Synthesis, structural determination, and ethylene polymerization chemistry of mono(salicylaldiminato) complexes of titanium(IV)

Article abstract of DOI:10.1016/S0022-328X(03)00454-6

Titanium(IV)mono(salicylaldiminato) complexes [L¹Ti(NMe₂)₃] (1) and [L¹TiCl₃] (2) have been synthesized by treatment of Ti(NMe₂)₄ or TiCl₄ with one equivalent of [4,6-Bu₂^t-2- (CH=NBu^t)C₆H₃OH] (L¹H) or [4,6-Bu₂^t-2-(CH=NBu^t) C₆H₃OSiMe₃] (L¹SiMe₃), respectively. The compounds are monomeric in solution and in the solid-state. Reactions of TiCl₄ with one equivalent of [4,6-Bu₂^t-2-(CH=NCH₂Ph) C₆H₃OH] (L²H) and [4,6-Bu₂^t-2-{CH=N(2- C₆H₄OH)}C₆H₃OH] (L³H₂) produced [L²TiCl₂ (μ-Cl)]₂ (3) and [L³TiCl₂] ₂ (4), respectively. [L³TiCl₂(THF)] (5) was also produced in quantitative yield when 4 was stirred in THF for 16 h. The reaction of TiCl₄ with L³H₂ (Two equivalents) in toluene gave [(L³)₂Ti] (6). The molecular structures of 2-4 and 6 were established by single-crystal X-ray diffraction studies; and 4 displayed a rare face to face π-π stacking interaction in its structure. Compounds 1 and 2 showed modest ethylene polymerization activities at 25 °C with 900 molar equivalents of methylalumoxane (MAO) as co-catalyst.

Full text of DOI:10.1016/S0022-328X(03)00454-6

Journal of Organometallic Chemistry 678 (2003) 134Á141
/
www.elsevier.com/locate/jorganchem
Synthesis, structural determination, and ethylene polymerization
chemistry of mono(salicylaldiminato) complexes of titanium(IV)
David Owiny, Sean Parkin, Folami T. Ladipo *
Department of Chemistry, University of Kentucky, Lexington, KY 40506-0055, USA
Received 20 February 2003; received in revised form 9 May 2003; accepted 15 May 2003
Abstract
Titanium(IV)mono(salicylaldiminato) complexes [L1Ti(NMe2)3] (1) and [L1TiCl3] (2) have been synthesized by treatment of
Ti(NMe2)4 or TiCl4 with one equivalent of [4; 6-But2-2-(CHÄNBut)C6H3OH] (L1H) or [4; 6-Bu2t -2-(CHÄNBut)C6H3OSiMe3]
(L1SiMe3), respectively. The compounds are monomeric in solution and in the solid-state. Reactions of TiCl4 with one equivalent
of [4; 6-But2-2-(CHÄNCH2Ph)C6H3OH] (L2H) and [4; 6-Bu2t -2-fCHÄN(2-C6H4OH)gC6H3OH] (L3H2) produced [L2TiCl2(m-Cl)]2 (3)
and [L3TiCl2]2 (4), respectively. [L3TiCl2(THF)] (5) was also produced in quantitative yield when 4 was stirred in THF for 16 h. The
reaction of TiCl4 with L3H2 (Two equivalents) in toluene gave [(L3)2Ti] (6). The molecular structures of 2Á
/4 and 6 were established
by single-crystal X-ray diffraction studies; and 4 displayed a rare face to face pÁ
/
p stacking interaction in its structure. Compounds 1
and 2 showed modest ethylene polymerization activities at 25 8C with 900 molar equivalents of methylalumoxane (MAO) as co-
catalyst.
# 2003 Elsevier Science B.V. All rights reserved.
Keywords: Titanium(IV) complexes; Olefin polymerization; Salicylaldiminato ligands; Schiff base ligands
1. Introduction
plexes in olefin polymerization chemistry, few mono(sa-
licylaldiminato)titanium(IV) complexes have been
described and their reaction chemistry is poorly devel-
oped [3,4]. This is surprising since salicylaldimines
There has been a great deal of interest in the
development of well-defined transition metal catalysts
for the polymerization of a-olefins since the discovery of
highly active Group 4 metallocene catalysts [1]. A wide
variety of ligand environments and transition metals
have been investigated and olefin polymerization cata-
lysts based on both early- and late transition metals have
been developed, some of which show activities superior
or comparable to those of Group 4 metallocenes [2]. In
fact, Group 4 metal complexes based on chelating
di(amido)- 2c2d2e2f, amine-bis(phenolato)- 2n, or
bis(salicylaldiminato) 2h2i2j2k ligands have furnished
highly active and/or living olefin polymerization cata-
lysts. However, despite extensive investigation of orga-
nometallic complexes of salicylaldiminato ligands and
the utility of bis(salicylaldiminato)titanium(IV) com-
(HOC6H4CHÄ
/
NR, Rꢀalkyl or aryl) are obtained by
/
easy synthetic routes and hence their steric and electro-
nic properties can be readily tuned, via substitution of
the aromatic ring or modification of the imino nitrogen
substitutent 2h2d2e2f2g2h2k[3]. Herein, we describe the
synthesis, X-ray crystallographic characterization, and
ethylene polymerization chemistry of mono(salicylaldi-
minato)titanium(IV)
[f4; 6-But2-2-(CHÄNBut)C6H3OgTiCl3]
complexes
(1) and
[f4; 6-But2-2-(CHÄNBut)C6H3OgTi(NMe2)3] (2).
2. Experimental
2.1. General
Ti(NMe2)4 [5], TiCl4(THF)2 [6], and salicylaldimine
compounds, 4,6-bis(tert-butyl)-2-{(tert-butyl)imino-
methyl}phenol [4; 6-But2-2-(CHÄNBut)C6H3OH] (L1H)
* Corresponding author. Tel.: ꢁ
1069.
E-mail address: fladip0@uky.edu (F.T. Ladipo).
/
1-859-257-7084; fax: ꢁ1-859-323-
/
0022-328X/03/$ - see front matter # 2003 Elsevier Science B.V. All rights reserved.
doi:10.1016/S0022-328X(03)00454-6

D. Owiny et al. / Journal of Organometallic Chemistry 678 (2003) 134Á
/141
135
[7], 4,6-bis(tert-butyl)-2-{(benzyl)iminomethyl}phenol
[4; 6-But2-2-(CHÄNCH2Ph)C6H3OH] (L2H) [8], and
4,6-bis(tert-butyl)-2-{(2-hydroxyphenyl)imino-
2.3. Synthesis of titanium compounds 1Á
/
6
2.3.1. [L1Ti(NMe2)3] (1)
methyl}phenol
A toluene (15 ml) solution of L1H (0.381 g, 1.32
mmol) was added drop-wise to a stirred toluene (8 ml)
solution of [Ti(NMe2)4] (0.297 g, 1.33 mmol) at r.t. After
[4; 6-But2-2-fCHÄN(2-C6H4OH)gC6H3OH] (L3H2) [9],
were prepared via modifications of literature methods.
All other experiments were performed under dry nitro-
gen atmosphere using standard Schlenk techniques or in
a MBraun glovebox. Benzene-d6, toluene, tetrahydro-
furan, pentane, and heptane were distilled from sodium
benzophenone ketyl (with 1 ml lꢂ1 of teraethyleneglycol
dimethyl ether added as a solubilizing agent in the case
of pentane and heptane). CD2Cl2 and CDCl3 were
distilled from calcium hydride. All solvents were stored
in the glovebox over 4A molecular sieves that had been
dried under vacuum at 150 8C for at least 48 h prior to
use. All other chemicals were purchased from Aldrich
Chemical Co. and used without further purification
(unless otherwise stated). 1H- and 13C-NMR spectra
were recorded on a Varian Gemini-200 spectrometer or
completion of the addition, the yellowÁ
mixture was stirred for 20 min. The solution was
stripped under reduced pressure to give a yellowÁorange
crystalline solid. Yield: 0.538 g, 92%. H-NMR (C6D6):
d 8.52 (s, 1H, ButNÄ
CH), 7.73 (d, 1H, JHH 2.4, arom
CH), 7.33 (d, 1H, JHH 2.4, arom CH), 3.20 (s, 18H,
NMe2), 1.66 (s, 9H, But), 1.38 (s, 9H, But), 1.06 (s, 9H,
CH), 160.9,
/
orange reaction
/
1
/
ꢀ
/
ꢀ
/
NBut). 13C-NMR (C6D6): d 166.5 (ButNÄ
/
140.2, 139.7, 129.3, 128.7, 122.6, 60.6 (NCMe3), 46.7
(NMe2), 35.9 (CMe3), 34.6 (CMe3), 32.0 (CMe3), 31.2
(CMe3), 30.1 (NCMe3). IR (CH2Cl2, cmꢂ1): 1612 n(CÄ
N). Anal. Calc. for C25H48N4OTi: C, 64.09; H, 10.32; N,
11.96. Found: C, 63.97; H, 10.10; N, 11.67%.
/
1
a Varian VXR-400 spectrometer at ca. 22 8C. H- and
2.3.2. [L1TiCl3] (2)
13C-chemical shifts were referenced to residual solvent
peaks. Infrared spectra were recorded on a Nicolet
Magna 560 spectrometer. Mass spectral data were
obtained from the University of Kentucky Mass Spec-
trometry Center on a Thermo Finnigan (San Jose, CA)
Polaris Q (quadruple ion trap) spectrometer. Elemental
analyses were performed by Complete Analysis Labora-
tories, Inc., Parsippany, NJ.
A toluene (12 ml) solution of L1SiMe3 (1.07 g, 3.27
mmol) was added drop-wise to a stirred toluene (20 ml)
solution of TiCl4 (0.830 g, 4.36 mmol) at 0 8C (ice bath).
Upon complete addition, the solution was stirred (0Á
/
2 8C) for 4 h. The resulting orangeÁbrown precipitate
/
was collected by filtration at r.t., washed once with
toluene (10 ml), and dried under vacuum. Yield: 0.830 g,
58%. 1H-NMR (CDCl3): d 8.59 (s, 1H, ButNÄ
/
CH),
2.4, arom CH), 7.44 (d, 1H, JHH
2.4, arom CH), 1.76 (s, 9H, But), 1.53 (s, 9H, But), 1.37
(s, 9H, NBut). 13C-NMR (CDCl3): d 163.7 (ButNÄ
7.66 (d, 1H, JHH
ꢀ
/
ꢀ
/
2.2. Synthesis of [4; 6-But2-2-(CHÄNBut)C6H3OSiMe3]
(L1SiMe3)
/
CH), 157.9, 144.7, 141.6, 134.1, 127.2, 118.2, 60.9
(NCMe3), 35.4 (CMe3), 35.0 (CMe3), 31.5 (CMe3),
30.1 (CMe3), 28.3 (NCMe3). IR (CH2Cl2, cmꢂ1): 1604
A Et2O (5 mL) solution of KOBut (257 mg, 2.29
mmol) was added in two portions to a Et2O (10 ml)
solution of 4,6-bis(tert-butyl)-2-{(tert-butyl)imino-
methyl}phenol (L1H, 54.4 mg, 1.88 mmol) at room
temperature (r.t.). The reaction mixture was allowed to
stir for 0.5 h, after which the yellowish-white precipitate
was collected by filtration under N2 atmosphere. After
washing the precipitate several times with Et2O, it was
put back into Et2O. Me3SiCl (0.25 ml, 1.97 mmol) was
added to the Et2O suspension and the resulting mixture
was stirred for 20 min. The reaction mixture was
stripped to dryness under reduced pressure, the residue
was extracted with pentane, and the solvent was
removed under vacuum to give a yellowish-white
crystalline solid. Yield: 0.510 g, 75%. 1H-NMR
n(CÄ
/
N). Anal. Calc. for C19H30Cl3NOTi: C, 51.55; H,
6.83. Found C, 51.52; H, 6.82%.
2.3.3. [L2TiCl2(m-Cl)]2 (3)
A heptane (18 ml) solution of L2H (1.15 g, 3.55 mmol)
was added drop-wise to a stirred heptane (30 ml)
solution of TiCl4 (0.690 g, 3.64 mmol) at ꢂ78 8C. After
the addition was complete, the brick-red reaction
mixture was allowed to warm gradually up to r.t. and
/
stirred for ꢀ
was collected by filtration, washed with pentane (4ꢃ
ml), and dried under vacuum to give an orangeÁred
powder. Yield: 3.01 g, 89%. H-NMR (CDCl3): d 8.22
(s, 1H, PhCH2NÄCH), 7.65(d, 1H, JHH 2.0, arom
CH), 7.55Á7.34 (m, 5H, PhCH2), 7.16 (d, 1H, JHH
2.0, arom CH), 5.36 (s, 2H, PhCH2), 1.54 (s, 9H, But),
1.30 (s, 9H, But). 13C-NMR (CDCl3):
166.1
(PhCH2NÄCH), 161.6, 148.4, 136.8, 135.6, 131.3,
/
10 h. The resulting redÁ/brown precipitate
/
15
/
1
/
ꢀ
/
(CDCl3): d 8.51 (s, 1H, ButNÄ
/
CH), 7.73 (d, 1H,
/
ꢀ
/
JHH
ꢀ
/
6.0 Hz, arom CH), 7.41 (d, 1H, JHH
ꢀ5.6 Hz,
/
arom CH), 1.41 (s, 9H, But), 1.32 (s, 18H, But, NBut),
d
0.32 (s, 9H, SiMe3). 13C-NMR (CDCl3): d 153.8
/
(ButNÄ
57.8 (NCMe3), 34.6 (CMe3), 34.3 (CMe3), 31.6 (CMe3),
/CH), 152.3, 143.7, 140.2, 128.8, 127.1, 123.1,
130.6, 129.5, 129.1, 129.0, 124.9, 63.2 (PhCH2), 35.4
(CMe3), 35.1 (CMe3), 31.4 (CMe3), 29.76 (CMe3). MS
(EI, 70 eV, m/z): 869 [MꢁꢂCl]. IR (CHCl2, cmꢂ1):
30.9 (CMe3), 30.0 (NCMe3), 2.3 (SiMe3).
/

136
D. Owiny et al. / Journal of Organometallic Chemistry 678 (2003) 134Á141
/
1613 n(CÄ
/
N). Anal. Calc. for C44H56 Cl6N2O2Ti2: C,
r.t. and stirred for ꢀ
filtered and the precipitate was washed with pentane
(3ꢃ15 ml), then dried under vacuum. Yield: 0.202 g,
71%. 1H-NMR (CDCl3,): d 8.86 (s, 2H, NÄ
CH), 7.46 (s,
2H, arom CH), 7.34 (d, 2H, JHH 8.0, arom CH), 7.32
(s, 2H, arom CH), 7.04 (t, 2H, JHH 8.0, arom CH),
6.75 (t, 2H, JHH 8.0, arom CH), 6.56 (d, 2H, JHH
8.0, arom CH), 1.34 (s, 18H, But), 1.13 (s, 18H, But).
CH), 158.0, 142.2,
/
16 h. The resulting red mixture was
55.43; H, 5.92. Found: C, 55.26; H, 5.73%.
/
2.3.4. [L3TiCl2]2 (4)
A toluene (20 ml) solution of L3H2 (0.435 g, 1.33
mmol) was added drop-wise to a stirred toluene (5 ml)
/
ꢀ
/
ꢀ
/
solution of TiCl4 (0.259 g, 1.36 mmol) at ꢂ
the addition was complete, the initially orangeÁ
reaction mixture was allowed to warm gradually up to
r.t. and stirred for ꢀ10 h. The resulting brown mixture
was filtered and the precipitate was washed with pentane
(3ꢃ15 ml), then dried under vacuum. Yield: 0.923 g,
79%. 1H-NMR (CDCl3): d 8.82 (s, 2H, NÄ
CH), 7.72 (d,
2H, JHH 2.4, arom CH), 7.38 (d, 2H, JHH 2.2 arom
CH), 7.34 (d, 2H, JHH 8.0, arom CH), 7.26 (t, 2H,
JHH 8.0 arom CH), 6.95 (t, 2H, JHH 8.0, arom CH),
6.82 (d, 2H, JHH
8.0, arom CH), 1.55 (s, 18H, But),
1.37 (s, 18H, But). 13C-NMR (CDCl3): d 157.9 (NÄ
/
78 8C. After
ꢀ
/
ꢀ
/
/red
13C-NMR (CDCl3): d 161.5 (NÄ
/
/
138.7, 136.6, 131.9, 130.1, 128.4, 121.7, 119.4, 115.2,
114.2, 35.0 (CMe3), 34.5 (CMe3), 31.5 (CMe3), 29.4
/
(CMe3). IR (CH2Cl2, cmꢂ1): 1604 n(CÄ
/
N). MS (EI, 70
eV, m/z): 694 [Mꢁ]. A sample of 6 was recrystallized
/
ꢀ
/
ꢀ
/
from CHCl3 prior to microanalysis. The resulting
ꢀ
/
crystals contained lattice CHCl3 molecules, ꢀ
of a CHCl3 molecule per titanium. Anal. Calc. for
(CHCl3)0.33: C, 69.20; H, 6.90; N, 3.81.
/
one-third
ꢀ
/
ꢀ
/
ꢀ
/
C42H50N2O4Ti×
/
/
Found: C, 69.58; H, 6.96; N, 4.03%.
CH), 146.7, 137.3, 133.6, 131.2, 129.5, 129.3, 128.4,
125.5, 122.5, 115.1, 114.7, 35.5 (CMe3), 34.86 (CMe3),
31.39 (CMe3), 29.92 (CMe3). MS (EI, 70 eV, m/z): 849
2.4. Ethylene polymerization studies
[MꢁꢂCl]. IR (CH2Cl2, cmꢂ1): 1600 n(CÄ
/
/
N). A sample
of 4 was recrystallized from CHCl3 prior to microana-
lysis and gave [L3TiCl2]2×
2CHCl3. Anal. Calc. for
Toluene (60 ml) was charged into a 250 ml two-
necked Schlenk flask under N2 atmosphere in a glove-
box. An excess of MAO (Al/Ti ratioꢀ900/1) was added
/
/
C44H52Cl10N2O4Ti2: C, 47.07; H, 4.64; N, 2.49. Found:
and the solution was stirred for several minutes. Next,
the catalyst precursor (0.027 mmol of Ti) was added as a
solid and the solution was stirred for 30 min. The N2
atmosphere was replaced with ethylene (passed through
a column of BASF catalyst R3-11 and a solution of
MAO) and the pressure was maintained at 1 atmosphere
by slow bubbling through the solution and controlling
the pressure with a bubbler at the outlet. The polymer-
ization was carried out for 10 min. Polymerizations were
quenched with MeOH (30 ml) and then 1 M HCl
solution (30 ml). The resulting suspension was vigor-
ously stirred until both layers were colorless and clearly
C, 47.64; H, 4.99; N, 2.23%.
2.3.5. [L3TiCl2(THF)] (5)
A toluene (6 ml) solution of L3H2 (0.155 g, 0.476
mmol) was added drop-wise to a stirred toluene (5 ml)
suspension of [TiCl4(THF)2] (0.153 g, 0.459 mmol) at
ꢂ
/
78 8C. After the addition was complete, the initially
orangeÁred reaction mixture was allowed to warm
gradually up to r.t. and stirred for ꢀ16 h. The resulting
brownÁblack mixture was filtered and the precipitate
was washed with pentane (2ꢃ10 ml), then dried under
vacuum. Yield: 0.137 g, 58%. 1H-NMR (CDCl3): d 8.46
(s, 1H, NÄCH), 7.55 (d, 1H, JHH 2.2, arom CH), 7.26
(t, 1H, JHH 8.0, arom CH), 7.18 (d, 1H, JHH 2.0,
arom CH), 7.09 (t, 1H, JHH 8.0, arom CH), 6.80 (t,
1H, JHH 8.0, arom CH), 6.49 (d, 1H, JHH 8.0, arom
/
/
/
/
separated (ꢀ10 min). Polyethylene was filtered off,
/
/
ꢀ
/
washed with 1 M HCl, and MeOH then dried at 70 8C
for 48 h.
ꢀ
/
ꢀ
/
ꢀ
/
ꢀ
/
ꢀ
/
2.5. Crystallographic study
CH), 4.20 (m, 4H, THF), 1.93 (m, 4H, THF), 1.47 (s,
9H, But), 1.33 (s, 9H, But). 13C-NMR (CDCl3): d 162.0
The crystal data for [L2TiCl2(m-Cl)]2 (3), [L3TiCl2]2
(4), and [(L3)2Ti] (6) are collected in Table 1. Further
details of the crystallographic study are given in Section
5.
(NÄ
/
CH), 160.6, 156.1, 145.4, 139.0, 136.7, 133.0, 131.2,
129.7, 124.2, 122.0, 114.6, 114.2, 73.2 (THF), 35.3
(CMe3), 34.7 (CMe3), 31.4 (CMe3), 30.0 (CMe3), 25.6
(THF). IR (CH2Cl2, cmꢂ1): 1604 n(CÄ
/N). Anal. Calc.
for C25H33Cl2NO3Ti: C, 58.39; H, 6.47; N, 2.72. Found:
C, 58.34; H, 6.22; N, 2.92%.
3. Results and discussion
2.3.6. [(L3)2Ti] (6)
The synthesis of the salicylaldiminato complexes of
titanium described in this report is summarized in
Scheme 1. The mono(salicylaldiminato)titanium(IV)
complex [L1Ti(NMe2)3] (1) was isolated in excellent
yield from reaction of Ti(NMe2)4 with one equivalent of
A toluene (6 ml) solution of L3H2 (0.256 g, 0.786
mmol) was added drop-wise to a stirred toluene (6 ml)
solution of TiCl4 (77.0 mg, 0.409 mmol) at ꢂ78 8C.
After the addition was complete, the initially red
reaction mixture was allowed to warm gradually up to
/
[4; 6-But2-2-(CHÄNBut)C6H3OH] (L1H) in toluene at ꢀ
/

D. Owiny et al. / Journal of Organometallic Chemistry 678 (2003) 134Á
/141
137
Table 1
Crystallographic data for 3×
/
C5H12, 4×
/
CHCl3, and 6×/CH2Cl2
3×C5H12
/
4×
/
CHCl3
6×CH2Cl2
/
Empirical formula
Formula weight
Temperature (K)
Crystal system
Space group
C49H68Cl6N2O2Ti2
1025.55
150(2)
C42.50H50.50Cl5.50 N2O4Ti2
944.12
90(2)
C43H52Cl2N2O4Ti
779.67
90(2)
Monoclinic
P21/c
Tetragonal
P-421c
15.9770(2)
15.9770(2)
17.5674(3)
90
Triclinic
¯
P1
/
˚
a (A)
12.4720(5)
21.1090(8)
19.7410(7)
90
11.7557(6)
14.2041(7)
14.2328(7)
104.837(3)
113.565(3)
99.152(3)
2012.01(17)
2
˚
b (A)
˚
c (A)
a (8)
b (8)
g (8)
V (A )
Z
90.6330(18)
90
90
90
3
˚
5196.9(3)
4
1.311
4484.33(11)
4
1.398
Dcalc (g cmꢂ3
)
1.287
0.0892, 0.1456
0.1207, 0.1544
Final R indices [I ꢁ
wR2, R1 (all data)
/
2s(I)]: R1, wR2
0.0789, 0.1598
0.1033, 0.1695
0.0378, 0.0717
0.0470, 0.0741
25 8C. The reaction between TiCl4 and L1H (one
equivalent) in heptane did not cleanly produce mono(sa-
licylaldiminato)titanium trichloride [L1TiCl3] (2) [10].
Instead, 2 was obtained in excellent yield from the
reaction of TiCl4 with one equivalent of
[4; 6-But2-2-(CHÄNBut)C6H3OSiMe3] (L1SiMe3) in tolu-
ene at 0 8C. Clean silylation of L1H was achieved as
shown in Eq. (1). Reaction of TiCl4 with one equivalent
of [4; 6-But2-2-(CHÄNCH2Ph)C6H3OH] (L2H) or
[4; 6-But2-2-fCHÄN(2-C6H4OH)gC6H3OH] (L3H2) at
ꢂ
/
78Á
25 8C produced [L2TiCl2(m-Cl)]2 (3) and
/
[L3TiCl2]2 (4), respectively. The fact that 3 and 4 are
dimers likely reflects the reduced steric constraint on
titanium by the respective salicylaldiminate ligand in
comparison to [4,6-/
But2
/
-2-(CHÄ
/
NBut)C6H3Oꢂ] (L1).
Consistent with this suggestion, the reaction of
TiCl4(THF)2 with L3H2 (one equivalent) in toluene
afforded monomeric [L3TiCl2(THF)] (5), which was
also produced in quantitative yield when 4 was dissolved
in THF and stirred for 16 h. [(L3)2Ti] (6) was obtained in
good yield from the reaction between TiCl4 and L3H2
(two equivalents) in toluene at ꢂ
/
78Á25 8C.
/
ð1Þ
All of the compounds 1Á
sensitive, thermally stable red to redÁ
/
6 are air- and moisture-
brown solids. They
/
are conveniently stored in the solid-state under N2
atmosphere at ambient temperature without any ob-
servable decomposition. All of the compounds are
readily soluble in polar hydrocarbon solvents, such as
THF, chloroform, and dichloromethane, and are prac-
tically insoluble in aliphatic hydrocarbon solvents, such
as pentane and heptane. While 1 is quite soluble in
aromatic hydrocarbon solvents, such as benzene and
toluene, 2Á/6 are only sparingly soluble in these solvents.
The formulations proposed for 1Á
/
6 were confirmed by
microanalysis, H-and 13C-NMR, and/or mass spectro-
metry (see Section 2). The molecular structures of
[L1TiCl3] (2), [L2TiCl2(m-Cl)]2 (3), [L3TiCl2]2 (4), and
1
Scheme 1.

138
D. Owiny et al. / Journal of Organometallic Chemistry 678 (2003) 134Á141
/
Fig. 3. An ORTEP diagram of the molecular structure of 4 showing
50% thermal ellipsoid probabilities.
(2), shown in Fig. 1, further supports the structural
assignment made for [L1Ti(NMe2)3] (1). The geometry
about the Ti center of 2 is trigonal bipyramidal, with one
chloride and the imino nitrogen coordinated at the axial
positions, and the remaining two chlorides and the
aryloxide group coordinated at the equitorial sites.
While the crystal of 2 utilized in the X-ray diffraction
study was twinned and the poor crystal quality limits the
accuracy of geometrical parameters, the connectivity is
unambiguous and bond lengths and angles are within
expected ranges 2h2i2j2k[11].
Fig. 1. An ORTEP diagram of the molecular structure of 2 showing
50% thermal ellipsoid probabilities.
[(L3)2Ti] (6) were also established by single-crystal X-ray
diffraction studies (Figs. 1Á4). Selected metrical para-
/
meters are listed in Tables 2 and 3. Room temperature
1H- and 13C-NMR data for [L1Ti(NMe2)3] (1) indicate
fast exchange of the NMe2 ligands on the NMR
timescale. For example, a singlet resonance at d 3.20
1
ppm (integrating as 18 protons) is observed in the H-
NMR spectrum of 1 for the NMe2 groups. We therefore
The six-coordinate complexes 3, 4, and 6 possess a
distorted octahedral geometry about their Ti centers.
The molecular structure of [L2TiCl2(m-Cl)]2 (3), pre-
sented in Fig. 2, confirms the Ci symmetry of the
1
conducted a variable temperature H-NMR study of 1
in toluene-d8 from 298Á193 K. The peaks in the NMR
/
spectrum slowly broadened as the temperature was
lowered, and the resonance at d 3.20 ppm split into
two broad peaks at d 3.53 and 2.76 ppm (integrating in
2:1 ratio) at 213 K. The peak at d 3.53 ppm split further
into two broad peaks (at d 3.59 and 3.48 ppm) at 203 K.
Three fairly sharp resonances integrating in 1:1:1 ratio
were observed at d 3.60, 3.47, and 2.70 ppm at 193 K.
The NMR data are consistent with a trigonal bipyr-
amidal geometry about Ti with two equitorial NMe2
ligands, one axial NMe2, and the bidentate salicylaldi-
minato ligand (L1) coordinated at the remaining axial
and equitorial sites. The molecular structure of [L1TiCl3]
1
molecule in solution (see H- and 13C-NMR data) and
metrical parameters for 3 (Table 2) are within the range
observed for related six-coordinate, chloride-bridged
Ti(IV) complexes 4a[11]. While mass spectral data
allowed the formulation of [L3TiCl2]2 (4) as a dimer
(m/zꢀ
/
849 for [Mꢁꢂ
Cl]) and NMR data revealed a
/
symmetric salicylaldiminato ligand environment, the
molecular structure of 4 was unambiguously established
Fig. 2. An ORTEP diagram of the molecular structure of 3 showing
50% thermal ellipsoid probabilities.
Fig. 4. An ORTEP diagram of the molecular structure of 6 showing
50% thermal ellipsoid probabilities.

D. Owiny et al. / Journal of Organometallic Chemistry 678 (2003) 134Á
/141
139
Table 2
by X-ray crystallography (Fig. 3) [12]. The Ti centers of
4 are surprisingly bridged by the oxygen atom of the
sterically less hindered aryloxide moiety of each salicy-
laldiminato ligand. Equally interesting, the salicylaldi-
minato ligands are oriented such that the phenyl ring of
the less substituted aryloxide moiety of one ligand is face
to face with the phenyl ring of the more substituted
aryloxide moiety of the second salicylaldiminato ligand.
˚
Selected bond distances (A) and angles (8) for 3 and 4
a
3
4
Bond distance
Ti(1)Ã
Ti(1)Ã
Ti(1)Ã
Ti(1)Ã
Ti(1)Ã
Ti(1)Ã
Ti(2)Ã
Ti(2)Ã
Ti(2)Ã
Ti(2)Ã
Ti(2)Ã
Ti(2)Ã
/
O(1)
N(1)
Cl(1)
Cl(2)
Cl(3)
Cl(4)
O(2)
N(2)
Cl(6)
Cl(5)
Cl(4)
Cl(3)
1.783(4)
2.185(5)
Ti(1)Ã
Ti(1)Ã
/
O(1)
1.7993(17)
2.0573(16)
2.0934(16)
2.1697(19)
2.2708(7)
2.2780(7)
3.2954(9)
1.291(3)
/
/O(2)
/
2.2431(19) Ti(1)Ã
2.2709(19) Ti(1)Ã
2.4486(18) Ti(1)Ã
2.5434(18) Ti(1)Ã
/O(2)#1
/
/N(1)
/
/
Cl(2)
Cl(1)
Ti(1)#1
The distance from plane of the ring labeled C16Ã
/
C21 to
the centroid of the di-tert-butyl-substituted ring facing it
/
/
/
1.791(4)
Ti(1)Ã
N(1)Ã
/
˚
is 3.293(3) A, consistent with a pÁp stacking interaction
/
/
2.194(5)
/C(15)
/
2.2518(19) N(1)Ã
2.2681(19) O(1)Ã
2.4379(18) O(2)Ã
2.5193(18) O(2)Ã
/
C(16)
C(1)
1.423(3)
1.348(3)
[13]. Bond distances and angles of 4 (Table 2) are within
the expected ranges although the Ti to terminal aryl-
/
/
/
/
C(21)
Ti(1)#1
1.382(3)
2.0934(16)
oxide oxygen bond is somewhat short [Ti(1)Ã
/
O(1)ꢀ
/
/
/
˚
1.7993(17) A]. This probably reflects increased donation
to Ti by this aryloxide oxygen due to its orientation
Bond angles
O(1)ÃTi(1)Ã
O(1)ÃTi(1)Ã
N(1)ÃTi(1)Ã
O(1)ÃTi(1)Ã
N(1)ÃTi(1)Ã
Cl(1)ÃTi(1)Ã
O(1)ÃTi(1)ÃCl(3) 159.28(14)
N(1)ÃTi(1)Ã
Cl(1)ÃTi(1)Ã
Cl(2)ÃTi(1)Ã
O(1)ÃTi(1)Ã
N(1)ÃTi(1)Ã
Cl(1)ÃTi(1)Ã
Cl(2)ÃTi(1)Ã
Cl(3)ÃTi(1)Ã
/
/
N(1)
83.23(17)
O(1)Ã
O(1)Ã
O(2)Ã
O(1)Ã
O(2)Ã
O(2)#1Ã
O(1)ÃTi(1)Ã
O(2)ÃTi(1)Ã
O(2)#1Ã
N(1)ÃTi(1)Ã
O(1)ÃTi(1)Ã
O(2)ÃTi(1)Ã
O(2)#1Ã
N(1)ÃTi(1)Ã
Cl(2)ÃTi(1)Ã
/
Ti(1)Ã
Ti(1)Ã
Ti(1)Ã
Ti(1)Ã
Ti(1)Ã
/
O(2)
151.93(7)
93.82(7)
74.35(6)
81.03(7)
74.13(7)
91.67(6)
98.77(6)
93.37(5)
trans to the bridging aryloxide oxygen [Ti(1)Ã
/
O(2) is
/
/
Cl(1) 102.71(14)
/
/
O(2)#1
O(2)#1
N(1)
˚
/
/
Cl(1)
87.66(14)
97.98(13)
/
/
much longer at 2.0573(16) A]. That the bridging
aryloxide is weakly-bound is evidenced by the quantita-
tive formation of monomeric [L3TiCl2(THF)] (5) when 4
was dissolved in THF and stirred for 16 h (vide infra).
The molecular structure of [(L3)2Ti] (6) revealed that the
tridentate salicylaldiminato ligands are coordinated in a
meridional fashion and orthogonal to one another (Fig.
4; selected bond distances and angles are presented in
Table 3). In addition, the structure provides support for
the molecule being C2-symmetric in solution, as deduced
/
/Cl(2)
/
/
/
/
Cl(2) 175.67(14)
/
/N(1)
/
/
Cl(2) 96.10(7)
/
Ti(1)ÃN(1)
/
/
/
/
/Cl(2)
/
/
Cl(3)
86.27(13)
94.62(7)
91.29(7)
83.11(13)
84.25(13)
/
/Cl(2)
/
/
Cl(3)
Cl(3)
/
Ti(1)Ã
/
Cl(2) 167.23(5)
/
/
/
/
Cl(2)
88.21(5)
101.04(6)
103.38(5)
86.16(5)
177.09(6)
93.48(3)
/
/Cl(4)
/
/Cl(1)
/
/
Cl(4)
/
/Cl(1)
/
/
Cl(4) 169.42(7)
/
Ti(1)Ã
Cl(1)
Cl(1)
/
Cl(1)
/
/
Cl(4)
Cl(4)
91.76(6)
78.09(6)
/
/
/
/
/
/
1
on the basis of H- and 13C-NMR data (see Section 2).
a
With methylalumoxane (MAO) (900 molar equiva-
lents) as co-catalyst, 1, and 2 showed ethylene polymer-
ization activities at 25 8C (Table 4) comparable to those
reported for several noncyclopentadienyl-based Ti and
Zr systems [14]. Thus, 1 and 2 are much less effective
catalyst precursors than Cp2ZrCl2, which was 28 times
more active under identical polymerization conditions,
or Group 4 metal complexes based on chelating
di(amido)- 2c2d2f], amine-bis(phenolato)- 2n, or bis(sa-
licylaldiminato) 2h2i2j2k ligands. The modest ethylene
polymerization activities may be due to several factors,
including a low equilibrium concentration of the puta-
Symmetry transformations used to generate equivalent atoms:
#1ꢂxꢁ2, 1ꢂy, z; #2y, 1ꢂx, 1ꢂz; #3 1ꢂy, x, 1ꢂz.
/
/
/
/
/
/
/
Table 3
˚
Selected bond distances (A) and angles (8) for 6
Bond distance
B
/
spꢀ
Ti(1)Ã
Ti(1)Ã
Ti(1)Ã
Ti(1)Ã
Ti(1)Ã
Ti(1)Ã
/
1/2ꢁ
/
/
O(3)
O(1)
O(4)
O(2)
N(2)
N(1)
1.862(3)
1.882(3)
1.911(3)
1.925(3)
2.171(4)
2.179(4)
/
/
/
/
/
tive active cationic species, [LTiMe2]ꢁ (LꢀL1 or L2).
/
Bond angles
O(3)ÃTi(1)Ã
O(3)ÃTi(1)Ã
O(1)ÃTi(1)Ã
O(3)ÃTi(1)Ã
O(1)ÃTi(1)Ã
O(4)ÃTi(1)Ã
O(3)ÃTi(1)Ã
O(1)ÃTi(1)Ã
O(4)ÃTi(1)Ã
O(2)ÃTi(1)Ã
O(3)ÃTi(1)Ã
O(1)ÃTi(1)Ã
O(4)ÃTi(1)Ã
O(2)ÃTi(1)Ã
N(2)ÃTi(1)Ã
/
/
O(1)
O(4)
O(4)
O(2)
O(2)
O(2)
N(2)
N(2)
N(2)
N(2)
N(1)
N(1)
N(1)
N(1)
88.44(13)
155.76(14)
90.34(13)
93.04(13)
156.97(13)
97.42(13)
81.29(14)
112.58(14)
76.86(14)
90.34(13)
110.24(13)
81.29(13)
93.47(13)
76.64(13)
162.78(14)
We presume that 2 is a somewhat more effective catalyst
precursor because the active catalyst species can be more
easily generated by chloride substitution. The fact that
mono(salicylaldiminato) complexes 1 and 2 are much
less effective catalyst precursors than bis(salicylaldimi-
nato)Ti(IV) complexes probably reflects a decreased
stability of the active cationic species, which will be
more electron deficient and stabilized to a less degree by
sterics than the active species generated from bis(salicy-
laldiminato)Ti(IV) complexes. The stabilization of the
cationic species would lead to an increased concentra-
tion of the active catalyst and hence to higher activity
2n[14].
/
/
/
/
/
/
/
/
/
/
/
/
/
/
/
/
/
/
/
/
/
/
/
/
/
/
/
/
N(1)

140
D. Owiny et al. / Journal of Organometallic Chemistry 678 (2003) 134Á141
/
Table 4
Ethylene polymerization at 25 8C
Catalyst
mmol of catalyst
Molar excess of MAO
Time (min)
Activity (kg molcatꢂ1 hꢂ1
)
1 a
0.028
0.027
0.025
0.025
900
900
900
900
10
10
10
10
14
30
2 a
a
Cp2ZrCl2
2 b
835
9
a
1 atm C2H4 pressure bubbled through toluene mixture of catalyst/MAO, which had been stirred under N2 atmosphere for 30 min.
1 atm C2H4 pressure bubbled through toluene mixture of catalyst/MAO immediately after mixing.
b
(2000) 1169;
4. Conclusions
(e) S. Matsui, M. Mitani, T. Fujita, Petrotech 24 (2001) 11.
[2] See for example:(a) D.P. Gates, S.A. Sveda, E. Onate, C.M.
Killan, L.K. Johnson, P.S. White, M. Brookhart, Macromole-
cules 33 (2000) 2320;
Monomeric mono(salicylaldiminato)Ti(IV) com-
plexes can be prepared through appropriate choice of
the salicylaldiminato ligand. With MAO as co-catalyst,
Ti(IV) tris(dimethylamide) and -trichloride complexes 1
and 2 showed modest activities in ethylene polymeriza-
tion. The complexes are much less effective catalyst
precursors than previously reported bis(salicylaldimi-
nato) complexes of the Group 4 metals. The design and
study of related complexes are currently underway in
our laboratory, with the aim of developing highly active
olefin polymerization catalysts.
(b) T.R. Younkin, E.F. Connor, J.I. Henderson, S.K. Friedrich,
R.H. Grubbs, Science 287 (2000) 460;
(c) J.D. Scollard, D.H. McConville, J. Am. Chem. Soc. 118 (1996)
10008;
(d) B. Tsuie, D.C. Swenson, R.F. Jordan, Organometallics 16
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(g) D.W. Stephan, F. Guerin, R.E.v.H. Spence, L. Koch, X. Gao,
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Harrison, Organometallics 18 (1999) 2046;
(h) Y. Yoshida, S. Matsui, Y. Takagi, M. Mitani, T. Nakano, H.
Tanaka, N. Kashiwa, T. Fujita, Organometallics 20 (2001) 4793;
(i) S.-i. Ishii, J. Saito, M. Mitani, J.-i. Mohri, N. Matsukawa, Y.
Tohi, S. Matsui, N. Kashiwa, T. Fujita, J. Mol. Catal. A 179
(2002) 11;
5. Supplementary material
Crystallographic data for the structural analysis have
been deposited with the Cambridge Crystallographic
(j) J. Tian, P.D. Hustad, G.W. Coates, J. Am. Chem. Soc. 123
(2001) 5134;
Data Centre, CCDC nos. 204405Á204408 for 2, 3, 4,
and 6, respectively. Copies of the information may be
obtained free of charge from The Director, CCDC, 12
/
(k) P.D. Hustad, J. Tian, G.W. Coates, J. Am. Chem. Soc. 124
(2002) 3614;
Union Road, Cambridge CB2 1EZ, UK (Fax: ꢁ44-
/
(l) T. Matsugi, S. Matsui, S. Kojoh, Y. Takagi, Y. Inoue, T.
Fujita, N. Kashiwa, Chem. Lett. (2001) 566;
1223-336033; email: deposit@ccdc.cam.ac.uk or www:
http://www.ccdc.cam.ac.uk).
(m) V.C. Gibson, B.S. Kimberley, A.J.P. White, D.J. Williams, P.
Howard, Chem. Commun. (1998) 313;
(n) E.Y. Tshuva, I. Goldberg, M. Kol, H. Weitman, H.; Z.
Goldschmidt, Chem. Commun. (2000) 379;
Acknowledgements
(o) Y. Yoshida, J. Saito, M. Mitani, Y. Takagi, S. Matsui, S.-i.
Ishii, T. Nakano, N. Kashiwa, T. Fujita, Chem. Commun. (2002)
1298.
Thanks are expressed to the US National Science
Foundation (grant number CHE-9984776) for financial
support of this work. NMR instruments utilized in this
research were funded in part by the CRIF program of
the US National Science Foundation (grant number
CHE-9974810).
[3] See for example:(a) A. de Blas, R. Bastida, M.J. Fuentes, Synth.
React. Inorg. Met.-Org. Chem. 21 (1991) 1273;
(b) M. Goyal, S. Mishra, A. Singh, Synth. React. Inorg. Met.-
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/
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/
0.5Cl and the other peak as
˚
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/
the imine nitrogen of [4,6-
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/
But2
/
-2-(CHÄ
/
NBut )C6H3OH] also oc-
-2-(CHÄ
NHBut )C6H3-
/
But2
/
/
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/
/
/
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