Titanium hydrazinediido half-sandwich complexes: Highly active catalysts for the hydrohydrazination of terminal alkynes at ambient temperature

Article abstract of DOI:10.1021/om900155t

Reaction of [Cp*Ti(N^XylN)(N^tBu)(NH ₂^tBu)] with 1 molar equiv of diphenylhydrazine yielded the hydrazinediido complex [Cp*Ti(N^XylN)(NNPh₂)(NH ₂^tBu)] (1a), whereas the o

Full text of DOI:10.1021/om900155t

Organometallics 2009, 28, 3381–3389
3381
Titanium Hydrazinediido Half-Sandwich Complexes: Highly Active
Catalysts for the Hydrohydrazination of Terminal Alkynes at
Ambient Temperature
Katharina Weitershaus, Hubert Wadepohl, and Lutz H. Gade*
Anorganisch-Chemisches Institut, UniVersita¨t Heidelberg, Im Neuenheimer Feld 270,
69120 Heidelberg, Germany
ReceiVed February 26, 2009
t
Reaction of [Cp*Ti(NXylN)(NtBu)(NH2 Bu)] with 1 molar equiv of diphenylhydrazine yielded the
t
hydrazinediido complex [Cp*Ti(NXylN)(NNPh2)(NH2 Bu)] (1a), whereas the orange pyridine adduct
t
[Cp*Ti(NXylN)(NNPh2)(py)] (1b) was obtained by reacting the imide [Cp*Ti(NXylN)(NtBu)(NH2 Bu)]
with diphenylhydrazine in the presence of pyridine. The tert-butylamine coordinated to the metal center
in 1a could be removed by heating the solid at 60 °C and 10-6 mbar for 72 h, yielding
[Cp*Ti(NXylN)(NNPh2)] (1c). In the presence of pyridine or 4-dimethylaminopyridine (dmap) as neutral
co-ligands the hydrazinediido complexes [Cp*Ti(NXylN)(NNMePh)(py)] (2a) and [Cp*Ti(NXylN)-
(NNMePh)(dmap)] (2b) as well as [Cp*Ti(NXylN)(NNMe2)(dmap)] (3) were prepared. Upon replacement
of dmap by the weaker donor ligand pyridine in the synthesis of the pyridine adduct analogous to 3, a
mixture of [Cp*Ti(NXylN)(NNMe2)(py)] (4a) and the dinuclear complex [Cp*2Ti2(NXylN)2(µ-η1,η1-
NNMe2)(µ-η1,η2-NNMe2)] (4b) was obtained. Reaction of the dimethylhydrazinediido complex 3 with
1
phenylacetylene gave the Markovnikov cycloadduct, which had sufficient lifetime to allow its H, 13C,
and 15N NMR spectroscopic characterization in solution. All three hydrazinediido compounds 1a, 2a,
and 3 were found to display remarkable activities in catalytic hydrohydrazinations at ambient temperatures.
For catalyst loadings of 5 mol % complete conversions of the terminal alkynes and diynes with
Markovnikov regioselectivities of over 99% selectivity were observed within 1 h.
4 metal-catalyzed reaction is based on the extensively studied
mechanistic scheme for hydroaminations of alkynes, in which
imido complexes are the key active species.
Introduction
The catalytic hydrohydrazination of alkynes provides an atom-
economic access to hydrazones, which are potentially valuable
reagents for further transformations.1 Homogeneous catalysts
employed for this reaction are titanium or zinc based, the latter
allowing the tandem combination of hydrohydrazination and
subsequent Fischer indole cyclization.2-4 For all reported
systems relatively harsh reaction conditions have been necessary
for substituted acetylenes, with reaction temperatures of 75 to
120 °C. Alternative catalytic protocols for hydrazones employ
more d-electron-rich transition metals, such as cobalt or
manganese, for which the hydrazines are replaced by azodicar-
boxylates.5
Given the considerable amount of published work on the
structures and reactivity of imido group 4 metal compounds,
the relative paucity of work on their corresponding hydrazides,
in particular hydrazinediides, is remarkable. Despite a report
of a hydrazinediidotitanium complex by Wiberg et al. as early
as 1978,16 the chemistry of this class of complexes has only
begun to be developed further during the past decade, mainly
through the work of Mountford17–23 and Odom.6,11,24 Access
to the hydrazido(-1) and hydrazinediido complexes of the
heavier group 4 metal homologues has been gained in the
pioneering study by Bergman and co-workers25 and in subse-
quent work from our group.26–28
Hydrazinediido complexes have been identified as active
species in the titanium-catalyzed hydrohydrazination6–11 and
iminohydrazination10,11 of alkynes and the subsequent trans-
formation of the hydrazones into indoles2,7,12–15 or tryptamine
derivatives.8 The postulated reaction mechanism of the group
(6) Li, Y.; Shi, Y.; Odom, A. L. J. Am. Chem. Soc. 2004, 126, 1794–
1803.
(7) Ackermann, L.; Born, R. Tetrahedron Lett. 2004, 45, 9541–9544.
(8) Khedkar, V.; Tillack, A.; Michalik, M.; Beller, M. Tetrahedron Lett.
2004, 45, 3123–3126.
* Corresponding author. Fax: +49-6221-545609. E-mail: lutz.gade@
uni-hd.de.
(1) Odom, A. L. Dalton Trans. 2005, 225–233.
(2) Alex, K.; Tillack, A.; Schwarz, N.; Beller, M. Angew. Chem., Int.
Ed. 2008, 47, 2304–2307.
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2377–2379.
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Chem.sEur. J. 2004, 10, 2409–2420.
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49, 4607–4609.
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Nambu, H.; Huber, P.; Carreira, E. M. Org. Lett. 2005, 7, 4249–4252.
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8875–8878.
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10.1021/om900155t CCC: $40.75
2009 American Chemical Society
Publication on Web 05/12/2009

3382 Organometallics, Vol. 28, No. 12, 2009
Scheme 1. Synthesis of the Hydrazinediido Complexes 1-3 by Imido/Hydrazine Exchange
Weitershaus et al.
The control of its reactivity by the ancillary ligand(s) is crucial
for the performance of the catalyst. In recent years amidinates
have been shown to be ideal ancillary ligands for a variety of
early transition metals, including the group 3 elements and
lanthanides,29 as well as for metals from groups 430 and 5.31
We have recently reported the synthesis of 2-aminopyrrolinato
ligands in which the amidinato binding unit is exocyclic with
respect to the heterocycle and which have proven to act as
particularly robust spectator ligands.32 The possibility of amidi-
nates to convert from κ2 to κ1 coordination and thus temporarily
to liberate a coordination site at the metal may be crucial in the
development of active molecular catalysts. Their use in the
preparation of a series of new titanium half-sandwich complexes,
which are shown to be active catalysts for hydrohydrazination
of alkynes, will be reported in this work.
Results and Discussion
Preparation and Structural Characterization of the Hy-
drazinediidotitanium Complexes. As starting material for the
hydrazinediido complexes 1-3, displayed in Scheme 1, we
employed the previously published imido complex [Cp*Ti-
(16) Wiberg, N.; Haering, H. W.; Huttner, G.; Friedrich, P. Chem. Ber.
1978, 111, 2708–2715.
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Mountford, P. Chem. Commun. 2007, 4937–4939.
(NXylN)(NtBu)(NH2 Bu)],33 which was converted to the hydra-
t
zinediide via imido/hydrazinediido exchange by reaction with
the corresponding hydrazines.34 In these transformations the
half-sandwich system proved to be tolerant with respect to the
nature of the Nꢀ substituent of the hydrazido ligand. However,
the less bulky and electron-withdrawing the substituents on the
(21) Selby, J. D.; Manley, C. D.; Schwarz, A. S.; Clot, E.; Mountford,
P. Organometallics 2008, 27, 6479–6494.
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Mountford, P. Chem. Commun. 2007, 4937–4939.
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(25) Walsh, P. J.; Hollander, F. J.; Bergman, R. G. J. Am. Chem. Soc.
1990, 112, 894–896.
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H.; Gade, L. H. Dalton Trans. 2008, 2111–2119.
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Wadepohl, H.; Gade, L. H. Chem.sEur. J. 2008, 14, 8131–8146.
(28) For a very recent overview of the N-N reactivity of hydrazides
and related complexes, see: Mindiola, D. J. Angew. Chem., Int. Ed. 2008,
47, 1557.
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D. A.; Sita, L. R. J. Am. Chem. Soc. 2000, 122, 10490–10491. (d) Littke,
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123, 6197–6198. (f) Li, C.; Thomson, R. K.; Gillon, B.; Patrick, B. O.;
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Zhang, Y.; Harney, M. B.; Sita, L. R. AdV. Synth. Catal. 2005, 347, 426–
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Titanium Hydrazinediido Half-Sandwich Complexes
Organometallics, Vol. 28, No. 12, 2009 3383
Figure 1. Molecular structure of complex 1c. Selected bond lengths
and angles are listed in Table 1.
Table 1. Selected Bond Lengths (Å) and Angles (deg) for the
Structurally Characterized Hydrazinediido Complexes 1c, 2a, and 3
Figure 2. Molecular structure of complex 2a. Selected bond lengths
and angles are listed in Table 1.
1c
2a
3
Ti-N(3)
1.736(2)
1.366(3)
2.112(2)
2.106(2)
168.2(2)
64.06(7)
1.421(3)
1.407(3)
1.739(2)
1.351(3)
2.192(2)
2.203(2)
174.8(2)
60.93(8)
1.456(3)
1.396(3)
1.735(2)
1.368(2)
2.216(2)
2.228(2)
172.6(1)
60.36(6)
1.458(3)
1.456(3)
N(3)-N(4)
Ti-N(1)
Ti-N(2)
Ti-N(3)-N(4)
N(1)-Ti-N(2)
N(4)-C(13)
N(4)-C(14)a, C(12), C(19)
a C(14) for [Cp*Ti(NXylN)(NNMePh)(py)] (2a), C(12) for [Cp*Ti-
(NXylN)(NNMe2)(dmap)] (3), and C(19) for [Cp*Ti(NXylN)(NNPh2)]
(1c).
Nꢀ atom, the greater the donor capacity of the added donor
ligand had to be, in order to obtain monomeric complexes.
t
Reaction of [Cp*Ti(NXylN)(NtBu)(NH2 Bu)] with 1 molar
equiv of diphenylhydrazine and subsequent workup by precipi-
tation with hexane yielded the green diamagnetic hydrazinediido
Figure 3. Molecular structure of complex 3. Selected bond lengths
and angles are listed in Table 1.
t
complex [Cp*Ti(NXylN)(NNPh2)(NH2 Bu)] (1a). Its formulation
1
and proposed structure is supported by analytical and H, 13C,
(py)] (2a) and [Cp*Ti(NXylN)(NNMePh)(dmap)] (2b). Finally,
the isolation of a hydrazinediido compound from dimethylhy-
drazine [Cp*Ti(NXylN)(NNMe2)(dmap)] (3) required the pres-
ence of the strongest donor, dmap. Single-crystal X-ray structure
analyses of both 2a and 3 were carried out, and their molecular
structures are displayed in Figures 2 and 3, respectively.
and 15N NMR spectroscopic data. Apart from the hydrazinediide,
one molecule of tert-butylamine is coordinated to the metal
center as a neutral donor, which could be removed by heating
solid 1a at 60 °C for 72 h under a high vacuum (10-6 mbar),
yielding [Cp*Ti(NXylN)(NNPh2)] (1c). As for the starting
t
material [Cp*Ti(NXylN)(NtBu)(NH2 Bu)], the proton resonances
A comparative study of the metric parameters of three
hydrazinediido species with different Nꢀ substituents has been
recently reported by Mountford et al. for several titanium
complexes bearing calix(4)arenes as spectrator ligands.18 The
general trends established in this study are mirrored in the results
of the crystal structure analyses of the three complexes reported
in this work. The TidN bond lengths lie in a narrow range
between 1.735(2) Å (for 3) and 1.739(2) Å (for 2a), which is
very similar to previously reported TidN distances in terminal
titanium hydrazides (14 crystallographically characterized ex-
amples: min: 1.708; max: 1.759 Å; average: 1.728 Å).35 The
hydrazinediido units in 1c, 2a, and 3 deviate significantly from
linearity, which is attributed to the sterics of the Nꢀ substituents.
Consequently, the bending is greatest for the diphenylhydrazide
in 1c, the Ti-N(3)-N(4) angle being 168.2(2)°, whereas the
1-methyl-1-phenyl-substituted hydrazide(-2) is almost linear
[174.8(2)°]. The NR-Nꢀ distances of between 1.351(3) (for 2a)
and 1.368(2) Å (for 3) are also in the expected range (min:
1.344; max: 1.403 Å; average: 1.366 Å),35 which lies charac-
of the coordinated primary amine in compound 1a were not
observed in the H NMR spectrum recorded at 295 K due to
1
dissociative chemical exchange. However, upon cooling to 208
K, two doublet resonances at 7.20 and 1.67 with a geminal
coupling constant 2JH-H of 10 Hz emerged. The large difference
in chemical shifts is attributed to ring-current effects of the
aromatic rings in the molecule.
Upon attempting to obtain single crystals of 1a by slow
crystallization, the donor (amine)-free derivative [Cp*Ti-
(NXylN)(NNPh2)] (1c) was obtained and characterized by X-ray
diffraction. Its molecular structure is depicted in Figure 1, and
selected bond lengths and angles are listed in Table 1.
Compound 1c was also obtained on a preparative scale by
reaction of the tert-butylamine adduct 1a with B(C6F5)3 (Scheme
1). Furthermore, the orange pyridine adduct [Cp*Ti(NXylN)
(NNPh2)(py)] (1b) was obtained directly by reacting the imide
[Cp*Ti(NXylN)(NtBu)(NH2 Bu)] with diphenylhydrazine in the
t
presence of pyridine. The preparation of the mononuclear
hydrazinediido complexes derived from 1-methyl-1-phenylhy-
drazine was only possible in the presence of either pyridine or
4-dimethylaminopyridine (dmap) as neutral co-ligands, yielding
the two hydrazinediido complexes [Cp*Ti(NXylN)(NNMePh)-
(35) (a) Allen, F. H.; Kennard, O. Chem. Des. Automation News 1993,
8, 1–31. (b) Fletcher, D. A.; McMeeking, R. F.; Parkin, D. J. Chem. Inf.
Comput. Sci. 1996, 36, 746.

3384 Organometallics, Vol. 28, No. 12, 2009
Weitershaus et al.
Scheme 2. Stabilization of the Dimethylhydrazinediido Complex with Pyridine as Co-ligand Resulting in the Partial Formation
of the Dinuclear Compound 4b
teristically between the computed values for N-N single bonds
in hydrazido(-2)-ligands and N-N double bonds in formally
neutral isodiazene ligands.36 For early transition metals in high
oxidation states the hydrazido(-2) resonance formula is thought
best to represent the bonding situation,19,21,24,27 while DFT
studies on late transition metal complexes imply a greater weight
of the isodiazene resonance form.37
The sum of the angles at the Nꢀ atom in the dimethyl-
substituted complex 3 is 336.2°, indicating significant pyrami-
dalization. On the other hand, the Nꢀ atoms of the other two
compounds are close to planar, ∑( N) being 359.4° for
[Cp*Ti(NXylN)(NNPh2)] (1c) and 357.0° in [Cp*Ti(NXylN)-
(NNMePh)(py)] (2a). This has been attributed to conjugation
between the π-system of the phenyl rings and the lone pair on
the Nꢀ.18,24 Furthermore, in [Cp*Ti(NXylN)(NNMePh)(py)] (2a),
the N(4)-C(13) distance of the methyl groups is significant
greater (1.456(3) Å) than that of the Nꢀ-Ph bond [N(4)-C(14)
) 1.396(3) Å], which is attributed primarily to the difference
in hybridization at the C atoms.
two Ti centers. For the latter, the Nꢀ atom of the hydrazide is
coordinated with its lone pair to the Ti(1) atom, and this
additional Ti-Nꢀ distance of 2.230(2) Å corresponds to the
longest Ti-N bond in the molecule. Whereas both Ti-NR bond
lengths of the symmetrically bridging hydrazide(-2) are similar
[1.931(2) Å for Ti(2)-N(3) and 1.994(2) Å for Ti(1)-N(3)],
the Ti(2)-N(5) bond of the unsymmetrical bridging ligand
[1.809(2) Å] is significantly shorter than the Ti-NR bond to
the second metal center [Ti(1)-N(5) 2.040(2) Å]. To date, there
is only one other example of a crystallographically characterized
hydrazinediidotitanium complex containing a (µ-η1,η1-NNMe2)
and a (µ-η1,η2-NNMe2) ligand, which was reported by Leigh
et al. in 1986.38 All other structurally characterized Ti complexes
with bridging hydrazides(-2) have been found to possess
µ-η1,η2-coordination for both hydrazido ligands.6,10,19,39 The
capability of the 2-aminopyrrolinato ligands to liberate a
coordination site at the metal by transferring from a κ2 to a κ1
coordination mode is indicated by the observation of the latter
in the molecular structure of 4b in the crystal.
By addition of dmap to 4b, the dinuclear compound was
converted into the mononuclear complex 3. Furthermore, by
Upon replacement of dmap by the weaker donor ligand
pyridine in the synthesis of the dimethylhydrazinediido complex,
a mixture of two molecular species in a relative ratio of 2.8:1
was obtained (Scheme 2). Whereas the major product could be
characterized only in solution by 1H and 13C NMR spectroscopy,
which is consistent with its formulation as the pyridine adduct
[Cp*Ti(NXylN)(NNMe2)(py)] (4a), the analogue of the DMAP
complex 3, the minor component in this mixture, was identified
as the dinuclear complex [Cp*2Ti2(NXylN)2(µ-η1,η1-NNMe2)(µ-
η1,η2-NNMe2)] (4b).
Single crystals of 4b, which were suitable for X-ray diffrac-
tion, were obtained by cooling a solution in diethyl ether at
-18 °C. Its molecular structure is represented in Figure 4 along
with the principal bond lengths and angles.
The two metal centers in the dinuclear complex 4b are linked
by two bridging dimethylhydrazido ligands. One of the µ-hy-
drazido(-2) units adopts a symmetrically bridging arrangement,
while the second hydrazide is unsymmetrically bonded to the
Figure 4. Molecular structure of complex 4b. Selected bond lengths
(Å) and angles (deg): Ti(1)-N(1) 2.058(2), Ti(1)-N(3) 1.994(2),
Ti(1)-N(5) 2.040(2), Ti(1)-N(6) 2.230(2), Ti(1)-Cent(1) 2.110,
Ti(2)-N(3) 1.931(2), Ti(2)-N(5) 1.809(2), Ti(2)-N(7) 2.087(2),
Ti(2)-Cent(2) 2.105, N(3)-N(4) 1.395(2), N(5)-N(6) 1.384(2),
N(4)-C(23) 1.460 (3), N(4)-N(24) 1.446(3), N(6)-C(25) 1.475(3),
N(6)-C(26) 1.474(3), N(3)-Ti(1)-N(5) 80.60(7), N(3)-Ti(1)-N(6)
116.87(7), N(5)-Ti(1)-N(6) 37.51(7), N(5)-Ti(2)-N(3) 88.44(8),
Ti(2)-N(3)-Ti(1) 93.96(7), Ti(2)-N(5)-Ti(1) 96.22(8).
(36) Kahlal, S.; Saillard, J. Y.; Hamon, J. R.; Manzur, C.; Carrillo, D.
J. Chem. Soc., Dalton Trans. 1998, 1229–1240.
(37) (a) Stephan, G. C.; Sivasankar, C.; Studt, F.; Tuczek, F. Chem.sEur.
J. 2008, 14, 644–652. (b) Mersmann, K.; Horn, K. H.; Boeres, N.; Lehnert,
N.; Studt, F.; Paulat, F.; Peters, G.; Ivanovic-Burmazovic, I.; Van Eldik,
R.; Tuczek, F. Inorg. Chem. 2005, 44, 3031–3045. (c) Studt, F.; Tuczek,
F. Angew. Chem., Int. Ed. 2005, 44, 5639–5642. (d) Lehnert, N.; Tuczek,
F. Inorg. Chem. 1999, 38, 1671–1682.

Titanium Hydrazinediido Half-Sandwich Complexes
Organometallics, Vol. 28, No. 12, 2009 3385
Scheme 3. In Situ Synthesis of a Markovnikov Cycloaddition Product via [2 + 2] Cycloaddition of Phenylacetylene to the
Dimethylhydrazido Ligand
Table 2. Hydrohydrazination of Terminal Alkynes
addition of an excess of pyridine to 4b the mononuclear pyridine
isolated yielda
compound 4a was obtained quantitatively in solution. Treating
the latter under vacuum in an attempted isolation again resulted
in the partial formation of the dinuclear compound 4b. Complex
4a could therefore not be isolated and was characterized by 1H,
13C, and 15N NMR spectroscopy only in solution (Scheme 2).
In Situ Characterization of a {2 + 2} Cycloadduct of the
Hydrazinediido Complex 3 with Phenylacetylene. In contrast
to the {2 + 2} cycloadducts of group 4 metal imido complexes
with alkynes, which in many cases are sufficiently stable to be
isolated and fully characterized, the corresponding cycloaddition
products of hydrazinediides with alkynes tend to be thermally
unstable. Mountford and co-workers have recently reported the
spectroscopic characterization of such a species;22 however, also
in that case thermal degradation in solution prevented the growth
of single crystals for an X-ray diffraction study. Of the systems
reported in this work, only the stoichiometric reaction of the
dimethylhydrazinediido complex 3 with phenylacetylene gave
a cycloadduct of sufficient lifetime to allow its 1H, 13C,
and 15N NMR spectroscopic characterization in solution
(Scheme 3).
entry
alkyne
PhCCH
PhCCH
PhCCH
p-TolCCH
hydrazine
catalyst
1
2
3
4
5
6
7
8
Ph2N-NH2
1a
2a
3
1a
2a
3
1a
2a
3
1a
2a
3
1a
2a
3
1a
2a
99%
88%
99%
96%
96%
99%
90%
95%
98%
98%
95%
94%
86%
98%
94%
95%
95%
MePhN-NH2
Me2N-NH2
Ph2N-NH2
MePhN-NH2
Me2N-NH2
Ph2N-NH2
MePhN-NH2
Me2N-NH2
Ph2N-NH2
MePhN-NH2
Me2N-NH2
Ph2N-NH2
p-TolCCH
p-TolCCH
p-tBuC6H4CCH
p-tBuC6H4CCH
p-tBuC6H4CCH
p-MeOC6H4CCH
p-MeOC6H4CCH
p-MeOC6H4CCH
p-FC6H4CCH
p-FC6H4CCH
p-FC6H4CCH
1-Octyne
9
10
11
12
13
14
15
16
17
MePhN-NH2
Me2N-NH2
Ph2N-NH2
1-Octyne
MePhN-NH2
a Reaction conditions: alkyne (1.2 mmol), hydrazine (1.32 mmol), 5
mol % cat. in 2 mL of toluene, 25 °C, 1 h. Yields determined after
column chromatography.
derivatives, acetylene was converted to the corresponding
hydrazides at ambient temperature within 2 h.40 In a first study
into the performances of the titanium half-sandwich complexes
reported in this work as hydrohydrazination catalysts for alkynes
we initially focused on terminal alkynes as substrates. Depending
on the hydrazine employed for the particular reactions, com-
plexes 1a, 2a, and 3 were tested in this study. We note that
compounds 1b and 2b possess very similar catalytic properties
to 1a and 2a and give rise to the corresponding reaction products
with identical selectivities. However, since 1a and 2a were
obtained in higher preparative yields and according to somewhat
simpler protocols, only these have been systematically tested.
All three hydrazinediido compounds 1a, 2a, and 3 were found
to display remarkable catalytic activities even at ambient
temperature. For catalyst loadings of 5 mol % complete
conversions of the terminal alkynes were observed within
reaction times of 1 h. All catalytic runs were performed under
the same conditions to allow comparison of the different
substrates. Complete conversion was confirmed by GC analysis
before workup in all cases. The yields listed in Tables 2 and 3
refer to the isolated products after chromatographic purification.
Remarkable regioselectivity was observed in all transformations,
which were found to have >99% Markovnikov selectivity.
We studied the reactions of the three substituted hydrazine
derivatives, namely, diphenyl-, 1-methyl-1-phenyl-, and dime-
thylhydrazine, with a series of para-substituted terminal ary-
lacetylenes and, as an example of an aliphatic alkyne, 1-octyne.
Whereas two of the products were obtained in only moderate
yields of 86% and 88% (entries 2 and 13 in Table 2), all others
were isolated in excellent yields of well over 90%.
The NMR spectra are consistent with the selective formation
of the Markovnikov cycloaddition product 5. A characteristic
proton singlet signal at 9.68 ppm is assigned to the proton
bonded in the metallacyclic ring and is shifted to higher field
compared to the previously characterized metallacyclic com-
pounds derived from half-sandwich titanium imido compounds
and terminal acetylenes (TiCH 11.1 ppm).33 This trend has been
also observed by Mountford and co-workers for an anti-
Markovnikov cycloaddition product derived from a hydrazido
compound and a terminal alkyne (TiCdCH 9.47 ppm).22 In the
15N NMR spectra the NR resonance of the converted hydra-
zinediido ligand in 5 is detected at 267.6 ppm. The assignment
is based on the long-range coupling to the proton at 9.68 ppm
discussed above. The regioselective formation of 5 is consistent
with the results of the hydrohydrazination catalyses performed
with 3.
Application of the Hydrazinediidotitanium Complexes as
Catalysts for the Hydrohydrazination of Terminal Alkynes.
For all published hydrohydrazination protocols with titanium
or zinc catalysts, elevated reaction temperatures between 75 and
100 °C and reaction times between 2 and 75 h at catalyst
loadings of 2-10 mol % are the norm.6–8,10,11,13,40,41 Generally,
catalytic reactions of terminal alkynes with hydrazines proceeded
under milder reaction conditions. In contrast to its substituted
(38) Latham, I. A.; Leigh, G. J.; Huttner, G.; Jibril, I. J. Chem. Soc.,
Dalton Trans. 1986, 377–383.
(39) Pietryga, J. M.; Jones, J. N.; Macdonald, C. L. B.; Moore, J. A.;
Cowley, A. H. Polyhedron 2006, 25, 259–265.
(40) Cao, C.; Shi, Y.; Odom, A. L. Org. Lett. 2002, 4, 2853–2856.
(41) Johnson, J. S.; Bergman, R. G. J. Am. Chem. Soc. 2001, 123, 2923–
2924.
The limitations of the catalyst system became apparent in
the conversion of 1,2-diethynylbenzene. No conversion was

3386 Organometallics, Vol. 28, No. 12, 2009
Weitershaus et al.
Table 3. Hydrohydrazination of Dialkynes
and glovebox techniques. Solvents were predried over molecular
sieves and then dried over Na/K alloy (pentane, diethyl ether), Na
(toluene), or K (THF, hexane), distilled, and stored over potassium
mirrors in Teflon-valve ampoules. Deuterated solvents were dried
over K (benzene-d6, toluene-d8), vacuum distilled, and stored under
argon in Teflon-valve ampoules. The protioligand NXylNH32 and
the starting materials [Cp*Ti(NXylN)Me2]33 and [Cp*Ti(NXylN)-
(NtBu)(NH2 Bu)] as well as the substrates 1,2-ethynylbenzene42
and 1,3-ethynylbenzene42 were prepared as previously described.
The 1,1-disubstituted hydrazines were dried over CaH2, vacuum
distilled, and stored in Teflon valve ampoules before use. All other
reagents were purchased from commercial suppliers and used as
received unless otherwise stated. Samples for NMR spectroscopy
were prepared under argon in 5 mm Wilmad tubes equipped with
J. Young Teflon valves. NMR spectra were recorded on Bruker
Avance II 400 or Bruker Avance III 600 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 NH3(l) (15NH3). Where necessary, NMR assignments
were confirmed by the use of two-dimensional 1H-1H and 1H-13C
correlation experiments. 15N NMR data were obtained by two-
dimensional 1H-correlated experiments or by direct detection using
a cryogenically cooled direct-detection NMR probe (QNP Cryo-
Probe). Microanalyses were performed by the analytical services
in the chemistry department of the Universita¨t Heidelberg. IR
spectra were recorded on a Varian 3100 Excalibur spectrometer as
33
t
a Reaction conditions: alkyne (0.6 mmol), hydrazine (1.32 mmol), 5
mol % catalyst dissolved in 2 mL of toluene, 25 °C, 1 h. Yields
determined after column chromatography. b Reaction conditions: alkyne
(0.6 mmol), hydrazine (1.32 mmol), 5 mol % cat. in 2 mL of toluene,
105 °C, 24 h.
KBr plates. Infrared data are quoted in cm-1
.
(A) Preparation of the Compounds. [Cp*Ti(NXylN)
(NNPh2)(tBuNH2)] (1a). To
a
solution of [Cp*Ti(NXylN)-
observed on stirring this compound for 1 h at ambient
temperature with either of the three hydrazines introduced above
in the presence of the respective catalyst. Likewise, heating the
reactants at 105 °C for 24 h and subsequent workup only led to
the almost quantitative reisolation of the hydrazines. The
nonreactivity of 1,2-diethynylbenzene in the attempted hydro-
hydrazination is probably due to steric constraints of the two
ethynyl units which are in close proximity. This interpretation
is consistent with the observation that 1,3-ethynylbenzene was
converted to the respective hydrazones in reactions with all three
hydrazine derivatives at ambient temperature and a reaction time
of 1 h. However, the yield varied somewhat more strongly than
for the previously described terminal monoacetylenes (entries
4-6, Table 3). As an example of an aliphatic diyne, 1,7-
octadiyne was tested and readily converted under the mild
conditions employed for the other substrates (again with >99%
Markovnikov selectivity). For diphenylhydrazine the isolated
yield of the corresponding reaction product was 97% (entry 7,
Table 3), whereas the product derived from 1-methyl-1-
phenylhydrazine was only obtained in 71% yield (entry 8,
Table 3).
(NtBu)(NH2 Bu)] (1 g, 2 mmol) in hexane (5 mL) was added
diphenylhydrazine (2 mmol). The solution was stirred at room
temperature for 30 min, at which stage precipitation of the
product set in. The green microcrystalline solid was isolated by
filtration and dried under reduced pressure. Isolated yield: 90%
t
1
(1.1 g, 1.8 mmol). H NMR (600.1 MHz, benzene-d6, 295 K): δ
1.07 (s, 9 H, NH2-C(CH3)2), 1.54 (br m, 2 H, NCH2CH2), 1.95 (s,
15 H, C5Me5), 2.11 (br m, 1 H, NCCH2), 2.28 (s, 6 H, C6H3Me2),
2.41 (br m, 1 H, NCCH2), 3.54 (br m, 1 H, NCH2), 3.68 (br m, 1
H, NCH2), 6.62 (s, 1 H, para-C6H3Me2), 6.68 (s, 2 H, ortho-
3
C6H3Me2), 6.85 (tr, JH-H ) 7.2 Hz, 2 H, para-Ph), 7.19-7.15
3
(m, 4 H, meta-Ph), 7.29 (d, JH-H ) 8.0 Hz, 4 H, ortho-Ph) ppm.
13C{1H} NMR (150.9 MHz, benzene-d6, 295 K): δ 11.4 (C5Me5),
21.7 (C6H3Me2), 24.8 (NCH2CH2), 29.8 (NCCH2), 31.8
(NH2-C(CH3)3), 49.1 (NH2-C(CH3)3), 55.2 (NCH2), 119.1 (C5Me5),
119.7 (ortho-Ph), 122.6 (ortho-C6H3Me2), 121.8 (para-Ph), 123.3
(para-C6H3Me2), 128.9 (meta-Ph), 138.2 (meta-C6H3Me2), 146.6
(ipso-Ph), 151.2 (ipso-C6H3Me2), 164.2 (br, NCN) ppm. 1H NMR
(399.9 MHz, toluene-d8, 208 K): δ 1.08 (s, 9 H, NH2-C(CH3)2);
2
1.59-1.49 (m, 2 H, NCH2CH2), 1.67 (d, JH-H ) 10 Hz, 1 H,
t
NH2 Bu), 1.93 (s, 15 H, C5Me5), 2.18-2.13 (m, 1 H, NCCH2),
2.30-2.20 (m, 1 H, NCCH2), 2.36 (s, 6 H, C6H3Me2), 3.63-3.53
(m, 1 H, NCH2), 4.07-4.00 (m, 1 H, NCH2), 6.60 (s, 1 H,
Conclusion
3
para-C6H3Me2), 6.73 (s, 2 H, ortho-C6H3Me2), 6.90 (tr, JH-H
)
In this work we have presented a simple and convenient
access to a new class of hydrazinediido-titanium half-sandwich
complexes, which have proven to be hydrohydrazination
catalysts for terminal alkynes that are active at ambient
temperature. To what extent the flexibility in the coordination
of the otherwise robust 2-aminopyrrolinato ligand plays a role
remains to be established. Extending the development of this
class of catalysts to the heavier group 4 metals and to assess
their capabilities in multicomponent reactions involving hydra-
zinediido intermediates will be investigated in future studies.
7.0 Hz, 2 H, para-Ph), 7.26-7.17 (m, 9 H, ortho- and meta-Ph
and NH2 Bu) ppm. 13C{1H} NMR (100.6 MHz, toluene-d8, 208
t
K): δ 11.6 (C5Me5), 24.0 (C6H3Me2), 26.0 (NCH2CH2), 30.3
(NCCH2), 30.7 (NH2-C(CH3)3), 50.8 (NH2-C(CH3)3), 58.0 (NCH2),
117.2 (C5Me5), 120.2 (ortho- or meta-Ph), 120.8 (ortho-C6H3Me2),
122.0 (para-Ph), 122.7 (para-C6H3Me2), 128.7 (ortho- or meta-
Ph), 138.0 (meta-C6H3Me2), 146.5 (ipso-Ph), 153.4 (ipso-
C6H3Me2), 173.1 (NCN) ppm. 15N NMR (60.8 MHz, benzene-d6,
t
295 K): δ 72.5 (NH2 Bu), 188.5 (TidN-NPh2), 201.6 (NCNXyl),
318.4 (TidN-NPh2) ppm, (NCNXyl) not obsd. IR (KBr plates,
cm-1): 2960.8 (m), 2911.2 (m), 2861.1 (m), 1594.4 (s), 1588.0
(s), 1550.1 (s), 1489.1 (s), 1374.7 (s), 1310.5 (s), 1261.0 (s).
Experimental Section
All manipulations of air- and moisture-sensitive compounds were
performed under an atmosphere of argon using standard Schlenk
(42) Zeidan, T. A.; Kovalenko, S. V.; Manoharan, M.; Alabugin, I. V.
J. Org. Chem. 2006, 71, 962–975.

Titanium Hydrazinediido Half-Sandwich Complexes
Organometallics, Vol. 28, No. 12, 2009 3387
Anal. Found (calcd for C38H51N5Ti): C, 72.4 (72.9); H, 8.2 (8.2);
N, 11.2 (11.2).
respective hydrazine (1 equiv) was added, and the solution was
stirred at room temperature for 30 min. The hydrazinediido compounds
started to precipitate as orange or red solids at that point, and after
stirring for another 1 h at room temperature, the supernatant solution
was removed by filtration and the isolated solid was dried in Vacuo.
Isolated yields of the reaction products: [Cp*Ti(NXylN)(NNMePh)(py)]
(2a) 605 mg (1.06 mmol, 74%), [Cp*Ti(NXylN)(NNMePh)(dmap)]
(2b) 414 mg (0.67 mmol, 68%), [Cp*Ti(NXylN)(NNMe2)(dmap] (3)
176 mg (0.32 mmol, 62%).
[Cp*Ti(NXylN)(NNPh2)(Py)] (1b). To
a
solution of
[Cp*Ti(NXylN)(NtBu)(NH2 Bu)] (452 mg, 0.89 mmol) in hexane
(5 mL) pyridine (72 µL, 0.89 mmol), dissolved in 1 mL of hexane,
was added. Diphenylhydrazine (164 mg, 0.89 mmol) was added
and the solution was stirred at room temperature for 30 min. The
hydrazinediido compound started to precipitate as an orange solid
at that point, and after stirring for another 1 h at room temperature,
the supernatant solution was removed by filtration and the isolated
solid was dried in Vacuo. The product was obtained in 76% yield
(476 mg, 0.67 mmol). 1H NMR (399.9 MHz, benzene-d6, 295 K):
δ 1.60 (br m, 2 H, NCH2CH2), 1.90 (s, 15 H, C5Me5), 2.23 (s, 6 H,
C6H3Me2), 3.53 (br m, 2 H, NCH2), 6.55-6.55 (m, 2 H, meta-
C5H5N), 6.61 (s, 1 H, para-C6H3Me2), 6.90-6.81 (m, 5 H,
overlapping para-Ph, para-C5H5N, ortho-C6H3Me2), 7.17-7.13 (m,
4 H, meta-Ph, overlapping with benzene-d6), 7.36 (d, 3JH-H ) 8.0
Hz, 4 H, ortho-Ph), 8.57 (m, 2 H, ortho-C5H5N) ppm, (NCCH2)
not obsd. 13C{1H} NMR (100.6 MHz, benzene-d6, 295 K): δ 11.6
(C5Me5), 21.6 (C6H3Me2), 23.9 (NCH2CH2), 29.4 (NCCH2), 54.0
(NCH2), 118.7 (C5Me5), 119.5 (ortho-Ph), 121.8 (ortho-C6H3Me2),
122.4 (para-Ph), 123.4 (meta-C5H5N), 123.7 (para-C6H3Me2), 129.0
(meta-Ph), 135.8 (para-C5H5N), 138.0 (meta-C6H3Me2), 147.0
(ipso-Ph), 151.2 (ipso-C6H3Me2), 151.2 (ortho-C5H5N), 169.3
(NCN) ppm. 15N NMR (60.8 MHz, benzene-d6, 295 K): δ 172.5
(NCNXyl or NCNXyl), 182.4 (NCNXyl or NCNXyl), 199.7 (TidN-
NPh2), 293.5 (C5H5N), 332.8 (TidN-NPh2) ppm. IR (KBr plates,
cm-1): 2960.6 (m), 2912.1 (m), 2854.3 (m), 1593.9 (s), 1585.5 (s),
1532.4 (s), 1487.1 (s), 1441.0 (m), 1313.2 (m), 1290.2 (m), 1169.2
(m), 1024.5 (m). Anal. Found (calcd for C39H45N5Ti): C, 74.5 (74.2);
H, 7.1 (7.2); N, 10.7 (11.1).
t
[Cp*Ti(NXylN)(NNMePh)(py)] (2a). Suitable crystals for X-ray
diffraction were grown from a concentrated hexane solution at -18
°C. 1H NMR (399.9 MHz, benzene-d6, 295 K): δ 1.68-1.61 (m, 2
H, NCH2CH2), 1.99 (s, 15 H, C5Me5), 2.21 (s, 6 H, C6H3Me2),
2.50-2.21 (br, 2 H, NCCH2), 3.47 (s, 3 H, NMePh), 3.71-3.25
(br 2 H, NCH2), 6.48-6.45 (m, 2 H, meta-C5H5N), 6.58 (s, 1 H,
para-C6H3Me2), 6.63 (tr, 3JH-H ) 7.2 Hz, 1 H, para-C5H5N), 6.78
(s, 2 H, ortho-C6H3Me2, overlapping with para-Ph), 6.81-6.78 (m,
1 H, para-Ph, overlapping with ortho-C6H3Me2), 6.93 (d, 3JH-H
)
8.1 Hz, 2 H, ortho-Ph), 7.14-7.10 (m, 2 H, overlapping with
benzene-d6, meta-Ph), 8.53 (d, 3JH-H ) 4.7 Hz, 2 H, ortho-C5H5N)
ppm. 13C{1H} NMR (100.6 MHz, benzene-d6, 295 K): δ 12.1
(C5Me5), 21.6 (C6H3Me2), 23.9 (NCH2CH2), 29.4 (NCCH2), 41.5
(NMePh), 54.0 (NCH2), 110.7 (ortho-Ph), 117.0 (para-C5H5N),
117.5 (C5Me5), 122.4 (ortho-C6H3Me2), 123.3 (meta-C5H5N), 123.4
(para-C6H3Me2), 128.8 (meta-Ph), 136.2 (para-Ph), 137.6 (meta-
C6H3Me2), 148.1 (ipso-Ph), 151.3 (ipso-C6H3Me2), 152.2 (ortho-
C5H5N), 169.7 (NCN) ppm. 15N NMR (60.8 MHz, benzene-d6, 295
K): δ 172.0 (NCN-Xyl), 180.2 (TidN-NMePh), 290.2 (NC5H5),
340.0 (TidN-NMePh) ppm, (NCN-Xyl) not obsd. IR (KBr plates,
cm-1): 2960.3 (m), 2906.2 (m), 2854.4 (m), 1598.8 (s), 1544.8 (s),
1489.8 (s), 1441.0 (s), 1324.7 (m), 1287.8 (s), 1174.1 (m), 1088.0
(w). Anal. Found (calcd for C34H43N5Ti): C, 71.3 (71.7); H, 7.6
(7.6); N, 12.2 (12.3).
[Cp*Ti(NXylN)(NNPh2)] (1c). To
a stirred solution of
[Cp*Ti(NXylN)(NNPh2)(tBuNH2)] (1a) (135 mg, 0.26 mmol) in
hexane (5 mL) B(C6F5)3 (133 mg, 0.26 mmol) was added at room
temperature. Immediately, an oily black precipitate formed, and
the mixture was stirred an hour at room temperature. The
supernatant solution was subsequently removed by filtration, and
all volatiles, were removed in Vacuo. The residue was triturated in
pentane, and the supernatant solution was removed by filtration
from the undissolved oily precipitate. The extract was evaporated
to dryness, yielding analytically pure [Cp*Ti(NXylN)(NNPh2)] (1c)
in 49% yield. (72 mg, 0.13 mmol). Suitable crystals for X-ray
diffraction were obtained from a concentrated hexane solution at
[Cp*Ti(NXylN)(NNMePh)(dmap)] (2b). 1H NMR (600.1 MHz,
benzene-d6, 295 K): δ 1.79-1.74 (NCH2CH2), 2.04 (s, 6 H,
NC5H4NMe2), 2.13 (s, 15 H, C5Me5), 2.23 (s, 6 H, C6H3Me2),
2.28-2.12 (br m, 1 H, NCCH2), 2.64 (br m, 1 H, NCCH2),
3.67-3.52 (m, 2 H, NCH2), 3.66 (s, 3 H, s, NMePh), 5.80 (br s, 2
H, meta-NC5H4NMe2), 6.58 (s, 1 H, para-C6H3Me2), 6.59 (m, 1
H, para-Ph), 6.89 (br s, 2 H, ortho-C6H3Me2), 7.12-7.05 (m, 4 H,
3
ortho-Ph and meta-Ph), 8.33 (d, JH-H ) 4.2 Hz, 2 H, ortho-
NC5H4NMe2) ppm. 13C{1H} NMR (150.9 MHz, benzene-d6, 295
K): δ 12.6 (C5Me5), 21.7 (C6H3Me2), 23.8 (NCH2CH2), 29.4
(NCCH2), 38.0 (NC5H4NMe2), 41.8 (NMePh), 54.3 (NCH2), 105.8
(meta-NC5H4NMe2), 110.5 (ortho- or meta-Ph), 116.3 (C5Me5),
116.6 (para-Ph), 119.2 (ortho-C6H3Me2), 123.6 (para-C6H3Me2),
128.8 (ortho- or meta-Ph), 137.3 (meta-C6H3Me2), 148.4 (ipso-
Ph), 152.2 (ortho-NC5H4NMe2), 152.4 (ipso-C6H3Me2), 153.9
(para-NC5H4NMe2), 171.6 (NCN) ppm. 15N NMR (60.8 MHz,
benzene-d6, 295 K): δ 57.9 (NC5H4NMe2), 183.3 (NCNXyl), 180.4
(TidN-NMePh), 245.8 (NC5H4NMe2), 345.4 (TidN-NMePh) ppm,
(NCNXyl) not obsd. IR (KBr plates, cm-1): 2944.4 (m), 2906.2
(m), 2853.2 (m), 1607.8 (s), 1543.1 (s), 1489.3 (s), 1291.8 (m),
1225.3 (m), 1006.7 (m). Anal. Found (calcd for C36H48N6Ti): C,
70.8 (70.6); H, 8.0 (7.9); N, 13.4 (13.7).
1
-18 °C. H NMR (399.9 MHz, benzene-d6, 295 K): δ 1.55-1.47
(m, 2 H, NCH2CH2), 1.94 (s, 15 H, C5Me5), 1.99-1.90 (m, 2 H,
NCCH2, overlapping with C5Me5), 2.25 (s, 6 H, C6H3Me2),
3.58-3.54 (m, 2 H, NCH2), 6.60 (s, 2 H, ortho-C6H3Me2), 6.62
3
(br s, 1 H, para-C6H3Me2), 6.82 (tr, JH-H ) 7.2 Hz, 2 H, para-
Ph), 7.17-7.15 (m, 4 H, meta-Ph, overlapping with benzene-d6),
7.34 (d, 3JH-H ) 7.8 Hz, 4 H, ortho-Ph) ppm. 13C{1H} NMR (100.6
MHz, benzene-d6, 295 K): δ 11.3 (C5Me5), 21.6 (C6H3Me2), 24.1
(NCH2CH2), 28.1 (NCCH2), 53.8 (NCH2), 118.1 (ortho-Ph), 119.2
(br, para-C6H3Me2 and C5Me5), 120.2 (para-Ph), 123.7 (ortho-
C6H3Me2), 128.1 (meta-Ph, overlapping with benzene-d6), 138.4
(meta-C6H3Me2), 147.3 (br, ipso-C6H3Me2 or ipso-Ph), 148.9 (br,
ipso-C6H3Me2 or ispo-Ph) ppm, (NCN) not obsd. 15N NMR (60.8
MHz, benzene-d6, 295 K): δ 174.5 (NCNXyl), 330.6 (TidN-NPh2)
ppm, (NCNXyl), (TidN-NPh2) not obsd. IR (KBr plates, cm-1):
2960.3 (w), 2909.7 (m), 2856.9 (w), 1592.9 (s), 1489.1 (s), 1375.0
(m), 1290.5 (s), 1275.1 (s), 1263.1 (s), 1185.2 (m), 1166.8 (m),
1101.2 (m), 1073.0 (m), 1025.6 (m), 838.9 (m), 788.3 (s), 745.0
(s), 691.7 (s). Anal. Found (calcd for C34H40N4Ti): C, 73.2 (73.9);
H, 7.6 (7.30); N, 9.8 (10.1).
[Cp*Ti(NXylN)(NNMe2)(dmap)] (3). Suitable crystals for X-ray
diffraction were grown from a concentrated hexane solution at -18
1
°C. H NMR (600.1 MHz, benzene-d6, 295 K): δ 1.74-1.66 (br
m, 2 H, NCH2CH2), 2.13 (s, 21 H, C5Me5 and NC5H4NMe2), 2.34
(s, 6 H, C6H3Me2), 2.52-2.39 (br m, 2 H, NCCH2), 2.79 (s, 6 H,
NMe2), 3.74-3.58 (br m, 2 H, NCH2), 5.97 (d, 3JH-H ) 5.9 Hz, 2
H, meta-NC5H4NMe2), 6.56 (s, 1 H, para-C6H3Me2), 7.02 (br s, 2
3
H, ortho-C6H3Me2), 8.59 (d, JH-H ) 4.9 Hz, 2 H, ortho-
General Procedure for the Synthesis of the Hydrazinediido
Complexes 2a, 2b, and 3. To a solution of [Cp*Ti(NXylN)-
(NtBu)(NH2tBu)] (1 equiv) in hexane (5 mL) the donor (pyridine or
dmap 1 equiv) dissolved in 1 mL of toluene was added. The
NC5H4NMe2) ppm. 13C{1H} NMR (150.9 MHz, benzene-d6, 295
K): δ 12.2 (C5Me5), 21.7 (C6H3Me2), 24.3 (NCH2CH2), 29.7
(NCCH2), 38.2 (NC5H4NMe2), 49.1 (NMe2), 105.9 (meta-
NC5H4NMe2), 115.9 (C5Me5), 122.3 (para-C6H3Me2), 122.6 (ortho-

3388 Organometallics, Vol. 28, No. 12, 2009
Weitershaus et al.
Table 4. Details of the Crystal Structure Determinations of the Complexes 1c, 2a, 3, and 4
1c 2a
3
4
formula
cryst syst
space group
C34H40N4Ti
monoclinic
P21/n
C34H43N5Ti
monoclinic
P21/n
C31H46N6Ti
triclinic
P1
C53H84N8Ti2
monoclinic
P21/n
j
a/Å
b/Å
c/Å
14.6088(15)
11.0619(11)
19.2644(19)
11.483(2)
17.855(3)
15.233(3)
11.1384(13)
11.9027(14)
12.5326(15)
89.894(2)
88.023(2)
66.001(2)
1516.9(3)
2
10.5635(13)
16.591(2)
29.458(4)
R/deg
ꢀ/deg
108.926(2)
92.644(4)
96.168(2)
γ/deg
V/Å3
2944.8(5)
4
3120.0(10)
4
5132.9(11)
4
Z
Mr
552.60
1.246
1176
569.63
1.213
1216
550.64
1.206
592
929.08
1.202
2008
dc/Mg · m-3
F000
µ(Mo KR)/mm-1
max., min transmn factors
X-radiation, λ/Å
θ range/deg
index ranges (indep set) h,k,l
reflns measd
unique [Rint]
observed [I g 2σ(I)]
params refined
1.246
0.7464, 0.6908
0.305
0.312
0.7464, 0.6908
0.354
0.7456, 0.6923
0.7464, 0.6598
Mo KR, graphite monochromated, 0.71073
2.1 to 27.5 1.6 to 30.0
2.1 to 29.6
1.4 to 27.6
-20... 19, 0... 15, 0... 26 -14... 14, 0... 23, 0... 19 -15... 15, -16... 16, 0... 17 -13... 13, 0... 21, 0... 38
68 100
8261 [0.0868]
5223
62 584
7153 [0.0940]
4572
35 412
8860 [0.0546]
6105
103 733
11 856 [0.0768]
8206
359
369
354
541
R indices [F > 4σ(F)] R(F), wR(F2) 0.0472, 0.1011
0.0484, 0.1078
0.1073, 0.1444
1.069
0.0456, 0.1017
0.0855, 0.1254
1.031
0.0478, 0.1222
0.0828, 0.1383
1.065
R indices (all data) R(F), wR(F2)
GooF on F2
0.1082, 0.1403
1.114
0.491, -0.467
largest residual peaks/e · Å-3
0.450, -0.623
0.429, -0.382
1.242, -0.426
C6H3Me2), 137.3 (meta-C6H3Me2), 151.9 (br, ortho-NC5H4NMe2
and ipso-C6H3Me2), 154.0 (para-NC5H4NMe2), 171.9 (NCN) ppm,
(NCH2) not obsd. 15N NMR (60.8 MHz, benzene-d6, 295 K): δ
56.5 (NC5H4NMe2), 251.3 (NC5H4NMe2), 379.9 (TidN-NMe2) ppm,
(TidN-NMe2), (NCNXyl) and (NCNXyl) not obsd. IR (KBr plates,
cm-1): 2962.9 (w), 2910.9 (w), 2856.4 (w), 1602.9 (2), 1536.8 (m),
1444.8 (m), 1226.3 (m), 789.1 (s). Anal. Found (calcd for
C31H46N6Ti): C, 67.5 (67.6); H, 8.5 (8.4); N, 14.6 (15.3).
(NCH2), 120.8 (ortho-C6H3Me2), 122.5 (para-C6H3Me2), 122.6
(C5Me5), 137.9 (meta-C6H3Me2), 155.3 (ipso-C6H3Me2), 171.5
(NCN) ppm. IR (KBr plates, cm-1): 2955.9 (m), 2910.5 (m), 2859.2
(m), 1608.0 (sh), 1577.6 (s), 1450.7 (w), 1353.2 (w), 1261.3 (m),
1247.8 (m), 1159.1 (w). Anal. Found (calcd for C48H72N8Ti2 + 1
equiv pentane): C, 68.3 (68.5); H, 9.1 (9.1); N, 11.9 (12.0).
[Cp*Ti(NXylN){K2N(NMe2)CPhdCH}] (5). [Cp*Ti(NXylN)-
(NNMe2)(dmap)] (3) (40 mg, 0.07 mmol) was dissolved in toluene-
d8 (0.5 mL) and cooled to -78 °C. Phenylacetylene (8 µL, 0.07
mmol) was then added, leading to an immediate change of color
from red to deep brown. The NMR spectra were recorded within
2 h after the in situ preparation. 1H NMR (600.1 MHz, toluene-d8,
295 K): δ 1.45-1.41 (m, 1 H, NCH2CH2), 1.52-1.46 (m, 1 H,
NCH2CH2), 1.96 (s, 15 H, C5Me5), 2.14 (s, 6 H, C6H3Me2,
overlapping with NCCH2), 2.17-2.12 (m, 2 H, NCCH2, overlapping
with C6H3Me2), 2.83 (br s, 3 H, NMe2), 3.30-3.20 (m, 2 H, NCH2),
6.23 (s, 1H, para-C6H3Me2), 6.39 (s, 2 H, ortho-C6H3Me2),
7.08-7.02 (m, 3 H, meta- and para-Ph), 7.81 (d, 3JH-H ) 7.2 Hz,
2 H, ortho-Ph), 9.68 (s, 1 H, CdCH) ppm. 13C{1H} NMR (150.9
MHz, toluene-d8, 295 K): δ 12.4 (C5Me5), 21.5 (C6H3Me2), 24.2
(NCH2CH2), 31.2 (NCCH2), 52.8 (NCH2), 53.2 (NMe2, br), 53.4
(NMe2, br), 118.3 (C5Me5), 120.2 (ortho-C6H3Me2), 121.8 (para-
C6H3Me2), 124.6 (overlapping with toluene-d8, meta- or para-Ph),
127.2 (ortho-Ph), 127.5 (meta- or para-Ph), 131.1 (ipso-C6H5),
136.7 (meta-C6H3Me2), 138.2 (CdCH), 149.3 (ipso-C6H3Me2),
167.3 (br, CdCH), 174.0 (NCN) ppm. 15N NMR (60.8 MHz,
toluene-d8, 295 K): δ 172.3 (NCNXyl), 267.6 (TidN-NPh2) ppm,
(TidN-NPh2), (NCN-Xyl) not obsd.
(B) General Procedure for the Intermolecular Hydrohydrazi-
nation of Terminal Alkynes. A Schlenk tube equipped with a
Teflon stopcock and a magnetic stirring bar was charged with the
terminal alkyne (1.2 mmol for monoalkyne and 0.6 mmol for
dialkyne), the hydrazine (1.32 mmol), and the catalyst (0.06 mmol,
5 mol %) dissolved in 2 mL of toluene. The resulting mixture was
stirred for 1 h at room temperature. At that stage the complete
conversion of the starting materials was confirmed by GC analysis.
The reaction mixture was subsequently filtered through a pad of
silica and washed with diethyl ether. After removing all volatiles
the crude product was subjected to column chromatography.
X-ray Crystal Structure Structure Determinations. Crystal
data and details of the structure determinations are listed in Table
[Cp*Ti(NXylN)(NNMe2)(py)] (4a) and [Cp*Ti(NXylN)-
(NNMe2)]2 (4b). Using pyridine for the stabilization of the
mononuclear dimethylhydrazinediido complex in the synthesis of
[Cp*Ti(NXylN)(NNMe2)(py)] (4a) gave a mixture of two com-
pounds in a 2.8:1 ratio. Single crystals of the minor compound,
which proved to be a dinuclear complex, were obtained from a
concentrated pentane solution at -18 °C and were used for the
X-ray diffraction study (Vide infra). The major component was
characterized in solution by NMR spectroscopy.
[Cp*Ti(NXylN)(NNMe2)(py)] (4a). 1H NMR (600.1 MHz, ben-
zene-d6, 295 K): δ 1.68-1.64 (m, 2 H, NCH2CH2), 2.00 (s, 15 H,
C5Me5), 2.30 (s, 6 H, C6H3Me2), 2.32-2.24 (br m, 2 H, NCCH2,
overlapping with C6H3Me2), 2.72 (s, 6 H, NMe2), 2.83-2.69 (br
m, 2 H, NCH2, overlapping with NMe2), 6.65-6.63 (m, 3 H, para-
C6H3Me2 and meta-C5H5N), 6.94-6.91 (m, 3 H, ortho-C6H3Me2
3
and para-C5H5N), 8.65 (d, JH-H ) 4.4 Hz, 2 H, ortho-C5H5N)
ppm. 13C{1H} NMR (150.9 MHz, benzene-d6, 295 K): δ 12.0
(C5Me5), 21.4 (C6H3Me2), 23.7 (NCH2CH2), 29.4 (NCCH2), 49.0
(NMe2), 55.2 (NCH2), 115.9 (C5Me5), 122.4 (para-C6H3Me2), 122.5
(ortho-C6H3Me2), 122.7 (meta-C5H5N), 135.5 (para-C5H5N), 137.1
(meta-C6H3Me2), 151.2 (ortho-C5H5N), 152.0 (ipso-C6H3Me2),
171.3 (NCN) ppm. 15N NMR (60.8 MHz, benzene-d6, 295 K): δ
155.0 (TidN-NMe2), 303.6 (C5H5N), 380.1 (TidN-NMe2) ppm,
(NCN-Xyl), (NCN-Xyl) not obs.
[Cp*Ti(NXylN)(NNMe2)]2 (4b). 1H NMR (600.1 MHz, benzene-
d6, 295 K): δ 1.65-1.53 (br m, 4 H, NCH2CH2), 2.11 (br s, 30 H,
C5Me5), 2.32-2.23 (br m, 4 H, NCCH2), 2.38 (s, 12 H, C6H3Me2),
2.51-2.46 (br m, 4 H, NCCH2), 2.83 (s, 6 H, NMe2), 3.12-3.02
(br m, 2 H, NCH2), 3.35-3.26 (br m, 1 H, NCH2), 3.38 (s, 6 H,
NMe2), 3.55-3.50 (br m, 1 H, NCH2), 6.69 (br s, 2 H, para-
C6H3Me2), 6.79 (br s, 4 H, ortho-C6H3Me2) ppm. 13C{1H} NMR
(150.9 MHz, benzene-d6, 295 K): δ 13.3 (C5Me5), 21.9 (C6H3Me2),
25.4 (NCH2CH2), 29.8 (NCCH2), 54.2 (NMe2), 54.6 (NMe2), 59.4

Titanium Hydrazinediido Half-Sandwich Complexes
Organometallics, Vol. 28, No. 12, 2009 3389
4. Intensity data were collected at 100(2) K with a Bruker AXS
Smart 1000 CCD diffractometer (Mo KR radiation, graphite
monochromator, λ ) 0.71073 Å). Data were corrected for air and
detector absorption and Lorentz and polarization effects;43 absorp-
tion by the crystal was treated with a semiempirical multiscan
method.44,45
hydrogen atoms were given anisotropic displacement parameters.
Hydrogen atoms were placed at calculated positions and refined
with a riding model. Due to severe disorder, electron density
attributed to solvent of crystallization (pentane) was removed from
the structures (and the corresponding Fobs) of 4 with the SQUEEZE
procedure,50 as implemented in PLATON.51
The structures were solved by the heavy atom method combined
with structure expansion by direct methods applied to difference
structure factors46 (complexes 1c, 2a, and 3) or by the charge flip
procedure47,48 (complex 4) and refined by full-matrix least-squares
methods based on F2 against all unique reflections.49 All non-
Acknowledgment. We thank the Deutsche Forschungs-
gemeinschaft for funding (SFB 623) and Anna-Maria Lo¨hr
for help with the catalysis studies.
Supporting Information Available: Characterization data of
the hydrazones obtained in the catalysis and crystallographic
information in CIF format. This material is available free of charge
via the Internet at http://pubs.acs.org.
(43) SAINT; Bruker AXS, 2007.
(44) Blessing, R. H. Acta Crystallogr. 1995, A51, 33–38.
(45) Sheldrick, G. M. SADABS; Bruker AXS, 2004-2008.
(46) Beurskens, P. T. In Crystallographic Computing 3; Sheldrick, G. M.,
Kru¨ger, C., Goddard, R., Eds.; Clarendon Press: Oxford, UK, 1985; p 216.
Beurskens, P. T.; Beurskens, G.; de Gelder, R.; Smits, J. M. M.; Garcia-
Granda, S.; Gould, R. O. DIRDIF-2008; Radboud University Nijmegen:
The Netherlands, 2008.
(47) (a) Oszla´nyi, G.; Su¨to¨, A. Acta Crystallogr. 2004, A60, 134–141.
(b) Oszla´nyi, G.; Su¨to¨, A. Acta Crystallogr. 2005, A61, 147–152.
(48) Palatinus, L.; Chapuis, G. J. Appl. Crystallogr. 2007, 40, 786.
PalatinusL. SUPERFLIP; EPF Lausanne: Switzerland, 2007.
OM900155T
(49) Sheldrick, G. M. Acta Crystallogr. 2008, A64, 112–122. Sheld-
rickG. M. SHELXL-97; University of Go¨ttingen, 1997.
(50) Sluis, P. v. d.; Spek, A. L. Acta Crystallogr. 1990, A46, 194–201.
(51) Spek, A. L. J. Appl. Crystallogr. 2003, 36, 7–13. Spek, A. L.
PLATON; Utrecht University: The Netherlands.