Tris[(pentafluorophenyl)trimethylsilylamido](tetrahydrofuran) samarium(III)

Article abstract of DOI:10.1107/S0108270100008775

The effects of electrophilic metal-amido complexes as catalysts for olefin polymerization were investigated. The structure of the monotetrahydrofuran adducts and the difference in C-F and C-H bonds with samarium was developed. The interactions between amido ligands with the metal center by the ortho-F atoms from two pentafluorophenyl groups were analyzed. The samarium metal center was coordinated by the three nitrogen atoms of the amido ligands in a highly distorted tetrahedral geometry.

Full text of DOI:10.1107/S0108270100008775

metal-organic compounds
Acta Crystallographica Section C
Crystal Structure
Communications
coordinated in a highly distorted tetrahedral geometry by the
three N atoms of the amido ligands and the O atom of the thf
ligand. The largest deviations from tetrahedral geometry are
found in the rather acute N3ÐSm1ÐO1 angle of 86.14 (13)ꢀ
and the signi®cantly larger N2ÐSm1ÐO1 angle of
ISSN 0108-2701
Tris[(pentafluorophenyl)trimethyl-
silylamido](tetrahydrofuran)-
samarium(III)
Damon R. Click,a Brian L. Scottb and John G. Watkinb*
aDepartment of Chemistry, Indiana University, Bloomington, IN 47405, USA, and
bCST-18, MS J514, Los Alamos National Laboratory, Los Alamos, New Mexico
87545, USA
137.14 (13)ꢀ. The SmÐN distances of 2.299 (4), 2.338 (4) and
Correspondence e-mail: jwatkin@lanl.gov
Ê
2.365 (4) A are very similar to those of 2.329 (8), 2.330 (7) and
Ê
2.362 (8) A found in the base-free analog [Sm{N(C6F5)(Si-
Received 14 February 2000
Accepted 22 June 2000
Me3)}3] (Click et al., 1999), while the SmÐO distance of
Ê
2.446 (3) A to the thf ligand is comparable with those found in
other thf adducts of SmIII (Clark et al., 1996; Butcher et al.,
1999).
In the title complex, [Sm(C9H9F5NSi)3(C4H8O)], the Sm metal
center is coordinated in a highly distorted tetrahedral
geometry by the three N atoms of the amido ligands and by
the O atom of the tetrahydrofuran ligand. Principal bond
In addition to the amido and thf ligands, signi®cant inter-
actions with the metal center are also made by the ortho-F
atoms from two penta¯uorophenyl groups [Sm1Á Á ÁF11 =
Ê
lengths include: SmÐN 2.299 (4), 2.339 (4) and 2.366 (4) A,
Ê
and SmÐO 2.446 (3) A, close SmÁ Á ÁF contacts of 2.536 (3)
Ê
2.536 (3) and Sm1Á Á ÁF17 = 2.555 (3) A] and by the CÐH
Ê
and 2.556 (3) A, and an `agostic' SmÁ Á ÁC interaction of
Ê
bonds of one methyl group [Sm1Á Á ÁC1 = 3.154 (4) A]. The
Ê
3.154 (4) A.
SmÁ Á ÁF interactions are very similar in magnitude to those of
Ê
2.561 (6), 2.566 (5) and 2.587 (6) A observed in the base-free
Comment
complex (Click et al., 1999), while the SmÁ Á ÁC1 agostic inter-
action distance is typical of those observed in many f-element
complexes containing bis(trimethylsilyl)amido ligands (Jeske
et al., 1985; Schaverien et al., 1989). The third penta¯uoro-
phenyl group features no CÐFÁ Á ÁSm interactions closer than
The chemistry of transition metals coordinated by mono-, di-
and triamido ligands has recently generated a considerable
amount of interest due to many interesting observations of
catalytic activity (Baumann et al., 1997), small molecule acti-
vation (Johnson et al., 1998) and unusual coordination modes
of neutral ligands (Roussel & Scott, 1998). A number of these
studies have involved amido ligands which have electron-
withdrawing ¯uorophenyl groups directly attached to nitrogen
(Rosenberger et al., 1997; Memmler et al., 1996). We are
currently interested in the chemistry of highly electrophilic
metal±amido complexes as potential catalysts for ole®n poly-
merization. We have recently described the structural char-
acterization of a series of lanthanide complexes bearing highly
¯uorinated amido ligands and have shown that the electro-
philic metal centers entered into multiple close contacts with
both the CÐF and CÐH bonds of the ligands (Click et al.,
1999). In one of these molecules, [Sm{N(C6F5)(SiMe3)}3], the
metal center displayed signi®cant interactions with the three
ortho-F atoms of the penta¯uorophenyl groups and with three
separate methyl groups from the trimethylsilyl portion of the
ligands. We report here a structural study of the monotetra-
hydrofuran (thf) adduct, i.e. [Sm{N(C6F5)(SiMe3)}3](thf), (I),
and describe the differences in CÐFÁ Á ÁSm and CÐHÁ Á ÁSm
interactions between the base-free and single-Lewis-base
adducts.
Ê
3.915 (3) A, while the next-closest SmÁ Á ÁC interactions are
Ê
Ê
made by C8 at 3.623 (4) A and C6 at 3.761 (4) A. The metal
center may therefore be considered a seven-coordinate
Figure 1
ORTEP plot (Johnson, 1965; 30% probability ellipsoids) showing the
molecular structure of (I) and the atom-numbering scheme. F atoms,
other than those interacting with the metal center, have been omitted for
clarity, as have all the H atoms.
Complex (I) crystallizes in space group P21/c with no
unusual intermolecular contacts. The Sm metal center is
ꢁ
Acta Cryst. (2000). C56, 1095±1096
# 2000 International Union of Crystallography Printed in Great Britain ± all rights reserved 1095

metal-organic compounds
Ê
The H-atom positions were idealized, with CÐH = 0.96 A for
Ê
methyl and 0.97 A for methylene and were re®ned using a riding
moiety, although the coordination geometry of the ON3F2C
donor-atom set does not de®ne any readily identi®able
geometry. As previously mentioned, the base-free complex
[Sm{N(C6F5)(SiMe3)}3] features a nine-coordinate geometry
with an N3F3C3 donor-atom set, and thus the coordination of a
single thf molecule has displaced two SiÐCÁ Á ÁSm interactions
and one CÐFÁ Á ÁSm interaction.
model, with isotropic displacement parameters set to 1.5 (methyl) or
1.2 (methylene) times the equivalent Uiso of the atom to which they
were bonded.
Data collection: XSCANS (Siemens, 1994); cell re®nement:
XSCANS; data reduction: XSCANS; program(s) used to solve
structure: SHELXS86 (Sheldrick, 1985); program(s) used to re®ne
structure: SHELXL97 (Sheldrick, 1997); molecular graphics:
SHELXL97; software used to prepare material for publication:
SHELXL97.
Experimental
[Sm{N(SiMe3)2}3] (0.500 g, 0.792 mmol) was dissolved in toluene
(10 ml) and N-trimethylsilylpenta¯uoroaniline (0.868 g, 3.40 mmol)
was added. The reaction was stirred at room temperature for 18 h and
the resulting solution ®ltered through a Celite pad. The ®ltrate was
pumped to dryness and the resulting yellow±orange solid was washed
three times with hexane. The solid was then redissolved in toluene
(10 ml), thf (0.1 ml) was added, and the solution was placed in a
freezer at 238 K to produce crystals of (I) over a period of several
days. The crystals were isolated, washed with hexane and allowed to
dry. Analysis calculated for C31H35N3F15Si3Sm: C 37.79, H 3.58, N
4.26%; found: C 37.03, H 3.49, N 4.04%.
We thank Dr David L. Clark for providing funding to DRC.
Los Alamos National Laboratory is operated by the Univer-
sity of California for the US Department of Energy under
Contract W-7405-ENG-36.
Supplementary data for this paper are available from the IUCr electronic
archives (Reference: FR1269). Services for accessing these data are
described at the back of the journal.
Crystal data
3
[Sm(C9H9F5NSi)3(C4H8O)]
Mr = 985.24
Dx = 1.675 Mg m
Mo Kꢁ radiation
Cell parameters from 31
re¯ections
Monoclinic, P21=c
Ê
Ê
References
a = 17.447 (3) A
b = 10.467 (2) A
ꢂ = 13.0±13.5ꢀ
ꢃ = 1.70 mm
T = 203 (2) K
Baumann, R., Davis, W. M. & Schrock, R. R. (1997). J. Am. Chem. Soc. 119,
3830±3831.
Butcher, R. J., Clark, D. L., Gordon, J. C. & Watkin, J. G. (1999). J. Organomet.
Chem. 577, 228±237.
1
Ê
c = 21.934 (4) A
ꢀ = 102.77 (1)ꢀ
V = 3906.5 (12) A
Z = 4
3
Ê
Block, yellow
0.45 Â 0.33 Â 0.25 mm
Clark, D. L., Gordon, J. C., Huffman, J. C., Watkin, J. G. & Zwick, B. D. (1996).
Polyhedron, 15, 2279±2289.
Click, D. R., Scott, B. L. & Watkin, J. G. (1999). J. Chem. Soc. Chem. Commun.
pp. 633±634.
Jeske, G., Schock, L. E., Swepston, P. N., Schumann, H. & Marks, T. J. (1985). J.
Am. Chem. Soc. 107, 8103±8110.
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D. G. & Morokuma, K. (1998). J. Am. Chem. Soc. 120, 2071±2085.
Johnson, C. K. (1965). ORTEP. Report ORNL-3794. Oak Ridge National
Laboratory, Tennessee, USA.
Memmler, H., Kauper, U., Gade, L. H., Scowen, I. J. & McPartlin, M. (1996). J.
Chem. Soc. Chem. Commun. pp. 1751±1752.
Rosenberger, C., Schrock, R. R. & Davis, W. M. (1997). Inorg. Chem. 36, 123±
125.
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Schaverien, C. J., Van der Heijden, H. & Orpen, A. G. (1989). Polyhedron, 8,
1850±1852.
Data collection
Siemens P4/PC diffractometer
! scans
Rint = 0.041
max = 25.01ꢀ
ꢂ
Absorption correction: empirical
(XSCANS; Siemens, 1994)
Tmin = 0.46, Tmax = 0.65
8237 measured re¯ections
6811 independent re¯ections
5303 re¯ections with I > 2ꢄ(I)
h = 20 ! 20
k = 12 ! 1
l = 1 ! 26
3 standard re¯ections
every 97 re¯ections
intensity decay: 13% (linear)
Re®nement
Re®nement on F2
R[F2 > 2ꢄ(F2)] = 0.038
wR(F2) = 0.101
S = 1.043
6811 re¯ections
w = 1/[ꢄ2(Fo2) + (0.0451P)2
+ 4.7821P]
where P = (Fo2 + 2Fc2)/3
(Á/ꢄ)max = 0.001
3
Ê
Ê
È
Sheldrick, G. M. (1985). SHELXS86. University of Gottingen, Germany.
Áꢅmax = 0.99 e A (1.0 A from
Sm1)
È
Sheldrick, G. M. (1997). SHELXL97. University of Gottingen, Germany.
Siemens (1994). XSCANS. Version 2.10b. Siemens Analytical X-ray Instru-
487 parameters
H-atom parameters constrained
3
1.02 e A (1.0 A from
Ê
Ê
Áꢅmin
=
ments Inc., Madison, Wisconsin, USA.
Sm1)
ꢁ
1096 Click, Scott and Watkin [Sm(C9H9F5NSi)3(C4H8O)]
Acta Cryst. (2000). C56, 1095±1096