Reactions of the zirconocene complexes of bis(trimethylsilyl)acetylene with formaldehyde, benzaldehyde, and benzophenone

Article abstract of DOI:10.1021/om950664v

In reactions .of the zirconocene derivative Cp₂ZrC(SiMe₃)=C(SiMe₃)(THF) with ketones and aldehydes the influence of the various substituents of the carbonyl compounds upon the formation of different products was investigated. Formaldehyde reacts by an insertion of the carbonyl unit into a Zr-C bond to give a metallacycle which is additionally stabilized by the formation of a coordination dimer [Cp₂ZrOCH₂C(SiMe₃)=C(SiMe₃)] ₂ (1). Benzaldehyde yields a monomeric metallacycle Cp₂ZrOCHPhC(SiMe₃)=C(SiMe₃) (2). Complex 2 is less stable than 1, and at higher temperatures it loses half of its moiety Me₃SiC₂SiMe₃, leaving {[Cp₂ZrOCHPhC(SiMe₃)=C(SiMe₃)][Cp ₂Zr(η²-O=CHPh)]} (3). Benzophenone gives no insertion, and the monomeric η²-ketone complex Cp₂Zr(THF)(η²-O=CPh₂) (4) was obtained.

Full text of DOI:10.1021/om950664v

1340
Organometallics 1996, 15, 1340-1344
Articles
Rea ction s of th e Zir con ocen e Com p lexes of
Bis(tr im eth ylsilyl)a cetylen e w ith F or m a ld eh yd e,
Ben za ld eh yd e, a n d Ben zop h en on e
N. Peulecke, A. Ohff, A. Tillack, W. Baumann, R. Kempe, V. V. Burlakov,† and
U. Rosenthal*,‡
Max-Planck-Gesellschaft, Arbeitsgruppe “Komplexkatalyse” an der Universita¨t Rostock,
Buchbinderstrasse 5-6, D-18055 Rostock, Germany
Received August 24, 1995X
In reactions of the zirconocene derivative Cp2ZrC(SiMe3)dC(SiMe3)(THF) with ketones
and aldehydes the influence of the various substituents of the carbonyl compounds upon
the formation of different products was investigated. Formaldehyde reacts by an insertion
of the carbonyl unit into a Zr-C bond to give a metallacycle which is additionally stabilized
by the formation of a coordination dimer [Cp2ZrOCH2C(SiMe3)dC(SiMe3)]2 (1). Benzaldehyde
yields a monomeric metallacycle Cp2ZrOCHPhC(SiMe3)dC(SiMe3) (2). Complex 2 is less
stable than 1, and at higher temperatures it loses half of its moiety Me3SiC2SiMe3, leaving
{[Cp2ZrOCHPhC(SiMe3)dC(SiMe3)][Cp2Zr(η2-OdCHPh)]} (3). Benzophenone gives no inser-
tion, and the monomeric η2-ketone complex Cp2Zr(THF)(η2-OdCPh2) (4) was obtained.
In tr od u ction
(L), L ) THF8 or pyridine,9 which gave the metallacycle
Zirconocene complexes of ketones or aldehydes1,2 are
of great interest for carbon-carbon bond formation
reactions with unsaturated compounds.2 The classical
example of such complexes, Cp2Zr(η2-OdCPh2), was
obtained in the carbonylation of diphenylzirconocene,
Cp2ZrPh2, by Erker.3-5 X-ray structural analysis of the
monomeric compound was not reported. The solid-state
structural characterization indicated a dimeric structure
[Cp2Zr(η2-OdCPh2)]2.2 The first structurally character-
ized monomeric η2-ketone complex of a group 4 metal
was (Ar′′O)2Ti(PMe3)(η2-OdCPh2) (Ar′′O ) 2,6-diphe-
nylphenoxide),6 but metallocene analogues are unknown
so far. The zirconocene-induced coupling reaction of
alkynes with carbonyl compounds to give zirconadihy-
drofurans is known,1,2,7 but detailed investigations
concerning the influence of the substituents of the
alkynes and carbonyl compounds on the nature of the
products have not been reported.
Cp2ZrOCMe2C(SiMe3)dC(SiMe3).10 This was rather
reactive and underwent acetylene exchange reactions,
e.g., with tolane. The resulting complex, Cp2ZrOCMe2C-
(Ph)dC(Ph), was much more stable and unreactive. The
difference in behavior of the two complexes was ex-
plained on the basis of electronic and/or steric factors
of the alkyne substituents SiMe3 and Ph.10 Recently,
the regiochemistry of the insertion of acetone into
Cp2ZrC(SiMe3)dC(tBu)(THF) was investigated.7 At first,
the kinetically controlled â-Si-substituted product
Cp2ZrOCMe2C(SiMe3)dC(tBu) was formed, and after
cycloreversion, the thermodynamically more favored
R-SiMe3 product Cp2ZrOCMe2C(tBu)dC(SiMe3) was iso-
lated. It seems that in this example the steric factor is
responsible for the isomerization. The R-position is less
hindered than the â-position, and the SiMe3 group is
Recently, we reported the insertion of acetone into
t
slightly larger than the Bu group.
zirconacyclopropene complexes Cp2ZrC(SiMe3)dC(SiMe3)-
To study the influence of the substituents of the
carbonyl compounds in detail we investigated the reac-
† On leave from the Institute of Organoelement Compounds of the
Russian Academy of Sciences, Moscow, Russia.
‡ email: urosen@chemiel.uni-rostock.de.
X Abstract published in Advance ACS Abstracts, February 1, 1996.
(1) Erker, G. Angew. Chem. 1989, 101, 411; Angew. Chem., Int. Ed.
Engl. 1989, 28, 397.
tion of Cp2ZrC(SiMe3)dC(SiMe3)(THF) with differently
substituted carbonyl compounds (CH2dO, PhCHdO,
and Ph2CdO).
(2) Erker, G.; Dorf, U.; Czich, P.; Petersen, J . L. Organometallics
1986, 5, 668.
(3) Rosenfeldt, F.; Erker, G. Tetrahedron Lett. 1980, 21, 1637.
(4) Erker, G.; Rosenfeldt, F. Tetrahedron 1982, 38, 1285.
(5) Skibbe, V.; Erker, G. J . Organomet. Chem. 1983, 241, 15.
(6) Hill, J . E.; Fanwick, P. E.; Rothwell, I. P. Organometallics 1992,
11, 1771.
(7) Lefeber, C.; Ohff, A.; Tillack, A.; Baumann, W.; Kempe, R.;
Burlakov, V. V.; Rosenthal, U. J . Organomet. Chem. 1995, 501, 189
and references cited therein.
(8) Rosenthal, U.; Ohff, A.; Michalik, M.; Go¨rls, H.; Burlakov, V.
V.; Shur, V. B. Angew. Chem. 1993, 105, 1228; Angew. Chem., Int. Ed.
Engl. 1993, 32, 1193.
(9) Rosenthal, U.; Ohff, A.; Baumann, W.; Tillack, A.; Go¨rls, H.;
Burlakov, V. V.; Shur, V. B. Z. Anorg. Allg. Chem. 1995, 621, 77.
(10) Rosenthal, U.; Ohff, A.; Baumann, W.; Tillack, A.; Go¨rls, H.;
Burlakov, V. V.; Shur, V. B. J . Organomet. Chem. 1994, 484, 203.
0276-7333/96/2315-1340$12.00/0 © 1996 American Chemical Society

Reactions of Zirconocene Derivatives
Organometallics, Vol. 15, No. 5, 1996 1341
trimeric η2-formaldehyde-zirconocene complex (Zr-O
2.179 Å)11 being in the same region as, e.g., in the
dimeric structure [Cp2Zr(η2-OdCPh2)]2 (2.287(2) and
2.304(2) Å 2). A comparison with other coordination
dimers is shown in Table 1.
The reaction of Cp2ZrC(SiMe3)dC(SiMe3)(THF) with
benzaldehyde yields the orange, crystalline insertion
product 2 (eq 2).
(2)
F igu r e 1. Molecular structure of complex 1, shown by an
ORTEP plot at the 50% probability level.
When complex 2 is heated above 100 °C, elimination
of the alkyne occurs and formation of complex 3 occurs
(see below). The 1H-NMR spectrum of 2 shows in
addition to the Ph signals singlets for the nonequivalent
SiMe3 (-0.10, 0.22 ppm) and Cp groups (6.24, 6.38 ppm).
The signal of the former aldehyde proton appears at 5.55
ppm. The 13C-NMR spectrum exhibits the typical
downfield shift for the R- and â-olefinic carbon atoms
at 222.2 and 185.8 ppm (cf. 213.3 and 193.2 ppm in
Resu lts a n d Discu ssion
The reaction of Cp2ZrC(SiMe3)dC(SiMe3)(THF) with
formaldehyde yields, comparable to the reaction with
acetone, by an insertion of the carbonyl compound into
a Zr-C bond, a metallacyclic product, which is addition-
ally stabilized by the formation of the coordination
dimer 1 (eq 1).
Cp2ZrOCMe2C(SiMe3)dC(SiMe3).10
The structure of complex 2 is shown in Figure 2. It
is very similar to that of the acetone insertion product
Cp2ZrOCMe2C(SiMe3)dC(SiMe3).10 The C(1)-C(2) dis-
tance of 1.365(4) Å in 2 is in the expected range for a
C-C double bond. The C-O distance of 1.423(4) Å is
in the C-O single bond range12). Compound 2, in
(1)
contrast to Cp2ZrOCMe2C(SiMe3)dC(SiMe3), is unreac-
tive toward carbon dioxide and tolane, but it is ther-
mally less stable than the coordination dimer 1. Com-
plex 2 decomposes in solution at 60 °C with elimination
of the acetylene. In the assumed reaction course the
resulting (not isolated) complex “Cp2Zr(η2-OdCHPh)”
reacts with a molecule of as yet undecomposed 2 to form
a coordination complex, 3, via the well-known four-
membered Zr-O-Zr-O ring (eq 3).
Complex 1 is a colorless, crystalline substance, which
is kinetically more stable than the acetone insertion
product Cp2ZrOCMe2C(SiMe3)dC(SiMe3). Thus, 1 does
not react with water and carbon dioxide nor with other
alkynes such as tolane. A possible reason for this lower
reactivity could be the dimeric structure, which prevents
the attack of substrates. A similar coupling product of
tolane and formaldehyde was obtained by Erker et al.11
in the reaction of the trimeric formaldehyde-zir-
conocene complex with tolane at 200 °C, for which a
monomeric structure Cp2ZrOCH2C(Ph)dC(Ph) was as-
sumed.
(3)
1
The H-NMR spectrum of 1 displays only one signal
for the Cp (5.85 ppm), one signal for the CH2 group (4.72
ppm), and two signals for SiMe3 units (0.40, 0.41 ppm).
Figure 1 shows the X-ray structure of complex 1.
The Zr-O distances in the two metallacyclic bridged
zirconadihydrofurans (O1-Zr2 2.125(2), O2-Zr1 2.131-
(2) Å) correspond to that in the trimeric η2-formalde-
hyde-zirconocene complex (2.135(5) Å).11 However, the
other bridging Zr-O distances (O1-Zr1 2.274(2), O2-
Zr2 2.269(2) Å) are significantly longer compared to the
Complex 3 is a pale yellow, crystalline solid. Unfor-
tunately the poor quality of the crystals (and elimination
of included solvent during X-ray measurement) did not
allow an exact determination of bond lengths and
(11) Erker, G.; Kropp, K.; Skibbe, V.; Kru¨ger, C. J . Am. Chem. Soc.
1983, 105, 3353.
(12) Allen, F. H.; Kennard, O.; Watson, D. G.; Brammer, L.; Guy
Orpen, A.; Taylor, R. J . Chem. Soc., Perkin Trans. 1987, 2, S1.

1342 Organometallics, Vol. 15, No. 5, 1996
Peulecke et al.
Ta ble 1. Com p a r ison of Selected NMR a n d Str u ctu r a l Da ta for Mon om er ic (n ) 1) a n d Dim er ic (n ) 2)
Zir con a cyclic Com p lexes
R1
R2
Cα
Cβ
Cp2Zr
R4
Cβ′
O
R3
n
monomeric complexes
coordination dimers
5 (R1 ) R2 ) SiMe3, 2 (R1 ) R2 ) SiMe3, 6 (R1 ) R2 ) Ph, 1 (R1 ) R2 ) SiMe3, 8 (R1 ) R2 ) SiMe3,
9 (R1 ) tBu,
R3 ) R4 ) Me)
R3 ) H, R4 ) Ph)
R3 ) R4 ) Me)
R3 ) R4 ) H)
R3, R4 ) O)
R2 ) SiMe3, R3, R4 ) O)
13C-NMR (δ/ppm)
CR (alkyne)
Câ (alkyne)
∆δ
213.3
193.2
20.1
222.2
185.8
36.4
185.2
165.2
20.0
213.6
158.7
54.9
249.0
152.9
96.1
a
a
a
angles (deg)
R1-CR-Câ
R2-Câ-CR
dists (Å)
M-CR
128.4(4)
125.6(4)
126.8(3)
129.3(3)
119.8(2)
123.2(3)
119.8(2)
135.2(2)
116.8(2)
138.4(3)
117.3(4)
139.5(3)
2.324(4)
1.371(7)
1.544(7)
1.426(6)
1.936(3)
2.324(4)
1.365(4)
1.527(5)
1.423(4)
1.944(2)
2.287(3)
1.348(4)
1.538(4)
1.436(4)
1.932(3)
2.388(3)
1.348(4)
1.514(4)
1.416(3)
2.131(2)
2.274(2)
2.376(3)
1.360(5)
1.488(5)
1.342(4)
2.197(2)
2.330(2)
2.436(4)
1.354(6)
1.467(6)
1.345(5)
2.163(3)
2.361(3)
CR-Câ
Câ-Câ′ (R3R4)
Câ′-O
M-O
M-O′
a
No NMR data available (low solubility).
(4)
analysis (Figure 3). Complex 4 was obtained at -30
°C as light yellow crystals, which contain a THF
molecule of crystallization in addition to the coordinated
THF. At room temperature all THF is lost and a white
powder containing the well-known dimers and trimers1
is formed. The 1H-NMR spectrum of 4 in THF-d8 shows,
in addition to the Ph multiplets, the signals of THF at
1.78 and 3.62 ppm together with a singlet for the Cp
units at 5.54 ppm. The 13C-NMR spectrum in THF-d8
exhibits together with the signals of THF and Ph units
the signals of the Cp groups at 109.9 ppm and of the
former carbonyl carbon atom at 94.7 ppm. The struc-
ture of 4 is shown in Figure 3.
F igu r e 2. Molecular structure of complex 2, shown by an
ORTEP plot at the 50% probability level.
angles. Nevertheless, the basic structure has been
established.
The η2-bound benzophenone in 4 shows some simi-
larities to that in (Ar′′O)2Ti(PMe3)(η2-OdCPh2) (Ar′′O
) 2,6-diphenylphenoxide).6 The C-O distances of 1.397-
(8) Å in ref 6 and 1.389(5) Å in 4 are almost identical
and are substantially longer than that in the free ketone
of 1.23 Å 13 but not as long as those in the coordination
dimer [Cp2Zr(η2-OdCPh2)]2 with values of 1.425(4) and
1.419(4) Å.2 The longer metal-ketone distances in 4
of Zr-C(7) ) 2.301(5) and Zr-O(1) ) 2.041(3) Å,
compared to the Ti complex of Ti-C ) 2.150(7) and
Ti-O ) 1.849(5) Å, result from the larger size of Zr.
But the data are in good agreement with analogous
averaged bond distances Zr-C ) 2.384(3) and Zr-O
) 2.111(2) Å in the coordination dimer [Cp2Zr(η2-
OdCPh2)]2,2 which are slightly enlarged by additional
interactions in the four-membered Zr-O ring. The
relatively long Zr-O bond distance of the complexed
THF of 2.321(3) Å is a proof of the loose Zr-THF
interaction also found in the zirconacyclopropene com-
A similar complex {[Cp2ZrOCHPhC(Ph)dC(Ph)][Cp2-
Zr(η2-OdCH2)]} was claimed as a product of the reaction
of a mixed dimeric zirconocene complex of benz- and
formaldehyde with an excess of tolane, but without a
structure determination, by Erker5 on the basis of the
products of its hydrolysis.
The 1H-NMR spectrum of 3 exhibits, besides four
signals for the nonequivalent Cp protons (5.07, 6.08,
6.21, 6.27 ppm), two signals for the SiMe3 units (-0.02,
0.41 ppm) and two signals for the former benzaldehyde
protons (4.24, 5.94 ppm) of which the first is assigned
to the µ-η1:η2 and the latter to the inserted benzaldehyde
unit (cf. 5.55 ppm in 2).
The reaction of Cp2ZrC(SiMe3)dC(SiMe3)(THF) with
benzophenone does not yield an insertion product of the
carbonyl unit into the zirconacyclopropene ring as found
for acetone, formaldehyde, and benzaldehyde but reacts
by apparent displacement of the alkyne by the ketone
to give complex Cp2Zr(THF)(η2-OdCPh2) (4) (eq 4). To
our knowledge compound 4 is the first isolated mono-
meric zirconocene η2-ketone complex whose structure
has been determined by NMR spectroscopy and X-ray
plex Cp2ZrC(SiMe3)dC(SiMe3)(THF), 2.390(5) Å.8
(13) Fleischer, E. B.; Sung, N.; Hawkinson, S. J . J . Phys. Chem.
1968, 72, 4311.

Reactions of Zirconocene Derivatives
Organometallics, Vol. 15, No. 5, 1996 1343
complexes. The formaldehyde insertion product 1 is
very stable, because two molecules form a coordination
dimer via the Zr-O-Zr-O bridge. The benzaldehyde
complex 2 is stabilized by loss of half of the alkyne and
the formation of 3. The reaction with benzophenone
could proceed via a much less stable insertion product
(not observed) which eliminates the acetylene very
rapidly, and the adduct “Cp2Zr(η2-OdCPh2)” can only
be stabilized by an additional solvent molecule (THF)
or by oligomerization.
Interestingly, the observed insertion of aldehydes and
ketones into zirconacyclopropenes are very similar to
the analogous reactions of carbonyl compounds with
group 14 silacyclopropenes found some years ago by
Seyferth et al.15
F igu r e 3. Molecular structure of complex 4, shown by an
ORTEP plot at the 50% probability level.
Exp er im en ta l Section
The NMR spectroscopic and structural data for
the obtained monomeric zirconacyclic complexes
All operations were carried out in an inert atmosphere
(argon) with standard Schlenk techniques. Solvents were
freshly distilled from sodium tetraethylaluminate under argon
prior to use. Deuterated solvents were treated with sodium
or sodium tetraethylaluminate, distilled, and stored under
argon. The following spectrometers were used: NMR, Bruker
ARX 400; IR, Nicolet Magna 550 (Nujol mulls using KBr
plates); MS, AMD 402. Melting points were measured in
sealed capillaries on a Bu¨chi 535 apparatus.
Cp2ZrOCR3R4C(R2)dC(R1), 2 (R1 ) R2 ) SiMe3, R3
)
H, R4 ) Ph), 5 (R1 ) R2 ) SiMe3, R3 ) R4 ) Me10), and
6 (R1 ) R2 ) Ph, R3 ) R4 ) Me10), formed by the
insertion of ketones or aldehydes into zirconacyclopro-
penes, can be discussed in connection with the observed
stability and reactivity. The formaldehyde complex 1
(R1 ) R2 ) SiMe3, R3 ) R4 ) H) with a dimeric structure
was compared with dimeric zirconafuranone complexes
P r ep a r a tion of [Cp 2Zr OCH2C(SiMe3)dC(SiMe3)]2 (1).
t
8 (R1 ) R2 ) SiMe3, R3, R4 ) O14) and 9 (R1 ) Bu, R2
An amount of 0.5 g (1.08 mmol) of Cp2ZrC(SiMe3)dC(SiMe3)-
(THF) was dissolved in 30 mL of THF, and paraformaldehyde
(35 mg, 1.1 mmol) was added to the solution. The mixture
was stirred for 3 h at 55 °C whereupon the color changed from
orange via dark green to pale yellow. After filtration and
evaporation to one-half volume an equivalent amount of
n-hexane was added. On standing at -30 °C for 4 days,
colorless crystals deposited, which were washed with cold
n-hexane and dried in vacuo to give 0.4 g (90%) of 1 (mp 216-
218 °C dec). Anal. Calcd for C38H60O2Si4Zr2 (843.6), monomer
421.8: C, 54.10; H, 7.17. Found: C, 53.50; H, 7.13. IR (Nujol
mull): 1245 cm-1 (δs(CH3Si)), 1074 cm-1 (ν(C-O-(Zr))). 1H-
NMR (C6D6): δ 0.40 (s, 18H, SiMe3), 0.41 (s, 18H, SiMe3, a
broad signal indicates a yet uninvestigated dynamic process),
4.72 (s, 4H, CH2), 5.85 (s, 20H, Cp). 13C-NMR (C6D6): δ 3.2,
5.7 (SiMe3), 91.3 (CH2), 110.5 (Cp), 213.6 (CR), 158.6 (Câ).
29Si-NMR (C6D6): δ -14.5, -15.9 (SiMe3). MS (70 eV), m/z:
) SiMe3, R3, R4 ) O7). Table 1 gives some relevant
data.
In both series of complexes the 13C-NMR signals of
the CR and Câ carbon atoms which carry SiMe3 groups
(e.g. 1, 2, 5, and 8) are shifted more downfield than in
6. As expected, the signals of the CR carbon atoms
appear more downfield compared to the Câ carbon
atoms, but the differences between the chemical shifts
of both atoms ∆δ seem to be larger for the dimeric
complexes, particularly with R3, R4 ) O. The steric
restrictions between the substituents at the ring
carbons especially at Câ and Câ′ (carbonyl C) atoms are
the explanation for smaller angles R2-Câ-CR in the
monomeric complexes compared to dimeric complexes.
In the case of dimeric complexes the Câ substituents
can move into the direction of the sterically less de-
manding groups in Câ′ (carbonyl C) position. Sterically
more demanding groups in this position prevent the
dimerization. Compared to the monomeric compounds
the dimeric complexes are more stable and do not
react with other substrates such as carbon dioxide or
alkynes.
Interestingly, in the series of the monomeric com-
plexes there are no significant differences in the Câ-
Câ′ bond distances, but the stability toward dissociation
differs markedly in the range 5 < 2 < 6. Therefore,
the repulsion of alkyne and carbonyl substituents is
assumed to be the reason for the easy dissociation of 5
and 2 (and also the lack of coupling with benzophenone
in the formation of 4), indicating the steric limitations
of the coupling reaction of alkynes with ketones and
aldehydes by zirconocene complexes.
415 M+ (monomer) - Me, 390 M+ - CH2O, 220 Cp2Zr+, 73
+
SiMe3
.
P r ep a r a t ion of Cp 2Zr OCHP h C(SiMe3)dC(SiMe3) (2).
To an amount of 0.56 g (1.21 mmol) of Cp2ZrC(SiMe3)dC-
(SiMe3)(THF) in 20 mL of THF was added benzaldehyde (122
µL, 1.21 mmol). The solution became light orange in color. It
was stirred for 1 h at room temperature. After evaporation
to dryness n-hexane was added. The solution was filtered, and
after 3 days at -30 °C orange crystals were formed. The
crystals were washed with cold n-hexane and dried in vacuo
to give 0.29 g (48%) of 2 (mp 103-105 °C, elimination of
alkyne). Anal. Calcd for C25H34OSi2Zr (497.9): C, 60.30; H,
6.88. Found: C, 59.30; H, 6.60. IR (Nujol mull): 1246 cm-1
(δs(CH3Si)), 1048 cm-1 (ν(C-O-(Zr))), 522 cm-1 (ν(Zr-O)). 1H-
NMR (THF-d8): δ 0.22 (s, 9H, SiMe3), -0.10 (s, 9H, SiMe3),
6.24 (s, 5H, Cp), 6.38 (s, 5H, Cp), 7.2-7.35 (m, 5H, Ph), 5.55
(s, 1H, CH). 13C-NMR (THF-d8): δ 2.5, 4.9 (SiMe3), 113.8,
114.3 (Cp), 90.0 (CH), 127.5, 128.5, 129.5, 145.6 (Ph), 222.2
(CR), 185.8 (Câ). MS (70 eV), m/z: 481 M+ - Me, 420 M+
-
Ph, 220 Cp2Zr+.
On the other hand, in the series of products with
H2CdO, PhHCdO, and Ph2CdO the stability of the
products depends on the possibilities to form dimeric
P r epar ation of {[Cp2Zr OCHP h C(SiMe3)dC(SiMe3)][Cp2-
Zr (η2-OdCHP h )]} (3). An amount of 0.3 g (0.6 mmol) of 2
(14) Rosenthal, U.; Ohff, A.; Michalik, H.; Go¨rls, H.; Burlakov, V.
V.; Shur, V. B. Organometallics 1993, 12, 5016.
(15) Seyferth, D.; Vick, S. C.; Shannon, M. L. Organometallics 1984,
3, 1897.

1344 Organometallics, Vol. 15, No. 5, 1996
Peulecke et al.
was dissolved in 20 mL of n-hexane and stirred for 2 h at 60
°C. The color of the mixture changed from light orange to pale
yellow. After evaporation to dryness, to remove the alkyne,
there remained 0.242 g (98%) of 3. The residue was dissolved
in n-hexane/THF (3:1) and the solution was kept at -30 °C
yielding yellow crystals (mp 160-162 °C dec). Anal. Calcd
for C42H50O2Si2Zr2 (822.1): C, 61.30; H, 6.13. Found: C, 60.73;
H, 6.14. IR (Nujol mull): 1244 cm-1 (δs(CH3Si)), 1040 cm-1
((ν(C-O-(Zr))). 1H-NMR (THF-d8): δ -0.02 (s, 9H, SiMe3),
0.41 (s, 9H, SiMe3), 4.24 (s, 1H, CH), 5.94 (s, 1H, CH), 5.07,
6.08, 6.21, 6.27 (each s, 5H, Cp), 6.85-7.75 (m, 10H, Ph). 13C-
NMR (THF-d8): δ 4.0, 6.8 (SiMe3), 80.1, 102.4 (CH), 109.6,
109.7, 112.4, 112.5 (Cp), 122.3, 122.6, 128.4, 128.6, 129.1,
142.9, 153.4, 165.3 (Ph), 218.7 (CR), 165.7 (Câ). MS (70 eV),
tometer using Mo KR radiation. The structures were solved
by direct methods (SHELXS-86: Sheldrick, G. M. Acta Crys-
tallogr., Sect. A 1990, 46, 467) and refined by full-matrix least-
squares techniques against F2 (SHELXL-93: Shedrick, G. M.
University of Go¨ttingen, Germany, 1993). Structural data:
(XP, Siemens) are as follows. 1: space group P1h; a ) 10.659-
(1), b ) 14.849(1), c ) 15.827(1) Å; R ) 116.87(1), â ) 107.44-
(1), γ ) 93.78(1)°; V ) 2071.3(3) Å3; crystal dimensions 0.5 ×
0.5 × 0.4 mm; Z ) 2; Dc ) 1.353 g/cm3; µ ) 0.649 mm-1; θ
range 2.28-24.97°; number of collected data at 20 °C, 7691;
number of unique data, 7265; number of observed data with I
> 2σ(I), 6084; non-hydrogen atoms refined anisotropically;
number of variables, 415; R1 ) 0.029 (I g 2σ(I)); wR2 ) 0.089
(all data). 2: space group P1h; a ) 9.4642(8), b ) 10.843(5), c
) 14.2391(8) Å; R ) 110.563(4), â ) 103.296(6), γ ) 103.033-
(6)°; V ) 1253.97(11) Å3; crystal dimensions 0.2 × 0.2 × 0.15
mm; Z ) 2; Dc ) 1.319 g/cm3; µ ) 0.547 mm-1; θ range 2.35-
25°; number of collected data at 20 °C, 4696; number of unique
data, 4405; number of observed data with I > 2σ(I), 3455; non-
hydrogen atoms refined anisotropically; number of variables,
278; R1 ) 0.034 (I g 2σ(I)); wR2 ) 0.108 (all data). 4: space
group P212121; a ) 8.9846(5), b ) 14.752(1), c ) 19.768(2) Å;
V ) 2620.1(4) Å3; crystal dimensions 0.3 × 0.3 × 0.3 mm; Z )
4; Dc ) 1.389 g/cm3; µ ) 0.45 mm-1; θ range 2.48-24.97°;
number of collected data at -80 °C, 2629; number of unique
data, 2629; number of observed data with I > 2σ(I), 2444; non-
hydrogen atoms refined anisotropically; number of variables,
311; R1 ) 0.035 (I g 2σ(I)); wR2 ) 0.089 (all data).
m/z: 652 M+ - alkyne, 496 M+ - Cp2ZrOCHPh, 220 Cp2Zr+,
+
73 SiMe3
.
P r ep a r a tion of [Cp 2Zr (THF )(η2-OdCP h 2)]‚THF (4). An
amount of 0.48 g (1.03 mmol) of Cp2ZrC(SiMe3)dC(SiMe3)-
(THF) in 20 mL of THF was treated with 0.187 g (1.03 mmol)
of benzophenone. The solution was stirred for 2 h at room
temperature whereupon the color changed from orange to
yellow. The solution was then reduced in volume to one-half,
and after standing for 2 days at -30 °C, light-yellow crystals
were obtained. After washing with cold THF 0.162 g (33%) of
4 was obtained. Anal. Calcd for C27H28O2Zr‚C4H8O (546.2):
C, 68.11; H, 6.64. Found: C, 66.72; H, 6.48. 1H-NMR (THF-
d8): δ 1.78, 3.62 THF; 5.54 (s, 10H, Cp), 6.83 (m, 2H, p-Ph)
7.05-7.65 (m, 8H, o,m-Ph). 13C-NMR (THF-d8): δ 26.3, 68.1
(THF), 94.7 (C-O), 109.9 (Cp), 122.2, 127.4, 157.4 (Ph, a
broadening of the Ph resonances indicates a yet uninvestigated
dynamic process). Crystals for the X-ray structural analysis
were obtained from a cold solution and contain two additional
THF molecules of solvation.
Su p p or tin g In for m a tion Ava ila ble: ORTEP diagrams
and tables of X-ray parameters, complete atomic and thermal
parameters, anisotropic thermal parameters, and bond dis-
tances and angles (28 pages). Ordering information is given
on any current masthead page.
P r ep a r a tion of [Cp 2Zr OCOC(SiMe3)dC(SiMe3)]2 (8).
This was published in ref 14. 13C-NMR (THF-d8): δ 3.8, 5.7
(SiMe3), 178.6 (CO2), 249.0 (CR), 152.9 (Câ) 112.7 (Cp).
X-r a y Cr ysta llogr a p h ic Stu d y of Com p lexes 1, 2, a n d
4. Diffraction data were collected on a CAD4 MACH3 diffrac-
OM950664V