Titanium and zirconium complexes with novel phenoxy-phosphinimine ligands

Article abstract of DOI:10.1016/j.jorganchem.2005.05.028

A series of novel phenoxy-phosphinimine ligands (L): L = 2-(Ph ₂PNR), 4, 6-(CMe₃)₂-C₆H ₂OH [2, R = SiMe₃; 3, R = Ph] have been prepared in the yield of 65-71%. And bis(phenoxy-phosphinimide

Full text of DOI:10.1016/j.jorganchem.2005.05.028

Journal of Organometallic Chemistry 690 (2005) 3946–3950
www.elsevier.com/locate/jorganchem
Titanium and zirconium complexes with novel
phenoxy-phosphinimine ligands
a,
a,b
Chang-He Qi a,b, Suo-Bo Zhang *, Jing-Hui Sun
a
State Key Laboratory of Polymer Physics and Chemistry, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences,
5625 Renmin Street, Changchun 130022, China
b
Graduate School of the Chinese Academy of Sciences, China
Received 8 April 2005; recieved in revised form 8 May 2005; accepted 19 May 2005
Available online 5 July 2005
Abstract
A series of novel phenoxy-phosphinimine ligands (L): L = 2-(Ph2P@NR), 4, 6-(CMe3)2-C6H2OH [2, R = SiMe3; 3, R = Ph] have
been prepared in the yield of 65–71%. And bis(phenoxy-phosphinimide) group 4 complexes of the type L2MCl2 [4, M = Ti,
R = SiMe3; 5, M = Zr, R = SiMe3; 6, M = Ti, R = Ph; 7, M = Zr, R = Ph] have been synthesized by the reaction of the ligands with
TiCl4 and ZrCl4. The structure of complex 7 has been determined by X-ray crystallography. The complexes 4–7 showed inactive to
ethylene polymerization in the presence of modified methylaluminoxane (MMAO) and i-Bu3Al/Ph3CB(C6 F5)4. These results should
be caused by overdoing the steric congestion around central metal.
ꢀ 2005 Elsevier B.V. All rights reserved.
Keywords: Phenoxy; Phosphinimine; Titanium; Zirconium; Complex
1. Introduction
catalysts with phenoxy-ketimine ligands. However, to
the best of our knowledge, there is no report of complex
based on the ligand of phenoxy-phosphinimine (PHPI)
(most recently, Piers et al. and Stephan et al. [6] reported
independently mono(anilido-phosphinimide) group 13
complexes). Compared to PHI ligands, PHPI ligands
should be more resistant to nucleophilic attack while
improving its ability as donor, and the replacement of
an imine-carbon with a PPh2 fragment will significantly
increase the steric environment around central metal.
Herein, we would like to report the synthesis and char-
acterization of a series of novel bis(phenoxy-phosphini-
mide) (PHPI) group 4 complexes.
The search for non-metallocene transition complexes
to catalyze olefin polymerization has resulted in a wide
range of new catalysts base on new or known ancillary
ligands [1]. And in recent years, there has been consider-
able and growing interest in the coordination chemistry
to steric hindered phosphinimine and phosphiniminato
complexes [2]. Among them, titanium complexes bearing
phosphinimide ligands have been shown by Stephan and
co-workers [3] to give highly active ethylene polymeriza-
tion catalysts. At the same time, Fujita and co-workers
[4] developed a series of group 4 transition metal com-
plexes containing bis(phenoxy-imine) (PHI) ligands,
and these complexes showed to be excellent precatalysts
for olefin polymerization. Subsequently, Coates et al. [5]
also reported living ethylene polymerization by titanium
2. Results and discussion
The synthesis of the ligands and complexes is outlined
in Scheme 1, and the (2-diphenylphosphanyl, 4,
6-di-tert-butyl) phenol 1 is obtained according to the
*
Corresponding author. Tel./fax: +86 431 5262347.
E-mail address: sbzhang@ciac.jl.cn (S.-B. Zhang).
0022-328X/$ - see front matter ꢀ 2005 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2005.05.028

C.-H. Qi et al. / Journal of Organometallic Chemistry 690 (2005) 3946–3950
3947
in Table 1, and selected bond lengths and angles (similar
data of complex (PHI)2ZrCl2 [8] are also listed for com-
parison) are collected in Table 2.
PPh2
OH
Ph2P
NR
OH
N3R
But
But
The structure of complex 7 is similar to that of
(PHI)2ZrCl2, with trans-O, cis-N, and cis-Cl arrange-
˚
ment. About the bond lengths, the Zr–N (2.251(2) A),
of complex 7 is shorter than that of (PHI)2ZrCl2
˚
(2.355(2) A), which may be resulted by the lower electro-
negative of phosphinimine-phosphorus compared with
imine-carbon. And the bond lengths of Zr–Cl
But
But
2-3
1
R
N
Ph2P
MCl2
1. n-BuLi
2. MCl4
But
O
2
˚
(2.4932(7) A) is somewhat longer than that of
˚
(PHI)2ZrCl2 (2.4234(9) A). The significant differences
But
4-7
can be found to the bond angles. The N–Zr–N
(96.65(10)ꢁ) increases by 22ꢁ comparing with
(PHI)2ZrCl2 (74.0(1)ꢁ) and the Cl–Zr–Cl (89.36(3)ꢁ) de-
creases by 11ꢁ comparing with (PHI)2ZrCl2 (100.38(5)ꢁ).
These important differences should be caused by the
introducing of PPh2, which make the environment of
central metal more congestion as expected.
2: R = SiMe3; 3: R = Ph; 4: M=Ti, R = SiMe3;
5: M = Zr, R = SiMe3; 6: M= Ti, R = Ph; 7: M= Zr, R = Ph.
Scheme 1. The synthesis of ligands and complexes.
literature [7]. Oxidation of 1 with phenyl azide or trim-
ethylsilyl azide resulted in the evolution of N2, and the
ligands 2–3 could be obtained by recrystallizing from
CH3CN in yield 65–71%. After deprotonation by n-
BuLi at À78 ꢁC in THF, ligands 2–3 could react with
TiCl4 or ZrCl4 to give the desired bis(phenoxy-phos-
phinimide) complexes 4–7 in good yields (4: 93%; 5:
88%; 6: 86%; 7: 81%). All of the new compounds were
characterized by NMR, element analysis, and mass
analysis. NMR data indicated that these octahedral
complexes are predominantly C2-symmetric in solution,
as they are in the solid state. Single crystals of the com-
plex 7 suited for X-ray diffraction study were grown
from CH2Cl2/hexane at À20 ꢁC under argon. The OR-
TEP is shown in Fig. 1. The crystal data are summarized
Preliminary evaluation of complexes 4–7 as ethylene
polymerization catalysts was performed (20 ꢁC and
1 atm) and several activation conditions were attempted.
But only traces of polymer can be obtained while using
either MMAO (Al/M = 2000/1) or i-Bu3Al/Ph3CB-
(C6F5)4 (Al/M/B4 = 100/1/2) as cocatalysts. These results
showed remarkable difference to those reported for the
species of bis(phenoxy-imine) group 4 complexes,
although they displayed the structure similarity each
other. These findings clearly suggested that such phen-
oxy-phosphinimide complexes are not simple analogs
of phenoxy-imine complexes, albeit the ligands (PHPI)
provide the sheltered metal environment which is
thought to be the very effective factor for the active
Fig. 1. ORTEP drawings of complex 7. Thermal ellipsoids at the 30% level are shown. The hydrogen atoms are omitted for clarity.

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C.-H. Qi et al. / Journal of Organometallic Chemistry 690 (2005) 3946–3950
Table 1
Crystal data and structure refinement for complex 7
3. Experimental
Empirical formula
Formula weight
Temperature (K)
Crystal size (mm)
Crystal system
Space group
C64H70Cl2N2O2P2Zr
1123.28
187 (2)
3.1. General
All preparations involving air and moisture sensitive
compounds were carried out under an atmosphere of
argon using standard Schlenk or cannula techniques.
Solvents were dried over Na/benzophenone (THF,
ether, toluene, and hexane) or CaH2 (CH2Cl2) and dis-
tilled prior to use. NMR data of ligands and complexes
were obtained on a Varian Unity 300 MHz spectrometer
at ambient temperature, C6D6 or CDCl3 as solvent.
Mass spectra were obtained using electron impact
(EI-MS) and LDI-1700 (Linear Scientific Inc.). Elemen-
tal analyses were recorded on an elemental Vario EL
spectrometer. The compound 1 was synthesized accord-
ing to the literature [7].
0.44 · 0.15 · 0.07
Monoclinic
C2/c
˚
a (A)
26.698(2)
˚
b (A)
11.8002(10)
20.9438 (18)
90
˚
c (A)
a (ꢁ)
b (ꢁ)
c (ꢁ)
118.2360(10)
90
5813.0(9)
3
˚
V (A )
Z
4
1.284
Density(calc.) (Mg cmÀ3
)
Absorption coefficient (mmÀ1
F(0 0 0)
)
0.381
2352
˚
Wavelength (A)
0.71073
1.73–25.03
14,719
h Range for data collection (ꢁ)
Reflection collected
3.2. Synthesis of ligands
Data/restrains/parameters
Independent reflections
Final R indices [I > 2r(I)]
R indices (all data)
5130/0/336
5130 (Rint = 0.0383)
R1 = 0.0425, wR2 = 0.1062
R1 = 0.0500, wR2 = 0.1111
Semi-empirical from
equivalents
1.054
3.2.1. Synthesis of ligand 2
Trimethylsilyl azide (4.6 g, 40 mmol) was injected
into (2-diphenylphosphanyl, 4,6-di-tert-butyl)phenol 1
(15.6 g, 40 mmol) and stirred for 5 h at 110 ꢁC. The pure
product was obtained after recrystallization from
CH3CN and dried in vacuo. Yield: 12.4 g (65%). 1H
NMR (300 MHz, CDCl3): d 7.72–7.65 (m, 4H, Ar-H);
7.57–7.45 (m, 6H, Ar-H); 6.84 (m, 1H, Ar-H); 1.45
(s, 9H, C(CH3)3); 1.17 (s, 9H, C(CH3)3); À0.06 (s, 9H,
Si(CH3)3). Anal. Calc. for C29H40NOPSi: C, 73.00; H,
8.39; N, 2.94. Found: C, 72.91; H, 8.37; N, 2.98%.
EI-MS: m/z = 477 [M+].
Absorption correction
Goodness-of-fit on F2
Maximum and minimum transmission
Largest difference peak and hole
0.9735 and 0.8504
1.100 and À0.404
Table 2
˚
Selected bond lengths (A) and angles (ꢁ) for complex 7
Complex 7
(PHI)2ZrCl2
Bond lengths
Zr–O(1)
Zr–N(1)
Zr–Cl(1)
P–N(1)
2.0012(16)
2.251(2)
1.985(2)
2.355(2)
2.4234(9)
3.2.2. Synthesis of ligand 3
2.4932(7)
1.629(2)
A solution of phenyl azide (5.5 g, 46.2 mmol) in THF
(10 ml) was added dropwise to a solution of (2-diphenyl-
phosphanyl, 4,6-di-tert-butyl)phenol 1 (12.8 g, 46 mmol)
in THF (40 ml) at 0 ꢁC and stirred for 10 h at room tem-
perature. The solvents were evaporated and yield a
crude product. The pure white crystals were obtained
after recrystallization from CH3CN and dried in vacuo.
Yield: 7.63 g (71%). 1H NMR (300 MHz, CDCl3): d
7.77–7.74 (m, 3H, Ar-H); 7.71–7.63 (m, 3H, Ar-H);
7.49–7.38 (m, 5H, Ar-H); 7.01–6.95 (m, 2H, Ar-H);
6.84–6.79 (m, 1H, Ar-H); 6.65–6.63 (m, 3H, Ar-H);
1.42 (s, 9H, C(CH3)3); 1.09 (s, 9H, C(CH3)3). Anal. Calc.
for C32H36NOP: C, 79.83; H, 7.48; N, 2.91. Found: C,
79.50; H, 7.51; N, 2.85%. EI-MS: m/z = 481 [M+].
Bond angles
O(1)–Zr–O(2)
N(1)–Zr–N(2)
Cl(1)–Zr–Cl(2)
P(1)–N(1)–Zr
C(1)–O(1)–Zr
168.35(10)
96.65(10)
89.36(3)
165.5(1)
74.0(1)
100.38(5)
130.40(11)
148.87(16)
olefin polymerization catalysts. Similar bis(phenoxy-
imine)-based group 4 complex (containing [N,O,P]
tridentate ligand) with more steric congestion but inac-
tive for olefin polymerization was also reported by Tang
and co-workers [9]. Thus, to the bis(phenoxy-imine)-
based group 4 complexes, overdoing the steric effects
will probably suppress the active species (which was pro-
duced from the reaction of complex and cocatalyst), be-
cause the strong steric congestion around central metal
will hinder the effective coordination of the olefin mono-
mers with the active species. Efforts to adjust the steric
environment of these complexes and apply in olefin
polymerization are underway.
3.3. Synthesis of complexes
3.3.1. Synthesis of complex 4
A 1.6 M solution of n-BuLi (2.56 ml, 4.1 mmol) was
added dropwise to a solution of ligand 2 (1.51 g,
4.1 mmol) in THF at À78 ꢁC, then the mixture was
warmed to room temperature and stirred for 3 h. The

C.-H. Qi et al. / Journal of Organometallic Chemistry 690 (2005) 3946–3950
3949
resulting solution was transferred by cannula to a solu-
tion of TiCl4 (0.38 g, 2 mmol) in Et2O at 78 ꢁC. After
stirring for 15 h at room temperature, the solvent was
removed under vacuum to give the crude product, then
40 ml of CH2Cl2 was added and stirred for 30 min and
filtered. The filtrate was concentrated under vacuum to
ca. 10 ml, and 60 ml hexane was added and cooled
slowly to À20 ꢁC. The pure product was obtained as
pale yellow crystals. Yield 1.92 g (93%). 1H NMR
(300 MHz, CDCl3): d 7.89–7.74 (m, 10H, Ar-H); 7.35–
7.29 (m, 8H, Ar-H); 7.11–7.09 (m, 4H, Ar-H); 6.97
(m, 2H, Ar-H); 1.53 (s, 18H, C(CH3)3); 1.27 (s, 18H,
C(CH3)3); 0.53 (s, 18H, Si(CH3)3). Anal. Calc. for
C58H78Cl2N2O2P2Si2Ti: C, 64.99; H, 7.28; N, 2.61.
Found: C, 65.08; H, 7.21; N, 2.55%. EI-MS:
m/z = 1036 [M+ À Cl].
was then injected into the flask to initiate the polymeri-
zation under atmospheric condition.
In the case of i-Bu3Al/Ph3BC(C6 F5)4 as cocatalyst,
toluene (50 ml) and i-Bu3Al (1/4 of the desired content)
were added into the dried flask. In a Schlenk flask, the
toluene solution of catalyst was mixed with i-Bu3Al
(the other 3/4 of the desired content) and stirred for
10 min at room temperature. The resulted solution was
added into the reactor. The borate in toluene solution
was added to initiate the polymerization under atmo-
spheric condition.
After 15 min, the polymerization was terminated with
the addition of HCl/EtOH.
4. Supplementary material
3.3.2. Synthesis of complex 5
Complex 5 was prepared via a procedure similar to
Crystallographic data for the structural analysis have
been deposited with the Cambridge Crystallographic
Data Center, CCDC no. 267151 for complex 7. Copies
of this information may be obtained free of charge from
The Director, CCDC, 12 Union Road, Cambridge CB2
1EZ, UK (Fax: +44 1223 336033; e-mail: deposit@
ccdc.cam.ac.uk or www: http://ccdc.cam.ac.uk).
1
that for 4 as white solid in the yield of 88%. H NMR
(300 MHz, CDCl3): d 8.11–7.94 (m, 8H, Ar-H); 7.86–
7.43 (b, 8H, Ar-H); 7.37–7.14 (m, 6H, Ar-H); 7.03
(m, 2H, Ar-H); 1.67 (s, 18H, C(CH3)3); 1.31 (s, 18H,
C(CH3)3); 0.49 (s, 18H, Si(CH3)3). Anal. Calc. for
C58H78Cl2N2O2P2Si2Zr: C, 62.48; H, 7.00; N, 2.51.
Found: C, 63.02; H, 6.97; N, 2.49%. EI-MS:
m/z = 1079 [M+ À Cl].
Acknowledgments
3.3.3. Synthesis of complex 6
The authors are grateful for the financial support by
the National Natural Science Foundation of China and
SINOPEC (No. 20334030).
Complex 6 was prepared via a procedure similar to
that for 4 as orange solid in the yield of 86%. 1H
NMR (300 MHz, CDCl3): d 8.54 (b, 2H, Ar-H); 7.91–
7.69 (b, 10H, Ar-H); 7.06–6.93 (b, 18H, Ar-H); 6.83–
6.78 (b, 4H, Ar-H); 1.94 (s, 18H, C(CH3)3); 1.05
(s, 18H, C(CH3)3) Anal. Calc. for C64H70Cl2N2O2P2Ti:
C, 71.18; H, 6.49; N, 2.59. Found: C, 70.75; H, 6.51;
N, 2.63. EI-MS: m/z = 1044 [M+ À Cl].
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Complex 7 was prepared via a procedure similar to
that for 4 as white crystals in the yield of 81%. 1H
NMR (300 MHz, CDCl3): d 8.37 (b, 2H, Ar-H); 7.75–
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