Synthesis of group 4 metal amides with new chiral biaryldiamine-based ligands and their use as catalysts for asymmetric hydroamination/cyclization

Article abstract of DOI:10.1021/om801061v

A new series of titanium(IV) and zirconium(IV) amides have been prepared from the reaction between M(NMe₂)₄ (M = Ti, Zr) and chiral ligands, (S)-2-(pyrrol-2-ylmethyleneamino)-2 -( dimethylamino)-l,l - binaphthyl (4H), (Z?)-2-(pyridin

Full text of DOI:10.1021/om801061v

Organometallics 2009, 28, 1127–1137
1127
Synthesis of Group 4 Metal Amides with New Chiral
Biaryldiamine-Based Ligands and Their Use as Catalysts for
Asymmetric Hydroamination/Cyclization
Guofu Zi,*,† Xue Liu,† Li Xiang,† and Haibin Song‡
Department of Chemistry, Beijing Normal UniVersity, Beijing 100875,
People’s Republic of China, and State Key Laboratory of Elemento-Organic Chemistry, Nankai UniVersity,
Tianjin 300071, People’s Republic of China
ReceiVed NoVember 12, 2008
A new series of titanium(IV) and zirconium(IV) amides have been prepared from the reaction between
M(NMe2)4 (M ) Ti, Zr) and chiral ligands, (S)-2-(pyrrol-2-ylmethyleneamino)-2′-(dimethylamino)-1,1′-
binaphthyl (4H), (R)-2-(pyridin-2-ylmethylamino)-2′-(dimethylamino)-6,6′-dimethyl-1,1′-biphenyl (6H),
(S)-2-(diphenylphosphinoylamino)-2′-(dimethylamino)-1,1′-binaphthyl (7H), (R)-2-(diphenylphosphinoy-
lamino)-2′-(dimethylamino)-6,6′-dimethyl-1,1′-biphenyl (8H), (S)-2-(mesitoylamino)-2′-(dimethylamino)-
1,1′-binaphthyl (9H), (R)-2-(mesitoylamino)-2′-(dimethylamino)-6,6′-dimethyl-1,1′-biphenyl (10H), and
(R)-5,5′6,6′7,7′8,8′-octahydro-2-(mesitoylamino)-2′-(dimethylamino)-1,1′-binaphthyl (11H), which are
derived from (S)-2-amino-2′-(dimethylamino)-1,1′-binaphthyl (1), (R)-2-amino-2′-(dimethylamino)-6,6′-
dimethyl-1,1′-biphenyl (2), or (R)-5,5′6,6′7,7′8,8′-octahydro-2-amino-2′-(dimethylamino)-1,1′-binaphthyl
(3). Reaction of M(NMe2)4 with 2 equiv of 4H or 6H gives, after recrystallization from an n-hexane
solution, the monoligated chiral titanium amides (4)Ti(NMe2)3 (12), (6)Ti(NMe2)3 (13), and zirconium
amide (6)Zr(NMe2)3 (14), respectively, in good yields. Under similar reaction conditions, treatment of
Zr(NMe2)4 with 2 equiv of diphenylphosphoramide 7H or 8H affords, after recrystallization from a toluene
solution, the bis-ligated chiral zirconium amides (7)2Zr(NMe2)2 · 2C7H8 (15 · 2C7H8) and (8)2Zr(NMe2)2
(16), respectively, in good yields. Reaction of M(NMe2)4 (M ) Ti, Zr) with 2 equiv of mesitoylamide
9H, 10H, or 11H also gives, after recrystallization from a toluene or n-hexane solution, the bis-ligated
chiral titanium amides (9)2Ti(NMe2)2 · 2.75C7H8 (17 · 2.75C7H8) and (10)2Ti(NMe2)2 (19) and zirconium
amides (9)2Zr(NMe2)2 · C7H8 (18 · C7H8), (10)2Zr(NMe2)2 (20), and (11)2Zr(NMe2)2 (21), respectively, in
good yields. All new compounds have been characterized by various spectroscopic techniques and
elemental analyses. The solid-state structures of compounds 1, 2, 9H, and 12-20 have further been
confirmed by X-ray diffraction analyses. The zirconium amides are active catalysts for the asymmetric
hydroamination/cyclization of aminoalkenes, affording cyclic amines in good to excellent yields with
good ee values, while the titanium amides are not.
is added to an unsaturated carbon-carbon bond, leading to the
formation of nitrogen heterocycles that are found in numerous
biologically and pharmacologically active compounds. To date,
the catalysts based on early transition metals (group 4 and
lanthanides) and lithium metal have been proved to be efficient
for this purpose.3-9 However, successful catalysts affording
significant enantioselectivity (>90% ee) are still scarcely
reported,6a,9e-g and those high enantioselective inductions are
observed only for one or two substrates. Thus, alkene hydroami-
nation remains an open area of research, and the development
of new catalysts for asymmetric alkene hydroamination is still
a desirable and challenging goal.
Introduction
The development of catalysts for intramolecular asymmetric
alkene hydroamination has been the subject of intense investiga-
tion over the past 17 years,1-9 since the hydroamination is a
highly atom-economical process in which an amine N-H bond
* Corresponding author. E-mail: gzi@bnu.edu.cn. Tel: +86-10-5880
2237. Fax: +86-10-5880 2075.
† Beijing Normal University.
‡ Nankai University.
(1) For reviews of asymmetric hydroamination, see: (a) Roesky, P. W.;
Mu¨ller, T. E. Angew. Chem., Int. Ed. 2003, 42, 2708–2710. (b) Hong, S.;
Marks, T. J. Acc. Chem. Res. 2004, 37, 673–686. (c) Hultzsch, K. C. Org.
Biomol. Chem. 2005, 3, 1819–1824. (d) Hultzsch, K. C. AdV. Synth. Catal.
2005, 347, 367–391. (e) Hii, K. K. Pure Appl. Chem. 2006, 78, 341–349.
(f) Aillaud, I.; Collin, J.; Hannedouche, J.; Schulz, E. Dalton Trans. 2007,
5105–5118. (g) Mu¨ller, T. E.; Hultzsch, K. C.; Yus, M.; Foubelo, F.; Tada,
M. Chem. ReV. 2008, 108, 3795–3892.
(2) For selected papers for asymmetric hydroaminations using lanthanide
metal catalysts with chiral Cp ligands, see: (a) Gagne´, M. R.; Stern, C. L.;
Marks, T. J. J. Am. Chem. Soc. 1992, 114, 275–294. (b) Gagne´, M. R.;
Brard, L.; Conticello, V. P.; Giardello, M. A.; Stern, C. L.; Marks, T. J.
Organometallics 1992, 11, 2003–2005. (c) Vitanova, D. V.; Hampel, F.;
Hultzsch, K. C. J. Organomet. Chem. 2007, 692, 4690–4701, and references
therein.
(4) (a) O’Shaughnessy, P. N.; Knight, P. D.; Morton, C.; Gillespie,
K. M.; Scott, P. Chem. Commun. 2003, 1770–1771. (b) O’Shaughnessy,
P. N.; Gillespie, K. M.; Knight, P. D.; Munslow, I. J.; Scott, P. Dalton
Trans. 2004, 2251–2256.
(5) Kim, J. Y.; Livinghouse, T. Org. Lett. 2005, 7, 1737–1739.
(6) (a) Gribkov, D. V.; Hultzsch, K. C.; Hampel, F. J. Am. Chem. Soc.
2006, 128, 3748–3759. (b) Gribkov, D. V.; Hultzsch, K. C. Chem. Commun.
2004, 730–731. (c) Gribkov, D. V.; Hampel, F.; Hultzsch, K. C. Eur.
J. Inorg. Chem. 2004, 409, 1–4101. (d) Gribkov, D. V.; Hultzsch, K. C.;
Hampel, F. Chem.-Eur. J. 2003, 9, 4796–4810. (e) Yu, X.; Marks, T. J.
Organometallics 2007, 26, 365–376. (f) Heck, R.; Schulz, E.; Collin, J.;
Carpentier, J.-F. J. Mol. Catal. A: Chem. 2007, 268, 163–168.
(3) Hong, S.; Tian, S.; Metz, M. V.; Marks, T. J. J. Am. Chem. Soc.
2003, 125, 14768–14783.
10.1021/om801061v CCC: $40.75
2009 American Chemical Society
Publication on Web 01/27/2009

1128 Organometallics, Vol. 28, No. 4, 2009
Zi et al.
Ligand modification has played a key role in developing
new catalyst precursors for asymmetric synthesis. Recently,
we have developed a new series of biaryl-based chiral non-
Cp multidentate ligands; their Zr(IV) and lanthanide com-
plexes are useful catalysts for the asymmetric hydroamination/
cyclization reaction.10 We found that the bis-ligated lanthanide
amides [(S)-2-(Me2N)-C20H12-2′-(NCHC4H3N)]2LnN(SiMe3)2
with the C1-symmetric monopyrrole-substituted ligand (S)-
2-(pyrrol-2-ylmethyleneamino)-2′-(dimethylamino)-1,1′-bi-
naphthyl (4H) are more effective chiral catalysts for this
transformation than C2-symmetric bis(pyrrolate) lanthanide
amides [(R)-C20H12(NCHC4H3N)2]LnN(SiMe3)2(thf), in which
good enantioselectivities (up to 71% ee) but low conversions
have been obtained.10a,b In our ongoing research, we are now
focusing on the preparation of this type of bis-ligated catalysts
coordinated by chiral C1-symmetric tridentate ligands. To
further explore the chemistry of 2,2′-diamino-1,1′-binaphthyl,
we have recently extended our work to new chiral C1-
symmetric versatile ligands, (S)-2-(diphenylphosphinoylamino)-
2′-(dimethylamino)-1,1′-binaphthyl (7H) and (S)-2-(mesitoy-
lamino)-2′-(dimethylamino)-1,1′-binaphthyl (9H). Each ligand
contains two σ-donating nitrogen atoms and one oxygen atom
that can act in bidentate or tridentate fashion. Herein, we
report the synthesis and properties of the new chiral ligands,
their use in the coordination chemistry of titanium(IV) and
zirconium(IV), and the applications of the resulting com-
plexes as catalysts for the asymmetric hydroamination/
cyclization of aminoalkenes. For better understanding and
comparison, the ligand (S)-2-(pyrrol-2-ylmethyleneamino)-
2′-(dimethylamino)-1,1′-binaphthyl (4H) and the new ligands
(R)-2-(pyridin-2-ylmethylamino)-2′-(dimethylamino)-6,6′-di-
methyl-1,1′-biphenyl(6H),(R)-2-(diphenylphosphinoylamino)-
2′-(dimethylamino)-6,6′-dimethyl-1,1′-biphenyl (8H), (R)-2-
(mesitoylamino)-2′-(dimethylamino)-6,6′-dimethyl-1,1′-
biphenyl (10H), and (R)-5,5′6,6′7,7′8,8′-octahydro-2-
(mesitoylamino)-2′-(dimethylamino)-1,1′-binaphthyl (11H)
will also be included in this contribution.
Experimental Section
General Methods. All experiments were performed under an
atmosphere of dry dinitrogen with rigid exclusion of air and moisture
using standard Schlenk or cannula techniques, or in a glovebox. All
organic solvents were freshly distilled from sodium benzophenone ketyl
immediately prior to use. (S)-2,2′-Diamino-1,1′-binaphthyl,11 (R)-
5,5′6,6′7,7′8,8′-octahydro-2,2′-diamino-1,1′-binaphthyl,12 (R)-2,2′-di-
amino-6,6′-dimethyl-1,1′-biphenyl,13 (S)-2-(pyrrol-2-ylmethyleneamino)-
2′-(dimethylamino)-1,1′-binaphthyl (4H),10b M(NMe2)4,14 2,2-
dimethylpent-4-enylamine,5 2,2′-dimethylhex-5-enylamine,5 and 1-
(aminomethyl)-1-allylcyclohexane7a were prepared according to literature
methods. All chemicals were purchased from Aldrich Chemical Co.
and Beijing Chemical Co. and used as received unless otherwise noted.
Infrared spectra were obtained from KBr pellets on an Avatar 360
Fourier transform spectrometer. 1H and 13C NMR spectra were
recorded on a Bruker AV 400 spectrometer at 400 and 100 MHz,
respectively. All chemical shifts are reported in δ units with reference
to the residual protons of the deuterated solvents for proton and carbon
chemical shifts. Melting points were measured on an X-6 melting point
apparatus and were uncorrected. Elemental analyses were performed
on a Vario EL elemental analyzer.
(7) (a) Riegert, D.; Collin, J.; Meddour, A.; Schulz, E.; Trifonov, A. J.
Org. Chem. 2006, 71, 2514–2517. (b) Collin, J.; Daran, J. C.; Jacquet, O.;
Schulz, E.; Trifonov, A. Chem.-Eur. J. 2005, 11, 3455–3462. (c) Collin,
J.; Daran, J. C.; Schulz, E.; Trifonov, A. Chem. Commun. 2003, 3048–
3049. (d) O’Shaughnessy, P. N.; Scott, P. Tetrahedron: Asymmetry 2003,
14, 1979–1983. (e) Meyer, N.; Zulys, A.; Roesky, P. W. Organometallics
2006, 25, 4179–4182. (f) Riegert, D.; Collin, J.; Daran, J. C.; Fillebeen, T.;
Schulz, E.; Lyubov, D.; Fukin, G.; Trifonov, A. Eur. J. Inorg. Chem. 2007,
115, 9–1168. (g) Kim, H.; Kim, Y. K.; Shim, J. H.; Kim, M.; Han, M.;
Livinghouse, T.; Lee, P. H. AdV. Synth. Catal. 2006, 348, 2609–2618. (h)
Aillaud, I.; Wright, K.; Collin, J.; Schulz, E.; Mazaleyrat, J.-P. Tetrahedron:
Asymmetry 2008, 19, 82–92. (i) Aillaud, I.; Collin, J.; Duhayon, C.; Guillot,
R.; Lyubov, D.; Schulz, E.; Trifonov, A. Chem.-Eur. J. 2008, 14, 2189–
2200. (j) Hannedouche, J.; Aillaud, I.; Collin, J.; Schulz, E.; Trifonov, A.
Chem. Commun. 2008, 3552–3554. (k) Aillaud, I.; Lyubov, D.; Collin, J.;
Guillot, R.; Hannedouche, J.; Schulz, E.; Trifonov, A. Organometallics 2008,
27, 5929–5936.
(8) For asymmetric hydroamination using late transition metal catalysts,
see: (a) Lo¨ber, O.; Kawatsura, M.; Hartwig, J. F. J. Am. Chem. Soc. 2001,
123, 4366–4367. (b) Patil, N. T.; Lutete, L. M.; Wu, H.; Pahadi, N. K.;
Gridnev, I. D.; Yamamoto, Y. J. Org. Chem. 2006, 71, 4270–4279. (c) Hu,
A.; Ogasaware, M.; Sakamoto, T.; Okada, A.; Nakajima, K.; Takahashi,
T.; Lin, W. AdV. Synth. Catal. 2006, 348, 2051–2056. (d) LaLonde, R. L.;
Sherry, B. D.; Kang, E. J.; Toste, F. D. J. Am. Chem. Soc. 2007, 129, 2452–
2453. (e) Zhang, Z.; Bender, C. F.; Widenhoefer, R. A. Org. Lett. 2007, 9,
2887–2889. (f) Zhang, Z.; Bender, C. F.; Widenhoefer, R. A. J. Am. Chem.
Soc. 2007, 129, 14148–14149.
(9) For examples of asymmetric hydroamination using other metal
catalysts, see: (a) Knight, P. D.; Munslow, I.; O’Shaughnessy, P. N.; Scott,
P. Chem. Commun. 2004, 894–895. (b) Gribkov, D. V.; Hultzcsh, K. C.
Angew. Chem., Int. Ed. 2004, 43, 5542–5546. (c) Martinez, P. H.; Hultzsch,
K. C.; Hampel, F. Chem. Commun. 2006, 2221–2223. (d) Watson, D. A.;
Chiu, M.; Bergman, R. G. Organometallics 2006, 25, 4731–4733. (e) Wood,
M. C.; Leitch, D. C.; Yeung, C. S.; Kozak, J. A.; Schafer, L. L. Angew.
Chem., Int. Ed. 2007, 46, 354–358. (f) Gott, A. L.; Clarke, A. J.; Clarkson,
G. J.; Scott, P. Organometallics 2007, 26, 1729–1737. (g) Ogata, T.; Ujihara,
A.; Tsuchida, S.; Shimizu, T.; Kaneshige, A.; Tomioka, K. Tetrahedron
Lett. 2007, 48, 6648–6650.
(10) (a) Xiang, L.; Wang, Q.; Song, H.; Zi, G. Organometallics 2007,
26, 5323–5329. (b) Zi, G.; Xiang, L.; Song, H. Organometallics 2008, 27,
1242–1246. (c) Xiang, L.; Song, H.; Zi, G. Eur. J. Inorg. Chem. 2008,
113, 5–1140. (d) Zi, G.; Wang, Q.; Xiang, L.; Song, H. Dalton Trans. 2008,
5930–5944. (e) Wang, Q.; Xiang, L.; Zi, G.; Song, H. Inorg. Chem. 2008,
47, 4319–4328. (f) Wang, Q.; Xiang, L.; Song, H.; Zi, G. J. Organomet.
Chem. published online 2008, http://dx.doi.org/10.1016/j.jorganchem.
2008.11.061.
Preparation of (S)-2-Amino-2′-dimethylamino-1,1′-binaph-
thyl (1). This compound was prepared according to the literature
starting from (S)-1,1′-binaphthyl-2,2′-diamine.15 First, one of the
amino groups in (S)-1,1′-binaphthyl-2,2′-diamine was protected
using acetic anhydride, followed by methylation of the other amino
group with an excess of formaldehyde (40%) in the presence of
acetic acid and NaBH3CN in THF. Finally the acetyl group was
removed with concentrated HCl in ethanol to give (S)-2-amino-2′-
dimethylamino-1,1′-binaphthyl in 70% total yield (from (S)-1,1′-
binaphthyl-2,2′-diamine). Colorless crystals suitable for X-ray
structural analysis were grown from an n-hexane solution at room
1
temperature. Mp: 144-146 °C. H NMR (CDCl3): δ 7.82 (d, J )
9.0 Hz, 1H, aryl), 7.73 (d, J ) 8.1 Hz, 1H, aryl), 7.69 (d, J ) 8.8
Hz, 2H, aryl), 7.43 (d, J ) 8.9 Hz, 1H, aryl), 7.21 (t, J ) 7.4 Hz,
1H, aryl), 7.02-7.16 (m, 5H, aryl), 6.93 (d, J ) 8.3 Hz, 1H, aryl),
3.76 (s, 2H, NH2), 2.52 (s, 6H, CH3). These spectroscopic data are
in agreement with those reported in the literature.15
Preparation of (R)-2-Amino-2′-(dimethylamino)-6,6′-dimethyl-
1,1′-biphenyl (2). This compound was prepared as colorless crystals
in 68% total yield staring from (R)-2,2′-diamino-6,6′-dimethyl-1,1′-
biphenyl by a similar procedure to that outlined for the synthesis
of 1. Mp: 72-74 °C. 1H NMR (CDCl3): δ 7.27 (m, 1H, aryl), 7.10
(t, J ) 7.7 Hz, 1H, aryl), 6.98 (d, J ) 7.7 Hz, 2H, aryl), 6.74 (d,
J ) 7.4 Hz, 1H, aryl), 6.66 (d, J ) 7.9 Hz, 1H, aryl), 3.53 (s, br,
(11) (a) Zi, G.; Xiang, L.; Zhang, Y.; Wang, Q.; Zhang, Z. Appl.
Organomet. Chem. 2007, 21, 177–183. (b) Brown, K. J.; Berry, M. S.;
Murdoch, J. R. J. Org. Chem. 1985, 50, 4345–4349.
(12) Korostylev, A.; Tararov, V. I.; Fischer, C.; Monsees, A.; Bo¨rner,
A. J. Org. Chem. 2004, 69, 3220–3221.
(13) Kanoh, S.; Goka, S.; Murose, N.; Kubo, H.; Kondo, M.; Sugino,
T.; Motoi, M.; Suda, H. Polym. J. 1987, 19, 1047–1065.
(14) Diamond, G. M.; Jordan, R. F.; Petersen, J. L. J. Am. Chem. Soc.
1996, 118, 8024–8033.
(15) (a) Wang, C.-J.; Shi, M. J. Org. Chem. 2003, 68, 6229–6237. (b)
Wang, J.; Li, H.; Duan, W.; Zu, L.; Wang, W. Org. Lett. 2005, 7, 4713–
4716.

Synthesis of Group 4 Metal Amides
Organometallics, Vol. 28, No. 4, 2009 1129
2H, NH2), 2.58 (s, 6H, NMe2), 2.00 (s, 3H, CH3), 1.95 (s, 3H, CH3).
13C NMR (CDCl3): δ 152.5, 143.7, 138.3, 137.2, 130.7, 128.1,
127.6, 125.9, 124.1, 120.2, 116.2, 112.8, 43.7, 19.9, 19.7. IR (KBr,
cm-1): ν 3467 (s), 3375 (s), 2937 (m), 1607 (vs), 1581 (s), 1466
(s), 1305 (s), 778 (s). Anal. Calcd for C16H20N2: C, 79.96; H, 8.38;
N, 11.66. Found: C, 80.04; H, 8.21; N, 11.49.
(s), 993 (s), 819 (s), 760 (s). Anal. Calcd for C34H29N2OP: C, 79.67;
H, 5.70; N, 5.47. Found: C, 79.47; H, 5.66; N, 5.42.
Preparation of (R)-2-(Diphenylphosphinoylamino)-2′-(di-
methylamino)-6,6′-dimethyl-1,1′-biphenyl (8H). This compound
was prepared as a white solid from the reaction of diphenylphos-
phinoyl chloride (1.10 g, 5.0 mmol) with (R)-2-amino-2′-(dimethy-
lamino)-6,6′-dimethyl-1,1′-biphenyl (2; 1.20 g, 5.0 mmol) in the
presence of pyridine (2 mL, 25.3 mmol) in dry toluene (30 mL) at
reflux and purification by flash column chromatography (hexane/
ethyl acetate ) 2:1) using a similar procedure to that in the synthesis
of 7H. Yield: 1.80 g (82%). Mp: 136-138 °C. 1H NMR (CDCl3):
δ 7.50 (m, 4H, aryl), 7.31 (m, 1H, aryl), 7.21 (m, 7H, aryl H and
NH), 6.93 (m, 2H, aryl), 6.83 (d, J ) 8.1 Hz, 1H, aryl), 6.77 (d, J
) 7.6 Hz, 1H, aryl), 6.00 (d, J ) 11.2 Hz, 1H, aryl), 2.35 (s, 6H,
NMe2), 1.96 (s, 3H, CH3), 1.86 (s, 3H, CH3). 13C NMR (CDCl3):
δ 150.6, 137.3, 136.5, 132.9, 130.9, 130.7, 130.6, 130.5, 129.7,
127.5, 127.4, 127.2, 126.7, 125.8, 123.5, 117.7, 114.5, 42.4, 19.2,
19.0. IR (KBr, cm-1): ν 3444 (m), 2949 (m), 1575 (s), 1446 (s),
1367 (s), 1287 (s), 1211 (vs), 1126 (s), 860 (s), 761 (s). Anal. Calcd
for C28H29N2OP: C, 76.34; H, 6.64; N, 6.36. Found: C, 76.12; H,
6.42; N, 6.40.
Preparation of (R)-5,5′6,6′7,7′8,8′-Octahydro-2-amino-2′-
dimethylamino-1,1′-binaphthyl (3). This compound was prepared
as a colorless oil in 71% total yield staring from (R)-5,5′6,6′7,7′8,8′-
2,2′-diamino-1,1′-binaphthyl by a similar procedure to that outlined
1
for the synthesis of 1. H NMR (CDCl3): δ 7.06 (d, J ) 8.2 Hz,
1H, aryl), 6.94 (m, 2H, aryl), 6.45 (d, J ) 8.0 Hz, 1H, aryl), 2.89
(br s, 2H, NH2), 2.70 (m, 4H, CH2), 2.60 (m, 2H, CH2), 2.47 (s,
6H, NMe2), 2.26 (m, 2H, CH2), 1.64 (m, 8H, CH2). 13C NMR
(CDCl3): δ 150.7, 141.7, 137.0, 135.6, 132.1, 131.9, 129.5, 129.1,
127.4, 125.4, 117.0, 113.4, 44.3, 30.1, 29.9, 27.8, 27.3, 24.0, 23.9,
23.8, 23.5. IR (KBr, cm-1): ν 3459 (m), 3370 (m), 2927 (s), 1607
(s), 1480 (s), 1303 (s), 1094 (s), 805 (s). Anal. Calcd for C22H28N2:
C, 82.45; H, 8.81; N, 8.74. Found: C, 82.24; H, 8.61; N, 8.49.
Preparation of (R)-2-(Pyridin-2-ylmethylamino)-2′-(dimethyl-
amino)-6,6′-dimethyl-1,1′-biphenyl (6H). Pyridine-2-carboxalde-
hyde (0.54 g, 5.0 mmol) was mixed with (R)-2-amino-2′-
(dimethylamino)-6,6′-dimethyl-1,1′-biphenyl (2; 1.20 g, 5.0 mmol)
in dry toluene (25 mL). A few 4 Å molecular sieves were added,
and the solution was warmed to 70 °C and kept for two days at
this temperature. The solution was filtered and the solvent was
removed under reduced pressure. The resulting yellow oily residue
(crude 5) was dissolved in methanol (40 mL), NaBH4 (2.00 g, 52.6
mmol) was added in small portions at 0 °C, and then the solution
was warmed to 50 °C and kept for 2 h at this temperature. The
solvent was removed, and the residue was decomposed with H2O
(20 mL), extracted with ethyl acetate (20 mL × 3), and washed
with brine (20 mL). The combined organic layers were dried with
anhydrous Na2SO4, and the solvent was removed under reduced
pressure to give a white solid, which was further purified by flash
column chromatography (hexane/ethyl acetate ) 8:1) to give 6H
Preparation of (S)-2-(Mesitoylamino)-2′-(dimethylamino)-
1,1′-binaphthyl (9H). This compound was prepared as a white solid
from the reaction of mesitoyl chloride (0.91 g, 5.0 mmol) with (S)-
2-amino-2′-dimethylamino-1,1′-binaphthyl (1; 1.56 g, 5.0 mmol)
in the presence of pyridine (2 mL, 25.3 mmol) in dry toluene (30
mL) at reflux and purification by flash column chromatography
(hexane/ethyl acetate ) 20:1) using a similar procedure to that in
the synthesis of 7H. Colorless crystals suitable for X-ray structural
analysis were grown from an ethyl acetate solution at room
1
temperature. Yield: 1.79 g (78%). Mp: 156-158 °C. H NMR
(CDCl3): δ 8.56 (d, J ) 8.9 Hz, 1H, aryl), 7.97 (d, J ) 8.9 Hz,
1H, aryl), 7.84 (t, J ) 9.8 Hz, 2H, aryl), 7.71 (t, J ) 8.2 Hz, 2H,
aryl), 7.33 (m, 2H, aryl H and NH), 7.20 (m, 2H, aryl), 7.08 (m,
2H, aryl), 6.92 (d, J ) 8.0 Hz, 1H), 6.60 (s, 2H, aryl), 2.40 (s, 6H,
NMe2), 2.11 (s, 3H, CH3), 1.84 (s, 6H, CH3). 13C NMR (CDCl3):
δ 168.8, 138.3, 134.9, 134.0, 133.8, 133.7, 133.5, 131.4, 130.5,
130.0, 129.7, 128.7, 128.2, 128.1, 127.8, 126.9, 126.5, 126.4, 125.5,
125.3, 125.0, 124.1, 123.2, 122.1, 118.6, 43.4, 21.1, 18.6. IR (KBr,
cm-1): ν 3393 (w), 2915 (w), 1667 (vs), 1596 (s), 1493 (vs), 1426
(s), 1331 (s), 1281 (s), 989 (s), 817 (s). Anal. Calcd for C32H30N2O:
C, 83.81; H, 6.59; N, 6.11. Found: C, 83.81; H, 6.42; N, 6.40.
1
as a white solid. Yield: 1.39 g (82%). Mp: 92-94 °C. H NMR
(C6D6): δ 8.31 (s, 1H, aryl), 7.15 (m, 2H, aryl), 6.95 (m, 4H, aryl),
6.77 (d, J ) 7.4 Hz, 1H, aryl), 6.56 (d, J ) 7.4 Hz, 1H, aryl), 6.50
(m, 1H, aryl), 4.19 (s, 2H, CH2), 2.46 (s, 6H, NMe2), 2.08 (s, 3H,
CH3), 2.03 (s, 3H, CH3); proton of NH was not observed. 13C NMR
(C6D6): δ 159.7, 149.1, 145.6, 139.0, 136.8, 136.1, 131.1, 128.7,
128.4, 127.8, 125.9, 124.7, 121.6, 121.2, 119.9, 116.9, 108.8, 49.6,
43.7, 32.2, 20.3, 20.1. IR (KBr, cm-1): ν 3366 (s), 2927 (w), 1583
(s), 1508 (s), 1473 (s), 1323 (s), 1277 (s), 760 (s). Anal. Calcd for
C22H25N3: C, 79.72; H, 7.60; N, 12.69. Found: C, 79.47; H, 7.56;
N, 12.42.
Preparation of (R)-2-(Mesitoylamino)-2′-(dimethylamino)-
6,6′-dimethyl-1,1′-biphenyl (10H). This compound was prepared
as a white solid from the reaction of mesitoyl chloride (0.91 g, 5.0
mmol) with (R)-2-amino-2′-(dimethylamino)-6,6′-dimethyl-1,1′-
biphenyl (2; 1.20 g, 5.0 mmol) in the presence of pyridine (2 mL,
25.3 mmol) in dry toluene (30 mL) at reflux and purification by
flash column chromatography (hexane/ethyl acetate ) 15:1) using
a similar procedure to that in the synthesis of 7H. Yield: 1.60 g
Preparation of (S)-2-(Diphenylphosphinoylamino)-2′-(di-
methylamino)-1,1′-binaphthyl (7H). Diphenylphosphinoyl chlo-
ride (1.10 g, 5.0 mmol) was mixed with (S)-2-amino-2′-dimethy-
lamino-1,1′-binaphthyl (1; 1.56 g, 5.0 mmol) in dry toluene (30
mL). Pyridine (2 mL, 25.3 mmol) was added, and the solution was
refluxed for two days. The solvent was removed, and the residue
was decomposed with H2O (20 mL), extracted with ethyl acetate
(20 mL × 3), and washed with brine (20 mL). The combined
organic layers were dried with anhydrous Na2SO4, and the solvent
was removed under reduced pressure to give a white solid, which
was further purified by flash column chromatography (hexane/ethyl
acetate ) 2:1) to give 7H as a white solid. Yield: 1.92 g (75%).
1
(83%). Mp: 88-90 °C. H NMR (CDCl3): δ 8.13 (d, J ) 8.1 Hz,
1H), 7.42 (s, 1H, NH), 7.27 (t, J ) 7.8 Hz, 1H, aryl), 7.12 (t, J )
7.8 Hz, 1H, aryl), 7.04 (d, J ) 7.5 Hz, 1H, aryl), 6.85 (d, J ) 7.5
Hz, 1H, aryl), 6.76 (d, J ) 8.1 Hz, 1H), 6.65 (s, 2H, aryl), 2.32 (s,
6H, NMe2), 2.14 (s, 3H, CH3), 1.99 (s, 6H, CH3), 1.95 (s, 3H, CH3),
1.85 (s, 3H, CH3). 13C NMR (CDCl3): δ 168.5, 151.5, 138.3, 138.2,
137.2, 135.2, 134.9, 133.9, 131.0, 130.1, 128.7, 128.0, 127.8, 126.6,
124.5, 120.1, 116.1, 43.4, 21.0, 20.0, 19.9, 18.6. IR (KBr, cm-1):
ν 3395 (s), 2921 (s), 1678 (vs), 1581 (s), 1507 (s), 1463 (s), 1260
(s), 1101 (s), 798 (s). Anal. Calcd for C26H30N2O: C, 80.79; H,
7.82; N, 7.25. Found: C, 80.81; H, 7.82; N, 7.40.
1
Mp: 222-224 °C. H NMR (CDCl3): δ 7.89 (d, J ) 9.0 Hz, 1H,
aryl), 7.71 (m, 4H, aryl), 7.37-7.05 (m, 14H, aryl H and NH),
6.95 (m, 2H, aryl), 6.80 (d, J ) 8.6 Hz, 1H, aryl), 6.36 (d, J )
11.8 Hz, 1H, aryl), 2.39 (s, 6H, NMe2). 13C NMR (CDCl3): δ 135.4,
133.1, 132.9, 132.6, 131.6, 131.4, 130.8, 130.5, 130.3, 129.9, 128.8,
127.9, 127.5, 127.4, 127.3, 127.2, 127.0, 125.6, 125.5, 124.9, 123.0,
122.0, 120.8, 117.3, 42.5. IR (KBr, cm-1): ν 3309 (m), 3049 (w),
2835 (m), 1590 (s), 1504 (s), 1436 (s), 1329 (s), 1200 (s), 1107
Preparation of (R)-5,5′6,6′7,7′8,8′-Octahydro-2-(mesitoyl
amino)-2′-(dimethylamino)-1,1′-binaphthyl (11H). This com-
pound was prepared as a white solid from the reaction of mesitoyl
chloride (0.91 g, 5.0 mmol) with (R)-5,5′6,6′7,7′8,8′-octahydro-2-
amino-2′-dimethylamino-1,1′-binaphthyl (3; 1.60 g, 5.0 mmol) in
the presence of pyridine (2 mL, 25.3 mmol) in dry toluene (30

1130 Organometallics, Vol. 28, No. 4, 2009
Zi et al.
mL) at reflux and purification by flash column chromatography
(hexane/ethyl acetate ) 20:1) using a similar procedure to that in
the synthesis of 7H. Yield: 1.75 g (75%). Mp: 58-60 °C. 1H NMR
(CDCl3): δ 8.00 (d, J ) 8.2 Hz, 1H, aryl), 7.19 (s, 1H, NH), 7.05
(d, J ) 8.2 Hz, 1H, aryl), 6.91 (d, J ) 8.2 Hz, 1H, aryl), 6.70 (d,
J ) 8.2 Hz, 1H, aryl), 6.62 (s, 2H, aryl H), 2.73-2.58 (m, 4H,
CH2), 2.27 (s, 6H, NMe2), 2.16 (m, 4H, CH2), 2.14 (s, 3H, CH3),
1.97 (s, 6H, CH3), 1.67-1.54 (m, 8H, CH2). 13C NMR (CDCl3): δ
167.4, 148.0, 137.0, 135.6, 134.8, 134.2, 133.3, 132.8, 131.2, 131.1,
129.3, 128.6, 127.6, 127.0, 119.1, 115.2, 42.7, 28.6, 28.5, 26.7,
26.3, 22.2, 22.1, 22.0, 21.9, 20.0, 17.6. IR (KBr, cm-1): ν 3391
(m), 2929 (s), 1679 (s), 1592 (s), 1502 (s), 1434 (s), 1293 (s), 1099
(s), 812 (s). Anal. Calcd for C32H38N2O: C, 82.36; H, 8.21; N, 6.00.
Found: C, 82.21; H, 8.42; N, 6.20.
(20 mL) and recrystallization from a toluene solution by a similar
procedure to that in the synthesis of 12. Yield: 0.26 g (75%). Mp:
1
260-262 °C (dec). H NMR (C6D6): δ 7.91 (m, 8H, aryl), 7.66
(m, 3H, aryl), 7.50 (m, 2H, aryl), 7.38 (m, 7H, aryl), 7.17-6.96
(m, 24H, aryl), 6.88 (m, 6H, aryl), 6.68 (m, 4H, aryl), 3.24 (s, 12H,
Zr(NMe2)2), 2.45 (s, 12H, NMe2), 2.12 (s, 6H, CH3). 13C NMR
(C6D6): δ 150.5, 147.6, 137.6, 136.3, 136.2, 135.6, 135.2, 132.6,
132.5, 130.9, 130.2, 129.7, 129.0, 128.3, 127.5, 127.4, 127.3, 127.0,
126.5, 126.4, 125.9, 125.7, 125.5, 125.4, 125.1, 123.4, 121.0, 120.4,
45.1, 44.1, 21.8. IR (KBr, cm-1): ν 2965 (w), 1589 (s), 1560 (s),
1499 (s), 1437 (s), 1330 (s), 1260 (s), 1080 (s), 1016 (s), 815 (s).
Anal. Calcd for C86H84N6O2P2Zr: C, 74.48; H, 6.11; N, 6.06. Found:
C, 74.64; H, 6.36; N, 6.24.
Preparation of (8)2Zr(NMe2)2 (16). This compound was
prepared as orange crystals from the reaction of 8H (0.22 g, 0.5
mmol) with Zr(NMe2)4 (0.07 g, 0.25 mmol) in toluene (20 mL)
and recrystallization from a toluene solution by a similar procedure
to that in the synthesis of 12. Yield: 0.19 g (73%). Mp: 204-206
°C (dec). 1H NMR (C6D6): δ 8.20 (m, 4H, aryl), 7.35 (m, 8H, aryl),
7.21 (d, J ) 7.6 Hz, 2H, aryl), 7.12 (d, J ) 7.6 Hz, 2H, aryl),
7.05-6.81 (m, 12H, aryl), 6.84 (m, 4H, aryl), 2.72 (s, 12H,
Zr(NMe2)2), 2.36 (s, 6H, CH3), 1.97 (s, 6H, CH3), 1.80 (s, 12H,
NMe2). 13C NMR (C6D6): δ 151.0, 145.5, 138.4, 137.6, 137.1,
136.7, 136.3, 133.3, 131.3, 131.2, 129.9, 126.9, 126.7, 124.5, 124.0,
118.2, 43.0, 42.8, 20.7, 19.9. IR (KBr, cm-1): ν 2918 (w), 1573
(s), 1461 (s), 1359 (s), 1287 (s), 1211 (s), 1121 (s), 1041 (s), 794
(s). Anal. Calcd for C60H68N6O2P2Zr: C, 68.09; H, 6.48; N, 7.94.
Found: C, 68.04; H, 6.36; N, 8.24.
Preparation of (4)Ti(NMe2)3 (12). A toluene solution (10 mL)
of 4H (0.39 g, 1.0 mmol), which was dried at 50 °C overnight
under vacuum, was slowly added to a toluene solution (10 mL) of
Ti(NMe2)4 (0.11 g, 0.5 mmol) with stirring at room temperature.
The solution was warmed to 60 °C and kept for one day at this
temperature. The solution was filtered and the solvent was removed
under reduced pressure. The resulting red solid was recrystallized
from an n-hexane solution to give 12 as red crystals. Yield: 0.18 g
1
(65%). Mp: 134-136 °C (dec). H NMR (C6D6): δ 7.75 (m, 5H,
aryl), 7.54 (m, 2H, aryl), 7.39-7.19 (m, 5H, aryl), 7.07 (m, 1H,
aryl), 7.02 (m, 1H, aryl), 6.89 (d, J ) 3.4 Hz, 1H, aryl), 6.37 (d,
J ) 2.1 Hz, 1H, aryl), 2.50 (s, 18H, Ti(NMe2)3), 2.23 (s, 6H, NMe2).
13C NMR (C6D6): δ 160.8, 151.5, 149.3, 137.8, 136.6, 135.2, 134.8,
131.7, 130.5, 129.5, 127.6, 127.3, 126.8, 126.7, 126.4, 126.3, 125.7,
125.1, 124.8, 123.8, 120.9, 119.6, 117.8, 112.6, 110.9, 46.5, 43.2.
IR (KBr, cm-1): ν 3055 (w), 2961 (m), 2923 (m), 2851 (w), 1616
(m), 1594 (m), 1569 (s), 1502 (s), 1261 (s), 1033 (vs), 802 (s).
Anal. Calcd for C33H40N6Ti: C, 69.71; H, 7.09; N, 14.78. Found:
C, 69.55; H, 6.83; N, 14.72.
Preparation of (9)2Ti(NMe2)2 · 2.75C7H8 (17 · 2.75C7H8). This
compound was prepared as red crystals from the reaction of 9H
(0.23 g, 0.5 mmol) with Ti(NMe2)4 (0.06 g, 0.25 mmol) in toluene
(20 mL) and recrystallization from a toluene solution by a similar
procedure to that in the synthesis of 12. Yield: 0.25 g (78%). Mp:
Preparation of (6)Ti(NMe2)3 (13). This compound was prepared
as red crystals from the reaction of 6H (0.33 g, 1.0 mmol) with
Ti(NMe2)4 (0.11 g, 0.5 mmol) in toluene (20 mL) and recrystalli-
zation from an n-hexane solution by a similar procedure to that in
the synthesis of 12. Yield: 0.19 g (76%). Mp: 178-180 °C (dec).
1H NMR (C6D6): δ 7.79 (d, J ) 5.1 Hz, 1H, aryl), 7.28 (m, 2H,
aryl), 7.15 (d, J ) 7.8 Hz, 1H, aryl), 7.00 (m, 2H, aryl), 6.86 (d,
J ) 8.0 Hz, 1H, aryl), 6.75 (t, J ) 7.8 Hz, 1H, aryl), 6.47 (d, J )
7.9 Hz, 1H, aryl), 6.42 (m, 1H, aryl), 4.61 (s, 2H, CH2), 3.17 (s,
18H, Ti(NMe2)3), 2.50 (s, 6H, NMe2), 2.28 (s, 3H, CH3), 2.14 (s,
3H, CH3). 13C NMR (C6D6): δ 162.8, 155.4, 151.3, 148.1, 145.5,
137.7, 134.8, 134.7, 129.4, 125.9, 125.1, 122.7, 122.0, 119.5, 118.8,
115.1, 61.8, 45.8, 42.7, 21.8, 19.8. IR (KBr, cm-1): ν 2821 (s),
1574 (s), 1440 (s), 1254 (s), 1141 (s), 1046 (s), 1020 (s), 945 (s),
755 (s). Anal. Calcd for C28H42N6Ti: C, 65.87; H, 8.29; N, 16.46.
Found: C, 65.72; H, 8.26; N, 16.48.
Preparation of (6)Zr(NMe2)3 (14). This compound was prepared
as orange crystals from the reaction of 6H (0.33 g, 1.0 mmol) with
Zr(NMe2)4 (0.14 g, 0.5 mmol) in toluene (20 mL) and recrystalli-
zation from an n-hexane solution by a similar procedure to that in
the synthesis of 12. Yield: 0.23 g (82%). Mp: 160-162 °C (dec).
1H NMR (C6D6): δ 7.97 (m, 1H, aryl), 7.29 (m, 2H, aryl), 7.11 (m,
1H, aryl), 6.97 (m, 2H, aryl), 6.80 (d, J ) 7.7 Hz, 1H, aryl), 6.71
(m, 1H, aryl), 6.39 (m, 2H aryl), 4.48 (s, 2H, CH2), 3.02 (s, 18H,
Zr(NMe2)3), 2.48 (s, 6H, NMe2), 2.24 (s, 3H, CH3), 2.11 (s, 3H,
CH3). 13C NMR (C6D6): δ 165.0, 153.8, 152.5, 147.4, 138.8, 137.9,
137.0, 136.7, 135.2, 132.8, 126.1, 125.7, 123.8, 123.6, 129.9, 120.6,
116.1, 61.4, 43.8, 43.7, 23.0, 21.0, 20.9. IR (KBr, cm-1): ν 2925
(w), 1577 (s), 1457 (s), 1317 (s), 1258 (s), 1140 (s), 1092 (s), 1046
(s), 939 (s), 754 (s). Anal. Calcd for C28H42N6Zr: C, 60.72; H, 7.64;
N, 15.17. Found: C, 60.72; H, 7.66; N, 14.98.
1
144-146 °C (dec). H NMR (C6D6): δ 7.98 (d, J ) 8.9 Hz, 8H,
aryl), 7.80 (d, J ) 8.9 Hz, 8H, aryl), 7.73 (d, J ) 8.8 Hz, 12H,
aryl), 7.62 (m, 16H, aryl), 7.44 (d, J ) 8.9 Hz, 8H, aryl), 7.15-6.97
(m, 75H, aryl), 6.81 (m, 8H, aryl), 6.32 (m, 8H, aryl), 6.20 (d, J )
8.6 Hz, 8H, aryl), 6.11 (s, 8H, aryl), 5.69 (s, 8H, aryl), 3.64 (s,
48H, Ti(NMe2)2), 2.36 (s, 48H, NMe2), 2.13 (s, 33H, CH3), 2.04
(s, 24H, CH3), 1.84 (s, 24H, CH3), 1.48 (s, 24H, CH3). 13C NMR
(C6D6): δ 181.4, 150.3, 142.4, 137.6, 137.2, 136.2, 135.8, 134.9,
134.5, 133.0, 132.8, 131.7, 130.1, 129.5, 129.0, 128.3, 127.4, 127.1,
126.8, 126.7, 125.8, 125.4, 125.1, 124.8, 124.3, 122.3, 119.2, 47.6,
43.9, 22.8, 21.1, 20.7, 19.7. IR (KBr, cm-1): ν 2933 (m), 1676 (s),
1593 (s), 1560 (s), 1490 (s), 1449 (s), 1424 (s), 1351 (s), 1256 (s),
1168 (s), 1095 (s), 814 (s). Anal. Calcd for C349H368N24O8Ti4: C,
80.33; H, 7.11; N, 6.44. Found: C, 80.64; H, 7.36; N, 6.24.
Preparation of (9)2Zr(NMe2)2 · C7H8 (18 · C7H8). This com-
pound was prepared as orange crystals from the reaction of 9H
(0.23 g, 0.5 mmol) with Zr(NMe2)4 (0.07 g, 0.25 mmol) in toluene
(20 mL) and recrystallization from a toluene solution by a similar
procedure to that in the synthesis of 12. Yield: 0.22 g (74%). Mp:
1
185-187 °C (dec). H NMR (C6D6): δ 7.98 (d, J ) 8.8 Hz, 2H,
aryl), 7.77 (d, J ) 8.9 Hz, 2H, aryl), 7.70 (d, J ) 8.8 Hz, 2H,
aryl), 7.59 (m, 4H, aryl), 7.41 (d, J ) 8.9 Hz, 2H, aryl), 7.15-6.96
(m, 11H, aryl), 6.80 (m, 2H, aryl), 6.32 (t, J ) 7.4 Hz, 2H, aryl),
6.18 (d, J ) 8.5 Hz, 2H, aryl), 6.08 (s, 2H, aryl), 5.64 (s, 2H,
aryl), 3.29 (s, 12H, Zr(NMe2)2), 2.39 (s, 12H, NMe2), 2.11 (s, 3H,
CH3), 2.03 (s, 6H, CH3), 1.80 (s, 6H, CH3), 1.42 (s, 6H, CH3). 13
C
NMR (C6D6): δ 181.3, 50.2, 141.4, 137.6, 137.5, 136.3, 135.6,
134.8, 132.8, 132.4, 131.7, 130.1, 129.6, 129.0, 128.3, 128.2,
128.16, 128.1, 127.9, 127.7, 127.1, 126.9, 126.6, 125.9, 125.8,
125.4, 124.5, 122.5, 119.4, 43.8, 42.8, 22.8, 21.0, 20.7, 19.6. IR
(KBr, cm-1): ν 2961 (w), 1679 (s), 1593 (s), 1488 (s), 1424 (s),
1275 (s), 1129 (s), 1023 (s), 815 (s). Anal. Calcd for C75H78N6O2Zr:
C, 75.91; H, 6.63; N, 7.08. Found: C, 75.64; H, 6.36; N, 7.24.
Preparation of (7)2Zr(NMe2)2 · 2C7H8 (15 · 2C7H8). This com-
pound was prepared as orange crystals from the reaction of 7H
(0.26 g, 0.5 mmol) with Zr(NMe2)4 (0.07 g, 0.25 mmol) in toluene

Synthesis of Group 4 Metal Amides
Organometallics, Vol. 28, No. 4, 2009 1131
Table 1. Crystal Data and Experimental Parameters for Compounds 1, 2, 9H, and 12-14
1
2
9H
C32H30N2O
458.58
monoclinic
P21
9.111(1)
15.673(2)
9.801(1)
111.02(1)
1306.5(3)
2
12
13
C28H42N6Ti
510.58
monoclinic
P21
11.986(2)
15.980(3)
15.163(3)
103.36(1)
2825.7(10)
4
14
C28H42N6Zr
553.90
monoclinic
P21
11.876(1)
16.096(2)
15.269(2)
102.17(1)
2853.0(5)
4
formula
fw
cryst syst
space group
a (Å)
C20H20N2
312.40
C16H20N2
240.34
C33H40N6Ti
568.61
orthorhombic
P212121
8.717(2)
10.984(3)
17.422(4)
90
orthorhombic
P212121
11.844(1)
11.855(1)
19.794(1)
90
orthorhombic
P212121
8.745(1)
18.336(2)
19.675(2)
90
b (Å)
c (Å)
ꢀ (deg)
V (Å3)
1668.1(7)
4
2779.4(2)
8
3155.0(7)
4
Z
Dcalc (g/cm3)
µ(Mo/KR)calc (mm-1
size (mm)
F(000)
1.244
0.073
1.149
0.068
1.166
0.070
1.197
0.302
1.200
0.329
1.290
0.412
)
0.28 × 0.26 × 0.20 0.26 × 0.24 × 0.18 0.28 × 0.24 × 0.20 0.18 × 0.16 × 0.14 0.32 × 0.30 × 0.24
0.26 × 0.22 × 0.16
664
2014
488
1208
1096
1168
2θ range (deg)
no. of reflns, collected 21 072
4.38 to 55.72
3.44 to 55.72
26 336
4.46 to 55.76
16 030
3.04 to 50.00
23 802
3.92 to 55.76
35 627
3.50 to 55.80
26 947
no. of unique reflns
no. of obsd reflns
2274 (Rint ) 0.0428) 3709 (Rint ) 0.0506) 3210 (Rint ) 0.0386) 5572 (Rint ) 0.1660) 13 336 (Rint ) 0.0413) 13 132 (Rint ) 0.0462)
2142
3535
3093
4820
11 728
0.93, 0.90
0.049
10 985
0.94, 0.90
0.045
abs corr (Tmax, Tmin
)
0.99, 0.98
0.035
0.088
0.090
1.05
0.99, 0.98
0.044
0.103
0.104
1.08
0.99, 0.98
0.042
0.099
0.101
1.09
0.96, 0.95
0.083
0.191
0.198
1.14
R
Rw
0.124
0.096
wR2 (all data)
gof
0.130
0.102
1.04
1.02
Preparation of (10)2Ti(NMe2)2 (19). This compound was
prepared as red crystals from the reaction of 10H (0.19 g, 0.5 mmol)
with Ti(NMe2)4 (0.6 g, 0.25 mmol) in toluene (20 mL) and
recrystallization from a toluene solution by a similar procedure to
that in the synthesis of 12. Yield: 0.15 g (64%). Mp: 132-134 °C
(dec). 1H NMR (C6D6): δ 7.62 (d, J ) 7.7 Hz, 2H, aryl), 7.12 (m,
4H, aryl), 6.96 (d, J ) 6.5 Hz, 2H, aryl), 6.88 (d, J ) 6.8 Hz, 2H,
aryl), 6.72 (d, J ) 7.3 Hz, 2H, aryl), 6.59 (s, 2H, aryl), 6.31 (s,
2H, aryl), 3.57 (s, 12H, Ti(NMe2)2), 2.44 (s, 12H, NMe2), 2.13 (s,
9H, CH3), 2.05 (s, 9H, CH3), 1.85 (s, 6H, CH3), 1.80 (s, 6H, CH3).
13C NMR (C6D6): δ 183.5, 151.3, 142.9, 139.6, 137.3, 137.0, 136.7,
133.6, 133.3, 132.9, 128.8, 127.8, 126.9, 125.9, 125.5, 124.2, 115.7,
46.6, 43.0, 23.9, 21.8, 20.2, 19.5, 18.8. IR (KBr, cm-1): ν 2958
(m), 2910 (m), 1677 (s), 1568 (s), 1513 (s), 1461 (s), 1259 (s),
1091 (s), 1013 (s), 796 (s). Anal. Calcd for C56H70N6O2Ti: C, 74.15;
H, 7.78; N, 9.27. Found: C, 73.84; H, 7.76; N, 9.24.
1367 (s), 1260 (s), 1093 (s), 1020 (s), 801 (s). Anal. Calcd for
C68H86N6O2Zr: C, 73.53; H, 7.80; N, 7.57. Found: C, 73.24; H,
7.76; N, 7.54.
Thermal Stability of the Complexes in Solution. A J. Young
NMR tube charged with complex 12, 13, 14, 15, 16, 17, 18, 19,
20, or 21 (about 15 mg) and C6D6 (0.5 mL) was heated at 120 °C
and monitored periodically by 1H NMR spectroscopy. In each case,
the spectrum did not show any change when kept at the above
temperature for 3 days.
General Procedure for Asymmetric Hydroamination/Cy-
clization. In a nitrogen-filled glovebox, precatalyst (0.016 mmol),
C6D6 (0.7 mL), and aminoalkene (0.16 mmol) were introduced
sequentially into a J. Young NMR tube equipped with a Teflon
screw cap. The reaction mixture was subsequently kept at 120 °C
to achieve hydroamination, and the reaction was monitored periodi-
1
cally by H NMR spectroscopy. The cyclic amine was vacuum
Preparation of (10)2Zr(NMe2)2 (20). This compound was
prepared as orange crystals from the reaction of 10H (0.19 g, 0.5
mmol) with Zr(NMe2)4 (0.07 g, 0.25 mmol) in toluene (20 mL)
and recrystallization from a toluene solution by a similar procedure
to that in the synthesis of 12. Yield: 0.18 g (74%). Mp: 234-236
transferred from the J. Young NMR tube into a 25 mL Schlenk
flask that contained 31 mg (0.16 mmol) of (S)-(+)-O-acetylmandelic
acid. This transfer was quantitated by washing the NMR tube with
a small amount of CDCl3. The resulting mixture was stirred at room
temperature for 2 h, and the volatiles were removed in Vacuo. The
resulting diastereomeric salt was then dissolved in CDCl3, and the
enantiomeric excesses were determined by 1H NMR spectroscopy.5
X-ray Crystallography. Single-crystal X-ray diffraction mea-
surements were carried out on a Rigaku Saturn CCD diffractometer
at 113(2) K using graphite-monochromated Mo KR radiation (λ )
0.71070 Å). An empirical absorption correction was applied using
the SADABS program.16 All structures were solved by direct
methods and refined by full-matrix least-squares on F2 using the
SHELXL-97 program package.17 All the hydrogen atoms were
geometrically fixed using the riding model. The crystal data and
experimental data for 1, 2, 9H, and 12-20 are summarized in Tables
1 and 2. Selected bond lengths and angles are listed in Table 3.
1
°C (dec). H NMR (C6D6): δ 7.63 (d, J ) 7.8 Hz, 2H, aryl), 7.14
(m, 4H, aryl), 6.96 (d, J ) 8.1 Hz, 2H, aryl), 6.88 (d, J ) 7.4 Hz,
2H, aryl), 6.71 (d, J ) 7.4 Hz, 2H, aryl), 6.56 (s, 2H, aryl), 6.30
(s, 2H, aryl), 3.26 (s, 12H, Zr(NMe2)2), 2.45 (s, 12H, NMe2), 2.12
(s, 9H, CH3), 2.04 (s, 9H, CH3), 1.84 (s, 6H, CH3), 1.76 (s, 6H,
CH3). 13C NMR (C6D6): δ 184.0, 152.5, 143.0, 140.6, 138.2, 137.8,
134.4, 134.3, 134.1, 128.6, 128.4, 126.9, 126.6, 125.9, 124.8, 116.3,
44.0, 43.0, 23.0, 20.9, 20.7, 19.9, 18.7. IR (KBr, cm-1): ν 2962
(m), 1635 (vs), 1509 (s), 1338 (s), 1317 (s), 1260 (s), 1091 (s),
1018 (s), 798 (s). Anal. Calcd for C56H70N6O2Zr: C, 70.77; H, 7.42;
N, 8.84. Found: C, 70.84; H, 7.36; N, 9.14.
Preparation of (11)2Zr(NMe2)2 (21). This compound was
prepared as orange microcrystals from the reaction of 11H (0.23
g, 0.5 mmol) with Zr(NMe2)4 (0.07 g, 0.25 mmol) in toluene (20
mL) and recrystallization from an n-hexane solution by a similar
procedure to that in the synthesis of 12. Yield: 0.20 g (72%). Mp:
Results and Discussion
Ligands. Treatment of the starting material (S)-2,2′-diamine-
1,1′-binaphthyl, (R)-2,2′-diamino-6,6′-dimethyl-1,1′-biphenyl or
(R)-5,5′6,6′7,7′8,8′-octahydro-2,2′-diamine-1,1′-binaphthyl with
1
210-212 °C (dec). H NMR (C6D6): δ 7.62 (d, J ) 8.2 Hz, 2H,
aryl), 7.06 (m, 4H, aryl), 6.98 (d, J ) 8.2 Hz, 2H, aryl), 6.53 (s,
2H, aryl), 6.35 (s, 2H, aryl), 3.28 (s, 12H, Zr(NMe2)2), 2.75-2.58
(m, 16H, CH2), 2.52 (s, 12H, NMe2), 2.23 (s, 6H, CH3), 2.08 (s,
6H, CH3), 1.78 (s, 6H, CH3), 1.57-1.47 (m, 16H, CH2). 13C NMR
(C6D6): δ 180.2, 149.7, 140.5, 138.7, 137.5, 135.9, 134.5, 133.7,
131.4, 129.3, 129.0, 128.6, 128.3, 127.1, 125.6, 125.4, 116.6, 44.0,
43.0, 29.7, 28.6, 27.0, 23.3, 23.0, 22.8, 22.5, 21.1, 20.7, 19.4. IR
(KBr, cm-1): ν 2931 (m), 1634 (s), 1590 (s), 1530 (s), 1478 (s),
(16) Sheldrick, G. M. SADABS, Program for Empirical Absorption
Correction of Area Detector Data; University of Go¨ttingen: Go¨ttingen,Ger-
many, 1996.
(17) Sheldrick, G. M. SHELXL-97, Program for the Refinement of
Crystal Structure from Diffraction Data; University of Go¨ttingen: Go¨ttingen,
Germany, 1997.

1132 Organometallics, Vol. 28, No. 4, 2009
Scheme 1. Synthesis of Complexes 12, 15, 17, and 18
Zi et al.
1 equiv of acetic anhydride, followed by methylation of the
other amino group with an excess of formaldehyde (40%) in
the presence of acetic acid and NaBH3CN in THF, then removal
of the acetyl group with concentrated HCl in ethanol, gives (S)-
2-amino-2′-dimethylamino-1,1′-binaphthyl (1),15 (R)-2-(amino)-
2′-(dimethylamino)-6,6′-dimethyl-1,1′-biphenyl (2), or (R)-
5,5′6,6′7,7′8,8′-octahydro-2-amino-2′-(dimethylamino)-1,1′-
binaphthyl (3), respectively, in good yields with no racemization
(Schemes 1-3). The C1-symmetric pyridine ligand, (R)-2-
(pyridin-2-ylmethylamino)-2′-(dimethylamino)-6,6′-dimethyl-
1,1′-biphenyl (6H), is readily prepared in 82% yield by
condensation of pyridine-2-carboxaldehyde with 1 equiv of (R)-
2-(amino)-2′-(dimethylamino)-6,6′-dimethyl-1,1′-biphenyl (2) in
the presence of molecular sieves in toluene at 70 °C, followed
by reduction with an excess of NaBH4 in methanol (Scheme
2). Treatment of (S)-2-amino-2′-dimethylamino-1,1′-binaphthyl
(1), (R)-2-(amino)-2′-(dimethylamino)-6,6′-dimethyl-1,1′-biphe-
nyl (2), or (R)-5,5′6,6′7,7′8,8′-octahydro-2-amino-2′-(dimethy-
lamino)-1,1′-binaphthyl (3) with 1 equiv of diphenylphosphinoyl
chloride or mesitoyl chloride in the presence of an excess of
pyridine in toluene at reflux, after purification by flash column
chromatography, gives diphenylphosphoramides (S)-2-(diphe-
nylphosphinoylamino)-2′-(dimethylamino)-1,1′-binaphthyl (7H)
and (R)-2-(diphenylphosphinoylamino)-2′-(dimethylamino)-6,6′-
dimethyl-1,1′-biphenyl (8H) and mesitoylamides (S)-2-(mesi-
toylamino)-2′-(dimethylamino)-1,1′-binaphthyl (9H), (R)-2-
(mesitoylamino)-2′-(dimethylamino)-6,6′-dimethyl-1,1′-
biphenyl(10H),and(R)-5,5′6,6′7,7′8,8′-octahydro-2-(mesitoylamino)-
2′-(dimethylamino)-1,1′-binaphthyl (11H), respectively, in good
yields (Schemes 1-3).
niques and elemental analyses. Their 1H and 13C NMR spectra
indicate that they are nonsymmetrical on the NMR time scale,
which is consistent with their C1-symmetric structures. The
infrared spectra of these compounds exhibit peaks corresponding
to aromatic stretches in addition to N-H stretches at about 3390
cm-1 and strong CdO stretches at about 1670 cm-1 for 9H,
10H, and 11H. The solid-state structures of compounds 1, 2,
and 9H have been further confirmed by X-ray diffraction
analyses.
The single-crystal X-ray diffraction analyses show that 1, 2,
and 9H crystallize in a C1-symmetric distorted-tetrahedral
geometry (Figures 1-3). The twisting between the aryl rings
of torsion angles are 86.0(2)° for 1, 81.6(2)° for 2, and 63.8(2)°
for 9H, which are comparable to those found in (R)-1,1′-
binaphthyl-2,2′-diamine (63.9(6)°),18 (R)-2-(2-nitrophenylamino)-
2′-(dimethylamino)-6,6′-dimethyl-1,1′-biphenyl (73.1(2)°),19 and
4H (75.6(3)°).10b
Complexes. Group 4 metal amide complexes can be ef-
ficiently prepared via amine elimination reaction between
M(NMe2)4 and protic reagents.10c,d,20 It is rational to propose
(18) Jones, M. D.; Almeida Paz, F. A.; Davies, J. E.; Johnson, B. F. G.
Acta Crystallogr. 2003, E59, o910–o912.
(19) Song, H.; Gu, L.-N.; Zi, G. J. Organomet. Chem., published online
2009, http://dx.doi.org/10.1016/j.jorganchem.2008.12.059.
(20) For selected recent papers, see: (a) Diamond, G. M.; Jordan, R. F.;
Petersen, J. L. Organometallics 1996, 15, 4045–4053. (b) Hughes, A. K.;
Meetsma, A;.; Teuben, J. H. Organometallics 1993, 12, 1936–1945. (c)
Carpenetti, D. W.; Kloppenburg, L.; Kupec, J. T.; Petersen, J. L. Organo-
metallics 1996, 15, 1572–1581. (d) Zi, G.; Li, H.-W.; Xie, Z. Organome-
tallics 2002, 21, 3850–3855. (e) Tonzetich, Z. J.; Schrock, R. R.; Hock,
A. S.; Mu¨ller, P. Organometallics 2005, 24, 3335–3342. (f) Crust, E. J.;
Clarke, A. J.; Deeth, R. J.; Morton, C.; Scott, P. Dalton Trans. 2004, 4050–
4058. (g) Majumder, S.; Odom, A. L. Organometallics 2008, 27, 1174–
1177.
All the new ligands are air-stable, soluble in CH2Cl2, CHCl3,
toluene, and benzene, and slightly soluble in n-hexane. They
have been fully characterized by various spectroscopic tech-

Synthesis of Group 4 Metal Amides
Organometallics, Vol. 28, No. 4, 2009 1133
Scheme 2. Synthesis of Complexes 13, 14, 16, 19, and 20
Scheme 3. Synthesis of Complex 21
or (R)-2-(pyridin-2-ylmethylamino)-2′-(dimethylamino)-6,6′-di-
methyl-1,1′-biphenyl (6H) gives, after recrystallization from an
n-hexane solution, the monoligated chiral titanium amides
(4)Ti(NMe2)3 (12) and (6)Ti(NMe2)3 (13) and zirconium amide
(6)Zr(NMe2)3 (14), respectively, in good yields (Schemes 1 and
2). Under similar reaction conditions, reaction of Zr(NMe2)4
with 2 equiv of diphenylphosphoramide (S)-2-(diphenylphos-
phinoylamino)-2′-(dimethylamino)-1,1′-binaphthyl (7H) or (R)-
2-(diphenylphosphinoylamino)-2′-(dimethylamino)-6,6′-dimethyl-
1,1′-biphenyl (8H) affords, after recrystallization from a toluene
solution, the chiral bis-ligated zirconium amides (7)2Zr(NMe2)2 ·
2C7H8 (15 · 2C7H8) and (8)2Zr(NMe2)2 (16), respectively, in good
yields (Schemes 1 and 2). Treatment of M(NMe2)4 (M ) Ti,
Zr) with 2 equiv of mesitoylamide (S)-2-(mesitoylamino)-2′-
(dimethylamino)-1,1′-binaphthyl (9H), (R)-2-(mesitoylamino)-
2′-(dimethylamino)-6,6′-dimethyl-1,1′-biphenyl (10H), or (R)-
5,5′6,6′7,7′8,8′-octahydro-2-(mesitoylamino)-2′-(dimethylamino)-
1,1′-binaphthyl (11H) also gives, after recrystallization from a
toluene solution or n-hexane, the bis-ligated chiral titanium
amides
(9)2Ti(NMe2)2 · 2.75C7H8
(17 · 2.75C7H8)
and
(10)2Ti(NMe2)2 (19) and zirconium amides (9)2Zr(NMe2)2 · C7H8
(18 · C7H8), (10)2Zr(NMe2)2 (20), and (11)2Zr(NMe2)2 (21),
respectively, in good yields (Schemes 1-3).
These complexes are stable in a dry nitrogen atmosphere and
stable in C6D6 solution at or below 120 °C, while they are very
sensitive to moisture. These complexes are soluble in organic
solvents such as THF, DME, pyridine, toluene, and benzene
and only slightly soluble in n-hexane. They have been charac-
terized by various spectroscopic techniques and elemental
that the acidic proton in the ligands 4H, 6H, 7H, 8H, 9H, 10H,
and 11H would allow the similar amine elimination to occur
between 4H, 6H, 7H, 8H, 9H, 10H, or 11H and metal amides.
In fact, treatment of M(NMe2)4 with 2 equiv of (S)-2-(pyrrol-
2-ylmethyleneamino)-2′-(dimethylamino)-1,1′-binaphthyl (4H)
1
analyses. The H NMR spectra of 12, 13, and 14 support that

1134 Organometallics, Vol. 28, No. 4, 2009
Zi et al.
Table 2. Crystal Data and Experimental Parameters for Compounds 15-20
15 · 2C7H8
16
17 · 2.75C7H8
18 · C7H8
19
20
formula
fw
cryst syst
space group
a (Å)
C86H84N6O2P2Zr
1386.75
monoclinic
P21
11.056(2)
25.058(4)
13.143(2)
101.20(1)
3571.7(11)
2
C60H68N6O2P2Zr
1058.36
orthorhombic
P212121
14.553(1)
46.461(1)
12.577(1)
90
C87.25H92N6O2Ti
1304.57
monoclinic
P21
16.195(2)
10.901(1)
21.080(2)
97.10(1)
3693.1(6)
2
C75H78N6O2Zr
1186.65
orthorhombic
P212121
11.234(1)
16.093(1)
34.879(2)
90
C56H70N6O2Ti
907.08
monoclinic
P21
9.705(1)
27.557(2)
9.999(1)
107.22(1)
2554.2(3)
2
C56H70N6O2Zr
950.40
monoclinic
P21
9.684(2)
28.265(4)
9.898(2)
107.22(1)
2587.7(7)
2
b (Å)
c (Å)
ꢀ (deg)
V (Å3)
8503.8(4)
6
1.240
6305.6(7)
4
1.250
Z
Dcalc (g/cm3)
µ(Mo/KR)calc (mm-1
size (mm)
1.289
0.253
1.173
0.168
1.179
0.214
1.220
0.258
)
0.297
0.226
0.16 × 0.14
0.32 × 0.22
0.18 × 0.16
0.24 × 0.22
0.32 × 0.28
0.32 × 0.22
× 0.12
× 0.20
× 0.14
× 0.16
× 0.26
× 0.20
F(000)
1456
3336
1391
2504
972
1008
2θ range (deg)
no. of reflns, collected
no. of unique reflns
3.16 to 55.70
35 589
15 548
3.68 to 55.76
70 287
19 998
3.00 to 51.98
24 032
12 426
4.32 to 52.00
31 987
12 306
4.26 to 55.80
24 060
11 722
4.64 to 54.00
18 905
10 216
(Rint ) 0.0498)
14 178
(Rint ) 0.0374)
18 319
(Rint ) 0.0619)
8976
(Rint ) 0.0905)
10 845
(Rint ) 0.0395)
9239
(Rint ) 0.0631)
7739
no. of obsd reflns
abs corr (Tmax, Tmin
R
)
0.97, 0.96
0.040
0.94, 0.91
0.042
0.98, 0.97
0.070
0.96, 0.95
0.055
0.95, 0.93
0.035
0.95, 0.92
0.057
Rw
0.086
0.091
0.173
0.140
0.079
0.119
wR2 (all data)
0.093
0.094
0.187
0.162
0.083
0.143
gof
1.03
1.11
1.03
1.06
0.96
1.02
Table 3. Selected Bond Distances (Å) and Bond Angles (deg) for Compounds 12-20
12 (Ti)
13 (Ti)
14 (Zr)
15 (Zr)
16 (Zr)
17 (Ti)
18 (Zr)
19 (Ti)
20 (Zr)
M-N (av)
M-N(4)
2.047(5)
1.907(4)
1.944(5)
1.909(4)
2.016(2)
1.951(2)
1.938(2)
1.918(2)
2.152(4)
2.051(4)
2.078(4)
2.097(4)
2.170(2)
2.178(2)
2.029(4)
2.181(4)
2.029(2)
2.171(3)
M--N(5)
2.044(2)
2.059(2)
2.291(2)
Zr-P
2.058(2)
2.060(2)
2.268(2)
Zr-P
1.919(4)
1.907(4)
2.147(3)
Ti-C
2.076(4)
2.041(4)
2.243(3)
Zr-C
1.902(2)
1.905(2)
2.119(1)
Ti-C
2.039(3)
2.034(3)
2.222(3)
Zr-C
M-N(6)
M-O (av)
M-X (av)
2.892(1)
2.890(1)
2.549(4)
2.667(4)
2.529(2)
2.664(5)
sum angles of N(4)
sum angles of N(5)
sum angles of N(6)
torsion (aryl-aryl)
359.8(5)
359.2(5)
359.4(5)
79.2(6)
359.7(2)
360.0(2)
359.8(2)
88.3(3)
359.8(4)
360.0(4)
359.9(4)
87.2(6)
359.5(2)
359.6(2)
84.0(3)
84.0(3)
359.7(2)
359.8(2)
86.8(3)
85.4(3)
359.6(4)
357.3(4)
70.4(2)
69.9(4)
360.0(4)
359.8(5)
71.6(5)
69.2(5)
359.9(2)
360.0(2)
70.0(2)
69.7(2)
359.9(4)
360.0(4)
71.1(6)
68.6(6)
the ratio of amino group NMe2 to ligand anion 4 or 6 is 3:1.
The H NMR spectra of 15, 16 17, 18, 19, 20, and 21 support
The single-crystal X-ray diffraction analyses show that there is
one molecule (7)2Zr(NMe2)2 and two solvate toluene molecules
for 15, two molecules (8)2Zr(NMe2)2 for 16, four molecules
(9)2Ti(NMe2)2 and 11 solvate toluene molecules for 17, and one
molecule (9)2Zr(NMe2)2 and one solvate toluene molecule for 18
in the lattice. In each molecule of (7)2Zr(NMe2)2, (8)2Zr(NMe2)2,
(9)2M(NMe2)2, or (10)2M(NMe2)2, the substituted Me2N groups
are far away from the metal center, and the M4+ is σ-bound to
two nitrogen atoms and two oxygen atoms from the two ligands
7, 8, 9, or 10 and two nitrogen atoms from amino groups NMe2 in
a distorted-octahedron geometry (Figures 6-9) with the average
distance of M-N ranging from 2.029(2) to 2.029(4) Å for Ti and
from 2.170(2) to 2.181(4) Å for Zr, and the average distance of
M-O ranging from 2.119(1) to 2.147(3) Å for Ti and from
2.222(3) to 2.291(2) Å for Zr, respectively. The short distances of
M-NMe2 ranged from 1.902(2) to 1.919(4) Å for Ti (Ti-N(5)
and Ti-N(6)) and from 2.034(3) to 2.076(4) Å for Zr (Zr-N(5)
and Zr-N(6)), and the planar geometry around the N(5) and N(6)
nitrogen atoms indicates that both nitrogen atoms with sp2
hybridization are engaged in N(pπ)fM(dπ) interactions. The torsion
angles between the aryl rings range from 68.6(6)° to 86.8(3)°, which
are comparable to those found in 1 (86.0(2)°), 2 (81.6(2)°), 4H
(75.6(3)°),10b 9H (63.8(2)°), 12 (79.2(6)°), 13 (88.3(3)°), 14
(87.2(6)°), (R)-1,1′-binaphthyl-2,2′-diamine (63.9(6)°),18 and (R)-
2-(2-nitrophenylamino)-2′-(dimethylamino)-6,6′-dimethyl-1,1′-bi-
phenyl (73.1(2)°).19
1
that the ratio of amino group NMe2 to ligand anion 7, 8, 9, 10,
or 11 is 2:2 and establish that two toluene molecules for 15
and one toluene molecule for 18, respectively, cocrystallized.
These results are consistent with their 13C NMR spectra. The
solid-state structures of complexes 12-20 have been further
confirmed by X-ray diffraction analyses.
The single-crystal X-ray diffraction analyses confirm that 13
and 14 are isostructural and show that there are two
(6)M(NMe2)3 molecules incorporated into the lattice. In each
molecule of (4)Ti(NMe2)3 or (6)M(NMe2)3, the substituted Me2N
group is far away from the metal center, and the M4+ is σ-bound
to two nitrogen atoms from the ligand 4 or 6 and three nitrogen
atoms from amino groups NMe2 in a distorted-trigonal-bipy-
ramidal geometry (Figures 4 and 5) with the average distance
of Ti-N (2.047(5) Å) for 12, Ti-N (2.016(2) Å) for 13, and
Zr-N (2.152(4) Å) for 14, respectively. The short M-N(4),
M-N(5), and M-N(6) bond distances (1.907(4), 1.944(5), and
1.909(4) Å for 12, 1.951(2), 1.938(2), and 1.918(2) Å for 13,
2.051(4), 2.078(4), and 2.097(4) Å for 14) and the planar
geometry around the N(4), N(5), and N(6) nitrogen atoms
indicate that three nitrogen atoms with sp2 hybridization are
engaged in N(pπ)fTi(dπ) interactions. These structural data are
very close to those found in the literature.10c,d,20 The aryl rings
are twisted by 79.2(6)° for 12, 88.3(3)° for 13, and 87.2(6)° for
14, indicating they are almost perpendicular to each other.

Synthesis of Group 4 Metal Amides
Organometallics, Vol. 28, No. 4, 2009 1135
Table 4. Enantioselective Hydroamination/Cyclization Catalyzed by Group 4 Complexesa
a Conditions: C6D6 (0.70 mL), aminoalkene (0.16 mmol), catalyst (0.016 mmol), at 120 °C. bDetermined by 1H NMR based on p-xylene as the
internal standard. N.R. ) no reaction. cDetermined by 1H NMR of its diastereomeric (S)-(+)-O-acetylmandelic acid salt.5 N.A. ) not applicable.
dConditions: C6D6 (0.70 mL), aminoalkene (0.16 mmol), catalyst (0.016 mmol), at 90 °C.
Figure 1. Molecular structure of 1 (thermal ellipsoids drawn at
Figure 2. Molecular structure of 2 (thermal ellipsoids drawn at
the 35% probability level).
the 35% probability level).
Asymmetric Hydroamination/Cyclization. To examine the
catalytic ability of the complexes 12-21, the asymmetric
hydroamination/cyclization of unactivated terminal aminoalk-
enes has been tested under the conditions given in Table 4. The

1136 Organometallics, Vol. 28, No. 4, 2009
Zi et al.
Figure 3. Molecular structure of 9H (thermal ellipsoids drawn at
the 35% probability level).
Figure 6. Molecular structure of 15 (thermal ellipsoids drawn at
the 35% probability level).
Figure 4. Molecular structure of 12 (thermal ellipsoids drawn at
the 35% probability level).
Figure 7. Molecular structure of 16 (thermal ellipsoids drawn at
the 35% probability level).
Figure 8. Molecular structure of 17 (M ) Ti) and 18 (M ) Zr)
(thermal ellipsoids drawn at the 35% probability level).
Figure 5. Molecular structure of 13 (M ) Ti) and 14 (M ) Zr)
(thermal ellipsoids drawn at the 35% probability level).
conversion can be complete with little loss of ee value, but needs
a longer reaction time (Table 4, entry 8). Upon decreasing the
reaction temperature (from 120 to 90 °C), both the rate and the
ee value fall slightly (Table 4, entries 7 and 9). When the less
bulky ligand 10 is used (Table 4, entry 11), the rate increases
while the ee falls significantly. When the more bulky ligands 7
and 11 are used, both the rate and the ee value fall significantly
(Table 4, entries 4 and 13). Under similar reaction conditions,
no detectable hydroamination activity is observed for titanium
complexes 12, 13, 17, and 19 even at 120 °C for one week
results of the hydroamination/cyclization of 2,2-dimethylpent-
4-enylamine clearly show that the zirconium amides are active
catalysts for this transformation (Table 4, entries 3, 4, 5, 7, 11,
and 13), and the monoligated complex 14 shows the most
effective catalyst for this transformation, but the enantioselec-
tivity is rather poor (only up to 5.2%; Table 4, entry 3).
However, the bis-ligated complex 18 gives a noticeably better
ee value (72%; Table 4, entry 7), but the rate is slow. This

Synthesis of Group 4 Metal Amides
Organometallics, Vol. 28, No. 4, 2009 1137
be mentioned that there are few group 4 catalysts for this
transformation that give a significant ee (>90%) at all.9e,f
Conclusions
In conclusion, a new series of chiral titanium(IV) and
zirconium(IV) amides have been prepared from the reactions
between M(NMe2)4 (M ) Ti, Zr) and chiral ligands 4H, 6H,
7H, 8H, 9H, 10H, and 11H. All the zirconium amides displayed
good to excellent catalytic activity for the asymmetric hy-
droamination/cyclization of representative aminoalkenes, while
the titanium amides did not. The bis-ligated mesitoylamidate
zirconium complexes 18 and 20 are effective chiral catalysts
for this transformation; in some cases, the corresponding
heterocycles products have been obtained with good ee values
(up to 72%), while the bis-ligated diphenylphosphoramidate
zirconium complexes 15 and 16 have not. How to fully optimize
both the rate and selectivity still remains a question for
asymmetric hydroamination. It seems that very precise control
of the metal coordination sphere is required for this transforma-
tion to be a realistic prospect. Our ligand set using peripheral
biaryl coupled with mesitoylamide or diphenylphosphoramide
ligation in multidentate systems does not provide a successful
suitable coordination sphere to achieve a significant enantiose-
lectivity (>90% ee), in contrast to the chiral biphenyl-based
N2O2 ligand system.9e,f However, this modification should
significantly expand the range of possibilities in designing
catalysts not only for hydroamination but also for many other
reactions. Further optimization of the ligand architecture to
improve the enantiomeric excess for this transformation and the
exploration of these catalysts toward other types of transforma-
tions are still underway.
Figure 9. Molecular structure of 19 (M ) Ti) and 20 (M ) Zr)
(thermal ellipsoids drawn at the 35% probability level).
(Table 4, entries 1, 2, 6, and 10), and none of the complexes
described above are effective catalysts for the cyclization of
1-aminopent-4-ene into 2-methylpyrrolidine, presumably due to
a lack of a Thorpe-Ingold effect21 from the unsubstituted
aminoalkene. Also, none of the complexes are effective catalysts
for the cyclization of aminoalkenes containing secondary amine
groups such as the substrate 1-(N-methylamino)-2,2-dimethyl-
pent-4-ene into the corresponding heterocycles, which is
consistent with the amine elimination followed by a [2+2]
cycloaddition mechanism postulated by Bergman.9d Substrate
23a reacts fast, but the ee values are moderate (Table 4, entries
14-19). We are pleased to find that the formation of a six-
membered ring can also be accomplished with our zirconium
catalysts (Table 4, entries 20-25), and a moderate enantiose-
lectivity (up to 38%), mediated by the catalyst 18, has been
obtained (Table 4, entry 23). The enantiomeric excesses obtained
remain moderate to good in our observation; however, it should
Acknowledgment. This work was supported by the
National Natural Science Foundation of China (Grant No.
20602003) and Beijing Municipal Commission of Education.
Supporting Information Available: X-ray crystallographic data,
in CIF format, for 1, 2, 9H, and 12-20. This material is available
free of charge via the Internet at http://pubs.acs.org.
(21) (a) Beesley, R. M.; Ingold, C. K.; Thorpe, J. F. J. Chem. Soc. 1915,
107, 1080–1106. (b) Ingold, C. K. J. Chem. Soc. 1921, 119, 305–329.
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