Titanium and zirconium benzyl complexes bearing bulky bis(amido) cyclodiphosph(III)azanes: Synthesis, structure, activation, and ethene polymerization studies

Article abstract of DOI:10.1021/om050725h

Benzyl-substituted bis(amido)cyclodiphosph(III)azane complexes [(RN)(t-BuNP)]₂M(CH₂Ph)_nCl_2-n (M = Zr, Ti; n = 1, 2) bearing t-Bu or bulky aryl substituents on amido nitrogens were prepared by direct alkylation o

Full text of DOI:10.1021/om050725h

Organometallics 2006, 25, 463-471
463
Titanium and Zirconium Benzyl Complexes Bearing Bulky
Bis(amido)cyclodiphosph(III)azanes: Synthesis, Structure,
Activation, and Ethene Polymerization Studies
Kirill V. Axenov,† Ilkka Kilpela¨inen,‡ Martti Klinga,† Markku Leskela¨,† and Timo Repo*,†
Laboratory of Inorganic Chemistry, Department of Chemistry, UniVersity of Helsinki, PO Box 55,
FIN-00014, Finland, and Laboratory of Organic Chemistry, Department of Chemistry, UniVersity of
Helsinki, PO Box 55, FIN-00014, Finland
ReceiVed August 22, 2005
Benzyl-substituted bis(amido)cyclodiphosph(III)azane complexes [(RN)(t-BuNP)]2M(CH2Ph)nCl2-n (M
) Zr, Ti; n ) 1, 2) bearing t-Bu or bulky aryl substituents on amido nitrogens were prepared by direct
alkylation of corresponding dichloro derivatives with PhCH2MgCl. The alkylation of Zr complexes
proceeded selectively. In the solid state of [(t-BuN)(t-BuNP)]2Zr(CH2Ph)2 the zirconium atom adopts a
distorted trigonal-bipyramidal configuration. The alkylation of [(t-BuN)(t-BuNP)]2TiCl2 with PhCH2-
MgCl in the presence of THF led to [(t-BuN)(t-BuNP)]2Ti(CH2Ph)2 simultaneously with [(t-BuN)(t-
BuNP)]2Ti(CHPh)(THF). According to NMR and X-ray single-crystal studies, the latter contains a Ti-C
double bond. Activation of the benzyl complexes with B(C6F5)3 led to the generation of the corresponding
1
“cationic” species, which were further investigated by H, 13C, 31P, and 19F NMR methods. In the solid
state the metal center of {[(t-BuN)(t-BuNP)]2Zr(η2-CH2Ph)(Et2O)}+[PhCH2B(C6F5)3]- has a distorted
trigonal bipyramidal configuration, where the benzyl group coordinates to Zr in a η2-fashion. In ethene
polymerization the mono- and dibenzyl Ti and Zr derivatives showed moderate to high catalytic activities
(up to 4600 kg/(mol × h)). The correlation between polymerization results and activation experiments,
especially in terms of electrophilicity of the metal center, is discussed.
to the variety of easily synthesized amido ligands, the possibility
to modify the electronic character at the metal center as well as
its geometry and steric protection is tempting. In this context,
we have developed synthetic methods to modify the literature
known [(t-BuN)(t-BuNP)]22- ligand framework4 by bulky alkyl
and aryl substituents.5 In our studies a series of dichloro Ti and
Zr complexes bearing bulky bis(amido)cyclodiphosph(III)azanes
were prepared, and moderate to high catalytic activities in ethene
polymerization were recorded after MAO activation.5,6 It was
concluded that the polymerization behavior of these catalysts
and the stability of the active species depend on the bulkiness
of the amido substituents.6
Introduction
During the last decades non-cyclopentadienyl complexes of
group 4 metals have attracted considerable attention as potential
catalyst precursors for the homogeneous Ziegler-Natta olefin
polymerization process.1 Besides the recently discovered highly
active bis(phenoxyimino) titanium and zirconium catalysts,2
group 4 metal complexes bearing bi-, tri-, or polydentante amido
ligands are promising candidates for catalyst precursors.3 A
highly electrophilic metal cation, [(R2N)2MR]+ (M ) group 4
metal), which is generally considered as the catalytically active
species in olefin polymerization, is generated after methylalu-
moxane (MAO) activation of bis(amido) complexes.1a Owing
Structural investigations in solution and in the solid state of
the cationic species generated from dimethyl hafnium bis-
(amido)cyclodiphosph(III)azanes by activation with tris(per-
fluorophenyl)borane have provided further understanding of how
the nature and size of the amido substituents influence the
activation process as well as the geometry of the metal center
when the cationic species are formed.7 However, unambiguous
correlations between the structure of the cationic metal center,
polymerization activity, and polymer properties could not be
established due to the exhibited low activity of the investigated
hafnium complexes. Evidently, the study of the cationic species
generated from more catalytically active Ti and Zr cyclodiphos-
* To whom correspondence should be addressed. E-mail: Timo.Repo@
helsinki.fi. Fax: +358-(0)9-19150198.
† Laboratory of Inorganic Chemistry.
‡ Laboratory of Organic Chemistry.
(1) (a) Britovsek, J. P.; Gibson, V. C.; Wass, D. F. Angew. Chem. 1999,
111, 448; Angew. Chem., Int. Ed. 1999, 38, 428. (b) Gibson, V. C.;
Spitzmesser, K. Chem. ReV. 2003, 103, 283.
(2) (a) Matsui, S.; Mitani, M.; Saito, J.; Tohi, Y.; Makio, H.; Matsukawa,
N.; Takagi, Y.; Tsuru, K.; Nitabaru, M.; Nakano, T.; Tanaka, H.; Kashiwa,
K.; Fujita, T. J. Am. Chem. Soc. 2001, 123, 6847. (b) Lamberti, M.;
Pappalardo, D.; Zambelli, A.; Pellechia, C. Macromolecules 2002, 35, 658.
(c) Mitani, M.; Mohri, J.; Yoshida, Y.; Saito, J.; Ishii, S.; Tsuru, K.; Matsui,
S.; Furuyama, R.; Nakano, T.; Tanaka, H.; Kojoh, S.; Matsugi, T.; Kashiwa,
N.; Fujita, T. J. Am. Chem. Soc. 2002, 124, 3327. (d) Furuyama, R.; Saito,
J.; Ishii, S.; Mitani, M.; Matsui, S.; Tohi, Y.; Makio, H.; Matsukawa, N.;
Tanaka, H.; Fujita, T. J. Mol. Catal., Ser. A: Chem. 2003, 200, 31.
(3) (a) Schrock, R. R.; Adamchuk, J.; Ruhland, K.; Lopez, L. P. H.
Organometallics 2005, 24, 857. (b) Mehrkhodavandi, P.; Schrock, R. R. J.
Am. Chem. Soc. 2001, 123, 10746. (c) Scollard, J. D.; McConville, D. H.
J. Am. Chem. Soc. 1996, 118, 10008. (d) Lee, C. H.; La, Y.-H.; Park, J. W.
Organometallics 2000, 19, 344. (e) Horton, A. D.; de With J.; van der
Linden, A. J.; van de Weg, H. Organometallics 1996, 15, 2672. (f) Kim,
S.-J.; Jung, I. N.; Yoo, B. R.; Kim, S. H.; Ko, J.; Byun, D.; Kang, S. O.
Organometallics 2001, 20, 2136. (g) Male, N. A. H.; Thornton-Pett, M.;
Bochmann, M. Dalton Trans. 1997, 2487.
(4) (a) Grocholl, L. P.; Stahl, L.; Staples, R. J. Chem. Commun. 1997,
1465. (b) Moser, D. F., Carrow, C. J.; Stahl, L.; Staples, R. J. J. Chem.
Soc., Dalton Trans. 2001, 1246. (c) Moser, D. F.; Grocholl, L.; Stahl, L.;
Staples, R. J. J. Chem. Soc., Dalton Trans. 2003, 1402.
(5) Axenov, K. V.; Klinga, M.; Leskela¨, M.; Kotov, V. V.; Repo, T.
Eur. J. Inorg. Chem. 2004, 695.
(6) Axenov, K. V.; Klinga, M.; Leskela¨, M.; Kotov, V. V.; Repo, T.
Eur. J. Inorg. Chem. 2004, 4702.
(7) Axenov, K. V.; Klinga, M.; Leskela¨, M.; Repo, T. Organometallics
2005, 24, 1336.
10.1021/om050725h CCC: $33.50 © 2006 American Chemical Society
Publication on Web 12/14/2005

464 Organometallics, Vol. 25, No. 2, 2006
AxenoV et al.
[(t-BuN)(t-BuNP)]2Ti(CH2Ph)2 (5). PhCH2MgCl in THF (2 M,
5.5 mL, 11 mmol) was added via a syringe into a solution of [(t-
BuN)(t-BuNP)]2TiCl2 (1) (2.4 g, 5.16 mmol) in Et2O (30 mL) at
-50 °C. The reaction mixture was allowed to warm to room
temperature and stirred overnight. All volatiles were removed in
vacuo, and the resulting red-brown residue was extracted by hexane
(20 + 10 mL) followed by filtration in a glovebox through PTFE
filters. After precipitation of complex 6, the hexane phase was
separated and evaporated in vacuo to give a red solid (1.2 g; 41.0%).
1H NMR (200 MHz, C6D6, 29 °C): δH 1.23 (s, 18H, t-Bu, P2N2
cycle), 1.70 (s, 18H, t-Bu), 3.36 (s, 4H, CH2Ph), 6.96-7.21 (m,
ph(III)azane complexes would be beneficial to gain more
information about the relationship between the structure of the
catalyst and its polymerization behavior. Here we report on the
synthesis of benzyl bis(amido)cyclodiphosph(III)azane Ti and
Zr complexes, their activation with B(C6F5)3, and their use in
homogeneous ethene polymerization.
Experimental Section
General Procedures. All manipulations were performed under
inert argon atmosphere using standard Schlenk techniques. The
hydrocarbon and ether solvents were refluxed over sodium and
benzophenone, distilled, and stored under inert atmosphere with
pieces of sodium. C6D6 was refluxed over sodium, CD2Cl2 and
C6D5Br were refluxed with CaH2, and then these solvents were
transferred into storage flasks by evaporation-condensation in a
vacuum and stored in a glovebox. EI-mass spectra were measured
on a JEOL SX102 spectrometer. ESI-HRMS spectra were per-
1
10H, Ph). H NMR (500 MHz, CD2Cl2, 27 °C): δH 1.16 (s, 18H,
t-Bu, P2N2 cycle), 1.55 (s, 18H, t-Bu), 3.03 (s, 4H, CH2Ph), 6.92
(d, JHH ) 7.8 Hz, 2H, Ph), 7.06 (t, JHH ) 7.8 Hz, 2H, Ph), 7.15
(m, JHH ) 7.8 Hz, 4H, Ph), 7.24 (t, JHH ) 7.8 Hz, 2H, Ph). 13C-
{1H} NMR (50.3 MHz, C6D6, 29 °C): δC 29.28 (t, JPC ) 6.9 Hz,
CH3, t-Bu, P2N2 cycle), 34.41 (d, JPC ) 11.06 Hz, CH3, t-Bu), 54.00
(t, JPC ) 14.1 Hz, C, t-Bu, P2N2 cycle), 63.9 (d, JPC ) 17.9 Hz, C,
t-Bu), 77.24 (CH2Ph), 122.76 (Ph), 129.37 (Ph), 129.66 (Ph), 145.33
(Ph). 31P{1H} NMR (202 MHz, CD2Cl2, 27 °C): δP 129.66 (s).
MS(EI): m/z (%) 576 (3, M+), 485 (11, M+ - CH2Ph), 347 (89,
ligand). HRMS (ESI): found m/z 577.3 (C30H51N4P2Ti+, error 7.17
ppm), 576.3 (C30H50N4P2Ti+•, error -1.72 ppm); calculated com-
position for [(t-BuN)(t-BuNP)]2Ti(CH2Ph)2 is C30H50N4P2Ti.
1
formed with a Bruker-MicroTOF spectrometer. The H, 13C, 31P,
and 19F NMR spectra were recorded on Varian Gemini 200 MHz,
Varian INOVA 500, and Bruker AMX 400 spectrometers. The 1H
and 13C NMR spectra were referenced relative to CHDCl2 (5.28
and 53.73 ppm, respectively), C6D4HBr (7.29 and 122.25 ppm,
respectively), and C6D5H (7.24 and 128.0 ppm, respectively).
Phosphorus signals were referenced relative to an external standard
(85% H3PO4 solution) and external Me3P solution in CD2Cl2 (-60.5
ppm); fluorine signals were referenced relative to CFCl3 standard
and external B(C6F5)3 in CD2Cl2 (-127.8, -143.4, -160.6 ppm).
Elemental analyses were performed at Prof. Dr. H. Malissa und G.
Reuter GmbH, Germany. High-temperature gel permeation chro-
matography of polyethylene samples (GPC) was performed in 1,2,4-
trichlorobenzene at 145 °C using a Waters HPLC 150C.
[(t-BuN)(t-BuNP)]2Ti(CHPh)(THF) (6). A small amount of
product was precipitated as a red solid at -20 °C from the hexane
1
extract obtained in the preparation of complex 5. H NMR (200
MHz, C6D6-CD2Cl2, 29 °C): δH 1.23 (s, 18H, t-Bu, P2N2 cycle),
1.56 (br m, 4H, THF), 1.60 (s, 18H, t-Bu), 3.64 (br m, 4H, THF),
4.05 (s, 1H, CHPh), 7.00-7.25 (m, 5H, Ph). 13C{1H} NMR (50.3
MHz, C6D6-CD2Cl2, 29 °C): δC 25.95 (THF), 28.54 (t, JPC ) 7.0
Hz, CH3, t-Bu, P2N2 cycle), 33.84 (d, JPC ) 11.9 Hz, CH3, t-Bu),
54.81 (t, JPC ) 10.5 Hz, C, t-Bu, P2N2 cycle), 65.6 (d, JPC ) 13.3
Hz, C, t-Bu), 68.00 (THF), 122.82 (Ph), 126.13 (Ph), 126.44 (Ph),
128.71 (Ph), 221.93 (d, JCH ) 162.9 Hz, CHPh). 31P{1H} NMR
(162 MHz, C6D6-CD2Cl2, 29 °C): δP 115.21 (s). The structure
was further confirmed by single-crystal X-ray diffraction studies.
tert-Butylamine and phosphorus trichloride were purchased from
Merck and purified by distillation under argon (t-BuNH2 over
sodium hydroxide). Arylamines were received from Aldrich and
distilled in vacuo over sodium hydroxide before use. Chlorotrim-
ethylsilane was purchased from Fluka and used as received. Ti-
(NMe2)4 and Zr(NMe2)4 were purchased from Aldrich and used as
a toluene solution. A 1 M solution of PhCH2MgCl in Et2O, a 2 M
solution of PhCH2MgCl in THF, and a 1.6 M solution of nBuLi in
hexane were purchased from Aldrich and used as received. Tris-
(perfluorophenyl)borane was purchased from Strem and stored in
a glovebox. Methylalumoxane (MAO, 30 wt % solution in toluene)
was received from Borealis Polymers Oy. [(t-BuN)(t-BuNP)]2TiCl2
(1),4b,5 [(2,5-t-Bu2C6H3N)(t-BuNP)]2TiCl2 (2),5 [(2,6-i-Pr2C6H3N)(t-
BuNP)]2TiCl2 (3),5 [(t-BuN)(t-BuNP)]2ZrCl2 (9),4c [(2,5-t-Bu2-
C6H3N)(t-BuNP)]2ZrCl2 (10),6 and [(2,6-i-Pr2C6H3N)(t-BuNP)]2-
ZrCl2 (11)6 were prepared according to literature procedures.
Synthesis of Complexes. [(t-BuN)(t-BuNP)]2Ti(CH2Ph)Cl (4).
PhCH2MgCl in Et2O (1 M, 3 mL, 3 mmol) was added via a syringe
into a solution of [(t-BuN)(t-BuNP)]2TiCl2 (1) (0.7 g, 1.5 mmol)
in Et2O (30 mL) at -50 °C. The reaction mixture was allowed to
warm to room temperature and stirred overnight. All volatiles were
removed in vacuo, and the resulting red-brown residue was extracted
by hexane (20 + 10 mL) followed by filtration in a glovebox
through PTFE filters. The clear hexane filtrate was then evaporated
in vacuo to give a red solid (0.43 g; 55.0%) (C23H43N4P2TiCl calcd
[(2,5-t-Bu2C6H3N)(t-BuNP)]2Ti(CH2Ph)2 (7). [(2,5-t-Bu2C6H3N)(t-
BuNP)]2TiCl2 (2) (1.0 g, 1.36 mmol) in Et2O (30 mL) was treated
with PhCH2MgCl in THF (2 M, 1.4 mL, 2.8 mmol), as described
for 5, and the separation of the product was carried out as reported
for [(t-BuN)(t-BuNP)]2Ti(CH2Ph)Cl. Ti complex 7 was isolated as
a red solid (0.7 g; 65.5%). 1H NMR (200 MHz, C6D6, 29 °C): δH
1.44 (s, 36H, t-BuAr), 1.57 (s, 18H, t-Bu), 2.91 (s, 4H, CH2Ph),
6.82 (d, J ) 7.3 Hz, 4H, Ph), 7.00 (d, 4H, J ) 7.7 Hz, Ph), 7.20
(m, 4H, t-Bu2C6H3), 7.38 (d, J ) 8.1 Hz, 2H, Ph), 8.25 (dd, 2H, 1J
2
) 2.9 Hz, J ) 2.2 Hz, t-Bu2C6H3). 13C{1H} NMR (50.3 MHz,
C6D6, 29 °C): δC 31.0 (CH3, 5-t-BuAr), 31.33 (t, JPC ) 6.5 Hz,
CH3, t-Bu), 31.54 (CH3, 2-t-BuAr), 34.00 (C, 5-t-BuAr), 34.50 (C,
2-t-BuAr), 51.71 (t, JPC ) 13.73 Hz, C, t-Bu), 87.08 (CH2Ph), 113.8
(Ar), 114.47 (Ar), 117.15 (Ar), 122.33 (Ph), 126.94 (Ph), 127.67
(Ph), 129.17 (Ph), 131.14 (Ar), 142.0 (d, J ) 9.9 Hz, Ar), 144.00
(Ph), 150.00 (t, J ) 1.2 Hz, Ar). 31P{1H} NMR (162 MHz, C6D6,
31 °C): δP 98.89 (s). MS(ESI): found m/z 841.5 (C50H75N4P2Ti+,
error 0.15 ppm), 840.5 (C50H74N4P2Ti+•, error -5.48 ppm);
calculated composition for [(2,5-t-Bu2C6H3N)(t-BuNP)]2Ti(CH2Ph)2
is C50H74N4P2Ti.
1
C, 53.03; H, 8.32, found C, 53.47; H, 7.87). H NMR (400 MHz,
[(2,6-i-Pr2C6H3N)(t-BuNP)]2Ti(CH2Ph)2 (8). [(2,6-i-Pr2C6H3N)(t-
BuNP)]2TiCl2 (3) (1.0 g, 1.49 mmol) in Et2O (30 mL) was treated
with PhCH2MgCl in Et2O (1 M, 3.0 mL, 3.0 mmol), as described
above, and separation of the product was carried out as reported
for [(t-BuN)(t-BuNP)]2Ti(CH2Ph)Cl. Ti complex 8 was isolated as
a red oil (0.84 g; 72.4%) (C46H66N4P2Ti calcd C, 70.39; H, 8.48;
C6D6, 31 °C): δH 1.23 (t, JHH ) 0.9 Hz, 9H, t-Bu, P2N2 cycle),
1.25 (s, 9H, t-Bu, P2N2 cycle), 1.71 (t, JHH ) 0.9 Hz, 18H, t-Bu),
2.82 (s, 2H, CH2Ph), 7.03 (t, JHH ) 7.35 Hz, 1H, Ph), 7.33 (t, JHH
) 7.35 Hz, 2H, Ph), 7.51 (d, JHH ) 7.8 Hz, 2H, Ph). 13C{1H} NMR
(50.3 MHz, C6D6, 29 °C): δC 31.66 (t, JPC ) 6.5 Hz, CH3, t-Bu,
P2N2 cycle), 34.30 (d, JPC ) 12.2 Hz, CH3, t-Bu), 55.67 (t, JPC
)
1
N, 7.14, found C, 70.37; H, 8.65; N, 7.34). H NMR (200 MHz,
14.9 Hz, C, t-Bu, P2N2 cycle), 63.9 (d, JPC ) 14.5 Hz, C, t-Bu),
91.76 (CH2Ph), 123.05 (Ph), 126.16 (Ph), 128.75 (Ph), 148.72 (Ph).
31P{1H} NMR (162 MHz, C6D6, 31 °C): δP 110.69 (s). MS(EI):
m/z (%) 521 (43, M+), 429 (32, M+ - CH2Ph), 347 (78, ligand).
CD2Cl2, 31 °C): δH 1.42 (s, 18H, t-Bu), 1.47 (d, 24H, CH3, i-Pr),
2.86 (two d, JHH ) 8.06 Hz, 4H, CH2Ph), 3.95 (m, 4H, CH, i-Pr),
7.15-7.50 (16H, H-Ar and Ph). 13C{1H} NMR (50.3 MHz, C6D6,

Ti and Zr Benzyl Complexes
Organometallics, Vol. 25, No. 2, 2006 465
29 °C): δC 24.18 (CH3, i-Pr), 29.16 (t, CH, i-Pr), 31.36 (t, JPC
)
mixture was vigorously shaken. Owing to high thermal instability
and very high air and moisture sensitivity, this substance could not
be isolated, and the resulting red solution was investigated only by
6.5 Hz, CH3, t-Bu), 51.60 (t, JPC ) 14.5 Hz, C, t-Bu), 68.64 (CH2-
Ph), 122.24 (Ph), 123.98 (Ar), 126.89 (Ph), 129.00 (Ph), 136.37
(Ar), 140.96 (Ar), 144.43 (Ar), 146.88 (Ph). 31P{1H} NMR (202
MHz, C6D6, 21 °C): δP 115.68 (s). MS (EI): m/z (%) 781 (2, M+),
695 (7, M+ - CH2Ph), 604 (10, M+ - 2 CH2Ph), 556 (30, ligand).
1
NMR methods. H NMR (500 MHz, CD2Cl2, 27 °C): δH 1.27-
1.64 (m, 36H, t-Bu), 2.79 (br s, 2H, PhCH2B), 2.89 (s, 2H, PhCH2-
Ti), 6.73 (d, J ) 7.3 Hz, 2H, PhCH2B), 6.76 (t, J ) 7.3 Hz, 1H,
PhCH2B), 6.85 (t, J ) 7.3 Hz, 2H, PhCH2B), 7.1-7.5 (m, 5H,
PhCH2Ti). 31P{1H} NMR (202 MHz, CD2Cl2, 27 °C): δP 64.46
(s). 19F NMR (470 MHz, CD2Cl2, 27 °C): δF -130.84 (d), -164.51
(t), -167.30 (d).
[(2,5-t-Bu2C6H3N)(t-BuNP)]2Zr(CH2Ph)Cl (12). [(2,5-t-Bu2C6-
H3N)(t-BuNP)]2ZrCl2 (10) (0.62 g, 0.8 mmol) in Et2O (30 mL) was
treated with PhCH2MgCl in THF (2 M, 1.0 mL, 2.0 mmol), as
described above, and separation of the product was carried out as
reported for [(t-BuN)(t-BuNP)]2Ti(CH2Ph)Cl. Complex 12 was
isolated as a yellow-brown solid (0.52 g; 78.5%) (C43H67N4P2ZrCl
calcd C, 62.33; H, 8.15; N, 6.76, found C, 61.89; H, 8.52; N, 7.05).
1H NMR (200 MHz, CD2Cl2, 29 °C): δH 1.25 (s, 18H, 2-t-BuAr),
1.26 (s, 18H, 5-t-BuAr), 1.42 (s, 18H, t-Bu), 3.24 (s, 2H, CH2Ph),
6.74 (dd, 2H, 1J ) 6.2 Hz, 2J ) 2.2 Hz, 4-H-Ar); 6.60-7.30 (5H,
Reaction of [(2,5-t-Bu2C6H3N)(t-BuNP)]2Ti(CH2Ph)2 with
B(C6F5)3. In a glovebox [(2,5-t-Bu2C6H3N)(t-BuNP)]2Ti(CH2Ph)2
(7) (89 mg, 106 µmol) and B(C6F5)3 (54 mg, 106 µmol) were mixed
in a NMR tube and dissolved in CD2Cl2, as described for [(t-BuN)-
(t-BuNP)]2Ti(CH2Ph)2 + B(C6F5)3. Owing to high thermal instabil-
ity and very high air and moisture sensitivity, the substance could
not be isolated, and the resulting red solution was investigated only
1
2
Ph), 7.16 (2H, 3-H-Ar), 7.69 (dd, 2H, J ) 3.3 Hz, J ) 2.2 Hz,
6-H-Ar). 13C{1H} NMR (50.3 MHz, CD2Cl2, 29 °C): δC 30.85
(CH3, 5-t-BuAr), 31.15 (t, JPC ) 6.5 Hz, CH3, t-Bu), 31.34 (CH3,
2-t-BuAr), 34.00 (C, 5-t-BuAr), 34.49 (C, 2-t-BuAr), 51.67 (t, JPC
) 13.73 Hz, C, t-Bu), 72.34 (CH2Ph), 113.47 (Ar), 114.16 (Ar),
116.51 (Ar), 126.66 (Ph), 128.52 (Ph), 128.70 (Ph), 131.27 (Ar),
141.9 (d, J ) 9.9 Hz, Ar), 142.18 (Ph), 149.98 (t, J ) 1.2 Hz, Ar).
31P{1H} NMR (162 MHz, CD2Cl2, 31 °C): δP 97.89 (s). MS(EI):
m/z (%) 829 (1, M+), 737 (3, M+ - CH2Ph), 612 (80, ligand).
1
by NMR methods. H NMR (500 MHz, CD2Cl2, 27 °C): δH 1.29
(s, 36H, t-BuAr), 1.46 (s, 18H, t-Bu), 2.82 (br s, 2H, PhCH2B),
2.90 (s, 2H, CH2PhTi), 6.74 (d, J ) 7.3 Hz, 2H, PhCH2B), 6.77
(br s, 1H, PhCH2B), 6.86 (t, J ) 7.3 Hz, 2H, PhCH2B), 7.10-7.28
(m, 9H, Ar and CH2PhTi), 7.74 (s, 2H, 6-H-Ar). 31P{1H} NMR
(202 MHz, CD2Cl2, 27 °C): δP 99.00 (s). 19F NMR (470 MHz,
CD2Cl2, 27 °C): δF -130.84 (d), -164.45 (t), -167.26 (d).
Reaction of [(t-BuN)(t-BuNP)]2Zr(CH2Ph)2 with B(C6F5)3. In
a glovebox [(t-BuN)(t-BuNP)]2Zr(CH2Ph)2 (14) (60 mg, 106 µmol)
and B(C6F5)3 (54 mg, 106 µmol) were mixed in a NMR tube and
dissolved in CD2Cl2 or C6D5Br, as described for [(t-BuN)(t-
BuNP)]2Ti(CH2Ph)2 + B(C6F5)3. Owing to high thermal instability
and very high air and moisture sensitivity, the substance could not
be isolated, and the resulting orange solution was investigated only
[(2,6-i-Pr2C6H3N)(t-BuNP)]2Zr(CH2Ph)Cl (13). [(2,6-i-Pr2C6-
H3N)(t-BuNP)]2ZrCl2 (11) (1.0 g, 1.4 mmol) in Et2O (30 mL) was
treated with PhCH2MgCl in THF (2 M, 1.4 mL, 2.8 mmol), as
described above, and separation of the product was carried out as
reported for [(t-BuN)(t-BuNP)]2Ti(CH2Ph)Cl. Complex 13 was
isolated as an orange oil (0.80 g; 74.1%) (C39H59N4P2ZrCl calcd
1
by NMR methods. H NMR (500 MHz, CD2Cl2, 27 °C): δH 1.36
1
C, 60.63; H, 7.70; N, 7.25; found C, 61.09; H, 8.06; N, 6.96). H
(s, 18H, t-Bu), 1.39 (s, 18H, t-Bu), 2.79 (br s, 2H, PhCH2B), 3.10
(s, 2H, PhCH2Zr), 6.72 (d, J ) 7.8 Hz, PhCH2B), 6.76 (t, J ) 7.3
Hz, PhCH2B), 6.84 (t, J ) 7.3 Hz, PhCH2B), 7.05-7.25 (m, PhCH2-
Zr and PhCH3). 1H NMR (200 MHz, C6D5Br, 27 °C): δH 1.20 (s,
18H, t-Bu), 1.32 (s, 18H, t-Bu), 3.10 (s, 2H, PhCH2Zr), 3.29 (br s,
2H, PhCH2B), 6.88-7.20 ppm (m, 10H, PhCH2B and PhCH2Zr).
13C{1H} NMR (50.3 MHz, CD2Cl2, 29 °C): δC 28.96 (m, BCH2-
NMR (200 MHz, CD2Cl2, 29 °C): δH 1.16 (s, 18H, t-Bu), 1.24 (d,
24H, CH3, i-Pr), 2.46 (d, 2H, CH2Ph), 3.63 (m, 4H, CH, i-Pr), 6.70-
7.30 (11H, H-Ar and Ph). 13C{1H} NMR (50.3 MHz, CD2Cl2, 29
°C): δC 24.03 (CH3, i-Pr), 29.03 (t, CH, i-Pr), 31.25 (t, JPC ) 6.5
Hz, CH3, t-Bu), 51.58 (t, JPC ) 14.5 Hz, C, t-Bu), 72.41 (CH2Ph),
121.72 (Ph), 123.71 (Ar), 128.55 (Ph), 128.72 (Ph), 136.41 (Ar),
141.11 (Ar), 144.44 (Ar), 146.38 (Ph). 31P{1H} NMR (162 MHz,
CD2Cl2, 27 °C): δP 113.74 (s). MS (EI): m/z (%) 772 (1, M+),
736 (3, M+ - Cl), 556 (30, ligand).
[(t-BuN)(t-BuNP)]2Zr(CH2Ph)2 (14). [(t-BuN)(t-BuNP)]2ZrCl2
(9) (1.0 g, 2.0 mmol) in Et2O (30 mL) was treated with PhCH2-
MgCl in THF (2 M, 2.0 mL, 4.0 mmol), as described above, and
separation of the product was carried out as reported for [(t-BuN)-
(t-BuNP)]2Ti(CH2Ph)Cl. Complex 14 was isolated as a yellow
crystalline solid (1.09 g; 89.3%) (C30H50N4P2Zr calcd C, 58.12; H,
8.13; found C, 58.41; H, 7.89). 1H NMR (200 MHz, C6D6, 29 °C):
δH 1.27 (s, 18H, t-Bu, P2N2 cycle), 1.46 (s, 18H, t-Bu), 2.78 (s,
4H, CH2Ph), 6.76 (t, JHH ) 7.33 Hz, 2H, Ph), 6.91 (d, JHH ) 7.0
Hz, 4H, Ph), 7.06 (t, JHH ) 7.33 Hz, 4H, Ph). 1H NMR (500 MHz,
CD2Cl2, 29 °C): δH 1.21 (s, 18H, t-Bu, P2N2 cycle), 1.33 (s, 18H,
t-Bu), 2.45 (s, 4H, CH2Ph), 6.76 (t, JHH ) 7.33 Hz, 2H, Ph), 6.89
(d, JHH ) 7.32 Hz, 4H, Ph), 7.07 (t, JHH ) 7.33 Hz, 4H, Ph). 13C-
{1H} NMR (50.3 MHz, C6D6, 29 °C): δC 30.00 (t, JPC ) 6.5 Hz,
CH3, t-Bu, P2N2 cycle), 34.10 (d, JPC ) 9.2 Hz, CH3, t-Bu), 54.41
(t, JPC ) 13.7 Hz, C, t-Bu, P2N2 cycle), 59.41 (d, JPC ) 17.2 Hz,
C, t-Bu), 76.49 (CH2Ph), 121.91 (Ph), 126.93 (Ph), 128.80 (Ph),
146.14 (ipso-C, Ph). 31P{1H} NMR (162 MHz, CD2Cl2, 27 °C):
δP 106.11 (s). MS(EI): m/z (%) 527 (80, M+ - CH2Ph), 349 (90,
ligand).
Ph); 29.93 (t, JPC ) 6 Hz, CH3, t-Bu, P2N2 cycle), 33.40 (d, JPC
)
8.4 Hz, CH3, t-Bu), 55.32 (t, JPC ) 13.7 Hz, C, t-Bu, P2N2 cycle),
57.60 (d, JPC ) 15.6 Hz, C, t-Bu), 71.6 (ZrCH2Ph), 122.63 (ZrCH2-
Ph), 125.72 (BCH2Ph), 127.0 (BCH2Ph), 128.86 (ZrCH2Ph), 128.95
(BCH2Ph), 129.46 (ZrCH2Ph), 132.66 (ipso-C, BCH2Ph), 135.0 (m,
C6F5), 139.7 (m, C6F5), 146.22 (m, C6F5), 148.95 (ipso-C, ZrCH2-
Ph), 151.2 (m, C6F5). 13C{1H} NMR (50.3 MHz, C6D5Br, 29 °C):
δC 33.6 (t, CH3, t-Bu, P2N2 cycle), 34.40 (d, CH3, t-Bu), 38.39 (m,
BCH2Ph), 54.76 (t, JPC ) 14.8 Hz, C, t-Bu, P2N2 cycle), 59.36 (d,
JPC ) 20.5 Hz, C, t-Bu), 71.04 (ZrCH2Ph), 122.25 (BCH2Ph),
125.58 (ZrCH2Ph), 128.64 (BCH2Ph), 128.98 (BCH2Ph), 129.2
(ZrCH2Ph), 129.47 (ZrCH2Ph), 134.1 (m, C6F5), 137.22 (ipso-C,
BCH2Ph), 139.1 (m, C6F5), 141.59 (ipso-C, ZrCH2Ph), 146.2 (m,
C6F5), 151.1 (m, C6F5). 31P{1H} NMR (202 MHz, CD2Cl2, 27 °C):
δP 108.52 (s, complex 14, traces), 103.66 (s, cation). 31P{1H} NMR
(202 MHz, C6D5Br, 27 °C): δP 106.6 (s, complex 14, traces), 102.1
(s, cation). 19F NMR (470 MHz, CD2Cl2, 27 °C): δF -127.74 (d,
B(C6F5)3), -130.89 (d, PhCH2B(C6F5)3-), -143.38 (s, B(C6F5)3),
-160.57 (q, B(C6F5)3), -164.64 (t, PhCH2B(C6F5)3-), -167.40 (d,
PhCH2B(C6F5)3-).
{[(t-BuN)(t-BuNP)]2Zr(CH2Ph)(Et2O)}+[PhCH2B(C6F5)3]- (15).
In a glovebox [(t-BuN)(t-BuNP)]2Zr(CH2Ph)2 (14) (120 mg, 212
µmol) and B(C6F5)3 (108 mg, 212 µmol) were mixed in a test tube
and dissolved in Et2O. The reaction occurred immediately and oily
material started to precipitate. The reaction mixture was separated
from that precipitation and transferred into another test tube. The
target product was slowly precipitated by addition of a hexane layer.
All solvents were removed with a syringe, and the yellow oily
Generation of Cationic Species. Reaction of [(t-BuN)(t-
BuNP)]2Ti(CH2Ph)2 with B(C6F5)3. In a glovebox a NMR tube
was charged with [(t-BuN)(t-BuNP)]2Ti(CH2Ph)2 (5) (55 mg, 106
µmol) and B(C6F5)3 (54 mg, 106 µmol), after which 0.6 mL of
CD2Cl2 was added via a syringe at room temperature and the

466 Organometallics, Vol. 25, No. 2, 2006
AxenoV et al.
product was dried in a vacuum (210 mg; 65.6%). Owing to high
thermal instability and very high air and moisture sensitivity, the
substance could not be characterized by elemental analysis methods.
1H NMR (500 MHz, CD2Cl2, 27 °C): δH 1.19 (CH3 from Et2O),
1.21 (s, t-Bu, P2N2 cycle), 1.31 (s, t-Bu, P2N2 cycle), 1.43 (s, t-Bu)
in total 36H, 2.77 (br s, 2H, PhCH2B), 2.84 (s, 2H, PhCH2Zr), 3.60
(br s) and 3.76 (q, J ) 7.1 Hz) 4H, CH2 from Et2O, 6.70 (d, J )
7.3 Hz, 2H, PhCH2B), 6.75 (t, J ) 7.3 Hz, 1H, PhCH2B), 6.84 (t,
J ) 7.3 Hz, 2H, PhCH2B), 7.10 (m, J ) 7.63 Hz, 2H, PhCH2Zr),
7.21 (m, J ) 7.63 Hz, 1H, PhCH2Zr), 7.42 (t, J ) 7.63 Hz, 2H,
Scheme 1
1
PhCH2Zr). H NMR (200 MHz, C6D5Br, 29 °C, excess of Et2O):
δH 1.01 (CH3 from Et2O), 1.07 (d, 18H, t-Bu, P2N2 cycle), 1.18 (s,
18H, t-Bu), 3.23 (br s, 2H, PhCH2B), 3.28 (s, 2H, PhCH2Zr), 3.5
(q, CH2 from Et2O), 6.82 (d, J ) 7.0 Hz, 2H, PhCH2B), 6.96 (t, J
) 7.0 Hz, 1H, PhCH2B), 7.03 (t, J ) 7.3 Hz, 2H, PhCH2B), 7.1-
7.3 (m, 5H, PhCH2Zr). 13C{1H} NMR (50.3 MHz, C6D5Br, 29
°C): δC 13.66 (CH3 from Et2O), 30.86 (m, BCH2Ph), 33.5 (t, CH3,
t-Bu, P2N2 cycle), 34.8 (d, JPC ) 10.7 Hz, CH3, t-Bu), 58.0 (t, JPC
) 14.8 Hz, C, t-Bu, P2N2 cycle), 61.2 (d, JPC ) 19.5 Hz, C, t-Bu),
67.37 (CH2 from Et2O), 70.2 (ZrCH2Ph), 122.25 (BCH2Ph), 122.82
(ZrCH2Ph), 127.13 (BCH2Ph), 128.9 (ZrCH2Ph), 129.03 (BCH2-
Ph), 129.52 (ZrCH2Ph), 134.1 (m, C6F5), 134.8 (ipso-C, BCH2Ph),
139.1 (m, C6F5), 146.2 (m, C6F5), 148.64 (ipso-C, ZrCH2Ph), 151.1
(m, C6F5). 31P{1H} NMR (202 MHz, CD2Cl2, 27 °C): δP 106.4
(s). 19F NMR (470 MHz, CD2Cl2, 27 °C): δF -130.94 (d,
PhCH2B(C6F5)3-), -164.55 (t, PhCH2B(C6F5)3-), -167.37 (PhCH2B-
(C6F5)3-). MS(ESI): found m/z 527.2 (C23H43N4P2Zr+, error 4.85
ppm); calculated composition for [(t-BuN)(t-BuNP)]2Zr(CH2Ph)+
is C23H43N4P2Zr+. The structure was further confirmed by single-
crystal X-ray diffraction studies
area-detector diffractometer at 173(2) K using Mo KR radiation
(graphite monochromator), 0.71073 Å. Data reduction: COLLECT.8
Absorption correction: SADABS.9 Structure solution: SHELX-
9710a or SIR 2002,10b direct methods. Refinement: SHELX-97.10a
Graphics: SHELXTL.11 All non-hydrogen atoms were refined
anisotropically. Hydrogen atoms were refined on calculated posi-
tions. In compound 6 the hydrogen atom H61a was located in a
residual electron density map and refined isotropically. One
disordered t-Bu group in 6 has two orientations with site occupation
factors of 0.25 and 0.75, respectively.
Results and Discussion
Reaction of [(2,5-t-Bu2C6H3N)(t-BuNP)]2Zr(CH2Ph)Cl with
B(C6F5)3. In a glovebox [(2,5-t-Bu2C6H3N)(t-BuNP)]2Zr(CH2Ph)-
Cl (8) (83 mg, 106 µmol) and B(C6F5)3 (54 mg, 106 µmol) were
mixed in a NMR tube and dissolved in CD2Cl2, as described for
[(t-BuN)(t-BuNP)]2Ti(CH2Ph)2 + B(C6F5)3. Owing to high thermal
instability and very high air and moisture sensitivity, the substance
could not be isolated, and the resulting orange solution was
investigated only by NMR methods. 1H NMR (500 MHz, CD2Cl2,
27 °C): δH 1.20-1.50 (m, 54H, t-BuAr and t-Bu), 2.81 (br s, 2H,
BCH2Ph), 6.75 (d, J ) 7.3 Hz, 2H, PhCH2B), 6.77 (br s, 1H,
PhCH2B), 6.86 (t, J ) 7.3 Hz, 2H, PhCH2B), 7.14-7.26 (m, 4H,
Ar), 7.74 (br s, 2H, 6-H-Ar). 31P{1H} NMR (162 MHz, CD2Cl2,
21 °C): δP 99.10 (s). 19F NMR (470 MHz, CD2Cl2, 27 °C): δF
-130.83 (d), -164.51 (t), -167.30 (d).
Polymerization Experiments. A 1 L Bu¨chi glass autoclave was
charged with 200 mL of toluene and cocatalyst (MAO or TIBA),
thermostated at the required temperature, and saturated with ethene,
after which the desired amount of complex solution (preliminary
mixed with TIBA and B(C6F5)3 when B(C6F5)3 was used as the
cocatalyst) was added. The benzyl complexes exhibited extremely
high air and moisture sensitivity and thermal instability. To prevent
the decomposition of the catalyst precursors as well as activated
complexes in the presence of moisture and air traces, TIBA was
added to the stock solutions of complexes (with M/TIBA ratio
1:200). The preparation of stock solutions of complexes and
complex activation with B(C6F5)3 were performed in a glovebox.
The catalyst solution was introduced into an autoclave under argon
pressure. The monomer pressure ((50 mbar) and reaction temper-
ature ((0.5 °C) were kept constant during each polymerization run.
Monomer consumption, polymerization temperature, and pressure
were controlled by real-time monitoring. The polymerizations were
quenched by pouring the resulting reaction mixture into 400 mL
of methanol acidified with aqueous hydrochloric acid. After
precipitation, the polymers were washed several times with
methanol and water and dried at 60 °C overnight.
Synthesis of Benzyl Complexes. We have previously
reported on the synthesis of the bulky dichloro titanium and
zirconium bis(amido)cyclodiphosph(III)azane complexes.5,6 The
literature-known homosubstituted [(t-BuN)(t-BuNP)]2TiCl2 (1)4b,5
and two titanium complexes having the bulkiest aryl substituents
[(ArN)(t-BuNP)]2TiCl2 (2, Ar ) 2,5-t-Bu2C6H3; 3, Ar ) 2,6-
i-Pr2C6H3)5 were chosen for the preparation of the corresponding
Ti benzyl derivatives.
Alkylation reaction of [(t-BuN)(t-BuNP)]2TiCl2 (1) with
PhCH2MgCl turned out to be rather sensitive to the applied
solvent. When 1 was treated with 2 molar equiv of PhCH2-
MgCl in Et2O at -50 °C, only monosubstituted [(t-BuN)(t-
BuNP)]2Ti(CH2Ph)Cl (4) was formed, which was confirmed by
1H NMR and elemental analysis (Scheme 1). In 1H NMR
spectrum of 4 two separate signals for the t-Bu groups attached
to the cyclodiphosph(III)azane ring appeared, which is due to
the chemical nonequivalence of these substituents. This is a
result of the unsymmetric substitution pattern in monobenzyl
complex 4, which lowers its molecule symmetry to Cs. Further
alkylation of 4 with 2 equiv of PhCH2MgCl in Et2O at -50 °C
gave a red sticky solid with very low yield (ca. 10%). According
1
to H NMR data, the resulting raw product consisted of the
desired dialkylated complex, [(t-BuN)(t-BuNP)]2Ti(CH2Ph)2 (5),
and dibenzyl, which was formed as a side-product. Isolation
and purification of 5 failed due to its thermal instability and
the presence of a large amount of dibenzyl. However, pure [(t-
BuN)(t-BuNP)]2Ti(CH2Ph)2 (5) was obtained as a red solid with
moderate yield when a tetrahydrofuran solution of benzylmag-
nesium chloride was used in the alkylation instead (Scheme 1).
(8) Nonius. COLLECT; Nonius BV: Delft, The Netherlands, 2002.
(9) Sheldrick, G. M. SADABS; University of Go¨ttingen: Germany, 1996.
(10) (a) Sheldrick, G. M. SHELX-97; University of Go¨ttingen: Germany,
1997. (b) Burla, M. C.; Camalli, M.; Carrozzini, G. L.; Cascarano, G.;
Giacovazzo, C.; Polidori, G.; Spagna, R. SIR 2002. J. Appl. Crystallogr.
2003, 36, 1103.
Single-Crystal X-ray Diffraction Studies. Crystal data of
compounds 6, 14, and 15 were collected with a Nonius KappaCCD

Ti and Zr Benzyl Complexes
Scheme 2
Organometallics, Vol. 25, No. 2, 2006 467
1
Comparison of H NMR spectra from mono- and dibenzyl Ti
complexes 4 and 5 shows that the signal of methylene hydrogens
from the benzyl groups of 5 is clearly downfield shifted (3.22
vs 2.82 ppm for 4). A similar tendency was also observed in
31P NMR (129.36 ppm for 5 vs 112.35 ppm for 4). This indicates
that titanium is a stronger Lewis acid in [(t-BuN)(t-BuNP)]2Ti-
(CH2Ph)Cl (4) than in [(t-BuN)(t-BuNP)]2Ti(CH2Ph)2 (5). This
observation is in accordance with the fact that chloride is a more
electron-withdrawing ligand than the benzyl group.
Figure 1. ORTEP plot of [(t-BuN)(t-BuNP)]2Ti(CHPh)(THF) (6)
with thermal ellipsoids drawn at the 50% probability level. Except
H61a all hydrogen atoms were omitted for clarity.
Table 1. Crystallographic Data for Complexes 6, 14, and 15
Surprisingly, the Ti benzylidene derivative, [(t-BuN)(t-
BuNP)]2Ti(CHPh)(THF) (6), was formed together with 5 in the
alkylation reaction (Scheme 1). This side-product was sparingly
soluble in hexane and was therefore separable from highly
6
14
15
formula
C27H50N4OP2Ti
C30H50N4P2Zr
C27H53N4OP2Zr,
C25H7BF15
1206.01
P21/n
10.870(1)
33.707(3)
15.506(1)
90.00
100.66(1)
90.00
5583.3(8)
1.435
1
soluble [(t-BuN)(t-BuNP)]2Ti(CH2Ph)2 (5). In the H NMR of
fw
556.56
P1h
619.90
P21/c
9.067(1)
18.639(3)
19.798(3)
90.00
77.56(1)
90.00
3267(1)
1.260
space group
a, Å
b, Å
6 the signal representing the carbene proton is shifted downfield
compared to the CH2 protons from the benzyl group of 5 (4.05
vs 3.22 ppm).12 The presence of the benzylidene carbon at
221.93 ppm (JCH ) 162.85 Hz) in the 13C NMR further
confirmed the carbene nature of 6.13 It can be proposed that
deprotonation of initially formed [(t-BuN)(t-BuNP)]2Ti(CH2-
Ph)Cl by PhCH2MgCl causes Cl- elimination, which is a
prerequisite to form the Ti carbene complex 6 (Scheme 2).14
The THF coordination seems to be the driving force for this
process, as in the absence of THF the reaction does not occur.
Crystals of 6 suitable for single-crystal X-ray diffraction
studies were grown from the saturated hexane solution. In the
solid state the titanium is pentacoordinated and adopts a distorted
trigonal bipyramidal configuration wherein two amido and one
cyclodiphosph(III)azane nitrogen atom, the carbon atom from
the benzylidene group, and the oxygen atom from THF are
located at vertexes of the coordination polyhedron (Figure 1,
Tables 1 and 2). The complex exhibits Cs symmetry as a result
of additional Ti-THF and Ti-N3 bondings. The Ti-CHPh
bond length is short (1.901(4) Å) and clearly distinguishable
from the Ti-CH2Ph bond in the benzyl Ti bis(amido)complexes
(in the range 2.1-2.2 Å),15 but resembles TidC distances in
9.737(1)
11.711(2)
14.758(2)
89.05(1)
70.79(1)
89.94(1)
1588.9(4)
1.165
c, Å
R, deg
â, deg
γ, deg
V, Å3
d
calc, g cm-3
Z
2
4
4
µ, mm-1
λ, Å
T, K
Ra
0.394
0.458
0.345
0.71073
173(2)
0.0536
0.1222
0.71073
173(2)
0.0669
0.1728
0.71073
173(2)
0.0336
0.0739
b
Rw
a R ) ∑||Fo| - |Fc||/∑|Fo| for observed reflections [I > 2σ(I)]. b Rw
)
2
2
2
{∑[w(Fo - Fc )2]/∑[w(Fo )2]}1/2 for all data.
known Ti carbene complexes.16 Although examples of Ti
carbenes have already been reported12,13 and various benzylidene
metal complexes17 are known, this represents, to the best of
our knowledge, the first defined solid-state structure of a
benzylidene Ti complex.
As electron density has moved from the metal center to the
benzylidene ligand, the titanium acquires a high Lewis acid
character, which materializes in the shortening of the Ti-N3
bond (2.206(3) vs 2.267(2) Å in [(t-BuN)(t-BuNP)]2TiCl2). The
C61-H61a hydrogen was located in the Fourier electron density
map and was refined isotropically. The configuration of the C61
carbene atom is highly distorted from the formal sp2-geometry,
as the angle between the TidC bond and Ph substituent is 163.3-
(5)°, and the carbene hydrogen atom is located so that the
H61a-C61-Ti1 angle is about 77°. This and the relatively short
(11) Sheldrick, G. M. SHELXTL, Version 5.10; Bruker AXS Inc.:
Madison, WI, 1997.
(12) In carbene complexes the 1H NMR signal of the carbene hydrogen
atom is usually considerably downfield shifted. In the case of the Ti-carbene
complexes this signal was observed in the range 3-12.3 ppm. See: (a)
Baumann, R.; Stumpf, W. M.; Davis, M. W.; Liang, L.-C.; Schrock, R. R.
J. Am. Chem. Soc. 1999, 121, 7822, (b) Van de Heisteeg, B. J. J.; Schat,
G.; Akkerman, O. S.; Bickelhaupt, F. J. Organomet. Chem. 1986, 310, C25.
(c) Van der Heijden, H.; Hessen, B. J. Chem. Soc., Chem. Commun. 1995,
145. (d) Basuli, F.; Bailey, B. C.; Watson, L. A.; Tomaszewski, J.; Huffman,
J. C.; Mindiola, D. J. Organometallics 2005, 24, 1886, and references
therein.
(15) (a) Carpentier, J.-F.; Martin, A.; Swenson, D. C.; Jordan, R. F.
Organometallics 2003, 22, 4999. (b) Mahanthappa, M. K.; Cole, A. P.;
Waymouth, R. M. Organometallics 2004, 23, 1405. (c) Minhas, R. K.;
Scoles, L.; Wong, S.; Gambarotta, S. Organometallics 1996, 15, 1113.
(16) Normal TidC bond lengths are in the range 1.9-2.0 Å. See refs
12, 13, and Beckhaus, R.; Santamaria, C. J. Organomet. Chem. 2001, 617-
618, 81.
(17) (a) Groysman, S.; Goldberg, I.; Kol, M.; Genizi, E.; Goldschmidt,
Z. Organometallics 2004, 23, 1880. (b) Gatard, S.; Kahlal, S.; Mery, D.;
Nlate, S.; Cloutet, E.; Saillard, J.-Y.; Astruc, D. Organometallics 2004,
23, 1313. (c) Messerle, L. W.; Jennische, P.; Schrock, R. R.; Stucky, G. J.
Am. Chem. Soc. 1980, 102, 6744. (d) Buijink, J.-K. F.; Teuben, J. H.;
Kooijman, H.; Spek, A. L. Organometallics 1994, 13, 2922.
(13) In carbene complexes the 13C NMR signal of the carbene atom is
remarkably downfield shifted. In the case of the Ti-carbene complexes
this signal was observed at frequencies above 200 ppm (JCH in the range
80-150 Hz). See ref 12 and (a) Van Doorn, J. A.; van der Heijden, H,;
Orpen, A. G. Organometallics 1994, 13, 4271. (b) Weng, W.; Yang, L.;
Foxman, B. M.; Ozerov, O. V. Organometallics 2004, 23, 4700, and
references therein.
(14) Carbene complex 6 formed in the alkylation reaction, and it is not
a decomposition product of complex 5. That rules out the possibility of
R-elimination. Complex 5 is decomposing with formation of dibenzyl,
indicating the reduction of Ti(IV).

468 Organometallics, Vol. 25, No. 2, 2006
AxenoV et al.
Table 2. Selected Structural Parameters for Complexes 6,
14, and 15
Scheme 4
6
14
15
Distances, Å
P1-N1
P1-N3
M-C
1.689(4)
1.794(3)
1.896(5)
1.6821(17)
1.7796(16)
2.278(2)
1.720(3)
1.799(3)
2.248(4)
2.284(2)
Zr1-C29
M-N1
2.697(4)
2.094(3)
2.073(3)
2.423(3)
2.243(2)
2.003(3)
2.015(3)
2.206(3)
2.120(3)
1.447(2)
2.1244(16)
2.1120(16)
2.4755(16)
M-N2
M-N3
M-O
C61-C62
C51-B40
C71-B40
1.653(5)
1.682(5)
Angles, deg
N3-P1-N4
N1-P1-N3
N1-M-N2
O-M-C
C17-Zr1-C24
Ti1-C61-C62
C-M-N3
80.23(16)
91.84(16)
117.38(14)
96.66(16)
79.24(7)
93.73(8)
125.51(6)
81.69(14)
91.95(14)
117.70(11)
85.27(13)
97.71(8)
163.3(5)
107.15(17)
122.78(7)
139.15(7)
134.16(13)
pounds [(RN)(t-BuNP)]2Zr(CH2Ph)Cl (12, R ) 2,5-t-Bu2C6H3;
13, R ) 2,6-i-Pr2C6H3) were isolated from the resulting reaction
mixtures (Scheme 4). Further attempts to prepare the dibenzyl
zirconium complexes were also performed by treatment of
[(RN)(t-BuNP)]2Zr(CH2Ph)Cl with a 2-fold excess of PhCH2-
MgCl. However, no desired complexes were recovered; ac-
cording to 1H and 31P NMR data only dibenzyl and unidentified
decomposition products were formed.
C71-B1-C61
C41-B1-C71
106.0(3)
116.0(3)
Scheme 3
On the contrary, the homosubstituted [(t-BuN)(t-BuNP)]2ZrCl2
(9) was directly converted to [(t-BuN)(t-BuNP)]2Zr(CH2Ph)2
(14) with an excellent yield when treated with PhCH2MgCl in
1
Et2O. According to H NMR, 14 is C2V symmetric and the Zr
atom exhibits a tetrahedral configuration in solution. In the solid
state the structure of 14 is analogous with [(t-BuN)(t-
BuNP)]2MCl2 (M ) Zr, Hf)4a,c and [(t-BuN)(t-BuNP)]2HfMe2.7
In 14 the Zr atom adopts a distorted trigonal-bipyramidal
configuration, which is defined by the two amido and one of
the cyclodiphosph(III)azane nitrogens together with the two
methylene groups from the benzyl moieties (Figure 2). The Zr-
CH2Ph distances (Zr1-C17 2.278(2) Å and Zr1-C24 2.284-
(2) Å) are in the normal range (Table 2).20 The C-Zr-C angle
(97.71(8)°) in 14 is less than the Cl-Zr-Cl angle (104.51(8)°)
in the parent complex [(t-BuN)(t-BuNP)]2ZrCl2 (9)4a and the
Me-Hf-Me angle (104.2(2)°) in [(t-BuN)(t-BuNP)]2HfMe2.7
Ti1-H61a distance (1.88(7) Å) indicate an agostic interaction
between titanium and H61a. The C61-C62 bond is 1.445(6)
Å, which is consistent with the length of standard C(sp2)-
C(sp2) bonds (1.48 Å).18 In the solid state the benzylidene group
and the THF ring are almost perpendicular. The Ti-O(THF)
distance is normal and 2.120(3) Å long.19
Bulky aryl-substituted bis(amido)cyclodiphosph(III)azane
titanium complexes [(ArN)(t-BuNP)]2TiCl2 (2, Ar ) 2,5-t-
Bu2C6H3; 3, Ar ) 2,6-i-Pr2C6H3) were converted to correspond-
ing moisture-, air-, and thermal-sensitive dibenzyl derivatives
(7, Ar - 2,5-t-Bu2C6H3; 8, Ar ) 2,6-i-Pr2C6H3) with high yields
(Scheme 3). The existence of the dibenzyl complexes 7 and 8
was validated by elemental analysis, HRMS(ESI), and 1H NMR
1
data. In the H and 13C NMR of 7 and 8 the t-Bu substituents
at the phosph(III)azane cycle were undistinguishable from each
other, and therefore in solution the C2 molecular symmetry can
be proposed for these complexes.
Alkylation of bis(amido)cyclodiphosph(III)azane Zr dichloro
complexes [(RN)(t-BuNP)]2ZrCl2 (9, R ) t-Bu;4c 10, R ) 2,5-
t-Bu2C6H3;6 11, R ) 2,6-i-Pr2C6H3)6 was carried out in
conditions similar to those applied for Ti derivatives. Two
equivalents of PhCH2MgCl per 1 equiv of zirconium compound
were used, but only monosubstituted benzyl zirconium com-
(18) March, J. AdVanced Organic Chemistry: Reactions, Mechanisms,
and Structure; Wiley: New York, 1992; p 21.
(19) (a) Li, Y.; Turnas, A.; Ciszewski, J. T.; Odom, A. L. Inorg. Chem.
2002, 41, 6298. (b) Ascenso, J. R.; de Azevedo, C. G.; Dias, A. R.; Duarte,
M. T.; Eleuterio, I.; Ferreira, M. J.; Gomes, P. T.; Martins, A. M. J.
Organomet. Chem. 2001, 632, 17.
Figure 2. ORTEP plot of [(t-BuN)(t-BuNP)]2Zr(CH2Ph)2 (14) with
thermal ellipsoids drawn at the 50% probability level. All hydrogen
atoms were omitted for clarity.

Ti and Zr Benzyl Complexes
Organometallics, Vol. 25, No. 2, 2006 469
Table 3. Ethene Polymerization Data for Complexes 4, 7, 8, and 12-14a
conc
(µmol)
reaction
temp (°C)
entry
catalyst
MAO/M
yield (g)
activityb
Mw (1)
Mw (2)
1
2
3
4
5
6
7
8
4
4
4
7
8
8
8
14
14
14
12
13
13
20
20
20
10
20
20
20
5
5
5
10
20
20
20
40
20
20
20
40
20
20
40
20
20
40
40
1000
1000
2000
1000
1000
1000
2000
1000
1000
2000
1000
1000
2000
2.9
0.7
1.5
0.46
1.2
1.1
1.1
11.5
9.5
5.6
0.53
2.4
3
290
70
150
92
120
110
110
4600
3800
2240
106
240
300
2.8 × 105
4.6 × 105
5.4 × 105
9.7 × 105
9.1 × 105
1.2 × 106
1.5 × 106
4.9 × 105
4.7 × 105
5.0 × 105
c
9.4 × 104
1.6 × 104
1.5 × 104
2.8 × 104
6.9 × 104
2.2 × 104
2.9 × 104
2.1 × 104
9
10
11
12
13
c
1.1 × 106
1.1 × 104
a 200 mL of toluene, pressure of ethylene 4 bar, polymerization time 30 min. b kg PE/(molcat × h). c Polymer stacked on the filters in a Waters chromatograph.
The cyclodiphosph(III)azane nitrogen-zirconium donor-ac-
ceptor interaction is weaker than in [(t-BuN)(t-BuNP)]2ZrCl2,
which materializes in the lengthening of the Zr-N3 bond
(2.4755(16) Å in 14 vs 2.398(3) Å in 94c). A similar tendency
was observed in the LHfMe2-LHfCl2 series (L ) [(t-BuN)(t-
BuNP)]22-) and can be explained by the fact that chlorine has
a stronger electron-withdrawing ability than the alkyl ligands.7
The benzyl groups are connected to zirconium in a η1-fashion,
as shown by the values of the C-C-Zr angles (C18-C17-
Zr1 115.05(14)°; C25-C24-Zr1 116.17(14)°).
Ethene Polymerization Results. The synthesized [(RN)(t-
BuNP)]2M(CH2Ph)nCl2-n (4, 7, 8, 12-14; M ) Ti, Zr; R )
t-Bu or bulky aryl) were introduced into the ethene polymeri-
zation studies. After activation with B(C6F5)3 (M:B ratio ) 1:1)
and in the presence of 500 equiv of TIBA, they showed very
low polymerization activity. The reason for such marked decline
in activity of the benzyl complexes compared to MAO-activated
Ti and Zr dichloro analogues5,6 could be the fast decomposition
of the benzyl complexes during the activation process due to
their high moisture sensitivity and thermal instability.
When MAO was used as a cocatalyst instead, moderate
catalytic activities were achieved (Table 3). Despite the precau-
tions taken (see Experimental Section), the alkyl precatalysts
decomposed to a certain extent before the ethene polymerization
was started. As a result, two or more kinds of catalytic species
were present in the polymerization mixture, which was reflected
in the bimodal molecular mass distribution of produced polymers
in the GPC measurements (see Supporting Information). How-
ever, the higher molar mass fractions exhibited Mw values
similar to what was observed earlier in ethene polymerization
with the parent dichloro complexes under similar polymerization
conditions.5,6 The lighter molar mass fractions were most
probably produced by decomposition products of the benzyl
complexes.
The MAO-activated Ti and Zr complexes bearing the t-Bu
groups (4 and 14, respectively) revealed very high initial activity,
which, in the case of the Ti derivative 4, severely declined after
a few minutes. As a result, the overall productivity of Ti catalyst
4/MAO was much lower than with its Zr analogue 14/MAO
(290 kgPE/(molcat × h) vs 4600 kgPE/(molcat × h)). As shown
in Table 3 (runs 2, 3 and 9, 10), both complexes were also highly
sensitive to the increased MAO concentration and polymeriza-
tion temperature, while the Zr catalyst 13/MAO containing very
bulky 2,6-di-isopropylphenyl groups was robust against the
changes in reaction conditions. 13/MAO was approximately 3
times more active than Ti and Zr complexes having less bulky
2,5-t-Bu2C6H3 substituents. Similar polymerization behavior was
observed earlier for analogous dichloro Ti and Zr complexes
[(RN)(t-BuNP)]2MCl2 (1, R ) t-Bu, M ) Ti; 9, R ) t-Bu, M
) Zr; 11, R ) 2,6-i-Pr2C6H3, M ) Zr); 1/MAO exhibited high
initial activity, but ethene consumption fell off sharply just after
a few minutes, while 9/MAO displayed the highest activity in
the series.5,6 Analogously, higher polymerization temperatures
and MAO concentrations markedly decrease the catalytic
activities of 1/MAO and to a lesser extent 9/MAO, while only
11/MAO revealed increasing activity in the range of MAO/Zr
ratios 500-2000 as well as in the temperature range 30-60
°C.6 The similar trends in the polymerization behavior affirm
that the structure of the actual catalytic species generated from
the analogous benzyl or chloro complexes bearing the same
amido substituents is similar or exactly the same regardless of
the original precatalyst. This is in accordance with the generally
accepted mechanism for the catalyst activation, where a dichloro
complex is alkylated, and the following abstraction of the metal
alkyl group by a cocatalyst leads to the formation of the
catalytically active species.21
Generation of the Cationic Species. To generate the cationic
species, the Ti and Zr benzyl complexes were involved in the
reaction with B(C6F5)3. The formation of the activated “cationic”
species was followed by 1H, 31P, and 19F NMR. Deuterobenzene
would have been a preferable choice of solvent for the study,
as it prevents complex decomposition through a stabilizing
coordination to the cationic metal center.22 Unfortunately, the
generated species became insoluble in C6D6, and therefore
further investigations were performed in CD2Cl2 instead. Some
of the reactions were also studied in C6D5Br to affirm the results
and to exclude possible solvent effects.
The addition of B(C6F5)3 and CD2Cl2 to the yellow [(t-BuN)-
(t-BuNP)]2Zr(CH2Ph)2 (14) caused a color change to orange.
(21) (a) Kaminsky, W.; Arndt, M. In Applied Homogeneous Catalysis
with Organometallic Compounds; Cornils, B., Herrmann, W. A., Eds.;
VCH: Weinheim, 1996; Vols. 1 and 2. (b) Alt, H. G.; Ko¨ppl, A. Chem.
ReV. 2000, 100, 1205. (c) Brintzinger, H. H.; Fischer, D.; Mu¨lhaupt, R.;
Rieger, B.; Waymouth, R. M. Angew. Chem. 1995, 107, 1255; Angew.
Chem., Int. Ed. Engl. 1995, 34, 1143.
(22) For arene coordination to group 4 metals see: (a) Doerrer, L. H.;
Green, M. L. H.; Ha¨ussinger, D.; Sassmannshausen, J. J. Chem. Soc., Dalton
Trans. 1999, 2111. (b) Gillis, D. J.; Quyoum, R.; Tudoret, M.-J.; Wang,
Q.; Jeremic, D.; Roszak, A. W.; Baird, M. C. Organometallics 1996, 15,
3600. (c) Lancaster, S. J.; Robinson, O. B.; Bochmann, M. Organometallics
1995, 14, 2456. For arene coordination to group 3 metals see: (d) Hayes,
P. G.; Piers, W. E.; Parvez, W. J. Am. Chem. Soc. 2003, 125, 5622, and
references therein.
(20) Zr-CH2Ph distances found in (a) (Zr-C ) 2.312(2) Å) Bazinet,
P.; Wood, D.; Yap, G. P. A.; Richeson, D. S. Inorg. Chem. 2003, 42, 6225.
(b) (Zr-C ) 2.250(6), 2.305(7) Å) Tshuva, E. Y.; Groysman, S.; Goldberg,
I.; Kol, M. Organometallics 2002, 21, 662.

470 Organometallics, Vol. 25, No. 2, 2006
AxenoV et al.
1
In the H NMR spectra of 14/B(C6F5)3 and the analogous Ti
coordinated to the cationic complex.24 In the 19F NMR spectra
of the activated complexes 5, 7, 12, and 14, regardless of the
ligand substitution and the metal, the positions of the fluorine
peaks in 19F NMR were very similar and found around -130.9,
-164.5, and -167.4 ppm with ∆δ(m,p-F) about 2.8 ppm (see
Supporting Information), indicating the presence of free
derivative 5/B(C6F5)3 two kinds of benzyl groups appeared due
to the abstraction of one of the benzyl groups by B(C6F5)3:
B-CH2Ph (broadened signal at 2.8 ppm, triplets at 6.84 and
6.96 ppm, and a doublet at 6.71 ppm) and M-CH2Ph (Ti-
CH2Ph sharp peak at 2.9 ppm, Zr-CH2Ph sharp peak at 3.1
1
PhCH2B(C6F5)3 as a counterion.25
-
ppm, Ph group multiplets at 7.0-7.21 ppm). Similar H NMR
spectra were also recorded for 14/B(C6F5)3 in C6D5Br. If
compared to the parent complex 14, the signal of Zr-CH2
protons shifted 0.65 ppm downfield. Comparable 1H NMR
spectra were also observed for B(C6F5)3-activated 2,5-Bu2C6H3-
substituted Ti di- and Zr monobenzyl complexes 7 and 12 (with
the exception of Zr-CH2Ph signals).
The peak of the activated “cationic” complex (103.66 ppm)
was found in the 31P NMR spectra of 14/B(C6F5)3 in CD2Cl2
or C6D5Br together with the downfield shifted signal of the
unreacted parent complex (108.52 ppm). A similar shift has also
been observed in the activation of [(t-BuN)(t-BuNP)]2HfMe2
by B(C6F5)3 (108.3 ppm for parent complex vs 91.54 ppm for
the corresponding cation).7 The cationic species formed upon
B(C6F5)3 activation of the Ti and Zr complexes 8 and 13 bearing
2,6-i-Pr2C6H3 groups appeared to be very unstable and rapidly
decomposed (in a few minutes) to the corresponding phosph-
(III)azane ligand.
On the basis of our experience with the bis(amido)cyclo-
diphosph(III)azane group 4 metal complexes, the changes in
the electrophilicity of the metal center after the activation can
be seen in the 31P NMR. The 31P NMR signal of the “cationic”
species is shifted upfield compared with the peak of the parent
complex (∆δP). On the basis of the calculated ∆δP values for
B(C6F5)3-activated benzyl derivatives, the clear correlation
between the catalytic activity of a certain complex and the
electrophilicity of the metal center in the activated species can
be established.
After activation of [(t-BuN)(t-BuNP)]2Ti(CH2Ph)2 (5) and 14
with B(C6F5)3, the largest ∆δP in the series of investigated
complexes were observed (∆δP ) 65.2 ppm for 5 and ∆δP )
5.0 ppm for 14). Accordingly, the catalysts [(t-BuN)(t-BuNP)]2Ti-
(CH2Ph)Cl (4)/MAO and [(t-BuN)(t-BuNP)]2Zr(CH2Ph)2 (14)/
MAO displayed here the highest initial polymerization activity,
although the activity of the former decays rapidly. Surrounded
by bulky aromatic substituents, [(ArN)(t-BuNP)]2M(CH2-
Ph)nCl2-n (M ) Ti, Zr; Ar ) bulky aryl) revealed moderate
activity, as well as small ∆δP values (below 0.5). Presumably,
the electron-rich aryl substituents donate electron density to
the metal center via the amide nitrogens and diminish elec-
tron deficiency of the metal. An analogous tendency was
also observed for Hf methyl complexes.7 While [(t-BuN)(t-
BuNP)]2HfMe2 (∆δP ) 6.8 ppm) exhibited moderate activity,
the related [(ArN)(t-BuNP)]2HfMe2 (∆δP ) 0.5-0.7 ppm) were
inactive in ethene polymerization.23
The full dissociation of the cationic complex-borate ion pair
in CD2Cl2 solution leaves the metal centers in the activated
species highly electrophilic. The unsaturated character of the
cationic metal center can also be confirmed by their ability to
coordinate additional donor ligands.26 After addition of Me3P
to the B(C6F5)3-activated benzyl Ti or Zr compounds 5, 7, 12,
and 14, the Me3P peak in 31P NMR shifted from -60.5 ppm to
the region between -6 and -20 ppm due to Me3P coordination
to the cationic metal center. At the same time no changes in
the 19F NMR spectrum were detected, which is consistent with
-
the uncoordinated character of the PhCH2B(C6F5)3 anion. At
ambient temperature and in the presence of a large excess of
trimethylphosphine, the fast exchange between free and coor-
dinated Me3P can be observed in the 31P NMR spectra as the
broadening of the Me3P signal (see Supporting Information).
The full cation-anion dissociation and the ability of the metal
in the cationic complexes to interact with donor molecules are
also connected to their instability.27
The B(C6F5)3-activated [(t-BuN)(t-BuNP)]2Ti(CH2Ph)2 (5)
undergoes partial decomposition during the course of the NMR
1
experiments. The H and 31P NMR spectra of the 5/B(C6F5)3
showed that the decomposition was occurring via degradation
of the diphosph(III)azane cycle. This is connected with the high
electrophilicity of the Ti center revealed in 5/B(C6F5)3 (δP )
64.44 ppm). The donor-acceptor interactions between the
highly positively charged Ti atom and the electron-rich diphos-
ph(III)azane cycle seem to destabilize the ligand bridge against
the destructive electrophilic attacks, either from neighboring
cationic species or B(C6F5)3 (in activation) or from MAO (in
polymerization).
To investigate the structural chemistry of the group 4 metal
bis(amido) benzyl-substituted cationic species bearing a cyclo-
diphosph(III)azane bridge, several attempts to crystallize the
generated Ti and Zr cationic complexes were carried out. As
the B(C6F5)3-activated complexes were isolable only as oily
material, the possibility to enhance the crystallization process
with incorporation of an additional donor ligand was considered.
Further experiments with Et2O as a donor gave {[(t-BuN)(t-
BuNP)]2Zr(CH2Ph)(Et2O)}+[PhCH2B(C6F5)3]- (15) as a yellow
solid, which was very sensitive to air, moisture, and elevated
temperatures. After recrystallization, crystals suitable for X-ray
single-crystal diffraction studies were grown. In {[(t-BuN)(t-
BuNP)]2Zr(CH2Ph)(Et2O)}+[PhCH2B(C6F5)3]- (15) the Zr atom
is pentacoordinated and adopts a highly distorted trigonal-
bipyramidal configuration (Figure 3, the crystal and structural
parameters are in Tables 1 and 2, respectively). Two amido-
zirconium bonds, Zr-N (from diphosph(III)azane cycle) and
The abstraction of a benzyl group by B(C6F5)3 leads to the
-
formation of the PhCH2B(C6F5)3 anion, which often stays
(23) A similar tendency can be observed for other group 4 metal
complexes having phosphorous atoms near the metal center. For example,
for R2TiMe2 (δP ) 25.72 ppm), R2TiCl2 (35.37 ppm), R2TiMe[MeB(C6F5)3]
(49.75 ppm), R2Ti[MeB(C6F5)3]2 (60.57 ppm) (R ) tBu3PN) the tendency
is the same, but the direction for the shift of the 31P NMR signal is opposite
for these complexes. In the case of other Ti and Zr complexes similar data
analysis can be made. See: (a) Gue´rin, F.; Steward, J. C.; Beddie, C.;
Stephan, D. W. Organometallics 2000, 19, 2994. (b) Gue´rin, F.; Stephan,
D. W. Angew. Chem., Int. Ed. 2000, 39, 1298. (c) Cabrera, L.; Hollink, E.;
Stewart, J. C.; Wei, P.; Stephan, D. W. Organometallics 2005, 24, 1091.
(d) Stephan, D. W.; Stewart, J. C.; Gue´rin, F.; Spence, R. E. v H.; Xu, W.;
Harrison, D. G. Organometallics 1999, 18, 1116. (e) Hollink, E.; Wei, P.;
Stephan, D. W. Organometallics 2004, 23, 1562. (f) Yue, N.; Hollink, E.;
Gue´rin, F.; Stephan, D. W. Organometallics 2001, 20, 4424.
(24) Examples are: (a) Shafir, A.; Arnold, J. Organometallics 2003, 22,
567. (b) Gountchev, T. I.; Tilley, T. D. Inorg. Chim. Acta 2003, 345, 81.
(c) Horton, A. D.; de With, J. Chem. Commun. 1996, 1375.
(25) The value of ∆δ(m,p-F) (19F NMR) is a good probe of the
coordination of [MeB(C6F5)3]- to cationic d0 metals (values of 3-6 ppm
indicate coordination; <3 ppm indicates noncoordination). See ref 24c.
(26) Schaper, F.; Geyer, A.; Brintzinger, H. H. Organometallics 2002,
21, 473.
(27) The CD2Cl2-LMR+ (M ) Ti, Zr, Hf) interactions were proposed
in some cases based on obtained NMR data. See: Bochmann, M.; Jaggar,
A. J.; Nicholls, J. C. Angew. Chem. 1990, 102, 830.

Ti and Zr Benzyl Complexes
Organometallics, Vol. 25, No. 2, 2006 471
solid state, it can be concluded then that in solution the benzyl
group coordinates to the central atom in η1-fashion. The 19F
-
NMR data obtained for 15 confirmed that the PhCH2B(C6F5)3
counteranion is free from coordination with the cationic
complex.
Conclusions
The cyclodiphosph(III)azane bis(amido) Ti and Zr benzyl
complexes were synthesized, and their catalytic behavior and
activation with B(C6F5)3 were investigated. From our previous
works5,6 and present studies it appeared that they are attractive
candidates for ethene polymerization, as they possess reasonable
catalytic activity and the ligand framework is tunable. The Zr
catalysts having a [(t-BuN)(t-BuNP)]22- ligand had the highest
activity and metallocene catalyst-like behavior, while the Ti and
Zr derivatives bearing bulky aromatic substituents gave lower
productivity and produced high molecular mass polyethene. For
benzyl Ti and Zr derivatives moderate up to high catalytic
activities in ethene polymerization (70-4600 kg/(molcat × h))
were recorded.
Figure 3. ORTEP plot of {[(t-BuN)(t-BuNP)]2Zr(η2-CH2Ph)}+
(15) with thermal ellipsoids drawn at the 50% probability level.
All hydrogen atoms were omitted for clarity.
Zr-O (from Et2O) donor-acceptor bonds, and the Zr-CH2Ph
η2-coordination define 15 as a 16e- species.
Benzyl-substituted Zr complexes did not show any sign of
the destruction of ligand during the activation with B(C6F5)3.
In ethene polymerization they revealed the highest average
catalytic activity in the series of studied complexes. Apparently,
too high electrophilicity of the cationic metal center in Ti
catalysts bearing tert-butyl groups destabilizes the ligand
framework for destructive attacks. The ligand degradation can
be detected in the 31P NMR, when [(t-BuN)(t-BuNP)]2Ti(CH2-
Ph)2 (5) was activated with B(C6F5)3. This is also supported by
the fact that initially highly active Ti catalysts [(t-BuN)(t-
BuNP)]2TiCl2/MAO5 and [(t-BuN)(t-BuNP)]2Ti(CH2Ph)Cl/
MAO rapidly become deactivated in ethene polymerization
conditions.
The P2N2 ring is almost planar and the Zr-N3 donor-
acceptor bond is shortened compared with the parent complex
(2.423(3) vs 2.4755(16) Å), but not as much as in a related
cationic methyl Hf complex (Hf-N was 2.315(4) Å).7 These
observations are consistent with the saturated 16e- character
of complex 15. The Zr-C28 distance is 2.248(4) Å, which is
usual for Zr benzyl complexes,19 and the Zr-Cipso bond is
relatively short (2.697(4) Å), indicating the Zr-η2-CH2Ph
coordination. A similar coordination type was observed ear-
lier;28,29 for example in the related [Cp2Zr(CH3CN)(η2-CH2Ph)]+
the Zr-CH2Ph distance is 2.344(8) Å and Zr-Cipso is 2.648(6)
Å.29a The donor-acceptor Zr-O bond length in 15 is 2.243(2)
Å.30 The structure of the PhCH2B(C6F5)3 anion is ordinary
-
All B(C6F5)3-activated Ti and Zr complexes displayed their
unsaturated character as they coordinate with donor Me3P. The
tendency to saturate the cationic metal center with additional
donor-acceptor coordination can also be clearly established in
the solid state. The {[(t-BuN)(t-BuNP)]2Zr(η2-CH2Ph)(Et2O)}+-
[PhCH2B(C6F5)3]- is a 16e- complex due to the additional
interaction with a donor nitrogen from the diphosph(III)azane
cycle, the Zr-OEt2 connection, and Zr-η2-CH2Ph bonding.
During the synthesis of the benzyl Ti and Zr bis(amido)-
cyclodiphosph(III)azane complexes, the new Ti carbene was also
isolated, and first solid-state structure of the Ti-benzylidene
complex was defined.
(see Supporting Information).
The structures of the activated complex 14/B(C6F5)3 and {-
[(t-BuN)(t-BuNP)]2Zr(CH2Ph)(Et2O)}+[PhCH2B(C6F5)3]- (15)
in solution were investigated by means of 1H, 31P, 13C, and 19
F
NMR methods. The positions of the methylene protons as well
as the aromatic protons (from BCH2Ph and ZrCH2Ph groups)
1
in the H NMR spectra of 15 (C6D5Br and CD2Cl2 were used
as solvents) were similar to those observed for B(C6F5)3-
activated complexes 5, 7, 12, and 14 (see above). In the 13C
NMR (C6D5Br) spectrum of 15, the signal for the methylene
carbon of the Zr-CH2Ph group appears at 70.2 ppm, and the
signal for the Cipso atom of the Zr-CH2Ph group was found at
148.6 ppm. Similar shifts for the carbon atoms of the benzyl
group were found in the 13C NMR spectra of 14/B(C6F5)3.
Despite the Zr-η2-CH2Ph coordination displayed for 15 in the
Acknowledgment. This work was financially supported by
Academy of Finland (project no. 204408 and 209739) and
Finnish National Technology Agency (TEKES). Erkki Aitola
is acknowledged for the GPC measurements of produced
polymers.
(28) Chen, E. Y.-X.; Marks, T. J. Chem. ReV. 2000, 100, 1391.
(29) For examples of the structurally characterized benzyl “cationic”
complexes see: (a) Jordan, R. F.; LaPointe, R. E.; Bajgur, C. S.; Echols,
S. F.; Willett, R. J. Am. Chem. Soc. 1987, 109, 4111. (b) Pellecchia, C.;
Grassi, A.; Immirzi, A. J. Am. Chem. Soc. 1993, 115, 1160. (c) Pellecchia,
C.; Immirzi, A.; Pappalardo, D.; Peluso, A. Organometallics 1994, 13, 3773.
(30) In the related bis(amido) Zr cation [(MesNCH2CH2)2NMe]ZrMe-
(Et2O)+ (Mes ) mesityl) the Zr-O distance is 2.234(5) Å. Schrock, R. R.;
Casado, A. L.; Goodman, J. T.; Liang, L.-C.; Bonitatebus, P. J.; Davis, W.
M. Organometallics 2000, 19, 5325.
Supporting Information Available: Listings of spectral
data, GPC results, and a figure showing the structure of the
-
PhCH2B(C6F5)3 anion. This material is available free of charge
via the Internet at http://pubs.acs.org.
OM050725H