Alkyllanthanum Biphenolate Complexes
FULL PAPER
in vacuo. The remaining yellow residue was dried in vacuo. Pentane
(2 mL) was added to the residue and the mixture was heated to 50
°C and left in a fridge overnight. The solvent was decanted at Ϫ30
°C, acetone bath) from a slightly yellow crystalline precipitate, and
the precipitate was washed with pentane (0.5 mL) and dried in va-
cuo. Yield 110 mg (35%). The crystals contain one equiv. of pen-
X-ray Crystallographic Study: Clear, colourless crystals of (R,R)-4
suitable for X-ray diffraction analysis were obtained by cooling a
concentrated pentane solution to Ϫ30 °C. Data were collected on
a
Nonius KappaCCD area detector. Crystal
data:
C62H102La2O4Si4·C5H12, Mr ϭ 1373.78, crystal size 0.10 ϫ 0.10 ϫ
0.10 mm, orthorhombic, space group P21212 (No. 18), a ϭ
tane per molecule of the dimer. 1H NMR (400.1 MHz, [D8]toluene, 16.3814(7) A, b ϭ 17.5277(5) A, c ϭ 12.9592(6) A, V ϭ 3721.0(3)
˚
˚
˚
3
A , Z ϭ 2, ρcalcd. ϭ 1.225 g cmϪ3, F(000) ϭ 1434, Mo-Kα radiation
˚
25 °C): δ ϭ 7.13 (br. s, 4 H, Biphen), 2.16 (br. s, 12 H, aryl-CH3),
1.53 (br. s, 12 H, aryl-CH3), 1.40 (br. s, 36 H, C(CH3)3], 0.30 [s, 18 (λ ϭ 0.71073 A), T ϭ 173(2) K, µ ϭ 1.237 mmϪ1, 8519 independent
˚
H, Si(CH3)3], Ϫ0.03 [s, 18 H, Si(CH3)3], Ϫ0.62 (s, 2 H, LaCH). 1H reflections measured, GOF ϭ 0.945, R [I Ͼ 2σ(I)] ϭ 0.0473, wR2
NMR (400.1 MHz, [D8]toluene, Ϫ30 °C): δ ϭ 7.24 (s, 2 H, Biphen),
7.08 (s, 2 H, Biphen), 2.22 (s, 6 H, aryl-CH3), 2.18 (s, 6 H, aryl-
(all data) ϭ 0. 1084, absolute structure parameter ϭ Ϫ0.04(2), larg-
est e-max, e-min ϭ 0.555 and Ϫ0.767 e·AϪ3. Cell parameters for
˚
CH3), 1.65 (s, 6 H, aryl-CH3), 1.55 (s, 6 H, aryl-CH3), 1.41 [s, 18 (R,R)-4 were obtained from 10 frames using a 10° scan and refined
H, C(CH3)3], 1.37 [s, 18 H, C(CH3)3], 0.33 [s, 18 H, Si(CH3)3], 0.07 with 4689 reflections. Lorentz, polarization, and empirical absorp-
[s, 18 H, Si(CH3)3], Ϫ0.63 (s, 2 H, LaCH) ppm. 13C{1H} NMR tion corrections were applied.[101,102] The space group was deter-
(100.6 MHz, [D8]toluene, Ϫ30 °C): δ ϭ 156.1, 150.3, 137.8, 137.3,
137.2, 137.0, 135.0, 133.4, 131.2, 130.1, 128.5, 126.6, (aryl), 55.0
(LaCH), 35.0 [C(CH3)3], 32.2, 30.7 [C(CH3)3], 20.0, 17.5 (aryl-
mined from systematic absences and subsequent least-squares re-
finement. The structures were solved by direct methods. The par-
ameters were refined with all data by full-matrix least-squares on
CH3), 4.8, 4.5 [Si(CH3)3] ppm. C62H102La2O4Si4·(C5H12) (1373.8): F2 using SHELXL-97.[103] Hydrogen atoms were fixed in idealized
calcd. C 58.58, H 8.36; found C 57.73, H 8.10.
positions using a riding model. Non-hydrogen atoms were refined
anisotropically. The methyl groups attached to C17 are disordered
and were refined with two independent orientations (position occu-
pation of 48.52% and 51.48%, respectively). Scattering factors and
∆fЈ and ∆fЈЈ values were taken from the literature.[104] Graphical
representations were prepared with ORTEP-III for Windows.[105]
CCDC-235041 contains the supplementary crystallographic data
for this paper. These data can be obtained free of charge at
www.ccdc.cam.ac.uk/conts/retrieving.html [or from the Cambridge
Crystallographic Data Centre, 12 Union Road, Cambridge CB2
1EZ, UK; Fax: ϩ44-1223-336-033; E-mail: deposit@ccdc.cam.ac.uk].
(R)-[La(Biphen){CH(SiMe3)2}(THF)3] [(R)-5]: THF (7.2 µL, 89
µmol, 3 equiv. per lanthanum) was added to a solution of (R,R)-4
(20 mg, 14.6 µmol) in [D6]benzene (0.5 mL). Removal of the solvent
in vacuo led to partial loss of THF, therefore the catalyst was al-
1
ways prepared in situ directly prior to use. H NMR (400.1 MHz,
[D6]benzene): δ ϭ 7.17 (s, 2 H, Biphen), 3.55 (br. m, 12 H, THF),
2.15 (s, 6 H, aryl-CH3), 1.74 (s, 6 H, aryl-CH3), 1.63 [s, 18 H,
C(CH3)3], 1.30 (br. m, 12 H, THF), 0.35 (s, 9 H, SiMe3), 0.33 (s, 9
H, SiMe3), Ϫ1.64 [s, 1 H, CH(SiMe3)2] ppm. 13C{1H} NMR
(100.6 MHz, [D6]benzene): δ ϭ 156.3, 138.3, 136.4, 130.7, 128.9,
124.4 (aryl), 68.9 (THF), 51.5 (LaCH), 35.2 [C(CH3)3], 30.7
[C(CH3)3], 25.4 (THF), 20.4 (aryl-CH3), 16.2 (aryl-CH3), 5.1
(SiMe3), 5.0 (SiMe3) ppm.
General Procedure for NMR-Scale Catalytic Hydroamination/Cycli-
zation Reactions: In a glovebox, a screw-cap NMR tube was
charged with 10 µmol of the catalyst, C6D6 (0.5 mL) and the sub-
strate (0.33 mmol) in that order. The NMR tube was then placed
in a pre-heated oil bath and conversion followed by 1H NMR spec-
troscopy (for acquisition parameters see below). Final conversion
(R)-[La(Biphen){N(SiHMe2)2}(THF)3] [(R)-6]: THF (6.3 µL, 78
µmol, 3.5 equiv. per lanthanum) was added to a solution of (R,R)-
4 (15 mg, 10.9 µmol) in [D8]toluene (0.5 mL). The solution was
kept at 25 °C for 30 min and then tetramethyldisilazane (4.0 µL,
23 µmol) was added. Removal of the solvent in vacuo led to partial
1
was determined by H NMR spectroscopy (disappearance of olef-
inic signals) and by GC analysis. Diastereomeric ratios of pyrroli-
dines 13 and 15 as well as piperidine 17 were determined by vac-
uum-transfer of all volatiles and subsequent 1H NMR spectro-
scopic analysis of characteristic signals.
1
loss of THF. H NMR (400.1 MHz, [D8]toluene, 25 °C): δ ϭ 7.14
3
(s, 2 H, Biphen), 5.00 (sept, JH,H ϭ 3.0 Hz, 2 H, SiH), 3.55 (m,
THF), 3.50 (br. m, THF), 2.17 (s, 6 H, aryl-CH3), 1.77 (s, 6 H,
General Procedure for Kinetic Catalytic Hydroamination/Cyclization
Reactions: In a glovebox, a screw-cap NMR tube was charged with
10 µmol of the catalyst, C6D6 (0.5 mL) and the substrate
(0.33 mmol) in that order. The NMR tube was then placed in the
thermostatted probe (Ϯ 0.5 °C) of the Bruker Avance 400 spec-
trometer. The conversion was monitored by 1H NMR spectroscopy
by following the disappearance of the olefinic signals of the sub-
strate relative to the internal standard CH2(SiMe3)2. NMR spectra
were taken at 5 min time intervals using the multizg script from the
Bruker XWin NMR software package. In order to ensure accurate
integration, a 10 s delay between 30° pulses was utilized (number
of scans ϭ 4, acquisition time ϭ 4 s). Substrate and catalyst con-
centration was verified by comparison of the integrals of character-
istic signals [olefinic signals for substrates; Si(CH3) signal of
CH2(SiMe3)2]. The linear part of the data (minimum two half-lives)
was fit by least-squares analysis and the turnover frequency (TOF)
was determined from the slope a. TOF ϭ a ϫ [subst]0/[cat]
aryl-CH3), 1.64 [s, 18 H, C(CH3)3], 1.38 (m, THF), 0.28 [d, 3JH,H ϭ
3
3.0 Hz, 6 H, SiH(CH3)2], 0.24 [d, JH,H ϭ 2.9 Hz, 6 H, SiH(CH3)2]
ppm. 13C{1H} NMR (100.6 MHz, [D8]toluene, 25 °C): δ ϭ 156.6,
139.1, 136.3, 131.4, 128.4, 123.9 (aryl), 68.6 (THF), 35.3 [C(CH3)3],
30.6 [C(CH3)3], 25.6 (THF), 16.2 (aryl-CH3), 3.0 [SiH(CH3)2], 2.9
[SiH(CH3)2] ppm.
(R,R)-[La(Biphen){N(SiHMe2)2}(THF)]2 [(R,R)-7]: THF (1.4 µL,
17.3 µmol, 1.2 equiv. per lanthanum) was added to a solution of
(R,R)-4 (10 mg, 7.3 µmol) in [D6]benzene (0.5 mL). The solution
was kept at 25 °C for 30 min and then tetramethyldisilazane (3.1
µL, 17.8 µmol) was added. The 1H and 13C NMR spectra show
1
broad signals for the biphenolate ligand at room temperature. H
NMR (400.1 MHz, [D6]benzene, 60 °C): δ ϭ 7.23 (s, 2 H, Biphen),
4.90 (br. sept, 2 H, SiH), 3.58 (br. m, THF), 3.50 (br. m, THF),
2.15 (br. s, 6 H, aryl-CH3), 1.80 (br. s, 6 H, aryl-CH3), 1.54 [br. s,
18 H, C(CH3)3], 1.33 (m, THF), 0.32 [m, 12 H, SiH(CH3)2] ppm.
13C{1H} NMR (100.6 MHz, [D6]benzene, 60 °C): δ ϭ 138.4, 137.3, General Procedure for NMR-Scale Catalytic Hydrosilylation Reac-
136.2, 129.6, 128.6, 124.7 (aryl), 69.3 (THF), 35.3 [C(CH3)3], 34.9
[C(CH3)3], 30.7 [C(CH3)3], 30.5 [C(CH3)3], 25.3 (THF), 20.0, 16.3 (R,R)-4 (5.0 mg, 3.6 µmol), C6D6 (0.5 mL), the olefin (0.30 mmol)
(aryl-CH3), 3.2 [SiH(CH3)2], 3.1 [SiH(CH3)2] ppm. and phenylsilane (33 mg, 0.30 mmol) in that order. The NMR tube
tions: In the glovebox, a screw-cap NMR tube was charged with
Eur. J. Inorg. Chem. 2004, 4091Ϫ4101
2004 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
4099