Evidence for α-Nitrogen Participation in the Internal C-H Activation Reaction at ((Dimethylamino)methyl)cyclopentadienyl-Derived Methylzirconocene Cations

Article abstract of DOI:10.1021/om990216d

Treatment of 6-(dimethylamino)-6-methylfulvene (1) with methyllithium followed by the reaction of the resulting [C₅H₄-CMe₂NMe₂]Li reagent with CpZrCl3 gave the complex [(η⁵-C₅H₄-CMe₂NMe ₂)CpZrCl₂] (2). Its treatment with 2 molar equiv of methyllithium furnished [(η⁵-C₅H₄-CMe₂NMe ₂)CpZr(CH₃)₂] (3). Complex 3 reacted with B(C₆F₅)₃ by methyl group transfer. The in situ [Zr]⁺-CH₃ cation system generated in this manner proved to be unstable under the reaction conditions and instantaneously eliminated methane with formation of 4. In the course of this reaction a N-CH₃ hydrogen atom was abstracted. Complex 4 was stabilized by the addition of 1 equiv of the alkyl isocyanide RN≡C (R = CMe₃, n-C₄H₉, -CMe₂-CH₂CMe₃) to yield the respective adducts 5. The complex [(η⁵:η²(C,N)-C₅H ₄-CMe2N(=CH2)-CH₃)CpZr(κC-C≡N-CMe ₃)]⁺[CH₃B(C₆F₅) ₃]^- (5a) was characterized by an X-ray crystal structure analysis. It exhibits an η²-coordination of the pendant formaldiminium moiety to zirconium (d(Zr-N) = 2.318(7) A?, d(Zr-C) = 2.272(7) A?). The (η-R₂NCH₂)Zr moiety shows a characteristic ¹⁵N NMR chemical shift (δ-376 ppm), deshielded by ca. Δδ ≈ -40 ppm relative to the ¹⁵NMe₂ NMR resonance found for 3. Complex 4 reacts with butadiene or isoprene by insertion into the Zr-CH₂ bond of the (η²-formaldiminium)Zr moiety to form the metallacyclic (π-allyl)metallocene complexes 6a,b The X-ray crystal structure analysis of 6b shows a close Zr-N contact at 2.491(4) A?. A corresponding ¹⁵N NMR feature was found at δ -357 ppm. The complex [(η⁵-C₅H₄-CMe₂NMe ₂)₂Zr(CH₃)₂] reacts analogously: upon treatment with B(C₆F₅)₃ in a 1:1 ratio, CH₃ is transferred from zirconium to boron, and 1 equiv of methane is liberated to give complex 8 (¹⁵N NMR signals at δ -357 and -372 ppm). Complex 8 was also characterized by X-ray diffraction. It shows coordination of both nitrogen atoms to zirconium: i.e., the presence of a (η²-R₂NCH₂)Zr⁺ three-membered-ring system, formed by C-H activation, and a κN-coordinated intact pendant -CMe₂-NMe₂ group. The latter is displaced upon the addition of tert-butyl isocyanide to yield the (κC-isonitrile)(η²-formaldiminium)metallocene cation complex 9.

Full text of DOI:10.1021/om990216d

3818
Organometallics 1999, 18, 3818-3826
Evid en ce for r-Nitr ogen P a r ticip a tion in th e In ter n a l
C-H Activa tion Rea ction a t
((Dim eth yla m in o)m eth yl)cyclop en ta d ien yl-Der ived
Meth ylzir con ocen e Ca tion s
J o¨rg Pflug, Axel Bertuleit, Gerald Kehr,† Roland Fro¨hlich,‡ and Gerhard Erker*
Organisch-Chemisches Institut der Universita¨t Mu¨nster, Corrensstrasse 40,
D-48149 Mu¨nster, Germany
Received March 29, 1999
Treatment of 6-(dimethylamino)-6-methylfulvene (1) with methyllithium followed by the
reaction of the resulting [C5H4-CMe2NMe2]Li reagent with CpZrCl3 gave the complex [(η5-
C5H4-CMe2NMe2)CpZrCl2] (2). Its treatment with 2 molar equiv of methyllithium furnished
[(η5-C5H4-CMe2NMe2)CpZr(CH3)2] (3). Complex 3 reacted with B(C6F5)3 by methyl group
transfer. The in situ [Zr]+-CH3 cation system generated in this manner proved to be unstable
under the reaction conditions and instantaneously eliminated methane with formation of 4.
In the course of this reaction a N-CH3 hydrogen atom was abstracted. Complex 4 was
stabilized by the addition of 1 equiv of the alkyl isocyanide RNtC (R ) CMe3, n-C4H9, -CMe2-
CH2CMe3) to yield the respective adducts 5. The complex [(η5:η2(C,N)-C5H4-CMe2N(dCH2)-
CH3)CpZr(κC-CtN-CMe3)]+[CH3B(C6F5)3]- (5a ) was characterized by an X-ray crystal
structure analysis. It exhibits an η2-coordination of the pendant formaldiminium moiety to
zirconium (d(Zr-N) ) 2.318(7) Å, d(Zr-C) ) 2.272(7) Å). The (η2-R2NCH2)Zr moiety shows
a characteristic 15N NMR chemical shift (δ -376 ppm), deshielded by ca. ∆δ ≈ -40 ppm
relative to the 15NMe2 NMR resonance found for 3. Complex 4 reacts with butadiene or
isoprene by insertion into the Zr-CH2 bond of the (η2-formaldiminium)Zr moiety to form
the metallacyclic (π-allyl)metallocene complexes 6a ,b. The X-ray crystal structure analysis
of 6b shows a close Zr-N contact at 2.491(4) Å. A corresponding 15N NMR feature was found
at δ -357 ppm. The complex [(η5-C5H4-CMe2NMe2)2Zr(CH3)2] reacts analogously: upon
treatment with B(C6F5)3 in a 1:1 ratio, CH3 is transferred from zirconium to boron, and 1
equiv of methane is liberated to give complex 8 (15N NMR signals at δ -357 and -372 ppm).
Complex 8 was also characterized by X-ray diffraction. It shows coordination of both nitrogen
atoms to zirconium: i.e., the presence of a (η2-R2NCH2)Zr+ three-membered-ring system,
formed by C-H activation, and a κN-coordinated intact pendant -CMe2-NMe2 group. The
latter is displaced upon the addition of tert-butyl isocyanide to yield the (κC-isonitrile)(η2-
formaldiminium)metallocene cation complex 9.
Sch em e 1
In tr od u ction
The chemistry of organometallic group 4 metal com-
plex cations that bear pendant donor groups (e.g.
-(CR2-)nNR2, -(CR2-)nPR2, or -(CR2-)nOR) is at-
tracting increased interest due to their potential im-
portance in the development of active carbon-carbon
coupling catalysts.1 We have recently described the
generation of methylzirconocene cations bearing sub-
stituted ((dimethylamino)methyl)cyclopentadienyl ligands
at the group 4 metal and found that such systems are
not stable but instantaneously eliminate methane.2 This
involves rupture of a C-H bond at one of the N-methyl
groups with formation of a pendant iminium moiety that
coordinates to zirconium (see Scheme 1). The resulting
products were characterized by 1H and 13C NMR
spectroscopy (including their dynamic behavior) and by
* To whom correspondence should be addressed. FAX: +49 251 83
36503. E-mail: erker@uni-muenster.de.
† NMR spectroscopy.
elemental analysis, but it had remained open whether
the nitrogen atom was involved in the coordination of
‡ X-ray crystal structure analyses.
10.1021/om990216d CCC: $18.00 © 1999 American Chemical Society
Publication on Web 08/18/1999

Methylzirconocenes Bearing (Me2NCH2)Cp Groups
Organometallics, Vol. 18, No. 19, 1999 3819
F igu r e 1. View of the molecular structure of 2. Selected
bond lengths (Å) and angles (deg): Zr-Cl1 ) 2.4398(6),
Zr-Cl2 ) 2.4438(6), Zr-CCp ) 2.511(3), C10-C11 ) 1.526-
(3), C11-N14 ) 1.499(3); Cl1-Zr-Cl2 ) 94.97(2), C10-
C11-N14 ) 105.3(2).
F igu r e 2. Molecular structure of 5a (cation only) with
(unsystematic) atom-numbering scheme. Selected bond
lengths (Å) and angles (deg): Zr-C1 ) 2.312(8), Zr-N23
) 2.318(7), Zr-C25 ) 2.272(7), C1-N2 ) 1.157(10), N2-
C3 ) 1.435(9), N23-C24 ) 1.453(10), N23-C25 ) 1.438-
(11), N23-C20 ) 1.554(10), C20-C19 ) 1.498(11); C1-
Zr-N23 ) 114.8(3), C1-Zr-C25 ) 78.3(3), Zr-C1-N2 )
178.8(6), C1-N2-C3 ) 179.1(8), Zr-N23-C25 ) 70.0(4),
Zr-C25-N23 ) 73.5(4), N23-Zr-C25 ) 36.5(3), Zr-N23-
C24 ) 130.0(6), Zr-N23-C20 ) 99.9(4), C20-N23-C24
) 117.8(7), C19-C20-N23 ) 101.3(5).
the newly formed iminium-type functionality. We have
actively pursued this question in the meantime and
obtained evidence by X-ray crystal structure analyses
and 15N NMR spectroscopy for a variety of such systems
indicating a varying degree of nitrogen-donor participa-
tion as an important structural and potentially kinetic
factor in this chemistry.
A methyl group is transferrred from zirconium to boron,
followed by an instantaneous formation of methane to
give the cation complex 4. This product was not isolated
but only characterized spectroscopically. We will come
to its characterization later. The complex could be
stabilized by adding a suitable donor ligand. Thus,
treatment of in situ generated 4 with 1 molar equiv of
an alkyl isocyanide cleanly yielded the 1:1 addition
products 5a -c (50-60% isolated yields). Diffusion of
pentane vapor into a solution of 5a in dichloromethane
gave single crystals that were suitable for an X-ray
crystal structure analysis.
In the crystal, the cation and anion of 5a are clearly
separated (Figure 2). The cation shows a bent-metal-
locene unit (Cp(centroid)-Zr-Cp(centroid) angle 135.8°)
that has three close contacts in the σ-ligand plane. The
methane elimination reaction has removed a hydrogen
atom from one of the former methyl groups at nitrogen.
This has resulted in a new zirconium-carbon bond, but
at the same time a bonding contact between zirconium
and the adjacent nitrogen atom has been established.
The structure of 5a shows the presence of a three-
membered ring containing Zr, C, and N atoms. The
formaldiminium unit formed by the methane extrusion
has become bonded to zirconium, in an η2 manner
similar to that for an olefin.4 The bond lengths within
the three-membered metallacycle are Zr-C25 ) 2.272-
(7) Å, Zr-N23 ) 2.318(7) Å, and C25-N23 ) 1.438(11)
Å, which are in the ranges of the respective σ-bonds.5,6
The angles inside the three-membered ring are 36.5-
Resu lts a n d Discu ssion
For the first part of this study we have used the (η5-
C5H4-CMe2NMe2)CpZr bent-metallocene framework.
The synthesis and some chemistry of its derivatives had
been mentioned in a recent review by us3 but will briefly
be outlined here for clarity. The C5H4-CMe2NMe2
ligand system was prepared by a fulvene route. Meth-
yllithium was added to 6-(dimethylamino)-6-methylful-
vene (1) to give the 1-methyl-1-(dimethylamino)ethyl-
substituted cyclopentadienide. Treatment with CpZrCl3
furnished the metallocene dichloride 2. Subsequent
treatment with methyllithium gave 3. Both metallocene
complexes were characterized by X-ray diffraction stud-
ies. The structure of 3 was depicted in the review
mentioned above. The molecular structure of 2 is shown
in Figure 1. The bonding features around zirconium are
unexceptional. It should be noted that there is clearly
no interaction between the nucleophilic dimethylamino
nitrogen center of the functionalized side chain and the
group 4 metal center. The -CMe2-NMe2 substituent
in 2 is oriented toward the lateral sector of the bent-
metallocene unit, and the -NMe2 group is oriented
away from the bent-metallocene nucleus (dihedral angle
C6-C10-C11-N14 ) -56.6(3)°).
Complex 3 was then treated with B(C6F5)3 (1 molar
equiv) in dichloromethane at low temperature (-50 °C).
(1) (a) J utzi, P.; Dahlhaus, J . Phosphorus, Sulfur Silicon Relat. Elem.
1994, 87, 73. J utzi, P.; Dahlhaus, J . Coord. Chem. Rev. 1994, 137, 179.
Okuda, J . Comments Inorg. Chem. 1994, 16, 185. J utzi, P.; Siemeling,
U. J . Organomet. Chem. 1995, 500, 175 and references therein. (b)
Rieger, B. J . Organomet. Chem. 1991, 420, C17. Ewen, I. M.; Ahlberg,
P. J . Am. Chem. Soc. 1992, 114, 10869. Shapiro, P. J .; Cotter, W. D.;
Schaefer, W. P.; Labinger, J . A.; Bercaw, J . E. J . Am. Chem. Soc. 1994,
116, 4623 and references therein. Dias, H. V. R.; Wang, Z.; Bott, S. G.
J . Organomet. Chem. 1996, 508, 91. Dias, H. V. R.; Wang, Z. J .
Organomet. Chem. 1997, 539, 77. Sinnema, P.-J .; van der Veen, L.;
Spek, A. L.; Veldman, N.; Teuben, J . H. Organometallics 1997, 16,
4245. Witte, P. T.; Meetsma, A.; Hessen, B.; Budzelaar, P. H. M. J .
Am. Chem. Soc. 1997, 119, 10561. Schwink, L.; Knochel, P.; Eberle,
T.; Okuda, J . Organometallics 1998, 17, 7. Duda, L.; Erker, G.;
Fro¨hlich, R.; Zippel, F. Eur. J . Inorg. Chem. 1998, 1153.
(4) Horton, A. D.; Orpen, A. G. Organometallics 1992, 11, 8. Wu,
Z.; J ordan, R. F.; Petersen, J . L. J . Am. Chem. Soc. 1995, 117, 5867.
Casey, C. P.; Hallenbeck, S. L.; Pollock, D. W.; Landis, C. R. J . Am.
Chem. Soc. 1995, 117, 9770. Galakhov, M. V.; Heinz, G.; Royo, P. J .
Chem. Soc., Chem. Commun. 1998, 17. Casey, C. P.; Fagan, M. A.;
Hallenbeck, S. L. Organometallics 1998, 17, 287.
(5) For examples of typical bond distances of Zr-C σ-bonds, see:
Atwood, J . L.; Barker, G. K.; Holton, J .; Hunter, W. E.; Lappert, M.
F.; Pearce, R. J . Am. Chem. Soc. 1977, 99, 6645. J effrey, J .; Lappert,
M. F.; Luong-Thi, N. R.; Webb, M.; Atwood, J . L.; Hunter, W. E. J .
Chem. Soc., Dalton Trans. 1981, 1593. Atwood, J . L.; Hunter, W. E.;
Hrncir, D. C.; Bynum, V.; Penttila, R. A. Organometallics 1983, 2, 750.
Kru¨ger, C.; Mu¨ller, G.; Erker, G.; Dorf, U.; Engel, K. Organometallics
1985, 4, 215. Review: Orpen, G. A.; Brammer, L.; Allen, F. H.;
Kennard, O.; Watson, D. G.; Taylor, R. J . Chem. Soc., Dalton Trans.
1989, S1.
(2) Bertuleit, A.; Fritze, C.; Erker, G.; Fro¨hlich, R. Organometallics
1997, 16, 2891.
(3) Bertuleit, A.; Ko¨nemann, M.; Duda, L.; Erker, G.; Fro¨hlich, R.
Top. Catal. 1999, 7, 37.

3820 Organometallics, Vol. 18, No. 19, 1999
Pflug et al.
(3)° (C25-Zr-N23), 73.5(4)° (Zr-C25-N23), and 70.0-
(4)° (Zr-N23-C25). The remaining angles at N23 are
found at 130.0(6)° (Zr-N23-C24), 114.5(7)° (C25-N23-
C24), 117.8(7)° (C20-N23-C24), and 116.2(6)° (C20-
N23-C25), indicating the ammonium character of the
four-coordinate nitrogen center. The respective N23-
C24 (1.453(10) Å) and N23-C20 (1.554(10) Å) bond
lengths are in the expected range.7 The bonding of the
nitrogen to zirconium has led to some distortion of the
C15-C19 Cp ring with a slight bending of the C19-
C20 vector toward Zr (Zr-C19 ) 2.395(7) Å, Zr-C16 )
2.538(7) Å). The C19-C20-N23 angle is compressed
(101.3(5)°). The η2-formaldiminium nitrogen atom (N23)
occupies a lateral coordination site in the central
σ-ligand plane at the bent-metallocene wedge8 in com-
plex 5a , and the H2C25 group is located in the corre-
sponding central position. The tert-butyl isocyanide
ligand is attached to zirconium using the remaining
lateral position opposite to N23, cis to C25 (angle C1-
Zr-N23 114.8(3)°). The Zr-C1 bond length is 2.312(8)
Å; the adjacent C1-N2 bond length is 1.157(10) Å. The
κC-isonitrile ligand framework is linear (Zr-C1-N2 )
178.8(6)°, C1-N2-C3 ) 179.1(8)°). Together with the
observed IR ν˜(CtNR) band at 2201 cm-1, this indicates
the absence of any significant metal to isonitrile ligand
back-bonding9 at this d0-metallocene cation complex.10
The (isonitrile)Zr+ bonding features in 5a are similar
to those observed previously for a variety of other early-
transition-metal isonitrile complexes,10,11 where electro-
static bonding contributions sometimes seem to pre-
vail.12
at δ -161.0 ppm (relative to external nitromethane, δ
0; free Me3C-NtC values δ -186.5 (15N), δ 153.5 (13C),
both in dichloromethane-d2). 5 is also chiral in solution.
For 5a this leads to the observation of four 1H NMR
methine resonances of the monosubstituted Cp-R moi-
ety (at δ 6.07, 5.88, 5.83, and 5.49 in dichloromethane-
d2). The adjacent C(CH3)2 group exhibits diastereotopic
methyl substituents (1H, δ 1.63, 1.20 ppm; 13C, δ 25.4
(1J CH ) 129 Hz), 17.7 (1J CH ) 128 Hz)). There is a single
CH3 group bonded to the nitrogen atom (13C, δ 44.2 ppm,
1
with a typical slightly enhanced J CH coupling constant
of 138 Hz). Most interesting are the NMR spectroscopic
features of the η2-CH2-NR2 group. Due to the persistent
chiral molecular structure, the methylene hydrogens at
the CH2-[N] unit are diastereotopic (1H NMR, δ 2.00,
2
1.39 ppm, J HH ) 8.8 Hz). The corresponding 13C NMR
signal is observed at δ 43.5 ppm. The CH coupling
constant amounts to 1J CH ) 153 Hz. This is significantly
higher than that for the adjacent N-CH3 methyl group
signal (see above). We assume that this increase (of ca.
15 Hz relative to the intramolecular [N]-CH3 reference)
is due to the heterocyclopropane character and, thus,
may serve as a diagnostic feature for the (η2-CH2-NR2)-
Zr bonding.13
In addition, we have observed the 15N NMR resonance
of the (η2-CH2-NR2)Zr moiety in the cation complex 5a
at δ -375.9 ppm. This may be compared with the
respective value of the three-coordinate nitrogen center
in the neutral starting material 3 (15N NMR, δ -338.7).14
We assume that the pronounced shifting of the 15N NMR
resonance to more negative δ values on going from 3 to
5 (5a , ∆δ ) -37 ppm; 5c, -38 ppm) may also serve as
a diagnostic tool to recognize such a (η2-CH2-NR2)Zr
coordinative situation. We tried to use these spectro-
scopic indications derived from the complexes 5 to
evaluate the NMR features of the reactive intermediate
4. The cation of 4 shows diastereotopic CH2-[N] hydro-
gen atom signals at δ 2.23 and 1.67 (2J HH ) 8.8 Hz).
The corresponding 13C NMR resonance is observed at δ
In solution, the complexes 5 adopt analogous struc-
tures. The κC-isonitrile ligand is still present. For 5a
this is evident from the δ(CN) 13C NMR feature at 148.5
ppm and a characteristic 15N NMR isonitrile resonance
(6) See for a comparison: Erker, G.; Kropp, K.; Kru¨ger, C.; Chiang,
A.-P. Chem. Ber. 1982, 115, 2447. Kropp, K.; Skibbe, V.; Erker, G.;
Kru¨ger, C. J . Am. Chem. Soc. 1983, 105, 3353. Erker, G.; Dorf, U.;
Czisch, P.; Petersen, J . L. Organometallics 1986, 5, 668. Erker, G.;
Hoffmann, U.; Zwettler, R.; Betz, P.; Kru¨ger, C. Angew. Chem. 1989,
101, 644; Angew. Chem., Int. Ed. Engl. 1989, 28, 630. Blasche, U.;
Erker, G.; Nissinen, M.; Wegelius, E.; Fro¨hlich, R. Organometallics
1999, 18, 1224. Blaschke, U.; Menges, F.; Erker, G.; Fro¨hlich, R. Eur.
J . Inorg. Chem. 1999, 621.
(7) Allen, F. H.; Kennard, O.; Watson, D. G.; Brammer, L.; Orpen,
A. G.; Taylor, R. J . Chem. Soc., Perkin Trans. 2 1987, S1.
(8) (a) Lauher, W.; Hoffmann, R. J . Am. Chem. Soc. 1976, 98, 1729.
(b) Tatsumi, K.; Nakamura, A.; Hofmann, P.; Stauffert, P.; Hoffmann,
R. J . Am. Chem. Soc. 1985, 107, 4440.
(9) For an electronically different situation see e.g.: Klazinga, A.
H.; Teuben, J . H. J . Organomet. Chem. 1980, 192, 75. Gambarotta,
S.; Floriani, C.; Chiesi-Villa, A.; Guastini, C. Inorg. Chem. 1984, 23,
1739. Martins, A. M.; Calhorda, M. J .; Roma˜o, C. C.; Vo¨lkl, C.; Kiprof,
P.; Filippou, A. C. J . Organomet. Chem. 1992, 423, 367.
(10) Guo, Z.; Swenson, D. C.; Guram, A. S.; J ordan, R. F. Organo-
metallics 1994, 13, 766 and references therein. See also: Hurlburt, P.
K.; Rack, J . J .; Luck, J . S.; Dec, S. F.; Webb, J . D.; Anderson, O. P.;
Strauss, S. H. J . Am. Chem. Soc. 1994, 116, 10003. Temme, B.; Erker,
G.; Karl, J .; Luftmann, H.; Fro¨hlich, R.; Kotila, S. Angew. Chem. 1995,
107, 1867; Angew. Chem., Int. Ed. Engl. 1995, 34, 1755. Antonelli, D.
M.; Tjaden, E. B.; Stryker, J . M. Organometallics 1994, 13, 763. Guram,
A. S.; Swenson, D. C.; J ordan, R. F. J . Am. Chem. Soc. 1992, 114,
8991.
1
46.5 with J CH ) 152 Hz. This is increased by ∆J ) +13
1
Hz relative to the J CH ) 139 Hz reference of the
adjacent N-CH3 13C NMR feature. The 15N NMR signal
of 4 is monitored at δ -358.8 (∆δ ) -20 ppm relative
to the reference of 3). From these data we assume that
complex 4 also contains an intramolecularly coordinated
(η2-CH2-NR2)Zr structural subunit, although the Zr-N
interaction is probably weaker than in the complexes
5. Whether ion pairing with the [CH3B(C6F5)3]- anion15
is also important for stabilizing the system 4 is hard to
ascertain from these data.
It is surprising that the isonitrile ligands in 5 just
simply coordinate to the electrophilic zirconium center
but do not insert into the adjacent metal-carbon
σ-bond,16 although analogous insertion reactions have
(13) A similar effect was previously observed for three-membered
(11) Martinez de Ilarduya, J . M.; Otero, A.; Royo, P. J . Organomet.
Chem. 1988, 340, 187. Gomez, M.; Martinez de Ilarduya, J . M.; Royo,
P. J . Organomet. Chem. 1989, 369, 197. de C. T. Carrondo, M. A. A.
F.; Morais, J .; Roma˜o, C. C.; Roma˜o, M. J .; Veiros, L. F. Polyhedron
1993, 12, 765. Dorer, B.; Prosenc, M.-H.; Rief, U.; Brintzinger, H.-H.
Collect. Czech. Chem. Commun. 1997, 62, 265. J acobsen, H.; Berke,
H.; Do¨ring, S.; Kehr, G.; Erker, G.; Fro¨hlich, R.; Meyer, O. Organo-
metallics 1999, 18, 1724.
(12) Goldman, A. S.; Krogh-J espersen, K. J . Am. Chem. Soc. 1996,
118, 12159. J acobsen, H.; Berke, H.; Brackemeyer, T.; Eisenbla¨tter,
T.; Erker, G.; Fro¨hlich, R.; Meyer, O.; Bergander, K. Helv. Chim. Acta
1998, 81, 1692.
M-O-C situations; see e.g.: Erker, G.; Schlund, R.; Kru¨ger, C. J .
Chem. Soc., Chem. Commun. 1986, 1403. See also ref 6.
(14) For other examples of 15N NMR studies at group 4 organome-
tallic systems, see e.g.: Alt, H. G.; Fo¨ttinger, K.; Milius, W. J .
Organomet. Chem. 1999, 572, 21.
(15) Yang, X.; Stern, C. L.; Marks, T. J . J . Am. Chem. Soc. 1994,
116, 10015 and references therein. Karl, J .; Erker, G. Chem. Ber. 1997,
130, 1261. Karl, J .; Erker, G.; Fro¨hlich, R.; Zippel, F.; Bickelhaupt, F.;
Schreuder Goedheijt, M.; Akkerman, O. S.; Binger, P.; Stannek, J .
Angew. Chem. 1997, 109, 2914; Angew. Chem., Int. Ed. Engl. 1997,
36, 2771. Schottek, J .; Erker, G.; Fro¨hlich, R. Angew. Chem. 1997, 109,
2585; Angew. Chem., Int. Ed. Engl. 1997, 36, 2475.

Methylzirconocenes Bearing (Me2NCH2)Cp Groups
Organometallics, Vol. 18, No. 19, 1999 3821
frequently been observed to occur readily, e.g. at (η2-
aldehyde)zirconocene complexes.17 We assume that
steric factors may hinder a facile RNtC insertion reac-
tion under the applied reaction conditions in the case
of 5, potentially because considerable strain would be
built up in the resulting product formation. We have,
therefore, treated the in situ generated system 4 with
conjugated dienes which could give rise to the formation
of much less strained insertion products.18 This is in fact
observed.
The reactive system 4 was generated at -50 °C and
then treated with 1,3-butadiene. Warming of the mix-
ture to room temperature leads to the precipitation of
the 1:1 addition product 6a (Scheme 2). The NMR
F igu r e 3. Molecular structure of 6b (cation only, with
unsystematic atom-numbering scheme). Selected bond
lengths (Å) and angles (deg): Zr-N ) 2.491(4), Zr-C22 )
2.484(6), Zr-C23 ) 2.562(7), Zr-C25 ) 2.424(7), C15-C16
) 1.515(8), C16-N ) 1.549(7), N-C20 ) 1.496(7), C20-
C21 ) 1.522(9), C21-C22 ) 1.493(9), C22-C23 ) 1.383-
(10), C23-C24 ) 1.509(10), C23-C25 ) 1.405(10); N-Zr-
C25 ) 124.5(2), N-Zr-C23 ) 92.0(2), N-Zr-C22 )
69.7(2), C22-Zr-C23 ) 31.8(2), C22-Zr-C25 ) 58.2(3),
C23-Zr-C25 ) 32.6(2), Zr-N-C20 ) 108.2(3), Zr-C25-
C23 ) 79.1(4), Zr-C23-C25 ) 68.3(4), Zr-C23-C22 )
71.0(4), C25-C23-C22 ) 117.9(6), C23-C22-C21 ) 127.2-
(7), C22-C21-C20 ) 111.2(5), C21-C20-N ) 110.8(5).
Additional values are given in the text.
Sch em e 2
Treatment of 4 with isoprene proceeds analogously
and results in the formation of the CC-coupling product
6b. Again, a single regio- and stereoisomer was observed
in solution. The characteristic spectroscopic data are
very similar to those for 6a (15N NMR, δ -357.0 ppm).
Single crystals suitable for the X-ray crystal structure
analysis were obtained from complex 6b. This analysis
has established the proposed structural properties from
the spectroscopic studies. Complex 6b shows the ex-
pected metallacyclic (π-allyl)metallocene-type structure
in the solid state (Figure 3).18 The allyl-containing
hydrocarbon chain is attached to a Cp ring by means of
the CMe2-N(Me)-CH2- unit that was derived from the
-CMe2-NMe2 substituent by C-H activation. The
isoprene reagent has reacted with 4 by carbon-carbon
coupling with the [N]-CH2- group. This has taken place
regioselectively:19 the isoprene vinyl group was coupled
with the CH2-[N] carbon, with the isoprene methyl
group becoming placed at the central carbon atom (C23)
of the resulting zirconium-bound π-allyl moiety.
spectra indicate that carbon-carbon coupling of the
butadiene has occurred with the CH2-[N] carbon atom.
This has resulted in the formation of a metallacyclic (π-
allyl)zirconium complex. A single stereoisomer is ob-
served in solution. This is characterized by the typical
NMR features of the substituted Cp ligand (1H, δ 6.59,
6.12, 5.89, 5.74 in dichloromethane-d2), a diastereotopic
pair of methyl groups at C4 (i.e. Cp-CMe2-: 13C, δ 26.0
(1J CH ) 128 Hz), 22.8 (1J CH ) 129 Hz)), and 13C NMR
signals of the π-allyl moiety at δ 47.7 (1J CH ) 154 Hz,
C11H2), 130.5 (C10H), and 105.4 (1J CH ) 156 Hz, C9H).
The hydrogen atoms at the C7H2-[N] group are again
diastereotopic (1H, δ 3.30 and 2.68 ppm). The corre-
sponding 13C NMR resonance is observed at δ 66.6 with
1
1J CH ) 140 Hz. The J CH coupling constant in this case
is identical with that of the internal [N]-C6H3 reference
(13C, δ 41.4, 1J CH ) 140 Hz). Complex 6a features a 15N
NMR resonance at δ -358.6 ppm, which indicates a
nitrogen to zirconium interaction.
The π-allyl group in 6b is rather symmetrically
bonded to zirconium (Zr-C25 ) 2.424(7) Å, Zr-C23 )
2.562(7) Å, Zr-C22 ) 2.484(6) Å), which is not often
observed for (π-allyl)zirconium complexes.18-20 The C23-
bonded, isoprene-derived methyl group is oriented
toward the sector of the substituted Cp ring of the bent
metallocene unit in 6b. The π-allyl ligand in 6b is syn-
(16) (a) Adams, R. D.; Chodosh, D. F. Inorg. Chem. 1978, 17, 41.
Elsner, F. H.; Tilley, T. D. J . Organomet. Chem. 1988, 358, 169.
Review: Durfee, L. D.; Rothwell, I. P. Chem. Rev. 1988, 88, 1059. (b)
For selected examples see e.g.: Erker, G.; Zwettler, R.; Kru¨ger, C.
Chem. Ber. 1989, 122, 1377. Beshouri, S. M.; Chebi, D. E.; Fanwick,
P. E.; Rothwell, I. P.; Huffman, J . C. Organometallics 1990, 9, 2375.
Lemke, F. R.; Szakla, D. J .; Bullock, R. M. Organometallics 1992, 11,
876. Guram, A. S.; Guo, Z.; J ordan, R. F. J . Am. Chem. Soc. 1993,
115, 4902. Valero, C.; Grehl, M.; Wingbermu¨hle, D.; Kloppenburg, L.;
Carpenetti, D.; Erker, G.; Petersen, J . L. Organometallics 1994, 13,
415. Temme, B.; Erker, G. J . Organomet. Chem. 1995, 488, 177.
Ahlers, W.; Erker, G.; Fro¨hlich, R. J . Organomet. Chem. 1998, 571,
83.
(17) Erker, G.; Mena, M.; Kru¨ger, C.; Noe, R. Organometallics 1991,
10, 1201. Bendix, M.; Grehl, M.; Fro¨hlich, R.; Erker, G. Organometallics
1994, 13, 3366. Schmuck, S.; Erker, G.; Kotila, S. J . Organomet. Chem.
1995, 502, 75.
(18) Erker, G.; Engel, K.; Dorf, U.; Atwood, J . L.; Hunter, W. E.
Angew. Chem. 1982, 94, 915; Angew. Chem., Int. Ed. Engl. 1982, 21,
914. Erker, G. Angew. Chem. 1989, 101, 411; Angew. Chem., Int. Ed.
Engl. 1989, 28, 397. Erker, G.; Noe, R.; Kru¨ger, C.; Werner, S.
Organometallics 1992, 11, 4174. Erker, G.; Noe, R.; Wingbermu¨hle,
D.; Petersen, J . L. Angew. Chem. 1993, 105, 1216; Angew. Chem., Int.
Ed. Engl. 1993, 32, 1213. Temme, B.; Erker, G.; Karl, J .; Luftmann,
H.; Fro¨hlich, R.; Kotila, S. Angew. Chem. 1995, 107, 1867; Angew.
Chem., Int. Ed. Engl. 1995, 34, 1755.
(19) Karl, J .; Erker, G.; Fro¨hlich, R. J . Am. Chem. Soc. 1997, 119,
11165.
(20) E.g.: Brauer, D. J .; Kru¨ger, C. Organometallics 1982, 1, 204.
Brauer, D. J .; Kru¨ger, C. Organometallics 1982, 1, 207. Erker, G.; Berg,
K.; Kru¨ger, C.; Mu¨ller, G.; Angermund, K.; Benn, R.; Schroth, G.
Angew. Chem. 1984, 96, 445; Angew. Chem., Int. Ed. Engl. 1984, 23,
455. Highcock, W. J .; Mills, R. M.; Spencer, J . L.; Woodward, P. J .
Chem. Soc., Chem. Commun. 1987, 128. Larson, E. J .; Van Dort, P.
C.; Dailey, J . S.; Lakanen, J . R.; Pederson, L. M.; Silver, M. E.;
Huffman, J . C.; Russo, S. O. Organometallics 1987, 6, 2141. Erker,
G.; Berg, K.; Angermund, K.; Kru¨ger, C. Organometallics 1987, 6, 2620.
Larson, E. J .; Van Dort, P. C.; Lakanen, J . R.; O’Neill, D. W.; Pederson,
L. M.; McCandless, J . J .; Silver, M. E.; Russo, S. O.; Huffman, J . C.
Organometallics 1988, 7, 1183. Hauger, B. E.; Vance, P. J .; Prins, T.
J .; Wemple, M. E.; Kort, D. A.; Silver, M. E.; Huffman, J . C. Inorg.
Chim. Acta 1991, 187, 91.

3822 Organometallics, Vol. 18, No. 19, 1999
Pflug et al.
configurated. The newly formed carbon-carbon bond
C20-C21 is in the typical single-bond range (1.522(9)
Å). The overall framework seems to be rather un-
strained. This becomes evident upon inspection of the
Zr-C(Cp) distances of the monosubstituted Cp-R ligand,
which are in close range with one minor deviation (Zr-
C13 ) 2.544(7), Zr-C12 ) 2.497(8), Zr-C11 ) 2.471-
(7), Zr-C15 ) 2.431(7), Zr-C14 ) 2.496(6) Å). Complex
6b also features a close contact between zirconium and
the nitrogen atom in the Cp side chain, although the
Zr-N distance in 6b (2.491(4) Å) is markedly larger
than the corresponding interaction observed in complex
5a (2.312(8) Å, see above). The sum of angles around
nitrogen in 6b is 656.7°, which is close to the limiting
value of an ideal tetrahedron, but some of the individual
bond angles deviate greatly from the 109° angle (C16-
N-C19 ) 114.3(5)°, C19-N-C20 ) 106.1(5)°, C16-N-
C20 ) 111.8(4)°, Zr-N-C19 ) 118.6(3)°, Zr-N-C20 )
108.2(3)°, and Zr-N-C16 ) 97.7(3)°).
F igu r e 4. Molecular structure of 8 (cation only, with
unsystematic atom-numbering scheme). Selected bond
lengths (Å) and angle (deg): Zr-N1 ) 2.4692(12), Zr-N2
) 2.2930(12), Zr-C20 ) 2.2510(14), N1-C6 ) 1.552(2),
C6-C5 ) 1.515(2), C20-N2 ) 1.4640(18), N2-C16 )
1.514(2), C16-C15 ) 1.516(2); N1-Zr-N2 ) 123.61(4),
N1-Zr-C20 ) 86.43(5), N2-Zr-C20 ) 37.58(5), Zr-N1-
C6 ) 97.36(8), N1-C6-C5 ) 101.57(12), Zr-N2-C20 )
69.66(7), Zr-N2-C16 ) 102.10(8), Zr-C20-N2 ) 72.77-
(7), C20-N2-C16 ) 116.78(12), N2-C16-C15 ) 101.14-
(11).
Then we turned again to the (η5-C5H4-CMe2NMe2)2-
Zr-derived systems that we had investigated earlier.2
The (η2-C5H4-CMe2NMe2)2Zr(CH3)2 starting material
7 was prepared analogously to the reaction sequence
depicted in Scheme 1 by treatment of the fulvene 1 with
methyllithium followed by the reaction of the resulting
[C5H4-CMe2NMe2]Li reagent with ZrCl4 in a 2:1 ratio.
Finally, metathetical σ-ligand exchange by treatment
with methyllithium yielded 7. Again, B(C6F5)3 was used
for abstracting a methyl anion from 7, and the resulting
Zr-CH3-containing cation was not stable but instanta-
neously eliminated methane to give 8. In this present
study, complex 8 was also characterized by 15N NMR
spectroscopy and by X-ray diffraction. It shows two
prominent 15N NMR resonances at δ -357.6 and -373.7
ppm (in dichloromethane-d2). Both features indicate the
presence of tetracoordinate pseudotetrahedral nitrogen
centers. We attribute the former resonance to the
[C]-NMe2-[Zr] nitrogen (NB; see Scheme 3) and sug-
This structural description is supported by the result
of the X-ray crystal structure analysis of 8. It shows the
presence of the two monosubstituted η5-cyclopentadienyl
ligands. There are five close contacts in the σ-ligand
plane at the front side of the bent-metallocene moiety.
Most importantly, the [N]-CH2- group is again η2-
coordinated to zirconium with its methylene carbon
atom (C20) occupying the central coordination site (Zr-
C20 ) 2.2510(14) Å). The η2-iminium nitrogen atom is
bonded closely to the metal center (Zr-N2 ) 2.2930-
(12) Å). The remaining C20-N2 bond inside the three-
membered ring has a length of 1.4640(18) Å. The angles
inside the Zr,N2,C20 three-membered ring are 37.58-
(5)° (C20-Zr-N2), 69.66(7)° (Zr-N2-C20), and 72.77-
(7)° (Zr-C20-N2). The tight Cp-C16Me2-N2(C19H3)-
C20H2 chelate ligand leads to marked distortions of the
ligand arrangement at the bent-metallocene nucleus.
The C15-C16 vector at the C11-C15 Cp ring is tilted
toward zirconium (Zr-C15 ) 2.4135(15) Å vs Zr-C12
) 2.5497(16) and Zr-C13 ) 2.5693(16) Å). The Zr-N2-
C16 angle is 102.10(8)°, C20-N2-C16 is 116.78(12)°,
and Zr-N2-C19 is 132.66(10)°. The nitrogen atom N1
of the Cp-CMe2-NMe2 ligand also coordinates to zirco-
nium, although the Zr-N1 bond is markedly longer at
2.4692(12) Å. The -NMe2 ligand occupies the other
lateral coordination site8,21 at the bent metallocene
wedge, trans to N2. It can be seen from the projection
of the molecular structure of complex 8, as it is depicted
in Figure 4, that the N1,Zr,C20,N2 plane is markedly
tilted (by ca. 17°) from the ideal Cp-M-Cp bisecting
major bent metallocene σ-ligand plane to avoid the
building up of considerable strain energy inside the
overall ligand system.22
Sch em e 3
Treatment of 8 with tert-butyl isocyanide resulted in
the displacement of the -NMe2 donor ligand from the
coordination sphere of the zirconium atom to yield the
isonitrile adduct 9. This was evident from the observa-
tion of only a single 1H (δ 1.90 ppm) and 13C NMR
gest that the latter corresponds to NA and is part of a
metallacyclic three-membered ring. The C7H2 group
1
adjacent to NA shows a H NMR AB-type pattern (δ 2.27
2
and 1.57 (at 263 K in dichloromethane-d2), J HH ) 9.8
Hz) and a 13C NMR resonance at δ 49.1 ppm with a
(21) Erker, G.; Rosenfeldt, F. J . Organomet. Chem. 1980, 188, C1.
Review: Erker, G. Acc. Chem. Res. 1984, 17, 103.
(22) For an analogous structural situation see e.g.: Bosch, B. E.;
Erker, G.; Fro¨hlich, R.; Meyer, O. Organometallics 1997, 16, 5449.
1
characteristically enhanced J CH coupling constant of
1
147 Hz (N-C6H3 reference: δ 43.5, J CH ) 139 Hz).

Methylzirconocenes Bearing (Me2NCH2)Cp Groups
Organometallics, Vol. 18, No. 19, 1999 3823
1
resonance (δ 39.2 ppm, J CH ) 133 Hz) for the pendant
δ ∼-375 ppm in complex 5, which exhibits a strong
Zr-N interaction (d(Zr-N) ) 2.318(7) Å). A similar
structural situation is found in 8 with a short Zr-N
bond (2.2930(12) Å) of the (η2-R2N+dCH2)Zr unit.
However, this corresponds to a 15N NMR signal at δ
-357 ppm, and the slightly longer metal-nitrogen bond
of the Zr-N(Me2)R linkage (2.4692(12) Å) coincides
with a 15N NMR chemical shift of δ -372 ppm. The
observed 15N NMR shift of the isoprene insertion
product 6b (d(Zr-N) ) 2.491(4) Å) is again observed at
δ -357 ppm.
Amine coordination probably also plays an important
role in the formation of the (η2-R2N+dCH2)Zr coordina-
tion products. In view of the very favorable N-Zr
coordination pattern observed, we assume that at the
stage of the likely intermediates (e.g. 10; Scheme 4) in
dimethylamino moiety. The corresponding 15N NMR
signal of 9 is observed at δ -338.5 ppm (NB, in
dichloromethane-d2 at 223 K). This corresponds to a
“downfield” shift of ∆δ ) +19 ppm relative to NB in the
precursor complex 8 (δ -357.6; for comparison, see 15N
NMR of 7 at δ -338.4 ppm). In addition, we must
assume a η2-C7H2-NAR2 coordination to zirconium in
complex 9. This is evident from the typical 15N NMR
resonance of NA at δ -375.1 ppm and is supported by
the observed C7H2 13C NMR feature at δ 44.1 ppm (1J CH
) 155 Hz) (internal reference [NA]-C6H3: δ 43.1 ppm,
1J CH ) 138 Hz).
The κC-isonitrile ligand 15N NMR resonance in 9 is
observed at δ -161.3 ppm; the corresponding RNtC 13
C
NMR resonance is at δ 150.0. Complex 9 shows an IR
ν˜(CtNR) band at 2193 cm-1 (in KBr), which is ca. ∆ν˜
≈50 cm-1 above the free alkyl isocyanide value.
Sch em e 4
Con clu sion s
Nitrogen to metal coordination seems to play an
important role in the thermal decomposition chemistry
of the alkylmetallocene cation systems derived by me-
thylanion abstraction from 3 or 7 and related systems.
The obtained products (i.e. 5 or 8/9) greatly benefit from
the electronic stabilization that comes along with the
formation of a new Zr-N bond in these products. C-H
activation at the N-CH3 group of these starting materi-
als has led to the formation of a formaldiminium moiety
(R2N+dCH2) that has become intramolecularly η2-
coordinated to the electron-deficient zirconium center
in these products. The overall bonding of the (η2-R2Nd
CH2)Zr+ subunit seems to be similar to that observed
previously in a few examples of pendant (η2-alkene)-
zirconocene cations4 or in the (η2-aldehyde)- or (η2-
ketone)ZrCp2 type complexes.6
the formation of these complexes amine bonding to
zirconium induces a substantial ammonium character
and thus leads to the marked increase in N-CH acidity
that seems to dominate this chemistry to a great extent.
The resulting (η2-formaldiminium)zirconocene com-
plexes show a selective insertion behavior toward added
unsaturated substrates. We are probing if this can be
developed into a synthetic tool in organometallic chem-
istry and catalysis.
Exp er im en ta l Section
Of course, the η2-coordination of the pendant R2N+d
CH2 unit is easily detected and characterized by X-ray
diffraction, but it seems that 13C and especially 15N
NMR spectroscopy may serve as suitable methods to
identify such a bonding situation. From the result of
the X-ray crystal structure analyses of 5 and 8 it may
be deduced that the (η2-R2N+dCH2)Zr moiety exhibits
a pronounced metallaaziridine character, which is prob-
ably due to a substantial back-bonding contribution to
the overall bonding situation.23 We notice that this
“heterocyclopropane character” seems to show up in the
13C NMR features of the -CH2 group in the expected
way, namely by a small but significant increase of the
corresponding 1J CH coupling constant (by ca. 10-15 Hz,
The reactions were carried out under an inert atmosphere
(argon) using Schlenk type glassware or in a glovebox. 15N
NMR spectra (60.7 MHz) were recorded on a Varian Unity Plus
600 NMR spectrometer by using a GHMBC pulse sequence
(nJ (15N,1H) ) 5 Hz, n ) 3, 4). The 15N chemical shift is given
with respect to a 2% benzamide-15N-0.2% Cr(acac)3 sample
in DMSO (δ(15N) -279.3 ppm, relative to neat CH3NO2, δ(15N)
0; ¥(15N) ) 10.1367 MHz). ESI-MS was carried out on a
Micromass Quattro LC-Z mass spectrometer. For additional
general information see ref 2. 6-(Dimethylamino)-6-methyl-
fulvene (1) was prepared according to the procedure of Hafner
et al.24 Complexes 2 and 3 (including their structures) were
briefly mentioned by us previously in a review.3 Some of the
data for these compounds are listed below for comparison. The
preparation of 8 was described by us previously.2 Additional
structural and spectroscopic data for 8 are given below.
relative to an acyclic reference). The changes in the 15
N
Complex 7,2 B(C6F5)3,25 and CpZrCl3 were prepared as
26
NMR spectra are equally pronounced. Upon ring forma-
tion, we observe an “upfield” shift of ∆δ between ca. -20
to -40 ppm of the (R2NdCH2)Zr nitrogen atom relative
to a suitable acyclic trigonal -CR2NR2 reference. Un-
fortunately, the magnitude of ∆δ(15N) does not seem to
correlate directly with the observed Zr-N bond length.
Thus, 15N NMR chemical shifts of δ ∼-338 ppm seem
to be typical for the -CMe2-NMe2 reference in com-
plexes 3 and 7. The 15N NMR chemical shift goes up to
described by us in the literature. For a compilation of the NMR
experiments used for characterization, see ref 27. Atom
(24) Hafner, K.; Vo¨pel, K. H.; Ploss, G.; Ko¨nig, C. Org. Synth. 1967,
47, 52 and references therein. Hafner, K.; Schultz, G.; Wagner, K.
Chem. Ber. 1964, 768, 539.
(25) Massey, A. G.; Park, A. J .; Stone, F. G. A. Proc. Chem. Soc.
1963, 212. Massey, A. G.; Park, A. J . J . Organomet. Chem. 1964, 2,
245. Massey, A. G.; Park, A. J . In Organometallic Syntheses; King, R.
B., Eisch, J . J ., Eds.; Elsevier: Amsterdam, 1986; Vol. 3, p 461.
(26) Erker, G.; Berg, K.; Treschanke, L.; Engel, K. Inorg. Chem.
1982, 21, 1277. Erker, G.; Berg, K.; Sarter, C. In Organometallic
Syntheses; King, R. B.; Eisch, J . J .; Eds.; Elsevier: Amsterdam, 1986;
Vol. 3, p 29.
(23) Dewar, M. J . S.; Dougherty, R. C. The PMO Theory of Organic
Chemistry; Plenum Press: New York, 1975; p 300. Dewar, M. J . S.;
Ford, G. P. J . Am. Chem. Soc. 1979, 101, 783 and references therein.
Cremer, D.; Kraka, E. J . Am. Chem. Soc. 1985, 107, 3800.
(27) Braun, S.; Kalinowski, H.; Berger, S. 100 and More Basic NMR
Experiments; VCH: Weinheim, Germany, 1996, and references therein.

3824 Organometallics, Vol. 18, No. 19, 1999
Pflug et al.
numbering is as given in the schemes. For RNtC reference
NMR values see ref 28.
and 1664 observed reflections [I g 2σ(I)], 178 refined param-
eters, R1 ) 0.055, wR2 ) 0.076, maximum residual electron
density 0.74 (-0.82) e Å-3, hydrogens calculated and riding.
These data have been deposited with the Cambridge Structural
Data Base under the deposition number CSD 101802.
P r ep a r a tion of [η5-(1-(Dim eth yla m in o)-1-m eth yleth yl)-
cyclopen tadien yl](η5-cyclopen tadien yl)zir con iu m Dich lo-
r ide (2). A solution of 1.70 g (10.8 mmol) of ((1-(dimethylamino)-
1-methylethyl)cyclopentadienyl)lithium (generated by treatment
of 1 with methyllithium) in 50 mL of a 1:1 mixture of
tetrahydrofuran and ether was added dropwise at -20 °C to
a suspension of 2.84 g (10.8 mmol) of CpZrCl3 in 100 mL of
ether. The mixture was warmed to room temperature and was
then stirred for another 1 h. The LiCl precipitate was removed
by filtration through Celite. The orange filtrate was brought
to dryness in vacuo. The residue was stirred overnight with
pentane (50 mL), and the resulting beige product was collected
by filtration to yield 3.11 g (76%) of 2, mp 119 °C dec. Complex
2 always contained a small amount (ca. 5-10%) of an as yet
unidentified byproduct. Anal. Calcd for C15H21NCl2Zr (377.5):
C, 47.73; H, 5.61; N, 3.71. Found: C, 46.13; H, 5.19; N, 3.10.
1H NMR (dichloromethane-d2, 599.99 MHz): δ 6.50, 6.39 (m,
each 2H, Cp′ H), 6.48 (s, 5H, Cp H), 1.98 (s, 6H, 6-H), 1.50 (s,
6H, 5-H). 13C NMR (dichloromethane-d2, 50.32 MHz): δ 137.3
(C1), 117.5, 113.0 (C5H4-), 116.5 (C-Cp), 57.8 (C4), 39.1 (C6),
24.4 (C5). 15N,1H-GHMBC NMR (dichloromethane-d2, 60.72/
599.99 MHz): δ -337.8/1.53 (N/5-H).
Tr ea tm en t of 3 w ith B(C6F 5)3. Gen er a tion of 4. In an
NMR-controlled experiment a sample of 11 mg (29.1 µmol) of
3 was dissolved in 0.5 mL of dichloromethane-d2 and this
mixture added at -78 °C to 15 mg (29.1 mmol) of solid
B(C6F5)3. The resulting solution was slowly raised in temper-
ature and monitored by NMR. At -50 °C the clean formation
of 4 was thus observed, which was complete after ca. 1 h at
that temperature. 1H NMR (dichloromethane-d2, 599.99 MHz,
223 K): δ 6.69, 5.52 (m, each 1H, C5H4), 6.17 (s, 5H, Cp H),
5.93 (m, 2H, C5H4), 2.55 (s, 3H, 6-H), 2.23, 1.67 (d, each 1H,
2J HH ) 8.8 Hz, 7-H, 7-H′), 1.52, 1.29 (s, each 3H, 5-H, 5′-H),
0.39 (br s, 3H, (C6F5)3B-CH3). 13C NMR (dichloromethane-d2,
150.84 MHz, 223 K): δ 114.9 (C1), 113.2 (1J CH ) 175 Hz), 110.9
(1J CH ) 174 Hz), 108.1 (1J CH ) 169 Hz), 97.7 (1J CH ) 173 Hz)
(C5H4), 110.0 (1J CH ) 174 Hz, C-Cp), 59.0 (C4), 46.5 (1J CH
)
152 Hz, C7), 44.3 (1J CH ) 139 Hz, C6), 24.6 (1J CH ) 127 Hz),
17.7 (1J CH ) 127 Hz) (C5, C5′), 9.5 (B(C6F5)3-CH3), 147.7 (d,
1J CF ) 239 Hz, o-B(C6F5)3), 137.0 (d, 1J CF ) 252 Hz, p-B(C6F5)3),
136.0 (d, 1J CF ) 244 Hz, m-B(C6F5)3), 127.8 (br, ipso-B(C6F5)3).
15N,1H-GHMBC NMR (dichloromethane-d2, 60.72/599.99 MHz,
223 K): δ -358.8/1.52, -358/1.29 (N/5-H, N/5′-H).
X-r a y Cr ysta l Str u ctu r e An a lysis of 2. Crystal data and
refinement details: formula C15H21NCl2Zr, Mr ) 377.45, 0.80
× 0.50 × 0.20 mm, a ) 12.827(1) Å, b ) 9.452(1) Å, c ) 13.594-
Rea ction of 4 w ith ter t-Bu tyl Isocya n id e: P r ep a r a tion
of 5a . A sample of 3 (100 mg, 0.30 mmol) was dissolved in 3
mL of dichloromethane. The solution was cooled to -36 °C and
then added to 152 mg (0.30 mmol) of solid B(C6F5)3. After 30
min 23 mg (0.30 mmol) of tert-butyl isocyanide was added, and
then the reaction mixture was warmed to room temperature
with stirring. The product was precipitated as a dark brown
oil by the dropwise addition of pentane (9 mL). The superna-
tant organic phase was carefully decanted. The remaining oil
was washed with pentane (3 × 3 mL). Then 9 mL of pentane
was added and the product stirred overnight to give a solid,
which was collected to yield 164 mg of 5a (60%). Single crystals
of 5a suitable for the X-ray crystal structure analysis (see
below) were obtained by allowing pentane vapor to diffuse into
a solution of 5a in dichloromethane at -36 °C; mp 115 °C.
Anal. Calcd for C39H32N2BF15Zr (915.7): C, 51.16; H, 3.52; N,
3.06. Found: C, 50.96; H, 3.61; N, 3.15. 1H NMR (dichlo-
romethane-d2, 599.99 MHz): δ 6.07, 5.88, 5.83, 5.49 (m, each
(1) Å, â ) 103.56(1)°, V ) 1602.2(2) Å3, Fcalcd ) 1.565 g cm-3
,
µ ) 10.06 cm-1, empirical absorption correction via ψ scan data
(0.846 e C e 0.999), Z ) 4, monoclinic, space group P21/c (No.
14), λ ) 0.710 73 Å, T ) 223 K, ω/2θ scans, 3384 reflections
collected (+h, -k, (l), (sin θ)/λ ) 0.62 Å-1, 3238 independent
and 2835 observed reflections [I g 2σ(I)], 176 refined param-
eters, R1 ) 0.028, wR2 ) 0.077, maximum residual electron
density 0.40 (-0.92) e Å-3, hydrogens calculated and riding.
These data have been deposited with the Cambridge Structural
Data Base under the deposition number CSD 101801.
P r ep a r a tion of [η5-(1-(Dim eth yla m in o)-1-m eth yleth yl)-
cyclop en t a d ien yl](η5-cyclop en t a d ien yl)d im et h ylzir co-
n iu m (3). An 8.3 mL (15.9 mmol) amount of a 1.93 M ethereal
methyllithium solution was added dropwise at -40 °C to a
suspension of 2 (3.00 g, 7.95 mmol) in 50 mL of ether. The
mixture was warmed to -20 °C over 2 h with stirring and then
brought to room temperature and stirred for an additional 30
min. A precipitate (LiCl) was removed by filtration through
Celite. Solvent was then removed from the clear filtrate in
vacuo, pentane (20 mL) added, and the product collected by
filtration. After this product was washed with pentane (5 mL)
and dried in vacuo, 1.78 g (67%) of 3 was obtained; mp 114 °C
(dec at 175 °C). Anal. Calcd for C17H27NZr (336.6): C, 60.66;
2
1H, C5H4), 5.96 (s, 5H, Cp H), 2.49 (s, 3H, 6-H), 2.00 (d, J HH
) 8.8 Hz, 1H, 7-H), 1.63, 1.20 (s, each 3H, 5-H, 5′-H), 1.57 (s,
2
9H, 10-H), 1.39 (d, J HH ) 8.8 Hz, 1H, 7-H′), 0.49 (br s, 3H,
B(C6F5)3-CH3). 13C NMR (dichloromethane-d2, 150.84 MHz):
δ 148.5 (C8, from GHMBC NMR), 111.7 (C1), 109.0 (1J CH
)
175 Hz), 106.7 (1J CH ) 175 Hz), 104.2 (1J CH ) 174 Hz), 96.6
(1J CH ) 173 Hz) (C5H4), 107.0 (1J CH ) 174 Hz, C-Cp), 59.8
(C9), 58.9 (C4), 44.2 (1J CH ) 138 Hz, C6), 43.5 (1J CH ) 153 Hz,
C7), 30.0 (1J CH ) 130 Hz, C10), 25.4 (1J CH ) 129 Hz), 17.7 (1J CH
) 128 Hz) (C5, C5′), 10.1 (B(C6F5)3-CH3), 148.7 (d, 1J CF ) 230
Hz, o-B(C6F5)3), 137.8 (d, 1J CF ) 238 Hz, p-B(C6F5)3), 136.6 (d,
1J CF ) 243 Hz, m-B(C6F5)3), 129.6 (br, ipso-B(C6F5)3). 15N,1H-
1
H, 8.08; N, 4.16. Found: C, 60.03; H, 7.98; N, 3.89. H NMR
(benzene-d6, 200.13 MHz): δ 5.79 (s, 5H, Cp H), 5.76 (m, 4H,
C5H4), 1.98 (s, 6H, 6-H), 1.19 (s, 6H, 5-H), -0.06 (s, 6H, 7-H).
1H NMR (dichloromethane-d2, 200.13 MHz): δ 6.10 (s, 5H, Cp
H), 6.08, 6.04 (m, each 2H, C5H4), 2.02 (s, 6H, 6-H), 1.28 (s,
6H, 5-H), -0.36 (s, 6H, 7-H). 13C NMR (benzene-d6, 50.32
MHz): δ 132.3 (C1), 110.8 (C-Cp), 109.7, 109.2 (each C5H4),
56.6 (C4), 39.2 (C6), 31.3 (C7), 25.1 (C5). 15N,1H-GHMBC NMR
(dichloromethane-d2, 60.72/599.99 MHz): δ -338.7/2.02 (N/
6-H), -338.7/1.28 (N/5-H).
GHMBC NMR (dichloromethane-d2, 60.72/599.99 MHz):
δ
-161.0/1.57 (NB/10-H), -375.9/1.63 (NA/5-H), -375.9/1.20 (NA/
5′-H). IR (KBr): ν˜ 2201 cm-1 (CtNR).
X-r a y Cr ysta l Str u ctu r e An a lysis of 5a . Crystal data and
refinement details: formula C39H32N2BF15Zr, Mr ) 915.70, 0.50
× 0.30 × 0.20 mm, a ) 14.325(1) Å, b ) 21.496(1) Å, c )
12.460(1) Å, V ) 3836.8(4) Å3, Fcalcd ) 1.585 g cm-3, µ ) 3.92
cm-1, absorption correction via SORTAV (0.828 e T e 0.926),
Z ) 4, orthorhombic, space group Pna21 (No. 33), λ ) 0.710 73
Å, T ) 198 K, ω and æ scans, 25 552 reflections collected ((h,
(k, (l), (sin θ)/λ ) 0.62 Å-1, 7629 independent and 6271
observed reflections [I g 2σ(I)], 530 refined parameters, R1 )
0.068, wR2 ) 0.169, maximum residual electron density 4.06
(-0.92) e Å-3 close to Zr (<0.9 Å), Flack parameter 0.00(6),
hydrogens calculated and riding.
X-r a y Cr ysta l Str u ctu r e An a lysis of 3. Crystal data and
refinement details: formula C17H27NZr, Mr ) 336.62, 0.30 ×
0.20 × 0.10 mm, a ) 12.891(4) Å, b ) 9.427(5) Å, c ) 13.985-
(4) Å, â ) 103.32(2)°, V ) 1653.8(11) Å3, Fcalcd ) 1.352 g cm-3
,
µ ) 6.54 cm-1, empirical absorption correction via ψ scan data
(0.969 e C e 0.999), Z ) 4, monoclinic, space group P21/c (No.
14), λ ) 0.710 73 Å, T ) 223 K, ω/2θ scans, 3490 reflections
collected ((h, +k, -l), (sin θ)/λ ) 0.62 Å-1, 3345 independent
(28) Gifford, M.; Cousseau, J .; Martin, G. M. J . Chem. Soc., Perkin
Trans. 2 1985, 157.

Methylzirconocenes Bearing (Me2NCH2)Cp Groups
Organometallics, Vol. 18, No. 19, 1999 3825
Rea ction of 4 w ith n -Bu tyl Isocya n id e: P r ep a r a tion
of 5b. Analogously as described above a sample of 150 mg (0.45
mmol) of 3 (in 3 mL of dichloromethane) was treated subse-
quently with 228 mg (0.45 mmol) of B(C6F5)3 (in 3 mL of
dichloromethane) and 39 mg (0.45 mmol) of n-C4H9-NtC to
yield the product 5b (231 mg, 56%) as a viscous red oil. The
oily product was only characterized spectroscopically. 1H NMR
(dichloromethane-d2, 599.99 MHz): δ 6.06, 5.88, 5.85, 5.51 (m,
Hz), 22.8 (1J CH ) 129 Hz) (C5, C5′), 25.6 (1J CH ) 129 Hz, C8),
10.5 (B(C6F5)3-CH3), 148.6 (d, 1J CF ) 249 Hz, o-B(C6F5)3), 137.8
(d, J CF ) 244 Hz, p-B(C6F5)3), 136.7 (d, J CF ) 246 Hz,
m-B(C6F5)3), 129.2 (br, ipso-B(C6F5)3). 15N,1H-GHMBC NMR
(dichloromethane-d2, 60.72/599.99 MHz): δ ) -358.6/1.61,
-358.6/1.36 (N/5-H, N/5′-H).
1
1
Rea ction of 4 w ith Isop r en e: P r ep a r a tion of 6b.
Complex 4 was generated analogously as described above by
treatment of 150 mg (0.45 mmol) of 3 with 228 mg (0.45 mmol)
of B(C6F5)3 in 3 mL of dichloromethane at -36 °C. Isoprene
(31 mg, 0.45 mmol) was added. The mixture was kept at -36
°C for 30 min and then warmed to room temperature. The
product was precipitated with pentane (9 mL). Workup
analogously as described above gave 318 mg (78%) of 6b.
Single crystals of 6b that were suitable for the X-ray crystal
structure analysis were obtained by crystallization from
dichloromethane; mp 137 °C (dec at 197 °C). Anal. Calcd for
C39H31NBF15Zr (900.7): C, 52.01; H, 3.47; N, 1.56. Found: C,
3
each 1H, C5H4), 3.74 (t, J HH ) 6.8 Hz, 2H, 9-H), 2.49 (s, 3H,
6-H), 2.02 (d, 2J HH ) 8.8 Hz, 1H, 7-H), 1.80 (quint., 3J HH ) 7.3
Hz, 2H, 10-H), 1.63, 1.19 (s, each 3H, 5-H, 5′-H), 1.48 (sext,
2
3J HH ) 7.5 Hz, 2H, 11-H), 1.38 (d, J HH ) 8.8 Hz, 1H, 7-H′),
3
1.00 (t, J HH ) 7.5 Hz, 3H, 12-H), 0.50 (br s, 3H, B(C6F5)3-
CH3). 13C NMR (dichloromethane-d2, 150.84 MHz): δ 152.2
(C8), 111.7 (C1), 109.0, 106.6, 104.1, 96.6 (C5H4), 106.9 (C-
Cp), 58.9 (C4), 45.2 (C9), 44.2 (C6), 43.5 (C7), 30.8 (C10), 25.4,
17.7 (C5, C5′), 20.0 (C11), 13.2 (C12), 10.5 (B(C6F5)3-CH3),
1
1
148.7 (d, J CF ) 242 Hz, o-B(C6F5)3), 137.9 (d, J CF ) 242 Hz,
1
51.47; H, 3.20; N, 1.59. ESI-MS:
C
20H28NZr+ (found/calcd
p-B(C6F5)3), 136.7 (d, J CF ) 247 Hz, m-B(C6F5)3), 129.2 (br,
ipso-B(C6F5)3). IR (KBr): ν˜ 2213 cm-1 (CtNR).
relative intensity in %) m/z 372 (100/100), 373 (42.5/44.9), 374
(38.6/38.2), 375 (7.6/7.6), 376 (30.7/33.7), 377 (6.6/7.8), 378 (5.5/
5.4). 1H NMR (dichloromethane-d2, 599.99 MHz): δ 6.55, 6.09,
5.76, 5.27 (m, each 1H, C5H4), 6.13 (s, 5H, Cp H), 5.47 (m, 1H,
Rea ction of 4 w ith 2,4,4-Tr im eth yl-2-p en tyl Isocya -
n id e: P r ep a r a tion of 5c. Analogously as described above
complex 4 (150 mg, 0.45 mmol) was treated with B(C6F5)3 (228
mg, 0.45 mmol) in dichloromethane and then (after 15 min)
with 62 mg of 2,4,4-trimethyl-2-pentyl isocyanide. Workup as
described above yielded 228 mg (52%) of complex 5c, mp 208
°C. Anal. Calcd for C43H40N2BF15Zr (971.8): C, 53.15; H, 4.15;
2
9-H), 3.44 (m, 1H, 7-H), 2.86 (d, J HH ) 4.8 Hz, 1H, 11-H),
2.68 (m, 1H, 7-H′), 2.39 (m, 1H, 8-H), 2.38 (pd, 3H, 6-H), 2.35
2
(d, J HH ) 4.8 Hz, 1H, 11-H′), 2.19 (m, 1H, 8-H′), 2.11 (s, 3H,
12-H), 1.65, 1.39 (s, each 3H, 5-H, 5′-H), 0.49 (br s, 3H,
B(C6F5)3-CH3). 13C NMR (dichloromethane-d2, 150.84 MHz):
δ 152.4 (C10), 118.6 (1J CH ) 177 Hz), 104.0 (1J CH ) 177 Hz),
102.6 (1J CH ) 175 Hz), 102.4 (1J CH ) 173 Hz) (C5H4), 117.7
(C1), 111.3 (1J CH ) 174 Hz, C-Cp), 94.1 (1J CH ) 143.9 Hz, C9),
68.4 (1J CH ) 138 Hz, C7), 62.3 (C4), 50.1 (1J CH ) 150 Hz, C11),
1
N, 2.88. Found: C, 52.15; H, 3.98; N, 2.87. H NMR (dichlo-
romethane-d2, 599.99 MHz, 298 K): δ 6.06, 5.89, 5.84, 5.47
(m, each 1H, C5H4), 5.96 (s, 5H, Cp H), 2.49 (s, 3H, 6-H), 2.01
2
(d, J HH ) 8.8 Hz, 1H, 7-H), 1.73 (s, 2H, 11-H), 1.63, 1.20 (s,
each 3H, 5-H, 5′-H), 1.62 (s, 6H, 10-H), 1.38 (d, 2J HH ) 8.8 Hz,
1H, 7-H′), 1.10 (s, 9H, 13-H), 0.50 (br s, 3H, B(C6F5)3-CH3).
13C NMR (dichloromethane-d2, 150.84 MHz, 298 K): δ 111.7
(C1), 109.0, 106.5, 103.9, 96.7 (C5H4), 106.9 (C-Cp), 62.6 (C9),
58.9 (C4), 51.8 (C11), 44.2 (C6), 43.4 (C7), 31.1 (C12), 31.1
(C10), 30.9 (C13), 25.4, 17.6 (C5, C5′), 10.5 (B(C6F5)3-CH3),
41.9 (1J CH ) 139 Hz, C6), 25.8 (1J CH ) 129 Hz), 23.1 (1J CH
)
128 Hz) (C5, C5′), 24.2 (C8), 23.9 (C12), 10.2 (B(C6F5)3-CH3),
1
1
148.6 (d, J CF ) 249 Hz, o-B(C6F5)3), 137.8 (d, J CF ) 244 Hz,
1
p-B(C6F5)3), 136.7 (d, J CF ) 246 Hz, m-B(C6F5)3), 129.2 (br,
ipso-B(C6F5)3). 15N,1H-GHMBC NMR (dichloromethane-d2,
60.72/599.99 MHz): δ -357.0/1.65, -357.0/1.39 (N/5-H, N/5′-
H).
1
1
148.7 (d, J CF ) 242 Hz, o-B(C6F5)3), 137.9 (d, J CF ) 242 Hz,
1
p-B(C6F5)3), 136.7 (d, J CF ) 247 Hz, m-B(C6F5)3), 129.2 (br,
ipso-B(C6F5)3). C8 not detected. 15N,1H-GHMBC NMR (dichlo-
romethane-d2, 60.72/599.99 MHz, 298 K): δ -160.5/1.73 (NB/
11-H), -160.5/1.62 (NB/10-H), -376.4/1.63, -376.4/1.20 (NA/
5-H, NA/5′-H). IR (KBr): ν˜ 2195 cm-1 (CtNR).
X-r a y Cr ysta l Str u ctu r e An a lysis of 6b. Crystal data and
refinement details: formula C39H31NBF15Zr‚CH2Cl2, Mr
)
985.60, 0.30 × 0.20 × 0.10 mm, a ) 10.114(1) Å, b ) 19.244-
(1) Å, c ) 20.443(1) Å, â ) 101.36(1)°, V ) 3900.9(5) Å3, Fcalcd
) 1.678 g cm-3, µ ) 5.23 cm-1, absorption correction via
SORTAV (0.859 e T e 0.950), Z ) 4, monoclinic, space group
P21/n (No. 14), λ ) 0.710 73 Å, T ) 198 K, ω and æ scans,
Rea ction of 4 w ith Bu ta d ien e: P r ep a r a tion of 6a . A
cold solution (-50 °C) containing 150 mg (0.45 mmol) of 3 in
3 mL of dichloromethane was added to a solution of 228 mg
(0.45 mmol) of B(C6F5)3 in 3 mL of dichloromethane at -50
°C. The mixture was stirred for 30 min to generate 4. Then 9
mL of gaseous 1,3-butadiene was introduced into the solution.
After 45 min at -50 °C the mixture was warmed to room
temperature and the product precipitated by the addition of
pentane (6 mL). The organic phase was decanted off. The
residue was washed 4 times with pentane (3 mL each) and
then solidified by stirring it with 6 mL of pentane for 12 h.
The product is obtained as a pale yellow solid; yield of 6a 239
mg (60%); mp 210 °C dec. Anal. Calcd for C38H29NBF15Zr
(886.7): C, 51.48; H, 3.30; N, 1.58. Found: C, 50.17; H, 3.44;
N, 1.30. ESI-MS: C19H26NZr+ (found/calcd relative intensity
in %) m/z 358 (100/100), 359 (42.1/43.7), 360 (38.4/40.4), 361
19 299 reflections collected ((h, (k, (l), (sin θ)/λ ) 0.59 Å-1
,
6831 independent and 4301 observed reflections [I g 2σ(I)],
552 refined parameters, R1 ) 0.066, wR2 ) 0.145, maximum
residual electron density 1.89 (-0.59) e Å-3 close to Zr (<1.0
Å), hydrogens at C25 from difference Fourier map, others
calculated and all refined riding.
Tr ea t m en t of 7 w it h B(C6F 5)3: P r ep a r a t ion of 8.
Complex 8 was prepared by treatment of 680 mg (1.61 mmol)
of 7 with 824 mg (1.61 mmol) of B(C6F5)3 in 20 mL of toluene
at -20 °C analogously as described by us in the literature2 to
give a yield of 1.04 g (71%) of 8. Anal. Calcd for C39H34N2BF15
-
Zr (917.7): C, 51.04; H, 3.73; N, 3.05. Found: C, 50.35; H, 3.67;
N, 2.77. Single crystals of 8 were obtained by diffusion of
pentane vapor into a solution of 8 in dichloromethane at -36
°C. 1H NMR (dichloromethane-d2, 599.99 MHz, 263 K): δ 6.57,
1
(7.3/7.8), 362 (31.5/34.4), 363 (6.6/7.4), 364 (5.7/6.1). H NMR
(dichloromethane-d2, 599.99 MHz): δ 6.59, 6.12, 5.89, 5.74 (m,
each 1H, C5H4), 6.10 (s, 5H, Cp H), 6.15 (m, 1H, 10-H), 5.70
(m, 1H, 9-H), 3.30 (m, 1H, 7-H), 2.68 (m, 1H, 7-H′), 2.62 (m,
1H, 11-H), 2.60 (m, 1H, 11-H′), 2.39 (m, 1H, 8-H), 2.31 (pd,
1H, 6-H), 2.13 (m, 1H, 8-H′), 1.61, 1.36 (s, each 3H, 5-H, 5′-
H), 0.50 (br s, 3H, B(C6F5)3-CH3). 13C NMR (dichloromethane-
d2, 150.84 MHz): δ 130.3 (C10), 119.2 (1J CH ) 178 Hz), 104.2
(1J CH ) 179 Hz), 100.6 (1J CH ) 174 Hz), 99.0 (1J CH ) 172 Hz)
(C5H4), 118.1 (C1), 110.3 (1J CH ) 175 Hz, C-Cp), 105.4 (1J CH
) 156 Hz, C9), 66.6 (1J CH ) 140 Hz, C7), 62.2 (C4), 47.7 (1J CH
) 154 Hz, C11), 41.4 (1J CH ) 140 Hz, C6), 26.0 (1J CH ) 128
6.52, 6.26, 5.95, 5.93, 5.76, 5.75, 5.55 (m, each 1H, Cp′ H), 2.45
2
(s, 3H, 6-H), 2.31, 2.30 (s, each 3H, 8-H, 8′-H), 2.27 (d, J HH
)
9.8 Hz, 1H, 7-H), 1.61, 1.49 (s, each 3H, 9-H, 9′-H), 1.57 (d,
2J HH ) 9.8 Hz, 1H, 7-H′), 1.50, 1.36 (s, each 3H, 5-H, 5′-H),
1
0.45 (br s, 3H, (C6F5)3B-CH3). H NMR (dichloromethane-d2,
599.99 MHz, 223 K): δ 6.54, 6.24, 5.73, 5.52 (m, each 1H, 2-H,
2′-H, 3-H, 3′-H), 6.53, 5.91, 5.90, 5.73 (m, each 1H, 12-H, 12′-
H, 13-H, 13′-H), 2.42 (s, 3H, 6-H), 2.27 (s, 6H, 8-H, 8-H′), 2.20
2
(d, J HH ) 9.8 Hz, 1H, 7-H), 1.58, 1.47 (s, each 3H, 9-H, 9′-H),
2
1.53 (d, J HH ) 9.8 Hz, 1H, 7-H′), 1.48, 1.33 (s, each 3H, 5-H,

3826 Organometallics, Vol. 18, No. 19, 1999
Pflug et al.
5′-H), 0.40 (br s, 3H, B(C6F5)3-CH3). 13C NMR (dichloromethane-
d2, 150.84 MHz, 223 K): δ 123.7 (C11), 115.3 (C1), 113.2 (1J CH
) 173 Hz), 112.0 (1J CH ) 175 Hz), 104.1 (1J CH ) 173 Hz), 99.3
(1J CH ) 170 Hz) (C12, C12′, C13, C13′), 110.1 (1J CH ) 174 Hz),
in vacuo to yield 80 mg (47%) of 9, mp 199 °C. Anal. Calcd for
C44H43N3BF15Zr (1000.9): C, 52.80; H, 4.33; N, 4.20. Found:
C, 51.14; H, 4.65; N, 4.20. 1H NMR (dichloromethane-d2, 599.99
MHz, 223 K): δ 6.29, 6.26, 5.73, 5.36 (12-H, 12-H′, 13-H, 13-
H′), 6.08, 5.89, 5.76, 5.44, (2-H, 2-H′, 3-H, 3-H′), 2.44 (6-H),
109.6 (1J CH ) 174 Hz), 106.7 (1J CH ) 174 Hz), 99.6 (1J CH
171 Hz) (C2, C2′, C3, C3′), 60.6 (C10), 58.2 (C4), 49.1 (1J CH
)
)
2
1.92 (d, J HH ) 8.7 Hz, 1H, 7-H), 1.90 (s, 6H, 8-H), 1.59, 1.14
147 Hz, C7), 47.7 (1J CH ) 139 Hz), 47.3 (1J CH ) 139 Hz) (C8,
C8′), 43.5 (1J CH ) 139 Hz, C6), 24.8 (1J CH ) 128 Hz), 17.5 (1J CH
) 128 Hz) (C5, C5′), 24.4 (1J CH ) 128 Hz), 24.2 (1J CH ) 128
(s, each 3H, 5-H, 5′-H), 1.50 (s, 9H, CMe3), 1.37 (d, J HH ) 8.7
2
Hz, 1H, 7-H′), 1.30, 1.27 (s, each 3H, 9-H, 9′-H), 0.40 (br s,
3H, B(C6F5)3-CH3). 13C NMR (dichloromethane-d2, 150.84
MHz, 298 K): δ 151.6 (C14), 128.8 (C11), 112.0 (C1), 111.3
(1J CH ) 172 Hz), 107.7 (1J CH ) 172 Hz), 105.2 (1J CH ) 173 Hz),
1
Hz) (C9, C9′) 9.4 (B(C6F5)3-CH3), 147.7 (d, J CF ) 237 Hz,
o-B(C6F5)3), 137.0 (d, 1J CF ) 242 Hz, p-B(C6F5)3), 135.9 (d, 1J CF
) 247 Hz, m-B(C6F5)3), 128.0 (br, ipso-B(C6F5)3). 15N,1H-
GHMBC NMR (dichloromethane-d2, 60.72/599.99 MHz, 263
K): δ -357.6/1.52, -357.6/1.40 (NB/5-H, NB/5′-H), -373.7/1.63,
-373.7/1.52 (NA/9-H, NA/9′-H). 15N,1H-GHMBC NMR (dichlo-
romethane-d2, 60.72/599.99 MHz, 223 K): δ -357.9/1.47,
-357.9/1.33 (NB/5-H, NB/5′-H), -372.9/1.58, -372.9/1.47 (NA/
9-H, NA/9′-H).
102.9 (1J CH ) 173 Hz) (C12, C12′, C13, C13′), 110.3 (1J CH
)
174 Hz), 106.3 (1J CH ) 174 Hz), 104.4 (1J CH ) 174 Hz), 97.0
(1J CH ) 173 Hz) (C2, C2′, C3, C3′), 59.9 (C15), 58.7 (C4), 56.5
(C10), 44.1 (1J CH ) 155 Hz, C7), 43.1 (1J CH ) 138 Hz, C6), 39.2
(1J CH ) 133 Hz, C8), 29.9 (1J CH ) 129 Hz, C16), 27.3 (1J CH
)
126 Hz), 25.4 (1J CH ) 126 Hz) (C9, C9′), 25.4 (1J CH ) 126 Hz),
17.8 (1J CH ) 128 Hz) (C5, C5′), 9.4 (B(C6F5)3-CH3); 148.6 (d,
1J CF ) 247 Hz, o-B(C6F5)3), 137.8 (d, 1J CF ) 244 Hz, p-B(C6F5)3),
136.6 (d, 1J CF ) 246 Hz, m-B(C6F5)3), 128.9 (br, ipso-B(C6F5)3).
15N,1H-GHMBC NMR (dichloromethane-d2, 60.72/599.99 MHz,
223 K): δ -161.3/1.50 (NC/16-H), -338.5/1.30, -338.5/1.27 (NB/
9-H, NB/9′-H), -375.1/1.59, -375.1/1.14 (NA/5-H, NA/5′-H). IR
(KBr): ν˜ 2193 cm-1 (CtNR).
X-r a y Cr ysta l Str u ctu r e An a lysis of 8. Crystal data and
refinement details: formula C39H34N2BF15Zr, Mr ) 917.71, 0.50
× 0.35 × 0.30 mm, a ) 12.032(1) Å, b ) 17.476(1) Å, c )
17.479(1) Å, â ) 91.57(1)°, V ) 3674.0(4) Å3, Fcalcd ) 1.659 g
cm-3, µ ) 4.09 cm-1, absorption correction via SORTAV (0.821
e T e 0.887), Z ) 4, monoclinic, space group P21/n (No. 14), λ
) 0.710 73 Å, T ) 198 K, ω and æ scans, 33 281 reflections
collected ((h, (k, (l), (sin θ)/λ ) 0.71 Å-1, 11 048 independent
and 9648 observed reflections [I g 2σ(I)], 531 refined param-
eters, R1 ) 0.033, wR2 ) 0.080, maximum residual electron
density 0.37 (-0.50) e Å-3, hydrogens calculated and refined
riding.
Ackn owledgm en t. Financial support from the Fonds
der Chemischen Industrie, the Deutsche Forschungs-
gemeinschaft, and the Ministerium fu¨r Schule und
Weiterbildung, Wissenschaft und Forschung des Landes
Nordrhein-Westfalen is gratefully acknowledged.
All data sets were collected with Enraf-Nonius CAD4,
MACH3, or KappaCCD diffractometers. Programs used: data
collection, EXPRESS and COLLECT; data reduction, MolEN
and DENZO-SMN; absorption correction for CCD data, SOR-
TAV; structure solution, SHELXS-86 and SHELXS-97; struc-
ture refinement, SHELXL-93 and SHELXL-97; graphics (with
unsystematical numbering schemes), SCHAKAL-92 and DIA-
MOND.29
Rea ction of 8 w ith ter t-Bu tyl Isocya n id e: P r ep a r a tion
of 9. A sample of 150 mg (0.17 mmol) of 8 was dissolved in 6
mL of dichloromethane and cooled to -36 °C. tert-Butyl
isocyanide (14 mg, 0.17 mmol) was added and the mixture kept
for 30 min at -36 °C. Then it was warmed to room tempera-
ture. The product was precipitated by the addition of pentane
(15 mL). The organic liquid phase was decanted from the solid.
The residue was washed with pentane (4 × 3 mL) and dried
Su p p or tin g In for m a tion Ava ila ble: Figures giving NMR
spectra of selected compounds and text and tables giving
additional information about the X-ray crystal structure
analyses of complexes 2, 3, 5a , 6b, and 8. This material is
available free of charge via the Internet at http://pubs.acs.org.
OM990216D
(29) Programs used: EXPRESS: Nonius BV, 1994. COLLECT:
Nonius BV, 1998. MolEN: Fair, K. Enraf-Nonius BV, 1990. Denzo-
SMN: Otwinowski, Z.; Minor, W. Methods Enzymol. 1997, 276, 307-
326. SORTAV: Blessing, R. H. Acta Crystallogr. 1995, A51, 33-37; J .
Appl. Crystallogr. 1997, 30, 421-426. SHELXS-86 and SHELXS-97:
Sheldrick, G. M. Acta Crystallogr. 1990, A46, 467-473. Sheldrick, G.
M. Universita¨t Go¨ttingen, 1997. SHELXL-93 and SHELXL-97: Sheld-
rick, G. M. Universita¨t Go¨ttingen, 1997. SCHAKAL: Keller, E.
Universita¨t Freiburg, 1997. DIAMOND: Brandenburg, K. Universita¨t
Bonn, 1996.