New titanium imido synthons: Syntheses and supramolecular structures

Article abstract of DOI:10.1021/ic050011z

Reactions of Ti(NMe₂)₂Cl₂ with a wide range of primary alkyl and arylamines RNH₂ afforded the corresponding 5-coordinate imido titanium compounds Ti(NR)Cl₂(NHMe ₂)₂ (R = ^tBu (1), ⁱPr (2), CH ₂Ph (3), Ph (4), 2,6-C₆H₃Me₂ (5), 2,6-C₆H₃ⁱPr₂ (6), 2,4,6-C ₆H₂F₃ (7), 2,3,5,6-C₆HF₄ (8), C₆F₅ (9), 4-C₆H₄Cl (10), 2,3,5,6-C₆HCl₄ (11), 2-C₆H₄CF ₃ (12), 2-C₆H₄^tBu (13)). The compounds 1-13 are monomeric in solution but in the solid state form either N-H...Cl hydrogen bonded dimers or chains or perfluorophenyl π-stacked chains, depending on the imido R-group. The compound 13 was also prepared in a one-pot synthesis from RNH₂ and Ti(NMe₂) ₄ and Me₃SiCl, Reaction of certain Ti(NR)Cl ₂(NHMe₂)₂ compounds with an excess of pyridine afforded the corresponding bis- or tris-pyridine analogues [Ti(NR)Cl ₂(py)_x]_y (x = 3, y = 1; x = y = 2), and the structure of Ti₂(NC₆F₅)₂Cl ₂(μ-Cl)₂(py)₄ shows π-stacking of perfluorophenyl rings. Reaction of Ti(NMe₂)₂Cl₂ with cross-linked aminomethyl polystyrene gave quantitative conversion to the corresponding solid-supported titanium imido complex. This paper represents the first detailed study of how supramolecular structures of imido compounds may be influenced by simple variation of the imido ligand N-substituent.

Full text of DOI:10.1021/ic050011z

Inorg. Chem. 2005, 44, 2882−2894
New Titanium Imido Synthons: Syntheses and Supramolecular
Structures
Nico Adams, Helen R. Bigmore, Timothy L. Blundell, Catherine L. Boyd, Stuart R. Dubberley,
Andrew J. Sealey, Andrew R. Cowley, Michael E. G. Skinner, and Philip Mountford*
Chemistry Research Laboratory, UniVersity of Oxford, Mansfield Road,
Oxford OX1 3TA, U.K.
Received January 4, 2005
Reactions of Ti(NMe2)2Cl2 with a wide range of primary alkyl and arylamines RNH2 afforded the corresponding
i
5-coordinate imido titanium compounds Ti(NR)Cl2(NHMe2)2 (R
)
tBu (1), Pr (2), CH2Ph (3), Ph (4), 2,6-C6H3Me2
i
(5), 2,6-C6H3 Pr2 (6), 2,4,6-C6H2F3 (7), 2,3,5,6-C6HF4 (8), C6F5 (9), 4-C6H4Cl (10), 2,3,5,6-C6HCl4 (11), 2-C6H4CF3
t
(12), 2-C6H4 Bu (13)). The compounds 1
−
13 are monomeric in solution but in the solid state form either N
−H‚‚‚Cl
hydrogen bonded dimers or chains or perfluorophenyl
π
-stacked chains, depending on the imido R-group. The
compound 13 was also prepared in a “one-pot” synthesis from RNH2 and Ti(NMe2)4 and Me3SiCl. Reaction of
certain Ti(NR)Cl2(NHMe2)2 compounds with an excess of pyridine afforded the corresponding bis- or tris-pyridine
analogues [Ti(NR)Cl2(py)x]y (x
) 3, y ) 1; x ) y ) 2), and the structure of Ti2(NC6F5)2Cl2(µ-Cl)2(py)4 shows
π
-stacking of perfluorophenyl rings. Reaction of Ti(NMe2)2Cl2 with cross-linked aminomethyl polystyrene gave
quantitative conversion to the corresponding solid-supported titanium imido complex. This paper represents the
first detailed study of how supramolecular structures of imido compounds may be influenced by simple variation of
the imido ligand N-substituent.
Introduction
especially interested in developing titanium imido
chemistry.13-15 As part of this work, we reported the synthesis
and structures of the imido tris(pyridine) compounds
Ti(NR)Cl2(py)3 (R ) tBu or aryl).16 These compounds have
been remarkably successful as synthons, allowing access to
many different types of new titanium imido complexes by
chloride or/and pyridine ligand metathesis. The origins of
our own work go back to Nielson’s17 and then Winter’s18,19
original investigations of the reactions of TiCl4 with primary
amines and subsequent reactions with Lewis bases.
Transition metal imido compounds have been a focus of
sustained activity for the past 20-25 years in particular. A
number of general reviews,1-3 as well as some more specific
ones,4-15 have documented the progress and achievements
within this area of chemistry. In our group we have been
* To whom correspondence should be addressed. E-mail:
philip.mountford@chemistry.oxford.
(1) Nugent, W. A.; Mayer, J. M. Metal-Ligand Multiple Bonds; Wiley-
Interscience: New York, 1988.
(2) Chisholm, M. H.; Rothwell, I. P. Amido and Imido Metal Complexes;
Wilkinson, G., Gillard, R. D., McCleverty, J. A., Eds.; Pergamon
Press: Oxford, 1987; Vol. 2.
(3) Wigley, D. E. Prog. Inorg. Chem. 1994, 42, 239.
(4) Romao, C. C.; Ku¨hn, F. E.; Herrmann, W. A. Chem. ReV. 1997, 97,
3197.
However, while the syntheses of certain Ti(NR)Cl2(py)3
compounds have been optimized, these compounds are not
without certain limitations. Only alkylimido derivatives (and
in particular tert-butyl systems) can be directly accessed by
the reaction of an excess of RNH2 with TiCl4 followed by
(5) Danopoulos, A. A.; Green, J. C.; Hursthouse, M. B. J. Organomet.
Chem. 1999, 591, 36.
(6) Cundari, T. R. Chem. ReV. 2000, 100, 807.
(15) Mountford, P. In PerspectiVes in Organometallic Chemistry; Screttas,
C. G., Steele, B. R., Eds.; Royal Society of Chemistry: Cambridge,
2003; pp 28-46.
(16) Blake, A. J.; Collier, P. E.; Dunn, S. C.; Li, W.-S.; Mountford, P.;
Shishkin, O. V. J. Chem. Soc., Dalton Trans. 1997, 1549.
(17) Nielson, A. J. Inorg. Chim. Acta 1988, 154, 177.
(18) Winter, C. H.; Sheridan, P. H.; Lewkebandara, T. S.; Heeg, M. J.;
Proscia, J. W. J. Am. Chem. Soc. 1992, 114, 1095.
(7) Sharp, P. R. J. Chem. Soc., Dalton Trans. 2000, 2647.
(8) Duncan A. P.; Bergman, R. G. Chem. Rec. 2002, 2, 431.
(9) Eikey, R. A.; Abu-Omar, M. M. Coord. Chem. ReV. 2003, 243, 83.
(10) Leung, W.-H. Eur. J. Inorg. Chem. 2003, 583.
(11) Radius, U. Z. Anorg. Allg. Chem. 2004, 630, 957.
(12) Giesbrecht, G. R.; Gordon, J. C. J. Chem. Soc., Dalton Trans. 2004,
2387.
(13) Mountford, P. Chem. Commun. 1997, 2127.
(14) Gade, L. H.; Mountford, P. Coord. Chem. ReV. 2001, 216-217, 65.
(19) Lewkebandra, T. S.; Sheridan, P. H.; Heeg, M. J.; Rheingold, A. L.;
Winter, C. H. Inorg. Chem. 1994, 33, 5879.
2882 Inorganic Chemistry, Vol. 44, No. 8, 2005
10.1021/ic050011z CCC: $30.25
© 2005 American Chemical Society
Published on Web 03/23/2005

New Titanium Imido Synthons
Scheme 1
addition of an excess of pyridine. Use of anilines gives
mixtures of products from which the anilinium salt side-
products RNH3Cl cannot be separated.16 Arylimido com-
pounds Ti(NAr)Cl2(py)3 are accessible by an aniline/tert-
butyl imide exchange protocol, but with the exception of
ortho-substituted anilines the products can be somewhat
insoluble and rather capricious with regard to their workup.
There can also be a tendency for residual tBuNH2 to remain
associated with the desired Ti(NAr)Cl2(py)3 products, which
sometimes forces the need for an additional treatment with
pyridine and recrystallization. Finally, one of the pyridine
ligands in Ti(NR)Cl2(py)3 is rather labile (due to the strong
trans influence of imido ligands) and can be lost under
dynamic vacuum giving dimeric, bis(imido) µ-chloride
bridged products Ti2(NR)2Cl2(µ-Cl)2(py)4.16,20,21
As part of their pioneering work in transition metal amido
chemistry, Bradley et al. reported that the reaction of
Ti(NMe2)4 with tBuNH2 affords the µ-imido bridged dimers
Ti2(µ-NtBu)2(NMe2)4 and Ti2(µ-NtBu)2(NMe2)2(NHtBu)2.22
In a related reaction, we recently found23 that monomeric
terminal imido ansa-linked macrocycle complexes could be
prepared by reaction of certain 1-aminopropyl-4,7-dialkyl-
triazacyclononanes with the dichloride-bis(amide) compound
Ti(NMe2)2Cl2. The compound Ti(NMe2)2Cl2 is easily pre-
pared24 on a multigram scale by the redistribution reaction
between TiCl4 and Ti(NMe2)4, both of which are com-
mercially available (Ti(NMe2)4 is also readily prepared from
TiCl4 and LiNMe225,30). The ready availability of Ti(NMe2)2-
Cl2 and its potential use as a precursor to new titanium imido
synthons prompted us to study the reactions between it and
primary amines RNH2 (R ) alkyl, aryl) in general. Our
preliminary results in this area have recently been com-
municated,26 and a complete study of the synthesis and
structures of compounds of the type Ti(NR)Cl2(NHMe2)2 is
the main topic of our present contribution. Very recently
published work has firmly demonstrated the potential of
compounds of the type Ti(NR)Cl2(NHMe2)2 in the metal-
organic chemical vapor deposition (MOCVD) synthesis of
TiN thin films27 and the synthesis of calix[4]arene-supported
imido complexes,28 as well as a 47-member library of
titanium imido-based olefin polymerization catalysts (the
compounds Ti(NR)Cl2(NHMe2)2 were generated and reacted
on in situ in this particular study).29
change to bright yellow. Subsequent evaporation of the
volatiles allowed the isolation of the target compound
Ti(NtBu)Cl2(NHMe2)2 (1) in 84% yield. When the reaction
1
was repeated on an NMR tube scale (benzene-d6), the H
NMR spectrum showed quantitative conversion to 1 with
no side-products. This general protocol was readily extended
to a range of other alkyl and arylamines affording the
compounds listed in Scheme 1 as orange or yellow, air- and
moisture-sensitive solids in 62-98% isolated yields. Full
details of the characterizing data are provided in the
Experimental Section, and detailed experimental procedures
are provided in the Supporting Information.
The NMR spectra of the 13 new compounds Ti(NR)Cl2-
(NHMe2)2 are all consistent with the structures proposed in
Scheme 1, the spectra showing resonances for imido R
groups and coordinated NHMe2 ligands (the NH atoms
appearing as a broad binomial septet and the NMe2 hydrogens
1
as a doublet in the H spectra). There is no evidence that
prolonged drying under dynamic vacuum at room temper-
ature leads to loss of NHMe2. Bearing in mind that
6-coordinate chloride-bridged dimers (at least in the solid
state) have been found for a number of compounds of the
type Ti(NR)Cl2(L)2, namely, Ti2(NR)2Cl2(µ-Cl)2(py)4 (R )
t
tBu, 2-C6H4Me, 2-C6H4 Bu, 2-C6H4Ph),20,21 Ti2(N-2-C6H4-
Ph)2Cl2(µ-Cl)2(TMEDA)2,20 Ti2(NtBu)2Cl2(µ-Cl)2(tBuNH2)4,20
and Ti2(NtBu)2Cl2(µ-Cl)2(MeCN)2(tBuNH2)2,31 we were care-
ful to confirm the monomeric, 5-coordinate nature of six of
the new compounds by X-ray crystallography as described
in detail below. A cryoscopic solution molecular weight
measurement of Ti(NiPr)Cl2(NHMe2)2 (2) in benzene gave
a value of 291 g‚mol-1 in reasonable agreement with the
(20) Nielson, A. J.; Glenny, M. W.; Rickard, C. E. F. J. Chem. Soc., Dalton
Trans. 2001, 232.
(21) Hazari, N.; Cowley, A. R.; Mountford, P. Acta Crystallogr. 2004, E60,
m1844.
(22) Bradley, D. C.; Torrible, E. G. Can. J. Chem. 1963, 41, 134.
(23) Male, N. A. H.; Skinner, M. E. G.; Bylikin, S. Y.; Wilson, P. J.;
Mountford, P.; Schro¨der, M. Inorg. Chem. 2000, 39, 5483.
(24) Froneman, M.; Cheney, D. L.; Modro, T. A. Phosphorus, Sulfur Silicon
Relat. Elem. 1990, 47.
(25) Bradley, D. C.; Thomas, I. M. J. Chem. Soc. 1990, 3857.
(26) Diamond, G. M.; Jordan, R. F.; Petersen, J. L. Organometallics 1996,
15, 4030.
(27) Adams, N.; Cowley, A. R.; Dubberley, S. R.; Sealey, A. J.; Skinner,
M. E. G.; Mountford, P. Chem. Commun. 2001, 2738.
(28) Carmalt, C. J.; Newport, A.; Parkin, I. P.; Mountford, P.; Sealey, A.
J.; Dubberley, S. R. J. Mater. Chem. 2003, 13, 84.
(29) Dubberley, S. R.; Friedrich, A.; Willman, D. A.; Mountford, P.; Radius,
U. Chem.sEur. J. 2003, 9, 3634.
(30) Adams, N.; Arts, H. J.; Bolton, P. D.; Cowell, D.; Dubberley, S. R.;
Friederichs, N.; Grant, C. M.; Kranenburg, M.; Sealey, A. J.; Wang,
B.; Wilson, P. J.; Cowley, A. R.; Mountford, P.; Schro¨der, M. Chem.
Commun. 2004, 434.
(31) Mommertz, A.; Leo, R.; Massa, W.; Dehnicke, K. Z. Naturforsch.
1998, B53, 887.
Results and Discussion
Synthesis of a Family of Compounds of the Type Ti-
(NR)Cl2(NHMe2)2. The reaction between a dark red solution
of Ti(NMe2)2Cl2 and tBuNH2 in benzene gave a rapid color
Inorganic Chemistry, Vol. 44, No. 8, 2005 2883

Adams et al.
Table 1. Selected IR Data for the Compounds Ti(NR)Cl2(NHMe2)2
at 80 °C (72% yield, cf. 74% for the route starting from
Ti(NMe2)2Cl2 and H2N-2-C6H4 Bu).
t
ν(N-H) Nujola
ν(N-H) CH2Cl2
b
compound (NR group)
(cm-1
)
(cm-1
)
Structural Studies of the Compounds Ti(NR)Cl2-
1 (R ) tBu)
3231
3228
3220
3220
3242
3244
3244
3258
3275
3228
3239
3264
c
(NHMe2)2. The X-ray crystal structures for the six com-
2 (R ) iPr)
3288
c
3284
c
i
pounds Ti(NR)Cl2(NHMe2)2 (R ) Pr (2), Ph (4), C6F5 (9),
3 (R ) CH2Ph)
4 (R ) Ph)
t
2,3,5,6-C6HCl4 (11), 2-C6H4CF3 (12), or 2-C6H4 Bu (13))
5 (R ) 2,6-C6H3Me2)
have been determined. Key bond distances and angles are
compared in Table 2, and views of the molecular structures
are collected together in Figure 1 (2, 4, 9, and 11) and Figure
2 (12 and 13). Details of the structure determinations are
given in the Experimental Section and Table 3 and will not
be further discussed. However, it should be noted that for
the purposes of discussion of the N-H‚‚‚Cl bonding (vide
infra), we refer in all instances to geometrically positioned
(N-H ) 0.87 Å, sp3 hybridized N) NHMe2 hydrogens
(regardless of whether the NHMe2 hydrogens for a particular
structure were found or not from Fourier difference maps).
i
6 (R ) 2,6-C6H3 Pr2)
c
7 (R ) 2,4,6-C6H2F3)
8 (R ) 2,3,5,6-C6HF4)
9 (R ) C6F5)
3282
3282
3280
c
3280
3284
3285
10 (R ) 4-C6H4Cl)
11 (R ) 2,3,5,6-C6HCl4)
12 (R ) 2-C6H4CF3)
13 (R ) 2-C6H4 Bu).
14 (R ) PSCH2)
3273d
3268
t
a Nujol mull between KBr or NaCl plates. b CH2Cl2 solution, 0.1 mm
path length NaCl cell. c Not recorded. d Partially resolved shoulder at 3258
cm-1
.
calculated value of 266.1 g‚mol-1 for monomeric 2 (com-
pound 2 is also monomeric in the solid state, vide infra).
The compounds 1-13 all feature ν(N-H) bands in their IR
spectra; these data are summarized in Table 1. In CH2Cl2
solution the values fall in the narrow range 3280-3288 cm-1
(8 compounds), but in the solid state the values span a much
wider range (3220-3273 cm-1). These data can be inter-
preted as reflecting the rather different N-H‚‚‚Cl hydrogen
bonded solid state structures formed (vide infra) whereas in
solution the compounds are discretely monomeric.
All six compounds exist as monomeric, 5-coordinate
complexes in the solid state. Crystals of 2, 4, and 9 feature
the same space group (C2/c) with the TidNim vectors lying
1
on crystallographic 2-fold rotation axes at (0, y, /4) or a
symmetry equivalent position; other molecules lie on general
positions, and crystals of 11 and 13 contain residual solvent
(benzene and pentane, respectively) of crystallization. The
geometries at titanium are approximately trigonal bipyramidal
(NHMe2 groups axial) with NimdTi-Cl angles in the range
108.62(2)-114.79(1)° (avg 111.3°) and NimdTi-Nam angles
in the range 95.34(3)-101.58(6)° (avg 98.3°). Only one
5-coordinate titanium imido dichloride compound with
monodentate Lewis base ligands is recorded in the
Cambridge Structural Database,34,35 namely Ti(NtBu)Cl2-
(OPPh3)2,18,19 and this appears to have a similar geometry
(avg NimdTi-Cl ) 108.1°, avg NimdTi-O ) 102.7°) to
those reported here. Solid state structures of three other
monomeric, 5-coordinate titanium imido dichloride com-
The new compounds 1-13 are analogues of Lorber et al.’s
vanadium(IV) complexes V(NAr)Cl2(NHMe2)2 (Ar ) Ph,
i
C6F5, 2,6-C6H3R2 (R ) Me, Pr, Cl)),32 prepared via “one-
pot” syntheses from V(NMe2)4, ArNH2, and Me3SiCl. We
were interested to see if the titanium compounds could also
be prepared via a one-pot route33 and found that Ti(N-2-
t
C6H4 Bu)Cl2(NHMe2)2 (13) could indeed be made directly
t
from Ti(NMe2)4, H2N-2-C6H4 Bu, and Me3SiCl in toluene
i
Table 2. Selected Bond Lengths (Å) and Angles (deg) for Ti(NR)Cl2(NHMe2)2 (R ) Pr (2), Ph (4), C6F5 (9), 2,3,5,6-C6HCl4 (11), 2-C6H4CF3 (12), or
t
2-C6H4 Bu (13))a
2
4
9
11
12
13
Distances
TidNim
Ti-Cl
1.672(2)
2.3544(5)
1.7024(14)
2.3406(3)
1.706(3)
2.3373(7)
1.7079(18)
2.3293(6)
2.3319(6)
2.1894(18)
2.1992(18)
1.367(3)
2.59
1.705(4) [1.694(4)]
2.3397(16) [2.3440(16)]
2.3486(18) [2.3401(18)]
2.205(5) [2.202(6)]
2.199(4) [2.197(4)]
1.378(6) [1.385(5)]
2.67 [2.68]
1.7023(17)
2.3209(6)
2.3638(7)
2.206(2)
2.2126(19)
1.395(3)
2.64
Ti-Nam
2.2067(17)
2.201(1)
2.201(2)
Nim-C
1.476(5)
2.53
1.380(2)
2.45
1.359(5)
2.95
NamH‚‚‚Cl
2.74
2.78 [2.81]
Angles
101.58(6)
N
imdTi-Nam
imdTi-Cl
97.72(5)
95.34(3)
100.00(8)
100.1(2) [100.1(2)]
97.4(2) [97.67(19)]
109.53(14) [109.37(14)]
110.90(14) [110.80(14)]
139.56(11) [139.82(11)]
162.4(3) [162.2(2)]
175.7(3) [175.6(3)]
140 [139]
98.07(8)
96.52(8)
110.49(6)
113.07(6)
136.41(3)
165.14(7)
165.84(16)
150
97.10(8)
110.54(7)
110.92(7)
138.51(3)
162.89(7)
173.11(16)
152.8
N
112.655(19)
114.79(1)
108.62(2)
Cl-Ti-Cl
134.69(4)
164.56(9)
164.46(17)
160
130.42(2)
169.32(6)
180
142.75(5)
156.83(13)
180
Nam-Ti-Nam
TidNim-C
Nam-H‚‚‚Cl
161
148
149.3
137 [134]
a Parameters involving N-H‚‚‚Cl interactions are calculated assuming N-H ) 0.87 Å and an sp3 hybridized Nam. Values in brackets for 12 correspond
to the other crystallographically independent molecule in the asymmetric unit. Molecules of 2, 4, and 9 lie on crystallographic C2 rotation axes and only have
only one crystallographically independent Ti-Cl and Ti-Nam unit. Molecules of 13 lie across crystallographic inversion centers. Nam and Nim refer to the
amino (NHMe2) and imido (TidNR) nitrogens, respectively.
2884 Inorganic Chemistry, Vol. 44, No. 8, 2005

New Titanium Imido Synthons
Figure 1. Displacement ellipsoid plots of Ti(NiPr)Cl2(NHMe2)2 (2, 25% probability, top left), Ti(NPh)Cl2(NHMe2)2 (4, 25% probability, top right), Ti-
(NC6F5)Cl2(NHMe2)2 (9, 25% probability, bottom left), and Ti(N-2,3,5,6-C6HCl4)Cl2(NHMe2)2 (11, 35% probability, bottom right). Solvent of crystallization
and H atoms bound to C are omitted. N-H atoms are drawn as spheres of arbitrary radius.
pounds are known,20,36 but these have cis-chelating TMEDA
Lewis bases and the geometries are better described as square
base pyramidal. Five 5-coordinate structures of the type
(NHMe2)2 complexes also feature trigonal bipyramidal
geometries in the solid state.32
In broad terms, the distances and angles associated with
the titanium centers and the ligands themselves are within
known ranges.34,35 In terms of specific comparisons with the
t
Ti(NR)(OR′)2(L)2 (R ) Bu, aryl; R′ ) aryl, BMes2, or
CH(Mes)2; L ) py or 4-NC5H4NC4H8) have been reported,
and in all these cases the metal center also has a trigonal
bipyramidal geometry.37-40 Lorber et al.’s V(NAr)Cl2-
16
t
6-coordinate complexes Ti(NR)Cl2(py)3 (R ) Bu, Ph,
4-C6H4Me, 4-C6H4NO2), the TidNim and Ti-Cl distances
for Ti(NR)Cl2(NHMe2)2 are somewhat shorter, presumably
reflecting both the decreased coordination number in the
latter cases and the better σ-donor Lewis bases in the tris-
(pyridine) systems. The TidNim distance is shorter and the
Ti-Cl longer for the alkylimido compound 2 compared to
the other five (arylimido) compounds. This mirrors trends
(32) Lorber, C.; Choukroun, R.; Donnadieu, B. Inorg. Chem. 2002, 41,
4217.
(33) While this work was in progress Lorber et al. also mentioned that
Ti(NPh)Cl2(NHMe2)2 (4) could be prepared by a one-pot method:
Lorber, C.; Choukroun, R.; Vendier, L. Organometallics 2004, 23,
1845 (footnote referencing unpublished results).
(34) Allen, F. H.; Kennard, O. Chem. Des. Automation News 1993, 8, 1 &
31.
(35) Fletcher, D. A.; McMeeking, R. F.; Parkin, D. J. Chem. Inf. Comput.
Sci. 1996, 36, 746.
(36) Duchateau, R.; Williams, A. J.; Gambarotta, S.; Chiang, M. Y. Inorg.
Chem. 1991, 30, 4863.
16
established in the 6-coordinate complexes Ti(NR)Cl2(py)3
and in alkyl- and aryl-imido compounds in general.34,35 There
(37) Hill, J. E.; Profilet, R. D.; Fanwick, P. E.; Rothwell, I. P. Angew.
Chem., Int. Ed. Engl. 1990, 29, 664.
(38) Zambrano, C. H.; Profilet, R. D.; Hill, J. E.; Fanwick, P. E.; Rothwell,
I. P. Polyhedron 1993, 12, 689.
(39) Cole, S. C.; Coles, M. P.; Hitchcock, P. B. J. Chem. Soc., Dalton
Trans. 2002, 4168.
(40) Collier, P. E.; Blake, A. J.; Mountford, P. J. Chem. Soc., Dalton Trans.
1997, 2911.
Inorganic Chemistry, Vol. 44, No. 8, 2005 2885

Adams et al.
Figure 2. Displacement ellipsoid plots of one of the two crystallographically independent molecules of Ti(N-2-C6H4CF3)Cl2(NHMe2)2 (12, 30% probability,
t
left) and Ti(N-2-C6H4 Bu)Cl2(NHMe2)2 (13, 30% probability, right). Solvent of crystallization and H atoms bound to C are omitted. N-H atoms are drawn
as spheres of arbitrary radius. A view of the other crystallographically independent molecule of 12 is provided in the Supporting Information (Figure S7).
i
Table 3. X-ray Data Collection and Processing Parameters for Ti(NR)Cl2(NHMe2)2 (R ) Pr (2), Ph (4), C6F5 (9), 2-C6H4CF3 (12)),
t
Ti(N-2,3,5,6-C6HCl4)Cl2(NHMe2)2‚0.5(C6H6) (11‚0.5(C6H6)), Ti(N-2-C6H4 Bu)Cl2(NHMe2)2‚0.5(C5H12) (13‚0.5(C5H12)), and Ti2(NC6F5)2Cl2(µ-Cl)2(py)4
(17)
2
4
9
11‚0.5(C6H6)
12
13‚0.5(C5H12)
17
empirical
formula
fw
temp/K
wavelength/Å
space group
a/Å
C7H21Cl2N3Ti C10H19Cl2N3Ti C10H14Cl2F5N3Ti C10H15Cl6N3Ti‚ C11H18Cl2F3N3Ti C14H27Cl2N3Ti‚ C32H20Cl4F10N6Ti2
0.5C6H6 0.5C5H12
476.92 392.27
266.07
175 K
0.71073
C2/c
16.913(1)
9.101(1)
12.044(1)
90
128.78(5)
90
1445.1
4
300.08
150
0.71073
C2/c
16.260(1)
10.303(1)
11.935(1)
90
131.01(1)
90
390.04
200
1.54180
C2/c
15.696(3)
15.569(1)
6.7371(9)
90
109.69(2)
90
368.08
150
916.14
150
0.71073
P21/n
7.2324(2)
18.1474(5)
13.7813(3)
90
103.425(1)
90
150
0.71073
P1h
150
0.71073
P21/n
10.5572(2)
11.4410(3)
18.3161(5)
90
96.8053(10)
90
0.71073
Pna21
16.1331(2)
6.5142(2)
32.3906(5)
90
90
90
3404.07
8
7.3945(1)
12.7544(2)
12.9622(2)
115.6105(9)
90.7721(8)
106.112(1)
1046.45
2
b/Å
c/Å
R/deg
â/deg
γ/deg
V/Å3
1508.8
4
1550.1
4
2196.72
4
1759.4
2
Z
d (calcd)/Mg‚m-3 1.22
1.321
1.671
1.513
1.436
1.186
1.73
abs coeff/mm-1
R indices R1, Rw
[I > 3σ(I)]a
0.930
0.902
8.334
1.175
0.838
0.635
0.84
R1 ) 0.0271,
Rw ) 0.0326
0.0250,
0.0307
0.0615,
0.0648
0.0341,
0.0408
0.0364,
0.0343
0.0324,
0.0357
0.0294,
0.0407
2
a R1 ) ∑||Fo| - |Fc||/∑|Fo|; Rw ) x{∑w(|Fo| - |Fc|)2/∑(w|Fo| }.
are few other features of distinction associated with the mole-
cular structures of individual compounds (the different rela-
tive orientation of the NHMe2 ligands in 13 will be discussed
below), and it is not clear to what extent some of the more
subtle differences between individual molecular structures
could be attributable to crystal packing effects and the various
supramolecular interactions which we shall now discuss.
2.52 Å), “intermediate” (2.52-2.95 Å), and “long” (2.95-
3.15 Å; NB, the sum of the van der Waals radii for H and
Cl, is 2.95 Å44).
Figures 3-5 illustrate the extended packing in the
compounds Ti(NR)Cl2(NHMe2)2 for R ) Ph (4), 2,3,5,6-
C6HCl4 (11), and 2-C6H4CF3 (12), respectively, with each
molecule donating two N-H‚‚‚Cl hydrogen bonds and
accepting two, and each Ti being a common member of two
eight-membered rings. The supramolecular arrangement of
the isopropylimido compound Ti(NiPr)Cl2(NHMe2)2 (2) is
similar to that of 4, and a partial packing diagram is given
in the Supporting Information (Figure S1). Both 2 and 4
crystallize in the C2/c space group with metals lying on
crystallographic 2-fold axes (passing through the TidNim
With the exception of Ti(NC6F5)Cl2(NHMe2)2 (9), the
supramolecular structures of all of the structurally character-
ized compounds are dominated by Me2N-H‚‚‚Cl hydrogen
bonding between the 5-coordinate complexes. Hydrogen
bonds in general41 have been described as “the most
important of all intermolecular interactions”.42 Of particular
relevance to this work are hydrogen bonds donated by N-H
to metal-bound chloride. These are well-established43 and
have been categorized as “short” (intermolecular contact e
1
bonds parallel with the b axis) at (0, y, /4). The infinite
N-H‚‚‚Cl hydrogen bonded chains propagate along the
(41) For leading references see ref 42, the following and references
therein: Desiraju, G. M. Acc. Chem. Res. 2002, 35, 565.
(42) Steiner, T. Angew. Chem., Int. Ed. 2002, 41, 48.
(43) Aullo´n, G.; Bellamy, D.; Brammer, L.; Bruton, E. A.; Orpen, A. G.
Chem. Commun. 1998, 653.
(44) Bondi, A. J. Phys. Chem. 1964, 68, 441.
2886 Inorganic Chemistry, Vol. 44, No. 8, 2005

New Titanium Imido Synthons
Figure 3. Partial packing diagram for Ti(NPh)Cl2(NHMe2)2 (4) showing a portion of the infinite N-H‚‚‚Cl hydrogen bonded chains. H atoms bound to
C are omitted, and all atoms are drawn as spheres of arbitrary radius. Symmetry operators: B, [3-x, y, -z+5/2]; C, [x, -y, z-1/2]; D, [3-x, -y, -z+2];
E, [x, y, z-1]; F, [3-x, y, -z+3/2]; G, [x, -y, z-3/2]; H, [3-x, -y, -z+1]; I, [3-x, 1-y, 2-z]; J, [x, 1-y, z-1/2].
Figure 5. Extended packing diagram for Ti(N-2-C6H4CF3)Cl2(NHMe2)2
(12) showing a portion of the infinite N-H‚‚‚Cl hydrogen bonded bilayers.
H atoms bound to C are omitted, and all atoms are drawn as spheres of
arbitrary radius. Symmetry operators: B, [x, y+1, z]; C, [x, y-1, z].
disordered across crystallographic inversion centers but
Figure 4. Cell packing diagram for Ti(N-2,3,5,6-C6HCl4)Cl2(NHMe2)2‚
exhibit no close contacts to the metal complexes. Molecules
0.5(C6H6) (11‚0.5C6H6) showing a portion of the infinite N-H‚‚‚Cl
of 11 also form infinite N-H‚‚‚Cl hydrogen bonded chains
hydrogen bonded chains. H atoms bound to C are omitted, and all atoms
are drawn as spheres of arbitrary radius. Symmetry operators: B, [-x, -y,
1-z]; C, [-x, -y, -z]; D, [1-x, 1-y, 1-z]; E, [1+x, 1-y, 1-z]; F, [1+x,
1+y, 1+z].
in which the TidNim bonds alternate “up and down” along
the chains just as for 2 and 4. The NH‚‚‚Cl distances are
“intermediate” (avg 2.67 Å), and the solid state ν(N-H) band
appears at 3239 cm-1. The CH2Cl2 solution ν(N-H) values
for 11 (3280 cm-1) and 4 (3284 cm-1) differ by only ∆ν )
4 cm-1. This is consistent with the differences between the
two values in the solid state (∆ν ) 19 cm-1) being
attributable to differing extents of N-H‚‚‚Cl hydrogen
bonding.
Although the arrangement of TidNR units (alternating “up
and down”) within the infinite chains is comparable for 4
and 11, there is a difference in the extent of π-π interaction
between the imido aryl groups between the chains as
indicated in Figure 4 (see also Figure S3 in the Supporting
Information). The N-bound C6HCl4 rings of Ti(1) and Ti(1D)
crystallographic c axis, and the NH‚‚‚Cl contacts (2.53 and
2.45 Å) can be classified as “short”. In this context we note
that the solid state ν(N-H) bands for 2 and 4 (3228 and
3220 cm-1, respectively) are among the lowest energy
stretches for the 14 compounds listed in Table 1, presumably
reflecting the strong N-H‚‚‚Cl hydrogen bonding. There are
no close contacts between the phenyl rings in 4 (the closest
intermolecular C‚‚‚C distance is 3.803(2) Å; the closest
C-H‚‚‚‚C inter-ring contact is 3.08 Å; see Figure S2 in the
Supporting Information).
Crystals of Ti(N-2,3,5,6-C6HCl4)Cl2(NHMe2)2 (11, Figure
4) contain benzene molecules of crystallization which are
Inorganic Chemistry, Vol. 44, No. 8, 2005 2887

Adams et al.
are arranged in a favorable45-47 offset face to face (off)
arrangement of π-π interactions. The closest inter-ring C‚‚‚C
contact is 3.436(3) Å, and the average interplanar spacing
is 3.44 Å. It appears that the presence of the four electron-
withdrawing Cl substituents on the arene rings is responsible
for the additional supramolecular interactions in 11. Accom-
modating these additional interactions might be correlated
with the slight disruption to the NH‚‚‚Cl hydrogen bond
contacts.
Crystals of Ti(N-2-C6H4CF3)Cl2(NHMe2)2 (12, Figure 5)
again feature N-H‚‚‚Cl hydrogen bonded chains, but the
detailed arrangements differ from the three systems discussed
so far. Whereas the chains of 2, 4, and 11 have alternating
“up and down” TidNR units (with additional off π-π
interactions between the chains for 11), the TidN-2-C6H4-
CF3 units in 12 are all oriented on the same side of the infinite
chains. The chains themselves are arranged in a pairwise
fashion by noncrystallographic inversion centers which relate
the two molecules in each asymmetric unit (Ti(1) and Ti(2)
in Figure 5). The NH‚‚‚Cl distances are again “intermediate”
(avg 2.73 Å, consistent with the solid state IR data (Table
1)), but unlike 11 (where longer hydrogen bonds are
accompanied by additional π-π interactions) the closest
C‚‚‚C contact between the neighboring C6H4CF3 rings is
3.872(6) Å and the separation between the C(1)-C(6) and
C(12)-C(17) least-squares planes is 3.85 Å (see Figure S4
in the Supporting Information). There are no other significant
close contacts.
Figure 6. Partial cell packing diagram for Ti(NC6F5)Cl2(NHMe2)2 (9)
showing a portion of the infinite π-stacked chains. H atoms bound to C are
omitted, and all atoms are drawn as spheres of arbitrary radius. Symmetry
operators: B, [-x, y, -z+3/2]; C, [x, -y-1, z-1/2]; D, [-x, -y-1, -z+1];
E, [x, y, z-1]; F, [-x, y, -z+1/2]; G, [x, -y-1, z-3/2], H [-x, -y-1, -z].
Crystals of Ti(NC6F5)Cl2(NHMe2)2 (9, Figure 6) possess
“long” (possibly negligible) N-H‚‚‚Cl hydrogen bonds
(NH‚‚‚Cl ) 2.95 Å which is the sum of the van der Waals
radii for H and Cl44). The disruption to the hydrogen bonding
is reflected in the higher solid state ν(N-H) value (3275
cm-1, Table 1). However, the hydrogen bonding is replaced
by well-defined π-π stacking of C6F5 rings arranged in an
offset face-to-face manner propagating along the crystal-
lographic c axis (see also Figure S5 in the Supporting
Information). The closest C‚‚‚F and C‚‚‚C intermolecular
contacts are 3.256(4) and 3.264(3) Å, respectively, and the
separation between C6F5 computed least-squares planes is
3.23 Å. Intermolecular π-π interactions between perfluo-
rophenyl rings have recently received increased attention both
computationally and experimentally,47-52 and the intermo-
lecular contacts found in 9 are comparable to the closest
contacts reported to date. It has been proposed that inter-
molecular interactions between perfluorinated aromatic rings
are slightly more attractive than the very well-established
ones between their hydro analogues (due mainly to an
increased van der Waals component).47 The structures of
Ti(NPh)Cl2(NHMe2)2 (4) and Ti(NC6F5)Cl2(NHMe2)2 (9)
appear to support this.
It is also interesting to compare the solid state and solution
ν(N-H) data (Table 1) for the series of compounds Ti(NAr)-
Cl2(NHMe2)2 (Ar ) Ph (4), 2,4,6-C6H2F3 (7), 2,3,5,6-C6HF4
(8), and C6F5 (9)). The solid state ν(N-H) increases by 55
cm-1 with increasing fluorination of the phenyl ring (3220
cm-1 for Ar ) Ph to 3275 cm-1 for Ar ) C6F5), whereas
there is only a small change in the solution phase ν(N-H)
(3284 cm-1 for Ar ) Ph to 3280 cm-1 for Ar ) C6F5) and
in the opposite sense (i.e., a lower value for Ar ) C6F5).
Although we were unable to obtain diffraction-quality
crystals of either 7 or 8, the IR data might be reflecting an
increased tendency for π-π stacking with increased fluo-
rination of the phenyl ring. We note also that the solid state
ν(N-H) data reported by Lorber et al. for V(NAr)Cl2-
(NHMe2)2 are 3232 and 3252 cm-1 for Ar ) Ph and C6F5,
respectively.32 Neither of these compounds was crystallo-
graphically characterized, but the difference of 20 cm-1
between the two ν(N-H) bands is consistent with a decrease
in NH‚‚‚Cl-V hydrogen bonding in the perfluorophenyl
imido complex.
(45) Hunter, C. A.; Lawson, K. R.; Perkins, J.; Urch, C. J. J. Chem. Soc.,
Perkin Trans. 2 2001, 651.
(46) Hunter, C. A.; Sanders, J. M. K. J. Am. Chem. Soc. 1990, 112, 5525.
(47) Lorenzo, S.; Lewis, G. R.; Dance, I. New J. Chem. 2000, 24, 295.
(48) Blanchard, M. D.; Hughes, R. P.; Concolino, T. E.; Rheingold, A. L.
Chem. Mater. 2000, 12, 1604.
(49) Deck, P. A.; Kroll, C. E.; Hollis, W. G.; Fronczek, F. R. J. Organomet.
Chem. 2001, 637-639, 107.
(50) Deck, P. A.; Lane, M. J.; Montgomery, J. L.; Slebodnick, C.; Fronczek,
F. R. Organometallics 2000, 19, 1013.
(51) Thornberry, M. P.; Slebodnick, C.; Deck, P. A.; Fronczek, F. R.
Organometallics 2000, 19, 5352.
(52) Hair, G. S.; Cowley, A. H.; Gorden, J. D.; Jones, J. N.; Jones, R. A.;
Macdonald, C. L. B. Chem. Commun. 2003, 424.
t
The supramolecular structure of Ti(N-2-C6H4 Bu)Cl2-
(NHMe2)2 (13, Figure 7) is again different from those already
discussed. Molecules of 13 form only hydrogen bonded
dimers across crystallographic inversion centers. Only one
NHMe2 hydrogen per metal center is involved in a significant
N-H‚‚‚Cl hydrogen bond (H(1)‚‚‚Cl(2A) ) 2.64 Å); the
2888 Inorganic Chemistry, Vol. 44, No. 8, 2005

New Titanium Imido Synthons
Scheme 2
angles were constrained to those values determined by single-
crystal X-ray diffraction methods. For 13 the cis N-H bond
orientation (N-H bonds on the same side as the tert-butyl
group) was found to be 5.2 kcal‚mol-1 more favorable than
the alternative trans N-H bond orientation. For 12, however,
the cis N-H bond orientation was 3.4 kcal‚mol-1 less stable
than the alternative trans N-H bond orientation (the same
side as the ortho CF3 group). The conformers in which cis
N-H bonds lie on the opposite side of the molecule from
the ortho tBu or CF3 groups (i.e., conformations not observed
in any of the crystal structures) were calculated to be 16.1
and 5.4 kcal‚mol-1 higher in energy than the minimum
energy conformations for 13 and 12, respectively. These
results suggest that the supramolecular structures of 12 and
13 are probably governed to some extent by quite subtle
intramolecular repulsions.
Further Studies. Solid phase supported reagents and
catalysts are an important area of current interest.54-57 Two
reports of cross-linked polystyrene (PS) supported imido
complexes have recently appeared in the context of olefin
polymerization catalysis, these being CpV(N-4-C6H4PS)Cl2,58
Ti(N-4-C6H4PS)Cl2(TMEDA), and Ti(NtBu)Cl2(Me2NCH2-
CH2NMeCH2PS).20 The first two of these compounds were
prepared indirectly via an arylamine/tert-butyl imide ex-
change protocol (tBuNH2 elimination) between H2N-4-C6H4-
PS and either CpV(NtBu)Cl2 or Ti(NtBu)Cl2(TMEDA). We
were interested to see if Ti(NMe2)2Cl2 could act as a direct
precursor to polystyrene-supported titanium imido complexes
as this approach would offer considerable scope for the
subsequent assembly of additional donor ligands around the
already-supported metal center (in the same way that the
solution phase compounds Ti(NR)Cl2(L)n (L ) py or
NHMe2, n ) 2 or 3) allow access to a wide number of new
titanium imido derivatives).
Figure 7. View of the N-H‚‚‚Cl hydrogen bonded dimer formed by
t
molecules of Ti(N-2-C6H4 Bu)Cl2(NHMe2)2 (13) in the solid state. H atoms
bound to C are omitted, and all atoms are drawn as spheres of arbitrary
radius. Atoms carrying the suffix A are related to their counterparts by the
symmetry operator [-x, 1-y, -z].
other (H(2)) is not. The solid state IR spectrum is consistent
with the X-ray structure and possesses two overlapping
ν(N-H) bands at 3273 cm-1 (assigned to the nonbridging
N-H bond) and 3258 cm-1 (attributed to the hydrogen
bonded N-H). In dichloromethane solution, a single
ν(N-H) of 3285 cm-1 is observed. The unexpected su-
pramolecular arrangement of 13 is reflected in the molecular
structure (Figure 2 compares the molecular structures of the
ortho-CF3 homologue 12 and that of 13). In 12 (and in all
the other structurally characterized compounds, Figure 1) the
Me2Nam-H bonds are oriented in a trans orientation across
the Nam-Ti-Nam unit, whereas in 13 the N-H bonds are in
a cis conformation. In other words the N-H bonds are
orientated in the same direction in 13 and in opposite
directions for the other five compounds. The cis arrangement
of N-H bonds in 13 removes the possibility of forming
analogous extended hydrogen bonded chains and appears to
lead to the dimeric structure shown in Figure 7. A N-H‚‚‚Cl
hydrogen bonded imido vanadium dimer reminiscent of that
found for 13 was reported recently (N-H‚‚‚Cl ) 2.31 Å).53
A closer examination of the molecular structure of 13
shows that the cis-orientated N-H bonds lie on the same
side of the molecule as the bulky ortho tert-butyl group. We
speculated that avoidance of intramolecular repulsions
between the NHMe2 methyl groups and the ortho tert-butyl
group that might result from a trans-N-H conformation (cf.
12) could be a reason for the different conformation found
in 13 (Figure S6 of the Supporting Information shows space-
filling models for 12 and 13). To probe for intramolecular
steric effects, molecular modeling studies were carried out
on different possible conformations of 12 and 13 generated
by rotations of the Ti-NHMe2 bonds using the semiempirical
method PM3 in SPARTAN ’04 (Wavefunction, Inc.).
Metal-ligand bond distances and ligand-metal-ligand
Shaking (to avoid mechanical damage by stirring) a pre-
swollen (benzene) sample of 1% cross-linked commercially
available aminomethyl polystyrene resin (H2NCH2-4-C6H4-
PS; 1.19 mmol‚g-1 loading) with Ti(NMe2)2Cl2
(1 equiv) in benzene over 16 h gave quantitative uptake of
the titanium to form dark red Ti(N-CH2-4-C6H4PS)Cl2-
(NHMe2)2 (14) and a colorless supernatant (Scheme 2). The
(54) Barrett, A. G. M.; Hopkins, B. T.; Ko¨bberling, J. Chem. ReV. 2002,
102, 3301.
(55) Dickerson, T. J.; Reed, N. N.; Janda, K. D. Chem. ReV. 2002, 102,
3325.
(56) Kobayashi, S. Curr. Opin. Chem. Biol. 2000, 4, 338.
(57) Leadbeater, N. E.; Marco, M. Chem. ReV. 2002, 102, 3217.
(58) Chan, M. C. W.; Chew, K. C.; Dalby, C. I.; Gibson, V. C.; Kohlmann,
A.; Little, I. R.; Reed, W. Chem. Commun. 1998, 1673.
(53) Pugh, S. M.; Blake, A. J.; Gade, L. H.; Mountford, P. Inorg. Chem.
2001, 40, 3992.
Inorganic Chemistry, Vol. 44, No. 8, 2005 2889

Adams et al.
Scheme 3
supernatant contained negligible Ti(NMe2)2Cl2 as judged by
1H NMR spectroscopy. The IR spectrum of 14 showed no
ν(N-H) bands for the primary amino groups of the starting
H2NCH2-4-C6H4PS resin, but a new band at 3268 cm-1 was
evident. This is attributed to ν(N-H) of the new NHMe2
ligands in 14 and may be contrasted with the value of 3220
cm-1 found in the solid state for Ti(NCH2Ph)Cl2(NHMe2)2
(3). The benzylimido compound 3 may be viewed as a
simplified model for 14. The substantially increased
ν(N-H) found in 14 is attributed to decreased intermolecular
N-H‚‚‚Cl hydrogen bonding associated with the greater site
Table 4. Selected Bond Lengths and Intermolecular Contacts (Å) and
Angles (deg) for Ti2(NC6F5)2Cl2(µ-Cl)2(py)4 (17)a
1
isolation in the supported system. The 400 MHz H gel-
Ti(1)-N(1)
1.720(3)
2.337(1)
2.445(1)
2.705(1)
2.216(3)
2.212(3)
165.9(3)
101.50(3)
100.2(1)
177.5(1)
C(1)‚‚‚F(4C)
C(4)‚‚‚F(4E)
C(4)‚‚‚F(5C)
C(5)‚‚‚C(6C)
C(5)‚‚‚F(3E)
3.317(4)
3.200(5)
3.303(5)
3.341(5)
3.068(5)
phase magic angle spinning (MAS) NMR spectrum of 14
showed a new resonance at 4.33 ppm attributed to TidNCH2
(shifted from 3.70 in the starting H2NCH2-4-C6H4PS resin,
this resonance being absent in the spectrum of 14) and new
resonances for the coordinated NHMe2 ligands at 3.27
(NHMe2) and 2.49 (NHMe2) ppm. The 13C-{1H} spectrum
was also consistent with the formation of 14, notably
featuring a distinctive resonance at 72.9 ppm for TidNCH2.
Regrettably, the elemental analysis of the product repeatedly
returned lower than expected % N, Cl, Ti values. This is
attributed to incomplete combustion or acid digestion, but
we believe that the spectroscopic data and other experimental
evidence discussed above provide firm evidence for the
formation of 14. Preliminary studies have shown that 14 is
indeed a useful precursor to new polymer-supported imido
complexes,59 and we will report on this chemistry in a future
contribution.
As mentioned, Cl or/and NHMe2 ligand substitution of
certain Ti(NR)Cl2(NHMe2)2 complexes have allowed direct
access to new classes of calix[4]arene28 and triazacy-
clononane-supported imido complexes.29 Nonetheless, it was
also of interest to determine whether the new compounds
would also allow access to new and/or previously reported
tris- or bis(pyridine) compounds [Ti(NR)Cl2(py)x]y (x ) 3,
y ) 1; x ) y ) 2) since in some of the new, reactive titanium
imido compounds (e.g., Cp2Ti(NR)(py), Ti(N2Npy)(NR)(py)
(N2Npy ) MeC(2-C5H4N)(CH2NSiMe3)2) pyridine is neces-
sary for stabilizing the product.
Preliminary NMR tube scale reactions of a number of the
compounds Ti(NR)Cl2(NHMe2)2 with 3-4 equiv of pyridine
in benzene-d6 gave rise to mixtures of products even where
the target compounds themselves have been prepared previ-
ously (e.g., attempting to form Ti(NtBu)Cl2(py)3 from
Ti(NtBu)Cl2(NHMe2)2). It appears that NHMe2 ligands can
be competitive with pyridine under these conditions. Similar
problems have been noted previously by Lorber et al. in the
NHMe2 substitution chemistry of V(NAr)Cl2(NHMe2)2.32
This problem can be circumvented to some extent by use of
neat pyridine at 80 °C (Scheme 3) which affords the
previously described16,21 Ti2(NtBu)2Cl2(µ-Cl)2(py)4 and the
new compounds Ti(NC6F5)Cl2(py)3 (15) and Ti(N-4-C6H4-
Cl)Cl2(py)3 (16) in reasonable to excellent yields. The NMR
and other data for 16 suggest that some loss of the trans-
pyridine has occurred, and the isolation of Ti2(NtBu)2Cl2(µ-
Ti(1)-Cl(1)
Ti(1)-Cl(2)
Ti(1)-Cl(2B)
Ti(1)-N(2)
Ti(1)-N(3)
Ti(1)-N(1)-C(1)
Ti(1)-Cl(2)-Ti(1B)
N(1)-Ti(1)-Cl(2)
N(1)-Ti(1)-Cl(2B)
N(1)-Ti(1)-N(2)
N(1)-Ti(1)-N(3)
N(1)-Ti(1)-Cl(1)
N(2)-Ti(1)-N(3)
91.8(1)
95.9(1)
98.1(1)
170.2(1)
a Atoms carrying the suffixes Β, C, and Ε are related to their counterparts
in the asymmetric unit by the operators [1-x, -y, 1-z], [1-x, -y, -z],
and [2-x, -y, -z], respectively.
Cl)2(py)4 (as opposed to the known16 Ti(NtBu)Cl2(py)3) is
also consistent with the tendency of tris(pyridine) titanium
imido compounds to lose the third pyridine ligand.16,20
However, even use of neat pyridine at 80 °C does not allow
the clean formation of certain Ti(NR)Cl2(py)n compounds
i
i
(for R ) Pr, CH2Ph, 2,6-C6H3 Pr2), even though, for R )
i
2,6-C6H3 Pr2, the target complexes may be prepared in pure
form by an alternative route.16 The reasons for these rather
subtle differences differences between the various Ti(NR)-
Cl2(NHMe2)2 systems are not clear.
Attempted recrystallization of a sample of Ti(NC6F5)Cl2-
(py)3 (15) (generated in situ by an aniline/tert-butylimido
exchange reaction16 between C6F5NH2 and Ti(NtBu)Cl2(py)3)
gave diffraction-quality crystals of the dimeric bis(pyridine)
derivative Ti2(NC6F5)2Cl2(µ-Cl)2(py)4 (17) which was crys-
tallographically characterized. Selected bond and intermo-
lecular distances and bond angles are summarized in Table
4. A view of the molecular structure and a portion of the
extended packing arrangement is shown in Figure 8. The
loss of the trans-pyridine from 15 to form 17 is precedented
as mentioned above and attributable to the strong trans
influence of imido ligands.
Molecules of 17 lie across crystallographic inversion
centers and are analogous to the previously reported homo-
logues Ti2(NR)2Cl2(µ-Cl)2(py)4 (R ) Bu, 2-C6H4R′ (R′ )
t
Me, tBu, or Ph)).16,20 Unlike any of these other compounds,
however, molecules of 17 show pronounced π-stacked
supramolecular arrangements as shown in Figure 8, bottom.
The π-interactions between the C6F5 rings give rise to infinite
offset face-to-face arranged stacks propagating in the direc-
tion of the crystallographic a axis. Unlike the π-stacking
arrangement for Ti(NC6F5)Cl2(NHMe2)2 (9, Figure 6), that
of 17 is different since the environments on either side of
any individual C6F5 ring are not equivalent. For example
the C6F5 ring is much less offset with respect to the
(59) Adams, N.; Mountford, P. Unpublished results.
2890 Inorganic Chemistry, Vol. 44, No. 8, 2005

New Titanium Imido Synthons
Figure 8. Top: Displacement ellipsoid plot of Ti2(NC6F5)2Cl2(µ-Cl)2(py)4 (17, 30% probability). H atoms are omitted. Atoms carrying the suffix B are
related to their counterparts by the symmetry operator. Bottom: a portion of the infinite π-stacked chains. H atoms are omitted, and all atoms are drawn as
spheres of arbitrary radius. Symmetry operators: B, [1-x, -y, 1-z]; C, [1-x, -y, -z]; D, [x, y, z-1]; E, [-x, -y, -z]; F, [1+x, y, z-1]; G, [1+x, y, z],
H [2-x, -y, 1-z]. The dashed lines indicate the closest intramolecular C‚‚‚F distances (cf. Table 4).
C(C)6F(C)5 ring than with respect to the C(E)6F(E)5 ring.
The shortest C‚‚‚F contacts are between the more offset rings
(e.g., C(5)‚‚‚F(3E) ) 3.068(5) and C(4)‚‚‚F(4E) ) 3.200(5)
whereas C(4)‚‚‚F(5C) ) 3.303(5) and C(5)‚‚‚C(6C) )
3.341(5) Å), possibly reflecting reduced electrostatic repul-
sions between ring π electron density in the more offset pairs.
(NR)Cl2(NHMe2)2 with pyridine are not straightforward but
do afford bis- and tris-pyridine derivatives in certain cases.
Experimental Section
General Methods and Instrumentation. All air- and moisture-
sensitive operations were carried out using standard Schlenk-line
(Ar) and drybox (N2) techniques. Protio- and deutero-solvents were
purified, dried, and distilled using conventional techniques. NMR
samples were prepared under dinitrogen in Wilmad 505-PS tubes
fitted with J. Young NMR/5 valves. Samples for MAS NMR
spectroscopy were prepared in 2 mm Zirconia rotors. 1H and
13C-{1H} NMR spectra were recorded on Varian Unity Plus 500
and Varian Mercury-VX 300 spectrometers. Spectra were referenced
internally to residual protio-solvent (1H) or solvent (13C) resonances
and are reported relative to tetramethylsilane (δ ) 0 ppm). 19F
spectra were externally referenced to CFCl3 (δ ) 0 ppm). Chemical
shifts are quoted in δ (ppm) and coupling constants in Hz. 1H and
13C-{1H} MAS NMR spectra were recorded on a Chemagnetics
400 Infinity spectrometer. Spectra were referenced internally to
tetramethylsilane. IR spectra were recorded on Perkin-Elmer 1600
and Perkin-Elmer 1710 spectrometers as Nujol mulls between KBr
or NaCl windows, and in some instances as CH2Cl2 solutions using
a 0.1 mm path length NaCl cell. All data are quoted in wavenumbers
Summary
Reaction of Ti(NMe2)2Cl2 with primary aryl and alky-
lamines provides a robust and reliable route to the synthons
Ti(NR)Cl2(NHMe2)2 which are promising new entry points
to certain new titanium imido compounds. An analogous
reaction provides a useful route to a polystyrene-supported
derivative. The supramolecular arrangements of six Ti(NR)-
Cl2(NHMe2)2 compounds show a great deal of variation in
the extent and type of interaction, with N-H‚‚‚Cl hydrogen
bonding being the dominant feature in the absence of
perhalogenated imido N-aryl rings. This paper represents the
first detailed study of how supramolecular structures of imido
compounds may be influenced by simple variation of the
imido ligand N-substituent. The substitution reactions of Ti-
Inorganic Chemistry, Vol. 44, No. 8, 2005 2891

Adams et al.
(cm-1). Mass spectra were recorded on a Micromass GCT TOF
instrument using a solid probe inlet temperature program. All data
are quoted in mass/charge ratio (m/z). Elemental analyses were
carried out by the analytical laboratory of the Inorganic Chemistry
Laboratory, University of Oxford.
558 (w), 518 (m), 494 (m), 454 (w). IR (NaCl cell, CH2Cl2,
ν(N-H), cm-1): 3284. Anal. found (calcd for C10H19Cl2N3Ti): C,
39.7 (40.1); H, 7.7 (6.4); N, 13.6 (14.0)%.
1
(e) Data for 5 (R ) 2,6-C6H3Me2). Yield ) 84%. H NMR
(C6D6, 500 MHz, 298 K): 6.89 (2 H, d, 3J ) 7.6 Hz, 3-C6H3Me2),
Starting Materials. The compounds Ti(NMe2)2Cl224 and Ti(Nt-
6.79 (1 H, t, J ) 7.1 Hz, 4-C6H3Me2), 2.75 (6 H, s, C6H3Me2),
3
16
3
Bu)Cl2(py)3 were prepared according to the literature methods.
2.64 (2 H, br m, NHMe2), 2.17 (12 H, d, J ) 6.1 Hz, NHMe2).
Pyridine and liquid primary amines were predried over freshly
ground CaH2 and distilled prior to use. Aminomethyl polystyrene
resin (Novabiochem; 100-200 mesh; loading, 1.19 mmol‚g-1) was
washed extensively with benzene, THF, dichloromethane, and
pentane (to remove any low molecular weight PS fractions) and
dried under dynamic vacuum (1 × 10-3 mbar, 24 h) prior to use.
All other compounds and reagents were purchased from commercial
chemical suppliers and used without further purification.
Ti(NR)Cl2(NHMe2)2 (1-13): General Synthetic Procedure.
A solution of Ti(NMe2)2Cl2 (ca. 1-5 mmol) and RNH2 (1 equiv)
in benzene (10-20 mL) was stirred for ca. 16 h. Removal of the
volatiles under reduced pressure yielded the target compounds as
spectroscopically pure air- and moisture-sensitive yellow or orange
powders. Samples of the products were recrystallized from sub-
saturated benzene solution where necessary but were typically
obtained in analytically pure form. Full details are provided in the
Supporting Information.
13C-{1H} NMR (C6D6, 125.7 MHz, 298 K): 160.3 (i-C6H3Me2),
133.9 (2-C6H3Me2), 127.5 (3-C6H3Me2), 122.6 (4-C6H3Me2), 40.7
(NHMe2), 19.5 (C6H3Me2). IR (KBr plates, Nujol, cm-1): 3242
(m), 1305 (m), 126 (m), 1155 (w), 1123 (w), 1092 (w), 1014 (m),
899 (m), 802 (w), 769 (m), 738 (m), 723 (m). Anal. found (calcd
for C12H23Cl2N3Ti): C, 44.0 (43.9); H, 7.8 (8.0); N, 12.4 (12.8)%.
i
1
(f) Data for 6 (R ) 2,6-C6H3 Pr2). Yield ) 86%. H NMR
i
(C6D6, 500 MHz, 298 K): 6.99 (2 H, d, 3J ) 7.8 Hz, 3-C6H3 Pr2),
i
6.85 (1 H, app t, app 3J ) 7.3 Hz, 4-C6H3 Pr2), 4.65 (1 H, sept, 3J
) 6.4 Hz, CHMe2), 2.87 (2 H, br m, NHMe2), 2.22 (12 H, d, 3J )
3
6.4 Hz, NHMe2), 1.40 (12 H, d, J ) 6.8 Hz, HCMe2). 13C-{1H}
i
NMR (C6D6, 125.7 MHz, 298 K): 157.6 (i-C6H3 Pr2), 144.5
i
i
i
(2-C6H3 Pr2), 123.6 (3-C6H3 Pr2), 122.5 (4-C6H3 Pr2), 40.6 (NHMe2),
27.7 (CHMe2), 24.4 (CHMe2). IR (KBr plates, Nujol, cm-1): 3244
(w), 1332 (w), 1308 (w), 1284 (w), 1212 (w), 1168 (w), 1156 (w),
1094 (m), 1054 (m), 1040 (m), 1020 (m), 986 (m), 932 (w), 864
(m), 798 (m), 752 (m), 722 (m). Anal. found (calcd for C16H31-
Cl2N3Ti): C, 49.8 (50.0); H, 8.3 (8.1); N, 10.8 (10.9)%.
(a) Data for 1 (R ) tBu). Yield ) 84%. 1H NMR (C6D6, 300.1
3
1
MHz, 298 K): 2.65 (2 H, br m, NHMe2), 2.24 (12 H, d, J ) 5.9
(g) Data for 7 (R ) 2,4,6-C6H2F3). Yield ) 92%. H NMR
Hz, NHMe2), 1.04 (9H, s, tBu). 13C-{1H} NMR (C6D6, 125.7 MHz,
298 K): 72.1 (CMe3), 40.3 (NHMe2), 31.5 (CMe3). IR (KBr plates,
Nujol, cm-1): 3231 (w), 1498 (w), 1352 (m), 1296 (m), 1260 (m),
1246 (m), 1206 (w), 1156 (w), 1074 (m), 1066 (m), 1012 (m), 1002
(m), 892 (w), 844 (w), 804 (m), 784 (m), 748 (w), 722 (s), 596
(w), 584 (w), 538 (m), 438 (w), 420 (w). Anal. found (calcd for
C8H23Cl2N3Ti): C, 33.7 (34.3); H, 8.2 (8.3); N, 13.9 (15.0)%.
Recrystallization did not lead to an improved % C, N analysis.
(b) Data for 2 (R ) iPr). Yield ) 75%. 1H NMR (C6D6, 500.1
MHz, 298 K): 3.29 (1H, sept, 3J ) 6.8 Hz, CHMe2), 2.65 (2 H, br
m, NHMe2), 2.25 (12 H, d, 3J ) 6.4 Hz, NHMe2), 0.94 (6 H, d, 3J
) 6.8 Hz, CHMe2). 13C-{1H} NMR (C6D6, 125.7 MHz, 298 K):
69.1 (CHMe2), 40.5 (CHMe2), 25.4 (NHMe2). IR (KBr plates, Nujol,
cm-1): 3228 (m), 1402 (w), 1354 (w), 1298 (m), 1258 (m), 1240
(m), 1214 (w), 1146 (w), 1120 (m), 1108 (m), 1062(m), 1018 (m),
900 (m), 800 (w), 722 (m), 634 (m), 500 (m). IR (NaCl cell, CH2Cl2,
ν(N-H), cm-1): 3288. Anal. found (calcd for C7H21Cl2N3Ti): C,
31.4 (31.6); H, 7.9 (8.0); N, 15.5 (15.8)%. EI-MS: m/z ) 266 (7%)
[M]+.
3
(C6D6, 300 MHz, 298 K): 6.18 (2H, dd, J ) 8.3 Hz, 3-C6H2F3),
2.78 (2 H, m, NHMe2), 2.25 (12 H, d, 3J ) 6.6 Hz, NHMe2). 13C-
2
{1H} NMR (C6D6, 75.5 MHz, 298 K): 99.5 (dd, J ) 29 Hz,
2J ) 26 Hz, 3-C6H2F3), 40.8 (NMe2). 13C-{19F} NMR (C6D6, 75.5
MHz, 298 K): 158.1 (2-C6H2F3), 155.5 (4-C6H2F3), 135.6
(i-C6H2F3).19F NMR (C6D6, 282.4 MHz, 298 K): -120.84 (2 F,
d,3J ) 7.6 Hz, 2-C6H2F3), -115.33 (1 F, d,3J ) 9.0 Hz, 4-C6H2F3).
IR (NaCl plates, Nujol, cm-1): 3244 (w), 1488 (m), 1312 (m),
1260 (m), 1118 (m), 1026 (m), 1012 (m), 984 (w), 896 (w), 830
(w), 806 (w), 722 (w). IR (NaCl cell, CH2Cl2, ν(N-H), cm-1):
3282. Anal. found (calcd for C10H16Cl2F3N3Ti): C, 33.8 (33.9); H,
4.5 (4.6); N, 11.7 (11.9)%.
1
(h) Data for 8 (R ) 2,3,5,6-C6HF4). Yield ) 86%. H NMR
(C6D6, 300.1 MHz, 298 K): 5.93 (1 H, m, 4-C6HF4), 2.72 (2 H,
m, NHMe2), 2.20 (12 H, d, 3J ) 6.0 Hz, NHMe2). 13C-{1H} NMR
2
(C6D6, 75.5 MHz, 298 K): 98.0 (t, J ) 23.3 Hz, 4-C6HF4), 41.0
(NMe2). 13C-{19F} NMR (C6D6, 75.5 MHz, 298 K): 145.9 (d,2J )
7.2 Hz, 2-C6HF4), 143.0 (d,2J ) 8.4 Hz, 3-C6HF4). 19F NMR (C6D6,
282.4 MHz, 298 K): -154.52 (m, C6HF4), -142.29 (m, C6HF4).
IR (NaCl plates, Nujol, cm-1): 3258 (w), 1626 (m), 1586 (m),
1496 (s), 1378 (s), 1310 (m), 1112 (m), 1008 (m), 932 (m), 892
(m), 822 (m). IR (NaCl cell, CH2Cl2, ν(N-H), cm-1): 3282. Anal.
found (calcd for C10H16Cl2F3N3Ti): C, 32.3 (32.3); H, 4.1 (4.1);
N, 11.2 (11.3)%.
1
(c) Data for 3 (R ) CH2Ph). Yield ) 62%. H NMR (C6D6,
3
500.1 MHz, 298 K): 7.51 (2 H, d, J ) 7.3, 2-C6H5), 7.26 (2H, t,
3
3J ) 7.8, 3-C6H5), 7.10 (1 H, t, J ) 7.8, 4-C6H5), 4.37 (2 H, s,
CH2), 2.68 (2 H, br m, NHMe2), 2.29 (12 H, d, 3J ) 6.4, NHMe2).
13C-{1H} NMR (C6D6, 125.7 MHz, 298 K): 141.7 (i-C6H5), 128.7
(2-C6H5), 127.1 (3-C6H5), 126.9 (4-C6H5), 72.8 (CH2), 40.4
(NHMe2). IR (KBr plates, Nujol, cm-1): 3220 (w), 1333 (m), 1305
(w), 1260 (s), 1208 (w), 1152 (w), 1014 (s), 896 (s), 802 (m), 723
(s), 574 (w). Anal. found (calcd for C11H21Cl2N3Ti): C, 41.9 (42.1);
H, 6.5 (6.7); N, 12.9 (13.3)%.
(i) Data for 9 (R ) C6F5). Yield ) 90%. 1H NMR (C6D6, 300.1
3
MHz, 298 K): 2.67 (2H, br m, NHMe2), 2.16 (12 H, d, J ) 6.1
Hz, NHMe2). 19F NMR (282.4 MHz, C6D6, 298 K): -155.28 (2 F,
3
3
br d, J ) 22.8 Hz, 2-C6F5), -166.01 (2 F, dt, J ) 22.9 Hz,
3-C6F5), -166.86 (1 F, t, 3J ) 21.4 Hz, 4-C6F5). 13C-{1H and 19F}
NMR (C6D6, 75.4 MHz, 298 K): 143.2 (2-C6F5), 137.3 (3-C6F5),
136.5 (4-C6F5), 134.0 (i-C6F5), 40.9 (NHMe2). IR (KBr plates,
Nujol, cm-1): 3275 (m), 1612 (m), 1338 (m), 1306 (m), 1249 (m),
1213 (m), 1156 (m), 1111 (m), 992 (m), 982 (m), 720 (s), 449
(m), 406 (m). IR (NaCl cell, CH2Cl2, ν(N-H), cm-1): 3280. Anal.
found (calcd for C10H12Cl2F5N3Ti): C, 30.7 (30.8); H, 3.7 (3.6); N
10.6 (10.8)%. EI-MS: m/z ) 598 (45%) [M - 2 NHMe2]2+, 345
(10%) [M - NHMe2]+, 298 (12%) [M - 2 NHMe2]+.
(d) Data for 4 (R ) Ph). Yield ) 95%. 1H NMR (C6D6, 300.1
MHz, 298 K): 1 proton obscured under residual C6D5H, 7.02
(3 H, m, C6H5), 6.76 (1H, m, C6H5), 2.64 (2H, br m, NHMe2),
3
2.23 (12 H, d, J ) 6.1 Hz, NHMe2). 13C-{1H} NMR (C6D6, 75.4
MHz, 298 K): 161.0 (i-C6H5), 128.5 (2-C6H5), 123.7 (3-C6H5),
122.7 (4-C6H5), 40.4 (NHMe2). IR (KBr plates, Nujol, cm-1): 3220
(w), 1326 (m), 1258 (w), 1210 (w), 1018 (m), 894 (m), 750 (m),
722 (m), 688 (m), 658 (w), 644 (w), 604 (w), 590 (w), 566 (w),
2892 Inorganic Chemistry, Vol. 44, No. 8, 2005

New Titanium Imido Synthons
(j) Data for 10 (R ) 4-C6H4Cl). Yield ) 98%. 1H NMR (500.1
after addition, the solution started to discolor and the initially off-
white resin took on a red-brown color. The resin was filtered off
and washed with benzene (5 × 10 mL) and hexanes (3 × 10 mL)
and dried in vacuo to afford a red-brown material. Yield: 1.862 g
3
MHz, 298 K, C6D6): 6.98 (2 H, d, J ) 8.8 Hz, 3-C6H4Cl), 6.72
3
(2 H, d, J ) 6.6 Hz, 2-C6H4Cl), 2.54 (2 H, br m, NHMe2), 2.18
(12 H, d, 3J ) 6.2 Hz, NHMe2). 13C-{1H} NMR (C6D6, 125.7 MHz,
298 K,): 158.9 (i-C6H4Cl), 128.6 (3-C6H4Cl), 127.6 (4-C6H4Cl),
125.0 (2-C6H4Cl), 40.5 (NHMe2). IR (KBr plates, Nujol, cm-1):
3228 (m), 1333 (m), 1261 (m), 1211 (w), 1167 (w), 1114 (m), 1091
(m), 1018 (s), 983 (m), 894 (m), 829 (m), 801 (m), 723 (s), 520
(w), 498 (w). Anal. Found (calcd for C10H18Cl2N3Ti): C, 35.9
(35.9); H, 5.3 (5.4); N, 12.9 (12.6)%.
1
(95%). H MAS NMR (399.9 MHz, 298 K, 4 kHz, swollen in
CDCl3): 7.1 (v br, PS resin aromatic H), 6.5 (v br, PS resin aromatic
H), 4.3 (br, PhCH2NdTi), 3.3 (br, NHMe2), 2.5 (br, NHMe2), 1.8
(v br, PS resin aliphatic H), 1.4 (v br, PS resin aliphatic H).
13C-{1H} MAS NMR (100.6 MHz, 298 K, 4 kHz, swollen in
CDCl3): 144.9 (br, PS resin aromatic C), 127.6 (v br, PS resin
aromatic C), 125.4 (v br, PS resin aromatic C), 72.9 (br,
PhCH2NdTi), 45.7 (v br, PS resin aliphatic C), 43.5 (v br, PS resin
aliphatic C), 40.3 (v br (overlapping), PS resin aliphatic C and
HNMe2). IR (KBr pellet, cm-1): 3268 (s), 3082 (s), 3055 (s), 3025
(s), 2972 (s), 2920 (s), 2848 (s), 2800 (s), 1946 (m), 1872 (m),
1814 (m), 1748 (w), 1646 (w), 1600 (s), 1582 (s), 1492 (s), 1450
(s), 1478 (s), 1400(m), 1372 (m), 1324 (m), 1246 (m), 1180 (m),
1154 (m), 1118 (m), 1068 (m), 1020 (s), 982 (s), 892 (s), 842 (m),
822 (m), 758 (s), 672 (s), 534 (s). Despite our best efforts, elemental
analysis of the product repeatedly returned lower than expected
%N, Cl, and Ti values. This is attributed to incomplete combustion
or acid digestion. The spectroscopic data and other experimental
observations (see Results and Discussion above) are consistent with
quantitative uptake of Ti(NMe2)2Cl2 to form the desired 14.
Ti2(NtBu)2Cl2(µ-Cl)2(py)4. A solution of Ti(NtBu)Cl2(NHMe2)2
(0.100 g, 0.357 mmol) in pyridine (5.0 mL, 62 mmol) was heated
at 80 °C for 16 h. The solution was concentrated to three-quarters
of the original volume, dichloromethane (15 mL) was added, and
the solution was filtered. Hexanes (20 mL) were added to the filtrate
which resulted in the formation of an orange precipitate which was
washed with hexanes (2 × 10 mL) and dried in vacuo to give an
(k) Data for 11 (R ) 2,3,5,6-C6HCl4). Yield ) 91%. 1H NMR
(C6D6, 499.9 MHz, 298 K): 6.67 (1 H, s, C6HCl4), 2.78 (2 H, br
m, NHMe2), 2.16 (12 H, d, 3J ) 5.9 Hz, NHMe2). 13C-{1H} NMR
(C6D6, 125.7 MHz, 298 K): 131.2 (C6HCl4), 128.5 (C6HCl4), 128.3
(C6HCl4), 123.3 (p-C6HCl4), 41.0 (NHMe2). IR (KBr plates, Nujol,
cm-1): 3239 (w), 1304 (w), 1260 (s), 1210 (w), 1150 (w), 1095
(m), 1045 (m), 1022 (m), 1014 (m), 893 (m), 806 (m), 722 (s),
713 (m), 678 (m). IR (NaCl cell, CH2Cl2, ν(N-H), cm-1): 3280.
Anal. found (calcd for C10H15Cl6N3Ti): C, 27.1 (27.4); H, 3.9 (3.5);
N, 9.3 (9.6)%.
1
(l) Data for 12 (R ) 2-C6H4CF3). Yield ) 85%. H NMR
3
(C6D6, 499.9 MHz, 298 K): 7.27 (1 H, d, J ) 8.1 Hz, 3-C6H4-
CF3), 7.21 (1 H, d, 3J ) 7.8 Hz, 6-C6H4CF3), 6.95 (1 H, app t, app
3J ) 7.6 Hz, 5-C6H4CF3), 6.49 (1 H, app t, app 3J ) 7.7 Hz, 4-C6H4-
CF3), 2.72 (2 H, br m, NHMe2), 2.20 (12 H, d, 3J ) 6.1 Hz,
NHMe2). 13C-{1H} NMR (C6D6, 125.7 MHz, 298 K): 156.4
(i- C6H4CF3), 132.1(5-C6H4CF3), 129.1 (6-C6H4CF3), 125.9 (2-C6H4-
CF3), 125.4 (3-C6H4CF3), 121.7 (4-C6H4CF3), 40.5 (NHMe2), no
signal observed for CF3. IR (KBr plates, Nujol, cm-1): 3264 (m),
2360 (w), 1592 (m), 1561 (m), 1342 (s), 1313 (s), 1251 (m), 1124
(s), 1055 (s), 1030 (s), 1002 (m), 894 (m), 802 (m), 756 (s), 503
(w). IR (NaCl cell, CH2Cl2, ν(N-H), cm-1): 3284. Anal. found
(calcd for C11H18Cl2F3N3Ti): C, 35.3 (35.9); H, 4.9 (4.9); N, 11.2
(11.4)%. EI-MS: m/z ) 281 (34%) [M - 2 Cl - CH4]+, m/z )
207 (100%) [M - 2 Cl - 2 NHMe2]+.
1
orange powder. Yield: 59 mg (48%). The H NMR spectrum of
the product confirmed the formation of spectroscopically pure
Ti2(NtBu)2Cl2(µ-Cl2)(py)4.16
Ti(NC6F5)Cl2(py)3 (15). A solution of Ti(NC6F5)Cl2(NHMe2)2-
Cl2 (0.300 g, 0.769 mmol) in pyridine (5.0 mL, 62 mmol) was
heated at 80 °C for 16 h. After cooling to room temperature, hexanes
(40 mL) were added and the mixture was stored at -15 °C for 16
h. The supernatant was decanted, and the solids were washed with
hexanes (3 × 15 mL) and dried in vacuo to afford 15 as a yellow
powder. Yield: 325 mg (89%). 1H NMR (CDCl3, 500.0 MHz, 298
K): 9.21 (4 H, d, J ) 4.5 Hz, o-cis-NC5H5), 8.77 (2 H, br s, o-trans-
NC5H5), 7.88 (2 H, apparent t, J ) 7.5 Hz, p-cis-NC5H5), 7.71
(1 H, br s, p-trans-NC5H5), 7.42 (4 H, t, J ) 6.5 Hz, m-cis-NC5H5),
7.29 (2 H, br s, m-cis-NC5H5). 13C-{1H} NMR (CDCl3, 125.7 MHz,
298 K): 152.1 (o-cis-NC5H5), 150.9 (o-trans-NC5H5), 138.9
(p-cis-NC5H5), 137.4 (p-trans-NC5H5), 124.0 (m-cis-NC5H5), 123.7
(m-trans-CN5H5). Resonances for C6F5 not observed. 19F NMR
(CDCl3, 282.4 MHz, 298 K): -153.1 (2 F, d, J ) 22.9 Hz, o-C6F5),
-166.8 (2 F, apparent t, J ) 19.8 Hz, m-C6F5), -166.9 (1 F, br s,
p-C6F5). IR (KBr plates, Nujol mull, cm-1): 3630 (w), 2454 (w),
1800 (s), 1716 (s, br), 1568 (m), 1538 (w), 1264 (m), 1196 (m,
br), 1166 (w), 1056 (m, br), 826 (m), 660 (m), 428 (w). Anal. found
(calcd for C21H15Cl2F5N4Ti): C, 47.0 (47.0); H, 3.1 (2.8); N, 10.5
(10.4)%.
t
1
(m) Data for 13 (R ) 2-C6H4 Bu). Yield ) 74%. H NMR
3
t
(C6D6, 499.9 MHz, 298 K): 7.83 (1 H, d, J ) 6.8 Hz, 6-C6H4 -
3
t
Bu), 7.16 (1 H, d, J ) 7.3 Hz, 3-C6H4 Bu), 7.04 (1 H, app t, app
3J ) 7.6 Hz, 5-C6H4 Bu), 6.78 (1 H, app t, app 3J ) 7.7 Hz, 4-C6H4 -
Bu), 2.76 (2 H, br m, NHMe2), 2.20 (12 H, d, 3J ) 6.3 Hz, NHMe2),
t
t
1.68 (9 H, s, Bu). 13C-{1H} NMR (C6D6, 125.7 MHz, 298 K):
t
t
t
160.2 (2-C6H4 Bu), 139.0 (i- C6H4(tBu)), 133.3 (6-C6H4 Bu), 126.7
t
t
t
(4-C6H4 Bu), 125.4 (3-C6H4 Bu), 123.2 (5-C6H4 Bu), 40.3 (NHMe2),
35.5 (CMe3), 30.8 (CMe3). IR (NaCl plates, Nujol, cm-1): 3583
(w), 3273 (m), 3258 (m), 3205 (w), 1581 (w), 1427 (m), 1304 (s),
1261 (w), 1021 (m), 983 (m), 894 (m), 801 (w), 764 (m), 665 (m).
IR (NaCl cell, CH2Cl2, ν(N-H), cm-1): 3285. Anal. found (calcd
for C14H27Cl2N3Ti): C, 46.2 (47.2); H, 6.8 (7.6); N, 11.3 (11.8)%.
EI-MS: m/z ) 265 (12%) [M - 2 NHMe2]+, m/z ) 134 (100%)
[M - Ti - 2 NHMe2 - 2 Cl]+.
t
Alternative Synthesis of Ti(N-2-C6H4 Bu)Cl2(NHMe2)2 (13).
To a yellow solution of Ti(NMe2)4 (0.18 g, 0.82 mmol) in toluene
(10 cm3) was added 2-tert-butyl aniline (0.13 g, 0.82 mmol) and
trimethylsilyl chloride (0.42 cm3, 3.3 mmol) via microliter syringe.
The yellow solution immediately darkened to orange. The mixture
was stirred at 80 °C for 1 h and filtered, and volatiles were removed
under reduced pressure. The product was obtained as a brown
powder. Yield: 0.21 g (72%).
Ti(N-CH2-4-C6H4PS)Cl2(NHMe2)2 (14). Aminomethyl poly-
styrene resin (1.57 g; loading 1.19 mmol‚g-1, 1.87 mmol) was
preswollen in benzene (20 mL) for 30 min. A deep orange solution
of Ti(NMe)2Cl2 (0.39 g, 1.87 mmol) in benzene (10 mL) was added,
and the mixture was shaken at room temperature for 16 h. Soon
Ti(N-4-C6H4Cl)Cl2(py)3 (16). A solution of Ti(N-4-C6H4Cl)-
Cl2(NHMe2)2 (0.300 g, 0.897 mmol) in pyridine (5.0 mL, 62 mmol)
was heated at 80 °C for 16 h and then cooled to 0 °C. Hexanes (20
mL) were added, and the resultant solids were washed with hexanes
(2 × 20 mL) and dried in vacuo to afford 16 as a brown powder.
Yield: 384 mg (89%). The trans-pyridine is fairly labile, and some
loss was always encountered during the drying process. This is
reflected in the elemental analysis. 1H NMR (CDCl3, 500.0 MHz,
Inorganic Chemistry, Vol. 44, No. 8, 2005 2893

Adams et al.
298 K): 9.06 (4 H, d, J ) 5.5 Hz, o-cis-NC5H5), 8.78 (2 H, br s,
o-trans-NC5H5), 7.80 (2 H, t, J ) 7 Hz, p-cis-NC5H5), 7.68 (1 H,
br s, p-trans-NC5H5), 7.47 (4 H, t, J ) 7.0 Hz, m-cis-NC5H5), 7.34
(2 H, apparent t, apparent J ) 6.5 Hz, m-trans-NC5H5), 6.96 (2 H,
d, J ) 8.0 Hz, m-C6H4Cl), 6.84 (2 H, d, J ) 8.0 Hz, o-C6H4Cl).
13C-{1H} (CDCl3, 125.7 MHz, 298 K): 151.4 (o-cis-NC5H5), 150.9
(o-trans-NC5H5), 138.7 (p-cis-NC5H5), 136.9 (p-trans-NC5H5),
157.1, 128.0, 124.9 (o-, m-, and p-C6H4Cl), 124.1 (m-cis-NC5H5),
123.8 (m-trans-NC5H5). Resonance for ipso-C6H4Cl not observed.
IR (KBr plates, Nujol mull, cm-1): 2724 (w), 2670 (w), 1602 (s),
1568 (w), 1328 (m), 1306 (w, br), 1262 (w), 1222 (w), 1212 (s),
1148 (m), 1090 (m), 1062 (s), 1042 (s), 1012 (m), 968 (w), 936
(w), 830 (s), 760 (m), 750 (m), 692 (s), 638 (s), 622 (w), 518 (s),
432 (m). Anal. found (calcd for C18.5H16.5Cl3N3.5Ti): C, 50.2 (50.3);
H, 3.8 (4.2); N, 11.1 (11.1)%.
program SIR92,62 which located all non-hydrogen atoms. Additional
electron density for 11‚0.5(C6H6) and 13‚0.5(C5H12) was modeled
as residual solvent of crystallization (benzene and pentane, respec-
tively) disordered across crystallographic inversion centers. Sub-
sequent full-matrix least-squares refinement was carried out using
the CRYSTALS program suite.63 For 2, 4, and 9, systematic
absences were consistent with either Cc or C2/c. Comparison of
the molecular structures obtained in the two spacegroups, along
with the more successful structure solution and refinement in the
latter, favored the centrosymmetric alternative. The compound 12
was satisfactorily solved and refined in the spacegroup Pna21 (as
opposed to the centrosymmetric alternative Pnam) and found to
contain two molecules in each asymmetric unit related by a
noncrystallographic center of inversion. Refinement of the Flack
enantiopole parameter64 gave a value of 0.47(4), showing the crystal
to be an inversion twin which is attributed to the locally centrosym-
metric packing.
Coordinates and anisotropic thermal parameters of all non-
hydrogen atoms were refined (with the exception of the C atoms
of the disordered benzene of crystallization in 11‚0.5(C6H6) which
were refined isotropically subject to bond length and angle
restraints). H atoms bonded to C were placed geometrically, as were
the N-H atoms (N-H ) 0.87 Å) in 2, 4, 9, and 11‚0.5C6H6. For
13‚0.5(C5H12) and 12 the N-H atoms could be located from Fourier
difference maps and refined isotropically. However, for the purposes
of geometric comparisons with 1, 4, 9, and 11, N-H distances of
0.87 Å were again used (for example in Table 2). Finally, weighting
schemes and secondary extinction correction were applied as
appropriate. A full listing of atomic coordinates, bond lengths and
angles, and displacement parameters for all the structures have been
deposited at the Cambridge Crystallographic Data Center. See
Notice to Authors, Issue No. 1.
Ti2(NC6F5)2Cl2(µ-Cl)2(py)4 (17). To a solution of Ti(NC6F5)-
Cl2(py)3 (15, prepared in situ from Ti(NtBu)Cl2(py)3 (0.300 g, 0.702
mmol) and C6F5NH2 (0.128 g, 0.702 mmol) in dichloromethane)
in dichloromethane (30 mL) was added pyridine (1.0 mL), and the
mixture was carefully layered with hexanes. After 48 h at room
temperature, dark yellow, diffraction-quality crystals were formed
which were washed with hexanes (2 × 10 mL) and dried in vacuo.
Yield: 71 mg (22%). 19F NMR (NC5D5, 282.4 MHz, 298 K):
-153.6 (2 F, d, J ) 22.9 Hz, o-C6F5), -167.3 (2 F, t, J ) 21.5
Hz, m-C6F5), -169.8 (1 F, t, J ) 21.2 Hz, p-C6F5). IR (KBr plates,
Nujol mull, cm-1): 1606 (s), 1506 (s, br), 1494 (w, br), 1350 (w),
1326 (s), 1260 (m, br), 1218 (s, br), 1068 (m), 1048 (s, br), 1016
(m), 986 (s), 800 (w, br), 752 (m), 720 (w), 692 (s), 640 (s), 504
(w), 464 (w), 416 (m). Anal. found (calcd for C32H20Cl4F10N6Ti2):
C, 41.5 (41.2); H, 2.2 (2.2); N, 9.1 (9.2)%. (The very insoluble
1
crystals of 17 could only be dissolved in pydrine-d5 making H
and 13C spectra meaningless as they showed only resonances for
NC5HxD5-x.)
Acknowledgment. We thank the EPSRC, DSM Research,
SABIC EuroPetrochemicals, and Millenium Pharmaceuticals
Ltd. for support and Professor J. D. Protasiewicz for
assistance with the PM3 calculations.
Crystal Structure Determinations of Ti(NR)Cl2(NHMe2)2 (R
i
) Pr (2), Ph (4), C6F5 (9), 2-C6H4CF3 (12)), Ti(N-2,3,5,6-
C6HCl4)Cl2(NHMe2)2‚0.5(C6H6) (11‚0.5(C6H6)), Ti(N-2-C6H4tBu)-
Cl2(NHMe2)2‚0.5(C5H12) (13‚0.5(C5H12)), and Ti2(NC6F5)2Cl2(µ-
Cl)2(py)4 (17). Crystal data collection and processing parameters
are given in Table 3. Crystals were mounted on glass fibers using
perfluoropolyether oil and cooled rapidly in a stream of cold N2
using an Oxford Cryosystems CRYOSTREAM unit. Diffraction
data were measured using either an Enraf-Nonius DIP2000,
KappaCCD, or MACH3 diffractometer. Intensity data were pro-
cessed using either the RC93 program60 or the DENZO-SMN
package.61 The structures were solved using the direct-methods
Supporting Information Available: X-ray crystallographic data
in CIF format for the structure determinations of 2, 4, 9, 12, 11‚
0.5(C6H6), 13‚0.5(C5H12), and 17; full synthetic procedures for
compounds 1-13; cell packing diagram for 2; views of 4, 9, and
12 projected onto the aryl ring carbons best-fit least-squares planes;
plot of the other crystallographically independent molecule of 12;
space-filling representations of 12 and 13. This material is available
free of charge via the Internet at http://pubs.acs.org.
IC050011Z
(60) Watkin, D. J.; Prout, C. K.; Lilley, P. M. deQ. RC93; Chemical
Crystallography Laboratory, University of Oxford: Oxford, U.K.,
1994.
(61) Otwinowski, Z.; Minor, W. Processing of X-ray Diffraction Data
Collected in Oscillation Mode; Methods in Enzymology, Vol. 276:
Macromolecular Crystallography, Part A; Carter, C. W., Jr., Sweet,
R. M., Eds.;Academic Press: 1997; pp 307-326.
(62) Altomare, A.; Cascarano, G.; Giacovazzo, G.; Guagliardi, A.; Burla,
M. C.; Polidori, G.; Camalli, M. J. Appl. Crystallogr. 1994, 27, 435.
(63) Watkin, D. J.; Prout, C. K.; Carruthers, J. R.; Betteridge, P. W.; Cooper,
R. I. CRYSTALS, issue 11; Chemical Crystallography Laboratory,
University of Oxford: Oxford, U.K., 2001.
(64) Flack, H. D.; Bernardinelli, G. J. Appl. Crystallogr. 2000, 33, 1143.
2894 Inorganic Chemistry, Vol. 44, No. 8, 2005