Synthetic, reactivity, and structural studies on borylcyclopentadienyl complexes of titanium: New CpB titanocene complexes with C-B-Cl, C-B-O, and C-B-N bridges (CpB = η5-C5H4B(C6F5) 2)

Article abstract of DOI:10.1021/om9909744

The (borylcyclopentadienyl)titanium complex (Cp^B)TiCl₃ (1; Cp^B = η⁵-C₅H₄B(C₆F₅) ₂) reacts with LiC₅H₅ (LiCp), LiC₅H₄SiMe₃ (LiCp′), and LiC₉H₇ (LiInd) to give the titanocene complexes (Cp^B)CpTiCl₂ (2), (Cp^B)Cp′TiCl₂ (3), and (Cp^B)(Ind)TiCl₂ (4), respectively. In contrast to 1, which possesses piano stool geometry with an uncoordinated, trigonal-planar boryl moiety, the -B(C₆F₅)₂ substituents in 2-4 act as intramolecular Lewis acids by coordinating to chloride ligands, with formation of B-Cl-Ti bridges that have relatively short B-Cl and elongated Ti-Cl bonds. The compounds are fluxional, with the -B(C₆F₅)₂ moiety switching rapidly from one chloride ligand to the other (2: ΔG? = 37 kJ mol^-1 (200 K)). Recrystallization of 2 in the presence of traces of moisture afforded (Cp^B)CpTi(μ-OH)Cl (5), with a rigid B-O-Ti chelate arrangement. Treatment of 1 with 1 or 2 equiv of LiHNCMe₃ gives the binuclear titanium imido complexes [(Cp^B)TiCl(μ-NCMe₃)]₂ (7) and [(Cp^B)TiCl(μ-NCMe₃)·H₂NCMe ₃]₂ (8), respectively. These complexes are based on Ti₂N₂ rings but show no boron-imide interactions. In contrast, the reaction of 2 with LiNHCMe₃ affords (Cp_B)CpTi(μ-NHCMe₃)Cl (9), which exhibits a constrained-geometry type Cp-B-N arrangement. The crystal structures of 4, 5, 8, and 9 have been determined.

Full text of DOI:10.1021/om9909744

Organometallics 2000, 19, 1599-1608
1599
Syn th etic, Rea ctivity, a n d Str u ctu r a l Stu d ies on
Bor ylcyclop en ta d ien yl Com p lexes of Tita n iu m : New Cp B
Tita n ocen e Com p lexes w ith C-B-Cl, C-B-O, a n d
C-B-N Br id ges (Cp B ) η5-C5H4B(C6F 5)2)
Simon J . Lancaster, Sarah Al-Benna, Mark Thornton-Pett, and
Manfred Bochmann*
School of Chemistry, University of Leeds, Leeds, U.K. LS2 9J T
Received December 8, 1999
The (borylcyclopentadienyl)titanium complex (CpB)TiCl3 (1; CpB ) η5-C5H4B(C6F5)2) reacts
with LiC5H5 (LiCp), LiC5H4SiMe3 (LiCp′), and LiC9H7 (LiInd) to give the titanocene complexes
(CpB)CpTiCl2 (2), (CpB)Cp′TiCl2 (3), and (CpB)(Ind)TiCl2 (4), respectively. In contrast to 1,
which possesses piano stool geometry with an uncoordinated, trigonal-planar boryl moiety,
the -B(C6F5)2 substituents in 2-4 act as intramolecular Lewis acids by coordinating to
chloride ligands, with formation of B-Cl-Ti bridges that have relatively short B-Cl and
elongated Ti-Cl bonds. The compounds are fluxional, with the -B(C6F5)2 moiety switching
rapidly from one chloride ligand to the other (2: ∆Gq ) 37 kJ mol-1 (200 K)). Recrystallization
of 2 in the presence of traces of moisture afforded (CpB)CpTi(µ-OH)Cl (5), with a rigid B-O-
Ti chelate arrangement. Treatment of 1 with 1 or 2 equiv of LiHNCMe3 gives the binuclear
titanium imido complexes [(CpB)TiCl(µ-NCMe3)]2 (7) and [(CpB)TiCl(µ-NCMe3)‚H2NCMe3]2
(8), respectively. These complexes are based on Ti2N2 rings but show no boron-imide
interactions. In contrast, the reaction of 2 with LiNHCMe3 affords (CpB)CpTi(µ-NHCMe3)Cl
(9), which exhibits a constrained-geometry type Cp-B-N arrangement. The crystal
structures of 4, 5, 8, and 9 have been determined.
In tr od u ction
made by Piers et al. by the hydroboration of allyl-Cp
complexes with HB(C6F5)2.6 A number of boron-bridged
ansa-titanocenes and -zirconocenes are also known.7 As
well as neutral boryl substituents on the cyclopentadi-
enyl ring, there have also been examples of anionic
borato-substituted complexes, formed either through the
electrophilic substitution reaction of a metallocene
complex8 or introduced as a borato-substituted cyclo-
pentadienyl ligand.9
Complexes with boron-substituted cyclopentadienyl
ligands have attracted much attention recently. Whereas
boryl-Cp complexes of 18-electron metallocenes are
accessible by direct borylation of cyclopentadienyl ligands
with BX3 (X ) Cl, Br, I), RBI2, or B2Cl4,1 this method is
not applicable to group 4 metallocenes.2 The first
examples of boryl-Cp titanium complexes were reported
in 1979 by J utzi and Seufert, who prepared the series
of half-sandwich compounds (C5H3RBX2)TiCl3 (R ) H,
Me; X ) Cl, Br, OEt, Me) by the dehalosilylation of
C5H3R(BX2)SiMe3,3 and more recently by Shapiro and
co-workers.4 Reetz et al. described a series of borylated
zirconocenes of the types (R2BC5H4)2ZrCl2 and (R2-
BC5H4)(C5H5)ZrCl2 (R ) Me, Et, OEt, C6F5).5 Related
complexes with pendant -(CH2)3B(C6F5)2 moieties were
We recently described the synthesis of ((pentafluo-
rophenyl)boryl)cyclopentadienyl half-sandwich com-
(6) (a) Spence, R. E. v. H.; Piers, W. E. Organometallics 1995, 14,
4617. (b) Piers, W. E.; Sun, Y.; Lee, L. W. M. Top. Catal. 1999, 7, 133
and references therein.
(7) (a) Rufanov, K. A.; Kotov, V. V.; Kazennova, N. B.; Lemenovskii,
D. A.; Avtomonov, E. V.; Lorberth, J . J . Organomet. Chem. 1996, 525,
287. (b) Rufanov, K. A.; Avtomonov, E. V.; Kazennova, N. B.; Kotov,
V. V.; Khvorost, A.; Lemenovskii, D. A.; Lorberth, J . J . Organomet.
Chem. 1997, 536-537, 361. (c) Stelck, D. S.; Shapiro, P. J .; Basickes,
N.; Rheingold, A. L. Organometallics 1997, 16, 4546. (d) Braunschweig,
H.; Dirk, R.; Mu¨ller, M.; Nguyen, P.; Resendes, R.; Gates, D. P.;
Manners, I. Angew. Chem., Int. Ed. Engl. 1997, 36, 2338. (e) Braun-
schweig, H.; von Koblinski, C.; Wang, R. Eur. J . Inorg. Chem. 1999,
69. (f) Ashe, A. J .; Fang, X.; Kampf, J . W. Organometallics 1999, 18,
2288. (g) Reetz, M. T.; Wiluhn, M.; Psiorz, C.; Goddard, R. J . Chem.
Soc., Chem. Commun. 1999, 1105.
(1) (a) McVey, S.; Morrison, I. G.; Pauson, P. L. J . Chem. Soc. C
1967, 1847. (b) Kotz, J . C.; Post, E. W. J . Am. Chem. Soc. 1968, 4503.
(c) Kotz, J . C.; Post, E. W. Inorg. Chem. 1970, 9, 1661. (d) Ruf, W.;
Fuller, M.; Siebert, W. J . Organomet. Chem. 1974, 64, C45. (e) Renk,
T.; Ruf, W.; Siebert, W. J . Organomet. Chem. 1976, 120, 1. (f)
Wrackmeyer, B.; Do¨rfler, V.; Herberhold, M. Z. Naturforsch., B. 1993,
48, 121. (g) Appel, A.; No¨th, H.; Schmidt, M. Chem. Ber. 1995, 128,
621. (h) J a¨ckle, F.; Priermeier, T.; Wagner, M. J . Chem. Soc., Chem.
Commun. 1995, 1765. (i) Appel, A.; J a¨ckle, F.; Priermeier, T.; Schmid,
R.; Wagner, M. Organometallics 1996, 15, 1188. (j) J a¨ckle, F.; Prier-
meier, T.; Wagner, M. Organometallics 1996, 15, 2033. (k) Hartwig,
J . F.; He, X. Organometallics 1996, 15, 5350.
(2) Deck, P. A.; Fisher, T. S.; Downey, J . S. Organometallics 1997,
16, 1193.
(3) J utzi, P.; Seufert, A. J . Organomet. Chem. 1979, 169, 373.
(4) Larkin, S. A.; Golden, J . T.; Shapiro, P. J .; Yap, G. P. A.; Foo, D.
M. J .; Rheingold, A. L. Organometallics 1996, 15, 2393.
(5) Reetz, M. T.; Bru¨mmer, H.; Kessler, M.; Kuhnigk, J . Chimia
1995, 49, 501.
(8) (a) Burlitch, J . M.; Burk, J . H.; Leonowicz, M. E.; Hughes, R. E.
Inorg. Chem. 1979, 18, 1702. (b) Braunschweig, H.; Wagner, T. Chem.
Ber. 1994, 127, 1613. (c) Bohra, R.; Hitchcock, P. B.; Lappert, M. F.;
Au-Yeung, S. F.; Leung, W. P. J . Chem. Soc., Dalton Trans. 1995, 2999.
(d) Ruwwe, J .; Erker, G.; Fro¨hlich, R. Angew. Chem., Int. Ed. Engl.
1996, 35, 80. (e) Sun, Y.; Spence, R. E. v. H.; Piers, W. E.; Parvez, M.;
Yap, G. P. A. J . Am. Chem. Soc. 1997, 119, 5132. (f) Song, X.;
Bochmann, M. J . Organomet. Chem. 1997, 545-546, 597.
(9) (a) Bochmann, M.; Lancaster, S. J .; Robinson, O. B. J . Chem.
Soc., Chem. Commun. 1995, 2081. (b) Lancaster, S. J .; Thornton-Pett,
M.; Dawson, D. M.; Bochmann, M. Organometallics 1998, 17, 3829.
10.1021/om9909744 CCC: $19.00 © 2000 American Chemical Society
Publication on Web 03/24/2000

1600 Organometallics, Vol. 19, No. 8, 2000
Lancaster et al.
Resu lts a n d Discu ssion
Sch em e 1
Tita n ocen e Com p lexes. The reaction of (CpB)TiCl3
(1) with ether-free LiCp leads to an immediate color
change from pale orange to red, from which reaction
mixture a red-brown solid was isolated (Scheme 2). The
reaction was carried out in toluene to prevent donor
1
coordination to the boron. The H and 13C NMR data
(Table 1) were consistent with the formation of the
expected titanocene dichloride (CpB)CpTiCl2, with a
singlet for the C5H5 ring and two AA′BB′ pseudotriplets
for the boryl-substituted Cp ring. However, the 11B
resonance was unusually low-field shifted, from δ 59.8
in 1 to δ 4.5 in 2, which is indicative of a change in boron
coordination from trigonal-planar to four-coordinate. A
similar chemical shift has, for example, been found for
the amine adduct (C6F5)2B(fluorenyl)‚H2NCMe3.10 The
NMR and elemental analysis data of 2 showed, however,
that electron donor molecules, such as a solvent or
coordinated LiCl, were absent.
plexes of titanium and zirconium, including (CpB)TiCl3
(1; CpB ) η5-C5H4B(C6F5)2).10 The presence of a Lewis
acidic substituent on the cyclopentadienyl ring promised
an interesting synthetic and catalytic chemistry. In
particular, complexes with -B(C6F5)2 functionalities are
of interest as self-activating olefin polymerization cata-
lysts,5,10 since it can be envisaged that the Lewis acidic
boron in A can abstract an alkyl ligand from the metal
to generate equilibrium concentrations of the catalyti-
cally active zwitterion B (Scheme 1).
The extent to which self-ionization occurs will depend
both on electronic (Lewis acidity of boron) and steric
parameters (interligand distances and angles). Thus,
although the Lewis acidity of the C5H4B(C6F5)2 ligand
in 1, as judged from the 11B NMR chemical shift (δ 59.8),
is comparable to that of B(C6F5)3 (δ 60), the equilibrium
for the intramolecular reaction shown in Scheme 1 (L
) Cl, R ) Me) lies essentially to the left, whereas adduct
formation between B(C6F5)3 and Cp2ZrMe2 to give Cp2-
ZrMe(µ-Me)B(C6F5)3 proceeds quantitatively.11 It was
therefore of interest to investigate the reactivity pat-
terns of borylcyclopentadienyl ligands and to determine
the factors that would favor the ability of boryl substit-
uents to act as intramolecular Lewis acids. Here we
report the reaction of 1 with a number of carbon and
nitrogen nucleophiles.
Attempts to obtain crystals of 2 suitable for X-ray
diffraction failed. To establish the origin of the anoma-
lous 11B resonance we prepared a series of titanocenes,
replacing the Cp ligand with (trimethylsilyl)cyclopen-
tadienyl (Cp′) and indenyl (Ind), to afford 3 and 4,
respectively (Scheme 2). The reactions proceeded readily
in toluene in an analogous manner. The NMR data were
consistent with the expected formation of titanocene
dichlorides, though again in both cases high-field 11B
resonances were observed (3, δ 4.7; 4, δ 4.8). While
compound 3 was obtained as a red oily solid which could
not be induced to crystallize, cooling saturated toluene
solutions of 4 yielded crystals suitable for crystal-
lography.
The structure of 4 (Figure 1) shows η5-bonded indenyl
and cyclopentadienyl groups. Crystal data are collected
Sch em e 2

Borylcyclopentadienyl Complexes of Titanium
Organometallics, Vol. 19, No. 8, 2000 1601
Ta ble 1. 1H, 11B, a n d 13C{1H} NMR Da ta for New Tita n iu m Com p lexes

1602 Organometallics, Vol. 19, No. 8, 2000
Lancaster et al.
Ta ble 1 (Con tin u ed )
C(14) and C(19) (average 2.479 Å). Despite the greater
steric bulk of the CpB ligand, the average Ti-C distance
is comparable, 2.346 Å.
In contrast to the half-sandwich complex 1, the
-B(C6F5)2 substituent in 4 is coordinated to one of the
chloride ligands, to form a B-Cl-Ti bridge. This
structural feature explains the observed 11B NMR
chemical shift. As a result, the Ti(1)-Cl(1) bond is
significantly longer than Ti(1)-Cl(2) (2.461(9) Å vs
2.3227(10) Å), as compared to the Ti-Cl bond in Cp2-
TiCl2 of 2.364 Å.12 The Cl(1)-B(1) bond distance of
2.007(4) Å is slightly longer than the B-Cl bond length
in the [ClB(C6F5)3]- anion (1.907(8) Å)13 and in Herber-
ich’s zwitterionic cobaltocene complex Co+(C5H4BPri )-
2
(C5H4B-Pri Cl) (1.982(3) Å), in which there is no inter-
2
action between the metal and the borato chloride.14 The
B(1)-Cl(1)-Ti(1) angle is 88.38(11)°. The Cl(2)-Ti(1)-
Cl(1) angle of 94.42(3)° is very similar to that in Cp2-
TiCl2.12 The geometry around B(1) is distorted tetrahe-
dral, with the C(1)-B(1)-Cl(1) angle of 95.8(2)° being
considerably more acute than the others.
1
The symmetrical H NMR AA′BB′ pattern observed
(10) Duchateau, R.; Lancaster, S. J .; Thornton-Pett, M.; Bochmann,
M. Organometallics 1997, 16, 4995.
(11) (a) Yang, X.; Stern, C. L.; Marks, T. J . J . Am. Chem. Soc. 1991,
113, 3623. (b) Yang, X.; Stern, C. L.; Marks, T. J . J . Am. Chem. Soc.
1994, 116, 10015. (c) Beswick, C. L.; Marks, T. J . Organometallics 1999,
18, 2410.
(12) Clearfield, A.; Warner, D. K.; Saldarriaga-Molina, C. H.; Ropal,
R. Can. J . Chem. 1975, 53, 1622.
(13) Bosch, B. E.; Erker, G.; Fro¨hlich, R.; Meyer, O. Organometallics
1997, 16, 5449.
F igu r e 1. Molecular structure of 4, showing the atomic
numbering scheme. Ellipsoids are drawn at 40% prob-
ability.
in Table 2 and selected bond lengths and angles in Table
3. The bonding mode to the indenyl ligand approaches
η3, with shorter bonds to C(11)-C(13) (average 2.348
Å, comparable to the Ti-Cp distances of 2.37 Å in Cp2-
TiCl212) and longer bonds to the bridge carbon atoms
(14) Herberich, G. E.; Fischer, A.; Wiebelhaus, D. Organometallics
1996, 15, 3106.

Borylcyclopentadienyl Complexes of Titanium
Organometallics, Vol. 19, No. 8, 2000 1603
Ta ble 2. Cr ysta l Da ta for Com p ou n d s 4, 5, 8, a n d 9a
4
5
8
9
empirical formula
fw
C
26H11BCl2F10Ti
C22H10BCl3F10OTi‚CH2Cl2
659.39
C50H48B2Cl2F20N4Ti2‚C7H8
1365.38
C26H19BClF10NTi
629.58
642.96
temp (K)
cryst size (mm)
cryst syst
space group
a, Å
100(2) K
0.42 × 0.30 × 0.25
triclinic
190(2)
190(2)
150(2)
0.14 × 0.12 × 0.12
monoclinic
P21/c
10.94500(10)
20.0643(2)
11.84640(10)
90
107.8110(6)
90
2476.82(4)
4
0.52 × 0.18 × 0.16
orthorhombic
Iba2
22.8457(3)
20.36130(10)
14.7565(3)
90
0.62 × 0.45 × 0.36
monoclinic
P21/n
9.4939(3)
15.8086(5)
16.5823(5)
90
100.426(2)
90
2447.67(13)
4
P1h
7.9206(5)
10.3269(6)
29.0675(12)
87.010(4)
83.816(4)
86.342(3)
2356.5(2)
4
b, Å
c, Å
R, deg
â, deg
90
90
γ, deg
V (Å3)
6864.3(2)
4
1.321
0.401
2776
Z
Dcalcd (g cm-3
)
1.812
0.686
1272
1.768
0.762
1304
1.708
0.554
1264
µ, mm-1
F(000)
max, min transmissn
θ range, deg
0.8471, 0.7614
2.83 e θ e 25.03
-9 e h e 8,
-11 e k e 12,
-30 e l e 34
10004
0.9141, 0.9008
1.95 e θ e 30.52
-14 e h e 14,
-28 e k e 27,
-16 e l e 16
13242
0.9386, 0.8184
2.47 e θ e 28.21
-27 e h e 29,
-25 e k e 26
-17 e l e 17
6844
0.8255, 0.7251
2.64 e θ e 26.00
-11 e h e 11,
-18 e k e 19,
-20 e l e 20
4300
index range
no. of rflns collected
no. of unique rflns, n
7727
6946
6844
4776
(R(int) ) 0.0856)
(R(int) ) 0.0105)
(R(int) ) 0.0419)
no. of rflns with
6893
5996
6304
4300
2
2
Fc > 2.0o´(Fc
)
no. of params, p
721
1.041
0.0560
0.1553
357
1.055
0.0474
0.1316
420
1.071
0.0422
0.1174
369
1.039
0.0353
0.1013
goodness of fit on F2, S
R1 (I > 2σ(I))
wR2 (all data)
weighting params a, b
extinctn param
0.0793, 2.5437
0.0728, 1.7879
0.0126(13)
1.020, -0.918
0.0769, 3.4463
0.0017(2)
0.458, -0.379
0.0572, 0.9417
0.001(2)
0.296, -0.349
largest diff peak, hole
0.706, -0.516
(e Å-3
)
Definitions: Rint ) (∑|Fo - Fo2(mean)|/∑Fo2); S ) ((∑w(Fo - Fc2)2/n - p))1/2; wR2 ) ((∑w(Fo - Fc2)2/∑w(Fo2)2)1/2; R1 ) (∑||Fo| - |Fc||/
2
2
2
∑|Fo|); weighting scheme w ) [σ2(Fo2) + (aP)2 + bP]-1, where P ) [2Fc + Max(Fo2,0)]/3.
2
for the CpB ligand in toluene solutions of 2 suggests that
there is rapid exchange between the two chloride
positions on the NMR time scale (Scheme 3). This
fluxional process is remarkably facile. To slow the
exchange sufficiently to resolve the four inequivalent
CpB 1H NMR signals expected from the solid-state
structure, it was necessary to lower the temperature to
-100 °C (1H NMR (CD2Cl2, 500 MHz): δ 7.18, 7.07,
6.33, and 6.11 (m, 1H each)). Even then the signals are
still broad, and the slow exchange limit is not reached.
was no longer identical with 2. There were now four
distinct multiplets for the CpB ligand at room temper-
ature, indicative of a nonfluxional structure, and the
boron chemical shift was observed at δ -1.0.
Crystallographic examination identified the com-
pound as a hydrolysis product, (CpB)CpTi(µ-OH)Cl (5;
Scheme 2 and Figure 2), and explains the spectroscopic
properties. Compound 5 possesses η5-bonded cyclopen-
tadienyl and borylcyclopentadienyl ligands with bonding
distances very similar to those discussed above for 4 (cf.
Table 3). The structure of 5 provides an interesting
comparison with another hydrolysis product of ti-
tanocene dichloride, (Cp2TiCl)2(µ-O). The Ti(1)-Cl(1)
distance of 2.3701(6) Å in 5 is very similar to that seen
in titanocene dichloride12 but is significantly shorter
than the average Ti-Cl bond length in (Cp2TiCl)2(µ-O)
(2.41 Å),16 whereas the Ti(1)-O(1) distance of 5 (2.0437-
(14) Å) is very much longer than the average Ti-O bond
length in (Cp2TiCl)2(µ-O) (1.84 Å). Evidently the Ti-O
bond in 5 is a simple donor-acceptor interaction without
significant π-bond character. This conclusion is borne
out by comparison with the Ti-O distances in [Cp*2Ti-
(OH)(H2O)]+, which has a short Ti-OH distance (1.853(5)
Å) as well as a much longer n-donor bond to a water
molecule (2.080(5) Å).17
1
A variable-temperature H NMR study between -100
q
and +20 °C and line-shape analysis give ∆Gc ) 37 kJ
mol-1 and a coalescence temperature of ca. 200 K.15
A
number of different processes can be envisaged to
account for the chloride exchange (Scheme 3). The ease
with which the exchange takes place encourages us to
propose an SN2-type substitution mechanism (C) as the
most likely. This is supported by the observation of a
negative entropy term (∆Sq ) -56 J K-1 mol-1, ∆Hq )
26 kJ mol-1). Both mechanisms A and B require discrete
bond-breaking steps and are thus expected to be higher
energy pathways.
As stated above, the recrystallization of 2 did not yield
material of good crystal quality. However, after repeated
recrystallization attempts some crystals formed which
1
The B(1)-O(1)-Ti(1) angle is 107.62(11)°, much wider
than the B-Cl-Ti angle in 4. The O(1)-Ti(1)-Cl(1)
were suitable for X-ray analysis. H NMR examination
of these crystals revealed, however, that this material
(16) Le Page, Y.; McGowan, J . D.; Hunter, B. K.; Heyding J .
Organomet. Chem. 1980, 193, 201.
(17) Bochmann, M.; J aggar, A. J .; Wilson, L. M. Hursthouse, M. B.;
Motevalli, M. Polyhedron 1989, 8, 1838.
(15) Because of the broadness of the CpB signals over
temperature range from ca. 180-230 K, the determination of the
coalescence temperature was subject to a degree of judgment.
a wide

1604 Organometallics, Vol. 19, No. 8, 2000
Lancaster et al.
Ta ble 3. Selected Bon d Dista n ces (Å) a n d An gles
(d eg) for Com p ou n d s 4, 5, 8, a n d 9
In view of the facile interaction of the -B(C6F5)2
moiety with donor atoms, the possible formation of
complexes with a DfB donor-acceptor bridge was of
obvious interest. For this reason 1 was reacted with
lithium 2-(dimethylamino)indenide to give (CpB)(2-Me2-
NInd)TiCl2 (6) as a red solid. The compound showed
variable-temperature NMR spectra very similar to those
of 4 and at -80 °C exhibited four resonances for the
four inequivalent CpB hydrogen atoms, very similar to
the case for 2 and 4. The exchange activation barrier of
6, ∆Gcq ) 43.6 kJ mol-1, is slightly higher than in 4, as
might be expected in a more crowded complex. The 11B
NMR chemical shift of 6 is almost identical with that
of 4. Although crystallographic confirmation of the
structure of 6 was not forthcoming, we believe the data
are more in agreement with B-Cl coordination similar
to that in 2-4, in preference to the formation of an ansa-
titanocene with a B-N bridge.20
Compound 4
Ti(1)-Cl(1)
Ti(1)-C(1)
Ti(1)-C(3)
Ti(1)-C(5)
Ti(1)-C(11)
Ti(1)-C(13)
Cl(1)-B(1)
B(1)-C(111)
2.4641(9)
2.319(3)
2.390(3)
2.288(3)
2.361(3)
2.330(3)
2.007(4)
1.625(5)
Ti(1)-Cl(2)
Ti(1)-C(2)
Ti(1)-C(4)
Ti(1)-C(19)
Ti(1)-C(12)
Ti(1)-C(14)
B(1)-C(121)
2.3227(10)
2.366(3)
2.368(3)
2.482(3)
2.352(3)
2.476(3)
1.616(5)
B(1)-Cl(1)-Ti(1)
C(1)-B(1)-C(121)
88.38(11) Cl(2)-Ti(1)-Cl(1)
112.1(3)
94.42(3)
C(1)-B(1)-C(111) 119.9(3)
C(1)-B(1)-Cl(1) 95.8(2)
C(111)-B(1)-Cl(1) 106.9(2)
C(121)-B(1)-C(111) 109.5(2)
C(121)-B(1)-Cl(1)
111.6(2)
Compound 5
2.306(2)
Ti(1)-C(1)
Ti(1)-C(3)
Ti(1)-C(5)
Ti(1)-C(6)
Ti(1)-C(8)
C(1)-B(1)
B(1)-C(11)
Ti(1)-Cl(1)
O(1)-H(1)
Ti(1)-C(2)
Ti(1)-C(4)
Ti(1)-C(10)
Ti(1)-C(7)
Ti(1)-C(9)
B(1)-O(1)
B(1)-C(21)
Ti(1)-O(1)
2.334(2)
2.382(2)
2.344(2)
2.386(2)
2.360(2)
1.532(3)
1.641(3)
2.0437(14)
2.402(2)
2.318(2)
2.339(2)
2.377(2)
1.616(3)
1.623(3)
2.3701(6)
0.75(4)
Tita n iu m Im id o Com p lexes. The reaction of 1 with
1 equiv of solvent-free LiNHCMe3 proceeded readily in
toluene at low temperature, as indicated by a color
change from dark yellow to rich red. The product 7 was
B(1)-O(1)-Ti(1)
Ti(1)-O(1)-H(1)
O(1)-B(1)-C(1)
107.62(11) B(1)-O(1)-H(1)
122(3) O(1)-Ti(1)-Cl(1)
94.24(14) O(1)-B(1)-C(11)
127(3)
97.48(4)
110.9(2)
112.3(2)
1
isolated as small dark red needles. The H NMR data
(Table 1) indicated the presence of both a NCMe3 group
and a substituted cyclopentadienyl ligand. There are
clearly two competing sites for nucleophilic attack in 1:
addition to boron and substitution of a chloride ligand
at titanium. In this case the 11B chemical shift at δ 59.9
ppm indicated no donor interaction with the boron. The
elemental analysis and the 1:1 N:Cl ratio were not
consistent with the formation of a monoamido dichloride
but suggested the formation of a titanium imido com-
plex, [(CpB)TiCl(NCMe3)]n. The compound crystallizes
with 0.3 toluene per titanium. Unfortunately, despite
several attempts, it proved impossible to obtain crystals
suitable for X-ray structure determination.
C(1)-B(1)-C(11) 116.6(2)
C(1)-B(1)-C(21) 112.9(2)
O(1)-B(1)-C(21)
C(11)-B(1)-C(21) 109.2(2)
Compound 8
1.904(2)
Ti(1)-N(4)
Ti(1)-Cl(1)
Ti(1)-C(1)
Ti(1)-C(3)
Ti(1)-Ti(1′)
N(3)-C(31)
B(1)-C(11)
N(4)-C(41)
Ti(1)-N(4′)
Ti(1)-C(5)
Ti(1)-C(2)
Ti(1)-C(4)
C(1)-B(1)
B(1)-N(3)
B(1)-C(21)
1.916(2)
2.403(3)
2.435(3)
2.351(3)
1.639(4)
1.622(4)
1.665(4)
2.3412(8)
2.491(2)
2.363(3)
2.7764(8)
1.531(3)
1.643(4)
1.492(4)
N(4)-Ti(1)-N(4′)
86.65(10) N(4)-Ti(1)-Cl(1)
N(4)-Ti(1)-Ti(1)
101.52(9)
43.56(7)
N(4′)-Ti(1)-Cl(1) 101.38(9)
N(4′)-Ti(1)-Ti(1′)
N(3)-B(1)-C(1)
C(1)-B(1)-C(11)
C(1)-B(1)-C(21)
C(41)-N(4)-Ti(1) 133.4(2)
Ti(1)-N(4)-Ti(1′)
43.21(6)
107.0(2)
112.5(2)
100.7(2)
Cl(1)-Ti(1)-Ti(1′) 108.32(2)
N(3)-B(1)-C(11)
N(3)-B(1)-C(21)
C(11)-B(1)-C(21) 115.0(2)
C(41)-N(4)-Ti(1′) 133.2(2)
110.5(2)
110.5(2)
The reaction of 1 with 2 equiv of LiNHCMe3 again
gave a rich red product. Cooling a saturated toluene
solution yielded dark red crystals of 8 (Scheme 4). The
1H NMR data (Table 1) showed two distinct Me3CN
environments in a 1:1 ratio, the boryl-substituted cy-
clopentadienyl resonances were shifted to high field of
those for 7, and the 11B NMR signal was observed at δ
-5.0, indicating the presence of four-coordinate boron.
Recrystallization from toluene led to crystals of 8
suitable for a structure determination.
93.23(10)
Compound 9
Ti(1)-N(1)
Ti(1)-Cl(1)
Ti(1)-C(2)
Ti(1)-C(4)
N(1)-C(11)
B(1)-C(15)
N(1)-H(15)
2.294(2)
Ti(1)-C(1)
Ti(1)-C(5)
Ti(1)-C(3)
C(1)-B(1)
B(1)-N(1)
B(1)-C(21)
2.303(2)
2.324(2)
2.413(2)
1.632(2)
1.617(2)
1.663(2)
2.3378(5)
2.320(2)
2.399(2)
1.527(2)
1.663(2)
0.84(2)
As the molecular structure shows (Figure 3), com-
pound 8 is a binuclear species, with the two titanium
atoms and the two bridging imido ligands forming a
four-membered ring (cf. Tables 2 and 3). The coordina-
tion sphere of titanium is completed by a terminal
chloride and an η5-bonded borylcyclopentadienyl ligand.
The geometric parameters resemble closely those found
for other structurally characterized examples of imido-
bridged titanium dimers, such as [CpTiCl(µ-NPh)]2 and
N(1)-Ti(1)-Cl(1) 105.70(4)
N(1)-Ti(1)-C(1)
63.86(6)
43.56(7)
C(1)-B(1)-N(1)
B(1)-N(1)-Ti(1)
96.87(13) N(4)-Ti(1)-Ti(1)
98.20(10) Ti(1)-N(1)-C(11) 120.85(11)
Ti(1)-N(1)-H(15) 102(2)
B(1)-N(1)-C(11)
124.31(13)
111.55(13)
C(1)-B(1)-C(15)
C(1)-B(1)-C(21)
105.96(13) C(15)-B(1)-N(1)
117.45(14) C(15)-B(1)-C(21) 104.99(13)
angle is 97.48(4)°, compared to 95.95° seen in (Cp2TiCl)2-
(µ-O).16 The geometry around boron is again distorted
tetrahedral, the angle for the C(1)-B(1)-O(1) linkage
being most acute at 94.24(14)°, which is similar to that
seen for the C-B-Cl linkage in 4. The B(1)-O(1)
distance is 1.532(3) Å; this is only 0.045 Å longer than
that of the free hydroxytris(pentafluorophenyl)borate
anion itself (1.487(3) Å).18 The B-O distance in the
hydroxyborate complex [Pt{HOB(C6F5)3}Me(bu2bpy)] is
very similar, 1.526(3) Å.19
(18) Siedle, A. R.; Newmark, R. A.; Lamanna, W. M.; Huffman, J .
C. Organometallics 1993, 12, 1491.
(19) Hill, G. S.; Manojlovic-Muir, L.; Muir, K. W.; Puddephatt, R.
J . Organometallics 1997, 16, 525.
(20) For ansa-metallocenes with B-P bridges see: Ostoja-Starze-
wski, K. A.; Kelly, W. M.; Stumpf, A.; Freitag, D. Angew. Chem., Int.
Ed. Engl. 1999, 38, 2439.

Borylcyclopentadienyl Complexes of Titanium
Organometallics, Vol. 19, No. 8, 2000 1605
Sch em e 3
distance at 1.622(4) Å is very similar to the value we
observed in (C6F5)2B(fluorenyl)‚H2NCMe3 (1.643(3) Å).10
Unlike 4 and 5, the boron-bearing cyclopentadienyl
carbon C(1) has the longest Ti-C distance, 2.491(2) Å,
evidently to minimize steric interactions in the absence
of a favorable interaction between the boron and either
a chloride or an imido ligand.
We propose that the structure of 7 is essentially the
same as 8, but without the coordinated amine. This is
consistent with the observation of imide-like NCMe3
resonances in the 1H and 13C NMR, the three-coordinate
B atom, and the elemental analysis. The observed
differences in the 1H NMR data for the cyclopentadienyl
ring protons and the 11B spectrum between 7 and 8 is
due to the coordination of a molecule of NH2CMe3 to
the boron atom.
A different type of compound is obtained from the
reaction of 2 with LiNHCMe3. The orange crystalline
product was identified as (CpB)CpTi(µ-NHCMe3)Cl (9),
with a B-N-Ti bridge strongly reminiscent of that in
“constrained geometry” catalysts, {(C5R4)SiMe2NCMe3}-
MCl2.22 The reaction of 4 with LiNHCMe3 gave (CpB)-
(Ind)Ti(µ-NHCMe3)Cl (10) as a red oil. The structure of
9 was confirmed by X-ray diffraction (Figure 4). The
complex contains a terminal chloride and a bridging
NHCMe3 ligand. The B(1)-N(1) bond of 1.617(2) Å is
comparatively long and similar to the B(1)-N(3) dis-
tance in 8, and certainly longer than the B-N distance
in amido borates such as the pyrazolylborate complex
Ph2B(pz)2AgP(p-tolyl)3 (average 1.574(6) Å).23 The Ti-
N(1) distance of 2.294(2) Å is consistent with the Ti-N
F igu r e 2. Molecular structure of 5, showing the atomic
numbering scheme.
[(C5H4SiMe3)TiCl(µ-NCMe3)]2.21 Each boron is tetrahe-
dral, with coordinated tert-butylamine. The B(1)-N(3)
(21) (a) Vroegop, C. T.; Teuben, J . H.; van Bolhuis, F.; van der
Linden, J . G. M. J . Chem. Soc., Chem. Commun. 1983, 550. (b) Bai,
Y.; Roesky, H. W.; Schmidt, H.-G.; Noltemeyer, M. Z. Naturforsch., B
1992, 47B, 603. (c) Grigsby, W. J .; Olmstead, M. M.; Power, P. P. J .
Organomet. Chem. 1996, 513, 173.
(22) McKnight, A. L.; Waymouth, R. M. Chem. Rev. 1998, 98, 2587.
(23) Bruce, M. I.; Walsh, J . D.; Skelton, B. W.; White, A. H. J . Chem.
Soc., Dalton Trans. 1981, 956.

1606 Organometallics, Vol. 19, No. 8, 2000
Lancaster et al.
Sch em e 4
F igu r e 3. Molecular structure of 8, showing the atomic numbering scheme.
n-donor interaction rather than a Ti-amide bond, as
shown by the comparison with the Ti-amido bond
lengths in {(C5Me4)SiMe2NBut}TiCl2 (1.907(4) Å) and
{(C5Me4)SiMe2NBut}Ti(NMe2)2 (N(1), 1.972(4); NMe2,
1.906(4) and 1.924(5) Å).24 The C(1)-B(1)-N(1) angle
in 9 of 96.87(3)° is slightly wider than the corresponding
C-Si-N angle of 93.9(2)° in {(C5Me4)SiMe2NBut}-
M(NMe2)2,24 while the B(1)-N(1)-Ti angle is 98.2(1)°.
The pertinent geometric features of the bridged
complexes 1, 4, 5, and 9 are shown in Chart 1. The B-X
and Ti-X bond length distribution, with comparatively
long Ti-X bonds (X ) Cl, OH, NHCMe3), seems to
suggest that these compounds are best described as
donor complexes between the cationic titanium centers
and X-BR3 borate anions, rather than as adducts
between the Cp-boryl group and a heteroatom lone pair
of the Ti-X bond. This description seems particularly
apt in the case of 5. It is also evident that the formation
of B-X-Ti bridges is a consequence of the reduction in
interligand angles and distances in the bis-Cp complexes
4, 5, and 9, as compared with the mono-Cp precursor
1. The wide C(1)-Ti-Cl angle of 87.2° in 1 does not
permit chloride abstraction by boron and the formation
of a Ti-Cl-B bridge, whereas the smaller corresponding
angles in 4 (68.4°), 5 (63.7°), and 9 (63.9°) facilitate
bridge formation. The ability of a -B(C6F5)2 substituent
(24) Carpenetti, D. W.; Kloppenburg, L.; Kupec, J . T.; Petersen, J .
L. Organometallics 1996, 15, 1572.

Borylcyclopentadienyl Complexes of Titanium
Organometallics, Vol. 19, No. 8, 2000 1607
bridges is reversible, as shown by the fluxional behavior
of (CpB)CpTiCl2 even at low temperatures, whereas
B-O-Ti bridges are rigid. The reaction of 1 with bulky
amides leads to binuclear µ-imido half-sandwich com-
plexes, while coordination of an amido nitrogen to boron,
to give borato-bridged compounds similar to the well-
known “constrained geometry” complexes (CpSiMe2NR)-
TiX2,22 is only observed in the case of the bis-Cp complex
9.
Exp er im en ta l Section
Gen er a l Con sid er a tion s. All manipulations were per-
formed under a dinitrogen atmosphere using Schlenk tech-
niques. Solvents were distilled under N2 over sodium (toluene),
Na/K alloy (diethyl ether, light petroleum (bp 40-60 °C)), or
CaH2 (dichloromethane). NMR solvents were dried over 4 Å
molecular sieves (C6D6, CD2Cl2, CDCl3, toluene-d8). NMR
spectra were recorded on Bruker DPX300 and DRX500 spec-
trometers. Chemical shifts are reported in ppm and referenced
to residual solvent resonances (1H, 13C NMR) or external BF3‚
OEt2 (11B). (CpB)TiCl3 (1) and 2-Me2NC9H7 were made accord-
ing to the literature procedures.10,25 LiC5H5 (LiCp), LiC9H7
(LiInd), LiC5H4SiMe3 (LiCp′), and LiNHCMe3 were prepared
by deprotonation of freshly distilled C5H6, C9H8, C5H5SiMe3,
and NH2CMe3, respectively, with BunLi in light petroleum
solution before filtration and thorough drying under vacuum.
(Cp B)Cp TiCl2 (2). To 2.69 g (4.8 mmol) of 1 dissolved in
20 mL of toluene and cooled to -78 °C was added 0.34 g (4.8
mmol) of solid LiCp in one portion with stirring. There was
an immediate color change to red, which intensified as the
solution was warmed to room temperature. The solution was
stirred at room temperature for 1 h and filtered. Removal of
the solvent gave a red-brown solid which was recrystallized
from CH2Cl2, yield 1.2 g (2.0 mmol, 42%). Anal. Calcd for C22H9-
BCl3F10Ti: C, 44.57; H,1.53; Cl, 11.96. Found: C, 44.70; H,
1.65; Cl, 11.95. 19F NMR (C6D6, 20 °C, 282.2 MHz): δ -130.75
(d, J F-F ) 21 Hz, o-C6F5), -155.65 (t, J F-F ) 21 Hz, p-C6F5),
-163.07 (t, J F-F ) 21 Hz, m-C6F5).
F igu r e 4. Molecular structure of 9, showing the atomic
numbering scheme.
Ch a r t 1
(Cp B)Cp ′TiCl2 (3). By a procedure similar to that for 2, 1.00
g (1.78 mmol) of 1 was treated with 0.26 g (1.80 mmol) of LiCp′
in 10 mL of toluene. When it was warmed to room tempera-
ture, the reaction mixture developed a deep red color. Filtra-
tion and removal of the solvents gave a red oil, yield 0.7 g (1.05
mmol, 58%). Anal. Calcd for C25H17BCl2F10SiTi: C, 45.15; H,
2.58; Cl, 10.66. Found: C, 47.90; H, 3.25; Cl, 9.55. 19F NMR
(C6D6, 20 °C, 282.2 MHz): δ -130.84 (d, J F-F ) 19 Hz, o-C6F5),
-156.23(t, J F-F ) 20 Hz, p-C6F5), -163.28 (t, J F-F ) 18 Hz,
m-C6F5).
(Cp B)(In d )TiCl2 (4). Following the procedure for 2, 0.98 g
(1.74 mmol) of 1 was treated with 0.21 g (1.70 mmol) of LiInd
in 10 mL of toluene. The solid slowly dissolved as the slurry
was warmed to room temperature. Filtration and removal of
the solvents gave a red-brown solid. Crystals suitable for a
structure determination were grown from a 2:1 light petroleum/
dichloromethane mixture cooled to 5 °C, yield 1.0 g (1.5 mmol,
86%). Anal. Calcd for C26H11BCl2F10Ti: C, 48.87; H, 1.73; Cl,
11.03. Found: C, 48.20; H, 1.85; Cl, 11.15.
to activate metallocene complexes by ligand abstraction
therefore not only depends on the Lewis acidity of the
boryl moiety, which is expected to differ little in
compounds 1-9, but is also very sensitive to geometric
changes. Interestingly, neither Shapiro’s Cp-BPh2 ti-
tanocene complexes4 nor Reetz’s zirconium analogue of
25 show any evidence for B-Cl interactions. The former
is evidently insufficiently Lewis acidic, whereas the
larger radius of zirconium disfavors the formation of a
B-Cl-Zr bridge.
Con clu sion
The results show that the ability of a -B(C6F5)2
cyclopentadienyl substituent to act as an intramolecular
Lewis acid and to activate metal complexes by σ-ligand
abstraction is not simply a function of boron Lewis
acidity but depends sensitively on geometric features.
Thus, the wide interligand angles of titanium half-
sandwich complexes with piano-stool geometry (e.g., Cl-
Ti-Cl ) 103.5° in 1) prevent the formation of B-Cl-
Ti bridges in the solid state or in solution in detectable
concentrations. On the other hand, formation of such
bridge arrangements is facile once interligand angles
have been reduced by the introduction of a second
cyclopentadienyl ligand. The formation of B-Cl-Ti
(Cp B)Cp TiCl(OH) (5). Repeated recrystallization of crude
2 from CH2Cl2 gave red crystals of the title complex suitable
for X-ray diffraction. 19F NMR (C6D6, 20 °C, 282.2 MHz): δ
-135.2 (d, J F-F ) 10.3 Hz, o-C6F5), -135.9 (d, J F-F ) 10.3 Hz,
o-C6F5), -157.2 (t, J F-F ) 20.7 Hz, p-C6F5), -157.6(t, J F-F
20.7 Hz, p-C6F5), -162.6 (m, m-C6F5) -163.4 (m, m-C6F5).
)
(Cp B)(2-Me2NIn d )TiCl2‚0.5(tolu en e) (6). By a procedure
similar to that for 2, 2.77 g (4.92 mmol) of 1 was treated with
0.82 g (4.92 mmol) of Li[2-Me2NInd] in 30 mL of toluene at
(25) J utz, C.; Wagner, R. M.; Kraatz, A.; Lo¨bering, H. G. J ustus
Liebigs Ann. Chem. 1975, 874.

1608 Organometallics, Vol. 19, No. 8, 2000
Lancaster et al.
-20 °C. There was an immediate color change to a rich red-
brown, and some solid precipitated. The solution was warmed
to room temperature for 2 h before filtration. Removal of the
solvent gave a red-brown solid, yield 3.0 g (4.4 mmol, 89%).
Anal. Calcd for C28H16BCl2F10NTi‚0.5C7H8: C, 51.68; H, 2.75;
N, 1.91; Cl, 9.69. Found: C, 50.85; H, 2.80; N, 1.65; Cl, 10.6.
[(Cp B)TiCl(µ-NCMe3)]2 (7). To a solution of 11.31 g (20.1
mmol) of 1 in 120 mL of toluene at -78 °C was added 1.59 g
(20.1 mmol) of solid LiNHCMe3. The solid dissolved slowly on
warming to give a rich red solution at room temperature. The
solution was stirred for a further 1 h, filtered, and cooled to
-20 °C, yielding deep red crystals of 6 (8 g, 6.7 mmol, 67%).
Anal. Calcd for C42H26B2Cl2F20N2Ti2‚2/3C7H8: C, 47.14; H, 2.65;
N, 2.36; Cl, 5.97. Found: C, 47.90; H, 3.20; N, 2.30; Cl, 6.00.
[(Cp B)TiCl(µ-NCMe3)‚NH2CMe3]2 (8). To a solution of 4.53
g (8 mmol) of 1 in 30 mL of toluene was added 1.27 g (16 mmol)
of LiHNCMe3. The reaction mixture was stirred at -78 °C for
1 h, slowly warmed to room temperature, and stirred for 3 h.
Filtration of the dark red solution and cooling to -20 °C
overnight yielded dark red crystals. Crystals suitable for a
structure determination were obtained by recrystallization
from toluene. Yield 3.0 g (2.2 mmol, 55%). Anal. Calcd for
for 1 h followed by filtration and removal of the solvents gave
a red-brown oil, yield 0.15 g (0.22 mmol, 79%).
X-r a y Cr ysta llogr a p h y. In each case a suitable crystal was
coated in an inert perfluoro polyether oil and mounted in a
nitrogen stream at 150 K on a Nonius Kappa CCD area-
detector diffractometer. Data collection was performed using
Mo KR radiation (λ ) 0.710 73 Å) with the CCD detector placed
30 mm from the sample via a mixture of 1° φ and ω scans at
different θ and κ settings using the program COLLECT.26 The
raw data were processed to produce conventional data using
the program DENZO-SMN.27 The data sets were corrected for
absorption using the program SORTAV.28 All structures were
solved by heavy-atom methods using SHELXS-9729 and were
refined by full-matrix least-squares refinement (on F2) using
SHELXL-97.30 All non-hydrogen atoms were refined with
anisotropic displacement parameters. Hydrogen atoms were
constrained to idealized positions. Crystallographic data for
compounds 4, 5, 8, and 9 are summarized in Table 2.
Ack n ow led gm en t. This work was supported by the
British Engineering and Physical Sciences Research
Council. S.A.-B. thanks BP-Amoco Chemicals Ltd.,
Sunbury, U.K., for a studentship.
C
50H48B2Cl2F20N4Ti2‚C7H8: C, 47.32; H, 3.49; N, 4.41; Cl, 5.59.
Found: C, 48.00; H, 3.95; N, 4.55; Cl, 5.25.
Su p p or tin g In for m a tion Ava ila ble: Tables of crystal-
lographic data and collection details, atomic coordinates, bond
distances and angles, anisotropic thermal parameters, and
hydrogen atom coordinates. This material is available free of
charge via the Internet at http://pubs.acs.org.
(Cp B)(Cp )Ti(µ-NHCMe3)Cl (9). To a solution of 3.19 g (5.4
mmol) of 2 dissolved in 60 mL of toluene at room temperature
was added 0.43 g (5.4 mmol) of solid LiNHCMe3. The solid
dissolved rapidly, and after a few moments the solution
lightened and a precipitate was observed. The solution was
stirred for a further 1 h, filtered, and concentrated, yielding
orange-red crystals (3.1 g, 4.9 mmol, 92%). Crystals suitable
for X-ray diffraction were grown by slow evaporation of a
toluene solution. Anal. Calcd for C26H19BF10NTiCl: C, 49.60;
H, 3.04; N, 2.22; Cl, 5.63. Found: C, 49.05; H, 3.15; N, 1.55;
Cl, 7.1.
OM9909744
(26) COLLECT, data collection software; Nonius BV, Delft, The
Netherlands, 1999.
(27) Otwinowski, Z.; Minor, W. In Methods in Enzymology; Carter,
C. W., J r., Sweet, R. M., Eds.; Academic Press: New York, 1996; Vol.
276, p 307.
(28) Blessing, R. H. Acta Crystollogr., Sect. A 1995, 51, 33.
(29) Sheldrick, G. M. Acta Crystallogr., Sect. A 1990, 46, 467.
(30) Sheldrick, G. M. SHELXL-97, Program for Crystal Structure
Refinement; University of Go¨ttingen, Go¨ttingen, Germany. 1997.
(Cp B)(In d )TiCl(NHCMe3) (10). By a procedure similar to
that for 9, 0.18 g (0.28 mmol) of 4 was treated with 0.022 g
(0.28 mmol) of solid LiNHCMe3 in 10 mL of toluene. Stirring