Tri- and tetravalent titanium alkyls supported by organic amides

Article abstract of DOI:10.1021/om9508288

The reactions of both trivalent [(Cy₂N)₂Ti(μ-Cl)₂Li(TMEDA)] (1) and tetravalent [(Cy₂N)₂-TiCl₂] (5) with R′Li in THF or diethyl ether gave Ti(IV) complexes (Cy₂N)₂TiR′₂ [R′ = CH₂-CMe₃ (7), CH₂CMe₂Ph (8), CH₂SiMe₃ (9)]. Conversely, the reactions of 1, [{(i-Pr)₂-N}₂TiCl₂][Li(TMEDA)₂] (2), and [{(Me₃Si)₂N}₂TiCl₂][Li(TMEDA) ₂] (3) with R′Li [R′ = Me, Ph, CH₂Ph] gave the corresponding trivalent derivatives [(Cy₂N)₂Ti(μ-Bz)₂Li(TMEDA)] (4a), [(Cy₂N)₂Ti(μ-Me)₂Li(TMEDA)] (4b), [{(i-Pr)₂N}₂TiPh₂][Li(TMEDA)₂] (11), and [{(Me₃Si)₂N}2Ti-(CH₂Ph) ₂][Li(TMEDA)₂] (12) via simple ligand replacement reactions. Oxidation of 12 with diphenylfulvene gave {(Me₃Si)₂N}2Ti(CH₂Ph)₂ (13). All these compounds are thermally labile and yielded intractable materials upon thermolysis. Only in the case of the neophyl derivative (Cy₂N)₂Ti(CH₂CMe₂C₆H ₅)₂ (8) a cyclometalated compound (Cy₂N)₂Ti(CH₂-CMe₂C ₆H₄) (10) was isolated and crystallized from the thermolyzed solution. The reaction of 1 with styrene oxide provided the Ti-oxo complex [(Cy₂N)₂TiCl]₂O (14) which gave, upon alkylation with MeLi, the corresponding dinuclear alkyl derivatives [(Cy₂N)₂TiMe]₂O (15). The molecular structures of 1 and 10-14 were demonstrated by X-ray diffraction analysis.

Full text of DOI:10.1021/om9508288

Organometallics 1996, 15, 1113-1121
1113
Tr i- a n d Tetr a va len t Tita n iu m Alk yls Su p p or ted by
Or ga n ic Am id es
Ravinder K. Minhas, Ludmila Scoles, Shirley Wong, and Sandro Gambarotta*
Department of Chemistry, University of Ottawa, Ottawa, Ontario K1N 6N5, Canada
Received October 20, 1995X
The reactions of both trivalent [(Cy2N)2Ti(µ-Cl)2Li(TMEDA)] (1) and tetravalent [(Cy2N)2-
TiCl2] (5) with R′Li in THF or diethyl ether gave Ti(IV) complexes (Cy2N)2TiR′2 [R′ ) CH2-
CMe3 (7), CH2CMe2Ph (8), CH2SiMe3 (9)]. Conversely, the reactions of 1, [{(i-Pr)2-
N}2TiCl2][Li(TMEDA)2] (2), and [{(Me3Si)2N}2TiCl2][Li(TMEDA)2] (3) with R′Li [R′ ) Me,
Ph, CH2Ph] gave the corresponding trivalent derivatives [(Cy2N)2Ti(µ-Bz)2Li(TMEDA)] (4a ),
[(Cy2N)2Ti(µ-Me)2Li(TMEDA)] (4b), [{(i-Pr)2N}2TiPh2][Li(TMEDA)2] (11), and [{(Me3Si)2N}2Ti-
(CH2Ph)2][Li(TMEDA)2] (12) via simple ligand replacement reactions. Oxidation of 12 with
diphenylfulvene gave {(Me3Si)2N}2Ti(CH2Ph)2 (13). All these compounds are thermally labile
and yielded intractable materials upon thermolysis. Only in the case of the neophyl
derivative (Cy2N)2Ti(CH2CMe2C6H5)2 (8) a cyclometalated compound (Cy2N)2Ti(CH2-
CMe2C6H4) (10) was isolated and crystallized from the thermolyzed solution. The reaction
of 1 with styrene oxide provided the Ti-oxo complex [(Cy2N)2TiCl]2O (14) which gave, upon
alkylation with MeLi, the corresponding dinuclear alkyl derivatives [(Cy2N)2TiMe]2O (15).
The molecular structures of 1 and 10-14 were demonstrated by X-ray diffraction analysis.
In tr od u ction
employed in a number of important industrial processes
(e.g. olefin cationic polymerization,5 insertion reactions,6
hydrogenation,7 and metal-promoted organic synthe-
sis8). A synthetically useful characteristic of titanium
alkyls is their ability to act as precursors for the
preparation of alkylidene9 derivatives via C-H σ-bond
Transition metal alkyl complexes (LnM-R) constitute
a very important class of compounds because of the
pivotal role played by these species in both synthesis
and catalysis.1 In particular, group IV organometallic
derivatives have been the target of intense study since
the initial discovery by Ziegler and Natta2 that mixtures
of TiCl3 and aluminium alkyls act as catalysts for
stereoselective olefin polymerization. As a result, inter-
est in the synthesis, characterization, and reactivity of
group IV organometallic species3 has grown steady and
titanium alkyls are today well-known4 and widely
(4) (a) DeBoer, H. J . R.; Akkermann, O. S.; Bickelhaupt, F.; Erker,
G.; Czisch, P.; Mynott, R.; Wallis, J . M.; Kruger, C. Angew. Chem.,
Int. Ed. Engl. 1986, 25, 639. (b) Van der Wal, W. F. J .; Van der Wal,
H. R. J . Organomet. Chem. 1978, 153, 335. (c) Olthof, G. J .; Van
Volhuis, F. J . Organomet. Chem. 1976, 122, 47. (d) Go´mez-Sal, P.;
Mena, M.; Palacios, F.; Royo, P.; Serrano, R. J . Organomet. Chem.
1989, 375, 59. (e) Garcia-Blanco, S.; Go´mez-Sal, M. P.; Martinez-
Carreras, S.; Mena, M.; Royo, P.; Serrano, R. J . Chem. Soc., Chem.
Commun. 1986, 1572. (f) Gomez, R.; Cuenca, T.; Royo, P.; Hovestreydt,
E. Organometallics 1991, 10, 2516. (g) Troyanov, S. I.; Mach, K.;
Varga, V. Organometallics 1993, 12, 3387. (h) Luinstra, G. A.; Tueben,
J . H. J . Am. Chem. Soc. 1992, 114, 3361. (i) Luinstra, G. A.; Vogelzang,
J .; Teuben, J . H. Organometallics 1992, 11, 2273. (j) Luinstra, G. A.;
Teuben, J . H. Organometallics 1992, 11, 1793. (k) TenCate, L. C.;
Heeres, H. J .; Pattiassina, J . W.; Meetsma, A.; Teuben, J . H. Orga-
nometallics 1992, 11, 1006.
(5) (a) Bochmann, M.; J aggar, A. J .; Nicholls, J . C. Angew. Chem.,
Int. Ed. Engl. 1990, 29, 780. (b) Howard, T. R.; Lee, J . B.; Grubbs, R.
H. J . Am. Chem. Soc. 1980, 102, 6876. (c) Kawamura-Kuribayashi,
H.; Koga, N.; Morokuma, K. J . Am. Chem. Soc. 1992, 114, 2359. (d)
Guo, B. C.; Castleman, A. W., J r. J . Am. Chem. Soc. 1992, 114, 6152.
(6) (a) Wojcicki, A. Adv. Organomet. Chem. 1974, 12, 31. (b) Klei,
E.; Telgen, J . H.; Teuben, J . H. J . Organomet. Chem. 1981, 209, 297.
(c) Martin, A.; Mena, M.; Pellinghelli, M. A.; Royo, P.; Serrano, R.;
Tiripicchio, A. J . Chem. Soc., Dalton Trans. 1993, 2117. (d) DeBoer,
E. J . M.; Teuben, J . H. J . Organomet. Chem. 1979, 166, 193. (e)
J ohnston, R. F.; Cooper, J . C. Organometallics 1987, 6, 2448. (f) Soto,
F.; Iijima, S.; Soto, M. J . Chem. Soc., Chem. Commun. 1981, 180. (g)
Serrano, R.; Flores, J . C.; Royo, P.; Mena, M.; Pellinghelli, M. A.;
Tiripicchio, A. Organometallics 1989, 8, 1404. (h) Kawamura-Kuriba-
yashi, H.; Koga, N.; Morokuma, K. J . Am. Chem. Soc. 1992, 114, 2359.
(i) Fandos, R.; Meetsma, R.; Teuben, J . H. Organometallics 1991, 10,
2665. (j) Doxsee, K. M.; J uliette, J . J . J .; Mouser, J . K. M.; Zientara,
K. Organometallics 1993, 12, 4682.
X Abstract published in Advance ACS Abstracts, J anuary 15, 1996.
(1) (a) J ames, B. R. Adv. Organomet. Chem. 1979, 17, 319. (b)
Pruett, R. L. Adv. Organomet. Chem. 1979, 17, 1. (c) Wilkinson, G.;
Stone, F. G. A.; Abel, E. W. Comprehensive Organometallic Chemistry;
Pergamon Press: New York, 1982; Vol. 8.
(2) (a) Ziegler, K. Angew. Chem. 1952, 64, 323. (b) Ziegler, K.
Belgium Patent 533 362, 1953. (c) Natta, G.; Pino, P.; Corradine, P.;
Danusso, F.; Mantica, E.; Mazzanti, G.; Moraglio, G. J . Am. Chem.
Soc. 1955, 77, 1708. (d) Natta, G.; Pino, P.; Mazzanti, G. Gazz. Chim.
Ital. 1957, 87, 528. (e) Pino, P.; Mulhaupt, R. Angew. Chem., Int. Ed.
Engl. 1980, 19, 857 and references cited therein.
(3) (a) Wilkinson, G.; Stone, F. G. A.; Abel, E. W. Comprehensive
Organometallic Chemistry; Pergamon Press: New York, 1982; Vol. 3.
(b) Wales, P. C.; Coutts, R. S. P.; Weigold, H. Organometallic Chemistry
of Titanium, Zirconium and Hafnium; Academic Press: New York,
1974. (c) Wilkinson, G.; Gillard, R. D. Comprehensive Coordination
Chemistry; Pergamon Press: New York, 1987; Vols. 1 and 2. (d)
Atwood, J . L.; Hunter, W. E.; Hrncir, D. C.; Samuel, E.; Alt, H.; Rausch,
M. D. Inorg. Chem. 1975, 14, 1757. (e) Hunter, W. E.; Hrncir, D. C.;
Bynum, R. V.; Penttila, R. A.; Atwood, J . L. Organometallics 1983, 2,
750. (f) Manriquez, J . M.; McAlister, D. R.; Sanner, R. D.; Bercaw, J .
E. J . Am. Chem. Soc. 1978, 100, 2716. (g) Buchwald, S. L.; Watson,
B. T.; Lum, R. T.; Nugent, W. A. J . Am. Chem. Soc. 1987, 109, 7137.
(h) Wolczanski, P.; Bercaw, J . E. Organometallics 1982, 1, 793. (i)
Roddick, D. M.; Fryzuk, M. D.; Seidler, P. F.; Hillhouse, G. L.; Bercaw,
J . E. Organometallics 1985, 4, 97. (j) Schock, L. E.; Brock, C. P.; Marks,
T. J . Organometallics 1987, 6, 232. (k) Finch, W. C.; Anslyn, E. V.;
Grubbs, R. H. J . Am. Chem. Soc. 1988, 110, 2406. (l) Tjaden, E. B.;
Casty, G. L.; Stryker, J . M. J . Am. Chem. Soc. 1993, 115, 9814. (m)
Spencer, M. D.; Morse, P. M.; Wilson, S. R.; Girolami, G. S. J . Am.
Chem. Soc. 1993, 115, 2057.
(7) Samuel, E. J . Organomet. Chem. 1980, 198, C65.
(8) (a) Yasuda, H.; Nakamura, A. Angew. Chem., Int. Ed. Engl. 1987,
26, 723. (b) Burk, M. J .; Tumas, W.; Ward, M. D.; Wheeler, D. R. J .
Am. Chem. Soc. 1990, 112, 6133. (c) Petasis, N. A.; Bzowej, E. I. J .
Am. Chem. Soc. 1990, 112, 6392. (d) Berk, S. C.; Grossman, R. B.;
Buchwald, S. L. J . Am. Chem. Soc. 1993, 115, 4912.
0276-7333/96/2315-1113$12.00/0 © 1996 American Chemical Society

1114 Organometallics, Vol. 15, No. 4, 1996
Minhas et al.
metathesis reactions. In this respect, sterically de-
manding alkyl groups lacking â-hydrogens (benzyl (Bz),
neophyl (Nf), neopentyl (Np)) seem to be particularly
versatile. In fact, by preventing â-H elimination reac-
tions, it is possible to obtain an unusually high stabil-
ity10 and thus favor R-H abstraction during C-H σ-bond
metathesis.11 Tetravalent titanium alkylidene com-
plexes have proven their potential use in important
applications like ROMP12 metathesis and polymeriza-
tion.13
As a result of the great potential offered by Ti alkyl
systems, their chemistry has been extensively studied
even though the major effort was directed toward using
cyclopentadienyl rings and related systems as support-
ing ligands.4 Titanium alkyls containing other support-
ing ligands are somewhat less known, since these
species are mainly generated in situ and usually not
completely characterized. Nevertheless, a few com-
plexes containing bulky phenoxides9a,14 and amide15 as
ancillary ligands have been fully characterized including
crystallographically. A large number of alkyltitanates
with a variety of supporting ligands have been success-
fully used in metal-promoted organic synthesis.16
The employment of anionic organic amides as ancil-
lary ligands has proven to be a viable alternative for
the stabilization of a wide range of oxidation states of
several transition elements. Such stability can be
ascribed to both the reducing ability of these anions and
the possibility of M-N π-bond formation, which obvi-
ously improves the stability of electron-rich complexes
via an increased electronic delocalization. In addition,
these ligands may function as bridging ligands, thus
promoting multinuclear aggregation through bridging
interactions of the nitrogen donor atom. The potential
offered by amide-supported titanium alkyls is under-
lined by their well-documented ability to promote ste-
reoselective organic reactions.16 Recently, we have
described the preparation and characterization of novel
titanium methyl and methylidene complexes9a,9c stabi-
lized by bulky organic amides. In this second paper,
we further describe the synthesis, characterization, and
thermal stability of other mono- and dinuclear Ti(III)
and Ti(IV) alkyls along with a preliminary discussion
of the factors influencing their stability.
Exp er im en ta l Section
All operations were performed under an inert atmosphere
of a nitrogen-filled drybox or by using standard Schlenk-type
glassware and a nitrogen-vacuum line. TiCl3 and TiCl4 were
used as received (Aldrich) and transformed into the corre-
sponding THF adducts by following literature procedures.17,18
Cy2NH, i-Pr2NH, (Me3Si)2NH, and TMEDA were distilled prior
to use over Na and K metals. The corresponding lithium salts
(R2NLi) were prepared by treating the hexane solutions of the
amines with stoichiometric amounts of n-BuLi. NpLi, NfLi,
and LiCH2SiMe3 were obtained according standard procedures.
The complexes [(Cy2N)2Ti(µ-Cl)2Li(TMEDA)] (1),9a [{(Me3-
Si)2N}2TiCl2][Li(TMEDA)2] (3),19 [(Cy2N)2Ti(µ-Me)2Li(TMEDA)]
(4b),9a and [(Cy2N)2TiCl2] (5)9a were synthesized according to
published procedures. C6D6 was dried over Na/K alloy,
vacuum transferred into an impule, and stored under nitrogen.
NMR spectra were recorded on a Varian Gemini 200 and on a
Bruker AMX-500 spectrometer using vacuum-sealed NMR
tubes prepared inside a drybox. Infrared spectra were re-
corded on a Mattson 3000 FTIR instrument from Nujol mulls
prepared inside the drybox. Samples for magnetic susceptibil-
ity measurements were prepared inside the drybox, and the
measurements were carried out at room temperature using a
Gouy balance (J ohnson Matthey). Magnetic moments were
calculated by following standard methods20 and corrections for
underlying diamagnetism were applied to the data.21 Com-
bustion analyses were obtained with a Perkin-Elmer Series
II CHN/O 2400 analyzer.
[(i-P r 2N)2TiCl2][Li(TMEDA)2] (2). A solution of i-Pr2NLi
(3.8 g, 35.5 mmol) in THF (50 mL) was added to a stirred
suspension of TiCl3‚3THF (6.5 g, 17.6 mmol) in THF (150 mL)
at -10 °C, followed by the addition of 2 equiv of TMEDA (5.0
mL, 33 mmol). The reaction was instantaneous, and the
resulting green solution was warmed to room temperature.
After the solution was stirred for an additional 30 min, the
solvent was evaporated in vacuo and the residue was dissolved
in hexane (150 mL). The LiCl was removed by filtration, and
the resulting solution was allowed to stand overnight at -30
°C, upon which forest green crystals of 2 (4.2 g, 7.5 mmol, 43%)
separated. Anal. Calcd (found) for C24H60N6TiLiCl2: C, 51.61
(51.56); H, 10.83 (10.04); N, 15.05 (14.64). IR (KBr, Nujol mull,
cm-1): 1461 (s), 1376 (m), 1292 (w), 1261 (w), 1168 (m), 1101
(m), 1035 (w), 931 (m), 811 (m), 792 (w), 723 (w), 605 (w), 493
(m). µeff ) 1.81 µB.
(9) (a) Scoles, L.; Minhas, R.; Duchateau, R.; J ubb, J .; Gambarotta,
S. Organometallics 1994, 13, 4978. (b) Klabunde, U.; Tebbe, F. N.;
Parshall, G. W.; Harlow, R. L. J . Mol. Catal. 1980, 8, 37. (c) For more
examples of Ti amide alkyl complexes see ref 9d-f. (d) Bradley, D.
C.; Chudzynska, H.; Backer-Durks, J . D. C.; Hursthouse, M. B.;
Ibrahim, A. A.; Motevalli, M.; Sullivan, A. C. Polyhedron 1990, 9, 1423.
(e) Wills, A. R.; Edwards, P. G. J . Chem. Soc., Dalton Trans. 1989,
1253. (f) Schubart, M.; O’Dwyer, L.; Gade, L. H.; Li, W. S.; McPartlin,
M. Inorg. Chem. 1994, 33, 3893.
(10) Guzman, I.; Adrov, O. I.; Bondarenko, G. N.; Tinyakova, E. I.;
Dolgoplosk, B. A. Organomet. Chem. USSR 1990, 3 (6), 694 and
references cited therein.
(11) (a) Hao, S.; Song, J . I.; Berno, P.; Gambarotta, S. Organome-
tallics 1994, 13, 1326. (b) Freudenberger, J . H.; Schrock, R. R.;
Churchill, M. R.; Rheingold, A. L.; Ziller, J . W. Organometallics 1984,
3, 1563. (c) Schrock, R.; Rocklage, S.; Wengrovius, J .; Rupprecht, G.;
Fellmann, J . J . Mol. Catal. 1980, 8, 73.
(12) (a) Dragutan, V.; Balaban, A.; Dimine, M. Olefin Metathesis
and Ring Opening Metathesis Polymerization of Cyclo-Olefins; Wiley
Interscience: Chichester, U.K., 1985. (b) Schrock, R. R. Acc. Chem.
Res. 1990, 23, 158. (c) Gilliom, L. R.; Grubbs, R. H. J . Am. Chem.
Soc. 1986, 108, 733. (d) Petasis, N. A.; Fu, D. K. J . Am. Chem. Soc.
1993, 115, 7208.
(13) (a) Ivin, K. J . Olefin Metathesis; Academic Press: London, 1983.
(b) Grubbs, R. H. In Comprehensive Organometallics Chemistry;
Wilkinson, G., Ed.; Pergamon Press Ltd.: Oxford, U.K., 1982; Vol. 8,
pp 499-551. (c) Howard, T. R.; Lee, J . B.; Grubbs, R. H. J . Am. Chem.
Soc. 1980, 102, 6876. (d) Katz, T. J .; Hacker, S. M.; Kendrick, R. D.;
Yammoni, C. S. J . Am. Chem. Soc. 1985, 107, 2182. (e) Straus, D. A.;
Grubbs, R. H. Organometallics 1982, 1, 1658. (f) Gilliom, L.; Grubbs,
R. H. J . Mol. Catal. 1988, 46, 255. (g) Lee, J . B.; Gajda, G. J .; Schaefer,
W. P.; Howard, T. R.; Ikariya, T.; Straus, D. A.; Grubbs, R. H. J . Am.
Chem. Soc. 1981, 103, 7358. (h) Lee, J . B.; Ott, K. C.; Grubbs, R. H.
J . Am. Chem. Soc. 1982, 104, 7491.
(14) (a) Zucchini, U.; Albizzati, E.; Giannini, U. J . Organomet. Chem.
1971, 26, 357. (b) Hill, J . E.; Fanwick, P. E.; Rothwell, I. P.
Organometallics 1990, 9, 2211. (c) Brauer, D. J .; Bu¨rger, H.; Wiegel,
K. J . Organomet. Chem. 1978, 150, 215. (d) Lubben, T. B.; Wolczanski,
P. T. J . Am. Chem. Soc. 1987, 109, 424. (e) Latesky, S. L.; McMullen,
A. K.; Rothwell, I. P.; Huffman, J . C. J . Am. Chem. Soc. 1985, 107,
5981. (f) Alvaro, L. M.; Cuenca, T.; Flores, J . C.; Royo, P.; Pellinghelli,
M. A.; Tiripicchio, A. Organometallics 1992, 11, 3301. (g) Ellis, W.
W.; Hollis, T. K.; Odenkirk, W.; Whelan, J .; Ostrander, R.; Rheingold,
R. L.; Bosnich, B. Organometallics 1993, 12, 4391.
(17) Manzer, L. E. Inorg. Synth. 1982, 21, 135.
(18) Dick, D. G.; Duchateau, R.; Edema, J . J . H.; Gambarotta, S.
Inorg. Chem. 1993, 32, 1959.
(19) Duchateau, R.; Gambarotta, S.; Beydoun, N.; Bensimon, C. J .
Am. Chem. Soc. 1991, 113, 8986.
(20) Mabbs, M. B.; Machin, D. Magnetism and Transition Metal
Compounds; Chapman & Hall: London, 1973.
(21) Foese, G.; Gorter, C. J .; Smits, L. Constantes, Selectionnees
Diamagnetisme, Paramagnetisme, Relaxation Paramagnetique;
Masson: Paris, 1957.
(15) (a) Burger, H.; Neese, H. J . Chimia 1970, 24, 209. (b) Burger,
H.; Neese, H. J . J . Organomet. Chem. 1972, 36, 101.
(16) (a) Roder, H.; Helmchen, G.; Peters, E. M.; Peters, K.; von
Schuering, H. G. Angew. Chem., Int. Ed. Engl. 1984, 23, 898. (b) von
Hulsen, E.; Hoppe, D. Tetrahedron Lett. 1985, 26, 411. (c) Reetz, M.
T.; Westermann, J .; Steinbach, R.; Wenderoth, B.; Peters, R.; Ostarek,
R.; Mans, S. Chem. Ber. 1985, 118, 1421. (d) Reetz, M. T. Organoti-
tanium Reagents in Organic Synthesis; Springer: Berlin, 1986.

Tri- and Tetravalent Titanium Alkyls
Organometallics, Vol. 15, No. 4, 1996 1115
[(Cy2N)2Ti(µ-CH2P h )2Li(TMEDA)] (4a ). A solution of 1
(1.0 g, 1.7 mmol) in ether (80 mL) was treated with BzLi-
(TMEDA) (0.75 g, 3.5 mmol). The color of the solution changed
immediately to the reddish brown, and stirring was continued
for about 30 min. The white precipitate was eliminated by
filtration and allowed to stand at room temperature for 2 h,
upon which purple microcrystalline 4a (0.4 g, 0.56 mmol, 33%)
separated. Anal. Calcd (found) for C44H74N4TiLi: C, 74.03
(73.85); H, 10.45 (10.41); N, 7.85 (7.79). IR (KBr, Nujol mull,
cm-1): 3056 (w), 1585 (m), 1288 (m), 1261 (m), 1213 (m), 1157
(m), 1143 (m), 1110 (s), 1097 (s), 1031 (s), 950 (s), 898 (s), 854
(m), 800 (s), 738 (s), 681 (s), 561 (m), 533 (m). µeff ) 1.88 µB.
Meth od B. A solution of 1 (1.16 g, 1.9 mmol) in ether (100
mL) was treated with freshly sublimed NfLi (0.52 g, 3.7 mmol).
The color of the solution gradually changed to green and finally
to brown. The mixture was stirred for another 2 h after which
the white insoluble material was removed by filtration. The
filtrate was concentrated to ca. 20 mL, and hexane (ca. 30 mL)
was added until the solution became cloudy. The mixture was
allowed to stand at -30 °C for 12 h, upon which brown
microcrystalline 8 separated (0.75 g, 1.1 mmol, 58%).
(Cy2N)2Ti(CH2SiMe3)2 (9). Meth od A. Addition of LiCH2-
SiMe3 (0.85 g, 10.5 mmol) to a stirred orange suspension of
(Cy2N)2TiCl2 (5) (2.5 g, 5.2 mmol) in THF (60 mL) at room
temperature slowly turned the color brown. The stirring was
continued overnight after which the small amount of white
insoluble material was eliminated by filtration. The filtrate
was cooled and allowed to stand overnight at -30 °C yielding
yellow microcrystals of 9 (1.6 g, 2.7 mmol, 53%).
Meth od B. Addition of LiCH2SiMe3 (0.42 g, 5.2 mmol) to
an emerald green solution of (Cy2N)2Ti(µ-Cl)2Li(TMEDA) (1)
(1.6 g, 2.6 mmol) in hexane (40 mL) at -10 °C turned the color
to brown. The solution was slowly warmed to room temper-
ature, and the stirring was continued at room temperature
for about 24 h. The resulting solution was filtered and allowed
to stand overnight at -30 °C yielding bright yellow, microc-
rystalline 9 (0.9 g, 1.5 mmol, 58%). Anal. Calcd (found) for
(Cy2N)2Ti(CH2P h )2 (6). Solid PhCH2Li‚TMEDA (1.75 g,
8.2 mmol) was added to an orange suspension of [(Cy2N)2TiCl2]
(5) (1.95 g, 4.0 mmol) in hexane (150 mL) yielding a dark
orange solution over a period of 2 days. After removal of the
small amount of white insoluble solid, the solvent was evapo-
rated in vacuo to yield an orange oil. Anal. Calcd (found) for
C
38H58N2Ti: C, 77.26 (77.01); H, 9.90 (9.76); N, 4.74 (4.64). 1H
NMR [C6D6, 200 MHz, δ (ppm)]: 7.25-6.85 (m, 5H, Ph), 3.7-
3.52 (m, 2H, Cy), 2.7 (s, 2H, Bz), 1.88-0.82 (m, 20H, Cy). 13C
NMR [C6D6, 50 MHz, δ(ppm)]: 150.74 (C, Ph), 129.2, 127.6,
122.8 (CH, Ph), 80.9 (CH2, Bz), 58.78 (CH, Cy), 36.8, 27.7, 26.6
(CH2, Cy).
(Cy2N)2Ti(CH2CMe3)2 (7). Meth od A. The addition of
NpLi (Np ) CH2CMe3, 0.8 g, 10.2 mmol) to an orange
suspension of [(Cy2N)2TiCl2] (5) (2.6 g, 5.4 mmol) in diethyl
ether (150 mL) at -10 °C turned the color greenish-yellow.
An insoluble light yellow-green solid separated, which was
isolated and redissolved in hexane at room temperature.
Yellow crystals of 7 were obtained after allowing the hexane
solution to stand overnight at 0 °C (1.6 g, 2.9 mmol, 54%).
C
32H66N2Si2Ti: C, 65.93 (65.76); H, 11.41 (11.48); N, 4.81
(4.62). IR (KBr, Nujol mull, cm-1): 1452 (s), 1376 (s), 1344
(m), 1245 (s), 1159 (m), 1143 (w), 1103 (s), 1068 (w), 1027 (s),
980 (m), 952 (s), 897 (s), 836 (s), 779 (w), 747 (m), 718 (s), 682
(m), 614 (m), 591 (m), 580 (m), 510 (m), 493 (m), 427 (m). 1H
NMR [200 MHz, C6D6, δ (ppm)]: 3.5 (m, 2H, Cy), 2.1-1.1 (bd
m, 20H, Cy), 1.3 (s, 2H, CH2), 0.3 (s, 9H, SiMe3). 13C [50 MHz,
C6D6, δ (ppm)]: 69.7 (CH2, CH2SiMe3), 58.2 (CH, Cy), 37.1,
27.8, 26.3 (CH2,Cy), 5.0 (CH3, SiMe3).
Meth od B. NpLi (0.4 g, 5.1 mmol) was added to a stirred
emerald green solution of 1 (1.5 g, 2.5 mmol) in diethyl ether
(60 mL) at -10 °C. The color turned brownish-orange, and
the stirring was continued for about 3 h at room temperature.
After the insoluble colorless material which had separated was
filtered off, the resulting clear solution was allowed to stand
overnight at -30 °C, upon which yellow microcrystalline 7
separated (0.5 g, 0.9 mmol, 36%). Anal. Calcd (found) for
(Cy2N)2Ti(CH2CMe2C6H4) (10). A solution of 8 (1.8 g, 2.7
mmol) in hexane (70 mL) was heated at 60 °C for 5 min. The
resulting clear yellow solution yield yellow crystals of 10 (1.2
g, 2.2 mmol, 81%) upon standing at -30 °C for 2 days. Anal.
Calcd (found) for C34H56N2Ti: C, 75.52 (75.38); H, 10.44 (10.61);
N, 5.18 (5.17). IR (KBr, Nujol mull, cm-1): 1567 (w), 1421
(w), 1392 (w), 1376 (w), 1365 (w), 1348 (w), 1251 (m), 1230
(w), 1162 (m), 1143 (m), 1118 (br), 1089 (w), 1066 (w), 1031
(br), 981 (m), 966 (br), 890 (s), 840 (sh), 806 (sh), 781 (sh), 761
(sh), 723 (m), 709 (sh), 686 (w), 603 (s), 590 (m), 586 (m), 503
(sh), 488 (sh), 453 (sh). 1H NMR [500 MHz, C6D6, δ (ppm)]:
7.27-7.16 (m, 2H, Ph), 7.12-7.0 (m, 2H, Ph), 3.85-3.79 (m,
4H, Cy), 2.02 (s, 2H, CH2, Nf), 1.69 (s, 6H, CH3, Nf), 1.99-
0.87 (m, 4-H, CH2, Cy). 13C NMR [125.7 MHz, C6D6, δ (ppm)]:
193.5, 160.5 (C, Ph, Nf), 131.0, 128.6, 124.9, 123.8, (CH, Ph,
Nf), 57.3 (CH, Cy), 41.8 (C, Nf), 37.02 (CH2, Nf), 36.9 (CH3,
Nf), 27.09, 26.92, 26.06 (CH2, Cy).
C
34H66N2Ti: C, 74.14 (74.57); H, 12.08 (12.27); N, 5.09 (5.11).
IR (KBr, Nujol mull, cm-1): 1455 (s), 1366 (s), 1252 (m), 1225
(m), 1158 (m), 1142 (m), 1107 (sh), 1091 (sh), 1025 (sh), 978
(m), 944 (sh), 887 (sh), 842 (sh), 803 (sh), 778 (sh), 750 (sh),
696 (sh), 680 (m), 589 (m), 579 (m), 546 (w), 506 (sh), 488 (sh),
453 (m). 1H NMR [500 MHz, C6D6, δ (ppm)]: 3.75-3.69 (m,
2H, Cy), 2.02-1.11 (m, 20H, Cy), 1.65 (s, 2H, Np), 1.3 (s, 9H,
Np). 13C NMR [125.7 MHz, C6D6, δ (ppm)]: 98.7 (CH2, Np),
58.2 (CH, Cy), 36.9 (C, Np), 34.8 (CH3, Np), 36.3, 27.1, 26.2
(CH2, Cy).
(Cy2N)2Ti(CH2CMe2P h )2 (8). Meth od A. Solid LiCH2-
CMe2Ph (1.35 g, 9.6 mmol) was added to a stirred solution of
[(Cy2N)2TiCl2] (5) (2.3 g, 4.8 mmol) in diethyl ether (50 mL) at
room temperature. The color turned instantaneously yellow,
and stirring was continued for a few hours. The solvent was
evaporated in vacuo, and the residual solid was redissolved
in hexane (40 mL). Removal of LiCl followed by overnight
standing at -30 °C afforded greenish-yellow crystals of 8 (1.7
g, 2.5 mmol, 52%). Anal. Calcd (found) for C44H70N2Ti: C,
78.30 (77.88); H, 10.45 (10.46); N, 4.15 (4.02). IR (KBr, Nujol
mull, cm-1): 1600 (w), 1494 (sh) 1454 (bd), 1376 (m), 1249 (m),
1188 (w), 1172 (w), 1157 (m), 1093 (m), 1081 (sh), 1029 (m),
1020 (m), 975 (w), 944 (sh), 887 (sh), 842 (sh), 806 (m), 779
(m), 761 (sh), 698 (sh), 582 (w), 551 (m). 1H NMR [500 MHz,
C6D6, δ (ppm)]: 7.52-7.5 (m, 2H, Ph), 7.28-7.24 (m, 2H, Ph),
7.1-7.07 (m, 1H, Ph), 3.7-3.65 (m, 2H, Cy), 1.93-0.88 (m,
20H, Cy), 1.78 (s, 2H, CH2, Nf), 1.54 (s, 6H, CH3, Nf). 13C NMR
[125.7 MHz, C6D6, δ (ppm)]: 153.7 (C, Ph, Nf), 127.8 (CH, Ph,
Nf), 126.0 (CH, Ph, Nf), 125.3 (CH, Ph, Nf), 97.5 (CH2, Nf),
58.5 (CH, Cy), 43.6 (C, Nf), 34.3 (CH3, Nf), 36.4, 27.0, 26.1
(CH2, Cy).
[(i-P r 2N)2TiP h 2][Li(TME DA)2] (11). The addition of
PhLi‚1.5Et2O (1.6 g, 8.2 mmol) to a forest green solution of
[(i-Pr2N)2TiCl2][Li(TMEDA)2] (2) (2.4 g, 4.3 mmol) in Et2O
turned the color cherry red. The reaction mixture was stirred
at room temperature for about 2 h and then filtered to remove
LiCl. Dark red crystals of 11 (1.7 g, 2.6 mmol, 60%) were
obtained upon allowing the resulting solution to stand over-
night at room temperature. Anal. Calcd (found) for C36H20
-
N6TiLi: C, 67.37 (66.69); H, 10.99 (10.75); N, 13.09 (12.78).
IR (KBr, Nujol mull, cm-1): 1610 (w), 1549 (s), 1457 (s), 1407
(m), 1381 (s), 1346 (s), 1287 (s), 1245 (m), 1228 (m), 1169 (s),
1126 (m), 1099 (s), 1068 (s), 1043 (m), 1029 (s), 1009 (s), 978
(s), 946 (s), 921 (s), 848 (s) 806 (s), 788 (s), 714 (m), 705 (s),
633 (w). µeff ) 1.77 µB.
[{(Me3Si)2N}2Ti(CH2P h )2][Li(TMEDA)2] (12). Neat TME-
DA (4.0 mL) was added to a solution of [{(Me3Si)2N)2TiCl2]-
[Li(TMEDA)2] (3) (1.9 g, 2.8 mmol) in toluene (40 mL) at room
temperature followed by the addition of t-BuLi (3.3 mL of 1.7
M, 5.6 mmol) at -78 °C. The reaction was instantaneous, and
orange crystals of 12 (1.9 g, 2.4 mmol, 86%) separated from
the resultant solution upon standing overnight at room tem-

1116 Organometallics, Vol. 15, No. 4, 1996
Minhas et al.
Ta ble 1. Cr ysta l Da ta a n d Str u ctu r a l An a lysis Resu lts
complex
1
10
11
12
13
14
formula
fw
C30H60TiCl2LiN4
602.58
C34H56N2Ti
540.73
C36H70N6TiLi
641.83
C38H82N6Si4TiLi
790.28
C26H50Si4N2Ti
550.94
C48H88N4Ti2Cl2O
903.96
cryst color
cryst system
space group
a (Å)
b (Å)
c (Å)
R (deg)
â (deg)
γ (deg)
V (Å)3
green, prism
monoclinic
P21/n
12.361(5)
19.616(4)
15.357(3)
golden, cube
triclinic
P1h
red, cube
monoclinic
P21/n
9.528(2)
21.675(5)
19.867(9)
yellow, block
monoclinic
P21/c
13.757(2)
17.329(7)
22.151(4)
red, prism
triclinic
P1h
orange, cube
monoclinic
C2/c
16.205(4)
14.804(3)
20.748(5)
10.318(1)
15.5144(9)
10.241(1)
98.909(9)
99.40(1)
86.106(9)
1596.2(5)
2
11.639(2)
17.188(2)
8.935(2)
90.35(1)
109.24(1)
102.16(1)
1644.2(4)
2
109.39(2)
97.86(2)
104.31(1)
96.11(2)
3512(2)
4
4065(4)
4
5117(2)
4
4949(4)
4
Z
radiation:
λ(Mo KR) (Å)
T (°C)
0.710 69
0.710 69
0.710 69
0.710 69
0.710 69
0.710 69
-160
1.139
4.16
1308
519
-144
1.125
2.86
592
334
3692
-153
1.049
2.35
1412
399
23
23
-161
1.213
4.64
1960
256
Dcalcd (g cm-3
)
0.875
2.76
1468
427
1.113
4.15
596
299
3970
µcalcd (cm-1
F000
)
no. of params
no. of observns
R, Rw, GoF
4601
4232
3046
2496
0.077, 0.091, 3.35 0.036, 0.047, 2.10 0.067, 0.081, 2.66 0.074, 0.065, 2.72 0.046, 0.067, 1.69 0.075, 0.087, 2.70
perature. Anal. Calcd (found) for C38H82N6Si4TiLi: C, 57.75
(57.45); H, 10.46 (10.12); N, 10.63 (10.52). IR (KBr, Nujol mull,
cm-1): 1589 (s), 1470 (br), 1376 (m), 1357 (m), 1288 (sh), 1249
(br), 1209 (m), 1182 (m), 1159 (m), 1128 (sh), 1097 (sh), 1068
(sh), 1029 (sh), 1014 (sh), 970-775 (v br), 746 (br), 698 (m),
665 (m), 624 (m), 588 (w), 559 (m), 512 (m), 493 (w), 439 (w).
µeff ) 1.73 µB.
(w), 1249 (m), 1159 (m), 1143 (m), 1112 (sh), 1087 (sh), 1029
(br), 981 (m), 968 (sh), 890 (sh), 842 (sh), 771 (br), 707 (m),
588 (m), 576 (w), 530 (w), 501 (br). 1H NMR [500 MHz, C6D6,
δ (ppm)]: 3.66 (m, 4H, Cy), 2.1-1.13 (br, m, 40H, Cy), 0.94 (s,
3H, Me). 13C NMR [125.7 MHz, C6D6, δ (PPM)]: 58.1 (CH,
Cy), 38.4 (CH3, Me), 36.4, 26.9, 26.8 (CH2, Cy).
X-r a y Cr ysta llogr a p h y. Data were collected at temper-
atures in the range -157 to -160 °C using the ω-2θ scan
technique to a maximum 2θ value of 50.0°, for suitable air-
sensitive crystals mounted on glass fibers. Cell constants and
orientation matrices were obtained from the least-squares
refinement of 25 carefully centered high-angle reflections.
Reducntant reflections were removed from the data set. The
intensities of three representative reflections were measured
after every 150 reflections to monitor crystal and instrument
stability. Data were corrected for Lorentz and polarization
effects but not for absorption. The structures were solved by
direct methods. The non-hydrogen atoms were refined aniso-
tropically. Hydrogen atom positions were located in the
difference Fourier maps. The final cycle of full-matrix least-
squares refinement was based on the number of observed
reflections with I > 2.5σ(I). Neutral atomic scattering factors
were taken from Cromer and Waber.22 Anomalous dispersion
effects were included in Fc. All calculations were performed
using the TEXSAN package on a Digital VAX station. Details
on data collection and structure refinement are reported in
Table 1. Final atomic coordinates for all the complexes are
given as Supporting Information. Selected bond distances and
angles are given in Table 2.
[{(Me3Si)2N}2Ti(CH2P h )2] (13). A solution of 12 (1.7 g,
2.1 mmol) in toluene (60 mL) was cooled to -10 °C and treated
with diphenylfulvene (0.5 g, 2.2 mmol). The color immediately
turned dark red, and the stirring was continued for 2 h at room
temperature. After removal of the solvent, the residual solid
was redissolved in Et2O and the resulting solution allowed to
stand at -30 °C overnight, upon which red cubes of 13 (0.7 g,
1.3 mmol, 62%) separated. Anal. Calcd (found) for C26H50
-
Si4N2Ti: C, 56.68 (56.06); H, 9.15 (8.88); N, 5.08 (4.76). IR
(KBr, Nujol mull, cm-1): 1596 (sh), 1488 (m), 1465 (br), 1376
(m), 1249 (s, br), 1207 (m), 1027 (w), 1012 (w), 993 (w), 871-
671 (br), 619 (w), 561 (m), 507 (m), 428 (m). 1H NMR [200
MHz, C6D6, δ (ppm)]: 0.49 (s, 18H, Me3Si), 3.32 (s, 2H, CH2,
Bz), 7.35-7.4 (m, 5H, Ph, Bz). 13C NMR [50 MHz, C6D6, δ-
(ppm)]: 148.7 (C, Ph, Bz), 128.3, 127.1, 123.5 (CH, Ph, Bz),
99.9 (CH2, Bz), 5.9 (Me, SiMe3).
[(Cy2N)2TiCl]2O (14). The addition of styrene oxide to a
green toluene solution of 1 (2.4 g, 4.0 mmol) at room temper-
ature changed the color to orange. The solution was filtered
to remove a small amount of white insoluble solid and allowed
to stand at -30 °C overnight, upon which bright yellow-orange
crystals of 14 separated (1.1 g, 2.4 mmol, 60%). Anal. Calcd
(found) for C48H88N4Ti2Cl2O: C, 63.78 (62.38); H, 9.81 (9.70);
N, 6.20 (5.93). IR (KBr, Nujol mull, cm-1): 1452 (sh, br), 1376
(sh), 1344 (w), 1251 (w), 1159 (m), 1143 (w), 1105 (s), 1079
(m), 1027 (br), 981 (m), 960 (sh), 892 (s), 842 (s), 808 (w), 786
(w), 746 (sh), 709 (w), 590 (w), 752 (m), 511 (m), 491 (w), 449
(m). 1H NMR [500 MHz, C6D6, δ (ppm)]: 3.85 (m, 1H, Cy),
2.3-1.1 (br m, 10H, Cy). 13C NMR [125.7 MHz, C6D6, δ (ppm)]:
60.3 (CH, Cy), 35.7, 26.7, 25.9 (CH2, Cy).
(Cy2N)2TiMe]2O (15). A solution of MeLi in ether (1.5 mL,
2.0 mmol of 1.4M) was added to a stirred suspension of 14
(0.9 g, 1.0 mmol) in THF (80 mL) at -70 °C. The solution
was warmed to room temperature, and the stirring was
continued for 24 h followed by removal of the solvent in vacuo.
The residual solid was recrystallized from toluene (25 mL)
yielding yellow microcrystalline 15 (80 mg, 0.09 mmol, 9%)
upon cooling for 2 days at -30 °C. Anal. Calcd (found) for
C50H94N4Ti2O: C, 69.58 (68.87); H, 10.98 (10.36); N, 6.49 (5.98),
IR (KBr, Nujol mull, cm-1): 1450 (sh), 1376 (s), 1344 (m), 1267
Resu lts a n d Discu ssion
The reaction of TiCl3(THF)3 with 2 equiv of R2NLi (R
) Cy, i-Pr, Me3Si) in THF and in the presence of
TMEDA (Scheme 1) yielded the corresponding bis-
(amido) titanium halide derivatives which were isolated
as air-sensitive green crystals. Depending upon the
nature of the dialkylamide organic substituent, het-
erodinuclear (R2N)2TiCl2Li(TMEDA) [R ) Cy (1)] or
ionic [(R2N)2TiCl2][Li(TMEDA)] [R ) i-Pr (2); R ) Me3-
Si (3)] complexes were isolated. Combustion analyses
were in agreement with the proposed formulation, while
X-ray fluorescence data gave for all the complexes the
(22) Cromer, D. T.; Waber, J . T. International Tables for X-ray
Crystallography; The Kynoch Press: Birmingham, England, 1974.

Tri- and Tetravalent Titanium Alkyls
Organometallics, Vol. 15, No. 4, 1996 1117
Ta ble 2. Selected Bon d Dista n ces (Å) a n d An gles
(d eg)
1
10
Ti1-Cl1
Ti1-Cl2
Ti1-N3
Ti1-N4
Cl1-Li1
Cl2-Li1
Cl1-Ti1-Cl2
Cl1-Ti1-N3
Cl1-Ti1-N4
Cl2-Ti1-N3
Cl2-Ti1-N4
N3-Ti1-N4
Ti1-Cl1-Li1
Ti1-Cl2-Li1
Ti1-N4-C1
Ti1-N4-C7
C1-N4-C7
2.436(2)
2.415(2)
1.906(4)
1.917(4)
2.35(1)
Ti1-N1
1.896(2)
1.879(2)
2.121(2)
2.089(2)
120.93(8)
111.98(8)
110.26(8)
110.81(8)
112.26(8)
84.92(9)
141.3(1)
103.2(1)
115.5(2)
Ti1-N2
Ti1-C25
Ti1-C30
N1-Ti1-N2
2.31(1)
N1-Ti1-C25
N1-Ti1-C30
N2-Ti1-C25
N2-Ti1-C30
C25-Ti1-C30
Ti1-N1-C1
Ti1-N1-C7
C1-N1-C7
93.18(5)
107.5(1)
107.6(1)
107.4(1)
116.9(1)
120.5(2)
83.5(2)
84.8(2)
106.2(3)
138.4(3)
115.0(4)
F igu r e 1. ORTEP plot of 1. Thermal ellipsoids are drawn
at the 50% probability level
11
12
Ti1-N3
1.962(4)
1.965(4)
2.173(5)
2.210(5)
2.12(1)
Ti1-N1
2.036(8)
2.027(8)
2.18(1)
2.18(1)
2.10(2)
2.12(2)
2.17(2)
2.12(2)
127.4(3)
108.1(3)
100.0(4)
99.9(4)
119.7(4)
116.5(4)
121.9(4)
121.6(5)
97.4(4)
expected for the d1 electronic configuration of Ti(III),
and displayed uninformative NMR spectra. The mo-
lecular structures of complexes 1 and 39a were eluci-
dated by X-ray crystal structures.
Ti1-N4
Ti1-N2
Ti1-C1
Ti1-C7
Ti1-C7
Ti1-C14
Li2-N1
N3-Li1
Li2-N2
2.13(1)
N4-Li1
Complex 1 is heterodinuclear with the titanium and
lithium atoms bridged by two chloride atoms (Figure
1). The distorted tetrahedral geometry of the titanium
atom is defined [N4-Ti1-N3 ) 120.5(2)°, N3-Ti1-Cl1
) 107.5(1)°, N3-Ti1-Cl2 ) 107.4(1)°, Cl2-Ti1-Cl1 )
93.18(5)°] by two nitrogen atoms of two amides and two
chlorides. The Ti-N and Ti-Cl bond distances are as
expected [Ti1-N3 ) 1.906(4) Å; Ti1-Cl1 ) 2.436(2) Å].
The geometry of the two nitrogen atoms of the two
amides slightly deviates from the regular trigonal
planar [C1-N4-Ti1 ) 106.2(3)°, Ti1-N4-C7 ) 138.4-
(3)°, Cl-N4-C7 ) 115.0(4)°] expected for the sp2
hybridization of the nitrogen atom. The TiCl2Li core is
almost planar [torsion angle Ti1-Cl1-Li1-C12 ) 2.5-
(3)°]. One molecule of TMEDA completes the tetrahe-
dral coordination geometry of the alkali cation.
Li2-N5
2.085(9)
2.153(9)
118.0(2)
109.6(2)
106.3(2)
105.6(2)
100.2(2)
108.8(3)
135.7(3)
115.2(4)
N5-Li1
Li2-N6
N6-Li1
N3-Ti1-N4
N3-Ti1-C1
N3-Ti1-C7
N4-Ti1-C1
C1-Ti1-C7
Ti1-N3-C19
Ti1-N3-C22
C19-N3-C22
N1-Ti1-N2
N1-Ti1-C7
N1-Ti1-C14
N2-Ti1-C7
N2-Ti1-C14
Ti1-N1-Si1
Ti1-N1-Si2
Si1-N1-Si2
C7-Ti1-C14
13
14
Ti1-N1
1.931(3)
1.939(3)
2.092(5)
2.109(4)
120.6(1)
108.4(2)
108.1(2)
109.1(2)
110.0(2)
98.4(2)
120.7(3)
119.2(3)
124.8(2)
117.5(2)
117.5(2)
Ti1-C12
2.296(2)
1.828(2)
1.910(6)
1.876(6)
109.3(2)
109.2(2)
109.9(2)
113.5(2)
108.5(2)
106.3(2)
154.9(4)
120.6(5)
123.5(4)
115.7(5)
Ti1-N2
Ti1-O1
Ti1-C13
Ti1-N1
Ti1-C20
Ti1-N2
N1-Ti1-N2
N1-Ti1-C13
N1-Ti1-C20
N2-Ti1-C13
N2-Ti1-C20
C13-Ti1-C20
Ti1-C13-C14
Ti1-C20-C21
Ti1-N1-Si1
Ti1-N1-Si2
Si1-N1-Si2
C12-Ti1-O1
C12-Ti1-N1
Cl2-Ti1-N2
O1-Ti1-N1
O1-Ti1-N2
N1-Ti1-N2
Ti1-O1-Ti1a
Ti1-N1-C1
Ti1-N1-C7
C1-N1-C7
Alkylation of 1 carried out with alkyllithium reagents
gave the corresponding tri- and tetravalent alkyl com-
plexes depending on the nature of the alkylating agent
employed. The reaction of 1 with either BzLi(TMEDA)
or MeLi gave simple chloride subsitution forming the
corresponding trivalent [(Cy2N)2TiR2Li(TMEDA)] [R )
CH2Ph (4a ), Me (4b)], where both the oxidation state
and the heterodinuclear frame were preserved.9a Con-
versely, in the case of bulkier alkylating agents, air-
sensitive tetravalent neutral complexes, formulated as
(R2N)2TiR′2 [R′′ ) CH2CMe3(7), CH2SiMe3(9)] were
formed (Scheme 2). The formulas were inferred from
combustion analysis data. X-ray fluorescence data and
qualitative analytical tests for Cl were also in agreement
with the proposed formulation. Complexes 6-9 were
conveniently synthesized in higher yield (50-55%) by
using the tetravalent complex (Cy2N)2TiCl2 (5) as start-
ing material. All the complexes were yellow in color and
have been isolated in crystalline form. The common
Sch em e 1
1
feature in the H NMR spectra of all these complexes
is the presence of a broad multiplet in the range 2.1-
1.0 ppm attributed to the methylene protons of the
cyclohexyl rings and a pseudotriplet in the range 3.5-
4.0 ppm due to the ipso protons of the cyclohexyl rings.
Complex 6 shows a sharp singlet at 2.7 ppm for the
expected 1:2 Ti:Cl ratios. Complexes 1-3 are paramag-
netic, with magnetic moments (µeff ) 1.7-1.8 µB) as

1118 Organometallics, Vol. 15, No. 4, 1996
Minhas et al.
Sch em e 2
Sch em e 3
Sch em e 4
methylene protons of benzyl along with a multiplet in
the aromatic region for the phenyl ring protons. 13C-
{1H} and HMQC spectra were also consistent with the
proposed formulation showing the appropriate cou-
1
plings. The H NMR spectrum of complex 7 showed a
sharp singlet at 1.65 ppm for the methylene protons of
the alkyl group and another singlet at 1.3 ppm for the
methyl protons of the neopentyl group in the ratio 2:9.
Complex 8 showed three multiplets in the aromatic
region (7.52-7.07 ppm) assigned to the phenyl groups.
In addition, two singlets respectively at 1.78 ppm for
the methylene protons and at 1.54 ppm for the methyl
protons of the neophyl substituent were found in the
correct ratio 1:3. The fact that only one methyne proton
resonance was determined in the spectra of all these
complexes indicates that the cyclohexyl rings are equiva-
lent. Two singlets at 1.3 ppm for the methylene protons
and at 0.3 ppm for the Me3Si protons, respectively, in
the ratio 2:9 are present in the 1H NMR spectrum of
complex 9. The methylene groups of the alkyl directly
connected to the titanium atom display chemical shifts
at fields (2.7-1.3 ppm) which are considerably lower
than those of the cyclopentadienyl analogues. This
trend, which becomes even more pronounced in the 13C
NMR spectra, indicates that the amide groups signifi-
cantly modify the nature of the Ti-C bond by introduc-
ing a higher degree of covalency.
In order to explain the oxidation of Ti(III) alkyls to
the corresponding Ti(IV) derivatives, we tentatively
suggest that the initially formed intermediate (Cy2N)2-
TiR′ species cannot be sufficiently stabilized by the
formation of ionic structures such as in the case of
complexes 1-4. This is also indicated by the fact that
the result of the reaction was not modified by a different
stoichiometric ratio or by the use of excess of alkylating
agent. We speculate that the coordinatively unsatur-
ated (Cy2N)2TiR′ moiety probably forms a dinuclear
complex where the two metal centers are bridged via
ether amide or alkyl. Subsequent disproportionation
(Scheme 3) forms both tetravalent and divalent species
through a mechanism analogous to that previously
described for 4 or Zr(III) dimers.23 However, different
from the case of Zr, attempts to isolate the correspond-
ing Ti(II) species, formed as result of such a dispropor-
tionation, remained unsuccessful in the present work.
The Ti(IV) alkyl complexes 6-9 display a moderate
thermal stability in the solid state. However, they were
found to be rather unstable in solution where all these
species showed a tendency to slowly decompose, even
at room temperature. Complex 7 completely decom-
poses at room temperature in about 4-5 days forming
neopentane together with intractable materials. How-
ever, complex 8 yielded the cyclometalated species 10
upon standing at room temperature for a period of 5-6
weeks (Scheme 4). As expected, the reaction was
greatly accelerated when an hexane solution of 8 was
heated for a few minutes at 50 °C. The 1H NMR
spectrum of complex 10 showed singlets attributed to
methylene and methyl protons being considerably shifted
to lower fields. For example, the methylene protons
were found at 2.02 ppm while the methyl protons of
neophyl were located at 1.69 ppm. The aromatic signals
were also significantly modified with respect to those
of complex 8. The integration of the spectrum showed
loss of one neophyl ligand. During a thermolysis in a
sealed NMR tube, 1 equiv of (CH3)3C(Ph) was formed
thus indicating that deprotonation of the remaining
neophyl molecule occurred, probably via metalation of
the aromatic ring and consequent formation of a met-
allacycle.
The molecular structure of 10 was confirmed by
single-crystal X-ray diffraction analysis. The molecule
is monomeric with the Ti atom bonded to two NCy2
groups and engaged into a five-membered metallacycle
with an ortho-metalated neophyl group (Figure 2). The
Ti atom possesses a slightly distorted tetrahedral
geometry [N1-Ti1-N2 ) 120.93(8)°, N1-Ti1-C25 )
111.98(8)°, N1-Ti1-C30 ) 110.26(8)°, N2-Ti1-C25 )
110.81(8)°, C25-Ti1-C30 ) 84.92(9)°], which is bound
by two N atoms of the amide groups and two C atoms
of one neophyl unit. The neophyl group chelates
titanium through the methylene group and one ortho
carbon atom of the phenyl group [Ti1-C25 ) 2.121(2)
Å, Ti1-C30 ) 2.089(2) Å]. The Ti atom was found
significantly elevated above the puckered plane [C30-
C29-C26-C25 ) -19.2(3)°] formed by the four C atoms
which compose part of the five-membered ring. Con-
versely, the metallacycle is nearly coplanar with the
(23) (a) Wielstra, Y.; Gambarotta, S.; Chiang, M. Rec. Trav. Chim.
Pay Bas 1989, 108, 1. (b) Wielstra, Y.; Gambarotta, S.; Meetsma, A.;
Spek, A. L. Organometallics 1989, 8, 2948.

Tri- and Tetravalent Titanium Alkyls
Organometallics, Vol. 15, No. 4, 1996 1119
F igu r e 2. ORTEP plot of 10. Thermal ellipsoids are
drawn at the 50% probability level.
F igu r e 3. ORTEP plot of 11. Thermal ellipsoids are
drawn at the 50% probability level.
Sch em e 5
TMEDA surrounding a slightly distorted tetrahedral Li
atom [N1-Li2-N2 ) 87.3(4)°, N1-Li2-N5 ) 123.7(4)°,
N1-Li2-N6 ) 118.6(4)°, N2-Li2-N5 ) 117.7(4)°, N5-
Li2-N6 ) 87.8(4)°] with Li-N distances in the expected
range [Li2-N1 ) 2.12(1) Å, Li2-N2 ) 2.13(1) Å].
An anionic Ti(III) dibenzyl complex [{(Me3Si)2N}2Ti-
(Bz)2][Li(TMEDA)2] (12) was obtained upon treatment
of the silylated amide derivative {[(Me3Si)2N]2TiCl2}-
{Li(TMEDA)2} (3) with t-BuLi in toluene (Scheme 5).
The complex was isolated as paramagnetic golden
yellow-orange crystals. A mixture of isobutene and
isobutane was found in both the gaseous mixture of the
reaction vessel and in the mother liquor. The origin of
the benzyl groups in complex 12 might be attributed to
the formation of PhCH2Li generated in situ by the fast
reaction of t-BuLi with toluene and subsequent reaction
with the Ti substrate. However, we cannot exclude the
possibility that 12 might also be originated by the
reaction of an in situ generated {[(Me3Si)2N]2Ti(t-Bu)2}--
[Li(TMEDA)2]+ complex with toluene. Reaction of 12
with t-BuLi in either hexane or ether gave only intrac-
table materials.
Complex 12 is monomeric and also ionic with a Li-
(TMEDA)2 cationic fragment very similar to that of
complex 11 (Figure 4). The anion consists of a titanium
atom with distorted tetrahedral geometry defined by
two N atoms from the amide units and two C atoms of
the two benzyl subsituents [N1-Ti1-N2 ) 127.4(3)°,
N1-Ti1-C7 ) 108.1(3)°, N1-Ti1-C14 ) 100.0(4)°, C7-
Ti1-C14 ) 97.4(4)°]. The nitrogen atoms of the amides
show the usual trigonal planar geometry indicative of
some extent of Ti-N π bonding [Ti1-N1-Si1 ) 116.5-
(4)°, Ti1-N1-Si2 ) 121.9(4)°, Si1-N1-Si2 ) 121.6(5)°].
The Ti-N [Ti1-N1 ) 2.036(8) Å, Ti1-N2 ) 2.027(8)
Å] and the Ti-C bond distances [Ti1-C7 ) 2.18(1) Å,
Ti1-C14 ) 2.18 Å] are comparable with those of
complex 11.
phenyl ring of the neophyl group. The distortion around
Ti is predominantly caused by the bulky amide ligands,
whose steric congestion is also indicated by the fact that
the coordination of the nitrogen atoms significantly
deviates from the regular trigonal planar geometry
expected for the sp2 hybridization [Ti1-N1-C7 ) 103.2-
(1)°, Ti1-N1-C1 ) 141.3(1)°, C1-N1-C7 ) 115.5(2)°,
Ti1-N2-C13 ) 108.3(1)°, C13-N2-C19 ) 117.2(2)°,
Ti1-N2-C19 ) 134.5(1)°].
The reaction of the isopropyl halide derivative [(i-
Pr2N)2TiCl2][Li(TMEDA)2] (2) with a number of alkyl-
lithium agents only yielded intractable materials. Only
in the case of PhLi was a clean reaction obtained
allowing the isolation of a new complex 11 in crystalline
form (Scheme 5). The magnetic moment (µeff ) 1.77 µB),
calculated on the basis of the formulation provided by
analytical data, was in agreement with a d1 electronic
configuration of a Ti(III) metal center.
The molecular structure of 11 was elucidated by X-ray
crystal structure. The complex is mononuclear and is
composed of two distinct ionic moieties (Figure 3). The
anion consists of a distorted tetrahedral titanium atom
with a coordination geometry defined by two nitrogen
atoms of two amides and two carbon atoms of two
phenyl groups. Once again the distortion of the coor-
dination geometry of Ti is caused by the steric bulk of
the amide substituents which are slightly bent toward
the phenyl groups [N3-Ti1-N4 ) 118.0(2)°, N3-Ti1-
C1 ) 109.6(2)°, N4-Ti1-C7 ) 115.6(2)°, C1-Ti1-C7
) 100.2(2)°]. The Ti-N [Ti1-N3 ) 1.962(4) Å, Ti1-
N4 ) 1.965(4) Å] and the Ti-C bond distances [Ti1-
C1 ) 2.173(5) Å, Ti1-C7 ) 2.210(5) Å] are in the
expected range. The angles around the nitrogen atoms
of the two amide ligands are severely distorted with
respect to the expected sp2 hybridization of the N atom.
The cationic fragment consists of two molecules of
Similar to the other Tl(III) and Ti(IV) alkyls reported
in this work, complex 12 was also found to be thermally
labile in both toluene and THF solutions, in which it
decomposed forming intractable materials. Neverthe-
less, the reaction of 12 with diphenylfulvene resulted
in the formation of a neutral Ti(IV) complex 13 which
crystallized as red cubes from hexane in about 59% yield
(Scheme 6). The complex was characterized by analyti-

1120 Organometallics, Vol. 15, No. 4, 1996
Minhas et al.
F igu r e 5. ORTEP plot of 13. Thermal ellipsoids are
drawn at the 50% probability level.
Sch em e 7
F igu r e 4. ORTEP plot of 12. Thermal ellipsoids are
drawn at the 50% probability level.
Sch em e 6
cal and spectroscopic data. Complex 13 could not be
synthesized by using the more straightforward synthetic
pattern described for the other Ti(IV) alkyls reported
above, since the starting {(Me3Si)2N}2TiCl2 could not
be prepared. However, the reaction of 12 with diphe-
nylfulvene provided the desired complex 13 in good yield
via a simple electron transfer mechanism. Similar to
the other Ti(IV) alkyl complexes reported in this work,
the CH2 benzilic resonance of complex 12 was found
(µ-O) (14) (Scheme 7), which was isolated as orange
crystals. The IR spectrum showed the Ti-O stretching
as a broad intense band at 746 cm-1. The 1H NMR
spectrum of the complex showed only one type of
cyclohexyl group, with a multiplet at 3.85 ppm and the
characteristic series of multiplets in the range 1.1-2.3
ppm.
1
shifted to considerably low field in the H NMR spec-
The X-ray crystal structure determination has proven
the molecule to be dimeric consisting of two identical
(Cy2N)2TiCl fragments bridged by an oxygen atom
(Figure 6). Each titanium atom possesses a tetrahedral
geometry [Cl2-Ti1-N2 ) 109.9(2)°, Cl2-Ti1-N1 )
109.2(2)°, Cl2-Ti1-O1 ) 109.3(2)°, O1-Ti1-N1 )
113.5(2)°, O1-Ti1-N2 ) 108.5(2)°, N1-Ti1-N2 )
106.3(2)°] defined by two nitrogen atoms from two
amides, one chloride, and the oxygen atom. The nitro-
gen atoms have a slightly distorted trigonal planar
geometry [Ti1-N1-C1 ) 120.6(5)°, Ti1-N1-C7 )
123.5(4)°, C1-N1-C7 ) 115.7(5)°]. The short Ti-N
distances [Ti1-N1 ) 1.910(6) Å, Ti1-N2 ) 1.876(6) Å]
are as expected. The Ti-O distances are remarkably
short [Ti1-O1 ) 1.828(2) Å] while the Ti-O-Ti frame
is bent. The angle subtended at the oxygen atom [Ti1-
O1-Ti1a ) 154.9(4)°] is rather similar to that of other
µ-oxo-bridged titanium complexes.4d,5k
trum.
The crystal structure of 13 revealed the complex to
be monomeric (Figure 5). Even in this case the steric
bulk of the amide ligands is likely to be responsible for
the significant distortion of the tetrahedral coordination
geometry of the Tl atom [N1-Ti1-N2 ) 120.6(1)°, N1-
Ti1-C13 ) 108.4(2)°, N1-Ti1-C20 ) 108.1(2)°, C13-
Ti1-C20 ) 98.4(2)°]. The geometry of the two amide
nitrogen atoms slightly deviates from the regular trigo-
nal planar geometry [Ti1-N1-Si1 ) 124.8(2)°, Ti1-
N1-Si2 ) 117.5(2)°, Si1-N1-Si2 ) 117.5(2)°]. Con-
versely, the angles subtended at the benzylic carbon,
C13 and C20 [Ti1-C13-C14 ) 120.7(3)°, Ti1-C20-C21
) 119.2(3)°], deviate severely from the normal tetrahe-
dral angle. The Ti-N [Ti1-N1 ) 1.931(3) Å, Ti1-N2
) 1.939(3) Å] and Ti-C [Ti1-C13 ) 2.092(5) Å, Ti1-
C20 ) 2.109(4) Å] bond distances are slightly shorter
with respect to complex 12 as a probable result of the
smaller atomic radius of the Ti(IV) atom.
Attempts to alkylate complex 14 were successful only
in the case of MeLi. The reaction yielded the corre-
sponding dimethyl complex [(Cy2N)2TiMe]2(µ-O) (15),
which was characterized on the basis of analytical and
Complex 1 reacted with styrene oxide in toluene at
room temperature to form a new complex [(Cy2N)2TiCl]2-

Tri- and Tetravalent Titanium Alkyls
Organometallics, Vol. 15, No. 4, 1996 1121
which is slightly shifted with respect to that of the
starting material 14. Unfortunately, numerous at-
tempts to prepare X-ray-quality crystals remained
unsuccessful. However, chemical degradation experi-
ments with gaseous HCl carried out in a closed vessel
connected to a Toepler pump yielded the expected
amount of methane.
In conclusion, in this work we have shown that
anionic organic amides are versatile supporting ligands
for the stabilization of a full series of reactive Ti alkyl
derivatives. A broad study on the chemical reactivity
of these new species will be described elsewhere.
Ack n ow led gm en t. This work was supported by the
Natural Sciences and Engineering Research Council of
Canada (operating and strategic grants).
F igu r e 6. ORTEP plot of 14. Thermal ellipsoids are
drawn at the 50% probability level.
Su p p or tin g In for m a tion Ava ila ble: ORTEP drawings
and tables giving details on structure determinations, atomic
positional and thermal parameters, anisotropic thermal pa-
rameters, and bond distances and angles (123 pages). Order-
ing information is given on any current masthead page.
spectroscopic data. In addition to the resonances of the
cyclohexyl groups shifted to slightly higher field, a new
sharp singlet at 0.94 ppm corresponding to the methyl
1
group was observed in the H NMR spectrum. 13C{1H}
and HMQC spectra also confirmed the formulation. The
IR spectrum showed a Ti-O resonance at 771 cm-1
,
OM9508288