Synthesis and structures of selected benzamidinates of Li, Na, Al, Zr and Sn(ii) using the C1-symmetric ligands [N(SiMe3)C(C 6H4Me-4 or Ph)NPh]-

Article abstract of DOI:10.1039/b614351b

Several compounds based on the C₁-symmetric ligands [N(R)C(Ar)NPh]^- [abbreviated as B¹ (Ar = C ₆H₄Me-4) or B² (Ar = Ph), R = SiMe₃] are reported. They are the crystalline metal b

Full text of DOI:10.1039/b614351b

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Synthesis and structures of selected benzamidinates of Li, Na, Al, Zr and
Sn(II) using the C1-symmetric ligands [N(SiMe3)C(C6H4Me-4 or Ph)NPh]−†
Peter B. Hitchcock,a Michael F. Lappert*a and Philippe G. Merleb
Received 3rd October 2006, Accepted 19th December 2006
First published as an Advance Article on the web 4th January 2007
DOI: 10.1039/b614351b
Several compounds based on the C1-symmetric ligands [N(R)C(Ar)NPh]− [abbreviated as B1 (Ar =
C6H4Me-4) or B2 (Ar = Ph), R = SiMe3] are reported. They are the crystalline metal benzamidinates
[Li(l:j2-B1)(OEt2)]2 (1), [Al(j2-B1)2Me] (2), [Al(j2-B1)2X] [X = Cl/Me, 1 : 1 (3)], [Sn(j2-B1)2] (4),
Zr(j2-B1)2Cl2 (5), [Zr(j2-B1)3Cl] (6), [Na(l:j2-B1)(tmeda)]2 (7), K[B1] (8), Li(B2)(OEt2) (9) and
Zr(j2-B1)3Cl (10) and the known benzamidine Z–H2NC(C6H4Me-4) = NPh (11). They were prepared
by (i) insertion of the nitrile 4-MeC6H4CN (1, 7, 8, 11) or PhCN (9) into the appropriate M–N(Rꢀ)Ph
[Rꢀ = R and M = Li (1, 9), Na (7), K (8)] bond and subsequent hydrolysis for 11 [Rꢀ = H and M = Li],
or (ii) a ligand transfer reaction using the lithium amidinate 1 and Al(Me)2Cl (2, 3), SnCl2 (4) or ZrCl4
(5, 6), or Li(B2) and ZrCl4 (10). The X-ray structures of 1, 2, 3, 4, 6b (i.e. 6·3PhMe), 7 and 11 are
presented. Exploratory polymerisation experiments are described, using 2, 5 or 6 as a procatalyst with
methylaluminoxane (MAO) (Al : Zr ca. 500 : 1) as promoter. Thus toluene solutions were exposed to
C2H4 under ambient conditions; while 2 was unresponsive, 5 and 6 showed modest activity in the
formation of polyethylene.
In its applications B is valuable in the main as a spectator ligand,
since (i) it is generally firmly bound to the metal (or metals), (ii) its
Amidines and amidinates are valuable reagents in organic
electronic and steric effects can be fine-tuned by a judicious choice
Introduction
synthesis1 and have a useful role in coordination chemistry. A
recent review dealt with amidines (and guanidines) as ligands.2 A
generalised amidine is shown in A in the Z-anti-configuration: Z
of the substituents R1, R2 and R3, and (iii) it can display a variety
of bonding modes to the metal(s). The majority of publications
have dealt with C2-symmetric ligands: i.e., R1 = R2 in B which is
either N,Nꢀ-chelating to a metal atom or bridges two metal atoms.
An early (1995) example of a C1-symmetric ligand B (R1 = R2)
was [N(R)C(C6H3Me2-2,5)NC(C6H3Me2-2,5) = C(H)R]− (R =
SiMe3 here and henceforth in this paper), as the potassium salt
prepared from 2(2,5-Me2C6H3CN) and successively Li[C(H)R2]
and 2 K[OBut].4 In many later publications the motivation to
make metal amidinates of C1-symmetric ligands was governed by
the notion of using them as catalysts or reagents for regio- or
even enantio-selective transformations. Examples of such ligands
include the optically active or racemic C (R2 = myrtanyl)5 and
D6 (R1 = Ph6a or R6b,c) as in [Zr(C)3Cl] as a procatalyst (with
methylaluminoxane, MAO) for the conversion of propene into iso-
tactic poly(propene).5 The zirconium complexes [ZrCp*(B)Me2]
with [NH(Me)2Ph][B(C6F5)4] were catalysts for the living poly-
merisation of hex-1-ene (R1, R2, R3 = But, Et, Me, respectively)7a
or styrene (R1, R2, R3 = But, Cy, Me, respectively).7b A variant of
ligand B is the dianionic oxalyl analogue E, as in [{Zr(NMe2)3}2(l-
E)].8 One of the earliest examples of a metal amidinate as a pro-
catalyst for olefin polymerisation was the zwitterionic aluminium
refers to the relative disposition of the NR1 and N(R2)H groups
3
=
about the C N bond, and anti to that of R and H about the
C–N bond.
The amidinato ligand is shown in B in its p-delocalised
form. Reviews in the mid-nineties of early work have been
concerned with metal N,Nꢀ-bis(trimethylsilyl)benzamidinates (in
B: R1 = SiMe3 = R2, R3 = an aryl group),3a d-block metal
amidinates,3b and “paddle-wheel” dinuclear formamidinates of
formula [M2(B)4Lax)n] (M = Mo, Ru, Rh, Ni,; R1 = aryl = R2,
R3 = H; Lax is an axial ligand, n = 0, 1, 2).3c The field has grown
remarkably, as evident by the more than 130 papers published
since the beginning of 2003 to mid-2006.
+
−
amidinate [{Al(B)(Me)} · · · {MeB(C6F5)3} ] (in B: R1 = Pri =
R2, R3 = Me); toluene solutions polymerised C2H4 at 2 atm.9
aChemistry Department, University of Sussex, Brighton, UK BN1 9QJ.
E-mail: m.f.lappert@sussex.ac.uk; Fax: +44 1273 677196; Tel: +44 1273
678316
bDepartment of Chemistry and Biochemistry, Concordia University, Mon-
treal, H4B 1R6, Canada
† Electronic supplementary information (ESI) available: Details of struc-
tural data for 3. See DOI: 10.1039/b614351b
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Our recent prior publications using C1-symmetric amidinato
ligands dealt with the synthesis and structures of (i) Li, Na
and Sn(II) benzamidinates using the ligand B with R1, R2 and
R3 = R, But and Ph (or C6H4OMe-4), respectively,10a and (ii) the
crystalline heavier alkali metal amidinates [{Na(B)}8], [K(B)(thf)2]
1
2
3
=
and [Ni(B)2] in which R , R and R = R, C(Ph) C(H)R and Ph,
respectively.10b
(1)
The present paper is concerned with ten crystalline metal benza-
midinates 1–10 using the C1-symmetric ligands [N(Rꢀ)C(Ar)NPh]−
[Rꢀ = R, Ar = C6H4Me-4 (B1) or Ph (B2)]; the X-ray structure of the
related benzamidine Z–(A) [A: R1 = R2 = H, R3 = C6H4Me-4] (11)
is also reported. The emphasis was on their synthesis and struc-
tures. We have recently found that some lithium benzamidinates
are reducible yielding trianionic benzamidinates;11 compounds 1–
10 will be available for study of their behaviour on reduction.
(2)
(3)
(4)
Results and discussion
Synthetic aspects
The crystalline, bright yellow lithium N,Nꢀ-disubstituted benza-
midinate [Li{l:j2-B1}(OEt2)]2 (1) was prepared in good yield by
the procedure of eqn (1). This involved insertion of 4-toluonitrile
into the Li–N bond of Li[N(R)Ph]12 (R = SiMe3 here and
hereafter) with either a synchronous or subsequent 1,3-SiMe3 N
→ Nꢀ rearrangement. A similar methodology was used to gain
access in high yields to the heavier alkali metal amidinates 7 and
8. Thus, addition of 4-toluonitrile to a suspension of Na[N(R)Ph]13
in toluene furnished an insoluble solid which upon addition
of a pentane solution of tmeda gave the crystalline [Na{l:j2-
B1}(tmeda)]2 (7), eqn (2). Likewise, interaction of 4-MeC6H4CN
and K[N(R)Ph] [prepared in situ from the lithium amide and
K[OBut] in diethyl ether gave [eqn (3)] the microcrystalline K(B1)
(8), which was sparingly soluble in Et2O or thf. The salt 8 was also
obtained in equally high yield by a ligand transfer reaction (i in
Scheme 1) from 1 and K[OBut]. Crystals of the binuclear lithium
benzamidinate 9 were isolated from Li[N(R)Ph] and PhCN; no
attempt was made to optimise the yield, eqn (4).
The lithium benzamidinate 1 was a useful precursor under
mild conditions for the ligand-exchange reactions summarised
in Scheme 1. Thus, 1 was the source not only of the potassium
analogue 8 (i in Scheme 1), but also of the selected aluminium,
tin(II) and zirconium complexes 2–6. The dimeric 1 and an
equimolar portion of methylaluminium dichloride yielded (ii in
Scheme 1) the crystalline [Al{j2-B1}2Me] (2). Interestingly, using
a two molar portion of AlMeCl2 under the same conditions
gave (iii in Scheme 1) [Al{j2-B1}2X] (X = Cl/Me, 1 : 1) (3)
rather than the expected Al(B1)(Cl)Me. Treatment of 1 with
SnCl2 or ZrCl4 in the appropriate stoichiometry furnished in high
Scheme 1 Reagents and conditions: i, K[OBut], C6H14, 20 ◦C; ii, AlMeCl2, C6H14, −78→20 ◦C; iii, 2 AlMeCl2, C6H14, −78→20 ◦C; iv, SnCl2, Et2O,
20 ◦C; v, ZrCl4, Et2O, 20 ◦C; vi, ZrCl4 (3 Li: 1 Zr), Et2O, 20 ◦C.
586 | Dalton Trans., 2007, 585–594
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yield each of the crystalline complexes [Sn{j2-B1}2] (4), [Zr{j2-
B1}2Cl2] (5) or [Zr{j2-B1}3Cl] (6) (iv–vi of Scheme 1, respectively).
Whereas 4 and 6 proved to be stable in toluene solutions, 5 slowly
redistributed, affording 6 and ZrCl4. This presumably implicated
a [{Zr(B1)2Cl(l-Cl)}2] intermediate or transition state, in which
one or both of the benzamidinato ligands may have changed
from being chelatingly N,Nꢀ-(j2) bound to the zirconium atom
membered rings arranged in transoid fashion, the barrier to a
cisoid isomer in solution may be low.
1
¯
=
to being simply N-bound (j ) as N(R)C(C6H4Me-4) NPh or
2
¯
=
N(Ph)C(C6H4Me-4) NR. Similarly, from Li(B )(OEt2) (9) and
half an equivalent of ZrCl4 in toluene, the isolated product [eqn
(5)] was [Zr(B2)3Cl] (10) rather than the corresponding Zr(IV)
dichloride.
Molecular structures of 1, 2, 3, 4, 6b, 7 and 11
The crystalline alkali metal benzamidinates [M{l:j2-
N(R)C(Ar)NPh}Do]2 (1: M = Li and Do = OEt2; 7: M =
Na and Do = tmeda) have a ladder-shaped backbone, with an
LiNLiꢀNꢀ or Na1N2Na2N4 rhomboidal core, flanked by the fused
non-pla◦nar rings LiN1C1N2 or Na1N1C1N2 (fold angles to
core: 55 for 1 and 62◦ for 7) and LiꢀN1ꢀCꢀ1ꢀN2ꢀ or Na2N3C18N4
(fold angles to core: 55◦ for 1 and 68◦ for 7). The structures
of type F are illustrated in Fig. 1 (1) and 2 (7) and selected
geometric parameters are listed in Tables 1 (1) and 2 (7). The
structures resemble that of [Li{l:j2-N(R)C(Ar)NR}(thf)]2 (12)
except that in 12 the LiNLiꢀNꢀ core is puckered, with a fold angle
of 26.3◦ along the Li · · · Liꢀ vector.16 The molecular structure of
[Na{l:j2-N(R)C(Ph)NR}(OEt2)]2·OEt2 (13) differs from that of
7 in that of its four nitrogen atoms, one (rather than the two,
N2 and N2ꢀ in 1, and N1 and N3 in 7) approximates to being
three-(rather than the other two amidinato nitrogen atoms N1
and N1ꢀ in 1, and N2 and N4 in 7) and one is two-coordinate; the
ladder bond lengths of 12 and 13 are shown in Fig. 3.16
(5)
The benzamidine 11 has long been known, having been prepared
by heating under reflux in benzene a mixture of aniline, 4-
toluonitrile and sodium, and subsequent hydrolysis.14 It was here
prepared as shown in eqn (6). In both procedures, the likely course
of reaction was successive metallation of aniline, insertion of 4-
MeC6H4CN into the M–N(H)Ph bond, and hydrolysis.
(6)
Each of the compounds 1–10 was characterised by microanal-
ysis (C, H and N; the values for C were low for 2, 6 and 7, which
is attributed to incomplete combustion), solution multinuclear
(including H, 13C and 29Si) NMR spectra in C6D6 at ambient
1
1
temperature, and EI-mass spectra. The H NMR spectrum of
each compound was consistent with its molecular formula [shown
in eqn (1)–(6) and Scheme 1]. Except for the binuclear lithium
1
compounds 1 and 9, the 29Si{ H} signals were singlets, ranging
from d 1.01 (the Zr compounds 5, 6 and 10), through d −1.68
0.01 (the Al compounds 2 and 3), d −11.1 (the Na compound 7)
to d −12.4 ppm (the K compound 8), which corresponds to their
increasing ionicity (Zr < Al ꢂ Na < K). The presence of a single
1
29Si{ H} chemical shift signal for the Na (7) and the K (8) com-
pounds may be due to their stereochemical rigidity or to their dis-
sociation in solution. By contrast, the binuclear lithium complexes
1
showed 29Si{ H} multiplets (d −2.09, −4.05, −4.37 and −6.49 ppm
for 1; and d −1.98, −4.10, −5.66 and −8.95 ppm for 9), which may
be due to fluxionality, the nature of which has not been elucidated.
Four different coordination modes for lithium amidinates
have been established: chelating (j2), bridging (l), bridging and
mono(chelating) [l: (j2)1] and bridging and bis(chelating) [l: (j2)2];
transitions between these types are fluid and assignment to the
differenttypes is somewhatarbitrary.15 For binuclear lithium amid-
inates [Li(B)(Do)]2 (Do = a neutral coligand), four types have been
observed: F, G, H and I (shown in two dimensional form), exem-
plified by [Li{(N(R))2CC6H4Me-4}(thf)]2,16 [Li{(N(R))2CC6H4F-
4}(OEt2)]2,15 [Li{(N(R))2CC6H4Me-4}(NCC6H4Me-4)]2,17 and
[Li{(N(R))2CC6F5}(OEt2)1/2]2,15 respectively. Furthermore, for the
crystalline ladder structures F and G having the outer four-
Fig. 1 Molecular structure of [Li{l:j2-N(R)C(C6H4Me-4)NPh}(OEt)2]2
(1) (20% ellipsoids; H atoms omitted).
While both the amidinato nitrogen atoms act as chelates in
1 and 7, it is regiospecifically only the N(Ph) atoms which in
addition function as bridges. For comparison, it is noted that for
the two related C1-symmetric amidinates of lithium and sodium,
the bridging atom is N(SiMe3) for [M{l:j2-N(R)C(Ph)NBut}Do]2
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The crystalline bis(amidinato)-aluminium (2 and 3) and -tin(II)
(4) complexes are monomeric and have a similar geometry. The two
[N(R)C(C6H4Me-4)NPh]− ligands in each are arranged around
the metal in a butterfly-like fashion, with the metal in a much
distorted trigonal bipyramidal environment, the fifth position
being occupied by the methyl (2), Me/Cl (not resolved, 3) group,
or the lone pair (4). In 2 and 3 the pseudo-equatorial sites are taken
up by the N1, N3 (N1 and N3 bear the SiMe3 substituents) and
C(35) [2 or 3 C(35)/Cl] atoms, while in 4 they are the N2, N3 and
N4 atoms. The widest endocyclic N–Sn–Nꢀ angle is the N2–Sn–
N4; each of the N2 and N4 atoms bears the SiMe3 substituent. As
the arrangement of the two amidinato ligands in the Al complexes
2 and 3 is very similar, and the Cl and C35 atoms of 3 could not be
resolved, the structural details of 3 are consigned to the ESI† (SUP
Fig. 1 and SUP Table 1 in ESI†). The molecular structures of 2
and 4 are shown in Fig. 4 (2) and 5 (4) and selected geometrical
parameters are listed in Tables 3 (2) and 4 (4).
Fig. 2 Molecular structure of [Na{lj2-N(R)C(C6H4Me-4)NPh}(tmeda)2]2
(7) (20% ellipsoids; H atoms omitted).
◦
˚
Table 1 Selected bond lengths [A] and angles [ ] for 1
Li · · · Lia
Li–N(1)
Li–N(2)
C(1)–N(1)
2.581(10)
2.193(6)
2.026(6)
1.357(4)
Li–N(1)a
Li–C(1)
Li–O
2.058(5)
2. 387(6)
1.953(5)
1.309(4)
C(1)–N(2)
N(1)–Li–N(2)
C(1)–N(1)–Li
C(1)–N(1)–Lia
Li–N(1)–Lia
65.9(2)
80.8(2)
129.6(2)
74.7(2)
N(1)–C(1)–N(2)
C(1)–N(2)–Li
N(2)–Li–N(1)a
N(1)–Li–N(1)a
119.1(2)
88.7(2)
125.3(3)
105.3(3)
Symmetry transformations to generate equivalent atoms:a −x, −y, −z.
◦
˚
Table 2 Selected bond lengths [A] and angles [ ] for 7
Na(1) · · · Na(2)
Na(1)–N(1)
Na(1)–N(2)
Na(1)–N(4)
Na(1)–N(5)
Na(1)–N(6)
C(1)–N(1)
2.173(3)
2.5201(17)
2.4717(17)
2.5887(16)
2.6535(19)
2.6151(19)
1.323(2)
Na(2)–N(3)
Na(2)–N(4)
Na(2)–N(2)
Na(2)–N(7)
Na(2)–N(8)
C(18)–N(3)
2.5118(17)
2.4609(17)
2.5147(17)
2.578(2)
2.5841(19)
1.320(2)
Fig. 4 Molecular structure of [Al{j2-N(R)C(C6H4Me-4)NPh}2Me] (2)
(20% ellipsoids; H atoms omitted).
C(1)–N(2)
1.335(2)
54.87(5)
119.87(17)
87.06(11)
88.86(13)
131.90(13)
79.05(5)
C(18)–N(4)
1.345(2)
55.29(5)
119.95(16)
87.17(11)
88.78(11)
125.00(12)
77.83(5)
The N1C1N2Al four-membered ring of 2 is almost planar
while the contiguous N3C18N4Al ring is puckered; the dihedral
angle between the N3C18N4 and N3AlN4 planes is 148.9◦. The
angle between the N1AlN2 and the N3C18N4 planes is 81.9◦.
The N1C1N2Sn ring of 4 is virtually planar with the ipso-C
(C2) also in that near-plane. The angle between the N1C1N2
N(1)–Na(1)–N(2)
N(1)–C(1)–N(2)
C(1)–N(1)–Na(1)
C(1)–N(2)–Na(1)
C(1)–N(2)–Na(2)
Na(1)–N(2)–Na(2)
N(3)–Na(2)–N(4)
N(3)–C(18)–N(4)
C(18)–N(3)–Na(2)
C(18)–N(4)–Na(2)
C(18)–N(4)–Na(1)
Na(1)–N(4)–Na(2)
◦
˚
and the N3C18N4 planes is 89.3 ; the tin atom is ca. 0.20 A
out of the N3C18N4. The geometric parameters of 2 and 4
are unexceptional: cf. those of [Al{j2-N(Pri)C(But)NPri}2Me]
(14)19 and [Sn{j2-N(R)C(Ph)NBut}2] (15)10 (the SiMe3 and But
substituents are disordered). As in 2, the N2 and N4 atoms of 14
(1: M = Li and Do = thf; 7: M = Na and Do = thf)10 but N(Prn)
for [Li{l:j2-N(R)C(Ph)NPrn}(OEt2)]2.18
We conclude that for such compounds the choice of bridging
group is governed by steric rather than electronic considerations.
16
˚
Fig. 3 Ladder bond lengths (A) for 12 and 13.
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◦
˚
Table 5 Selected bond lengths [A] and angles [ ] for 6b (3 toluene)
Zr–Cl
Zr–N(1)
Zr–N(3)
Zr–N(5)
C(1)–N(1)
C(18)–N(3)
C(35)–N(5)
2.464(2)
2.284(4)
2.305(4)
2.303(4)
1.336(6)
1.329(7)
1.331(7)
Zr–N(2)
Zr–N(4)
Zr–N(6)
C(1)–N(2)
C(18)–N(4)
C(35)–N(6)
2.221(4)
2.219(4)
2.227(4)
1.340(7)
1.340(7)
1.330(7)
N(1)–Zr–N(2)
N(3)–Zr–N(4)
N(5)–Zr–N(6)
N(1)–Zr–Cl
N(3)–Zr–Cl
N(5)–Zr–Cl
59.20(15)
58.99(15)
58.89(15)
128.82(11)
129.70(11)
126.50(11)
112.6(4)
N(1)–Zr–N(4)
N(3)–Zr–N(6)
N(5)–Zr–N(2)
N(2)–Zr–Cl
N(4)–Zr–Cl
N(6)–Zr–Cl
141.57(16)
142.53(16)
144.66(15)
85.89(12)
86.08(12)
85.55(12)
113.2(5)
N(1)–C(1)–N(2)
N(5)–C(35)–N(6)
N(3)–C(18)–N(4)
113.6(4)
are trans relative to the chlorine atom, while the aryl groups at
N1, N3 and N5 have the opposite orientation. These features are
broadly similar to those in the C3-symmetric [Zr{N(R)C(C6H4Me-
4)NRꢀ}3Cl] (Rꢀ = cis-myrtanyl); some comparative bond lengths in
Fig. 5 Molecular structure of [Sn{j2-N(R)C(C6H4Me-4)NPh}2] (4) (20%
ellipsoids; H atoms omitted).
◦
˚
Table 3 Selected bond lengths [A] and angles [ ] for 2
the latter are Zr–Cl 2.679(6), Zr–N1 2.293(5), Zr–N2 2.249(5), N1–
5
˚
C1 1.322(9) and N2–C1 1.348(9) A. Another related crystalline
Al · · · C(1)
Al–C(35)
Al–N(1)
Al–N(2)
C(1)–N(1)
C(1)–N(2)
2.421(2)
1.954(2)
1.9361(16)
2.0635(17)
1.344(2)
1.323(2)
Al · · · C(18)
2.393(2)
complex is [Zr{N(R)C(Ph)NR}3Cl]·CH2Cl2,20 having geometrical
parameters close to those of 6b.
Al–N(3)
Al–N(4)
C(18)–N(3)
C(18)–N(4)
1.9390(16)
2.0589(18)
1.340(2)
1.325(2)
N(1)–Al–N(2)
N(1)–Al–N(3)
N(1)–Al–N(4)
N(1)–C(1)–N(2)
C(1)–N(1)–Al
C(1)–N(2)–Al
66.76(6)
112.74(7)
94.60(7)
111.37(17)
93.36(11)
88.46(12)
N(3)–Al–N(4)
N(3)–Al–N(2)
N(4)–Al–N(2)
N(3)–C(18)–N(4)
C(18)–N(3)–Al
C(18)–N(4)–Al
67.08(6)
93.67(7)
146.42(7)
112.10(17)
91.86(11)
87.17(12)
◦
˚
Table 4 Selected bond lengths [A] and angles [ ] for 4
Sn–N(1)
Sn–N(3)
Sn · · · C(1)
C(1)–N(1)
C(1)–N(2)
2.215(2)
2.210(2)
2.718(4)
1.330(3)
1.322(3)
Sn–N(2)
Sn–N(4)
Sn · · · C(18)
C(18)–N(3)
C(18)–N(4)
2.365(2)
2.380(2)
2.722(4)
1.338(3)
1.321(3)
N(1)–Sn–N(2)
N(1)–Sn–N(4)
N(1)–Sn–N(3)
N(1)–C(1)–N(2)
C(1)–N(1)–Sn
C(1)–N(2)–Sn
58.17(8)
82.53(8)
94.92(9)
114.5(2)
96.91(15) C(18)–N(3)–Sn
90.41(15) C(18)–N(4)–Sn
N(3)–Sn–N(4)
N(3)–Sn–N(2)
N(2)–Sn–N(4)
N(3)–C(18)–N(4)
58.15(8)
83.12(8)
122.30(8)
114.4(2)
97.17(15)
89.97(15)
Fig. 6 Molecular structure of [Zr{j2-N(R)C(C6H4Me-4)NPh}3Cl] (3
toluene) (6b) (20% ellipsoids; H atoms omitted).
Table 6 provides a summary of the mean intrametallacyclic
MN(R)C(Ar)NPh bond lengths and angles and the sum of the
angles subtended at N(R) and N(Ph) for complexes 2–4 and 6b;
also shown are the deviations from planarity for each ring as
manifested by the bending along each N(R) · · · N(Ph) vector. For
2–4 bond lengths decrease in the sequence M–N(R) > M–N(Ph)
and N(Ph)–C(Ar) > N(R)–C(Ar) and angles in the order M–
N(Ph)–C(Ar) > M–N(R)–C(Ar). For 6b both trends are reversed;
which is attributed to its greater steric compression (compared
with each of 2–4), as also manifested in that none of its three four-
membered rings is as close to planarity as is one of the two rings
in 2–4.
and 15 are pseudo-axial, with the angle N2–Al–N4 = 146.4◦ (2
and 14) and = 146.3◦ in 15.
Two forms of the tris(j2-benzamidinato)zirconium chloride 6
were crystallised as toluene solvates: 6·2.5PhMe (6a) and 6·3PhMe
(6b). Although the X-ray structures for both were solved, the
data for 6a were limited and hence only those for 6b are
presented. The molecular structure of 6b is illustrated in Fig. 6 and
selected geometrical parameters are in Table 5. The three chelated
C1-symmetric benzamidinato ligands are disposed around the
zirconium atom in a propeller-like fashion, the Zr being the centre
of a chloride-capped severely distorted octahedron with each of
the pairs of N1/N4, N2/N5 and N3/N6 atoms in a pseudo-
transoid arrangement. The SiMe3 substituents at N2, N4 and N6
The molecular structure of the crystalline benzamidine
=
H2NC(C6H4Me-4) NPh (11) is illustrated in Fig. 7. Selected
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Table 6 The ligand [N(R)C(Ar)N(Ph)]− (R = SiMe3, Ar = C6H4Me-4): some average structural parameters for the metal benzamidinates 2–4 and 6b
Compound
d/A
a/◦
b/◦
c /◦
d/◦
RN(R)/◦
RN(Ph)/◦
a
˚
a/A
˚
b/A
˚
c/A
˚
2
1.937
1.933
2.213
2.297
2.062
2.007
2.373
2.222
1.342
1.345
1.334
1.332
1.324
1.320
1.322
1.337
92.6
91.65
97.1
92.0
87.9
89.2
90.2
95.2
111.7
111.2
114.4
113.1
66.9
67.8
58.2
59.0
359.0
359.4
357.3
360.0
356.0
360.0
358.3
355.9
2.7, 14.9
1.3, 4.2
2.6, 5.8
3
4
6b
8.2, 8.8, 8.3
a Deviation from planarity: bending along the N(Ph)–N(R) vector for each benzamidinato ligand.
◦
21
˚
=
Table 7 Selected bond lengths [A] and angles [ ] for 11 and H2NC(C6H4NO2-4) NPh (16)
11
16
11
16
C(1)–N(2)
C(1)–N(1)
N(2)–H(2a)
1.348(3)
1.297(3)
0.884
1.355(5)
1.280(5)
C(1)–C(2)
N(1)–C(9)
N(2)–H(2b)
1.491(3)
1.424(3)
0.927
1.495(4)
1.404(4)
N(1)–C(1)–N(2)
124.0(2)
118.48(16)
76.9
125.9(2)
120.9(3)
78.9
N(1)–C(1)–C(2)
N(2)–C(1)–C(2)
118.68(17)
117.27(18)
117.8(3)
116.3(3)
C(1)–N(1)–C(9)
aa
bb
24.6
21.4
a Angle between the C6H5 and N(1)C(1)N(2) planes. b Angle between the C6H4X-4 and N(1)C(1)N(2) planes.
Table 8 Ethylene polymerisation activity for 5 and 6
Concentration
M/mol L−1
Polymer
yielda /g
Activity/kg polyethylene
mol Zr−1 h−1 bar−1
Catalyst
5
6
0.33 × 10−3
0.51
0.2
7.7
8.6
0.12 × 10−3
a Polymerisation conditions: cocatalyst MAO (Al : Zr 500 : 1), solvent
toluene, reaction time 1 h.
=
Fig. 7 Molecular structure of H2NC(C6H4Me-4) N(Ph) (11) (20%
ellipsoids; H atoms omitted).
Experimental
geometrical parameters are listed in Table 7 which also shows
comparative and broadly similar data for H2NC(C6H4NO2-4) =
NPh (16).21 Both have the Z-configuration and are monomers,
All manipulations were carried out under argon or in vacuo
using standard Schlenk techniques. Solvents were pre-dried over
sodium, distilled from sodium (toluene), sodium–potassium al-
loy (pentane, hexane) or sodium-benzophenone (diethyl ether,
˚
although 11 has a relatively short contact of ca. 2.96 A between
the amino H(2a) atom and the imino nitrogen atom N1ꢀ of a
˚
tetrahydrofuran) and stored over molecular sieves (4 A). Deu-
neighbouring molecule.
teriated benzene was likewise stored over such molecular sieves
and degassed prior to use. Tetramethylethylenediamine (tmeda),
benzonitrile, p-toluonitrile, aniline, AlMeCl2, SnCl2, ZrCl4 and n-
butyllithium in hexanes (1.6 mol dm−3, FMC corporation) were
commercial samples used without further purification. The com-
pounds NH(R)Ph, Li[N(R)Ph] and Na[N(R)Ph] were obtained as
previously described.12 K[N(R)Ph] was prepared in situ by direct
transmetallation in diethyl ether of Li[N(R)Ph] with K[OBut]. The
NMR solution spectra were recorded on Bruker DPX 300 (1H,
13C and 7Li) or AMX 500 (for 23Na, 29Si and 27Al) instruments and
referenced externally (using aqueous LiNO3 with a D2O lock for
7Li, aqueous NaOH with a D2O lock for 23Na, aqueous Al(OH)3
Polymerisation experiments
The bis(benzamidinato)metal derivatives 2 and 5 and the
tris(benzamidinato)zirconium chloride 6 were tested as procata-
lysts for ethylene polymerisation with methylaluminoxane (MAO)
(Al : M = 500 : 1) as activator under the mild conditions of ambient
temperature and 1 bar ethylene pressure in toluene, see Table 8.
Both 5 and 6 showed moderate activity (producing about 8 kg
polyethylene mol Zr−1 h−1 bar−1), unlike 2. Whereas MAO has the
role of both a methylating agent and a Lewis acid with 5 and 6,
for 2 only the latter function would have been relevant.
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with a D2O lock for 27Al, or SiMe4 for 29Si) or internally (1H, 13C) to
the residual solvent resonances; chemical shift data in d. All NMR
spectra were examined at 293 K in C6D6 and, except for 1H, were
proton-decoupled. Electron impact mass spectra were taken on a
Kratos MS 80 RF instrument. Elemental analyses were carried
out by Medac Ltd., UK, Brunel University. Melting points were
taken in sealed capillaries and are uncorrected.
2.1 mmol) in hexane (150 cm3), which was kept at −78 ◦C for
30 min, then allowed to warm to ambient temperature and set
aside for 2 d. The mixture was filtered; the concentrated filtrate
at −20 ◦C yielded white crystals of compound 4 (0.70 g, 55%)
(Found: C, 67.4; H, 7.05; N, 9.02. C34.5H43.5AlCl0.5N4Si2 requires
C, 67.4; H, 7.12; N, 9.10%), mp 180 ◦C. 1H NMR: d −0.06 (s, 9H,
Si(CH3)3; X = Me), 0.03 (s, 9 H, Si(CH3)3; X = Cl), 0.15 (s, 1.5 H,
1/2 CH3), 1.91 (s, 6 H, C6H4CH3), 6.70–7.11 (m, 18 H, C6H5 +
C6H4); 13C NMR: d −0.2 (AlCH3), 1.5 (Si(CH3)3; X = Me), 1.7
(Si(CH3)3; X = Cl), 20.9 (C6H4CH3), 123.8, 124.3, 126.5, 126.8,
132.0, 133.2, 138.9, 139.4, 144.1 and 145.5 (C6H5 + C6H4), 179.2
(central diazaallyl C); 27Al NMR: d 21.5 (broad s, Dx1/2 850 Hz,
Al–CH3), 60.3 (broad s, Dx1/2 1.5 kHz, Al–Cl); 29Si NMR: d −1.67
(Si(CH3)3; X = Me), 0.65 (Si(CH3)3; X = Cl). MS (m/z, %): 589
([Al{N(R)C(C6H4Me)NPh}2Me–X]+, 100).
Preparations
[Li{l:j2-N(R)C(C6H4Me-4)NPh}(OEt2)]2 (1). LiBun (31 cm3
of a 1.6 mol dm−3 solution in hexanes, 49.6 mmol) was added
dropwise over 15 min to a cold (0 ◦C) solution of NH(R)Ph
(7.99 g, 48.34 mmol) in Et2O (100 cm3). After ca. 2 h the
light yellow solution was set aside at ambient temperature. A
solution of p-toluonitrile (5.81 g, 49.6 mmol) in Et2O (20 cm3)
was added dropwise over 10 min; the resulting orange solution
was set aside overnight at ambient temperature. After partial
removal of the volatiles in vacuo (to ca. 1/3 original volume),
crystallisation at ambient temperature yielded bright yellow
crystals of compound 1 (10.02 g, 60%) (Found; C, 69.0; H, 8.38;
N, 7.94. C42H62Li2N4O2Si2 requires C, 69.6; H, 8.62; N, 7.72%),
[Sn{j2-N(R)C(C6H4Me-4)NPh}2] (4). Solid SnCl2 (0.36 g,
1.9 mmol) was added to a solution of compound 1 (1.14 g,
3.15 mmol) in diethyl ether (100 cm3) at ambient temperature.
The mixture was kept at ambient temperature overnight. Volatiles
were removed in vacuo to yield a brown solid, which was extracted
with toluene (2 × 15 cm3). The concentrated extract at −20 ◦C
yielded colourless crystals of compound 4 (0.99 g, 75%) (Found:
C, 59.2; H, 6.16; N, 8.62.◦C34H42N4Si2Sn requires C, 59.9; H, 6.21;
◦
1
mp 108–110 C. H NMR: d 0.07 (bs, 9 H, Si(CH3)3), 1.11 (t,
3JHH = 7 Hz, 6 H, CH3–CH2), 1.91 (s, 3 H, C6H4CH3), 3.29
3
(q, JHH = 7 Hz, 4 H, CH3–CH2), 6.80 (m, 3 H, arom.), 7.1
1
(br m, 6 H, arom.); 13C NMR: d 3.4 (Si(CH3)3), 15.4 (CH3–
CH2), 21.1 (C6H4CH3), 65.8 (CH3–CH2), 116.6, 122.0, 126.4,
129.6, 132.2, 136.8, 139.2 and 151.6 (C6H5 + C6H4), 177.1 (central
N, 8.22%), mp 126–128 C. H NMR: d 0.03 (s, 9 H, Si(CH3)3),
3
1.83 (s, 3 H, C6H4CH3), 6.67 (d, JHH = 7 Hz, 2 H, 3,5-H of
3
C6H4CH3), 6.77 (t, JHH = 8 Hz, 1 H, 4-H of C6H5), 6.84 (d,
3
3JHH = 7 Hz, 2H, 3,5-H of C6H5), 6.98 (d, JHH = 8 Hz, 2 H,
7
diazaallyl C); 29Si NMR: d 2.09, −4.05, −4.37 and −6.49; Li
3
NMR: d 1.69. MS (m/z, %): 282 ([H{N(R)C(C6H4Me)NPh}]+,
45), 267 ([H{N(R)C(C6H4Me)NPh}–Me]+, 45), 191 ([H{N(R)-
C(C6H4Me)NPh}–Ph–Me]+, 50), 165 ([H{N(R)C(C6H4Me)-
NPh}–Ph–Me–CN]+, 60), 150 ([165-N]+, 75), 117 ([H{N(R)-
C(C6H4Me-4)NPh}–Ph–Me–SiMe3]+, 40), 73 ([SiMe3]+, 70).
2,6-H of C6H5), 7.05 (d, JHH = 7 Hz, 2 H, 2,6-H of C6H4CH3);
13C NMR: d 2.2 (Si(CH3)3), 21.1 (C6H4CH3), 119.5, 123.1, 126.1,
128.8, 138.7, 141.4 and 146.6 (C6H5 + C6H4), 173.2 (central
diazaallyl C); 119Sn NMR: d −228.3 (v. small), −140.1; 29Si NMR: d
2.24 (Si(CH3)3). MS (m/z, %): 681 ([Sn{N(R)C(C6H4Me)NPh}2]+,
75), 401 ([Sn{N(R)C(C6H4Me)NPh}2–{N(R)C(C6H4Me)NPh}]+,
85), 281 ([{N(R)C(C6H4Me)NPh}]+, 30), 211 (100), 190
([{C(C6H4Me)N(SiMe3)]+, 85), 149 (25), 73 ([SiMe3]+, 100), 45
(20).
[Al{j2-N(R)C(C6H4Me-4)NPh}2Me] (2).
A
solution of
AlMeCl2 (3.6 cm3, 1 mol dm−3 in hexane, 3.6 mmol) was added
to a cold (−78 ◦C) solution of compound 1 (2.61 g, 7.2 mmol)
in hexane (120 cm3), which was kept at −78 ◦C for 10 min,
then allowed to warm to ambient temperature overnight. The
mixture was filtered and the precipitate extracted with hexane
(20 cm3). The extract was filtered; crystallisation of the filtrate
at −20 ◦C yielded colourless crystals of compound 2 (1.15 g,
60%) (Found: C, 66.9 (duplicate analyses); H, 7.27; N, 8.69.
C35H45AlN4Si2 requires C, 69.5; H, 7.50; N, 9.26%), mp 169–
170 ◦C. 1H NMR: d 0.21 (s, 9 H, Si(CH3)3), 0.29 (s, 1.5 H,
[Zr{j2-N(R)C(C6H4Me-4)NPh}2Cl2] (5). Solid ZrCl4 (0.73 g,
3.13 mmol) was added to a solution of compound 1 (2.30 g,
6.35 mmol) in diethyl ether (50 cm3) at ambient temperature. The
yellow suspension was kept at ambient temperature overnight.
Volatiles were removed in vacuo to yield a clear solid which
was extracted with pentane (2 × 15 cm3). Evaporation of the
extract yielded compound 5 as a white powder (2.27 g, 95%)
(Found: C, 56.8; H, 5.92; N, 7.67. C34H◦42Cl2N4Si2Zr requires
3
1/2 CH3), 1.85 (s, 3 H, C6H4CH3), 6.68 (d, JHH = 8 Hz, 2
3
H, 3,5-H of C6H4), 6.81 (t, JHH = 7 Hz, 1 H, 4-H of C6H5),
1
C, 56.3; H, 5.84; N, 7.73%), mp 255–257 C. H NMR: d 0.37
7.10 − 6.99 (6 signals, 6 H); 13C NMR: d −7.6 (AlCH3), 1.8
(Si(CH3)3), 21.1 (C6H4CH3), 123.9, 126.8, 127.7, 128.6, 129.9,
123.2, 138.9 and 145.5 (C6H5 + C6H4), 177.7 (central diazaallyl
C); 27Al NMR: d 25 (broad s, Dx1/2 1.2 kHz); 29Si NMR:
d −1.6. MS (m/z, %): 589 ([Al{N(R)C(C6H4Me)NPh}2Me–
Me]+, 100), 514 ([Al{N(R)C(C6H4Me)NPh}2Me–C6H4Me +
H]+, 15), 307 ([Al{N(R)C(C6H4Me)NPh}Me–Me]+, 30), 190
([{C(C6H4Me)N(SiMe3)]+, 55), 149 (25), 73 ([SiMe3]+, 75).
3
(s, 9 H, Si(CH3)3), 1.83 (s, 3 H, C6H4CH3), 6.70 (d, JHH
=
3
8 Hz, 2 H, 3,5-H of C6H4CH3), 6.79 (t, JHH = 7 Hz, 1 H, 4-
3
H of C6H5), 7.03 (m, 4 H, 2,3,5,6-H of C6H5), 7.37 (d, JHH
=
8 Hz, 2 H, 2,6-H of C6H4CH3); 13C NMR: d 2.5 (Si(CH3)3),
21.1 (C6H4CH3), 123.2, 125.9, 129.0, 134.1, 139.2 and 147.3
(C6H5 + C6H4), 177.4 (central diazaallyl C); 29Si NMR: d 1.01
(Si(CH3)3). MS (m/z, %): 970 ([Zr{N(R)C(C6H4Me)NPh}3Cl]+,
35), 687 ([Zr{N(R)C(C6H4Me)NPh}2Cl]+, 55), 570 (10),
407 (5), 281 ([{N(R)C(C6H4Me)NPh}]+, 25), 210 ([{N(R)-
C(C6H4Me)NPh}–R]+, 25), 190 ([{C(C6H4Me)N(SiMe3)]+, 95),
149 (20), 73 ([SiMe3]+, 100), 45 (20).
[Al{j2-N(R)C(C6H4Me-4)NPh}2X] (X = Cl/Me, 1 : 1) (3).
A
solution of AlMeCl2 (2.1 cm3, 1 mol dm−3 in hexane, 2.1 mmol)
was added to a cold (−78 ◦C) solution of compound 1 (1.54 g,
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4 H, 3,5-H of C6H5 and of C6H4CH3), 7.15 (d, 3JHH = 6 Hz, 4 H,
2,6-H of C6H5 and C6H4CH3); 13C NMR: d 3.5 (Si(CH3)3), 21.2
(C6H4CH3), 119.2, 124.5, 128.8, 129.7, 132.0, 136.2, 142.6 and
155.1 (C6H5 + C6H4), 171.8 (central diazaallyl C); 29Si NMR: d
−12.4. MS (m/z, %): 282 ([H{N(R)C(C6H4Me)NPh}]+, 30), 281
([{N(R)C(C6H4Me)NPh}]+, 30), 267 ([{N(R)C(C6H4Me)NPh}–
Me]+, 35), 210 ([H{N(R)C(C6H4Me)NPh}–R + 2H]+, 100), 165
([H{N(R)Ph}]+, 15), 147 (80), 118 (70), 104 (20), 93 (80), 77 ([Ph]+,
85), 73 ([SiMe3]+, 40).
Alternatively, 8 was prepared from 1. Solid KOBut (1.45 g,
12.92 mmol) was added to a hexane solution (200 cm3) of
1 (4.65 g, 12.84 mmol). The suspension was left for 60 h at
ambient temperature, and the precipitate was rinsed with hexane
(20 cm3) and dried in vacuo to yield 8 (3.80 g, 90%) as a white
powder.
[Zr{j2-N(R)C(C6H4Me-4)NPh}3Cl] (6). Solid ZrCl4 (0.30 g,
1.3 mmol) was added to a solution of compound 1 (1.41 g,
3.9 mmol) in diethyl ether (50 cm3) at ambient temperature. The
yellow suspension was kept at ambient temperature overnight.
Volatiles were removed in vacuo to give a clear solid which
was extracted with pentane (2 × 15 cm3). Evaporation of the
extract yielded the white powder of compound 6 (1.22 g, 97%).
X-Ray quality single crystals were obtained by crystallisation
from toluene at −30 ◦C (Found: C, 61.3; H, 6.48; N, 8.59.
C51H63ClN6Si3Zr requires C, 63.1; H, 6.54; N, 8.65%), mp
290 ◦C (decomp.). 1H NMR: d 0.37 (s, 9 H, Si(CH3)3), 1.84
3
(s, 3 H, C6H4CH3), 6.69 (d, JHH = 8 Hz, 2 H, 3,5-H of
3
C6H4CH3), 6.81 (t, JHH = 7 Hz, 1 H, 4-H of C6H5), 7.04 (t,
3
3JHH = 7 Hz, 4 H, 2,3,5,6-H of C6H5), 7.34 (d, JHH = 8 Hz,
2 H, 2,6-H of C6H4CH3); 13C NMR: d 2.5 (Si(CH3)3), 21.1
(C6H4CH3), 123.2, 126.0, 129.0, 129.1, 134.1, 139.1 and 147.4
(C6H5 + C6H4), 177.5 (central diazaallyl C); 29Si NMR: d 1.01
(Si(CH3)3). MS (m/z, %): 970 ([Zr{N(R)C(C6H4Me)NPh}3Cl]+,
2), 687 ([Zr{N(R)C(C6H4Me)NPh}2Cl]+, 5), 210 ([{N(R)-
C(C6H4Me)NPh}–R]+, 100), 73 ([SiMe3]+, 65), 45 (20).
Li[N(R)C(Ph)NPh](OEt2) (9). A solution of benzonitrile
(1.32 g, 12.80 mmol) in Et2O (20 cm3) was added dropwise
over 10 min to a cold (0 ◦C) solution of Li[N(R)Ph] (2.20 g,
12.81 mmol); the resulting orange solution was set aside for 30 min
at 0 ◦C and then overnight at ambient temperature. After partial
removal of the volatiles in vacuo (to ca. 1/3 original volume),
crystallisation at ambient temperature yielded colourless crystals
of compound 9 (1.78 g, 40%) (Found; C, 68.7; H, 8.18; N, 7.86.
[Na{l:j2-N(R)C(C6H4Me-4)NPh}(tmeda)]2 (7). A solution of
p-toluonitrile (1.38 g, 11.80 mmol) in toluene (20 cm3) was added
dropwise over 15 min to a cold (0 ◦C) suspension of Na[N(R)Ph]
(2.22 g, 48.34 mmol) in toluene (100 cm3). The orange suspension
was set aside for 30 min at 0 ◦C, then for 2 h at ambient
temperature; it was refluxed for 5 min and left overnight at
ambient temperature. The solvent was removed in vacuo. The
brown residual solid was triturated in pentane (40 cm3) and tmeda
(1.35 g, 11.61 mmol) was added to afford a clear solution, which
at −30 ◦C yielded colourless crystals of compound 7 (3.91 g, 80%)
(Found; C, 64.4; H, 6.33; N, 12.55. C46H74NaN82Si2 requires C,
C20H29LiN2OSi requires C, 68.9; H, 8.39; N, 8.04%), mp 155–
◦
1
3
160 C. H NMR: d 0.01 (bs, 9 H, Si(CH3)3), 1.11 (t, JHH
=
3
7 Hz, 6 H, CH3–CH2), 3.33 (q, JHH = 7 Hz, 4 H, CH3–CH2),
3
3
6.75 (t, JHH = 7 Hz, 1 H, 4-H of C6H5), 6.89 (t, JHH = 7 Hz,
3
1 H, 4-H of C6H5), 6.96–7.09 (6s, 6 H, arom.), 7.23 (d, JHH
=
7 Hz, 2 H, 2,6-H of C6H5); 13C NMR: d 3.3 (Si(CH3)3), 15.2
(CH3–CH2), 65.7 (CH3–CH2), 122.0, 126.4, 141.8, and 151.4
(C6H5 + C6H4), 177.0 (central diazaallyl C); 29Si NMR: d −1.97,
7
−4.10, −5.66 and −8.95; Li NMR: d 1.58. MS (m/z, %): 555
([Li2{N(R)C(Ph)NPh}2 + Li]+, 25), 445 ([Li2{N(R)C(Ph)NPh}2–
PhCN]+, 20), 349 ([Li{N(R)C(Ph)NPh}(OEt2)]+, 40), 342
([Li{N(R)C(Ph)NPh}(OEt2)–Li]+, 50), 281 ([Li2{N(R)C(Ph)-
NPh}]+, 80), 178 ([Li2{N(R)C(Ph)NPh}–PhCN]+, 80), 165
([HN(R)Ph]+, 75), 150 ([HN(R)Ph–Me]+, 100), 103 (95), 73
([SiMe3]+, 55).
◦
1
67.3; H, 6.63; N, 13.64%), mp 91–95 C. H NMR: d 0.15 (s,
9 H, Si(CH3)3), 1.86 (s, 4 H, CH2 of tmeda), 1.95 (s, 12 H, CH3
of tmeda), 2.02 (s, 3 H, C6H4CH3), 6.69 (t, 3JHH = 6 Hz, 1 H, 4-H
of C6H5), 6.90 and 6.93 (2 bs, 4 H, 2,3,5,6-H of C6H5), 7.06–7.11
3
(bm, 2 H, 3,5-H of C6H4CH3), 7.16 (d, JHH = 6 Hz, 2 H, 2,6-H
of C6H4CH3); 13C NMR: d 3.8 (Si(CH3)3), 19.6 (C6H4CH3), 45.6
(CH2 of tmeda), 57.3 (CH3 of tmeda), 119.2, 129.1, 129.6, 132.0,
135.7, 141.4 and 154.7 (C6H5 + C6H4), 174.4 (central diazaallyl
C); 29Si NMR: d −11.1; 23Na NMR: d 5.5, Dx1/2 2.6 kHz. MS
(m/z, %): 210 ([H{N(R)C(C6H4Me)NPh}–R + H]+, 100), 190
([H{N(R)C(C6H4Me)NPh}–Ph–Me]+, 45), 118 (30), 91 (80), 73
([SiMe3]+, 25).
[Zr{N(R)C(Ph)NPh}3Cl] (10). Solid ZrCl4 (0.60 g, 2.57 mmol)
was added to a solution of compound 9 (1.78 g, 5.11 mmol)
in toluene (50 cm3) at ambient temperature. The yellow suspen-
sion was kept at ambient temperature overnight, then filtered.
The filtrate was concentrated and cooled (at −30 ◦C) yielding
colourless crystals of compound 10 (1.92 g, 60%) (Found: C,
62.2; H, 6.20; N, 9.13. C48H57ClN6Si3Zr requires C, 62.1; H,
6.18; N, 9.05%), mp 265–272 ◦C. 1H NMR: d 0.34 (s, 9 H,
K[N(R)C(C6H4Me-4)NPh] (8). A solution of p-toluonitrile
(1.57 g, 13.40 mmol) in Et2O (20 cm3) was added dropwise
over 15 min to a cold (0 ◦C) suspension of K[N(R)Ph] (2.71 g,
13.34 mmol) in Et2O (120 cm3). The yellow mixture was kept for
30 min at 0 ◦C, then 2 h at ambient temperature, and filtered.
The precipitate was rinsed with Et2O (20 cm3); the combined
washings were concentrated to dryness to yield a white fluffy solid
which upon crystallisation from Et2O (40 cm3) at −30 ◦C yielded
colourless crystals of compound 8 (3.81 g, 90%) (Found; C, 63.5;
H, 6.47; N,◦9.05. C17H21KN2Si requires C, 63.7; H, 6.60; N, 8.74%),
3
Si(CH3)3), 6.78 (t, JHH = 7 Hz, 1H, 4-H of C6H5), 6.85 (br s,
3
3 H, C6H5), 7.01 (m, 3 H, C6H5), 7.11 (d, JHH = 7 Hz, 2 H,
3
2,6-H of C6H5), 7.28 (d, JHH = 8 Hz, 2 H, 2,6-H of C6H5);
13C NMR: d 2.4 (Si(CH3)3), 123.4, 125.7, 125.9, 139.3, 136.8
and 147.1 (C6H5), 177.2 (central diazaallyl C); 29Si NMR: d 1.01
(Si(CH3)3). MS (m/z, %): 928 ([Zr{N(R)C(Ph)NPh}3Cl]+, 25), 659
([Zr{N(R)C(Ph)NPh}2Cl]+, 85), 556 ([Zr{N(R)C(Ph)NPh}2Cl–
PhCN]+, 10), 267 ([Zr{N(R)C(Ph)NPh}2Cl–PhCN–ZrCl]+, 10),
176 ([{N(R)C(Ph)NPh}–Ph]+, 95), 73 ([SiMe3]+, 100).
1
=
mp 90–91 C. H NMR: d 0.06 (s, 9 H, Si(CH3)3), 2.07 (s, 3 H,
H2NC(C6H4Me-4) NPh (11). LiBun (28 cm3 of
a
3
C6H4CH3), 6.55 (t, JHH = 6 Hz, 1 H, 4-H of C6H5), 6.95 (m,
1.6 mol dm−3 solution in hexanes, 44.8 mmol) was added
592 | Dalton Trans., 2007, 585–594
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dropwise over 10 min to a cold (0 ◦C) solution of aniline (4.00 g,
42.9 mmol) in Et2O (60 cm3). The light yellow solution was
set aside for ca. 2 h at ambient temperature. A solution of
p-toluonitrile (5.18 g, 44.0 mmol) in Et2O (10 cm3) was then
added dropwise over 5 min. After 1 h, the Et2O was removed in
vacuo and replaced by thf (200 cm3). The resulting suspension
was then refluxed for 16 h and filtered at ambient temperature.
The white precipitate was rinsed with hexanes (2 × 20 cm3), dried
in vacuo and dissolved in Et2O (100 cm3) containing water (0.8 g,
44.4 mmol). The cloudy suspension was filtered. After partial
removal of the volatiles in vacuo (to ca. 1/3 original volume),
crystallisation at ambient temperature yielded colourless plates of
compound 11 (5.8 g, 65%), mp 153 ◦C. 1H NMR (acetone-d6): d
2.12 (s, 3 H, CH3), 2.86 and 3.79 (2 br s, 2 H, NH2), 6.87 (d, 3JHH
=
7 Hz, 2 H, 3,5-H of C6H5), 6.96 (t, 3JHH = 7 Hz, 1 H, 4-H of C6H5),
7.91 (d, 3JHH = 7 Hz, 2 H, 2,6-H of C6H5); 13C NMR: d 20.8 (CH3),
=
68.7 (C N), 121.9, 122.4, 127.3, 129.0, 129.6, 133.7, 140.4, 151.4
and 154.2 (C6H5 and central diazaallyl C). MS (m/z, %): 210
+
=
=
([NH2C(C6H4Me) NPh}] , 100), 194 ([NH2C(C6H4Me) NPh}–
+
+
=
MeH] , 40), 118 ([NH2C(C6H4Me) NPh}–PhNH] , 30), 93
([C6H5Me]+, 45), 77 ([C6H5]+, 40), 65 (15).
Ethylene polymerisation
In a typical polymerisation experiment, a glass reactor was fitted
with an inlet/outlet for ethylene/vacuum/argon. The reactor was
dried and degassed in vacuo for 1 h and then purged with argon.
The solvent was transferred via syringe and a toluene solution of
the catalyst was added. Finally MAO (10% by weight in toluene)
was transferred to the reaction mixture which was stirred for
5 min under argon pressure. The reactor was briefly depressurised
and ethylene entry was allowed at 1.1 bar pressure. The reaction
mixture was quenched after one hour with a 1 : 1 mixture
MeOH–aq. HCl 2M (20 cm3) and stirred for 15 min. The mixture
was filtered, and the precipitate rinsed with 10% aq. HCl then
EtOH and dried in vacuo at ambient temperature until constant
weight.
Crystal data and refinement details for 1–4, 6b and 11
Diffraction data were collected on a Enraf-Nonius CAD4 (1,
4) or Nonius Kappa-CCD (2, 3, 6b and 11) diffractometer at
˚
173(2) K, using monochromated Mo-Ka radiation, k 0.71073 A.
Crystals were mounted on the diffractometer under a stream
of cold nitrogen gas at 173(2) K. The structures were refined
on all F2 with H atoms in riding mode, using SHELXL-97.22
Absorption corrections were only applied for 4 (using psi-scans)
and 6b (using MULTISCAN). For 3, the Cl atom and C(35)
(of the Al–Me) could not be resolved and were included as a
single site; consequently geometric parameters involving these
atoms are not meaningful. One of the three toluene solvate
molecules of 6b was distorted over two partially overlapping
positions and was refined with bond length constraints. For 11, all
hydrogen atoms were freely refined. Further details for are found in
Table 9.
CCDC reference numbers 622818–622824.
For crystallographic data in CIF or other electronic format see
DOI: 10.1039/b614351b
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8 C.-T. Chen, L. H. Rees, A. R. Cowley and M. L. H. Green, J. Chem.
Soc., Dalton Trans., 2001, 1761.
Acknowledgements
9 M. P. Coles and R. F. Jordan, J. Am. Chem. Soc., 1997, 119, 8125.
10 (a) F. Antolini, P. B. Hitchcock, A. V. Khvostov and M. F. Lappert,
Can. J. Chem., 2006, 84, 269; (b) P. B. Hitchcock, M. F. Lappert and
R. Sablong, Dalton Trans., 2006, 4146.
We thank the European Commission for the award of a Marie
Curie fellowships for P. G. M. and Dr A. V. Protchenko for useful
comments.
11 A. V. Khvostov, P. B. Hitchcock and M. F. Lappert, unpublished work.
12 J.-P. Bezombes, P. B. Hitchcock, M. F. Lappert and P. G. Merle, J. Chem.
Soc., Dalton Trans., 2001, 816.
13 F. Antolini, P. B. Hitchcock, M. F. Lappert and P. G. Merle, Chem.
Commun., 2000, 1301.
14 F. C. Cooper and M. W. Partridge, J. Chem. Soc., 1953, 255.
15 C. Knapp, E. Lork, P. G. Watson and R. Mews, Inorg. Chem., 2002, 41,
2014.
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594 | Dalton Trans., 2007, 585–594
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©