Structural features of Me2Si-bridged Cp/phosphido group 4 metal complexes, CpSiP constrained-geometry Ziegler-Natta catalyst precursors

Article abstract of DOI:10.1021/om0200959

Double deprotonation of [(C₅Me₄H)-SiMe₂-PH(cyclohexyl)] (4) was achieved by treatment with n-butyllithium in THF/pentane to afford the dianionic ligand [(C₅Me₄)-SiMe₂-P(cyclohexyl)]^2- as its dilithio salt (5). The reagent 5 was transmetalated by subsequent treatment with [Cl₂Ti(NMe₂)₂] (6a) to yield the dimethylsilanediyl-bridged Cp*/phosphido titanium complex [(C₅Me₄)-SiMe₂-PCy]Ti(NMe₂)₂ (7a; 67% isolated yield). The analogous reaction of 5 with [Cl₂Zr(NEt₂)₂(THF)₂] (6b) gave [(C₅Me₄)-SiMe₂-PCy]Zr(NEt₂)₂ (7b; isolated in 59% yield). Single crystals of the complexes 7a,b were obtained from pentane. The X-ray crystal structure analyses revealed distorted constrained geometry group 4 metal complex structures due to the presence of a chiral, nonplanar coordination geometry at the phosphorus atom. Complexes 7a,b both give active homogeneous Ziegler-Natta catalysts for ethene/1-octene copolymerization upon activation with excess methylalumoxane.

Full text of DOI:10.1021/om0200959

4084
Organometallics 2002, 21, 4084-4089
Str u ctu r a l F ea tu r es of Me2Si-Br id ged Cp /P h osp h id o
Gr ou p 4 Meta l Com p lexes, “Cp SiP ”
Con str a in ed -Geom etr y Ziegler -Na tta Ca ta lyst
P r ecu r sor s
Gereon Altenhoff, Stephane Bredeau, Gerhard Erker,* Gerald Kehr,
Olga Kataeva,† and Roland Fro¨hlich†
Organisch-Chemisches Institut der Universita¨t Mu¨nster, Corrensstrasse 40,
D-48149 Mu¨nster, Germany
Received February 8, 2002
Double deprotonation of [(C5Me4H)-SiMe2-PH(cyclohexyl)] (4) was achieved by treatment
with n-butyllithium in THF/pentane to afford the dianionic ligand [(C5Me4)-SiMe2-
P(cyclohexyl)]2- as its dilithio salt (5). The reagent 5 was transmetalated by subsequent
treatment with [Cl2Ti(NMe2)2] (6a ) to yield the dimethylsilanediyl-bridged Cp*/phosphido
titanium complex [(C5Me4)-SiMe2-PCy]Ti(NMe2)2 (7a ; 67% isolated yield). The analogous
reaction of 5 with [Cl2Zr(NEt2)2(THF)2] (6b) gave [(C5Me4)-SiMe2-PCy]Zr(NEt2)2 (7b;
isolated in 59% yield). Single crystals of the complexes 7a ,b were obtained from pentane.
The X-ray crystal structure analyses revealed distorted “constrained geometry” group 4 metal
complex structures due to the presence of a chiral, nonplanar coordination geometry at the
phosphorus atom. Complexes 7a ,b both give active homogeneous Ziegler-Natta catalysts
for ethene/1-octene copolymerization upon activation with excess methylalumoxane.
In tr od u ction
were connected by means of methylene (H2C) or alkyli-
dene (R1R2C) linkers.7 These “CpCN” metal catalysts
produce ethene/1-octene copolymers with similarly high
1-alkene incorporations as compared to the original
“CpSiN” group 4 metal complex derived systems.
Other element combinations are rare. Royo and
Cuenca have described “CpSiO” systems,8 and we have
recently published related “CpCO”MIV-derived cata-
lysts.9 Both organometallic catalyst precursor types are
dimeric (see Chart 1). We have also described the first
examples of C1-bridged constrained-geometry “CpCP”
catalysts.7 These titanium or zirconium complexes
contain an alkylidene-linked Cp/phosphido ligand com-
bination. Some examples of this series showed an
excellent ethene/1-alkene copolymerization catalyst be-
havior with regard to both very high catalyst activities
and high R-olefin incorporation. Surprisingly little has
been known about the related “CpSiP” group 4 metal
catalyst systems. An arylphosphido example has been
reported in the patent literature.10 Hey-Hawkins et al.
had described the corresponding “CpSiP”Li2 dianion
equivalent but reported an unexpected reaction pathway
that proceeded with dephosphorylation upon its treat-
The Me2Si-bridged Cp*/amido titanium (and zirco-
nium) complexes of the type A (in Chart 1) have become
the precursors of an important class of homogeneous
Ziegler-Natta catalysts.1,2 In contrast to many bis-Cp
and bis(indenyl) Group 4 derived systems, they have
been especially useful in the formation of ethene/1-
alkene copolymers when activated with, for example,
methylalumoxane.3 Most of these “constrained geom-
etry” catalysts are actually derived from the parent
compound A, where a substituted Cp-type ligand is
connected to some alkyl- or arylamido group by means
of a bridging R1R2Si unit.4 Other bridging units have
only seldom been used; we have contributed examples
that contain a vinylidene bridge (H2CdC)5,6 and recently
reported catalysts where the Cp and amido moieties
† X-ray crystal structure analyses.
(1) (a) Bunel, E. E.; Burger, B. J .; Bercaw, J . E. J . Am. Chem. Soc.
1988, 110, 976-978. (b) Piers, W. E.; Shapiro, P. J .; Bunel, E. E.;
Bercaw, J . E. Synlett 1990, 2, 74-84. (c) Shapiro, P. J .; Bunel, E. E.;
Schaefer, W. P.; Bercaw, J . E. Organometallics 1990, 9, 867-869. (d)
Shapiro, P. J .; Cotter, W. D.; Schaefer, W. P.; Labinger, J . A.; Bercaw,
J . E. J . Am. Chem. Soc. 1994, 116, 4623-4640.
(2) Okuda, J . Chem. Ber. 1990, 123, 1649-1651.
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420436-A1, 1991. (b) Canich, J . M.; Hlatky, G. G.; Turner, H. W. PCT
Appl. WO 92-00333, 1992. See also: (c) Devore, D. D.; Timmers, F. J .;
Hasha, D. L.; Rosen, R. K.; Marks, T. J .; Deck, P. A.; Stern, C. L.
Organometallics 1995, 14, 3132-3134. (d) Stevens, J . C. Stud. Surf.
Sci. Catal. 1996, 101, 11-20.
(4) Reviews: (a) McKnight, A. L.; Waymouth, R. M. Chem. Rev.
1998, 98, 2587-2598. (b) Okuda, J .; Eberle, T. Half-Sandwich Com-
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Weinheim, Germany, 1998; Vol. 1, pp 415-453.
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Bredeau, S.; Kehr, G.; Fro¨hlich, R. Organometallics 2002, 21, 1513-
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(8) (a) Ciruelos, S.; Cuenca, T.; Go´mez-Sal, P.; Manzanero, A.; Royo,
P. Organometallics 1995, 14, 177-185. (b) Ciruelos, S.; Cuenca, T.;
Go´mez-Sal, P.; Manzanero, A.; Royo, P. Organometallics 1996, 15,
5577-5585. (c) Park, J . T.; Yoon, S. C.; Bae, B.-J .; Seo, W. S.; Suh,
I.-H.; Han, T. K.; Park, J . R. Organometallics 2000, 19, 1269-1276.
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(6) See also: Kunz, D.; Erker, G.; Fro¨hlich, R.; Kehr, G. Eur. J .
Inorg. Chem. 2000, 409-416.
10.1021/om0200959 CCC: $22.00 © 2002 American Chemical Society
Publication on Web 08/24/2002

Me2Si-Bridged Cp/ Phosphido Group 4 Metal Complexes
Organometallics, Vol. 21, No. 20, 2002 4085
Ch a r t 1
Sch em e 1
Resu lts a n d Discu ssion
The synthesis of the “CpSiP” ligand system followed
the pathways originally outlined by Bercaw and Sha-
piro1 and later modified by Stevens et al.10 and by Hey-
Hawkins et al.11 for the introduction of the phosphido
group. Tetramethylcyclopentadiene was deprotonated
by treatment with n-butyllithium in hexane, followed
by treatment with dimethyldichlorosilane. The silylated
CpH system was then reacted with the (cyclohexyl)PHLi
reagent in THF/pentane. Nucleophilic substitution at
silicon was achieved selectively, and the neutral ligand
system 4 was isolated in >80% yield (Scheme 1). Double
deprotonation was achieved by treatment of 4 with
n-butyllithium in THF/pentane to give the dilithio
derivative of the “CpSiP” ligand system (5), again in
>80% yield. The dianionic ligand system features a
single 31P NMR resonance in [D8]THF at δ -137.9 (the
neutral precursor 4 shows a 31P NMR doublet in [D6]-
benzene at δ -129.2 (1J PH ) 192 Hz)).
The reaction of the dilithio CpSiP reagent 5 with TiCl4
or ZrCl4 turned out to give complicated product mixtures
that probably contained some of the compounds already
described by Hey-Hawkins et al.11 In contrast, the
reactions of 5 with the corresponding group 4 metal
dichlorobis(dialkylamido) reagents were very clean and
gave the corresponding CpSiP group 4 metal complexes
in good yield.
ment with ZrCl4.11 Hou et al. recently reported the
attachment of such ligands to lanthanoid metals and
described the first X-ray crystal structure analysis, to
our knowledge, of such a “CpSiP”Ln constrained-
geometry complex.12 We have now prepared a pair of
[(Me4C5)-SiMe2-P(cyclohexyl)]TiX2 and -ZrX2 com-
plexes. These are, to the best of our knowledge, the first
examples of such “CpSiP”MIVX2 systems that were
characterized by X-ray diffraction. The structural fea-
tures, which are quite different from those of the related
conventional “CpSiN”MIVX2 complexes, and some chemi-
cal characteristics of these complexes are described in
this paper.13,14
(11) (a) Koch, T.; Blaurock, S.; Somoza, F. B.; Voigt, A.; Kirmse, R.;
Hey-Hawkins, E. Organometallics 2000, 19, 2556-2563. (b) Koch, T.;
Hey-Hawkins, E. Polyhedron 1999, 18, 2113-2116.
(12) Tardif, O.; Hou, Z.; Nishiura, M.; Koizumi, T.; Wakatsuki, Y.
Organometallics 2001, 20, 4565-4573.
(13) For other examples of CpCP-ligand syntheses see e.g.: (a)
Heidemann, T.; J utzi, P. Synthesis 1994, 777-778. (b) Bildmann, U.
J .; Mu¨ller, G. Z. Naturforsch. 2000, 55, 895-900.
The reaction of the (CpSiP)Li2 reagent 5 with Cl2Ti-
(NMe2)2 (6a )15 was carried out in THF at -78 °C. After
workup at room temperature the corresponding (CpSiP)-
Ti(NMe2)2 complex (7a ) was obtained in close to 70%
yield. The corresponding (CpSiP)Zr complex was pre-
pared analogously by treatment of the doubly deproto-
nated ligand system (5) with Cl2Zr(NEt2)2(THF)2 (6b)16
in tetrahydrofuran. The (CpSiP)Zr(NEt2)2 complex 7b
(14) Many examples of complexes that contain Cp-(R)-X ligands
with longer linking hydrocarbyl chains are known. For selected typical
examples see e.g.: (a) Rieger, B. J . Organomet. Chem. 1991, 420, C17-
C20. (b) Hughes, A. K.; Meetsma, A.; Teuben, J . H. Organometallics
1993, 12, 1936-1945. (c) Trouve´, G.; Laske, D.; Meetsma, A.; Teuben,
J . H. J . Organomet. Chem. 1996, 511, 255-262. (d) Sinnema, P.-J .;
van der Veen, L.; Speck, A. L.; Veldman, N.; Teuben, J . H. Organo-
metallics 1997, 16, 4245-4247. (e) Witte, P. T.; Meetsma, A.; Hessen,
B.; Budzelaar, P. H. M. J . Am. Chem. Soc. 1997, 119, 10561-10562.
(f) Gomes, P. T.; Green, M. L. H.; Martins, A. M. J . Organomet. Chem.
1998, 551, 133-138. (g) Gielens, E. E. C. G.; Tiesnitsch, J . Y.; Hessen,
B.; Teuben, J . H. Organometallics 1998, 17, 1652-1654. (h) Christie,
S. D. R.; Man, K. W.; Whitby, R. J .; Slawin, A. M. Z. Organometallics
1999, 18, 348-359. (i) Rau, A.; Schmitz, S.; Luft, G. J . Organomet.
Chem. 2000, 608, 71-75. (j) van Leusen, D.; Beetstra, D. J .; Hessen,
B.; Teuben, J . H. Organometallics 2000, 19, 4084-4089.
(15) Benzing, E.; Kornicker, W. Chem. Ber. 1961, 94, 2263-2267.
(16) (a) Kempe, P.; Brenner, S.; Arndt, P. Z. Anorg. Allg. Chem.
1995, 621, 2021-2024. (b) See also: Warren, T. H.; Erker, G.; Fro¨hlich,
R.; Wibbeling, B. Organometallics 2000, 19, 127-134.

4086 Organometallics, Vol. 21, No. 20, 2002
Altenhoff et al.
F igu r e 2. Backside projection of the molecular structure
of complex 7b, showing the significantly distorted ligand
framework. Selected bond lengths (Å) and angles (deg):
Zr-N18 ) 2.059(2), Zr-N23 ) 2.027(2), Zr-P ) 2.648(1),
P-Si ) 2.223(1), P-C12 ) 1.873(2), Si-C1 ) 1.884(2);
N18-Zr-N23 ) 101.2(1), N18-Zr-P ) 104.9(1), N23-
Zr-P ) 117.7(1), Zr-P-Si ) 86.9(1), Zr-P-C12 ) 122.7-
(1), Si-P-C12 ) 111.6(1), P-Si-C1 ) 94.2(1). For addi-
tional data see the text.
F igu r e 1. Side view of the molecular structure of the
titanium complex 7a (the independent molecule 7a -B is
depicted). Selected bond lengths (Å) and angles (deg): Ti1-
N18 ) 1.924(2), Ti1-N23 ) 1.904(2), Ti1-P1 ) 2.504(1),
P1-Si1 ) 2.213(1), P1-C12 ) 1.877(3), Si1-C1 ) 1.879-
(3); N18-Ti1-N23 ) 101.7(1), N18-Ti1-P1 ) 98.1(1),
N23-Ti1-P1 ) 112.8(1), Ti1-P1-Si1 ) 87.4(1), Ti1-P1-
C12 ) 121.0(1), Si1-P1-C12 ) 112.7(1), P1-Si1-C1 )
91.8(1).
of the bonding angles at P1 in the molecule 7a -B
amounts to 321.1°. In the independent molecule 7a -A
this value is also far away from 360° but also substan-
tially different from the 7a -B value at 310.1°. This
indicates a rather shallow energy profile for a distortion
of the bond angles at phosphorus in complex 7a with
regard to inversion via planar tricoordinate P.18
The individual bond angles at phosphorus are deter-
mined by the constrained ligand framework and they
are, therefore, quite different from one another. The
C12-P1-Si1 angle is found in the typical tetrahedral
range at 106.1(1)° [112.7(1)°], whereas the C12-P1-Ti
angle is slightly larger at 117.9(1)° [121.0(1)°] and the
endocyclic Si1-P1-Ti angle is at an expected low value
of 86.1(1)° [87.4(1)°]. The corresponding bond lengths
are 1.880(3) Å [1.877(3) Å] (P1-C12) and 2.220(1) Å
[2.213(1) Å] (P1-Si1).
The strongly bent geometry at phosphorus signifi-
cantly influences the remaining bond angles at tita-
nium. The dimethylamido group oriented syn to the
phosphorus lone pair shows a smaller N18-Ti-P1 bond
angle at titanium (96.7(1)° [98.1(1)°]) than the dimethyl-
amido group that is located on the side of the cyclohexyl
substituent (N23-Ti-P1 ) 108.1(1)° [112.8(1)°]).
The steric constraints of the ligand framework also
influence the observed bonding features at the bridging
Me2Si moiety. The C1-Si1 bond length is in the normal
range (1.880(3) Å [1.879(3) Å]), but the endocyclic C1-
Si1-P1 angle at silicon is greatly reduced (93.1(1)°
[91.8(1)°]). However, the C1-Si1 vector is only margin-
ally tilted toward the center of the molecule (sum of
bonding angles at C1 356.0° [355.7°]).
was obtained in close to 60% yield. Single crystals of
7a ,b were obtained from concentrated pentane solutions
of these group 4 metal amide complexes at room
temperature. This allowed us to characterize each of the
complexes (7a ,b) by an X-ray crystal structure analysis.
The X-ray crystal structure analysis of the titanium
complex 7a (Figure 1) shows the presence of a con-
strained-geometry framework that is substantially dis-
torted and thus different from the typical appearance
of the usual Cp/amido examples of this general class of
compounds.5,7 In the crystal two independent (enantio-
morphic) molecular entities of 7a were found. They are
chemically equivalent but show variations in a few
details. Therefore, the characteristic structural proper-
ties of molecule 7a -A will be given with the correspond-
ing 7a -B values in brackets.
In 7a the tetramethylcyclopentadienyl ring is rather
uniformly η5 coordinated to the transition-metal center.
The respective Ti-C(Cp) bond lengths range from 2.359-
(3) to 2.455(3) Å [7a -B: 2.378(3)-2.436(3) Å]. The
remaining ligands at titanium complement its pseudo-
tetrahedral coordination geometry. The nitrogen atoms
of the two dimethylamido ligands are each trigonal-
planar coordinated (sum of bonding angles at N18
356.9° [360.0°] and at N23 359.4° [360.0°]).
The Ti-N23 bond length amounts to 1.904(3) Å
[1.904(2) Å], and the Ti-N18 bond is in the same range
at 1.917(3) Å [1.924(2) Å]. The σ-ligand angle N18-Ti-
N23 was found at 103.2(2)° [101.7(1)°]. The adjacent
titanium to phosphorus bond is much longer at 2.544-
(1) Å [2.504(1) Å].17 It is the coordination geometry at
phosphorus that makes the complexes 7 so different
from the previously reported constrained-geometry sys-
tems. As expected, the bonds at P1 are not coplanar but
the coordination geometry at the phosphorus atom in
7a is strongly distorted toward tetrahedral. The sum
The zirconium complex 7b shows a similar structure
(Figure 2). The individual bond lengths of the ligand
atoms to the heavier central metal atom are, of course,
longer than in 7a , but the overall characteristics are
related. The zirconium atom is pseudotetrahedrally
coordinated to a η5-Me4C5-[Si] ligand (with Zr-C(Cp)
bonds ranging from 2.509(2) to 2.561(2) Å), the amido
(17) Hey-Hawkins, E. Chem. Rev. 1994, 94, 1661-1717. Stephan,
D. W. Angew. Chem. 2000, 112, 322-338; Angew. Chem., Int. Ed. 2000,
39, 314-329.
(18) (a) Baker, R. T.; Whitney, J . F.; Wreford, S. S. Organometallics
1983, 2, 1049-1051. (b) Weber, L.; Meine, G.; Boese, R.; Augart, N.
Organometallics 1987, 6, 2484-2488.

Me2Si-Bridged Cp/ Phosphido Group 4 Metal Complexes
Organometallics, Vol. 21, No. 20, 2002 4087
Ch a r t 2. Com p a r ison of
Cp (cen tr oid )-Meta l-Nitr ogen /P h osp h or u s
F r a m ew or k An gles Th a t Ch a r a cter ize th e
In cr ea sin g Ba ck bon e Str a in in a Ser ies of
Con str a in ed -Geom etr y System sa
F igu r e 3. Top projection of complex 7b.
nitrogen centers N18 (Zr-N18 ) 2.059(2) Å) and N23
(Zr-N23 ) 2.027(2) Å), and the phosphido moiety (Zr-P
) 2.648(1) Å). In nonbridged Cp2Zr(X)-PHAr or Cp2-
Zr(X)-PR2 systems the Zr-P bond lengths are typically
found in a range between ca. 2.51 and 2.73 Å. From
representative reference compounds it must be assumed
that the lower values indicate significant metal-
phosphorus π-interaction. The value observed here for
complex 7b, Zr-P ) 2.648(1) Å, is rather long (as
compared with e.g. Cp2Zr(Cl)-P(SiMe3)2 at 2.547(6) Å
or Cp2Zr(Cl)-PH(aryl) at 2.543(3) Å).20 The N18-Zr-
N23 angle in 7b amounts to 101.2(1)°. Again the
N-Zr-P angles are quite different (N18-Zr-P ) 104.9-
(1)°, N23-Zr-P ) 117.7(1)°). This difference again
probably originates from the strongly pyramidalized
coordination geometry at phosphorus (sum of bonding
angles 321.2°; Zr-P-Si ) 86.9(1)°, C12-P-Zr ) 122.7-
(1)°, C12-P-Si ) 111.6(1)°). The Si-P bond length in
7b is found at 2.223(1) Å, and the endohedral angle at
silicon (C1-Si-P) amounts to 94.2(1)° (sum of bonding
angles at C1 356.1°).
Figures 2 and 3 provide two views that illustrate the
significantly distorted frameworks of these constrained-
geometry catalyst precursors. The characteristic distor-
tion originates from the introduction of the phosphorus
chirality center. In contrast, the Me2Si- and R1R2C-
bridged Cp/amido group 4 metal complexes contain a
nonchiral planar-tricoordinate nitrogen center as part
of their bridged, formally dianionic ligand system.
The alleged characteristic feature of the “constrained
geometry” systems is their rather open space in front
of the (Cp′-SiMe2-NR/PR)M unit at the active catalyst
stage.4 Therefore, it had been suggested to use the Cp-
(centroid)-metal-NR(PR) framework angle as a quan-
titative measure for this potentially characteristic fea-
ture. The smaller this framework angle, the more
pronounced the typical “constrained geometry” features
should be, according to this rather narrow, specific
a
The footnote a denotes this work.
definition. We are not so sure whether this large and
important family of Ziegler-Natta catalysts should (and
can) be classified by such a singular structural feature,
but a comparison of the Cp(centroid)-M-NR(PR) angle
among a series of examples may provide one useful
parameter for a relative structural characterization.
In the (Cp*-SiMe2-NR)TiX2-type complexes, which
are the precursors of the most active ethene/1-alkene
copolymerization catalysts of the “constrained geometry”
type, Cp(centroid)-Ti-N angles of ca. 105° are observed
(see Chart 2). The (Cp-CHR1-NR)Ti(NR2)2 systems
recently reported by us contain considerably more
constrained ligand frameworks, exhibiting Cp(centroid)-
Ti-N angles that are smaller by ca. 10°. Nevertheless,
the catalysts derived from 9 seem to be of lower activity
than the typical (Cp*-SiMe2-NR)Ti systems, although
their 1-octene incorporation ratio in the copolymer is
in the same range. The (Cp*-SiMe2-PR)Ti(NR2)2 sys-
tem described here (7a ) is almost in the same Cp-
(centroid)-Ti-P framework angle range with the con-
ventional (Cp-SiMe2-NR)Ti systems; e.g., 7a deviates
only by less than 2° from the corresponding value
observed in 8 (see Chart 2).
A similar trend is observed in the zirconium series.
The phosphorus-containing system 7b exhibits a Cp-
(centroid)-Zr-P framework angle of 98.2° that deviates
only marginally from the Cp(centroid)-Zr-N angle
(100.2°) of the corresponding silylene-bridged Cp/amido
zirconium complex 10 (see Chart 2).
1
The H NMR spectrum of the zirconium complex 7b
shows only one set of signals of the N(Et2)2 groups, two
signals of the C5(CH3)4 moiety (δ 2.18, 1.89), and a single
Si(CH3)2 resonance at δ 0.67 at room temperature in
d8-toluene solvent in addition to the complex cyclohexyl
resonances. This “symmetric” appearance is, however,
not due to a different structure of 7b in solution. It
originates from a dynamic NMR behavior caused by a
rapid enantiomerization process of the chiral phospho-
rus center. This inversion process could be slowed and
(19) (a) Carpenetti, D. W.; Kloppenburg, L.; Kupec, J . T.; Petersen,
J . L. Organometallics 1996, 15, 1572-1581. (b) Diaz, H. V. R.; Wang,
Z.; Bott, S. G. J . Organomet. Chem. 1996, 508, 91-99.
(20) (a) Hey, E.; Lappert, M. F.; Atwood, J . L.; Bott, S. G. Polyhedron
1988, 19-20, 2083-2086. (b) Lindenberg, F.; Hey-Hawkins, E. J .
Organomet. Chem. 1992, 435, 291-297. (c) Ho, J .; Rousseau, R.;
Stephan, D. W. Organometallics 1994, 13, 1918-1926. (d) Hey-
Hawkins, E.; Kurz, S. J . Organomet. Chem. 1994, 479, 125-133. (e)
Hey-Hawkins, E.; Kurz, S.; Baum, G. Z. Naturforsch. 1995, 239-242.
(f) Breen, T. L.; Stephan, D. W. Organometallics 1996, 15, 4223-4227.
(g) Chen, T.; Duesler, E. N.; No¨th, H.; Paine, R. T. J . Organomet. Chem.
2000, 614-615, 99-106. (h) Urne˘ zˇius, E.; Klippenstein, S. J .; Prota-
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1
eventually frozen out on the H NMR time scale at very

4088 Organometallics, Vol. 21, No. 20, 2002
Altenhoff et al.
Ta ble 1. Deta ils of th e Eth en e P olym er iza tion a n d
Eth en e/1-Octen e Cop olym er iza tion Rea ction s
Ca r r ied ou t w ith th e Hom ogen eou s 7a (Ti)/MAO
a n d 7b(Zr )/MAO Ziegler -Na tta Ca ta lyst System s
(a) Ethene Polymerization, in Toluene
at 60 °C, 1 h Reaction Time
amt of
cat., mg
amt of
PE, g
mp,
°C
cat.
Al/M
acta
7a (Ti)
15
15
16
14
1100
1100
1100
1650
2.4
2.1
4.0
1.4
127
125
126
125
40
35
66
35
7b(Zr)
(b) Ethene/1-Octene Copolymerization,
in 50% Toluene/50% 1-Octene at 90 °C,
1 h Reaction Time
F igu r e 4. 13C NMR spectrum of the ethene/1-octene co-
polymer obtained with the 7a (Ti)/MAO catalyst at 90 °C
(2 bar of ethene pressure) in toluene/50% 1-octene solution
(Al/Ti ratio 1100).
amt of cat.,
mg
press. of
amt of
ethene/
cat.
Al/M C2H4, bar copolym, g octeneb acta
7a (Ti)
13.2
12.9
15.9
13.2
1070
1100
1100
1320
1
2
1
2
0.4
0.9
0.4
0.5
7:1
6:1
9:1
6:1
13
16
14
9
molecular weight of Mw ≈ 50 000 (GPC relative to
polystyrene at 145 °C in 1,2,4-trichlorobenzene) with
Mw/Mn ) 2.1. Mw ≈ 30 000 (Mw/Mn ) 1.6) was found
for the ethene/1-octene copolymer obtained with the 7b/
MAO catalyst under the same conditions.
7b(Zr)
a
Catalyst activity in g of polymer/((mmol of cat.)(bar of ethene)
h). Ethene/1-octene ratio in the obtained copolymer.
b
low temperatures in a CDClF2/CDCl2F Freon solvent
1
mixture.21 In the low-temperature H NMR spectrum
Exp er im en ta l Section
in this specific solvent one eventually observes at 143
K the expected two differentiated pairs of η5-C5(CH3)4
resonances (∆v ) 75 and 87 Hz) as well as a 1:1
intensity pair of Si(CH3)2 1H NMR signals. From the
decoalescence behavior of the Si(CH3)2 1H NMR signals
(Tc ) 160 K in the Freon solvent mixture) the Gibbs
activation energy of the intramolecular inversion pro-
cess at the adjacent phosphorus atom was estimated22
Reactions with organometallic reagents were carried out
under argon using Schlenk-type glassware or in a glovebox.
Solvents were dried and distilled under argon prior to use.
Polymerization and copolymerization reactions were carried
out as previously described by us for related (CpCN)MX2/MAO
catalysts.7 The [Cp*-SiMe2-P(cyclohexyl)]Li2 ligand system
(5) was prepared analogously, as recently described by Hey-
Hawkins et al.11
at ∆G+invP(160 K) ) 7.5 ( 0.5 kcal mol-1
.
Bis(d im e t h yla m id o)[((cycloh e xylp h osp h id o-κP )d i-
m et h ylsilyl)-η5-t et r a m et h ylcyclop en t a d ien yl]t it a n iu m
(7a ). A suspension of 153 mg (0.50 mmol) of the dilithiated
ligand system 5 in 5 mL of THF was cooled to -78 °C. A
solution of 98 mg (0.47 mmol) of Cl2Ti(NMe2)2 (6a ) in 2 mL of
THF was added dropwise to the suspension. The mixture was
then warmed to room temperature with stirring. After 4 h of
stirring at ambient temperature the solvent was removed in
vacuo and the brown residue taken up in pentane. Precipitated
lithium chloride was removed by filtration. Removal of the
solvent from the clear pentane solution gave complex 7a as a
brown oil. Yield of 7a : 144 mg (67%, relative to the amount
of the starting material 5). Single crystals for the X-ray crystal
structure analysis were obtained from a concentrated pentane
solution at room temperature: mp 127 °C, 254 °C dec. Anal.
Calcd for C21H41N2PSiTi (428.5): C, 58.86; H, 9.64; N, 6.54.
The complexes 7a (Ti) and 7b (Zr) were both activated
by treatment with methylalumoxane23 (Al:transition
metal ratios ca. 1070-1650) in toluene solution to give
active homogeneous Ziegler-Natta catalysts. We carried
out a few ethene polymerizations at 2 bar of ethylene
pressure. Polyethylene was obtained in each case with
a moderate activity (see Table 1). The 7a /MAO and 7b/
MAO catalysts were active in ethene/1-octene copolym-
erization. Generally, good incorporation ratios of the
1-alkene were observed in the reactions carried out at
1 or 2 bar of ethylene pressure in 50% 1-octene solutions
in toluene at 90 °C, but the catalyst activities were much
lower than previously observed with the very active
[Cp*-SiMe2N(tert-butyl)]TiX2 or [Cp-CMe2-P(cyclo-
hexyl)]TiX2/MAO catalyst systems.4,5,7 The ethene/1-
octene ratio in the obtained copolymer samples was
determined by 13C NMR spectroscopy.24 Figure 4 shows
a typical example. The copolymer obtained with the 7a /
MAO catalyst at 1 bar of ethene pressure has a
1
Found: C, 58.73; H, 9.53; N, 6.41. H NMR (toluene-d8, 599.8
MHz, 298 K): δ 3.05 (s, 12H, NCH3), 2.15 (1H), 1.95 (2H), 1.76
(2H), 1.58 (2H), 1.47 (2H), 1.28 (2H), 1.22 (2H) (each broad,
5
Cy), 2.08 (d, ∑(4J PH + J PH) ) 0.7 Hz, 6H, 2,5-CH3), 1.71 (s,
6H, 3,4-CH3), 0.65 (d, 3J PH ) 2.5 Hz, 6H, SiMe2). 13C{1H} NMR
(toluene-d8, 150.8 MHz, 298 K): δ 127.8 (C-2,5), 125.3 (C-3,4),
104.9 (C-1), 46.8 (d, 3J PC ) 6.1 Hz, NCH3), 37.5 (d, nJ PC ) 10.0
Hz, Cy), 34.8 (d, 1J PC ) 23.4 Hz, C-1′), 27.8 (d, nJ PC ) 10.2 Hz,
(21) Siegel, J . S.; Anet, F. A. J . Org. Chem. 1988, 53, 2629-2630.
(22) (a) Green, M. L. H.; Wong, L.-L.; Sella, A. Organometallics 1992,
11, 2660-2668 and references therein. (b) Kleier, D. A.; Binsch, G.
DNMR3; Indiana University, Bloomington, IN, 1970. Kleier, D. A.;
Binsch, G. J . Magn. Reson. 1970, 3, 146-160. Marat, K. XSIM;
University of Manitoba, 1997.
(23) (a) Brintzinger, H.-H.; Fischer, D.; Mu¨lhaupt, R.; Rieger, B.;
Waymouth, R. M. Angew. Chem. 1995, 107, 1255-1283; Angew. Chem.,
Int. Ed. Engl. 1995, 34, 1143-1170. (b) Kaminsky, W. J . Chem. Soc.,
Dalton Trans. 1998, 1413-1418. (c) Sinn, H.; Kaminsky, W. Adv.
Organomet. Chem. 1980, 18, 99-149.
4
Cy), 26.8 (s, Cy), 15.4 (d, ∑(3J PC + J PC) ) 8.9 Hz, 2,5-CH3),
2
10.9 (3,4-CH3), 5.1 (d, J PC ) 10.8 Hz, Si(CH3)2). GHSQC
(toluene-d8, 150.8/599.8 MHz, 298 K): δ(13C)/δ(1H) 46.8/3.05
(NCH3/NCH3), 37.5/1.95, 1.47; 27.8/1.76, 1.28; 26.8/1.58, 1.22
(Cy/Cy), 34.8 /2.15 (C-1′/1′-H), 15.4/2.08 (2,5-CH3/2,5-CH3),
10.9/1.71 (3,4-CH3/3,4-CH3), 5.1/0.65 (C-6 /6-H). GHMBC
(toluene-d8, 150.8/599.8 MHz, 298 K): δ(13C)/δ(1H) 127.8/2.08,
1.71 (C-2,5/2,5-CH3, 3,4-CH3), 125.3/2.08, 1.71 (C-3,4/2,5-CH3,
3,4-CH3), 104.9/2.08, 0.65 (C-1/2,5-CH3, 6-H). 31P{1H} NMR
(toluene-d8, 242.5 MHz): δ31P (ν1/2, T) 16.1 (20 Hz, 298 K), 11.4
(28 Hz, 273 K), 3.1 (51 Hz, 233 K), -1.6 (48 Hz, 213 K), -7.2
(24) (a) Randall, J . C. J MS-Rev. Macromol. Chem. Phys. 1989,
C29(2 & 3), 201-317. See also: (b) Wang, W.-J .; Kolodka, E.; Zhu, S.;
Hamielec, A. E. J . Polym. Sci. A 1999, 37, 2949-2957. (c) Liu, W.;
Ray, D. G., III; Rinaldi, P. L. Macromolecules 1999, 32, 3817-3819.

Me2Si-Bridged Cp/ Phosphido Group 4 Metal Complexes
Organometallics, Vol. 21, No. 20, 2002 4089
(70 Hz, 193 K). 29Si{INEPTRD} (toluene-d8, 39.8 MHz): δ -8.2
1.89 (C-3,4/2,5-CH3, 3,4-CH3), 104.7/2.18, 0.67 (C-1/2,5-CH3,
6-H), 40.8/3.33, 3.18, 0.94 (NCH2/NCH2CH3), 15.5/3.33, 3.18
(NCH2CH3/NCH2). 31P{1H} NMR (toluene-d8, 242.5 MHz): δ31P
(v1/2, T) -75.5 (40 Hz, 298 K), -79.5 (183 Hz, 253 K), -81.3
(40 Hz, 233 K), -83.1 (28 Hz, 213 K). 29Si{INEPTRD} (toluene-
1
(d, J PSi ) 33.1 Hz).
X-r ay Cr ystal Str u ctu r e An alysis of 7a: formula C21H41N2-
PSiTi, M ) 428.52, red crystal, 0.35 × 0.30 × 0.15 mm, a )
8.835(1) Å, b ) 9.865(1) Å, c ) 31.069(1) Å, R ) 89.50(1)°, â )
88.60(1)°, γ ) 63.88(1)°, V ) 2430.6(4) Å3, Fcalcd ) 1.171 g cm-3
,
d8, 202.6 MHz): δ -10.6 (d, J PSi ) 30.6 Hz).
1
µ ) 4.75 cm-1, empirical absorption correction via SORTAV
(0.851 e T e 0.932), Z ) 4, triclinic, space group P1h (No. 2), λ
) 0.710 73 Å, T ) 198 K, ω and æ scans, 15 211 reflections
collected ((h, (k, (l), (sin θ)/λ ) 0.66 Å-1, 11 200 independent
(Rint ) 0.028) and 7946 observed reflections (I g 2σ(I)), 489
refined parameters, R1 ) 0.057, wR2 ) 0.156, maximum
X-r ay Cr ystal Str u ctu r e An alysis of 7b: formula C25H49N2-
PSiZr, M ) 527.94, yellow crystal, 0.35 × 0.25 × 0.10 mm, a
) 9.371(1) Å, b ) 9.983(1) Å, c ) 16.397(1) Å, R ) 73.10(1)°, â
) 84.84(1)°, γ ) 83.74(1)°, V ) 1456.2(2) Å3, Fcalcd ) 1.204 g
cm-3, µ ) 4.87 cm-1, empirical absorption correction via
SORTAV (0.848 e T e 0.953), Z ) 2, triclinic, space group P1h
(No. 2), λ ) 0.710 73 Å, T ) 198 K, ω and æ scans, 13 774
reflections collected ((h, (k, (l), (sin θ)/λ ) 0.66 Å-1, 6849
independent (Rint ) 0.036) and 5713 observed reflections (I g
2σ(I)), 281 refined parameters, R1 ) 0.034, wR2 ) 0.075,
maximum (minimum) residual electron density 0.34 (-0.38)
e Å-3, hydrogens calculated and refined as riding atoms. Data
sets were collected with a Nonius KappaCCD diffractometer,
equipped with a Nonius FR591 rotating anode generator.
Programs used: data collection, COLLECT (Nonius BV, 1998);
data reduction, Denzo-SMN;25 absorption correction, SOR-
TAV;26 structure solution, SHELXS-97;,27 structure refine-
ment, SHELXL-97;28 graphics, DIAMOND29 and SCHAKAL.30
(minimum) residual electron density 1.12 (-0.61) e Å-3
hydrogens calculated and refined as riding atoms.
,
Bis(d ieth yla m id o)[((cycloh exylp h osp h id o-KP )d im eth -
ylsilyl)-η5-tetr a m eth ylcyclop en ta d ien yl]zir con iu m (7b).
Analogously to the method described above, 153 mg (0.50
mmol) of 5 in 5 mL of THF was reacted with 214 mg (0.47
mmol) of Cl2Zr(NEt2)2(THF)2 (6b) in 2 mL of THF. Workup as
described above gave 156 mg (59%) of 7b as an orange oil
(single crystals from pentane): mp 121 °C, 249 °C dec). Anal.
Calcd for C25H49N2PSiZr (528.0): C, 56.87; H, 9.35; N, 5.31.
1
Found: C, 56.33; H, 9.14; N, 5.07. H NMR (toluene-d8, 599.8
MHz, 298 K): δ 3.33, 3.18 (ABX3, each 4H, NCH2CH3), 2.18
5
(d, ∑(4J PH + J PH) ) 0.6 Hz, 6H, 2,5-CH3), 2.00 (m, 1H, 1′-H),
1.92, 1.50 (each m, each 2H, 2′-H), 1.89 (s, 6H, 3,4-CH3), 1.75,
1.25 (each m, each 2H, 3′-H), 1.55, 1.20 (each m, each 1H, 4′-
H), 0.94 (t, 3J HH ) 6.9 Hz, 12H, NCH2CH3), 0.67 (d, 3J PH ) 2.6
Hz, SiMe2). GCOSY (toluene-d8, 599.8 MHz, 298 K): δ(1H)/δ-
(1H) ) 3.33/3.18, 0.94 (NCH2/NCH2CH3, NCH2CH3), 1.92/1.50
(2′-CH2/2′-CH2), 1.75/ 1.25 (3′-CH2/3′-CH2), 1.55/1.20 (4′-CH2/
4′-CH2). 13C{1H} NMR (toluene-d8, 150.8 MHz, 298 K): δ 128.2
Ackn owledgm en t. Financial support from the Fonds
der Chemischen Industrie (and the BMBF) and the
Deutsche Forschungsgemeinschaft is gratefully acknowl-
edged. We thank Professor B. Rieger and co-workers for
helping us with the molecular weight determinations.
Su p p or tin g In for m a tion Ava ila ble: Tables giving de-
tails of the X-ray crystal structure analyses. This material is
available free of charge via the Internet at http://pubs.acs.org.
3
(d, ∑(2J PC + J PC) ) 1.5 Hz, C-2,5), 123.3 (C-3,4), 104.7 (d, ∑-
2
1
3
(2J PC + J PC) ) 13.0 Hz, C-1), 40.8 (d, J CH ) 130 Hz, J PC
)
1.9 Hz, NCH2CH3), 38.2 (d, 2J PC ) 11.7 Hz, C-2′), 32.2 (d, 1J PC
3
4
) 18.1 Hz, C-1′), 28.0 (d, J PC ) 10.9 Hz, C-3′), 26.7 (d, J PC
)
)
OM0200959
0.6 Hz, C-4′), 15.5 (1J CH ) 126 Hz, NCH2CH3), 15.2 (d, J CH
1
4
127 Hz, ∑(3J PC + J CP) ) 9.7 Hz, 2,5-CH3), 11.2 (1J CH ) 129
Hz, 3,4-CH3), 5.58 (d, 1J CH ) 120 Hz, 2J PC ) 10.8 Hz, Si(CH3)2).
GHSQC (toluene-d8, 150.8/599.8 MHz, 298 K): δ(13C)/δ(1H)
40.8/3.33, 3.18 (NCH2/NCH2), 38.2/1.92, 1.50 (C-2′/2′-CH2),
32.2/2.00 (C-1′/1′-CH), 28.0/1.75, 1.25 (C-3′/3′-CH2), 26.7/1.55,
1.20 (C-4′/4′-CH2), 15.5/0.94 (NCH2CH3/NCH2CH3), 15.2/2.18
(2,5-CH3/2,5-CH3), 11.2/1.89 (3,4-CH3/3,4-CH3), 5.58/0.67 (C-
6/6-H). GHMBC (toluene-d8, 150.8/599.8 MHz, 298 K): δ(13C)/
δ(1H) δ 128.2/2.18, 1.89 (C-2,5/2,5-CH3, 3,4-CH3), 123.3/2.18,
(25) Otwinowski, Z.; Minor, W. Methods Enzymol. 1997, 276, 307-
326.
(26) Blessing, R. H. Acta Crystallogr. 1995, A51, 33-37. Blessing,
R. H. J . Appl. Crystallogr. 1997, 30, 421-426.
(27) Sheldrick, G. M. Acta Crystallogr. 1990, A46, 467-473.
(28) Sheldrick, G. M. SHELXL-97; Universita¨t Go¨ttingen, Go¨ttingen,
Germany, 1997.
(29) Brandenburg, K. DIAMOND; Universita¨t Bonn, Bonn, Ger-
many, 1997.
(30) Keller, E. SCHAKAL; Universita¨t Freiburg, Freiburg, Germany,
1997.