Synthesis, structure, and reactivity of titanacyclopentadiene complexes bearing ancillary pyridine diamide ligands

Article abstract of DOI:10.1021/om960964s

Titanium complexes bearing the pyridine diamide ligands [2,6-(RNCH₂)₂NC₅H₃]^2- (R, = 2,6-diisopropylphenyl (BDPP); R = 2,6-dimethylphenyl (BDMP)) have been synthesized. Reduction of the dichloride precursors (BDPP)TiCl₂ (1a) and (BDMP)TiCl₂ (1b) with excess 1% Na/Hg amalgam in the presence of >2 equiv of internal (PhC=CPh, EtC=CEt, PrC=CPr) or terminal (HC≡CSiMe₃, PhC≡CH) alkynes yields metallacyclopentadiene derivatives in good yield. The α,β′-substituted titanacycle (BDPP)Ti[C₄H₂(SiMe₃)₂] (5a) was characterized by X-ray crystallography and is best described as a distorted square pyramid with the metallacycle carbon C(4) occupying the apical position. The α,α′-substituted titanacycle (BDMP)Ti[C₄H₂(SiMe₃)₂] (5b) reacts with excess 3-hexyne and 4-octyne to give the asymmetric metallacycles (BDMP)Ti[C₄Et₂H(SiMe₃)] (7b) and (BDMP)Ti[C₄Pr₂H(SiMe₃)] (8b), respectively. No cyclotrimerization of alkyne is observed. Ligand activation is observed in certain cases for complexes bearing the BDMP ligand.

Full text of DOI:10.1021/om960964s

Organometallics 1997, 16, 1491-1496
1491
Syn th esis, Str u ctu r e, a n d Rea ctivity of
Tita n a cyclop en ta d ien e Com p lexes Bea r in g An cilla r y
P yr id in e Dia m id e Liga n d s
Fre´de´ric Gue´rin,† David H. McConville,*,† and J agadese J . Vittal‡
Departments of Chemistry, University of British Columbia, 2036 Main Mall,
Vancouver, British Columbia, Canada V6T 1Z1, and University of Western Ontario,
London, Ontario, Canada N6A 5B7
Received November 15, 1996X
Titanium complexes bearing the pyridine diamide ligands [2,6-(RNCH2)2NC5H3]2- (R )
2,6-diisopropylphenyl (BDPP); R ) 2,6-dimethylphenyl (BDMP)) have been synthesized.
Reduction of the dichloride precursors (BDPP)TiCl2 (1a ) and (BDMP)TiCl2 (1b) with excess
1% Na/Hg amalgam in the presence of >2 equiv of internal (PhCtCPh, EtCtCEt, PrCtCPr)
or terminal (HCtCSiMe3, PhCtCH) alkynes yields metallacyclopentadiene derivatives in
good yield. The R,â′-substituted titanacycle (BDPP)Ti[C4H2(SiMe3)2] (5a ) was characterized
by X-ray crystallography and is best described as a distorted square pyramid with the
metallacycle carbon C(4) occupying the apical position. The R,R′-substituted titanacycle
(BDMP)Ti[C4H2(SiMe3)2] (5b) reacts with excess 3-hexyne and 4-octyne to give the asym-
metric metallacycles (BDMP)Ti[C4Et2H(SiMe3)] (7b) and (BDMP)Ti[C4Pr2H(SiMe3)] (8b),
respectively. No cyclotrimerization of alkyne is observed. Ligand activation is observed in
certain cases for complexes bearing the BDMP ligand.
In tr od u ction
and triamide23-25 ligand systems take advantage of
what is anticipated to be a relatively rigid stereoelec-
tronic environment.
The organometallic chemistry of Ti(IV) has been
dominated by complexes bearing cyclopentadienyl
ligands.1 There is, however, a growing interest in the
use of alternative ligands such as alkoxides2-6 and
amides7-11 which may be viewed as electron deficient
cyclopentadienyl equivalents. In particular, titanium
amide complexes have been shown to stabilize reactive
species such as methylidene ligands,12 and alkyl groups
with â-hydrogens13 and are precursors for both the
highly active14 and living polymerization15 of R-olefins.
Titanium complexes bearing multidentate diamide16-22
Metallacyclopentadiene complexes are key intermedi-
ates in a number of cyclization reactions,26 for example,
the catalytic cyclotrimerization of alkynes. Previously,27
we have reported the synthesis and structure of alkyne
derivatives of tantalum stabilized by a pyridine diamide
ligand (eq 1).
† University of British Columbia.
‡ University of Western Ontario.
X Abstract published in Advance ACS Abstracts, February 15, 1997.
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materials for studying the insertion of an alkyne into a
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12162, 1992.
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1996, 15, 3825.
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1992, 11, 1452.
(14) Scollard, J . D.; McConville, D. H.; Vittal, J . J . Macromolecules
1996, 29, 5241.
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1995, 14, 3154.
S0276-7333(96)00964-8 CCC: $14.00 © 1997 American Chemical Society

1492 Organometallics, Vol. 16, No. 7, 1997
Gue´rin et al.
Sch em e 1. P r ep a r a tion of Tita n a cyclop en ta d ien e
Der iva tivesa
a
Reagents and conditions: toluene, 23 °C, excess Na/Hg
amalgam, >2 equiv alkyne; (i) R′CtCR′, R′ ) Et, Pr, Ph; (ii)
R′CtCH, R′ ) SiMe3, Ph; (iii) R′CtCH, R′ ) SiMe3.
metal-carbon bond,28 the coupling of two alkynes to
give a tantalacyclopentadiene derivative is thwarted by
the presence of the remaining apical chloride ligand. As
a result, we decided to investigate the intramolecular
coupling of alkynes at a reduced titanium center; for
example, via the reduction of the known dichloride
precursor [2,6-(RNCH2)2NC5H3]TiCl2 (R ) 2,6-iPr2C6H3,
2,6-Me2C6H3).29 In this paper we report a series of
titanacyclopentadiene derivatives containing pyridine
diamide ligands. The preparation and reactivity of
these new compounds is compared to metallacyclic
analogues bearing the fragments Cp2Ti30 and (RO)2Ti.31
F igu r e 1. Variable-temperature proton NMR spectra of
the ligand methylene (CH2N) region of compound 4a .
Sch em e 2
Resu lts
The titanacyclopentadiene complexes 2a -4a ,4b were
prepared by the reduction of the dichloride precursors
(BDPP)TiCl2 (1a , BDPP ) 2,6-(R′NCH2)2NC5H3, R′ )
2,6-iPr2C6H3) and (BDMP)TiCl2 (1b, BDMP ) 2,6-
(R′NCH2)2NC5H3, R′ ) 2,6-Me2C6H3)29 with excess 1%
Na/Hg amalgam in toluene at 23 °C in the presence of
>2 equiv of alkyne (Scheme 1). Orange-red solutions
of the dichlorides 1a ,b slowly become dark red-brown
over 12 h. Filtration of the crude toluene solutions and
recrystallization from pentane affords the titanacyclic
products in good yield (∼65%). Although the metalla-
cyclic products 2b and 3b (not shown) were observed
by 1H NMR spectroscopy, they proved too soluble to
separate from the byproducts in the reaction (vide infra).
The aryloxide supported titanacycle (Ar′′O)2Ti(C4Ph4)
(Ar′′ ) 2,6-Ph2C6H3) cannot be obtained via the reduc-
tion of the dichloride precursor (Ar′′O)TiCl2.31 In con-
trast, the metallacycles 4a ,b are obtained in ∼65% yield,
which suggests that the pyridine diamide ligand plays
an important role in stabilizing reduced titanium in-
termediates. Metallacycles 2a -4a ,b do not react fur-
ther with additional alkyne even at elevated tempera-
tures (110 °C, 24 h).
The proton NMR spectra of complexes 2a , 3a , and 4b
show a singlet for the ligand methylene protons (NCH2),
consistent with meridional coordination of the pyridine
diamide ligand. The carbon spectra of compounds 2a -
4a ,b show characteristic30,31 low-field resonances (>190
ppm) for the R-carbons of the metallacycle. The 1H
NMR spectra of compounds 2a and 3a display chemi-
cally inequivalent ethyl and propyl substituents (R and
â) for the titanacycles. The 1H NMR spectrum of
compound 4a , however, is quite broad at 23 °C.
A
stacked plot of the ligand methylene (CH2N) region of
compound 4a at various temperatures is shown in
Figure 1.
As the temperature is increased, the resonance at
about 5.47 ppm (C-H o-phenyl) shifts to lower field
while the resonances at 4.99 ppm (CHMe2) and 2.79
ppm (CHMe2snot shown) coalesce to a single resonance
at 3.88 ppm. The high temperature limiting spectrum
(80 °C) shows a single broad resonance (∆) for the
methylene protons at about 5.05 ppm. The low tem-
perature limiting spectrum (-20 °C) shows an AB
quartet (2J HH ) 20.63 Hz) for the methylene protons
(*). We interpret this exchange process to the restricted
rotation (∆G q ) 14.7(5) kcal mol-1) of the phenyl rings
of the titanacycle (Scheme 2).
(28) Gue´rin, F.; McConville, D. H.; Vittal, J . J . Manuscript in
preparation.
(29) Gue´rin, F.; McConville, D. H.; Payne, N. C. Organometallics
1996, 15, 5085.
(30) Alt, H. G.; Englehardt, H. E.; Rausch, M. D.; Kool, L. B. J . Am.
Chem. Soc. 1985, 107, 3717.
(31) Hill, J . E.; Balaich, G.; Fanwick, P. E.; Rothwell, I. P. Orga-
nometallics 1993, 12, 2911.
The bulky 2,6-diisopropylphenyl substituents on the
amide nitrogens prevent free rotation of the phenyl
rings in the R and R′ positions which in turn affects the
orientation of the phenyl groups in the â and â′ positions

Titanacyclopentadiene Complexes
Organometallics, Vol. 16, No. 7, 1997 1493
Ta ble 1. Su m m a r y of Cr ysta llogr a p h ic Da ta ,
Collection P a r a m eter s, a n d Refin em en t
P a r a m eter s for Com p ou n d 5a a
empirical formula
fw
C41H61N3Si2Ti1
700.01
cryst color, habit
cryst dimens (mm)
cryst system
orange, plate
0.38 × 0.34 × 0.18
monoclinic
reflcns used for unit cell
determination (2θ range (deg))
a (Å)
23 (18.2-22.6)
10.630(3)
b (Å)
36.650(9)
c (Å)
12.200(4)
â (deg)
110.73(2)
4445(2)
V (Å3)
space group
P21/n
Z
4
F (calc) (g/mol)
collcn temp ( °C)
F000
1.046
25
1512
Mo KR
scan mode
graphite (monochromated)
ω (variable 2-20 deg/min)
tot. no. of unique reflcns
no. of observns with F0 g 4σ(F0)
no. of variable params
R1a
6646
5362
258
0.102
0.203
0.996
wR2a
goodness of fit (GooF)a
a
2
4 1/2
R1 ) ∑(||Fo | - | Fc ||)/∑|Fo|; wR2 ) [∑w(Fo - Fc2)2/∑wFo
] ;
GooF ) [∑w(Fo - Fc2)2/(n - p)]1/2 (where n is the number of
reflections and p is the number of parameters refined).
2
F igu r e 2. Top: Chem 3D representation of the molecular
structure of 5a . Bottom: Chem 3D representation of the
core of 5a .
of the titanacycle. Thus, the low temperature limiting
structure would have C2 symmetry while the high
temperature limiting structure would have C2v sym-
metry. The solid-state structure of Cp2Ti(C4Ph4) shows
a propeller arrangement of the phenyl rings as proposed
here.32
Ta ble 2. Selected Bon d Dista n ces (Å) a n d An gles
(d eg) for 5a
Bond Distances
Ti(1)-C(1)
Ti(1)-N(1)
Ti(1)-N(3)
C(2)-C(3)
2.046(11)
1.989(8)
2.172(8)
1.553(14)
Ti(1)-C(4)
Ti(1)-N(2)
C(1)-C(2)
C(3)-C(4)
2.070(10)
2.009(8)
1.348(13)
1.357(13)
Terminal alkynes reacts with the dichlorides 1a ,b
under reducing conditions to yield the metallacycles
5a ,b and 6a . Assuming that compounds 5a ,b and 6a
proceed through a common mono(alkyne) intermediate
(I), the regiochemistry of the insertion of the second
alkyne can be rationalized in the following way:
Bond Angles
N(2)-Ti(1)-N(3)
N(2)-Ti(1)-N(1)
Ti(1)-N(3)-C(1)
C(30)-N(1)-C(17)
C(17)-N(1)-Ti(1)
Ti(1)-N(1)-C(30)
74.1(3)
141.5(3)
155.6(4)
109.8(7)
121.8(6)
128.3(6)
C(1)-Ti(1)-C(4)
N(3)-Ti(1)-N(1)
Ti(1)-N(3)-C(4)
C(18)-N(2)-C(11)
Ti(1)-N(2)-C(11)
Ti(1)-N(2)-C(18)
100.7(4)
73.6(3)
103.6(4)
112.3(7)
122.1(6)
125.3(6)
ture of complex 5a can be found in Figure 2, and
relevant bond distances and angles, in Table 2. The
structure is best described as a distorted square pyra-
mid with the metallacycle carbon C(4) occupying the
apical position. The alternating short-long-short bond
distances in the titanacycle are consistent with its diene
formulation. The titanium atom lies about 0.45 Å above
the basal plane defined by the three nitrogens and C(1).
The Ti-amide distances are comparable to the Ti-
amide distances in the square pyramidal complex
(BDMP)TiBr(CH2CMe2Ph) (1.979(5) and 1.977(6) Å).29
The rigid coordination of the ligand and enforced
location of the aryl isopropyl groups necessarily protect
the metal above and below the N3 plane. In fact, the
congested environment about the titanium may in part
explain the lack of insertion chemistry associated with
this complex (vide infra).
Back-side attack of the second alkyne to intermediate
I is hindered by the R′ substituent (Ph or SiMe3). Thus,
when the pyridine diamide ligand bears the larger 2,6-
diisopropylphenyl substituents at nitrogen and the
incoming alkyne is bulky (HCtCSiMe3), the bulk of this
alkyne is directed away from the isopropyl groups of the
ligand to give the R,â′ product (5a ). When the incoming
alkyne is relatively small (HCtCPh), the more favorable
R,R′ product is obtained (6a ). In contrast, for the less
sterically demanding 2,6-dimethylphenyl substituted
ligand, the second alkyne inserts with the R′ substituent
directed toward the ligand, resulting in the R,R′ isomer
(5b). For comparison, Cp2Ti(C4H2Ph2) display the R,â′
regiochemistry while Cp2Ti(C4H2Me2) displays the R,R′
regiochemistry, reflecting the difference in steric bulk
of the two alkynes.32 Compounds 5a ,b and 6a do not
isomerize when heated to 80 °C in benzene.
The aryloxide complex (Ar′′O)2Ti(C4Et4) is a catalyst
for the cyclotrimerization of alkynes.31 In contrast,
there are no reports of alkyne cyclization catalyzed by
titanacyclopentadiene derivatives of the type Cp2Ti-
(C4R4). Although compounds 2a , 4b, and 5a do not react
The solid-state structure of 5a was determined by
X-ray crystallography (Table 1). The molecular struc-
(32) Atwood, J . L.; Hunter, W. E.; Alt, H.; Rausch, M. D. J . Am.
Chem. Soc. 1976, 98, 2454.

1494 Organometallics, Vol. 16, No. 7, 1997
Gue´rin et al.
Sch em e 3. P r op osed Mech a n ism for th e
with alkynes (110 °C, 24 h), compound 5b reacts with
excess alkyne at 80 °C to give the asymmetric metal-
lacycle derivatives 7b and 8b in quantitative yield by
1H NMR spectroscopy (eq 2).
F or m a tion of 9b
The regiochemistry of the metallacycle (R, â, R′) in
compound 7b was assigned on the basis of NOE experi-
ments. For example, irradiation of the methylene signal
of the ethyl group in the â-position (2.14 ppm) caused
an enhancement of the metallacycle proton at 8.23 ppm,
confirming the proximity of these two groups (irradia-
tion of other groups was consistent with this assign-
ment). Fragmentation of a metallacycle to an interme-
diate bis(alkyne) derivative has been proposed to explain
the substitution of the alkynes in (Ar′′O)2Ti(C4Et4).31,33
In addition, disruption of the metallacycle to a mono-
(alkyne) adduct and free alkyne has been proposed for
alkyne exchange in tantalum alkoxide systems.34 Al-
though we can not distinguish between these mecha-
nism at present, it is interesting that only one of the
alkynes is displaced. We are currently exploring the
scope and mechanism of this transformation.
cessful. It is not clear why this ligand-activated complex
forms in such high yield for certain alkynes; for example,
we see no evidence of ligand metalation when compound
1b is reduced in the presence of diphenylacetylene.
Con clu sion s
Pyridine diamide complexes of titanium can be re-
duced in presence of internal and terminal alkynes to
give the corresponding metallacyclopentadiene deriva-
tives in good yield. The titanacycles 2a -4a ,b, 5a , and
6a do not react further with excess alkyne. The R,R′-
substituted metallacycle (BDMP)Ti[C4(SiMe3)2] reacts
with excess alkyne via an apparent bis(alkyne) inter-
mediate to give an unusual mixed titanacycle; the
symmetrical metallacycles (LnTiC4R4, R ) Et, Pr) are
not observed. Activation of the aryl methyl group of the
BDMP ligand appears to compete with metallacycle
formation in certain cases. The BDPP ancillary which
bears 2,6-diisopropylphenyl substituents at nitrogen is
not activated under the conditions studied; however, the
steric bulk of this ligand precludes further reaction of
the metallacycles. The next generation of pyridine
diamide ligands (alkyl substituents at nitrogen) which
are less bulk and less susceptible to activation may
provide a more useful stereochemical environment for
these derivatives.
As noted above, the reduction of (BDMP)TiCl2 in the
presence of 3-hexyne or 4-octyne yields an inseparable
mixture of the corresponding titanacycle and a byprod-
uct. In the presence of >2 equiv of MeCtCPh, however,
the byproduct (9b) is formed in high yield and is easily
separable from small amounts of the metallacycle.
Proton and carbon NMR spectra clearly show the
presence of a vinyl moiety likely derived from the
insertion of MeCtCPh into a Ti-H bond (-PhCdCHMe).
Curiously, only three aryl methyl resonances are ob-
served for the BDMP ligand. C1 symmetry can be
assigned to complex 9b on the basis of the presence of
separate resonances for all four ligand methylene
protons (NCH2). Using a combination of 1H homo-
1
nuclear decoupling and H-13C correlation spectroscopy
experiments, the proposed structure of this complex and
a possible mechanism for its formation are shown in
Scheme 3. Reduction of the dichloride 1b yields an
intermediate Ti(II) complex (A) which activates the
methyl group of the arene. Presumably this does not
occur at any significant rate during the reduction of
complex 1a since the methine proton is well protected
by the isopropyl methyls. The newly formed alkyl-
hydride complex (B) inserts MeCtCPh to give the
observed vinyl moiety as shown in C. The regiochem-
istry of the insertion is based on the observed coupling
between the vinylic C-H and the methyl group (6.2 Hz).
Insertion of a second equivalent of MeCtCPh into the
Ti-C bond formed via the metalation (D), followed by
a 1,3-hydrogen shift, yields the final product 9b. The
proton shift may occur in an attempt to relieve ring
strain. Attempts to prepare an authentic Ti(II) complex
(e.g., (BDMP)TiL2, L ) phosphine) have been unsuc-
Exp er im en ta l Section
Gen er a l Deta ils. All experiments were performed under
a dry nitrogen atmosphere using standard Schlenk techniques
or in an Innovative Technology Inc. glovebox. Solvents were
distilled from sodium/benzophenone ketyl (DME, THF, hex-
anes, diethyl ether, and benzene) or molten sodium (toluene)
under argon and stored over activated 4 Å molecular sieves.
Phenylacetylene, diphenylacetylene, 1-phenylpropyne, 3-hex-
yne, 4-octyne, and (trimethylsilyl)acetylene were purchased
from Aldrich and distilled prior to use. The complexes (BDPP)-
TiCl2 (1a ) and (BDMP)TiCl2 (1b) were synthesized by a
literature method.29 Unless otherwise specified, proton (300
MHz) and carbon (75.46 MHz) NMR spectra were recorded in
C6D6 at approximately 22 °C on a Varian Gemini-300 spec-
trometer. The proton chemical shifts were referenced to
internal C6D5H (δ ) 7.15 ppm), and the carbon resonances to
C6D6 (δ ) 128.0 ppm). Some carbon resonances are obscured
by C6D6 and/or are overlapping. The elemental analysis were
performed using sealed tin cups on a Fisons Instruments
Model 1108 elemental analyzer by Mr. Peter Borda of this
department.
(33) Hill, J . E.; Fanwick, P. E.; Rothwell, I. P. Organometallics 1990,
9, 2211.
(34) Smith, D. P.; Strickler, J . R.; Gray, S. D.; Bruck, M. A.; Holmes,
R. S.; Wigley, D. E. Organometallics 1992, 11, 1275.

Titanacyclopentadiene Complexes
Organometallics, Vol. 16, No. 7, 1997 1495
(BDP P )Ti(C4Et4) (2a ). A toluene (30 mL) solution of
compound 1a (0.100 g, 0.174 mmol) and 3-hexyne (0.035 g,
0.426 mmol) was added to an excess of 1% Na/Hg amalgam
(0.074 g of Na, 3.22 mmol; 7.40 g of Hg). The mixture was
stirred for 12 h. The solution was decanted from the amalgam
and filtered through a medium-porosity frit with the aid of
Celite. The solvent was removed in vacuo to yield an orange-
brown solid. Due to its high solubility, compound 2a was not
isolated in crystalline form (>95% yield by 1H NMR): 1H NMR
7.25-7.10 (m, 6H, Ar), 6.93 (t, 1H, py), 6.48 (d, 2H, py), 5.02
(s, 4H, NCH2), 3.62 (sept, 4H, CHMe2), 2.13 (m, 8H, R,â CH2-
Me), 1.35 (d, 12H, CHMe2), 1.28 (d, 12H, CHMe2), 0.92 and
0.39 (t, 6H each, R,â CH2Me); 13C{1H} NMR δ 229.33 (CR),
162.35, 154.12, 143.72, 137.97, 124.90, 123.78, 116.65, 68.72
(NCH2), 28.86, 28.37, 28.16, 26.73, 24.49, 24.29, 22.20, 15.96.
(BDP P )Ti(C4P r 4) (3a ). The preparation of compound 3a
is identical to that for 2a . Compound 1a (0.250 g, 0.435 mmol),
4-octyne (0.120 g, 1.09 mmol), and excess 1% Na/Hg amalgam
(0.30 g, 13.0 mmol; 30.0 g Hg) gave dark red 3a (0.213 g, 0.294
mmol, 68%) when recrystallized from diethyl ether at -30
°C: 1H NMR 7.25-7.10 (m, 6H, Ar), 6.93 (t, 1H, py), 6.46 (d,
2H, py), 5.05 (br s, 4H, NCH2), 3.64 (br sept, 4H, CHMe2), 2.21
and 2.11 (m, 8H, R,â CH2CH2Me), 1.38 (d, 12H, CHMe2), 1.24
(d, 12H, CHMe2), 0.90 (m, 12H, R,â CH2CH2Me), 0.71 (br m,
8H, R,â CH2CH2Me); 13C{1H} NMR δ 229.33 (CR), 162.22,
154.06, 143.80, 137.86, 124.94, 123.80, 116.57, 68.69 (NCH2),
68.73, 39.09, 32.35, 28.42, 26.71, 25.05, 24.38, 23.25, 15.24.
Anal. Calcd for C47H69N3Ti: C, 77.97 ; H, 9.61; N, 5.80.
Found: C, 78.18; H, 9.49; N, 6.20.
(BDP P )TiC4P h 4 (4a ). The preparation of compound 4a is
identical to that for 2a . Compound 1a (0.500 g, 0.870 mmol),
diphenylacetylene (0.310 g, 1.74 mmol), and excess 1% Na/
Hg amalgam (0.60 g, 26.1 mmol; 60.0 g Hg) gave red crystalline
4a (0.423 g, 0.620 mmol, 71%) when recrystallized from diethyl
ether at -30 °C: 1H NMR (23 °C) δ 7.2-6.1 (br m, Ar, Ph,
py), 6.27 (d, 2H, py), 5.56 (br m, 2H, CH2N), 4.95 (br m, 2H,
CHMe2), 4.51 (br m, 2H, CH2N), 2.83 (br m, 2H, CHMe2), 1.87
(br m, 6H,CHMe2), 1.53 (br m, 6H, CHMe2), 0.87 (br m, 12H,
CHMe2). 1H NMR (-20 °C, toluene-d8) δ 7.4-6.5 (m, Ar, Ph
and py), 6.22 (d, py, 2H), 5.47 (d, 2H, Pho), 5.03 (AB quartet,
2J HH ) 20.63 Hz, 4H, NCH2), 4.99 (sept, 2H, CHMe2), 2.79
(sept, 2H, CHMe2), 1.93 (d, 6H, CHMe2), 1.62 (d, 6H, CHMe2),
0.91 (d, 6H, CHMe2), 0.82 (d, 6H, CHMe2); 13C{1H} NMR (-40
°C, toluene-d8) δ 161.16, 152.28, 146.88, 138.03, 131.89, 131.60
(br), 131.78, 129.95, 127.27, 126.57, 126.17, 125.74, 124.23 (br),
123.19, 116.59, 69.21, 29.75 (br), 28.40 (br), 27.26 (br), 25.84
(br), 23.75. Anal. Calcd for C59H61N3Ti: C, 82.40; H, 7.15; N,
4.89. Found: C, 82.37; H, 7.21; N, 5.13.
123.64, 117.25, 67.35, 28.72, 27.10, 26.65, 26.41, 24.87, 23.78,
-0.38, -1.86. Anal. Calcd for C41H61N3Si2Ti: C, 70.35; H,
8.78; N, 6.00. Found: C, 69.97; H, 8.94; N, 6.02.
(BDMP )Ti[C4H2(SiMe3)2] (5b). The preparation of com-
pound 5b is identical to that for 2a . Compound 1b (0.100 g,
0.216 mmol), Me3SiCtCH (0.047 g, 0.476 mmol), and excess
Na/Hg amalgam (0.074 g of Na, 3.22 mmol; 7.40 g of Hg) gave
yellow crystalline 5b (0.431 g, 0.609 mmol, 70%) when
recrystallized from pentane at -30 °C: 1H NMR δ 8.50 (s, 2H,
â,â′-CH), 7.03 (d, 4H, Ar), 6.94 (t, 1H, py), 6.91 (m, 2H, Ar),
6.55 (d, 2H, py), 4.59 (s, 4H, NCH2), 2.27 (s, 12H, Me), -0.23
(s, 18H, R,R′-SiMe3). 13C{1H} NMR δ 228.41 (CSiMe3), 163.15,
156.02, 138.25, 133.72, 132.26, 124.70, 117.43, 65.45, 20.10,
-0.28. Anal. Calcd for C33H45N3Si2Ti: C, 67.43; H, 7.72; N,
7.15. Found: C, 67.83; H, 7.93; N, 7.29.
(BDP P )Ti[C4H2P h 2] (6a ). The preparation of compound
6a is identical to that for 2a . Compound 1a (0.500 g, 0.870
mmol), phenylacetylene (0.267 g, 2.61 mmol), and excess Na/
Hg amalgam (0.60 g, 26.0 mmol; 60.0 g Hg) gave dark-red
crystalline 6a (0.431 g, 0.609 mmol, 70%) when isolated from
diethyl ether at -30 °C: 1H NMR δ 7.45 (s, 2H, â,â′-CH), 7.21
(m, 6H, Ar), 7.00 (t, 4H, Ph), 6.89 (m, 3H, Ph and py), 6.41 (d,
2H, py), 6.18 (d, 4H, Ph), 4.99 (s, 4H, NCH2), 2.65 (sept, 4H,
CHMe2), 1.18 (d, 12H, CHMe2), 1.20 (d, 12H, CHMe2); 13C{1H}
NMR δ 220.77 (R-CPh), 161.88, 153.74, 148.02 (â-CH), 143.50,
138.18, 125.65, 125.39, 125.25, 124.46, 124.16, 117.23, 68.32,
28.04, 26.70, 23.37. Anal. Calcd for C47H53N3Ti: C, 79.75; H,
7.55; N, 5.94. Found: C, 79.35; H, 7.91; N, 5.99.
(BDMP )Ti[C4Et2H(SiMe3)] (7b). A benzene (5 mL) solu-
tion containing complex 5b (0.025g, 0.043 mmol) and 3-hexyne
(0.030g, 0.365 mmol) was heated to 80 °C for 12 h. The solvent
was removed in vacuo and the sample dissolved in C6D6. A
quantitative yield was determined by 1H NMR. 1H NMR δ
8.23 (s, 1H, â′-CH), 7.05-6.95 (m, 5H, Ar and py), 6.88 (t, 2H,
Ar), 6.55 (d, 2H, py), 4.65 (AB quartet, 1J HH ) 21.1 Hz, CH2N),
2.28 (s, 12H, Me), 2.14 and 1.89 (q, 2H each, CH2Me), 0.87
and 0.27 (t, 3H each, CH2Me), -0.08 (s, 9H, SiMe3); 13C{1H}
NMR δ 228.35, 221.93, 162.96, 155.30, 137.74, 135.44, 134.60,
134.00, 132.73, 123.88, 117.01, 64.99, 31.87, 27.82, 19.84,
19.11, 12.80, 12.63, -0.38.
(BDMP )Ti[C4P r 2H(SiMe3)] (8b). A benzene (5 mL) solu-
tion containing complex 5b (0.025g, 0.043 mmol) and 4-octyne
(0.030g, 0.272 mmol) was heated to 80 °C for 12 h. The solvent
was removed in vacuo and the sample dissolved in C6D6. A
quantitative yield was determined by 1H NMR. 1H NMR δ
8.29 (s, 1H, â′-CH), 7.10-6.95 (m, 5H, Ar and py), 6.90 (t, 2H,
Ar), 6.57 (d, 2H, py), 4.66 (AB quartet, 2J HH ) 21.1 Hz, CH2N),
2.30 (s, 12H, Me), 2.8 and 1.85 (m, 2H each, CH2CH2Me, 1.38
(m, 2H, CH2CH2Me), 0.82 and 0.70 (t, 3 each, CH2CH2Me), 0.58
(m, 2H, CH2CH2Me), -0.07 (s, 9H, SiMe3); 13C{1H} NMR δ
228.64, 221.78, 162.95, 155.36, 137.78, 134.66, 133.90, 132.84,
129.25, 127.24, 127.04, 124.76, 123.95, 122.24, 120.20, 117.03,
65.18,41.40, 37.94, 22.04, 21.64, 19.86, 19.08, 15.28, 14.68,
-0.34.
(BDMP )TiC4P h 4 (4b). The preparation of compound 4b
is identical to that for 2a . Compound 1b (0.500 g, 1.08 mmol),
diphenylacetylene (0.482 g, 2.70 mmol), and excess 1% Na/
Hg (0.25 g, 10.9 mmol; 24.9 g Hg) gave red crystalline 4b (0.497
g, 0.665 mmol, 62%) when recrystallized from diethyl ether
at -30 °C: 1H NMR δ 7.21(d, 4H, Ar), 7.08 (t, 2H, Ar), 6.92
(m, 4H, Ph), 6.76 (m, 8H, Ph), 6.66 (m, 5H, Ph and py), 6.34
(d, 2H, py), 5.96 (m, 4H, Ph), 4.71 (s, 4H, CH2N), 2.52 (s, 12H,
Me); 13C {1H} NMR δ 221.66 (CR), 161.72, 153.74, 146.02,
143.66, 140.22, 137.99, 134.07, 131.91, 130.48, 129.25, 127.08,
126.98, 125.80, 125.36, 123.31, 116.88, 66.16 (NCH2), 19.24.
(BDP P )Ti[C4H2(SiMe3)2] (5a ). The preparation of com-
pound 5a is identical to that for 2a . Compound 1a (0.200 g,
0.348 mmol), Me3SiCtCH (0.088 g, 0.696 mmol), and excess
1% Na/Hg amalgam (0.240 g of Na, 10.4 mmol; 24.0 g of Hg)
gave yellow crystalline 5a (0.157 g, 0.224 mmol, 64%) when
recrystallized from pentane at -30 °C: 1H NMR δ 8.68, 8.66
(s, 1H each, R,â′-CH), 7.15-7.05 (m, 6H, Ar), 6.95 (t, 1H, py),
(BDMP ′)Ti(MeCCP h )2 (9b). A THF (30 mL) solution of
compound 1b (0.500 g, 1.08 mmol) and 1-phenylpropyne (0.314
g, 2.70 mmol) was added to an excess of Mg (0.250 g, 10.3
mmol). The mixture was stirred for 12 h. The solution was
decanted from the magnesium and filtered through Celite. The
solvent was removed in vacuo to yield a dark brown solid. The
solid was dissolved in a minimum amount of diethyl ether and
cooled to -30 °C for 12 h. Dark red crystalline 9b was isolated
by filtration and dried under vacuum (0.371 g, 0.595 mmol,
55%): 1H NMR δ 7.20-6.80 (m, 15H, Ph, Ar and py), 6.63 and
6.41 (d, 1H each, py), 6.19 (m, 2H, Ph), 4.96 (AB quartet, 2J HH
2
) 21.3 Hz, 2H, CH2N), 4.71 (AB quartet, J HH ) 19.9 Hz, 2H
2
6.53 (d, 2H, py), 4.92 (AB quartet, J HH ) 21.15, 4H, NCH2),
CH2N), 3.65 (q, 1H, CdCHMe), 3.13 (m, 2H), 2.78 (m, 2H),
2.40 (s, 3H, ArMe), 1.97 (d, 3H, CdCHMe), 1.85 (m, 1H), 1.82
(s, 3H, ArMe), 0.94 (s, 3H, ArMe); 13C{1H} δ 166.32, 162.63,
154.66, 148.25, 147.98, 142.48, 141.40, 140.49, 137.30, 136.85,
135.47, 131.20, 129.01, 128.73, 127.44, 147.21, 126.93, 126.82,
126.53, 126.00, 122.62, 121.81, 120.62, 117.51, 117.09, 84.78,
3.66 (sept, 2H, CHMe2), 3.46 (sept, 2H, CHMe2), 1.43 (d, 6H,
CHMe2), 1.28 (d, 6H, CHMe2), 1.24 (d, 6H, CHMe2), 1.15 (d,
6H, CHMe2), 0.04 and -0.15 (s, 9H each, R,â′-SiMe3); 13C{1H}
NMR δ 218.81 (R-CH), 215.04 (R-CSiMe3), 163.12, 153.33,
144.06, 142.71, 138.14 (â-CH), 137.63, 128.59, 124.94, 124.20,

1496 Organometallics, Vol. 16, No. 7, 1997
Gue´rin et al.
71.57, 69.09, 67.55, 64.73, 39.54, 21.64, 18.10, 17.47, 15.96.
The compound crystallizes with MgCl2 present (confirmed by
a qualitative Ag ion test).
X-r a y Cr ysta llogr a p h ic An a lysis. A suitable crystal of
5a was grown from a saturated hexane solution at -30 °C.
Crystal data may be found in Table 1. A preliminary inves-
tigation showed that the crystals were weakly diffracting. Data
were collected on a Siemans P4 diffractometer with the
XSCANS software package.35 The Laue symmetry 2/m was
occupy two positions (occupancies 0.5 and 0.5). Common
isotropic thermal parameters were refined for these disordered
carbon atoms. An empirical absorption correction was applied
to the data using the ψ scan data. No attempt was made to
locate hydrogen atoms, were placed in calculated positions. The
phenyl groups were constrained to be regular hexagons with
C-C distances of 1.395 Å. In the final difference Fourier
synthesis the electron density fluctuates in the range 0.385
3
-
to -0.346 e Å
.
determined by merging symmetry equivalent positions.
A
total of 6646 data were collected in the range of θ ) 1.9-22.0°
(-1 e h e 11, -1 e k e 38, -12 e l e 12). Three standard
reflections monitored at the end of every 297 reflections
collected showed no decay of the crystal. In the shell 38 e 2θ
e 44° only 3% of the reflections were found to be significant.
The data processing, solution, and refinement were done using
SHELXTL-PC programs.36 The methyl carbons attached to
Si(2) were found to have two different orientations with
occupancies of 0.6 and 0.4. Similarly, the two methyl carbon
atoms of the isopropyl group attached to C(27) were found to
Ack n ow led gm en t . Funding from the NSERC
(Canada) in the form of a Research Grant to D.H.M. is
gratefully acknowledged.
Su p p or t in g In for m a t ion Ava ila b le: Text describing
X-ray procedures, tables of final crystallographic atomic
coordinates, equivalent isotropic thermal parameters, hydro-
gen atom parameters, anisotropic thermal parameters, com-
plete bond lengths and angles, and X-ray parameters, and an
ORTEP diagram for 5a (12 pages). Ordering information is
given on any current masthead page.
(35) XSCANS: Siemans Analytical X-ray Instruments Inc., Madison
WI, 1990.
(36) SHELXTL Version 5: Siemans Analytical X-ray Instruments
Inc., Madison WI, 1994.
OM960964S