Synthesis and complexation behavior of indenyl and cyclopentadienyl ligands functionalized with a naphthyridine unit

Article abstract of DOI:10.1021/om2009638

Lithium indenide (Li-Ind) or cyclopentadienide (Li-Cp) derivatives react as nucleophiles with 8-(methylsulfinyl)- 1,5-naphthyridine (Naph), leading to donor-functionalized ligands Ind^Naph or Cp^Naph, respectively. The new ligands comprise two N-donor atoms, which, for geometric reasons, cannot bind to the same metal atom. In complexes, where the metal atom is bound by the Cp or Ind moiety, the N5-donor atom is located in a distal position. The coordination behavior to Rh or Zr metal centers has been investigated. The Cp-based ligands show the expected chelating coordination mode with ν⁵-Cp and N coordination, whereas the indenyl units act as dihapto, trihapto, or pentahapto ligands. The dinuclear Rh(I) complex 12 shows a rare coordination geometry with two ν³ ligands bridging a Rh ₂(CO)₃ fragment.

Full text of DOI:10.1021/om2009638

Article
pubs.acs.org/Organometallics
Synthesis and Complexation Behavior of Indenyl and
Cyclopentadienyl Ligands Functionalized with a Naphthyridine Unit
†
†
†
†
†
‡
David Sieb, Katrin Schuhen, Michael Morgen, Heike Herrmann, Hubert Wadepohl, Nigel T. Lucas,
,
§
,†
Robert W. Baker,* and Markus Enders*
†
Anorganisch-Chemisches Institut der Ruprecht-Karls-Universitat
̈
Heidelberg, Im Neuenheimer Feld 270, D-69120 Heidelberg,
Germany
‡
Department of Chemistry, University of Otago, Dunedin 9054, New Zealand
§School of Chemistry, University of Sydney, NSW 2006, Australia
S Supporting Information
*
ABSTRACT: Lithium indenide (Li-Ind) or cyclopentadienide
Li-Cp) derivatives react as nucleophiles with 8-(methylsulfinyl)-
(
1
,5-naphthyridine (Naph), leading to donor-functionalized
Naph
Naph
ligands Ind
or Cp , respectively. The new ligands com-
prise two N-donor atoms, which, for geometric reasons, cannot
bind to the same metal atom. In complexes, where the metal
atom is bound by the Cp or Ind moiety, the N5-donor atom is
located in a distal position. The coordination behavior to Rh or
Zr metal centers has been investigated. The Cp-based ligands
5
show the expected chelating coordination mode with η -Cp
and N coordination, whereas the indenyl units act as dihapto, trihapto, or pentahapto ligands. The dinuclear Rh(I) complex 12
3
shows a rare coordination geometry with two η ligands bridging a Rh (CO) fragment.
2
3
INTRODUCTION
Donor-functionalized cyclopentadienides or indenides play an
important role as spectator ligands in organometallic chemistry.
reactions of 1-isoquinolinyl and 2-pyridyl sulfoxides with
-naphthyl Grignard reagents could be used to obtain axially
chiral isoquinoline and pyridine ligands. A logical extension
of this work is the potential for ligand-coupling reactions of
azaheterocyclic sulfoxides with fluorenides, indenides, or
cyclopentadienides.
Since the nitrogen atom in an 8-quinolyl sulfoxide is not in a
position to activate a ligand-coupling reaction, we decided to
examine the reactions of 8-sulfinyl-1,5-naphthyridenes, where
N5 is in a position to activate potential ligand-coupling reac-
tions, while N1 can coordinate to a metal in a manner analogous
to 8-quinolyl-functionalized Cp and Ind ligands. Metal complexes
of 1,5-naphthyriden-8-yl-functionalized Cp and Ind ligands would
be of particular interest as the distal N5 is in strong electronic
communication with the coordinating Cp or Ind group, whereas
N1 may coordinate to the same metal as the five-membered ring.
This opens up interesting possibilities to “tune” the reactivity of
the metal complex through the coordination of a Lewis acid to the
■
1
5
1
The combination of anionic cyclopentadienides or indenides
−
−
(
Cp or Ind ) with a neutral donor function leads to systems
that can act as chelating ligands or as hemilabile ligands, de-
pending on the metal atom used. The spacer between the
donor function and the C ring has to be of suitable length and
geometry. By incorporation of the spacer and the donor atom
into an aromatic ring system, rigid and well-coordinating chelate
ligands are obtained. Therefore, the C ring has to be directly
5
5
connected to an aromatic group. Cyclopentadienides or
indenides (e.g., LiC H or LiC H ) are easily available com-
5
5
9
7
pounds, but unfortunately, they rarely react with aromatic rings.
We have used and developed several routes for the synthesis of
aromatically substituted cyclopentadienes and indenes.
2
In previous work, we have incorporated a C spacer as well
2
2
as an sp nitrogen atom into a rigid heterocycle by using
5
-nitrogen.
8
-quinolyl-functionalized Cp and Ind ligands. Their pre-
defined geometry allows the coordination of the N atom to
the cyclopentadienyl- or indenyl-bonded metal center. We have
There have been only a few examples of cyclopentadienides
3
or indenides being involved in aromatic substitution reactions,
and in those examples, strong electron-withdrawing groups are
also prepared a number of 9-(1-naphthyl)-9H-fluorene and 3-(1-
naphthyl)-1H-indene ligand precursors containing an additional
coordinating group at the naphthalene 2-position through the
use of various synthetic approaches, including the use of ligand-
coupling reactions of 1-naphthyl sulfoxides, activated by
carboxylate esters at the naphthalene 2-position, with fluorenyl
2c,6
required to facilitate the reaction.
While sulfoxide ligand-
coupling reactions also require the presence of electron-withdraw-
ing groups at positions consistent with an S Ar mechanism,
N
Received: October 11, 2011
Published: December 15, 2011
4
and indenyllithiums. We also described how ligand-coupling
©
2011 American Chemical Society
356
dx.doi.org/10.1021/om2009638 | Organometallics 2012, 31, 356−364

Organometallics
Article
Scheme 1. Synthetic Route to the Ligands 5−7
Oae and Furakawa and their co-workers have carried out
extensive studies that demonstrate that these reactions
proceed through the intermediacy of hypervalent σ-sulfuranes
3-heteoaryl-1H-indene tautomers. However, when 2 equiv of
Li-Ind are used, together with a longer reaction time (1 h), only
the 3-heteroaryl-1H-indene tautomer 5 is isolated in a yield
7
formed through initial nucleophilic attack at sulfur. Apicophilic
of 85%. The reaction of 4a with 2 equiv of Li-CpMe , which
4
groups that can stabilize this intermediate greatly facilitate the
reaction, making the method ideally suited for stabilized
carbanions, such as cyclopentadienides or indenides. In
addition to preparing 1,5-naphthyriden-8-yl-functionalized Cp
and Ind ligands, we were also interested in preparing
benzo[b][1,5]naphthyridin-10-yl-functionalized Ind ligands
with a view to generating systems with a stable rotational axis
around the heteroaryl−indene bond that could then be used to
also results in the formation of an intensely violet solution of
the lithium salt of 7, affords on hydrolysis the ligand 7 in 85%
isolated yield. In the case of sulfoxide 4b, the ligand-coupling
reaction was carried out using lithium-2-methylindenide (Li-2-
MeInd), the 2-methyl substituent being used to raise the barrier
to rotation around the heteroaryl−indene bond. When this
reaction was carried out using the same conditions as for 4a, the
3-heteroaryl-1H-indene tautomer of the product was formed,
but this proved to be quite unstable to light and air, and under-
went substantial decomposition during attempts to purify it.
To isolate the 1-heteroaryl-1H-indene tautomer, the reaction
was carried at −110 °C with 1.3 equiv of Li-2-MeInd for only
30 min. The 1-heteroaryl-1H-indene tautomer 6, which was
stable, was isolated in 57% yield.
2a,b
generate planar-chiral metal complexes stereospecifically
or
to constrain the coordination of the 1-nitrogen to metals
8
coordinating the Ind moiety.
RESULTS AND DISCUSSION
Ligand Synthesis. The synthesis of the required sulfoxides
commenced with 8-hydroxy-1,5-naphthyridine (1a) and
■
9
Formation of Metal Complexes. It is well known that
rhodium complexes with a Cp ligand and additional labile
ligands can be activated thermally or photochemically. The
resulting complexes are highly reactive and can, for example,
benzo[b][1,5]naphthyridin-10(5H)-one (1b drawn as the hydroxy
10
tautomer in Scheme 1 for convenience), which were prepared
following literature procedures. Both 1a and 1b have been
previously converted into the corresponding chloro derivatives
11
activate CH bonds in hydrocarbons. It was also shown that
8
9
hemilabile donors stabilize the reactive intermediates so that
(
2a, 2b), using either phosphorus oxychloride or thionyl chloride,
12
cleaner catalytic transformations are possible.
respectively; however, we found it more convenient to use the
Vilsmeier reagent generated from oxalyl chloride and DMF
The synthesis of complex 8 is achieved by reaction of the
deprotonated ligand 7 with the rhodium precursor di-μ-
chlorodicyclooctadienyldirhodium(I) in 45% yield. Exposure to
UV light in deuterated chloroform allows the quantitative
conversion to the red Rh(III) complex 9 (see Scheme 2). The
(Scheme 1). In the case of 1a, the chloro derivative 2a was
isolated and subsequently treated with sodium methanethiolate
to furnish the methylsulfanyl derivative 3a. In the case of 1b,
the chlorination and subsequent reaction with methanethiolate
to provide 3b were carried out in the one pot, since the chloro
derivative 2b proved too reactive to isolate without significant
conversion back to 1b. The sulfides 3a and 3b were then
oxidized to the sulfoxides 4a and 4b, respectively, by using 1
equiv of m-CPBA. The sulfoxide 4a rapidly reacts with either
Li-Ind or lithium 1,2,3,4-tetramethylcyclopentadienide (Li-CpMe4)
at −78 °C in THF solution. While the initial ligand-coupling
product in the reaction with Li-Ind is the 1-heteroaryl-1H-
indene tautomer, the presence of the heteroaryl substituent
appears to lead to an increased acidity of the indene so that the
product is deprotonated by the starting Li-Ind present in the
reaction mixture, as evident by a deeply violet color (the same
color develops when the isolated ligand 5 is reacted with n-BuLi
in THF). When using only a slight excess of Li-Ind, the reaction
fails to go to completion, and on hydrolysis, the ligand-coupling
product is isolated as a mixture of the 1-heteroaryl-1H- and
5
η -hapticity in 8 and in 9 is confirmed by the presence of scalar
couplings between the 1 Rh nuclei and all five quaternary
03
1
1
carbon atoms of the C
Hz). The coordination of the naphthyridine unit to the Rh
rings (8: JRh,C ≈ 8.5 Hz; 9: JRh,C ≈ 4.0
5
atom in 9 is confirmed by 15N NMR. Noncoordinating
15
N
atoms of the ligand precursors or of the complexes 8 and 9 give
rise to signals in the region between δ = 300 and 320 ppm.
The 15N− H correlated spectrum of 9 (see Figure 1) shows
two resonances, one at δ = 241.4 ppm for the coordinating
N1 atom and the other at δ = 318.0 ppm for the distal N5
atom. The high field shift upon coordination is, therefore, about
70 ppm.
1
Crystals of the ligand precursor 7 and of the complexes 8 and
9 suitable for single-crystal X-ray diffraction analysis have been
obtained from dichloromethane solutions. Their molecular struc-
12,13
tures are very similar to the corresponding quinoline systems.
3
57
dx.doi.org/10.1021/om2009638 | Organometallics 2012, 31, 356−364

Organometallics
Article
Scheme 2. Synthesis of 8 and 9
benzonaphthyridene N1 atom, as evident from a strong cross-
peak in the NOESY spectrum between H1′ of the indene and
H9 of the benzonaphthyridene (Scheme 3). Reaction of 6 with
Scheme 3. Synthesis of 10a and 10b
[
Rh(CO) Cl] leads to a product 10, which shows only coordina-
2 2
15
1
tion to the N5 atom, as evident from the N− H correlated
HMBC spectrum, no doubt owing to steric hindrance of the
N1 atom by the indene moiety. The IR spectrum of 10 shows
two signals for the valence vibration of the two carbonyl units
Figure 1. 15N−1H correlated NMR spectrum (HMBC) of 9.
−1
at ν
̃
(CO) = 2084 and 2009 cm . The almost equal intensity
of the two bands is indicative for two CO ligands in a cis
arrangement. Compared to other complexes of the type
The chelating coordination mode with the well-suited geometry
of the new ligand is visible in the molecular structure of complex
14
Rh(CO) Cl(L) (L = ClPy, HOPy, Py, MePy), the influence
9
(see Figure 2).
2
On the basis of our previous studies with 1- and 3-(1-
of the benzonaphthyridene unit lies between pyridine and
2a,c,4b,d
15
napthyl)-1H-indenes,
the benzonaphthyridene ligand 6
methylpyridine. NMR analysis reveals that a 1:1 mixture of
13
was expected to exhibit a stable rotational axis around the
C−C single bond between the benzonaphthyridene and the
indene moieties. The ligand-coupling reaction affords 6 as a
single rotational isomer in which the indene H1′ is anti to the
very similar compounds has formed. The C NMR shows a
double set of signals. For instance, there are four CO resonances
that are each split into doublets due to coupling to 1 Rh ( J
03
1
=
Rh,C
72.2 Hz for two doublets at δ = 180 ppm and 68.6 Hz for two
Figure 2. Solid-state molecular structures of 7, 8, and 9. Selected bond lengths [Å] and angles [deg]. 7: C(11)−C(12) 1.513(2); C(11)−C(15)
.523(2); C(12)−C(13) 1.350(2); C(13)−C(14) 1.480(2); C(14)−C(15) 1.343(2). 8 (only one of the two independent molecules of 8 is shown;
1
values refer to the molecule shown): Rh(1)−C(11) 2.240(3); Rh(1)−C(12) 2.201(3); Rh(1)−C(13) 2.277(3); Rh(1)−C(14) 2.277(3); Rh(1)−
C(15) 2.232(3); Rh(1)−C(20) 2.109(4); Rh(1)−C(21) 2.103(4); Rh(1)−C(24) 2.115(3); Rh(1)−C(25) 2.109(4). 9: Rh−N(1) 2.101(2); Rh−
Cl(1) 2.395(1); Rh−Cl(2) 2.417(1); Rh−C(11) 2.073(2); Rh−C(12) 2.121(2); Rh−C(13) 2.193(2); Rh−C(14) 2.186(2); Rh−C(15) 2.126(2);
N(1)−Rh−Cl(1) 91.19(4); N(1)−Rh−Cl(2) 90.07(4); Cl(1)−Rh−Cl(2) 93.19(4); C(11)−C(15) 1.441(2); C(11)−C(12) 1.445(2); C(12)−
C(13) 1.454(2); C(13)−C(14) 1.423(3); C(14)−C(15) 1.453(2).
3
58
dx.doi.org/10.1021/om2009638 | Organometallics 2012, 31, 356−364

Organometallics
Article
doublets at δ = 183 ppm). Consistent with these data are iso-
meric structures 10a and 10b where the CO ligands are mutually
cis; however, the structures differ from one another through
restricted rotation along the Rh−N bond. The peri-H sub-
stituents to 5-nitrogen in the benzonaphthyridene unit are
presumably responsible for this behavior. To date, all attempts to
prepare complexes of ligand 6 where the metal is coordinated to
the indenyl moiety have been unsuccessful.
about the metal−N interaction in solution: whereas the distal
N5 atom gives rise to a signal at 308.4 ppm (free ligand 5: δ =
310.5 and 312.6 ppm), the coordinated N1 atom resonates at
244.9 ppm and is thus shifted by approximately 65 ppm upfield
upon complexation.
We attempted to deprotonate complex 11 in order to
5
promote the formation of a η -complex. However, reaction with
potassium hydride led to the formation of a mixture where
no products could be identified. Reaction with silver carbonate
or iodine (either alone or in the presence of base) did not
Whereas the benzonaphthyridene ligand 6 coordinates to the
Rh(CO) Cl unit with the N5 atom, ligand 5 binds to the same
2
5
fragment with the N1 atom and additionally by the double
lead to the formation of a η -complex either. We, therefore,
2
bond of the indene unit. The rhodium-η -complex 11 could
deprotonated ligand 5 with n-BuLi and reacted it with
5
be obtained easily by reaction of 5 with tetracarbonyldi-μ-
chlorodirhodium(I) at room temperature (Scheme 4).
[Rh(CO)
Cl]
2
2
. Again, no η Rh complex formed, but the
unexpected dinuclear complex 12 was isolated (Scheme 5).
Scheme 5. Formation of Complex 12
Scheme 4. Synthesis of 11
Crystal structure analysis as well as NMR analysis confirmed
Crystals of 11 were obtained from dichloromethane solu-
tions. Figure 3 shows the well-suited geometry of the ligand for
the C -symmetric structure of complex 12, which requires the
2
coordination of the same planar-chiral face of two ligands to the
Rh (CO) fragment. Complex 12 is a coordinatively saturated
2
3
rhodium dimer containing one metal−metal bond, one bridging
CO, and one terminal CO per rhodium. The two deprotonated
8
-(1-indenyl)-1,5-naphthyridine ligands are binding each with
the N1 atom to one of the rhodium atoms. The indenyl parts of
3
these ligands are both binding with three carbon atoms (η ) to
13
1
both rhodium atoms (μ ) at once. In the C{ H} NMR spec-
2
trum of 12, the indenyl C1′ and C3′ atoms appear as doublets
through scalar couplings to 1 Rh, with J
03
1
= 10.9 and 9.4 Hz,
Rh,C
respectively. The indenyl C2′ atom is, however, a singlet. The
1
terminal CO ligands appear as a doublet with J
= 99.6 Hz,
= 38.2 Hz.
Rh,C
1
while the bridging CO appears as a triplet with J
Rh,C
The IR spectrum of 12 shows two signals for the vibrations of
−
1
the terminal carbonyl units at ν
whereas the bridging carbonyl shows only one signal at ν
1
̃
(CO) = 2022 and 1988 cm ,
̃
(CO) =
−1
776 cm .
To date, there are just a few complexes known that contain a
3
bridging η -indenyl ligand. The dimeric complex (indenyl) Cr Cl
3
2
A and its derivative (indenyl) Cr B are representatives of a
4
2
chromium species (Figure 4). They are available by reduction
of chromium(III) chloride with sodium indenide, followed by
Figure 3. Solid-state molecular structure of 11. Selected bond lengths
[
Å] and angles [deg]: Rh(1)−C(11) 2.152(2); Rh(1)−C(12) 2.121(2);
Rh(1)−C(20) 1.838(2); Rh(1)−Cl(1) 2.3448(6); Rh(1)−N(1)
.1004(18); C(20)−O(1) 1.135(1); C(19)−C(11)−Rh(1) 115.2(1);
16
gradual substitution of chloride with an indenyl group. Complexes
3
2
representing palladium are the dimeric species (μ,η -Ind)(μ-
C(13)−C(12)−Rh(1) 119.13(15); C(20)−Rh(1)−N(1) 173.03(9);
C(20)−Rh(1)−C(12) 92.57(9); C(20)−Rh(1)−C(11) 96.44(9);
N(1)−Rh(1)−C(12) 89.33(8); N(1)−Rh(1)−C(11) 80.86(7);
C(12)−Rh(1)−C(11) 38.99(8); C(20)−Rh(1)−Cl(1) 89.91(7);
N(1)−Rh(1)−Cl(1) 90.97(5); O(1)−C(20)−Rh(1) 177.6(2).
Cl)Pd (PR ) (R = Cy, Ph) C, which are accessible via a
2
3 2
reversible conproportionation of Ind-Pd(II) and Pd(0)(PR )
3
n
17
species. Figure 5 shows two different views of the complex
Naph
[
Rh (Ind ) (CO) ] 12.
2 2 3
5
The formation of an η -complex with ligand 5 could be
accomplished by reaction with Zr(NMe) . Both components
react quickly at room temperature with formation of complex
13 together with free HNMe as the only products. However,
a chelating coordination. The rhodium atom is in a square-
planar coordination environment with the CO ligand in a trans
position to the N-donor atom. The angles around N1 add to
almost 360° (359.5°), which indicates that the lone pair of the
N atom is in an ideal position for the interaction with the Rh
center. The bond of Rh to two carbon atoms from the indene
4
2
after 1 h in a sealed NMR tube, decomposition products are
observable in the NMR spectrum and, after one day, 13 is
transformed completely into a mixture of unidentified products.
1
3
1
103
13
1
13
1
13
leads to doublets in the C NMR spectra with J( Rh, C) of
1
Therefore, 13 could be analyzed only by H, C, and H− C
1
5
3.6 and 14.7 Hz, respectively. N NMR gives information
correlation NMR spectroscopy. The three NMe groups are
2
3
59
dx.doi.org/10.1021/om2009638 | Organometallics 2012, 31, 356−364

Organometallics
Article
3
Figure 4. Literature examples of metal complexes with bridging η -indenyl ligands.
Figure 5. Solid-state molecular structure of [Rh (IndNaph)2(CO) ] 12 (left: side-view; right: top-view). A molecule of dichloromethane in the
2
3
asymmetric unit has been omitted for clarity. Selected bond lengths [Å] and angles [deg]: Rh(1)−Rh(1*) 2.7044(6); Rh(1)−C(11) 2.209(4);
Rh(1)−C(12) 2.472(4); Rh(1)−C(12*) 2.475(3); Rh(1)−C(13*) 2.203(4); Rh(1)−C(20) 1.871(4); Rh(1)−C(21) 1.979(4); Rh(1)−N(1)
2
.250(3); C(20)−O(1) 1.131(5); C(21)−O(2) 1.193(6); C(19)−C(11)−Rh(1) 113.5(2); C(14)−C(13)−Rh(1*) 115.6(2); C(12)−C(11)−
Rh(1) 81.9(2); C(12)−C(13)−Rh(1*) 83.0(2); C(11)−Rh(1)−C(13*) 162.3(1); C(11)−Rh(1)−C(12*) 128.8(1); C(8)−C(11)−Rh(1)
1
05.7(3); N(1)−Rh(1)−C(11) 77.84(13); N(1)−Rh(1)−C(13*) 94.06(13); O(1)−C(20)−Rh(1) 171.2(4); O(2)−C(21)−Rh(1) 136.9(1);
C(20)−Rh(1)−C(11) 102.1(2); C(20)−Rh(1)−C(13*) 94.6(2); N(1)−Rh(1)−C(20) 98.6(2); N(1)−Rh(1)−C(21) 168.0(1).
Scheme 6. Formation of Complexes 13 and 14
equivalent in the H as well as in the 13C NMR spectra. In
1
and 314.2 ppm for the noncoordinating atom N5 (see Table 1).
Therefore, the N NMR resonance is shifted 141 ppm upfield
1
15
addition to that, the H NMR shifts of the naphthyridine unit
are similar to those of the free ligand 5. This is in agreement
upon coordination, a value that is much higher compared with
complexation to the more electron-rich Rh(III) or Rh(I)
centers in complexes 9−12. Similar upfield shifts are well-
with a noncoordinating naphthyridine unit leading to a three-
18
legged piano stool arrangement. However, we cannot exclude
20
the possibility of a weak naphthyridine−Zr interaction com-
documented in the literature.
bined with a fast exchange of the NMe units. A similar behavior
A single-crystal X-ray analysis of the complex reveals that two
molecules of THF are present in the asymmetric unit. One of them
is coordinated to the Zr center and thus completes its coordina-
tion sphere to an octahedral environment where the indenyl
unit occupies one coordination site (see Figure 6). The Zr−N
2
has been observed by Kol et al. for a closely related zirconium
complex where X-ray crystallography showed a very long Zr−N
interaction between the additional N-donor and the zirconium
19
atom. Complex 13 can be converted to the stable chloro deriv-
18
ative 14 by addition of Me SiCl (see Scheme 6).
distance is within the usual range of such interactions. We
have tested complex 14 as an olefin polymerization catalyst.
Addition of 1000 equiv of MAO (Al/Zr ratio) and ethylene
saturation of the toluene solution lead to the formation of small
3
The coordination of the naphthyridine unit to the metal
15
center in solution is proven by two well-separated N NMR
1
5
resonances with δ( N) = 172.3 ppm for the coordinated N1
3
60
dx.doi.org/10.1021/om2009638 | Organometallics 2012, 31, 356−364

Organometallics
Article
Table 1. Comparison of the 15N NMR Data of the Free Ligands and upon Ligand Coordination to the Metal Centers
1
5
15
15
15
Δδ( N coord − 15N noncoord)
15
complex
metal center
δ( N1/ N5)
corresponding ligand
δ( N1/ N5)
9
Rh(III)
Rh(I)
Rh(I)
Rh(I)
Zr(IV)
241/318
318/225
245/308
252/302
172/314
7
6
5
5
5
312/303
319/311
313/310
313/310
313/310
−71
−86
−68
−61
−141
1
1
1
1
0
1
2
4
EXPERIMENTAL SECTION
■
Materials and General Considerations. Unless noted other-
wise, all manipulations were carried out under an inert argon or
nitrogen atmosphere using standard Schlenk techniques. All glassware
was heated and dried under vacuum before use. Toluene, THF,
dichloromethane, and n-hexane were dried using a solvent purifier
system based on molecular sieves supplied by VAC and were degassed
prior to use.
NMR spectra were recorded on a Bruker DRX 200, Bruker Avance
II 400, or Bruker Avance III 600 spectrometer. The latter spectrometer
was equipped with a direct detection cryoprobe for maximum sen-
sitivity in the detection of 13C. H and C NMR chemical shifts were
referenced to signals of the solvent. NMR assignments were confirmed
by H,H−COSY, HSQC, and HMBC experiments. Mass spectra were
recorded on a Finnigan MAT8230 and a JEOL JMS-700 spectrometer.
Elemental analyses were performed on a CHN-O-vario EL by the
Mikroanalytisches Labor, Organisch-Chemisches Institut, University of
Heidelberg. X-ray crystallographic data were collected using a Bruker
AXS SMART 1000 CCD diffractometer (7−9, 11, 14) or a Bruker-
Nonius Kappa Apex II diffractometer with an FR591 rotating anode
source (12).
1
13
X-ray Crystal Structure Determinations. Crystal data and
details of the structure determinations are listed in Table 1SI (see
the Supporting Information). Full shells of intensity data were col-
lected at low temperature with a Bruker AXS Smart 1000 CCD diffrac-
tometer (Mo Kα radiation, graphite monochromator, λ = 0.71073 Å)
Figure 6. Solid-state molecular structures of 14. An additional
molecule of THF in the asymmetric unit has been omitted for clarity.
Selected bond lengths [Å] and angles [deg]: Zr−O(1) 2.315(1); Zr−
N(1) 2.416(1); Zr−Cl(1) 2.4431(4); Zr−Cl(2) 2.4676(4); Zr−Cl(3)
(
compounds 7−9, 11, and 14) or with a Bruker-Nonius Kappa Apex II
2
.4834(4); Zr−C(12) 2.454(1); O(1)−Zr−N(1) 78.98(4); O(1)−
Zr−Cl(1) 82.75(3); O(1)−Zr−Cl(2) 79.35(3); O(1)−Zr−Cl(3)
7.35(3); N(1)−Zr−Cl(1) 161.69(3); Cl(1)−Zr−C(12) 120.54(3).
diffractometer with an FR591 rotating anode source (compound 12).
Data were corrected for air and detector absorption, and Lorentz
7
2
1
and polarization effects; absorption by the crystal was treated with a
2
2
semiempirical multiscan method. The structures were solved by
amounts of linear polyethylene. The activity of 80 (g [polymer]
2
3
mmol−1 [Zr] h bar ) is quite low so that we did not evaluate
−1
−1
conventional direct methods (7, 12), by the heavy atom method
combined with structure expansion by direct methods applied to dif-
this reactivity in more detail.
24
25
2
ference structure factors (8, 11, 14) or by the charge flip procedure
(
13) and refined by full-matrix least-squares methods based on F
against all unique reflections.
2
6,23b
CONCLUSION
All non-hydrogen atoms were given
■
anisotropic displacement parameters. Hydrogen atoms were generally
input at calculated positions and refined with a riding model. When
justified by the quality of the data, the positions of some hydrogen
atoms (the nonmethyl hydrogens in 7, those on the carbon atoms
involved in coordination to Rh 8 and 12) were taken from difference
Fourier syntheses and refined.
The synthesis of N-donor-functionalized indenyl and cyclo-
pentadienyl ligands, where a second N atom is in a distal
position, has been demonstrated by the coupling of the
naphthyridine unit with the indenyl or the cyclopentadienyl
ring, respectively. The coordination behavior of the new ligands
has been evaluated in a series of rhodium complexes and two
Zr(IV) complexes. Depending on the substitution pattern, Rh
Synthesis of 2a. 8-Hydroxy-1,5-naphthyridine (1.00 g, 6.8 mmol)
was suspended in a mixture of dry DMF (10 mL) and dry CH Cl
2
2
(
10 mL) and cooled to −10 °C. Oxalyl chloride (700 μL, 8.16 mmol)
1
2
3
5
coordinates to the ligands in κ , η , η , or η mode. The axially
chiral ligand 6 forms two diastereomeric complexes (10a and
was added dropwise, and the solution was warmed to rt. The CH Cl
2
2
was removed under vacuum, and the remaining DMF solution was
stirred at 50 °C for 4 h. The mixture was diluted with CH Cl (100
2
2
10b) due to restricted rotation of the coordinated square-planar
mL) and washed with dilute NH (100 mL of water + 2 mL of conc.
3
Rh(CO) Cl unit. The dinuclear complex 12 shows a rare
2
NH ). The CH Cl layer was filtered through Celite 545 to remove
3
2
2
coordination environment where two ligands are bridging a
insoluble material, and the Celite was washed with further CH Cl .
2
2
Rh (CO) unit. Zr complex 14 shows the expected geometry,
The combined CH Cl filtrate was washed a further four times with
2
3
2 2
and it has been evaluated as an olefin polymerization catalyst.
N NMR spectroscopy was used as a highly reliable tool for
the validation of metal−N interactions in solution. This work is
the basis for a wider application of donor-functionalized ligands
with distal donors to other metal centers and for the investiga-
tion of the influence of the distal donor.
water and dried with MgSO , and the solvent was evaporated. The
4
1
5
crude chloride is a tan-colored solid. Yield: 710 mg (4.3 mmol = 63%).
1
3
3
H NMR (CDCl , 400 MHz): δ 7.71 (dd, 1H, J
= 4.1 Hz, J
=
=
3
H2,H3
H3,H4
3
3
8
8
(
.5 Hz, H3), 7.75 (d, 1H, J
= 4.6 Hz, H7), 8.34 (dd, 1H, J
H6,H7
H3,H4
4
3
.5 Hz, J
= 1.5 Hz, H4), 8.84 (d, 1H, J
= 4.6 Hz, H6), 9.08
H2,H4
H6,H7
13 1
3
4
dd, 1H, J
= 4.1 Hz, J
= 1.5 Hz, H2). C{ H} NMR (CDCl ,
H2,H3
H2,H4 3
100 MHz): δ 124.5, 125.3, 138.0 (3×CH), 140.9, 144.2, 144.9 (3×Cq),
3
61
dx.doi.org/10.1021/om2009638 | Organometallics 2012, 31, 356−364

Organometallics
Article
+
50.6, 151.6 (2×CH). MS(EI) m/z (%): 164 (100) [M] , 129 (45)
(CHInd), 137.7 (C4), 140.8, 142.5, 143.8, 143.9, 144.3, 144.3 (6×C ),
q
+
2
2
15
150.7 (t, J = 3.2 Hz, C2), 151.1 (t, J = 3.0 Hz, C6). N NMR
H,N H,N
Synthesis of 3a. 8-Chloro-1,5-naphthyridine (1b) (1.43 g, 8.7
(CDCl , 61 MHz): δ 310.5 (N5/H4, H6, H7), 312.6 (N1/H2, H3,
3
+
+
mmol) was dissolved in 10 mL of dry DMF, and 730 mg (10.4 mmol)
of NaSMe was added. The reaction was exothermic. The mixture was
stirred at rt overnight, then diluted with CH Cl and washed five times
H7). MS(EI) m/z (%): 243 (100) [M − H] , 216 (8) [M − C H ] .
2
3
C H N (244.28) Calcd: C, 83.58; H, 4.95; N, 11.47. Found: C,
17
12
2
82.87; H, 4.92; N, 11.35.
2
2
with water. The organic layer was dried and the solvent evaporated.
The crude product was isolated as a brown powder that was dried at
Synthesis of 6. The sulfide 3b (1.0 g, 4.4 mmol) was dissolved in
50 mL of CH Cl . The solution was cooled to 0 °C, and m-CPBA (1.1
2
2
6
0 °C under high vacuum for 20 min in order to remove the last traces
g of 70−75% purity, 4.6 mmol) was added. After 15 min, the solution
1
of DMF. Yield: 1.36 g (7.72 mmol = 89%). H NMR (CDCl , 400
MHz): δ 2.55 (s, 3H, CH ), 7.26 (d, 1H, J
was extracted twice with saturated aqueous NaHCO solution and
3
3
3
= 4.8 Hz, H7), 7.63
dried with MgSO , and the solvent was evaporated. The crude
3
H6,H7
4
3
3
3
(
dd, 1H, J
= 4.2 Hz, J
= 8.5 Hz, H3), 8.33 (dd, 1H, J =
product (4b) was used directly in the next step. A solution of
2-methylindenyllithium was prepared by dissolving 2-methylindene (710
μL, 5.3 mmol) in 70 mL of THF at 0 °C and adding n-BuLi (3.4 mL of
1.6 M, 5.4 mmol) dropwise. The solution was cooled to −110 °C, and
the crude sulfoxide 4b (1.0 g, 4.1 mmol) dissolved in 20 mL of dry
CH Cl was added dropwise. After 30 min at −110 °C, the reaction
H2,H3
H3,H4
H3,H4
4
3
8
.5 Hz, J
= 1.6 Hz, H4), 8.74 (d, 1H, J
= 4.8 Hz, H6), 8.91
= 1.6 Hz, H2). C{ H} (CDCl , 100
H2,H4 3
H2,H4
H6,H7
13
3
4
1
(
dd, 1H, J
= 4.2 Hz, J
H2,H3
MHz): δ 13.6 (CH ), 117.1, 124.9, 137.6 (3×CH), 141.7, 142.3
3
(
(
2×C ), 149.4, 150.1 (2×CH), 151.6 (C ). MS(EI) m/z (%): 176
q q
+ +
100) [M] , 129 (45) [M − SCH ] .
3
2
2
Synthesis of 3b. Benzo[b][1,5]naphthyridin-10(5H)-one (2.0 g,
was quenched by addition of 10% aqueous NH Cl (100 mL). The
4
1
0.2 mmol) was suspended in a mixture of dry DMF (20 mL) and dry
mixture was diluted with CH Cl , and the organic layer was separated.
2
2
CH Cl (20 mL) and cooled to −10 °C. Oxalyl chloride (1.45 g, 11.4
mmol) was added dropwise and the solution warmed to rt. The
The CH Cl layer was then washed twice with water and dried with
2
2
2 2
MgSO , and the solvent was evaporated. Flash chromatography (silica
4
CH Cl was removed under vacuum. The solution was cooled to 0 °C,
gel 60, 230−400 mesh) eluting with 5% EtOAc in CH Cl gave the
2
2
2
2
and NaSMe (2.2 g, 31.4 mmol) was added. The mixture was stirred at
indene product as a gum contaminated with a bright yellow impurity.
The yellow impurity can be removed by dissolving the product in a
little CH Cl and then adding n-hexane: the yellow impurity then
0
°C for 10 min and was allowed to warm to rt over 30 min. The
mixture was diluted with CH Cl (150 mL) and extracted with dilute
2
2
2
2
NH (150 mL of water + 2 mL of conc. NH ). The CH Cl layer was
precipitates as a gum on the walls of the flask. The mother liquor is
separated and heated to boil off the CH Cl ; the pure indene then
3
3
2
2
filtered through Celite 545 to remove insoluble material. The com-
bined CH Cl filtrate was washed a further four times with water and
2
2
2
2
crystallizes from the n-hexane solution as a colorless solid. Yield: 780
1
dried, and the solvent was evaporated. Flash chromatography (silica
mg (2.53 mmol = 58% calculated from 3b). H NMR (C D , 400
6
6
3
gel 60, 230−400 mesh) eluting with 15% EtOAc + 1% NEt in CH Cl
MHz): δ 1.82 (s, 3H, CH ), 5.41 (s, 1H, H1′), 6.68 (dd, 1H, J
= 3.9 Hz, H3), 6.83 (m, 2H, H3′/H7′), 6.94, (dd, 1H,
J ′ ′ = 7.5 Hz, J ′ ′ = 7.5 Hz, H5′), 7.31 (m, 2H, H6′/H8), 7.54
=
3
2
2
3
H3,H4
4
gave the sulfide as a pale yellow solid. Yield: 950 mg (4.2 mmol =
8.6 Hz, J
H2,H3
1
3
3
4
1
(
1%). H NMR (CDCl , 400 MHz): δ 2.87 (s, 3H, CH ), 7.64 (m,
3
3
H4 ,H5 H5 ,H6
3
3
3
H, H8), 7.68 (dd, 1H, J
m, 1H, H7), 8.20 (d, 1H, J
.8 Hz, J
= 8.8 Hz, J
= 3.8 Hz, H3), 7.82
(m, 2H, H4′/H7), 8.23 (d, 1H, J
= 8.9 Hz, H9), 8.34 (m, 2H,
= 8.8 Hz, H6). C{ H} NMR (CDCl ,
H6,H7 3
H3,H4
H2,H3
H8,H9
3
3
3
13
1
= 8.8 Hz, H9), 8.51 (dd, 1H, J
=
H2/H4), 8.61 (d, 1H, J
H8,H9
H3,H4
4
3
8
= 1.5 Hz, H4), 8.81 (d, 1H, J
= 8.8 Hz, H6), 9.12
100 MHz): δ 15.7 (CH ), 53.2 (C1′), 120.5 (CH), 122.6 (C3′), 123.5
H2,H4
H6,H7
13
3
3
4
1
(
dd, 1H, J
= 3.8 Hz, J
= 1.5 Hz, H2). C{ H} NMR (CDCl ,
(CHInd), 124.1, 124.6 (2×CH), 126.7, 127.8, 129.6 (3×CHInd), 130.1,
H2,H3
H2,H4
3
1
1
00 MHz): δ = 20.5 (CH ), 124.7, 126.6, 126.8 (3×CH), 129.8 (C ),
131.7, 137.5 (3×CH), 129.5, 138.8, 144.7, 144.8, 145.6, 148.8, 150.0,
3 q
30.1, 130.9, 138.1 (3×CH), 140.7, 144.3, 148.6, 149.4 (4×C ), 151.0
15
q
150.7 (8×C ), 150.8 (CH). N-HMBC NMR (C D , 41 MHz): δ
q 6 6
+
+
(CH). MS (EI) m/z (%): 226 (10) [M] , 180 (100) [M − SCH ] .
311.5 (N5/H4, H6), 319.1 (N1/H2, H3, H4). MS(FAB) m/z (%):
3
+
+
Synthesis of 4a. The sulfide 3a (1.36 g, 7.7 mmol) was dissolved
309 (100) [M + H] , 293 (53) [M − CH − H] .
3
in 70 mL of CH Cl , the solution cooled to 0 °C, and m-CPBA (2.21 g
Synthesis of 7. A solution of 1,2,3,4-tetramethylcyclopentadie-
nyllithium was prepared by dissolving 1,2,3,4-tetramethylcyclopenta-
diene (220 mg, 1.8 mmol, 85% purity) in 10 mL of THF and adding
n-BuLi (1.2 mL of 1.6 M, 1.9 mmol) dropwise over 10 min at 0 °C.
The solution was cooled to −78 °C, and the sulfoxide 4a (170 mg,
0.9 mmol) dissolved in 10 mL of THF was added dropwise. After 2 h
at −78 °C, the reaction was quenched by addition of 10% aqueous
NH Cl (50 mL). The mixture was diluted with CH Cl , and the
2
2
of 70−75% purity, 9.6 mmol) was added. The mixture was allowed to
warm to rt over 10 min. The CH Cl solution was washed twice with
2
2
saturated aqueous NaHCO solution and dried with MgSO , and the
3
4
solvent was evaporated. The crude sulfoxide is a pale yellow solid.
1
Yield: 1.15 g (6.0 mmol, 78%). H NMR (CDCl , 600 MHz): δ 3.07
3
3
3
(
s, 3H, CH ), 7.73 (dd, 1H, J
= 4.1 Hz, J
= 8.5 Hz, H3),
= 8.5 Hz, H4),
= 4.3 Hz, H6).
3
H2,H3
H3,H4
3
3
8
8
.20 (d, 1H, J
.94 (d, 1H, J
= 4.3 Hz, H7), 8.50 (d, 1H, J
= 4.1 Hz, H2), 9.17 (d, 1H, J
C{ H} (CDCl , 150 MHz): δ = 41.9 (CH ), 119.7, 125.2, 137.8
H6,H7
H3,H4
H6,H7
4
2
2
3
3
H2,H3
organic layer was separated. The CH Cl layer was washed a further
2
2
1
3
1
3
3
two times with water and dried with MgSO , and the solvent was
4
(
3×CH), 139.2, 143.2 (2×C ), 150.7, 151.3 (2×CH), 154.3 (C ).
evaporated. Flash chromatography (silica gel 60, 230−400 mesh)
q
q
Synthesis of 5. A solution of indenyllithium was prepared by
eluting with 25% EtOAc in CH Cl gave the product as an orange
2
2
1
dissolving indene (1.65 mL, 14.0 mmol) in 30 mL of THF at 0 °C and
adding n-BuLi (8.6 mL of 1.6 M, 13.8 mmol) dropwise. The solu-
tion was cooled to −78 °C, and the sulfoxide 4a (1.21 g, 6.3 mmol)
dissolved in 15 mL of THF was added dropwise. After 1 h at −78 °C,
compound. Yield: 188 mg (0.75 mmol = 83%). H NMR (CDCl , 600
3
MHz): δ 1.60 (s, 6H, 2×CH ), 1.85 (s, 6H, 2×CH ), 5.43 (s, 1H,
3
3
3
3
CpH), 6.89 (d, 1H, J
= 4.5 Hz, H7), 7.64 (dd, 1H, J
= 4.4 Hz, H3), 8.40 (dd, 1H, J
= 4.5 Hz, H6), 9.01 (dd, 1H, J
= 1.2 Hz, H2). C{ H} NMR (CDCl , 100 MHz): δ 11.1
H2,H4 3
= 8.5
= 1.2
= 4.4
H7,H6
H3,H4
3
3
4
Hz, J
= 8.5 Hz, J
H3,H2
H4,H3
H4,H2
3
3
the reaction was quenched by addition of 10% aqueous NH Cl (100
Hz, H4), 8.77 (d, 1H, J
4
H6,H7
13
H2,H3
4
1
mL). The mixture was diluted with CH Cl and the organic layer
Hz, J
2
2
separated. The CH Cl layer was washed a further two times with
(CH ), 11.8 (CH ), 55.4 (CH ), 121.0 (C7), 123.9 (C3), 136.9 (C ),
2
2
3 3 Cp q
water and dried with MgSO , and the solvent was evaporated. Flash
137.4 (C4), 137.9 (C ), 143.6, 143.8, 144.4 (3×C ), 149.6 (C2), 150.9
q q
4
(C6). 15N-HMBC NMR (CDCl , 41 MHz): δ 302.6 (N5/H4, H6,
chromatography (silica gel 60, 230−400 mesh) eluting with 25%
3
+
EtOAc in CH Cl gave the indene product as a pale pink solid. Yield:
H7), 311.8 (N1/H3). MS(EI) m/z (%): 250 (100) [M] , 235 (95)
[M − CH ] , 220 (30) [M − 2×CH ] , 205 (12) [M −3×CH ] .
2
2
1
+
+
+
1
2
.31 g (5.36 mmol = 85%). H NMR (CDCl , 400 MHz): δ 3.69 (d,
H, J ′ ′ = 1.8 Hz, (H1′) ), 6.95 (t, 1H, J ′ ′ = 1.8 Hz, H2′),
.19−7.26 (m, 3H, H4/H5/H6), 7.56 (m, 1H, H7), 7.66 (dd, 1H,
= 4.1 Hz, J
H7), 8.46 (dd, 1H, J
3
3
3
3
3
3
H1 ,H2
2
H1 ,H2
Synthesis of 8. Ligand 7 (497 mg, 1.99 mmol) was dissolved in
100 mL of THF, and KH (84 mg, 2.09 mmol) was added at rt. After
stirring overnight, di-μ-chlorodicyclooctadienyldirhodium(I) (490 mg,
0.99 mmol) in 100 mL of toluene was added, and the reaction mixture
was stirred for a further 2 days. The solvent was evaporated and the
residue extracted with diethylether. Flash chromatography (Alox,
230−400 mesh) eluting with CH Cl gave the product as a red solid.
́
́
́
́
7
3
3
3
J
= 8.5 Hz, H3), 7.73 (d, 1H, J
= 8.5 Hz, J
= 4.4 Hz,
H2,H3
H3,H4
H6,H7
3
4
= 1.7 Hz, H4), 8.96 (dd,
H3,H4
H2,H4
3
4
3
1H, J
= 4.1 Hz, J
= 1.7 Hz, H2), 9.02 (d, 1H, J
= 4.4
H6,H7
H2,H3
H2,H4
1
3
1
Hz, H6). C{ H} (CDCl , 100 MHz): δ 38.7 (C1′), 120.9 (C2′),
3
123.7 (C7), 124.0 (CHInd), 124.5 (C3), 125.7, 126.1 (2×CHInd), 136.5
2
2
3
62
dx.doi.org/10.1021/om2009638 | Organometallics 2012, 31, 356−364

Organometallics
Article
1
14.7 Hz, C2′), 90.7 (d, 1JRh,C = 13.6 Hz, C3′), 120.5 (CH), 122.0
(CHInd), 125.3 (CH), 126.1, 127.5, 127.8 (3×CHInd), 139.9 (CH),
Yield: 412 mg (0.9 mmol = 45%). H NMR (CDCl , 400 MHz): δ
3
1
2
8
.52 (s, 6H, 2×CH ), 2.02 (m, 4H, CH2‑COD), 2.05 (s, 6H, 2×CH ),
3 3
3
.32 (m, 4H, CH2‑COD), 3.17 (m, 4H, CH ), 7.62 (dd, 1H, J
=
142.5, 144.5, 145.2, 145.4, 148.0 (5×C ), 151.1 (CH), 152.7 (CH),
COD
H3,H4
q
3
3
1
15
.4 Hz, J
= 4.1 Hz, H3), 8.32 (d, 1H, J
= 1.5 Hz, H4), 9.01 (dd, 1H, J =
= 1.5 Hz, H2), 9.05 (d, 1H, J
= 4.3 Hz, H7), 8.45
183.3 (d, J
= 74.7 Hz, CO). N-HMBC NMR (C D , 41 MHz): δ
H3,H2
H6,H7
Rh,C 6 6
3
4
3
−1
(
dd, 1H, J
= 8.4 Hz, J
244.9 (N1/H2), 308.4 (N5/H6). FT-IR (toluene): ν (cm ) =
̃
H4,H3
H4,H2
H2,H3
4
3
−1
+
4
.1 Hz, J
= 4.3 Hz, H6).
2034 cm (s, ν
). MS(EI) m/z (%): 410 (5) [M] , 346 (100)
H2,H4
H6,H7
CO
1
3
1
+
+
C{ H} NMR (CDCl , 100 MHz): δ 9.9, 10.6 (2×CH ), 32.4 (CH2‑COD),
= 14.0 Hz, CH ), 96.8 (d, J
JRh,C = 4.0 Hz, C ), 102.3 (d, J = 4.6 Hz, C ), 123.8 (C3), 130.0 (C7),
37.4 (C4), 143.9, 144.1, 144.5 (3×C ), 150.3 (C2), 150.6 (C6). N-
HMBC NMR (CDCl , 61 MHz): δ 306.9 (N5/H4, H6, H7), 313.9
[M − Cl − CO] , 243 (25) [M − Rh(CO)Cl] . C H ClN ORh
(410.66 g/mol) Calcd: C, 52.69; H, 2.95; N, 6.83. Found: C, 52.16; H,
3.02; N, 6.71.
3
3
18 12
2
1
1
7
1.4 (d, J
= 4.1 Hz, C ), 99.6 (d,
Rh,C
COD
Rh,C
q
1
1
q
Rh,C
q
15
1
Synthesis of 12. In a Schlenk flask under an argon atmosphere, 5
(300 mg, 1.23 mmol) was dissolved in degassed THF (30 mL), and
the solution was cooled to −78 °C. A solution of n-BuLi in n-hexane
(0.89 mL of 1.53 M, 1.36 mmol) was added dropwise and the mixture
q
3
+
(
N1/H2, H3). MS(EI) m/z (%): 460 (24) [M] , 352 (77) [M −
+
+
COD] , 249 (49) [M − RhCOD] . C H N Rh (460.42 g/mol)
25
29
2
Calcd: C, 65.22; H, 6.35; N, 6.08. Found: C, 64.55; H, 6.44; N, 6.49.
stirred for 10 min. At this temperature, [Rh(CO) Cl] (240 mg, 0.62
2 2
Synthesis of 9. An NMR tube was charged with complex 8
mmol) was added. The mixture was stirred under an argon atmo-
sphere overnight, allowing it to warm up slowly to rt in the acetone/
dry ice bath. The volatiles were evaporated under vacuum, and the
remaining dark, reddish-brown residue was dissolved in degassed
(
30 mg, 0.07 mmol) in CDCl (0.6 mL) and irradiated with ultraviolet
3
light for 7 days. After evaporating the solvent, 28 mg of the crude product
was obtained, which showed good NMR spectra, but unsatisfactory
1
elemental analysis data. H NMR (CDCl , 400 MHz): δ 1.68 (s, 6H,
CH Cl (15 mL) and filtered through Celite 545 under an argon
2 2
3
3
2
(
8
1
(
9
1
(
3
×CH ), 1.83 (s, 6H, 2×CH ), 7.77 (d, 1H, J
= 4.3 Hz, H7), 7.79
atmosphere. This solution was concentrated to approximately 10 mL
under vacuum. Stirring under an argon atmosphere, approximately
5 mL of degassed n-hexane was added dropwise. After standing
overnight at rt, the supernatant was removed from the red solid via a
3
3
H6,H7
3
3
3
dd, 1H, J
.7 Hz, J
= 8.7 Hz, J
= 1.0 Hz, H4), 8.71 (dd, 1H, J
.0 Hz, H2), 9.11 (d, 1H, J
= 4.9 Hz, H3), 8.56 (dd, 1H, J
=
=
H3,H4
H3,H2
H4,H3
= 4.9 Hz, J
H2,H3 H2,H4
4
3
4
H4,H2
3
13
1
= 4.3 Hz, H6). C{ H} NMR
H6,H7
1
CDCl , 100 MHz): δ 8.8, 9.2 (2×CH ), 90.0 (d, J = 9.0 Hz, Cq),
cannula. The solid was then recrystallized from CH Cl /n-hexane
2 2
3
3
Rh,C
1
1
8.7 (d, J
= 7.1 Hz, C ), 106.3 (d, J
= 8.8 Hz, C ), 125.6 (C7),
using the same procedure as above. After drying under high vacuum,
the product was obtained as an orange solid (200 mg, 0.26 mmol,
Rh,C
q
Rh,C
q
27.7 (C3), 137.6, 145.1, 153.9 (3×C ), 139.2 (C4), 152.3 (C6), 155.2
q
C2). 15N-HMBC NMR (CDCl , 61 MHz): δ 241.4 (N1/H2, H3),
1
3
42%). H NMR (CD
Cl
, 600 MHz): δ 4.85 (d, 1H, JH2
′
,H3′ = 4.0 Hz,
3
2
2
+
3
18.0 (N5/H6, H7). MS(EI) m/z (%): 422 (16) [M] , 387 (100)
M − Cl] , 352 (31) [M − 2×Cl] , 250 (16) [M − RhCl ] .
Synthesis of 10. Ligand 6 (44 mg, 0.14 mmol) was dissolved in
H2′), 6.02 (broad d, 1H, JH2
′
,H3′ = 4.0 Hz, H3′), 7.01 (ddd, 1H,
+
+
+
3
3
4
[
J ′ ′ = 7.8 Hz, J ′ ′ = 7.2 Hz, J ′ ′ = 1.1 Hz, H5′), 7.12 (ddd,
2
H4 ,H5
3
H5 ,H6
3
H5 ,H7
4
1H, J ′ ′ = 7.9 Hz, J ′ ′ = 7.2 Hz, J ′ ′ = 1.1 Hz, H6′), 7.52
H6 ,H7 H5 ,H6 H5 ,H7
3
3
diethylether (10 mL). The solution was added to a solution of
tetracarbonyldi-μ-chlorodirhodium(I) (27 mg, 0.07 mmol) in diethylether
10 mL). After stirring overnight, the yellow precipitate was filtered,
washed with diethylether, and dried under high vacuum. The product
(broad d, 1H, J ′ ′ = 7.8 Hz, H4′), 7.55 (dd, 1H, J
JH2,H3 = 4.6 Hz, H3), 7.87 (broad d, 1H, J ′ ′ = 7.9 Hz, H7′), 8.12
dd, 1H, J
.6 Hz, H7), 8.42 (dd, 1H, J
d, 1H, J
50.1 (d, J
= 8.5 Hz,
H3,H4
H4 ,H5
3
3
H6 ,H7
3
4
3
(
(
= 4.6 Hz, J
= 1.4 Hz, H2), 8.18 (d, 1H, J
=
H2,H3
H2,H4
H6,H7
3
4
4
(
= 8.5 Hz, J
= 1.4 Hz, H4), 8.89
H3,H4
13
H2,H4
3
1
was obtained as a pale yellow powder. Yield: 30 mg (0.06 mmol =
= 4.6 Hz, H6). C{ H} NMR (CD Cl , 150 MHz): δ
H6,H7 2 2
1
1
1
4
3%). H NMR (CDCl , 400 MHz): δ 1.86 (s, 3H, CH ), 5.55 (s, 1H,
3
3
= 9.4 Hz, C3′), 61.0 (d, J
= 10.9 Hz, C1′), 82.9
C,Rh
C,Rh
H1′), 6.75−6.82 (m, 2H, H3′/CHInd), 6.90 (m, 1H, CHInd), 7.23 (m,
(C2′), 121.05 (C7′), 122.42 (C4′), 122.94 (C7), 124.08 (C6′), 124.17
(C5′), 124.64 (C3), 139.22 (C4), 139.80 (C7a′), 142.48 (C3a′), 144.63
(C4a), 146.44 (C8a), 148.29 (C2), 152.34 (C6), 154.10 (C8), 190.41
1
H, CH ), 7.40 (m, 1H, CH ), 7.67 (m, 1H, H3), 7.85 (ddd, 1H,
Ind
Ind
3
3
4
JH7,H8 = 7.6 Hz, J
JH7,H8 = 7.6 Hz, J
= 3.7 Hz, J
Hz, H9), 9.58 (broad d, 1H, J
= 8.8 Hz, J
= 8.8 Hz, J
= 1.1 Hz, H8), 8.11 (ddd, 1H,
H6,H8
H8,H9
3
3
4
1
1
= 1.1 Hz, H7), 8.69 (dd, 1H,
(d, J
= 99.6 Hz, terminal CO), 205.68 (t, J
= 38.2 Hz, μ-CO).
H6,H7
H7,H9
C,Rh
C,Rh
3J
4
= 1.5 Hz, H2), 8.76 (broad d, 1H, J
3
= 8.8
15
H2,H3
H2,H4
H8,H9
N NMR (CDCl , 61 MHz): δ 251.6 (N1/H2, H3), 302.4 (N5/H4,
H6, H7). FT-IR (KBr): ν
terminal ν
3
3
−1
= 8.8 Hz, H6), 9.64 (dd, 1H,
̃
(cm ) = 2022 (s, terminal ν
), 1988 (s,
H6,H7
CO
3
4
13
1
JH3,H4 = 8.7 Hz, J
= 1.5 Hz, H4). C{ H} NMR (CDCl , 150
), 1776 (m, μ-ν
). MS(ESI+) m/z (%): 777 (8)
H2,H4
3
CO
CO
+
+
+
MHz) (two isomers): δ 15.81, 15.93 (2×CH ), 53.03, 53.04 (2×CH ),
[M + H] , 749 (31) [M + H − CO] , 693 (100) [M + H − 3×CO] .
3
Cp
1
20.22, 120.34, 121.98, 122.35, 123.58, 123.89, 125.10, 125.15, 126.27,
C
37
H
30
N
4
O
3
Rh (776.41) Calcd: C, 57.24; H, 2.86; N, 7.22. Found: C,
2
126.29, 126.52, 126.81, 126.90, 127.71, 129.84, 129.87 (16×CH + 2
57.05; H, 2.90; N, 7.07.
overlapping CH signals), 130.04, 130.05 (2×C ), 132.97, 132.99, 136.13,
Synthesis of 13. Ligand 5 (5 mg, 0.025 mmol) was dissolved in
q
6
1
36.19 (4×CH), 138.72, 138.73 (2d, JRh,C = 0.9 Hz, 2×C ), 144.61,
1
d -benzene (0.5 mL), and tetrakis(dimethylamido)zirconium(IV) (6.6
q
6
44.65, 144.85, 145.17, 147.42, 147.53, 148.94, 148.96, 149.83, 150.56 5
mg, 0.025 mmol) dissolved in d -benzene (0.5 mL) was added. An
(
10×C ), 150.64, 150.677, (2×CH), 151.85, 151.89 (2×C ), 179.93 (d,
intense reddish-violet solution formed. The NMR data showed that
only one product is formed. Because of the low stability of the
compound, the characterization was performed by NMR and by the
q
q
1
1
JRh,C = 72.2 Hz, CO), 180.03 (d, J
= 72.2 Hz, CO), 183.02 (d,
= 68.7 Hz, CO). N NMR
Rh,C
1J
= 68.6 Hz, CO), 183.03 (d, J
1
15
Rh,C
Rh,C
1
subsequent derivatization to 14. H NMR (C D , 600 MHz): δ 2.83
(
(
(
CDCl , 61 MHz): δ 225.5 (N5/H4, H6), 318.4 (N1/H2, H3). FT-IR
6
6
3
3
−1
(
s, 18H, 3×N(CH ) ), 6.84 (d, 1H, J ′ ′ = 3.5 Hz, H2′ or 3′), 6.92−
toluene): ν
̃
(cm ) = 2084 (s, ν
), 2009 (s, ν
). MS(EI) m/z
3
2
H2 ,H3
CO
CO
+
+
6
.94 (m, 2H, H3′ or 2′/H3), 7.14−7.16 (m, 1H, H4′ or 7′), 7.20−7.23
%): 474 (5) [M − CO] , 410 (50) [M − Cl − 2CO] , 307 (100)
3
+
(
m, 1H, H4′ or 7′), 7.44 (d, 1H, J
= 4.3 Hz, H7), 7.62 (ddd, 1H,
H6,H7
[
M − Rh(CO) Cl] . C H ClN O Rh (502.75 g/mol) Calcd: C,
2
24 16
2
2
3
3
4
5
7.34; H, 3.21; N, 5.57. Found C, 57.25; H, 3.47; N, 5.36.
JH,H = 8.4 Hz, JH,H = 8.4 Hz, JH,H = 1.1 Hz, H5′ or 6′), 7.83 (ddd,
1H, JH,H = 8.4 Hz, JH,H = 8.4 Hz, JH,H = 1.1 Hz, H5′ or 6′), 8.29 (dd,
1H, JH2,H3 = 4.4 Hz, JH2,H4 = 1.6 Hz, H2), 8.34 (dd, 1H, JH3,H4 = 8.2
Hz, JH2,H4 = 1.6 Hz, H4), 8.85 (d, 1H, JH6,H7 = 4.3 Hz, H6). C-
3
3
4
Synthesis of 11. Tetracarbonyldi-μ-chlorodirhodium(I) (39 mg,
.1 mmol) was dissolved in diethylether (10 mL). At rt, ligand 5 (51 mg,
.21 mmol) was added. The reaction mixture was stirred for 6 h. A
3
4
3
0
0
4
3
13
1
yellow precipitate was formed, which was filtered, washed with
diethylether, and dried under high vacuum. The product was obtained
as pale yellow crystals. Yield: 60 mg (0.15 mmol = 71%). H NMR
Dept{ H} NMR (C D , 150 MHz): δ 44.8 (3×N(CH ) ), 102.5
6
6
3
2
(CHCp), 119.5 (CHCp), 119.5 (CHInd), 122.4 (CHInd), 123.1 (C7),
123.4 (2 x CHInd), 137.9 (C4), 148.6 (C2), 151.6 (C6).
1
3
(
CDCl , 400 MHz): δ 3.46 (d, 2H, J ′ ′ = 2.8 Hz, (1′H) ), 5.30 (t,
Synthesis of 14. To a stirred solution of Zr(NMe ) (110 mg,
3
H1 ,H2
2
2 4
3
1
1
H, J ′ ′ = 2.8 Hz, H2′), 7.37−7.44 (m, 3H, 3×CH ), 7.79 (dd,
0.41 mmol) in toluene (15 mL) was added a solution of 5 (100 mg,
0.41 mmol) in toluene (15 mL) at −78 °C. The colorless solution
immediately turned dark purple and was stirred for 1 h. At −78 °C, the
H1 ,H2
Ind
3
3
3
H, J
= 4.8 Hz, J
= 8.7 Hz, H3), 7.83 (d, 1H, J
= 4.4
= 8.7
= 4.8
H2,H3
H3,H4
H6,H7
3
3
Hz, H7), 7.95 (d, 1H, J = 7.3 Hz, CHInd), 8.59 (d, 1H, J
H,H
H3,H4
3
3
Hz, H4), 8.96 (d, 1H, J
= 4.4 Hz, H6), 9.24 (d, 1H, J
solvent was evaporated to 10 mL, followed by addition of Me SiCl
H6,H7
H2,H3
1
3
Hz, H2). 13C{ H} (CDCl , 150 MHz): δ 43.8 (C1′), 78.0 (d, J
1
=
(0.2 mL, 1.64 mmol) dropwise over 5 min. After stirring the reaction
3
Rh,C
3
63
dx.doi.org/10.1021/om2009638 | Organometallics 2012, 31, 356−364

Organometallics
Article
mixture at rt for 18 h, the solution was filtered. The crude product was
(d) Baker, R. W.; Reek, J. N. H.; Wallace, B. J. Tetrahedron Lett. 1998,
39, 6573.
(5) Baker, R. W.; Rea, S. O.; Sargent, M. V.; Schenkelaars, E. M. C.;
washed with pentane (3 × 10 mL) and dried under vacuum to yield
complex 14 (120 mg, 0.23 mmol, 56%) as a yellow solid. Green single
Naph
crystals of [Zr(Ind )Cl (THF)] for X-ray diffraction were grown
Tjahjandarie, T. S.; Totaro, A. Tetrahedron 2005, 61, 3733.
3
from a saturated THF solution at rt. The compound cocrystallizes with
one additional molecule of THF (see X-ray analysis and elemental
̈
(6) (a) Moberg, C.; Wennerstrom, O. Acta Chem. Scand. 1971, 25,
2871. (b) Deck, P. A.; Jackson, W. F.; Fronczek, F. R. Organometallics
1996, 15, 5287.
1
3
analysis). H NMR (d -THF, 600 MHz): δ 6.93 (d, 1H, J ′ ′ = 3.4
8
H2 ,H3
3
Hz, H2′ or 3′), 7.15 (d, 1H, J ′ ′ = 3.4 Hz, H3′ or 2′), 7.24−7.33
m, 3H, HInd), 7.77 (d, 1H, J
(7) (a) Oae, S.; Furakawa, N. Adv. Heterocycl. Chem. 1990, 48, 1.
(b) Oae, S.; Uchida, Y. Acc. Chem. Res. 1991, 24, 202.
(8) Baker, R. W.; Luck, I. J.; Turner, P. Inorg. Chem. Commun. 2005,
8, 817.
(9) Adams, J. T.; Bradsher, C. K.; Breslow, D. S.; Amore, S. T.;
Hauser, C. R. J. Am. Chem. Soc. 1946, 68, 1317.
(10) Denny, W. A.; Atwell, G. J.; Cain, B. F. J. Med. Chem. 1977, 20,
1242.
H2 ,H3
3
(
= 8.4 Hz, H ), 7.93 (dd, 1H,
H,H Ind
3
3
3
JH3,H4 = 8.6 Hz, J
H7), 8.72 (d, 1H, J
H2), 9.11 (d, 1H, J
= 4.6 Hz, H3), 7.97 (d, 1H, J
= 8.6 Hz, H4), 9.02 (d, 1H, J
= 4.3 Hz,
= 4.6 Hz,
H2,H3
H6,H7
3
3
H3,H4
H2,H3
3
13
1
= 4.3 Hz, H6). C{ H} NMR (d -THF, 151
H6,H7
8
MHz): δ 109.2 (CHInd), 113.9 (C ), 122.9 (CHInd), 124.7 (C7), 124.9
q
(
C3), 125.7 (CHInd), 126.4 (CHInd), 126.7, 127.0 (2×CHInd), 128.2,
1
1
3
4
29.3 (2×C ), 141.2 (C4), 142.0, 144.2, 147.2 (3×C ), 151.4 (C2),
q
q
15
52.4 (C6). N-HMBC NMR (d -THF, 61 MHz): δ = 172.3 (N1),
8
(11) (a) Jones, W. D.; Feher, F. J. J. Am. Chem. Soc. 1984, 106, 1650.
(b) Janowicz, A. H.; Bergman, R. G. J. Am. Chem. Soc. 1982, 104, 352.
c) Seiwell, L. P. J. Am. Chem. Soc. 1974, 96, 7134. (d) Yung, C. M.;
14.2 (N5). C H Cl N O Zr (585.06 g/mol) Calcd: C, 51.32; H,
25
27
3
2
2
.65; N, 4.79. Found: C, 49.89; H, 4.39; N, 4.76.
(
Skaddan, M. B.; Bergman, R. G. J. Am. Chem. Soc. 2004, 126, 13033.
(e) Bell, T. W.; Brough, A.-A.; Pwartridge, M. G.; Perutz, R.; Rooney,
A. D. Organometallics 1993, 12, 2933.
ASSOCIATED CONTENT
■
*
S
Supporting Information
CIF files giving crystallographic data for compounds 7, 8, 9, 11,
2, and 14. Table 1SI with crystal data and structure refinement
details of 7−9, 11, 12, and 14. This material is available free of
charge via the Internet at http://pubs.acs.org.
(
2
(
4
12) Kohl, G.; Rudolph, R.; Pritzkow, H.; Enders, M. Organometallics
005, 24, 4774.
13) Kohl, G.; Pritzkow, H.; Enders, M. Eur. J. Inorg. Chem. 2008,
230.
1
(14) Pribula, A. J.; Drago, R. S. J. J. Am. Chem. Soc. 1976, 98, 2784.
(
(
15) Dutta, D. K.; Singh, M. M. Trans. Met. Chem. 1994, 19, 290.
16) (a) Heinemann, O.; Jolly, P. J.; Kruger, C.; Verhovnik, G. P. J.
̈
AUTHOR INFORMATION
Corresponding Author
Tel: +49-6221-546247 (M.E.), +61-2-93514049 (R.W.B.).
Fax: +49-6221-541616247 (M.E.), +61-2-93513329 (R.W.B.).
E-mail: markus.enders@uni-hd.de (M.E.), robert.baker@
sydney.edu.au (R.W.B.).
■
*
Organometallics 1996, 15, 5462. (b) Meredith, M. B.; Crisp, J. A.;
Brady, E. D.; Hanusa, T. P.; Yee, G. T.; Brooks, N. R.; Kucera, B. E.;
Young, V. G. Jr. Organometallics 2006, 25, 4945.
(17) (a) Werner, H.; Tune, D.; Parker, G.; Kru
̈
ger, C.; Brauer, D. J.
hn, A.; Tune,
Angew. Chem., Int. Ed. 1975, 14, 185. (b) Werner, H.; Ku
D. Chem. Ber. 1977, 110, 1763. (c) Sui-Seng, C.; Enright, G. D.;
̈
Zargarian, D. J. Am. Chem. Soc. 2006, 128, 6508.
(18) An, J.; Urrieta, L.; Williams, R.; Tikkanen, W.; Bau, R.;
Yousufuddin, M. J. Organomet. Chem. 2005, 690, 4376.
ACKNOWLEDGMENTS
■
This work was supported by the Deutsche Forschungsgemein-
schaft (SFB 623). Dr. Paul Jensen is thanked for assistance with
X-ray diffraction data collection.
(19) Ziniuk, Z.; Goldberg, I.; Kol, M. J. Organomet. Chem. 1997, 545,
4
(
41.
20) Martin, G. J.; Martin, M. L.; Gouesnard, J.-P. 15N-NMR
Spectroscopy: NMR 18 Basic Principles and Progress; Springer-Verlag:
Berlin, 1981.
REFERENCES
■
(
1) (a) Okuda, J. Comments Inorg. Chem. 1994, 16, 185. (b) Jutzi, P.;
Siemeling, U. J. Organomet. Chem. 1995, 500, 175. (c) Jutzi, P.;
(
(
21) SAINT; Bruker AXS: Madison, WI, 1997−2008.
22) (a) Blessing, R. H. Acta Crystallogr. 1995, A51, 33.
Redeker, T. Eur. J. Inorg. Chem. 1998, 6, 663. (d) Mu
Jutzi, P. J. Organomet. Chem. 2000, 600, 127. (e) Butenscho
Chem. Rev. 2000, 100, 1527. (f) Siemeling, U. Chem. Rev. 2000, 100,
495. (g) Qian, Y.; Huang, J.; Bala, M. D.; Lian, B.; Zhang, H. Chem.
Rev. 2003, 103, 2633. (h) Downing, S. P.; Danopoulos, A. A.
Organometallics 2006, 25, 1337.
2) (a) Baker, R. W.; Wallace, B. J. Chem. Commun. 1999, 1405.
b) Baker, R. W.; Foulkes, M. A.; Turner, P. J. Chem. Soc., Dalton
Trans. 2000, 431. (c) Baker, R. W.; Taylor, J. A. Tetrahedron Lett.
000, 41, 4471. (d) Baker, R. W.; Foulkes, M. A.; Griggs, M.; Nguyen,
B. N. Tetrahedron Lett. 2002, 43, 9319. (e) Alt, H. G.; Baker, R. W.;
Dakkak, M.; Foulkes, M. A.; Schilling, M. O.; Turner, P. J. Organomet.
Chem. 2004, 689, 1965. (f) Enders, M.; Kohl, G.; Pritzkow, H.
Organometallics 2004, 23, 3832. (g) Enders, M.; Baker, R. W. Curr.
Org. Chem. 2006, 10, 937.
̈
ller, C.; Vos, D.;
(
b) Sheldrick, G. M. SADABS; Bruker AXS: Madison, WI, 2004−2008.
23) (a) Sheldrick, G. M. SHELXS-86; University of Gottingen:
Gottingen, Germany, 1986. (b) Sheldrick, G. M. Acta Crystallogr.
990, A46, 467.
24) (a) Beurskens, P. T.; Beurskens, G.; de Gelder, R.; Smits, J. M.
̈
n, H.
(
̈
̈
1
1
(
M.; Garcia-Granda, S.; Gould, R. O. DIRDIF-2008; Radboud
University Nijmegen: Nijmegen, The Netherlands, 2008. (b) Beursk-
(
(
ens, P. T. In Crystallographic Computing 3; Sheldrick, G. M., Kru
C., Goddard, R., Eds.; Clarendon Press: Oxford, U.K., 1985; p 216.
25) (a) Palatinus, L. SUPERFLIP; EPF Lausanne: Lausanne,
Switzerland, 2007. (b) Palatinus, L.; Chapuis, G. J. Appl. Crystallogr.
007, 40, 786.
26) Sheldrick, G. M. SHELXL-97; University of Go
Gottingen, Germany, 1997.
̈
ger,
2
(
2
(
̈
ttingen:
̈
(
3) (a) Enders, M.; Rudolph, R.; Pritzkow, H. Chem. Ber. 1996, 129,
59. (b) Enders, M.; Fernandez, P.; Kaschke, M.; Kohl, G.; Ludwig,
G.; Pritzkow, H.; Rudolph, R. J. Organomet. Chem. 2002, 641, 81.
4
́
(
c) Kohl, G.; Pritzkow, H.; Enders, M. Eur. J. Inorg. Chem. 2008, 4230.
(
d) Fernandez, P.; Pritzkow, H.; Carbo, J. J.; Hofmann, P.; Enders, M.
Organometallics 2007, 26, 4402. (e) Litlabø, R.; Enders, M.; To
K. W.; Anwander, R. Organometallics 2010, 29, 2588.
4) (a) Baker, R. W.; Hambley, T. W.; Turner, P. J. Chem. Soc., Chem.
̈
rnroos,
(
Commun. 1995, 2509. (b) Baker, R. W.; Hambley, T. W.; Turner, P.;
Wallace, B. J. Chem. Commun. 1996, 2571. (c) Baker, R. W.;
Foulkes, M. A.; Taylor, J. A. J. Chem. Soc., Perkin Trans. 1 1998, 1047.
3
64
dx.doi.org/10.1021/om2009638 | Organometallics 2012, 31, 356−364