3754 Organometallics, Vol. 15, No. 17, 1996
Hiller et al.
cooling of the solution to room temperature, 50 mL of aqueous
HCl was added. After standing overnight in air, light greenish
crystals were filtered from a green mother liquor. The crude
products were recrystallized from hot toluene to give fine
needlelike crystals. The purity of the compounds was checked
by MS analysis. IR spectra (regions 400-1600 cm-1) are listed
below.
(C5H4Me)2Zr Cl2 (1B). The yield of colorless crystals was
7.5 g (65%); mp 182 °C (lit. mp 180 °C18a). IR (KBr, cm-1):
1496 s, 1455 m, 1443 m, 1414 w, 1374 s, 1352 w, 1243 m, 1074
w, 1048 s, 1042 s, 1033 s, 936 m, 880 m, 852 s, 841 vs, 816 s,
618 m.
turally characterized complex without an additional
ligand, encouraged us to communicate results of our
investigation of the influence of methyl substituents at
the cyclopentadienyl ligands on the stability of zir-
conocene-acetylene complexes. Here we report the
synthesis of the (C5H5-nMen)2Zr[η2-C2(SiMe3)2] (n )
2-5) complexes which are stable in the absence of
electron donor ligands and the crystal structures of the
complexes for n ) 4 and 5 and of a dimeric product of
rearrangement of the labile (C5H4Me)2Zr[η2-C2(SiMe3)2]
complex.
(C5H3Me2)2Zr Cl2 (1C). The yield of colorless crystals was
4.6 g (37%); mp 173 °C. IR (KBr, cm-1): 1507 s, 1452 s, 1440
s, 1380 s, 1277 w, 1137 w, 1050 s, 1028 m, 944w, 901 m, 847
vs, 828 s, 620 m.
(C5H2Me3)2Zr Cl2 (1D). The yield of colorless crystals was
4.9 g (36%); mp 252 °C. IR (KBr, cm-1): 1489 s, 1474 m, 1448
s, 1374 s, 1302 w, 1196 m, 1028 s, 914 w, 904 w, 877 w, 834 s,
818 vs, 710 w, 616 w, 455 w.
(C5HMe4)2Zr Cl2 (1E). The yield of slightly yellow crystals
was 8.0 g (55%); mp 262 °C (lit. mp 211 °C18b). IR (KBr, cm-1):
1485 m, 1448 m, 1431 m, 1383 s, 1370 s, 1323 w, 1150 w, 1116
vw, 1024 s, 976 w, 902 m, 862 vs, 601 m.
(C5Me5)2Zr Cl2 (1F ). The yield of yellow crystals was 8.4 g
(54%); mp 311 °C. IR (KBr, cm-1): 1483 s, 1446 s, 1423 s,
1376 vs, 1163 w, 1062 w, 1021 s, 952 w, 805 w, 598 w. The
reported NMR data for 1E17a and 1F 17b agreed with our
records.
Exp er im en ta l Section
Gen er a l Da ta . All manipulations with reagents, synthe-
ses, and most of the spectroscopic measurements were carried
out under vacuum using all-sealed glass devices equipped with
breakable seals. The adjustment of single crystals into capil-
laries for X-ray analysis and the preparation of KBr pellets
for infrared measurements were performed in an atmosphere
of purified nitrogen. 1H and 13C NMR spectra were measured
on
a Varian VXR-400 spectrometer (400 and 100 MHz,
respectively) in C6D6 at 25 °C. Chemical shifts (given in the
δ scale) were referenced to the solvent signal (δH 7.15 ppm, δC
128.0 ppm). Assignment of spectra of the C5H5-nMen ligands
was carried out using a delayed COSY experiment. UV-vis
spectra were registered in the range 270-2000 nm on a Varian
Cary 17D spectrometer using all-sealed quartz cuvettes (Hell-
ma). Mass spectra were obtained on a J EOL D-100 spectrom-
eter at 70 eV (only important mass peaks and peaks of
intensity g5% are reported). Samples in capillaries were
opened and inserted into the direct inlet under argon. Infrared
spectra were measured on a UR-75 (Zeiss, J ena, Germany) or
on a Mattson Galaxy 2020 FTIR single beam spectrometer.
KBr pellets from estimated amounts of solid samples were
prepared in a glovebox (mBraun labmaster 130) under purified
nitrogen and were measured in a cuvette under a nitrogen
atmosphere. EDX measurements were carried out with a Zeiss
DSM-962 scanning electron microscope equipped with an
EDAX X-ray detector. An acceleration voltage of 25 kV was
used for the generation of cathodic radiation.
Ch em ica ls. The solvents THF, hexane, toluene, and
benzene-d6 were purified by conventional methods, dried by
refluxing over LiAlH4, and stored as solutions of dimeric
titanocene (C10H8)[(C5H5)Ti(µ-H)]2.15 Bis(trimethylsilyl)acet-
ylene (BTMSA) (Fluka) was degassed, stored as a solution of
dimeric titanocene for 4 h, and distilled into ampules. Mag-
nesium turnings (Fluka, purum for Grignard reactions) were
weighed and evacuated. Methylcyclopentadiene was obtained
by cracking of the dimer (Fluka) and was immediately used
for the preparation of the lithium salt. 1,3-Dimethylcyclopen-
tadiene,16 1,2,3-trimethylcyclopentadiene, tetramethylcyclo-
pentadiene, and pentamethylcyclopentadiene were prepared
as reported earlier.11d Zirconocene dichlorides (C5H5-nMen)2ZrCl2
(n ) 1-5) (1B-F ) were prepared by a modified general
method17a,b as follows. The lithium salts of the cyclopenta-
dienes were obtained by adding BuLi in hexane (1.6 M, 52 mL,
83 mmol; Chemetall GmbH, Frankfurt a.M., Germany) to the
cyclopentadiene (80 mmol) in 400 mL of toluene. After 1 h of
stirring at room temperature finely powdered ZrCl4 (8.4 g, 36
mmol; Merck) was added under argon and the mixture was
refluxed (from minimum 4 h for C5H4Me to 48 h for C5Me5).
Half the amount of toluene (200 mL) was distilled off, and after
P r ep a r a tion of (C5H5-n Men )2Zr [η2-C2(SiMe3)2] (n ) 2-5)
Com p lexes 2C-F . (C5H5-nMen)2ZrCl2 (1C-F ) (2 mmol) and
Mg (0.050 g, 2.1 mmol) were charged into an ampule equipped
with
a Teflon-coated magnetic stirrer. The ampule was
evacuated, and BTMSA (0.6 mL, 2.7 mmol) and THF (30 mL)
were distilled in on a vacuum line. The mixture was frozen
by liquid nitrogen, sealed off, and stirred at 60 °C until all
magnesium had disappeared. Turquoise solutions were ob-
tained from 1D-F , and a honey-yellow solution was obtained
from 1C. The solutions were evaporated in vacuo (the product
from 1C turned to turquoise), and the residues were extracted
with hexane. In order to remove all MgCl2 these solutions
were evaporated and the residues were extracted by a mini-
mum amount of hexane. Crystalline compounds 2E,F were
obtained by cooling of the concentrated solutions. Compounds
2C,D formed amorphous solids both by cooling and by slow
evaporation of hexane. They were purified by removing
mother liquors at -70 °C. All the compounds were also
prepared by the same procedure using a 5-fold molar excess
of magnesium with respect to 1C-F . The reaction time was
shortened to ca. 30 min at 60 °C.
(C5H3Me2)2Zr [η2-C2(SiMe3)2] (2C). The yield of green
amorphous solid was 0.76 g (85%). 1H NMR (C6D6): δ 0.03
(s, 18H, SiMe3), 1.73 (s, 12H), 5.79 (s, 4H, H-4, H-5), 6.09 (s,
2H, H-2). 13C NMR (C6D6): δ 2.1 (q, 6C), 15.2 (q, 4C), 111.0
(d, 4C), 112.1 (d, 2C), 125.1 (s, 2C), 258.2 (s, 2C). IR (KBr):
1566 (m), 1512 (w), 1462 (m), 1445 (m), 1375 (w), 1242 (s),
1028 (w), 835 (vs, b), 748 (m), 725 (w), 685 (m), 664 (m), 638
(m), 617 (w), 598 (w), 548 (vw), 470 (w). UV-vis (hexane,
green) (nm): 775 (w); THF, yellow (nm), strong absorption
decreasing in intensity to 570, 750 (vw). MS (direct inlet, 70
eV, 75-80 °C, m/z (%)): 446 (M+, 8), 276 (100). Anal. Calcd
for C22H36Si2Zr: C, 59.0; H, 8.1. Found: C, 59.8; H, 8.3.
(C5H2Me3)2Zr [η2-C2(SiMe3)2] (2D). The yield of green
amorphous solid was 0.88 g (92%); mp 214 °C. 1H NMR
(C6D6): δ 0.14 (s, 18H, SiMe3), 1.78 (s, 12H), 1.89 (s, 6H), 5.52
(s, 4H). 13C NMR (C6D6): δ 2.8 (q, 6C), 12.0 (q, 2C), 14.0 (q,
4C), 108.5 (d, 4C), 114.1 (s, 4C), 122.4 (s, 2C), 260.0 (s, 2C). IR
(KBr): 1535 (m), 1487 (w), 1445 (m), 1383 (m), 1242 (s), 1024
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