Synthesis and characterisation of novel zirconium(IV) derivatives containing the bis-amido ligand SiMe2(NRR′)2

Article abstract of DOI:10.1039/b212705a

The silicon compounds SiMe₂(NRR′)₂ [NRR′ = NMe₂ (1), NEt₂ (2), NC₄H₈ (3), NHEt (4), NHⁱPr (5), NH^tBu (6), NMeBu (7)] have been synthesised via aminolysis of the dichloro species SiMe₂Cl ₂ and their ligating ability has been investigated towards zirconium(IV). The dimer zirconium compound {Zr[(NⁱPr) ₂SiMe₂]₂}₂ (8) has been synthesised by reacting ZrCl₄ with the lithium salt Li₂[(N ⁱPr)₂SiMe₂] and its molecular structure has been determined in the solid state by X-ray diffraction analysis. The reaction of ZrCl₄ with SiMe₂(NRR′)₂ yields the Lewis adducts ZrCl₄[(NRR′)₂SiMe₂] [NRR′ = NMe₂ (10), NC₄H₈ (11), NHEt (12), NHⁱPr (13), NH^tBu (14), NMeBu (15)]. On the other hand, the mixed amido derivative Zr(NMe₂)₃(NHMe)[(N′Bu) SiMe₂(NH′Bu)] (9) has been obtained from the reaction of Zr(NMe₂)₄ with SiMe₂(NH^tBu) ₂. The solution molecular structure and dynamics of the zirconium derivatives have been elucidated by 1D and 2D multinuclear NMR spectroscopy.

Full text of DOI:10.1039/b212705a

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Synthesis and characterisation of novel zirconium(IV) derivatives
containing the bis-amido ligand SiMe2(NRRЈ)2
Vincenzo Passarelli,* Franco Benetollo, Pierino Zanella, Giovanni Carta and Gilberto Rossetto
ICIS–CNR, Area della Ricerca di Padova, Corso Stati Uniti 4, I–35127 Padova, Italy
Received 2nd January 2003, Accepted 3rd February 2003
First published as an Advance Article on the web 18th February 2003
The silicon compounds SiMe2(NRRЈ)2 [NRRЈ = NMe2 (1), NEt2 (2), NC4H8 (3), NHEt (4), NHiPr (5), NHtBu (6),
NMeBu (7)] have been synthesised via aminolysis of the dichloro species SiMe2Cl2 and their ligating ability has been
investigated towards zirconium(). The dimer zirconium compound {Zr[(NiPr)2SiMe2]2}2 (8) has been synthesised by
reacting ZrCl4 with the lithium salt Li2[(NiPr)2SiMe2] and its molecular structure has been determined in the solid
state by X-ray diffraction analysis. The reaction of ZrCl4 with SiMe2(NRRЈ)2 yields the Lewis adducts ZrCl4[(NRRЈ)2-
SiMe2] [NRRЈ = NMe2 (10), NC4H8 (11), NHEt (12), NHiPr (13), NHtBu (14), NMeBu (15)]. On the other hand,
the mixed amido derivative Zr(NMe2)3(NHMe)[(NtBu)SiMe2(NHtBu)] (9) has been obtained from the reaction of
Zr(NMe2)4 with SiMe2(NHtBu)2. The solution molecular structure and dynamics of the zirconium derivatives have
been elucidated by 1D and 2D multinuclear NMR spectroscopy.
1
The H and 13C NMR spectra of the compounds show the
Introduction
resonances of the [SiMe2] moiety and of the amido groups
(Table 1).
Amido or amino zirconium derivatives have been synthesised1
and used in the deposition of zirconium nitride via CVD2
As far as the isopropyl derivative 6 is concerned, additional
or ceramic processes,3 showing that the nature of the amino or
comments are in order. Besides the ordinary coupling of the
amido ligands affects the composition and consequently the
methyne proton with the methyl ones (3JHH = 6.4 Hz), vicinal
properties of the final materials. In this connection, the syn-
coupling with NH (3JHH = 10.0 Hz) is also observed, the
thesis of novel volatile amido or amino zirconium derivatives
methyne resonance appearing as a double septet at 3.08 ppm.
is an attractive field. Moreover, a survey of the literature has
As a confirmation, the proton COSY spectrum shows a cross-
shown that a few data are available concerning the ligating
peak between the resonance at 0.42 (NH) and 3.08 ppm (CH).
ability4 of bis-amido–dialkylsilanes (I) towards zirconium().
Nevertheless, the 1H NMR spectrum shows the NH resonance
as a broad line reasonably due to the quadrupolar effect of the
14N nucleus. A similar phenomenon has already been observed
for Si(NHiPr)4.9
Synthesis and characterisation of {Zr[(NiPr)2SiMe2]2}2
The reaction of ZrCl4 with the lithium salt Li2[(NiPr)2SiMe2]
[obtained from the reaction of LiBu with SiMe2(NHiPr)2]
(eqn. (2)) yields the dimer zirconium derivative {Zr[(NiPr)2-
As a matter of fact, the spirocyclic species Zr[(NtBu)2SiMe2]2
SiMe2]2}2 (8), obtained as a microcrystalline pure material after
crystallisation from toluene–pentane at 243 K (58% yield).
has been synthesised from SiMe2(NHtBu)2 and eventually
structurally characterised,5 and some data have appeared
relating to the adduct ZrCl4[(NMe2)2SiMe2].6, 7 In addition,
recently Gibson et al.8 have synthesised and structurally charac-
terised the pentacoordinated zirconium derivative Zr(NMe2)2-
(NHMe2)[(NPh)2SiMe2)] (Ph = 2,6-Me2C6H3).
(2)
In this connection, we report on the synthesis of novel bis-
amido–dialkylsilanes and on the investigation of their ligating
ability towards zirconium().
The crystal structure of 8 shows that the compound is a
dimer, containing a [Zr2N2] core, formed by the coupling of
Results and discussion
two Zr[(NiPr)2SiMe2]2 units (Fig. 1(A)). The bridging ligands
are asymmetrically coordinated to the zirconium centres, each
containing one µ2 nitrogen atom [N(2), N(3)] and an η1 one
[N(1), N(4)]. The coordination polyhedron of each zirconium
centre is a distorted trigonal bipyramid (Fig. 1(B)), with N(3),
N(4), N(8) and N(1), N(2), N(6) in the equatorial planes, and
N(2), N(7) and N(3), N(5) in the apical positions, respectively.
Selected bond distances and angles are reported in Table 2.
Due to the different coordination modes of the SiMe2(NiPr)2
ligands, different Zr–N bond distances are observed (Table 2).
Moreover, also the N–Zr–N and N–Si–N angles vary as a
function of the hapticity of the ligand: N(5)–Zr(1)–N(6), N(7)–
Zr(2)–N(8), 76.5Њ av.; N(1)–Zr(1)–N(3), N(2)–Zr(2)–N(4),
69.1Њ, av.; N(5)–Si(3)–N(6), N(7)–Si(4)–N(8), 94.2Њ, av.; N(1)–
Si(1)–N(3), N(2)–Si(2)–N(4), 98Њ, av. (Table 2).
Synthesis of SiMe2(NRRЈ)2
The silicon derivatives SiMe2(NRRЈ)2 [NRRЈ = NMe2 (1), NEt2
(2), NC4H8 (3), NMeBu (4), NHEt (5), NHiPr (6), NHtBu (7)]
have been synthesised by aminolysis of SiMe2Cl2 with the
appropriate amine (eqn. (1)), the chlorides being eliminated as
the ammonium salt [NH2RRЈ]Cl.
(1)
T h i s j o u r n a l i s © T h e R o y a l S o c i e t y o f C h e m i s t r y 2 0 0 3
D a l t o n T r a n s . , 2 0 0 3 , 1 4 1 1 – 1 4 1 8
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Table 1 Selected 1H and 13C NMR data for SiMe2(NRRЈ)2
δH
δC
Compound
SiCH3
R
SiCH3
R
Ref.
SiMe2(NMe2)2 (1)
SiMe2(NEt2)2 (2)
SiMe2(NC4H8)2 (3)
SiMe2(NMeBu)2 (4)
Ϫ0.08
0.14
0.18
2.44 (CH3)
2.82 (CH2), 0.99 (CH3)
Ϫ3.4
Ϫ0.9
Ϫ2.9
Ϫ2.20
37.6 (CH3)
39.6 (CH2), 15.8 (CH3)
46.9 (NCH2), 27.2 (NCH2CH2)
50.1 (NCH2), 34.2 (NCH2CH2), 31.8
(NCH3), 20.6 (CH2CH3), 14.4
(CH2CH3)
36.0 (CH2), 20.5 (CH3)
42.3 (CH), 27.9 (CH3)
49.2 (C), 33.8 (CH3)
7,a
a
a
a
2.97 (NCH2), 1.61 (NCH2CH2)
2.73 (NCH2), 2.45 (NCH3), 1.43
(NCH2CH2), 1.26 (CH2CH3), 0.92
(CH2CH3)
2.77 (CH2), 1.05 (CH3), 0.42 (NH)
3.08 (CH), 1.03 (CH3), 0.42 (NH)
1.19 (CH3), 0.52 (NH)
0.12
a
a
SiMe2(NHEt)2 (5)
SiMe2(NHiPr)2 (6)
SiMe2(NHtBu)2 (7)
0.01
Ϫ0.01
0.18
Ϫ1.33
Ϫ0.38
3.7
5,a
a This work.
Table 2 Selected bond distances (Å) and angles (Њ) for {Zr[(NiPr)2-
SiMe2]2}2 (8)
Zr(1)–N(1)
Zr(1)–N(2)
Zr(1)–N(3)
Zr(1)–N(5)
Zr(1)–N(6)
Si(1)–N(1)
Si(2)–N(2)
Si(3)–N(5)
Si(4)–N(7)
2.075(6)
2.240(6)
2.496(6)
2.075(6)
2.082(6)
1.737(7)
1.768(6)
1.751(7)
1.753(8)
Zr(2)–N(2)
Zr(2)–N(3)
Zr(2)–N(4)
Zr(2)–N(7)
Zr(2)–N(8)
Si(1)–N(3)
Si(2)–N(4)
Si(3)–N(6)
Si(4)–N(8)
2.577(6)
2.269(6)
2.082(7)
2.078(6)
2.064(7)
1.763(7)
1.717(7)
1.752(7)
1.756(7)
N(1)–Zr(1)–N(2)
N(1)–Zr(1)–N(5)
N(2)–Zr(1)–N(3)
N(2)–Zr(1)–N(6)
N(5)–Zr(1)–N(6)
N(2)–Zr(2)–N(4)
N(2)–Zr(2)–N(8)
N(3)–Zr(2)–N(7)
N(4)–Zr(2)–N(7)
N(7)–Zr(2)–N(8)
N(2)–Si(2)–N(4)
N(5)–Si(3)–N(6)
110.9(2)
99.1(3)
84.1(2)
127.6(2)
76.2(3)
68.9(2)
98.4(2)
109.8(2)
103.4(3)
76.7(3)
99.9(3)
94.1(3)
N(1)–Zr(1)–N(3)
N(1)–Zr(1)–N(6)
N(2)–Zr(1)–N(5)
N(3)–Zr(1)–N(5)
N(3)–Zr(1)–N(6)
N(2)–Zr(2)–N(3)
N(2)–Zr(2)–N(7)
N(3)–Zr(2)–N(4)
N(3)–Zr(2)–N(8)
N(4)–Zr(2)–N(8)
N(1)–Si(1)–N(3)
N(7)–Si(4)–N(8)
69.3(2)
119.9(3)
111.4(2)
163.6(2)
98.9(2)
81.7(2)
168.4(2)
116.8(3)
122.9(2)
116.1(3)
97.0(3)
94.2(3)
Zr(2)–N(7), Zr(2)–N(8) 2.07 Å, av.], while similar N–Si–N
angles are observed for the two compounds (tert-butyl deriva-
tive,5 94.8Њ; isopropyl derivative, terminal ligand, 94.2Њ, av.).
As far as the solution molecular structure elucidation is con-
cerned, the 29Si NMR spectrum of 8 shows two resonances at
Ϫ12.2 and Ϫ38.0 ppm, thus indicating the presence of two non-
equivalent [SiMe2(NiPr)2] ligands. The monomer derivative
Zr[(NtBu)2SiMe2]2 † shows the 29Si signal at Ϫ40.5 ppm, thus
suggesting that the above mentioned resonance at Ϫ38.0 ppm
is due to a chelating bidentate (NiPr)2SiMe2 ligand.
On the other hand, as far as the isopropyl substituents are
concerned, two sets of signals have been observed in the 1D
(1H, 13C) and 2D (proton COSY, 1H–13C HMQC) NMR spectra
(Table 3). Moreover, two resonances appear for the [SiMe2]
moieties in the 1H and 13C NMR spectra (Table 3).
Fig. 1 (A) ORTEP view of the {Zr[(NiPr)2SiMe2]2}2 molecule (with
the numbering scheme adopted). (B) Coordination polyhedrons of the
zirconium centres in {Zr[(NiPr)2SiMe2]2}2 (8).
Furthermore, the proton NOESY spectrum shows negative
crosspeaks between the resonances at 1.44 (CCH3, 1) and 4.36
ppm (CH, 2), 1.32 (CCH3, 2) and 4.01 (CH, 1) ppm, 1.44
(CCH3, 1) and 1.32 (CCH3, 2) ppm, and 4.01 (CH, 1) and 4.36
(CH, 2) ppm, indicating that a dipolar correlation exists
between the two isopropyl groups (i.e. one “looks” at the
other), and suggesting that the dimer structure is reasonably
preserved in solution.
Interestingly, the titanium derivative Ti[(NiPr)2SiMe2]2 is a
monomer10 according to IR and multinuclear NMR spectro-
scopy, while for the tert-butyl derivative Zr[(NtBu)2SiMe2]2 a
monomeric structure has been reported5 (X-ray investigation),
containing two SiMe2(NtBu)2 groups, chelating the zirconium
centre via monodentate nitrogens (defining a pseudo-tetra-
hedral coordination polyhedron).
In our opinion, the different molecular structures of ZrL2
Moreover, the intense negative crosspeaks between the
resonances at 0.63 (SiCH3, b) and 1.32 ppm (CCH3, 2), and 0.56
(SiCH3, a) and 1.44 ppm (CCH3, 1) indicate that the a-labelled
i
t
[L = SiMe2(NR)2, R = Pr, Bu] are reasonably related to the
reduced steric hindrance of the isopropyl group with respect to
the tert-butyl group. On the other hand, the lower coordination
number in Zr[(NtBu)2SiMe2]2 with respect to {Zr[(NiPr)2Si-
Me2]2}2 causes a reduction of the Zr–N bond distances in
Zr[(NtBu)2SiMe2]2 (2.05 Å5) compared with the corresponding
bonds of the isopropyl derivative [Zr(1)–N(5), Zr(1)–N(6),
† The compound has been prepared according to the literature5 and the
1H, 13C and 29Si NMR spectra have been recorded (293 K, C6D6): δH,
1.33 (s, CCH3, 9H), 0.51 (s, SiCH3, 3H); δC, 56.2 (C), 36.3 (CCH3), 6.7
(SiCH3); δSi, 40.5.
D a l t o n T r a n s . , 2 0 0 3 , 1 4 1 1 – 1 4 1 8
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Table 3 Selected 1H and 13C NMR data for {Zr[(NiPr)2SiMe2]2}2 (8)
1
2
δH
4.01 (Ha)
1.44 (Hb)
4.36 (Ha)
1.32 (Hb)
δC
50.8 (Ca)
29.1 (Cb)
50.9 (Ca)
28.3 (Cb)
a
0.56
6.02
b
0.63
9.13
[SiMe2]
δH
δC
[SiMe2] moiety bears the 1-type [NiPr] groups, and that the
b-labelled [SiMe2] moiety bears the 2-type [NiPr] groups. In
addition, on one hand, the presence of negative crosspeaks
between the resonances at 0.56 ppm (SiCH3, a) and those at
4.01 (CH, 1) and 4.36 ppm (CH, 2), and, on the other, the
absence of crosspeaks between the resonances at 0.63 (SiCH3,
b) and 4.01 (CH, 1) and 4.36 ppm (CH, 2) indicates that (a)
the a-labelled SiMe2 moiety and the 1-type isopropyl groups
reasonably belong to the bridging ligand, (b) the 2-labelled
isopropyl groups (of the terminal ligand) are oriented so that
the methyne hydrogen points far from the [SiMe2] moiety,
i.e. towards the [Zr2N2] core, similar to the solid state structure
(Fig. 1(A)).
Provided that the solid state molecular structure is reason-
ably preserved in solution, one should expect three non-equiv-
alent isopropyls, i.e. (a) the two equivalent isopropyl groups
of the chelating ligands, and (b) the two non-equivalent iso-
propyls of the bridging ligands (Fig. 1(A)). As far as this
point is concerned, we propose that a fast chemical exchange
could occur between the [NiPr] groups of the bridging ligand
(Scheme 1), thus making them equivalent at 293 K.
Fig. 2 1H NMR spectra of {Zr[(NiPr)2SiMe2]2}2 (8) at different
temperatures (toluene-d8).
reasonably it occurs via a concerted attack/dissociation of the
nitrogens of the bridging ligand (Scheme 1). The mechanism
should be concerted (Scheme 1(A)), because the cleavage of the
bond between zirconium and the nitrogen atom of the bridging
ligand (Scheme 1(B)) should allow the terminal ligand to par-
ticipate to the exchange mechanism, making the terminal
and bridging ligands equivalent, and this can be reasonably
excluded on the basis of the collected data, and by taking into
1
account that the H NMR spectrum is not affected by raising
the temperature up to 343 K.
Reaction of Zr(NMe2)4 with SiMe2(NHtBu)2
The binary amido derivative Zr(NMe2)4 reacts with SiMe2-
(NHtBu)2 (molar ratio = 1 : 1) yielding Zr(NMe2)3(NHMe)-
[(NtBu)SiMe2(NHtBu)] (9) (eqn. (3)), no further reaction being
observed even after 5 h stirring at 373 K.
(3)
1
The H and 13C NMR§ spectra of the compound show the
characteristic resonance of the dimethylamido (1H, 3.03 ppm;
13C, 43.7 ppm) and the dimethylamino ligands (1H, 2.13 ppm,
13C, 39.0 ppm).¶ On the other hand, two non-equivalent
tert-butyl groups have been observed (CH3, 1H: a, 1.31 ppm, b,
1.04 ppm; 13C: a, 35.5 ppm; b, 31.7 ppm; C, 13C: a, 55.2; b,
52.7 ppm). Interestingly, the tert-butyl groups in the zirconium
1
derivative Zr[(NtBu)2SiMe2]2 yields the H resonance at 1.33
ppm (CH3) and the 13C resonances at 56.2 and 36.3 ppm, thus
suggesting that the tert-butylamido group is responsible for the
a-labelled set of resonances and that the b-labelled set of signals
is due to the uncomplexed tert-butylamino moiety. In addition,
the resonances of the SiMe2 moiety are observed at 0.36 ppm
(1H) and 6.86 ppm (13C), and a broad signal at 0.85 ppm (1H) is
present due to the NH protons.
Scheme 1
In this connection, the 1H NMR spectrum of the compound
at 183 K (Fig. 2) shows three resonances for the methyne pro-
tons at 4.6, 4.3 and 3.8 ppm (integral ratio 1 : 2 : 1), the reson-
ances at 4.6 and 3.8 ppm coalescing at 193 K,‡ thus confirming
the proposed exchange (Scheme 1).
On heating the C6D6 solution of the compound at 343 K, the
§ The 13C NMR resonances have been assigned through the 1H–13C
HMQC spectrum.
As far as the mechanism of this exchange is concerned,
‡ As far as the methyl resonances of the isopropyl groups and the SiMe2
moiety of the bridging ligand are concerned (1 and a in Table 3), vari-
ations are observed as a function of the temperature. However, the H
resonances at 1.44 (CCH3) and 0.56 ppm (SiCH3) broaden and appear
unresolved even at 183 K, thus preventing the assignment.
¶ Gibson et al. have reported8 that Zr(NMe2)4 reacts with SiMe2-
(NHPh)2 (Ph = 2,6-Me2C6H3) yielding the mixed amido derivative
Zr(NMe2)2(NHMe2)[(NPh)2SiMe2] the NMR spectra of which show
the resonances of the dimethylamido and dimethylamino ligands at
2.79 and 1.68 ppm (1H) and 41.65 and 39.43 ppm (13C), respectively.
1
D a l t o n T r a n s . , 2 0 0 3 , 1 4 1 1 – 1 4 1 8
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Table 4 Selection of 1H NMR data of ZrCl4[(NC4H8)2SiMe2] (11)
coalescences of the signals at 3.03 and 2.14 ppm, on one hand,
and those at 1.31 and 1.04 ppm, on the other, were observed,||
thus indicating that a chemical exchange occurs between (a)
the two non-equivalent [NMe2] moieties of the dimethylamido
ligand and of the coordinated dimethylamine (Scheme 2(A))
and (b) the two non-equivalent tert-butyl groups (of the coordi-
nated and uncoordinated NtBu moiety) with the consequent
proton 1,3-shift from one nitrogen to the other (Scheme 2(B)).
δH
Ha
3.23
3.39
0.82
1.28
Ϫ0.18
HaЈ
Hbv
HbЈ
SiMe2
indicative of the [NMe2] and [SiMe2] moieties, respectively.**
Correspondingly, the 13C NMR spectrum show two signals at
48.0 and Ϫ3.15 ppm, assigned to the dimethylamido and the
dimethylsilylene groups, respectively.
The 13C NMR spectrum of ZrCl4[(NC4H8)2SiMe2] (11) shows
two resonances at 57.3 (NCH2CH2) and 24.5 ppm (NCH2CH2),
indicative of the pyrrolidinide group, and at Ϫ3.0 ppm, due to
the dimethylsilylene moiety. On the other hand, in the 1H NMR
spectrum, two signals have been observed for each methylene
(3.39, 3.23 ppm, NCH2CH2; 1.28, 0.82 ppm, NCH2CH2), thus
indicating that the methylene protons experiment different
chemical environments. As a matter of fact, due to the co-
ordination of the ligand, the two faces of the C4H8N ring are
non-equivalent, one facing zirconium and the other silicon
(Table 4). This picture is fairly confirmed by the proton
NOESY spectrum, (a) negative crosspeaks being observed
between the resonance at Ϫ0.18 ppm (SiCH3) and those at
3.23 (NCH2CH2) and 0.82 ppm (NCH2CH2); (b) no crosspeaks
(i.e. dipolar correlation) being detected between the resonance
of the dimethylsilylene group and those at 3.39 and 1.28 ppm.
The proposed molecular structure and the assignment of the
1H NMR resonances are reported in Table 4.
Scheme 2
The proton NOESY spectrum of the compound (298 K)
shows positive crosspeaks between the resonances at 3.03
(NMe2) and 2.14 ppm (NHMe), and those at 1.31 (tert-butyl-
amido group) and 1.04 ppm (tert-butylamino group), confirm-
ing the above proposed chemical exchanges. Moreover, negative
crosspeaks have been detected between the resonances of the
tert-butyl groups and the dimethylamido ligand, and no corre-
lation peaks have been observed between the resonance of the
coordinated dimethylamine and the tert-butyl protons, thus
suggesting that the coordination polyhedron of the zirconium
could be a trigonal bipyramid, the equatorial positions being
occupied by the dimethylamido ligand, and the apical positions
by the coordinated dimethylamine and the (NtBu)SiMe2(NHt-
Bu) group.
NRRЈ ؍ NHEt, NHiPr, NHtBu, NMeBu. Some preliminary
considerations are in order. Due to the presence of two different
groups in the [NRRЈ] moiety of SiMe2(NRRЈ)2, the chelation
of the ligand to a metal centre yields two different isomers,
namely syn and anti (Scheme 3).
Synthesis of ZrCl4[(NRRЈ)2SiMe2]
The Lewis adducts ZrCl4[(NRRЈ)2SiMe2] [NRRЈ = NMe2 (10),
NC4H8 (11), NHEt (12), NHiPr (13), NHtBu (14), NMeBu (15)]
have been prepared by reacting ZrCl4 with the appropriate sili-
con compound in toluene (12 h, room temperature) (eqn. (4)).
Scheme 3
The anti isomer has a C2 rotational axis (passing through the
silicon and zirconium centres), making the two methyls of
SiMe2 equivalent; on the other hand, a mirror plane (containing
the SiMe2 group) is present in the syn isomer, leaving the
two methyl groups of SiMe2 non-equivalent. Therefore, as far
as 1H and 13C NMR spectra are concerned, one signal
(4)
(i.e. one H and one 13C resonance) is expected for the di-
1
methylsilylene moiety of the anti isomer, and two signals
1
(i.e. two H and two 13C resonances) should appear for the
syn isomer. Moreover, the tetra-substitution of the nitrogen
For convenience, the adducts will be discussed separately
according to the kind of the nitrogen substitution, i.e. asym-
metric (NRRЈ) or symmetric (NR2).
atoms makes these centres stereogenic, and therefore non-
1
equivalency is expected as far as the H nuclei of the alkyl
groups are concerned (vide infra).
The ethyl derivative ZrCl4[(NHEt)2SiMe2] (12) shows low
solubility in C6D6; therefore, in order to record satisfactory
1H and 13C NMR spectra, the acquisitions were performed at
1
NRRЈ ؍ NMe2, NC4H8. The H NMR spectrum of ZrCl4-
[(NMe2)2SiMe2] (10) show two singlets at 2.43 and Ϫ0.28 ppm,
|| The 13C NMR spectrum of the compound is also affected by the
temperature. The resonances of the dimethylamido ligand and that of
the coordinated dimethylamine coalesce at 343 K, yielding a broad
signal at ca. 42.7 ppm (∆ν1/2 ≈ 200 Hz). On the other hand, the signals of
both the tert-butyl CH3 appear as partially merging broad lines (∆ν1/2
130 Hz; ∆δ = 2.6 ppm.
** ZrCl4[(NMe2)2SiMe2] (10) has already been described in the liter-
ature,6,7 and the authors report that the dimethylamido group yields two
resonances (2.15, 2.09 ppm), due to the proposed non-planar [SiN2Zr]
core. This discrepancy with our data is mysterious, and there was no
way for us to reproduce the published data.
≈
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1
Table 5 Selected H and 13C NMRa data for ZrCl4[(NHiPr)2SiMe2]
(13)
1
2
δH
2.96 (Ha)
0.45 (Hb)
1.21 (Hc)
2.48 (Hd)
3.05 (Ha)
0.38 (Hb)
1.23 (Hc)
2.14 (Hd)
δC
49.6 (Ca)
25.8 (Cb)
25.7 (Cc)
49.4 (Ca)
25.8 (Cb)
25.9 (Cc)
Scheme 4
1
a The 13C resonances have been assigned through the H–13C HMQC
spectrum.
(a) negative crosspeaks between the resonances at 1.21 (CCH3,
1) and 2.48 ppm (NH, 1), 0.45 (CCH3, 1) and 2.48 ppm (NH, 1),
0.38 (CCH3, 2) and 2.14 ppm (NH, 2), 1.23 (CCH3, 2) and 2.14
ppm (NH, 2), and (b) the absence of crosspeaks between the
methyne resonances (2.96 ppm, 1; 3.05 ppm, 2) and the amine
proton signals (2.48 ppn, 1; 2.14 ppm, 2) indicate that the
methyne hydrogen points far from the [SiN2Zr] ring, and, on the
other hand, both the methyls “look” at the NH proton (Scheme
4(B)).
343 K, the observed chemical shifts being reported in the
1
following: H, 2.92 (CH2), 2.40 (NH), 0.49 (CH2CH3),†† 0.03
(SiCH3) ppm; 13C, 42.5 (CH2), 17.5 (CH2CH3), 5.0 (SiCH3)
ppm. One H and one 13C NMR signals are observed for the
1
SiMe2 moiety, thus suggesting that the anti isomer is present.
Nevertheless, two considerations are in order: (a) a mixture of
the syn and anti isomers could be present, ready interconversion
occurring and making the methyls of SiMe2 equivalent; (b)
it cannot be excluded that the two isomers have different solu-
bility, the anti one being more soluble and therefore the only
one detected.
The 1H NMR spectrum of the adduct ZrCl4[(NHtBu)2SiMe2]
(14) shows a broad signal at 3.26 ppm (NH), a sharp singlet
at 1.16 ppm (CCH3) and two signals at 0.54 and Ϫ0.04 ppm
due to the dimethylsilylene moiety, thus indicating that the syn
isomer is present. The coalescence of the resonances at 0.54
and Ϫ0.04 ppm is observed at 333 K, and at 343 K a single
broad signal is observed at 0.32 ppm (∆ν1/2 = 50 Hz). On this
basis, we propose that a dynamic process occurs making the two
methyls in SiMe2 equivalent (Scheme 5). As a confirmation, the
proton NOESY spectrum of 14 shows positive crosspeaks
between the resonances of the dimethylsylilene moiety. As far
as the mechanism is concerned, reasonably, the deprotonation/
protonation of the coordinated nitrogen atoms could allow the
interconversion to occur.¶¶
The isopropyl derivative ZrCl4[(NHiPr)2SiMe2] (13) is more
soluble than the ethyl analogue, thus making possible a more
accurate NMR investigation. In the H and 13C NMR spectra
1
(Table 5), we have observed three resonances for the SiMe2
moiety (1H: 0.10, 0.06, 0.05 ppm, 13C: 3.9, 0.09, Ϫ4.1 ppm), two
resonances for the methyne protons (1H: 2.96, 3.05 ppm; 13C:
49.6, 49.4 ppm), four resonances for the methyls of the iso-
propyl group (1H, 1.21, 1.23, 0.45, 0.38 ppm; 13C: 25.7, 25.8,‡‡
25.9 ppm), and two resonances for the amine proton (1H: 2.48,
2.14 ppm).§§
This set of experimental data suggests the presence of the
two isomers, namely syn and anti (1 : 1 based on the integral
ratios). As a matter of fact, the proton COSY spectrum indi-
cates two non-equivalent isopropyl groups, each containing two
non-equivalent methyls (Table 5), reasonably due to the presence
of the two stereogenic nitrogens in each isomer (vide supra). In
this connection, it is reported that the non-equivalency of the
methyl groups in [CH(CH3)2] is observed even if eight bonds
are present between the isopropyl group and the stereogenic
centre.11 Finally, the NOESY spectrum of 13 shows positive
crosspeaks between all the resonances of the methyls of the
isopropyl groups, between the resonances of the methyls of
SiMe2, and between the NH signals, thus indicating that
chemical exchanges exist between these groups (reasonably, via
the syn–anti interconversion, Scheme 4(A)). On the other hand,
Scheme 5
On the other hand, a stronger dipolar correlation (i.e.
more intense negative crosspeaks) of the SiCH3 protons at
Ϫ0.04 ppm and NH (with respect to the SiCH3 protons at
0.54 ppm) has been observed in the proton NOESY spectrum,
thus suggesting that the methyl protons at Ϫ0.04 and the NH
proton are on the same side of the [SiN2Zr] core.
The 13C resonances of 14 are reported in the following,
the assignment being based on the H–13C HMQC spectrum:
1
†† Despite the observation of the triplet at 0.49 ppm for CH3 of the ethyl
group, the resonance of the methylene protons at 2.92 ppm appears
broad and unresolved. In our opininion this is related to the presence of
the stereogenic nitrogen atoms, making the methylene protons dia-
stereotopic. Because of the low solubility of the compound, this point
was not investigated further, but related insightful considerations have
been drawn for the zirconium derivative ZrCl4[(NMeBu)2SiMe2] (15),
vide infra.
0.3 and 7.9 (SiCH3), 32.1 (CCH3), and 57.1 ppm (C).
¶¶ The step-by-step interconversion via the anti isomer could be pro-
posed (see below), but reasonably the formation of the anti isomer
should be observed, as a consequence. In this connection, we have
1
observed no signals in the H NMR spectrum attributable to the anti
‡‡ As reported in Table 5, two methyl groups are responsible for the 13
C
isomer, even after one week.
resonance at 25.8 ppm. As a confirmation, the intensity of this signal is
about double with respect to the others.
§§ The 1H resonances of the NH protons appear as doublets, thus
indicating that vicinal coupling occurs between NH and CH of
the isopropyl groups (3JHH = 10.0 Hz). On the other hand, the direct
observation of the coupling in the CH pattern was prevented by the
overlap of the resonances of the CH protons of the two isomers.
Nevertheless, as a confirmation, the proton COSY spectrum shows
crosspeaks between the resonances at 2.96 (CH) and 2.48 ppm (NH),
and those at 3.05 (CH) and 2.14 ppm (NH).
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1
Table 6 Selected H and 13C NMR data for ZrCl4[(NMeBu)2SiMe2]
syn) and between the resonances at 2.67 (NCH3, anti) and 3.33
and 3.10 ppm (NCH2, anti) allow the assignment of the butyl
(15)
resonances to the appropriate isomer (Table 6).
syn
anti
δC
δH
δC
δH
Conclusions
Si(CH3)2
Ϫ0.64
Ϫ1.19
58.4
0.04
0.32
3.32, 3.28
2.66
Ϫ1.01
0.16
The aminolysis of the Si–Cl bond in SiMe2Cl2 readily affords
the bis-amido derivatives SiMe2(NRRЈ)2 [NRRЈ = NMe2 (1),
NEt2 (2), NC4H8 (3), NMeBu (4), NHEt (5), NHiPr (6), NHtBu
(7)]. As far as their ligating ability towards the zirconium()
centre is concerned, this study has shown that coordination
compounds containing the above mentioned species as neutral,
monoanionic and dianionic ligand can be prepared.
NCH2
NCH3
NCH2CH2
CH2CH3
CH2CH3
59.1
43.0
3.33, 3.10
2.67
43.6
29.9 or 29.8a 1.65
29.9 or 29.8a 1.75
20.8
14.1
1.01
0.82
20.7
14.0
1.05
0.79
a Due to the broad correlation peaks observed for the 13C signals at 29.9
and 29.8 ppm, we could not confidently assign the related proton
resonances.
The Lewis adducts ZrCl4[(NRRЈ)2SiMe2] [NRRЈ = NMe2
(10), NC4H8 (11), NHEt (12), NHiPr (13), NHtBu (14), NMeBu
(15)] result from the treatment of SiMe2(NRRЈ)2 with ZrCl4.
If R ≠ RЈ, the [ZrN2Si] ring contains two stereogenic nitrogen
atoms, and, as a consequence, the diasterotopicity of the NCH2
protons in 15 and the non-equivalency of the methyls in the
isopropyl groups of 13 have been observed.
The 13C NMR spectrum of ZrCl4[(NMeBu)2SiMe2] (15)
shows three resonances for the SiMe2 moiety, thus indicating
the presence of both the syn and anti isomers (1 : 1 based on the
integral ratios). Moreover, as a confirmation, two series of
resonances have been observed for the NMeBu group (Table 6).
The 1H NMR spectrum is quite complicated, nevertheless,
The reaction of SiMe2(NHtBu)2 and Zr(NMe2)4 yields the
mixed amido derivative Zr(NMe2)3(NHMe2)[(NtBu)SiMe2-
(NHtBu)] (9), containing the monodentate monoanionic
ligand (NtBu)SiMe2(NHtBu). Reasonably because of the bulky
tert-butyl groups, the chelation of the ligand is not observed
and correspondingly the transfer of only one proton from the
silicon species to the coordinated NMe2 groups occurs.
1
1
the H–13C HMQC spectrum allows full elucidation of the H
NMR spectrum through the correlation peaks, the observed
1H chemical shifts being reported in Table 6, with the proposed
assignment (vide infra for further details).
As far as the NCH2 resonances are concerned, some com-
ments are in order. As anticipated, the nitrogen atoms of 15 are
stereogenic, thus making the methylene protons diasterotopic.
The 1H–13C HMQC spectrum indicates that the methylene
carbon atoms of both the syn and anti isomers bear two non-
equivalentprotons(Fig.3(A)XX).Moreover,the1HNMRpattern
of the methylene protons at 3.10 ppm (Fig. 3) allows the
determination of both the geminal and vicinal 1H–1H coupling
Finally, the dianionic ligand SiMe2(NiPr)2 coordinates
zirconium() yielding the binary dimer derivative {Zr[(NiPr)2-
SiMe2]2}2 (8), whose molecular structure has been elucidated
both in the solid state (X-ray diffraction analysis) and in solu-
tion (1D and 2D multinuclear NMR spectroscopy).
Experimental
constants (2JHH = 3.7 Hz; JHH = 12.3 Hz). In this connection,
3
All operations were carried out in a glove-box, under an
atmosphere of dinitrogen. Elemental analyses (C, H, N) were
performed using a Fisons Instruments analyser (Mod. EA
1108); the chlorine content in the samples was determined by
potentiometric titration using a standard solution of silver
the proton COSY spectrum shows a characteristic system
of crosspeaks between the methylene resonances (Fig. 3(B))
indicating the geminal coupling between the resonances at 3.10
and 3.33 ppm.
nitrate (Aldrich). NMR spectra were recorded with
a
1
1
BRUKER AMX 300 spectrometer (300 MHz for H). H, 13C
and 29Si NMR spectra are referred to TMS. Multiplicity is
indicated as s (singlet), d (doublet), t (triplet), q (quartet),
sp (septet), ds (double septet), m (multiplet).
Zirconium tetrachloride (ZrCl4, Fluka) was washed with
boiling toluene, then with pentane, dried in vacuo and stored
i
under an atmosphere of dinitrogen. Isopropylamine (NH2 Pr,
t
Aldrich), tert-butylamine (NH2 Bu, Aldrich), diethylamine
(NHEt2, Aldrich), pyrrolidine (C4H8NH, Aldrich) were
refluxed over BaO for one day, then distilled and stored under
dinitrogen. Dichlorodimethylsilane (SiCl2Me2, Aldrich), di-
methylamine (NHMe2, Fluka) and ethylamine (NH2Et, Fluka)
were used as received. Zr(NMe2)4 was prepared according to
the published procedure.12
1
Fig. 3 Selected areas of the H–13C HMQC (A) and of the proton
COSY (B) spectra of ZrCl4[(NMeBu)2SiMe2] (15).
Synthesis of SiMe2(NRRЈ)2 (NRRЈ ؍ NHEt, NHiPr, NHtBu,
NMe2, NEt2, NC4H8)
Moreover, in the proton COSY and NOESY spectra, two
sets of resonances have been recognised for the butyl groups
(Table 6), and the assignment of the configuration have been
done on the basis of the correlation peaks of the NOESY
spectrum. Negative crosspeaks have been detected between the
resonances at 2.66 (NCH3, syn) and 0.04 ppm (SiCH3, syn), and
between the resonances at 2.67 (NCH3, anti) and 0.16 ppm
(SiCH3, anti), thus indicating that: (a) the NCH3 group yielding
the signal at 2.66 ppm belongs to the syn isomer; (b) the methyl
of the dimethylsilylene moiety of the syn isomer “looking”
at the NCH3 methyl is that responsible for the resonance at
0.04 ppm. On the other hand, the negative crosspeaks between
the resonances at 2.66 (NCH3, syn) and 3.32, 3.28 ppm (NCH2,
Only the reaction for NRRЈ = NMe2 is described in detail, the
others being similar.
The gaseous amine NHMe2 was bubbled into a pentane
(30 ml) solution of SiMe2Cl2 (1.3 g, 10.1 mmol). A colourless
solid readily precipitated out. After 15 min bubbling, the sus-
pension was filtered and the solid washed with pentane, dried
in vacuo and spectroscopically (1H NMR) and analytically
(C, H, N, Cl) identified as [NH2Me2]Cl (1.51 g, 92% yield).
The filtrate was evaporated yielding a colourless liquid identi-
fied as SiMe2(NMe2)2 (1, 1.40 g, 95% yield). Found: C, 49.0; H,
12.7; N, 19.0. C6H18N2Si requires C, 49.3; H, 12.4; N, 19.1%.
D a l t o n T r a n s . , 2 0 0 3 , 1 4 1 1 – 1 4 1 8
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Table 7 Crystallographic data for {Zr[(NiPr)2SiMe2]2}2 (8)
δH (C6D6, 298 K): 2.44 (s, 2H, NCH3), Ϫ0.08 (s, 1H, SiCH3).
δC (C6D6, 298 K): 37.6 (NCH3), Ϫ3.4 (SiCH3).
SiMe2(NEt2)2 (2, 97% yield, colourless liquid). Found: C,
Chemical formula
Formula weight
Crystal system
Space group
C32H80N8Si4Zr2
871.84
Monoclinic
P21/n
59.0; H, 12.5; N, 13.5. C10H26N2Si requires C, 59.3; H, 12.9;
3
N, 13.8%. δH (C6D6, 298 K): 2.82 (q, 4H, CH2, JCH = 7.0 Hz),
3
0.99 (t, 6H, CH2CH3, JCH = 7.0 Hz), 0.14 (s, 3H, SiCH3).
a/Å
b/Å
c/Å
10.033(3)
46.986(5)
10.498(3)
110.12(3)
4647(2)
4
δC (C6D6, 298 K): 39.6 (CH2), 15.8 (CH2CH3), Ϫ0.9 (SiCH3).
SiMe2(NC4H8)2 (3, 95% yield, colourless liquid). Found: C,
61.0; H, 11.0; N, 14.0. C10H22N2Si requires C, 60.5; H, 11.2;
N, 14.1%. δH (C6D6, 298 K): 2.97 (m, 4H, NCH2CH2), 1.61 (m,
4H, NCH2CH2), 0.18 (s, 3H, SiCH3). δC (C6D6, 298 K): 46.9
(NCH2CH2), 27.2 (NCH2CH2), Ϫ2.9 (SiCH3).
β/Њ
V/Å3
Z
Dc/g cmϪ3
1.246
F(000)
1856
0.581
7761
6971
µ(Mo-Kα)/mmϪ1
Reflections collected
Reflections observed [I ≥ 2σ(I )]
Final R1, wR2
SiMe2(NMeBu)2 (4, 90% yield, colourless liquid). Found: C,
62.3; H, 13.3; N, 12.0. C12H30N2Si requires C, 62.5; H, 13.1; N,
3
12.2%. δH (C6D6, 298 K): 2.73 (t, 2H, NCH2, JHH = 7.1 Hz),
0.079, 0.180
2.45 (s, 3H, NCH3), 1.43 (tt, 2H, NCH2CH2, 3JHH = 7.1, 8.2 Hz),
2
½
R1 = Σ||Fo| Ϫ |Fc||/Σ|Fo|; wR2 = [Σ[w(Fo2 Ϫ Fc2)2]/Σw(Fo )2]] .
3
1.26 (tq, 2H, CH2CH3, JHH = 7.1, 8.2 Hz), 0.92 (t, 3H,
CH2CH3, 3JHH = 7.1 Hz), 0.12 (s, 3H, SiCH3). δC (C6D6, 298 K):
50.1 (NCH2), 34.2 (NCH3), 31.8 (NCH2CH2), 20.6 (CH2CH3),
14.4 (CH2CH3), Ϫ2.20 (SiCH3).
perature factors for all non-hydrogen atoms. The H-atoms were
placed in calculated positions with fixed, isotropic thermal
parameters (1.2Uequiv of the parent carbon atom). The cal-
culations were performed with the SHELXL-97 program,15
implemented in the WinGX package,16 and drawings were pro-
duced using ORTEP3.17 Crystallographic and experimental
details for the structure are summarized in Table 7.
CCDC reference number 200050.
See http://www.rsc.org/suppdata/dt/b2/b212705a/ for crystal-
lographic data in CIF or other electronic format.
SiMe2(NHEt)2 (5, 90% yield, colourless liquid). Found: C,
49.0; H, 12.4; N, 19.3. C6H18N2Si requires C, 49.3; H, 12.4; N,
3
19.1%. δH (CDCl3, 298 K): 2.77 (q, 2H, CH2, JHH = 7.0 Hz),
3
1.05 (t, 3H, CH2CH3, JHH = 7.0 Hz), 0.42 (br, 1H, NH), 0.01
(s, 3H, SiCH3). δC (CDCl3, 298 K): 36.0 (CH2), 20.5 (CH2CH3),
Ϫ1.33 (SiCH3).
SiMe2(NHiPr)2 (6, 92% yield, colourless liquid). Found: C,
55.0; H, 12.5; N, 16.0. C8H22N2Si requires C, 55.1; H, 12.7; N,
16.1%. δH (C6D6, 298 K): 3.08 (ds, 1H, CH, 3JHH = 10.0, 6.4 Hz),
1.03 (d, 6H, CHCH3, 3JHH = 6.4 Hz), 0.42 (br, 1H, NH), Ϫ0.01
(s, 3H, SiCH3). δC (C6D6, 298 K): 42.3 (CH), 27.9 (CHCH3),
Ϫ0.38 (SiCH3).
Reaction of Zr(NMe2)4 with SiMe2(NHtBu)2
A toluene solution (25 ml) of Zr(NMe2)4 (870 mg, 3.25 mmol)
was added dropwise to a toluene solution (10 ml) of SiMe2-
(NHtBu)2 (660 mg, 3.26 mmol). After 12 h stirring the solution
was evaporated yielding a colourless solid which was identified
as Zr(NMe2)3(NHMe2)[(NtBu)SiMe2(NHtBu)] (9, 1.34 g,
88% yield, colourless solid). Found: C, 45.8; H, 10.5; N, 17.7.
C18H50N6SiZr requires: C, 46.0; H, 10.7; N, 17.9%. δH (C6D6,
298 K): 3.03 (s, 18H, NCH3), 2.13 (br, 6H, HNCH3), 1.31
(s, 9H, CCH3), 1.04 (s, 9H, CCH3), 0.85 (br, 2H, NH), 0.36 (s,
6H, SiCH3). δC (C6D6, 298 K): 55.2.(C), 52.8 (C), 43.7 (NCH3),
39.0 (HNCH3), 35.5 (CCH3), 31.7 (CCH3), 6.86 (SiCH3).
SiMe2(NHtBu)2 (7, 95% yield, colourless liquid). Found: C,
59.5; H, 12.5; N, 13.8. C10H26N2Si requires C, 59.3; H, 12.9; N,
13.8%. δH (C6D6, 298 K): 1.19 (s, 9H, CCH3), 0.52 (br, 1H, NH),
0.18 (s, 3H, SiCH3). δC (C6D6, 298 K): 49.2 (C), 33.8 (CCH3),
3.7 (SiCH3).
Synthesis of {Zr[(NiPr)2SiMe2]2}2
A pentane (15 ml) solution of Li2[(NiPr)2SiMe2] [obtained by
reacting LiBu, 1.6 M, in hexane, 7.20 ml, 11.5 mmol, with
SiMe2(NHiPr)2, 1.00 g, 5.74 mmol, in pentane, 15 ml] was
added dropwise to a toluene (25 ml) suspension of ZrCl4
(665 mg, 2.85 mmol). The ready precipitation of a colourless
solid was observed. After 18 h stirring, the solid was filtered off
and the solution was evaporated (residual 10 ml), pentane
added (20 ml) and then cooled at 243 K for a week. The precipi-
tated solid was filtered off, dried in vacuo and identified as
{Zr[(NiPr)2SiMe2]2}2 (8, 720 mg, 58% yield, colourless solid).
Found: C, 44.2; H, 9.1; N, 13.0. C16H40N4Si2Zr requires: C,
44.1; H, 9.2; N, 12.9%. δH (C6D6, 298 K): 4.36 (sp, 1H, CH,
Reaction of ZrCl4 with SiMe2(NRRЈ)2 (NRRЈ ؍ NHEt, NHiPr,
NHtBu, NMe2, NC4H8, NMeBu)
Only the procedure for NRRЈ = NMe2 is reported in details, the
others being similar.
A toluene (25 ml) solution of SiMe2(NMe2)2 (510 mg, 3.49
mmol) was treated with ZrCl4 (800 mg, 3.43 mmol). After
18 h stirring, the suspension was filtered, the solid washed with
toluene and pentane, dried in vacuo and finally identified as
ZrCl4[(NMe2)2SiMe2] (10, 1.21 g, 93% yield, colourless solid).
Found: C, 19.2; H, 5.0; Cl, 37.3; N, 7.0. C6H18Cl4N2SiZr
requires C, 19.0; H, 4.8; Cl, 37.4; N, 7.4%. δH (C6D6, 298 K):
2.43 (s, 2H, NCH3); Ϫ0.28 (s, 1H, SiCH3). δC (C6D6, 298 K):
48.0 (NCH3), Ϫ3.15 (SiCH3).
3
3JHH = 6.5 Hz), 4.01 (sp, 1H, CH, JHH = 6.5 Hz), 1.44 (d, 6H,
3
3
CCH3, JHH = 6.5 Hz), 1.32 (d, 6H, CCH3, JHH = 6.5 Hz),
0.63 (s, 3H, SiCH3), 0.56 (s, 3H, SiCH3). δC (C6D6, 298 K): 50.9
(CH), 50.8 (CH), 29.1 (CCH3), 28.3 (CCH3), 9.13 (SiCH3), 6.02
(SiCH3). δSi (C6D6, 298 K): Ϫ12.2, Ϫ38.0 ppm
ZrCl4[(NC4H8)2SiMe2] (11, 90% yield, colourless solid).
Found: C, 27.7; H, 5.0; Cl, 33.3; N, 6.8. C10H22Cl4N2SiZr
requires C, 27.8; H, 5.1; Cl, 32.9; N, 6.5%. δH (C6D6, 298 K):
3.39 (m, 2H, NCH2CH2), 3.23 (m, 2H, NCH2CH2), 1.28
(m, 2H, NCH2CH2), 0.82 (m, 2H, NCH2CH2), Ϫ0.18 (s, 3H,
SiCH3). δC (C6D6, 298 K): 57.3 (NCH2CH2), 24.5 (NCH2CH2),
Ϫ3.0 (SiCH3).
ZrCl4[(NHEt)2SiMe2] (12, 97% yield, colourless solid).
Found: C, 19.1; H, 5.0; Cl, 37.2; N, 7.5. C6H18Cl4N2SiZr
requires C, 19.0; H, 4.8; Cl, 37.4; N, 7.4%. δH (C6D6, 298 K):
2.92 (br, 2H, CH2), 2.40 (br, 1H, NH), 0.49 (t, 3H, CH2CH3,
3JHH = 6.9 Hz), 0.03 (s, 3H, SiCH3). δC (C6D6, 298 K): 42.5
(CH2), 17.5 (CH2CH3), 5.0 (SiCH3).
Crystal structure determination of {Zr[(NiPr)2SiMe2]2}2
Single crystals suitable for X-ray analysis were obtained by
cooling at 243 K a pentane solution of the compound. The
intensities data were collected at room temperature using a
Philips PW1100 single-crystal diffractometer (FEBO system)
using a graphite-monochromator (Mo-Kα radiation), following
the standard procedures. There were no significant fluctuations
of intensities other than those expected from Poisson statistics.
All intensities were corrected for Lorentz polarization and
absorption.13 The structure was solved by direct methods
using SIR-92.14 Refinement was carried out by full-matrix
2
least-squares procedures (based on Fo ) using anisotropic tem-
D a l t o n T r a n s . , 2 0 0 3 , 1 4 1 1 – 1 4 1 8
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ZrCl4[(NHiPr)2SiMe2] (13, 90% yield, colourless solid).
Found: C, 23.5; H, 5.4; Cl, 34.9; N, 7.2. C8H22Cl4N2SiZr
requires C, 23.6; H, 5.4; Cl, 34.8; N, 6.9%. δH (C6D6, 298 K):
2 H. Berndt, A.-Q. Zeng, H.-R. Stock and P. Mayr, Surf. Coat.
Technol., 1995, 74–75, 369; K.-T. Rie, A. Gebauer and J. Wöhle,
Surf. Coat. Technol., 1995, 74–75, 362; D. M. Hoffman, Polyhedron,
1994, 13, 1169, and references therein.
3 C. K. Nakula and L. F. Allard, J. Mater. Chem., 1998, 8,
1881.
4 S.-J. Kim, I. N. Jung, B. R. Yoo, S. H. Kim, J. Ko, D. Byun and
S. O. Kang, Organometallics, 2001, 20, 2136; M. Veith, W. Frank,
F. Töllner and H. Lange, J. Organomet. Chem., 1987, 326, 315;
D. J. Brauer, H. Bürger, G. R. Liewald and J. Wilke, J. Organomet.
Chem., 1986, 310, 317; D. J. Brauer, H. Bürger and G. R. Liewald,
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2003, 413.
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Identification of Organic Compounds, J. Wiley, New York, 5th edn.,
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12 D. C. Bradley and I. M. Thomas, J. Chem. Soc., 1960, 3857.
13 A. T. C. North, D. C. Philips and F. S. Mathews, Acta Crystallogr.,
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3
3.05 (m, 2H, CH), 2.96 (m, 2H, CH), 2.48 (d, 2H, NH, JHH
=
10.0 Hz), 2.14 (d, 2H, NH, 3JHH = 10.0 Hz), 1.23 (d, 12H, CH3,
3JHH = 6.4 Hz), 1.21 (d, 12H, CH3, 3JHH = 6.4 Hz), 0.45 (d, 12H,
CH3, 3JHH = 6.4 Hz), 0.38 (d, 12H, CH3, 3JHH = 6.4 Hz), 0.10 (s,
3H, SiCH3), 0.06 (s, 6H, SiCH3), 0.05 (s, 3H, SiCH3). δC (C6D6,
298 K): 49.6 (CH), 49.4 (CH), 25.9 (CCH3), 25.8 (CCH3), 25.7
(CCH3), 3.9 (SiCH3), 0.09 (SiCH3), Ϫ4.1 (SiCH3).
ZrCl4[(NHtBu)2SiMe2] (14, 90% yield, colourless solid).
Found: C, 27.5; H, 6.2; Cl, 32.8; N, 6.5. C10H26Cl4N2SiZr
requires C, 27.6; H, 6.0; Cl, 32.6; N, 6.4%. δH (C6D6, 298 K):
3.26 (br, 2H, NH), 1.16 (s, 18H, CCH3), 0.54 (s, 3H, SiCH3),
Ϫ0.04 (s, 3H, SiCH3). δC (C6D6, 298 K): 57.1 (C), 32.1 (CCH3),
7.9 (SiCH3), 0.3 (SiCH3).
ZrCl4[(NMeBu)2SiMe2] (15) (the solid is soluble in toluene,
therefore the reaction mixture was evaporated and the residue
suspended in pentane. Finally, the zirconium compound was
filtered off and dried in vacuo; 72% yield, colourless solid).
Found: C, 31.0; H, 6.4; Cl, 31.0; N, 6.1. C12H30Cl4N2SiZr
requires C, 31.1; H, 6.5; Cl, 30.6; N, 6.0%. δH (C6D6, 298 K):
3.33 (m, NCH2), 3.32 (m, NCH2), 3.28 (m, NCH2), 3.10 (dt,
3
2
NCH2, JHH = 12.3 Hz, JHH = 3.7 Hz), 2.67 (s, NCH3), 2.66
(s, NCH3), 1.75 (m, NCH2CH2), 1.65 (m, NCH2CH2), 1.05 (m,
CH2CH3), 1.01 (m, CH2CH3), 0.82 (t, CH2CH3, 3JHH = 7.3 Hz),
3
0.79 (t, CH2CH3 JHH = 7.3 Hz), 0.32 (s, SiCH3), 0.16 (s, SiCH3),
0.04 (s, SiCH3). δC (C6D6, 298 K): 59.1 (NCH2), 58.4 (NCH2),
43.6 (NCH3), 43.0 (NCH3), 29.9 (NCH2CH2), 29.8 (NCH2-
CH2), 20.8 (CH2CH3), 20.7 (CH2CH3), 14.1 (CH2CH3), 14.0
(CH2CH3), Ϫ0.64 (SiCH3), Ϫ1.01 (SiCH3), Ϫ1.19 (SiCH3).
14 SIR-92: A. Altomare, M. C. Burla, M. Camalli, G. Cascarano,
C. Giacovazzo, A. Guagliardi and G. Polidori, J. Appl. Crystallogr.,
1994, 27, 435.
15 G. M. Sheldrick, SHELXL-97, Program for the Refinement of
Crystal Structures, University of Göttingen, Germany, 1997.
16 L. J. Farrugia, J. Appl. Crystallogr., 1999, 32, 837.
17 ORTEP3 for Windows – L. J. Farrugia, J. Appl. Crystallogr., 1997,
30, 565.
References
1 Zirconium, Hafnium, in Comprehensive Coordination Chemistry,
ed. Sir G. Wilkinson, Pergamon Press, 1987, vol. 3, p. 375, and
references therein.
D a l t o n T r a n s . , 2 0 0 3 , 1 4 1 1 – 1 4 1 8
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