Ammonolysis of mono(pentamethylcyclopentadienyl) titanium(IV) derivatives

Article abstract of DOI:10.1021/ic9907718

Ammonolyses of mono(pentamethylcyclopentadienyl) titanium(IV) derivatives [Ti(η⁵-C₅Me₅)X₃] (X = NMe₂, Me, Cl) have been carried out in solution to give polynuclear nitrido complexes. Reaction of the tris(dimethylamido) derivative [Ti(η⁵-C₅Me₅)(NMe₂)₃] with excess of ammonia at 80-100 °C gives the cubane complex [{Ti(η⁵-C₅Me₅)}₄(μ₃-N)₄] (1). Treatment of the trimethyl derivative [Ti(η⁵-C₅Me₅)Me₃] with NH₃ at room temperature leads to the trinuclear imido-nitrido complex [{Ti(η⁵-C₅Me₅)(μ-NH)}₃(μ3-N)] (2) via the intermediate [{Ti(η⁵-C₅Me₅)Me}₂(μ-NH)₂] (3). The analogous reaction of [Ti(η⁵-C₅Me₅)Me₃] with 2,4,6-trimethylaniline (ArNH₂) gives the dinuclear imido complex [{Ti(η⁵-C₅Me₅)Me}₂(μ-NAr)₂] (4) which reacts with ammonia to afford [{Ti-(η⁵-C₅Me₅)(NH₂)}₂(μ-NAr)₂] (5). Complex 2 has been used, by treatments with the tris(dimethylamido) derivatives [Ti(η⁵-C₅H₅-(n)R(n))(NMe₂)₃], as precursor of the cubane nitrido systems [{Ti₄(η⁵-C₅Me₅)₃(η⁵-C₅H₅-(n)R(n))}(μ₃-N)₄] [R = Me n = 5 (1), R = H n = 0 (6), R = SiMe₃ n = 1 (7), R = Me n = 1 (8)] via dimethylamine elimination. Reaction of [Ti(η⁵-C₅Me₅)Cl₃] Or [Ti(ν⁵-C₅Me₅)(NMe₂)Cl₂] with excess of ammonia at room temperature gives the dinuclear complex [{Ti2(η⁵-C₅Me₅)₂Cl₃(NH₃)}(μ-N)] (9) where an intramolecular hydrogen bonding and a nonlineal nitrido ligand bridge the 'Ti(η⁵-C₅Me₅)Cl(NH₃)' and 'Ti(η⁵-C₅Me₅)Cl₂' moieties. The molecular structures of [{Ti(η⁵-C₅Me₅)Me}₂ (μ-NAr)₂] (4.) and [{Ti₂(η⁵-C₅Me₅)₂Cl₃(NH₃)}(μ-N)] (9) have been determined by X-ray crystallographic studies. Density functional theory calculations also have been conducted on complex 9 to confirm the existence of an intramolecular N-H···Cl hydrogen bond and to evaluate different aspects of its molecular disposition.

Full text of DOI:10.1021/ic9907718

642
Inorg. Chem. 2000, 39, 642-651
Ammonolysis of Mono(pentamethylcyclopentadienyl) Titanium(IV) Derivatives§
Angel Abarca,† Pilar Go´mez-Sal,† Avelino Mart´ın,† Miguel Mena,*,† Josep Mar´ıa Poblet,‡ and
Carlos Ye´lamos†
Departamento de Qu´ımica Inorga´nica, Universidad de Alcala´, Campus Universitario,
28871 Alcala´ de Henares, Madrid, Spain, and Departament de Qu´ımica F´ısica i Inorga´nica,
Universitat Rovira i Virgili, Imperial Tarraco 1, 43005 Tarragona, Spain
ReceiVed June 30, 1999
Ammonolyses of mono(pentamethylcyclopentadienyl) titanium(IV) derivatives [Ti(η5-C5Me5)X3] (X ) NMe2,
Me, Cl) have been carried out in solution to give polynuclear nitrido complexes. Reaction of the tris(dimethylamido)
derivative [Ti(η5-C5Me5)(NMe2)3] with excess of ammonia at 80-100 °C gives the cubane complex [{Ti(η5-
C5Me5)}4(µ3-N)4] (1). Treatment of the trimethyl derivative [Ti(η5-C5Me5)Me3] with NH3 at room temperature
leads to the trinuclear imido-nitrido complex [{Ti(η5-C5Me5)(µ-NH)}3(µ3-N)] (2) via the intermediate [{Ti(η5-
C5Me5)Me}2(µ-NH)2] (3). The analogous reaction of [Ti(η5-C5Me5)Me3] with 2,4,6-trimethylaniline (ArNH2)
gives the dinuclear imido complex [{Ti(η5-C5Me5)Me}2(µ-NAr)2] (4) which reacts with ammonia to afford [{Ti-
(η5-C5Me5)(NH2)}2(µ-NAr)2] (5). Complex 2 has been used, by treatments with the tris(dimethylamido) derivatives
[Ti(η5-C5H5-nRn)(NMe2)3], as precursor of the cubane nitrido systems [{Ti4(η5-C5Me5)3(η5-C5H5-nRn)}(µ3-N)4]
[R ) Me n ) 5 (1), R ) H n ) 0 (6), R ) SiMe3 n ) 1 (7), R ) Me n ) 1 (8)] via dimethylamine elimination.
Reaction of [Ti(η5-C5Me5)Cl3] or [Ti(η5-C5Me5)(NMe2)Cl2] with excess of ammonia at room temperature gives
the dinuclear complex [{Ti2(η5-C5Me5)2Cl3(NH3)}(µ-N)] (9) where an intramolecular hydrogen bonding and a
nonlineal nitrido ligand bridge the “Ti(η5-C5Me5)Cl(NH3)” and “Ti(η5-C5Me5)Cl2” moieties. The molecular
structures of [{Ti(η5-C5Me5)Me}2 (µ-NAr)2] (4) and [{Ti2(η5-C5Me5)2Cl3(NH3)}(µ-N)] (9) have been determined
by X-ray crystallographic studies. Density functional theory calculations also have been conducted on complex
9 to confirm the existence of an intramolecular N-H‚‚‚Cl hydrogen bond and to evaluate different aspects of its
molecular disposition.
Introduction
films of [TiN] have been prepared with chemical vapor
deposition (CVD) techniques involving a variety of precursors,
especially amido complexes.7-9 The presence of ammonia is
crucial to the growth of pure [TiN] in order to remove significant
amounts of carbon from the precursors.
In this context, it is important to understand the reaction
mechanism of metal amido and halide compounds with am-
monia.10,11 Gas-phase studies on the reaction of [Ti(NR2)4] and
NH3 provided mechanistic insight, suggesting transamination
reactions as the rate-limiting step in the deposition of TiN.7-9,12
Intermediates involving amido NH2 and imido NH groups have
been postulated in those processes. Often references to solution-
chemistry studies are used to understand the intermediate stages
and to explain spectroscopic data obtained in the gas
phase.7-9,13-15 The reactivity of amido complexes with second-
Tremendous interest exists in the use of chemical processing
routes to ceramics.1-5 Traditional synthetic methods to refractory
metal nitrides involve high-temperature combinations of the
elements or treatment of anhydrous metal halides with ammonia.
Recent synthetic strategies to new and existing metal nitrides
involve the use of molecular precursors, which reduce the energy
requirements to produce the desired materials. For instance,
titanium nitride [TiN] is a refractory, gold-colored material that
has been used in several industrial applications because of its
important properties, including extreme hardness, excellent
chemical resistance, desirable optical properties, and good
electrical conductivity.6 These characteristics have motivated
its use as coatings in several technological applications. Thin
* To whom correspondence should be addressed. Fax: +34 1 8854683.
E-mail: miguel.mena@uah.es.
(6) Toth, L. E. Transition Metal Carbides and Nitrides; Academic Press:
New York, 1971.
(7) For leading references, see: Hoffman, D. M. Polyhedron 1994, 13,
1169 and references 8 and 9 of this paper.
(8) Dubois, L. H. Polyhedron 1994, 13, 1329.
(9) Fix, R. M.; Gordon, R. G.; Hoffman, D. M. J. Am. Chem. Soc. 1990,
112, 7833.
(10) Maya, L. Inorg. Chem. 1986, 25, 4213 and references therein.
(11) Winter, C. H.; Lewkebandara, T. S.; Heeg, M. J.; Proscia, J. W.;
Rheingold, A. L. Inorg. Chem. 1994, 33, 1227 and references therein.
(12) Weiller, B. H. J. Am. Chem. Soc. 1996, 118, 4975.
(13) For recent examples, see: Jayaratne, K. C.; Yap, G. P. A.; Haggerty,
B. S.; Rheingold, A. L.; Winter, C. H. Inorg. Chem. 1996, 35, 4910
and references 14 and 15 of this paper.
§ Dedicated to Alexander von Humboldt on the occasion of his
commemorative year 1999.
† Universidad de Alcala´.
‡ Universitat Rovira i Virgili. Fax: +34 77 559563. E-mail: poblet@
argo.urv.es.
(1) Laine, R. M., Ed. Transformation of Organometallics into Common
and Exotic Materials: Design and ActiVation; NATO Advanced
Science Institute Series; Martinus Nijhoff: Dordrecht, The Netherlands,
1988.
(2) Segal, D. Chemical Synthesis of AdVanced Ceramic Materials;
Cambridge University Press: Cambridge, England, 1989.
(3) Lee, B. I.; Pope, E. J. A. Chemical Processing of Ceramics; Marcel
Dekker Inc.: New York, 1994.
(4) Interrante, L. V., Casper, L. A., Ellis, A. B., Eds. Materials
Chemistry: An Emergent Discipline; ACS Series 245; American
Chemical Society: Washington, DC, 1995.
(14) Cheon, J.; Rogers, D. M.; Girolami, G. S. J. Am. Chem. Soc. 1997,
119, 6804.
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119, 6814.
(5) Baldus, H.-P.; Jansen, M. Angew. Chem., Int. Ed. Engl. 1997, 36, 328.
10.1021/ic9907718 CCC: $19.00 © 2000 American Chemical Society
Published on Web 01/28/2000

Ammonolysis of [Ti(η5-C5Me5)X3] Derivatives
Inorganic Chemistry, Vol. 39, No. 4, 2000 643
ary and primary amines has been studied extensively in
solution,16-18 but analogous reactions with ammonia have
received little attention. Brown and Maya19 studied the reaction
between [Ti(NMe2)4] and liquid ammonia to produce an
insoluble polymeric material formulated as [Ti3(NMe2)(NH2)2-
(N)3] on the basis of analytical and IR data. Thermolysis of
this material yielded bulk titanium nitride at 800 °C. More
recently, Chisholm and co-workers reported the treatment of
[Ti(NRR’)4] with NH3 in hydrocarbon solvents to give insoluble
precipitates which yielded titanium nitride upon heating.20
Several polynuclear early transition metal nitrido complexes
have been obtained in the solution ammonolysis of organo-
metallic derivatives21-27 and the structural characterization
revealed the presence of nitrido (N3-), imido (NH2-), and amido
(NH21-) ligands bridging the metal centers. The solubility and
stability of this group of titanium,22 zirconium,23,24 and
tantalum25-27 compounds arise from the bulky ancillary ligands
(cyclopentadienyl, alkoxido, etc.) at the metal centers. In
particular, the ability of cyclopentadienyl groups to support
metallonitrido oligomers has been proved in Ta28,29 and V30,31
compounds prepared by distinct routes. We have previously
communicated the synthesis and structural characterization of
the first organometallic nitrido cubane [{Ti(η5-C5Me5)}4(µ3-N)4]
by treatment of [Ti(η5-C5Me5)(NMe2)3] with NH3.32 Herein we
report the solution treatment with ammonia of amido, alkyl,
and chlorocomplexes of titanium containing the pentamethyl-
cyclopentadienyl ligand. Several polynuclear nitrido derivatives
have been characterized in these processes, and interesting
spectroscopic and structural data are offered. Density functional
theory (DFT) calculations on the complex [{Ti2(η5-C5Me5)2-
Cl3(NH3)}(µ-N)] (9) were performed to confirm the intramo-
lecular N-H‚‚‚Cl hydrogen bond and to explain the geometrical
features found in the crystal structure determination.
Scheme 1. Ammonolysis of the Complex
[Ti(η5-C5Me5)(NMe2)3]
structure of cubic TiN.32 More recently, Bottomley and co-
workers described the preparation of a vanadium nitrido cluster
[{V(η5-C5Me5)}4(µ3-N)4] with a very similar structure.31
Attempts to detect or isolate any intermediate in the formation
of 1 failed. A NMR tube experiment of a sample of [Ti(η5-C5-
Me5)(NMe2)3] in benzene-d6 sealed under NH3 atmosphere was
monitored by 1H NMR spectroscopy. At temperatures close to
55 °C resonances for NHMe2 clearly appeared as the only new
species present in solution. Compound 1 exhibits good solubility
in chloroform and very poor solubility in other common
solvents. Solutions of 1 in chloroform-d1 remain unaltered under
argon atmosphere for long periods even after heating at 100 °C
for several days. Nevertheless, it is very sensitive to hydrolysis
in solid state and solution to give the oxoderivative [{Ti(η5-
C5Me5)}4(µ-O)6].33,34
Results and Discussion
The 15N NMR spectrum of [{Ti(η5-C5Me5)}4(µ3-15N)4] (1-
15N) showed a singlet at 500.6 ppm (CH3NO2 used as external
reference). To our knowledge, this shift is unusual in the
literature for organometallic or inorganic diamagnetic com-
pounds.21-27,35-37 We recently reported that the methylidyne
groups of the isoelectronic complex [{Ti(η5-C5Me5)}4(µ3-CH)4]
appear at very low field in 13C NMR spectroscopy (δ ) 490.8
ppm).38 The strong deshielding in both cases is evident and
consistent with the parallelism proposed in the literature between
15N and 13C chemical shifts.39
We next sought to study the similar reaction of complex [Ti-
(η5-C5Me5)Me3] with NH3 (Scheme 2). Treatment of [Ti(η5-
C5Me5)Me3] with excess of ammonia in toluene at room
temperature gave [{Ti(η5-C5Me5)(µ-NH)}3(µ3-N)] (2) as a
yellow solid. Heating of the reaction mixture at 150 °C did not
lead to a different result, and only compound 2 was isolated.
Furthermore, a benzene-d6 solution of 2 heated at 200 °C did
not show any detectable change in the 1H NMR spectrum. This
Treatment of [Ti(η5-C5Me5)(NMe2)3] with excess of ammonia
in hexane, toluene, or tetrahydrofuran (THF) at 80-100 °C
afforded [{Ti(η5-C5Me5)}4(µ3-N)4] (1) as a dark green crystalline
solid (Scheme 1). We have previously communicated the cubane
structure for 1 and established the geometrical relationship
between the Ti4N4 core of this complex and the rock-salt
(16) Bradley, D. C.; Thomas, I. M. J. Chem. Soc. 1960, 3857.
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and Metalloid Amides; John Wiley & Sons: New York, 1980.
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(20) Baxter, D. V.; Chisholm, M. H.; Gama, G. J.; DiStasi, V. F.; Hector,
A. L.; Parkin, I. P. Chem. Mater. 1996, 8, 1222.
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1989, 28, 754.
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A.; Zax, D. B. Chem. Mater. 1996, 8, 2468.
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Commun. 1987, 858.
(34) Go´mez-Sal, P.; Mena, M.; Royo, P.; Serrano, R. J. Organomet. Chem.
1988, 358, 147.
(35) For leading references to 15N NMR of early transition metal nitrido
complexes, see: Nugent, W. A.; Mayer, J. M. Metal-Ligand Multiple
Bonds; John Wiley & Sons: New York, 1988 and references 36 and
37 of this paper.
(29) Roesky, H. W.; Lu¨cke, M. J. Chem. Soc., Chem. Commun. 1989, 748.
(30) Haddad, T. S.; Aistars, A.; Ziller, J. W.; Doherty, N. M. Organome-
tallics 1993, 12, 2420.
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Organometallics 1996, 15, 1758.
(32) Go´mez-Sal, P.; Mart´ın, A.; Mena, M.; Ye´lamos, C. J. Chem. Soc.,
Chem. Commun. 1995, 2185.
(36) Glassman, T. E.; Liu, A. H.; Schrock, R. R. Inorg. Chem. 1991, 30,
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10, 4046.
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Ye´lamos, C. Angew. Chem., Int. Ed. Engl. 1997, 36, 115.
(39) Mason, J. Chem. ReV. 1981, 81, 205.

644 Inorganic Chemistry, Vol. 39, No. 4, 2000
Abarca et al.
Scheme 2. Ammonolysis of the Complex
[Ti(η5-C5Me5)Me3]
Scheme 3. Reaction of [Ti(η5-C5Me5)Me3] with
2,4,6-Trimethylaniline
complex has been previously prepared and characterized by
Roesky and co-workers.22 However, to compare it with other
complexes, we report its 1H and 13C{1H} NMR in C6D6, mass
spectra (EI), and full-detailed IR data (see the Experimental
Section). The 15N NMR spectrum reported for 2 was a doublet
(1JN-H ) 63.5 Hz) at 90.7 ppm corresponding to the three µ-NH
groups.22 In addition to this resonance, analysis of a sample
prepared with isotopically enriched NH3 (10% 15N) revealed a
singlet at 461.9 ppm assignable to the nitrido which bridges
the three titanium centers. The chemical shift for the nitrido
groups in the 15N NMR spectra of 1 (500.6 ppm) and 2 (461.9
ppm) are rare in the literature and could offer insight in other
studies. For example, the magic-angle spinning (MAS) 15N
(KBr, 3352 cm-1). The 1H and 13C{1H} NMR spectra reveal a
symmetric arrangement for both the terminal methyl and
pentamethylcyclopentadienyl ligands with respect to the central
Ti2(µ-NH)2 core, showing also a broad signal at δ ) 10.90 for
t
solid-state NMR spectrum of [{Ta(CH2 Bu)2(N)}5] revealed
resonances at δ ) 406 and 397 which were not assigned by the
authors.27
1
the NH groups in the H NMR spectrum.
Complex 2 was initially prepared in hexane.22 Nevertheless,
reactions run in this solvent without any magnetic stirring lead
to the precipitation of orange crystals from the solution. The
composition of these crystals as [{Ti(η5-C5Me5)Me}2(µ-NH)2]
(3) was established by spectroscopic and analytical data. The
mass spectrum was consistent with a dimeric formulation for
3, in good agreement to the well-known tendency of titanium
imido complexes.16-18,40-52 The IR spectrum shows one υNH
absorption at 3349 cm-1, in a range similar to that found in 2
Compound 3 is stable in solid state under argon at -30 °C
for at least several months, but it decomposes in a few hours in
hexane, benzene, or toluene solutions to give an unidentified
dark solid insoluble in common solvents. When a recently
prepared benzene-d6 solution of 3 was exposed to ammonia,
1
the H NMR showed the quantitative transformation in 2 and
concomitant loss of methane within a few minutes. The
characterization of complex 3 by 15N NMR spectroscopy was
1
not possible because of its lack of stability. However, the H
(40) Thorn, D. L.; Nugent, R. L.; Harlow, R. L. J. Am. Chem. Soc. 1981,
spectrum from a 15N isotopically enriched sample displays a
coupling constant (1JNH ) 63.0 Hz) analogous to that found in
2. Despite many attempts, suitable single crystals of complex 3
for an X-ray structure determination were not obtained.
103, 357.
(41) Jekel-Vroegop, C. T.; Teuben, J. H. J. Organomet. Chem. 1985, 286,
309.
(42) Hughes, D. L.; Latham, I. A.; Leigh, G. J. J. Chem. Soc., Dalton Trans.
1986, 393.
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T.; Edith Chan, A. W.; Hoffmann, R. J. Am. Chem. Soc. 1991, 113,
2985.
(44) Bai, Y.; Roesky, H. W.; Schmidt, H.-G.; Noltemeyer, M. Z. Natur-
forsch. 1992, B47, 603.
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Kalikhman, I. D.; Voronkov, M. G. J. Organomet. Chem. 1993, 461,
75.
(46) Lewkebandara, T. S.; Sheridan, P. H.; Heeg, M. J.; Rheingold, A. L.;
Winter, C. H. Inorg. Chem. 1994, 33, 5879.
(47) Grigsby, W. J.; Olmstead, M. M.; Power, P. P. J. Organomet. Chem.
1996, 513, 173.
(48) Liu, F.-Q.; Herzog, A.; Roesky, H. W.; Uso´n, I. Inorg. Chem. 1996,
35, 741.
The IR spectra recorded in the gas-phase ammonolysis of
[Ti(NMe2)4] showed absorptions assigned to NHx fragments of
oligomeric intermediates with [Ti2(µ-NH)2] cores.7,8 Further-
more, prominent bands in the range 3350-3190 cm-1 have been
described for the insoluble precipitates obtained in the analogous
solution reaction.19,20 It is very likely that species with NH
bridging fragments, similar to the existing in complexes 2 and
3, are formed during the ammonolysis process.
The treatment of [Ti(η5-C5Me5)Me3] with a primary amine
was studied to gain insight into the ammonolysis process and
also the structure of 3 (Scheme 3). Reaction of [Ti(η5-C5Me5)-
Me3] with 2,4,6-trimethylaniline (NH2Ar) in hexane at room
(49) Bettenhausen, R.; Milius, W.; Schnick, W. Chem. Eur. J. 1997, 3,
1337.
(50) Collier, P. E.; Blake, A. J.; Mountford, P. J. Chem. Soc., Dalton Trans.
1997, 2911.
(51) Mountford, P. Chem. Commun. 1997, 2127.
(52) Hughes, A. K.; Marsh, S. M. B.; Howard, J. A. K.; Ford, P. S. J.
Organomet. Chem. 1997, 528, 195.

Ammonolysis of [Ti(η5-C5Me5)X3] Derivatives
Inorganic Chemistry, Vol. 39, No. 4, 2000 645
Scheme 4. Reaction of [{Ti(η5-C5Me5)(µ-NH)}3(µ3-N)] (2)
with [Ti(η5-C5H5-nRn)(NMe2)3]
Figure 1. Perspective view of [{Ti(η5-C5Me5)Me}2(µ-NAr)2] (4).
Thermal ellipsoids correspond to 50% of probability.
Table 1. Selected Lengths (Å) and Angles (deg) for Complex 4a
Ti(1)-N(1)
Ti(1)-C(1)
N(1)-C(21)
1.946(3)
2.129(4)
1.422(4)
Ti(1)-N(1)a
Ti(1)‚‚‚Ti(1)a
Ti(1)-C5Me5(1)
1.953(3)
2.829(1)
2.097
N(1)-Ti(1)-N(1)a
N(1)a-Ti(1)-C(1)
C(21)-N(1)-Ti(1)a
87.0(1) N(1)-Ti(1)-C(1)
102.3(1) C(21)-N(1)-Ti(1)
132.7(2) Ti(1)-N(1)-Ti(1)a
102.8(2)
134.3(2)
93.0(1)
C5Me5(1)-Ti(1)-N(1) 126.9
C5Me5(1)-Ti(1)-N(1)a 128.3
C5Me5(1)-Ti(1)-C(1) 105.3
an undistorted Ti(µ-NR)2Ti fragment.40,44,45,47,48,52 The geometry
at the bridging nitrogen atoms is trigonal planar [sum of angles
) 360.0(2)°] and perpendicular to the Ar imido groups.
Treatment of complex 4 with ammonia in toluene at room
temperature afforded the dinuclear imido derivative [{Ti(η5-
C5Me5)(NH2)}2(µ-NAr)2] (5) as a light brown precipitate in 88%
yield. Complex 5 is only soluble in chloroform and can be
washed with other solvents without significant waste of product.
The IR spectrum shows two bands at 3394 and 3321 cm-1 for
the NH2 stretching vibrations and one absorption at 1537 cm-1
consistent with an NH2 bending mode.58 The 1H NMR spectrum
manifested the symmetric arrangement of the molecule and also
the presence of NH2 groups affording a broad signal at δ )
3.78 (4H). Complex 5 might be similar to an intermediate “[{Ti-
(η5-C5Me5)(NH2)}2(µ-NH)2]” hypothetically formed in the am-
monolysis of 3 to give 2 (Scheme 2).
A striking feature in our ammonolysis studies is the different
products, 1 and 2, obtained under similar conditions from [Ti-
(η5-C5Me5)(NMe2)3] and [Ti(η5-C5Me5)Me3]. For this reason,
the relationship between 1 and 2 has been investigated. We have
found that treatment of 2 with proportional amounts (1:1) of
tris(dimethylamido) titanium derivatives59-61 [Ti(η5-C5H5nRn)-
(NMe2)3] in benzene or toluene at 110-160 °C affords the
cubane nitrido complexes [{Ti4(η5-C5Me5)3(C5H5nRn)}(µ3-N)4]
[R ) Me n ) 5 (1), R ) H n ) 0 (6), R ) SiMe3 n ) 1 (7),
R ) Me n ) 1 (8)] via dimethylamine elimination. As shown
in Scheme 4, these reactions formally represent the addition of
a Symmetry transformations used to generate equivalent atoms: a,
-x, -y, -z + 1. C5Me5 is the centroid of the η5-C5Me5 ligand ring.
temperature gave the dinuclear imido complex [{Ti(η5-C5Me5)-
Me}2(µ-NAr)2] (4) as a brown precipitate in 40% yield after
workup.
The composition of 4 was established by a combination of
spectral and analytical data. NMR spectra showed a symmetric
structure in solution and the trans arrangement of the terminal
groups was confirmed by an X-ray crystal structure determi-
nation (Figure 1). Selected distances and angles are presented
in Table 1. Compound 4 is a dimer, with one pentamethylcy-
clopentadienyl, one methyl, and one imido ligand per metal
atom. The two titanium centers are held together [Ti1‚‚‚Ti1a
) 2.829(1)] by the two bridging imido ligands. Each molecule
of 4 lies on a crystallographic inversion center and the titanium
atoms possess a classical three-legged piano-stool arrangement.
The titanium-C5Me5(centroid) (2.097 Å) and titanium-carbon-
(Me) [2.129(4) Å] bond lengths are in the normal range for
this type of complex.53-57 Bond lengths and angles associated
with the imido linkages [Ti(1)-N(1) 1.946(3), Ti(1)-N(1a)
1.953(3) Å, Ti(1)-N(1)-Ti(1a) 93.0(1)°] are similar to those
found in other structurally characterized complexes containing
(53) Blanco, S. G.; Go´mez-Sal, M. P.; Carreras, S. M.; Mena, M.; Royo,
P.; Serrano, R. J. Chem. Soc., Chem. Commun. 1986, 1572.
(54) Go´mez-Sal, M. P.; Mena, M.; Royo, P.; Serrano, R. J. Organomet.
Chem. 1988, 358, 147.
(55) Flores, J. C.; Mena, M.; Pellinghelli, M. A.; Royo, P.; Serrano, R.;
Tiripicchio, A. Organometallics 1989, 8, 1404.
(56) Blom, R.; Rypdal, K.; Mena, M.; Royo, P.; Serrano, R. J. Organomet.
Chem. 1990, 391, 47.
(57) Go´mez-Sal, P.; Mart´ın, A.; Mena, M.; Ye´lamos, C. Inorg. Chem. 1996,
35, 242.
(58) Nakamoto, K. Infrared and Raman Spectra of Inorganic and Coor-
dination Compounds, 4th ed.; J. Wiley & Sons: New York, 1986.
(59) Chandra, G.; Lappert, M. F. J. Chem. Soc. A 1968, 1940.
(60) Burger, H.; Dammgen, U. J. Organomet. Chem. 1975, 101, 295.
(61) Mart´ın, A.; Mena, M.; Serrano, R.; Ye´lamos, C.; Raithby, P. R. J.
Organomet. Chem. 1994, 467, 79.

646 Inorganic Chemistry, Vol. 39, No. 4, 2000
Scheme 5. Ammonolysis of the Complexes
Abarca et al.
soluble in aromatic and aliphatic solvents. 1H and 13C{1H} NMR
spectra revealed resonances for two different (η5-C5Me5) groups
and a broad signal at δ ) 2.70 (3H) in the proton spectrum
assigned to an NH3 ligand. 15N NMR spectrum showed a singlet
at δ ) 431.6 for the nitrido ligand and a broad signal at δ )
-360.8 for the NH3 molecule. This chemical shift of the
ammonia present in compound 9 is similar to the values found
in the complexes [TiCl4(NH3)2] (-361.2 ppm),11 and [Ta5(CH2-
tBu)10(µ3-N)3(µ-N)2‚NH3] (-360 ppm).26 Mass spectrometry
showed the easy elimination of NH3 from a dinuclear structure.
The infrared spectrum presents weak υNH bands at values (3286,
3227, 3144, and 3040 cm-1) similar to those reported for [TiCl4-
(NH3)2] where N-H‚‚‚Cl hydrogen bonding was proposed.11
Also the IR spectrum showed a very strong absorption at 931
cm-1 assigned to the TidNdTi fragment established by an
X-ray structure determination.
[Ti(η5-C5Me5)(NMe2)xCl3-x
]
the fourth metal vertex to the precubane structure complex 2.
We are currently exploring this reaction path with a variety of
other metal complexes.
The molecular structure of [{Ti2(η5-C5Me5)2Cl3(NH3)}(µ-N)]
(9) is shown in Figure 2 and selected distances and angles in
Table 2. Inspection of the unit cell reveals molecular association
along the crystal by intermolecular hydrogen bonding between
one of the hydrogen atoms in the NH3 ligand and the chlorine
atom Cl(1) of other molecules [length N(2)‚‚‚Cl(1) ) 3.478 Å].
Complex 9 is a dimer, with two asymmetric moieties “Ti(η5-
C5Me5)L2” held together by a bridging nitrido ligand. Each
titanium atom has a classical three-legged piano-stool arrange-
ment, with two chlorine, and the nitrido for Ti(1), and one
chlorine, one ammonia, and one nitrido ligand for Ti(2). The
pseudotetrahedral angles around the titanium atoms span 95.2-
117.2°. The titanium-C5Me5(centroid) and titanium-chlorine
bond lengths are in the normal range,53-57,70-72 and those for
Ti(2) [Ti(2)-(C5Me5)(2) 2.036 Å, and Ti(2)-Cl(3) 2.283(2) Å]
are slightly shorter than the corresponding Ti(1) [Ti(1)-(C5-
Me5)(1) 2.050 Å, Ti(1)-Cl(1) 2.326(1) Å, and Ti(1)-Cl(2)
2.320(2) Å]. The titanium-nitrogen(ammonia) distance of
2.158(4) Å exceeds the sum of the covalent radii for Ti and N
(1.32 + 0.75 ) 2.07 Å)73 but is shorter than those found in
amine titanium(IV) adducts.74,75 To our knowledge, there are
no other crystallographic characterized titanium organometallic
complexes with ammonia and the only group 4 structurally
documented example is [Zr(η8-C8H8)(η4-C8H8)(NH3)].76
The bridging nitrido ligand of 9 is characterized by titanium-
nitrogen bond lengths of 1.784(4) [Ti(2)-N(1)] and 1.792(3)
Å [Ti(1)-N(1)]. Monomeric titanium imido complexes reported
to date show titanium-nitrogen bond lengths in the range 1.65-
1.74 Å consistent with a formal triple bond.77-80 The Ti(2)-
N(1) distance in the nitrido group is longer and it should be
Complexes 6-8 were isolated in 41-51% yields as dark
crystalline solids soluble in aromatic and aliphatic solvents. The
extreme air sensitivity of these complexes did not allow us to
obtain analytically pure samples of 7 and 8, but spectroscopic
data for all the compounds agreed with a cubane nitrido structure
similar to that reported for [{Ti(η5-C5Me5)}4(µ3-N)4] (1).32 IR
spectra of the cubane complexes 1 and 6-8 show very strong
absorptions in the range 651-644 cm-1, assignable to the
titanium-nitrogen bonds. Analogous bands have been reported
for amido60,62,63 and bridging imido64,65 titanium complexes, and
even binary nitrides MNy.66 Very strong bands at 59019 and 63020
cm-1 also have been reported for the insoluble precipitates
obtained in the solution ammonolysis of [Ti(NMe2)4].
It is very interesting to consider the Ti4N4 fragment of
complexes 1 and 6-8 as building blocks in the gas phase to
form a film of titanium nitride on a surface (CVD).67 Chen and
Castleman68 showed the particular stability of clusters (TiN)x
in the gas phase when the clusters corresponded to a piece of
the cubic NaCl structure (x ) 2, 3, 4, 6, 9, ..., the so-called
“magic numbers”). Significantly, the most stable structures of
the clusters are cuboids.
We next examined the reaction of the chloroderivatives [Ti-
(η5-C5Me5)(NMe2)xCl3-x] with ammonia (Scheme 5). Treatment
of [Ti(η5-C5Me5)Cl3] with NH3 in toluene, diethyl ether, or THF
at room temperature gave the dinuclear complex [{Ti2(η5-C5-
Me5)2Cl3(NH3)}(µ-N)] (9) with concomitant ammonium chloride
formation. Although the ammonolysis reaction seemed to
proceed quantitatively, the presence of NH4Cl and small
amounts of the oxoderivative [{Ti(η5-C5Me5)Cl2}2(µ-O)]69
complicated the isolation of 9 and only low yields were obtained
(25%). Reaction of [Ti(η5-C5Me5)(NMe2)Cl2] with NH3 in
toluene produces 9 in 40% isolated yield with dimethylamine
and ammonium chloride as secondary species. Analogous
treatment of [Ti(η5-C5Me5)(NMe2)2Cl] afforded an intractable
mixture of products.
(70) See for example [Ti(η5-C5Me5)(NtBu)ClPy]: Bai, Y.; Noltemeyer, M.;
Roesky, H. W. Z. Naturforsch. 1991, 46B, 1357, and refs 71 and 72
of this paper.
(71) [Ti(η5-C5Me5)(NiPr2)Cl2]; Pupi, R. M.; Coalter, J. N.; Petersen, J. L.
J. Organomet. Chem. 1995, 497, 17.
(72) Carpenetti, D. W.; Kloppenburg, L.; Kupec, J. T.; Petersen, J. L.
Organometallics 1996, 15, 1572 and references therein.
(73) Miessler, G. L.; Tarr, D. A. Inorganic Chemistry, 2nd ed.; Prentice
Hall: NJ, 1999; p 43.
The resultant compound 9 was isolated as an orange solid
very soluble in chloroform and dichloromethane but scarcely
(74) TirTMEDA (2.23-2.28 Å); ref 46 and the following: Duchateau,
R.; Williams, A. J.; Gambarotta, S.; Chiang, M. Y. Inorg. Chem. 1991,
30, 4863.
(75) TirNMe2H (2.355(3) Å); Fuhrmann, H.; Brenner, S.; Arndt, P.;
Kempe, R. Inorg. Chem. 1996, 35, 6742.
(62) Weidlein, J.; Mu¨ller, U.; Dehnicke, K. Schwingungsfrequenzen II.
Nebengruppenelemente; Georg Thieme Verlag: Stuttgart, 1986.
(63) Irigoyen, A. M.; Mart´ın, A.; Mena, M.; Palacios, F.; Ye´lamos, C. J.
Organomet. Chem. 1995, 494, 255.
(64) Lappert, M. F.; Sanger, A. R. J. Chem. Soc. A 1971, 874.
(65) Vroegop, C. T.; Teuben, J. H.; van Bolhuis, F.; Van der Linden, G.
M. J. Chem. Soc., Chem. Commun. 1983, 550.
(66) Hector, A. L.; Parkin, I. P. Polyhedron 1995, 14, 913.
(67) Unfortunately, the lack of volatility of cubane 1 rules out its use as
CVD precursor.
(68) Chen, Z. Y.; Castleman, A. W. J. Chem. Phys. 1993, 98, 231.
(69) Palacios, F.; Royo, P.; Serrano, R.; Balca´zar, J. L.; Fonseca, Y.;
Florencio, F. J. Organomet. Chem. 1989, 375, 51.
(76) Berno, P.; Floriani, C.; Chiesi-Villa, A.; Rizzoli, C. J. Chem. Soc.,
Dalton Trans. 1991, 3085.
(77) For a comprehensive review of terminal imido complexes, see: Wigley,
D. E. Prog. Inorg. Chem. 1994, 42, 239. For some recently published
articles, see refs 78-80.
(78) Swallow, D.; McInnes, J. M.; Mountford, P. J. Chem. Soc., Dalton
Trans. 1998, 2253.
(79) Stewart, P. J.; Blake, A. J.; Mountford, P. Organometallics 1998, 17,
3271.

Ammonolysis of [Ti(η5-C5Me5)X3] Derivatives
Inorganic Chemistry, Vol. 39, No. 4, 2000 647
Figure 2. Perspective view of [{Ti2(η5-C5Me5)2Cl3(NH3)}(µ-N)] (9). Thermal ellipsoids correspond to 50% of probability.
Table 2. Selected Lengths (Å) and Angles (deg) for Complex 9a
Ti(1)-N(1)
Ti(1)-Cl(1)
Ti(2)-N(2)
Ti(1)-C5Me5(1)
N(2)-Cl(2)
1.792(3)
2.326(1)
2.158(4)
2.051
Ti(1)-Cl(2)
Ti(2)-N(1)
Ti(2)-Cl(3)
Ti(2)-C5Me5(2)
2.320(2)
1.784(4)
2.283(2)
2.036
3.404(5)
N(1)-Ti(1)-Cl(2)
Cl(2)-Ti(1)-Cl(1)
N(1)-Ti(2)-Cl(3)
Ti(2)-N(1)-Ti(1)
C5Me5(1)-Ti(1)-Cl(2) 115.8
C5Me5(2)-Ti(2)-Cl(3) 116.0
C5Me5(2)-Ti(2)-N(2) 115.9
103.2(1) N(1)-Ti(1)-Cl(1)
100.4(1) N(1)-Ti(2)-N(2)
108.1(1) N(2)-Ti(2)-Cl(3)
105.4(1)
101.6(2)
95.2(2)
153.1(2) C5Me5(1)-Ti(1)-Cl(1) 114.7
C5Me5(1)-Ti(1)-N(1) 115.5
C5Me5(2)-Ti(2)-N(1) 117.1
a C5Me5 are the centroids of the η5-C5Me5 ligand rings.
considered as a double bond, TidN. An analogous distance
[1.81(1) Å] has been reported for the complex [{Cp2(PMe3)-
TidNC(Ar)C(Ar)NdTiCp2(PMe3)].81 On the other hand, Ti-
(1)-N(1) bond length is shorter than the usual bond length in
amido18,72 and bridging imido40-52 titanium complexes, and can
be rationalized by an important donation of the nitrogen lone
pair to this metal center. A similar argument has been proposed
to explain the Ti-N distance [1.800(1) Å] in the amido
derivative [TiCl{N(SnMe3)}(2,6-Ph2C6H3O)2].82 From these
features, we suggest that the bonding for the bridging fragment
can be described as Ti(2)dN(1)dTi(1) similar to those reported
for [{N(CH2CH2N-iPr)3Ti}2(µ3-N)Na(THF)],83 [(η5-C5Me5)-
Me3W(µ-N)WMe3(η5-C5Me5)],36 [(Ph4P){Cl5W(µ-N)WCl5}],21
and [(NH4)3{X5Ta(µ-N)TaX5}] (X ) Br, I).21 The titanium-
nitrogen-titanium angle in our case [153.1(2)°] is narrower than
the almost linear disposition found in those complexes (M-
N-M ) 170-180° M ) Ti, W, Ta). Angles also notably
smaller than 180° have been described for the compounds [Cl3-
OW(µ-N)(µ-O2PCl2)WOCl3]2- (166.2°),21 [Cl2(η5-C5Me5)Mo(µ-
N)(µ-N2CCH3)Mo(η5-C5Me5)Cl2] (161.4°),84 and [{Ta(η5-C5-
Me5)X}3(µ-N)3] (X ) Cl,28 128°, X ) Me,25 127°) where an
additional bridging ligand is always present. Furthermore, in
complex 9 the planarity of the Ti(1)Ti(2)N(1)N(2)Cl(2) system
and a N(2)‚‚‚Cl(2) distance [3.404(5) Å] slightly longer than
the sum of the van der Waals radii of the N and Cl atoms (1.50
Figure 3. View of the molecular structures of [{Ti2(η5-C5Me5)2Cl3-
(NH3)}(µ-N)] (9) (A) and [(Ti(η5-C5Me5)Cl)3(µ-O)3] (B) without the
(η5-C5Me5) ligands.
and 1.80 Å,85 respectively) suggest an intramolecular hydrogen
bonding interaction between N(2) and Cl(2) atoms. The
structural disposition of cyclopentadienyl and chlorine ligands
with respect to the fragment Ti(1)Ti(2)N(1)N(2)Cl(2) is shown
in Figure 3A and compares well with that found for analogous
groups in the trinuclear complexes [{Ti(η5-C5Me5)X}3(µ-O)3]
[X ) Cl (Figure 3B),86 Br,87 Me,53 crotyl88] and [{Ta(η5-C5-
Me5)X}3(µ-N)3] (X ) Cl,28 Me25).
(80) Ye´lamos, C.; Heeg, M. J.; Winter, C. H. Organometallics 1999, 18,
1168.
(81) Doxsee, K. M.; Garner, L. C.; Juliette, J. J. J.; Mouser, J. K. M.;
Weakley, T. J. R. Tetrahedron 1995, 51, 4321.
(82) Dilworth, J. R.; Hanich, J.; Krestel, M.; Beck, J.; Stra¨hle, J. J.
Organomet. Chem. 1986, 315, C9.
(83) Duan, Z.; Verkade, J. G. Inorg. Chem. 1996, 35, 5325.
(84) Herrmann, W. A.; Bogdanovic, S.; Priermeier, T.; Poli, R.; Fettinger,
J. C. Angew. Chem., Int. Ed. Engl. 1995, 34, 112.
(85) Greenwood, N. N.; Earnshaw, A. Chemistry of the Elements; Perga-
mon: Oxford, England, 1994; p 65.
(86) Carofligio, T.; Floriani, C.; Sgamellotti, A.; Rosi, M.; Chiesi-Villa,
A.; Rizzoli, C. J. Chem. Soc., Dalton Trans. 1992, 1081.
(87) Troyanov, S. I.; Varga, V.; Mach, K. J. Organomet. Chem. 1989, 402,
201.
(88) Andre´s, R.; Galakhov, M.; Go´mez-Sal, M. P.; Mart´ın, A.; Mena, M.;
Santamar´ıa, C. J. Organomet. Chem. 1996, 526, 135.

648 Inorganic Chemistry, Vol. 39, No. 4, 2000
Abarca et al.
Table 3. Some Computed and Experimental Bond Lengths and
Angles for 9 and the Model 10
DFT
X-ray
10
9
9
Ti(1)-N(1)
1.835
1.768
2.199
2.353
1.837
1.787
2.194
2.367
1.792(3)
1.784(4)
2.158(4)
2.320(2)
Ti(2)-N(1)
Ti(2)-N(2)
Ti(1)-Cl(2)
Ti(1)-N(1)-Ti(2)
151.1
150.7
153.1(2)
Theoretical Study of Complex 9. DFT calculations were
conducted to characterize these N-H‚‚‚Cl and TidNdTi
intramolecular interactions and to explain the molecular disposi-
tion found for compound 9. The first series of calculations were
conducted on [{Ti2Cp2Cl3(NH3)}(µ-N)] (10), as the model
complex for 9. Although the methyl groups were substituted
by hydrogen atoms, the DFT calculations reproduced the
molecular structure of 9 very well (Table 3). The major
discrepancies between the experimental and the theoretical bond
lengths appear in the N(1)-Ti(1) bond distance and in the long
Ti(2)-N(2) bond length. In both cases the deviation is ap-
proximately 0.04 Å. The computed Ti(1)-N(1)-Ti(2) angle
(151.1°) also compares very reasonably with the experimental
one (153.1°).
Figure 4. Electron density plot for the DFT optimized model complex
[{Ti2(Cp)2Cl3(NH3)}(µ-N)] (10) in its optimal structure.
fragments. The formation of the six-membered ring via attractive
N-H‚‚‚Cl interaction also stabilizes the bent conformation when
a Cl- is substituted by a NH3. The short distance (2.163 Å)
between one of the hydrogen atoms in the NH3 ligand and the
chlorine atom Cl(2) (Figure 3A) clearly suggests the existence
of an intramolecular hydrogen bond. Stabilization by the
formation of a hydrogen bond is also suggested, because the
alternative geometry with two hydrogens of the NH3 group
oriented toward the chlorine is higher than the minimum by 5
kJ‚mol-1. In this new conformation the H‚‚‚Cl(2) separations
are now 2.65 and 2.82 Å.
Bottomley and Goh analyzed the structure of 283 complexes
of the [(MLm)(µ-A)(M′L′n)] type by statistical methods.89 For
compounds [{M(η5-C5R5)L2}2(µ-A)], a special case of the
[(ML5)2(µ-A)] complexes, they showed from the extended
Hu¨ckel calculations that the energy of the complexes depends
very little on the M-A-M angle (180-140°) when the number
of metal electrons is less than 9. Our calculations for model
compound 10 seems to confirm this hypothesis, because the
energy of the linear complex with the Ti-N-Ti angle fixed to
180° was computed to be higher than the bent complex by only
According to the theory of “atoms in molecules” (AIM), the
presence of a bond critical point (bcp) in the charge density
distribution linking two nuclei at the equilibrium geometry is a
necessary and sufficient condition for the existence of a
bond.92,93 The basic idea of the AIM scheme is that atomic nuclei
correspond to electron density maxima, and a bond path,
characterized by a bcp, can be rigorously defined between each
bound pair of atoms. The AIM scheme seems particularly
suitable for cases in which chemical bonding between atoms
cannot be clearly assigned only from geometrical features.
Figure 4 shows the electron density plot for the DFT optimized
complex 10 in its optimal structure in a plane defined by N(2),
Cl(2), and the H in the NH3 ligand closest to the Cl(2) atom.
Although a larger scale would be more appropriate for a general
view, we have chosen this illustration because it highlights the
particular interaction among these three atoms. In the charge
density distribution, we can clearly identify a maximum charge
density on each of the three nuclei. The maximum on the
hydrogen atom is less pronounced, because this atom has only
1 e-. When going from hydrogen to chlorine, the density
decreases, reaches a minimum in this direction, and then
increases again. The minimum point in this particular direction
corresponds to a density maximum in the perpendicular direc-
tion. It would also correspond to a maximum in the third
dimension, which is perpendicular to the plane of the drawing.
The point at which the gradient of the charge density is zero
and the density is minimum in one direction and maximum in
the other two is called the bcp in the AIM theory. Such a point
in the charge distribution of complex 10 linking the chlorine
and hydrogen nuclei confirms the previously mentioned forma-
tion of a six-membered ring via a hydrogen bond. The values
of the charge density (F) and laplacian of the charge density
7.5 kJ‚mol-1
.
Another feature that deserves attention in molecules of the
[{M(η5-C5R5)L2}2(µ-A)] type is the relative arrangement be-
tween the two cyclopentadienyl ligands. In this article, we
specify the relative orientation of the two “TiCpL2” halves using
the dihedral angle φ defined by the two centroids of the Cp
groups and the titanium atoms. In the structure of minimum
energy for 10, the value of this torsion angle φ was 148°. The
energy of this compound in the staggered conformation (φ )
180°, the most common arrangement of the η5-C5R5 ligands
with linear M-A-M units) is 26.4 kJ‚mol-1 higher than the
minimum. What is the origin of this relatively important
difference in energy between the minimum (or bent structure)
and the staggered conformation? To answer this question, we
have also analyzed these two conformations for the still
unknown anion [{(TiCpCl2)2(µ-N)}-]. In this case, the linear
and bent structures have similar energies (∆E ≈ 1.3 kJ‚mol-1),
which shows that the energy of the molecule does not change
rotating one “TiCpL2” fragment by ≈30°. This result, which is
completely consistent with the two observed conformations for
[(TiCpCl2)2(µ-O)],90,91 an analogue complex of [{(TiCpCl2)2-
(µ-N)}-], suggests that the steric repulsion between the two Cp’s
does not increase when going from the staggered structure to
the bent one. However, the rotation moves the ammonia in
complex 10 away from the Cp ligand of the other half, thus
lowering the steric repulsion between the two “TiCpL2”
(89) Bottomley, F.; Goh, S.-K. Polyhedron 1996, 15, 3045.
(90) Thewalt, U.; Schomburg, D. J. Organomet. Chem. 1977, 127, 169.
(91) Gowik, P.; Klapo¨tke, T.; Pickardt, J. J. Organomet. Chem. 1990, 393,
343.
2
(∇ F) at the bcp define the topological properties of a bond in
2
the AIM theory. In this case, the values of F and ∇ F (0.028

Ammonolysis of [Ti(η5-C5Me5)X3] Derivatives
Inorganic Chemistry, Vol. 39, No. 4, 2000 649
and 0.069 au, respectively) are in the range reported for other
hydrogen bonds.94
Although incorporating the methyl groups into the calcula-
tions does not modify significantly the geometry of the complex
(see Table 3), the new structure has two short distances between
the chlorine atoms Cl(1) and Cl(2) and one methyl hydrogen
of the other half of the molecule. The computed C-H‚‚‚Cl
distances (2.707 and 2.531 Å, respectively) are clearly longer
than the N-H‚‚‚Cl(2) distance (2.167 Å). Scholz et al. recently
characterized intramolecular C-H‚‚‚Cl hydrogen bonds in
titanium and niobium complexes, with distances between 2.59
and 2.69 Å.95 All these distances are significantly shorter than
the sum of the van der Waals radii of chlorine and hydrogen
(≈3 Å85). The existence of three hydrogen bonds in 9 is
confirmed by analyzing the charge density. Besides the bcp
associated with the N-H‚‚‚Cl(2) hydrogen bond, two additional
bcp’s were found associated with C-H‚‚‚Cl interactions. In
these hydrogen bonds, the values of F at the bcp’s were lower
than in the hydrogen bond that forms Cl(2) with one hydrogen
of ammonia because of the existing inverse correlation between
the bond distance and the density at the bcp.96
The staggered conformation was also computed for 9.
Substituting hydrogen atoms by methyl groups in the Cp ligands
did not change our general conclusions for complex 10. The
energy difference between the bent and staggered conformations
in complex 9 (27.2 kJ‚mol-1) is almost identical with the energy
computed for 10 (26.4 kJ‚mol-1). This similarity can be
attributed to the fact that in the staggered conformation of 9
there are also two short C-H‚‚‚Cl distances, whose values are
2.62 and 2.72 Å. So, the new interactions that appear with the
methyl groups do not produce a further stabilization of the bent
structure. Opening the Ti-N-Ti angle from 151° to 180° in
complex 9 requires an energy of ∼4 kJ‚mol-1, which is
somewhat less than for 10.
Another interesting feature of complex 9 mentioned above
is the presence of two short titanium-nitrido distances, which
suggests that there are two π Ti-N bonds. Analysis of the
molecular orbitals fully confirms this interpretation for the Ti-
N-Ti interaction. Figure 5A shows a plot of the highest
occupied molecular orbital (HOMO)-2 in the plane defined by
the two titaniums and the bridging nitrogen. If we consider that
the two metals define the z-axis and that the bridging nitrogen
is in the xz-plane, from Figure 5A we can clearly identify the
π-donation from the px(N) orbital to the dxz orbitals of the two
metals. The π interaction in the plane yz is also delocalized
between the three atoms and appears in the HOMO, a plot of
which is presented in Figure 5B in a plane defined by the two
titaniums and the Cl(3) atom. Notice that this plane is ap-
proximately perpendicular to the plane that contains the atoms
Ti(1), Ti(2), and N(1) (the dihedral angle between the two planes
is 83°).
Figure 5. Plot of the π orbitals HOMO-2 (A) and HOMO (B) in the
planes defined by the two metals and N(1), and the two metals and
Cl(3), respectively.
N)4] (1), [{Ti(η5-C5Me5)(µ-NH)}3(µ3-N)] (2), and [{Ti2(η5-C5-
Me5)2Cl3(NH3)}(µ-N)] (9). The precubane structure of 2 is
capable of incorporating the fourth metal vertex by reaction with
tris(dimethylamido) titanium(IV) derivatives, and generating a
family of tetranuclear nitrido complexes containing different
cyclopentadienyl groups: [{Ti4(η5-C5Me5)3(η5-C5H5-nRn)}(µ3-
N)4] (6-8). The crystal structure of the unprecedented ammonia
titanium organometallic adduct 9 shows a bent disposition
around the nitrido ligand and suggests the existence of inter/
intramolecular hydrogen bond interactions N-H‚‚‚Cl. DFT
calculations carried out on this complex show that the structure
of minimum energy (bent conformation with φ ) 144°, φ is
the dihedral angle defined by the two centroids of the η5-C5-
Me5 ligands and the metal atoms) is 27.2 kJ‚mol-1 less than
the staggered conformation (φ ) 180°) with a linear Ti-N-Ti
unit. In the most stable arrangement, N-H‚‚‚Cl and C-H‚‚‚Cl
hydrogen bonds were characterized by means of the topology
of the charge density.
Conclusions
We have described that the ammonolysis of mono(penta-
methylcyclopentadienyl) titanium(IV) derivatives [Ti(η5-C5-
Me5)X3] (X ) NMe2, Me, Cl) in solution is a suitable route to
obtain polynuclear nitrido complexes as [{Ti(η5-C5Me5)}4(µ3-
(92) Bader, R. F. W. Atoms in Molecules. A Quantum Theory; Clarendon
Press: Oxford, 1990.
Experimental Section
(93) Bader, R. F. W. Chem. ReV. 1992, 91, 893.
General Considerations. All manipulations were carried out under
argon atmosphere using Schlenk line or glovebox techniques. Hexane
and pentane were distilled from Na/K amalgam just before use. Toluene
was freshly distilled from sodium. Tetrahydrofuran and diethyl ether
were distilled from purple solutions of sodium/benzophenone ketyl
(94) Reference 92, p 290.
(95) Spaniel, T.; Go¨rls, H.; Scholz, J. Angew. Chem., Int. Ed. 1998, 37, 7,
1862.
(96) Kempf, J. Y.; Rohmer, M. M.; Poblet, J. M.; Bo, C.; Benard, C. J.
Am. Chem. Soc. 1992, 114, 1136.

650 Inorganic Chemistry, Vol. 39, No. 4, 2000
Abarca et al.
immediately before use. NMR solvents were dried with P2O5 (CDCl3)
or Na/K amalgam (C6D6) and vacuum-distilled. Oven-dried glassware
was repeatedly evacuated with a pumping system (ca. 1 × 10-3 Torr)
and subsequently filled with inert gas. 2,4,6-Trimethylaniline (purchased
from Aldrich Chemical Co.) was distilled from sodium. Electronic grade
ammonia (purity > 99.995%, O2 < 2 ppm, and H2O < 10 ppm) was
purchased from Sociedad Espan˜ola del Ox´ıgeno and used as received.
NH3 (15N 10%) was purchased from Cambridge Isotope Laboratories
(1-L glass ampules) and used without further purification. [Ti(η5-
C5H5-nRn)(NMe2)3],59,60 [Ti(η5-C5Me5)(NMe2)xCl3-x],61 and [Ti(η5-
C5Me5)Me3]97 were prepared by known procedures.
Samples for infrared spectroscopy were prepared as KBr pellets. 1H
and 13C{1H} NMR spectra were recorded on a Varian Unity-300 and/
or Unity-500 Plus spectrometer. Chemical shifts (δ, ppm) are given
relative to residual protons or to carbon of the solvent. 15N NMR spectra
were recorded on a Varian Unity-500 Plus (50.7 MHz) in 10-mm NMR
tubes sealed by flame. Chemical shifts (δ, ppm) were measured with
respect to CH3NO2 (δ ) 0.0 ppm) as external reference. Electron impact
mass spectra were obtained at 70 eV. Microanalysis (C, H, N) were
performed in a Heraeus CHN-O-Rapid microanalyzer.
Me)+, 2], 396 [(M - 2CH3)+, 33]. Anal. Calcd for C22H38N2Ti2
(426.36): C, 61.98; H, 8.98; N, 6.57. Found: C, 62.17; H, 8.89; N,
6.84.
Synthesis of [{Ti(η5-C5Me5)Me}2(µ-NAr)2] (4). 2,4,6-Trimethyl-
aniline (0.30 g, 2.22 mmol) was added to a solution of [Ti(η5-C5Me5)-
Me3] (0.50 g, 2.19 mmol) in hexane (20 mL). After 20 h at room
temperature a brown solution was separated from brown crystals by
filtration. The crystals were isolated, washed with hexane (5 mL), and
dried under vacuum to yield 4 (0.30 g, 41%). IR (KBr, cm-1): 2981s,
2911s, 2726w, 1464vs, 1376s, 1301w, 1203vs, 1152vs, 1062w, 1020m,
956m, 853s, 734m, 637s, 586s, 519vs, 476s, 377s; 1H NMR (C6D6, 20
°C, δ): 6.72 (s, 4H, C6H2Me2Me), 2.42 (s, 12H, C6H2Me2Me), 2.13
(s, 6H, C6H2Me2Me), 1.62 (s, 30H, C5Me5), 1.34 (s, 6H, TiMe); 13C{1H}
NMR (C6D6, 20 °C, δ): 155.5, 131.0, 128.6, 127.3 (C6H2Me2Me), 121.9
(C5Me5), 53.4 (TiMe), 23.0 (C6H2Me2Me), 20.5 (C6H2Me2Me) 11.1
(C5Me5); MS (70 eV) m/e [assignment, rel int. (%)]: 647 [(M - MeH)+,
9], 631 [(M - 2MeH)+, 46], 496 [(M - 2MeH - C5Me5)+, 26], 316
[(Ti(η5-C5Me5)(NAr))+, 75]. Anal. Calcd for C40H58N2Ti2 (662.71): C,
72.50; H, 8.82; N, 4.23. Found: C, 72.86; H, 8.86; N, 4.19.
Synthesis of [{Ti(η5-C5Me5)(NH2)}2(µ-NAr)2] (5). A 150-mL
ampule (Teflon stopcock) was charged with [{Ti(η5-C5Me5)Me}2(µ-
NAr)2] (4) (0.17 g, 0.26 mmol), toluene (25 mL), and a stir bar. The
argon atmosphere was changed to ammonia and cooled at -78 °C.
After stirring at room temperature for 20 h, the brown solution was
separated from a fine light brown powder. The powder was vacuum-
dried for 6 h to afford 5 (0.15 g, 88%). IR (KBr, cm-1): 3394m, 3321w,
1538m, 1462vs, 1415s, 1376w, 1305vs, 1284vs, 1161w, 1024w, 971m,
929w, 849m, 791w, 739m, 676vs, 631w, 620w, 595w, 572w, 510w,
Synthesis of [{Ti(η5-C5Me5)}4(µ3-N)4] (1). We have communicated
the preparation, spectroscopic, analytic, and crystallographic data for
1.32 The synthesis of 1-15N isotopically enriched 10% in 15N was carried
out in a similar procedure. A solution of [Ti(η5-C5Me5)(NMe2)3] (1.75
g, 5.55 mmol) in hexane (50 mL) was transferred into a Carius tube
(capacity, 200 mL). The argon atmosphere was changed to ammonia
(1 L, 15N 10%) and cooled to -78 °C, and the Carius tube was flame-
sealed. After being heated for 3 days at 90 °C, the tube was opened,
and the resultant dark green crystals were washed with hexane (2 ×
25 mL) to yield 0.77 g (77%). 15N NMR (CDCl3, 20 °C, δ): 500.6 (s).
Synthesis of [{Ti(η5-C5Me5)(µ-NH)}3(µ3-N)] (2). Although Roesky
and co-workers have reported a synthesis for 2,22 we used a procedure
similar to the one described for 1. A solution of [Ti(η5-C5Me5)Me3]
(0.63 g, 2.76 mmol) in toluene (20 mL) was transferred via cannula
into a Carius tube (capacity, 120 mL) equipped with a stir bar. The
argon atmosphere was changed to ammonia and cooled to -78 °C,
and the Carius tube was flame-sealed. The reaction mixture was stirred
at room temperature for 24 h. The Carius tube was opened in a
glovebox, and the volatile components were removed under reduced
pressure to give an orange powder. The orange powder was washed
with cold hexane (20 mL) and then dried under vacuum to yield yellow
2 (0.41 g, 73%). IR (KBr, cm-1): 3352m, 2910vs, 2722w, 1669w,
1490w, 1433s, 1374s, 1255w, 1160w, 1064w, 1023m, 955w, 869w,
1
478vs, 414m, 385w; H NMR (CDCl3, 20 °C, δ): 6.64 (s, 4H, C6H2-
Me2Me), 3.78 (s broad, 4H, NH2), 2.18 (s, 6H, C6H2Me2Me), 2.12 (s,
12H, C6H2Me2Me), 1.95 (s, 30H, C5Me5); 13C{1H} NMR (CDCl3, 20
°C, δ): 154.8, 131.3, 127.7, 127.6 (C6H2Me2Me), 118.6 (C5Me5), 20.9
(C6H2Me2Me), 19.1 (C6H2Me2Me), 11.1 (C5Me5); MS (70 eV) m/e
[assignment, rel int. (%)]: 665 [M+, 9], 530 [(M - C5Me5)+, 7], 513
[(M - C5Me5 - NH3)+, 60], 496 [(M - C5Me5 - 2NH3)+, 13]. Anal.
Calcd for C38H56N4Ti2 (664.69): C, 68.67; H, 8.49; N, 8.43. Found:
C, 68.11; H, 8.60; N, 7.81.
Reaction of [{Ti(η5-C5Me5)(µ-NH)}3(µ3-N)] (2) with [Ti(η5-
C5Me5)(NMe2)3]. A 5-mm NMR tube was charged with 2 (0.008 g,
0.013 mmol), [Ti(η5-C5Me5)(NMe2)3] (0.004 g, 0.0013 mmol), and
benzene-d6 (0.80 mL). The tube was flame-sealed, and the course of
the reaction at different temperatures was monitored by 1H NMR. After
heating at temperatures near 160 °C, the spectra showed resonances
for NHMe2 with concomitant minor intensity for those of the starting
complexes. The temperature was maintained for 2 days until the
complete consumption of the initial products to afford green crystals
1
797s, 711vs, 674vs, 654vs, 532s, 505s, 453m, 415m, 391s; H NMR
(C6D6, 20 °C, δ): 13.80 (s broad, 3H, µ-NH), 2.01 (s, 45H, C5Me5);
13C{1H} NMR (C6D6, 20 °C, δ): 117.1 (C5Me5), 11.8 (C5Me5); MS
(70 eV) m/e [assignment, relative intensity (rel int.) (%)]: 608 [M+,
68], 591 [(M - NH3)+, 9], 473 [(M - C5Me5)+, 11], 456 [(M - NH3
- C5Me5)+, 23], 438 [(M - 2NH3 - C5Me5H)+, 22], 319 [(M - 2NH3
- 2C5Me5H)+, 36], 200 [(M - 3C5Me5H)+, 24].
1
and a red solution. The H and 13C{1H} NMR spectra of the crystals
in chloroform-d were identical with those of [{Ti(η5-C5Me5)}4(µ3-N)4]
(1).1H NMR (CDCl3, 20 °C, δ): 1.99 (s, 60H, C5Me5); 13C{1H} NMR
(CDCl3, 20 °C, δ): 119.1 (C5Me5), 12.0 (C5Me5).
Synthesis of [{Ti4(η5-C5Me5)3(η5-C5H5)}(µ3-N)4] (6). A 120-mL
Carius tube was charged with 2 (0.50 g, 0.82 mmol), [Ti(η5-C5H5)-
(NMe2)3] (0.20 g, 0.82 mmol), and hexane (50 mL). The tube was
flame-sealed and heated at 135 °C for 2 days. The Carius tube was
opened in a glovebox, and the dark green solution was concentrated to
a volume of about 10 mL. Crystallization at -40 °C for 24 h afforded
6 as green crystals (0.25 g, 42%). IR (KBr, cm-1): 2964s, 2909s, 1437s,
2-15N (15N 10%) was prepared in the same way from 1.60 g (7.01
mmol) of [Ti(η5-C5Me5)Me3] and 1 L of NH3 (15N, 10%) to give 1.02
1
g (72%). 15N NMR (CDCl3, 20 °C, δ): 461.9 (s, µ3-N), 89.5 (d, JNH
) 63.0 Hz, µ-NH).
Synthesis of [{Ti(η5-C5Me5)Me}2(µ-NH)2] (3). A 200-mL ampule
(Teflon stopcock) was charged with [Ti(η5-C5Me5)Me3] (0.90 g, 3.94
mmol) and hexane (20 mL). The argon atmosphere was changed to
ammonia and cooled to -78 °C. The reaction mixture was allowed to
warm to room temperature for 12 h. Orange crystals were collected by
filtration, washed with cold hexane (20 mL), and vacuum-dried to yield
3 (0.20 g, 24%). The filtrate was pump-dried to afford an orange solid.
1
1374s, 1261s, 1197vs, 1019vs, 782vs, 650vs, 451s; H NMR (C6D6,
20 °C, δ): 6.12 (s, 5H, C5H5), 2.03 (s, 45H, C5Me5); 13C{1H} NMR
(C6D6, 20 °C, δ): 119.7 (C5Me5), 110.3 (C5H5), 11.9 (C5Me5); MS (70
eV) m/e [assignment, rel int. (%)]: 718 [M+, 0.3], 583 [(M - C5Me5)+,
4], 518 [(M - C5Me5 - Cp)+, 0.2], 448 [(M - 2C5Me5)+, 9], 383 [(M
- 2C5Me5 - Cp)+, 2], 313 [(M - 3C5Me5)+, 32], 248 [(M - 3C5Me5
- Cp)+, 8]. Anal. Calcd for C35H50N4Ti4 (718.41): C, 58.52; H, 7.02;
N, 7.80. Found: C, 58.44; H, 7.26; N, 7.63.
1
Analysis of this solid by H NMR showed that it was a mixture of
compounds 2 and 3. Spectral and analytical data for 3: IR (KBr, cm-1):
3349m, 2912s, 1489w, 1431s, 1375s, 1238w, 1100w, 1022m, 787vs,
1
735s, 650vs, 500s, 385s; H NMR (C6D6, 20 °C, δ): 10.90 (s broad,
Synthesis of [{Ti4(η5-C5Me5)3(η5-C5H4SiMe3)}(µ3-N)4] (7). In a
fashion similar to the preparation of 6, 2 (0.80 g, 1.32 mmol) and [Ti-
(η5-C5H4SiMe3)(NMe2)3] (0.42 g, 1.32 mmol) were heated at 140 °C
to afford 7 as green crystals (0.53 g, 51%). IR (KBr, cm-1): 2912s,
2860s, 2722w, 2207w, 1633w, 1493w, 1441s, 1375s, 1246s, 1171m,
1070m, 1041s, 904m, 837s, 789vs, 651vs, 623s, 451s; 1H NMR (C6D6,
2H, µ-NH), 1.95 (s, 30H, C5Me5), 0.78 (s, 6H, TiMe); 13C{1H} NMR
(C6D6, 20 °C, δ): 120.1 (C5Me5), 35.8 (TiMe), 11.8 (C5Me5); MS (70
eV) m/e [assignment, rel int. (%)]: 425 [(M - H)+, 3], 411 [(M -
(97) Mena, M.; Pellinghelli, M. A.; Royo, P.; Serrano, R.; Tiripicchio, A.
Organometallics 1989, 8, 476.

Ammonolysis of [Ti(η5-C5Me5)X3] Derivatives
Inorganic Chemistry, Vol. 39, No. 4, 2000 651
Table 4. Crystal Data and Structure Refinement for Complexes 4
and 9a
components were removed under reduced pressure, and the resultant
orange solid was washed with toluene (3 × 20 mL) to afford 9 (0.22
g, 25%).
4
9
Method B. In a fashion similar to method A, [Ti(η5-C5Me5)(NMe2)-
Cl2] (2.00 g, 6.71 mmol) in toluene (50 mL) was treated with ammonia
for 2 days. An orange solution was filtered off from an orange solid.
The solid was extracted with THF (75 mL), and the resultant solution
was carried out to dryness to give an orange solid. The orange solid
was washed with toluene (20 mL) and then dried under vacuum to
yield 9 (0.67 g, 40%). IR (KBr, cm -1): 3286w, 3227w, 3144w, 3040w,
2911s, 1595w, 1483w, 1428m, 1409w, 1379s, 1272s, 1068w, 1024 m,
931vs, 788m, 761m, 729w, 682w, 663w, 622w, 465w, 441s, 412m,
color
empirical formula
fw
temp (K)
λ (Å)
brown
orange
C40H58N2Ti2
662.68
293(2)
C20H33Cl3N2Ti2
503.63
293(2)
0.71073
triclinic
P1h
0.71073
monoclinic
C2/c
cryst syst
space group
a (Å); R (deg)
b (Å); â (deg)
c (Å); γ (deg)
vol (Å3)
8.684(1); 66.11(1) 28.272(6); 90
11.074(1); 71.44(1) 8.452(2); 111.85(3)
11.174(1); 87.92(1) 22.260(4); 90
1
363w, 347m, 316m; H NMR (CDCl3, 20 °C, δ): 2.70 (s broad, 3H,
926.1(2)
1
4937(2)
NH3), 2.123 (s, 15H, C5Me5), 2.117 (s, 15H, C5Me5); 13C{1H} NMR
(CDCl3, 20 °C, δ): 127.8 (C5Me5), 125.9 (C5Me5), 12.8 (C5Me5), 12.3
(C5Me5); MS (70 eV) m/e [assignment, rel int. (%)]: 487 [(M - NH3)+,
40], 451 [(M - NH3 - HCl)+, 3], 351 [(M - NH3 - C5Me5H)+, 87],
315 [(M - NH3 - C5Me5H - HCl)+, 17]. Anal. Calcd for C20H33N2-
Cl3Ti2 (503.65): C, 47.70; H, 6.60; N, 5.56. Found: C, 47.61; H, 6.55;
N, 4.84.
Z
8
F calcd (g/cm3)
1.188
0.460
356
1.355
µ (mm-1
F(000)
)
0.979
2096
GOF on F2
0.577
0.966
final R indices [I > 2σ(I)] R1 ) 0.048,
R1 ) 0.033,
wR2 ) 0.081
R1 ) 0.076,
wR2 ) 0.095
0.277 and -0.224
wR2 ) 0.137
R indices (all data)
R1 ) 0.076,
9-15N (15N 10%) was prepared following method B in the amounts
and yields described above. 15N NMR (CDCl3, 20 °C, δ): 431.6 (s,
µ-N), -360.8 (broad, NH3).
wR2 ) 0.177
largest diff peak and
hole (e Å3)
0.393 and -0.304
X-ray Crystal Structure Determination of Complexes 4 and 9.
Brown crystals of compound 4 were crystallized from a hexane solution
at room temperature, whereas the orange crystals of 9 were obtained
from toluene. Table 4 provides a summary of the crystal data and
refinement parameters for complexes 4 and 9. Both data were collected
on an ENRAF NONIUS CAD4 diffractometer at room temperature.
Intensity measurements were performed by ω-2θ scans in the range
6° < 2θ < 50° for 4, and ω scans in the range 6° < 2θ < 44° for 9.
Of the 3474 measured reflections for 4, 3243 were independent; R1 )
0.048 and wR2 ) 0.137 [for 2561 reflections with F > 4σ(F)]. Of the
5999 measured reflections for 9, 3005 were independent; R1 ) 0.033
and wR2 ) 0.081 [for 2032 reflections with F >4σ(F)]. The structures
were solved by direct methods (SHELXS-90)98 and refined by least-
squares against F2 (SHELXL-93).99 All non-hydrogen atoms were
refined anisotropically and the hydrogen atoms positioned geometrically
and refined by using a riding model in the last cycles of refinement,
except those linked to N(2) in complex 9, which were located and
refined isotropically.
Computational Details. All the DFT calculations were carried out
with the ADF program100-103 using triple-ú + polarization Slater basis
set to describe the valence electrons of C, N, and Cl. For titanium a
frozen core composed of the 1s, 2s, and 2p was described by double-ú
Slater functions, 3d and 4s by triple-ú functions, and 4p by a single
orbital. Hydrogens were described by triple-ú + polarization functions.
The geometries and binding energies were calculated using gradient
corrections. We used the local spin density approximation characterized
by the electron gas exchange (XR with R ) 2/3) together with Vosko-
Wilk-Nusair parametrization104 for correlation. Becke’s nonlocal
corrections105 to the exchange energy and Perdew’s nonlocal correc-
tions106 to the correlation energy were added. The topological properties
of the charge density were computed with a modified version of the
AIMPAC package107 and the Xaim software.108
a R1 ) ∑||F0| - |Fc||/∑|F0|. wR2 ) {[∑w(F02 - Fc2)2]/∑w(F0 )2]}1/2
.
2
GOF ) {∑[w(F0 - Fc2)2]/(n - p)}1/2. n is the number of reflections,
and p is the total number of parameters refined.
2
20 °C, δ): 6.44, 6.22 (m, A2B2 spin system, 4H, C5H4SiMe3), 2.05 (s,
45H, (C5Me5), 0.41 (s, 9H, C5Me4SiMe3); 13C{1H} NMR (C6D6, 20
°C, δ): 119.7 (C5Me5), 119.2, 115.4, 115.3 (C5H4SiMe3), 12.1 (C5Me5),
0.8 (C5H4SiMe3). Anal. Calcd for C38H58N4SiTi4 (790.59): C, 57.73;
H, 7.40; N, 7.09. Found: C, 58.24; H, 7.88; N, 5.93.
Synthesis of [{Ti4(η5-C5Me5)3(η5-C5H4Me)}(µ3-N)4] (8). In a way
similar to the preparation of 6, 2 (0.80 g, 1.32 mmol) and [Ti(η5-C5H4-
Me)(NMe2)3] (0.34 g, 1.31 mmol) were heated at 140 °C to afford 8
as green crystals (0.40 g, 42%). IR (KBr, cm-1): 2911s, 2858s, 2721w,
1494w, 1437m, 1373m, 1259w, 1083m, 1029m, 932w, 829m, 779vs,
1
728m, 649vs, 621s, 453s; H NMR (C6D6, 20 °C, δ): 6.05, 5.84 (m,
A2B2 spin system, 4H, C5H4Me), 2.25 (s, 3H, C5H4Me), 2.04 (s, 45H,
C5Me5); 13C{1H} NMR (C6D6, 20 °C, δ): 119.6 (C5Me5), 119.1, 110.9,
110.4 (C5H4Me), 12.3 (C5H4Me), 12.0 (C5Me5). Anal. Calcd for
C36H52N4Ti4 (732.43): C, 59.04; H, 7.16; N, 7.65. Found: C, 58.52;
H, 7.31; N, 6.55.
Synthesis of [{Ti2(η5-C5Me5)2Cl3(NH3)}(µ-N)] (9). Method A. A
Carius tube (capacity, 200 mL) was charged with [Ti(η5-C5Me5)Cl3]
(1.00 g, 3.45 mmol), diethyl ether (70 mL), and a stir bar. The argon
atmosphere was changed to ammonia and cooled to -78 °C, and the
Carius tube was flame-sealed. The reaction mixture was allowed to
warm to room temperature and stirred for 16 h. The orange solution
was separated from an orange solid by filtration. The orange solid was
extracted with THF (2 × 25 mL) until it became white, and the THF
extracts were combined with the diethyl ether filtrate. The volatile
(98) Sheldrick, G. M. Acta Crystallogr. 1990, A46, 467.
(99) Sheldrick, G. M. SHELXL-93: Program for the Refinement of Crystal
Structures; Universita¨t Go¨ttingen: Go¨ttingen, Germany, 1993.
(100) ADF 2.3, Department of Theoretical Chemistry, Vrije Universiteit,
Amsterdam.
(101) Baerends, E. J.; Ellis, D. E.; Ros, P. Chem. Phys. 1973, 2, 41.
(102) te Velde, G.; Baerends, E. J. J. Comput. Phys. 1992, 99, 84.
(103) Fonseca Guerra, C. METECC-95 1995, 305.
(104) Vosko, S. H.; Wilk, L.; Nusair, M. Can. J. Phys. 1980, 58, 1200.
(105) Becke, A. D. J. Chem. Phys. 1986, 84, 4524; Phys. ReV. A 1988, 38,
3098.
(106) Perdew, J. P. Phys. ReV. B 1986, 33, 7406; 1986, 34, 8882.
(107) Biegler-Ko¨nig, F. W.; Bader, R. F. W.; Tang, T. H. J. Comput. Chem.
1982, 3, 317.
(108) Xaim software developed by Ortiz, J. C.; Bo, C. Universitat Rovira
i Virgili, Tarragona, Spain, 1998.
Acknowledgment. We are grateful to the Spanish DGES
(PB96-0672 and PB95-0639-C02-02), the CIRIT of Generalitat
of Catalunya (SGR97-17), and the Universidad de Alcala´ (E003/
98 and E027/99) for support of this research. We thank Dr. M.
Galakhov for the 15N NMR spectra. C. Ye´lamos also thanks
the CAM for a Postdoctoral Grant.
Supporting Information Available: X-ray crystallographic files
in CIF format for the structure determinations of 4 and 9. This material
is available free of charge via the Internet at http://pubs.acs.org.
IC9907718