Synthesis and structural characterization of new organo-diimido and organo-imido niobium and titanium complexes

Article abstract of DOI:10.1039/b002743j

The organo-diimido complexes [{Nb(L₂)Cl₃}₂(μ-l,₄-NC ₆H₄N)], L = CH₃CN 1a or 4-'Bupy 2a, [{Nb(L₂)Cl₃}₂(μ-1,3-NC₆H ₄N)], L = CH₃CN Ib or 4-′Bupy 2b, and [{Nb(L₂)Cl₃}₂(μ-1,2-NC₆H ₄N)], L = CH₃CN le or 4-'Bupy 2c were isolated by treating NbCl₅ in the presence of CH₃CN or 4-'Bupy with the appropriate amount of the corresponding aniline A′,N,N′,N′-tetrakis(trimethylsilyl)-1,4-, -1,3-, or -1,2-phenylenediamine, respectively. Compound la reacts with appropriate alkylating reagents to give the corresponding alkyl complexes, namely [{NbLR₃}₂(μ-1,4-NC₆H₄N)], L = CH₃CN, R = CH₂SiMe₃ 3a; or CH₂CMe₃ 3b; L = THF, R = CH₂SiMe₃ 4a or CH₂CMe₃ 4b. The crystal structure determination of 3a was carried out. Reaction of [Ti(py)₃Q₂(N′Bu)] with N′,N′,N′-tetramethyl-M-phenylenediamine, in 2:1 or 1:1 stoichiometric ratio, afforded the organo-imido complexes [Ti(py)_nCl₂(1,4-NC₆Me₄NH ₂)], n = 3 (5a) or 2 (5b), while analogous reactions with 1,4- or 1,3-phenylenediamine give intractable mixtures of products. Organo-imido and organo-diimido titanium complexes were easily prepared by treating TiCl₄ with the appropriate N′,N′,N′-tetrakisftrimethylsirytyphenylenediamines in CH₂Cl₂ in 1:1 and 2:1 molar ratios in the presence of 4-tert-butylpyridine or W.A^W.W-tetramethylethylenediamine (TMEDA). The compounds prepared in this way are [Ti(4-Bupy)₂Cl₂{1,4-NC₆H₄N(SiMe ₃)₂}] 6a, [Ti(TMEDA)-Cl₂{1,4-NC₆H₄N(SiMe ₃)₂}] 6b, [Ti(TMEDA)Cl₂{1,3-NC₆H₄N(SiMe₃) ₂}] 7b, [{Ti(4-'Bupy)₂C₂(μ-1,4-NC₆H₄N)] 8a, [{Ti(TMEDA)Cl₂}₂(μ3-1,4-NC₆H₄N)] 8b, [{Ti(4-′Bupy)2Cl₂}2(u-l,3-NC₆H₄N)] 9a and [{Ti(TMEDA)Cl2}₂-(μ-1,3-NC₆H₄N)] 9b. Finally, the same reaction with N′,N′,N′.-tetrakisOrimethylsilyO-1,2-phenylenediamine, in the presence of 4-'Bupy or TMEDA, gives the diamido complexes [Ti(4-'Bupy)₂Cl₂{ 1,2-C₆H₄(NH)₂}] 10a and [Ti(TMEDA)Cl₂{1,: 2-C₆H₄(NH)₂} lOb. The structures of the different families of complexes were determined by spectroscopic methods. The Royal Society of Chemistry 2000.

Full text of DOI:10.1039/b002743j

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Synthesis and structural characterization of new organo-diimido
and organo-imido niobium and titanium complexes
Iván Dorado,a Andrés Garcés,a Carmen López-Mardomingo,b Mariano Fajardo,c
Ana Rodríguez,d Antonio Antiñolod and Antonio Otero*d
a Departamento de Química Inorgánica, Campus Universitario, Universidad de Alcalá,
28871 Alcalá de Henares (Madrid), Spain
b Departamento de Química Orgánica, Campus Universitario, Universidad de Alcalá,
28871 Alcalá de Henares (Madrid), Spain
c Departamento de Ciencias Experimentales e Ingeniería, E.S.C.E.T.,
Universidad Rey Juan Carlos, 28993 Móstoles (Madrid), Spain
d Departamento de Química Inorgánica, Orgánica y Bioquímica, Facultad de Química,
Universidad de Castilla-La Mancha, 13071 Ciudad Real, Spain
Received 6th April 2000, Accepted 31st May 2000
Published on the Web 30th June 2000
The organo-diimido complexes [{Nb(L2)Cl3}2(µ-1,4-NC6H4N)], L = CH3CN 1a or 4-tBupy 2a, [{Nb(L2)Cl3}2-
(µ-1,3-NC6H4N)], L = CH3CN 1b or 4-tBupy 2b, and [{Nb(L2)Cl3}2(µ-1,2-NC6H4N)], L = CH3CN 1c or 4-tBupy
2c were isolated by treating NbCl5 in the presence of CH3CN or 4-tBupy with the appropriate amount of the
corresponding aniline N,N,NЈ,NЈ-tetrakis(trimethylsilyl)-1,4-, -1,3-, or -1,2-phenylenediamine, respectively.
Compound 1a reacts with appropriate alkylating reagents to give the corresponding alkyl complexes, namely
[{NbLR3}2(µ-1,4-NC6H4N)], L = CH3CN, R = CH2SiMe3 3a; or CH2CMe3 3b; L = THF, R = CH2SiMe3 4a or
CH2CMe3 4b. The crystal structure determination of 3a was carried out. Reaction of [Ti(py)3Cl2(NtBu)] with
N,N,NЈ,NЈ-tetramethyl-1,4-phenylenediamine, in 2:1 or 1:1 stoichiometric ratio, afforded the organo-imido
complexes [Ti(py)nCl2(1,4-NC6Me4NH2)], n = 3 (5a) or 2 (5b), while analogous reactions with 1,4- or 1,3-phenylene-
diamine give intractable mixtures of products. Organo-imido and organo-diimido titanium complexes were easily
prepared by treating TiCl4 with the appropriate N,N,NЈ,NЈ-tetrakis(trimethylsilyl)phenylenediamines in CH2Cl2
in 1:1 and 2:1 molar ratios in the presence of 4-tert-butylpyridine or N,N,NЈ,NЈ-tetramethylethylenediamine
(TMEDA). The compounds prepared in this way are [Ti(4-tBupy)2Cl2{1,4-NC6H4N(SiMe3)2}] 6a, [Ti(TMEDA)-
Cl2{1,4-NC6H4N(SiMe3)2}] 6b, [Ti(TMEDA)Cl2{1,3-NC6H4N(SiMe3)2}] 7b, [{Ti(4-tBupy)2Cl2}2(µ-1,4-NC6H4N)]
8a, [{Ti(TMEDA)Cl2}2(µ-1,4-NC6H4N)] 8b, [{Ti(4-tBupy)2Cl2}2(µ-1,3-NC6H4N)] 9a and [{Ti(TMEDA)Cl2}2-
(µ-1,3-NC6H4N)] 9b. Finally, the same reaction with N,N,NЈ,NЈ-tetrakis(trimethylsilyl)-1,2-phenylenediamine,
in the presence of 4-tBupy or TMEDA, gives the diamido complexes [Ti(4-tBupy)2Cl2{1,2-C6H4(NH)2}] 10a and
[Ti(TMEDA)Cl2{1,2-C6H4(NH)2}] 10b. The structures of the different families of complexes were determined by
spectroscopic methods.
We recently reported6 the preparation of niobocene organo-
Introduction
diimido complexes, namely [{Nb(η5-C5H4SiMe3)2Cl}2(µ-N2C6-
H4)], from the reaction of [{Nb(η5-C5H4SiMe3)2Cl}2] with the
appropriate amount of the corresponding aniline, 1,4- or 1,3-
phenylenediamine. As a continuation of our research in this
field we examined the reactivity of NbCl5 and TiCl4 towards
different phenylenediamines in the presence of different ancil-
lary ligands in order to synthesize new types of binuclear
organo-diimido niobium and titanium complexes with both
centres linked by conjugated π systems.
Metal imido complexes of Groups 5 and 6 early transition
metals have widely been studied and, in particular, a great
number of well established imido functional groups of d0
niobium and tantalum are known.1 In contrast, the first
titanium imido species to be structurally well characterized
were described in 1990 and these were the six-co-ordinate
[Ti(py)3Cl2(NP(S)Ph2)] and the five-co-ordinate [Ti(pyЈ)2(OC6-
i
H3 Pr2-2,6)2(NPh)] (pyЈ = 4-pyrrolidinopyridine) complexes.2,3
Since then, however,
a significant number of titanium
complexes containing the Ti᎐NR functional group have been
᎐
described and such systems are mainly prepared by a straight-
Results and discussion
forward metathetical route from the complexes [Ti(L)nCl2(NR)]
t
(L = py or NC5H4 Bu-4; n = 2 or 3; R = tBu or aryl) with
First, the preparation of organo-diimido niobium com-
plexes was considered. In fact, NbCl5 reacts with the appro-
priate N,N,NЈ,NЈ-tetrakis(trimethylsilyl)-1,4-, -1,3-, or
-1,2-phenylenediamine in the presence of acetonitrile or
4-tBupy to afford the corresponding organo-diimido complexes
[{Nb(L)2Cl3}2(µ-x,y-NC6H4N)] 1 and 2 and SiMe3Cl, eqn. (1).
Previously we described6 the formation of analogous
niobocene complexes by the reaction of [{Nb(η5-C5H4-
SiMe3)Cl}2] with the appropriate aniline. In this case it was
different ancillary ligands.4
In addition, transition metal complexes in which the metal
centres are linked by a bridging ligand possessing a delocalized
π system are well known and have been the subject of intense
research due to their potential applications in the design of
low-dimensional, polymeric materials with novel electrical
and/or magnetic properties. In this respect, several complexes
that incorporate aryldiimido bridges have been described.5
DOI: 10.1039/b002743j
J. Chem. Soc., Dalton Trans., 2000, 2375–2382
This journal is © The Royal Society of Chemistry 2000
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(1)
Fig. 1 Crystal structure of complex 3a.
unable to isolate crystals suitable for X-ray diffraction studies,
by analogy with the structures described for the niobocene
organo-diimido complexes mentioned above,6 it appears
reasonable that a diimidophenylene group bridges two niobium
atoms, which are probably located in the plane formed by this
ligand.
In addition, we propose that both nitrogen atoms –are sp
+
᎐
hybridized with the following two limiting descriptions Nb᎐N–
᎐
˙˙
R and Nb᎐N–R, that are an accurate representation of the
᎐
bonding situation.8
proposed that an initial oxidative addition of the amine gave
rise to an amido intermediate, which underwent subsequent
thermolytic expulsion of H2.7 In our reactions a selective
elimination of SiMe3Cl by interaction of the tetrakis(trimethyl-
silyl)diamine with NbCl5 takes place. The reactions were carried
out under mild experimental conditions and complete substitu-
tion of the four trimethylsilyl groups was achieved to give the
appropriate organo-diimido species in high yields.
Complex 1a was alkylated using the appropriate Grignard
reagent in a 1:6 molar ratio and the reaction afforded the
corresponding alkyl complexes [{NbL(R)3}2(µ-1,4-NC6H4N)]
(L = CH3CN, R = CH2SiMe3 3a or CH2CMe3 3b; L = THF,
R = CH2SiMe3 4a or CH2CMe3 4b) in good yields (80–90%),
eqn. (2). Alternatively, thesecomplexescanbepreparedinsimilar
The reactions can be carried out by two alternative experi-
mental methods. The first involves initial formation of the
corresponding NbCl5ؒL adduct, L = acetonitrile or 4-tBupy,
followed by addition of the appropriate phenylenediamine. The
second method consists of the initial formation of the corre-
sponding organo-diimido species and subsequent addition of
the ligand. These methods can be used in all cases except for
complex 2c, where the first experimental method failed. Steric
factors could explain this behaviour since the initial co-
ordination of the bulky 4-tBupy ligand to the niobium centre
could hinder the subsequent interaction with 1,2-phenylene-
diamine, where the functional groups are adjacent in the 1 and 2
positions. Alternatively, complex 2 can be prepared from a solu-
tion of 1 by simple addition of 4-tBupy because the ligand
displaces the more labile acetonitrile.
(2)
yields by treating 1a with dialkylmagnesium reagents MgR2-
(THF)2 (see, as illustrative examples, the preparation of 3b and
4b in the Experimental section). Complexes 3 were isolated
when the alkylation reactions were carried out in diethyl ether,
but when THF was employed as the solvent the acetonitrile was
replaced by THF to give 4. Moreover, these complexes can be
obtained from 3 by simple addition of THF. The different alkyl
complexes were isolated as air-sensitive yellow crystalline solids
after the appropriate work-up and all are sparingly soluble in
alkanes and soluble in Et2O or THF. The structural character-
ization of the alkyl complexes was carried out by spectroscopic
and X-ray diffraction studies. The 1H and 13C NMR spectra for
complexes 3a,3b and 4a,4b show the characteristic resonances
of alkyl groups bound to a niobium atom (see Experimental
section). When the co-ordinated acetonitrile was replaced by
The method described above constitutes a very easy and
selective route to prepare imido complexes because the form-
ation of the volatile SiMe3Cl by-product facilitates the isolation
of the corresponding imido complex. This method was sub-
sequently employed to prepare analogous titanium species (see
below). In addition, non-reductive processes of the niobium()
or titanium() centres were implied in the processes. The
organo-diimido niobium complexes, as well as the other com-
1
plexes described in this work, were characterized by H, 13C
NMR and IR spectroscopy (see Experimental section).
It is noteworthy that, on the basis of both spectroscopic and
analytical data, two acetonitrile or tBupy ligands are present in
1
the proposed octahedral environment. Thus, H NMR reson-
t
1
ances of two non-equivalent Bupy units appear for complexes
THF the H and the 13C resonances were shifted slightly. The
2. The spectra for complexes 1 in CD3CN each show a signal
corresponding to free CH3CN, which is removed by the deuteri-
ated solvent. In order to confirm the presence of two co-
ordinated acetonitrile ligands in this type of complex, the
spectrum of 1a was obtained in CD3NO2. In this case a broad
signal was observed that was shifted to low field with respect to
free acetonitrile and corresponds to the two ligands (see
Experimental section).
13C NMR spectra of these complexes exhibit a broad signal
between δ 60 and 93 for the methylene group bound to the
niobium atom.
In order unequivocally to establish the structural disposition
of these alkyl complexes an X-ray molecular structural analysis
of 3a was carried out. The molecular structure and atomic
numbering scheme are shown in Fig. 1 and selected bond
distances and angles are given in Table 1.
Given the data described above, octahedral structures for
these complexes can be proposed. Although we have been
Complex 3a crystallizes in the monoclinic space group
C2/c and the asymmetric unit contains half an independent
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Table 1 Selected bond lengths (Å) and angles (Њ) for complex 3a
of the titanium complex was used, were unsuccessful. Terminal
titanium imido complex 5a, which has a proposed pseudo-
octahedral disposition, was isolated as an air-sensitive solid
that tends to lose the trans-co-ordinated pyridine ligand to give
5b, which is proposed to have a square-pyramidal structure.
Similar behaviour has previously been found in analogous
complexes.9
As stated above, the reactivity of silylated phenylenediamines
towards early transition metal halides has been confirmed as a
useful synthetic route to prepare organo-imido and organo-
diimido species of these metals in high yields. This method
functions well due to the ease of removal of the SiMe3Cl that
is formed as a by-product. Thus, the reaction of TiCl4 with
the appropriate N,N,NЈ,NЈ-tetrakis(trimethylsilyl)phenylene-
diamine in a 1:1 molar ratio in the presence of 4-tert-
Nb(1)–N(1)
Nb(1)–N(2)
Nb(1)–C(20)
Nb(1)–C(30)
Nb(1)–C(40)
N(1)–C(12)
N(2)–C(15)
C(12)–C(13)
C(12)–C(14)
C(13)–C(14i)
C(15)–C(16)
1.762(7)
2.402(8)
2.170(9)
2.149(9)
2.198(9)
1.402(10)
1.120(11)
1.363(10)
1.375(11)
1.380(11)
1.454(14)
N(1)–Nb(1)–C(30)
N(1)–Nb(1)–C(20)
C(30)–Nb(1)–C(20)
N(1)–Nb(1)–C(40)
C(30)–Nb(1)–C(40)
C(20)–Nb(1)–C(40)
N(1)–Nb(1)–N(2)
C(30)–Nb(1)–N(2)
C(20)–Nb(1)–N(2)
C(40)–Nb(1)–N(2)
C(12)–N(1)–Nb(1)
C(15)–N(2)–Nb(1)
Si(1)–C(20)–Nb(1)
Si(2)–C(30)–Nb(1)
Si(3)–C(40)–Nb(1)
98.7(3)
99.3(3)
116.5(3)
96.1(3)
118.1(4)
119.6(3)
177.2(3)
82.8(3)
82.0(3)
81.1(3)
174.4(6)
178.3(10)
124.2(4)
121.3(5)
121.6(5)
3
1
butylpyridine
or
N,N,NЈ,NЈ-tetramethylethylenediamine
–
–
Symmetry transformation: i Ϫx ϩ 2, Ϫy ϩ 2, Ϫz.
(TMEDA) as an ancillary ligand gives the corresponding
terminal imido complexes [Ti(4-tBupy)2Cl2{1,4-NC6H4N-
(SiMe3)2}] 6a, [Ti(TMEDA)Cl2{1,4-NC6H4N(SiMe3)2}] 6b and
[Ti(TMEDA)Cl2{1,3-NC6H4N(SiMe3)2}] 7b, eqn. (4).
molecule. The structure shows a binuclear arrangement. Each
Nb atom has trigonal bipyramidal geometry with an aceto-
nitrile ligand and an imido ligand in apical positions, and three
CH2SiMe3 groups in equatorial positions. The Nb–N1 distance
is 1.762(7) Å and the angle at the imido nitrogen atom is in the
range normally associated with linear imido ligands [Nb–N1–
C12 174.4(6)Њ]. The Nb–N2 distance of 2.402(8) Å is within the
typical range. The three CH2SiMe3 groups at each niobium
centre are staggered with regard to the corresponding groups of
the other niobium atom centre, as indicated by the value of the
torsion angle C20–Nb1–Nb1A–C30A of 60.2Њ.
(4)
On the basis of the molecular structure for complex 3a, a
trigonal bipyramidal disposition for each niobium centre in a
binuclear situation, in which the acetonitrile ligand is located in
a trans disposition to the imido ligand, can be proposed for the
different alkylniobium species. This structural disposition,
where a labile ligand such as acetonitrile or pyridine is located
in a co-ordination site trans to the imido ligand, has been found
in several imido-containing early transition metal complexes.9
In the second part of this work we undertook a study into
the synthesis and characterization of organo-imido and
organo-diimido titanium complexes. First, we employed the
metathetical reaction of [Ti(py)3Cl2(NtBu)] with 1,4- or 1,3-
phenylenediamine9 in order to prepare the corresponding
organo-diimido complexes, but the reactions in different molar
ratios (1:1 or 1:2) gave rise to intractable mixtures of products.
However, when the same reaction was carried out using
tetramethyl-1,4-phenylenediamine, in 1:1 or 2:1 molar ratios,
the organo-imido complex [Ti(py)3Cl2(1,4-NC6Me4NH2)] 5a
was isolated as the only organometallic species, eqn. (3).
When
N,N,NЈ,NЈ-tetrakis(trimethylsilyl)-1,4-phenylene-
diamine was used the corresponding complexes 6a and 6b
were obtained in high yields as the only products. However,
when the same reaction was carried out using N,N,NЈ,NЈ-
tetrakis(trimethylsilyl)-1,3-phenylenediamine a mixture of the
corresponding mononuclear compound 7 and the binuclear
compound 9 (see below) was obtained. When TMEDA was the
ancillary ligand the mixture could be resolved since the mono-
nuclear complex 7b is soluble in chloroform while the binuclear
complex 9b is completely insoluble. This behaviour can tenta-
tively be explained in terms of the possibility of deactivation of
the second SiMe3 group in the para position when one equiv-
alent of titanium is co-ordinated to the N,N,NЈ,NЈ-tetrakis-
(trimethylsilyl)-1,4-phenylenediamine. This fact would make
attack of a second TiCl4 molecule on unchanged N,N,NЈ,NЈ-
Attempts to prepare the corresponding organo-diimido
species [{Ti(py)3Cl2}2(1,4-NC6Me4N)], even when a large excess
(3)
tetrakis(trimethylsilyl)-1,4-phenylenediamine
much
more
favourable kinetically than the corresponding reaction with the
N(SiMe3)2 moiety of the mononuclear product.
The choice of dichloromethane as solvent was a crucial
factor in the success of the reaction, as well as in the subsequent
processes described below for the preparation of organo-
diimido species. In fact, when other solvents (such as toluene,
THF or acetonitrile) were used, a mixture of products was
1
obtained that exhibits several SiMe3 signals in the H NMR
spectrum. This indicates that a partial desilylation of the
diamine has taken place, probably because the co-ordination
ability of the solvent diminishes the acidity of the metal centre.
Complexes 6a, 6b and 7b were isolated as air-sensitive solids.
Complex 6a is soluble in toluene, dichloromethane, THF,
J. Chem. Soc., Dalton Trans., 2000, 2375–2382
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diethyl ether and chloroform, while 6b and 7b are only soluble
in chloroform. When the reaction of TiCl4 and the appropriate
silylated phenylenediamine was carried out in a 2:1 molar
ratio, the organo-diimido binuclear complexes [{Ti(L2)Cl2}2-
(µ-x,y-NC6H4N)] (L = 4-tBupy, x = 1, y = 4 8a; L2 = TMEDA,
x = 1, y = 4 8b; L = 4-tBupy, x = 1, y = 3 9a; L2 = TMEDA,
x = 1, y = 3 9b) were isolated, eqn. (5). These compounds were
were isolated as air-sensitive solids after the appropriate work-
up; 10a is soluble in toluene, dichloromethane, THF and diethyl
ether and 10b in dichloromethane, THF and diethyl ether. Both
compounds were characterized spectroscopically (see Experi-
mental section). The 1H NMR spectrum of 10a shows a broad
signal at δ 11.14 for the amido protons, two pseudodoublets
at ca. δ 9.13 and 7.50 for the pyridine protons, and a singlet at
δ 1.35 for the tert-butyl groups, indicating that in a proposed
octahedral geometry the two amido groups as well as both
4-tBupy ligands are occupying equivalent co-ordination sites.
Scheme 1 shows the different possible structural dispositions
(5)
isolated in high yields as air-sensitive solids after the appropri-
ate work-up. Complexes 8a and 9a are soluble in toluene,
dichloromethane, THF and diethyl ether, while 8b and 9b are
insoluble in these solvents. It is noteworthy that under our
experimental conditions a selective desilylation process takes
place to give cleanly the organo-diimido species.
Scheme 1
1
for complex 10a and, on the basis of the aforementioned H
NMR as well as the 13C NMR data, the structures C and D, in
which the titanium atom is a chiral centre, must be ruled out.
Structure B could be seen as more favourable on the basis of
steric arguments, although A cannot be ruled out. In contrast,
the 1H NMR spectrum of 10b shows two signals at δ 11.79 and
9.55 for the amido protons and four signals at δ 3.22, 3.20, 3.00
and 2.32 for the methyl groups of the TMEDA ligand. These
signals indicate that an asymmetric disposition in a proposed
octahedral geometry must be considered. The three possible
structural dispositions are depicted in Scheme 2 and, on the
basis of the spectroscopic data, structure C can be discarded.
The mononuclear and binuclear imido titanium complexes
1
were spectroscopically characterized by H, 13C NMR and IR
spectroscopy (see Experimental section). The similarity
between the spectra of the mononuclear titanium compounds
6, 7 and the analogous complexes previously described3,9
suggests that monomeric terminal imido square-pyramidal
structures could be proposed. In addition, a diimidophenylene
group that bridges two titanium atoms, which are probably
located in the plane formed by this ligand, can also be con-
sidered for 8, 9 as a possibility in a similar way to the previously
discussed niobium complexes. Finally, the reaction of TiCl4
with N,N,NЈ,NЈ-tetrakis(trimethylsilyl)-1,2-phenylenediamine
in 1:1 or 2:1 molar ratios, in the presence of 4-tBupy or
TMEDA as ancillary ligand, gave the diamido complexes
[Ti(4-tBupy)2Cl2{1,2-C6H4(NH)2}] 10a and [Ti(TMEDA)Cl2-
{1,2-C6H4(NH)2}] 10b, eqn. (6), as the only organometallic
species isolated.
(6)
Scheme 2
In conclusion, we have reported a straightforward method to
prepare organo-imido and organo-diimido complexes with
metals of Groups 4 and 5 by reaction of the corresponding
halide with silylated phenylenediamines. The new species were
isolated in high yields and from selective processes due to the
formation of the volatile SiMe3Cl by-product. New efforts to
assess the scope of the method and to study the reactivity of the
imido-containing complexes are in progress.
The reaction was carried out under extremely anhydrous
conditions and there is no clear explanation for the source
of the protonation process on the nitrogen of the proposed
initially formed imido ligand. We have subsequently confirmed
the formation of 10a and 10b by the direct reaction of TiCl4
with N,NЈ-bis(trimethylsilyl)-1,2-phenylenediamine in the pres-
ence of 4-tBupy or TMEDA, eqn. (6). Complexes 10a and 10b
Experimental
General methods and instrumentation
All manipulations were carried out under an argon atmosphere
using either standard Schlenk techniques or an MBraun glove-
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Table 2 Crystal data and structure refinement for complex 3a
was required during the addition. The initial yellow solution
changed to deep red for 1a and 1c, and to pale red for com-
plex 1b. The mixture was vigorously stirred overnight at room
temperature. The solvent was removed under vacuum and
the residual solids were washed several times with hexane and
identified as 1a, 1b and 1c, respectively.
Empirical formula
Formula weight
T/K
λ/Å
Crystal system, space group
a/Å
b/Å
c/Å
C34H76N4Nb2Si6
895.34
293(2)
0.71070
Monoclinic, C2/c
19.306(8)
16.0717(7)
19.428(4)
117.19(2)
5362(2)
4
Complex 1a: from NbCl5 (1.93 g, 7.14 mmol) and 1,4-
{(Me3Si)2N}2C6H4 (1.42 g, 3.57 mmol), 2.1 g of a green solid
1
were obtained (yield 88%). H NMR (300 MHz): (CD3CN)
β/Њ
δ 1.95 (s, 12 H, free CH3CN) and 7.21 (s, 4 H, phenylene ring);
(CD3NO2) δ 2.90 (broad signal, 12 H, CH3CN) and 7.79 (s, 4 H,
phenylene ring). 13C-{1H} NMR (CD3CN, 75 MHz): δ 1.7
(CH3CN), 126.3 (phenylene ring), 127.2 (CH3CN) and 153.4
(Cipso of phenylene ring). IR: 2313m, 2282m, 1479s, 1408w,
1366m, 1321m, 1007m, 942w, 846m, 832m, 529m, 425m and
376m cmϪ1 [Found (Calc. for C7H8Cl3N3Nb): C, 25.3 (25.2); H,
2.4 (2.4); N, 12.0 (12.6)%)].
V/Å3
Z
µ/cmϪ1
5.85
Reflections collected/unique
Data/restraints/parameters
Final R indices [I > 2σ(I)]
Largest diff. peak and hole/e ÅϪ3
6471/6471
6471/34/196
R1 = 0.0800, wR2 = 0.1545
0.666 and Ϫ0.529
Complex 1b: from NbCl5 (1.79 g, 6.64 mmol) and 1,3-
{(Me3Si)2N}2C6H4 (1.32 g, 3.32 mmol), 2.0 g of a pink solid
were obtained (yield 90%). 1H NMR (CD3CN, 300 MHz):
δ 1.95 (s, 12 H, free CH3CN), 7.00 (part A2 of an A2MX spin
system, 2 H, phenylene ring), 7.1 (part M of an A2MX spin
system, 1 H, phenylene ring) and 7.34 (part X of an A2MX,
1 H, phenylene ring). 13C-{1H} NMR (CD3CN, 75 MHz): δ 1.7
(CH3CN), 121.7, 124.6, 129.8 (phenylene ring), 129.5 (CH3CN)
and 154.4 (Cipso of phenylene ring). IR: 2314m, 2285m, 1567m,
1554m, 1417m, 1365m, 1346m, 1312s, 1244m, 1029s, 977w,
943m, 879m, 790s, 678m, 578w, 512m, 488m and 388s cmϪ1
[Found (Calc. for C7H8Cl3N3Nb): C, 24.9 (25.2); H, 2.5 (2.4);
N, 11.6 (12.6)%].
Complex 1c: from NbCl5 (1.63 g, 6.04 mmol) and 1,2-
{(Me3Si)2N}2C6H4 (1.20 g, 3.02 mmol), 1.8 g of a dark brown
solid were obtained (yield 89%). 1H NMR (CD3CN, 300 MHz):
δ 1.95 (s, 12 H, CH3CN), 7.13 (part AAЈ of an AAЈXXЈ spin
system, 2 H, phenylene ring) and 7.51 (part XXЈ of an AAЈXXЈ
spin system, 2 H, phenylene ring). 13C-{1H} NMR (CD3CN, 75
MHz): δ 1.7 (CH3CN), 128.0, 129.9 (phenylene ring), 129.1
(CH3CN) and 148.2 (Cipso of phenylene ring). IR: 2317s, 2287s,
1399w, 1339w, 1261w, 1152w, 1115w, 1025m, 993w, 975w,
949m, 848m, 806m, 760m, 668w, 592w, 522w and 379m cmϪ1
[Found (Calc. for C7H8Cl3N3Nb): C, 25.1 (25.2); H, 2.6 (2.4); N,
11.7 (12.6)%].
box. Solvents were dried and distilled under argon: tetrahydro-
furan and diethyl ether from sodium–benzophenone, hexane
and pentane from sodium and potassium alloy, acetonitrile and
CDCl3 from finely ground calcium hydride.
Titanium tetrachloride was distilled under argon from
copper; 4-tert-butylpyridine was dried over activated 4 Å mol-
ecular sieves and used without further purification; pyridine,
aniline and N,N,NЈ,NЈ-tetramethylethylenediamine were
dried over finely ground calcium hydride and distilled under
argon; 2,3,5,6-tetramethyl-1,4-phenylenediamine was sublimed
prior to use and stored under argon. Other reagents were
obtained from commercial sources and used as received or pre-
pared as reported elsewhere: N,N,NЈ,NЈ-tetrakis(trimethylsilyl)-
phenylenediamine.10
IR spectra were recorded in Nujol mulls between CsI pellets
over the range 4000–370 cmϪ1 on a Perkin-Elmer model 883
and IR-FT 2000 spectrophotometer; 1H and 13C NMR spectra
on a Gemini-200 and/or UNITY-300 (Varian) spectrometers.
1
Chemical shifts (δ ppm) were measured relative to residual H
and 13C resonances for acetonitrile-d3, chloroform-d1 and
benzene-d6 as solvents. C, H and N analyses were carried out
with a Perkin-Elmer 240-13, 240 C and/or Heraeus-CHN-O-
Rapid microanalyser.
Crystallographic study of complex 3a
[{Nb(tBupy)2Cl3}2(ꢀ-1,4-NC6H4N)] 2a and [{Nb(tBupy)2Cl3}2-
(ꢀ-1,3-NC6H4N)] 2b. To a vigorously stirred suspension of
NbCl5 in CH2Cl2 was added Bupy in molar ratio 1:2. The
A single crystal of approximate dimensions 0.3× 0.2 × 0.2 mm
was mounted in a glass capillary. Intensity data were collected
on a NONIUS-MACH3 diffractometer, equipped with graphite
monochromated Mo-Kα radiation source, using an ω–2θ scan
technique to a maximum value of 56Њ. Data were corrected in
the usual fashion for Lorentz and polarization effects and
empirical absorption correction was not necessary. The struc-
ture was solved using direct methods (SHELXS).11 Refinement
of F2 was carried out by full-matrix least-squares techniques.11
The SiMe3 groups showed rotational disorder with an occu-
pation factor of 0.5 and were refined isotropically. All the other
non-hydrogen atoms were refined with anisotropic thermal
parameters. The hydrogen atoms were included in their calcu-
lated positions and refined isotropically. Crystal data are given
in Table 2.
t
initial yellow suspension changed to a yellow solution. To this
was added dropwise, during 45 min, a solution of the corre-
sponding N,N,NЈ,NЈ-tetrakis(trimethylsilyl)phenylenediamine
in CH2Cl2 at room temperature. Vigorous stirring was required
during the addition. The initial yellow solution changed to dark
red for complex 2a and pale red for 2b. The mixture was vigor-
ously stirred for 2 h at room temperature. The solvent was
removed under vacuum and the solids were washed several
times with hexane and identified as 2a and 2b.
Complex 2a: from NbCl5 (1.04 g, 3.83 mmol), 1,4-
{(Me3Si)2N}2C6H4 (0.76 g, 1.92 mmol) and 4-tert-butylpyridine
(1.13 ml, 7.68 mmol), 2.0 g of a pink solid were obtained (yield
t
90%). 1H NMR (CDCl3, 300 MHz): δ 1.30 (s, 18 H, NC5H4 Bu),
CCDC reference number 186/2013.
See http://www.rsc.org/suppdata/dt/b0/b002743j/ for crystal-
lographic files in .cif format.
t
1.34 (s, 18 H, NC5H4 Bu), 7.32 (s, 4 H, phenylene ring), 7.33
t
(AAЈ part of an AAЈXXЈ spin system, 4 m-H of NC5H4 Bu),
7.41 (AAЈ part of an AAЈXXЈ spin system, 4 m-H of NC5H4-
tBu), 8.57 (XXЈ part of an AAЈXXЈ spin system, 4 o-H of
Preparations
t
NC5H4 Bu) and 9.0 (XXЈ part of an AAЈXXЈ spin system,
t
[{Nb(CH3CN)2Cl3}2(ꢀ-1,4-NC6H4N)] 1a, [{Nb(CH3CN)2-
Cl3}2(ꢀ-1,3-NC6H4N)] 1b, and [{Nb(CH3CN)2Cl3}2(ꢀ-1,2-
NC6H4N)] 1c. To a solution of NbCl5 in acetonitrile was added
dropwise, at room temperature during 45 min, a solution of the
4 o-H of NC5H4 Bu). 13C-{1H} NMR (CDCl3, 75 MHz): δ 29.8
[NC5H4C(CH3)3], 30.0 [NC5H4C(CH3)3], 34.9 [NC5H4C(CH3)3],
t
35.1 [NC5H4C(CH3)3], 121.0 (m-C, NC5H4 Bu), 121.4 (m-C,
t
t
NC5H4 Bu), 125.5 (phenylene ring), 150.9 (o-C, NC5H4 Bu),
t
corresponding
N,N,NЈ,NЈ-tetrakis(trimethylsilyl)phenylene-
151.1 (o-C, NC5H4 Bu), 152.3 (Cipso of phenylene ring), 163.1
t
t
diamine in CH2Cl2 in a molar ratio of 2:1. Vigorous stirring
(Cipso of NC5H4 Bu) and 164.7 (Cipso of NC5H4 Bu). IR: 1635w,
J. Chem. Soc., Dalton Trans., 2000, 2375–2382 2379

View Article Online
1617s, 1543w, 1501m, 1421s, 1320s, 1276m, 1235m, 1203w,
1093w, 1067s, 1019s, 1006m, 993s, 842s, 572s, 531m, 421m and
377m cmϪ1 [Found (Calc. for C21H28Cl3N3Nb): C, 48.4 (48.3);
H, 5.7 (5.4); N, 7.5 (8.0)%].
(CH3CN), 125.4 (phenylene ring) and 154.3 (Cipso of phenylene
ring). IR: 2309w, 2280w, 1488m, 1327s, 1242, 992w, 900s, 847s,
741m, 699m, 668m, 609w, 577w, 504w, 484w, 465w and 451w
cmϪ1 [Found (Calc. for C17H38N2NbSi3): C, 45.7 (45.6); H, 8.3
(8.6); N, 6.5 (6.3)%].
Complex 2b: from NbCl5 (0.86 g, 3.18 mmol), 1,3-{(Me3Si)2-
N}2C6H4 (0.63 g, 1.59 mmol) and 4-tert-butylpyridine (0.94 ml,
6.36 mmol), 1.5 g of a pink solid were obtained (yield 90%). 1H
[{Nb(CH3CN)(CH2CMe3)3}2(ꢀ-1,4-NC6H4N)] 3b. To a sus-
pension of complex 1a (0.635 g, 0.95 mmol) in Et2O (40 ml) was
added dropwise a solution of MgNp2ؒ2THF [Np = (CH3)3-
CCH2] (0.88 g, 2.85 mmol) in Et2O (40 ml) at Ϫ78 ЊC. The
mixture was stirred overnight at room temperature. The initial
green suspension became yellow. The solid was filtered off and
afterwards extracted with Et2O (4 portions of 15 ml). The sol-
vent was removed in vacuo to give a yellow solid, which was
identified as 3b (0.6 g, 0.75 mmol) (yield 79%). 1H NMR (C6D6,
300 MHz): δ 0.50 (s, 6 H, CH3CN), 1.28 [s, 54 H, (CH3)3CCH2],
1.36 (s, 12 H, (CH3)3CCH2) and 7.89 (s, 4 H, NC6H4N);
13C-{1H} NMR (C6D6, 75 MHz): δ 1.37 (CH3CN), 34.5
[(CH3)3CCH2], 35.8 [(CH3)3CCH2], 91.2 (Me3CCH2), 119.3
(CH3CN), 126.2 (NC6H4N) and 154.5 (Cipso of phenylene ring).
IR: 2308w, 2275w, 1497m, 1358m, 1315s, 1230m, 988m, 880w,
843m, 770w, 744w, 668w, 552w, 504w and 405w cmϪ1 [Found
(Calc. for C20H38N2Nb): C, 60.4 (60.3); H, 9.3 (9.5); N, 7.1
(7.0)%].
t
NMR (CDCl3, 300 MHz): δ 1.29 (s, 18 H, NC5H4 Bu), 1.33 (s,
t
18 H, NC5H4 Bu), 7.21 (m, 3 H, phenylene ring), 7.35 (m, 1 H,
phenylene ring), 7.36 (AAЈ part of an AAЈXXЈ spin system,
t
4 m-H of NC5H4 Bu), 7.41 (AAЈ part of an AAЈXXЈ spin sys-
t
tem, 4 m-H of NC5H4 Bu), 8.61 (XXЈ part of an AAЈXXЈ spin
t
system, 4 o-H of NC5H4 Bu) and 9.01 (XXЈ part of an AAЈXXЈ
spin system, 4 o-H of NC5H4 Bu); 13C-{1H} NMR (CDCl3,
t
75 MHz): δ 30.1 [NC5H4C(CH3)3], 30.2 [NC5H4C(CH3)3],
35.1 [NC5H4C(CH3)3], 35.4 [NC5H4C(CH3)3], 121.3 (m-C,
t
t
NC5H4 Bu), 121.8 (m-C, NC5H4 Bu), 121.0, 124.9, 128.2
t
(phenylene ring), 151.1 (o-C, NC5H4 Bu), 151.4 (o-C, NC5H4-
tBu), 153.4 (Cipso of phenylene ring), 163.3 (Cipso of NC5H4 Bu)
t
t
and 165.0 (Cipso of NC5H4 Bu). IR: 1636w, 1616s, 1567m,
1553m, 1501m, 1420s, 1342w, 1310w, 1293w, 1275m, 1233m,
1202w, 1068s, 1015s, 972w, 876w, 830s, 788m, 679m, 571s,
542m, 513m, 489w and 464w cmϪ1 [Found (Calc. for
C21H28Cl3N3Nb): C, 47.9 (48.3); H, 5.8 (5.4); N, 7.9 (8.0)%].
[{Nb(tBupy)2Cl3}2(ꢀ-1,2-NC6H4N)] 2c. To
a
vigorously
[{Nb(THF)(CH2SiMe3)3}2(ꢀ-1,4-NC6H4N)] 4a. To a suspen-
sion of complex 1a (1.423 g, 2.13 mmol) in THF (40 ml) was
added dropwise a 1.0 M solution of Me3SiCH2MgCl (12.8 ml,
12.8 mmol) diluted in THF (40 ml) at Ϫ78 ЊC. The mixture was
stirred overnight at room temperature. The initial green suspen-
sion became yellow. The solvent was removed and the residue
extracted with Et2O (4 portions of 20 ml). The solvent was
removed in vacuo to give a yellow solid, which was identified as
4a (1.8 g, 1.77 mmol) (yield 85%). 1H NMR (C6D6, 300 MHz):
δ 0.20 [s, 54 H, Si(CH3)3CH2], 0.80 (s, 12 H, SiMe3CH2), 3.91
(m, 8 H, C4H8O), 1.43 (m, 8 H, C4H8O) and 7.64 (s, 4 H,
phenylene ring). 13C-{1H} NMR (C6D6, 75 MHz): δ 3.0 [Si-
(CH3)3CH2], 25.5 (C4H8O), 60.9 (SiMe3CH2), 70.4 (C4H8O),
125.4 (NC6H4N) and 154.2 (Cipso of phenylene ring). IR: 1487s,
1407w, 1322s, 1245s, 922w, 877m, 846s, 742w, 694m, 604w and
530w cmϪ1 [Found (Calc. for C19H43NNbOSi3): C, 47.7 (47.7);
H, 9.0 (9.0); N, 3.4 (2.9)%].
stirred suspension of NbCl5 (0.527 g, 1.95 mmol) in CH2Cl2 (30
ml) was added dropwise a solution of 1,2-{(Me3Si)2N}2C6H4
(0.39 g, 0.97 mmol) in CH2Cl2 (30 ml). The initial yellow suspen-
sion became green. The mixture was stirred for 3 h and 4-tert-
butylpyridine (0.576 ml, 3.90 mmol) was added. The suspension
changed to a deep red solution. After 90 min the solvent was
removed under vacuum, the solid washed several times with
hexane and the resulting dark brown solid identified as complex
2c (0.9 g, 0.86 mmol) (yield 88%). 1H NMR (CDCl3, 300 MHz):
t
t
δ 1.24 (s, 18 H, NC5H4 Bu), 1.33 (s, 18 H, NC5H4 Bu), 7.08 (AAЈ
part of an AAЈXXЈ spin system, 2 H, phenylene ring), 7.36
t
(AAЈ part of an AAЈXXЈ spin system, 4 m-H of NC5H4 Bu),
7.38 (AAЈ part of an AAЈXXЈ spin system, 4 m-H of NC5H4-
tBu), 7.87 (XXЈ part of an AAЈXXЈ spin system, 2 H, phenylene
ring), 8.9 (XXЈ part of an AAЈXXЈ spin system, o-H of
t
NC5H4 Bu) and 9.02 (XXЈ part of an AAЈXXЈ spin system, o-H
t
of NC5H4 Bu). 13C-{1H} NMR (CDCl3, 75 MHz); δ 30.0
[NC5H4C(CH3)3], 30.2 [NC5H4C(CH3)3], 35.1 [NC5H4C(CH3)3],
[{Nb(THF)(CH2CMe3)3}2(ꢀ-1,4-NC6H4N)] 4b. To a suspen-
sion of complex 1a (0.872 g, 1.31 mmol) in THF (40 ml) was
added dropwise a solution of MgNp2ؒ2THF (1.22 g, 3.92
mmol) in THF (40 ml) at Ϫ78 ЊC. The mixture was stirred
overnight at room temperature. The initial green suspension
changed to yellow. The solvent was removed and the residue
extracted with Et2O (4 portions of 20 ml). The solvent was
removed in vacuo to give a yellow solid, which was identified as
4b (0.9 g, 1.04 mmol) (yield 80%). 1H NMR (C6D6, 300 MHz):
δ 1.19 [s, 54 H, (CH3)3CCH2], 1.21 (s, 12 H, Me3CCH2), 1.37 (m,
8 H, C4H8O), 3.67 (m, 8 H, C4H8O) and 7.74 (s, 4 H, NC6H4N).
13C-{1H} NMR (C6D6, 75 MHz): δ 25.7 (C4H8O), 34.4
[(CH3)3CCH2], 35.7 [(CH3)3CCH2], 69.47 (C4H8O), 92.7 (Me3-
CCH2), 125.9 (phenylene ring) and 154.9 (Cipso of phenylene
ring). IR: 1581w, 1315s, 1231m, 990w, 914w, 874m, 837m,
722m, 668w, 554w and 500 cmϪ1 [Found (Calc. for C22H43-
NNbO): C, 61.2 (61.4); H, 10.1 (9.9); N, 3.2 (3.2)%].
t
35.3 [NC5H4C(CH3)3], 121.1 (m-C, NC5H4 Bu), 121.8 (m-C,
t
NC5H4 Bu), 126.9, 130.8 (phenylene ring), 147.7 (Cipso of
t
phenylene ring), 151.3 (o-C, NC5H4 Bu), 152.1 (o-C, NC5H4-
t
t
tBu), 163.1 (Cipso of NC5H4 Bu) and 164.5 (Cipso of NC5H4 Bu).
IR: 1615s, 1542w, 1502m, 1421s, 1325m, 1275m, 1233m, 1113w,
1068m, 1016m, 987w, 965w, 831m, 756m, 572m and 392w cmϪ1
[Found (Calc. for C21H28Cl3N3Nb): C, 48.8 (48.3); H, 5.6 (5.4);
N, 7.2 (8.0)%].
Complexes 1a–1c and 2a,2b could alternatively be prepared
by a similar procedure to that described for 2c, although the
latter complex could not be prepared by the first method
described for these complexes.
[{Nb(CH3CN)(CH2SiMe3)3}2(ꢀ-1,4-NC6H4N)] 3a. To
a
suspension of complex 1a (1.346 g, 2.02 mmol) in Et2O (40 ml)
was added dropwise a 1.0 M solution of Me3SiCH2MgCl (12.1
ml, 12.1 mmol) diluted in Et2O (40 ml) at Ϫ78 ЊC. The mixture
was stirred overnight at room temperature. The initial green
suspension became yellow. The solid was filtered off and after-
wards extracted with Et2O (4 portions of 15 ml). From the
combined solutions the solvent was removed in vacuo to give a
yellow solid, which was identified as 3a (1.6 g, 1.78 mmol) (yield
[Ti(py)3Cl2(1,4-NC6Me4NH2)] 5a. To a solution of [Ti(py)3-
Cl2(NtBu)] (0.5 g, 1.17 mmol) in CH2Cl2 (25 ml) was added
dropwise
a solution of 2,3,5,6-tetramethyl-1,4-phenylene-
diamine (0.19 g, 1.17 mmol) in CH2Cl2. The mixture was stirred
for 2 h at room temperature and the volatile materials were
removed under reduced pressure to give complex 5a (0.59 g,
1.07 mmol) as a dark yellow solid. An analytically pure sample
was obtained by careful layering of a dichloromethane solution
of the compound with hexane at room temperature. The
1
88%). H NMR (C6D6, 300 MHz): δ 0.27 [s, 54 H, Si(CH3)3-
CH2], 0.59 (s, 6 H, CH3CN), 1.18 (s, 12 H, Si(CH3)3CH2) and
7.74 (s, 4 H, phenylene ring). 13C-{1H} NMR (C6D6, 75 MHz):
δ 0.2 (CH3CN), 2.93 [Si(CH3)3CH2], 63.0 (Si(CH3)3CH2), 121.7
2380
J. Chem. Soc., Dalton Trans., 2000, 2375–2382

View Article Online
t
product contained ca. 0.4 equivalent of residual CH2Cl2 (by 1H
NMR spectroscopy and elemental analysis). Yield for C25H29-
Cl2N5Tiؒ0.4CH2Cl2: 91%. 1H NMR (CDCl3, 300 MHz): δ 1.94
and 2.49 (s, 12 H, Me of amine), 3.47 (s br, 2 H, NH2), 7.23 (m,
2 H, m-H of trans NC5H5), 7.44 (m, 4 H, m-H of cis NC5H5),
7.65 (m, 1 H, p-H of trans NC5H5), 7.86 (m, 2 H, p-H of
cis NC5H5), 8.60 (m, 2 H, o-H of trans NC5H5) and 9.11 (m,
4 H, o-H of cis NC5H5). 13C-{1H} NMR (CDCl3, 75 MHz):
δ 13.4 and 15.3 (Me of amine), 116.6 and 131.6 (o- and m-C of
phenylene ring), 123.6 and 124.3 (m-C of cis and trans NC5H5),
136.1 and 138.7 (p-C of cis and trans NC5H5), 150.1 and 151.2
(o-C of cis and trans NC5H5), 155.6 (Cipso of phenylene ring)
and 151.5 (p-C of phenylene ring). IR: 3451m, 3363m, 1626m,
1602s, 1570m, 1484s, 1445s, 1216m, 1070s, 1041s, 1012s, 760s,
734s, 697s, 637m, 484m and 464m cmϪ1 [Found (Calc. for
C25H29Cl2N5Tiؒ0.4CH2Cl2): C, 55.4 (55.2); H, 5.7 (5.4); N, 12.9
(12.7)%].
121.4 (m-C of NC5H4 Bu), 123.7 (phenylene ring), 150.6 (o-C
t
of NC5H4 Bu), 157.0 (Cipso of phenylene ring) and 163.4 (p-C of
t
NC5H4 Bu). IR: 1613s, 1543m, 1419m, 1274s, 1229s, 1203s,
1071s, 1022s, 989m, 833s, 572s, 399s and 209m cmϪ1 [Found
(Calc. for C21H28Cl2N3Ti): C, 57.0 (57.2); H, 6.3 (6.4); N, 9.4
(9.5)%].
Complex 9a: from 1,3-[(Me3Si)2N]2C6H4 (3.0 g, 7.56 mmol),
TiCl4 (1.66 ml, 15.1 mmol) and 4-tert-butylpyridine (4.4 ml, 30
mmol), 5.8 g of a red solid were obtained (yield 85%). 1H NMR
(CDCl3, 300 MHz): δ 1.29 (s, 36 H, NC5H4CMe3), 6.40 and 6.71
(M and X parts of A2MX spin system, 2 H, phenylene ring),
6.46 (A2 part of A2MX spin system, 2 H, phenylene ring), 7.33
t
(XXЈ part of an AAЈXXЈ spin system, 8 H, m-H of NC5H4 Bu)
and 8.97 (AAЈ part of an AAЈXXЈ spin system, 8 H, o-H of
NC5H4 Bu). 13C-{1H} NMR (CDCl3, 75 MHz): δ 30.2 (NC5H4-
t
CMe3), 35.2 (NC5H4CMe3), 116.5, 119.3, 127.5 (phenylene
ring), 121.5 (m-C of NC5H4 Bu), 150.5 (o-C of NC5H4 Bu),
160.4 (Cipso of phenylene ring) and 163.5 (p-C of NC5H4 Bu).
t
t
t
[Ti(py)2Cl2(1,4-NC6Me4NH2)] 5b. The complex [TiCl2(py)3-
(1,4-NC6Me4NH2)] (0.5 g, 0.91 mmol) was heated at 65 ЊC
under a dynamic vacuum for 6 h to give 5b (0.38 g, 0.86 mmol)
IR: 1613s, 1555s, 1498m, 1419s, 1329m, 1300s, 1276s, 1230s,
1201m, 1151m, 1068s, 1025s, 870m, 834s, 782s, 571s, 390s and
251m cmϪ1 [Found (Calc. for C21H28Cl2N3Ti): C, 57.1 (57.2); H,
6.5 (6.4); N, 9.3 (9.5)%].
1
as a green-yellow powder (yield 95%). H NMR (CDCl3, 300
MHz): δ 1.98 and 2.59 (s, 12 H, Me of amine), 3.51 (s br, 2 H,
NH2), 7.48 (m, 4 H, m-H of NC5H5), 7.89 (m, 2 H, p-H of
NC5H5) and 9.11 (m, 4 H, o-H of NC5H5). 13C-{1H} NMR
(CDCl3, 75 MHz): δ 13.5 and 15.4 (Me of amine), 116.6 and
131.5 (o- and m-C of phenylene ring), 124.6 (m-C of NC5H5),
138.9 (p-C of NC5H5), 150.9 (o-C of NC5H5), Cipso of phenylene
ring not observed. IR: 3467m, 3371m, 1626m, 1603s, 1487m,
1444s, 1218m, 1154m, 1043s, 1012s, 760s, 698s, 635m and 457m
cmϪ1 [Found (Calc. for C20H24Cl2N4Ti): C, 55.2 (54.7); H, 5.9
(5.5); N, 12.9 (12.8)%].
[Ti(TMEDA)Cl2{1,4-NC6H4N(SiMe3)2}] 6b, [{Ti(TMEDA)-
Cl2}2(ꢀ-1,4-NC6H4N)] 8b and [{Ti(TMEDA)Cl2}2(ꢀ-1,3-NC6-
H4N)] 9b. To a solution of N,N,NЈ,NЈ-tetrakis(trimethylsilyl)-
1,4-phenylenediamine in CH2Cl2 (30 ml) was added dropwise at
0 ЊC a solution of TiCl4 in CH2Cl2 (30 ml). After stirring the
mixture for 16 h at room temperature the solvent was evapor-
ated to dryness to give a black solid, which was washed with
toluene (2 × 10 ml) and hexane (3 × 10 ml). The resulting black
powder was added to hexane (30 ml) and the suspension treated
with N,N,NЈ,NЈ-tetramethylethylenediamine to give, after
24 h, a suspension. The solid was filtered off and washed with
hexane (2 × 10 ml), dried in vacuo and identified as complex
6b, 8b or 9b.
[Ti(4-tBupy)2Cl2{1,4-NC6H4N(SiMe3)2}] 6a, [{Ti(4-tBupy)2-
Cl2}2(ꢀ-1,4-NC6H4N)] 8a and [{Ti(tBupy)2Cl2}2(ꢀ-1,3-NC6H4N)]
9a. To a solution of the corresponding N,N,NЈ,NЈ-tetrakis-
(trimethylsilyl)phenylenediamine in CH2Cl2 (50 ml) was added
dropwise at 0 ЊC a solution of TiCl4 in CH2Cl2 (50 ml). After
stirring the mixture for 16 h at room temperature the solvent
was evaporated to dryness to give a black solid, which was
washed with toluene (2 × 15 ml) and hexane (3 × 15 ml). The
resulting black powder was added to toluene (40 ml) and the
suspension obtained treated with 4-tert-butylpyridine to give a
red solution. After 6 h the solvent was evaporated to dryness to
yield a solid, which was washed with hexane (2 × 20 ml), dried
in vacuo and identified as complex 6a, 8a or 9a.
Complex 6b: from 1,4-[(Me3Si)2N]2C6H4 (1.0 g, 2.52 mmol),
TiCl4 (0.25 ml, 2.27 mmol) and N,N,NЈ,NЈ-tetramethylethyl-
enediamine (0.34 ml, 2.27 mmol), 0.92 g of a yellow solid was
1
obtained (yield 84%). H NMR (CDCl3, 300 MHz): δ 0.03 (s,
18 H, SiMe3), 2.94 (s, 12 H, Me of TMEDA), 3.16 (s br, 4 H,
CH2 of TMEDA), 6.50 and 6.68 (AAЈ and BBЈ part of an
AAЈBBЈ spin system, 4 H, phenylene ring). 13C-{1H} NMR
(CDCl3, 75 MHz): δ 2.1 (SiMe3), 51.3 (Me of TMEDA), 58.9
(CH2 of TMEDA), 122.6 and 129.4 (o- and m-C of phenylene
ring), 142.6 (p-C of phenylene ring) and 158.7 (Cipso of
phenylene ring). IR: 1593m, 1313s, 1250s, 1213s, 1093m,
1067m, 971s, 928s, 901s, 842s, 804s, 518m and 451m cmϪ1
[Found (Calc. for C18H38Cl2N4Si2Ti): C, 44.2 (44.5); H, 7.6
(7.9); N, 12.1 (11.5)%].
Complex 6a: from 1,4-[(Me3Si)2N]2C6H4 (1.0 g, 2.52 mmol),
TiCl4 (0.25 ml, 2.27 mmol) and 4-tert-butylpyridine (0.68 ml,
4.56 mmol), 1.2 g of a green solid were obtained (yield 85%).
1H NMR (CDCl3, 300 MHz): δ Ϫ0.01 (s, 18 H, SiMe3), 1.33 (s,
18 H, NC5H4CMe3), 6.53 and 6.72 (AAЈ and BBЈ part of an
AAЈBBЈ spin system, 4 H, phenylene ring), 7.45 (XXЈ part of
Complex 8b: from 1,4-[(Me3Si)2N]2C6H4 (0.37 g, 0.94 mmol),
TiCl4 (0.21 ml, 1.88 mmol) and N,N,NЈ,NЈ-tetramethylethyl-
enediamine (0.29 ml, 1.88 mmol), 0.41 g of a green solid was
t
an AAЈXXЈ spin system, 4 H, m-H of NC5H4 Bu) and 9.03
t
1
(AAЈ part of an AAЈXXЈ spin system, 4 H, o-H of NC5H4 Bu).
obtained (yield 76%). H NMR (DMSO, 300 MHz): δ 2.16 (s,
13C-{1H} NMR (CDCl3, 50 MHz): δ 2.0 (SiMe3), 30.2 (NC5H4-
24 H, Me of TMEDA), 2.36 (s, 4 H, CH2 of TMEDA) and 6.50
(s br, 4 H, phenylene ring). 13C-{1H} NMR (CDCl3, 75 MHz):
δ 45.4 (Me of TMEDA), 56.9 (CH2 of TMEDA), 123.1
(phenylene ring) and 153.7 (Cipso of phenylene ring). IR: 1515m,
1316s, 1211m, 1011m, 982m, 948s, 849s, 803s, 510s and 472m
cmϪ1 [Found (Calc. for C9H19Cl2N3Ti): C, 37.5 (37.5); H, 6.1
(6.6); N, 13.8 (14.6)%].
t
CMe3), 35.2 (NC5H4CMe3), 121.5 (m-C of NC5H4 Bu), 123.4
and 129.4 (o- and m-C of phenylene ring), 142.7 (p-C of
t
phenylene ring), 150.4 (o-C of NC5H4 Bu), 158.4 (Cipso of
t
phenylene ring) and 163.3 (p-C of NC5H4 Bu). IR: 1615s,
1490m, 1417m, 1320m, 1258s, 1211s, 1067m, 1023m, 978s, 904s,
837s, 827s, 755m, 729m, 572s and 441s cmϪ1 [Found (Calc. for
C30H48Cl2N4Si2Ti): C, 55.7 (56.3); H, 7.6 (7.6); N, 8.8 (8.8)%].
Complex 8a: from 1,4-[(Me3Si)2N]2C6H4 (3.0 g, 7.56 mmol),
TiCl4 (1.66 ml, 15.1 mmol) and 4-tert-butylpyridine (4.4 ml, 30
Complex 9b: from 1,3-[(Me3Si)2N]2C6H4 (0.37 g, 0.94 mmol),
TiCl4 (0.21 ml, 1.88 mmol) and N,N,NЈ,NЈ-tetramethylethyl-
enediamine (0.29 ml, 1.88 mmol), 0.41 g of a red solid was
1
1
mmol), 5.1 g of a green solid were obtained (yield 76%). H
obtained (yield 72%). H NMR (DMSO, 300 MHz): δ 2.16 (s,
NMR (CDCl3, 300 MHz): δ 1.33 (s, 36 H, NC5H4CMe3), 6.64
(s, 4 H, phenylene ring), 7.43 (XXЈ part of an AAЈXXЈ spin
24 H, Me of TMEDA), 2.36 (s, 4 H, CH2 of TMEDA), 6.15,
6.56, 6.66 (m br, 4 H, phenylene ring). 13C-{1H} NMR (CDCl3,
75 MHz): δ 45.4 (Me of TMEDA), 56.9 (CH2 of TMEDA),
116.1, 119.1, 128.2 (phenylene ring) and 158.7 (Cipso of phenyl-
ene ring). IR: 1555s, 1542m, 1398m, 1337s, 1299s, 1285s, 1233s,
t
system, 8 H, m-H of NC5H4 Bu) and 8.99 (AAЈ part of an
t
AAЈXXЈ spin system, 8 H, o-H of NC5H4 Bu). 13C-{1H} NMR
(CDCl3, 50 MHz): δ 30.3 (NC5H4CMe3), 35.2 (NC5H4CMe3),
J. Chem. Soc., Dalton Trans., 2000, 2375–2382
2381

View Article Online
1146m, 1068m, 1021m, 995m, 945s, 881m, 803s, 790m, 501m,
461m and 399m cmϪ1 [Found (Calc. for C9H19Cl2N3Ti): C, 37.3
(37.5); H, 6.3 (6.6); N, 14.0 (14.6)%].
solution of TiCl4 (0.44 ml, 3.96 mmol) in CH2Cl2 (40 ml). After
stirring the mixture for 16 h at room temperature the solvent
was evaporated to dryness to give a brown solid, which was
washed with toluene (2 × 10 ml) and hexane (3 × 10 ml). The
resulting brown powder was added to CH2Cl2 (75 ml) and the
suspension obtained treated with TMEDA (0.59 ml, 3.96
mmol) to give a red solution. After 2 h the solvent was removed
and the resulting dark red solid recrystallized from acetonitrile
and dried in vacuo to give complex 10b (1.1 g, 3.22 mmol) as a
dark red solid (yield 82%).
Method B. To a solution of N,N,NЈ,NЈ-tetrakis(trimethyl-
silyl)-1,2-phenylenediamine (1.00 g, 2.52 mmol) in CH2Cl2 (40
ml) was added dropwise, at 0 ЊC, a solution of TiCl4 (0.55 ml,
5.05 mmol) in CH2Cl2 (40 ml). After stirring the mixture for 16
h at room temperature the solvent was evaporated to dryness to
give a brown solid, which was washed with toluene (2 × 15 ml)
and hexane (3 × 15 ml). The resulting black powder was added
to hexane (40 ml) and the suspension obtained treated with
TMEDA (0.76 ml, 5.05 mmol) to give a dark red suspension
after 2 h. The solid was filtered off and washed with cold
(Ϫ40 ЊC) dichloromethane, purified by recrystallization from
acetonitrile and identified as complex 10b (0.38 g, 1.33 mmol)
(yield 45%). 1H NMR (CDCl3, 300 MHz): δ 2.32 (s, 3 H, Me of
TMEDA), 2.47 (m, 4 H, CH2 of TMEDA), 3.00, 3.20, 3.22 (s,
9 H, Me of TMEDA), 5.59 and 6.26 (m, 4 H, phenylene ring),
9.55, 11.79 (s br, 2 H, NH). 13C-{1H} NMR (CDCl3, 75 MHz):
δ 49.7, 51.4, 51.5, 54.4, 57.9 and 58.4 (CH2 and CH3 or
TMEDA), 110.1, 111.3, 122.7, 123.6 (phenylene ring), 153.0,
155.2 (Cipso of phenylene ring). IR: 3344m, 3283s, 1576m,
1276m, 1191m, 1064m, 1013m, 949m, 801s, 752s, 745s, 662s,
629m, 449m and 392m cmϪ1 [Found (Calc. for C14H22Cl2N4Ti):
C, 41.6 (42.3); H, 6.6 (6.5); N, 16.3 (16.4)%].
[Ti(TMEDA)Cl2{1,3-NC6H4N(SiMe3)2}] 7b. To a solution of
N,N,NЈ,NЈ-tetrakis(trimethylsilyl)-1,3-phenylenediamine (2.0
g, 5.04 mmol) in CH2Cl2 (40 ml) was added dropwise at 0 ЊC a
solution of TiCl4 (0.5 ml, 4.56 mmol) in CH2Cl2 (50 ml). After
stirring the mixture for 16 h at room temperature the solvent
was evaporated to dryness to give a black solid, which was
washed with toluene (2 × 10 ml) and hexane (3 × 10 ml). The
resulting black powder was added to hexane (40 ml), the
suspension obtained treated with N,N,NЈ,NЈ-tetramethyl-
ethylenediamine (0.68 ml, 4.56 mmol) to give, after 24 h, a red
suspension. The solid was filtered off, washed with hexane
(2 × 10 ml) and extracted with chloroform (5 × 15 ml). The
resulting red solution was evaporated to dryness to give com-
plex 7b (1.08 g, 2.22 mmol) as a red solid (yield 44%). 1H NMR
(CDCl3, 300 MHz): δ 0.00 (s, 18 H, SiMe3), 2.92 (s, 12 H,
Me of TMEDA), 3.13 (s, 4 H, CH2 of TMEDA), 6.35, 6.40,
6.53, 6.83 (m, 4 H, phenylene ring). 13C-{1H} NMR (CDCl3,
75 MHz): δ 2.0 (SiMe3), 51.3 (Me of TMEDA), 58.9 (CH2 of
TMEDA), 117.5, 123.9, 125.2 and 127.6 (phenylene ring), 142.6
(p-C of phenylene ring) and 161.4 (Cipso of phenylene ring). IR:
1569s, 1407m, 1320m, 1249s, 1186s, 1521m, 1019m, 967s, 910s,
841s, 801m, 697m, 632m, 445m and 387m [Found (Calc. for
C18H38Cl2N4Si2Ti): C, 44.1 (44.5); H, 7.6 (7.9); N, 11.9 (11.5)%].
[Ti(4-tBupy)2Cl2{1,2-C6H4(NH)2}] 10a. Method A. To a solu-
tion of N,NЈ-bis(trimethylsilyl)-1,2-phenylenediamine (0.68 g,
2.69 mmol) in CH2Cl2 (30 ml) was added dropwise, at 0 ЊC, a
solution of TiCl4 (0.30 ml, 2.69 mmol) in CH2Cl2 (30 ml). After
stirring the mixture for 16 h at room temperature the solvent
was evaporated to dryness to give a brown solid, which was
washed with toluene (2 × 10 ml) and hexane (3 × 10 ml). The
resulting brown powder was added to CH2Cl2 (40 ml) and the
suspension obtained treated with 4-tert-butylpyridine (0.68 ml,
4.56 mmol) to give a red solution. After 2 h the solvent was
removed and the resulting red solid washed with hexane (2 × 20
ml) and dried in vacuo to give complex 10a (1.22 g, 2.47 mmol)
as a red solid (yield 92%).
Acknowledgements
The authors gratefully acknowledge financial support from the
Dirección General de Enseñanza Superior y de Investigación
Científica y Técnica (grant no. PB98-0159-C02-01-02) and the
Comunidad de Madrid (grant no. 07N/0036/98).
References
Method B. To a solution of N,N,NЈ,NЈ-tetrakis(trimethyl-
silyl)-1,2-phenylenediamine (2.00 g, 5.04 mmol) in CH2Cl2 (30
ml) was added dropwise, at 0 ЊC, a solution of TiCl4 (1.10 ml,
10.1 mmol) in CH2Cl2 (30 ml). After stirring the mixture for 16 h
at room temperature the solvent was evaporated to dryness to
give a brown solid, which was washed with toluene (2 × 15 ml)
and hexane (3 × 15 ml). The resulting black powder was added
to toluene (40 ml) and the suspension obtained treated with
4-tert-butylpyridine (2.9 ml, 20 mmol) to give a red solution.
After 2 h the solution was cooled to Ϫ40 ЊC for 10 h and the red
solid obtained filtered off, washed with hexane (2 × 10 ml) and
dried in vacuo to give complex 10a (1.20 g, 2.42 mmol) (yield
1 D. E. Wigley, Prog. Inorg. Chem., 1994, 42, 239.
2 H. W. Roesky, H. Voelker, M. Witt and M. Noltemeyer, Angew.
Chem., Int. Ed. Engl., 1990, 29, 669.
3 J. E. Hill, R. D. Profilet, P. E. Fanwick and I. P. Rothwell, Angew.
Chem., Int. Ed. Engl., 1990, 29, 664.
4 See, for example, the following review: P. Mountford, Chem.
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5 E. A. Maatta and D. D. Devore, Angew. Chem., Int. Ed., 1998, 27,
569; E. A. Maatta and C. Kim, Inorg. Chem., 1989, 28, 624; R. K.
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1990, 112, 4588; W. Clegg, R. J. Errington, D. C. R. Hockless,
J. M. Kirk and C. Redshaw, Polyhedron, 1992, 11, 381; C. Redshaw,
G. Wilkinson, B. Hussain-Bates and M. B. Hursthouse, J. Chem.
Soc., Dalton Trans., 1992, 555; G. Hogarth, R. L. Mallors and
T. Norman, J. Chem. Soc., Chem. Commun., 1993, 1721; D. E.
Wheeler, J. F. Wu and E. A. Maatta, Polyhedron, 1998, 17, 969.
6 A. Antiñolo, F. Carrillo-Hermosilla, A. Otero, M. Fajardo, A.
Garcés, P. Gómez-Sal, C. López-Mardomingo, A. Martín and
C. Miranda, J. Chem. Soc., Dalton Trans., 1998, 59.
7 A. Antiñolo, P. Espinosa, M. Fajardo, P. Gómez-Sal, C. López-
Mardomingo, A. Martín and A. Otero, J. Chem. Soc., Dalton
Trans., 1995, 1007.
8 G. Parkin, A. Van Asselt, D. J. L. Leahy, R. N. Whinnery,
N. G. Hua, R. W. Quan, L. M. Henling, W. P. Schaefer, B. D.
Santarsiero and J. E. Bercaw, Inorg. Chem., 1992, 31, 82.
9 See for example: A. J. Blake, P. E. Collier, S. C. Dunn, W. S. Li,
P. Mountford and O. V. Shishkin, J. Chem. Soc., Dalton Trans., 1997,
1549.
1
48%). H NMR (CDCl3, 300 MHz): δ 1.35 (s, 18 H, NC5H4-
CMe3), 5.69, 6.34 (AAЈ and XXЈ part of an AAЈXXЈ spin
system, 4 H, phenylene ring), 7.50 (XXЈ part of an AAЈXXЈ
t
spin system, 4 H, m-H of NC5H4 Bu), 9.13 (AAЈ part of an
t
AAЈXXЈ spin system, 4 H, o-H of NC5H4 Bu) and 11.14 (s br,
2 H, NH). 13C-{1H} NMR (CDCl3, 50 MHz): δ 30.2 (NC5H4-
CMe3), 35.2 (NC5H4CMe3), 110.7 and 123.0 (phenylene ring),
t
121.4 (m-C of NC5H4 Bu), 144.7 (Cipso of phenylene ring), 149.2
t
t
(o-C of NC5H4 Bu) and 163.7 (p-C of NC5H4 Bu). IR 3299s,
1612s, 1271s, 1191m, 1069m, 1021m, 834s, 748s, 627m, 568m
and 395m cmϪ1 [Found (Calc. for C24H32Cl2N4Ti): C, 57.6
(58.2); H, 6.6 (6.5); N, 11.0 (11.3)%].
10 H. Bock, J. Meuret, C. Näther and U. Krynitz, Chem. Ber., 1994,
127, 55.
11 G. M. Sheldrick, SHELXS, Program for the Refinement of Crystal
Structures from Diffraction Data, University of Göttingen, 1997.
[Ti(TMEDA)Cl2{1,2-C6H4(NH)2}] 10b. Method A. To a solu-
tion of N,NЈ-bis(trimethylsilyl)-1,2-phenylenediamine (1.0 g,
3.96 mmol) in CH2Cl2 (40 ml) was added dropwise, at 0 ЊC, a
2382
J. Chem. Soc., Dalton Trans., 2000, 2375–2382