Inorganic Chemistry Communications 13 (2010) 666–670
Inorganic Chemistry Communications
Synthesis, structure, and catalytic activity of group 4 complexes with new chiral
binaphthyldiamine-based ligands
Li Xiang a,1, Furen Zhang a,1, Jiaxin Zhang a, Haibin Song b, Guofu Zi a,
⁎
a
Department of Chemistry, Beijing Normal University, Beijing 100875, China
b
State Key Laboratory of Elemento-Organic Chemistry, Nankai University, Tianjin 300071, China
a r t i c l e i n f o
a b s t r a c t
Article history:
Five group 4 metal complexes (1)2Zr(NMe2)2 (5), (2)2Ti(NMe2)2 (6), (2)2Zr(NMe2)2 (7), (3)2Zr (8) and
(4)2Ti(NMe2)2 (9) have been readily prepared from the reaction between M(NMe2)4 (M=Ti, Zr) and
chiral binaphthyldiamine-based ligands, (R)-2,2′-bis(diphenylthiophosphoramino)-1,1′-binaphthyl (1H2),
(R)-5,5′,6,6′,7,7′,8,8′-octahydro-2,2′-bis(diphenylthiophosphoramino)-1,1′-binaphthyl (2H2), (R)-5,5′,6,6′,7,7′,8,8′-
octahydro-2,2′-bis(methanesulphonylamino)-1,1′-binaphthyl (3H2), and C1-symmetric ligand, (R)-2-(mesitylene-
sulphonylamino)-2′-(dimethylamino)-1,1′-binaphthyl (4H). All the complexes have been characterized by various
spectroscopic techniques, elemental analyses and X-ray diffraction analyses. The zirconium amides are active
catalysts for the asymmetric hydroamination/cyclization of aminoalkenes, affording cyclic amines in good yields with
moderate ee (enantiomeric excess) values.
Received 20 January 2010
Accepted 2 March 2010
Available online 11 March 2010
Keywords:
2,2′-Diamino-1,1′-binaphthyl
Chiral group 4 metal complexes
Synthesis
Crystal structure
© 2010 Elsevier B.V. All rights reserved.
Asymmetric hydroamination/cyclization
Chiral group 4 metal complexes based on non-Cp multidentate
ligands have received growing attention in the past decades [1–13].
One of the initial driving forces for this work is the interest in the
development of catalysts for intramolecular asymmetric alkene
hydroamination [10–13], because the hydroamination is a highly
atomic economical process in which an amine N–H bond 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. Although chiral catalysts based
on group 4 metals for asymmetric alkene hydroamination have been
intensively studied in recent years [14–24], only a small number of
highly enantioselective reactions (N90% ee) have been reported
[19,20]. Thus, the development of new group 4 metal catalysts for
asymmetric alkene hydroamination is a desirable and challenging goal.
Recently, we have developed a series of Zr(IV) and lanthanide
complexes with chiral biaryl-based nitrogen-containing multidentate
ligands, and found that they are effective catalysts for the asymmetric
hydroamination/cyclization, in which excellent enantioselectivities (up
to 93% ee) have been obtained [25–34]. In our endeavors to further
explore the chiral biaryl ligand system, we have recently extended our
research work to new ligands, (R)-2,2′-bis(diphenylthiophosphora-
mino)-1,1′-binaphthyl (1H2), (R)-5,5′,6,6′,7,7′,8,8′-octahydro-2,2′-bis
(diphenylthiophosphoramino)-1,1′-binaphthyl (2H2), (R)-5,5′,6,6′,7,7′,
8,8′-octahydro-2,2′-bis(methanesulphonylamino)-1,1′-binaphthyl
(3H2), and C1-symmetric ligand, (R)-2-(mesitylenesulphonylamino)-
2′-(dimethylamino)-1,1′-binaphthyl (4H), which are derived from (R)-
2,2′-diamino-1,1′-binaphthyl. We report herein the synthesis and
properties of the chiral ligands, their use in the coordination chemistry
of titanium(IV) and zirconium(IV), and the applications of the resulting
complexes as catalysts for the asymmetric hydroamination/cyclization
of aminoalkenes.
Treatment of the starting material (R)-2,2′-diamine-1,1′-binaphthyl
or (R)-5,5′,6,6′,7,7′,8,8′-octahydro-2,2′-diamine-1,1′-binaphthyl with 2
equiv of diphenylthiophosphinic chloride or methanesulphonyl chlo-
ride in the presence of an excess of pyridine in toluene at reflux gives,
after purification by flash column chromatography, the C2-symmetric
ligands, (R)-2,2′-bis(diphenylthiophosphoramino)-1,1′-binaphthyl
(1H2), (R)-5,5′,6,6′,7,7′,8,8′-octahydro-2,2′-bis(diphenylthiophosphor-
amino)-1,1′-binaphthyl (2H2) and (R)-5,5′,6,6′,7,7′,8,8′-octahydro-
2,2′-bis(methanesulphonylamino)-1,1′-binaphthyl (3H2), respectively,
in good yields (Schemes 1–2). Of course, the C1-symmetric ligand, (R)-
2-(mesitylenesulphonylamino)-2′-(dimethylamino)-1,1′-binaphthyl
(4H), is also readily prepared in 84% yield by reaction of (R)-2-amino-2′-
(dimethylamino)-1,1′-binaphthyl with 1 equiv of mesitylenesulphonyl
chloride in the presence of an excess of pyridine in toluene at reflux,
followedbypurificationwithflashcolumnchromatography(Scheme 3).
All new ligands are air-stable, and are soluble in CH2Cl2, CHCl3, toluene
and benzene, and slightly soluble in n-hexane. They have been fully
characterized by various spectroscopic techniques, and elemental
analyses. The 1H and 13C NMR spectra of 1H2, 2H2 and 3H2 indicate
that they are symmetrical on the NMR timescale, which are consistent
with their C2-symmetric structures. And the 1H and 13C NMR spectra of
4H confirm that it is non-symmetrical on the NMR timescale consistent
with its C1-symmetric structure. The infrared spectra of these com-
pounds exhibit peaks corresponding to aromatic stretches in addition to
⁎
Corresponding author. Tel.: +86 10 5880 7843; fax: +86 10 5880 2075.
These authors contributed equally to this work.
N–H stretches at about 3300 cm−1
.
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