Reaction of p-Toluenesulfonylamide and M(NMe2)4 (M = Ti, V): Generation of electron-deficient imido complexes of early transition metals

Article abstract of DOI:10.1021/ic062404j

p-Toluenesulfonamide (p-TsNH₂) was succesfully employed as an imido ligand precursor in the synthesis of highly air- and moisture-sensitive titanium(IV) and vanadium(IV) complexes. Reaction of M(NMe₂) ₄ (M = Ti, V) with Ts

Full text of DOI:10.1021/ic062404j

Inorg. Chem. 2007, 46, 3192−3202
Reaction of p-Toluenesulfonylamide and M(NMe2)4 (M
)
Ti, V):
Generation of Electron-Deficient Imido Complexes of Early Transition
Metals
Christian Lorber,* Robert Choukroun, and Laure Vendier
Laboratoire de Chimie de Coordination, CNRS UPR 8241, lie´ par conVention a` l’UniVersite´ Paul
Sabatier, 205 route de Narbonne, 31077 Toulouse Cedex 04, France
Received December 15, 2006
p-Toluenesulfonamide (p-TsNH2) was succesfully employed as an imido ligand precursor in the synthesis of highly
air- and moisture-sensitive titanium(IV) and vanadium(IV) complexes. Reaction of M(NMe2)4 (M Ti, V) with TsNH2
in toluene afforded [M( -NTs)(NMe2)2]2 dimer complexes (M Ti (1), V (2)). By contrast, the reaction carried out
in dichloromethane led to [Ti{µ-N,O-NTs Cl(NMe2)(NHMe2)2]2 (3) and [Ti{µ-N,O-NTs Cl2(NHMe2)2]n (4) through
solvent activation. The same reaction of M(NMe2)4/TsNH2 conducted in the presence of an excess of
trimethylchlorosilane produced [V( NTs)Cl2(NHMe2)2] (5) and [(Me2HN)Cl2Ti( 2-N-NTs-
2N,O)2TiCl2(NHMe2)2] (6).
Alternatively, compound has also been prepared from TiCl2(NMe2)2 and TsNH2. was reacted with
trimethylchlorosilane to afford the amide complex [Ti{µ-N,O -N(SiMe3)Ts-
3N,O,O′}Cl2(NMe2)]2 (7) in which the
)
µ
)
}
}
d
µ
κ
6
1
′
κ
tosylimide bond has been silylated. Compounds 1
−6 represents the first examples of sulfonylimido complexes for
titanium and vanadium.
Introduction
C-H activation,24-28 reactions with unsaturated C-C29-35
or C-X bonds,36-39 alkyne or alkene hydroamination (for
The chemistry of N-organoimido complexes continues to
be an attractive focus.1-7 Compounds containing the dian-
ionic π-donor terminal imido ligand [NR]2- (R ) alkyl or
aryl) have found applications in a variety of stoichiometric
or catalytic transformations. Selected examples include
alkene8 and imine9-13 metathesis, olefin polymerization,3,14-23
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* To whom correspondence should be addressed. E-mail: lorber@lcc-
toulouse.fr. Phone: (+33) 5 61 33 31 44. Fax: (+33) 5 61 55 30 03.
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3192 Inorganic Chemistry, Vol. 46, No. 8, 2007
10.1021/ic062404j CCC: $37.00
© 2007 American Chemical Society
Published on Web 03/16/2007

Electron-Deficient Imido Complexes
some examples of hydroamination using imido catalysts, see
refs 40-45, and for selected recent examples of hydroami-
nation using group 4 precatalyst, see refs 46-51, carboami-
nation reaction,52-54 and strained heterocycle opening.27,55
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imido compounds of general formula [M(dN-R)Cl2Ln] (M
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Cl2(NHMe2)2] complexes (M ) Ti,60 V)16,61 on the basis of
a very convenient one-pot reaction of M(NMe2)4 with RNH2
in the presence of an excess of Me3SiCl. This procedure
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including functional amines, enantiomerically pure amines
(giving chiral imido functions), and diamines (giving diimido
complexes).
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imido group allows the fine-tuning of catalysts containing
imido spectator ligands. Among the strongest electron-
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Inorganic Chemistry, Vol. 46, No. 8, 2007 3193

Lorber et al.
Os)90,91 and the only two reported early transition metal
tosylimide [Cp2Zr(µ-NSO2Ar)]2 (Ar ) 4-Br-C6H4)92 and
triflimide [Nb(dNSO2CF3){N(R)Ar′}3] (R ) C(CD3)2CH3;
Ar′ ) 4,5-Me2C6H3).93
In this paper, we report on the synthesis and structural
characterization of the first members of a new family of
electron-deficient titanium(IV) and vanadium(IV) complexes
that possess a tosylimido function [tosyl ) p-toluenesulfonyl
(Ts)].
cryojet from Oxford Instrument and using a graphite-monochro-
mated Mo KR radiation (λ ) 0.710 73 Å). Final unit cell parameters
were obtained by means of a least-squares refinement of a set of
8000 well-measured reflections. The crystals were monitored for
decay during data collection by measuring the intensities of 200
check reflections, but no significant fluctuation of intensities was
observed. Structures have been solved by means of direct methods
using the program SIR9296 and subsequent difference Fourier maps;
models were refined by least-squares procedures on a F2 by using
SHELXL-9797 integrated in the package WINGX version 1.64,98
and empirical absorption corrections were applied on all data sets.99
For coordination polymer 4, the structure appeared to be in
monoclinic system, and the systematic absences suggested two
space groups C2/c or Cc, with a better CFOM for C2/c. The
E-statistics suggested a centrosymmetric structure. We then solved
and refined in C2/c, and we obtained a clean and stable final
refinement (a trial in Cc led to unsatisfactory results with a poor
checkcif detecting a center of symmetry and suggesting a new space
group: C2/c). The S3 atom is located on a symmetry axis. When
the whole molecule was generated by applying the symmetries, S3
has either two nitrogen or two oxygen atoms on each side. From a
chemical point of view, these sequences N-S-N or O-S-O are
unacceptable, and therefore, the whole sequence -Ti-N-S-O-
was treated as a statistic disorder. Details of the structure solution
and refinements are given in the Supporting Information (CIF file).
A full listing of atomic coordinates, bond lengths and angles, and
displacement parameters for all structures have been deposited at
the Cambridge Crystallographic Data Centre.
[Ti(NTs)(NMe2)2]2 (1). To a toluene solution (5 mL) of 250 mg
of Ti(NMe2)4 (1.115 mmol) was added by portions 1 equiv of
p-TsNH2 (191 mg, 1.115 mmol) at room temperature. The resulting
red solution was stirred for 6 h at RT (room temperature). The
volatiles were pumped off, and the orange solid was washed with
pentane (2 × 10 mL) and dried under vacuum to give analytically
and spectroscopically pure material. Single crystals of 1, suitable
for X-ray diffraction studies, were obtained by recrystallization from
toluene solution of 1 layered with pentane. Yield: 220 mg (64%)
(orange). 1H NMR (250 MHz, C6D6): δ 7.95 (d, 3J ) 6.5 Hz, 4H,
C6H4), 6.79 (d, 3J ) 6.5 Hz, 4H, C6H4), 3.26 (s, 24H, NMe2), 1.90
(s, 6H, MeTs). 13C{1H} NMR (125.81 MHz, C6D6): δ 142.3, 141.6,
129.2, 126.3 (C6H4), 45.4 (NMe2), 20.9 (MeTs). IR: 2861 (m), 2817
(w), 2775 (m), 1595 (m, νCdC), 1496 (w), 1445 (m), 1413 (m),
1253 (vs), 1117 (vs), 1085 (s), 1021 (m), 980 (s), 935 (s), 819 (s),
684 (s), 643 (m), 629 (m), 598 (m), 582 (m), 554 (s), 512 (w), 465
(m). Anal. Calcd for C22H38N6O4S2Ti2 (Mr ) 610.44): C, 43.29;
H, 6.27; N, 13.77. Found: C, 43.34; H, 6.33; N, 13.33.
Experimental Section
General Methods and Instrumentation. All manipulations were
carried out using standard Schlenk line or drybox techniques under
an atmosphere of argon. Solvents were refluxed and dried over
appropriate drying agents under an atmosphere of argon and
collected by distillation. NMR spectra were recorded on Bruker
AM200, AM250, ARX250, DPX300, and Avance500 spectrometers
and referenced internally to residual protio-solvent (1H) resonances
and are reported relative to tetramethylsilane (δ ) 0 ppm). 29Si
NMR (99.4 MHz) and 51V NMR (131.60 MHz) spectra were
recorded on Bruker Avance500 spectrometer. Chemical shifts are
quoted in δ (ppm). Infrared spectra were prepared as KBr pellets
under argon in a glovebox and were recorded on a Perkin-Elmer
Spectrum GX FT-IR spectrometer. Infrared data are quoted in
wavenumbers (cm-1). EPR spectra were recorded on a Bruker
ESP300E spectrometer. Elemental analyses were performed at the
Laboratoire de Chimie de Coordination (Toulouse, France) (C, H,
N) or by the Service Central de Microanalyses du CNRS at
Vernaison, France (C, H, N, Cl).
The Ti(NMe2)4 used in this study was prepared by a modification
of a literature procedure94 or purchased from commercial sources
(Aldrich, Acros, 99.999%). V(NMe2)4 was prepared by a modifica-
tion of a literature procedure.95 Trimethylchlorosilane was distilled
and stored over 4 Å molecular sieves under argon before use.
p-TsNH2 (Aldrich, g99%) was recrystallized from anhydrous
ethanol and dried under vacuum.
Crystal Structure Determinations. The structures of nine
compounds were determined. Crystal data collection and processing
parameters are given in Table 2. Crystals of 1 (yellow-orange
plates), 2 (dark-red sticks), 3 (red-orange parallelepipeds), 4 (yellow
blocks), 5 (orange-brown needles), 6 (yellow sticks), 7 (light green
blocks), [VCl3Py3] (green blocks), and [V2OCl4Py6] (dark-purple
plates) were obtained. The selected crystals, sensitive to air and
moisture, were mounted on a glass fiber using perfluoropolyether
oil and cooled rapidly to 180 K in a stream of cold N2. For all the
structures data were collected at low temperature (T ) 180 K) on
a Stoe imaging plate diffraction system (IPDS), equipped with an
Oxford Cryosystems Cryostream cooler device or an Oxford
Diffraction Kappa CCD Excalibur diffractometer equipped with a
[V(NTs)(NMe2)2]2 (2). To a toluene solution (10 mL) of 200
mg of V(NMe2)4 (0.880 mmol) was added by portions 1 equiv of
p-TsNH2 (150 mg, 1.115 mmol) at room temperature. The resulting
brown solution was left at RT for 2 days. A first crop of crystals
(suitable for X-ray diffraction studies) was collected (110 mg), and
the solution was layered with pentane to afford a second crop of
crystals (50 mg). The dark brown crystals were washed with pentane
(2 × 5 mL) and dried under vacuum. Yield: 160 mg (59%) (dark
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3
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3194 Inorganic Chemistry, Vol. 46, No. 8, 2007

Electron-Deficient Imido Complexes
Table 1. Comparison of Average Interatomic Distances (Å) and Angles (deg) in Complexes 1-6
param
M-Nimido
1
2
3
4a
5b
6
2.106(4) [Ti1-N1]
1.974(4) [Ti1-N1]
1.542(4)
1.866(4) [Ti1-N2]
1.889(4) [Ti1-N3]
1.9183(14)
1.6000(14)
1.8391(16)
1.945 1.672(3)
2.0707(19) [Ti1-N1]
1.931(2) [Ti2-N1]
1.563(2)
Nimido-S
M-NMe2
1.5344(16)
1.9148(16)
1.519 1.612(3)
1.8107(15) [V1-N2]
1.8349(15) [V1-N3]
M-Cl
SdO
2.4530(6)
2.347 2.2603(12) [V1-Cl1]
2.2855(12) [V1-Cl2]
1.430 1.436(3) [S1-O1]
1.435(3) [S1-O2]
2.3417(5) [Ti1-Cl1]
2.3197(8) [Ti2-Cl2]
1.4264(18) [S1-O2]
1.438(3) [S1-O1]
1.4409(13) [S1-O1]
1.4379(13) [S1-O2]
1.4622(14) [S1-O1]
S-O
1.507(3) [S1-O2]
2.125(4) [Ti1-O2]
1.4791(14) [S1-O2]
2.1780(13) [Ti1-O2]
2.2366(16) [Ti1-N3]
2.2572(17) [Ti1-N4]
1.7718(19)
1.515
1.4917(18) [S1-O1]
2.1509(18) [Ti1-O1]
2.296(4) [Ti1-N2]
Ti-O (or V‚‚‚O)
(3.435, 3.691)
1.958 (3.904; 4.094)
2.204 2.144(3) [V1-N2]
2.141(3) [V1-N3]
M-NNHMe
2
2.244(2) [Ti2-N3]
S1-C1
1.759(5)
1.7678(18)
2.6027(6)
1.785 1.755(4)
1.755(2)
M‚‚‚S
2.7128(16) [Ti1‚‚‚S1]
2.7450(6) [Ti1‚‚‚S1]
M‚‚‚M
3.1297(19)
5.279
5.45
3.1637(8)
M-Nimido-S
94.8(2) [Ti1-N1-S1] 138.37(9) [V1-N1-S1] 149.46(11)
145.6(2) [Ti1-N1-S1] 134.79(9) [V1-N1-S1]
167.71(2)
97.15(9) [Ti1-N1-S1]
158.40(13) [Ti2-N1-S1]
104.44(9) [Ti1-N1-Ti2]
72.45(11) [N1-Ti1-N1]
78.66(12) [N1-Ti2-N1]
170.81(4) [Cl1-Ti1-Cl1]
93.26(5) [Cl1-Ti2-Cl1]
179.96(12) [N3-Ti2-N3]
151.44(10) [N1-Ti1-N2]c
135.28(8) [N1-Ti1-N2]c
88.61(8) [N1-Ti2-N3]
91.42(8) [N1-Ti2-N3]
M-Nimido-M
Nimido-M-Nimido
100.14(18)
79.86(18)
86.69(6)
93.31(6)
Cl-M-Cl
177.87 135.48(5)
NNHMe -M-NNHMe
167.31(6)
98.16(7)
88.44(7)
178.59 163.21(12)
89.63 99.14(13) [N1-V1-N3]
2
2
Nimido-M-NNHMe
2
99.59(14) [N1-V1-N2]
Nimido-M-Cl
167.54(5)
89.90 112.43(11) [N1-V1-Cl2] 170.81 [Cl1-Ti1-Cl1]
112.09(11) [N1-V1-Cl1] 93.26 [Cl2-Ti2-Cl2]
114.1 109.47(17); 108.13(17)
108.3
153.4
N-SdO
N-S-O
Ti-O-S
O‚‚‚H-N
(dist, angle)
118.6(2) [N1-S1-O1] 110.42(8); 109.60(8)
101.9(2) [N1-S1-O2]
113.34(9) [N1-S1-O1]
113.28(8) [N1-S1-O2]
137.87(8)
114.88(11) [N1-S1-O2]
99.63(10) [N1-S1-O1]
96.11(9) [Ti1-O1-S1]
95.13(18)
2.07, 159.2 [O1‚‚‚H4-N 4]
2.12, 154.1 [O3‚‚‚H2A-N2]
2.16, 141.4 [O1‚‚‚H5A-N5]
2.22, 152.3 [O2‚‚‚H6A-N6]
2.24, 138.3 [O4‚‚‚H3A-N3]
117.14(18) [01-S1-O2]
103.88(17) [N1-S1-C1]
other
113.1(2) [01-S1-O2] 116.96(8) [01-S1-O2] 111.98(9) [01-S1-O2]
110.2(2) [N1-S1-C1] 103.97(7) [N1-S1-C1] 107.67(9) [N1-S1-C1]
116.35(11) [01-S1-O2]
109.79(11) [N1-S1-C1]
a Average values. b Geometric parameters are given for molecule A. c Two values for the two positions of the disordered NHMe2.
2.36 (s, 6H, MeTs). 13C{1H} NMR (100.62 MHz, CD2Cl2): δ 142.0,
140.9, 129.1, 126.4 (C6H4), 43.1 (NMe2), 21.1 (MeTs). 51V NMR
(131.60 MHz, CD2Cl2): δ +15.6 (w1/2 ) 150 Hz). IR: 2861 (m),
2777 (w), 1597 (m, νCdC), 1494 (w), 1453 (m), 1423 (m), 1414
(m), 1274 (vs), 1158 (m), 1142 (vs), 1079 (vs), 1021 (w), 956 (s),
919 (m), 812 (m), 714 (s), 706 (s), 659 (m), 622 (w), 592 (m), 553
(m). Anal. Calcd for C22H38N6O4S2V2 (Mr ) 612.60): C, 42.85;
H, 6.21; N, 13.63. Found: C, 42.79; H, 6.25; N, 13.36.
[Ti{µ-N,O-NTs}Cl(NMe2)(NHMe2)2]2 (3). This compound was
crystallized from a complex mixture of products obtained using a
procedure similar to the synthesis of 1 but using dichloromethane
as solvent and a reaction time of 24 h. The crystals were of good
quality for X-ray diffraction studies, but the amount of 3 was not
enough for full characterization. A 1H NMR spectrum of the mixture
of products obtained is given as Supporting Information.
1035 (vs), 1015 (vs), 896 (m), 813 (m), 682 (s), 559 (s), 461 (w).
Anal. Calcd for C11H21Cl2N3O2S1Ti1 (Mr ) 378.14): C, 34.94; H,
5.60; N, 11.11. Found: C, 34.95; H, 5.77; N, 10.78.
[V(dNTs)Cl2(NHMe2)2] (5). To a toluene solution (15 mL) of
250 mg of V(NMe2)4 (1.100 mmol) was added by portions 1 equiv
of p-TsNH2 (188 mg, 1.100 mmol), and subsequently 1.2 g of Me3-
SiCl was slowly added at room temperature. The resulting solution
was stirred for 12 h at RT. Filtration (to remove about 60 mg of a
brown solid residue) afforded a yellow solution. Addition of pentane
(1 mL) to this solution afforded upon standing at -20 °C orange
needles of 5 that were washed with pentane (2 × 5 mL) and dried
under vacuum. Yield: 110 mg (26%) (orange). EPR (CH2Cl2,
RT): g ) 1.983, A(51V) ) 87.0 G. 51V NMR (131.60 MHz, CD2-
Cl2): δ -402.6 (w1/2 ) 200 Hz). IR: 3144 (s, br, NH), 2969 (w),
1597 (w, CdC), 1466 (s), 1250 (s), 1154 (s), 1094 (s), 1019 (s),
850 (s), 818 (m), 678 (m), 555 (m). Anal. Calcd for C11H21Cl2N3O2-
SV (Mr ) 381.22): C, 34.66; H, 5.55; N, 11.02. Found: C, 34.56;
H, 5.52; N, 10.95.
[Ti{µ-N,O-NTs}Cl2(NHMe2)2]n (4). This compound was pre-
pared using the procedure described for 3 by allowing to stand at
room temperature for 3 days a dichloromethane solution (3 mL)
composed of 125 mg of Ti(NMe2)4 and 95 mg of TsNH2. Removal
of the volatiles gave a yellow solid that was washed with some
pentane (yield: 175 mg). Complex 4 was obtained as yellow crystals
from a dichloromethane solution layered with toluene and pentane.
Due to its polymeric nature, the low solubility of 4 in CD2Cl2
[(Me2HN)Cl2Ti(µ2-N-NTs-κ2N,O)2TiCl2(NHMe2)2] (6). Method
1 (One-Pot Synthesis from TiN(Me2)4/TsNH2/Me3SiCl). The
procedure was similar to the one described for 5, starting with
T(NMe2)4 (250 mg), p-TsNH2 (188 mg), and 1.0 g of Me3SiCl. A
total of 200 mg of 6 was obtained, contaminated with unknown
products. Selective recrystallizations from toluene/pentane solutions
1
precluded NMR studies. In addition, the H NMR spectrum of a
1
suspension of 4 in CD2Cl2 rapidly evolves to show signals attributed
to compound 6 and decomposition products. IR: 3211 (br, s, NH),
2924 (s), 1597 (m, νCdC), 1465 (s), 1250 (s), 1118 (vs), 1094 (vs),
afforded low amounts of pure 6 (30 mg). H NMR (250 MHz,
C6D6): two isomers (A and B) in a ratio A:B ) 2:1. Isomer A
3
3
(6a): δ 8.44 (d, J ) 8.3 Hz, 4H, m-C6H4), 6.81 (d, J ) 8.2 Hz,
Inorganic Chemistry, Vol. 46, No. 8, 2007 3195

Lorber et al.
Table 2. Crystallographic Data, Data Collection, and Refinement Parameters for Compounds 1-7
param
1
2
3
4
5
6
chem formula
fw
C22H38N6O4S2Ti2 C22H38N6O4S2V2
C26H54Cl2N2O4S2Ti2
773.55
C110H210Cl20N31O19S10Ti10 C11H21Cl2N3O2SV C20H35Cl4N5O4S2Ti2
610.50
616.60
3779.69
381.22
711.27
cryst system
space group
a, Å
b, Å
c, Å
R, deg
â, deg
γ, deg
V, Å3
monoclinic
P21/n
8.0903(10)
21.086(2)
9.5039(12)
90.0
114.395(13
90.0
1476.5(3)
2
monoclinic
P21/c
8.0142(5)
8.8093(8)
20.0954(14)
90.0
94.020(8)
90.0
1415.23(18)
2
monoclinic
P21/n
9.6076(7)
12.2159(9)
15.8021(12)
90.0
97.555(6)
90.0
1838.5(2)
2
monoclinic
C2/c
35.005(2)
12.4083(8)
25.2366(17)
90.0
128.269(8)
90.0
8606.1(13)
2
monoclinic
P21/n
9.9919(8)
18.2905(13)
19.6658(16)
90.0
101.128(7)
90.0
3526.5(5)
8
monoclinic
C2/c
22.652(2)
11.4504(8)
15.357(1)
90.0
128.659(5)
90.0
3110.5(4)
4
Z
D
calc, g cm-3
1.373
0.719
640
1.447
0.846
644
1.397
0.735
816
1.459
0.932
3918
1.436
0.987
1576
1.52
1.026
1464
µ(Mo KR), mm-1
F(000)
θ range (deg)
measd reflcns
unique reflcns/Rint
params/restraints
2.54-26.12
3.08-25.97
2.71-32.10
2.94-25.68
2.74-26.37
3-32
14 536
12 049
18 768
29 219
25 499
31 117
2908/0.2115
168/0
2749/0.0308
168/0
6092/0.0340
206/ 0
8135/0.0420
470/6
7210/0.0779
371/0
5123/0.02
174/0
final R indices [I > 2σ(I)] R1 ) 0.0549
R1 ) 0.0272
wR2 ) 0.0738
R1 ) 0.0335
wR2 ) 0.075
1.036
R1 ) 0.0359
wR2 ) 0.0948
R1 ) 0.0599
wR2 ) 0.1143
1.022
R1 ) 0.0700
wR2 ) 0.01522
R1 ) 0.0938
wR2 ) 0.1625
1.074
R1 ) 0.0411
wR2 ) 0.0852
R1 ) 0.1073
wR2 ) 0.1026
0.883
R1 ) 0.0317
wR2 ) 0.0758
wR2 ) 0.0380
final R indices all data
R1 ) 0.1627
wR2 ) 0.1001
0.859
goodness of fit
1.080
∆Fmax, ∆Fmin
0.469 and -0.616 0.309 and -0.327 0.537 and -0.972
1.072 and -1.005
0.288 and -0.336 0.57 and -0.88
4H, o-C6H4), 3.95 (br m, 2H, NHMe2), 3.37 (m, 1H, NHMe2), 2.57
(d, 3J ) 6.2 Hz, 6H, NHMe2), 2.44 (d or s depending on the
0.27 (s, 18H, SiMe3). 13C{1H} NMR (125.81 MHz, C6D6): δ
414.40, 137.26, 129.88, 127.69, (C6H4), 49.41 (NHMe2), 20.84
(MeTs), 1.13 (SiMe3). 29Si NMR (99.4 MHz, C6D6): δ 10.43. IR:
2959 (w), 1597 (w, νCdC), 1459 (w), 1254 (s), 1223 (s), 1157 (vs),
1117 (m), 1127 (s), 1095 (s), 1021(m), 999 (m), 933 (m), 852 (vs),
815 (m), 782 (m), 743 (m), 579 (m), 541 (m), 458 (m). Anal. Calcd
for C24H44Cl4N4O4S2Si2Ti2 (Mr ) 810.48): C, 35.57; H, 5.47; N,
6.91. Found: C, 35.43; H, 5.51; N, 6.83.
Method 2 (from Ti(NMe2)4, without Isolating 1). To a toluene
solution (5 mL) of 250 mg of Ti(NMe2)4 (1.115 mmol) was added
by portions 1 equiv of p-TsNH2 (191 mg, 1.115 mmol) at room
temperature. The resulting solution was stirred for 12 h at RT. The
volatiles were pumped off, to afford an orange solid. To be sure
that no dimethylamine was retained, 4 mL of toluene was added to
this solid, and the solvent was removed under vacuum, followed
by addition of 5 mL of pentane, trituration of the solid, and removal
of the solvent under vacuum (twice). The solid was solubilized in
5 mL of dichloromethane, and 1.0 g of Me3SiCl was slowly added
to give a red solution that was left overnight at RT. This step has
also been performed in toluene at RT for 12 h, or 80 °C for 1 h
without noticeable difference, but heating the solution at 110 °C
for longer period of time led to decomposition products. The
solution was concentrated to 2 mL, followed by addition of 3 mL
of toluene and layering with a solution of pentane, affording after
5 days green crystals that were collected and washed with pentane.
Yield: 215 mg (48%) (green). Analytical and spectroscopic data
were similar to those obtained by method 1.
3
concentration, J ) 5.7 Hz, 6H, NHMe2), 2.14 (d or s depending
on the concentration, 3J ) 5.8 Hz, 6H, NHMe2), 1.83 (s, 6H, MeTs).
3
3
Isomer B (6b): δ 8.39 (d, J ) 8.3 Hz, 4H, m-C6H4), 6.74 (d, J
) 8.1 Hz, 4H, o-C6H4), 3.95 (br m, 2H, NHMe2), 3.37 (m, 1H,
NHMe2), 2.97 (br s, 6H, NHMe2), 2.57 (d, 3J ) 6.2 Hz, 6H,
NHMe2), 1.78 (s, 6H, MeTs), 2.59 (br s, 6H, NHMe2). 13C{1H} NMR
(125.81 MHz, C6D6): isomer A (6a), δ 144.58, 137.42, 129.38,
128.70 (C6H4), 44.27 (NMe2), 44.22 (NMe2), 42.62 (NMe2), 21.02
(MeTs); isomer B (6b), δ 144.29, 137.73, 129.38, 128.70 (C6H4),
45.64 (NMe2), 42.77 (NMe2), 41.90 (NMe2), 21.02 (MeTs). IR: 3222
(m, NH), 3192 (m, NH), 1596 (w, νCdC), 1466 (m), 1276 (m), 1255
(m), 1148 (m), 1113 (s), 1093 (s), 1075 (s), 1036 (vs), 1023 (s),
1011 (vs), 981 (s), 896 (s), 813 (m), 705 (m), 682 (vs), 595 (m),
554 (s), 496 (w), 458 (w), 420 (w), 415 (w). Anal. Calcd for C20H35-
Cl4N5O4S2Ti2 (Mr ) 711.20): C, 33.78; H, 4.96; N, 9.85. Found:
C, 35.89; H, 5.16; N, 9.38. We were unable to obtain a satisfactory
elemental analysis for this compound, probably because of its high
moisture sensitivity (similar problems were reported for related
(sulfonamido)titanium complexes).100
Method 2 (from TiCl2(NMe2)2 and TsNH2). Solid TsNH2 (82
mg) was added to a toluene solution (5 mL) of TiCl2(NMe2)2
(0.4833 mM). The resulting red solution was stirred for 1 day and
then concentrated to 1 mL. Pentane (10 mL) was slowly added to
this concentrate, which induced the formation of yellow crystals.
The crystals were washed with pentane (2 × 5 mL) and dried under
vacuum (yield: 150 mg, 87%). Analytical and spectroscopic data
were similar to those obtained by method 1.
Results and Discussion
[Ti{µ-N,O′-N(SiMe3)Ts-κ3N,O,O′}Cl2(NMe2)]2 (7). Method 1.
Me3SiCl (142 mg, 0.6553 mM) was slowly added to a 3 mL
dichloromethane solution of 1 (50 mg, 0.08191 mM). The solution
turned red and was stirred for 1 day at RT. Volatiles were removed
under vacuum, and the green solid was washed with pentane (3 ×
The synthesis and proposed structures of the tosylimido
complexes of titanium(IV) and vanadium(IV) are sum-
marized in Schemes 1-3. Structures of nine complexes are
set out in Figures 1-8 or are given as Supporting Informa-
tion; selected metric data are collected in Table 1.
1. Synthesis and Characterization of the Bridged Imido
Complexes [M(NTs)(NMe2)2]2 (M ) Ti, V). In previous
studies,40,61 we described the synthesis of diamagnetic
arylimido vanadium complexes [V(NAr)(NMe2)2]2, from the
1
3 mL) and dried under vacuum. Yield: 40 mg (60%). H NMR
3
3
(250 MHz, C6D6): δ 7.88 (d, J ) 8.2 Hz, 4H, C6H4), 6.57 (d, J
) 8.2 Hz, 4H, C6H4), 3.40 (s, 12H, NMe2), 1.74 (s, 6H, MeTs),
(100) Hamura, S.; Oda, T.; Shimizu, Y.; Matsubara, K.; Nagashima, H.
Dalton Trans. 2002, 1521-1527.
3196 Inorganic Chemistry, Vol. 46, No. 8, 2007

Electron-Deficient Imido Complexes
Figure 2. Molecular structure of 2, showing 50% probability ellipsoids
and partial atom-labeling schemes. Hydrogen atoms are omitted for clarity.
Figure 1. Molecular structure of 1, showing 50% probability ellipsoids
and partial atom-labeling schemes. Hydrogen atoms are omitted for clarity.
other metal center in this dimeric complex. The coordination
geometry of titanium is distorted square pyramidal (τ )
0.14);103 the Ti atom is 1.43(4) Å out of the mean plane
through N3O2N1N1′ [mean deviation 0.063(2) Å]. The Ti2N2
core is planar (torsion angle ) 0°) and is characterized by a
short Ti···Ti distance common in imido dimers60,101,104,105 [Ti1·
··Ti1′ ) 3.1297(19) Å] and two Ti-Nimido bond distances of
2.106(4) and 1.974(4) Å. These Ti-Nimido distances are
longer by ca. 0.2 Å than in the terminal tosylimido complex
3 (vide infra) and are, as expected, in the range observed
for sulfonamido complexes of titanium(IV).106-109 The
(Me2N)2Ti moiety is normal101 and displays expected Ti-N
bond distances and angles [Ti-Namido 1.866(4) and 1.889-
(4) Å]. Coordination of the sulfonyl oxygen to titanium
results in a lengthening of the S-O bond distance of about
0.06 Å and in a decrease of the N-S-O bond angle by ca.
8° with respect to N-S-O bond parameters of uncoordinated
sulfonyl oxygen (e.g., in complexes 2 and 5). The Ti-O
distance of 2.125(4) Å is much shorter than the sum of the
van der Waals radii, and the difference in the S1-O1 and
S1-O2 distances confirms that this is a single bond.
Scheme 1. Synthesis of Tosylimido-Bridged Dimer Complexes 1 and
2 and Terminal Tosylimido Complexes 3 and 4
reaction of an aniline ArNH2 with V(NMe2)4 in toluene.
Titanium analog alkylimido dimers have also been prepared
from Ti(NMe2)4.101,102 Inspired by these results, we attempted
the synthesis of related titanium- and vanadium-tosylimido
analog complexes (tosyl ) p-toluenesulfonyl).
As shown in Scheme 1, treatment of Ti(NMe2)4 with 1
equiv of tosylamine TsNH2 in toluene rapidly produced the
imido-bridged compound [Ti(NTs)(NMe2)2]2 (1) as an orange
solid with good yields. A similar reaction starting with
V(NMe2)4 and 1 equiv of TsNH2 in toluene gave the
vanadium congener [V(NTs)(NMe2)2]2 (2) as dark brown
crystals in 59% yields. This formulation for 1 and 2 follows
from NMR spectroscopic studies, IR, and microanalysis and
has been confirmed unequivocally through a crystal structure
determination. Single crystals of both complexes 1 and 2
were obtained (see Experimental Section) and were suitable
for structural characterization by X-ray crystallography.
Thermal ellipsoid plots are presented in Figures 1 and 2.
Metric parameters for 1 and 2 are summarized in Table 1 to
facilitate comparison between them.
The molecular structure of 2 is shown in Figure 2, and
selected bond distances and angles are reported in Table 1.
The complex is a dimer [V(NTs)(NMe2)2]2 with two imido
ligands bridging two (Me2N)2V moieties. The main differ-
(103) τ is the angular parameter commonly used to describe the geometry
around the metal center in pentacoordinate complexes and is defined
as τ ) (R - â)/60 (R and â are the two largest L-M-L bond angles,
with R g â): Addison, A. W.; Rao, T. N.; Reedijk, J.; van Rijn, J.
V. J. Chem. Soc., Dalton Trans. 1984, 1349-1356.
(104) Nugent, W. A.; Haymore, B. L. Coord. Chem. ReV. 1980, 31, 123-
175.
The X-ray structure analysis confirmed that the Ti complex
1 is a centrosymmetric dimer (monoclinic, P21/n), composed
of two (Me2N)2Ti moieties bridged by two tosylimido
ligands. Both Ti atoms are pentacoordinated because one
sulfonyl oxygen of each monomeric unit is bonded to the
(105) Gambarotta, S.; Floriani, C.; Chiesi-Villa, A.; Guastini, C. J. Chem.
Soc., Chem. Commun. 1982, 1015-1017.
(106) Royo, E.; Betancort, J. M.; Davis, T. J.; Carroll, P.; Walsh, P. J.
Organometallics 2000, 19, 4840-4851.
(107) Pritchett, S.; Gantzel, P.; Walsh, P. J. Organometallics 1999, 18,
823-831.
(108) Armistead, L. T.; White, P. S.; Gagne´, M. R. Organometallics 1998,
17, 216-220.
(101) Thorn, D. L.; Nugent, W. A.; Harlow, R. L. J. Am. Chem. Soc. 1981,
103, 357-363.
(102) Nugent, W. A.; Harlow, R. L. Inorg. Chem. 1979, 18, 2030-2032.
(109) Lensink, C.; Gainsford, G. J.; Brandsma, M. J. R. Acta Crystallogr.,
Sect. C 2002, 58, m529-m530.
Inorganic Chemistry, Vol. 46, No. 8, 2007 3197

Lorber et al.
ence observed in the structure of 2 vs 1 is a coordination
geometry around the vanadium centers that is distorted
tetrahedral with no additional coordination of a sulfonyl
oxygen atom. The V2N2 core is planar (torsion angle 0°) with
a short V···V distance of 2.6027(6) Å. Such a short distance
has been found in other dinuclear complexes of vanadium
and may be indicative of a V-V bond.110-116 For comparison
it is longer by ca. 0.1 Å than one of the shortest distances
found in related arylimido dimers [V(NAr)(NMe2)2]2.40,61 The
angle formed by the bridging nitrogen atoms with the two
vanadium atoms [V1-N1-V2 ) 86.69(6)°] deviates sig-
nificantly from that expected for an sp2 nitrogen atom. The
V-Nimido distance of 1.9183(14) Å is slightly longer than
the one found in related arylimido dimers [V(NAr)(NMe2)2]2
(typically in the range 1.84-1.87 Å),40,61 which reflects of
the higher electron-withdrawing nature of the tosyl substitu-
ent. The V-Namido bond distances are in the normal range
[1.8107(15) and 1.8349(15) Å] but are shorter by ca. 0.06
Å than the one reported for 1.
Figure 3. Molecular structure of 3, showing 50% probability ellipsoids
and partial atom-labeling schemes. Hydrogen atoms are omitted for clarity.
Complexes 1 and 2 could later be characterized by 1H and
13C NMR spectroscopy (the sharpness of the peaks of the
well-solved 1H NMR spectrum of 2 indicates that the
dinuclear structure is retained in CD2Cl2 solution), IR,
elemental analysis, and the absence of magnetic moment for
2. The diamagnetism of 2 indicates a strong electronic
coupling between the two metal centers, either through the
nitrogen atoms of the imido bridges or as a result of the
short V-V distance.
2. Reaction of Ti(NMe2)4 and p-TsNH2 in Dichlo-
romethane. Interestingly, using dichloromethane as solvent
in the room-temperature reactions between Ti(NMe2)4 and
TsNH2 gave less clear-cut observations, since a complex
mixture of compounds arose with several unassigned signals
observed in the 1H NMR spectrum. Moreover the composi-
tion of these mixtures was dependent on the reaction time117
and, therefore, will not be discussed further here, except for
complexes 3 and 4 which crystallized directly from the
solution and thereby permitted X-ray structural analysis.
Thermal ellipsoid plots of the structures of 3 and 4 are
presented in Figures 3 and 4, and Table 1 gives a comparison
of their structural parameters.
In the solid state, compound 3 is a dimer formulated as
[Ti{µ-N,O-NTs}Cl(NMe2)(NHMe2)2]2 with two six-coordi-
nated titanium centers linked by two bridging (N,O)-
coordinated terminal tosylimido ligands thus forming an
Figure 4. Molecular structure of the asymmetric unit of 4 (top) and part
of the infinite chain (bottom), showing 50% probability ellipsoids and partial
atom-labeling schemes. Hydrogen atoms are omitted for clarity.
(110) Solan, G. A.; Cozzi, P. G.; Floriani, C.; Chiesi-Villa, A. Organo-
metallics 1994, 2572-2574.
8-membered cycle. The additional ligands on each metal
center are one dimethylamido ligand (Ti-N ) 1.9148(16)
Å), one chloro ligand (Ti-Cl ) 2.4530(6) Å) cis to the
-NMe2 group, and two trans dimethylamino groups (Ti-N
) average 2.25 Å). The presence of a Ti-Cl bond is
explained by chloride abstraction from dichloromethane
solvent. Compound 3 represents the first group 4 metal
complex with a terminal tosylimido group, and therefore the
geometric parameters associated with the tosylimido ligand
deserves some comment. The titanium-nitrogen bond dis-
tance of the imido fragment of 1.8391(16) Å is shorter by
ca. 0.2 Å than the Ti-Nimido bond distance in the bridged-
(111) Ruiz, J.; Vivanco, M.; Floriani, C.; Chiesi-Villa, A.; Rizzoli, C.
Organometallics 1993, 12, 1811-1822.
(112) Preuss, F.; Becker, H.; Wieland, T. Z. Naturforsch., B 1988, 43,
1195-1200.
(113) Minhas, R. K.; Edema, J. J. H.; Gambarotta, S.; Meetsma, A. J. Am.
Chem. Soc. 1993, 115, 6710-6717.
(114) Edema, J. J. H.; Meetsma, A. J.; van Bolhris, F.; Gambarotta, S.
Inorg. Chem. 1991, 30, 2056-2061.
(115) Dorfman, J. R.; Holm, R. H. Inorg. Chem. 1983, 22, 3179-3181.
(116) Buijink, J.-K. F.; Meetsma, A.; Teuben, J. H.; Kooijman, H.; Spek,
A. L. J. Organomet. Chem. 1995, 497, 161-170.
(117) Composition vs time of a dichloromethane solution containing
equimolar amounts of Ti(NMe2)4 and TsNH2: After 5 h the major
compound is 1. After 1 day we noted the presence of several species
(or isomers) including 3. After 3 days the major compound is 4.
3198 Inorganic Chemistry, Vol. 46, No. 8, 2007

Electron-Deficient Imido Complexes
Scheme 2. Synthesis of Terminal Tosylimido Complex 5 and
Dinuclear Tosylimido-Bridged Complex 6
tosylimido complex 1. However, such a value (1.8391(16)
Å) for a terminal Ti-N imido bond is slightly above the
upper limit118 found in structurally established terminal alkyl-
and (arylimido)titanium(IV) complexes.119 A comparison
with the normal VdNTs bond in compound 5 (vide infra)
would suggest that the long TidNTs in 3 is indeed because
of the (N,O)-bridging nature of the tosylimido linkage. The
imido fragment is further characterized by a Ti-N-S angle
of 149.46(11)° that deviates significantly from linearity. The
reason for that is unclear, and we cannot compare with other
complexes as 3 is the only example of group 4 metal complex
with a terminal MdNTs function. A possible explanation
would be the delocalization of the nitrogen lone pair on the
sulfonyl fragment but could also be due to strong intramo-
lecular hydrogen bonding between the sulfonyl oxygen and
the hydrogen atom of one dimethylamine ligand (O1···H4 )
2.069 Å, O1-H4-N4 ) 159.2°).
Complex 4 was obtained as the only characterizable
product when the previous reaction was left for a longer
period of time (3 days). As revealed by an X-ray structure
determination illustrated in Figure 4, 4 is a coordination
polymer composed of infinite O-Ti-N-S- chains with
repetitive [Ti(dNTs)Cl2(NHMe2)2]n units. The compound
crystallized in the monoclinic space group C2/c, with an
asymmetric unit containing 2.5 of the [Ti(dNTs)Cl2-
(NHMe2)2] structural motifs. The sulfur atom S3 lies in a
general position and is therefore necessarily disordered about
the C2 axis, with 50% occupancy at each position. The
O-Ti-N-S- sequence as a whole is described by this
crystallographically imposed disorder. As a consequence of
the high degree of uncertainty, the metric parameters in 4
have limited value for comparison (Table 1). Each [Ti(d
NTs)Cl2(NHMe2)2] unit contains an octahedral Ti center
surrounded by two chlorine atoms with trans configuration,
two trans-oriented NHMe2 ligands, and one nitrogen atom
of the imido group that is in a position trans to the sulfonyl
oxygen atom. Each of the two titanium centers is connected
to neighboring titanium centers through (N,O)-tosylimido
bridges and forms an infinite polymeric network as shown
in Figure 4 (bottom). The nonbonding Ti···Ti separation
amounts to 5.45 Å. Unfortunately, but not surprisingly for
an inorganic polymer, 4 is insoluble in most common
noncoordinating solvents, except in dichloromethane, a
solvent in which it seems to be slightly soluble. Nevertheless,
1H NMR studies of a suspension of 4 in CD2Cl2 suggests its
rapid evolution into complex 6 (i.e., resulting from the loss
of a NHMe2 ligand; vide infra) accompanied by signals
attributed to decomposition products.
on the basis of a very convenient single step and one-pot
reaction of M(NMe2)4 with RNH2 in the presence of an
excess of trimethylchlorosilane. In this reaction Me3SiCl acts
as a chlorinating agent.120 In an attempt to prepare the elusive
tosylimido congeners M(dNTs)Cl2(NHMe2)2, we initially
reacted M(NMe2)4 with p-TsNH2 in the presence of an excess
of Me3SiCl.
A toluene solution of V(NMe2)4, when reacted at RT with
1 equiv of p-TsNH2 in the presence of an excess of Me3-
SiCl (8 equiv), afforded a yellow solution from which orange
needles (suitable for X-ray study; vide infra) of complex 5
separated upon addition of pentane and slow cooling
(Scheme 2).
The well-resolved electron paramagnetic resonance (EPR)
spectrum of 5 at room temperature in dichloromethane
solution revealed a resonance at g ) 1.985 with the
characteristic octet pattern (Aiso(51V) ) 87.0 G) expected for
the interaction of an unpaired electron of VIV with the 51V
nucleus (I ) 7/2). In agreement, the magnetic moment is
consistent with a d1 electronic configuration (µeff ) 1.71 µB).
The solid-state structure determination revealed the struc-
ture of the desired vanadium complex V(dNTs)Cl2(NHMe2)2.
Two independent molecules are present in the asymmetric
unit cell. Figure 5 shows the structure of one of these
molecules (molecule A), and selected bond distances and
angles are given in Table 1 (only for molecule A; metric
parameters for the second molecule are almost the same)
for a comparison of their structural parameters. In the solid
state, the molecular structure of 5 lies between square
pyramidal and trigonal bipyramidal (τ ) 0.46 and 0.38
respectively for molecules A and B) with no coordination
of the sulfinyl oxygen atoms to the metal center. The
distances and angles associated with the vanadium center
and the ligands are broadly comparable to those found in
other M(dNR)Cl2(NHMe2)2 complexes [M ) Ti,60,63 V].16,61
5 exhibits a short V-Nimido bond distance of 1.672(3) Å.
Although shorter by ca. 0.25 Å than in the bridged tosylimido
V complex 2 described in this study, this value is in the range
of those found in related terminal arylimides V(dNAr)Cl2-
(NHMe2)2 (1.65-1.70 Å).16,61 One would have expected a
longer V-N bond distance (as in titanium compound 3) due
to the highly electron-withdrawing nature of the tosyl
substituent, but examination of the M-Nimido bond distance
3. One-Pot Reaction of M(NMe2)4/p-TsNH2/Me3SiCl [M
) Ti, V]. Previously, we have reported the direct synthesis
of terminal imido complexes of titanium and vanadium of
general formula M(dNR)Cl2(NHMe2)2 [M ) Ti,60 V]16,22,61
(118) Ti-N bond distances in structurally characterized terminal imido
complexes usually range 1.66-1.76 Å (Cambridge Crystallographic
Database).
(119) For representative examples of TidN bond distances, see refs 17,
57, 60, 63, and the following: Roesky, H. W.; Voelker, H.; Witt,
M.; Noltemeyer, M. Angew. Chem., Int. Ed. Engl. 1990, 29, 669-
670.
(120) For some typical examples of use of Me3SiCl as chlorinated agent
by cleavage of Ti-N(amido) bond in group 4 complexes, see the
following: (a) Arney, D. J.; Bruck, M. A.; Huber, S. R.; Wigley, D.
E. Inorg. Chem. 1992, 31, 3749-3755. (b) Diamond, G. M.; Jordan,
R. F.; Petersen, J. L. Organometallics 1996, 15, 4030-4037. (c)
Baumann, R.; Davis, W. M.; Schrock, R. R. J. Am. Chem. Soc. 1997,
119, 3830-3831.
Inorganic Chemistry, Vol. 46, No. 8, 2007 3199

Lorber et al.
O-H-N of 138-154°). Figure 5 (bottom) illustrates the
extended packing in 5 with each molecule donating two
N-H···O hydrogen bonds and accepting two hydrogen bonds
and thus consisting of infinite bilayers (with the second
infinite chains based on molecule B) running parallel to the
crystallographic axis a.
Although it is a generally clean transformation in related
arylimido complexes V(NAr)Cl2(NHMe2)2, attempted dis-
placement of NHMe2 ligands in 5 by pyridines in dichlo-
romethane failed, with formation of the known, reduced,
122
vanadium(III) complexes VCl3Py3 and V2OCl4Py6.123 It
is conceivable that these vanadium(III) complexes are formed
along with other uncharacterizedsorganic and/or inorganics
products via ligands redistribution or redox reactions that
are common features in vanadium chemistry.124 Nevertheless,
we were unable to isolate other species out of the reaction,
but this unexpected reactivity is currently under further
examination in our group. Both vanadium(III) compounds
were characterized by X-ray diffraction analyses that are
given as Supporting Information, as they crystallized in space
groups different from those previously reported.125
If we turn now to titanium, the one-pot reaction of Ti-
(NMe2)4 with 1 equiv of p-TsNH2 in the presence of an
excess of Me3SiCl (8 equiv) appeared more complicated, as
it gave mixtures of products or isomers (as we will see
below).126,127 However, we have been able to crystallize
selectively one of these compounds (compound 6) and to
determine its molecular structure by an X-ray crystallographic
analysis.128 The molecular structure of 6 is shown in Figure
6, and selected bond distances and angles are reported in
Table 1. This study revealed the structure of an unexpected
dinuclear titanium complex formulated as [(Me2HN)Cl2Ti-
(µ2-N-NTs-κ2N,O)2TiCl2(NHMe2)2], composed of two tita-
nium centers (one six- and one seven-coordinate metal atom)
Figure 5. Molecular structure of one of the two independent molecules
of 5 (molecule A, top), showing 50% probability ellipsoids and partial atom-
labeling schemes, and hydrogen bond networks (bottom). Hydrogen atoms
are omitted for clarity.
in molybdenum complexes Mo(NR)2(Et2dtc)2 reveals little
or no difference between R ) Ts and Ar. The imido linkage
is almost linear [V-Nimido-S angle ) 167.7(2) and 172.8-
(2)° respectively for molecules A and B], which, together
with the short V-Nimido bond, is consistent with the lone
pair on nitrogen being donated to an acceptor orbital on
vanadium. As a consequence, the imido V-N bond in 5 can
be considered as a triple bond with the imido acting as a
six-electron donor ligand. The two trans dimethylamino
(122) Fowles, G. W.; Greene, P. T. J. Chem. Soc. A 1967, 1869-1874.
(123) Zhang, Y.; Holm, R. H. Inorg. Chem. 1990, 29, 911-917.
(124) Lorber, C. Vanadium Organometallics. In ComprehensiVe Organo-
metallic Chemistry III; Crabtree, R. H., Mingos, D. M. P., Eds.;
Elsevier: Oxford, U.K., 2006; Vol. 5, pp 1-60.
(125) (a) We crystallized VCl3Py3 both in P21/n (as reported by the
following: Sorensen, K. L.; Ziller, J. W.; Doherty, N. M. Acta
Crystallogr. 1994, C50, 407-409) and in P21/c (a ) 13.2975(10), b
) 8.5345(8), and c ) 15.5771(14) ?, and â ) 98.878(10)°; see
Supporting Information). (b) V2OCl4Py6 crystallized in P1h with cell
parameters a ) 15.306(3), b ) 15.806(3), and c ) 16.916(3) ? and
R ) 98.44(3), â ) 96.79(3), and γ ) 98.97(3)° (see Supporting
Information). This compound was already reported to crystallize in
two different space groups (C2/c and P21/c): Zhang, Y.; Holm, R.
H. Inorg. Chem. 1990, 29, 911-917. Rambo, J. R. Castro, S. L.;
Folting, K.; Bartley, S. L.; Heintz, R. A.; Christou, G. Inorg. Chem.
1996, 35, 6844-6852.
(126) The composition of these mixtures (the amount of unknown byprod-
ucts) is also dependent on the experimental conditions and, in
particular, on the time between the addition of TsNH2 to Ti(NMe2)4
and the addition of Me3SiCl. The optimum conditions for maximum
yield in 6 were not optimized.
(127) At this point, we do not know the exact nature of the byproducts,
but we suggest that they result from electrophylic attack of the
trimethylchlorosilane on either Ti-Namido or Ti-Nimido of Ti(NMe2)4
or preformed 1 or 6.
ligands have mean V-N
bond distances of ca. 2.14 Å.
NHMe2
Most interestingly, some authors have used the metal-
chlorine bond lengths as a probe for comparison of molyb-
denum Lewis acidity in a series of structurally characterized
bis(imido) complexes.82 In 5, the two vanadium-chlorine
bond distances of 2.2603(12) and 2.2855(12) Å are shorter
than those measured in related arylimides V(dNAr)Cl2-
(NHMe2)2 (2.32-2.33 Å),16,61 which reflects the higher
electron-withdrawing nature of the tosyl substituent. More-
over, this value is even shorter than the V-Cl bond distances
found in the oxo analog complex V(dO)Cl2(NHMe2)2 (V-
Cl ) 2.3085(11) Å).121
The supramolecular structure is dominated by strong
hydrogen bonding between the sulfonyl oxygen atoms and
the hydrogen atoms of a dimethylamine ligand of a neigh-
boring molecule in the asymmetric unit (with O···H bond
distances in the range 2.12-2.24 Å and associated angles
(128) Complex 5 has also been obtained as yellow plates that crystallized
in the triclinic space group P1h (a ) 12.866(3), b ) 15.240(3), c )
17.991(4) ?; â ) 102.37(3)°). Bond distances and angles in the two
diamorphs are very similar, but two independent molecules are
present in the cell of the triclinic diamorph and the overall structure
differs by the respective position of the N-H bonds of the trans
NHMe2 ligands in one of these molecules (syn vs anti).
(121) Lorber, C. Unpublished result. The synthesis and crystal structure
of V(dO)Cl2(NHMe2)2 will be described elsewhere.
3200 Inorganic Chemistry, Vol. 46, No. 8, 2007

Electron-Deficient Imido Complexes
Figure 7. Possible Structures for isomers A and B (6a,b).
Scheme 3. Silylation Reaction of 1 Leading to Amido Complex 7
we suggest these two isomers to be the species 6a,b presented
in Figure 7, which differ from each other by the respective
position of the sulfonyl oxygen atom and tolyl substituent
of the two bridging tosylimide ligands. The major isomer
(6a) would have the two SdO bonds (or the two tolyl
substituents) in anti position, as suggested by the NOESY
studies, an arrangement that corresponds to the solid-state
structure determination of the material that crystallized from
the solution (Figure 6). Under strictly anhydrous conditions,
6 is stable in benzene solution for hours and in the solid
state for several months. However, its high reactivity is
reflected by the pronounced sensitivity toward hydrolysis.
In summary, the one-pot procedure that consisted of
reacting Ti(NMe2)4/TsNH2/Me3SiCl gave unsatisfactory re-
sults: 6 was formed in low yields after necessary recrystal-
lization steps to separate it from byproducts that, most
certainly, arose from side reactions involving Me3SiCl (vide
infra).127 To avoid the problem of possible competing
reactions with chlorosilane, we attempted to generate 6 from
alternative methods. First, we reacted the imido precursor
Ti(dNBut)Cl2(NHMe2)2 with TsNH2 but we did not observe
the transamination reaction. Then we used TiCl2(NMe2)2 as
starting material; TiCl2(NMe2)2 is known to generate Ti(d
NR)Cl2(NHMe2)2 complexes in presence of RNH2.63 The
reaction of TiCl2(NMe2)2 with 1 equiv of TsNH2 proceeded
smoothly in toluene and afforded yellow crystals as in the
previous reaction with Ti(NMe2)4/Me3SiCl. Spectroscopic
studies (IR, NMR), elemental analysis, and X-ray studies
(cell parameters determination) confirmed these yellow
Figure 6. Molecular structure of 6, showing 50% probability ellipsoids
and partial atom-labeling schemes. Hydrogen atoms are omitted for clarity.
separated by 3.16 Å and linked by two µ-N-tosylimido
groups. The striking difference in 6, as compared to the
expected Ti(dNTs)Cl2(NHMe2)2 complex which is analo-
gous to the vanadium compound 5, is the loss of one
dimethylamine ligandsas a result of the coordination of a
sulfinyl oxygen atom of each bridging tosylimido moiety to
the same metal center (Ti1). Loss of NHMe2 ligands has
already been observed in dimethylamine adducts Ti(dNR)-
Cl2(NHMe2)2.60 The six-coordinate titanium center (Ti2) has
an approximately octahedral geometry, with two trans
dimethylamine ligands, two cis chloride ligands, and two
cis bridging tosylimido groups, whereas the seven-coordinate
titanium (Ti1) possesses two trans chloride ligands, one
dimethylamine group in the plane of the two coordinated
oxygen atoms of the sulfynyl groups, and the two nitrogen
atoms of the bridging imido ligands. The Ti-Nimido bond
distances of 2.0707(19) and 1.931(2) Å are comparable with
those found in the bridging tosylimido complex 1. All other
bond distances are in the expected range. The Ti-Cl [Ti1-
Cl1 2.3417(5) Å, Ti2-Cl2 2.33197(8) Å] and Ti-Nimido
[Ti1-N1 2.0707(19) Å, Ti2-N1 1.931(2) Å] distances for
Ti1 are longer than those for Ti2, consistent with the
higher coordination number of Ti1. Coordination of the
sulfonyl oxygen atom to the titanium center (Ti1-O1 bond
distance of 2.1509(18) Å) results in a lengthening of the
S-O bond distance of about 0.05 Å and in a decrease
of the N-S-O bond angle by ca. 11° with respect to
N-S-O bond parameters of uncoordinated sulfonyl oxygen
(e.g., in complexes 2 and 5), as already noted in titanium
complex 3.
1
crystals to be complex 6. As judged by H NMR spectro-
scopic studies, the reaction that uses TiCl2(NMe2)2 appeared
very clean (no byproduct) and in C6D6 solution the same
ratio of isomers 6a:6b was observed (2:1). Therefore, this
synthetic route is preferable as it gives higher yields of
pure 6.
4. Reaction of Tosylimido Bonds with Me3SiCl. To
verify the foregoing suggested hypothesis concerning the
reactivity of the titanium-tosylimide bond vs Si-Cl, we
reacted selected Ti and V complexes reported above with
an excess of Me3SiCl.
The NMR tube reaction of vanadium compound 2 with
an excess of trimethylchlorosilane in CD2Cl2 at room
temperature suggested a complete transformation with pre-
cipitation of a black solid. The low solubility and probable
paramagnetism of this material precluded further studies.
It is noteworthy that the 1H NMR (C6D6 solution, 287 K)
spectrum of a single crystal of 6 appears more complex than
expected. The spectrum exhibits two sets of signals in a ratio
2:1 for each of the three types of protons (o-H, m-H, and
Me) of the tosyl ligand and magnetically inequivalent methyl
groups in the NHMe2 ligands. This is likely due to the
presence of two isomers in solution at RT (in a ratio 2:1)
and to hindered rotation of some NHMe2 groups. In
accordance with the NOESY and VTP NMR experiments,
Inorganic Chemistry, Vol. 46, No. 8, 2007 3201

Lorber et al.
Figure 9. Mechanistic considerations for the silylation of the tosylimide
function and oxo group.
Finally, the reaction of 6 with an excess of trimethylchlo-
rosilane in CD2Cl2 at room temperature gave inconclusive
results. A very slow evolution and formation of small
amounts of an insoluble green material was noted, which
could not be further characterized owing to its poor solubility.
Figure 8. Molecular structure of one of the two independent molecules
of 7, with partial atom-labeling schemes. Atoms are drawn as spheres of
arbitrary radius, and hydrogen atoms are omitted for clarity.
Conclusions
We have demonstrated that use of the amine elimination
method in the reaction of TsNH2 and M(NMe2)4 (M ) Ti,
V) or TiCl2(NMe2)2 precursors has allowed the generation
of the first p-toluenesulfonylimide complexes of titanium-
(IV) and vanadium(IV). These imido complexes are unusual
in that they bear strongly electron-withdrawing groups at the
nitrogen atom. The structural data reveal the electron-
deficient character of the tosylimido group but also display
high structural diversity for the complexes bearing the
tosylimide function. Currently, we are continuing to inves-
tigate in more detail the reactivity and catalytic properties
of these and related early transition metal electron-poor
complexes.
A yellow-orange solution of 1 treated with excess trim-
ethylchlorosilane turned deep red, in dichloromethane for
12 h or in toluene at 80 °C for 1 h,129 and afforded after
suitable workup green crystals of 7 (Scheme 3).130 Multi-
nuclear NMR experiments (1H, 13C, 29Si) showed the
presence of signals typical of -SiMe3 and -NMe2, as well
as Ts groups, and indicated a ligand SiMe3/NMe2/Ts ratio
of 1:1:1. A X-ray structure determination analysis (see
Supporting Information) on a single crystal of 7 identified
this compound as the dimer {TiCl2(NMe2)[µ2-N,O′-N(Ts)-
(SiMe3)-κ3N,O,O′]}2, illustrated in Figure 8. The poor quality
of the crystals of 7 prevents discussion of its structural details
but confirms the silylation of the tosylimide group with
formation of an -N(Ts)(SiMe3) amide ligand. The structure
is composed of two six-coordinate titanium centers that are
bridged by two -N(Ts)(SiMe3) amide ligands, thus forming
an 8-member cyclic system. The -N(Ts)(SiMe3) ligand is
coordinated to one Ti atom via the nitrogen atom and one
sulfonyl oxygen atom and to the other Ti center via the
second sulfonyl oxygen atom. The coordination sphere
around the metal center is completed by two chlorine atoms
(in a cis configuration) and one dimethylamide group in a
position trans to the oxygen atom of the symmetry related
tosylamide ligand.
Acknowledgment. We are grateful to the CNRS for
financial support.
Supporting Information Available: CIF files and tables of
atomic coordinates, bond distances, and angles for the X-ray crystal
structures of complexes 1-7, VCl3Py3, and V2OCl4Py6, H NMR
spectra of 6 (mixture of isomers A and B, from a diluted solution
at 293 K and from a concentrated solution at 283s293 and 333
K), 2D NOESY experimental data for 6, and an 1H NMR spectrum
of the mixture of products obtained from the reaction of Ti(NMe2)4
with TsNH2 in CH2Cl2. This material is available free of charge
via the Internet at http://pubs.acs.org.
1
IC062404J
Therefore, we propose the mechanism depicted in Figure
9 for the reactivity of the Ti-Ntosylimido bond of 1 with a
Si-Cl bond of Me3SiCl. This mechanism is highly remi-
niscent to the reactivity of chlorosilanes with MdO groups
observed in some oxometal complexes.131
(131) For selected examples of reaction of MdO bonds (in V, Cr, Mo, W,
and Re complexes) with R3SiCl, see the following: (a) Nugent, W.
A.; Mayer, J. M. Metal-Ligand Multiple Bonds; Wiley-lnterscience:
New York, 1988. (b) Lorber, C.; Donahue, J. P.; Goddard, C. A.;
Nordlander, E.; Holm, R. H. J. Am. Chem. Soc. 1998, 120, 8102-
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(129) Heating a toluene solution of 1 to higher temperatures (110 °C) led
to the formation of intractable products.
(130) Note that 7 could also be obtained in a two-step reaction from Ti-
(NMe2)4 and TsNH2, without isolation of 1 but by removing under
vacuum HNMe2 and subsequent reaction with Me3SiCl.
3202 Inorganic Chemistry, Vol. 46, No. 8, 2007