New titanium complexes containing an amidinate-imide supporting ligand set: Cyclopentadienyl, alkyl, borohydride, aryloxide, and amide derivatives

Article abstract of DOI:10.1021/om9802156

A range of chloride metathesis reactions of the monomeric titanium N,N′-bis(trimethylsilyl)-benzamidinato-imido complexes [Ti(NBu^t){(4-C₆H₄R)C(NSiMe₃) ₂}Cl(py)₂] (R = H (1) or OMe (2)) are described. Thus, reaction of 1 or 2 with LiC₅H₅ gave the half-sandwich compounds [Ti(NBu^t){(4-C₆H₄R)C(NSiMe₃) ₂}(η-C₅H₅)] (R = H (3) or OMe (4)). Reaction of 1 with LiCH₂-SiMe₃ or LiCH(SiMe₃)₂ gave the 14-electron, first fully characterized group 4 imido-alkyl derivatives [Ti(NBu^t){PhC(NSiMe₃)₂}{CH(R)SiMe ₃}(py)] (R = H (5) or SiMe₃ 6)). For comparative purposes, the 16-electron half-sandwich imido-alkyl complex [Ti(NBu^t)(η-C₅Me₅)(CH₂SiMe ₃)(py)] (7) was prepared from LiCH₂SiMe₃ and [Ti(NBu^t)(η-C₅Me₅)Cl(py)]. Reaction of 1 with LiBH₄ gave the η³-borohydride derivative [Ti(NBu^t){PhC(NSiMe₃)₂}(η ³-BH₄)(py)] (8) while treatment of 1 with LiN(SiMe₃)₂, LiO-2,6-C₆H₃R₂ (R = Me or Bu^t), or LiPhC(NSiMe₃)₂, gave the corresponding aryloxide, amide, or bis(benzamidinate) titanium imido complexes [Ti(NBu^t){PhC(NSiMe₃)₂}{N(SiMe ₃)₂}(py)] (9) [Ti(NBu^t){PhC(NSiMe₃)₂}-(O-2,6-C ₆H₃R₂)(py)] (R = Me (10) or Bu^t (11)), or [Ti(NBu^t){PhC(NSiMe₃)₂}₂(py)] (13). Activation parameters for the concerted, restricted rotation of the aryloxide and benzamidinate ligands in 11 are reported and point to a dissociatively activated mechanism. The X-ray structures of 5 and 7 have been determined.

Full text of DOI:10.1021/om9802156

Organometallics 1998, 17, 3271-3281
3271
New Tita n iu m Com p lexes Con ta in in g a n
Am id in a te-Im id e Su p p or tin g Liga n d Set:
Cyclop en ta d ien yl, Alk yl, Bor oh yd r id e, Ar yloxid e, a n d
Am id e Der iva tives
Peter J . Stewart, Alexander J . Blake, and Philip Mountford*
Department of Chemistry, University of Nottingham, Nottingham NG7 2RD, U.K.
Received March 23, 1998
A range of chloride metathesis reactions of the monomeric titanium N,N′-bis(trimethylsilyl)-
benzamidinato-imido complexes [Ti(NBut){(4-C6H4R)C(NSiMe3)2}Cl(py)2] (R ) H (1) or OMe
(2)) are described. Thus, reaction of 1 or 2 with LiC5H5 gave the half-sandwich compounds
[Ti(NBut){(4-C6H4R)C(NSiMe3)2}(η-C5H5)] (R ) H (3) or OMe (4)). Reaction of 1 with LiCH2-
SiMe3 or LiCH(SiMe3)2 gave the 14-electron, first fully characterized group 4 imido-alkyl
derivatives [Ti(NBut){PhC(NSiMe3)2}{CH(R)SiMe3}(py)] (R ) H (5) or SiMe3 (6)). For
comparative purposes, the 16-electron half-sandwich imido-alkyl complex [Ti(NBut)(η-
C5Me5)(CH2SiMe3)(py)] (7) was prepared from LiCH2SiMe3 and [Ti(NBut)(η-C5Me5)Cl(py)].
Reaction of 1 with LiBH4 gave the η3-borohydride derivative [Ti(NBut){PhC(NSiMe3)2}(η3-
BH4)(py)] (8), while treatment of 1 with LiN(SiMe3)2, LiO-2,6-C6H3R2 (R ) Me or But), or
LiPhC(NSiMe3)2 gave the corresponding aryloxide, amide, or bis(benzamidinate) titanium
imido complexes [Ti(NBut){PhC(NSiMe3)2}{N(SiMe3)2}(py)] (9), [Ti(NBut){PhC(NSiMe3)2}-
(O-2,6-C6H3R2)(py)] (R ) Me (10) or But (11)), or [Ti(NBut){PhC(NSiMe3)2}2(py)] (13).
Activation parameters for the concerted, restricted rotation of the aryloxide and benzamidi-
nate ligands in 11 are reported and point to a dissociatively activated mechanism. The
X-ray structures of 5 and 7 have been determined.
In tr od u ction
new N,N′-bis(trimethylsilyl)benzamidinate-supported
complexes [Ti(NR){PhC(NSiMe3)2}Cl(py)2] (R ) But (1),
2,6-C6H3Me2 and 2,6-C6H3Pri2).17 The overall trianionic,
seven-electron donor amidinate-terminal imide ligand
set in 1 and its homologues is a relatively unusual
combination in transition-metal chemistry and has not
been explored to any extent as a supporting ligand
environment for preparing new compounds.12,17-20 We
were particularly interested to explore its potential for
supporting new organometallic and related chemistry
of titanium which has, to a considerable extent, been
dominated by compounds with one or two cyclopenta-
dienyl co-ligands.21 Here, we report the synthesis,
solution dynamics, and structures of new cyclopentadi-
enyl, alkyl, borohydride, amide, and aryloxide titanium
complexes containing the amidinate-imide ligand set
and some related chemistry.22
The organoimido (NR, where R is typically an alkyl
or aryl)1-4 and amidinate (RC(NR′)2 where R is usually
H, alkyl or aryl and R′ is alkyl, aryl or trimethylsilyl)5-15
groups are important supporting ligands in transition
-metal chemistry. As part of an ongoing study of
titanium imido chemistry,16 we recently described the
* To whom correspondence should be addressed. Philip Mountford
is the Royal Society of Chemisty Sir Edward Frankland Fellow.
E-mail: Philip.Mountford@Nottingham.ac.uk. WWW: http://www.not-
tingham.ac.uk/∼pczwww/Inorganic/PMount.html.
(1) Nugent, W. A.; Haymore, B. L. Coord. Chem. Rev. 1980, 31, 123.
(2) Chisholm, M. H.; Rothwell, I. P. In Comprehensive Coordination
Chemistry; Wilkinson, G., Gillard, R. D., McCleverty, J . A., Eds.;
Pergamon Press: Oxford, 1987; Vol. 2, p 162.
(3) Nugent, W. A.; Mayer, J . M. Metal-Ligand Multiple Bonds;
Wiley-Interscience: New York, 1988.
(4) Wigley, D. E. Prog. Inorg. Chem. 1994, 42, 239.
(5) Edelmann, F. T. Coord. Chem. Rev. 1994, 137, 403.
(6) Barker, J .; Kilner, M. Coord. Chem. Rev. 1994, 133, 219.
(7) Go´mez, R.; Duchateau, R.; Chernega, A. N.; Meetsma, A.;
Edelmann, F. T.; Teuben, J . H.; Green, M. L. H. J . Chem. Soc., Dalton
Trans. 1995, 217.
(8) Duchateau, R.; van Wee, C. T.; Meetsma, A.; van Duijnen, P. T.;
Teuben, J . H. Organometallics 1996, 15, 2279.
(9) Duchateau, R.; van Wee, C. T.; Teuben, J . H. Organometallics
1996, 15, 2291.
(10) Hagadorn, J . R.; Arnold, J . J . Chem. Soc., Dalton Trans. 1997,
3087.
(16) Mountford, P. Chem. Commun. 1997, 2127 (Review Feature
Article). Wilson, P. J .; Blake, A. J .; Mountford, P.; Schro¨der, M. Chem.
Commun. 1998, 1007. Blake, A. J .; Dunn, S. C.; Green, J . C.; J ones,
N. M.; Moody, A. G.; Mountford, P. Chem. Commun. 1998, 1235.
(17) Stewart, P. J .; Blake, A. J .; Mountford, P. Inorg. Chem. 1997,
36, 3616.
(11) Hagadorn, J . R.; Arnold, J . Inorg. Chem. 1997, 36, 2928.
(12) Hagadorn, J . R.; Arnold, J . J . Am. Chem. Soc. 1996, 118, 893.
(13) Hao, S.; Feghali, K.; Gambarotta, S. Inorg. Chem. 1997, 36,
1745.
(14) Cotton, F. A.; Matonic, J . H.; Murillo, C. A. J . Am. Chem. Soc.
1997, 119, 7889.
(18) Ribeiro da Costa, M. H.; Avilez, M. T.; Teuben, J . H. Unpub-
lished results cited in ref 5.
(19) Stewart, P. J .; Blake, A. J .; Mountford, P. Inorg. Chem. 1997,
36, 1982.
(20) Dawson, D. Y.; Arnold, J . Organometallics 1997, 16, 1111.
(21) Bochmann, M. In Comprehensive Organometallic Chemistry II;
Abel, E. W., Stone, F. G. A., Wilkinson, G., Eds.; Elsevier: New York,
1995; Vol. 4, p 273.
(15) Cotton, F. A.; Daniels, L. M.; Murillo, C. A.; Wang, X. P. Inorg.
Chem. 1997, 36, 896.
S0276-7333(98)00215-5 CCC: $15.00 © 1998 American Chemical Society
Publication on Web 07/02/1998

3272 Organometallics, Vol. 17, No. 15, 1998
Stewart et al.
123.6 (meta-NC5H5), 112.5 (meta-C6H4), 67.7 (NCMe3), 55.0
(OMe), 31.0 (NCMe3), 2.6, 1.7 (2 × SiMe3). IR (CsBr plates,
Nujol): 1937 (w), 1886 (w), 1650 (w), 1606 (vs), 1574 (m), 1514
(s), a series of strong peaks from 1495 to 1350, 1291 (s), 1250
(vs), 1214 (s), 1205 (s), 1170 (s), 1154 (m), 1108 (m), 1070 (m),
1041 (s), 1013 (s), 980 (s), 843 (vs), 799 (m), 755 (s), 743 (s),
723 (s), 702 (s), 645 (s), 634 (s), 595 (w), 545 (m), 526 (m), 434
(w) cm-1. Anal. Found (calcd for C28H44ClN5OSi2Ti): C, 55.4
(55.5); H, 7.4 (7.3); N, 11.5 (11.6)
1H NMR data for 2′ (CDCl3, 300.1 MHz, 0 °C): 8.95 (d, J )
4.5 Hz, 2 H, ortho-NC5H5), 7.94 (t, J ) 7.4 Hz, 1 H, para-
NC5H5), 7.57 (apparent t, apparent J ) 6.3 Hz, 2 H, meta-
NC5H5), 7.16 (d, J ) 8.2 Hz, 2 H, C6H4), 6.89 (d, J ) 8.3 Hz,
2 H, C6H4), 3.85 (s, 3 H, OMe), 1.14 (s, 9 H, NBut), -0.24 (s,
18 H, SiMe3).
[Ti(NBu t){P h C(NSiMe3)2}(η-C5H5)] (3). An orange solu-
tion of LiC5H5 (0.035 g, 0.48 mmol) and [Ti(NBut){PhC-
(NSiMe3)2}Cl(py)2] (0.274 g, 0.48 mmol) in toluene (25 mL) at
room temperature became red upon stirring for 1 h and was
then stirred for a further 15 h before being filtered. Volatiles
were removed under reduced pressure to leave 3 as a red oil.
Recrystallization from pentane at -80 °C yielded red crystals
of 3, which were washed with pentane (2 × 5 mL) and dried
in vacuo. Yield: 0.145 g (68%).
1H NMR (CDCl3, 300.1 MHz, 25 °C): 7.38 (m, 3 H, ortho-
and para-C6H5), 7.24 (m, 2 H, meta-C6H5), 6.39 (s, 5 H, C5H5),
0.99 (s, 9 H, NBut), -0.16 (s, 18 H, SiMe3). 13C{1H} NMR
(CDCl3, 75.5 MHz, 25 °C): 169.0 (C6H5CN2), 139.5 (ipso-C6H5),
128.3, 127.9, 127.1 (ortho-, meta- and para-C6H5), 110.5 (C5H5),
67.0 (NCMe3), 32.2 (NCMe3), 1.7 (SiMe3). IR (KBr plates, Nujol
mull): 3098 (w), 3058 (w), 2919 (vs), 1951 (w), 1770 (w), 1662
(w), 1576 (w), 1540 (w), 1348 (m), 1246 (s), 1209 (w), 1176 (w),
1124 (w), 1073 (w), 1032 (w), 1006 (s), 996 (m), 921 (w), 843
(vs), 836 (vs), 806 (m), 793 (s), 777 (m), 763 (s), 712 (w), 700
(m), 688 (w), 618 (w), 603 (w), 592 (w), 546 (m), 523 (w), 507
(m), 478 (w) cm-1. Anal. Found (calcd for C22H37N3Si2Ti): C,
58.4 (59.0); H, 8.3 (8.3); N, 9.2 (9.4).
Exp er im en ta l Section
Gen er a l Meth od s a n d In str u m en ta tion . All manipula-
tions were carried out under an atmosphere of dinitrogen or
argon using standard Schlenk-line or drybox techniques. All
protio solvents and commercially available reagents were
predried over activated molecular sieves, refluxed over an
appropriate drying agent under an atmosphere of dinitrogen,
and collected by distillation. CDCl3 was dried over freshly
ground calcium hydride at room temperature, C6D6 was dried
over molten potassium, and C6D5CD3 was dried over molten
sodium. All NMR solvents were distilled under reduced
pressure and stored under N2 in a J . Young ampule. NMR
samples were prepared in the drybox in 5 mm Wilmad tubes
equipped with a Young’s Teflon valve.
1H, 13C, and 11B NMR spectra were recorded on a Bruker
DPX 300 spectrometer. 1H and 13C spectra were referenced
internally to residual protio solvent (1H) or solvent (13C)
resonances and are reported relative to tetramethylsilane (δ
) 0 ppm). The 11B spectrum was referenced externally to BF3
in ethanol (δ ) 0 ppm). Chemical shifts are quoted in δ (ppm)
and coupling constants in hertz. Assignments were supported
by DEPT-135 and DEPT-90, homo- and heteronuclear, one-
and two-dimensional experiments as appropriate. IR spectra
were recorded on a Nicolet 205 FTIR spectrometer in the range
4000-400 cm-1
. Samples were prepared in the drybox be-
tween KBr or CsBr plates as Nujol mulls or as thin films, and
data are quoted in wavenumbers (ν, cm-1). Elemental analy-
ses were carried out by the analysis laboratory of this depart-
ment.
Liter a tu r e P r ep a r a tion s. Li(4-C6H4R)C(NSiMe3)2 (R )
H or OMe),23,24 LiCH2SiMe3,25 LiCH(SiMe3)2,26 LiN(SiMe3)‚
OEt2,27 [Ti(NBut){PhC(NSiMe3)2}Cl(py)2] (1),17 [Ti(NBut)-
Cl2(py)3],28 [Ti(NBut)(η5-C5Me5)Cl(py)],29 and LiO-2,6-C6H3R2
(R ) Me or But)30 were prepared according to literature
methods. LiC5H5 was prepared from n-butyllithium and
freshly cracked C5H6 in cold hexanes.
[Ti(NBu t){(4-C6H4OMe)C(NSiMe3)2}Cl(p y)2] (2). A solu-
tion of Li(4-C6H4OMe)C(NSiMe3)2 (0.760 g, 2.53 mmol) in THF
(20 mL) was added over 10 min to a stirred solution of
[Ti(NBut)Cl2(py)3] (1.064 g, 2.53 mmol) in THF (20 mL) at -40
°C. The solution was allowed to warm to room temperature
and then stirred for 17 h. Volatiles were removed under
reduced pressure, and the resulting orange residue was
dissolved in dichloromethane and filtered. Evaporation of the
solvent and recrystallization from hexane yielded bright
orange crystals of 2, which were washed with pentane (2 ×
10 mL) and dried in vacuo. Yield: 0.74 g (54%).
Characterization data for 3. 1H NMR (CDCl3, 300.1 MHz,
-15 °C): 9.37 (d, J ) 5.0 Hz, 4 H, ortho-NC5H5), 7.89 (t, J )
7.6 Hz, 2 H, para-NC5H5), 7.48 (apparent t, apparent J ) 6.9
Hz, 4 H, meta-NC5H5), 6.75 (s, 4 H, ortho- and meta-C6H4),
3.79 (s, 3 H, OMe), 0.94 (s, 9 H, NBut), -0.17 (s, 9 H, SiMe3),
-0.48 (s, 9 H, SiMe3). 13C{1H} NMR (CDCl3, 75.5 MHz, -15
°C): 178.9 (C6H4CN2), 158.5 (ipso-C6H4), 151.0 (ortho-NC5H5),
137.9 (para-NC5H5), 135.4 (para-C6H4), 126.6 (ortho-C6H4),
[Ti(NBu t){(4-C6H4OMe)C(NSiMe3)2}(η-C5H5)] (4). A mix-
ture of LiC5H5 (0.007 g, 0.97 mmol) and [Ti(NBut){(4-C6H4-
OMe)C(NSiMe3)2}Cl(py)2] (0.059 g, 0.097 mmol) in toluene (15
mL) was heated at 90 °C under reduced pressure in a J . Young
ampule for 64 h to give a red solution. The cooled solution
was filtered, and volatiles were removed under reduced
pressure to leave 4 as a red oil, which could not be crystallized.
Yield: 0.043 g (95%).
1H NMR (CDCl3, 300.1 MHz, 298 K): 7.16 (d, J ) 8.7 Hz, 2
H, C6H4), 6.90 (d, J ) 8.7 Hz, 2 H, C6H4), 6.37 (s, 5 H, C5H5),
3.86 (s, 3 H, OMe), 0.98 (s, 9 H, NBut), -0.15 (s, 18 H, SiMe3).
13C{1H} NMR (CDCl3, 75.5 MHz, 298 K): 169.5 (C6H4CN2),
159.7 (ipso-C6H4), 132.0 (para-C6H4), 128.4 (ortho-C6H4), 113.3
(meta-C6H4), 110.5 (C5H5), 66.9 (NCMe3), 55.3 (OMe), 32.2
(NCMe3), 1.8 (SiMe3). IR (KBr plates, thin film): 2958 (s), 2895
(m), 2837 (w), 1609 (s), 1577 (w), 1515 (m), 1425 (vs), 1403 (s),
1350 (w), 1293 (m), 1248 (vs), 1209 (w), 1172 (s), 1122 (w),
1107 (w), 1037 (w), 1018 (s), 1001 (s), 936 (w), 840 (vs), 792
(s), 779 (s), 758 (s), 686 (w), 648 (s), 602 (w), 544 (w), 504 (w)
cm-1
. Satisfactory elemental analysis was not obtained for
(22) Although for ease of representation all terminal titanium-imido
bonds are drawn “TidNR”, the formal metal-ligand multiple bond
order in the complexes described herein is probably best thought of as
three (pseudo-σ2π4; triple bonds) rather than as two.4
(23) Wedler, M.; Kno¨sel, F.; Noltemeyer, M.; Edelmann, F. T.;
Behrens, U. J . Organomet. Chem. 1990, 388, 21.
(24) Boere´, R. T.; Oakley, R. T.; Reed, R. W. J . Organomet. Chem.
1987, 331, 161.
(25) Tessier-Youngs, C.; Beachley, O. T. Inorg. Synth. 1986, 24, 95.
(26) Davidson, P. J .; Harris, D. H.; Lappert, M. F. J . Chem. Soc.,
Dalton Trans. 1976, 2268.
(27) Wannagat, U.; Niederprum, H. Chem. Ber. 1961, 94, 1540.
(28) Blake, A. J .; Collier, P. E.; Dunn, S. C.; Li, W.-S.; Mountford,
P.; Shishkin, O. V. J . Chem. Soc., Dalton Trans. 1997, 1549.
(29) Dunn, S. C.; Mountford, P.; Robson, D. A. J . Chem. Soc., Dalton
Trans. 1997, 293.
(30) Collier, P. E.; Blake, A. J .; Mountford, P. J . Chem. Soc., Dalton
Trans. 1997, 2911.
this compound, which was an oil.
[Ti(NBu t){P h C(NSiMe3)2}(CH2SiMe3)(py)] (5). Cold ben-
zene (40 mL) was added to a mixture of [Ti(NBut){PhC-
(NSiMe3)2}Cl(py)2] (1.117 g, 1.94 mmol) and LiCH2SiMe3 (0.183
g, 1.94 mmol) at 10 °C. The resulting orange solution was
allowed to warm to room temperature and was then stirred
for 19 h. After filtration, volatiles were removed under reduced
pressure. The red-brown solid was dissolved in pentane and
cooled to -25 °C for 2 days to give 5 as orange crystals.
Yield: 0.268 g (25%).
1H NMR (C6D5CD3, 300.1 MHz, -50 °C): 8.58 (d, J ) 4.5
Hz, 2 H, ortho-NC5H5), 7.20 (br s, 2 H, ortho-C6H5), 6.95 (m, 3
H, meta- and para-C6H5), 6.58 (t, 3J ) 7.7 Hz, 1 H, para-
NC5H5), 6.35 (apparent t, apparent J ) 6.7 Hz, 2 H, meta-

New Titanium Complexes
Organometallics, Vol. 17, No. 15, 1998 3273
NC5H5), 1.52 (s, 9 H, NBut), 0.51 (d, 2J ) 11.4 Hz, 1 H,
585 (w), 536 (m), 519 (m), 488 (w) cm-1. Anal. Found (calcd
for C23H40N2SiTi): C, 65.7 (65.7); H, 9.8 (9.6); N, 6.7 (6.7).
NMR -Sca le H yd r ogen olysis of [Ti(NBu t ){P h C-
(NSiMe3)2}{CH(SiMe3)2}(p y)] (6). A solution of [Ti(NBut)-
{PhC(NSiMe3)2}{CH(SiMe3)2}(py)] (10.7 mg, 0.017 mmol) in
C6D6 (1.0 mL) was placed under 9.2 bar pressure of H2 gas in
a Fisher-Porter bottle at room temperature. After the orange-
brown solution was stirred for 16 h, it became a very pale
yellow. NMR analysis showed the formation of several
products including ButNH2, CH2(SiMe3)2, and pyridine.
[Ti(NBu t){P h C(NSiMe3)2}(η3-BH4)(p y)] (8). An orange
mixture of [Ti(NBut){PhC(NSiMe3)2}Cl(py)2] (0.334 g, 0.58
mmol) and an excess of LiBH4 (0.120 g, 5.51 mmol) in toluene
(30 mL) was stirred for 72 h at room temperature and then
filtered. Volatiles were removed under reduced pressure to
leave an orange-brown oil. Extraction into hexane (20 mL)
followed by cooling to -80 °C for 48 h afforded 8 as a yellow
solid, which was washed with pentane (2 × 5 mL) and dried
in vacuo. Yield: 0.170 g (62%).
2
CHaHbSiMe3), 0.30 (d, J ) 11.4 Hz, 1 H, CHaHbSiMe3), 0.25
(s, 9 H, CH2SiMe3), 0.22 and -0.47 [2 × br s, 2 × 9 H, 2 ×
PhC(NSiMe3)2]. 13C{1H} NMR (C6D5CD3, 75.5 MHz, -50 °C):
181.1 (C6H5CN2), 151.9 (ortho-NC5H5), 141.3 (ipso-C6H5), 138.3
(para-NC5H5), 128.4, 128.1, 127.2 (ortho-, meta-, and para-
1
C6H5), 124.3 (meta-NC5H5), 69.2 (NCMe3), 49.5 (d of d, J CH(a)
) 1J CH(b) ) 104 Hz, CH2SiMe3), 33.5 (NCMe3), 3.7 (CH2SiMe3),
2.7 [2 × PhC(NSiMe3)2]. Note: 1J for the δ 49.5 CH2SiMe3
resonance was obtained from
a
gated-coupled 13C NMR
spectrum of 5 in the same solvent and at the same tempera-
ture. IR (CsBr plates, Nujol mull): 1602 (w), 1501 (m), 1246
(s), 1214 (w), 1176 (w), 1071 (w), 1040 (w), 1030 (w), 1003 (m),
992 (m), 978 (m), 917 (m), 842 (vs), 784 (m), 761 (s), 722 (m),
700 (s), 645 (w), 605 (w), 502 (m), 441 (w), 420 (w) cm-1. Anal.
Found (calcd for C26H48N4Si3Ti): C, 55.9 (56.9); H, 9.0 (8.8);
N, 10.0 (10.2).
[Ti(NBu t ){P h C(NSiMe3)2}{CH(SiMe3)2}(p y)] (6). Cold
benzene (30 mL) was added to a mixture of [Ti(NBut){PhC-
(NSiMe3)2}Cl(py)2] (0.255 g, 0.44 mmol) and LiCH(SiMe3)2
(0.074 g, 0.44 mmol) at 10 °C. The resulting brown solution
was stirred for 3 h at 10 °C, and then volatiles were removed
under reduced pressure. Extraction with pentane (2 × 10 mL)
followed by filtration gave a brown solution. Cooling to -25
°C for 7 days gave 6 as brown crystals. Yield: 0.107 g (39%).
1H NMR (C6D5CD3, 300.1 MHz, -10 °C): 9.01 (br s, 2 H,
ortho-NC5H5), 7.30 (m, 2 H, ortho-C6H5), 6.95 (m, 3 H, meta-
and para-C6H5), 6.63 (t, J ) 7.8 Hz, 1 H, para-NC5H5), 6.45
(apparent t, apparent J ) 6.7 Hz, 2 H, meta-NC5H5), 1.46 (s,
9 H, NBut), 0.34 [s, 18 H, CH(SiMe3)2], 0.25 [s, 9 H, PhC-
(NSiMe3)(NSiMe3)], -0.24 [s, 1 H, CH(SiMe3)2], -0.49 [s, 9 H,
PhC(NSiMe3)(NSiMe3)]. 13C{1H} NMR (C6D5CD3, 75.5 MHz,
-10 °C): 181.2 (C6H5CN2), 152.6 (ortho-NC5H5), 141.1 (ipso-
C6H5), 138.8 (para-NC5H5), 124.2 (meta-NC5H5), 69.9 (NCMe3),
1H NMR (C6D5CD3, 300.1 MHz, 25 °C): 8.60 (d, J ) 4.5 Hz,
2 H, ortho-NC5H5), 7.20 (m, 2 H, meta-C6H5), 6.99 (m, 3 H,
ortho- and para-C6H5), 6.69 (t, 3J ) 7.3 Hz, 1 H, para-NC5H5),
6.43 (apparent t, apparent J ) 5.9 Hz, 2 H, meta-NC5H5), 1.53
1
(1:1:1:1 quart, J BH ) 86 Hz, 4 H, BH4), 1.33 (s, 9 H, NBut),
-0.08 (s, 18 H, NSiMe3). 13C{1H} NMR (C6D5CD3, 75.5 MHz,
-30 °C): 179.7 (C6H5CN2), 151.0 (ortho-NC5H5), 141.8 (ipso-
C6H5), 138.2 (para-NC5H5), 128.4 (para-C6H5), 128.0 (ortho-
C6H5), 127.0 (meta-C6H5), 124.1 (meta-NC5H5), 69.7 (NCMe3),
32.4 (NCMe3), 2.5 (2 × PhC(NSiMe3)2). 11B NMR (C6H6, 96.3
MHz, 25 °C): -10.7 (quint, 1J ) 86 Hz). IR (KBr plates, Nujol
mull): 2464 (s) ν(B-Hterminal), 2208 (m) and 2145 (m) ν(B-
H
bridging), 1605 (m), 1351 (m), 1247 (vs), 1214 (w), 1185 (m),
1156 (w), 1129 (w), 1090 (w), 1070 (w), 1042 (w), 1002 (s), 989
(vs), 922 (w), 841 (vs), 789 (m), 764 (s), 749 (s), 717 (m), 696
(s), 637 (w), 605 (w), 505 (m) cm-1. IR (hexane solution, KBr
cell, selected data): 2493 (m) ν(B-Hterminal), 2205 (m) and 2151
(w) ν(B-Hbridging) cm-1. Anal. Found (calcd for C22H41BN4Si2-
Ti): C, 54.7 (55.5); H, 8.9 (8.7); N, 11.7 (11.8).
[Ti(NBu t){P h C(NSiMe3)2}{N(SiMe3)2}(p y)] (9). A solu-
tion of LiN(SiMe3)2‚OEt2 (0.419 g, 1.81 mmol) in toluene (15
mL) was added over 5 min to a stirred solution of [Ti(NBut)-
{PhC(NSiMe3)2}Cl(py)2] (1.041 g, 1.81 mmol) in toluene (15
mL) at room temperature. The solution was stirred for 40 h
and then filtered. Volatiles were removed under reduced
pressure to leave 9 as an orange oil, which could not be
crystallized. Yield: 1.062 g (91%).
1H NMR (CDCl3, 300.1 MHz, -5 °C): 9.07 (br s, 2 H, ortho-
NC5H5), 7.90 (t of t, 3J ) 7.7 Hz, 4J ) 1.6 Hz, 1 H, para-NC5H5),
7.59 (overlapping m, 2 H, meta-NC5H5), 7.36 (m, 4 H, ortho-
and meta-C6H5), 7.15 (m, 1 H, para-C6H5), 1.18 (s, 9 H, NBut),
0.12 and 0.06 [2 × s, 2 × 9 H, N(SiMe3)2], -0.05 and -0.67 [2
× s, 2 × 9 H, PhC(NSiMe3)2]. 13C{1H} NMR (CDCl3, 75.5 MHz,
-5 °C): 180.0 (C6H5CN2), 152.7 (ortho-NC5H5), 141.5 (ipso-
C6H5), 138.5 (para-NC5H5), 128.0, 127.7, 127.6, 127.0 (ortho-
and meta-C6H5), 126.3 (para-C6H5), 124.0 (meta-NC5H5), 69.5
(NCMe3), 32.5 (NCMe3), 6.4 and 4.2 [N(SiMe3)2], 2.8 and 2.1
[PhC(NSiMe3)2]. Satisfactory elemental analysis was not
obtained for this compound, which was an oil.
[Ti(NBu t){P h C(NSiMe3)2}(O-2,6-C6H3Me2)(p y)] (10). A
mixture of [Ti(NBut){PhC(NSiMe3)2}Cl(py)2] (0.200 g, 0.35
mmol) and LiO-2,6-C6H3Me2 (0.044 g, 0.35 mmol) in toluene
(40 mL) was heated at 95 °C under reduced pressure in a J .
Young ampule for 18 h. The solution was filtered, volatiles
were removed under reduced pressure, and the orange residue
was dissolved in pentane. Cooling to -80 °C for 2 days gave
10 as an orange-brown solid, which was washed with cold
pentane (2 × 5 mL) and dried in vacuo. Yield: 0.112 g (55%).
1H NMR (CDCl3, 300.1 MHz, 25 °C): 8.88 (br m, 2 H, ortho-
NC5H5), 7.84 (t, J ) 7.6 Hz, 1 H, para-NC5H5), 7.43 (apparent
t, apparent J ) 7.3 Hz, 2 H, meta-NC5H5), 7.37 (m, 3 H, ortho-
and para-C6H5), 7.29 (m, 2 H, meta-C6H5), 6.90 (d, J ) 7.4 Hz,
1
52.9 [d, J CH ) 94 Hz, CH(SiMe3)2], 33.0 (NCMe3), 5.2
[CH(SiMe3)(SiMe3)], 4.4 [CH(SiMe3)(SiMe3)], 3.4 [PhC(NSiMe3)-
(NSiMe3)], 2.3 [PhC(NSiMe3)(NSiMe3)]. Note: 1J for the δ
52.9CH(SiMe3)2 resonance was obtained from a gated-coupled
13C NMR spectrum of 6 in the same solvent and at the same
temperature; the ortho-, meta- and para-C6H5 resonances were
obscured by solvent. IR (CsBr plates, Nujol mull): 1650 (w),
1604 (w), 1578 (w), 1303 (w), 1246 (s), 1213 (w), 1169 (w), 1070
(w), 1042 (w), 1031 (w), 1003 (m), 993 (m), 918 (w), 843 (vs),
785 (m), 762 (m), 723 (m), 701 (m), 662 (w), 636 (w), 603 (w),
504 (m), 442 (w), 429 (w), 411 (w) cm-1. Anal. Found (calcd
for C29H56N4Si4Ti): C, 54.6 (56.1); H, 9.0 (9.1); N, 8.9 (9.0).
[Ti(NBu t)(η-C5Me5)(CH2SiMe3)(p y)] (7). Cold benzene
(20 mL) was added to a mixture of [Ti(NBut)(η-C5Me5)Cl(py)]
(0.399 g, 1.08 mmol) and LiCH2SiMe3 (0.103 g, 1.09 mmol) at
5 °C. The resulting brown solution was allowed to warm to
room temperature and was then stirred for 17 h. After
filtration, volatiles were removed under reduced pressure. The
brown solid was dissolved in pentane and cooled to -80 °C
for 2 days to give 7 as orange-brown crystals. Yield: 0.182 g
(40%).
1H NMR (C6D6, 300.1 MHz, 25 °C): 8.14 (d, J ) 4.8 Hz, 2
H, ortho-NC5H5), 6.68 (t of t, 3J ) 7.7 Hz, 4J ) 1.6 Hz, 1 H,
para-NC5H5), 6.37 (apparent t, apparent J ) 7.0 Hz, 2 H, meta-
2
NC5H5), 1.94 (s, 15 H, C5Me5), 1.43 (s, 9 H, NBut), 0.54 (d, J
2
) 10.9 Hz, 1 H, CHaHbSiMe3), 0.37 (s, 9 H, SiMe3), 0.14 (d, J
) 10.9 Hz, 1 H, CHaHbSiMe3). 13C{1H} NMR (C6D6, 75.5 MHz,
25 °C): 150.5 (ortho-NC5H5), 137.9 (para-NC5H5), 123.8 (meta-
1
NC5H5), 117.1 (C5Me5), 66.9 (NCMe3), 42.4 (d of d, J CH(a)
)
1J CH(b) ) 106 Hz, CH2SiMe3), 33.6 (NCMe3), 12.1 (C5Me5), 4.3
(SiMe3). Note:1J for the δ 42.4 CH2SiMe3 resonance was
obtained from a gated-coupled 13C NMR spectrum of 7 in the
same solvent and at the same temperature. IR (KBr plates,
Nujol mull): 1928 (w), 1717 (w), 1653 (w), 1604 (m), 1483 (w),
1346 (m), 1234 (vs), 1204 (m), 1152 (w), 1111 (w), 1069 (w),
1043 (w), 1015 (w), 984 (w), 914 (m), 863 (s), 820 (m), 802 (w),
755 (m), 746 (w), 725 (m), 698 (s), 670 (w), 640 (w), 604 (w),

3274 Organometallics, Vol. 17, No. 15, 1998
Stewart et al.
Ta ble 1. X-r a y Da ta Collection a n d P r ocessin g P a r a m eter s for [Ti(NBu t){P h C(NSiMe3)2}(CH2SiMe3)(p y)]
(5) a n d [Ti(NBu t)(η-C5Me5)(CH2SiMe3)(p y)] (7)
complex
5
7
mol formula
fw
C
26H48N4Si3Ti
C23H40N2SiTi
420.57
548.86
temp/°C
cryst syst
space group
unit cell dimens
a/Å
-123(2)
triclinic
P1h (No. 2)
-123(2)
monoclinic
P21/n (No. 14)
10.741(3)
9.287(4)
b/Å
10.919(2)
28.019(8) Å
c/Å
16.318(2)
9.819(2)
R/deg
73.676(12)
80.68(2)
63.357(15)
1640.2(4)
90
â/deg
105.88(5)
90
2457.7(13)
γ/deg
vol/Å3
Z
2
1.11
0.38
592
4
1.14
0.40
912
density (calcd)/Mg m-3
abs coeff/mm-1
F(000)
cryst description
cryst size/mm
θ range for data collection/deg
scan type
index ranges
no. of reflns collected
no. of indep reflns
R(merge)
yellow block
orange cuboid
0.48 × 0.42 × 0.40
0.51 × 0.44 × 0.42
2.54-25.01
2.60-25.05
ω-θ with learnt profile
ω
-12 e h e 12, -12 e k e 12, -12 e l e 19
-11 e h e 11, -33 e k e 33, -11 e l e 11
5995
5517
0.043
4774
none
8276
4312
0.020
3530
no. of obsd reflns [I > 2σ(I)]
abs corr
integration
max and min transmission
decay correction/%
no. of data used in refinement
no. of restraints applied
no. of params refined
weighting scheme
ext coeff
0.868 and 0.797
random variation (7.8
4312
0
264
Chebychev polynomial
none
R1 ) 0.0419, wR2 ) 0.0473
R1 ) 0.0550, wR2 ) 0.0583
1.115 (on F2)
0.04
0.49 and -0.41
14.0
5505
0
322
Chebychev polynomial
43(7)
R1 ) 0.0576, wR2 ) 0.0628
R1 ) 0.0659, wR2 ) 0.0797
1.105 (on F2)
0.03
0.70 and -0.46
final R indicesa [I > 2σ(I)]
R indices (all data)
goodness-of-fit
final (∆/σ)max
largest residual peaks/e Å-3
a
2
R1 ) ∑||Fo| - |Fc||/∑|Fo|; wR2 ) x{∑w(Fo - Fc2)2/∑(w(Fo2)2}.
2 H, meta-O-2,6-C6H3Me2), 6.52 (t, J ) 7.4 Hz, 1 H, para-O-
2,6-C6H3Me2), 2.26 (s, 6 H, O-2,6-C6H3Me2), 1.17 (s, 9 H, NBut),
-0.30 (s, 18 H, SiMe3). 13C{1H} NMR (CDCl3, 75.5 MHz, 25
°C): 179.3 (C6H5CN2), 161.6 (ipso-O-2,6-C6H3Me2), 151.6 (ortho-
NC5H5), 141.5 (ipso-C6H5), 138.7 (para-NC5H5), 128.2, 127.8,
127.5 (ortho-, meta-, and para-C6H5), 126.9 (meta-O-2,6-C6H3-
Me2), 126.5 (ortho-O-2,6-C6H3Me2), 124.4 (meta-NC5H5), 116.5
(para-O-2,6-C6H3Me2), 68.8 (NCMe3), 32.7 (NCMe3), 17.5 (O-
2,6-C6H3Me2), 1.9 (SiMe3). IR (CsBr plates, Nujol mull): 1650
(w), 1603 (w), 1591 (w), 1504 (w), 1428 (s), 1401 (s), 1350 (w),
1303 (m), 1294 (m), 1261 (m), 1247 (s), 1235 (s), 1175 (w), 1128
(w), 1092 (m), 1070 (m), 1044 (m), 1030 (m), 1014 (m), 1003
(m), 993 (m), 916 (m), 892 (m), 840 (vs), 804 (m), 790 (m), 760
(s), 719 (m), 703 (m), 690 (m), 637 (w), 616 (w), 602 (w), 552
(w), 509 (s), 444 (w) cm-1. Anal. Found (calcd for C30H46N4-
OSi2Ti): C, 60.2 (61.8); H, 8.1 (8.0); N, 9.2 (9.6).
Me2), 1.55 and 1.28 (2 × br s, 2 × 9 H, 2 × O-2,6-C6H3But),
1.13 (s, 9 H, NBut), 0.05 and -0.63 (2 × br s, 2 × 9 H, 2 ×
SiMe3). 13C{1H} NMR (CDCl3, 75.5 MHz, 25 °C): 178.8
(C6H5CN2), 164.3 (ipso-O-2,6-C6H3But ), 152.1 (ortho-NC5H5),
2
141.4 (ipso-C6H5), 138.4 (para-NC5H5), 128.3, 127.8, 127.3
(ortho-, meta-, and para-C6H5), 125.0 (meta-O-2,6-C6H3But ),
2
123.8 (meta-NC5H5), 116.7 (para-O-2,6-C6H3But ), 70.1 (NC-
2
Me3), 35.3 [O-2,6-C6H3(CMe3)2], 32.2 (NCMe3), 31.8 [O-2,6-
C6H3(CMe3)2], 2.3 (SiMe3). Note: ortho resonances of the
O-2,6-C6H3But ligand were not observed. IR (CsBr plates,
2
Nujol mull): 3064 (w), 1734 (w), 1602 (w), 1578 (w), 1544 (w),
1444 (vs), 1429 (vs), 1407 (vs), 1351 (w), 1311 (w), 1272 (s),
1260 (s), 1246 (s), 1233 (vs), 1207 (m), 1171 (w), 1152 (w), 1123
(w), 1105 (w), 1070 (w), 1042 (w), 1031 (w), 1003 (m), 994 (s),
917 (w), 874 (s), 842 (vs), 795 (w), 784 (m), 764 (m), 750 (s),
728 (w), 700 (s), 666 (w), 634 (w), 593 (w), 568 (w), 548 (w),
506 (m), 490 (w), 460 (w), 444 (w), 428 (w), 412 (w) cm-1. Anal.
Found (calcd for C36H58N4OSi2Ti): C, 62.9 (64.8); H, 8.9 (8.8);
N, 7.3 (8.4).
[Ti(NBu t){P h C(NSiMe3)2}(O-2,6-C6H3Bu t2)(p y)] (11). A
mixture of [Ti(NBut){PhC(NSiMe3)2}Cl(py)2] (0.303 g, 0.53
mmol) and LiO-2,6-C6H3But (0.112 g, 0.53 mmol) in benzene
2
(40 mL) was heated at 80 °C under reduced pressure for 14 h.
The solution was allowed to cool and then filtered. The
volatiles were removed under reduced pressure to leave a
yellow-orange oil, which was redissolved in pentane and
filtered again. Cooling to -80 °C for 3 days gave yellow
crystals of 11. The mother liquor was decanted off, and the
crystals were dried in vacuo. Yield: 0.296 g (84%).
[Ti(NBu t ){(4-C6H 4OMe)C(NSiMe3)2}(O-2,6-C6H 3Me2)-
(p y)] (12). A mixture of [Ti(NBut){(4-C6H4Me)C(NSiMe3)2}-
Cl(py)2] (0.484 g, 0.80 mmol) and LiO-2,6-C6H3Me2 (0.102 g,
0.80 mmol) in toluene (25 mL) was heated at 100 °C under
reduced pressure in a J . Young ampule for 65 h. The solution
was allowed to cool, and the volatiles were removed under
reduced pressure. Extraction with CH2Cl2 and filtration gave
a red solution. Volatiles were removed under reduced pressure
to give 12 as a viscous red oil, which could not be crystallized.
Yield: 0.455 g (93%).
1H NMR (CDCl3, 300.1 MHz, 25 °C): 8.87 (br m, 2 H, ortho-
NC5H5), 7.79 (t, J ) 7.6 Hz, 1 H, para-NC5H5), 7.44 (br m, 4
H, C6H5), 7.34 (apparent t, apparent J ) 7.0 Hz, 2 H, meta-
NC5H5), 7.23 (d, J ) 7.8 Hz, 2 H, meta-O-2,6-C6H3Me2), 7.21
(br s, 1 H, C6H5), 6.69 (t, J ) 7.8 Hz, 1 H, para-O-2,6-C6H3-
1H NMR (CDCl3, 300.1 MHz, 25 °C): 8.87 (d, J ) 4.2 Hz, 2
H, ortho-NC5H5), 7.83 (t, J ) 7.3 Hz, 1 H, para-NC5H5), 7.41

New Titanium Complexes
Organometallics, Vol. 17, No. 15, 1998 3275
Ta ble 2. Selected Bon d Len gth s (Å) a n d An gles
(apparent t, apparent J ) 6.1 Hz, 2 H, meta-NC5H5), 7.21 (d,
J ) 7.3 Hz, 2 H, meta-O-2,6-C6H3Me2), 6.89 (m, 4 H, C6H4),
6.51 (t, J ) 7.3 Hz, 1 H, para-O-2,6-C6H3Me2), 3.85 (s, 3 H,
OMe), 2.25 (s, 6 H, O-2,6-C6H3Me2), 1.16 (s, 9 H, NBut), -0.28
(s, 18 H, SiMe3). 13C{1H} NMR (CDCl3, 75.5 MHz, 25 °C):
179.5 (C6H4CN2), 159.6 (ipso-O-2,6-C6H3Me2 or ipso-C6H4),
151.5 (ortho-NC5H5), 138.6 (para-NC5H5), 134.3 (para-C6H4),
128.2 (meta-O-2,6-C6H3Me2), 127.4 (ortho-C6H4), 126.5 (ortho-
O-2,6-C6H3Me2), 124.4 (meta-NC5H5), 116.4 (para-O-2,6-C6H3-
Me2), 113.1 (meta-C6H4), 68.7 (NCMe3), 55.2 (OMe), 32.7
(NCMe3), 17.5 (C6H3Me2), 1.9 (SiMe3). Note: one of the two
phenyl ring ipso carbons was not observed, or they are
coincident with each other. IR (KBr plates, Nujol mull): 1609
(w), 1292 (w), 1249 (s), 1234 (w), 1171 (w), 1089 (w), 1016 (m),
997 (m), 842 (vs), 799 (m), 761 (w), 722 (w), 647 (w) cm-1. Anal.
Found (calcd for C31H48N4O2Si2Ti): C, 57.8 (60.8); H, 7.7 (7.9);
N, 7.9 (9.1).
(d eg) for [Ti(NBu t){P h C(NSiMe3)2}(CH2SiMe3)(p y)]
(5)
Ti(1)-N(1)
Ti(1)-N(2)
Ti(1)-N(4)
Ti(1)‚‚‚H(11)
Ti(1)‚‚‚H(12)
1.690(2)
2.194(2)
2.217(2)
2.54(3)
N(1)-C(5)
Ti(1)-N(3)
Ti(1)-C(1)
C(1)-H(11)
C(1)-H(12)
1.460(3)
2.122(2)
2.187(3)
0.97(3)
2.38(4)
0.88(4)
N(1)-Ti(1)-N(2)
N(1)-Ti(1)-N(3)
N(2)-Ti(1)-N(3)
N(1)-Ti(1)-N(4)
N(3)-Ti(1)-N(4)
N(3)-Ti(1)-C(1)
Ti(1)-C(1)-H(11)
110.89(9) Ti(1)-N(1)-C(5)
106.18(9) N(1)-Ti(1)-C(1)
63.74(8) N(4)-Ti(1)-C(1)
168.0(2)
111.7(1)
89.8(1)
89.20(8)
136.7(1)
126.9(2)
91(3)
101.5(1)
N(2)-Ti(1)-N(4)
146.60(8) N(2)-Ti(1)-C(1)
96.9(1)
100(2)
Ti(1)-C(1)-Si(1)
Ti(1)-C(1)-H(12)
H(11)-C(1)-H(12) 107(3)
Ta ble 3. Selected Bon d Len gth s (Å) a n d An gles
[Ti(NBu t ){P h C(NSiMe3)2}2(p y)] (13). Toluene (30 mL)
was added to a mixture of [Ti(NBut){PhC(NSiMe3)2}Cl(py)2]
(0.120 g, 0.21 mmol) and LiPhC(NSiMe3)2 (0.056 g, 0.21 mmol),
and the resulting orange solution was heated at 90 °C under
reduced pressure in a J . Young ampule for 16 h. After the
solution was cooled, it was filtered and volatiles were removed
to give 13 as an orange oil. Crude yield: 0.142 g (94%).
Recrystallization from pentane failed to give a solid product.
Attempts at sublimation led to decomposition.
(d eg) for [Ti(NBu t)(η-C5Me5)(CH2SiMe3)(p y)] (7)a
Ti(1)-N(1)
Ti(1)-N(2)
Ti(1)-C(1)
C(1)-H(11)
Ti(1)-Cpcent
1.727(2)
2.202(2)
2.167(2)
0.86(3)
2.204
Ti(1)‚‚‚H(11)
Ti(1)‚‚‚H(12)
N(1)-C(5)
2.62(3)
2.63(3)
1.447(3)
0.99(3)
C(1)-H(12)
N(1)-Ti(1)-C(1)
N(2)-Ti(1)-C(1)
106.33(9) Ti(1)-C(1)-Si(1)
98.25(8) Ti(1)-C(1)-H(11)
123.8(1)
113(2)
107(2)
Cpcent-Ti(1)-N(1) 125.9
Cpcent-Ti(1)-N(2) 110.4
Ti(1)-C(1)-H(12)
1H NMR (CDCl3, 300.1 MHz, 25 °C): 9.36 (br s, 2 H, ortho-
NC5H5), 7.01 (t, J ) 7.6 Hz, 1 H, para-NC5H5), 7.46 (apparent
t, apparent J ) 6.2 Hz, 2 H, meta-NC5H5), 7.29 (br s, 5 H,
C6H5), 1.20 (s, 9 H, NBut), -0.14 (br s, 36 H, SiMe3). Satisfac-
tory elemental analysis was not obtained for this compound,
which was an oil.
Cpcent-Ti(1)-C(1) 114.5
a
Cpcent is the computed centroid for the ring containing atoms
C(9)-C(13).
Ad d ition a l Deta ils for [Ti(NBu t)(η-C5Me5)(CH2SiMe3)-
(p y)] (7). All H atoms were located from Fourier difference
syntheses. The positions and the isotropic displacement
parameters of the H atoms of the CH2 linkage of the (tri-
methylsilyl)methyl group were freely refined. Other H atoms
were refined in a riding model with equivalent isotropic
displacement parameters for each CH3 group and for the
pyridine H atoms.
NMR Kin etic An a lysis for [Ti(NBu t){P h C(NSiMe3)2}-
(O-2,6-C6H3Bu t2)(p y)] (11).35,36 1H NMR spectra of a solution
of 11 in CDCl3 were recorded between 268 and 283 K.
Lorentzian curve fitting of the tert-butyl and trimethylsilyl
group resonances afforded ν1/2(obs) (observed line widths at half-
height) values. Subtraction of the estimated natural line width
(obtained at the low-temperature limit) from ν1/2(obs) gave the
Cr ysta l Str u ctu r e Deter m in a tion s for [Ti(NBu t){P h C-
(NSiMe3)2}(CH2SiMe3)(p y)] (5) a n d [Ti(NBu t )(η-C5Me5)-
(CH2SiMe3)(p y)] (7). Gen er a l P r oced u r e. Crystal data
collection and processing parameters are given in Table 1.
Crystals were mounted in a film of RS3000 perfluoropolyether
oil (Hoechst) on a glass fiber and transferred to a Stoe¨ Stadi-4
four-circle diffractometer equipped with an Oxford Cryosys-
tems low-temperature device.31 Data were collected using Mo
KR radiation (λ ) 0.710 73 Å). For 7, an absorption correction
was applied to the data. Equivalent reflections were merged,
and the structures were solved by direct methods using
SIR92.32 Subsequent difference Fourier syntheses revealed the
positions of all other non-hydrogen atoms: these were refined
anisotropically against F2. Data for 5 were corrected for
extinction via an overall secondary extinction parameter;33 for
7, examination of the refined extinction parameter and an
agreement analysis suggested that no extinction correction was
required. All crystallographic calculations were performed
using SIR92 and CRYSTALS-PC.34 A full listing of atomic
coordinates, bond lengths and angles, and thermal parameters
have been deposited at the Cambridge Crystallographic Data
Centre. See Notice to Authors, Issue No. 1 of this J ournal.
Ad d it ion a l Det a ils for [Ti(NBu t ){P h C(NSiMe3)2}-
(CH2SiMe3)(p y)] (5). H atoms for the phenyl and pyridine
groups and for the CH2 of the (trimethylsilyl)methyl group
were located from difference maps. H atoms for the SiMe3 and
But groups were placed geometrically. The positions and the
isotropic displacement parameters of the H atoms of the
trimethylsilylmethyl CH2 group were freely refined, and other
H atoms were refined in a riding model with common isotropic
temperature factors for the phenyl, pyridine, tert-butyl, and
three trimethylsilyl groups of H atoms.
corrected excess line widths at half-height ν1/2(corr)
. At each
temperature, the NMR first-order rate constant kobs was
calculated according to kobs ) πν1/2(corr). Chemical exchange rate
35
constants (kexch) were calculated as 2kobs
.
The ν1/2(corr) values,
exchange rate constants, and activation parameters derived
from standard Eyring plots (provided as Supporting Informa-
tion) are listed in Table 4.
Resu lts a n d Discu ssion
Sta r tin g Com p lexes. The previously reported17
titanium tert-butyl imido compound [Ti(NBut){PhC-
(NSiMe3)2}Cl(py)2] (1 at center in Scheme 1) is readily
available in good yields by treatment of [Ti(NBut)Cl2-
(py)3]28 with LiPhC(NSiMe3)2.23,24 Since introduction of
a para-substituent into the benzene ring of the N,N′-
bis(trimethylsilyl)benzamidinate ligand can sometimes
aid crystallization of the complexes, we report here the
homologous complex [Ti(NBut){(4-C6H4OMe)C(NSiMe3)2}-
Cl(py)2] (2). Thus, addition of Li(4-C6H4OMe)C(NSiMe3)2
to a THF solution of [Ti(NBut)Cl2(py)3] gave the air- and
(31) Cosier, J .; Glazer, A. M. J . Appl. Crystallogr. 1986, 19, 105.
(32) Altomare, A.; Cascarano, G.; Giacovazzo, G.; Guagliardi, A.;
Burla, M. C.; Polidori, G.; Camalli, M. J . Appl. Crystallogr. 1994, 27,
435.
(33) Larson, A. C. Acta Crystallogr. 1967, 23, 664.
(34) Watkin, D. J .; Prout, C. K.; Carruthers, J . R.; Betteridge, P.
W. CRYSTALS Issue 10; Chemical Crystallography Laboratory, Uni-
versity of Oxford, 1996.
(35) Green, M. L. H.; Wong, L.-L.; Sella, A. Organometallics 1992,
11, 2660.

3276 Organometallics, Vol. 17, No. 15, 1998
Stewart et al.
Ta ble 4. Excess Lin e Wid th s, Exch a n ge Ra tea Con sta n ts, a n d Activa tion P a r a m eter s for
[Ti(NBu t){P h C(NSiMe3)2}(O-2,6-C6H3Bu t2)(p y)] (11)a
Excess Line Widths and Rate Constantsb
tert-butyl resonances
1/2(corr) (s-1 kexch (s-1
trimethylsilyl resonances
1/2(corr) (s-1 kexch (s-1
)
temp (K)
ν
)
)
ν
)
268
273
278
283
0.185
0.466
1.167
2.422
1.16
2.93
7.33
0.157
0.306
0.965
1.948
0.989
1.93
6.06
15.2
12.25
Activation Parameters
∆Hq (kJ mol-1
)
∆Sq (J mol-1‚K-1
)
∆Gq (kJ mol-1
)
278
But group exchange
SiMe3 group exchange
106 ( 12
107 ( 17
155 ( 31
155 ( 58
62.9 ( 2.4
62.9 ( 3.6
a
b
See the text and Experimental Section for further details. These are average (for the two different Butor SiMe3 groups) values for
ν
1/2(corr) and kexch, where ν1/2(corr) is the excess line width and kexch is the associated chemical exchange rate constant (see Experimental
Section for further details).
moisture-sensitive, red complex 2 in 54% yield after
recrystallization from hexane. Full characterization
data for 2 and all the new complexes described herein
are given in the Experimental Section and will not be
discussed if interpretation is straightforward.
The half-sandwich compounds 3 and 4 are proposed
to possess the 16-electron, monomeric structures il-
lustrated in Scheme 1. Although we have been unable
to obtain diffraction-quality crystals, we found that the
solution molecular weight of 3 in CH2Cl2 (using the
Signer vapor diffusion method37) was 395; this is 12%
lower than that expected for a monomer (447.6) but
consistent with this complex (and presumably therefore
4) adopting mononuclear, nonbridged structures in
solution.
The pyridine-free 16-electron compounds [Ti(NBut)-
{RC(NR′)2}(η-C5H5)] (3 and 4) may be compared with
the formally 20-electron bis(cyclopentadienyl) complexes
[Ti(η-C5H5)(η-C5R5)(NBut)(L)] (R ) H or Me, L ) py or
py-But)38 and the 18-electron cyclopentadienyl-indenyl
complex [Ti(η-C5H5)(η-C9H7)(NBut)(py)], all of which
exist as pyridine adducts.29 On the other hand, the
bis(pentamethylcyclopentadienyl) complexes [Ti(η-C5-
Me5)2(NAr)] do not contain coordinated pyridine.39 On
the basis of Brintzinger’s “coordination aperture” ap-
proach,40 Teuben has recently suggested that the steric
requirements of the N,N′-bis(trimethylsilyl)benzamidi-
nate ligand are similar to those of C5Me5 and greater
than those of C5H5.8 In the two systems that we have
studied (i.e., 3 and 4), the amidinate-cyclopentadienyl
set behaves as though it is sterically comparable to bis-
(pentamethylcyclopentadienyl).
The solution NMR behavior of 2 is analogous to that
reported previously for the complexes [Ti(NR){PhC-
(NSiMe3)2}Cl(py)2] (R ) But, 2,6-C6H3Me2, or 2,6-C6H3-
Pri ) in that it exists in a temperature-dependent
2
equilibrium with the corresponding mono(pyridine) ad-
duct [Ti(NBut){(4-C6H4OMe)C(NSiMe3)2}Cl(py)] (2′) as
illustrated in eq1. The structures of 2 and 2′ are
(1)
Alk yl Der iva tives. Syn th eses. Reaction of [Ti-
(NBut){PhC(NSiMe3)2}Cl(py)2] (1) with 1 equiv of the
lithiated bulky alkyls LiCH(R)SiMe3 (R ) H or SiMe3)
in cold benzene followed by recrystallization from pen-
tane afforded the orange-brown, highly air-sensitive 14-
electron alkyl derivatives [Ti(NBut){PhC(NSiMe3)2}-
{CH(R)SiMe3}(py)] (R ) H 5 or SiMe3 6) in ca. 30% yield
(Scheme 1). The crystals of 5 were suitable for X-
diffraction analysis (vide infra). Reaction of 1 with
Mg(CH2Ph)2, MeLi, or ZnMe2 in hexane or benzene gave
inseparable mixtures of products.
proposed by analogy with those reported before for the
non-para-substituted homologues. The complexes 1 and
2 are useful precursors to new organometallic and
coordination complexes of titanium as described below
and illustrated in Scheme 1.
Cyclop en ta d ien yl Der iva tives. The half-sandwich
complex [Ti(NBut){PhC(NSiMe3)2}(η-C5H5)] (3) was pre-
pared by a straightforward metathesis reaction between
[Ti(NBut){PhC(NSiMe3)2}Cl(py)2] (1) and LiC5H5 in
toluene (Scheme 1). Recrystallization from pentane
gave 3 in 68% yield. The para-methoxy-substituted
benzamidinate derivative [Ti(NBut){(4-C6H4OMe)C-
(NSiMe3)2}(η-C5H5)] (4) was synthesized from 2 and
LiC5H5 in toluene. Compound 4 is an oil, however, and
could not be crystallized.
For the purposes of comparison we also prepared the
new 16-electron, half-sandwich alkyl complex [Ti(N-
(36) Sandstro¨m, J . Dynamic NMR Spectroscopy; Academic Press:
London, 1992.
(37) Clark, E. P. Ind. Eng. Chem., Anal. Ed. 1941, 13, 820.
(38) For a discussion of the metal-ligand interactions and electron
counting problems in [Ti(η-C5H5)(η-C5R5)(NBut)(py)], see ref 29.
(39) Andersen, R. A.; Bergman, R. G. Personal communication.
(40) Hortmann, K.; Brintzinger, H. H. New J . Chem. 1992, 16, 51.

New Titanium Complexes
Organometallics, Vol. 17, No. 15, 1998 3277
Sch em e 1a
a
Reagents and conditions: (i) LiC5H5, toluene, room temperature (for 3) or 90 °C, 15-64 h, 68-95%; (ii) LiCH2SiMe3 or
LiCH(SiMe3)2, benzene, 10 °C then room temperature, 3-19 h, 25-29%; (iii) LiBH4 (9.5 equivs), toluene, room temperature, 72
h, 62%; (iv) LiN(SiMe3)2‚OEt2, toluene, room temperature, 40 h, 91%; (v) LiO-2,6-C6H3Me2 or LiO-2,6-C6H3But , benzene or toluene,
2
80-100 °C, 14-65 h, 55-93%; (vi) LiPhC(NSiMe3)2, toluene, 90 °C, 16 h, 94%.
But)(η-C5Me5)(CH2SiMe3)(py)] (7, see eq 2) from LiCH2-
SiMe3 and [Ti(NBut)(η-C5Me5)Cl(py)]29,41 in cold ben-
zene. Cooling a saturated pentane solution of 7 to
monomeric titanium imido alkyl complexes, namely
[Ti(NSiBut )(NHSiBut )(R)(THF)] (R ) Me or But (quite
3
3
thermally unstable)).42 σ-Bond hydrogenolysis of these
complexes afforded the transient hydride [Ti(NSiBut )-
3
(NHSiBut )(H)(THF)] and ultimately [Ti2(µ-NSiBut ) -
3
3 2
(NHSiBut ) ]. We were, therefore, interested in explor-
3 2
ing the reactions of our alkyl complexes toward H2.
However, an NMR-scale hydrogenolysis of [Ti(NBut)-
{PhC(NSiMe3)2}{CH(SiMe3)2}(py)] (6) in C6D6 gave
extensive reduction and several products including
ButNH2, CH2(SiMe3)2, and pyridine. These reactions
were therefore not pursued.
(2)
X-r a y Str u ctu r es of 5 a n d 7. Details of data
collection, processing, and structure solution are given
in Table 1 and the Experimental Section. To facilitate
H-atom location,43 X-ray data were collected at -123(2)
°C.
-80 °C for 48 h gave orange-brown, diffraction-quality
crystals in 40% yield. The modest crystallized yields
of 5-7 reflect the high solubility of these complexes in
hydrocarbon solvents. When crude reaction mixtures
were examined, or the reactions were carried out in
C6D6 in NMR tubes, the yields were effectively quan-
titative and no other organometallic products were
observed.
A
view of the molecular structure of [Ti-
(NBut){PhC(NSiMe3)2}(CH2SiMe3)(py)] (5) is shown in
Figure 1, and important bond lengths and angles are
listed in Table 2. Compound 5 has a five-coordinate
Complexes 5-7 are rare examples of group 4 terminal
imido alkyl derivatives and the first to be structurally
characterized.4 Wolczanski was the first to report
(42) Cummins, C. C.; Schaller, C. P.; Van Duyne, G. D.; Wolczanski,
P. T.; Chan, A. W. E.; Hoffmann, R. J . Am. Chem. Soc. 1991, 113, 2985.
(43) The location and refinement of H atoms in X-ray work is often
difficult because the peaks due to H atoms in Fourier difference maps
are typically of similar magnitude to the noise level.53 Low-temperature
data collection reduces thermal motion and can aid H atom treatment.
(41) Bai, Y.; Noltemeyer, M.; Roesky, H. W. Z. Naturforsch. 1991,
46b, 1357.

3278 Organometallics, Vol. 17, No. 15, 1998
Stewart et al.
pentamethylcyclopentadienyl ligand is thought of as
occupying a single coordination site, can be considered
to be four-coordinate. The Ti-alkyl carbon bond length
[Ti(1)-C(1) ) 2.167(2) Å] is slightly shorter than the
corresponding distance of 2.187(3) Å in 5. As for 5, the
methylene hydrogen atoms of the CH2SiMe3 ligand were
located from Fourier difference syntheses and were
positionally refined in an isotropic model; the Ti(1)‚‚‚
H(11) and Ti(1)‚‚‚H(12) distances of 2.62(3) and 2.63(3)
Å, respectively, are equivalent within estimated experi-
mental error.
1
Sp ectr oscop ic Ch a r a cter iza tion of 5-7. The H
and 13C NMR data for 5-7 (see Experimental Section)
are broadly consistent with the structures proposed in
Scheme 1 and eq 2 and the X-ray structure determina-
tions. Assignments were confirmed by homo- and
heteronuclear correlation and nOe experiments. We
shall mention only those NMR data pertinent to the
fluxional behavior and to probing any possible R-agostic
interactions in these electron-deficient alkyl complexes
(see also Discussion section below). In the IR spectra
of complexes 5-7 there were no low-frequency ν(C-H)
bands that could be indicative of agostic interactions.52
At room temperature, the SiMe3 groups of the ben-
zamidinate ligand in [Ti(NBut){PhC(NSiMe3)2}(CH2-
SiMe3)(py)] (5) appeared as a broad resonance in
toluene-d8 solution. At -50 °C, these appear as two
singlets and the chemically inequivalent methylene
hydrogen atoms of the (trimethylsilyl)methyl group give
rise to two mutually coupled, well-resolved doublets at
0.30 and 0.51 ppm with a geminal 2J coupling constant
of 11.4 Hz. The gated-decoupled 13C NMR spectrum at
this temperature shows an apparent triplet (formally a
doublet of doublets) at δ 49.5 ppm for the methylene
F igu r e 1. Displacement ellipsoid plot (30% probability)
of [Ti(NBut){PhC(NSiMe3)2}(CH2SiMe3)(py)] (5). Hydrogen
atoms except those of the methylene linkage of the CH2-
SiMe3 ligand are omitted.
titanium (4+) center which possesses a distorted square-
based pyramidal geometry, with the tert-butylimido
ligand in the apical position. The titanium-imido
nitrogen bond distance in 5 [Ti(1)-N(1) ) 1.690(2) Å]
lies in the middle of the range of values (ca. 1.67-1.73
Å) usually found for this linkage.44,45 The angle sub-
tended at the imido nitrogen atom [Ti(1)-N(1)-C(5)]
is 168.0(2)°, and so the NBut ligand is capable of being
a four-electron donor. The small benzamidinate ligand
bite angle [N(2)-Ti(1)-N(3) ) 63.74(8)°] is typical of
this ligand,5,6 although the Ti-N(amidinate) bond lengths
are similar [Ti(1)-N(2) ) 2.194(2) Å and Ti(1)-N(3) )
2.122(2) Å], the longer is trans to the (trimethylsilyl)-
methyl group, reflecting the stronger trans influence of
this ligand. The Ti(1)-C(1) distance of 2.187(3) Å is just
beyond the upper end of the range of Ti-C single bonds
using this silylated alkyl ligand [range from 2.051(4) to
2.179(2) Å for six previous examples].46-51 The R-hy-
drogen atoms of the methylene carbon were readily
located from Fourier difference maps and positionally
refined with individual isotropic displacement param-
eters. One of these hydrogen atoms has a significantly
shorter distance to titanium [Ti(1)‚‚‚H(12) ) 2.38(4) Å]
than the other [Ti(1)‚‚‚H(11) ) 2.54(3) Å]; the difference
[0.09(5) Å] between the C(1)-HR distances, however, is
not significant.
1
carbon with a J CH coupling constant of 104 Hz.
The alkyl methine carbon in 6 gave rise to a doublet
1
(δ 52.9 ppm) with a J CH coupling constant of 93 Hz at
-10 °C. For [Ti(NBut)(η5-C5Me5)(CH2SiMe3)(py)] (7),
the methylene hydrogens of the (trimethylsilyl)methyl
ligand appeared as two mutually coupled doublets at
0.14 and 0.54 ppm with a geminal coupling constant of
10.9 Hz; the methylene carbon appeared as an apparent
1
triplet at δ 42.4 ppm with a J CH coupling constant of
106 Hz.
Discu ssion of 5-7. Compounds 5-7 are rare ex-
amples of group 4 terminal imido-supported alkyl
complexes and the first in this class to be structurally
characterized. Transition-metal imido complexes with
alkyl ligands are well-established for the subsequent
triads.4 The compounds have formal 14- (5 or 6) or 16-
(7) valence electron counts for titanium, and this raises
the possibility of Ti-H-CR agostic52 interactions. Well-
established examples of R- and â-agostic alkyltitanium
compounds, namely [TiCl3Me(dmpe)] and [TiCl3Et-
(dmpe)] [dmpe ) 1,2-bis(dimethylphosphino)ethane],
respectively, were first reported by Green and co-
workers.53
Displacement ellipsoid plots of [Ti(NBut)(η-C5Me5)(CH2-
SiMe3)(py)] (7) are shown in Figure 2, and important
bond lengths and angles are listed in Table 3. Com-
pound 7 contains a titanium (4+) center which, if the
(44) Allen, F. H.; Kennard, O. Chem. Des. Automation News 1993,
8, 1, 31.
(45) Fletcher, D. A.; McMeeking, R. F.; Parkin, D. J . Chem. Inf.
Comput. Sci. 1996, 36, 746.
(46) Latesky, S. L.; McMullen, A. K.; Rothwell, I. P.; Huffmann, J .
C. J . Am. Chem. Soc. 1985, 107, 5931.
(47) Chamberlain, L. R.; Durfee, L. D.; Fanwick, P. E.; Kobriger,
L.; Latesky, S. L.; McMullen, A. K.; Rothwell, I. P.; Folting, K.;
Huffmann, J . C.; Streib, W. E.; Wang, R. J . Am. Chem. Soc. 1987, 109,
390.
(48) Chesnut, R. W.; Durfee, L. D.; Fanwick, P. E.; Rothwell, I. P.;
Folting, K.; Huffmann, J . C. Polyhedron 1987, 6, 2019.
(49) Eisch, J . J .; Caldwell, K. R.; Werner, S.; Kruger, C. Organo-
metallics 1991, 10, 3417.
(50) Gomez-Sal, P.; Mena, M.; Palacios, F.; Royo, P.; Serrano, R.;
Carreras, S. M. J . Organomet. Chem. 1989, 375, 59.
(51) Gomez, R.; Cuenca, T.; Royo, P.; Herrmann, W. A.; Herdtweck,
E. J . Organomet. Chem. 1990, 382, 103.
For 5, the 14-valence electron count for titanium and
the location of H(12) and Ti(1)‚‚‚H(12) distance of 2.38(4)
Å raises a priori the possibility of an R-agostic interac-
(52) Brookhart, M.; Green, M. L. H.; Wong, L.-L. Prog. Inorg. Chem.
1988, 36, 1.
(53) Dawoodi, Z.; Green, M. L. H.; Mtetwa, V. S. B.; Prout, K.;
Schultz, A. J .; Williams, J . M.; Koetzle, T. F. J . Chem. Soc., Dalton
Trans. 1986, 1629 and references therein.

New Titanium Complexes
Organometallics, Vol. 17, No. 15, 1998 3279
F igu r e 2. Two displacement ellipsoid plots (30% probability) of [Ti(NBut)(η-C5Me5)(CH2SiMe3)(py)] (7): (a) general view,
(b) view showing the location of the methylene hydrogen atoms with respect to the Ti(NBut)(η-C5Me5) equatorial plane.
Hydrogen atoms except those of the methylene linkage of the CH2SiMe3 ligand are omitted.
tion, since the Ti‚‚‚H distance in the R-agostic complex
[TiCl3Me(dmpe] was 2.447(3) Å as determined by neu-
tron diffraction at 20 K.53 The other two Ti‚‚‚HR
distances were 2.803(3) and 2.737(3) Å. Before consid-
eration of the NMR data, it will be helpful to discuss
the structure of [Ti(NBut)(η-C5Me5)(CH2SiMe3)(py)] (7,
Figure 2).
ene (in-place or dissociative55,56) such that each R-hy-
drogen spends half of its time in an agostic interaction,
this appears to be unlikely given the normal value for
1
the observed J CH in 5 and 7.
In summary, the structural and NMR data for 7
militate against an agostic interaction. For complexes
5 and 6, we suggest that neither has a strong agostic
interaction. This may mean that the apparently close
Ti‚‚‚H contact in the solid state for 5 is simply a
consequence of the inherent difficulty in accurately
locating H atoms with X-ray data or alternatively that
the agostic interaction is not sufficient to perturb the
1J CH coupling constant. In this context we note that the
authentic R-agostic interaction in [TiCl3Me(dmpe)] did
Like 5, compound 7 contains a CH2SiMe3 alkyl ligand
bound to an apparently electron-deficient titanium
center but in this case the X-ray structure does not
reveal a sufficiently close Ti‚‚‚H contact [Ti(1)‚‚‚H(11)
) 2.62(3), Ti(1)‚‚‚H(12) ) 2.63(3) Å] to suggest a
significant R-agostic interaction. Furthermore, the
C(1)-Ti(1)-N(2) angle of 98.25(8)° in 7 is very similar
to that in the 16-electron chloride precursor [Ti(NBut)(η-
C5Me5)Cl(py)] where the Cl-Ti-N(pyridine) angle is
97.3(1)°.41 This implies, therefore, that the C(1)-Ti(1)-
N(2) angle in 7 shows no tendency to open up to
accommodate an R-agostic interaction. We conclude
that there is no structural evidence for an R-agostic
interaction in 7.
1
not lead to any detectable lowering of the averaged J CH
coupling constant.53
η3-Bor oh yd r id e Der iva tive. Reaction of [Ti(NBut)-
{PhC(NSiMe3)2}Cl(py)2] (1) with an excess of LiBH4 in
toluene for 72 h gave, after standard workup, the yellow,
hexane-soluble borohydride complex [Ti(NBut){PhC-
(NSiMe3)2}(η3-BH4)(py)] (8) in 62% recrystallized yield.
1
The J CH coupling contants for the alkyl R-carbons in
5 (104 Hz), 6 (93 Hz), and 7 (106 Hz) are significantly
lower than those expected for normal C(sp3)-H bonds
(120-130 Hz) but do not necessarily imply R-agostic
(55) Green, M. L. H.; Sella, A.; Wong, L.-L. Organometallics 1992,
11, 2650.
(56) Green, M. L. H.; Wong, L.-L. J . Chem. Soc., Dalton Trans. 1989,
2133.
(57) J arid, A.; Lledos, A.; J ean, Y.; Volatron, F. Chem. Eur. J . 1995,
1, 436.
(58) Marks, T. J .; Kolb, J . R. Chem. Rev. 1977, 77, 263.
(59) Dick, D. G.; Duchateau, R.; Edema, J . J . H.; Gambarotta, S.
Inorg. Chem. 1993, 32, 1959.
1
interactions. These low J CH values are in fact most
likely due to the bulky, electropositive SiMe3 groups.
In the authentic R-agostic complex [Y(η-C5Me5)2{CH-
1
(SiMe3)2}], for example, the methine R-carbon J CH is
84.2 Hz, which is considerably lower than that of 6.54
The appearance of the methylene resonances as appar-
ent triplets in the 13C spectra of 5 and 7 (for which the
methylene hydrogens are chemically inequivalent) sug-
gests that the two 1J CH coupling constants are identical.
This in turn is consistent with neither R-hydrogen of
the methylene group being strongly agostic. Although
there could be a fast, dynamic “rocking” of the methyl-
(60) Unpublished results cited in ref 12.
(61) Wedler, M.; Kno¨sel, F.; Edelmann, F. T.; Behrens, U. Chem.
Ber. 1992, 125, 1313.
(62) Pyridine exchange via an equilibrium between 11 and 11‚py
would be analogous to the well-characterized equilibrium between [Ti-
(NR){PhC(NSiMe3)2}Cl(py)2] and [Ti(NR){PhC(NSiMe3)2}Cl(py)] + py
as described in ref 17.
(63) The temperature at which the two benzamidinate SiMe3 group
resonances decoalesce (and hence any implications for the associated
∆Gq for exchange) will depend on their frequency separation (δν) in
the slow-exchange limit.36 For 9 and 11, the slow-exchange 1H NMR
δν is 186 and 204 Hz, respectively. It was not possible to measure δν
for 10 or 12, but we feel that it is reasonable to assume that the values
will be comparable to those of 9 and 11.
(54) Bruno, J . W.; Smith, J . M.; Marks, T. J .; Fair, C. K.; Schultz,
A. J .; Williams, M. J . Am. Chem. Soc. 1986, 108, 40.

3280 Organometallics, Vol. 17, No. 15, 1998
Stewart et al.
To our knowledge, this is the first borohydride deriva-
tive of a group 4 imido complex.
pyridine adduct [Ti(NBut){PhC(NSiMe3)2}2(py)] (13) as
an orange oil. The pyridine-free compound [Ti(NBut)-
{PhC(NSiMe3)2}2] has been previously reported60 and
is not available via our route, which gives the pyridine
adduct only. The new compound 13 is extremely soluble
in hydrocarbon solvents and could not be crystallized;
attempts to sublime 13 under high vacuum led to
decomposition.
The 1H NMR spectrum of 8 at room temperature
revealed resonances for fluxional benzamidinate (i.e.,
the SiMe3 groups appear as a single sharp singlet), tert-
butylimido, and pyridine groups, along with a broad 1:1:
1:1 quartet (1J BH ) 86 Hz) at 1.53 ppm which integrated
1
as four H atoms; this was assigned as a highly fluxional
BH4 ligand. These data do not distinguish between
possible borohydride (i.e., η1-, η2-, or η3-) ground-state
coordination modes. Cooling the sample to -70 °C did
not affect the borohydride or benzamidinate SiMe3
resonances. The 11B NMR spectrum at room temper-
Complexes 9-13 are fluxional in solution on the NMR
time scale. The NMR spectra for all four compounds
show the expected resonances for pyridine, But, and
1
benzamidinate phenyl groups. The H NMR spectrum
of 9 at room temperature contains additional broad
resonances in the SiMe3 region, indicating fluxionality
of the amide and benzamidinate ligands. Cooling a
CDCl3 sample of 9 to -5 °C froze out these processes,
and the spectra showed four separate resonances as-
signable to the two inequivalent SiMe3 groups of the
benzamidinate ligand and to the two inequivalent SiMe3
groups of the bis(trimethylsilyl)amide ligand.
1
ature is a binomial quintet at -10.73 ppm with a J BH
coupling of 86 Hz. This is consistent with the fast
exchange of bridging and terminal BH4 hydrogen atoms
proposed to account for the 1H NMR spectrum. The
rapid exchange of bridging and terminal hydrogen
atoms in such complexes is normal due to the small
energy differences between bonding modes for the BH4
ligand.57 Although we were unable to obtain diffraction-
quality crystals of 8, the coordination mode of the BH4
ligand could be elucidated from IR data.
The ortho-substituted aryloxide derivatives 9-12 are
also fluxional. At room temperature, the NMR spectra
of 10 and 12 showed one resonance for the chemically
inequivalent benzamidinate SiMe3 groups and one
resonance for the ortho-methyl groups, consistent with
fluxional behavior of the two types of ligand on the NMR
time scale. Cooling a CDCl3 sample of 10 caused the
signal for SiMe3 to broaden substantially but not to
decoalesce; likewise, only one relatively sharp ortho-
methyl group singlet was observed at low temperature.
For the considerably more sterically crowded complex
11, the room-temperature NMR spectra show four broad
resonances for the two benzamidinate SiMe3 and two
phenoxide ortho-tert-butyl groups and the exchange
processes are completely frozen out at ca. -10 °C. We
have studied the dynamic behavior of 11 by variable-
temperature 1H NMR line shape analysis for the
exchanging SiMe3 and ortho-But resonances. Further
details are provided in the Experimental Section; excess
line widths, rate constants, and activation parameters
(derived from standard Eyring plots provided in the
Supporting Information) for SiMe3 and ortho-But ex-
change are listed in Table 4.
Infrared spectroscopy can be useful in inferring the
coordination mode of the BH4 ligand.58 In the solid state
(Nujol mull), 8 gave rise to three IR bands in the B-H
stretching region, namely a strong absorption at 2464
cm-1 assigned to ν(B-Hterminal) and two weaker bands
at 2208 and 2145 cm-1 assigned to ν(B-Hbridging). The
other ligands present in 8 do not give strong absorptions
in this region. The solution infrared spectrum in hexane
showed a ν(B-Hterminal) absorption at 2493 cm-1 and two
ν(B-Hbridging) absorptions at 2205 and 2151 cm-1
,
confirming that the coordination mode. The shift in the
position of the ν(B-Hterminal) absorption in solution is
presumably due to matrix effects. This pattern of
absorptions indicates a tridentate coordination mode;58
the three bands may be designated as A1 (terminal) and
A1 and E (bridging), respectively, if local C3v symmetry
for the Ti(µ-Η)3BH moiety is assumed. A bidentate
tetrahydroborate ligand should give rise to two strong
ν(B-Hterminal) absorptions, as in the bis(N,N′-bis(tri-
methylsilyl)benzamidinato) titanium (+3) tetrahydrobo-
rate complex, [Ti{PhC(NSiMe3)2}2(η2-BH4)].59
The striking similarity of the two sets of ∆Hq, ∆Sq,
q
Am id e, Ar yloxid e, a n d Bis(N,N′-bis(tr im eth ylsi-
lyl)ben za m id in a te) Der iva tives. Reaction of 1 equiv
of LiN(SiMe3)2‚Et2O with [Ti(NBut){PhC(NSiMe3)2}Cl-
(py)2] (1) in toluene at room temperature afforded the
amido complex [Ti(NBut){PhC(NSiMe3)2}{N(SiMe3)2}-
(py)] (9) as an orange oil (Scheme 1), which could not
be crystallized. The use of the less bulky LiNMe2 led
to a mixture of products. Reaction of 1 equiv of LiO-
2,6-C6H3Me2 with 1 in toluene at 90 °C followed by
recrystallization from pentane at -80 °C afforded the
aryloxide complex [Ti(NBut){PhC(NSiMe3)2}(O-2,6-C6H3-
Me2)(py)] (10) as an orange-brown solid in 55% yield.
Analogous procedures gave [Ti(NBut){PhC(NSiMe3)2}(O-
and ∆G278 activation parameters in Table 4 suggest
that SiMe3 group exchange and But group exchange are
concerted processes and share a common transition
state. The ∆G278 values of ca. 63 kJ mol-1 are within
q
the range found previously for SiMe3 exchange in
fluxional benzamidinate complexes.8,61 The line widths
of the SiMe3 and But resonances were unaffected by
addition of ca. 1.5 equiv of free pyridine to a CDCl3
sample of 11 at room temperature (although a slight
broadening of the coordinated pyridine resonances was
observed, possibly due a separate associative exchange
process for the pyridine molecules62). It is, therefore,
likely that the SiMe3 and But exchange process does not
involve loss of pyridine in the rate-determining step.
2,6-C6H3But )(py)] (11) as a yellow solid in 84% yield.
2
The para-methoxy-substituted benzamidinate deriva-
tive [Ti(NBut){(4-C6H4OMe)C(NSiMe3)2}(O-2,6-C6H3-
Me2)(py)] (12) was also synthesized.
Reaction of 1 equiv of LiPhC(NSiMe3)2 with [Ti(NBut)-
{PhC(NSiMe3)2}Cl(py)2] (1) in toluene at 90 °C followed
by filtration and removal of volatiles afforded the
Simple aryl ring rotation about the O-Cipso bond axis
provides an adequate mechanism for the tert-butyl
group exchange in 15. For the SiMe3 group exchange,
at least two mechanisms are possible. These include
either a process involving in-place rotation of the
benzamidinate ligand about the Ti‚‚‚C(N2) axis8 or one

New Titanium Complexes
Organometallics, Vol. 17, No. 15, 1998 3281
in which a nitrogen atom of the benzamidinate ligand
dissociates (partially or entirely) to facilitate exchange,
as proposed previously by Edelmann.61 The latter
(dissociatively activated) possibility is better supported
by the large positive values of ∆Sq and would also be
consistent with the large value for ∆Hq, as such a
process would involve bond-breaking in the transition
state.
In conclusion, it appears that the correlated SiMe3
and But group exchange processes in 11 involve some
degree of Ti-N(benzamidinate) bond cleavage to give a
four-coordinate intermediate or transition state by
which exchange occurs. In the absence of activation
parameter data, it is not possible to identify the type of
process involved in exchanging the benzamidinate
ligand SiMe3 groups in 9, 10, or 12. However, it is likely
that the readily frozen out exchange in the bis(trimeth-
ylsilyl)amido complex 9 also involves some degree of Ti-
N(benzamidinate) bond cleavage.63 In 10 and 12, the
SiMe3 group exchange activation energy appears to be
much lower63 so a mechanism involving in-place ben-
zamidinate ligand rotation about the Ti‚‚‚C(N2) axis
may be the more probable and the SiMe3 and aryloxide
ortho-Me group exchange processes may or may not be
correlated.
pentadienyl, alkyl, borohydride, amide, and aryloxide
derivatives. There was no evidence for competing redox
chemistry or amidinate or imide ligand-centered reac-
tions (such as have been found in certain Schiff-base-
supported titanium alkyl complexes64). Neither the 14-
electron [Ti(NBut){PhC(NSiMe3)2}{CH(R)SiMe3}(py)] (R
) H or SiMe3) nor the 16-electron [Ti(NBut)(η-C5-
Me5){CH2SiMe3}(py)] show conclusive evidence for an
R-agostic C-H-Ti interaction. The fluxional processes
in the amide and aryloxide have been examined and
suggest that two types of mechanism (dissociative and
nondissociative) may be possible depending on the steric
constraints.
Ack n ow led gm en t. This work was supported by
grants (to P.M.) from the EPSRC, Leverhulme Trust
and Royal Society. We thank the EPSRC for a student-
ship (to P.J .S.) and the provision of an X-ray diffracto-
meter. We are also very grateful to Dr. W.-S. Li for help
with the X-ray data acquisition. We acknowledge the
use of the EPSRC Chemical Database Service at Dares-
bury Laboratory.
Su p p or tin g In for m a tion Ava ila ble: Eyring plots for 11
(2 pages). X-ray crystallographic files, in CIF format, for 5
and 7 are available on the Internet only. Ordering and access
information is given on any current masthead page.
Su m m a r y a n d Con clu sion s
OM9802156
We have shown that the unusual amidinate-imide
ligand set can support a range of titanium substitution
chemistry leading to new complexes, including cyclo-
(64) Solari, E.; Floriani, C.; Chiesi-Villa, A.; Rizzoli, C. J . Chem. Soc.,
Dalton Trans. 1992, 367.