A zirconium hydrazide as a synthon for a metallanitrene equivalent: Atom-by-atom assembly of [EN2]2- units (E = S, Se) by chalcogen-atom transfer in the coordination sphere of a transition metal

Article abstract of DOI:10.1002/anie.200703938

(Figure Presented) Piece by piece: Hydrazides at zirconium centers undergo facile N-N bond cleavage and react as equivalents for metallanitrenes, thus allowing the atom-by-atom assembly of bridging dinitridosulfate(IV) and dinitridoselenate(IV) ligands (see scheme; TBS = tBuMe₂Si).

Full text of DOI:10.1002/anie.200703938

Communications
DOI: 10.1002/anie.200703938
Metal Hydrazides
A Zirconium Hydrazide as a Synthon for a Metallanitrene Equivalent:
Atom-by-Atom Assembly of [EN2]2À Units (E = S, Se) by Chalcogen-
Atom Transfer in the Coordination Sphere of a Transition Metal**
Heike Herrmann, Julio Lloret Fillol, Hubert Wadepohl, and Lutz H. Gade*
Interest in transition-metal hydrazides has been primarily due
to the role they are thought to play in the stoichiometric and
catalytic reduction of dinitrogen to ammonia.[1] In this
context, complexes of the transition metals in the middle of
the d block have been most thoroughly studied.[2,3] On the
other hand, hydrazidotitanium complexes appear to be key
intermediates in stoichiometric and catalytic hydrazinations
of alkynes[4] and in related reactions,[5] which has recently
directed attention to the Group 4 elements.[6] For the heavier
Group 4 metals, only one example, [Cp2Zr(N2Ph2)(dmap)]
(Cp = C5H5, dmap = 4-dimethylaminopyridine), has been
reported, by Bergman and co-workers. In a preliminary
study into the reactivity of the compound,
bine the remaining metal-bonded N atom with other reactive
fragments.
Reaction of the dichloro complex [Zr(N2 Npy)Cl2] (1,
Scheme 1) with one molar equivalent of LiHNNPh2 gave a
TBS
75:25 mixture of the two stereoisomers 2a and 2b of the
TBS
chloro hydrazido (1À charge) complex [Zr(N2 Npy)-
(HNNPh2)Cl].[9] The assignment given in Scheme 1 for the
two isomers was confirmed by an X-ray diffraction study of
the major component 2a.[10] This mixture of isomers could be
TBS
cleanly converted to the deep green complex [Zr(N2 Npy)-
(NNPh2)(py)] (3) by dehydrohalogenation with lithium
hexamethyldisilazide (LiHDMS) in the presence of one
À
a tendency for N N bond cleavage in
reactions with alkynes and CO was
observed.[7] This contrasts with the known
reactive behavior of the Ti complexes (e.g.
in hydrazinations), in which coupling of
À
substrates occurs with the N N unit intact.
Hydrazidozirconium compounds may
therefore give rise to new patterns of
reactivity in the coordination sphere of
early-transition-metal elements.
We introduced a tridentate diamido-
pyridyl ligand [N2 Npy]2À as a supporting
R
ligand to stabilize early-transition-metal
=
complexes containing reactive M N bonds
and their derivatives,[8] thus allowing,
among other things, the isolation of key
intermediates of the catalytic hydroamina-
tion of alkynes.[8d] This ligand platform
appeared particularly suited for the inves-
tigation of the reactivity of hydrazidozir-
conium complexes with respect to a poten-
Scheme 1. Synthesis of the hydrazindiido zirconium complex 3 and formalinsertion of
À
tBuNC into the N N bond to give the tert-butylcarbodiimido complex 4.
À
tial cleavage of the N N bond, which in
turn would offer the opportunity to com-
molar equivalent of pyridine (py). The linearly coordinated
[*] H. Herrmann, Dr. J. Lloret Fillol, Prof. Dr. H. Wadepohl,
Prof. Dr. L. H. Gade
hydrazide in 3 is characterized by 15N NMR spectroscopy
Anorganisch-Chemisches Institut
Universität Heidelberg
Im Neuenheimer Feld 270, 69120 Heidelberg (Germany)
Fax: (+49)6221-545-609
=
resonances of d = 287.8 ppm for Zr Na and 178.2 for the
NbPh2 nuclei (NH3 used as external reference). The molecular
structure of 3 was established by X-ray diffraction and is
depicted in Figure 1.[11]
E-mail: lutz.gade@uni-hd.de
The overall molecular structure of 3 is best described as
approximately trigonal bipyramidal with the pyridyl fragment
of the polydentate ligand and the pyridine molecule occupy-
[**] We thank the Deutsche Forschungsgemeinschaft for financial
support and Dr. M. Enders for help with 15N NMR spectroscopy. J.L.
thanks the MEC (Spain) for a postdoctoral fellowship.
À
À
ing the axial positions (Zr(1) N(3) 2.256(2), Zr(1) N(4)
2.303(2) Š). The two amido functionalities and the almost
Supporting information for this article is available on the WWW
under http://www.angewandte.org or from the author.
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soft bending mode, leading to a second, almost isoenergetic
local minimum structure 3b in which the hydrazide moiety is
bent (Figure 2). Such a bent hydrazide has been observed by
NMR spectroscopy in [Cp*WMe3(N2H2)] (Cp* = C5Me5), a
model for an intermediate in the N2 reduction cycle.[13]
The bent hydrazide 3b possesses low-lying acceptor
orbitals primarily located on the Na atom and a slightly
À
elongated N N bond. The constitutional isomer 3c, the
À
amidozirconium “nitride” complex, in which the N N bond is
broken, represents another local minimum, which is, however,
approximately 60 kcalmolÀ1 higher in energy. Terminal
=
Group 4 nitrides are unknown, and the Zr N bonding is
best described by the doubly bonded formally zwitterionic
structure, with a very low lying acceptor orbital located on the
nitride N atom.[12] Such a species is expected to display the
reactivity of a “metallanitrene”,[14] that is, to engage in
coupling reactions with suitable unsaturated nucleophiles.
In a first probe for this type of reaction pattern (emanat-
ing from 3b or 3c), 3 was treated with one molar equivalent of
Figure 1. Molecular structure of complex 3. Selected bond lengths [Š]
and angles [8]: Zr(1)–N(1) 2.121(3), Zr(1)–N(2) 2.165(2), Zr(1)–N(3)
2.256(2), Zr(1)–N(4) 2.303(2), Zr(1)–N(5) 1.899(2), N(5)–N(6)
1.398(3); N(1)-Zr(1)-N(2) 104.18(9), N(1)-Zr(1)-N(3) 81.72(9), N(1)-
Zr(1)-N(5) 126.00(11), N(2)-Zr(1)-N(3) 83.45(9), N(2)-Zr(1)-N(5)
128.17(10), N(3)-Zr(1)-N(4) 173.79(9), N(3)-Zr(1)-N(5) 91.05(9), N(4)-
Zr(1)-N(5) 94.82(10), Zr(1)-N(5)-N(6) 172.7(2).
À
tBuNC (Scheme 1), which led instantaneously to N N bond
cleavage, thus giving the carbodiimido complex [Zr-
TBS
(N2 Npy)(NPh2)(NCNtBu)] (4). Its molecular structure is
linearly coordinated hydrazindiido ligand are coordinated in
depicted in Figure 3and displays the metal-bonded diazacu-
À
À
À
the equatorial sites. The Zr(1) N(5) bond length of
mulene NCNtBu (N(4) C(22) 1.194(3), N(5) C(22)
1.233(3) Š, N(4)-C(22)-N(5) 174.6(2)8), which has resulted
from a formal nitrene–isocyanide coupling similar to that
observed in the thermal degradation of palladium azides.[15]
À
1.899(2) Š and the N(5) N(6) bond length of 1.398(3) Š as
well as the Zr(1)-N(5)-N(6) angle (172.7(2)8) are similar to
the corresponding parameters in [Cp2Zr(N2Ph2)(dmap)]
(1.873(7), 1.364(10) Š, and 174.4(3)8, respectively).[7] The
À
observed N N bond cleavage in reactions of the latter led us
to investigate this aspect more closely.
The axially bound pyridine molecule in 3 is very labile
towards substitution, as established in the exchange with free
pyridine by 1H NMR spectroscopy line-shape analysis (k
ꢀ 20 sÀ1 at 295 K), and the reactive species in transformations
of 3 is therefore thought to be the four-coordinate hydrazide
3a (Figure 2). The latter was modeled using the DFT B3LYP-
6-31G(d) computational tool combined with an ONIOM
modeling of the ligand substituents in N2 Npy.[12] Remark-
TBS
ably, the almost linear hydrazido ligand in 3a possesses a very
Figure 3. Molecular structure of complex 4. Selected bond lengths [Š]
and angles [8]: Zr–N(1) 2.010(2), Zr(1)–N(2) 2.068(2), Zr(1)–N(3)
2.408(2), Zr(1)–N(4) 2.106(2), Zr(1)–N(6) 2.161(2), N(4)–C(22)
1.194(3), C(22)–N(5) 1.233(3), N(5)–C(23) 1.478(4); N(3)-Zr(1)-N(6)
177.21(8), N(4)-Zr(1)-N(6) 99.53(7), Zr(1)-N(4)-C(22) 174.6(2), N(4)-
C(22)-N(5) 175.2(3), C(22)-N(5)-C(23) 125.61(2).
It has been shown that certain terminal nitrido ligands in
late-transition-metal complexes may react with chalcogen-
atom transfer reagents to give NO, NS, or NSe units,[16] and
this type of reaction was thought to provide a further
indication of the reactive behavior of the activated hydrazido
fragment in 3. The reaction of 3 with 0.5 molar equivalents of
the chalcogen-atom transfer reagents propylene sulfide[17] or
triphenylphosphine selenide[18] gave the dinuclear complexes
Figure 2. Energy profile of three local enery minima found for the four-
coordinate hydrazido complex: the linear (3a) and the bent hydrazide
(3b) as well as a potential amido nitride 3c, which is destabilized by
approximately 60 kcalmolÀ1 according to a DFT (B3LYP)/ONIOM
study.
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Communications
TBS
[{Zr(N2 Npy)(NPh2)}2(m-N2E)] (E = S:
5, Se: 6) in high yield (Scheme 2). The
trigonal-bipyramidal zirconium complex
fragments are linked by a central bridg-
ing {EN2} fragment. As in the formation
À
of 4, the N N bond of the hydrazide
moiety has been cleaved in both com-
plexes, and the {Ph2N} unit has migrated
to the Zr atom, to which it is bonded as
an apical amido ligand. Formally, the Na
atom of the hydrazido unit has remained
as a nitrene/nitride at the equatorial
coordination site.[14] Two of these units
have assembled with the transferred
chalcogen atom to generate the bridging
dinitridosulfate(IV)[19] and dinitridose-
lenate(IV) ligands in 5 and 6, respec-
tively. The 15N NMR spectroscopy reso-
nances in the [EN2]2À units are observed
at extremely low field (5: d = 448.0 ppm,
6: 588.2, NH3 used as external refer-
ence), the 15N nuclei of complex 6 being
among the most deshielded ever
observed.[20]
Scheme 2. Reaction of 3 with chalcogen-atom donors to give the dinuclear [m-EN2]2À complexes
(E=S, Se) 5 and 6.
In order to establish the details of the molecular structures
of 5 and 6, X-ray diffraction studies of both compounds have
been carried out. The two complexes are isomorphous and
possess overall similar molecular structures displayed in
Figure 4 for complex 6.
The most interesting feature in the structure of complex 5
À
is the central SN2 unit [SeN2 unit in 6]. The S N bond lengths
À
À
À
for S N(5) (1.501(3) Š) and S N(10) (1.506(3) Š) [Se N(5)
À
1.671(1), Se N(10) 1.670(1) Š] and the N(5)-S-N(10) angle of
118.45(15)8 [N(5)-Se-N(10) 112.28(8)8] are consistent with
the formulation of the [EN2]2À unit as a dianion (a dinitrido-
sulfate (IV) or dinitridoselenate(IV)) with one lone pair at
the sulfur [selenium] atom.[21,22] The metal–ligand bonds to
À
À
the two Zr centers of Zr(1) N(5) 2.076(2) and Zr(2) N(10)
À
À
2.066(2) Š [6: Zr(1) N(5) 2.055(1), Zr(2) N(10) 2.054(1) Š]
are very similar to those of the Zr-bonded amido groups. A
natural bond order (NBO) analysis of the molecular structure
of complex 5, based on a DFT (B3LYP)/ONIOM study, has
Figure 4. Molecular structure of complex 6. Selected bond lengths [Š]
and angles [8]: Zr(1)–N(1) 2.077(1), Zr(1)–N(2) 2.036(1), Zr(1)–N(3)
2.409(1), Zr(1)–N(4) 2.178(1), Zr(1)–N(5) 2.055(1), N(5)–Se 1.671(1),
N(10)–Se 1.670(1), Zr(2)–N(6) 2.048(1), Zr(2)–N(7) 2.064(1), Zr(2)–
N(8) 2.398(1), Zr(2)–N(9) 2.178(1), Zr(2)–N(10) 2.054(1); Zr(1)-N(5)-
Se 158.83(10), N(5)-Se-N(10) 112.28(8), Zr(2)-N(10)-Se 150.69(9).
Selected bond lengths [Š] and angles [8] of the isostructuralcompound
5: Zr(1)–N(1) 2.072(2), Zr(1)–N(2) 2.029(2), Zr(1)–N(3) 2.405(2),
Zr(1)–N(4) 2.175(2), Zr(1)–N(5) 2.076(2), N(1)–Si(1) 1.726(3), N(5)–S
1.501(3), N(10)–S 1.506(3), Zr(2)–N(6) 2.043(2), Zr(2)–N(7) 2.058(2),
Zr(2)–N(8) 2.400(2), Zr(2)–N(9) 2.168(2), Zr(2)–N(10) 2.066(2);
Zr(1)-N(5)-S 160.86(17), N(5)-S-N(10) 118.45(15), Zr(2)-N(10)-S
155.66(17).
À
revealed a formal N S bond order for the NSN unit of
approximately 1.5.[12] This situation resembles the bonding in
the organoelement analogues, the sulfur and selenium
diimides,[19b] which has been established in detail both
experimentally and theoretically.[23] The bonding is best
described by the two resonance structures A and B.
As to the formation of both 5 and 6, the high energy of a
potential nitrido complex 3c makes an attack of the chalcogen
atom at the hydrazide 3b prior to N N bond cleavage the
most likely process. A DFT study of a S adduct of 3b at the
Na atom has established a local energy minimum out of which
the subsequent transformation is expected to occur.[12]
À
Terminal nitride complexes of the Group 4 elements have
so far been elusive and, given their reactive nature, are
unlikely to be isolated with highly charged supporting ligands
such as the diamido donor system employed herein. However,
hydrazido complexes may serve as readily accessible synthons
À
for {M N} units (M = Group 4 metal), which are expected to
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Chemie
have a rich synthetic and catalytic[4,5] potential that remains to
be tapped.[24]
[10] To be published. Crystal data of 2a: C33H52ClN5Si2Zr, ortho-
rhombic, space group Pna21, a = 10.2241(15), b = 35.855(5), c =
9.8844(15) Š, V= 3623.5(9) Š3, Z = 4, m = 0.472 mmÀ1, F000
=
1480.
Received: August 27, 2007
[11] Crystal data of 3: C38H56N6Si2Zr, monoclinic, space group P21/c,
a = 10.2312(9), b = 12.4990(11), c = 30.880(3) Š, b = 97.632(2)8,
V= 3913.9(6) Š3, Z = 4, m = 0.376 mmÀ1, F000 = 1576. Reflections
measured: 75589, independent: 8979 [Rint = 0.098], index ranges
À13 % h % 13, À16 % k % 0, À40 % l % 12, q range 1.8 to 28.58.
Final R values [I > 2s(I)]: R1 = 0.0486, wR2 = 0.1142, GooF =
1.033. 4: C38H60N6Si2Zr, monoclinic, space group Cc, racemically
twinned (refined fractions of the two crystallites 0.945 and
0.055), a = 11.7568(8), b = 18.3226(12), c = 18.9636(13) Š, b =
Published online: October 8, 2007
Keywords: density functional calculations · hydrazides ·
.
nitrogen · X-ray diffraction · zirconium
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1592. Reflections measured: 100972, independent: 13059
[Rint = 0.0379], index ranges À17 % h % 17, À27 % k % 27, À26 %
l % 28,
q range 2.1 to 32.08. Final R values [I > 2s(I)]:
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wR2 = 0.0825,
GooF = 1.183.
5:
¯
C66H102N10SSi4Zr2·0.5C7H8, triclinic, space group P1, a =
13.6391(3), b = 16.3628(3), c = 18.3324(3) Š, a = 77.4440(11),
b = 89.7670(12), g = 67.5910(11)8, V= 3677.80(12) Š3, Z = 2,
m = 0.423mm À1, F000 = 1490. Reflections measured: 69600, inde-
pendent: 15625 [Rint = 0.0850], index ranges À17 % h % 17,
À20 % k % 20, 0 % l % 23, q range 1.6 to 26.7 8. Final R values
[I > 2s(I)]: R1 = 0.0439, wR2 = 0.0948, GooF = 1.019. 6:
¯
C66H102N10SeSi4Zr2·0.5C7H8, triclinic, space group P1, a =
13.6511(6), b = 16.4735(7), c = 18.3587(8) Š, a = 77.1450(10),
b = 89.3640(10), g = 67.4010(10)8, V= 3703.3(3) Š3, Z = 2, m =
0.883mm À1, F000 = 1526. Reflections measured: 93395, inde-
pendent: 24353 [Rint = 0.0424], index ranges À20 % h % 20,
À23 % k % 24, 0 % l % 27, q range 1.9 to 32.28. Final R values
[I > 2s(I)]: R1 = 0.0342, wR2 = 0.0806, GooF = 1.059. Intensity
data were collected at low temperature (3: 150 K; 4–6: 100 K;
Bruker AXS Smart 1000 CCD diffractometer, MoKa radiation,
graphite monochromator, l = 0.71073Š) and corrected for
Lorentz, polarization, and absorption effects (semiempirical,
SADABS).[11a] Structure solution: heavy-atom method com-
bined with structure expansion by direct methods (DIRDIF).[11b]
Refinement: full-matrix least-squares methods based on F2;[11c]
all non-hydrogen atoms anisotropic, hydrogen atoms at calcu-
lated positions (refined riding). CCDC-658106 (3), -658494 (4),
-658107 (5), and -658108 (6) contain the supplementary crystal-
lographic data for this paper. These data can be obtained free of
charge from The Cambridge Crystallographic Data Centre via
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[12] All of the molecular systems were optimized using X-ray
diffraction data as input structures. Hybrid quantum mechan-
ical:molecular mechanical (QM:MM, B3LYP:UFF) computa-
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segment (QM: B3LYP; (C, N: 6-31g(d); H: 6-31g; Zr:
LANL2DZ)) was defined by only the essential elements of the
first coordination sphere. Stationary points were characterized
by frequency analysis. Compound 3a was used as reference,
which is ca. 20 kcalmolÀ1 higher in energy (in the gas phase) than
compound 3. All the calculations, including orbital analysis
(NBO 3.0), have been carried out using Gaussian 03 program
package.[12a] A detailed description of the methods is provided in
the supporting info. a) Gaussian 03, Revision B.03, M. J. Frisch,
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Communications
[14] A substituent-free N atom bonded to a metal atom is normally
[19] a) K. Dehnicke, U. Müller, Comments Inorg. Chem. 1985, 4, 213;
b) M. Herberhold, Comments Inorg. Chem. 1988, 7, 53 ; c) H. W.
Roesky in Rings, Clusters and Polymers of Main Group and
Transition Elements (Ed.: H. W. Roesky), Elesevier, Amster-
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2001, 113, 4082; Angew. Chem. Int. Ed. 2001, 40, 3960.
[20] a) J. Mason, L. F. Larkworthy, E. A. Moore, Chem. Rev. 2002,
102, 913; b) R. Marek, A. Lycka, Curr. Org. Chem. 2002, 6, 3 5.
[21] NSN: a) K. Hösler, F. Weller, K. Dehnicke, Z. Naturforsch. B
1989, 44, 1325; b) H. Martan, J. Weiss, Z. Anorg. Allg. Chem.
1984, 515, 225; c) A. Dietrich, B. Neumüller, K. Dehnicke, Z.
Anorg. Allg. Chem. 2002, 628, 243.
referred to as a “nitrido ligand”. However, these ligands are to
be understood as formally trianionic and triply bonded to the
À
metal. This situation is not the case for the hypothetical Zr N
species referred to in this discussion. This species has different
bonding characteristics, and the required formal oxidation state
of the metal center in the case of its formulation as a nitride
(+ VI) is not accessible. For reviews of the chemistry of nitride
complexes, see: a) K. Dehnicke, J. Strähle, Angew. Chem. 1981,
93, 451; Angew. Chem. Int. Ed. Engl. 1981, 20, 413; b) K.
Dehnicke, J. Strähle, Angew. Chem. 1992, 104, 978; Angew.
Chem. Int. Ed. Engl. 1992, 31, 955; as well as ref. [19d].
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Trans. 2004, 3699; b) Y.-J. Kim, Y.-S. Joo, J.-T. Han, W. S. Han,
S. W. Lee, J. Chem. Soc. Dalton Trans. 2002, 3611; c) Y.-J. Kim,
Y.-S. Kwak, Y.-S. Joo, S. W. Lee, J. Chem. Soc. Dalton Trans.
2001, 144; d) Y.-J. Kim, Y.-S. Kwak, S. W. Lee, J. Organomet.
Chem. 2000, 603, 152. Ti carbodimides have been synthesized by
other routes: e) H. Plenio, H. W. Roesky, Z. Naturforsch. B 1989,
44, 94; f) G. Veneziani, S. Shimada, M. Tanaka, Organometallics
1998, 17, 2926.
[22] There are no previous reports of the [SeN2]2À fragment
coordinated to metals, nor—to our knowledge—any character-
izing data on the unit itself. Organic selenodiimides have been
reported: a) M. Herberhold, W. Jellen, Z. Naturforsch. B 1986,
41, 144; b) T. Maaninen, H. M. Tuononen, K. Kosunen, R.
Oilunkaniemi, J. Hiitola, R. Laitinen, T. Chivers, Z. Anorg. Allg.
Chem. 2004, 630, 1947; an X-ray diffraction study of AdNSe-
NAd: c) T. Maaninen, R. Laitinen, T. Chivers, Chem. Commun.
2002, 1812; for a SnIV complex of (Me3SiN)2Se, see: d) J. Gindl,
M. Börgvinsson, H. W. Roesky, C. Freire-Erdbrügger, G. M.
Sheldrick, J. Chem. Soc. Dalton Trans. 1993, 811; the only
substituent-free selenium–nitrogen fragment characterized as a
ligand is the {Se2N2} cycle in Group 10 metal complexes: e) P. F.
Kelly, A. M. Z. Slawin, Angew. Chem. 1995, 107, 1903; Angew.
Chem. Int. Ed. Engl. 1995, 34, 1758; f) P. F. Kelly, A. M. Z.
Slawin, A. Soriano-Rama, J. Chem. Soc. Dalton Trans. 1997, 559.
[23] a) D. Leusser, B. Walfort, D. Stalke, Angew. Chem. 2002, 114,
2183; Angew. Chem. Int. Ed. 2002, 41, 2079; b) D. Leusser, J.
Henn, N. Kocher, B. Engels, D. Stalke, J. Am. Chem. Soc. 2004,
126, 1781.
[16] T. J. Crevier, S. Lovell, J. M. Mayer, A. L. Rheingold, I. A.
Guzei, J. Am. Chem. Soc. 1998, 120, 6607.
[17] Recent examples of the use of propylene sulfide a S-atom
transfer reagent: a) S. Blum, V. A. Rivera, R. T. Ruck, F. E.
Michael, R. G. Bergman, Organometallics 2005, 24, 1647; S. M.
Mullins, A. P. Duncan, R. G. Bergman, J. Arnold, Inorg. Chem.
2001, 40, 6952.
[18] Examples of the use of triphenylphosphine selenide as a Se-atom
transfer reagent: a) S. M. Stuczynski, Y.-U. Kwon, M. L. Stei-
gerwald, J. Organomet. Chem. 1993, 449, 167; b) M. L. Steiger-
wald, T. Siegrist, E. M. Gyorgy, B. Hessen, Y.-U. Kwon, S. M.
Tanzler, Inorg. Chem. 1994, 33, 3389; c) R. D. Adams, O.-Sung
Kwon, S. Sanyal, J. Organomet. Chem. 2003, 681, 258; d) D.
Belletti, D. Cauzzi, C. Graiff, A. Minarelli, R. Pattacini, G.
Predieri, A. Tiripicchio, J. Chem. Soc. Dalton Trans. 2002, 3160.
À
[24] Note added in proof: While this work was in press the N N
fragmentation of a Ti hydrazide has been reported: J. D. Selby,
C. D. Manley, M. Feliz, A. D. Schwarz, E. Clot, P. Mountford,
Chem. Commun. 2007, DOI: 10.1039/b711941k.
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