Reactivity at the β-Diketiminate Ligand Nacnac- on Titanium(IV) (Nacnac- = [Ar]NC(CH3)CHC(CH 3)N[Ar], Ar = 2,6-[CH(CH3)2]2C 6H3). Diimine-alkoxo and Bis-anilido Ligands Stemming from the Nacnac-Skeleton

Article abstract of DOI:10.1021/ic034853e

The reaction of ketene OCCPh₂ with the four-coordinate titanium(IV) imide (L₁)Ti=NAr(OTf) (L₁^- = [Ar]NC(CH₃)-CHC(CH₃)N[Ar], Ar = 2,6-[CH(CH ₃)₂]₂C₆H₃) affords the tripodal dimine-alkoxo complex (L₂)Ti=NAr(OTf) (L₂ ^- = [Ar]NC(CH₃)CHC(O)=CPh₂C(CH ₃)N[Ar]). Complex (L₂)Ti=NAr(OTf) forms from electrophilic attack of the β-carbon of the ketene on the γ-carbon of the Nacnac^- NCCγCN ring. On the contrary, nucleophiles such as LiR (R^- = Me, CH₂^tBu, and CH ₂SiMe₃) deprotonate cleanly in OEt₂ the methyl group of the β-carbon on the former Nacnac^- backbone to yield the etherate complex (L₃)Ti=NAr(OEt₂), a complex that is now supported by a chelate bisanilido ligand (L₃^2- = [Ar]NC(CH₃)CHC(CH₂)N[Ar]). In the absence of electrophiles or nucleophiles, the robust (L₁)Ti=NAr(OTf) template was found to form simple adducts with Lewis bases such as CN^tBu or NCCH₂(2,4,6-Me₃C₆H₂). Complexes (L₂)Ti=NAr(OTf), (L₃)Ti=NAr(OEt₂), and the adducts (L₁)Ti=NAr(OTf)(XY) [XY = CN^tBu and NCCH ₂(2,4,6-Me₃C₆H₂)] were structurally characterized by single-crystal X-ray diffraction studies.

Full text of DOI:10.1021/ic034853e

Inorg. Chem. 2003, 42, 8003−8010
Reactivity at the â-Diketiminate Ligand Nacnac- on Titanium(IV)
(Nacnac- ) [Ar]NC(CH )CHC(CH )N[Ar], Ar ) 2,6-[CH(CH ) ] C H ).
3
3
3 2 2 6 3
Diimine-alkoxo and Bis-anilido Ligands Stemming from the Nacnac-
Skeleton
Falguni Basuli, John C. Huffman, and Daniel J. Mindiola*
Department of Chemistry and Molecular Structure Center, Indiana UniVersity,
Bloomington, Indiana 47405
Received July 18, 2003
The reaction of ketene OCCPh2 with the four-coordinate titanium(IV) imide (L1)TidNAr(OTf) (L1- ) [Ar]NC(CH )-
3
CHC(CH )N[Ar], Ar ) 2,6-[CH(CH ) ] C H ) affords the tripodal dimine-alkoxo complex (L2)TidNAr(OTf) (L2-
)
3
3 2 2 6 3
[Ar]NC(CH )CHC(O)dCPh2C(CH )N[Ar]). Complex (L2)TidNAr(OTf) forms from electrophilic attack of the â-carbon
3
3
of the ketene on the γ-carbon of the Nacnac- NCC CN ring. On the contrary, nucleophiles such as LiR (R- )
γ
Me, CH tBu, and CH SiMe3) deprotonate cleanly in OEt2 the methyl group of the â-carbon on the former Nacnac-
2
2
backbone to yield the etherate complex (L3)TidNAr(OEt2), a complex that is now supported by a chelate bis-
anilido ligand (L32- ) [Ar]NC(CH )CHC(CH )N[Ar]). In the absence of electrophiles or nucleophiles, the robust
3
2
t
(L1)TidNAr(OTf) template was found to form simple adducts with Lewis bases such as CNBu or NCCH (2,4,6-
2
t
Me3C H ). Complexes (L2)TidNAr(OTf), (L3)TidNAr(OEt2), and the adducts (L1)TidNAr(OTf)(XY) [XY ) CNBu
6
2
and NCCH (2,4,6-Me3C H )] were structurally characterized by single-crystal X-ray diffraction studies.
2
6 2
Introduction
metric forms) have been described in depth in a current
review.3 Second, â-diketimines are easy to modify at the
R-nitrogens,3,6-10 the â-carbons,6 and the γ-carbon positions
(Figure 1).8,11-13 Variation of these substituents provides an
Although â-diketimines (often referred to as NacnacH)
were prepared over 30 years ago,1 the coordination chemistry
developed from such a simple class of molecules is just
currently undergoing a dramatic renaissance.2,3 Several
features make this class of ligands attractive. First and
foremost, general syntheses of Schiff bases are often achieved
easily by condensation reactions stemming from com-
mercially available starting materials such as the amine and
the corresponding dione.3-6 This feature allows the ligands
to be prepared, conveniently, in multigram scales. More novel
methods for preparing â-diketimines (symmetric and asym-
(5) Some examples include: (a) Kakaliou, L.; Scanlon, W. J., IV; Qian,
B.; Baek, S. W.; Smith, M. R., III; Motry, D. H. Inorg. Chem. 1999,
38, 5964. (b) Chamberlain, B. M.; Cheng, M.; Moore, D. R.; Ovitt,
T. M.; Lobkovsky, E. B.; Coates, G. W. J. Am. Chem. Soc. 2001,
123, 3229. (c) Hardman, N. J.; Power, P. P. J. Am. Chem. Soc. 2001,
40, 2474. (d) MacAdams, L. A.; Kim, W.-K.; Liable-Sands, L. M.;
Guzei, I. A.; Rheingold, A. L.; Theopold, K. H. Organometallics 2002,
21, 952. (e) Prust, J.; Hohmeister, H.; Stasch, A.; Roesky, H. W.;
Magull, J.; Alexopoulos, E.; Uso´n, I.; Schmidt, H.-G.; Noltemeyer,
M. Eur. J. Inorg. Chem. 2002, 2156. (f) Harder, S. Organometallics
2002, 21, 3782. (g) Clegg, W.; Cope, E. K.; Edwards, A. J.; Mair, F.
S. Inorg. Chem. 1998, 37, 2317. (h) Qian, B.; Scanlon, W. J.; Smith,
M. R., III; Motry, D. H. Organometallics 1999, 18, 1693.
(6) Budzelaar, P. H. M.; van Oort, A. B.; Orpen, A. G. Eur. J. Inorg.
Chem. 1998, 1485.
(7) (a) Kuhn, N.; Lanfermann, H.; Schmitz, P. Liebigs Ann. Chem. 1987,
727. (b) Kuhn, N.; Kuhn, A.; Boese, R.; Augart, N. J. Chem. Commun.
1989, 975. (c) Kuhn, N.; Kuhn, A.; Speis, M.; Blaeser, D.; Boese, R.
Chem. Ber. 1990, 123, 1301.
* To whom correspondence should be addressed. E-mail: mindiola@
indiana.edu.
(1) (a) McGeachin, S. G. Can. J. Chem. 1968, 46, 1903. (b) Dorman, L.
C. Tetrahedron Lett. 1966, 4, 459. (c) Barry, W. J.; Finar, I. L.;
Mooney, E. F. Spectrochim. Acta 1965, 21, 1095. (d) Parks, J. E.;
Holm, R. H. Inorg. Chem. 1968, 7, 1408. (e) Holm, R. H.; O’Connor,
M. J. Prog. Inorg. Chem. 1971, 14, 241.
(2) Piers, W. E.; Emslie, D. J. H. Coord. Chem. ReV. 2002, 233, 131.
(3) Bourget-Merle, L.; Lappert, M. F.; Severn, J. R. Chem. ReV. 2002,
102, 3031.
(4) Stender, M.; Wright, R. J.; Eichler, B. E.; Prust, J.; Olmstead, M. M.;
Roesky, H. W.; Power, P. P. J. Chem. Soc., Dalton Trans. 2001, 3465
and references therein.
(8) Spencer, D. J. E.; Reynolds, A. M.; Holland, P. L.; Jazdzewski, B.
A.; Duboc-Toia, C.; Le Pape, L. L.; Yokota, S.; Tachi, Y.; Itoh, S.;
Tolman, W. B. Inorg. Chem. 2002, 41, 6307 ands references therein.
(9) Cheng, M.; Moore, D. R.; Reczek, J. J.; Chamberlain, B. M.;
Lobkovsky, E. B.; Coates, G. W. J. Am. Chem. Soc. 2001, 123, 8738.
(10) Yokota, S.; Tachi, Y.; Itoh, S. Inorg. Chem. 2002, 41, 1342.
10.1021/ic034853e CCC: $25.00 © 2003 American Chemical Society
Published on Web 10/31/2003
Inorganic Chemistry, Vol. 42, No. 24, 2003 8003

Basuli et al.
the reaction. Thus, â-diketiminates can potentially be “non-
innocent” ligands in the context of organometallic chemistry.
One common degradation of Nacnac- is C-H abstraction
in the aryl groups on the R-nitrogens, leading to metalation
or metal hydride formation.3,5h,17b,23 Other, more unusual
reactions of the ligand include electrophilic activation of the
γ-carbon3,7,8,13,24 and deprotonation of the methyl group
attached to the â-carbon in the NCCCN ring.3,25 More
recently, cross-metathesis of the imine functionality of
Nacnac- with a neopentylidene18 or phosphinidene26 unit has
also been reported (imine-alkylidene cross-metathesis, or
a Wittig/Staudinger-like reaction).18 Inspired by the work of
the groups of Budzelaar,6 Jordan,13 Lappert,24 Roesky,25 and
Theopold5d,21a,21d,21e in the chemistry of electrophilic Nacnac-
based complexes of the p-, d-, and f-block elements, we
sought reactivity of Nacnac- with electrophiles and nucleo-
philes when this ligand is coordinated to titanium(IV).
Herein, we report the preliminary reactivity of the four-
Figure 1. Representation of R-, â-, and γ-positions in the â-diketiminate
t
ligand. The R group is Me or Bu, and Ar represents a substituted or
unsubstituted aryl group.
opportunity to examine both the electronic and the steric
effects governing these class of ligands.
One of the most important aspects associated with the
Nacnac- ligand is its ability to support reactive metal
fragments.3,8,14-18 Hence, the robust nature of Nacnac- has
prompted the use of such ligands in catalysis,17,19-22 and
Nacnac-based complexes are just now becoming common
targets for carrying out catalytic transformations such as
olefin polymerization,5,17,21,22 ring-opening polymerization,
and copolymerization reactions.19,20
-
coordinate imide complex (L1)TidNAr(OTf) (L1 ) [Ar]-
Although regarded as robust, the supporting â-diketiminate
ligand in a complex can occasionally become involved in
NC(CH3)CHC(CH3)N[Ar], Ar ) 2,6-[CH(CH3)2]2C6H3) with
unsaturated organic substrates. Our interest in exploring the
chemistry of the TidNAr fragment has led unexpectedly to
two new class of ligands defined as L2 and L3 (L2- ) [Ar]-
NC(CH3)CHC(O)dCPh2C(CH3)N[Ar], L32- ) [Ar]NC(CH3)-
CHC(CH2)N[Ar]), both of which are derived from the
titanium-Nacnac template “(Nacnac)Ti”. When Nacnac- is
coordinated to titanium(IV), two modifications of the ligand
are accomplished readily. One modification occurs by
electrophilic activation of the γ-carbon of the NCCCN ring
with diphenylketene, whereas the other takes place from the
deprotonation of the methyl group attached to the â-carbon
of the Nacnac- ring with nucleophiles (e.g., alkyllithiums).
These transformations occur cleanly and yield novel titanium
complexes containing a tripodal diimine-alkoxo and a chelate
bis-anilido ligand, respectively.
(11) Yokota, S.; Tachi, Y.; Nishiwaki, N.; Ariga, M.; Itoh, S. Inorg. Chem.
2001, 40, 5316.
(12) Davies, I. W.; Marcoux, J.-F.; Wu, J.; Palucki, M.; Corley, E. G.;
Robbins, M. A.; Tsou, N.; Ball, R. G.; Dormer, P.; Larsen, R. D.;
Reider, P. J. J. Org. Chem. 2000, 65, 4571.
(13) Radzewich, C. E.; Coles, M. P.; Jordan, R. F. J. Am. Chem. Soc. 1998,
120, 9384.
(14) (a) Cui, C.; Roesky, H. W.; Hao, H.; Schmidt, H.-G.; Noltemeyer,
M. Angew. Chem., Int. Ed. 2000, 39, 1815. (b) Hitchcock, P. B.; Hu,
J.; Lappert, M. F.; Layh, M.; Liu, D.-S.; Severn, J. R.; Shun, T. An.
Quim. Int. Ed. 1996, 92, 186. (c) Hardman, N. J.; Cui, C.; Roesky, H.
W.; Fink, W. H.; Power, P. P. Angew. Chem., Int. Ed. 2001, 40, 2172.
(d) Cui, C.; Ko¨pke, S.; Herbst-Irmer, R.; Roesky, H. W.; Noltemeyer,
M.; Schmidt, H.-G.; Wrackmeyer, B. J. Am. Chem. Soc. 2001, 123,
9091. (e) Cui, C.; Roesky, H. W.; Schmidt, H.-G.; Noltemeyer, M.
Angew. Chem., Int. Ed. 2000, 39, 4531. (f) Hardman, N. J.; Eichler,
B. E.; Power, P. P. Chem. Commun. 2000, 1991. (g) Hardman, N. J.;
Power, P. P. Inorg. Chem. 2001, 40, 2474. (h) Hardman, N. J.; Power,
P. P. Chem. Commun. 2001, 1184. (i) Bai, G. C.; Peng, Y.; Roesky,
H. W.; Li, J. Y.; Schmidt, H. G.; Noltemeyer, M. Angew. Chem., Int.
Ed. 2003, 42, 1132. (j) Jancik, V.; Peng, Y.; Roesky, H. W.; Li, J. Y.;
Neculai, D.; Neculai, A. M.; Herbst-Irmer, R. J. Am. Chem. Soc. 2003,
125, 1452 and references therein. (k) Neculai, A. M.; Neculai, D.;
Roesky, H. W.; Magull, J.; Baldus, M.; Andronesi, O.; Jansen, M.
Organometallics 2002, 21, 2590.
Experimental Section
General Considerations. Unless otherwise stated, all operations
were performed in an M. Braun Lab Master double drybox under
(15) (a) Holland, P. L.; Tolman, W. B. J. Am. Chem. Soc. 1999, 121, 7270.
(b) Holland, P. L.; Tolman, W. B. J. Am. Chem. Soc. 2000, 122, 6331.
(c) Randall, D. W.; DeBeer, S.; Holland, P. L.; Hedman, B.; Hodgson,
K. O.; Tolman, W. B.; Solomon, E. I. J. Am. Chem. Soc. 2000, 122,
11632. (d) Jazdzewski, B. A.; Holland, P. L.; Pink, M.; Young, V.
G., Jr.; Spencer, D. J. E.; Tolman, W. B. Inorg. Chem. 2001, 40, 6097.
(16) (a) Dai, X.; Warren, T. H. Chem. Commun. 2001, 1998. (b) Wiencko,
H. L.; Kogut, E.; Warren, T. H. Inorg. Chim. Acta 2003, 345, 199.
(17) (a) Zhang, S.; Piers, W. E.; Gao, X.; Parvez, M. J. Am. Chem. Soc.
2000, 122, 5499 and references therein. (b) 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. (c) Hayes, P. G.; Piers,
W. E.; Parvez, M. J. Am. Chem. Soc. 2003, 125, 5622.
(18) (a) Basuli, F.; Bailey, B. C.; Tomaszewski, J.; Huffman, J. C.;
Mindiola, D. J. J. Am. Chem. Soc. 2003, 125, 6052. (b) Basuli, F.;
Bailey, B. C.; Huffman, J. C.; Mindiola, D. J. Chem. Commun. 2003,
1554.
(19) (a) Cheng, M.; Ovitt, T. M.; Hustad, P. D.; Coates, G. W. Polym.
Prepr. (Am. Chem. Soc., DiV. Polym. Chem.) 1999, 40, 542. (b) Cheng,
M.; Attygalle, A. B.; Lobkovsky, E. B.; Coates, G. W. J. Am. Chem.
Soc. 1999, 121, 11583. (c) Cheng, M.; Darling, N. A.; Lobkovsky, E.
B.; Coates, G. W. Chem. Commun. 2000, 2007.
(21) (a) Richeson, D. S.; Mitchell, J. F.; Theopold, K. H. Organometallics
1989, 8, 2570. (b) Gibson, V. C.; Newton, C.; Redshaw, C.; Solan,
G.; White, A. J. P.; Williams, D. J.; Maddox, P. J. Chem. Commun.
1998, 1651. (c) Gibson, V. C.; Newton, C.; Redshaw, C.; Solan, G.
A.; White, A. J. P.; Williams, D. J. Eur. J. Inorg. Chem. 2001, 1895.
(d) MacAdams, L. A.; Kim, W.-K.; Liable-Sands, L. M.; Guzei, I.
A.; Rheingold, A. L.; Theopold, K. H. Organometallics 2002, 21, 952.
(e) Kim, W.-K.; Fevola, M. J.; Liable-Sands, L. M.; Rheingold, A.
L.; Theopold, K. H. Organometallics 1998, 17, 4541.
(22) Radzewich, C. E.; Guzei, I. A.; Jordan, R. F. J. Am. Chem. Soc. 1999,
121, 8673 and references therein.
(23) Fekl, U.; Kaminsky, W.; Goldberg, K. I. J. Am. Chem. Soc. 2001,
123, 6423.
(24) Electrophilic substitution with Ph2P+ or PhClP+ at the γ-carbon of
the Nacnac backbone has been recently reported: (a) Hitchcock, P.
B.; Lappert, M. F.; Nycz, J. E. Chem. Commun. 2003, 1142. (b)
Ragogna, P. J.; Burford, N.; D’eon, M.; McDonald, R. Chem. Commun.
2003, 1052 and references therein. In addition, R-alkoxylithium-â-
diimine ligands have been prepared from the reaction of the lithium
Nacnac salt and the corresponding ketone: Carey, D. T.; Cope-
Eatough, E. K.; Vilaplana-Mafe´, E.; Mair, F. S.; Pritchard, R. G.;
Warren, J. E.; Woods, R. J. J. Chem. Soc., Dalton Trans. 2003, 1083.
(25) Ding, Y.; Hao, H.; Roesky, H. W. Noltemeyer, M.; Schmidt, H.-G.
Organometallics 2001, 20, 4806.
(20) (a) Chisholm, M. H.; Huffman, J. C.; Phomphrai, K. J. Chem. Soc.,
Dalton Trans. 2001, 222. (b) Chisholm, M. H.; Gallucci, J.; Phomphrai,
K. Chem. Commun. 2003, 48. (c) Chisholm, M. H.; Gallucci, J.;
Phomphrai, K. Inorg. Chem. 2002, 41, 2785.
(26) Basuli, F.; Tomaszewski, J.; Huffman, J. C.; Mindiola, D. J. J. Am.
Chem. Soc. 2003, 125, 10170.
8004 Inorganic Chemistry, Vol. 42, No. 24, 2003

ReactiWity at the Ligand Nacnac- on Titanium(IV)
an atmosphere of purified nitrogen or using high-vacuum standard
Schlenk techniques under an argon atmosphere.27 Anhydrous
n-hexane, pentane, toluene, and benzene were purchased from
Aldrich in sure-sealed reservoirs (18 L) and dried by passage
through one column of activated alumina and one of Q-5.28 Diethyl
ether and CH2Cl2 were dried by passage through two columns of
activated alumina.28 THF was distilled, under nitrogen, from purple
sodium benzophenone ketyl and stored over sodium metal. Distilled
THF was transferred under vacuum into bombs before being
pumped into the drybox. C6D6 and CD2Cl2 were purchased from
Cambridge 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. Celite, alumina, and 4-Å molecular sieves were activated
under vacuum overnight at 200 °C. Li(Nacnac)4 (Nacnac- ) [Ar]-
NC(Me)CHC(Me)N[Ar], Ar ) 2,6-(CHMe2)2C6H3), (Nacnac)TiCl2-
(THF),6,18a (Nacnac)TidNAr(OTf),18b and OC2Ph229 were prepared
according to the literature procedures. Solid LitBu was collected
by cooling a saturated pentane solution to -78 °C followed by
rapid filtration. LiNHAr was prepared by deprotonation of freshly
distilled aniline at -35 °C with n-BuLi in hexanes. The white solid
was collected via filtration, washed with pentane, and dried under
reduced pressure. All other chemicals were used as received.
Solution infrared spectra (CaF2 plates) were measured using a
Nicolet 510P FTIR spectrometer. CHN analysis was performed by
Desert Analytics, Tucson, AZ. 1H, 13C, and 19F NMR spectra were
recorded on Varian 400- or 300-MHz NMR spectrometers. 1H and
13C NMR chemical shifts are reported with reference to solvent
resonances (residual C6D5H in C6D6, 7.16 and 128.0 ppm; residual
CHDCl2 in CD2Cl2, 5.32 ppm 53.8 ppm). 19F NMR chemical shifts
are reported with respect to external HOCOCF3 (-78.5 ppm). X-ray
diffraction data were collected on a SMART6000 (Bruker) system
under a stream of N2(g) at low temperatures.
26.01 (CHMe2), 25.89 (CHMe2), 25.51 (CHMe2), 25.25 (CHMe2),
25.19 (CHMe2), 24.94 (CHMe2), 24.80 (CHMe2), 24.73 (CHMe2),
24.64 (CHMe2), 24.38 (CHMe2), 24.24 (CHMe2), 23.67 (CHMe2).
19F NMR (23 °C, 282.3 MHz, C6D6): δ -77.19 (OSO2CF3). IR
(CaF2, C6H6): 3098 (m), 3071 (s), 3029 (s), 2967 (s), 2868 (m),
2213 (m, νC≡N), 1818 (w), 1529 (s), 1483 (s), 1464 (m), 1437 (m),
1378 (s), 1341 (s), 1315 (s), 1274 (m), 1255 (m), 1236 (m), 1200
(s), 1103 (w), 1039 (s), 1003 (s) cm-1. Anal. Calcd for C47H67N4O3F3-
STi: C, 64.66; H, 7.34; N, 6.42. Found: C, 65.00; H, 7.73; N,
6.31.
Synthesis of (L1)TidNAr(OTf)(NCH2Mes). In 5 mL of pentane
was suspended (L1)TidNAr(OTf) (77 mg, 0.097 mmol), and the
solution was cooled to -35 °C. To the cold solution was added a
cold pentane solution (5 mL) containing mesitylacetonitrile (15.5
mg, 0.097 mmol). After 5 min, a yellow-brown precipitate began
to form, and the reaction mixture was allowed to stir for an
additional 40 min. The solid was collected by filtration and washed
with cold pentane. Recrystallization from Et2O at -35 °C afforded
two crops of brown crystals of (L1)TidNAr(OTf)(NCCH2Mes)
(64.6 mg, 0.068 mmol, 70% yield). 1H NMR (23 °C, 399.8 MHz,
C6D6): δ 7.3-6.5 (m, C6H3, 9H), 6.61 (s, C6H2, 2H), 5.48 [s, C(Me)-
CHC(Me), 1H], 4.32 (septet, CHMe2, 1H), 4.07 (septet, CHMe2,
1H), 3.82 (septet, CHMe2, 1H), 3.61 (septet, CHMe2, 1H), 3.31
(dd, NCCH2Mes, 2H), 2.61 (septet, CHMe2, 1H), 2.45 (septet,
CHMe2, 1H), 2.09 (s, p-Me3C6H2, 3H), 2.01 (s, o-Me3C6H2, 6H),
1.78 (s, C(Me)CHC(Me), 3H), 1.71 [s, C(Me)CHC(Me), 3H], 1.46
(d, CHMe2, 3H), 1.39 (d, CHMe2, 3H), 1.30-1.18 (overlapping d,
CHMe2,18H), 1.15 (d, CHMe2, 3H), 1.07 (d, CHMe2, 6H), 0.96 (d,
CHMe2, 3H). 13C NMR (25 °C, 100.6 MHz, C6D6): δ 168.0 [C(Me)-
CHC(Me)], 166.7 [C(Me)CHC(Me)], 159.8 (NCCH2), 147.6 (aryl),
146.5 (aryl), 145.0 (aryl), 143.4 (aryl), 142.4 (aryl), 141.9 (aryl),
141.4 (aryl), 140.4 (aryl), 138.0 (aryl), 137.1 (aryl), 129.4 (aryl),
128.1 (aryl), 127.9 (aryl), 127.5 (aryl), 127.4 (aryl), 127.2 (aryl),
127.0 (aryl), 126.6 (aryl), 124.8 (aryl), 124.5 (aryl), 124.2 (aryl),
124.2 (aryl), 123.0 (aryl), 122.8 (aryl), 122.3 (aryl), 122.1 (aryl),
29.18, 27.94 27.79, 27.73, 26.03, 25.89, 25.77, 25.47, 25.20, 24.97,
24.91, 24.78 (Me), 24.21 (Me), 24.10 (Me), 23.54 (Me), 23.32 (Me),
20.87 (Me), 20.40 (Me), 18.48 (Me). 19F NMR (23 °C, 282.3 MHz,
C6D6): δ -78.16 (OSO2CF3). IR (CaF2, C6H6): 3077 (s), 3029
(s), 3023 (w), 2965 (w), 1960 (m, νC≡N), 1815 (m), 1586 (w), 1529
(w), 1474 (s), 1351 (w), 1227 (w), 1199 (w), 1007 (s) cm-1. Anal.
Calcd for C53H71N4O3F3STi: C, 67.07; H, 7.54; N, 5.90. Found:
C, 67.39; H, 7.82; N, 5.89.
Synthesis of (L1)TidNAr(OTf)(CNtBu). In 10 mL of pentane
was suspended (L1)TidNAr(OTf) (97 mg, 0.12 mmol), and the
solution was cooled to -35 °C. To the cold solution was added a
cold pentane solution (5 mL) containing CNtBu (10.21 mg, 0.12
mmol). After being stirred for 1 h, the solution was filtered,
concentrated, and cooled overnight at -35 °C to afford in two crops
yellow-brown crystals of (L1)TidNAr(OTf)(CNtBu) (86.4 mg,
1
0.099 mmol, 82% yield). H NMR (23 °C, 399.8 MHz, C6D6): δ
7.30-6.50 (m, C6H3, 9H), 5.47 (s, C(Me)CHC(Me), 1H), 4.34
(septet, CHMe2, 1H), 4.01 (septet, CHMe2, 1H), 3.75 (septet,
CHMe2, 1H), 3.67 (septet, CHMe2, 1H), 2.62 (septet, CHMe2, 1H),
2.51 (septet, CHMe2, 1H), 1.77 [s, C(Me)CHC(Me), 3H], 1.66 [s,
C(Me)CHC(Me), 3H], 1.50 (d, CHMe2, 3H), 1.35 (overlapping d,
CHMe2, 6H), 1.30-1.17 (overlapping d, CHMe2, 15H), 1.14 (d,
CHMe2, 3H), 1.08 (d, CHMe2, 3H), 1.04 (d, CHMe2, 3H), 1.00 (d,
CHMe2, 3H), 0.98 (s, Me3CNC, 9H). 13C NMR (25 °C, 100.6 MHz,
C6D6): δ 168.2 [C(Me)CHC(Me)], 166.3 [C(Me)CHC(Me)], 159.5
(CNtBu), 144.4 (aryl), 144.1 (aryl), 143.5 (aryl), 143.2 (aryl), 142.4
(aryl), 141.7 (aryl), 128.1 (aryl), 127.9 (aryl), 127.0 (aryl), 127.0
(aryl), 125.1 (aryl), 124.9 (aryl), 124.4 (aryl), 124.2 (aryl), 124.1
(aryl), 122.8 (aryl), 122.2 (aryl), 101.7 [C(Me)CHC(Me), 1H], 57.33
(CNCMe3), 29.24 (CHMe2), 29.06 (CNCMe3), 28.02 (CHMe2),
27.82 (CHMe2), 27.79 (CHMe2), 27.67 (CHMe2), 26.26 (CHMe2),
Synthesis of (L2)TidNAr(OTf). In 5 mL of Et2O was dissolved
(L1)TidNAr(OTf) (60.8 mg, 0.08 mmol), and the solution was
cooled to -35 °C. To the cold solution was added an equally cold
Et2O solution (5 mL) containing OC2Ph2 (17 mg, 0.09 mmol). After
10 min, a yellow-brown precipitate began to form, and the reaction
mixture was allowed to stir for an additional 40 min. The solid
was collected by filtration and washed with cold pentane. Recrys-
tallization from THF layered with pentane at -35 °C afforded two
crops of brown crystals of (L2)TidNAr(OTf) (65.26 mg, 0.07 mmol,
87% yield). 1H NMR (23 °C, 399.8 MHz, C6D6): δ 7.86 [d,
(C6H5)2CdC-O, 2H], 7.30-6.60 (m, C6H3 and C6H5, 17H), 4.64
[s, C(Me)CHC(Me), 1H], 4.60 (septet, CHMe2, 1H), 3.81 (septet,
CHMe2, 1H), 3.00 (septet, CHMe2, 1H), 2.90 (septet, CHMe2, 1H),
2.77 (septet, CHMe2, 1H), 2.38 (septet, CHMe2, 1H), 1.70 (d,
CHMe2, 3H), 1.63 (d, CHMe2, 3H), 1.52 (d, CHMe2, 3H), 1.49 (d,
CHMe2, 3H), 1.43 [s, C(Me)CHC(Me), 3H], 1.20 (d, CHMe2, 3H),
1.16 (d, CHMe2, 3H), 1.13 [s, C(Me)CHC(Me), 3H], 1.08 (d,
CHMe2, 3H), 1.05 (d, CHMe2, 3H), 0.97 (d, CHMe2, 3H), 0.82 (d,
CHMe2, 3H), 0.67 (d, CHMe2, 3H), 0.39 (d, CHMe2, 3H). 13C NMR
(25 °C, 100.6 MHz, C6D6): δ 179.5 [C(Me)CHC(Me)], 171.5
(27) 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) Pangborn, A. B.; Giardello, M. A.; Grubbs, R. H.; Rosen, R. K.;
Timmers, F. J. Organometallics 1996, 15, 1518.
(29) Taylor, E. C.; McKillop, A.; Hawks, G. H. Org. Synth. 1988, 50, 549.
Inorganic Chemistry, Vol. 42, No. 24, 2003 8005

Basuli et al.
Scheme 1. Synthetic Route to the Four-Coordinate Titanium Imide
Complex (L1)TidNAr(OTf) by Oxidatively Induced R-Hydrogen
Abstraction.
[C(Me)CHC(Me)], 158.2 (Ph2C)CO), 150.1 (aryl), 149.3 (aryl),
146.3 (aryl), 143.7 (aryl), 142.5 (aryl), 142.1 (aryl), 141.3 (aryl),
141.2 (aryl), 140.9 (aryl), 140.1 (aryl), 139.4 (aryl), 131.6 (aryl),
129.9 (aryl), 129.1 (aryl), 128.5 (aryl), 127.6 (aryl), 127.4 (aryl),
127.2 (aryl), 126.2 (aryl), 126.0 (aryl), 125.0 (aryl), 124.5 (aryl),
124.2 (aryl), 123.3 (aryl), 122.4 (aryl), 122.1 (aryl), 116.1
(Ph2C)CO), 63.63 [C(Me)CHC(Me), JC-H ) 134 Hz], 29.22
(CHMe2), 28.84 (CHMe2), 28.55 (CHMe2), 28.49 (CHMe2), 27.87
(CHMe2), 27.56 (CHMe2), 26.09 (Me), 25.62 (Me), 25.47 (Me),
25.29 (Me), 25.98 (Me), 24.95 (Me), 24.91 (Me), 24.74 (Me), 24.68
(Me), 24.03 (Me), 23.86 (Me), 23.76 (Me), 22.75 (Me). 19F NMR
(23 °C, 282.3 MHz, C6D6): δ -75.20 (OSO2CF3). IR (CaF2,
C6H6): 3071 (s), 3040 (s), 3029 (s), 2965 (s), 2869 (s), 1642 (m),
1585 (m), 1492 (w), 1474 (m), 1464 (m), 1442 (m), 1351 (s), 1324
(w), 1275 (w), 1227 (s), 1199 (s), 1136 (m), 1069 (m), 1039 (s),
1034 (s), 1007 (s), 963 (m), 912 (m) cm-1. Anal. Calcd for
C56H68N3O4F3STi: C, 68.34; H, 6.96; N, 4.27. Found: C, 68.54;
H, 7.12; N, 4.55.
(SAINT).30 The structure was solved using SHELXS-97 and refined
with SHELXL-97.31 A direct-methods solution was calculated that
provided most non-hydrogen atoms from the E-map. Full-matrix
least-squares/difference Fourier cycles were performed that located
the remaining non-hydrogen atoms. All non-hydrogen atoms were
refined with anisotropic displacement parameters, and all hydrogen
atoms were refined with isotropic displacement parameters (unless
otherwise specified).
(L1)TidNAr(OTf)(CNtBu). Single crystals were grown at -35
°C from a saturated pentane solution. Intensity statistics and
systematic absences suggested the centrosymmetric space group
Cc, and subsequent solution and refinement confirmed this choice.
All non-hydrogen atoms were refined with anisotropic displacement
parameters. All hydrogen atoms were located in subsequent Fourier
maps and included as isotropic contributors in the final cycles of
refinement.
(L1)TidNAr(OTf)(NCCH2Mes). Single crystals were grown at
-35 °C from a saturated pentane solution. Intensity statistics and
systematic absences suggested the centrosymmetric space group
P21/n, and subsequent solution and refinement confirmed this
choice. All non-hydrogen atoms were refined with anisotropic
displacement parameters. All hydrogen atoms were located in
subsequent Fourier maps and included as isotropic contributors in
the final cycles of refinement.
(L2)TidNAr(OTf)‚2THF. Single crystals were grown at -35
°C from a saturated THF solution layered with pentane. Intensity
statistics and systematic absences suggested the centrosymmetric
space group P-1. In addition to the titanium complex, two THF
solvent molecules are present. One is well-defined, and the other
is disordered. All non-hydrogen atoms were refined with anisotropic
displacement parameters. All hydrogen atoms with the exception
of those associated with one disordered THF were located in
subsequent Fourier maps and included as isotropic contributors in
the final cycles of refinement.
(L3)TidNAr(OEt2). Single crystals were grown at -35 °C from
a saturated pentane solution. Intensity statistics and systematic
absences suggested the centrosymmetric space group P-1 and
subsequent solution and refinement confirmed this choice. All non-
hydrogen atoms were refined with anisotropic displacement pa-
rameters. All hydrogen atoms were located in subsequent Fourier
maps and included as isotropic contributors in the final cycles of
refinement.
Synthesis of (L3)TidNAr(OEt2). In 10 mL of Et2O was
dissolved (L1)TidNAr(OTf) (190 mg, 0.24 mmol), and the solution
was cooled to -35 °C. To the cold solution was added a cold Et2O
t
solution (5 mL) of LiCH2 Bu (20.64 mg, 0.26 mmol) (alternatively,
1.1 equiv of LiMe and LiCH2SiMe3 can be used). After being stirred
for 30 min, the solution was filtered and dried under reduced
pressure. The yellow powder was extracted with pentane, filtered,
concentrated, and cooled to -35 °C to afford two crops of yellow
crystals of (L3)TidNAr(OEt2) (138.2 mg, 0.19 mmol, 80% yield).
1H NMR (23 °C, 399.8 MHz, C6D6): δ 7.30-6.60 (m, C6H3, 9H),
5.14 [s, C(Me)CHC(CH2), 1H], 4.70 [m, O(CH2CH3)2, 2H], 4.00
(septet, CHMe2, 1H), 3.91 [m, O(CH2CH3)2, 2H], 3.79 (septet,
CHMe2, 1H), 3.61 [s, C(Me)CHC(CH2), 1H], 3.49 (septet, CHMe2,
2H), 3.33 [s, C(Me)CHC(CH2), 1H], 3.29 (d, CHMe2, 2H), 1.53
[s, C(Me)CHC(CH2), 3H], 1.50 (d, CHMe2, 3H), 1.46 (d, CHMe2,
3H), 1.44 (d, CHMe2, 3H), 1.43 (d, CHMe2, 3H), 1.36 (d, CHMe2,
3H), 1.30 (d, CHMe2, 3H), 1.19 (d, CHMe2, 3H), 1.06 (d, CHMe2,
3H), 0.99 (d, CHMe2, 6H), 0.81 [t, O(CH2CH3)2, 6H], 0.74 (d,
CHMe2, 6H). 13C NMR (25 °C, 100.6 MHz, C6D6): δ 157.5 [C(Me)-
CHC(CH2)], 152.8 (aryl), 148.2 (aryl), 147.8 (aryl), 144.8 (aryl),
144.2 (aryl), 143.3 (aryl), 142.7 (aryl), 142.6 (aryl), 141.9 (aryl),
125.8 (aryl), 125.6 (aryl), 124.8 (aryl), 124.2 (aryl), 123.9 (aryl),
123.6 (aryl), 122.2 (aryl), 121.2 (aryl), 100.4 [C(Me)CHC(CH2),
JC-H ) 156 Hz], 86.28 [C(Me)CHC(CH2), JC-H ) 157 Hz], 70.48
[O(CH2CH3)2], 28.66 (CHMe2), 28.53 (CHMe2), 28.31 (CHMe2),
28.16 (CHMe2), 27.81 (CHMe2), 26.52 (Me), 25.67 (Me), 25.50
(Me), 25.17 (Me), 25.14 (Me), 25.11 (Me), 25.04 (Me), 24.44 (Me),
24.05 (Me), 23.75 (Me), 23.69 (Me), 13.12 (O(CH2CH3)2). IR (CaF2,
C6H6): 3098 (s), 3071 (s), 3029 (s), 2962 (s), 2927 (s), 2867 (s),
1814 (w), 1597 (m), 1495 (m), 1463 (s), 1438 (s), 1420 (s), 1359
(s), 1325 (s), 1277 (s), 1254 (s), 1240 (m), 1202 (s), 1109 (m),
1039 (s), 1000 (s), 974 (m) cm-1. Anal. Calcd for C45H67N3OTi:
C, 75.70; H, 9.46; N, 5.89. Found: C, 75.96; H, 9.84; N, 6.25.
X-ray Crystallography. Inert-atmosphere techniques were used
to place the crystal onto the tip of a diameter glass capillary (0.06-
0.20 mm) mounted on a SMART6000 (Bruker) at 113(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
Results and Discussion
When an ether-based solution of the four-coordinate
titanium imide complex (L1)TidNAr(OTf)18b (prepared ac-
cording to Scheme 1) is treated with Lewis bases such as
XY (XY ) CNtBu or NCCH2Mes), the adduct (L1)TidNAr-
(OTf)(XY) (XY ) CNtBu, 82%; XY ) NCCH2Mes, Mes
(30) SAINT 6.1; Bruker Analytical X-ray Systems: Madison, WI.
(31) SHELXTL-Plus V5.10; Bruker Analytical X-ray Systems: Madison,
WI.
8006 Inorganic Chemistry, Vol. 42, No. 24, 2003

ReactiWity at the Ligand Nacnac- on Titanium(IV)
Table 1. Crystallographic Data for Complexes (L1)TidNAr(OTf)(CNtBu), (L1)TidNAr(OTf)(NCCH2Mes), (L2)TidNAr(OTf), and (L3)TidNAr(OEt2)
parameter
(L1)TidNAr(OTf)(CNtBu)
(L1)TidNAr(OTf)(NCCH2Mes)
(L2)TidNAr(OTf)‚2THF
(L3)TidNAr(OEt2)
empirical formula
fw
C47H67F3N4O3STi
873.01
C53H71F3N4O3STi
949.10
C64H84F3N3O6STi
1128.30
C45H67N3OTi
713.92
crystal system
space group
a (Å)
b (Å)
c (Å)
monoclinic
Cc
18.9125(15)
20.0232(16)
12.5736(10)
monoclinic
P2(1)/n
11.3530(9)
23.7155(17)
19.1055(14)
triclinic
P-1
triclinic
P-1
12.455(3)
14.406(4)
18.099(5)
81.171(7)
72.595(7)
81.697(7)
3045.2(14)
2
9.7831(9)
10.1479(9)
21.7959(19)
79.492(2)
87.819(2)
80.713(2)
2099.6(3)
2
R (°)
â (°)
98.115(2)
90.474(2)
γ (°)
V (Å3)
Z
4713.8(6)
4
1.230
5143.8(7)
4
1.226
D
calc (g‚cm-3
)
1.231
1.129
crystal size (mm)
solvent habit, color
(h, k, l)
0.35 × 0.28 × 0.18
Et2O, yellow-brown
-24 e h e 24,
-25 e k e 26,
-16 e l e 16
1864
0.30 × 0.25 × 0.25
Et2O, yellow-brown
-14 e h e 14,
-30 e k e 30,
-24 e l e 24
2024
0.26 × 0.24 × 0.24
THF/pentane, orange
-16 e h e 16,
-18 e k e 18,
-23 e l e 23
1204
0.28 × 0.28 × 0.12
Et2O, yellow
-12 e h e 12,
-13 e k e 13,
-28 e l e 28
776
F(000)
Θ range
2.32-27.50
1.99-27.52
1.97-27.58
2.31-27.49
linear abs. coeff. (mm-1
total reflcns collected
independent reflcns
unique reflcns
Rint
)
0.280
0.263
0.236
0.239
44443
10742
9927
0.0558
57739
11827
6156
0.1054
67596
14002
9398
0.1646
34820
9642
7848
0.0602
data/parameter
R1, wR2 (for I > 2σ(I)
GoF
10 742/801
0.0304, 0.0742
1.005
11 827/870
0.0448, 0.0964
0.813
14 002/1029
0.0544, 0.1662
0.992
9642/719
0.0398, 0.1095
1.044
peak/hole (e/Å-3
)
0.252, -0.199
0.319, -0.328
0.887, -0.443
0.566, -0.278
Scheme 2. Synthetic Routes to (L1)TidNAr(OTf)(XY) and the
Nacnac- Derivatives (L2)TidNAr(OTf) and (L3)TidNAr(OEt2) [XY )
t
CN'tBu or NCCH2(2,4,6-Me3C6H2); R- ) Me, CH2 Bu, or CH2SiMe3;
Ar ) 2,6-[CH(CH3)2]2C6H3].
Figure 2. Molecular structure of base adducts (L1)TidNAr(OTf)(CNt-
Bu) (left) and (L1)TidNAr(OTf)(NCCH2Mes) (right) showing atom-labeling
scheme with thermal ellipsoids at the 50% probability level. H-atoms and
aryl groups on the nitrogens with the exception of the ipso-carbon have
been omitted for clarity. O2SCF3 groups on the O(52) and O(58) of the
triflate ligand have also been excluded.
is characteristic for electrophilic metal centers binding
CNtBu.33 The solution IR spectrum of complex (L1)TidNAr-
(OTf)(NCCH2Mes) also displays a νN≡C stretch centered at
1960 cm-1, characteristic of a bound nitrile.
Single crystals of the adduct (L1)TidNAr(OTf)(XY) were
grown from pentane at -35 °C. The molecular representation
for each complex is depicted in Figure 2. Crystallographic
data are displayed in Table 1, and selected metrical param-
eters are listed in Table 2. Each molecule adopts a pseudo-
square-pyramidal geometry with the Lewis base occupying
the axial site. Inspection of each structure reveals a chemi-
cally unperturbed “(Nacnac)TidNAr(OTf)” framework, where
coordination of the base only induced geometrical rearrange-
ments in the complex. The Ti-Otriflate, Ti-NNacnac, and Ti-
Nimide bond lengths are not deviated considerably from that
) 2,4,6-Me3C6H2, 70%) is formed in good yield (Scheme
1
2). Complex (L1)TidNAr(OTf)(XY) displays H and 13C
NMR resonances in accordance with a C1 symmetric
molecule. Hence, coordination of the base disrupts the former
Cs symmetry observed in the imide precursor, thus rendering
both aryl groups on â-diketiminate R-nitrogens and â-methyl
1
groups on the Nacnac- backbone nonequivalent. Other H
and 13C NMR spectroscopic features diagnostic of low
symmetry include the observation of four nonequivalent
isopropyl groups, each having two diasteriotopic methyls and
thus portraying a total of eight doublets. Solution IR spectra
of (L1)TidNAr(OTf)(CNtBu) indicates that the νC≡N stretch
(2213 cm-1) shifts significantly to higher wavenumbers from
that of the corresponding free base, CNtBu (2134 cm-1).32
The shift to higher energies in (L1)TidNAr(OTf)(CNtBu)
(32) Solution IR (C6H6, CaF2) stretches for free CNtBu and NCCH2(2,4,6-
Me3C6H2) are 2134 and 2249 cm-1, respectively.
(33) For an example of an electrophilic Ti(IV) complex having a bound
CNtBu ligand see: Carofiglio, T.; Floriani, C.; Chiesi-Villa, A.;
Guastini, C. Inorg. Chem. 1989, 28, 4417.
Inorganic Chemistry, Vol. 42, No. 24, 2003 8007

Basuli et al.
Table 2. Selected Interatomic Distances (Å) and Angles (°)
(L1)TidNAr(OTf)(CNtBu)
Ti(1)-N(33)
1.712(3)
2.300(6)
1.398(2)
1.458(2)
121.84(11)
111.32(6)
161.03(5)
128.0(5)
Ti(1)-O(52)
2.037(1)
1.342(2)
1.143(2)
173.2(3)
82.02(5)
87.64(5)
88.14(5)
123.1(5)
Ti(1)-N(6)
2.086(3)
1.402(2)
1.390(2)
173.2(1)
89.11(5)
103.42(6)
95.44(6)
Ti(1)-N(2)
2.098(3)
1.336(2)
1.452(2)
123.5(1)
138.99(5)
109.19(6)
123.8(5)
Ti(1)-C(46)
N(6)-C(5)
C(3)-C(4)
N(2)-C(3)
C(4)-C(5)
N(2)-C(7)
Ti(1)-N(2)-C(3)
O(52)-Ti(1)-N(33)
N(2)-Ti(1)-C(46)
C(3)-C(4)-C(5)
C(46)-N(47)
N(33)-C(34)
N(6)-C(21)
Ti(1)-C(46)-N(47)
O(52)-Ti(1)-C(46)
N(2)-Ti(1)-N(6)
N(6)-Ti(1)-C(46)
N(6)-C(5)-C(4)
Ti(1)-N(33)-C(34)
O(52)-Ti(1)-N(2)
N(2)-Ti(1)-N(33)
N(33)-Ti(1)-C(46)
C(46)-N(47)-C(48)
Ti(1)-N(6)-C(5)
O(52)-Ti(1)-N(6)
N(6)-Ti(1)-N(33)
N(2)-C(3)-C(4)
(L1)TidNAr(OTf)(NCCH2Mes)
Ti(1)-N(33)
2.211(9)
1.138(3)
1.697(7)
177.2(6)
167.4(8)
98.13(7)
112.15(7)
105.13(7)
Ti(1)-O(58)
2.051(4)
1.337(3)
1.402(3)
121.8(4)
80.98(6)
123.6(9)
128.2(2)
87.38(6)
Ti(1)-N(2)
2.090(7)
1.335(3)
1.449(2)
123.0(4)
88.26(6)
142.24(6)
113.5(2)
Ti(1)-N(6)
2.088(7)
1.393(3)
1.455(2)
123.4(2)
156.82(7)
88.66(6)
104.98(7)
N(33)-C(34)
N(2)-C(3)
N(6)-C(5)
C(5)-C(4)
Ti(1)-N(45)
N(45)-C(46)
N(2)-C(7)
N(6)-C(21)
Ti(1)-N(45)-C(46)
Ti(1)-N(33)-C(34)
N(33)-Ti(1)-N(45)
O(58)-Ti(1)-N(45)
N(45)-Ti-N(2)
Ti(1)-N(6)-C(5)
O(58)-Ti(1)-N(33)
N(6)-C(5)-C(4)
C(3)-C(4)-C(5)
N(6)-Ti(1)-N(2)
Ti-N(2)-C(3)
N(33)-Ti(1)-N(2)
O(58)-Ti(1)-N(2)
C(34)-C(35)-C(36)
N(2)-C(3)-C(4)
N(33)-Ti(1)-N(6)
O(58)-Ti(1)-N(6)
N(45)-Ti(1)-N(6)
(L2)TidNAr(OTf)
Ti(1)-N(48)
1.729(2)
2.262(6)
1.448(3)
1.516(3)
124.1(2)
101.04(8)
118.5(4)
114.4(8)
Ti(1)-N(6)
2.477(2)
2.219(6)
1.287(3)
1.332(3)
100.11(8)
84.22(7)
128.9(3)
63.16(6)
Ti(1)-O(33)
1.930(5)
1.388(3)
1.290(3)
2.794(1)
82.69(7)
114.8(5)
118.1(2)
171.8(5)
Ti(1)-N(2)
2.187(9)
1.465(3)
1.517(3)
1.356(3)
177.20(7)
79.16(6)
121.2(9)
Ti(1)-O61
Ti(1)-O62
N(48)-C(49)
N(2)-C(7)
N(6)-C(21)
C(5)-C(4)
O(33)-C(34)-C(35)
N(48)-Ti(1)-O(33)
Ti(1)-N(2)-C(3)
O(33)-C(34)-C(4)
N(2)-C(3)
O(33)-C(34)
N(48)-Ti(1)-N(2)
N(2)-Ti(1)-O(33)
Ti(1)-O(33)-C(34)
O62-Ti(1)-O61
N(6)-C(5)
Ti(1)-S63
N(2)-Ti(1)-N(6)
Ti(1)-N(6)-C(5)
N(6)-C(5)-C(4)
Ti(1)-N(48)-C(49)
C(3)-C(4)
C(34)-C(35)
N(48)-Ti(1)-N(6)
N(6)-Ti(1)-O(33)
N(2)-C(3)-C(4)
(L3)TidNAr(OEt2)
Ti(1)-N(33)
1.726(2)
1.435(7)
1.442(8)
1.348(2)
112.83(5)
110.77(5)
131.8(3)
Ti(1)-N(6)
1.966(1)
Ti(1)-O(46)
2.100(1)
Ti(1)-N(2)
1.939(2)
1.357(2)
1.505(2)
168.9(1)
100.26(5)
118.0(3)
N(2)-C(7)
N(6)-C(21)
1.442(8)
1.408(7)
111.55(9)
113.40(5)
116.89(5)
N(33)-C(34)
1.391(7)
1.406(7)
103.19(8)
103.10(5)
119.3(3)
C(3)-C(4)
N(6)-C(21)
C(5)-C(20)
N(33)-Ti(1)-N(2)
N(2)-Ti(1)-O(46)
C(3)-C(4)-C(5)
N(2)-C(3)
N(6)-C(5)
C(3)-C19
Ti(1)-N(6)-C(5)
N(33)-Ti(1)-N(6)
N(6)-Ti(1)-O(46)
Ti(1)-N(2)-C(3)
N(2)-Ti(1)-N(6)
C(4)-C(3)-C19
Ti(1)-N(33)-C(34)
N(33)-Ti(1)-O(46)
C(4)-C(5)-C(20)
of the base-free precursor (L1)TidNAr(OTf).18b The isoni-
trile- and nitrile-titanium bond lengths are merely dative
[2.300(6) and 2.211(9) Å), respectively], whereas the NtC
and CtN bonds are very short [1.143(2) and 1.138(3) Å,
respectively] and relatively unperturbed from that of the free
Lewis base.33,34
Formation of the adducts was somewhat surprising as
precedent in the literature concerning the chemistry of four-
coordinate titanium imido species suggests that low-
coordination environments triggers interesting reactivity.35,36
In fact, four-coordinate group 4 imido complexes are
exceedingly rare,35,37 presumably because of their inherent
reactivity. Complex (L1)TidNAr(OTf) fails to react with
polar molecules such as CO2, azides, and N2CPh2. Such a
result in combination with formation of the adduct (L1)Tid
NAr(OTf)(XY) indicates clearly the robust nature of the
(Nacnac)TidNAr framework. We also have no evidence to
suggest that the bound -OTf ligand in complex (L1)TidNAr-
(OTf)(XY) is dissociating in solution. Lewis bases such as
THF or Et2O do not appear to displace the XY ligands bound
to complex (L1)TidNAr(OTf).
Our interest in group-transfer reactions stimulated us to
investigate the reactivity the TidNAr functionality in (L1)-
TidNAr(OTf). Titanium is oxophilic; hence, it was thought
that reactions of imido (L1)TidNAr(OTf) with unsaturated
organic reagents having an O-group could lead to imide
group transfer.36a,38 Treatment of (L1)TidNAr(OTf) with
OC2Ph2 does not attack the TidNAr motif inasmuch as a
new single product is formed in which the Nacnac- ligand
has undergone electrophilic attack at the γ-carbon of the
(37) (a) Cummins, C. C.; Baxter, S. M.; Wolczanski, P. T. J. Am. Chem.
Soc., 1988, 110, 8731. (b) Schaller, C. P.; Wolczanski, P. T. Inorg.
Chem. 1993, 32, 131. (c) Schaller, C. P.; Cummins, C. C.; Wolczanski,
P. T. J. Am. Chem. Soc. 1996, 118, 591. (d) Bennett, J. L.; Wolczanski,
P. T. J. Am. Chem. Soc. 1997, 119, 10696. (e) Schafer, D. F.;
Wolczanski, P. T. J. Am. Chem. Soc. 1998, 120, 4881. (f) Gade, L.
H.; Mountford, P. Coord. Chem. ReV. 2001, 216-217, 65. (g) Blake,
A. J.; Collier, P. E.; Gade, L. H.; Mountford, P.; Lloyd, J.; Pugh, S.
M.; Schubart, M.; Skinner, M. E. G.; M.; Tro¨sch, D. J. M. Inorg.
Chem. 2001, 40, 870. (h) Mountford, P. Perspect. Organomet. Chem.
2003, 28. (i) Blake, A. J.; Collier, P. E.; Gade, L. H.; McPartlin, M.;
Mountford, P.; Schubart, M.; Scowen, I. J. Chem. Commun. 1997,
1555. (j) Bashall A.; Collier, P. E.; Gade, L. H.; McPartlin, M.;
Mountford, P.; Schubart, M.; Scowen, I. J.; Tro¨sch, D. J. M.
Organometallics 2000, 19, 4784. (k) Nikiforov, G. B.; Roesky, H.
W.; Magull, J.; Labahn, T.; Vidovic, D.; Noltemeyer, M.; Schmidt,
H.-G.; Hosmane, N. S. Polyhedron 2003, 22, 2669.
(34) A search in the Structural Database shows crystallized free nitriles to
have bond lengths between 1.13 and 1.16 Å: Britton, D. Cryst. Struct.
Commun. 1979, 8, 667. For a bound nitrile to an electrophilic early-
transition metal center see: Chen, C.-T.; Doerrer, L. H.; Williams,
V. C.; Green, M. L. H. J. Chem. Soc., Dalton Trans. 2000, 297.
(35) (a) 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.
(b) Bennett, J. L.; Wolczanski, P. T., J. Am. Chem. Soc. 1994, 116,
2179.
(38) For some recent examples in the literature see: (a) Brown, S. D.;
Betley, T. A.; Peters, J. C. J. Am. Chem. Soc. 2003, 125, 322 and
references therein. (b) Jenkins, D. M.; Betley, T. A.; Peters, J. C. J.
Am. Chem. Soc. 2002, 124, 11238. (c) Mindiola, D. J.; Hillhouse, G.
H. Chem. Commun. 2002, 1840.
(36) (a) Wigley, D. E. Prog. Inorg. Chem., 1994, 42, 239. (b) Cummins,
C. C. Prog. Inorg. Chem. 1998, 47, 685.
8008 Inorganic Chemistry, Vol. 42, No. 24, 2003

ReactiWity at the Ligand Nacnac- on Titanium(IV)
Figure 4. Molecular structure of (L3)TidNAr(OEt2) showing atom-
labeling scheme with thermal ellipsoids at the 50% probability level.
H-atoms with the exception of those on C(20), ethyl groups on O(46), and
aryl groups on the nitrogen atoms with the exception of the ipso-carbons
have been omitted for clarity (left). A perspective view of the ligand down
the Ti(1)-C(4) axis is also shown (right), and the imide and OEt2 groups
on titanium, as well as H-atoms, have been omitted for clarity.
Figure 3. Molecular structure of (L2)TidNAr(OTf) showing atom-labeling
scheme with thermal ellipsoids at the 50% probability level. H-atoms and
the aryl groups on the nitrogen atoms with the exception of the ipso-carbons
have been omitted for clarity (left). A perspective view (right) of the ligand
down the Ti(1)-C(4) axis is also shown, and the imide and OTf groups on
titanium have been omitted for clarity. Two disordered THF molecules
present in the asymmetric unit have also been excluded.
plex (L2)TidNAr(OTf) is stable both as a solid and in solu-
tion, which is not surprising as η2-coordination of the -OTf
and π-donation of the alkoxo, the two imines, and the imide
functionalities saturate the coordination environment as well
as supply the titanium center with sufficient electron density.
Facile and clean coordination of diphenylketene across the
γ-carbon and titanium center of complex (L1)TidNAr(OTf)
is intriguing because it provides a strategy to assemble novel
ligands on titanium retaining the Nacnac-Ti core.
NCCCN ring to form (L2)TidNAr(OTf) (Scheme 2). It has
been demonstrated previously that electrophiles attack the
γ-carbon of â-diketiminates, and in some cases, the func-
tionalized ligand can be coordinated to metals.13,24 Thus,
diphenylketene, having an oxygen atom, an electrophilic
â-carbon, and a low HOMO-LUMO gap at the CdO
bond,39 makes a suitable reagent for the (Nacnac)Ti frame.
A key spectroscopic feature in the formation of (L2)TidNAr-
(OTf) is the dramatic shift in the 13C NMR spectrum of the
sp2 CγH in the NCCγCN ring from 94.4 ppm [for complex
(L1)TidNAr(OTf)] to 63.6 ppm [for complex (L2)TidNAr-
(OTf)]. This feature is not surprising because such a carbon
Deprotonation of the â-carbon methyl group on the
Nacnac- ligand has been reported for Ge complexes bearing
this ligand.25 Likewise, when ether-based solutions of (L1)-
TidNAr(OTf) are treated with nucleophiles such as LiR (R
t
) Me, CH2 Bu, and CH2SiMe3), complex (L3)TidNAr(OEt2)
has undergone rehybridization to an sp3 CH with JC-H
)
is formed cleanly (Scheme 2). Significant and diagnostic
1
134 Hz.13,40 Both 1H and 13C NMR spectra are in accordance
with complex (L2)TidNAr(OTf) retaining C1 symmetry in
solution.
features for (L3)TidNAr(OEt2) include observation by H
NMR spectroscopy of two methylene protons of the former
â-carbon methyl centered at 3.61 and 3.33 ppm. The two
resonances were unambiguously correlated to the sp2-
hydridized carbon at 86.3 ppm by HMQC experiments (JC-H
) 157 Hz).40 A result from the methyl being deprotonated
is the loss of symmetry from Cs to C1, which is evident by
the spectroscopic observation of four nonequivalent isopropyl
groups on Nacnac-, each having two diasteriotopic methyl
groups. Hindered rotation of the aryl group attached to the
imido gives rise to two additional nonequivalent isopropyl
groups. Coordination of Et2O is also observed in both the
1H and 13C NMR spectra of (L3)TidNAr(OEt2). Overall,
deprotonation concurrent with triflate elimination generates
a dianionic amide ligand lacking C2 symmetry. Thus,
complex (L3)TidNAr(OEt2) represents a unique example of
a four-coordinate titanium imide complex supported by an
anionic and chelate bis-anilide ligand. When (L1)TidNAr-
(OTf) is treated with LiR in hexane or toluene, no reaction
is observed (even upon heating of the mixture), hinting that
solvent plays a key role in the formation of (L3)TidNAr-
(OEt2). Complex (L3)TidNAr(OEt2) is remarkably stable,
and heating samples under dynamic vacuum does not lead
to substantial decomposition or evidence of Et2O loss [even
in the presence of a Lewis acid such as B(C6F5)3].
Single crystals suitable for X-ray diffraction were grown
from a THF solution layered with pentane at -35 °C, and
the molecular structure is depicted in Figure 3. Crystal data
and selected metrical parameters are shown in Tables 1 and
2, respectively. Salient features in the crystal structure of
(L2)TidNAr(OTf) include a short and unperturbed Tid
N
{imido} functionality [Ti(1)-N(48), 1.729(2) Å]. The former
Nacnac- ligand has undergone electrophilic attack at the
γ-carbon and is now transformed into a monoanionic tripodal
ligand (Figure 3, right side) containing an alkoxo and two
imine functionalities with short NdC bonds [N(6)-C(5),
1.290(3) Å; N(2)-C(3), 1.287(3) Å]. The molecule has C1
symmetry in the solid state, which is also consistent with
1H and 13C NMR solution spectra (vide supra). The Ti(1)-
N{imine} distances are considerably longer [Ti(1)-N{imine}
,
2.187(9) and 2.477(2) Å] when compared to the Ti-N{Nacnac}
distances of the former (L1)TidNAr(OTf) complex [Ti-
N
{Nacnac}, 1.978(5) and 2.029(5) Å].18b In fact, the latter bond
length for Ti(1)-N(6) suggests that the imine is weakly
bound to the metal. The structure of the titanium complex
containing the L2- ligand also reveals an olefinic functional-
ity [C(34)-C(35), 1.356(3) Å] present in the â-carbon of
the now-bound R-alkoxide [Ti(1)-O(33), 1.930(5) Å]. Com-
Single crystals of (L3)TidNAr(OEt2) were grown from a
saturated pentane solution cooled to -35 °C. Upon inspec-
tion, the molecular structure of (L3)TidNAr(OEt2) displays
a rare four-coordinate titanium imide complex supported by
a chelating bis-anilide ligand (Figure 4). Crystal data and
(39) Hofmann, P.; Perez-Moya, L. A.; Steigelmann, O.; Riede, J. Orga-
nometallics 1992, 11, 1167.
(40) For a detailed description of HMQC experiments: Summers, M. F.;
Marzilli, L. G.; Bax, A. J. J. Am. Chem. Soc. 1986, 108, 4285.
Inorganic Chemistry, Vol. 42, No. 24, 2003 8009

Basuli et al.
relevant metrical parameters for the structure of (L3)TidNAr-
(OEt2) are listed in Tables 1 and 2, respectively. The
dianionic nature of the ligand is supported clearly by the
short Ti(1)-N{anilide} bonds [1.939(2) and 1.966(1) Å], which
are substantially shorter than typical Ti(IV)-N{Nacnac} dis-
tances.18,37k As a consequence of the Ti-N distances being
asymmetric and dianionic bis-anilide chelate ligand. For
instance, the present L2- ligand exhibits all of the traits of a
robust and attractive ligand: it lacks â-hydrogens, has good
donicity (yet a low overall negative charge), and is sterically
encumbering. These features are also present in the dianionic
and asymmetric ligand L32-. The stability of the imido
functionality in (L1)TidNAr(OTf) arises likely from ther-
modynamic reasons as small molecules do not appear to react
under normal conditions. However, the possibility remains
that the substrates themselves are too large to react with the
hindered TidNAr fragment, which leaves unresolved the
issue of thermodynamic preference. We are currently pursu-
ing the synthesis of three-coordinate titanium imide com-
plexes (both neutral and cationic) with the more robust
Nacnac- ligand [Ar]NC(tBu)CHC(tBu)N[Ar].6,37k Titanium
systems tuned properly for the clear illustration of this
coordination environment remain attractive as synthetic
targets.
2-
shorter, the N-â-C distances are longer for L3 [N(2)-
C(3), 1.365(2) Å; N(6)-C(5), 1.330(2) Å] than that reported
for the Nacnac- ligand L1 (vide supra).18b Most notably,
deprotonation of the methyl on the â-carbon is evident from
shortening of the H3C-C bond to an sp2 H2CdC bond
[1.501(3) Å for an sp3 CH3-C bond vs 1.348(2) Å for the
sp2 CH2dC bond]. When (L3)Ti is viewed down the Ti(1)-
C(4) axis, it is apparent that the ligand has distorted
considerably from planarity (Figure 4, right view). More
indicative of this distortion are the dihedral angles defined
between the carbons H2C(20)dC(5)-C(4)HdC(3)-C(19)-
H3 [C(20)-C(5)-C(4)-C(3), 144.2(7)°; C(19)-C(3)-C(4)-
C(5), 171.2(5)°]. Such a deviation from planarity is signifi-
cant when compared to the dihedral angles for the former
Nacnac- ligand in (L1)TidNAr(OTf) [C(20)-C(5)-C(4)-
C(3), 167.2(8)°; C(19)-C(3)-C(4)-C(5), 172.3(7)°].18b
Other parameters are the short Ti(1)-N(33) bond of 1.726-
(2) Å, which is consistent with a Ti-N multiple bond,36a
and a relatively short Ti(1)-O(46) dative bond of 2.100(1)
Å for the tightly bound Et2O. Coordination of Et2O is not
surprising because of the exceedingly low-coordinate (three-
coordinate) and electron-deficient titanium center being
generated during deprotonation of (L1)TidNAr(OTf).
Acknowledgment. We thank Indiana University-Bloom-
ington, the Camille and Henry Dreyfus Foundation, and the
Ford Foundation for financial support of this research. D.J.M.
thanks Prof. P. Mountford for insightful comments.
Supporting Information Available: Complete crystallographic
data for compounds (L1)TidNAr(OTf)(XY) (XY ) CNtBu and
NCCH2Mes), (L2)TidNAr(OTf), and (L3)TidNAr(OEt2) (CIF files
in text format). This material is available free of charge via the
Internet at http://pubs.acs.org.
Conclusion
The (Nacnac)Ti frame “(L1)Ti” is an excellent platform
for the design of both a tripodal monoanionic ligand and an
IC034853E
8010 Inorganic Chemistry, Vol. 42, No. 24, 2003