Reactions of aromatic N-heterocycles with yttrium and lutetium benzyl complexes supported by a pyridine-diamide ligand

Article abstract of DOI:10.1021/om901052e

A comparison between the reactivity behavior of yttrium and lutetium benzyl complexes supported by a pyridine diamide, on one hand, and by a ferrocene diamide, on the other hand, toward aromatic N-heterocycles, such as 1-methylimidazole, isoquinoline, acridine, and 2-picoline, is presented. The ring opening of 1-methylimidazole by the pyridine-diamide complexes was observed, analogously to the ring opening of the same substrate by group 3 benzyl complexes supported by the ferrocenediamide ligand. Also, analogous products were observed in the reactions with 2-picoline and isoquinoline. However, when acridine was employed, different products were obtained for the two metal centers: alkyl transfer for yttrium and ortho-metalation for lutetium.

Full text of DOI:10.1021/om901052e

1222 Organometallics 2010, 29, 1222–1230
DOI: 10.1021/om901052e
Reactions of Aromatic N-Heterocycles with Yttrium and Lutetium Benzyl
Complexes Supported by a Pyridine-Diamide Ligand
Suyun Jie‡ and Paula L. Diaconescu*
Department of Chemistry & Biochemistry, University of California, Los Angeles, California 90095.
‡Present address: State Key Laboratory of Chemical Engineering, Department of Chemical and Biological
Engineering, Zhejiang University, Hangzhou 310027, People’s Republic of China
Received December 8, 2009
A comparison between the reactivity behavior of yttrium and lutetium benzyl complexes supported
by a pyridine diamide, on one hand, and by a ferrocene diamide, on the other hand, toward aromatic
N-heterocycles, such as 1-methylimidazole, isoquinoline, acridine, and 2-picoline, is presented. The
ring opening of 1-methylimidazole by the pyridine-diamide complexes was observed, analogously to
the ring opening of the same substrate by group 3 benzyl complexes supported by the ferrocene-
diamide ligand. Also, analogous products were observed in the reactions with 2-picoline and
isoquinoline. However, when acridine was employed, different products were obtained for the two
metal centers: alkyl transfer for yttrium and ortho-metalation for lutetium.
Introduction
kinetic stability and the high reactivity of the resulting
complexes.3,5,15 We have been interested in the reactivity of
d0fn complexes supported by chelating-ferrocene ligands16-21
and proposed that a weak interaction, of donor-acceptor
type, between iron and the metal takes place in alkyl ferrocene-
diamide (NNfc = fc(NSitBuMe2)2) complexes.22,23 According
to our previous investigations, a substrate-dependent beha-
vior was found with aromatic N-heterocycles: ring opening
of 1-methylimidazole,16,20 C-C coupling of pyridines,19,20
and alkyl transfer to isoquinoline (Scheme 1).24
Interest in non-cyclopentadienyl group 3 metal complexes
has been increasing in recent years1-4 with the goal of
expanding their reactivity toward challenging substrates,
such as saturated5 or unsaturated6,7 hydrocarbons and polar
molecules.8-10 Owing to the electrophilic metal centers pre-
sent even in neutral alkyl complexes, group 3 metal mono-
alkyl complexes supported by dianionic ancillary ligands
engage in σ-bond metathesis reactions.11-15
The reactivity of group 3 metal alkyl compounds is a result
of the metal’s electrophilicity and of available coordination
sites and can be substantially modulated by tuning the
electronic and steric properties of the ancillary ligand frame-
work. As a consequence, the design of new coordination
environments is crucial in maintaining a balance between the
In order to probe the importance of the iron-metal
interaction in determining the reactivity of the ferrocene-
diamide alkyl complexes, we decided to employ a tridentate,
dianionic, supporting ligand, 2,6-bis(2,6-di-iso-propylanilido-
methyl)pyridine (NNpy), with which the metal center is likely
to engage in a stronger interaction with the pyridine nitrogen
than that with iron in the ferrocene ligands. The NNpy ligand
coordinates exclusively in a meridional fashion to the metal
center as a consequence of the high rigidity of its backbone
*Corresponding author. E-mail: pld@chem.ucla.edu.
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pubs.acs.org/Organometallics
Published on Web 02/08/2010
2010 American Chemical Society

Article
Organometallics, Vol. 29, No. 5, 2010 1223
Scheme 1. Reactions of Group 3 Metal Benzyl
Complexes Supported by a Ferrocene-Diamide Ligand with
Aromatic N-Heterocycles
1Lu-CH2Ar had better solubility in hydrocarbon solvents than
the yttrium congener 1Y-CH2Ph, likely because of the increased
hydrophobicity of the dimethyl-substituted benzyl group in
1Lu-CH2Ar. The desired products were isolated in good yield
after recrystallization.
The 1H NMR spectrum of 1Y-CH2Ph in C6D6 at ambient
temperature showed a singlet at 4.78 ppm that was assigned
to the methylene groups of NNpy and a doublet at 2.23 ppm
that was assigned to the benzyl group. A multiplet at 3.83 ppm
and a doublet at 1.33 ppm were assigned to the methine and
methyl groups, respectively, of the four iso-propyl substitu-
ents. For the lutetium derivative 1Lu-CH2Ar, two distinct
doublets, at 5.09 and 4.48 ppm, were observed for the two
methylene groups of NNpy, likely because of a lesser flux-
ional behavior shown by 1Lu-CH2Ar than by 1Y-CH2Ph,
although the benzyl methylene appeared as a broad singlet at
2.16 ppm. Likewise, two multiplets for the methine and four
doublets for the methyl groups were found for the iso-propyl
substituents. A fluxional behavior was also observed for the
yttrium and lutetium alkyl complexes 1M-(CH2SiMe3)-
(THF).34 Similar to the present case, it was reported that
the fluxional behavior increased with the size of the metal
center: the analogous scandium complex, 1Sc-(CH2SiMe3),
showed behavior similar to 1Lu-CH2Ar, whereas the
yttrium and lutetium complexes showed behavior similar
to 1Y-CH2Ph.
and, thus, mimics the coordination of the ferrocene-diamide
ligand. Complexes of Ti(IV),25-27 Zr(IV),28-31 Ta(V),32,33
lanthanides,34-36 and Th(IV)37,38 supported by pyridine-
diamide ligands have been known. Herein we report the
synthesis of yttrium and lutetium benzyl complexes bearing
NNpy and their reactivity toward aromatic N-heterocycles.
Results and Discussion
Synthesis and Characterization of Benzyl Complexes. The
benzyl diamidopyridine complexes (NNpy)M(CH2Ar)(THF)
(1M-CH2Ar; M = Y, Ar = Ph; M = Lu, Ar = 3,5-Me2C6H3)
were prepared by alkane elimination from H2(NNpy) and
M(CH2Ar)3(THF)x (M = Y, x = 3; M = Lu, x = 2)19,20
in toluene, analogously to the route described by us for NNfc-
supported complexes (eq 1).19,20 An instantaneous color
change of the reaction mixture from colorless to orange
evidenced the coordination of the pyridine-diamide ligand to
the metal center. It was also noticed that the lutetium complex
The thermal stability of 1Y-CH2Ph was investigated
by heating a C6D6 solution gradually to 70 °C for three
days; under these conditions, 1Y-CH2Ph was relatively
stable. Total decomposition was observed only upon
prolonged heating at 85 °C (3 days); attempts to identify
the products were unsuccessful. The lutetium congener
(25) Guerin, F.; McConville, D. H.; Payne, N. C. Organometallics
1996, 15, 5085–5089.
(26) Guerin, F.; McConville, D. H.; Vittal, J. J. Organometallics 1997,
16, 1491–1496.
(27) Kang, K. K.; Hong, S.-P.; Jeong, Y.-T.; Shiono, T.; Ikeda, T. J.
Polym. Sci. A: Polym. Chem. 1999, 37, 3756–3762.
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15, 5586–5590.
1
Lu-CH2Ar showed similar behavior. The solids and
solutions of 1Y-CH2Ph and 1Lu-CH2Ar could be stored
at -35 °C in the glovebox for several weeks without
decomposition.
(29) Guerin, F.; McConville, D. H.; Vittal, J. J.; Yap, G. A. P.
Organometallics 1998, 17, 5172–5177.
ꢀ
(30) Guerin, F.; Del Vecchio, O.; McConville, D. H. Polyhedron
1998, 17, 917–923.
Reactions with 1-Methylimidazole. We had reported re-
cently the unprecedented ring opening of 1-methylimidazole
by scandium and yttrium complexes supported by NNfc.20
Because this reaction had not been observed with metallo-
cene complexes, it was considered a good test to compare the
reactivity of NNfc and NNpy complexes. The reaction of a
yellow toluene solution of 1Y-CH2Ph or 1Lu-CH2Ar with three
equivalents of 1-methylimidazole resulted in the formation of a
dark-red solution, after heating at 70 °C, from which a dark-red
solid was isolated for either yttrium (2Y) or lutetium (2Lu)
(Scheme 2). The products were analogous to those obtained
for the NNfc-based complexes, and we propose that a similar
mechanism operates.19,20
(31) Ziniuk, Z.; Goldberg, I.; Kol, M. Inorg. Chem. Commun. 1999, 2,
549–551.
(32) Guerin, F.; McConville, D. H.; Vittal, J. J. Organometallics 1995,
14, 3154–3156.
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Organometallics 1998, 17, 1290–1296.
(34) Estler, F.; Eickerling, G.; Herdtweck, E.; Anwander, R. Orga-
nometallics 2003, 22, 1212–1222.
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Anwander, R. Organometallics 2007, 26, 6029–6041.
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(36) Zimmermann, M.; Tornroos, K. W.; Waymouth, R. M.; An-
wander, R. Organometallics 2008, 27, 4310–4317.
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Robertson, C. M. Organometallics 2007, 26, 692–701.
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E.; Jenkins, H. A.; Britten, J. F. Organometallics 2009, 28, 1891–1899.

1224 Organometallics, Vol. 29, No. 5, 2010
Jie and Diaconescu
Scheme 2. Ring Opening of 1-Methylimidazole by 1M-CH2Ar
(M = Y, Lu) and Proposed Mechanism
Figure 1. Thermal-ellipsoid (50% probability) representation
of 2Y. Hydrogen atoms were omitted for clarity. Only one of the
two independent molecules present in the unit cell is shown.
The reaction was faster for the lutetium complex (15 h)
than for the yttrium one (48 h). The reaction of the yttrium
complex was significantly slower for the NNpy than for the
NNfc complex (5 h).20 DFT calculations established that, for
the reaction of (NNfc)Sc(CH2Ar)(THF) with 1-methylimi-
dazole, the step with the highest activation barrier, a rotation
along the carbon-carbon bond between the two coupled
rings to allow the coordination of the nitrogen bearing the
methyl group, follows the coupling of the two imidazole
rings.19 It is possible that the much slower reaction of
1Y-CH2Ph than of (NNfc)Y(CH2Ph)(THF) with 1-methyl-
imidazole is a consequence of the increased steric crowding in
1Y-CH2Ph that hinders this rotation, although other factors
cannot be ruled out.
Scheme 3. Reactions of 1M-CH2Ar with 2-Picoline and Subse-
quent C-C Coupling Reactions with 3-Methylisoquinoline
1
that mixture by H NMR spectroscopy indicated the pre-
Single crystals suitable for X-ray diffraction analysis were
obtained by the slow diffusion of n-pentane into a diethyl
ether solution of 2Y at -35 °C. X-ray crystallography (Figure 1)
revealed that the yttrium center is coordinated to six nitrogen
atoms, three from the pyridine-diamide ligand and the other
three from the imidazole-imine-amide fragment, which con-
tains an open imidazole ring. Metrical parameters are consis-
tent with the structure drawn in Scheme 2 (parameters for only
one of the two independent molecules in the unit cell are
discussed). For example, the N-C distances to the imine
sence of olefinic peaks, similarly to what was observed when
the corresponding ferrocene-diamide complexes were em-
ployed. On the basis of the reactivity behavior reported by us
for substituted pyridines and isoquinoline,19,20,24 we propose
that multiple, competitive pathways are operative when
pyridine is involved, leading to a mixture of products that
proved intractable. However, when pyridine was replaced by
2-phenylpyridine or 8-methylquinoline, the products of the
C-H activation reaction could be isolated and character-
ized.19,20 Therefore, the reactions between 1M-CH2Ar with
2-phenylpyridine or 8-methylquinoline were targeted, but in
both cases a mixture of products was formed that proved
intractable. These results indicate that 2-phenylpyridine and
8-methylquinoline behave like pyridine in the present reac-
tions. It is possible that the aryl iso-propyl groups, which
point toward the plane to be used by the substrate to
coordinate, change some reaction profiles, making multiple
pathways competitive; however, other factors may be
operative.
˚
nitrogen are 1.3132(40) and 1.3414(41) A, with the shortest
distance corresponding to the NdC bond. In addition, the
˚
C-C distance corresponding to the CdC bond is 1.3972(48) A.
The sum of the angles around the imine-nitrogen atom of
359.9° with individual angles of 126.08(29)°, CNC, and
118.20(21) and 115.59(21)°, YNC, also supports the above
structural assignment. The Y-N distances to the modified
˚
imidazole fragment are similar: 2.4454(27) A for Y-Nim,
˚
˚
2.4942(26) A for Y-Nimine, and 2.4218(27) A for Y-Namide
.
All these three distances are slightly longer than the Y-NNNpy
distance of 2.3968(26) A to the pyridine ring of the ancil-
Next, the reaction between 1M-CH2Ar and 2-picoline was
investigated. When one equivalent of 2-picoline was used,
C-H activation of the methyl instead of the ortho-carbon
was observed (Scheme 3), supported by the appearance in the
1H NMR spectrum of 3M-CH2Ar of a singlet at 2.30 ppm for
the methylene group. The reaction proceeds at room tem-
perature in 18 h for yttrium, but it requires heating to 50 °C
overnight for lutetium. An analogous compound was iso-
lated for yttrium supported by the ferrocene-diamide li-
gand.39 Similar results have been reported for other
yttrium40 and thorium alkyl complexes.41 DFT calculations
˚
˚
lary ligand and at least 0.15 A longer than the Y-NNNamide
distances of 2.2571(26) and 2.2666(26) A to the ancillary ligand.
˚
Reactions with 2-Picoline and Subsequent C-C Coupl-
ing Reactions with 3-Methylisoquinoline. The reactions of
1M-CH2Ar with pyridines were investigated next since the
ferrocene-diamide group 3 metal benzyl complexes can C-H
activate substituted pyridines and effect their coupling.19,20
The reaction between 1M-CH2Ar and four equivalents of
pyridine at 50 °C gave a mixture of products. Investigation of

Article
Organometallics, Vol. 29, No. 5, 2010 1225
Scheme 4. Reactions of Isoquinoline Mediated by the Benzyl
Complexes 1M-CH2Ar (M = Y, Lu)
are also consistent with the dearomatization of the pyridine
ring in the coupled-isoquinoline fragment. For example, the
N-C distances in the coordinated isoquinoline are
Figure 2. Thermal-ellipsoid (50% probability) representation
of 4Y-pic-iqnMe. Hydrogen atoms and 2,6-di-iso-propylphenyl
groups were omitted for clarity.
˚
1.3304(32) and 1.3805(31) A, while in the dearomatized
were used to investigate which isomer of 3Y-pic is preferred
and indicate that 3Y-pic is more stable by 1.3 kcal/mol than
3Y-pic0, in which the coordinated THF ligand points away
from the methylene group. Although the energy difference
between the two isomers is not large, the same isomer was
identified for the analogous ferrocene-diamide complex.39
Also, the preferential sp3 C-H activation is supported by
the fact that the two η2-N,C-pyridyl isomers are less stable
than 3Y-pic by as little as 3.2 kcal/mol and as much as
4.4 kcal/mol.
˚
fragment they are 1.3802(31) and 1.4821(31) A, with the
longest distance to the sp3-carbon atom. In addition, C-C
distances also reflect the dearomatization of the isoquinoline
fragment: the values for the pyridine ring of the coordinated
isoquinoline are 1.4115(35), 1.4004(36), 1.4159(36), and
˚
1.3776(35) A, while in the dearomatized one they are
˚
1.3682(35), 1.4351(38), 1.4100(36), and 1.5177(34) A, with
the longest distance involving the sp3-carbon atom. The
NCC angle around the sp3-carbon atom of 109.05(20)° and
the CCC angle of 110.53(20)° also support the above struc-
tural assignment.
Since a C-C coupling reaction between the ferrocene
analogue of 3Y-pic and 3-methylisoquinoline was ob-
served,39 the reaction of 3Y-pic with the same substrate was
also investigated. The two compounds reacted at room
temperature to form the expected biheterocyclic product
4Y-pic-iqnMe, in which the heterocyclic ring of 3-methyliso-
quinoline was dearomatized (Scheme 3). Single crystals of
4Y-pic-iqnMe suitable for X-ray diffraction analysis were
obtained by the slow diffusion of hexanes into an Et2O
solution of 4Y-pic-iqnMe at -35 °C. The X-ray structure
analysis (Figure 2) revealed that a 3-methylisoquinoline
ligand was also coordinated to the yttrium center. The
presence of a methylene group in the six-membered metallo-
cycle allows a near-perpendicular orientation of the two
heterocyclic rings. The complex 4Y-pic-iqnMe features a short
Reactions with Isoquinoline. The initial reaction between
the benzyl complexes and 1-methylimidazole, after displace-
ment of THF, is the C-H activation of the imidazole.19,20
The same ortho-metalation reaction was observed when
substituted pyridines were used as substrates.19 If the sub-
strate employed is changed to isoquinoline, C-H activation
does not occur and, instead, alkyl migration takes place
with the ferrocene-based group 3 metal complexes.24 There-
fore, we decided to investigate whether the same behavior
will be observed with the present systems. The complexes
1M-CH2Ar reacted with three equivalents of isoquinoline in
toluene at room temperature to give a red solution, from
which an orange solid was isolated (5M-(iqn)2, Scheme 4).
The reaction is analogous to the one previously reported for
ferrocene-diamide complexes.24 According to 1H NMR
spectroscopy in C6D6, the benzyl group was transferred to
the 1-position of isoquinoline with its concomitant dearo-
matization. Two other isoquinoline molecules were coordi-
nated to the yttrium center to form 5Y-(iqn)2. In the 1H NMR
spectrum of 5Y-(iqn)2, two doublets, at 6.15 and 5.65 ppm,
were assigned to the protons of the CHdCH bond in the
dearomatized heterocycle. Because of the C1-stereogenic
center, two distinct resonances for the CH2 protons of the
benzyl group were found, at 4.65 and 2.60 ppm, as a doublet
of doublets. The triplet at 3.86 ppm revealed the presence of
the proton on the newly sp3-hybridized carbon in the dear-
omatized heterocycle.
˚
Y-Namide distance of 2.2772(20) A to the dearomatized
pyridine ring and two long Y-Npy distances of 2.5505(20)
and 2.5750(20) A to the pyridine rings of 2-picoline and of
3-methylisoquinoline, respectively. The first distance,
˚
Y-Namide, is comparable to the Y-NNNamide distances of
2.2890(19) and 2.3119(19) A to the ancillary ligand, while the
˚
˚
Y-Npy distances are ca. 0.1 A longer than the Y-NNNpy
distance of 2.4533(19) A to the pyridine ring of the ancillary
˚
ligand. A close contact to the sp3-hybridized carbon atom
of the dearomatized isoquinoline fragment is evidenced by a
˚
Y-C distance of 2.9590(24) A (Figure 2). Metrical parameters
(39) Carver, C. T.; Williams, B. N.; Ogilby, K. R.; Diaconescu, P. L.
Organometallics 2010, asap.
(40) Duchateau, R.; Brussee, E. A. C.; Meetsma, A.; Teuben, J. H.
Organometallics 1997, 16, 5506–5516.
(41) Kiplinger, J. L.; Scott, B. L.; Schelter, E. J.; Pool Davis Tour-
near, J. A. J. Alloys Compd. 2007, 444-445, 477–482.
When toluene solutions of 1M-CH2Ar and four equiva-
lents of isoquinoline were heated at 70 °C, their color
changed gradually from orange to brown (Scheme 4). After
workup, a new product, 6M-(iqn)2, was identified together

1226 Organometallics, Vol. 29, No. 5, 2010
Jie and Diaconescu
Scheme 5. Reactions of 1M-CH2Ar (M = Y, Lu) with Acridine
Reactions with Acridine. The reactivity behavior of
1M-CH2Ar toward acridine was also investigated in order
to determine whether C-H activation or alkyl transfer
would occur.24,39 The reaction between 1Y-CH2Ph and one
equivalent of acridine in toluene at room temperature led to
the alkyl-transfer product 8 (Scheme 5), in which the benzyl
group migrated from the yttrium center to the 9-position of
acridine and the heterocycle was dearomatized. This reaction
is similar to the benzyl-transfer reaction observed for scan-
dium and lutetium benzyl complexes supported by the
ferrocene-diamide ligand and 2,20-bipyridine.24 However,
the reaction of the same scandium benzyl complex and
acridine resulted in the C-H activation of acridine. The
formulation of 8 was based on its 1H NMR spectrum since
protons for two equivalent phenyl groups were identified for
the acridine fragment. A triplet at 4.30 ppm corresponding to
one proton was assigned to the 9-position of acridine, and a
doublet at 3.11 ppm corresponding to two protons was
assigned to the methylene group of the benzyl substituent.
These chemical shifts are comparable to those reported for
9-benzyl-9,10-dihydroacridine (4.15 and 2.82 ppm).43
Figure 3. Thermal-ellipsoid (50% probability) representation
of 6Y-(iqn)2. Hydrogen atoms and 2,6-di-iso-propylphenyl
groups were omitted for clarity.
with 1-benzylisoquinoline (7Ar).42 The conversion of the
lutetium complex 1Lu-CH2Ar to 6Lu-(iqn)2 was much slower
(100 h) than that observed for the yttrium complex (24 h).
The formation of 6Y-(iqn)2 was confirmed by the appearance
in its 1H NMR spectrum of a singlet at 4.35 ppm correspond-
ing to the two protons of the methylene group in the
dearomatized isoquinoline and by characteristic olefinic
peaks at 6.60 and 5.70 ppm.
The reaction between 1Lu-CH2Ar and one equivalent of
acridine in C6D6 was very slow at room temperature, so the
reaction mixture was heated at 50 °C for 4 h. Surprisingly, a
different product than 8 was isolated (9, Scheme 5). The
identity of 9 was established by analyzing the 1H NMR
spectrum of the reaction mixture that indicated mesitylene
formation and two different sets of peaks for the two phenyl
rings in acridine. As mentioned earlier, the scandium benzyl
complex supported by NNfc leads to the formation of an
analogous product.39 DFT calculations support the propo-
sal that the structure drawn for 9 in Scheme 5 is preferred by
1.4 kcal/mol to the isomer in which THF was coordinated
next to the acridine-nitrogen atom. Although this value is
small, the analogous complex was also identified for scan-
dium supported by the the ferrocene-diamide ligand.
Single crystals of 6Y-(iqn)2 suitable for X-ray diffraction
analysis were obtained by the slow diffusion of hexanes into
an Et2O/THF solution at -35 °C (Figure 3). The structure
analysis revealed that two isoquinoline molecules were co-
ordinated to the yttrium center in addition to the dearoma-
tized ligand and that the geometry around the six-coordinate
yttrium center can be described as distorted octahedral.
Metrical parameters are consistent with the dearomatization
of the pyridine ring in one of the isoquinoline ligands. For
example, the N-C distances in the coordinated isoquino-
˚
lines are 1.3204(30) and 1.3709(31) A for one ligand and
˚
1.3383(33) and 1.3680(33) A for the other ligand, while in the
˚
dearomatized one they are 1.3623(33) and 1.4685(33) A, with
the longest distance to the sp3-carbon atom. In addition,
the C-C distances also reflect the dearomatization of one
isoquinoline ligand: the values for the pyridine ring of
the coordinated isoquinolines are 1.4084(34), 1.4204(37),
Conclusions
˚
The synthesis and characterization of yttrium and lute-
tium benzyl complexes supported by a pyridine-diamide
ligand were accomplished. The reactions of these benzyl
complexes with aromatic heterocycles, such as 1-methylimi-
dazole, 2-picoline, isoquinoline, and acridine, were investi-
gated and the results compared to those obtained when
benzyl complexes supported by a ferrocene-diamide ligand
were employed. Similar behavior for the two classes of
complexes was observed when 1-methylimidazole, 2-pico-
line, and isoquinoline were used. In the case of acridine,
the yttrium and lutetium benzyl complexes 1M-CH2Ar led to
the formation of different products: that of alkyl transfer
for yttrium and that of sp2 C-H activation for lutetium.
The difference between the two classes of complexes was
1.4093(36), and 1.3539(36) A for one ligand and 1.4069(36),
˚
1.4138(38), 1.4165(38), and 1.3651(36) A for the other
ligand, while in the dearomatized one they are 1.3675(35),
˚
1.4508(35), 1.4101(34), and 1.5003(36) A, with the longest
distance involving the sp3-carbon atom. The NCC angle
around the sp3-carbon atom of 112.96(21)° also supports
the above structural assignment. The Y-N distance to the
˚
dearomatized isoquinoline (2.3099(21) A) is shorter by ca.
˚
˚
0.2 A than the Y-N distances (2.4987(21) and 2.5617(21) A)
to the aromatic, coordinated isoquinolines. The first dis-
tance, Y-Namide, is comparable to the Y-NNNamide dis-
˚
tances of 2.2790(20) and 2.2924(20) A to the ancillary ligand,
while the Y-Npy distances are ca. 0.1 A longer than the
Y-NNNpy distance of 2.4173(20) A to the pyridine ring of the
ancillary ligand.
˚
˚
^
(43) Noyori, R.; Kato, M.; Kawanisi, M.; Nozaki, H. Tetrahedron
(42) Uff, B. C.; Kershaw, J. R. J. Chem. Soc. (C) 1969, 666–668.
1969, 25, 1125–1136.

Article
Organometallics, Vol. 29, No. 5, 2010 1227
manifested in the reactions with 2-phenylpyridine and
8-methylisoquinoline, which were too complex and did not
allow the isolation of single products for the pyridine-
diamide complexes. This difference notwithstanding, the
behavior of yttrium and lutetium benzyl complexes sup-
ported by the pyridine-diamide ligand is similar to that of
the analogous complexes supported by the ferrocene-dia-
mide ligand. It is likely that the dominant features in
predicting the reactivity behavior of these complexes are
(1) the presence of a diamide donor set and (2) the geometry
imposed by the rigid backbone of the ligands. The results
presented herein also suggest that the interaction between
iron from the ferrocene ligand and the group 3 metal center
is as relevant in determining the reactivity behavior of
the corresponding benzyl complexes as is the interaction
between the pyridine nitrogen of the pyridine diamide and
group 3 metal centers. In order to determine whether the
presence of this interaction is important, an analogue of the
pyridine-diamide ligand, in which pyridine is replaced by
benzene, is currently under study.
then combined. The reaction mixture was stirred for 3 h at 0 °C.
The volatiles were removed under reduced pressure, and the
residue was dissolved in hexanes and filtered through Celite. The
solution was concentrated and cooled at -35 °C to give a yellow
1
crystalline solid. Yield: 223.7 mg, 76%. H NMR (500 MHz,
C6D6), δ (ppm): 7.25-7.10 (m, 6 H, NC6H3), 6.93 (s, 2 H, o-3,5-
Me2C6H3), 6.85 (t, J = 8.0 Hz, 1 H, NC5H3), 6.49 (d, J = 8.0 Hz,
2 H, NC5H3), 5.94 (s, 1 H, p-3,5-Me2C6H3), 5.09 (d, J = 19.0 Hz,
2 H, NCH2), 4.73 (m, 2 H, CH(CH3)2), 4.48 (d, J = 19.0 Hz, 2 H,
NCH2), 3.37 (m, 2 H, CH(CH3)2), 2.95 (m, 4 H, OCH2CH2),
2.17 (s, 2 H, CH2Ar), 2.15 (s, 6 H, 3,5-(CH3)2C6H3), 1.60 (d, J =
6.0 Hz, 6 H, CH(CH3)2), 1.48 (d, J = 6.0 Hz, 6 H, CH(CH3)2),
1.17 (d, J = 6.0 Hz, 6 H, CH(CH3)2), 1.12 (d, 6 H, J = 6.0 Hz,
CH(CH3)2), 0.77 (m, 4 H, OCH2CH2). 13C NMR (126 MHz,
C6D6), δ (ppm): 164.1 (py-ortho), 153.7, 149.8, 136.8, 136.4,
128.5, 123.6, 123.0, 122.5, 120.8, 116.7 (aromatic-C), 70.1
(OCH2CH2), 65.2 (NCH2), 52.9 (Lu-CH2), 28.0, 25.1, 24.7,
and 21.9 (CHMe2, CH(CH3)2, Ar-CH3, and OCH2CH2). Anal.
(%) Calcd for C44H60LuN3O (821.93): C, 64.30; H, 7.36; N,
5.11. Found: C, 63.72; H, 7.23; N, 4.91.
Synthesis of 2Y. 1Y-CH2Ph (90.0 mg, 0.13 mmol) and 3 equiv
of 1-methylimidazole (32.5 mg, 0.39 mmol) were combined in
6 mL of toluene in a Schlenk tube. The reaction mixture was
heated at 70 °C for 48 h. After the volatiles were removed under
reduced pressure, the residue was extracted with diethyl ether
and filtered through Celite. The filtrate was layered with
n-pentane to give a red crystalline solid. Yield: 63.5 mg, 74%.
Experimental Section
All experiments were performed under a dry nitrogen atmo-
sphere using standard Schlenk techniques or an MBraun inert-
gas glovebox. Solvents were purified using a two-column solid-
state purification system by the method of Grubbs44 and
transferred to the glovebox without exposure to air. NMR
solvents were obtained from Cambridge Isotope Laboratories,
degassed, and stored over activated molecular sieves prior to
use. Yttrium and lutetium oxides were purchased from Stan-
ford Materials Corporation (Aliso Viejo, CA) and used as
received. H2(NNpy),28 Y(CH2Ph)3(THF)3,20 and Lu(CH2-3,5-
19
Me2C6H3)3(THF)2 were prepared according to published
1H NMR (500 MHz, C6D6), δ (ppm): 7.17-7.02 (m, 7 H,
NC6H3 and NC5H3), 6.85 (s, 1 H, a), 6.72 (d, J = 7.5 Hz, 2 H,
NC5H3), 6.39 (s, 1 H, b), 6.18, 6.09, and 5.47 (s, 1 H each, c, d, or
e), 5.13 (d, J = 20.0 Hz, 2 H, NCH2), 4.89 (d, J = 20.0 Hz, 2 H,
NCH2), 3.85 (sept, J = 6.5 Hz, 2 H, CH(CH3)2), 3.70 (sept, J =
6.5 Hz, 2 H, CH(CH3)2), 2.76 (s, 3 H, f), 1.95 (s, 3 H, g), 1.41 (d,
J = 6.5 Hz, 6 H, CH(CH3)2), 1.34 (d, J = 6.5 Hz, 6 H,
CH(CH3)2), 1.28 (d, J = 6.5 Hz, 6 H, CH(CH3)2), 1.24 (d,
J = 6.5 Hz, 6 H, CH(CH3)2). 13C NMR (126 MHz, C6D6), δ
(ppm): 165.6 (py-ortho), 161.5 (NC), 152.1 (NCH, e), 153.8,
146.4, 145.9, 136.6, 123.4, 123.3, 122.5, and 117.1 (aromatic-C),
126.7 (NCH, b), 118.2 (NCH, a), 110.4, and 109.3 (NCH, c and
d), 66.2 (NCH2), 43.5 (NCH3, g), 31.0 (NCH3, f), 27.7, 27.6,
27.2, 26.7, 24.6, 24.4 (CHMe2 and CH(CH3)2). Anal. (%) Calcd
for C39H52N7Y (707.78): C, 66.18; H, 7.41; N, 13.85. Found: C,
65.79; H, 7.25; N, 13.56.
procedures. The aromatic N-heterocycles were distilled or re-
crystallized before use; all other materials were used as received.
1H NMR spectra were recorded on Bruker500 spectrometers
(work supported by the NSF grants CHE-9974928 and CHE-
0116853) at room temperature in C6D6 unless otherwise speci-
fied. Chemical shifts are reported with respect to internal
solvent, 7.16 ppm (C6D6). CHN analyses were performed by
UC Berkeley Micro-Mass Facility, College of Chemistry, Uni-
versity of California, Berkeley, CA.
Synthesis of 1Y-CH2Ph. Y(CH2Ph)3(THF)3 (184.6 mg, 0.32
mmol) and H2(NNpy) (146.1 mg, 0.32 mmol) were cooled in 4
and 2 mL of toluene, respectively, to 0 °C and then combined.
The reaction mixture was stirred for 3 h at 0 °C. The resulting
orange solution was concentrated to ca. 2 mL and filtered
through Celite. The filtrate was layered with n-pentane to yield
a yellow solid. Yield: 198.2 mg, 88%. 1H NMR (500 MHz,
C6D6), δ (ppm): 7.23-7.14 (m, 5 H, CH2C6H5), 6.96-6.87 (m, 6
H, NC6H3), 6.56 (d, J = 7.5 Hz, 2 H, NC5H3), 6.25 (t, 1 H, J =
7.0 Hz, NC5H3), 4.78 (s, 4 H, NCH2), 3.83 (sept, J = 6.0 Hz, 4 H,
CH(CH3)2), 3.10 (m, 4 H, OCH2CH2), 2.23 (d, J = 4.0 Hz, 2 H,
CH2Ph), 1.33 (d, J = 6.0 Hz, 24 H, CH(CH3)2), 0.98 (m, 4 H,
OCH2CH2). 13C NMR (126 MHz, C6D6), δ (ppm): 164.9 (py-
ortho), 152.6, 151.3, 146.8, 136.6, 129.7, 123.7, 123.2, 122.8, and
117.2 (aromatic-C), 69.8 (OCH2CH2), 65.3 (NCH2), 50.0 (d,
JY-C = 30.4 Hz, Y-CH2), 28.1, 26.9, 25.0, and 24.8 (CHMe2,
CH(CH3)2 and OCH2CH2). Anal. (%) Calcd for C42H56N3OY
(707.82): C, 71.27; H, 7.97; N, 5.94. Found: C, 70.86; H, 7.76; N,
5.72.
Synthesis of 2Lu. 1Lu-CH2Ar (116.9 mg, 0.14 mmol) and 3 equiv
of 1-methylimidazole (35.5 mg, 0.43 mmol) were combined in 6
mL of toluene in a Schlenk tube. The reaction mixture was heated
at 70 °C for 15 h to yield a deep-red solution. After the volatiles
were removed under reduced pressure, the residue was extracted
with diethyl ether and filtered through Celite. The filtrate was
layered with n-pentane to give a red solid. Yield: 83.9 mg, 74%.
Synthesis of 1Lu-CH2Ar. Lu(CH2-3,5-Me2C6H3)3(THF)2
(243.8 mg, 0.36 mmol) and H2(NNpy) (165.2 mg, 0.36 mmol)
were cooled in 4 and 2 mL of toluene, respectively, to 0 °C and
1H NMR (500 MHz, C6D6), δ (ppm): 7.17-7.13 (m, 4 H,
NC6H3), 7.07 (t, J = 7.5 Hz, 1 H, NC5H3), 7.01 (t, J = 7.0 Hz,
(44) Pangborn, A. B.; Giardello, M. A.; Grubbs, R. H.; Rosen, R. K.;
Timmers, F. J. Organometallics 1996, 15, 1518–1520.

1228 Organometallics, Vol. 29, No. 5, 2010
Jie and Diaconescu
2 H, NC6H3), 6.90 (s, 1 H, a), 6.71 (d, J = 7.5 Hz, 2 H, NC5H3),
6.34 (s, 1 H, b), 6.25, 6.14, 5.47 (s, 1 H each, c, d, or e), 5.19 (d,
J = 20.0 Hz, 2 H, NCH2), 4.98 (d, J = 20.0 Hz, 2 H, NCH2),
3.85 (sept, J = 6.5 Hz, 2 H, CH(CH3)2), 3.70 (sept, J = 6.5 Hz, 2
H, CH(CH3)2), 2.70 (s, 3 H, f), 1.98 (s, 3 H, g), 1.40 (d, J = 6.5
Hz, 6 H, CH(CH3)2), 1.32 (d, J = 6.5 Hz, 6 H, CH(CH3)2), 1.27
(d, J = 6.5 Hz, 6 H, CH(CH3)2), 1.24 (d, J = 6.5 Hz, 6 H,
CH(CH3)2). 13C NMR (126 MHz, C6D6), δ (ppm): 165.8 (py-
ortho), 162.0 (NC), 152.6 (NCH, e), 154.9, 146.5, 146.0, 136.6,
123.3, 123.2, 122.3, and 117.0 (aromatic-C), 127.1 (NCH, b),
118.3 (NCH, a), 110.7, and 109.5 (NCH, c and d), 66.2 (NCH2),
43.8 (NCH3, g), 31.1 (NCH3, f), 27.6, 27.5, 27.3, 26.9, 24.4, and
24.1 (CHMe2 and CH(CH3)2). Anal. (%) Calcd for
C39H52LuN7 (793.84): C, 59.01; H, 6.60; N, 12.35. Found: C,
58.20; H, 6.62; N, 12.06.
aromatic-CH), 6.93-6.89 (m, 3 H, aromatic-CH), 6.82 (d, J =
8.0 Hz, 1 H, aromatic-CH), 6.79 (d, J = 8.0 Hz, 1 H, aromatic-
CH), 6.74 (t, J = 8.0 Hz, 1 H, aromatic-CH), 6.34-6.30 (m, 2 H,
aromatic-CH), 5.68 (d, J = 7.0 Hz, 1 H, aromatic-CH), 5.62 (s, 1
H, iqn-NC(CH3)CH), 5.27-5.16 (m, 3 H, NCH2 and pic-CH2),
4.96 (d, J = 21.0 Hz, 1 H, NCH2), 4.86 (d, J = 21.0 Hz, 1 H,
NCH2), 4.09 (dd, J1 = 18.5 Hz, J2 = 9.5 Hz, 1 H, NCHCH2),
3.52 (sept, J = 7.0 Hz, 1 H, CH(CH3)2), 3.34 (sept, J = 7.0 Hz, 1
H, CH(CH3)2), 3.14 (sept, J = 7.0 Hz, 1 H, CH(CH3)2), 3.01
(sept, J = 7.0 Hz, 1 H, CH(CH3)2), 2.46 (s, 3 H, NC(CH3)), 2.22
(d, J = 18.5 Hz, 1 H, pic-CH2), 1.37 (s, 3 H, iqn-CH3), 1.27 (d,
J = 7.0 Hz, 3 H, CH(CH3)2), 1.16 (d, J = 7.0 Hz, 3 H,
CH(CH3)2), 1.12 (d, J = 7.0 Hz, 3 H, CH(CH3)2), 0.83 (d,
J = 7.0 Hz, 3 H, CH(CH3)2), 0.54 (d, J = 7.0 Hz, 3 H,
CH(CH3)2), 0.31 (d, J = 7.0 Hz, 3 H, CH(CH3)2), -0.00 (d,
J = 7.0 Hz, 3 H, CH(CH3)2), -0.06 (d, J = 7.0 Hz, 3 H,
CH(CH3)2). 13C NMR (126 MHz, C6D6), δ (ppm): 166.2, 165.6,
and 164.9 (py-ortho and pic-2-C), 156.5, 154.6, 151.8, 147.5,
147.0, 146.9, 146.5, 145.9, 143.0, 137.6, 137.4, 136.9, 136.6,
126.5, 126.4, 124.6, 124.2, 123.9, 123.7, 123.4, 122.7, 122.1,
120.5, 119.5, 117.6, and 117.5 (aromatic-C and iqn*-3-C), 93.7
(iqn*-4-C), 68.0 (NCH2), 67.7 (NCH2), 52.7 (iqn*-1-C), 42.0
(pic-CH2), 27.9, 27.7, 27.5, 27.3, 27.2, 26.9, 26.8, 26.6, 24.4, 24.3,
23.8, 22.7 (CHMe2, CH(CH3)2, iqn-CH3, and iqn*-CH3). Anal.
(%) Calcd for C57H65N6Y (923.07): C, 74.17; H, 7.10; N, 9.10.
Found: C, 73.95; H, 7.26; N, 8.81.
Synthesis of 3Y-pic. 1Y-CH2Ph (126.0 mg, 0.18 mmol) and 1
equiv of 2-picoline (16.4 mg, 0.18 mmol) were combined in 5 mL
of toluene, and the reaction mixture was stirred at room
temperature for 18 h. The volatiles were removed under reduced
pressure, and the residue was filtered through Celite in diethyl
ether and hexanes. The filtrate was stored in the -35 °C freezer
to give a yellow crystalline solid. Yield: 115.1 mg, 92%. 1H
NMR (500 MHz, C6D6), δ (ppm): 7.19-7.09 (m, 6 H, NC6H3),
7.02 (t, J = 7.5 Hz, 1 H, NC5H3), 6.93 (d, J = 5.5 Hz, 1H, pic-
CH), 6.71 (t, J = 7.5 Hz, 1 H, pic-CH), 6.68 (d, J = 7.5 Hz, 2 H,
NC5H3), 6.56 (d, J = 8.5 Hz, 1 H, pic-CH), 5.73 (t, J = 6.0 Hz, 1
H, pic-CH), 4.83 (br s, 4 H, NCH2), 3.68 (m, 4 H, CH(CH3)2),
3.15 (m, 4 H, OCH2CH2), 2.30 (s, 2 H, pic-CH2), 1.27 (d, J = 7.0
Hz, 24 H, CH(CH3)2), 1.02 (br s, 4 H, OCH2CH2). 13C NMR
(126 MHz, C6D6), δ (ppm): 167.5 and 165.2 (py-ortho and pic-2-
C), 153.7, 146.8, 145.8, 136.7, 135.3, 123.6, 122.9, 119.6, 117.1,
and 107.7 (aromatic C), 70.3 (OCH2CH2), 65.5 (NCH2), 51.1
(Y-CH2), 27.9, 26.9, 24.9, and 24.6 (CHMe2, CH(CH3)2, and
OCH2CH2). Anal. (%) Calcd for C41H55N4OY (708.81):
C, 69.47; H, 7.82; N, 7.90. Found: C, 69.42; H, 8.03; N, 7.68.
Synthesis of 3Lu-pic. 1Lu-CH2Ar (109.3 mg, 0.13 mmol) and 1
equiv of 2-picoline (12.2 mg, 0.13 mmol) were combined in 5 mL
of toluene. The reaction mixture was stirred at 50 °C for 12 h.
The volatiles were removed under reduced pressure, and the
residue was extracted in diethyl ether and hexanes. The filtrate
was concentrated and cooled at -35 °C overnight to give
a yellow crystalline solid. Yield: 108.7 mg, 88%. 1H NMR
(500 MHz, C6D6), δ (ppm): 7.20-7.10 (m, 6 H, NC6H3), 7.03
(t, J = 7.5 Hz, 1 H, NC5H3), 6.81 (d, J = 6.0 Hz, 1 H, pic-CH),
6.74 (t, J = 7.5 Hz, 1 H, pic-CH), 6.68 (d, J = 7.5 Hz, 2 H,
NC5H3), 6.63 (d, J = 8.0 Hz, 1 H, pic-CH), 5.79 (t, J = 6.0 Hz, 1
H, pic-CH), 4.86 (br s, 4 H, NCH2), 3.73 (m, 4 H, CH(CH3)2),
3.17 (m, 4 H, OCH2CH2), 2.36 (s, 2 H, pic-CH2), 1.26 (d, J =
6.5 Hz, 24 H, CH(CH3)2), 1.00 (m, 4 H, OCH2CH2). 13C NMR
(126 MHz, C6D6), δ (ppm): 169.8 and 165.1 (py-ortho and pic-2-
C), 155.0, 147.0, 146.0, 136.7, 136.2, 123.5, 122.8, 119.7, 116.9,
and 108.7 (aromatic-C), 70.6 (OCH2CH2), 65.5 (NCH2), 49.2
(Lu-CH2), 27.8, 27.0, 24.8, and 24.5 (CHMe2, CH(CH3)2, and
OCH2CH2). Anal. (%) Calcd for C41H55LuN4O (794.87):
C, 61.95; H, 6.97; N, 7.05. Found: C, 61.80; H, 7.05; N, 6.97.
Synthesis of 4Y-pic-iqnMe. 1Y-CH2Ph (120.0 mg, 0.17 mmol)
and 1 equiv of 2-picoline (15.8 mg, 0.17 mmol) were combined in
5 mL of toluene, and the reaction mixture was stirred at room
temperature for 18 h. The formation of 3Y-pic was considered
complete by checking an aliquot of the reaction mixture by 1H
NMR spectroscopy. Then, 3-methylisoquinoline (50.0 mg, 0.34
mmol) in 2 mL of toluene was added, and the reaction mixture
was stirred at room temperature for another 1 h. The volatiles
were removed under reduced pressure, the residue was extracted
with THF, and the resulting solution was filtered through Celite.
After THF was removed under reduced pressure, diethyl ether
was added to give an orange crystalline solid. Yield: 122.6 mg,
78%. 1H NMR (500 MHz, C6D6), δ (ppm): 9.60 (br s, 1 H, iqn-1-
CHN), 8.16 (d, J = 5.5 Hz, 1 H, iqn-3-CHN), 7.66 (br s, 1 H,
aromatic-CH), 7.25-7.07 (m, 10 H, aromatic-CH), 7.01 (s, 1 H,
Synthesis of 5Y-(iqn)2. 1Y-CH2Ph (107.8 mg, 0.15 mmol) and 3
equiv of isoquinoline (59.2 mg, 0.46 mmol) were combined in 6
mL of toluene to give a red solution. The reaction mixture was
stirred at ambient temperature for 3 h. The volatiles were
removed under reduced pressure, and the residue was extracted
in diethyl ether and filtered through Celite. The filtrate was
layered with hexanes to give an orange solid. Yield: 90.5 mg,
58%. 1H NMR (500 MHz, C6D6), δ (ppm): 9.55 (s, 2 H, iqn-1-
CH), 8.08 (br s, 2 H, iqn-4-CH), 7.25-6.98 (m, 21 H, aromatic-
CH), 6.95 (d, J = 6.0 Hz, 2 H, aromatic-CH), 6.88 (d, J = 8.0
Hz, 2 H, aromatic-CH), 6.68 (t, J = 7.5 Hz, 1 H, aromatic-CH),
6.57 (d, J = 7.5 Hz, 2 H, aromatic-CH), 6.15 (d, J = 7.5 Hz, 1 H,
NC(CH3)CH), 5.65 (d, J = 6.5 Hz, 1 H, aromatic-CH), 5.11 (q,
J = 21.0 Hz, 4 H, NCH2), 4.65 (dd, J1 = 10.0 Hz, J2 = 4.5 Hz, 1
H, CH2Ph), 3.86 (t, J = 11.0 Hz, 1 H, NCHCH2), 3.21 (m, 4 H,
CH(CH3)2), 2.60 (dd, J1 = 11.5 Hz, J2= 4.5 Hz, 1 H, CH2Ph),
1.00 (d, J = 6.5 Hz, 6 H, CH(CH3)2), 0.91 (d, J = 6.5 Hz, 6 H,
CH(CH3)2), 0.35 (d, J = 6.5 Hz, 6 H, CH(CH3)2), 0.23 (d, J =
6.5 Hz, 6 H, CH(CH3)2). 13C NMR (126 MHz, C6D6), δ (ppm):
166.3 (py-ortho), 156.3, 153.8, 147.3, 147.0, 142.2, 141.2, 139.5,
137.3, 136.9, 135.9, 132.0, 130.7, 129.2, 129.1, 128.5, 127.2,
126.5, 125.9, 125.3, 124.1, 124.0, 123.4, 121.5, 121.1, 120.7,
and 117.7 (aromatic-C and iqn*-3-C), 94.8 (iqn*-4-C), 67.1
(NCH2), 62.0 (iqn*-1-C), 40.7 (CH2Ph), 27.7, 27.4, 27.3, 27.2,
23.8, and 23.7 (CHMe2 and CH(CH3)2). Anal. (%) Calcd for
C65H69N6Y (1023.19): C, 76.30; H, 6.80; N, 8.21. Found: C,
75.73; H, 6.82; N, 7.98.
Synthesis of 5Lu-(iqn)2. 1Lu-CH2Ar (106.1 mg, 0.13 mmol) and
3 equiv of isoquinoline (54.2 mg, 0.42 mmol) were combined in 6
mL of toluene to give a red solution. The reaction mixture was
stirred at ambient temperature for 3 h. The volatiles were
removed under reduced pressure, and the residue was extracted
in diethyl ether and filtered through Celite. The filtrate was
layered with n-pentane to give an orange solid. Yield: 124.0 mg,
85%. 1H NMR (500 MHz, C6D6), δ (ppm): 9.52 (br s, 2 H, iqn-1-
CH), 7.96 (br s, 2 H, iqn-3-CH), 7.23-6.93 (m, 20 H, aromatic-
CH), 6.86 (d, J = 8.0 Hz, 2 H, aromatic-CH), 6.68 (m, 2 H,
aromatic-CH), 6.29 (s, 2 H, o-Me2C6H3), 6.19 (d, J = 7.0 Hz, 1
H, NC(CH3)CH), 5.66 (d, J = 7.0 Hz, 1 H, aromatic-CH), 5.18
(q, J = 21.0 Hz, 4 H, NCH2), 4.57 (dd, J1 = 10.5 Hz, J2 = 4.5
Hz, 1 H, CH2-C6H3), 3.88 (t, J = 11.0 Hz, 1 H, NCHCH2), 3.19
(m, 2 H, CH(CH3)2), 3.13 (m, 2 H, CH(CH3)2), 2.56 (dd, J1 =
11.0 Hz, J2 = 4.5 Hz, 1 H, CH2-C6H3), 2.17 (s, 6 H, CH3-C6H3),
1.02 (d, J = 6.5 Hz, 6 H, CH(CH3)2), 0.94 (d, J = 6.5 Hz, 6 H,

Article
Organometallics, Vol. 29, No. 5, 2010 1229
CH(CH3)2), 0.43 (d, J = 6.5 Hz, 6 H, CH(CH3)2), 0.34 (d, J =
6.5 Hz, 6 H, CH(CH3)2). 13C NMR (126 MHz, C6D6), δ (ppm):
166.5 (py-ortho), 156.3, 154.5, 147.7, 147.3, 142.1, 141.2, 139.2,
137.4, 136.8, 136.4, 135.9, 132.1, 129.3, 129.2, 128.6, 127.5,
127.1, 126.4, 125.9, 124.1, 123.9, 123.6, 121.6, 120.9, 120.5,
and 117.7 (aromatic-C and iqn*-3-C), 95.0 (iqn*-4-C), 67.2
(NCH2), 62.0 (iqn*-1-C), 39.9 (CH2Ar), 27.6, 27.4, 27.2, 24.1,
24.0, and 21.3 (CHMe2, CH(CH3)2, and Ar-CH3).
(py-ortho), 156.1, 154.1, 147.4, 147.3, 141.2, 138.6, 137.2,
135.9, 132.0, 129.4, 129.2, 126.8, 125.9, 125.8, 123.8, 123.4,
122.4, 121.6, 119.8, and 117.6 (aromatic-C and iqn*-3-C), 96.8
(iqn*-4-C), 67.3 (NCH2), 50.7 (iqn*-NCH2), 27.5, 27.2, and 23.7
(CHMe2 and CH(CH3)2). Anal. (%) Calcd for C58H63LuN6
(1019.13): C, 68.35; H, 6.23; N, 8.25. Found: C, 68.01; H, 6.10;
N, 7.98.
Synthesis of 8. 1Y-CH2Ph (104.9 mg, 0.15 mmol) and 1 equiv
of acridine (26.2 mg, 0.15 mmol) were combined in 6 mL of
toluene. The reaction mixture was stirred at room temperature
for 2 h. The volatiles were removed under reduced pressure, and
the residue was dissolved in diethyl ether and filtered through
Celite. The filtrate was layered with hexanes and stored in a -35 °C
freezer to give a yellow solid. Yield: 96.3 mg, 74%. 1H NMR (500
MHz, C6D6), δ (ppm): 7.13-7.05 (m, 9 H, aromatic-CH), 6.99 (t,
J = 8.0 Hz, 1 H, aromatic-CH), 6.89 (d, J = 7.0 Hz, 2 H,
aromatic-CH), 6.85 (d, J = 7.5 Hz, 2 H, aromatic-CH), 6.74 (t,
J = 7.0 Hz, 2 H, acr), 6.64 (t, J = 7.5 Hz, 2 H, acr), 6.61 (d, J = 7.5
Hz, 2 H, aromatic-CH), 6.48 (d, J = 7.5 Hz, 2 H, aromatic-CH),
5.37 (d, J = 20.0 Hz, 2 H, NCH2), 4.57 (d, J = 20.0 Hz, 2 H,
NCH2), 4.30 (t, J = 7.0 Hz, 1 H, acr-9-CH), 3.93 (m, 2 H,
CH(CH3)2), 3.43 (m, 2 H, CH(CH3)2), 3.11 (d, J = 7.0 Hz, 2 H,
CH2Ph), 3.07 (m, 4 H, OCH2CH2), 1.21 (m, 18 H, CH(CH3)2),
1.04 (d, J = 6.5 Hz, 6 H, CH(CH3)2), 0.86 (m, 4 H, OCH2CH2).
13C NMR (126 MHz, C6D6), δ (ppm): 165.3 (py-ortho), 153.1,
148.1, 147.8, 145.6, 140.5, 137.4, 130.5, 130.3, 126.8, 126.0, 125.2,
124.1, 123.4, 123.2, 117.9, 117.4, and 114.3 (aromatic-C), 70.8
(OCH2CH2), 65.3 (NCH2), 48.4(CHCH2Ph), 46.2(CH2Ph), 28.8,
28.2, 27.7, 26.3, 24.8, 24.7, and 23.9 (CHMe2, CH(CH3)2, and
OCH2CH2). Anal. (%) Calcdfor C55H65N4OY (887.04): C, 74.47;
H, 7.39; N, 6.32. Found: C, 74.21; H, 7.35; N, 6.53.
Synthesis of 6Y-(iqn)2. 1Y-CH2Ph (107.8 mg, 0.15 mmol) and 4
equiv of isoquinoline (77.8 mg, 0.60 mmol) were combined in
6 mL of toluene to give a red solution. The reaction mixture was
stirred at 70 °C for 24 h. The volatiles were removed under
reduced pressure, and the residue was extracted with diethyl
ether and filtered through Celite. The filtrate was layered with
hexanes. The product was isolated as a brown solid and dried
under vacuum. Yield: 83.9 mg, 59%.
1H NMR (500 MHz, C6D6), δ (ppm): 9.34 (s, 2 H, d), 8.09 (br
s, 2 H, e), 7.23-6.95 (m, 21H, aromatic-CH), 6.87 (d, J = 8.0
Hz, 2 H, aromatic-CH), 6.60 (d, J = 7.0 Hz, 1 H, b), 5.70 (d, J =
6.5 Hz, 1H, c), 5.13 (s, 4 H, NCH2), 4.35 (s, 2 H, a), 3.17 (sept,
J = 7.0 Hz, 4 H, CH(CH3)2), 0.95 (d, J = 7.0 Hz, 12 H,
CH(CH3)2), 0.26 (d, J = 7.0 Hz, 12 H, CH(CH3)2). 13C NMR
(126 MHz, C6D6), δ (ppm): 166.5 (py-ortho), 156.0, 153.3, 147.0,
141.3, 138.7, 137.2, 135.9, 131.9, 129.3, 129.1, 126.7, 125.9,
125.7, 125.5, 123.8, 123.0, 122.3, 121.5, 119.8, and 117.6
(aromatic-C and iqn*-3-C), 96.0 (iqn*-4-C), 67.0 (NCH2), 50.6
(iqn*-NCH2), 27.6, 27.2, and 23.6 (CHMe2 and CH(CH3)2).
Anal. (%) Calcd for C58H63N6Y (933.07): C, 74.66; H, 6.81; N,
9.01. Found: C, 74.61; H, 6.50; N, 8.96.
Synthesis of 9. 1Lu-CH2Ar (108.0 mg, 0.13 mmol) and 1 equiv
of acridine (23.4 mg, 0.13 mmol) were combined in 6 mL of
toluene. The reaction mixture was stirred under heating at 50 °C
for 4 h. The volatiles were removed under reduced pressure, and
the residue was washed with small amount of diethyl ether and
hexanes. A bright yellow solid was obtained. Yield: 91.9 mg,
1
80%. H NMR (500 MHz, C6D6), δ (ppm): 8.35 (s, 1 H, acr),
8.11 (d, J = 6.0 Hz, 1 H, acr), 7.67 (d, J = 8.0 Hz, 1 H, acr), 7.59
(d, J = 8.0 Hz, 1 H, acr), 7.48 (t, J = 7.5 Hz, 1 H, acr), 7.26 (t,
J = 7.5 Hz, 1 H, acr), 7.18-6.97 (m, 8 H, aromatic-CH), 6.86 (d,
J = 7.5 Hz, 2 H, NC5H3), 6.59 (d, J = 7.5 Hz, 1 H, acr), 5.31 (d,
J = 20.0 Hz, 2 H, NCH2), 4.88 (d, J = 20.0 Hz, 2 H, NCH2),
3.66 (sept, J = 6.5 Hz, 2 H, CH(CH3)2), 3.57 (m, 4 H,
OCH2CH2), 3.41 (sept, J = 6.5 Hz, 2 H, CH(CH3)2), 1.33 (d,
J = 6.5 Hz, 6 H, CH(CH3)2), 1.24 (m, 4 H, OCH2CH2), 1.20 (d,
J = 6.5 Hz, 6 H, CH(CH3)2), 0.60 (d, J = 6.5 Hz, 6 H,
CH(CH3)2), 0.34 (d, J = 6.5 Hz, 6 H, CH(CH3)2). 13C NMR
(126 MHz, C6D6), δ (ppm): 166.5 (py-ortho), 161.7, 155.0, 147.4,
146.4, 146.2, 140.2, 138.2, 137.0, 129.5, 129.1, 126.9, 126.6,
126.2, 125.5, 124.2, 123.8, 123.1, 123.0, 122.6, and 117.5
(aromatic-C), 70.3 (OCH2CH2), 66.5 (NCH2), 27.9, 27.5, 27.1,
26.6, 25.3, 24.7, and 22.4 (CHMe2, CH(CH3)2, and OCH2CH2).
Anal. (%) Calcd for C48H57LuN4O (880.96): C, 65.44; H, 6.52;
N, 6.36. Found: C, 65.10; H, 6.40; N, 6.25.
Synthesis of 6Lu-(iqn)2. 1Lu-CH2Ar (100.7 mg, 0.12 mmol) and
4 equiv of isoquinoline (63.3 mg, 0.49 mmol) were combined in
6 mL of toluene to give a red solution. The reaction mixture was
stirred at 70 °C for 100 h. The volatiles were removed under
reduced pressure, and the residue was extracted in diethyl ether
and filtered through Celite. The filtrate was layered with
n-pentane to give a brown solid. Yield: 95.4 mg, 76%.
X-ray Crystal Structures. X-ray quality crystals were obtained
from various concentrated solutions placed in a -35 °C freezer
in the glovebox. Inside the glovebox, the crystals were coated
with oil (STP Oil Treatment) on a microscope slide, which was
brought outside the glovebox. The X-ray data collections were
carried out on a Bruker AXS single-crystal X-ray diffractometer
using Mo KR radiation and a SMART APEX CCD detector.
The data were reduced by SAINTPLUS, and an empirical
absorption correction was applied using the package SADABS.
The structures were solved and refined using SHELXTL
(Bruker 1998, SMART, SAINT, XPREP, and SHELXTL,
Bruker AXS Inc., Madison, WI).45 All atoms were refined
anisotropically, and hydrogen atoms were placed in calculated
1H NMR (500 MHz, C6D6), δ (ppm): 9.37 (br s, 2 H, d), 7.99
(br s, 2 H, e), 7.22-6.82 (m, 23 H, aromatic-CH), 6.59 (d, J =
7.0 Hz, 1 H, b), 5.73 (d, J = 7.0 Hz, 1 H, c), 5.19 (s, 4 H, NCH2),
4.28 (s, 2 H, a), 3.13 (sept, J = 7.0 Hz, 4 H, CH(CH3)2), 0.94 (d,
J = 7.0 Hz, 12 H, CH(CH3)2), 0.31 (d, J = 7.0 Hz, 12 H,
CH(CH3)2). 13C NMR (126 MHz, C6D6), δ (ppm): 166.7
(45) Sheldrick, G. Acta Crystallogr. A 2008, 64, 112–122.

1230 Organometallics, Vol. 29, No. 5, 2010
Jie and Diaconescu
positions unless specified otherwise. Tables with atomic coordi-
nates and equivalent isotropic displacement parameters, with all
the bond lengths and angles and with anisotropic displacement
parameters, are listed in the cifs.
glovebox. A total of 44 508 reflections (-24 e h e 24, -15 e k e
15, -31 e l e 30) were collected at T = 100(2) K with 2θmax
=
56.38°, of which 12 043 were unique (Rint = 0.0771). The
residual peak and hole electron density were 0.38 and -0.42 e
X-ray Crystal Structure of 2Y. X-ray quality crystals were
obtained by slow diffusion of n-pentane into a diethyl ether
solution of 2Y placed in a -35 °C freezer in the glovebox. A total
of 38 525 reflections (-20 e h e 20, -21 e k e 21, -24 e l e 25)
were collected at T = 100(2) K with 2θmax = 56.66°, of which
20 595 were unique (Rint = 0.0459). The residual peak and hole
A
-3. The least-squares refinement converged normally with
residuals of R1 = 0.0476 and GOF = 1.008. Crystal and
˚
refinement data for 6Y-(iqn)2: formula C58H63N6Y, space group
˚
P21/n, a = 18.347(3) A, b = 11.7235(17) A, c = 23.396(4) A,
β = 99.929(2)°, V = 4956.9(13) A , Z = 4, μ = 1.220 mm
F(000) = 1968, R1 = 0.0884 and wR2 = 0.1047 (based on all
˚
˚
3
-1
˚
,
electron density were 2.54 and -0.84 e A-3. The unit cell
12 043 data, I > 2σ(I)).
˚
contains two independent molecules of 2Y and two molecules
of n-pentane solvent. Some methyl groups and solvent atoms
were slightly disordered; this disorder was not modeled. The
least-squares refinement converged normally with residuals of
R1 = 0.0565 and GOF = 1.026. Crystal and refinement data for
DFT Calculations. The Amsterdam Density Functional
(ADF) package (version ADF2008.01) was used to perform
geometry optimizations on Cartesian coordinates of the model
compounds specified in the text. For the yttrium, silicon, and
iron atoms, standard triple-ζ STA basis sets from the ADF
database ZORA TZP were employed with 1s-2p (Si), 1s-3p (Fe),
and 1s-4p (Y) electrons treated as frozen cores. For all the other
elements, standard double-ζ STA basis sets from the ADF
database ZORA DZP were used, with the 1s electrons treated
as a frozen core for non-hydrogen atoms. The local density
approximation (LDA) by Becke-Perdew was used together
with the exchange and correlation corrections that are employed
by default by the ADF2008.01 program suite. Calculations for
all model compounds were carried out using the spin-unrest-
ricted, scalar spin-orbit relativistic formalism.
Y
˚
2 : formula C44H64N7Y, space group P1, a = 15.316(3) A, b =
˚
˚
16.488(4) A, c = 18.773(4) A, R = 68.659(2)°, β = 78.608(2)°,
3
-1
˚
γ = 76.991(2)°, V = 4267.5(16) A , Z = 4, μ = 1.404 mm
,
F(000) = 1664, R1 = 0.0984 and wR2 = 0.1450 (based on all
20 595 data, I > 2σ(I)).
X-ray Crystal Structure of 4Y-pic-iqnMe. X-ray quality crystals
were obtained by the slow diffusion of hexanes into an Et2O
solution of 4Y-pic-iqnMe placed in a -35 °C freezer in the
glovebox. A total of 46 597 reflections (-26 e h e 26, -18 e
k e 18, -27 e l e 28) were collected at T = 100(2) K with
2θmax = 58.36°, of which 12 971 were unique (Rint = 0.0667).
The residual peak and hole electron density were 0.72 and -0.56
Acknowledgment. This work was supported by
UCLA, the Sloan Foundation, and the NSF (Grant
CHE-0847735).
e A-3. The least-squares refinement converged normally with
˚
residuals of R1 = 0.0476 and GOF = 1.012. Crystal and
refinement data for 4Y-pic-iqnMe: formula C57H65N6Y, space
˚
group P21/c, a = 19.098(3) A, b = 13.646(2) A, c = 20.466(3) A,
˚
˚
3
-1
˚
β = 114.859(2)°, V = 4839.4(12) A , Z = 4, μ = 1.249 mm
,
Supporting Information Available: Details of the NMR
spectroscopy experiments, DFT calculations, and full crystal-
lographic descriptions (as cif) are available free of charge
via the Internet at http://pubs.acs.org. CCDC numbers for 2Y,
4Y-pic-iqnMe, and 6Y-(iqn)2 are 756843, 756844, and 756845,
respectively.
F(000) = 1952, R1 = 0.0845 and wR2 = 0.1180 (based on all
12 971 data, I > 2σ(I)).
X-ray Crystal Structure of 6Y-(iqn)2. X-ray quality crystals
were obtained by the slow diffusion of hexanes into an Et2O/
THF solution of 6Y-(iqn)2 placed in a -35 °C freezer in the