Coupling of aromatic N-Heterocycles mediated by group 3 complexes

Article abstract of DOI:10.1021/om900943m

Group 3 η²-N,C-pyridyl complexes supported by a ferrocene-diamide ligand have been known to mediate the coupling of η²-N,C-pyridyl and coordinated-pyridine ligands with a concomitant dearomatization of the pyridine ligand. Examples reported previously by us were limited to a few cases. In order to investigate the scope of the coupling reaction, various η²-N,C-pyridyl scandium complexes were isolated and characterized. Their reactivity toward other aromatic N-heterocycles is presented along with the characterization of the subsequent reaction products. The coupling reaction is favored by ortho substitution, the presence of fused aromatic rings on the pyridine ligand, and chelating substrates. In one instance, the product of the coupling reaction between a scandium rc2-N, C-pyridyl complex and 7,8-benzoquinoline could not be isolated because a subsequent isomerization reaction was favored. The coupling reaction is not restricted to η²-N,C-pyridyl fragments, and it proceeds also from CH₂ groups bound to the metal center and connected to a pyridine ligand. The reaction between η²-N,C-imidazolyl scandium complexes and 2,2'-bipyridine is also discussed.

Full text of DOI:10.1021/om900943m

Organometallics 2010, 29, 835–846 835
DOI: 10.1021/om900943m
Coupling of Aromatic N-Heterocycles Mediated by Group 3 Complexes
Colin T. Carver, Bryan N. Williams, Kevin R. Ogilby, and Paula L. Diaconescu*
Department of Chemistry & Biochemistry, University of California, Los Angeles, California 90095
Received October 27, 2009
Group 3 η2-N,C-pyridyl complexes supported by a ferrocene-diamide ligand have been known to
mediate the coupling of η2-N,C-pyridyl and coordinated-pyridine ligands with a concomitant
dearomatization of the pyridine ligand. Examples reported previously by us were limited to a few
cases. In order to investigate the scope of the coupling reaction, various η2-N,C-pyridyl scandium
complexes were isolated and characterized. Their reactivity toward other aromatic N-heterocycles is
presented along with the characterization of the subsequent reaction products. The coupling reaction
is favored by ortho substitution, the presence of fused aromatic rings on the pyridine ligand, and
chelating substrates. In one instance, the product of the coupling reaction between a scandium η2-N,
C-pyridyl complex and 7,8-benzoquinoline could not be isolated because a subsequent isomerization
reaction was favored. The coupling reaction is not restricted to η2-N,C-pyridyl fragments, and it
proceeds also from CH2 groups bound to the metal center and connected to a pyridine ligand. The
reaction between η2-N,C-imidazolyl scandium complexes and 2,20-bipyridine is also discussed.
Introduction
with functionalization reactions, such as the insertion of
unsaturated substrates, leading to derivative heterocyclic
structures.15-24
Alkyl complexes of d0fn metal centers have been shown to
react with C-H bonds by σ-bond metathesis.1-3 Among
substrates for C-H activation, aromatic N-heterocycles repre-
sent an important class of compounds because of their rele-
vance to biology4-7 and to the hydrodenitrogenation (HDN)
process.8-14 In some cases, the C-H activation event is coupled
We have reported that d0f n benzyl complexes25,26 sup-
ported by a ferrocene-diamide ligand, NNfc (NNfc = fc-
(NSitBuMe2)2, fc = 1,10-ferrocenylene), show diverse reacti-
vity with aromatic N-heterocyclic substrates.27-30 In all cases
studied by us so far, the initial C-H activation event was
followed by the coupling of two N-heterocycles, leading to
the dearomatization of one of the substrates. We have also
observed that this dearomatization poises the heterocycle for
ring-opening (1-methylimidazole, Scheme 1)29,30 or isomer-
ization (pyridines, Scheme 2).28 Since the coupling reaction is
common to both types of subsequent reactivity, we became
interested in determining its scope when group 3 alkyl
complexes are involved. Previous to our work, examples
of metal-mediated coupling of pyridines were limited to
*Corresponding author. E-mail: pld@chem.ucla.edu.
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836 Organometallics, Vol. 29, No. 4, 2010
Carver et al.
Scheme 1. Ring-Opening of 1-Methylimidazole Mediated by the
Scandium Alkyl Complex 1-CH2Ar
ortho-metalated2,14,17,34-49 complex 2-pyPh or 2-qnMe, res-
pectively, as the THF adduct (Scheme 2).28,29 Although
two isomers may exist for 2-pyPh or 2-qnMe, depending on the
relative orientation of the pyridyl and the coordinated THF
ligands, only one isomer was observed in solution for both
cases. For 2-phenylpyridine, it is difficult to make a definitive
structural assignment, since the isomer containing the THF
ligand coordinated next to the η2-N,C-pyridyl nitrogen atom
was more stable by only 0.9 kcal/mol than the one for which
THF is coordinated next to the η2-N,C-pyridyl carbon atom,
as assessed from DFT calculations. Furthermore, a different
situation was observed for the product of the reaction
between (NNfc)Sc(Me)(THF)2 and pyridine that forms
(NNfc)Sc(η2-N,C-pyridyl)(py), which was crystallographi-
cally characterized and showed that pyridine was coordi-
nated next to the η2-N,C-pyridyl nitrogen atom.27 DFT
calculations agreed with the experimental findings and in-
dicated that for (NNfc)Sc(η2-N,C-pyridyl)(py) the isolated
compound was more stable by 31.2 kcal/mol than its isomer.
However, for 8-methylquinoline, the difference between the
two isomers was 11.4 kcal/mol, in favor of the isomer for
which the THF ligand was coordinated next to the η2-N,C-
pyridyl carbon atom. The Jordan group has also reported that
η2-N,C-pyridyl zirconocene complexes exist as single isomers
in solution, with the exception of quinoline and 7,8-benzo-
quinoline, when both isomers were observed in solution.50
The C-H activation reaction was extended to 2-trimethyl-
silylpyridine, 2,6-lutidine, 7,8-benzoquinoline, and acridine
to give 2-pySi, 2-lut, 2-bqn, and 2-acr, respectively (Scheme 3).
All the reactions were carried out in toluene for 16 h, and the
reaction temperatures varied from room temperature (2-bqn),
to 35 °C (2-pySi), 50 °C (2-lut), and 70 °C (2-acr). All the
isolated products, except 2-pySi, were sparingly soluble in
hexanes and readily soluble in toluene and showed colors
varying from yellow (2-pySi, 2-lut) to orange (2-acr) and red
(2-bqn). The yields of all reactions were very good, ranging
from 76% for 2-acr to 99% for 2-lut; the new complexes were
Scheme 2. Coupling of Pyridines and Subsequent Isomerization
Mediated by the Scandium Alkyl Complex 1-CH2Ar
1
characterized by elemental analysis and H and 13C NMR
spectroscopy. Since only one isomer was observed in solution
for 2-pySi, 2-bqn, and 2-acr, DFT calculations and 1H NMR
spectroscopy experiments were used to establish its identity. It
was found that for 2-bqn and 2-acr the isomer for which THF
was coordinated next to the η2-N,C-pyridyl carbon atom was
alkali metals,31 tantalum,32 and one uncharacterized com-
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Article
Organometallics, Vol. 29, No. 4, 2010 837
Scheme 3. C-H Activation of Aromatic N-Heterocycles
Mediated by 1-CH2Ar
Figure 1. ORTEP representation of 2-lut with ellipsoids drawn
at 50% probability (hydrogen atoms were removed for clarity).
The reaction between 1-CH2Ar and excess pyridine gives a
mixture of products; by 1H NMR spectroscopy, it was
identified that some components of that mixture show sig-
nals in the olefinic region of the spectrum. At present, we believe
that multiple and competing reaction pathways are possible
with pyridine;28,29 the reaction mixtures proved intractable in
our hands. However, as reported earlier,28,29 if pyridine is
replaced by 2-phenylpyridine or 8-methylquinoline, one reac-
tion pathway is favored: the coupling of pyridine rings from the
more stable than the one for which THF was coordinated next
to the η2-N,C-pyridyl nitrogen atom (by 9.4 and 34.2 kcal/
mol, respectively). For 2-pySi, DFT calculations on the full
molecule indicated that the other isomer was more stable by
2.6 kcal/mol. Given that the calculated energy difference was
small, a nuclear Overhauser enhancement spectroscopy
(NOESY) experiment was undertaken. The NMR spectro-
scopy experiment showed that the isomer found in solution was
the one corresponding to the drawing in Scheme 3. In order to
understand the different results obtained from the DFT
calculations and the NOESY experiment, calculations were
also carried out by using a solvent correction. When benzene
was used as a solvent, the isomer detected by the NOESY
experiment was found to be more stable by 2.3 kcal/mol than
the other isomer. The new results do not invalidate the
calculations for the other complexes since calculations carried
out with or without solvent corrections usually follow similar
stability trends and such reversals are only to be suspected
when one method shows small differences in the energies of
the two isomers (likely less than 5 kcal/mol).
two aromatic heterocycles (Scheme 2, 3-pyPh-iqnMe and 3-qnMe
-
iqnMe). By heating the coupled products 3-pyPh-iqnMe and
3-qnMe-iqnMe, a subsequent isomerization took place (Sch-
eme 2).28 In the course of evaluating substrates that would
undergo this isomerization reaction, it was found that the C-C
coupling reaction is remarkably general.
The reaction of the complexes 2-pyPh, 2-pySi, 2-bqn, and 2-
acr with various pyridines (phenanthridine, 2,20-bipyridine,
and 3-methylisoquinoline) yielded the products 3-pyPh-phan,
3-pyPh-bipy, 3-pySi-iqnMe, 3-bqn-phan, and 3-acr-phan, which
ranged in color from blood red to brown (Table 1). During
the formation of all these products, the pyridine solvates (the
presumed intermediates before the coupling products) could
not be isolated or observed by 1H NMR spectroscopy.
All the complexes 3 were uniformly less soluble in hydro-
carbon solvents than their respective starting materials, a
property exploited in the case of 3-pyPh-phan, 3-bqn-phan,
and 3-acr-phan, for which analytically pure crystals were
collected directly from the reaction mixture by either
cooling or addition of n-pentane. Complexes 3 are charac-
terized by the chemical shift of the proton on the sp3 carbon
of the dearomatized pyridine that ranges from 8.01 ppm
in 3-acr-phan to 5.84 ppm in 3-pySi-iqnMe. In agreement with
the crystal structures (see below), the coupled products 3
exhibit C1 symmetry in solution as well, as probed by 1H and
13C spectroscopy (when the collection was practical, see
Experimental Section for details), because of the nonplanar
arrangement of the two coupled pyridines; the C-H acti-
vated complexes 2, for which the pyridyl and THF ligands
could assume a coplanar arrangement, exhibited Cs symme-
try in solution.
The complex 2-lut was also characterized by X-ray crystal-
lography (Figure 1), which indicated a κ3-N,C,C-coordination
of lutidine: Sc-CCH2, Sc-Cpy, and Sc-Npy distances were
2.3246(20), 2.6804(20) (the sum of the covalent radii for
51
scandium and carbon is 2.46 A), and 2.2703(16) A, respec-
˚
˚
tively. The Sc-CCH2 distance was slightly longer than that
25
˚
analogous in 1-CH2Ar (Sc-CCH2Ar, 2.2640(37) A), the
Sc-Cpy distance was shorter than the distances between scan-
dium and the ipso-carbon atoms of the ferrocene ligand
˚
(2.7279(18) and 2.7443(19) A), and the Sc-Npy distance was
similar to the distance between scandium and the nitrogen
donor of the coordinated pyridine (as opposed to the η2-N,C-
27
fc
2
˚
pyridyl one) in (NN )Sc(η -N,C-pyridyl)(py) (2.2758(27) A).
Next, the reactivity of the newly synthesized pyridyl
complexes toward pyridine substrates was investigated.
(51) Cordero, B.; Gomez, V.; Platero-Prats, A. E.; Reves, M.; Eche-
verria, J.; Cremades, E.; Barragan, F.; Alvarez, S. Dalton Trans. 2008,
2832–2838.
The complexes 3-pyPh-phan and 3-acr-phan were also
characterized by X-ray crystallography (Figure 2). Because

838 Organometallics, Vol. 29, No. 4, 2010
Table 1. Coupling of Aromatic N-Heterocyclesa
Carver et al.
a All reactions occurred in toluene or toluene/n-pentane at room temperature.
Figure 2. ORTEP representation of 3-pyPh-phan (left) and 3-acr-phan (right) with ellipsoids drawn at 50% probability (irrelevant
hydrogen atoms were removed for clarity).
of the larger size of the ring formed by coupling in 3-acr-phan
than in 3-pyPh-phan (six versus five atoms), the two bulky
heterocycles in 3-acr-phan can adopt a perpendicular orientation
relative to each other (see Figure SX3b in the Supporting In-
formation for a different view). The increased flexibility of the
six-membered ring in 3-acr-phan also allows the biheterocyclic
fragment to come in close proximity to the metal center, as
evidenced by the shorter scandium-nitrogen distances in
3-acr-phan than in 3-pyPh-phan (Sc-Namide, 2.0690(17) versus
˚
˚
2.0900(12) A; Sc-Npy, 2.2811(17) versus 2.2961(12) A). Fur-
thermore, the complex 3-acr-phan features a close contact bet-
ween scandium and the newly sp3-hybridized carbon atom (Sc-
Ph
˚
C distance of 2.8094(20) versus 3.0860(14) A in 3-py -phan; the
51
˚
sum of the covalent radii for scandium and carbon is 2.46 A).
It is also interesting to note that the iron-scandium
distance of 3.0063(5) A in 3-acr-phan is shorter than that of
˚

Article
Organometallics, Vol. 29, No. 4, 2010 839
Scheme 4. Reaction of 2-pyPh with 7,8-Benzoquinoline
3.1358(4) A in 3-pyPh-phan, and it is even shorter than the
˚
sum of covalent radii for iron and scandium (3.02 A).51 Both
˚
these distances are shorter than those in the other two coupled
˚
products characterized by X-ray crystallography: 3.2371(11) A
Ph
Me 28
.
for 3-pyPh-pyPh29 and 3.3156(8) A for 3-py -iqn
It is
˚
proposed that this feature is a direct consequence of the steric
crowding experienced by the amide substituents of the ferro-
cene ligand: the more these substituents are likely to interact
with the new biheterocyclic fragment, as in 3-acr-phan, the
further apart the two ferrocene nitrogen donors are pushed and
the closer the iron center is to scandium. This proposal is
supported by the inverse correlation between the scan-
dium-iron and the scandium-Nfc distances: the longest
Sc-Nfc distances are found in 3-acr-phan: 2.0804(17) and
Ph
2.0992(17) A versus 2.0556(12) and 2.0852(12) A in 3-py -
˚
˚
Ph
Ph
˚
phan, 2.0697(36) and 2.0706(35) A in 3-py -py , and
Ph
2.0505(25) and 2.0665(25) A in 3-py -iqn
Me 28
.
˚
There are several factors promoting the coupling reactions
of the C-H activated complexes 2 with pyridine substrates:
(1) Ortho-substituents accelerate the coupling reaction;
however, large substituents inhibit it, as evidenced by the fact
that in the coupling reaction of 2-pyPh with 2-phenylpyridine
most of 2-pyPh is recovered and only small amounts of 3-pyPh-
pyPh are formed. These observations are supported by the fact
that 3-pyPh-pyPh was found to be 7.2 kcal/mol higher in energy
than the corresponding noncoupled product (see the Supporting
Information for details). Although an X-ray crystal structure of
3-pyPh-pyPh was obtained,29 the reaction was not facile. In light
of the DFT results and experimental observations, it is likely
that the formation of 3-pyPh-pyPh is driven by its decomposition
to other stable products (a similar reaction starting from the
analogous yttrium complex will be reported elsewhere).
(2) The use of chelating substrates is beneficial, as illu-
strated by the reaction of 2-pyPh with 2-phenylpyridine
versus that with 2,20-bipyridine. While the reaction of 2-pyPh
with 2-phenylpyridine was sluggish even at elevated tem-
peratures and the isolation of 3-pyPh-pyPh in any reasonable
yield was difficult, the reaction of 2-pyPh with 2,20-bipyridine
was facile and the isolation of 3-pyPh-bipy in high yield was
possible (Table 1).
Figure 3. ORTEP representation of 4-pyPh-bqn with ellipsoids
drawn at 50% probability (irrelevant hydrogen atoms were
removed for clarity).
product was observed (Scheme 4). The final product was
identified as 4-pyPh-bqn, in which the sp3-hydrogen atom
migrated to the benzyl carbon of the dearomatized pyridine
ring (Figure 3).28 The energy difference between 3-pyPh-bqn
and 4-pyPh-bqn was calculated to be 6.2 kcal/mol in favor
of 4-pyPh-bqn. It is likely that the activation energy to
form 4-pyPh-bqn is slightly lower than that to form 3-pyPh-bqn,
making the two reactions competitive. Attempts to isolate
3-pyPh-bqn have been unsuccessful so far.
The complex 4-pyPh-bqn was characterized by 1H and 13
C
NMR spectroscopy, X-ray diffraction (Figure 3), and ele-
mental analysis. It is important to note that in order to form
4-pyPh-bqn, a 1,3-hydrogen migration is required (Scheme 4),
an event different than the isomerization reactions pre-
viously reported by our group, when a 1,4-hydrogen migra-
tion was observed.28 It is likely that the 1,4-hydrogen
migration in 3-pyPh-bqn is not favorable since it would result
in the formation of an sp3 carbon that would disrupt the
aromaticity of the two benzoquinoline phenyl rings, a situa-
tion not encountered for the 1,3-hydrogen migration.
(3) Fused aromatic rings on the coupling partner have an
accelerating effect. The reaction of 2-pyPh with isoquinoline
to form 3-pyPh-iqn was significantly faster than the reaction
of 2-pyPh with 5,6,7,8-tetrahydroisoquinoline, from which
no coupling product could be isolated.
The coupling reaction between 2-pyPh and 7,8-benzoqui-
noline was also attempted. The monitoring of the reaction
1
mixture by H NMR spectroscopy indicated that the con-
version to a C1-symmetric complex, identified as the coupled
product 3-pyPh-bqn, was very slow (several days at room
temperature). However, before the formation of 3-pyPh-bqn
was complete, the formation of a second, Cs-symmetric
It became apparent that the coupling reaction was not
restricted to η2-N,C-pyridyl complexes when an analogous

840 Organometallics, Vol. 29, No. 4, 2010
Carver et al.
Figure 4. ORTEP representation of 5-lut-iqnMe (left) and 6-pyEt-iqnMe (right) with ellipsoids drawn at 50% probability (irrelevant
hydrogen atoms were removed for clarity).
Scheme 5. Coupling of 2-Picoline and 3-Methylisoquinoline Mediated by 1M-CH2Ph (M = Y, La)
reaction was observed from the CH2 group of 2-lut (eq 1). The
reaction of 2-lut with 3-methylisoquinoline led to a coupled
product, 5-lut-iqnMe, in which the two heterocyclic rings were
bridged by a methylene group, isolated in 99% yield. The
reaction was rather facile; the monitoring of the reaction
mixture in C6D6 by 1H NMR spectroscopy indicated that the
reaction was complete by the time a spectrum could be collected
at room temperature. The complex 5-lut-iqnMe was also char-
acterized by X-ray crystallography (Figure 4). The presence of
a methylene group in the six-membered metallocycle allows a
near-perpendicular orientation of the two heterocyclic rings, as
was observed for 3-acr-phan (Figure 2).
lanthanum, an analogous experiment showed that the rotation
of the coordinated picoline is faster than the NMR spectroscopy
time scale at room temperature; at -50 °C, both isomers are
present in solution (see the Supporting Information for details).
Also, the preferential sp3 C-H activation is supported by the
fact that the four η2-N,C-pyridyl isomers were all less stable
than 2Y-pic by as little as 5.7 kcal/mol and as much as 13.6 kcal/
mol (see the Supporting Information for more details).
The coupling reaction between 2M-pic and 3-methylisoqui-
noline (Scheme 4) led indeed to a product, 5M-pic-iqnMe (M =
Y, La), analogous to 5-lut-iqnMe. One dissimilarity was ob-
served between the complexes of type 5 and the coupled
products discussed earlier, 3: whereas all compounds 3 show
markedly different (and more vibrant) colors than their parent
compounds 2, 5-lut-iqnMe and 5M-pic-iqnMe are either yellow
or orange. The different color change for the two types of
coupled products correlates with a larger HOMO-LUMO
gap for 5-lut-iqnMe (0.0455 eV) than for 3-pyPh-iqnMe (0.0371
eV), as estimated from DFT calculations. Another difference
between the complexes 3 and 5 was the fact that, in contrast
In order to probe whether the formation of 5-lut-iqnMe was
restricted to scandium complexes, the yttrium and lanthanum
compounds obtained by the C-H activation of 2-picoline, 2M-
pic (M = Y, La), were isolated and characterized (Scheme 5). It
is interesting to note that the C-H activation of 2-picoline by
1M-CH2Ph gives exclusively 2M-pic, featuring an sp3-CMe-M
bond instead of an sp2-Cpyridyl-M bond. Similar results have
been reported for some yttrium52 and thorium alkyl com-
plexes.41 The C-H activation of the methyl group was con-
firmed by X-ray crystallography for 2Y-pic. However, because
of the poor quality of the data set, it was not possible to deter-
mine the exact isomer formed as a consequence of 2-picoline
coordination: the one with the methyl group pointing toward
the methylene carbon (2Y-pic) or the one with the methyl group
pointing away from it (2Y-pic0). DFT calculations indicated that
2Y-pic was more stable than 2Y-pic0 by 1.6 kcal/mol, a value that
may explain why the two isomers cocrystallized. However, 2Y-
pic is found in solution, as assessed by a 1H NOESY experiment
(see the Supporting Information for details). In the case of
to 3-pyPh-iqnMe and 3-qnMe-iqnMe 28
prolonged heating
,
of 5-lut-iqnMe or 5M-pic-iqnMe did not induce an isomerization
reaction (as assessed by 1H NMR spectroscopy).
In light of the somewhat unexpected coupling reactivity
of 2-lut toward 3-methylisoquinoline, the reactivity of the
(52) Duchateau, R.; Brussee, E. A. C.; Meetsma, A.; Teuben, J. H.
Organometallics 1997, 16, 5506–5516.

Article
Organometallics, Vol. 29, No. 4, 2010 841
Figure 5. ORTEP representation of [2-im]2 (left, thermal ellipsoids drawn at 50% probability) and 3-im-bipy (right, thermal ellipsoids
drawn at 35% probability). Irrelevant hydrogen atoms were removed for clarity.
Scheme 6. Coupling of 1-Methylimidazole and 2,20-Bipyridine
previously reported compound 2-pyEt-py, which contains a
Sc-CH2CH2-pyridine motif,27 toward 3-methylisoquinoline
was also investigated. Consequently (eq 2), the coupling
product 6-pyEt-iqnMe (Figure 4) was formed by the addition
of 1 equiv of 3-methylisoquinoline to 2-pyEt-py after heating
to 70 °C for 16 h. It is interesting to note that by effecting the
coupling with 3-methylisoquinoline, this substrate was pre-
ferred to pyridine, which was present in the reaction mixture
since it had to decoordinate from 2-pyEt-py. Despite the
presence of two different pyridines, 6-pyEt-iqnMe was isolated
in 86% yield and no other products were observed in the 1H
NMR spectrum of the reaction mixture. As was the case for
5-lut-iqnMe, prolonged heating of 6-pyEt-iqn showed no ob-
servable change by 1H NMR spectroscopy.
In an attempt to determine whether the nucleophilic attack
of an η2-imidazolyl ligand is capable of leading to the ring-
opening of other N-heterocycles and generalize the ring-
opening reaction of 1-methylimidazole previously reported
by our group (Scheme 1),29 efforts were made to prepare
solvates and coupled products starting from a (NNfc)Sc(η2-
N,C-imidazolyl) fragment. Although the 1-methylimidazole
solvate of the η2-imidazolyl complex Sc(fc[NSitBuMe2]2)(η2-
N,C-2-(1-methylimidazolyl)(1-methylimidazole), 2-im-im,
was isolated (Scheme 6), all attempts to isolate a THF or
nonchelating-pyridine solvate of (NNfc)Sc(η2-N,C-imi-
dazolyl) resulted in the formation of [(NNfc)Sc(μ2,κ2-N,C-
2-(1-methylimidazolyl)]2, [2-im]2 (Scheme 6), in which the
two scandium centers are bridged by two imidazolyl ligands.
The complex [2-im]2 was characterized by X-ray crystal-
lography (Figure 5) and features an iron-scandium distance
of 3.081 A, which is shorter than the corresponding one in 1-
˚
25
˚
CH2Ar (3.1582(17) A). The iron-scandium distance was
previously correlated by us to the electrophilicity of the
scandium center in alkyl complexes: the shorter the distance,
the more electrophilic the scandium center.25 However, the
different ligands in [2-im]2 (bridging imidazolyl versus alkyl)
and the insolubility of [2-im]2 invalidate a direct comparison
between the reactivity of 1-CH2Ar and that of [2-im]2.
Although neither 2-im-im nor [2-im]2 reacted with pyri-
dines, both complexes reacted with 2,20-bipyridine at 50 °C
and yielded the bright red-orange coupled product 3-im-bipy
(Scheme 6, Figure 5). Attempts to study a further transfor-
mation of 3-im-bipy by prolonged heating (72 h at 70 °C)
were not successful (no difference was observed by 1H NMR
spectroscopy).
Conclusions
We have shown that the C-C coupling between η2-N,C-
pyridyl and pyridine ligands coordinated to a group 3 metal
center supported by a ferrocene-diamide ligand is rather
general; in fact, the list of complexes reported herein is by
no means exhaustive. The observed coupling can be ratio-
nalized by invoking standard reactivity arguments: the pyr-
idyl fragments coordinated to early transition metals possess
a polarized metal-carbon bond, rendering the carbon center

842 Organometallics, Vol. 29, No. 4, 2010
Carver et al.
1
toluene, and filtered through Celite. Yield: 450 mg, 86%. H
nucleophilic. Meanwhile, the ortho positions of coordinated
pyridine ligands contain an electrophilic carbon center, as
seen in pyridinium salts. A report by Cronin et al. showed
that phenanthridinium salts reacted with amines: nucleophi-
lic attack of a primary amine on the iminium moiety of the
heteroaromatic ring and cyclization to form a five-mem-
bered ring, followed by hydride loss, yielded a rearomatized
phenanthridinium derivative.53,54 Three factors were
found to influence the outcome of the C-C coupling reac-
tions: (1) the use of bulky ortho substituents on the η2-N,C-
pyridyl ligands promotes the coupling of the two hetero-
cycles; (2) the use of chelating substrates is beneficial; (3)
fused aromatic rings on the coupling partner have an accel-
erating effect.
The coupling and dearomatization reaction is not re-
stricted to η2-N,C-pyridyl fragments, and it can proceed
from methylene or ethylene groups bound to the metal center
and connected to a pyridine ligand. Also, the reaction is not
limited to the nucleophilic attack of η2-N,C-pyridyl ligands,
and it can be accomplished by the attack of η2-N,C-imida-
zolyl ligands on bipy. Unfortunately, reactions with mono-
pyridines could be achieved neither from [2-im]2, likely
because of its high stability and insolubility, nor from 2-im-
im, because of the lower Lewis basicity of pyridines than
that of 1-methylimidazole that does not allow imidazole
displacement. Given that in HDN catalysis the dearomatiza-
tion of N-heterocycles precedes ring-opening and nitrogen
removal, the dearomatization reactions presented herein are
relevant to the modeling of HDN processes, although the
ring-opening of pyridines remains a tantalizing but difficult
goal.
NMR (500 MHz, C6D6), δ (ppm): 7.77 (d, 1H, py), 7.27-7.21
(m, 2H, py), 4.20 (br s, 2H, fc-CH), 4.17 (s, 4H, OCH2CH2), 4.11
(br s, 2H, fc-CH), 3.76 (br s, 2H, fc-CH), 3.28 (br s, 2H, fc-CH),
1.50 (s, 4H, OCH2CH2), 0.90 (s, 18H, SiC(CH3)3), 0.48 (s, 9H,
Si(CH3)3), -0.00 and -0.31 (s, 12H, Si(CH3)2). 13C NMR (126
MHz, C6D6), δ (ppm): 162.3 (py), 132.0 (py), 129.6 (py), 128.8
(py), 101.2 (fc-CN), 72.7 (OCH2CH2), 67.9 (fc-CH), 66.5 (fc-
CH), 27.8 (SiC(CH3)3), 25.5 (OCH2CH2), 20.4 (SiC(CH3)3),
-0.7 (SiCH3), -2.3 and -3.2 (Si(CH3)2). Anal. Calcd (%) for
C34H58FeN3OSi2Sc: C, 57.52; H, 8.23; N, 5.92. Found: C, 57.41;
H, 8.27; N, 5.91.
Synthesis of 2-lut. 1-CH2Ar (500 mg, 0.737 mmol) was com-
bined with 1.03 equiv of 2,6-lutidine (81.3 mg, 0.758 mmol) in
toluene and stirred for 16 h at 50 °C. The volatiles were removed
under reduced pressure, and the resulting yellow solid was
washed with hexanes (2 mL), extracted in toluene, and filtered
through Celite. Yield: 485 mg, 99%. 1H NMR (500 MHz,
C6D6), δ (ppm): 6.98 (t, 1H, lut-CH), 6.84 (d, 1H, lut-CH),
6.17 (d, 1H, lut-CH), 4.09 (s, 4H, fc-CH), 3.96 (s, 4H,
OCH2CH2), 3.34 (s, 4H, fc-CH), 2.39 (s, 2H, Sc-CH2), 2.35 (s,
3H, lut-CH3), 1.38 (s, 4H, OCH2CH2), 0.94 (s, 18H, SiC(CH3)3),
0.17 (s, 12H, Si(CH3)2). 13C NMR (126 MHz, C6D6), δ (ppm):
169.8 (lut), 155.0 (lut), 137.6 (lut), 120.4 (lut), 112.8 (lut), 101.5
(fc-CN), 71.8 (OCH2CH2), 67.9 (fc-CH), 67.6 (fc-CH), 49.9 (Sc-
CH2), 27.9 (SiC(CH3)3), 25.1 (OCH2CH2), 24.3 (lut-CH3), 20.4
(SiC(CH3)3), -2.3 (Si(CH3)2). Anal. Calcd (%) for C33H54Fe-
N3OSi2Sc: C, 59.53; H, 8.17; N, 6.31. Found: C, 59.62; H, 8.35;
N, 6.31.
Synthesis of 2-bqn. 1-CH2Ar (400 mg, 0.589 mmol) was
combined with 1 equiv of 7,8-benzoquinoline (105.6 mg, 0.589
mmol) in toluene and stirred for 16 h at 25 °C. The volatiles were
removed under reduced pressure, and the resulting yellow solid
was washed with hexanes (2 mL), extracted in toluene, and
filtered through Celite. Yield: 351 mg, 81%. 1H NMR (500
MHz, C6D6), δ (ppm): 9.56 (d, 1H, bqn), 8.15 (d, 1H, bqn), 7.87
(d, 1H, bqn), 7.61, (t, 1H, bqn), 7.52 (d, 1H, bqn), 7.43, (t, 1H,
bqn), 7.41 (d, 1H, bqn), 4.39 (s, 2H, fc-CH), 4.25 (s, 4H,
OCH2CH2), 4.18 (s, 2H, fc-CH), 4.05 (s, 2H, fc-CH), 3.33 (s,
2H, fc-CH), 1.52 (s, 4H, OCH2CH2), 0.74 (s, 18H, SiC(CH3)3),
-0.27 and -0.33 (s, 12H, Si(CH3)2). 13C NMR (126 MHz,
C6D6), δ (ppm): 143.0 (bqn), 134.3 (bqn), 133.6 (bqn), 129.3
(bqn), 128.6 (bqn), 127.0 (bqn), 126.7 (bqn), 126.4 (bqn), 126.2
(bqn), 125.8 (bqn), 101.6 (fc-C-N), 72.7 (OCH2CH2), 68.6 (fc-
CH), 68.1 (fc-CH), 67.3 (fc-CH), 66.8 (fc-CH), 27.5
(SiC(CH3)3), 25.5 (OCH2CH2), 20.1 (SiC(CH3)3), -2.4 and
-3.0 (Si(CH3)2). Anal. Calcd (%) for C39H54FeN3OSi2Sc: C,
63.48; H, 7.37; N, 5.69. Found: C, 63.12; H, 7.19; N, 5.50.
Synthesis of 2-acr. 1-CH2Ar (300 mg, 0.442 mmol) was
combined with 1.05 equiv of acridine (83.1 mg, 0.464 mmol) in
toluene (10 mL) and stirred for 16 h at 70 °C. The volatiles were
removed under reduced pressure, and the resulting yellow solid
was washed with hexanes (2 mL), extracted in toluene, and
filtered through Celite. Yield: 248 mg, 76%. 1H NMR (600
MHz, C6D6), δ (ppm): 8.59 (d, 1H, acr), 8.28 (s, 1H, acr), 8.25 (d,
1H, acr), 7.68 (t, 1H, acr), 7.06 (t, 2H, acr), 7.47 (t, 1H, acr), 7.12
(t, 1H, acr), 4.36 (s, 2H, fc-CH), 4.31 (s, 4H, OCH2CH2), 4.18 (s,
2H, fc-CH), 4.04 (s, 2H, fc-CH), 3.31 (s, 2H, fc-CH), 1.59 (s, 4H,
OCH2CH2), 0.74 (s, 18H, SiC(CH3)3), -0.37 and -0.41 (s, 12H,
Si(CH3)2). 13C NMR (150 MHz, C6D6), δ (ppm): 160.0 (acr),
145.1 (acr), 138.2 (acr), 136.5 (acr), 130.0 (acr), 129.1 (acr), 127.5
(acr), 127.3 (acr), 126.3 (acr), 126.1 (acr), 125.0 (acr), 123.8 (acr),
101.6 (fc-CN), 72.2 (OCH2CH2), 69.0 (fc-CH), 68.1 (fc-CH),
67.0 (fc-CH), 66.9 (fc-CH), 27.6 (SiC(CH3)3), 25.5 (OCH2CH2),
20.3 (SiC(CH3)3), -2.2 and -2.8 (Si(CH3)2). Anal. Calcd (%)
for C39H54FeN3OSi2Sc: C, 63.48; H, 7.37; N, 5.69; Found: C,
64.09; H, 7.45; N, 5.72.
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 Grubbs55 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. K(CH2Xy-3,5), KCH2Ph, 1-CH2Ar, 1Y-CH2Ph, and 1La-
CH2Ph were prepared following published procedures.25,28,56 The
aromatic heterocycles were distilled or recrystallized before use;
all other materials were used as received. 1H NMR spectra were
recorded on Bruker300, Bruker500, or Bruker600 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, and by Midwest Microlab,
LLC, Indianapolis, IN.
Synthesis of 2-pySi. 1-CH2Ar (500 mg, 0.737 mmol) was
combined with 1 equiv of 2-trimethylsilylpyridine (110 mg,
0.758 mmol) in toluene and stirred for 16 h at 35 °C. The
volatiles were removed under reduced pressure, and the result-
ing yellow solid was washed with hexanes (2 mL), extracted in
(53) Parenty, A. D. C.; Smith, L. V.; Pickering, A. L.; Long, D.-L.;
Cronin, L. J. Org. Chem. 2004, 69, 5934–5946.
(54) Parenty, A. D. C.; Song, Y.-F.; Richmond, C. J.; Cronin, L. Org.
Lett. 2007, 9, 2253–2256.
(55) Pangborn, A. B.; Giardello, M. A.; Grubbs, R. H.; Rosen, R. K.;
Timmers, F. J. Organometallics 1996, 15, 1518–1520.
(56) Miller, K. L.; Williams, B. N.; Benitez, D.; Carver, C. T.; Ogilby,
K. R.; Tkatchouk, E.; Goddard, W. A.; Diaconescu, P. L. J. Am. Chem.
Soc. 2010, 132, 342-355.
Synthesis of 3-pyPh-phan. 2-pyPh (120 mg, 0.168 mmol) was
dissolved in toluene (2 mL) and combined with a solution of
phenanthridine (30.1 mg, 0.168 mmol) in toluene (1 mL). The

Article
Organometallics, Vol. 29, No. 4, 2010 843
solution was allowed to stand at room temperature for 2 h
without stirring. Analytically pure red crystals were collected
directly from the reaction mixture. Yield: 106.3 mg, 77%. H
mmol) was dissolved in n-pentane (2 mL). The solutions were
combined and allowed to stand at room temperature for 30 min
before cooling to -35 °C overnight. Analytically pure red
crystals were collected the next morning. Yield: 168.7 mg,
1
NMR (600 MHz, C4D8O), δ (ppm): 8.35 (t, 1H, pyPh-phan),
8.01 (d, 1H, pyPh-phan), 7.96 (d, 2H, pyPh-phan), 7.91, (d, 1H,
pyPh-phan), 7.79 (d, 1H, pyPh-phan), 7.74, (d, 1H, pyPh-phan),
7.65-7.58 (m, 3H, pyPh-phan), 7.29 (t, 1H, pyPh-phan), 7.19 (t,
1H, pyPh-phan), 7.16-7.12 (m, 2H, pyPh-phan), 7.02 (t, 1H,
pyPh-phan), 6.70 (d, 1H, pyPh-phan), 6.65 (t, 1H, pyPh-phan),
5.96 (s, 1H, sp3-CH), 4.41 (br s, 2H, fc-CH), 3.96 (s, 2H, fc-CH),
3.52 (br s, 1H, fc-CH), 3.19 (br s, 1H, fc-CH), 2.31 (s, 2H, fc-
CH), 0.44 and 0.29 (br s, 18H, SiC(CH3)3), -0.21, -0.26, -0.64,
1
91% as the first crop from toluene/n-pentane. H NMR (600
MHz, C6D6), δ (ppm): 8.98 (d, 1H, bqn-phan), 8.02 (d, 1H, bqn-
phan), 7.87 (d, 1H, bqn-phan), 7.69 (t, 1H, bqn-phan), 7.58 (d,
1H, bqn-phan), 7.54 (d, 1H, bqn-phan), 7.43 (d, 1H, bqn-phan),
7.34 (t, 1H, bqn-phan), 7.30 (q, 2H, bqn-phan), 7.21 (t, 2H, bqn-
phan), 7.19 (d, 1H, bqn-phan), 7.02 (d, 2H, bqn-phan), 6.94 (t,
1H, bqn-phan), 6.11 (s, 1H, sp3-CH), 4.47 (s, 1H, fc-CH), 4.21 (s,
1H, fc-CH), 4.03 (s, 1H, fc-CH), 3.87 (br s, 3H, fc-CH), 3.67 (s,
1H, fc-CH), 3.01 (s, 1H, fc-CH), 0.63 and 0.23 (s, 18H, SiC-
(CH3)3), 0.23 (br s, 6H, Si(CH3)2), 0.05 and 0.02 (s, 6H, Si-
(CH3)2). 13C NMR (150 MHz, C6D6), δ (ppm): 166.2 (bqn-
phan), 152.8 (bqn-phan), 145.9 (bqn-phan), 137.9 (bqn-phan),
135.2 (bqn-phan), 134.1 (bqn-phan), 130.2 (bqn-phan), 130.0
(bqn-phan), 129.8 (bqn-phan), 129.5 (bqn-phan), 129.3 (bqn-
phan), 128.8 (bqn-phan), 126.7 (bqn-phan), 126.2 (bqn-phan),
125.7 (bqn-phan), 125.6 (bqn-phan), 124.7 (bqn-phan), 124.1
(bqn-phan), 124.0 (bqn-phan), 122.9 (bqn-phan), 122.3 (bqn-
phan), 119.3 (bqn-phan), 118.2 (bqn-phan), 101.6 (fc-CN),
100.9 (fc-CN), 71.6, 69.7, 69.2, 68.7, 68.0, 67.9, 67.0, and 65.8
(fc-CH), 27.2 and 26.8 (SiC(CH3)3), 19.8 and 19.4 (SiC(CH3)3),
-2.5, -2.6, -3.0, and -4.7 (Si(CH3)2). Anal. Calcd (%) for
and -0.73 (s, 12H, Si(CH3)2). The limited solubility of 3-pyPh
-
phan prevented the collection of its 13C NMR spectrum. Anal.
Calcd (%) for C46H55FeN4ScSi2: C, 67.30; H, 6.75; N, 6.83.
Found: C, 67.36; H, 6.75; N, 6.87.
Synthesis of 3-pyPh-bipy. 2-pyPh (120 mg, 0.168 mmol) was
combined with 1 equiv of 2,20-bipyridine (26.3 mg, 0.168 mmol)
in toluene (10 mL) and stirred overnight at 50 °C. The volatiles
were removed under reduced pressure, and the resulting orange-
brown solid was washed with hexanes, extracted in toluene, and
filtered through Celite. Yield: 114.2 mg, 85.2% as two crops
from toluene/n-pentane. 1H NMR (500 MHz, C6D6), δ (ppm):
9.32 (d, 1H, pyPh-bipy), 7.77 (d, 2H, pyPh-bipy), 7.40 (d, 1H,
pyPh-bipy), 7.35 (t, 2H, pyPh-bipy), 7.05 (t, 1H, pyPh-bipy), 7.02
(t, 1H, pyPh-bipy), 6.90 (t, 1H, pyPh-bipy), 6.68 (d, 1H, pyPh
-
C48H55FeN4ScSi2 0.5(toluene): C, 69.42; H, 6.67; N, 6.29.
3
bipy), 6.54 (t, 1H, pyPh-bipy), 6.42 (t, 1H, pyPh-bipy), 6.13 (d,
1H, sp3-CH), 5.70 (s, 1H, pyPh-bipy), 5.33 (dd, 1H, pyPh-bipy),
4.29, 4.22, 3.96, 3.84, 3.69, 3.47, 3.34, and 1.85 (s, 8H, fc-CH),
0.85 and 0.73 (br s, 18H, SiC(CH3)3), 0.37, 0.28, -0.23, and
-0.26 (s, 12H, Si(CH3)2). 13C NMR (150 MHz, C6D6), δ (ppm):
168.2 (pyPh-bipy), 160.1 (pyPh-bipy), 159.9 (pyPh-bipy), 152.2
Found: C, 69.38; H, 6.62; N, 6.24.
Synthesis of 3-acr-phan. 2-acr (222.6 mg, 0.301 mmol) was
combined with 1.05 equiv of phenanthridine (56.7 mg, 0.316
mmol) in toluene (10 mL). The reaction mixture was stirred
overnight at room temperature. The volatiles were removed
under reduced pressure, and the resulting orange-brown solid
was washed with hexanes, toluene, and diethyl ether, extracted
in THF, and filtered through Celite. Yield: 222.6 mg, 87.4%.
Crystals suitable for elemental analysis were obtained directly
from a reaction run in diethyl ether by adding n-pentane to the
reaction mixture and cooling to -35 °C after the reaction was
complete. 1H NMR (600 MHz, C6D6), δ (ppm): 8.75 (d, 1H, acr-
phan), 8.09 (s, 1H, acr-phan), 8.01 (s, 1H, sp3-CH), 7.99, (d, 1H,
acr-phan), 7.94 (d, 1H, acr-phan), 7.92 (d, 1H, acr-phan), 7.57 (t,
1H, acr-phan), 7.48 (d, 1H, acr-phan), 7.39 (d, 1H, acr-phan),
7.33 (t, 1H, acr-phan), 7.27 (t, 1H, acr-phan), 7.19 (t, 1H, acr-
phan), 7.18 (d, 1H, acr-phan), 7.14 (d, 2H, acr-phan), 6.83 (t,
1H, acr-phan), 6.68 (t, 1H, acr-phan), 4.32 (s, 1H, fc-CH), 4.23
(s, 1H, fc-CH), 4.13 (br s, 2H, fc-CH), 3.84 (s, 1H, fc-CH), 3.77
(s, 1H, fc-CH), 3.66 (s, 1H, fc-CH), 3.42 (s, 1H, fc-CH), 0.99 and
0.60 (s, 18H, SiC(CH3)3), 0.32, -0.21, -0.62, and -1.13 (s, 12H,
Si(CH3)2). The limited solubility of 3-acr-phan prevented the
collection of its 13C NMR spectrum. Anal. Calcd (%) for
C48H55FeN4ScSi2: C, 68.23; H, 6.56; N, 6.63. Found: C, 68.54;
H, 6.32; N, 6.53.
(pyPh-bipy), 148.7 (pyPh-bipy), 140.6 (pyPh-bipy), 138.4 (pyPh
-
bipy), 137.3 (pyPh-bipy), 130.1 (pyPh-bipy), 129.3 (pyPh-bipy),
129.1 (pyPh-bipy), 124.9 (pyPh-bipy), 120.5 (pyPh-bipy), 119.6
(pyPh-bipy), 114.0 (pyPh-bipy), 100.2 (fc-CN), 99.0 (fc-CN), 98.2
(pyPh-bipy), 70.6 (fc-CH), 70.1 (fc-CH), 69.3 (fc-CH), 68.6 (fc-C-
H), 67.8 (pyPh-bipy), 66.2 (fc-CH), 65.7 (fc-CH), 65.6 (fc-CH),
64.4 (pyPh-bipy), 27.8 and 27.6 (SiC(CH3)3), 20.4 and 20.1
(SiC(CH3)3), -1.1, -2.7, -3.0, and -4.4 (Si(CH3)2). Anal.
Calcd (%) for C43H54FeN5ScSi2: C, 64.73; H, 6.82; N, 8.72.
Found: C, 64.97; H, 6.74; N, 8.76.
Synthesis of 3-pySi-iqnMe. 2-pySi (200 mg, 0.293 mmol) was
combined with 3-methylisoquinoline (40.3 mg, 0.293 mmol) in
toluene (10 mL) and stirred for 1 h at room temperature. The
volatiles were removed under reduced pressure, and the result-
ing red solid was washed with hexanes, extracted in toluene, and
filtered through Celite. Yield: 219 mg, 99% (precipitate from
1
toluene). H NMR (500 MHz, C6D6), δ (ppm): 7.25-7.19 (m,
2H, pySi-iqnMe), 7.08-6.99 (m, 4H, pySi-iqnMe), 6.67 (d, 1H,
pySi-iqnMe), 5.84 (s, 1H, sp3-CH) 5.66 (s, 1H, pySi-iqnMe), 4.26
(s, 1H, fc-CH), 4.19 (s, 1H, fc-CH), 4.04 (s, 1H, fc-CH), 3.99 (s,
1H, fc-CH), 3.48 (s, 1H, fc-CH), 3.40 (s, 1H, fc-CH), 3.39 (s, 1H,
fc-CH), 3.30 (s, 1H, fc-CH), 2.28 (s, 3H, iqn-CH3), 0.88 and 0.79
(s, 18H, SiC(CH3)3), 0.33 (s, 9H, Si(CH3)3), -0.05, -0.09,
-0.18, and -0.37 (s, 12H, Si(CH3)2). 13C NMR (126 MHz,
C6D6), δ (ppm): 166.9 (pySi-iqnMe), 165.4 (pySi-iqnMe), 152.9
(pySi-iqnMe), 139.3 (pySi-iqnMe), 136.2 (pySi-iqnMe), 129.7 (pySi-
iqnMe), 128.6 (pySi-iqnMe), 127.5 (pySi-iqnMe), 127.1 (pySi-
iqnMe), 126.7 (pySi-iqnMe), 125.7 (pySi-iqnMe), 122.9 (pySi-
iqnMe), 122.4 (pySi-iqnMe), 121.2 (pySi-iqnMe), 98.6 (fc-CN),
98.4 (fc-CN), 97.8 (pySi-iqnMe), 69.7 (fc-CH), 69.6 (fc-CH),
69.1 (fc-CH), 69.0 (fc-CH), 68.6 (fc-CH), 68.5 (fc-CH), 68.1
(fc-CH), 67.5 (pySi-iqnMe), 67.1 (fc-CH), 27.8 and 27.6
(SiC(CH3)3), 23.6 (iqnMe), 20.3 and 19.9 (SiC(CH3)3), -0.5
(Si(CH3)2), -2.6, -3.4, and -4.3 (Si(CH3)2). Anal. Calcd (%)
Synthesis of 4-pyPh-bqn. 2-pyPh (200 mg, 0.280 mmol) was
combined with 1 equiv of 7,8-benzoquinoline (50.2 mg, 0.280
mmol) in C6D6 (1.5 mL). The reaction was allowed to stand at
room temperature for 21 days and at 50 °C for 3 days while
monitoring by 1H NMR spectroscopy. When the reaction
mixture contained an approximate 1:1.1 ratio of 2-pyPh to 4-
pyPh-bqn and almost no 3-pyPh-bqn, the reaction was stopped.
The volatiles were removed under reduced pressure, and the
resulting dark green, oily solid was washed with hexanes, while
the remaining orange solid was extracted with toluene and
filtered through Celite. 1H NMR spectroscopy showed that
the green hexanes fraction contained mainly (>90%) 2-pyPh
,
while the orange toluene fraction contained mainly 4-pyPh-bqn.
1
Yield: 128 mg, 55.6%. H NMR (500 MHz, C6D6), δ (ppm):
7.88 (d, 1H, pyPh-bqn), 7.68 (t, 3H, pyPh-bqn), 7.47 (d, 1H, pyPh
-
for [C40H59FeN4ScSi2]2 toluene: C, 63.17; H, 7.68; N, 6.77.
bqn), 7.37 (t, 1H, pyPh-bqn), 7.29 (d, 1H, pyPh-bqn), 7.23 (t, 2H,
pyPh-bqn), 7.19 (t, 1H, pyPh-bqn), 7.07-7.00 (m, 3H, pyPh-bqn),
6.72 (d, 1H, pyPh-bqn), 5.28 (t, 1H, pyPh-bqn), 4.29 (d, 2H, bqn-
CH2), 4.07, 4.01, 3.36, and 2.41 (s, 2H, fc-CH), 0.70 (s, 18H,
3
Found: C, 63.23; H, 7.86; N, 6.54.
Synthesis of 3-bqn-phan. 2-bqn (150 mg, 0.207 mmol) was
dissolved in toluene (3 mL), and phenanthridine (37.1 mg, 0.207

844 Organometallics, Vol. 29, No. 4, 2010
Carver et al.
SiC(CH3)3), 0.17 and 0.11 (s, 6H, Si(CH3)2). 13C NMR (126
MHz, C6D6), δ (ppm): 162.1 (pyPh-bqn), 157.5 (pyPh-bqn), 146.0
(Si(CH3)2). Anal. Calcd (%) for C34H51N4FeLaSi2: C, 53.26;
H, 6.70; N, 7.31. Found: C, 53.26; H, 6.52; N, 6.92.
(pyPh-bqn), 144.8 (pyPh-bqn), 139.4 (pyPh-bqn), 138.4 (pyPh
-
Synthesis of 5Y-pic-iqnMe. 2Y-pic (132.1 mg, 0.184 mmol) and
2 equiv of 3-methylisoquinoline (54.9 mg, 0.383 mmol) were
combined in a capped 20 mL scintillation vial and stirred for 2 h
in toluene at room temperature. The volatiles were removed
under reduced pressure, and the resulting crude mixture was
dissolved in n-pentane and left at -35 °C overnight to precipi-
tate 5Y-pic-iqnMe. Yield: 49.6% (85.8 mg, 0.0942 mmol) of a red-
bqn), 135.2 (pyPh-bqn), 130.2 (pyPh-bqn), 130.1 (pyPh-bqn),
130.0 (pyPh-bqn), 129.4 (pyPh-bqn), 129.3 (pyPh-bqn), 128.8
(pyPh-bqn), 128.7 (pyPh-bqn), 128.6 (pyPh-bqn), 127.5 (pyPh
-
bqn), 127.2 (pyPh-bqn), 125.7 (pyPh-bqn), 124.9 (pyPh-bqn),
122.6 (pyPh-bqn), 120.7 (pyPh-bqn), 120.6 (pyPh-bqn), 120.2
(pyPh-bqn), 113.2 (pyPh-bqn), 103.5 (pyPh-bqn), 99.1 (fc-CN),
69.4, 68.4, 68.2, and 67.3 (fc-CH), 31.1 (bqn-CH2), 27.5
(SiC(CH3)3), 20.0 (SiC(CH3)3), -3.4 and -3.6 (Si(CH3)2). Anal.
Calcd (%) for C46H55FeN4ScSi2: C, 67.34; H, 6.75; N, 6.82.
Found: C, 66.97; H, 6.81; N, 6.90.
1
orange powder. H NMR (500 MHz, C6D6), δ (ppm): 9.94 (s,
1H, aromatic-CH), 8.87 (d, 1H, aromatic-CH), 7.71 (d, 1H,
aromatic-CH), 7.27, 7.23, 7.18, 7.09, 7.05, 7.01, 6.87 (m, 8H,
aromatic-CH), 6.61 (t, 1H, aromatic-CH), 6.45 (d, 1H, aro-
matic-CH), 6.02 (d, 1H, aromatic-CH), 5.26 (s, 1H, iqn-NC-
(CH3)CH), 4.35 (dd, 1H, NCHCH2), 4.06 and 3.78 (m, 8H, fc-
CH), 2.83 (s, 3H, NC(CH3)), 2.52 (d, 2H, pic-CH2), 1.84 (s, 3H,
iqn-CH3), 1.01 (s, 18H, SiC(CH3)3), 0.12 (br d, 12H, Si(CH3)2).
13C NMR (126 MHz, C6D6), δ (ppm): 163.9, 153.8, 151.4, 150.1,
147.1, 138.6, 138.1, 136.7, 131.0, 128.3, 128.1, 127.2, 126.6,
126.1, 125.7, 125.0, 121.7, 120.1, 119.9, and 119.7 (aromatic-
CH), 92.0, 67.2, 65.9, and 64.2 (fc-CH), 55.9 (NC(CH3)), 43.8
(pic-CH2), 27.8 (SiC(CH3)3), 25.3 (iqn*-CH3), 24.3 (iqn-CH3),
20.5 (SiC(CH3)3), -1.7 and -4.5 (Si(CH3)2). Anal. Calcd (%)
for C48H63N5FeYSi2: C, 63.29; H, 6.97; N, 7.69. Found: C,
62.46; H, 6.79; N, 7.76.
Synthesis of 5-lut-iqnMe. 2-lut (200 mg, 0.300 mmol) was
combined with 3-methylisoquinoline (43.0 mg, 0.300 mmol) in
toluene (10 mL) and stirred for 1 h at 25 °C. The volatiles were
removed under reduced pressure, and the resulting orange solid
was washed with hexanes and extracted with toluene/THF. The
resulting solution was passed through Celite, concentrated, and
placed in a -35 °C freezer overnight. Yield: 218.5 mg, 99%. 1H
NMR (500 MHz, C6D6), δ (ppm): 7.19 (m, 4H, lut-iqnMe), 7.05
(d, 2H, lut-iqnMe), 6.80 (t, 2H, lut-CH2), 6.35 (t, 1H, lut-iqnMe),
6.30 (d, 1H, lut-iqnMe), 5.32 (s, 1H, lut-iqnMe), 4.34 (s, 1H, fc-
CH), 4.26 (dd, 1H, sp3-CH), 4.04 (s, 1H, fc-CH), 3.94 (s, 1H, fc-
CH), 3.86 (s, 1H, fc-CH), 3.74 (s, 1H, fc-CH), 3.67 (s, 1H, fc-
CH), 3.53 (s, 1H, fc-CH), 3.37 (s, 1H, fc-CH), 2.67 (d, 1H, lut-
iqnMe), 2.62 (s, 3H, lut-iqnMe-CH3), 2.44 (s, 3H, lut-iqnMe-CH3),
0.94 and 0.85 (s, 18H, SiC(CH3)3), 0.20, -0.04, -0.23, and
-0.32 (s, 12H, Si(CH3)2). The limited solubility of 5-lut-iqnMe
prevented the collection of its 13C NMR spectrum. Anal. Calcd
(%) for C39H54FeN4ScSi2: C, 63.65; H, 7.40; N, 7.61. Found: C,
63.58; H, 7.51; N, 7.58.
Synthesis of 5La-pic-iqnMe. 2La-pic (486.7 mg, 0.635 mmol)
and 2 equiv of 3-methylisoquinoline (181.8 mg, 1.269 mmol)
were dissolved in toluene and cooled to -78 °C. The two
solutions were combined, and the mixture was stirred at room
temperature for 1 h. The volatiles were removed under reduced
pressure, and the resulting crude mixture was washed with
hexanes. The solid was dissolved in toluene, and the solution
was filtered through Celite, layered with n-pentane, and placed
in a -35 °C freezer overnight to precipitate 5La-pic-iqnMe. Yield:
67.9% (413.6 mg, 0.413 mmol) of red-orange crystals. 1H NMR
(500 MHz, C6D6), δ (ppm): 9.80 (s, 1H, aromatic-CH), 8.77 (d,
1H, aromatic-CH), 7.62 (d, 1H, aromatic-CH), 7.33 (d, 1H,
aromatic-CH), 7.24 (t, 1H, aromatic-CH), 7.10 (t, 1H, aromatic-
CH), 7.02 (m, 2H, aromatic-CH), 6.90 (t, 1H, aromatic-CH),
6.81 (s, 1H, aromatic-CH), 6.66 (t, 1H, aromatic-CH), 6.51 (d,
1H, aromatic-CH), 5.98 (d, 1H, aromatic-CH), 5.17 (s, 1H, iqn-
NC(CH3)CH), 4.26 (dd, 1H, NCHCH2), 4.10 (s, 2H, fc-CH),
3.96 (s, 2H, fc-CH), 3.63 (s, 2H, fc-CH), 3.29 (s, 1H, fc-CH), 2.78
(s, 3H, NC(CH3)), 2.66 (d, 2H, pic-CH2), 1.86 (s, 3H, iqn-CH3),
1.00 (s, 18H, SiC(CH3)3), 0.13 (br s, 12H, Si(CH3)2). 13C NMR
(126 MHz, C6D6), δ (ppm): 164.5, 153.3, 150.9, 150.6, 146.5,
138.9, 138.7, 137.3, 132.0, 128.6, 127.5, 127.4, 126.7, 126.6,
126.1, 125.4, 121.7, 120.9, 120.5, and 120.2 (aromatic-CH),
107.3 (fc-CN), 91.2 and 66.7 (fc-CH), 56.2 (NC(CH3)), 44.8
(pic-CH2), 28.0 (SiC(CH3)3), 24.0 (iqn-CH3), 20.9 (SiC(CH3)3),
-1.6 (Si(CH3)2). Anal. Calcd (%) for C48H63N5FeLaSi2: C,
60.06; H, 6.51; N, 7.30. Found: C, 59.97; H, 6.65; N, 7.23.
Synthesis of 6-pyEt-iqnMe. 2-pyEt-py (133.3 mg, 0.194 mmol)
was combined with 1 equiv of 3-methylisoquinoline (27.7 mg,
0.194 mmol) in C6D6 (1 mL). The reaction mixture was heated to
70 °C for 16 h. The volatiles were removed under reduced
pressure, the resulting yellow solid was washed with hexanes
and extracted in toluene, and the solution was filtered through
Celite. Yield: 122.7 mg, 86% (precipitate from toluene). 1H
NMR (600 MHz, C6D6), δ (ppm): 8.58 (d, 1H, pyEt-iqnMe), 7.18
(m, 2H, pyEt-iqnMe), 7.09 (d, 1H, pyEt-iqnMe), 7.04, (t, 1H, pyEt-
iqnMe), 6.89 (t, 1H, pyEt-iqnMe), 6.56 (t, 1H, pyEt-iqnMe), 6.49 (d,
1H, pyEt-iqnMe), 5.57 (dd, 1H, pyEt-iqnMe), 5.46 (s, 1H, pyEt-
iqnMe), 4.12 (s, 1H, fc-CH), 3.98 (s, 1H, fc-CH), 3.96 (s, 1H, fc-
CH), 3.09 (s, 1H, fc-CH), 3.77 (s, 1H, fc-CH), 3.63 (m, 1H, CH2),
3.53 (s, 1H, fc-CH), 3.48 (s, 1H, fc-CH), 3.46 (s, 1H, fc-CH),
2.68 (m, 1H, CH2), 2.53 (s, 3H, iqn-CH3), 2.63 (m, 1H, CH2),
1.53 (m, 1H, CH2), 0.93 and 0.92 (s, 18H, SiC(CH3)3), 0.06, 0.05,
-0.11, and -0.39 (s, 12H, Si(CH3)2). 13C NMR (150 MHz,
C6D6), δ (ppm): 163.0 (pyEt-iqnMe), 149.5 (pyEt-iqnMe), 148.5
Synthesis of 2Y-pic. 1Y-CH2Ph (120.0 mg, 0.176 mmol) and
2 equiv of 2-picoline (33.2 mg, 0.356 mmol) were combined
in a Schlenk tube and stirred in toluene for 17 h at 50 °C. The
volatiles were removed under reduced pressure, and the result-
ing crude mixture was dissolved in hexanes and left at -35 °C
overnight, precipitating the desired product as yellow-orange
crystals and powder. Yield: 88.6% (111.9 mg, 0.156 mmol).
1H NMR (500 MHz, C6D6), δ (ppm): 9.26 (s, 1H, pic-CH),
7.88 (d, 1H, pic-CH), 6.94 (t, 1H, pic-CH), 6.87 (t, 2H, pic-CH),
6.58 (t, 1H, pic-CH), 6.49 (d, 1H, pic-CH), 6.09 (t, 1H, pic-CH),
4.31 (s, 2H, fc-CH), 3.97 (s, 2H, fc-CH), 3.57 (s, 2H, fc-CH),
3.39 (s, 2H, fc-CH), 2.81 (s, 2H, pic-CH2), 2.64 (s, 3H, pic-CH3),
0.88 (s, 18H, SiC(CH3)3), -0.01 (s, 6H, Si(CH3)2), -0.17 (s,
6H, Si(CH3)2). 13C NMR (126 MHz, C6D6), δ (ppm): 168.0,
158.8, 150.6, 147.2, 138.4, 136.3, 124.7, 120.9, 120.0, and 108.9
(pic-CH), 104.9 (fc-CN), 68.5, 68.3, 67.1, 64.0, and 53.3 (fc-CH),
53.2 (pic-CH2), 27.0 (SiC(CH3)3), 23.7 (pic-CH3), 19.8
(SiC(CH3)3), -3.60 (Si(CH3)2). Anal. Calcd (%) for C34H51-
N4FeYSi2: C, 56.98; H, 7.17; N, 7.82. Found: C, 56.88; H, 7.09;
N, 7.56.
Synthesis of 2La-pic. 1La-CH2Ph (535.7 mg, 0.719 mmol) and 2
equiv of 2-picoline (134.0 mg, 1.439 mmol) were dissolved in
toluene and cooled to -78 °C. The two solutions were combined
and allowed to stir at room temperature for 2 h. The volatiles
were removed under reduced pressure, the resulting mixture was
dissolved in hexanes, and the solution was filtered through
Celite, concentrated, and placed in a -35 °C freezer overnight.
The desired product precipitated as yellow-orange crystals and
1
powder. Yield: 89.6% (494.2 mg, 0.645 mmol). H NMR (500
MHz, C6D6), δ (ppm): 8.94 (s, 1H, pic-CH), 7.80 (d, 1H, pic-
CH), 6.88 (t, 1H, pic-CH), 6.83 (t, 1H, pic-CH), 6.79 (t, 1H, pic-
CH), 6.55 (t, 1H, pic-CH), 6.47 (d, 1H, pic-CH), 5.97 (t, 1H,
pic-CH), 4.15 (s, 4H, fc-CH), 3.38 (s, 4H, fc-CH), 3.03 (s, 2H,
pic-CH2), 2.52 (s, 3H, pic-CH3), 0.87 (s, 18H, SiC(CH3)3), -0.01
(s, 12H, Si(CH3)2). 13C NMR (126 MHz, C6D6), δ (ppm):
164.1, 158.5, 149.5, 147.0, 139.0, 135.5, 125.1, 121.7, 120.2, and
106.9 (pic-CH), 105.2(fc-CN), 66.5 (fc-CH), 62.1 (pic-CH2),
27.2 (SiC(CH3)3), 22.8 (pic-CH3), 20.2 (SiC(CH3)3), -3.71

Article
Organometallics, Vol. 29, No. 4, 2010 845
(pyEt-iqnMe), 140.6 (pyEt-iqnMe), 136.4 (pyEt-iqnMe), 131.0
(pyEt-iqnMe), 127.2 (pyEt-iqnMe), 125.7 (pyEt-iqnMe), 125.5
(pyEt-iqnMe), 122.6 (pyEt-iqnMe), 121.9 (pyEt-iqnMe), 106.8 and
105.3 (fc-CN), 94.7 (pyEt-iqnMe), 70.6, 69.6, 69.2, 68.8, 68.5,
68.0, 66.9, and 65.8 (fc-CH), 53.0 (pyEt-iqnMe), 35.5 and 32.6
((CH2)2), 28.4 and 28.0 (SiC(CH3)3), 24.9 (iqn-CH3), 20.5 and
20.4 (SiC(CH3)3), -1.4, -1.7, -2.8, and -3.3 (Si(CH3)2). Anal.
Calcd (%) for C39H55FeN4ScSi2: C, 63.57; H, 7.52; N, 7.60.
Found: C, 63.25; H, 7.41; N, 7.32.
Synthesis of [2-im]2. 1-CH2Ar (200 mg, 0.295 mmol) was
combined with 0.95 equiv of 1-methylimidazole (23.0 mg,
0.280 mmol) in toluene (5 mL) and stirred at 70 °C for 48 h.
The volatiles were removed under reduced pressure, the result-
ing yellow solid was washed with hexanes and extracted in
toluene, and the solution was filtered through Celite. Yield:
150.7 mg, 90%. 1H NMR (500 MHz, C6D6), δ (ppm): 7.59 (d,
2H, im), 6.44 (d, 2H, im), 4.23, 3.88, 3.81, and 3.79 (s, 4H each,
fc-CH), 3.77 (s, 6H, im-CH3), 0.99 (s, 36H, SiC(CH3)3), -0.08
and -0.11 (s, 12H each, Si(CH3)2). The limited solubility of [2-
im]2 prevented the collection of its 13C spectrum. Anal. Calcd
(%) for C52H86Fe2N8Sc2Si4: C, 54.92; H, 7.62; N, 9.85. Found:
C, 54.86; H, 7.51; N, 9.54.
Synthesis of 2-im-im. 1-CH2Ar (200 mg, 0.295 mmol) was
combined with 1.99 equiv of 1-methylimidazole (48 mg, 0.586
mmol) in toluene (8 mL) and heated to 50 °C for 24 h. The
volatiles were removed under reduced pressure, the resulting
solid was washed with a small (ca. 2 mL) amount of cold hexanes
and extracted with hexanes, and the solution was filtered
through Celite. Yield: 142 mg, 74.1%. 1H NMR (500 MHz,
C6D6), δ (ppm): 7.80 (br s, 1H, im), 7.45 (br s, 1H, im), 7.23(s,
1H, im), 6.92 (s, 1H, im), 5.95 (s, 1H, im), 4.18 (s, 4H, fc-CH),
3.59 (br s, 4H, fc-CH), 3.42 (s, 3H, im-CH3), 2.35 (s, 3H, im-
CH3), 1.01 (s, 18H, SiC(CH3)3), 0.06 (s, 12H, Si(CH3)2). 13C
NMR (126 MHz, C6D6), δ (ppm): 200.8 (im), 140.0 (im), 130.0
(im), 126.8 (im), 124.8 (im), 119.8 (im), 103.3 (fc-CN), 67.5 and
67.2 (fc-CH), 36.0, 32.6, and 28.5 (im-CH3), 27.9 (SiC(CH3)3),
20.4 (SiC(CH3)3), -2.6 (Si(CH3)2). Anal. Calcd (%) for C30H49-
FeN6ScSi2: C, 55.37; H, 7.59; N, 12.91. Found: C, 55.00; H, 7.68;
N, 12.61.
Synthesis of 3-im-bipy. 2-im-im (212.6 mg, 0.327 mmol) was
combined with 1 equiv of 2,20-bipyridine in toluene and stirred
for 16 h at room temperature. The volatiles were removed under
reduced pressure, the remaining red solid was washed with a
generous portion (15 mL) of hexanes and extracted in toluene,
and the solution was filtered through Celite. Yield: 209.5 mg,
88.4%. 1H NMR (500 MHz, C6D6), δ (ppm): 8.23 (d, 1H, bipy),
7.45 (d, 1H, bipy), 6.96 (t, 1H bipy), 6.87 (s, 1H, im), 6.56 (m, 2H,
bipy), 6.02 (d, 1H, bipy), 6.01 (s, 1H, im), 5.38 (s, 1H, bipy), 4.84
(d, 1H, bipy), 4.32 (s, 2H, fc-CH), 4.12, 4.10, and 3.68 (s, 1H, fc-
CH), 3.56 (s, 2H, fc-CH), 3.54 (s, 1H, fc-CH), 2.65 (s, 3H, im-
CH3), 0.90 and 0.77 (s, 9H, SiC(CH3)3), 0.02, -0.07, -0.11, and
-0.20 (s, 3H, Si(CH3)2). 13C NMR (126 MHz, C6D6), δ (ppm):
159.5 (im-bipy), 155.4 (im-bipy), 153.0 (im-bipy), 145.9 (im-
bipy), 137.4 (im-bipy), 129.4 (im-bipy), 125.6 (im-bipy), 121.4
(im-bipy), 121.2 (im-bipy), 120.1 (im-bipy), 103.2 (im-bipy),
102.4 and 102.1 (fc-CN), 96.7 (im-bipy), 68.2, 68.1, 67.9, 65.4,
65.3, and 57.5 (fc-CH), 32.4 (im-CH3), 27.9 and 27.5
(SiC(CH3)3), 20.5 and 20.1 (SiC(CH3)3), -3.4, -3.6, and -3.7
(Si(CH3)2). Anal. Calcd (%) for C36H51FeN6ScSi2: C, 59.66; H,
7.09; N, 11.59. Found: C, 59.47; H, 7.16; N, 11.56.
(Bruker 1998, SMART, SAINT, XPREP AND SHELXTL,
Bruker AXS Inc., Madison, WI).57 All atoms were refined
anisotropically, and hydrogen atoms were placed in calculated
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.
X-ray Crystal Structure of 2-lut. X-ray quality crystals were
obtained from a concentrated toluene/n-pentane solution
placed in a -35 °C freezer in the glovebox. A total of 31 986
reflections (-13 e h e 13, -16 e k e 16, -38 e l e 39) were
collected at T = 110(2) K with 2θmax = 56.53°, of which 8738
were unique (Rint = 0.0460). The residual peak and hole electron
density were 0.57 and -0.53 e A-3. The least-squares refinement
˚
converged normally with residuals of R1 = 0.0379 and GOF =
1.032. Crystal and refinement data for 2-lut: formula C33H54N3-
˚
Si2FeScO, space group P21/c, a = 10.0439(14) A, b = 12.1154(17)
3
˚
˚
˚
A, c = 29.315(4) A, β = 95.686(1)°, V = 3549.7(9) A , Z = 4,
μ = 0.696 mm-1, F(000) = 1424, R1 = 0.0544 and wR2 = 0.0987
(based on all 8738 data, I > 2σ(I)).
X-ray Crystal Structure of 3-pyPh-phan. X-ray quality crystals
were obtained from a concentrated C6D6 solution stored at room
temperature in the glovebox. A total of 20 229 reflections (-14 e h
e 13, -17 e k e 17, -26 e l e 25) were collected at T = 100(2) K
with 2θmax = 61.03°, of which 11 291 were unique (Rint = 0.0196).
The residual peak and hole electron density were 0.49 and -0.37 e
A
-3. The least-squares refinement converged normally with resi-
duals of R1 = 0.0343 and GOF = 1.030. Crystal and refinement
˚
data for 3-pyPh-phan: formula C46H55N4Si2FeSc, space group P1,
˚
˚
˚
a = 9.9201(8) A, b = 12.3794(10) A, c = 18.301(2) A, R =
3
˚
102.853(1)°, β = 101.442(1)°, γ = 103.688(1)°, V = 2052.7(3) A ,
Z = 2, μ = 0.615 mm-1, F(000) = 868, R1 = 0.0437 and wR2 =
0.0894 (based on all 11 291 data, I > 2σ(I)).
X-ray Crystal Structure of 3-acr-phan. X-ray quality crystals
were obtained from the slow diffusion of n-pentane into a con-
centrated C6D6 solution stored at room temperature in the glove-
box. A total of 40 459 reflections (-24 ehe24, -18 eke18, -23
e l e 23) were collected at T = 100(2) K with 2θmax = 57.43°, of
which 11 169 were unique (Rint = 0.0579). The residual peak and
hole electron density were 0.45 and -0.38 e A-3. The least-squares
˚
refinement converged normally with residuals of R1 = 0.0424 and
GOF = 1.005. Crystal and refinement data for 3-acr-phan: for-
˚
mula C48H55N4Si2FeSc, space group P21/c, a = 18.4379(15) A,
˚
˚
b = 13.7392(11) A, c = 17.1780(14) A, β = 93.435(1)°, V =
4343.7(6) A , Z = 4, μ = 0.583 mm-1, F(000) = 1784, R1 =
3
˚
0.0735 and wR2 = 0.1046 (based on all 11 169 data, I > 2σ(I)).
X-ray Crystal Structure of 4-pyPh-bqn. X-ray quality crystals
were obtained from the slow diffusion of n-pentane into a con-
centrated toluene solution placed in a -35 °C freezer in the
glovebox. A total of 23 249 reflections (-12 e h e 12, -19 e k
e 19, -24 e l e 25) were collected at T = 100(2) K with 2θmax
=
55.82°, of which 12 281 were unique (Rint = 0.0410). The residual
peak and hole electron density were 0.51 and -0.36 e A-3. The
˚
least-squares refinement converged normally with residuals of
R1 = 0.0538 and GOF = 0.973. Crystal and refinement data for
4-pyPh-bqn: formula C46H55N4Si2FeSc, space group P1, a =
˚
˚
˚
9.7843(15) A, b = 14.976(2) A, c = 19.261(3) A, R =
3
˚
90.224(2)°, β = 97.913(2)°, γ = 108.405(2)°, V = 2649.2(7) A ,
Z = 2, μ = 0.477 mm-1, F(000) = 868, R1 = 0.0778 and wR2 =
0.1612 (based on all 12281 data, I > 2σ(I)).
X-ray Crystal Structure of 5-lut-iqnMe. X-ray quality crystals
were obtained from a concentrated C6D6 solution stored at room
temperature in the glovebox. A total of 36 605 reflections (-24 e h
e 24, -17 e k e 17, -23 e l e 23) were collected at T = 100(2) K
with 2θmax = 56.52°, of which 9960 were unique (Rint = 0.0348).
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
The residual peak and hole electron density were 0.52 and -0.55 e
A
-3. The least-squares refinement converged normally with resi-
duals of R1 = 0.0361 and GOF = 1.034. Half of a molecule of
˚
(57) Sheldrick, G. Acta Crystallogr. A 2008, 64, 112–122.

846 Organometallics, Vol. 29, No. 4, 2010
Carver et al.
C6D6 was found in the unit cell. Crystal and refinement data
-3. There are two independent molecules in the unit cell.
˚
A
for 5-lut-iqnMe: formula C42H58N4Si2FeSc, space group P21/c,
Several tert-butyl groups were disordered. To some extent, this
disorder was modeled with occupancies over two sites. The high
residual electron density is due to a small amount of disorder of
Si3. This disorder was not modeled. The least-squares refine-
ment converged normally with residuals of R1 = 0.0772 and
GOF=1.040. A molecule of n-pentane was found in the unit cell.
˚
˚
˚
a = 18.2657(11) A, b = 13.1113(8) A, c = 17.9123(11) A, β =
109.625(1)°, V=4040.6(4) A , Z=4, μ=0.620 mm-1, F(000)=
3
˚
1652, R1 = 0.0482 and wR2 = 0.0933 (based on all 9960 data,
I > 2σ(I)).
X-ray Crystal Structure of 6-pyEt-iqnMe. X-ray quality crystals
were obtained from the slow diffusion of n-pentane into a con-
centrated Et2O solution placed at -35 °C in the glovebox. A total
of 44 359 reflections (-37 e h e 38, -19 e k e 19, -34 e l e 36)
were collected at T = 100(2) K with 2θmax = 61.73°, of which
12 957 were unique (Rint = 0.0446). The residual peak and hole
Crystal and refinement data for 3-im-bipy: formula C77H113
˚
-
N8Si4Fe2Sc2, space group P1, a = 11.7625(14) A, b = 17.923(2)
˚
˚
A, c = 19.918(2) A, R = 78.960(1)°, β = 80.862(1)°, γ =
3
-1
˚
81.288(1)°, V = 4037.3(8) A , Z = 2, μ = 0.621 mm
F(000) = 1618, R1 = 0.1436 and wR2 = 0.2251 (based on all
19 461 data, I > 2σ(I)).
,
electron density were 1.11 and -1.13 e A-3. The least-squares
˚
refinement converged normally with residuals of R1=0.0487 and
GOF=1.026. A molecule of n-octane solvent was found in the unit
cell. Crystal and refinement data for 6-pyEt-iqnMe: formula
DFT Calculations. The Amsterdam Density Functional
(ADF) package (version ADF2008.01) was used to do geometry
optimizations on Cartesian coordinates of the model com-
pounds specified in the text. For the scandium, 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),
1s-3p (Sc), 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.
˚
C43H63N4Si2FeSc, space group C2/c, a = 26.971(2) A, b =
˚
˚
13.7216(12) A, c=25.022(2) A, β=109.414(1)°, V=8733.5(13)
A , Z=8, μ=0.575 mm-1, F(000) = 3392, R1 = 0.0752 and
3
˚
wR2 = 0.1463 (based on all 12 957 data, I > 2σ(I)).
X-ray Crystal Structure of [2-im]2. X-ray quality crystals were
obtained from a concentrated C6D6 solution stored at room
temperature in the glovebox. A total of 12 932 reflections (-14 e
h e 14, -16 e k e 16, -17 e l e 17) were collected at T = 110(2)
K with 2θmax = 56.61°, of which 7005 were unique (Rint
=
0.0357). The residual peak and hole electron density were 1.10
and -0.77 e A-3. The least-squares refinement converged
˚
normally with residuals of R1 = 0.0458 and GOF = 1.029.
Crystal and refinement data for [2-im]2: formula C52H86N8Si4-
Acknowledgment. This work was supported by the
UCLA, Sloan Foundation, and NSF (Grant CHE-
0847735).
˚
Fe2Sc2, space group P1, a = 10.821(2) A, b = 12.104(4) A, c =
˚
˚
13.158(2) A, R = 108.410(3)°, β = 111.857(2)°, γ = 96.849(3)°,
V = 1461.7(6) A , Z = 1, μ = 0.831 mm-1, F(000) = 604, R1 =
3
˚
0.0767 and wR2 = 0.1086 (based on all 7005 data, I > 2σ(I)).
X-ray Crystal Structure of 3-im-bipy. X-ray quality crystals
were obtained from the slow diffusion of n-pentane into a
concentrated C6D6 solution placed at room temperature in the
glovebox. A total of 36 271 reflections (-15 e h e 15, -23 e k e
Supporting Information Available: Experimental details for
compound characterizations, structural representations indicat-
ing a full atom-labeling scheme, DFT calculation details, and
full crystallographic descriptions (as cif) are available free of
charge via the Internet at http://pubs.acs.org. CCDC numbers
for 2-lut, 3-pyPh-phan, 3-acr-phan, 4-pyPh-bqn, 5-lut-iqnMe, 6-
pyEt-iqnMe, [2-im]2, and 3-im-bipy are 756852, 756853, 756854,
756855, 756856, 756857, 756858, and 756859, respectively.
23, -26 e l e 26) were collected at T = 125(2) K with 2θmax
=
56.59°, of which 19 461 were unique (Rint = 0.0528). The
residual peak and hole electron density were 3.16 and -1.29 e