2)3-
NMe2}]2 [≡ (LiL)2] 1 was obtained (step iv of Scheme 1) from
the foregoing lithium amide by treatment with an equivalent
portion of benzonitrile.
DOI: 10.1039/b005824f
J. Chem. Soc., Dalton Trans., 2000, 4093–4097
This journal is © The Royal Society of Chemistry 2000
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Table 1 Selected bond lengths (Å) angles (Њ) for (LiL)2 1
Table 2 Selected bond lengths (Å) angles (Њ) for Al(L)Cl2 2 and
Ga(L)Cl2 3
Li–N(1)Ј
Li–N(2)Ј
Li–C(1)
N(1)–C(1)
N(2)–C(1)
1.989(3)
2.232(3)
2.386(3)
1.321(2)
1.327(2)
Li–N(2)
Li–N(3)
Li ؒ ؒ ؒ LiЈ
N(2)–C(2)
Si–N(1)
2.015(3)
2.050(3)
2.420(6)
1.461(2)
1.698(2)
M = Al (2)
M = Ga (3)
M–N(1)
M–N(2)
M–N(3)
M ؒ ؒ ؒ C(1)
M–Cl(1)
M–Cl(2)
N(1)–C(1)
N(2)–C(1)
N(2)–C(11)
Si–N(1)
2.0182(16)
1.9053(15)
2.0929(16)
2.3738(17)
2.1782(6)
2.1610(8)
1.324(2)
1.322(2)
1.451(2)
1.7396(16)
2.1130(17)
1.9592(15)
2.1407(18)
2.4486(18)
2.2085(5)
2.1940(6)
1.317(3)
1.325(3)
1.453(3)
1.7364(18)
N(1)Ј–Li–N(2)
N(2)–LiЈ–N(3)
N(2)–Li–N(2)Ј
N(1)–C(1)–N(2)
137.6(2)
104.7(2)
106.1(2)
119.0(2)
N(1)Ј–Li–N(3)
N(1)Ј–Li–N(2)Ј
N(3)–Li–N(2)Ј
116.3(2)
65.12(11)
117.2(2)
N(2)–M–N(1)
N(1)–M–N(3)
N(2)–M–N(3)
N(1)–M–Cl(2)
N(2)–M–Cl(1)
N(3)–M–Cl(1)
N(2)–M–Cl(2)
N(3)–M–Cl(2)
N(1)–M–Cl(1)
Cl(2)–M–Cl(1)
N(2)–C(1)–N(1)
67.53(6)
151.64(7)
88.17(7)
103.00(6)
139.95(7)
92.59(5)
108.90(6)
98.48(5)
96.92(5)
65.08(6)
149.47(6)
88.18(7)
103.58(5)
138.69(6)
93.20(5)
109.78(6)
99.07(5)
97.58(5)
110.56(3)
111.20(15)
110.73(2)
112.27(16)
Fig. 1 The molecular structure of (LiL)2 1.
general, the Li–N bond lengths [1.989(3), 2.232(3) and 2.015(3)
Å] are either similar or slightly shorter than in most other
lithium benzamidinates or guanidinates: e.g. 1.993(9), 2.387(9)
and 2.051(10)
Å
in [Li{(NSiMe3)2CC6H4Me-4}(thf)2]2,7a
2.076(6), 2.188(6), 2.162(6), 2.235(6) and 2.139(6) Å in [Li-
{(NPh)2CPh}(pmdeta)]2,7b 1.995(10), 2.080(7), 2.108(10) and
2.260(19) Å in [Li{(NSiMe3)2CC6H4Me-4}(NCC6H4Me-4)]2,7c
2.046(7), 2.054(7) and 2.173(7) Å in [Li{(NPh)2CPh}(hmpa)]2,7d
2.034(3), 2.023(4), 2.003(4) in [Li{(NPh)2CPh}(tmen)],7d
or 1.98(3), 2.03(3) and 2.03(3)
Å in [Li{(NC6H11-c)2C-
[N(SiMe3)2]}]2.7e
Reaction of equimolar portions of (LiL)2 1 and Al2Cl6 in
diethyl ether (i in Scheme 2) yielded the white crystalline com-
Fig. 2 The molecular structure of Al(L)Cl2 2.
Cl(1) and Cl(2) in “equatorial” [N(1)–Al–Cl(1) 96.92(5); N(1)–
Al–Cl(2) 103.00(6)Њ] positions. Selected bond lengths and
angles are listed in Table 2. The N(2)–Al–N(1) bite angle of
67.53(6)Њ is narrower than that reported for aluminium amidi-
nates with a pendant pyridine moiety [72.3Њ],6 but quite close to
those reported for various other aluminium bis(amidinate)s
[67.18 to 70.0(4)Њ].8 The Al–N(1)–C(1)–N(2) ring is planar, the
angles subtended at C(1), N(1) and N(2) being 111.20(15),
87.96(11) and 92.93(11)Њ, respectively; the N(1) [or N(2)]–C(1)
bonds lengths are equal, 1.322(2) Å, and similar to those in 1.
The Al–N [2.018(2), 1.905(2), and 2.093(2) Å] bond lengths
are unexceptional.8 The two Al–Cl bond distances are almost
equal and slightly longer than those reported for other benz-
amidinatoaluminium dichlorides, but very close to those for
bis(amidinato)aluminium chlorides.8a
Scheme 2 Preparation of compounds 2–5. Reagents and conditions:
(i) Al2Cl6 for 2 or Ga2Cl6 for 3, ca. 20 ЊC, Et2O and crystallisation from
hexane; (ii) LaCl3 for 4 or CeCl3 for 5, ca. 20 ЊC, thf and crystallisation
from hexane.
The gallium amidinate Ga(L)Cl2 3 was prepared (step i in
plex Al(L)Cl2 2. The IR spectrum showed characteristic bands
Scheme 2) analogously to the aluminium complex 2, from
(1658 and 1543 cmϪ1) of a chelating amidinatometal complex.
Ga2Cl6 and 1 in diethyl ether. The IR and H NMR spectra
1
1
The H NMR spectrum revealed only one set of signals of the
were closely similar to those for 2. The structure of the gallium
complex 3 shows it to be isostructural and isomorphous to 2
(Fig. 2). Selected bond lengths and angles for 3 are presented
in Table 2. The N(2)–Ga–N(1) bite angle of 65.08(6)Њ is quite
acute and narrower than that in either the aluminium analogue
2 or other amidinatogallium dichlorides [68.1 and 69.4Њ].8b,9
[L]Ϫ ligand.
The crystal structure of complex 2 shows it to be a monomer
(Fig. 2), having the central five-co-ordinated Al atom, in a very
distorted trigonal bipyramidal arrangement. The N(1) and
N(3) atoms are in “axial” [N(1)–Al–N(3) 151.64(7)Њ] and N(2),
4094
J. Chem. Soc., Dalton Trans., 2000, 4093–4097

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Table 3 Selected bond lengths (Å) angles (Њ) for [{Ce(L)2(µ-Cl)}] 5
atoms is bound in a chelate manner by the amidinato fragments
[N(1)C(1)N(2) and N(4)C(16)N(15)] of the two LϪ ligands,
only one of which is tridentate [having a Ce–N(3) bond]. Both
the CeN(1)C(1)N(2) and CeN(4)C(16)N(5) rings are planar,
having almost identical endocyclic angles, that at Ce being the
narrowest, 54.2(1)Њ, and that at C(1) or C(16) the widest,
116.9(9)Њ. Three of the endocyclic Ce–N distances in the two
rings are closely similar [2.492(4), 2.496(4), Ce–N(4) 2.503(4) Å]
but the Ce–N(2) bond of 2.438(4) Å is much shorter, while the
Ce–NMe2 [i.e. Ce–N(3)] bond is rather longer, 2.716(4) Å. The
seven-co-ordinate Ce atom may be regarded as being at the
centre of a distorted N(4)-monocapped octahedron, with N(5)
and ClЈ in axial and N(1), N(2), N(3) and Cl in equatorial
positions. An example of a bis(amidinato)metal complex hav-
ing a ligand containing a pendant NMe2 group is known;
[Cr{N(C6H11-c)C(C6H4CH2NMe2-2)NC6H11-c}2(thf)2], but the
NMe2 substituent has no close Cr ؒ ؒ ؒ N contact.11 Various
lanthanide metal amidinates are known,2,6,12 but there is only
one which is structurally similar, namely [La{N(CH2CH2-
C5H4N-2)C(C6H4Me-4)NPh}2{N(SiMe3)2}];6 in the latter the
seven-co-ordinate lanthanum atom has La–N bond distances
[2.491(4), 2.753(4), 2.609(4), 2.747(4) and 2.453(4) Å] which are
close to the Ce–N distances in 5.
Ce–N(1)
Ce–N(3)
Ce–N(5)
Ce–ClЈ
N(1)–C(1)
N(4)–C(16)
2.492(4)
2.761(4)
2.496(4)
2.884(2)
1.332(6)
1.344(6)
Ce–N(2)
Ce–N(4)
Ce–Cl
Ce ؒ ؒ ؒ CeЈ
N(2)–C(1)
N(2)–C(1)
2.438(4)
2.503(4)
2.866(2)
4.540
1.314(7)
1.314(6)
Cl–Ce–ClЈ
75.71(4)
54.2(1)
79.6(1)
125.5(1)
73.2(1)
85.1(1)
128.9(1)
115.7(1)
145.2(1)
113.9(1)
117.6(1)
Ce–Cl–CeЈ
104.29(4)
92.9(2)
141.0(2)
54.0(1)
123.8(1)
82.9(1)
88.6(1)
87.7(1)
88.1(1)
163.4(1)
79.3(1)
N(2)–Ce–N(1)
N(1)–Ce–N(5)
N(1)–Ce–N(4)
N(2)–Ce–N(3)
N(5)–Ce–N(3)
N(2)–Ce–Cl
N(5)–Ce–Cl
N(3)–Ce–Cl
N(1)–Ce–ClЈ
N(4)–Ce–ClЈ
N(2)–Ce–N(5)
N(2)–Ce–N(4)
N(5)–Ce– N(4)
N(1)–Ce–N(3)
N(4)–Ce–N(3)
N(1)–Ce–Cl
N(4)–Ce–Cl
N(2)–Ce–ClЈ
N(5)–Ce–ClЈ
N(3)–Ce–ClЈ
Owing to the presence of a non-co-ordinating (CH2)3-
NMe2 group the complexes 4 and 5 are potential precursors
for novel intermolecular aggregates. We plan to treat the
compounds with various Lewis acids in order to gain access
to heterometallic oligomers or polymers. In summary, the
amidinate [N(SiMe3)C(Ph)N(CH2)3NMe2]Ϫ has been shown to
be a versatile ligand, which can behave in either a bridging or
chelating fashion and function in either a bi-(4-electron) or tri-
(6-electron) dentate mode. Depending on the nature of the
metal, it can adopt either a facial (2, 3) or a meridional
(5) geometry. At present, it does not seem that an expansion
of the chain length of the pendant amine functionality from
β [(CH2)2NMe2)] to γ [(CH2)3NMe2] has a significant effect on
the structures of several of their derived metal amidinate com-
plexes. The versatility of such amidinato ligands makes it likely
that they will fulfil an increasingly useful role in co-ordination
chemistry.
Fig. 3 The molecular structure of [{Ce(L)2(µ-Cl)}2] 5.
The Ga–N, Ga–C and Ga–Cl distances in 3 are slightly longer
[0.030–0.095 Å] than those in the isoleptic aluminium complex
2, due to the larger ionic radius of Ga.
Experimental
General procedures
Reaction of LaCl3 with complex 1 in THF, followed by
extraction of the products with hexane, gave the colourless
compound [{La(L)2(µ-Cl)}2] 4 (step ii in Scheme 2), which was
characterised by satisfactory elemental analysis and IR spectral
bands at 1676, 1625, 1604 and 1566 cmϪ1. The 1H NMR spec-
trum in C6D6 showed two sets of closely similar signals, attrib-
uted to two magnetically inequivalent amidinato ligands. This is
consistent with the view (see below) that one of the LϪ ligands
is bidentate and the other tridentate. The cerium() f1 complex
[{Ce(L)2(µ-Cl)}2] 5 was prepared analogously. Crystals of 5
(from pentane) showed an identical IR spectrum to those of 4
All manipulations were carried out under vacuum or argon by
Schlenk techniques. Solvents were dried and distilled over
sodium–potassium alloy under argon prior to use and then
condensed into a reaction flask under vacuum shortly before
use. 1-Amino-3-(dimethylamino)propane was obtained from
Aldrich and distilled over CaH2 prior to use. Microanalyses
were carried out by Medac Ltd (Brunel University). The NMR
spectra were recorded using a Bruker DPX 300 (1H, 300.1; 7Li,
116.64 MHz) or Varian 400 (1H, 400 MHz) instrument in
benzene-d6 at ambient temperature unless stated otherwise and
1
and analysed satisfactorily. The H NMR spectrum in C6D6
revealed a number of very broad and paramagnetically shifted
signals between δ 11.92 and Ϫ4.29. Although the spectrum
was quite complicated (integration clearly demonstrated (see
Experimental section) the presence of two sets of signals as in
the spectrum of 4) due to inequivalent (CH2)3NMe2 groups,
consistent with the crystal structure showing that one of the LϪ
ligands is bidentate and the other tridentate.
From the above data we conclude that the structures of
complexes 4 and 5 are very similar. It was considered adequate
crystallographically to characterise only one of them and the
choice fell on the paramagnetic cerium complex 5. The struc-
ture is illustrated in Fig. 3 and selected bond lengths and angles
are shown in Table 3. Complex 5 is dinuclear, having an
inversion centre at the midpoint of the planar CeClCeЈClЈ ring,
which has endocyclic bond lengths and angles very similar to
those in [{Ce(η5-C5H3But2-1,3}2(µ-Cl)}2].10 Each of the cerium
1
referenced for H internally to residual solvent resonances; the
7Li at 116.64 MHz in C6D6 at ambient temperature spectra was
referenced externally to 7Li[NO3]. Deuteriated benzene was
dried over a potassium metal mirror and distilled prior to use.
IR spectra (500–4000 cmϪ1) were recorded as “Nujol” mulls,
using KBr discs and a Perkin-Elmer instrument. Melting
points were taken in sealed capillaries under argon and are
uncorrected.
Syntheses
HN(SiMe3)(CH2)3NMe2. A solution of LiBun in hexane (263
cm3 of a 1.6 mol dmϪ3 solution, 0.42 mol) was added dropwise
to a solution of 1-amino-3-(dimethylamino)propane (43.0 g,
0.42 mol) in diethyl ether (100 cm3) at 0 ЊC. The mixture
was stirred for ca. 12 h, then cooled to Ϫ78 ЊC and
J. Chem. Soc., Dalton Trans., 2000, 4093–4097
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Table 4 Crystal data and structure refinement for complexes 1–3 and 5
1
2
3
5
Formula
M
C30H52Li2N6Si2
566.80
C15H26AlCl2N3Si
374.36
C15H26GaCl2N3Si
417.10
C60H104Ce2Cl2N12Si4ؒ2C5H12
1601.3
Crystal system
Space group
a/Å
b/Å
Monoclinic
C2/c (no. 15)
17.151(4)
9.616(7)
22.314(9)
105.27(4)
3550(3), 4
0.13
Monoclinic
P21 (no. 4)
8.8881(3)
11.4278(5)
10.3472(5)
109.373(2)
991.47(7), 2
0.43
Monoclinic
P21 (no. 4)
8.8921(3)
11.4453(3)
10.4095(3)
109.221(2)
1000.35(4), 2
1.70
Monoclinic
P21/c (no. 14)
10.034(4)
18.888(3)
22.335(4)
94.28(2)
4221(2), 2
1.23
6230
c/Å
β/Њ
U/Å3, Z
µ(Mo-Kα)/mmϪ1
Reflections collected
Independent reflections (Rint
Reflections with [I > 2σ(I)]
Final R1
3221
3122 (0.035)
2471
8799
4202 (0.032)
3972
8110
4427 (0.027)
4347
)
5853 (0.027)
4426
0.038
0.042
0.029
0.023
wR2
0.108
0.075
0.057
0.088
chlorotri(methyl)silane (45.6 g, 0.42 mol) added. It was stirred
at ambient temperature for 12 h and filtered. Volatiles were
removed from the filtrate in vacuo. Distillation of the residue
afforded the diamine (45.3 g, 62%), bp 54–56 ЊC/15 mmHg:
H, 3J(1H–1H) = 5.52, CH2NMe2], 2.17 (s, 6 H, NMe2), 0.98
3
[quin, 2 H, J(1H–1H) = 6.03 Hz, CCH2C] and 0.023 (s, 9 H,
SiMe3).
3
1H NMR (CDCl3, 300 MHz): δ 2.55 [t, 2 H, J(1H–1H) = 6.9,
[Ga{N(SiMe3)C(Ph)N(CH2)3NMe2}Cl2] 3. Using the pro-
cedure of the preceding experiment, the white, crystalline com-
pound 3 (1.04 g, 78%) (Found: C, 42.9; H, 6.12. C15H26Cl2-
GaN3Si requires C, 43.2; H, 6.23%), mp ca. 120 ЊC, was
obtained from 1 (0.90 g, 3.2 mmol) and gallium trichloride
(0.56 g, 3.2 mmol). The IR spectrum 3 was identical to that of
CH2NSiMe3], 2.1 [t, 2 H, 3J(1H–1H) = 7.1, CH2NMe2], 2.03 (s, 6
3
H, NMe2), 1.38 [quin, 2 H, J(1H–1H) = 7.1 Hz, CCH2C), 0.58
(br, 1 H, NH) and Ϫ0.16 (s, 9 H, SiMe3).
LiN(SiMe3)(CH2)3NMe2. A solution of LiBun in hexane (163
cm3 of a 1.6 mol dmϪ3 solution, 0.26 mol) was added dropwise
to the above diamine (45.3 g, 0.26 mol) in diethyl ether (80 cm3)
at Ϫ33 ЊC. The mixture was allowed to warm to ambient
temperature and stirred for ca. 12 h. The solvent was removed
in vacuo. The residue was extracted with hexane (60 cm3). The
extract was concentrated to ca. 15 cm3 and cooled at Ϫ22 ЊC,
yielding white crystals of the lithium amide (41.6 g, 89%)
(Found: C, 54.0; H, 12.02. C8H21LiN2Si requires C, 53.3; H,
1
2. H NMR (400 MHz): δ 6.99 (m, 5 H, Ph), 2.77 (br, 2 H,
CH2NCPh), 2.18 (br, 2 H, CH2NMe2), 2.13 (s, 6 H, NMe2), 0.96
(br, 2 H, CCH2C) and 0.21 (s, 9 H, SiMe3).
[{La[N(SiMe3)C(Ph)N(CH2)3NMe2]2(ꢁ-Cl)}2] 4. The lithium
amide 1 (1.52 g, 2.68 mol) was added slowly in portions to a
suspension of lanthanum() chloride (0.33 g, 1.34 mol) in thf
(60 cm3) at 0 ЊC. The mixture was stirred for 24 h at ambient
temperature. The solvent was removed in vacuo. The residue
was extracted with hexane (ca. 80 cm3). The extract was concen-
trated to ca. 20 cm3 and cooled at 0 ЊC, affording white crystals
of compound 4 (1.30 g, 67%) (Found: C, 50.9; H, 7.34. C30H52-
1
3
11.67%); H NMR (300 MHz): δ 3.27 [t, 2 H, J(1H–1H) = 5.2,
CH2NSiMe3], 2.18 [t, 2 H, J(1H–1H) = 5.2, CH2NMe2], 1.92
3
(s, 6 H, NMe2), 1.47 [quin, 2 H, J(1H–1H) = 5.2 Hz, CCH2C]
3
and 0.21 (s, 9 H, SiMe3). 7Li-{1H} NMR: δ 1.97.
ClLaN6Si2 requires C, 49.6; H, 7.16%). IR, νmax
/cmϪ1: 1676s,
˜
[Li{N(SiMe3)C(Ph)N(CH2)3NMe2}]2 1. Benzonitrile (3.61 g,
35 mmol) was added slowly (ca. 30 min) to a solution of LiN-
(SiMe3)(CH2)3NMe2 (6.30 g, 35 mmol) in diethyl ether (60 cm3)
at 0 ЊC. The mixture was stirred for ca. 12 h at ambient temper-
ature. The solvent was removed in vacuo and the residue
extracted with hexane (100 cm3). The extract was concentrated
to ca. 20 cm3 and cooled at Ϫ30 ЊC, yielding white crystals of
compound 1 (7.9 g, 80%) (Found: C, 62.8; H, 9.02. C15H26-
1625m, 1604m, 1566m, 1376m, 1301m, 1238m, 1154w, 1043m,
967s, 838m, 733m, 682w and 590w. 1H NMR (400 MHz):
δ 7.4– 7.03 (m, 10 H, Ph), 3.25 and 3.14 [ts, 4 H ϩ 4 H, 3J(1H–
1H) 6.48 and 6.99 Hz, CH2NCPh], 2.40 (s ϩ sh, 4 H ϩ 12 H,
CH2NMe2), 2.33 (br m, 4 H, CH2NMe2), 2.21 (s, 12 H,
NMe2), 1.88–1.74 (ms, 8 H, CCH2C), 0.35 and 0.23 (ss, 18 H,
SiMe3).
LiN3Si requires C, 63.5; H, 9.17%), mp ca. 150 ЊC. IR, νmax/
˜
[{Ce[N(SiMe3)C(Ph)N(CH2)3NMe2]2(ꢁ-Cl)}2] 5. From com-
pound 1 (0.64 g, 2.28 mmol) and cerium() chloride (0.28 g,
1.14 mmol), using the procedure of the preceding experiment,
there were obtained pale yellow crystals (from C5H12 at ambient
temperature) of compound 5 (1.12 g, 58%) (Found: C, 50.1; H,
cmϪ1: 1645m, 1599m, 1577m, 1498w, 1403m, 1299m, 1240m,
1170w, 1071w, 1028s, 956w, 919m, 831m, 722m, 700m and
1
620w. H NMR (300 MHz): δ 7.18–7.01 (m, 5 H, Ph), 2.87 [t,
3
2 H, J(1H–1H) = 5.02, CH2NCPh], 2.16 (br, 2 H, CH2NMe2),
1.96 (s, 6 H, NMe2), 1.24 [quin, 2 H, 3J(1H–1H) = 5.02 Hz,
CCH2C] and 0.07 (s, 9 H, SiMe3). 7Li-{1H} NMR: δ 0.19.
1
7.21. C30H52CeClN6Si2 requires C, 49.5; H, 7.15%). H NMR
(440 MHz): δ 11.92–9.16 (br ms, 20 H, Ph), 3.24 (m, 4 H,
CH2NMe2), 2.11 (br m, 4 H, CH2NMe2), 1.22 (br, 12 H, NMe2),
1.13 (m, 4 H, CCH2C), 0.88 (s, 12 H, NMe2), 0.35 (br m, 4 H,
CCH2C), Ϫ2.66 and Ϫ2.98 (br ms, 4 H ϩ 4 H, CH2NCPh),
Ϫ4.29 (v br, 36 H, SiMe3). The IR spectrum was identical to
that of 4.
[Al{N(SiMe3)C(Ph)N(CH2)3NMe2}Cl2] 2. The lithium amide
1 (0.743 g, 2.6 mmol) was added slowly in portions to a solution
of aluminium trichloride (0.35 g, 1.3 mmol) in diethyl ether (60
cm3) at 0 ЊC. The mixture was stirred for ca. 24 h at ambient
temperature. The solvent was removed in vacuo. The residue
was extracted with hexane (80 cm3). The extract was concen-
trated to ca. 20 cm3 and cooled at Ϫ22 ЊC, yielding white
crystals of compound 2 (0.83 g, 85%) (Found: C, 47.8; H, 6.72.
C15H26AlCl2N3Si requires C, 48.1; H, 6.95%), mp ca. 110 ЊC. IR
X-Ray crystallography
Data sets for complexes 1 and 5 were measured on an Enraf-
Nonius CAD4 and for 2 and 3 on Kappa CCD diffractometers
at 173(2) K using monochromated Mo-Kα radiation. A crystal
of each of the salts 1, 2, 3 and 5 was coated in oil and cooled.
Refinement was based on F2, with H atoms in riding mode,
νmax
˜
/cmϪ1: 2240s, 1658s, 1543s, 1239m, 1180w, 1054s, 961s,
1
837m, 722m and 615w. H NMR (400 MHz): δ 7.35–6.91 (m,
5 H, Ph), 2.68 [t, 2 H, J(1H–1H) = 6.03, CH2NCPh], 2.25 [t, 2
3
4096
J. Chem. Soc., Dalton Trans., 2000, 4093–4097

View Article Online
using SHELXL-93.13 Further details on the crystal data are
given in Table 4.
CCDC reference number 186/2189.
See http://www.rsc.org/suppdata/dt/b0/b005824f/ for crystal-
lographic files in .cif format.
R. E. Mulvey, P. R. Raithby and R. Snaith, J. Chem. Soc., Dalton
Trans., 1997, 951; (e) G. R. Giesbrect, A. Shafir and J. Arnold,
J. Chem. Soc., Dalton Trans., 1999, 3601.
8 (a) M. P. Coles, D. C. Swenson and R. F. Jordan, Organometallics,
1997, 16, 5183; (b) S. Dagorne, I. A. Guzei, M. P. Coles and R. F.
Jordan, J. Am. Chem. Soc., 2000, 122, 274.
9 S. Dagorne, R. F. Jordan and V. G. Young, Organometallics, 1999,
18, 4619.
10 E. B. Lobkovsky, Yu. K. Gun’ko, B. M. Bulychev, V. K. Belsky,
G. L. Soloveichik and M. Yu. Antipin. J. Organomet. Chem., 1991,
406, 343.
Acknowledgements
We thank EPSRC and Trinity College for support.
11 S. K. Hao, S. Gambarotta, C. Bensimon and J. J. H. Edema, Inorg.
Chim. Acta, 1993, 213, 65.
References
12 (a) A. Recknagel, F. Knösel, H. Gornitzka, M. Noltemeyer,
F. T. Edelmann and U. Behrens, J. Organomet. Chem., 1991, 417,
363; (b) M. Wedler, F. Knösel, U. Pieper, D. Stalke, F. T. Edelmann
and H.-D. Amberger, Chem. Ber., 1992, 125, 2171; (c) F. T.
Edelmann, J. Alloys Comp., 1994, 207, 182; (d) U. Kilimann and F.
T. Edelmann, J. Organomet. Chem., 1994, 469, C5; (e) H. Schumann,
J. Winterfeld, H. Hemling, F. E. Hahn, P. Reich, K.-W. Brzezinka,
F. T. Edelmann, U. Kilimann, M. Schäfer and R. Herbst-Irmer,
Chem. Ber., 1995, 128, 395; ( f ) R. Duchateau, A. Meetsma and
J. H. Teuben, Organometallics, 1996, 15, 1656.
1 J. Barker and M. Kilner, Coord. Chem. Rev., 1994, 133, 219.
2 F. T. Edelmann, Coord. Chem. Rev., 1994, 137, 403.
3 M. P. Coles and R. F. Jordan, J. Am. Chem. Soc., 1997, 119,
8125.
4 J. Barker, N. C. Blacker, P. R. Phillips, N. W. Alcock, W. Errington
and M. G. H. Wallbridge, J. Chem. Soc., Dalton Trans., 1996,
431.
5 M. J. R. Brandsma, E. A. C. Brussee, A. Meetsma, B. Hessen and
J. H. Teuben, Eur. J. Inorg. Chem., 1998, 1867.
6 K. Kincaid, C. P. Gerlach, G. R. Giesbrecht, J. R. Hagadorn,
G. D. Whitener, A. Shafir and J. Arnold, Organometallics, 1999, 18,
5360.
7 (a) D. Stalke, M. Wedler and F. T. Edelmann, J. Organomet. Chem.,
1992, 431, C1; (b) I. Cragg-Hine, M. G. Davidson, F. S. Mair,
P. R. Raithby and R. Snaith, J. Chem. Soc., Dalton Trans., 1993,
2423; (c) M. S. Eisen and M. Kapon, J. Chem. Soc., Dalton Trans.,
1994, 3507; (d) J. Barker, D. Barr, N. D. R. Barnett, W. Clegg,
I. Cragg-Hine, M. G. Davidson, R. P. Davies, S. M. Hodgson,
J. A. K. Howard, M. Kilner, C. W. Lehmann, I. Lopez-Solera,
13 (a) G. M. Sheldrick, in Crystallographic Computing 3, G. M.
Sheldrick, C. Krüger and R. Goddard, eds., Oxford University
Press, 1985, 175; (b) G. M. Sheldrick, SHELXL-93, a program for
crystal structure refinement, University of Göttingen, 1993.
14 Note added at proof. Since submission of this manuscript, a paper
has appeared describing the preparation and structure of [YL2-
(CH2Ph)], in which one of the chelating LϪ ligands is bi- and the
other tri-dentate (S. Bambirra, M. J. R. Brandsma, E. A. C. Brussee,
A. Meetsma, B. Hessen and J. H. Teuben, Organometallics, 2000, 19,
3197.
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4097