Zirconium and hafnium (1-pyridinio)imido complexes: Functionalized terminal hydrazinediido analogues

Article abstract of DOI:10.1039/b807808d

Reaction of the diamidozirconium complex [Zr(N₂ ^TBSN_py)(NMe₂)₂] (1) (N ₂^TBSN_py = CH₃C(C₅H ₄N)(CH₂NSiMe₂tBu)₂) or the diamidohafnium complex [Hf(N₂^TBSN_py)(NMe ₂)₂] (2) with one molar equiv. of 1-aminopyridinium triflate in the presence of one equiv. of pyridine gave the corresponding (1-pyridinio)imido complexes [Zr(N₂^TBSN _py)(N-NC₅H₅)(OTf)(py)] (3) and [Hf(N ₂^TBSN_py)(N-NC₅H₅)(OTf) (py)] (4). These were converted to the acetylide complexes [Zr(N ₂^TBSN_py)(N-NC₅H₅)(CCPh) (py)] (5) and [Hf(N₂^TBSN_py)(N-NC ₅H₅)(CCPh)(py)] (6) by reaction with lithium phenylacetylide and substitution of the triflato ligand. Upon reaction of 3 and 4 with one molar equivalent of R-NC (R = tBu, Cy, 2,6-xyl), N-N bond cleavage in the (1-pyridinio)imido unit took place and the respective carbodiimido complexes [M(N₂^TBSN_py](NCNR)(OTf)(py)] (7-12) were formed instantaneously. A similar type of reaction with CO gave the isocyanato complex [Zr(N₂^TBSN_py](NCO)(OTf)(py)] (13). Finally, the abstraction of the pyridine ligand in compounds 3 and 4 with B(C₆F₅)₃ led to the formation of the triflato-bridged dinuclear complexes [Zr(N₂^TBSN _py)(N-NC₅H₅)(OTf)]₂ (14) and [Hf(N₂^TBSN_py)(N-NC₅H ₅)(OTf)]₂ (15). The Royal Society of Chemistry 2008.

Full text of DOI:10.1039/b807808d

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PAPER
www.rsc.org/dalton | Dalton Transactions
Zirconium and hafnium (1-pyridinio)imido complexes: functionalized terminal
hydrazinediido analogues†‡
Heike Herrmann, Thorsten Gehrmann, Hubert Wadepohl and Lutz H. Gade*
Received 8th May 2008, Accepted 31st July 2008
First published as an Advance Article on the web 30th September 2008
DOI: 10.1039/b807808d
TBS
TBS
Reaction of the diamidozirconium complex [Zr(N2 Npy)(NMe2)2] (1) (N2
N
=
py
TBS
CH3C(C5H4N)(CH2NSiMe2tBu)2) or the diamidohafnium complex [Hf(N2 Npy)(NMe2)2] (2) with
one molar equiv. of 1-aminopyridinium triflate in the presence of one equiv. of pyridine gave the
TBS
=
corresponding (1-pyridinio)imido complexes [Zr(N2 Npy)( N–NC5H5)(OTf)(py)] (3) and
TBS
=
=
[Hf(N2 Npy)( N–NC5H5)(OTf)(py)] (4). These were converted to the acetylide complexes
[Zr(N2 Npy)( N–NC5H5)(CCPh)(py)] (5) and [Hf(N2 Npy)( N–NC5H5)(CCPh)(py)] (6) by reaction
with lithium phenylacetylide and substitution of the triflato ligand. Upon reaction of 3 and 4 with one
TBS
TBS
=
molar equivalent of R-NC (R = tBu, Cy, 2,6-xyl), N–N bond cleavage in the (1-pyridinio)imido unit
TBS
= =
took place and the respective carbodiimido complexes [M(N2 Npy](N C NR)(OTf)(py)] (7–12) were
formed instantaneously. A similar type of reaction with CO gave the isocyanato complex
TBS
[Zr(N2 Npy](NCO)(OTf)(py)] (13). Finally, the abstraction of the pyridine ligand in compounds 3
and 4 with B(C6F5)3 led to the formation of the triflato-bridged dinuclear complexes
TBS
TBS
=
=
[Zr(N2 Npy)( N–NC5H5)(OTf)]2 (14) and [Hf(N2 Npy)( N–NC5H5)(OTf)]2 (15).
exciting new patterns of reactivity based on N–N bond cleavage
Introduction
and N–E (E = main group element) bond formation, in which
the group 4 metal hydrazide reacts as a synthon for a Zr–N
“metallanitrene” fragment.9,11 Given this potential combination
of N–N scission and N–E coupling, we decided to synthesize (1-
pyridinio)imido zirconium and hafnium complexes to gain further
insight into these processes.12 (1-Pyridinio)imide derivatives are
of special interest in this context, since a hydrazide activation
pathway involving bent species with Nb–metal coordination are
most likely to be disfavoured for aromatics. In this work we report
the synthesis and full characterization of such complexes along
with some aspects of their reactivity. Furthermore, this type of
chemistry is extended to the heavier group 4 element hafnium for
the first time.
Transition metal hydrazides have been studied as key intermediates
in the reductive activation of dinitrogen1,2 as well as transition
metal catalysed hydrohydrazinations of carbon-carbon multiple
bonds.3 Whereas the latter has found direct application in the
synthesis of substituted indoles4 and has been extended to three
component reactions such as the iminohydrazination of alkynes,5
other efforts have been directed at the transformation of the metal-
bonded NNH2 fragment to more complex organic, in particular
N-heterocyclic structures.
The latter has been pioneered in Leigh’s and Hidai’s groups
who studied the conversion of a metal bonded hydrazide to
an N-heterocycle and the subsequent (reductive) scission of
the N–N bond, giving the organic product and the (frequently
unidentified) reduction products of the metal complex.6,7 This
aspect, in particular, has been investigated in some detail for
(1-pyridinio)imido complexes of tungsten as well as titanium.8
The conversion of hydrazides, which have been obtained by the
reductive activation of N2, to more complex organics provides
one of the principal challenges of dinitrogen activation beyond
Haber-Bosch equivalent chemistry.
Results and discussion
Synthesis and structural characterization of the (1-pyridinio)-
TBS
=
imido complexes [Zr(N2 Npy)( N–NC5H5)(OTf)(py)] (3) and
TBS
=
[Hf(N2 Npy)( N–NC5H5)(OTf)(py)] (4) and their conversion to
the corresponding phenylacetylide complexes [Zr(N2 Npy)( N–
NC5H5)(CCPh)(py)] (5) and [Hf(N2 Npy)( N–NC5H5)(CCPh)-
TBS
=
TBS
=
We have recently reported the synthesis and structural charac-
terization of zirconium hydrazides9 using a tridentate diamidopy-
(py)] (6).
ridyl ligand [N2 Npy]2- ([N2 Npy]2- = [CH3C(C5H4N)(CH2NR)2]2-)
Reacting the diamidozirconium complex [Zr(N2 Npy)-
(NMe2)2] (1) or the diamidohafnium complex [Hf(N2 Npy)-
R
R
TBS
TBS
as a supporting ligand.10 A first study of its reactivity revealed
(NMe2)2] (2) with one molar equiv. of 1-aminopyridinium triflate
in the presence of one equiv. of pyridine gave the corresponding (1-
Anorganisch-Chemisches Institut, Universita¨t Heidelberg, Im Neuenheimer
Feld 270, 69120, Heidelberg, Germany. E-mail: lutz.gade@uni-hd.de;
Fax: +49-6221-545609
† CCDC reference numbers 679492–679494 and 687175–687177. For
crystallographic data in CIF or other electronic format see DOI:
10.1039/b807808d
TBS
=
pyridinio)imido complexes [Zr(N2 Npy)( N–NC5H5)(OTf)(py)]
TBS
=
(3) and [Hf(N2 Npy)( N–NC5H5)(OTf)(py)] (4) in good yield
(Scheme 1).
The analytical data as well as the 1H, 13C and 29Si NMR
spectra are consistent with the molecular structures of 3 and 4 as
displayed in Scheme 1. Both complexes undergo rapid pyridine
‡ Dedicated to Professor Brian F. G. Johnson on the occasion of his 70th
birthday.
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Scheme 1 Synthesis of the zirconium and hafnium pyridinioimido
complexes 3 and 4 and the substitution of the triflato ligands by phenyl
acetylide.
dissociation and association on the NMR time scale which
renders them effectively CS-symmetric. Complex 3 and 4 also
displayed characteristic 15N-NMR spectroscopic features which
are discussed in detail for the zirconium complex. The assignment
1
15
of the signals in the { H} N-NMR spectrum of 3 (recorded
at 335 K) was partially achieved by 15N-HMBC in which the
resonance of the ortho protons of the pyridinioimido unit correlate
with the 15N signal at 276.9 ppm, which is therefore assigned as that
of the Nb atom. In an analogous way, the resonances at 156.5 ppm
and 314.4 ppm were identified as those of the silylamido groups
and the pyridyl group of the ancillary tripod ligand. The signal
of the Na nucleus of the pyridinioimido group was not observed
in the 15N-HMBC experiment but could be detected in a directly
recorded 15N NMR spectrum at 317.1 ppm (all 15N chemical shifts
relative to 15NH3 as reference).
In order to establish the structural details of both complexes,
single crystal X-ray structure analyses were carried out. Their
very similar molecular structures are depicted in Fig. 1a and
b and a comparison of the principal bond lengths and angles
is provided in Table 1. The overall structural arrangement in
3 and 4 is best described as distorted octahedral with the (1-
pyridinio)imido ligand in trans disposition to the pyridyl unit of
Fig. 1 Molecular structures of complexes 3 (a) and 4 (b, only one of the
two independent molecules is shown). Selected bond lengths and angles
are listed in Table 1.
and 1.364(10), respectively],13 however, the latter is similar to
the N–N distances previously reported by Hidai and coworkers
˚
the facially coordinating polydentate ligand [M–N(3) 2.405(3) A
for titanium compounds with the pyridinioimido ligand (1.361–
8
˚
˚
=
(M = Zr); 2.408(5), 2.420(4) A (M = Hf)]. The two amido
1.369 A) and indicates the conjugation of the Zr N and pyridine
functions, the pyridine and the triflato ligand lie in the plane
orthogonal to the (1-pyridinio)imido ligand. In both structures
the latter bends away from the bulky tBuMe2Si substituents of
the amides [N(3)–M–N(4) 166.6(1)◦ (M = Zr); 166.3(2), 167.0(2)◦
p-systems.
Reaction of complexes 3 and 4 with lithium phenylacetylide
led to
a substitution of the triflato ligand (Scheme 1)
while leaving the pyridinioimido unit intact. Both reac-
TBS
=
=
=
(M = Hf)] and the Zr N–N chain in the “hydrazido” Zr N–
tion products [Zr(N2 Npy)( N–NC5H5)(CCPh)(py)] (5) and
TBS
=
NC5H5 fragment also deviates slightly from linearity [M–N(4)–
[Hf(N2 Npy)( N–NC5H5)(CCPh)(py)] (6) were isolated as yellow
◦
◦
=
N(5) 171.4(3) (M = Zr); 172.5(5), 171.2(4) (M = Hf)]. Its Zr N
powders. The moderate isolated yields are due to the extreme
sensitivity of both compounds towards oxygen and moisture
as well as their high solubility in both aliphatic and aromatic
˚
bond is longer [Zr(1)–N(4) 1.945(3) A] whilst the adjacent N–
˚
N bond is significantly shorter [N(4)–N(5) 1.321(4) A] than in
1
Bergman’s hydrazido complex [Cp2Zr(N2Ph2)(dmap)] [1.873(7)
hydrocarbon solvents. Whilst the general H, 13C and 29Si NMR
6232 | Dalton Trans., 2008, 6231–6241
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Table 1 Selected bond lengths and angles of the compounds 3 and 4 (data
for the second independent molecule of 4 in the unit cell in brackets)
3 (M = Zr)
4 (M = Hf)
M(1)–N(1)
M(1)–N(2)
M(1)–N(3)
M(1)–N(4)
M(1)–N(6)
N(4)–N(5)
M(1)–O(1)
2.102(3)
2.088(3)
2.405(3)
1.945(3)
2.456(3)
1.321(4)
2.286(2)
2.067(5) [2.086(4)]
2.074(5) [2.072(5)]
2.373(5) [2.377(5)]
1.933(5) [1.940(5)]
2.408(5) [2.420(4)]
1.331(7) [1.318(6)]
2.283(4) [2.241(4)]
N(1)–M(1)–N(2)
N(1)–M(1)–N(3)
N(1)–M(1)–N(4)
N(1)–M(1)–N(6)
N(1)–M(1)–O(1)
N(2)–M(1)–N(3)
N(2)–M(1)–N(4)
N(2)–M(1)–N(6)
N(2)–M(1)–O(1)
N(3)–M(1)–N(4)
N(3)–M(1)–N(6)
N(3)–M(1)–O(1)
N(4)–M(1)–N(6)
N(4)–M(1)–O(1)
N(6)–M(1)–O(1)
M(1)–N(4)–N(5)
93.85(10)
82.28(10)
106.37(12)
85.11(10)
156.03(10)
83.27(10)
105.85(12)
161.56(10)
93.74(10)
166.64(11)
78.34(9)
93.3(2) [94.8(2)]
84.3(2) [83.4(2)]
105.7(2) [105.0(2)]
162.3(2) [162.3(2)]
93.9(2) [93.0(2)]
82.0(2) [82.9(2)]
106.2(2) [106.0(2)]
84.5(2) [86.0(2)]
156.4(2) [156.3(2)]
166.3(2) [167.0(2)]
78.0(2) [79.2(2)]
76.4(2) [75.8(2])
91.7(2) [91.72(2)]
93.5(2) [93.5(2)]
81.9(2) [80.10(1)]
172.5(5) [171.2(4)]
76.09(9)
˚
Fig. 2 Molecular structure of complex 5. Selected bond lengths [A]
92.05(11)
93.32(11)
80.57(9)
and angles [◦]: Zr–N(1) 2.095(3), Zr–N(2) 2.154(3), Zr–N(3) 2.406(3),
Zr–N(4)1.954(3), Zr–N(6) 2.486(3), Zr–C(32) 2.359(4), N(4)–N(5)
1.335(4), C(32)–C(33) 1.220(5), C(33)–C(34) 1.431(5); N(1)–Zr–N(2)
92.51(11), N(1)–Zr–N(3) 83.0(1), N(1)–Zr–N(4) 106.5(1), N(1)–Zr–N(6)
161.8(1), N(1)–Zr–C(32) 100.0(1), N(2)–Zr–N(3) 80.4(1), N(2)–Zr–N(4)
106.9(1), N(2)–Zr–N(6) 83.7(1), N(2)–Zr–C(32) 155.3(1), N(3)–Zr–N(4)
167.5(1), N(3)–Zr–N(6) 78.8(1), N(3)–Zr–C(32) 80.1(1), N(4)–Zr–N(6)
91.7(1), N(4)–Zr–C(32) 90.0(1), N(6)–Zr–C(32) 77.7(1), Zr–N(4)–N(5)
163.0(2), Zr–C(32)–C(33) 178.9(3), C(32)–C(33)–C(34) 173.4(4).
171.4(3)
spectroscopic patterns of 5 and 6 are similar to those of the starting
materials, albeit slightly shifted, both compounds display the
characteristic 13C NMR signals of the phenyl acetelide at d = 77.8
and 110.9 for 5 [d = 82.6 and 112.7 for 6]. These are comparable to
i
i
∫
those reported for [Cp*Zr(N( Pr)CMeN( Pr))(C2H4Ph)(C CPh)]
which were found at 72.7 ppm and 108.8.14
A potential coupling reaction of the acetylide and the imido unit
was not observed even upon heating. Compound 5 remained stable
in toluene solution upon prolongued heating at 110 ◦C.
The molecular structure of 5 (Fig. 2) may be best described as
distorted octahedral with the pyridinioimido ligand occupying
the coordination site trans to the pyridyl unit of the tripod
ligand [N(3)–Zr–N(4) 167.5(1)◦]. The two amido groups of the
˚
˚
latter [Zr–N(1) 2.095(3) A, Zr–N(2) 2.154(3) A], the pyridine and
the formally anionic phenylacetylide unit are almost perfectly
arranged in a plane orthogonal to the pyridinioimide. The
acetylide in the equatorial position adopts the expected almost
linear coordination [Zr–C(32)–C(33) 178.9(3)◦], the C(32)–C(33)
˚
∫
bond length of 1.220(5) A corresponds to a C C triple bond
˚
and the Zr–C(32) distance of 2.359(4) A is slightly longer than
the average Zr–Csp bond [2.237(13) A]. For comparison, in the
related complex Li[Cp2Zr(C CPh)(h -1,2-PhC2C CPh)] the Zr–
C bond length was found to be 2.314(2) A and the C C contiguous
15
˚
2
∫
∫
∫
˚
Scheme 2 N–N bond cleavage and C–N coupling in the reaction of 3 and
4 with isonitriles to give the carbodiimido complexes 7–12.
16
˚
distance 1.223(2) A.
-1
˜
products display a characteristic band at around n ª 2100 cm ,
N–N bond cleavage and N–C bond formation in the reactions of
which is assigned to a NCN stretching vibration.
TBS
TBS
=
=
[Zr(N2 Npy)( N–NC5H5)(OTf)(py)] (3) and [Hf(N2 Npy)( N–
NC5H5y)(OTf)(py)] (4) with isonitriles and CO
The analytical data as well as the 1H, 13C and 29Si NMR
spectra are consistent with the molecular structures displayed in
Scheme 2. As for 3 and 4, rapid pyridine exchange (or, possibly,
exchange involving the triflato ligand) renders these complexes
CS-symmetric on the NMR time scale. In the 15N-NMR spectra of
7–12 the carbodiimido ligand displayed characteristic resonances:
Whereas the signals of the g-nitrogen were observed between
Upon reaction of 3 and 4 with one molar equivalent of R–
NC (R = tBu, Cy, 2,6-xyl), N–N bond cleavage in the (1-
pyridinio)imido unit took place and the respective carbodi-
TBS
= =
imido complexes [M(N2 Npy](N C NR)(OTf)(py)] (7–12) were
formed instantaneously (Scheme 2). The IR spectra of the reaction
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d = 76.1 and 64.0 the Na nuclei of these groups resonate between
193.1 ppm and 197.8 ppm.
The details of the molecular structure of complex 7 have been
established by X-ray diffraction and are depicted in Fig. 3 along
with the principal bond lengths and angles. The arrangement
of the ligands in 7 is similar to that in the starting material,
the (1-pyridinio)imido group having been replaced by the tert-
butylcarbodiimido unit. The latter has a typical diazacumu-
˚
˚
lene structure [C(22)–N(4) 1.201(3) A, C(22)–N(5) 1.227(3) A,
N(4)–C(22)–N(5) 172.7(2)◦] which has resulted from a for-
mal nitrene–isocyanide coupling, similar to that observed
in the thermal degradation of palladium azides.17 We re-
cently reported the related carbodiimido–zirconium compounds
Scheme 3 Cleavage of the hydrazide and N–CO coupling in the synthesis
of the isocyanato complex 13.
TBS
9a
= =
[Zr(N2 Npy)(N C NR)(NPh2)], while there is no precedent in
hafnium chemistry. However, several titanium complexes have
been reported which were synthesized by reaction of a Ti precursor
with metallated preformed carbodiimide.18
NCO unit. Its formation was unambiguously established by a
single crystal X-ray structure analysis of 13. Its molecular structure
is displayed in Fig. 4 along with selected bond lengths and angles.
˚
Fig. 3 Molecular structure of complex 7. Selected bond lengths [A]
and angles [◦]: Zr(1)–N(1) 2.048(2), Zr(1)–N(2) 2.060(2), Zr(1)–N(3)
2.353(2), Zr(1)–N(4) 2.081(2), Zr(1)–N(6) 2.457(2), Zr(1)–O(1) 2.261(1),
C(22)–N(4) 1.201(3), C(22)–N(5) 1.227(3); N(1)–Zr(1)–N(2) 92.85(7),
N(1)–Zr(1)–N(3) 86.72(6), N(1)–Zr(1)–N(4) 102.19(7), N(1)–Zr(1)–N(6)
84.85(6), N(1)–Zr(1)–O(1) 163.02(6), N(2)–Zr(1)–N(3) 79.87(6), N(2)–
Zr(1)–N(4) 111.10(7), N(2)–Zr(1)–N(6) 157.60(6), N(2)–Zr(1)–O(1)
98.80(6), N(3)–Zr(1)–N(4) 165.17(6), N(3)–Zr(1)–N(6) 77.76(6), N(3)–
Zr(1)–O(1) 83.25(6), N(4)–Zr(1)–N(6) 91.12(6), N(4)–Zr(1)–O(1) 85.14(6),
N(6)–Zr(1)–O(1) 79.66(5), Zr(1)–N(4)–C(22) 174.6(2), N(4)–C(22)–N(5)
172.7(2), C(22)–N(5)–C(23) 126.2(2).
Fig. 4 Molecular structure of complex 13. Selected bond lengths
[A] and angles [◦]: Zr–N(1) 2.0453(15), Zr–N(2) 2.0353(16),
˚
Zr–N(3) 2.3480(15), Zr–N(4) 2.1212(16), Zr–N(5) 2.4312(16), Zr–O(2)
2.2573(13), N(4)–C(22) 1.177(3), C(22)–O(1) 1.187(3); N(1)–Zr–N(2)
93.78(6), N(1)–Zr–N(3) 83.00(6), N(1)–Zr–N(4) 108.58(6), N(1)–Zr–N(5)
163.19(6), N(1)–Zr–O(2) 93.08(5), N(2)–Zr–N(3) 85.17(6), N(2)–Zr–N(4)
104.67(6), N(2)–Zr–N(5) 88.43(6), N(2)–Zr–O(2) 162.89(6), N(3)–Zr–N(4)
163.89(6), N(3)–Zr–N(5) 80.58(5), N(3)–Zr–O(2) 80.14(5), N(4)–Zr–N(5)
86.87(6), N(4)–Zr–O(2) 87.91(6), N(5)–Zr–O(2) 80.59(5), Zr–N(4)–C(22)
167.5(1), N(4)–C(22)–O(1) 179.1(3).
The formation of an isocyanato complex by reaction of
[Cp2ZrNNPh2] with CO has been described previously by
Bergman et al.13 Bubbling purified and dried (P4O10 column)
CO through a solution of 3 for 10 minutes gave the complex
[Zr(N2 Npy](NCO)(OTf)(py)] (13) in 67% yield (Scheme 3).
The generation of an isocyanato ligand was first indicated by the
Similar to the carbodiimide group in 7–12, the isocyanato
ligand in 13 is trans disposed with respect to the pyridyl donor
of the tripodal diamido donor ligand [N(3)–Zr–N(4) 163.89(6)◦].
The NCO unit is slightly bent [Zr–N(4)–C(22) 167.5(2)◦] which
we attribute to electronic rather than steric factors in view
of the almost linear coordination of the sterically more bulky
carbodiimide 7 [Zr–N(4)–C(22) 174.6(2)◦]. We note that in the
previously published [Cp2Zr(NCO)2] the Zr–N–C angles were
found to be 172.6(3)◦ and 177.5(3)◦ and are thus closer to the
expected linearity than in 13.19 However, the Zr–N distances
TBS
˜
IR spectrum of 13 which displayed an intense absorption band n =
2206 cm-1 which is consistent with an NCO unit and similar to the
vibrational band reported for the same unit in [{Cp2Zr(NCO)}2O]
-1 19
1
(n = 2210 cm ). The signal patterns in the H and 13C NMR
spectra of 13 are very similar to those of 7–12, however, we were
unable to detect the 13C signal of the quarternary C atom in the
˜
˚
˚
˚
[2.119(3) A and 2.101(3) A] and N–C bond lengths [1.140(5) A and
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Scheme 4 Abstraction of the equatorial pyridine ligand in 3 and 4 with B(C6F5)3 and dimerization to the dinuclear m-triflato complexes 14 and 15.
˚
1.156(5) A] in [Cp2Zr(NCO)2] are close to those of 13 (2.121(2)
˚
and 1.177(3) A, respectively). All other structural features of 13
are very similar to those established for the analogous carbodii-
mide 7.
Synthesis and structural characterization of the triflato-bridged
TBS
=
dimeric complexes [Zr(N2 Npy)( N–NC5H5)(OTf)]2 (14) and
TBS
=
[Hf(N2 Npy)( N–NC5H5)(OTf)]2 (15)
Upon reaction of compounds 3 and 4 with B(C6F5)3 in C6D6
(Scheme 4) only one signal at -3.4 ppm is observed in the 11B
NMR spectra, which is assigned to the borane–pyridine adduct.
No further transformation involving the borane occurs. Apart
from the proton resonances of the borane–pyridine adduct, the
virtually identical NMR spectra of both product solutions display
the signal patterns of a new CS-symmetric species, barely shifted
signals of the pyridinioimido unit and the absence of free pyridine.
Within several hours crystalline solids, light yellow 14 and
yellow 15 (Scheme 4), precipitated from the C6D6 solutions which
proved to be insoluble in aromatic solvents but were readily
dissolved in THF. Single crystals of the zirconium complex 14,
which were suitable for X-ray diffraction, were used to establish
its detailed structure. The molecular structure of 14 is depicted in
Fig. 5 along with the principal bond lengths and angles.
Fig. 5 Molecular structure of complex 14. Selected bond lengths
[A] and angles [◦]: Zr–N(1) 2.073(4), Zr–N(2) 2.079(4), Zr–N(3)
˚
2.429(4), Zr–N(4) 1.928(4), Zr–O(1) 2.352(3), ZrA–O(2) 2.379(4), N(4)–
N(5) 1.347(6); N(1)–Zr(1)–N(2) 92.47(16), N(1)–Zr(1)–N(3) 85.83(15),
N(1)–Zr–N(4) 106.22(17), N(1)–Zr–N(3) 85.83(15), N(2)–Zr–N(3)
80.89(15), N(2)–Zr–N(4) 106.09(19), N(3)–Zr–N(4) 165.50(18), N(1)–
Zr(1)–O(1) 158.33(14), N(2)–Zr–O(1) 93.36(14), N(3)–Zr(1)–O(1)
74.54(14), N(4)–Zr–O(1) 92.15(16), N(1)–Zr–O(2A) 91.44(15), N(2)–Zr–
O(2A) 161.76(14), N(3)–Zr–O(2A) 81.64(14), N(4)–Zr–O(2A) 89.86(19),
O(1)–Zr–O(2A) 76.92(13), Zr(1)–N(4)–N(5) 170.8(4). Operator for gener-
ating equivalent atoms: -x + 1, -y, -z.
Complex 14 adopts a dimeric structure in the solid state in which
the zirconium atoms possess distorted octahedral coordination
geometries similar to that of the starting material 3. Both molecu-
lar halves are related by a centre of symmetry which coincides
with the crystallographic inversion centre. The pyridinioimido
ligand at each Zr fragment is trans disposed with respect to the
pyridyl group of the tridentate ligand [N(3)–Zr–N(4) 165.5(2)◦].
The two triflato ligands are bridging the metal centres, with Zr–O
solvent. Compared with the mononuclear starting material 3 (D =
1.6 ¥ 10-9 m2 s-1) complex 14 was found to possess an almost
identical diffusion constant of D = 1.8 ¥ 10-9 m2 s-1. In contrast
to aromatic solvents, in which 14 and 15 are insoluble, the donor
solvent THF appears to be capable of stabilizing the mononuclear
species. The coordinated THF seems to undergo rapid exchange
processes as is indicated by the 1H and 13C NMR resonance pattern
which are consistent with an effective molecular CS-symmetry.
This interpretation is also consistent with the observation of only
four signals for the five nitrogen atoms in the 15N-NMR spectrum
of the monomeric species. The signal assigned to the a-nitrogen
atom of the pyridinioimido ligand is observed at 315.9 ppm while
Nb resonates at d = 276.6. The signals of the silylamido groups
are found at a characteristic 155.5 ppm and the resonance of the
pyridyl unit appears at d = 280.9.
˚
distances of 2.352(3) and 2.379(4) A being slightly greater than the
˚
corresponding distance in complex 3 [2.286(2) A]. As in complex
3 the nearly linear pyridinioimido unit is slightly tilted away
from the sterically demanding tert-butyl groups of the SiMe2tBu
substituents at the amido groups [Zr–N(4)–N(5) 170.8(4)◦].
Whereas the dinuclear structure of complex 14 in the solid state
was thus unambiguously established, the question concerning its
structure in solution remained open. In order to gain additional
1
insight H-DOSY-NMR experiments of solutions of 14 in THF
were carried out which indicated a monomeric structure in this
This journal is
The Royal Society of Chemistry 2008
Dalton Trans., 2008, 6231–6241 | 6235
©

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1
3JH6pyH5py = 5.3 Hz, 4JH6pyH4py = 1.1 Hz, 1H, H6py); 13C { H} NMR
Conclusions
(100 MHz, C6D6, 296 K): d = -4.1, -3.8 (Si(CH3)2), 20.2 (Si–
C(CH3)3), 24.5 (CH3), 27.9 (Si–C(CH3)3), 42.1, 45.0 (N(CH3)2),
47.8 (C–CH3), 63.0 (CH2), 120.3 (C3py), 121.7 (C5py), 138.3 (C4py),
In this work, we have provided a general synthetic method for the
preparation of group 4 metal pyridinioimido complexes and have
extended previous efforts involving titanium compounds in this
field to their heavier metal congeners.8 As recently found for Nb-
disubstituted hydrazinediides,9 the systems reported here undergo
N–N bond cleavage and N–element bond formation reactions. A
first assessment of their reactivity has shown them to be somewhat
less reactive that the diphenylhydrazinediido complexes which may
prove to be beneficial in the quest for selective transformations
involving the N–N bond. We attribute this trend to the partial
conjugation of the N–N bond with the aromatic heterocycle,12
a notion which is consistent with the shorter N–N bond found
for the pyridinioimides as compared to more “conventional”
hydrazides(2-). Current work in our lab focuses on the possibility
of cleaving the pyridinioimido N–N bond reductively, as probed
by Hidai8 for Ti and the attempt to identify the metal containing
fragments.
147.1 (C6py), 163.2 (C2py); 29Si { H} NMR (80 MHz, C6D6, 296 K):
1
d = 3.4 (Si(CH3)2 Bu); 15N NMR (60 MHz, C6D6, 296 K): d =
t
t
133.9, 138.6 (NMe2), 144.8 (N-Si(CH3)2 Bu), 292.7 (L-Npy).
TBS
[Zr(N2 Npy)(NNC5H5)(OTf)(py)] (3). A Schlenk tube was
charged with [Zr(N2 Npy)(NMe2)2] (1) (1.76 g, 3.1 mmol), 180 ml
TBS
pyridine (3.1 mmol) and 40 ml of toluene. Aminopyridiniumtri-
flate (0.53 g, 3.1 mmol) was added slowly in small portions. The
reaction mi◦xture was placed under partial vacuum and stirred for
18 h at 40 C. After filtration, the volatiles were removed under
reduced pressure and the crude product was washed with pentane
(3 ¥ 20 ml) and dried in vacuo to yield 1.71 g (2.1 mmol, 68%) of an
orange powder. Single crystals for X-ray diffraction were grown
from a saturated toluene solution at 10 ◦C. (Found: C, 52.00; H,
6.62; N, 9.57. Calc. for C32H51F3N6SO3Si2Zr (+C7H8): C, 52.26;
H, 6.63; N, 9.38%); umax(Nujol)/cm-1 1601 w, 1455 m, 1318 m,
1237 m, 1169 w, 895 w, 849 m; 1H NMR (600 MHz, d8-thf, 335 K):
d = -0.12, 0.12 (s, 6H, Si(CH3)2), 0.89 (s, 18H, Si–C(CH3)3), 1.47
Experimental section
(s, 3H, CH3), 3.37 (d, 2JHH = 12.0 Hz, 2H, CHH), 3.72 (d, 2JHH
=
All manipulations of air- and moisture-sensitive materials were
performed under an inert atmosphere of dry argon using standard
Schlenk techniques or by working in a glove box. Solvents were
dried over sodium (toluene), potassium (hexanes) or sodium–
potassium alloy (pentane, diethyl ether), distilled, and degassed
prior to use. Deuterated solvents were dried over potassium (C6D6,
THF-d8), vacuum distilled and stored in Teflon valve ampoules
under argon. Samples for NMR spectroscopy were prepared
under argon in 5 mm Wilmad tubes equipped with J. Young
3
12.0 Hz, 2H, CHH), 7.12 (t, JpHmH = 7.6 Hz, 1H, p-HB), 7.23
(pt, 3JmHo/pH = 6.2 Hz, 4 H, m-HA/B), 7.32 (dd, 3JH5pyH4py = 6.6 Hz,
3JH5pyH6py = 5.0 Hz, 1H, H5py), 7.59 (d, JH3pyH4py = 8.1 Hz, 1 H,
3
3
H3py), 7.65 (t, JpHmH = 7.6 Hz, 1H, p-HA), 7.95 (m, 1H, H4py),
8.39 (d, 3JoHmH= 6.7 Hz, 2H, o-HB), 8.54 (d, 3JoHmH = 4.3 Hz, 2H,
3
1
o-HA), 8.96 (d, JH6pyH5py = 5.0 Hz, 1H, H6py); 13C { H} NMR
(100 MHz, d8-thf, 335 K): d = -4.0, -2.5 (Si(CH3)2), 20.9 (Si–
C(CH3)3), 24.7 (C-CH3), 29.1 (Si–C(CH3)3), 51.9 (C-CH3), 63.2
(CH2), 121.1 (C3py), 122.1 (C5py), 124.4 (m-CA/B), 124.7 (p-CB),
126.7 (m-CA/B), 136.8 (p-CA), 140.8 (C4py, o-CB), 148.6 (C6py),
Teflon valves. H, 13C, 29Si and 15N NMR spectra were recorded
1
on Bruker Avance 200, 400 and 600 NMR spectrometers and
were referenced internally, using the residual protio solvent (1H)
or solvent (13C) resonances or externally to SiMe4 and 15NH3.
Elemental analyses were recorded by the analytical service of the
Heidelberg Chemistry Department. The diamido-pyridine protio-
151.3 (o-CA), 166.2 (C2py), n.o. (CF3); 29Si { H} NMR (80 MHz,
1
t
1
d8-thf, 296 K): d = 3.1 (Si(CH3)2 Bu); 19F { H} NMR (376 MHz,
d8-thf, 296 K): d = -78.3(CF3); 15N-NMR (d8-thf, 60MHz, 335K):
t
d = 156.5 (N-Si(CH3)2 Bu), 276.9 (Zr–NNpy), 281.6 (L-Npy), 314.4
(Zr–Npy), 317.1 (Zr–NNpy).
TBS
TBS
ligand H2N2
N
and [Zr(N2 Npy)(NMe2)2] (1) were prepared
py
TBS
according to published procedures.9,10 All other reagents were
obtained from commercial sources and used as received unless
explicitly stated.
Preparation of [Hf(N2 Npy)(NNC5H5)(OTf)(py)] (4).
A
TBS
Schlenk tube was charged with [Hf(N2 Npy)(NMe2)2] (2) (1.24 g,
1.9 mmol), 146 ml pyridine (1.9 mmol) and 20 ml of toluene.
Aminopyridiniumtriflate (356 mg, 1.9 mmol) was added slowly
in small portions. The reaction mixture was placed under partial
vacuum and stirred for 40 h at 50 ◦C. After filtration the volatiles
were removed under reduced pressure and the crude product was
washed with pentane (3 ¥ 10 ml) and dried in vacuo to yield 1.10 g
(1.3 mmol, 66%) of an orange powder. Single crystals for X-ray
diffraction were grown from a saturated toluene solution at 10 ◦C.
(Found: C, 42.69; H, 5.72; N, 9.32. Calc. for C32H51N6SF3Si2Hf:
C, 43.11; H, 5.77; N, 9.43%); umax(Nujol)/cm-1 1602 m, 1464 s,
1377 m, 1339 m, 1170 w, 1032 m, 903 w, 857 m, 755 w, 633 s.; 1H
(A) Preparation of the complexes
TBS
[Hf(N2 Npy)(NMe2)2] (2). Hf(NMe2)4 (0.97 g, 2.7 mmol)
TBS
and H2N2
N
(1.08 g, 2.7 mmol) were dissolved in toluene
py
(20 ml) and placed under partial vacuum. After stirring the
reaction mixture at 95 ◦C for 18 h, the solution was filtered
and the volatiles were removed under reduced pressure to yield
TBS
[Hf(N2 Npy)(NMe2)2] as a yellow solid. Yield 1.78 g (2.6 mmol,
98%). (Found: C, 45.61; H, 8.11; N, 10.64. Calc. for C23H48N5Si2Hf:
C, 44.99; H, 7.98; N, 10.53%); umax(Nujol)/cm-1 2764 m, 1600 w,
1461 s, 1381 w, 1248 m, 1151 m, 965 w, 900 m, 873 s, 767 m,
663 w; 1H NMR (600 MHz, C6D6, 296 K): d = 0.25, 0.29 (s, 6H,
Si(CH3)2), 0.78 (s, 18H, Si–C(CH3)3), 1.02 (s, 3H, CH3), 3.16,
NMR (600 MHz, d8-thf, 335 K): d = -0.15, 0.06 (s, 6H, Si(CH3)2),
2
0.89 (s, 18H, Si–C(CH3)3), 1.44 (s, 3H, CH3), 3.48 (d, JHH
=
12.0 Hz, 2H, CHH), 3.85 (d, 2JHH = 12.0 Hz, 2H, CHH), 7.03 (t,
3JpHmH = 7.7 Hz, 1H, p-HB), 7.19 (t, JmHo/pH = 7.1 Hz, 2H, m-
3
2
3.23 (s, 6H, N(CH3)2), 3.55 (d, JHH = 12.4 Hz, 2H, CHH),
HB), 7.26 (t, 3JmHo/pH = 6.0 Hz, 2H, m-HA), 7.31 (t, 3JH5pyH4py/H6py
=
2
3
3.81 (d, JHH = 12.4 Hz, 2H, CHH), 6.56 (ddd, JH5pyH4py
=
6.2 Hz, 1H, H5py), 7.62 (d, 3JH3pyH4py = 6.0 Hz, 1H, H3py), 7.70 (t,
3
4
3
7.5 Hz, JH5pyH6py = 5.3 Hz, JH5pyH3py = 1.1 Hz, 1H, H5py), 6.84
3JpHmH = 7.9 Hz, 1H, p-HA), 7.96 (t, JH4pyH5py/H6py = 7.9 Hz, 1H,
3
3
(d, JH3pyH4py = 8.0 Hz, 1H, H3py), 7.03 (m, 1H, H4py), 8.29 (dd,
H4py), 8.31 (d, JoHmH= 6.5 Hz, 2H, o-HB), 8.57 (bs, 2H, o-HA),
6236 | Dalton Trans., 2008, 6231–6241
This journal is
The Royal Society of Chemistry 2008
©

View Article Online
1
8.88 (bs, 1H, H6py); 13C { H} NMR (100 MHz, d8-thf, 335 K):
296 K): d = -4.2, -3.5 (Si(CH3)2), 20.8 (Si–C(CH3)2), 24.9 (CH3),
∫
28.3 (Si–C(CH3)2), 49.7 (C-CH3), 63.0 (CH2), 82.6, 112.7 (C C),
d = -3.89, -2.5 (Si(CH3)2), 21.2 (Si–C(CH3)3), 25.8 (C-CH3),
29.3 (Si–C(CH3)3), 51.7 (C-CH3), 63.1 (CH2), 120.0 (q, |1JCF| =
319 Hz, CF3), 121.3 (C3py), 122.5 (C5py), 123.2 (p-CB), 124.7 (m-
CA), 126.6 (m-CB), 137.6 (p-CA), 141.1 (C4py), 141.8 (o-CB), 149.9
118.9 (p-CB), 119.0 (C3py), 121.3 (C5py), 121.5 (m-CA), 125.3 (m-
CB), 126.0 (p-CPh), 128.5 (m-CPh), 131.5 (o-CPh), 136.9 (p-CA),
138.5 (C4py), 139.5 (o-CB), 150.8 (C6py), 151.8 (o-CA), 158.7 (i-
1
CPh), 164.0 (C2py); 29Si { H} NMR (80 MHz, C6D6, 296 K): d =
(C6py), 151.7 (o-CA), 166.8 (C2py); 29Si { H} NMR(80 MHz, d8-thf,
1
2.7 (Si(CH3)2 Bu); 15N-NMR (60 MHz, C6D6, 296 K): d = 146.6
t
296 K): d = 3.2 (Si(CH3)2 Bu); 19F { H} NMR (376 MHz, d8-thf,
t
1
t
296 K): d = -78.3 (CF3); 15N-NMR (d8-thf, 60 MHz, 335 K):
(N-Si(CH3)2 Bu), 284.6 (Hf-NNpy), 286.4 (L-Npy), 295.3 (Hf-Npy),
t
353.5 (Hf-NNpy).
d = 141.1 (N-Si(CH3)2 Bu), 281.6 (Hf-NNpy), 282.2 (L-Npy), 332.7
(Hf-NNpy), n.o. (Hf-Npy).
TBS
[Zr(N2 Npy)(OTf)(NCNtBu)(py)] (7). To a stirred solution
TBS
[Zr(N2 Npy)(NNC5H5)(CCPh)(py)] (5). To a stirred solution
of [Zr(N2 Npy)(NNC5H5)(OTf)(py)] (3) (1.0 g, 1.24 mmol) in
TBS
of [Zr(N2 Npy)(NNC5H5)(OTf)(py)] (3) (350 mg, 0.44 mmol) in
TBS
toluene (20 ml) tBuNC (46.7 ml, 0.44 mmol) was added dropwise.
The red reaction mixture was stirred overnight before removing
the solvent in vacuo to yield (7) as a red solid. Quantitative
Yield. Crystals suitable for X-Ray diffraction were grown from
a saturated toluene solution at 10 ◦C. (Found: C, 47.76; H, 6.93;
N, 10.46. Calc. for C32H55F3N6O3SSi2Zr: C, 47.55; H, 6.86; N,
10.40%); umax(Nujol)/cm-1 2149 sh, 2094 s, 1604 w, 1464 m, 1375 w,
1330 m, 1238 m, 1203 s, 1091 w, 1013 m, 903 w, 825 m, 776 m,
631 m; 1H NMR (600 MHz, d8-thf, 335 K): d = -0.01, 0.26 (s, 6H,
Si(CH3)2), 0.91 (s, 18H, Si–C(CH3)3), 1.30 (s, 9H, NC(CH3)3), 1.55
toluene (50 ml) LiCCPh (135 mg, 1.24 mmol) was added in
small portions over 5 min. The mixture was stirred for 18 h. The
precipitated LiOTf was removed by filtration and the volatiles were
removed under reduced pressure. The brown solid was extracted
with pentane (40 ml) and filtered away from insoluble impurities.
The solvent was removed from the extract under reduced pressure
and the yellow solid was finally washed with cold pentane (-78 ◦C,
2 ¥ 10 ml). Yield 378 mg (0.5 mmol, 40%). Single crystals for
X-ray diffraction were grown from a saturated toluene solution
at -40 ◦C.; (Found: C, 61.83; H, 7.39; N, 10.87. Calc. for
C39H56N6Si2Zr: C, 61.94; H, 7.46; N, 11.11%); umax(Nujol)/cm-1
1597 m, 1450 s, 1315 s, 1248 w, 1170 w, 1053 m, 1011 m, 891 m,
(s, 3H, CH3), 3.35 (d, 2JHH = 12.4 Hz, 2H, CHH), 3.88 (d, 2JHH
=
12.3 Hz, 2H, CHH), 7.25 (m, 2H, m-Hpy), 7.43 (m, 1H, H5py),
7.68 (t, 3JpHmH = 7.6 Hz, 1H, p-Hpy), 7.71 (d, 3JH3pyH4py = 8.1 Hz,
1
848 s, 757 w; H NMR (400 MHz, C6D6, 296 K): d = 0.16, 0.40
3
4
1H, H3py), 8.08 (ddd, JH4pyH3/5py = 8.0 Hz, JH4pyH6py = 1.7 Hz,
(s, 6H, Si(CH3)2), 1.12 (s, 18H, Si–C(CH3)3), 1.26 (s, 3H, CH3),
3.58 (d, 2JHH = 12.3 Hz, 2H, CHH), 4.03 (d, 2JHH = 12.3 Hz, 2H,
3
1H, H4py), 8.52 (bs, 2H, o-Hpy), 8.85 (d, JH6pyH5py = 4.7 Hz, 1H,
H6py); 13C { H} NMR (100 MHz, d8-thf, 335 K): d = -5.3, -3.2
1
3
3
CHH), 6.08 (t, JpHmH = 7.5 Hz, 1H, p-HB), 6.27 (pt, JmHo/pH
=
(Si(CH3)2), 20.0 (Si–C(CH3)3), 23.3 (C-CH3), 27.7 (Si–C(CH3)3),
32.0 (NC(CH3)3), 50.7 (C-CH3), 53.9 (NC(CH3)3), 62.2 (CH2N),
120.7 (p-Cpy), 122.3 (C5py), 123.6 (m-Cpy), 136.0 (C3py), 141.1
(C4py), 148.1 (C6py), 150.3 (o-Cpy), 163.3 (C2py), n.o. (CF3); 29Si
7.1 Hz, 2H, m-HB), 6.53 (dd, 3JH4pyH3/5py = 6.4 Hz, 1H, H4py), 6.58
(m, 1H, m-HA), 6.89 (t, 3JpHmH = 7.2 Hz, 1H, p-HA), 6.97–7.14 (sh,
5H, m/p-HPh, H3py, H5py), 7.67 (d, 3JoHmH = 7.3 Hz, 2H, o-HPh),
3
3
8.58 (d, JoHmH = 6.3 Hz, 2H, o-HB), 8.69 (d, JoHmH = 4.3 Hz,
{ H} NMR (80 MHz, d8-thf, 296 K): d = 4.7 (Si(CH3)2 Bu); 19F
1
t
2 H, o-HA), 10.01 (d, JH5pyH6py = 4.4 Hz, 1H, H6py); 13C { H}
NMR (100 MHz, C6D6, 296 K): d = -4.2, -3.2 (Si(CH3)2), 20.8
(Si–C(CH3)2), 28.4 (Si–C(CH3)2), 50.3 (C-CH3), 63.2 (CH2), 77.8,
3
1
{ H} NMR (376 MHz, d8-thf, 296 K): d = -77.7 (CF3); 15N-NMR
1
(d8-thf, 60 MHz, 335 K): d = 76.1 (tBuN), 166.9 (N-Si(CH3)2 Bu),
t
193.1 (Zr–NCN), 275.6 (L-Npy), n.o. (Zr–Npy).
∫
110.9 (C C), 119.9 (p-CB), 120.1, 125.3, 128.4 (C3py, C5py, m/p-
CPh), 123.4 (p-CA), 125.3 (m-CB), 128.4 (m-CA), 131.5 (o-CPh),
138.5 (o-CB), 138.9 (C4py), 151.0 (C6py), 151.3 (o-CA), 164.2 (C2py);
TBS
[Hf(N2 Npy)(OTf)(NCNtBu)(py)] (8). To a stirred solution
TBS
of [Hf(N2 Npy)(NNC5H5)(OTf)(py)] (4) (400 mg, 0.45 mmol) in
1
t
29Si { H} NMR (80 MHz, C6D6, 296 K): d = 2.1 (Si(CH3)2 Bu).
toluene (20 ml) tBuNC (51.1 ml, 0.45 mmol) was added dropwise.
The red reaction mixture was stirred overnight and the volatiles
were removed under reduced pressure. The residue was washed
with pentane (2 ¥ 5 ml) and dried in vacuo to yield 250 mg
(0.28 mmol, 62%) of (8) as a yellow solid. (Found: C, 42.42; H,
6.03; N, 9.10. Calc. for C32H55F3N6O3SSi2Hf: C, 42.92; H, 6.19; N,
9.38%); umax(Nujol)/cm-1 2157 sh, 2103 s, 1606 w, 1463 s, 1377 w,
TBS
[Hf(N2 Npy)(NNC5H5)(CCPh)(py)] (6). To a stirred solution
TBS
of [Hf(N2 Npy)(NNC5H5)(OTf)(py)] (4) (0.5 g, 0.56 mmol) in
toluene (20 ml) LiCCPh (61 mg, 0.56 mmol) was added in small
portions over 5 min. The mixture was stirred for 18 h. The
precipitated LiOTf was removed by filtration and the volatiles
were removed under reduced pressure. Yield 300 mg (0.36 mmol,
64%). (Found: C, 53.95; H, 6.79; N, 9.56. Calc. for C39H56N6Si2Hf:
C, 55.53; H, 6.69; N, 9.96%); umax(Nujol)/cm-1 1599 s, 1459 s,
1378 m, 1335 s, 1248 m 1201 w, 1134 w, 1090 m, 1052 s, 1008 s,
1
1328 w, 1212 m, 1020 w, 840 m, 732 m; H NMR (600 MHz,
d8-thf, 335 K): d = -0.04, 0.16 (s, 6H, Si(CH3)2), 0.92 (s, 18H,
Si–C(CH3)3), 1.30 (s, 9H, NC(CH3)3), 1.50 (s, 3H, CH3), 3.50 (d,
2JHH = 12.3 Hz, 2H, CHH), 4.03 (d, 2JHH = 12.2 Hz, 2H, CHH),
7.29 (bs, 2H, m-Hpy), 7.43 (m, 1H, H5py), 7.70-7.74 (sh, 2H, H3py,
p-Hpy), 8.10 (t, 3JH4pyH3/5py = 8.0 Hz, 1H, H4py), 8.55 (bs, 2H, o-Hpy),
1
898 s, 856 s, 827 s, 767 m, 694 w, 637 sh; H NMR (600 MHz,
C6D6, 296 K): d = 0.14, 0.40 (s, 6H, Si(CH3)2), 1.09 (s, 18 H, Si–
C(CH3)3), 1.19 (s, 3H, CH3), 3.70 (d, 2JHH = 12.1 Hz, 2H, CHH),
4.10 (d, 2JHH = 12.0 Hz, 2H, CHH), 6.06 (t, 3JpHmH = 7.5 Hz, 1H,
p-HB), 6.29 (t, 3JmHo/pH = 7.1 Hz, 2H, m-HB), 6.55 (m, 2H, m-HA),
6.84-6.89 (sh, p-HA, H5py), 6.99–7.03 (sh, 2H, p-HPh, H3py), 7.07
(dt, 3JH4pyH3py/H5py = 7.7 Hz, 4JH4py/H6py = 1.8 Hz, 1H, H4py), 7.11 (t,
8.81 (bs, 1H, H6py); 13C { H} NMR (100 MHz, d8-thf, 335 K): d =
1
-3.6, -2.1 (Si(CH3)2), 21.4 (Si–C(CH3)3), 25.4 (C-CH3), 29.0 (Si–
C(CH3)3), 33.1 (NC(CH3)3), 51.7 (C-CH3), 54.8 (NC(CH3)3), 62.6
(CH2N), 122.2 (C3py), 123.6 (C5py), 124.9 (m-Cpy), 137.8 (p-Cpy),
142.6 (C4py), 149.3 (o-Cpy), 151.7 (C6py), 165.3 (C2py), n.o. (CF3);
3
3JmHo/pH = 7.5 Hz, 2H, m-HPh), 7.68 (d, JoHmH = 7.5 Hz, 2H, o-
HPh), 8.45 (d, 3JoHmH = 6.3 Hz, 2H, o-HB), 8.74 (d, 3JoHmH = 3.5 Hz,
29Si { H} NMR (80 MHz, d8-thf, 296 K): d = 4.8 (Si(CH3)2 Bu);
1
t
1
1
2H, o-HA), 10.20 (bs, 1H, H6py); 13C { H} NMR (100 MHz, C6D6,
19F { H} NMR (376 MHz, d8-thf, 296 K): d = -77.5 (CF3).
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Dalton Trans., 2008, 6231–6241 | 6237
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View Article Online
TBS
[Zr(N2 Npy)(OTf)(NCNCy)(py)] (9). To a stirred solution of
1329 m, 1235 w, 1207 m, 1181 w, 1019 m, 902 w, 830 m, 770 w,
TBS
1
[Zr(N2 Npy)(NNC5H5)(OTf)(py)] (3) (300 mg, 0.37 mmol) in
633 m; H NMR (600 MHz, d8-thf, 335 K): d = -0.01, 0.30 (s,
toluene (20 ml) CyNC (46.7 ml, 0.37 mmol) was added dropwise.
The red solution was stirred overnight before removing the solvent
in vacuo to yield (9) as a red solid. Quantitative Yield (Found: C,
48.57; H, 6.81; N, 10.03. Calc. for C34H57F3N6O3SSi2Zr: C, 48.95;
H, 6.89; N, 10.07%); umax(Nujol)/cm-1 2113 s, 1604 m, 1463 s,
1376 m, 1326 m, 1257 w, 1206 m, 1065 w, 900 m, 828 s, 778 m,
632 m; 1H NMR (600 MHz, d8-thf, 335 K): d = -0.03, 0.26 (bs, 6H,
Si(CH3)2), 0.91 (s, 18H, Si–C(CH3)3), 1.29 (m, 4H, m/p-HCy), 1.43
(m, 2H, o-HCy), 1.51 (m, 2H, m-HCy), 1.55 (s, 3H, CH3), 1.89 (m,
2H, o-HCy), 3.29 (m, 1H, HCy), 3.35 (d, 2JHH = 12.5 Hz, 2H, CHH),
6H, Si(CH3)2), 0.91 (s, 18H, Si–C(CH3)3), 1.56 (s, 3H, CH3), 2.33
2
(s, 6H, (CH3)2C6H3), 3.36 (d, JHH = 12.8 Hz, 2H, CHH), 3.92
2
3
(d, JHH = 12.8 Hz, 2H, CHH), 6.70 (t, JpHmH = 7.4 Hz, 1H, p-
3
3
H
Xyl), 6.86 (d, JmHpH = 7.4 Hz, 2H, m-HXyl), 7.23 (dd, JmHoH =
5.8 Hz, 3JmHpH = 7.6 Hz, 2H, m-Hpy), 7.44 (dd, 3JH5pyH6py = 4.9 Hz,
3JH5pyH4py = 7.9 Hz, 1H, H5py), 7.66 (t, 3JpHmH = 7.6 Hz, 1H, p-Hpy),
3
3
7.72 (d, JH3pyH4py = 7.9 Hz, 1H, H3py), 8.09 (ddd, JH4pyH3py/5py
=
7.9 Hz, 4JH4pyH6py = 1.7 Hz, 1H, H4py), 8.51 (bs, 2H, o-Hpy), 8.88 (d,
3JH6pyH5py = 4.9 Hz, 1H, H6py); 13C { H} NMR (100 MHz, d8-thf,
1
335 K): d = -5.4, -3.4 (Si(CH3)2), 18.4 (CH3)2C6H3), 19.9 ((Si–
C(CH3)3), 25.9 (C-CH3), 27.6 (Si–C(CH3)3), 50.8 (C-CH3), 61.9
(CH2N), 120.9(C3py), 121.9 (p-CXyl), 122.2 (C5py), 123.4 (m-Cpy),
127.3 (m-CXyl), 131.9 (o-CXyl), 136.0 (p-Cpy), 137.7 (CXyl), 141.3
(C4py), 148.0 (C6py), 150.1 (o-Cpy), 163.0 (C2py), n.o. (CF3); 29Si
2
3.88 (d, JHH = 12.3 Hz, 2H, CHH), 7.27 (m, 2H, m-Hpy), 7.44
3
(bs, 1H, H5py), 7.69 (bs, 1H, p-Hpy), 7.72 (d, JH3pyH4py = 8.2 Hz,
3
4
1H, H3py), 8.08 (ddd, JH4pyH3py/5py = 7.9 Hz, JH4pyH6py = 1.6 Hz,
1H, H4py), 8.53 (bs, 2H, o-Hpy), 8.86 (bs, 1H, H6py); 13C { H}
1
1
t
NMR (100 MHz, d8-thf, 335 K): d = -5.2, -3.3 (Si(CH3)2), 20.0
(Si–C(CH3)3), 24.5 (C-CH3), 24.7 (p-CCy), 26.0 (m-CCy), 27.9 (Si–
C(CH3)3), 36.0 (o-CCy), 50.7 (C-CH3), 54.5 (CCy), 62.0 (CH2N),
120.7 (p-Cpy), 122.0 (C5py), 123.4 (m-Cpy), 136.0 (C3py), 141.1
(C4py), 148.0 (C6py), 150.1 (o-Cpy), 163.2 (C2py), n.o. (CF3);); 29Si
{ H} NMR (80 MHz, d8-thf, 296 K): d = 5.7 (Si(CH3)2 Bu); 19F
{ H} NMR (376 MHz, d8-thf, 296 K): d = -77.8 (CF3); 15N-NMR
1
t
(d8-thf, 60 MHz, 335 K): d = 64.0 (tBuN), 160.9 (N-Si(CH3)2 Bu),
197.8 (Zr–NCN), 274.9 (L-Npy), n.o. (Zr–Npy).
TBS
[Hf(N2 Npy)(OTf)(NCNXyl)(py)] (12). To a stirred solution
1
t
{ H} NMR (80 MHz, d8-thf, 296 K): d = 4.6 (Si(CH3)2 Bu); 19F
TBS
of [Hf(N2 Npy)(NNC5H5)(OTf)(py)] (4) (300 mg, 0.34 mmol) in
{ H} NMR (376 MHz, d8-thf, 296 K): d = -77.6 (CF3); 15N-NMR
1
toluene (10 ml) a solution of 2,6-XylNC (44.1 mg, 0.34 mmol) in
toluene (5 ml) was added dropwise. The red reaction mixture was
stirred overnight and the volatiles were removed under reduced
pressure. The residue was washed with pentane (2 ¥ 5 ml) and dried
in vacuo, to yield 193 mg (0.20 mmol, 60%) of (12) as a yellow solid.
(Found: C, 45.52; H, 5.81; N, 8.67. Calc. for C36H55F3N6O3SSi2Hf:
C, 45.82; H, 5.88; N, 8.91%); umax(Nujol)/cm-1 2200 sh, 2138 s,
1605 w, 1462 s, 1377 m, 1331 m, 1208 m, 1019 s, 909 w, 814 s, 799
t
(d8-thf, 60 MHz, 335 K): d = 64.0 (CyN), 164.2 (N-Si(CH3)2 Bu),
192.9 (Zr–NCN), 275.6 (L-Npy), n.o. (Zr–Npy).
TBS
[Hf(N2 Npy)(OTf)(NCNCy)(py)] (10). To a stirred solution
TBS
of [Hf(N2 Npy)(NNC5H5)(OTf)(py)] (4) (200 mg, 0.22 mmol) in
toluene (10 ml) CyNC (27.9 ml, 0.22 mmol) was added dropwise.
The red reaction mixture was stirred overnight and the volatiles
were removed under reduced pressure. The residue was washed
with pentane (2 ¥ 2 ml) and dried in vacuo, to yield 150 mg
(0.17 mmol, 74%) of (10) as an orange solid. (Found: C, 44.20;
H, 5.94; N, 9.15. Calc. for C34H57F3N6O3SSi2Hf: C, 44.31; H, 6.23;
N, 9.12%); umax(Nujol)/cm-1 2123 s, 1606 m, 1463 s, 1260 m, 1203 s,
1023 sh, 907 w, 841 m, 633 m; 1H NMR (600 MHz, d8-thf, 335 K):
d = -0.03, 0.26 (bs, 6H, Si(CH3)2), 0.91 (s, 18H, Si–C(CH3)3), 1.29
(m, 4H, m/p-HCy), 1.43 (m, 2H, o-HCy), 1.51 (m, 2H, m-HCy),
1.55 (s, 3H, CH3), 1.89 (m, 2H, o-HCy), 3.29 (m, 1H, HCy), 3.35 (d,
2JHH = 12.5 Hz, 2H, CHH), 3.88 (d, 2JHH = 12.3 Hz, 2H, CHH),
7.27 (m, 2H, m-Hpy), 7.44 (bs, 1H, H5py), 7.69 (bs, 1H, p-Hpy),
1
w; H NMR (600 MHz, d8-thf, 335 K): d = 0.00, 0.20 (s, 6 H,
Si(CH3)2), 0.96 (s, 18H, Si–C(CH3)3), 1.55 (s, 3H, CH3), 2.37 (s,
2
6H, (CH3)2C6H3), 3.57 (d, JHH = 12.2 Hz, 2H, CHH), 4.12 (d,
2JHH = 12.2 Hz, 2H, CHH), 6.73 (t, 3JpHmH = 7.5 Hz, 1 H, p-HXyl),
6.90 (d, 3JmHpH = 7.4 Hz, 2H, m-HXyl), 7.35 (bs, 2H, m-Hpy), 7.45
(t, 3JH5pyH4py/H6py = 4.9 Hz, 3JH5py = 5.8 Hz, 1H, H5py), 7.75-7.82 (sh,
2H, p-Hpy, H3py), 8.13 (t, 3JH4pyH3py/5py = 7.7 Hz, 1H, H4py), 8.59 (bs,
1
2H, o-Hpy), 8.88 (bs, 1H, H6py); 13C { H} NMR (100 MHz, d8-thf,
335 K): d = -4.2, -2.5 (Si(CH3)2), 19.5 (CH3)2C6H3), 21.1 (Si–
C(CH3)3), 25.1 (C-CH3), 28.7 (Si–C(CH3)3), 51.4 (C-CH3), 62.4
(CH2N), 120.9 (q, |1JCF| = 319 Hz, CF3), 122.1(C3py), 122.8 (p-
3
3
7.72 (d, JH3pyH4py = 8.2 Hz, 1H, H3py), 8.08 (ddd, JH4pyH3py/5py
=
4
7.9 Hz, JH4pyH6py = 1.6 Hz, 1H, H4py), 8.53 (bs, 2H, o-Hpy), 8.86
CXyl), 123.4 (C5py), 124.8 (m-Cpy), 128.3 (m-CXyl), 132.9 (o-CXyl),
(bs, 1H, H6py); 13C { H} NMR (100 MHz, d8-thf, 335 K): d =
138.3 (p-Cpy), 138.5 (CXyl), 142.5 (C4py), 148.9 (C6py), 151.6 (o-
1
1
-5.2, -3.3 (Si(CH3)2), 20.0 (Si–C(CH3)3), 24.5 (C-CH3), 24.7 (p-
CCy), 26.0 (m-CCy), 27.9 (Si–C(CH3)3), 36.0 (o-CCy), 50.7 (C-CH3),
54.5 (CCy), 62.0 (CH2N), 120.7 (p-Cpy), 122.0 (C5py), 123.4 (m-
Cpy), 136.0 (C3py), 141.1 (C4py), 148.0 (C6py), 150.1 (o-Cpy), 163.2
Cpy), 164.8 (C2py); 29Si { H} NMR (80 MHz, d8-thf, 296 K): d =
5.9 (Si(CH3)2 Bu); 19F { H} NMR (376 MHz, d8-thf, 296 K): d =
-74.2 (CF3).
t
1
TBS
TBS
[Zr(N2 Npy)(OTf)(NCO)(py)] (13). [Zr(N2 Npy)(NNC5H5)-
(OTf)(py)] (3) (500 mg, 0.54 mmol) was dissolved in toluene
(30 ml) and dry CO was bubbled through the solution for 10 min.
The saturated solution was stirred overnight before removing
the volatiles under reduced pressure. The resulting red solid was
washed with pentane (2 ¥ 20 ml) and dried in vacuo to yield
13 as an orange solid. Yield 269 mg (0.36 mmol, 67%). Single
crystals suitable for X-ray diffraction were grown from a saturated
toluene solution at 10 ◦C. (Found: C, 43.54; H, 6.23; N, 9.34.
Calc. for C28H46F3N5O4SSi2Zr: C, 44.65; H, 6.16; N, 9.30%);
(C2py), n.o. (CF3); 29Si { H} NMR (80 MHz, d8-thf, 296 K): d =
1
4.6 (Si(CH3)2 Bu); 19F { H} NMR (376 MHz, d8-thf, 296 K): d =
-77.6 (CF3).
t
1
TBS
[Zr(N2 Npy)(OTf)(NCNXyl)(py)] (11). To a stirred solution
TBS
of [Zr(N2 Npy)(NNC5H5)(OTf)(py)] (3) (500 mg, 0.54 mmol) in
toluene (30 ml) a solution of 2,6-XylNC (71.4 mg, 0.54 mmol) in
toluene (10 ml) was added dropwise. The red reaction mixture was
stirred overnight before removing the solvent in vacuo to yield (11)
as a red solid. Quantitative Yield. (Found: C, 49.63; H, 6.36; N,
9.66. Calc. for C36H55F3N6O3SSi2Zr: C, 50.49; H, 6.47; N, 9.81%);
u
max(Nujol)/cm-1 2206 s, 1605 w, 1463 s, 1331 m, 1236 m, 1203 s,
1089 w, 1018 m, 903 w, 828 m, 776 w, 634 m; 1H NMR (600 MHz,
u
max(Nujol)/cm-1 2195 sh, 2130 s, 2107 s, 1604 w, 1591 w, 1462 m,
6238 | Dalton Trans., 2008, 6231–6241
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This journal is
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©

View Article Online
d8-thf, 335 K): d = -0.00, 0.31 (s, 6H, Si(CH3)2), 0.91 (s, 18H, Si–
C(CH3)3), 1.58 (s, 3H, CH3), 3.36 (d, 2JHH = 12.5 Hz, 2H, CHH),
3.94 (d, 2JHH = 12.5 Hz, 2H, CHH), 7.23 (bs, 2H, m-Hpy), 7.44 (bs,
123.2 (p-C), 126.5 (m-CB), 141.0 (C4py), 141.4 (o-C), 149.4 (C6py),
1
29
166.2 (C2py), n.o. (CF3); { H} Si-NMR (d8-thf, 80 MHz, 296 K):
d = 4.2 (Si(CH3)2 Bu); 19F-NMR (d8-thf, 380 MHz, 296K): d =
t
3
1H, H5py), 7.65 (bs, 1H, p-Hpy), 7.77 (d, JH3pyH4py = 8.1 Hz, 1H,
-78.2 (CF3); 15N-NMR (d8-thf, 60 MHz, 296 K): d = 140.2 (N-
t
H3py), 8.14 (m, 1H, H4py), 8.53 (bs, 2H, o-Hpy), 8.93 (d, 3JH6pyH5py
=
Si(CH3)2 Bu), 281.4 (Hf-NNpy), (L-Npy), 327.9 (Hf-NNpy).
1
5.0 Hz, 1H, H6py); 13C { H} NMR (100 MHz, d8-thf, 335 K): d =
-5.5, -3.4 (Si(CH3)2), 20.1 (Si–C(CH3)3), 24.0 (C-CH3), 27.9 (Si–
C(CH3)3), 50.7 (C-CH3), 61.8 (CH2N), 121.0 (p-Cpy), 122.4 (C5py),
123.3 (m-Cpy), 136.0 (C3py), 141.6 (C4py), 148.4 (C6py), 149.9 (o-
(B) Crystal Structure Determinations
Crystal data and details of the structure determinations are listed
in Table 2. Intensity data were collected at low temperature
(complex 3: 150(2) K, all others: 100(2) K) with a Bruker AXS
Smart 1000 CCD diffractometer (Mo-Ka radiation, graphite
1
Cpy), 162.6 (C2py), n.o. (CF3); 29Si { H} NMR (80 MHz, d8-thf,
296 K): d = 5.4 (Si(CH3)2 Bu); 19F { H} NMR (376 MHz, d8-thf,
296 K): d = -77.6 (CF3).
t
1
˚
monochromator, l = 0.71073 A) and corrected for Lorentz,
TBS
polarization and absorption effects (semiempirical, SADABS).20
The structures were solved by the heavy atom method combined
with structure expansion by direct methods applied to difference
structure factors21 (complexes 3, 4, 7, 13), by conventional direct
methods22,23 (complex 5) or by direct methods with dual-space
recycling (“Shake-and-Bake”, complex 14)24 and refined by full-
matrix least squares methods based on all unique F2.23,25 All non-
hydrogen atoms were given anisotropic displacement parameters.
Hydrogen atoms were placed calculated positions and refined with
a riding model. Where required, the solvent of crystallization
(toluene) was subjected to planarity and appropriate bond length
similarity restraints.
[Zr(N2 Npy)(NNC5H5)(OTf)]2 (14). To
a
solution of
TBS
[Zr(N2 Npy)(NNC5H5)(OTf)(py)] (3) (200 mg, 0.25 mmol) in
toluene (6 ml) a solution of B(C6F5)3 (128 mg, 0.25 mmol)
in 2 ml of toluene was added dropwise. The red solution was
concentrated and stored at room temperature for two days.
Light yellow crystals precipitated directly from the reaction
mixture and were washed with toluene and dried in vacuo. Yield:
100 mg (0.07 mmol, 56%). (Found: C, 44.58; H, 6.44; N, 9.62.
Calc. for C54H92F6N10O6S2Si4Zr2: C, 44.72; H, 6.39; N, 9.66%);
u
max(Nujol)/cm-1 1602 m, 1458 s, 1376 m, 1239 m, 1188 w, 1172 w,
1164 w, 1087 w, 1035 m, 913 w, 826 w, 764 m, 731 w, 675 w,
627 m; 1H-NMR (d8-thf, 400 MHz, 296 K) d = -0.12, 0.13 (s, 6H,
Si(CH3)2), 0.88 (s, 18H, Si–C(CH3)3), 1.45 (s, 3H, CH3), 3.33 (d,
2JHH = 12.3 Hz, 2H, CHH), 3.69 (d, 2JHH = 12.3 Hz, 2H, CHH),
7.14 (t, 3JpHmH = 7.7 Hz, 1H, p-H), 7.26 (t, 3JmHo/pH = 7.4 Hz, 2H,
Crystallographic data (excluding structure factors) for the
structures reported in this paper have been deposited with the
Cambridge Crystallographic Data Center: CCDC-679492 (3),
687175 (4), 687176 (5), 679493 (7), 679494 (13) and 687177 (14).
For crystallographic data in CIF or other electronic format see
DOI: 10.1039/b807808d
m-H), 7.32 (t, 3JH5pyH4/6py = 6.0 Hz, 1H, H5py), 7.60 (d, 3JH3pyH4py
=
8.3 Hz, 1H, H3py), 7.98 (dt, 3JH4pyH3/5py = 7.9 Hz, 3JH4pyH6py = 1.9 Hz,
1H, H4py), 8.38 (d, 3JoHmH= 6.2 Hz, 2H, o-H), 9.01 (d, 3JH6pyH5py
=
1
13
5.9 Hz, 1H, H6py); { H} C-NMR (d8-THF, 600 MHz, 296 K): d =
-5.2, -3.7 (Si(CH3)2), 19.8 (Si–C(CH3)3), 24.9 (C-CH3), 28.0 (Si–
C(CH3)3), 50.5 (C-CH3), 61.8 (CH2), 120.0 (C3py), 121.0 (C5py),
123.7 (p-C), 125.7 (m-CB), 139.5 (C4py), 139.8 (o-C), 148.4 (C6py),
Acknowledgements
We thank the Deutsche Forschungsgemeinschaft for funding.
1
29
164.7 (C2py), n.o. (CF3); { H} Si-NMR (d8-thf, 80 MHz, 296 K):
d = 2.8 (Si(CH3)2 Bu); 15N-NMR (d8-thf, 60 MHz, 296 K): d =
t
References
t
155.5 (N-Si(CH3)2 Bu), 276.6 (Zr–NNpy), 280.9 (Npy), 315.9 (Z-r-
1 Reviews: (a) B. A. MacKay and M. D. Fryzuk, Chem. Rev., 2004, 104,
385; (b) M. P. Shaver and M. D. Fryzuk, Adv. Synth. Catal., 2003, 345,
1061; (c) R. R. Schrock, Acc. Chem. Res., 2005, 38, 955; (d) Y. Ohki
and M. D. Fryzuk, Angew. Chem., Int. Ed., 2007, 46, 3180; (e) N2-
activation by group 4 metal complexes. Key references: M. D. Fryzuk,
T. S. Haddad and S. J. Rettig, J. Am. Chem. Soc., 1990, 112, 8185; (f) R.
Duchateau, S. Gambarotta, N. Beydoun and C. Bensimon, J. Am.
Chem. Soc., 1991, 113, 8986; (g) M. D. Fryzuk, J. B. Love, S. J. Rettig
and V. G. Young, Science, 1997, 275, 1445; (h) H. Basch, D. G. Musaev,
K. Morokuma, M. D. Fryzuk, J. B. Love, W. W. Seidel, A. Albinati, T. F.
Koetzle, W. T. Klooster, S. A. Mason and J. Eckert, J. Am. Chem. Soc.,
1999, 121, 523; (i) J. A. Pool, E. Lobkovsky and P. J. Chirik, Nature,
2004, 427, 527.
2 (a) L. Morello, J. B. Love, B. O. Patrick and M. D. Fryzuk, J. Am. Chem.
Soc., 2004, 126, 9480; (b) W. H. Bernskoetter, A. V. Olmos, J. A. Pool,
E. Lobkovsky and P. J. Chirik, J. Am. Chem. Soc., 2006, 128, 10696;
(c) W. H. Bernskoetter, E. Lobkovsky and P. J. Chirik, Angew. Chem.,
Int. Ed., 2007, 46, 2858.
3 (a) J. S. Johnson and R. G. Bergmann, J. Am. Chem. Soc., 2001, 123,
2923; (b) C. Cao, Y. Shi and A. L. Odom, Org. Lett., 2002, 4, 2853;
(c) V. Khedkar, A. Tillack, M. Michalik and M. Beller, Tetrahedron
Lett., 2004, 45, 3123; (d) L. Ackermann and R. Born, Tetrahedron
Lett., 2004, 45, 9541.
NNpy); 19F-NMR (d8-thf, 380 MHz, 296K): d = -78.3 (CF3).
TBS
[Hf(N2 Npy)(NNC5H5)(OTf)]2 (15). To
a
solution of
TBS
[Hf(N2 Npy)(NNC5H5)(OTf)(py)] (4) (300 mg, 0.34 mmol) in
toluene (10 ml) a solution of B(C6F5)3 (172 mg, 0.34 mmol)
in 4 ml of toluene was added dropwise. The red solution was
concentrated and stored at room temperature for two days. The
yellow crystals, which precipitated, were washed with toluene and
dried in vacuo. Yield: 150 mg (0.09 mmol, 54%). (Found: C, 39.84;
H, 5.76; N, 8.62. Calc. for C54H92F6N10O6S2Si4Hf2: C, 39.92; H,
5.71; N, 8.62%); umax(Nujol)/cm-1 1605 m, 1459 s, 1377 w, 1315 s,
1
1129 m, 1090 w, 903 s, 856 s, 764 m, 771 m, 670 w, 635 m; H-
NMR (d8-thf, 600 MHz, 296 K) d = -0.12, 0.12 (s, 6H, Si(CH3)2),
2
0.89 (s, 18H, Si–C(CH3)3), 1.42 (s, 3H, CH3), 3.43 (d, JHH
=
2
11.9 Hz, 2H, CHH), 3.82 (d, JHH = 11.9 Hz, 2H, CHH), 7.07
(t, 3JpHmH = 7.5 Hz, 1H, p-H), 7.22 (t, 3JmHo/pH = 7.4 Hz, 2H, m-
3
3
H), 7.41 (t, JH5pyH4/6py = 7.1 Hz, 1H, H5py), 7.63 (d, JH3pyH4py
=
8.1 Hz, 1H, H3py), 8.00 (dt, 3JH4pyH3/5py = 7.8 Hz, 3JH4pyH6py = 1.4 Hz,
1H, H4py), 8.29 (d, 3JoHmH= 6.3 Hz, 2H, o-H), 9.05 (d, 3JH6pyH5py
=
4 A. Tillack, H. Jiao, I. Garcia Castro, C. G. Hartung and M. Beller,
Chem. Eur. J., 2004, 10, 2410.
5 (a) S. Banerjee, Y. Shi, C. Cao and A. L. Odom, J. Organomet. Chem.,
2005, 690, 5066; (b) S. Banerjee and A. L. Odom, Organometallics,
2006, 25, 3099.
1
13
4.9 Hz, 1H, H6py); { H} C-NMR (d8-THF, 600 MHz, 296 K): d =
-4.1, -2.7 (Si(CH3)2), 20.9 (Si–C(CH3)3), 25.6 (C-CH3), 29.0 (Si–
C(CH3)3), 51.3 (C-CH3), 65.5 (CH2), 121.1 (C3py), 122.3 (C5py),
6240 | Dalton Trans., 2008, 6231–6241
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