Reactions of group 4 metal cyclopentadienyl trifluorides with a trimeric iminoalane

Article abstract of DOI:10.1021/om9800748

Reaction of CpMF₃ (M = Ti, Zr) with [MeAlN(2,6-ⁱPr₂C₆H₃)]₃ leads to fluorine-nitrogen exchange and the formation of isostructural adamantanelike cages. This reaction proceeds with activation of metal-fluorine bonds and can be regarded as a new route to aluminum-containing mixed group 4 amidofluorides.

Full text of DOI:10.1021/om9800748

Organometallics 1998, 17, 1919-1921
1919
Rea ction s of Gr ou p 4 Meta l Cyclop en ta d ien yl
Tr iflu or id es w ith a Tr im er ic Im in oa la n e
Helge Wessel, Carsten Rennekamp, Herbert W. Roesky,* Mavis L. Montero,
Peter Mu¨ller, and Isabel Uso´n
Institut fu¨r Anorganische Chemie der Universita¨t Go¨ttingen, Tammannstrasse 4,
37077 Go¨ttingen, Germany
Received February 3, 1998
Sch em e 1a
Summary: Reaction of CpMF3 (M ) Ti, Zr) with
[MeAlN(2,6-iPr2C6H3)]3 leads to fluorine-nitrogen ex-
change and the formation of isostructural adamantane-
like cages. This reaction proceeds with activation of
metal-fluorine bonds and can be regarded as a new
route to aluminum-containing mixed group 4 amido-
fluorides.
In recent years, the activation of a variety of C-F,1
Si-F,2 and P-F3 bonds has been described. It is
assumed that the dissociation of these bonds can be
markedly facilitated using an electrophilic support. In
this respect, metallocenes of group 4 elements have been
intensively investigated in the past few years.4,5 Reac-
tions of organometallic fluorides of group 4 with alkyl
derivatives of aluminum are of particular interest with
regard to the mechanism of homogeneous catalysis for
the polymerization of olefins. The formation of adducts
of group 4 metallocene halides with AlMe3 is assumed
to be the first step of activation of a polymerization cata-
lyst when AlMe3-containing methylaluminoxane (MAO)
is used. The subsequent methylation of the metallocene
centers is markedly facilitated by the electrophilic
support.
a
Ar ) (2,6-iPr2C6H3).
To understand the catalytic activity of these com-
pounds, it is necessary to examine whether a selective
activation of the metal-fluorine bond and exchange for
alkyl and amino groups, respectively, is possible using
aluminum compounds.
slightly orange to bright red until all of the solid has
dissolved (Scheme 1). The color change is typical for
nitrogen-containing titanium compounds and for Ti-F
activation,6 respectively. Compounds 2 and 3 can be
isolated in analytically pure form after recrystallization
from n-hexane. The compounds were characterized by
elemental analysis and mass, IR, and NMR spectro-
scopic measurements.8,9 Furthermore, the molecular
structures have been determined by X-ray crystal-
lography, Figures 1 and 2.10
Both structures 2 and 3 are very similar with slight
geometrical differences derived from the somewhat
longer bond distances for Zr as compared to Ti and the
more bulky substituents on the Cp ligand in the case of
3. The adamantane-like cores of the molecules are built
from one Al3F2N, one MAl2FN2, and two MAl2F2N six-
membered rings in a chair conformation with µ2-
bridging F and N atoms. Each aluminum atom is
methyl substituted, and a 2,6-iPr2C6H3-ligand binds to
each nitrogen atom. The metal on top of the cage (Ti
in 2, Zr in 3) binds to η5-C5H5 (2) and η5-C5H3(SiMe3)2
(3), respectively. All metal atoms are distorted tetra-
hedrally coordinated: The endocyclic angles are in the
range from 91.9(1)° (F(2)-Al(3)-N(3)) to 115.7(1)°
(N(1)-Al(3)-N(3)) in 2 and 91.80(6)° (F(3)-Zr(1)-N(2))
Recently, we reported on adducts of a titanium fluor-
ide oxide with AlMe3 containing activated Ti-F bonds.6
These products are formed as intermediates in the
methylation of compounds with sterically crowded ti-
tanium centers.
Herein, we report the reaction of an alumazene7 (1)
with CpTiF3 and η5-C5H3(SiMe3)2ZrF3.
The reaction of a suspension of 1 and CpTiF3 in
toluene at room temperature gives a color change from
(1) Plenio, H.; Diodone, R. J . Am. Chem. Soc. 1996, 118, 356.
(2) Walter, S.; Klingebiel, U. Coord. Chem. Rev. 1994, 130, 481.
(3) Driess, M.; Winkler, U.; Imhof, W.; Zsolnai, L.; Huttner, G. Chem.
Ber. 1994, 127, 1031.
(4) Brintzinger, H.-H.; Fischer, D.; Mu¨lhaupt, R.; Rieger, B.; Way-
mouth, R. Angew. Chem. 1995, 107, 1255; Angew. Chem., Int. Ed. Engl.
1995, 34, 1143.
(5) Chen, Y.-X.; Stern, C. L.; Yang, S.; Marks, T. J . J . Am. Chem.
Soc. 1996, 118, 12451.
(6) Yu, P.; Roesky, H. W.; Demsar, A.; Albers, T.; Schmidt, H.-G.;
Noltemeyer, M. Angew. Chem. 1997, 109, 1846; Angew. Chem., Int.
Ed. Engl. 1997, 36, 1766.
(7) Power, P. P.; Waggoner, K. M.; Hope, H. Angew. Chem. 1988,
100, 1765; Angew. Chem., Int. Ed. Engl. 1988, 27, 1699.
S0276-7333(98)00074-0 CCC: $15.00 © 1998 American Chemical Society
Publication on Web 04/18/1998

1920 Organometallics, Vol. 17, No. 10, 1998
Communications
F igu r e 1. X-ray structure of 2 with atomic numbering
scheme. Hydrogen atoms have been omitted for clarity.
Selected bond distances (Å): Ti(1)-N(2) 1.905(3), Ti(1)-
N(3) 1.875(3), Ti(1)-F(3) 2.028(2), Al(1)-N(1) 1.799(3),
Al(1)-F(1) 1.825(2), Al(1)-F(3) 1.773(2), Al(2)-N(2)
1.846(3), Al(2)-F(1) 1.791(2), Al(2)-F(2) 1.766(2), Al(3)-
N(1) 1.827(3), Al(3)-N(3) 1.934(3), Al(3)-F(2) 1.896(2).
F igu r e 2. X-ray structure of 3 with atomic numbering
scheme. Hydrogen atoms have been omitted for clarity.
Selected bond distances (Å): Zr(1)-N(2) 2.051(2), Zr(1)-
N(3) 1.998(2), Zr(1)-F(3) 2.125(1), Al(1)-N(1) 1.786(2),
Al(1)-F(1) 1.812(1), Al(1)-F(3) 1.786(1), Al(2)-N(2)
1.848(2), Al(2)-F(1) 1.795(1), Al(2)-F(2) 1.766(1), Al(3)-
N(1) 1.829(2), Al(3)-N(3) 1.944(2), Al(3)-F(2) 1.903(1).
to 117.41(8)° (N(1)-Al(3)-N(3)) in 3 and are smaller
than the exocyclic ones which vary from 107.3(2)° (F(1)-
Al(1)-C(1)) to 129.5(2)° (N(1)-Al(1)-C(1)) in 2 and
106.17(9)° (F(1)-Al(1)-C(1)) to 130.8(1)° (N(1)-Al(1)-
C(1)) in 3.
In summary, reactions of group 4 metal cyclopenta-
dienyl trifluorides lead to intramolecular fluorine-
nitrogen exchange, activation of metal-fluorine bonds,
and the formation of isostructural adamantane-like
cages. Moreover, the reported synthesis is a new route
to aluminum-containing mixed group 4 amidofluorides.
Ack n ow led gm en t. We are grateful for financial
support of the Deutsche Forschungsgemeinschaft, the
(8) 2: A solution of 1 (980 mg, 1.5 mmol) in toluene (30 mL) was
added to a suspension of CpTiF3 (255 mg, 1.5 mmol) in toluene (50
mL). The mixture was then stirred for 36 h at room temperature, until
all of the solids had dissolved. The solvent was removed in vacuo, and
the residue was treated with n-hexane (30 mL), affording 2 as a red
compound. Yield: 860 mg (70%). Mp: 180 °C. 1H NMR (C6D6): δ (ppm)
-1.04 (d, AlCH3, 3 H), -0.65 (m, AlCH3, 3 H), -0.45 (m, AlCH3, 3 H),
1.13-1.42 (m, CH3(iPr), 36 H), 3.00 (sept, CH(iPr), 1 H), 3.25 (sept,
CH(iPr), 1 H), 3.60 (sept, CH(iPr), 1 H), 3.85 (sept, CH(iPr), 2 H), 4.10
(sept, CH(iPr), 1 H), 5.84 (s, CpH, 2 H), 5.97 (s, CpH, 1 H), 6.18 (s,
CpH, 1 H), 6.60 (s, CpH, 1 H), 7.05 (m, arom H, 9 H). 19F NMR (C6D6):
δ (ppm) -158.8 (d, 1 F), -133.3 (m, 1 F), -131.8 (m, 1 F). MS EI (m/
e): 162 (ArH, 100). IR (ν, cm-1): 1587, 1425, 1307, 1252, 1229, 1207,
1167, 1107, 1038, 1019, 930, 888, 870, 818, 796, 781, 760, 733, 714,
686, 641, 600, 570, 533. Anal. Calcd for C44H65Al3F3N3Ti: C, 64.3; H,
7.9; N, 5.1. Found: C, 63.8; H, 8.0; N, 5.1. 3: A solution of 1 (980 mg,
1.5 mmol) in toluene (30 mL) was added dropwise to a solution of η5-
C5H4(SiMe3)2ZrF3 (540 mg, 1.5 mmol) in toluene (50 mL). The mixture
was then stirred for 12 h at room temperature. The solvent was
removed in vacuo, and the residue was treated with n-hexane (30 mL),
affording 3 as a slightly yellow product. Yield: 1.21 g (80%). Mp: 236
°C. 1H NMR (C6D6): δ (ppm) -1.20 (m, AlCH3, 3 H), -0.65 (m, AlCH3,
3 H), -0.50 (m, AlCH3, 3 H), 0.25 (s, Si(CH3)3, 18 H), 1.13-1.34 (m,
CH3(iPr), 36 H), 3.25 (sept, CH(iPr), 3 H), 4.00 (sept, CH(iPr), 3 H),
6.05 (m, CpH, 1 H), 6.60 (m, CpH, 1 H), 7.05 (m, arom H, 9 H), 7.40
(m, CpH, 1 H). 19F NMR (C6D6): δ (ppm) -137.5 (m, 1 F), -132.5 (m,
1 F), -126.4 (m, 1 F). MS EI (m/e): 1007 (M+, 20), 162 (ArH, 100). IR
(ν, cm-1): 1617, 1589, 1425, 1383, 1310, 1260, 1202, 1167, 1088, 1074,
1019, 919, 892, 838, 799, 766, 724, 707, 680, 640, 612, 556, 473, 432.
Anal. Calcd for C50H81Al3F3N3Si2Zr: C, 59.5; H, 8.0; N, 4.2. Found: C,
58.7; H, 7.9; N, 4.1. It is known in the literature that the analysis of
carbon in aluminum compounds is often incorrect due to the generation
of noncombustable aluminum carbide.9
(10) The crystals were mounted on a glass fiber in a rapidly cooled
perfluoropolyether.11 Diffraction data were collected on
a
Stoe-
Siemens-Huber four-circle diffractometer coupled to a Siemens CCD
area-detector at 133(2) with graphite-monochromated Mo KR
K
radiation (λ ) 0.710 73 Å), performing æ and ω scans. The structures
were solved by direct methods using SHELXS-9612 and refined against
F2 on all data by full-matrix least squares with SHELXL-97.13 All non-
hydrogen atoms were refined anisotropically. All hydrogen atoms were
included in the model at geometrically calculated positions and refined
using a riding model. The disordered Cp ring in 2 was modeled with
the help of similarity restraints for 1-2 and 1-3 distances and
displacement parameters as well as rigid bond restraints for anisotropic
displacement parameters. The final fractional atomic coordinates are
given in the Supporting Information. Crystallographic data for 2:
C
44H65Al3F3N3Ti, M ) 821.83, crystal size: 0.30 × 0.10 × 0.05 mm3,
triclinic, P1h, unit cell dimensions a ) 9.284(2) Å, b ) 13.236(3) Å, c )
20.435(4) Å, R ) 75.53(3)°, â ) 85.01(3)°, γ ) 69.77(3)°, unit cell volume
2281.4(8) Å3, Z ) 2, Fcalcd ) 1.196 g cm-1, µ ) 0.290 mm-1; total number
of reflections measured 42 698, unique 7675 (Rint ) 0.0710). Data/
restraints/parameters: 7675/236/547. Final R indices: R1 ) 0.0682,
wR2 ) 0.1091 on data with I > 2σ(I) and R1 ) 0.1032, wR2 ) 0.1246
on all data, goodness-of-fit S ) 1.216; weighting scheme w-1 ) σ2(Fo)2
+ (0.0049P)2 + 4.4342P; largest difference peak and hole 0.596 and
-0.475 e A-3. Crystallographic data for 3‚0.5C6H14
: C53H88Al3F3N3-
Si2Zr, M ) 1052.64, crystal size 0.40 × 0.20 × 0.20 mm3 triclinic, P1h,
unit cell dimensions a ) 12.488(3) Å, b ) 12.638(3) Å, c ) 20.838(8) Å,
R ) 91.42(2)°, â ) 90.88(2)°, γ ) 117.524(9)°, unit cell volume 2914(2)
Å3, Z ) 2, Fcalcd ) 1.200 g cm-1, µ ) 0.319 mm-1; total number of
reflections measured 44 920, unique 13 269 (Rint ) 0.0383). Data/
restraints/parameters: 13269/0/620. Final R indices: R1 ) 0.0388, wR2
) 0.0765 on data with I > 2σ(I) and R1 ) 0.0536, wR2 ) 0.0825 on all
data, goodness-of-fit S ) 1.094. (R1 ) ∑||Fo| - |Fc||/∑|Fo|, wR2 )
[∑w(Fo2 - Fo2)2/∑w(Fo2)2]1/2, S ) [∑w(Fo2 - Fc2)2/∑(n - p)]1/2); weighting
scheme w-1 ) σ2(Fo)2 + (0.0144P)2 + 3.0498P; P ) [Fo2 + 2Fc2]/3; largest
(9) Paciorek, K. J . L.; Nakahara, J . H.; Hoferkamp, L. A.; George,
C.; Flippen-Anderson, J . L.; Gilardi, R.; Schmidt, W. R. Chem. Mater.
1991, 3, 82.
difference peak and hole: 0.405 and -0.303 e A-3
(11) Kottke, J .; Stalke, D. J . Appl. Crystallogr. 1993, 26, 615.
.

Communications
Organometallics, Vol. 17, No. 10, 1998 1921
Su p p or tin g In for m a tion Ava ila ble: Text giving details
of the X-ray crystal structure studies and tables of crystal
structure determination data, atomic coordinates, anisotropic
thermal parameters, and bond lengths and angles for com-
pounds 2 and 3 (18 pages). Ordering information is given on
any current masthead page.
Witco GmbH, Bergkamen, the Bundesministerium fu¨r
Bildung und Forschung, and the Go¨ttinger Akademie
der Wissenschaften. H.W. and C.R. are grateful to the
Fonds der Chemischen Industrie for a fellowship.
(12) Sheldrick, G. M. Acta Crystallogr., Sect. A 1990, 46, 467.
(13) Sheldrick, G. M. SHELXS 96; University of Go¨ttingen: Go¨t-
tingen, Germany, 1996.
OM9800748