Conformationally rigid diamide complexes: Synthesis and structure of titanium(IV) alkyl derivatives

Article abstract of DOI:10.1021/om9604841

Titanium complexes bearing a pyridinediamide ligand [2,6-(RNCH₂)₂NC₅H₃]² (R = 2,6-diisopropylphenyl (BDPP); R = 2,6-dimethylphenyl (BDMP)) have been synthesized. The dichloride complexes [2,6-(RNCH

Full text of DOI:10.1021/om9604841

Organometallics 1996, 15, 5085-5089
5085
Con for m a tion a lly Rigid Dia m id e Com p lexes: Syn th esis
a n d Str u ctu r e of Tita n iu m (IV) Alk yl Der iva tives
Fre´de´ric Gue´rin,† David H. McConville,*,† and Nicholas C. Payne
Department of Chemistry, University of Western Ontario, London, Ontario, Canada N6A 5B7
Received J une 17, 1996X
Titanium complexes bearing a pyridinediamide ligand [2,6-(RNCH2)2NC5H3]2- (R ) 2,6-
diisopropylphenyl (BDPP); R ) 2,6-dimethylphenyl (BDMP)) have been synthesized. The
dichloride complexes [2,6-(RNCH2)2NC5H3]TiCl2 are prepared in high yield from {2,6-[(Me3-
Si)RNCH2]2NC5H3} and TiCl4 via the elimination of 2 equiv of CiSiMe3. Mono(alkyl) and
bis(alkyl) complexes are prepared from [2,6-(RNCH2)2NC5H3]TiCl2 and various Grignard
reagents. A single-crystal X-ray diffraction study of (BDMP)TiBr(CH2CMe2Ph)‚C6H6
(8b‚C6H6) revealed a distorted square pyramid structure with the neophenyl group occupying
the axial position.
In tr od u ction
including alkyl groups with â-hydrogens23 and meth-
ylidene ligands.24 Our interest in the steric and elec-
tronic effects of conformationally rigid ligands led us to
explore the synthesis of bulky chelating diamide ancil-
laries,25,26 in particular, amides which bear bulky 2,6-
disubstituted aryl groups. Recently, we reported that
chelating diamide complexes of the type [RN(CH2)3NR]-
TiMe2 (R ) 2,6-iPr2C6H3, 2,6-Me2C6H3) are active cata-
lyst precursors for the polymerization of R-olefins.27
Hence, we became interested in investigating the ability
of other diamide ligand systems to stabilize Ti(IV)
alkyls. We report here the synthesis, structure, and
characterization of alkyl complexes of titanium sup-
ported by a conformationally rigid diamide ligand.
The organometallic chemistry of Ti(IV) has been
dominated by complexes supported by the cyclopenta-
dienyl ligand.1 In contrast, the alkyl chemistry of Ti-
(IV) in non-Cp ligand environments remains relatively
unexplored.2-13 Amide complexes of titanium14-22 have
been shown to stabilize a number of reactive species
† Current address: Department of Chemistry, University of British
Columbia, 2036 Main Hall, Vancouver, BC, Canada V6T 1Z1.
X Abstract published in Advance ACS Abstracts, November 1, 1996.
(1) Bochmann, M. In Comprehensive Organometallic Chemistry II;
Abel, E. W.; Stone, F. G. A., Wilkinson, G., Eds.; Elsevier Science
Ltd.: New York, 1995; Vol. 4, pp 273-431.
(2) Dawoodi, Z.; Green, M. H. L.; Mtetwa, V. S. B.; Prout, K. J . Chem.
Soc., Chem. Commun. 1982, 1410.
Resu lts a n d Discu ssion
(3) Lubben, T. V.; Wolczanski, P. T.; Van Duyne, G. D. Organome-
tallics 1984, 3, 977.
(4) Duff, A. W.; Kamarudin, R. A.; Lappert, M. F.; Norton, R. J . J .
Chem. Soc., Dalton Trans. 1986, 489.
(5) J ensen, J . A.; Wilson, S. R.; Schultz, A. J .; Girolami, G. S. J .
Am. Chem. Soc. 1987, 109, 8094.
(6) Miyatake, T.; Mizunuma, K.; Seki, Y.; Kakugo, M. Makromol.
Chem., Rapid Commun. 1989, 10, 349.
(7) Floriani, C.; Corazza, F.; Lesueur, W.; Chiesi-Villa, A.; Guestini,
C. Angew. Chem., Int. Ed. Engl. 1989, 28, 66.
(8) Durfee, L. D.; Hill, J . E.; Fanwick, P. E.; Rothwell, I. P.
Organometallics 1990, 9, 75.
(9) Hill, J . E.; Fanwick, P. E.; Rothwell, I. P. Organometallics 1990,
9, 2211.
(10) Hill, J . E.; Balaich, G. J .; Fanwick, P. E; Rothwell, I. P.
Organometallics 1991, 9, 3428.
We have reported28 that the aminolysis reaction
between the diamines 2,6-(RHNCH2)2NC5H3 (R ) 2,6-
iPr2C6H3, 2,6-Me2C6H3) and Zr(NMe2)4 provides 2 equiv
of HNMe2 and the mixed amide complexes [2,6-(RNCH2)2-
NC5H3]Zr(NMe2)2 in greater than 90% yield. These
mixed amide complexes serve as excellent precursors
to dichloride derivatives. Surprisingly, no reaction
occurs between the diamines 2,6-(RHNCH2)2NC5H3 and
Ti(NMe2)4, even at elevated temperatures (110 °C).
Therefore, an alternative route to pyridinediamide
complexes of titanium was necessary.
(11) 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.
(12) Solari, E.; Floriani, C.; Chiesi-Villa, A.; Rizzoli, C. J . Chem. Soc.,
Dalton Trans. 1992, 367.
(13) van der Linden, A.; Schaverien, C. J .; Meijboom, N.; Ganter,
C.; Orpen, A. G. J . Am. Chem. Soc. 1995, 117, 3008.
(14) Bu¨rger, H.; Kluess, C. J . Organomet. Chem. 1976, 108, 69.
(15) J ones, R. A.; Seeberger, M. H.; Atwood, J . L.; Hunter, W. E. J .
Organomet. Chem. 1983, 247, 1.
The addition of 2 equiv of LiNR(SiMe3) (a , R ) 2,6-
iPr2C6H3;29 b, R ) 2,6-Me2C6H3) to a dimethoxyethane
(DME) solution of 2,6-bis(bromomethyl)pyridine30 at
-30 °C affords the white crystalline silylated diamines
(23) Cummins, C. C.; Schrock, R. R.; Davis, W. M. Organometallics
1992, 11, 1452.
(16) tom Dieck, H.; Rieger, H. J .; Fendesak, G. Inorg. Chim. Acta
1990, 177, 191.
(17) Bradley, D. C.; Chudzynska, H.; Backer-Dirks, J . D. J .; Hurst-
house, M. B.; Ibrahim, A. A.; Motevalli, M.; Sullivan, A. C. Polyhedron
1990, 9, 1423.
(18) Herrmann, W. A.; Denk, M.; Albach, R. W.; Behm, J.; Herdtweck,
E. Chem. Ber. 1991, 124, 683.
(19) Friedrich, S.; Gade, L. H.; Edwards, A. J .; McPartlin, M. J .
Chem. Soc., Dalton Trans. 1993, 2861.
(24) Scoles, L.; Minhas, R.; Duchateau, R.; J ubb, J .; Gambarotta,
S. Organometallics 1994, 13, 4978.
(25) Gue´rin, F.; McConville, D. H.; Vittal, J . J . Organometallics
1995, 14, 3154.
(26) Scollard, J . D.; McConville, D. H.; Vittal, J . J . Organometallics
1995, 14, 5478.
(27) (a) Scollard, J . D.; McConville, D. H.; Payne, N. C.; Vittal, J . J .
Macromolecules 1996, 29, 5241. (b) Scollard, J . D.; McConville, D. H.
J . Am. Chem. Soc., in press.
(20) Dick, D. G.; Duchateau, R.; Edema, J . J . H.; Gamborotta, S.
Inorg. Chem. 1993, 32, 1959.
(21) Clark, H. C. S.; Cloke, F. G. N.; Hitchcock, P. B.; Love, J . B.;
Wainwright, A. P. J . Organomet. Chem. 1995, 501, 333.
(22) Aoyagi, K.; Gantzel, P. K.; Kalai, K.; Tilley, T. D. Organome-
tallics 1996, 15, 923.
(28) Gue´rin, F.; McConville, D. H.; Vittal, J . J . Organometallics, in
press.
(29) Kennepohl, D. K.; Brooker, S.; Sheldrick, G. M.; Roesky, H. W.
Chem. Ber. 1991, 124, 2223.
(30) Haeg, M. E.; Whitlock, B. J .; Whitlock, H. W., J r. J . Am. Chem.
Soc. 1989, 111, 692.
S0276-7333(96)00484-0 CCC: $12.00 © 1996 American Chemical Society

5086 Organometallics, Vol. 15, No. 24, 1996
Gue´rin et al.
Sch em e 1
at -78 °C affords the dimethyl derivatives 3a ,b in good
yield. Compounds 3a ,b are thermally sensitive in the
absence of coordinating ligands; for example, they can
be crystallized readily from ether or THF but decompose
slowly in toluene or benzene. In contrast, the isoelec-
tronic zirconium dimethyl derivatives [2,6-(RNCH2)2-
NC5H3]ZrMe2 (R ) 2,6-iPr2C6H3, 2,6-Me2C6H3) are
thermally stable.28 Titanium dimethyl complexes bear-
ing amide ligands are known to form methylidene
species24 via R-elimination, and we are examining this
possible transformation.
The addition of 1 equiv of PhCH2MgCl or LiCH2SiMe3
to an ether suspension of 2a at 22 °C yields the
monoalkyl derivatives 4a and 5a , respectively, in high
yield (Scheme 2). The proton NMR spectra of complexes
4a and 5a show characteristic AB quartet patterns for
the methylene protons (CHAHBN) of the ligand indicat-
ing that there is asymmetry above and below the N3
plane. In addition, two isopropyl methine and four
isopropyl methyl resonances are observed which is in
agreement with the Cs symmetry of the complexes and
the restricted rotation of the N-Cipso bond. The addition
of excess alkylating reagent does not afford bis(alkyl)
derivatives; evidently, the steric bulk of the 2,6-diiso-
propylphenyl-substituted ligand precludes formation of
these species.
Sch em e 2. Alk yla tion of Com p ou n d s 2a ,ba
a
Reagents and conditions: (i) 2 equiv of MeMgBr, Et2O, -78
°C; (ii) 1 equiv of PhCH2MgCl or LiCH2SiMe3, Et2O, 22 °C;
(iii) 2 equiv of PhCH2MgCl or LiCH2SiMe3, Et2O, 22 °C; (iv) 1
equiv of NaCp‚DME or PhMe2CCH2MgCl, Et2O, -30 °C.
The alkylation chemistry of the dichloride complex 2b
clearly demonstrates the difference in steric bulk be-
tween the two ligand systems. The addition of 2 equiv
of PhCH2MgCl or LiCH2SiMe3 to an ether suspension
of 2b at 22 °C yields the bis(alkyl) derivatives 4b and
5b, respectively, in high yield (Scheme 2). The C2v
symmetry of complexes 4b and 5b is supported by the
observed singlet in the proton NMR for the methylene
protons (CH2N) of the ligand. The addition of 1 equiv
of PhCH2MgCl or LiCH2SiMe3 at -78 °C affords a 50%
2,6-[(Me3Si)RNCH2]2NC5H3 (1a ,b) in moderate yield
after workup (Scheme 1). Ligands 1a ,b can be prepared
in about 40% yield on a scale of 2-5 g. The silylated
ligand precursors react cleanly with TiCl4 to give 2 equiv
of ClSiMe3 (confirmed by 1H NMR spectroscopy) and the
red dichloride complexes (2a ,b) in >80% yield (Scheme
1). The dichlorides are insoluble in aliphatic hydrocar-
bons, slightly soluble in ether, and soluble in aromatic
solvents and THF.
The proton NMR spectra of complexes 2a ,b are
consist with a meridional coordination of the ligand as
evidenced by the singlet observed for the methylene
protons (CH2N) of the ligand. Similar shifts are ob-
served for the analogous zirconium dichloride deriva-
tives [2,6-(RNCH2)2NC5H3]ZrCl2 (R ) 2,6-iPr2C6H3, 2,6-
Me2C6H3).28 In contrast, a facial coordination geometry
is enforced by the pyridinediamide ligand in [CH(2-
C5H4N)(CH2NSiMe3)2]TiBr2.19 The isopropyl methyl
groups of complex 2a are diastereotopic, which we
interpret as a consequence of restricted rotation about
the N-Cipso bond. We have no direct spectroscopic
means of determining whether the same restricted
rotation exists in the 2,6-dimethylphenyl-substituted
derivative 2b; however, modeling studies31 and a struc-
turally characterized halooalkyl derivative (vide infra)
indicate that the barrier to rotation is likely high. The
rigid coordination of the ligand and enforced location
of the aryl groups creates a “pocket” opposite the
pyridine and necessarily protects the metal above and
below the N3 plane.
1
yield (by H NMR spectroscopy) of 4b and 5b.
The η5-cyclopentadienyl derivative 6b is obtained
from the dichloride complex 2b and 1 equiv of NaCp‚-
DME in ether (Scheme 2). No reaction is observed
between the bulkier dichloride compound 2a and NaCp‚-
DME. The proton NMR spectrum of 6b reveals a Cs-
symmetric complex as evidenced by a AB quartet
pattern for the methylene protons (CHAHBN) of the
ligand. In addition, the aryl methyl groups of 6b are
inequivalent suggesting that free rotation about the
N-Cipso bond is hindered by the presence of the Cp
group. Surprisingly, the reaction of 2b with 2 equiv of
PhMe2CCH2MgCl affords only the mono(alkyl) complex
7b and not the expected bis(neophyl) derivative. Spec-
troscopic data are consistent with a Cs-symmetric
complex and restricted rotation about the N-Cipso bond
of 7b (no evidence of N-Cipso bond rotation is observed
to 80 °C). Although we have been unable to grow X-ray-
quality crystals of complex 7b, the bromide analogue
8b does provide suitable crystals. The bromide complex
8b was obtained from complex 7b and excess MgBr2-
(OEt2) in ether (eq 1).
With the aim of preparing titanium alkyl derivatives,
the reaction of compounds 2a ,b with various alkylating
reagents has been investigated (Scheme 2). The addi-
tion of 2 equiv of MeMgBr to ether suspensions of 2a ,b
The solid-state structure of 8b‚C6H6 was determined
by X-ray crystallography (Table 1). The molecular
(31) Calculations were performed on an appropriate model using
CAChe Scientific Inc. software.

Conformationally Rigid Diamide Complexes
Organometallics, Vol. 15, No. 24, 1996 5087
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
Ta ble 2. Selected Bon d Dista n ces (Å) a n d An gles
(d eg) for 8b‚C6H6
a
P a r a m eter s for Com p ou n d 8b‚C6H6
Bond Distances
Ti-Br
2.399(2)
2.126(6)
2.121(7)
Ti-N(1)
1.979(5)
1.977(6)
empirical formula
fw
C39H44BrN3Ti
682.58
298(2)
Mo KR (0.710 73)
monoclinic
P21/n
14.892(2)
Ti-N(2)
Ti-C(8)
Ti-N(3)
temp (K)
wavelength (Å)
cryst system
space group
a (Å)
Bond Angles
N(1)-Ti-N(3)
C(8)-Ti-Br
C(8)-Ti-N(2)
C(8)-Ti-N(1)
142.1(2)
102.8(2)
101.4(3)
102.7(3)
Br-Ti-N(3)
Br-Ti-N(1)
Br-Ti-N(2)
C(8)-Ti-N(3)
100.3(2)
98.1(2)
155.8(2)
105.1(3)
b (Å)
c (Å)
14.741(3)
16.080(3)
â (deg)
98.66(2)
3489.8(12)
V (Å3)
Å above the basal plane defined by the bromide, amides,
and pyridine ligands. The Ti-amide distances (1.979-
(5) and 1.977(6) Å) are comparable to other titanium-
amide complexes.15,18,19,21-24,27 Each amide is nearly
sp2-hybridized as evidenced by the sum of the angles
about each nitrogen (N(1) ) 359.1° and N(3) ) 359.3°).
The rigid coordination of the ligand and enforced
location of the aryl methyl groups (the aryl rings lie
perpendicular to the plane of the ligand) necessarily
protects the metal above and below the N3 plane.
Z
4
F(calc) (g/cm-3
)
1.299
1.421
1424
abs coeff (mm-1
F(000)
cryst dimens (mm)
θ range for data collcn (deg)
index ranges
)
0.29 × 0.24 × 0.15
1.74-24.97
-1 e h e 17, -1 e k e 17,
-19 e l e 18
reflcns collcd
indepdt reflcns
7094
6115 [R(int) ) 0.0323]
full-matrix least squares on F2
0/403
refinement method
restraints/params
goodness of fit on F2 (GooF)
final R indices [I > 2σ(I)]
R indices (all data)
largest diff peak and
1.059
R1 ) 0.0706, wR2 ) 0.1869
R1 ) 0.1769, wR2 ) 0.2404
0.585 and -1.037
Con clu sion
A high yield route to pyridinediamide complexes of
titanium has been demonstrated. Restricted rotation
about the N-Cipso bond of the ligand and the availability
of substituted anilines provides an opportunity to vary
the sterics with little change to the electronic environ-
ment about the metal. Both mono(alkyl) and bis(alkyl)
complexes are stabilized by these pyridinediamide
ligand systems; however, the dimethyl derivatives are
thermally unstable. On the basis of preliminary results,
compounds 2a ,b show very low activities for the polym-
erization of ethylene when activated with methyl alu-
minoxane (MAO), presumably due to reduction to
Ti(III). Successful preparation of Ti(III) derivatives via
reduction of the mono(alkyl) complexes will be reported
shortly.
hole (e Å-3
)
R1 ) ∑(||Fo| - |Fc||)/∑|Fo|; wR2 ) [∑w(Fo - Fc2)2/∑wFo
] ;
a
2
4 1/2
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
Exp er im en ta l Section
Gen er a l Deta ils. All experiments were performed under
a dry dinitrogen atmosphere using standard Schlenk tech-
niques or in an Innovative Technology Inc. glovebox. Solvents
were distilled from sodium/benzophenone ketyl (DME, THF,
hexanes, diethyl ether, benzene) or molten sodium (toluene)
under argon and stored over activated 4 Å molecular sieves.
TiCl4 and MeMgBr were purchased from Aldrich and used as
received. 2,6-Diisopropylaniline and 2,6-dimethylaniline were
purchased from Aldrich and distilled under reduced pressure
before use. LiNR(SiMe3) (R ) 2,6-iPr2C6H3, 2,6-Me2C6H3) was
prepared as noted in the literature.29 A CH2Cl2 solution of
2,6-bis(bromomethyl)pyridine‚HBr30 was extracted with satu-
rated NaHCO3 to yield 2,6-bis(bromomethyl)pyridine.
MgBr2(Et2O) was made from Mg and BrCH2CH2Br in ether.
Me3SiCH2Li32 and NaC5H5‚DME33 were prepared using previ-
ously reported syntheses. Proton (300 MHz) and carbon (75.46
MHz) NMR spectra were recorded in C6D6, unless otherwise
F igu r e 1. Top: Chem 3D drawing of the molecular
structure of 8b‚C6H6. (The benzene molecule is not shown.)
Bottom: Chem 3D drawing of the core 8b‚C6H6.
noted, at approximately 22 °C on
a Varian Gemini-300
spectrometer. The proton chemical shifts were referenced to
internal C6D5H (δ ) 7.15 ppm), and the carbon resonances, to
C6D6 (δ ) 128.0 ppm). Elemental analyses were performed
by Oneida Research Services, Inc., Whitesboro, NY. Ar ) 2,6-
structure of complex 8b‚C6H6 can be found in Figure 1,
and relevant bond distances and angles, in Table 2. The
structure is best described as a distorted square pyra-
mid with the neophyl carbon (C(8)) occupying the axial
position (Figure 1). The titanium atom lies about 0.48
(32) Schrock, R. R.; Fellmann, J . D. J . Am. Chem. Soc. 1978, 100,
3359.
(33) Smart, J . C.; Curtis, C. J . Inorg. Chem. 1977, 16, 1788.

5088 Organometallics, Vol. 15, No. 24, 1996
Gue´rin et al.
diisopropylphenyl, Ar′ ) 2,6-dimethylphenyl, [2,6-(ArNCH2)2-
NC5H3]2- ) BDPP, and [2,6-(Ar′NCH2)2NC5H3]2- ) BDMP.
2,6-[(Me3Si)Ar NCH2]2NC5H3 (1a ). A DME (150 mL) solu-
tion of LiNR(SiMe3) (8.820 g, 35.53 mmol) was added slowly
to a DME (100 mL) solution of 2,6-bis(bromomethyl)pyridine
(4.621 g, 17.44 mmol) at -30 °C. The mixture was allowed to
warm to room temperature and stirred for 12 h. The solvent
was removed in vacuo and the resulting solid extracted with
hexanes (3 × 100 mL) and filtered through Celite. The volume
of the filtrate was reduced to 50 mL and cooled to -30 °C for
12 h. White crystalline 1a was isolated by filtration and dried
under vacuum (4.530 g, 7.502 mmol, 44%): 1H NMR δ 7.15 (t,
2H, Ar), 7.02 (d, 4H, Ar), 6.48 (t, 1H, py), 6.47 (d, 2H, py),
4.28 (s, 4H, NCH2), 3.31 (sept, 4H, CHMe2), 1.17 (d, 12H,
CHMe2), 0.90 (d, 12H, CHMe2), 0.27 (s, 18H, SiMe3); 13C{1H}
NMR δ 159.88, 148.69, 143.40, 135.88, 126.30, 124.24, 122.28,
58.78, 27.94, 25.18, 1.06; MS (EI) m/ z 601.423 (M+), calcd for
δ 7.21 (d, 4H, Ar), 7.08 (t, 2H, Ar), 6.91 (t, 1H, py), 6.47 (d,
2H, py), 4.73 (s, 4H, NCH2), 2.38 (s, 12H, Me), 1.08 (s, 6H,
TiMe); 13C{1H} NMR δ 163.49, 153.08, 137.50, 135.09, 129.09,
125.41, 117.13, 65.96, 62.28 (TiCH3), 18.62.
(BDP P )TiCl(CH2P h ) (4a ). To a diethyl ether (30 mL)
suspension of 2a (0.500 g, 0.870 mmol) was added 1 equiv of
PhCH2MgCl (0.62 mL, 1.4 M, 0.87 mmol) at room temperature.
The solution changed from orange to dark red within minutes
and was stirred for 12 h. The solvent was removed in vacuo.
The resulting solid was extracted with toluene (3 × 10 mL)
and filtered through Celite to give a red-brown solution. The
solvent was removed in vacuo, the solid dissolved in
a
minimum amount of hot hexanes, and the solution cooled to
-40 °C for 12 h. Red crystalline 4a was isolated by filtration
and dried under vacuum (0.418 g, 0.663 mmol, 75%): 1H NMR
δ 7.30-6.80 (Ar and CH2Ph), 6.69 (t, 1H, py), 6.54 (d, 2H,
2
CH2Ph), 6.19 (d, 2H, py), 4.92 (AB quartet, J HH ) 22.7, 4H,
C
37H59N3Si2 601.424.
NCH2), 4.71 (sept, 2H, CHMe2), 3.72 (s, 2H, CH2Ph), 3.09 (sept,
2H, CHMe2), 1.60 (d, 6H, CHMe2), 1.52 (d, 6H, CHMe2), 1.30
(d, 6H, CHMe2), 1.06 (d, 6H, CHMe2); 13C{1H} NMR δ 161.57,
154.84, 149.49, 143.83, 142.69, 138.27, 127.52, 126.66, 125.30,
124.52, 124.39, 121.81, 117.04, 79.89, 69.41, 28.87, 26.17,
25.79, 24.96, 24.81. Anal. Calcd for C38H45N3TiCl‚C6H14: C,
73.78; H, 8.72; N, 5.87. Found: C, 73.98; H, 8.42; N, 5.90.
2,6-[(Me3Si)Ar ′NCH2]2NC5H3 (1b). The preparation of
compound 1b is identical to that for 1a . LiNR(SiMe3) (4.500
g, 23.30 mmol) and 2,6-bis(bromomethyl)pyridine (3.083 g,
11.73 mmol) gave white crystalline 1b (2.389 g, 4.882 mmol,
42%): 1H NMR δ 6.88-6.98 (t, 6H, Ar), 6.72 (t, 1H, py), 6.34
(d, 2H, py), 4.18 (s, 4H, NCH2), 2.01 (S, 12H, Me), 0.23 (s, 18H,
SiMe3); 13C{1H} NMR δ 159.89, 146.32, 138.22, 135.54, 128.74,
125.09, 121.51, 56.50, 19.30, 0.87; MS (EI) m/ z (M+) 489.2997,
calcd for C29H43N3Si2 489.2995.
(BDP P )TiCl2 (2a ). A toluene solution of TiCl4 (9.37 mL,
1.04 M, 9.752 mmol) was added in small portions to a toluene
(100 mL) solution of 1a (5.880 g, 9.737 mmol) at -40 °C. The
solution immediately turned bright red, was warmed to room
temperature, and heated to 80 °C for 12 h. The solution was
filtered through Celite and the solvent removed in vacuo. The
resulting solid was washed with cold hexanes (3 × 50 mL) to
yield 2a as a bright red powder (4.450 g, 7.747 mmol, 80%):
1H NMR δ 7.14 (m, 6H, Ar), 6.75 (t, 1H, py), 6.27 (d, 2H, py),
4.87 (s, 4H, NCH2), 3.75 (sept, 4H, CHMe2), 1.53 (d, 12H,
CHMe2), 1.19 (d, 12H, CHMe2); 13C{1H} NMR δ 161.58, 154.08,
142.83, 138.88, 124.80, 117.56, 103.30, 70.60, 28.58, 26.33,
25.12. Anal. Calcd for C31H41N3TiCl2: C, 64.81; H, 7.19; N,
7.31. Found: C, 64.35; H, 7.08; N, 6.95.
(BDMP )TiCl2 (2b ). The preparation of compound 2b is
identical to that for 2a . TiCl4 (2.35 mL, 1.04 M, 2.44 mmol)
and 1b (1.088 g, 2.223 mmol) gave 2b as a red powder (0.839
g, 1.815 mmol, 82%): 1H NMR δ 6.95-7.05 (m, 6H, Ar), 6.85
(t, 1H, py), 6.36 (d, 2H, py), 4.52 (s, 4H, NCH2), 2.42 (S, 12H,
Me); 1H NMR (CD2Cl2) δ 8.09 (t, 1H, Py), 7.58 (d, 2H, py),
7.00-7.15 (m, 6H, Ar), 5.8 (s, 4H, NCH2), 2.32 (S, 12H, Me);
13C{1H} NMR (CD2Cl2) δ 163.51, 154.50, 140.29, 133.54,
129.22, 126.91, 118.96, 69.13 (CH2N), 19.48.
(BDP P )TiMe2 (3a ). To a diethyl ether (25 mL) suspension
of 2a (0.500 g, 0.870 mmol) was added 2.2 equiv of MeMgBr
(0.58 mL, 3.0 M, 1.7 mmol) at -78 °C. The solution changed
from orange to dark red within minutes and was stirred for
12 h. The solvent was removed in vacuo. The resulting solid
was extracted with toluene (3 × 10 mL) and filtered through
Celite to give a red-brown solution. The solvent was removed
in vacuo, the solid dissolved in a minimum amount of diethyl
ether, and the solution cooled to -30 °C for 12 h. Yellow
crystalline 3a was isolated by filtration and dried under
vacuum (0.314 g, 0.461 mmol, 53%). The solid is thermally
sensitive but can be stored at -40 °C to prevent decomposi-
tion: 1H NMR δ 7.02 (m, 6H, Ar), 6.76 (t, 1H, py), 6.30 (d, 2H,
py), 4.98 (s, 4H, NCH2), 3.69 (sept, 4H, CHMe2), 1.28 (d, 12H,
CHMe2), 1.11 (d, 12H, CHMe2), 1.06 (s, 6H, TiMe); 13C{1H}
NMR δ 162.93, 145.41, 137.87, 129.29, 126.33, 124.51, 117.03,
68.33, 64.40 (TiCH3), 28.11, 28.04, 24.35.
(BDP P )TiCl(CH2SiMe3) (5a ). To a diethyl ether (30 mL)
suspension of 2a (0.500 g, 0.870 mmol) was added 1 equiv of
LiCH2SiMe3 (0.082 g, 0.871 mmol) at room temperature. The
solution changed from orange to yellow within minutes and
was stirred for 12 h. The solvent was removed in vacuo. The
resulting solid was extracted with toluene (3 × 10 mL) and
filtered through Celite. The solvent was removed in vacuo,
the solid dissolved in a minimum amount of diethyl ether, and
the solution cooled to -40 °C for 12 h. Yellow crystalline 5a
was isolated by filtration and dried under vacuum (0.430 g,
0.687) mmol, 79%): 1H NMR δ 7.25-7.15 (Ar), 6.83 (t, 1H,
py), 6.38 (d, 2H, py), 5.07 (AB quartet, 2J HH ) 22.0, 4H, NCH2),
4.39 (sept, 2H, CHMe2), 3.25 (sept, 2H, CHMe2), 2.89 (s, 2H,
CH2Si), 1.54 (d, 6H, CHMe2), 1.45 (d, 6H, CHMe2), 1.40 (d, 6H,
CHMe2), 1.11 (d, 6H, CHMe2), -0.18 (s, 9H, SiMe3); 13C{1H}
NMR δ 162.76, 154.21, 143.74, 142.95, 138.62, 127.00, 126.52,
124.77, 124.35, 117.31, 83.70, 69.47, 38.83, 27.66, 26.81, 26.34,
25.28, 24.63, 2.34. Anal. Calcd for C35H52N3SiTiCl: C, 67.13;
H, 8.37; N, 5.71. Found: C, 67.08; H, 8.44; N, 5.79.
(BDMP )Ti(CH2P h )2 (4b). To a diethyl ether (30 mL)
suspension of 2b (0.100 g, 0.216 mmol) was added 2.2 equiv
of PhCH2MgCl (2.2 mL, 0.22 M, 0.48 mmol) at room temper-
ature. The solution changed from orange to dark red within
minutes and was stirred for 12 h. The solvent was removed
in vacuo. The resulting solid was extracted with toluene (3 ×
10 mL) and filtered through Celite to give a red-brown solution.
The volume of the solvent was reduced (5 mL) and the solution
cooled to -40 °C. Dark red crystalline 4b was isolated by
filtration (0.089 g, 0.124 mmol, 72%): 1H NMR δ 7.17 (d, 4H,
Ar), 7.05 (m, 2H, Ar), 6.88 (t, 4H, CH2Ph), 6.77 (t, 1H, py),
6.62 (t, 2H, CH2Ph), 6.60 (d, 4H, CH2Ph), 6.25 (d, 2H, py), 4.59
(s, 4H, NCH2), 2.62 (s, 4H, CH2Ph), 2.46 (s, 12H, Me); 13C{1H}
NMR δ 161.85, 156.88, 145.89, 137.83, 134.43, 129.26, 128.63,
125.49, 124.81, 122.31, 118.16, 116.83, 65.49, 19.92.
(BDMP )Ti(CH2SiMe3)2 (5b). To a diethyl ether (30 mL)
suspension of 2b (0.100 g, 0.216 mmol) was added 2.2 equiv
of LiCH2SiMe3 (0.045 g, 0.476 mmol) at -40 °C. The solution
changed from orange to yellow within minutes and was stirred
for 12 h. The solvent was removed in vacuo. The resulting
solid was extracted with toluene (3 × 10 mL) and filtered
through Celite. The solvent was removed in vacuo, the solid
dissolved in a minimum amount of hexanes, and the solution
cooled to -40 °C for 12 h. Yellow crystalline 5b was isolated
by filtration and dried under vacuum (0.112 g, 0.198 mmol,
92%): 1H NMR δ 7.17 (d, 4H, Ar), 7.03 (m, 2H, Ar), 6.89 (t,
1H, py), 6.45 (d, 2H, py), 4.76 (s, 4H, NCH2), 2.52 (s, 12H, Me),
1.84 (s, 4H, CH2Si), -0.19 (s, 18H, SiMe3); 13C{1H} NMR δ
(BDMP )TiMe2 (3b). The preparation of compound 3b is
identical to that for 3a . 2b (0.100 g, 0.216 mmol) and 2.2 equiv
of MeMgBr (0.2 mL, 2.40 M, 0.48 mmol) gave yellow crystalline
3b (0.072 g, 0.171 mmol, 79%). The solid is thermally sensitive
but can be stored at -40 °C to prevent decomposition: 1H NMR

Conformationally Rigid Diamide Complexes
Organometallics, Vol. 15, No. 24, 1996 5089
162.64, 156.36, 138.17, 134.07, 129.35, 125.29, 117.10, 83.16,
66.23, 19.62, 2.38.
CH2CMe2), 2.80 (s, 6H, Me), 2.03 (s, 6H, Me), 1.08 (S, 6H,
CH2CMe2); 13C{1H} NMR δ 163.36, 158.33, 152.80, 138.22,
133.34, 132.51, 129.03, 128.88, 125.53, 125.51, 117.28, 102.03,
66.50, 46.89, 31.96, 20.78, 19.66. Anal. Calcd for
(BDMP )TiCl(η5-C5H5) (6b). To a diethyl ether (30 mL)
suspension of 2b (0.100 g, 0.216 mmol) was added 1.3 equiv
of NaC5H5‚DME (0.049 g, 0.275 mmol) at -40 °C. The solution
changed from orange to yellow within minutes and was stirred
for 12 h. The solvent was removed in vacuo. The resulting
solid was extracted with toluene (3 × 10 mL) and filtered
through Celite. The solvent was removed in vacuo, the solid
dissolved in a minimum amount of diethyl ether, and the
solution cooled to -40 °C for 12 h. Orange crystalline 6b was
isolated by filtration and dried under vacuum (0.097 g, 0.197
mmol, 77%): 1H NMR δ 7.17-7.00 (m, 7H, Ar and py), 6.50
C
33H38N3TiBr‚C6H6: C, 68.62; H, 6.50; N, 6.16. Found: C,
68.61; H, 6.69; N, 5.76.
X-r a y Cr ysta llogr a p h ic An a lysis. A suitable crystal of
4b was grown from a saturated THF/benzene solution at room
temperature. Crystal data may be found in Table 1. Data
were collected on a Enraf-Nonius CAD4F diffractometer using
CAD4F software.34 Intensity data were recorded in ω-2θ scan
mode at variable scan speeds within a maximum time per
datum of 45 s. Moving background estimates were made at
25% scan extensions on each side. Standard reflections were
monitored every 180 min of X-ray exposure time. Lorentz,
polarization, and decay corrections were applied. Crystal faces
were identified by optical goniometry, and a Gaussian absorp-
tion correction made to the data, which were averaged to yield
6115 unique data for structure solution and refinement. The
structure was solved by a combination of SHELXS and
difference Fourier syntheses using SHELXL-93 software.35
Anisotropic thermal parameters were refined for all non-
hydrogen atoms. All phenyl hydrogen atoms were located by
difference Fourier methods, placed in calculated positions
(C-H ) 0.9 Å), and included in the structure factor calcula-
tions. The four methyl groups C(27), C(28), C(37), and C(38)
showed disorder. The idealized tetrahedral groups were
assigned 0.5 multiplicities. The benzene solvent molecule
showed considerable thermal motion but refined well to an
acceptable geometry.
2
(d, 2H, py), 6.02 (s, 5H, Cp), 4.47 (AB quartet, J HH ) 21.83
Hz, 4H, NCH2), 2.44 (s, 6H, Me), 1.80 (s, 6H, Me); 13C{1H}
NMR δ 163.98, 159.76, 136.62, 133.44, 130.99, 129.29, 128.52,
124.53, 119.63 (Cp), 116.15, 69.26, 18.65.
(BDMP )TiCl(CH2CMe2P h ) (7b). To a diethyl ether (30
mL) suspension of 2b (0.400 g, 0.865 mmol) was added 1.1
equiv of PhMe2CCH2MgCl (1.09 mL, 0.867 M, 0.952 mmol) at
-40 °C. The solution changed from orange to dark red within
minutes and was stirred for 12 h. The solvent was removed
in vacuo. The resulting solid was extracted with toluene (3 ×
10 mL) and filtered through Celite. The solvent was removed
in vacuo, the solid dissolved in a minimum amount of a 20:1
mixture of THF/benzene, and the solution cooled to -40 °C
for 12 h. Red crystalline 7b was isolated by filtration and dried
under vacuum (0.400 g, 0.627 mmol, 72%): 1H NMR δ 7.19-
6.98 (m, 11H, Ar and Ph), 6.89 (t, 1H, py), 6.39 (d, 2H, py),
2
4.59 (AB quartet, J HH ) 21.98 Hz, 4H, NCH2), 2.92 (s, 2H,
CH2CMe2), 2.75 (s, 6H, Me), 2.10 (s, 6H, Me), 1.10 (s, 6H,
CH2CMe2); 13C{1H} NMR δ 163.38, 157.73, 152.96, 138.26,
133.36, 132.50, 128.99, 128.87, 125.55, 125.42, 125.22, 117.35,
97.42, 66.33, 46.33, 32.05, 20.67, 18.50. Anal. Calcd for
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.
C
33H38N3TiCl‚C6H6: C, 73.40; H, 6.95; N, 6.48. Found: C,
73.60; H, 7.26; N, 6.16.
Su p p or tin g In for m a tion Ava ila ble: Text describing
X-ray procedures, tables of final crystallographic atomic
coordinates, equivalent isotropic thermal parameters, hydro-
gen atom parameters, anisotropic thermal parameters, and
complete bond lengths and angles, and ORTEP diagrams for
8b‚C6H6 (11 pages). Ordering information is given on any
current masthead page.
(BDMP )TiBr (CH2CMe2P h ) (8b). To a diethyl ether (30
mL) solution of 7b (0.400 g, 0.714 mmol) was added 10 equiv
of MgBr2(Et2O) (2.373 g, 7.14 mmol) at room temperature. The
solution was stirred for 12 h. The solvent was removed in
vacuo. The resulting solid was extracted with toluene (3 ×
10 mL) and filtered through Celite. The solvent was removed
in vacuo, the solid dissolved in a minimum amount of a 20:1
mixture of THF/benzene, and the solution cooled to -40 °C
for 12 h. Red crystalline 8b was isolated by filtration and dried
under vacuum (0.356 g, 0.522 mmol, 73%): 1H NMR δ 7.19-
6.98 (m, 11H, Ar and Ph), 6.86 (t, 1H, py), 6.36 (d, 2H, py),
OM9604841
(34) Enraf-Nonius. Enraf-Nonius Data Collection Package, Version
5.0, Enraf-Nonius, Delft, The Netherlands, 1984.
(35) Sheldrick, G. M. SHELXL-93, Institute fuer Anorg. Chemie,
Goettingen, Germany, 1993.
2
4.59 (AB quartet, J HH ) 21.98 Hz, 4H, NCH2), 2.95 (s, 2H,