IAN amines: Chiral C2-symmetric zirconium(IV) complexes from readily modified axially chiral C1-symmetric β-diketimines

Article abstract of DOI:10.1021/om049897p

A general synthesis of β-diketimines derived from Isoquinoline and AminoNaphthalene components (IAN amines) is reported. Beginning from inexpensive 2-naphthol and isoquinoline, the sequence of reactions leading to R-IAN amines is convergent, short, and high-yielding. Several new derivatives are reported (e.g., R = Bn, ⁱPr, ^tBu, Ph, 2,6-Me₂Ph, 2,6-ⁱPr₂Ph, 2-Np). All of these were complexed to zirconium(IV) by transamination with Zr(NMe₂)₄, and in all cases 1:1 R-IAN:Zr complexes immediately formed at 25°C. Except in cases of severe steric hindrance (ⁱPr-IAN and 2,6-Me₂Ph), the corresponding 2:1 IAN:Zr complexes formed at temperatures ranging from 25 to 100°C in toluene. A feature conserved among all 2:1 IAN:Zr complexes was a remarkable degree of diastereoselectivity favoring a C₂-symmetric bis(β-diketiminate) isomer bearing cis-NMe₂ and cis-pyridyl ligands. Although all complexations were performed from rac-IAN, the resulting complexes are composed solely of homochiral ligands. The configurational integrity of Me-IAN and its ability to transfer asymmetry upon metal coordination was demonstrated in the catalyzed enantioselective addition of diethylzinc to benzaldehyde. Given the topographical similarity between these and metallocene complexes, several derivatives were preliminarily evaluated in ethylene polymerization.

Full text of DOI:10.1021/om049897p

2238
Organometallics 2004, 23, 2238-2250
Articles
IAN Am in es: Ch ir a l C2-Sym m etr ic Zir con iu m (IV)
Com p lexes fr om Rea d ily Mod ified Axia lly Ch ir a l
C1-Sym m etr ic â-Dik etim in es
Sarah B. Cortright,† J ohn C. Huffman,† Ryan A. Yoder,†
J oseph N. Coalter III,‡ and J effrey N. J ohnston*,†
Department of Chemistry, Indiana University, Bloomington, Indiana 47405-7102, and
The Dow Chemical Company, 3200 Kanawha Terrace, South Charleston, West Virginia 25303
Received February 7, 2004
A general synthesis of â-diketimines derived from Isoquinoline and AminoNaphthalene
components (IAN amines) is reported. Beginning from inexpensive 2-naphthol and isoquino-
line, the sequence of reactions leading to R-IAN amines is convergent, short, and high-
i
t
yielding. Several new derivatives are reported (e.g., R ) Bn, Pr, Bu, Ph, 2,6-Me2Ph, 2,6-
iPr2Ph, 2-Np). All of these were complexed to zirconium(IV) by transamination with
Zr(NMe2)4, and in all cases 1:1 R-IAN:Zr complexes immediately formed at 25 °C. Except in
cases of severe steric hindrance (iPr-IAN and 2,6-Me2Ph), the corresponding 2:1 IAN:Zr
complexes formed at temperatures ranging from 25 to 100 °C in toluene. A feature conserved
among all 2:1 IAN:Zr complexes was a remarkable degree of diastereoselectivity favoring a
C2-symmetric bis(â-diketiminate) isomer bearing cis-NMe2 and cis-pyridyl ligands. Although
all complexations were performed from rac-IAN, the resulting complexes are composed solely
of homochiral ligands. The configurational integrity of Me-IAN and its ability to transfer
asymmetry upon metal coordination was demonstrated in the catalyzed enantioselective
addition of diethylzinc to benzaldehyde. Given the topographical similarity between these
and metallocene complexes, several derivatives were preliminarily evaluated in ethylene
polymerization.
In tr od u ction
Diastereoselection in metal coordination chemistry is
also a central issue to the development of new polym-
erization catalysts and asymmetric reaction catalysts,
where it is commonly postulated that a single diaster-
eomeric ligand-metal-substrate complex is responsible
when high levels of stereoselection (diastereo- or enan-
tioselection) are observed.3 Yet, this assumption is
confirmed experimentally only a fraction of the time.4,5
Notwithstanding, this is a reasonable proposition when
ligands of high symmetry are implemented and 1:1
ligand-to-metal complexes are created. The use of chiral
C2-symmetric ligands6 dramatically simplifies the num-
ber of diastereomeric metal complexes that can form in
a catalytic system.7,8
We recently became interested in the isoquinoline-
derived binaphthyl ligands 1-5, for which amino de-
rivatives 1 had not been reported.9 Naphthyl isoquin-
oline derivatives 2-510,11 have attracted attention
primarily as ligands for late transition metal complexes.
Their value is best demonstrated by the use of Brown’s
P,N-ligand “Quinap” (4)12 in asymmetric hydrobora-
Diastereoselective complexation of a ligand to a metal
is a fundamental principle of coordination chemistry,
yet few control elements have been elucidated for this
phenomenon. Among these, the trans-influence/effect is
certainly the most prominent.1 Single isomer complexes
of high symmetry are most often attained either through
careful synthesis of a ligand designed specifically for a
1:1 ligand:metal complex and/or by employing a ligand
with a higher symmetry element in the formation of 2:1
complexes. Although the former is by far the most
common, the latter approach is now accepted to be quite
effective, particularly with C2-symmetric ligands. Rarely
are examples characterized in which high-symmetry
coordination complexes are formed from ligands of low
symmetry,2 and there are no examples where this
behavior has been generalized.
* Address correspondence to this author. E-mail: jnjohnst@
indiana.edu.
† Indiana University.
‡ The Dow Chemical Company.
(1) (a) Chernyaev, I. I. Ann. Inst. Platine USSR 1926, 4, 261. (b)
Basolo, F.; Pearson, R. G. Prog. Inorg. Chem. 1962, 4, 381. (c) Pearson,
R. G. Inorg. Chem. 1973, 12, 712. (d) Pidcock, A.; Richards, R. E.;
Venanzi, L. M. J . Chem. Soc. A 1966, 1707.
(2) For an example of high-symmetry complex formation from a low-
symmetry ligand, see: Davies, H. M. L.; Bruzinski, P. R.; Lake, D. H.;
Kong, N.; Fall, M. J . J . Am. Chem. Soc. 1996, 118, 6897.
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Asymmetric Catalysis; Springer-Verlag: Berlin, Germany, 1999; Vols.
1-3.
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J . Science 1982, 217, 401. (b) Norrby, P.-O.; Becker, H.; Sharpless, K.
B. J . Am. Chem. Soc. 1996, 118, 35.
10.1021/om049897p CCC: $27.50 © 2004 American Chemical Society
Publication on Web 04/10/2004

IAN Amines: Highly Diastereoselective Complexations
Organometallics, Vol. 23, No. 10, 2004 2239
ground for future development.23 More recently, Sibi
developed the use of chiral â-bisimidates 7 in the
enantioselective alkyl addition to enamidomalonates (eq
3).24 Modest to high enantioselection is observed with
absolute stereocontrol for either enantiomer when using
homochiral ligands.
tion,13 allylic alkylation,14 Diels-Alder cycloaddition,15
enolate arylation,16 and Mannich additions.17 In all of
these examples, the 1:1 ligand-metal complexes have
been the sole object of attention.
Amines 1 are bidentate N,N ligands formally of the
â-diketimine class. In recent years, activity in the
â-diketimine ligand area has intensified due to the
search for alternatives to metallocene catalysts.18 These
studies of Group IV metal â-diketiminate complexes and
their ability to polymerize R-olefins have elucidated
some of the challenges that face this ligand motif.19 Yet
only one chiral, nonracemic â-diketiminate has been
developed for a similarly small number of asymmetric
reactions.20 Pfaltz’s seminal work demonstrated the
utility of semicorrin-derived â-diketimine 6 in copper-
(I/II)-catalyzed cyclopropanation (eq 1)21 and cobalt(II)-
catalyzed conjugate reduction (eq 2),22 suggesting fertile
(5) Review: (a) Girard, C.; Kagan, H. B. Angew. Chem., Int. Ed.
Engl. 1998, 37, 2923. (b) Kagan, H. B. Synlett 2001, 888. (c) Kagan,
H. B.; Luukas, T. O. In Comprehensive Asymmetric Catalysis I-III;
Springer: New York, 1999; Vol. 1, pp 101-118. Selected recent
examples: (d) Steigelmann, M.; Nisar, Y.; Rominger, F.; Goldfuss, B.
Chem. Eur. J . 2002, 8, 5211. (e) Buono, F.; Walsh, P. J .; Blackmond,
D. G. J . Am. Chem. Soc. 2002, 124, 13652. (f) Balsells, J .; Davis, T. J .;
Carroll, P.; Walsh, P. J . J . Am. Chem. Soc. 2002, 124, 10336.
(6) Whitesell, J . K. Chem. Rev. 1989, 89, 1581.
(7) For example: (a) Shibasaki, M.; Sasai, H. Top. Stereochem. 1999,
22, 201-225. (b) Shibasaki, M.; Sasai, H. Adv. Asymmetric Synth. 1998,
3, 191-233.
(8) Kobayashi has postulated a rapid interconversion of two high-
symmetry complexes of (Br2-BINOL)2Zr(OR)2 during an enantioselec-
tive Mannich reaction: Ishitani, H.; Ueno, M.; Kobayashi, S. J . Am.
Chem. Soc. 2000, 122, 8180.
(9) For reviews on nitrogen-containing ligands for asymmetric
catalysis, see: (a) Fache, F.; Schulz, E.; Tommasino, M. L.; Lemaire,
M. Chem. Rev. 2000, 100, 2159. (b) McCarthy, M.; Guiry, P. J .
Tetrahedron 2001, 57, 3809.
(10) 2,3: Chelucci, G.; Bacchi, A.; Fabbri, D.; Saba, A.; Ulgheri, F.
Tetrahedron Lett. 1999, 40, 553. 5: Baker, R. W.; Reo, S. O.; Sargent,
M. V.; Schenkelaars, E. M. C.; Skelton, B. W.; White, A. H. Tetrahe-
dron: Asymmetry 1994, 5, 45. Baker, R. W.; Sargent, M. V. Pure Appl.
Chem. 1994, 66, 2143.
(11) For other derivatives within this class not shown, see: (a)
Tucker, S. C.; Brown, J .; Oakes, J .; Thornthwaite, D. Tetrahedron 2001,
57, 2545. (b) Brunner, H.; Olschewski, G.; Nuber, B. Synthesis 1999,
3, 429. (c) Tsue, H.; Fujinami, H.; Itakura, T.; Tsuchiya, R.; Kobayashi,
K.; Takahashi, H.; Hirao, K. J . Chem. Soc., Perkin Trans. 1 1999, 3677.
(d) Meyers, A. I.; Lutomski, K. A. J . Am. Chem. Soc. 1982, 104, 879.
(12) Alcock, N.; Brown, J .; Hulmes, D. Tetrahedron: Asymmetry
1993, 4, 743.
(13) (a) Brown, J . M.; Hulmes, D. I.; Layzell, T. P. J . Chem. Soc.,
Chem. Commun. 1993, 1673. (b) Doucet, H.; Fernandez, E.; Layzell,
T.; Brown, J . M. Chem. Eur. J . 1999, 5, 1320. (c) Fernandez, E.; Maeda,
K.; Hooper, M. W.; Brown, J . M. Chem. Eur. J . 2000, 6, 1840. (d) Perez
Luna, A.; Bonin, M.; Micouin, L.; Husson, H.-P. J . Am. Chem. Soc.
2002, 124, 12098.
The slow development of â-diketimine-based chiral
reagents might be attributed to several limitations.
Collins25 and Lappert26 noted the formation but flux-
ional nature (via Bailar twist) of simple 2:1 â-diketimi-
nate:zirconium(IV) amido complexes (Figure 1). Addi-
tionally, alkyl migration to azomethine carbon (Floriani27
and J ordan28) and intervention of an η5 coordination
mode have been noted.25,29 It is significant to note that
all chelate rings of â-diketimines studied prior to our
work were largely planar. An emphasis has also been
placed on symmetrical â-diketimines, although excep-
tions clearly exist (e.g. 9). These limitations notwith-
standing, the pioneering work of Smith,30 Collins,31
J ordan,28 and Lappert,26 among others,32 has provided
a basis for development of single site group IV metal
catalysts supported by achiral â-diketimines.
Hence, we targeted ligands derived from Isoquinoline
and AminoNaphthalene (IAN amines) 1 as axially chiral
(21) Fritischi, H.; Leutenegger, U.; Pfaltz, A. Angew. Chem. 1986,
98, 1028.
(22) Leutenegger, U.; Madin, A.; Pfaltz, A. Angew. Chem. 1989, 101,
61.
(23) (a) Pfaltz, A. Enantioselective Catalysis With Chiral Cobalt And
Copper Complexes; Scheffold, R., Ed.; Modern Synthetic Methods, Vol.
5; Springer-Verlag: Berlin, Germany, 1989. (b) Fritischi, H.; Leu-
tenegger, U.; Pfaltz, A. Helv. Chim. Acta 1988, 71, 1553.
(24) Sibi, M. P.; Asano, Y. J . Am. Chem. Soc. 2001, 123, 9708.
(25) Rahim, M.; Taylor, N. J .; Xin, S.; Collins, S. Organometallics
1998, 17, 1315.
(14) Brown, J . M.; Hulmes, D. I.; Guiry, P. J . Tetrahedron 1994,
50, 4493.
(15) Faller, J . W.; Grimmond, B. J . Organometallics 2001, 20, 2454.
(16) Hamada, T.; Chieffi, A.; Ahman, J .; Buchwald, S. L. J . Am.
Chem. Soc. 2002, 124, 1261.
(17) Koradin, C.; Polborn, K.; Knochel, P. Angew. Chem., Int. Ed.
Engl. 2002, 41, 2535.
(18) For an excellent, timely review of â-diketimine coordination
chemistry see: Bourget-Merle, L.; Lappert, M. F.; Severn, J . R. Chem.
Rev. 2002, 102, 3031.
(19) Reviews: (a) Britovsek, G. J . P.; Gibson, V. C.; Wass, D. F.
Angew. Chem., Int. Ed. Engl. 1999, 38, 428. (b) With Group 3 metals:
Piers, W. E.; Emslie, D. J . H. Coord. Chem. Rev. 2002, 233, 131.
(20) For the use of a planar chiral (neutral) â-diketimine in the
enantioselective copper(I)- catalyzed alkyne/nitrone coupling, see: Lo,
M.-C. L.; Fu, G. C. J . Am. Chem. Soc. 2002, 124, 4572.
(26) Deelman, B.-J .; Hitchcock, P. B.; Lappert, M. F.; Leung, W.-L.;
Lee, H.-K.; Mak, T. C. W. Organometallics 1999, 18, 1444.
(27) Giannini, L.; Solari, E.; De Angelis, S.; Ward, T. R.; Floriani,
C.; Chiesi-Villa, A.; Rizzoli, C. J . Am. Chem. Soc. 1995, 117, 5801.
(28) Martin, A.; Uhrhammer, R.; Gardner, T. G.; J ordan, R. F.;
Rogers, R. D. Organometallics 1998, 17, 382.
(29) (a) Lappert, M. F.; Liu, D.-S. J . Organomet. Chem. 1995, 500,
203. (b) Hitchcock, P. B.; Lappert, M. F.; Liu, D.-S. J . Chem. Soc.,
Chem. Commun. 1994, 2637.
(30) Qian, B.; Scanlon, W. J ., IV; Smith, M. R., III; Motry, D. H.
Organometallics 1999, 18, 1693.
(31) Vollmerhaus, R.; Rahim, M.; Tomaszewski, R.; Xin, S.; Taylor,
N. J .; Collins, S. Organometallics 2000, 19, 2161.
(32) J in, X.; Novak, B. M. Macromolecules 2000, 33, 6205.

2240 Organometallics, Vol. 23, No. 10, 2004
Cortright et al.
Ta ble 1. Develop m en t of a Dir ect Cou p lin g Rou te
to IAN Am in e Liga n d s (Eq 4)
% yielda
entry
conditions
10
1a
1
2
3
4
5
6
7
KHMDS, THF, 0-50 °C
LHMDS, THF, 0-50 °C
EtMgBr, THF, 0-70 °C
Sc(OTf)3, C6H6, 80 °C
EtAlCl2, tol, 100 °C
64
60
11
15
0
0
0
9
15
5
76
83
Et2AlCl, tol, 100 °C
Me3Al, tol, 100 °C
0
0
a
F igu r e 1. Relevant 2:1 â-diketiminate zirconium(IV)
complexes of Collins and Lappert.
Isolated yield after chromatography.
carbon-carbon bond to the exclusion of coupling through
nitrogen (Table 1, entries 5-7). Our study included
trimethylaluminum (TMA) and the mixed chloroalkyl-
aluminum Lewis acids. TMA furnished the desired
Me-IAN (1a ) in high yield (83%) and selectivity (>95:5
1a :10), and with the lowest reaction time among any of
the aluminum Lewis acids (Table 1, entry 7).
â-diketimines that not only address these current
limitations but might also provide unique stereodefined
coordination complexes despite their lack of a higher
symmetry element. From the outset several intriguing
questions arose regarding the potential electronic dis-
symmetry (and therefore chelating ability) of the nitro-
gens due to the nonplanar biaryl rings, and the ability
to modify the resulting complexes at the naphthylamine
nitrogen substituent.
This optimized coupling protocol then became the
basis for a general synthesis of the R-IAN amines
studied (Table 2). Bucherer reaction of aqueous methyl-
amine with 2-naphthol provided a convenient, scalable
route to 2-(methylamino)naphthalene.34 This approach
also worked well for other derivatives. Yet the need to
use an excess of the amine not only becomes wasteful
but is also impractical as it necessitates removal of the
amine during workup. The solution to this is the
conversion of 2-naphthol to its trifluoromethane sul-
fonate derivative35 and treatment with 1.5 equiv of the
amine and the appropriate palladium catalyst.36 tert-
Butylamine was most effectively coupled by using a
Buchwald protocol (Table 2, entry 4).37 Naphthylamines
12 were then readily coupled to chloroisoquinoline12,38
(13) with the assistance of trimethylaluminum. This
protocol is the method of choice to access all secondary
IAN amines, nearly all of which are light yellow crystal-
line solids (Table 2).
Resu lts a n d Discu ssion
IAN Am in e Syn th esis. The utility of ligands in
metal-based chemistry is often determined in part by
the ease of synthesis. The IAN amine scaffold offers a
convergent disconnection at the conjoining biaryl σ-bond.
Furthermore, the nucleophilicity of the 2-aminonaph-
thalene synthon is suitably matched to the electrophilic
1-position of the isoquinoline subunit. However, a
survey of conditions to activate the aniline precursor
revealed that coupling via the nitrogen to deliver
amidinate 10 was almost exclusively observed (Table
Me-IAN. Me-IAN (1a ) readily crystallized from a
variety of solvents. Slow diffusion involving an ethyl
acetate-hexanes solvent system yielded orange crystals
suitable for structural elucidation. The structure was
deduced to be two independent but chemically equiva-
lent molecules (1a , 1a ′) in the asymmetric unit (Figure
2), and hydrogen atoms were located.39 Despite the fact
that rac-Me-IAN was used in the crystallization, these
1). Metalated 2-(methylamino)naphthalene consistently
furnished the N-coupled product irrespective of coun-
terion (Table 1, entries 1 and 2). Only the bromomag-
nesium metalloenamine provided small amounts of the
desired C-C coupling product.33 Many Lewis acids
behaved similarly, providing either 10 or starting mate-
rial with a variety of promoter loadings (1-10 equiv),
temperatures (25-130 °C), and solvents (THF, Et2O,
benzene, toluene, CH2Cl2). From these experiments,
only scandium(III) triflate showed promising signs of
the desired coupling (Table 1, entry 4).
(34) In accord with typical safe laboratory practice, the most recent
toxicological data should be sought when preparing any organic
compound. Although 2-aminonaphthalene is commercially labeled as
a mutagen and should be handled appropriately, N-phenyl-2-naph-
thylamine was not found to be mutagenic in the Ames test: Kubo, T.;
Urano, K.; Utsumi, H. J . Health Sci. 2002, 48, 545.
(35) Stang, P. J .; Hanack, H.; Subramanian, L. R. Synthesis 1982,
85.
(36) Louie, J .; Driver, M. S.; Hamann, B. C.; Hartwig, J . F. J . Org.
Chem. 1997, 62, 1268.
Interestingly, aluminum Lewis acids were uniquely
capable of effecting the coupling with formation of the
(37) Wolfe, J . P.; Buchwald, S. L. J . Org. Chem. 2000, 65, 1144.
(38) Robinson, M. M.; Robinson, B. L. J . Org. Chem. 1957, 21, 1337.
(33) Powers, J . C. J . Org. Chem. 1965, 30, 2534.

IAN Amines: Highly Diastereoselective Complexations
Organometallics, Vol. 23, No. 10, 2004 2241
Ta ble 2. P r ep a r a tion of R-IAN Am in es
naphthylamine
coupling
entry
R
method
product
yielda (%)
product
mp (°C)
yielda (%)
1
2
3
4
5
6
7
8
9
Me
Bn
iPr
tBu
Ph
2,6-Me2Ph
2,4,6-Me3Ph
3,5-Me2Ph
2,6-iPr2Ph
2-Np
A
A
12a
12b
12c
12d
12e
12f
12g
12h
12i
75
54
88
87
1a
1b
1c
1d
1e
1f
1g
1h
1i
159-160
107.5-108.5
oil
83
80
92
71
84
87
86
79
52
77
A
Bc
oil
b
b
-
B
B
B
B
B
-
163-164
186.5-187.5
157-158
174.5-175.5
171.5-172.5
168-170
53
60
61
53
65
10
12j
1j
a
b
Isolated yield. Commercially available. c Formed from 2-bromonaphthalene and tert-butylamine, but with BINAP instead of dppf.
Ta ble 3. Selected Bon d Dista n ces a n d An gles for
Me-IAN (1a )
distances (Å)
angles (deg)
N(14)-H(48)
2.53(3)
2.05(3)
2.25(3)
2.83(3)
0.93(3)
0.94(3)
N(2)-H(48)-N(14)
N(2)-H(48)-N(36)
N(14)-H(64)-N(24)
N(24)-H(64)-N(36)
123.2
143.4
157.0
119.8
N(14)-H(64)
N(36)-H(48)
N(36)-H(64)
N(2)-H(48)
N(24)-H(64)
constraints and features. As the remaining structural
information reveals, these characteristics are also con-
served upon metal coordination.40
(Bn -IAN)2Zr (NMe2)2. The more sterically demanding
rac-Bn-IAN (1b) was combined with Zr(NMe2)4 in a 1:1
ratio in d8-toluene at room temperature. 1H NMR
analysis (Figure 3) revealed that 1:1 complex formation
(14b ; deep red color in solution) was immediate. Di-
methylamine, presumably bound, is evident by a sharp
resonance at δ 2.15 that is absent after vacuum removal
of solvent. Also significant are upfield shifts of the
isoquinoline ortho-CH from δ 8.71 to 8.33, as well as
many of the aromatic ring hydrogens more distant from
the site of coordination indicating a significant change
in the binaphthyl dihedral angle.
F igu r e 2. Two independent molecules of Me-IAN (1a and
1a ′) as they exist in the unit cell. The thermal ellipsoids
are drawn at the 50% probability level and most hydrogen
atoms are removed for clarity. See the Supporting Informa-
tion for complete details.
two forms exhibited the same absolute configuration and
differed primarily by the dihedral angle between the
binaphthyl ring systems (68° and 83°).
The s-cis biaryl conformation and lack of an intramo-
lecular hydrogen bond between the amine N-H and the
pyridine nitrogen are the most significant features of
the solid-state structure. The intramolecular distances
(for 1a /1a ′) between the pyridine nitrogen atom and the
amine hydrogen are 2.53/2.83 Å, and the N-H-N bond
angles are 123.2°/119.8° (Table 3). Intermolecular hy-
drogen bonding is weak but perhaps a significant effect
between the two forms in the unit cell, with intermo-
lecular N- -H-N distances and angles characterized by
2.25/2.05 Å and 143.4/157.0°, respectively.
Addition of a second equivalent of rac-Bn-IAN allows
observation of both complexed and free ligand simulta-
1
neously without exchange by H NMR at room temper-
ature. It is not until the application of heat (80 °C) that
formation of the (Bn-IAN)2Zr(NMe2)2 complex (16b) is
observed by amine metathesis.41 Complete consumption
of free ligand, concomitant with the formation of a single
new product occurs after 12 h (Figure 3). Significantly,
a single new complex (>15:1) is observed throughout
the warming process, indicating a highly stereoselective
reaction. The new species is characterized by further
shifts upfield of most resonances, including the iso-
These characteristics are rather typical of this rep-
resentative IAN amine, since all solvates (CH2Cl2, C6D6)
that we have isolated to-date display similar bonding
(40) Cortright, S. B.; J ohnston, J . N. Angew. Chem., Int. Ed. Engl.
2002, 41, 345.
(41) Diamond, G. M.; Rodewald, S.; J ordan, R. F. Organometallics
1995, 14, 5.
(39) In this and all subsequent crystal structures, the asymmetric
unit cell is always paired with its mirror image. That is, the single
crystals are (presumably) optically inactive.

2242 Organometallics, Vol. 23, No. 10, 2004
Cortright et al.
F igu r e 3. 1H NMR (C6D6) of complexation of Bn-IAN (1b) to Zr(NMe2)4.
Ta ble 4. Selected Bon d Dista n ces a n d An gles for
(Bn -IAN)2Zr (NMe2)2 (16b)
distances (Å)
angles (deg)
Zr-N(2)
Zr-N(22)
Zr-N(30)
2.428(3)
2.173(3)
2.083(3)
N(2)-Zr-N(2)
100.78(15)
77.12(11)
80.56(11)
170.92(11)
144.68(16)
90.28(17)
N(2)-Zr-N(22)
N(2)-Zr-N(22)
N(2)-Zr-N(30)
N(22)-Zr-N(22)
N(30)-Zr-N(30)
the 68° minimum observed among the various uncom-
plexed forms of the ligand (vide supra). Yet, the angle
is quite large if one considers the possibility to form a
nearly planar six-membered-ring chelate.
The aminonaphthalene nitrogen of each ligand oc-
cupies the axial coordination site, each with a Zr-N
bond distance of 2.17 Å (Table 4). This distance is only
slightly longer (0.03 Å) than the analogous bond to the
trimethylsilylamido ligand in 9, but substantially shorter
(0.09 Å) than the arylamido ligand in 8. These distances
are contrasted by the distance of 2.43 Å to each
isoquinoline nitrogen in the square plane, which is
elongated by 0.04 Å relative to 8. Not unexpectedly, the
dimethylamido nitrogens are in close range (2.08 Å) to
the zirconium center within the distorted square plane.
By using the isoquinoline nitrogens and zirconium to
arbitrarily assign three of the five points of the square
plane, the dimethylamido ligands are canted by 10°.
The aminonaphthalene nitrogen is significantly py-
ramidalized, with the sum of bond angles at nitrogen
equalling 354°. This degree of pyramidalization is only
marginally greater than that observed in (Me-IAN)2Zr-
(NMe2)2 in which the sum of bond angles at the apical
nitrogen equals 357°. Bonding between the isoquinoline
nitrogen and zirconium is slightly compromised by dis-
tortion of the isoquinoline plane relative to zirconium.
The zirconium atom formally sits 27° out of the iso-
quinoline plane in which the nitrogen lone pair resides.
This is most likely the result of the chelating ligand’s
demand to optimize bonding of both nitrogens to zirco-
nium simultaneously. This effect also seems to work
synergistically with the electronic demands of the di-
methylamido ligands. That is, the pyridine ligands
occupy the square plane as the more appropriate weak
ligand trans to the strongly donating dimethylamido
ligands. This underscores an important feature of the
IAN amine design. Unlike all other â-diketimines, in-
cluding “â-anilido imines” congeners reported more re-
cently,43 the nonplanarity of the binaphthyl rings at-
F igu r e 4. X-ray crystal structure of (Bn-IAN)2Zr(NMe2)2
(16b). The thermal ellipsoids are drawn at the 50%
probability level with hydrogen atoms removed for clarity.
See the Supporting Information for complete details.
Sch em e 1
quinoline ortho-CH from 8.33 to 8.22 ppm.42 Whereas
the degree of selectivity can be adequately ascertained
by NMR spectroscopy, the preferred relative stereo-
chemistry of the favored complex can only be deduced
by using X-ray crystallography. Orange crystals of the
putative 2:1 complex were obtained by slow evaporation
of toluene, and the structure was solved as depicted in
Figure 4.
The Bn-IAN ligands in 16b are clearly homochiral,
and the enantiomeric (Bn-IAN)2Zr(NMe2)2 is present in
the unit cell (not shown) and oriented with the binaph-
thyl rings of each complex pointing toward the other.
The binaphthyl dihedral angle of both bound Bn-IAN
ligands is 62°. This value is significantly depressed from
(42) Zirconium amido complexes 14-18 immediately decompose to
free ligand (1) upon contact with water.

IAN Amines: Highly Diastereoselective Complexations
Organometallics, Vol. 23, No. 10, 2004 2243
tenuates the extent of electron delocalization when the
parent amine is deprotonated. As a result, the chelating
â-diketimine framework is substantially differentiated
electronically and perhaps better described as a â-amido
Schiff base. It is significant to note that the thermody-
namic affinity for a proton is nearly equal for the two
nitrogens when in neutral form (5 < pKa < 6).44
(P h -IAN)2Zr (NMe2)2. Coupling of commercially avail-
able N-(2-naphthyl)aniline to chloroisoquinoline fur-
nished Ph-IAN (1e) in 84% yield (Table 2, entry 5). The
resulting light yellow crystalline solid was combined
with Zr(NMe2)4 in a 1:1 ratio in d8-toluene as before,
completely producing the 1:1 complex (14e) and 1 equiv
of dimethylamine (presumably bound) within 5 min. The
dimethylamine was removed by application of a vacuum,
followed by reconstitution in d8-toluene and addition of
a second equivalent of Ph-IAN. Unlike both Me-IAN and
Bn-IAN complexation with zirconium(IV), the 2:1 com-
plex (Ph-IAN)2Zr(NMe2)2 (16e) did not require heating
and slowly formed at room temperature over the course
of 12 h. The process is complete within 6 h when the
temperature is raised to 60 °C. On the basis of a reduced
pKa for the aminonaphthalene nitrogen (pKa(Ph2NH) )
25.0, DMSO)45 and the diminished steric hindrance at
a nitrogen bearing two sp2-hybridized carbons, the faster
2:1 complex formation from Ph-IAN might not be
surprising. Significantly, a single complex emerged from
this reaction as the major product, consistent with the
behavior of both Me- and Bn-IAN. Of all the cases
examined, complexation of Ph-IAN was the only case
in which formation of a second identifiable isomeric
complex was observed (∼15%).
F igu r e 5. X-ray crystal structure of (Ph-IAN)2Zr(NMe2)2
(16e). The thermal ellipsoids are drawn at the 50% prob-
ability level with hydrogen atoms removed for clarity. See
the Supporting Information for complete details.
Ta ble 5. Selected Bon d Dista n ces a n d An gles for
(P h -IAN)2Zr (NMe2)2 (16e)
distances (Å)
angles (deg)
Zr-N(2)
2.4384(23)
2.2049(22)
2.4577(22)
2.1903(22)
2.0730(23)
2.0809(23)
N(2)-Zr-N(22)
77.20(8)
96.10(7)
79.99(8)
171.78(8)
78.29(8)
144.65(8)
77.69(8)
170.78(8)
93.84(9)
Zr-N(22)
Zr-N(29)
Zr-N(49)
Zr-N(56)
Zr-N(59)
N(2)-Zr-N(29)
N(2)-Zr-N(49)
N(2)-Zr-N(59)
N(22)-Zr-N(29)
N(22)-Zr-N(49)
N(29)-Zr-N(49)
N(29)-Zr-N(56)
N(56)-Zr-N(59)
(NMe2)2 (16a ) and (Bn-IAN)2Zr(NMe2)2 (16b), the di-
methylamido ligands are canted approximately 12° out
of the ideal square plane, again defined by the isoquino-
line nitrogens and zirconium. The sum of bond angles
at the aminonaphthalene nitrogen is now 359°, indicat-
ing all but complete planarity of this chelating atom.
And again, the zirconium atom formally sits 32° above
the isoquinoline plane.
Pale orange single crystals were grown from the crude
reaction mixture by slow evaporation from toluene. The
structure was subsequently determined by X-ray dif-
fraction and is depicted in Figure 5. The ligands are
again homochiral and arranged in identical relative
fashion about the distorted octahedron of zirconium.
Moreover, the 2:1 complex is C2-symmetric as in the
analogous complexes of Me- and Bn-IAN. The binaph-
thyl dihedral angle of the bound Ph-IAN ligand is 63°,
nearly identical with that of the analogous Bn-IAN
complex.
Zr-N bond distances of 2.438 and 2.458 Å (Table 5)
for the isoquinoline nitrogens are also within 0.01 Å of
the distance observed in the Bn-IAN complex 16b.
However, subtle elongation of the aminonaphthalene
nitrogen-zirconium bonds is observed, characterized by
distances of 2.190 and 2.205 Å. These distances are
substantially shorter than the analogous bonds to the
arylamido ligand in 8 (2.26 Å), thereby indicating
localization of electrons on the naphthylamido nitrogen
in 16b. Distances of 2.081 and 2.073 Å from zirconium
to the dimethylamido nitrogens are unremarkable.
Consistent with observations in both (Me-IAN)2Zr-
(2-Np -IAN)2Zr (NMe2)2. 2-Naphthyl-IAN (2-Np-IAN,
1j) was made via palladium-catalyzed amination of
2-naphthol triflate with 2-aminonaphthalene (Table 2,
Method B) and subsequent coupling to chloroisoquino-
line (50% overall yield). The complexation behavior of
2-Np-IAN was nearly indistinguishable from that of
Ph-IAN, rapidly providing the 1:1 complex (14j) at room
temperature, followed by slower formation of the 2:1
complex (16j) once additional ligand had been added.
Qualitatively, the rate of complexation of a second lig-
and equivalent was also nearly identical in rate to the
Ph-IAN case. Spectroscopic features of the reaction were
also similar to all ligands studied previously, forming a
major diastereomer (>10:1 by 1H NMR) in the crude
reaction mixture, from which red single crystals were
grown and analyzed by X-ray diffraction (Figure 6).
Although the inner coordination sphere is again C2-
symmetric, the orientations of the naphthyl substituents
are not equivalent, rendering the overall complex pseudo-
C2-symmetric. Binaphthyl dihedral angles of 58° and
64° are observed in this homochiral complex. Isoquino-
line nitrogen-zirconium bond distances of 2.434 and
2.485 Å (Table 6) are quite similar to those of the
analogous Ph-IAN complex, as are the naphthylamine-
zirconium distances of 2.232 and 2.192 Å. Again,
(43) (a) Weymann, C.; Danopoulos, A. A.; Wilkinson, G. Polyhedron
1996, 15, 3605. (b) Porter, R. M.; Winston, S.; Danopoulos, A. A.;
Hursthouse, M. B. J . Chem. Soc., Dalton Trans. 2002, 3290. (c) Hayes,
P. G.; Welch, G. C.; Emslie, D. J . H.; Noack, C. L.; Piers, W. E.; Parvez,
M. Organometallics 2003, 22, 1577.
(44) pKa values for pyridinium tosylate and dimethylanilinium
tosylate are 5.21 and 5.20, respectively. March, J . Advanced Organic
Chemistry, 3rd. ed.; Wiley: New York, 1985. Unpublished results of
W. P. J encks.
(45) Bordwell, F. G.; Branca, J . C.; Hughes, D. L.; Olmstead, W. N.
J . Org. Chem. 1980, 45, 3305.

2244 Organometallics, Vol. 23, No. 10, 2004
Cortright et al.
F igu r e 7. X-ray crystal structure of (Bn-IAN)2ZrI2 (18b).
Atoms are drawn as arbitrary spheres and hydrogen atoms
are removed for clarity. See the Supporting Infomation for
complete details.
F igu r e 6. X-ray crystal structure of (2-Np-IAN)2Zr(NMe2)2
(16j). The thermal ellipsoids are drawn at the 50% prob-
ability level with hydrogen atoms removed for clarity. See
the Supporting Information for complete details.
Ta ble 7. Selected Bon d Dista n ces a n d An gles for
(Bn -IAN)2Zr I2 (18b)
Ta ble 6. Selected Bon d Dista n ces a n d An gles for
(2-Np -IAN)2Zr (NMe2)2 (16j)
distances (Å)
angles (deg)
distances (Å)
angles (deg)
Zr-N(4)
2.291(11)
2.094(9)
2.289(10)
2.088(9)
2.8864(15)
2.8630(17)
N(4)-Zr-N(24)
80.1(4)
83.7(3)
115.0(3)
116.5(3)
160.8(4)
78.4(3)
156.1(2)
157.4(2)
104.83(5)
Zr-N(24)
Zr-N(32)
Zr-N(52)
Zr-I(2)
N(4)-Zr-N(32)
N(4)-Zr-N(52)
N(24)-Zr-N(32)
N(24)-Zr-N(52)
N(32)-Zr-N(52)
I(2)-Zr-N(32)
I(3)-Zr-N(4)
Zr-N(2)
2.434(3)
2.192(3)
2.485(3)
2.232(2)
2.075(3)
2.086(3)
N(2)-Zr-N(22)
77.02(9)
95.86(9)
81.59(9)
174.04(9)
78.59(9)
145.29(11)
76.77(9)
171.64(9)
93.66(11)
Zr-N(22)
Zr-N(33)
Zr-N(53)
Zr-N(64)
Zr-N(67)
N(2)-Zr-N(33)
N(2)-Zr-N(53)
N(2)-Zr-N(64)
N(22)-Zr-N(33)
N(22)-Zr-N(53)
N(33)-Zr-N(53)
N(33)-Zr-N(67)
N(64)-Zr-N(67)
Zr-I(3)
I(2)-Zr-I(3)
(NMe2)2 (16b) with 2 equiv of methyl iodide in dilute
benzene at room temperature resulted in complete
consumption of the bis(dimethylamido) complex and
precipitation of red single crystals that were subse-
quently examined by X-ray crystallography (Figure 7).46
In contrast to the conservation of most structural
features when converting (Me-IAN)2Zr(NMe2)2 (16a ) to
(Me-IAN)2ZrCl2 (17a ),40 the replacement of the di-
methylamido ligands in 16b by iodide to produce 18b
results in greater distortion of the octahedral coordina-
tion geometry. The geometry at zirconium is best
described as trigonal antiprismatic.
The degree of pyramidalization at the aminonaph-
thalene nitrogen is identical with that of the bis(di-
methylamido) derivative, and the binaphthyl dihedral
angle is within the range observed for the complexes
described above (63° and 59°). Hence, the distortion
results from a combination of bonding changes: (a)
shortening at the aminonaphthalene Zr-N bond to
2.088 and 2.094 Å (Table 7), (b) contraction at the
isoquinoline Zr-N bond to 2.289 and 2.291 Å, and (c)
elongation of the bonds from zirconium to the ancillary
ligands (I-) with distances of 2.863 and 2.886 Å. Perhaps
the most important feature that can be concluded from
distances of 2.086 and 2.075 Å from zirconium to the
dimethylamido nitrogens are unremarkable. The di-
methylamido ligands are canted approximately 10° out
of the ideal square plane and the naphthylamine
nitrogen is now completely planar. The zirconium atom
resides at an angle of 22° relative to the isoquinoline
plane.
A significant difference between the 2:1 complex of
2-Np-IAN and those above is the loss of ideal C2-sym-
metry, at least in the solid state. The 2,2′-substitution
of the naphthyl rings does not present any identifiable
intermolecular steric repulsion, yet the additional fused
benzene ring relative to the Ph-IAN complex carves out
significantly greater coordination space near the di-
methylamido ligands. In support of this notion, the
naphthyl rings clearly prefer the extended conformation
about the N-2′-Np σ bond. However, there is significant
flexibility in this degree of conformational freedom, since
the dihedral angle defined by the two naphthylamine
planes varies from 70° to 87°.
(Bn -IAN)2Zr I2. Conversion of bis(dimethyl)amido
complexes 16 to dichloride derivatives 17 normally
provides a precatalyst more readily activated in single-
site polymerizations. However, dichlorides 17 are only
sparingly soluble in most nonpolar solvents. Therefore,
diiodide derivatives 18 were targeted as potentially
more soluble alternatives. Treatment of (Bn-IAN)2Zr-
(46) Crystals were invariably twinned, but the Gemini programs
(Bruker) readily resolved the twinning. Ligand exchange method:
J ohnson, A. R.; Wanandi, P. W.; Cummins, C. C.; Davis, W. M.
Organometallics 1994, 13, 2907.

IAN Amines: Highly Diastereoselective Complexations
Organometallics, Vol. 23, No. 10, 2004 2245
comparison of the bis(dimethylamido) and iodide com-
plexes is the flexibility of the Bn-IAN ligand to geo-
metrically and electronically accommodate a change
from strong (hard) to weak (soft) ancillary ligands with-
out affecting the overall C2-symmetry. Unfortunately,
diiodide 18b was no more soluble than its dichloride
counterpart (17b).
Gen er a l Obser va tion s. The synthesis and coordina-
tion chemistry of IAN amines is essentially uncompli-
cated by the variable hapticity and azomethine reac-
tivity noted for the â-diketimines of Floriani and J ordan.
Unintended chemical modification of the â-diketimine
at the â-carbon of the diketimine backbone is also
notably absent. The steric demand of â-diketimines 1
is a factor distinguishing this ligand from both cyclo-
pentadienyl and amidinate classes. It is equally straight-
forward to complex cyclopentadiene ligands or their
isoelectronic counterparts47 in a controlled manner to
access 1:1 (half sandwich)48 and 2:1 ligand:metal (sand-
wich) complexes. The amidinate literature is also replete
with examples of 1:1 to even 3:1 amidinate:metal
complexes,49 again underscoring the sterically unimpos-
ing nature of these ligands.
â-Diketimines of the IAN amine class impart sub-
stantially greater steric bias that retards the rate at
which a second ligand can bind. This effect is observed
clearly in the alkyl-IAN series in which Me- and
i
Bn-IAN 2:1 complexes (16a , 16b) readily form, but Pr-
and tBu-IAN provide only 1:1 complexes (14c, 14d )
resistant to further IAN ligand binding. Similarly,
although aromatic-IANs form their respective 2:1 com-
plexes more rapidly than the alkyl-IANs, 2,6-disubsti-
tuted aryl-IANs (1f, 1g, 1i) form only 1:1 complexes with
Zr(IV). 3,5-Disubstituted aryl-IANs (e.g. 1h ) readily
form 2:1 complexes (16h ). While the steric nature of the
naphthylamine nitrogen limits the formation of some
2:1 complexes, it clearly exerts a beneficial stereodif-
ferentiation effect.
Dia ster eoselection . Perhaps the most notable fea-
ture of the IAN amines described here is the electronic
differentiation offered by the nonplanar â-diketiminate
ligand. The ramifications of this were observed in all of
the solid state structures: the isoquinoline nitrogens
paired consistently with dimethylamido ligands in the
square plane while the naphthylamido ligands of inter-
mediate donor ability consistently occupy apical posi-
tions. This electronic differentiation of donor ability is
likely the single most important factor contributing to
the high levels of stereoselection.
F igu r e 8. Possible 2:1 diastereomeric complexes formed
from a Chiral C1-symmetric ligand and octahedral coordi-
nation geometry.
(R-IAN)2Zr(NMe2)2. The use of racemic ligand results
in the possible formation of eight homochiral complexes
(A/A′-D/D′) and five heterochiral complexes (U-Z),
with only one lacking an enantiomeric counterpart (Z).
The belief that these processes are kinetically con-
trolled (and perhaps thermodynamically as well) is
based on two observations. First, identical diastereo-
control is observed when complexing Me-IAN by either
thermal (80 °C) amine metathesis with Zr(NMe2)4 or
low-temperature (0 °C) deprotonation/addition to ZrCl4.40
Additionally, all spectroscopic data of the 2:1 complexes
reported here suggest that the Bailar twist is not
operable in these cases, a likely consequence of the
nonplanarity of these â-diketimines. Such an intercon-
version would require correlated motion in which the
biaryl σ-bond is epimerized in both ligands as the
pyridine nitrogens formally exchange positions in the
square plane.50 We recently determined the barrier to
atropisomerization in a series of IAN amines by mea-
suring the kinetics for thermal isomerization of the free
amines IAN, Me-IAN, and Me2-IAN.51 The free energy
for the racemization process for these three examples
ranged from 29.8 to 31.3 kcal/mol, indicating not only
indefinite configurational integrity at room temperature
(an approximate half-life of 6 days at 70 °C) but also a
relative insensitivity of the atropisomerization barrier
to the size of the naphthylamine substituent.
The stereochemical analysis for formation of 6-coor-
dinate complexes from rac-C1-symmetric R-IAN amines
is decidedly more complex than most prior examples in
the literature. It is therefore worthwhile to identify the
design principles that underlay highly stereoselective
complexations such as these to generalize this behavior.
Figure 8 describes the possibilities for conversion of
racemic R-IAN to complexes of the molecular formula
(47) Tanski, J . M.; Parkin, G. Organometallics 2002, 21, 587.
(48) (a) Keaton, R. J .; J ayaratne, K. C.; Henningsen, D. A.; Koterwas,
L. A.; Sita, L. R. J . Am. Chem. Soc. 2001, 123, 6197. (b) Keaton, R. J .;
J ayaratne, K. C.; Fettinger, J . C.; Sita, L. R. J . Am. Chem. Soc. 2000,
122, 12909. (c) J ayaratne, K. C.; Keaton, R. J .; Henningsen, D. A.; Sita,
L. R. J . Am. Chem. Soc. 2000, 122, 10490.
(49) (a) Barker, J .; Kilner, M. Coord. Chem. Rev. 1994, 133, 219.
(b) Averbuj, C.; Tish, E.; Eisen, M. S J . Am. Chem. Soc. 1998, 120,
8640.
(50) For a discussion of correlated motion of aromatic rings, see:
Eliel, E. L.; Willen, S. H. Stereochemistry of Carbon Compounds;
Wiley: New York, 1994; pp 1160-1163.
(51) Cortright, S. B.; Yoder, R. A.; J ohnston, J . N. Heterocycles 2004,
62, 223.

2246 Organometallics, Vol. 23, No. 10, 2004
Cortright et al.
Sch em e 2. Dem on str a tion of (-)-Me-IAN
Con figu r a tion a l In tegr ity d u r in g 2:1 Meta l
Com p lexa tion
optimal pairing of strong and weak donors is uniquely
achieved by A and A′ among the homochiral complex
possibilities, and U in the heterochiral series.
To discriminate among these three diastereomers
that bear isoquinoline nitrogens in the square plane and
naphthylamido nitrogens in the apical positions (A, A′,
U), a closer look at the interligand interactions is
necessary. A telling feature of the crystal structures of
2:1 IAN:Zr(IV) complexes reported here is the near-
parallel arrangement between the aminonaphthalene
rings of each ligand. The angle between the planes
defined by these naphthalene rings spans the range
0.8-11.1°. It is also significant to note that the distance
between the planes not only is outside the constraints
of π-stacking, but the naphthalene rings also overlap
only minimally in the solid state. This sterically favor-
able parallel alignment, perhaps attained optimally by
this diastereomeric complex, is the best explanation for
why this complex is favored above all others. Unfortu-
nately, attempts to use molecular mechanics calcula-
tions to arrive at convincing low-energy structures for
these complexes were unsuccessful. The contention that
A lacks the steric congestion of A′ also implies that
conversion of A to A′ is endothermic regardless of
mechanism (Bailar53 or Ray-Dutt twist). This stands in
stark contrast to the fluxional bis(â-diketiminate) zir-
conium dichloride complexes described by Collins.25
P olym er iza tion . Chiral C2-symmetric metallocene
complexes have emerged over the past two decades as
powerful olefin polymerization catalysts. The use of 2:1
R-IAN zirconium(IV) complexes as precatalysts in single
site ethylene polymerization was therefore investigated
to benchmark these unusual bis(â-diketimine) com-
plexes. The complexes that were evaluated fell into two
groups based on solubility. The bis(dimethylamido)
complexes of all ligands were soluble in a variety of
solvents, whereas the dihalide complexes were only
sparingly soluble in most nonpolar solvents.
F igu r e 9. X-ray crystal structure of (Me-IAN)2Zn (19). The
thermal ellipsoids are drawn at the 50% probabiity level
with hydrogen atoms removed for clarity. See the Support-
ing Information for complete details.
Ta ble 8. Bon d Dista n ce a n d An gles for
(Me-IAN)2Zn (19)
distances (Å)
angles (deg)
Zn-N(2)
Zn-N(22)
2.041(6)
1.929(6)
N(2)-Zn-N(22)
94.48(25)
113.83(26)
113.8(4)
N(2)-Zn-N(22)′
N(2)-Zn-N(2)′
N(22)-Zn-N(2)
127.6(5)
The ability of Me-IAN to complex a metal without
atropisomerization was demonstrated most clearly by
the finding that (-)-Me-IAN catalyzes diethyl zinc
addition to benzaldehyde to give 20 in 85% ee at 25 °C.52
Moreover, the C2-symmetric 2:1 Me-IAN-Zn(II) com-
plex 19 analogous to (Me-IAN)2Zr(NMe2)2 could be
formed by stirring Me-IAN with diethylzinc at room
temperature, followed by crystallization from toluene.
The X-ray crystal structure and associated bond dis-
tances and angles are shown in Figure 9 and Table 8,
respectively. This complex serves as the resting state
in the diethyl zinc addition as evidenced by its formation
in the absence of benzaldehyde, its rapid decomposition
concomitant with formation of enantioenriched carbinol
20 upon benzaldehyde addition, and its reformation
(with excess diethyl zinc present) following benzalde-
hyde consumption. All of these events are conveniently
observed by 1H NMR spectroscopy. (-)-Me-IAN Isolated
from this crude reaction mixture exhibited less than 1%
ee loss.
Dichloride 17a could be prepared and precipitated in
analytically pure form. Entries 1 and 2 (Table 9)
represent trial conditions for ethylene polymerization
with 17a and MMAO as activator at 85 °C. Moderate
activity was observed in these runs (1500-1600 g
(mmol/h/100 psi)-1), translating to an efficiency of 15
kg of polyethylene/g of zirconium. To determine whether
solubility and/or counterion affected the catalyst ef-
ficiency, the bis(dimethylamido) derivative was com-
pared directly to the dichloride. In the event (Table 9,
entry 3), precatalyst 16a provided a higher, but com-
parable activity of 1727 g (mmol/h/100 psi)-1 and
efficiency of 19 kg of polyethylene/g of zirconium. This
Why is the level of diastereocontrol so high? That the
complexation selectivity can be first rationalized with
kinetic control is supported by the finding that (+)-Me-
IAN can be deprotonated and added to ZrCl4 at 0 °C to
form ((+)-Me-IAN)2ZrCl2. Hydrolytic decomposition of
this complex allowed (+)-Me-IAN to be reisolated with
<3% ee loss. In most examples described above, the
relative donating ability of the coordinating groups
correlates well, considering Me2N > ArNR > Npy. The
(52) The axially chiral bis(dimethylamino) binaphthylene derivative
reported by Salvadori catalyzes the diethyl zinc addition in up to 64%
ee: Rosini, C.; Franzini, L.; Iuliano, A.; Pini, D.; Salvadori, P.
Tetrahedron: Asymmetry 1991, 2, 363. Reviews: (a) Pu, L.; Yu, H.-B.
Chem. Rev. 2001, 101, 757. (b) Soai, K.; Niwa, S. Chem. Rev. 1992,
92, 833. (c) Noyori, R.; Kitamura, M. Angew. Chem., Int. Ed. Engl.
1991, 30, 49.
(53) (a) Bailar, J . C. J . Inorg. Nucl. Chem. 1958, 8, 165. (b)
Wentworth, R. A. D. Coord. Chem. Rev. 1972, 9, 171.

IAN Amines: Highly Diastereoselective Complexations
Organometallics, Vol. 23, No. 10, 2004 2247
Ta ble 9. Eth ylen e P olym er iza tion by
C2-Sym m etr ic Bis-â-d ik etim in e (IAN Am in e)
Zir con iu m (IV) Com p lexesa
Despite their lack of symmetry, IAN amines 1 undergo
highly stereoselective complexation with Zr(IV) chloride
and tetrakis(dimethylamide) to give chiral C2-symmetric
2:1 complexes. Assembly of the 2:1 ligand:Zr(IV) com-
plexes from a racemic ligand source gave only homo-
chiral complexes. This behavior is remarkable consid-
ering the possibility of 13 diastereomeric 2:1 ligand:
metal complexes in this single reaction. Additionally,
crystal structures of a series of 2:1 complexes demon-
strate the generality of this phenomenon and provide
insight into the design of ligands that stereoselectively
complex to a metal coordination center. Finally, promis-
ing preliminary data regarding the use of these unusual
zirconium amido complexes as precatalyts in olefin
polymerization are provided. It is significant to note that
ligand constraints result in complexes resembling con-
strained geometry metallocenes. The chiral C2-sym-
metric topology characteristic of 16-18 bodes well for
stereoselective olefin polymerization, by analogy to both
ansa-metallocene catalysts58 and the more recent PHI
catalysts developed by Coates59 and Fujita.60
cat.
(µmol)
time
(h)
eff
entry
precatalyst
activityb
(g PE/g Zr)
1
2
3
4
5
17a
17a
16a
16e
16b
2.6
5.2
2.2
5
0.67
0.67
0.5
0.5
0.5
1500
1600
1700
780
15000
16000
19000
8600
5
420
4600
a
All runs were performed with 1 L batch reactors, using 1000
equiv of MMAO and iBu3Al scavenger (1000 µmol for entries 1
and 2, 200 µmol for entries 3-5) at 85 °C. Ethylene pressure is
135 psi for entries 1 and 2, and 200 psi for entries 3-5. Polymer
molecular weights of 386 000/407 000 and PDI of 3.53/3.77 were
b
obtained for entries 1/2. g (mmol/h/100 psi)-1
.
data suggests that the bis(dimethylamido) leaving
groups are readily activated by MAO and that no effi-
ciency advantage is gained by transformation to poorly
soluble dihalide derivatives. To our knowledge, no
polymerization data for bis(â-diketimine) metal amido
precatalysts has been previously reported for compari-
son.54 Although a direct comparison is not possible,
these precatalysts compare favorably to those evaluated
by Collins (2461-3990 g (mmol/h/100 psi)-1 at 70 °C)31
and Lappert (9.5 g (mmol/h/100 psi)-1 at 25 °C).26,55
The effect of the IAN amine substituent on catalyst
activity was next examined. This structural feature was
expected to have the greatest impact since it resides
above/below the square plane in the putative active
cationic zirconium complex. By varying the substituent
along the series Me, Ph, and Bn, decreasing catalyst
activity was observed (Table 9, entries 3-5). Such an
effect is counterintuitive to the notion that a possible
catalyst deactivation pathway is dimerization through
hydride bridges to form 21 after â-hydride elimination
The transfer of asymmetry from enantiopure IAN
amine-metal complexes to organic substrates repre-
sents an exciting direction considering the longstanding
success of chiral amines in asymmetric synthesis. The
use of enantiopure IAN amines will generate enan-
tiopure C2-symmetric complexes, a motif common within
asymmetric synthesis. Developments along these lines
will be the subject of future reports.
Exp er im en ta l Section 61
Bn -IAN Am in e (1b). 2-(N-Benzylamino)naphthalene (4.16
g, 17.8 mmol) and 1-chloroisoquinoline (2.93 g, 17.9 mmol)
were dissolved in toluene (80 mL) and treated with AlMe3 (32.0
mL, 2.0 M in hexanes) via syringe prior to heating at 110 °C
for 3 d. The solution was cooled to room temperature, added
to 6 M aq NaOH, and diluted with EtOAc and Rochelle’s salt
solution. The mixture was stirred for 1 h, the phases were
separated, and the aqueous layer was further extracted with
EtOAc. The combined organic layers were dried, filtered, and
concentrated, and the residue was purified by flash chroma-
tography (SiO2, 20% ethyl acetate in hexanes) to give the
desired amine as a tan powder (4.81 g, 75%). Alternately, the
crude product may be purified by crystallization from a hot
toluene solution with an equivalent volume of hexanes added.
Mp 109-110 °C, Rf 0.28 (40% EtOAc/hexanes); IR (film) 3431,
from the polymer and olefin decoordination, by analogy
to neutral hydride-bridged metallocenes.56,57 However,
this polymerization data are only a preliminary indica-
tion of R-IAN-supported catalyst activity.
The flexibility of the IAN amine-supported zirconium
complexes bodes well for their use in olefin polymeri-
zation, and our initial findings suggest that the soluble
bis(dimethylamido) precatalysts 16 are readily activated
with MAO and may serve as ideal developmental
candidates.
1
3054, 1620 cm-1; H NMR (400 MHz, CDCl3) δ 8.80 (d, J )
5.6 Hz, 1H), 7.96 (d, J ) 8.3 Hz, 1H), 7.83 (d, J ) 9.0 Hz, 1H),
7.79 (d, J ) 5.7 Hz, 1H), 7.76 (d, J ) 8.6 Hz, 1H), 7.72 (dd, J
) 8.1, 8.1 Hz, 1H), 7.60 (d, J ) 8.3 Hz, 1H), 7.44 (dd, J ) 8.1,
8.1 Hz, 1H), 7.25-7.13 (m, 8H), 6.82 (d, J ) 8.3 Hz, 1H), 4.44
(s, 2H), 4.21 (br s, 1H); 13C NMR (100 MHz, CDCl3) δ 159.0,
(56) Chirik, J .; Day, M.; Bercaw, J . Organometallics 1999, 18, 1873.
(57) Decomposition pathways for dialkyl zirconium complexes: Di-
oumaev, V. K.; Harrod, J . F. Organometallics 1997, 16, 1452
(58) Brintzinger, H. H.; Fischer, D.; Mulhaupt, R.; Rieger, B.;
Waymouth, R. M. Angew. Chem., Int. Ed. Engl. 1995, 34, 1143.
(59) (a) Tian, J .; Coates, G. W. Angew. Chem., Int. Ed. Engl. 2000,
39, 3626. (b) Tian, J .; Hustad, P. D.; Coates, G. W. J . Am. Chem. Soc.
2001, 123, 5134. (c) Hustad, P. D.; Tian, J .; Coates, G. W. J . Am. Chem.
Soc. 2002, 124, 3614.
Con clu sion
We have described an improved IAN amine ligand
synthesis that is general, high-yielding, and convergent.
(54) An example of a zirconium complex with amine, amido, and
chloro ligands has been reported for olefin polymerization: Fuhrmann,
H.; Brenner, S.; Arndt, P.; Kempe, R. Inorg. Chem. 1996, 35, 6742.
(55) A very loose comparison may be made to the activity of
Cp2ZrCl2/MMAO for ethylene polymerization - activity ) 79000 g
(mmol/h/100 psi)-1 and efficiency ) 64000 g PE/g Zr: Alonso-Moreno,
C.; Antinolo, A.; Lopez-Solera, I.; Otero, A.; Prashar, S.; Rodriguez, A.
M.; Villasenor, E. J . Organomet. Chem. 2002, 656, 129.
(60) (a) Matsui, S.; Mitani, M.; Saito, J .; Tohi, Y.; Makio, H.; Tanaka,
H.; Fujita, T. Chem. Lett. 1999, 1263. (b) Matsui, S.; Tohi, Y.; Mitani,
M.; Saito, J .; Makio, H.; Tanaka, H.; Nitabaru, M.; Nakano, T.; Fujita,
T. Chem. Lett. 1999, 1065. (c) Matsui, S.; Mitani, M.; Saito, J .;
Matsukawa, N.; Tanaka, H.; Nakano, T.; Fujita, T. Chem. Lett. 2000,
554.
(61) Complete experimental details can be found in the Supporting
Information.

2248 Organometallics, Vol. 23, No. 10, 2004
Cortright et al.
144.0, 143.6, 139.8, 134.0, 130.8, 130.3, 128.7 (3C), 128.2, 127.8
(3C), 127.3, 127.2, 127.1 (2C), 126.7, 124.1, 122.1, 120.7, 114.6,
45.0; HRMS (EI), exact mass calcd for C26H20N2 [M]+ 360.1626,
found 360.1616. Anal. Calcd for C26H20N2: C, 86.64; H, 5.59;
N, 7.77. Found: C, 86.48; H, 5.63; N, 7.87.
(Bn -IAN)Zr (NMe2)3 (15b). Bn-IAN amine (20.0 mg, 55.5
µmol) and Zr(NMe2)4 (14.9 mg, 55.7 µmol) were weighed into
a flame-dried vial in a glovebox. d6-Benzene was then added
and the clear orange solution was transferred to a J -Young
tube. 1H NMR, analyzed 5 min after mixing, revealed complete
complexation. 1H NMR (400 MHz, C6D6) δ 8.33 (d, J ) 6.2 Hz,
1H), 7.58 (d, J ) 9.1 Hz, 1H), 7.53-7.47 (m, 3H), 7.29 (d, J )
8.2 Hz, 1H), 7.10 (d, J ) 6.2 Hz, 1H), 7.06 (dd, J ) 8.1, 8.1 Hz,
1H), 7.00-6.95 (m, 2H), 6.86-6.82 (m, 3H), 6.76-6.74 (m, 3H),
6.67 (dd, J ) 8.1, 8.1 Hz, 1H), 5.09 (s, 2H), 3.00 (s, 18H); 13C
NMR (100 MHz, C6D6) δ 158.7, 149.3, 142.7, 140.1, 136.7,
135.6, 131.9, 130.9, 130.4, 128.4, 128.1, 127.5 (2C), 127.3,
127.2, 126.6 (2C), 126.1, 125.6, 122.1, 119.7, 119.4, 117.1, 53.9,
43.0.
(2-Np -IAN)Zr (NMe2)3 (15j). 2-Np-IAN amine (8.6 mg, 21.7
µmol) and Zr(NMe2)4 (5.8 mg, 21.7 µmol) were combined in a
flame-dried vial in the glovebox. d6-Benzene was then added
and the clear red-orange solution was transferred to a J -Young
tube. 1H NMR, analyzed 5 min after mixing, revealed complete
complexation. 1H NMR (400 MHz, C6D6) δ 8.26 (d, J ) 6.2 Hz,
1H), 7.82 (d, J ) 9.0 Hz, 1H), 7.72 (d, J ) 8.5 Hz, 1H), 7.62 (d,
J ) 9.0 Hz, 1H), 7.60-7.55 (m, 4H), 7.48 (s, 1H), 7.46-7.45
(m, 1H), 7.26 (d, J ) 8.2 Hz, 1H), 7.25-7.20 (m, 1H), 7.12-
7.03 (m, 5H), 6.89 (ddd, J ) 7.7, 7.7, 1.1 Hz, 1H), 6.79 (ddd, J
) 7.7, 7.7, 1.1 Hz, 1H), 3.07 (s, 18H); 13C NMR (100 MHz, C6D6)
δ 157.6, 151.9, 145.4, 140.5, 136.8, 136.1, 134.7, 132.0, 131.2,
129.7, 129.5, 129.1, 128.5 (2C), 127.8, 127.7 (2C), 127.6, 126.8,
126.7, 126.6, 126.1, 126.0, 124.2, 124.0, 122.4, 122.3, 120.8,
113.8, 42.9.
2-Np -IAN Am in e (1j). 2,2′-Dinaphthylamine (108.6 mg,
403.2 µmol) and 1-chloroisoquinoline (66.5 mg, 406.5 µmol)
were dissolved in toluene (4.0 mL) and treated with AlMe3
(0.64 mL, 2.0 M in toluene) via syringe prior to heating at
110 °C for 24 h. The solution was cooled to room tempera-
ture, added to 6 M aq NaOH, and diluted with EtOAc and
Rochelle’s salt solution. The mixture was stirred for 30 min,
the phases were separated, and the aqueous layer was fur-
ther extracted with EtOAc. The combined organic layers were
dried, filtered, and concentrated, and the residue was puri-
fied by flash chromatography (SiO2, 10% ethyl acetate in
hexanes) to give the desired amine as a tan powder (122.4 mg,
77%). Mp 168-170 °C; Rf 0.19 (20% EtOAc/hexanes); IR
(film) 3404, 3053, 1619 cm-1 1H NMR (400 MHz, CDCl3) δ
;
8.79 (d, J ) 5.6 Hz, 1H), 7.94-7.91 (m, 2H), 7.86 (d, J ) 7.8
Hz, 1H), 7.81-7.79 (m, 2H), 7.69-7.64 (m, 4H), 7.59 (d, J )
8.3 Hz, 1H), 7.41-7.28 (m, 5H), 7.23-7.20 (m, 1H), 7.11 (dd,
J ) 8.9, 2.0 Hz, 1H), 6.95 (d, J ) 8.6 Hz, 1H), 6.23 (br s,
1H); 13C NMR (100 MHz, CDCl3) δ 158.7, 143.2, 140.8, 139.4,
137.0, 134.7, 134.1, 130.9, 129.9, 129.7, 129.5, 129.3, 128.8,
128.3, 128.0, 127.8, 127.6, 127.3, 126.9, 126.7, 126.6, 125.2,
123.9, 123.8, 122.6, 120.9, 120.7, 119.6, 112.9; HRMS (CI, CH4),
exact mass calcd for C29H19N2 [M - H]+ 395.1548, found
395.1558.
(Bn -IAN)2Zr (NMe2)2 (16b). Bn-IAN amine (110.6 mg,
306.8 µmol) and Zr(NMe2)4 (41.8 mg, 156.2 µmol) were weighed
into a flame-dried vial in a glovebox. Benzene was then added
and the clear, orange solution was transferred to a J -Young
tube, which was sealed and heated at 90 °C for 17 h. The
solvent was removed, leaving the product as a red-orange solid
2-(N-Ben zyla m in o)n a p h th a len e (12b). 2-Naphthol (14.42
g, 100.0 mmol), ammonium chloride (11.86 g, 221.7 mmol),
benzylamine (200 mL, 1.83 mol), and ethanol (20 mL) were
combined. The solution was heated at 200 °C in a Parr reactor
for 4 d. After being cooled to room temperature, excess
benzylamine and ethanol were removed from the crude reac-
tion mixture by distillation, leaving an oily residue. The
residue was dissolved in EtOAc, washed with 6 M aq NaOH,
dried, filtered, and concentrated, and the residue was purified
by flash chromatography (SiO2, 5% ethyl acetate in hexanes)
to give the desired product as a tan powder (12.59 g, 54%).
The product can also be purified by recrystallization from a
hot toluene solution with an equivalent amount of hexanes.
Mp 68-69 °C; Rf 0.51 (20% EtOAc/hexanes); IR (film) 3421,
1
(236.4 mg, 86%). H NMR (400 MHz, C6D6) δ 8.22 (d, J ) 6.3
Hz, 2H), 7.43-7.38 (m, 4H), 7.29 (d, J ) 8.7 Hz, 2H), 7.21 (d,
J ) 7.9 Hz, 2H), 7.16 (d, J ) 7.3 Hz, 4H), 7.01 (d, J ) 8.2 Hz,
2H), 6.94 (d, J ) 6.3 Hz, 2H), 6.91-6.84 (m, 6H), 6.82 (dd, J
) 7.9, 7.9 Hz, 2H), 6.68 (dd, J ) 7.8, 7.8 Hz, 2H), 6.51 (dd, J
) 8.1, 8.1 Hz, 2H), 6.44 (dd, J ) 8.1, 8.1 Hz, 2H), 5.95 (d, J )
16.8 Hz, 2H), 5.90 (d, J ) 8.5 Hz, 2H), 5.56 (d, J ) 16.8 Hz,
2H), 3.00 (s, 12H); 13C NMR (100 MHz, C6D6) δ 159.1, 152.4,
143.0 (2C), 139.9, 136.1, 134.8, 130.7, 130.3, 129.9, 128.2,
127.8, 127.4 (2C), 126.8, 126.5, 126.4, 126.3, 125.7, 125.6,
121.2, 119.1, 118.3, 52.3, 45.7.
1
3053, 1629 cm-1; H NMR (400 MHz, CDCl3) δ 7.77 (d, J )
8.2 Hz, 1H), 7.72 (d, J ) 8.9 Hz, 1H), 7.69 (d, J ) 8.2 Hz, 1H),
7.50-7.37 (m, 6H), 7.29 (ddd, J ) 8.0, 8.0, 1.2 Hz, 1H), 6.97
(dd, J ) 8.8, 2.2 Hz, 1H), 6.92 (d, J ) 1.6 Hz, 1H), 4.49 (s,
2H), 4.17 (br s, 1H); 13C NMR (100 MHz, CDCl3) δ 146.1, 139.5,
135.5, 129.3, 129.0 (2C), 128.0 (2C), 127.7, 126.7, 126.3, 122.4,
118.2, 104.9, 48.6; HRMS (CI, CH4), exact mass calcd for
(P h -IAN)2Zr (NMe2)2 (16e). Ph-IAN amine (1.259 g, 3.635
mmol) and Zr(NMe2)4 (0.499 mg, 1.868 mmol) were combined
in a flame-dried vial in the glovebox. Benzene was added and
the clear red solution was transferred to a J -Young tube, which
was heated in an oil bath at 60 °C for 18 h. The solvent was
removed, leaving a red powder. The solid was dissolved in
warm toluene and then cooled to -25 °C to yield red crystals
(1.393 g, 88%). 1H NMR (400 MHz, C6D6) δ 8.77 (d, J ) 6.2
Hz, 2H), 7.45-7.35 (m, 4H), 7.30-7.19 (m, 6H), 7.10-7.02 (m,
4H), 6.96 (d, J ) 6.2 Hz, 2H), 6.91-6.80 (m, 6H), 6.71-6.63
(m, 4H), 6.52 (dd, J ) 8.1, 8.1 Hz, 2H), 6.16 (dd, J ) 8.1, 8.1
Hz, 2H), 5.51 (d, J ) 8.6 Hz, 2H), 2.74 (s, 12H); 13C NMR (100
MHz, C6D6) δ 159.2, 155.9, 153.0, 140.4, 136.1, 134.3, 130.7,
130.0, 128.9 (2C), 128.2, 127.9, 127.5, 127.1, 127.0, 126.5,
126.0, 125.7, 124.1 (2C), 122.7, 120.1, 119.1, 46.5.
(2-Np -IAN)2Zr (NMe2)2 (16j). 2-Np-IAN amine (11.3 mg,
28.5 µmol) and Zr(NMe2)4 (3.9 mg, 14.6 µmol) were combined
in a flame-dried vial in the glovebox. Benzene was added and
the clear red solution was transferred to a J -Young tube, which
was heated in an oil bath at 60 °C for 6 h. The solvent was
removed, leaving the desired product as a red powder. 1H NMR
(400 MHz, C6D6) δ 8.89 (d, J ) 6.2 Hz, 2H), 8.15 (br s, 2H),
7.86 (d, J ) 8.1 Hz, 2H), 7.66 (d, J ) 7.9 Hz, 2H), 7.63 (d, J )
8.7 Hz, 2H), 7.58-7.34 (m, 8H), 7.31 (dd, J ) 7.5, 7.5 Hz, 2H),
7.20-7.05 (m, 6H), 7.01 (d, J ) 6.0 Hz, 2H), 6.93 (dd, J ) 7.5,
C
C
17H13N [M]+ 233.1204, found 233.1198. Anal. Calcd for
17H13N: C, 87.52; H, 6.48; N, 6.00. Found: C, 87.51; H, 6.55;
N, 6.01.
Din a p h th a len -2-yla m in e (12j). Pd(dba)2 (191 mg, 332
µmol), dppf (533 mg, 961 µmol), and NaOtBu (478 mg, 4.97
mmol) were loaded into a round-bottom flask in a glovebox
and then transferred to a hood. Toluene (120 mL) was added
to the mixture followed by 2-aminonaphthalene (712 mg, 4.97
mmol). 2-Naphthyl triflate (915 mg, 3.32 mmol) was dissolved
in toluene and added before warming the reaction mixture to
85 °C for 65 h. The reaction mixture was cooled to room
temperature and concentrated to an oil that was purified by
flash chromatography (SiO2, 5% ether in hexanes) to give the
desired amine as a white solid (820 mg, 92%). Mp 172-174
°C; Rf 0.53 (20% EtOAc/hexanes); IR (film) 3414, 3392, 3048,
1
1628 cm-1; H NMR (400 MHz, CDCl3) δ 7.81 (m, 2H), 7.70
(d, J ) 8.2 Hz, 1H), 7.56 (d, J ) 2.0 Hz, 1H), 7.45 (m, 1H),
7.35 (m, 2H), 6.06 (s, 1H); 13C NMR (100 MHz, CDCl3) δ 140.9,
134.9, 129.6, 129.5, 127.9, 126.8 (2C), 123.9, 120.5, 112.5;
HRMS (CI, CH4), exact mass calcd for C20H15N [M]+ 269.1204,
found 269.1194.

IAN Amines: Highly Diastereoselective Complexations
Organometallics, Vol. 23, No. 10, 2004 2249

2250 Organometallics, Vol. 23, No. 10, 2004
Cortright et al.
7.5 Hz, 2H), 6.73 (dd, J ) 7.5, 7.5 Hz, 2H), 6.63 (dd, J ) 7.5,
7.5 Hz, 2H), 6.23 (dd, J ) 7.5, 7.5 Hz, 2H), 5.60 (d, J ) 8.5 Hz,
2H), 2.83 (s, 12H); 13C NMR (100 MHz, C6D6) δ 159.3, 153.4,
152.6, 140.6, 136.3, 135.7 134.3, 130.8, 130.1, 130.0, 129.6,
128.6 (2C), 128.2, 127.9, 127.3 (2C), 127.2, 127.1, 127.0, 126.6,
126.2, 126.1, 125.7, 124.9, 123.1, 122.8, 119.3, 118.8, 46.7.
(-)-Me-IAN-Ca ta lyzed Dieth yl Zin c Ad d ition to Ben -
za ld eh yd e. (-)-Me-IAN amine (17.5 mg, 61.5 µmol, 96% ee)
was dissolved in d8-toluene (0.70 mL) and treated with
diethylzinc (161.9 mg, 1.31 mmol), resulting in immediate
formation of a clear red-orange solution. After 10.5 h at room
temperature, 1H NMR revealed complete ligand complexation,
forming ((-)-Me-IAN)2Zn. Benzaldehyde (63 µL, 0.620 mmol)
was added and immediately the solution lightened to a pale
orange-yellow. The solution had returned to red-orange after
being stirred for 19 h, at which point it was cooled to 0 °C and
MeOH was added. Dilution with water was followed by
extraction with CH2Cl2. The combined organic layers were
dried, filtered, and concentrated. Purification via flash chro-
matography (SiO2, 5% Et2O in hexanes) gave the product as a
light yellow liquid (65.7 mg, 78%) and recovered (-)-Me-IAN
(16.9 mg). HPLC analysis was used to determine the enan-
tioenrichment of the product (OD column, 1.0 mL/min, 2%
iPrOH in hexanes) at 85% ee (major peak ) 13.7 min, minor
peak ) 16.3 min), and recovered (-)-Me-IAN amine (OD
Data were corrected for Lorentz and polarization effects and
equivalent reflections were averaged with use of the Bruker
SAINT62 software as well as utility programs from the XTEL
library. The structures were solved with SHELXTL63 and
Fourier techniques. ORTEP drawings were constructed with
ORTEP-III.64
Gen er a l P olym er iza tion P r oced u r e. A mechanically
stirred 1-L autoclave with an oven-dried stainless steal bottom
was thoroughly purged with N2 and charged with 400 g of
hexanes. Via syringe under N2 purge, triisobutylaluminum
(200 or 1000 µmol) was added as a toluene solution to scavenge
residual impurities. Over 20-30 min, the stirred mixture was
brought to 85 °C, and the reactor was pressurized to 135 or
200 psi with ethylene. The activated precatalyst/MAO mixture
(2-5 µmol of Zr; 1000 equiv of Al), stirred for 10-15 min, was
injected into the reactor via a pressurized bomb followed by a
few milliliters of a hexane “chaser” to ensure complete injec-
tion. The temperature was maintained at ∼85 °C during the
30 or 40 min run, using an external cooling jacket, and
ethylene was fed on demand to maintain reactor pressure. The
reactor was then vented, cooled, and opened to expose the
polymer. The polyethylene yields were determined after drying
in a vacuum oven overnight.
Ack n ow led gm en t. This work was supported by
Indiana University. Acknowledgment is also made to
Amgen and Boehringer-Ingelheim (Young Investigator
Awards to J .N.J .), the Yamanouchi USA Foundation,
and the GAANN program (S.B.C. and R.A.Y.). We also
thank Dow technologists Mike Allen and Gorden O’Dell
for their contributions to the polymerization studies.
i
column, 1.0 mL/min, 10% PrOH in hexanes) at 95% ee.
((+)-Me-IAN)2Zr Cl2 ((+)-17a ). (+)-Me-IAN amine (24.5
mg, 86.2 µmol, 99% ee) and LiNMe2 (4.4 mg, 86.2 µmol) were
combined in a vial and dissolved in toluene. The opaque purple
solution was allowed to mix at room temperature for 30 min,
after which the solvent and volatiles were removed by vacuum.
The residue was redissolved in d6-benzene and ZrCl4 (10.0 mg,
42.9 µmol) was added. After 30 min at room temperature, a
red solution and orange precipitate resulted. 1H NMR revealed
the desired complex present in ∼70% purity. To the reaction
mixture was added H2O. The mixture was extracted with
CH2Cl2, and the organic layer was dried, concentrated, and
purified by flash chromatography (SiO2, 30% EtOAc in hex-
anes) to give recovered (+)-Me-IAN amine that was analyzed
by HPLC (OD column, 1.0 mL/min, 10% iPrOH in hexanes) to
reveal a 96% ee.
Su p p or tin g In for m a tion Ava ila ble: General experimen-
tal procedures and spectral data for all new compounds (PDF)
and complete X-ray structural data (CIF). This material is
available free of charge via the Internet at http://pubs.acs.org.
OM049897P
(62) SAINT 6.1; Bruker Analytical X-Ray Systems: Madison, WI.
(63) SHELXTL-Plus V 5.10; Bruker Analytical X-Ray Systems:
Madison, WI.
(64) Burnett, M. N.; J ohnson, C. K. ORTEP-III, Oak Ridge Thermal
Ellipsoid Plot Program for Crystal Structure Illustrations; Oak Ridge
National Laboratory Report ORNL-6895, 1996.
Gen er a l P r oced u r e for X-r a y An a lysis. X-ray diffraction
data were collected on a Bruker diffractometer (SMART
6000CCD). Crystals were attached to a glass fiber with silicone
grease and cooled to near lN2 temperature for data collection.