Alkylation, cation formation, and insertion reactions in titanium tris(ketimide) complexes

Article abstract of DOI:10.1021/om060554w

Ti(N=C^tBu₂)₃Cl (1) reacts with TlPF ₆ in acetonitrile to afford [Ti(N=C^tBu₂) ₃(N≡CCH₃)]PF₆ (2), which proved to be unstable and decomposed at room temperature either in solution or in the solid state. Attempts to recrystallize 2 from a CH₂Cl₂/hexane mixture led to [Ti₃(N=C^tBu₂) ₆(μ₂-F)₃(μ₃-F) ₂][PF₆ (3). Treatment of 1 with LiMe and PhCH ₂MgCl gave the compounds Ti(N=C^tBu₂) ₃CH₂Ph (4) and Ti(N=C^tBu₂) ₃Me (5), respectively. 4 was treated with B(C₆F ₅)₃ to afford [Ti(N=C^tBu₂) ₃(CH₂Ph)B(C₆F₅)₃] (6), which exists in solution as a mixture of two species, the zwitterion [Ti(N=C^tBu₂)₃][(μ-CH₂Ph)B(C ₆F₅)₃] (6A) and the solvate cation [Ti(N=C ^tBu₂)₃(Solv)][(CH₂Ph)B(C ₆F₅)₃] (6B). Above 60 °C, C ₆F₅ is transferred to the metal center and Ti(N=C ^tBu₂)₃(C₆F₅) (9) forms. This compound participates in a dynamic process in solution involving Ti...F interactions. The fluxional process observed for 6 can be stopped upon addition of 1 equiv of C≡NMes, giving [Ti(N=C^tBu ₂)₃(C=NMes)][(CH₂Ph)B(C₆F ₅)₃] (7). C≡NMes does not insert into Ti-N bonds, but it readily inserts into the Ti-C bond of Ti(N=C^tBu ₂)₃(Me) (5) to afford [Ti(N=C^tBu ₂)₃{η²-C(CH₃)=NMes}] (8).

Full text of DOI:10.1021/om060554w

Organometallics 2007, 26, 119-127
119
Alkylation, Cation Formation, and Insertion Reactions in Titanium
Tris(ketimide) Complexes
M. Joa˜o Ferreira,† Ineˆs Matos,† Jose´ R. Ascenso,† M. Teresa Duarte,† M. Merceˆs Marques,†
Claire Wilson,‡ and Ana M. Martins*,†
Centro de Qu´ımica Estrutural, Instituto Superior Te´cnico, AV. RoVisco Pais, 1, 1049-001 Lisboa, Portugal,
and School of Chemistry, UniVersity of Nottingham, Nottingham NG7 2RD, U.K.
ReceiVed June 26, 2006
Ti(NdCtBu2)3Cl (1) reacts with TlPF6 in acetonitrile to afford [Ti(NdCtBu2)3(NtCCH3)]PF6 (2), which
proved to be unstable and decomposed at room temperature either in solution or in the solid state. Attempts
to recrystallize 2 from a CH2Cl2/hexane mixture led to [Ti3(NdCtBu2)6(µ2-F)3(µ3-F)2][PF6] (3). Treatment
of 1 with LiMe and PhCH2MgCl gave the compounds Ti(NdCtBu2)3CH2Ph (4) and Ti(NdCtBu2)3Me
(5), respectively. 4 was treated with B(C6F5)3 to afford [Ti(NdCtBu2)3(CH2Ph)B(C6F5)3] (6), which exists
in solution as a mixture of two species, the zwitterion [Ti(NdCtBu2)3][(µ-CH2Ph)B(C6F5)3] (6A) and the
solvate cation [Ti(NdCtBu2)3(Solv)][(CH2Ph)B(C6F5)3] (6B). Above 60 °C, C6F5 is transferred to the
metal center and Ti(NdCtBu2)3(C6F5) (9) forms. This compound participates in a dynamic process in
solution involving Ti‚‚‚F interactions. The fluxional process observed for 6 can be stopped upon addition
of 1 equiv of CtNMes, giving [Ti(NdCtBu2)3(CtNMes)][(CH2Ph)B(C6F5)3] (7). CtNMes does not
insert into Ti-N bonds, but it readily inserts into the Ti-C bond of Ti(NdCtBu2)3(Me) (5) to afford
[Ti(NdCtBu2)3{η2-C(CH3)dNMes}] (8).
We have recently shown that the titanium tris(ketimide)
complex Ti(NdCtBu2)3Cl (1) is a good ethylene polymerization
catalyst when activated by MAO.10 In this work we present
further results involving titanium tris(ketimide) complexes,
namely alkylation, cation generation, and stability, as well as
insertion reactions, which are relevant to the behavior of tris-
(ketimide) compounds as olefin polymerization catalysts.
Introduction
Preliminary work on early-transition-metal ketimide com-
plexes emerged from nitrile reactivity studies, namely insertions
into metal-carbon or metal-hydride bonds. The resulting
ketimide ligands proved to be relatively inert toward nucleophilic
and electrophilic reagents, being nevertheless susceptible to
hydrolysis, leading to ketimines or ketones.1 This robustness
remained unexplored until recently, when ketimide ligands were
investigated as supports of early-transition-metal complex
reactivity. Compounds of the type Cp′Ti(NdCtBu2)Cl2 (Cp′ )
Results and Discussion
Cp, Cp*, Ind, C5H4 Bu), patented by Nova Chemicals,2 have
t
Scheme 1 presents all the new compounds discussed in this
work.
proven to be extremely active catalysts in ethylene,3-6 propyl-
ene,3 and 1-hexene4,5 homopolymerizations and show good
activities in syndiospecific styrene homopolymerization.5 These
complexes are also capable of copolymerizing ethylene with
polar (10-undecen-1-ol3) and apolar monomers (1-hexene4 and
styrene6). Particularly noteworthy is the ethylene-styrene
copolymerization that was obtained in a living manner by
Nomura et al.6,7 The cationic complexes [Cp′Ti(NdCR1R2)-
Me]+, which are accepted as the active species in olefin
Ti(NdCtBu2)3Cl10 (1) reacts in acetonitrile with TlPF6 to
afford [Ti(NdCtBu2)3(NtCCH3)]PF6 (2) as a bright yellow
-
solid. Salt formation was confirmed by the presence of the PF6
ion, as attested by the doublet at -67.4 ppm in the 19F NMR
spectrum and the septet at -138.7 ppm in the 31P NMR
spectrum, both with 1JPF ) 708.6 Hz, and the singlet at δ 1.98
ppm due to the coordinated CH3CN proton resonance. This
complex is not stable, however, decomposing at room temper-
ature, as indicated by a dramatic color change from yellow to
green. The decomposition process involves fluoride transfer to
titanium, as suggested by the formation of [Ti3(NdCtBu2)6(µ2-
F)3(µ3-F)2][PF6] (3) while attempting to recrystallize 2 from a
CH2Cl2/hexane solution, at -20 °C. The formation of 3 from
complex 2 attests to the lability of the acetonitrile ligand and is
suggestive of ion-pair contact between the very acidic titanium
8,9
polymerization catalysis, have been studied by Piers et al.
* To whom correspondence should be addressed. Tel: +351-218419172.
Fax: +351-218464457. E-mail: ana.martins@ist.utl.pt.
† Instituto Superior Te´cnico.
‡ University of Nottingham.
(1) Ferreira, M. J.; Martins, A. M. Coord. Chem. ReV. 2006, 250, 118-
132.
(2) McMeeking, J.; Gao, X.; Spence, R. E. V. H.; Brown, S. J.; Jeremic,
D. Patent WO 99/14250, 1999.
-
-
cation and the PF6 ion. Fluoride abstraction from PF6 has
(3) Dias, A. R.; Duarte, M. T.; Fernandes, A. C.; Fernandes, S.; Marques,
M. M.; Martins, A. M.; da Silva, J. F.; Rodrigues, S. S. J. Organomet.
Chem. 2004, 689, 203-213.
(8) Zhang, S.; Piers, W. E.; Gao, X.; Parvez, M. J. Am. Chem. Soc. 2000,
122, 5499-5509.
(9) Zhang, S.; Piers, W. E. Organometallics 2001, 20, 2088-2092.
(10) Martins, A. M.; Marques, M. M.; Ascenso, J. R.; Dias, A. R.; Duarte,
M. T.; Fernandes, A. C.; Fernandes, S.; Ferreira, M. J.; Matos, I.; Oliveira,
M. C.; Rodrigues, S. S.; Wilson, C. J. Organomet. Chem. 2005, 690, 874-
884.
(4) Nomura, K.; Fujita, K.; Fujiki, M. J. Mol. Catal. A: Chem. 2004,
220, 133-144.
(5) Nomura, K.; Fujita, K.; Fujiki, M. Catal. Commun. 2004, 5, 413-
417.
(6) Zhang, H.; Nomura, K. J. Am. Chem. Soc. 2005, 127, 9364-9365.
(7) Zhang, H.; Nomura, K. Macromolecules 2006, 39, 5266-5274.
10.1021/om060554w CCC: $37.00 © 2007 American Chemical Society
Publication on Web 12/05/2006

120 Organometallics, Vol. 26, No. 1, 2007
Ferreira et al.
a
Scheme 1
a Legend: (i) TlPF6, CH3CN; (ii) CH2Cl2/hexane, -20 °C; (iii) CH2PhMgCl; (iv) LiMe; (v) B(C6F5)3; (vi) CtNMes; (vii) CtNMes; (viii)
heating above 60 °C; (ix) C6F5MgCl.
very rarely been reported11 and reflects the extremely acidic
nature and accessibility of the cationic metal center. The removal
of one ketimide ligand from the metal coordination sphere is
most probably promoted by the solvent that should act as a
proton source. The proton and carbon NMR spectra of 3 show
only one set of signals for the ketimide ligands. The 19F NMR
The formulation of 3 was confirmed by single-crystal X-ray
analysis. The molecular structure of 3 is depicted in Figure 1,
and selected bond lengths and angles are given in Table 1.
Compound 3 crystallizes in the monoclinic system, space
group P21/c with a ) 12.479(5) Å, b ) 13.679(5) Å, c )
39.391(5) Å, and â ) 92.646(5)°. In the [{(tBu2CdN)2Ti(µ2-
F)}3(µ3-F)2]+ core the three titanium atoms define an equilateral
triangle with inner angles between 59.82(8) and 60.20(8)° and
Ti-Ti distances between 3.095(3) and 3.107(4) Å. This ar-
rangement is maintained by the five bridging fluoride ligands.
The µ2-fluoride ligands F1, F2, and F3 are coplanar with the
titanium atoms and bridge two adjacent metal centers, whereas
F4 and F5 are positioned above and below the plane defined
by the titanium centers (at 1.1937(62) and 1.2000(61) Å from
the plane, respectively), with a µ3-bridging arrangement between
the metals (Figure 1b). The occurrence of Ti-Ti interactions
in 3 may be excluded, since the Ti-Ti distances exceed the
double of the titanium covalent radius (1.32 Å) by a considerable
amount. The Ti-F distances observed in 3 are consistent with
values reported in the literature for similar bridging fluorides.16,17
spectrum displays one doublet for the PF6 ion (1JPF ) 705.8
-
Hz) at -71.0 ppm, one triplet at -63.1 ppm (2JFF ) 91.1 Hz)
assigned to µ2-F, and one quartet at -91.2 ppm (2JFF ) 91.1
Hz) corresponding to the µ3-F ligands. According to the
literature, the resonances due to µ2-bridging fluorides appear at
lower field than those of µ3-F ligands, as observed in 3. In
comparison to literature reported values (µ2-19F, δ -3.4 to
-52.8;12-16 µ3-19F, δ -10.4 to -130.213,15,17,18), the µ2-19F
resonances in 3 are shifted to high field. This shift is notable
when it is compared to the value observed for [Ti(µ-NMe2)-
(NMe2)(µ-F)F]6 (δ -3.4 ppm). We tentatively suggest that
the difference reflects the polar nature of the Ti‚‚‚F‚‚‚Ti
bond between the hard Lewis acidic metal center and the hard
fluoride donor in the cationic [{(tBu2CdN)2Ti(µ2-F)}3(µ3-F)2]+
core.
The geometry around each Ti(IV) atom can be considered
distorted octahedral. For Ti1 the axial positions are defined by
F4 and N2 (N2-Ti1-F4 is the larger angle (172.3(4)°)), while
the equatorial positions are occupied by F1, F3, F5, and N1.
For Ti2, the axial positions are occupied by N4 and F4 (the
N4-Ti2-F4 angle is 165.8(4)°) whereas F1, F2, F5, and N3
define the equatorial positions. The axial positions of Ti3 are
occupied by F5 and N5 (the N5-Ti3-F5 angle is 165.2(4)°),
while F2, F3, F4, and N6 define the equatorial positions. The
ketimide ligands in 3 are positioned above and below the plane
defined by the three titanium atoms to minimize steric repulsion
(see Figure 1b) and are as usual close to linearity (the Ti-
N-C angles lie between 169.4(10) and 177.6(11)°). All other
(11) Jordan, R. F.; Dasher, W. E.; Echols, S. F. J. Am. Chem. Soc. 1986,
108, 1718-1719.
(12) Shah, S. A. A.; Dorn, H.; Gindl, J.; Noltemeyer, M.; Schmidt, H.-
G.; Roesky, H. W. J. Organomet. Chem. 1998, 550, 1-6.
(13) Demsar, A.; Pevec, A.; Golic, L.; Petricek, S.; Petric, A.; Roesky,
H. W. Chem. Commun. 1998, 1029-1030.
(14) Santamar´ıa, C.; Beckhaus, R.; Haase, D.; Saak, W.; Koch, R. Chem.
Eur. J. 2001, 7, 622-626.
(15) Pevec, A.; Demsar, A.; Gramlich, V.; Petricek, S.; Roesky, H. W.
J. Chem. Soc., Dalton Trans. 1997, 2215-2216.
(16) Perdih, F.; Pevec, A.; Demsar, A. J. Fluorine Chem. 2005, 126,
1065-1071.
(17) Schormann, M.; Varkey, S. P.; Roesky, H. W.; Noltemeyer, M. J.
Organomet. Chem. 2001, 621, 310-316.
(18) Perdih, F.; Demsar, A.; Pevec, A.; Petricek, S.; Leban, I.; Giester,
G.; Sieler, J.; Roesky, H. W. Polyhedron 2001, 20, 1967-1971.

Titanium Tris(ketimide) Complexes
Organometallics, Vol. 26, No. 1, 2007 121
Table 1. Selected Bond Angles (deg) and Distances (Å) for 3
Ti1-Ti2
Ti1-Ti3
Ti2-Ti3
Ti1-F1
Ti1-F3
Ti1-F4
Ti1-F5
Ti1-N1
Ti1-N2
Ti2-F1
Ti2-F2
Ti2-F4
Ti2-F5
Ti2-N3
3.107(4)
3.100(4)
3.095(3)
2.017(7)
2.031(7)
2.143(7)
2.188(7)
1.848(14)
1.820(14)
2.043(7)
2.008(7)
2.150(7)
2.043(7)
1.832(14)
Ti2-N4
Ti3-F2
Ti3-F3
Ti3-F4
Ti3-F5
Ti3-N5
Ti3-N6
N1-C10
N2-C20
N3-C30
N4-C40
N5-C50
N6-C60
1.837(14)
2.055(7)
2.054(8)
2.162(7)
2.133(7)
1.797(13)
1.811(14)
1.263(16)
1.261(16)
1.259(16)
1.274(16)
1.250(17)
1.241(16)
N2-Ti1-F4
N2-Ti1-F5
F3-Ti1-F4
F1-Ti1-F4
F1-Ti1-N2
N1-Ti1-N2
N3-Ti2-F5
N4-Ti2-F4
F1-Ti2-F4
F1-Ti2-N4
F4-Ti2-F2
F2-Ti2-N4
N5-Ti3-F5
N6-Ti3-F4
F3-Ti3-F4
F4-Ti3-F2
F2-Ti3-N6
F3-Ti3-N6
172.3(4)
105.8(4)
75.1(3)
Ti1-F1-Ti2
Ti2-F2-Ti3
Ti3-F3-Ti1
Ti1-F4-Ti2
Ti1-F4-Ti3
Ti2-F4-Ti3
Ti1-F5-Ti2
Ti1-F5-Ti3
Ti2-F5-Ti3
Ti2-Ti1-Ti3
Ti1-Ti2-Ti3
Ti1-Ti3-Ti2
Ti1-N1-C10
Ti1-N2-C20
Ti2-N3-C30
Ti2-N4-C40
Ti3-N5-C50
Ti3-N6-C60
99.9(3)
99.2(3)
98.7(3)
92.7(3)
92.1(3)
91.7(3)
91.6(3)
91.7(3)
92.7(3)
59.82(8)
59.98(8)
60.20(8)
169.4(10)
177.1(11)
175.9(11)
176.0(10)
177.6(11)
172.8(11)
75.3(3)
105.7(4)
100.2(5)
162.1(4)
165.8(4)
74.6(3)
106.6(4)
73.6(3)
98.9(4)
165.2(4)
161.8(4)
74.3(3)
72.4(3)
100.2(4)
104.9(4)
Scheme 2
Figure 1. (a) Molecular structure of 3 showing the atom-labeling
scheme. Hydrogen atoms are omitted for clarity (thermal ellipsoids
are given at the 30% probability level). (b) Molecular structure of
3 showing top and lateral views. Hydrogen atoms are omitted for
clarity.
ketimide structural features are similar to those found in the
structure of 1.10
A different approach in the synthesis of cationic tris(ketimide)
complexes consisted in the reaction of alkyl derivatives with
Lewis acids. Alkyl derivatives were obtained by treatment of
Ti(NdCtBu2)3Cl10 (1) with an excess of PhCH2MgCl and with
an equimolar amount of LiMe to afford Ti(NdCtBu2)3(CH2-
Ph) (4) and Ti(NdCtBu2)3(Me) (5) as a red oil and a bright
orange solid, respectively (Scheme 1). In the 1H and 13C NMR
spectra of 4 and 5 the tert-butyl resonances are comparable to
those found in 1, whereas the 13C NdC signals appear slightly
shielded (194.7 ppm for 4 and 194.5 ppm for 5 vs 197.3 ppm
for 1), consistent with somewhat less acidic metal centers. The
extreme sensitivity of these compounds to air and moisture led
to poor elemental analysis results. Compound formulations were
based on the NMR data (see the Supporting Information, Figures
S7-S10) and were confirmed by high-resolution mass spec-
trometry that showed a signal at 559.437 43, corresponding to
[C34H61N348Ti]-, for 4, and a signal at 483.378 85, correspond-
ing to [C28H57N348Ti]-, for 5, with the correct isotopic patterns.
Ti(NdCtBu2)3(CH2Ph) (4) reacts with B(C6F5)3 at -80 °C
in toluene-d8 to afford the complex [Ti(NdCtBu2)3(CH2Ph)B-
(C6F5)3] (6) as a dark red solid in quantitative yield, as
determined by NMR. Complex 6 is stable enough to be isolated
when the reaction is carried out in a Schlenk tube. However,
the extreme sensitivity of 6 to air and moisture led to slightly
low experimental values for elemental analysis. In the mass spec-
trum only the anion was detected (603.040 67 for [C25H7BF15]-).
Nevertheless, NMR data support the formulation of 6 and show
that in solution it exists as a mixture of two species that undergo
an exchange process (Scheme 2).
Benzyl abstraction is attested by the 11B spectrum, which
1
exhibits a single sharp resonance at -7.5 ppm. In the H, 13C,
and 19F NMR spectra two sets of signals, corresponding to
species 6A and 6B, are observed. The presence of the zwitte-
rionic complex is supported by the value of ∆δ ) 4 ppm (∆δ
) δ(Fp) - δ(Fm)) in the 19F spectrum19 and by the upfield shift
of Hp and Hm benzyl resonances (δ 6.12 and 6.33 ppm) in
comparison to those of [PhCH2B(C6F5)3]-.20 The 19F resonances
due to 6B are consistent with a cationic species (∆δ ) 2.5 ppm
1
for the free anion). In the H NMR spectrum the Hp and Hm
resonances overlap at 7.01 ppm.19-25 Two sets of tert-butyl (δ
1.05 (6B) and 1.00 ppm (6A)) and CH2Ph resonances (δ 3.46
(19) Horton, A. D.; de With, J. Chem. Commun. 1996, 1375-1376.
(20) Pellecchia, C.; Grassi, A.; Zambelli, A. J. Mol. Catal. 1993, 82,
57-65.
(21) Pellecchia, C.; Immirzi, A.; Grassi, A.; Zambelli, A. Organometallics
1993, 12, 4473-4478.

122 Organometallics, Vol. 26, No. 1, 2007
Ferreira et al.
Figure 3. Molecular structure of 8 showing the atom-labeling
scheme. Hydrogen atoms are omitted for clarity (thermal ellipsoids
are given at the 50% probability level).
Table 2. Selected Bond Angles (deg) and Distances (Å) for 8
Ti1-C1
Ti1-N1
Ti1-N2
Ti1-N3
Ti1-N4
N1-C1
2.104(6) N2-20
2.074(5) N3-C30
1.916(5) N4-C40
1.899(5) C1-C2
1.882(5) N4-(N1-C1-N2-N3)
1.282(7)
1.257(8)
1.259(7)
1.273(7)
1.498(9)
2.5087(47)
Figure 2. NOESY of 6 showing the dynamic exchange between
the two phenyl rings.
(6A) and 3.40 ppm (6B)) are observed in the 1H spectrum, and
the 13C NMR data also reveal two sets of tert-butyl signals (δ
30.4 and 46.8 ppm for 6A and 30.6 and 44.8 ppm for 6B). The
resonances due to the methylenic benzyl carbons are not visible.
They may either be broadened by 11B coupling or overlapped
by the methyl resonances of the tert-butyl groups. 6B is
formulated as a solvent adduct, although solvent coordination
is not detected in the NMR spectrum, due to rapid exchange
with free solvent. The existence of two species in solution is
corroborated by NOESY experiments, which show two different
CH2 groups correlating with two different ortho protons (Figure
2). The same experiment established that the two species exist
in dynamic exchange, anion coordination being thus a fluxional
process, as represented in Scheme 2.
N1-Ti1-C1
N1-Ti1-N2
35.7(2)
95.2(2)
Ti1-C1-C2
163.2(5)
Ti1-N1-C3
158.6(4)
173.7(4)
175.2(4)
175.4(4)
77.30(19)
13.81(36)
63.29(44)
N2-Ti1-N3 101.4(2)
N3-Ti1-C1 102.7(2)
C1-Ti1-N4 106.8(2)
N1-Ti1-N4 116.7(2)
N2-Ti1-N4 109.6(2)
N3-Ti1-N4 104.2(2)
Ti1-N2-C20
Ti1-N3-C30
Ti1-N4-C40
(N1-C1-N2-N3)-(Mes)
(Mes)-(Ti1-N4)
(Mes)-(N1-C1)
in bromobenzene-d5. The isonitrile carbon resonance in the 13
C
NMR spectrum was found at 143.7 ppm, in accordance with
values of group 4 coordinated isonitriles reported in the
literature.28-30 Coordination of the isonitrile was further con-
firmed by the observation of NOE between the o-methyl groups
of the mesityl moiety and the tBu groups of the ketimide ligands.
The imine carbon resonance appears at 202.3 ppm, close to the
value observed for 6B (205.6 ppm).
The NdC imine carbon chemical shift for 6B is shifted
downfield in comparison to that for complex 1 (205.6 ppm vs
197.3 ppm, respectively), consistent with a more acidic metal
center. However, the same is not applied to 6A, which exhibits
a 13C NdC chemical shift of 191.7 ppm. This implies a strong
coordination of the anion to the metal center, as supported by
the large ∆δ value encountered in the 19F spectra23,26 and the
Further insertions of CtNMes have not been observed at
50 °C for 18 h in the presence of an excess of isonitrile. The
lack of isonitrile insertion in the Ti-N bond reflects strong
π-bonding between the ketimide ligands and the metal center.
a Steric hindrance does not play any relevant influence in this
result, since insertion of the isocyanide in the Ti-C bond of
Ti(NdCtBu2)3(Me) (5) occurs readily and quantitatively at room
temperature, leading to Ti(NdCtBu2)3(η2-MeCdN-Mes) (8),
which is obtained as a bright red crystalline solid (Scheme 1).
Compound formulation was confirmed by high-resolution mass
spectrometry that gave a signal at m/z 628.489 12 corresponding
to [C38H68N448Ti]-, with the correct isotopic pattern. The
1
upfield shift of the meta and para proton resonances in the H
spectrum.27
The equilibrium depicted in Scheme 2 is temperature- and
solvent-dependent. At low temperatures in toluene-d8 (<20 °C)
it is shifted toward 6B, whereas at 20 °C and above, 6A becomes
predominant. In bromobenzene-d5, 6A is always the major
species and above 50 °C is the only one detected in solution.
The equilibrium between 6A and 6B is stopped upon addition
of an L-type σ-donor. Treatment of 6 with 1 equiv of CtNMes
afforded [Ti(NdCtBu2)3(CtNMes)][(CH2Ph)B(C6F5)3] (7), which
was characterized by NMR. The 1H NMR spectrum shows the
anion aromatic protons between 7.00 and 7.20 ppm, in ac-
cordance with the presence of free anion. Consistently, in the
19F NMR spectrum, ∆δ is 2.4 ppm in toluene-d8 and 2.6 ppm
inserted methyl group shows significantly different 1H and 13
resonances in comparison to those found in 5 (2.30 ppm vs 1.10
ppm and 23.0 ppm vs 41.3 ppm, respectively), in agreement
with values found in the literature for similar ligands.31,32 η2-
C
(28) Pflug, J.; Bertuleit, A.; Kehr, G.; Frohlich, R.; Erker, G. Organo-
metallics 1999, 18, 3818-3826.
(22) Horton, A. D.; de With, J.; van der Linden, A.; van der Weg, H.
Organometallics 1996, 15, 2672-2674.
(23) Horton, A. D.; de With, J. Organometallics 1997, 16, 5424-5436.
(24) Shafir, A.; Arnold, J. Organometallics 2003, 22, 567-575.
(25) Pellecchia, C.; Grassi, A.; Immirzi, A. J. Am. Chem. Soc. 1993,
115, 1160-1162.
(26) Pindado, G. J.; Thornton-Pett, M.; Hursthouse, M. B.; Coles, S. J.;
Bochmann, M. J. Chem. Soc., Dalton Trans. 1999, 1663-1668.
(27) Amor, F.; Butt, A.; du Plooy, K. E.; Spaniol, T. P.; Okuda, J.
Organometallics 1998, 17, 5836-5849.
(29) Ahlers, W.; Erker, G.; Frohlich, R. J. Organomet. Chem. 1998, 571,
83-89.
(30) Ahlers, W.; Erker, G.; Frohlich, R. Eur. J. Inorg. Chem. 1998, 889-
895.
(31) Martins, A. M.; Ascenso, J. R.; Azevedo, C. G.; Dias, A. R.; Duarte,
M. T.; da Silva, J. F.; Veiros, L. F.; Rodrigues, S. S. Organometallics 2003,
22, 4218-4228.
(32) Bochmann, M.; Wilson, L. M.; Hursthouse, M. B.; Short, R. L.
Organometallics 1987, 6, 2556-2563.

Titanium Tris(ketimide) Complexes
Organometallics, Vol. 26, No. 1, 2007 123
Iminoacyl coordination was inferred from the 13C chemical shift
of the NdC carbons of the ketimide ligands, which is
significantly shifted to high field in comparison with that of 5
(184.6 vs 194.5 ppm in 5) and from the 13C resonance of the
Mes-NdC iminoacyl carbon (256.2 ppm), which is close to
those reported in the literature for similar ligands.31,32
exists in toluene-d8 as a mixture of two species that are in
equilibrium and displays signals with complex multiplicity.
Two Fo resonances at -111.6 and -136.8 ppm are assigned
to 9A and 9B, respectively (Scheme 3). The Ti‚‚‚F interaction
in 9B is responsible for the shift of the Fo resonance to high
field8,35 and for the observation of five different resonances for
the C6F5 ring.37-40 However, the similarity between the chemical
shifts of the two Fo and the two Fm resonances is indicative of
a fast exchange between the coordinated and free Fo substituents
(species 9B in Chart 2). Accordingly, the five fluorine nuclei
in complex 9B give rise to three complex peaks that are
integrated in the ratio 2:1:2 and correspond to Fo, Fp, and Fm,
respectively. At 110 °C, 9B is fully converted to the solvent
adduct Ti(NdCtBu2)3(C6F5)(solv) (9A), which is responsible for
the other set of fluorine resonances observed in the 19F NMR
spectra. The Fo resonance at -111.6 ppm is indicative of no
interaction between the ortho fluorides and the titanium
center.8,35 Once again, the multiplicity of the set of signals
attributed to 9A indicates that the there are five different fluorine
atoms in the ring which appear as three average complex signals.
This effect might result from hindered rotation around the Ti-
C6F5 bond. The fact that the multiplicity of fluorine resonances
is temperature-independent suggests that the coordination of the
solvent is ultimately responsible for the restriction of C6F5
rotation. This idea is reinforced by the observation that a change
in the solvent dramatically changes the 9A:9B ratio. Spectra
run at room temperature in toluene-d8 show both species whereas
in C6D6 the spectrum at the same temperature shows only 9A,
a result that is observed in toluene-d8 at 110 °C.
These results are consistent with the molecular structure of
8 that is depicted in Figure 3. Selected bond lengths and angles
are given in Table 2. The compound crystallizes in the triclinic
system, space group P21/n. The geometry around the titanium
is best described as distorted square pyramidal, with the base
defined by C1, N1, N2, and N3 (the maximum deviation from
the plane is 0.1354(56) Å for C1) and the tip of the pyramid
occupied by N4. The titanium lies at 0.6398(10) Å above the
basal plane. The iminoacyl ligand is η2-coordinated to the metal,
since N1 and C1 lie at similar distances from the titanium center
(2.074(5) and 2.104(6) Å, respectively) and the N1-C1 distance
is comparable to those of other titanium η2-iminoacyl complexes
found in the literature.33,34 The methyl and mesityl groups pull
away from the N1-C1 bond to minimize steric repulsion (with
angles of 163.2 and 158.6(4)°, respectively). The mesityl group
makes an angle of 63.29(44)° with the N1-C1 bond and of
77.30(19)° with the plane that defines the base of the square
pyramid and is almost aligned with the Ti-N4 axis (13.81-
(36)°). This orientation is adopted to minimize steric effects,
since there are no π-contacts between the mesityl groups of
adjacent molecules in the unit cell. The ketimide ligands are
linear (angles between 173.7(4)° and 175.4(4)°) with Ti-N
distances commonly found in group 4 ketimide complexes.10
The Ti1-N2 distance is slightly larger than the other two,
possibly due to the trans effect of the iminoacyl ligand.
The equilibrium constant (K ) C9A/C9B) was calculated from
the 19F NMR integral ratio in the temperature range of 169-
364 K. The plot of ln K versus 1/T (Figure S24 and Tables
S1-S3 in Supporting Information) led to the values of ∆H )
2.38 ( 0.4 kJ mol-1 and ∆S ) 18 ( 2 J mol-1 K-1. These
very small values attest to the fact that the process occurs with
negligible energy variation, which is consistent with the
proposed equilibrium that does not involve variation in the metal
coordination number or major rearrangements in the coordina-
tion sphere.
The compound [Ti(NdCtBu2)3][(CH2Ph)B(C6F5)3] (6) is
stable in toluene and bromobenzene solutions up to 60 °C.
Above this temperature, however, partial decomposition is
observed with formation of Ti(NdCtBu2)3(C6F5) (9), obtained
by C6F5 transfer from the anion to the titanium center. This
relatively common rearrangement8,35,36 is not the only process
occurring in solution, since other minor species, which have
not been identified, were detected. Nevertheless, 9 is clearly
the major component in solution, which makes C6F5 transfer
the preferred thermal decomposition pathway for 6. Formation
of 9 was initially inferred by the 19F NMR spectrum, which
showed a new set of signals in which the Fo resonance appears
at -112.2 ppm (vs -123.0 ppm for Fo of 6) and resonances
attributed to (CH2Ph)B(C6F5)2 at -129.6 ppm (Fo), -155.6 ppm
(Fp), and -161.0 ppm (Fm).8 This assignment was made possible
by 19F COSY NMR. Furthermore, the formulation of 9 was
confirmed by direct synthesis via alkylation of 1 with C6F5-
MgCl (Scheme 1) that led to quantitatively to Ti(NdCtBu2)3-
(C6F5) (9) as a bright red solid. The 13C NdC chemical shift of
9, which appears shifted downfield in comparison with that of
1, is consistent with the presence of a more electron withdrawing
group (199.5 ppm for 9 vs 197.3 ppm for 1). The 19F NMR
spectrum of the compound shows that it is involved in an
intramolecular fluxional process, as depicted in Figure 4, which
shows the temperature variation study of the 19F spectra and
the 19F NMR spectrum at -40 °C. Between -80 and 110 °C 9
Concluding Remarks
The results discussed above indicate that it is possible to
stabilize species of the type [Ti(NdCtBu2)3]+, provided that the
correct counterion is present. Counterions that establish π
interactions with the cation, such as [(PhCH2)B(C6F5)3]-, lead
to more stable compounds than counterions that establish σ
interactions, such as PF6-. For the latter, the acidity of the metal
center is strong enough to abstract fluorine from the anion, as
attested to by the formation of [Ti3(NdCtBu2)6(µ2-F)3(µ3-F)2]-
[PF6] (3). This result, together with the fluxional processes
observed in solution for [Ti(NdCtBu2)3][(PhCH2)B(C6F5)3] (6)
and Ti(NdCtBu2)3(C6F5) (9), show that titanium ketimide
complexes are hard Lewis acids. In addition, ketimide ligands
(37) Jia, L.; Yang, X.; Stern, C. L.; Marks, T. J. Organometallics 1997,
16, 842-857.
(38) Burlakov, V. V.; Arndt, P.; Baumann, W.; Spannenberg, A.;
Rosenthal, U.; Letov, A. V.; Lyssenko, K. A.; Korlyukov, A. A.; Strunkina,
L. I.; Minacheva, M. K.; Shur, V. B. Organometallics 2001, 20, 4072-
4079.
(39) Woodman, T. J.; Thornton-Pett, M.; Hughes, D. L.; Bochmann, M.
Organometallics 2001, 20, 4080-4091.
(40) Siedle, A. R.; Newmark, R. A.; Lammana, W. M.; Huffman, J. C.
Organometallics 1993, 12, 1491-1492.
(33) Chamberlain, L. R.; Durfee, L. D.; Fanwick, P. E.; Kobriger, L.;
Latesky, S. L.; McMullen, A. K.; Rothwell, I. P.; Folting, K.; Huffman, J.
C.; Streib, W. E.; Wang, R. J. Am. Chem. Soc. 1987, 109, 390-402.
(34) van Bolhuis, F.; de Boer, E. J. M.; Teuben, J. H. J. Organomet.
Chem. 1979, 170, 299-308.
(35) Go´mez, R.; Go´mez-Sal, P.; del Real, P. A.; Royo, P. J. Organomet.
Chem. 1999, 588, 22-27.
(36) Gue´rin, F.; Stewart, J. C.; Beddie, C.; Stephan, D. W. Organome-
tallics 2000, 19, 2994-3000.

124 Organometallics, Vol. 26, No. 1, 2007
Ferreira et al.
Figure 4. (a) Temperature study of 19F NMR spectra of 9 in toluene-d8. (b) 19F NMR spectrum of 9 at -40 °C in toluene-d8.

Titanium Tris(ketimide) Complexes
Organometallics, Vol. 26, No. 1, 2007 125
Scheme 3
H, tBu). 19F NMR (CD2Cl2, 282 MHz): δ -70.87 (d, 1JF-P ) 708.9
Hz). 31P NMR (CD2Cl2, 121 MHz): δ -141.9 (ps t, 1JF-P ) 708.6
Hz). 13C{1H} NMR (CD2Cl2, 75 MHz): δ 201.5 (CdN), 42.4
(C(CH3)3), 29.9 (C(CH3)3), 2.03 (NCCH3).
fail to offer good steric protection to the metal center, allowing
the formation of small aggregates as well as metal-solvent
interactions.
[Ti3(NdCtBu2)6(µ2-F)3(µ3-F)2][PF6] (3). Compound 2 was dis-
solved in CH2Cl2 and hexane was added as a double layer. Solvent
diffusion was allowed to proceed slowly at -20 °C, affording dark
Experimental Section
All manipulations were carried out under nitrogen, using either
standard Schlenk-line or drybox techniques.
1
green needles. H NMR (CD2Cl2, 300 MHz): δ 1.38 (s, 108 H,
2
tBu). 19F NMR (CD2Cl2, 282 MHz): δ -63.1 (t, JFF ) 91.1 Hz,
Solvents were predried using 4 Å molecular sieves, refluxed over
sodium-benzophenone (diethyl ether, tetrahydrofuran, and toluene)
or calcium hydride (dichloromethane, acetonitrile, and n-hexane)
under an atmosphere of nitrogen, and collected by distillation.
Deuterated solvents were dried with molecular sieves and freeze-
pump-thaw-degassed prior to use.
µ2-F), -71.0 (d, JF-P ) 705.8 Hz, PF6-), -91.2 (q, JFF ) 91.1
1
2
Hz, µ3-F). 31P NMR (CD2Cl2, 121 MHz): δ -141.9 (ps t, 1JF-P
)
711.5 Hz). 13C{1H} NMR (CD2Cl2, 75 MHz): δ 42.6 (C(CH3)3),
29.6 (C(CH3)3). Anal. Calcd for C54H108F11N6PTi3: C, 52.94; H,
8.89; N, 6.86. Found: C, 44.40; H, 8.49; N, 5.49. The elemental
analysis results of the crystals were repeated, and the results always
showed deviations from the calculated values. The NMR spectra
(see Figures S3-S6 in the Supporting Information) and the analysis
of several crystals always confirmed the results. The discrepancy
is probably due to the high fluorine content of the sample.
1H, 13C, 19F, 31P, and 11B NMR spectra were recorded on a Varian
1
Unity 300 instrument, at 298 K unless stated otherwise. H and
13C NMR spectra were referenced internally to residual protio-
solvent (1H) or solvent (13C) resonances and reported relative to
tetramethylsilane (δ 0). 19F, 31P, and 11B spectra were referenced
externally to CF3COOH (δ -76 ppm), H3PO4, and BF3‚Et2O,
respectively. Peak assignments were based on one- and two-
dimensional NOE experiments and on 13C{1H}-1H hetero-correla-
tions, as appropriate.
Ti(NdCtBu2)3(CH2Ph) (4). A solution of 1 (0.835 g, 1.66 mmol)
in 40 mL of hexane was cooled to -50 °C, and a solution of PhCH2-
MgCl in ether (1.5 M, 4.18 mmol) was added. A white precipitate
formed immediately. The mixture was warmed slowly to room
temperature over a period of 2.5 h. The solvent was pumped off
and the residue extracted with hexane. Solvent removal afforded
0.890 g of a red oil (96.0% yield). 1H NMR (C7D8, 300 MHz): δ
7.13 (m, 2H, Ho), 7.11 (m, 2H, Hm), 6.81 (t, J ) 6.9 Hz, 1H, Hp),
High-resolution electron ionization (EI) mass spectra were
obtained by a Fourier transform ion cyclotron resonance mass
spectrometer (Finnegan FT/MS 2001-DT spectrometer), equipped
with a 3 T superconducting magnet. Elemental analyses were
obtained from the Laborato´rio de Ana´lises do IST (Fisons Instru-
ment 1108).
t
2.89 (s, 2H, CH2), 1.21 (s, 54H, Bu). 13C{1H} NMR (C7D8, 75
MHz): δ 194.7 (CdN), 149.1 (Cipso), 128.1 (Co), 127.4 (Cm), 121.0
(Cp), 68.8 (CH2), 45.6 (C(CH3)3), 30.9 (C(CH3)3). EI/FT ICR-MS:
559.437 43 (100) ([C34H61N348Ti]-). Anal. Calcd for C34H61N3Ti:
C, 72.96; H, 10.98; N, 7.51. Found: C, 70.04; H, 11.47; N, 6.82.
Ti(NdCtBu2)3(Me) (5). LiMe (1.8 M, 0.88 mmol) was added
to a solution of 1 (0.441 g, 0.88 mmol) in 20 mL of hexane cooled
to -50 °C. The reaction medium turned bright orange immediately.
The mixture was warmed to room temperature, and the solvent was
pumped off. Subsequent extraction with hexane afforded 0.369 g
PhCH2MgCl (1.5 mol dm-3 in ether) and C6F5MgCl (0.5 mol
dm-3 in ether) were purchased from Aldrich and titrated by the
usual methods before use. LiMe (1.8 M in ether) was purchased
from Merck and titrated prior to use. The compounds LiNdCt-
42
44
Bu2,41 Ti(NdCtBu2)3Cl (1),10 B(C6F5)3 CtNMes,43 and TlPF6
were prepared according to literature methods.
[Ti(NdCtBu2)3(NtCCH3)][PF6] (2). A solution of 1 (0.512 g,
1.02 mmol) in acetonitrile was added to a suspension of TlPF6
(0.394 g, 1.13 mmol) in acetonitrile, cooled to -30 °C. A bright
orange solution formed immediately. The mixture was warmed to
room temperature and was stirred overnight. The mixture was
filtered through Celite, but a solid residue persisted. Solvent removal
afforded a bright yellow solid (0.607 g, 91% yield) that upon
standing at room temperature turns green. 1H NMR (CD3CN, 300
1
of a bright orange solid (87% yield). H NMR (C7D8, 300 MHz):
t
δ 1.30 (s, 54H, Bu), 1.10 (s, 3H, Ti-Me). 13C{1H} NMR (C7D8,
75 MHz): δ 194.5 (CdN), 45.5 (C(CH3)3), 41.3 (Ti-CH3), 31.0
(C(CH3)3). EI/FT ICR-MS: 483.378 85 (100) ([C28H57N348Ti]-).
Anal. Calcd for C28H57N3Ti: C, 69.53; H, 11.87; N, 8.69. Found:
C, 67.86; H, 12.18; N, 8.41.
t
MHz): δ 1.26 (s, 54H, Bu). 19F NMR (CD3CN, 282 MHz): δ
[Ti(NdCtBu2)3][(CH2Ph)B(C6F5)3] (6). Method A. Complex
4 (0.122 g, 0.22 mmol) was dissolved in 0.3 mL of toluene-d8 in
a NMR tube adapted to be sealed. The solution was degassed and
frozen, and B(C6F5)3 (0.122 g, 0.24 mmol) in 0.3 mL of toluene-d8
was added. The tube was sealed under vacuum and was unfrozen
in a bath at -80 °C, prior to its introduction in the NMR instrument,
where it was warmed to room temperature, as it was monitored.
The reaction was complete instantly at -80 °C, in quantitative yield.
Method B. Complex 4 (0.606 g, 1.08 mmol) was dissolved in
approximately 20 mL of toluene, and the solution was cooled to
-80 °C. B(C6F5)3 (0.607 g, 1.19 mmol) in 30 mL of toluene was
added, and a dark red precipitate was readily formed. The reaction
-67.4 (d, JF-P ) 705.8 Hz. 31P NMR (CD3CN, 121 MHz): δ
1
-138.7 (ps t, J ) 708.6 Hz). 13C{1H} NMR (CD3CN, 75 MHz):
δ 201.6 (CdN), 43.1 (C(CH3)3), 29.7 (C(CH3)3), 2.03 (NCCH3).
1H NMR (CD2Cl2, 300 MHz): δ 1.98 (br s, CH3CN), 1.19 (s, 13.7
(41) Clegg, W.; Snaith, R.; Shearer, H. M. M.; Wade, K.; Whitehead,
G. J. Chem. Soc., Dalton Trans. 1983, 1309-1317.
(42) Chernega, A.; Graham, A. J.; Green, M. L. H.; Haggit, J. L.; Lloyd,
J.; Mehnert, C. P.; Metzler, N.; Souter, J. J. Chem. Soc., Dalton Trans.
1997, 2293-2303.
(43) Obrecht, R.; Hermann, R.; Ugi, I. Synthesis 1985, 04, 400-401.
(44) Herrmann, W. A.; Salzer, A. Literature, Laboratory Techniques and
Common Starting Materials; Thieme: Stuttgart, Germany, 1996.

126 Organometallics, Vol. 26, No. 1, 2007
Ferreira et al.
Table 3. Crystallographic Data for 3 and 8
mixture was warmed slowly to 10 °C, and the solution was filtered
off. The residue was washed with hexane, affording 0.790 g of a
3
8
1
dark red solid (68% yield). H NMR (C7D8, 10 °C, 300 MHz): δ
empirical formula
formula wt
temp (K)
wavelength (Å)
cryst syst
space group
a (Å)
C54H108F11N6PTi3
1206.99
C38H68N4Ti
628.86
7.24 (d, 7.2 Hz, HAo), 7.01 (m, HBo + HBm), 6.85 (m, HB ), 6.33 (t,
p
7.5 Hz, HAm), 6.12 (t, 7.5 Hz, HAp), 3.46 (s, CH2BA), 3.40 (s,
CH2BB), 1.04 (tBuA), 0.97 (tBuB). 19F NMR (C7D8, 10 °C, 282
MHz): δ -123.0 (d, J ) 22.6 Hz, 2F, FAo), -123.6 (d, J ) 20
150(2)
150(2)
0.710 69
monoclinic
P21/c
12.486(5)
13.689(5)
39.421(5)
90
0.710 73
monoclinic
P21/n
11.7679(10)
19.8939(18)
17.5605(16)
90
99.372(7)
90
4056.2(6)
4
Hz, 2F, FB ), -154.5 (t, J ) 20.9 Hz, 1F, FAp), -157.7 (t, J )
o
20.9 Hz, 1F, FB ), -158.5 (t, J ) 20.9 Hz, 2F, FAm), -160.2 (t, J
p
b (Å)
c (Å)
) 20.9 Hz, 2F, FBm). 11B NMR (C7D8, 10 °C, 96 MHz): δ -7.5.
13C{1H} NMR (C7D8, 75 MHz): δ 205.6 (NdCB), 191.7 (NdCA),
150.5 and 147.5 (d, JCF ) 225 Hz, Co-F), 149.4 (Cipso CH2PhB),
138.9 and 136.3 (d, JCF ) 195 Hz, Cm-F), 127.2 (Co), 126.8 (Cm),
R (deg)
â (deg)
92.643(5)
90
γ (deg)
V (Å3)
6731(4)
4
1.191
0.437
B
B
123.0 (CpA), 122.3 (Cp ), 46.8 (C(CH3)3A), 44.8 (C(CH3)3 ), 31.6
Z
B
(BCH2, br), 30.6 (CH3 ), 30.4 (CH3A). 1H NMR (C6D5Br, 300
Dc (g cm-3
abs coeff
F(000)
)
1.030
0.238
1384
MHz): δ 7.65-7.10 (br, Harom, 5H), 3.82 (br s, CH2, 2H), 1.57
t
1
and 1.53 (s, Bu, 54 H, ∼1.5:1). H NMR (C6D5Br, 50 °C, 300
2544
cryst size
cryst morphology
color
θ range for data collecn (deg)
limiting indices
0.1 × 0.1 × 0.4
0.2 × 0.2 × 0.3
MHz): δ 7.57 (d, 7.2 Hz, Ho, 2H), 7.37 (t, Hm, 7.0 Hz, 2H), 7.23
(t, Hp, 6.9 Hz, 1H), 3.80 (s, CH2, 2H), 1.56 (s, Bu, 54 H). 19F
t
needle
green
block
red
NMR (C6D5Br, 282 MHz): δ -128.4 (br, 2F, FoA+B), -158.9 (t,
2.47-23.45
-13 e h e 13
-15 e k e 15
-43 e l e 43
68 686/9451
(0.2165)
95.5 (θ ) 23.45°)
3.29-23.25
-6 e h e 13
-21 e k e 22
-19 e l e 17
17 783/5666
(0.1023)
97.4 (θ ) 23.25°)
J ) 20.3, 1F, FAp), -161.8 (br, 1F, FB ), -162.8 (br, 2F, FAm),
p
-164.5 (br, 2F, FBm); 6A:6B ) 1.4:1. 19F NMR (C6D5Br, 50 °C,
282 MHz): δ -128.6 (d, J ) 20.7 Hz, 2F, Fo), -159.9 (br, 2F,
Fp), -163.9 (br, 1F, Fm). 11B NMR (C6D5Br, 96 MHz): δ -12.8.
13C{1H} NMR (C6D5Br, 75 MHz): δ 211.6 (NdCB), 205.2 (Nd
CA), 148.8 (Cipso), 150.0 and 146.8 (d, JCF ) 238.6 Hz, Co-F),
138.9 and 135.9 (d, JCF ) 226.4 Hz, Cp-F), 138.1 and 134.9 (d,
JCF ) 240.3 Hz, Cm-F), 128.9 (Co), 127.0 (Cm), 122.7 (Cp), 46.4
no. of rflns collected/
unique (Rint
)
completeness to θ (%)
refinement method
no. of data/restraints/
params
full-matrix least squares on F2
9451/54/677
5666/0/392
goodness of fit on F2
final R indices (I > 2σ(I))
R1
1.000
1.025
B
(C(CH3)3A), 41.7 (C(CH3)3 ), 30.1 (CH3A+B). EI/FT ICR-MS:
603.040 67 (100) ([C25H7BF15]-). Anal. Calcd for C52H61BF15N3-
Ti: C, 58.28; H, 5.74; N, 3.92. Found: C, 57.02; H, 5.85; N, 3.75.
0.0945
0.2153
0.0960
0.1947
wR2
R indices (all data)
R1
[Ti(NdCtBu2)3(CtNMes)][(CH2Ph)B(C6F5)3] (7). Compound
6 (0.030 g, 0.03 mmol) was dissolved in 300 µL of toluene-d8, and
CtNMes (0.004 g, 0.03 mmol), also in 300 µL of toluene-d8, was
0.1905
0.2476
0.1195
0.2138
0
wR2
extinction coeff
largest diff peak,
0.0332(19)
0.692, -0.386
1
added. A dark red oil formed immediately. H NMR (C7D8, 300
0.515, -0.500
MHz): δ 7.20 (d, J ) 7.8 Hz, 2H, Ho), 7.13 (t, J ) 7.2 Hz, 2H,
Hm), 7.00 (m, 2H, Hp), 6.54 (s, Cm-Mes-H), 3.40 (s, 2H, CH2Ph),
hole (e Å-3
)
t
2.16 (s, 6H, Co-CH3), 2.00 (s, 3H, Cp-CH3), 1.13 (s, 54H, Bu).
(Co), 129.1 (Cp), 128.9 (Cm), 44.1 (C(CH3)3), 31.3 (C(CH3)3), 23.0
(CH3), 20.9 (p-CH3), 18.9 (o-CH3). EI/FT ICR-MS: 628.48912
(100) ([C38H68N448Ti]-). Anal. Calcd for C38H68N4Ti: C, 72.58;
H, 10.90; N, 8.91. Found: C, 69.25; H, 11.43; N, 8.35.
Ti(NdCtBu2)3(C6F5) (9). A solution of 1 (0.520 g, 1.03 mmol)
in 40 mL of hexane was cooled to -50 °C, and a solution of C6F5-
MgCl in ether (0.5 M, 1.14 mmol) was added. The mixture was
warmed slowly to room temperature. After the mixture was stirred
for 2 h at room temperature, the volatiles were removed and the
residue was reextracted in hexane. Solvent removal gave 0.599 g
19F NMR (C7D8, 282 MHz): δ -123.1 (d, J ) 22.0 Hz, 2F, Fo),
-157.8 (t, J ) 20.6 Hz, 1F, Fp), -160.2 (t, J ) 20.6 Hz, 2F, Fm).
11B NMR (C7D8, 96 MHz): δ -7.45. 13C{1H} NMR (C7D8, 75
MHz): δ 135.5 (Co of CtN-Mes), 129.7 (Co of CH2Ph), 127.2
(Cm of CH2Ph), 122.8 (Cp of CH2Ph), 46.1 (C(CH3)3), 30.6
1
(C(CH3)3), 21.0 (p-CH3), 18.5 (o-CH3). H NMR (C6D5Br, 300
MHz): δ 7.64 (d, J ) 7.2 Hz, 2H, Ho), 7.46 (t, J ) 7.2 Hz, 2H,
Hm), 7.31 (t, J ) 7.2 Hz, 2H, Hp), 7.11 (s, Cm-Mes-H), 3.83 (s,
2H, CH2Ph), 2.69 (s, 6H, Co-CH3), 2.53 (s, 3H, Cp-CH3), 1.63
t
(s, 54H, Bu). 19F NMR (C6D5Br, 282 MHz): δ -128.5 (d, J )
1
of a bright red solid (91% yield). H NMR (C6D6, 300 MHz): δ
22.0 Hz, 2F, Fo), -162.4 (t, J ) 20.6 Hz, 1F, Fp), -165.0 (t, J )
20.6 Hz, 2F, Fm). 11B NMR (C6D5Br, 96 MHz): δ -12.6. 13C-
{1H} NMR (C6D5Br, 75 MHz): δ 202.3 (NdC), 150.1 and 147.0
(d, J ) 232.5 Hz, CF-o), 148.8 (Cipso of CH2Ph), 143.7 (CtN),
139.1 and 135.9 (d, J ) 240.0 Hz, CF-p), 138.1 and 135.0 (d, J )
232.5 Hz, CF-m), 135.5 (Co of CtN-Mes), 130.0 (Cipso of CtN-
Mes), 129.6 (Cm of CtN-Mes), 128.8 (Co of CH2Ph), 127.9 (Cm
of CH2Ph), 126.9 (Cp of CtN-Mes), 122.5 (Cp of CH2Ph), 45.8
(C(CH3)3), 30.3 (C(CH3)3), 21.0 (p-CH3), 18.4 (o-CH3).
1.21 (s, 54H, tBu). 19F NMR (C6D6, 282 MHz): δ -112.2 (d, 3JF F
o
m
3
) 20.9 Hz, 2F, Fo), -154.8 (t, JF F ) 19.7 Hz, 1F, Fp), -160.8
p
m
(t, JF ) 19.5 Hz, 2F, Fm). 13C{1H} NMR (C6D6, 75 MHz): δ
3
mFp
199.5 (CdN), 145.9 and 141.9 (d, 1JCF ) 300.0 Hz, Co-F), 138.5
1
and 134.7 (d, JCF ) 285.0 Hz, Cp-F), 45.8 (C(CH3)3), 30.7
(C(CH3)3). H NMR (C7D8, 300 MHz): δ 1.21 (s, 54H, Bu). 19F
1
t
NMR (C7D8, 282 MHz): δ -111.6 (m, 2F, FoA), -136.8 (m, 2F,
B
B
Fo ), -151.8 (t, J ) 20.8 Hz, 1F, Fp ), -154.1 (t, J ) 19.5 Hz,
1F, FpA), -160.0 (m, 2F + 2F, FmA + FmB). 13C{1H} NMR (C7D8,
75 MHz): δ 199.4 (CdN), 45.8 (C(CH3)3), 30.7 (C(CH3)3). EI/FT
ICR-MS: 635.315 17 (100) ([C33H54F5N348Ti]-).
Ti(NdCtBu2)3(η2-MeCdN-Mes) (8). 5 (0.319 g, 0.66 mmol)
was dissolved in toluene, and CtNMes (0.10 g, 0.66 mmol), also
dissolved in toluene, was added, at room temperature. An immediate
deepening of the red color was observed. The mixture was stirred
for 1 h at room temperature. The solvent was then removed and
the residue extracted with hexane. Upon solvent removal a bright
General Procedures for X-ray Crystallography. Pertinent
details for the individual compounds can be found in Table 3.
Crystallographic data were collected using graphite-monochromated
Mo KR (λ ) 0.710 73 Å) on a Bruker AXS-KAPPA APEX II area
detector diffractometer equipped with an Oxford Cryosystem open-
flow nitrogen cryostat, and data were collected at 150 K. Cell
parameters were retrieved using Bruker SMART software and
refined using Bruker SAINT on all observed reflections. Absorption
1
red solid was obtained (0.39 g, 96% yield). H NMR (C6D6, 300
MHz): δ 6.79 (s, CH-Mes, 2H), 2.30 (s, CH3, 3H), 2.14 (s, p-CH3,
3H), 1.99 (s, o-CH3, 6H), 1.31 (s, tBu, 54H). 13C{1H} NMR (C6D6,
75 MHz): δ 256.2 (CdN-Mes), 184.6 (NdC), 145.0 (Cipso), 134.3

Titanium Tris(ketimide) Complexes
Organometallics, Vol. 26, No. 1, 2007 127
corrections were applied using SADABS. The structures were
solved by direct methods using either SHELXS-9745 or SIR 9746and
refined using full-matrix least-squares refinement against F2 using
SHELXL-97.47 All programs are included in the package of
programs WINGX, version 1.64.05.48 All non-hydrogen atoms were
refined anisotropically, and the hydrogen atoms were inserted in
idealized positions riding on the parent C atom. The molecular
structures were done with ORTEP3 for Windows,49 included in
the software package.
Both crystals have low quality and poor diffracting power, which
explain the low resolution, the small data to parameter ratio, and
the high R values. Nevertheless, both structures were unequivocally
determined and are in agreement with the remaining characterization
data.
Data for complexes 3 and 9 were deposited with the CCDC under
the deposit numbers 612083 and 612084, respectively, and can be
obtained free of charge from the Cambridge Crystallographic Data
Center, 12 Union Road, Cambridge CB2 1EZ, U.K. (tel +44 1223
336408, fax +44 1223 336033).
Acknowledgment. We thank Doctor M. Conceic¸a˜o Oliveira
for EI/FT ICR-MS measurements. We are also grateful to the
Fundac¸a˜o para a Cieˆncia e Tecnologia for financial support
(Projects POCTI/QUI/29734/2001 and POCTI/QUI/46206/
2002). M.J.F. and I.M. are thankful for Ph.D. grants (BD2869/
2000 and BD10338/2002, respectively) from the same institution
and from the FSE.
Supporting Information Available: CIF files giving X-ray
crystallographic data for compounds 3 and 8, Figures S1-S23,
giving NMR spectra of compounds 2-9, Figure S24 giving the ln
K vs 1/T plot for complex 9, and Tables S1-S3, giving data for
the ln K vs 1/T plot for 9, the linear regression output, and regression
statistics. This material is available free of charge via the Internet
at http://pubs.acs.org.
(45) Sheldrick, G. M. Acta Crystallogr. 1990, A46, 467-473.
(46) Altomare, A.; Burla, M. C.; Camalli, M.; Cascarano, G. L.;
Giacovazzo, C.; Guagliardi, A.; Moliterni, A. G. G.; Polidori, G.; Spagna,
R. J. Appl. Crystallogr. 1999, 32, 115-119.
(47) Sheldrick, G. M. SHELXL-97, a Computer Program for the
Refinement of Crystal Structures; University of Go¨ttingen, Go¨ttingen,
Germany, 1997.
(48) Farrugia, L. J. J. Appl. Crystallogr. 1999, 32, 837-838.
(49) Farrugia, L. J. J. Appl. Crystallogr. 1997, 30, 565.
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