Donor-ligand-substituted cyclopentadienylchromium(III) complexes: A new class of alkene polymerization catalyst. 1. Amino-substituted systems

Article abstract of DOI:10.1021/om990643r

Me₂NC₂H₄C₅Me₄Li reacts with Cr(THF)₃Cl₃ to give (η¹:η⁵-Me₂NC₂H ₄C₅Me₄)CrCl₂, in which the complexation of the N-donor atom to the metal atom has been confirmed by X-ray crystallography. A series of related compounds, e.g. (η¹:η⁵-cyclo-C₄H₈NSiMe ₂OSiMe₂C₅H₄)CrCl₂, has been prepared by varying the substituents on the organic ligand. Further reaction with organomagnesium reagents leads to formation of the corresponding dialkyl-Cr complexes. Related species have been prepared containing imine-, alkoxy-, and alkylthio-substituted cyclopentadienyl groups as well as the C-donor ligand tetramethylimidazol-2-ylidene. Treatment of these compounds with methylalumoxane (MAO) leads to the formation of highly active catalysts for the oligomerization, polymerization, and copolymerization of ethylene.

Full text of DOI:10.1021/om990643r

388
Organometallics 2000, 19, 388-402
Don or -Liga n d -Su bstitu ted
Cyclop en ta d ien ylch r om iu m (III) Com p lexes: A New Cla ss
of Alk en e P olym er iza tion Ca ta lyst. 1. Am in o-Su bstitu ted
System s
A. Do¨hring, J . Go¨hre,1 P. W. J olly,* B. Kryger, J . Rust, and G. P. J . Verhovnik2
Max-Planck-Institut fu¨r Kohlenforschung, Kaiser-Wilhelm-Platz 1,
D-45470 Mu¨lheim an der Ruhr, Germany
Received August 9, 1999
Me2NC2H4C5Me4Li reacts with Cr(THF)3Cl3 to give (η1:η5-Me2NC2H4C5Me4)CrCl2, in which
the complexation of the N-donor atom to the metal atom has been confirmed by X-ray
crystallography. A series of related compounds, e.g. (η1:η5-cyclo-C4H8NSiMe2OSiMe2C5H4)-
CrCl2, has been prepared by varying the substituents on the organic ligand. Further reaction
with organomagnesium reagents leads to formation of the corresponding dialkyl-Cr
complexes. Related species have been prepared containing imine-, alkoxy-, and alkylthio-
substituted cyclopentadienyl groups as well as the C-donor ligand tetramethylimidazol-2-
ylidene. Treatment of these compounds with methylalumoxane (MAO) leads to the formation
of highly active catalysts for the oligomerization, polymerization, and copolymerization of
ethylene.
In tr od u ction
In this publication we describe in detail the prepara-
tion and properties of the amino-substituted cyclopen-
tadienyl chromium species and a number of related
systems. The analogous phosphine-substituted systems
will be reported separately.
Whereas chromium played a key role in the early
development of heterogeneous catalysts for the polym-
erization of alkenes, this metal has been largely ignored
in the development of the homogeneous methylalumox-
ane (MAO)-activated systems that have attracted so
much attention in the past decade.3 A number of neutral
single-component catalysts, e.g. (η3-C3H5)3Cr, Cp(η3-
C3H5)2Cr, (Me5C5)Cr(CH2SiMe3)2, and (indenyl)4Cr2, as
well as a few ionic species, e.g. [(Me5C5)Cr(THF)2Me]+-
BPh4- and [(t-C4H9N:)2CrCH2Ph]+B(C6F5)4-, have been
reported.4 In contrast, the MAO-activated systems are
apparently limited to the donor-ligand-substituted cy-
clopentadienylchromium(III) compounds which we have
reported5-7 and compounds containing N,O- or N,N-
chelate ligands,8,9 whereby in the latter case Et2AlCl
has been shown to be a far more effective activator.
Resu lts a n d Discu ssion
The organochromium compounds described here are
members of a relatively large class of amino-substituted
cyclopentadienylmetal complexes which are known for
many of the transition metals and which have recently
been reviewed.10 The first examples involving chromium
were actually prepared by J onas et al.11 but were not
investigated further. Their synthesis is straightforward
and involves reacting an alkali-metal salt of the ap-
propriate amino-substituted cyclopentadiene derivative
with Cr(THF)3Cl3.
P r ep a r a tion of th e Am in o-Su bstitu ted Cyclo-
p en ta d ien e Der iva tives. The amino-substituted cy-
clopentadiene derivatives 1a -e and 2a -c have been
prepared using a standard procedure involving the
appropriate (dialkylamino)ethyl or (dialkylamino)propyl
chloride (Scheme 1).
The preparation of the corresponding diphenylamino
derivatives proved more difficult, and whereas Ph2-
NC2H4Cl could not be obtained pure from the reaction
between Ph2NLi and ClC2H4OTos or between LiAlH4
and Ph2NCOCH2Cl, Ph2NC3H6C5H6 (2d ) was prepared
(1) Part of the doctoral thesis submitted to the Ruhr-Universita¨t-
Bochum in 1999. Present address: BASF (Department of Polyolefins),
D-67056 Ludwigshafen, Germany.
(2) Part of the doctoral thesis submitted to the Ruhr-Universita¨t-
Bochum in 1996. Present address: Witco (Europe) SA, 7 rue du Pre´-
Bouvier, CH-1217 Meyrin, Geneva, Switzerland.
(3) For recent reviews see: Kaminsky, W. J . Chem. Soc., Dalton
Trans. 1998, 1413. McKnight, A. L.; Waymouth, R. M. Chem. Rev.
1998, 98, 2587. Britovsek, G. J . P.; Gibson, V. C.; Weiss, D. F. Angew.
Chem. 1999, 111, 448.
(4) For a recent review see: Theopold, K. H. Eur. J . Inorg. Chem.
1998, 15.
(5) Emrich, R.; Heinemann, O.; J olly, P. W.; Kru¨ger, C.; Verhovnik,
G. P. J . Organometallics 1997, 16, 1511.
(6) J olly, P. W.; J onas, K.; Verhovnik, G. P. J .; Do¨hring, A.; Go¨hre,
J .; Weber, J . C. WO-98/04570, 1998; Chem. Abstr. 1998, 128, 167817.
(7) Do¨hring, A.; Go¨hre, J .; J olly, P. W.; Weber, J . C. XVIIIth
International Conference on Organometallic Chemistry, Munich, Aug
16-21, 1998; Abstracts II, p B27.
(8) Gibson, V. C.; Maddox, P. J .; Newton, C.; Redshaw, C.; Solan,
G. A.; White, A. J . P.; Williams, D. J . J . Chem. Soc., Chem. Commun.
1998, 1651. See also: Coles, M. P.; Gibson, V. C. Polym. Bull. (Berlin)
1994, 33, 529. Gibson, V. C.; Newton, C.; Redshaw, C.; Solan, G. A.;
White, A. J . P.; Williams, D. J . J . Chem. Soc., Dalton Trans. 1999,
827.
(9) Kim, W.-K.; Fevola, M. J .; Liable-Sands, L. M.; Rheingold, A.
L.; Theopold, K. H. Organometallics 1998, 17, 4541.
(10) J utzi, P.; Redeker, T. Eur. J . Inorg. Chem. 1998, 663.
(11) J onas, K. Unpublished results. Swarat, K. Doctoral dissertation,
Ruhr-Universita¨t-Bochum, 1990. Klusmann, P. Diplom dissertation,
Technische Hochschule Aachen, 1991. Beller, M. Doctoral dissertation,
Ruhr-Universita¨t-Bochum, 1992.
(12) Gresham, T. L.; J ansen, J . E.; Shaver, F. W.; Bankert, R. A.;
Fiedorek, F. T. J . Am. Chem. Soc. 1951, 73, 3168.
10.1021/om990643r CCC: $19.00 © 2000 American Chemical Society
Publication on Web 01/21/2000

Substituted Cyclopentadienyl Cr(III) Complexes
Organometallics, Vol. 19, No. 4, 2000 389
Sch em e 1
in modest yield by a multistep synthesis by starting
(eq 2).14
from â-propiolactone (eq 1).12
A procedure analogous to that presented above has
been described by J onas et al.11 to prepare amino-
substituted indenyl ligands. Substitution occurs exclu-
sively in the 2-position of the indenyl group to give 4
and has been extended to a Me3Si-substituted analogue
(5) (eq 3).
The isolated cyclopentadiene derivatives needed no
further purification. The NMR-spectra show that they
exist as a mixture of two (A, B) of three possible isomers
in approximately equal amounts.13
Treatment with NaH or KH in THF or alternatively
with BuLi in pentane or diethyl ether leads to the
formation of the substituted cyclopentadienylmetal salts
as pale pink or white crystalline solids. The reagent of
choice is KH, since the resulting product is practically
free from complexed THF and the KCl formed in the
subsequent reaction with CrCl3 is more easily removed
than either NaCl or LiCl.
Disubstituted cyclopentadiene derivatives are in gen-
eral prepared by reacting a monosubstituted cyclopen-
tadienyl species with an electrophile, and this procedure
has been used to introduce a Me3Si group to give 3
(13) Charrier, C.; Mathey, F. Tetrahedron Lett. 1978, 2407.
(14) Herrmann, W. A.; Morawietz, M. J . A.; Priermeier, T.; Mashima,
K. J . Organomet. Chem. 1995, 486, 291.

390 Organometallics, Vol. 19, No. 4, 2000
Ta ble 1. Am in o-Su bstitu ted Cyclop en ta d ien ylch r om iu m Dich lor id e Com p ou n d s
Do¨hring et al.
anal. found (calcd)
Cl
compd
yield (%)
C
H
Cr
N
(H2NC2H4C5H4)CrCl2 (10)
63
62
95
56
66
35
73
55
81
66
31
86
82
70
79
35.5 (36.4)
41.7 (41.7)
46.5 (46.3)
48.1 (48.2)
43.8 (44.0)
48.0 (48.2)
49.0 (49.9)
47.1 (47.1)
50.4 (50.5)
53.6 (53.8)
53.4 (53.1)
49.5 (49.5)
52.8 (52.8)
57.9 (58.0)
39.9 (40.1)
4.6 (4.4)
5.3 (5.4)
5.8 (5.7)
6.1 (6.1)
5.8 (5.9)
6.2 (6.1)
6.5 (6.5)
6.8 (6.8)
5.3 (5.2)
5.4 (5.4)
6.2 (6.4)
6.9 (7.0)
7.0 (7.1)
7.2 (7.2)
6.3 (6.2)
30.9 (30.7)
27.4 (27.4)
24.8 (24.9)
23.6 (23.7)
24.6 (26.0)
23.8 (23.7)
23.1 (22.6)
19.8 (19.8)
22.9 (22.9)
21.1 (21.2)
17.7 (17.4)
22.6 (22.5)
20.9 (20.8)
18.1 (18.0)
18.2 (18.2)
22.1 (22.5)
20.2 (20.1)
18.2 (18.2)
17.3 (17.4)
20.6 (19.1)
17.3 (17.3)
16.9 (16.6)
14.5 (14.6)
16.8 (16.8)
15.7 (15.5)
12.5 (12.8)
16.5 (16.5)
15.3 (15.2)
13.4 (13.2)
13.3 (13.4)
5.7 (6.1)
5.4 (5.4)
4.9 (4.9)
4.6 (4.7)
5.0 (5.1)
4.6 (4.7)
4.5 (4.5)
3.9 (3.9)a
4.5 (4.5)
4.1 (4.2)
3.7 (3.4)b
4.4 (4.4)
4.1 (4.1)
3.5 (3.6)
3.6 (3.6)c
(Me2NC2H4C5H4)CrCl2 (11)11
(cyclo-C4H8NC2H4C5H4)CrCl2 (12)
(cyclo-C5H10NC2H4C5H4)CrCl2 (13)
(Me2NC3H6C5H4)CrCl2 (14)
(cyclo-C4H8NC3H6C5H4)CrCl2 (15)
(cyclo-C5H10NC3H6C5H4)CrCl2 (16)
(1,3-cyclo-C4H8NC2H4(Me3Si)C5H3)CrCl2 (17)
(1-Me2NC2H4-indenyl)CrCl2 (18)
(1-cyclo-C4H8NC2H4-indenyl)CrCl2 (19)
(1,3-cyclo-C4H8NC2H4(Me3Si)-indenyl)CrCl2 (20)
(Me2NC2H4C5Me4)CrCl2 (21)
(cyclo-C4H8NC2H4C5Me4)CrCl2 (22)
(cyclo-C4H8NC2H4-fluorenyl[H8])CrCl2 (23)
(cyclo-C4H8NSiMe2OSiMe2C5H4)CrCl2 (24)
a% Si: 7.8 (7.9). % Si: 6.7 (6.9). c % Si: 14.5 (14.4).
b
The synthetic procedure for preparing amino-substi-
tuted tetraalkylcyclopentadienyl derivatives has been
well worked out,10,11,15 and we have used it to prepare
the lithium salts of 1-(2-(N-pyrrolidinyl)ethyl)tetra-
methylcyclopentadiene (6) and of 9-(2-(N-pyrrolidinyl)-
ethyl)octahydrofluorene (7).
In addition to the species described above containing
C2H4 or C3H6 fragments bridging the ring and the amino
group, we have prepared two examples (8 and 9) in
which the bridge contains Si-atoms (eqs 4 and 5).16 The
F igu r e 1. Changes in the stretching frequency pattern
upon formation of (cyclo-C4H8NC2H4C5H4)CrCl2 (12).
tadienyl derivatives described in the preceding section
react with Cr(THF)3Cl3 in THF to give the expected
amino-substituted cyclopentadienylchromium dichloride
complexes (10-24) as blue, crystalline solids (e.g., eq
6), and the isolated compounds are listed in Table 1
along with their analytical data.
NMR spectra of 8 and 9 show that at -30 °C they have
the structures shown, while at higher temperatures the
molecules are fluxional. Reaction with BuLi in pentane
(8) or with NaH in THF (9) has been used to convert
them into the corresponding cyclopentadienyl salt.
P r ep a r a tion a n d Str u ctu r e of th e Or ga n och r o-
m iu m Com p ou n d s. Most of the alkali-metal cyclopen-
(15) Threlkel, R. S.; Bercaw, J . E. J . Organomet. Chem. 1977, 136,
1.
(16) Washburne, S. S.; Peterson, W. R. J . Organomet. Chem. 1970,
21, 59.

Substituted Cyclopentadienyl Cr(III) Complexes
Organometallics, Vol. 19, No. 4, 2000 391
F igu r e 2. Molecular structures of (a) (1,3-cyclo-C4H8NC2H4(Me3Si)C5H3)CrCl2 (17), (b) (Me2NC2H4C5Me4)CrCl2 (21), and
(c) (cyclo-C4H8NSiMe2OSiMe2C5H4)CrCl2 (24).
The compounds are paramagnetic, and coordination
of the N-donor atom to the metal has been confirmed
by X-ray crystallography for selected examples. Support
for N-complexation comes from the absence of a strong
absorption in the C-H stretching region of the IR
spectra which is present in the cyclopentadiene precur-
sor. This is illustrated in Figure 1 for the complex
involving cyclo-C4H8NC2H4C5H4 complexation and is
(cyclo-C4H8NSiMe2OSiMe2C5H4)CrCl2 (24) have been
determined by X-ray diffraction, and the molecular
structures and selected bond parameters are shown in
Figure 2 and Table 2. The crystals of both 21 and 24
contain two independent molecules which differ in the
arrangement of the fragment bridging the ring and the
N-donor atom, and the data shown are for only one
molecule. In all three cases the Cr-N distance of 2.1-
2.2 Å confirms that the N-donor atom is complexed to
the metal and comparison of the data for 24 with those
for Me3SiOSiMe3 (Si-O-Si ) 148(3)°, Si-O ) 1.631(3)
associated with a shift in the absorption at 2784 cm-1
.
The crystal structures of (1,3-cyclo-C4H8NC2H4(Me3-
Si)C5H3)CrCl2 (17), (Me2NC2H4C5Me4)CrCl2 (21), and

392 Organometallics, Vol. 19, No. 4, 2000
Do¨hring et al.
Ta ble 2. Selected Str u ctu r a l Da ta for th e
Å)17 suggests that this occurs in a strain-free manner.
The pyrrolidine rings in both 24 and 17 are displaced
to one side and take up positions opposite the N-bonded
SiMe2 group in 24 and the CH2 group in 17. The ring
methyl groups in 21 are displaced by an average of 0.10
Å out of the ring plane and away from the metal atom.
In a few cases, the reaction of the amino-substituted
cyclopentadienyl salt with CrCl3 did not lead to the
expected product. Although the expected blue solution
Am in o-Su bstitu ted Cyclop en ta d ien ylch r om iu m
Dich lor id e Com p lexes 17, 21, a n d 24a
17
21b
24b
Interatomic Distances (Å, esd)
Cr-D1c
Cr-N1
Cr-Cl1
Cr-Cl2
C1-C6
C6-C7
C7-N1
C3-Si1
1.866
Cr-D1
1.882
Cr-D1
1.903
2.125(3) Cr-N1
2.286(1) Cr-Cl1
2.284(1) Cr-Cl2
1.498(5) C1-C6
1.534(5) C6-C7
1.493(4) C7-N1
1.882(3)
2.175(2) Cr-N1
2.300(1) Cr-Cl1
2.294(1) Cr-Cl2
1.506(4) C1-Si1
1.525(5) Si1-O1
1.492(4) O1-Si2
Si2-N1
2.175(4)
2.302(2)
2.311(2)
1.863(6)
1.636(4)
1.625(4)
1.804(4)
was obtained upon treating Cr(THF)3Cl3 with Pri -
2
NC2H4C5H4K in THF, evaporation of the solution gave
an insoluble, ill-defined residue which decomposed in
the mass spectrometer. The IR spectrum of this material
suggests that the amino group is complexed to the
metal, while the insolubility suggests that this occurs
in an intermolecular rather than an intramolecular
manner to give oligomeric or polymeric material (25),
thereby relieving ring strain associated with the rela-
Bond Angles (deg)
Cl1-Cr-Cl2 100.6(1) Cl1-Cr-Cl2 97.4(1) Cl1-Cr-Cl2 98.3(1)
Cl1-Cr-N1 97.0(1) Cl1-Cr-N1 98.2(1) Cl1-Cr-N1 95.4(1)
Cl2-Cr-N1 95.7(1) Cl2-Cr-N1 95.4(1) Cl2-Cr-N1 93.4(1)
D1-Cr-Cl1 123.3
D1-Cr-N1 112.7
D1-Cr-Cl1 121.4
D1-Cr-N1 113.6
D1-Cr-Cl1 118.6
D1-Cr-N1 126.1
C1-C6-C7 109.5(3) C1-C6-C7 109.7(2) C1-Si1-O1 105.9(2)
C6-C7-N1 110.4(3) C6-C7-N1 110.6(3) Si1-O1-Si2 140.7(3)
C7-N1-Cr 105.1(2) C7-N1-Cr 105.3(2) O1-Si2-N1 106.8(2)
Si2-N1-Cr 114.9(2)
tively bulky Pri N group.
2
a
b
Esd’s are given in parentheses. The data are for one of the
two independent molecules present in the unit cell. c D1 corre-
sponds to the centroid of the five-membered cyclopentadienyl ring.
in Table 3 along with their analytical data. In addition,
we have reported earlier the metallacyclic compounds
(Me2NC2H4C5Me4)CrCH2(CH2)nCH2 (n ) 2, 4).5
The crystal structures of two examples, viz. (cyclo-
C4H8NC2H4C5Me4)CrMe2 (37) and (cyclo-C4H8NC2H4-
fluorenyl[H8])CrMe2 (38), have been determined, and
the molecular structures and selected bonding param-
eters are shown in Figure 4 and Table 4. Although the
π-bonded organic ligands are not identical, the struc-
tures can be usefully compared to those of the CrCl2
compounds 17, 21, and 24 (Figure 2). The formation of
the CrMe2 compounds is apparently accompanied by a
significant shortening (up to 0.05 Å) of the Cr-N bond,
a decrease (up to 7°) in the X-Cr-X angle, and an
increase (up to 0.05 Å) of the separation between the
metal and C5 ring (Cr-D1) with respect to the CrCl2
species. The Cr-Me bond length does not significantly
differ from that in other Cr(III)-alkyl complexes.18 The
[H8]fluorenyl ligand in 38 is essentially planar, with
only C15 and C20 lying ca. 0.7 Å out of the C3/C5/C6
plane, and it has a mirror symmetry with respect to the
D1/Cr1/C3 plane, whereas related complexes of Ti or Zr
have C2 symmetry.19
Attempts to prepare CrMe2 species stabilized by the
amino-substituted indenyl group were unsuccessful:
treatment of (1-cyclo-C4H8NC2H4indenyl)CrCl2 with
MeMgCl in THF at -78 °C led to decomposition. The
Me group is less electronegative than a Cl atom, and
presumably its introduction favors the rearrangement
of the η5-indenyl group to the less stable η3-form, which
decomposes.
The product of the reaction between (Me2NC2H4C5H4)-
CrCl2 and allylmagnesium chloride is unusual in that
it is orange (instead of dark green) and less stable than
the other dialkylchromium species, decomposing in
The product of an analogous reaction with Ph2-
NC3H6C5H4K is green instead of the expected blue. The
mass spectrum indicates that this species is dinuclear,
while the IR spectrum is similar to that of the substi-
tuted cyclopentadiene precursor, suggesting that the
compound may well have the dimeric structure 26 with
uncomplexed diphenylamino groups.
Similar behavior is observed in the reaction with Et2-
NSiMe2C5H4Li, but in this case the dimeric nature of
the product (27) has been confirmed by an X-ray
diffraction study (Figure 3). The bridging Cl atoms and
the Cr atoms lie in the same plane with a nonbonding,
intermetallic separation of 3.352(1) Å. Presumably,
coordination of the amine to the metal is prevented by
excessive strain.
Treatment of the CrCl2 species with organomagne-
sium or -lithium reagents results, in most cases, in
chloride exchange to give the corresponding dialkyl-
Cr species as dark green, air-sensitive compounds which
are stable at room temperature in solution or as pure
compounds. The isolated compounds (28-38) are listed
(17) Csa´kva´ri, B.; Wagner, Z.; Go¨mo¨ry, P.; Mijlhoff, F. C.; Rozsondai,
B.; Hargittai, I. J . Organomet. Chem. 1976, 107, 287.
(18) Theopold, K. H. Acc. Chem. Res. 1990, 23, 263.
(19) Leino, R.; Luttikhedde, H. J . G.; Lehtonen, A.; Wilen, C.;
Nasman, J . H. J . Organomet. Chem. 1997, 545, 219.
(20) Betz, P.; Do¨hring, A.; Emrich, R.; Goddard, R.; J olly, P. W.;
Kru¨ger, C.; Roma˜o, C. C.; Scho¨nfelder, K. U.; Tsay, Y.-H. Polyhedron
1993, 12, 2651.
(21) Cowley, A. H.; Fairbrother, F.; Scott, N. J . Chem. Soc. 1959,
717.
(22) Marks, T. J .; Yang, X.; Stern, C. L. J . Am. Chem. Soc. 1991,
113, 3623.
(23) Brookhart, M.; Grant, B.; Volpe, A. F. Organometallics 1992,
11, 3920.

Substituted Cyclopentadienyl Cr(III) Complexes
Organometallics, Vol. 19, No. 4, 2000 393
F igu r e 3. Molecular structure of [(Et2NSiMe2C5H4)CrCl2]2 (27). Selected bond distances (Å) and angles (deg) are as
follows: Cr-D1 ) 1.862, Cr-Cl1 ) 2.365(1), Cr-Cl1* ) 2.375(1), Cr-Cl2 ) 2.268, Cr-Cr* ) 3.352(1); D1-Cr-Cl1 )
121.3, D1-Cr-Cl2 ) 126.3, Cl1-Cr-Cl1* ) 91.4, Cl1-Cr-Cl2 ) 95.1(1)°.
Ta ble 3. Am in o-Su bstitu ted Cyclop en ta d ien ylch r om iu m Dia lk yl a n d Rela ted Com p ou n d s
anal. found (calcd)
compd
yield (%)
C
H
Cr
N
(Me2NC2H4C5H4)CrMe2 (28)
(Me2NC2H4C5H4)CrEt2 (29)
84
76
71
64
46
33
80
60
97
86
56
60.4 (60.5)
63.3 (63.4)
65.8 (65.7)
56.1 (56.3)
64.1 (63.9)
65.2 (65.1)
61.9 (62.0)
60.7 (60.7)
59.8 (59.9)
68.1 (68.0)
71.7 (71.6)
9.2 (9.2)
9.8 (9.8)
10.2 (10.3)
9.4 (10.0)
9.0 (9.1)
9.3 (9.4)
9.4 (9.6)
9.7 (9.6)
8.6 (8.5)
10.1 (10.1)
9.7 (9.7)
23.9 (23.8)
21.1 (21.1)
18.9 (19.0)
14.3 (14.3)
21.2 (21.3)
20.0 (20.1)
22.5 (22.4)
16.3 (16.4)
16.3 (16.2)
17.3 (17.3)
14.7 (14.8)
6.5 (6.4)
5.7 (5.7)
5.0 (5.1)
3.9 (3.9)
5.7 (5.7)
5.3 (5.4)
6.1 (6.0)
4.4 (4.4)a
4.4 (4.4)b
4.6 (4.7)
4.0 (4.0)
(Me2NC2H4C5H4)CrPri (30)
2
(Me2NC2H4C5H4)Cr(CH2SiMe3)2 (31)
(cyclo-C4H8NC2H4C5H4)CrMe2 (32)
(cyclo-C5H10NC2H4C5H4)CrMe2 (33)
(Me2NC3H6C5H4)CrMe2 (34)
(1,3-cyclo-C4H8NC2H4(Me3Si)C5H3)CrMe2 (35)
(cyclo-C4H8NC2H4C5Me4)Cr(Me)Cl (36)
(cyclo-C4H8NC2H4C5Me4)CrMe2 (37)
(cyclo-C4H8NC2H4fluorenyl[H8])CrMe2 (38)
a
b
% Si: 8.9 (8.9). % Cl: 11.0 (11.1).
Ta ble 4. Selected Str u ctu r a l Da ta for th e
Am in o-Su bstitu ted Cyclop en ta d ien ylch r om iu m
Dim eth yl Com p lexes 37 a n d 38a
solution at -20 °C. The presence of absorptions in the
IR spectrum at 1640 and 1491 cm-1 suggest that this
compound has the 17-electron structure 39 and contains
both η3- and η1-allyl groups (eq 7).
37
38
Interatomic Distances (Å)
Cr-D1
Cr-N1
Cr-C1
Cr-C2
C3-C8
C8-C9
C9-N1
1.920
Cr-D1
Cr-N1
Cr-C1
Cr-C2
C3-C8
C8-C9
C9-N1
1.919
2.130(2)
2.080(3)
2.079(3)
1.509(3)
1.529(4)
1.500(3)
2.128(4)
2.097(8)
2.088(9)
1.496(8)
1.516(9)
1.494(9)
Bond Angles (deg)
C1-Cr-C2
C1-Cr-N1
C2-Cr-N1
D1-Cr-C1
D1-Cr-N1
C3-C8-C9
C8-C9-N1
C9-N1-Cr
96.5(1)
C1-Cr-C2
C1-Cr-N1
C2-Cr-N1
D1-Cr-C1
D1-Cr-N1
C3-C8-C9
C8-C9-N1
C9-N1-Cr
93.3(3)
97.4(2)
97.8(2)
123.3
97.0(1)
97.9(1)
122.0
113.5
114.3
110.6(2)
111.7(2)
105.1(1)
111.2(5)
111.8(5)
105.8(3)
Decomposition is also observed upon reacting (cyclo-
C4H8NC2H4C5Me4)CrCl2 (22) with (C4H6)Mg(THF)2.
However, if the reaction is carried out using active-Mg/
butadiene in the presence of PMe3, an orange, pentane-
soluble complex (40) is formed. A crystal structure
determination (Figure 5) established that 40 contains
a cis-η4-bonded butadiene molecule bonded in a prone
manner and that a PMe3 molecule has displaced the
amino group from the metal atom. Related compounds
have been prepared previously by reacting (Me5C5)Cr-
(PR3)Cl2 with (C4H6)Mg(THF)2.20 The displacement of
the “hard” N-donor atom by a “soft” P-donor ligand is
a
Esd’s are given in parentheses.
presumably a result of the formal reduction of the metal
from Cr(III) to Cr(I).
As part of an attempt to obtain some insight into the
mechanism of the MAO-activated, olefin polymerization
catalysts (vide infra), we prepared monomethylchro-
mium compounds as precursors to ionic compounds. We
were, however, unable to prepare such species by
reacting the appropriate CrCl2 compounds with 1 equiv

394 Organometallics, Vol. 19, No. 4, 2000
Do¨hring et al.
F igu r e 4. Molecular structures of (a) (cyclo-C4H8NC2H4C5Me4)CrMe2 (37) and (b) (cyclo-C4H8NC2H4-fluorenyl[H8])CrMe2
(38).
22
of MeMgCl and had to resort to the partial protolysis
of a CrMe2 system. This was accomplished by treatment
either with ethereal HCl or with (Cl2AlOSiMe3)2 in
hexane, whereby the latter reagent is preferred since
the reagent is more soluble in hexane than the product
(eq 8).
acid. The products (41, 42) of the reaction with B(C6F5)3
or the oxonium acid [H(OEt2)]+[B(3,5-(CF3)2C6H3)4]- 23
are dark violet solids which are insoluble in toluene and
only slightly soluble in diethyl ether or methylene
dichloride (eq 9). Although the elemental analyses for
21
Unfortunately, attempts to convert 36 into an ionic
species by chloride extraction failed. However, such
species could be prepared by reacting 37 with a Lewis
41 and 42 support the suggested formulation, their
inactivity for the catalytic polymerization of ethylene
suggests that the compounds do not exist as separated
ions, and because we have not be able to prepare
crystals suitable for an X-ray diffraction study, their
true nature remains unknown.
(24) J ohnson, L. K.; Killian, C. M.; Brookhart, M. J . Am. Chem. Soc.
1995, 117, 6414. J ohnson, L. K.; Killian, C. M.; Brookhart, M. J . Am.
Chem. Soc. 1996, 118, 11664.
(25) De Kimpe, N.; Verhe´, R.; De Buyck, L.; Moe¨ns, L.; Schamp, N.
Synthesis 1982, 43.
(26) van der Zeijden, A. A. H.; Mattheis, C.; Fro¨hlich, R. Organo-
metallics 1997, 16, 2651.
(27) Qian, C.; Wang, B.; Deng, D.; Sun, J .; Hahn, F. E.; Chen, J .;
Zheng, P. J . Chem. Soc., Dalton Trans. 1996, 955.
(28) Draganjac, M.; Ruffing, C. J .; Rauchfuss, T. B. Organometallics
1985, 4, 1909. Amarasekera, J .; Rauchfuss, T. B. Inorg. Chem. 1989,
28, 3875.
Violet compounds are also formed upon reacting 37
with (Me2AlCl)2 or AlMe3. In contrast to 41 and 42, the
products 43 and 44 are soluble in toluene and saturated
hydrocarbons and these are assumed to be nonionic and

Substituted Cyclopentadienyl Cr(III) Complexes
Organometallics, Vol. 19, No. 4, 2000 395
to have structures having groups bridging the two metal
atoms (eq 10). A similar reaction is observed between
F igu r e 5. Molecular structure of (cyclo-C4H8NC2H4C5-
Me4)(η4-C4H6)CrPMe3 (40). Selected bond distances (Å) and
angles (deg) are as follows: Cr1-D1 ) 1.865, Cr1-P1 )
2.336(1), Cr1-C1 ) 2.166(5), Cr1-C2 ) 2.079(4), C1-C2
) 1.394(6), C2-C3 ) 1.394(6), C3-C4 ) 1.433; D1-C1-
P1 ) 119.2, D1-Cr1-C1 ) 137.2, D1-Cr1-C2 ) 120.8,
C1-C2-C3 ) 121.6(4), C2-C3-C4 ) 120.7(3)°.
AlMe3 and (cyclo-C4H8NC2H4C5Me4)CrCl2 (22).
Or ga n och r om iu m Com p ou n d s Con ta in in g Re-
la ted Don or Liga n d s. In addition to the amino-
substituted cyclopentadienyl ligands presented above
and the phosphino-substituted cyclopentadienyl ligands
which will be discussed in a later paper, we have
prepared, for comparison purposes, a few related orga-
nochromium compounds containing an imine or O-, S-,
and C-donor ligands.
compounds containing alkoxy-substituted cyclopenta-
dienyl groups are well-known,26,27 examples involving
a thio group are far less common.28 Treatment of CrCl3
with both MeOC2H4C5H4K and MeSC2H4C5H4K led to
the expected organochromium compounds (eq 12). Struc-
Our interest in an imine-substituted cyclopentadi-
enylchromium catalyst stems from the research on the
MAO-activated diimine complexes of the late transition
metals24 and on the geometrically related amido-
substituted cyclopentadienyltitanium(IV) complexes.3
The synthesis of the Pri-substituted species (45) is
shown in eq 11.25 The blue, air-stable compound 45
tural characterization of the methoxy compound 46
follows from the mass spectrum (M+) and the complex-
ation shift of the C-O stretching frequences from 1119
cm-1 in the parent cyclopentadiene derivative to 1039
cm-1 in the chromium complex. The methylthio deriva-
tive 47 also shows a parent ion in the mass spectrum.
Complexation of the S-donor atom to the metal is
suggested by the stability in air, but no obvious support
can be found in the IR spectrum. The tetramethylcy-
clopentadienyl analogue of 47, viz. (MeSC2H4C5Me4)-
CrCl2 (48), has been prepared analogously by reacting
the lithium salt of the organic ligand. The compound is
also blue and air-stable, and a parent ion is present in
the mass spectrum.
Related ligands containing the tert-butoxy and tert-
butylthio groups have been prepared by reacting spiro-
[4.2]hepta-4,6-diene29 with KOBut or KSBut in refluxing
THF. The structure of the product of the further reaction
with CrCl3 depends, however, upon the nature of the
donor atom (Scheme 2). The mass spectra of the product
confirm that the tert-butylthio derivative (50) is mono-
nuclear whereas the tert-butoxy derivative (49) is bi-
dissolves readily in methylene dichloride but is only
slightly soluble in toluene. The mass spectrum shows a
parent ion, and fragmentation occurs with loss of a Cl
atom and the Pri group. Complexation of the imine to
the metal is accompanied by a shift in the C-N
stretching frequency of 45 cm-1 to 1603 cm-1. Surpris-
ingly, attempts to convert the compound into the related
CrMe2 species by reaction with MeMgCl were unsuc-
cessful.
An obvious extension is to involve ligands having O
or S as the donor atom. Whereas transition-metal
(29) Wilcox, C. F.; Craig, R. R. J . Am. Chem. Soc. 1961, 83, 3866.

396 Organometallics, Vol. 19, No. 4, 2000
Do¨hring et al.
Sch em e 2
compare the activity of the various organochromium
compounds, and we have not investigated the morphol-
ogy of the polymer in detail.
In view of the high activity of many of the species,
the isothermal reaction conditions necessary for a
reliable comparison could only be obtained by decreasing
the concentration of the Cr component to homeopathic
levels, and the values obtained probably represent lower
limits. Selected results are shown in Table 5 for reac-
tions carried out with a Cr:MAO ratio of 1:100. Two
trends are clearly established in the table: the activity
increases considerably upon either substituting the ring
H atoms with alkyl groups or the Cl atoms with Me
groups. The catalyst (cyclo-C4H8NC2H4C5Me4)CrMe2
(37)-MAO (Cr:MAO ) 1:100) has the remarkable
activity of 10 500 kg of PE/((mol of Cr) h) at 21 °C and
2 atm.
The activities of (Me2NC2H4C5H4)CrCl2 (11), (Me2-
NC3H6C5H4)CrCl2 (14), and (cyclo-C4H8NSiMe2OSiMe2-
C5H4)CrCl2 (24) under the standard conditions are all
similar, suggesting that an extension of the chain
between the N atom and the ring and the type of linkage
have only a minor influence. In contrast, the lower
activity (ca. 200 kg of PE/((mol of Cr) h) observed for
[(Et2NSiMe2C5H4)CrCl2]2 (27), in which the N atom is
not bonded to the Cr atom, suggest that interaction of
the donor atom with the metal is probably essential for
high activity.
It has already been shown that the activity of the
ansa-zirconocene-MAO catalysts increases dramati-
cally upon increasing the Zr:Al ratio and that frequently
maximum activity is obtained only in the presence of a
very large excess of MAO.34 We have also studied the
effect of varying the Cr:Al ratio upon the (cyclo-C4H8-
NC2H4C5Me4)CrCl2 (22)-catalyzed reaction (Table 6).
The results indicate that a ratio of at least 1:100 is
necessary while a 4-fold increase in activity is observed
up to 1:1000 and that higher concentrations have little
effect.
Since any industrial application of these systems
would presumably involve more robust reaction condi-
tions, it is noteworthy that the (cyclo-C4H8NC2H4C5-
Me4)CrCl2 (22)-MAO catalyst remains highly active at
80 °C (activity 50 750 kg of PE/((mol of Cr) h); toluene,
Al:Cr ) 500:1) and, furthermore, the rate of polymeri-
zation remained constant for an extended period. Under
these conditions, the polyethylene formed remains dis-
solved and precipitates upon cooling the toluene solu-
tion.
The Cr-based catalysts are far less active for the
polymerization of alkenes other than ethylene. Both
propene and 1-hexene are polymerized by (cyclo-C4H8-
NC2H4C5Me4)CrMe2 (37)-MAO, but the activity is low
(200-300 kg of polymer/((mol of Cr) h)) and the catalyst
is quickly deactivated. In both cases an atactic polymer
is formed. More promising results are obtained for the
copolymerization of 1-alkenes with ethylene. In contrast
to propene (which does not copolymerize), ethylene and
1-hexene react together in the presence of (cyclo-C4H8-
NC2H4C5Me4)CrMe2 (37)-MAO (Cr:Al ) 1:100, T ) 21
°C) in neat 1-hexene as solvent to give a low-molecular-
weight elastomer (activity 40 000 kg of polymer/((mol
of Cr) h)) which is soluble in chloroform or toluene at
nuclear, while the IR spectrum indicates that the tert-
butoxy group is not complexed to the metal atom.
We next turned our attention to systems containing
C-donor ligands. Whereas numerous chromium com-
pounds containing Fischer carbene ligands have been
reported, examples involving the heterocyclic imidazol-
2-ylidene ligand were unknown at the time we started
our investigations;30 Arduengo31 and Herrmann32 had
prepared a series of transition-metal complexes contain-
ing this ligand and have shown that the metal-donor
atom bond is particularly strong. We have concentrated
on the 1,3,4,5-tetramethylimidazol-2-ylidene ligand, and
the results are summarized in Scheme 3. The carbene
ligand was prepared by reacting 1,3,4,5-tetramethylimi-
dazole-2-thione with potassium.33 Reaction with CpCr-
(THF)Cl2 occurs with displacement of the THF molecule
to give 51 as a violet, air-stable compound which is only
slightly soluble in THF and precipitates. Subsequent
treatment of 51 with excess MeMgCl gives the CrMe2
derivative 52 in high yield. The product of the analogous
reaction with Cp*Cr(THF)Cl2 is the blue, THF-soluble
compound 53. The mass spectral results indicate that
the product of the further reaction with an excess of
either MeMgCl or MeLi is a mixture of monomethyl-
and dimethyl-Cr species which could not be separated.
Characteristic for these chromium-carbene compounds
is the presence of an absorption at ca. 1660 cm-1 in the
infrared spectrum, which is assigned to a CdC stretch-
ing frequency of the carbene ligand.
Ca ta lytic P olym er iza tion a n d Oligom er iza tion
of Alk en es. The preparative organochromium chemis-
try described in detail in the preceding sections was
undertaken in part to provide precursors for an inves-
tigation of the catalytic polymerization of ethylene in
the presence of methylalumoxane (MAO).5-7 The prod-
uct is in most cases a highly linear polyethylene having
a melting point (DSC) in the range 128-132 °C, a
crystallinity (IR) of 70-75%, and a molecular weight of
1-3 × 106. Our main objective was, however, to
(30) While our investigations were in progress, three examples
involving the 1,3-dimesitylimidazol-2-ylidene ligand were reported:
Voges, M. H.; Rømming, C.; Tilset, M. Organometallics 1999, 18, 529.
See also: Abernethy, C. D.; Clyburne, J . A. C.; Cowley, A. H.; J ones,
R. A. J . Am. Chem. Soc. 1999, 121, 2329.
(31) Arduengo, A. J .; Harlow, R. L.; Kline, M. J . J . Am. Chem. Soc.
1991, 113, 361.
(32) Herrmann, W. A.; Ko¨cher, C. Angew. Chem. 1997, 109, 2256.
(33) Kuhn, N.; Kratz, T. Synthesis 1993, 561.
(34) Herfert, N.; Fink, G. Makromol. Chem. 1992, 193, 1359.

Substituted Cyclopentadienyl Cr(III) Complexes
Organometallics, Vol. 19, No. 4, 2000 397
Sch em e 3
Ta ble 5. P olym er iza tion of Eth ylen e u n d er Isoth er m a l Con d ition sa
amt of Cr
(µmol)
T/∆T
(°C)
amt of
PE (g)
activity (kg of PE/
((mol of Cr) h))
TM
(°C)
cryst
(%)
compd
10-6Mw
Mw/Mn
(Me2NC2H4C5H4)CrCl2 (11)
5.19
11.22
1.71
5.95
5.27
1.05
1.23
21/2
21/3
21/3
21/4
21/4
21/2
21/4
0.66
1.37
0.86
1.48
1.87
0.77
1.35
1660
1730
7170
3640
4630
2.18
0.90
1.91
0.84
2.50
3.14
1.89
4.05
13.47
2.11
2.73
3.15
1.58
1.56
127
127
131
127
129
129
133
67
71
73
68
69
74
73
(cyclo-C4H8NC2H4C5H4)CrCl2 (12)
(cyclo-C4H8NC2H4C5Me4)CrCl2 (22)
(cyclo-C4H8NC2H4-fluorenyl[H8])CrCl2 (23)
(Me2NC2H4C5H4)CrMe2 (28)
(cyclo-C4H8NC2H4C5Me4)CrMe2 (37)
(cyclo-C4H8NC2H4-fluorenyl[H8])CrMe2 (38)
10480
10680
a
Conditions: solvent, toluene (250 mL); Pethylene, 2 atm; Cr:MAO ) 1:100; t ) 4 min.
Ta ble 6. (cyclo-C4H8NC2H4C5Me4)Cr Cl2 (22)-MAO
with (cyclo-C4H8NC2H4fluorenyl[H8])CrMe2 (38)-MAO.
This system can also copolymerize norbornene with
ethylene under mild conditions (21 °C; 2 bar of ethylene;
Cr:Al ) 1:3800). The product of the reaction when it is
carried out in 74% toluene/26% norbornene as solvent
is a low-melting-point amorphous solid. Its 13C NMR
spectrum indicates that ca. 25% norbornene has been
incorporated in an exo manner.35
The imino-substituted cyclopentadienylchromium com-
plex (PriNdCMeCH2C5H4)CrCl2 (45) in the presence of
MAO gives a system having an activity similar to that
of the (Me2NC2H4C5H4)CrCl2 (11)-MAO system for the
polymerization of ethylene. The methylthio-substituted
system (MeSC2H4C5H4)CrCl2 (47)-MAO has a moder-
ate activity (activity 4025 kg of polymer/((mol of Cr) h);
P ) 2 atm; T/∆T ) 27/36 °C; Cr:Al ) 1:100) to give a
product which consists of a 1:1 mixture of polyethylene
and oligomers (C4-C36; GC). The corresponding meth-
oxy-substituted compound (MeOC2H4C5H4)CrCl2 (46)
reacts with MAO in the absence of ethylene to give an
Ca ta lyzed P olym er iza tion of Eth ylen ea
amt of
Cr (µmol)
T/∆T
(°C)
amt of
PE (g)
activity (kg of PE/
((mol of Cr) h))
Cr:MAO
1:50
3.64
3.19
2.73
0.91
0.68
0.57
0.57
21.0/0
0
0
4 550
8 860
18 320
25 370
28 460
29 540
1:100
1:200
1:500
1:1000
1:5000
1:10000
21.0/1.7
21.0/2.8
21.0/2.3
21.0/2.8
21.0/2.8
21.0/2.9
1.11
1.78
1.17
1.15
1.19
1.39
a
Conditions: solvent, toluene (250 mL); Pethylene, 2 atm; t ) 4
min.
room temperature. The 13C NMR spectrum indicates
that ca. 15% 1-hexene has been incorporated in a
random manner into the polyethylene chain. If the
reaction is carried out in 80% toluene/20% 1-hexene as
solvent, an insoluble polymer is formed at a reduced rate
(6900 kg of polymer/((mol of Cr) h)). Although this
material has not been investigated further, the low
melting point (112 °C) indicates that some 1-hexene
incorporation has occurred. Similar behavior in the
copolymerization of 1-hexene and ethylene is observed
(35) Cherdon, H.; Brekner, M.-J .; Osan, F. Angew. Makromol. Chem.
1994, 223, 121. Bergstro¨m, C. H.; Sperlich, B. R.; Ruotoistenma¨ki, J .;
Seppa¨la¨, J . V. J . Polym. Sci., A: Polym. Chem. 1998, 36, 1633.

398 Organometallics, Vol. 19, No. 4, 2000
Do¨hring et al.
insoluble product which is not catalytically active.
However, if the compound is treated with MAO in the
presence of ethylene, normal polymerization behavior
is observed (activity 2870 kg of PE/((mol of Cr) h); P )
2 atm; T/∆T ) 26/34 °C) to give a high-molecular-weight
polyethylene (MW 4.7 × 106). The behavior of the Cr-
carbene complex CpCr(tetramethylimidazol-2-ylidene)-
Cl2 (51) was disappointing: the low solubility necessi-
tated the use of a toluene/CH2Cl2 solvent mixture, and
the activity, after treatment with MAO, was low. The
polymer formed, however, was unusual in that it is
highly branched and melts in two steps (89/120 °C),
while the GPC measurement indicates the presence of
low- and high-molecular-weight fractions, suggesting
that more than one active species is involved.
Mech a n istic Con sid er a tion s. Because we have no
direct evidence of mechanistic relevancesthe ionic spe-
cies [(cyclo-C4H8NC2H4C5Me4)CrMe]+X- (X ) B(C6H3-
(CF3)2-3,5)4 (42), MeB(C6F5)3 (41)) were, unfortunately,
inactiveswe can only assume that the Cr-catalyzed
reaction occurs in a manner analogous to that suggested
for the ansa-zirconocene-MAO systems and involves
ethylene complexation to a cationic Cr-Me species
followed by multiple insertion with agostic-H-Cr sta-
bilization with chain termination proceeding through
â-H-transfer from the growing alkyl chain to a com-
plexed ethylene molecule. Details of a theoretical treat-
ment which support this concept are presented in a
separate publication.36
methyl substitution of the five-membered ring (Table
5) could have a steric origin: the separation of the cation
and anion (54) is enhanced, and hence, the reacting
ethylene molecule has more facile access to the metal.
The fluorenyl-substituted system (Table 5) is less con-
gested, and as expected the activity is lower. In addition,
methyl substitition of the five-membered ring will
strengthen the bond between the ring and the metal
atom, which may be expected to facilitate the transfer
of an Me or Cl group to the aluminum.
Exp er im en ta l Section
All experiments and manipulations were carried out under
argon. The organochromium compounds have been character-
ized by a combination of infrared spectroscopy (Nicolet 7199
and 750 FI/IR), mass spectroscopy (Finnigan MAT 8200) and
elemental analyses as well as by crystal structure determina-
tions of selected examples. (η1:η5-Me2NC2H4C5H4)CrCl2 and (η1:
η5-Me2NC3H6C5H4)CrCl2 were prepared according to the lit-
erature.11 The substituted cyclopentadiene derivative were
prepared by modification of published procedures10 and typical
examples are described below.
cyclo-C4H8NC2H4C5H5 (1d ). A solution of NaC5H5(THF)0.27
(7.04 g, 65.5 mmol) in THF (200 mL) was cooled to -10 °C
and solid (2-chloroethyl)pyrrolidine hydrochloride (5.06 g,
29.75 mmol) added slowly. The reaction mixture was stirred
for 16 h at room temperature and evaporated to dryness. The
red-brown residue was then treated with pentane (200 mL)
and distilled water (100 mL). The organic material was
extracted with pentane and the combined extract dried with
MgSO4 and evaporated to dryness to give the product as a
yellow liquid. Yield: 4.29 g (88%). Anal. Calcd for C11H17N:
C, 80.9; H, 10.5; N, 8.6. Found: C, 80.5; H, 10.4; N, 8.7. IR
(KBr): ν 2964 s, 2784 s cm-1. MS: m/e 163 (M+), 84, 42. 1H
NMR (CDCl3): δ 6.43/6.25/6.19/6.04 (dCH), 2.94/2.90 (CH2),
2.64 (C2H4), 2.54/1.79 (NC2H4). 13C NMR (CDCl3): δ 147.4/
145.0, 134.5/133.5/132.3/130.5/126.7/126.3 (dCH), 56.4/55.8/
54.1/54.0 (NCH2), 43.1/41.1/30.4/29.6/23.3 (CH2).
We have also no original contribution to make on the
role of the MAO in the chromium-catalyzed reactions
and assume that, as previously suggested,37 the active
component is AlMe3, which is present at a level of 10-
20% in MAO and which acts both as an alkylating agent
and as a Lewis acid to produce the active cationic Cr-
Me species. One or more of the components in the
oligomethylalumoxane may well encapsulate the result-
Treatment of this compound with KH or NaH in THF or
BuLi in pentane or diethyl ether led to formation of the
corresponding cyclopentadienyl derivative.
-
ing AlMe4 or AlMe3Cl- anion and act as a spacer to
separate the ions.
cyclo-C4H8NC3H6C5H5 (2b) and cyclo-C5H10NC3H6C5H5 (2c)
were prepared similarly.
In keeping with this suggestion is the observation
that, for the (cyclo-C4H8NC2H4C5Me4)CrCl2 (22)-MAO
system, the addition of 20 equiv of AlMe3 to 100 equiv
of MAO results in a significant increase in activity (Cr:
MAO:AlMe3 ) 1:100:0, activity 4550 kg PE/((mol of Cr)
h); Cr:MAO:AlMe3 ) 1:100:20, activity 7730 kg of PE/
((mol of Cr) h)), while 80% of the aluminum in MAO
can be replaced by AlMe3 without a significant decrease
in activity.
1-(cyclo-C4H8NC2H4)C9H7 (4b) was prepared as a yellow-
ish liquid by adding (2-chloroethyl)pyrrolidine hydrochloride
(9.56 g, 56 mmol) portionwise to a solution of lithium indenide
(20.76 g, 170 mmol) in THF (200 mL) at -10 °C. The reaction
mixture was stirred at room temperature for 16 h and at 50
°C for 2 h and evaporated to dryness under high vacuum. The
red-brown residue was taken up in pentane (200 mL) and
treated with distilled water (100 mL). The aqueous phase was
washed with pentane (2 × 100 mL) and the combined organic
phases dried with MgSO4 and evaporated under oil-pump
vacuum. The resulting yellowish oil was heated at 50 °C under
a high vacuum for 3 h to remove traces of indene. Yield: 11.2
g (94%). Anal. Calcd for C15H19N: C, 84.5; H, 9.0; N, 6.6.
Found: C, 84.3; H, 9.1; N, 6.6. MS: m/e 213 (M+), 128, 115.
The significantly higher activity of the dimethylchro-
mium compounds compared to the dichlorochromium
compounds (Table 5) is perhaps a consequence of the
relatively low Cr:MAO concentration (1:100) used in the
standard reactions and suggests that anions such as
AlMe4 and AlMe3Cl- might be involved whereby the
-
1
IR (liquid): ν 2962 s, 2783 s, 769 s cm-1. H NMR (CDCl3): δ
separation from the chromium-methyl cation of the
former might be expected to be more complete. At higher
MAO concentrations complete alkylation of the chro-
mium will occur, and as expected, the difference be-
comes less significant. The increase in activity upon
7.39/7.27/7.16/6.20/3.28 (indene), 2.77/2.57/1.79 (CH2). 13C
NMR (CDCl3): δ 145.1/144.1/142.4/128.0/126.1/124.3/123.5/
118.7/37.6 (indene), 55.0/54.1/27.4/23.3 (CH2).
The compound was converted into the cyclopentadienyl
derivative 1-(cyclo-C4H8NC2H4)C9H6K by treatment with KH
in THF at 50 °C.
(36) J ensen, V. R.; Angermund, K.; J olly, P. W.; Børve, K. J .
Organometallics 2000, 19, 403.
(37) Bliemeister, J .; Hagendorf, W.; Harder, A.; Heitman, B.; Schim-
mel, I.; Schmedt, E.; Schnuchel, W.; Sinn, H.; Tikwe, L.; von Thienen,
N.; Urlass, K.; Winter, H.; Zarncke, O. In Ziegler Catalysts; Fink, G.,
Mu¨lhaupt, R., Brintzinger, H. H., Eds.; Springer: Berlin, 1995; p 57.
Et2NSiMe2C5H5 (8) was prepared as a yellow oil by adding
a solution of Et2NSiMe2Cl16 (27.68 g, 0.17 mol) in pentane (300
mL) to NaC5H5(THF)0.27 (19.76 g, 0.18 mol) in THF (100 mL)
at -30 °C over 4 h. The reaction mixture was stirred for a
further 4 h at room temperature and evaporated to dryness.

Substituted Cyclopentadienyl Cr(III) Complexes
Organometallics, Vol. 19, No. 4, 2000 399
The residue was dissolved in pentane (150 mL), the solution
filtered, and the solvent removed under oil-pump vacuum.
Yield: 27.1 g (83%). IR (liquid): ν 2964 s, 1204 s, 1173 s, 1029
distilled under an oil-pump vacuum at 62 °C. Yield: 33.9 g
(62%). IR (liquid): ν 1522 w, 1472 m, 1458 m, 1363 m, 677 s
1
cm-1. MS: m/e 182 (M+), 126, 103. H NMR (CDCl3): δ 6.42/
1
s, 1251 s, 805 s cm-1. H NMR (CDCl3, -30 °C): δ 6.63/6.53
6.24/6.07 (dCH), 2.95/2.91 (CH2), 2.69 (C2H4), 1.33 (Me). 13C
NMR (CDCl3): δ 147.7/145.3, 133.8/133.3/132.2/130.8/127.2/
126.6 (dCH), 45.9/45.4 (SC), 43.1/40.2 (CH2), 30.9 (Me), 31.1/
30.4 (SCH2), 28.2/27.5 (CH2).
(t, dCH), 3.59 (s, CH), 2.81 (q, NCH2), 0.98 (t, Me), -0.06 (s,
Me2Si). 13C NMR (CDCl3, -70 °C): δ 132.8/129.5 (dCH), 55.8
(CH), 38.9 (NCH2), 15.2 (Me), -3.9 (SiMe2).
Treatment with BuLi in pentane led to the formation of the
cyclopentadienyl derivative Et2NSiMe2C5H4Li.
5
(η1:η -H2NC2H4C5H4)Cr Cl2 (10) was prepared by adding
a solution of KC5H4C2H4NH2 (0.32 g, 2.16 mmol) in THF (20
mL) to a stirred suspension of Cr(THF)3Cl3 (0.90 g, 2.4 mmol)
in THF (50 mL) at -78 °C. The suspension was stirred for 2
h at -78 °C and then for 12 h at room temperature. The
resulting cloudy blue solution was evaporated to dryness under
vacuum and the blue residue washed with hot toluene and
dried under high vacuum for 24 h at 100 °C. Yield: 0.32 g
(63%). IR (KBr): ν 3197 s, 3098 s, 2919 s, 1570 s, 1481 s, 1460
s, 822 s cm-1. MS: m/e 230 (M+), 194, 165, 108.
(η1:η5-cyclo-C4H8NC2H4C5H4)Cr Cl2 (12) was prepared by
adding ether-HCl (3.8 mL of a 1.1 M solution in diethyl ether;
4.2 mmol) to a green solution of (η1:η5-cyclo-C4H8NC2H4C5H4)-
CrMe2 (0.46 g, 1.88 mmol) in diethyl ether (60 mL) at -70 °C.
The resulting violet suspension was stirred at -30 °C for 1 h,
and the blue precipitate was isolated and dried at room
temperature under high vacuum. Yield: 0.51 g (95%). IR
(KBr): ν 3067 s, 2970 s, 2937 s, 2866 s, 1442 s, 842 s cm-1 (see
Figure 1). MS: m/e 284 (M+), 248, 212, 162.
(η1:η5-cyclo-C5H10NC2H4C5H4)Cr Cl2 (13) was prepared by
adding a solution of KC5H4C2H4NC5H10-cyclo (1.28 g, 5.97
mmol) in THF (20 mL) to a stirred suspension of Cr(THF)3Cl3
(1.31 g, 3.5 mmol) in THF (50 mL) at room temperature. The
solution was stirred for 2 h and evaporated to dryness under
high vacuum and the resulting blue residue extracted with
CH2Cl2 (70 mL). The extract was evaporated to dryness and
the residue extracted with hot toluene (80 mL). The extract
was cooled to -50 °C, and the compound precipitated as blue
needles, which were washed with pentane at room tempera-
ture and dried under high vacuum. Yield: 0.99 g (56%). IR
(KBr): ν 3070 m, 2935 s, 2857 s, 2800 m, 1467 s, 1445 s, 860
s, 841 s, 817 s cm-1. MS: m/e 298 (M+), 262, 226, 176.
(η1:η5-cyclo-C4H8NC3H6C5H4)Cr Cl2 (15) was prepared as
described above as blue crystals by reacting NaC5H4C3H6-
NC4H8-cyclo with Cr(THF)3Cl3 in THF. Yield: 35%. IR (KBr):
ν 2959 s, 2878 s, 1440 s, 816 s cm-1. MS: m/e 298 (M+), 263,
176.
(η1:η5-cyclo-C5H10NC3H6C5H4)Cr Cl2 (16) was prepared as
described above as blue crystals by reacting NaC5H4C3H6-
NC5H10-cyclo with Cr(THF)3Cl3 in THF. Yield: 73%. IR (KBr):
ν 2928 s, 2855 s, 835 s cm-1. MS: m/e 312 (M+), 277, 240, 190.
(η1:η5-1,3-cyclo-C4H8NC2H4(Me3Si)C5H3)Cr Cl2 (17) was
prepared by reacting a solution of 1,3-cyclo-C4H8NC2H4(Me3-
Si)C5H4 (1.75 g, 7.45 mmol) in THF (20 mL) with a solution of
n-butyllithium in hexane (4.5 mL of a 1.66 M solution; 7.45
mmol) at -10 °C. The resulting yellow solution was stirred at
room temperature for 1 h and added to a suspension of Cr-
(THF)3Cl3 (2.79 g, 7.46 mmol) in THF (50 mL). The resulting
blue solution was stirred for 2 h and evaporated to dryness
and the residue extracted with toluene (150 mL). The extract
was concentrated and cooled to give the compound as blue
needles, which were washed with pentane and dried under
vacuum. Yield: 1.46 g (55%). IR (KBr): ν 3063 m, 2964 m, 2878
m, 1244 s, 845 s, 758 s cm-1. MS: m/e 356 (M+), 341, 320,
234. Crystal structure determination: see Figure 2.
cyclo-C4H8SiMe2OSiMe2C5H5 (9) was prepared as a pale
yellow oil by adding a solution of NaC5H5(THF)0.27 (10.9 g,
101.2 mmol) in THF (70 mL) dropwise to a solution of cyclo-
C4H8SiMe2OSiMe2Cl (23.3 g, 98.0 mmol) in pentane (250 mL)
at -30 °C. The reaction mixture was stirred at room temper-
ature for 4 h and the solvent removed under oil-pump vacuum.
The residue was taken up in pentane (100 mL), the solution
filtered, and the solvent distilled off. Yield: 23.1 g (88%). IR
(liquid): ν 2960 s, 1256 s, 795 s, 1058 sbr cm-1. MS: m/e 267
(M+), 252, 202. 1H NMR (CDCl3): δ 6.62/6.51 (dCH), 3.50 (CH),
2.99 (NCH2), 1.71 (CH2), 0.12/-0.08 (Me2Si). 13C NMR (CD2-
Cl2): δ 132.8/130.7 (dCH), 54.6 (CH), 46.4 (NCH2), 27.0 (CH2),
-1.0/-1.4 (SiMe2).
Treatment with NaH in THF led to the formation of the
cyclopentadienyl derivative cyclo-C4H8NSiMe2OSiMe2C5H4Na.
cyclo-C4H8SiMe2OSiMe2Cl was prepared as a colorless oil
by adding a solution of pyrrolidine (36 mL, 0.43 mol) in
pentane (70 mL) to a solution of ClSiMe2OSiMe2Cl (43.7 g,
0.22 mol) in pentane at -50 °C. The reaction mixture was
stirred for 4 h at room temperature, filtered and the solvent
removed under oil-pump vacuum. Yield: 48.2 g (94%). IR
(liquid): ν 2964 s, 1204 s, 1173 s, 1029 s, 1251 s, 805 s cm-1
.
1H NMR (CDCl3, -30 °C): δ 6.63/6.53 (t, dCH), 3.59 (s, CH),
2.81 (q, NCH2), 0.98 (t, Me), -0.06 (s, Me2Si). 13C NMR (CDCl3,
-70 °C): δ 132.8/129.5 (dCH), 55.8 (CH), 38.9 (NCH2), 15.2
(Me), -3.9 (SiMe2).
P r iNdC(Me)CH2C5H5 was prepared as a red-brown, sensi-
tive liquid by adding a solution of NaC5H5(THF)0.27 in THF
(100 mL) to a solution of PriNdC(Me)CH2Cl (14.7 g, 0.11 mol)25
in diethyl ether (100 mL) at -10 °C. The reaction mixture was
stirred at room temperature for 12 h. The solvent was removed
under oil-pump vacuum and the red-brown residue taken up
in pentane (200 mL) and treated with distilled water (100 mL).
The aqueous phase was separated and extracted with pentane
(2 × 100 mL) and the combined pentane solution dried with
MgSO4 and evaporated under an oil-pump vacuum. Yield: 15.2
g (82%). Anal. Calcd for C11H17N: C, 80.9; H, 10.5; N, 8.6.
Found: C, 78.6; H, 10.7; N, 8.9. MS: m/e 163 (M+), 148, 120,
1
106. IR (liquid): ν 2966 s, 1658 s cm-1. H NMR (CDCl3, -30
°C): δ 6.44/6.32-6.08 (dCH), 3.73/3.60 (CMe2), 3.33/3.29
(CH2Cd), 3.00/2.88 (CH2), 1.80 (MeCd), 1.17 (CH).
MeSC2H4C5H5 was prepared by adding a solution of NaC5H5-
(THF)0.27 (12.2 g, 108 mmol) in THF (100 mL) to 2-chloroethyl
methyl sulfide (11.9 g, 108 mmol) in pentane (80 mL) at room
temperature. The reaction mixture was stirred for 12 h and
evaporated to dryness. The residue was taken up in pentane
(100 mL), and water (100 mL) was added. The aqueous phase
was extracted with pentane (2 × 50 mL) and the combined
extract dried over MgSO4 and evaporated to dryness to give
the compound as a yellowish oil. Yield: 12.8 g (84%). 1H NMR
(CDCl3): δ 6.45-6.40/6.26/6.21/6.06 (dCH), 2.95/2.90 (CH2),
2.68 (C2H4), 2.11/2.10 (Me). 13C NMR (CDCl3): δ 147.2/145.0/
134.0/133.6/132.1/130.7/127.2/126.6 (dCH), 43.0/41.0 (CH2),
34.0/33.2 (SCH2), 30.3/29.7 (CH2), 15.3/15.2 (Me).
Bu tSC2H4C5H5 was prepared by adding spiro[4.2]heptane-
4,6-diene (30.3 g, 0.33 mol) to a suspension of NaSBut (33.2 g,
0.3 mol) in THF (250 mL) and heating under reflux for 5 days.
The resulting red solution was evaporated to dryness and the
product treated with pentane (250 mL) and distilled water (250
mL). The aqueous phase was extracted with pentane (2 × 50
mL) and the combined extract dried over MgSO4 and evapo-
rated to dryness under a vacuum. The resulting yellow oil was
(η1:η5-1-Me2NC2H4C9H6)Cr Cl2 (18) was prepared as de-
scribed above as a green crystalline solid by reacting (1-Me2-
NC2H4-indenyl)K with Cr(THF)3Cl3 in THF. Yield: 81%. IR
(KBr): ν 816 s, 760 s, 734 s cm-1. MS: m/e 308 (M+), 272, 186.
(η1:η5-1-cyclo-C4H8NC2H4C9H6)Cr Cl2 (19) was prepared as
described above as a green crystalline solid by reacting (1-
cyclo-C4H8NC2H4-indenyl)K with Cr(THF)3Cl3 in THF. Yield:

400 Organometallics, Vol. 19, No. 4, 2000
Do¨hring et al.
66%. IR (KBr): ν 3075 m, 3051 m, 2963 s, 2948 s, 2877 s, 1454
s, 1439 s, 823 s, 805 s, 753 s, 745 s cm-1. MS: m/e 334 (M+),
299, 212.
(η1:η5-1,3-cyclo-C4H8NC2H4(Me3Si)C9H5)Cr Cl2 (20) was
prepared as described above as a green crystalline solid by
reacting (1,3-cyclo-C4H8NC2H4(Me3Si)-indenyl)K with Cr(THF)3-
Cl3 in THF. Yield: 31%. IR (KBr): ν 3054 m, 2961 s, 2883 s,
1450 s, 1244 s, 841 s, 756 s cm-1. MS: m/e 406 (M+), 391, 370,
284.
(η1:η5-Me2NC2H4C5Me4)Cr Cl2 (21) was prepared by adding
a solution of Me2NC2H4C5Me4Li (1.25 g, 6.3 mmol) in THF (20
mL) to a suspension of Cr(THF)3Cl3 (2.36 g, 6.3 mmol) in THF
(50 mL) at room temperature. The reaction mixture was stirred
for 15 h and evaporated to dryness and the residue extracted
with boiling toluene. The extract was cooled to -70 °C to give
the product as dark blue needles, which were isolated, washed
with diethyl ether, and dried under high vacuum. Yield: 1.70
g (86%). IR (KBr): ν 2922 s, 1473 s, 1457 s, 1437 s, 1379 s,
1015 s, 1004 s, 915 s, 769 s cm-1. MS: m/e 314 (M+), 278.
Crystal structure determination: see Figure 2.
(η1:η5-Me2NC2H4C5H4)Cr P r i (30) was prepared as de-
2
scribed above as dark green crystals by reacting PriMgBr with
(Me2NC2H4C5H4)CrCl2 in diethyl ether/THF at -80 °C to room
temperature. Yield: 71%. IR (KBr): ν 2943 s, 2908 s, 2828 s,
794 s, 771 s cm-1. MS: m/e 231 (M+ - Pri), 187.
(η1:η5-Me2NC2H4C5H4)Cr (CH2SiMe3)2 (31) was prepared
as dark green needles by reacting LiCH2SiMe3 with (Me2-
NC2H4C5H4)CrCl2 in pentane/THF at -20 °C to room temper-
ature. Yield: 64%. IR (KBr): ν 2943 s, 2877 s, 2828 s, 1250 s,
1236 s, 855 s, 845 s, 796 s cm-1. MS: m/e 362 (M+), 347, 275,
187.
(η1:η5-cyclo-C4H8NC2H4C5H4)Cr Me2 (32) was prepared as
described below (see 34), as dark green crystals, by reacting
Cr(THF)3Cl3 successively with cyclo-C4H8NC2H4C5H4Li and
MeMgCl in THF at -20 °C to room temperature. Yield: 46%.
IR (KBr): ν 2958 s, 2903 s, 2856 s, 2781 s, 797 s, 785 s cm-1
MS: m/e 244 (M+), 229, 143, 131.
.
(η1:η5-cyclo-C5H10NC2H4C5H4)Cr Me2 (33) was prepared as
olive green crystals by reacting MeMgCl with (cyclo-C5H10
-
NC2H4C5H4)CrCl2 in THF at -20 °C to room temperature. The
compound decomposes slowly at room temperature. Yield:
33%. IR (KBr): ν 2973 s, 2910 s, 2861 s, 786 s cm-1. MS: m/e
257 (M+), 172, 157, 131.
(η1:η5-cyclo-C4H8NC2H4C5Me4)Cr Cl2 (22) was prepared by
adding cyclo-C4H8NC2H4C5Me4Li (2.20 g, 9.77 mmol) dissolved
in THF (150 mL) to a suspension of Cr(THF)3Cl3 (3.66 g, 9.77
mmol) in THF (150 mL) at room temperature and stirring for
2 h. The resulting solution was evaporated to dryness and the
residue extracted with toluene (100 mL). The extract was
concentrated and cooled to -40 °C to give the compound as
blue needles, which were isolated, washed at room tempera-
ture with a small amount of pentane, and dried under high
vacuum. Yield: 2.72 g (82%). IR (KBr): ν 2958 s, 2925 s, 2884
s, 1453 s, 1378 s cm-1. MS: m/e 340 (M+), 304, 218.
(η1:η5-9-cyclo-C4H8NC2H4C13H16)Cr Cl2 (23) was prepared
as described above as blue needles by reacting (9-cyclo-C4H8-
NC2H4-octahydrofluorenyl)Li with Cr(THF)3Cl3 in THF.
(η1:η5-Me2NC3H6C5H4)Cr Me2 (34) was prepared by adding
Me2NC3H6C5H4Na (3.12 g, 18.01 mmol) dissolved in THF (100
mL) to a suspension of Cr(THF)3Cl3 (7.92 g, 21.15 mmol) in
THF (60 mL) at room temperature. The resulting dark blue
solution was cooled to -20 °C, and MeMgCl (15 mL of a 2.82
M solution in THF, 43 mmol) in THF (15 mL) was added slowly
over 1 h. The resulting green-blue solution was stirred for 2 h
at room temperature and evaporated to dryness and the
residue extracted with pentane (total 300 mL). The extract
was cooled to give the compound as dark blue crystals. Yield:
3.4 g (80%). IR (KBr): ν 2908 s, 2861 s, 2787 s, 779 s cm-1
MS: m/e 233 (M+ - H), 218, 174, 131.
.
Yield: 70%. IR (KBr): ν 2940 s, 2868 s, 1452 s, 1427 s cm-1
MS: m/e 392 (M+), 356, 270.
.
(η1:η5-1,3-cyclo-C4H8NC2H4(Me3Si)C5H3)Cr Me2 (35) was
prepared as a dark green oil by reacting MeMgCl with (1,3-
cyclo-C4H8NC2H4(Me3Si)C5H3)CrCl2 in THF at -20 °C to room
temperature. Yield: 60%. IR (KBr): ν 2952 s, 2918 s, 2859 s,
1247 s, 836 s, 756 s cm-1. MS: m/e 316 (M+), 301.
(η1:η5-cyclo-C4H8NSiMe2OSiMe2C5H4)Cr Cl2 (24) was pre-
pared as described above (see 13) by reacting NaC5H4SiMe2-
OSiMe2NC4H8-cyclo with Cr(THF)3Cl3 in THF at room tem-
perature and isolated as blue needles by extracting the
evaporated residue with diethyl ether. Yield: 79%. IR (KBr):
(η1:η5-cyclo-C4H8NC2H4C5Me4)Cr (Me)Cl (36) was pre-
pared by reacting (cyclo-C4H8NC2H4C5Me4)CrMe2 (0.97 g, 3.21
ν 3105 m, 3078 m, 2957 m, 2886 m, 1259 s, 1038 s, 828 s cm-1
.
21
MS: decomposes. Crystal structure determination: see Figure
2.
mmol) with a solution of (Cl2AlOSiMe3)2 (0.33 g, 1.77 mmol)
in hexane (60 mL) at room temperature. The compound
precipitates out as violet crystals, which were isolated and
dried under high vacuum. Yield: 1.0 g (97%). IR (KBr): ν 2961
s, 2916 s, 2865 s cm-1. MS: decomposes.
The compound can also be prepared (yield 90%) by reacting
(cyclo-C4H8NC2H4C5Me4)CrMe2 with 1 equiv of HCl in diethyl
ether at -70 °C.
[(η 5-E t 2NSiMe2C5H 4)Cr Cl2]2 (27). A solution of Et2-
NSiMe2C5H4Li (3.47 g, 17.24 mmol) in THF (50 mL) was added
at room temperature to a suspension of Cr(THF)3Cl3 (6.60 g,
17.62 mmol) in THF (100 mL). The resulting deep blue solution
was evaporated to dryness and the oily residue extracted with
pentane (200 mL). Cooling the extract to 0 °C give the
compound as a black crystalline solid. Yield: 3.07 g (56%).
Anal. Calcd for C22H40Cl4Cr2N2Si2: C, 41.6; H, 6.4; Cl, 22.4;
Cr, 16.4; N, 4.4; Si, 8.9. Found: C, 41.6; H, 6.3; Cl, 22.6; Cr,
16.5; N, 4.4; Si, 8.7. IR (KBr): ν 2962 s, 2924 s, 2866 s, 1166 s,
1251 s, 831 s, 815 s, 785 s cm-1. MS: decomposes. Crystal
structure determination: see Figure 3.
(η1:η5-Me2NC2H4C5Me4)Cr C4H8-cyclo5 was prepared by
adding slowly a solution of 1,4-dilithiobutane (16.0 mL of a
0.32 M solution in diethyl ether, 5.1 mmol) in THF (20 mL) to
(Me2NC2H4C5Me4)CrCl2 (1.43 g, 4.5 mmol) in THF (50 mL) at
-20 °C. The reaction mixture was stirred at -10 °C for 15 h
and evaporated to dryness at -10 °C. The residue was
extracted with pentane at 0 °C and the extract cooled to -70
°C to give the compound as dark green needles, which were
recrystallized from pentane at -30 °C. Yield: 1.04 g (77%).
Anal. Calcd for C17H30CrN: C, 68.0; H, 10.1; Cr, 17.3; N, 4.7.
Found: C, 67.9; H, 10.0, Cr, 17.4; N, 4.6. IR (KBr): ν 2912 s,
2817 s, 1461 s cm-1. MS: m/e 272 (M+ - C2H4), 244, 187.
Crystal structure determination: see ref 5.
The compound has also been prepared by reacting (Me2-
NC2H4C5Me4)CrCl2 (0.55 g, 1.7 mmol) with PMe3 (0.4 mL, 3.8
mmol) in THF (50 mL). The solution was cooled to -80 °C and
saturated with ethylene for 15 min. Active Mg38 (0.09 g, 3.7
mmol) was added and the solution stirred under an atmo-
sphere of ethylene for 15 h at -30 °C. The dark green reaction
(η1:η5-Me2NC2H4C5H4)Cr Me2 (28) was prepared by adding
MeMgCl (3.5 mL of a 2.82 M solution in THF, 9.85 mmol) in
THF (10 mL) dropwise into a suspension of (Me2NC2H4C5H4)-
CrCl2 in THF (40 mL) at -20 °C. The resulting dark green
solution was stirred for 1 h at room temperature and then
evaporated to dryness. The residue was extracted with pentane
(total 100 mL) and the extract cooled to give the compound as
dark green crystals. Yield: 0.81 g (84%). IR (KBr): ν 2946 s,
2884 s, 2817 s, 2768 s, 1461 s, 815 s, 799 s cm-1. MS: m/e 219
(M+ + H), 204.
(η1:η5-Me2NC2H4C5H4)Cr Et2 (29) was prepared as de-
scribed above as dark green crystals by reacting EtMgBr with
(Me2NC2H4C5H4)CrCl2 in diethyl ether/THF at -80 °C to room
temperature. Yield: 76%. IR (KBr): ν 2914 s, 2870 s, 2839 s,
2776 s, 792 s, 773 s cm-1. MS: m/e 217 (M+ - Et), 187.
(38) Bogdanovic´, B. Angew. Chem. 1985, 97, 253.

Substituted Cyclopentadienyl Cr(III) Complexes
Organometallics, Vol. 19, No. 4, 2000 401
mixture was filtered and evaporated to dryness at -30 °C and
the residue extracted with pentane at -10 °C. The extract was
cooled to -70 °C to give the compound as dark green needles.
Yield: 0.47 g (90%).
50.8; H, 3.8; B, 0.9; Cr, 4.4; F, 37.3; N, 1.1. IR (KBr): ν 1355 s,
1278 s, 1162 s, 1124 s cm-1
.
(η1:η5-cyclo-C4H8NC2H4C5Me4)Cr (Me)Cl‚AlMe3 (43) was
prepared by adding AlMe2Cl (3.65 mL of a 0.18 M solution in
toluene, 0.65 mmol) to (cyclo-C4H8NC2H4C5Me4)CrMe2 (0.20
g, 0.65 mmol) dissolved in toluene (20 mL) at room tempera-
ture. The resulting violet solution was filtered and evaporated
to dryness and the residue washed with pentane. The residue
was dissolved in toluene and the solution cooled to -40 °C to
give the compound as violet quadratic crystals. Yield: 0.44 g
(92%). Anal. Calcd for C19H36AlClCrN: C, 58.1; H, 9.3; Al, 6.9;
Cl, 9.0; Cr, 13.2; N, 3.6. Found: C, 58.0; H, 9.0; Al, 7.1; Cl,
9.2; Cr, 13.1; N, 3.4. IR (KBr): ν 2921 s, 2880 s, 1185 s, 696 s
cm-1. MS: decomposes.
(η1:η5-cyclo-C4H8NC2H4C5Me4)Cr Me2‚AlMe3 (44) was pre-
pared by reacting a solution of (cyclo-C4H8NC2H4C5Me4)CrMe2
(0.37 g, 1.2 mmol) in toluene (30 mL) with AlMe3 (1.26 mL of
a 0.97 M solution in toluene, 1.30 mmol). The color of the
solution changed immediately from green to violet. The solu-
tion was filtered and evaporated to dryness and the residue
dissolved in hexane (20 mL). Cooling the solution to -40 °C
gave the compound as violet needles. Yield: 0.40 g (88%). Anal.
Calcd for C20H39AlCrN: C, 64.5; H, 10.6; Al, 7.2; Cr, 14.0; N,
3.8. Found: C, 64.6; H, 10.5; Al, 7.2; Cr, 14.1; N, 3.7. IR (KBr):
ν 2959 s, 2916 s, 2886 s, 1185 s, 704 s cm-1. MS: decomposes.
(η1:η5-cyclo-C4H8NC2H4C5Me4)Cr (Me)Cl‚AlMe2Cl was pre-
pared by reacting a solution of (cyclo-C4H8NC2H4C5Me4)CrCl2
(0.56 g, 1.63 mmol) in toluene (70 mL) with AlMe3 (8 mL of a
0.41 M solution in toluene, 3.3 mmol) at room temperature.
The resulting violet solution was evaporated to dryness and
the residue washed with pentane and dried under high
vacuum. The residue was dissolved in toluene and the solution
cooled to -30 °C to give the compound as a violet solid. Yield:
0.47 g (70%). Anal. Calcd for C18H33AlCl2CrN: C, 52.3; H, 8.1;
Al, 6.5; Cl, 17.2; Cr, 12.6; N, 3.4. Found: C, 52.2; H, 8.1; Al,
6.4; Cl, 17.0; Cr, 12.7; N, 3.4. IR (KBr): ν 2924 s, 2868 s, 682
s cm-1. MS: decomposes.
(η1:η5-Me2NC2H4C5Me4)Cr C6H10-cyclo5 was prepared by
adding slowly a solution of 1,6-C6H12(MgCl)2 (15.0 mL of a 0.30
M solution in THF, 4.5 mmol) in THF (50 mL) to (Me2NC2H4C5-
Me4)CrCl2 (1.41 g, 4.5 mmol) in THF (100 mL) at -30 °C. The
reaction mixture was stirred for 15 h at -10 °C and evaporated
to dryness and the residue extracted with pentane at -10 °C.
The extract was concentrated to 20 mL and cooled to -70 °C
to give the compound as dark green prisms. Yield: 0.73 g
(49%). Anal. Calcd for C19H34CrN: C, 69.5; H, 10.4; Cr, 15.8;
N, 4.3. Found: C, 65.7; H, 10.0, Cr, 15.4; N, 4.2. IR (KBr): ν
2907 s, 2840 s, 1463 s, 1435 s cm-1. MS: m/e 328 (M+), 242,
187. Crystal structure determination: see ref 5.
(η1:η5-cyclo-C4H8NC2H4C5Me4)Cr Me2 (37) was prepared
as described above (see 34), as dark green crystals, by reacting
Cr(THF)3Cl3 successively with cyclo-C4H8NC2H4C5Me4Li and
MeMgCl in THF at -20 °C to room temperature. Yield: 86%.
IR (KBr): ν 2963 s, 2900 s, 2849 s, 2778 s cm-1. MS: m/e 301
(M+ + H), 285, 199. Crystal structure determination: see
Figure 4.
(η1:η5-9-cyclo-C4H8NC2H4C13H16)Cr Me2 (38) was prepared
as described above (see 34), as dark green needles, by reacting
Cr(THF)3Cl3 successively with (9-cyclo-C4H8NC2H4-octahydrof-
luoreny)Li and MeMgCl in THF at -20 °C to room tempera-
ture. Yield: 56%. IR (KBr): ν 2930 s, 2854 s, 1437 s cm-1. MS:
m/e 337 (M+ - Me), 268. Crystal structure determination: see
Figure 4.
(η1:η5-Me2NC2H4C5H4)Cr (η1:η3-C3H5)2 (39) was prepared
as an orange crystalline solid by reacting C3H5MgCl with (Me2-
NC2H4C5H4)CrCl2 in diethyl ether/THF at -80 to -30 °C.
Yield: 80%. Anal. Calcd for C15H24CrN: C, 66.6; H, 9.0; Cr,
19.2; N, 5.2. Found: C, 66.7; H, 9.1; Cr, 19.2; N, 5.2. IR (KBr):
ν 2940 s, 2815 s, 2765 s, 1640 w (η1-C3H5), 1462 s, 800 s cm-1
MS: m/e 270 (M+), 229, 187.
.
(η5-cyclo-C4H8NC2H4C5Me4)(η4-C4H6)Cr P Me3 (40). A sus-
pension of Cr(THF)3Cl3 (1.95 g, 5.21 mmol) in THF (50 mL)
was treated at room temperature with cyclo-C4H8NC2H4C5Me4-
Li (1.11 g, 4.95 mmol) in THF (50 mL). The resulting dark
blue solution was stirred for 2 h, cooled to -70 °C, and treated
successively with PMe3 (1.2 mL, 11 mmol), butadiene (20 mL),
and active Mg38 (0.29 g, 11.7 mmol). The resulting red solution
was stirred for 12 h at -30 °C and filtered and then evaporated
to dryness. The red-brown residue was extracted with pentane.
Cooling the extract gave the compound as dark red cubes.
Yield: 1.87 g (94%). Anal. Calcd for C20H39CrNP: C, 66.0; H,
9.8; Cr, 13.0; N, 3.5; P, 7.7. Found: C, 65.9; H, 9.9; Cr, 12.9;
N, 3.6; P, 7.8. IR (KBr): ν 2927, 2805, 1456, 1429, 1374, 1348
cm-1. MS: m/e 324 (M+ - PMe3), 270, 266. Crystal structure
determination: see Figure 5.
[(η1:η5-cyclo-C4H8NC2H4C5Me4)Cr Me]+[MeB(C6F5)3]- (41)
was prepared as a violet solid by reacting a solution of (cyclo-
C4H8NC2H4C5Me4)CrMe2 (0.30 g, 1.0 mmol) in toluene (20 mL)
with a solution of B(C6F5)3 (0.52 g, 1.0 mmol) in toluene (20
mL) at -10 °C. The solution was separated from a small
amount of an oily residue and evaporated to dryness. Yield:
0.57 g (69%). Anal. Calcd for C35H30BCrF15N: C, 51.7; H, 3.7;
B, 1.3; Cr, 6.4; F, 35.1; N, 1.7. Found: C, 51.8; H, 3.8; B, 1.5;
Cr, 6.4; F, 34.9; N, 1.8. IR (KBr): ν 1511 s, 1457 s, 1087 s, 949
s cm-1. MS: m/e 797 (M+ - Me), 630.
(η1:η5-P r iNdC(Me)CH2C5H4)Cr Cl2 (45). A solution of PriNd
C(Me)CH2C5H4Li (0.92 g, 5.63 mmol) in THF (30 mL) was
added to a suspension of Cr(THF)3Cl3 (2.23 g, 5.96 mmol) in
THF (50 mL) at -78 °C. The reaction mixture was stirred at
room temperature for 3 h and evaporated to dryness and the
residue extracted with CH2Cl2 (50 mL). The extract was cooled
to -70 °C to give the compound as a microcrystalline blue
solid. Yield: 1.12 g (70%). Anal. Calcd for C11H16Cl2CrN: C,
46.3; H, 5.7; Cl, 24.9; Cr, 18.2; N, 4.9. Found: C, 46.4; H, 5.7;
Cl, 25.0; Cr, 18.2; N, 4.8. IR (KBr): ν 2971 s, 2928 s, 2870 s,
1604 s, 1379 s, 1365 s, 809 s cm-1. MS: m/e 284 (M+), 249,
212, 206.
(η:η5-MeOC2H4C5H4)Cr Cl2 (46) was prepared by adding
a solution of LiC5H4C2H4OMe (1.23 g, 9.5 mmol) in THF (50
mL) to a suspension of Cr(THF)3Cl3 (3.68 g, 9.8 mmol) in THF
(70 mL) at room temperature. The reaction mixture was stirred
for 2 h and evaporated to dryness and the blue residue
extracted with boiling toluene (250 mL). The extract was
evaporated to dryness and the residue taken up in CH2Cl2 (20
mL). The extract was filtered and cooled to -70 °C to give the
compound as blue needles, which were washed with pentane
at room temperature and dried under vacuum. Yield: 1.7 g
(71%). Anal. Calcd for C8H11Cl2CrO: C, 39.1; H, 4.5; Cl, 28.8;
Cr, 21.1. Found: C, 38.9; H, 4.6; Cl, 28.7; Cr, 21.3. IR (KBr):
ν 1054 s, 1039 s, 833 s, 814 s cm-1. MS: m/e 245 (M+), 210,
143.
[(η1:η5-cyclo-C4H 8NC2H 4C5Me4)Cr Me]+[B(C6H 3(CF 3)2-
3,5]4-‚0.5Et2O (42) was prepared by reacting a solution of
(cyclo-C4H8NC2H4C5Me4)CrMe2 (0.09 g, 0.3 mmol) in diethyl
ether (50 mL) with a solution of HB(C6H3(CF3)2-3,5)4‚2Et2O23
at -10 °C. The reaction mixture was stirred at room temper-
ature for 1 h and the resulting violet precipitate isolated,
washed with diethyl ether (10 mL), and dried under high
(η1:η5-MeSC2H4C5H4)Cr Cl2 (47) was prepared as blue
needles as described above by reacting NaC5H4C2H4SMe with
Cr(THF)3Cl3 in THF at room temperature. Yield: 75%. Anal.
Calcd for C8H11Cl2CrS: C, 36.7; H, 4.2; Cl, 27.1; Cr, 19.8; S,
12.1. Found: C, 36.8; H, 4.3; Cl, 27.0; Cr, 19.7; S, 12.6. IR
(KBr): ν 1477 m, 1418 m, 832 s cm-1. MS: m/e 261 (M+), 225,
190, 178.
vacuum. Yield: 0.28 g (78%). Anal. Calcd for C50H44BCrF24
-
NO: C, 50.6; H, 3.8; B, 0.9; Cr, 4.4; F, 38.5; N, 1.2. Found: C,

402 Organometallics, Vol. 19, No. 4, 2000
Ta ble 7. Cr ysta llogr a p h ic Da ta
Do¨hring et al.
24
17
21
37
38
27
40
formula
mol wt
cryst size, mm
C
13H24Cl2CrNOSi2 C14H24Cl2CrNSi C13H22Cl2CrN C17H30CrN
C21H34CrN
352.49
C11H20Cl2CrNSi C22H39CrNP
389.41
0.42 × 0.49 ×
0.49
7287.5(11)
1.419
20
0.710 69
16
357.33
0.48 × 0.32 ×
0.18
1737.5(2)
1.366
315.23
0.63 × 0.42 ×
0.25
2967.5(7)
1.411
300.42
317.27
400.51
0.46 × 0.49 ×
0.63
2222.7(2)
1.197
0.39 × 0.46 × 0.28 × 0.53 × 0.32 × 0.53 ×
0.60
1638.2(2)
1.218
0.81
3858.9(13)
1.213
20
0.710 69
8
0.56
792.8(2)
1.329
V (Å3)
Fcalcd (g/cm3)
TMessung (°C)
λ(Mo KR) (Å)
Z
20
20
-173
20
20
0.710 69
4
0.710 69
8
0.710 69
4
0.710 69
2
0.710 69
4
µabs (mm-1
)
1.034
1.023
1.110
0.687
0.593
4630
1.111
0.592
no. of rflns measd 7373
4129
6756
2699
3213
2864
no. of obsd rflns
no. of variables
space group (No.)
a (Å)
b (Å)
c (Å)
3016
361
3948
172
5294
334
2509
169
2773
415
2076
145
P1h (2)
2518
250
Pbca (16)
14.3798(13)
27.6664(10)
18.318(2)
90
90
90
0.0515
0.1301
0.447
P21/a (14)
12.4723(8)
11.6609(7)
12.5696(12)
90
108.118(6)
90
0.0432
0.1259
0.614
P21/a (14)
14.957(3)
11.7539(18)
18.3102(16)
90
112.796(9)
90
0.0376
0.1092
0.380
P212121(19)
10.8358(9)
11.3905(9)
13.2727(8)
90
90
90
0.0433
0.1251
0.508
Pna21 (33)
22.5207(8)
15.451(5)
11.0900(12)
90
90
90
0.0482
0.1291
0.348
P212121 (19)
9.6215(4)
12.9841(5)
17.792(2)
90
90
90
0.0396
0.1059
0.314
7.6250(11)
7.821(2)
14.054(2)
75.982(11)
83.044(14)
77.86(2)
0.0539
0.1635
0.680
R (deg)
â (deg)
γ (deg)
R
Rw
resid electron
density (e Å-3
)
(η1:η5-MeSC2H4C5Me4)Cr Cl2 (48) was prepared as blue
needles as described above by reacting LiC5Me4C2H4SMe with
Cr(THF)3Cl3 in THF at room temperature. Yield: 75%. Anal.
Calcd for C12H19Cl2CrS: C, 43.3; H, 6.0; Cl, 22.3; Cr, 16.3; S,
10.1. Found: C, 45.4; H, 5.9; Cl, 22.4; Cr, 16.3; S, 10.0. IR
(KBr): ν 1421 s, 1377 s cm-1. MS: m/e 317 (M+), 281, 266, 235.
(η1:η5-Bu tSC2H4C5H4)Cr Cl2 (50) was prepared as a blue
solid as described above by reacting KC5H4C2H4SBut with
Cr(THF)3Cl3 in THF at room temperature. Yield: 78%. Anal.
Calcd for C11H17Cl2CrS: C, 43.4; H, 5.6; Cl, 23.3; Cr, 17.1; S,
10.5. Found: C, 43.3; H, 5.6; Cl, 23.2; Cr, 17.5; S, 10.5. IR
(KBr): ν 1476 s, 1462 s, 1429 s, 1365 s, 827 s cm-1. MS: m/e
303 (M+), 268, 247, 211, 165.
CpCr (1,3,4,5-tetr am eth ylim idazol-2-yliden e)Cl2 (51) was
prepared by adding a solution of 1,3,4,5-tetramethylimidazol-
2-ylidene (0.33 g, 2.7 mmol) in THF (25 mL) to a suspension
of CpCr(THF)Cl2 (0.69 g, 2.7 mmol) in THF (25 mL) at room
temperature. The resulting violet precipitate was isolated,
washed with THF, and dried under high vacuum. Yield: 0.78
g (94%). Anal. Calcd for C12H17Cl2CrN2: C, 46.2; H, 5.5; Cl,
22.7; Cr, 16.7; N, 9.0. Found: C, 46.0; H, 5.5; Cl, 22.8; Cr, 16.6;
N, 8.9. IR (KBr): ν 1653 m, 1432 s, 1374 s, 804 s cm-1. MS:
m/e 311 (M+), 276, 246, 211.
Ca ta lytic Rea ction s. The polymerization reactions were
carried out in a thermostated glass autoclave (Bu¨chi, BEP 280)
and stirred with a glass paddle stirrer (1000 rotations/min)
coupled to an external magnet. The gas flow and reactor
temperature were recorded automatically. The autoclave was
filled with toluene (240 mL) and the solvent saturated with
ethylene at 2 atm. The catalyst solution was prepared exter-
nally by dissolving the chromium compound in toluene and
treating it with a known concentration of a toluene solution
of MAO. The required solution was then diluted to 10 mL and
injected into the stirred reaction solution. The reaction was
terminated by simultaneously closing the ethylene valve and
injecting methanol (10 mL) into the reactor. The contents of
the reactor were treated with dilute HCl/MeOH, and the
toluene fraction was tested (GC) for the presence of oligomers.
The polymer suspension was stirred overnight and the PE
collected and washed with methanol. The procedure was
repeated and the polymer dried under high vacuum. The
melting point and crystallinity of the polymer was determined
by standard methods (DSC, du Pont, 912/9900; IR, Nicolet
7199/750). The average molecular weight and distribution were
determined by gel-permeation chromatography (GPC).
Cr ysta l Str u ctu r e Deter m in a tion s. The crystal structure
analysis of compounds 17, 21, 24, 27, 37, 38, and 40 were
carried out using a CAD-4 single-crystal diffractometer (Enraf-
Nonius). Crystallographic data and details of the refinement
are listed in Table 7. Final coordinates and equivalent isotropic
thermal parameters are included in the Supporting Informa-
tion.
Cp Cr (1,3,4,5-tetr a m eth ylim id a zol-2-ylid en e)Me2 (52)
was prepared by adding a solution of MeMgCl (0.6 mL of a
1.07 M solution in THF; 0.63 mmol) in THF (20 mL) to a
suspension of CpCr(1,3,4,5-tetramethylimidazol-2-ylidene)Cl2
(0.09 g, 0.3 mmol) in THF (20 mL) at room temperature,
whereupon the color of the solution changed from blue to red.
The solution was evaporated to dryness and the residue
extracted with diethyl ether (40 mL). The compound crystal-
lized as red needles upon cooling the extract to 0 °C. Yield:
0.07 g (83%). Anal. Calcd for C14H23CrN2: C, 62.0; H, 8.6; Cr,
19.2; N, 10.3. Found: C, 62.2; H, 8.5; Cr, 19.1; N, 10.2. IR
(KBr): ν 2919 s, 2866 s, 1657 m, 1430 s, 1373 s, 795 s, 776 s.
MS: m/e 271 (M+), 256, 241, 176, 117.
(Me5C5)Cr (1,3,4,5-tetr am eth ylim idazol-2-yliden e)Cl2 (53)
was prepared as described above (see 51) as a violet solid by
reacting the carbene with (Me5C5)CrCl2 in THF at room
temperature. Yield: 90%. Anal. Calcd for C17H27Cl2CrN2: C,
53.4; H, 7.1; Cl, 18.6; Cr, 13.6; N, 7.3. Found: C, 53.6; H, 7.2;
Cl, 18.6; Cr, 13.6; N, 7.3. IR (KBr): ν 1660 m, 1569 m, 1433 s,
1371 s cm-1. MS: m/e 381 (M+), 346, 257, 222.
Ack n ow led gm en t. We thank Borealis Polymers Oy
(Dr. O. Andell) for financial support.
Su p p or tin g In for m a tion Ava ila ble: Detailed informa-
tion on the crystal structure determinations, including tables
of data collection parameters, final atomic positional and
thermal parameters, and interatomic distances and angles as
well as ORTEP diagrams. This material is available free of
charge via the Internet at http://pubs.acs.org.
OM990643R