Intramolecular C-H activation reactions derived from a terminal titanium neopentylidene functionality. redox-controlled 1,2-addition and α-hydrogen abstraction reactions

Article abstract of DOI:10.1021/om049318g

The alkylation of the neopentylidene titanium(IV) complex resulting from the intramolecular C-H activation reactions, was analyzed along with the redox-controlled 1,2-addition and α-hydrogen abstraction reactions. The titanium(IV) complex was fully characterized, and the molecular structure disclosed a four-coordinate titanium complex having significant α-hydrogen agostic interaction. It was also found that one-electron reduction of the four-coordinate titanium alkylidene complexes afforded the Ti(III) metallacycles. The results show that the redox-controlled 1,2-addition and α-abstraction reactions are specific only to the isopropyl methyl attached to the aryl group of the β-diketiminate ligand.

Full text of DOI:10.1021/om049318g

Organometallics 2005, 24, 3321-3334
3321
Intramolecular C-H Activation Reactions Derived from
a Terminal Titanium Neopentylidene Functionality.
Redox-Controlled 1,2-Addition and r-Hydrogen
Abstraction Reactions
Falguni Basuli, Brad C. Bailey, John C. Huffman, and Daniel J. Mindiola*
Department of Chemistry and Molecular Structure Center, Indiana University,
Bloomington, Indiana 47405
Received September 1, 2004
-
Alkylation of the terminal neopentylidene titanium(IV) complex (L1)TidCHtBu(OTf) (L1
) [Ar]NC(Me)CHC(Me)N[Ar], Ar ) 2,6-(CHMe2)2C6H3) with LiCH2SiMe3 resulted in
formation of the alkylidene-alkyl species (L1)TidCHtBu(CH2SiMe3) (1) in 82% yield.
Compound 1 was fully characterized, and the molecular structure disclosed a four-coordinate
titanium complex having significant R-hydrogen agostic interaction and possessing terminal
alkylidene and alkyl functionalities. Attempts to alkylate (L1)TidCHtBu(OTf) with KCH2-
Ph in THF resulted in clean deprotonation of the methyl group attached to the â-carbon of
the diketiminate ligand to form the four-coordinate titanium(IV) neopentylidene-tetrahy-
2-
drofuran complex (L2)TidCHtBu(THF) (2; L2 ) [Ar]NC(Me)CH(CH2)N[Ar], 64% isolated
yield). Complex 2 was fully characterized and revealed a low-coordinate titanium(IV) in a
C1 environment, which is supported by a chelating bis-anilide ligand. Alkylation of the
-
alkylidene derivative (L3)TidCHtBu(OTf) (L3 ) [Ar]NC(tBu)CHC(tBu)N[Ar], Ar ) 2,6-
(CHMe2)2C6H3) with LiCH2SiMe3 or KCH2Ph resulted in clean formation of (L3)TidCHtBu-
(R) (R ) CH2SiMe3 (3), CH2Ph (4)). Complexes 3 and 4 were fully characterized, and the
structure of 4 was determined by single-crystal X-ray diffraction studies. Complex 1 was
found to decompose rapidly to several products, of which the titanacycle Ti[2,6-(CMe2)-
(CHMe2)C6H3]NC(Me)CHC(Me)N[2,6-(CMe2)(CHMe2)C6H3](CH2Si(Me)3) (5) and dimer [Tid
NAr([Ar]NC(Me)CHC(µ-CH2)dCHtBu)]2 (6) were formed. Complex 5 was prepared in better
yield through an independent synthesis involving Ti[2,6-(CMe2)(CHMe2)C6H3]NC(Me)CHC-
(Me)N[2,6-(CMe2)(CHMe2)C6H3](OTf) and LiCH2SiMe3. In THF complex 6 dissociated into
the corresponding monomer (tBuHCdC(CH2)CHC(CH3)N[Ar])TidNAr(THF) (8), quantita-
tively. Unlike complex 1, complexes 3 and 4 are kinetically more stable to intramolecular
Wittig-like and C-H abstraction reactions. It was also found that one-electron reduction of
the four-coordinate titanium alkylidene complexes (L1)TidCHtBu(OTf) and (L3)TidCHtBu-
(OTf) afforded the Ti(III) metallacycles ([Ar]NC(R)CHC(R)N[2,6-(CHMe2)(CH(CH2)(Me))-
t
t
C6H3])TiCH2 Bu (L42-, R ) Me (9); L52-, R ) Bu (10)), both resulting from 1,2-addition of
the proximal isopropyl CH3 group across the TidCHtBu bond. One-electron oxidation of 10
with AgOTf promotes R-abstraction to generate back the alkylidene precursor (L3)TidCHt-
Bu(OTf). The redox-controlled 1,2-addition and R-abstraction reactions are specific only to
the isopropyl methyl attached to the aryl group of the â-diketiminate ligand.
Introduction
reaction is Theopold’s putative CodO and CodNR
systems, which can activate a C-H bond of the methyl
group attached to a pyrazole arm of the Tp ligand.3 In
contrast to the later metals, seminal work by Wolczan-
ski and co-workers has shown
The activation and functionalization of carbon-
hydrogen bonds are important classes of reactions which
have generated considerable attention in the field of
organometallic chemistry. Selective functionalization of
alkanes typically involves late-transition-metal catalysts
composed of platinum,1 and these systems often contain
coordinately unsaturated metal centers.2 One possible
strategy to activate an inert C-H bond is to utilize
transition-metal complexes containing metal-ligand
multiple bonds. A clear illustration of this type of
(2) For some leading reviews and a general overview: (a) Pud-
dephatt, R. J. Coord. Chem. Rev. 2001, 219-221, 157-185. (b)
Crabtree, R. H., Ed. The Organometallic Chemistry of the Transition
Metals; Wiley: New York, 2001. (c) Activation and Functionalization
of Alkanes; Hill, C. L., Ed.; Wiley-Interscience: New York, 1989. (d)
Shilov, A. E.; Shul’pin, G. B. Activation and Catalytic Reactions of
Saturated Hydrocarbons in the Presence of Metal Complexes; Kluwer
Academic: Dordrecht, The Netherlands, 2000. (e) Crabtree, R. H.
Chem. Rev. 1985, 85, 245-269. (f) Amdtsen, B. A.; Bergman, R. G.;
Mobley, T. A.; Peterson, T. H. Acc. Chem. Res. 1995, 28, 154-162. (g)
Crabtree, R. H. Chem. Rev. 1995, 95, 987. (h) Shilov, A. E.; Shul’pin,
G. B. Chem. Rev. 1997, 97-98, 2879-2932. (i) Crabtree, R. H. Dalton
2001, 2437-2450.
* To whom correspondence should be addressed. Phone: 812-855-
2399. Fax: 812-855-8300. E-mail: mindiola@indiana.edu.
(1) (a) Labinger, J. A.; Bercaw, J. E. Nature 2002, 417, 507-514
and references therein. (b) Stahl, S. S.; Labinger, J. A.; Bercaw, J. E.
Angew. Chem., Int. Ed. 1998, 37, 2180-2192.
10.1021/om049318g CCC: $30.25 © 2005 American Chemical Society
Publication on Web 05/26/2005

3322 Organometallics, Vol. 24, No. 13, 2005
Basuli et al.
Scheme 1
that low-coordinate group 4 complexes supported by
sterically demanding ligands (tBu3SiNH- and tBu3SiO-)
can generate, through an R-abstraction process, three-
and four-coordinate imido complexes capable of activat-
ing C-H bonds.4 Likewise, Bergman and co-workers
have established that alkanes and sp2 C-H bonds can
be activated under mild conditions by zirconium bis-
(cyclopentadienide) imido systems.5 Girolami, Gibson,
Hessen, and Legzdins have also established that un-
saturated complexes having an alkylidene ligand can
promote intermolecular C-H activation reactions.6
As opposed to intermolecular C-H activation reac-
tions in group 4, Chirik and co-workers recently pro-
posed that a transient titanium diphenylalkylidene
species can activate, via an intramolecular reaction, two
sp3 C-H bonds from SiMe3 groups attached to a Cp
ring.7a This type of reaction follows pioneering work by
Bercaw and co-workers on group 4 metals.7b,c Previous
work has also proposed that unsaturated and electron-
deficient metal systems of group 4 alkylidenes can
engage in intramolecular C-H activation reactions.8
One such transformation occurs by addition of one C-H
bond of a phenyl group in a bulky (phenylphosphino)-
alkoxide ligand across the double-bond system of a
transient titanium-alkylidene species.8a
Our interest in low-coordinate and early-transition-
metal systems having metal-ligand multiple bonds9
stimulated the quest for group 4 complexes having the
capability of activating rather inert and hindered C-H
bonds. â-Diketiminates have become popular ligands in
the past few years10 and are pivotal in the construction
of reactive metal fragments. Such fragments are capable
of activating innocent molecules such as N2,11 as well
as inert C-H bonds.12 In addition, the ligand has been
demonstrated to kinetically stabilize low-coordinate and
reactive metal-ligand multiple bonds.9,13 Recently, we
discovered that four-coordinate titanium alkylidenes,
when thermolyzed, can undergo facile C-H activation
of two tertiary carbons.14,15 This work established a
C-H bond cleavage reaction by which two methine
groups are selectively activated under mild conditions.14
Scheme 1 depicts three distinct intramolecular reactions
in which a reactive TidCalkylidene functionality becomes
involved with primary,7b secondary,8a and tertiary14
C-H bonds.
(3) (a) Egan, J. W., Jr.; Haggerty, B. S.; Rheingold, A. L.; Sendlinger,
S. C.; Theopold, K. H. J. Am. Chem. Soc. 1990, 112, 2445-2446. (b)
Thyagarajan, S.; Incarvito, C. D.; Rheingold, A. L.; Theopold, K. H.
Chem. Commun. 2001, 2198-2199. (c) Thyagarajan, S.; Shay, D. T.;
Incarvito, C. D.; Rheingold, A. L.; Theopold, K. H. J. Am. Chem. Soc.
2003, 125, 4440-4441. C-H activation in V(NR)2 has been reported:
(d) De With, J.; Horton, A. D. Angew. Chem., Int. Ed. Engl. 1993, 32,
903-905. A terminal imido complex of cobalt was recently isolated and
found to undergo intramolecular C-H activation: (e) Shay, D. T.; Yap,
G. P. A.; Zakharov, L. N.; Rheingold, A. L.; Theopold, K. H. Angew.
Chem., Int. Ed. 2005, 44, 1508-1510.
(4) (a) Cummins, C. C.; Baxter, S. M.; Wolczanski, P. T. J. Am.
Chem. Soc., 1988, 110, 8731-8733. (b) Cummins, C. C.; Schaller, C.
P.; Van Duyne, G. D.; Wolczanski, P. T.; Chan, A. W.; Hoffmann, R. J.
Am. Chem. Soc. 1991, 113, 2985-2994. For C-H activation reactions
involving Zr systems see: (c) Bennett, J. L.; Wolczanski, P. T. J. Am.
Chem. Soc. 1994, 116, 2179-2180. (d) Cummins, C. C.; Baxter, S. M.;
Wolczanski, P. T. J. Am. Chem. Soc. 1988, 110, 8731-8733. (e)
Schaller, C. P.; Wolczanski, P. T. Inorg. Chem. 1993, 32, 131-144. (f)
Schaller, C. P.; Cummins, C. C.; Wolczanski, P. T. J. Am. Chem. Soc.
1996, 118, 591-564. (g) Bennett, J. L.; Wolczanski, P. T. J. Am. Chem.
Soc. 1997, 119, 10696-10719. (h) Schafer, D. F.; Wolczanski, P. T. J.
Am. Chem. Soc. 1998, 120, 4881-4882.
(5) (a) Walsh, P. J.; Hollander, F. J.; Bergman, R. G. J. Am. Chem.
Soc. 1988, 110, 8729-8731. (b) Hoyt, H. M.; Michael, F. E.; Bergman,
R. G. J. Am. Chem. Soc. 2004, 126, 1018-1019 and references therein.
(6) (a) Adams, C. S.; Legzdins, P.; Tran, E. Organometallics 2002,
21, 1474-1486. (b) Wada, K.; Pamplin, C. B.; Legzdins, P. J. Am. Chem.
Soc. 2002, 124, 9680-9681. (c) Tran, E. Legzdins, P. J. Am. Chem.
Soc. 1997, 119, 5071-5072. (d) Coles, M. P.; Gibson, V. C.; Clegg, W.;
Elsegood, M. R. J.; Porreli, P. A. Chem. Commun. 1996, 1963-1964.
(e) Cheon, J.; Rogers, D. M.; Girolami, G. S. J. Am. Chem. Soc. 1997,
119, 6804-6813. (f) van der Heijden, H.; Hessen, B. Chem. Commun.
1995, 145-146.
(7) (a) Hanna, T. E.; Keresztes, I.; Lobkovsky, E.; Bernkoetter, W.
H.; Chirik, P. J. Organometallics 2004, 23, 3448-3458. (b) Bulls, A.
R.; Schaefer, W. P.; Serfas, M.; Bercaw, J. E. Organometallics 1987,
6, 1219-1226. (c) McDade, C.; Green, J. C.; Bercaw, J. E. Organome-
tallics 1982, 1, 1629-1634.
(8) (a) van Doorn, J. A.; van der Heijden, H.; Orpen, A. G. Organo-
metallics 1994, 13, 4271-4277. (b) van Doorn, J. A.; van der Heijden,
H.; Orpen, A. G. Organometallics 1995, 14, 1278-1283. For examples
of transient alkylidene species engaging in intramolecular C-H
activation reactions: (c) Deckers, P. J. W.; Hessen, B. Organometallics
2002, 21, 5564-5575. (d) Kickham, J. E.; Gue´rin, F.; Stephan, D. W.
J. Am. Chem. Soc. 2002, 124, 11486-11494. (e) Vilardo, J. S.;
Lockwood, M. A.; Hanson, L. G.; Clark, J. R.; Parkin, B. C.; Fanwick,
P. E.; Rothwell, I. P. J. Chem. Soc., Dalton Trans. 1997, 3353-3362.
(f) Chamberlain, L. R.; Rothwell, I. P.; Huffman, J. C. J. Am. Chem.
Soc. 1986, 108, 1502-1509. (g) Duncalf, D. J.; Harrison, R. J.;
McCamley, A.; Royan, B. W. J. Chem. Soc., Chem. Commun. 1995,
2421-2422.

Intramolecular C-H Activation Reactions
Organometallics, Vol. 24, No. 13, 2005 3323
Scheme 2
Figure 1. Perspective view of 1 with thermal ellipsoids
at the 50% probability level. Hydrogens, with the exception
of R-hydrogens, and aryl groups on the â-diketiminate, with
the exception of ipso carbons C(7) and C(21), have been
omitted for clarity. The R-hydrogens on C(33) and C(38)
were located and refined isotropically. Table 1 lists perti-
nent metrical parameters.
The present work describes the pursuit of titanium
alkylidynes as well as three-coordinate titanium alkyl-
idenes via a family of four-coordinate titanium alkyl-
idene species. In the process we discovered that the Tid
CHtBu unit can activate 1° and 3° C-H bonds. Hence,
one-electron reduction of Ti(IV) alkylidene complexes
leads to 1,2-addition of a 1° C-H bond to generate a
Ti(III) metallacycle, while one-electron oxidation of such
a metallacycle can regenerate the four-coordinate tita-
nium(IV) neopentylidene precursor via an oxidatively
induced R-hydrogen abstraction reaction. Low-coordi-
nate titanium alkylidenes and reversible 1,2-addition
and R-abstraction reactions of C-H bonds which appear
to be redox controlled will also be described.
(Me)CHC(Me)N[Ar], Ar ) 2,6-(CHMe2)2C6H3) reacts
rapidly with LiCH2Si(CH3)3 at -35 °C to yield the
titanium alkylidene-alkyl species (L1)TidCHtBu(CH2-
SiMe3) (1) as dark red blocks in 82% yield (Scheme 2).
Solutions of 1 must be worked up rapidly in order to
avoid significant decomposition (vide infra). 1H and 13
C
NMR spectra of isolated samples of 1 display features
consistent with the molecule retaining Cs symmetry in
solution. A CR resonance centered at δ 271 with a JC-H
coupling constant of 99 Hz was diagnostic of this
complex having a terminal alkylidene functionality.9a,16-18
No R-hydrogen abstraction or migration occurred during
the alkylation reaction, and the neopentylidene func-
tionality is thus conserved in complex 1. The JC-H
coupling values from the 13C NMR spectral data suggest
significant R-hydrogen agostic interaction with the
Results and Discussion
A pentane solution of the four-coordinate titanium
alkylidene complex (L1)TidCHtBu(OTf) (L1- ) [Ar]NC-
(9) (a) Basuli, F.; Bailey, B. C.; Tomaszewski, J.; Huffman, J. C.;
Mindiola, D. J. J. Am. Chem. Soc. 2003, 125, 6052-6053. (b) Basuli,
F.; Tomaszewski, J.; Huffman, J. C.; Mindiola, D. J. J. Am. Chem. Soc.
2003, 125, 10170-10171. (c) Basuli, F.; Bailey, B. C.; Huffman, J. C.;
Mindiola, D. J. Chem. Commun. 2003, 1554-1555. (d) Basuli, F.;
Huffman, J. C.; Mindiola, D. J. Inorg. Chem. 2003, 42, 8003-8010. (e)
Basuli, F.; Watson, L. A.; Huffman, J. C.; Mindiola, D. J. Dalton 2003,
4228-4229. (f) Basuli, F.; Bailey, B. C.; Huffman, J. C.; Baik, M.-H.;
Mindiola, D. J. J. Am. Chem. Soc. 2004, 126, 1924-1925. (g) Basuli,
F.; Kilgore, U. J.; Hu, X.; Meyer, K.; Pink, M.; Huffman, J. C.; Mindiola,
D. J. Angew. Chem., Int. Ed. 2004, 43, 3156-3159. (h) Basuli, F.;
Bailey, B. C.; Brown, D.; Tomaszewski, J.; Huffman, J. C.; Baik, M.-
H.; Mindiola, D. J. J. Am. Chem. Soc. 2004, 126, 10506-10507. (i)
Bailey, B. C.; Huffman, J. C.; Mindiola, D. J.; Weng, W.; Ozerov, O. V.
Organometallics 2005, 24, 1390-1393.
1
electron-deficient metal center.17,18 In addition, the H
NMR TidCHR resonance in 1 was located at 5.05 ppm
and differentiated from the CHγ resonance for the
Nacnac- backbone using HMQC NMR methods.19 To the
best of our knowledge, compound 1 represents the first
example of a relatively stable titanium system contain-
ing both terminal alkylidene and alkyl functionalities.
(10) For recent reviews on early-transition-metal nonmetallocene
and â-diketiminate complexes see: (a) Piers, W. E.; Emslie, D. J. H.
Coord. Chem. Rev. 2002, 233-234, 131-155. (b) Bourget-Merle, L.;
Lappert, M. F.; Severn, J. R. Chem. Rev. 2002, 102, 3031-3066.
(11) Smith, J. M.; Lachicotte, R. J.; Pittard, K. A.; Cundari, T. R.;
Lukat-Rodgers, G.; Rodgers, K. R.; Holland, P. L. J. Am. Chem. Soc.
2001, 123, 9222-9223.
(12) (a) Fekl, U.; Goldberg, K. I. J. Am. Chem. Soc. 2002, 124, 6804-
6805. (b) Fekl, U.; Kaminsky, W.; Goldberg, K. I. J. Am. Chem. Soc.
2003, 125, 15286-15287. (c) Fekl, U.; Goldberg, K. I. Adv. Inorg. Chem.
2003, 54, 259-320. C-H activation reactions have been reported for
analogous â-diketiminate Ir-hydride complexes: (d) Bernskoetter, W.
H.; Lobkovsky, E.; Chirik, P. J. Chem. Commun. 2004, 764-765.
(13) (a) Dai, X.; Kapoor, P.; Warren, T. H. J. Am. Chem. Soc. 2004,
126, 4798-4799. (b) Dai, X.; Warren, T. H. J. Am. Chem. Soc. 2004,
126, 10085-10094.
Single crystals of 1 were grown from pentane at -35
°C, and the molecular structure is depicted in Figure 1.
The structure of 1 reveals a low-coordinate titanium
center in a tetrahedral environment, having terminal
alkylidene and alkyl functionalities and displaying Cs
symmetry in the solid state. As with other four-
coordinate neopentylidene complexes prepared by our
group, complex 1 also possesses a short TidC bond
(16) Beckhaus, R. Angew. Chem., Int. Ed. 1997, 36, 687-713.
(17) Baumann, R.; Stumpf, R.; Davis, W. M.; Liang, L.-C.; Schrock,
R. R. J. Am. Chem. Soc. 1999, 121, 7822.
(14) Basuli, F.; Bailey, B. C.; Watson, L. A.; Tomaszewski, J.;
Huffman, J. C.; Mindiola, D. J. Organometallics 2005, 24, 1886-1906.
(15) Double C-H activation of two 1° carbons has been documented
recently for electron-deficient Rh(III) systems: (a) Dorta, R.; Stevens,
E. D.; Nolan, S. P. J. Am. Chem. Soc. 2004, 126, 5054-5055. (b) Scott,
N. M.; Dorta, R.; Stevens, E. D.; Correa, A.; Cavallo, L.; Nolan, S. P.
J. Am. Chem. Soc. 2005, 127, 3516-3526.
(18) (a) Schrock, R. R. Acc. Chem. Res. 1979, 12, 98-104. (b) Schrock,
R. R. Acc. Chem. Res. 1990, 23, 158-165. (c) Schrock, R. R. Chem.
Rev. 2002, 102, 145-179. (d) Schrock, R. R. In Reactions of Coordinated
Ligands; Braterman, P. R., Ed.; Plenum: New York, 1986. (e) Feldman,
J.; Schrock, R. R. Prog. Inorg. Chem. 1991, 39, 1.
(19) Summers, M. F.; Marzilli, L. G.; Bax, A. J. Am. Chem. Soc.
1986, 108, 4285-4294.

3324 Organometallics, Vol. 24, No. 13, 2005
Basuli et al.
Table 1. Selected Metrical Parameters for the Four-Coordinate Titanium Alkylidene
Structures 1, 2, and 4a
2
1
4
TidCR
Ti(1)-C(33) ) 1.855(4)
Ti(1)-N(2) ) 2.058(1)
Ti(1)-N(6) ) 2.046(1)
Ti(1)-C(38) ) 2.126(4)
Ti(1)-H ) 2.02(3)
Ti(1)-C(33) ) 1.86(1)
Ti(1)-N(2) ) 1.993(8)
Ti(1)-N(6) ) 1.942(9)
Ti(1)-O(38) ) 2.130(8)
n/a
Ti(1)-C(39) ) 1.852(6)
Ti-Na
Ti(1)-N(2) ) 2.031(2)
Ti-Na
Ti-XR
Ti-HR (agostic)
CR-HR
Ti(1)-N(6) ) 2.064(2)
Ti(1)-C(44) ) 2.162(6)
Ti(1)-H ) 1.96(8)
C(33)-H ) 0.93(3)
n/a
C(39)-H ) 0.99(8)
NR-Câ (N-ligand)
NR-Câ (N-ligand)
Câ-Cγ (N-ligand)
Câ-Cγ (N-ligand)
Ti-CR-Câ
CR-Ti-XR
NR-Ti-NR
CR-Ti-NR
CR-Ti-NR
XR-Ti-NR
XR-Ti-NR
Ti-NR-Cipso
Ti-NR-Cipso
Ti-CR-HR
Ti-NR-Câ
Ti-NR-Câ
NR-Câ-Cγ
NR-Câ-Cγ
Câ-Cγ-Câ
N(2)-C(3) ) 1.331(8)
N(6)-C(5) ) 1.348(8)
C(3)-C(4) ) 1.418(9)
C(5)-C(4) ) 1.407(2)
Ti(1)-C(33)-C(34) ) 158.3(1)
C(33)-Ti(1)-C(38) ) 108.58(6)
N(2)-Ti(1)-N(6) ) 93.66(5)
C(33)-Ti(1)-N(2) ) 106.48(5)
C(33)-Ti(1)-N(6) ) 116.03(5)
C(38)-Ti(1)-N(2) ) 111.61(5)
C(38)-Ti(1)-N(6) ) 118.93(5)
Ti(1)-N(2)-C(7) ) 126.46(9)
Ti(1)-N(6)-C(21) ) 132.13(9)
Ti(1)-C(33)-H ) 86(6)
N(2)-C(3) ) 1.42(2)
N(6)-C(5) ) 1.48(2)
C(3)-C(4) ) 1.39(3)
C(5)-C(4) ) 1.51(3)
Ti(1)-C(33)-C(34) ) 161.7(8)
C(33)-Ti(1)-O(38) ) 104.9(4)
N(2)-Ti(1)-N(6) ) 101.5(4)
C(33)-Ti(1)-N(2) ) 115.7(4)
C(33)-Ti(1)-N(6) ) 114.4(4)
O(38)-Ti(1)-N(2) ) 107.2(3)
O(38)-Ti(1)-N(6) ) 113.3(3)
Ti(1)-N(2)-C(7) ) 133.3(6)
Ti(1)-N(6)-C(21) ) 126.7(6)
n/a
N(2)-C(3) ) 1.355(9)
N(6)-C(5) ) 1.331(9)
C(3)-C(4) ) 1.401(2)
C(5)-C(4) ) 1.426(2)
Ti(1)-C(39)-C(40) ) 165.5(2)
C(39)-Ti(1)-C(44) ) 112.72(7)
N(2)-Ti(1)-N(6) ) 94.84(5)
C(39)-Ti(1)-N(2) ) 114.44(6)
C(39)-Ti(1)-N(6) ) 104.16(6)
C(44)-Ti(1)-N(2) ) 119.70(7)
C(44)-Ti(1)-N(6) ) 107.79(6)
Ti(1)-N(2)-C(7) ) 128.0(1)
Ti(1)-N(6)-C(27) ) 122.92(9)
Ti(1)-C(39)-H, 81(1)
Ti(1)-N(2)-C(3) ) 112.14(9)
Ti(1)-N(6)-C(5) ) 107.74(9)
N(2)-C(3)-C(4) ) 122.5(3)
N(6)-C(5)-C(4) ) 124.0(2)
C(3)-C(4)-C(5) ) 130.2(3)
Ti(1)-N(2)-C(3) ) 107.9(6)
Ti(1)-N(6)-C(5) ) 115.9(6)
N(2)-C(3)-C(4) ) 125.8(9)
N(6)-C(5)-C(4) ) 113.7(9)
C(3)-C(4)-C(5) ) 134(1)
Ti(1)-N(2)-C(3) ) 105.71(9)
Ti(1)-N(6)-C(5) ) 111.19(9)
N(2)-C(3)-C(4) ) 120.7(3)
N(6)-C(5)-C(4) ) 119.4(3)
C(3)-C(4)-C(5) ) 134.2(4)
a X represents -CH2Si(CH3)3 for 1, THF for 2, and -CH2Ph for 4. Bond distances are reported in Å and bond angles in deg.
length of 1.855(4) Å,9a,16,17,18c,20 In the structure of 1, the
tert-butyl group is along the σ-plane bisecting the
N-Ti-N plane and is oriented syn with respect to the
-CH2SiMe3 ligand. The TidCRHR hydrogen was located
and refined isotropically, and its position indicated
interaction with the metal center (Ti-HR ) 2.02(3) Å;
Table 1). Consequently, the CR-HR distance follows the
reciprocal trend and becomes much longer as a result
of R-hydrogen agostic interaction with the titanium
center (Table 1). As expected, the TidCR-Câ angle
(158.3(1)°) is obtuse and significantly different from that
for the Ti-CR-Siâ angle of the alkyl group (129.78(8)°).
Selected metrical parameters are displayed in Table 1,
and crystal data for 1 are shown in Table 2.
The choice of alkylating agent and solvent are critical,
inasmuch as attempts to alkylate (L1)TidCHtBu(OTf)
with KCH2Ph in THF do not lead to formation of
(L1)TidCHtBu(CH2Ph). Instead of alkylation, deproto-
nation of the methyl group attached to the â-carbon on
the Nacnac- ligand occurs to afford the four-coordinate
titanium(IV) neopentylidene-tetrahydrofuran complex
(L2)TidCHtBu(THF) (2) (L22- ) [Ar]NC(Me)CH(CH2)N-
[Ar]) in 64% yield (Scheme 2). Similar reactions have
been reported for titanium imides9d and Ge21 complexes
bearing this type of ligand. Previous work has also
demonstrated that deprotonation of the Me group at-
tached to the â-carbon on a â-diketiminate can often
lead to unprecedented binding of the ligand.22 Diagnos-
tic features for complex 2 include the observation (by
1H NMR spectra) of two inequivalent protons for the
â-carbon methylene group centered at 3.64 and 3.25
ppm. The two resonances were correlated to the sp2-
hydridized carbon at 83.0 ppm via HMQC experiments
(JC-H ) 161 Hz).19 A result from the methyl being
deprotonated is the loss of symmetry from Cs to C1,
which explains the spectroscopic observation of four
inequivalent isopropyl groups on the supporting N-
ligand. The alkylidene CR resonance was centered at δ
254 with a JC-H coupling constant of 93 Hz. As observed
in 1, the JC-H coupling from the 13C NMR spectral data
suggests an R-hydrogen agostic interaction taking place
in 2. Coordination of THF is also observed in both the
1H and 13C NMR spectra of 2. Interestingly, the 1H NMR
spectrum of 2 displays four diastereotopic methylene
protons for the bound THF (see the Experimental
Section). Complex 2 does not dissociate THF readily to
generate the three-coordinate species (L2)TidCHtBu.
Hence, solvent appears to play a significant role in the
formation and stability of 2. In fact, efforts to generate
three-coordinate alkylidene species such as [(L1)TidCHt-
Bu]+ have also been unsuccessful, since (L1)TidCHtBu-
(OTf) fails to react with salts such as Na[B(3,5-
(CF3)2C6H3)4]andLi[B(C6F5)4].Unlike(L1)TidCHtBu(OTf)
or 1, compound 2 is remarkably stable. Only upon
extensive thermolysis (10 h, 40 °C) will complex 2
undergo significant decomposition. It thus appears
obvious that the transformation of the â-diketiminate
ligand to an imine-free, bis-anilide system in 2 prohibits
(20) Group 4 terminal alkylidenes are scarce, and few have been
structurally characterized: (a) Fryzuk, M. D.; Mao, S. S. H.; Zaworotko,
M. J.; MacGillivray, L. R. J. Am. Chem. Soc. 1993, 115, 5336-5337.
(b) Fryzuk, M. D.; Duval, P. B.; Mao, S. S. H.; Zaworotko, M. J.;
MacGillivray, L. R. J. Am. Chem. Soc. 1999, 121, 2478-2487. (c)
Fryzuk, M. D.; Duval, P. B.; Patrick, B. O.; Rettig, S. J. Organometallics
2001, 20, 1608-1613. (d) Barger, P. T.; Santarsiero, B. D.; Armantrout,
J.; Bercaw, J. E. J. Am. Chem. Soc. 1984, 106, 5178-5186. (e) Cheon,
J.; Rogers, D. M.; Girolami, G. S. J. Am. Chem. Soc. 1997, 119, 6804-
6813. (f) Ivin, K. J.; Rooney, J. J.; Stewart, C. D.; Green, M. L. H.;
Mahtab, R. J. Chem. Soc., Chem. Commun. 1978, 604-606. (g) Rice,
G. W.; Ansell, G. B.; Modrick, M. A.; Zentz, S. Organometallics 1983,
2, 154-157. (h) Meinhart, J. D.; Anslyn, E. V.; Grubbs, R. H.
Organometallics 1989, 8, 583-589. (i) Gilliom, L. R.; Grubbs, R. H.
Organometallics 1986, 5, 721-724. (j) Hartner, F. W., Jr.; Schwartz,
J.; Clift, S. M. J. Am. Chem. Soc. 1983, 105, 640-641. (k) Weng, W.;
Yang, L.; Foxman, B. M.; Ozerov, O. V. Organometallics 2004, 23,
4700-4705. Attempts to prepare group 4 alkylidene species have been
reported: (l) Wengrovius, J. H.; Schrock, R. R. J. Organomet. Chem.
1981, 205, 319-327.
(21) Ding, Y.; Hao, H.; Roesky, H. W.; Noltemeyer, M.; Schmidt, H.-
G. Organometallics 2001, 20, 4806-4811.
(22) Harder, S. Angew. Chem., Int. Ed. 2003, 42, 3430-3434 and
references therein.

Intramolecular C-H Activation Reactions
Organometallics, Vol. 24, No. 13, 2005 3325
Table 2. Summary of Crystallographic Data and Structure Refinement Details for Complexes 1, 2, 4, and
6‚C5H12
1
2
4
6‚C5H12
formula
C
38H62N2SiTi
C38H58N2OTi
606.76
C47H70N2Ti
710.95
C73H112N4Ti2
1141.47
fw
622.89
space group
a (Å)
P1h
P31
P21/n
P1h
9.9829(7)
10.3129(8)
10.5462(8)
105.068(2)
94.188(2)
113.742(2)
940.1(2)
29.025(4)
29.025(4)
12.170(2)
90.00
13.0516(9)
22.653(7)
14.487(2)
90.00
98.217(2)
90.00
9.158(3)
b (Å)
13.307(4)
14.680(4)
80.214(7)
81.987(7)
72.650(7)
1675.3(8)
1
c (Å)
R (deg)
â (deg)
90.00
γ (deg)
120.00
V (Å3)
8879(2)
4239.2(6)
4
Z
1
9
Dcalcd
1.100
1.021
1.114
1.131
linear abs coeff
F(000)
0.286
0.244
0.234
0.281
340
2970
1552
622
cryst color, solvent
cryst form
cryst size (mm)
θ range (lattice, deg)
index ranges
brown-red, pentane
block
red-orange, hexane
prism
brown-red, hexane
cleaved fragment
0.30 × 0.30 × 0.25
2.16-27.53
-16 e h e 12,
-27 e k e 29,
-18 e l e 18
30 675
orange, pentane
needle
0.35 × 0.30 × 0.25
2.28-30.01
-14 e h e 14,
-14 e k e 14,
-14 e l e 14
25 640
0.24 × 0.26 × 0.30
2.14-26.91
-36 e h e 36,
-12 e k e 36,
-15 e l e 14
30 989
0.25 × 0.08 × 0.02
2.00-27.57
-11 e h e 11,
-17 e k e 17,
-19 e l e 19
18 020
no. of rflns collected
no. of unique rflns, F > 4σ(F)
no. of obsd rflns
10 411
23 806
9739
7683
10 047
6962
6637
0.0632
R1 ) 0.0378,
wR2 ) 0.0792
R1 ) 0.0617,
wR2 ) 0.0847
0.872
2489
Rint
0.0469
0.2267
0.2364
final R indices (I > 2σ(I))
R1 ) 0.0355,
wR2 ) 0.0871
R1 ) 0.0369,
wR2 ) 0.0885
1.035
R1 ) 0.1062,
wR2 ) 0.1909
R1 ) 0.2936,
wR2 ) 0.2629
0.870
R1 ) 0.0682,
wR2 ) 0.0848
R1 ) 0.1244,
wR2 ) 0.2371
0.740
R indices (all data)
GOF on F 2
structure of 2 is of poor quality (several different crystals
were examined, and all were badly split with large
mosaic character), the connectivity was unambiguously
confirmed. In addition, three crystallographically inde-
pendent but chemically equivalent molecules of 2 were
confined in the asymmetric unit. In the molecular
structure of 2 the dianionic nature of the ligand is
supported clearly by the short Ti-Nanilide bond lengths
(1.942(9) and 1.993(8) Å), which are different from
typical TiIV-NNacnac distances observed in four-coordi-
nate alkylidenes (the Ti-N distance can range between
2.03 and 2.06 Å).9a,14 In the dianionic bis-anilide system
the N-Câ distances are considerably longer than those
reported for the Nacnac- ligand.9a,21 Other structural
parameters worth noting are the short TidC bond of
1.86(1) Å and the rather obtuse T-CR-Câ angle (161.7-
(8)°). The latter characteristic is consistent with a Ti-H
R-agostic interaction occurring in 2.18c Judging from the
orientation of the neopentyl tert-butyl group, the R-hy-
drogen appears to reside along the NCCCN plane and
not along the σ-plane bisecting N-Ti-N. This feature
is in sharp contrast to the four-coordinate titanium
alkylidene system (L1)TidCHtBu(OTf), which contains
the neopentyl tert-butyl group along the σ-plane bisect-
ing N-Ti-N and oriented syn with respect to the
triflato ligand.9a We should not, however, rely heavily
on metrical parameters in the crystal structure of 2, due
to the poor data quality.
Figure 2. Perspective view of 2 with thermal ellipsoids
at the 50% probability level. Hydrogens, with the exception
of the R-hydrogen and hydrogens on C(20), have been
omitted for clarity. Aryl groups on the â-diketiminate, with
the exception of ipso carbons C(7) and C(21), have also been
omitted for clarity. Table 1 lists pertinent metrical param-
eters.
the intramolecular Wittig-like transformation previ-
ously encountered with (L1)TidCHtBu(OTf).9a,14
Single crystals of 2 suitable for X-ray diffraction
studies were grown from a saturated hexane solution
cooled to -35 °C. Relevant metrical parameters and
crystal data for the structure of 2 are listed in Tables 1
and 2, respectively. The molecular structure of 2 dis-
plays a rare four-coordinate titanium-alkylidene com-
plex supported by a chelating bis-anilide ligand (Figure
2). Intensity statistics and systematic absences sug-
gested the structure of 2 to be in the noncentrosymmet-
ric, trigonal space group P31. Although the molecular
Realizing that (L3)TidCHtBu(OTf)14 lacks Me groups
in the â-carbon position that are prone to deprotonation
-
(L3 ) [Ar]NC(tBu)CHC(tBu)N[Ar]), we carried out
alkylation reactions of this complex in pursuit of much
more stable titanium alkylidene-alkyl species. Accord-
ingly, alkylation of the sterically hindered alkylidene

3326 Organometallics, Vol. 24, No. 13, 2005
Basuli et al.
Scheme 3
considerations involving in-plane orbitals of σ-symmetry
in the â-diketiminate ligand or from steric contributions
involving the maximum bite angle of the ligand and size
of the metal ion.23,24 Table 1 lists relevant metrical
parameters, while Table 2 reports crystallographic data
for 4.
Our recent discovery of four-coordinate vanadium
alkylidynes stimulated the pursuit of an isoelectronic
titanium-alkylidyne system.9h It was found, however,
that complexes 3 and 4 are both kinetic products and
that such species decompose gradually in solution.
Gentle heating of 3 or 4 (30-40 °C) leads to a myriad
of products, as evidenced by 1H NMR spectroscopy.
Addition of THF, PMe3, p-(dimethylamino)pyridine, and
OdPMe3 to complex 3 or 4 results in decomposition to
multiple products. In fact, treatment of 3 with [PPN]-
[OTf]25 (PPN+ ) bis(triphenylphosphoranylidene)am-
monium) does not result in a reaction to promote
R-abstraction to produce the hypothetical alkylidyne-
ate complex [PPN][(L3)TitCtBu(OTf)].
Since complex 1 decomposes rapidly in solution (vide
supra), we decided to examine the nature of the com-
pounds generated. It was found that complex 1 trans-
formed to several products, from which the titanacycle
Ti[2,6-(CMe2)(CHMe2)C6H3]NC(Me)CHC(Me)N[2,6-(C-
Me2)(CHMe2)C6H3](CH2SiMe3) (5) and the dimer [Tid
NAr([Ar]NC(Me)CHC(µ-CH2)dCHtBu)]2 (6) were iso-
lated (Scheme 3). Examination of the volatiles of the
reaction mixture revealed both SiMe4 and CMe4 to be
produced. The connectivity in complex 5 was confirmed
via an independent synthesis (vide infra), while the
degree of aggregation of complex 6 was established by
single-crystal X-ray diffraction studies (Figure 4).
Formation of a complex such as 5 is uncommon, since
previous work has documented C-H abstraction of the
supporting Nacnac- ligand in the ortho aryl positions,
in the substituents on the â-carbon of the backbone, and
in 1° carbons attached to groups in the ortho aryl
positions.10,22,23a In general, C-H activation of 1° car-
bons in the 2,6-dialkyl substituents on the aryl rings is
often encountered for the Nacnac- ligand used in the
present study.12,23a The C-H activation of both the
methine and methyl groups of the isopropyl of Nacnac-
(L1-) via reductive elimination of a Pt(IV) species and
subsequent oxidative addition leading to formation of
Figure 3. Perspective view of 4 with thermal ellipsoids
at the 50% probability level. Hydrogens, with the exception
of R-hydrogens, and aryl groups on the â-diketiminate, with
the exception of ipso carbons C(7) and C(27), have been
omitted for clarity. The R-hydrogens on C(39) and C(44)
were located and refined isotropically. Table 1 lists perti-
nent metrical parameters.
(L3)TidCHtBu(OTf)14 with LiCH2SiMe3 or KCH2Ph af-
fords in excellent yield the alkylidene-alkyl complexes
(L3)TidCHtBu(R) (R ) CH2SiMe3 (3), 89%; R ) CH2Ph
(4), 72% yield; Scheme 2). Diagnostic features for 3 and
4 include a 13C NMR resonance for the alkylidene
carbon centered at 261 and 254 ppm, respectively. The
coupling constant for the CR-HR component for both
systems was found to be ∼88 Hz, which is in accord with
the titanium centers engaging significantly with the
R-hydrogen via an agostic interaction. Both systems
retain Cs symmetry in solution, and the JC-H values also
compare well with those of the alkylidene-alkyl deriva-
tive 1. Single-crystal X-ray diffraction studies were
carried out for complex 4, and the molecular structure
is shown in Figure 3. Although the molecular structure
of 4 resembles that of complex 1 (TidC ) 1.852(6) Å,
Ti-H ) 1.96(8) Å, C-H ) 0.99(8) Å), the steric bulk
offered by the flanking aryl groups is more significant
in 4 than in 1. Steric bulk arises from the encumbering
tBu group on the â-carbon position, which pushes the
aryl groups closer to the metal. This feature is clearly
reflected by the Ti-N-Cipso angles in 4 (128.0(1) and
122.92(9)°) vs those observed in 1 (127.3(9) and 126.1-
(9)°). The steric hindrance induced by L3- is presumably
the main factor governing the kinetic stability of 4.
Another significant structural aspect worth mentioning
in the molecular structure of 4 is deviation of the
titanium metal center from the NCCCN plane. Steric
encumbrance pushes the metal center further out of the
mean plane defined by NCCCN. Hence, complex 4
displays a greater degree of deviation (∼1.053 Å) vs
complex 1 (∼1.027 Å). This feature has been observed
with the d0-scandium bis-alkyl species (L3)ScR2 pre-
pared by Piers and co-workers, in which the Sc atom
sits 1.1-1.3 Å out of the NCCCN plane.23 The “out of
plane” structural features have been linked to bonding
(24) Randall, D. W.; DeBeer George, S.; Holland, P. L.; Hedman,
B.; Hodgson, K. O.; Tolman, W. B.; Solomon, E. L. J. Am. Chem. Soc.
2000, 122, 11632-11648.
(23) (a) Hayes, P. G.; Piers, W. E.; Lee, L. W. M.; Knight, L. K.;
Parvez, M.; Elsegood, M. R. J.; Clegg, W. Organometallics 2001, 20,
2533-2544. (b) Piers, W. E.; Emslie, D. J. H. Coord. Chem. Rev. 2002,
233-234, 131-155. (c) Knight, L. K.; Piers, W. E.; McDonald, R. Chem.
Eur. J. 2000, 6, 4322-4326.
(25) [PPN][OTf] was prepared by addition of a THF solution of
AgOTf to a THF solution of [PPN]Cl. The precipitate was filtered and
washed with THF and Et2O. The solids were extracted with CH2Cl2
and filtered to remove AgCl, and the filtrate was dried under reduced
pressure to afford pure product.

Intramolecular C-H Activation Reactions
Organometallics, Vol. 24, No. 13, 2005 3327
Scheme 4
Experimental Section). However, attempts to collect 1H
NMR spectra of 6 were hampered by its insolubility in
solvents such as benzene, toluene, and CH2Cl2. Complex
6 does dissolve gradually in THF, but the combination
Figure 4. Perspective view of complex 6 with thermal
ellipsoids at the 50% probability level. Hydrogens, with the
exception of R-hydrogens, have been omitted for clarity.
Aryl groups on the â-diketiminate nitrogens, with the
exception of ipso carbons C(26) and C(11), and solvent have
also been omitted for clarity. The R-hydrogens were located
and refined isotropically. Selected bond lengths (Å) for 6:
Ti(1)-N(25), 1.732(4); Ti(1)-N(2), 1.994(4); Ti(1)-C(6),
2.209(5); Ti(1)-C(24), 2.253(5); Ti(1)-C(5), 2.661(5); Ti(1)-
C(3), 2.665(5); Ti(1)-H, 2.16(4); N(2)-C(3), 1.366(5); N(2)-
C(11), 1.433(6); C(3)-C(4), 1.393(7); C(4)-C(5), 1.454(6).
Selected angles (deg) for 6: N(25)-Ti(1)-N(2), 111.9(7);
N(25)-Ti(1)-C(6), 106.9(7); N(2)-Ti(1)-C(6), 94.7(7);
N(25)-Ti(1)-C(24), 105.4(8); C(26)-N(25)-Ti(1), 173.8(4).
1
of H, 13C NMR, and HMQC19 experiments in addition
to single-crystal X-ray diffraction studies revealed that
a novel complex was generated upon solvation (vide
infra).19
To probe whether an intermediate such as 7 was a
precursor to 6, we prepared complex 7 independently
and thermolyzed it. Accordingly, alkylation of the known
complex (HtBuCdC(Me)CHC(Me)N[Ar])TidNAr(OTf)9a
with LiCH2SiMe3 in pentane cleanly forms 7 in 83%
yield as red blocks (Scheme 4). 1H and 13C NMR spectra
are analogous to those of the triflate-precursor deriva-
tive (HtBuCdC(Me)CHC(Me)N[Ar])TidNAr(OTf).9a The
terminal olefinic carbon and hydrogen were located by
1H and 13C NMR at 2.43 and 131.6 ppm, respectively.
In addition, the JC-H coupling of 123 Hz for the terminal
olefinic CH indicates that substantial R-hydrogen ago-
stic interaction occurs in solution.26 Single crystals of 7
suitable for X-ray diffraction analysis were grown from
pentane at -35 °C, and crystal data for the molecular
structure of 7 are reported in Table 3. The molecular
structure of 7 reveals a titanium center supported by
an amide-diene, an imido, and an alkyl ligand (Figure
5). The titanium center in complex 7 interacts strongly
with the olefinic carbons (Ti(1)-C(6), 2.260(2) Å; Ti(1)-
C(5), 2.563(2) Å), and there is proximity to the â- and
γ-carbons of the NCCCC ring (Figure 5). The R-hydro-
gen was located and refined isotropically, and its posi-
tion suggests significant interaction with the metal
center (Ti-H, 2.10(9) Å). The low JC-H value for the
terminal CH group coupled with the strong agostic
interaction observed in the crystal structure could
indicate significant rehybridization of the terminal
carbon. Similar R-hydrogen agostic interactions have
been reported for 1-aza,1,3-diene ligands coordinated to
titanium.26 In fact, previous work has determined that
the molecular structures of the derivatives (HtBuCd
C(Me)CHC(Me)N[Ar])TidNAr(X) (X- ) OTf, I, η2-BH4)
also engage in R-agostic interactions.14 Upon thermoly-
sis, complex 7 generates complex 6 (confirmed by LDI
MS), albeit not cleanly (Scheme 4). Deprotonation of the
methyl group attached to the â-carbon of the Nacnac-
ligand has been reported previously,9d,21,22 but given the
an isopropenyl(hydrido)platinum(II) complex has also
been reported.12a-c Our work establishes a C-H activa-
tion reaction by which two methine groups are selec-
tively cleaved under room-temperature conditions.15
Although 5 is formed in poor yields, synthetic access to
this complex is easily achieved (87% isolated yield) by
direct treatment of the known titanacycle Ti[2,6-(CMe2)-
(CHMe2)C6H3]NC(Me)CHC(Me)N[2,6-(CMe2)(CHMe2)-
C6H3](OTf)14 with LiCH2SiMe3 in Et2O. 1H and 13C
NMR spectra are consistent with complex 5 retaining
Cs symmetry in solution, and spectral features are
analogous to the those of the Ti[2,6-(CMe2)(CHMe2)-
C6H3]NC(Me)CHC(Me)N[2,6-(CMe2)(CHMe2)C6H3](O-
Tf)14 precursor.
The second product generated from the thermolysis
of 1 was complex 6. Formation of complex 6 likely occurs
through an intramolecular Wittig-like reaction to give
the imido species (HtBuCdC(Me)CHC(Me)N[Ar])Tid
NAr(CH2SiMe3) (7) (Scheme 4), which then undergoes
deprotonation of the methyl group attached to the
â-carbon of the L1- ligand. We favor an intra- vs inter-
molecular rearrangement, since the complex (L1)TidCHt-
Bu(OTf) also transforms via an analogous mechanism.14
The second step in the formation of 6 is rather unusual,
in the sense that deprotonation of the methyl group
occurs preferably over migratory insertion of the olefinic
group into the Ti-CH2SiMe3 bond. The latter type of
reaction has been invoked in the transformation of
terminal titanium phosphinidenes supported by the
present L1- system.9b Upon deprotonation of the â-CH3
group, Cs symmetry in the ligand in complex 6 is
expected to be disrupted. LDI-MS of complex 6 is
consistent with a dimer being generated (see the
(26) Similar spectroscopic features have been suggested for 1-aza-
1,3-diene ligands containing R-hydrogens which are bonded to tita-
nium: Scholz, J.; Kahlert, S, Gorls, H. Organometallics 1998, 17,
2876-2884.

3328 Organometallics, Vol. 24, No. 13, 2005
Basuli et al.
Table 3. Summary of Crystallographic Data and Structure Refinement Details for Complexes 7-10
7
8
9
10
formula
C
38H62N2SiTi
C38 H58.46N2OTi
607.23
C34H51N2Ti
535.67
C40H63N2Ti
619.82
fw
622.89
space group
a (Å)
P21/c
P21/n
P21/c
P21/n
19.030(5)
11.355(1)
18.246(5)
90.00
12.9907(8)
19.171(1)
15.3903(9)
90.00
8.977(3)
12.140(1)
17.375(4)
17.852(4)
90.00
b (Å)
15.620(5)
23.026(8)
90.00
c (Å)
R (deg)
â (deg)
108.729(3)
90.00
106.712(2)
90.00
99.198(8)
90.00
96.395(2)
90.00
γ (deg)
V (Å3)
3733.8(6)
4
3671.0(4)
4
3187(9)
3742.1(5)
4
Z
4
Dcalcd
1.108
1.099
1.116
1.100
linear abs coeff
F(000)
0.288
0.262
0.291
0.256
1360
1322
1164
1356
cryst color, solvent
cryst form
cryst size (mm)
θ range (lattice, deg)
index ranges
ruby red, hexane
diamond shape
0.28 × 0.28 × 0.23
2.12-27.53
-17 e h e 24,
-14 e k e 14,
-23 e l e 23
20 961
pale orange, Et2O
plates
green, hexane
cleaved fragment
0.25 × 0.20 × 0.20
2.22-27.60
-11 e h e 11,
-20 e k e 20,
-30 e l e 29
70 591
dark green, pentane
diamond shape
0.25 × 0.25 × 0.12
2.06-27.53
-15 e h e 15,
-22 e k e 22,
-23 e l e 20
66 446
0.25 × 0.25 × 0.25
2.10-30.06
-18 e h e 18,
-26 e k e 27,
-21 e l e 21
99 525
no. of rflns collected
no. of unique rflns, F > 4σ(F)
no. of obsd rflns
8538
10 731
7384
8628
4168
5592
3434
5942
Rint
0.0805
0.1079
0.2015
0.0755
final R indices (I > 2σ(I))
R1 ) 0.0445,
wR2 ) 0.0676
R1 ) 0.1031,
wR2 ) 0.0820
0.714
R1 ) 0.0425,
wR2 ) 0.0843
R1 ) 0.1019,
wR2 ) 0.1006
0.856
R1 ) 0.0483,
wR2 ) 0.0913
R1 ) 0.1122,
wR2 ) 0.1323
0.815
R1 ) 0.0441,
wR2 ) 0.1055
R1 ) 0.0708,
wR2 ) 0.1134
0.947
R indices (all data)
GOF on F 2
formation of multiple byproducts in such a thermolysis
of 7, it is difficult to ascertain whether an insertion
reaction is also taking place.
Recognizing that three-coordinate species of group 4
can activate inert C-H bonds,4 we pursued the one-
electron reduction of the alkylidene-triflato complex
(L1)TidCHtBu(OTf) with KC8 in THF. It was observed
that solutions of (L1)TidCHtBu(OTf) rapidly changed
from brown to green and then gradually to brown.
Examination of the reaction mixture by 1H NMR spectra
revealed several products along with starting material.
However, it was found that the one-electron reduction
improves if the reaction is carried out in toluene with a
small trace of THF or PMe3. Workup of the persisting
green solution afforded several paramagnetic products,
of which the titanium(III) metallacycle-alkyl complex
(L4)Ti(CH2 Bu) (9; L4 ) [Ar]NC(Me)CHC(Me)N[2,6-
(CHMe2)(CH(CH2)(Me))C6H3]) could be isolated as a
crude powder (Scheme 6). Rapid decomposition and
significant contamination of 9 with other products
precluded satisfactory characterization via spectroscopic
assessment techniques (EPR, Evans, elemental analy-
sis). However, a few single crystals of 9 were grown from
the reaction mixture, and X-ray data confirmed the
proposed connectivity (Figure 6 lists selected metrical
parameters, and Table 3 lists crystallographic and
refinement data for the molecular structure of 9).
Although crystals were found to be badly split and
twinned, the molecular structure of 9 reveals a Ti(III)
metallacycle resulting from C-H activation of the
nearby isopropyl methyl group. In the molecular struc-
ture of 9 there is a slight disorder, with 7.3% of the site
having an alternate Ti position. The azametallacyclo-
hexene ring generated in 9 results from 1,2-addition of
the C-H bond across the putative titanium(III)-alkyl-
idene species “(L1)TidCHtBu”, which was generated
from the one-electron reduction of (L1)TidCHtBu(OTf).
The molecular structure of 9 also reveals ring strain,
which is evident from the torsion angle defined by the
atoms N(6)-C(21)-C(22)-C(30) (-171.5(2)°). 1,2-Ad-
dition of the proximal C-H bond across the TidC bond
was not surprising, since the putative “(L1)TidCHtBu”
is three-coordinate and contains a radical centered at
Interestingly, it was found that compound 6 is in-
soluble in most common organic solvents except for THF
(vide supra). In fact, the dimeric nature of 6 is not
1
conserved in THF solutions, inasmuch as H and 13C
NMR spectra are consistent with a novel product being
generated. As suggested by NMR spectral data, complex
6 appears to transform quantitatively and gradually to
the monomer (H2CdC(CHtBu)CHC(Me)N[Ar])TidNAr-
(THF) (8) (Scheme 5). The nature of the monomer was
established by a combination of 1H and 13C NMR spectra
as well as HMQC19 NMR experiments (see the Experi-
mental Section). We propose that THF promotes het-
erolytic Ti-C bond cleavage in 6 to generate a conju-
t
2-
t
gated species such as ( BuHCdC(CH2)CHC(Me)N[Ar])Tid
NAr(THF), which rapidly isomerizes to form 8 (Scheme
5). It is very likely that rotation about the Câ-Cγ bond
containing the allyl motif occurs for steric reasons.
Single crystals of 8 were grown from Et2O at -35 °C,
and the structure is depicted in Figure 5. Crystal data
for the molecular structure of 8 are reported in Table
3. The structure of complex 8 depicts a monomeric
titanium system possessing an anilide-alkyl-diene
ligand system, which results from THF coordination and
Ti-C bond cleavage (Figure 5). There is disparity in the
C-C linkages within the NCCCC motif, which is evident
from the CdC bond lengths (Figure 5). The NCCCC ring
is far from being planar, which is reflected by the
dihedral angle defined by the atoms C(6)-C(5)-C(4)-
C(3) (29.1(3) °C). X-ray data suggest that no R-H agostic
interactions are present, thus indicating that the NC-
CCC ligand system in 8 is best described as a chelating
amide-alkyl with a diene motif. In that respect, com-
plex 8 is remarkable in that it represents a rare example
of a low-coordinate titanium imido and alkyl complex.
As a result, complex 8 is exceedingly unstable at room
temperature (as a solid or in solution), decomposing to
a myriad of products.

Intramolecular C-H Activation Reactions
Organometallics, Vol. 24, No. 13, 2005 3329
Figure 5. Perspective views of complexes 7 and 8 with thermal ellipsoids at the 50% probability level. Hydrogens, with
the exception of the R-hydrogens on C(6) and C(7) (complex 8), have been omitted for clarity. Aryl groups on the
â-diketiminate nitrogens, with the exception of those located in carbons C(7) and C(26) for complex 7 and C(26) and C(12)
for complex 8, have also been omitted for clarity. Disorder involving a diethyl ether is present at the THF site of complex
8 but was easily modeled. Selected bond lengths (Å) for 7: Ti(1)-N(25), 1.725(9); Ti(1)-N(2), 2.032(8); Ti(1)-C(6), 2.260(2);
Ti(1)-C(5), 2.563(2); Ti(1)-C(4), 2.704(2); Ti(1)-C(3), 2.671(2); Ti(1)-H, 2.10(9); Ti(1)-C(38), 2.130(3); N(2)-C(3), 1.350(3);
N(2)-C(7), 1.436(3); C(3)-C(4), 1.393(3); C(4)-C(5), 1.440(3); C(5)-C(6), 1.381(3); C(6)-C(21), 1.528(3); N(25)-C(26),
1.398(3). Selected angles (deg) for 7: N(25)-Ti(1)-N(2), 112.09(8); N(25)-Ti(1)-C(6), 109.12(9); N(25)-Ti(1)-C(38),
107.91(10); N(2)-Ti(1)-C(6), 91.18(8); N(2)-Ti(1)-C(38), 122.03(9); Ti(1)-N(25)-C(26), 174.3(7); N(2)-C(3)-C(4), 120.7(2);
C(3)-C(4)-C(5), 131.0(2); C(4)-C(5)-C(6), 126.0(2); C(5)-C(6)-Ti(1), 85.9(5); C(5)-C(6)-C(21), 129.2(2); Ti(1)-C(38)-
Si(39), 130.9(5). Selected bond lengths (Å) for 8: Ti(1)-N(25), 1.720(4); Ti(1)-N(2), 1.952(4); Ti(1)-C(6), 2.121(9); Ti(1)-
O(38), 2.055(1); Ti(1)-C(5), 2.589(7); N(2)-C(3), 1.411(2); N(2)-C(12), 1.428(2); N(25)-C(26), 1.395(2); C(3)-C(4), 1.353(2);
C(3)-C(24), 1.502(3); C(4)-C(5), 1.471(3); C(5)-C(7), 1.370(3); C(5)-C(6), 1.463(3). Selected angles (deg) for 8: Ti(1)-
N(25)-C(26), 167.9(2); Ti(1)-N(2)-C(3), 109.1(1); Ti(1)-C(6)-C(5), 90.6(1); O(38)-Ti(1)-N(25), 105.37(6); O(38)-Ti(1)-
N(2), 114.39(5); O(38)-Ti(1)-C(6), 119.21(7); C(6)-Ti(1)-N(2), 93.49(7); C(6)-Ti(1)-N(25), 111.68(7); N(25)-Ti(1)-N(2),
112.74(6); N(2)-C(3)-C(4), 122.8(7); C(3)-C(4)-C(5), 129.9(7); C(4)-C(5)-C(6), 117.5(7); C(4)-C(5)-C(7), 116.6(7); C(6)-
C(5)-C(7), 125.7(9).
Scheme 5
Scheme 6
in the Nacnac- ligand has been invoked in intermolecu-
lar alkane activation.12
-
Given the precedent for L1 to undergo transforma-
the TidC bond. Theoretical studies on the four-coordi-
nate titanium alkylidene (L1)TidCHtBu(OTf) have es-
tablished that the HOMO is mostly of TidC π character,
while the LUMO consists of L1 π* augmented with π*
character in the TidC bond.14 Hence, the one-electron
reduction of (L1)TidCHtBu(OTf) would likely populate
the TidC π* orbital, thus giving rise to a TidC-centered
radical. Analogous metallacycles have been reported in
the thermolysis of (L1)ScR2 systems studied by Piers and
co-workers.23a In the context of late-transition-metal
complexes, the intramolecular cleavage of C-H bonds
tions,9d,10b our inability to isolate complex 9 in good
yield, and the lack of experimental data not conclusive
for the identity of such species, we proceeded to carry
out the one-electron reduction of the kinetically stable
alkylidene complex (L3)TidCHtBu(OTf).14 Accordingly,
reduction of (L3)TidCHtBu(OTf) with KC8 or LitBu
t
affords the Bu-titanacycle derivative of 9, namely
t
(L5)Ti(CH2 Bu) (10; L52- ) [Ar]NC(tBu)CHC(tBu)N[2,6-
(CHMe2)(CH(CH2)(Me))C6H3]) as dark green crystals
from pentane at -35 °C (Scheme 7). The use of LitBu
as a reductant improves tremendously the yield of 10

3330 Organometallics, Vol. 24, No. 13, 2005
Basuli et al.
Figure 6. Perspective views of the titanacycles 9 and 10, with thermal ellipsoids at the 50% probability level. Hydrogens,
with the exception of R-hydrogens, have been omitted for clarity. Aryl groups on the â-diketiminate nitrogens, with the
exception of the C(7) ipso carbons, have also been omitted for clarity. The R-hydrogens were located and refined isotropically.
There is a disorder present with the titanium atom in the structure for complex 10 and appears shifted to the other side
of the plane defined by the atoms N(2), N(6), and C(39). Selected bond lengths (Å) for 9: Ti(1)-N(2), 1.988(2); Ti(1)-N(6),
2.009(2); Ti(1)-C(33), 2.124(3); Ti(1)-C(32), 2.167(3); Ti(1)-H(on C(33)), 2.27(3); N(2)-C(3), 1.357(3); C(3)-C(4), 1.390(4);
C(4)-C(5), 1.396(4); C(5)-N(6), 1.349(3). Selected angles (deg) for 9: Ti(1)-C(33)-C(34), 135.6(2); Ti(1)-C(32)-C(30),
111.1(2); Ti(1)-N(2)-C(3), 131.5(7); N(2)-Ti(1)-N(6), 86.06(9); Ti(1)-N(6)-C(5), 130.0(8); C(33)-Ti(1)-C(32), 107.7(3);
Ti(1)-N(6)-C(21), 105.5(6); Ti(1)-N(2)-C(7), 107.0(5); N(2)-C(3)-C(4), 121.0(2); C(4)-C(5)-N(6), 120.9(2); N(6)-C(21)-
C(22), 116.9(2; C(21)-C(22)-C(30), 119.3(2); C(22)-C(30)-C(32), 109.2(2). Selected bond lengths (Å) for 10: Ti(1)-N(2),
2.021(4); Ti(1)-N(6), 2.004(4); Ti(1)-C(39), 2.143(2); Ti(1)-C(34), 2.173(2); Ti(1)-H(on C(39)), 2.27(3); N(2)-C(3), 1.351(2);
C(3)-C(4), 1.390(2); C(4)-C(5), 1.407(2); C(5)-N(6), 1.340(2). Selected angles (deg) for 10: Ti(1)-C(39)-C(40), 138.0(5);
Ti(1)-C(34)-C(33), 111.2(3); Ti(1)-N(2)-C(3), 130.1(1); N(2)-Ti(1)-N(6), 87.05(6); Ti(1)-N(6)-C(5), 130.2(1); C(39)-
Ti(1)-C(34), 109.4(9); Ti(1)-N(6)-C(27), 100.6(1); Ti(1)-N(2)-C(7), 100.3(1); N(2)-C(3)-C(4), 119.8(5); C(4)-C(5)-N(6),
118.8(5); N(6)-C(27)-C(32), 117.3(5); C(27)-C(32)-C(33), 118.8(5); C(32)-C(33)-C(34), 109.0(5).
Scheme 7
t
(65%), inasmuch as BuH, isobutene, and hexamethyl-
ethane are generated as organic side products from the
one-electron reduction reaction (confirmed by 1H NMR
spectra of the volatiles).27 Solution magnetic measure-
ments by the method of Evans, solution X-band EPR
spectra, and single-crystal X-ray diffraction studies
(Figure 6) are all consistent with the proposed con-
nectivity in 10. At room temperature, complex 10
exhibits a solution magnetic moment of 1.83 µΒ, which
is in close agreement with the calculated value obtained
by applying the giso value from the EPR spectrum.
However, room-temperature manipulation of the prod-
uct leads to gradual decomposition.
In the molecular structure of 10, the Ti(III) center
resides in a highly distorted tetrahedral environment
(Figure 6) and resembles closely the gross structural
features of complex 9. 1,2-Addition of the nearby methyl
across the TidCHtBu bond gives rise to two Ti-alkyl
ligands, which are manifested by the Ti-C bond lengths
of 2.143(2) and 2.173(2) Å. These values compare well
with typical Ti(III) bis-alkyl distances reported in the
literature.28 As in complex 9, there appears to be
significant ring strain resulting from the cyclometala-
tion, which is manifested by the dihedral angle (4.6-
(27) Weydert, M.; Brennan, J. G.; Andersen, R. A.; Bergman, R. G.
Organometallics 1995, 14, 3942-3951.

Intramolecular C-H Activation Reactions
Organometallics, Vol. 24, No. 13, 2005 3331
-
(2)°) defined by the atoms N(6)-C(27)-C(32)-C(33) and
angles constructing the metallacycle (Figure 6 gives
selected bond lengths and angles for 10, and Table 3
lists crystallographic and refinement data). Such a claim
is speculative, since there is a disorder present with the
titanium atom, which appears to shift to the other side
of the plane defined by the atoms N(2), N(6), and C(39).
Most notably, it was found that one-electron oxidation
of 10 with AgOTf generates back the alkylidene precur-
sor (L3)TidCHtBu(OTf) quantitatively, as suggested by
both 1H and 13C NMR spectra (Scheme 7). Oxidation of
10 likely results from formation of the putative five-
coordinate species 10-OTf (Scheme 7),29 which rapidly
undergoes R-hydrogen abstraction to generate (L3)Tid
CHtBu(OTf). Similarly, when the isotopomer 10-d130 is
oxidized with AgOTf, the complex (L3)TidCH(D)tBu-
(OTf)-d1 is generated back and deuterium scrambling
is observed in all isopropyl methyl groups, as evidenced
more sterically hindered NacnactBu derivative was
used, the alkylidene-alkyl systems were found to be
more kinetically stable by blocking C-H activation and
intramolecular Wittig reactions observed with the con-
ventional [Ar]NC(Me)CHC(Me)N[Ar] (Ar ) 2,6-(CHMe2)2-
C6H3) ligand. It was found that reduction of the complex
(L3)TidCHtBu(OTf) to 10 and one-electron oxidation of
the product back to the alkylidene provide a reversible
and intramolecular 1,2-addition and R-abstraction reac-
tion which is controlled by a one-electron redox switch.
1,2-CH addition across the titanium-alkylidene is likely
mitigated by the radical nature of the TidC bond, while
R-hydrogen abstraction takes place exclusively at the
t
Ti-CH2 Bu ligand. In addition, the redox-controlled 1,2-
addition and R-abstraction reactions are specific only
to the isopropyl methyl attached to the aryl group of
the â-diketiminate ligand. We are currently exploring
what factors govern the preference of 1° vs 3° C-H
bonds when activated by low-coordinate titanium-
alkylidenes as well as exploring alternate surrogates for
the present ligand in order to stabilize the elusive
titanium alkylidyne functionality.
1
2
by H and H NMR spectra. Hence, the one-electron
reduction of (L3)TidCHtBu(OTf) to 10 and its one-
electron oxidation back to the alkylidene is best de-
scribed as a redox-controlled 1,2-addition and R-hydro-
gen abstraction reaction. This type of reaction parallels
Cummins’ reversible â-hydride elimination reactions of
Nb and Mo metallaaziridine systems.31
Experimental Section
General Considerations. Unless otherwise stated, all
operations were performed in a M. Braun Lab Master double-
dry box under an atmosphere of purified nitrogen or using
high-vacuum standard Schlenk techniques under an argon
atmosphere.32 Anhydrous n-hexane, pentane, toluene, and
benzene were purchased from Aldrich in Sure-Seal reservoirs
(18 L) and dried by passage through one column of activated
alumina and one of Q-5.32 Diethyl ether and CH2Cl2 were dried
by passage through two columns of activated alumina.33 THF
was distilled, under nitrogen, from purple sodium benzophen-
one ketyl and stored over sodium metal. Distilled THF was
transferred under vacuum into bombs before being pumped
into a drybox. C6D6 and CD2Cl2 were purchased from Cam-
bridge Isotope Laboratory (CIL), degassed, and dried over 4
Å molecular sieves and CaH2, respectively. CD2Cl2 was vacuum-
transferred from the CaF2 mixture and stored in a reaction
vessel under N2. Et2O-d10 and THF-d8 were purchased from
CIL and stored over Na film. Celite, alumina, and 4 Å
molecular sieves were activated under vacuum overnight at
Despite complex 10 having a â-hydrogen, this system
appears to be relatively stable under low-temperature
conditions. Similar stability has been observed in analo-
gous Ti(III) bis-alkyl species studied by Budzelaar and
co-workers.28 We speculate that the unusual stability
observed in 10 arises likely from the rigidity of the
metal-based ring. Hence, the orientation of the methine
carbon places the â-hydrogen on C(33) away from the
metal center and less susceptible to elimination or
abstraction processes. However, the possibility remains
that â-hydride elimination and reinsertion of the puta-
tive titanium-hydride into the pendant olefin exists in
solution. This process has been observed in Pt systems
studied by Goldberg and co-workers12 and could give rise
to two isomers resulting from hydride insertion into the
terminal or proximal sites of the pendant olefinic arm
200 °C. Li(L1)34 (L1 ) [Ar]NC(Me)CHC(Me)N[Ar], Ar ) 2,6-
-
-
of the NacnactBu ligand.
(CHMe2)2C6H3), (Nacnac)TiCl2(THF),9a,28 LiCH2 Bu,35 KC8,36
t
KCH2Ph,37 Li(L3)28 (L3- ) [Ar]NC(tBu)CHC(tBu)N[Ar]), (L1)Tid
CHtBu(OTf),9a (η2-HtBuCdC(Me)CHC(Me)N[Ar])TidNAr(O-
Tf),9a Ti[2,6-(CMe2)(CHMe2)C6H3]NC(Me)CHC(Me)N[2,6-(C-
Me2)(CHMe2)C6H3](OTf),14 and (L3)TidCHtBu(OTf)14 were pre-
pared according to the literature. Solid LitBu was collected by
cooling a saturated pentane solution to -78 °C followed by
rapid filtration. Crystals of LiCH2Si(CH3)3 were collected by
cooling of a saturated pentane solution to -35 °C. All other
chemicals were used as received. CHN analysis was performed
by Desert Analytics, Tucson, AZ. 1H, 2H, 13C, and 19F NMR
Conclusions
Alkylation of a series of the four-coordinate titanium
alkylidene complexes was found to generate alkylidene-
alkyl species of the type (Nacnac)TidCHtBu(alkyl)
(Nacnac- ) [Ar]NC(R)CHC(R)N[Ar], Ar ) 2,6-(CHMe2)2-
t
C6H3), R ) CH3, Bu). Depending on the nature of the
Nacnac- ligand and alkyl group, deprotonation of the
methyl group attached to the â-carbon can occur to yield
a four-coordinate titanium alkylidene species supported
by a dianionic chelating bis-anilide ligand. When the
(32) For a general description of the equipment and techniques used
in carrying out this chemistry, see: Burger, B. J.; Bercaw, J. E. In
Experimental Organometallic Chemistry; Wayda, A. L., Darensbourg,
M. Y., Eds.; ACS Symposium Series 357; American Chemical Society;
Washington, DC, 1987; pp 79-98.
(28) Budzelaar, P. H. M.; Van Oort, A. B.; Orpen, A. G. Eur. J. Inorg.
Chem. 1998, 1485-1494.
(29) For an example describing R-hydrogen abstraction stemming
from a five-coordinate complex see: Schrock, R. R.; Murdzek, J. S.;
Bazan, G. C.; Robbins, J.; DiMare, M.; O’Regan, M. J. Am. Chem. Soc.
1990, 112, 3875-3886.
(33) Pangborn, A. B.; Giardello, M. A.; Grubbs, R. H.; Rosen, R. K.;
Timmers, F. J. Organometallics 1996, 15, 1518.
(34) Stender, M.; Wright, R. J.; Eichler, B. E.; Prust, J.; Olmstead,
M. M.; Roesky, H. W.; Power, P. P. Dalton 2001, 3465-3469 and
references therein.
(30) The complex 10-d was prepared from (L3)TidCDtBu(OTf) and
LitBu in Et2O at -35 °C. Preparation of the precursor (L3)TidCDtBu-
(OTf) was analogous to that of the protio derivative, but instead,
(35) Schrock, R. R.; Fellmann, J. D. J. Am. Chem. Soc. 1978, 100,
3359-3379.
LiCD2 Bu6e was used as the alkylating reagent.
t
(31) (a) Figueroa, J. S.; Cummins, C. C. J. Am. Chem. Soc. 2003,
125, 4020-4021. (b) Tsai, Y.-C.; Johnson, M. J. A.; Mindiola, D. J.;
Cummins, C. C.; Klooster, W. T.; Koetzle, T. F. J. Am. Chem. Soc. 1999,
121, 10426-10427.
(36) Schwindt, M.; Lejon, T.; Hegedus, L. S. Organometallics 1990,
9, 2814-2819.
(37) Schlosser, M.; Hartmann, J. Angew. Chem., Int. Ed., Engl. 1973,
12, 508.

3332 Organometallics, Vol. 24, No. 13, 2005
Basuli et al.
spectra were recorded on Varian 400 and 300 MHz NMR
77.41 (THF), 47.85 (TidCHCMe3), 32.09 (TidCHCMe3), 28.89
(CHMe2), 28.81 (CHMe2), 28.72 (CHMe2), 28.54 (CHMe2), 26.42
(Me), 26.30 (Me), 25.93 (Me), 25.87 (Me), 25.89 (Me), 25.16 (Me),
25.02 (THF), 24.66 (Me), 24.21 (Me), 23.85 (Me). Anal. Calcd
for C38H58N2OTi: C, 75.22; H, 9.63; N, 4.62. Found: C, 74.00;
H, 9.50; N, 4.72.
1
spectrometers. H and 13C NMR are reported with reference
to solvent resonances (residual C6D5H in C6D6, 7.16 and 128.0
ppm; residual CHDCl2 in CD2Cl2, 5.32 and 53.8 ppm). 19F NMR
chemical shifts are reported with respect to external HOCOCF3
(-78.5 ppm). Magnetic moments were obtained by the method
of Evans.38 Room-temperature and solution X-band EPR
spectra were recorded on a Bruker EMX spectrometer. Acqui-
sition and simulation were performed using an integrated
WIN-EPR software package (Bruker).39 LDI MS was collected
using a Bruker Biflex III time-of-flight mass spectrometer. The
mass spectrum was recorded by irradiating the sample spot
with 337 nm light from a nitrogen laser. X-ray diffraction data
were collected on a SMART6000 (Bruker) system under a
stream of N2(g) at low temperatures.
Synthesis of 3. In a vial was dissolved (L3)TidCHtBu(OTf)
(116 mg, 0.15 mmol) in 10 mL of pentane, and the solution
was cooled to -35 °C. To the cold solution was added a cold
pentane solution (∼5 mL) containing LiCH2SiMe3 (14.42 mg,
0.15 mmol). After it was warmed, the mixture was stirred for
an additional 20 min. The solution was filtered and the filtrate
concentrated and stored at -35 °C for 24 h to afford dark
blocks of (L3)TidCHtBu(CH2SiMe3) (3; 96 mg, 0.13 mmol, 89%
yield, two crops).
Synthesis of 1. In a vial containing 10 mL of pentane was
dissolved (L1)TidCHtBu(OTf) (411 mg, 0.60 mmol), and the
solution was cooled to -35 °C. To the cold solution was added
a cold pentane solution (∼5 mL) of LiCH2SiMe3 (56.50 mg, 0.60
mmol), and the reaction mixture was warmed to room tem-
perature and stirred for an additional 45 min. The solution
was filtered and the filtrate concentrated and cooled overnight
at -35 °C to afford in two crops dark large blocks of
(L1)TidCHtBu(CH2SiMe3) (1; 305 mg, 0.49 mmol, 82% yield).
Data for 1 are as follows. 1H NMR (23 °C, 399.8 MHz,
C6D6): δ 7.21-7.02 (m, C6H3, 6H), 5.69 (s, TidCHtBu, 1H),
4.82 (s, C(Me)CHC(Me), 1H), 3.72 (septet, CH(Me)2, 2H), 3.07
(septet, CH(Me)2, 2H), 2.37 (s, Ti-CH2SiMe3, 2H), 1.64 (d,
CHMe2, 6H), 1.57 (s, C(Me)CHC(Me), 6H), 1.45 (d, CHMe2, 6H),
1.26 (d, CHMe2, 6H), 1.21 (d, CHMe2, 6H), 0.74 (s, TidCHtBu,
9H), 0.15 (s, Ti-CH2SiMe3, 9H). 13C NMR (25 °C, 100.6 MHz,
C6D6): δ 270.7 (TidCHtBu, JC-H ) 99 Hz), 167.3 (C(Me)-
CHC(Me)), 145.6 (ipso-C6H3), 142.6 (o-C6H3), 140.8 (o-C6H3),
126.6 (p-C6H3), 124.4 (m-C6H3), 124.3 (m-C6H3), 96.35 (C(Me)-
CHC(Me), JC-H ) 159 Hz), 57.79 (Ti-CH2SiMe3, JC-H ) 103
Hz), 47.03 (TidCHCMe3), 31.80 (TidCHtBu), 28.86 (CHMe2),
28.45 (CHMe2), 26.55 (Me), 24.99 (Me), 24.81 (Me), 24.16 (Me),
3.48 (Ti-CH2SiMe3). Anal. Calcd for C38H62N2SiTi: C, 73.27;
H, 10.03; N, 4.50. Found: C, 72.70; H, 10.10; N, 4.99.
Synthesis of 2. In a vial containing 10 mL of THF was
dissolved (L1)TidCHtBu(OTf) (150 mg, 0.22 mmol) and the
solution cooled to -35 °C. To the cold solution was added a
cold THF solution (∼5 mL) containing KCH2Ph (29.9 mg, 0.23
mmol). After it was warmed to room temperature, the mixture
was stirred for an additional 25 min and solvent was evapo-
rated under reduced pressure. The solid was extracted with
hexane, the extract filtered, and the filtrate concentrated and
stored at -35 °C for 24 h to afford dark red crystals of
(L2)TidCHtBu(THF) (2; 84 mg, 0.14 mmol, 64% yield, two
crops).
Data for 2 are as follows. 1H NMR (23 °C, 399.8 MHz,
C6D6): δ 7.48-7.18 (m, C6H3, 6H), 5.05 (s, TidCHtBu, 1H,
based on HMQC), 4.92 (s, C(Me)CHC(CH2), 1H), 4.16 (septet,
CHMe2, 1H), 4.03 (septet, CHMe2, 1H), 4.02 (m, THF, 2H),
3.87 (m, THF, 2H), 3.64 (s, C(Me)CHC(CH2), 1H), 3.51 (septet,
CHMe2, 1H), 3.31 (septet, CHMe2, 1H), 3.25 (s, C(Me)CHC-
(CH2), 1H), 1.78 (d, CHMe2, 3H), 1.76 (d, CHMe2, 3H), 1.70 (d,
CHMe2, 3H), 1.67 (d, CHMe2, 3H), 1.65 (s, C(Me)CHC(CH2),
3H), 1.63 (d, CHMe2, 3H), 1.62 (d, CHMe2, 3H), 1.55 (d, CHMe2,
3H), 1.45-1.41 (m, THF and CHMe2, 7H), 0.83 (s, TidCHtBu,
9H). 13C NMR (25 °C, 100.6 MHz, C6D6): δ 254 (TidCHtBu,
JC-H ) 93 Hz), 153.2 (C(Me)CHC(CH2)), 148.7 (ipso-C6H3),
147.0 (ipso-C6H3), 145.2 (o-C6H3), 145.0 (o-C6H3), 142.7 (o-
C6H3), 142.6 (o-C6H3), 141.9 (C(Me)CHC(CH2)), 125.6 (p-C6H3),
125.5 (p-C6H3), 124.7 (m-C6H3), 124.0 (m-C6H3), 123.1 (m-
C6H3), 122.9 (m-C6H3), 99.21 (C(Me)CHC(CH2), JC-H ) 154
Hz), 82.99 (based on HMQC, C(Me)CHC(CH2), JC-H ) 162 Hz),
Data for 3 are as follows. 1H NMR (23 °C, 399.8 MHz,
C6D6): δ 7.13-7.05 (m, C6H3, 6H), 5.47 (s, ((tBu)CCHC(tBu),
1H, based on HMQC), 4.54 (s, TidCHtBu, 1H), 3.49 (septet,
CHMe2, 2H), 3.37 (septet, CHMe2, 2H), 1.77 (d, CHMe2, 6H),
1.75 (s, Ti-CH2SiMe3, 2H), 1.42 (d, CHMe2, 12H), 1.33 (d,
CHMe2, 6H), 1.05 (s, (tBu)CCHC(tBu), 18H), 0.68 (s, TidCHt-
Bu, 9H), 0.39 (s, Ti-CH2SiMe3, 9H). 13C NMR (25 °C, 100.6
MHz, C6D6): δ 260.8 (TidCHtBu, JC-H ) 88 Hz), 174.5 ((tBu)-
CCHC(tBu)), 147.8 (ipso-C6H3), 142.6 (o-C6H3), 139.9 (o-C6H3),
126.0 (p-C6H3), 124.3 (m-C6H3), 124.1 (m-C6H3), 93.58 ((tBu)-
CCHC(tBu), JC-H ) 152 Hz), 56.00 (Ti-CH2SiMe3, JC-H ) 98
Hz), 47.49 (TidCHCMe3), 44.49 ((CMe3)CCHC(CMe3)), 32.35
((CMe3)CCHC(CMe3)), 31.60 (TidCHCMe3), 29.06 (CHMe2),
28.75 (CHMe2), 27.94 (Me), 26.63 (Me), 24.92 (Me), 24.86 (Me),
4.25 (TiCH2SiMe3). Anal. Calcd for C44H74N2SiTi: C, 74.74;
H, 10.55; N, 3.96. Found: C, 74.05; H, 10.81; N, 4.12.
Synthesis of 4. In a vial was dissolved (L3)TidCHtBu(OTf)
(108 mg, 0.14 mmol) in 10 mL of THF and the solution cooled
to -35 °C. To the cold solution was added a cold THF solution
(∼5 mL) containing KCH2Ph (18.78 mg, 0.14 mmol). After it
was warmed, the mixture was stirred for an additional 20 min.
Solvent was then removed under reduced pressure, the solid
extracted with hexane, the extract filtered, and the filtrate
concentrated and stored at -35 °C for 24 h to afford dark
blocks of (L3)TidCHtBu(CH2Ph) (4; 74 mg, 0.10 mmol, 72%
yield, two crops).
Data for 4 are as follows. 1H NMR (23 °C, 399.8 MHz,
C6D6): δ 7.32-6.91 (m, aryl, 11H), 5.31 (s, ((tBu)CCHC(tBu),
1H), 3.70 (s, TidCHtBu, 1H), 3.35 (septets, CHMe2, 4H), 3.29
(s, Ti-CH2Ph, 2H), 1.67 (d, CHMe2, 6H), 1.40 (d, CHMe2, 6H),
1.36 (d, CHMe2, 6H), 1.30 (d, CHMe2, 6H), 0.99 (s, (tBu)CCHC-
(tBu), 18H,) 0.65 (s, TidCHtBu, 9H). 13C NMR (25 °C, 100.6
MHz, C6D6): δ 253.9 (TidCHtBu, JC-H ) 88 Hz), 174.1 ((tBu)-
CCHC(tBu)), 152.0 (ipso-aryl), 148.0 (ipso-aryl), 142.7 (o-aryl),
139.5 (o-aryl), 127.9 (o-aryl), 126.6 (p-aryl), 126.1 (p-aryl), 124.3
(m-aryl), 123.8 (m-aryl), 120.6 (m-aryl), 90.74 ((tBu)CCHC(tBu),
JC-H ) 152 Hz), 67.13 (Ti-CH2Ph, JC-H ) 114 Hz), 48.42 (Tid
CHCMe3), 44.67 ((CMe3)CCHC(CMe3)), 32.14 ((CMe3)CCHC-
(CMe3)), 31.41 (TidCHCMe3), 29.60 (CHMe2), 28.80 (CHMe2),
27.44 (Me), 26.29 (Me), 24.73 (Me), 24.60 (Me). Anal. Calcd for
C47H70N2Ti: C, 79.40; H, 9.92; N, 3.94. Found: C, 78.98; H,
9.36; N, 3.61.
Synthesis of 5 and 6 from Thermolysis of 1. In a vial
was dissolved (L1)TidCHtBu(CH2SiMe3) (1; 175 mg, 0.28
mmol) in 10 mL of hexane. After 10 days at 25 °C red crystals
of Ti[2,6-(CMe2)(CHMe2)C6H3]NC(Me)CHC(Me)N[2,6-(CMe2)-
(CHMe2)C6H3](CH2SiMe3) (5; 22 mg, 0.04 mmol, 14% yield)
slowly precipitated. The crystals were separated, and the
filtrate was cooled to -35 °C for 15 days to afford orange-yellow
crystals of [TidNAr([Ar]NC(Me)CHC(µ-CH2)dCHtBu)]2 (6; 57
mg, 0.05 mmol). After separation of 5 and 6, examination of
the filtrate revealed a myriad of products present, including
complex 6. Crystals of 6 are sparingly soluble in most common
organic solvents, as well as in CH2Cl2. Complex 6 does dissolve
slowly in THF, but upon solvation it gradually transforms over
several minutes to complex 8.
(38) (a) Sur, S. K. J. Magn. Reson. 1989, 82, 169-173. (b) Evans,
D. F. J. Chem. Soc. 1959, 2003-2005.
(39) Neese, F. QCPE Bull. 1995, 15, 5.

Intramolecular C-H Activation Reactions
Organometallics, Vol. 24, No. 13, 2005 3333
Data for 5 are as follows. 1H NMR (23 °C, 399.8 MHz,
C6D6): δ 7.54-7.08 (m, C6H3, 6H), 5.45 (s, C(Me)CHC(Me),
1H), 2.82 (septet, CHMe2, 2H), 2.28 (s, CMe2, 6H), 2.06 (s,
CMe2, 6H), 1.22 (d, CHMe2, 6H), 0.77 (s, C(Me)CHC(Me), 6H),
0.61 (d, CHMe2, 6H), 0.05 (s, Ti-CH2SiMe3, 9H), -1.38 (s, CH2-
SiMe3, 2H). 13C NMR (25 °C, 100.6 MHz, C6D6): δ 160.6
(C(Me)CHC(Me)), 142.8 (ipso-C6H5), 141.5 (o-C6H3), 136.0 (o-
C6H3), 130.9 (p-C6H3), 127.9 (m-C6H3), 124.6 (m-C6H3), 104.5
(C(Me)CHC(Me)), 80.06 (CMe2), 63.13 (Ti-CH2SiMe3), 27.93
(CMe2), 27.75 (CHMe2), 25.20 (Me), 24.38 (Me), 22.09 (Me),
21.65 (Me), 2.89 (TiCH2SiMe3). Anal. Calcd for C33H50N2SiTi:
C, 71.97; H, 9.15; N, 5.09. Found: C, 71.82; H, 9.25; N, 5.32.
Data for 6 are as follows. 1H NMR (23 °C, 399.8 MHz, THF-
d8): δ 7.20-7.10 (m, C6H3, 3H), 6.84 (d, C6H3, 2H), 6.62 (t,
C6H3, 1H), 5.51 (br, tBuHCC(CH2)CHC(Me), based on HMQC,
) 107 Hz), 35.23 (Me3CHCC(Me)CHC(Me)), 32.51 (Me3CHCC-
(Me)CHC(Me)), 29.65 (CHMe2), 28.21 (CHMe2), 25.52 (Me),
25.28 (Me), 25.13 (Me), 24.72 (Me), 24.28 (Me), 24.14 (Me),
23.34 (Me), 22.85 (Me), 3.33 ((TiCH2SiMe3). Anal. Calcd for
C38H62N2SiTi: C, 73.28; H, 10.03; N, 4.50. Found: C, 73.11;
H, 9.95; N, 4.60.
Synthesis of (H2CdC(CHtBu)CHC(Me)N[Ar])TidNAr-
(THF) (8). In a vial was dissolved complex 6 in 10 mL of THF
(75 mg, 0.75 mmol), and after a few minutes the solvent was
evaporated under reduced pressure to afford (H2CdC(CHtBu)-
CHC(Me)N[Ar])TidNAr(THF) (8) quantitatively. Single crys-
tals can be readily obtained from Et2O at -35 °C.
Data for 8 are as follows. 1H NMR (23 °C, 399.8 MHz, THF-
d8): δ 7.16-6.89 (m, C6H3, 6H), 5.29 (s, tBuHCC(CH2)CHC(Me)
t
and BuHCC(CH2)CHC(Me), 2H, based on HMQC), 3.86 (br,
t
THF, 4H), 3.79 (septet, CH(Me)2, 2H), 3.67 (d, tBuHCC(CH2)-
CHC(Me), 1H, JH-H ) 9 Hz), 3.46 (septet, CHMe2, 1H), 3.05
(septet, CHMe2, 1H), 2.78 (d, tBuHCC(CH2)CHC(Me), 1H, JH-H
) 9 Hz), 1.59 (s, tBuHCC(CH2)CHC(Me), 3H), 1.36 (d, CHMe2,
3H), 1.32 (s, (Me3C)HCC(CH2)CHC(Me), 9H), 1.30 (br, THF,
4H), 1.27 (d, CHMe2, 3H), 1.22 (mixture of two doublet CHMe2,
6H), 1.34 (d, CHMe2, 9H), 0.88 (d, CHMe2, 3H). 13C NMR (25
°C, 100.6 MHz, THF-d8): δ 157.9 (tBuHCC(CH2)CHC(Me)),
147.9 (tBuHCC(CH2)CHC(Me)), 144.0 (C6H3), 143.3 (C6H3),
142.8 (C6H3), 138.3 (C6H6), 136.2 (C6H6), 136.2 (tBuHCC(CH2)-
CHC(Me), based on HMQC, JC-H ) 146 Hz), 125.4 (C6H6),
124.1 (C6H3), 123.0 (C6H3), 122.4 (C6H6) 119.7 (C6H3), 103.7
(tBuHCC(CH2)CHC(Me), JC-H ) 159 Hz), 74.92 (br, tBuHCC-
(CH2)CHC(Me), based on HMQC), 71.04 (THF), 33.00 (Me3C-
HCC(CH2)CHC(Me)), 31.47 (Me3CHCC(Me)CHC(Me)), 28.89
(CHMe2), 28.28 (CHMe2), 25.44 (THF), 25.22 (Me), 25.09 (Me),
24.61 (Me), 24.40 (Me), 24.20 (Me), 23.36 (Me), 22.94 (Me).
Complex 8 is thermally unstable, and multiple attempts to
obtain satisfactory elemental analysis were unsuccessful.
Synthesis of 9. In a vial was dissolved (L1)TidCHtBu(CH2-
SiMe3) in 3 mL of toluene (175 mg, 0.256 mmol) and the brown
solution cooled to -35 °C. To the cold solution was added
dropwise a cooled (-35 °C) suspension of KC8 (38 mg, 281
mmol) in THF (∼3 mL). The solution quickly changes to a dark
green-brown and was stirred for 1 h. The solution was dried
in vacuo, and the residue was extracted with pentane. The
green-brown solution was filtered and then pumped dry to give
crude Ti([Ar]NC(Me)CHC(Me)N[2,6-(CHMe2)(CH(CH2)(Me))-
1H), 5.07 (br, BuHCC(CH2)CHC(Me), based on HMQC, 1H),
3.97 (br, CHMe2, 2H), 3.74 (br, CHMe2, 2H), 3.01 (br, tBuHCC-
t
(CH2)CHC(Me), 1H), 2.30 (br, BuHCC(CH2)CHC(Me), 1H),
1.80 (s, tBuHCC(CH2)CHC(Me), 3H), 1.38 (s, (Me3C)HCC(CH2)-
CHC(Me), 9H), 1.33 (overlapping doublets, CHMe2, 12H), 1.16
(d, CHMe2, 6H), 1.09 (d, CHMe2, 6H). 13C NMR (25 °C, 100.6
MHz, THF-d8): δ 157.8 (tBuHCC(CH2)CHC(Me)), 150.1 (br,
tBuHCC(CH2)CHC(Me)), 143.8 (C6H3), 142.9 (C6H3), 140.4
(C6H3), 131.3 (br, tBuHCC(CH2)CHC(Me)), 124.4 (C6H6), 123.7
t
(C6H3), 122.3 (C6H3), 119.5 (C6H3), 103.1 (br, BuHCC(CH2)-
CHC(Me)), 69.23 (br, tBuHCC(CH2)CHC(Me)), 33.47 (Me3-
CHCC(Me)CHC(Me)), 32.60 (br), 28.82 (br), 27.9 (br), 25.9 (br),
24.40 (br). Anal. Calcd for C68H100N4Ti2: C, 76.38; H, 9.43; N,
4.24. Found: C, 76.04; H, 9.25; N, 5.14. LDI MS for C63H88N4-
Ti2: calcd m/z, 1069 (M)+; found m/z, 1068.
Independent Synthesis of Complex 5. In a vial was
loaded Ti[2,6-(CMe2)(CHMe2)C6H3]NC(Me)CHC(Me)N[2,6-
(CMe2)(CHMe2)C6H3](OTf) (75 mg, 0.12 mmol),the solid dis-
solved in 10 mL of Et2O, and the solution cooled to -35 °C. To
the cold solution was added a cold Et2O solution (∼5 mL)
containing LiCH2SiMe3 (12.1 mg, 0.13 mmol). After the reac-
tion mixture was warmed to room temperature it was stirred
for an additional 1 h. Solvent was then evaporated under
reduced pressure, the solid extracted with benzene, the extract
filtered, and solvent again evaporated under reduced pressure.
The solid was then dissolved in Et2O, the solution filtered, and
the filtrate concentrated and stored at -35 °C for 24 h to afford
dark red crystals of Ti[2,6-(CMe2)(CHMe2)C6H3]NC(Me)CHC-
(Me)N[2,6-(CMe2)(CHMe2)C6H3](CH2SiMe3) (5; 59 mg, 0.11
t
C6H3])(CH2 Bu) (9; 135 mg). Examination of the product by
1
mmol, 87% yield, two crops). H and 13C NMR spectra were
1H NMR spectra reveals a myriad of products including
starting material. Attempts to recrystallize the crude material
led to formation of a few single crystals of 9 along with
significant decomposition. The crude product gave µeff ) 1.756
µB (C6D6, 298 K, Evans’ method). X-band EPR of the crude
product gives giso ) 1.957 G (in an 1/1 Et2O/pentane mixture).
EPR spectra also display signals consistent with other para-
magnetic Ti species present in solution. Coupling is observed
but not adequately simulated. Attempts to obtain satisfactory
elemental analysis were unsuccessful.
identical with independent samples of 5 prepared via ther-
molysis of 1.
Synthesis of Complex 7. In a reaction vessel was dissolved
(HtBuCdC(Me)CHC(Me)N[Ar])TidNAr(OTf) (200 mg, 0.29
mmol) in pentane (10 mL), and the solution was cooled to -35
°C. To the cold solution was added a cold pentane solution (∼5
mL) containing LiCH2SiMe3 (27.5 mg, 0.29 mmol). After the
mixture was stirred for 30 min, the solution was filtered and
the filtrate concentrated and stored at -35 °C for 24 h to afford
red blocks of (HtBuCdC(Me)CHC(Me)N[Ar])TidNAr(CH2-
SiMe3) (7; 151 mg, 0.24 mmol, 83% yield, two crops).
Data for 7 are as follows. 1H NMR (23 °C, 399.8 MHz,
C6D6): δ 7.07-6.84 (m, C6H3, 6H), 5.00 (s, tBuHCC(Me)CHC-
(Me), 1H), 3.53 (septet, CHMe2, 2H), 2.43 (s, tBuHCC(Me)CHC-
Synthesis of 10. In a vial was dissolved (L3)TidCHtBu-
(OTf) (108 mg, 0.14 mmol) in 10 mL of Et2O, and the solution
was cooled to -35 °C. To the cold solution was added a cold
Et2O solution (5 mL) containing LitBu (10.18 mg, 0.16 mmol).
After it was warmed, the mixture was stirred for an additional
5 min and solvent was evaporated under reduced pressure.
The solid was extracted with pentane, the extract filtered, and
the filtrate concentrated and stored at -35 °C for 24 h to afford
dark green crystals of Ti([Ar]NC(tBu)CHC(tBu)N[2,6-(CHMe2)-
t
(Me), 1H), 2.23 (septet, CH(Me)2, 2H), 1.97 (s, BuHCC(Me)-
CHC(Me), 3H), 1.92 (d, TiCH2SiMe3, 1H, JH-H ) 10 Hz), 1.74
t
(s, BuHCC(Me)CHC(Me), 3H), 1.39 (d, CHMe2, 6H), 1.23 (s,
tBuHCC(Me)CHC(Me), 9H), 1.14 (d, CHMe2, 6H), 1.08 (d,
CHMe2, 6H), 1.04 (d, CHMe2, 6H), 0.25 (d, TiCH2SiMe3, 1H,
JH-H ) 10 Hz), 0.22 (s, TiCH2SiMe3, 9H). 13C NMR (25 °C,
100.6 MHz, C6D6): δ 160.9 (tBuHCC(Me)CHC(Me)), 157.6
(tBuHCC(Me)CHC(Me)), 155.2 (C6H3), 145.7 (C6H3), 142.8
(C6H3), 139.8 (C6H3), 131.6 (tBuHCC(Me)CHC(Me), based on
HMQC, JC-H ) 123 Hz), 127.9 (C6H6), 126.7 (C6H3), 125.2
(C6H3), 123.5 (C6H3), 122.6 (C6H3), 121.8 (C6H6), 97.71 (tBuH-
CC(Me)CHC(Me), JC-H ) 163 Hz), 54.23 (TiCH2SiMe3, JC-H
t
(CH(CH2)(Me))C6H3])(CH2 Bu) (10; 58 mg, 0.09 mmol, 65%
yield, three crops). The compound (L3)TidCHtBu(OTf) can also
be reduced with 1.2 equiv of KC8 (0.5 h) in THF/toluene and
worked up analogously to afford 10 in low yield.
Data for 10 are as follows. 1H NMR (23 °C, 399.8 MHz,
C6D6): δ 8.22 (∆ν1/2 ) 957 Hz), 7.86 (∆ν1/2 ) 257 Hz), 5.78 (∆ν1/2
) 153 Hz), 2.65 (∆ν1/2 ) 1210 Hz), 2.05 (∆ν1/2 ) 116 Hz), 0.29
(∆ν1/2 ) 203 Hz), -0.92 (∆ν1/2 ) 2085 Hz). µeff ) 1.83 µΒ (C6D6,

3334 Organometallics, Vol. 24, No. 13, 2005
Basuli et al.
298 K, Evans’ method). Complex 10 is thermally unstable, and
multiple attempts to obtain satisfactory elemental analysis
were unsuccessful.
the centrosymmetric space group P21/n, and subsequent solu-
tion and refinement confirmed this choice. All non-hydrogen
atoms were refined with anisotropic displacement parameters.
A disorder involving a diethyl ether is present at the THF site
but was easily modeled. All hydrogen atoms except those
associated with the partial occupancy diethyl ether were
located in subsequent Fourier maps and included as isotropic
contributors in the final cycles of refinement. The hydrogen
atoms associated with the ether were placed in ideal positions
and refined as riding atoms with relative isotropic displace-
ment parameters. The remaining electron density was located
in bonds.
For 9, the crystals occur as dark green clusters of crystals
with few well-defined faces. Several crystals were examined
and found to be badly split and twinned. It was finally possible
to locate a fragment which had only three components, with
one that was clearly dominant. Intensity statistics and sys-
tematic absences suggested the centrosymmetric space group
P21/c, and subsequent solution and refinement confirmed this
choice. A direct-methods solution was calculated which pro-
vided 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.
There is a slight disorder, with 7.3% of the sites having an
alternate Ti position. All hydrogen atoms were located in
subsequent Fourier maps and included as isotropic contribu-
tors in the final cycles of refinement.
For 10, intensity statistics and systematic absences sug-
gested the centrosymmetric space group P21/n, and subsequent
solution and refinement confirmed this choice. 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. There is a disorder present
with the titanium atom shifted to the other side of the plane
defined by N(2), N(6), and C(39). All non-hydrogen atoms were
refined with anisotropic displacement parameters. All hydro-
gen atoms were located in subsequent Fourier maps and
included as isotropic contributors in the final cycles of refine-
ment. The final full-matrix least-squares refinement converged
to R1 ) 0.0441 and wR2 ) 0.1134 (F 2, all data). The remaining
electron density is located on bonds.
Oxidation of 10 to (L3)TidCHtBu(OTf). In a reaction
vessel was dissolved 10 (103 mg, 0.17 mmol) in 10 mL of THF,
and the solution was cooled to -35 °C. To the cold solution
was added a cold THF solution (∼5 mL) containing AgOTf
(44.8 mg, 0.17 mmol), causing an immediate color change from
green to brown. After the mixture was stirred for 15 min, the
solution was filtered, and the filtrate was evaporated under
reduced pressure. The solid was dissolved in pentane, the
solution filtered, and the filtrate concentrated and stored at
-35 °C for 24 h to afford dark crystals of (L3)TidCHtBu(OTf)
1
(120 mg, 0.16 mmol, 94% yield, two crops). H and 13C NMR
spectra of the product were compared to samples prepared
independently.
Structure Solution and Refinement. A summary of
crystal data and refinement details for all structures are given
in Tables 2 and 3.
General Parameters for Data Collection and Refine-
ment. Single crystals of 1 (pentane), 2 (hexane), 4 (hexane),
6‚C5H12 (pentane), 7 (hexane), 8 (Et2O), 9 (hexane), and 10
(pentane) were grown at -35 °C. Inert-atmosphere techniques
were used to place the crystal onto the tip of a glass capillary
(0.06-0.20 mm), which was mounted on a SMART6000
diffractometer (Bruker) at 127-140(2) K. A preliminary set
of cell constants was calculated from reflections obtained from
three nearly orthogonal sets of 20-30 frames. The data
collection was carried out using graphite-monochromated Mo
KR radiation with a frame time of 3 s and a detector distance
of 5.0 cm. A randomly oriented region of a sphere in reciprocal
space was surveyed. Three sections of 606 frames were
collected with 0.30° steps in ω at different φ settings with the
detector set at -43° in 2θ. Final cell constants were calculated
from the xyz centroids of strong reflections from the actual data
collection after integration (SAINT).40 The structure was solved
using SHELXS-97 and refined with SHELXL-97.41 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 (unless
otherwise mentioned). All hydrogen atoms were refined with
isotropic displacement parameters (unless otherwise men-
tioned).
For 2, intensity statistics and systematic absences suggested
the noncentrosymmetric trigonal space group P31, and subse-
quent solution and refinement confirmed this choice. Several
different crystals were examined, and all were badly split with
large mosaic character. Three crystallographically independent
but chemically equivalent molecules were confined in the cell.
For 6‚C5H12, intensity statistics and systematic absences
suggested the centrosymmetric triclinic space group P1h, and
subsequent solution and refinement confirmed this choice. 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, including a disordered
pentane solvent. All non-hydrogen atoms were refined with
anisotropic displacement parameters. With the exception of
those associated with the solvent molecule, all hydrogen atoms
were located in subsequent Fourier maps and included as
isotropic contributors in the final cycles of refinement.
For 8, intensity statistics and systematic absences suggested
Acknowledgment. We thank Indiana Universitys
Bloomington, the Camille and Henry Dreyfus Founda-
tion, the Ford Foundation, and the National Science
Foundation (Grant No. CHE-0348941) for financial
support of this research. D.J.M. wishes to thank Prof.
K. G. Caulton for insightful discussions and Indiana
University for a Summer Faculty Fellowship and Start-
up grant. B.C.B. acknowledges the Department of
Education for a GAANN Fellowship. Dr. Jon Karty is
also acknowledged for assistance in collecting LDI MS
data.
Supporting Information Available: CIF files giving
complete details for data sets, including tables with atomic
coordinates, bond lengths and angles, anisotropic displacement
parameters, hydrogen coordinates, and structural diagrams
for complexes 1, 2, 4, 6‚C5H12, and 7-10, and figures giving
additional NMR spectra. This material is available free of
charge via the Internet at http://pubs.acs.org.
(40) SAINT 6.1; Bruker Analytical X-ray Systems, Madison, WI.
(41) SHELXTL-Plus V5.10; Bruker Analytical X-ray Systems, Madi-
son, WI.
OM049318G