Insertion reactions involving a triamidoamine-supported zirconium complex

Article abstract of DOI:10.1039/c0dt00636j

The reactivity of a triamidoamine-supported zirconium complex, [κ⁵-N,N,N,N,C-(Me₃SiNCH₂CH ₂)₂NCH₂CH₂NSiMe₂CH ₂]Zr (1), toward polar, small-molecule substrates including isocyanides, organic azides, carbodiimides, nitriles, and ketones has been explored. The small-molecule substrates were found to react with the Zr-C bond of complex 1via 1,1- or 1,2-insertion modes, affording ring-expanded products containing new zirconium-carbon, zirconium-nitrogen, or zirconium-oxygen bonds. Solid-state structures of a 1,1-insertion product [κ⁶-N,N,N,N, N,N-(Me₃SiNCH₂CH₂)₂NCH ₂CH₂NSiMe₂CH₂N(NNCH ₂Ph)]Zr (3) and a 1,2-insertion product [κ⁵-N,N,N,N, O-(Me₃SiNCH₂CH₂)₂NCH ₂CH₂NSiMe₂CH₂CPh₂O]Zr (5) are reported. The Royal Society of Chemistry 2010.

Full text of DOI:10.1039/c0dt00636j

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PAPER
www.rsc.org/dalton | Dalton Transactions
Insertion reactions involving a triamidoamine-supported zirconium complex†
Sarah Leshinski,a Tamila Shalumova,b Joseph M. Tanskib and Rory Waterman*a
Received 10th June 2010, Accepted 21st July 2010
DOI: 10.1039/c0dt00636j
5
The reactivity of a triamidoamine-supported zirconium complex, [k -N,N,N,N,C-
(Me3SiNCH2CH2)2NCH2CH2NSiMe2CH2]Zr (1), toward polar, small-molecule substrates including
isocyanides, organic azides, carbodiimides, nitriles, and ketones has been explored. The small-molecule
substrates were found to react with the Zr–C bond of complex 1 via 1,1- or 1,2-insertion modes,
affording ring-expanded products containing new zirconium–carbon, zirconium–nitrogen, or
6
zirconium–oxygen bonds. Solid-state structures of a 1,1-insertion product [k -N,N,N,N,N,N-
(Me3SiNCH2CH2)2NCH2CH2NSiMe2CH2N(N NCH2Ph)]Zr (3) and a 1,2-insertion product
5
[k -N,N,N,N,O-(Me3SiNCH2CH2)2NCH2CH2NSiMe2CH2CPh2O]Zr (5) are reported.
metal-mediated transformations,5–10 yet little reaction chemistry
Introduction
has been reported at the metal–carbon bond of these complexes.
As an alternative to cyclopentadienyl complexes in bond-
Two instances of insertion reactions into the metal–carbon bond
forming catalysis utilizing group 4 metals, we have been
of transition-metal or actinide tuck-in complexes have been ob-
exploring the chemistry of triamidoamine-supported metal
served. Evans reported the double 1,1-insertion reactions of isoni-
species. For the trimethylsilyl-substituted derivative, we
triles and carbon monoxide into the U–C bonds of a double tuck-
5
5
1
in complex, [(h :h -C5Me4SiMe2CH2)2U].11 Likewise, Varga and
have prepared
a
metalated complex, [k -N,N,N,N,C-
(Me3SiNCH2CH2)2NCH2CH2NSiMe2CH2]Zr (1),1 shown in
Fig. 1, which is analogous to a tert-butyldimethylsilyl derivative
discovered prior to 1 by Scott and coworkers.2 An aesthetic
analogy between 1 and group 4 cyclometallated alkyl- or
silyl-substituted cyclopentadienyl, or tuck-in, complexes can be
drawn. More important, 1 is a precursor to a family (N3N)ZrX
(N3N = N(CH2CH2NSiMe3)33-) of complexes via ring opening
with reactive X–H bonds.1 Here as well there is a relationship to
tuck-in species. A similar metathetical ring opening of a doubly
tucked-in tungsten complex with silanes had been executed by
Mork and Tilley.3 Furthermore, such a ring-opening strategy
has been suggested for lanthanide complexes featuring metalated
ligands.4
coworkers demonstrated the insertion of ketone substrates into a
tuck-in titanocene complex, [Ti(h -C5Me5)(h :h -C5Me4CH2)].12
However, reactions of group 4 metal tuck-in complexes have
most often been the restoration of the cleaved C–H bond with
the notable exception of electrophilic abstraction reactions of
permethylzirconocene derivatives by Piers and coworkers.13
It was anticipated that a basic understanding of triamidoamine-
supported zirconium complexes such as 1 will positively impact
efforts to apply these species toward catalysis.14–18 Moreover, reac-
tion at the Zr–C bond of 1 was hypothesized as an alternative route
to functionalized triamidoamine ligands, which have been useful
in bioinorganic chemistry.19–20 Herein, we report the reactions of 1
with small-molecule substrates. For various polar small molecules,
complex 1 readily undergoes insertion reactions at the Zr–C bond.
5
5
1
Results and discussion
The initial goal of this work, to rationally expand the metallacyclic
ring of complex 1 in an effort to functionalize the triamidoamine
ligand, was addressed by reactions of 1 with polar small molecules.
In general, complex 1 readily undergoes insertion reactions of
polar, small molecules into the Zr–C bond of the metallacycle
(vide infra). The exact mode of reactivity, 1,1- versus 1,2-insertion,
appears to be governed by the nature of the small-molecule
substrate. This chemistry in some way mimics the generality
observed in reactions of 1 with E–H bonds.1
5
Fig.
1
Molecular structure of [k -N,N,N,N,C-(Me3SiNCH2CH2)2-
NCH2CH2NSiMe2CH2]Zr (1).
While the metalated derivative 1 has proven a useful synthetic
precursor, the fundamental chemistry of this complex has not
been explored. This is also somewhat similar to group 4 tuck-in
complexes, which are often chemically important intermediates in
1,1-Insertion reactions
aDepartment of Chemistry, University of Vermont, Burlington, VT, 05405,
USA. E-mail: rory.waterman@uvm.edu; Fax: +1 802 656-8705; Tel: +1-
802-656-0278
Treatment of
insertion product, aminoacyl complex [k -N,N,N,N,C-
Me3SiNCH2CH2)2NCH2CH2NSiMe2CH2C( NtBu)]Zr
(2),
1 with tert-butylisocyanide gave the 1,1-
5
bDepartment of Chemistry, Vassar College, Poughkeepsie, NY, 12604, USA
† CCDC reference numbers 780977 and 780978 for compounds 3 and
5. For crystallographic data in CIF or other electronic format see DOI:
10.1039/c0dt00636j
as analytically pure colorless microcrystals in 82% yield (eqn (1)).
Investigation of 2 by H NMR spectroscopy revealed that the
1
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◦
˚
Table 2 Selected bond lengths (A) and angles ( ) for complex 3
resonances for the trimethylsilyl substituents and methyl groups
of the metallacycle varied little from those of the starting material,
complex 1. Three significant spectroscopic features emerged in
identifying the ring-expanded product 2 from metallacyclic 1.
First, the ethylene backbone protons, which appear coincidentally
as two complex resonances for complex 1,16 become more disperse
and appear as five resonances in the 1H NMR spectrum of
complex 2. The second feature in the 1H NMR spectrum of 2 is a
dramatic change in chemical shift of the metallacycle methylene
protons from d 0.31 for 1 to two inequivalent resonances
at d 4.64 and 4.27. The assignment of which was confirmed
by an HMQC experiment. The inequivalence is likely due to
slowed pseudorotation of the five-membered metallacycle.21
Inequivalence of the metallacycle methylene protons is unique to
complex 2 and was not observed for the other insertion products.
Finally, a diagnostic imine carbon resonance at d 157 was
observed in the 13C NMR spectrum of 2. A related transformation
was reported by Evans and coworkers, where insertion of
tBuN C into a U–C bond of a doubly metalated uranocene
afforded a bis(tethered iminoacyl) actinide metallocene.11
Zr–N(1)
Zr–N(2)
Zr–N(3)
Zr–N(4)
Zr–N(5)
Zr–N(7)
2.123(2)
2.116(2)
2.094(2)
2.440(2)
2.251(2)
2.308(2)
N(5)–N(6)
N(6)–N(7)
1.307(3)
1.316(3)
107.6(2)
116.6(2)
95.8(1)
N(5)–N(6)–N(7)
C(15)–N(5)–N(6)
N(6)–N(5)–Zr
C(15)–N(5)–Zr
130.1(2)
Hillhouse and Bercaw for hafnocene systems22 followed by a report
from Wilkinson and coworkers for a series of metals including
zirconocene derivatives.23 The most recent example, from Whitby
2
and coworkers, included crystallographic data for an h -bound
triazenido zirconocene complex.24
Confirmation of the structure of these azide-insertion products
was obtained by an X-ray diffraction study. Suitable crystals of
3 were grown by cooling a concentrated Et2O solution to -30 ◦C
for extended periods. The molecular structure of 3, shown in Fig.
2, revealed that the diazo functionality acts as a ligand. This is
an interesting observation in the solid state because phosphido
complexes of (N3N)Zr that possess a pendent phosphine arm
only display coordination of that pendent phosphine only when it
is geometrically constrained.18 This also appears to be the case
with complex 3, which is odd given the greater propensity of
amido ligands to p-donate to the (N3N)Zr fragment.1 Structural
parameters suggest that the metallacycle amine ligand engages
in only sigma bonding to zirconium based on the bond length,
(1)
A 1,1-insertion mode was realized for the reaction of azides
with 1 (eqn (2)). Reaction of complex 1 with organic azides,
MesN3 or PhCH2N3, in benzene solution gave the 1,1-insertion
˚
Zr–N(5) = 2.251(2) A, and non-planar nitrogen, where the sum
of angles at N(5) ~345◦. This stands in contrast to the set,
albeit limited, of other (N3N)Zr-amido complexes, which all have
structural evidence for p-donation to the metal center.1,25 The
remaining bonds and angles for the triazenido ligand (Table
2) compare favorably with those for the zirconium complex
structurally characterized by Whitby and coworkers.24 Complex
4 is expected to have a similar structure, and neither complex
displayed evidence for dynamic behavior in solution by 1H NMR
spectroscopy.
6
products at the g-nitrogen of the organic azide [k -N,N,N,N,N,N-
(Me3SiNCH2CH2)2NCH2CH2NSiMe2CH2N(N NR)]Zr (R
=
CH2Ph, 3; R = Mes, 4) as analytically pure yellow microcrystals for
3 and orange microcrystals for 4 in 81% and 61% yield, respectively
(eqn (2)). Similar to complex 2, there was a greater chemical shift
dispersion for the ethylene resonances in the 1H NMR spectrum. In
each product, the metallacycle methylene resonance was consistent
with that of 1. Relevant spectroscopic data for the complexes is
summarized in Table 1.
(2)
A number of triazenido complexes are known for a variety of
metals. For group 4 metals, all previously reported triazenido
complexes have been prepared by organoazide insertion into a
metal–alkyl bond. This kind of reactivity was first observed by
Table 1 Selected NMR spectroscopic data (d) for 3 and 4
13C NMR
1H NMR
Metallacycle
CH2
SiMe2
CH2
Trimethylsilyl
CH3
Metallacycle
CH2
Compound
6
Fig.
2
Molecular structure of [k -N,N,N,N,N,N-(Me3SiNCH2-
3
4
47.0
46.8
0.20
0.23
0.13
0.10
3.65
3.61
CH2)2NCH2CH2NSiMe2CH2(N3CH2Ph)]Zr (3) with thermal ellipsoids
drawn at the 35% level. Hydrogen atoms are omitted for clarity.
9074 | Dalton Trans., 2010, 39, 9073–9078
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1,2-Insertion reactions
Broadening the scope of insertion reactivity of 1, a 1,2-insertion
mode was realized for a different set of small-molecule substrates.
Treatment of
1 with benzophenone in benzene solu-
5
tion afforded the 1,2-insertion product, [k -N,N,N,N,O-
(Me3SiNCH2CH2)2NCH2CH2NSiMe2CH2CPh2O]Zr (5), as col-
orless microcrystals in 84% yield (Scheme 1).
5
Fig. 3 Molecular structure of [k -N,N,N,N,O-(Me3SiNCH2CH2)2NCH2-
CH2NSiMe2CH2(Ph2CO)]Zr (5) with thermal ellipsoids drawn at the 35%
level. Hydrogen atoms are omitted for clarity.
◦
˚
Table 3 Selected bond lengths (A) and angles ( ) for complex 5
Zr–N(1)
Zr–N(2)
Zr–N(3)
Zr–N(4)
2.108(1)
2.112(1)
2.091(1)
2.383(1)
Zr–O
C(16)–O
C(16)–O–Zr
1.955(8)
1.422(1)
148.62(7)
Table 4 Selected NMR spectroscopic data (d) for 7, 8, and 9
Scheme 1 Insertion reactions of complex 1.
13C NMR 1H NMR
Compared to complexes 3 and 4, a similar trend was observed
in the 1H NMR spectrum of 5, where the ethylene bridge protons
were more dispersed than for 1. The methylene protons of the
metallacycle displayed a downfield shift to d 2.43 in the 1H NMR
spectrum. A 13C NMR resonance was observed at d 150 that
was assigned as the new carbon atom of the metallacycle, shifted
downfield likely due to the adjacent oxygen atom and phenyl
ring current. An X-ray diffraction study confirmed the solution
structure of 5. Single crystals of 5◦were obtained by cooling a
concentrated Et2O solution to -30 C for extended periods. The
molecular structure of 5, shown in Fig. 3, features Zr–O = 1.955(8)
Trimethylsilyl
CH3
Metallacycle
CH2
Compound
C
N
SiMe2 CH2
7
8
9
152.2
162.9
169.5
0.20
0.37
0.15
0.46
0.20
0.43
2.39
2.33
2.29
(Me3SiNCH2CH2)2NCH2CH2NSiMe2CH2C C(NCy) NCy)]Zr
5
(7) in 69% yield, [k -N,N,N,N,N-(Me3SiNCH2CH2)2-
NCH2CH2NSiMe2CH2C(NPh) NPh]Zr (8) in 78% yield, and
5
[k - N,N,N,N,N - (Me3SiNCH2CH2)2NCH2CH2NSiMe2CH2C -
˚
˚
A (Table 3). The C(16)–O bond length of 1.422(1) A is typical of
C–O single bonds.26
(NiPr) NiPr]Zr (9) in 68% yield (Scheme 1). Each of the
carbodiimide-insertion products gave similar 13C and H NMR
1
The insertion of ketone substrates has been examined for a
variety of metals. A recent, related reaction was reported by Guan
and coworkers, who observed the addition of benzophenone to
zirconocene-1-aza-1,3-diene complexes to afford a product by 1,2-
insertion into the Zr–C bond.27
spectroscopic data. Furthermore, this data was consistent with
complexes 5 and 6. Relevant spectroscopic data for compounds
7, 8, and 9 is summarized in Table 4. The disparities observed for
data pertaining to complex 8 are attributed to the effects of the
ring current of the N,N¢-diphenylcarbodiimide substrate.
Reaction of
1
with benzonitrile in benzene solution
5
gave
[k -N,N,N,N,N-(Me3SiNCH2CH2)2NCH2CH2NSiMe2-
CH2C(Ph) N]Zr (6) as analytically pure colorless microcrystals
in 51% yield (Scheme 1). The 1H NMR spectrum of 6 was
consistent with that of 5 as the metallacycle methylene protons
were resolved significantly downfield at d 2.46 and the ethylene
bridge protons were observed as four different resonances. The
13C NMR spectrum of 6 featured a diagnostic imine resonance at
d 163.
Conclusions
The reactivity of 1 was examined with a variety of small, polar
substrates including isocyanides, organic azides, nitriles, ketones,
and carbodiimides. It was demonstrated that insertion into the
Zr–C bond of 1 is facile and produces a variety of one- and two-
atom ring-expanded products via 1,1- and 1,2-insertion reactions,
respectively. Furthermore, these reactions generate products in
moderate to high yields. The relative stability of the Zr–N and
Zr–O bonds formed in these reactions has only led to observation
Complex 1 was reacted with a family of carbodiimides in
benzene solution. In each case, analytically pure colorless micro-
5
crystals were obtained by lyophilization to give [k -N,N,N,N,N-
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of functionalization at one trimethylsilyl arm of the triamidoamine
ligand. Further studies of this kind of reactivity are ongoing.
C22H43N7Si3Zr: C, 45.31; H, 7.78; N, 16.89. Found: C, 45.37; H,
8.09; N, 16.12.
[j5 -N,N,N,N,N-(Me3SiNCH2CH2)2NCH2CH2NSiMe2CH2N-
(N NMes)]Zr (4). A 50 mL round bottom flask was charged
with 1 (50 mg, 0.11 mmol) and ca. 5 mL of benzene. To the stirring
solution was added a 3 mL benzene solution of mesitylazide
(18 mg, 0.11 mmol). Gradual change in the solution from colorless
to dark orange was observed upon stirring for 12 h. The benzene
solution was lyophilized yielding the title compound as a colorless
powder. The powder was dissolved in 5 mL of Et2O, and the
solution was filtered through Celite then cooled to -30 ◦C. After
2 d, orange crystals formed (42 mg, 0.069 mmol, 61%). 1H
(500.1 MHz):d 6.84 (s, 2 H, C6Me3H2), 3.61 (s, 2 H, ZrCH2),
3.41 (m, 2 H, CH2), 3.14 (t, JHH = 5.5, 2 H, CH2), 3.10 (m, 2 H,
CH2), 2.73 (s, 6 H, CH3), 2.40 (m, 6 H, CH2), 2.16 (s, 3 H, CH3),
Experimental details
Preparation of compounds
General considerations. All manipulations were performed un-
der an atmosphere of dry nitrogen using Schlenk or high vacuum
techniques and/or in an M. Braun glovebox. Dry, oxygen-free
solvents were employed throughout. Benzene-d6 was purchased
from Cambridge Isotope Laboratory, then degassed and dried
over NaK alloy. Infrared spectra (Nujol mulls, KBr plates) were
recorded using a Perkin-Elmer System 2000 FT-IR spectrometer at
a resolution of 1 cm-1. 1H and 13C NMR spectra were recorded on
Bruker AXR or Varian 500 MHz NMR spectrometers in benzene-
d6 and are reported with reference to residual solvent resonances
(d 7.16 and d 128.0). All chemicals were dried and degassed by
standard techniques. Complex 1 and N,N¢-diphenylcarbodiimide
were synthesized according to literature preparations.1,28
1
0.23 (s, 6 H, CH3), 0.10 (s, 18 H, CH3). 13C{ H} (125.8 MHz): d
131.6 (s, C6Me3H6), 131.2 (s, C6Me3H6), 129.6 (s, C6Me3H6), 128.3
(s, C6Me3H6), 59.4 (s, CH3), 59.2 (s, CH3), 47.6 (s, CH2), 47.1 (s,
CH2), 46.8 (s, CH2), 23.5 (s, CH2), 20.5 (s, CH2), 1.31 (s, CH3),
0.67 (s, CH3). IR (KBr, Nujol): 2909 s, 2855 s, 2848 m, 1463 w,
1295 w, 1243 m, 1180 w, 1001 w, 948 w, 909 w, 838 w, 791 w, 741 w
cm-1. Anal Calcd for C24H49N7Si3Zr: C, 47.16; H, 8.08; N, 16.04.
Found: C, 47.38; H, 8.09; N, 15.00.
[j5 -N,N,N,N,C -(Me3SiNCH2CH2)2NCH2CH2NSiMe2CH2C-
(
NtBu)]Zr (2). A 50 mL round bottom flask was charged with
1 (50 mg, 0.11 mmol) and 5 mL of benzene. To the stirring solution
was added a 3 mL benzene solution of tert-butylisocyanide (9 mg,
0.11 mmol). After stirring for 12 h, the mixture was frozen and
lyophilized, yielding 2 as a colorless powder. The powder was
dissolved in 5 mL of Et2O, and the solution was filtered through
Celite then cooled to -30 ◦C. After 3 d, colorless crystals formed
(49 mg, 0.092 mmol, 82%). 1H (500.1 MHz): d 4.64 (s, 1 H, CH2),
4.27 (s, 1 H, CH2), 3.32 (m, 2 H, CH2), 3.08 (t, JHH = 5.52 H, CH2),
2.97 (dd, JHH = 15.4, JHH = 4.5, 2 H, CH2), 2.45 (m, 4 H, CH2),
2.23 (dd, JHH = 12.0, JHH = 3.5, 2 H, CH2), 1.63 (s, 9 H, C(CH3)3),
[j5 -N,N,N,N,O-(Me3SiNCH2CH2)2NCH2CH2NSiMe2CH2C-
Ph2O]Zr (5). A 50 mL round bottom flask was charged with
1 (50 mg, 0.11 mmol) and ca. 5 mL of benzene. To the stirring
solution was added a 3 mL benzene solution of benzophenone
(20 mg, 0.11 mmol). After stirring for 12 h the mixture was frozen
and lyophilized, yielding 5 as a colorless powder. The powder was
dissolved in 5 mL of Et2O, and the solution was filtered through
Celite then cooled to -30 ◦C. After 3 d, colorless crystals formed
(59 mg, 0.093 mmol, 84%). 1H (500.1 MHz): d 7.68 (d, 4 H, C6H5),
7.21 (t, 4 H, C6H5), 7.03 (t, 2 H, C6H5), 3.22 (m, 6 H, CH2), 2.43
(m, 4 H, CH2), 2.36 (t, JHH = 6.0, 2 H, CH2), 2.11 (s, 2 H, CH2),
0.42 (s, 6 H, CH3), 0.27 (s, 18 H, CH3). 13C{ H} (125.8 MHz): d
1
157.5 (s, C N), 92.1 (s, CH2), 66.5 (s, CH2), 64.7 (s, CH2), 48.4
(s, CH2), 45.8 (s, CH2), 27.5 (s, C(CH3)3), 14.1 (s, C(CH3)3), 2.0 (s,
CH3), 0.2 (s, CH3). IR (KBr, Nujol): 2919 s, 2854 w, 1613 w (nCN),
1538 m, 1462 s, 1377 m, 1244 w, 1108 w, 1062 w, 933 w, 937 w, 834
w, 774 w cm-1. Anal Calcd for C20H47N5Si3Zr: C, 45.06; H, 8.89;
N, 13.14. Found: C, 44.58; H, 8.83; N, 12.67.
1
0.24 (s, 18 H, CH3), 0.17 (s, 6 H, CH3). 13C{ H} (125.8 MHz): d
150.8 (s, CO), 128.5 (s, C6H5), 128.3 (s, C6H5), 126.8 (s, C6H5),
126.3 (s, C6H5), 85.4 (s, CH2), 57.1 (s, CH2), 56.4 (s, CH2), 48.5 (s,
CH2), 46.3 (s, CH2), 1.2 (s, CH3), 0.7 (s, CH3). IR (KBr, Nujol):
2851 w, 1598 w, 1463 s, 1377 m, 1349 m, 1245 m, 1089 w, 1059 m,
999 w, 836 m, 792 m, 701 w cm-1. Anal Calcd for C28H48N4OSi3Zr:
C, 53.20; H, 7.65; N, 8.86. Found: C, 53.04; H, 7.76; N, 8.81.
[j5 -N,N,N,N,N-(Me3SiNCH2CH2)2NCH2CH2NSiMe2CH2N-
(N NCH2Ph)]Zr (3). A 50 mL round bottom flask was charged
with 1 (50 mg, 0.11 mmol) and 5 mL of benzene. To the stirring
solution was added a 3 mL benzene solution of benzylazide (50 mg,
0.11 mmol). A gradual color change from colorless to yellow
was observed upon stirring for 12 h. The benzene solution was
lyophilized yielding 3 as a colorless powder. This powder was then
dissolved in 5 mL of Et2O, and the solution was filtered through
Celite then cooled to -30 ◦C. After 2 d, yellow crystals formed
(53 mg, 0.090 mmol, 81%). 1H (500.1 MHz): d 7.43 (d, 2 H, C6H5),
7.18 (t, 2 H, C6H5), 7.08 (t, 1 H, C6H5), 5.03 (s, 2 H, NCH2), 3.65
(s, 2 H, ZrCH2), 3.39 (m, 2 H, CH2), 3.11 (m, 4 H, CH2), 2.39 (m,
4 H, CH2), 2.42 (t, JHH = 5.0, 2 H, CH2), 0.20 (s, 6 H, CH3), 0.13
[j5 -N,N,N,N,N-(Me3SiNCH2CH2)2NCH2CH2NSiMe2CH2C-
(Ph) N)]Zr (6). A 50 mL round bottom flask was charged with
1 (50 mg, 0.11 mmol) and ca. 5 mL of benzene. To the stirring
solution was added a 3 mL benzene solution of benzonitrile
(12 mg, 0.11 mmol). A gradual change in the solution from
colorless to yellow was observed upon stirring for 12 h. The
benzene solution was lyophilized yielding 6 as a colorless powder.
The powder was dissolved in 5 mL of Et2O, and the solution was
filtered through Celite then cooled to -30 ◦C. After 3 d, yellow
1
crystals formed (38 mg, 0.069 mmol, 51%). H (500.1 MHz): d
1
(s, 18 H, CH3). 13C{ H} (125.8 MHz): d 140.0 (s, CH2), 129.7 (s,
8.10 (d, 2 H, C6H5), 7.20 (m, 2 H, C6H5), 6.96 (d, 2 H, C6H5), 6.63
(t, 2 H, C6H5), 3.40 (m, 2 H, CH2), 3.38 (t, JHH = 5.5, 2 H, CH2),
3.15 (m, 4 H, CH2), 2.60 (m, 4 H, CH2), 2.46 (s, 2 H, CH2), 0.26
C6H5), 128.7 (s, C6H5), 128.8 (s, C6H5), 127.5 (s, C6H5), 62.8 (s,
CH2), 60.7 (s, CH2), 60.8 (s, CH2), 47.9 (s, CH2), 47.0 (s, CH2) 1.8
(s, CH3), 0.5 (s, CH3). IR (KBr, Nujol): 2922 w, 2113 w, 1603 w,
1467 s, 1377 m, 1245 m, 1208 w, 1071 m, 1029 w, 938 m, 909 w,
836 s, 785 m, 743 w, 697 w, 579 w, 446 w cm-1. Anal Calcd for
1
(s, 18 H, CH3), 0.16 (s, 6 H, CH3). 13C{ H} (125.8 MHz): d 162.9
(s, C N), 128.7 (s, C6H5), 126.6 (s, C6H5), 128.5 (s, C6H5), 128.3
(s, C6H5), 59.6 (s, CH2), 58.0 (s, CH2), 49.1 (s, CH2), 46.7 (s, CH2),
9076 | Dalton Trans., 2010, 39, 9073–9078
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Table 5 Crystal data and structure refinement parameters for 5 and 3
1.6 (s, CH3), 0.2 (s, CH3). IR (KBr, Nujol): 2860 s, 2646 w, 1946 w,
1614 w (nCN), 1589 m, 1463 s, 1377 s, 1338 m, 1244 s, 1135 m, 929
s, 842 s, 784 w, 696 w, 565 w cm-1. Anal Calcd for C22H43N5Si3Zr:
C, 47.77; H, 7.84; N, 12.66. Found: C, 47.49; H, 7.92; N, 11.72.
3
5
Formula
M
C28H48N4OSi3Zr
632.19
C22H45N7Si3Zr
583.14
Monoclinic
Yellow
10.729(3)
15.794(4)
17.897(5)
90
92.125(4)
90
3030.8(15)
P21/n
4
1.72 to 27.88
1.278
36 906
[j5 -N,N,N,N,N-(Me3SiNCH2CH2)2NCH2CH2NSiMe2CH2C-
(NCy) NCy]Zr (7). A 50 mL round bottom flask was charged
with 1 (50 mg, 0.11 mmol) and ca. 5 mL of benzene. To the
stirring solution was added a 3 mL benzene solution of N,N¢-
dicyclohexylcarbodiimide (23 mg, 0.11 mmol). After stirring for 12
h the mixture was frozen and lyophilized, yielding 7 as a colorless
powder, which was dissolved in 5 mL of Et2O. The solution was
filtered through Celite then cooled to -30 ◦C. After 3 d, colorless
Crystal system
Color
Monoclinic
Colorless
10.0807(3)
15.3755(5)
20.9774(6)
90
90.42
90
3251.32(17)
P21/n
4
1.64 to 30.46
1.292
45 315
9295
0.0242
0.0240
0.0600
0.430 and –0.208
1.036
˚
a/A
˚
b/A
˚
c/A
a/◦
b/◦
g /◦
3
˚
Unit cell vol./A
Space group
1
crystals formed (50 mg, 0.076 mmol, 69%). H (500.1 MHz): d
Z
q range/◦
m/mm-1
N
3.42 (m, 2 H, C6H11), 3.28 (m, 4 H, CH2), 2.93 (t, JHH = 6.0, 2 H,
CH2), 2.54 (m, 2 H, CH2), 2.39 (m, 2H, CH2), 2.33 (m, 2 H, CH2),
2.29 (s, 2 H, CH2), 1.83 (m, 10 H, C6H11), 1.62 (m, 2H, C6H11),
1.33–1.25 (m, 8H, C6H11), 0.46 (s, 18 H, CH3), 0.20 (s, 6 H, CH3).
Nind
7212
0.0454
0.0351
0.0802
0.595 and –0.290
1.111
Rint
a
R1 (I > 2s(I))
1
13C{ H} (125.8 MHz): d 152.2 (s, C N), 68.6 (s, CH2), 60.8 (s,
b
wR2 (I > 2s(I))
C6H11), 60.6 (s, C6H11), 49.6 (s, C6H11), 36.1 (s, C6H11), 33.0 (s,
CH2), 26.6 (s, CH2), 25.6 (s, CH2), 25.0 (s, CH2) 2.9 (s, CH3), 0.6
(s, CH3). IR (KBr, Nujol): 2922 s, 2854 s, 1610 w (nCN), 1461 s,
1377 s, 1260 s, 1082 w, 932 w, 834 w, 722 w cm-1. Anal Calcd for
C28H60N6Si3Zr: C, 51.24; H, 9.21; N, 12.81. Found: C, 50.99; H,
9.25; N, 12.21.
3
˚
Drmax; Drmin/e A
GoF on R1
ꢀ
ꢀ
ꢀ
aR1 = ꢀFo| - |Fcꢀ/ |Fo|. bwR2 = { [w(Fo - Fc2)2]/ [w(Fo2)2]}
.
2
1/2
(s, CH3). IR (KBr, Nujol): 2924 s, 2853 s, 2361 m, 1631 w (nCN),
1579 m, 1462 w, 1378 s, 1250 s, 1078 s, 930 s, 836 s, 788 m, 748 w
cm-1. Anal Calcd for C22H52N6Si3Zr: C, 45.86; H, 9.10; N, 14.59.
Found: C, 46.35; H, 9.09; N, 14.37.
[j5 -N,N,N,N,N-(Me3SiNCH2CH2)2NCH2CH2NSiMe2CH2C-
(NPh) NPh]Zr (8). A 50 mL round bottom flask was charged
with 1 (50 mg, 0.11 mmol) and ca. 5 mL of benzene. To the
stirring solution was added a 3 mL benzene solution of N,N¢-
diphenylcarbodiimide (21 mg, 0.11 mmol). After stirring for 12 h
the mixture was frozen and lyophilized yielding 8 as a colorless
powder, which was dissolved in 5 mL of Et2O. The solution was
filtered through Celite then cooled to -30 ◦C. After 3 d, colorless
X-Ray structure determinations
X-Ray diffraction data were collected on a Bruker APEX 2
˚
CCD platform diffractometer (MoKa, l = 0.71073 A) at 125 K.
Suitable crystals of either complex 3 or 5 were mounted in a
nylon loop with Paratone-N cryoprotectant oil. The structures
were solved using direct methods and standard difference map
techniques and were refined by full-matrix least squares procedures
on F2 with SHELXTL (version 6.14).29 All non-hydrogen atoms
were refined anisotropically. Hydrogen atoms were included in
calculated positions and were refined using a riding model. Data
and refinement parameters are summarized in Table 5.
1
crystals formed (50 mg, 0.078 mmol, 78%). H (500.1 MHz): d
7.24–6.99 (m, 10 H, C6H5), 3.45 (m, 4 H, CH2), 3.01 (t, JHH
=
6.0, 2 H, CH2), 2.57 (m, 4 H, CH2), 2.44 (t, 2 H, CH2), 2.33
1
(s, 2 H, CH2), 0.20 (s, 18 H, CH3), 0.37 (s, 6 H, CH3). 13C{ H}
(125.8 MHz): d 162.9 (s, C N), 134.2 (s, C6H5), 134.1 (s, C6H5),
128.7 (s, C6H5), 128.3 (s, C6H5), 64.8 (s, CH2), 50.2 (s, CH2), 50.2
(s, CH2), 47.7 (s, CH2), 25.9 (s, CH2), 2.8 (s, CH3), 0.2 (s, CH3). IR
(KBr, Nujol): 2917 s, 2852 s, 2361 w, 1620 w (nCN), 1596 m, 1458
s, 1377 s, 1259 s, 1076 m, 925 s, 837 s, 789 w cm-1. Anal Calcd for
C28H48N6Si3Zr: C, 52.21; H, 7.52; N, 13.04. Found: 51.96; H, 7.79;
N, 13.45.
Acknowledgements
The authors thank Dr Bruce Deker (UVM) for assistance with 2D
NMR experiments. This work was supported by the U. S. National
Science Foundation (CHE-0747612). X-Ray crystallographic fa-
cilities were provided by the U. S. National Science Foundation
(CHE-0521237 to JMT). RW is a Research Fellow of the Alfred
P. Sloan Foundation.
[j5 -N,N,N,N,N-(Me3SiNCH2CH2)2NCH2CH2NSiMe2CH2C-
(
NiPr)NiPr]Zr (9). A 50 mL round bottom flask was charged
with 1 (50 mg, 0.11 mmol) and 5 mL of benzene. To the
stirring solution was added a 3 mL benzene solution of N,N¢-
diisopropylcarbodiimide (14 mg, 0.11 mmol). After stirring for 2
h, the mixture was frozen and lyophilized yielding 9 as a colorless
powder, which was dissolved in 5 mL of Et2O. The solution was
filtered through Celite then cooled to -30 ◦C. After 3 d, colorless
Notes and references
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crystals formed (44 mg, 0.076 mmol, 68%). H (500.1 MHz): d
3.83 (m 2 H, CH(CH3)2), 3.27 (m, 4 H, CH2), 2.93 (t, JHH = 6.0,
2 H, CH2), 2.54 (m, 2 H, CH2), 2.39 (m, 4 H, CH2), 2.23 (s, 2 H,
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1
13C{ H} (125.8 MHz): d 169.5 (s, C N), 60.0 (s, CH2), 58.6 (s,
CH2), 50.7 (s, CH2), 47.6 (s, CH2), 46.7 (s, CH2), 1.9 (s, CH3), 1.8
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9078 | Dalton Trans., 2010, 39, 9073–9078
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The Royal Society of Chemistry 2010
©