Controlled alkene and alkyne insertion reactivity of a cationic zirconium complex stabilized by an open diamide ligand

Article abstract of DOI:10.1021/om970504e

The chemistry of electrophilic zirconium complexes stabilized by a sterically open diamide ligand has been studied. Treatment of Me₂Si(NLiCMe₃)₂ with ZrCl₄(THF)₂ afforded {Me₂Si(NCMe₃)₂}ZrCl₂(THF) ₂ (1), which, in solution, was in equilibrium with a dimeric zirconium dichloride species [{Me₂Si(NCMe₃)₂}ZrCl₂] ₂(THF). Complex 1 was converted to dialkyl complexes {Me₂Si(NCMe₃)₂}ZrR₂ (R = CH₂Ph, 4; CH₂CMe₃, 5) using MgBz₂(dioxane)_0.5 and LiCH₂CMe₃, respectively, but dimethylation was unsuccessful. Alkyl abstraction from 4 using B(C₆F₅)₃ cleanly afforded {Me₂Si(NCMe₃)₂}Zr(CH₂Ph){η ⁶-PhCH₂B(C₆F₅)₃} (6), in which the anion strongly coordinates to the benzylzirconium cation via the aromatic ring. Protonolysis of 4 using [PhMe₂NH][B(C₆F₅)₄] afforded the Lewis-base adduct [{Me₂Si(NCMe₃)₂}Zr{CH₂Ph)(NMe ₂Ph)]⁺ (7), whereas [Ph₃C][B(C₆F₅)₄] gave 1 equiv of Ph₃CCH₂Ph and a mixture of two cationic species, 9a/b, proposed to be monomeric and dimeric benzylzirconium cations. Reaction of 4 with 0.5 equiv of the trityl reagent afforded the dizirconium complex [{Me₂Si(NCMe₃)₂}₂Zr ₂(CH₂Ph)₃]⁺. Cations 6, 7, and 9a/b cleanly and rapidly reacted with 2-butyne to afford the single insertion product, [{Me₂Si(NCMe₃)₂}Zr{η¹,η ⁶C(Me)=C(Me)CH₂Ph]⁺, stabilized by a chelating π-coordination of the benzene ring of the hydrocarbyl ligand. Structurally similar insertion products were obtained from the reaction of 9a with a range of alkenes, [{Me₂Si(NCMe₃)₂}Zr{η¹,η ⁶-CH₂CH(R)CH₂Ph]⁺ (R = H, Me, n-Bu, CH₂Ph). Benzylborate adduct 6 also underwent single alkene insertion giving {Me₂Si(NCMe₃)₂}Zr{η¹-CH ₂CH(R)CH₂Ph}{η⁶-PhCH₂B(C ₆F₅)₃} (R = H, Me), stabilized by anion coordination to zirconium. The dramatic effects of anion, Lewis base, solvent, and substrate variation on the rate of insertion have been rationalized in terms of the facility of anion or base dissociation from the benzylzirconium cation.

Full text of DOI:10.1021/om970504e

5424
Organometallics 1997, 16, 5424-5436
Con tr olled Alk en e a n d Alk yn e In ser tion Rea ctivity of a
Ca tion ic Zir con iu m Com p lex Sta bilized by a n Op en
Dia m id e Liga n d
Andrew D. Horton* and J an de With
Shell Research and Technology Centre, Amsterdam, Postbus 38000,
1030 BN Amsterdam, The Netherlands
Received J une 13, 1997X
The chemistry of electrophilic zirconium complexes stabilized by a sterically open diamide
ligand has been studied. Treatment of Me2Si(NLiCMe3)2 with ZrCl4(THF)2 afforded {Me2-
Si(NCMe3)2}ZrCl2(THF)2 (1), which, in solution, was in equilibrium with a dimeric zirconium
dichloride species [{Me2Si(NCMe3)2}ZrCl2]2(THF). Complex 1 was converted to dialkyl
complexes {Me2Si(NCMe3)2}ZrR2 (R ) CH2Ph, 4; CH2CMe3, 5) using MgBz2(dioxane)0.5 and
LiCH2CMe3, respectively, but dimethylation was unsuccessful. Alkyl abstraction from 4
using B(C6F5)3 cleanly afforded {Me2Si(NCMe3)2}Zr(CH2Ph){η6-PhCH2B(C6F5)3} (6), in which
the anion strongly coordinates to the benzylzirconium cation via the aromatic ring.
Protonolysis of 4 using [PhMe2NH][B(C6F5)4] afforded the Lewis-base adduct [{Me2Si-
(NCMe3)2}Zr{CH2Ph)(NMe2Ph)]+ (7), whereas [Ph3C][B(C6F5)4] gave 1 equiv of Ph3CCH2Ph
and a mixture of two cationic species, 9a /b, proposed to be monomeric and dimeric
benzylzirconium cations. Reaction of 4 with 0.5 equiv of the trityl reagent afforded the
dizirconium complex [{Me2Si(NCMe3)2}2Zr2(CH2Ph)3]+. Cations 6, 7, and 9a /b cleanly and
rapidly reacted with 2-butyne to afford the single insertion product, [{Me2Si(NCMe3)2}Zr{η1,η6-
C(Me)dC(Me)CH2Ph]+, stabilized by a chelating π-coordination of the benzene ring of the
hydrocarbyl ligand. Structurally similar insertion products were obtained from the reaction
of 9a with a range of alkenes, [{Me2Si(NCMe3)2}Zr{η1,η6-CH2CH(R)CH2Ph]+ (R ) H, Me,
n-Bu, CH2Ph). Benzylborate adduct 6 also underwent single alkene insertion giving {Me2-
Si(NCMe3)2}Zr{η1-CH2CH(R)CH2Ph}{η6-PhCH2B(C6F5)3} (R ) H, Me), stabilized by anion
coordination to zirconium. The dramatic effects of anion, Lewis base, solvent, and substrate
variation on the rate of insertion have been rationalized in terms of the facility of anion or
base dissociation from the benzylzirconium cation.
In tr od u ction
and amido- and alkoxy-pyridines.8,9 In contrast to the
industrial application of cyclopentadienyl-amide cata-
lysts in ethene (co)polymerization,10 diamide catalysts
have, until very recently,11,12 been studied little, despite
the straightforward synthesis of group 4 diamide com-
The utility of “uniform site” metallocene-based alkene
polymerization catalysts1 has spawned an intensive
academic and industrial effort to develop related cata-
lysts in which the cyclopentadienyl groups are replaced
by other ligands. Much attention has focused on
nitrogen-containing ligands, such as porphyrins,2 tet-
raazaannulenes,3 tetradentate Schiff-base ligands,4 (hy-
droxyphenyl)oxazolines,5 benzamidinates,6 pyrollyls,7
(8) (a) Hakala, K.; Lo¨fgren, B.; Polamo, M.; Leskela¨, M. Macromol.
Rapid Commun. 1997, 18, 635. (b) Fuhrmann, H.; Brenner, S.; Arndt,
P.; Kempe, R. Inorg. Chem. 1996, 35, 6742. (c) Oberthu¨r, M.; Arndt,
P.; Kempe, R. Chem. Ber. 1996, 129, 1087.
(9) Nagy, S.; Krishnamurti, R.; Tyrell, J . A.; Cribbs, L. V.; Cocoman,
M. (Occidental) World Pat. Appl. WO 96/33202, 1996.
(10) (a) Stevens, J . C.; Timmers, F. J .; Schmidt, G. F.; Nickias, P.
N.; Rosen, R. K.; Knight, G. W.; Lai, S.-Y. (Dow) Eur. Pat. Appl. 416
815, 1990. (b) Cannich, J . A. M. (Exxon) Eur. Pat. Appl. 420 436, 1990.
(c) Chen, Y.-X.; Marks, T. J . Organometallics 1997, 16, 3649. (d)
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. (e) Shapiro,
P. J .; Cotter, W. D.; Schaefer, W. P.; Labinger, J . A.; Bercaw, J . E. J .
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ligands in polymerization catalysis, see the following: (a) Male, N. A.
M.; Thornton-Pett, M.; Bochmann, M. J . Chem. Soc., Dalton Trans.
1997, 2487. (b) Baumann, R.; Davis, W. M.; Schrock, R. R. J . Am.
Chem. Soc. 1997, 119, 3830. (c) J a¨ger, F.; Roesky, H. W.; Dorn, H.;
Shah, S.; Noltemeyer, M.; Schmidt, H.-G. Chem. Ber./ Recl. 1997, 130,
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1997, 16, 1810. (e) Scollard, J . D.; McConville, D. H. J . Am. Chem.
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C.; Vittal, J . J . Macromolecules 1996, 29, 5241. (g) Oberthu¨r, M.; Arndt,
P.; Kempe, R. Chem. Ber. 1996, 129, 1087. (h) Tinkler, S.; Deeth, R.
J .; Duncalf, D. J .; McCamley, A. Chem. Commun.1996, 2623. (i) Mack,
H.; Eisen, M. S. J . Organomet. Chem. 1996, 526, 81. (j) Cloke, F. G.
N.; Geldbach, T. J .; Hitchcock, P. B.; Love, J . B. J . Organomet. Chem.
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X Abstract published in Advance ACS Abstracts, November 15, 1997.
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S0276-7333(97)00504-9 CCC: $14.00 © 1997 American Chemical Society

Alkene and Alkyne Insertion Reactivity
Organometallics, Vol. 16, No. 25, 1997 5425
plexes13 and the wide potential for ligand variation. By
simple extrapolation from cyclopentadienyl-amide ca-
talysis10 and due to their extreme metal electrophilic-
ity,14 diamide complexes might be expected to act as
novel polymerization catalysts. We have recently re-
ported that cationic zirconium complexes stabilized by
amide ligands exhibit ethene and, in some cases, pro-
pene polymerization activity.15 In order to explore the
limits of steric unsaturation in diamide catalysis, we
choose to synthesize cationic complexes based on the
These differences were expected to result in an ex-
tremely high sensitivity of the reactivity of such dia-
mide-stabilized cations to donor molecule coordination.
This has indeed turned out to be the case, as the new
cationic complexes reported here, although generally
inactive in alkene polymerization, undergo controlled
single insertion reactivity with rates depending on the
anion, Lewis base, and solvent, as well as the substrate.
Controlled alkyne insertion into the Zr-methyl bond
of [Cp′2ZrMe]+ has previously been examined as a
model20,21 for alkene insertion: insertion of a second
alkyne molecule is generally slower than the first
insertion, allowing successive insertion products to be
isolated in some cases.20 Controlled insertion of alkenes
into a group 4 metallocene-hydrocarbyl bond has been
observed when the insertion product is particularly
stabilized, for example by a chelating Lewis-base coor-
dination.21 During the course of our studies, the single
insertion of alkenes into the Zr-benzyl bond of Zr(CH2-
Ph)3{PhCH2B(C6F5)3} and (C5Me5)Zr(CH2Ph)2{PhCH2B-
(C6F5)3} was described by Pellecchia:22 spectroscopic and
NMR evidence for stabilization of the single insertion
product by chelating coordination of the 3-phenylpropyl
ligand via the benzene ring was provided. Unfortu-
nately, the NMR studies were complicated both by the
rapid exchange of the different zirconium benzyl groups
and by aromatic ring current effects, and no attempt
was made to study the effect of anion or solvent
variation on insertion. We now report the preparation
of diamide-stabilized cationic benzyl complexes and the
study of their single insertion reactivity with 2-butyne
and alkenes.
“open” diamide ligand [Me2Si(NCMe3)2]2- 16-19
.
Ligand chelation rather than bridging diamide coor-
dination, as well as ligand robustness, were expected
to be favored by the presence of tert-butyl substituents
on nitrogen.16,17 In comparison to the well-studied
cyclopentadienyl-amide complexes, such as [{Me2Si-
(NCMe3)(C5Me5)}MR]+ (M ) Ti, Zr), putative diamide
analogues, [{Me2Si(NCMe3)2}MR]+, should be both elec-
tronically more unsaturated (maximum of a 10- com-
pared to 12-electron metal) and sterically more open.19
(12) For recent studies of group 4 complexes with nonbridged amide
ligands in polymerization catalysts, see the following: (a) Shah, S. A.
A.; Dorn, H.; Voight, A.; Roesky, H. W.; Parsini, E.; Schmidt, H.-G.;
Noltemeyer, M. Organometallics 1996, 15, 3176. (b) Fuhrmann, H.;
Brenner, S.; Arndt, P.; Kempe, R. Inorg. Chem. 1996, 35, 6742. (c)
Sasaki, T.; Shiraishi, H.; J ohoji, H.; Katayama, H. (Sumitomo) Eur.
Pat. Appl. 571 945, 1993. (d) Canich, A. M.; Turner, H. W. (Exxon)
World Pat. Appl. 92/12162, 1992.
(13) For recent references to other group 4 complexes with chelating
diamide ligands, see the following: (a) Blake, A. J .; Collier, P. E.; Gade,
L. H.; McPartlin, M.; Mountford, P.; Schubart, M.; Scowen, I. J . J .
Chem. Soc., Chem. Commun. 1997, 1555. (b) Grocholl, L.; Stahl, L.;
Staples, R. J . J . Chem. Soc., Chem. Commun. 1997, 1465. (c) Roger,
A. J .; Solari, E.; Floriani, C.; Chiesi-Villa, A.; Rizzoli, C. J . Chem. Soc.,
Dalton Trans. 1997, 2385. (d) Lee, L.; Berg, D. J .; Bushnell, G. W.
Organometallics 1997, 16, 2556. (e) Fryzuk, M. D.; Love, J . B.; Rettig,
S. J .; Young, V. G. Science 1997, 275, 1445. (f) Tsuie, B.; Swenson, D.
C.; J ordan, R. F.; Petersen, J . L. Organometallics 1997, 16, 1392. (g)
Gue´rin, F.; McConville, D. H.; Vittal, J . J . Organometallics 1996, 15,
5586. (h) Scollard, J . D.; McConville, D. H.; Vittal, J . J . Organometallics
1995, 14, 5478. (i) Gue´rin, F.; McConville, D. H.; Payne, N. C.
Organometallics 1995, 14, 5085. (j) Warren, T. H.; Schrock, R. R.;
Davis, W. M. Organometallics 1996, 15, 562. (k) Aoyagi, K.; Gantzel,
P. K.; Kalai, K.; Tilley, T. D. Organometallics 1996, 15, 923. (l)
Friedrich, S.; Gade, L. H.; Scowen, I. J .; McPartlin, M. Angew. Chem.,
Int. Ed. Engl. 1996, 35, 1338. (m) Friedrich, S.; Gade, L. H.; Scowen,
I. J .; McPartlin, M. Organometallics 1995, 14, 5344. (n) Friedrich, S.;
Gade, L. H.; Edwards, A. J .; McPartlin, M. J . Chem. Soc., Dalton Trans.
1993, 2861. (o) Clark, H. C. S.; Cloke, F. G. N.; Hitchcock, P. B.; Love,
J . B.; Wainwright, A. P. J . Organomet. Chem. 1995, 503, 333. (p) Cloke,
F. G. N.; Hitchcock, P. B.; Love, J . B. J . Chem. Soc., Dalton Trans.
1995, 25. (q) Herrmann, W. A.; Denk, M.; Albach, R. W.; Behm, J .;
Herdtweck, E. Chem. Ber. 1991, 124, 683.
Resu lts
Syn th esis of Dich lor ozir con iu m Com p lexes. The
known diamine ligand16,17 Me2Si(NHCMe3)2 was readily
prepared by reaction of Me2SiCl2 with a 4-fold excess
of Me3CNH2.23 Deprotonation with a 2-fold excess of
n-BuLi in hexane solution under reflux, followed by
cooling to -40 °C, afforded large colorless crystals of
the dilithium salt in 92% yield. Reaction of the dil-
ithium salt with an equimolar amount of ZrCl4 in
toluene gave a 1:1 mixture of the known bis(ligand)
complex {Me2SiN(CMe3)}2Zr17 and ZrCl4. In contrast,
reaction with ZrCl4(THF)2 in toluene (Scheme 1), fol-
lowed by extraction of the crude residue with a THF/
(14) (a) Shapiro, P. J .; Bunel, E.; Schaefer, W. P.; Bercaw, J . E.
Organometallics 1990, 9, 867. (b) Woo, T. K.; Margl, P. M.; Lohrenz,
J . C.; Blochl, P. E.; Ziegler, T. J . Am. Chem. Soc. 1996, 118, 13021. (c)
Fan, L.; Harrison, D.; Woo, T. K.; Ziegler, T. Organometallics 1995,
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(15) (a) Horton, A. D.; de With, J .; van der Linden, A. J .; van de
Weg, H. Organometallics 1996, 15, 2672. (b) Horton, A. D.; de With,
J . Chem. Commun. 1996, 1375.
(16) (a) J ones, R. A.; Seeberger, M. H.; Atwood, J . L.; Hunter, W. E.
J . Organomet. Chem. 1983, 247, 1. (b) Bu¨rger, H.; Beierersdorf, D. Z.
Anorg. Allg. Chem. 1979, 459, 111.
(17) For other examples of group 4 and 5 complexes containing the
[Me2Si(NCMe3)2]2- ligand, see the following: (a) Brauer, D. J .; Bu¨rger,
H.; Essig, E.; Geschwandtner, W. J . Organomet. Chem. 1980, 190, 343.
(b) Brauer, D. J .; Bu¨rger, H.; Liewald, G. R.; Wilke, J . J . Organomet.
Chem. 1986, 310, 317.
(18) For other examples of silyl-bridged diamide ligands in group 4
chemistry, see the following: (a) Mignani, G.; Seyferth, D. Synth. React.
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D. J .; Bu¨rger, H. Z. Anorg. Allg. Chem. 1981, 475, 56. (c) Bu¨rger, H.;
Geschwandtner, W.; Liewald, G. R. J . Organomet. Chem. 1983, 259,
145.
(20) (a) Horton, A. D.; Orpen, A. G. Organometallics 1992, 11, 8.
(b) Horton, A. D. J . Chem. Soc., Chem. Commun. 1992, 185. (c) Horton,
A. D.; Orpen, A. G. Organometallics 1991, 10, 3910. (d) Crowther, D.
J .; Baenziger, N. C.; J ordan, R. F. J . Am. Chem. Soc. 1991, 113, 1455.
(e) Kreuder, C.; J ordan, R. F.; Zhang, H. Organometallics 1995, 14,
2993. (f) J ordan, R. F.; LaPointe, R. E.; Bradley, P. K.; Baenziger, N.
Organometallics 1989, 8, 2892.
(21) For references to alkene and alkyne insertion reactivity involv-
ing hydrocarbyl ligands containing a Lewis base fragment, see the
following: Rodewald, S.; J ordan, R. F. J . Am. Chem. Soc. 1994, 116,
4491. Guram, A. S.; J ordan, R. F. J . Org. Chem. 1993, 58, 5595. Guram,
A. S.; Guo, Z.; J ordan, R. F. J . Am. Chem. Soc. 1993, 115, 4902. Guram,
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R. F.; Taylor, D. F. J . Am. Chem. Soc. 1991, 113, 1833. Guram, A. S.;
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D. F.; Baenziger, N. C. Organometallics 1990, 9, 1546. Guram, A. S.;
J ordan, R. F. J . Am. Chem. Soc. 1989, 111, 778.
(19) The silicon-bridged diamide ligand obviously occupies less space
at the metal than similarly substituted diamide ligands with longer
bridging groups (Si2 or C3): the endocyclic N-Ti-N angle of 83.5(3)°
in bis(ligand) complex {Me2Si(NCMe3)2}2Ti17a compared to that of
107.1° in {(Me2SiNMe)2}2Ti containing five-membered rings, see:
Bu¨rger, H.; Wiegel, K.; Thewalt, U.; Schomburg, D. J . Organomet.
Chem. 1975, 87, 301.
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Chem. 1994, 479, C9. (c) Pellecchia, C.; Grassi, A.; Zambelli, A. J .
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5426 Organometallics, Vol. 16, No. 25, 1997
Horton and de With
Sch em e 1
Sch em e 2
a single resonance for each of the CMe3 and SiMe2
groups in C7D8 at 75 °C.
hexane mixture, afforded, in 48% yield, a colorless
microcrystalline complex containing 2 equiv of THF per
diamide ligand and formulated as {Me2SiN(CMe3)2}-
ZrCl2(THF)2 (1). Pure crystalline 1 was obtained by
cooling a THF solution to -40 °C.
Dissolution of complex 1 in aromatic solvents or CD2-
Cl2 resulted in partial loss of THF and the observation
of resonances for approximately equal amounts (on the
basis of Zr atoms) of complex 1 and a second species 2
containing 0.5 equiv of THF per zirconium (eq 1).
Preliminary studies using diethyl ether instead of
toluene as the solvent in the reaction of Me2Si-
(NLiCMe3)2 with ZrCl4 have indicated that the mono-
ether adduct, 3, is cleanly formed (Scheme 1). Complex
3 was obtained in spectroscopically pure crystalline form
by cooling an ether/hexane solution of the crude product.
The greater steric bulk of Et2O than THF appears to
favor a five-coordinate monomeric structure for 3.
Interestingly, the base-free titanium analogue of com-
plexes 1-3, {Me2Si(NCMe3)2}TiCl2, has been shown by
X-ray structural analysis to exhibit a monomeric struc-
ture with a pseudotetrahedral titanium.17 For com-
parison, the complexes {Me2Si(NSiMe3)2}MCl2 (M ) Zr,
Hf) are believed to be polymeric in structure with
bridging chloride ligands (IR evidence); formation of a
soluble 1:1 adduct with diethyl ether (similar to 3) has
been reported.18
Although attempts to remove the THF in vacuo from
the crude product mixture at elevated temperatures led
to decomposition, complex 2 could be obtained as a
spectroscopically pure solid by cooling a dichloromethane/
hexane solution of 1 to -40 °C.
Dia lk ylzir con iu m Com p lexes. The dibenzyl com-
plex 4 and the dineopentyl complex 5 were obtained
from 1 using standard alkylation methodology, as shown
in Scheme 2. Crystallization of 4 from hexane at -40
°C afforded pure yellow crystalline product in 60% yield.
Cooling a pentane solution of 5 afforded colorless
crystals of the dineopentyl complex, which melted on
warming to 25 °C. The crystals contained 0.5 equiv of
(noncoordinated) THF as a solvent of crystallization,
removable in vacuo. The dialkyl complexes have been
1
characterized by H and 13C NMR spectroscopy and, in
the case of 4, by elemental analysis. A symmetrical
pseudotetrahedral geometry for the complexes is evi-
denced by the observation of single resonances for the
SiMe2, CMe3, and alkyl fragments. Despite the rather
New complexes 1 and 2 have been characterized by
1H and 13C NMR spectroscopy and, in the case of 1, by
elemental analysis. The observation of single reso-
nances for the SiMe2 and the CMe3 groups in 1 is
consistent with a pseudo-octahedral structure or, per-
haps, a lower symmetry species undergoing rapid THF
exchange. The latter is supported by the observation
of a more complex pattern of resonances on cooling a
toluene solution of 1 to -75 °C.
Complex 2 appears to be a dizirconium species. One
possible structure with bridging chloride ligands,18
which is consistent with the observation at 25 °C of
resonances for two inequivalent CMe3 groups and four
SiMe groups (or, in some cases, three in a 1:1:2 ratio),
is shown above. More rapid THF exchange at higher
tempeartures may be responsible for the observation of
1
high J CH coupling constant of 129 Hz for the Zr-benzyl
methylene in 4, normal η1-benzyl coordination is sug-
gested by the characteristic downfield location of the
ipso-carbon resonance at δ 145.5 ppm.24,25
The sterically undemanding nature of this diamide
ligand is reflected both in the facile formation, under
NMR conditions, of a dialkyl derivative with the bulky
CH(SiMe3)2 ligand (for comparison, in metallocene
chemistry, only the monoalkyl derivative (C5H5)2Zr{CH-
(SiMe3)2}Cl may be obtained)26 and the synthetic inac-
(24) (a) Scholz, J .; Rehbaum, R.; Thiele, K.-H.; Goddard, R.; Betz,
P.; Kru¨ger, C. J . Organomet. Chem. 1993, 443, 93. (b) Lkatesky, S. L.;
McMullen, A. K.; Niccolai, G. P.; Rothwell, I. P.; Huffman, J . C.
Organometallics 1985, 4, 902.

Alkene and Alkyne Insertion Reactivity
Organometallics, Vol. 16, No. 25, 1997 5427
Sch em e 3
cessibility of the dimethyl complex. Reaction of dichlo-
ride 1 with a 2-fold excess of LiMe in diethyl ether
afforded a poorly characterized mixture of complexes
exhibiting broad methyl resonances in the region δ 1.0-
0.2 ppm and containing coordinated THF. It is possible
that additional LiMe or LiCl coordinates to the putative
sterically open dimethylzirconium species.27
P r ep a r a tion of Ca tion ic Ben zylzir con iu m Com -
p lexes. Alkyl abstraction28-31 from dialkyl complexes
using Lewis acidic reagents or protonolysis were inves-
tigated as potential routes to diamide-based cationic
alkylzirconium complexes. Given the sterically open
nature of the silicon-bridged diamide ligand, it was
expected that the cations would exhibit distinct struc-
tural and reactive chemistry compared to the analogous
metallocene cations.
Addition of cold toluene to a mixture of dibenzyl
complex 4 and B(C6F5)3 at -30 °C resulted in a virtually
instantaneous intense orange color, indicating rapid
alkyl abstraction.28,29 The product exhibited high solu-
bility in toluene and was more conveniently isolated as
an orange precipitate in virtually quantitative yield on
mixing hexane solutions of the reactants. Large crystals
of 6 were obtained from a dichloromethane/hexane
solution at -40 °C. Unfortunately, attempts to char-
acterize 6 by X-ray structural analysis were frustrated
by loss of the solvent of crystallization. The complex
nances of inequivalent SiMe groups in all solvents
studied at 25 °C and up to 75 °C in C7D8 solution (1H
NMR). 2-D NMR COSY studies in C7D8 solution
indicated that anion coordination results in an upfield
shift of the o- and p-hydrogens of the B-benzyl (over-
lapping resonance at δ 6.1 ppm; free anion, δ 7.24 and
6.89 ppm, respectively), while the m-hydrogen resonance
is slightly downfield-shifted (δ 7.14 ppm; free anion, δ
7.04 ppm).32-34 The Zr-benzyl group exhibited aro-
matic resonances at δ 6.69, 6.85, and 7.08 ppm (o-, p-,
and m-hydrogens, respectively).24,25 Caution should be
exercised in drawing conclusions on the exact coordina-
tion mode of the anion and Zr-benzyl group, based on
the benzyl 1H NMR resonances, because of possible ring
1
has been characterized by H, 11B, 13C, and 19F NMR
spectroscopy as a cationic benzylzirconium species
coordinated by the [PhCH2B(C6F5)3]- anion (Scheme
3).32-34
Strong nonfluxional anion coordination in complex 6
1
resulted in the observation of H and 13C NMR reso-
(25) For examples of benzyl coordination in cationic complexes, see
the following: (a) Pellecchia, C.; Immirzi, A.; Pappalardo, D.; Peluso,
A. Organometallics 1994, 13, 3773. (b) Bochmann, M.; Lancaster, S.
J . Organometallics 1993, 12, 633. (c) Bochmann, M.; Lancaster, S. J .
Makromol. Chem., Rapid Commun. 1993, 14, 807. (d) Crowther, D.
J .; Borkowsky, S. L.; Swenson, D.; Meyer, T. Y.; J ordan, R. F.
Organometallics 1993, 12, 2897. (e) Borkowsky, S. L.; Baenziger, N.
C.; J ordan, R. F. Organometallics 1993, 12, 486. (f) J ordan, R. F.;
LaPointe, R. E.; Bajgur, C. S.; Echols, S. F.; Willett, R. J . Am. Chem.
Soc. 1987, 109, 4111. (g) Bhandari, G.; Kim, Y.; McFarland, J . M.;
Rheingold, A. L.; Theopold, K. H. Organometallics 1995, 14, 738. (h)
Amor, J . I.; Cuenca, T.; Galakhov, M.; Royo, P. J . Organomet. Chem.
1995, 497, 127.
1
current effects.22 Interestingly, the aromatic H NMR
resonances are highly sensitive to the solvent: in C6D5-
Br and in CD2Cl2 solutions, no far-downfield B-benzyl
resonances were observed.
Anion coordination to zirconium via a π-benzene
interaction was clearly indicated by the characteristic
downfield location of the B-benzyl ipso-carbon reso-
nance at δ 160.4 ppm in 6, compared to δ 148.5 for the
free anion (C2D2Cl4).32 The similar shift of the ipso-
carbon in C6D6 solution (δ 160.1 ppm) suggests that the
solvent-dependence of the 1H NMR resonances may
reflect only very subtle structural differences. The
downfield location of the Zr-benzyl ipso-carbon (δ 147.6)
(26) Lappert, M. F.; Riley, P. I.; Yarrow, P. I. W.; Atwood, J . L.;
Hunter, W. E.; Zaworotko, M. J . J . Chem. Soc., Dalton Trans. 1981,
814.
(27) LiMe coordination to lanthanide metals is well-precedented,
see: Schaverien, C. J . Adv. Organomet. Chem. 1994, 34, 283.
(28) (a) Massey, A. G.; Park, A. J . J . Organomet. Chem. 1966, 5,
218. (b) Massey, A. G.; Park, A. J . J . Organomet. Chem. 1964, 2, 245.
(29) (a) Chen, Y.-X.; Stern, C. L.; Yang, X.; Marks, T. J . J . Am. Chem.
Soc. 1996, 118, 12451. (b) Deck, P. A.; Marks, T. J . J . Am. Chem. Soc.
1995, 117, 6128. (c) Yang, X.; Stern, C. L.; Marks, T. J . J . Am. Chem.
Soc. 1994, 116, 10015. (d) Yang, X.; Stern, C. L.; Marks, T. J . J . Am.
Chem. Soc. 1991, 113, 3623. (e) Siedle, A. R.; Newmark, R. A. J .
Organomet. Chem. 1995, 497, 119. (f) Bochmann, M.; Lancaster, S. J .;
Hursthouse, M. B.; Malik, K. M. A. Organometallics 1993, 12, 2235.
(30) (a) Ewen, J . A.; Elder, M. J . (Fina) Eur. Pat. Appl. 426 637,
1991. (b) Chien, J . C. W.; Tsai, W.-M.; Rausch, M. D. J . Am. Chem.
Soc. 1991, 113, 8570.
1
and the “normal” J CH coupling constant (123 Hz) for
the methylene group at δ 52.4 ppm are consistent with
η1-benzyl coordination to zirconium.24,25 In this context,
the somewhat downfield location of the Zr-benzyl o-H
in 6 (C7D8, δ 6.69 ppm) may reflect the ring current
effect of the B-benzyl.
We have previously shown that unlike 11B spectros-
copy, which is relatively insensitive to anion coordina-
tion, 19F NMR spectroscopy is a very useful probe of the
coordination of alkylborate anions, [RB(C6F5)3]-, to
cationic complexes, insensitive to solvent or ring-current
effects.15 A difference in the chemical shifts of the meta-
and para-fluorine resonances [∆δ(m,p-F)] greater than
(31) Turner, H. W.; Hlatky, G. G. (Exxon) Eur. Pat. Appl. 277 004,
1988.
(32) For examples of the coordination of [PhCH2B(C6F5)3]- to a
cationic d0 metal center, see the following: (a) Pellecchia, C.; Grassi,
A.; Immirzi, A. J . Am. Chem. Soc. 1993, 115, 1160. (b) Pellecchia, C.;
Immirzi, A.; Grassi, A.; Zambelli, A. Organometallics 1993, 12, 4473.
(c) Pellecchia, C.; Grassi, A.; Zambelli, A. J . Mol. Catal. 1993, 82, 57.
(33) For examples of the coordination of [B(C6H5)4]- to a cationic d0
metal center, see the following: (a) Horton, A. D.; Frijns, J . H. G.
Angew. Chem., Int. Ed. Engl. 1991, 30, 1152. (b) Bochmann, M.; J aggar,
A. J .; Nicholls, J . C. Angew. Chem., Int. Ed. Engl. 1990, 29, 780. (c)
Bochmann, M.; Karger, G.; J aggar, A. J . J . Chem. Soc., Chem.
Commun. 1990, 1038. (d) Schaverien, C. J . Organometallics 1992, 11,
3476.
(34) For examples of the coordination of a benzene ring to a cationic
group 4 metal center, see the following: (a) Lancaster, S. J .; Robinson,
O. B.; Bochmann, M.; Coles, S. J .; Hursthouse, M. B. Organometallics
1995, 14, 2456. (b) Gillis, D. J .; Tudoret, M.-J .; Baird, M. C. J . Am.
Chem. Soc. 1993, 115, 2543. (c) Pellecchia, C.; Grassi, A.; Immirzi, A.
J . Am. Chem. Soc. 1993, 115, 1160.

5428 Organometallics, Vol. 16, No. 25, 1997
Horton and de With
Sch em e 4
3.5 ppm is associated with coordination, whereas a value
less than 3.0 ppm indicates noncoordination. In the
case of 6, anion coordination is associated with a
significant downfield shift of the m- and p-fluorine
resonances relative to those of the free anion, with a
∆δ(m,p-F) value of 4.1 ppm; the ortho-fluorine resonance
is much less strongly shifted on coordination.
The high solubility of 6 in toluene or benzene solution
(0.3 M) is also consistent with benzylborate anion
coordination to the metal, rather than a solvent-
separated ionic structure or facile anion dissociation.
Strong anion coordination in 6 may also explain the high
stability in chlorinated solvents: dichloromethane solu-
tions at 25 °C decomposed slowly over several hours,
whereas solutions in 1,1,2,2-tetrachloroethane were
stable over several days. Solutions of 6 in bromoben-
zene or toluene at 25 °C remained unchanged over
prolonged periods, but decomposition was accelerated
in C7D8 at 75 °C: clean conversion over 2 h to two
organometallic products and a mixture of boranes,
B(Bz)n(C6F5)3-n (n ) 1-3) was observed by 1H NMR
spectroscopy. The zirconium products have been ten-
tatively identified as {Me2Si(NCMe3)2}Zr(CH2Ph)(C6F5)
and {Me2Si(NCMe3)2}Zr(C6F5)2, resulting from pen-
tafluorphenyl-benzyl exchange between zirconium and
boron. There are a number of literature examples of
pentafluorphenyl transfer from [RB(C6F5)3]- (R ) alkyl)
to cationic metallocene or benzamidinate cations,6e,29c
whereas phenyl transfer from [B(C6F5)4]- and related
fluorinated-tetraphenylborate anions is less common.35
Both the benzylborate anion in 6 and the N,N-
dimethylaniline in 7 were cleanly displaced by THF
(Scheme 3). The bis(THF) adduct 8 was conveniently
isolated as a colorless solid by protonolysis of 4 in THF
solution, followed by precipitation and washing with
hexane. Solutions of 8 exhibited 1H and 13C NMR
resonances for a single highly symmetric species. How-
ever, rapid THF exchange in solution is indicated by
the observation of dramatic changes in the cation 1H
NMR shifts and of averaged THF resonances on addi-
tion of excess THF.
Abstraction of a hydrocarbyl group using the trityl
reagent, [Ph3C][B(C6F5)4],30 has been widely utilized in
metallocene chemistry for the formation of highly elec-
trophilic Lewis-base-free cations. Reaction with diben-
zyl 6 cleanly afforded 1 equiv of Ph3CCH2Ph, but the
organometallic product mixture was rather complex. In
C6D5Br solution, an insoluble orange product mixture
was obtained. The same mixture of two complexes (9a
and 9b) was conveniently formed in CD2Cl2 solution,
in which it is soluble and relatively stable (in the
absence of excess trityl reagent). The noninterconvert-
ing complexes, obtained in a 3:1 ratio (based on Zr
atoms), reacted with THF to give known bis(THF)
complex 8 and another THF adduct, again in a 3:1 ratio.
This and the fact that the relative amount of 9a formed
in the reaction increases on decreasing the reaction
concentration has led us to propose that complex 9a is
a monomeric cationic and 9b a dimeric dicationic species
(Scheme 4).
Each complex exhibits a 2:2:1 pattern of downfield
resonances (δ 8.0-7.4 ppm) for the benzyl group and
single ZrCH2, CMe3, and SiMe2 resonances. Extensive
speculation on the structures of 9a and 9b is unwar-
ranted in the absence of 13C NMR data (due to the low
solubility) or X-ray structural data. However, the
downfield location of the ring resonances of “monomeric”
9a suggest that the presumed ηn-benzyl coordination
likely involves a very significant interaction with the
aromatic ring.37 The equivalent benzyl ligands in 9b
might, perhaps, bridge the two zirconium atoms via a
σ-interaction with one metal (ZrCH2) and a π-interaction
of the ring with the other.37 These unusual bonding
modes would be expected to be favored by the sterically
open environment at zirconium.
Protonolysis of dibenzyl 4 was found to be a clean
route to a cationic complex. Addition of C6D5Br or C2D2-
Cl4 at -30 °C to a mixture of 4 and [PhMe2NH]-
[B(C6F5)4]31 at -30 °C resulted in the almost instanta-
neous formation of an orange complex characterized by
1H and 19F NMR spectroscopy as the benzyl cation, 7,
stabilized by coordination of the NMe2Ph coproduct of
protonolysis (Scheme 3). Although solutions of complex
7 were found to be stable over 1 h at 25 °C, no attempt
was made to isolate the complex, as such efforts
normally lead to poorly defined oils with less than 1
equiv of Lewis base per metal.
Coordination of NMe2Ph is reflected in the observa-
tion of 1H NMR resonances for inequivalent SiMe groups
above and below the SiN2Zr plane (C2D2Cl4, -25 °C) and
resonances (identified by 2-D COSY) for the meta- and
para-phenyl hydrogens (δ 7.55 and 7.11 ppm, respec-
tively) downfield from the trace of free aniline being
present (δ 7.25 and 7.00 ppm, respectively); the shift of
the ortho-hydrogen is identical to that of the free base.
The presence of resonances for a small amount of free
aniline in 7 is consistent with aniline exchange being
slow on the NMR time scale. The NMe2Ph-Zr interac-
tion might involve either nitrogen atom or π-benzene
ring coordination, but it is not possible to distinguish
these alternative modes due to the the possible ring-
current effect of the benzyl ligand.4,20c,36 As expected,
no evidence was found for coordination of the [B(C6F5)4]-
counteranion: 19F NMR resonances were unperturbed
from the free anion values.
(35) J ia, L.; Yang, X.; Stern, C. L.; Marks, T. J . Organometallics
1997, 16, 842.
(36) For examples of the cooordination of NMe2Ph to a cationic group
4 metal, see refs 4 and 19c and the following: Grossman, R. B.; Doyle,
R. A.; Buchwald, S. L. Organometallics 1991, 10, 1501.
(37) A structurally characterized case of η7-benzyl coordination to
zirconium has recently been reported, see: Pellecchia, C.; Immirzi, A.;
Pappalardo, D.; Peluso, A. Organometallics 1994, 13, 3773.

Alkene and Alkyne Insertion Reactivity
Organometallics, Vol. 16, No. 25, 1997 5429
Sch em e 5
The reaction of dibenzyl 4 with 0.5 equiv of the trityl
reagent at -30 °C in dichloromethane gave 0.5 equiv
of Ph3CCH2Ph and an interesting dizirconium complex,
10, containing three benzyl groups (Scheme 4). At-
tempts to obtain crystalline material were unsuccessful,
and the complex was isolated as an orange solid by
hexane addition to the reaction mixture. The dizirco-
nium complex gave, with excess THF, a 1:1 mixture of
recovered 4 and bis(THF) cation 8. Complex 10 was also
formed on reaction of 4 with <1 equiv of the borane or
N,N-dimethylanilinium reagent, but in this case, an
equilibrium mixture of 4, the dimer, and the monome-
tallic benzyl cations, 6 or 7, respectively, was observed.
Resonances for two kinds of benzyl ligands in 10 in a
1
2:1 ratio have been identified by H NMR (2-D COSY)
1
and 13C NMR spectroscopy. The rather large J CH
values associated with the ZrCH2 groups of 130.5 Hz (δ
53.8 ppm, 2C) and 132.5 Hz (δ 53.3 ppm, 1C) might be
consistent with ηn-benzyl coordination. However, the
downfield location of the ipso-carbon resonances at δ
144.4 (2C) and 162.2 ppm (1C) appear more in line with
η1-benzyl coordination. The observation of resonances
for equivalent CMe3 groups and two kinds of SiMe
groups in a 1:1 ratio is consistent with a symmetrical
structure in which one benzyl group symmetrically
bridges the zirconium atoms, which are also coordinated
by terminal benzyl and diamide ligands.38 Related
methyl-bridged dimetallic complexes of the form
[(L2MMe)2(µ-Me)]+ are known in metallocene and dia-
mide chemistry.15a,29a,39
Sch em e 6
Partly driven by the mechanistic interest in the
â-methyl elimination reaction, preliminary studies were
also made of neopentyl group abstraction from dine-
opentyl complex 5. The reaction of 5 with B(C6F5)3 is
slow at 25 °C, requiring the use of a 3-fold excess of
borane and long reaction times. Under these conditions
(2 h, C6D5Br), a pale yellow complex tentatively identi-
fied as neopentyl cation 11 was formed, contaminated
by a small amount of 5. The [Me3CCH2B(C6F5)3]- anion
exhibited resonances at δ 2.09 (BCH2) and 0.97 ppm
(CMe3), which did not change on addition of THF. The
cationic neopentyl species exhibited two CMe3 reso-
nances (18H, 9H) and one SiMe2 resonance (6H), as
expected. It is likely that the ionic complex is stabilized
by weak solvent coordination. No evidence for the
formation of 2-methyl-1-propene by â-methyl elimina-
tion was obtained.
Two minor species were obtained, one of which is
probably the methyl cation obtained by elimination of
2-methyl-1-propene (0.1 equiv), while the identity of the
other species is uncertain. Protonolysis of 5 in THF
solution using [PhMe2NH][B(C6H5)4], followed by prod-
uct precipitation and washing with hexane, afforded bis-
(THF) adduct 12 as a colorless solid, characterized by
1H and 13C NMR spectroscopy (Scheme 5). Partial THF
dissociation occurs on dissolution of neopentyl cation 12
in C6D5Br. In addition to the concentration-dependent
1H NMR resonances of 12, additional minor resonances
were observed, which disappear with excess THF, and
are tentatively ascribed to a monoTHF adduct.
Con tr olled In ser tion of Un sa tu r a ted Su bstr a tes.
Study of the reaction of electrophilic early transition
metal (ETM) complexes with unsaturated molecules can
give important information on such fundamental steps
in catalysis as insertion, chain transfer, and decomposi-
tion. Understanding the effect of ligand and anion
variation on these steps should assist in the develop-
ment of superior catalysts. As already discussed,
controlled insertion of alkenes and alkynes in metal-
hydocarbyl bonds has previously been examined as a
model for alkene insertion during polymerization.20,21
We have now observed controlled alkyne and alkene
insertion in diamide-stabilized complexes.
Reaction of 5 with [PhMe2NH][B(C6F5)4] in C6D5Br
solution afforded one major organometallic species, as
well as 1 equiv of CMe4 (Scheme 5). The major product
is tentatively proposed to be a neopentyl cation, on the
basis of the observation of resonances for CMe3 (2:1
ratio), SiMe2 (1:1 ratio), and ZrCH2 (δ 0.37 ppm) groups
and coordinated NMe2Ph. The ortho- and para-phenyl
hydrogens (δ 6.41, 6.52 ppm, respectively) of the coor-
dinated Lewis base are shifted upfield from the free
molecule, the meta-hydrogen downfield (δ 7.18 ppm).
(38) For examples of different bridging benzyl coordination modes,
see the following: Bhandari, G.; Rheingold, A. L.; Theopold, K. H.
Chem. Eur. J . 1995, 1, 199.
(39) Bochmann, M.; Lancaster, S. J . Angew. Chem., Int. Ed. Engl.
1994, 33, 1634.
(40) (a) Horton, A. D.; Orpen, A. G. Organometallics 1996, 15, 2675.
(b) Guo, Z.; Swenson, D. C.; J ordan, R. F. Organometallics 1994, 13,
1424. (c) Hajela, S.; Bercaw, J . E. Organometallics 1994, 13, 1147. (d)
Watson, P. L.; Roe, D. C. J . Am. Chem. Soc. 1982, 104, 6471.
Reaction of a small excess of 2-butyne with benzylzir-
conium cations 6, 7, or 9a /b afforded the cationic
complex 13, stabilized by the chelating coordination of
the phenyl ring of the hydrocarbyl ligand to zirconium
(Scheme 6). Assuming η6 ring coordination, the zirco-
nium center in the single insertion product may adopt

5430 Organometallics, Vol. 16, No. 25, 1997
Horton and de With
Sch em e 7
F igu r e 1. Hydrogen atom labeling in complexes 15a -17a .
14b-17b, and by the NMR identification of PhCH2CH-
(R)CH3 formed on hydrolysis.
All of the insertion products exhibited phenyl reso-
nances in the region δ 8.1-7.8 ppm in CD2Cl2 solution,
characteristic of a chelating ring coordination, as shown
in Scheme 7,32-34 similar to complex 13. More upfield
ring resonances were observed in C6D5Br solution (δ
7.52-7.38 ppm). Ring coordination was also reflected
in the observation of a downfield resonance for the ipso-
carbon at δ 159.0 ppm in 16a , which shifted to δ 143.0
ppm in THF adduct 16b. The R-, â-, and γ-hydrogens
of the Zr-trimethylene fragment in 14a resonated at δ
1.08, 2.62, and 3.11 ppm, respectively.21 Such downfield
resonances were found to be highly characteristic of
chelating coordination and shifted upfield to δ 0.44, 2.06,
and 2.44 ppm, respectively, in THF adduct 14b.
Of course, the 1H NMR spectra of the substituted
complexes were more complicated than that of 14a , with
resonances for five inequivalent hydrogens in the three-
carbon linking group. For 16a and 17a , 2-D COSY
NMR analysis was used to assign the resonances. In
the 1-hexene insertion product 16a (Figure 1), reso-
nances for two diasterotopic methylene groups were
a formal 16-electron configuration. The reaction with
9a /b in dichloromethane was almost instantaneous at
25 °C, as shown by the rapid change in the solution color
from orange to yellow. The reaction of 6 with 2-butyne
(3-fold excess) in C6D5Br solution was slightly slower
(complete in 5 min) and in toluene much slower (75%
in 20 min). This difference presumably reflects stronger
anion coordination to zirconium (less facile dissociation)
in the less polar solvent. Complex 13, with [BzB(C6F5)3]-
as a noncoordinating anion, was obtained in analytically
pure yellow microcrystalline form on cooling a dichlo-
romethane/hexane solution to -40 °C.
Complex 13 has been further characterized by 1H, 11B,
13C, and 19F NMR spectroscopy and by the clean
formation of PhCH2CMedCHMe on hydrolysis. The
cation exhibits resonances for inequivalent SiMe groups,
equivalent CMe3 groups, and the ZrC(Me)dC(Me)CH2-
Ph fragment. The far-downfield location of the phenyl
group resonances at δ 8.16 (o-H), 8.12 (m-H), and 7.88
2
observed at δ 1.88/0.03 ppm (Ha, Hb, respectively, J HH
1
ppm (p-H) in the H NMR spectrum (CD2Cl2) and the
) 13.5 Hz, ZrCH2) and δ 3.42/2.55 ppm (He, Hd,
respectively, 2J HH ) 11.8 Hz, CH2Ph), together with the
-CH(n-Bu)- resonance at δ 2.41 ppm. The observation
of a significant long-range coupling between Ha and Hd
(4J HH ) 1.7 Hz), also found by Pellecchia in closely
related adducts,22 is consistent with a sterorigid W-
conformation of the four bonds joining the two hydro-
gens.
observation of free anion resonances (in particular, for
[BzB(C6F5)3]-) are consistent with coordination of the
phenyl ring of the hydrocarbyl ligand to zirconium.32-34
The coordinated ring resonates at δ 156.8 (ipso-C), 136.4
(o/m-C), 130.4 (o/m-C), and 127.0 ppm (p-C) in the 13C
NMR spectrum. Addition of excess THF results in
dissociation of the phenyl ring giving adduct 13b
1
(Scheme 6), exhibiting “normal” phenyl H NMR reso-
Complex 17a was synthesized in order to examine
whether exchange of the coordinated and free benzene
rings occurred. Apart from some slight broadening of
the hydrocarbyl ligand resonances at 50 °C, there was
no evidence for ring exchange and the inequivalency of
the methyl groups on silicon was maintained. It is clear
that the benzene ring coordinates strongly to the
zirconium center in 14a -17a , presumably affording
(with amide-Zr π-bonding) a 16-electron metal center.
Complex 6 also cleanly inserted one molecule of
ethene or propene into the Zr-benzyl bond, but replace-
ment of the [B(C6F5)4]- by the [BzB(C6F5)3]- anion
resulted both in a dramatic deceleration of the reaction
and in a remarkably different product structure (eq 2).
Ethene insertion in 6 was 60% complete in 60 min (4.5
mL of ethene added to 0.03 mmol of 6 in 0.7 mL CD2-
Cl2 at 25 °C), compared to 100% complete in 5 min at
25 °C for 9a . As with 2-butyne insertion, the nature of
the solvent also plays an important role, the reaction
rate decreases as the solvent polarity decreases (bro-
mobenzene-d5, t1/2 of 76 min; toluene, 20% reaction in
nances at δ 7.24 (m,p-H) and 7.13 ppm (o-H).
Sin gle In ser tion of Alk en es. A remarkable aspect
of the fomation of 13 is that both the “monomeric” and
“dimeric” isomers 9a and 9b, respectively, reacted to
give 13. Alkenes also gave single-insertion products,
but in this case only 9a was reactive; 9b remained as a
minor contaminant in the product. A range of alkenes
afforded cationic single insertion products 14a -17a ,
stabilized by a chelating coordination of a benzene ring
(Scheme 7). In CD2Cl2 solution, the reaction was
complete within 2-20 min at 25 °C (depending on the
alkene). The products of the insertion of 1-hexene (16a )
and allylbenzene (17a ) were isolated as yellow solids,
free of 9b, by cation formation in the presence of excess
alkene, followed by hexane addition. Repeated attempts
to obtain ethene insertion product 14a in solid form led
only to unidentified decomposition products. As the
complexes could not be obtained in analytically pure
1
form, they were characterized by H and (for 16a ) 13C
NMR spectroscopy, by the formation of the THF adducts

Alkene and Alkyne Insertion Reactivity
Organometallics, Vol. 16, No. 25, 1997 5431
Sch em e 8
20 h). Propene insertion in 6 was even slower, with a
t1/2 of 280 min in C6D5Br solution.
In complexes 14c and 15c, strong anion coordination
to zirconium resulted in noncoordination of the benzene
ring of the 3-phenylpropyl ligand. For 14c (CD2Cl2), this
was reflected in the upfield location of the phenyl
resonances at δ 7.6-7.1 ppm, compared to δ 8.0 ppm in
14a , and of the R-, â-, and γ-hydrogen resonances of the
trimethylene group at δ 0.60, 1.88, and 2.45 ppm,
respectively, compared to δ 1.08, 2.62, and 3.11 ppm in
14a . Coordination of the [BzB(C6F5)3]- anion was very
clearly reflected in the large value of ∆δ(m,p-F) of 4.0
ppm in the 19F NMR spectrum.
characterized product mixtures being obtained with
excess alkyne over long periods. The low reactivity and
lack of catalysis are presumably the result of strong
coordination of the chelating hydrocarbyl ligand, the
anion [BzB(C6F5)3]-, N,N-dimethylaniline, or solvent to
the sterically open zirconium cation. The neopentyl
cations appear more reactive toward ethene: cation 11
and the related N,N-dimethylaniline adduct rapidly
polymerized excess ethene (minutes) under NMR condi-
tions.
To complete the study of the alkene reactivity of the
sterically open benzyl cations, NMe2Ph adduct 7 was
examined in C6D5Br solution. Single ethene insertion
was complete within 11 min, whereas propene insertion
required 25 min. As shown in Scheme 8, a mixture of
the already discussed chelate product 14a /15a and a
nonchelated species with coordinated NMe2Ph (14d ,
15d ) was obtained. As expected, substitution of the
trimethylene group favored ligand chelation, with 15a
as the major species present (78%) in the propene
reaction, whereas with ethene, 14a was the minor
component (35%). The mixtures of 14a /14d and 15a /
15d were cleanly converted to THF adducts 14b and
15b, respectively, with an excess of the Lewis base.
Far-upfield resonances of the ortho- and para-
hydrogens of the coordinated NMe2Ph ligand in 14d
were observed at δ 6.47 and 6.34 ppm, respectively,
indicating strong Lewis-base coordination, perhaps even
involving Ph-N rather than N-Zr coordination. The
hydrocarbyl ligand in 14d afforded a similar resonance
pattern to the related adducts containing coordinated
THF or [BzB(C6F5)3]-. For example, the R-, â-, and
γ-hydrogen resonances for the trimethylene group in
14d were located at δ 0.2 (obscured), 1.86, and 2.44 ppm,
respectively.
Eth en e P olym er iza tion Rea ctivity? We have
shown that cationic benzylzirconium complexes undergo
clean single insertion reactions with alkenes and 2-bu-
tyne, the rate of insertion increasing in the series
1-alkenes < ethene < 2-butyne. The insertion rate was
higher for the more poorly coordinating anion [B(C6F5)4]-
and in more polar solvents. Remarkably, the alkene
reaction does not proceed beyond the single insertion
product, with no polymerization under NMR conditions.
(In some cases, a trace of polyethylene (PE) was formed
almost instantaneously, but the polymer yield did not
increase during the reaction and probably arose from
catalysis by a trace impurity). Only for the 2-butyne
reaction was there evidence for further reaction, un-
The ethene polymerization activity of the electrophilic
complexes was also briefly examined under high-pres-
sure conditions. Benzyl complex 6 afforded only traces
of polyethene in toluene or dichloromethane solvent (25
°C, 20 bar). The product of the reaction of dibenzyl
complex 4 with the trityl reagent exhibited an activity
of 330 g/g of Zr‚h when tested under more forcing
conditions in dichloromethane solvent (0.69 g of PE from
0.04 mmol of catalyst, 50 °C, 20 bar, 30 min).
Neopentyl cation 7 was also found to be inactive in
toluene solvent, but the related cation obtained by
protonolysis exhibited a (low) activity of 130 g/g of Zr‚h
in bromobenzene (0.37 g of PE from 0.03 mmol of
catalyst, 25 °C, 20 bar, 40 min).
For comparison, dichloride complex 1, in combination
with MAO in toluene at 25 °C, showed an activity for
PE of 700 g/g of Zr‚h (0.70 g of PE from 0.01 mmol of
catalyst, 2.0 mmol of MAO, 20 bar, 30 min). Increasing
the temperature did not result in a significantly in-
creased activity with MAO as the cocatalyst: at 44 °C,
a PE activity of 370 g/g of Zr‚h was observed (0.37 g of
PE from 0.01 mmol of catalyst, 5.0 mmol of MAO, 3.2
bar, 120 min), whereas at 60 °C, only traces of PE were
obtained. Complex 1 with MAO afforded no polypro-
pene under similar conditions. Given the low alkene
polymerization activities, no attempt was made to
systematically investigate the effect of the process
conditions on catalysis or to further characterize the
polymers formed.
Discu ssion
Application of the methodology developed in metal-
locene chemistry has allowed a range of cationic diamide
complexes of zirconium to be synthesized by alkyl
abstraction. Recurring features of this chemistry are
the strong anion or Lewis base coordination to the
diamide cations and, in the absence of such donors, the
apparent formation of oligomeric cations. These fea-

5432 Organometallics, Vol. 16, No. 25, 1997
Horton and de With
tures may be traced to the high steric and electronic
from the preference of such sterically crowded complexes
for coordination of alkene rather than a bulky anion or
solvent/base. Higher polymerization activities in dia-
mide-based systems11 may require the use of ligands
with bulky (but metalation-resistant) substituents on
nitrogen.
unsaturation of the fragment [{Me2Si(NCMe3)2}ZrR]2+
.
The maximum formal 10-electron count (including
π-donation from nitrogen) for [N2MR]+ compares to 14
for metallocene analogues and 12 for cyclopentadienyl-
amide cations. A benzyl ligand may, of course, provide
more than two electrons,24,25,37 but this is apparently
not enough to prevent the formation of dimeric complex
10. Whereas cationic metallocenes [Cp′2MR]+ exhibit
a restricted wedgelike opening, the ligand bulk in the
diamides lies close to the N-M-N plane, leaving room
for two extra ligands of moderate bulk to coordinate to
[N2MR]+. Thus, for example, whereas cationic alkyl-
metallocenes coordinate one molecule of THF,41 diamide
analogues [N2MR]+ form bis(THF) adducts. Analogous
bis(alkene) adducts1a,42 [N2MR(alkene)2]+ might be im-
plicated in the propagation and chain-transfer steps of
polymerization by diamide catalysts.
Exp er im en ta l Section
Gen er a l P r oced u r es. All experiments were performed
under nitrogen in a Braun MB 200-G drybox or under argon
using standard Schlenk techniques. Solvents were dried by
refluxing over and distilling from standard reagents. Deu-
terated solvents and liquid alkenes were dried over 4 Å
molecular sieves. B(C6F5)3,28 [PhMe2NH][B(C6F5)4],31 [Ph3-
CMe][B(C6F5)4],30 and LiNp46 were synthesized following lit-
erature procedures. Mg(CH2Ph)2(dioxane)0.5 was prepared
from the reaction of (PhCH2)MgCl with dioxane. All other
reagents were purchased from commercial suppliers and used
without further purification.
The high degree of unsaturation at zirconium also
appears to play a role in the observation of the controlled
insertion of unsaturated molecules.22 Stabilization of
the single insertion products is not, as had been initially
thought, in all cases due to blocking π-coordination of
the benzene ring of the 3-phenylpropyl group to the
zirconium. Such stabilization is found in the 2-butyne
insertion products (both anions), as well as in alkene
insertion products 14a -17a with the poorly coordinat-
ing anion [B(C6F5)4]-. However, when the anion is
[BzB(C6F5)3]-, the single alkene insertion product co-
ordinates the anion strongly, resulting in a pendant
ligand benzene ring. It may be postulated that stronger
anion coordination to the cationic 3-phenylpropyl com-
plex than to the cationic benzyl precursor underlies the
inertness of 14c and 15c toward further ethene or
propene insertion.
1H NMR spectra were recorded on a Varian XL-200 (200.0
MHz) or a Varian VXR-300 (300.0 MHz) instrument, 13C NMR
spectra were recorded on a Varian VXR-300 instrument (75.43
MHz), 11B NMR (96.24 MHz) spectra were recorded on a
Varian VXR-300 instrument, and 19F NMR (188.16 or 282.24
MHz) spectra were recorded on either instrument. NMR data
are listed in parts per million downfield from TMS for proton
and carbon measurements and are referenced relative to an
aqueous solution of NaBF4 (δ -40 ppm) for boron measure-
ments and CF3C6H5 in C6D6 (δ -64 ppm) for fluorine. El-
emental analyses were performed by Analytische Laboratorien,
Engelskirchen, Germany.
P r ep a r a tion of Neu tr a l P r ecu r sor s. Me2Si(NHCMe3)2.
Reaction of Me2SiCl2 (47.6 g, 370 mmol) with t-BuNH2 (113.3
g, 1550 mmol) in hexane (700 mL) at room temperature,
followed by brief reflux (10 min), filtration, solvent removal,
and fractional vacuum distillation, afforded Me2Si(NHCMe3)2
in 98% purity. 1H NMR (C6D6, 25 °C): δ 1.18 (s, 18H, CMe3),
0.51 (br, 2H, NH), 0.17 (s, 6H, SiMe2).
NMR study of anion and ligand effects on alkene
reactivity has led to the conclusion that the relative
rates of insertion are largely determined by the ease of
displacement from the cation of the counteranion or
Lewis base, which appears to follows the order
[B(C6F5)4]- > NMe2Ph > [PhCH2B(C6F5)3]- and, for
different solvents, dichloromethane > bromobenzene >
toluene. The low polymerization activity of the dichlo-
rozirconium complex with MAO may be due to strong
coordination of the anion (derived from MAO by halide
abstraction) or solvent to the putative alkylzirconium
cation. Vulnerability to blocking anion43 or toluene
coordination11 might explain the generally low alkene
polymerization activity of electrophilic group 4 catalysts
based on sterically open and/or poorly electron-donating
ligands.44 The high activity of metallocenes and related
species such as boratabenzene45 complexes may derive
Me2Si(NLiCMe3)2. To a stirred solution of (Me2SiNHCMe3)2
(14.7 g, 72 mmol) in hexane (200 mL) was added dropwise 93.4
mL of a 1.6 M n-BuLi solution in hexane (149 mmol). The
mixture was then refluxed for 20 min, the solvent removed in
vacuo, and a solution of the crude product in hexane cooled to
-40 °C to give 14.3 g (3 crops, 92% yield) of colorless crystalline
Me2Si(NLiCMe3)2. 1H NMR (C6D6, 25 °C): δ 1.23 (s, 18H,
CMe3), 0.41 (s, 6H, SiMe2). 13C NMR (C6D6, 25 °C): δ 51.6
(2C, NCMe3), 36.8 (6C, NCMe3), 11.3 (2C, SiMe2).
{Me2Si(NCMe3)2}Zr Cl2(THF )n (1, 2). Toluene (150 mL)
at -78 °C was added to a mixture of Me2Si(NLiCMe3)2 (4.01
g, 18.7 mmol) and ZrCl4(THF)2 (7.04 g, 18.7 mmol) at -78 °C,
and the mixture was allowed to warm to 25 °C and stirred for
90 min. The solvent was removed in vacuo, and the residue
was extracted with a mixture of THF and hexane. The extract
was reduced to dryness and then once again extracted with a
THF/hexane mixture. Colorless microcrystalline 1 (3 crops,
4.5 g, 48% yield), containing about two THF molecules per
zirconium (1H NMR), was obtained on cooling the solution to
-40 °C. Solutions of the product exhibited resonances for
approximately equal amounts (on the basis of Zr atoms) of two
species, {Me2Si(NCMe3)2}ZrCl2(THF)2 (1) and [{Me2Si-
(NCMe3)2}ZrCl2]2(THF) (2); the latter complex is formed on
THF dissociation. Analytically pure 1 was obtained as white
crystals on cooling a THF solution to -40 °C. Spectroscopically
pure 2 was obtained by cooling a dichloromethane/hexane
solution to -40 °C.
(41) For examples of monoTHF adducts of cationic alkylmetal-
locenes, see ref 20c and the following: (a) Guo, Z.; Swenson, D. C.;
J ordan, R. F. Organometallics 1994, 13, 1424. (b) Borkowsky, S. L.;
J ordan, R. F.; Hinch, G. D. Organometallics 1991, 10, 1268. (c) J ordan,
R. F.; LaPointe, R. E.; Bradley, P. K.; Baenziger, N. Organometallics
1989, 8, 2892. (d) J ordan, R. F.; LaPointe, R. E.; Bajgur, C. S.; Echols,
S. F.; Willett, R. J . Am. Chem. Soc. 1987, 109, 4111.
(42) Ystenes, M. J . Catal. 1991, 129, 383.
(43) For very recent reports of the effect of anion variation on
metallocene catalysis, see refs 29a and 35 and the following: Chen,
Y. X.; Stern, C. L.; Marks, T. J . J . Am. Chem. Soc. 1997, 119, 2582.
(44) (a) Flores, J . C.; Chien, J . C. W.; Rausch, M. D. Organometallics
1994, 13, 4140. (b) van der Linden, A. J .; Schaverien, C. J .; Neijboom,
N.; Ganter, C.; Orpen, A. G. J . Am. Chem. Soc. 1995, 117, 3008.
(45) (a) Bazan, G. C.; Rodriguez, G.; Ashe, A. J ., III; Al-Ahmad, S.;
Mu¨ller, C. J . Am. Chem. Soc. 1996, 118, 2291. (b) Krishnamurti, R.;
Nagy, S.; Etherton, B. P. (Occidental) World Pat. Appl. 96/23004, 1996.
Complex 1. 1H NMR (C7D8, -75 °C): δ 3.96, 3.58 (m, 4H,
THF), 1.60, 1.56 (s, 9H, CMe3), 1.06 (m, 8H, THF), 0.82, 0.50
(s, 3H, SiMe2); resonances for a minor unidentified species were
(46) Schrock, R. R.; Fellman, J . D. J . Am. Chem. Soc. 1978, 100,
3359.

Alkene and Alkyne Insertion Reactivity
Organometallics, Vol. 16, No. 25, 1997 5433
also observed. 1H NMR (C7D8, -25 °C): δ 3.67 (m, 8H, THF),
1.53 (br, 18H, CMe3), 1.39 (m, 8H, THF), 0.74, 0.52 (s, 3H,
SiMe2); resonances for a minor unidentified species were also
observed. 1H NMR (C7D8, 25 °C): δ 3.68 (m, 8H, THF), 1.61
(s, 18H, CMe3), 1.39 (m, 8H, THF), 0.62 (s, 6H, SiMe2). 1H
NMR (CD2Cl2, 25 °C): δ 3.72 (m, 8H, THF), 1.84 (m, 8H, THF),
1.39 (obscured, CMe3), 0.53 (obscured, SiMe2). 13C NMR (THF-
d8, 25 °C): δ 58.2 (2C, NCMe3), 34.5 (6C, NCMe3), 6.8 (2C,
SiMe2). 13C NMR (CD2Cl2, 25 °C): δ 68.9 (4C, THF), 58.7 (2C,
NCMe3), 34.7 (6C, NCMe3), 25.9 (4C, THF), 6.1 (2C, SiMe2).
Anal. Calcd for C18H40Cl2N2O2Si2Zr: C, 42.66; H, 7.96; Cl,
13.99; N, 5.53; Si, 5.54. Found: C, 42.45; H, 7.80; Cl, 14.20;
N, 5.49; Si, 5.36.
Complex 2. 1H NMR (C7D8, -25 °C): δ 3.93 (m, 4H, THF),
1.66, 1.38 (s, 18H, CMe3), 1.04 (m, 4H, THF), 0.69, 0.65, 0.52,
0.32 (s, 3H, SiMe2). 1H NMR (C7D8, 25 °C): δ 4.03 (m, 4H,
THF), 1.63, 1.40 (br, 18H, CMe3), 1.21 (m, 4H, THF), 0.66 (s,
6H, SiMe2), 0.53, 0.39 (s, 3H, SiMe2). 1H NMR (C7D8, 75 °C):
δ 4.02 (m, 4H, THF), 1.60 (s, 36H, CMe3), 1.46 (m, 4H, THF),
0.56 (s, 12H, SiMe2). 1H NMR (CD2Cl2, 25 °C): δ 4.44 (m, 4,
THF), 2.09 (m, 4H, THF), 1.39 (s, 36H, CMe3), 0.61, 0.58 (s,
3H, SiMe2), 0.53 (s, 6H SiMe2).13C NMR (CD2Cl2, 25 °C): δ
77.8 (2C, THF), 60.0, 59.7 (2C, NCMe3), 34.7, 34.6 (6C, NCMe3),
26.0 (2C, THF), 6.5, 5.9 (2C, SiMe2).
{Me2Si(NCMe3)2}Zr Cl2(OEt2) (3). Diethyl ether (60 mL,
-78 °C) was added to a mixture of Me2Si(NLiCMe3)2 (1.80 g,
8.4 mmol) and ZrCl4 (1.96 g, 8.4 mmol) at -78 °C, and the
mixture was allowed to warm to room temperature over 2 h
and stirred for 1 h. The solvent was removed in vacuo, and
the residue was extracted with toluene. The extract was
reduced to dryness and then washed with hexane to remove
soluble {Me2Si(NCMe3)2}2Zr. The residue was then extacted
with ether (7 mL), to which hexane (2 mL) was added. Cooling
to -40 °C afforded microcrystalline 3 (3 crops, 1.60 g, 44%
yield). 1H NMR (C6D6, 25 °C): δ 3.27 (q, 4H, OEt2), 1.54 (s,
18H, CMe3), 1.07 (t, 6H, OEt2), 0.57 (s, 6H, SiMe2).
{Me2Si(NCMe3)2}Zr Bz2 (4). Toluene (40 mL) at -30 °C
was added to a Schlenk tube at -40 °C containing a mixture
of 1 (0.83 g, 1.7 mmol) and Mg(Bz)2(dioxane)0.5 (0.50 g, 1.7
mmol). The mixture was allowed to warm to room tempera-
ture and then stirred for 30 min. A hexane/ether mixture (30
mL, 2:1) was added, and the reaction mixture was then
filtered. The solvent was removed in vacuo, the residue
extracted with hexane, and the extract reduced to dryness.
Redissolution of the residue in minimum hexane and cooling
to -40 °C afforded 0.47 g (2 crops; 60% yield) of analytically
pure yellow crystalline product. 1H NMR (C6D6, 25 °C): δ 7.09
(t, 4H, m-Bz), 6.86 (t, 2H, p-Bz), 6.72 (d, 4H, o-Bz), 1.83 (s,
4H, ZrCH2), 1.09 (s, 18H, CMe3), 0.40 (s, 6H, SiMe2). 13C NMR
(C2D2 Cl4, 25 °C): δ -145.5 (2C, ipso-Bz), 131.0 (4C, Bz), 128.8
(4C, Bz), 121.6 (2C, Bz), 58.6 (2C, CMe3), 53.2 (t, 1J CH ) 129.2
Hz, 2C, ZrCH2), 34.7 (6C, CMe3), 6.1 (2C, SiMe2). Anal. Calcd
for C24H38N2SiZr: C, 60.83; H, 8.08; N, 5.91; Si, 5.93. Found:
C, 60.55; H, 7.91; N, 5.70; Si, 5.81.
4 in hexane (2 mL) was added dropwise to a solution of 38 mg
(0.074 mmol) of B(C6F5)3 in hexane (2 mL), resulting in the
immediate precipitation of an orange solid. The mixture was
stirrred for 5 min, and the solid was collected by decantation
of the solvent, washing (twice) with hexane and drying in
vacuo. A 68 mg (93% yield) amount of spectroscopically pure
material was obtained. The complex was also conveniently
obtained by carrying out the reaction in toluene, removal of
the solvent in vacuo, and washing the residue (3 times) with
hexane. Cooling a dichloromethane/hexane solution to -40
°C afforded large red crystals of complex 6. 1H NMR (C6D5-
Br, 25 °C): δ 7.3-6.7 (m, 10H, Bz), 3.36 (br, 2H, BCH2), 1.95
(s, 2H, ZrCH2), 1.02 (s, 18H, CMe3), 0.32, 0.22 (s, 3H, SiMe2).
1H NMR (C7D8, -25 °C): δ 7.14 (t, 2H, m-BzB), 7.08 (d, 2H,
m-BzZr), 6.85 (t, 1H, p-BzZr), 6.69 (d, 2H, o-BzZr), 6.1 (m, 3H,
o-BzB and p-BzB), 3.44 (br, 2H, BCH2), 1.77 (s, 2H, ZrCH2),
0.88 (s, 18H, CMe3), 0.26, 0.03 (s, 3H, SiMe2); resonances
assigned using a 2-D COSY experiment. 1H NMR (CD2Cl2,
25 °C): δ 7.53 (m, 3H, Bz), 7.37 (d, 2H, o-Bz), 7.14 (t, 2H,
m-Bz), 6.87 (m, 3H, Bz), 3.23 (br, 2H, BCH2), 2.13 (s, 2H,
ZrCH2), 1.27 (s, 18H, CMe3), 0.54, 0.45 (s, 3H, SiMe2). 13C
NMR (C2D2Cl4, 25 °C): δ 160.4 (1C, ipso-BzB), 148.2 (d, 6C,
C6F5), 147.6 (1C, ipso-BzZr), 138.6 (d, 3C, C6F5), 136.9 (d, 6C,
C6F5), 131.2 (2C, Bz), 131.1 (1C, p-BzZr), 129.3 (2C, Bz), 126.4
1
(2C, Bz), 122.5 (1C, p-BzB), 61.4 (2C, CMe3), 52.4 (t, J CH
)
122.5 Hz, 1C, ZrCH2), 35.1 (6C, CMe3), 5.8, 5.4 (1C, SiMe2);
resonances for ipso-C6F5 and BCH2 were not observed. 13C
NMR (C6D6, 25 °C): δ 160.1 (1C, ipso-BzB), 148.6 (d, 6C, C6F5),
147.6 (1C, ipso-BzZr), 138.9 (d, 3C, C6F5), 137.4 (d, 6C, C6F5),
130.8 (4C, Bz), 129.0 (1C?, Bz), 126.6 (2C, Bz), 124.2 (br q,
1C, ipso-C6F5), 122.4 (1C, p-BzB), 60.9 (2C, CMe3), 52.5 (t, 1J CH
) 122.5 Hz, 1C, ZrCH2), 36.2 (br q, 1C, BCH2), 34.6 (6C, CMe3),
5.2, 4.7 (1C, SiMe2); one benzyl resonances was obscured. 11B
NMR (C6D6, 25 °C): δ -12.2 (∆ν1/2 ) 32.7 Hz). 19F NMR (C6D6,
25 °C): δ -132.48 (d), -162.30 (t), -166.44 (m).
Th er m a l Decom p osition of Com p lex 6. The decomposi-
tion of a 0.032 M solution of 6 in C7D8 in an NMR probe at 70
°C was monitored by 1H NMR spectroscopy. After 2 h, a stable
product distribution was observed, consisting of a 1:1 mixture
of two organometallic complexes, as well as the three boranes,
BBzn(C6F5)3-n (n ) 1-3). Me2Si(NCMe3)2}ZrBz(C6F5) (50%):
1H NMR (C7D8, 75 °C) δ 7.42 (d, 2H, o-Bz), 2.58 (s, 2H, ZrCH2),
1.27 (s, 18H, CMe3), 0.44, 0.22 (s, 3H, SiMe2); other resonances
obscured. {Me2Si(NCMe3)2}Zr(C6F5)2 (50%): 1H NMR (C7D8,
75 °C) δ 1.01 (s, 18H, CMe3), 0.48 (s, 6H, SiMe2). BCH2
resonances were observed at δ 3.41 (br, B(Bz)(C6F5)2), 2.92 (s,
B(Bz)2(C6F5)), and 2.58 (s, B(Bz)3).
[{Me2Si(NCMe3)2}Zr (Bz)(NMe2P h )][B(C6F 5)4] (7). C2D2-
Cl4 or C6D5Br (0.7 mL) at -30 °C was added to a mixture of 4
(9.0 mg, 0.019 mmol) and [PhMe2NH][B(C6F5)4] (15.2 mg, 0.019
mmol) in a reaction bottle at -40 °C. An orange solution was
obtained almost instantaneously. After the mixture was
1
warmed to 25 °C, the solution was used for NMR studies. H
NMR (C6D5Br, 25 °C): δ 7.2-7.0 (m, m-Ph), 6.88 (t, 1H, p-Ph),
6.70 (d, 2H, o-Ph), 6.67 (t, 1H, p-Ph), 6.34 (d, 2H, o-Ph), 2.54
(s, 6H, NMe2), 1.99 (s, 2H, ZrCH2), 0.96 (s, 18H, CMe3), 0.21
(s, 6H, SiMe2). 1H NMR (C2D2Cl4, -25 °C): δ 7.55 (m, m-PhN),
7.22 (obscured, m-Bz), 7.11 (t, 1H, p-PhN), 6.98 (t, 1H, p-Bz),
6.82 (d, 2H, o-Bz), 6.74 (d, 2H, o-PhN), 3.08 (s, 6H, NMe2),
2.11 (s, 2H, ZrCH2), 1.14 (s, 18H, CMe3), 0.39, 0.27 (s, 3H,
SiMe2). The resonances were assigned using a 2-D COSY
NMR experiment. 11B NMR (C6D6, 25 °C): δ -15.8. 19F NMR
(C2D2Cl4, 25 °C): δ -134.31 (d), -163.19 (t), -167.15 (m).
{Me2Si(NCMe3)2}Zr (CH2CMe3)2 (5). Treatment of 1 with
a 2-fold excess of LiCH2CMe3 in Et2O (-40 °C to 25 °C),
followed by hexane extraction, and crystallization from hexane
at -40 °C afforded {Me2Si(NCMe3)2}ZrNp2(THF)0.5 as colorless
crystals which melt at room temperature. The THF-free
complex 5 was obtained as a white solid by placing the above
product under high vacuum (30 min, 25 °C). 1H NMR (C6D6,
25 °C): δ 1.38, 1.20 (s, 18H, CMe3), 0.91 (s, 4H, ZrCH2), 0.42
1
(s, 6H, SiMe2). 13C NMR (C2D2Cl4, -20 °C): δ 80.0 (t, J CH
)
104 Hz, 2C, ZrCH2), 57.9 (2C, NCMe3), 35.8, 35.3 (6C, CMe3),
34.9 (2C, ZrCH2CMe3), 31.8 (2C, ZrCH2CMe3), 6.6 (2C, SiMe2).
{Me2Si(NCMe3)2}Zr {CH(SiMe3)2}2. The complex was pre-
pared in situ in an NMR tube by reaction of 1 with a 2-fold
excess of LiCH(SiMe2)2 in C7D8. 1H NMR (C7D8, 25 °C): δ 1.43
(s, 18H, CMe3), 0.50 (s, 6H, SiMe2), 0.38, 0.34 (s, 18H, SiMe2),
-0.13 (s, 2H, ZrCH).
[{Me2Si(NCMe3)2}Zr (Bz)(THF )2][B(C6F 5)4] (8). THF at
0 °C was added to a mixture of {Me2Si(NCMe3)2}ZrBz2 (30 mg,
0.062 mmol) and [PhMe2NH][B(C6F5)4] (51 mg, 0.62 mmol) in
a reaction bottle. Hexane was added to the resulting pale
yellow solution to give a colorless oil. The oil was washed with
hexane and dried in vacuo to give a colorless solid, shown by
1H NMR spectroscopy to be a bis(THF) adduct. 1H NMR (CD2-
Cl2, 25 °C): δ 7.28 (t, 2H, m-Bz), 7.00 (t, 1H, p-Bz), 6.92 (m,
2H, o-Bz), 4.03 (br, 8H, THF), 2.29 (br, 2H, ZrCH2), 2.07 (br,
P r epar ation of Cation ic Com plexes. {Me2Si(NCMe3)2}-
Zr Bz{BzB(C6F 5)3} (6). A solution of 35 mg (0.074 mmol) of

5434 Organometallics, Vol. 16, No. 25, 1997
Horton and de With
8H, THF), 1.27 (s, 18H, CMe3), 0.54 (s, 6H, SiMe2). Addition
of a large excess of THF afforded the following spectrum: δ
7.09 (t, 2H, m-Bz), 6.91 (d, 2H, o-Bz) 6.79 (t, 1H, p-Bz), 2.13
(s, 2H, ZrCH2), 1.31 (s, 18H, CMe3), 0.50 (br, 6H, SiMe2).
[{Me2Si(NCMe3)2}Zr (Np )(THF )2][B(C6H5)4] (12). THF
(1.5 mL) at -40 °C was added to a mixture of 5‚(THF)0.5 (210
mg, 0.45 mmol) and [PhMe2NH][B(C6H5)4] (203 mg, 0.46 mmol)
in a reaction bottle. After the mixture was warmed to 25 °C
and stirred for 30 min, hexane was added to the resulting pale
yellow solution to give a colorless oil. The oil was washed with
hexane and dried in vacuo to give a colorless solid, shown by
1H NMR spectroscopy to be a bis(THF) adduct. Partial THF
dissociation occurs in solution, and the exact NMR shifts are
concentration-dependent. 1H NMR (THF-d8, 25 °C): δ 1.27
(s, 18H, CMe3), 0.95 (s, 9H, CMe3), 0.76 (s, 2H, ZrCH2), 0.54,
0.43 (br, 3H, SiMe2). 1H NMR (C6D5Br, 25 °C): δ 3.36 (m, 8H,
THF), 1.36 (m, 8H, THF), 1.11 (s, 18H, CMe3), 1.04 (s, 9H,
CMe3), 0.45, 0.33 (br, 3H, SiMe2); the ZrCH2 resonance was
obscured by resonances for a second species, believed to be a
monoTHF adduct. Addition of excess THF resulted in disap-
pearance of the “monoTHF” resonances and changes in the
chemical shifts of 12: δ 1.13 (s, 18H, CMe3), 1.04 (s, 9H, CMe3),
0.85 (s, 2H, ZrCH2), 0.48, 0.32 (br, 3H, SiMe2). 13C NMR of
12 (C2D2Cl4, 25 °C): δ 85.4 (t, 1J CH ) 112 Hz, 1C, ZrCH2), 71.6
(4C, THF), 59.7 (2C, NCMe3), 36.3 (1C, ZrCH2CMe3), 35.3 (3C,
CH2CMe3), 35.1 (6C, CH2CMe3), 25.6 (4C, THF), 7.5, 6.4 (1C,
SiMe2). Resonances for the [BPh4]- anion are omitted.
Addition of an excess of THF to a solution of 6 gave an
analogous THF adduct. 1H NMR (C7D8, 25 °C): δ 7.2-6.8 (m,
10H, Bz), 3.34 (br, 2H, BCH2), 1.89 (s, 2H, ZrCH2), 1.03 (s,
18H, CMe3), 0.28 (s, 6H, SiMe2). 1H NMR (C6D5Br, 25 °C): δ
7.2-6.8 (m, 10H, Bz), 3.27 (br, 2H, BCH2), 1.93 (s, 2H, ZrCH2),
1.07 (s, 18H, CMe3), 0.33 (s, 6H, SiMe2). 13C NMR (C2D2Cl4,
-20 °C): δ 148.5 (1C, ipso-BzB), 148.1 (d, 6C, C6F5), 146.8 (1C,
ipso-BzZr), 137.5 (d, 3C, p-C6F5), 136.4 (d, 6C, C6F5), 130.0 (2C,
BzZr), 128.8 (2C, BzB), 127.2 (2C, BzB), 126.1 (2C, BzZr), 122.9
(2C, p-BzB), 74.2 (obscured, THF), 60.3 (2C, CMe3), 54.7 (t,
1J CH ) 117 Hz, 1C, ZrCH2), 34.6 (6C, CMe3), 32 (vbr, BCH2),
25.7 (4C, THF), 6.3, 5.7 (1C, SiMe2); resonances for ipso-C6F5
were not observed; at 25 °C, the ZrCH2 resonance is very broad.
19F NMR (C6D5Br, 25 °C): δ -131.89 (d), -164.93 (t), -167.89
(m).
Rea ction of 4 w ith Tr ityl Rea gen t. CH2Cl2 (0.7 mL) at
-40 °C was added to a mixture of 4 (2.2 mg, 4.6 µmol) and
[Ph3C][B(C6F5)4] (4.2 mg, 4.6 µmol) in a reaction bottle at 25
°C. 1H NMR spectroscopy revealed complexes 9a and 9b to
be present in a 73:27 ratio. At lower concentrations, the
proportion of 9b decreased. [{Me2Si(NCMe3)2}ZrBz][B(C6F5)4]
(9a ): 1H NMR (CD2Cl2, 25 °C) δ 7.97 (t, 2H, m-Bz), 7.61 (d,
2H, o-Bz), 7.44 (t, 1H, p-Bz), 2.53 (s, 2H, ZrCH2), 1.39 (s, 18H,
CMe3), 0.75, 0.66 (s, 3H, SiMe2). [{Me2Si(NCMe3)2}2Zr2Bz2]-
[B(C6F5)4]2 (9b): 1H NMR (CD2Cl2, 25 °C) δ 7.99 (t, 2H, p-Bz),
7.52 (t, 4H, m-Bz), 7.43 (d, 4H, o-Bz), 2.19 (s, 4H, ZrCH2), 1.17
(s, 36H, CMe3), 0.63, 0.00 (s, 6H, SiMe2).
P r oton olysis of Com p lex 5. C6D5Br was added to a
mixture of complex 5 (8.5 mg, 0.020 mmol) and [PhMe2NH]-
[B(C6F5)4] (15.7 mg, 0.020 mmol) at -30 °C and the reaction
warmed to 25 °C. 1H NMR monitoring indicated the formation
of one major species, together with two minor species and a
small amount of 2-methyl-1-propene (about 10% on a molar
basis). Major product: 1H NMR (C6D5Br, 25 °C) δ 7.18 (t, 2H,
m-PhN), 6.52 (t, 1H, p-PhN), 6.41 (d, 2H, o-PhN), 2.65 (s, 6H,
NMe2Ph), 1.06 (s, 18H, CMe3), 0.90 (s, 9H, CMe3), 0.44 (s, 3H,
SiMe2), 0.37 (s, 2H, ZrCH2), 0.23 (s, 3H, SiMe2). Minor
resonances: 1H NMR δ 6.63, 6.32 (d, o-PhN), 2.57, 2.55 (s,
NMe2Ph), 1.02, 0.85 (s, CMe3), 0.63, 0.33, 0.06 (s, SiMe2).
Addition of excess of THF afforded the cationic bis(THF)
adduct 12.
Addition of excess THF gave a mixture of complex 8 and
another species proposed to be [{Me2Si(NCMe3)2}2Zr2(Bz)2-
(THF)n][B(C6F5)4]2. 1H NMR (CD2Cl2, 25 °C): δ 1.38 (s, 36H,
CMe3), 0.63, 0.08 (s, 6H, SiMe2); other resonances were
obscured.
[{Me2Si(NCMe3)2}2Zr 2Bz3][B(C6F 5)4] (10). CH2Cl2 (3.0
mL) at -40 °C was added to a mixture of 4 (0.100 g, 0.21 mmol)
and [Ph3C][B(C6F5)4] (97 mg, 0.11 mmol) in a reaction bottle
at -40 °C. After the mixture was warmed to 25 °C and hexane
was added (4 mL), an orange oil was obtained, which was
washed with hexane (twice). The oil solidified on drying in
vacuo. NMR spectroscopy showed the solid to be primarily
the title complex; attempts to obtain an analytically pure
sample by crystallization were unsuccessful. Addition of an
excess of THF afforded a 1:1 mixture 4 and 8. 1H NMR (CD2-
Cl2, -25 °C): δ 7.39 (t, 2H, m-Bz), 7.26 (t, 4H, m-Bz), 7.10 (t,
1H, p-Bz), 6.99 (d, 2H, o-Bz), 6.95 (t, 2H, p-Bz), 6.68 (d, 4H,
o-Bz), 2.27 (s, 4H, ZrCH2), 1.13 (s, 36H, CMe3), 1.03 (s, 2H,
ZrCH2), 0.39, 0.31 (s, 6H, SiMe2); the resonances were assigned
using a 2-D COSY experiment.13C NMR (C2D2 Cl4, 25 °C): δ
162.2 (1C, ipso-Bz), 148.3 (d, 6C, C6F5), 144.4 (2C, ipso-Bz),
137.9 (dm, 3C, p-C6F5), 136.5 (dm, 6C, C6F5), 131.9 (4C, Bz),
131.7 (2C, Bz), 126.8 (4C, Bz), 124.7 (2C, Bz), 123.6 (2C, Bz),
P r ep a r a t ion of Sin gle In ser t ion P r od u ct s. [{Me2Si-
(NCMe3)2}Zr {C(Me)dC(Me)CH2P h }][An ion ] (13) (An ion
) [B(C6F 5)4]-). A solution of 2-butyne (100 µL, 1.28 mmol)
in CH2Cl2 (1.5 mL) at -40 °C was added to a mixture of 4
(100 mg, 0.21 mmol) and [Ph3C][B(C6F5)4] (194 mg, 0.21 mmol)
in a reaction bottle at -40 °C. The solution color changed from
orange to yellow on warming the stirred reaction to 25 °C.
After 5 min at 25 °C, hexane (5 mL) was added, precipitating
a yellow oil, which was washed twice with hexane. The oil
crystallized on cooling. The resulting microcrystalline solid
was spectroscopically pure. Addition of excess THF afforded
13b.
Complex 13. 1H NMR (CD2Cl2, 25 °C): δ 8.16 (d, 2H, o-Bz),
8.12 (t, 2H, m-Bz), 7.88 (t, 1H, p-Bz), 3.84 (s, 2H, CH2Ph), 1.89,
1.76 (s, 3H, dCMe), 1.27 (s, 18H, CMe3), 0.68, 0.46 (s, 3H,
SiMe2). 1H NMR (C2D2Cl4, 25 °C): δ 8.14 (m, 2H, o-Ph), 8.05
(t, 2H, m-Ph), 7.86 (t, 1H, p-Ph), 3.82 (s, 2H, CH2Ph), 1.86,
1.77 (s, 3H, dCMe), 1.25 (s, 18H, CMe3), 0.67, 0.45 (s, 3H,
SiMe2). 1H NMR (C6D5Br, 25 °C): δ 7.52-7.38 (m, 4H, Bz),
3.32 (s, 2H, CH2Ph), 1.70, 1.53 (s, 3H, dCMe), 0.97 (s, 18H,
CMe3), 0.41, 0.22 (s, 3H, SiMe2). 13C NMR (C2D2 Cl4, 25 °C):
δ 195.5 (1C, ZrCMe), 169.1 (1C, dCMeCH2), 156.8 (1C, ipso-
Bz), 148.2 (d, 6C, C6F5), 138.2 (3C, p-C6F5), 136.4 (d, 6C, C6F5),
136.4 (2C, Ph), 130.4 (2C, Ph), 127.0 (1C, p-Ph), 121.8 (m, ipso-
C6F5), 60.8 (2C, CMe3), 48.1 (1C, CH2Ph), 35.7 (6C, CMe3), 25.6,
22.9 (1C, dCMe), 6.7, 4.5 (2C, SiMe2). 11B NMR (C2D2Cl4, 25
°C): δ -15.5 (∆ν1/2 ) 23 Hz). 19F NMR (CD2Cl2, 25 °C): δ
-133.88 (m), -163.72 (m), -167.64 (m).
1
116.5 (1C, p-Bz), 60.4 (4C, CMe3), 53.8 (t, J CH ) 132.5 Hz,
1
1C, ZrCH2), 53.3 (t, J CH ) 130.5 Hz, 2C, ZrCH2), 34.9 (12C,
CMe3), 6.1, 5.1 (2C, SiMe2). 11B NMR (CD2Cl2, 25 °C): δ -15.0
(∆ν1/2 ) 24 Hz). 19F NMR (CD2Cl2, 25 °C): δ -134.69 (m),
-165.00 (m), -168.85 (m).
Reaction of a ca. 2:1 molar ratio of 4 and B(C6F5)3 in C6D5-
Br (0.014 M in Zr) gave the following mixture (%Zr): 44% 4;
36% 6; 20% 10. Reaction of a ca. 2:1 molar ratio of 4 and
[PhMe2NH][B(C6F5)4 in C6D5Br (0.014 M in Zr) afforded the
following mixture (%Zr): 3% 4; 14% 7; 83% 10.
[{Me2Si(NCMe3)2}Zr Np ][Np B(C6F 5)3] (11). Reaction of
5 (THF-free) with a 3-fold excess of B(C6F5)3 at 25 °C after 2
h afforded the title complex as the major species in solution,
contaminated with a small amount of 5. 1H NMR (C6D5Br,
25 °C): δ 2.09 (br, 2H, BCH2), 1.04 (s, 18H, NCMe3), 0.97 (s,
9H, ZrCH2CMe3), 0.88 (s, 9H, ZrCH2CMe3), 0.33 (br, 6H,
SiMe2); the ZrCH2 resonance was obscured.
Complex 13b. 1H NMR (CD2Cl2, 25 °C): δ 7.24 (d, 3H, m,p-
Bz), 7.13 (d, 2H, o-Bz), 3.68 (s, 2H, CH2Ph), 1.85, 1.55 (s, 3H,
dCMe), 1.27 (s, 18H, CMe3), 0.52, 0.47 (s, 3H, SiMe2). 13C NMR
(C2D2 Cl4, -30 °C): δ 128.8 (4C, Ph), 59.6 (2C, CMe3), 51.8
(1C, CH2Ph), 35.0 (6C, CMe3), 6.4 (2C, SiMe2); other resonances
were obscured.

Alkene and Alkyne Insertion Reactivity
Organometallics, Vol. 16, No. 25, 1997 5435
A spectroscopically identical cationic species, 13, was ob-
tained on reacting a 0.043 M solution of 7 in C6D5Br solution
with a 3-fold excess of 2-butyne. The reaction was complete
within 10 min at 25 °C; resonances for noncoordinated PhNMe2
were observed (δ 6.73, 6.60, 2.66). After 1 h, 25% conversion
of the product to another unidentified species was observed.
Addition of MeOH to a solution of 13 afforded MeCHdC-
(Me)CH2Ph. 1H NMR (CD2Cl2, 25 °C): δ 7.4-7.1 (m, 5H, Ph),
obscured. 19F NMR (C6D5Br, 25 °C): δ -131.92 (d), -165.01
(t), -167.94 (t).
[{M e 2 S i (N C M e 3 )2 }Zr {C H 2 C H 2 C H 2 P h }(N M e 2 P h )]-
[B(C6F 5)4] (14d ). Ethene (1 bar, 4.5 mL, 0.20 mmol) was
added to a solution of 0.03 mmol of 7 in C6D5Br (0.7 mL) (in
an NMR tube with a septum cap), and the reaction was
monitored by 1H NMR spectroscopy. Clean and complete
conversion to a mixture of 14d (65%) and 14a (35%) was
observed within 11 min. Addition of excess THF afforded 14b.
Complex 14d . 1H NMR (C6D5Br, 25 °C): δ 7.3-7.0 (m, Ph),
6.47 (t, 1H, p-PhN), 6.34 (d, 2H, o-PhN), 2.51 (m, NMe2Ph),
3
5.3 (m, 1H, dCHMe), 1.60 (d, J HH ) 6.6 Hz, dCHMe), 1.51
(m, 3H, dCMe); other resonances were obscured.
An ion ) [P h CH2B(C6F 5)3]-. A solution of 2-butyne (20
µL, 0.26 mmol) in C6D5Br (1.5 mL) at -40 °C was added to a
mixture of 4 (35 mg, 0.074 mmol) and B(C6F5)3 (38 mg, 0.074
mmol) at -40 °C. The solution color changed from orange to
yellow on warming to 25 °C. After 5 min at 25 °C, hexane (3
mL) was added, precipitating a yellow oil, which was washed
twice with hexane. Analytically pure yellow microcrystalline
product was obtained from a CH2Cl2/hexane solution at -40
°C. NMR monitoring of the reaction of a 0.043 M solution of
6 with a 3-fold excess of 2-butyne indicated that the reaction
was much slower in toluene-d8 (conversion 70% in 20 min, 95%
in 60 min) than in C6D5Br (100% conversion in 5 min). Within
20 min in C6D5Br, further reaction afforded unidentified
complexes. THF addition to 13 afforded 13b.
3
2.44 (t, J HH ) 7.1 Hz, 2H, CH2Ph), 1.86 (m, 2H, ZrCH2CH2),
1.00 (s, 18H, CMe3), 0.40, 0.22 (s, 3H, SiMe2), 0.2 (obscured,
ZrCH2).
Complex 14a . 1H NMR (C6D5Br, 25 °C): δ 0.95 (s, 18H,
CMe3), 0.69 (t, 2H, ZrCH2?), 0.31, 0.25 (s, 3H, SiMe2); reso-
nances for free NMe2Ph were also observed.
Under similar conditions in C2D2Cl4, a 50:50 mixture of 14d
and 14a was obtained. THF addition afforded 14b. In CD2-
Cl2, 14d was the major product, but significant decomposition
was evident after 1 h.
Complex 14d . 1H NMR (C2D2Cl4, 25 °C): δ 3.05 (m, NMe2-
Ph), 2.48 (t, 2H, CH2Ph), 1.96 (m, 2H, ZrCH2CH2), 1.23 (s, 18H,
CMe3), 0.61, 0.44 (s, 3H, SiMe2), 0.38 (obscured, ZrCH2); other
resonances were obscured.
Complex 14a . 1H NMR (C2D2Cl4, 25 °C): δ 7.98 (m, 5H,
CH2Ph), 2.62 (m, 2H, CH2CH2Ph), 1.23 (s, 18H, CMe3), 1.06
(m, 2H, ZrCH2), 0.57, 0.48 (s, 3H, SiMe2); other resonances
were obscured.
Complex 13. 1H NMR (C6D5Br, 25 °C): δ 7.5-6.9 (m, Bz),
3.32 (s, 2H, BCH2 and CH2Ph), 1.70, 1.53 (s, 3H, dCMe), 0.97
(s, 18H, CMe3), 0.41, 0.22 (s, 3H, SiMe2). 19F NMR (C6D5Br,
25 °C): δ -131.79 (d), -164.74 (t), -167.62 (t). Anal. Calcd
for C46H44BF15N2SiZr: C, 53.13; H, 4.26; F, 27.40; N, 2.69.
Found: C, 52.86; H, 4.36; F, 27.23; N, 2.54.
[{Me 2Si(NCMe 3)2}Zr {CH 2CH (Me )CH 2P h }][B(C6F 5)4]
(15a ). Addition of a small excess of propene to the solution
in CD2Cl2 obtained on reacting 4 with [Ph3C][B(C6F5)4] afforded
the title complex (complete in 20 min), contaminated by 9b.
1H NMR (CD2Cl2, 25 °C): δ 8.1-7.9 (m, 5H, Ph), 3.42 (m, 1H,
Hd), 2.7-2.5 (m, 2H, Hc and He), 2.55 (t, 1H), 1.26 (s, 18H,
CMe3), 1.17 (obscured, CHMe), 0.60, 0.50 (s, 3H, SiMe2), 0.22
Complex 13b. 1H NMR (C6D5Br, 25 °C): δ 7.3-6.8 (m, Bz),
3.58 (s, 2H, CH2Ph), 3.28 (br, 2H, BCH2), 1.65, 1.45 (s, 3H,
dCMe), 1.07 (s, 18H, CMe3), 0.33, 0.32 (s, 3H, SiMe2).
[{Me2Si(NCMe3)2}Zr {CH2CH2CH2P h }][B(C6F 5)4] (14a ).
CD2Cl2 (0.7 mL) was added at -30 °C to a mixture of 4 (10
mg, 0.021 mmol) and [Ph3C][B(C6F5)4] (19.4 mg, 0.021 mmol)
in an NMR tube, and the reaction mixture was warmed to 5
°C. Addition of excess ethene by syringe afforded the title
complex (5 min), contaminated by about 20% (Zr atoms) of 9b.
THF addition converted 14a to complex 14b. Repeated
attempts to isolate 14a by hexane addition to the crude product
mixture in CH2Cl2 in a Schlenk tube led only to the isolation
of a complicated mixture. In some cases, the initially deposited
yellow oil suddenly turned an intense red color on removing
the septum cap under an argon stream.
2
3
(t, J ab ) J bc ) 13.1 Hz, Hb); resonance for Ha obscured.
{Me2Si(NCMe3)2}Zr {CH 2CH (Me)CH 2P h }{BzB(C6F 5)3}
(15c). Propene (1 bar, 4.5 mL, 0.20 mmol) was added to a
solution of 0.03 mmol of 6 in C6D5Br (0.7 mL), and the reaction
was monitored by 1H NMR spectroscopy. Clean and complete
conversion to the title complex was observed within 20 h (t1/2
) 280 min). THF addition afforded 15b. In CD2Cl2, insertion
was somewhat faster (60% conversion in 60 min), and in
toluene-d8, the reaction was noticeably slower (25% conversion
in 20 h).
Complex 14a . 1H NMR (CD2Cl2, 25 °C): δ 8.03 (m, 3H, o,m-
3
Complex 15c. 1H NMR (C6D5Br, 25 °C): δ 7.3-6.8 (m, Ph),
Ph), 7.98 (t, 1H, p-Ph), 3.11 (t, J HH ) 6.4 Hz, 2H, CH2Ph),
2
3
2.62 (m, 2H, CH2CH2Ph), 1.26 (s, 18H, CMe3), 1.08 (m, 2H,
ZrCH2), 0.59, 0.50 (s, 3H, SiMe2).
3.33 (br, 2H, BCH2), 2.44 (dd, J HH ) 12.6 Hz, J HH ) 6.0 Hz,
3
1H, CH2Ph), 2.14 (m, 1H, CH2Ph), 1.93 (octet, J HH ) 6.7 Hz,
3
Complex 14b. 1H NMR (CD2Cl2, 25 °C): δ 7.25-7.05 (m,
1H, CHMe), 1.04, 0.98 (s, 9H, CMe3), 0.88 (d, 3H, J HH ) 6.4
3
3
Hz, CHMe), 0.48 (d, 2H, J HH ) 6.1 Hz, ZrCH2), 0.36, 0.29 (s,
5H, Ph), 2.44 (t, J HH ) 6.5 Hz, 2H, CH2Ph), 2.06 (m, 2H,
3H, SiMe2). 19F NMR (C6D5Br, 25 °C): δ -131.78 (d), -161.36
(t), -165.42 (t).
ZrCH2CH2), 1.26 (s, 18H, CMe3), 0.56 (s, 6H, SiMe2), 0.44 (m,
2H, ZrCH2).
Complex 15b. 19F NMR (C6D5Br, 25 °C): δ -131.92 (d),
-165.03 (t), -167.95 (t).
{Me2Si(NCMe3)2}Zr {CH2CH2CH2P h }{BzB(C6F 5)3} (14c).
Ethene (1 bar, 4.5 mL, 0.20 mmol) was added to a solution of
0.03 mmol of 6 in C6D5Br (0.7 mL), and the reaction was
monitored by 1H NMR spectroscopy. Clean and complete
[{Me2Si(NCMe3)2}Zr {CH 2CH (Me)CH 2P h }(NMe2P h )]-
[B(C6F 5)4] (15d ). Propene (1 bar, 4.5 mL, 0.20 mmol) was
added to a solution of 0.03 mmol of 7 in C6D5Br (0.7 mL), and
conversion to the title complex was observed within 5 h (t1/2
)
1
76 min). In CD2Cl2, the reaction is somewhat faster (60%
conversion in 60 min), and in toluene-d8, it is noticeably slower
(25% conversion in 20 h). THF addition afforded 14b.
Complex 14c. 1H NMR (C6D5Br, 25 °C): δ 7.3-6.8 (m, Ph),
the reaction was monitored by H NMR spectroscopy. Clean
and complete conversion to a 22:78 mixture of 15d and 15a
was observed within 25 min.
Complex 15d . 1H NMR (C6D5Br, 25 °C): δ 6.47 (t, 1H,
p-PhN), 6.34 (d, 2H, o-PhN), 2.5 (vbr, NMe2Ph), 0.96 (s, CMe3),
0.42, 0.21 (s, 3H, SiMe2); other resonances were obscured.
Complex 15a . 1H NMR (C6D5Br, 25 °C): δ 7.5-7.0 (m, Ph),
3
3.36 (br, 2H, BCH2), 2.44 (t, J HH ) 6.9 Hz, 2H, CH2Ph), 1.79
(m, 2H, ZrCH2CH2), 1.00 (s, 18H, CMe3), 0.50 (m, 2H, ZrCH2),
0.35, 0.32 (s, 3H, SiMe2). 1H NMR (CD2Cl2, 25 °C): δ 7.6-7.1
3
2
3
(m, 10H, Ph), 3.21 (m, 2H, BCH2Ph), 2.45 (t, J HH ) 6.3 Hz,
2.88 (dd, J de ) 11.6 Hz, J cd ) 5.0 Hz, 1H, Hd), 0.96 (s, 18H,
CMe3), 0.69 (t, 2H, ZrCH2), 0.32, 0.27 (s, 3H, SiMe2), -0.12 (t,
3J HH ) 13.1 Hz, Ha); other resonances were obscured.
2H, CH2CH2Ph), 1.88 (m, 2H, ZrCH2CH2), 1.26 (s, 18H, CMe3),
0.60 (m, 2H, ZrCH2), 0.59, 0.50 (s, 3H, SiMe2). 19F NMR (C6D5-
Br, 25 °C): δ -132.21 (d), -161.69 (t), -165.7 (t).
[{Me2Si(NCMe3)2}Zr {CH 2CH (n -Bu )CH 2P h }][B(C6F 5)4]
(16a ). A solution of 1-hexene (100 µL, 0.80 mmol) in CH2Cl2
(1.5 mL) at -30 °C was added to a mixture of 4 (100 mg, 0.21
mmol) and [Ph3C][B(C6F5)4] (194 mg, 0.21 mmol) at -30 °C.
Complex 14b. 1H NMR (C6D5Br, 25 °C): δ 3.25 (s, 2H,
BCH2), 2.50 (t, 2H, CH2Ph), 2.05 (m, 2H, ZrCH2CH2), 1.12 (s,
18H, CMe3), 0.45 (br, 6H, SiMe2); other resonances were

5436 Organometallics, Vol. 16, No. 25, 1997
Horton and de With
The solution color changed to yellow on warming to 25 °C (2
min), after which hexane (5 mL) was added, precipitating a
yellow oil. Hexane washing (twice) and drying in vacuo
afforded a yellow solid which was spectroscopically pure. THF
addition afforded 16b.
m-Ph), 7.21 (t, 1H, p-Ph), 7.12 (d, 2H, o-Ph), 3.24 (m, 1H, Hd),
2
2.62 (m, 2H, CH2Ph), 2.52 (m, 2H, Hc and He), 1.78 (d, J ab
)
13.4 Hz, 1H, Ha), 1.16, 1.10 (s, 9H, CMe3), 0.49, 0.42 (s, 3H,
2
SiMe2), 0.05 (t, 1H, J bc ) 12.7 Hz, Hb); resonances were
assigned using a 2-D COSY experiment.
Complex 16a . 1H NMR (CD2Cl2, -20 °C): δ 7.96 (m, 5H,
2
Complex 17b. 1H NMR (CD2Cl2, 25 °C): δ 2.53 (d, J HH
)
2
3
4
Ph), 3.42 (ddd, J de ) 11.8 Hz, J cd ) 5.5 Hz, J ad ) 1.7 Hz,
6.4 Hz, 4H, CH2Ph), 2.40 (m, ZrCH2CH), 1.33 (s, 18H, CMe3),
3
3
1H, Hd), 2.55 (t, 1H, J ce ) 11.8 Hz, He), 2.41 (m, 1H, J bc
)
2
2
0.68 (d, 2H, J HH ) 6.7 Hz, ZrCH2), 0.52 (s, 6H, SiMe2).
13.5 Hz, Hc), 1.88 (dt, J ab ) 13.5 Hz, 1H, Ha), 1.21 (s, 18H,
CMe3), 0.86 (obscured, 3H, CH3), 0.57, 0.46 (s, 3H, SiMe2), 0.03
(t,1H, Hb); resonances were assigned using a 2-D COSY
experiment. 13C NMR (C2D2Cl4, 25 °C): δ 159.0 (1C, ipso-Ph),
134.7, 131.2 (2C, Ph), 125.6 (1C, p-Ph), 60.4 (2C, CMe3), 55.9
(1C, CH), 55.6, 43.0, 41.7 (1C, CH2), 35.5, 35.4, (3C, CMe3),
29.6, 22.9 (1C, CH2), 14.4 (1C, CH3), 6.1, 5.6 (1C, SiMe2); anion
resonances omitted. 11B NMR (C2D2Cl4, 25 °C): δ -15.5 (∆ν1/2
) 23 Hz). 19F NMR (CD2Cl2, 25 °C): δ -133.88 (m), -163.63
(m), -167.58 (m).
P r oced u r e for P olym er iza tion Testin g. A 25 mL steel
autoclave with a glass liner was used for screening the ethene
polymerization activity. A toluene (10 mL) solution of the
cationic complex (0.03 mmol) or a mixture of complex 1 (0.01
mmol), MAO (2.0 mmol; 10% solution in toluene), and toluene
(10.5 mL) were loaded into the autoclave in the glovebox. The
autoclave was then placed in a constant temperature bath and
pressurized with ethene (20 bar). The reaction was stopped
by rapidly venting the system, followed by decanting the
product mixture under air. The polyethene remaining in the
autoclave was washed out with toluene, and the toluene
fractions were combined and added to methanol. The poly-
ethene was removed by filtration, stirred with MeOH and then
1 N HCl solution, filtered again, washed with water followed
by acetone, and then dried (vacuum, 70 °C, 3 days). The low
ethene polymerization activities in the small autoclave were
consistent with the results obtained in a 1 L steel autoclave
under conditions of higher dilution and lower pressure (3 bar).
Cationic complexes were freshly prepared and immediately
introduced into the 25 mL autoclave; no alkylaluminium
scavenger was utilized.
Complex 16b. 13C NMR (C2D2 Cl4, 25 °C): δ 143.0 (1C, ipso-
Ph), 130.0, 128.2 (2C, Ph), 125.9 (1C, p-Ph), 64.9 (1C, CH2),
59.7 (2C, CMe3), 45.5 (1C, CH2), 44.4 (1C, CH), 38.8 (1C, CH2),
35.0 (6C, CMe3), 30.3, 23.6 (1C, CH2), 14.7 (1C, CH3), 7.0 (2C,
SiMe2); anion resonances omitted.
[{Me2Si(NCMe3)2}Zr {CH2CH(CH2P h )2}][B(C6F 5)4] (17a ).
A solution of allylbenzene (100 µL, 0.75 mmol) in CH2Cl2 (1.5
mL) at -30 °C was added to a mixture of 4 (70 mg, 0.15 mmol)
and [Ph3C][B(C6F5)4] (135 mg, 0.15 mmol) at -30 °C. The
solution color changed to yellow on warming to 25 °C (5 min),
after which hexane (5 mL) was added, precipitating a yellow
oil. Hexane washing (twice) and drying in vacuo afforded a
yellow solid. THF addition afforded 17b.
Complex 17a . 1H NMR (C2D2Cl4, -25 °C): δ 8.01 (t, 1H,
PhZr), 7.94 (m, 1H, PhZr), 7.85 (m, 3H, PhZr), 7.30 (t, 2H,
OM970504E