1,3-Diphenylindenyl zirconium complexes. Synthesis, structure, and reduction reactions

Article abstract of DOI:10.1007/s11172-008-0216-3

New zirconium sandwich complexes (η⁵-C₉H ₅Ph₂)₂ZrCl₂ (1) and (η⁵-C₉H₅Ph₂)-(η⁵- C₅(CH₃)₅)ZrCl₂ (2) were synthesized and characterized. The molecular structures of complexes 1 and 2 were established by X-ray diffraction. The reduction of 1 and 2 does not stop at the formation of the Zr^II derivatives with the η⁹- coordinated indenyl ligand; instead the reaction results in the destruction of the metallocene structure.

Full text of DOI:10.1007/s11172-008-0216-3

Russian Chemical Bulletin, International Edition, Vol. 57, No. 8, pp. 1657—1660, August, 2008
1657
1,3ꢀDiphenylindenyl zirconium complexes.
Synthesis, structure, and reduction reactions
S. A. Belov,a D. P. Krut´ko,a R. S. Kirsanov,a D. A. Lemenovskii,a and A. V. Churakovb
aDepartment of Chemistry, M. V. Lomonosov Moscow State University,
1 Leninskie Gory, 119992 Moscow, Russian Federation.
Fax: +7 (495) 932 8846. Eꢀmail: kdp@org.chem.msu.ru
bN. S. Kurnakov Institute of General and Inorganic Chemistry, Russian Academy of Sciences,
31 Leninsky prosp., 119991 Moscow, Russian Federation.
Fax: +7 (495) 954 1279
5
5
New zirconium sandwich complexes (η ꢀC9H5Ph2)2ZrCl2 (1) and (η ꢀC9H5Ph2)ꢀ
5
(η ꢀC5(CH3)5)ZrCl2 (2) were synthesized and characterized. The molecular structures of
complexes 1 and 2 were established by Xꢀray diffraction. The reduction of 1 and 2 does not stop
9
at the formation of the ZrII derivatives with the η ꢀcoordinated indenyl ligand; instead the
reaction results in the destruction of the metallocene structure.
Key words: 1,3ꢀdiphenylindenyl ligand, zirconium, reduction, Xꢀray diffraction study.
The recently synthesized1—4 ZrII derivatives with the
sterically crowded indenyl ligands are rare examples of
thermally stable divalent zirconium compounds. The reꢀ
active metal centers in such complexes are stabilized
through an additional reversible coordination of the sixꢀ
membered ring to the metal atom (the η9ꢀcoordination
mode) (Scheme 1). Derivatives of ZrII with the 1,3ꢀdisubꢀ
stituted ligands containing bulky alkyl (But or Pri) or silyl
(SiMe3 or SiPhMe2) substituents have been studied. With
the aim of examining the possibility of the use of diarylꢀ
substituted indenyl ligands for the preparation of divalent
zirconium compounds, we synthesized the new bisꢀindenyl
complexes (η5ꢀ1,3ꢀC9H5Ph2)2ZrCl2 (1) and (η5ꢀ1,3ꢀC9H5Ph2)ꢀ
(η5ꢀC5(CH3)5)ZrCl2 (2) and studied their reduction
reactions.
Results and Discussion
Lithium 1,3ꢀdiphenylindenide (3) required for the synꢀ
thesis of the target complexes was prepared by metallation
of 1,3ꢀdiphenylindene with nꢀbutyllithium. The pure
product was isolated as an orange compound, which is
extremely sensitive to atmospheric oxygen and moisture
and is readily soluble in toluene, diethyl ether, and THF
(unlike the first two solvents, a solution of compound 3 in
THF exhibits strong fluorescence).
Sandwich complexes 1 and 2 were synthesized by heatꢀ
ing compound 3 with ZrCl4 and Cp*ZrCl3, respectively,
Scheme 2
Ph
Cp*ZrCl3
ZrCl4
–
Scheme 1
i
i
Li+
Ph
3
R
R
R´
R´
[H]
Ph
Cl
Ph
Ph
Zr
Cl
Cl
Zr
Cl
Cl
Zr
Zr
Cl
Ph
Ph
R´
R´
R
R
Ph
1
2
i
t
R,R´ = Pr , Bu , SiMe , SiMe Ph
3
2
i, Toluene, 100 °C.
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 8, pp. 1626—1629, August, 2008.
1066ꢀ5285/08/5708ꢀ1657 © 2008 Springer Science+Business Media, Inc.

1658
Russ.Chem.Bull., Int.Ed., Vol. 57, No. 8, August, 2008
Belov et al.
Table 1. Selected bond lengths (d) and bond angles (ω) in the
structure of compound 1*
in toluene (Scheme 2). The target compounds, which are
moderately stable in air, were isolated in the crystalline
state and characterized. The molecular structures of comꢀ
plexes 1 and 2 were established by Xꢀray diffraction.
Studies of the reduction of 1 and 2 with magnesium
amalgam in THF or with sodium in benzene showed that
this reaction always affords magnesium or sodium 1,3ꢀdipheꢀ
nylindenide, respectively, as the major product, i.e., this
reaction is accompanied by destruction of the metallocene
structure. At the same time, the reactions of their isoproꢀ
pyl analogs (η5ꢀ1,3ꢀC9H5Pri2)2ZrCl2 (see Ref. 2) and
(η5ꢀ1,3ꢀC9H5Pri2)(η5ꢀCp*)ZrCl2 (see Ref. 4) with sodium
amalgam give the thermally stable ZrII derivatives, viz.,
(η9ꢀ1,3ꢀC9H5Pri2)(η5ꢀ1,3ꢀC9H5Pri2)Zr and (η9ꢀ1,3ꢀC9H5Pri2)ꢀ
(η5ꢀCp*)Zr, respectively (Scheme 3). Attempts to reduce
compounds 1 and 2 with isobutyllithium2 also failed. These
reactions afforded mixtures of unidentified products. This
difference in the results is apparently attributed to a much
higher stability of the 1,3ꢀdiphenylindenyl anion compared
to the diisopropylꢀsubstituted analog, which substantially
facilitates the reductive decomposition of the probable
ZrII intermediates.
Bond
d/Å
Parameter
Value
Zr—Cl(1)
2.4021(13)
Bond
d/Å
Zr—Pl(1)* 2.255(2)
Zr—C(19)
Zr—C(18)
Zr—Cl(2)
Zr—C(11)
2.564(4)
2.617(4)
2.4147(14)
2.486(3)
Zr—C(1)
Zr—C(9)
Zr—C(2)
Zr—C(3)
Zr—C(8)
Zr—C(12)
2.500(4)
2.510(4)
2.565(4)
2.613(3)
2.632(4)
2.501(4)
Angle
Cl(1)—Zr—Cl(2)
ω/deg
94.45(5)
* The parameters Pl(1) and Pl(2) are the mean planes of the
fiveꢀmembered indenyl rings.
Molecular structures of complexes 1 and 2
The molecular structure of bisꢀindenyl complex 1 is
shown in Fig. 1. Selected bond lengths and bond angles
are given in Table 1. Compound 1 is a skewed metal
sandwich. The angle between the η5ꢀcoordinated fiveꢀ
membered rings is 61.5(1)°. The indenyl ligands adopt a
staggered conformation. The phenylene moieties of the
indenyl fragments are directed outward the zirconocene
wedge. Both ligands are planar within 0.084(3) Å. The
geometric parameters of 1 are, on the whole, similar to
those found earlier in bisꢀindenyl zirconocene dichlorides
(Cambridge Structural Database, version 5.28, 2007).5
The molecular structure of the mixed pentamethylꢀ
cyclopentadienyl indenyl zirconocene 2 is shown in Fig. 2.
Selected bond lengths and bond angles are given in Table 2.
Compound 2 is a skewed metal sandwich. The angle
between the η5ꢀcoordinated fiveꢀmembered rings is 54.6(2)°.
The fiveꢀmembered rings are in the mutually staggered
conformation. The phenylene moiety of the indenyl
ligand, like that in compound 1, is directed outward the
zirconocene wedge. It should be noted that this conforꢀ
mation has not been described earlier for mixed cyclopentaꢀ
Scheme 3
R = Pri
R = Ph
i
ii
R
R
ZrLCl2
Pri
Ph
–
Pri
M+
ZrL
Ph
M = 1/2 Mg, Na; L = C Me , 1,3ꢀC H R
5
5
9
5
2
i, Mg/Hg in THF or Na/Hg in C D ; ii, Na/Hg, toluene.
6
6
С(5)
С(6)
С(7)
C(39)
С(4)
С(3)
C(40)
C(34)
С(38)
C(33)
С(23)
С(24)
С(22)
C(35)
C(36)
С(8)
С(2)
C(32)
C(37)
C(31)
Cl(1)
С(9)
С(1)
С(31)
Сl(1)
С(25)
С(26)
С(32)
С(33)
Cl(2)
Zr
C(2)
Сl(2)
Zr
С(36)
С(11)
C(3)
C(11)
C(12)
C(13)
C(14)
С(45)
С(34)
С(52)
C(22)
C(23)
С(46)
С(41)
С(35)
C(1)
C(21)
С(19)
С(18)
С(17)
С(53)
С(44)
С(43)
C(24)
C(16)
C(4)
C(15)
C(26)
C(8)
C(25)
С(14)
C(9)
C(5)
С(51) С(56)
С(54)
С(15)
С(55)
С(16)
С(13)
С(42)
C(6)
C(7)
Fig. 2. Molecular structure of complex 2. Hydrogen atoms are
Fig. 1. Molecular structure of complex 1. Hydrogen atoms are
omitted.
omitted.

1,3ꢀDiphenylindenyl zirconium complexes
Russ.Chem.Bull., Int.Ed., Vol. 57, No. 8, August, 2008
1659
5
Table 2. Selected bond lengths (d) and bond angles (ω) in the
structure of compound 2*
Bis(η ꢀ1,3ꢀdiphenylindenyl)dichlorozirconium (adduct with
5
one toluene molecule), (η ꢀ1,3ꢀC9H5Ph2)2ZrCl2•C6H5CH3 (1).
A mixture of ZrCl4 (300 mg, 1.29 mmol) and salt 3 (790 mg,
2.88 mmol) in toluene was heated for 16 h in a boiling water
bath. The solution was separated from the precipitate by decanꢀ
tation and concentrated to dryness. The residue was washed
with hexane and dried under high vacuum. The product was
obtained as an orange powder in a yield of 740 mg (0.94 mmol,
73%). Found (%): C, 75.01; H, 5.10. C49H38Cl2Zr. Calculated
(%): C, 74.60; H, 4.85. 1H NMR (C6D6), δ 2.10 (s, 3 H, PhCH3);
6.70 (s, 2 H, H(2)); 6.85 (m, 4 H, H(4,7) or H(5,6)); 6.99—7.12
(m, 5 H, PhCH3); 7.04 (m, 12 H, mꢀH, pꢀH); 7.44 (m, 8 H,
oꢀH); 7.82 (m, 4 H, H(5,6) or H(4),H(7)). 13C{1H} NMR, δ:
21.36 (PhCH3); 116.38 (CH(2)); 119.30 (C(1),C(3) or C(3a),
C(7a)); 125.64 (pꢀCH in PhCH3); 124.58, 127.10, 127.39
(pꢀCH, CH(4—7)); 128.51 (mꢀCH in PhCH3); 128.56, 128.73
(oꢀCH, mꢀCH); 129.28 (oꢀCH in PhCH3); 133.92 (ipsoꢀC);
137.86 (ipsoꢀC в PhCH3).
Bond
d/Å
Parameter
Value
Zr—Cl(1)
Zr—Pl(1)*
Zr—Pl(2)*
Zr—C(2)
Zr—C(3)
Zr—C(1)
Zr—C(4)
Zr—C(9)
Zr—C(34)
2.4239(16) Bond
d/Å
2.211(2)
2.264(2)
2.500(3)
2.540(6)
2.550(6)
2.630(6)
2.637(5)
2.495(5)
Zr—C(33)
2.497(5)
2.513(6)
2.519(6)
2.532(6)
Zr—C(31)
Zr—C(32)
Zr—C(35)
Angle
Zr—Cl(2)
Cl(1)—Zr—Cl(2)
ω/deg
2.4219(15)
94.80(7)
* The parameters Pl(1) and Pl(2) are the mean planes of the
fiveꢀmembered cyclopentadienyl and indenyl rings, respectively.
dienyl indenyl zirconocenes. Both ligands are planar
within 0.072(3) Å. As in most of the known indenyl comꢀ
plexes of ZrIV, the Zr—C(2) distance (2.500(3) Å) is the
shortest Zr—Cind distance.5 The geometric parameters of 2
are, on the whole, similar to those found earlier in the related
pentamethylcyclopentadienyl indenyl zirconium comꢀ
plexes (Me5C5)(Ind)ZrCl2 (see Ref. 6) and (Me5C5)ꢀ
(2ꢀPhꢀInd)ZrCl2.7
Single crystals suitable for Xꢀray diffraction were grown by
crystallization from hexane.
5
5
(η ꢀ1,3ꢀDiphenylindenyl)(η ꢀpentamethylcyclopentadienyl)ꢀ
5
5
dichlorozirconium, (η ꢀ1,3ꢀC9H5Ph2)(η ꢀC5(CH3)5)ZrCl2 (2).
A mixture of Cp*ZrCl3 (640 mg, 1.92 mmol) and salt 3 (710 mg,
2.59 mmol) in toluene was heated for 16 h in a boiling water
bath. The solution was separated from the precipitate by decanꢀ
tation and concentrated to dryness. The residue was washed
with hexane and dried under high vacuum. The product was
obtained as an orange powder in a yield of 1.03 g (1.82 mmol,
95%). Found (%): C, 66.13; H, 5.40. C31H30Cl2Zr. Calculated
(%): C, 65.94; H, 5.35. 1H NMR (THFꢀd8), δ: 1.64 (s, 15 H,
C5Me5); 7.12 (s, 1 H, H(2)); 7.30 (m, 2 H, H(4),H(7) or
Experimental
All operations, including the preparation of samples for NMR
spectroscopy, were carried out under an inert atmosphere or in
sealed evacuated Schlenkꢀtype glassware. All solvents, including
deuterated solvents, were purified according to standard procedures,8
degassed, and recondensed under high vacuum (10–3 Torr)
directly into a reaction vessel or an NMR tube. Commercial
ZrCl4 (Fluka) was used without additional purification. Magnesium
3
H(5),H(6)); 7.34 (t, 2 H, pꢀH, JH,H = 7.4 Hz); 7.47 (t, 4 H,
3
mꢀH, JH,H = 7.6 Hz); 7.95 (m, 6 H, oꢀH, H(5),H(6) or
H(4),H(7)). 13C{1H} NMR, δ: 12.25 (C5Me5); 115.20 (CH(2));
117.46, 130.53 (C(1),C(3),C(3a),C(7a)); 125.03, 126.77, 128.07
(pꢀCH, C(4)H—C(7)H); 125.86 (C5Me5); 129.16, 130.65 (oꢀCH,
mꢀCH); 134.48 (ipsoꢀC).
1H NNMR (C6D6), δ: 1.53 (s, 15 H, C5Me5); 6.58 (s, 1 H,
H(2)); 7.13 (m, 4 H, pꢀH, H(4),H(7) or H(5),H(6)); 7.27 (t,
4 H, mꢀH, 3JH,H = 7.3 Hz); 7.85 (d, 4 H, oꢀH, 3JH,H = 7.6 Hz);
8.06 (m, 2 H, H(5),H(6) or H(4),H(7)). 13C{1H} NMR, δ: 12.16
(C5Me5); 113.83 (CH(2)); 116.82 (C(1),C(3) or C(3a),C(7a));
124.54, 126.84, 127.49 (pꢀCH, C(4)HꢀC(7)H); 125.24 (C5Me5);
128.63 (mꢀCH); 130.15 (oꢀCH, C(3a),C(7a) or C(1),C(3));
133.90 (ipsoꢀC).
amalgam,9 1,3ꢀdiphenylindene,10 and Cp ZrCl3 were synthesized
according to procedures described in the literature.
*
11
The 1H and 13C NMR spectra were recorded on a Bruker
Avanceꢀ400 spectrometer (400 and 100 MHz, respectively) at
27 °C using the chemical shifts of the signals of the correspondꢀ
ing deuterated solvents (7.15 and 128.0 ppm for C6D6 and 1.73
and 25.3 ppm for THFꢀd8, respectively) as the internal standard.
The elemental analysis was carried out on an automated Carloꢀ
Erba analyzer.
Single crystals suitable for Xꢀray diffraction were grown by
crystallization from hexane.
Lithium 1,3ꢀdiphenylindenide, (1,3ꢀIndPh2)Li (3). A 2.45 M
nꢀBuLi solution in hexane (7.2 mL) was added with vigorous
stirring and strong cooling to a solution of 1,3ꢀdiphenylindene
(4.7 g, 17.5 mmol) in diethyl ether (50 mL). The yellow crystals
that precipitated were separated by decantation, washed with
diethyl ether, and dried under high vacuum. The mother liquor
was concentrated, hexane was added, and the orange precipitate
was separated, washed with a mixture of hexane and diethyl
ether, and dried under high vacuum. The total yield was 3.94 g
(14.4 mmol, 82%). 1H NMR (THFꢀd8), δ: 6.53 and 7.75 (both br.m,
2 H, H(4)—H(7)); 6.63 (br.t, 2 H, pꢀH); 7.07 (br.t, 4 H, mꢀH);
7.17 (s, 1 H, H(2)); 7.60 (br.d, 4 H, oꢀH). 13C{1H} NMR, δ:
111.77, 119.55 (C(1,3,3a,7a)); 115.19, 118.12 (C(4)H—C(7)H);
119.36 (pꢀCH); 125.14 (oꢀCH); 128.52 (mꢀCH); 131.65 (C(2)H);
144.46 (ipsoꢀC).
Reduction of complexes 1 and 2 with activated manganese.
A solution of complex 1 or 2 (~50 mg) in THFꢀd8 (0.6 mL) was
stirred with Mg/Hg (30 mg, ~15 equiv.) at 25 °C for 2 days. The
darkꢀbrown solution was separated from the precipitate and
quantitatively transferred into an NMR tube. The main signals
in the 1H and 13C NMR spectra of the reaction mixtures are
assigned to diphenylindenide anion 3.
Xꢀray diffraction study of complexes 1 and 2. The Xꢀray
diffraction data sets were collected on automated EnrafꢀNonius
CAD 4 (for 1) and Bruker SMART APEX II (for 2) diffractoꢀ
meters (MoKα radiation, λ = 0.71073 Å, graphite monochroꢀ
mator). The structures of 1 and 2 were solved by direct methods
(SHELXꢀ86).12 All nonhydrogen atoms were refined anisotroꢀ
pically by the fullꢀmatrix leastꢀsquares method based on F2

1660
Russ.Chem.Bull., Int.Ed., Vol. 57, No. 8, August, 2008
Belov et al.
Table 3. Crystallographic characteristics and the Xꢀray diffraction data collection and refinement
statistics for compounds 1 and 2
Parameter
1
2
M
696.78
564.67
Crystal dimensions/mm
Crystal system
Space group
0.40Ѕ0.20Ѕ0.03
Orthorhombic
Pbca
0.25Ѕ0.20Ѕ0.15
Monoclinic
P21
a/Å
b/Å
c/Å
b/deg
V/Å3
Z
13.098(5)
13.289(3)
37.290(14)
90
6491(4)
8
8.922(4)
14.153(7)
10.940(5)
110.568(4)
1293.3(11)
2
dcalc/g cmꢀ3
µ/mm–1
1.426
0.533
1.450
0.650
F(000)
2848
580
Т/°К
293(2)
303(2)
θ Scan range/deg
2.25—25.48
10016
2.83—28.00
11863
Number of measured reflections
Number of independent reflections (Rint
Number of reflections with I ≥ 2σ(I)
Number of refined parameters
R1 (I ≥ 2σ(I))
)
6018 (0.0701)
2239
6029 (0.0339)
5084
406
288
0.0371
0.0474
wR2 (based on all reflections)
Goodnessꢀofꢀfit on F2
Residual electron density (min/max) /e Å
0.0771
0.1138
0.852
1.075
–3
0.353/–0.511
0.610/–0.495
(SHELXLꢀ97).13 All hydrogen atoms were positioned geometriꢀ
cally and refined using a riding model. The structure of 2 is
pseudosymmetric and can be solved in the centrosymmetric space
group P21/m, but the refinement in this space group gave unsatꢀ
isfactory results. In addition, the crystal of 2 was a racemic twin
(the Flack parameter is 0.22(6)). The Xꢀray diffraction data
collection and refinement statistics are given in Table 3.
6. M. A. Schmid, H. G. Alt, W. Milius, J. Organomet. Chem.,
1996, 514, 45.
7. R. Kravchenko, A. Masood, R. M. Waymouth, C. L. Myers,
J. Am. Chem. Soc., 1998, 120, 2039.
8. W. L. F. Armarego, Purification of Laboratory Chemicals,
Pergamon Press, 4 ed., Oxford, 1996, 529.
9. D. P. Krut’ko, M. V. Borzov, L. G. Kuz’mina, A. V.
Churakov, D. A. Lemenovskii, O. A. Reutov, Inorg. Chim.
Acta, 1998, 280, 257.
10. W. G. Miller, C. U. Pittman, J. Org. Chem., 1974, 39, 1955.
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J. Organomet. Chem., 1988, 340, 37.
12. G. M. Sheldrick, Acta Cryst., Section A, 1990, A46, 467.
13. G. M. Sheldrick, SHELXLꢀ97. Program for the Refinement of
Crystal Structures, (University of Göttingen, Germany), 1997.
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