Expanding heteroscorpionates. Facile synthesis of new hybrid scorpionate/cyclopentadienyl ligands and their lithium and group 4 metal compounds: A combined experimental and density functional theory study

Article abstract of DOI:10.1021/om7003942

The preparation of new hybrid scorpionate/cyclopentadienyl ligands in the form of the lithium derivatives [Li(bpzcp)(THF)] (1) [bpzcp = 2,2-bis(3,5-dimethylpyrazol-1-yl)-1,1-diphenylethylcyclopentadienyl] and [Li(bpztcp)(THF)] (2) [bpztcp = 2,2-bis(3,5-dimethylpyrazol-1-yl)-1-tert- butylehylcyclopentadienyl] or as a mixture of the two scorpionate/ cyclopentadiene regioisomers (bpzpcpH) 1-[2,2-bis(3,5-dimethylpyrazol-1-yl)-1- phenylethyl]-1,3-cyclopentadiene(3a) and 2-[2,2-bis(3,5-dimethylpyrazol-1-yl)-1- phenylethyl]-1,3-cyclopentadiene (3b) has been carried out by reaction of bis(3,5-dimethylpyrazol-1-yl)methane (bdmpzm) with BuⁿLi and 6,6-diphenylfulvene, 6-tert-butylfulvene, or 6-phenylfulvene, respectively. However, when this insertion reaction was carried out with 6,6-dimethylfulvene, the compound [Li(^isopr-cp)(bdmpzm)(THF)] (4) [^isoprcp = isopropenylcyclopentadienyl] was obtained. Compounds 1 and 2 reacted with [TiCl₄(THF)₂] or [MCl₄] (M = Zr, Hf) to give the complexes [MCl₃(bpzcp)] (M = Ti, 5; Zr, 6; Hf, 7) and [MCl ₃(bpztcp)] (M = Ti, 8; Zr, 9; Hf, 10). Similar reactions do not take place with the mixture of the two isomers 3a and 3b. However, when a THF solution of 3a-3b and [MCl₄] (M = Zr, Hf) was heated under reflux, the complexes [MCl₃(bpzpcp)] (M = Zr, 11; Hf, 12) [bpzpcp = 2,2-bis(3,5-dimethylpyrazol-1-yl)-1-phenylethylcyclopentadienyl] were obtained. In addition, alkyl complexes [ZrClMe₂(bpztcp)] (13) and [ZrMe ₃(bpztcp)] (14) were also prepared. The structures of these complexes have been determined by spectroscopic and DFT methods, and in addition, the X-ray crystal structures of 1, 2, 3b, and 6 were also established.

Full text of DOI:10.1021/om7003942

4310
Organometallics 2007, 26, 4310-4320
Expanding Heteroscorpionates. Facile Synthesis of New Hybrid
Scorpionate/Cyclopentadienyl Ligands and Their Lithium and
Group 4 Metal Compounds: A Combined Experimental and
Density Functional Theory Study
Antonio Otero,*,† Juan Ferna´ndez-Baeza,*,† Antonio Antin˜olo,† Juan Tejeda,†
Agust´ın Lara-Sa´nchez,† Luis F. Sa´nchez-Barba,†,‡ Margarita Sa´nchez-Molina,†
Ana M. Rodr´ıguez,† Carles Bo,§, and Manuel Urbano-Cuadrado§
Departamento de Qu´ımica Inorga´nica, Orga´nica y Bioqu´ımica, UniVersidad de Castilla-La Mancha,
13071-Ciudad Real, Spain, Departamento de Qu´ımica Inorga´nica y Anal´ıtica, UniVersidad Rey Juan
Carlos, Mostoles-28933-Madrid, Spain, Institute of Chemical Research of Catalonia (ICIQ), AVenida
Pa¨ısos Catalans 16, 43007-Tarragona, Spain, and Departament de Qu´ımica F´ısica i Inorga`nica,
UniVersitat RoVira i Virgili, Campus Sescelades, Macelli Domingo s/n, 43007 Tarragona, Spain
ReceiVed April 24, 2007
The preparation of new hybrid scorpionate/cyclopentadienyl ligands in the form of the lithium derivatives
[Li(bpzcp)(THF)] (1) [bpzcp ) 2,2-bis(3,5-dimethylpyrazol-1-yl)-1,1-diphenylethylcyclopentadienyl] and
[Li(bpztcp)(THF)] (2) [bpztcp ) 2,2-bis(3,5-dimethylpyrazol-1-yl)-1-tert-butylethylcyclopentadienyl] or
as a mixture of the two scorpionate/cyclopentadiene regioisomers (bpzpcpH) 1-[2,2-bis(3,5-dimethylpyra-
zol-1-yl)-1-phenylethyl]-1,3-cyclopentadiene (3a) and 2-[2,2-bis(3,5-dimethylpyrazol-1-yl)-1-phenylethyl]-
1,3-cyclopentadiene (3b) has been carried out by reaction of bis(3,5-dimethylpyrazol-1-yl)methane
(bdmpzm) with BunLi and 6,6-diphenylfulvene, 6-tert-butylfulvene, or 6-phenylfulvene, respectively.
However, when this insertion reaction was carried out with 6,6-dimethylfulvene, the compound [Li(isopr
-
cp)(bdmpzm)(THF)] (4) [isoprcp ) isopropenylcyclopentadienyl] was obtained. Compounds 1 and 2 reacted
with [TiCl4(THF)2] or [MCl4] (M ) Zr, Hf) to give the complexes [MCl3(bpzcp)] (M ) Ti, 5; Zr, 6; Hf,
7) and [MCl3(bpztcp)] (M ) Ti, 8; Zr, 9; Hf, 10). Similar reactions do not take place with the mixture
of the two isomers 3a and 3b. However, when a THF solution of 3a-3b and [MCl4] (M ) Zr, Hf) was
heated under reflux, the complexes [MCl3(bpzpcp)] (M ) Zr, 11; Hf, 12) [bpzpcp ) 2,2-bis(3,5-
dimethylpyrazol-1-yl)-1-phenylethylcyclopentadienyl] were obtained. In addition, alkyl complexes
[ZrClMe2(bpztcp)] (13) and [ZrMe3(bpztcp)] (14) were also prepared. The structures of these complexes
have been determined by spectroscopic and DFT methods, and in addition, the X-ray crystal structures
of 1, 2, 3b, and 6 were also established.
cyclopentadienyl-based complexes of group 4 metals, with
particular attention focused on nitrogen- and/or oxygen-contain-
ing ligands.3 In this context, scorpionate ligands such as poly-
(pyrazolyl)borates are also attractive ancillary ligands for the
synthesis of transition metal complexes.4 More recentlysand
related with the tris(pyrazolyl)boratessnew, mixed pyrazolyl/
cyclopentadienyl ligands have been described.5 In this important
field of ligand design, we have previously reported the synthesis
Introduction
Cyclopentadienyl systems with an additional donor function
are attracting increased interest in the chemistry of early
transition metals because of their potential applications as
catalysts in polymerization processes.1 Ligands possessing both
a cyclopentadienyl ring and heteroatoms connected by an
appropriate spacer are receiving considerable interest in synthesis
and catalysis, as they lead to significant changes in both steric
and electronic effects on the metal centers.2 Furthermore, the
most recent strategy in the design and modification of catalysts
for olefin polymerization have involved the development of non-
(2) See for example: (a) McKnight, A. L.; Waymouth R. M. Chem. ReV.
1998, 98, 2587-2598. (b) Siemeling, U. Chem. ReV. 2000, 100, 1495-
1526. (c) Butenscho¨n, H. Chem. ReV. 2000, 100, 1527-1564. (d) Qian,
Y.; Huang, J.; Bala, M. D.; Lian, B.; Zhang, H.; Zhang. H. Chem. ReV.
2003, 103, 2633-2690.
(3) See, for example: (a) Scollard, J. D.; McConville, D. H. J. Am. Chem.
Soc. 1996, 118, 10008-10009. (b) Scollard, J. D.; McConville, D. H.; Vittal,
J. J. Organometallics 1997, 16, 4415-4420. (c) Fokken, S.; Spaniol, T. P.;
Okuda, J.; Serentz, F. G.; Mullhaupt, R. Organometallics 1997, 16, 4240-
4242. (d) Gibson, V. C.; Kimberly, B. S.; White, A. J. R.; Williams, D. J.;
Houd, P. Chem. Commun. 1998, 313-314. (e) Warren, T. H.; Schrock, R.
R.; Davis W. M. Organometallics 1998, 17, 308-321.
(4) (a) Trofimenko, S. Scorpionates. The Coordination Chemistry of
Polypyrazolylborate Ligands; Imperial College Press: London, 1999. (b)
Etienne, M.; Donnadieu, B.; Mathieu, R.; Ferna´ndez-Baeza, J.; Jalo´n, F.
A.; Otero, A.; Rodrigo-Blanco, M. E. Organometallics 1996, 15, 4597-
4603. (c) Antin˜olo, A.; Carrillo-Hermosilla, F.; Ferna´ndez-Baeza, J.;
Lanfranchi, M.; Lara-Sa´nchez, A.; Otero, A.; Palomares, E.; Pellinghelli,
M. A.; Rodr´ıguez, A. M. Organometallics 1998, 17, 3015-3019.
* Corresponding author. E-mail: antonio.otero@uclm.es.
† Universidad de Castilla-La Mancha.
‡ Universidad Rey Juan Carlos.
§ ICIQ.
Universitat Rovira i Virgili
(1) See for example: (a) Deng, D.; Qian, C.; Wu, G.; Zheng, P. J. Chem.
Soc., Chem. Commun. 1990, 880-881. (b) Qian, C.; Wang, B.; Wu, G.;
Zheng, P. J. J. Organomet. Chem. 1992, 427, C29-C32. (c) Anwander,
R.; Hermann, W. A.; Scherer, W.; Munck, F. C. J. Organomet. Chem. 1993,
462, 163-174. (d) Molander, G.; Schumann, H.; Rosenthal, E. C. E.;
Demtschuk, J. Organometallics 1996, 15, 3817-3824. (e) Schumann, H.;
Rosenthal, E. C. E.; Demtschuk, J. Organometallics 1998, 17, 5324-5333.
(f) Britovsek, G. J. P.; Gibson, V. C.; Wass, D. F. Angew. Chem., Int. Ed.
1999, 38, 428-447. (g) Gibson, V. C.; Spitzmesser, S. K. Chem. ReV. 2003,
103, 283-315.
10.1021/om7003942 CCC: $37.00 © 2007 American Chemical Society
Publication on Web 07/13/2007

Expanding Heteroscorpionates
Organometallics, Vol. 26, No. 17, 2007 4311
Scheme 1. Synthesis of the First Hybrid Scorpionate/
Cyclopentadienyl Lithium Precursor of the Ligand Bpzcp
Scheme 2. Synthesis of [Li(bpzcp)(THF)] (1) and
[Li(bpztcp)(THF)] (2)
of new “heteroscorpionate” ligands based on bis(pyrazol-1-yl)-
methane,6 and these contain two pyrazole rings and a carboxy-
late, dithiocarboxylate, or methoxide group. These classes of
tridentate ligands can coordinate to a wide variety of elements,
e.g., from early to late transition metals. We have reported
heteroscorpionate complexes containing group 4 and 5 metals,7
and more recently, we developed the synthesis of the first
complexes of scandium and yttrium with these heteroscorpionate
ligands.8
However, despite the development of donor-functionalized
cyclopentadienyl ligands and the emerging importance of the
“heteroscorpionate” ligands, hybrid scorpionate/cyclopentadienyl
lithium precursors for the introduction of this type of ligand
into transition metal complexes were unknown until we recently
published the first hybrid scorpionate/cyclopentadienyl ligand.9
The unprecedented preparation of this new class of tridentate
ligand [bpzcp ) 2,2-bis(3,5-dimethylpyrazol-1-yl)-1,1-diphe-
nylethylcyclopentadienyl] by a simple and efficient synthetic
route led us to develop and fully explore the potential offered
by this type of ligand (Scheme 1).
have potential uses in asymmetric catalysis. These ligands have
been coordinated to group 4 metals, and a new series of hybrid
scorpionate/cyclopentadienyl complexes for these elements were
isolated and characterized. The reactivity of some of these
toward alkylating lithium reagents has also been studied. Some
structures were determined by means of a DFT-based method,
which was also applied to discuss the nature of the metal-
ligand interaction.
Herein we describe the synthesis and structural characteriza-
tion of the lithium salts of several hybrid scorpionate/cyclo-
pentadienyl ligands by a simple one-pot procedure, which opens
up a new, broad way to prepare this type of interesting ligand.
In addition, two of the compounds prepared contain a chiral
center in the backbone of the ligand; thus the introduction of
chirality into these systems opens the possibility of obtaining
new enantiopure scorpionate ligands10 in the future, and these
Results and Discussion
Ligand Syntheses. Deprotonation at the methylene group of
bis(3,5-dimethylpyrazol-1-yl)methane (bdmpzm)11 with BunLi,
followed by reaction with 6,6-diphenylfulvene or 6-tert-butyl-
fulvene,12 yielded the lithium compounds [Li(bpzcp)(THF)] (1)
[bpzcp ) 2,2-bis(3,5-dimethylpyrazol-1-yl)-1,1-diphenylethyl-
cyclopentadienyl] and [Li(bpztcp)(THF)] (2) [bpztcp ) 2,2-bis-
(3,5-dimethylpyrazol-1-yl)-1-tert-butylethylcyclopentadienyl] as
colorless and orange solids, respectively, in good yield (ca. 85%)
after the appropriate workup (see Scheme 2). However, when
(5) (a) Lopes, I.; Lin, G. Y.; Domingos, A.; McDonald, R.; Marques,
N.; Takats, J. J. Am. Chem. Soc. 1999, 121, 8110-8111. (b) Roitershtein,
D.; Domingos, A.; Marques, N. Organometallics 2004, 23, 3483-3487.
(6) (a) Otero, A.; Ferna´ndez-Baeza, J.; Antin˜olo, A.; Tejeda J.; Lara-
Sa´nchez, A. Dalton Trans. 2004, 1499-1510 (perspective article). (b)
Pettinari, C.; Pettinari, R. Coord. Chem. ReV. 2005, 249, 663-691.
(7) For group 5 metal complexes see for example: (a) Otero, A.;
Ferna´ndez-Baeza, J.; Tejeda, J.; Antin˜olo, A.; Carrillo-Hermosilla, F.; Diez-
Barra, E.; Lara-Sa´nchez, A.; Ferna´ndez-Lopez, M.; Lanfranchi M.; Pel-
linghelli, M. A. J. Chem. Soc., Dalton Trans. 1999, 3537-3539. (b) Otero,
A.; Ferna´ndez-Baeza, J.; Antin˜olo, A.; Tejeda, J.; Lara-Sa´nchez, A.;
Sa´nchez-Barba, L.; Rodr´ıguez, A. M. Eur. J. Inorg. Chem. 2004, 260-
266. For group 4 metal complexes see for example: (c) Otero, A.;
Ferna´ndez-Baeza, J.; Antin˜olo, A.; Carrillo-Hermosilla, F.; Tejeda, J.; D´ıez-
Barra, E.; Lara-Sa´nchez, A.; Sa´nchez-Barba, L.; Lo´pez-Solera, I.; Ribeiro
M. R.; Campos, J. M. Organometallics 2001, 20, 2428-2430. (d) Otero,
A.; Ferna´ndez-Baeza, J.; Antin˜olo, A.; Tejeda, J.; Lara-Sa´nchez, A.;
Sa´nchez-Barba, L.; Ferna´ndez-Lo´pez M.; Lo´pez-Solera, I. Inorg. Chem.
2004, 43, 1350-1358.
the same reaction was carried out with 6-phenylfulvene,12
a
mixture of two scorpionate/cyclopentadiene regioisomers (bpz-
pcpH), 1-[2,2-bis(3,5-dimethylpyrazol-1-yl)-1-phenylethyl]-1,3-
cyclopentadiene (3a) and 2-[2,2-bis(3,5-dimethylpyrazol-1-yl)-
1-phenylethyl]-1,3-cyclopentadiene (3b), was isolated as colorless
solids (see Schemes 3). Although the latter reaction was carried
out in anhydrous THF, a hydrolysis process from the adventi-
tious water in the workup occurred. These compounds (3a, 3b)
are the first examples of bis(pyrazol-1-yl)methanes to contain
a cyclopentadiene moiety in the carbon bridge. The deproto-
nation of 3 with BunLi was also carried out, but the expected
lithium scorpionate/cyclopentadienyl compound was not iso-
lated, because an uncontrolled hydrolysis process in the workup
occurred to give 3 again.
(8) Otero, A.; Ferna´ndez-Baeza, J.; Antin˜olo, A.; Tejeda, J.; Lara-
Sa´nchez, A.; Sa´nchez-Barba, L.; Martinez-Caballero, E.; Rodr´ıguez, A. M.;
Lopez-Solera, I. Inorg. Chem. 2005, 44, 5336-5344.
(9) Otero, A.; Ferna´ndez-Baeza, J.; Antin˜olo, A.; Tejeda, J.; Lara-
Sa´nchez, A.; Sa´nchez-Barba, L.; Rodr´ıguez, A. M.; Maestro, M. A. J. Am.
Chem. Soc. 2004, 126, 1330-1331.
Finally, when the insertion process was carried out with 6,6-
dimethylfulvene, a cyclopentadienyl lithium complex, [Li(isopr
-
(10) (a) Otero, A.; Ferna´ndez-Baeza, J.; Antin˜olo, A.; Tejeda, J.; Lara-
Sa´nchez, A.; Sa´nchez-Barba, L.; Sanchez-Molina, M.; Franco, S.; Lopez-
Solera, I.; Rodr´ıguez A. M. Eur. J. Inorg. Chem. 2006, 707-710 (Short
Communication). (b) Otero, A.; Ferna´ndez-Baeza, J.; Antin˜olo, A.; Tejeda,
J.; Lara-Sa´nchez, A.; Sa´nchez-Barba, L.; Sanchez-Molina, M.; Franco, S.;
Lopez-Solera, I.; Rodr´ıguez A. M. Dalton Trans. 2006, 4359-4370.
(11) (a) Sebastian, J.; Sala, P.; Del Mazo, J.; Sancho, M.; Ochoa, C.;
Elguero, J.; Fayet J. P.; Vertut, M. C. J. Heterocycl. Chem. 1982, 19, 1141-
1145. (b) D´ıez-Barra, E.; de la Hoz, A.; Sa´nchez-Migallon A.; Tejeda, J. J.
Chem. Soc., Perkin Trans. 1 1993, 1079-1083.
(12) Stone, K. J.; Little, R. D. J. Org. Chem. 1984, 49, 1849-1853.

4312 Organometallics, Vol. 26, No. 17, 2007
Scheme 3. Synthesis of the Scorpionate/Cyclopentadiene Compounds 3a and 3b (bpzpcpH)
Otero et al.
Scheme 4. Synthesis of [Li(isoprcp)] (4)
one set of resonances for the pyrazole rings, indicating that the
pyrazoles are equivalent, and two multiplets for the cyclopen-
tadienyl protons in 1H NMR. These results are consistent with
a tetrahedral disposition in which a symmetry plane exists that
contains the lithium atom, the bridging carbons of the pyrazolyl
1
rings, and atoms Ca and Cb (Scheme 2). However, the H and
13C{1H} NMR spectra of 2 exhibit two distinct sets of pyrazole
resonances, indicating the existence of two types of pyrazole
rings. Furthermore, the 1H NMR spectrum shows four multiplets
for the cyclopentadienyl protons. A tetrahedral environment for
the lithium atom can be proposed in which the two pyrazole
rings are located in cis and trans positions with respect to the
tert-butyl group (see Scheme 2). The phase-sensitive 1H
NOESY-1D spectra were also obtained in order to confirm the
assignments of the signals for the Me3, Me5, and H4 groups of
each pyrazole ring. In this complex the carbon atom (Ca) is a
stereogenic center, and we confirmed the presence in solution
of the corresponding two enantiomers by adding a chiral shift
reagent, namely, (R)-(-)-(9-anthryl)-2,2,2-trifluoroethanol. This
process gave rise to two signals for each proton in the 1H NMR
spectrum, resulting from the two diastereoisomers of the
corresponding two enantiomers. In addition, X-ray diffraction
studies on 1 and 2 were carried out (see Figures 1 and 2). X-ray
crystal studies on organolithium compounds containing carbon
rings with delocalized π-electrons, such as benzyl, fluorenyl,
and cyclopentadienyl, have been carried out, and a variety of
η2-, η3-, and η5-bonding arrangements have been described.14
In this field, additional structural studies on other related
compounds, such as 1 and 2, would be quite useful in helping
to further define the bonding in these complexes. The most
representative bond lengths and angles are presented in Table
1. Both complexes have a monomeric structure. In both
complexes the geometry around the Li atom can be described
as a distorted tetrahedron with a “heteroscorpionate” ligand that
acts in a tridentate fashion (two coordinated pyrazole rings and
a cyclopentadienyl ring) and one molecule of THF. The Li-N
distances [2.37(1) and 2.13(1) Å] for 1 and [2.150(5) and 2.131-
(5) Å] for 2 are in good agreement with others determined for
lithium scorpionate or poly(pyrazolyl)methane complexes.7a,15
The C5H4 ring is unsymmetrically bonded to the Li atom with
Li-C bond lengths ranging from 2.25(1) to 2.50(6) Å. The
X-ray diffraction study confirms that the presence in solution
cp)] (4) [isoprcp ) isopropenylcyclopentadienyl], was obtained
as a white solid (Scheme 4). The preparation of 4 involved the
deprotonation of a methyl group of the fulvene by the bis-
(pyrazol-1-yl)methyllithium. This type of reaction has been
described previously on using different organolithium reagents.13
At this point, it is worth mentioning the differences in the
reactivities of the fulvenes in the processes described above. In
fact, with 6,6-diphenylfulvene and 6-tert-butylfulvene the cor-
responding lithium scorpionate/cyclopentadienyl derivatives 1
and 2 were isolated, while with 6-phenylfulvene a similar lithium
compound has been shown to be unstable to hydrolysis and a
scorpionate/cyclopentadiene derivative 3 was the only isolable
compound. It is possible that electronic effects due to the
substituents on the fulvene carbon atom play an important role
in the stabilization of the lithium scorpionate/cyclopentadienyl
derivatives, meaning that the choice of substituents would be
critical in designing a successful synthetic route. Indeed, the
effects of the fulvene carbon atom substituents on the geometry
of the scorpionate/cyclopentadiene ligand were investigated by
determining the structures of isolated scorpionate/cyclopenta-
dienyl ligands as well as their lithium derivatives. The geometric
parameter that changes most is the bond angle of the fulvene
carbon, since the values calculated for fulvene (122.9°), a
6-phenylfulvene (120.3°), and a 6,6-diphenylfulvene (113.9°)
(as isolated ligands) show a clear trend. A similar trend was
also found in the lithium derivatives (118.5°, 116.2°, 111.9°)
(vide supra), and the low stability of the 6-phenylfulvene
derivative may be related to pure electronic effects.
The different compounds were characterized spectroscopi-
cally. The mass spectra (FAB) of 1 and 2 indicate a mononuclear
formulation. The 1H and 13C{H} NMR spectra of 1 show only
(13) (a) Macomber, D. W.; Hart, W. P.; Rausch, M. D. J. Am. Chem.
Soc. 1982, 104, 884-886. (b) Knu¨ppel, S.; Erker, G.; Fro¨hlich, R. Angew.
Chem., Int. Ed. 1999, 38, 1923-1926. (c) Bai, S. D.; Wei, X. H. Guo, J.
P.; Liu, D. S. Zhou, Z. Y. Angew. Chem., Int. Ed. 1999, 38, 1926-1928.
(14) (a) Qian, B.; Henling, L. M.; Peters, J. C. Organometallics 2000,
19, 2805-2808. (b) Culp, R. D.; Cowley, A. H. Organometallics 1996,
15, 5380-5384.

Expanding Heteroscorpionates
Organometallics, Vol. 26, No. 17, 2007 4313
Figure 1. ORTEP view of [Li(bpzcp)(THF)] (1). Ellipsoids are at
the 30% probability level, and hydrogen atoms have been omitted
for clarity.
Figure 4. ORTEP view of 1,1′-[2-(1,3-cyclopentadien-2-yl)-2-
phenylethylidene]bis(3,5-dimethylpyrazole) (3b). Ellipsoids are at
the 30% probability level, and hydrogen atoms have been omitted
for clarity.
substituents at C(6) were either two hydrogen atoms, one
hydrogen atom and one phenyl group, or two phenyl groups.
The agreement between the X-ray results and the computed
values is remarkable. When R1 ) R2 ) H, the shortest Li-
C(Cp) distance corresponds to the Li-C(1) bond (2.262 Å),
while the bond lengths to C(2) (2.377 Å) and C(5) (2.376 Å)
are slightly longer but equivalent. The same trend is observed
for Li-C(3) and Li-C(4), and this indicates that the Cp ring
lies horizontal and symmetric on top of the Li atom. The
geometry of this model compound matches perfectly well the
X-ray parameters obtained for compound 2. It is worth noting
that since the angle C(1)-C(6)-C(7) is calculated as being
slightly wider than its value in 2, all the computed carbon-
lithium bonds are calculated as being slightly longer. As we
mentioned above, the nature of substituents on the fulvene
carbon affects, to a large extent, the bond angle of the isolated
ligands as well as the angle C(1)-C(6)-C(7) in the Li
complexes. Note that this angle became narrower when H atoms
were substituted by phenyl groups. An additional effect was
observed in the molecular structure of compounds 1 and 2: the
rotation of the Cp ring around the C(1)-C(6) bond that breaks
the symmetry in the Li-C(Cp) bond distances. This is clearly
visible in the difference between the Li-C(3) and Li-C(4) bond
lengths in 1 and 2, but also in the computed structures when R1
) H and R2 ) Ph and when R1 ) R2 ) Ph. This tilting results
in a shorter Li-C(5) bond distance that in 1 is indeed the
shortest lithium-carbon bond. Also, the computed values
reproduce fairly well these features. Although the computed
values are not able to reproduce the Li-C(5) bond as the
shortest, the difference between the Li-C(1) and the Li-C(5)
is rather small. Indeed, the Li-C(1) is the only carbon-lithium
bond that is characterized by the presence of a bond critical
point in the electronic charge density function.16
Figure 2. ORTEP view of [Li(S-bpztcp)(THF)] (2). Ellipsoids are
at the 30% probability level, and hydrogen atoms have been omitted
for clarity.
Figure 3. Proposed structures for the three isomers of compound
3.
of the corresponding two enantiomers for complex 2 (R + S) is
maintained in the solid state.
Selected geometrical parameters are given in Table 1 for the
DFT-optimized structure of a model of 1 and 2 in which the
In the hydrolysis process that leads to compound 3 it is
1
possible to form three isomers (see Figure 3). Two sets of H
NMR signals are observed for this mixture, which is consistent
with the presence of only two tautomers. In both compounds
(15) (a) Otero, A.; Ferna´ndez-Baeza, J.; Tejeda, J.; Antin˜olo, A.; Carrillo-
Hermosilla, F.; Diez-Barra, E.; Lara-Sa´nchez, A.; Ferna´ndez-Lopez, M. J.
Chem. Soc., Dalton Trans. 2000, 2367-2374. (b) Reger, D. L.; Collins, J.
E.; Matthews, M. A.; Rheingold, A. L.; Liable-Sands, L. M.; Guzei, I. A.
Inorg. Chem. 1997, 36, 6266-6269.
(16) Bader, R. W. F. Atoms in Molecules: A Quantum Theory; Clarendon
Press, 1994.

4314 Organometallics, Vol. 26, No. 17, 2007
Otero et al.
Table 1. Selected Geometrical Parameters for the X-ray Studies of 1, 2, and 3b and for Computed Structures of Models of 1
and 2 (distances in Å, angles in deg)
1 (R1 ) R2 ) Ph)
2 (R1 ) H, R2 ) tBu)
exp
Bond Lengths
2 (R1 ) R2 ) H) 2 (R1 ) H, R2 ) Ph)
3b
exp
calc
calc
calc
exp
Li(1)-O(1)
Li(1)-N(1)
Li(1)-N(3)
Li(1)-C(1)
Li(1)-C(2)
Li(1)-C(3)
Li(1)-C(4)
Li(1)-C(5)
N(2)-C(7)
N(4)-C(7)
C(1)-C(6)
C(6)-C(7)
1.96(1)
2.37(1)
2.13(1)
2.28(1)
2.38(1)
2.44(1)
2.35(1)
2.25(1)
1.462(6)
1.463(6)
1.520(7)
1.581(7)
2.103 Li(1)-O(1)
2.196 Li(1)-N(1)
2.132 Li(1)-N(3)
2.270 Li(1)-C(1)
2.340 Li(1)-C(2)
2.415 Li(1)-C(3)
2.389 Li(1)-C(4)
2.294 Li(1)-C(5)
1.466 N(2)-C(7)
1.468 N(4)-C(7)
1.529 C(1)-C(6)
1.626 C(6)-C(7)
1.968(5)
2.150(5)
2.131(5)
2.252(5)
2.372(5)
2.504(6)
2.469(5)
2.321(5)
1.458(3)
1.453(3)
1.509(4)
1.570(4)
2.028
2.188
2.210
2.262
2.377
2.521
2.521
2.376
1.459
1.459
1.499
1.573
2.055
2.235
2.174
2.260
2.429
2.544
2.461
2.290
1.463
1.459
1.507
1.593
N(1)-C(11)
N(3)-C(11)
C(11)-C(12)
C(12)-C(13)
C(12)-C(18)
C(13)-C(14)
C(13)-C(17)
C(14)-C(15)
C(15)-C(16)
C(16)-C(17)
1.457(3)
1.458(3)
1.514(4)
1.503(4)
1.539(4)
1.355(4)
1.477(4)
1.496(4)
1.439(5)
1.396(5)
Angles
O(1)-Li(1)-N(3) 105.4(5)
O(1)-Li(1)-N(1) 103.5(5)
N(3)-Li(1)-N(1) 83.4(4)
C(1)-C(6)-C(7) 113.0(4)
104.3
104.5
86.5
O(1)-Li(1)-N(3) 103.6(2)
101.5
102.2
85.0
103.5
102.8
84.9
N(1)-C(11)-N(3)
110.5(2)
O(1)-Li(1)-N(1) 102.0(2)
N(3)-Li(1)-N(1) 85.9(2)
C(1)-C(6)-C(7) 115.8(2)
N(1)-C(11)-C(12) 111.7(2)
N(3)-C(11)-C(12) 116.4(2)
C(13)-C(12)-C(11) 113.4(2)
C(13)-C(12)-C(18) 110.0(2)
C(11)-C(12)-C(18) 107.1(2)
111.9
118.5
116.2
Scheme 5. Synthesis of Complexes [MCl3(bpzcp)] (5-7) and
[MCl3(bpztcp)] (8-10)
the H5 signal in the 1H NMR spectrum integrates for two
protons, meaning that the regioisomer 3c [in which the cyclo-
pentadiene group is bonded by C5 to the bis(pyrazol-1-yl)-
methane unit] can be ruled out. In the solid state one isomer
was crystallized and characterized by X-ray diffraction (Figure
4). Selected bond lengths and angles are collected in Table 1.
The short C(13)-C(14) [1.355(4) Å] and C(16)-C(17) [1.396-
(5) Å] distances are indicative of a double bond, whereas the
C(14)-C(15) [1.496(4) Å], C(15)-C(16) [1.439(5) Å], and
C(13)-C(17) [1.477(4) Å] distances are indicative of a single
bond. These results are consistent with the structural disposition
described for isomer 3b. The C-C distances found in this
cyclopentadiene moiety can be compared to those typically
found for the classic cyclopentadiene.17 The pyrazole rings of
this compound are orientated in a quasi-antiparallel manner with
respect to each other, presumably to minimize the intramolecular
steric interaction between the N(2) and N(4) atoms of the two
rings. This conformation is similar to that found with the (2-
hydroxyphenyl)bis(pyrazolyl)methane derivative.18 The cyclo-
pentadiene and phenyl rings are probably in this quasi-
antiparallel disposition to minimize steric interactions between
the two rings.
Scheme 6. Synthesis of Complexes [MCl3(bpzpcp)] (11 and
12)
Group 4 Halide Compounds. Having prepared this new
class of hybrid scorpionate/cyclopentadienyl compounds in the
form of their lithium salts, we explored their potential utility as
tridentate ligands in the preparation of new group 4 metal
complexes. Compounds 1-3 proved to be useful reagents for
the synthesis of new titanium, zirconium, and hafnium com-
plexes. The lithium compounds 1 and 2 were reacted at -70 °C
with [TiCl4(THF)2] or [MCl4] (M ) Zr, Hf) in a 1:1 molar ratio
in THF to give, after the appropriate workup, the complexes
[MCl3(bpzcp)] (M ) Ti, 5; Zr, 6; Hf, 7) and [MCl3(bpztcp)]
(M ) Ti, 8; Zr, 9; Hf, 10), which were isolated as red or orange
solids in good yield (Scheme 5). An interesting reactivity was
observed when a mixture of [MCl4] (M ) Zr, Hf) and 3a-3b
was heated under reflux for 12 h, as the new complexes [MCl3-
(bpzpcp)] (M ) Zr, 11; Hf, 12) [bpzpcp ) 2,2-bis(3,5-
dimethylpyrazol-1-yl)-1-phenylethylcyclopentadienyl] were ob-
tained, after the appropriate workup procedure, as yellow and
orange solids, respectively (Scheme 6). The analogous reaction
with TiCl4(THF)2 gave a complex mixture of products that could
not be separated. The preparation of 11 and 12 involved an
unusual deprotonation of the cyclopentadiene moiety with the
formation of hydrogen chloride. The deprotonation of cyclo-
pentadiene is a well-known procedure, and it normally proceeds
by either acid-base or protonolysis processes; for example, the
reaction of scandium or yttrium tris(alkyl) complexes and
cyclopentadiene gives the corresponding mono(cyclopentadi-
enyl)metal-bis(alkyl) complexes with the elimination of an
alkane.19 Furthermore, there are well-documented processes20
(17) (a) Haumann, T.; Benet-Buchholz, J.; Boese, R. J. Mol. Struct. 1996,
374, 299-304. (b) Liebling, G.; Marsh, R. E. Acta Crystallogr. 1965, 19,
202-208.
(19) (a) Hultzsch, K. C.; Spaniol, T. P.; Okuda, J. Angew. Chem., Int.
Ed. 1999, 38, 227-230. (b) Li, X.; Baldamus, J.; Hou, Z. Angew. Chem.,
Int. Ed. 2005, 44, 962-965.
(18) Higgs, T. C.; Carrano, C. J. Inorg. Chem. 1997, 36, 291-297.

Expanding Heteroscorpionates
Organometallics, Vol. 26, No. 17, 2007 4315
Scheme 7. Synthesis of Alkyl Complexes 13 and 14
in which the transformation of a cyclopentadiene to a cyclo-
pentadienyl moiety is facilitated by the presence of a good
leaving group, such as SiMe3 in the form of SiMe3Cl. However,
the reaction reported here does not correspond to either of the
processes outlined above. A novel and direct one-pot procedure
has recently been published for the synthesis of monocyclo-
pentadienyl titanium trichloride complexes with a side chain
containing a group able to coordinate to the Ti center by reaction
of TiCl4 and several cyclopentadienes.21 Our process represents
the second example of this interesting type of reactivity. As
indicated above,21 the two pyrazole rings of 3a and 3b probably
interact with the metal center (Zr or Hf) in a first step to give
an intermediate in which the subsequent intramolecular reaction
between the MCl4- and -C5H5 moieties may be favored and
lead to the formation of the heteroscorpionate ligand with κ2-
NNη5-Cp coordination to the metal center.
Figure 5. ORTEP view of [ZrCl3(bpzcp)] (6). Ellipsoids are at
the 30% probability level, and hydrogen atoms have been omitted
for clarity.
dinated to three chlorine atoms. This center has a distorted
octahedral environment with a major distortion in the N(1)-
Zr(1)-Cl(1) angle, which has a value of 158.32(9)°. The Zr-
(1)-Cl(1) and Zr(1)-Cl(3) bond distances of 2.479(1) and
2.468(1) Å, respectively, are as one would expect for a Zr
pyrazolyl complex,22 but the elongated Zr(1)-Cl(2) distance
of 2.513(1) Å indicates that the cyclopentadienyl ring exerts a
trans influence. In this complex, in contrast to lithium complexes
1 and 2, the C5H4 ring is symmetrically bonded to the metal
center with Zr-C bond distances of 2.523(4) to 2.572(4) Å.
The structures of complexes 5, 6, and 7 were obtained by
means of full geometry optimizations at a DFT level. Initially
we considered models of the real complexes in which R1 ) R2
) H and then investigated a full model of complex 6 (R1 ) R2
) Ph). The data for complex 6 are collected in Table 2, and
these show that the agreement between computed and X-ray
values is fairly good, although the metal-nitrogen bond
distances are slightly overestimated. The most striking difference
is found in the C(5)-C(6)-C(7) bond angle, which is 109.2°
in the X-ray structure but is computed to be 116.4° in the model
of complex 6. However, when the full structure of complex 6
was considered, i.e., replacing the hydrogen substituents in C(6)
by phenyl groups, the computed value was almost identical to
the experimental one. The origin of this effect is purely
electronic, as stated above, since steric hindrance is not expected
to play any role. Significant differences in the structures are
not observed on going from the Ti to the Zr and Hf complexes
(see data in Table 2), although there is a clear trend in the
metal-nitrogen and metal-chlorine bond lengths Ti < Zr ≈
Hf. As it was found in the lithium complexes, when R1 ) R2 )
H, the shortest distance between the metal (Ti, Zr, or Hf) and
the cyclopentadienyl ligand corresponds to that with the C(5)
carbon atom, in disagreement with the X-ray structure of 6 (see
Table 2). As it was found for complexes 1 and 2, this was the
only metal-carbon bond characterized by the presence of a bond
critical point in the charge density. However, when R1 ) R2 )
Ph, and with the narrowing of the C(5)-C(6)-C(7) angle and
the tilting of the Cp ring, the zirconium atom became more
centered in relation to the Cp ring, and as a consequence, the
The different group 4 metal complexes were characterized
1
spectroscopically. The H and 13C{H} NMR spectra of 5-7
(nonchiral compounds) exhibit a singlet for each of the H4, Me3,
and Me5 pyrazole protons, indicating that the pyrazoles are
equivalent, along with two multiplets for the cyclopentadienyl
protons. These results are consistent with an octahedral disposi-
tion in which a symmetry plane exists (see Scheme 5). The 1H
NMR spectra of complexes 8-12 (chiral compounds) show two
singlets for each of the H4, Me3, and Me5 pyrazole protons and
four multiplets for the Hc, Hd, He, and Hf cyclopentadienyl
protons. These results also are consistent with an octahedral
structural disposition where a κ2-NNη5-Cp coordination for the
scorpionate ligand is also proposed. The assignment of the 13C-
1
{H} NMR signals was made on the basis of H-13C hetero-
nuclear correlation (g-HSQC) experiments. In these asymmetric
complexes we confirmed the presence in solution of the
corresponding two enantiomers by addition of the chiral shift
reagent discussed previously. Complexes 5-12 constitute the
first examples of group 4 metal complexes bearing a hybrid
scorpionate/cyclopentadienyl ligand.
In order to confirm the proposed structure for these com-
plexes, an X-ray crystal structure analysis was carried out on
complex 6 (see Figure 5). Selected bond lengths and angles are
collected in Table 2. The structure consists of a heteroscorpi-
onate ligand bonded to the zirconium atom through the two
nitrogen atoms and the cyclopentadienyl ring in a κ2-NNη5-Cp
coordination mode. In addition, the zirconium center is coor-
(20) (a) Blais, M. S.; Chien, J. C. W.; Rausch, M. D. Organometallics
1998, 17, 3775-3783. (b) Zeijden, A. A. H.; Mattheis, C.; Fro¨hlich, R.
Organometallics 1997, 16, 2651-2658.
(22) Oshiki, T.; Mashima, K.; Kawamura, S.; Tani, K.; Kitaura, K. Bull.
Chem. Soc. Jpn. 2000, 73, 1735-1748.
(21) Zhang, Y.; Mu, Y. Organometallics 2006, 25, 631-634.

4316 Organometallics, Vol. 26, No. 17, 2007
Otero et al.
Table 2. Selected Geometrical Parameters for the X-ray Structure of 6 and for Computed Structures of Models of 5, 6, and 7
6
6
5
7
M ) Zr
R1 ) R2 ) Ph
M ) Zr
R1 ) R2 ) H
M ) Ti
R1 ) R2 ) H
M ) Hf
R1 ) R2 ) H
exp
calc
calc
calc
calc
Bond Lengths
M(1)-N(3)
M(1)-N(1)
M(1)-Cl(3)
M(1)-Cl(1)
M(1)-Cl(2)
M(1)-C(1)
M(1)-C(2)
M(1)-C(3)
M(1)-C(4)
M(1)-C(5)
N(2)-C(7)
N(4)-C(7)
C(5)-C(6)
C(6)-C(7)
C(6)-C(8)
C(6)-C(14)
2.391(4)
2.424(4)
2.468(1)
2.479(1)
2.513(1)
2.529(4)
2.572(4)
2.548(4)
2.523(4)
2.534(4)
1.440(5)
1.465(5)
1.525(6)
1.568(6)
1.550(6)
1.568(6)
2.524
2.530
2.489
2.498
2.508
2.614
2.644
2.636
2.593
2.630
1.458
1.465
1.531
1.591
1.560
1.571
2.576
2.557
2.483
2.492
2.499
2.628
2.682
2.678
2.627
2.603
1.452
1.457
1.499
1.540
2.517
2.528
2.353
2.361
2.380
2.515
2.588
2.580
2.509
2.489
1.451
1.455
1.499
1.536
2.551
2.570
2.480
2.488
2.497
2.627
2.681
2.676
2.625
2.602
1.452
1.457
1.500
1.539
Angles
N(3)-M(1)-N(1)
N(1)-M(1)-Cl(3)
N(3)-M(1)-Cl(1)
Cl(3)-M(1)-Cl(1)
N(3)-M(1)-Cl(2)
N(1)-M(1)-Cl(2)
Cl(3)-M(1)-Cl(2)
Cl(1)-M(1)-Cl(2)
C(5)-C(6)-C(7)
N(2)-C(7)-N(4)
N(2)-C(7)-C(6)
N(4)-C(7)-C(6)
76.0(1)
91.27(9)
92.33(9)
94.70(5)
79.75(9)
78.06(9)
83.42(5)
81.94(4)
109.2(3)
109.3(3)
114.6(3)
112.9(3)
74.1
90.5
93.5
97.9
78.8
78.9
86.3
84.5
110.3
110.9
115.2
113.7
71.0
90.1
94.3
99.3
78.5
78.0
86.2
84.6
116.4
112.4
113.0
113.2
73.7
89.8
92.9
98.0
77.0
76.9
84.8
83.9
115.8
112.6
112.4
112.7
72.1
90.1
94.3
99.3
78.4
77.9
86.2
84.6
116.3
112.2
113.0
113.2
Table 3. Deformation Energy of the Scorpionate Ligand,
Zr-C(1) and Zr-C(4) bonds became the shortest, in accordance
with X-ray values. Indeed, bond critical points corresponding
to the three Zr-C(1), Zr-C(4), and Zr-C(5) bonds where
characterized when the topological analysis of the electronic
charge density function was carried out for the computed
structure of 6. Hence, although simple models were able to
capture the essential features of these scorpionate/cyclopenta-
dienyl compounds, subtle effects such as those arising from
substitution on the fulvene carbon are required to take into
account the whole structure of the complexes.
Several issues regarding the structure and the nature of the
bonding between the scorpionate/cyclopentadienyl ligands and
the lithium and group 4 metal centers are discussed below. The
geometric parameters shown in Tables 1 and 2 for our model
systems indicate that, as one would expect, the metal-carbon
bond distances are slightly shorter in the lithium complex than
the titanium system, although this difference is not large. The
difference is related to the bending angle of the ligand C(1)-
C(6)-C(7) or C(5)-C(6)-C(7) and to the pyramidalization
angle of carbon C(1) or C(5) in the cyclopentadienyl moiety,
which is connected to the bis-pyrazolyl fragment. Indeed, when
the ligand coordinates to the metal, it bends more in the case
of titanium than it does with lithium, as indicated in Table 3,
and at the same time the C(1) or C(5) atom acquires a non-
negligible degree of pyramidalization. Such a deformation in
the ligand structure is not very energetically demanding, as
shown in Table 3. Note that a bond critical point (bcp) in the
charge density16 was characterized between C(1) or C(5) and
the two metal centers Li and Ti. Furthermore, although the bond
distance is longer for titanium, the bond is stronger since the
value of the charge density at the bcp is higher (0.039 e-au-3
for Ti, 0.019 e.au-3 for Li). A Mulliken population analysis
showed a larger charge transfer from the ligand to the metal
moiety in the titanium complex (see Table 3) in comparison to
Energy Decomposition Analysis Terms (∆Eint ) ∆Eelstat
+
∆EPauli + ∆Eorb. see ref 23), Charge Transferred to the
Metallic Moiety (∆q), and Some Geometrical Parameters for
Li(THF)+ and TiCl3 Model Complexes (values in
+
kcal‚mol-1, electrons, and deg, respectively)
Scorp-Li(THF)
Scorp-TiCl3
ligand deformation energy
∆ pyramidalization angle
∆ bending angle
∆EPauli
∆Eelstat
∆Eorb
+2.6
6.5
4.4
+7.0
8.5
7.
162.3
-229.8
-200.3
-267.9
-1.35
26.1
-135.3
-50.3
-159.5
-0.29
∆Eint
∆q
the lithium complex, probably a consequence of the different
nature of the bonding. An energy decomposition analysis
(EDA)23 was performed and showed the different contributions
to the bonding between the heteroscorpionate ligand and the
metal moiety: ∆Eelstat and ∆EPauli account for the pure elec-
trostatic interaction between the unperturbed electron densities
of the isolated fragments and for the repulsion between electron
pairs in the fragments, respectively; ∆Eorb is the energy
associated with charge transfer and polarization of the fragments
to reach the final situation in the molecule. It can be seen from
the values in Table 3 that the Pauli repulsion is much larger
between the titanium fragment and the ligand than in the case
of lithium, as is the electrostatic interaction. Moreover, the sum
of both terms (Pauli + elstat), which accounts for the total
interaction between unperturbed fragments, is more favorable
in the case of lithium (-109.2 kcal‚mol-1) than titanium (-67.5
(23) (a) Morokuma, K. J. Chem. Phys. 1971, 55, 1236-1238. (b) Ziegler,
T.; Rauk, A. Inorg. Chem. 1979, 18, 1558-1565. (c) Ziegler, T.; Rauk, A.
Inorg. Chem. 1979, 18, 1755-1759.

Expanding Heteroscorpionates
Organometallics, Vol. 26, No. 17, 2007 4317
for the monoalkyl zirconium derivative, the difference in
stability for the cis and trans isomers with regard to the
cyclopentadienyl ligand is low. Since the difference in stability
is maximized in the case of titanium, the calculations predict
that in this instance the isolation of one single isomer would be
expected. Although for the Zr and Hf derivatives the difference
in energy between the two isomers is small, the relative stability
is reversed for Hf.
Figure 6. Proposed structures for the three possible diastereoiso-
mers of complex 13.
1
The H and 13C{1H} NMR spectra of the trialkyl complex
14 also contain two resonances for each of the H4, Me3, and
Me5 pyrazole groups. These results are consistent with an
octahedral structural disposition with a κ2-NNη5-Cp scorpionate
coordination with three methyl ligands occupying the other three
coordination positions (see Scheme 7). Further experiments are
in progress aimed at preparing new types of alkyl(aryl)-
containing complexes and studying their reactivity toward
unsaturated molecules such as isocyanides or Lewis acids.
Table 4. Computed Relative Energies (in kcal‚mol-1) for the
Isomers of Alkyl-Containing Ti, Zr, and Hf Compounds
Conclusions
The preparation of lithium derivatives of novel scorpionate/
cyclopentadienyl ligands is described and involves an easy one-
pot synthetic procedure based on the reaction of bis(3,5-
dimethylpyrazol-1-yl)methane with BunLi and fulvenes. However,
the selection of appropriate substituents in the fulvene carbon
atom is critical to enable the stabilization of the resulting lithium
compounds. The potential utility of these ligands as valuable
scaffolds in organometallic/coordination chemistry has been
verified through the preparation of new group 4 metal complexes
in which the ligands behave as tridentate systems with a κ2-
N,N-η5-Cp coordination mode. In addition, the structures of both
lithium and group 4 metal compounds were established on the
basis of full geometry optimizations at a DFT level, and it was
found that they agree very well with those determined by X-ray
crystal structure studies. Furthermore, energy decomposition
analysis (EDA) was carried out in order to evaluate the different
contributions to the bonding between the ligand and the lithium
and titanium moiety in these compounds. The results indicate
that the titanium fragment interacts much more strongly through
donor-acceptor interactions, while the interaction of the lithium
fragment is mainly electrostatic in nature. We also explored the
reactivity of one scorpionate/cyclopentadienyl zirconium com-
plex, and new alkyl complexes were prepared. DFT-based
calculations reproduced the molecular structures of these new
compounds, and they supported the assignment of the isomers
present in solution on the basis of their NMR data. Work is
currently under way to increase the scope of this field.
kcal‚mol-1), and it is mainly dominated by electrostatic interac-
tions. However, when the fragments are allowed to relax, the
titanium moiety interacts more strongly with the ligand because,
as mentioned above, the amount of charge transfer is larger.
Titanium metal d orbitals mix efficiently with ligand electrons,
while the lithium empty shell does not. Therefore, the titanium
fragment interacts much more strongly with the ligand through
donor-acceptor interactions, while the interaction between the
ligand and lithium is mainly electrostatic and has negligible
charge transfer.
Reactivity Studies. Alkyl derivatives of scorpionate-contain-
ing group 4 metal complexes are relatively rare,24 although
several examples of alkyl-containing half-sandwich group 4
metal complexes have been documented.2 We proceeded to
explore the synthesis of alkyl derivatives starting from one of
the scorpionate/cyclopentadienyl group 4 metal complex de-
scribed above. However, the alkylation of [ZrCl3(bpztcp)] (9)
with alkyl magnesium bromide reagents, such as MeMgBr or
EtMgBr, in different molar ratios proved unsuccessful. Fur-
thermore, treatment of 9 with 1 equiv of MeLi gave a complex
mixture of products that could not be separated, but when this
reaction was carried out in a 1:2 or 1:3 molar ratio, the dialkyl
and the trialkyl complexes [ZrClMe2(bpztcp)] (13) and [ZrMe3-
(bpztcp)] (14), respectively, were isolated as white solids in low
yields (25% and 30%, respectively) (see Scheme 7).
1
The H and 13C{1H} NMR spectra of the dialkyl complex
13 show two resonances for each of the H4, Me3, and Me5
pyrazole groups, indicating that in this case the two pyrazole
rings are not equivalent and that in solution only one of the
three possible diastereoisomers is present (see Figure 6). The
response in the 1H NOESY-1D experiment from the cyclopen-
tadienyl protons on irradiating each of the alkyl groups suggests
that this is the isomer in which the alkyl ligands are simulta-
neously in cis and trans positions to the nitrogen atoms of the
pyrazole rings (a in Figure 6). Indeed, the relative stabilities of
isomers a and b for the dialkyl derivatives (see Table 4) fully
confirm the assignment of the NMR data. For the derivatives
of the three metals, the chloride ligand sits trans to the
cyclopentadienyl ring in the most stable isomer. Furthermore,
Experimental Section
All reactions were performed using standard Schlenk-tube
techniques under an atmosphere of dry nitrogen. Solvents were
distilled from appropriate drying agents and degassed before use.
Microanalyses were carried out with a Perkin-Elmer 2400 CHN
analyzer. Mass spectra were recorded on a VG Autospec instrument
using the FAB technique and nitrobenzyl alcohol as matrix. 1H and
13C NMR spectra were recorded on a Varian Inova FT-500
spectrometer and referenced to the residual deuterated solvent. The
NOESY-1D spectra were recorded with the following acquisition
parameters: irradiation time 2 s and number of scans 256, using
standard VARIANT-FT software. Two-dimensional NMR spectra
were acquired using standard VARIANT-FT software and processed
using an IPC-Sun computer.
(24) (a) Milione, S.; Bertolasi, V.; Cuenca, T.; Grassi, A. Organometallics
2005, 24, 4915-4925. (b) Reger, R,; Tarquini, M. E.; Lebioda, L.
Organometallics 1983, 2, 1763-1769. (c) Lee, H.; Jordan, R. F. J. Am.
Chem. Soc. 2005, 127, 9384-9385. (d) Ipaktschi, J.; Sulzbach, W. J.
Organomet. Chem. 1992, 426, 59-70.
The compounds TiCl4(THF)2, ZrCl4, HfCl4, 6,6-diphenylfulvene,
and 6,6-dimethylfulvene were purchased from Aldrich. The com-
pounds 6-tert-butylfulvene,12 6-phenylfulvene,12 and bdmpzm [bd-

4318 Organometallics, Vol. 26, No. 17, 2007
Otero et al.
mpzm ) bis(3,5-dimethylpyrazol-1-yl)methane]11 were prepared
297 K): δ 58.4 (CH2), 149.4, 140.8 (C3 or 5), 106.1 (C4), 12.8 (Me3),
10.4 (Me5), 21.2 (MeCd), 85.7 (MeCd), 98.5 (dCH2), 121.6,
102.5, 104.8 (CCp), 68.5, 26.1 (THF).
as reported previously.
Synthesis of [Li(bpzcp)(THF)] (1). In a 250 cm3 Schlenk tube,
bdmpzm (1.00 g, 4.89 mmol) was dissolved in dry THF (70 cm3)
and cooled to -70 °C. A 1.6 M solution of BunLi (3.06 cm3, 4.89
mmol) in hexane was added, and the suspension was stirred for 1
h. The reaction mixture was warmed to 0 °C, and the resulting
yellow suspension was treated with 6,6-diphenylfulvene (0.75 g,
4.89 mmol), after which the solution was stirred for 10 min. The
solvent was removed to give a volume of 10 cm3, and on addition
of hexane (70 cm3) a white solid was obtained. This solid was
crystallized from a mixture of THF/hexane. Yield: 86%. Anal.
Calcd for C33H37LiN4O: C, 77.32; H, 7.27; N, 10.93. Found: C,
77.43; H, 7.28; N, 10.55. 1H NMR (CD3CN, 297 K): δ 7.20 (s, 1
H, CH), 5.77 (s, 2 H, H4), 2.02 (s, 6 H, Me3), 2.05 (s, 6 H, Me5),
7.43-7.09 (m, 10 H, Ph), 5.68 (m, 2 H, H2Cp), 5.20 (m, 2 H, H3Cp),
3.66 (m, 4 H, THF), 1.86 (m, 4 H, THF). 13C{1H} NMR (CD3CN,
297 K): δ 73.6 (CH), 147.6, 141.1 (C3 or 5), 106.2 (C4), 11.6 (Me3),
13.6 (Me5), 149.9, 131.0, 128.0, 126.4 (Ph), 63.1 (Ca), 113.7 (C1Cp),
Synthesis of [TiCl3(bpzcp)] (5). To a cooled (-70 °C) THF
(50 cm3) solution of TiCl4(THF)2 (0.50 g, 1.49 mmol) was added
an equimolar quantity of [Li(bpzcp)(THF)] (1) (0.76 g, 1.49 mmol).
The solution was stirred for 12 h at low temperature. The solvent
was removed under vacuum and the solid extracted with CH2Cl2.
A red solid was obtained after removal of the solvents. Yield: 90%.
Anal. Calcd for C29H29Cl3N4Ti: C, 59.26; H, 4.97; N, 9.53.
1
Found: C, 59.57; H, 5.08; N, 9.35. H NMR (CDCl3, 293 K): δ
6.99 (s, 1 H, CH), 6.01 (s, 2 H, H4), 2.19 (s, 6 H, Me3), 2.43 (s, 6
H, Me5), 7.35-7.25 (m, 10 H, Ph), 6.99 (m, 2 H, H2,5Cp), 6.08 (m,
2 H, H3,4Cp). 13C{1H} NMR (CDCl3): δ 72.8 (CH), 146.8, 129.2
or
5
(C3 ), 106.3 (C4), 15.8 (Me3), 11.0 (Me5), 149.9-113.1 (Ph), 68.8
(Ca), 111.3 (C1Cp), 122.0 (C2,5Cp), 113.8 (C3,4Cp). MS [FAB (m/z
assignment, % intensity)]: 551 [M - Cl].
Synthesis of [ZrCl3(bpzcp)] (6). The synthetic procedure was
the same as for complex 5, using ZrCl4 (0.50 g, 2.14 mmol) and
[Li(bpzcp)(THF)] (1) (1.09 g, 2.14 mmol), to give 6 as a red solid.
Yield: 93%. Anal. Calcd for C29H29Cl3N4Zr: C, 55.14; H, 4.52;
N, 8.87. Found: C, 55.26; H, 4.66; N, 8.95. 1H NMR (CDCl3, 293
K): δ 7.18 (s, 1 H, CH), 6.01 (s, 2 H, H4), 2.16 (s, 6 H, Me3), 2.68
(s, 6 H, Me5), 7.27-6.88 (m, 10 H, Ph), 7.26 (m, 2 H, H2,5Cp),
5.97 (m, 2 H, H3,4Cp). 13C{1H} NMR (CDCl3): δ 72.9 (CH), 143,9,
7
101.9 (C2Cp), 113.8 (C3Cp), 68.2, 26.2 (THF). Li NMR (CD3CN,
297 K): δ 1.21 (s). MS (m/z assignment, % intensity): 440 [Li-
(bpzcp)], 100.
Synthesis of [Li(bpztcp)(THF)] (2). The synthetic procedure
was the same as for complex 1, using bdmpzm (1.00 g, 4.89 mmol),
a 1.6 M solution of BunLi (3.06 cm3, 4.89 mmol), and 6-tert-
butylfulvene (0.66 g, 4.89 mmol), to give 2 as an orange solid.
Yield: 90%. Anal. Calcd for C25H37LiN4O: C, 72.11; H, 8.89; N,
or
142.9 (C3 5), 110.5 (C4), 17.8 (Me3), 12.4 (Me5), 156.9-128.8
(Ph), 58.6 (Ca), 122.9 (C1Cp), 118.7 (C2,5Cp), 126.2 (C3,4Cp). MS [FAB
1
13.46. Found: C, 72.24; H, 8.91; N, 13.25. H NMR (CD3CN,
(m/z assignment, % intensity)]: 595 [M - Cl].
297 K): δ 6.66 (s, 1 H, CH), 5.85 (s, 1 H, H4), 5.84 (s, 1 H, H4′),
2.15 (s, 3 H, Me3), 2.07 (s, 3 H, Me3′), 2.44 (s, 6 H, Me5,5′), 2.95
(s, 1H, CHa), 1.05 [s, 9 H, C(CH3)3], 4.95 (m, 1 H, H2Cp), 5.50 (m,
1 H, H3Cp), 5.70 (m, 1 H, H4Cp), 5.58 (m, 1 H, H5Cp), 3.68 (m, 4 H,
THF), 1.84 (m, 4 H, THF). 13C{1H} NMR (CD3CN, 297 K): δ
66.8 (CH), 147.2, 147.1, 140.3, 138.2 (C3,3′ or 5,5′), 106.0 (C4), 105.6
(C4′), 13.3 (Me3), 13.2 (Me3′), 12.0, 11.2 (Me5,5′), 60.6 (Ca), 35.4
[C(CH3)3], 29.6 [C(CH3)3], 107.5 (C1Cp), 112.5 (C2Cp), 107.1 (C3Cp),
Synthesis of [HfCl3(bpzcp)] (7). The synthetic procedure was
the same as for complex 5, using HfCl4 (0.50 g, 1.56 mmol) and
[Li(bpzcp)(THF)] (1) (0.80 g, 1.56 mmol), to give 7 as a red solid.
Yield: 90%. Anal. Calcd for C29H29Cl3HfN4: C, 48.48; H, 4.07;
N, 7.80. Found: C, 48.58; H, 4.23; N, 7.75. 1H NMR (CDCl3, 293
K): δ 6.23 (s, 1 H, CH), 6.01 (s, 2 H, H4), 2.18 (s, 6 H, Me3), 2.59
(s, 6 H, Me5), 7.35-7.24 (m, 10 H, Ph), 6.90 (m, 2 H, H2,5Cp),
5.80 (m, 2 H, H3,4Cp). 13C{1H} NMR (CDCl3): δ 73.1 (CH), 145.8,
7
104.0 (C4Cp), 100.9 (C5Cp), 68.2, 26.1 (THF). Li NMR (CD3CN,
or
129.9 (C3 5), 106.4 (C4), 13.8 (Me3), 11.2 (Me5), 130.9-112.9
297 K): δ 1.35 (s). MS (m/z assignment, % intensity): 416 [Li-
(bpztcp)(THF)], 100.
(Ph), 68.9 (Ca), 112.3 (C1Cp), 123.9 (C2,5Cp), 121.2 (C3,4Cp). MS [FAB
(m/z assignment, % intensity)]: 682 [M - Cl].
Synthesis of a Mixture of Isomers 3a and 3b (bpzpcpH). The
synthetic procedure was the same as for complex 1, using bdmpzm
(1.00 g, 4.89 mmol), a 1.6 M solution of BunLi (3.06 cm3, 4.89
mmol), and 6-phenylfulvene (0.75 g, 4.89 mmol), to give 3 as a
white solid. Yield: 81%. Anal. Calcd for C23H26N4: C, 77.06; H,
7.31; N, 15.63. Found: C, 77.11; H, 7.45; N, 15.25. 1H NMR (CD3-
Synthesis of [TiCl3(bpztcp)] (8). The synthetic procedure was
the same as for complex 5, using TiCl4(THF)2 (0.50 g, 1.49 mmol)
and [Li(bpztcp)(THF)] (2) (0.62 g, 1.49 mmol), to give 8 as an
orange solid. Yield: 95%. Anal. Calcd for C21H29Cl3N4Ti: C, 51.30;
1
H, 5.94; N, 11.39. Found: C, 51.65; H, 6.02; N, 11.11. H NMR
(CDCl3, 293 K): δ 6.63 (s, 1 H, CH), 5.77 (s, 1 H, H4′), 5.48 (s,
1 H, H4), 2.21 (s, 3 H, Me3′), 2.08 (s, 3 H, Me3), 2.47 (s, 3 H,
Me5′), 2.31 (s, 3 H, Me5), 2.76 (s, 1H, CHa), 0.80 [s, 9 H, C(CH3)3],
6.39 (m, 1 H, H5Cp), 6.28 (m, 1 H, H2Cp), 6.14 (m, 2 H, H3,4Cp).
13C{1H} NMR (CDCl3, 297 K): δ 72.1 (CH), 147.1, 145.8, 138.3,
138.2 (C3,3′ or 5,5′), 106.9 (C4), 105.2 (C4′), 13.9 (Me3′), 13.6 (Me3),
12.1, 11.9 (Me5,5′), 51.5 (Ca), 34.8 [C(CH3)3], 28.7 [C(CH3)3], 104.5
(C1Cp), 128.1 (C2Cp), 125.5 (C5Cp), 107.2, 105.1 (C3,4Cp). MS [FAB
(m/z assignment, % intensity)]: 455 [M - Cl].
CN, 297 K): δ 6.73 (d, JHH ) 8.8 Hz, 1 H, CH), 6.70 (d, JHH
)
8.8 Hz, 1 H, CH), 5.75 (s, 1 H, H4), 5.73 (s, 1 H, H4), 5.52 (s, 2 H,
H4), 2.41 (s, 3 H, Me3), 2.40 (s, 3 H, Me3), 2.19 (s, 3 H, Me3),
2.18 (s, 3 H, Me3), 2.11 (s, 3 H, Me5), 2.10 (s, 3 H, Me5), 2.04 (s,
3 H, Me5), 2.03 (s, 3 H, Me5), 5.73 (s, 1H, CHa), 5.54 (s, 1H, CHa),
7.33-7.15 (m, 10 H, Ph), 6.40-6.00 (m, 6 H, CH-Cp), 2.82 (br s,
2 H, CH2-Cp), 2.75 (br s, 2 H, CH2-Cp). 13C{1H} NMR (CD3CN,
297 K): δ 73.7, 73.5 (CH), 148.9, 148.7, 147.9, 146.4, 141.2, 140.9,
or
140.5, 140.2 (C3 5), 107.0, 106.9, 106.2 (C4), 13.6, 13.5, 13.4,
(Me3), 11.7, 11.3 (Me5), 128.7-127.0 (Ph), 50.5, 50.1 (Ca), 128.9,
127.6 (C-Cp), 134.6, 134.3, 127.8, 127.6 (CH-Cp), 43.6, 42.1 (CH2-
Cp).
Synthesis of [ZrCl3(bpztcp)] (9). The synthetic procedure was
the same as for complex 5, using ZrCl4 (0.50 g, 2.14 mmol) and
[Li(bpztcp)(THF)] (2) (0.89 g, 2.14 mmol), to give 9 as a pale
orange solid. Yield: 85%. Anal. Calcd for C21H29Cl3N4Zr: C,
47.14; H, 5.46; N, 10.47. Found: C, 47.23; H, 5.61; N, 10.21. 1H
NMR (CDCl3, 293 K): δ 6.76 (s, 1 H, CH), 6.07 (s, 1 H, H4′),
5.98 (s, 1 H, H4), 2.65 (s, 3 H, Me3′), 2.64 (s, 3 H, Me3), 2.59 (s,
3 H, Me5′), 2.45 (s, 3 H, Me5), 2.83 (s, 1H, CHa), 1.05 [s, 9 H,
C(CH3)3], 7.32 (m, 1 H, H4Cp), 7.06 (m, 1 H, H3Cp), 5.90 (m, 1 H,
H2Cp), 5.85 (m, 1 H, H5Cp). 13C{1H} NMR (CDCl3, 297 K): δ 65.5
Synthesis of [Li(isoprcp)]‚bdmpzm‚THF (4). The synthetic
procedure was the same as for complex 1, using bdmpzm (1.00 g,
4.89 mmol), a 1.6 M solution of BunLi (3.06 cm3, 4.89 mmol),
and 6,6-dimethylfulvene (0.52 g, 4.89 mmol), to give 4 as a white
solid. Yield: 87%. Anal. Calcd for C23H33LiN4O: C, 71.11; H,
8.56; N, 14.42. Found: C, 71.43; H, 8.74; N, 14.19. 1H NMR (CD3-
CN, 297 K): δ 5.96 (s, 2 H, CH2), 5.87 (s, 2 H, H4), 2.13 (s, 6 H,
Me3), 2.43 (s, 6 H, Me5), 2.01 (s, 3H, MeCd), 4.81, 4.31 (two
singlets, 1H, 1H, dCH2), 5.76 (m, 2 H, HCp), 5.51 (m, 2 H, HCp),
3.68 (m, 4 H, THF), 1.84 (m, 4 H, THF). 13C{1H} NMR (CD3CN,
or
(CH), 155.2, 154.9, 141.9, 138.9 (C3,3′ 5,5′), 110.3 (C4′), 109.3
(C4), 17.4 (Me3), 17.2 (Me3′), 12.7 (Me5′), 11.8 (Me5), 55.7 (Ca),
34.8 [C(CH3)3], 28.3 [C(CH3)3], 119.2 (C1Cp), 130.7 (C4Cp), 124.2

Expanding Heteroscorpionates
Organometallics, Vol. 26, No. 17, 2007 4319
(C3Cp), 118.5 (C2Cp), 112.6 (C5Cp). MS [FAB (m/z assignment, %
intensity)]: 500 [M - Cl].
56.8 (Ca), 35.2 [C(CH3)3], 28.7 [C(CH3)3], 116.7 (C1Cp), 129.3
(C3Cp), 125.5 (C4Cp), 116.8 (C2Cp), 111.8 (C5Cp), 28.4, 28.3 (Me′,
Me).
Synthesis of [HfCl3(bpztcp)] (10). The synthetic procedure was
the same as for complex 5, using HfCl4 (0.50 g, 1.56 mmol) and
[Li(bpztcp)(THF)] (2) (0.65 g, 1.56 mmol), to give 10 as a pale
orange solid. Yield: 90%. Anal. Calcd for C21H29Cl3Hf N4: C,
Synthesis of [ZrMe3(bpztcp)] (14). The synthetic procedure was
the same as for complex 23, using [ZrCl3(bpztcp)] (9) (0.50 g, 0.94
mmol) and MeLi (1.76 cm3, 2.82 mmol) to give 24 as a pale yellow
solid. Yield: 29%. Anal. Calcd for C24H38N4Zr: C, 60.84; H, 8.08;
1
40.53; H, 4.70; N, 9.00. Found: C, 40.61; H, 4.87; N, 8.96. H
NMR (CDCl3, 293 K): δ 6.67 (s, 1 H, CH), 6.01 (s, 1 H, H4′),
5.92 (s, 1 H, H4), 2.64 (s, 3 H, Me3′), 2.62 (s, 3 H, Me3), 2.50 (s,
3 H, Me5′), 2.35 (s, 3 H, Me5), 2.72 (s, 1H, CHa), 0.98 [s, 9 H,
C(CH3)3], 7.11 (m, 1 H, H4Cp), 6.86 (m, 1 H, H3Cp), 5.67 (m, 1 H,
H2Cp), 5.62 (m, 1 H, H5Cp). 13C{1H} NMR (CDCl3, 297 K): δ 66.0
1
N, 11.82. Found: C, 60.91; H, 8.21; N, 11.58. H NMR (CDCl3,
293 K): δ 6.59 (s, 1 H, CH), 5.92 (s, 1 H, H4), 5.86 (s, 1 H, H4′),
2.38 (s, 3 H, Me5), 2.35 (s, 3 H, Me5′), 2.34 (s, 3 H, Me3), 2.29 (s,
3 H, Me3′), 2.59 (CHa), 0.98 [s, 9 H, C(CH3)3], 6.65 (m, 1 H, H4Cp),
6.30 (m, 1 H, H5Cp), 5.60 (m, 1 H, H3Cp), 5.32 (m, 1 H, H2Cp),
0.46, 0.20, 0.14 (s, 9 H, 3 Me-Zr). 13C{1H} NMR (CDCl3): δ
65.1 (CH), 153.1, 153.0, 140.5, 138.0 (C3,3′ or 5,5′), 109.7 (C4),
108.5 (C4′), 16.6, 16.4 (Me3, 3′), 15.7 (Me5′), 14.3 (Me5), 56.8 (Ca),
35.3 [C(CH3)3], 25.8 [C(CH3)3], 114.9 (C1Cp), 121.7 (C3Cp), 119.9
(C4Cp), 115.7 (C2Cp), 111.8 (C5Cp), 46.9 (Me-Zr).
or
(CH), 155.6, 155.4, 141.4, 138.3 (C3,3′ 5,5′), 110.6 (C4′), 109.6
(C4), 17.8 (Me3), 17.6 (Me3′), 12.7 (Me5), 11.7 (Me5′), 55.8 (Ca),
34.9 [C(CH3)3], 28.3 [C(CH3)3], 115.8 (C1Cp), 129.0 (C4Cp), 122.4
(C3Cp), 116.3 (C2Cp), 110.1 (C5Cp). MS [FAB (m/z assignment, %
intensity)]: 587 [M - Cl].
Synthesis of [ZrCl3(bpzpcp)] (11). To a THF (50 cm3) solution
of ZrCl4 (0.50 g, 2.14 mmol) was added an equimolar quantity of
the mixture of 3a and 3b (0.76 g, 2.14 mmol). The reaction mixture
was heated under reflux and stirred for 12 h. The solvent was
removed under vacuum, and the solid was washed with THF (20
cm3) and hexane (50 cm3) to yield 11 as a pale yellow solid.
Yield: 75%. Anal. Calcd for C23H25Cl3N4Zr: C, 49.77; H, 4.54;
X-ray Crystallography. Suitable crystals of compounds 1, 2,
3b, and 6 were mounted in glass capillaries and sealed under
nitrogen. Crystallographic data are listed in Table 5. For 1 data
were collected on a Nonius-Mach3 diffractometer using Mo KR
radiation (graphite monochromator, λ ) 0.71073 Å) with an ω/2θ
scan technique to a maximum value of 56°. The intensities were
corrected in the usual fashion for Lorentz and polarization effects
and empirical absorption correction was carried out on the basis of
an azimuthal scan.25
1
N, 10.09. Found: C, 49.83; H, 4.68; N, 10.06. H NMR (CDCl3,
293 K): δ 6.49 (s, 1 H, CH), 6.09 (s, 1 H, H4′), 6.06 (s, 1 H, H4),
2.78 (s, 3 H, Me3′), 2.71 (s, 3 H, Me3), 2.51 (s, 3 H, Me5′), 1.91 (s,
3 H, Me5), 4.62 (s, 1H, CHa), 7.18-7.37 (m, 5 H, Ph), 7.36 (m, 1
H, H4Cp), 6.92 (m, 1 H, H3Cp), 6.08 (m, 1 H, H2Cp), 5.89 (m, 1 H,
H5Cp). 13C{1H} NMR (CDCl3, 297 K): δ 69.5 (CH), 155.5, 154.9,
142.3, 136.8 (C3,3′ or 5,5′), 109.8 (C4′), 109.7 (C4), 17.3 (Me3), 17.1
(Me3′), 12.0 (Me5′), 11.4 (Me5), 50.8 (Ca), 130.1-127.5 (Ph), 119.0
(C1Cp), 129.6 (C4Cp), 128.2 (C3Cp), 116.3 (C5Cp), 113.5 (C2Cp). MS
[FAB (m/z assignment, % intensity)]: 520 [M - Cl].
For 2, 3b, and 6, data were collected on a Bruker SMART CCD-
based diffractometer operating at 50 kV and 30 mA using 0.3° wide
ω scans with a crystal-to-detector distance of 5.0 cm. The substantial
redundancy in data allows empirical absorption corrections (SAD-
ABS26) to be applied using multiple measurements of symmetry-
equivalent reflections. The unit cell parameters were calculated and
refined from the full data set. The raw intensity data frames were
integrated with the SAINT27 program, which also applied correc-
tions for Lorentz and polarization effects.
Synthesis of [HfCl3(bpzpcp)] (12). The synthetic procedure was
the same as for complex 11, using HfCl4 (0.50 g, 1.56 mmol) and
the mixture of 3a and 3b (0.55 g, 1.56 mmol), to give 12 as an
orange solid. Yield: 80%. Anal. Calcd for C23H25Cl3HfN4: C,
For 1, 2, 3b, and 6 the structures were solved by direct methods
(SHELXS-9728a), completed with difference Fourier syntheses, and
refined with full-matrix least-squares using SHELXL-9728b mini-
1
43.01; H, 3.92; N, 8.72. Found: C, 43.21; H, 3.98; N, 8.65. H
mizing w(Fo - Fc2)2. Weighted R factors (Rw) and all goodness
2
NMR (CDCl3, 293 K): δ 6.35 (s, 1 H, CH), 6.10 (s, 1 H, H4′),
6.08 (s, 1 H, H4), 2.81 (s, 3 H, Me3′), 2.75 (s, 3 H, Me3), 2.47 (s,
3 H, Me5′), 1.89 (s, 3 H, Me5), 4.58 (s, 1H, CHa), 7.18-7.37 (m,
5 H, Ph), 7.37 (m, 1 H, H4Cp), 6.98 (m, 1 H, H3Cp), 5.98 (m, 1 H,
H2Cp), 5.78 (m, 1 H, H5Cp). 13C{1H} NMR (CDCl3, 297 K): δ 68.2
of fit S are based on F2; conventional R factors (R) are based on
F. All non-hydrogen atoms were refined with anisotropic displace-
ment parameters. All scattering factors and anomalous dispersions
factors are contained in the SHELXTL 6.1029 program library.
The hydrogen atom positions were calculated geometrically and
were allowed to ride on their parent carbon atoms with fixed
isotropic U.
or
(CH), 154.5, 152.6, 141.4, 135.8 (C3,3′ 5,5′), 107.8 (C4′), 106.7
(C4), 15.3 (Me3), 14.9 (Me3′), 12.8 (Me5′), 11.9 (Me5), 58.3 (Ca),
130.1-127.5 (Ph), 115.8 (C1Cp), 132.6 (C4Cp), 127.3 (C3Cp), 113.2
(C5Cp), 112.7 (C2Cp). MS [FAB (m/z assignment, % intensity)]: 607
[M - Cl].
Computational Details. All DFT calculations were carried out
using the Amsterdam Density Functional (ADF2005.01) program
developed by Baerends et al.30 The numerical integration scheme
Synthesis of [ZrClMe2(bpztcp)] (13). To a cooled (-20 °C)
solution of [ZrCl3(bpztcp)] (9) (0.50 g, 0.94 mmol) in dry THF
(20 cm3) was added dropwise a 1.6 M solution of MeLi in diethyl
ether (1.17 cm3, 1.88 mmol). The reaction mixture was stirred for
15 min at low temperature. The solvent was removed under vacuum,
and the solid was extracted with toluene. The volatiles were
removed under vacuum to give a pale orange solid, which was
washed with hexane (2 × 10 cm3) to afford 23 as a pale yellow
solid. Yield: 25%. Anal. Calcd for C23H35ClN4Zr: C, 55.89; H,
(25) North, A. C. T.; Phillips, D. C.; Mathews, F. S. Acta Crystallogr.
A 1968, 351-358.
(26) Sheldrick, G. M. SADABS version 2.03, a Program for Empirical
Absorption Correction; Universita¨t Go¨ttingen, 1997-2001.
(27) SAINT+ NT ver. 6.04, SAX Area-Detector Integration Program;
Bruker AXS: Madison, WI, 1997-2001.
(28) (a) Sheldrick, G. M. SHELXS-97, Programs for Crystal Structure
Analysis (Release 97-2); Institu¨t fu¨r Anorganische Chemie der Universi-
ta¨t: Go¨ttingen, Germany, 1997. (b) Sheldrick, G. M. SHELXL-97, Programs
for Crystal Structure Analysis (Release 97-2); Institu¨t fu¨r Anorganische
Chemie der Universita¨t: Go¨ttingen, Germany, 1997.
(29) Bruker AXS. SHELXTL version 6.10, Structure Determination
Package; Bruker AXS: Madison, WI, 2000.
(30) (a) Baerends, E. J.; Ellis, D. E.; Ros, P. Chem. Phys. 1973, 2, 41-
51. (b) Baerends, E. J.; Ros, P. Chem. Phys. 1973, 2, 52-59. (c) Baerends,
E. J.; et al. ADF2004.01; SCM, Theoretical Chemistry, Vrije Universiteit:
Amsterdam, The Netherlands, 2004; http://www.scm.com. (d) Guerra, C.
F.; Snijders, J. G.; te Velde, G.; Baerends, E. J. Theor. Chem. Acc. 1998,
99, 391-403.
1
7.14; N, 11.34. Found: C, 55.99; H, 7.40; N, 11.10. H NMR
(CDCl3, 293 K): δ 6.55 (s, 1 H, CH), 5.93 (s, 1 H, H4), 5.86 (s, 1
H, H4′), 2.49 (s, 3 H, Me3′), 2.45 (s, 3 H, Me3), 2.48 (s, 3 H, Me5),
2.35 (s, 3 H, Me5′), 2.80 (CHa), 1.03 [s, 9 H, C(CH3)3], 6.90 (m, 1
H, H4Cp), 6.58 (m, 1 H, H5Cp), 5.77 (m, 1 H, H3Cp), 5.74 (m, 1 H,
H2Cp), 0.50 (s, 3 H, Me), 0.45 (s, 3 H, Me′). 13C{1H} NMR
(CDCl3): δ 65.5 (CH), 154.4, 153.1, 140.6, 138.1 (C3,3′ or 5,5′),
109.7 (C4), 108.8 (C4′), 16.7, 16.5 (Me3, 3′), 12.7, (Me5′), 11.8, (Me5),

4320 Organometallics, Vol. 26, No. 17, 2007
Table 5. Crystal Data and Structure Refinement for 1, 2, 3b, and 6
Otero et al.
1
2
3b
6
empirical formula
fw
C33H37LiN4O
512.61
C25H37LiN4O
416.53
C23H26N4
358.48
C29H29Cl3N4Zr‚2THF
775.34
temp (K)
250(2)
173(2)
100(2)
173(2)
wavelength (Å)
cryst syst, space group
a (Å)
b (Å)
c (Å)
0.71073
0.71073
monoclinic P2(1)/n
8.980(1)
15.405(2)
17.817(3)
0.71073
triclinic P
8.933(1)
9.630(1)
0.71073
monoclinic P2(1)/n
12.222(1)
23.628(2)
12.889(1)
monoclinic P2(1)/a
16.576(3)
11.509(4)
17.059(2)
12.151(2)
R (deg)
106.294(3)
96.654(3)
94.664(3)
994.5(9)
2, 1.203
â (deg)
115.36(2)
98.094(3)
100.935(2)
ø (deg)
volume (A3)
Z, calcd density (g/cm3)
2941(12)
4, 1.158
0.70
1096
2440.1(6)
4, 1.134
0.69
904
3654.6(6)
4, 1.409
5.58
1608
absorp coeff (cm-1
F(000)
)
0.73
384
cryst size (mm)
θ range for data collection
limiting indices
0.30 × 0.20 × 0.20
2.21 to 25.00
-19 e h e 17
0 e k e 13
0 e l e 20
0.24 × 0.22 × 0.16
1.76 to 26.39
-11 e h e 11
-19 e k e 19
-22 e l e 15
10 415/4995
[R(int) ) 0.0600]
4995/0/280
1.025
0.23 × 0.18 × 0.17
1.76 to 28.31
-11 e h e 11
-12 e k e 12
-16 e l e 16
13 538/4883
[R(int) ) 0.0513]
4883/0/248
1.058
0.34 × 0.15 × 0.13
1.72 to 26.39
-15 e h e 14
-21 e k e 29
-13 e l e 16
20 933/7472
[R(int) ) 0.0454]
7472/0/399
1.038
no. of reflns collected/unique
5290/5107
[R(int) ) 0.0805]
5107/0/352
0.902
no. of data/restraints/params
goodness-of-fit on F2
final R indices [I > 2σ(I)]
R1 ) 0.0745
wR2 ) 0.1333
R1 ) 0.3313
wR2 ) 0.1996
0.231 and -0.199
R1 ) 0.0647
wR2 ) 0.1574
R1 ) 0.1421
wR2 ) 0.1894
0.476 and -0.265
R1 ) 0.0754
wR2 ) 0.1918
R1 ) 0.1344
wR2 ) 0.2199
1.034 and -0.335
R1 ) 0.0538
wR2 ) 0.1530
R1 ) 0.0837
wR2 ) 0.1716
1.430 and -0.553
R indices (all data)
largest diff peak and hole (e‚Å-3
)
applied for the calculations was developed by te Velde et al.31 The
geometry optimization procedure was based on the method reported
by Versluis and Ziegler.32 The BP86 functional described as a
combination between local VWN exchange-correlation potential
with nonlocal Becke’s exchange correction33 and Perdew’s cor-
relation correction was used.34 Relativistic corrections were intro-
duced by scalar-relativistic zero-order regular approximation (ZO-
RA).35 A triple-ê plus two polarization basis set was used for Ti,
Zr, and Hf atoms and a plus one polarization function for the other
atoms. For non-hydrogen and non-lithium atoms a relativistic
frozen-core potential was used, including 2p for Ti, 3d for Zr, 4d
for Hf, 2p for chlorine, and 1s for carbon and oxygen. A numerical
integration parameter of 4.5 was employed in optimization and
single-point calculations. Geometry convergence criteria were raised
1 order of magnitude to 10-3 hartree‚Å-1. Symmetry constraints
were not used. The topological analysis of the electron density
function was carried out using the Xaim program package.36
Acknowledgment. We gratefully acknowledge financial
support from the Ministerio de Educacio´n y Ciencia (MEC),
Spain (Grant Nos. CTQ2005-08123-CO2-01/BQU, BQU2002-
04110-C02-02, and CSD2006-0003) and the Junta de Comu-
nidades de Castilla-La Mancha (Grant Nos. PAC-02-003, GC-
02-010, and PAI-02-016). We are also indebted to the Generalitat
de Catalunya (SGR01-00315) and to the ICIQ Foundation for
financial support. M.U. thanks the Torres Quevedo program of
the Ministerio de Educacio´n y Ciencia, Spain.
(31) (a) Boerrigter, P. M.; te Velde, G.; Baerends, E. J. Int. J. Quantum
Chem. 1988, 33, 87-113. (b) te Velde, G.; Baerends, E. J. J. Comput. Chem.
1992, 99, 84-98.
Supporting Information Available: Details of data collection,
refinement, atom coordinates, anisotropic displacement parameters,
and bond lengths and angles for complexes 1, 2, 3b, and 6. This
materialisavailablefreeofchargeviatheInternetathttp://pubs.acs.org.
(32) Versluis, L.; Ziegler, T. J. Chem. Phys. 1988, 88, 322-328.
(33) Becke, A. D. Phys. ReV. A 1988, 38, 3098-3100.
(34) (a) Perdew, J. P. Phys. ReV. B 1986, 34, 7406-7406. (b) Perdew,
J. P. Phys. ReV. B 1986, 33, 8822-8824.
(35) (a) van Lenthe, E.; Baerends, E. J.; Snijders, J. G. J. Chem. Phys.
1993, 99, 4597-4610. (b) van Lenthe, E.; Baerends, E. J.; Snijders, J. G.
J. Chem. Phys. 1994, 101, 9783-9792. (c) van Lenthe E.; Ehlers, A.;
Baerends, E. J. J. Chem. Phys. 1999, 110, 8943-8953.
OM7003942
(36) Ortiz Alba, J. C.; Bo, C. Xaim-1.0; Universitat Rovira I Virgili:
Tarragona, Spain; http://www.quimica.urv.es/XAIM.