Unsymmetrically substituted dimethyldiaminosilanes as ligands towards zirconium(IV)

Article abstract of DOI:10.1002/ejic.200400043

Unsymmetrically substituted dimethyldiaminosilanes of the general formula SiMe₂(NR₂) (NR′₂) have been prepared by treating LiNR₂ with SiMe₂C1(NR′₂) (NR₂, NR′₂ = NMe₂, NC₄H ₈, NHiPr, NHtBu, NHCH₂CH₂NMe₂ or NHCH₂CH₂-OMe). Their ligating properties towards zirconium(iv) have been investigated as a function of the nitrogen substituents and the syntheses of the binary compound Zr[SiMe₂-(NiPr)(NiBu)] ₂ and of the zirconium derivatives ZrX₃(L) [X = Cl, NMe₂; L = SiMe(NR) (NR′₂), NR = NiPr, NtBu, NCH ₂CH₂NMe₂, NCH₂CH₂OMe; NR′₂ = NMe₂, NC₄H₈, NHiPr, NHtBu] are also reported. The solution structures and dynamics of the compounds have been elucidated by 1D/2D multinuclear NMR spectroscopy. Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004.

Full text of DOI:10.1002/ejic.200400043

FULL PAPER
Unsymmetrically Substituted Dimethyldiaminosilanes as Ligands towards
Zirconium(IV
)
Vincenzo Passarelli*[a][‡] and Pierino Zanella[a]
Keywords: Zirconium / N ligands / Chelates / Silicon
Unsymmetrically substituted dimethyldiaminosilanes of the
general formula SiMe2(NR2)(NRЈ2) have been prepared by
treating LiNR2 with SiMe2Cl(NRЈ2) (NR2, NRЈ2 = NMe2,
NC4H8, NHiPr, NHtBu, NHCH2CH2NMe2 or NHCH2CH2-
OMe). Their ligating properties towards zirconium(iv) have
been investigated as a function of the nitrogen substituents
Cl, NMe2; L = SiMe(NR)(NRЈ2), NR = NiPr, NtBu,
NCH2CH2NMe2, NCH2CH2OMe; NRЈ2 = NMe2, NC4H8,
NHiPr, NHtBu] are also reported. The solution structures and
dynamics of the compounds have been elucidated by 1D/2D
multinuclear NMR spectroscopy.
and the syntheses of the binary compound Zr[SiMe2- ( Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim,
(NiPr)(NtBu)]2 and of the zirconium derivatives ZrX3(L) [X =
Germany, 2004)
Introduction
ii) the binary amido derivative Zr[SiMe2(NR)2]2 is a dimer
when R ϭ iPr[3] and a monomer when R ϭ tBu.[5]
Moreover, as a consequence of the different structures,
different physical and/or chemical properties are observed
and expected for the metal derivatives. For instance, the
above mentioned tert-butyl derivative Zr[SiMe2(NtBu)2]2 is
volatile,[5] while the isopropyl analogue decomposes at
about 430 K without subliming.[3]
Based on this background, it seemed interesting to en-
large the class of dimethyldiaminosilanes and their metal
complexes and, since little[6Ϫ8] is known about the ligating
ability of unsymmetrically substituted diaminosilanes, we
have pursued a) the synthesis of novel compounds of this
class (eventually containing additional ligating sites)
(Scheme 1, IIϪIII) and b) the investigation of their ligating
properties towards zirconium().
The discovery of novel nonmetallocene polymerisation
catalysts[1] has raised new interest in amido metal chemistry.
As far as silylamides are concerned, a large number of data
exist on SiR3 N-substituted amido ligands (see refs.[1aϪ1c]
for examples) but only a few papers[2Ϫ8] describe the syn-
thesis, starting from diaminosilanes, of coordination com-
pounds (Scheme 1, IϪII).
Scheme 1
Results and Discussion
Nevertheless diaminosilanes appear to be flexible ligands,
their coordination mode strongly depending on the nature
of the nitrogen substituents. Examples of the zirconium
systems include, i) Zr(NMe2)4 reacts with SiMe2(NHR)2
yielding Zr(NMe2)3(NHMe2)[SiMe2(NtBu)(NHtBu)][3] or
Zr(NMe2)2(NHMe2)[SiMe2(NPh)2] (Ph ϭ 2,6-Me2C6H3);[4]
Synthesis of SiMe2XY (X ؍ NR2, Y ؍ Cl, NRЈ2)
According to the literature procedures,[7,9] the following
general route to SiMe2(NR2)(NRЈ2) was followed
(Scheme 2): a) ligand exchange reactions between SiMe2Cl2
and SiMe2(NR2)2;[10] b) treatment of the resultant Si-
Me2Cl(NR2) with LiNRЈ2.
[a]
ICISϪCNR,
1
The H and 13C NMR spectra of 1Ϫ11 show high field
Corso Stati Uniti 4, 35127 Padova, Italy
Fax (internat.): ϩ39-049-8702911
resonances for SiMe2, while the signals of the NR2 moieties
can be observed in the range δ ϭ 1Ϫ4 ppm (1H) and
20Ϫ80 ppm (13C). In addition, note that the nature of the
amido group and the degree of substitution of the SiMe2
core affect δSi (cf. ESI).
E-mail: passarel@dcci.unipi.it
[‡]
`
Present address: Universita degli Studi di Pisa, Dipartimento di
Chimica e Chimica Industriale,
Via Risorgimento 35, 56126 Pisa, Italy
Supporting information for this article is available on the
WWW under http://www.eurjic.org or from the author.
Eur. J. Inorg. Chem. 2004, 4439Ϫ4446
DOI: 10.1002/ejic.200400043
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V. Passarelli, P. Zanella
FULL PAPER
and tBu group even at 200 K, thus suggesting an approxi-
mately tetrahedral arrangement of the donor atoms around
the zirconium centre. Finally, the two methyls of each
1
SiMe2 moiety are nonequivalent, i.e. two H and two 13C
signals have been observed for the SiMe2 group. Thus, the
solution molecular structure of 12 should be similar to that
of Zr[SiMe2(NtBu)2]2.
Synthesis of ZrCl3(L)
Treatment of ZrCl4 with LiL (prepared in situ by treating
LiMe with HL, 1:1 molar ratio; HL ϭ 7, 8, 10 and 11)
yielded the trichloro derivatives ZrCl3(L) (Scheme 3).
Scheme 2
Synthesis of Zr[SiMe2(NtBu)(NiPr)]2
As alluded to in the introduction, the binary species
Zr[SiMe2(NR)2]2 adopts a different molecular structure
(both in the solid state and in solution) depending on the
identity of R (R ϭ iPr, dimer;[3] R ϭ tBu, monomer[5]) and
elsewhere[3] we proposed that the different steric hindrances
of iPr and tBu should be responsible for this observation.
Therefore, elucidation of the molecular structure of Zr[Si-
Me2(NtBu)(NiPr)]2 (12) appeared interesting. Compound
12 was prepared by treating ZrCl4 with Li2[SiMe2(N-
iPr)(NtBu)] (1:2 molar ratio) and it was obtained as a pure
material after crystallisation from an Et2O/pentane solution
at 243 K, Equation (1).
Scheme 3
For convenience, 13 will be discussed separately from the
other compounds in order to illustrate in detail, the corre-
lation between the spectroscopic data and the proposed mo-
lecular structure.
(1)
1
The H and 13C NMR spectra of 13 show high field res-
onances for SiMe2 (1H, δ ϭ 0.18 ppm; 13C, 1.4 ppm), the
signals of the hydrocarbyl moieties being observed in the
Despite a large number of attempts, we were unable to range 1Ϫ3.5 ppm (1H) and 20Ϫ60 ppm (13C). As far as the
obtain suitable crystals for a single-crystal X-ray diffraction CH2NCH2 moiety (pyrrolidinide) is concerned, i) the 13C
1
study of the structure. Nevertheless, 1H, 13C and 29Si NMR and H 13C HMQC spectra show that the two carbons are
spectroscopy allowed at least the solution molecular struc- equivalent (54.0 ppm) and that two nonequivalent methyl-
ture to be elucidated. Provided that the 29Si chemical shifts ene protons (δH ϭ 3.49, 3.35 ppm) are bonded to each car-
reported for ZrL2 are Ϫ40.5 [L ϭ SiMe2(NtBu)2,[5] chelat- bon; ii) a negative crosspeak was observed in the 1H
ing], Ϫ38.0 [L ϭ SiMe2(NiPr)2,[3] chelating] and Ϫ12.2 ppm NOESY spectrum of 13 between the resonances at δ ϭ 3.35
[L ϭ SiMe2(NiPr)2,[3] bidentate bridging], the only 29Si res- and 0.18 ppm (SiMe2) and iii) the 13C resonances of
onance of 12 at Ϫ40.5 ppm indicates that two equivalent CH2NCH2 are shifted with respect to the uncomplexed li-
ligands are present and that they are both chelating. In ad- gand (Table 1), thus suggesting that 13 contains Si-
1
dition, the H and 13C spectra show only one kind of iPr Me2(NtBu)(NC4H8) as a bidentate ligand.
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Unsymmetrically Substituted Dimethyldiaminosilanes as Ligands towards Zirconium(IV)
FULL PAPER
Table 1. Shifts of the 13C resonances of the CHxNCHx moiety in
ZrX3(SiMe2YZ) (X ϭ Cl, NMe2) (∆δC ϭ δCZrX3(L) Ϫ δCHL), cf.
Schemes 3 and 4
SiNR2 moiety is also coordinated to the metal centre, mak-
ing the silane ligands tridentate.[3]
As far as 14 is concerned, further comments are appro-
priate. In contrast with the proposed coordination of the
SiNC4H8, the two faces of the pyrrolidinide ring appear
equivalent at room temperature, i.e. one 1H resonance is
observed for each NCH2 and NCH2CH2 proton set. In or-
der to further elucidate this feature, we undertook a variable
temperature NMR investigation and we observed that at
213 K i) the 1H NCH2 (pyrrolidinide) signal broadened and
appeared unresolved and the NCH2CH2 (pyrrolidinide) res-
onance split into two signals at δ ϭ 1.86 and 1.54 ppm (1:1
molar ratio) ii) in the 1H NOESY spectrum a negative cros-
speak was observed only between the NCH2CH2 resonance
at 1.54 and the signal at δ ϭ 0.39 ppm (SiMe2) and iii) the
carbon responsible for the resonance at δ ϭ 25.1 ppm is
bonded to the protons which yield the resonances at δ ϭ
1.86 and 1.54 ppm (1H 13C HMQC). Therefore, the pro-
posed coordination of the SiNC4H8 moiety is confirmed
and it appears that the two faces of the pyrrolidinide ring
are nonequivalent at 213 K and exchange at room tempera-
ture.
Compound
Y
Z
∆δC
X ϭ Cl
13
14
15
16
NtBu
N(CH2CH2)2
N(CH2CH2)2
NMe2
7.3
3.0
7.4
6.6
N(CH2)2NMe2
N(CH2)2NMe2
N(CH2)2OMe
NMe2
X ϭ NMe2
17
18
19
20
21
22
N(CH2)2NMe2
N(CH2)2OMe
N(CH2)2NMe2
NtBu
NiPr
NtBu
N(CH2CH2)2
NMe2
NMe2
N(CH2CH2)2
NMe2
NMe2
0.7
0.8
0.7
4.8
4.8
5.2
Similar to 13, the H and 13C spectra of 14Ϫ16 show
high field resonances for the SiMe2 moiety (1H, about δ ϭ
0.3 ppm; 13C, about Ϫ2.2 ppm) and signals of the hydrocar-
byl groups in the range 2Ϫ4.5 ppm (1H) and 20Ϫ80 ppm
1
Synthesis of Zr(NMe2)3(L)
(13C). In addition, i) the downfield shift of the H and 13C
Compounds 5Ϫ11 readily react with Zr(NMe2)4 displac-
1
resonances of the amino NMe2 moieties in 14 and 15 and ing one NMe2 group as NHMe2 and yielding the mixed
of the ethereal OMe group in 16 with respect to the uncom- amido derivatives Zr(NMe2)3(L) (17Ϫ24) (Scheme 4).
plexed ligands, and ii) the equivalent methylene protons of
The NMR spectra of 17Ϫ19 show i) 13C chemical shifts
the ethylene chain, even at 190 K, indicate that the NMe2 of the CHxN(Si)CHx (x ϭ 2, 3) moiety similar to the un-
and the OMe groups coordinate to the metal centre and complexed ligands (Table 1) and ii) downfield shifted
that a mirror plane containing the ZrNC2X moiety should CH2N(CH3)2 and CH2OCH3 resonances (1H and 13C), thus
exist in the molecule (X ϭ OMe, NMe2).
suggesting that 17Ϫ19 should contain the diaminosilane as
Moreover, similar to 13, the observed 13C shifts for the a bidentate ligand coordinating to the metal centre through
pyrrolidinide CH2N(Si)CH2 moiety in 14 and for the the amido SiNCH2 nitrogen atom and the amino NMe2 or
SiNMe2 group in 15 and 16 (Table 1) suggest that the the ethereal OMe moieties, while the SiNR2 group is un-
Scheme 4
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V. Passarelli, P. Zanella
FULL PAPER
1
complexed. As confirmation, the H methylene NC4H8 res- were observed for 23ЈЈ as a consequence of the asymmetric
onances of 17 appear as unique multiplets even at 190 K zirconium coordination sphere.
(cf. 13 and 14).
As far as 20Ϫ22 are concerned, since the 13C
CHxN(Si)CHx resonances are noticeably shifted with re-
spect to those of the uncomplexed ligand (Table 1) and the
Table 2. Proposed assignment of 1H and 13C signals of Zr(NMe2)3-
[SiMe2(NtBu)(NHiPr)] (23ЈЈ)
two faces of the pyrrolidinide ring of 20 appear nonequiva-
lent at 200 K (1H NMR), the mixed amido derivatives
20Ϫ22 should contain the SiN2 core coordinated to the me-
tal centre.
The microcrystalline powder obtained from the reaction
of Zr(NMe2)4 with SiMe2(NHiPr)(NHtBu) (H2L) was
identified as Zr(NMe2)3(HL) (23) and the NMR spectra of
a C6D6 solution indicated that two isomers were present
in solution, namely Zr(NMe2)3[SiMe2(NiPr)(NHtBu)] (23Ј)
δH (188 K)
δC (188 K)
and Zr(NMe2)3[SiMe2(NtBu)(NHiPr)] (23ЈЈ) [Eqn. (2)]. In
fact, the 29Si NMR spectrum shows two signals (Ϫ2.8,
0.29 (Ha)
0.33 (Hb)
0.72 (Hc)
0.86 (Hd)
1.40 (He)
2.79 (Hf)
Ϫ
7.20 (Ca)
1.29 (Cb)
27.3 (Cc)
25.0 (Cd)
35.3 (Ce)
45.7 (Cf)
54.7 (Cg)
1
1
Ϫ5.9 ppm) and the H COSY and H 13C HMQC spectra
indicate two nonequivalent SiMe2, iPr and tBu moieties
(vide infra, cf. Exp. Sect.).
The equilibrium constants K ϭ [23ЈЈ]/[23Ј] [Equation (2)]
at different temperatures [198Ϫ293 K] were calculated from
the integrals of the SiCH3 1H NMR resonances and the
van’t Hoff plot yielded ∆Hr ϭ Ϫ3.4Ϯ0.4 kJ·molϪ1 and
∆Sr ϭ Ϫ7.3Ϯ1.8 J·molϪ1·KϪ1. Reasonably, the negative
∆Sr results from the loss of entropy due to the chelation of
the SiN2 system and the negative ∆Hr should be related to
a) the different basicities of the SiNiPr and SiNtBu moiet-
ies, b) the formation of a novel ZrϪN bond and c) the reor-
ganisation of the zirconium coordination sphere. Reason-
ably, the difference between the two Brønsted sites is negli-
gible and the enthalpy contribution of ZrϪN bond forma-
tion (esothermic) is higher with respect to that of the
(2)
As far as 23Ј is concerned, the H and 13C NMR reson-
1
ances are little affected by the temperature (188Ϫ298 K)
and the signal of the tert-butyl quaternary 13C nucleus is
slightly shifted with respect to the uncomplexed ligand, thus
indicating that the NHtBu moiety is probably not com-
plexed and that we are dealing with the mono-hapto Si-
Me2(NiPr)(NHtBu) ligand [Equation (2)].
On the other hand the H and 13C signals of 23ЈЈ are reorganisation of the donor atoms set on increasing the zir-
strongly affected by the temperature. At 188 K, one 29Si conium coordination number (endothermic). Nevertheless,
resonance and two nonequivalent methyls both in the the small absolute value of ∆Hr clearly indicates that the
SiMe2 and the iPr moiety (1H, 13C) suggest that the above mentioned effects are comparable.
1
SiNHiPr unit is coordinated. For confirmation, and rel-
For comparison (vide infra), the mixed amido derivative
evant to the molecular structure elucidation, the following Zr(NMe2)3[SiMe2(NiPr)(NHiPr)] (24) was prepared
1
comments can be made i) the H COSY spectrum shows (Scheme 4) and its solution molecular structure elucidated.
1
correlation peaks between the two isopropyl methyl groups Only one 29Si resonance was observed and the H and 13C
(δ ϭ 0.86, 0.72 ppm) and the methyne resonance (δ ϭ NMR spectra show one resonance for the SiMe2 and two
2.79 ppm), confirming that we are dealing with one isopro- nonequivalent iPr moieties (i.e. two nonequivalent CH3 and
1
pyl group containing two nonequivalent methyls; ii) both two nonequivalent CH proton sets). Moreover, the H and
the SiCH3 resonances are correlated (1H NOESY) with the 13C signals of the SiMe2 and iPr moieties are little affected
tert-butyl CH3, confirming that only one SiMe2 moiety is by the temperature and appear as single well-shaped reson-
present with the methyls in different chemical environ- ances even at 188 K. Finally, at room temperature, positive
ments; iii) a strong correlation (1H NOESY) exists between crosspeaks between both the CH3 and the CH resonances
the SiMe2 methyl at δ ϭ 0.29 ppm and the isopropyl methyl of the two nonequivalent iPr groups were observed in the
groups, suggesting that this methyl and the iPr group are in 1H NOESY spectrum and the coalescences of the CH and
a syn configuration with respect to the SiN2Zr ring CH3 1H resonances occur above 370 K. Therefore, the
(Table 2). Finally, at 188 K, three nonequivalent ZrNMe2 SiNHiPr group is not coordinated and the chemical ex-
groups (δH, δC ϭ 3.36, 45.97; 3.12, 46.00; 3.04, 45.2 ppm) change between the two halves of SiMe2(NHiPr)(NiPr) op-
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Unsymmetrically Substituted Dimethyldiaminosilanes as Ligands towards Zirconium(IV)
FULL PAPER
erates with the consequent 1,3-shift of the NH proton binary derivatives ZrL2 are concerned, in contrast to
(Scheme 5).
{Zr[SiMe2(NiPr)2]2}2 (Scheme 6, A) and similar to Zr[Si-
Me2(NtBu)2]2 (Scheme 6, B), Zr[SiMe2(NiPr)(NtBu)]2 is
mononuclear indicating that the formal substitution of one
methyne proton with CH3 in each silane ligand of
{Zr[SiMe2(NiPr)2]2}2 makes the ligand itself too bulky to
be accommodated in the dimer frame.
Scheme 5
This phenomenon has been investigated by variable tem-
perature 13C NMR spectroscopy in the range of 298Ϫ358 K
and a line shape analysis of the isopropyl methyl resonances
enabled us to calculate the kinetic constant k (Scheme 5)
at different temperatures and to determine the activation
parameters using the Eyring plot (∆Hact ϭ 47.1Ϯ1.2
kJ·molϪ1; ∆Sact ϭ Ϫ73.8Ϯ3.8 J·molϪ1·KϪ1). The negative
value of ∆Sact suggests that the mechanism should be con-
certed, the 1,3-shift of the Zr(NMe2)3 fragment being
reasonably the rate determining step (Scheme 5), yielding a
23ЈЈ-type transition state. In this respect, the positive ∆Hact
is reasonably indicative of the kinetic influence of the pro-
posed rate-determining labilisation of the amido
ZrϪN(Si)iPr bond.
Scheme 6
Finally, a comparison among compounds 20Ϫ24 throws
light on the influence of the nitrogen substituents on the
coordination mode of L in Zr(NMe2)3(L) [HL ϭ 5, 6, 9,
10, SiMe2(NHiPr)2]. Provided that the coordination of the
SiNHR moiety (R ϭ iPr, tBu) is observed only in 23ЈЈ and
not in 23Ј or in 24, we propose that the steric hindrance of
SiNHR is hardly relevant in determining its ligating ability
and that the steric interactions within the SiN(R)Zr group
should be decisive, i.e. the more sterically demanding tBu
group in 23ЈЈ encourages the chelation. This could reason-
ably be due to the consequent reduction of unfavourable
steric interactions within the SiN(tBu)Zr fragment itself.
Conversely, compounds 20Ϫ22 contain SiMe2(NR)(NRЈ2)
as a chelating ligand, regardless of the nature of R (R ϭ
iPr, tBu), thus suggesting that the SiNRЈ2 moieties, namely
SiNMe2 and SiNC4H8, have better ligating abilities with re-
spect to SiNHiPr and SiNHtBu (in 23Ј and 24).
The coordination mode of SiMe2(NRЈ)(NR2) (NR2
ϭ
NMe2 or NC4H8; NRЈ ϭ NiPr, NtBu, NCH2CH2NMe2 or
NCH2CH2OMe) to the ZrX3 moiety (X ϭ Cl, NMe2) is
strictly determined by the ancillary ligands. In fact, Si-
Me2(NR2)(NCH2CH2Y) (NR2ϭNMe2 or NC4H8; Y ϭ
NMe2 or OMe) is tridentate when X ϭ Cl (Scheme 6, C)
and bidentate when X ϭ NMe2 (Scheme 6, D). This could
reasonably be due to the higher steric hindrance of the am-
ido NMe2 with respect to Cl and to the ability of NMe2 to
act as a π-donor. In addition, when X ϭ NMe2, the forma-
tion of the more stable five membered ring ZrNC2Y (Y ϭ
NMe2, OMe) can be observed rather than the four mem-
bered SiN2Zr one. On the other hand, SiMe2(NRЈ)(NR2)
(RЈ ϭ iPr or tBu; NR2 ϭ NMe2 or NC4H8) exhibit similar
ligating properties towards ZrX3 (X ϭ Cl, NMe2) regardless
of the nature of X and the formation of chelates is always
observed (Scheme 6, E).
Finally, the hapticity of the silane ligand in Zr(NMe2)3-
[SiMe2(NR)(NHRЈ)] is related to the steric hindrance of the
nitrogen substituent R. As a matter of fact, the chelation of
SiMe2(NtBu)(NHiPr) (Scheme 6, E) in Zr(NMe2)3[Si-
Conclusions
The ligating ability of SiMe2(NR2)(NRЈ2) towards zir- Me2(NtBu)(NHiPr)] and the mono-hapto coordination of
conium() is affected by the nitrogen substituents and SiMe2(NiPr)(NHR) (Scheme 6, F) in Zr(NMe2)3[SiMe2-
eventually by the zirconium ancillary ligands. As far as the (NiPr)(NHR)] (R ϭ iPr, tBu) indicate that the release of
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V. Passarelli, P. Zanella
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0.74 (br., 1 H, NH), 0.27 (s, 6 H, SiCH3) ppm. 13C NMR (C6D6,
298 K): δ ϭ 43.3 (CH), 27.1 (CHCH3), 2.07 (SiCH3) ppm. 29Si
NMR (C6D6, 298 K): δ ϭ 8.4. ppm
some steric congestion within the amido moiety SiN(R)Zr
is decisive.
SiMe2Cl(NHtBu) (4): Reaction time: 80 h, colourless liquid, 91%
yield. C6H16ClNSi (165.74): calcd. C 43.5, H 9.7, Cl 21.4, N 8.5;
found C 43.2, H 10.0, Cl 21.3, N 8.2. 1H NMR (C6D6, 298 K): δ ϭ
1.14 (s, 9 H, CCH3), 0.55 (br., 1 H, NH), 0.34 (s, 6 H, SiCH3) ppm.
13C NMR (C6D6, 298 K): δ ϭ 50.3 (C), 33.2 (CCH3), 4.52 (SiCH3)
ppm. 29Si NMR (C6D6, 298 K): δ ϭ 5.6 ppm.
Experimental Section
All operations were carried out in a glove-box under dinitrogen.
Elemental analyses (C, H, N) were performed using a Fisons In-
struments analyser (Mod. EA 1108). The chlorine content in the
samples was determined by potentiometric titration using a stand-
ard solution of silver nitrate (Aldrich). NMR spectra were recorded
Synthesis of SiMe2(NR2)(NRЈ2): Only the synthesis of SiMe2(N-
Me2)(NHtBu) is reported in detail, the others being similar. A solu-
tion of SiMe2Cl(NMe2) (1, 900 mg, 6.54 mmol) in Et2O (30 mL)
was treated with an Et2O suspension of LiNHtBu (4.1 mL of an
Et2O solution, 1.6 , 6.6 mmol of LiMe ϩ485 mg, 6.63 mmol of
NH2tBu) and the resultant suspension stirred for 3 h. The colour-
less solid was filtered (270 mg) and the solvent was removed in
vacuo from the filtrate yielding a pale yellow liquid identified as
SiMe2(NMe2)(NHtBu) (5).
with a  AMX 300 spectrometer (300 MHz for 1H). H, 13C
1
and 29Si NMR spectra are referred to TMS. The multiplicity is
indicated as s (singlet), d (doublet), t (triplet), dt (doublet of trip-
lets), q (quadruplet), sp (septet), ds (doublet of septets), m (mul-
tiplet) and br. was used to indicate broad signals.
The mass spectra (100Ϫ800 amu) were recorded with a Thermo-
Finnigan Trace GC-MS instrument equipped with an accessory for
the direct introduction of the sample into the source. The probe
temperature was initially maintained at 373 K for 10 min, then
raised to 473 K (50 K/min) and finally maintained at 473 K for
10 min. The source temperature was 473 K.
Zirconium tetrachloride (ZrCl4, Fluka) was washed with boiling
toluene then with pentane, dried in vacuo and stored under dinitro-
gen. tert-Butylamine (C4H11N, Aldrich), isopropylamine (C3H9N,
Aldrich) and N,N-dimethylethylenediamine (C4H12N2, Aldrich)
were refluxed over BaO for one day, then distilled and stored under
dinitrogen. Dichlorodimethylsilane (SiMe2Cl2, Aldrich), 2-methoxy-
ethyleneamine (C3H9NO, Aldrich), LiMe (Et2O solution, 1.6 ,
SiMe2(NMe2)(NHtBu) (5): 1.05 g, 92% yield. C8H22N2Si (174.36):
calcd. C 55.1, H 12.7, N 16.1; found C 55.1, H 12.9, N 16.0. 1H
NMR (C6D6, 298 K): δ ϭ 2.41 (s, 6 H, SiNCH3), 1.12 (s, 9 H,
CCH3), 0.53 (br., 1 H, NH), 0.10 (s, 6 H, SiCH3) ppm. 13C NMR
(C6D6, 298 K): δ ϭ 48.8 (C), 37.6 (SiNCH3), 33.5 (CCH3), Ϫ0.08
(SiCH3) ppm. 29Si NMR (C6D6, 298 K): δ ϭ Ϫ10.8 ppm.
SiMe2(NMe2)(NHiPr) (6): Colourless liquid, 90% yield, from Si-
Me2Cl(NMe2) (1) ϩ LiNHiPr. C7H20N2Si (160.33): calcd. C 52.4,
H 12.6, N 17.5; found C 52.0, H 12.5, N 17.3. 1H NMR (C6D6,
3
Aldrich) and dimethylamine (C2H7N, Aldrich) were used as re-
298 K): δ ϭ 2.99 (ds, JH,H ϭ 10.2, 6.3 Hz, 1 H, CH), 2.49 (s, 6 H,
[3,9]
3
ceived. SiMe2(NR2)2
(NR2 ϭ NHiPr, NHtBu, NMe2 or
SiNCH3), 1.00 (d, JH,H ϭ 6.3 Hz, 6 H, CHCH3), 0.29 (br., 1 H,
[11]
NH), 0.07 (s, 6 H, SiCH3) ppm. 13C NMR (C6D6, 298 K): δ ϭ 42.6
(CH), 37.5 (SiNCH3), 27.8 (CHCH3), Ϫ1.96 (SiCH3) ppm. 29Si
NMR (C6D6, 298 K): δ ϭ Ϫ7.5 ppm.
NC4H8) and Zr(NMe2)4
were prepared according to the pub-
lished procedures. The lithium amides LiNR2 (NR2 ϭ NHiPr,
NHtBu, NHCH2CH2NMe2 or NHCH2CH2OMe) were prepared
by treating NHR2 with LiMe in Et2O (1:1 molar ratio) and the
resultant mixture was used without isolating the product.
SiMe2(NMe2)(NHCH2CH2NMe2) (7): Colourless liquid, 91%
yield, from SiMe2Cl(NMe2) (1)
ϩ
LiNHCH2CH2NMe2.
Synthesis of SiMe2Cl(NR2) (NR2 ؍ NHiPr, NHtBu, NMe2 or
NC4H8)
C8H23N3Si (189.37): calcd. C 50.7, H 12.2, N 22.2; found C 51.0,
3
H 11.9, N 22.1. 1H NMR (C6D6, 298 K): δ ϭ 2.74 (dt, JH,H
ϭ
3
6.9, 6.2 Hz, 2 H, SiNCH2), 2.48 (s, 6 H, SiNCH3), 2.18 (t, JH,H ϭ
6.2 Hz, 2 H, CH2NCH3), 2.08 (s, 6 H, CH2NCH3), 1.15 (br., 1
H, NH), 0.04 (SiCH3) ppm. 13C NMR (C6D6, 298 K): δ ϭ 63.2
(CH2NCH3), 45.5 (CH2NCH3), 39.2 (SiNCH2), 37.7 (SiNCH3),
Ϫ2.38 ppm. 29Si NMR (C6D6, 298 K): δ ϭ Ϫ5.3 ppm.
Only the synthesis of SiMe2Cl(NMe2) is described in detail, the
others being similar except for the reaction time (vide infra).
A solution of SiMe2(NMe2)2 (1.20 g, 8.20 mmol) in pentane (50
mL) was treated with SiMe2Cl2 (1.07 g, 8.29 mmol). After 10 min
stirring volatiles were removed in vacuo yielding a colourless liquid
material, identified as SiMe2Cl(NMe2) (1).
SiMe2(NMe2)(NHCH2CH2OMe) (8): Colourless liquid, 95% yield,
from SiMe2Cl(NMe2) (1) ϩ LiNHCH2CH2OMe. C7H20N2OSi
(176.33): calcd. C 47.7, H 11.4, N 15.9; found C 47.7, H 11.0, N
SiMe2Cl(NMe2) (1): 2.15 g, 95% yield. C4H12ClNSi (137.68): calcd.
C 34.9, H 8.8, Cl 25.7, N 10.2; found C 34.8, H 8.9, Cl 25.5,
N 10.1. 1H NMR (C6D6, 298 K): δ ϭ 2.28 (s, 1 H, NCH3), 0.28 (s,
1 H, SiCH3) ppm. 13C NMR (C6D6, 298 K): δ ϭ 37.1 (NCH3),
1.32 (SiCH3) ppm. 29Si NMR (C6D6, 298 K): δ ϭ 13.9 ppm.
1
3
15.8. H NMR (C6D6, 298 K): δ ϭ 3.19 (t, JH,H ϭ 5.6 Hz, 2 H,
3
OCH2), 3.13 (s, 3 H, OCH3), 2.87 (dt, JH,H ϭ 7.7, 5.6 Hz, 2 H,
SiNCH2), 2.48 (s, 6 H, SiNCH3), 0.99 (br., 1 H, NH), 0.06 (s, 6 H,
SiCH3) ppm. 13C NMR (C6D6, 298 K): δ ϭ 76.0 (OCH2), 58.4
(OCH3), 41.3 (SiNCH2), 37.6 (SiNCH3), Ϫ2.38 (SiCH3) ppm. 29Si
NMR (C6D6, 298 K): δ ϭ Ϫ5.0 ppm.
SiMe2Cl(NC4H8) (2): Reaction time: 10 min, colourless liquid, 96%
yield. C6H14ClNSi (163.72): calcd. C 44.0, H 8.6, Cl 21.7, N 8.6;
found C 44.2, H 8.8, Cl 21.7, N 8.4. H NMR (C6D6, 298 K): δ ϭ
2.85 (m, 2 H, NCH2), 1.53 (m, 2 H, NCH2CH2), 0.33 (s, 3 H,
SiCH3) ppm. 13C NMR (C6D6, 298 K): δ ϭ 46.5 (NCH2), 26.9
(NCH2CH2), 1.82 (SiCH3) ppm. 29Si NMR (C6D6, 298 K): δ ϭ
10.1 ppm.
1
SiMe2(NHiPr)(NHtBu) (9): Colourless liquid, 88% yield, from Si-
Me2Cl(NHiPr) (3) ϩ LiNHtBu. C9H24N2Si (188.39): calcd. C 57.4,
H 12.8, N 14.9; found C 57.3, H 12.8, N 14.7. 1H NMR (C6D6,
298 K): δ ϭ 3.13 (ds, 3JH,H ϭ 10.4, 6.3 Hz, 1 H, CH), 1.19 (s, 9 H,
3
CCH3), 1.04 (d, JH,H ϭ 6.3 Hz, 6 H, CHCH3), 0.56 (br., 1 H,
SiMe2Cl(NHiPr) (3): Reaction time: 18 h, colourless liquid, 92%
NH), 0.24 (br., 1 H, NH), 0.12 (s, 6 H, SiCH3) ppm. 13C NMR
yield. C5H14ClNSi (151.71): calcd. C 39.6, H 9.3, N 9.2; found C (C6D6, 298 K): δ ϭ 49.1 (C), 42.6 (CH), 33.8 (CCH3), 28.0
39.7, H 9.1, N 9.0. H NMR (C6D6, 298 K): δ ϭ 3.00 (ds, 3JH,H ϭ (CHCH3), 1.74 (SiCH3) ppm. 29Si NMR (C6D6, 298 K): δ ϭ
1
3
10.7, 1 H, CH, 6.4 Hz), 0.95 (d, JH,H ϭ 6.4 Hz, 6 H, CHCH3), Ϫ15.0 ppm.
4444
 2004 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjic.org
Eur. J. Inorg. Chem. 2004, 4439Ϫ4446

Unsymmetrically Substituted Dimethyldiaminosilanes as Ligands towards Zirconium(IV)
FULL PAPER
SiMe2(NC4H8)(NHtBu) (10): Colourless liquid, 92% yield, from Si-
ZrCl3[SiMe2(NC4H8)(NCH2CH2NMe2)] (14): Colourless solid,
Me2Cl(NC4H8) (2) ϩ LiNHtBu. C10H24N2Si (200.40): calcd. C 91% yield. MS: m/z (%) ϭ 339 (17.8) [Mϩ· Ϫ NCH2CH2CH2CH2],
59.9, H 12.1, N 14.0; found C 60.0, H 12.0, N 14.1. 1H NMR 332 (75.3) [Mϩ· Ϫ CH2CH2CH2 Ϫ Cl]. C10H24Cl3N3SiZr (411.98):
(C6D6, 298 K): δ ϭ 2.97 (m, 4 H, NCH2), 1.61 (m, 4 H, calcd. C 29.2, H 5.9, N 10.2; found C 29.3, H 5.8, N 10.1. 1H NMR
3
NCH2CH2), 1.14 (s, 9 H, CCH3), 0.58 (br., 1 H, NH), 0.12 (s, 6 H,
(CDCl3, 298 K): δ ϭ 3.48 (t, JH,H ϭ 5.5 Hz, 1 H, SiNCH2), 3.36
SiCH3) ppm. 13C NMR (C6D6, 298 K): δ ϭ 48.9 (C), 46.7 (NCH2), (m, 2 H, NCH2 pyrrolidinide), 2.98 (t, JH,H ϭ 5.5 Hz, 1 H,
3
33.7 (CCH3), 27.2 (NCH2CH2), 0.14 (SiCH3) ppm. 29Si NMR CH2NMe2), 2.72 (s, 3 H, NCH3), 1.61 (m, 2 H, NCH2CH2 pyrroli-
(C6D6, 298 K): δ ϭ Ϫ14.4 ppm.
dinide), 0.31 (s, 3 H, SiCH3) ppm. 13C NMR (CDCl3, 298 K): δ ϭ
66.6 (CH2NMe2), 53.3 (NCH3), 49.8 (NCH2 pyrrolidinide), 47.5
(SiNCH2), 25.1 (NCH2CH2 pyrrolidinide), Ϫ2.14 (SiCH3) ppm.
SiMe2(NC4H8)(NHCH2CH2NMe2) (11): Colourless liquid, 90%
yield, from SiMe2Cl(NC4H8) (2)
ϩ
LiNHCH2CH2NMe2.
ZrCl3[SiMe2(NMe2)(NCH2CH2OMe)] (16): Colourless solid, 88%
yield. MS: m/z (%) ϭ 355 (15.9) [Mϩ· Ϫ CH3], 319 (29.4) [Mϩ· Ϫ
CH3 Ϫ H Ϫ Cl]. C7H19Cl3N2OSiZr (372.91): calcd. C 22.5, H 5.1,
Cl 28.5, N 7.5; found C 22.3, H 5.0, Cl 28.8, N 7.6. 1H NMR
C10H25N3Si (215.41): calcd. C 55.8, H 11.7, N 19.5; found C 55.6,
H 11.5, N 19.5. 1H NMR (C6D6, 298 K): δ ϭ 2.99 (m, 4 H,
3
NCH2CH2), 2.81 (dt, JH,H ϭ 7.0, 6.2 Hz, 2 H, SiNHCH2), 2.21
3
(t, JH,H ϭ 6.2 Hz, 2 H, CH2NCH3) 2.09 (s, 6 H, NCH3), 1.61 (m,
3
(CDCl3, 298 K): δ ϭ 4.24 (t, JH,H ϭ 5.3 Hz, 2 H, OCH2), 3.94 (s,
4 H, NCH2CH2), 1.18 (br., 1 H, NH), 0.13 (s, 6 H, SiCH3) ppm.
13C NMR (C6D6, 298 K): δ ϭ 63.4 (CH2NCH3), 46.8 (NCH2CH2),
45.5 (NCH3), 39.4 (SiNHCH2), 27.3 (NCH2CH2), Ϫ2.05 (SiCH3)
ppm. 29Si NMR (C6D6, 298 K): δ ϭ Ϫ8.9 ppm.
3
3 H, OCH3), 3.56 (t, JH,H ϭ 5.3 Hz, 2 H, NCH2), 2.74 (s, 6 H,
NCH3), 0.32 (s, 6 H, SiCH3) ppm. 13C NMR (CDCl3, 298 K): δ ϭ
81.5 (OCH2), 65.4 (OCH3), 47.5 (NCH2), 44.2 (NCH3), Ϫ2.16
(SiCH3) ppm.
Synthesis of Zr[SiMe2(NiPr)(NtBu)]2: An Et2O solution of Si-
Me(NHiPr)(NHtBu) (9, 1.25 g, 6.64 mmol) was treated with LiMe
(Et2O solution, 1.6 , 8.3 mL, 13.3 mmol), stirred for 1.5 h and
then cooled to 243 K. ZrCl4 (780 mg, 3.35 mmol) was added and
after 2 h stirring at 243 K the mixture was warmed to the room
temperature and the solid was filtered (540 mg). The pale yellow
solution was partially evaporated, pentane was added and Zr[Si-
Me2(NiPr)(NtBu)]2 (12) was finally obtained as a microcrystalline
powder on cooling the resultant solution to 240 K overnight
(985 mg, 64% yield). C18H44N4Si2Zr (463.96): calcd. C 46.6, H 9.6,
N 12.1; found C 46.4, H 9.4, N 12.0. 1H NMR (C6D6, 298 K): δ ϭ
Synthesis of Zr(NMe2)3(L): Only the procedure for L ϭ SiMe2(N-
iPr)(NMe2) is reported in detail, the others being similar except for
the reaction time (vide infra). A solution of SiMe2(NHiPr)(NMe2)
(6, 540 mg, 3.37 mmol) in toluene (20 mL) was treated with
Zr(NMe2)4 (900 mg, 3.36 mmol). After 3 h stirring, the solution
was evaporated yielding a pale yellow solid which was identified as
Zr(NMe2)3[SiMe2(NiPr)(NMe2)] (21).
Zr(NMe2)3[SiMe2(NiPr)(NMe2)] (21): Colourless solid, 1.20 g, 93%
yield. C13H37N5SiZr (382.78): calcd. C 40.8, H 9.7, N 18.3; found
C 40.5, H 9.9, N 18.5. 1H NMR (C6D6, 298 K): δ ϭ 3.53 (sp,
3JH,H ϭ 6.4 Hz, 1 H, CH), 3.04 (s, 18 H, ZrNCH3), 2.24 (s, 6 H,
3
3.35 (sp, JH,H ϭ 6.2 Hz, 1 H, CH), 1.32 (s, 9 H, CCH3), 1.24 (d,
3JH,H ϭ 6.2 Hz, 6 H, CHCH3), 0.44 (s, 3 H, SiCH3), 0.43 (s, 3 H,
SiCH3) ppm. 13C NMR (C6D6, 298 K): δ ϭ 55.6 (C), 50.6 (CH),
36.2 (CCH3), 31.2 (CHCH3), 4.3 (SiCH3), 4.1 (SiCH3) ppm. 29Si
NMR (C6D6, 298 K): δ ϭ Ϫ40.5 ppm.
3
SiNCH3), 1.23 (d, JH,H ϭ 6.4 Hz, 6 H, CHCH3), 0.14 (SiCH3)
ppm. 13C NMR (C6D6, 298 K): δ ϭ 50.2 (CH), 43.2 (ZrNCH3),
42.3 (SiNCH3), 28.9 (CHCH3), 0.67 (SiCH3) ppm. 29Si NMR
(C6D6, 298 K): δ ϭ 3.2 ppm.
Synthesis of ZrCl3(L): Only the procedure for L ϭ SiMe2(N-
Me2)(NCH2CH2NMe2) is described in detail, the others being simi-
lar. A solution of SiMe2(NMe2)(NHCH2CH2NMe2) (7, 780 mg,
4.12 mmol) in Et2O (40 mL) was treated with LiMe (Et2O solution,
1.6 , 2.6 mL, 4.2 mmol). After gas evolution ceased, the solution
was cooled to 243 K and ZrCl4 (960 mg, 4.12 mmol) was added.
The suspension was stirred at 243 K for 3 h and was then warmed
to the room temperature and stirred overnight. The resultant sus-
pension was filtered (165 mg of colourless solid) and the filtrate
was evaporated yielding a sticky material which was recrystallized
from Et2O/pentane yielding a microcrystalline powder, identified as
ZrCl3[SiMe2(NMe2)(NCH2CH2NMe2)] (15): Colourless solid,
1.35 mg, 85% yield. MS: m/z (%) ϭ 368 (9) [Mϩ· Ϫ CH3], 332 (100)
[Mϩ· Ϫ CH3 Ϫ H Ϫ Cl]. C8H22Cl3N3SiZr (385.95): calcd. C 24.9,
Zr(NMe2)3[SiMe2(NC4H8)(NCH2CH2NMe2)] (17): Reaction time:
3 h, colourless solid, 90% yield. C16H42N6SiZr (437.86): calcd. C
43.9, H 9.7, N 19.2; found C 44.0, H 9.5, N 19.0. 1H NMR (C6D6,
3
298 K): δ ϭ 3.26 (t, JH,H ϭ 5.6 Hz, 1 H, SiNCH2), 3.07 (m, 2 H,
3
NCH2 pyrrolidinide), 2.99 (s, 9 H, ZrNCH3), 2.42 (t, JH,H
ϭ
5.6 Hz, 1 H, CH2NMe2), 1.96 (s, 3 H, NCH3), 1.68 (m, 2 H,
NCH2CH2 pyrrolidinide), 0.28 (s, 3 H, SiCH3) ppm. 13C NMR
(C6D6, 298 K): δ ϭ 61.0 (CH2NMe2), 47.5 (NCH2 pyrrolidinide),
46.4 (SiNCH2), 46.2 (CH2NCH3), 43.4 (ZrNCH3), 27.3
(NCH2CH2 pyrrolidinide), Ϫ0.7 (SiCH3) ppm. 29Si NMR (C6D6,
298 K): δ ϭ Ϫ5.9 ppm.
Zr(NMe2)3[SiMe2(NMe2)(NCH2CH2OMe)] (18): Reaction time:
3 h, colourless solid, 92% yield. C13H37N5OsiZr (398.78): calcd. C
39.2, H 9.4, N 17.6; found C 39.0, H 9.4, N 17.5. 1H NMR (C6D6,
1
H 5.7, Cl 27.6, N 10.9; found C 25.0, H 5.5, Cl 27.5, N 11.0. H
NMR (CDCl3, 298 K): δ ϭ 3.51 (t, 3JH,H ϭ 5.6 Hz, 1 H, SiNCH2),
3
3
298 K): δ ϭ 3.31 (t, JH,H ϭ 5.4 Hz, 2 H, CH2O), 3.19 (t, JH,H
ϭ
3
3.00 (t, JH,H ϭ 5.6 Hz, 1 H, CH2NMe2), 2.71 (s, 3 H, SiNCH3),
5.4 Hz, 2 H, SiNCH2), 3.05 (s, 18 H, ZrNCH3), 2.98 (s, 3 H,
OCH3), 2.56 (s, 6 H, SiNCH3), 0.24 (s, 6 H, SiCH3) ppm. 13C NMR
(C6D6, 298 K): δ ϭ 79.2 (SiNCH2), 59.2 (OCH3), 46.5 (CH2O),
43.2 (ZrNCH3), 38.4 (SiNCH3), Ϫ1.0 (SiCH3) ppm. 29Si NMR
(C6D6, 298 K): δ ϭ Ϫ3.9 ppm.
2.70 (s, 3 H, CH2NCH3), 0.35 (s, 3 H, SiCH3) ppm. 13C NMR
(CDCl3, 298 K): δ ϭ 67.1 (CH2NMe2), 50.5 (CH2NCH3), 47.8
(SiNCH2), 45.1 (SiNCH3), Ϫ2.5 (SiCH3) ppm.
ZrCl3[SiMe2(NC4H8)(NtBu)] (13): Colourless solid, 70% yield.
C10H23Cl3N2SiZr (396.97): calcd. C 30.3, H 5.8, Cl 26.8, N 7.1; Zr(NMe2)3[SiMe2(NMe2)(NCH2CH2NMe2)] (19): Reaction time:
found C 30.0, H 5.6, Cl 27.2, N 7.2. 1H NMR (CDCl3, 298 K): 3 h, colourless solid, 87% yield. C14H40N6SiZr (411.82): calcd. C
δ ϭ 3.49 (br., 2 H, NCH2), 3.35 (br., 2 H, NCH2), 1.48 (s, 9 H, 40.8, H 9.8, N 20.4; found C 41.0, H 10.0, N 20.0. 1H NMR (C6D6,
3
CCH3), 1.01 (br., 4 H, NCH2CH2), 0.18 (s, 6 H, SiCH3) ppm. 13C 298 K): δ ϭ 3.21 (t, 1 H, SiNCH2, JH,H ϭ 5.9 Hz), 3.02 (s, 18 H,
3
NMR (CDCl3, 298 K): δ ϭ 58.2 (C), 54.0 (NCH2), 34.1 (CCH3), ZrNCH3), 2.62 (s, 3 H, SiNCH3), 2.36 (t, JH,H ϭ 5.9 Hz, 1 H,
24.9 (NCH2CH2), 1.4 (SiCH3) ppm.
Eur. J. Inorg. Chem. 2004, 4439Ϫ4446
CH2NMe2), 1.90 (s, 3 H, CH2NCH3), 0.32 (s, 3 H, SiCH3) ppm.
www.eurjic.org
 2004 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
4445

V. Passarelli, P. Zanella
FULL PAPER
13C NMR (C6D6, 298 K): δ ϭ 60.7 (CH2NMe2), 46.5 (SiNCH2),
46.0 (CH2NCH3), 43.3 (ZrNCH3), 38.4 (SiNCH3), Ϫ0.93 (SiCH3)
ppm.
Acknowledgments
V. P. is indebted to Dr. Sergio Tamburini (ICISϪCNR, Padova) for
meaningful comments and insightful discussions. The authors
thank Ms. Anna Rosa Moresco (ICISϪCNR, Padova) for the
elemental analysis and Prof. G. Paolucci and Dr. L. Sperini
Zr(NMe2)3[SiMe2(NtBu)(NC4H8)] (20): Reaction time: 30 h,
colourless solid, 85% yield. C16H41N5SiZr (422.84): calcd. C 45.5,
H 9.8, N 16.6; found C 45.7, H 9.5, N 16.5. 1H NMR (C6D6,
298 K): δ ϭ 3.04 (s, 18 H, ZrNCH3), 2.74 (m, 4 H, NCH2), 1.37
(m, 4 H, NCH2CH2), 1.33 (s, 9 H, CCH3), 0.23 (SiCH3) ppm. 13C
NMR (C6D6, 298 K): δ ϭ 55.1 (C), 51.5 (NCH2), 43.9 (ZrNCH3),
35.5 (CCH3), 24.7 (NCH2CH2), 3.5 (SiCH3) ppm. 29Si NMR
(C6D6, 298 K): δ ϭ Ϫ2.7 ppm.
`
(Universita di Venezia) for the MS measurements.
[1] [1a]
[1b]
R. Kempe, Angew. Chem. Int. Ed. 2000, 39, 468.
L. H.
[1c]
Gade, Chem. Commun. 2000, 173.
G. J. P. Britovsek, V. C.
Gibson, D. F. Wass, Angew. Chem. Int. Ed. 1999, 38, 428.
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D. W. von Beiersdorf, D. J. Brauer, H. Bürger, Z. Anorg.
[2b]
Allg. Chem. 1981, 475, 56.
G. R. Liewald, J. Organomet. Chem. 1983, 259, 145.
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Geschwandtner, G. R. Liewald, C. Krüger, J. Organomet.
H. Bürger, W. Geschwandtner,
Zr(NMe2)3[SiMe2(NtBu)(NMe2)] (22): Reaction time: 28 h, colour-
less solid, 88% yield. C14H39N5SiZr (396.80): calcd. C 42.4, H 9.9,
N 17.6; found C 42.3, H 10.0, N 17.8. 1H NMR (C6D6, 298 K):
δ ϭ 3.04 (s, 18 H, ZrNCH3), 2.19 (s, 6 H, SiNCH3), 1.33 (s, 9 H,
CCH3), 0.20 (s, 6 H, SiCH3) ppm. 13C NMR (C6D6, 298 K): δ ϭ
54.8 (C), 43.8 (ZrNCH3), 42.8 (SiNCH3), 35.4 (CCH3), 3.4 (SiCH3)
ppm. 29Si NMR (C6D6, 298 K): δ ϭ 1.0 ppm.
[2c]
R. A.
[2d]
D. J. Brauer, H. Bürger, W.
[2e]
Chem. 1983, 248, 1.
rick, Z. Naturforsch., Teil B 1985, 40, 1040.
F. Preuss, E. Fuchslocher, W. S. Sheld-
[2f]
M. Veith, H.
Lange, A. Belo, O. Recktenwald, Chem. Ber. 1985, 118, 1600.
[2g] D. J. Brauer, H. Bürger, G. R. Liewald, J. Organomet. Chem.
[2h]
When Zr(NMe2)4 was reacted with SiMe2(NHiPr)(NHtBu) (9,
H2L) (1:1 molar ratio) a microcrystalline powder was obtained
which was analytically identified as Zr(NMe2)3(HL) (23).
1986, 307, 177.
D. J. Brauer, H. Bürger, G. R. Liewald, J.
[2i]
Wilke, J. Organomet. Chem. 1986, 310, 317.
M. Veith, W.
Frank, F. Töllner, H. Lange, J. Organomet. Chem. 1987, 326,
[2j]
315.
M. Veith, L. Stahl, V. Huch, J. Chem. Soc., Chem.
[2k]
Zr(NMe2)3(HL) (23): Colourless sticky material, 95% yield.
Commun. 1990, 359.
M. Veith, M. Noetzel, L. Stahl, V.
Huch, Z. Anorg. Allg. Chem. 1994, 620, 1264. [2l] A. D. Horton,
C15H41N5SiZr (410.83): calcd. C 43.9, H 10.1, N 17.1; found C
1
[2m]
44.0, H 10.2, N 17.4. The H, 13C and 29Si NMR spectra (298 K,
J. de With, Organometallics 1997, 16, 5424.
S.-J. Kim, I.
N. Jung, B. R. Yoo, S. H. Kim, J. Ko, D. Byun, S. O. Kang,
C6D6) indicated the presence of two isomers, namely Zr(NMe2)3[Si-
Me2(NiPr)(NHtBu)] (23Ј) and Zr(NMe2)3[SiMe2(NHiPr)(NtBu)]
(23ЈЈ) (23Ј/23ЈЈ molar ratio about 0.7). Zr(NMe2)3[SiMe2(N-
iPr)(NHtBu)] (23Ј): 1H NMR (C6D6, 298 K): δ ϭ 3.38 (sp, 3JH,H ϭ
6.4 Hz, 1 H, CH), 3.07 (s, 18 H, ZrNCH3), 1.23 (d, 3JH,H ϭ 6.4 Hz,
6 H, CHCH3), 1.05 (s, 9 H, CCH3), 0.25 (s, 6 H, SiCH3) ppm. 13C
NMR (C6D6, 298 K): δ ϭ 52.0 (C), 50.3 (CH), 43.7 (ZrNCH3),
32.1 (CCH3), 29.0 (CHCH3), 3.6 (SiCH3) ppm. 29Si NMR (C6D6,
298 K): δ ϭ Ϫ4.6 ppm.
Organometallics 2001, 20, 2136. [2n] M. S. Hill, P. B. Hitchcock,
[2o]
Organometallics 2002, 21, 3258.
S.-J. Kim, Y.-J. Lee, S. H.
Kim, J. Ko, S. Cho, S. O. Kang, Organometallics 2002, 21, 5358.
[2p]
V. Passarelli, F. Benetollo, P. Zanella, Eur. J. Inorg. Chem.
2004, 1714.
[3]
[4]
[5]
[6]
[7]
[8]
V. Passarelli, F. Benetollo, P. Zanella, G. Carta, G. Rossetto,
Dalton Trans. 2003, 1411.
V. C. Gibson, B. S. Kimberley, A. J. P. White, D. J. Williams,
P. Howard, Chem. Commun. 1998, 313.
D. J. Brauer, H. Bürger, E. Essig, W. Geschwandtner, J. Or-
ganomet. Chem. 1980, 190, 343.
R. Buheitel, W. Milius, W. Schnick, Z. Naturforsch., Teil B
1996, 51, 1141.
F. J. Schattenmann, R. R. Schrock, W. M. Davis, Organometall-
ics 1998, 17, 989.
Zr(NMe2)3[SiMe2(NHiPr)(NtBu)] (23ЈЈ): 1H NMR (C6D6, 298 K):
3
δ ϭ 2.93 (sp, JH,H ϭ 6.1 Hz, 1 H, CH), 3.06 (s, 18 H, ZrNCH3),
3
1.32 (s, 9 H, CCH3), 0.88 (d, JH,H ϭ 6.1 Hz, 6 H, CHCH3), 0.32
(s, 6 H, SiCH3) ppm. 13C NMR (C6D6, 298 K): δ ϭ 54.9 (C), 45.9
(CH), 43.3 (ZrNCH3), 35.5 (CCH3), 26.6 (CHCH3), 4.6 (SiCH3)
ppm. 29Si NMR (C6D6, 298 K): δ ϭ Ϫ5.9 ppm.
H. Schumann, J. Gottfriedsen, S. Dechert, F. Girgsdies, Z.
Anorg. Allg. Chem. 2000, 626, 747.
[9]
U. Wannagat, G. Schreiner, Monatsh. Chem. 1965, 96, 1889.
The rate of the reaction is strongly affected by the nature of R.
In fact Cl/NR2 exchange occurs within the mixing time when
NR2 ϭ NMe2, NC4H8, whereas the reaction is markedly slower
when NR2 ϭ NhiPr or NHtBu, the conversion being complete
after 12 h for NR2 ϭ NHiPr and 70 h for NR2ϭNHtBu.
D. C. Bradley, I. M. Thomas, J. Chem. Soc. 1960, 3857.
Received January 17, 2004
Zr(NMe2)3[SiMe2(NiPr)(NHiPr)] (24): Colourless solid, 95% yield.
C14H39N5SiZr (396.80): calcd. C 42.4, H 9.9, N 17.6; found C 42.7,
[10]
3
H 9.8, N 18.0. 1H NMR (C6D6, 298 K): δ ϭ 3.45 (sp, JH,H
ϭ
3
6.4 Hz, 1 H, CH), 3.08 (s, 18 H, ZrNCH3), 2.92 (sp, JH,H
ϭ
3
6.4 Hz, 1 H, CH), 2.0 (br., 1 H, NH), 1.23 (d, JH,H ϭ 6.4 Hz, 6
3
H, CHCH3), 0.89 (d, JH,H ϭ 6.4 Hz, 6 H, CHCH3), 0.22 (s, 6 H,
[11]
SiCH3) ppm. 13C NMR (C6D6, 298 K): δ ϭ 50.2 (CH), 45.6 (CH),
43.4 (ZrNCH3), 29.0 (CHCH3), 26.6 (CHCH3), 1.7 (SiCH3) ppm.
29Si NMR (C6D6, 298 K): δ ϭ Ϫ2.8 ppm.
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Eur. J. Inorg. Chem. 2004, 4439Ϫ4446