Chelate-Controlled Synthesis of rac- and meso-Me2Si(3- tBu-C5H3)2ZrCl2

Article abstract of DOI:10.1021/om034184c

The reaction of the chelated bis-amide complex Zr{PhN(CH₂) ₃NPh}Cl₂(THF)₂ (2) with Li₂[Me ₂Si(3-^tBu-C₅H₃)₂] yields meso-Me₂Si(3-^tBu-C₅H₃) ₂Zr{PhN(CH₂)₃NPh} (meso-3) in >98% yield. In contrast, the reaction of Zr{Me₃SiN(CH₂) ₃NSiMe₃}Cl₂(THF)₂ (4) or the related mono-THF adduct Zr{Me₃SiN(CH₂) ₃NSiMe₃}Cl₂(THF) (5) with Li ₂[Me₂Si(3-^tBu-C₅H₃) ₂] yields rac-Me₂Si(3-^tBu-C₅H ₃)₂Zr{Me₃SiN(CH₂) ₃NSiMe₃} (rac-6) in quantitative NMR yield and 89% isolated yield. X-ray crystallographic analyses show that the Zr{RN(CH ₂)₃NR} chelate ring in rac-6 has a pronounced twist conformation, while that in meso-3 has a flatter, envelope conformation. It is proposed that the conformations of the Zr{RN(CH₂)₃NR} chelate rings in the stereodetermining transition states for addition of the second Cp^- ring in these reactions are similar to those in the metallocene products and control the diastereoselectivity. meso-3 and rac-6 are converted to meso-Me₂Si(3-^tBu-C₅H ₃)₂ZrCl₂ (meso-1) and rac-1, respectively, by reaction with HCl in Et₂O.

Full text of DOI:10.1021/om034184c

5498
Organometallics 2003, 22, 5498-5503
Ch ela te-Con tr olled Syn th esis of r a c- a n d
m eso-Me2Si(3-tBu -C5H3)2Zr Cl2
Matthew D. LoCoco and Richard F. J ordan*
Department of Chemistry, The University of Chicago, 5735 South Ellis Avenue,
Chicago, Illinois 60637
Received September 22, 2003
The reaction of the chelated bis-amide complex Zr{PhN(CH2)3NPh}Cl2(THF)2 (2) with
Li2[Me2Si(3-tBu-C5H3)2] yields meso-Me2Si(3-tBu-C5H3)2Zr{PhN(CH2)3NPh} (meso-3) in >98%
yield. In contrast, the reaction of Zr{Me3SiN(CH2)3NSiMe3}Cl2(THF)2 (4) or the related mono-
THF adduct Zr{Me3SiN(CH2)3NSiMe3}Cl2(THF) (5) with Li2[Me2Si(3-tBu-C5H3)2] yields rac-
Me2Si(3-tBu-C5H3)2Zr{Me3SiN(CH2)3NSiMe3} (rac-6) in quantitative NMR yield and 89%
isolated yield. X-ray crystallographic analyses show that the Zr{RN(CH2)3NR} chelate ring
in rac-6 has a pronounced twist conformation, while that in meso-3 has a flatter, envelope
conformation. It is proposed that the conformations of the Zr{RN(CH2)3NR} chelate rings
in the stereodetermining transition states for addition of the second Cp- ring in these
reactions are similar to those in the metallocene products and control the diastereoselectivity.
meso-3 and rac-6 are converted to meso-Me2Si(3-tBu-C5H3)2ZrCl2 (meso-1) and rac-1,
respectively, by reaction with HCl in Et2O.
In tr od u ction
lation with ZrCl4 to produce rac-1 (>98% de, 60% overall
isolated yield).6 Here we describe highly stereoselective
syntheses of rac-1 and meso-1.
The application of structurally complex ansa-zir-
conocenes, particularly bis-indenyl systems, as stereo-
selective catalysts has been studied extensively.1 This
field would be advanced significantly by the develop-
ment of efficient syntheses of rac-metallocenes derived
from simple, easily accessible, bis-Cp- ligands. In this
regard, the synthesis of rac-Me2Si(3-tBu-C5H3)2ZrCl2
(rac-1) has attracted considerable interest.2 This met-
allocene has been prepared by salt elimination and
amine elimination reactions, which produce rac/meso
mixtures,3,4 and by photochemical isomerization of rac-
1/ meso-1 mixtures.5 To date, the most efficient route
to 1, developed by Brintzinger and co-workers, com-
prises reaction of Sn(NMe2)4 with Me2Si(3-tBu-C5H3)2
to yield a silastannaindacene, followed by transmeta-
We recently reported a highly selective, “chelate
controlled” synthesis of rac-ansa-bis(indenyl) zircono-
cenes, which is based on the reaction of lithium ansa-
bis(indenyl) salts with the chelated bis-amide compound
Zr{PhN(CH2)3NPh}Cl2(THF)2 (2) and is shown in Scheme
1.7 This procedure works well for rac-(SBI)Zr{PhN-
(CH2)3NPh} and 2-Me-substituted and 2-Me-4-aryl-
substituted derivatives thereof, as well as for rac-(EBI)-
Zr{PhN(CH2)3NPh}.7
The key to Scheme 1 is the use of the [PhN(CH2)3N-
Ph]2- ligand to control diastereoselectivity. The Zr{PhN-
(CH2)3NPh} chelate rings in 2 and several (C5R5)2Zr-
{PhN(CH2)3NPh} metallocenes adopt twist conforma-
tions which place the N-Ph groups on opposite sides of
the N-Zr-N plane, as shown in Scheme 1.7 This
arrangement complements the rac-metallocene struc-
ture but strongly disfavors the meso isomer. The mech-
anism of [X(indenyl)2]2- substitution of the chloride and
THF ligands of 2 is unknown and may be complicated
by ion-pairing, solvation, and other factors.3 However,
the simple model in Scheme 1 provides useful insights.
We postulate that, while rotation around the Zr-
(indenyl centroid) in the mono-indenyl intermediate A
can occur, the bridge (X) must be close to the “back”
position in the transition state for the second indenyl
* Corresponding author.
(1) (a) Brintzinger, H. H.; Fischer, D.; Mu¨lhaupt, R.; Rieger, B.;
Waymouth, R. M. Angew. Chem., Int. Ed. Engl. 1995, 34, 1143. (b)
Resconi, L.; Cavallo, L.; Fait, A.; Piemontesi, F. Chem. Rev. 2000, 100,
1253. (c) Hoveyda, A. H.; Morken, J . P. Angew. Chem., Int. Ed. Engl.
1996, 35, 1262. (d) Halterman, R. L. In Synthesis of Chiral Titanocene
and Zirconocene Dichlorides; Togni, A., Halterman, R. L., Eds.;
Metallocenes: Synthesis, Reactivity, Applications: Wiley-VCH: Wein-
heim, 1998; Vol. 1, Chapter 8.
(2) For polymerization studies using 1 see: (a) Suzuki, N.; Yamagu-
chi, Y.; Fries, A.; Mise, T. Macromolecules 2000, 33, 4602. (b) Mise,
T.; Miya, S.; Yamazaki, H. Chem. Lett. 1989, 1853. (c) Ro¨ll, W.;
Brintzinger, H. H.; Rieger, B.; Zolk, R. Angew. Chem., Int. Ed. Engl.
1990, 29, 279. For other examples of metallocenes based on ansa-bis-
(3-R-C5H3) ligands see: (d) Sutton, S. C.; Nantz, M. H.; Parkin, S. R.
Organometallics 1993, 12, 2248. (e) Collins, S.; Hong, Y.; Taylor, N. J .
Organometallics 1990, 9, 2695. (f) Chen, Z.; Halterman, R. L. Organo-
metallics 1994, 13, 3932. (g) Schnutenhaus, H.; Brintzinger, H. H.
Angew. Chem., Int. Ed. Engl. 1979, 18, 777. (h) Kuntz B. J .; Ram-
achandran, R.; Taylor N. J .; Guan, J .; Collins, S. J . Organomet. Chem.
1995, 497, 133.
(6) (a) Hu¨ttenhofer, M.; Weeber, A.; Brintzinger, H. H. J . Organomet.
Chem. 2002, 663, 58. (b) Hu¨ttenhofer, M.; Schaper, F.; Brintzinger,
H. H. Angew. Chem., Int. Ed. 1998, 37, 2268.
(7) (a) Zhang, X.; Zhu, Q.; Guzei, I. A.; J ordan, R. F. J . Am. Chem.
Soc. 2000, 122, 8093. (b) LoCoco, M. D.; J ordan, R. F. Abstracts of
Papers, 225th ACS National Meeting, New Orleans, LA, March 23-
27, 2003, INOR-723. (c) SBI ) Me2Si(indenyl)2, EBI ) 1,2-bis(indenyl)-
ethane. (d) X-ray crystallographic analyses show that the Zr{PhN-
(CH2)3NPh} chelate rings in Cp2Zr{PhN(CH2)3NPh}, rac-(SBI)-
Zr{PhN(CH2)3NPh}, and rac-{Me2Si(2-Me-4,5-benz-1-indenyl)2}Zr{Ph-
N(CH2)3NPh} adopt twist conformations.7a,b
(3) Wiesenfeldt, H.; Reinmuth, A.; Barsties, E.; Evertz, K.; Brintz-
inger, H. H. J . Organomet. Chem. 1989, 369, 359.
(4) Diamond, G. M.; J ordan, R. F.; Petersen, J . F. Organometallics
1996, 15, 4045.
(5) Schmidt, K.; Reinmuth, A.; Rief, U.; Diebold, J .; Brintzinger, H.
H. Organometallics 1997, 16, 1724.
10.1021/om034184c CCC: $25.00 © 2003 American Chemical Society
Publication on Web 11/21/2003

rac- and meso-Me2Si(3-tBu-C5H3)2ZrCl2
Organometallics, Vol. 22, No. 26, 2003 5499
a
Sch em e 1
Sch em e 2
ment is required to maintain a normal N(1)-Zr(1)-N(2)
angle of 95.3(1)°. The C(10) phenyl group on the crowded
side of the molecule lies in the N-Zr-N plane. The
steric crowding associated with the tBu groups is
t
manifested in several other ways. The Bu groups are
bent 9.5° out of their respective Cp planes, and the Zr-
C(tBu) distances (Zr-C(28) 2.693(3) Å; Zr-C(17) 2.782-
(3) Å) are longer than the other Zr-Cp distances (range
2.49-2.65 Å). Additionally, the two Cp rings are canted
such that the angle between the C(27)-C(28) and
C(18)-C(17) bond vectors is 24.9°. The Cp rings are
rotated around the Zr-centroid axes such that the
SiMe2 bridge is displaced by 16.3° from the back position
addition, as required in the ansa-metallocene product.
As the second indenyl adds, N-Ph/indenyl steric inter-
actions block formation of the meso product by path (ii),
and the rac product forms by path (i). Significant N-Ph/
indenyl steric interactions would arise on the crowded
side of the meso isomer (and transition state leading
thereto) unless the Zr{PhN(CH2)3NPh} chelate ring
adopted a different conformation, which is unfavor-
able.7,8
t
of the metallocene, and the Bu groups are displaced
toward the front of the metallocene by a corresponding
amount. This “lateral distortion”10 is smaller than those
in meso-Me2Si(3-tBu-C5H3)2Zr(1,1′-binaphth-2′-ol-2-ola-
to)Cl (27.1°)5 and meso-Me2Si(3-tBu-C5H3)2ZrMe2 (24.6°)11
and appears to be limited by steric crowding between
the C(10) phenyl group and the Cp and C(34) methyl
groups.12
Application of this strategy to the synthesis of 1 led
to a surprising result. The reaction of Li2[Me2Si(3-tBu-
C5H3)2] with 2 in Et2O yields pure meso-Me2Si(3-
tBu-C5H3)2Zr{PhN(CH2)3NPh} (meso-3) quantitatively
1
(Scheme 2)! The H NMR spectrum of meso-3 contains
These structural data provide clues to the origin of
the surprising selectivity for the meso product in Scheme
2. As for Scheme 1, we postulate that steric interactions
in the mono-Cp intermediate and the transition state
for addition of the second Cp- ring are similar to those
in the metallocene product. That is, as illustrated in
Scheme 3, we postulate that steric interactions force the
Zr{PhN(CH2)3NPh} chelate ring of mono-Cp intermedi-
ate B into an envelope conformation. Steric interactions
two sets of phenyl resonances and two Si-Me reso-
nances, which establishes the meso stereochemistry.
Reaction of meso-3 with HCl (1 M Et2O solution) in
benzene yields meso-1 in >95% NMR yield. The use of
4 equiv of HCl in Scheme 2 facilitates the identification
of meso-1 by precipitation of the HNPh(CH2)3NPhH
coproduct as [H2NPh(CH2)3NPhH2]Cl2.
To probe the stereocontrol mechanism in Scheme 2,
the molecular structure of meso-3 was determined by
X-ray diffraction (Figure 1). Surprisingly, the Zr{PhN-
(CH2)3NPh} ring adopts an envelope conformation in
which C(10), C(9), and C(8) are close to the N(1)-Zr-
(1)-N(2) plane (respective deviations: -0.056, 0.083,
0.148 Å), while C(7) lies 0.63 Å below and C(1) lies 0.56
Å above this plane. This unusual conformation is
t
between the Bu group of the incoming Cp- ligand and
the puckered segment of the chelate ring block forma-
tion of rac-3 via path (i), so that meso-3 forms via path
(ii).
To favor the formation of a rac-Me2Si(3-tBu-C5H3)2-
Zr{RN(CH2)3NR} metallocene, we sought to modify the
controlling [RN(CH2)3NR]2- ligand to increase the steric
t
enforced by the bulky Bu groups, which make close
contact with and thus flatten the C(10)-C(8) segment
(9) Close contacts (Å): H(24C)- -H(9B) 2.30, H(9A)- -H(31A) 2.43,
H(32C)- -H(8A) 2.20, H(23A)- -H(7A) 2.13, C(10)- -H(24C) 2.75.
(10) (a) Burger, P.; Diebold, J .; Gutman, S.; Hund, H. U.; Brintz-
inger, H. H. Organometallics 1992, 11, 1319. (b) Burger, P.; Hortman,
K.; Brintzinger, H. H. Makromol. Chem., Macromol. Symp. 1993, 66,
127.
(11) Chirik, P. J .; Henling, L. M.; Bercaw, J . E. Organometallics
2001, 20, 534.
(12) Close H-H contacts (Å): H(15)- -H(29) 2.26, H(15)- -H(16) 2.47,
H(15)- -H(34A) 2.40.
of the chelate.9 Puckering of the C(8)-C(7)-N(1) seg-
(8) In contrast, metallocene syntheses using Ti binaphtholate or Zr
biphenolate compounds that adopt twist conformations gave low yieldsa
or rac/meso mixtures that were isomerized to rac products using
TEMPO.b (a) Erikson, M. S.; Fronczek, F. R.; McLaughlin, M. L. J .
Organomet. Chem. 1991, 415, 75. (b) Damrau, H.-R.; Royo, E.; Obert,
S.; Schaper, F.; Weeber, A.; Brintzinger, H.-H. Organometallics 2001,
20, 5258.

5500 Organometallics, Vol. 22, No. 26, 2003
LoCoco and J ordan
Sch em e 3
Sch em e 4
F igu r e 1. Molecular structure and corresponding space-
filling diagram of meso-Me2Si(3-tBu-C5H3)2Zr{PhN(CH2)3-
NPh} (meso-3). H atoms are omitted in the ORTEP view.
Bond distances (Å): Zr-N(1) 2.076(3), Zr-N(2) 2.176(3),
Zr-{C(16)-C(20) centroid} 2.328(3), Zr-{C(25)-C(29) cen-
troid} 2.308(3). Bond angles (deg): centroid-Zr-centroid
124.2(9).
crowding between the Cp-tBu and N-R groups, to
provide a stronger preference for the chelate twist
conformation in the metallocene product (and presum-
ably the transition state for the second Cp- addition).
This can be achieved by replacing the N-Ph groups with
N-SiMe3 groups, which feature greater three-dimen-
sional steric bulk. The reaction of Zr{Me3SiN(CH2)3-
NSiMe3}Cl2(THF)2 (4)13 or the related mono-THF ad-
duct Zr{Me3SiN(CH2)3NSiMe3}Cl2(THF)(5)with Li2[Me2Si(3-
tBu-C5H3)2] in THF yields pure rac-Me2Si(3-tBu-C5H3)2-
Zr{Me3SiN(CH2)3NSiMe3} (rac-6) in quantitative NMR
necessary because the Me3SiNH(CH2)3NHSiMe3 coprod-
uct reacts with HCl to yield [H3N(CH2)3NH3]Cl2 and
ClSiMe3.
The molecular structure of rac-6 is shown in Figure
2. rac-6 has approximate C2 symmetry with the C2 axis
lying along the Zr- - -C(12) vector. In contrast to meso-
3, the Zr{Me3SiN(CH2)3NSiMe3} chelate ring has the
familiar twist conformation,7 which places the N-SiMe3
groups in the sterically open quadrants of the rac-
metallocene and minimizes SiMe3/tBu steric interac-
tions.14,15 We propose that the twist conformation
1
yield and 89% isolated yield (Scheme 4). The H NMR
t
spectrum of rac-6 contains singlets for the Bu, SiMe2,
and SiMe3 groups, which confirms the rac stereochem-
istry. rac-6 is cleanly converted to rac-1 by reaction with
6 equiv of HCl in Et2O. The 3-fold excess of HCl is
(14) (a) Deviations (Å) of C and Si atoms from the N(1)-Zr-N(2)
plane: Si(2) 0.88, C(11) -0.87, C(12) 0.10, C(13) 0.71, Si(1) -0.61. (b)
The conformation of the Zr{Me3SiN(CH2)3NSiMe3} chelate ring in rac-6
is similar to that in 4; see ref 13b.
(13) (a) Freidrich, S.; Gade, L. H.; Scowen, I. J .; McPartlin, M.
Organometallics 1995, 14, 5344. (b) Freidrich, S.; Gade, L. H.; Trosch,
D. J . M.; Scowen, I. J .; McPartlin, M. Inorg. Chem. 1999, 38, 5295.

rac- and meso-Me2Si(3-tBu-C5H3)2ZrCl2
Organometallics, Vol. 22, No. 26, 2003 5501
a nitrogen-filled drybox. Nitrogen was purified by passage
through columns containing activated molecular sieves and
Q-5 oxygen scavenger. Pentane, hexanes, toluene, and benzene
were distilled from sodium/benzophenone or purified by pas-
sage through columns of activated alumina and BASF R3-11
oxygen removal catalyst. Benzene-d6 was distilled from sodium/
benzophenone. The compounds Me2Si(3-tBu-C5H3)2,3 Zr{PhN-
(CH2)3NPh}Cl2(THF)2,7a,b Zr{Me3SiN(CH2)3NSiMe3}2,13a and
13a
Zr{Me3SiN(CH2)3NSiMe3}Cl2(THF)2
were prepared by lit-
erature procedures.
Elemental analyses were performed by Midwest Microlabs.
ESI-mass spectra were obtained with an Agilent 1100 instru-
ment using direct injection via a syringe pump (ca. 10-6
M
solutions). Good agreement between observed and calculated
isotope patterns was observed in all cases. 1H and 13C NMR
spectra were recorded on a Bruker AC-500 or AC-400 spec-
trometer in flame-sealed or Teflon-valved tubes at ambient
1
probe temperatures. H and 13C chemical shifts are reported
relative to SiMe4 and were determined by reference to the
residual 1H and 13C solvent resonances. Coupling constants
are given in Hz.
Li2[Me2Si(3-tBu -C5H3)2].3 A Schlenk flask was charged
with a solution of Me2Si(3-tBu-C5H3)2 (2.75 g, 9.03 mmol) in
Et2O (50 mL). The solution was cooled to -78 °C, and a
solution of n-BuLi in hexanes (2.5 M, 7.22 mL, 18 mmol) was
added by syringe. The mixture was stirred for 4 h at -78 °C,
warmed to 0 °C in an ice bath, and then stirred overnight while
being allowed to warm gradually to room temperature. The
volatiles were removed under vacuum to yield a white solid.
Toluene (50 mL) was added by cannula transfer. The slurry
was stirred for 30 min and filtered through a medium-porosity
glass frit (10-20 µm pore size) to yield a white solid. The solid
was dried under vacuum overnight (2.55 g, 89%). 1H NMR
(THF-d8): δ 5.86 (m, 4H, Cp), 5.74 (t, J ) 3, 2H, Cp), 1.21 (s,
t
18H, Bu), 0.26 (s, 6H, SiMe2).
m eso-Me2Si(3-tBu -C5H3)2Zr {P h N(CH2)3NP h } (m eso-3). A
flask was charged with Li2[Me2Si(3-tBu-C5H3)2] (0.705 g, 2.22
mmol) and Zr{PhN(CH2)3NPh}Cl2(THF)2 (1.18 g, 2.22 mmol).
Diethyl ether (100 mL) was added by vacuum transfer at -196
°C. The mixture was warmed to 0 °C and stirred for 6 h and
then warmed to room temperature and stirred overnight. The
volatiles were removed under vacuum at 25 °C to yield a red
solid. Toluene (100 mL) was added by vacuum transfer at -196
°C, and the mixture was warmed to room temperature and
stirred for 30 min. The mixture was filtered through a Celite
column, and the volatiles were removed from the filtrate under
vacuum at 25 °C. The remaining red solid was dried under
vacuum (1.36 g, 99%). This material, which was spectroscopi-
cally pure, was recrystallized from pentane/hexamethyldisi-
loxane.16 1H NMR (C6D6): δ 7.28 (t, J ) 8, 2H, m-Ph), 7.22 (t,
J ) 8, 2H, m-Ph), 6.96 (t, J ) 8, 1H, p-Ph), 6.79 (m, 3H, o-Ph
and p-Ph), 6.47 (d, J ) 8.0 2H, o-Ph), 6.22 (m, 4H, Cp), 6.00
(t, J ) 3.0, 2H, Cp), 3.57 (t, J ) 6, 2H, NCH2), 3.26 (t, J ) 6,
F igu r e 2. Molecular structure and corresponding space-
filling diagram of rac-Me2Si(3-tBu-C5H3)2Zr{Me3SiN(CH2)3-
NSiMe3} (rac-6). H atoms are omitted from the ORTEP
view. Bond distances (Å): Zr-N(1) 2.114(2), Zr-N(2) 2.103-
(2), N(1)-Si(1) 1.725(2), N(2)-Si(2) 1.737(2), Zr-{C(1)-
C(5) centroid} 2.328(3), Zr-{C(6)-C(10) centroid} 2.340(3).
Bond angles (deg): N(1)-Zr-N(2) 92.63(8), centroid-Zr-
centroid 122.5(9).
dictates the formation of rac-6 in a manner analogous
to Scheme 1.
Con clu sion s
t
2H, NCH2), 1.67 (p, J ) 6, 2H, CH2), 0.92 (s, 18H, Bu), 0.60
This work expands the scope of the “chelate-con-
trolled” approach to metallocene synthesis to include
simple ansa-bis-Cp systems. The present results suggest
that suitable modification of the controlling bis-amide
ligand may enable the synthesis of a wide range of rac-
metallocenes by this method. These studies also provide
new insights into the factors that control diastereose-
lectivity in ansa-metallocene formation.
(s, 3H, SiMe), 0.55 (s, 3H, SiMe). 13C{1H} NMR (THF-d8): δ
162.9, 160.0, 148.4, 129.2, 128.5, 122.6, 120.8, 120.4, 118.3,
117.4, 111.8, 109.7, 106.0, 53.6, 52.9, 33.7, 31.5, 29.7, -2.6,
-5.4; the signal at δ 118.3 is broadened by restricted rotation
around an N-Ph bond at room temperature but is sharp at
60 °C. Anal. Calcd for C35H46N2SiZr: C, 68.45; H, 7.54; N, 4.56.
Found: C, 68.30; H, 7.52; N, 4.61.
m eso-Me2Si(3-t Bu -C5H3)2Zr Cl2 (m eso-1). An NMR tube
was charged with meso-Me2Si(3-tBu-C5H3)2Zr{PhN(CH2)3NPh}
(0.023 g, 0.037 mmol), and C6D6 (1.0 mL) was added by syringe.
A solution of HCl in Et2O (1.0 M, 77.5 µL, 0.077 mmol) was
added by syringe. The volatiles were removed under vacuum
Exp er im en ta l Section
Gen er a l P r oced u r es. All reactions were performed under
nitrogen or vacuum using standard Schlenk techniques or in
(15) In contrast to meso-3, rac-6 does not display a significant lateral
distortion. However, the Zr-N bond distances, N-Zr-N bond angle,
(16) For other examples of the use of hexamethyldisiloxane as a
recrystallization solvent see: (a) Kloppenburg, L.; Petersen, J . L.
Polyhedron 1995, 14, 69. (b) Strauch, J . W.; Petersen, J . L. Organo-
metallics 2001, 20, 2623.
t
displacement of the Bu groups from the Cp planes, and the trend in
Zr-C(Cp) distances in rac-6 are similar to the data for meso-3. The
angle between the C(2)-C(3) and C(10)-C(9) bond vectors is 9.9°.

5502 Organometallics, Vol. 22, No. 26, 2003
LoCoco and J ordan
Ta ble 1. Su m m a r y of Cr ysta l Da ta for m eso-3
a n d r a c-6
immediately, and fresh C6D6 was added by vacuum transfer
at -196 °C. The tube was warmed to room temperature, and
a
1H NMR spectrum was obtained, which showed that com-
meso-3
rac-6
plete conversion to Me2Si(3-tBu-C5H3)2ZrCl2 (meso/rac 30:1)3
and HNPh(CH2)3NHPh had occurred. 1H NMR (C6D6) for meso-
Me2Si(3-tBu-C5H3)2ZrCl2: δ 6.84 (t, J ) 2, 2H, Cp), 5.87 (t, J
formula
cryst syst
space group
a (Å)
b (Å)
c (Å)
C
35H46N2SiZr
C29H54N2Si3Zr
monoclinic
P21/n
14.712(7)
11.872(6)
19.306(9)
104.373(8)
3266(3)
monoclinic
P21/n
t
) 2, 2H, Cp), 5.54 (t, J ) 2, 2H, Cp), 1.45 (s, 18H, Bu), 0.29
(s, 3H, SiMe), 0.08 (s, 3H, SiMe). H NMR (C6D6) for HNPh-
10.324(2)
18.201(3)
16.753(3)
100.203(2)
3094.8(8)
4
1
(CH2)3NPhH: δ 7.17 (t, J ) 7, 4H, Ph), 6.76 (t, J ) 7, 2H, Ph),
6.46 (d, J ) 7, 4H, Ph), 3.50 (br s, 2H, NH), 2.73 (t, J ) 7, 4H,
NCH2), 1.32 (p, J ) 7, CH2).
â (deg)
V (Å3)
Z
Gen er a tion of m eso-Me2Si(3-tBu -C5H3)2Zr Cl2 (m eso-1)
fr om m eso-3 a n d 4 Equ iv of HCl. An NMR tube was charged
with meso-Me2Si(3-tBu-C5H3)2Zr{PhN(CH2)3NPh} (0.028 g,
0.045 mmol), and C6D6 (1.0 mL) was added by syringe. A
solution of HCl in Et2O (1.0 M, 181.0 µL, 0.181 mmol) was
added by syringe. The volatiles were removed under vacuum
immediately, and fresh C6D6 was added by vacuum transfer
at -196 °C. The tube was warmed to room temperature to
yield a slurry of a white precipitate in a yellow supernatant.
The supernatant was decanted from the precipitate to yield a
4
µ (mm-1
)
0.420
0.466
cryst dimens (mm)
cryst color, habit
T (K)
0.2 × 0.2 × 0.2
red, fragment
100
0.40 × 0.25 × 0.25
yellow, fragment
135
diffractometer
radiation, λ (Å)
θ range (deg)
Bruker Smart Apex Bruker Smart Apex
Mo KR, 0.71073
Mo KR, 0.71073
2.24-25.03
2.03-25.02
data collected: h;k;l (12; -21,19; -18,19 (17; (14; (22
no. of reflns
19 612
23 087
no. of indep reflns
5476 (0.0322)
5755 (0.0252)
a
(Rint
)
1
clear yellow solution. H NMR analysis of the solution estab-
abs corr
SADABS
SADABS
lished that complete conversion to Me2Si(3-tBu-C5H3)2ZrCl2
(meso/rac 20:1) had occurred. The white solid was isolated and
identified as [H2NPh(CH2)3NH2Ph]Cl2 by NMR and ESI-MS.
[H2NP h (CH2)3NH2P h ]Cl2. A flask was charged with a
solution of HNPh(CH2)3NHPh (1.12 g, 4.94 mmol) in benzene
(25 mL). A solution of HCl in Et2O (1.0 M, 9.89 mL, 9.89 mmol)
was added over a 10 min period by syringe. The mixture was
stirred for 1 h at room temperature and filtered to afford a
white solid. The solid was washed with hexanes (2 × 20 mL)
and benzene (20 mL). The solid was then taken up as a slurry
in hexanes (20 mL), and the volatiles were removed under
max., min. transmn
1.00, 0.854
1.00, 0.852
5755/0/330
no. of data/restraints/ 5467/0/360
params
R indices (I > 2σ(I))b R1 ) 0.0456
wR2 ) 0.0899
R1 ) 0.0331
wR2 ) 0.0817
R1 ) 0.0347
wR2 ) 0.0826
R indices (all data)b R1 ) 0.0465
wR2 ) 0.0904
a
2
2
2
b
Rint ) ∑|Fo - Fo |/∑|Fo |. R1 ) ∑||Fo| - |Fc||/∑|Fo|; wR2 )
[∑[w(Fo2 - Fc2)2]/∑[w(Fo2)2]]1/2, where w ) q[σ2(Fo2) + (aP)2 + bP]-1
.
tBu), 1.00 (br m, 2H, CH2), 0.47 (s, 6H, SiMe2), 0.27 (s, 18H,
SiMe3). 13C{1H} NMR: δ 148.8, 116.1, 111.3, 107.9, 106.5, 46.2,
33.7, 31.3, 28.5, 3.6, -4.3. Anal. Calcd for C29H54N2Si3Zr: C,
57.45; H, 8.98; N, 4.57. Found: C, 57.19; H, 8.97; N, 4.57.
1
vacuum to yield a white solid. H NMR (D2O): δ 7.46 (br m,
6H, Ph), 7.32 (br d, J ) 7, 4H, Ph), 3.43 (t, J ) 8, 4H, NCH2),
2.03 (p, J ) 8, 2H, CH2). 13C{1H} NMR (D2O): δ 134.0, 130.3,
129.7, 122.0, 47.6, 21.4. ESI-MS: [HNPh(CH2)3NH2Ph]+ calcd
m/z 227.1, found 227.1.
r a c-Me2Si(3-tBu -C5H3)2Zr Cl2 (r a c-1). NMR Sca le. An
NMR tube was charged with rac-Me2Si(1-C5H3-3-tBu)2Zr{Me3-
SiN(CH2)3NSiMe3} (0.0274 g, 0.0451 mmol) and C6D6 (1 mL).
A solution of HCl in Et2O (1.0 M, 271 µL, 0.271 mmol) was
added by syringe. The volatiles were removed under vacuum
to yield a yellow solid. THF-d8 (1 mL) was added by vacuum
transfer at -196 °C, and the tube was warmed to room
temperature to yield a slurry of a white solid in a yellow
supernatant. The supernatant was decanted off and trans-
ferred to a new NMR tube. NMR analysis confirmed that
quantitative conversion to rac-Me2Si(3-tBu-C5H3)2ZrCl2 had
occurred. 1H NMR of rac-Me2Si(3-tBu-C5H3)2ZrCl2 (THF-d8):
δ 6.74 (t, J ) 3, 2H), 6.06 (t, J ) 3, 2H, Cp), 5.92 (t, J ) 3, 2H,
Zr {Me3SiN(CH 2)3NSiMe3}Cl2(TH F ) (5). A flask was
charged with Zr{Me3SiN(CH2)3NSiMe3}2 (3.04 g, 5.79 mmol)
and ZrCl4 (1.35 g, 5.79 mmol). Toluene (100 mL) was added,
and the mixture was heated to 60 °C for 3 days. The volatiles
were removed under vacuum, and the resulting white solid
was washed with pentane (75 mL) and dried under vacuum
(4.20 g, 95%). The solid was dissolved in THF (40 mL). The
bis-THF adduct Zr{Me3SiN(CH2)3NSiMe3}Cl2(THF)2 (4) can be
isolated from this solution by crystallization at -35 °C as
described by Gade13a,b or by removal of the volatiles under
vacuum and vacuum-drying the sample for a few minutes.
Drying under vacuum overnight yielded Zr{Me3SiN(CH2)3-
NSiMe3}Cl2(THF) as a white solid (5.01 g, 95%). 1H NMR
(C6D6): δ 3.72 (m, 4H, OCH2), 3.23 (t, J ) 5, 4H, NCH2CH2),
1.74 (p, J ) 5, 2H, NCH2CH2), 1.25 (m, 4H, OCH2CH2), 0.31
(s, 18H, SiMe3).
r a c-Me2Si(3-tBu -C5H3)2Zr {Me3SiN(CH2)3NSiMe3} (r a c-
6). A flask was charged with Li2[Me2Si(3-tBu-C5H3)2] (0.853
g, 2.69 mmol) and Zr{Me3SiN(CH2)3NSiMe3}Cl2(THF) (1.21 g,
2.69 mmol), and THF (100 mL) was added by vacuum transfer
at -196 °C. The mixture was warmed to 0 °C in an ice bath
and then stirred for 20 h while the bath was allowed to warm
to room temperature. The volatiles were removed under
vacuum at 25 °C to yield a yellow solid. Benzene (100 mL)
was added by vacuum transfer at -196 °C, and the mixture
was warmed to room temperature and stirred for 3 h. The
mixture was filtered through a medium-porosity glass frit, and
the volatiles were removed from the filtrate under vacuum at
25 °C. The resulting yellow solid was dried under vacuum (1.46
g, 89%). This material, which was spectroscopically pure, was
recrystallized from pentane. 1H NMR (C6D6): δ 6.85 (t, J ) 2,
2H, Cp), 5.91 (t, J ) 2, 2H, Cp), 5.84 (t, J ) 2, 2H, Cp), 3.32
(dt, J ) 16, 4; 2H, NCH2), 3.04 (m, 2H, NCH2), 1.23 (s, 18H,
t
Cp), 1.32 (s, 18H, Bu), 0.68 (s, 6H, SiMe2). The white solid
was washed with benzene (2 mL) and hexanes (2 mL) and
dried under vacuum. NMR and ESI-MS analysis established
that the white solid was [H3N(CH2)3NH3]Cl2. Data for
[H3N(CH2)3NH3]Cl2: 1H NMR (D2O): δ 3.14 (t, J ) 8, 4H,
NCH2), 2.10 (p, J ) 8, 2H, CH2). 13C{1H} NMR (D2O): δ 36.59,
25.41. ESI-MS (DMSO): [H3N(CH2)3NH2]+ calcd m/z 75.1,
found 75.2.
r a c-Me2Si(3-tBu -C5H3)2Zr Cl2 (r a c-1). P r ep a r a tive Sca le.
A flask was charged with rac-Me2Si(3-tBu-C5H3)2Zr{Me3SiN-
(CH2)3NSiMe3} (1.554 g, 2.563 mmol) and benzene (80 mL). A
solution of HCl in Et2O (1.0 M, 15.38 mL, 15.38 mmol) was
added by syringe over a 10 min period. The volatiles were
removed under vacuum to yield a yellow solid. Benzene (50
mL) was added by vacuum transfer at -196 °C, and the
mixture was warmed to room temperature and stirred for 45
min. The mixture was filtered through a medium-porosity
glass frit. The volatiles were removed from the filtrate under
vacuum. The remaining yellow solid was dried under vacuum
1
(1.00 g, 84%). H NMR (C6D6): δ 6.72 (t, J ) 3, 2H), 5.69 (t, J
t
) 3, 2H, Cp), 5.65 (t, J ) 3, 2H, Cp), 1.40 (s, 18H, Bu), 0.18

rac- and meso-Me2Si(3-tBu-C5H3)2ZrCl2
Organometallics, Vol. 22, No. 26, 2003 5503
(s, 6H, SiMe2). 13C{1H} NMR: δ 152.9, 125.8, 116.2, 110.2,
105.4, 33.6, 30.3, -5.8.
to 80 °C and then allowed to cool to room temperature over a
24 h period. Crystals of rac-6 were obtained from a saturated
pentane solution cooled to -35 °C.
Rea ction of Me3SiNH(CH2)3NHSiMe3 w ith 4 Equ iv of
HCl. An NMR tube was charged with a solution of Me3SiNH-
(CH2)3NHSiMe3 (0.049 g, 0.23 mmol) in C6D6 (2 mL). A solution
of HCl in Et2O (1.0 M, 0.9 mL, 0.9 mmol) was added by syringe,
and a white precipitate formed. The volatiles were vacuum
transferred to a new NMR tube. The white solid was identified
as [H3N(CH2)3NH3]Cl2 by NMR and ESI-MS. The presence of
ClSiMe3 in the volatiles was established by 1H NMR and
confirmed by spiking with additional ClSiMe3.
X-r a y Str u ctu r e Deter m in a tion s. Crystal data, data
collection details, and solution and refinement procedures are
summarized in Table 1, and full details are provided in the
Supporting Information. Crystals of meso-3 were obtained from
a 5:1 pentane/hexamethyldisiloxane solution which was heated
Ack n ow led gm en t. We thank Dr. Ian Steele for
assistance with the X-ray crystallographic analyses.
This work was supported by the National Science
Foundation (CHE-0212210).
Su p p or tin g In for m a tion Ava ila ble: Additional experi-
mental details and tables of crystallographic data for meso-3
and rac-6; data are also available for these compounds in CIF
format. This material is available free of charge via the
Internet at http://pubs.acs.org.
OM034184C