Simple synthesis of oligosilyl-α,ω-dipotassium compounds

Article abstract of DOI:10.1002/1521-3773(20020315)41:6<989::AID-ANIE989>3.0.CO;2-A

Multiply metalated oligosilanes: Treatment of bridged bis[tris(trimethylsilyl)silyl] compounds with two equivalents of potassium tert-butoxide leads to the formation of 1,3- and 1,4-dipotassium silanes [Eq. (1)]. Reaction of the latter with zirconocene di

Full text of DOI:10.1002/1521-3773(20020315)41:6<989::AID-ANIE989>3.0.CO;2-A

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tions.[1] Recently, in this context, we have reported the
synthesis of oligosilyl anions by cleavage of trimethylsilyl
groups with potassium tert-butoxide.[2] This reaction can be
regarded as a variation of the method developed by Gilman
et al. for the synthesis of oligosilyllithium compounds by
cleavage of trimethylsilyl groups with methyllithium.[3] An
advantage of using potassium alkoxides instead of alkyllithi-
um compounds becomes evident in the reaction with higher
[14] a) D. S. McGuiness, K. J. Cavell, B. W. Skelton, A. H. White, Organo-
metallics 1999, 18, 1596 1605; b) V. P. W. Bˆhm, C. W. K. Gstˆttmayr,
T. Weskamp, W. A. Herrmann, J. Organomet. Chem. 2000, 595, 186
190.
[15] J. Krause, G. Cestanic, K.-J. Haack, K. Seevogel, W. Storm, K.-R.
Pˆrschke, J. Am. Chem. Soc. 1999, 121, 9807 9823.
[16] A. J. Arduengo, H. V. R. Dias, R. L. Harlow, M. Kline, J. Am. Chem.
Soc. 1992, 114, 5530 5534.
[17] [Pd2(dae)3] (405 mg, 0.8 mmol) were suspended in 1,1,3,3-tetramethyl-
1,3-divinyl-disiloxane (5 mL). The mixture was immediately cooled to
À308C and 1,3-dimesitylimidazol-2-ylidene (340 mg, 1.1 mmol) was
added. After warming up to room temperature the solution was
stirred for 1 h at this temperature. Then the white complex formed was
collected by filtration, washed with pentane (2 Â 5 mL), and dried
in vacuo. X-ray structural analysis of 5: STOE-IPDS diffractometer,
graphite monochromatized MoKa radiation, l ˆ 0.71069 ä, structure
solved by direct methods (SHELXS-86: G. M. Sheldrick, Acta
Crystallogr. Sect. A 1990, 46, 467) and refined with the full-matrix
least-squares method against F 2 (SHELXL-93: G. M. Sheldrick,
Gˆttingen, Germany, 1993), structural representation: XP (Siemens),
0.4  0.3  0.2mm, yellow prism, space group P21/n, monoclinic, a ˆ
13.100(3), b ˆ 18.235(4), c ˆ 13.467(3) ä, b ˆ 105.07(3)8, Vˆ
3106.3(12) ä3, Z ˆ 4, 1calcd ˆ 1.277 gcmÀ3, 6157 measured reflections,
3279 were independent of symmetry, of which 2412 were observed
(I > 2s(I)), R ˆ 0.033, wR2(all data) ˆ 0.076, 316 parameters. CCDC-
171440 contains the supplementary crystallographic data for this
paper. These data can be obtained free of charge via www.ccdc.ca-
m.ac.uk/conts/retrieving.html (or from the Cambridge Crystallo-
graphic Data Centre, 12, Union Road, Cambridge CB21EZ, UK;
fax: (‡44)1223-336-033; or deposit@ccdc.cam.ac.uk).
À
oligosilanes. In cases where there are additional Si Si bonds
besides the ones between the central silicon atom and the
peripheral trimethylsilyl groups, these ×inner× bonds are
cleaved exclusively by methyllithium,[3] whereas potassium
tert-butoxide selectively removes a trimethylsilyl group.[2, 4]
The access to these higher silyl anions opened the possibility
of studying the prospects for the synthesis of multiply
metalated oligosilanes.[4, 5]
Therefore, we treated bis[tris(trimethylsilyl)silyl] com-
pounds, bridged with one (1a)[2, 6] or two (2a)[7] dimethylsi-
lylene units with potassium tert-butoxide in THF at elevated
temperatures (Scheme 1). Following a fast first metalation
step,[2, 5, 8] the subsequent formation of the dianion takes place
more easily when the negative charges are further apart.
Whereas the reaction of 2a to the dianion, occurs at a very low
rate, even at room temperature, the conversion of 1a requires
prolonged heating to 608C.
[18] L. Xu, W. Chen, J. F. Bickley, A. Steiner, J. Xiao, J. Organomet. Chem.
2000, 598, 409 416, and references therein.
Simple Synthesis of Oligosilyl-a,w-dipotassium
Compounds**
Scheme 1. Synthesis of mono- and dipotassium compounds.
Christian Kayser, Guido Kickelbick, and
Christoph Marschner*
Concerning their reactivity 1c and especially 2c behave
almost like isolated silyl anions. Derivatization reactions like
hydrolysis (!4), alkylation with dimethyl sulfate (!3)[9] and
the formation of homo- and heterocyclic rings by the reactions
with dimethylsilyl (!5),[10] dimethyltin (!6),[11] and metal-
locene dihalides (!7, 8) proceed very cleanly (Scheme 2). In
contrast to what is found for lithium silanides,[12] the THF
molecules of 1b,c and 2b,c are not bound very firmly. They
can be removed in part in vacuum; therefore, depending on
the conditions of isolation a different content of donor
molecules can be observed for these compounds.
The chemistry of electrophilic silicon compounds is a well
established and intensively studied area, whereas their
nucleophilic counterparts, the so-called silyl anions, enjoyed
much less attention for a long time. This is quite astonishing,
considering the high popularity of the tris(trimethylsilyl)silyl
group, which is mainly introduced through the respective silyl
anion, in main group and organometallic chemistry. However,
over the last few years this situation has changed and anionic
silyl compounds are now the subject of increased investiga-
Control of conversion and characterization of the silyl
anions can be achieved most easily by 29Si NMR spectroscopy.
The formal exchange of one trimethylsilyl group for a
potassium atom results in a shift of the resonance signal of
the affected silicon atom of Ddꢀ60 to lower frequencies. At
the same time the trimethylsilyl groups in b-position experi-
ence a shift of Dd ꢀ 4 5 in the opposite direction. The second
metalation step from 2b to 2c effects an additional slight shift
of the 29Si resonance signal of the metalated nucleus to lower
frequency (d ˆÀ 192), which is in accordance with previous
observations with alkylidene-bridged dianions.[5] In contrast
to this 1c exhibits an NMR signal for the metalated silicon
[*] Prof. Dr. C. Marschner, Dr. C. Kayser
Institut f¸r Anorganische Chemie
Technische Universit‰t Graz
Stremayrgasse 16, 8010 Graz (Austria)
Fax :(‡43)316-873-8701
E-mail: marschner@anorg.tu-graz.ac.at
Dr. G. Kickelbick
Institut f¸r Anorganische Chemie
Technische Universit‰t Wien
Getreidemarkt 9/153, 1060 Vienna (Austria)
[**] This work was supported by the Austrian science fund (FWF). C. M.
thanks the Austrian Academy of Science for an APART fellowship.
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Figure 2. Structure of 8 in the crystal. Selected bond lengths [ä] and angles
[8]: Si(1)-Hf(1) 2.791(14), Si(4)-Hf(1) 2.823(15), Si(2)-Si(3) 2.342(3), Si(1)-
Si(2) 2.385(2), Si(3)-Si(4) 2.379(2), Si(1)-Si(5/6) 2.374(2)/2.371(3), Si(4)-
Si(7/8) 2.382(2)/2.381(2), Si(1)-Si(2)-Si(3) 108.05(9), Si(2)-Si(3)-Si(4)
111.38(9), Si(6)-Si(1)-Si(5) 100.84(9), Si(8)-Si(4)-Si(7) 99.22(9), Si(1)-
Si(5)-Hf(1) 119.90(7), Si(1)-Hf(1)-Si(4) 96.41(5).
Scheme 2. Reactions of 2c.
atoms at d ˆ À173. Compared to the resonance of the
monometalated compound (1b) this corresponds to a shift
of Dd ꢀ 15 to higher frequencies.[13]
We oriented our studies of the reactivity of these metal-
lacyclopentanes on work by Tilley et al. on silyl metal-
locenes,[18, 19] and carried out reactions with hydrogen, 1-iso-
cyano-2,6-dimethylbenzene, and carbon monoxide. As ex-
pected the reaction of 7 with hydrogen led to the quantitative
formation of the dihydridometallocene and 1,4-dihydro-
The silyl compounds of the early transition metals can be
synthesized most easily by the salt elimination reaction of silyl
anions with metal halides.[14] Because of the limited avail-
ability of silyl dianions, early metal compounds with bidentate
silyl ligands are only scarcely known.[15] Therefore, 2c was
tested for its reactivity with zircono-
1,1,4,4-tetrakis(trimethylsilyl)tetramethylsilane
(4)
(Scheme 3). Reaction of 7 with the isonitrile also proceeded
cene and hafnocene dichlorides
(Scheme 2). The respective reac-
tions proceeded very cleanly to give
the expected zirconocena- (7) and
hafnocenacyclopentasilanes
(8),
which, to the best of our knowledge,
are the first examples of these types
of compounds.[15] Both compounds
could be characterized unambigu-
ously by single-crystal X-ray struc-
ture analysis (Figures 1 and 2).[16, 17]
Scheme 3. Reactions of 7.
very cleanly to the insertion product (9) (Scheme 3). Even in
the presence of excess isonitrile only one insertion step occurs.
In contrast to this, reactions of 7 and 8 with CO did not lead to
uniform products. However, it could be shown that the first
reaction step of insertion of CO into a silcon metal bond is
reversible.[19a] This reaction is currently under investigation.
Experimental Section
All manipulations were carried out under exclusion of oxygen and
moisture, either by conventional Schlenk techniques or through the use
of a glove box under a nitrogen atmosphere.
1c, 2c: The starting material (1a, 2a; 0.61 mmol) was mixed with two
equivalents (0.135 g, 1.22 mmol) of potassium tert-butoxide, THF (2mL)
and C6D6 (1 mL) were added, and the mixture was heated to 608C in a 10-
mm NMR tube, either with an attached teflon stop cock or flame sealed.
The conversion was monitored by 29Si NMR spectroscopy.
Figure 1. Structure of 7 in the crystal. Selected bond lengths [ä] and angles
[8]: Si(1)-Zr(1) 2.8264(19), Si(4)-Zr(1) 2.8497(19), Si(2)-Si(3) 2.351(4),
Si(1)-Si(2) 2.387(3), Si(3)-Si(4) 2.378(3), Si(1)-Si(5/6) 2.369(3)/2.376(3),
Si(4)-Si(7/8) 2.380(3)/2.386(3), Si(1)-Si(2)-Si(3) 109.25(11), Si(2)-Si(3)-
Si(4) 112.79(11), Si(6)-Si(1)-Si(5) 101.42(11), Si(8)-Si(4)-Si(7) 99.46(11),
Si(1)-Si(5)-Zr(1) 121.09(9), Si(1)-Zr(1)-Si(4) 97.70(6).
1c: 1H NMR (300 MHz, THF, C6D6, 2 58C, TMS): d ˆ 0.91 (s, 6H; SiMe2),
0.51 (s, 36H; SiMe3); 13C-NMR (75.4 MHz, THF, C6D6, 2 58C, TMS):
990
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d ˆ 8.50 (SiMe3), 2.28 (SiMe2); 29Si NMR (99.3 MHz, THF, C6D6, 2 58C,
TMS): d ˆ À5.3 (SiMe3), À16.5 (SiMe2), À172.0 (SiK).
[1] Excellent compilations of the progress in the field of silyl anions can
be found in the following reviews: a) P. D. Lickiss, C. M. Smith, Coord.
Chem. Rev. 1995, 145, 75; b) K. Tamao, A. Kawachi, Adv. Organomet.
Chem. 1995, 39, 1; c) J. Belzner, U. Dehnert in The Chemistry of
Organic Silicon Compounds, Vol. 2 (Eds.: Z. Rappoport, Y. Apeloig),
Wiley, New York, 1998, Chap. 14, p. 779.
2c: 1H NMR (500 MHz, THF, C6D6, 2 58C, TMS): d ˆ 0.67 (s, 12H; SiMe2),
0.57 (s, 36H; SiMe3); 13C-NMR (125.9 MHz, THF, C6D6, 2 58C, TMS): d ˆ
8.66 (SiMe3), 3.33 (SiMe2); 29Si NMR (99.3 MHz, THF, C6D6, 2 58C, TMS):
d ˆ À4.1 (SiMe3), À26.7 (SiMe2), À191.6 (SiK).
[2] C. Marschner, Eur. J. Inorg. Chem. 1998, 2 2 1.
7: Zirconocene dichloride (0.50 g, 1.90 mmol, 30% excess) and 2c
(1.46 mmol) were dissolved at room temperature with toluene (5 mL),
and the reaction mixture immediately became deep red. After two hours
the solvent was removed at reduced pressure, and the residue was dissolved
in pentane. After filtration the product was crystallized at À308C and
obtained as deep red crystals. Yield: 0.90 g (1.30 mmol, 89%). A suitable
single crystal was used for an X-ray structure analysis. 1H NMR (500 MHz,
[3] a) H. Gilman, J. M. Holmes, C. L. Smith, Chem. Ind. (London) 1965,
848; b) Y. Apeloig, M. Yuzefovich, M. Bendikov, D. Bravo-Zhivo-
tovskii, K. Klinkhammer, Organometallics 1997, 16, 1265.
[4] Recently Apeloig et al. showed that in the reaction of 2a with
À
methyllithium also no cleavage of the inner Si Si bonds occurs and
that the dilithio analogue of 2c is obtained. Y. Apeloig, G.
Korogodsky, D. Bravo-Zhivotovskii, D. Bl‰ser, R. Boese, Eur. J.
Inorg. Chem. 2000, 1091. But Pannell et al.[7a] have reported previously
À
C6D6, 2 58C, TMS): d ˆ 6.29 (s, 10H; Cp H), 0.45 (s, 12H; SiMe2), 0.43 (s,
36H; SiMe3); 13C NMR (125.9 MHz, C6D6, 2 58C, TMS): d ˆ 108.80 (Cp),
6.93 (SiMe3), 2.19 (SiMe2); 29Si NMR (99.3 MHz, pentane/D2O capillary,
258C, TMS): d ˆ À2.4 (SiMe3), À29.2 (SiMe2), À65.2(SiZr); elemental
analysis(%) calcd for C26H58Si8Zr (Mr ˆ 686.65): C 45.48, H 8.51; found: C
45.01, H 8.47; UV (cyclohexane): lmax (e) ˆ 302(4000), 466 (800), 556 nm
(250).
À
the cleavage of the inner Si Si bonds of 2a under the same conditions.
Also the reaction of hexamethyldisilane with methyllithium yields
either trimethylsilyllithium or pentamethyldisilanyllithium depending
on conditions (K. Krohn, K. Khanbabaee, Angew. Chem. 1994, 106,
100; Angew. Chem. Int. Ed. Engl. 1994, 33, 99). This leads to the
assumption that the different results reported by Apeloig et al. and
Pannell et al. are caused by subtle differences in the conditions which
lead to different reaction mechanisms.
8: Synthesis and isolation of
8 ([Cp2HfCl2] (0.64 g, 1.68 mmol); 2c
(1.28 mmol)) were accomplished analogously to that of 7. Compound 8
was obtained as deep red crystals in 85% yield (0.84 g; 1.08 mmol), which
were suitable for a single crystal X-ray structure analysis. 1H NMR
(500 MHz, C6D6, 2 58C, TMS): d ˆ 6.21 (s, 10H; Cp), 0.49 (s, 12H; SiMe2),
0.44 (s, 36H; SiMe3); 13C NMR (125.9 MHz, C6D6, 2 58C, TMS): d ˆ 108.32
(Cp), 7.05 (SiMe3), 2.43 (SiMe2); 29Si NMR (99.3 MHz, pentane/D2O
capillary, 258C, TMS): d ˆ À2.0 (SiMe3), À27.8 (SiMe2), À52.2 (SiHf);
elemental analysis (%) calcd for C26H58HfSi8 (Mr ˆ 773.91): C 40.35, H 7.55;
found: C 39.79, H 7.56; UV (cyclohexane): lmax (e) ˆ 210 (50000), 344
(3100), 412(3100), 504 nm (250).
[5] For the syntheses of a,w-alkylidene-bridged silyldipotassium com-
pounds see: C. Mechtler, C. Marschner, Tetrahedron Lett. 1999, 40,
7777.
[6] M. Ishikawa, J. Iyoda, H. Ikeda, K. Kotake, T. Hashimoto , M.
Kumada, J. Am. Chem. Soc. 1981, 103, 4845.
[7] a) S. M. Whittaker, M.-C. Brun, F. Cervantes-Lee, K. H. Pannell, J.
Organomet. Chem. 1995, 499, 247; b) J. B. Lambert, J. L. Pflug, A. M.
Allgeier, D. J. Campbell, T. B. Higgins, E. T. Singewald, C. L. Stern,
Acta Crystallogr. Sect. C 1995, 51, 713.
[8] The conversion of 2a with one equivalent of potassium tert-butoxide
leads, similarly as reported in reference [2] for 1a very cleanly to the
monopotassium compound 2b: 1H NMR (300 MHz, C6D6, 2 08C,
TMS): d ˆ 3.67 (m, 8H; THF), 1.45 (m, 8H; THF), 0.66 (s, 6H;
SiMe2), 0.55 (s, 6H; SiMe2), 0.47 (s, 18H; KSi(SiMe3)2), 0.40 (s, 27H;
Si(SiMe3)3); 29Si NMR (59.6 MHz, THF/D2O capillary, 208C, TMS):
d ˆ À4.34, À9.24, À20.62 (SiMe2), À34.58 (SiMe2), À130.70 (Si-
(SiMe3)3, À189.77 (SiK).
Isonitrile insertion into compound 7: Compound 7 (0.057 g, 0.08 mmol) was
dissolved in C6D6 (2mL) and treated with 1-isocyano-2,6-dimethylbenzene
(0.011 g, 0.08 mmol). The initially deep red solution turned orange
immediately. NMR spectroscopy showed the exclusive formation of the
expected insertions product. Addition of a second equivalent of isonitrile
did not lead to another insertion step. The solvent and excess isonitrile were
removed in vacuum; the residue was dissolved in pentane and crystallized
at À358C as yellow crystals. Yield of 9: 0.030 g (0.04 mmol, 50%). 1H NMR
[9] Compound 3 was obtained by reaction of 2c with dimethyl sulfate in
toluene at À788C in about 85% yield. 1H NMR (300 MHz, C6D6,
208C, TMS): d ˆ 0.40 (s, 12H; SiMe2), 0.24 (s, 36H; SiMe3), 0.23 (s,
6H; SiMe); 13C NMR (75 MHz, C6D6, 2 08C, TMS): d ˆ 1.01 (SiMe3),
À1.58 (SiMe2), À11.32(SiMe); 29Si NMR (59.6 MHz, THF/D2O
capillary, 208C, TMS): d ˆ À12.15 (SiMe3), À34.80 (SiMe2), À82.08
(Si(SiMe3)3). The same compound was obtained by treatment of
(Me3Si)2(Me)SiMe2H with di-tert-butyl peroxide: M. Ishikawa, A.
Nakamura, M. Kumada, J. Organomet. Chem. 1973, 59, C11.
[10] The homocyclic five-membered ring 5 was obtained in 62% yield by
reaction of 2c with dimethyldichlorosilane at room temperature in
toluene. Spectroscopic and physical data correspond to those of the
compound obtained by Blinka and West by AlCl3-catalyzed rear-
rangement of octadecamethylcyclononasilane: T. A. Blinka, R. West,
Organometallics, 1986, 5, 128.
À
(500 MHz, C6D6, 2 58C, TMS): d ˆ 6.85 (m, 3H; Ar H), 5.69 (s, 10H; Cp),
À
1.94 (s, 6H; Ar Me), 0.78 (s, 6H; SiMe2), 0.52(s, 18H; SiMe 3), 0.51 (s, 6H;
SiMe2), 0.10 (s, 18 H SiMe3); 13C NMR (125.9 MHz, THF, C6D6, 2 58C,
ˆ
TMS): d ˆ 279.6 (C N), 154.16 (NCar), 129.56 (Car), 128.96 (Car), 128.36
(Car), 106.46 (Cp), 21.56 (CarMe), 7.16 (SiMe3), 4.36 (SiMe3), 2.16 (SiMe2),
À0.16 (SiMe2); 29Si NMR (99.3 MHz, pentane/D2O capillary): À4.36
(SiMe3), À10.06 (SiMe3), À33.06 (SiMe2), À36.36 (SiMe2), À79.06 (ZrSi),
À117.26 (NCSi); elemental analysis(%) calcd for C35H67NSi8Zr (Mr ˆ
817.82): C 51.40, H 8.26; found: C 50.97, H 8.37.
Reactions of
7 and 8 with hydrogen and of 2c with acid to give
dihydrosilane 4: The respective metallacyclosilane (0.07 mmol) was
dissolved in C6D6 in an NMR tube. The solution was frozen with liquid
nitrogen, evacuated, and flushed with hydrogen. After warming up to
ambient temperature the tube was shaken whereupon the red color
disappeared. For the isolation of the hydrosilane the solvent was removed
in vacuum, the residue dissolved in pentane, and after filtration to remove
the insoluble metallocene hydride, the sample was evaporated and the
residue 4 crystallized as colorless crystals from acetone. Yield: 0.029 g
(0.06 mmol, 85%). Alternatively, 4 was obtained from 2c, analogously to
the previously described hydrolysis procedure with sulfuric acid[2] in almost
quantitative yield. 1H NMR (500 MHz, C6D6, 2 58C, TMS): d ˆ 2.68 (s, 2H;
[11] Compound 6 was obtained analogously to 5 in the reaction of 2c with
dimethyldichlorostannane. 1H NMR (300 MHz, C6D6, 2 08C, TMS):
d ˆ 0.57 (s, 6H; SnMe2), 0.37 (s, 12H; SiMe2), 0.30 (s, 36H; SiMe3);
29Si NMR (59.6 MHz, hexane/D2O capillary, 208C, TMS): d ˆ À5.4
(2J
(1J
Sn44 Hz, SiMe3), À22.2 (2J
61 Hz, SiMe2), À137.5
29Si-119
29Si-119Sn
192/186 Hz, SiSn); 119Sn NMR (186.4 MHz, hexane/D2O
29Si-119Sn/117Sn
capillary, 208C): d ˆ À118.6 (1J
196.6 Hz, J
Sn 65.5 Hz).
29Si-119
2
29Si-119Sn
Si H), 0.42(s, 12H; SiMe 2), 0.27 (s, 54H; SiMe3); 13C NMR (125.9 MHz,
À
[12] M. Nanjo, A. Sekiguchi, H. Sakurai, Hideki, Bull. Chem. Soc. Jpn.
1998, 71, 741.
THF, C6D6, 2 58C, TMS): d ˆ 2.47 (SiMe3), À1.40 (SiMe2); 29Si NMR
(99.3 MHz, pentane/D2O capillary): d ˆ À11.1 (SiMe3), À36.4 (SiMe2),
[13] This anomaly in the behavior of the 29Si NMR spectra can be
interpreted as a mutual perturbation of charge stabilization. Ab initio
calculations (MP2/6 31 ‡ G*) of the dilithio analogues of 1c and 2c
and subsequent calculation of 29Si NMR shift (DFT/IGLO-B2)
reproduce the phenomenon of the relative shift of 1c to higher
frequencies (M. Flock, Ch. Marschner, unpublished results).
[14] Review articles about metal silyl compounds: a) T. D. Tilley in The
Chemistry of Organic Silicon Compounds (Eds.: S. Patai, Z. Rappo-
‡
À
À116.4 (Si H, J ˆ 155.9 Hz); MS (70 eV): m/z (%): 392(9)
[
M À
‡
‡
HSiMe3], 318 (89) [M À H2Si2Me6], 218 (25) [M À HSi(SiMe3)3], 73
(100) [SiMe3]; elemental analysis (%) calcd for C16H50Si8 (Mr ˆ 467.25) C
41.13, H 10.79; found: C 40.82, H 10.78.
Received: April 23, 2001
Revised: November 28, 2001 [Z16976]
Angew. Chem. Int. Ed. 2002, 41, No. 6
¹ WILEY-VCH Verlag GmbH, 69451 Weinheim, Germany, 2002
1433-7851/02/4106-0991 $ 17.50+.50/0
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port), Wiley, Chichester, 1989, Chap. 24, p. 1415; b) T. D. Tilley in The
Silicon-Heteroatom Bond (Eds.: S. Patai, Z. Rappoport), Wiley,
Chichester, 1991, Chap. 10, p. 309; c) M. S. Eisen in The chemistry of
Organic Silicon Compounds, Vol. 2 (Eds.: Z. Rappoport, Y. Apeloig),
Wiley, New York, 1998, Chap. 35, p. 2037.
Crystallographic Data Centre, 12Union Road, Cambridge CB21EZ,
UK; fax: (‡44)1223-336-033; or e-mail: deposit@ccdc.cam.ac.uk).
À
[17] The Si Zr bond lengths of 7 are 2.8264(19) ä and 2.8497(19) ä, which
is within the range of previously found values: a) W. Muir, J. Chem.
Soc. (A) 1971, 2663; b) T. Imori, R. H. Heyn, T. D. Tilley, A. L.
Rheingold, J. Organomet. Chem. 1995, 493, 83; c) L. H. McAlexander,
J. B. Diminnie, Z. Xue, Organometallics 1998, 17, 4853; d) R. H. Heyn,
T. D. Tilley, Inorg. Chem. 1989, 28, 1768; e) K. A. Kreutzer, R. A.
Fisher, W. M. Davis, E. Spaltenstein, S. L. Buchwald, Organometallics
1991, 10, 4031; f) T. Takahashi, M. Hasegawa, N. Suzuki, M. Saburi,
C. J. Rousset, P. E. Fanwick, E.-i. Negishi, J. Am. Chem. Soc. 1991, 113,
8564; g) T. D. Tilley, Organometallics 1985, 4, 1452. Similarly the
[15] Interestingly, there are two titanacyclosilanes, which were obtained by
the reaction of titanocene dichloride with the corresponding 1,4- or
1,5- dilithiosilanes:a) V. A. Igonin, Yu. E. Ovchinnikov, V. V. De-
ment×ev, V. E. Shklover, T. V. Timofeeva, T. M. Frunze, Yu. T.
Struchkov, J. Organomet. Chem. 1989, 371, 187; b) M. S. Holtman,
E. P. Schram, J. Organomet. Chem. 1980, 187, 147.
[16] X-ray analyses: Crystals of 7 and 8 were mounted in glass capillaries
and measured on a Bruker SMART Platform/CCD diffractometer at
temperatures of 213 K (7) and 296 K (8), respectively. Crystal data for
7: C26H58Si8Zr, Mr ˆ 686.66, monoclinic, P21/c; a ˆ 11.2474(13), b ˆ
16.5181(18), c ˆ 21.959(3) ä; b ˆ 103.770(2); Vˆ 3962.4(8) ä3; Z ˆ 4;
À
Si Hf bond lengths in 8 (2.791(14) ä and 2.823(15) ä) are also within
the range of previously found data; h) H. G. Woo, R. H. Heyn, T. D.
Tilley, J. Am. Chem. Soc. 1992, 114, 5698; i) G. L. Casty, C. G.
Lugmair, N. S. Radu, T. D. Tilley, J. F. Walzer, D. Zargarian, Organo-
metallics 1997, 16, 8; j) J. Arnold, D. M. Roddick, T. D. Tilley, A. L.
Rheingold, S. J. Geib, Inorg. Chem. 1988, 27, 3510. In compound 7 the
metallacyclopentasilane ring exhibits a twisted half-chair conforma-
tion, in which the two Si(SiMe3)2 groups lie 108 or À268, respectively,
under or above the ring plane. In contrast to this compound 8 exists in
an envelope conformation with one trimethylsilyl-substituted silicon
atom 208 above the plane.
1calcd ˆ 1.151 MgmÀ3
F(000) ˆ 1464, 317 parameters: R1 ˆ 0.0528,
,
wR2 ˆ 0.1465, GOF ˆ 1.038 for all 4123 data (I > s(I)); max./min.
residual electron density: 1.061/ À 0.440 eÀAÀ3. Crystal data for 8:
C26H58HfSi8, Mr ˆ 773.93, monoclinic, P21/c; a ˆ 11.292(2), b ˆ
16.518(3), c ˆ 21.975(4) ä; b ˆ 104.191(4); Vˆ 3973.7(13) ä3; Z ˆ 4;
1calcd ˆ 1.294 MgmÀ3
F(000) ˆ 1592, 317 parameters: R1 ˆ 0.0351,
,
wR2 ˆ 0.0915, GOF ˆ 1.084 for all 6771 data (I > s(I)); max./min.
residual electron density: 2.006/ À 0.793 eÀAÀ3. CCDC-162782 (7) and
CCDC-162781 (8) contain the supplementary crystallographic data
for this paper. These data can be obtained free of charge via
www.ccdc.cam.ac.uk/conts/retrieving.html (or from the Cambridge
[18] H. G. Woo, J. F. Walzer, T. D. Tilley, J. Am. Chem. Soc. 1992, 114, 7047.
[19] a) B. K. Campion, J. Falk, T. D. Tilley, J. Am. Chem. Soc. 1987, 109,
2049; b) F. H. Elsner, T. D. Tilley, A. L. Rheingold, S. J. Geib, J.
Organomet. Chem. 1988, 358, 169.
992
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Angew. Chem. Int. Ed. 2002, 41, No. 6