Zirconium and hafnium hydrazinediido half-sandwich complexes: Synthesis and reactivity

Article abstract of DOI:10.1021/om500087s

The hydrazinediido complexes [Cp*M(N_xylN)(NNPh ₂)(dmap)] (M = Zr, 3a; M = Hf, 3b; N_xylN = 2-(N-xylylamino)pyrrolinate) have been synthesized, and their reactivity has been investigated. Both complexes were prepared from [C

Full text of DOI:10.1021/om500087s

Article
pubs.acs.org/Organometallics
Zirconium and Hafnium Hydrazinediido Half-Sandwich Complexes:
Synthesis and Reactivity
Peter D. Schweizer, Hubert Wadepohl, and Lutz H. Gade*
Anorganisch-Chemisches Institut, Universitat Heidelberg, Im Neuenheimer Feld 270, 69120 Heidelberg, Germany
̈
S
* Supporting Information
ABSTRACT: The hydrazinediido complexes [Cp*M(NxylN)-
(NNPh2)(dmap)] (M = Zr, 3a; M = Hf, 3b; NxylN = 2-(N-
xylylamino)pyrrolinate) have been synthesized, and their
reactivity has been investigated. Both complexes were prepared
from [Cp*M(NxylN)Cl2] (1a,b) and [Cp*M(NxylN)-
(NHNPh2)Cl] (2a,b), respectively, as precursors. While 3a
was obtained by dehydrohalogenation of 2a using LiHMDS in
the presence of dmap, reaction of 2b with LiHMDS initially
afforded a mixture of [Cp*Hf(NxylN)(NHNPh2)2] (6) and
[Cp*Hf(NxylN)(NNPh2)LiHMDS] (4), which was thermo-
lyzed subsequently in the presence of dmap to yield 3b.
[Cp*Zr(NxylN)(NNPh2)(dmap)] (3a) reacted with diisopro-
pylcarbodiimide, giving the rearranged [2 + 2] cycloaddition
product [Cp*Zr(NXylN){κ2-NiPrC(NNPh2)NiPr}] (7) and the six-membered zirconacycle [Cp*Zr(NXylN){κ2-N(NPh2)C-
(NiPr)NiPrC(NiPr)NiPr}] (8a). With N-phenylbenzimine the cycloaddition product [Cp*Zr(NXylN){κ2-N(NPh2)CHPhNPh}]
(9) was isolated, and upon reaction with diphenylacetylene the seven-membered zirconacycle [Cp*Zr(NXylN){κ2-N(Ph)-o-
TBS
phenylene-C(Ph)C(Ph)NH}] (10) was obtained. Reaction of the previously synthesized compound [Zr(N2 Npy)(NNPh2)-
i
TBS
py] (11) with PrNCNiPr and with PhCHNPh gave the four-membered zirconacycles [Zr(N2 Npy){κ2-N(NPh2)C(NiPr)-
NiPr}] (12) and [Zr(N2 Npy){κ2-N(NPh2)CHPhNPh}] (13), respectively.
TBS
hafnium complexes containing 2-(N-xylylamino)pyrrolinate
(NxylN) as a spectator ligand.33 A first account of their
synthesis and reactivity is given in this work.
INTRODUCTION
■
Since the first report of a titanium hydrazinediido complex in
1978,1 a great variety of such compounds featuring different
types of ancillary ligands have been reported,2−13 and their
reactivity has been studied in some detail in recent years.6−15
Stoichiometric reactions with alkynes,4,5,7,8,12 allenes,14 and
heteroallenes, such as isocyanates,3,10,11,14 isothiocya-
nates,10,11,14 carbon dioxide,3,9,11 carbodiimides,16 and carbon
disulfide,11 resulted in formal [2 + 2] cycloadditions. In some
cases this initial reaction step was followed by Ti−X
insertion,10,17 or insertion into the N−N bond of the
hydrazinediido unit, depending on the ancillary ligand.
Complexes of this type have been employed as catalysts in
the hydrohydrazination of alkynes7,12,18 and carbodiimides16
and related three-component coupling reactions.19
RESULTS AND DISCUSSION
■
Preparation and Structural Characterization of
[Cp*M(NxylN)(NNPh2)(dmap)] (M = Zr, 3a; M = Hf, 3b).
The dichlorido complexes [Cp*M(NxylN)Cl2] (M = Zr, 1a; M
= Hf, 1b) were prepared from Cp*MCl3 by a modified
procedure based on work by Sita and co-workers.34 Cp*MCl3
was reacted with MeLi in order to generate a monomethyl
complex in situ, which was then reacted with the protio ligand
HNxylN, giving 1a,b in 89% and 93% yields, respectively
(Scheme 1).
Addition of LiNHNPh2 then resulted in the formation of the
monohydrazido(1−) complexes [Cp*M(NxylN)(NHNPh2)Cl]
(2a,b). As compound 2a was thermally unstable, it was directly
reacted in situ with LiHMDS in the presence of dmap.21,22,35
The corresponding hydrazinediido complex [Cp*Zr(NxylN)-
(NNPh2)dmap] (3a) was obtained in 84% yield as a yellow-
However, zirconium20−25 and hafnium21 hydrazinediido
complexes remain relatively scarce, despite the interesting and
diverse reactive behavior found for some of them.26−31 For
stoichiometric reactions with disubstituted alkynes, formation
of seven-membered zirconacycles via N−N-bond scission was
observed,20 which provided the basis for a new catalytic indole
synthesis.23,24,32 This illustrates why further investigation into
the chemistry of the heavier group 4 metals is desirable. To this
end and in order to investigate the dependence of
stoichiometric reactivity on both the ancillary ligand and
metal, we have prepared new half-sandwich zirconium and
1
ocher powder. H, 13C, and 15N NMR spectra indicated a
mixture of two isomers in a ratio of 2:1; in particular, the 15N
NMR spectrum displayed two signals in the characteristic
Received: January 24, 2014
Published: March 18, 2014
© 2014 American Chemical Society
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Scheme 1. Synthesis of the Hydrazinediido Complexes 3a,b
region for ZrNNR2 (286 and 281 ppm). The 1H NOESY NMR
spectrum revealed cross relaxation between o-dmap and o-xylyl
protons for the minor isomer but not for the major isomer. The
isomers could thus be assigned to the diastereomers shown in
Figure 1.
and LiHMDS also resulted in the formation of 3b, no reaction
was observed upon heating 6 in the presence of dmap without
LiHMDS. Compound 6 could also be isolated by employing a
different route via the bis(dimethylamido) complex 5, which
was obtained by reacting 1b with 2 equiv of LiNMe2 and was
then treated with 2 equiv of diphenylhydrazine.
Single crystals suitable for X-ray diffraction were obtained for
hydrazinediides 3a,b. Their crystal and molecular structures are
very similar (Table 1). There are two independent molecules in
the asymmetric unit which both correspond to the main
diastereomer (Figure 1), with only a minor difference in the
orientation of one of the phenyl groups (Figure 2).
Both M(1)−N(3) and N(3)−N(4) bond lengths (mean
values for 3a, Zr(1)−N(3) 1.875 Å and N(3)−N(4) 1.379 Å,
mean values for 3b, Hf(1)−N(3) 1.856 Å and N(3)−N(4)
1.389 Å, respectively) are in good agreement with those of
previously reported zirconium hydrazinediido complexes, as is
the slight deviation from linearity for the M(1)−N(3)−N(4)
units (mean values Zr(1)−N(3)−N(4) 171.7° and Hf(1)−
N(3)−N(4) 171.3°, respectively).21−25,32 In both cases, the 2-
(N-xylylamino)pyrrolinato ligand is bound in a κ2 mode
similarly to the analogous titanium complex, while the Zr(1)−
N(1)/N(2) distances (mean values 2.306 and 2.293 Å) as well
as the Hf(1)−N(1)/N(2) distances (2.272 and 2.270 Å) are
as expectedlonger than those for comparable titanium
complexes (mean values 2.273 and 2.265 Å).7
Figure 1. Diastereomers of 3a (M = Zr) and 3b (M = Hf).
However, this procedure was not successful for the
preparative conversion of the Hf complex 2b to the
corresponding hydrazinediide. When 2b was reacted with
LiHMDS without addition of dmap, a mixture of the hafnium
{LiHMDS} hydrazinediido complex 4 and hafnium bis-
(hydrazido) complex 6 was obtained. The mixture of 4 and 6
was then heated to 60 °C for 3 h in the presence of dmap,
which yielded the hafnium hydrazinediido complex 3b as a
mixture of the two diastereomers depicted in Figure 1 in a ratio
of 3:1. While thermal treatment of 6 in the presence of dmap
Preparation and Structural Characterization of
[Cp*Hf(NxylN)(NNPh2){N(SiMe3)2}Li] (4). As mentioned
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a
Table 1. Selected Bond Lengths (Å) and Angles (deg) for 3a (M = Zr) and 3b (M = Hf)
Zr
Hf
Zr
Hf
M(1)−N(1)
M(1)−N(2)
M(1)−N(3)
N(3)−N(4)
2.3019(9) [2.3092(9)]
2.3012(10) [2.2856(10)]
1.8745(9) [1.8746(10)]
1.380(1) [1.378(1)]
2.272(3) [2.273(3)]
2.270(3) [2.260(3)]
1.860(3) [1.852(3)]
1.385(4) [1.393(4)]
M(1)−N(5)
N(1)−C(4)
N(2)−C(4)
2.3361(9) [2.3364(9)]
1.327(2) [1.330(2)]
1.323(2) [1.322(1)]
2.303(3) [2.306(3)]
1.327(5) [1.322(5)]
1.318(4) [1.320(4)]
M(1)−N(3)−N(4)
N(1)−M(1)−N(2)
171.67(8) [171.75(8)]
58.06(4) [58.50(3)]
171.0(2) [171.6(2)]
58.6(1) [58.9(1)]
N(1)−C(4)−N(2)
114.9(1) [115.7(1)]
114.3(3) [114.9(3)]
a
Values in brackets refer to the second molecule.
The 15N NMR spectrum displays a resonance at 263 ppm,
which could be assigned unambiguously to the metal-bonded
Nα atom by 15N labeling, and a second resonance assigned to
the hydrazinediido unit at 147 ppm for Nβ. The chemical shift
values for 15N hydrazide resonances lie between the respective
shifts for hafnium hydrazinediido complex 3b (280 and 172
ppm) and those observed for the hydrazides(1−) 2b (211 and
91 ppm) and 6 (206 and 119 ppm). This may indicate that the
electronic structure is intermediate between that of a
hydrazinediido(2−) and hydrazido(1−) complex. For the Nα
signal of 4 significant line broadening was observed in
comparison to that of 6 under the same conditions (Δν1/2
=
14.7 Hz for 4 vs 1.5 Hz for 6), indicating a Li−N bonding
interaction and thus unresolved coupling of 15N to 7Li (I = 3/2)
and 6Li (I = 1). For 15Nα-labeled 4, splitting of the Li signal was
7
6
observed in both the Li and Li NMR spectra (Figure 3).
1
The coupling constants were determined to be J(15N,7Li) =
Figure 2. Molecular structure of 3a. Only one of the two independent
molecules is shown. Hydrogen atoms are omitted for clarity, and
ellipsoids are drawn at the 50% probability level. For selected bond
lengths (Å) and angles (deg) for 3a,b, see Table 1.
1
5.1(2) Hz and J(15N,6Li) = 2.0(1) Hz. We note that the
1J(15N,7Li) value is somewhat smaller than coupling constants
previously reported for lithium amido compounds (8.1−13.1
Hz).36 The J(15N,6Li) coupling constant lies in the typical
1
range for lithium amide compounds (1.6−6.6 Hz).37 In order
to determine whether 4 existed in solution as a monomeric or
an oligomeric species, a 1H DOSY NMR experiment was
carried out for a mixture of 4 and 6. The ratio D(4)/D(6) = 1.1
above, reaction of 2b with 1 equiv of LiHMDS afforded a
mixture of bis(hydrazido) complex 6 and [Cp*Hf(NxylN)-
(NNPh2){N(SiMe3)2}Li] (4). Compound 4 could also be
obtained selectively by reacting 2b with 2 equiv of LiHMDS.
Figure 3. (left) 7Li NMR spectrum for non-isotope-labeled (bottom) and 15N-labeled 4 at room temperature (middle) and 50 °C (top). (right) 6Li
NMR spectrum for 15N-labeled 4 at room temperature.
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for the diffusion constants was found, which is consistent with 4
being a monomeric species.
findings are consistent with the bonding situation in a
hydrazinediido complex coordinated by Li, rather than an Nα-
lithiated hydrazide(1−). This corrobates the interpretation of
the 15N NMR data as well as the structural data from the X-ray
diffraction study referred to above.
Cycloadditions to the ZrN Bond and Related in the
Hydrazinediido Complex 3a. We recently showed that
reaction of carbodiimides with the analogous titanium
hydrazinediido complex leads to four-membered titanacycles.16
However, upon reaction of 3a with iPrNCNiPr we observed the
formation of a mixture of two different reaction products, the
six-membered zirconacycle 8 and a rearranged four-membered
zirconacycle 7 (Scheme 2).
Single crystals of complex 4 suitable for X-ray diffraction
were obtained from a concentrated hexane solution at −40 °C.
In the molecular structure the Li atom is bound to the NCNxyl,
Nα, and Nβ atoms, while the aminopyrrolinato ligand is
coordinated in a κ1 mode to Hf via the NCNxyl atom (Figure
4). The Hf−Nα distance (1.878 Å) lies between those found for
Single crystals suitable for X-ray diffraction of compound 7
were obtained from a concentrated diethyl ether/hexane
solution. The structure features a symmetric N-amino-
guanidinato ligand coordinated in a κ2 mode to zirconium
(Figure 6). The three bonds to C(13) (C(13)−N(3) 1.413 Å,
C(13)−N(4) 1.354 Å, C(13)−N(5) 1.325 Å) within the planar
(RMSD of CN3 0.0007 Å) aminoguanidinate lie between
typical distances for single and double bonds. We note that the
C(13)−N(5) distance (1.325 Å) is the shortest of the three C−
N bonds, which is consistent with an exocyclic double bond.
Both Zr−N bonds within the metallacycle (Zr−N(3) 2.124 Å,
Zr−N(4) 2.248 Å) have lengths consistent with (amido type)
single bonds and are indicative of slightly asymmetric bonding
of the aminoguanidinate to Zr. The aminopyrrolinato ligand is
also coordinated in a κ2 mode; both Zr−N bond lengths (Zr−
N(1) 2.313 Å, Zr−N(2) 2.290 Å) are slightly longer then those
for the aminoguanidinato ligand, which can be attributed to the
formally dianionic nature of the latter.
Figure 4. Molecular structure of 4. Hydrogen atoms are omitted for
clarity, and ellipsoids are drawn at the 50% probability level. Minor
conformational disorder in the C5N ring is not shown. Selected bond
lengths (Å) and angles (deg): Hf−N(1) 2.204(1), Hf−N(3) 1.878(1),
N(3)−N(4) 1.412(1), N(2)−Li 1.928(2), N(3)−Li 1.947(2), N(4)−
Li 2.082(3), Hf−N(5) 2.149(1); Hf−N(3)−N(4) 172.30(8), N(1)−
Hf−N(3) 96.18(4), N(1)−C(4)−N(2) 124.6(1).
Upon addition of 2 equiv of diisopropylcarbodiimide, the six-
membered zirconacycle 8 was obtained selectively. The NMR
spectra are consistent with the structure shown in Scheme 2.
1
The H NMR spectrum featured eight doublets and three
the hydrazinediido compound 3b and zirconium hydrazi-
do(1−) complexes (2.080−2.123 Å).21,35 This structural
feature is similar to that for the lithium zirconimidate
complexes reported by Bergman and co-workers which were
obtained by the reaction of imido complexes with methyl-
lithium or of [Cp*2ZrClMe] with LiNHR.38
A comparison of the Mulliken charge distributions calculated
for compounds 3b and 4 by DFT (B3PW91),39,40 using a
pseudopotential for Hf (SDD)41−45 and a 6-31G(d) basis set
for all other atoms,46 shows a significantly higher negative
charge at both the Nα atom (−0.561 and −0.649 au,
respectively) and the Nβ atom (−0.444 and −0.560 au,
respectively) of the hydrazinediido unit for complex 4 (Figure
5). This indicates partial negative charges at these two atoms
rather than a localized negative charge at the Nα atom. These
septets (one consisting of two overlapping signals) correspond-
1
ing to four diastereotopic isopropyl groups. In the H−13C
HMBC NMR spectrum, two signals in the 13C NMR spectrum
with shifts characteristic14,16 for imino group carbon atoms
(147.7 and 145.5 ppm) featured long-range coupling to the
CHMe2 protons of two isopropyl groups. The 15N NMR
spectrum displays eight resonances, which were assigned using
1H−15N HMBC NMR spectroscopy (Figure 7).
In addition, the molecular structures for both possible
isomers featuring different orientations of the 2-amino-
pyrrolinato ligand, similar to the isomers found for 3a (see
Figure 1), were computationally modeled using DFT methods
(B3PW91, SDD+f for Zr and 6-31G(d) for all other atoms; see
Figure 8).39−45 The isomer with increased steric interaction
between the xylyl group of the aminopyrrolinate and the NPh2
group was found to be higher in energy by 41.2 kJ/mol. We
then calculated the 13C and 15N NMR shifts for both isomers
by the GIAO method,47−49 using a pseudopotential for Zr
(SDD+f) and a 6311++G(2d,2p) basis set for all other atoms.
The chemical shifts found for the isomer lower in energy gave
good agreement with the experimental data (see Figure 9).
The groups of Odom and Mountford previously postulated a
sequence of [2 + 2] cycloaddition of an alkyne and Ti−N
insertion of a isonitrile or nitrile, respectively, for the formation
of six-membered titanacycles10,17 in analogy to a similar
reaction of a titanium imido complex,50 and an analogous
pathway was proposed for the reaction with carbon dioxide11
and the reaction of a tert-butoxyimido complex with 2 equiv of
Figure 5. Comparison of the calculated Mulliken charge distributions
for compounds 3b and 4.
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Scheme 2. Stoichiometric Reactions of 3a To Give 7, 8a,b, 9, and 10
reacts with another 1 equiv of carbodiimide to give 8 or
rearranges to 7.
Another indication for the presence of the cycloaddition
product is that the corresponding aminoguanidine was isolated
in 99% yield when 3a was employed as catalyst (5 mol %) in
the hydrohydrazination of diisopropylcarbodiimide with
diphenylhydrazine. The analogous titanium cycloaddition
product was previously found to be an intermediate in the
corresponding catalytic cycle (Scheme 4).16
While the reaction of zirconium imido complexes with
imines has been studied in some detail by the groups of
Bergman52 and Mountford,53 to the best of our knowledge, this
reaction has not been reported for group 4 hydrazinediido
complexes to date. When 3a was reacted with N-phenyl-
benzimine, the four-membered metallacycle 9 was formed by [2
+ 2] cycloaddition (see Scheme 2). The NMR spectra are
consistent with the structure shown in Scheme 2. Moreover, in
1
the H NMR spectrum a singlet signal for the CHPh proton is
1
observed. In the H−15N HMBC NMR spectrum, coupling to
the NNPh2 (335 ppm) and the NPh atom (149 ppm, additional
coupling to ortho−NPh protons) was detected.
Figure 6. Molecular structure of 7. Hydrogen atoms are omitted for
clarity, and ellipsoids are drawn at the 50% probability level. Selected
bond lengths (Å) and angles (deg): Zr−N(1) 2.3134(9), Zr−N(2)
2.2904(9), Zr−N(3) 2.1243(9), Zr−N(4) 2.2482(9), N(3)−C(13)
1.413(1), N(4)−C(13) 1.354(1), C(13)−N(5) 1.325(1), N(5)−N(6)
1.428(1), Zr−N(7) 2.3244(9); N(1)−Zr−N(2) 58.11(3), N(3)−Zr−
N(4) 61.06(3), N(3)−C(13)−N(4) 107.00(9), C(13)−N(5)−N(6)
117.67(9).
Previously reported zirconium hydrazinediido complexes
reacted with alkynes under N−N bond scission to yield
seven-membered zirconacycles.20,23,32 Complex 3a exhibited
the same behavior and reacted with diphenylacetylene to give
the metallacyclic species 10. The NMR spectra are consistent
with the structure shown in Scheme 2. The NH and NPh 15N
NMR signals at 200 and 214 ppm, respectively, could be
assigned via 1H−15N HMBC NMR and are in good agreement
with shifts for similar complexes.23,32 Of the two possible
isomers for 10, only the isomer shown in Scheme 2 is formed.
The structural assignment is based on the observed cross
relaxation between the CH2N protons and the phenylene-5
TolNCO.51 In order to determine whether a similar mechanism
leads to the formation of 7 and 8, we monitored the reaction of
1
3a with 0.5 equiv of diisopropylcarbodiimide by H NMR
1
proton in the H NOESY NMR spectrum.
spectroscopy (Scheme 3).
We observed initial formation of an intermediate product,
Structural Characterization of Cycloadducts of [Zr-
TBS
i
(N2 Npy)(NNPh2)py] (11) with PrNCNiPr and PhCH
NPh. Since we were not successful in obtaining single crystals
of 8 and 9 that were suitable for an X-ray diffraction study, we
chose to investigate the corresponding transformations with the
zirconium complex 11, which had been previously studied in
our group (Scheme 5).21−23,26−28,30−32
which was then rapidly converted to 8. Although it could not be
1
fully characterized due to its highly reactive nature, the H
NMR signals detected for this intermediate were found to be
consistent with a four-membered zirconacycle formed by [2 +
2] cycloaddition of the carbodiimide to 3a. This suggests initial
formation of a [2 + 2] cycloaddition product, which then either
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Figure 7. 15N NMR spectrum for 8 along with the assignment of the resonances.
Figure 8. DFT-optimized structures of the two possible isomers of 8 and calculated and experimental 13C shifts for both imino group carbon atoms.
Figure 9. Correlation of calculated and experimental 13C and 15N NMR shifts for 8.
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Scheme 3. Possible Formation of 7 and 8 from 3a via a [2 + 2] Cycloaddition Product
i
Even in the presence of a large excess of PrNCNiPr
compound 11 only formed the four-membered zirconacyclic
species 12, as inferred from the NMR spectra of the isolated
Scheme 4. Mechanism for the Ti-Catalyzed
Hydrohydrazination of Carbodiimides via [2 + 2]
Cycloaddition16
1
product: in the H NMR spectrum, two doublets and two
septets at 1.78 and 1.19 ppm corresponding to two isopropyl
groups (ZrNCHMe2 and CNCHMe2) were detected,
1
indicating Cs symmetry. On the basis of a H 13C HMBC
experiment, a signal at 153.7 ppm in the characteristic 13C
NMR chemical shift region for imino group carbon atoms and
comparable to a similar titanium complex16 could be assigned
to CNCHMe2. Twinned single crystals of 12 were obtained
from a concentrated solution in toluene, and an X-ray
diffraction study revealed two independent molecules in the
asymmetric unit which only show differences in the rotational
orientation of the phenyl and silyl groups (the latter being
partially disordered). One of the conformers is depicted in
Figure 10. While the exocyclic CN bond length is consistent
with a double bond (C(72)−N(57) 1.275 Å), both endocyclic
Scheme 5. Stoichiometric Reactions of 11 To Give 12 and 13
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Figure 10. Molecular structure of 12. Only one of the two
independent molecules is shown. Hydrogen atoms are omitted for
clarity, and ellipsoids are drawn at the 50% probability level. Selected
bond lengths (Å) (values in brackets refer to the second molecule):
Zr(51)−N(51) 2.042(3) [2.047(3)], Zr(51)−N(52) 2.050(3)
[2.050(3)], Zr(51)−N(53) 2.327(3) [2.314(3)], Zr(51)−N(54)
2.181(3) [2.188(3)], Zr(51)−N(56) 2.092(3) [2.096(4)], N(54)−
N(55) 1.405(4) [1.407(4)], N(54)−C(72) 1.421(5) [1.409(5)],
N(56)−C(72) 1.399 [1.406(5)], C(72)−N(57) 1.275(5) [1.279(6)].
Figure 11. Molecular structure of 13. All hydrogen atoms but H(22)
are omitted for clarity, and ellipsoids are drawn at the 50% probability
level. Selected bond lengths (Å) and angles (deg): Zr−N(1) 2.062(2),
Zr−N(2) 2.051(2), Zr−N(3) 2.329(2), Zr−N(4) 2.108(2), Zr−N(5)
2.146(2), N(4)−C(22) 1.460(2), N(5)−C(22) 1.495(2), N(5)−N(6)
1.412(2); N(4)−Zr−N(5) 63.76(6), N(4)−C(22)−N(5) 99.0(1).
EXPERIMENTAL SECTION
■
All manipulations of air- and moisture-sensitive species were carried
out under an atmosphere of argon (Argon 5.0) using standard Schlenk
and glovebox techniques (glovebox: M. Braun Unilab 2000). Solvents
were predried over molecular sieves and dried over Na/K alloy
(pentane, diethyl ether), K (THF, hexane, toluene), or CaH2
(dichloromethane), distilled, or dried over activated alumina columns
using a solvent purification system (M. Braun SPS 800) and stored
over potassium mirrors (except for dichloromethane) or sodium
mirror (THF) in Teflon valve ampules. The deuterated solvent
benzene-d6 was purchased from Deutero GmbH, dried over K,
vacuum-distilled, and stored under argon in Teflon valve ampules.
Ph2NNH2 was prepared from the hydrochloride salt purchased from
Acros and purified by column chromatography (over silica, dichloro-
methane) prior to use. LiNHNPh2 was prepared according to a
modified literature procedure,54 using toluene instead of benzene, and
the precipitated product was purified by filtration. Li15NHNPh2 was
prepared the same way from Ph2N15NH2, which was prepared
according to literature procedures for the unlabeled compound.55 The
2-iminopyrrole HNxylN was also prepared according to the literature,33
CN bonds feature interatomic distances typical for single bonds
(1.421 and 1.399 Å). These parameters are very similar to those
of the corresponding titanium N-aminoguanidinato complex,16
and all other parameters are in good agreement with those of
other previously reported cycloaddition products of 11.27,30
Upon reaction of 11 with N-phenylbenzimine, formation of
the zirconacycle 13 was observed (Scheme 5). The NMR
spectra are consistent with the structure shown in Scheme 5.
Again, a singlet corresponding to the CHPh proton was
observed in the 1H NMR spectrum. The signals for the NNPh2
and NPh atoms were detected at 335 and 183 ppm, which are
similar to the corresponding shifts found for the half-sandwich
complex 9 (335 and 149 ppm). Single crystals of 13 were
obtained from a concentrated toluene solution, and the
molecular structure determined by X-ray diffraction confirms
the structural assignment based on NMR spectroscopic
methods (Figure 11). Both the N(Ph)−CHPh and the
N(NPh2)−CHPh bond lengths (1.460 and 1.495 Å) are typical
for CN single bonds, and the other bond lengths and angles are
in good agreement with those found in related cycloaddition
products reported previously.27,30
21
TBS
as was Zr(N2 Npy)(NNPh2)py (11). All other chemicals were
purchased from commercial sources (Acros/Thermo Fisher, ABCR/
Strem, and Sigma-Aldrich). Diisopropylcarbodiimide was degassed and
stored in a glovebox. Samples for NMR spectroscopy of moisture-
sensitive compounds were prepared under argon in 5 mm Wilmad
tubes equipped with J. Young Teflon valves. NMR spectra were
recorded with Bruker Avance II 400 and Bruker Avance III 600 (with
QNP-CryoProbe) NMR spectrometers. NMR spectra are quoted in
ppm and were referenced internally relative to the residual protio
solvent (1H) or solvent (13C) resonances or externally to 15NH3 (15N),
7LiCl (aqueous 7Li), and 29SiMe4 (29Si). Where necessary, NMR
CONCLUSIONS
■
1
assignments were confirmed by the use of two-dimensional H−1H
In this work we reported the synthesis and reactivity of the first
zirconium and hafnium half-sandwich hydrazinediido com-
plexes. In addition, we were able to isolate a LiHMDS adduct of
an anionic hafnium hydrazinediido complex, which can be
regarded as an intermediate structure between deprotonated
hydrazido and Li-coordinated hydrazinediido complexes. The
reactivity of the hydrazinediido complexes with unsaturated
substrates displayed similarities but also interesting differences
in comparison to the case for analogous titanium and zirconium
complexes, illustrating the importance of the choice of ancillary
ligand.
1
and H−13C correlation experiments. 13C spectra were recorded with
1H broad-band decoupling; the multiplicity of the resonances was
determined using DEPT-135 experiments. 15N data were obtained by
two-dimensional 1H correlated experiments or by direct detection
using a cryogenically cooled direct-detection NMR probe (QNP
CryoProbe). Microanalyses were performed by the microanalytical
service of the chemistry department of the Universitat Heidelberg on a
̈
Vario MIKRO Cube (Elementar) or a Vario EL (Elementar) CHN
analyzer. Mass spectra were recorded by the Institute of Organic
Chemistry of the Universitat Heidelberg on a JMS 700 magnetic sector
̈
(JEOL) spectrometer in FAB (NBA or NPOE as matrix) and EI (70
1733
dx.doi.org/10.1021/om500087s | Organometallics 2014, 33, 1726−1739

Organometallics
Article
eV) modes. IR spectra were recorded on a Varian 3100 Exalibur FT-IR
spectrometer as KBr plates. Infrared data are quoted in wavenumbers
(cm−1).
m, 1 H, NCH2-b), 2.25 (s, 6 H, C6H3Me2), 2.01 (s, 15 H, C5Me5),
1.34−1.26 (broad m, 1 H, CH2CH2CNN-a), 1.07−0.99 (broad m, 1
H, CH2CH2CNN-b); CH2CNN not observed ppm. 13C NMR
(benzene-d6, 150.9 MHz, 295 K): δ 178.9 (s, NCN), 153.1 (s, ipso-
ZrNHN(C6H5)2), 137.6 (s, m-C6H3Me2), 128.5 (d, m-ZrNHN-
(C6H5)2), 124.8 (d, p-ZrNHN(C6H5)2), 123.0 (d, p-C6H3Me2),
121.9 (d, o-ZrNHN(C6H5)2), 120.4 (s, C5Me5), 51.8 (t, NCH2),
30.3 (t, CH2CNN), 23.2 (t, CH2CH2CNN), 21.7 (q, C6H3Me2), 11.9
(q, C5Me5) ppm. 15N NMR (benzene-d6, 60.81 MHz, 295 K): δ 216
[Cp*Zr(NxylN)Cl2] (1a). A 1.000 g portion of Cp*ZrCl3 (3.005
mmol) was suspended in 20 mL of toluene in an oven-dried Schlenk
flask, and the solution was cooled to −40 °C. A 1.88 mL portion of
methyllithium (1.6 mol/L in diethyl ether, 3.005 mmol) was slowly
added dropwise. The solution was warmed to −30 °C over 2 h and
then cooled to −40 °C again. A 0.566 g portion of HNxylN (3.005
mmol) was dissolved in 30 mL of toluene under sonification and the
solution slowly added dropwise at −40 °C. The reaction mixture was
warmed to room temperature under static vacuum and stirred for 3 h
and then centrifuged and filtered. The supernatant was evaporated
under reduced pressure to yield 1.302 g (2.687 mmol, 89%) of a
1
(d, JN−H = 74 Hz, ZrNHNPh2), 94 (ZrNNPh2) ppm; NCNxyl,
NCNxyl not observed. IR (KBr, cm−1): ν 3297 (w, NH), 2963 (m),
2908 (m), 2858 (m), 1590 (s), 1522 (m), 1491 (s), 1291 (m), 1262
(s), 1181 (m), 1098 (s), 1026 (s), 804 (s), 750 (s), 693 (s), 612 (m).
Due to the compound’s instability, no elemental analysis could be
performed.
1
brown solid. H NMR (benzene-d6, 600.1 MHz, 295 K): δ 6.99 (s, 2
3
[Cp*Hf(NxylN)(NHNPh2)Cl] (2b). A 500 mg portion (0.874 mmol)
of Cp*Hf(NxylN)Cl2 was dissolved in 15 mL of toluene and cooled to
−78 °C. A 166 mg portion (0.874 mmol) of LiNHNPh2 was dissolved
in 10 mL of toluene and slowly added dropwise to the reaction
solution at this temperature. The reaction mixture was stirred at room
temperature for 40 h and then centrifuged (10 min at 2000 rpm) and
filtered. The solvent was removed from the supernatant under reduced
pressure to yield 510 mg (0.709 mmol, 81%) of a light brown solid.
For labeling experiments, a batch of this compound which had been
15N-labeled in the Nα position was synthesized the same way using
Li15NHNPh2. 1H NMR (benzene-d6, 600.1 MHz, 295 K): δ 7.19 (d, 4
H, p-C6H3Me2), 6.62 (s, 1 H, o-C6H3Me2), 3.39 (t, 2 H, JH−H = 6.9
Hz, NCH2), 2.21 (s, 6 H, C6H3Me2), 2.01 (s, 15 H, C5Me5), 1.89 (t, 2
3
3
H, JH−H = 7.9 Hz, CH2CNN) 1.21 (qin, 2 H, JH−H = 7.0 Hz,
CH2CH2CNN) ppm. 13C NMR (benzene-d6, 150.9 MHz, 295 K): δ
147.2 (s, NCN), 138.2 (s, N-C6H3Me2), 125.8 (s, m-C6H3Me2), 125.4
(d, p-C6H3Me2), 125.0 (s, C5Me5), 121.5 (d, o-C6H3Me2), 53.3 (t,
NCH2), 29.2 (t, CH2CNN), 22.9 (t, CH2CH2CNN), 21.3 (q,
C6H3Me2), 12.2 (q, C5Me5) ppm. 15N NMR (benzene-d6, 60.81
MHz, 295 K): δ 192.3 (NCNXyl), 177.0 (NCNXyl) ppm. IR (KBr,
cm−1): ν 2963 (w), 2909 (w), 1670 (s), 1597 (s), 1507 (m), 1466
(m), 1378 (m), 1262 (s), 1099 (s), 1023 (s), 801 (s). HR-MS (HR-EI
+): calcd 482.0833 u, 484.0804 u (C22H30Cl2N2Zr), found: 482.0813 u
(Δ = −2.0 mmu), 484.0807 u (Δ = +0.3 mmu). Anal. Calcd: C, 54.52;
H, 6.24; N, 5.78. Found: C, 54.82; H, 6.22; N, 5.36.
3
3
H, JH−H = 8.3 Hz, o-HfNHN(C6H5)2), 7.00 (t, 4 H, JH−H = 8.3 Hz,
3
m-HfNHN(C6H5)2), 6.96 (s, 2 H, o-C6H3Me2), 6.81 (t, 2 H, JH−H
=
7.4 Hz, p-HfNHN(C6H5)2), 6.62 (s, 1 H, p-C6H3Me2), 6.38 (s, 1 H,
HfNHN(C6H5)2), 3.07 (broad m, 1 H, CH2N-a), [CH2CNN-a and b
overlaid, but observed in HSQC: 2.25, 2.15 ppm], 2.24 (s, 6 H,
C6H3Me2), 2.05 (s, 15 H, C5Me5), 1.29 (broad s, 1 H, CH2CH2CNN-
a), 1.04 (broad s, 1 H, CH2CH2CNN-a) ppm. 13C NMR (benzene-d6,
150.9 MHz, 295 K): δ 178.6 (s, NCN), 153.3 (s, ipso-HfNHN-
(C6H5)2), 137.6 (s, m-C6H3Me2), 129.2 (d, m-HfNHN(C6H5)2), 124.6
(d, p-C6H3Me2), 123.0 (d, p-HfNHN(C6H5)2), 121.9 (d, o-C6H3Me2),
119.8 (d, o-HfNHN(C6H5)2), 118.7 (s, C5Me5), 51.7 (t, CH2N), 30.5
(t, CH2CNN), 23.5 (t, CH2CH2CNN), 21.7 (q, C6H3Me2), 11.7 (q,
C5Me5) ppm. 15N NMR (benzene-d6, 60.81 MHz, 295 K): δ 211 (d,
1JN−H = 74 Hz, HfNHNPh2), 183 (NCNxyl), 168 (NCNxyl), 91
(HfNHNPh2) ppm. IR (KBr): ν 3328 (w, NH), 2962 (m), 2908 (m),
1589 (s), 1522 (s), 1490 (s), 1291 (m), 1184 (m), 1101 (m), 1026
(m), 749 (m), 693 (m), 612 (w) cm−1. Anal. Calcd: C, 56.74; H, 5.74;
N, 7.79. Found: C, 56.27; H, 5.71; N, 7.45.
[Cp*Hf(NxylN)Cl2] (1b). A 500 mg portion (1.190 mmol) of
Cp*HfCl3 was suspended in 10 mL of toluene. A 0.74 mL portion of
MeLi (1.6 mol/L in diethyl ether, 1.190 mmol) was slowly added at
−45 °C. The purple reaction mixture was warmed to −30 °C over 2 h,
turning colorless. A 224 mg portion (1.190 mmol) of HNxylN was then
dissolved in toluene and slowly added at −40 °C. A slight static
vacuum was applied, and the reaction mixture was warmed to room
temperature, stirred for 2 h, centrifuged (13 min at 2000 rpm), and
filtered. The solvent was removed under reduced pressure to yield 611
1
mg (1.068 mmol, 90%) of a light brown solid. H NMR (benzene-d6,
600.1 MHz, 295 K): δ 6.99 (s, 2 H, o-C6H3Me2), 6.62 (s, 1 H, p-
3
C6H3Me2), 3.34 (t, 2 H, JH−H = 7.0 Hz, CH2N), 2.21 (s, 6 H,
3
C6H3Me2), 2.07 (s, 15 H, C5Me5), 1.89 (t, 2 H, JH−H = 7.8 Hz,
CH2CNN), 1.19 (qin, 2 H, 3JH−H = 7.4 Hz, CH2CH2CNN) ppm. 13
C
NMR (benzene-d6, 150.9 MHz, 295 K): δ 177.5 (s, NCN), 147.1 (s,
ipso-C6H3Me2), 138.4 (s, m-C6H3Me2), 125.7 (d, o-C6H3Me2), 123.5
(s, C5Me5), 121.8 (d, p-C6H3Me2), 52.9 (t, CH2N), 29.6 (t,
CH2CNN), 23.5 (t, CH2CH2CNN), 21.6 (q, C6H3Me2), 12.1 (q,
C5Me5) ppm. 15N NMR (benzene-d6, 60.81 MHz, 295 K): δ 190
(NCNxyl), 174 (NCNxyl) ppm. IR (KBr): ν 2913 (m), 2864 (m),
1653 (s), 1595 (m), 1507 (s), 1465 (m), 1379 (m), 1294 (m), 1190
(m), 1107 (m), 1026 (m), 850 (m), 803 (m), 731 (w), 682 (w) cm−1.
Mass spectrometry (HR-EI+): calcd 572.1234 u, 570.1222 u, 571.1227
(C22H30Cl2N2Hf); found 572.1215 u (Δ = 2.1 mmu), 570.1218 u (Δ
= −0.5 mmu), 571.1191 u (Δ = 0.3 mmu). Anal. Calcd: C, 46.20; H,
5.29; N, 4.90. Found: C, 45.98; H, 5.17; N, 4.40.
[Cp*Zr(NxylN)(NNPh2)DMAP] (3a). A 300 mg portion (0.619
mmol) of Cp*Zr(NXylN)Cl2 (6 ) was dissolved in 20 mL of THF and
cooled to −78 °C. A 118 mg portion (0.619 mmol) of LiNHNPh2 was
dissolved in 10 mL of THF and slowly added dropwise at this
temperature. The reaction mixture was warmed to room temperature
and stirred for 27 h. Then 84 mg (0.619 mmol) of DMAP was added,
and 104 mg (0.619 mmol) LiHMDS was dissolved in THF and slowly
added dropwise at −78 °C. The reaction mixture was slowly warmed
to room temperature and stirred for 23 h, the solvent was subsequently
evaporated under reduced pressure, the residue was taken up in
toluene, and this solution was filtered. Toluene was evaporated under
reduced pressure, and the resulting foam was washed with pentane,
yielding 620 mg (0.863 mmol, 84%) of a bronze-colored solid
(major:minor 2:1). Crystals of the major isomer suitable for X-ray
diffraction could be obtained from a concentrated solution in hexane at
[Cp*Zr(NxylN)(NHNPh2)Cl] (2a). A 500 mg portion (1.032 mmol)
of Cp*Zr(NXylN)Cl2 (6) was dissolved in 10 mL of THF in an oven-
dried Schlenk-flask and cooled to −78 °C. A 196 mg portion of
LiNHNPh2 (1.032 mmol) was dissolved in 20 mL of THF and slowly
added dropwise at this temperature. The reaction mixture was then
warmed to room temperature and stirred for 24 h. The solvent was
evaporated under reduced pressure, the residue was redissolved in 40
mL of toluene, and this solution was centrifuged and filtered. Toluene
was evaporated under reduced pressure, and the residue was washed
with pentane to yield 457 mg (0.723 mmol, 70%) of a violet-brown
solid. 1H NMR (benzene-d6, 600.1 MHz, 295 K): δ 7.19 (d, 4 H, 3JH−H
1
room temperature. Data for the major component are as follows. H
3
NMR (benzene-d6, 600.1 MHz, 295 K): δ 8.57 (d, 2 H, JH−H = 6.6
3
Hz, o-NMe2C5H4N), 7.69 (d, 4 H, JH−H = 8.4 Hz, o-ZrNN(C6H5)2),
7.20 (t, 6 H, 3JH−H = 7.1 Hz, m-ZrNN(C6H5)2 and o- and p-C6H3Me2),
3
6.81 (t, 2 H, JH−H = 7.2 Hz, p-ZrNN(C6H5)2), 6.62 (s, 1 H, p-
C6H3Me2), 5.78 (d, 2 H, 3JH−H = 6.6 Hz, m-NMe2C5H4N), 3.63 (dt, 1
2
3
H, JH−H = 11.1 Hz, JH−H = 6.9 Hz, NCH2-a), 3.22 (m, 1 H, NCH2-
b), 2.61 (m, 1 H, CH2CNN-a), 2.26 (s, 6 H, C6H3Me2), 2.07 (s, 15 H,
C5Me5), 2.02 (s, 6 H, NMe2C5H4N), 1.70 (broad m, 2 H,
CH2CH2CNN-a and -b) ppm. 13C NMR (benzene-d6, 150.9 MHz,
295 K): δ 175.6 (s, NCN), 154.3 (s, ipso-C6H3Me2), 152.5 (d, o-
3
= 7.9 Hz, o-ZrNHN(C6H5)2), 6.98 (t, 4 H, JH−H = 7.5 Hz, m-
ZrNHN(C6H5)2), 6.98 (s, 2 H, o-C6H3Me2), 6.81 (t, 2 H, 3JH−H = 7.4
Hz, p-ZrNHN(C6H5)2), 6.63 (s, 1 H, p-C6H3Me2), 6.07 (s, 1 H,
ZrNHNPh2), 3.64−3.55 (broad m, 1 H, NCH2-a), 3.15−3.06 (broad
1734
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Organometallics
Article
NMe2C5H4N), 149.1 (s, ipso-ZrNN(C6H5)2), 137.7 (s, m-C6H3Me2),
128.8 (d, m-ZrNN(C6H5)2), 123.8 (d, p-C6H3Me2), 122.8 (d, o-
C6H3Me2), 120.1 (d, p-ZrNN(C6H5)2), 119.5 (d, o-ZrNN(C6H5)2),
116.4 (s, C5Me5), 105.9 (d, m-NMe2C5H4N), 53.0 (t, NCH2), 38.2 (q,
C6H3Me2), 29.9 (t, CH2CNN), 23.9 (t, CH2CH2CNN), 21.7 (q,
C6H3Me2), 11.8 (q, C5Me5) ppm. 15N NMR (benzene-d6, 60.81 MHz,
295 K): δ 286 (ZrNNPh2), 238 (NMe2C5H4N), 177 (ZrNNPh2), 175
(NCNxyl) 173 (NCNxyl), 62 (Me2NC5H4N) ppm. Data for the minor
component are as follows. 1H NMR (benzene-d6, 600.1 MHz, 295 K): δ
13C NMR (benzene-d6, 150.9 MHz, 295 K): δ 179.1 (s, NCN), 152.7
(d, o-NMe2C5H4N), 151.3 (s, ipso-C6H3Me2), 149.8 (s, ipso-
HfNN(C6H5)2), 137.5 (s, m-C6H3Me2), 128.7 (d, m-HfNN-
(C6H5)2),124.2 (d, p-C6H3Me2), 123.3 (d, o-C6H3Me2), 115.4 (s,
C5Me5), 105.5 (d, m-NMe2C5H4N), 52.3 (t, CH2N), 38.0 (q,
NMe2C5H4N), 30.0 (t, CH2CNN), 24.0 (t, CH2CH2CNN), 21.5 (q,
C6H3Me2), 11.7 (q, C5Me5) ppm. IR (KBr): ν 3023 (w), 2908 (m),
2857 (m), 1601 (s), 1523 (s), 1489 (s), 1444 (m), 1377 (m), 1290
(m), 1262 (m), 1227 (m), 1185 (m), 1100 (m), 1065 (m), 1012 (m),
994 (m), 950 (w), 877 (w), 805 (m), 749 (m), 693 (m), 623 (w), 534
(w), 499 (w) cm−1. Anal. Calcd: C, 61.14; H, 6.26; N, 10.44. Found:
C, 60.68; H, 6.49; N, 9.82.
3
3
8.29 (d, 2 H, JH−H = 6.7 Hz, o-NMe2C5H4N), 7.70 (d, 4 H, JH−H
=
3
8.6 Hz, o-ZrNN(C6H5)2), 7.27 (t, 4 H, JH−H = 7.7 Hz, m-
3
ZrNN(C6H5)2), 6.88 (t, 2 H, JH−H = 7.2 Hz, p-ZrNN(C6H5)2),
6.57 (s, 1 H, p-C6H3Me2), 6.43 (s, 2 H, o-C6H3Me2), 5.58 (d, 2 H,
[Cp*Hf(NxylN)(NNPh2){N(SiMe3)2}Li] (4). A 169 mg portion
(0.236 mmol) of Cp*Hf(NXylN)Cl(NHNPh2) was dissolved in 10
mL of toluene, and 81 mg (0.472 mmol, 2 equiv) of LiHMDS was
added. After it was stirred overnight, the reaction mixture was filtered,
and the filtrate was evaporated to dryness under reduced pressure and
washed with hexane to yield 41 mg (0.060 mmol, 25%) of a crystalline
yellow solid. Crystals suitable for X-ray diffraction were grown from a
3JH−H = 6.5 Hz, m-NMe2C5H4N), 3.92 (m, 1 H, NCH2-a), 3.71 (dt, 1
2
3
H, JH−H = 11.3 Hz, JH−H = 7.4 Hz, NCH2-b), 2.10 (s, 6 H,
C6H3Me2), 2.09 (s, 15 H, C5Me5), 1.95 (s, 6 H, NMe2C5H4N);
CH2CNN and CH2CH2N not observed directly ppm. 13C NMR
(benzene-d6, 150.9 MHz, 295 K): δ 175.8 (s, NCN), 154.1 (s, ipso-
C6H3Me2), 152.6 (d, o-NMe2C5H4N), 149.1 (s, ipso-ZrNN(C6H5)2),
137.4 (s, m-C6H3Me2), 124.1 (d, o-C6H3Me2), 123.8 (d, p-C6H3Me2),
120.0 (d, p-ZrNN(C6H5)2), 119.7 (d, o-ZrNN(C6H5)2), 116.1 (s,
C5Me5), 105.5 (d, m-NMe2C5H4N), 55.3 (t, NCH2), 38.0 (q,
NMe2C5H4N), 29.9 (t, CH2CNN), 23.8 (t, CH2CH2CNN), 21.5 (q,
C6H3Me2), 11.8 (q, C5Me5) ppm; m-ZrNN(C6H5)2 could not be
assigned. 15N NMR (benzene-d6, 60.81 MHz, 295 K): δ 281
(ZrNNPh2), 236 (Me2NC5H4N), 171 (ZrNNPh2), 59 (Me2NC5H4N)
ppm; NCNxyl, NCNxyl not observed. IR (KBr, cm−1): ν 3054 (w),
3023 (w), 2962 (m), 2906 (m), 20855 (m), 1605 (s), 1523 (s), 1487
(s), 1378 (m), 1289 (m), 1226 (m), 1095 (m), 1010 (m), 805 (m),
748 (m), 693 (m), 624 (w), 534 (w), 500 (w). Anal. Calcd: C, 68.58;
H, 7.02; N, 11.70. Found: C, 67.99; H, 7.33; N, 10.78.
1
concentrated solution in hexane at −40 °C. H NMR (benzene-d6,
3
600.1 MHz, 295 K): δ 7.32 (d, 4 H, JH−H = 8.1 Hz, o-Ph), 7.15 (t, 4
H, 3JH−H = 7.9 Hz, m-Ph), 6.89 (t, 2 H, 3JH−H = 7.4 Hz, p-Ph), 6.56 (s,
1 H, p-C6H3Me2), 6.36 (s, 2 H, o-C6H3Me2), 3.82−3.76 (m, 2 H,
CH2N), 2.13 (CH2CNN, only observed in H,H-Cosy and HSQC), 2.11
(s, 6 H, C6H3Me2), 2.10 (s, 15 H, C5Me5), 1.66−1.57 (m, 2 H,
CH2CH2CNN), 0.25 (broad s, 18 H, N(SiMe3)2) ppm. 13C NMR
(benzene-d6, 150.9 MHz, 295 K): δ 179.5 (NCN), 153.1 (m-
C6H3Me2), 151.2 (ipso-Ph), 138.9 (ipso-C6H3Me2), 128.6 (m-Ph),
124.9 (p-C6H3Me2), 121.6 (o-C6H3Me2), 121.1 (p-Ph), 120.3 (o-Ph),
118.2 (C5Me5), 55.4 (CH2N), 30.9 (CH2CNN), 25.6
(CH2CH2CNN), 21.4 (C6H3Me2), 12.8 (C5Me5), 6.7 (SiMe3) ppm.
15N NMR (benzene-d6, 60.81 MHz, 295 K): δ 263 (NNPh2), 196
(NCNxyl), 147 (NNPh2) ppm; NCNxyl, N(SiMe3)2 not observed. 29Si
NMR (benzene-d6, 79.45 MHz, 295 K): δ −22 ppm. 7Li NMR
(benzene-d6, 155.4 MHz, 295 K): δ 1.89 ppm. A 15N-labeled version of
4 was generated in situ by dissolving 20 mg of 15N-2b in 0.5 mL of
benzene-d6 in a J. Young NMR tube and adding 9.6 mg of LiHMDS.
After 2 h, spectra were recorded on a 600 MHz (15N) or a 400 MHz
[Cp*Hf(NxylN)(NNPh2)DMAP] (3b). A 500 mg portion (0.695
mmol) of Cp*Hf(NXylN)Cl(NHNPh2) was dissolved in 40 mL of
toluene. A 120 mg portion (0.695 mmol) of LiHMDS was dissolved in
10 mL of toluene and slowly added dropwise at −78 °C. The reaction
mixture was slowly warmed to room temperature over 7 h and stirred
at room temperature overnight. An 85 mg portion (0.695 mmol) of
dmap was added, and the reaction mixture was then heated to 60 °C
for 3 h and subsequently filtered. The solvent was removed from the
filtrate under reduced pressure to yield 560 mg (0.695 mmol, 98%) of
a brown solid, composed of of two isomers (3:1). Single crystals
suitable for X-ray diffraction were obtained from a concentrated
hexane solution. Data for the major component are as follows. 1H NMR
7
(6Li, 7Li). Li NMR (benzene-d6, 155.4 MHz, 323 K): δ 1.92 (d,
6
1J7Li,15N = 5.1 Hz) ppm. Li NMR (benzene-d6, 58.8 MHz, 295 K): δ
1.91 ppm (d, 1J6Li,15N = 2.0 Hz) ppm. IR (KBr): ν 3061 (w), 2954 (m),
2901 (m9, 2861 (m), 1588 (m), 1560 (s), 1489 (s), 1449 (m), 1372
(m), 1260 (s), 1189 (w), 1164 (m), 1136 (m), 1076 (w), 1025 (w),
996 (w), 916 (s), 853 (s), 784 (m), 751 (m), 669 (m), 620 (w), 576
(w), 538 (w) cm−1. Mass spectrometry (HR-FAB): calcd 684.2718 u,
682.2690 u, 681.2685 u (C34H40N4Hf); found 684.2721 u (Δ = 0.2
mmu), 682.2685 u (Δ = −0.5 mmu), 681.2709 u (Δ = 2.2 mmu).
Anal. Calcd: C, 56.49; H, 6.87; N, 8.23. Found: C, 56.59; H, 6.95; N,
8.14.
3
(benzene-d6, 600.1 MHz, 295 K): δ 8.60 (d, 2 H, JH−H = 6.5 Hz, o-
3
4
NMe2C5H4N), 7.77 (dd, 4 H, JH−H = 8.5 Hz, JH−H = 1.1 Hz, o-
3
HfNN(C6H5)2), 7.25 (s, 2 H, o-C6H3Me2), 7.21 (t, 4 H, JH−H = 8.5
Hz, m-HfNN(C6H5)2), 6.80 (t, 2 H, JH−H = 7.8 Hz, p-HfNN-
3
(C6H5)2), 6.63 (s, 1 H, p-C6H3Me2), 5.74 (d, 2 H, 3JH−H = 6.8 Hz, m-
NMe2C5H4N), 3.56 (dt, 1 H, 2JH−H = 11.2 Hz, 3JH−H = 7.1 Hz, CH2N-
a), 3.17 (m, 1 H, CH2N-b), 2.58 (dt, 1 H, 2JH−H = 8.5 Hz, 3JH−H = 16.3
Hz, CH2CNN-a), 2.26 (s, 6 H, C6H3Me2), 2.22−2.17 (m, 1 H,
CH2CNN-b), 2.09 (s, 15 H, C5Me5), 1.98 (s, 6 H, NMe2C5H4N), 1.97
(broad m, 1 H, CH2CH2CNN-a), 1.14 (broad m, 1 H, CH2CH2CNN-
b) ppm. 13C NMR (benzene-d6, 150.9 MHz, 295 K): δ 175.2 (s,
NCN), 152.6 (d, o-NMe2C5H4N), 151.1 (s, ipso-C6H3Me2), 149.7 (s,
ipso-HfNN(C6H5)2), 137.8 (s, m-C6H3Me2), 128.7 (d, m-HfNN-
(C6H5)2), 124.0 (d, p-C6H3Me2), 122.9 (d, o-C6H3Me2), 119.8 (d, p-
HfNN(C6H5)2), 119.5 (d, o-HfNN(C6H5)2), 115.7 (s, C5Me5), 105.8
(d, m-NMe2C5H4N), 52.7 (t, CH2N), 38.1 (q, NMe2C5H4N), 29.9 (t,
CH2CNN), 24.1 (t, CH2CH2CNN), 21.7 (q, C6H3Me2), 11.8 (q,
C5Me5) ppm. 15N NMR (benzene-d6, 60.81 MHz, 295 K): δ 280
(HfNNPh2), 237 (NMe2C5H4N), 172 (HfNNPh2), 62 (NMe2C5H4N)
[Cp*Hf(NxylN)(NMe2)2] (5). A 200 mg portion (0.350 mmol) of
Cp*Hf(NxylN)Cl2 (2b) was dissolved in 10 mL of toluene, 36 mg
(0.699 mmol, 2 equiv) of LiNMe2 was added, and the mixture was
stirred for 41 h and then centrifuged (10 min at 2000 rpm) and
filtered. The filtrate was evaporated under reduced pressure to yield
1
148 mg (0.251 mmol, 72%) of a brown solid. H NMR (benzene-d6,
600.1 MHz, 295 K): δ 6.59 (s, 1 H, p-C6H3Me2), 6.51 (s, 2 H, o-
3
C6H3Me2), 3.41 (t, 2 H, JH−H = 6.8 Hz, CH2N), 3.09 (s, 12 H,
NMe2), 2.30 (s, 6 H, C6H3Me2), 2.30−2.27 (m, 2 H, CH2CNN), 2.03
3
(C5Me5), 1.47 (quin, 2 H, JH−H = 7.2 Hz, CH2CH2CNN) ppm. 13C
NMR (benzene-d6, 150.9 MHz, 295 K): δ 176.9 (NCN), 148.0 (ipso-
C6H3Me2), 137.8 (m-C6H3Me2), 122.5 (p-C6H3Me2), 119.8 (o-
C6H3Me2), 117.4 (C5Me5), 51.7 (CH2N), 43.6 (NMe2), 31.6
(CH2CNN), 24.2 (CH2CH2CNN), 21.9 (C6H3Me2), 11.3 (C5Me5)
ppm. 15N NMR (benzene-d6, 60.81 MHz, 295 K): δ 184 (NCNxyl),
167 (NCNxyl) ppm. IR (KBr): ν 2964 (w), 2908 (w), 2860 (w), 2757
(w), 1638 (w), 1592 (m), 1521 (m), 1455 (m), 1375 (w), 1322 (w),
1294 (m), 1262 (m), 1187 (m), 1097 (s), 1021 (s), 957 (m), 928 (m),
867 (m), 799 (s), 686 (m), 524 (m) cm−1. Mass spectrometry (HR-
EI): calcd 590.2879 u, 589.2873 u, 588.2851 u, 587.2843 u
(C26H42N4Hf); found 590.2891 u (Δ = 1.6 mmu), 589.2911 u (Δ =
1
ppm. Data for the minor component are as follows. H NMR (benzene-
3
d6, 600.1 MHz, 295 K): δ 8.35 (d, 2 H, JH−H = 7.1 Hz, o-
3
NMe2C53H4N), 7.72 (d, 4 H, JH−H = 8.2 Hz, o-HfNN(C6H5)2), 7.30
3
(t, 4 H, JH−H = 7.8 Hz, m-HfNN(C6H5)2), 6.88 (t, 2 H, JH−H = 7.2
Hz, m-HfNN(C6H5)2), 6.68 (s, 1 H, p-C6H3Me2), 5.56 (d, 2 H, 3JH−H
= 7.2 Hz, m-NMe2C5H4N), 3.86 (m, 1 H, CH2N-a), 3.70 (dt, 1 H,
3
2JH−H = 11.1 Hz, JH−H = 7.2 Hz, CH2N-b), 2.10 (s, 6 H, C6H3Me2),
1.93 (s, 15 H, C5Me5) ppm; CH2CNN, CH2CH2CNN not observed.
1735
dx.doi.org/10.1021/om500087s | Organometallics 2014, 33, 1726−1739

Organometallics
Article
4.3 mmu), 588.2891 u (Δ = 4.4 mmu), 587.2844 u (Δ = 0.2 mmu).
Anal. Calcd: C, 53.01; H, 7.19; N, 9.51. Found: C, 53.50; H, 6.53; N,
9.09.
C6H3Me2, CHMe2 not observed. IR (KBr): ν 2964 (m), 2912 (m), 2860
(m), 1595 (s), 1560 (m), 1541 (m), 1522 (m), 1490 (s), 1383 (m),
1319 (w), 1292 (w), 1229 (w), 1262 (m), 1099 (m), 1026 (m), 885
(s), 749 (m), 693 (m), 617 (w) cm−1. Despite numerous attempts, we
have not been able to obtain an elemental analysis, probably due to the
instability of the compound.
[Cp*Hf(NxylN)(NHNPh2)2] (6). A 170 mg portion (0.289 mmol) of
Cp*Hf(NxylN)(NMe2)2 (19) and 106 mg (0.577 mmol, 2 equiv) of
Ph2NNH2 were dissolved in 10 mL of toluene and heated to 70 °C for
14 h. Subsequently the reaction mixture was filtered, and the solvent
was removed under reduced pressure to yield 218 mg (0.240 mmol,
[Cp*Zr(NXylN){κ2-N(NPh2)C(NiPr)NiPrC(NiPr)NiPr}] (8). A 300 mg
portion (0.418 mmol) of Cp*Zr(NXylN)(NNPh2)dmap (3a) was
dissolved in toluene (10 mL), and 130 μL (0.836 mmol) of
iPrNCNiPr was added. After the mixture was stirred for 30 min at
room temperature, the solvent was removed under reduced pressure,
and the residue was washed with hexane to yield 234 mg (0.241 mmol,
1
83%) of a brown oil. H NMR (benzene-d6, 600.1 MHz, 295 K): δ
7.20 (d, 4 H, 3JH−H = 8.2 Hz, o-Ph), 7.1 (t, 4 H, 3JH−H = 7.7 Hz, m-Ph),
6.78 (t, 2 H, 3JH−H = 7.3 Hz, p-Ph), 6.69 (s, 2 H, o-C6H3Me2), 6.55 (s,
3
2 H, p-C6H3Me2), 5.90 (s, 2 H, NHNPh2), 3.31 (t, 2 H, JH−H = 6.8
1
Hz, CH2N), 2.12 (s, 6 H, C6H3Me2), 1.98 (CH2CNN, only observed in
H,H−COSY and HSQC), 1.93 (s, 15 H, C5Me5), 1.15 (quin, 2 H,
3JH−H = 7.2 Hz, CH2CH2CNN) ppm. 13C NMR (benzene-d6, 150.9
MHz, 295 K): δ 179.1 (NCN), 150.7 (ipso-Ph), 148.3 (m-C6H3Me2),
137.9 (ipso-C6H3Me2), 128.6 (m-Ph), 124.9 (p-C6H3Me2), 123.3 (o-
C6H3Me2), 122.4 (p-Ph), 121.8 (o-Ph), 118.5 (C5Me5), 52.3 (CH2N),
30.5 (CH2CNN), 23.2 (CH2CH2CNN), 21.4 (C6H3Me2), 11.4
(C5Me5) ppm. 15N NMR (benzene-d6, 60.81 MHz, 295 K): δ 206
58%) of a dark brown solid. H NMR (benzene-d6, 600.1 MHz, 295
K): δ 7.52 (d, 4 H, 3JH−H = 8.0 Hz, o-Ph), 7.30 (t, 2 H, 3JH−H = 7.8 Hz,
3
3
m-Ph-a), 7.22 (t, 2 H, JH−H = 7.9 Hz, m-Ph-b), 6.88 (t, 1 H, JH−H
=
7.3 Hz, p-Ph-b), 6.84 (s, 2 H, o-C6H3Me2), 6.84 (m, 1 H, p-Ph-a), 6.59
(s, 1 H, p-C6H3Me2), 5.32 (sep, 1 H, 3JH−H = 5.9 Hz, ZrN(NPh2)C
NCHMe2), 4.65 (sep, 1 H, 3JH−H = 6.5 Hz, ZrNiPrC(NiPr)NCHMe2),
4.39−4.31 (sep, sep, ZrNiPrCNCHMe2 and ZrNCHMe2), 3.64−
3.54 (m, 2 H, CH2N), 2.74−2.67 (m, 1 H, CH2CNN-a), 2.32 (s, 6 H,
C6H3Me2), 2.30−2.24 (m, 1 H, CH2CNN-b), 2.12 (d, 3 H, 3JH−H = 6.8
1
(d, JN−H = 66 Hz, NHNPh2), 169 (NCNxyl), 119 (NHNPh2) ppm.
3
IR (KBr): ν 3342 (w), 3057 (w), 2963 (w), 2910 (w), 2859 (w), 2859
(w), 1587 (m), 1522 (m), 1490 (m), 1457 (m), 1376 (m), 1319 (m),
1262 (m), 1184 (m), 1154 (m), 1099 (m), 1072 (m), 1027 (m), 954
(w), 800 (m), 749 (s), 693 (s), 619 (m), 567 (w) cm−1. Anal. Calcd:
C, 60.73; H, 5.76; N, 9.24 (for 6-LiCl). Found: C, 61.29; H, 6.11; N,
9.36.
Hz, ZrNiPrCNCHMe2-a), 1.95 (d, 3 H, JH−H = 6.5 Hz, ZrNiPrC
NCHMe2-b), 1.66 (s, 15 H, C5Me5), 1.64−1.60 (m, 1 H,
CH2CH2CNN-a), 1.58−1.54 (m, 1 H, CH2CH2CNN-b), 1.31 (d, 3
3
3
H, JH−H = 6.7 Hz, ZrNiPrC(NiPr)NCHMe2-a), 1.29 (d, 3 H, JH−H
=
3
6.1 Hz, ZrN(NPh2)CNCHMe2-a), 1.17 (d, 3 H, JH−H = 6.0 Hz,
3
ZrNCHMe2-a), 1.08 (d, d, 6 H, JH−H = 6.1 and 5.5 Hz,
[Cp*Zr(NXylN){κ2-NiPrC(NNPh2)NiPr}] (7). A 300 mg portion
(0.418 mmol) of Cp*Zr(NXylN)(NNPh2)dmap (3a) was dissolved in
ZrNiPrC(NiPr)NCHMe2-b and ZrN(NPh2)CNCHMe2-b), 0.57 (d,
3 H, JH−H = 6.0 Hz, ZrNCHMe2-b) ppm. 13C NMR (benzene-d6,
3
i
toluene (10 mL), and 52 μL (0.334 mmol, 0.8 equiv) of PrNCNiPr
150.9 MHz, 295 K): δ 176.3 (NCNxyl), 147.7 (ZrNiPrCNiPr), 146.6
(ipso-C6H3Me2), 146.1 (ipso-Ph), 145.5 (ZrN(NPh2)CNiPr), 137.9
(m-C6H3Me2), 129.2 (m-Ph-a), 128.5 (m-Ph-b), 123.3 (p-C6H3Me2),
123.2 (C5Me5), 120.7 (p-Ph-b), 120.5 (o-C6H3Me2), 120.4 (p-Ph-a),
120.2 (o-Ph-a), 116.2 (o-Ph-b), 53.7 (CH2N), 52.8 (ZrNiPrC
NCHMe2), 50.6 (ZrNiPrC(NiPr)NCHMe2), 45.3 (ZrNCHMe2), 45.2
(ZrN(NPh2)CNCHMe2), 33.1 (CH2CNN), 26.4 (ZrN(NPh2)C
NCHMe2-a), 26.1 (ZrNCHMe2-a), 25.2 (ZrNCHMe2-b), 24.3
(ZrNiPrCNCHMe2-a), 24.0 (ZrNiPrCNCHMe2-b), 23.4
(CH2CH2CNN), 21.6 (C6H3Me2), 21.3 (ZrN(NPh2)CNCHMe2-
b), 20.8 (ZrNiPrC(NiPr)NCHMe2-a), 20.5 (ZrNiPrC(NiPr)NCHMe2-b),
11.7 (C5Me5) ppm. 15N NMR (benzene-d6, 60.81 MHz, 295 K): δ 114
(ZrNiPrC(NiPr)NiPr), 123 (NNPh2), 168 (NCNxyl), 184 (NCNxyl),
211 (NNPh2), 216 (ZrNiPrCNiPr), 224 (ZrNiPr), 244 (Zr(NNPh2)-
CNiPr) ppm. IR (KBr): ν 2962 (m), 2911 (m), 2859 (m), 1662 (s),
1602 (s), 1521 (s), 1490 (s), 1446 (m), 1375 (m), 1319 (m), 1292
(m), 1228 (m), 1191 (m), 1098 (m), 1011 (m), 951 (w), 887 (w),
804 (m), 746 (m), 693 (m), 534 (w) cm−1. Anal. Calcd: C, 67.96; H,
8.08; N, 13.21. Found: C, 67.95; H, 7.39; N, 13.64.
was added. After the mixture was stirred for 30 min at room
temperature, the solvent was removed under reduced pressure and the
residue washed with hexane. The residue was then dissolved in diethyl
ether (5 mL) and this solution was layered with hexane (10 mL),
which resulted in precipitation of a solid. After 30 min, the suspension
was filtered, the filtrate was cooled to −30 °C for 2 days, the solution
was again filtered, and the filtrate was evaporated to dryness under
reduced pressure and washed with hexane to yield 20 mg (0.024
mmol, 6%) of a brown solid. Single crystals of the DMAP adduct
suitable for X-ray diffraction were obtained from a concentrated
solution in diethyl ether/hexane. Data for the major component are as
1
follows. H NMR (benzene-d6, 600.1 MHz, 295 K): δ 7.44 (d, 4 H,
3JH−H = 7.8 Hz, o-Ph), 7.31 (s, 2 H, o-C6H3Me2), 7.20 (t, 4 H, 3JH−H
=
8.0 Hz, m-Ph), 6.87−6.82 (m, 2 H, p-Ph), 6.61 (s, 1 H, p-C6H3Me2),
3.84−3.78 (m, 1 H, CHMe2-a), 3.77−3.71 (m, 1 H, CH2N-a), 3.62−
3.55 (m, CH2N-b), 3.45−3.38 (m, 1 H, CHMe2-b), 2.86−2.80 (m, 1
H, CH2CNN-a), 2.34 (s, 6 H, C6H3Me2), 2.31−2.29 (m, 1 H,
CH2CNN-b), 1.86 (s, 15 H, C5Me5), 1.72−1.66 (m, 2 H,
[Cp*Zr(NXylN){κ2-N(NPh2)CHPhNPh}] (9). A 300 mg portion
(0.418 mmol) of Cp*Zr(NxylN)(NNPh2)dmap (3a) was dissolved in
10 mL of toluene, and 68 mg (0.376 mmol) of N-phenylbenzimine
was added. After the mixture was stirred for 2 days, the solvent was
removed under reduced pressure and the residue washed with hexane
to yield 193 mg (0.215 mmol, 51%) of a brown solid. 1H NMR
3
CH2CH2CNN), 1.54 (d, 3 H, JH−H = 6.6 Hz, CHMe2-a), 1.07 (d, 3
3
H, 3JH−H = 6.3 Hz, CHMe2-a), 0.53 (d, 3 H, JH−H = 6.2 Hz, CHMe2-
b), 0.50 (d, 3 H, 3JH−H = 6.0 Hz, CHMe2-a) ppm. 13C NMR (benzene-
d6, 150.9 MHz, 295 K): δ 173.7 (NCN), 165.9 (CNNPh2), 159.3
(m-C6H3Me2), 150.4 129.1 (m-Ph), 123.9 (C5Me5), 123.3 (p-
C6H3Me2), 122.1 (p-Ph), 121.3 (o-C6H3Me2), 121.0 (o-Ph), 52.7
(CH2N), 47.5 (CHMe2-a), 45.7 (CHMe2-b), 31.6 (CH2CNN), 24.2
(CHMe2-a), 24.1 (CHMe2-b), 23.9 (CHMe2-a), 23.7 (CHMe2-b), 22.9
(CH2CH2CNN), 21.9 (C6H3Me2), 12.1 (C5Me5) ppm. Data for the
minor component are as follows. 1H NMR (benzene-d6, 600.1 MHz, 295
K): δ 7.61 (d, 4 H, 3JH−H = 8.5 Hz, o-Ph), 7.26 (t, 4 H, 3JH−H = 8.3 Hz,
m-Ph), 6.78 (s, 2 H, o-C6H3Me2), 6.77−6.74 (m, 2 H, p-Ph), 6.60 (s, 1
H, p-C6H3Me2), 3.94 (sep, 1 H, 3JH−H = 6.6 Hz, CHMe2-a), 3.77−3.71
(m, 1 H, CH2N-a), 3.68−3.63 (m, 1 H, CH2N-b), 3.62−3.55 (m,
CHMe2-b), 2.35 (s, 6 H, C6H3Me2), 1.89 (s, 15 H, C5Me5), 1.49 (d, 3
3
(benzene-d6, 600.1 MHz, 295 K): δ 7.53 (d, 2 H, JH−H = 7.1 Hz, o-
CHPh), 7.24 (t, 2 H, 3JH−H = 7.4 Hz, m-NNPh), 7.22 (s, 1 H, CHPh),
7.14−7.07 (m, H, CH-Ar, o- and m-ZrNPh, p-C6H3Me2), 7.06−7.02
(m, H, CH-Ar,), 6.96−6.91 (m, H, CH-Ar, p-NNPh), 6.77 (d, 2 H,
3JH−H = 7.3 Hz, o-NPh), 6.69 (s, 2 H, o-C6H3Me2), 6.61 (d, 2 H, 3JH−H
= 7.8 Hz, o-Ph), 3.63−3.55 (m, 1 H, CH2N-a), 3.47−3.41 (m, 1 H,
CH2N-b), 2.37 (m, 1 H, CH2CNN-a), 2.05 (m, 1 H, CH2CNN-b),
2.04 (s, 6 H, C6H3Me2), 1.94 (s, 15 H, C5Me5), 1.47 (m, 1 H,
CH2CH2CNN-a), 1.36 (m, 1 H, CH2CH2CNN-b) ppm. 13C NMR
(benzene-d6, 150.9 MHz, 295 K): δ 175.2 (NCN), 148.1 (ipso-
C6H3Me2), 145.1 (ipso-Ph), 144.2 (ipso-Ph), 138.5 (m-C6H3Me2),
136.8 (ipso-Ph), 135.7, 130.1 (CH Ar), 128.8 (CH Ar), 126.7 (o-
CHPh), 126.1 (o-Ph-b), 124.7 (p-C6H3Me2), 123.0 (o-C6H3Me2),
122.9 (C5Me5), 117.9 (o-NNPh2), 116.9 (o-Ph-c), 66.7 (CHPh), 54.4
(CH2N), 29.8 (CH2CNN), 23.7 (CH2CH2CNN), 21.3 (C6H3Me2),
11.3 (C5Me5) ppm. 15N NMR (benzene-d6, 60.81 MHz, 295 K): δ 335
3
H, 3JH−H = 5.9 Hz, CHMe2-a), 1.05 (d, 3 H, JH−H = 6.5 Hz, CHMe2-
a), 0.73 (d, 3 H, 3JH−H = 6.3 Hz, CHMe2-b), 0.65 (d, 3 H, 3JH−H = 6.1
Hz, CHMe2-b) ppm. 13C NMR (benzene-d6, 150.9 MHz, 295 K): δ
143.8 (ipso-Ph), 129.0 (m-Ph), 123.7 (C5Me5), 129.9 (o-C6H3Me2),
121.9 (p-Ph), 119.2 (o-Ph), 53.1 (CH2N), 47.8 (CHMe2-a), 46.4
(CHMe2-b), 32.0 (CH2CNN), 23.1 (CH2CH2CNN), 21.7
(C6H3Me2), 12.1 (C5Me5) ppm; NCN, CNNPh2, ipso-, m- and p-
1736
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Organometallics
Article
2
2
(ZrNNPh2), 196 (ZrNNPh2), 173 (NCNxyl), 149 (ZrNPh) ppm. IR
(KBr): ν 3025 (w), 2908 (m), 2857 (m), 1602 (s), 1560 (m), 1522
(s), 1490 (s), 1376 (m), 1289 (m), 1263 (m), 1229 (m), 1176 (w),
1095 (m), 1063 (w), 1025 (w), 1009 (w), 950 (w), 874 (w), 805 (m),
751 (m), 693 (m), 657 (w) cm−1. Anal. Calcd: C, 72.64; H, 6.61; N,
9.01. Found: C, 72.31; H, 6.88; N, 8.20.
(d, JH−H = 12.3 Hz, CH2-b), 3.11 (d, JH−H = 12.2 Hz, CH2-a), 3.09
(d, 2JH−H = 12.2 Hz, CH2-b), 2.81 (m, 1 H, ZrNCHMe2), 1.34 (s, 3 H,
3
CH3), 1.10 (d, 6 H, JH−H = 6.4 Hz, CNCHMe2), 0.92 (s, 18 H,
SiCMe3), 0.68 (d, 6 H, 3JH−H = 6.0 Hz, ZrNCHMe2), 0.01 (SiMe), 0.00
(SiMe) ppm; Py-H3 not observed. 13C NMR (benzene-d6, 150.9 MHz,
295 K): δ 166.3 (Py-C2), 159.2 (CNCHMe2), 150.3 (ipso-Ph),
149.1 (Py-C6), 135.7 (Py-C4), 129.0 (m-Ph), 122.0 (p-Ph), 121.8 (Py-
C5), 121.0 (o-Ph), 51.2 (CH2), 48.5 (Py-C1), 43.8 (CNCHMe2),
42.7 (ZrNCHMe2), 26.8 (SiCMe3), 21.1 (CH3), 18.7 (SiCMe3), −4.7
(SiMe), −4.8 (SiMe) ppm. IR (KBr): ν 3064 (w), 2955 (m), 2927
(m), 2882 (m), 2854 (m), 1592 (s), 1491 (s), 1472 (m), 1387 (m),
1310 (w), 1246 (m), 1175 (m), 1044 (m), 1020 (m), 908 (w), 851
(m), 830 (s), 774 (m), 748 (m), 691 (m), 669 (m), 593 (w), 511 (w)
cm−1. Anal. Calcd: C, 60.71; H, 8.28; N, 12.39. Found: C, 60.37; H,
7.87; N, 12.27.
[Cp*Zr(NXylN){κ2-N(Ph)-o-phenylene-C(Ph)C(Ph)NH}] (10).
A 200 mg portion (0.279 mmol) of Cp*Zr(NXylN)(NNPh2)dmap
(3a) was dissolved in 10 mL of toluene, 50 mg (0.279 mmol) of
diphenylacetylene was added, and the solution was stirred for 3 days at
room temperature. The solvent was subsequently removed under
reduced pressure, and 5 mL of pentane was added and removed under
reduced pressure to yield 135 mg (0.133 mmol, 48%) of the DMAP
adduct as a brown solid. 1H NMR (benzene-d6, 600.1 MHz, 295 K): δ
3
7.45 (d, 1 H, JH−H = 7.9 Hz, ZrN(Ph)phenylene-5), 7.30 (td, 1 H,
[Zr(N2 Npy){κ2-N(NPh2)CHPhNPh}] (13). A 350 mg portion
(0.470 mmol) of Zr(N2 Npy)(NNPh2)py (11) was dissolved in 10
mL of toluene, and 85 mg (0.470 mmol) of N-phenylbenzimine (N-
benzylideneaniline) was added. After the mixture was stirred for 3 h,
the solvent was removed under removed pressure and the residue
washed with hexane to yield 228 mg (0.269 mmol, 57%) of a yellow
solid. Crystals suitable for X-ray diffraction were grown from a
TBS
4
3JH−H = 7.1 Hz, JH−H = 2.2 Hz, ZrN(Ph)phenylene-2), 7.27 (t, 2 H,
TBS
3
3JH−H = 7.8 Hz, m-NPh), 7.22 (d, 2 H, JH−H = 7.2 Hz, o-Ph-b), 7.08
3
(d, 2 H, JH−H = 7.9 Hz, o-NPh), 6.91 (t, 1 H, p-NPh), 6.90 (d, 2 H,
3JH−H = 7.5 Hz, o-Ph-a), 6.87 (t, 2 H, 3JH−H = 7.3 Hz, m-Ph), 6.82 (d, 2
H, 3JH−H = 7.1 Hz, m-Ph), 6.81−6.75 (m, 4 H, CH ar), 6.69 (s, 2 H, o-
C6H3Me2), 6.68 (s, 1 H, p-C6H3Me2), 6.12 (s, 1 H, NH), 3.48−3.39
(m, 2 H, CH2N), 2.38 (s, 6 H, C6H3Me2), 1.90 (s, 15 H, C5Me5) ppm.
13C NMR (benzene-d6, 150.9 MHz, 295 K): δ 174.3 (NCN), 154.4
(ipso-Ph), 154.1 (NHC(Ph)CPh), 153.0 (ipso-NPh), 151.6 (ZrN-
(Ph)phenylene-1), 149.6 (ipso-C6H3Me2), 148.2 (ipso-ZrNHC(Ph)
C(Ph)), 147.4 (ipso-Ph), 140.8 (ipso-NHC(Ph)CPh), 137.6 (m-
C6H3Me2), 135.2 (CH ar), 134.4 (C ar), 133.1 (o- and p-Ph), 129.3 (C
ar), 128.5, 128.4 (m-Ph and p-Ph), 127.5 (CH ar), 126.3 (o-Ph), 124.8
(p-C6H3Me2), 124.5 (CH ar), 124.0 (CH ar), 122.8 (o-Ph), 122.7 (o-
C6H3Me2), 122.3 (CH ar), 120.4 (C5Me5), 111.8 (NHC(Ph)CPh),
52.3 (CH2N), 29.4 (CH2CNN), 24.3 (CH2CH2CNN), 21.8
(C6H3Me2), 11.9 (C5Me5) ppm. 15N NMR (benzene-d6, 60.81 MHz,
295 K): δ 214 (ZrNPh), 200 (d, 1JN−H = 65 Hz, ZrNH), 177 (NCNxyl)
ppm. IR (KBr, cm−1): ν 3386 (w), 3023 (w), 2963 (m), 2908 (m),
2857 (m), 1594 (s), 1521 (s), 1492 (s), 1446 (s), 1375 (m), 1315
(m), 1289 (m), 1262 (m), 1228 (m), 1182 (w), 1097 (m), 1069 (m),
950 (w), 875 (w), 804 (m), 748 (s), 694 (s), 619 (w), 535 (w). Anal.
Calcd: C, 74.47; H, 6.51; N, 7.24. Found: C, 74.34; H, 6.91; N, 6.96.
1
concentrated solution in toluene. H NMR (benzene-d6, 600.1 MHz,
295 K): δ 9.05 (d, 1 H, 3JH−H = 5.2 Hz, Py-H6), 7.80 (d, 2 H, 3JH−H
=
7.5 Hz, o-CHPh), 7.24−7.17 (m, 8 H, m-CHPh, o-NPh, o-NNPh2),
7.08 (t, 1 H, 3JH−H = 7.3 Hz, p-CHPh), 6.98 (t, 1 H, 3JH−H = 7.7 Hz, p-
3
NPh), 6.94−6.76 (broad m, 2 H, NNPh2), 6.83 (t, 1 H, JH−H = 7.7
Hz, Py-H4), 6.72 (d, 1 H, 3JH−H = 8.1 Hz, Py-H3), 6.70−6.64 (m, 3 H,
3
m-NPh and NNPh2), 6.35 (s, 1 H, CHPh), 6.31 (t, 1 H, JH−H = 6.5
2
Hz, Py-H5), 4.15 (d, 1 H, JH−H = 12.5 Hz, CH2-a), 4.08 (d, 1 H,
2JH−H = 12.2 Hz, CH2-b), 3.39 (d, 1 H, 2JH−H = 11.9 Hz, CH2-b), 3.37
2
(d, 1 H, JH−H = 12.1 Hz, CH2-a), 1.02 (s, 3 H, CH3), 0.87 (s, 9 H,
CMe3-a), 0.80 (s, 9 H, CMe3-b), 0.46 (s, 3 H, SiMe-b), 0.23 (s, 3 H,
SiMe-b), 0.19 (s, 3 H, SiMe-a), −0.27 (s, 3 H, SiMe-a) ppm. 13C NMR
(benzene-d6, 150.9 MHz, 295 K): δ 160.9 (Py-C2), 151.9 (ipso-
CHPh), 147.0 (Py-C6), 142.3 (ipso-NPh), 140.3 (Py-C4), 129.1 (o-
CHPh), 129.0 (CH Ar), 127.3 (CH Ar), 126.1 (CH Ar), 123.5 (CH
Ar), 122.6 (Py-C5), 121.3 (CH Ar), 121.0 (Py-C3), 116.8 (m-NPh),
74.6 (CHPh), 63.0 (CH2-a), 62.8 (CH2-b), 48.5 (Py-C1), 28.2 (CMe3-
a), 27.8 (CMe3-b), 25.5 (CH3), 19.6, 19.5 (CMe3-a and b), −2.4
(SiMe-b), −3.0 (SiMe-b), −3.6 (SiMe-a), −5.1 (SiMe-a) ppm. 15N
NMR (benzene-d6, 60.81 MHz, 295 K): δ 335 (ZrNNPh2), 301
(NSitBuMe2-b), 299 (NSitBuMe2-a), 278 (PyN), 183 (ZrNPh) ppm;
NNPh2 not observed. IR (KBr): ν 3061 (w), 3025 (w), 2952 (w), 2926
(w), 2853 (w), 1588 (m), 1489 (m), 1385 (w), 1316 (m), 1257 (m),
1109 (m), 1085 (m), 1039 (m), 995 (m), 909 (m), 849 (s), 830 (s),
775 (s), 750 (s), 693 (s), 669 (m), 636 (w), 611 (w), 587 (m) cm−1.
Anal. Calcd; C, 65.27; H, 7.38; N, 9.93. Found: C, 65.82; H, 7.45; N,
9.50.
General Procedure for Catalytic N-Aminoguanidine Syn-
thesis. A 0.05 mmol portion of catalyst 3a was dissolved in 1 mL of
toluene. A 1.0 mmol portion of diisopropylcarbodiimide and 1.1 mmol
of diphenylhydrazine were dissolved in 1 mL of toluene, and the
solutions were combined and heated to 105 °C for 24 h. The reaction
mixture was then diluted with 120 mL of diethyl ether and filtered
through a pad of alumina, the solvent was removed under reduced
pressure, and the crude product was purified by column chroma-
tography (DCM with 5% MeOH, 0.5% NEt3, 80 g of silica). A 309 mg
amount (0.99 mmol, 99%) of a yellow solid was obtained. NMR
spectra were in good agreement with those found in the literature.56
Computational Studies. All molecular structures were optimized
using the B3PW91 hybrid functional39,40 with a 631G(d) basis set46
for C, H, N, Li, and Si and a pseudopotential for Zr (SDD+f) and Hf
(SDD)41−45 using the Gaussian09 program package.57 Energy minima
were verified by frequency analysis. The coordinates of the minimum
structures are provided in the Supporting Information.
TBS
[Zr(N2 Npy){κ2-N(NPh2)C(NiPr)NiPr}] (12). A 300 mg portion
TBS
(0.400 mmol) of Zr(N2 Npy)(NNPh2)py (11) was dissolved in
i
toluene, and 62 μL (0.400 mmol) of PrNCNiPr was added. After the
mixture was stirred at room temperature for 30 min, the solvent was
removed under reduced pressure and the residue washed with pentane
to yield 185 mg (0.234 mmol, 54%) of a yellow solid. The product
contained two isomers in a 5:1 ratio. Crystals suitable for X-ray
diffraction were grown from a concentrated toluene solution. Data for
the major component are as follows. 1H NMR (benzene-d6, 600.1 MHz,
295 K): δ 9.02 (d, 1 H, 3JH−H = 5.6 Hz, Py-H6), 7.67 (d, 4 H, 3JH−H
=
7.9 Hz, o-Ph), 7.22 (t, 4 H, 3JH−H = 7.6 Hz, m-Ph), 6.94 (t, 1 H, 3JH−H
3
= 7.6 Hz, Py-H4), 6.80 (t, 2 H, JH−H = 7.1 Hz, p-Ph), 6.75 (d, 1 H,
3
3JH−H = 7.9 Hz, Py-H3), 6.38 (t, 1 H, JH−H = 6.5 Hz, Py-H5), 4.72
(sep, 1 H, 3JH−H = 5.8 Hz, CNCHMe2), 4.40 (sep, 1 H, 3JH−H = 6.2
Hz, ZrNCHMe2), 3.90 (d, 2 H, 2JH−H = 12.4 Hz, CH2-a), 3.26 (d, 2 H,
2JH−H = 12.4 Hz, CH2-b), 1.78 (d, 6 H, 3JH−H = 6.2 Hz, ZrNCHMe2),
1.19 (d, 6 H, 3JH−H = 5.8 Hz, CNCHMe2), 0.97 (s, 3 H, CH3), 0.78
(s, 18 H, SiMe2CMe3), 0.39 (s, 6 H, SiMe2CMe3-a), −0.02 (s, 6 H,
SiMe2CMe3-b) ppm. 13C NMR (benzene-d6, 150.9 MHz, 295 K): δ
160.6 (Py-C2), 153.7 (CNiPr), 148.3 (ipso-Ph), 147.2 (Py-C6),
140.4 (Py-C4), 129.0 (m-Ph), 122.6 (Py-C5), 121.2 (Py-C3), 120.9 (p-
Ph), 119.4 (o-Ph), 62.5 (CH2), 48.4 (Py-C1), 48.0 (ZrNCHMe2), 44.7
(CNCHMe2), 27.9 (SiCMe3), 27.6 (CNCHMe2), 26.8 (CH3),
25.2 (ZrNCHMe2), 19.8 (SiCMe3), −3.3 (SiMe3), −4.4 (SiMe3) ppm.
15N NMR (benzene-d6, 60.81 MHz, 295 K): δ 277 (Py-N), 214
(ZrNiPr), 203 (CNiPr), 64 (TBS-NZr) ppm. Data for the minor
component are as follows. 1H NMR (benzene-d6, 600.1 MHz, 295 K): δ
8.48 (d, 1 H, 3JH−H = 5.6 Hz, Py-H6), 7.42 (d, 4 H, 3JH−H = 7.9 Hz, o-
Ph), 7.18 (m, overlaid by benzene-d6, m-Ph), 7.12 (m, 1 H, Py-H3), 6.87
The modeling of the NMR chemical shifts has been carried out,
utilizing the DFT-optimized structures, with the GIAO method47−49
employing the B3PW91 hybrid functional with a 6311++G(2d,2p)
basis set for C, H, and N and a pseudopotential (SDD+f) for Zr.
3
3
(t, 2 H, JH−H = 7.3 Hz, p-Ph), 6.60 (t, 1 H, JH−H = 6.0 Hz, Py-H5),
4.26 (m, 1 H, CNCHMe2), 3.31 (d, 2JH−H = 12.3 Hz, CH2-a), 3.30
1737
dx.doi.org/10.1021/om500087s | Organometallics 2014, 33, 1726−1739

Organometallics
Article
X-ray Crystal Structure Determinations. Crystal data and
details of the structure determinations are given in the Supporting
Information. Full shells of intensity data were collected at low
temperature (complex 13, 100 K; all others, 110 K) with a Bruker AXS
Smart 1000 CCD diffractometer (Mo Kα radiation, sealed tube,
graphite monochromator) (complex 13) or a Agilent Technologies
Supernova-E CCD diffractometer (Mo or Cu Kα radiation, microfocus
tube, multilayer mirror optics). Data were corrected for air and
detector absorption, Lorentz, and polarization effects;58,59 absorption
by the crystal was treated with a semiempirical multiscan method
(complexes 3a, 12, and 13)60−62 or was treated analytically (complex
7)59,63 or numerically (Gaussian grid) (complexes 3b and 4).59 The
structures were solved by the charge flip procedure64 and refined by
full-matrix least-squares methods based on F2 against all unique
reflections.65 All non-hydrogen atoms were given anisotropic displace-
ment parameters. Hydrogen atoms were generally input at calculated
positions and refined with a riding model. When justified by the
quality of the data, the positions of some hydrogen atoms were taken
from difference Fourier syntheses and refined. When found necessary,
disordered groups and/or solvent molecules were subjected to suitable
geometry and adp restraints. Crystals of 12 were twinned; after
detwinning (approximately twin fractions 0.52:0.48) refinement was
carried out against all singles and composites involving both domains.
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ASSOCIATED CONTENT
* Supporting Information
■
S
Tables, text, figures, and CIF, .mol, and .xyz files giving
crystallographic data for 3a,b, 4, 7, 12, and 13, all computed
molecule Cartesian coordinates in a format for convenient
visualization, and details on the computational studies. This
material is available free of charge via the Internet at http://
pubs.acs.org.
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1991, 113, 6343.
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Wadepohl, H.; Gade, L. H. Chem. Eur. J. 2008, 14, 8131.
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Gade, L. H. Angew. Chem., Int. Ed. 2011, 50, 5757.
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AUTHOR INFORMATION
Notes
The authors declare no competing financial interest.
■
ACKNOWLEDGMENTS
We thank the Deutsche Forschungsgemeinschaft for funding
(SFB 623, TP A7), Alexander Kochan for help with ligand
■
synthesis, Tim Bleith and Jurgen Schulmeister for help with the
̈
DFT calculations, and Markus Enders and Beate Termin for
support in connection with the NMR studies.
Organometallics 2010, 29, 28.
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