Menthyl-functionalized chiral nonracemic bis(indenyl) complexes of zirconium, iron, nickel, and ruthenium

Article abstract of DOI:10.1021/om001084n

Optically active complexes of Zr, Fe, Ni, and Ru containing the chiral, menthyl-substituted indenyl ligands (-)-3-menthyl-4,7-dimethylindene and (-)-2-menthylindene are described. Metathetic reaction of the chiral main-group-metal salts of these indenyl s

Full text of DOI:10.1021/om001084n

Organometallics 2001, 20, 1983-1991
1983
Men th yl-F u n ction a lized Ch ir a l Non r a cem ic Bis(in d en yl)
Com p lexes of Zir con iu m , Ir on , Nick el, a n d Ru th en iu m
Herbert Schumann,* Oleg Stenzel, and Sebastian Dechert
Institut fu¨r Anorganische and Analytische Chemie der Technischen Universita¨t Berlin,
Strasse des 17. J uni 135, 10623 Berlin, Germany
Ronald L. Halterman*
Department of Chemistry and Biochemistry, University of Oklahoma, 620 Parrington Oval,
Norman, Oklahoma 73019
Received December 22, 2000
Optically active complexes of Zr, Fe, Ni, and Ru containing the chiral, menthyl-substituted
indenyl ligands (-)-3-menthyl-4,7-dimethylindene and (-)-2-menthylindene are described.
Metathetic reaction of the chiral main-group-metal salts of these indenyl systems with the
appropriate starting materials of Zr, Fe, and Ni yielded the complexes (pR)(pR)-/(pR)(pS)-
(1-menthyl-4,7-dimethylindenyl)2ZrCl2 (4a /4b), (pR)-/(pS)-(cyclopentadienyl)(1-menthyl-4,7-
dimethylindenyl)ZrCl2 (5a/5b), (pR)(pR)-/(pR)(pS)-/(pS)(pS)-(1-menthyl-4,7-dimethylindenyl)2Fe
(6a /6b/6c), (pR)(pR)-/(pR)(pS)-/(pS)(pS)-(1-menthyl-4,7-dimethylindenyl)2Ni (7a /7b/7c), (+)-
(2-menthylindenyl)2Fe (8), and (-)-(2-menthylindenyl)2Ni (9). Ru(acac)3 reacts with (-)-(2-
menthylindenyl)lithium (3), yielding (-)-(2-menthylindenyl)2Ru (10). Depending on the
reaction conditions, compounds 4-7 were formed as mixtures of diastereomers with respect
to the planar chirality of the indenyl ring system. The apparent diasteromeric excess varied
between 13 and 50% de. The Fe, Ni, and Ru complexes were purified by chromatography
via dried alumina under nitrogen. The structures of 4b and 8 were determined by single-
crystal X-ray diffractometry.
In tr od u ction
applied chiral metallocenes are conformationally con-
strained ansa-metallocenes such as 1′,2′-ethylbis(tet-
rahydroindenyl)zirconium dichloride,5 which are always
formed as mixtures of stereoisomers and must be
separated before application.6
Chiral indenyl complexes of the group 4 metals are
very important catalysts for olefin polymerization, ste-
reoselective hydrogenations, carboaluminations, poly-
merizations,1 or other carbon-carbon2 and carbon-
hydrogen3 bond formations. Late-transition-metal com-
plexes have been shown to be active catalysts for
hydrogenations, hydroformylations, isomerizations, or
cycloadditions,4 but chiral indenyl complexes of these
metals have been only barely exploited. The most widely
As part of our investigations to find new nonracemic
chiral metallocenes,6-9 this paper describes the synthe-
(3) (a) Halterman, R. L.; Vollhardt, K. P. C.; Welker, M. E.; Blaser,
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Baird, M. C. Transition Met. Chem. 1982, 7, 288. (c) Eisen, M.; Blum,
J .; Schumann, H.; Gorella, B. J . Mol. Catal. 1989, 56, 329. (d) Ikura,
K.; Tyu, I.; Ogawa, A.; Kambe, N.; Sonoda, N. Tetrahedron Lett. 1989,
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H.; Gorella, B.; Go¨rlitz, F. H. Inorg. Chim. Acta 1991, 188, 167. (f)
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34, 2391; Angew. Chem., Int. Ed. Engl. 1995, 34, 2207. (h) Castellanos-
Pa´ez, A.; Castillo´n, S.; Claver, C. J . Organomet. Chem. 1997, 539, 1.
(i) Nozaki, K.; Nanno, T.; Takaya, H. J . Organomet. Chem. 1997, 527,
103. (j) Zhu, G.; Zhang, X. J . Org. Chem. 1998, 63, 3133. (k) Zhang,
F.-Y.; Pai, C.-C.; Chan, A. S. C. J . Am. Chem. Soc. 1998, 120, 5808. (l)
Witulski, B.; Stengel, T. Angew. Chem. 1999, 111, 2521; Angew. Chem.,
Int. Ed. 1999, 38, 2426. (m) Beller, M.; Zimmermann, B.; Geist, H.
Chem. Eur. J . 1999, 5, 1301.
* To whom correspondence should be addressed. E-mail: H.S.,
schumann@chem.tu-berlin.de; R.H., rlhalterman@chemdept.chem.ou.edu.
(1) (a) Kaminsky, W.; Ku¨lper, K.; Brintzinger, H. H.; Wild, F. R. W.
P. Angew. Chem. 1985, 97, 507; Angew. Chem., Int. Ed. Engl. 1985,
24, 507. (b) Brintzinger, H. H. In Transition Metals and Organome-
tallics as Catalysts for Olefin Polymerization; Kaminsky, W., Sinn, H.,
Eds.; Springer: Berlin, 1988. (c) Kaminsky, W.; Ahlers, A.; Mo¨ller-
Lindenhof, Angew. Chem. 1989, 101, 1304; Angew. Chem., Int. Ed.
Engl. 1989, 28, 1216. (d) Ro¨ll, W.; Brintzinger, H. H.; Rieger, B.; Zolk,
R. Angew. Chem. 1990, 102, 339; Angew. Chem., Int. Ed. Engl. 1990,
29, 279. (e) Spaleck, W.; Antberg, M.; Rohrmann, J .; Winter, A.;
Bachmann, B.; Kiprof., P.; Behm, J .; Herrmann, W. A. Angew. Chem.
1992, 104, 1373; Angew. Chem., Int. Ed. Engl. 1992, 31, 1347. (f) Erker,
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Angew. Chem., Int. Ed. Engl. 1995, 34, 1143. (i) Kondakov, D. Y.;
Negishi, E. J . Am. Chem. Soc. 1995, 117, 10771. (j) Fink, G.;
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10.1021/om001084n CCC: $20.00 © 2001 American Chemical Society
Publication on Web 04/18/2001

1984 Organometallics, Vol. 20, No. 10, 2001
Schumann et al.
Dich lor ob is(η5-1-m en t h yl-4,7-d im et h ylin d en yl)zir co-
n iu m (IV) (4a /4b). Meth od A. To a suspension of zirconium
tetrachloride (0.79 g, 3.39 mmol) in toluene (40 mL) was added
(-)-(η5-1-menthyl-4,7-dimethylindenyl)lithium (1; 2.17 g, 7.52
mmol) at -78 °C. The mixture was stirred for 3 h, warmed to
25 °C over 8 h, and stirred for an additional 10 h. The
suspension was filtered with a d4-frit, and the residue was
extracted with toluene (10 mL). The solvent was removed
under vacuum (10-2 mbar), leaving a yellow solid as a mixture
of the (pR)(pR)- and (pR)(pS)-diastereomers 4a and 4b in the
ratio 0.8:1. The crude product was suspended in n-pentane (10
mL) and the suspension filtered with a d4-frit. The residue of
the filtration was recrystallized from dichloromethane (10 mL)
at -78 °C, giving 0.81 g (33%) of yellow crystals of the (pR)-
(pS) diastereomer 4b, while recrystallization of the filtrate
from dichloromethane (10 mL) at -78 °C gave 0.62 g (25%) of
yellow crystals of the (pR)(pR) diastereomer 4a .
Ch a r t 1
sis and characterization of some new stereomerically
pure bis(indenyl)metal complexes of zirconium, iron,
ruthenium, and nickel containing (-)-3-menthyl-4,7-
dimethylindene and (-)-2-menthylindene bonded to the
transition metal. We have demonstrated that metathetic
reactions of the alkali-metal salts of chiral menthyl-
substituted indenyl ligands, such as (-)-3-menthyl-4,7-
dimethylindene, (-)-4,7-diisopropyl-3-menthylindene,
and (+)-3-neomenthylindene with [RhCl(COD)]2, [IrCl-
(COD)]2, CoCl2(dppe), and Mo(CO)6 provide a convenient
entry into chiral nonracemic mono(indenyl) transition-
metal complexes.10 In order for the 4,7-dialkyl-1-men-
thylindenyl ligands to favor the formation of one specific
diastereomeric transition-metal complex, the chiral
auxiliary should direct metalation to only one ligand
face. As illustrated for mono(indenyl)- and bis(indenyl)-
metal complexes in Chart 1, the 7-alkyl substituent is
used to orient the 1-menthyl moiety in such a way that
its isopropyl group blocks one diastereotopic face, re-
sulting in diastereoselective metalation.9 Metalations of
the 2-menthylindenyl ligand can provide only a single
stereoisomer.
Meth od B. In analogy to method A, a solution of zirconium
tetrachloride (0.38 g, 1.63 mmol) in toluene (15 mL) was
treated at -78 °C with (-)-(1-menthyl-4,7-dimethylindenyl)-
potassium (2; 1.04 g, 3.24 mmol). The workup gave 1.02 g
(87%) of a yellow solid as a mixture of the (pR)(pR) and (pR)-
(pS) diastereomers 4a and 4b in the ratio 0.9:1.
(pR)(pR) Dia ster eom er 4a . 1H NMR (dichloromethane-
d2, 400 MHz): δ 6.87 (m, 2H, H5), 6.78 (m, 2H, H6), 6.70 (d, 3J
3
) 3.2 Hz, 2H, H2), 6.37 (d, J ) 3.2 Hz, 2H, H3), 3.21 (m, 2H,
H3′), 2.72 (s, 6H, H11), 2.47 (m, 2H, H2′), 2.31 (m, 2H, H8′), 2.30
(s, 6H, H10), 1.88 (m, 2H, H6′), 1.73 (m, 2H, H5′), 1.55 (m, 2H,
H1′), 1.29 (m, 2H, H2′), 1.25 (m, 2H, H5′), 1.19 (m, 2H, H4′), 1.10
(m, 2H, H6′), 1.04 (d, 3J ) 6.5 Hz, 6H, H7′), 0.61 (d, 3J ) 6.7
3
Hz, 6H, H9′/10′), 0.54 (d, J ) 6.5 Hz, 6H, H9′/10′). 13C{1H} NMR
(dichloromethane-d2, 100.64 MHz): δ 139.41, 134.19, 133.32,
132.98 (C4,7,8,9), 127.66 (C6), 127.42 (C5), 127.19 (C1), 116.06
(C2), 95.88 (C3), 54.62 (C4′), 45.51 (C2′), 41.03 (C3′), 35.80 (C6′),
33.93 (C1′), 27.29 (C8′), 25.99 (C5′), 22.66 (C7′), 22.52 (C9′/10′),
21.96 (C11), 19.59 (C10), 16.63 (C9′/10′).
(pR)(pS) Dia ster eom er 4b. The first signal set is as
follows (1H/13C pairs are correlated). 1H NMR (dichloromethane-
d2, 400 MHz): δ 6.89 (m, 1H, H5/6), 6.86 (m, 1H, H5/6), 6.56 (d,
3J ) 3.3 Hz, 1H, H2), 5.36 (s br, 1H, H3), 3.34 (m, 1H, H3′),
2.72 (s, 3H, H10/11), 2.63 (s, 3H, H10/11), 2.55 (m, 1H, H2′), 1.87
(m, 1H, H6′), 1.81 (m, 1H, H5′), 1.53 (m, 1H, H1′), 1.52 (m, 1H,
Exp er im en ta l Section
All operations involving organometallic compounds were
carried out under an inert atmosphere of nitrogen or argon
using standard Schlenk techniques in dry, oxygen-free sol-
vents. Melting points were measured in sealed capillaries with
a Bu¨chi 510 melting point determination apparatus and are
uncorrected. Optical rotations were determined on a Schmidt+
Haensch Polartronic-D polarimeter. The NMR spectra were
recorded on a Bruker ARX 200 (1H, 200 MHz; 13C, 50.32 MHz)
or ARX 400 (1H, 400 MHz; 13C, 100.64 MHz) spectrometer at
ambient temperature. Chemical shifts are reported in ppm
3
H4′), 1.39 (m, 1H, H2′), 1.32 (m, 1H, H5′), 1.15 (d, J ) 6.8 Hz,
3H, H9′/10′), 0.96 (d, 3J ) 6.4 Hz, 3H, H7′), 0.90 (m, 1H, H6′),
0.71 (m, 1H, H8′), 0.58 (d, 3J ) 6.8 Hz, 3H, H9′/10′). 13C{1H} NMR
(dichloromethane-d2, 100.64 MHz): δ 134.78, 134.42, 133.23,
133.20 (C4,7,8,9), 125.34 (C1), 125.33, 125.04 (C5,6), 122.85 (C2),
96.89 (C3), 45.52 (C4′), 43.90 (C2′), 41.45 (C3′), 35.83 (C6′), 33.05
(C1′), 27.20 (C8′), 25.46 (C5′), 22.80 (C7′), 22.49 (C9′/10′), 21.89
(C10/11), 20.79 (C10/11), 17.10 (C9′/10′). The second signal set is as
follows (1H/13C pairs are correlated). 1H NMR (dichloromethane-
d2, 400 MHz): δ 6.99 (m, 1H, H5/6), 6.88 (m, 1H, H5/6), 6.49 (d,
3J ) 3.3 Hz, 1H, H2), 4.89 (s br, 1H, H3), 3.19 (m, 1H, H3′),
2.46 (s br, 3H, H10/11), 2.02 (s br, 3H, H10/11), 1.78 (m, 1H, H6′),
1.67 (m, 1H, H5′), 1.52 (m, 1H, H2′), 1.51 (m, 1H, H1′), 1.18 (m,
relative to the H and 13C residue of the deuterated solvents.
1
The IR spectra were recorded on a Nicolet Magna System 750
spectrometer. Mass spectra (EI, 70 eV) were obtained using a
Varian MAT 311 A/AMD instrument. Only characteristic
fragments containing the isotopes of the highest abundance
are listed. Relative intensities in percent are given in paren-
theses. Elemental analyses were performed on a Perkin-Elmer
Series II CHNS/O Analyzer 2400. (-)-(1-Menthyl-4,7-dimethyl-
indenyl)lithium (1), (-)-(1-menthyl-4,7-dimethylindenyl)-
3
1H, H5′), 1.13 (m, 1H, H4′), 0.88 (m, 1H, H6′), 0.81 (d, J ) 6.5
Hz, 3H, H9′/10′), 0.75 (d, 3J ) 6.5 Hz, 3H, H7′), 0.68 (m, 1H,
H8′), 0.53 (d, 3J ) 6.5 Hz, 3H, H9′/10′), 0.42 (m, 1H, H2′). 13C-
{1H} NMR (dichloromethane-d2, 100.64 MHz): δ 134.55,
134.32, 134.06, 133.41 (C4,7,8,9), 129.37 (C1), 127.04, 126.52
(C5,6), 120.96 (C2), 97.15 (C3), 54.74 (C4′), 47.95 (C2′), 41.27 (C3′),
35.36 (C6′), 33.74 (C1′), 27.28 (C8′), 26.25 (C5′), 22.77 (C9′/10′),
22.48 (C7′), 19.12 (C10/11), 18.79 (C10/11), 17.92 (C9′/10′).
potassium (2), (-)-(2-menthylindenyl)lithium (3),9 CpZrCl3-
12
(DME),11 FeCl2(THF)1.15
,
and NiCl2(DME)13 were prepared
according to published procedures. Zirconium tetrachloride
was used as purchased.
(7) (a) Halterman, R. L.; Tretyakov, A.; Combs, D.; Chang, J .; Khan,
M. A. Organometallics 1997, 15, 3333. (b) Halterman, R. L.; Tretyakov,
A.; Khan, M. A. J . Organomet. Chem. 1998, 568, 41. (c) Halterman, R.
L.; Combs, D.; Khan, M. A. Organometallics 1998, 17, 3900.
(8) Halterman, R. L.; Fahey, D. R.; Bailly, E. F.; Dockter, D. W.;
Stenzel, O.; Shipman, J . L.; Khan, M. A.; Dechert, S.; Schumann, H.
Organometallics 2000, 19, 5464.
(pR)(pR) a n d (pR)(pS) Dia ster eom er s 4a a n d 4b in th e
Ra tio 1:1.2. Mp: 231 °C dec. [R]2D5 ) -91.8° (c 0.7, n-hexane).
IR (CsI; cm-1): vj 3096 (w), 3018 (m), 2955 (s), 2928 (s), 2868
(9) Schumann, H.; Stenzel, O.; Girgsdies, F.; Halterman, R. L.
Organometallics 2001, 20, 1743-1751.
(10) Schumann, H.; Stenzel, O.; Dechert, S.; Girgsdies, F.; Halter-
man, R. L. Organometallics, in press.
(11) Lund, E. C.; Livinghouse, T. Organometallics 1990, 9, 2426.
(12) Alias, F. M.; Barlow, S.; Tudor, J . S.; O’Hare, D.; Perry, R. T.;
Nelson, J . M.; Manners, I. J . Organomet. Chem. 1997, 528, 47.
(13) Ward, L. G. L. Inorg. Synth. 1972, 13, 154.

Bis(indenyl) Complexes of Zr, Fe, Ni, and Ru
Organometallics, Vol. 20, No. 10, 2001 1985
(m), 2859 (m), 2730 (w), 1850 (w), 1700 (m), 1646 (w), 1606
(m), 1491 (m), 1459 (s), 1384 (m), 1377 (m), 1367 (m), 1346
(m), 1301 (w), 1252 (m), 1176 (w), 1149 (w), 1106 (m), 1084
(w), 1067 (m), 1035 (w), 1009 (w), 992 (w), 824 (s), 787 (s), 656
(m), 321 (m), 304 (m). MS (191 °C; m/z (%)): 722 (20) [M]+,
687 (3) [(C21H29)2ClZr]+, 583 (2) [(C11H10)(C21H29)Cl2Zr]+, 441
(97) [(C21H29)Cl2Zr]+, 371 (3) [(C21H29)Zr]+, 158 (100) [C12H14]+.
Anal. Calcd for C42H58Cl2Zr (mol wt 725.04): C, 69.58; H, 8.06.
Found: C, 69.24; H, 7.69.
tions. The solvent of the black fractions was removed under
vacuum (10-2 mbar), yielding solids which were recrystallized
from n-pentane at -28 °C, giving 1.80 g (49%) of black crystals
of the diastereomers 6a , 6b, and 6c in the ratio (pR)(pR):(pR)-
(pS):(pS)(pS) ) 4.8:1.8:1.
(pR)(pR) Dia ster eom er 6a . 1H NMR (benzene-d6, 200
MHz): δ 6.53 (m, 1H, H5/6), 6.37 (m, 1H, H5/6), 4.98 (d, 3J )
3
2.5 Hz, 1H, H2), 4.36 (d, J ) 2.5 Hz, 1H, H3), 3.25-0.60 (m,
10H, H1′,2′,3′,4′,5′,6′,8′), 2.60 (s, 3H, H10/11), 1.81 (s, 3H, H10/11), 1.18
3
3
(d, J ) 6.2 Hz, 3H, H7′), 0.55 (d, J ) 6.9 Hz, 3H, H9′/10′), 0.46
Dich lor o(η5-cyclopen tadien yl)(η5-1-m en th yl-4,7-dim eth -
ylin den yl)zir con iu m (IV) (5a/5b). To a suspension of trichloro-
(η5-cyclopentadienyl)zirconium(IV)(DME) (0.26 g, 0.74 mmol)
in THF (20 mL) was added 2 (0.18 g, 0.56 mmol) at -78 °C.
The mixture was stirred for 3 h, warmed to 25 °C over 8 h,
and stirred for an additional 10 h. The suspension was filtered
with a d4-frit, and the residue was extracted with THF (10
mL). The solvent was removed under vacuum (10-2 mbar),
leaving a yellow solid as a mixture of the (pR) and (pS)
diastereomers 5a and 5b in the ratio 1:1.3. The crude product
was suspended in n-pentane (15 mL) and filtered with a d4-
frit. The residue of the filtration was recrystallized from
dichloromethane (10 mL) at -78 °C, giving 0.62 g (25%) of
yellow crystals of the (pR) and (pS) diastereomers 5a and 5b
in the ratio 1:2.7.
3
(d, J ) 6.8 Hz, 3H, H9′/10′). 13C{1H} NMR (benzene-d6, 50.32
MHz): δ 132.80, 127.80 (C4,7), 123.61, 120.73 (C5,6), 89.77,
88.75, 84.09 (C1,8,9), 68.90, 60.91 (C2,3), 52.09, 38.93, 34.35,
26.95 (C1′,3′,4′,8′), 47.13, 35.47, 25.66 (C2′,5′,6′), 23.14, 22.59, 22.03,
19.35, 16.13 (C7′,9′,10,10′,11).
(pR)(pR), (pR)(pS), a n d (pS)(pS) Dia ster eom er s 6a , 6b,
a n d 6c in th e Ra tio 4.8:1.8:1. Mp: 81 °C. [R]2D5 ) -46.6° (c
0.1, diethyl ether). IR (CsI; cm-1): vj 3026 (w), 2953 (s), 2927
(s), 2867 (s), 1737 (m), 1698 (m), 1679 (m), 1650 (w), 1608 (m),
1556 (w), 1483 (m), 1463 (s), 1405 (w), 1383 (m), 1375 (m),
1367 (m), 1345 (m), 1327 (w), 1275 (m), 1251 (m), 1093 (m),
1062 (m), 915 (m), 810 (s), 594 (m), 580 (m), 458 (m), 303 (m).
MS (136 °C; m/z (%)): 618 (100) [M]+, 603 (1) [(C20H26)(C21H29)-
Fe]+, 575 (1) [(C18H22)(C21H29)Fe]+, 479 (4) [(C11H10)(C21H29)-
Fe]+, 309 (1) [M]2+, 198 (2) [(C11H10)Fe]+. Anal. Calcd for
Dia st er eom er 5a . 1H NMR (dichloromethane-d2, 200
MHz): δ 6.91-6.70 (m, 2H, H5,6), 6.49 (d, 3J ) 3.2 Hz, 1H,
C
42H58Fe (mol wt 618.77): C, 81.53; H, 9.45. Found: C, 81.09;
3
H2/3), 6.36 (s, 5H, C5H5), 6.23 (d, J ) 3.2 Hz, 1H, H2/3), 3.41-
H, 9.36. Mol wt (cryoscopy in benzene; m/z): 602.
0.45 (m, 10H, H1′,2′,3′,4′,5′,6′,8′), 2.82 (s, 3H, H10/11), 2.27 (s, 3H,
Bis(η5-1-m en t h yl-4,7-d im et h ylin d en yl)n ick el(II) (7a /
7b/7c). In analogy with the synthesis of 6, a solution of NiCl2-
(DME) (0.26 g, 1.18 mmol) in THF (20 mL) was treated at -78
°C with 1 (0.75 g, 2.60 mmol). The workup gave a violet solid
as a mixture of the (pR)(pR), (pR)(pS), and (pS)(pS) diaster-
eomers 7a , 7b, and 7c in the ratio 5.9:4.0:1. Fractional
chromatography under nitrogen with alumina gave 0.69 g
(47%) of a violet oil as a mixture of the diastereomers 7a , 7b,
and 7c in the ratio (pR)(pR):(pR)(pS):(pS)(pS) ) 5.9:4.0:1.
(pR)(pR) Dia ster eom er 7a . 1H NMR (benzene-d6, 200
MHz): δ 5.88 (m, 2H, H5,6), 5.56 (s br, 1H, H2), 5.42 (s br, 1H,
H3), 3.03-0.59 (m, 10H, H1′,2′,3′,4′,5′,6′,8′), 2.38 (s, 3H, H10/11), 1.97
3
3
H10/11), 1.00 (d, J ) 6.4 Hz, 3H, H7′/9′/10′), 0.90 (d, J ) 7.0 Hz,
3H, H7′/9′/10′), 0.88 (d, J ) 6.5 Hz, 3H, H7′/9′/10′). 13C{1H} NMR
3
(dichloromethane-d2, 50.32 MHz): δ 133.57, 133.23, 133.02,
129.97, 120.81 (C1,4,7,8,9), 127.66, 126.97 (C5,6), 116.90 (C2/3),
116.22 (C5H5), 96.34 (C2/3), 46.24, 40.86, 33.69, 27.33 (C1′,3′,4′,8′),
44.86, 35.61, 26.04 (C2′,5′,6′), 22.60, 22.15, 21.68, 19.24, 16.88
(C7′,9′,10,10′,11).
Dia st er eom er 5b . 1H NMR (dichloromethane-d2, 200
MHz): δ 6.90-6.69 (m, 2H, H5,6), 6.47 (d, 3J ) 3.3 Hz, 1H,
3
H2/3), 6.31 (s, 5H, C5H5), 6.29 (d, J ) 3.3 Hz, 1H, H2/3), 3.39-
0.55 (m, 10H, H1′,2′,3′,4′,5′,6′,8′), 2.73 (s, 3H, H10/11), 2.21 (s, 3H,
H10/11), 1.10 (d, J ) 7.0 Hz, 3H, H7′/9′/10′), 0.83 (d, J ) 6.6 Hz,
(s, 3H, H10/11), 0.99 (d, J ) 6.1 Hz, 3H, H7′), 0.86 (d, J ) 6.6
3
3
3
3
3
3
3H, H7′/9′/10′), 0.77 (d, J ) 6.5 Hz, 3H, H7′/9′/10′). 13C{1H} NMR
Hz, 3H, H9′/10′), 0.70 (d, J ) 6.6 Hz, 3H, H9′/10′). 13C{1H} NMR
(dichloromethane-d2, 50.32 MHz): δ 138.30, 135.90, 134.00,
133.38, 124.20 (C1,4,7,8,9), 127.30, 126.75 (C5,6), 116.03 (C5H5),
112.73, 94.49 (C2,3), 48.24, 35.26, 25.36 (C2′,5′,6′), 45.26, 41.86,
33.05, 28.06 (C1′,3′,4′,8′), 22.50, 22.27, 21.04, 18.89, 17.67
(C7′,9′,10,10′,11).
Dia ster eom er s 5a a n d 5b in th e Ra tio 1:2.7. Mp: 148
°C dec. [R]2D5 ) -63.2° (c 0.2, diethyl ether). IR (CsI; cm-1): vj
3108 (m), 2959 (s), 2947 (s), 2927 (m), 2867 (m), 2844 (w), 1653
(m), 1623 (m), 1617 (m), 1492 (m), 1463 (m), 1454 (m), 1441
(m), 1391 (w), 1377 (w), 1369 (w), 1257 (m), 1247 (m), 1139
(w), 1107 (w), 1072 (w), 1069 (w), 1019 (m), 851 (s), 819 (s),
656 (m), 652 (m), 516 (m), 328 (m), 313 (m), 303 (m), 278 (m),
254 (m). MS (204 °C; m/z (%)): 506 (6) [M]+, 471 (2) [(C21H29)-
(C5H5)ClZr]+, 421 (2) [(C20H26)(C5H5)Zr]+, 121 (100) [C9H13]+.
Anal. Calcd for C26H34Cl2Zr (mol wt 508.68): C, 61.39; H, 6.74.
Found: C, 60.91; H, 6.33.
Bis(η5-1-m en th yl-4,7-d im eth ylin d en yl)ir on (II) (6a /6b/
6c). To a solution of FeCl2(THF)1.5 (0.54 g, 2.58 mmol) in THF
(20 mL) was added 1 (1.25 g, 4.33 mmol) at -78 °C. The
mixture was stirred for 2 h, warmed to 25 °C over 8 h, and
stirred for an additional 10 h. The solvent was removed under
vacuum (10-2 mbar), leaving a black solid which was sus-
pended in n-hexane (10 mL) and filtered with a d4-frit. The
residue was extracted twice with n-hexane (10 mL). The
solvent was removed under vacuum (10-2 mbar), leaving a
black solid as a mixture of the (pR)(pR), (pR)(pS), and (pS)-
(pS) diastereomers 6a , 6b, and 6c in the ratio 4.8:1.8:1. The
solid was suspended in n-hexane (2 mL) and the suspension
fractionally chromatographed under nitrogen with alumina.
Elution with n-hexane gave colorless and finally black solu-
(benzene-d6, 50.32 MHz): δ 129.29, 127.41 (C5,6), 124.66,
123.71, 123.38, 122.93, 121.64 (C1,4,7,8,9), 104.57 (C2), 64.48 (C3),
55.52, 45.05, 34.56, 28.30 (C1′,3′,4′,8′), 53.26, 35.52, 26.17 (C2′,5′,6′),
23.46, 22.75, 21.08, 18.22, 17.06 (C7′,9′,10,10′,11).
(pR)(pR), (pR)(pS), a n d (pS)(pS) Dia ster eom er s 7a , 7b,
a n d 7c in th e Ra tio 5.9:4.0:1. [R]2D5 ) +38.3° (c 0.2, diethyl
ether). IR (CsI; cm-1): vj 3012 (m), 2952 (s), 2918 (s), 2868 (s),
2730 (w), 1868 (w), 1834 (w), 1700 (s), 1589 (m), 1566 (m), 1491
(s), 1456 (s), 1383 (s), 1368 (s), 1345 (m), 1333 (m), 1291 (m),
1280 (m), 1259 (m), 1211 (m), 1177 (m), 1139 (m), 1047 (m),
1031 (m), 992 (m), 981 (m), 933 (m), 922 (m), 916 (m), 901 (m),
874 (m), 841 (m), 802 (s), 787 (m), 775 (m), 770 (m), 640 (m),
533 (m), 491 (m), 457 (m), 303 (m). MS (149 °C; m/z (%)): 620
(43) [M]+, 577 (1) [(C18H22)(C21H29)Ni]+, 562 (6) [(C18H22)-
(C20H26)Ni]+, 310 (2) [M]2+, 200 (1) [(C11H10)Ni]+, 158 (100)
[C12H14]+. Anal. Calcd for C42H58Ni (mol wt 621.61): C, 81.15;
H, 9.40. Found: C, 81.63; H, 9.81.
(+)-Bis(η5-2-m en th ylin d en yl)ir on (II) (8). In analogy with
the synthesis of 6, a solution of FeCl2(THF)1.5 (0.49 g, 2.34
mmol) in THF (20 mL) was treated at 0 °C with (-)-(2-
menthylindenyl)lithium (3; 1.12 g, 4.30 mmol). The workup
and fractional chromatography under nitrogen with alumina
gave a black solid. Recrystallization from n-pentane gave 1.05
g (90%) of black crystals of 8. Mp: 147 °C. [R]2D5 ) +31.8° (c
0.1, diethyl ether). 1H NMR (benzene-d6, 200 MHz): δ 7.37
(m, 2H, H4), 6.90 (m, 2H, H5), 6.88 (m, 2H, H6), 6.65 (m, 2H,
H7), 4.39 (d, 4J ) 0.6 Hz, 2H, H3), 4.33 (d, 4J ) 0.6 Hz, 2H,
H1), 3.13 (m, 2H, H2′), 2.12 (m, 2H, H3′), 1.80 (m, 2H, H6′), 1.64
(m, 2H, H1′), 1.60 (m, 2H, H5′), 1.48 (m, 2H, H2′), 1.47 (m, 2H,
3
H8′), 1.22 (d, J ) 6.2 Hz, 6H, H7′), 1.02 (m, 2H, H5′), 0.93 (m,

1986 Organometallics, Vol. 20, No. 10, 2001
Schumann et al.
2H, H6′), 0.75 (d, 3J ) 6.8 Hz, 6H, H9′/10′), 0.74 (m, 2H, H4′),
0.57 (d, 3J ) 6.9 Hz, 6H, H9′/10′). 13C{1H} NMR (benzene-d6,
50.32 MHz): δ 129.19 (C4), 125.70 (C7), 123.34 (C5), 122.74
(C6), 95.88 (C2), 85.88, 85.82 (C8,9), 65.06, 59.63 (C1,3), 50.62
(C4′), 43.23 (C2′), 39.61 (C3′), 35.68 (C6′), 33.97 (C1′), 26.89 (C8′),
25.17 (C5′), 23.27 (C7′), 21.51, 15.60 (C9′,10′). IR (CsI; cm-1): vj
3076 (w), 3057 (m), 3007 (m), 2957 (s), 2946 (s), 2938 (s), 2924
(s), 2874 (s), 2848 (s), 1714 (m), 1610 (m), 1457 (m), 1384 (m),
1369 (m), 1346 (m), 1295 (w), 1176 (w), 1078 (w), 999 (w), 921
(m), 834 (m), 749 (m), 738 (s), 716 (m), 576 (m), 461 (m), 203
(w). MS (40 °C; m/z (%)): 562 (100) [M]+, 547 (1) [(C18H22)-
(C19H25)Fe]+, 519 (6) [(C16H18)(C19H25)Fe]+, 423 (3) [(C9H6)-
(C19H25)Fe]+, 309 (2) [(C19H25)Fe]+. Anal. Calcd for C38H50Fe
(mol wt 562.65): C, 81.12; H, 8.96. Found: C, 81.59; H, 8.47.
Ta ble 1
4b
8
empirical formula
fw
C
42H58Cl2Zr
C38H50Fe
562.65
725.04
cryst syst
space group
a (Å), R (deg)
b (Å), â (deg)
c (Å), γ (deg)
V (Å3)
orthorhombic
P212121 (No. 19)
11.7782(2), 90
17.7250(2), 90
18.2727(1), 90
3814.77(8)
4
1.262
0.456
1536
orthorhombic
P212121 (No. 19)
9.9996(2), 90
10.8994(2), 90
29.3406(7), 90
3197.82(12)
4
Z
D(calcd) (g/cm3)
1.169
0.495
1216
µ(Mo KR) (mm-1
F(000)
)
cryst size (mm3)
0.85 × 0.52 × 0.48 0.22 × 0.18 × 0.08
(-)-Bis(η5-2-m en th ylin d en yl)n ick el(II) (9). In analogy
with the synthesis of 6, a suspension of NiCl2(DME) (0.38 g,
1.73 mmol) in THF (25 mL) was treated at 0 °C with 3 (0.86
g, 3.30 mmol). The workup and fractional chromatography
under nitrogen with alumina gave a red solid. Recrystallization
from n-pentane at -78 °C gave 0.53 g (57%) red crystals of 9.
Mp: 140 °C dec. [R]2D5 ) -276.8° (c 0.5, benzene). 1H NMR
(benzene-d6, 200 MHz): δ 7.33-6.33 (m, 8H, H4,5,6,7), 5.23 (d,
θ
min, θmax (deg)
1.60, 27.50
-12 e h e 15
-23 e k e 21
-23 e l e 23
29 161
1.39, 26.50
-12 e h e 11
-13 e k e 11
-36 e l e 34
22 627
6619 (Rint )
0.1175)
0.9705, 0.6329
6619, 0, 358
index ranges
no. of rflns collected
no. of indep rflns
8721 (Rint
0.0377)
0.8492, 0.7172
8721, 0, 416
)
max, min transmissn
no. of data, restraints,
params
4
4J ) 1.6 Hz, 2H, H1/3), 4.88 (d, J ) 1.6 Hz, 2H, H1/3), 2.37-
GOF on F2
1.061
1.025
3
0.70 (m, 20H, H1′,2′,3′,4′,5′,6′,8′), 1.00 (d, J ) 6.3 Hz, 6H, H7′/9′/10′),
R indices (I > 2σ(I))
R1 ) 0.0239
wR2 ) 0.0552
R1 ) 0.0272
wR2 ) 0.0571
-0.04(2)
R1 ) 0.0655
wR2 ) 0.1048
R1 ) 0.1241
wR2 ) 0.1225
-0.01(2)
0.92 (d, 3J ) 6.9 Hz, 6H, H7′/9′/10′), 0.82 (d, 3J ) 6.6 Hz, 6H,
H7′/9′/10′). 13C{1H} NMR (benzene-d6, 50.32 MHz): δ 135.20,
133.82, 133.76 (C2,8,9), 123.75, 123.39 (C4,7), 116.35, 116.06
(C5,6), 68.29, 63.98 (C1,3), 51.38, 42.11, 32.77, 27.82 (C1′,3′,4′,8′),
40.59, 35.34, 24.92 (C2′,5′,6′), 22.25, 21.38, 15.61 (C7′,9′,10′). IR (CsI;
cm-1): vj 3069 (m), 2956 (s), 2933 (s), 2914 (s), 2867 (s), 2855
(s), 2844 (s), 2031 (m), 1964 (m), 1713 (m), 1606 (w), 1459 (s),
1444 (m), 1431 (m), 1384 (m), 1370 (m), 1346 (m), 1331 (m),
1320 (m), 1298 (w), 1249 (w), 1226 (m), 1134 (w), 1119 (w),
1079 (w), 1015 (m), 999 (w), 966 (m), 955 (m), 920 (s), 873 (m),
858 (m), 846 (m), 747 (s), 744 (s), 716 (m), 703 (m), 689 (m),
452 (m), 429 (m), 395 (m). MS (46 °C; m/z (%)): 564 (100) [M]+,
506 (2) [(C16H18)(C18H22)Ni]+, 425 (1) [(C9H6)(C19H25)Ni]+, 382
(3) [(C9H6)(C16H18)Ni]+, 311 (8) [(C19H25)Ni]+. Anal. Calcd for
R indices (all data)
abs structure param
residual electron density max 0.273
max 0.447
(e/Å3)
min -0.360
min -0.619
X-r a y St r u ct u r e Det er m in a t ion . The crystal data and
details of data collection are given in Table 1. Data were
collected on a Siemens SMART CCD diffractometer (graphite-
monochromated Mo KR radiation, λ ) 0.710 73 Å) with area
detector by use of ω scans at 173 K for 4b and 8. The structures
were solved by direct methods using SHELXS-9714 and refined
on F2 using all reflections with SHELXL-97.15 All non-
hydrogen atoms were refined anisotropically. The hydrogen
atoms were placed in calculated positions and assigned to an
isotropic displacement parameter of 0.08 Å2. The idealized
methyl groups were allowed to rotate about their C-C bond.
Absolute structure parameters were determined according to
Flack16 with SHELX-97. SADABS17 was used to perform area-
detector scaling and absorption corrections. The maximum and
minimum transmission factors and the resulting crystal-
lographic data are summarized in Table 1. The geometrical
aspects of the structures were analyzed by using the PLATON
program.18
C
38H50Ni (mol wt 565.51) C, 80.71; H, 8.91. Found: C, 81.16;
H, 9.26. Mol wt (cryoscopy in benzene; m/z): 593.
(-)-Bis(η5-2-m en th ylin d en yl)r u th en iu m (II) (10). To a
red solution of tris(acetylacetonato)ruthenium(III) (0.26 g, 0.65
mmol) in benzene (25 mL) was added 3 (0.55 g, 2.11 mmol) at
0 °C. The brown suspension was heated for 40 h to 80 °C. The
solvent was removed under vacuum (10-2 mbar), leaving a
black solid which was suspended in n-hexane (3 mL) and
fractionally chromatographed under nitrogen with alumina.
Elution with n-hexane and finally with diethyl ether gave
colorless and then orange solutions. The solvents of the orange
fractions were removed under vacuum (10-2 mbar), yielding a
yellow solid. Recrystallization from warm n-pentane (5 mL)
gave 0.28 g (70%) of orange crystals of 10. Mp: 67 °C. [R]D25
)
Resu lts a n d Discu ssion
-111.1° (c 0.1, diethyl ether). 1H NMR (benzene-d6, 200
MHz): δ 7.20-6.60 (m, 8H, H4,5,6,7), 5.12 (s, 2H, H1/3), 4.65 (s,
Meta llocen es w ith Dia ster eotop ic In d en yl Lig-
a n d s. Substituted unbridged planar chiral19 indenyl
ligands having enantiotopic faces tend to give upon
metalation three stereoisomeric bis(indenyl)metal com-
plexes (pR)(pR), (pR)(pS), and (pS)(pS) in the statistical
ratio 1:2:1. If indenyl ligands with chiral substituents
are used, the metalation ratio for these diastereotopic
3
2H, H1/3), 2.79-0.68 (m, 20H, H1′,2′,3′,4′,5′,6′,8′), 1.16 (d, J ) 6.4
3
3
Hz, 3H, H7′/9′/10′), 1.05 (d, J ) 6.9 Hz, 3H, H7′/9′/10′), 0.95 (d, J
3
) 6.9 Hz, 3H, H7′/9′/10′), 0.90 (d, J ) 6.4 Hz, 3H, H7′/9′/10′), 0.72
(d, 3J ) 6.9 Hz, 3H, H7′/9′/10′), 0.27 (d, 3J ) 6.8 Hz, 3H, H7′/9′/10′).
13C{1H} NMR (benzene-d6, 50.32 MHz): δ 125.99, 121.63,
121.03, 120.32 (C4,5,6,7), 99.54, 90.61, 88.32 (C2,8,9), 68.19, 63.86
(C1,3), 50.75, 40.59, 34.15, 27.47 (C1′,3′,4′,8′), 43.98, 35.66, 25.27
(C2′,5′,6′), 23.12, 21.61, 15.66 (C7′,9′,10′). IR (CsI; cm-1): vj 3053
(w), 3017 (m), 2956 (s), 2919 (s), 2869 (m), 2848 (m), 1611 (m),
1518 (m), 1463 (s), 1385 (m), 1368 (m), 1345 (w), 1005 (w),
982 (w), 903 (w), 843 (w), 764 (m), 760 (m), 753 (m), 732 (m),
727 (m), 722 (m), 572 (w), 491 (w), 418 (w), 350 (w). MS (128
°C; m/z (%)): 608 (100) [M]+, 593 (2) [(C18H22)(C19H25)Ru]+, 565
(14) [(C16H18)(C19H25)Ru]+, 469 (10) [(C9H6)(C19H25)Ru]+, 355
(1) [(C19H25)Ru]+. Anal. Calcd for C38H50Ru (mol wt 607.88):
C, 75.08; H, 8.29. Found: C, 75.52; H, 8.23.
(14) Sheldrick, G. M. SHELXS-97: Program for the Solution of
Crystal Structures; Universita¨t Go¨ttingen, Go¨ttingen, Germany, 1997.
(15) Sheldrick, G. M. SHELXL-97: Program for the Refinement of
Crystal Structures; Universita¨t Go¨ttingen, Go¨ttingen, Germany, 1997.
(16) Flack, H. D. Acta Crystallogr. 1983, A39, 876.
(17) Sheldrick, G. M. SADABS: Program for Empirical Absorption
Correction of Area Detector Data; Universita¨t Go¨ttingen, Go¨ttingen,
Germany, 1996.
(18) Spek, A. L. Acta Crystallogr. 1990, A46, C34.
(19) (a) Schlo¨gl, K. Fortschr. Chem. Forsch. 1966, 6, 479. (b) Schlo¨gl,
K. Top. Stereochem. 1967, 1, 39.

Bis(indenyl) Complexes of Zr, Fe, Ni, and Ru
Organometallics, Vol. 20, No. 10, 2001 1987
Sch em e 1
ligands no longer tends to be statistically determined
but is strongly influenced by steric interactions, as
illustrated in Scheme 1, where the 4′-isopropyl group
of the menthyl moiety is more sterically demanding than
the corresponding 1′-methyl group. The metathetic
reaction of 2 equiv of the lithium (1) or sodium (2) salts
of (-)-3-menthyl-4,7-dimethylindene with ZrCl4 in tolu-
ene at -78 °C gave the (pR)(pR)- and (pR)(pS)-bis(1-
menthyl-4,7-dimethylindenyl)zirconium dichloride com-
plexes 4a and 4b in 58-87% isolated yield without any
trace of the (pS)(pS) diastereomer 4c.
F igu r e 1. ORTEP plot25 of the molecular structure and
numbering scheme of 4b, with 50% probability thermal
ellipsoids. For clarity, all hydrogens are removed. Selected
bond lengths (Å) and bond angles (deg) with estimated
standard deviations:25 Zr-Cg(1) ) 2.2492(8), Zr-Cg(2) )
2.2517(7), Zr-Cl(1) ) 2.4305(5), Zr-Cl(2) ) 2.4200(4),
C(101)-C(102) ) 1.406(2), C(102)-C(103) ) 1.413(2),
C(103)-C(104) ) 1.424(3), C(104)-C(109) ) 1.443(2),
C(101)-C(109) ) 1.456(2), C(201)-C(202) ) 1.407(2),
C(202)-C(203) ) 1.421(3), C(203)-C(204) ) 1.427(2),
C(204)-C(209) ) 1.436(2), C(201)-C(209) ) 1.452(2); Cg-
(1)-Zr-Cg(2) ) 129.84(3), Cg(1)-Zr-Cl(1) ) 109.75(2), Cg-
(1)-Zr-Cl(2) ) 105.76(2), Cl(1)-Zr-Cl(2) ) 94.244(17),
Cg(2)-Zr-Cl(1) ) 104.65(2), Cg(2)-Zr-Cl(2) ) 106.90(2).
The compounds 4a , 4b, and 4c were formed in the
ratio 0.8:1:0 when the lithium salt 1 is used, where as
the potassium salt 2 gives the products in the ratio 0.9:
1:0. The corresponding metalation ratios are therefore
(pR):(pS) ) 2.6:1 and (pR):(pS) ) 2.8:1, giving rise to
apparent diastereoselectivities of 44% and 47%. Given
this selectivity, the (pS)(pS) diastereomer 4c should be
formed in about 7% yield. Since this isomer was not
observed, its formation could be disfavored by additional
ligand-ligand interactions beyond the ligand-metal
interactions assumed for the ratios above. It is particu-
larly noteworthy that even though the lithium salt 1
itself can be synthesized almost quantitively in the (pR)
configuration, the following reaction is surprisingly
much less selective. In the course of the metathesis, the
diastereotopic faces of the indenyl moiety are therefore
not well energetically discriminated by the menthyl
functionality. The apparent diastereoselectivities in the
syntheses of 4 depend only slightly on the main-group
cation of the (-)-3-menthyl-4,7-dimethylindene ligand.
They do not vary as much as in the synthesis of (pR)-
and (pS)-(-)-(η4-cycloocta-1,5-diene)(η5-1-menthyl-4,7-
dimethylindenyl)rhodium(I), where the (pR) complex is
formed with +39% de when the lithium salt 1 is used,
whereas the potassium salt 2 gives the (pS) complex
with 50% de.10 The similar complex bis(4,7-dimethyl-
3-neomenthylindenyl)zirconium dichloride could be syn-
thesized with an increased apparent diastereoselectivity
of 97%.20
HPLC, or column chromatography (using SiO2 or re-
versed-phase C18-modified SiO2). Repeatedly washing
of the crude mixture with small amounts of n-pentane
results in the less soluble (pR)(pS) diastereomer 4b,
forming a solid residue, and the (pR)(pR) diastereomer
4a remaining in solution. Recrystallization of both from
dichloromethane yields the diastereomerically pure
compounds 4b and 4a .
Crystals of 4b suitable for single-crystal X-ray dif-
fraction analysis were obtained by recrystallization from
dichloromethane. The solid-state structure was deter-
mined by X-ray diffraction methods. 4b crystallizes in
the space group P212121 with four superimposable
molecules in the unit cell. The monomeric, solvent-free
complex is diastereomerically pure and shows the
desired three stereocenters of the menthyl moiety. The
zirconium atom is coordinated pseudo-tetrahedrally by
the centroids of the five-membered indenyl rings and
the two chlorine atoms (Figure 1). The indenyl ligands
differ by the Zr metal being attached either on the
prochiral (pR) or on the (pS) side. It is particularly
The air- and moisture-sensitive mixtures of 4a and
4b and their solutions do not allow separation by GC,
(20) Knickmeier, M.; Erker, G.; Fox, T. J . Am. Chem. Soc. 1996,
118, 9623.

1988 Organometallics, Vol. 20, No. 10, 2001
Schumann et al.
noteworthy that regardless of the (pR) or (pS) metala-
tion the terpene moiety adopts similar conformations
(+anticlinal and +synclinal) with the menthyl moiety
being more or less perpendicular to the indenyl plane
with the protons at C(112) and C(212) pointing toward
C(111) and C(211), respectively. No rotation of ap-
proximately 180° is observed for the energetically
disfavored (pS) metalated ligand to lower the steric
constraint, as the menthyl group is sterically too
hindered by the methyl group C(211) to perform this
motion. The bond lengths of Zr to the centroids of the
five-membered rings are slightly longer than in (pR)-
(pR)-(+)-dichlorobis(η5-neoisomenthylindenyl)zirconium-
(IV) (2.243 Å) and in (pS)(pS)-(-)-dichlorobis(η5-neo-
menthylindenyl)zirconium(IV) (2.238 Å),21 because of
the steric hindrance of both isopropyl groups of the
indenyl ligands. The average bond lengths Zr-Cl (2.43
Å in 4b compared to 2.43 and 2.42 Å, respectively) as
well as the angles Cg(1)-Zr-Cg(2) (129.8° in 4b com-
pared to 130.3 and 129.5°, respectively) and Cl(1)-Zr-
Cl(2) (94.2° in 4b compared to 96.7 and 91.6°, respec-
tively) are in agreement with those in the other two
compounds. The main axes of the indenyl systems show
a rotation angle of 102.5°. The bent angle22 between the
two indenyl planes is 54.9°. The five-membered rings
of the indenyl systems are not equally bound to the
zirconium atom but resemble an unsymmetrical η5-
coordination. For example, the bond lengths of the
carbon atoms C(101), C(102), and C(103) to the metal
are the shortest ones in the case of the (pR)-indenyl
ligand, while in the (pS)-metalated ligand the atoms
C(202), C(203), and C(204) show the shortest bond
lengths. The steric interactions between the menthyl
F igu r e 2. Conformation of 4b in the solid state (R1* )
R2* ) menthyl). Thermal ellipsoids are shown with 50%
probability.
Ch a r t 2. Tor sion a l Isom er s of
Bis(1-h yd r oca r bylin d en yl)zir con iu m (IV)
Dich lor id e Com p ou n d s
and the metal moieties give rise to slip distortions23
∆
of 0.063 and 0.079 Å as well as ring slippages RS23 of
0.098 and 0.210 Å for the (pR) and the (pS) ligand. The
tendency for slight η3-coordination which is higher for
the (pS) metalated ligand accounts for the nonplanar
cyclopentadienyl rings and therefore to hinge angles HA
as well as fold angles FA.24 The values for the HA and
FA are 3.4 and 8.8° for the (pR) ligand and are 2.5 and
5.2° for the (pS) ligand.
This first molecular structure of a meso-like menthyl-
substituted metallocene proves that the chiral auxiliary
menthyl itself is not able to allow a high diastereose-
lectivity with regard to the metalation of the planar
chiral indenyl moiety, as the ligands are metalated on
the sterically free and the sterically hindered side as
well. This is due to the insufficient steric demand of the
menthyl’s isopropyl group. In contrast to the literature,
the formation of the mixture is independent from the
conformational rigidity along the C(101)-C(112) and
C(201)-C(212) axes,20,27 which would more or less
interconvert the sterically free and hindered sides. The
solid-state conformation of 4b is shown in Figure 2. Both
chlorine atoms show interactions with the two menthyl
moieties so that interesting catalytical properties can
be expected.28 Comparison with the torsional isomers
of other hydrocarbylindenyl ligands depicted in Chart
2, whose arrangements are derived from conformational
analysis,29 NMR spectroscopy, and X-ray diffraction
analyses,20 shows that 4b gives rise to a new minimum
structure which shows similarities to the meso-III
isomer.
(21) Erker, G.; Aulbach, M.; Knickmeier, M.; Wingbermu¨hle, D.;
Kru¨ger, C.; Nolte, M.; Werner, S. J . Am. Chem. Soc. 1993, 115, 4590.
(22) Bent angle ) angle between the least-squares ring planes
defined by C(101), C(102), C(103), C(104), C(109) and C(201), C(202),
C(203), C(204), C(209).
(23) Slip distortion ∆ ) difference in the average metal to carbon
distances: 0.5(M-C(x04) + M-C(x09)) - 0.5(M-C(x01) + M-C(x03));
ring slippage RS ) distance from the normal of the least-squares ring
plane defined by C(x01), C(x02), C(x03), C(x08), C(x09) to the metal
atom and the centroid of the five-membered ring. Kakkar, A.; Taylor,
N. J .; Marder, T. B.; Shen, J . K.; Hallinan, N.; Basolo, F. Inorg. Chim.
Acta 1992, 198, 219.
(25) Zsolnai, L.; Pritzkow, H. ZORTEP: ORTEP Program for PC;
Universita¨t Heidelberg, Heidelberg, Germany, 1994.
(26) C(g) defines the centroid of the ring atoms C(x01), C(x02),
C(x03), C(x04), C(x09).
(24) Hinge angle ) angle between normals to the least-squares
planes defined by C(x01), C(x02), C(x03) and C(x01), C(x09), C(x04),
C(x03); fold angle ) angle between normals to the least-squares planes
defined by C(x01), C(x02), C(x03) and C(x04), C(x05), C(x06), C(x07),
C(x08), C(x09). Kakkar, A.; Taylor, N. J .; Marder, T. B.; Shen, J . K.;
Hallinan, N.; Basolo, F. Inorg. Chim. Acta 1992, 198, 219.
(27) Knickmeier, M. Dissertation, Universita¨t Mu¨nster, Mu¨nster,
Germany, 1995.
(28) Raubenheimer, H. G.; Halterman, R. L.; Stenzel, O.; Dechert,
S.; Schumann, H. Manuscript in preparation.
(29) Kru¨ger, C.; Lutz, F.; Nolte, M.; Erker, G.; Aulbach, M. J .
Organomet. Chem. 1993, 452, 79.

Bis(indenyl) Complexes of Zr, Fe, Ni, and Ru
Organometallics, Vol. 20, No. 10, 2001 1989
Sch em e 2
Sch em e 3
The indenyl-Zr bond in 4 can be opened and closed
reversibly, which was proven by heating a 1:4 mixture
of the diastereomers 4a and 4b in THF to 65 °C over 5
h and slow cooling to room temperature within 3 h. After
three additional heating and cooling cycles the ratio
changed to 4a :4b ) 1:2, with the thermodynamical more
stable (pR)(pR) diastereomer being enriched. 4a and 4b
are soluble in polar solvents such as THF, pyridine, and
diethyl ether as well as in aromatic solvents such as
toluene and nonpolar solvents such as n-hexane. 1H
NMR measurements at low temperatures, as well as
13C{1H} NMR, 1H,1H COSY, 1H,13C correlated, and
COLOC measurements were performed to assign the
1H,13C signal pairs to the complicated NMR spectra. The
(pR)(pR) diastereomer shows sharp signals, while the
(pR)(pS) diastereomer, which consists of two signal sets
for the diastereotopic indenyl protons, already gives rise
to broadened signals due to slow conversions of the
torsional isomers depicted in Chart 2 on the NMR time
scale.
Sch em e 4
Cyclopentadienylzirconium trichloride reacts with
(-)-(1-menthyl-4,7-dimethylindenyl)potassium (2) in tolu-
ene at -78 °C with formation of a yellow crystalline air-,
light-, and moisture-sensitive product consisting of the
(pR) and (pS) diastereomers 5a and 5b in the ratio 1:1.3
with an apparent diastereomeric excess of 13% (Scheme
2).
The iron complex of (-)-3-menthyl-4,7-dimethylindene
was synthesized in a metathetic reaction similar to the
synthesis of 4 using 2 equiv of the lithium salt 1 and
FeCl2(THF)1.15 in THF at -78 °C (Scheme 3).
of 45%. In both of these last two cases, more of the (pR)-
(pS) and (pS)(pS) isomers were formed, given expecta-
tions based on the 45-50% facial selectivity. Again,
direct ligand-ligand interactions could explain these
deviations from ideal behavior.
Meta llocen es w ith Hom otop ic In d en yl Liga n d s.
Using indenyl ligands with homotopic faces which are
substituted by a chiral organic group should avoid the
formation of different diastereomers during the meta-
lation. This was proved by the reaction of (-)-2-men-
thylindenyllithium (3)8 with FeCl2(THF)1.15 in THF at
0 °C, which resulted in the formation of the iron complex
8 in 90% yield (Scheme 4). After recrystallization from
n-pentane black crystals of 8 were obtained. The analo-
gous metathetic reaction of 3 with NiCl2(DME) in THF
at 0 °C and recrystallization from n-pentane gives the
nickel complex 9 as red crystals in 57% yield (Scheme
4).
The (pR)(pR)-, (pR)(pS)-, and (pS)(pS)-bis(η5-1-men-
thyl-4,7-dimethylindenyl)iron(II) compounds 6a , 6b, and
6c were formed in the ratio 4.8:1.8:1 in 49% yield as
black moisture- and air-sensitive solids. In contrast to
the zirconocenes 4a /4b, the energetically least favorable
(pS)(pS) diastereomer of 6 is formed also, even though
the overall apparent diastereomeric excess is, at 50%,
slightly higher than in the synthesis of 4. The separation
of the diastereomers by fractional crystallization was
not possible.
The nickel complex 7 of (-)-3-menthyl-4,7-dimethyl-
indene was synthesized in a similiar metathetic reaction
(Scheme 3). All three possible diastereomers were
formed in 47% yield in the ratio (pR)(pR):(pR)(pS):(pS)-
(pS) ) 5.9:4.0:1 with an apparent diastereomeric excess
In contrast, the analogous ruthenium compound can-
not be synthesized via metathetic methods at low
temperature but can in general be obtained by reaction
of alkali-metal salts of cyclopentadienyl systems with
compounds such as Ru3(CO)12, Ru(acac)3, [RuCl2(COD)]x,

1990 Organometallics, Vol. 20, No. 10, 2001
Schumann et al.
Sch em e 5
and [RuCl2(p-cymol)]2 between 80 and 180 °C.30 This
excludes the use of ligands with diastereotopic faces
which require kinetically controlled reaction conditions.
Ligands with homotopic faces do not need to fulfill this
requirement. Ru(acac)3 reacts smoothly with 3 equiv of
3 in benzene at 80 °C, forming orange crystals of (-)-
bis(η5-2-menthylindenyl)ruthenium(II) (10) in 70% yield
(Scheme 5).
The mass spectra of 8, 9, and 10 give the molecular
ion as the peak of highest mass and highest intensity.
1
The H as well as the 13C NMR spectra show only one
signal set for both indenyl systems, proving either a
symmetrical, fixed arrangement of both indenyls or a
fast rotation of them around the indenyl-metal axes.
The molecular structure of 8 (Figure 3) shows the iron
atom coordinated linearly by the centroids of the five-
membered indenyl rings. The indenyl planes are almost
parallel to each other, giving rise to a bent angle22 of
2.1°. The terpene moieties adopt in both ligands a
+synclinal arrangement to the indenyl plane, with each
of the isopropyl groups pointing away from the metal.
The average bond lengths of both five-membered-ring
centroids to the metal are 2.07 Å. These lengths cor-
relate with the bond lengths of 2.07 Å in bis(η5-
heptamethylindenyl)iron(II), which are 0.01 Å longer
than the bond lengths in bis(η5-indenyl)iron(II).31 The
main axes of the indenyl systems form a rotation angle
of 134°, which is probably due to intramolecular steric
interactions of the terpene units with the indenyl
ligands, as the sterically less constrained bis(η5-inde-
nyl)iron(II) complex shows a rotation angle of only 9.1°.
In bis(η5-heptamethylindenyl)iron(II) an increased angle
of 151.3° is found, which was attributed to orbital
effects.32 The five-membered rings of the indenyl sys-
tems are not equally bound but resemble an unsym-
metrical η5-coordination with slip distortions of 0.065
and 0.051 Å as well as ring slippages toward the C(102)
and the C(202) atom of 0.052 and 0.058 Å, respectively.
The tendency to a slight η3- coordination accounts for
HA values of 4.9 and 2.5° as well as FA values of 6.0
and 4.1°. For the bis(η5-heptamethylindenyl)iron(II) and
bis(η5-indenyl)iron(II) complexes lower values of ∆ )
F igu r e 3. ORTEP plot25 of the molecular structure and
numbering scheme of 8, with 50% probability thermal
ellipsoids. For clarity, all hydrogens are removed. Selected
bond lengths (Å) and bond angles (deg) with estimated
standard deviations:25 Fe-Cg(1) ) 1.676(2), Fe-Cg(2) )
1.675(2), C(101)-C(102) ) 1.442(6), C(102)-C(103) )
1.424(6), C(103)-C(104) ) 1.437(6), C(104)-C(109) )
1.445(7), C(101)-C(109) ) 1.433(7), C(201)-C(202) )
1.418(7), C(202)-C(203) ) 1.443(7), C(203)-C(204) )
1.437(7), C(204)-C(209) ) 1.455(7), C(201)-C(209) )
1.419(7); Cg(1)-Fe-Cg(2) ) 177.78(11).
0.030 and 0.043 Å, HA ) 2.5 and 2.2°, and FA ) 4.4
and 0.8° are found, which are probably due to packing
effects.
Con clu sion
Novel chiral nonracemic transition-metal complexes
of Zr, Fe, and Ni containing optically active, menthyl-
substituted indenyl ligands were prepared by metathetic
reactions of chiral main-group-metal salts of (-)-3-
menthyl-4,7-dimethylindene and (-)-2-menthylindene
and ZrCl4, CpZrCl3(DME), FeCl2(THF)1.15, and NiCl2-
(DME). Ru(acac)3 is reduced by excess (-)-(2-menthyl-
indenyl)lithium, yielding (-)-(2-menthylindenyl)2Ru.
Depending on the reaction conditions, compounds with
diastereotopic indenyl ligands were formed as mixtures
of diastereomers with apparent diastereomerical ex-
cesses of 13-50% with regard to the planar chirality of
the indenyl ring system. Compounds with homotopic
indenyl ligands were obtained as stereomerically pure
complexes. X-ray diffraction analyses of 4b and 8
showed the monomeric, free of solvent, diastereomeri-
cally pure compounds with the indenyl moiety being η2
(30) Stenz, S. Dissertation, Technische Universita¨t Berlin, Berlin,
Germany, 1999.
(31) Westcott, S. A.; Kakkar, A. K.; Stringer, G.; Taylor, N. J .;
Marder, T. B. J . Organomet. Chem. 1990, 394, 777.
(32) Crossley, N. S.; Green, J . C.; Nagy, A.; Stringer, G. J . Chem.
Soc., Dalton Trans. 1989, 2139.

Bis(indenyl) Complexes of Zr, Fe, Ni, and Ru
Organometallics, Vol. 20, No. 10, 2001 1991
+ η3 coordinated. 4b is the first molecular structure of
a meso-like menthyl-substituted metallocene. It proves
that the chiral auxiliary menthyl is not able to allow a
high diastereoselectivity with regard to the planar
chirality of the indenyl moiety, independently from the
conformational rigidity along the indenyl-menthyl axis.
lin (Erwin-Stephan-Scholarship), and the Partnership
between the Technical University of Berlin and the
University of Oklahoma.
Su p p or tin g In for m a tion Ava ila ble: Full details of the
X-ray structures of complexes 4b and 8, including complete
tables of crystal data, atomic coordinates, bond lengths and
angles, and positional and anisotropic thermal parameters.
This material is available free of charge via the Internet at
http://pubs.acs.org.
Ack n ow led gm en t. This work was supported by the
Fonds der Chemischen Industrie, the Deutschen For-
schungsgemeinschaft (Graduate College “Synthetische,
mechanistische und reaktionstechnische Aspekte von
Metallkatalysatoren”), the Technical University of Ber-
OM001084N