Organometallic consequences of a redox reaction: Terminal trimethylsilylmethylidene titanium complexes prepared by a one-electron oxidation step

Article abstract of DOI:10.1016/j.jorganchem.2007.03.033

One-electron oxidation of the titanium(III) bis-trimethylsilylmethyl complex (nacnac)Ti(CH₂SiMe₃)₂ (1) (nacnac^- = [ArNC(Me)]₂CH, Ar = 2,6-ⁱPr₂C₆H₃), readily prepared from (nacnac)TiCl₂(THF) and 2 equiv. of LiCH₂SiMe₃ in Et₂O, with AgOTf results in formation of the five-coordinate and terminal titanium alkylidene complex (nacnac)Ti{double bond, long}CHSiMe₃(OTf)(THF) (2)-THF concurrent with extrusion of tetramethylsilane and precipitation of silver metal. Complex 2-THF eliminates THF slowly under dynamic vacuum to generate the four-coordinate alkylidene 2 along with some decomposition products. Alternatively, the four-coordinate and non-solvento alkylidene complex, 2, can be prepared from 1 and AgOTf in pentane. Complex 2 undergoes cross-metathesis transformation to afford [ArNC(Me)CHC(Me){double bond, long}CHSiMe₃]Ti{double bond, long}NAr(OTf) (3) as the major product after 34 h at room temperature. Complexes 1, 2, 2-THF, and 3 have been fully characterized spectroscopically, and single crystal X-ray diffraction analysis for 1 and 2-THF are presented.

Full text of DOI:10.1016/j.jorganchem.2007.03.033

Journal of Organometallic Chemistry 692 (2007) 3115–3120
www.elsevier.com/locate/jorganchem
Communication
Organometallic consequences of a redox reaction: Terminal
trimethylsilylmethylidene titanium complexes prepared by a
one-electron oxidation step
*
Falguni Basuli, Debashis Adhikari, John C. Huffman, Daniel J. Mindiola
Department of Chemistry and Molecular Structure Center, Indiana University, Bloomington, IN 47405, USA
Received 22 November 2006; received in revised form 1 March 2007; accepted 1 March 2007
Available online 30 March 2007
Abstract
One-electron oxidation of the titanium(III) bis-trimethylsilylmethyl complex (nacnac)Ti(CH2SiMe3)2 (1) (nacnacÀ = [ArNC
(Me)]2CH, Ar = 2,6-iPr2C6H3), readily prepared from (nacnac)TiCl2(THF) and 2 equiv. of LiCH2SiMe3 in Et2O, with AgOTf results
in formation of the five-coordinate and terminal titanium alkylidene complex (nacnac)Ti@CHSiMe3(OTf)(THF) (2)-THF concurrent
with extrusion of tetramethylsilane and precipitation of silver metal. Complex 2-THF eliminates THF slowly under dynamic vacuum
to generate the four-coordinate alkylidene 2 along with some decomposition products. Alternatively, the four-coordinate and non-sol-
vento alkylidene complex, 2, can be prepared from 1 and AgOTf in pentane. Complex 2 undergoes cross-metathesis transformation to
afford [ArNC(Me)CHC(Me)@CHSiMe3]Ti@NAr(OTf) (3) as the major product after 34 h at room temperature. Complexes 1, 2, 2-
THF, and 3 have been fully characterized spectroscopically, and single crystal X-ray diffraction analysis for 1 and 2-THF are presented.
Ó 2007 Elsevier B.V. All rights reserved.
Keywords: Alkyl; Alkylidene; Oxidation; Titanium complexes; X-ray structure
1. Introduction
[C5H3(SiMe2PiPr2)2]Zr@CHSiMe3(Cl) [24,25], respectively.
In most cases, the M = CHSiMe3 functionality in question
must be trapped or generated in situ, to avoid decomposi-
tion pathways from occurring [26–29]. In rare cases
however, dimers arise from bridging of the trim-
ethylsilylmethylidene unit [30,31]. Hence, the relatively
few examples of group 4 alkylidene complexes bearing
the trimethylsilyl group is surprising since the sterically
demanding alkyl reagent LiCH2SiMe3 is both commer-
cially available and affordable much more so than the cor-
High-oxidation state transition metal complexes of
groups such as 5 [1–7], 6 [8–13,2,14] and 7 [2] share a com-
mon ground in stabilizing the terminal trimethylsilylmethy-
lidene ligand (M = CHSiMe3) [2,15,16]. However, the
number of terminal trimethylsilylmethylidene metal com-
plexes plummets dramatically when the metal in question
represents the lighter congener for each group (e.g., Ti,
V, Cr) [2,15–18]. In contrast, group 4 transition metal com-
pounds bearing the terminal trimethylsilylmethylidene
ligand are even more scant, with the only reported exam-
ples (isolable) being the titanium and zirconium complexes
(PNP)Ti@CHSiMe3(X) (PNPÀ = N[2-P(CHMe2)2-4-meth-
ylphenyl]2) [19–22]; XÀ = OTf [23], CH2SiMe3 [17]) and
t
responding salts LiCH2 Bu [32], LiCH2CMe2Ph [33], and
LiCH2Ph [34]. Likewise, nucleophilic charge at the a-alky-
lidene carbon should be expected to be lower given the
inherent electron withdrawing effect of trimethylsilyl group
and sigma-hyperconjugation.
In this manuscript we report a facile synthetic route to
low-coordinate and terminal titanium complexes possess-
ing the terminal trimethylsilylmethylidene motif, namely
the compounds (nacnac)Ti@CHSiMe3(OTf)(THF) and its
*
Corresponding author. Tel.: +1 812 855 2399; fax: +1 812 855 8300.
E-mail address: mindiola@indiana.edu (D.J. Mindiola).
0022-328X/$ - see front matter Ó 2007 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2007.03.033

3116
F. Basuli et al. / Journal of Organometallic Chemistry 692 (2007) 3115–3120
non-solvento,
nac)Ti@CHSiMe3(OTf)
four-coordinate
counterpart
(nac-
displays a magnetic moment of 1.91 lB thus consistent with
a d1 electronic configuration. In order to establish an accu-
rate connectivity for 1, we collected single crystal X-ray dif-
fraction data. Consequently, complex 1 crystallizes in the
Monoclinic space group P2(1)/n, and as indicated in
Fig. 1, the molecule structure adopts a pseudo tetrahedral
geometry whereby the b-diketiminate ligand occupies the
remaining two coordination sites. The Ti–C distances
(nacnacÀ = [ArNC(Me)]2CH,
Ar = 2,6-iPr2C6H3) [35]. Our strategy involves a one-elec-
tron oxidation reaction of a Ti(III) bis-alkyl precursor
(nacnac)Ti(CH2SiMe3)2 to promote the a-hydrogen
abstraction step.
The only examples of a titanium complexes bearing the
terminal trimethylsilylmethylidene unit were recently
reported by us, and involved the compounds (PNP)Ti@
CHSiMe3(X) (XÀ = OTf [23], CH2SiMe3 [17]). Rothwell
and co-workers have reported bridging trimethylsilylme-
thylidene complexes of titanium [30,31]. In their case,
dimerization presumably occurs due to the unsaturated
nature of the putative, three-coordinate Ti(IV) complex,
in combination with the unhindered composition of the
supporting ancillary ligand [30,31]. In the case of terminal
and stable titanium trimethylsilylmethylidene complexes,
spectroscopic discrepancies arise when these ligands are
compared to the C-based neopentylidene analogues. When
˚
(2.104(3) and 2.139(3) A) are within range to similar bis-
alkyl titanium complexes reported by us [36–38] and Bud-
zelaar and co-workers [39]. Although all hydrogens in the
molecule were located and refined isotropically, their loca-
tion does not suggest an a-hydrogen agostic interaction
taking place with the Ti(III) center. The Ti center in 1 devi-
˚
ates 0.601 A out of the imaginary NCCCN plane. Each
flanking aryl group bound to the a-nitrogens is oriented
perpendicular to the N–Ti–N plane, placing the sterically
measured up against (PNP)Ti@CHtBu(CH2 Bu), the alky-
t
lidene carbon resonance for (PNP)Ti@CHSiMe3(CH2-
SiMe3) (310.5 ppm) shifts further downfield in the
13C{1H} NMR spectrum (D = 50.5 ppm) [17]. This param-
eter reflects the electronic effect imposed by the trimethylsi-
lyl unit on the a-C. In addition, the JC–H of 99 Hz (vs.
86 Hz for (PNP)Ti@CHtBu(CH2 Bu)) lends support for
t
the trimethylsilylmethylidene complex having a weaker
a-hydrogen agostic interaction taking place with the Ti(IV)
center. This implies then that the Ti(IV) center is more elec-
tron rich when supported by a trimethylsilylmethylidene
ligand as opposed to the neopentylidene motif (the role
of steric effects might also be contributing to this parameter
and we cannot discard this possibility). Therefore, the
above spectroscopic features arguably imply that the Ti@
CHSiMe3 derivative is less electron hungry than the
Ti@CHtBu, which is a dichotomy considering the relative
few examples reported for the former system.
Our approach into incorporating the trimethylsilylme-
thylidene ligand onto Ti(IV) involved a similar protocol
for the synthesis of (nacnac)Ti@CHtBu(OTf) [36]. Accord-
ingly, complex (nacnac)TiCl2(THF) [36] can be readily
alkylated with LiCH2SiMe3 to afford green-blue crystals
of (nacnac)Ti(CH2SiMe3)2 (1) in 73% isolated yields upon
work-up of the reaction mixture (Scheme 1). Complex 1
Fig. 1. Molecular structure of 1 displaying thermal ellipsoids at the 50%
probability level. Hydrogen atoms have been omitted for the purpose of
˚
clarity. Selected metrical parameters are reported in A (distances) and °
(angles). Ti1–C33, 2.104(3); Ti1–C38, 2.139(3); Ti1–N2, 2.017(1); Ti1–N8,
2.033(1); N2–C3, 1.354(5); C3–C5, 1.396(8); C5–C6, 1.405(8); C6–N8,
1.348(5); Ti1–C33–Si34, 130.72(7); Ti1–C38–Si39, 125.85(7); N8–Ti1-N2,
91.95(4); C38–Ti1–C33, 109.62(5); C38–Ti1–N2, 112.58(5); C38–Ti1–N8,
118.65(5); C33–Ti1–N2, 118.46(5); C33–Ti1–N8, 104.81(5).
H
SiMe3
Ar
SiMe3
Ti
Ar
Ar
N
AgOTf
THF
Cl
N
2 LiCH2SiMe3
N
N
Ti THF
OTf
Ti
THF
Cl
N
-Ag0
N
-THF
-2 LiCl
SiMe3
Ar
-
SiMe4
Ar
Ar
2-THF
1
-Ag0
AgOTf
pentane
H
Ar
Ar
-
SiMe4
THF
-THF
OTf
SiMe3
OTf
N
N
C6H6
60 oC
70 min
Ti
Ti
another
product
+
N
NAr
CH
Ar
2
SiMe3
Scheme 1.

F. Basuli et al. / Journal of Organometallic Chemistry 692 (2007) 3115–3120
3117
hulking isopropyl groups up and down relative to the
TiNCCCN framework. Consequently, this feature maxi-
mizes steric repulsion with the trimethylsilyl group, hence
making these ligands orient opposite of each other and in
one direction (propeller-like fashion). A selected list of met-
rical parameters for the molecular structure of 1 are dis-
played with Fig. 1.
mined one of the compounds resulting from solution
decomposition of 2 and found it to be the cross-metathesis
product [ArNC(Me)CHC(Me)@CHSiMe3]Ti@NAr(OTf)
(3) along with another species (which we have not
identified) in a 3:1 ratio, respectively (Scheme 1). Based
1
on H NMR spectra, the latter product does not appear
to be the intramolecular double C–H metallated product:
an analogous byproduct formed from the decomposition
of (nacnac)Ti@CHtBu(OTf), namely the complex
Ti(OTf){[2,6-(CMe2)(CHMe2)C6H3]NC(Me)}2CH [38,36].
We do however, observe SiMe4 in the mixture, but have
not been able to separate the second metal-based product.
Separation of 3 was achieved by extracting the reaction
mixture with hexane, filtering, and crystallizing the filtrate
at À35 °C. Formation of compound 3 is supported by a
In the absence of oxidants or moisture, compound 1 is
remarkably stable. However, exposure of 1 to an oxidant
such as AgOTf in THF evinces an immediate color change
from blue-green to red-brown concurrent with formation
of Ag0 mirror. Filtration of the metal, and subsequent
work-up of the reaction mixture results in the isolation of
brown blocks of the trimethylsilylmethylidene complex
(nacnac)Ti@CHSiMe3(OTf)(THF) (2)-THF (Scheme 1).
1
1
The H NMR spectrum of 2-THF reveals a highly down-
combination of H, 13C, and 19F NMR spectra as well as
field a-alkylidene hydrogen resonance at 12.30 ppm as well
as a complex retaining an equivalent of THF. In addition,
the 13C NMR spectrum clearly exposes a highly deshielded
alkylidene carbon resonance at 319.4 ppm with a JC–H
component of 106 Hz. This latter feature suggests moder-
ate a-hydrogen agostic interaction taking place with the
metal center and presents 2-THF to be less electrophilic
at Ti(IV), when compared to (nacnac)Ti@CHtBu(OTf)
(JC–H = 96 Hz) [38,36]. Formation of a OTfÀ complex in
2-THF is also evident from the 19F NMR spectrum (singlet
resonance at À77.8 ppm). We speculated whether complex
2-THF possessed a smaller a-hydrogen agostic interaction
due to higher coordination number at Ti(IV) via binding of
THF to the metal center. With this hypothesis in mind,
complex 2-THF was subjected to dynamic vacuum over
several hours, with only partial elimination of THF (20%
conversion to a new product after 24 h), which we attribute
to the low-coordinate species (nacnac)Ti@CHSiMe3(OTf)
(2) (Scheme 1). Solutions of 1 also decompose at room tem-
perature and in the absence of dynamic vacuum. However,
solutions of 2 were marred with content of starting mate-
rial, in addition to two new decomposition products (vide
infra). Independently, complex 2 can be generated cleanly,
via one-electron oxidation of 1 with AgOTf in pentane
comparison of its spectral shifts with the previously
reported
analogue
[ArNC(Me)CHC(Me)@CHtBu]Ti
@NAr(OTf) [38,36]. Our earlier reports revealed that com-
plex (nacnac)Ti@CHtBu(OTf) had an estimated t1/2 of 45
min at 57 °C and that complete decomposition typically
occurred over ꢀ2 h [38,36]. In comparison, compound 2
transforms at room temperature over a period of 34 h
and decomposes completely within 70 min at 60 °C. There-
fore, it appears that the titanium trimethylsilylmethylidene
is thermally less stable than the neopentylidene derivative,
but not significantly. This implies that complex 2, despite
having a more delocalized charge at the alkylidene carbon,
might display enhanced reactivity given the more exposed
nature of the alkylidene unit. The latter property could
facilitate faster intramolecular cross-metathesis of the alky-
lidene with the nacnac imine residue more than with the
bulkier neopentylidene ligand.
Single crystal X-ray analysis of 2-THF clearly exposes a
rare example of a five-coordinate titanium complex bearing
a terminal trimethylsilylmethylidene functionality (Ti@C,
˚
1.863(3) A, Fig. 2). Binding of a THF ligand is also evident
˚
(Ti–O, 2.155(2) A) thus resulting in a pseudo square pyra-
mid geometry at titanium, whereby the alkylidene moiety
˚
occupies the axial position. The Ti atom sits ꢀ0.448 A
1
(76% isolated yield, Scheme 1). H, 13C, and 19F NMR
above the mean plane defined by the b-diketiminate nitro-
gens, and the THF and OTfÀ oxygen atoms. Distortion
about the trimethylsilylmethylidene unit is clearly evident
from the obtuse Ti–C–Si angle of 156.4(2)°, which is also
diagnostic of 2-THF enjoying from an a-hydrogen agostic
interaction. Coordination of THF renders the system C1
symmetric in the solid state structure. However, the solu-
tion NMR (1H and 13C, vide supra) spectrum of 2-THF
is consistent with this system having Cs symmetry thus
implying that a rapid fluxional process by which THF dis-
sociates in solution, might be operational. Other salient
parameters associated with the solid state structure of 2-
THF are shown with Fig. 2.
spectra are essentially analogous to its solvated counter-
1
part, 2-THF. Despite this similarity, the H NMR spec-
trum shows a slight deviation in the chemical shift for the
alkylidene hydrogen (12.39 ppm), while the 13C NMR
spectrum displays a further downfield chemical shift at
320.1 ppm, congruently with a stronger TiÁ Á ÁH a-hydrogen
agostic interaction (when compared to 2-THF) taking
place with the four-coordinate metal center (JC–H
=
98 Hz) [38,36]. This feature implies that coordination of
THF is not a necessity for the stability of 2, and that
binding of the Lewis base to the Ti(IV) center reduces the
a-hydrogen agostic interaction. As anticipated, addition
of THF to 2 rapidly generates 2-THF quantitatively
(Scheme 1).
The two alkylidene systems presented here represent a
new class of titanium trimethylsilylmethylidene complexes
that can be readily assembled by a facile one-electron
oxidatively induced a-hydrogen abstraction reaction
As observed with 2-THF, complex 2 also decomposes in
solution at room temperature over 34 h. We have deter-

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F. Basuli et al. / Journal of Organometallic Chemistry 692 (2007) 3115–3120
˚
4 A molecular sieves were activated under vacuum over-
night at 200 °C. Li(nacnac)[35] (nacnacÀ = [ArNC
(Me)]2CH, Ar = 2,6-iPr2C6H3) and (nacnac)TiCl2(THF)
[39,36] were prepared according to the literature. LiCH2-
SiMe3 was purchased from Aldrich in a pentane solution,
filtered, concentrated and cooled to À35 °C to afford white
crystals of the alkyl reagent. All other chemical were used
as received. CHN analyses were performed by Desert Ana-
1
lytics, Tucson, AZ. H, 13C, 19F, and 31P NMR spectra
were recorded on Varian 400 or 300 MHz NMR spectrom-
1
eters. H and 13C NMR are reported with reference to sol-
vent resonances (residual C6D5H in C6D6, 7.16 ppm and
128.0 ppm). 19F NMR chemical shifts are reported with
respect to external HOCOCF3 (À78.5 ppm). Solution mag-
netization measurements were determined by the method
of Evans [42,43]. X-ray diffraction data were collected on
a SMART6000 (Bruker) system under a stream of N2 (g)
at low temperatures [44,45].
Fig. 2. Molecular structure of 2-THF displaying thermal ellipsoids at the
50% probability level. Hydrogen atoms have been omitted for the purpose
of clarity. Selected metrical parameters are reported in A (distances) and °
˚
2.2. Preparation of (nacnac)Ti(CH2SiMe3)2 (1)
(angles). Ti1–C33, 1.863(3); Ti1–O46, 2.155(2); Ti1–N2, 2.048(2); Ti1–N6,
2.136(2); Ti1–O38, 2.073(2); N2–C3, 1.363(4); C3–C4, 1.378(4); C4–C5,
1.402(4); C5–N6, 1.331(3); Ti1–C33–Si34, 156.4(2); N6–Ti1–N2, 89.05(9);
O38–Ti1–C33, 111.9(2); O38–Ti1–N2, 143.72(9); O38–Ti1–N6, 85.43(8);
O38–Ti1–O46, 83.07(8); O46–Ti1–N2, 93.99(9); O46–Ti1–N6, 164.40(9);
O46–Ti1–C33, 95.2(1); C33–Ti1–N2, 104.4(2); C33–Ti1–N6, 98.9(1).
In
a round bottom flask was suspended (nac-
nac)TiCl2(THF) [300 mg, 0.49 mmol] in Et2O (50 mL)
and the solution was cooled to À35 °C. To the cold solu-
tion was added an equally cold Et2O (ꢀ20 mL) solution
containing LiCH2SiMe3 [95.2 mg, 1.01 mmol]. After stir-
ring for 5 h the blue-green solution was filtered and dried
in vacuo. The filtrate residue was dissolved in pentane
and re-filtered. The pentane filtrate was reduced in volume
and cooled to À35 °C to afford 1 as dark blue-green crys-
tals [233 mg, 0.36 mmol, 73% yield]. For 1: 1H NMR
(C6D6, 300.1 MHz, 25 °C): d 5.64 (Dm1/2 = 21 Hz), 5.26
[15,16,40]. Depending on the nature of the solvent (THF
vs. pentane), higher coordination numbers about the metal
center can be conveniently suppressed. Consequently, the
lower coordination number results in a more electron defi-
cient metal center, and an enhanced interaction of the
metal with the a-hydrogen on the alkylidene ligand. Given
the unsaturated nature and oxophilicity of the titanium
presented here, compounds such 2 and 2-THF might be
excellent scaffolds for olefin metathesis or Wittig-like trans-
formations [28], and we are currently exploring their reac-
tion potential.
(Dm1/2 = 18 Hz), 3.09 (Dm1/2 = 28 Hz), 2.78 (Dm1/2
=
63 Hz), À0.11 (Dm1/2 = 38 Hz). Evans Magnetic Moment
(C6D6, 298 K): leff = 1.91 lB. Anal. Calc. for C37H63-
N2Si2Ti: C, 69.44; H, 9.92; N, 4.38. Found: C, 69.08; H,
9.71; N, 4.46%.
2. Experimental
2.3. Preparation of (nacnac)Ti = CHSiMe3(OTf)(THF)
(2)-THF
2.1. General considerations
In
a scintillation vial was dissolved 1 [100 mg,
Unless otherwise stated, all operations were performed
in a M. Braun Lab Master double-dry box under an atmo-
sphere of purified nitrogen or using high vacuum standard
Schlenk techniques under an argon atmosphere. Anhy-
drous n-hexane, pentane, toluene, and benzene were pur-
chased from Aldrich in sure-sealed reservoirs (18 L) and
dried by passage through two columns of activated alu-
mina and a Q-5 column [41]. Diethylether was dried by pas-
sage through a column of activated alumina [41]. THF was
distilled, under nitrogen, from purple sodium benzophe-
none ketyl and stored under sodium metal. Distilled THF
was transferred under vacuum into bombs before being
transferred into a dry box. C6D6 was purchased from Cam-
bridge Isotope Laboratory (CIL), degassed and vacuum
0.16 mmol] in THF (10 mL) and the solution was cooled
to À35 °C. To the cold blue-green solution was added a
cold (À35 °C) THF (5 mL) solution of AgOTf [40.95 mg,
0.16 mmol] which caused a rapid color change to red-
brown concurrent with formation of a silver mirror. The
solution was stirred for 30 min and filtered. The filtrate
was then dried in vacuo and dissolved in pentane. This
was followed by filtration, and the resulting red-brown
solution was reduced in volume under vacuo and cooled
to À35 °C to yield 2-THF as dark blocks [98 mg,
0.13 mmol, 81% yield]. For 2-THF: 1H NMR (23 °C,
399.8 MHz, C6D6): d 12.30 (s, 1H, Ti@CHSiMe3), 7.20–
7.14 (m, 6H, ArH), 4.86 (s, 1H, ArN(Me)CCHC(Me)NAr),
3.64 (br, 4H, THF), 3.47 (septet, 2H, CHMe2), 2.86 (septet,
2H, CHMe2), 1.63 (d, 6H, CHMe2), 1.49 (s, 6H, ArN
˚
transferred to 4 A molecular sieves. Celite, alumina, and

F. Basuli et al. / Journal of Organometallic Chemistry 692 (2007) 3115–3120
3119
(Me)CCHC(Me)NAr), 1.45 (br, 4H, THF), 1.39 (d, 6H,
CHMe2), 1.29 (d, 6H, CHMe2), 1.10 (d, 6H, CHMe2),
À0.25 (s, 9H, Ti@CHSiMe3). 13C NMR (23 °C, 100.6
MHz, C6D6): d 319.4 (Ti@CHSiMe3, JC–H = 106 Hz),
167.7 (ArN(Me)CCHC(Me)NAr), 145.3 (C6H3), 142.8
(C6H3), 140.5 (C6H3), 124.6 (C6H3), 124.5 (C6H3), 96.77
(ArN(Me)CCHC(Me)NAr), 69.14 (THF), 30.17 (CHMe2),
28.82 (CHMe2), 27.51 (THF), 25.80 (Me), 24.72 (Me),
24.54 (Me), 24.44 (Me), 23.67 (Me), 0.80 (Ti@CH–SiMe3).
19F NMR (23 °C, 282.3 MHz, C6D6): d À77.76 (s,
TiO3SCF3). Anal. Calc. for C38H59N2SiO4SF3Ti : C,
59.04; H, 7.69; N, 3.62. Found: C, 58.96; H, 7.89; N, 3.63%.
399.8 MHz, C6D6): d 7.09–6.80 (m, 6H, ArH), 5.06 (s,
1H, ArN(Me)CCHC(Me)NAr), 3.80 (septet, 2H, CHMe2),
2.01–2.11 (br, 5H, isopropyl methine and backbone Me
resonances overlapped), 1.81 (s, 1H, HCSiMe3C(-
Me)CHC(Me)), 1.58 (s, 3H, ArN(Me)CCHC(Me)CH-
SiMe3), 1.44 (d, 6H, CHMe2), 1.18 (d, 6H, CHMe2), 1.06
(d, 6H, CHMe2), 0.87 (d, 6H, CHMe2), 0.25 (s, 9H,
CHSiMe3). 13C NMR (23 °C, 100.6 MHz, C6D6): d 168.3
(ArN(Me)CCHC(Me)), 158.7 (SiMe3CHC(Me)CHC(Me)),
145.4 (C6H3), 143.3 (SiMe3CHC(Me)CHC(Me)), 139.6
(C6H3), 125.5 (C6H3), 123.9 (C6H3), 123.8 (C6H3), 122.6
(br, CF3), 119.5 (C6H3), 100.7 (ArN(Me)CCHC(Me)CH-
SiMe3), 31.97 (CHMe2), 29.56 (CHMe2), 28.43 (Me),
27.85 (Me), 24.81(Me), 24.32 (Me), 23.41 (Me), 14.35
(Me), 1.02 (CHSiMe3). 19F NMR (23 °C, 282.3 MHz,
C6D6): d À75.78 (s, TiO3SCF3).
2.4. Preparation of (nacnac)Ti@CHSiMe3(OTf) (2)
In a vial was dissolved 1 [215 mg, 0.33 mmol] in pentane
(10 mL) and the solution was cooled to À35 °C. To the
blue-green solution was added solid AgOTf [103.58 mg,
0.40 mmol] causing a color change to red-brown with for-
mation of silver metal. The solution was stirred for
45 min. The solution was then filtered and the resulting
red-brown filtrate solution was reduced in volume under
vacuo, and cooled to À35 °C to yield 2 as dark crystals
[176 mg, 0.25 mmol, 76% yield]. Note: Complex 2 can be
generated from the evacuation of 2-THF, albeit at a very
slow rate (after 24 h only 20% conversion occurred). Com-
plete conversion of 2-THF to 2 is never observed. For 2: 1H
NMR (23 °C, 399.8 MHz, C6D6): d 12.39 (s, 1H, Ti@CH-
SiMe3), 7.20–7.09 (m, 6H, ArH), 4.77 (s, 1H, ArN(-
Me)CCHC(Me)NAr), 3.39 (septet, 2H, CHMe2), 2.94
(septet, 2H, CHMe2), 1.70 (d, 6H, CHMe2), 1.46 (s, 6H,
ArN(Me)CCHC(Me)NAr), 1.38 (d, 6H, CHMe2), 1.33 (d,
6H, CHMe2), 1.06 (d, 6H, CHMe2), À0.31 (s, 9H, Ti@CH-
SiMe3). 13C NMR (23 °C, 100.6 MHz, C6D6): d 320.1
(Ti@CHSiMe3, JC–H = 98 Hz), 167.8 (ArN(Me)CCHC(-
Me)NAr), 145.0 (C6H3), 142.8 (C6H3), 140.3 (C6H3),
124.6 (C6H3), 124.5 (C6H3), 96.07 (ArN(Me)CCHC(Me)-
NAr), 30.28 (CHMe2), 28.91 (CHMe2), 25.95 (Me), 24.69
(Me), 24.49 (Me), 24.39 (Me), 23.51 (Me), 0.69 (Ti@CH-
SiMe3). 19F NMR (23 °C, 282.3 MHz, C6D6): d À77.86
(s, TiO3SCF3).
2.6. X-ray crystallographic data
Crystal data for C37H63N2Si2Ti, 1: M = 639.97, Mono-
clinic, space group P2(1)/n, a = 10.1486(5), b = 21.5396
˚
(10), c = 17.9677(9) A, b = 91.2250(10)°, a = c = 90°,
U = 3926.8(3) A [3], Z = 4, Dc = 1.083 g cmÀ3
, l(Mo
˚
Ka) = 0.304 mmÀ1, T = 138(2) K, Bruker SMART 6000,
total reflections 169,258, unique reflections F > 4r(F)
14,252, observed reflections 9426 (Rint = 0.0780). The
structure was solved using SHELXS-97 and refined with
SHELXL-97. A direct-methods solution was calculated which
provided most non-hydrogen atoms from the E-map. Full-
matrix least squares/difference Fourier cycles were per-
formed which located the remaining non-hydrogen atoms.
All non-hydrogen atoms were refined with anisotropic dis-
placement parameters. All hydrogen atoms were located in
subsequent Fourier maps and included as isotropic con-
tributors in the final cycles of refinement. GOF = 0.991
and the final refinement converged at R(F) = 0.0403
(observed data) and wR(F2) = 0.1136 (refinement data).
Crystal
data
for
C38H59F3N2O4SSiTi,
2-THF:
M = 772.92, Orthorhombic, space group Pbca, a =
˚
19.4455(14), b = 18.7889(13), c = 22.4337(16) A, a = b =
3
c = 90°, U = 8196.4(10) A , Z = 8, Dc = 1.253 g cmÀ3
,
˚
l(Mo Ka) = 0.342 mmÀ1, T = 136(2) K, Bruker SMART
6000, total reflections 117,790, unique reflections
F > 4r(F) 9427, observed reflections 5824 (Rint = 0.0938).
The structure was solved using SHELXS-97 and refined with
SHELXL-97.2. A direct-methods solution was calculated
which provided most non-hydrogen atoms from the
E-map. Full-matrix least squares/difference Fourier cycles
were performed which located the remaining non-hydrogen
atoms. All non-hydrogen atoms were refined with
anisotropic displacement parameters. Many of the hydro-
gen atoms were visible in subsequent difference Fourier
synthesis maps, and all hydrogens were included as either
isotropically refined or in idealized riding positions.
GOF = 1.033, and the final refinement converged at
R(F) = 0.0612 (observed data) and wR(F2) = 0.1845
(refinement data).
2.5. Thermolysis of (nacnac)Ti@CHSiMe3(OTf) (2):
synthesis of
[ArNC(Me)CHC(Me)@CHSiMe3]Ti@NAr(OTf) (3)
In a Schlenk flask was dissolved 2 [250 mg, 0.36 mmol]
in 20 ml of benzene and the solution was heated to 60 °C
for 70 min, upon which a benzene insoluble precipitate
formed. Monitoring the reaction mixture revealed two
products to form in a 3:1 ratio approximately. The mixture
was filtered, dried under reduced pressure and extracted
with hexane. Recrystallization from concentrated hexane
solution afforded brown color crystals of 3 [major product,
165 mg, 0.24 mmol, 66% yield]. Attempts to isolate the sec-
ond product were hampered by its high solubility in most
common organic solvents. For 3: 1H NMR (23 °C,

3120
F. Basuli et al. / Journal of Organometallic Chemistry 692 (2007) 3115–3120
[16] D.J. Mindiola, B.C. Bailey, F. Basuli, Eur. J. Inorg. Chem. (2006)
Acknowledgements
3335–3346.
[17] B.C. Bailey, H. Fan, E.W. Baum, J.C. Huffman, M.-H. Baik, D.J.
Mindiola, J. Am. Chem. Soc. 127 (2005) 16016–16017.
[18] J. Yamada, M. Fujiki, K. Nomura, Organometallics 24 (2005) 2248–
2250.
[19] L. Fan, B.M. Foxman, O.V. Ozerov, Organometallics 23 (2004) 326–
328.
[20] L. Fan, L. Yang, C. Guo, B.M. Foxman, O.V. Ozerov, Organomet-
allics 23 (2004) 4778–4787.
[21] O.V. Ozerov, C. Guo, L. Fan, B.M. Foxman, Organometallics 23
(2004) 5573–5580.
We thank Indiana University-Bloomington, the Camille
and Henry Dreyfus Foundation, the Alfred P. Sloan Foun-
dation (fellowship award to D.J.M.), and the National Sci-
ence Foundation (CHE-0348941, PECASE award) for
financial support of this research.
Appendix A. Supplementary material
[22] O.V. Ozerov, C. Guo, V.A. Papkov, B.M. Foxman, J. Am. Chem.
Soc. 126 (2004) 4792–4793.
[23] B.C. Bailey, J.C. Huffman, D.J. Mindiola, W. Weng, O.V. Ozerov,
Organometallics 24 (2005) 1390–1393.
[24] M.D. Fryzuk, P.B. Duval, S.S.S.H. Mao, M.J. Zaworotko, L.R.
MacGillivray, J. Am. Chem. Soc. 121 (1999) 2478–2487.
[25] M.D. Fryzuk, P.B. Duval, S.S.S.H. Mao, S.J. Rettig, M.J.
Zaworotko, L.R. MacGillivray, J. Am. Chem. Soc. 121 (1999)
1707–1716.
CCDC 628378 and 628379 contain the supplementary
crystallographic data for this paper. These data can be
obtained free of charge via http://www.ccdc.cam.ac.uk/
conts/retrieving.html, or from the Cambridge Crystallo-
graphic Data Centre, 12 Union Road, Cambridge CB2
1EZ, UK; fax: (+44) 1223-336-033; or e-mail: depos-
it@ccdc.cam.ac.uk. Supplementary data associated with
this article can be found, in the online version, at
doi:10.1016/j.jorganchem.2007.03.033.
[26] J.L. Polse, A.W. Kaplan, R.A. Andersen, R.G. Bergman, J. Am.
Chem. Soc. 120 (1998) 6316–6328.
[27] J.L. Polse, R.A. Andersen, R.G. Bergman, J. Am. Chem. Soc. 118
(1996) 8737–8738.
References
[28] N.A. Petasis, J.P. Staszewski, D.-K. Fu, Tetrahedron Lett. 36 (1995)
3619–3622.
´
´
[1] M.V. Galakhov, M. Gomez, P. Gomez-Sal, P. Velasco, Eur. J. Inorg.
[29] T.E. Hanna, I. Keresztes, E. Lobkovsky, W.H. Bernskoetter, P.J.
Chirik, Organometallics 23 (2004) 3448–3458.
[30] P.N. Riley, P.E. Fanwick, I.P. Rothwell, Chem. Commun. (1997)
1109–1110.
Chem. (2006) 4242–4253.
[2] R.R. Schrock, Chem. Rev. 102 (2002) 145–179.
[3] J.B. Diminnie, H.D. Hall, Z. Xue, Chem. Commun. (1996) 2383–
2384.
[31] P.N. Riley, P.E. Fanwick, I.P. Rothwell, Dalton Trans. (2001) 181–
186.
[4] I. De Castro, J. De la Mata, M. Gomez, P. Gomez-Sal, P. Royo,
J.M. Selas, Polyhedron 11 (1992) 1023–1027.
[32] R.R. Schrock, J.D.J. Fellmann, J. Am. Chem. Soc. 100 (1978) 3359–
3370.
[5] L. Li, J.B. Diminnie, X. Liu, J.L. Pollitte, Z. Xue, Organometallics
15 (1996) 3520–3527.
[33] H. Zieger, C. Perri, K. Bharucha, Tetrahedron Lett. 28 (1987) 5989–
5992.
[6] L.R. Chamberlain, I.P. Rothwell, K. Folting, J.C. Huffman, Dalton
Trans. (1972–1999) (1987) 155–162.
[34] M. Hage, C.A. Ogle, T.L. Rathman, J.L. Hubbard, Main Group
Metal Chem. 21 (1998) 777–781.
[7] L. Chamberlain, I.P. Rothwell, J.C. Huffman, J. Am. Chem. Soc. 104
(1982) 7338–7340.
[35] M. Stender, R.J. Wright, B.E. Eichler, J. Prust, M.M. Olmstead,
H.W. Roesky, P.P. Power, Dalton Trans. (2001) 3465–3469.
[36] F. Basuli, B.C. Bailey, J. Tomaszewski, J.C. Huffman, D.J. Mindiola,
J. Am. Chem. Soc. 125 (2003) 6052–6053.
[8] A.V. Safronova, L.N. Bochkarev, N.E. Stolyarova, I.K. Grigorieva,
I.P. Malysheva, G.V. Basova, G.K. Fukin, Y.A. Kurskii, S.Y.
Khorshev, G.A.J. Abakumov, Organomet. Chem. 689 (2004) 1127–
1130.
[37] F. Basuli, B.C. Bailey, J.C. Huffman, D.J. Mindiola, Organometallics
24 (2005) 3321–3334.
[9] P.A. Van der Schaaf, W.J.J. Smeets, A.L. Spek, G. Van Koten,
Chem. Commun. (1992) 717–719.
[38] F. Basuli, B.C. Bailey, L.A. Watson, J. Tomaszewski, J.C. Huffman,
D.J. Mindiola, Organometallics 24 (2005) 1886–1906.
[39] P.H.M. Budzelaar, A.B. Van Oort, A.G. Orpen, Eur. J. Inorg. Chem.
(1998) 1485–1494.
[40] K.M. Smith, Organometallics 24 (2005) 778–784.
[41] A.B. Pangborn, M.A. Giardello, R.H. Grubbs, R.K. Rosen, F.J.
Timmers, Organometallics 15 (1996) 1518–1520.
[42] S.K. Sur, J. Magnet. Reson. (1969–1992) 82 (1989) 169–173.
[43] D.F. Evans, J. Chem. Soc. (1959) 2003–2005.
[44] SAINT 6.1, B.A.X.-R.S., Madison, WI.
[10] P.A. van der Schaaf, D.M. Grove, W.J.J. Smeets, A.L. Spek, G. van
Koten, Organometallics 12 (1993) 3955–3963.
[11] P.A. Van der Schaaf, R.A.T.M. Abbenhuis, D.M. Grove, W.J.J.
Smeets, A.L. Spek, G. Van Koten, Chem. Commun. (1993) 504–
506.
[12] P.A. van der Schaaf, R.A.T.M. Abbenhuis, W.P.A. van der Noort,
R. de Graaf, D.M. Grove, W.J.J. Smeets, A.L. Spek, G. van Koten,
Organometallics 13 (1994) 1433–1444.
[13] L.A. Morton, R. Wang, X. Yu, C.F. Campana, I.A. Guzei, G.P.A.
Yap, Z.-L. Xue, Organometallics 25 (2006) 427–434.
[14] C.B. Pamplin, P. Legzdins, Acc. Chem. Res. 36 (2003) 223–233.
[15] D.J. Mindiola, Acc. Chem. Res. 39 (2006) 813–821.
[45] SHELXTL-PLUS V5.10, Bruker Analytical X-ray Systems, Madison,
WI.