Titanium and zirconium complexes with the new ancillary diamido ligand N,N′-bis(trimethylsilyl)amidobenzylamido(2-): Syntheses, structures, and α-olefin polymerization activities

Article abstract of DOI:10.1021/om990121b

Using the disymmetric N,N′-bis(trimethylsilyl)aminobenzylamine (H₂MABA; 1) ligand, the new group 4 metal complexes (MABA)TiCl₂ (2), (MABA)TiMe₂ (3), (MABA)Ti(CH₂Ph)₂ (4), (MABA)ZrCl₂ (5), a

Full text of DOI:10.1021/om990121b

Organometallics 1999, 18, 4107-4113
4107
Tita n iu m a n d Zir con iu m Com p lexes w ith th e New
An cilla r y Dia m id o Liga n d
N,N′-Bis(tr im eth ylsilyl)a m id oben zyla m id o(2-):
Syn th eses, Str u ctu r es, a n d r-Olefin P olym er iza tion
Activities
You-Moon J eon, J ungseok Heo, Won Mok Lee, Taihyun Chang, and
Kimoon Kim*
Department of Chemistry and National Creative Research Initiative Center for Smart
Supramolecules, Pohang University of Science and Technology, San 31 Hyojadong,
Pohang 790-784, South Korea
Received February 22, 1999
Using the disymmetric N,N′-bis(trimethylsilyl)aminobenzylamine (H2MABA; 1) ligand,
the new group 4 metal complexes (MABA)TiCl2 (2), (MABA)TiMe2 (3), (MABA)Ti(CH2Ph)2
(4), (MABA)ZrCl2 (5), and (MABA)2Zr (6) were prepared. X-ray crystal structures of 2, 4,
and 6 were determined. The crystal structure of 2 suggests that an agostic interaction
between the titanium metal center and benzylic protons exists in the solid state. However,
the agostic interaction is not sustained in solution, as indicated by NMR spectroscopy.
Complexes 2 and 5, activated by MMAO, and 4, activated by B(C6F5)3, have moderate catalytic
activities for the polymerization of R-olefins.
In tr od u ction
complexes often exhibit novel types of polymerization
activities such as living polymerization of R-olefins. For
example, titanium complexes with propylene-bridged
aryl-substituted diamido ligands reported by McConville
catalyze the living polymerization of terminal olefins at
room temperature.1 Zirconium complexes of oxo-bridged
dianiline derivatives reported by Schrock are also good
catalyst precursors for the living polymerization of
terminal olefins.3c We also recently reported zirconium
complexes containing the novel diamido ancillary
ligand 2,2′-ethylenebis(N,N′-(triisopropylsilyl)aniline)
(EBTiP), which exhibit remarkable activities of living
polymerization of terminal olefins.10 Here we report
titanium and zirconium complexes of another new
ancillary ligand, N,N′-bis(trimethylsilyl)amidobenzyl-
amido (MABA)2-, and their catalytic activities of olefin
polymerization.
Group 4 metal complexes containing chelating di-
amido or dialkoxo ligands have attracted much
attention1-10 as potential catalysts for the polymeriza-
tion of terminal olefins because of their close relation-
ship with the well-known metallocene and cyclopenta-
dienyl-amidecomplexes.11 Not onlyaresuch noncyclopenta-
dienyl ligands easily accessible but also their metal
(1) (a) Scollard, J . D.; McConville, D. H.; Vittal, J . J . Organometallics
1997, 16, 1810. (b) Scollard, J . D.; McConville, D. H. J . Am. Chem.
Soc. 1996, 118, 10008. (c) Scollard, J . D.; McConville, D. H.; Payne, N.
C.; Vittal, J . J . Macromolecules 1996, 29, 5241. (d) Guerin, F.;
McConville, D. H.; Vittal, J . J . Organometallics 1995, 14, 3154.
(2) (a) Britovsek, G. J . P.; Gibson, V. C.; Duncan, F. W. Angew.
Chem., Int. Ed. 1999, 38, 428. (b) Tsuie, B.; Swenson, D. C.; J ordan,
R. F. Organometallics 1997, 16, 1392. (c) Lee, C. H.; Na, Y.-H.; Park,
S, J .; Park, J . W. Organometallics 1998, 17, 3648.
(3) (a) Schrock, R. R.; Schattenmann, F.; Aizenberg, M.; Davis, M.
D. Chem. Commun. 1998, 199. (b) Warren, T. H.; Schrock, R. R.; Davis,
W. M. Organometallics 1996, 15, 562. (c) Baumann, R.; Davis, W. M.;
Schrock, R. R. J . Am. Chem. Soc. 1997, 119, 3830. (d) Schrock, R. R.;
Seidel, S. W.; Schrodi, Y.; Davis, W. M. Organometallics 1999, 18, 428.
(e) Graf, D. D.; Schrock, R. R.; Davis, W. M.; Stumpf, R. Organome-
tallics 1999, 18, 428.
Resu lts a n d Discu ssion
Tita n iu m Com p lexes. The free base ligand H2-
(MABA) (1) was synthesized in a moderate yield by the
reaction of lithiated 2-aminobenzylamine and 2 equiv
of trimethylsilyl chloride in THF. Reaction of the lithium
salt of 1 with TiCl4(THF)2 in refluxing toluene produces
(4) (a) Clark, H. C. S.; Cloke, F. G. N.; Hitchcock, P. B.; Love, J . B.;
Wainwright, A. P. J . Organomet. Chem. 1995, 501, 333. (b) Cloke, F.
G. N.; Hitchcock, P. B.; Love, J . B. J . Chem. Soc., Dalton Trans. 1995,
25. (c) Cloke, F. G.; Geldbach, T. J .; Hichcoke, P. B.; Love, J . B. J .
Organomet. Chem. 1995, 506, 343.
(5) (a) Horton, A. D.; de With, J . Organometallics 1997, 16, 5424.
(b) Horton, A. D.; de With, J .; van der Linden, A. J .; van de Weg, H.
Organometallics 1996, 15, 2672. (c) Horton, A. D.; de With, J . Chem.
Commun. 1996, 1375. 6.
(6) Tinkler, S.; Deeth, R. J .; Duncalf, D. J .; McCamley, A. Chem.
Commun. 1996, 2623.
(7) Aoyagi, K.; Gantzel, P. K.; Kalai, K.; Tilley, T. D. Organometallics
1996, 15, 923.
(10) J eon, Y.-M.; Park, S. J .; Heo, J .; Kim, K. Organometallics 1998,
17, 3161.
(11) (a) Guram, A. S.; J ordan, R. F. In Comprehensive Organome-
tallic Chemistry, 2nd ed.; Lappert, M. F., Ed.; Pergamon: Oxford, U.K.,
1995; Vol. 4, pp 589-625. (b) McKnight, A. L.; Waymouth, R. M. Chem.
Rev. 1998, 98, 2587. (c) Kaminsky, W. J . Chem. Soc., Dalton Trans.
1998, 1413. (d) Brintzinger, H. H.; Fischer, D.; Mulhaupt, R.; Rieger,
B.; Waymouth, R. M. Angew. Chem., Int. Ed. Engl. 1995, 34, 1143. (e)
Mohring, P. C.; Coville, N. J . J . Organomet. Chem. 1994, 479, 1.
(8) Pritchett, S.; Gantzel, P.; Walsh, P. J . Organometallics 1997, 16,
5130.
(9) Male, N. A. H.; Thornton-Pett, M.; Bochmann, M. J . Chem. Soc.,
Dalton Trans. 1997, 2487.
10.1021/om990121b CCC: $15.00 © 1999 American Chemical Society
Publication on Web 09/01/1999

4108 Organometallics, Vol. 18, No. 20, 1999
J eon et al.
be due to the fact that 2 and McConville’s compound
have a six-membered metallacycle while o-C6H4(NSii-
Pr3)2TiCl2 contains a five-membered chelate ring. The
Cl-Ti-Cl angle (112.17(4)° for molecule 1 and 112.91-
(4)° for molecule 2) is larger than that in McConville’s
complex (107.77(9)°), presumably due to the smaller
substituent on the nitrogen atom in 2. A planar geom-
etry of the nitrogen atoms indicates that the sp2-
hybridized atoms have pπ-dπ interactions with the
metal center.
Interestingly, the bond angles Ti(1)-N(2)-C(7) (mol-
ecule 1) and Ti(2)-N(4)-C(20) (molecule 2) in the six-
membered titanacycles are small (97.36(15)° and 97.16-
(15), respectively) and the interatomic distances Ti(1)‚
‚‚C(7) (molecule 1) and Ti(2)‚‚‚C(20) (molecule 2) are
short (2.506(3) and 2.500(3) Å, respectively), which
suggests that there is an agostic (three-center-two-
electron) interaction between C(7)-H and Ti(1) (mol-
ecule 1) and C(20)-H and Ti(2) (molecule 2).12,13 In the
1H NMR spectrum of 2 at ambient temperature, the
benzylic protons resonate at 5.32 ppm as a singlet in
chloroform-d, which is considerably shifted to lower field
compared to those of the free ligand 1 and the Ti
complex 4, 3.86 (singlet) and 4.58 (singlet) ppm, respec-
tively (vide infra). However, the large C-H coupling
constant for C(7)-H (or C(20)-H) (137.6 Hz) in 2
suggests that the agostic interaction between the Ti and
C(7)-H (or C(20)-H) is not sustained in solution.
Furthermore, the signal for the benzylic protons re-
mains as a singlet even at -90 °C in dichloromethane-
d2 or toluene-d8 solution, indicating a rapid fluxional
behavior even at the low temperature.
F igu r e 1. X-ray crystal structure of 2. Only one of the
two independent molecules (molecule 1) is depicted.
Ta ble 1. Selected Bon d Dista n ces (Å) a n d Bon d
An gles (d eg) for 2
molecule 1
molecule 2
Ti(1)-N(1)
1.895(2)
1.825(2)
Ti(2)-N(3)
Ti(2)-N(4)
1.904(2)
1.827(2)
2.2272(11)
2.2697(13)
2.500(3)
2.33(3)
Ti(1)-N(2)
Ti(1)-Cl(1)
Ti(1)-Cl(2)
Ti(1)‚‚‚C(7)
Ti(1)‚‚‚H(7A)
2.2316(11) Ti(2)-Cl(3)
2.2714(12) Ti(2)-Cl(4)
2.506(3)
2.36(3)
Ti(2)‚‚‚C(20)
Ti(2)‚‚‚H(20A)
N(1)-Ti(1)-N(2)
99.25(9)
N(3)-Ti(2)-N(4)
99.25(9)
Cl(3)-Ti(2)-Cl(4) 112.91(4)
Ti(2)-N(4)-C(20) 97.16(15)
Cl(1)-Ti(1)-Cl(2) 112.17(4)
Ti(1)-N(2)-C(7)
97.36(15)
Ti(1)-N(2)-Si(2) 140.34(12) Ti(2)-N(4)-Si(4) 139.79(13)
Si(2)-N(2)-C(7)
119.39(16) Si(4)-N(4)-C(20) 120.11(17)
The complex 2 was treated with MeMgI in ether
solution to give the dimethyl derivative 3 (eq 2).
the dark red product (MABA)TiCl2 (2) (eq 1). The
Although the reaction produces the desired product
almost quantitatively, as indicated by NMR spectros-
copy, we failed to isolate analytically pure crystalline
product. The product was isolated as a sticky solid which
was difficult to recrystallize due to its high solubility
even in pentane.
The dibenzyltitanium complex 4 was synthesized
analogously by the reaction of 2 and benzylmagnesium
chloride in ether solution at room temperature (eq 3).
1
product has been characterized by H/13C NMR spec-
troscopy, mass spectrometry, elemental analysis, and
X-ray crystallography. Although the reaction proceeds
almost quantitatively, as indicated by 1H NMR spec-
troscopy, the isolation yield is much lower because of
the high solubility of the product in most hydrocarbon
solvents, including pentane.
Single crystals of 2 suitable for X-ray crystallography
were obtained from a chilled pentane solution. The
asymmetric unit contains two independent molecules
with almost identical structures, one of which is shown
in Figure 1. Selected bond distances and angles are
summarized in Table 1. No unusual bond parameters
are observed. The titanium ion is coordinated by two
nitrogen atoms and two chloride ions in a distorted-
tetrahedral geometry. The N-Ti-N angle (99.25(9)° for
both molecule 1 and molecule 2) is quite similar to that
in McConville’s catalyst ([ArNCH2CH2CH2NAr]TiCl2
(Ar ) 2,6-iPr2C6H3; 99.2(2)°)1c but much larger than that
in o-C6H4(NSiiPr3)2TiCl2 (92.6(2)°).7 This difference may
1
In the H NMR spectrum, the benzylic protons of the
(12) (a) Scherer, W.; Priermeier, T.; Haaland, A.; Volden, V.;
McGrady, G. S.; Downs, A. J .; Boese, R.; Blaser, D. Organometallics
1998, 17, 4406. (b) Scherer, W.; Hieringer, W.; Spiegler, M.; Sirsch,
P.; McGrady, G. S.; Downs, A. J .; Haaland, A.; Pedersen, B. Chem.
Commun. 1998, 2471. (c) Braga, D.; Grepioni, F.; Biradha, K.; Desiraju,
G. R. J . Chem. Soc., Dalton Trans. 1996, 3925. (d) Crabtree, R. H.
Angew, Chem., Int. Ed. Engl. 1993, 32, 789. (e) Brookhart, M.; Green,
M. J . Organomet. Chem. 1983, 250, 395. (f) Ujaque, G.; Cooper, A. C.;
Maseras, F.; Einstein, O.; Caulton, K. G. J . Am. Chem. Soc. 1998, 120,
361.

Ti and Zr Complexes with a New Diamido Ligand
Organometallics, Vol. 18, No. 20, 1999 4109
Å, Ti(2)-N(4)-C(37) ) 100.9(2)° (molecule 2). It is also
interesting to note that, in molecule 1, one of the benzyl
groups attached to the metal center has a normal Ti-
CH2-Ph angle (Ti(1)-C(21)-C(22) ) 118.5(2)°), whereas
the other benzyl group has an acute Ti-CH2-Ph angle
(Ti(1)-C(14)-C(15) ) 92.5(3)°) and a short Ti‚‚‚Cipso
distance (Ti(1)‚‚‚C(15) ) 2.647(4) Å). This structure
suggests that the former benzyl group is bound to the
metal center in an η1 fashion whereas the latter is bound
in an η2 fashion. A similar η2 coordination mode of the
benzyl groups has been observed in other Ti com-
plexes: Ti(CH2Ph)4 (Ti-C-Cipso ) 88(2), 98(2)°, Ti‚‚‚
Phipso ) 2.61(2), 2.81(3) Å);14a,b [{Ti(CH2Ph)3}2(µ-η5:η5-
C10H8)] (Ti-C-Cipso ) 90.9(3)°, Ti‚‚‚Phipso ) 2.611(4)
Å);14c µ-[o-(CH2)2C6H4]{Cp*Ti[o-(CH2)2C6H4]}2 (Ti-C-
Cipso ) 84.7(8)°, Ti‚‚‚Phipso ) 2.47(1) Å);14d (Ben)Ti(CH2-
Ph)Cl (Ti-C-Cipso ) 87.0(5)°, Ti‚‚‚Phipso ) 2.500(8) Å).14e
However, only an η1 coordination mode of the benzyl
groups is observed in molecule 2: Ti(2)‚‚‚C(45) ) 3.188-
(4) Å, Ti(2)‚‚‚C(52) ) 2.992(4) Å. Furthermore, the η2-
benzyl interaction is not observed in solution. As
mentioned above, the metal-bound benzylic protons in
4 show a diastereotopic AB pattern with δA 2.43, δB 2.59,
and J A-B ) 10.5 Hz. This large geminal coupling
constant suggests that the benzyl ligand has an sp3-
hybridized methylene carbon. In the 13C NMR spectrum,
the Ti-CH2 resonance occurs farther downfield (82.5
ppm, J C-H ) 123.4 Hz) compared to those of previously
known (η2-benzyl)titanium complexes (δ <75 ppm, J C-H
> 130 Hz).15 These NMR data suggest that such an η2-
benzyl interaction is not sustained in solution.
F igu r e 2. X-ray crystal structure of 4. Only one of the
two independent molecules (molecule 1) is depicted.
Ta ble 2. Selected Bon d Dista n ces (Å) a n d Bon d
An gles (d eg) for 4
molecule 1
molecule 2
Ti(1)-N(1)
1.942(3)
1.873(3)
2.138(4)
2.114(4)
2.614(4)
2.647(4)
3.110(4)
Ti(2)-N(3)
1.934(3)
1.854(3)
2.111(4)
2.129(4)
2.597(4)
3.188(4)
2.992(4)
Ti(1)-N(2)
Ti(1)-C(14)
Ti(1)-C(21)
Ti(1)‚‚‚C(7)
Ti(1)‚‚‚C(15)
Ti(1)‚‚‚C(22)
Ti(2)-N(4)
Ti(2)-C(44)
Ti(2)-C(51)
Ti(2)‚‚‚C(37)
Ti(2)‚‚‚C(45)
Ti(2)‚‚‚C(52)
N(1)-Ti(1)-N(2)
99.84(13) N(3)-Ti(2)-N(4)
99.61(13)
C(14)-Ti(1)-C(21) 120.7(2)
C(44)-Ti(2)-C(51) 109.2(2)
Zir con iu m Com p lexes. At the outset of this work
we expected to synthesize the dichlorozirconium com-
plex (MABA)ZrCl2 (5) in a way analogous to that for
the corresponding titanium complex (MABA)TiCl2 (2).
However, the reaction of the dilithium salt of 1 and
ZrCl4(THF)2 in refluxing toluene results in (MABA)2Zr
(6) (eq 4), instead.
Ti(1)-N(1)-C(1)
Ti(1)-N(2)-C(7)
Ti(1)-C(14)-C(15) 92.5(3)
Ti(1)-C(21)-C(22) 118.5(2)
121.8(2)
101.0(2)
Ti(2)-N(3)-C(31)
Ti(2)-N(4)-C(37)
120.3(2)
100.9(2)
Ti(2)-C(44)-C(45) 123.6(3)
Ti(2)-C(51)-C(52) 110.6(3)
chelate ring appear at 4.58 ppm as a singlet signal while
the metal-bound benzylic protons appear at 2.43 and
2.59 ppm as two doublets. No decoalescence of the
chelate benzylic proton signal was observed, even at -60
°C in chloroform-d solution. Although complex 4 is a
gelatinous solid at room temperature, slow cooling of a
pentane solution of 4 to -50 °C produced single crystals
suitable for X-ray work. The unit cell contains two
independent molecules with similar geometrical param-
eters. The molecular structure of one of them (molecule
1) is depicted in Figure 2, and selected bond distances
and bond angles are summarized in Table 2. The
average Ti-N distances are 1.908(3) Å (molecule 1) and
1.884(3) Å (molecule 2). The N-Ti-N angles are
99.84(13)° (molecule 1) and 99.61(13)° (molecule 2). The
Ti(1)-C(14) and Ti(1)-C(21) distances are 2.138(4) and
2.114(4) Å, respectively, and the C(14)-Ti(1)-C(21)
angle is 120.7(2)° for molecule 1. Similar metric param-
eters are found for molecule 2. In contrast to 2, no
agostic interaction between the benzylic hydrogen atoms
of the chelate ring and the metal center is evident in
this structure: Ti(1)‚‚‚C(7) ) 2.614(4) Å, Ti(1)-N(2)-
C(7) ) 101.0(2)° (molecule 1) and Ti(2)‚‚‚C(37) ) 2.597(4)
The first evidence for the formation of the 2:1 complex
1
6 came from its H NMR spectrum. In contrast to the
1:1 complexes 2-4, the benzylic protons in 6 show a
typical AB spin pattern at 4.23 and 4.54 ppm (doublet,
J H-H ) 15.3 Hz) in chloroform-d solution at room
temperature. For unequivocal structural characteriza-
tion we decided to determine the structure by X-ray
crystallography. Single crystals of 6 suitable for X-ray
work were obtained from a chilled pentane solution. The
asymmetric unit contains two independent molecules
(14) For leading references for titanium-benzyl bonding, see: Bo-
chmann, M. In Comprehensive Organometallic Chemistry, 2nd ed.;
Lappert, M. F., Ed.; Pergamon: Oxford, U.K., 1995; Vol. 4, pp 273-
431. See also: (a) Bassi, I. W.; Allegra, R.; Scordamaglia, G.; Chioccola,
G. J . Am. Chem. Soc. 1971, 93, 3787. (b) Davies, G. R.; J arvis, J . A. J .;
Kilbourn, B. T. J . Chem. Soc. D. 1971, 1511. (c) Alvaro, L. M.; Flores,
J . C.; Royo, P.; Pellinghelli, M. A.; Tiripicchio, A. Organometallics 1992,
11, 3301. (d) Mena, M.; Royo, P.; Serrano, R.; Pellinghelli, M. A.;
Tiripicchio, A. Organometallics 1989, 8, 476. (e) Warren, T. H.; Schrock,
R. R.; Davis, W. M. Organometallics 1996, 15, 562.
(13) Although accurate positions of hydrogen atoms are difficult to
obtain by X-ray diffraction methods, the hydrogen atoms attached to
C(7) and C(20) were located from the difference electron density map
and refined isotropically. The short Ti‚‚‚H distances (Ti(1)‚‚‚H(7A) )
2.36(3) Å (molecule 1), Ti(2)‚‚‚H(20A) ) 2.33(3) Å (molecule 2)) also
support the agostic interaction in the solid state.
(15) (a) Latesky, S. L.; McMullen, A. K.; Niccolai, G. P.; Rothwell,
I. P.; Huffman, J . C. Organometallics 1985, 4, 902. (b) Hughes, A. K.;
Meetsma, A.; Teuben, J . H. Organometallics 1993, 12, 1936.

4110 Organometallics, Vol. 18, No. 20, 1999
J eon et al.
days, which indicates formation of the dichlorozirconium
complex 5 (eq 5). Complex 5 is a slightly yellow solid,
sparingly soluble in nonpolar hydrocarbon solvents but
soluble in polar solvents such as diethyl ether, THF,
dichloromethane, and toluene. In 5, one THF molecule
is coordinated to the zirconium metal center, as indi-
cated by 1H/13C NMR spectroscopy and elemental
analysis. A similar ligand redistribution reaction of [Ti-
(Me3SiNCH2CH2NSiMe3)2] with 1 equiv of TiCl4(THF)2
has been reported to produce the dichloro complex [Ti-
(Me3SiNCH2CH2NSiMe3)Cl2].6
This ligand redistribution reaction led us to examine
the mechanism of formation of 2 by monitoring the
reaction of the lithium salt of 1 with TiCl4(THF)2 (eq 1)
by 1H NMR spectroscopy. Interestingly, the NMR
spectrum of the reaction mixture after 1 h reflux shows
a doublet of doublets pattern for the benzylic protons
of the chelate ring, as observed in 6. However, only a
singlet signal was observed after 3 h reflux. This
observation suggests that, in this reaction, the 2:1
complex (MABA)2Ti forms first, which quickly under-
goes a ligand redistribution reaction with remaining
TiCl4(THF)2 to form the 1:1 complex 2 (eq 6). The 2:1
F igu r e 3. X-ray crystal structure of 6. Only one of the
two independent molecules (molecule 1) is depicted.
Ta ble 3. Selected Bon d Dista n ces (Å) a n d Bon d
An gles (d eg) for 6
molecule 1
molecule 2
Zr(1)-N(1) 2.0543(16) Zr(2)-N(5)
2.0532(16)
2.0950(16)
2.0536(15)
2.0926(16)
2.7344(19)
2.7217(19)
Zr(1)-N(2)
Zr(1)-N(3)
Zr(1)-N(4)
Zr(1)‚‚‚C(7)
Zr(1)‚‚‚C(20)
2.0949(16) Zr(2)-N(6)
2.0554(16) Zr(2)-N(7)
2.0884(16) Zr(2)-N(8)
2.715(2)
Zr(2)‚‚‚C(33)
2.7306(19) Zr(2)‚‚‚C(46)
N(1)-Zr(1)-N(2)
N(1)-Zr(1)-N(3)
N(1)-Zr(1)-N(4)
N(2)-Zr(1)-N(3)
N(2)-Zr(1)-N(4)
N(3)-Zr(1)-N(4)
Zr(1)-N(1)-C(1)
Zr(1)-N(2)-C(7)
98.52(6)
115.08(6)
118.22(6)
119.59(6)
108.58(6)
97.92(6)
N(5)-Zr(2)-N(6)
98.31(6)
113.84(6)
119.03(6)
119.53(6)
109.03(6)
98.32(6)
N(5)-Zr(2)-N(7)
N(5)-Zr(2)-N(8)
N(6)-Zr(2)-N(7)
N(6)-Zr(2)-N(8)
N(7)-Zr(2)-N(8)
107.67(12) Zr(2)-N(5)-C(40) 108.51(11)
99.05(12) Zr(2)-N(6)-C(46) 99.29(11)
Zr(1)-N(3)-C(14) 108.04(12) Zr(2)-N(7)-C(27) 108.11(11)
Zr(1)-N(4)-C(20) 100.09(11) Zr(2)-N(8)-C(33) 100.04(11)
of 6 with nearly identical structures. The molecular
structure of one of them (molecule 1) is shown in Figure
3, and selected bond distances and angles are listed in
Table 3. No unusual bond parameters are observed. As
we suspected, the Zr ion is coordinated by four nitrogen
atoms of the two MABA ligands in a distorted-tetrahe-
dral geometry. The Zr-N bond distances range from
2.054 to 2.095 Å. The aromatic amide has a longer Zr-N
distance than the benzylic amide: e.g., Zr(1)-N(1) )
2.0543(16) Å; Zr(1)-N(2) ) 2.0949(16) Å. The average
bite angle of the ligand is 98.22(2)°. All the nitrogen
atoms coordinated to zirconium have a trigonal-planar
geometry. It is interesting to note that the bond angles
Zr(1)-N(2)-C(7) (99.05(12)°) and Zr(1)-N(4)-C(20)
(100.09(11)°) are considerably smaller than the angles
Zr(1)-N(1)-C(1) (107.67(12)°) and Zr(1)-N(3)-C(14)
(108.04(12)°).
complex (MABA)2Ti appears to be less stable than the
corresponding Zr complex 6. The higher stability of the
Zr complex appears to be due to the larger radius of the
Zr ion. With these results we now can synthesize any
of the 1:1 and 2:1 complexes of titanium and zirconium
by controlling the reaction time and conditions carefully.
P olym er iza tion . Complexes 2 and 5 activated by
modified methylaluminoxane (MMAO) and 4 activated
by B(C6F5)3 have moderate catalytic activities for the
polymerization of olefins. A summary of the polymeri-
zation results is shown in Table 4. Although their
catalytic activities are not as high as those of the best
known noncyclopentadienyl group 4 metal complexes
such as McConville’s Ti complexes,1 Schrock’s Zr
complexes,2c and our (EBTiP)ZrMe2,10 these systems are
active catalysts for the polymerization of terminal
olefins. In the case of ethylene polymerization, polymers
prepared from 2/MMAO or 5/MMAO are high-density
polyethylene, as judged by their Tm values (130.2 and
131.0 °C, respectively), though these are not soluble in
refluxing 1,2,4-trichlorobenzene (entry 1 and 4). How-
ever, we could not obtain any polyethylene or polypro-
pylene with 4/B(C6F5)3. Nevertheless, 4/B(C6F5)3 shows
The desired dichlorozirconium complex (MABA)ZrCl2
(5) was finally prepared by the ligand redistribution
reaction of 6 with 1 equiv of ZrCl4(THF)2 in refluxing
toluene. The reaction was monitored by NMR spectros-
copy. The two doublet signals of the benzylic protons of
the chelate ring in 6 merged into a singlet peak in 3

Ti and Zr Complexes with a New Diamido Ligand
Organometallics, Vol. 18, No. 20, 1999 4111
Ta ble 4. P olym er iza tion of r-Olefin sa
Exp er im en ta l Section
cat. (amt,
µmol)
T
Mw/
All manipulations were carried out under an inert atmo-
sphere by using a glovebox or standard Schlenk techniques.
Solvents were degassed by three freeze-pump-thaw cycles.
Pentane, dichloromethane, and chloroform were dried over
calcium hydride under argon and vacuum-transferred. Hexane,
tetrahydrofuran, toluene, ether, and benzene were vacuum-
transferred from their sodium benzophenone ketyl solutions.
Deuterated solvents for NMR experiments were dried by the
same methods as their nondeuterated analogues. Methyl
aluminoxane (MAO) modified with isobutyl groups was pur-
chased as a toluene solution (Akzo, type 4). After the solvent
was removed, the solid aluminoxane was dried under vacuum
at room temperature for 24 h. Ethylene (99.5+%) and propy-
lene (99+%) gases were purchased from Aldrich and purified
by the passage of successive columns of molecular sieves and
Redox. NMR spectra were obtained with a Bruker 300 or 500
MHz spectrometer. GPC analyses were carried out on a Waters
instrument in 1,2,4-trichlorobenzene (TCB) at 140 °C relative
to narrow polystyrene standards (Shodex styrene gel columns).
Elemental analyses were performed on a Vario EL elemental
analyzer.
H2(MABA) (1). A solution of 2-aminobenzylamine (4.97 g,
40.66 mmol) in THF (200 mL) was cooled to 0 °C, and then
n-BuLi (2.5 M in hexane, 34 mL, 85 mmol) was added dropwise
over 30 min with stirring. The reaction mixture was warmed
to room temperature, and stirring was continued for 12 h. The
reaction mixture was then cooled to 0 °C again, and Me3SiCl
(10.5 mL, 81.9 mmol) was added dropwise over 30 min. The
ice bath was removed, and the reaction mixture was heated
at reflux for 12 h and then stirred at room temperature for an
additional 12 h. After removal of the volatile material from
the reaction mixture the residue was extracted with pentane
(3 × 50 mL). Evaporation of the solvent yielded a brownish
liquid which was dried in vacuo and used in the synthesis of
metal complexes without further purification (9.93 g, 92%).
1H NMR (CDCl3): δ 0.15 (s, 9H, -SiMe3), 0.31 (s, 9H, -SiMe3),
0.56 (t, 1H, -CH2NH-), 3.86 (d, 2H, -NHCH2-), 5.18 (bs, 1H,
-C6H4NH-), 6.65-7.14 (m, 4H, -C6H4-). 13C NMR (CDCl3):
δ 0.50 (-SiMe3), 1.27 (-SiMe3), 46.33 (-NCH2-, J C-H ) 133.6
Hz), 116.76, 117.94, 128.93, 129.03, 130.33, 148.22. MS (HR-
EI): m/e calcd 266.1635, found 266.1641.
(MABA)TiCl2 (2). To a solution of 1 (1.68 g, 6.32 mmol) in
toluene (50 mL) was added 8 mL of n-BuLi (1.6 M in hexane,
12.8 mmol) by syringe. The reaction mixture was stirred for 4
h, and TiCl4(THF)2 (2.18 g, 6.33 mmol) was added to the
solution. The reaction mixture was heated at reflux for 3 h
and then stirred at room temperature for an additional 12 h.
Removal of the volatile materials from the reaction mixture
left a dark brown solid which was extracted with pentane (3
× 20 mL). Concentration and cooling (-50 °C) of this solution
afforded 415 mg of product (19%) as dark red crystals. 1H
NMR (CDCl3): δ 0.18 (s, 9H, -SiMe3), 0.54 (s, 9H, -SiMe3),
5.32 (s, 2H, -NCH2-), 6.65-7.28 (m, 4H, -C6H4-). 13C NMR
(CDCl3): δ 1.35 (-SiMe3), 2.25 (-SiMe3), 52.79 (-NCH2-, J C-H
) 137.6 Hz), 116.63, 124.58, 128.34, 128.69, 132.37, 153.57.
MS (FAB): 383.07 (M + H)+. Anal. Calcd for C13H24N2Si2Cl2-
Ti: C, 40.77; H, 6.26; N, 7.31. Found: C, 40.85; H, 6.52; N,
7.12.
b
b
entry
monomer (°C) Mn
Mw
Mn activityc
1d
2
2 (5.22)
2 (5.22)
2 (5.22)
5 (5.02)
5 (5.02)
5 (5.02)
4 (5.06)
ethylene 28 insol
propylene 28 3110 27400 8.80
1-hexene 28 2120
ethylene 28 insol
propylene 28 1730 41900 24.2
1-hexene 28 718 5840 8.12
1-hexene 11100 56600 5.10
12.4
3.22
0.92
0.71
0.84
0.31
9.25
3
6990 3.29
4e
5
6
7
0
a
Conditions: cocatalyst 1000 equiv of MMAO for 2 and 5 and
1 equiv of B(C6F5)3 for 4; 5 min of polymerization. By GPC in
b
1,2,4-trichlorobenzene vs polystyrene standards; insol ) insoluble.
c 104 g of polymer/(mol of catalyst‚h). Tm ) 130.2 °C. e Tm ) 131.0
d
°C.
a moderate activity in 1-hexene polymerization, which
is even better than those of 2/MMAO or 5/MMAO. We
therefore suspect that deactivation of the active catalytic
species in 4/B(C6F5)3 occurs rapidly without substrates
or in the presence of ethylene or propylene but the
deactivation is relatively slow in the presence of 1-hex-
ene for unknown reasons.
Olefinic resonances are observed in the H/13C NMR
1
spectra of the polymers or oligomers prepared with these
catalytic systems. For example, the poly(1-hexene)
produced by 2/MMAO (entry 3) shows only terminal
olefins (one olefin signal per ∼28 monomer units). The
molecular weight (Mn ) 2350) of the polymer estimated
by the NMR analysis agrees reasonably well with that
by GPC measurement (Mn ) 2120). All the resulting
polypropylenes and polyhexenes are atactic. The low
catalytic activities of 2, 4, and 5 are presumably due to
decomposition of the active catalysts generated with
MMAO or B(C6F5)3. However, how these catalysts are
deactivated is not clear at the moment.
To get some idea of the catalyst activation/deactiva-
tion in 4/B(C6F5)3, we monitored the reaction of 4 with
B(C6F5)3 in the absence of monomers by 1H and 19F
NMR spectroscopy. As B(C6F5)3 is added to the toluene-
d8 solution of 4, the solution turns to brownish red
immediately and the signal for the benzylic protons of
the chelate ring disappears while the signals for the
trimethylsilyl groups are shifted to higher field by ∼0.2
ppm. Furthermore, the signal for the methylene protons
of the terminal benzyls disappears while a new signal
for free toluene, which is apparently liberated during
the deactivation process, appears. The liberation of
toluene was also observed when the same experiment
was done in dichloromethane-d2 solution. Despite con-
siderable efforts, however, attempts to isolate and
characterize the decomposition product have been un-
successful. Therefore, the activation/deactivation pro-
cess remains to be established.
In summary, we report titanium and zirconium
complexes with the new ancillary diamido ligand MABA
that are fully characterized by various means including
X-ray crystallography. These titanium and zirconium
diamido complexes are easily accessible and serve as
precursors for polymerization catalysts for terminal
olefins. However, the activities of these catalytic systems
are not as high as those of the best known noncyclopet-
andienyl group 4 metal catalysts, presumably owing to
rapid deactivation of the active catalytic species.
(MABA)TiMe2 (3). To a solution of 2 (79 mg, 0.21 mmol)
in Et2O was added MeMgI (3.0 M in ether, 0.2 mL, 0.60 mmol)
by syringe. The reaction mixture was stirred for 12 h at room
temperature. Removal of the volatile materials from the
reaction mixture produced a dark black solid which was
extracted with hexane (3 × 10 mL). Evaporation of the solvent
yielded a sticky solid which was difficult to further purify
because of its high solubility even in hydrocarbon solvents.
1H NMR (C6D6): δ 0.26 (s, 9H, -SiMe3), 0.61 (s, 9H, -SiMe3),
1.14 (s, 6H, Ti-Me), 4.61 (s, 2H, -NCH2-), 6.95 ∼ 7.22 (m,
4H, -C6H4-). 13C NMR (C6D6): δ 0.74 (-SiMe3), 2.05 (-SiMe3),

4112 Organometallics, Vol. 18, No. 20, 1999
J eon et al.
Ta ble 5. Cr ysta llogr a p h ic Da ta for (MABA)TiCl2 (2), (MABA)Ti(CH2P h )2 (4), a n d (MABA)2Zr (6)
2
4
6
formula
mol wt
space group
a, Å
b, Å
c, Å
R, deg
â, deg
γ, deg
V, Å3
C
13H24N2Si2Cl2Ti
C27H58N2Si2Ti
494.32
P21/c
29.990(6)
11.404(2)
16.728(4)
90
98.07(2)
90
C26H48N4Si4Zr
620.18
P1h
383.32
P21/c
12.619(6)
22.784(10)
14.269(5)
90
105.37(3)
90
3956(3)
8
10.8312(2)
17.0329(3)
19.4166(4)
83.4060(10)
76.9400(10)
79.3080(10)
3418.91(11)
4
5664(2)
4
1.160
Z
d
calcd, g cm-3
1.287
1.185
radiation (λ, Å)
Mo KR (0.710 73)
F(000)
1600
8.17
188(2)
2112
4.03
1272
4.81
293(2)
µ, cm-1
T, K
188(2)
scan method
abs cor
ω
semiempirical from ψ scans
no. of measd rflns
no. of indep rflns
refinement method
goodness of fit on F2
final R indices (I > 2σ(I))
R indices (all data)
15 874
6237
22 033
8764
14 529
9625
full-matrix least squares on F2
1.045
1.026
1.021
R1 ) 0.0348, wR2 ) 0.0823
R1 ) 0.0528, wR2 ) 0.0922
R1 ) 0.0514, wR2 ) 0.1016
R1 ) 0.0928, wR2 ) 0.1228
R1 ) 0.0239, wR2 ) 0.0611
R1 ) 0.0280, wR2 ) 0.0630
30.69 (Ti-Me), 52.23 (-NCH2-), 119.44, 121.32, 125.81,
129.45, 135.97, 151.85.
solution afforded 200 mg of product (46%) as yellowish
crystalline materials. 1H NMR (CDCl3): δ 0.04 (s, 9H, -SiMe3),
0.43 (s, 9H, -SiMe3), 1.97 (t, THF, 4H), 4.14 (t, THF, 4H), 4.82
(s, 2H, -NCH2-), 6.79-7.15 (m, 4H, -C6H4-). 13C NMR
(CDCl3): δ 0.79 (-SiMe3), 1.62 (-SiMe3), 25.84 (THF), 48.53
(-NCH2-), 72.91 (THF), 120.61, 120.91, 128.24, 128.31,
133.49, 151.50. Anal. Calcd for C13H24N2Si2Cl2Zr‚C4H8O: C,
40.96; H, 6.42; N, 5.62. Found: C, 40.58; H, 6.49; N, 5.17.
P olym er iza tion w ith 2 a n d MMAO. A stock solution
(10.44 mM in toluene) of 2 (0.5 mL, 5.22 µmol) and MMAO
(310 mg, 5.35 mmol) were added to toluene to make the volume
of the solution 20 mL. After the solution was stirred for 20
min, ethylene or propylene gas was bubbled into the solution
for 5 or 30 min with vigorous stirring at room temperature.
The polymerization was quenched with acidic methanol. In the
case of 1-hexene polymerization, 2 mL of monomer was added
to 18 mL of the toluene solution containing the same amounts
of 2 and MMAO as above. After 5 min of stirring, the reaction
was quenched with acidic methanol. The resulting polymer
and/or oligomer was isolated by the general workup procedure
and dried under vacuum, which gave 54 mg of PE, 14 mg of
PP, and 4 mg of PH within 5 min. The polymerization with a
longer period of time (30 min) did not improve the yield.
Molecular weights of the samples were estimated by GPC
measurement.
(MABA)Ti(CH2P h )2 (4). To a solution of 2 (90 mg, 0.24
mmol) in diethyl ether (30 mL) was added dropwise 0.5 mL of
PhCH2MgCl (1.0 M in diethyl ether, 0.5 mmol). The reaction
mixture was stirred for 12 h at room temperature. After
removal of the volatile materials, the reaction mixture was
extracted with pentane. The extract was concentrated to nearly
1 mL and cooled to -50 °C to produce a reddish purple
crystalline solid which was collected and dried under vacuum
(105 mg, 90%). 1H NMR (CDCl3): δ 0.07 (s, 9H, -SiMe3), 0.27
(s, 9H, -SiMe3), 2.43 (d, 2H, J H-H ) 10.5 Hz, Ti-CHHPh),
2.59 (d, 2H, J H-H ) 10.5 Hz, Ti-CHHPh), 4.58 (s, 2H, N-CH2),
6.84-7.15 (m, 14H, -CH2C6H5, -C6H4-). 13C NMR (CDCl3):
δ 1.44 (-SiMe3), 2.79 (-SiMe3), 52.19 (-NCH2-, J C-H ) 135.7
Hz), 82.55 (Ti-CH2Ph, J C-H ) 123.4 Hz), 120.74, 122.20,
123.38, 127.67, 128.18, 128.71, 129.47, 137.10, 147.31, 152.50.
Anal. Calcd for C27H38N2Si2Ti: C, 65.59; H, 7.69; N, 5.67.
Found: C, 64.67; H, 7.57; N, 5.67. Despite several trials with
crystalline materials, a low carbon content was found in the
elemental analysis.
(MABA)2Zr (6). To a solution of 1 (1.38 g, 5.16 mmol) in
hexane (30 mL) was added 6.8 mL of n-BuLi (1.6 M in hexane,
10.9 mmol) by syringe. The reaction mixture was stirred for
12 h, and the volatiles were removed under vacuum. The
residue was dissolved in toluene (30 mL), and ZrCl4(THF)2
(2.10 g, 5.57 mmol) was added to the solution. The reaction
mixture was heated at reflux for 3 h and then stirred at room
temperature for an additional 12 h. Removal of the volatile
materials from the reaction mixture left a brownish white solid
which was extracted with pentane (3 × 20 mL). Concentration
and cooling (-50 °C) of this solution afforded 675 mg of product
P olym er iza tion w ith 5 a n d MMAO. The same procedure
as above was employed, except that a stock solution (10.03
mM in toluene) of 5 (0.5 mL, 5.02 µmol) and MMAO (290 mg,
5.00 mmol) were used and polymerization was carried out for
5 min at ambient temperature.
P olym er iza tion w ith 4 a n d B(C6F 5)3. The same procedure
as above was employed, except that a stock solution of 4 (10.12
mM in toluene; 0.5 mL, 5.06 µmol) and B(C6F5)3 (10.16 mM in
toluene; 0.5 mL, 5.08 µmol) were used and polymerization was
carried out for 5 min at 0 °C. In the case of ethylene or
propylene polymerization, 10 equiv of triisobutylaluminum
(TIBA) was added as scavenger, but no polymerization prod-
ucts were obtained. In the case of 1-hexene polymerization,
39 mg of atactic poly(1-hexene) was obtained within 5 min.
NMR Exp er im en t on 4/B(C6F 5)3. Complex 4 (20 mg, 40.5
µmol) was dissolved in 0.5 mL of toluene-d8, and the 1H
spectrum was recorded. 1H NMR (toluene-d8, 25 °C): δ 0.26
(s, 9H, -SiMe3), 0.46 (s, 9H, -SiMe3), 2.76 (d, 2H, -CH2Ph),
2.92 (d, 2H, -CH2Ph), 4.73 (s, 2H, -NCH2-), 6.95-7.35 (m,
1
(42%) as colorless crystals. H NMR (CDCl3): δ 0.07 (s, 18H,
-SiMe3), 0.21 (s, 18H, -SiMe3), 4.22 (d, 2H, -NCHH-, J H-H
) 15.3 Hz), 4.53 (d, 2H, -NCHH-, J H-H ) 15.3 Hz), 6.80-
7.14 (m, 8H, -C6H4-). 13C NMR (CDCl3): δ 1.67 (-SiMe3),
2.71 (-SiMe3), 50.43 (-NCH2-), 121.21, 124.04, 129.03,
129.86, 136.56, 151.04. Anal. Calcd for C26H48N4Si4Zr: C,
50.38; H, 7.74; N, 9.04. Found: C, 49.41; H, 7.84; N, 8.75.
Despite several trials with crystalline materials, a low carbon
content was found in the elemental analysis.
(MABA)Zr Cl2‚THF (5). ZrCl4(THF)2 (403 mg, 1.07 mmol)
was added to a toluene solution of 6 (545 mg, 0.88 mmol). The
reaction mixture was refluxed for 3 days. Removal of volatile
components gave a yellowish residue which was extracted with
diethyl ether. Concentration and cooling (-50 °C) of this
1
14H, -Ph). H and 19F NMR spectra were obtained after the
addition of 1.0 equiv of B(C6F5)3 to 4. The initial yellowish red

Ti and Zr Complexes with a New Diamido Ligand
Organometallics, Vol. 18, No. 20, 1999 4113
solution immediately turned to brownish red. The 1H NMR
spectrum taken after a few minutes of the borane addition
shows the higher field shift of trimethylsilyl groups by ∼0.2
ppm: δ 0.05 (s, 9H, -SiMe3), 0.27 (s, 9H, -SiMe3). The
increased toluene signal at 2.30 ppm indicates the liberation
program package SHELEXTL. All the non-hydrogen atoms
were refined anisotropically. Hydrogen atom positions were
calculated and included in the final cycle of refinement.
However, for 2, which shows an agostic interaction between
C(7)-H or C(20)-H and the Ti center, the hydrogens attached
to C(7) and C(20) were located from the difference electron
density map and refined isotropically. Crystallographic data
of the compounds 2, 4, and 6 are summarized in Table 5.
1
of free toluene. Other parts of the H NMR spectrum are too
complex to assign unambiguously. However, the 19F NMR
spectrum shows one fluorinated benzene ring: 19F NMR
(toluene-d8) δ -56.31 (d, 2F), -86.88 (m, 1F), -90.94 (m, 2F).
Despite considerable efforts, attempts to isolate and character-
ize the decomposition product have been unsuccessful.
Ack n ow led gm en t. We gratefully acknowledge the
Korea Science and Engineering Foundation for support
of this work. We also thank Dr. J aheon Kim for help in
X-ray work and Professor G. V. Smith for reading the
manuscript.
X-r a y Cr ysta llogr a p h y. A suitable crystal coated with
Paratone was mounted on a Siemens SMART diffractometer
equipped with a graphite-monochromated Mo KR (λ ) 0.710 73
Å) radiation source and a CCD detector. Data collection was
performed with a detector distance of 6 cm. For each structure,
a total of 1271 frames of two-dimensional diffraction images
were collected. The raw data collected were processed to
produce conventional intensity data by the program SAINT.
The intensity data were corrected for Lorenz and polarization
effects. Absorption correction was also applied on the basis of
ψ scans. The structure was solved by a combination of
Patterson and difference Fourier methods provided by the
Su p p or tin g In for m a tion Ava ila ble: Structural diagrams
with full atom labeling and tables of bond distances, angles,
anisotropic thermal parameters, and atomic coordinates for
2, 4, and 6. This material is available free of charge via the
Internet at http://pubs.acs.org.
OM990121B