Amido/amine triazacyclononane-based zirconium complexes: Syntheses, reactivity, and structures

Article abstract of DOI:10.1021/ic061588z

The reactions of [Zr(NMe₂)₄]₂ with triamido-triazacyclonane ligand precursors, {NH(Ph)SiMe₂} ₃tacn (H₃N₃[9]N₃) and {NH(C ₆H₄F)SiMe₂}₃tacn (H ₃N₃-_F[9]N₃), led to the formation of complexes [Zr(NMe₂)₂{N(Ph)SiMe2}2{NH(Ph) SiMe ₂}tacn], 1, and [Zr(NMe₂)₂{N(o-C ₆H₄F)SiMe₂}₂{NH(o-C ₆H₄F)SiMe₂} tacn], 2, where the zirconium is coordinated to two remaining dimethylamido ligands and to a dianionic tacn-based ligand, [{N(Ph′)SiMe₂}₂{NH(Ph′)SiMe ₂}tacn]^2-, that formed from deprotonation of two amine pendent arms of the ligands' precursors. The third pendent arm of H ₃N₃[9]N₃ and H₃N_3-F[9] N₃ remains neutral and not bonded to the zirconium. Treatment of 1 with NaH led to the synthesis of [Zr(NMe2){N(Ph)SiMe₂} ₂tacn], 3, that results from the cleavage of the N-Si bond of the original neutral pendent arm. Complexes [ZrCl{N(Ph′)SiMe₂} ₂tacn] (Ph′ = C₆H₅, 4, and C ₆H₄F, 5) have been obtained by reactions of ZrCl ₄ with {MN(Ph′)SiMe₂}₃tacn·2THF (M = Li, Na). Reactions of 4 and 5 with LiC≡CPh led to the syntheses of [Zr(CCPh){N(Ph′)SiMe₂}₂tacn] (Ph′ = C ₆H₅, 6, and C₆H₄F, 7). The solid-state structure of 3 shows a chiral metal center.

Full text of DOI:10.1021/ic061588z

Inorg. Chem. 2007, 46, 750−755
Amido/Amine Triazacyclononane-Based Zirconium Complexes:
Syntheses, Reactivity, and Structures
Humberto Ferreira, Alberto R. Dias, M. Teresa Duarte, Jose´ R. Ascenso, and Ana M. Martins*
Centro de Qu´ımica Estrutural, Instituto Superior Te´cnico, AV. RoVisco Pais 1,
1049-001 Lisboa, Portugal
Received August 22, 2006
The reactions of [Zr(NMe2)4]2 with triamido
and NH(C6H4F)SiMe2 3tacn (H3N3 F[9]N3), led to the formation of complexes [Zr(NMe2)2
SiMe2 tacn], 1, and [Zr(NMe2)2
−
triazacyclonane ligand precursors,
{
NH(Ph)SiMe2
}3tacn (H3N3[9]N3)
{
}
}
{N(Ph)SiMe2}2{NH(Ph)
-
{
N(o-C6H4F)SiMe2}2{NH(o-C6H4F)SiMe2
}
tacn], 2, where the zirconium is coordinated
-
tacn]2
to two remaining dimethylamido ligands and to a dianionic tacn-based ligand, [
{
N(Ph
′
)SiMe2}2{NH(Ph
′
)SiMe2
}
,
that formed from deprotonation of two amine pendent arms of the ligands’ precursors. The third pendent arm of
H3N3[9]N3 and H3N3 F[9]N3 remains neutral and not bonded to the zirconium. Treatment of 1 with NaH led to the
-
synthesis of [Zr(NMe2)
pendent arm. Complexes [ZrCl
{
N(Ph)SiMe2
N(Ph
3tacn 2THF (M
}
2tacn], 3, that results from the cleavage of the N
)SiMe2 2tacn] (Ph′ ) C6H5, 4, and C6H4F, 5) have been obtained by reactions
Li, Na). Reactions of 4 and 5 with LiC CPh led to the syntheses
−Si bond of the original neutral
{
′
}
of ZrCl4 with
of [Zr(CCPh)
{
MN(Ph
′
)SiMe2
}
‚
)
t
{N(Ph )SiMe2
′
}
2tacn] (Ph′ ) C6H5, 6, and C6H4F, 7). The solid-state structure of 3 shows a chiral
metal center.
Introduction
tacn and imido donors or anionic amido tacn-derived
moieties, in particular, have been thought as alternatives to
Amido ligands (R2N-) proved to be very useful tools for
the design of new polydentate ligand frameworks1-3 where
peculiar balances of electronic and steric properties, resulting
from variations of the nitrogen substituents and combinations
with other functionalities, led to new and varied metal
reactivity patterns.4-9 In this context, the incorporation of
amido ligands in macrocyclic topologies, either as pendent
arms of macrocyclic backbones10-17 or in the macrocyclic
skeleton,18-20 was explored. Ligands obtained by combining
cyclopentadienyl ligands.19,21 The results reported so far have
shown that, despite the classical role of neutral macrocycles
as support ligands of transition metals chemistry, anionic
macrocyclic-amido transition metal derivatives are versatile
compounds that require extensive studies before a pattern
of their reactivity might be established. Our previous work
(11) Robson, D. A.; Rees, L. H.; Mountford, P.; Schro¨der, M. J. Chem.
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Inorg. Chem. 1995, 34, 6440.
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T.; Henriques, R. T. Inorg. Chem. 2003, 42, 2675.
* To whom correspondence should be addressed. E-mail:
ana.martins@ist.utl.pt. Phone: +351-218419284. Fax: +351-218464457.
(1) Kempe, R. Eur. J. Inorg. Chem. 2003, 791.
(2) Male, N. A. H.; Thornton-Pett, M.; Bochmann, M. J. Chem. Soc.,
Dalton Trans. 1997, 2487.
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(4) Axenov, K. V.; Kilpelainen, I.; Klinga, M.; Leskela, M.; Repo, T.
Organometallics 2006, 25, 463.
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R. J. Am. Chem. Soc. 1999, 121, 7822.
(14) Martins, A. M.; Ascenso, J. R.; Azevedo, C. G.; Dias, A. R.; Duarte,
M. T.; Ferreira, H.; Ferreira, M. J.; Henriques, R. T.; Lemos, M. A.;
Li, L.; Ferreira da Silva, J. L. Eur. J. Inorg. Chem. 2005, 1689.
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A. M.; Domingos, A.; Marques, N. Inorg. Chem. 2003, 42, 4223.
(16) Martins, A. M.; Ascenso, J. R.; Costa, S. M. B.; Dias, A. R.; Ferreira,
H.; Ferreira, J. A. B. Inorg. Chem. 2005, 44, 9017.
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Kryatov, S. V.; Rybak-Akimova, E. V.; McDonough, J. E.; Hoff, C.
D. J. Am. Chem. Soc. 2005, 127, 15191.
(8) Morello, L.; Yu, P. H.; Carmichael, C. D.; Patrick, B. O.; Fryzuk, M.
D. J. Am. Chem. Soc. 2005, 127, 12796.
(17) Bambirra, S.; Tsurugi, H.; Van Leusen, D.; Hessen, B. Dalton Trans.
2006, 1157.
(18) Porter, R. M.; Danopoulos, A. A.; Reid, G.; Titcomb, L. R. Dalton
Trans. 2005, 427.
(19) Schmidt, J. A. R.; Giesbrecht, G. R.; Cui, C. M.; Arnold, J. Chem.
Commun. 2003, 1025.
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N. J. Am. Chem. Soc. 1999, 121, 10444.
(10) Bambirra, S.; Van Leusen, D.; Meetsma, A.; Hessen, B.; Teuben, J.
H. J. Chem. Soc., Chem. Commun. 2001, 637.
(20) Fletcher, J. S.; Male, N. A. H.; Wilson, P. J.; Rees, L. H.; Mountford,
P.; Schro¨der, M. J. Chem. Soc., Dalton Trans. 2000, 4130.
(21) Male, N. A. H.; Skinner, M. E. G.; Bylikin, S. Y.; Wilson, P. J.;
Mountford, P.; Schroder, M. Inorg. Chem. 2000, 39, 5483.
750 Inorganic Chemistry, Vol. 46, No. 3, 2007
10.1021/ic061588z CCC: $37.00
© 2007 American Chemical Society
Published on Web 01/05/2007

Tacn-Based Zr Complexes
Scheme 1
Scheme 2
Chart 1
on titanium triamido-triazacyclononane compounds has
shown that although the hexadentate ligand prevents the
approach to the metal center, radical transfer from Ti(III)
led to a singular reactivity.16,22 The results here described
extend the work to zirconium complexes, which reveal a very
different behavior from that of titanium.
relation to a plane containing the two dimethylamido ligands,
the metal and the tacn nitrogen atom opposite to the NMe2
ligands (represented in red). B represents a chiral molecule
which NMR spectra may display an average Cs symmetry
plane if a fluxional process, corresponding to a pendulum
movement of the tacn nitrogen atom attached to the nonco-
ordinated pendent arm, interconverts the two Zr-N-Si-N
metallacycles. The definite assignment of a type A or B
structure to complexes 1 and 2 was not possible on the basis
of VT NMR experiments. Nevertheless, on the basis of the
molecular structure of 3 (Scheme 1) obtained by single-
crystal X-ray diffraction (see below), it is likely that 1 and
2 have type B structures for which low activation energy
racemization equilibrium is responsible by the average Cs
symmetry observed. An analogous situation was identified
to take place with titanium triamido-tacn complexes.16,22
The unequivocal confirmation that the NH proton reso-
nance (δ 3.12 ppm) is due to a protonated pendent arm rather
than being part of a NMe2H ligand was obtained through a
1H-15N HMBC of 1 (Supporting Information, Figure S1)
that showed the coupling between the proton at 3.12 ppm
and a nitrogen atom (1JNH ) 75 Hz) that is simultaneously
coupled to the dimethylsilyl (δ 0.11 ppm, H12 in Chart 1)
and the ortho-phenyl protons (δ 6.56 ppm, H14 in Chart 1)
of the noncoordinated pendent arm. Consistent with this
result is the observation of two resonances in the 19F NMR
spectrum of 2, one broad singlet at -44.4 ppm that
correspond to the metal-coordinated N(C6H4F)SiMe2 frag-
ments and one multiplet at -57.1 ppm due to the noncoor-
dinated pendent arm. The fluorine chemical shift and the
signal multiplicity of the free pendent arm (δ -57.1 ppm)
are reminiscent of what is observed for the ligand precursor
H3N3-F[9]N3 (δ -57.5 ppm), where the couplings with the
Results and Discussion
The reactions of [Zr(NMe2)4]2 with triamido-triazacyclo-
nane ligand precursors, {NH(Ph)SiMe2}3tacn (H3N3[9]N3)13
and {NH(C6H4F)SiMe2}3tacn (H3N3-F[9]N3),14 are repre-
sented in Scheme 1.
As shown, acid-base reactions between [Zr(NMe2)4]2 and
H3N3[9]N3 or H3N3-F[9]N3 led to the formation of com-
plexes 1 and 2 where the zirconium is coordinated to two
remaining dimethylamido ligands and to a dianionic tacn-
based ligand, [{N(Ph′)SiMe2}2{NH(Ph′)SiMe2}tacn]2- that
formed from deprotonation of two amine pendent arms
of the ligands’ precursors. The third pendent arm of
H3N3[9]N3 or H3N3-F[9]N3 remains neutral and not bonded
1
to zirconium. The H NMR spectra of 1 and 2 display an
average Cs symmetry with two dimethylamido resonances,
two different sets of phenyl resonances integrating 2:1, three
different silicon methyl groups, six multiplets due to the
methylenic macrocyclic protons, and one singlet due to the
NH proton. The carbon spectra of 1 and 2 are also consistent
with the presence of an average symmetry plane that con-
tains the NMe2 nitrogen atoms, the noncoordinated pendent
arm and bisects the opposite C-C bond of the tacn ring.
The proton and carbon NMR patterns observed for the
[{N(Ph′)SiMe2}2{NH(Ph′)SiMe2}tacn]2- moieties in 1 and
2 (Ph′ ) C6H5, C6H4F) may be assigned to two different
structures, as depicted in Scheme 2. In A the macrocyclic
amine bearing the noncoordinated pendent arm (represented
in red) bisects the Me2N-Zr-NMe2 angle and the two
Zr-N-Si-N metallocycles are symmetrically arranged in
(22) Barroso, S.; Cui, J. L.; Dias, A. R.; Duarte, M. T.; Ferreira, H.;
Henriques, R. T.; Oliveira, M. C.; Ascenso, J. R.; Martins, A. M. Inorg.
Chem. 2006, 45, 3532.
Inorganic Chemistry, Vol. 46, No. 3, 2007 751

Ferreira et al.
Scheme 3
Table 1. Selected Bond Lengths (Å) and Angles (deg) for 3
Zr(1)-N(4)
Zr(1)-N(3)
Zr(1)-N(11)
Zr(1)-N(21)
Zr(1)-N(2)
Zr(1)-N(1)
N(11)-C(11)
N(3)-C(4)
N(3)-C(5)
2.061(5) N(1)-C(1)
2.088(5) N(1)-C(6)
2.134(5) N(4)-C(17)
2.197(5) N(4)-C(18)
2.418(5) N(21)-C(21)
2.528(5) N(2)-C(2)
1.412(7) N(2)-C(3)
1.461(8) C(1)-C(2)
1.465(8)
1.479(7)
1.490(8)
1.453(8)
1.455(8)
1.396(7)
1.483(7)
1.492(8)
1.511(8)
(4)-Zr(1)-N(3)
93.5(2)
N(11)-Zr(1)-N(2) 137.43(17)
N(4)-Zr(1)-N(11)
N(3)-Zr(1)-N(11)
N(4)-Zr(1)-N(21)
N(3)-Zr(1)-N(21)
109.16(19) N(21)-Zr(1)-N(2)
109.8(2)
97.1(2)
67.19(18)
163.62(19)
73.43(18)
67.69(17)
99.23(18)
73.28(16)
N(4)-Zr(1)-N(1)
N(3)-Zr(1)-N(1)
N(11)-Zr(1)-N(1)
N(21)-Zr(1)-N(1)
140.2(2)
N(11)-Zr(1)-N(21) 102.6(2)
N(4)-Zr(1)-N(2)
N(3)-Zr(1)-N(2)
113.05(18) N(2)-Zr(1)-N(1)
73.34(18)
equatorial plane that is highly distorted toward a tetra-
hedral arrangement.The N-Zr-N angles within the macro-
cycle are similar to the ones found in similar Ti com-
plex,13,16,22 with a mean value of 73°. Considering the planes
defined by atoms N(1)-N(2)-N(3) and N(4)-N(21)-N(11)
and the centroids of those triangles, cent(1) and cent(2),
respectively, the angle cent(1)-Zr-cent(2) is 156.1(7)°, the
dihedral angle between the two planes is 8.2(2)°, and the
torsion angles, θ, that characterize the distortion of the
octahedral structure between N(i)-cent(1)-Zr-cent(2)-N(j)
(where N(i) ) N(1)-N(3) and N(j) ) N(4), N(21), and
N(31)) are respectively 27.6(8), 30.1(8), and 30.8(8)°. The
angles N(3)-Zr(1)-N(4) and N(1)-Zr(1)-N(4) that are not
constrained by the ligand frame have values close to those
expected for the octahedral coordination geometry being
respectively 93.5(2) and 163.62(19)°.
The angles Nmacrocycle-Zr-Namido, imposed by the ligand
backbone, have values of 67.7(2)° (N(1)-Zr(1)-N(11)) and
67.2(2)° (N(2)-Zr(1)-N(21)), and the angle between the
two planes defined by these atoms is 10°. The sum of angles
around the amido nitrogens is close to 360° for N(4), N(21),
and N(11), but due to constrains imposed by the macrocycle
framework, the sum of angles around N(3) is only 345.6.
This constraint, however, does not imply a weaker metal-
nitrogen bond as confirmed by the Zr-N(3) and Zr-N(4)
distances that are very similar (2.088(5) and 2.061(5) Å,
respectively)23-25 and slightly shorter than the Zr-N(21) and
Zr-N(11) bond lenghts (2.197(5) Å and 2.134(5) Å). These
values reflect the influence of the nitrogen substituents on
the metal-amido bonding and evidence the role of the SiMe2
and phenyl groups as electron density acceptors.26-28 The
two Zr-Namine bond lengths also differ, with Zr-N(1) (2.528-
(5) Å) being considerably longer than Zr-N(2) (2.418(5)
Å) in consequence of the trans effect caused by N(4).
NH and the aromatic protons are responsible for the splitting
of the 19F resonance into a multiplet.14
Treatment of 1 with NaH led to the synthesis of
[Zr(NMe2){N(Ph)SiMe2}2tacn], 3 (Scheme 1), that results
from the cleavage of the N-Si bond of the original neutral
pendent arm. This reaction transforms the tacn amine into
one anionic nitrogen moiety and requires the elimination of
one dimethylamido ligand. This pathway is sustained by the
reactions of ZrCl4 with M3N3[9]N3(THF)2 and M3N3-F[9]-
N3(THF)2 (M ) Li, Na), which give rise to [ZrCl{N(Ph′)-
SiMe2}2tacn] (Ph′ ) C6H5, 4, and C6H4F, 5) (see Scheme
3). A related N-Si bond cleavage was observed in cationic
titanium complexes [Ti{N3[9]N3}]+ (N3[9]N3 ) N(Ph)-
SiMe2}3tacn) in consequence of nucleophilic attack at the
silicon of one pendent arm.22
The molecular structure of 3 is shown in Figure 1, and
relevant bond lengths and angles are presented in Table 1.
The zirconium is coordinated by the five nitrogen atoms
of the ligand framework and by an NMe2 in an asymmetric
environment. Coordination geometry is best described as a
distorted pseudoctahedron, with atoms N(4) and N(1) oc-
cupying apical positions (N(4)-Zr-N(1) angle of 163.62-
(19)°). Atoms N(2), N(3), N(11), and N(21) define an
(23) Morton, C.; Munslow, I. J.; Sanders, C. J.; Alcock, N. W.; Scott, P.
Organometallics 1999, 18, 4608.
(24) Gade, L. H.; Renner, P.; Memmler, H.; Fecher, F.; Galka, C. H.;
Laubender, M.; Radojevic, S.; McPartlin, M.; Lauher, J. Chem.sEur.
J. 2001, 7, 2563.
(25) Skinner, M. E. G.; Li, Y. H.; Mountford, P. Inorg. Chem. 2002, 41,
1110.
(26) Fuhrmann, H.; Brenner, S.; Arndt, P.; Kempe, R. Inorg. Chem. 1996,
35, 6742.
(27) Turculet, L.; Tilley, T. D. Organometallics 2002, 21, 3961.
(28) Doufou, P.; Abboud, K. A.; Boncella, J. M. J. Organomet. Chem.
2000, 603, 213.
Figure 1. View of complex 3 along the equatorial plane, showing the
octahedral coordination of zirconium and the labeling scheme adopted.
Thermal ellipsoids are drawn at 30% probability.
752 Inorganic Chemistry, Vol. 46, No. 3, 2007

Tacn-Based Zr Complexes
Chart 2
shift to low field of the H1syn resonances in 6 (δ 3.90-3.82
ppm) and 7 (δ 4.01-3.93 ppm) is more pronounced than
that observed in 3 (δ 3.86-3.78 ppm). This effect reflects
that in the alkynyl derivatives 6 and 7 the macrocyclic amido
moiety acts as a better electron donor than in 3 where the
dimethylamido ligand reduces the electropositive character
of the metal center. The result is thus in agreement with the
higher basicity of the dimethylamido ligand when compared
to the alkynyl moiety. The fact that the metal coordination
to anionic amido diamine tacn-based ligands is mainly
reflected in the chemical shift of the macrocyclic Hsyn protons
differs from what we have observed for Ti(IV) complexes
of general formula [Ti{N(Ph)SiMe2}3tacn]+, for which metal
coordination induces a high-field shift that mainly affects
the Hanti resonances.16 In the 13C NMR spectra of 6 and 7,
the C1 carbon resonances suffer a high-yield shift whereas
an opposite shift occurs in the C2 carbon resonance. These
modifications in the macrocyclic resonances allow a definite
distinction between anionic and neutral tacn-derived mac-
rocycles. The coupling between the ortho-fluorine phenyl
substituents and the CR of ZrCCPh in 7 gives rise to a triplet
in the carbon NMR spectrum (δ 140.6 ppm)29-31 with a
coupling constant of 9 Hz, and the 19F NMR resonance of 7
is observed as a broad singlet at δ -43.2 ppm. These data
are indicative of Zr‚‚‚F interactions in solution that have
previously been reported to occur in polyamidozirconium
complexes.32
The trends observed in the NMR spectra are consistent
with the acidity increase of the HR protons of amido moieties,
frequently observed upon coordination to electrophilic metal
centers, which often lead to C-H bond activation.33-35 This
effect may also originate competitive secondary reactions
when compounds suitable to act either as bases or nucleo-
philes are used, as is the case of halide metathesis reactions
carried out with alkylating reagents. Attempts to prepare
other compounds of general formula [Zr(R){N(Ph′)SiMe2}2-
tacn] (R ) Me, NMe2, CH2Ph) have been unsuccessful, and
the yields attained in the syntheses of 6 and 7 are low (ca.
20%).
The proton and carbon NMR data for 3 show Cs average
symmetry which is consistent with a rapid exchange that
corresponds to the compound’s racemization by a process
similar to that proposed in Scheme 2 for 1 and 2. Thus, the
two phenyl rings exhibit one set of three aromatic resonances,
the methylenic macrocyclic proton resonances appear as six
multiplets that correlate to three carbon resonances, and the
dimethylsilyl protons give rise to one apparent singlet that
shows a correlation with two different carbon resonances.
The most remarkable difference between the macrocyclic
resonances of 3 and those of 1 is the shift to low field of
H1syn (δ 3.86-3.78 ppm vs δ 3.29 ppm in 1) that is adjacent
to the macrocyclic anionic nitrogen. This shift is symptomatic
of the formation of an anionic nitrogen functionality in the
macrocycle by cleavage of one N-Si bond. In reality, the
methylenic macrocyclic proton resonances of 3 result from
two different spin systems. Four multiplets corresponding
to H1syn, H2syn, H1anti, and H2anti constitute an ABCD system
whereas the protons H3syn and H3anti give rise to an AA′XX′
system. The simulation of the signals allowed the estimation
of the coupling constants for the two spin systems (Sup-
porting Information, Figure S2 and Table S1).
As mentioned above, complexes [ZrCl{N(Ph′)SiMe2}2-
tacn] (Ph′ ) C6H5, 4, and C6H4F, 5) have been obtained
by reactions of ZrCl4 with {MN(Ph)SiMe2}3tacn‚2THF
(M3N3[9]N3(THF)2)) and {MN(C6H4F)SiMe2}3tacn‚2THF-
(M3N3-F[9]N3(THF)2) (M ) Li, Na) (Scheme 3). These
complexes have not been fully characterized since it was
not possible to obtain them free of solvents and LiCl or NaCl
that result from the chloride metathesis reactions. The
formulation of 4 and 5 as neutral rather than anionic ate
complexes was inferred from 1H and 13C NMR data, which
are closely related to those of 3. The macrocyclic resonance
patterns confirm the cleavage of one tacn pendent arm, and
the similarity between these spectra and those of 3 suggests
that the zirconium coordination sphere in all compounds
should be comparable. Particularly noteworthy are the low-
field shift of H1syn and the high-field shifts of C2 and C3
macrocyclic resonances. Further evidence on the formulation
of 4 and 5 was obtained through their reactions with
LiCtCPh that led to the syntheses of [Zr(CCPh){N(Ph′)-
SiMe2}2tacn] (Ph′ ) C6H5, 6, and C6H4F, 7) (Scheme 3).
The NMR spectra of 6 and 7 (Chart 2) are consistent with
Cs symmetry and the occurrence of racemization through an
exchange process analogous to that discussed for 1-3
(Scheme 2). The methylenic proton resonances display a
pattern similar to the one observed for 3, namely an ABCD
system for H1 and H2 and an AA′XX′ system for H3. The
Conclusions
The reactions of ligand precursors H3N3[9]N3 and
H3N3-F[9]N3 with Zr(NMe2)4 led to the formation of
complexes 1 and 2 that maintain two original dimethylamido
ligands. The metals’ coordination sphere is completed
through the bonding of three tacn amines and two amide
pendent arms. The noncoordinated pendent arm remains
(29) Findeis, B.; Schubart, M.; Gade, L. H.; Mo¨ller, F.; Scowen, I. J.;
McPartlin, M. J. Chem. Soc., Dalton Trans. 1996, 125.
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1995, 34, 4062.
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2000, 2135.
Inorganic Chemistry, Vol. 46, No. 3, 2007 753

Ferreira et al.
[Zr(NMe2)2{N(o-C6H4F)SiMe2}2{NH(o-C6H4F)SiMe2}tacn] (2).
A solution of {NH(o-C6H4F)SiMe2}3tacn (1.32 g; 2.09 mmol) in
15 mL of toluene was added to a suspension of [Zr(NMe2)4]2 (0.59
g; 2.12 mmol) in 40 mL of the same solvent, and the mixture was
heated at 60 °C during 24 h. The solvent was evaporated to dryness,
and the residue was extracted at -30 °C with hexane. The solution
was filtered and the solvent evaporated to dryness leading to a
vitreous material that was cooled to liquid-nitrogen temperature
and scrapped. The pale yellow solid obtained was allowed to warm
to room temperature under vacuum. A contamination of 2 with free
ligand in ca. 20% was determined by NMR.
7.03-6.95 (m, 2H, H11), 6.96-6.89 (m, 1H, H17), 6.91-6.84 (m,
3H, H8, H19), 6.89-6.81 (m, 3H, H10, H20), 6.60-6.48 (m, 3H, H9,
H18), 3.77 (m, 1H, H21), 3.48-3.39 (m, 2H, H1syn), 3.37-3.31 (m,
2H, H3syn), 3.31-3.22 (m, 2H, H2syn), 3.10-3.02 (m, 2H, H3anti),
2.83 (s, 6H, H12), 2.80-2.68 (m, 2H, H2anti), 2.56-2.47 (m, 2H,
neutral. Cleavage of one Ntacn-Si bond and transformation
of one neutral tacn nitrogen into an anionic nitrogen moiety
contained in the macrocycle occurs upon deprotonation of
the amine pendent arms of 1 and 2. The reaction converts
the neutral tris(amine) macrocycle into an anionic amido-
bis(amine) moiety. Thus, complexes of the general formula
[Zr(X){N(Ph′)SiMe2}2tacn], where X ) NMe2, 3, Cl, 4 and
5, and CCPh, 6 and 7, display an amido fragment in the
tacn framework formed by cleavage of a N-Si bond. In these
complexes, the R-nitrogen Hsyn resonances are sensitive to
the X ligands that are coordinated to the zirconium. In the
case of the alkynyl derivatives 6 and 7 the shift of Hsyn
resonances to high field is more pronounced than those for
the other complexes that have π-donor ligands (NMe2 and
Cl) coordinated to the zirconium. In complex 7 the fluorine
atoms of the phenyl rings interact with the metal and give
rise to a triplet for the Zr-CCPh resonance (2JF-C ) 9 Hz)
in the carbon NMR spectrum.
1H NMR (C6D6): δ
H
1anti), 2.55 (s, 6H, H13), 0.29 (s, 6H, H5), 0.20 (s, 6H, H4), 0.12
1
(s, 6H, H14). 13C{1H} NMR (C6D6): δ 157.6 (d, JCF ) 236, C7),
1
2
153.2 (d, JCF ) 237, C16), 142.1 (d, JCF ) 13.5, C6), 135.6 (d,
2JCF ) 13.6, C15), 128.2 (C11), 124.7 (C19), 123.6 (C10), 120.8 (d,
3JCF ) 6.7, C9), 118.5 (d, JCF ) 6.8, C18), 117.3 (C20), 115.4 (d,
3
Experimental Section
2JCF ) 19.3, C17), 114.8 (d, JCF ) 22.2 Hz, C8), 54.1 (C1, C2),
2
51.3 (C3), 43.1 (C13), 41.8 (C12), 0.6 (C5), -0.6 (C4), -1.4 (C14).
19F NMR (C6D6): δ -44.4 (br, 2F, F16), -57.1 (m, 1F, F7).
[Zr(NMe2){N(Ph)SiMe2}2tacn] (3). A solution of 1 (4.33 g; 5.75
mmol) in THF (120 mL) was treated with an excess of NaH (0.24
g; 10 mmol) during 20 h under reflux. The solvent was evaporated
to dryness, and the residue was extracted with hexane and filtered.
The hexane was removed in vacuum, and the complex was
dissolved in diethyl ether. The solution was cooled until -20 °C
leading to the formation of white crystals that were separated by
filtration and dried in vacuum. Yield: 2.08 g, 64%. 1H NMR
General Procedures and Starting Materials. All reactions were
conducted under a nitrogen atmosphere. Solvents were predried
using 4 Å molecular sieves and refluxed over sodium benzophenone
(diethyl ether, tetrahydrofuran, and toluene) or calcium hydride (n-
hexane) under an atmosphere of nitrogen and distilled. Deuterated
solvents were dried with molecular sieves and freeze-pump-
thaw-degassed prior to use. Proton (300 MHz) and carbon (75.419
MHz) NMR spectra were recorded in a Varian Unity 300, at 298
K unless stated otherwise, referenced internally to residual protio
solvent (1H) or solvent (13C) resonances and reported relative to
tetramethylsilane (δ 0). The complete assignment of proton and
carbon resonances of all complexes was based on HETCOR,
NOESY, and COSY experiments. Elemental analyses were obtained
from Laborato´rio de Ana´lises, IST, Lisbon, Portugal. {NH(Ph)-
SiMe2}3tacn, {NH(C6H4F)SiMe2}3tacn, {NaN(Ph)SiMe2}3tacn‚
(C6D6): δ 7.21 (t, 3J
) 3J
) 7.8, 4H, H8), 6.99 (d, 3J
)
H8H7
H8H9
H7H8
7.8, 4H, H7), 6.80 (t, 3J
) 7.8 Hz, 2H, H9), 3.86-3.78 (m, 2H,
H9H8
H1syn), 3.16 (s, 6H, H10), 3.09-3.00 (m, 2H, H2syn), 2.85-2.80 (m,
2H, H3syn, H3’syn), 2.80-2.73 (m, 2H, H1anti), 2.45-2.37 (m, 2H,
H
2anti), 2.31-2.24 (m, 2H, H3anti, H3′anti), 0.29 (s, 6H, H4), 0.27 (s,
6H, H5). 13C{1H} NMR (C6D6): δ 152.3 (C6), 129.3 (C8), 122.1
(C7), 119.2 (C9), 54.2 (C1), 50.5 (C2), 48.7 (C3), 46.3 (C10), 0.2
(C5), -0.5 (C4). MS (EI), m/z: 559 ([M]+). Anal. Calcd for
C24H40N6Si2Zr: C, 51.45; H, 7.20; N, 15.01. Found: C, 51.14; H,
7.47; N, 14.94.
36
2THF, {NaN(C6H4F)SiMe2}3tacn‚2THF,13,14 and [Zr(NMe2)4]2
were prepared according to described procedures. ZrCl4 and LiCCPh
were purchased from Aldrich and used as received.
[Zr(NMe2)2{N(Ph)SiMe2}2{NH(Ph)SiMe2}tacn] (1). A solution
of {NH(Ph)SiMe2}3tacn (1.62 g; 2.81 mmol) in 10 mL of toluene
was added to a suspension of [Zr(NMe2)4]2 (0.83 g; 3.12 mmol) in
30 mL of the same solvent, and the mixture was heated at 60 °C
during 24 h. The volatiles were evaporated to dryness, and the
residue was extracted at -30 °C with hexane. The solution was
filtered and the solvent evaporated to dryness leading to a vitreous
material that was cooled to liquid-nitrogen temperature and scraped.
The pale yellow solid obtained was allowed to warm to room
temperature under vacuum. Yield: 1.99 g, 94%. 1H NMR (C6D6):
[ZrCl{N(Ph)SiMe2}2tacn] (4). A solution of {NaN(Ph)SiMe2}3-
tacn‚2THF (1.00 g; 1.28 mmol) in diethyl ether (15 mL) was added
at -60 °C to a suspension of ZrCl4 (0.31 g; 1.32 mmol) in 30 mL
of the same solvent. The mixture was stirred for 26 h, and the
temperature was allowed to warm until room temperature. The
solution was filtered, and the filtrate was concentrated and cooled
at -20 °C leading to the formation of a small amount of a white
solid that was separated of the mother liquor by filtration. 1H NMR
3
3
3
(C6D6): δ 7.16 (t, JH H ) JH H ) 7.8 Hz, 4H, H8), 6.90-6.68
δ 7.09 (m, 6H, H8, H15), 6.85 (d, JHH ) 7.2, 4H, H7), 6.75 (m,
8
7
8 9
3H, H9, H16), 6.56 (d, 3JHH ) 7.2 Hz, 2H, H14), 3.38-3.20 (m, 6H,
(m, 6H, H7, H9), 3.64 (m, 2H, H1syn), 2.99 (m, 2H, H2syn), 2.71 (m,
2H, H3syn, H3’syn), 2.58 (m, 2H, H1anti), 2.40 (m, 2H, H2anti), 2.33
(m, 2H, H3anti, H3′anti), 0.29 (s, 12H, H4, H5). 13C{1H} NMR
(C6D6): δ 152.1 (C6), 129.2 (C8), 121.6 (C7), 120.2 (C9), 54.1 (C1),
50.1 (C2), 48.7 (C3), 0.2, -0.5 (C4, C5).
[Zr(CtCPh){N(Ph)SiMe2}2tacn] (6). A solution of {NaN(Ph)-
SiMe2}3tacn‚2THF (1.15 g; 1.46 mmol) in diethyl ether (15 mL)
was added at -40 °C to a suspension of ZrCl4 (0.36 g; 1.55 mmol)
in 40 mL of the same solvent. The mixture was stirred for 15 h,
and the temperature was allowed to warm until room temperature.
The precipitate was filtered off and washed with Et2O. The filtrate
was cooled to -60 °C, and a 1 M solution of LiCCPh (1.50 mL;
H
1syn, H2syn, H3syn), 3.12 (s br, 1H, H17), 3.05-2.98 (m, 2H, H3anti),
2.79-2.71 (m, 2H, H1anti), 2.73 (s, 6H, H10), 2.48-2.40 (m, 2H,
2anti), 2.42 (s, 6H, H11), 0.16 (s, 6H, H5), 0.11 (s, 6H, H12), 0.09
H
(s, 6H, H4). 13C{1H} NMR (C6D6): δ 153.9 (C6), 147.1 (C13), 129.6
(C15), 128.3 (C8), 126.0 (C7), 120.6 (C9), 118.6 (C14), 54.5 (C1),
54.1 (C2), 51.5 (C3), 42.9 (C11), 41.6 (C10), 0.6 (C5), -0.5 (C4),
-1.1 (C12). MS (EI), m/z: 737 ([M - CH4]+). Anal. Calcd for
C34H58N8Si3Zr: C, 54.11; H, 7.75; N, 14.86. Found: C, 53.85; H,
8.01; N, 14.67.
(36) Bradley, D. C.; Thomas, I. M. J. Chem. Soc. 1960, 3857.
754 Inorganic Chemistry, Vol. 46, No. 3, 2007

Tacn-Based Zr Complexes
Table 2. Data Collection and Refinement Parameters for Complex 3
1.50 mmol) in THF was added. The mixture was again allowed to
warm to room temperature, and the volatiles were then removed
in vacuum. The residue was extracted with hexane and filtered.
The concentrate solution was cooled to -20 °C overnight, and a
powder formed. The solvent was filtered off, and the solid was
extracted in Et2O. Slow diffusion of hexane into the ether solution
led to the formation of a white microcrystalline precipitate that was
cryst system, space group
unit cell dimens
monoclinic, P21/c
a ) 15.446(3), b ) 11.050(2),
c ) 18.125(6) Å; â ) 114.55(2)°
2813.9(12) Å3
V
Z
4
calcd density
abs coeff
1.322 Mg/m3
0.499 mm-1
1
separated by filtration. Yield: 20% (0.18 g). H NMR (C6D6): δ
F(000)
1176
3
θ range for data collcn
limiting indices
reflcns collcd/unique
completeness to θ (25.99°)
refinement method
data/restraints/params
goodness-of-fit on F2
final R indices [I > 2σ(I)]
R indices (all data)
largest diff peak and hole
2.22-25.99°
7.41 (d, JH
) 7.2, 2H, H13), 7.04-7.02 (m, 2H, H9), 7.02 (d,
13H14
0 e h e 19, -13 e k e 0, -22 e l e 20
5726/5515 [R(int) ) 0.0402]
99.7%
3JH H ) 7.8, 4H, H7), 6.99 (t, JH
) JH
) 7.2, 2H, H14),
3
3
14H15
14H13
7
8
3
3
3
6.90 (t, JH
) 7.2, 1H, H15), 6.74 (t, JH H ) JH H ) 7.8 Hz,
14H15
8
7
8 9
full-matrix least-squares on F2
5515/0/338
4H, H8), 3.90-3.82 (m, 2H, H1syn), 3.71-3.63 (m, 2H, H2syn), 3.17-
3.09 (m, 2H, H3syn), 2.85-2.76 (m, 2H, H1anti), 2.49-2.40 (m, 4H,
H
2anti, H3anti), 0.59 (s, 6H, H4), 0.30 (s, 6H, H5). 13C{1H} NMR
1.042
R1 ) 0.0513, wR2 ) 0.1165
R1 ) 0.1001, wR2 ) 0.1723
0.450 and -0.740 e Å-3
(C6D6): δ 153.1 (C6), 141.9 (C10), 131.6 (C13), 128.2 (C9, C14),
127.4 (C12), 126.2 (C15), 124.5 (C7), 119.1 (C8), 111.5 (C11), 56.2
(C1), 50.5 (C3), 50.0 (C2), 0.7 (C5), 0.3 (C3). Anal. Calcd for
C30H39N5Si2Zr: C, 58.39; H, 6.37; N, 11.35. Found: C, 58.46; H,
6.47 N, 11.26.
[Zr(CtCPh){N(C6H4F)SiMe2}2tacn] (7). The synthetic pro-
cedure used for 4 was applied to prepare 5 using {NaN-
(C6H4F)SiMe2}3tacn‚2THF (1.32 g; 1.15 mmol), ZrCl4 (0.28 g; 1.24
mmol), and a 1 M solution of LiCCPh (1.10 mL; 1.10 mmol) in
THF. The product was obtained in 22% yield (0.13 g) from diethyl
and refined using SHELXL38 within the pack of programs
WINGX.39 Non-hydrogen atoms were refined anisotropically, and
hydrogen atoms were inserted in idealized positions and allowed
to refine riding on the parent carbon atom. Data have been deposited
under CCDC 164823. Data collection and refinement details are
presented in Table 2.
ether/hexane as described for 4. 1H NMR (C6D6): δ 7.38 (d, 3JH
15H16
Acknowledgment. We are thankful to the Fundac¸a˜o para
a Cieˆncia e a Tecnologia of Portugal that funded this work
(Research Projects POCTI/QUI/39734/2001 and POCTI/
QUI/46206/2002).
) 6.9, 2H, H15), 7.11 (d br, 2H, H11), 6.98 (t, 3JH
) 3JH
)
16H15
16H17
3
3
6.9, 2H, H16), 6.90 (d, JH
) 6.9, 1H, H17), 6.81 (t br, JH14H15
17H16
) 7.2 Hz, 2H, H10), 6.56 (m br, 2H, H8), 6.38 (m br, 2H, H9),
4.01-3.93 (m, 2H, H1syn), 3.67-3.58 (m, 2H, H2syn), 3.29-3.22
1
Supporting Information Available: NMR spectra, Η-15Ν
(m, 2H, H3syn), 2.87-2.79 (m, 2H, H1anti), 2.50-2.42 (m, 4H, H2anti
,
H3anti), 0.65 (s, 6H, H4), 0.35 (s, 6H, H5). 13C{1H} NMR (C6D6):
δ 157.8 (d, 1JCF ) 236, C7), 141.3 (d, 2JCF ) 7, C6), 140.6 (t, 2JCF
) 9, C12), 131.6 (C15), 128.1 (C16), 127.5 (C14), 126.1 (C17), 124.2
HMBC of 1 (Figure S1), experimental and simulated ABCD and
AA′BB′ spin systems of 3 (Figure S2), simulated coupling constants
for the macrocycle proton spins systems of 3 (Table S1), and
crystallographic data for 3 in CIF format. This material is available
free of charge via the Internet at http://pubs.acs.org.
3
2
(C11), 123.5 (C10), 118.6 (d, JCF ) 7.5, C9), 114.4 (d, JCF ) 21
Hz, C8), 109.6 (C13), 57.3 (C1), 50.4 (C3), 49.7 (C2), -0.1 (C5),
-0.5 (C4). 19F NMR (C6D6): δ -43.2 (br). Anal. Calcd for
C30H37N5F2Si2Zr: C, 55.18; H, 5.71; N, 10.72. Found: C, 55.26;
H, 5.77 N, 10.36.
IC061588Z
(37) Altomare, A.; Burla, M. C.; Camalli, M.; Cascarano, G.; Giacovazzo,
C.; Guagliardi, A.; Moliterni, A. G. G.; Polidori, G.; Sparna, R. J.
Appl. Crystallogr. 1999, 32, 115.
(38) Sheldrick, G. M. SHELXL-97: A program for refining crystal
structures (208); Univ. of Go¨ttingen: Go¨ttingen, Germany, 1998.
(39) WINGIX, Version 1.64.05, An Integrated System of Window Programs
for the Solution, Refinement of Single Crystal X-ray Diffraction Data;
1999.
X-ray Experimental Details. Data were collected, at room
temperature, on a MACH3 Bruker Nonius diffractometer equipped
with Mo (0.710 69 Å) radiation. Data were corrected for Lorentz
and polarization effects but not for absorption. Cell dimensions were
determined from the setting angles of 25 reflections, within θ values
of 15-17°. Structure was solved by direct methods using SIR9737
Inorganic Chemistry, Vol. 46, No. 3, 2007 755