Chiral biarylamido complexes of zirconium

Article abstract of DOI:10.1021/om020471p

The palladium-catalyzed arylation of 2,2′-diamino-6,6′-dimethylbiphenyl with (variously) bromo-3,5-di-fe/t-butylbenzene, 2-bromopyridine, 2-methylbromopyridine, bromomesitylene, and 2-bromo-4-methylanisole gives three C₂-symmetric and three C₂-symmetric biaryl-bridged diamino proligands H₂L. The subsequent amine elimination (protonolysis) reactions of these with tetrakis(dimethylamido)zirconium yields a range of crystalline complexes [Zr(L)(NMe₂)₂]. X-ray crystallography reveals molecular structures of five examples with ligated amido, aminopridinato, and aminoanisolato units.

Full text of DOI:10.1021/om020471p

4496
Organometallics 2002, 21, 4496-4504
Ch ir a l Bia r yla m id o Com p lexes of Zir con iu m
Paul N. O’Shaughnessy, Kevin M. Gillespie, Colin Morton,
Ian Westmoreland, and Peter Scott*
Department of Chemistry, University of Warwick, Coventry CV4 7AL, United Kingdom
Received J une 14, 2002
The palladium-catalyzed arylation of 2,2′-diamino-6,6′-dimethylbiphenyl with (variously)
bromo-3,5-di-tert-butylbenzene, 2-bromopyridine, 2-methylbromopyridine, bromomesitylene,
and 2-bromo-4-methylanisole gives three C2-symmetric and three C1-symmetric biaryl-bridged
diamino proligands H2L. The subsequent amine elimination (protonolysis) reactions of these
with tetrakis(dimethylamido)zirconium yields a range of crystalline complexes [Zr(L)(NMe2)2].
X-ray crystallography reveals molecular structures of five examples with ligated amido,
aminopridinato, and aminoanisolato units.
In tr od u ction
addition of dialkylzinc reagents to aldehydes with high
enantioselectivity. Cloke et al. have reported a zirco-
nium complex in which two amido groups are linked by
the atropisomeric 2,2′-diamino-6,6′-dimethylbiphenyl
backbone in 1.6 Tilley and co-workers have reported an
yttrium complex containing a similar ligand system that
gave high enantioselectivity in the hydrosilation of
norbornene.7
We have been interested in the design of inherently
chiral ligands, and particularly a group of quadridentate
N2O2 Schiff bases based on 1, which give metallocene-
like complex structures.8 Our most successful catalyses
using these Schiff-base ligands have used middle and
later transition metals,9 the early metal catalysts suf-
For metal complexes to be successful in enantioselec-
tive catalysis, the chirality of the system must be well
expressed in the region of the active coordination sites.
In early transition metal and lanthanide chemistry, the
number of systems which achieve this is rather limited.
Perhaps the best examples are provided by the group 4
ansa-metallocenes such as I.1,2 In such complexes, cis-
coligands in the symmetry-equivalent active sites ex-
perience a high degree of diastereofacial discrimination.
This manifests itself in the excellent levels of tacticity
control achieved by the racemic catalysts in R-alkene
polymerization,3 and the success of nonracemic catalysts
in enantioselective processes.4
(2) (a) Haltermann, R. L. Chem. Rev. 1992, 92, 965. (b) Chen, Z.;
Haltermann, R. L. J . Am. Chem. Soc. 1992, 114, 2276. (c) Haltermann,
R. L.; Ramsey, T. M.; Chen, Z. J . Org. Chem. 1994, 59, 2642. (d)
Giardello, M. A.; Yamamoto, Y.; Brard, L.; Marks, T. J . J . Am. Chem.
Soc. 1995, 117, 3276. (e) Urabe, H.; Yoshikawa, K.; Sato, F. Tetrahe-
dron Lett. 1995, 36, 5595. (f) Mitchell, J . P.; Hajela, S.; Brookhart, S.
K.; Hardcastle, K. L.; Henling, L. M.; Bercaw, J . E. J . Am. Chem. Soc.
1996, 118, 1045. (g) Taber, D. F.; Balijepalli, B.; Liu, K. K.; Kong, S.;
Rheingold A. L.; Askham, F. R. J . Org. Chem. 1999, 64, 4525. (h) Ewen,
J . A.; Elder, M. J .; J ones, R. L.; Rheingold, A. L.; Liable-Sands, L. M.;
Sommer, R. D. J . Am. Chem. Soc. 2001, 123, 4763.
(3) (a) Brintzinger, H. H.; Fischer, D.; Mulhaupt, R.; Rieger, B.;
Waymouth, R. M. Angew. Chem., Int. Ed. Engl. 1995, 34, 1143. (b)
Resconi, L.; Cavallo, L.; Fait, A.; Piemontes, F. Chem. Rev. 2000, 100,
1253.
Amido (R2N-) ligands are widespread in early metal
chemistry, but reports of chiral nonracemic diamido
ligands, which might provide an alternative to the ansa-
Cp2 unit, are rare. There are a number of examples of
1,2-daminocyclohexane-based systems, most notably the
sulfonamides5 which have been found to catalyze the
(4) (a) Hong, Y.; Kuntz, B. A.; Collins, S. Organometallics 1993, 12,
964. (b) J aquith, J . B.; Guan, J . Y.; Wang, S. T.; Collins, S. Organo-
metallics 1995, 14, 1079. (c) J aquith, J . B.; Levy, C. J .; Bondar, G. V.;
Wang, S.; Collins, S. Organometallics 1998, 17, 914. (d) Willoughby,
C. A.; Buchwald, S. L. J . Am. Chem. Soc. 1994, 116, 8952. (e) Carter,
M. B.; Schiott, B.; Gutierrez, A.; Buchwald, S. L. J . Am. Chem. Soc.
1994, 116, 11667. (f) Didiuk, M. T.; J ohannes, C. W.; Morken, J . P.;
Hoveyda, A. H. J . Am. Chem. Soc. 1995, 117, 7097. (g) Verdauguer,
X.; Lange, U. E. W.; Reding, M. T.; Buchwald, S. L. J . Am. Chem. Soc.
1996, 118, 6784. (h) Hicks, F. A.; Buchwald, S. L. J . Am. Chem. Soc.
1996, 118, 11688. (i) Yamaura, Y.; Hyakutake, M.; Mori, M. J . Am.
Chem. Soc. 1997, 119, 7615.
(5) (a) Ackermann, L.; Bergman, R. G. Org. Lett. 2002, 4, 1475. (b)
Pritchett, S.; Woodmansee, D. H.; Gantzel, P.; Walsh, P. J . J . Am.
Chem. Soc. 1998, 120, 6423 and references therein.
(6) Cloke, F. G. N.; Geldbach, T. J .; Hitchcock, P. B.; Love, J . B. J .
Organomet. Chem. 1996, 506, 343.
(7) Gountchev, T. I.; Tilley, T. D. Organometallics 1999, 18, 5661.
(8) Woodman, P. R.; Munslow, I. J .; Hitchcock, P. B.; Scott, P. J .
Chem. Soc., Dalton Trans. 1999, 4069.
(9) (a) Sanders, C. J .; Gillespie, K. M.; Bell, D.; Scott, P. J . Am.
Chem. Soc. 2000, 122, 7132. (b) Gillespie, K. M.; Crust, E. J .; Deeth,
R. J .; Scott, P. Chem. Commun. 2001, 785. (c) Munslow, I. J .; Gillespie,
K. M.; Deeth, R. J .; Scott, P. Chem. Commun. 2001, 1638.
* Address correspondence to this author. E-mail: peter.scott@
warwick.ac.uk. Fax: 024 7657 2710.
(1) (a) Ewen, J . A. J . Am. Chem. Soc. 1984, 106, 6355. (b) Ewen, J .
A.; Atwood, J . L.; Zhang, H. J . Am. Chem. Soc. 1987, 109, 6544. (c)
Kaminsky, W.; Kulper, K.; Brintzinger, H. H.; Wild, F. R. W. P. Angew.
Chem., Int. Ed. Engl. 1985, 24, 507. (d) Kaminsky, W.; Ahlers, A.;
Moller-Lindenhof Angew. Chem., Int. Ed. Engl. 1989, 28, 1216. (e) Roll,
W.; Brintzinger, H. H.; Rieger, B.; Zolk, R. Angew. Chem., Int. Ed. Engl.
1990, 29, 279. (f) Spaleck, W.; Antberg, M.; Rohrmann, J .; Winter, A.;
Bachmann, B.; Kiprof., P.; Behm, J .; Hermann W. A. Angew. Chem.,
Int. Ed. Engl. 1992, 31, 1347. (g) Kondakov, D. Y.; Negishi, E. J . Am.
Chem. Soc. 1995, 117, 10771. (h) Schaverien, C. J .; Ernst, R.; Schut,
P.; Skiff, W. M.; Resconi, L.; Barbassa, E.; Balboni, D.; Dubitsky, Y.
A.; Orpen, A. G.; Mercandelli, P.; Moret, M.; Sironi, A. J . Am. Chem.
Soc. 1998, 120, 9945. (i) Negishi, E. Chem. Eur. J . 1999, 5, 411. (j)
Schaverien, C. J .; Ernst, R.; Schut, P.; DallOcco, T. Organometallics
2001, 20, 3436.
10.1021/om020471p CCC: $22.00 © 2002 American Chemical Society
Publication on Web 09/11/2002

Chiral Biarylamido Complexes of Zirconium
Organometallics, Vol. 21, No. 21, 2002 4497
Sch em e 1. Syn th esis of th e C2-Sym m etr ic
Dia m in e Liga n d s H2L1, H2L2, a n d H2L3 a
Schrock’s tridentate diamido ligands (ArNHCH2CH2)2E
(E ) N, or O; Ar ) 2,6-Me2C6H3, 2,6-Et2C6H3, and 2,6-
i-Pr2C6H3),15 Gibson’s bis(arylsilylaminoethane) and 2,6-
bis(dimethylphenylamino)diphenylsilane systems,16 and
Bochmann’s dimethylethylene bridged bis-phenylamine
ligand.17 In each of the above cases the aryl groups are
introduced by treating the N-lithiated anilines with an
appropriate precursor. Schrock and co-workers have
previously used Pd-catalyzed amine arylation in the
synthesis of amido ligands.15e
We have noted in the above reactions i and iii (Scheme
1) that the rate of the first arylation of diamine 1 is
generally much faster than that of the second, making
it possible to monoarylate with high selectivity. This has
some precedent in the work of Beletskaya et al.,18 and
opens up the possibility of synthesis of unsymmetrically
substituted analogues of H2L1-3 via sequential aryla-
tions. Schrock and co-workers have prepared an un-
symmetrically substituted chiral diamine complex sys-
tem based on cis-2,5-bis(amidomethyl)tetrahydrofuran
using a protecting group strategy.15(f)
Hence the reactions of 1 with 0.5 equiv of 3,5-di-tert-
butylbromobenzene, bromomesitylene, and 2-bromo-4-
methylanisole yield the respective monoarylated prod-
ucts 2, 3, and 4 in good yields (>70%). In the crude
materials, the disubstituted species were observed as
minor products (<10%) necessitating the use of flash
chromatography to yield analytically pure compounds.
Increasing the stoichiometric ratio of diamine to bro-
moarene leads to still higher chemoselectivity for mono-
substited product. In the case of 4, lowering the catalyst
loading effects a similar result, but there is a concomi-
tant increase in reaction time. To exemplify the method,
a chiral nonracemic version of 4 was prepared in
essentially the same manner.
a
Reagents and conditions: all reactions used Na(OBut) in
toluene at 90 °C. (i) bromo-3,5-di-tert-butylbenzene, [Pd2(DBA)3],
BINAP; (ii) 2-bromopyridine, [Pd2(DBA)3], DPPP; (iii) 2-bromo-
4-methylanisole, [Pd2(DBA)3], BINAP.
fering from decomposition via 1,2-migratory insertion
reactions10 and radical processes.11 While these trouble-
some reactions can be eliminated almost completely in
some instances,12 we recognize that it will be difficult
to produce complexes as durable and robust as the
metallocenes using Schiff-base ligands. In response to
this we set out to synthesize a range of new diamido
ligands based on the diamine 1 with bulky and hetero-
atom donor aryl groups.
The unsymmetrically substituted diamine H2L4 can
be synthesized by arylation of 2 with 2-bromo-4-methyl-
anisole or 4 with 2,5-di-tert-butylbromobenzene (Scheme
2). The latter is the preferred route since the precursor
4 is obtained in higher yield (vide supra) and is easier
to purify than is 2. The diamine H2L4 is obtained in
good yield as a pale yellow crystalline solid. The reac-
tions of 3 and 4 with 2-bromo-6-methylpyridine under
Pd/phosphine catalysis gave the expected diamines
H2L5 and H2L6 in good yield. While these reactions
require the presence of a slight excess of the bro-
moarene, the final products are readily isolated as a
yellow crystalline solid and a viscous oil, repectively.
Zir con iu m Com p lexes of th e C2-Sym m etr ic Di-
a m in e Liga n d s. The C2-symmetric proligand H2L1
Resu lts a n d Discu ssion
Liga n d Design a n d Syn th esis. 2,2′-Diamino-6,6′-
dimethylbiphenyl (1) reacts readily with 2 equiv of
bromo-3,5-di-tert-butylbenzene, 2-bromopyridine, and
2-bromo-4-methylanisole under palladium catalysis13 to
give the corresponding C2-symmetric diamines H2L1,
H2L2, and H2L3 in good yield (Scheme 1). The analogous
reactions with bromomesitylene and 2-bromo-6-meth-
ylpyridine gave mixtures of products.
(15) (a) Schrock, R. R.; Schattenmann, F.; Aizenberg, M.; Davis, W.
M. Chem. Commun. 1998, 199. (b) Aizenberg, M.; Turculet, L.; Davis,
W. M.; Schattenmann, F.; Schrock, R. R. Organometallics 1998, 17,
4795. (c) Schrock, R. R.; Seidel, S. W.; Schrodi Y.; Davis, W. M.
Organometallics 1999, 18, 428. (d) Graf, D. D.; Schrock, R. R.; Davis,
W. M.; Stumpf, R. Organometallics 1999, 18, 843. (e) Lan-Chang, L.;
Schrock, R. R.; Davis, W. M.; McConville, D. H. J . Am. Chem. Soc.
1999, 121, 5797. (f) Flores, M. A.; Manzoni, M. R.; Baumann, R.; Davis,
W. M.; Schrock, R. R. Organometallics 1999, 18, 3220. (g) Baumann,
R.; Stumpf, R.; Davis, W. M.; Liang, L.-C.; Schrock, R. R. J . Am. Chem.
Soc. 1999, 121, 7822. (h) Schrock, R. R.; Baumann, R.; Reid, S. M.;
Goodman, J . T.; Stumpf, R.; Davis, W. M. Organometallics 1999, 18,
3649.
(16) Gibson, V. C.; Kimberley, B. S.; White, A. J . P.; Williams, D.
J .; Howard, P. Chem. Commun. 1998, 313.
(17) Male, N. A. H.; Thornton-Pett, M.; Bochmann, M. J . Chem. Soc.,
Dalton Trans. 1997, 2487.
(18) Beletskaya, I. P.; Bessmertnyk, A. G.; Guilard, R. Tetrahedron
Lett. 1997, 38, 6462
Previous examples of arylated diamido ligand systems
include McConville’s bis(arylaminomethyl)pyridines,14
(10) Woodman, P. R.; Alcock, N. W.; Munslow, I. J .; Sanders, C. J .;
Scott, P. J . Chem. Soc., Dalton Trans. 2000, 3340.
(11) Woodman, P. R.; Sanders, C. J .; Alcock, N. W.; Munslow, I. J .;
Hitchcock P. B.; Scott, P. New J . Chem. 1999, 23, 815.
(12) Knight, P. D.; Clarke, A. J .; Kimberley, B. S.; J ackson R. A.;
Scott, P. Chem. Commun. 2002, 352.
(13) Yang, B. H.; Buchwald, S. L. J . Organomet. Chem. 1999, 576,
125.
(14) (a) Scollard, J . D.; McConville, D. H.; Vittal, J . J . Macromol-
ecules 1996, 29, 5241. (b) Guerin, F.; McConville, D. H.; Vittal, J . J .
Organometallics 1995, 14, 3154. (c) Guerin, F.; McConville, D. H.;
Payne, N. C. Organometallics 1996, 15, 5085. (d) Guerin, F.; McCon-
ville, D. H.; Vittal, J . J . Organometallics 1996, 15, 5586. (e) Guerin,
F.; McConville, D. H.; Vittal, J . J .; Yap, G. A. P. Organometallics 1998,
17, 5172.

4498 Organometallics, Vol. 21, No. 21, 2002
O’Shaughnessy et al.
Sch em e 2. Syn th esis of th e Un sym m etr ica lly Su bstitu ted Dia m in es H2L1, H2L2, a n d H2L3 P r oliga n d s via
Sequ en tia l Mon oa r yla tion sa
a
Reagents and conditions: all reactions used Na(OBut) in toluene at 90 °C. (i) 2-bromo-4-methylanisole, [Pd2(DBA)3], BINAP;
(ii) bromo-3,5-di-tert-butylbenzene, [Pd2(DBA)3], BINAP; (iii) bromomesitylene, [Pd2(DBA)3], BINAP; (iv) 2-bromo-6-methylpyridine,
[Pd2(DBA)3], DPPP.
reacts with Zr(NMe2)4 in toluene at room temperature
to give the crystalline zirconium amido complex [L1Zr-
(NMe2)2] (eq 1). Most 4-coordinate (tetrahedral) zirco-
nium amido complexes contain silylamido units,16,17,19
but examples with aryl and other substiuents are
known.20
around N(1) and N(2) [355.93° and 359.93°] indi-
cates sp2 hybridization, in both cases the individual
Zr-N-Cipso angles are significantly distorted away from
ideal at 133.63° and 141.83° away from Zr. This is
ascribed to the steric influence of the tert-butyl groups.
The potentially quadridentate H2L2 gives a complex
mixture of products when treated with Zr(NMe2)4 which
we were not able to separate, although the 1H NMR
spectrum of the crude reaction mixture does indicate
complete deprotonation of the diamine ligand. In con-
trast, the reaction between H2L3 and Zr(NMe2)4 in
toluene gives exclusively the desired monomeric C2-
symmetric complex [L3Zr(NMe2)2]. Removal of the tolu-
ene under reduced pressure yields a foamy material, but
the complex may be recrystallized from pentane in good
yield. Zirconium amido complexes that contain ad-
ditional donor functionalities at the periphery of the
ligand are relatively rare.17,21
H2L1 + Zr(NMe2)4 f [L1Zr(NMe2)2] + 2NMe2H (1)
1
The H and 13C NMR NMR spectra of [L1Zr(NMe2)2]
are consistent with a C2-symmetric complex in solution.
The molecular structure determined by X-ray crystal-
lography (Figure 1) shows the monomeric structure with
a distorted tetrahedral geometry about zirconium. As
can be seen in Figure 1a, C(29) lies further away from
the N(2)-Zr(1)-N(1) plane (+0.63 Å) than does C(14)
(-0.10 Å), although of course this difference is not likely
to persist in solution. The two di-tert-butylphenyl rings
also adopt slightly different orientations: that con-
taining C(29) is twisted 44.5° with respect to the
N(2)-Zr(1)-N(1) plane while the phenyl ring containing
C(14) is twisted by only 24.0°. One effect of the combined
orientations of these rings is that the dimethylamido
substituents experience very different steric environ-
ments, as can be seen in Figure 1b. The zirconium-to-
diamido nitrogen bond lengths in L1Zr(NMe2)2 [ca. 2.11
Å] are in the middle-to-high end of the range for such
distances in similar tetrahedral zirconium environments
[1.999-2.214 Å].16,17,19 While the sum of the angles
An X-ray crystallographic study on [L3Zr(NMe2)2]
revealed two independent but similar molecules in the
asymmetric unit; the molecular structure of one is
shown in Figure 2 with selected bond lengths and angles
in Table 1. Both methoxy groups are bound to the metal
center forming five-membered planar chelate rings with
bite angles of 68.99(11)° and 67.32(11)° for N(1)-Zr(1)-
O(1) and N(2)-Zr(1)-O(2), respectively. Both chelate
rings are essentially planar. The 6-coordinate zirconium
atom adopts, as a result of the constaints of the ligand,
a geometry strongly distorted from octahedral. Interest-
ingly, the coordination mode of the L3 ligand is different
1
from that expected on the basis of the H and 13C NMR
(19) (a) J oen, Y. M.; Park, S. J .; Heo, J .; Kim, K. Organometallics
1998, 17, 3161. (b) Grocholl, L.; Huch, V.; Stahl, L.; Staples, R. J .;
Steinhart, P.; J ohnson, A. Inorg. Chem. 1997, 36, 4451. (c) Lorber, C.;
Donnadieu, B.; Choukroun, R. Organometallics 2000, 19, 1963.
(20) (a) Warren, T. H.; Schrock, R. R.; Davis, W. M. Organometallics
1998, 17, 308. (b) Latesky, S. L.; McMullen, A. K.; Niccolai, G. P.;
Rothwell, I. P.; Huffman, J . C. Organometallics 1985, 4, 1896.
spectra which indicate the presence of C2-symmetry on
these chemical shift time scales. In the solid-state
(21) Amor, F.; Butt, A.; Du Ploy, K. E.; Spaniol, T. P.; Okuda, J .
Organometallics 1998, 17, 5836.

Chiral Biarylamido Complexes of Zirconium
Organometallics, Vol. 21, No. 21, 2002 4499
F igu r e 2. Molecular structure of [L3Zr(NMe2)2].
from their twist orientations with respect to the biaryl
backbone. The Zr-N(biaryl) distances in [L3Zr(NMe2)2]
(ca. 2.15 Å) are marginally longer than those in [L1Zr-
(NMe2)2] (ca. 2.11 Å).
Zir con iu m Com p lexes of th e C1-Sym m etr ic Di-
a m in e Liga n d s. The reaction of 1 equiv of H2L4 with
Zr(NMe2)4 gave the desired C1-symmetric complex
[L4Zr(NMe2)2] (eq 2 ). X-ray quality crystals of this five-
H2L4 + Zr(NMe2)4 f [L4Zr(NMe2)2] + 2NMe2H (2)
coordinate complex were obtained from a concentrated
pentane solution at 0 °C. The geometry around the Zr
atom may be described as a distorted trigonal bipyramid
(Figure 3), with the methoxy O(1) and the biaryldiamido
N(2) occupying the axial positions. In this arrangement
the methoxy group sits trans to the biaryl-diamido group
on the opposite arm of the ligand in a mer-type arrange-
ment similar to the [NON]MMe2 (M ) Ti, Zr, and Hf)
systems.15a,b,f,g The five-membered anisolyl chelate ring
has similar distances and angles to those in [L3Zr-
(NMe2)2] [e.g. O(1)-Zr(1)-N(1) ) 68.07(17)° cf. 68.99-
(11)°, and Zr-O(1) ) 2.382(4) Å cf. 2.389(3) Å]. The di-
tert-butylphenyl ring, which is otherwise free to rotate,
is oriented such that it is essentially coplanar with the
amido Zr(1)-N(2)-C(22) plane, perhaps in order to
maximize overlap of the pz “lone pair” at N(2) with the
π system of the phenyl ring. This is in contrast to
Schrock’s aryl-substituted [NON2-] systems where the
planes of the phenyl rings are generally twisted at 90°
to the amido planes. The presence of o-alkyl substituents
on the aryl rings are likely to disfavor such an arrange-
ment in the latter systems. This phenyl ring is also close
to coplanarity with the Zr(1)-N(4) bond.
F igu r e 1. Views of the molecular structure of [L1Zr-
(NMe2)2] (a) along the approximate C2 axis and (b) showing
the different steric environments of the dimethylamido
units.
The Zr-N(biaryl) distances in five-coordinate [L4Zr-
(NMe2)2] [ca. 2.129 Å] are intermediate between those
of the four- and six-coordinate complexes [L1Zr(NMe2)2]-
[ca. 2.108 Å] and [L3Zr(NMe2)2] [ca. 2.149 Å].
structure, one methoxy donor group is effectively trans
to one of the amidos of the ligand groups while the other
is cis. Clearly then, in contrast to the case of our
titanium Schiff-base complexes based on 1,10 the â-cis
orientation of [L3Zr(NMe2)2] undergoes facile molecular
rearrangement, possibly via reversible decoordination
of methoxy groups. The Zr-O distances in [L3Zr-
(NMe2)2] (Table 1) fall within the range seen in the few
examples for MeOfZr dative interactions.21,22 The
Zr(1)-O(1) and Zr(1)-O(2) distances are significantly
different [2.389(3) and 2.466(3) Å, respectively], perhaps
as a result of the differential angle strains resulting
A similar reaction of H2L5 with Zr(NMe2)4 does not
1
yield the desired [L5Zr(NMe2)2] species. Instead the H
(22) (a) Evans, W. J .; Ansari, M. A.; Ziller, J . W. Inorg. Chem. 1999,
38, 1160. (b) van der Zeijden, A. A. H.; Mattheis, R.; Frohlich, R Acta
Crystallogr., Sect. C 1998, 54, 458. (c) van der Zeijden, A. A. H.;
Mattheis, R.; Frohlich, R.; Zippel, F. Inorg. Chem. 1997, 36, 4444. (d)
van der Zeijden, A. A. H.; Mattheis, R.; Frohlich, R Organometallics
1997, 16, 2651. (e) Caselli, A.; Giannini, L.; Solari, E.; Floriani, C.;
Chiesi-Cilla, A.; Rizzoli, C.; Re, N.; Sgamelloti, A. Organometallics
1997, 16, 5457. (f) Giannini, L.; Caselli, A.; Solari, E.; Floriani, C.; Re,
N.; Chiesi-Cilla, A.; Rizzoli, C. Organometallics 1997, 16, 5457.

4500 Organometallics, Vol. 21, No. 21, 2002
O’Shaughnessy et al.
Ta ble 1. Cr ysta llogr a p h ic Da ta , Collection P a r a m eter s, a n d Refin em en t P a r a m eter s for L1Zr (NMe2)2,
L3Zr (NMe2)2, (HL5)2Zr (NMe2)2‚C5H12, L4Zr (NMe2)2, a n d L6Zr (NMe2)2
L1Zr(NMe2)2
L3Zr(NMe2)2
(HL5)2Zr(NMe2)2‚C5H12
L4Zr(NMe2)2
L6Zr(NMe2)2
empirical formula
fw
C
46H66N4Zr
C34H42N2O2Zr
629.94
0.31 × 0.23 × 0.14
monoclinic
P21
11.587(10)
16.203(14)
17.005(15)
90
92.256(17)
90
C67H84N8Zr
1092.64
0.26 × 0.18 × 0.11
monoclinic
P21/c
20.250(7)
20.197(9)
16.306(5)
90
110.313(18)
90
6254(4)
1.160
C40H54N4OZr
698.09
0.35 × 0.27 × 0.15
monoclinic
Ia
14.4964(19)
18.818(3)
15.159(2)
90
113.613
90
C32H39N5OZr
600.90
0.21 × 0.14 × 0.08
monoclinic
P21/c
10.6816(16)
10.8516(16)
26.123(4)
90
99.99(2)
90
766.25
cryst size (mm3)
cryst system
space group
a (Å)
0.22 × 0.20 × 0.06
orthorhombic
P212121
10.4593(10)
13.2155(13)
31.978(3)
90
b (Å)
c (Å)
R (deg)
â (deg)
90
90
γ (deg)
V
4420.2 (8)
1.151
0.282
3190(5)
1.312
0.380
3788.9(9)
1.224
0.325
2982.0(8)
1.338
0.401
Dcalcd (Mg/m3)
µ (mm-1
F000
)
0.221
2328
1640
1320
1480
1256
total reflns
27481
21738
29681
12634
18862
independent reflns
Rint
7783
0.1150
14733
0.0275
8159
0.1166
6707
0.065
7272
0.1062
data/restraints/
parameters
7783/18/479
14733/1/759
8159/133/759
6707/20/429
7272/0/362
R1,a [I > 2σ(I)]
wR2b
0.0797
0.1388
1.110
0.0455
0.0970
1.034
0.0895
0.2304
1.188
0.0574
0.1282
0.962
0.0700
0.1363
1.008
GoFc on F2
abs struct parameterb
0.03(6)
0.01(3)
0.00(2)
Conventional R ) ∑||Fo| - |Fc||/∑|Fo| for observed reflections having Fo > 2σ(Fo2). wR2 ) [∑w(Fo - Fc2)2/∑w(Fo2)2]1/2 for all data.
a
2
b
2
c GoF ) [∑w(Fo - Fc2)2/(no. of unique reflections - no. of parameters)]1/2
.
Checked by refinement of the ∆f ′′ multiplier.
2
b
F igu r e 4. Molecular structure of [(HL5)2Zr(NMe2)2].
conium bis-aminopyridinato complex, [(HL5)2Zr(NMe2)2].
2H2L5 + Zr(NMe2)4 f [(HL5)2Zr(NMe2)2] +
2NMe2H (3)
X-ray quality crystals of [(HL5)2Zr(NMe2)2] were
obtained from a concentrated pentane solution. The
zirconium center is coordinated by two aminopyridinate
units (Figure 4). Both biaryl units within the complex
have the same absolute configuration, i.e., the com-
plex is homochiral with respect to these units (vide
infra). The severe trigonal distortion of the metal
geometry away from octahedral is a consequence of the
small bite angles [N(2)-Zr(1)-N(1) ) 57.7(2)° and
N(5)-Zr(1)-N(4) ) 57.8(2)°] of the aminopyridinate
ligands. The molecule is C2-symmetric such that the
dimethylamido groups are mutually cis, the amido
nitrogens from each ligand unit are mutually trans, and
the pyridyl donor nitrogens are mutually cis to each
other. This arrangement minimizes the steric interac-
tion between the methyl groups on the pyridine rings
and the bulky biaryl fragments on each ligand.
F igu r e 3. Molecular structure of [L4Zr(NMe2)2].
NMR spectrum indicated the presence of a species
[L52ZrX2] in which only the NH group adjacent to the
pyridine had undergone deprotonation. We have previ-
ously noted the sluggish deprotonation of mesityl-
substituted amines,23 which may be attributed to the
highly sterically demanding nature of the -NHMes
unit. Here, intramolecular metalation of these units is
evidently unfavorable in comparison to intermolecular
reaction with a second aminopryridine proligand. A
subsequent reaction between 2 equiv of H2L5 and
Zr(NMe2)4 (eq 3) gives exclusively the monomeric zir-
Since the proligand H2L5 used in the synthesis of this
complex was racemic we might expect the formation of
two sets of diastereomers, ignoring for the moment the
(23) Morton, C.; Gillespie, K. M.; Sanders, C. J .; Scott, P. J .
Organomet. Chem. 2000, 606, 141.

Chiral Biarylamido Complexes of Zirconium
Organometallics, Vol. 21, No. 21, 2002 4501
Ta ble 2. Selected Bon d Len gth s a n d An gles for
th e C2-Sym m etr ic Zir con iu m Dia m id es
L1Zr (NMe2)2a n d L3Zr (NMe2)2
L3Zr(NMe2)2 (1 of 2 molecule
L1Zr(NMe2)2
in asymmetric unit)
Zr(1)-N(1) ) 2.114(5)
Zr(1)-N(1) ) 2.149(3) ;
Zr(2)-N(5) ) 2.144(3)
Zr(1)-N(2) ) 2.148(3);
Zr(2)-N(6) ) 2.155(3)
Zr(1)-N(3) ) 2.050(3);
Zr(2)-N(7) ) 2.045(3)
Zr(1)-N(4) ) 2.023(3);
Zr(2)-N(8) ) 2.042(3)
Zr(1)-O(1) ) 2.389(3);
Zr(2)-O(3) ) 2.485(3)
Zr(1)-O(2) ) 2.466(3) ;
Zr(2)-O(4) ) 2.386(3)
Zr(1)-N(2) ) 2.102(5)
Zr(1)-N(3) ) 2.021(5)
Zr(1)-N(4) ) 2.015(5)
N(2)-Zr(1)-N(1) ) 119.22(17) O(1)-Zr(1)-O(2) ) 115.86(11)
N(3)-Zr(1)-N(1) ) 103.2(2)
N(4)-Zr(1)-N(1) ) 111.8(2)
N(3)-Zr(1)-N(2) ) 111.0(2)
N(4)-Zr(1)-N(2) ) 107.0(2)
N(4)-Zr(1)-N(3) ) 103.5(2)
N(1)-Zr(1)-O(1) ) 68.99(11)
N(2)-Zr(1)-O(1) ) 158.09(10)
N(3)-Zr(1)-O(1) ) 82.97(12)
N(4)-Zr(1)-O(1) ) 82.98(11)
N(1)-Zr(1)-O(2) ) 82.40(12)
N(2)-Zr(1)-O(2) ) 67.32(11)
N(3)-Zr(1)-O(2) ) 79.10(13)
N(4)-Zr(1)-O(2) ) 161.11(12)
F igu r e 5. Molecular structure of [(L6)Zr(NMe2)2].
chirality-at-metal: homochiral (R,R)/(S,S) and meso
(R,S)/(S,R). Examination of crude reaction mixtures
indicates that only one such pair is formed, i.e. the
homochiral system. Given that intermolecular exchange
of aminopyridinate ligands does not occur in related
systems24 this diastereoselection must be kinetically
controlled, i.e., the formation of the homochiral complex
is much faster than that of the meso diastereomer. In a
conceptually similar pyridinealcoholate system, J ordan
measured a kinetic diastereomeric ratio of ca. 97:3.25
The complex [(HL5)2Zr(NMe2)2] is also chiral-at-
metal.26 We are currently investigating a number of
rather simpler but related complexes in the hope that
we will be able to predetermine27 the absolute sense of
this element of chirality.
N(2)-Zr(1)-N(1) ) 90.73(13)
N(3)-Zr(1)-N(1) ) 135.00(14)
N(4)-Zr(1)-N(1) ) 107.32(13)
N(3)-Zr(1)-N(2) ) 118.37(13)
N(4)-Zr(1)-N(2) ) 95.86(13)
N(4)-Zr(1)-N(3) ) 103.13(15)
We are currently engaged in the application of these
and related complexes in enantioselective catalysis, and
hope to be able to relate the relative efficiencies of the
systems to the structural motifs we have recorded here.
Exp er im en ta l Section
The C1-symmetric proligand H2L6 reacts in a manner
similar to H2L4 with 1 equiv of Zr(NMe2)4 in toluene to
yield the monomeric complex [L6Zr(NMe2)2] after crys-
Gen er a l Com m en ts. All manipulations were carried out
with standard Schlenk/glovebox techniques under an atmo-
sphere of dry argon, except for the workup procedures for the
ligands which were performed under aerobic conditions.
Solvents were distilled from Na/K alloy (pentane, diethyl
ether), potassium (THF), or sodium (toluene) under an atmo-
sphere of dinitrogen. Deuterated benzene and toluene were
heated to reflux in vacuo over potassium for 3 days, dis-
tilled under vacuum, degassed by 3 freeze-pump-thaw cycles,
and stored in a glovebox. The reagent tris(dibenzylidene-
acetone)dipalladium [Pd2(DBA)3] was obatined from Strem.
The reagents 2,2′-bis(diphenylphosphino)-1,1′-binaphthyl
[BINAP], 1,3-bis(diphenylphosphino)propane [DPPP], 2-bro-
mopyridine, 2-bromo-6-methylanisole, 2-bromomesitylene, and
Na(OBut) were obtained from Aldrich and used as purchased.
Zr(NMe2)4,28 2,2′-diamino-6,6′-dimethylbiphenyl 1,29 and 1-bro-
mo-3,5-di-tert-butylbenzene30 were synthesized by literature
procedures.
1
tallization from pentane. The H and 13C NMR spectra
exhibit two distinct NMe2 resonances. The molecular
structure is shown in Figure 5. The six-coordinate
geometry is close to trigonal prismatic. The five-
membered chelate ring containing the anisole chelate
has similar bite angle (68.24°) and bond lengths to those
in [L3Zr(NMe2)2] and [L4Zr(NMe2)2]. However, while the
Zr(1)-N(1)pyridine distance is comparable to those ob-
served in [(HL5)2Zr(NMe2)2], the Zr(1)-N(2) distance
[2.204(4) Å] is shorter than the analogous distances in
this complex. This could be attributed to the absence of
a destabilizing trans influence on this bond in [L6Zr-
(NMe2)2], unlike in [(L5)2Zr(NMe2)2] where the amido
N atoms are mutually trans.
H2L1. 1 (0.43 g, 2.10 mmol), 1-bromo-3,5-di-tert-butylben-
zene (1.10 g, 4.20 mmol), [Pd2(DBA)3] (50.0 mg, 1.3 mol %),
BINAP (58.0 mg, 2.2 mol %), and Na(OBut) (0.64 g, 6.65 mmol)
were loaded into a Schlenk flask containing a magnetic stirrer
bar. Toluene (50 mL) was added and the mixture was stirred
at 90 °C for 24 h. A small aliquot was removed from the
solution under argon and analyzed by TLC and 1H NMR
spectroscopy. Conversion was >90%. The toluene was removed
in vacuo and diethyl ether was added (50 mL). The mixture
Con clu d in g Rem a r k s
The versatile palladium-catalyzed arylation of 1 with
simple and donor-atom functionalized arenes provides
an efficient route to a range of new chiral amido ligand
environments with various denticities and geometries.
(24) Morton, C.; O’Shaughnessy, P. N.; Scott, P. Chem. Commun.
2000, 2099.
(25) Kim, I.; Nishihara, Y.; J ordan, R. F.; Rodgers, R. D.; Rheingold,
A. L.; Yap, G. P. A. Organometallics 1997, 16 (15), 3314-3323.
(26) Brunner, H. Angew. Chem., Int. Ed. 1999, 38, 1194.
(27) Knof, U.; von Zelewsky, A. Angew. Chem., Int. Ed. 1999, 38,
302.
(28) Bradley, D. C.; Thomas, I. M. J . Chem. Soc. 1960, 3857.
(29) (a) Carlin, R. B.; Foltz, G. E. J . Am. Chem. Soc. 1956, 78, 1997.
(b) Meisenheimer, J .; Horing, M. Chem. Ber. 1927, 60, 1425.
(30) Bartlett, P. D.; Roha, M.; Stiles, R. M. J . Am. Chem. Soc. 1954,
76, 2349.

4502 Organometallics, Vol. 21, No. 21, 2002
O’Shaughnessy et al.
Ta ble 3. Selected Bon d Len gth s a n d An gles for th e C1-Sym m etr ic Zir con iu m Dia m id es L4Zr (NMe2)2,
(HL5)2Zr (NMe2)2, a n d L6Zr (NMe2)2
L4Zr(NMe2)2
(HL5)2Zr(NMe2)2•C5H12
L6Zr(NMe2)2
Zr(1)-O(1) ) 2.383(4)
Zr(1)-N(1) ) 2.134(5)
Zr(1)-N(2) ) 2.123(5)
Zr(1)-N(3) ) 2.047(6)
Zr(1)-N(4) ) 2.012(5)
Zr(1)-N(1) ) 2.369(6)
Zr(1)-N(2) ) 2.271(6)
Zr(1)-N(4) ) 2.354(6)
Zr(1)-N(5) ) 2.283(6)
Zr(1)-N(7) ) 2.037(6)
Zr(1)-N(8) ) 2.043(6)
Zr(1)-O(1) ) 2.372(3)
Zr(1)-N(1) ) 2.394(4)
Zr(1)-N(2) ) 2.204(4)
Zr(1)-N(3) ) 2.191(4)
Zr(1)-N(4) ) 2.033(5)
Zr(1)-N(5) ) 2.047(4)
N(1)-Zr(1)-O(1) ) 68.07(17)
N(2)-Zr(1)-O(1) ) 157.65(15)
N(3)-Zr(1)-O(1) ) 79.7(2)
N(4)-Zr(1)-O(1) ) 94.2(2)
N(2)-Zr(1)-N(1) ) 96.3(2)
N(3)-Zr(1)-N(1) ) 130.4(15)
N(4)-Zr(1)-N(1) ) 111.2(2)
N(3)-Zr(1)-N(2) ) 100.9(2)
N(4)-Zr(1)-N(2) ) 106.6(2)
N(4)-Zr(1)-N(3) ) 107.82(16)
N(2)-Zr(1)-N(1) ) 57.7(2)
N(4)-Zr(1)-N(1) ) 78.8(2)
N(5)-Zr(1)-N(1) ) 104.0(2)
N(7)-Zr(1)-N(1) ) 144.1(2)
N(8)-Zr(1)-N(1) ) 92.3(2)
N(2)-Zr(1)-N(4) ) 104.0(2)
N(2)-Zr(1)-N(5) ) 158.0(2)
N(7)-Zr(1)-N(2) ) 90.5(2)
N(8)-Zr(1)-N(2) ) 102.3(3)
N(5)-Zr(1)-N(4) ) 57.8(2)
N(7)-Zr(1)-N(4) ) 95.4(2)
N(8)-Zr(1)-N(4) ) 141.5(2)
N(7)-Zr(1)-N(5) ) 102.4(2)
N(8)-Zr(1)-N(5) ) 89.2(3)
N(7)-Zr(1)-N(8) ) 112.0(3)
O(1)-Zr(1)-N(1) ) 162.27(13)
O(1)-Zr(1)-N(2) ) 134.84(14)
O(1)-Zr(1)-N(3) ) 68.24(13)
O(1)-Zr(1)-N(4) ) 78.46 (15)
O(1)-Zr(1)-N(5) ) 89.27 (14)
N(2)-Zr(1)-N(1) ) 57.30 (14)
N(3)-Zr(1)-N(1) ) 129.45(13)
N(4)-Zr(1)-N(1) ) 87.76(15)
N(5)-Zr(1)-N(1) ) 87.28 (15)
N(3)-Zr(1)-N(2) ) 80.15(14)
N(4)-Zr(1)-N(2) ) 96.58(16)
N(5)-Zr(1)-N(2) ) 130.19(16)
N(4)-Zr(1)-N(3) ) 126.06(15)
N(5)-Zr(1)-N(3) ) 103.52(15)
N(5)-Zr(1)-N(4) ) 117.57(16)
was passed through a short pad of silica gel on a sinter funnel,
and the ether was removed in vacuo. The product was further
purified by flash chromatography (6:1 hexane/ether) to give
H2L1 as a yellow powder. Anal. Calcd for C42H56N2: C, 85.66;
NH), 6.46 (d, 2H, Ar-H), 6.68 (d, 2H, Ar-H), 6.71 (d, 2H,
Ar-H), 6.98 (d, 2H, Ar-H), 7.20 (t, 2H, Ar-H), 7.52 (s, 2H,
Ar-H). 13C{1H} NMR (C6D6, 297 K): δ 20.4 (biaryl-CH3), 21.5
(anisole-CH3), 55.6 (OCH3), 111.5, 114.0, 118.5, 121.6, 122.8,
126.5, 129.1, 130.0, 133.2, 138.9. 142.6, 148.4 (Ar). MS (EI)
m/z 452 [M+], 437 [M+ - CH3], 315, 226.
1
H, 9.58; N, 4.76. Found: C, 85.45; H, 9.61; N, 4.71. H NMR
(C6D6, 297 K): δ 1.19 (s, 36H, t-Bu), 2.10 (s, 6H, biaryl-Me),
5.73 (s, 2H, NH), 6.80 (d, 2H, biaryl-ArH), 7.05 (s, 6H, Ar-H),
7.11 (m, 2H, biaryl-ArH), 7.44 (d, 2H, biaryl-ArH). 13C{1H}
NMR (C6D6, 297 K): δ 20.45 (biaryl-Me), 31.9 [C(CH3)3], 35.24
[C(CH3)3], 113.8, 116.2, 117.1, 122.6, 125.0, 129.4, 139.0, 143.2,
143.9, 152.5 (Ar).
(R)-H2L3. As for (R,S)-H2L3, but with R-1. Yield 1.70 g, 75%.
Anal. Calcd for C30H32N2O2: C, 79.57; H, 7.17; N, 6.19.
Found: C, 79.22; H, 7.25; N, 5.90. Spectroscopic data were
indistinguishable from the racemic compound.
N-Mesityl-2,2′-diam in o-6,6′-dim eth ylbiph en yl (3). 1 (2.00
g, 9.44 mmol), [Pd2(DBA)3] (64 mg, 1.5 mol %), BINAP (120
mg, 4 mol %), and Na(OBut) (0.67 g, 6.97 mmol) were loaded
into a Schlenk flask containing a magnetic stirrer bar. Toluene
(50 mL) was added followed by 2-bromomesitylene (0.95 g, 4.77
mmol). The resulting purple solution was stirred at 90 °C until
all 1 was consumed, as judged by TLC (ca. 12 h). The toluene
was removed in vacuo and diethyl ether was added. The
mixture was passed through a pad of silica gel on a sinter
funnel, and the ether was removed in vacuo to give a brown
oil that was further purified by flash chromatography (6:1
hexane/ether) to yield 3 as a yellow powder. Yield 1.04 g, 66%.
Anal. Calcd for C23H26N2: C, 83.59; H, 7.93; N, 8.48. Found:
H2L2. 1 (0.98 g, 4.71 mmol,), [Pd2(DBA)3] (86.2 mg, 1.1 mol
%), DPPP (78.4 mg, 2 mol %), and Na(OBut) (0.63 g, 6.55 mmol)
were loaded into a Schlenk flask containing a magnetic stirrer
bar. Toluene (50 mL) was added followed by 2-bromopyridine
(0.89 mL, 9.42 mmol) via syringe. The solution was stirred for
48 h at room temperature until all 1 was consumed as judged
by TLC. The toluene was removed in vacuo and diethyl ether
(50 mL) was added. The mixture was passed through a pad of
silica gel on a sinter funnel, and the ether was removed in
vacuo to give a yellow solid. This was washed with a 1:1
mixture of diethyl ether and petroleum ether until colorless.
The remaining solid H2L2 was dried in vacuo for 2 h. Yield
1.18 g, 68%. Anal. Calcd for C24H22N4: C, 78.66; H, 6.05; N,
15.29. Found: C, 78.55; H, 6.00; N, 15.34. 1H NMR (C6D6, 297
K): δ 1.89 (s, 6H, biaryl-Me), 5.95 (d, 2H, Ar-H), 6.24 (t, 2H,
Ar-H), 6.33 (s, 2H, NH), 6.74 (t, 2H, Ar-H), 6.86 (d, 2H,
Ar-H), 7.23 (t, 2H, Ar-H) 8.09 (d, 2H, Ar-H), 8.43 (d, 2H,
Ar-H). 13C{1H} NMR (C6D6, 297 K): δ 20.3 (biaryl-CH3), 110.4,
115.5, 118.3, 124.6, 126.7, 129.4, 137.5, 138.2, 140.1, 148.6,
156.5 (Ar).
1
C, 83.51; H, 8.01; N, 8.43. H NMR (C6D6, 297 K): δ 2.07 (s,
9H, 3-mesityl-Me), 2.16 (s, 3H, biaryl-Me), 2.22 (s, 3H, biaryl-
Me), 3.05 (s, 2H, NH2), 4.79 (s, 1H, NH), 6.31 (d, 1H, Ar-H),
6.44 (s, 1H, Ar-H), 6.76 (s, 1H, Ar-H), 6.79 (s, 1H, Ar-H),
6.70 (s, 2H, Mes), 7.13 (t, 1H, Ar-H), 7.17 (t, 1H, Ar-H).
13C{1H} NMR (C6D6, 297 K): δ 18.6 (Mes), 20.1 (biaryl-Me),
20.3 (biaryl-Me), 21.4 (Mes), 109.3, 113.3, 115.2, 120.2, 120.7,
129.3, 129.4, 129.8 (Ar).
H2L3. 1 (1.00 g, 4.71 mmol), [Pd2(DBA)3] (91.3 mg, 1 mol
%), BINAP (125 mg, 2 mol %), and Na(OBut) (1.34 g, 13.9
mmol) were loaded into a Schlenk flask containing a magnetic
stirrer bar. 2-Bromo-6-methylanisole (1.45 mL, 10.0 mmol) was
added to the Schlenk flask via syringe under argon flow.
Toluene (50 mL) was added and the resulting purple solution
was stirred at 90 °C until all 1 was fully converted, as judged
by TLC (ca. 12 h). The toluene was removed in vacuo and
diethyl ether (50 mL) was added. The mixture was passed
through a pad of silica gel on a sinter funnel, and the ether
was removed in vacuo. The product was further purified by
flash chromatography (4:1 hexane/ether) to give H2L3 as pale
yellow crystals. Yield 1.61 g, 71.2%. Anal. Calcd for
N-(4-Met h yl-2-a n isolyl)-2,2′-d ia m in o-6,6′-d im et h ylb i-
p h en yl (4). 1 (2.00 g, 9.44 mmol), [Pd2(DBA)3] (21 mg, 0.5 mol
%), BINAP (47 mg, 1.5 mol %), and Na(OBut) (0.67 g, 6.97
mmol) were loaded into a Schlenk flask containing a magnetic
stirrer bar in a glovebox. 2-Bromo-4-methylanisole (0.71 mL,
4.97 mmol) was added to the flask via syringe. Toluene (50
mL) was added, and the resulting purple solution was stirred
at 90 °C until all 1 was consumed, as judged by TLC (ca. 12
h). The toluene was removed in vacuo and diethyl ether (50
mL) was added. The mixture was passed through a silica pad
on a sinter funnel, and the ether was removed in vacuo to give
a yellow oil. Flash chromatography (5:1 hexane/ether) gave
the major product 4 as a bright yellow crystalline solid. Yield
1.45 g, 87% (H2L3 is also isolated as a minor product, yield
0.23 g, 10%). Anal. Calcd (for 4) for C22H24N2O: C, 79.48; H,
7.28; N, 8.43. Found: C, 79.53; H, 7.40; N, 8.34. 1H NMR (C6D6,
C
30H32N2O2: C, 79.57; H, 7.17; N, 6.19. Found: C, 79.41; H,
7.23; N, 6.16. 1H NMR (C6D6, 297 K): δ 2.21 (s, 6H, biaryl-
Me), 2.23 (s, 6H, anisole-Me), 3.15 (s, 6H, OMe), 6.30 (s, 2H,

Chiral Biarylamido Complexes of Zirconium
Organometallics, Vol. 21, No. 21, 2002 4503
297 K): δ 2.15 (s, 6H, biaryl-Me), 2.27 (s, 3H, anisole-Me), 3.09
(s, 2H, NH2), 3.21 (s, 3H, OMe), 6.24 (s, 1H, NH), 6.50 (t, 2H,
Ar-H), 6.71 (d, 1H, Ar-H), 6.83 (d, 1H, Ar-H), 6.94 (d, 1H,
Ar-H), 7.17 (t, 1H, Ar-H), 7.20 (t, 1H, Ar-H), 7.50 (s, 1H,
Ar-H), 7.62 (d, 1H, Ar-H). 13C{1H} NMR (C6D6, 297 K): δ
20.3 (biaryl-CH3), 20.3 (biaryl-CH3), 21.5 (anisolyl-CH3), 55.7
(OCH3), 111.6, 113.4, 114.1, 117.8, 120.6, 121.5, 122.4, 122.8,
126.7, 128.9, 129.2, 130.5, 133.4, 138.4, 139.0, 142.3, 145.5,
of petroleum ether (40-60, 2 mL) and scratching yielded H2L4
as a pale yellow crystalline solid. Yield 1.81 g, 89%. Anal. Calcd
for C36H44N2O: C, 83.03; H, 8.52; N, 5.38. Found: C, 82.49;
H, 8.33; N, 5.20. 1H NMR (C6D6, 297 K): δ 1.24 (s, 18H, t-Bu),
2.10 (s, 3H, anisyl-Me), 2.15 (s, 6H, biaryl-Me), 3.11 (s, 3H,
OMe), 5.76 (s, 1H, NH), 6.21 (s, 1H, NH), 6.43 (d, 1H, Ar-H),
6.62 (d, 1H, Ar-H), 6.87 (d, 2H, Ar-H), 7.06 (d, 2H, Ar-H),
7.20 (m, 3H, Ar-H), 7.32 (d, 1H, Ar-H), 7.51 (d, 2H, Ar-H).
13C{1H} NMR (C6D6, 297 K): δ 20.4 (biaryl-CH3), 20.5 (anisolyl-
CH3), 21.5 (biaryl-CH3), 31.9 (t-Bu), 55.8 (OCH3), 111.7, 113.3,
114.2, 116.4, 117.0, 118.8, 122.1, 122.4, 123.0, 125.1, 126.1,
129.2, 129.3, 130.6, 133.1, 138.9, 139.0, 140.1, 142.7, 143.2,
143.5, 143.9, 148.6, 152.4 (Ar).
148.2 (Ar). MS (EI) m/z 332 [M+], 317 [M+ - CH3], 302 [M+
-
OCH3], 210 [M+ - C6H3OMe], 195, 180.
(R)-N-(4-Meth yl-2-a n isolyl)-2,2′-d ia m in o-6,6′-d im eth yl-
bip h en yl (4). As for (R,S)-4, with (R)-(+)-1. Yield 1.19 g, 72%.
Anal. Calcd for C22H24N2O: C, 79.48; H, 7.28; N, 8.43. Found:
C, 79.37; H, 7.36; N, 8.39. Spectroscopic data were indistin-
guishable from the racemic compound.
(R)-H2L4. As for (R,S)-H2L4, with (R)-(+)-1. Yield 1.73 g,
85%. Anal. Calcd for C36H44N2O: C, 83.03; H, 8.52; N, 5.38.
Found: C, 82.61; H, 8.29; N, 5.51. Spectroscopic data were
indistinguishable from the racemic compound.
N-(3,5-Di-ter t-bu tyl-1-p h en yl)-2,2′-d ia m in o-6,6′-d im eth -
ylbip h en yl (2). 1 (0.86 g, 2.10 mmol), bromo-3,5-di-tert-
butylbenzene (0.50 g 1.86 mmol), [Pd2(DBA)3] (20 mg 1.2 mol
%), BINAP (30 mg, 2.5 mol %), and Na(OBut) (0.32 g, 3.33
mmol) were loaded into a Schlenk flask containing a magnetic
stirrer bar. Toluene (50 mL) was added and the solution was
stirred at 90 °C overnight. The toluene was removed in vacuo
and diethyl ether (50 mL) was added. The mixture was passed
through silica pad on a sinter funnel and the solvent was
removed. TLC and 1H NMR indicated the presence of some
disubstituted diamine H2L1 as a minor product. Flash chro-
matography (6:1 hexane/ether) gave 2 as a pale yellow powder.
Yield 0.52 g, 70%. Anal. Calcd for C28H36N2: C, 83.95; H, 9.06;
H2L6. 4 (1.26 g, 3.82 mmol), [Pd2(DBA)3] (84 mg, 2 mol %),
DPPP (63.0 mg, 4 mol %), and Na(OBut) (0.51 g, 5.31 mmol)
were loaded into a Schlenk flask containing a magnetic stirrer
bar. 2-Bromo-6-methylpyridine (0.45 mL, 4.06 mmol) was
added to the flask via syringe. Toluene (50 mL) was added,
and the resulting purple solution was stirred at 90 °C until
all 1 was converted, as judged by TLC (ca. 24 h). The toluene
was removed in vacuo and diethyl ether (50 mL) added. The
mixture was passed through a pad of silica on a sinter funnel,
and the ether removed in vacuo to give a yellow oil. Excess
2-Bromo-6-methylpyridine was removed by distillation at 100
°C and rotary pump vacuum. Flash chromatography (5:1
hexane/ether) gave H2L4 as a yellow viscous oil. Yield 1.44 g,
89%. Anal. Calcd for C28H29N3O: C, 79.40; H, 6.90; N, 9.92.
1
N, 6.99. Found: C, 83.89; H, 9.12; N, 6.93. H NMR (CDCl3 ,
297 K): δ 1.28 (s, 18H, t-Bu), 2.00 (s, 3H, biaryl-Me), 2.01 (s,
3H, biaryl-Me), 3.51 (s, 2H, NH2), 5.30 (s, 1H, NH), 6.67 (d,
1H, Ar-H), 6.74 (d, 1H, Ar-H), 6.81 (d, 1H, Ar-H), 6.89 (s,
2H, Ar-H), 7.01 (t, 1H, Ar-H), 7.08-7.25 (m, 3H, Ar-H).
13C{1H} NMR (CDCl3, 297 K): δ 15.9 (biaryl-Me), 31.5
[C(CH3)3], 35.2 [C(CH3)3], 111.2, 111.6, 111.7, 113.8, 116.4,
120.2, 120.7, 128.3, 128.5 (Ar).
1
Found: C, 79.29; H, 7.10; N, 9.74. H NMR (C6D6, 297 K): δ
2.08 (s, 3H, anisole-Me), 2.19 (s, 3H, biaryl-Me), 2.23 (s, 3H,
biaryl-Me), 2.36 (s, 3H, pyridyl-Me), 3.17 (s, 3H, OMe), 6.08
(s, 1H, NH), 6.30 (d, 1H, Ar-H), 6.36 (d, 1H, Ar-H), 6.45 (d,
1H, Ar-H), 6.59 (s, 1H, NH), 6.71 (d, 1H, Ar-H), 6.88 (d, 1H,
Ar-H), 6.94 (t, 1H, Ar-H), 7.02 (d, 1H, Ar-H), 7.19 (t, 1H,
Ar-H), 6.34 (s, 1H, Ar-H), 6.38 (t, 1H, Ar-H), 7.51 (d, 1H,
Ar-H), 8.49 (d, 1H, Ar-H). 13C{1H} NMR (C6D6, 297 K): δ
20.4 (anisole-CH3), 20.4 (biaryl-CH3), 21.4 (biaryl-CH3), 55.6
(OCH3), 106.7, 11.5, 113.6, 114.6, 117.5, 120.1, 122.5, 122.7,
124.3, 125.4, 127.0, 129.1, 129.4, 130.4, 132.7, 137.8, 138.5,
138.6, 140.3, 143.0, 148.9, 157.7 (Ar).
H2L5. 3 (1.09 g, 3.29 mmol), [Pd2(DBA)3] (60 mg, 2 mol %),
DPPP (54 mg, 4 mol %), and Na(OBut) (0.44 g, 1.4 equiv) were
loaded into a Schlenk flask containing a magnetic stirrer.
2-Bromo-6-methylpyridine (0.36 mL, 3.25 mmol) was added
to the flask via syringe. Toluene (50 mL) was added and the
resulting purple solution was stirred at 90 °C until all the
diamine was consumed, as judged by TLC (ca. 12 h). The
toluene was removed in vacuo and diethyl ether (50 mL) added.
The mixture was passed through a silica pad on a sinter
funnel, and the ether was removed to give a yellow oil. Flash
chromatography (6:1 hexane/ether) gave H2L5 as a yellow
powder. This compound rapidly absorbs moisture from the
atmosphere. Yield 1.81 g, 89%. Anal. Calcd for C29H31N3: C,
82.62; H, 7.41; N, 9.97. Found: C, 82.41; H, 7.32; N, 10.14. 1H
NMR (CDCl3, 297 K): δ 1.74 (br, 3H, 2,6-mesityl-Me), 1.90 (s,
3H, biaryl-Me), 2.02 (br, 3H, 2,6-mesityl-Me), 2.07 (s, 3H,
biaryl-Me), 2.15 (s, 3H, 4-mesityl-Me), 2.30 (s, 3H, pyridyl-
Me), 4.63 (s, 1H, NH), 5.94 (d, 1H, Ar-H), 6.18 (s, 1H, NH),
6.45 (d, 1H, Ar-H), 6.51 (d, 1H, Ar-H), 6.60 (d, 1H, Ar-H),
6.71 (br, 2H, Ar-H), 6.90 (m, 2H, Ar-H), 7.19 (m, 2H,
Ar-H), 7.92 (d, 1H, Ar-H). 13C{1H} NMR (CDCl3, 297 K): δ
15.9 (2,6-mesityl-Me), 17.8 (biaryl-Me), 17.9 (biaryl-Me), 18.9
(pyridyl-Me), 22.3 (4-mesityl-Me), 104.1, 106.6, 112.4, 114.3,
117.5, 118.7, 121.6, 124.1, 126.3, 127.0, 127.1, 133.1, 133.5,
134.3, 135.6, 135.8, 136.5, 137.3, 142.0, 153.2, 155.2 (Ar).
H2L4. 4 (1.28 g, 3.89 mmol), bromo-3,5-di-tert-butylbenzene
(1.05 g 3.90 mmol), [Pd2(DBA)3] (84.0 mg, 2 mol %), BINAP
(97 mg, 4 mol %), and Na(OBut) (0.52 g, 5.41 mmol) were
loaded into a Schlenk flask containing a magnetic stirrer bar.
Toluene (50 mL) was added and the reaction was stirred at
90 °C for 4 days. The toluene was removed in vacuo and diethyl
ether (50 mL) was added. The mixture was passed through a
pad of silica on sintered funnel and the solvent removed on a
rotary evaporator. The product was purified by flash chroma-
tography (5:1 hexane/ether) to give a pale yellow oil. Addition
(R)-H2L6. As for (R,S)-H2L6, with (R)-(+)-1. Yield 1.73 g,
85%. Anal. Calcd for C36H44N2O: C, 83.03; H, 8.52; N, 5.38.
Found: C, 82.61; H, 8.29; N, 5.51. Spectroscopic data were
indistinguishable from the racemic compound.
[L1Zr (NMe2)2]. H2L1 (0.35 g 0.59 mmol) and [Zr(NMe2)4]
(0.16 g 0.59 mmol) were loaded into a Schlenk flask in a
glovebox. Toluene (5 mL) was added and the solution was
stirred at room temperature for 2 d. The toluene was removed
in vacuo to give a yellow powder. Pentane was added until
most of the solid dissolved. The solution was filtered via
cannula and the pentane was removed in vacuo to give
[L1Zr(NMe2)2] as a yellow powder. Yield 0.28 g, 61.5%. X-ray
quality crystals were obtained from a concentrated pentane
solution at 0 °C. Anal. Calcd for C46H66N4Zr: C, 72.10; H, 8.68;
N, 7.31. Found: C, 71.92; H, 8.58; N, 7.41. 1H NMR (C6D6,
297 K): δ 1.35 (s, 36H, t-Bu), 2.04 (s, 6H, biaryl-Me), 2.87 (s,
12H, NMe2), 6.69 (d, J ) 7.28 Hz, 2H, Ar-H), 7.04 (t, J )
7.28 Hz, 2H, Ar-H), 7.13 (m, 12H, Ar-H), 7.35 (d, J ) 8.03
Hz, 2H, Ar-H). 13C{1H} NMR (C6D6, 297 K): δ 32.2 (biaryl-
Me), 35.4 (t-Bu), 41.1 (NMe2), 114.4, 114.8, 123.6, 125.4, 125.9,
130.3, 132.4, 137.7, 140.0, 144.8, 146.0, 152.4 (Ar). MS (EI)
m/z 764 [M+], 588, 383, 294.
[L3Zr (NMe2)2]. H2L3 (0.20 g, 0.49 mmol) and [Zr(NMe)2]
(0.13 g, 0.49 mmol) were loaded into a Schlenk flask. Toluene
(10 mL) was added and the pale yellow solution was stirred
overnight at ambient temperature. The toluene was removed
in vacuo to give a foamy material. On addition of pentane (ca.
1 mL) followed by vigorous stirring, a colorless crystalline solid

4504 Organometallics, Vol. 21, No. 21, 2002
O’Shaughnessy et al.
L3Zr(NMe2)2 began to precipitate from solution. After standing
at 0 °C overnight the mother liquor was filtered off and the
remaining solid was washed with pentane (ca. 1 mL). The
combined filtrate and washings were concentrated and kept
at 0 °C for 2 days to give X-ray quality crystals of [L3Zr-
(NMe2)2]. Combined yield 0.21 g, 69%. Anal. Calcd for
[L6Zr (NMe2)2]. H2L6 (0.40 g, 0.95 mmol) and Zr(NMe2)4
(0.25 g 9.5 mmol) were loaded into a Schlenk flask. Toluene
(10 mL) was added and the resulting yellow solution was
stirred overnight at ambient temperature. The solvent was
removed in vacuo to yield a foamy material. Pentane (ca. 1
mL) was added and the solution was stirred vigorously for 1-2
min resulting in the formation of an off-white precipitate. The
solution was then placed in a fridge overnight at 0 °C. The
mother liquor was decanted and the solid was washed with a
minimal amount of pentane and dried under vacuum for 30
min. Combined yield 0.41 g, 72.2%. Anal. Calcd for C32H39N5-
OZr: C, 63.96; H, 6.54; N, 11.62. Found: C, 63.82; H, 6.45; N,
11.74. 1H NMR (C6D6, 297 K): δ 2.09 (s, 3H, pyridyl-Me), 2.11
(s, 3H, biaryl-Me), 2.12 (s, 3H, biaryl-Me), 2.21 (s, 3H, anisole-
Me), 2.76 (s, 6H, NMe2), 2.77 (s, 6H, 6H, NMe2), 3.51 (s, 3H,
OMe), 5.81 (d, J ) 7.28 Hz 1H, Ar-H), 6.20 (d, J ) 8.53 Hz,
1H, Ar-H), 6.28 (m, 2H, Ar-H), 6.41 (s, 1H, Ar-H), 6.77 (m,
2H, Ar-H), 6.94 (d, J ) 7.28 Hz, 1H, Ar-H), 7.06 (m, 3H,
Ar-H), 7.19 (d, J ) 1.76 Hz, 1H, Ar-H).13C{1H} NMR (C6D6,
297): δ 20.6 (Me), 20.8 (Me), 21.6 (Me), 22.2 (Me), 41.8 (NMe2),
41.9 (NMe2), 57.9 (OMe), 102.82, 108.9, 109.4, 114.4, 115.42,
118.8, 125.4, 126.6, 126.8, 133.4, 135.0, 138.1, 138.4, 140.67,
146.1, 147.5, 149.4, 154.9, 167.2 (Ar).
C
34H42N4O2Zr: C, 64.83; H, 6.72; N, 8.89. Found: C, 64.51;
1
H, 6.85; N, 9.01. H NMR (d8-toluene, 297 K): δ 2.05 (s, 6H,
biaryl-Me), 2.10 (s, 6H, anisole-Me), 2.71 (s, 12H, NMe2), 3.52
(s, 6H, OMe), 2.29 (m, 4H, Ar-H), 6.40 (m, 2H, Ar-H), 6.76
(m, 2H, Ar-H), 7.00-7.12 (m, 4H, Ar-H).13C{1H} NMR (C6D6,
297 K): δ 20.8 (biaryl-Me), 21.0 (anisole-Me), 42.3 (NMe2), 58.6
(OMe), 109, 115.8, 116.1, 125.2, 125.5, 125.8, 125.9, 126.4,
127.6, 132.8, 136.5, 137.8 (Ar).
[(H L5)2Zr (NMe2)2]. H2L5 (0.52 g, 1.23 mmol) and
[Zr(NMe2)4] (0.16 g, 0.62 mmol) were loaded into a Schlenk
flask. Toluene (10 mL) was added and the yellow solution was
stirred overnight at ambient temperature. The toluene was
removed in vacuo to yield a foamy material. Pentane (ca. 1
mL) was added and the solution stirred vigorously for 5-10
min after which time a yellow precipitate had formed. The
mother liquor was filtered off and the solid [(HL6)2Zr(NMe2)2]
was washed once with a minimal amount of pentane (1 mL)
and dried under vacuum for 2 h. Yield 0.31 g, 52%. Pentane
was carefully added to the solid [(HL6)2Zr(NMe2)2] until most
had dissolved; a few drops of diethyl ether was subsequently
added to dissolve the remaining solid. The resulting solution
was kept at 0 °C for 2 d yielding X-ray quality crystals of
[(HL5)2Zr(NMe2)2‚C5H12]. The solvent of crystallization, pen-
tane, is lost after prolonged exposure to Schlenk line vacuum
(>5 h). Anal. Calcd for C67H84N8Zr: C, 72.97; H, 7.11; N, 10.98.
Cr ysta llogr a p h y. Crystals were coated in an inert oil prior
to transfer to a cold nitrogen gas stream on a Bruker-AXS
SMART three-circle CCD area detector diffractometer system
equipped with Mo KR radiation (λ ) 0.71073 Å). Data were
collected with narrow (0.3° in ω) frame exposures. Intensities
were corrected semiempirically for absorption, based on sym-
metry-equivalent and repeated reflections (SADABS). Reflec-
tion data for [(HL5)2Zr(NMe2)2‚C5H12] were weak and no
significant data were collected for 2θ > 45°. The structures
[L3Zr(NMe2)2], [L4Zr(NMe2)2], [(HL5)2Zr(NMe2)2‚C5H12], and
[L6Zr(NMe2)2] were solved by direct methods (SHELXS) with
additional light atoms found by Fourier methods The zirco-
nium atoms in L1Zr(NMe2)2 were located by Patterson methods
(SHELXS); subsequent least-squares refinements revealed the
atomic positions of the remaining non-hydrogen atoms. The
crystal structure of [(HL5)2Zr(NMe2)2‚C5H12] contains one
disorded molecule of the crystallization solvent, pentane,
within the asymmetric unit of the unit cell. This disorder was
modeled across two alternative positions and geometrical and
displacement parameter restraints were applied to aid refine-
ment. All structures were refined on F2 values for all unique
data. Table 1 gives further details. All non-hydrogen atoms
were refined anisotropically, and the carbon atoms C10, C12,
and C14 in [L1Zr(NMe2)2] and C28, C29, and C33 in [L4Zr-
(NMe2)2] were subject to displacement parameter restraints.
All H atoms were constrained with a riding model; U(H) was
set at 1.2 (1.5 for methyl groups) times Ueq for the parent atom.
Programs used were Bruker AXS SMART (control) and SAINT
(integration) and SHELXTL for structure solution, refinement,
and molecular graphics.
1
Found: C, 72.59; H, 6.94; N, 11.06. H NMR (C6D6, 297 K): δ
1.66 (br, 6H, biaryl-Me), 2.06 (br, 6H, biaryl-Me), 2.09 (s, 12H,
2,6-mesityl-Me), 2.10 (s, 6H, 4-mesityl-Me), 2.11 (s, 6H, py-
ridyl-Me), 4.83 (s, 2H, NH), 5.57 (d, 2H, Ar-H), 5.88 (d, 2H,
Ar-H), 6.16 (d, 2H, Ar-H), 6.41 (t, 2H, Ar-H), 6.68 (d, 2H,
Ar-H), 6.75 (br, 4H, Ar-H), 6.92 (t, 2H, Ar-H), 7.17 (d, 2H,
Ar-H), 7.28 (t, 2H, Ar-H), 7.42 (d, 2H, Ar-H). 13C{1H} NMR
(C6D6, 297 K): δ 19.5 (biaryl-Me), 20.8 (biaryl-Me), 21.2 (4-
mesityl-Me), 21.3 (2,6-mesityl-Me), 23.3 (pyridyl-Me), 41.8
(NMe2), 103.3, 108.3, 108.9, 109.7, 118.2, 119.5, 120.8, 125.9,
126.6, 127.3, 128.2, 128.6, 129.9, 133.5, 135.3, 136.0, 136.5,
140.0, 145.6, 147.4, 148.3, 150.5, 155.7 (Ar). MS (EI) m/z 1018
[M+], 928, 597, 556, 552, 507, 421.
[L4Zr (NMe2)2]. H2L4 (0.44 g, 0.84 mmol) and [Zr(NMe2)4]
(0.25 g, 9.34 mmol) were loaded into a Schlenk flask. Toluene
(10 mL) was added and the resulting yellow solution was
stirred overnight at ambient temperature. The solvent was
removed in vacuo to yield a foamy material. Pentane (ca. 1
mL) was added and the solution was stirred vigorously for 1-2
min resulting in the formation of an off-white precipitate. The
solution was left at 0 °C. The mother liquor was decanted and
the remaining solid was washed with a minimal amount of
pentane and dried under vacuum for 30 min. The combined
filtrate and washings were concentrated and kept at 0 °C for
2 days to give X-ray quality crystals of L5Zr(NMe2)2. Combined
yield 0.48 g, 82%. Anal. Calcd for C40H54N4OZr: C, 68.82; H,
7.80; N, 8.03. Found: C, 69.19; H, 7.93; N, 8.21. 1H NMR (C6D6,
297 K): δ 1.37 (s, 18H, t-Bu), 2.09 (s, 6H, biaryl-Me), 2.14 (s,
3H, anisole-Me), 2.62 (s, 6H, NMe2), 3.16 (s, 6H, NMe2), 3.47
(s, 3H, OMe), 6.37 (t, J ) 8.1 Hz, 2H, NMe2), 6.65 (d, J ) 7.53
Hz, 1H, Ar-H), 6.85 (m, 4H, Ar-H), 6.94 (s, 1H, Ar-H), 7.05
(t, J ) 7.53 Hz, 1H, Ar-H), 7.20 (m, 2H, Ar-H), 7.35 (d, J )
8.1 Hz, 1H, Ar-H). 13C{1H} NMR (C6D6, 297): δ 21.1 (biaryl-
Me), 21.3 (biaryl-Me), 21.6 (anisole-Me), 32.4 (t-Bu), 41.3
(NMe2), 42.3 (NMe2), 57.9 (OMe), 109.8, 111.9, 113.0, 114.4,
116.6, 122.4, 126.4, 127.8, 130.5, 133.7, 134.3, 134.5, 138.1,
142.2, 143.0, 145.0, 146.3, 147.1, 149.1, 147.3, 148.0, 151.2,
154.8 (Ar).
Ack n ow led gm en t. P.S. wishes to thank EPSRC for
postdoctoral fellowships (P.N.O., C.M., K.M.G.) and the
University of Warwick for a Postgraduate Research
Fellowship (I.W.).
Su p p or tin g In for m a tion Ava ila ble: Tables of crystal
data, atomic coordinates, distances and angles, anisotropic
displacement parameters, and hydrogen coordinates, as well
as molecular structure drawings. This material is available
free of charge via the Internet at http://pubs.acs.org.
OM020471P