[Zr{Me2C(ꢀ-C5H4)2}Ph2] 3. The compound [Zr{Me2C(η-
C5H4)2}Cl2] (7.2 g, 21.6 mmol) was dissolved in THF (50 ml)
and the solution cooled to Ϫ78 ЊC. Aluminium foil was
wrapped round the Schlenk tube to exclude light and phenyl
magnesium bromide (3 M in diethyl ether, 14.6 ml, 44 mmol)
added. The solution was slowly warmed to room temperature
over a period of 1 h and the stirring continued for a further 12 h
period during which time the yellow solution deepened in
colour to light brown. The solvent was then removed under
reduced pressure, and the residue washed with light petroleum
ether (bp 40–60 ЊC) to leave a pale brown solid. Recrystallis-
ation from toluene at Ϫ25 ЊC gave beige, light sensitive crystals
of [Zr{Me2C(η-C5H4)2}Ph2]. Yield 4.4 g (50%).
1,4-diphenylbutadiene in THF (5 ml) was then added and the
mixture allowed to warm, with stirring, to room temperature
over a period of 1–2 h. During this time a colour change from
yellow to red could be observed. The solvent was then removed
under reduced pressure and the residue extracted into toluene
(30 ml) to produce a deep red solution, to which pentane (50
ml) was added and the product recrystallised as a deep red
powder at Ϫ80 ЊC. Yield 335 mg, (75%).
Reaction of cis-[Zr{Me2C(ꢀ-C5H4)2}(ꢀ-C4H6)] with Cl3CCO-
Cl. The compound cis-[Zr{Me2C(η-C5H4)2}(C4H4Me2)] (100
mg, 0.3 mmol) was dissolved in toluene (30 ml), and a solution
of trichloroacetyl chloride in toluene added (0.3 mmol). The
red solution immediately turned yellow with the deposition of a
yellow precipitate over a period of 1 h. Precipitation was com-
pleted by the addition of light petroleum ether (bp 40–60 ЊC)
(100 ml) and the supernatant liquor was filtered off. The result-
ing powder was recrystallised by dissolving in THF (5 ml) and
layering with pentane (20 ml). Large yellow crystals were
obtained over a period of 2 days which were shown by NMR
and elemental analysis to be [Zr{Me2C(η-C5H4)2}Cl2]. Yield ca.
90%.
[Zr{Me2C(C5H4)2}(cis-ꢀ4-C4H4Me2)] 4. The compound
[Zr{Me2C(η-C5H4)2}Ph2] (100 mg, 0.24 mmol) was suspended
in toluene (25 ml) and an excess of freshly distilled 2,3-
dimethylbutadiene added (ca. 2 ml). The white suspension was
irradiated with uv light for 15 h, by which time the reaction
mixture had turned red/orange. Filtration followed by the
removal of volatiles under reduced pressure gave a red residue
consisting of an approximate 5:1 mixture of cis-[Zr{Me2C(η-
C5H4)2}(η-C4H4Me2)] and [Zr{Me2C(η-C5H4)2}Ph2]. Recrystal-
lisation from THF at Ϫ25 ЊC afforded large red crystals of the
butadiene complex. Yield ca. 10 mg (8%).
Reaction of cis-[Zr{Me2C(ꢀ-C5H4)2}(ꢀ-C4H6)] with CH3-
COCl: synthesis of [Zr{Me2C(ꢀ-C5H4)2l}2-ꢁ-O] 6. The com-
pound cis-[Zr{Me2C(η-C5H4)2}(C4H4Me2)] (320 mg, 1 mmol)
was dissolved in THF (20 ml) and acetyl chloride (1 mmol)
added. The solution was stirred for 12 h by which time the
colour had changed from red to yellow. The volatiles were
removed under reduced pressure to leave an oily precipitate.
This was stirred vigorously with pentane (50 ml) for two hours
to become a pale yellow powder which was isolated by filtration
and dried in vacuo. This was then recrystallised from diethyl
ether by slow cooling to Ϫ80 ЊC to give colourless crystals of
[(Me2C(η-C5H4)2ZrCl)2-µ-O]. Yield ca. 150 mg (56%).
trans,trans-1,4-Diphenylbutadiene dilithium salt. The com-
pound trans,trans-1,4-diphenylbutadiene (10 g, 49 mmol) was
dissolved in THF (100 ml), and lithium shot (700 mg, 100
mmol) added under an atmosphere of argon. The mixture was
placed in a sonication bath for two hours, during which time
the solution turned a very deep metallic purple colour and the
lithium metal was seen to dissolve. The solution was filtered and
the solvent removed under reduced pressure to yield a dark
green solid. This was shown to be the bis-THF adduct of the
required product. Yield 17.3 g (95%).
[Zr{Me2C(ꢀ-C5H4)2}{ꢀ3-C4H6B(C6F5)3}] 7. The compound
cis-[Zr{Me2C(η-C5H4)2}(η-C4H6)] (1 g, 3 mmol) was dissolved
in toluene (50 ml) and a solution of B(C6F5)3 in toluene (20 ml)
added dropwise at Ϫ80 ЊC. The solution was allowed to warm
to room temperature, with stirring over a period of two hours,
during which time the solution had become orange. Pentane
(250 ml) was then added, and the supernatant filtered off of the
oily precipitate. This solution of [Zr{Me2C(η-C5H4)2}{η3-C4-
H6B(C6F5)3}] was then immediately used in further reactions.
A pure sample of the solid for characterisation was prepared
by dissolving cis-[Zr{Me2C(η-C5H4)2}(η-C4H6)]. (321 mg, 1
mmol) in light petroleum ether (bp 40–60 ЊC) (100 ml) and add-
ing a solution of B(C6F5)3 in light petroleum ether (bp 40–
60 ЊC) (20 ml) dropwise over a period of 10 min. The solution
immediately turned from red to orange, and an orange precipi-
tate was deposited. The suspension was stirred for 30 min, and
the supernatant filtered off. The precipitate was washed with
light petroleum ether (bp 40–60 ЊC) (20 ml) and dried in vacuo,
giving a yellow powder. Yield ca. 80%.
[Zr{Me2C(ꢀ-C5H4)2}(cis-ꢀ4-PhC4H4Ph)] 5. The compound
Li2(PhC4H4Ph)ؒ2THF (437 mg, 1.2 mmol) and [Me2C(C5H4)2-
ZrCl2] (400 mg 1.2 mmol) were weighed into a dried Schlenk
tube which was placed in an ice bath. Toluene (20 ml) was
added at its freezing point, and the mixture stirred whilst
warming to room temperature. During this time the mixture
darkened to a deep red colour. Stirring was continued for 6 h
before the solvent was removed under reduced pressure. The red
residue was extracted into petroleum ether (bp 100–120 ЊC),
and the impurities removed by crystallisation at Ϫ25 ЊC. The
filtrate was then cooled to Ϫ80 ЊC for 3 days, affording a dark
red, thermally-sensitive powder of cis-[Zr{Me2C(η-C5H4)2}-
(η4-PhC4H4Ph)]. Yield 112 mg (20%).
An alternative method of synthesis, analogous to the
preparation of [Zr{Me2C(η-C5H4)2}(η4-C4H4Me2)] was also
employed. [Zr{Me2C(η-C5H4)2}Ph2] (1 g, 2.4 mmol) was sus-
pended in benzene (25 ml) and an excess of trans,trans-1,4-
diphenylbutadiene added (ca. 2 g). The white suspension was
irradiated with uv light for 25 h, by which time the reaction
mixture had turned dark red in colour. Filtration followed by
the removal of volatiles under reduced pressure gave a dark red
residue consisting of a mixture of cis-[Zr{Me2C(η-C5H4)2}-
(η4-PhC4H4Ph)], unreacted diphenylbutadiene and [Zr{Me2C-
(η-C5H4)2}Ph2]. Recrystallisation from THF at Ϫ25 ЊC afforded
colourless crystals of the starting materials, whilst repeated
crystallisations of the resulting supernatant gave pure cis-
[Zr{Me2C(η-C5H4)2}(η4-PhC4H4Ph)]. This red powder could
be observed to decompose over 6 h at room temperature to a
bright yellow solid. Yield ca. 60 mg (5%).
[Zr{Me2C(ꢀ-C5H4)2}{exo-ꢀ3-C4H6B(C6F5)3}PMe3] 8. A sat-
urated solution of [Zr{Me2C(η-C5H4)2}{η3-C4H6B(C6F5)3}] 7
(0.25 mmol) in pentane–toluene (4:1) was prepared as
described above, and an excess of PMe3 (ca. 1 ml) added to
the orange solution. A fine white precipitate was deposited
and allowed to settle. Filtration afforded a pale yellow powder
which was recrystallised by dissolving in THF (5 ml) and
layering with pentane (20 ml). Large pale yellow crystals of
[Zr{Me2C(η-C5H4)2}{η3-C4H6B(C6F5)3}PMe3ؒTHFؒC5H12]
were formed as the layers diffused together. Yield ca. 200 mg.
A third method of synthesis was also employed. [Zr{Me2C-
(η-C5H4)2}Cl2] (332 mg, 1 mmol) was dissolved in THF (10 ml)
and the solution cooled to Ϫ78 ЊC. n-BuLi (2 mmol) was added
and the mixture stirred for 1 h. One equivalent of trans-trans-
[Zr{Me2C(ꢀ-C5H4)2}{endo-ꢀ3-C4H6B(C6F5)3}C6H5N] 9. This
compound was synthesised by a method analogous to the
preparation of [Zr{Me2C(η-C5H4)2}{η3-C4H6B(C6F5)3}PMe3]
J. Chem. Soc., Dalton Trans., 2000, 317–327
325
Green, Jennifer C.
