(
)
454
V.C. Gibson et al.rJournal of Organometallic Chemistry 550 1998 453–456
˚
Ž .
A
Fig. 1. The molecular structure of 1. Key bond distances
and
Ž .
Ž .
Ž .
Ž .
Ž
Ž .
.
Ž .
Ž .
Ž .
angles 8 : Al–N 1.919 2 , Al–C 15 1.958 4 , Al–C 16 1.970 5 ,
X
Ž .
Ž .
Ž .
N–C 1 1.362 4 , N–C 2 1.442 3 ; N–Al–N 84.3 2 , C 15 –Al–
Ž
.
Ž .
C 16 113.4 2 .
˚
Ž .
Fig. 2. The molecular structure of 2. Key bond distances
A
and
Ž .
Al–C 2 1.970 2 , N 3 –C 8 1.344 2 , N 10 –C 9 1.458 2 , C 8 –
Ž . Ž . Ž . Ž . Ž .
Ž
.
angles 8 : Al–N 3 1.983 2 , Al–N 10 1.837 2 , Al–C 1 1.960 2 ,
Ž . Ž . Ž . Ž . Ž . Ž . Ž . Ž .
C 9 1.512 2 ; N 3 –Al–N 10 84.48 6 , C 1 –Al–C 2 114.41 10 .
Ž
.
plexes. Crystals of 1 suitable for an X-ray crystal
Ž .
Ž . Ž .
Ž
.
Ž . Ž .
Ž .
Ž .
3
structure determination were grown from acetonitrile
at room temperature. The asymmetric complex crys-
tallises in the centrosymmetric space group Pnma with
four molecules in the unit cell, thus requiring the
molecule to have Cs symmetry about a plane passing
through the aluminium and its two methyl substituents
A potentially powerful development of this approach
is its extension to hybrid mono-anionic ligand systems.
w
For example, treatment of the pyridyl-imine ArN5CH-
x
2-py with trimethylaluminium affords a racemic mix-
Ž
.
Fig. 1 . As a consequence the position of the ‘trans-
ture of the two enantiomers of the pyridyl-amide com-
via a rearrange-
ment process that is presumed to be analogous to that
5
w
Ž
.x
ferred’ methyl group C 14 is indeterminate, being
w
Ä
Ž
.
4x Ž .
plex AlMe2 ArN-CH Me -2-py 2
X
4
Ž .
Ž .
either on C 1 or C 1 . The coordination geometry at
aluminium is distorted tetrahedral with angles ranging
operating in the formation of 1. Crystals of 2 suitable
6
Ž .
Ž .
between 84.3 2 and 114.8 1 8, the former being due to
the bite of the chelating imino-amide ligand. The het-
erometallocyclic ring has a slightly folded geometry
for an X-ray structure determination were readily
Ž
grown from acetonitrile at room temperature Tables
.
1–5 . The asymmetric unit contains four molecules of
˚
with the aluminium atom lying 0.32 A out of the plane
the metal complex. The molecular structure is shown in
Fig. 2 and reveals the chiral nature of the ligand, though
of the other four atoms. The 2,6-diisopropylphenyl rings
are each rotated by ca. 858 out of the metallocyclic ring
plane, in contrast to derivatives containing sterically
unhindered phenyl substituents in which one phenyl
5 An analogous procedure to that described for the synthesis of
compound 1 was employed, affording pale-yellow cubes of 2 in ca.
70% isolated yield. Selected spectroscopic data for 2: 1H NMR
w x
group is virtually coplanar with the AlN2C2 ring 6 .
There is nothing noteworthy in the packing of the
molecules.
Ž
.
Ž
.
Ž
.
C6 D6, 500 MHz d: y0.34 s, 3H, Al Me , y0.18 s, 3H, Al Me ,
3
3
Ž
.
Ž
1.18 d, 3H, JHH 6.6 Hz, CH Me , 1.24 d, 3H, JHH 6.8 Hz,
CH Me2 , 1.29 d, 3H, JHH 6.8 Hz, CH Me2 , 1.39 d, 3H, JHH 6.9
3
3
.
Ž
.
Ž
.
3
.
Ž
Ž
Hz, CH Me2 , 1.42 d, 3H, JHH 6.8 Hz, CH Me2 , 3.27 spt, 1H,
3 Crystal data for 1: C29 H44 N2 Al, Ms447.6, orthorhombic,
JHH 6.8 Hz, C H Me2 , 4.28 spt, 1H, JHH 6.9 Hz, C H Me2 , 4.51
3
3
.
Ž
.
3
3
Ž
.
Ž .
Ž .
Ž
. Ž . Ž
space group Pnma no. 62 , as12.516 1 , bs21.403 2 , cs
q, 1H, JHH 6.6 Hz, C H Me , 6.25 m, 1H, pyH , 6.48 d, 1H, JHH
3
˚
˚
Ž .
Ž .
Ž
.
Ž
.
Ž
.
Ž
10.541 1 A, Vs2823.7 4 A , Zs4 the molecule has crystallo-
8.2 Hz, pyH , 6.74 m, 1H, pyH , 7.23 m, 2H, aryl , 7.29 m, 1H,
13
y3
y1
.
Ž
.
.
Ž
.
Ž
.
graphic Cs symmetry , Dc s1.053 g cm , m Cu–Ka s7.37 cm
,
aryl , 7.58 m, 1H, pyH . C NMR C6 D6, 100.6 MHz d: y9.23
q
Ž
.
Ž
.
Ž
.
Ž
.
Ž
.
.
F 000 s980. A yellow prism of dimensions 0.33=0.27=0.20 mm
was used. 2153 independent reflections respectively were measured
on a Siemens P4 rotating anode diffractometer at 213 K with Cu–Ka
s, Al Me , y6.17 s, Al Me . M.S. E.I. : 338 M
6 Crystal data for 2: C21H31N2 Al, Ms338.5, monoclinic, space
Ž
.
Ž . Ž . Ž .
group P21 rn no. 14 , as14.420 2 , bs9.296 1 , cs16.879 2
3
y3
˚
˚
Ž .
.
Ž
.
Ž .
radiation graphite monochromator using v-scans. The structure was
solved by the heavy atom method and all the non-hydrogen atoms
were refined anisotropically using full-matrix least-squares based on
F2 to give R1s0.064, wR2 s0.157 for 1657 independent observed
A, b s112.69 1 8, Vs2087.5 3 A , Zs4, Dc s1.077 g cm
,
y1
Ž
.
Ž
m Cu–Ka s8.57 cm , F 000 s736. A yellow prism of dimen-
sions 0.83=0.67=0.67 mm was used. 3373 independent reflections
respectively were measured on a Siemens P4 rotating anode diffrac-
w<
<
Ž< <.
x
Ž
.
reflections Fo )4s Fo , 2u F1208 and 155 parameters respec-
tometer at 203 K with Cu–Ka radiation graphite monochromator
using v-scans. The structure was solved by the heavy atom method
and all the non-hydrogen atoms were refined anisotropically using
full-matrix least-squares based on F2 to give R1s0.046, wR2 s
tively.
4 Analysis of the thermal vibration parameters of this atom clearly
indicate that its occupancy should be 0.5, and hence the molecular
image we observe is a consequence of the space group symmetry and
the true structure has only one of the ring carbon atoms substituted.
w<
<
Ž< <.
0.116 for 2923 independent observed reflections Fo )4s Fo ,
2u F1288 and 218 parameters respectively.
x
Gibson, Vernon C.
