Versatile scorpionates and new developments in the denticity changes of NNCp hybrid scorpionate/cyclopentadienyl ligands in Sc and Y compounds: From κ1-Nη5-Cp to κ2- NNη5-Cp

Article abstract of DOI:10.1021/ic800267v

Reaction of hybrid scorpionate/cyclopentadienyl ligands in the form of the lithium derivatives [Li(bpzcp)(THF)] [bpzcp = 2,2-bis(3,5-dimethylpyrazol-1-yl)- 1,1-diphenylethylcyclopentadienyl], [Li(bpztcp)(THF)] [bpztcp = 2,2-bis(3,5-dimethylpyrazol-1-yl)-1

Full text of DOI:10.1021/ic800267v

Inorg. Chem. 2008, 47, 4996-5005
Versatile Scorpionates and New Developments in the Denticity Changes
of NNCp Hybrid Scorpionate/Cyclopentadienyl Ligands in Sc and Y
1
2
Compounds: From K -Nη5-Cp to K -NNη5-Cp
Antonio Otero,*,† Juan Ferna´ndez-Baeza,*,† Agust´ın Lara-Sa´nchez,*,† Antonio Antin˜olo,† Juan Tejeda,†
Emilia Mart´ınez-Caballero,† Isabel Ma´rquez-Segovia,† Isabel Lo´pez-Solera,† Luis F. Sa´nchez-Barba,‡
and Carlos Alonso-Moreno†
Departamento de Qu´ımica Inorga´nica, Orga´nica y Bioqu´ımica, UniVersidad de Castilla-La
Mancha, 13071 Ciudad Real, Spain, and Departamento de Qu´ımica Inorga´nica y Anal´ıtica,
UniVersidad Rey Juan Carlos, 28933 Mo´stoles, Madrid, Spain
Received February 12, 2008
Reaction of hybrid scorpionate/cyclopentadienyl ligands in the form of the lithium derivatives [Li(bpzcp)(THF)] [bpzcp
) 2,2-bis(3,5-dimethylpyrazol-1-yl)-1,1-diphenylethylcyclopentadienyl], [Li(bpztcp)(THF)] [bpztcp ) 2,2-bis(3,5-
dimethylpyrazol-1-yl)-1-tert-butylethylcyclopentadienyl], and the in situ-generated “Li(bpzpcp)” [bpzpcp ) 2,2-bis(3,5-
dimethylpyrazol-1-yl)-1-phenylethylcyclopentadienyl] with MCl3(THF)3 afforded the group 3 halide compounds
[MCl2(bpzcp)(THF)] (M ) Sc, 1; Y, 2), [MCl2(bpztcp)(THF)] (M ) Sc, 3; Y, 4), and [MCl2(bpzpcp)(THF)] (M ) Sc,
5; Y, 6). The H2O adduct of 4, [YCl2(bpztcp)(H2O)] (7), was formed when a solution of 4 was allowed to stand at
room temperature in the presence of moisture. Complexes 1-7 adopt a pseudo-octahedral structure with
5
heteroscorpionate ligands κ2-NNη -Cp coordinated to the metal through the cyclopentadienyl group and two imino
nitrogens of pyrazole rings. The alkyl heteroscorpionate scandium and yttrium complexes recently reported by our
group, [M(CH2SiMe3)2(bpzcp)], react with 2,6-dimethylphenol and 3,5-dimethylphenol to give the bis(aryloxide)
derivatives [M(OAr)2(bpzcp)] (M ) Sc, OAr ) 2,6-dimethylphenoxide, 8; M ) Y, OAr ) 2,6-dimethylphenoxide,
9; M ) Y, OAr ) 3,5-dimethylphenoxide, 10). Complex 9 underwent an interesting hydrolysis process to give the
1
tetranuclear complex [{Y(bpzcp)}(µ-OH)2(µ3-OH){Y(OAr)2}]2 (11). Variable-temperature H NMR experiments on 9
and 10 revealed a rapid fluxional exchange between coordinated and noncoordinated pyrazolyl rings, producing
5
interconversion between the two enantiomers in which the scorpionate ligand can be coordinated in a κ1-Nη -Cp
form. The structures of the complexes were determined by spectroscopic methods and the X-ray crystal structures
of 2, 7, and 11 were also established. Complexes 1 and 2 are active olefin polymerization catalysts after activation
with methylaluminoxane. These compounds gave atactic polystyrenes with narrow molecular weight distribution
(Mn/Mw 1.26-1.91) and with low molecular weights.
Introduction
is well established,2 there has been increasing interest in
recent years in the respective chemistry employing noncy-
clopentadienyl ligands.3 In this context, scorpionate ligands
such as poly(pyrazolyl)borates are also attractive ancillary
ligands for the synthesis of complexes of these metals.4
Related with the tris(pyrazolyl)borates, in this important field
of ligand design we and others have reported the synthesis
Group 3 and lanthanide complexes have been extensively
employed as catalysts for the polymerization of olefins.1
While the chemistry of cyclopentadienyl-based complexes
* To whom correspondence should be addressed. E-mail: Antonio.Otero@
uclm.es (A.O.), Juan.FBaeza@uclm.es (J.F.-B.), Agustin.Lara@uclm.es
(A.L.-S.). Tel.: +34926295300. Fax: +34926295318.
†
Universidad de Castilla-La Mancha.
Universidad Rey Juan Carlos.
(2) (a) Ballard, D. G. H.; Coutis, A.; Holton, J.; McMeeking, J.; Pearce,
R. J. Chem. Soc., Chem. Commun. 1978, 994. (b) Burger, B. J.;
Thompson, M. E.; Cotter, W. D.; Bercaw, J. E. J. Am. Chem. Soc.
1990, 112, 1566. (c) Hou, Z.; Zhang, Y.; Nishiura, M.; Wakatsuki,
Y. Organometallics 2003, 22, 129. (d) Li, X.; Hou, Z. Macromolecules
2005, 38, 6767.
‡
(1) (a) Gromada, J.; Carpentier, J.-F.; Mortroux, A. Coord. Chem. ReV.
2004, 248, 397. (b) Arndt, S.; Okuda, J. AdV. Synth. Catal. 2005, 347,
339. (c) Zeimentz, P. M.; Arndt, S.; Elvidge, B. R.; Okuda, J. Chem.
ReV. 2006, 106, 2404.
4996 Inorganic Chemistry, Vol. 47, No. 11, 2008
10.1021/ic800267v CCC: $40.75  2008 American Chemical Society
Published on Web 04/30/2008

Versatile NNCp Scorpionate Ligands in Sc and Y Compounds
Chart 1. Hybrid Scorpionate/Cyclopentadienyl Ligands and Their
of new “heteroscorpionate” ligands based on bis(pyrazol-1-
yl)methane that contain two pyrazole rings and different
anionic “arms”.5
Possible Coordination Modes
Bearing in mind the development of donor-functionalized
cyclopentadienyl ligands6 and the emerging importance of
the heteroscorpionate ligands, a new class of heteroscorpi-
onate, namely, a family of hybrid scorpionate/cyclopenta-
dienyl, ligands have been reported (Chart 1a) by us.7 Mixed
pyrazole/cyclopentadienyl ligands have also been described
by other authors.8 The easy preparation of heteroscorpionate
ligands bearing a cyclopentadienyl anionic arm led us to
develop and fully explore the potential offered by this type
of ligand. Thus, it was found that the hybrid scorpionate/
cyclopentadienyl ligands 2,2-bis(3,5-dimethylpyrazol-1-yl)-
1,1-diphenylethylcyclopentadienyl (bpzcp), 2,2-bis(3,5-
dimethylpyrazol-1-yl)-1-tert-butylethylcyclopentadienyl(bpztcp),
and 2,2-bis(3,5-dimethylpyrazol-1-yl)-1-phenylethylcyclo-
pentadienyl (bpzpcp) bind in a facial, tripodal fashion that
is κ2-NNη5-Cp in lithium complexes (for the two first ligands)
and in group 4 transition-metal complexes (see Chart 1b).7
However, we recently reported new dialkylscandium and
-yttrium complexes that display an unprecedented κ1-Nη5-
Cp bonding mode (see Chart 1c) with these ligands,9
although these complexes show dynamic behavior in solution
with an exchange process between the coordinated and
noncoordinated pyrazole rings.
As a continuation of our research into the coordination
chemistry of these hybrid scorpionate/cyclopentadienyl ligands
(Chart 1a) and subsequent catalytic applications of their
complexes, we describe here the application of these ligands
in the synthesis of neutral scandium and yttrium halide and
alkoxide complexes. In addition, an interesting hydrolysis
process to give an air- and moisture-stable hydroxo multi-
nuclear derivative of yttrium (complex 11) has been studied.
Finally, complexes 1 and 2 were tested as catalysts in the
polymerization of styrene.
(3) (a) Piers, W. E.; Emslie, D. J. H. Coord. Chem. ReV. 2002, 233/234,
131. (b) Edelmann, F. T.; Freckmann, D. M. M.; Schumann, H. Chem.
ReV. 2002, 102, 1851. (c) Mountford, P.; Ward, B. D. Chem. Commun.
2003, 1797. and references cited therein. (d) Lawrence, S. C.; Ward,
B. D.; Dubberley, S. R.; Kozak, C. M.; Mountford, P. Chem. Commun.
2003, 2880. (e) Otero, A.; Ferna´ndez-Baeza, J.; Antin˜olo, A.; Tejeda,
J.; Lara-Sa´nchez, A.; Sa´nchez-Barba, L.; Mart´ınez-Caballero, E.;
Rodr´ıguez, A. M.; Lo´pez-Solera, I. Inorg. Chem. 2005, 44, 5336. (f)
Tredgdet, C. S.; Lawrence, S. C.; Ward, B. D.; Howe, G. R.; Cowley,
A. R.; Mountford, P. Organometallics 2005, 24, 3136. (g) Howe, R. G.;
Tredget, C. S.; Lawrence, S. C.; Subongkoj, S.; Cowley, A. R.;
Mountford, P. Chem. Commun. 2006, 223.
(4) (a) Trofimenko S. Scorpionates: the coordination chemistry of
polypyrazolylborate ligands; Imperial College Press: London, 1998.
(b) Marques, N.; Sella, A.; Takats, J. Chem. ReV. 2002, 102, 2137.
(5) (a) For example, see: Otero, A.; Ferna´ndez-Baeza, J.; Antin˜olo, A.;
Tejeda, J.; Carrillo-Hermosilla, F.; Diez-Barra, E.; Lara-Sa´nchez, A.;
Ferna´ndez-Lo´pez, M.; Lanfranchi, M.; Pellinghelli, M. A. J. Chem.
Soc., Dalton Trans. 1999, 3537. (b) Otero, A.; Ferna´ndez-Baeza, J.;
Antin˜olo, A.; Tejeda, J.; Carrillo-Hermosilla, F.; Lara-Sa´nchez, A.;
Sa´nchez-Barba, L.; Ferna´ndez-Lo´pez, M.; Rodr´ıguez, A. M.; Lo´pez-
Solera, I. Inorg. Chem. 2002, 41, 5193. (c) Otero, A.; Ferna´ndez-
Baeza, J.; Antin˜olo, A.; Tejeda, J.; Lara-Sa´nchez, A.; Sa´nchez-Barba,
L.; Sa´nchez-Molina, M.; Franco, S.; Lo´pez-Solera, I.; Rodr´ıguez, A. M.
Dalton Trans. 2006, 4359. (d) Otero, A.; Ferna´ndez-Baeza, J.;
Antin˜olo, A.; Tejeda, J.; Lara-Sa´nchez, A.; Sa´nchez-Barba, L.; Lo´pez-
Solera, I.; Rodr´ıguez, A. M. Inorg. Chem. 2007, 46, 1760. (e) Otero,
A.; Ferna´ndez-Baeza, J.; Antin˜olo, A.; Tejeda, J.; Lara-Sa´nchez, A.
Dalton Trans. 2004, 1499, perspective article. (f) Pettinari, C.; Pettinari,
R. Coord. Chem. ReV. 2005, 249, 525. (g) Pettinari, C.; Pettinari, R.
Coord. Chem. ReV. 2005, 249, 663.
Results and Discussion
Synthesis and Structure of Halide Complexes. Com-
pounds [Li(bpzcp)(THF)]7 and [Li(bpztcp)(THF)]7b (THF )
tetrahydrofuran) and the mixture of the two scorpionate/
cyclopentadiene regioisomers 1-[2,2-bis(3,5-dimethylpyrazol-
1-yl)-1-phenylethyl]-1,3-cyclopentadiene and 2-[2,2-bis(3,5-
dimethylpyrazol-1-yl)-1-phenylethyl]-1,3-cyclopentadiene
(bpzpcpH)7b were used to prepare scandium and yttrium
complexes. These compounds (the latter with prior addition
of BunLi) reacted with a solution of MCl3(THF)3 (M ) Sc,
Y; Scheme 1) in THF to give, after stirring for 12 h at room
temperature, a solution from which the THF adduct com-
plexes [MCl2(bpzcp)(THF)] (M ) Sc, 1; Y, 2), [MCl2(bpztcp)-
(THF)] (M ) Sc, 3; Y, 4), and [MCl2(bpzpcp)(THF)] (M )
Sc, 5; Y, 6) were isolated as white (1, 3, and 5) and pale-
yellow (2, 4, and 6) solids after the appropriate workup
procedure. Complexes 1-6 are slightly air-sensitive and
slowly decompose in air. In one attempt to obtain crystals
of 4 in CH2Cl2, we obtained its water adduct [YCl2(bpztcp)-
(H2O)] (7). The formation of this compound is probably due
(6) (a) For example, see: Deng, D.; Qian, C.; Wu, G.; Zheng, P. J. Chem.
Soc., Chem. Commun. 1990, 880. (b) Qian, C.; Wang, B.; Wu, G.;
Zheng, P. J. J. Organomet. Chem. 1992, 427, C29. (c) Anwander, R.;
Hermann, W. A.; Scherer, W.; Munck, F. C. J. Organomet. Chem.
1993, 462, 163. (d) Molander, G.; Schumann, H.; Rosenthal, E. C. E.;
Demtschuk, J. Organometallics 1996, 15, 3817. (e) Schumann, H.;
Rosenthal, E. C. E.; Demtschuk, J. Organometallics 1998, 17, 5324.
(f) Britovsek, G. J. P.; Gibson, V. C.; Wass, D. F. Angew. Chem., Int.
Ed. 1999, 38, 428. (g) Gibson, V. C.; Spitzmesser, S. K. Chem. ReV.
2003, 103, 283.
(7) (a) 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. (b) Otero, A.; Ferna´ndez-Baeza,
J.; Antin˜olo, A.; Tejeda, J.; Lara-Sa´nchez, A.; Sa´nchez-Barba, L.;
Sa´nchez-Molina, M.; Rodr´ıguez, A. M.; Bo, C.; Urbano-Cuadrado,
M. Organometallics 2007, 26, 4310.
(8) (a) Lopes, I.; Lin, G. Y.; Domingos, A.; McDonald, R.; Marques, N.;
Takats, J. J. Am. Chem. Soc. 1999, 121, 8110. (b) Roitershtein, D.;
Domingos, A.; Marques, N. Organometallics 2004, 23, 3483. (c) Kunz,
K.; Vitze, H.; Botte, M.; Lerner, H.-W.; Wagner, M. Organometallics
2007, 26, 4663.
(9) Otero, A.; Ferna´ndez-Baeza, J.; Antin˜olo, A.; Lara-Sa´nchez, A.; Tejeda,
J.; Sa´nchez-Barba, L.; Mart´ınez-Caballero, E.; Alonso-Moreno, C.;
Lo´pez-Solera, I. Organometallics 2008, 27, 976.
Inorganic Chemistry, Vol. 47, No. 11, 2008 4997

Otero et al.
Scheme 1. Synthesis of Complexes 1-7
Figure 1. ORTEP view of 2. Ellipsoids are at the 30% probability level,
and hydrogen atoms have been omitted for clarity.
to the presence of trace amounts of water in the solvent. We
believe that the lower coordinative capacity of CH2Cl2 in
comparison to THF probably enables the formation of the
water adduct 7. We rationalized the synthesis of 7; in fact,
the addition of an appropriate amount of water to a CH2Cl2
solution of complex 4 gives rise to the isolation of 7 after
the appropriate workup. Complexes 1-7 constitute the first
examples of group 3 metal halide complexes bearing a hybrid
scorpionate/cyclopentadienyl ligand.
The different group 3 metal halide complexes were
characterized spectroscopically. The mass spectra of these
complexes indicate a mononuclear formulation (see the
Figure 2. ORTEP view of 7. Ellipsoids are at the 30% probability level,
and hydrogen atoms have been omitted for clarity.
1
Experimental Section). The H and 13C{1H} NMR spectra
of 1 and 2 (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 and two multiplets for the THF
protons. These results are consistent with an octahedral
disposition, where the THF donor lies trans to the cyclo-
pentadienyl ring, for which a symmetric plane exists (see
Scheme 1). However, the 1H NMR spectra of complexes 3-7
(chiral compounds) show two singlets for each of the H4,
Me3, and Me5 pyrazole protons and four multiplets for the
H2, H3, H4, and H5 cyclopentadienyl protons, along with two
multiplets for the THF protons in complexes 3-6 or a broad
singlet at 3.50 ppm for the H2O protons in complex 7. These
results are also consistent with an octahedral structural
disposition where a κ2-NNη5-Cp coordination for the scor-
pionate ligand is proposed. The phase-sensitive 1H NOESY-
1D NMR spectra were also obtained in order to confirm the
assignments of the signals for the Me3, Me5, and H4 groups
of each pyrazole ring. The assignment of the 13C{1H} NMR
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 H NMR spectrum,
resulting from the two diastereoisomers of the corresponding
two enantiomers.
1
In order to confirm the proposed structure for these
complexes, X-ray diffraction studies on 2 and 7 were carried
out (see Figures 1 and 2). It is worth noting that complex 7
crystallized enantiopure. Crystallographic data and selected
interatomic distances and angles are given in Tables 1 and
2, respectively. The molecular structures determined by X-ray
diffraction are in good agreement with the solution structures
deduced from the NMR experiments. The structures of both
complexes are similar and consist of the heteroscorpionate
ligand bonded to the yttrium atom through the two nitrogen
atoms and the cyclopentadienyl ring in a κ2-NNη5-Cp
coordination in the expected fac coordination mode. In
addition, the yttrium center is coordinated to two chloride
atoms and one THF or H2O molecule, trans to the cyclo-
pentadienyl ring, in 2 and 7, respectively. The overall
1
signals was made on the basis of H-13C heteronuclear
correlation (g-HSQC) experiments. In these asymmetric
complexes, the carbon atom (Ca) is a chiral center, and we
4998 Inorganic Chemistry, Vol. 47, No. 11, 2008

Versatile NNCp Scorpionate Ligands in Sc and Y Compounds
Table 1. Experimental Data for the Crystal Structure Determination of 2, 7, and [{Y(bpzcp)}(µ-OH)2(µ3-OH){Y(O-2,6-C6H3Me2)2}]2 (11)
2
7
11
empirical formula
fw
temperature (K)
wavelength (Å)
cryst syst, space group
a (Å)
C33H37Cl2N4OY·THF
737.58
200(2)
0.710 73
monoclinic, P21/c
21.111(6)
C21 H31Cl2N4OY·3THF
C90 H100N8O10Y4 ·8CH2Cl2
731.62
2484.83
180(2)
200(2)
0.710 73
orthorhombic, Pna21
24.480(4)
0.710 73
triclinic, P1
j
12.473(3)
b (Å)
8.692(3)
14.790(2)
13.904(3)
c (Å)
20.747(6)
10.266(2)
16.673(4)
R (deg)
90
90
90
90
3717(1)
4, 1.307
1.752
1544
102.857(4)
90.188(4)
106.033(4)
2703(1)
1, 1.529
2.58
1268
ꢀ (deg)
113.315(4)
90
3496(2)
4, 1.401
1.857
1536
γ (deg)
volume (Å3)
Z, Dcalcd (g/cm3)
abs coeff (cm-1
F (000)
)
cryst size (mm)
limiting indices
0.45 × 0.22 × 0.17
-20 e h e 20
-8 e k e 8
-19 e l e 16
13 201/3139 [R(int) ) 0.3139]
3139/0/464
0.46 × 0.10 × 0.31
-21 e h e 20
-13 e k e 13
-9 e l e 9
11 551/2684 [R(int) ) 0.0800]
2684/1/414
0.52 × 0.31 × 0.25
-12 e h e 12
-12 e k e 14
-17 e l e 17
12 735/5954 [R(int) ) 0.1168]
5954/0/621
reflns collected/unique
data/restraints/param
GOF on F2
0.728
1.093
1.013
final R indices [I > 2σ(I)]
R1 ) 0.0674, wR2 ) 0.1586
R1 ) 0.1234, wR2 ) 0.1911
+0.607 and -0.727
R1 ) 0.0590, wR2 ) 0.1522
R1 ) 0.0747, wR2 ) 0.1656
+0.383 and -0.259
R1 ) 0.0876, wR2 ) 0.1862
R1 ) 0.1832, wR2 ) 0.2403
+0.997 and -0.774
R indices (all data)
largest diff peak and hole (e/Å3)
Table 2. Bond Lengths [Å] and Angles [deg] for 2 and 7
is longer than the Y1-O1 bond distance of 2.34(1) Å in
complex 7, a situation that is attributed to the higher steric
demands of the THF ring.
2
7
Bond Lengths
2.609(3)
Finally, it is worth noting that in complexes 1-7 (both in
solution and in the solid state) a κ2-NNη5-Cp coordination
mode was found for the ligand; however, with ligands that
are bulkier than chloride, such as in alkyl-containing
complexes [M(CH2SiMe3)2(bpzcp)] or [M(CH2SiMe3)2-
(bpztcp)] (M ) Sc, Y), the ligand adopts a κ1-Nη5-Cp mode
in the solid state (see Figure 3)9 and, furthermore, dynamic
behavior in solution κ1-Nη5-Cpsκ2-NNη5-Cpsκ1-Nη5-Cp
was observed.
Y1-Cl1
Y1-Cl2
Y1-O1
Y1-N1
Y1-N4
Y1-C21
Y1-C22
Y1-C23
Y1-C24
Y1-C25
Y1-Cl1
Y1-Cl2
Y1-O1
Y1-N1
Y1-N4
Y1-C21
Y1-C22
Y1-C23
Y1-C24
Y1-C25
2.606(5)
2.620(4)
2.34(1)
2.53(1)
2.52(1)
2.65(1)
2.67(1)
2.69(2)
2.67(2)
2.66(1)
2.618(3)
2.399(8)
2.497(9)
2.538(9)
2.69(1)
2.67(1)
2.62(1)
2.62(1)
2.62(1)
Angles
Cl1-Y1-Cl2
Cl1-Y1-O1
N1-Y1- Cl1
Cl1-Y1-N4
Cl2-Y1-O1
Cl2-Y1-N1
N4-Y1-Cl2
O1-Y1-N1
O1-Y1-N4
N1-Y1-N4
C2-C1-C21
93.6(1)
85.5(2)
159.8(2)
91.4(2)
81.1(2)
95.7(2)
154.7(2)
78.3(3)
74.5(3)
72.9(3)
112.8(9)
Cl1-Y1-Cl2
Cl1-Y1-O1
Cl1-Y1-N1
Cl1-Y1-N4
Cl2-Y1-O1
Cl2-Y1-N1
Cl2-Y1-N4
O1-Y1-N1
O1-Y1-N4
N1-Y1-N4
C1-C2-C21
92.3(2)
85.8(3)
158.7(3)
92.7(4)
80.7(3)
96.6(3)
156.0(3)
76.6(4)
76.4(4)
71.6(4)
115.8(13)
Synthesis and Structure of Aryloxide Derivatives. First,
complexes 1-7 were employed as starting materials to
prepare alkyl-containing complexes analogous to previously
prepared [M(CH2SiMe3)2(bpzcp)]9 by means of reactions
with either Grignard or lithium alkyl reagents, but unfortu-
nately in all cases under different experimental conditions,
mixtures of untractable products were isolated. Afterward,
we proceeded to explore the synthesis of aryloxide deriva-
tives starting from the dichloride scorpionate/cyclopentadi-
enyl group 3 metal complexes described above. Alkoxide
or aryloxide derivatives of scorpionate-containing group 3
metal complexes are relatively rare,3d–f although several
examples of alkoxide- or aryloxide-containing noncyclopen-
tadienyl and cyclopentadienyl group 3 metal complexes have
been documented.3f,11 However, the reaction of [MCl2(bpzcp)-
(THF)] (1 and 2) with sodium or potassium salts of different
phenol derivatives, such as MOAr (M ) Na, K; OAr ) 2,6-
geometries at the yttrium centers show a distorted octahedral
environment with major distortions in the N1-Y1-Cl1 and
N4-Y1-Cl2 angles of 159.8(2) and 154.7(2)° for complex
2 and 158.7(3) and 156.0(3)° for complex 7, respectively.
The Y-Cl and Y-N bond distances of around 2.60 and 2.50
Å, respectively, in the two complexes are as one would
expect for yttrium pyrazolyl complexes.3d–f,10 In these
complexes, the C5H4 ring is symmetrically bonded to the
metal center with Y-C bond distances of 2.62(1)-2.69 (1)
Å. The Y1-O1 bond distance of 2.399(8) Å in complex 2
(11) (a) Yamashita, M.; Takemoto, Y.; Ihara, E.; Yasuda, H. Macromol-
ecules 1996, 29, 1798. (b) Evans, W. J.; Sollberger, M. S.; Shreeve,
J. L.; Olofson, J. M.; Hain, J. H., Jr.; Ziller, J. W. Inorg. Chem. 1992,
31, 2492. (c) Evans, W. J.; Ulibarri, T. A.; Ziller, J. W. Organome-
tallics 1991, 10, 134. (d) Maginn, R. E.; Manastyrskyj, S.; Dubeck,
M. J. Am. Chem. Soc. 1985, 85, 672. (e) Ma, H.; Spaniol, T. P.; Okuda,
J. Angew. Chem., Int. Ed. 2006, 45, 7818. (f) Ma, H.; Melillo, G.;
Oliva, L.; Spaniol, T. P.; Englert, U.; Okuda, J. Dalton Trans. 2005,
721.
(10) (a) For example, see: Moffat, W. D.; Stainer, M. V. R.; Takats, J.
Inorg. Chim. Acta 1987, 139, 75. (b) Moss, M. A. J.; Jones, C. J.;
Edwards, A. J. J. Chem. Soc., Dalton Trans. 1989, 1393. (c)
Roitershtein, D.; Domingos, A.; Pereira, L. C. J.; Ascenso, J. R.;
Marques, N. Inorg. Chem. 2003, 42, 7666.
Inorganic Chemistry, Vol. 47, No. 11, 2008 4999

Otero et al.
Scheme 3. Mechanism Proposed for the Dynamic Behavior in Solution
of Complexes 9 and 10
detected by 1H NMR spectroscopy. These results are
consistent with a tetrahedral structural disposition with a κ1-
Nη5-Cp scorpionate coordination mode with two aryloxide
ligands occupying the other two coordination positions (see
1
Scheme 2). The room-temperature H and 13C{1H} NMR
spectra of complexes 9 and 10 show one set of resonances
for each of the H4, Me3, and Me5 pyrazole groups and for
ortho and meta groups on the Ar substituents due to the
presence of a very fast interconversion of two tetrahedral
complexes with a κ1-Nη5-Cp scorpionate coordination (see
below). Moreover, the signals of the ortho and meta methyl
groups of the Ar substituents appear as single broad
resonances at 2.00 ppm for complex 9 and at 2.20 ppm for
complex 10. The variable-temperature (VT) NMR analysis
shows that at subambient temperature the resonances of the
methyl group on the aryloxide ligands, along with those of
the pyrazole rings and the resonance of the H4 of the same
rings, broaden and resolve into two separate peaks. At
-100 °C, the resonances become well-resolved and the NMR
spectrum becomes consistent with a tetrahedral structural
disposition with κ1-Nη5-Cp scorpionate coordination and two
aryloxide ligands occupying the other two coordination
positions (see Scheme 2). This picture indicates the presence
of an exchange process between the coordinated and non-
coordinated pyrazole rings, resulting in interconversion from
one stereoisomer to the other (Scheme 3). This dynamic
behavior has been observed previously in other scorpionate-
containing metal complexes.9,12
Free-energy values, ∆Gq, for complexes 9 and 10 were
calculated13 from VT NMR studies. Complex 9 has higher
activation barriers, with a coalescence temperature of
-80 °C and ∆Gq ) 11.3 ( 0.1 kcal/mol, whereas 10 has a
coalescence point of -90 °C with ∆Gq ) 10.5 ( 0.1 kcal/
mol. The different behavior of 8 in comparison to 9 and 10
can probably be explained on the basis of the larger size of
the yttrium atom in comparison to scandium.
Finally, an interesting hydrolysis process was observed
when we attempted to use different procedures to obtain
single crystals suitable for X-ray diffraction studies from the
solution of complex 9 in CH2Cl2. For example, when a
CH2Cl2 solution of 9 was slowly evaporated at room
temperature in air for 48 h, white crystals were deposited
from the solution, and these were identified as the poly-
Figure 3. ORTEP drawing of the complex [Sc(CH2SiMe3)2(bpzcp)].9
Scheme 2. Synthesis of Bis(aryloxide) Complexes 8-10
dimethylphenoxide, OAr ) 3,5-dimethylphenoxide), in dif-
ferent molar ratios and under different conditions proved
unsuccessful. Thus, we attempted to prepare aryloxide
derivatives of scorpionate-containing compounds using the
dialkyl complexes [M(CH2SiMe3)2(bpzcp)]9 through an al-
coholysis reaction with ArOH (2 equiv; Ar ) 2,6-C6H3Me2,
3,5-C6H3Me2) to yield analytically pure [M(OAr)2(bpzcp)]
(M ) Sc, Ar ) 2,6-C6H3Me2, 8; M ) Y, Ar ) 2,6-C6H3Me2,
9; M ) Y, Ar ) 3,5-C6H3Me2, 10) in ca. 80% isolated yield
(Scheme 2). The corresponding reaction of 3,5-C6H3Me2OH
with [Sc(CH2SiMe3)2(bpzcp)] did not give a clean product
on either the preparative or NMR-tube scale (toluene-d8).
1
The room-temperature H and 13C{1H} NMR spectra of
complex 8 show two sharp resonances for each of the H4,
Me3, and Me5 pyrazole groups and broad resonances for ortho
groups of the Ar substituents. The sharpness of the 1H NMR
signals of the heteroscorpionate ligand suggests a high
coordination energy of the ligand to the metal center and
the absence of any fluxional equilibrium involving the two
N,N donors at room temperature. The signals indicate that
in this case the two pyrazole rings are not equivalent and
that in solution a fluxional process does not exist between
the coordinated and noncoordinated pyrazole rings, unlike
the bis(alkyl) complex precursor, which shows dynamic
behavior in solution between the two pyrazole rings.9 The
stereorigid environment is stable at least up to 340 K, up to
which fluxional behavior involving the ligand was not
(12) (a) Milione, S.; Grisi, F.; Centore, R.; Tuzi, A. Organometallics 2006,
25, 266. (b) Milione, S.; Bertolasi, V.; Cuenca, T.; Grassi, A.
Organometallics 2005, 24, 4915. (c) Chisholm, M. H.; Eilerts, N. W.;
Huffman, J. C. Inorg. Chem. 1996, 35, 445.
(13) Sandstro¨m, J. Dynamic NMR Spectroscopy; Academic Press: New
York, 1982.
5000 Inorganic Chemistry, Vol. 47, No. 11, 2008

Versatile NNCp Scorpionate Ligands in Sc and Y Compounds
yttrium hydroxo complexes.14 The Y-O(aryloxide) bond
distances [Y2-O4, 2.12 (1) Å; Y2-O5, 2.12(1) Å] are
slightly longer than the range reported for five- and six-
coordinated yttrium aryloxides [2.046(6)-2.103(10) Å].15
The angle around the aryloxide oxygen is 171-175°.15d
However, the angle around the aryloxide oxygen O5
[Y2-O5-C61] is 165.4(9)°,15d which is probably due to the
steric hindrance caused by the methyl group, Me3, of the
pyrazolyl ring closest to this aryloxide ligand. The Y-Cp
carbon distances of 2.66(1)-2.74(1) Å indicate that the C5H4
rings are symmetrically bonded to the metal centers.
Although a number of the oxo/hydroxo clusters or poly-
nuclear complexes of yttrium are known,14 the compound
reported here represents the first example of this type of
complex containing a scorpionate ligand.
Scheme 4. Synthesis of Polynuclear Yttrium Complex 11
nuclear complex 11. This complex results from partial
hydrolysis of the scorpionate/aryloxide-containing complex.
We subsequently rationalized the synthesis of 11; in fact,
the addition of an appropriate amount of water to a CH2Cl2
solution of complex 9 gives rise to the isolation of 11 after
the appropriate workup (see Scheme 4).
Styrene Polymerization Catalyzed by 1 and 2. Prelimi-
nary styrene polymerization experiments catalyzed by 1 and
2 were carried out in toluene at room temperature using
methylaluminoxane (MAO) as the cocatalyst. The results of
these experiments are summarized in Table 4.
When the process was followed in an NMR tube (CD2Cl2),
the reaction was quantitative after 12 h and the only side
products were bpzcpH, 2-[2,2-bis(3,5-dimethylpyrazol-1-yl)-
1,1-diphenylethyl]-1,3-cyclopentadiene,9 and free phenol 2,6-
C6H3Me2OH. Compound 11 was characterized spectroscopi-
cally. The IR spectrum shows a broad strong band at 3150
cm-1, and this is assigned to ν(OH) of the bridging groups.
The chloride derivatives 1 and 2, activated with MAO,
showed moderate but significant activity in styrene polym-
erization. GPC analyses of the polystyrenes obtained indicate
that they have narrow molecular weight distributions (Mw/
Mn ) 1.26-1.91), with the polystyrene produced showing
low molecular weights and reproducibly exhibiting molecular
weight distributions of less than 2, as expected for single-
site catalysts. The molecular weight of the resulting polymers
increased as the monomer-to-catalyst ratio was increased,
while the molecular weight distribution remained very narrow
1
The H and 13C{1H} NMR spectra show single sets of
resonances for the pyrazole rings and for the aryloxide
substituents, indicating that the pyrazoles from scorpionate
and aryloxide ligands, at least in solution, are equivalent.
This finding is consistent with a structural disposition with
a κ2-NNη5-Cp scorpionate coordination mode. The molecular
structure of this complex was determined by X-ray diffrac-
tion, and the structure is shown in Figure 4. Crystallographic
data and significant bond distances and angles are listed in
Tables 1 and 3, respectively. The centrosymmetric tetra-
nuclear yttrium hydroxo complex consists of four yttrium
atoms in the same plane in a rhombic disposition, with
bridging by two µ3-OH groups and four µ2-OH groups (see
Figure 5). Each yttrium atom has a pseudo-octahedral
coordination.
The complex exhibits two different yttrium environments:
Y1 is bonded to three hydroxo groups and a hybrid
scorpionate/cyclopentadienyl ligand with a κ2-NNη5-Cp
coordination mode, whereas Y2 is bonded to two aryloxide
ligands with an octahedral disposition and to four hydroxo
groups, which complete its coordination sphere. Furthermore,
Y1 shows a distorted octahedral environment, with O2 out
of the plane defined by N1, N3, O1, and Y1 by 0.89(1) Å,
whereas Y2 is practically in the plane defined by O1, O2,
O5, and O3A, probably because of constraints imposed by
the scorpionate ligand. The Y-O core bond lengths are in
the range 2.208(8)-2.403(8) Å and follow the order Y-OAr
< Y-µ2-OH < µ3-OH. The Y-OH bond distances are
consistent with the values reported for other polynuclear
(Table 4; Mn/Mw ) 1.67-1.91, runs 1-3; Mn/Mw
)
1.26-1.87, runs 4-6). The low molecular weights of the
resulting polymers are most likely caused by chain-transfer
reactions.16
It is worth noting that there are some reports of group 3
and 4 metals combined with scorpionate and heteroscorpi-
onate ligands that exhibit moderate and high activitysmainly
in ethylene but also in propene polymerization3f,g,13,17 sbut
in styrene polymerization, complexes containing scorpionate
(14) (a) Roesky, P. W.; Canseco-Melchor, G.; Zulys, A. Chem. Commun.
2004, 738. (b) Mahe´, N.; Guillou, O.; Daiguebonne, C.; Gerault, Y.;
Caneschi, A.; Sangregorio, C.; Chene-Ching, J. Y.; Car, P. E.; Roisnel,
T. Inorg. Chem. 2005, 44, 7743. (c) Fang, X.; Anderson, T. M.;
Benelli, C.; Hill, C. L. Chem.sEur. J. 2005, 11, 712. (d) Bu¨nzli, J.-
C. G.; Piguet, C. Chem. ReV. 2002, 102, 1897. (e) Mishra, S.; Daniele,
S.; Hubert-Pfalzgraf, L. G.; Jeanneau, E. Eur. J. Inorg. Chem. 2007,
2208. (f) Hubert-Pfalzgraf, L. G.; Cauro-Gamet, L.; Brethon, A.;
Daniele, S.; Richard, P. Inorg. Chem. Commun. 2007, 10, 143. (g)
Hubert-Pfalzgraf, L. G.; Miele-Pajot, N.; Papiernik, R.; Vaissermann,
J. J. Chem. Soc., Dalton Trans. 1999, 4127.
(15) (a) Schaverien, C. J.; Frijn, J. H. G.; Heeres, H. J.; van den Hende,
J. R.; Teuben, J. H.; Spek, A. L. J. Chem. Soc., Chem. Commun. 1991,
643. (b) Evans, W. J.; Ansari, M. A.; Ziller, J. W. Inorg. Chem. 1995,
34, 3079. (c) Evans, W. J.; Olofson, J. M.; Ziller, J. W. Inorg. Chem.
1989, 28, 4309. (d) Evans, W. J.; Ansari, M. A.; Ziller, J. W.; Khan,
S. I. J. Organomet. Chem. 1998, 553, 141. (e) Gendron, R. A. L.;
Berg, D. J.; Shao, P.; Barclay, T. Organometallics 2001, 20, 4279.
(16) Hultzsch, K. C.; Voth, P.; Beckerle, K.; Spaniol, T. P.; Okuda, J.
Organometallics 2000, 19, 228.
(17) (a) 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. Organometallics 2001, 20, 2428. (b) Milione, S.;
Montefusco, C.; Cuenca, T.; Grassi, A. Chem. Commun. 2003, 1176.
(c) Cuomo, C.; Milione, S.; Grassi, A. Macromol. Rapid Commun.
2006, 27, 611.
Inorganic Chemistry, Vol. 47, No. 11, 2008 5001

Otero et al.
Figure 4. ORTEP view of 11. Ellipsoids are at the 30% probability level, and hydrogen atoms have been omitted for clarity.
Table 3. Bond Lengths [Å] and Angles [deg] for 11a
Conclusions
bond lengths
angles
The hybrid scorpionate/cyclopentadienyl ligands bpzcp,
bpztcp, and bpzpcp were used to prepare a series of halide
and aryloxide complexes of scandium and yttrium. Halide
complexes 1-6 exhibit in the solid state a pseudo-octahedral
geometry in which the scorpionate ligand is κ2-NNη5-Cp-
coordinated to the metals along with one THF ligand. The
solid-state structure is retained in solution. The H2O adduct
of 4, [YCl2(bpztcp)(H2O)] (7), is formed when a solution of
4 is allowed to stand at room temperature in the presence of
moisture.
The aryloxide complexes 8-10 consist of a racemic
mixture in which each stereoisomer adopts a pseudotetra-
hedral structure. The more sterically demanding of aryloxide
ligands induces a κ1-Nη5-Cp coordination mode of the bpzcp
ligand in complex 8. However, a fluxional coordinative
behavior of the bpzcp ligand was monitored in solution, and
an exchange between coordinated and noncoordinated pyra-
zole rings is observed in yttrium complexes 9 and 10. In
addition, the hydrolysis of complex 9 gives a tetranuclear
yttrium complex with a Y4(µ-OH)4(µ3-OH)2 core that has
two different yttrium environments; two yttrium atoms are
Y1-O1
2.21(1)
2.38(1)
2.20(1)
2.57(1)
2.48(1)
2.73(1)
2.74(1)
2.70(1)
2.66(1)
2.67(1)
2.27(1)
2.40(1)
2.40(1)
2.27(1)
2.12(1)
2.12(1)
O1-Y1-O2
O1-Y1-O3
O2-Y1-O3
O1-Y1-N1
O2-Y1-N1
O3-Y1-N1
O1-Y1-N3
O2-Y1-N3
O3-Y1-N3
N1-Y1-N3
O1-Y2-O2
O1-Y2-O3A
O1-Y2-O4
O1-Y2-O5
O2-Y2-O4
O2-Y2-O5
O3A-Y2-O4
O3A-Y2-O5
O4-Y2-O5
Y1-O1-Y2
Y1-O2-Y2
Y1-O2-Y2A
Y2-O2-Y2A
Y1-O3-Y2A
72.7(3)
92.6(3)
71.6(3)
153.3(4)
128.5(3)
81.6(3)
84.6(4)
147.0(4)
86.2(3)
69.1(4)
71.3(3)
162.7(3)
102.9(3)
91.2(4)
95.7(3)
157.6(3)
90.6(3)
96.5(4)
102.0(4)
112.4(4)
102.3(3)
103.5(3)
106.4(3)
114.6(4)
Y1-O2
Y1-O3
Y1-N1
Y1-N3
Y1-C21
Y1-C22
Y1-C23
Y1-C24
Y1-C25
Y2-O1
Y2-O2
Y2-O2A
Y2-O3A
Y2-O4
Y2-O5
a Symmetry transformations used to generate equivalent atoms: 2 - x,
1 - y, 1 - z.
ligands have not been reported to date. The polymers
obtained were examined by 13C{1H} NMR spectroscopy to
obtain detailed information on the microstructure of poly-
styrenes isolated.18 The crude polymers were substantially
stereoirregular in the 13C NMR analysis, showing five main
peaks in the range 145.2-146.7 ppm due to phenyl C1
carbons, which correspond to the various configurational
sequences of atactic polystyrene and are in agreement with
the symmetry of the catalyst precursors.
(18) Ishihara, N.; Seimiya, T.; Kuramoto, M.; Uoi, M. Macromolecules
1986, 19, 2465.
Figure 5. Tetranuclear core of complex 11.
5002 Inorganic Chemistry, Vol. 47, No. 11, 2008

Versatile NNCp Scorpionate Ligands in Sc and Y Compounds
Table 4. Polymerization of Styrene with Scorpionate Scandium and Yttrium Complexes 1 and 2a
d
d
d
run no.
complex
Al/M
[Mo]/[cat]
t (min)
yieldb (%)
activityc
Mn
Mw
Mw/Mn
1
2
3
4
5
6
7
8
9
1
1
1
2
2
2
1
1
2
2
2000
2000
2000
2000
2000
2000
500
1000
500
1000
500
1000
1500
500
1000
1500
500
500
500
500
15
15
15
15
15
15
15
15
15
15
90
68
78
75
68
80
34
63
31
65
186
278
464
154
280
494
17
130
16
134
5107
5271
6202
5671
6584
8869
4760
4808
4693
5289
9036
10060
10341
10634
9986
11214
8449
8824
1.77
1.91
1.67
1.87
1.52
1.26
1.77
1.83
1.82
1.91
8553
10107
10
a Conditions: M, 6.0 µmol. Mo ) styrene. T ) 25 °C. Solvent ) toluene. b Weight of the polymer obtained/weight of the monomer used. c Given in kg
of PS/(mol of M ·h). d Measured by GPC at 40 °C in THF with antioxidant, using a Polymer Laboratories GPC-220 instrument equipped with PL Gel
mixed-B columns relative to a polystyrene standard.
(s, 6 H, Me3), 2.02 (s, 6 H, Me5), 7.26-6.99 (m, 10 H, Ph), 6.78
supported by a scorpionate ligand with a κ2-NNη5-Cp
coordination mode and bridged by two yttrium atoms bonded
to two aryloxide ligands with an octahedral disposition.
Finally, complexes 1 and 2 were active styrene polymer-
ization catalysts after activation with excess MAO, producing
atactic polystyrenes with low molecular weights but char-
acterized by narrow molecular weight distributions.
(m, 2 H, H3,4-Cp), 5.80 (m, 2 H, H2,5-Cp), 3.75 (m, 4 H, THF),
1.85 (m, 4 H, THF). 13C{1H} NMR (CDCl3, 297 K): δ 74.2 (CH),
or
143.8, 143.1 (C3
5), 109.3 (C4), 16.6 (Me3), 12.1 (Me5),
153.6-127.9 (Ph), 59.9 (Ca), 121.7 (C2,5-Cp), 115.7 (C3,4-Cp), 106.3
(C1-Cp), 68.1 (THF), 25.8 (THF). MS [FAB (m/z [assignment], %
intensity)]: 513 [M - THF - Cl], 100.
Synthesis of [YCl2(bpzcp)(THF)] (2). The synthetic procedure
was the same as that for complex 1, using [YCl3(THF)3] (0.50 g,
1.21 mmol) and [Li(bpzcp)(THF)] (0.62 g, 1.21 mmol), to give 2
as a pale-yellow solid. Yield: 90%. Anal. Calcd for C33H37Cl2N4OY:
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 fast atom bombardment (FAB) technique and nitrobenzyl
1
C, 59.56; H, 5.60; N, 8.42. Found: C, 59.74; H, 5.62; N, 8.23. H
NMR (CDCl3, 297 K): δ 7.29 (s, 1 H, CH), 5.97 (s, 2 H, H4), 2.47
(s, 6 H, Me3), 2.06 (s, 6 H, Me5), 7.17-6.92 (m, 10 H, Ph), 6.55
(m, 2 H, H3,4-Cp), 5.64 (m, 2 H, H2,5-Cp), 3.66 (m, 4 H, THF),
1.80 (m, 4 H, THF). 13C{1H} NMR (CDCl3, 297 K): δ 73.8 (CH),
1
or
alcohol as the matrix. H and 13C NMR spectra were recorded on
146.3, 143.5 (C3
5), 108.8 (C4), 15.5 (Me3), 12.1 (Me5),
a Varian Inova FT-500 spectrometer (1H NMR 500 MHz and 13C
NMR 125 MHz) and referenced to the residual deuterated solvent.
The NOESY-1D NMR spectra were recorded with the following
acquisition parameters using standard VARIAN-FT software:
irradiation time 2 s and number of scans 256. Two-dimensional
NMR spectra were acquired using standard VARIAN-FT software
and processed using an IPC-Sun computer. GPC measurements
were performed on a Polymer Laboratories PL-GPC-220 instrument
equipped with a PL Gel 5 Å mixed-C column, a refractive index
detector, and a PD2040 light-scattering detector. The GPC column
was eluted with THF at 40 °C at 1 mL/min and was calibrated
using eight monodisperse polystyrene standards in the range
580-483 000 Da.
153.3-126.9 (Ph), 60.5 (Ca), 116.3 (C1-Cp), 114.9 (C3,4-Cp), 106.2
(C2,5-Cp), 68.9 (THF), 25.6 (THF). MS [FAB (m/z [assignment],
% intensity)]: 557 [M - THF - Cl], 100.
Synthesis of [ScCl2(bpztcp)(THF)] (3). The synthetic procedure
was the same as that for complex 1, using [ScCl3(THF)3] (0.35 g,
0.95 mmol) and [Li(bpztcp)(THF)] (0.39 g, 0.95 mmol), to give 3
as a white solid. Yield: 85%. Anal. Calcd for C25H37Cl2N4OSc: C,
1
57.10; H, 7.09; N, 10.65. Found: C, 57.24; H, 7.18; N, 10.45. H
NMR (CDCl3, 297 K): δ 6.80 (s, 1 H, CH), 5.92 (s, 1 H, H4′), 5.86
(s, 1 H, H4), 2.53 (s, 6 H, Me3,3′), 2.53 (s, 3 H, Me5′), 2.44 (s, 3 H,
Me5), 3.02 (s, 1 H, CHa), 1.09 [s, 9 H, C(CH3)3], 5.60 (m, 1 H,
H5-Cp), 5.51 (m, 1 H, H2-Cp), 6.42 (m, 1 H, H3-Cp), 6.20 (m, 1 H,
H4-Cp), 3.75 (m, 4 H, THF), 1.86 (m, 4 H, THF). 13C{1H} NMR
(CDCl3, 297 K): δ 68.1 (CH), 143.7, 143.5, 141.1, 140.8
(C3,3′ or 5,5′), 109.2 (C4), 107.8 (C4′), 15.4 (Me3,3′), 12.9 (Me5′), 11.9
(Me5), 35.6 [C(CH3)3], 28.6 [C(CH3)3], 57.4 (Ca), 111.0 (C2-Cp),
117.5 (C3-Cp), 113.8 (C4-Cp), 116.1 (C5-Cp), 107.6 (C1-Cp), 68.2
(THF), 21.3 (THF). MS [FAB (m/z [assignment], % intensity)]:
418 [M - THF - Cl], 100.
The compounds [Li(bpzcp)(THF)],7 [Li(bpztcp)(THF)],7 (bpz-
pcpH),7 and [M(CH2SiMe3)2 (bpzcp)] (M ) Sc, Y),9 were prepared
according to literature procedures. Anhydrous trichlorides of
scandium and yttrium (Aldrich and Strem) were used as received,
and all other chemicals were commercially available and used after
appropriate purification. Styrene was purchased from Aldrich and
was dried by stirring with CaH2 for 48 h followed by distillation
under reduced pressure.
Synthesis of [YCl2(bpztcp)(THF)] (4). The synthetic procedure
was the same as that for complex 1, using [YCl3(THF)3] (0.50 g,
1.21 mmol) and [Li(bpztcp)(THF)] (0.51 g, 1.21 mmol), to give 4
as a pale-yellow solid. Yield: 80%. Anal. Calcd for C25H37Cl2N4OY:
Synthesis of [ScCl2(bpzcp)(THF)] (1). A solution of [Li(b-
pzcp)(THF)] (0.48 g, 0.95 mmol) in THF (25 mL) was added to a
solution of [ScCl3(THF)3] (0.35 g, 0.95 mmol) in THF (25 mL).
The reaction mixture was stirred for 12 h at room temperature,
after which a pale-yellow suspension was formed. The solvent was
removed under vacuum and the solid extracted with CH2Cl2. A
white solid was obtained after removal of the solvents. This material
was recrystallized from THF/hexane, yielding white crystals of the
title compound. Yield: 86%. Anal. Calcd for C33H37Cl2N4OSc: C,
1
C, 52.69; H, 6.54; N, 9.83. Found: C, 52.75; H, 6.66; N, 9.58. H
NMR (CDCl3, 297 K): δ 6.81 (s, 1 H, CH), 6.06 (s, 1 H, H4′), 5.98
(s, 1 H, H4), 2.53 (s, 6 H, Me3,3′), 2.56 (s, 3 H, Me5′), 2.45 (s, 3 H,
Me5), 3.00 (s, 1 H, CHa), 0.99 [s, 9 H, C(CH3)3], 6.46 (m, 1 H,
H3-Cp), 6.26 (m, 1 H, H4-Cp), 5.64 (m, 1 H, H5-Cp), 5.55 (m, 1 H,
H2-Cp), 3.61 (m, 4 H, THF), 1.82 (m, 4 H, THF). 13C{1H} NMR
(CDCl3, 297 K): δ 67.0 (CH), 143.5, 143.2, 141.7, 141.0
(C3,3′ or 5,5′), 109.0 (C4), 107.9 (C4′), 15.5 (Me3,3′), 12.1 (Me5′), 11.8
(Me5), 35.7 [C(CH3)3], 28.7 [C(CH3)3], 57.4 (Ca), 118.0 (C3-Cp),
1
63.77; H, 5.99; N, 9.01. Found: C, 63.85; H, 6.11; N, 8.94. H
NMR (CDCl3, 297 K): δ 7.19 (s, 1 H, CH), 5.88 (s, 2 H, H4), 2.59
Inorganic Chemistry, Vol. 47, No. 11, 2008 5003

Otero et al.
116.2 (C5-Cp), 113.8 (C4-Cp), 111.0 (C2-Cp), 107.9 (C1-Cp), 68.2
(THF), 21.3 (THF). MS [FAB (m/z [assignment], % intensity)]:
462 [M - THF - Cl], 100.
afford 8 as a yellow solid. This material was recrystallized from
THF/hexane, yielding pale-yellow crystals of the title compound.
Yield: 62%. Anal. Calcd for C45H47N4O2Sc: C, 74.98; H, 6.57; N,
7.77. Found: C, 75.10; H, 6.83; N, 7.55. 1H NMR (CDCl3, 297 K):
δ 7.19 (s, 1 H, CH), 5.89, 5.88 (s, 1 H, 1 H, H4,4′), 2.60, 2.19 (s,
3 H, 3 H, Me3,3′), 2.04, 2.02 (s, 3 H, 3 H, Me5,5′), 7.25-6.69 (m,
Synthesis of [ScCl2(bpzpcp)(THF)] (5). To a cooled (-70 °C)
solution of bpzpcpH (0.34 g, 0.95 mmol) in dry THF (50 mL) was
added a 1.6 M solution of BunLi (0.60 mL, 0.95 mmol) in hexane,
and the mixture was stirred for 30 min. A suspension of
[ScCl3(THF)] (0.35 g, 0.95 mmol) in THF (50 mL) was added,
and the reaction mixture was stirred for 12 h at room temperature.
The solvent was removed under vacuum and the solid extracted
with CH2Cl2. A white solid was obtained after removal of the
solvents. Yield: 78%. Anal. Calcd for C27H33Cl2N4OSc: C, 59.45;
10 H, Ph), 6.67, 6.54 (m, 1 H, 1 H, H2,5-Cp), 5.82, 5.73 (m, 1 H,
3
1 H, H3,4-Cp), 2.18 (br s, 12 H, -O-2,6-PhMe2), 6.89 (d, JHH
)
7.3 Hz, 4 Hm, -O-2,6-PhMe2), 6.53 (t, 3JHH ) 7.3 Hz, 2 Hp, -O-
2,6-PhMe2). 13C{1H} NMR (CDCl3, 297 K): δ 72.7 (CH), 145.3,
144.8, 142.1, 140.4 (C3,3′ 5,5′), 108.3, 107.1 (C4,4′), 13.8, 13.4
or
(Me3,3′), 11.9 (Me5,5′), 151.0-128.2 (Ph), 68.2 (Ca), 114.7 (C1-Cp),
107.4 (C2,5-Cp), 120.2 (C3,4-Cp), 15.9, 14.2 (-O-2,6-PhMe2),
160.2-116.5 (-O-2,6-PhMe2). MS [FAB (m/z [assignment], %
intensity)]: 600 [M - OAr], 100.
1
H, 6.10; N, 10.27. Found: C, 59.68; H, 6.51; N, 10.03. H NMR
(CDCl3, 297 K): δ 6.50 (br s, 1 H, CH), 5.85, (s, 1 H, H4), 5.58 (s,
1 H, H4′), 2.36, (s, 3 H, Me3), 2.13 (s, 3 H, Me3′), 2.35 (s, 3 H,
Me5′), 2.08 (s, 3 H, Me5), 7.35-7.20 (m, 5 H, Ph), 5.28 (s, 1 H,
Ha), 6.35 (m, 1 H, H5-Cp), 6.31 (m, 1 H, H2-Cp), 6.21 (m, 1 H,
H3-Cp), 6.13 (m, 1 H, H4-Cp), 3.71 (m, 4 H, THF), 1.82 (m, 4 H,
THF). 13C{1H} NMR (CDCl3, 297 K): δ 68.1 (CH), 145.8, 143.5,
141.8, 140.3 (C3,3′ or 5,5′), 106.0 (C4), 105.4 (C4′), 12.8 (Me3), 10.4
(Me3′), 12.9 (Me5′), 10.7 (Me5), 152.2-128.5 (Ph), 52.2 (Ca), 107.6
(C1-Cp), 117.5 (C5-Cp), 116.1 (C2-Cp), 113.8 (C4-Cp), 111.0 (C3-
Cp), 68.0 (THF), 25.4 (THF). MS [FAB (m/z [assignment], %
intensity)]: 438 [M - THF - Cl], 100.
Synthesis of [Y(O-2,6-C6H3Me2)2(bpzcp)] (9). The synthetic
procedure was the same as that for complex 8, using
[Y(CH2SiMe3)2(bpzcp)] (0.15 g, 0.20 mmol) and 2,6-dimethylphe-
nol (49 mg, 0.40 mmol), to give 9 as a white solid. Yield: 60%.
Anal. Calcd for C45H47N4O2Y: C, 70.67; H, 6.57; N, 7.77. Found:
C, 70.84; H, 6.71; N, 7.35. 1H NMR (CDCl3, 297 K): δ 7.37 (s, 1
H, CH), 5.96 (s, 2 H, H4), 2.28 (s, 6 H, Me3), 2.04 (s, 6 H, Me5),
7.31-7.05 (m, 10 H, Ph), 6.39 (m, 2 H, H2,5-Cp), 5.59 (m, 2 H,
3
H3,4-Cp), 2.09 (br s, 12 H, -O-2,6-PhMe2), 6.93 (d, JHH ) 7.3
Synthesis of [YCl2(bpzpcp)(THF)] (6). The synthetic procedure
was the same as that for complex 5, using bpzpcpH (0.43 g, 1.21
mmol), BunLi (0.75 mL, 1.21 mmol) and [YCl3(THF)3] (0.50 g,
1.21 mmol), to give 6 as a pale-yellow solid. Yield: 82%. Anal.
Calcd for C27H33Cl2N4OY: C, 55.02; H, 5.64; N, 9.50. Found: C,
55.36; H, 5.84; N, 9.21. 1H NMR (CDCl3, 297 K): δ 6.49 (s, 1 H,
CH), 6.09 (s, 1 H, H4′), 6.05 (s, 1 H, H4), 2.67 (s, 3 H, Me3′), 2.64
(s, 3 H, Me3), 2.46 (s, 3 H, Me5), 1.81 (s, 3 H, Me5′), 7.32-7.00
(m, 5 H, Ph), 4.73 (br s, 1 H, Ha), 5.78 (m, 1 H, H2-Cp), 5.54 (m,
1 H, H5-Cp), 6.36 (m, 1 H, H3-Cp), 6.33 (m, 1 H, H5-Cp), 3.66 (m,
4 H, THF), 1.81 (m, 4 H, THF). 13C{1H} NMR (CDCl3, 297 K):
Hz, 4 H, Hm, -O-2,6-PhMe2), 6.52 (m, 2 H, Hp, -O-2,6-PhMe2).
13C{1H} NMR (CDCl3, 297 K): δ 74.8 (CH), 145.4, 142.5 (C3 or 5),
108.2 (C4), 13.9 (Me3), 11.7 (Me5), 152.6-128.2 (Ph), 61.3 (Ca),
117.7 (C1-Cp), 109.5 (C2,5-Cp), 118.2 (C3,4-Cp), 17.6 (-O-2,6-
PhMe2), 161.9 (Cipso-O-2,6-PhMe2), 125.6 (Co-O-2,6-PhMe2), 127.5
(Cm-O-2,6-PhMe2), 115.0 (Cp-O-2,6-PhMe2). MS [FAB (m/z [as-
signment], % intensity)]: 644 [M - OAr], 100.
Synthesis of [Y(O-3,5-C6H3Me2)2(bpzcp)] (10). The synthetic
procedure was the same as that for complex 8, using
[Y(CH2SiMe3)2(bpzcp)] (0.15 g, 0.20 mmol) and 3,5-dimethylphe-
nol (49 mg, 0.40 mmol), to give 10 as a white solid. Yield: 58%.
Anal. Calcd for C45H47N4O2Y: C, 70.67; H, 6.57; N, 7.77. Found:
C, 70.89; H, 6.81; N, 7.82. 1H NMR (CDCl3, 297 K): δ 7.38 (s, 1
H, CH), 5.82 (s, 2 H, H4), 2.40 (s, 6 H, Me3), 2.05 (s, 6 H, Me5),
7.60-6.96 (m, 10 H, Ph), 6.27 (m, 2 H, H2,5-Cp), 5.61 (m, 2 H,
H3,4-Cp), 2.20 (br s, 12 H, -O-3,5-PhMe2), 6.41 (s, 4 H, Ho, -O-
3,5-PhMe2), 6.96 (br s, 2 H, Hp, -O-3,5-PhMe2). 13C{1H} NMR
or
δ 70.8 (CH), 146.4, 144.4, 141.5, 141.0 (C3,3′ 5,5′), 106.1 (C4),
105.5 (C4′), 14.6 (Me3′), 14.5 (Me3), 11.0 (Me5), 10.8 (Me5′),
149.7-128.7 (Ph), 51.7 (Ca), 106.1 (C1Cp), 115.6 (C4Cp), 116.0
(C3Cp), 114.2 (C2Cp), 106.2 (C5Cp), 67.8 (THF), 25.3 (THF). MS
[FAB (m/z [assignment], % intensity)]: 482 [M - THF - Cl], 100.
Synthesis of [YCl2(bpztcp)(H2O)] (7). To a solution of
[YCl2(bpztcp)(THF)] (6; 0.20 g, 0.35 mmol) in CH2Cl2 (50 mL)
was added H2O (6.3 µL, 0.35 mmol). The mixture was stirred for
1 h at room temperature and then concentrated to 15 mL and cooled
at -10 °C, affording a white microcrystalline powder. Yield: 95%.
Anal. Calcd for C21H31Cl2N4OY: C, 48.94; H, 6.06; N, 10.87.
or
(CDCl3, 297 K): δ 73.9 (CH), 144.5, 142.9 (C3 5), 107.8 (C4),
14.1 (Me3), 11.6 (Me5), 153.5-138.0 (Ph), 60.4 (Ca), 117.1 (C1-
Cp), 110.0 (C2,5-Cp), 118.2 (C3,4-Cp), 18.4 (-O-3,5-PhMe2), 162.0
(Cipso-O-3,5-PhMe2), 126.3 (Co-O-3,5-PhMe2), 128.8 (Cm-O-3,5-
PhMe2), 130.8 (Cp-O-3,5-PhMe2). MS [FAB (m/z [assignment], %
intensity)]: 644 [M - OAr], 100.
1
Found: C, 49.08; H, 6.21; N, 10.68. H NMR (CDCl3, 297 K): δ
6.79 (s, 1 H, CH), 5.95 (s, 1 H, H4), 6.00 (s, 1 H, H4′), 2.55, 2.53
(s, 3 H, 3 H, Me3,3′), 2.42 (s, 3 H, Me5), 2.54 (s, 3 H, Me5′), 0.97
[s, 9 H, C(CH3)3], 2.97 (br s, 1 H, CHa), 6.42 (m, 1 H, H3-Cp),
6.23 (m, 1 H, H5-Cp), 5.60 (m, 1 H, H5-Cp), 5.51 (m, 1 H, H2-Cp),
3.50 (br s, 2 H, H2O). 13C{1H} NMR (CDCl3, 297 K): δ 67.1 (CH),
144.4, 143.4, 141.1, 140.9 (C3,3′ or 5,5′), 109.1 (C4), 107.5 (C4′), 15.4,
14.9 (Me3,3′), 11.8 (Me5), 12.8 (Me5′), 35.7 [C(CH3)3], 28.5
[C(CH3)3], 58.2 (Ca), 108.0 (C1-Cp), 118.2 (C3-Cp), 116.4 (C5-
Cp), 113.5 (C4-Cp), 111.0 (C2-Cp). MS [FAB (m/z [assignment],
% intensity)]: 462 [M - H2O - Cl], 100.
Synthesis of [{Y(bpzcp)}(µ-OH)2(µ3-OH){Y(O-2,6-C6H3Me2)2}]2
(11). To a solution of 9 (0.200 g, 0.26 mmol) in CH2Cl2 (30 mL)
was added dropwise H2O (9 µL, 0.50 mmol). The reaction mixture
was stirred for 12 h at room temperature, during which time a white
precipitate appeared. The solid was filtered off and dried under
reduced pressure to give 11 as a white solid. Yield: 81%. Anal.
Calcd for C90H100N8O10Y4: C, 59.74; H, 5.57; N, 6.19. Found: C,
60.20; H, 5.85; N, 6.07. 1H NMR (DMSO, 297 K): δ 7.74 (s, 2 H,
CH), 5.76 (s, 4 H, H4), 2.36 (s, 12 H, Me3), 2.01 (s, 12 H, Me5),
7.32-6.86 (m, 20 H, Ph), 6.27 (m, 4 H, H2,5-Cp), 5.77 (m, 4 H,
H3,4-Cp), 2.18 (br s, 24 H, -O-2,6-PhMe2), 6.92 (m, 8 H, Hm, -O-
2,6-PhMe2), 6.42 (m, 4 H, Hp, -O-2,6-PhMe2). 13C{1H} NMR
(DMSO, 297 K): δ 75.2 (CH), 145.8, 142.0 (C3 or 5), 106.8 (C4),
13.5 (Me3), 10.6 (Me5), 152.8-128.5 (Ph), 62.3 (Ca), 116.3 (C1-
Cp), 108.8 (C2,5-Cp), 117.9 (C3,4-Cp), 16.6 (-O-2,6-PhMe2),
Synthesis of [Sc(O-2,6-C6H3Me2)2 (bpzcp)] (8). To a stirred
solution of [Sc(CH2SiMe3)2(bpzcp)] (0.15 g 0.23 mmol) in cold
(0 °C) toluene (20 mL) was added dropwise a solution of
2,6-dimethylphenol (55 mg, 0.46 mmol) in cold toluene (20 mL).
The reaction mixture was warmed to room temperature and stirred
for 1 h before removal of the volatiles under reduced pressure to
5004 Inorganic Chemistry, Vol. 47, No. 11, 2008

Versatile NNCp Scorpionate Ligands in Sc and Y Compounds
160.3-116.4 (-O-2,6-PhMe2). IR (Nujol mull, cm-1): 3150 [ν(µ-
OH) and ν(µ3-OH)].
methods using SHELXTL21 and refined by full-matrix least-squares
methods based on F.2 All non-hydrogen atoms were refined with
anisotropic thermal parameters. Hydrogen atoms were placed using
a “riding model” and included in the refinement at calculated
positions, except some hydrogen atoms from OH groups in complex
11, which are not clear of its direction. Complexes 2 and 7
crystallize with THF molecules as the solvent, which show several
atoms in a disordered position (approximately 0.50 population).
Because of the poor quality of the crystals for 2 and 11, the
calculated values of R(int) and wR2 are high.
Polymerization of Styrene. A typical polymerization reaction
is described (run 3, Table 4). A toluene solution of MAO (Witco,
10 wt %, solution in toluene; 6.96 mL) was added to a toluene
solution (5 mL) of 2 (4 mg, 6.0 µmol) in a 100 mL Schlenk tube.
The mixture was stirred at room temperature for a few minutes,
and styrene (0.936 g, 9 mmol) was added with vigorous stirring.
After ca. 15 min, methanol (5 mL) was added to terminate the
polymerization. The mixture was poured into methanol (200 mL)
to precipitate the polymeric product. The white polymer powder
was collected by filtration and dried under vacuum at 60 °C to a
constant weight (0.730 g, 78%).
X-ray Crystallography. A summary of crystal data collection
and refinement parameters for all compounds is given in Tables
1–3. Data for compounds 2, 7, and 11 were collected on a Bruker
X8 APPEX II CCD-based diffractometer, equipped with a graphite-
monochromated Mo KR radiation source (λ ) 0.710 73 Å). The
crystal data, data collection, structural solution, and refinement
parameters are summarized in Table 1. Data were integrated using
SAINT,19 and an absorption correction was performed with the
program SADABS.20 The structure of 2 was solved by the Patterson
method, whereas the structures of 7 and 11 were solved by direct
Acknowledgment. We gratefully acknowledge financial
support from the Ministerio de Educacio´n y Ciencia (MEC),
Spain (Grants CTQ2005-08123-CO2-01/BQU and Con-
solider-Ingenio 2010 ORFEO CSD2007-00006), and the
Junta de Comunidades de Castilla-La Mancha, Spain (Grant
PBI05-023).
Supporting Information Available: CIF file giving details of
data collection, refinement, atom coordinates, anisotropic displace-
ment parameters, and bond lengths and angles for complexes 2, 7,
and 11. This material is available free of charge via the Internet at
http://pubs.acs.org.
(19) SAINT+, Area-Detector Integration Program, version 7.12a; Bruker-
Nonius AXS: Madison, WI, 2004.
(20) Sheldrick, G. M. SADABS, A Program for Empirical Absorption
Correction, version 2004/1; University of Go¨ttingen: Go¨ttingen,
Germany, 2004.
IC800267V
(21) SHELXTL-NT, Structure Determination Package, version 6.12; Bruker-
Nonius AXS: Madison, WI, 2001.
Inorganic Chemistry, Vol. 47, No. 11, 2008 5005