Synthesis and structure of acyclic bis(ketenimine) complexes of zirconium

Article abstract of DOI:10.1021/om970862h

Mono- and disubstituted bis(ketenimine) complexes of zirconium (1 and 2, respectively) can be readily prepared by reaction of these ligands (3) with Zr(NMe)₄ or, in some cases, the homoleptic tetrabenzyl derivative ZrBn₄. Treatment o

Full text of DOI:10.1021/om970862h

Organometallics 1998, 17, 1315-1323
1315
Syn th esis a n d Str u ctu r e of Acyclic Bis(k eten im in e)
Com p lexes of Zir con iu m
Marufur Rahim, Nicholas J . Taylor, Shixuan Xin, and Scott Collins*
Department of Chemistry, University of Waterloo, Waterloo, Ontario, Canada N2L 3G1
Received October 3, 1997
Mono- and disubstituted bis(ketenimine) complexes of zirconium (1 and 2, respectively)
can be readily prepared by reaction of these ligands (3) with Zr(NMe)4 or, in some cases, the
homoleptic tetrabenzyl derivative ZrBn4. Treatment of 1 (Ar ) Ph, p-CF3Ph; X ) NMe2)
with Me2NH‚HCl and of 2 (Ar ) Ph, X ) NMe2) with either Me2NH‚HCl or TMSCl provides
the corresponding chloro derivatives in high yield. Alkyl derivatives of 2 (X ) Me, Bn) can
be readily prepared by reaction of the corresponding chloro derivatives with Grignard or
organolithium reagents. Monocyclopentadienyl bis(ketenimine) complexes 4 (Ar ) Ph,
p-CF3Ph; Cp ) η5-C5H5, η5-C9H7; X ) Cl) were prepared from 1 (Ar ) Ph, p-CF3Ph; X ) Cl)
by reaction with CpLi or IndLi in high yield, and methyl derivatives 4 (Ar ) Ph, p-CF3Ph;
Cp ) η5-C5H5, η5-C9H7; X ) Me) were accessible by treatment of the chloro precursors with
methyllithium. The X-ray structure of 2 (Ar ) Ph; X ) NMe2) reveals a distorted-octahedral
geometry in which the bis(ketenimine) ligands are σ-bound to the metal and the dimethyl-
amido groups are cis to one another, and the corresponding dichloro derivative also adopts
a similar structure in the solid state, whereas the bis(ketenimine) ligands adopt a distorted,
η5 binding mode in the monoindenyl derivative 4 (Ar ) Ph; Cp ) η5-C9H7; X ) Cl).
Enantiomers of 2 (Ar ) Ph, X ) Cl) readily interconvert in solution via a Bailar-twist
1
mechanism, as revealed by variable-temperature H NMR spectroscopic studies; activation
parameters for this process were determined (∆H‡ ) 9.0 ( 0.45 kcal mol-1; ∆S‡ ) -9.9 (
1.0 cal mol-1 K-1).
Ch a r t 1
In tr od u ction
There is considerable current interest in the prepara-
tion and chemistry of electron-deficient complexes of the
group 4 transition metals in connection with their use
in olefin polymerization and related processes. The vast
majority of such studies deal with bis(cyclopentadienyl)
complexes of group 41 and the related, but more electron
deficient, monocyclopentadienyl derivatives.2 More re-
cently, attention has been focused on the use of isoelec-
tronic alternatives to the cyclopentadienyl anion3 and
other electron-deficient complexes such as bis(amido),4
bis(amidinato),5 and porphine derivatives.6 In contrast,
there are few reports concerning the use of acyclic,
mono- or disubstituted bis(ketenimine) complexes of
group 4 (1 and 2, respectively; Chart 1) in olefin
polymerization, the work of J ordan and co-workers3a
being confined to macrocyclic versions of this ligand
class.
Given the isoelectronic relationship between bis-
(ketenimine) ligands and cyclopentadienyl anions, the
paucity of work in this area seemed surprising, particu-
larly because the steric and electronic properties of the
bis(ketenimine) ligand can be readily altered through
an appropriate choice of amine and â-diketone used in
(1) For recent reviewe see: (a) Brintzinger, H. H.; Fischer, D.;
Mu¨lhaupt, R.; Reiger, B.; Waymouth, R. M. Angew. Chem., Int. Ed.
Engl. 1995, 34, 1143. (b) Bochmann, M. J . Chem. Soc., Dalton Trans.
1996, 255.
(2) (a) Okuda, J . Chem. Ber. 1990, 123, 1644. (b) Canich, J . A.
(Exxon) Eur. Pat. Appl. EP-420-436 A1, April 4, 1991. (c) Stevens, J .
C.; Timmers, F. J .; Wilson, D. R.; Schmidt, G. F.; Nickias, P. N.; Rosen,
R. K.; Knight, G. W.; Lai, S. Y. (Dow) Eur. Pat. Appl. EP-416-815-A2,
March 13, 1991. (d) Kucht. A.; Kucht, H.; Barry, S.; Chein, J . C. W.;
Rausch, M. D. Organometallics 1993, 12, 3075. (e) Kucht, H.; Kucht,
A.; Chien, J . C. W.; Rausch, M. D. Appl. Organomet. Chem. 1994, 8,
393. (f) Gillis, D. J .; Tudoret, M.-J .; Baird, M. C. J . Am. Chem. Soc.
1993, 115, 2543. (g) Quyoum, R.; Wang, Q.; Tudoret, M.-J .; Baird, M.
C.; Gillis, D. J . J . Am. Chem. Soc. 1994, 116, 6435. (h) Wang, Q.;
Quyoum, R.; Gills, D. J .; Tudoret, M.-J .; J eremic, D.; Hunter, B. K.;
Baird, M. C. Organometallics 1996, 15, 693.
(3) (a) Uhrhammer, R.; Black, D. G.; Gardner, T. G.; Olsen, J . D.;
J ordan, D. C. J . Am. Chem. Soc. 1993, 115, 8493. (b) Black, D. G.;
Swenson, D. C.; J ordan, R. F.; Rogers, R. D. Organometallics 1995,
14, 3539. (c) Crowther, D. J .; Baenziger, N. C.; J ordan, R. F. J . Chem.
Soc., Chem. Commun. 1994, 2607. (d) Kreuder, C.; J ordan, R. F.;
Zhang, H. Organometallics 1995, 14, 2993. (e) Rodriguez, G.; Bazan,
G. C. J . Am. Chem. Soc. 1997, 119, 343. (f) Bazan, G. C.; Rodriguez,
G.; Cleary, B. P. J . Am. Chem. Soc. 1994, 116, 2177. (g) Guan, R. W.;
Bazan, G. C.; Kiely, A. F.; Schaefer, W. P.; Bercow, J . E. J . Am. Chem.
Soc. 1994, 116, 4489.
(4) (a) Scollard, J . D.; McConville, D. H. J . Am. Chem. Soc. 1996,
118, 10008. (b) Scollard, J . D.; McConville, D. H.; Vittal, J . J .
Organometallics 1995, 14, 5478.
(5) (a) Gomez, R.; Green, M. L. H.; Haggizz, J . L. J . Chem. Soc.,
Chem. Commun. 1994, 2607. (b) Duchateau, R.; Cornelis, T. W.;
Meetsma, A.; van Duijnen, P. T.; Teuben, J . H. Organometallics 1996,
15, 2279. (c) Herskovics-Korine, D.; Eisen, M. S. J . Organomet. Chem.
1995, 503, 307.
(6) (a) Brand, H.; Capriotti, J . A.; Arnold, J . Organometallics 1994,
13, 4469. (b) Cozz, P. G.; Gallo, E.; Floriani, C.; Chiesi-Villa, A.; Rizzoli,
C. Organometallics 1995, 14, 4994.
S0276-7333(97)00862-5 CCC: $15.00 © 1998 American Chemical Society
Publication on Web 03/05/1998

1316 Organometallics, Vol. 17, No. 7, 1998
Ta ble 1. 1H NMR Sp ectr a l Da ta for Com p lexes 1a
Rahim et al.
compd (solvent)
Ar
X
δ (ppm)
appearance
assignt
1a (C6D6)
Ph
CH2Ph
7.07
6.90
6.72
5.01
2.60
1.51
7.13
6.90
6.70
5.02
2.73
1.75
7.45
6.56
5.02
2.58
1.55
7.10
4.80
1.84
7.65
7.30
5.69
1.70
m, 10 H
m, 5 H
m, 10H
s, 1H
s, 6H
s, 12H
d, J ) 8.3 Hz, 2H
t, J ) 8.3 Hz, 4H
d, J ) 8.3 Hz, 4H
s, 1H
s, 18H
s, 6H
d, J ) 10 Hz, 4H
d, J ) 10 Hz, 4H
s, 1H
s, 18H
s, 6H
m, 10H
s, 1H
NP h
ZrCH2P h
ZrCH2P h
PhNC(Me)CHC(Me)NPh
ZrCH2Ph
PhNC(Me)CHC(Me)NPh
NP h
1b (C6D6)
Ph
NMe2
NMe2
NP h
NP h
PhNC(Me)CHC(Me)NPh
NMe2
PhNC(Me)CHC(Me)NPh
NC6H4CF3
NC6H4CF3
ArNC(Me)CHC(Me)NAr
NMe2
ArNC(Me)CHC(Me)NAr
NP h
PhNC(Me)CHC(Me)NPh
PhNC(Me)CHC(Me)NPh
NC6H4CF3
NC6H4CF3
ArNC(Me)CHC(Me)NAr
ArNC(Me)CHC(Me)NAr
1c (C6D6)
p-CF3Ph
1d (C6D6)
Ph
Cl
Cl
s, 6H
1e (THF-d8)
p-CF3Ph
d, J ) 8 Hz, 4H
d, J ) 8 Hz, 4H
s, 1H
s, 6H
a
Recorded at 250 MHz in the solvent indicated.
their synthesis.7 This latter feature prompted us to
develop efficient and general synthetic routes to both 1
and 2, the results of which are reported here.8 While
this work was in progress, Lappert and co-workers9
independently described the preparation of some ex-
amples of complexes 1 (X ) Cl); X-ray studies revealed
that the bis(ketenimine) ligand is η5-coordinated to the
metal, thus highlighting the similarity between these
ligands and Cp anions.
important in facilitating alkane elimination reactions
(and that, perversely, the thermal lability of complexes
1 appears also to be correlated in the same manner)
rather than their thermodynamic acidity.
Spectroscopic data for complex 1a appear in Table 1.
The benzyl groups appear to be conventionally bound
to the metal in this complex, and the data obtained are
reminiscent of simple monocyclopentadienylzirconium
tribenzyl compounds.10 Attempts to obtain suitable
single crystals of this compound to delineate the mode
of binding of the bis(ketenimine) ligand to the metal
were not successful; we suspect that in complex 1a the
ligand adopts the η5 coordination mode, on the basis of
structural characterization of related materials.9
Attempts to prepare complex 2a (Ar ) Ph, R′ ) Me,
X ) Bn) by reaction of 1a with an additional 1 equiv of
ligand 3a were not successful; a mixture of several
compounds was formed, none of which appears to be 2a ,
on the basis of its successful synthesis by another route
(vide infra). As alkane elimination reactions did not
appear to provide a general method for the synthesis of
complexes 1 and to a greater extent 2, we elected to
investigate amine elimination reactions11 as an alterna-
tive approach.
Resu lts a n d Discu ssion
Our initial synthetic efforts focused on the use of
alkane elimination reactions as a route to complexes 1
and 2, as these had been reported to be successful in
the case of macrocyclic versions.3a Indeed, reaction of
ZrBn4 with ligand 3a (Ar ) Ph, R′ ) Me), in toluene
solution at 40-50 °C, cleanly furnished the 1:1 complex
1a (Ar ) Ph, R′ ) Me, X ) Bn) in high yield (eq 1). Quite
(1)
As shown in Scheme 1, this process and allied
chemistry appear to offer reasonable access to a range
of complexes 1 and 2. Reaction of 1 or 2 equiv of 3a (Ar
) Ph) with Zr(NMe2)4 in toluene solution cleanly
furnished the tris- and bis(dimethylamido) derivatives
1b and 2b, respectively. Similar chemistry was en-
countered using the p-CF3Ph analogue 3b; although
monosubstituted adduct 1c could be cleanly prepared
by this route, the bis(dimethylamido) derivative 2c could
surprisingly, the (much) more acidic ligand 3b (Ar )
p-CF3Ph, R′ ) Me) failed to react with ZrBn4 under the
same conditions; at higher temperatures, reaction did
occur to give a complex analogous to 1a but, under the
conditions employed (toluene, 80-90 °C), this compound
competitively decomposed to provide a complex mixture
of products. This surprising result seems to indicate
that it may be the donor properties of ligand 3 that are
(10) (a) Pellecchia, C.; Grassi, A.; Immirzi, A. J . Am. Chem. Soc.
1993, 115, 1160. (b) Pellecchia, C.; Grassi, A.; Zambelli, A. J . Mol.
Catal. 1993, 82, 57. (c) Pellecchia, C.; Immirzi, A.; Grassi, A.; Zambelli,
A. Organometallics 1994, 13, 298. (d) Pellecchia, C.; Grassi, A.;
Zambelli, A. Organometallics 1993, 12, 3856.
(11) (a) Diamond, G. M.; Rodewald, S.; J ordan, R. F. Organometallics
1995, 14, 5. (b) Hughes, A. K.; Meetsma, A.; Teuben, J . H. Organo-
metallics 1993, 12, 1936. (c) Gauthier, W. J .; Corrigan, J . F.; Taylor,
N. J .; Collins, S. Macromolecules 1995, 28, 3771.
(7) See e.g.: McGeachin, S. G. Can. J . Chem. 1968, 46, 1903 and
references therein.
(8) We have screened a number of the complexes reported here in
olefin polymerization, and the results will be reported elsewhere:
Rahim, M.; Collins, S. Manuscript in preparation.
(9) (a) Hitchcock, P. B.; Lappert, M. F.; Liu, D.-S. J . Chem. Soc.,
Chem. Commun. 1994, 2637. (b) Lappert, M. F.; Liu, D.-S. J . Organo-
met. Chem. 1995, 500, 203.

Bis(ketenimine) Complexes of Zirconium
Organometallics, Vol. 17, No. 7, 1998 1317
Sch em e 1
Sch em e 2
the resonance(s) due to the methyl groups were also
largely unaffected. Interestingly, in the spectrum of 2b,
a high-field doublet at 5.8 ppm, integrated to two
protons, was observed (Table 2, entry 1) and was
assigned to aromatic protons ortho to N (vide infra). In
addition, two singlets due to methyl groups of the bis-
(ketenimine) ligand were present. Finally, the signal
due to the NMe2 groups was line-broadened, suggesting
restricted rotation about the Zr-N bond.13 In the other
complexes, derived from 2b, only one methyl resonance
was present at 298 K and the high-field doublet was
absent; in addition, the aromatic protons were line-
broadened, which suggested fluxionality in solution.
Finally, mixed cyclopentadienyl-bis(ketenimine) com-
plexes 4a -c could be prepared by reaction of the
trichloride complexes 1d ,e with either CpLi or IndLi in
ether solution. Following purification by recrystalliza-
tion, the mixed complex 4a could be converted to the
corresponding dimethyl derivative 4d on reaction with
MeLi in ether solution (Scheme 2). Spectroscopic data
for these mixed complexes are included in the Experi-
mental Section; the spectroscopic properties of the bis-
(ketenimine) ligand in these complexes were surpris-
ingly similar to those observed for complexes 1 and 2.
A number of these bis(ketenimine) complexes were
characterized by X-ray crystallography to delineate the
binding mode(s) of this ligand to Zr.
The molecular structure of the bis(dimethylamido)
derivative 2b appears in Figure 1, while selected bond
lengths and angles appear in Table 3 and crystal-
lographic data are summarized in Table 5. In this
complex, the bis(ketenimine) ligands are σ-bound to the
metal and the complex assumes a distorted, cis-
octahedral geometry at the metal, in which the N-Zr-N
angles involving the bis(ketenimine) ligands and the cis
dimethylamido groups differ significantly from 90°
(N(5)-Zr-N(6) ) 80.3(1)°; N(3)-Zr-N(4) ) 79.6(1)°;
N(1)-Zr-N(2) ) 92.8(1)°). The trans influence of the
dimethylamido ligands is clearly seen in the longer Zr-
N(4) and Zr-N(6) distances of 2.380(1) and 2.397(2) Å
not be isolated in pure form on treatment either of
Zr(NMe2)4 with 2 equiv of 3b or of 1c with 1 equiv of
this ligand, due to thermal instability in solution. The
corresponding chloro derivatives (1d ,e, 2d ) were acces-
sible by treatment of 1b and 1c or of 2b with 3 or 2
equiv of Me2NH‚HCl, respectively, in dichloromethane
solution or, in certain cases, a slight excess of Me3SiCl
in toluene solution.12
Direct conversion of 1b or 2b to the dimethyl deriva-
tives was attempted using AlMe3 in toluene; unlike their
metallocene analogues,12 complexes 1b and 2b proved
resistant to alkylation at room temperature in toluene.
At higher temperatures, reaction occurred but it proved
difficult to obtain the dimethyl derivatives 2 in pure
form due to competing decomposition and formation of
aluminum amide byproducts. We thus resorted to
synthesis of dialkyl derivatives 2 using conventional
metathetical reactions on the corresponding chloro
derivatives; in this way methyl and benzyl derivatives
(2e,f) were obtained in high yield (Scheme 2).
1
The H NMR spectroscopic data for complexes 1a -e
and 2b-f appear in Tables 1 and 2, respectively. Aside
from the aromatic region which was, in general, difficult
to assign, the spectral data are readily interpreted. The
chemical shift of the methine proton of the bis(keten-
imine) ligand appears as a sharp singlet at ca. 5 ppm,
and the position of this resonance was somewhat
insensitive with respect to the identity of the other
ligands present on the metal in complexes 2 (Table 2);
(13) At low temperatures in toluene-d8, two separate signals in a
ratio of 1:1 are observed for the NMe2 protons. Simulation of these
spectra16 provided the activation parameters ∆Hq ) 16.1 ( 0.8 kcal
mol-1 and ∆Sq ) 13.2 ( 1.3 cal mol-1 K-1) for rotation about the Zr-N
bond.
(12) Kim, I.; J ordan, R. F. Macromolecules 1996, 29, 489.

1318 Organometallics, Vol. 17, No. 7, 1998
Ta ble 2. 1H NMR Sp ectr a l Da ta for Com p lexes 2a
Rahim et al.
compd (solvent)
Ar
X
δ (ppm)
appearance
assignt
2b (C6D6)
Ph
NMe2
7.10
6.85
5.80
5.10
2.50
1.70
1.41
6.90
5.10
1.45
7.15
6.90
6.62
4.90
1.50
1.32
7.20
7.05
6.90
6.50
5.05
2.50
1.42
m, 14H
m, 4H
d, J ) 8 Hz, 2H
s, 2H
br s, 12H
s, 6H
s, 6H
br m, 20H
s, 2H
s, 12H
d, J ) 8.2 Hz, 8H
t, J ) 8.2 Hz, 4H
d, J ) 8.2, 8H
s, 2H
s, 12H
s, 6H
m, 6H
m, 8H
m, 10H
m, 6H
s, 2H
NP h
NP h
NP h (o-H)
PhNC(Me)CHC(Me)NPh
NMe2
PhNC(Me)CHC(Me)NPh
PhNC(Me)CHC(Me)NPh
NP h
PhNC(Me)CHC(Me)NPh
PhNC(Me)CHC(Me)NPh
NP h
NP h
2d (THF-d8)
2e (C6D6)
Ph
Ph
Cl
Me
NP h
PhNC(Me)CHC(Me)NPh
PhNC(Me)CHC(Me)NPh
ZrMe2
NP h
NP h
ZrCH2P h
NP h
PhNC(Me)CHC(Me)NPh
ZrCH2Ph
PhNC(Me)CHC(Me)NPh
2f (C6D6)
Ph
CH2Ph
s, 4H
s, 6H
a
Recorded at 250 MHz in the solvent indicated at 298 K.
Ta ble 3. Selected Bon d Len gth s (Å) a n d An gles
(d eg) for Com p lexes 2b a n d 2d a
complex 2b
complex 2d
Bond Lengths
Zr(1)-N(1)
2.078(1) Zr(1)-Cl(1)
2.074(1) Zr(1)-Cl(2)
2.266(1) Zr(1)-N(1)
2.397(1) Zr(1)-N(2)
2.262(1) Zr(1)-N(3)
2.380(1) Zr(1)-N(4)
1.337(2) N(1)-C(1)
1.394(2) C(1)-C(2)
1.399(2) C(2)-C(3)
1.330(2) N(2)-C(3)
2.439(1)
2.426(1)
2.216(2)
2.275(2)
2.197(2)
2.279(2)
1.329(4)
1.403(4)
1.399(4)
1.332(3)
Zr(1)-N(2)
Zr(1)-N(3)
Zr(1)-N(4)
Zr(1)-N(5)
Zr(1)-N(6)
N(5)-C(8)
C(8)-C(9)
C(9)-C(10)
N(6)-C(10)
Bond Angles
N(1)-Zr(1)-N(2)
N(4)-Zr(1)-N(3)
N(5)-Zr(1)-N(6)
Zr(1)-N(5)-C(8)
N(5)-C(8)-C(9)
C(8)-C(9)-C(10)
92.8(1)
79.6(1)
80.3(1)
130.1(1)
124.6(1)
130.0(1)
Cl(1)-Zr(1)-Cl(2)
90.0(1)
79.9(1)
78.9(1)
128.1(2)
122.8(3)
127.1(3)
124.2(2)
125.3(2)
N(1)-Zr-N(2)
N(4)-Zr(1)-N(3)
Zr(1)-N(1)-C(1)
N(1)-C(1)-C(2)
C(1)-C(2)-C(3)
C(2)-C(3)-N(2)
C(3)-N(2)-Zr(1)
C(9)-C(10)-N(6) 124.7 (1)
C(10)-N(6)-Zr(1) 126.8 (1)
a
F igu r e 1. Molecular structure of complex 2b with 50%
probability thermal ellipsoids depicted and most H-atoms
omitted for clarity. For bond lengths and angles see Table
3; for crystallographic data see Table 5.
Estimated standard deviations in parentheses.
Ta ble 4. Selected Bon d Len gth s (Å) a n d An gles
(d eg) for Com p lex 4ba
Bond Lengths
compared with the Zr-N(3) and Zr-N(5) bond lengths
of 2.266(1) and 2.263(1) Å, respectively. The dimethyl-
amido ligands are planar at nitrogen (sum of the bond
angles 360(2) and 360(2)° at N(1) and N(2), for Zr-N(1)
and Zr(2), respectively), suggesting considerable π-dona-
tion to the metal, which is borne out by the significantly
shorter Zr-N distances of 2.078(1) and 2.074(2) Å,
respectively. The five atoms in the bis(ketenimine)
ligands are coplanar, and the two C-C distances of
1.394(2) and 1.399(2) Å and the two C-N distances of
1.337(2) and 1.339(2) Å suggest significant delocaliza-
tion within the π-system of these ligands. Overall, the
complex has approximate C2 symmetry and the obser-
vation of two 1H NMR signals for the methyl groups of
the bis(ketenimine) ligands in solution is consistent with
the solid-state structure. Moreover, the observation of
the high-field doublet due to the ortho-H’s on the
Zr(1)-Cl(1)
Zr(1)-N(1)
Zr(1)-C(1)
Zr(1)-C(3)
Zr(1)-C7(a)
Zr(1)-C(9)
N(1)-C(8)
C(8)-C(9)
2.505(1)
2.201(2)
2.515(2)
2.463(2)
2.592(2)
2.703(2)
1.318(3)
1.421(3)
Zr(1)-Cl(2)
Zr(1)-N(2)
Zr(1)-C(2)
Zr(1)-C3(a)
Zr(1)-C(8)
Zr(1)-C(10)
N(2)-C(10)
C(9)-C(10)
2.480(1)
2.192(1)
2.484(2)
2.554(2)
2.748(2)
2.713(2)
1.328(3)
1.412(2)
Bond Angles
Cl(1)-Zr(1)-Cl(2)
Zr(1)-N(1)-C(8)
N(1)-C(8)-C(9)
C(8)-C(9)-C(10)
85.8(1)
99.6(1)
119.1(2)
126.0(2)
N(1)-Zr(1)-N(2)
Zr(1)-N(2)-C(10)
N(2)-C(10)-C(9)
79.7(1)
97.8(1)
119.9(2)
a
Estimated standard deviations in parentheses.
aromatic rings can be rationalized from the solid-state
structure; as is evident from Figure 1, H(30) is directly
over the shielding cone of the opposite aromatic ring and

Bis(ketenimine) Complexes of Zirconium
Organometallics, Vol. 17, No. 7, 1998 1319
Ta ble 5. Su m m a r y of Cr ysta llogr a p h ic Da ta
compd
2b
2d
4b
formula
mw
T (K)
C
678.0
180
38H46N6Zr
C34H34Cl2N4Zr
660.8
160
C26H24Cl2N2Zr
536
160
radiation
cryst syst
space group
unit cell
a (Å)
b (Å)
c (Å)
R (deg)
â (deg)
γ (deg)
V (Å3)
Mo KR
triclinic
P1h
Mo KR
Mo KR
triclinic
P1h
orthorhombic
P212121
9.26(1)
11.438(1)
16.024(2)
16.923(2)
9.9399(7)
10.9317(7)
12.1965(8)
112.560(4)
103.200(4)
96.177(6)
1163.1(2)
2
11.565(1)
17.352(2)
74.376(6)
89.059(7)
73.216(7)
1710.5(5)
2
3101.7(6)
4
1.415
Z
D(calcd) (g cm-3
)
1.316
3.57
1.504
7.19
abs coeff (cm-1
)
5.57
F(000)
712
1360
536
cryst size (mm)
2θ range (deg)
index ranges
0.30 × 0.30 × 0.20
4.0-50.0
-10 e h e 10
-12 e k e 13
-20 e l e 20
11 902
5970 (Rint ) 1.67%)
5204
8.8:1
1.80
0.25 × 0.40
4.0-52.0
0 e h e 14
0 e k e 19
0 e l e 20
3414
3414
3054
6.0:1
1.43
0.42 × 0.21 × 0.28
4.0-52.0
0 e h e 12
-12 e k e 12
-15 e l e 14
4705
4433 (Rint ) 1.07%)
4045
10.7:1
2.37
no. of collected rflns
no. of indep. rflns
no. of obsd rflns (F > 6.0σ(F))
data to param ratio
GOF (F2)
final R indices (I > 2σ(I)) (%)
R ) 2.09
Rw ) 2.44
R ) 2.51
Rw ) 2.47
0.35, -0.20
R ) 1.94
Rw ) 2.10
R ) 2.24
Rw ) 2.13
0.24, -0.28
R ) 2.04
Rw ) 2.61
R ) 2.27
Rw ) 2.62
0.29, -0.32
R indices (all data) (%)
diff peak, hole (e Å-3
)
pared to Zr-N(2) ) 2.275(1) Å and Zr-N(4) ) 2.279(1)
Å suggest a similar trans influence, but it is weaker
than in 2b, because the amido is a stronger σ, π-donor
than chloride. As noted previously, the room-tem-
1
perature H NMR spectrum of the dichloride complex
2d exhibits only one resonance for the methyl groups
of the bis(ketenimine) ligand, and this is inconsistent
with the solid-state structure. Even the 1H NMR
spectra of the dialkyl analogues 2e,f were consistent
with a more symmetrical structure in a variety of NMR
solvents.
To resolve this ambiguity, variable-temperature 1H
NMR spectra of 2d were obtained. As the temperature
was lowered, the singlet at δ 1.47 starts to broaden (see
Figure 3) and at 237 K the peak starts to decoalesce.
Finally, at 200 K two separate singlets appear at δ 1.32
and 1.53, respectively; the low-temperature spectrum
is consistent with the solid-state structure, wherein the
two methyl groups on the backbone of the ligand are
inequivalent. Note also in the spectrum obtained at 200
K that the characteristic, high-field doublet for two
ortho, aromatic protons is observed, suggesting that 2d
adopts a similar conformation in solution as 2b.14
This fluxional process can be explained by a Bailar
twist mechanism.15 At room temperature, the two
enantiomers interconvert rapidly on the NMR time scale
via a trigonal-prismatic intermediate where all the
F igu r e 2. Molecular structure of complex 2d with 50%
probability thermal ellipsoids depicted and most H-atoms
omitted for clarity. For bond lengths and angles see Table
3; for crystallographic data see Table 5.
would experience strong deshielding in solution on a
time-averaged basis.
Similarly, the dichloride analogue 2d also shows a
distorted-octahedral geometry at the metal center with
two cis chloride atoms at an angle of 90.0(1)° (Figure 2,
Tables 3 and 5). However, the angles involving the
metal center and the bis(ketenimine) ligand deviate
significantly from 90° (N(3)-Zr-N(4) ) 79.6(1)°; N(1)-
Zr-N(2) ) 78.9(1)°). The shorter bond distances Zr-
N(1) ) 2.216(1) Å and Zr-N(3) ) 2.197(1) Å as com-
(14) The fact that this high-field doublet is integrated to only two
protons also implies that rotation about the N-Ph bond is hindered
in 2d at 200 K, and in the case of 2b, this same process is slow on the
NMR time scale even at room temperature.
(15) (a) Bailar, J . C. J . Inorg. Nucl. Chem. 1958, 8, 165. (b)
Wentworth, R. A. D. Coord. Chem. Rev. 1972, 9, 171. (c) Fleischer, E.
B.; Gebala, A. E.; Swift, D. R.; Tasker, P. A. Inorg. Chem. 1972, 11,
2775. (d) Churchill, M. R.; Reis, A. H. Inorg. Chem. 1972, 11, 1811. (e)
Vanquickenborne, L. G.; Pierloot, K. Inorg. Chem. 1981, 20, 3673. (f)
Darensbonrg, D. J .; Kump, R. L. Inorg. Chem. 1984, 23, 2993.

1320 Organometallics, Vol. 17, No. 7, 1998
Rahim et al.
F igu r e 4. Molecular structure of complex 4b with 50%
probability thermal ellipsoids depicted and H-atoms omit-
ted for clarity. For bond lengths and angles see Table 4;
for crystallographic data see Table 5.
1
F igu r e 3. Variable-temperature 300 MHz H NMR spec-
tra of complex 2d in toluene-d8.
Sch em e 3
F igu r e 5. Eyring plot for interconversion of the two
enantiomers of complex 2d in toluene-d8.
5). The bis(ketenimine) ligand adopts a “η5-coordina-
tion” mode in this structure, and the N-Ph substi-
tutents are directed toward the rear of the “wedge”
defined by the two π-bound ligands. In this structure,
the metal atom distances involving the bis(ketenimine)
ligand are significantly longer (Zr-N(1) ) 2.201(1) Å,
Zr-N(2) ) 2.192(1) Å, Zr-C(9) ) 2.703(2) Å, Zr-C(10)
) 2.713(2) Å, Zr-C(8) ) 2.748(2) Å) than those found
in Lappert’s monoadduct complexes.9 The indenyl
ligand assumes an asymmetric conformation with re-
spect to the bis(ketenimine) and chloride ligands, and
the metal-carbon distances within the five-membered
ring are significantly different (Zr-C(1) ) 2.515(2) Å,
Zr-C(2) ) 2.480(2) Å, Zr-C(3) ) 2.463(2) Å, Zr-C(3a)
) 2.554(2) Å, Zr-C7a ) 2.592(2) Å), suggesting possible
slip distortion18 of the indenyl ligand in this complex;
however, they are roughly comparable to those found
in bis(indenyl)zirconium complexes.19 The Cl-Zr-Cl
methyl groups are equivalent (Scheme 3). The rate
constants of this interconversion process at various
temperatures were obtained from spectral simulation
by using the DNMR4 program.16 From an Eyring plot
(Figure 5) ∆Hq ) 9.0 ( 0.45 kcal mol-1 and ∆Sq ) -9.9
( 1.0 cal mol-1 K-1 were determined. The low value of
∆Hq and the negative value of ∆Sq are consistent with
an internal twist mechanism and not a dissociative
pathway involving the bis(ketenimine) ligand.15f,17
The X-ray structure of complex 4b was also deter-
mined for comparison purposes, and the molecular
structure is depicted in Figure 4 (data in Tables 4 and
(16) Bushweller C. H.; Letenare, L. J .; Brunelle, J . A.; Bilorsky, H.
J .; Whalon, M. J .; Fiels, S. H. Calculation of Chemically Exchanging
Spectra; (QCPE Program No. 466; Department of Chemistry, Univer-
sity of Vermont, Burlington, VT 05401.
(17) Although we cannot rule out a dissociative process for the
fluxional behavior, the observation that the barrier to interconversion
for the bis(dimethylamido) complex 2b is higher (i.e. slow exchange
on the NMR time scale at 298 K) than that in 2d seems inconsistent
with a dissociative process; the trans effect of the dimethylamido
ligands in 2b should facilitate dissociation of the bis(ketenimine)
ligand.
(18) (a) O’Connor, J . M.; Casey, C. P. Chem. Rev. (Washington, D.C.)
1987, 87, 307. (b) Rerek, M. E.; Basolo, F. J . Am. Chem. Soc. 1984,
106, 5908. (c) J i, L.-N.; Rerek, M. E.; Basolo, F. Organometallics 1984,
3, 740.

Bis(ketenimine) Complexes of Zirconium
Organometallics, Vol. 17, No. 7, 1998 1321
Waterloo. Elemental analyses were determined by M. H. W.
Laboratories of Phoenix, AZ, and Oneida Research Services,
Inc., New York, NY.
angle of 85.8(1)° is more acute compared to that typically
observed in bent-metallocene complexes.20 Somewhat
surprisingly, the chemical shift of the signal due to the
methine proton in the bis(ketenimine) ligand is insensi-
tive to the coordination mode adopted by these ligands
in solution. It could be that π f σ interconversion is very
facile in solution.
Syn th esis of Liga n d 3b. Syn th esis of 4-((p-(Tr iflu or o-
m eth yl)ph en yl)am in o)pen t-3-en -2-on e (5). A 4 mL amount
of p-(trifluoromethyl)aniline (0.031 mol) was added to 3.50 mL
of 2,4-pentanedione (0.034 mol), and the resulting mixture was
heated at 150 °C for 4 h. The water produced from the reaction
mixture was collected via a condenser. The resulting solution
was left in the freezer overnight, and a bright yellow solid was
produced. The compound was recrystallized from hexane (7.46
g, 98%). 1H NMR (250 MHz, C6D6): δ 13.26 (s, 1H, HNC6H4-
It is apparent from a comparison of these various
complexes that the bis(ketenimine) ligand can readily
modify its mode of coordination to the metal in response
to the donor properties of the other ligands bonded to
zirconium. Presumably, in the presence of strong
π-donors, as in 2b, the bis(ketenimine) ligand acts
primarily as a 2σ, 4 e- donor for a formal count of 16 e-
in such complexes, while in the more electron deficient
complexes such as 4 it distorts to π-coordination so as
to maintain a 16 e- count at the metal center, at least
in the solid state. While this flexibility is appealing as
a mechanism for modifying the reactivity of these
complexes, it would appear from the structure of 4b that
the π-donor ability of this ligand appears to be consider-
ably weaker21 than in Cp (or even pentadienyl22)
complexes of group 4. This feature will obviously modify
the reactivity of more electron deficient versions of group
4 complexes incorporating this ligand, and studies
directed toward elucidating these effects in, for example,
olefin polymerization are being actively pursued.8
p-CF3), 7.48 (d, J HH ) 9 Hz, 2H, N(C6H4CF3)), 6.83 (d, J HH
)
9 Hz, 2H, N(C6H4CF3)), 5.28 (s, 1H, p-CF3C6H4NHC(Me)-
CHCOMe), 2.33 (s, 3H, p-CF3C6H4NHC(Me)CHCOMe), 1.81
(s, 3H, p-CF3C6H4NHC(Me)CHCOMe). 13C{1H} NMR (75
MHz, C6D6): δ 196.5, 157.6, 142.5, 125.5 (q, J CF ) 30 Hz), 124.8
(q, J CF ) 270 Hz), 126.2, 123.0, 99.5, 29.5, 19.5. 19F NMR (188
MHz, C6D6): δ -61.90. High-resolution mass spectrum: calcd
for C12H12NF3O 243.0949, found 243.0992. IR (KBr disk):
3037, 3080, 1592, 1535, 1483, 1393, 1021, 824, 704, 690 cm-1
.
Syn th esis of 4-((p-(Tr iflu or om eth yl)p h en yl)a m in o)-2-
((p-(tr iflu or om eth yl)p h en yl)im in o)p en t-3-en e (3b). Tri-
ethyloxonium tetrafluroborate (2.50 g, 0.013 25 mol) dissolved
in 20 mL of CH2Cl2 was added dropwise to a stirred solution
of 5 (3.22 g, 0.013 mol) in the same solvent. The reaction
mixture was allowed to react for 20 min, and then 1.8 mL
(0.013 mol) of dry p-(trifluoromethyl)aniline was added to
it. The reaction mixture was stirred overnight. The reaction
solution was then evaporated to dryness. The resulting solid
was then redissolved in 140 mL of THF and cooled to 0 °C.
Excess solid NaH (0.3369 g, 0.014 mol) was added in one
portion from a solid addition funnel over 30 min. The reaction
mixture was warmed to room temperature after 2 h and then
stirred overnight. The solvent was then removed under
vacuum, and the resulting yellow solid was extracted with 200
mL of hexane. The volume of the extract was reduced to 25
mL and then cooled to -35 °C overnight to obtain the title
compound (4.61 g, 90%). 1H NMR (250 MHz, C6D6): δ 12.84
(s, 1H, HNC6H4-p-CF3), 7.24 (d, J HH ) 10 Hz, 4H, N(C6H4-
CF3)), 6.58 (d, J HH ) 10 Hz, 4H, N(C6H4CF3)), 4.72 (s, 1H,
p-CF3C6H4NC(Me)CH C(Me)NC6H4-p-CF3), 1.60 (s, 6H,
p-CF3PhNC(Me)CHC(Me)NC6H4-p-CF3). 13C{1H} NMR (75
MHz, C6D6): δ 159.3, 148.9, 126.4, 125.4 (q, J CF ) 34.3 Hz),
125.15 (q, J CF ) 279.2 Hz), 121.9, 99.6, 22.7. 19F NMR (188
MHz, C6D6): δ -61.42. High-resolution mass spectrum: calcd
for C19H17N2F6 387.1296, found (EI) 387.1282. IR (KBr disk):
3036, 3054, 1652, 1611, 1564, 1387, 1326, 1281, 1193, 1089,
Exp er im en ta l Section
All solvents and chemicals were reagent grade and purified
as required. All synthetic reactions were conducted under an
atmosphere of dry nitrogen in dry glassware unless otherwise
noted. Tetrahydrofuran, diethyl ether, hexanes, and toluene
were dried by distillation from sodium-benzophenone ketyl
while dichloromethane was dried and distilled from CaH2. The
23
24
compounds Zr(Bn)4 and Zr(NMe2)4 were prepared as de-
scribed in the literature. The bis(ketenimine) ligand 3a was
prepared as described previously.7 Routine 1H, 13C, and 19F
NMR spectra were recorded in THF-d8 or C6D6 solution on a
Bruker AM-250, AC-200, or AM-300 spectrometer; 1H and 19F
chemical shifts are referenced with respect to residual pro-
tonated solvent or internal CFCl3, respectively. Low-temper-
ature NMR spectra were recorded using these spectrometers
in toluene-d8 or CD2Cl2 solution using a solution of methanol
in CD3OD for calibration purposes. IR spectra were recorded
on a Bomem MB-100 FTIR spectrometer. Mass spectra were
obtained using a VG-7070 instrument at the University of
1065, 854, 829, 769, 587 cm-1
.
Syn th esis of (P h NC(Me)CHC(Me)NP h )Zr (CH2P h )3 (1a).
To a stirred solution of Zr(CH2Ph)4 (0.302 g, 0.66 mmol) in
toluene was added a toluene solution of 3a (0.157 g, 0.628
mmol). The reaction mixture was stirred with exclusion of
light for 8 h at room temperature, and the resulting orange
solution was concentrated to dryness in vacuo. The resulting
orange oil was extracted with hexane. The hexane solution
was concentrated and cooled to -40 °C which resulted in the
precipitation of complex 1a as a yellow solid. The solid was
collected by filtration and dried by blowing with nitrogen gas
(yield 0.284 g, 60%). 1H NMR (250 MHz, C6D6): δ 7.07 (m,
10H, NP h ), 6.90 (m, 5H, CH2P h ), 6.72 (m, 10H, NP h , CH2P h ),
5.01 (s, 1H, PhNC(Me)CHC(Me)NPh), 2.60 (s, 6H, CH2Ph),
1.51 (s, 6H, PhNC(Me)CHC(Me)NPh). 13C{1H} NMR (75
MHz, C6D6): δ 160.1, 146.1, 146.04, 128.9, 128.4, 127.2, 126.0,
125.4, 121.5, 101.3, 75.4, 21.31. Anal. Calcd for C38H38N2Zr:
C, 71.08; H, 6.23. Found: C, 71.35; H, 6.09. IR (KBr disk):
3060, 3038, 1633, 1593, 1543, 1483, 1449, 1483, 1449, 1373,
(19) Rausch, M. D.; Moriarty, K. J .; Atwood, J . L.; Hunter, W. E.;
Samuel, E. J . Organomet. Chem. 1987, 327, 39.
(20) (a) J effery, J .; Lappert, M. F.; Luong-Thi, N. T.; Webb, M. J .
Chem. Soc., Dalton Trans. 1981, 1593. (b) Prout, K.; Cameron, T. S.;
Forder, R. A.; Critchley, S. R.; Denton, B.; Ress, G. V. Acta Crystallogr.
1974, B30, 2290. (c) Lauer, J . W.; Hoffmann, R. J . Am. Chem. Soc.
1976, 98, 1729. (d) Sikora, D. J .; Rausch, M. D.; Rogers, R. D.; Atwood,
J . L. J . Am. Chem. Soc. 1981, 103, 1265. (e) Bush, M. A.; Sinn, G. A.
J . Chem. Soc. A 1971, 2225.
(21) The nitrogen atoms in the acyclic bis(ketenimine) ligand will
lower the energy of the π-orbitals on N, and indirectly those on adjacent
C atoms, compared with an analogous all-C π system.
(22) (a) Ernst, R. D. Chem. Rev. 1988, 88, 1255. (b) Bleeke, J . R.;
Earl, P. L. Organometallics 1989, 8, 2735. (c) Freeman, J . W.; Hallinan,
N. C.; Arif, A. M.; Gedridge, R. W.; Ernst, R. D.; Basolo, F. J . Am.
Chem. Soc. 1991, 113, 6509. (d) Hyla-Kryspin, I.; Waldman, T. E.;
Melendez, E.; Trakarnpruk, W.; Arif, A. M.; Ziegler, M. L.; Ernst, R.
D.; Gleiter, R. Organometallics 1995, 14, 5030.
(23) (a) Zucchini, U.; Albizzati, E.; Giannini, U. J . Organomet. Chem.
1971, 26, 357. (b) Davidson, P. J .; Lappert, M. F.; Pearce, R. J .
Organomet. Chem. 1973, 57, 269.
1282, 1203, 1117, 1070, 1023, 743, 698, 521 cm-1
.
(P h NC(Me)CHC(Me)NP h )Zr (NMe2)3 a n d (p-CF 3P h NC-
(Me)CHC(Me)NP h -p-CF 3)Zr (NMe2)3 (1b,c). A common pro-
cedure was employed for the syntheses of these zirconium
(24) (a) Bradley, D. C.; Thomas, I. M. Proc. Chem. Soc., London 1959,
225. (b) Bradley, D. C.; Thomas, I. M. Proc. Chem. Soc., London 1960,
3857.

1322 Organometallics, Vol. 17, No. 7, 1998
Rahim et al.
tris(amido) complexes. In each case, 0.374 g (2.8 mmol) of
Zr(NMe2)4 was dissolved in toluene (30 mL). One equivalent
of the corresponding bis(ketenimine) ligand 3a or 3b, also
dissolved in toluene (10 mL), was added to the solution
containing the zirconium amide complex, and the solution was
stirred for 10 min. During this period, the solution turned
from pale yellow to bright yellow. Once the completion of the
reaction was ascertained from an NMR spectrum of the
reaction mixture, the solution was evacuated to dryness to
leave a orange solid. Extraction of the solid with pentane,
filtration through Celite, and concentration of the extract
precipitated bright yellow, microcrystalline solids. Further
precipitation was accomplished by cooling the mixture to -40
°C for 10 h. The supernatant was syringed off and discarded,
and the orange solids were pumped to dryness. Yields ranged
from 70 to 83%.
yellow solution was stirred at 92 °C for 24 h, after which time
it was evacuated to dryness. The gummy yellow solid residue
was then washed with hexane. The solid was then redissolved
in toluene and filtered through a 1/2 in. pad of Celite to give a
clear yellow solution. Concentrating the toluene solution
under vacuum and cooling to -40 °C for 12 h yielded a bright
yellow microcrystalline solid, which was separated by filtration
(yield 0.757 g, 80%). 1H NMR (250 MHz, C6D6): δ 7.10 (m,
14H, NP h ), 6.85 (m, 4H, NP h ), 5.80 (d, J HH ) 8.0 Hz, 2H,
NPh o-H), 5.10 (s, 2H, PhNC(Me)CHC(Me)NPh), 2.50 (br s,
12H, NMe2), 1.70 (s, 6H, PhNC(Me)CHC(Me)NPh), 1.41 (s,
6H, PhNC(Me)CHC(Me)NPh). 13C{1H} NMR (75 MHz,
C6D6): δ 164.9, 164.1, 153.2, 150.2, 128.1, 127.9, 127.1, 126,
124.9, 124.1, 100.1, 47.1, 25.2, 25.4. Anal. Calcd for C38H46N6-
Zr: C, 67.28; H, 6.83; N, 12.39. Found: C, 67.35; H, 6.61; N,
12.18. IR (KBr disk): 1630, 1550, 1436, 1375, 1278, 1186,
1071, 1025, 950, 804, 748, 698 cm-1
.
Data for 1b are as follows. 1H NMR (250 MHz, C6D6): δ
7.13 (d, J HH ) 8.3 Hz, 4H), 6.90 (t, J ) 8.3 Hz, 2H), 6.70 (d,
J HH ) 8.3 Hz, 4H), 5.02 (s, 1H, PhNC(Me)CHC(Me)NPh), 2.73
(s, 18H, NMe2), 1.75 (s, 6H, PhNC(Me)CHC(Me)NPh). 13C{1H}
NMR (75 MHz, C6D6): δ 164.6, 160.0, 128.65, 125.41, 124.19,
100.40, 42.46, 24.39. Anal. Calcd for C23H35N5Zr: C, 58.30;
H, 7.44; N, 14.78. Found: C, 57.98; H, 7.28; N, 14.60. IR (KBr
disk): 2822, 2758, 1631, 1593, 1558, 1513, 1482, 1450, 1383,
Syn th esis of cis-(P h NC(Me)CHC(Me)NP h )2Zr Cl2 (2d ).
Complex 2b (0.225 g, 0.332 mmol) was dissolved in toluene
(10 mL) and was added to a slurry of [Me2NH2][Cl] (0.054 g,
0.664 mmol) at room temperature. The mixture was stirred
for 24 h at 55 °C. At the end of this period, the cloudy mixture
was pumped to dryness. The solid residues were dissolved in
a large volume of toluene at 50 °C, and this solution was
filtered through Celite to give a clear yellow solution. Con-
centration of the filtrate yielded bright yellow crystals (0.29
g, 90% yield) of the title compound. 1H NMR (250 MHz,
C6D6): δ 6.90 (m, 20 H, NPh), 5.10 (s, 2H, PhNC(Me)CHC-
(Me)NPh), 1.45 (s, 12H, PhNC(Me)CHC(Me)NPh). 13C{1H}
NMR (75 MHz, THF-d8): δ 167.0, 150.2, 130.3, 128.1, 125.3,
105.2, 25.2. Anal. Calcd for C34H34N4Cl2Zr: C, 61.79; H, 5.18;
N, 10.72. Found: C, 61.54; H, 5.21; N, 10.51. IR (KBr disk):
1597, 1529, 1484, 1442, 1368, 1300, 1256, 1205, 1180, 1072,
1258, 1184, 1160, 1022, 959, 939, 832, 752, 700, 524 cm-1
.
Data for 1c are as follows. 1H NMR (250 MHz, C6D6): δ
7.45 (d, J HH ) 10 Hz, 4H, N(C6H4CF3)), 6.56, (d, J HH ) 10 Hz,
4H, N(C6H4CF3)), 5.02 (s, 1H, p-CF3C6H4NC(Me)CHC(Me)-
NC6H4-p-CF3), 2.58 (s, 18H, NMe2), 1.55 (s, 6H, p-CF3C6H4-
NC(Me)CHC(Me)NC6H4-p-CF3). 13C{1H} NMR (75 MHz,
C6D6): δ 164.7, 153.7, 126.5 (q, J CF ) 52.8 Hz), 125.5 (q, J CF
) 253.5 Hz), 125.0, 123.3, 100.6, 41.9, 24.2. 19F NMR (188
MHz, C6D6): δ 62.12. Anal. Calcd for C25H33N5F6Zr: C, 49.29;
H, 5.46. Found: C, 49.25; H, 5.50. IR (KBr): 1655, 1610,
1024, 929, 836, 795, 755, 710, 698 cm-1
.
1561, 1386, 1325, 1284, 1167, 1108, 1065, 855 cm-1
Syn th esis of (P h NC(Me)CHC(Me)NP h )Zr Cl3 (1d ).
.
Syn th esis of cis-(P h NC(Me)CHC(Me)NP h )2Zr Me2 (2e)
a n d cis-(P h NC(Me)CHC(Me)NP h )2Zr Bn 2 (2f). To 150 mg
(0.22 mmol) of 2d dissolved in 2 mL of toluene was added 2
equiv of MeLi (185 µL of 1.2 M solution). After 10 min the
yellow solution became a clear orange solution. The toluene
solution was removed under vacuum to give an orange solid.
The solid was extracted with hexane and filtered, and the
crude product 2e was recrystallized from hexane or dichloro-
methane. A similar procedure was followed for synthesizing
benzyl derivative 2f using PhCH2MgCl as the alkylating agent
(yield 75-85%).
A
solution of Me3SiCl (0.068 g, 0.63 mmol) in hexane (10 mL)
was added dropwise to a toluene solution of 1b (0.100 g, 0.21
mmol) at room temperature. The yellow solution was then
heated at 60 °C for 24 h, resulting in the formation of a yellow
slurry. The slurry was cooled to -35 °C, and the solid was
collected by filtration, washed with hexane, and dried under
vacuum. The yield was 75%. 1H NMR (250 MHz, C6D6): δ
7.10 (m, 10H, NPh), 4.80 (s, 1H, PhNC(Me)CHC(Me)NPh), 1.84
(s, 6H, PhNC(Me)CHC(Me)NPh). 13C{1H} NMR (75 MHz,
THF-d8): δ 168.4, 148.1, 129.5, 128.9, 127.1, 107.5, 24.6. Anal.
Calcd for C17H17N2Cl3Zr: C, 45.68; H, 3.85; N, 6.26. Found:
C, 45.38; H, 4.34; N, 6.24. IR (KBr disk): 2590, 1995, 1580,
1528, 1495, 1482, 1361, 1286, 1197, 1028, 744, 686, 475, 434
Data for 2e are as follows. 1H NMR (250 MHz, C6D6): δ
7.15 (d, J HH ) 8.2, 8H, NP h ), 6.90 (t, J HH ) 8.2, 4H, NP h ),
6.62 (d, J HH ) 8.2, 8H, NP h ), 4.90 (s, 2H, PhNC(Me)CHC-
(Me)NPh), 1.50 (s, 12H, PhNC(Me)CHC(Me)NPh), 1.32 (s, 6H,
ZrMe2). 13C{1H} NMR (75 MHz, THF-d8): δ 165.0, 150.8,
129.0, 128.7, 125.1, 106.7, 53.9, 25.0. Anal. Calcd for
cm-1
.
Syn th esis of (p-CF3C6H4NC(Me)CHC(Me)NC6H4-p-CF3)-
Zr Cl3‚NHMe2 (1e). Three equivalents of solid NHMe2‚HCl
(2.4 mmol) was added to a solution of 1c (506 mg, 0.796 mmol)
dissolved in 20 mL of THF. The solution was stirred overnight,
affording a yellow slurry. The yellow solid was collected by
filtration, washed with hexane, and dried under vacuum.
Yield: 80% (400 mg). 1H NMR (250 MHz, THF-d8): δ 7.65
(d, J ) 8 Hz, 4H, N(C6H4CF3)), 7.30 (d, J ) 8 Hz, 4H, N(C6H4-
CF3)), 5.69 (s, 1H, p-CF3C6H4NC(Me)CHC(Me)NC6H4-p-CF3),
3.10 (br s, 1H, NHMe2), 2.26 (br s, 6H, NHMe2) 1.70 (s, 6H,
p-CF3C6H4NC(Me)CHC(Me)NC6H4-p-CF3). 13C{1H} NMR (75
MHz, C6D6) δ 165.6, 155.3, 129.6, 127.7 (q, J CF ) 234 Hz), 126.5
(q, J CF ) 37.5 Hz): 124.19, 115.4, 44.3, 25.0. 19F NMR (188
MHz, C6D6): δ -62.12. Anal. Calcd for C21H22N3F6Cl3Zr: C,
40.16; H, 3.53; N, 6.69. Found: C, 39.37; H, 3.68; N, 7.81. IR
(KBr disk): 3035, 2950, 1608, 1528, 1378, 1323, 1284, 1167,
C
36H40N4Zr‚1/6CH2Cl2: C, 68.45; H, 6.38. Found: C, 68.32; H,
6.28. IR (KBr disk): 1631, 1595, 1544, 1484, 1439, 1373, 1277,
1184, 1023, 827, 750, 699, 497 cm-1
.
Data for 2f are as follows. 1H NMR (250 MHz, C6D6): δ
7.20 (m, 6H, NP h ), 7.05 (m, 8H, NP h ), 6.90 (m, 10H, CH2P h ),
6.50 (m, 6H, NP h ), 5.05 (s, 2H, PhNC(Me)CHC(Me)NPh), 2.50
(s, 4H, Zr-CH2Ph), 1.42 (s, 12H, PhNC(Me)CHC(Me)NPh).
13C{1H} NMR (75 MHz, THF-d8): δ 165.1, 153.5, 129.3, 127.6,
127.5, 127.3, 125.4, 120.3, 103.1, 93.2, 85.6, 25.5. Anal. Calcd
for C48H48N4Zr: C, 74.62; H, 6.26; N, 7.20. Found: C, 74.42;
H, 6.21; N, 7.15. IR (KBr disk): 3054 (w), 1636, 1590, 1533,
1482, 1442, 1389, 1254, 1203, 1181, 1025, 990, 935, 827, 798,
748, 702, 514 cm-1
.
Syn th esis of (P h NC(Me)CHC(Me)NP h )(η5-Cp)Zr Cl2 (4a).
To a stirred solution of 1d (400 mg, 0.89 mmol) in benzene
(50 mL) was added solid CpNa (88 mg, 0.98 mmol) over 30
min. After the solution was stirred for 24 h, the reaction
mixture was filtered and the pale yellow filtrate evaporated
to give a light yellow solid. The compound was recrystallized
from toluene. Yields ranged from 70 to 83%. 1H NMR (250
1116, 1065, 1015, 943, 876 cm-1
.
Syn th esis of cis-(P h NC(Me)CHC(Me)NP h )2Zr (NMe2)2
(2b). This complex was prepared by dissolving Zr(NMe2)4
(0.187 g, 1.4 mmol) in toluene and adding 2 equiv of 3a (0.7 g,
2.8 mmol), also dissolved in toluene. The resulting bright

Bis(ketenimine) Complexes of Zirconium
Organometallics, Vol. 17, No. 7, 1998 1323
MHz, C6D6): δ 6.96 (m, 10H, NP h ), 6.16, (s, 5H, Cp H), 5.23
(s, 1H, PhNC(Me)CHC(Me)NPh), 1.70 (s, 6H, PhNC(Me)CHC-
(Me)NPh). 13C{1H} NMR (75 MHz, C6D6): δ 164.0, 150.4,
129.1, 126, 124.2, 117.2, 90.8, 22.0. Anal. Calcd for
113.2, 94.3, 27.0, 23.3. 19F NMR (188 MHz, C6D6): δ -62.09.
Anal. Calcd for C26H26N2F6Zr: C, 54.63; H, 4.58; N, 4.90.
Found: C, 54.57; H, 4.32; N, 4.78. IR (KBr disk): 2920, 2862,
1610, 1538, 1502, 1395, 1323, 1240, 1166, 1117, 1066, 1012,
C
22H22Cl2N2Zr‚1/3C6H6: C, 57.35; H, 4.81; N, 5.57. Found: C,
873, 805, 737, 691, 598, 550, 458 cm-1
.
57.44; H, 4.51; N, 5.62. IR (KBr): 1592, 1534, 1483, 1392,
X-r a y Str u ctu r e Deter m in a tion s. Selected crystallo-
graphic and refinement data appear in Table 5 for compounds
2b,d and 4b. In all cases, a suitable single crystal was glued
to a glass fiber using epoxy resin, and the fiber was then
mounted on a Siemens P4 diffractometer. Unit cell param-
eters were determined and refined from a set of 25 general
reflections (20.0 < 2θ < 30.0°) well distributed in reciprocal
space.
Intensity data were collected using graphite-monochromated
Mo KR radiation at the temperature indicated in Table 5 by
employing the ω-scan technique over the 2θ range indicated
in Table 5 with variable scan speeds (3.00-30.00° min-1) and
a 1.20° scan width. Background measurements using the
stationary crystal, stationary counter method were made at
the beginning and end of each scan, each for 25% of the total
scan time. Three standard reflections were measured after
every 100 reflections and showed no significant loss in
intensity during data acquisition.
Intensities were corrected for Lorentz and polarization
effects. A face-indexed numerical method was employed to
correct for adsorption effects in all cases. Collected, inde-
pendent and observed reflections (F > 6.0σ(F)) are summarized
in Table 5, and the last group was used in the structure
solution and refinement. The minimum and maximum trans-
mission factors through the crystals were calculated to be
0.8771 and 0.9367, 0.8519 and 0.8947, and 0.7967 and 0.8843
for 2b,d and 4b, respectively.
The structures were solved by Patterson and Fourier
methods and refined by full-matrix least-squares techniques
using the Siemens SHELXTL PLUS software. Anisotropic
refinement of all non-H atoms allowed location of all hydrogen
atoms from a difference map in all cases. In the final cycles
of refinement, the hydrogens were included at their found
positions and were refined isotropically.
1291, 1237, 1188, 1072, 1020, 825, 755, 706, 690 cm-1
.
Syn th esis of (P h NC(Me)CHC(Me)NP h )(η5-C9H7)Zr Cl2
(4b). This compound was synthesized in a manner analogous
to that described above (yield 80%). 1H NMR (250 MHz,
C6D6): δ 7.55 (m, 4H, H4-H7 of the indene ring), 7.00 (m, 10H,
NP h ), 6.25 (d, J HH ) 2.3 Hz, 2H, H1 and H3 of the indenyl
ring), 6.05 (t, J ) 2.3 Hz, 1H, H2), 4.90 (s, 1H, PhNC(Me)-
CHC(Me)NPh), 1.70 (s, 6H, PhNC(Me)CHC(Me)NPh). 13C{1H}
NMR (75 MHz, THF-d8): δ 164.5, 151.1, 129.8, 127.8, 127.3,
126.8, 126.0, 125.1, 121.4, 106.6, 89.9, 22.4. Anal. Calcd for
C
33H24N2Cl2Zr: C, 59.10; H, 5.00; N, 5.32. Found: C, 59.25;
H, 4.60; N, 5.32. IR (KBr disk): 3050, 3100, 1593, 1484, 1450,
1395, 1237, 1022, 831, 754, 703, 454 cm-1
.
Syn th esis of (p-CF3C6H4NC(Me)CHC(Me)NC6H4-p-CF3)-
(η5-Cp )Zr Cl2 (4c). A 320 mg (0.51 mmol) amount of 1e was
slurried in 30 mL of benzene. Solid NaCp (49 mg, 0.55 mmol)
was added in portions over 15 min, and the slurry of the
complex was stirred overnight. A color change from yellow to
orange was observed over 24 h, and the reaction mixture was
then filtered. The orange filtrate was evaporated to provide
a yellow-orange solid. Recrystallization from toluene at -35
°C yielded a pure yellow-orange, crystalline solid (185 mg, yield
60%). 1H NMR (250 MHz, C6D6): δ 7.32 (d, J ) 10 Hz, 2H,
N(C6H4CF3)), 6.90 (d, J ) 10 Hz, 2H, N(C6H4CF3)), 6.00 (s,
5H, CpH), 5.11 (s, 1H, p-CF3C6H4NC(Me)CHC(Me)NC6H4-p-
CF3) 1.60 (s, 6H, p-CF3PhNC(Me)CHC(Me)NPhp-CF3). 13C{1H}
NMR (75 MHz, THF-d8) δ 165.6, 154.3, 128.0 (q, J CF ) 32.2),
127.5 (q, J CF ) 272.2), 127.2, 125.8, 117.9, 92.5, 22.5. 19F NMR
(188 MHz, C6D6): δ -62.32. Anal. Calc′d for C24H20N2Cl2F6-
Zr: C, 47.06; H, 3.29; N, 4.57. Found: C, 47.10; H, 3.45; N,
4.35. IR (KBr disk): 3027, 2875, 2800, 1610, 1537, 1504, 1406,
1321 cm-1
.
Syn t h esis of (P h NC(Me)CH C(Me)NP h )(η5-Cp )Zr Me2
(4d ). Compound 4a (600 mg, 1.25 mmol) was dissolved in 100
mL of benzene and was allowed to react with 2 equiv of MeLi
(1.79 mLof 1.4 M solution in ether) for 3 h at room tempera-
ture. The light yellow reaction mixture turned brown. The
solution was filtered through Celite and the solvent was
removed under reduced pressure, yielding an orange solid. The
yellow solid residue was extracted with hexane, and cooling
the hexane extract at -10 °C produced 4d as an orange
microcrystalline solid (300 mg, yield 60%). 1H NMR (250 MHz,
C6D6): δ 7.35 (d, 4H, J HH ) 8.3, NP h ), 7.29 (t, 2H, J HH ) 8.3,
NP h ), 7.13 (d, 4H, J HH ) 8.3, NP h ), 6.24, (s, 5H, CpH), 5.60
(s, 1H, PhNC(Me)CHC(Me)NPh), 1.54 (s, 6H, PhNC(Me)CHC-
(Me)NPh), 0.46 (s, 6H, ZrMe2). 13C{1H} NMR (75 MHz,
C6D6): δ 161.7, 150.9, 128.9, 124.8, 124.6, 113.1, 94.0, 27.0,
22.3. Anal. Calcd for C24H28N2Zr: C, 66.17; H, 6.47; N, 6.23.
Found: C, 66.37; H, 6.38; N, 6.13. IR (KBr disk): 1620, 1550,
Scattering factors for non-hydrogen atoms were taken from
ref 25, while the data of Stewart et al.26 were used for hydrogen
atoms. Full details of the crystallographic data, solution, and
refinement, as well as atomic coordinates, thermal parameters,
and bond lengths and angles are included in the Supporting
Information.
Ack n ow led gm en t. We thank the Natural Sciences
and Engineering Research Council and Nova Chemicals
Ltd. for financial support of this work. We also acknowl-
edge the donation of B(C6F5)3 and [DMANH][B(C6F5)4]
by Nova Chemicals Ltd and BFGoodrich Co., respec-
tively.
Su p p or tin g In for m a tion Ava ila ble: Tables of crystal-
lographic data, atomic coordinates with isotropic thermal
coefficients, bond lengths, bond angles, anisotropic thermal
coefficients, and H-atom coordinates and isotropic thermal
coefficients for compounds 2b,d and 4b (25 pages). Ordering
information is given on any current masthead page.
1383, 1312, 1191, 1184, 1088, 1074, 925, 854 cm-1
.
Syn th esis of (p-CF 3C6H4P h NC(Me)CHC(Me)NC6H4-p-
CF 3)(η5-Cp )Zr Me2 (4e). A similar procedure was followed, as
described above for the preparation of 4d , using 4c. Yield:
65%. 1H NMR (200 MHz, C6D6): δ 7.35 (d, J HH ) 10 Hz, 2H,
N(C6H4CF3)), 6.55 (d, J HH ) 10 Hz, 2H, N(C6H4CF3)), 6.82 (s,
5H, CpH), 5.30 (s, 1H, p-CF3C6H4NC(Me)CHC(Me)NC6H4-p-
CF3), 1.54 (s, 6H, p-CF3C6H4NC(Me)CHC(Me)NC6H4-p-CF3),
0.43 (s, 6H, ZrMe2). 13C{1H} NMR (THF-d8): δ 162.5, 153.7,
126.2 (q, J CF ) 34.0 Hz), 124.7 (q, J CF ) 272 Hz), 122.7, 115.1,
OM970862H
(25) International Tables for X-ray Crystallography; Kynoch Press:
Birmingham, U.K., 1974; Vol. 4.
(26) Stewart, R. F.; Davidson, E. R.; Simpson, W. T. J . Chem. Phys.
1965, 42, 3175.