Table 1 Selected geometric parameters for crystalline b-diketinimatoaluminium methyls
Property
Deviation (Å) of Al and CH
Compound
av. Al–C/Å av. Al–N/Å C–Al–CA/°
N–Al–NA/°
from NC…CANA plane
[Al(LL)Me2]8 (LLNI, RNC6H3Pri2-2,6)
1.964(3)
1.928(2)
115.4(2)
96.18(9)
94.72(14)
97.1(2)
100.8(2)
102.6(2)
0.33, —
0.72, —
0.95, 0.12
0.75, 0.13
0.78, 0.13
[Al(LL)Me2]8 (LLNI, RNC6H4Me-4)
1.958(4)
1.959(5)
1.868(4)
1.872(4)
1.906(3)
1.921(4)
1.941(5)
1.951(5)
117.4(1)
111.3(2)
—
1
2
3
—
The NMR spectra of compounds 1–3 in C6D6 (1 and 3) or
CDCl3 (2) indicate that the solution structures of 1–3 are
identical to those in the crystal, except that in 1 there is only one
1H or 13C(1H) signal for the two methyl groups, indicating that
they undergo fast exchange.
The present results demonstrate once again [e.g.15 the
monomeric [Ce(LL)2Cl] (LL = J)] that the b-diketiminato
ligand J is exceptionally sterically demanding, having allowed
us to prepare the well separated ion pairs in 2 and 3; reactivity
and catalytic studies are in hand. This ligand can be fine-tuned
by varying the substituents in its skeleton.
We thank EPSRC for support.
Notes and references
Fig. 1 Molecular structure of 2 with selected bond distances (Å) and angles
(°) (see also Table 1). Cation: av. Si–N 1.787(3), Al–O(1) 1.875(3); N(2)–
Al–C(16) 123.2(2), N(1)–Al–C(16) 122.9(2), av. N–Al–O 100.0(2), C–Al–
O 103.4(2). Anion: B–C(27) 1.635(6), av. B–C(aryl) 1.656(6); C(28)–B–
C(34) 104.4(3), C(28)–B–C(40) 112.2(3), C(28)–B–C(27) 114.7(3).
‡
Crystallographic data for 1/2/3: C23H35AlN2Si2/C45H43AlBF15-
N2OSi2·0.5(C4H10O)/C50H42AlBF20N2OSi2·0.5(C4H10O),
422.69/1043.8/1197.9, triclinic for all, space group P1 for all, a
6.335(2)/12.016(3)/13.503(5), b = 12.139(3)/13.439(5)/14.557(11), c =
17.103(4)/16.409(7)/15.403(7) Å, a = 78.55(2)/99.44(3)/69.39(5), b =
M
=
=
¯
79.90(3)/91.80(3)/88.02(3),
g
=
74.84(3)/108.31(7)/74.04°,
U
=
1233.6(6)/2472(2)/2718(3) Å3, Z = 2/2/2, l(Mo-Ka) = 0.71073 Å, m =
0.19/0.19/0.19 mm21. Data were collected at 173(2) K on an Enraf Nonius
CAD4 diffractometer in the w–2q mode for the range of 2 < q < 25°. Final
residuals for 4338/8664/9546 independent reflections were wR2
0.235/0.201/0.214 and for the 3026/5806/6098 with I > 2s(I), R1
=
=
1999/705/ for crystallographic files in .cif format.
1 Selected references: J. D. Scollard, D. H. McConville and J. Vittal,
Macromolecules, 1996, 29, 5241; B. L. Small, M. S. Brookhart and
A. M. A. Bennett, J. Am. Chem. Soc., 1998, 120, 4049; G. J. Britovskek,
V. C. Gibson, B. S. Kimberley, P. J. Maddox, S. J. McTavish, G. A.
Solan, A. J. P. White and D. J. Williams, Chem. Commun., 1998, 849
and references therein.
2 M. P. Coles and R. F. Jordan, J. Am. Chem. Soc., 1997, 119, 8125.
3 M. Bruce, V. C. Gibson, C. Redshaw, G. A. Solan, A. J. P. White and
D. J. Williams, Chem. Commun., 1998, 2523.
Fig. 2 Molecular structure of 3 with selected bond distances (Å) and angles
(°) (see also Table 1). Cation av. Si–N 1.801(4), Al–O(1) 1.887(4); N(2)–
Al–C(22) 123.7(2), N(1)–Al–C(22) 122.8(2), av. N–Al–O 101.6(2), C–Al–
O 102.3(2). Anion av. B–C 1.653(4); C(27)–B–C(33) 113.5(4), C(27)–B–
C(39) 113.8(4), C(27)–B–C(45) 102.4(4).
4 E. Ihara, V. G. Young and R. F. Jordan, J. Am. Chem. Soc., 1998, 120,
8277.
5 D. Kottmair-Maieron, R. Lechler and J. Weidlein, Z. Anorg. Allg.
Chem., 1991, 593, 111; R. Lechler, H.-D. Hausen and J. Weidlein,
J. Organomet. Chem., 1989, 359, 1; M. P. Coles, D. C. Swenson, R. F.
Jordan and V. G. Young, Organometallics, 1997, 16, 5183.
6 S. L. Aeilts, M. P. Coles, D. C. Swenson, R. F. Jordan and V. G. Young,
Organometallics, 1998, 17, 3265.
7 H. V. R. Dias, W. Jin and R. E. Ratcliff, Inorg. Chem., 1995, 34,
6100.
8 B. Qian, D. L. Ward and M. R. Smith, Organometallics, 1998, 17,
3070.
9 M. P. Coles, D. C. Swenson, R. F. Jordan and V. G. Young,
Organometallics, 1998, 17, 4042.
10 N. Emig, H. Nguyen, H. Krautscheid, R. Re´au, J.-B. Cazaux and G.
Bertrand, Organometallics, 1998, 17, 3599.
11 C. E. Radzewich, M. P. Coles and R. F. Jordan, J. Am. Chem. Soc., 1998,
120, 9384.
12 P. B. Hitchcock, M. F. Lappert and D.-S. Liu, J. Chem. Soc., Chem.
Commun., 1994, 1699.
The molecular geometry of crystalline 1 (details to be
published in the full paper) and the two compounds
[Al(LL)Me2] (LL = I)8 are closely similar, Table 1. The
AlNCCCN fragment in 1 has the boat conformation, as
previously found inter alia in [Li(LL)]2 and Sn(LL)Me3,12
although sometimes this b-diketiminatometal moiety is planar,
as in [Co(LL)2]13 (LL = J).
The molecular structures of the cations of the crystalline salts
2 and 3 are illustrated in Fig. 1 (2) and 2 (3); the anions will be
described in the full paper. The four-coordinate aluminium
atom in each cation has a distorted monopyramidal (TMP)
geometry, with a similar distortion from tetrahedral to TMP.
The Al–C distances are significantly shorter in each cation than
in the neutral precursor 1, but the Al–N bonds are slightly longer
due to the widening of the N–Al–NA angle in 2 or 3 compared
with 1, Table 1. The remaining geometric parameters of the b-
diketiminato ligand are very similar in 1–3. The sum of the
angles at each nitrogen atom (of 1–3) is close to 360°. There is
no evidence of significant cation–anion interaction; the anion
structures are unexceptional.14
13 M. F. Lappert and D.-S. Liu, J. Organomet. Chem., 1995, 500, 203.
14 Cf. Y.-X. Chen, M. V. Metz, L. Li, C. L. Stern and T. J. Marks, J. Am.
Chem. Soc., 1998, 120, 6287 and references therein.
15 P. B. Hitchcock, M. F. Lappert and S. Tian, J. Chem. Soc., Dalton
Trans., 1997, 1945.
Communication 9/00003H
706
Chem. Commun., 1999, 705–706