Bulky and modular 3,3′-bipyrazoles as ligands: Synthesis, characterization, and catalytic activity of Pd complexes

Article abstract of DOI:10.1002/ejic.201100694

In the present study, the properties of a new bidentate N,N′-chelating ligand class that bears an electron-excessive 3,3′-bipyrazole core have been investigated. The ligands are easily accessible in a three-step procedure by condensation with diethyl oxalate followed by tandem condensation with hydrazine hydrate and finally by aryl- or alkylation exclusively at the N-1,1′-pyrazole positions to furnish overall eleven new ligands with different electronic properties. After structural analysis of the ligands, their coordination to palladium, copper, and cobalt has been studied. These ligands coordinate the 2,2′-pyrazolyl nitrogen atoms in a bidentate fashion to the metals to realize complexes with an (L)MX ₂ motif. We present two crystal structures of Pd and Cu complexes, which to the best of our knowledge represent the first d⁸ and d ⁹ 2,2′-bipyrazole compounds coordinated through bidentate complexation. Initial catalytic experiments have been performed with palladium complexes with three bipyrazole ligands of this new class; the palladium-catalyzed copper-free Wacker oxidation of different alkenes showed superior activity compared to 2,2′-bipyridines. We attribute this to a higher redox potential of the 3,3′-bipyrazoles, which are- besides electronic effects- also strongly influenced by steric effects. These might be enforced by the extended ligand backbone, the choice of the wingtip substitution, and the smaller coordination cavity within the N ²,N^2′ atoms compared to 2,2′-bipyridine ligands. A sterically bulky 3,3′-bipyrazole ligand class was synthesized in excellent yields using camphor as a building block. The highly modular nature of the system gave rise to a series of 11 new ligands with tunable steric and electronic properties. The derived catalysts with increasing electron-donating properties revealed higher conversions in Cu-free Wacker oxidations of terminal alkenes.

Full text of DOI:10.1002/ejic.201100694

FULL PAPER
DOI: 10.1002/ejic.201100694
Bulky and Modular 3,3Ј-Bipyrazoles as Ligands: Synthesis, Characterization,
and Catalytic Activity of Pd Complexes
Markus J. Spallek,[a] Skrollan Stockinger,[a] Richard Goddard,[b] Frank Rominger,[a] and
Oliver Trapp*[a]
Keywords: Homogeneous catalysis / Palladium / N ligands / Rigid ligands
In the present study, the properties of a new bidentate N,NЈ-
chelating ligand class that bears an electron-excessive 3,3Ј-
bipyrazole core have been investigated. The ligands are eas-
ily accessible in a three-step procedure by condensation with
diethyl oxalate followed by tandem condensation with hy-
drazine hydrate and finally by aryl- or alkylation exclusively
at the N-1,1Ј-pyrazole positions to furnish overall eleven new
ligands with different electronic properties. After structural
analysis of the ligands, their coordination to palladium, cop-
per, and cobalt has been studied. These ligands coordinate
the 2,2Ј-pyrazolyl nitrogen atoms in a bidentate fashion to
the metals to realize complexes with an (L)MX2 motif. We
present two crystal structures of Pd and Cu complexes, which
to the best of our knowledge represent the first d8 and d9
2,2Ј-bipyrazole compounds coordinated through bidentate
complexation. Initial catalytic experiments have been per-
formed with palladium complexes with three bipyrazole li-
gands of this new class; the palladium-catalyzed copper-free
Wacker oxidation of different alkenes showed superior ac-
tivity compared to 2,2Ј-bipyridines. We attribute this to a
higher redox potential of the 3,3Ј-bipyrazoles, which are Ϫ
besides electronic effects Ϫ also strongly influenced by steric
effects. These might be enforced by the extended ligand
backbone, the choice of the wingtip substitution, and the
smaller coordination cavity within the N2,N2Ј atoms com-
pared to 2,2Ј-bipyridine ligands.
and electronically diverse substitution pattern. Further-
more, this ligand system should be preliminarily screened
for catalytic activity, thereby enabling further insights into
the development of stereoselective transformations. To the
best of our knowledge, there is so far no literature about
backbone-fused 3,3Ј-bipyrazoles and their use as potential
ligands for metal-complex-catalyzed transformations. Natu-
ral (+)-(1R,4R)-camphor proved to be the building block of
choice in the design of our new ligand class, since (+)-cam-
phor fulfills all the above-mentioned criteria and further-
more enabled us to extend this strategy to the majority of
bicyclic monoterpenes commonly found in catalyst de-
signs.[2,9,16–19]
Introduction
2,2Ј-Bipyridines are well known and established ligands
in addition to being among one of the most explored che-
late systems in coordination chemistry.[1] Due to their redox
properties and ease of functionalization, they are com-
monly used as catalysts[2] (i.e., allylic oxidations,[3,4] substi-
tutions,[5–7] cyclopropanations,[8,9] and transfer hydrogena-
tions[10]). Surprisingly, 3,3Ј-bipyrazoles have been less used
and investigated as potential ligands.[11–13] Intrigued by the
converse electronic nature of the π-excessive 3,3Ј-bipyr-
azoles[14,15] relative to 2,2Ј-bipyridines, which are π ac-
ceptors, we became interested in their coordination proper-
ties and catalytic activity by considering the influence of
steric as well as electronic effects. Therefore, we designed a
new ligand pattern that fulfills the following criteria: (1) Results and Discussion
short synthesis from readily available starting materials, (2)
steric bulkiness with the possibility of introducing different
moieties, and (3) a modular ligand system with a sterically
The bipyrazole ligands 3a–k were readily synthesized in
a three-step procedure starting from (+)-camphor (see
Scheme 1).
1,3,4,6-Tetraketone 1 was obtained in two tautomeric
enol forms as identified by X-ray crystallographic analysis
by double Claisen condensation with diethyl oxalate in 93%
yield. A third condensation with hydrazine hydrate[20,21] fur-
nished the key intermediate 3,3Ј-bicamphorpyrazole (bcpz)
2 as an insoluble powder in 91% yield. After several
attempts to solubilize 2, we found that prolonged heating
under basic conditions resulted in complete solvation of the
3,3Ј-bipyrazolate, which in turn provided a useful indicator
[a] Organisch-Chemisches Institut,
Ruprecht-Karls Universität Heidelberg,
Im Neuenheimer Feld 270, 69120 Heidelberg, Germany
Fax: +49-6221-544904
E-mail: trapp@oci.uni-heidelberg.de
[b] Department for Chemical Crystallography and Electron
Microscopy,
Max-Planck-Institut für Kohlenforschung,
Kaiser-Wilhelm-Platz 1, 45470 Mülheim a. d. Ruhr, Germany
Supporting information for this article is available on the
WWW under http://dx.doi.org/10.1002/ejic.201100694.
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Bulky and Modular 3,3Ј-Bipyrazoles as Ligands
Figure 1. X-ray crystal structure of ligand 3i (left) and 3j (right)
showing the transoid structure. Thermal ellipsoids are plotted at
50% probability level and hydrogen atoms are omitted for clarity.
Selected bond lengths [pm] for 3i: N1–N2 136.6(4), N1Ј–N2Ј
135.8(4), N2–C3 134.3(5), N2Ј–C3Ј 134.8(5); 3j: N1–N2 139.0(10),
N1Ј–N2Ј 135.6(10), N2–C3 136.5(11), N2Ј–C3Ј 136.7(10).
Scheme 1. Synthesis of 3,3Ј-bipyrazoles 3a–k. i) NaH, THF, 65 °C,
3 d; then 1.0 equiv. (CO2Et)2, 65 °C, 1 d, 93%. ii) N2H5OH, EtOH,
78 °C, 2 d, 91%. iii) NaH, THF, 65 °C, 2 h; then 2.0 equiv. RCH2X,
65 °C, 4 h (16 h for 3c and 3i), 79–98%.
these two crystal structures represent Ϫ in addition to d6
complexes (Ru) Ϫ the first examples of d8 (Pd) and d9 (Cu)
3,3Ј-bipyrazole complexes with bidentate coordination of
the 2,2Ј nitrogen atoms.[11,28] All complexes were charac-
terized by elemental analyses, NMR spectroscopy (except
paramagnetic Cu, Co complexes), IR, and FAB-MS.
of the reaction progress. Furthermore, dialkylation was
achieved exclusively at the pyrazole 1,1Ј-positions without
formation of regioisomeric mixtures, which often hampers
synthesis and requires additional separation steps.[22–24] We
attribute this to steric congestion and metal complexation
of the 2,2Ј nitrogen atoms in the center of the ligand under
these experimental conditions. It should be emphasized
that, due to the here developed and optimized synthetic
protocol and crystallizability of the intermediates, the syn-
thesis of the ligands 3a–i was achieved in only three steps
without the need of tedious workup procedures or chroma-
tographic separations and with overall excellent yields be-
tween 67 and 82%. Single crystals of the free ligands were
obtained by slow evaporation of saturated solutions in eth-
anol and revealed a C2-symmetric transoid structure state
with respect to the pyrazole nitrogen atoms, which were ob-
tained for all ligand structures reported here (solid states of
3e–j). The crystal structures of the sterically most de-
manding ligands mesitylene-3,3Ј-bicamphorpyrazole 3i and
naphthalene-3,3Ј-bicamphorpyrazole 3j are depicted in Fig-
ure 1 with an N–C–C–N torsion angle of 172.8(8)° (3i) and
165.0(10)° (3j), respectively.
Scheme 2. Preparation of palladium–(bcpz) complexes 4a–k.
The monomeric palladium complexes of all eleven new
ligands were obtained by conversion with [PdCl2(CH3CN)2]
in acetonitrile at room temperature in good yields (see
Scheme 2). To confirm the ability of complex formation of
the novel ligands, the monomeric bidentate copper(II) and
cobalt(II) complexes of ligands 3h and 3j were prepared and
Figure 2. Distorted geometry observed in the copper(II) complex
of 3h. Thermal ellipsoids are plotted at 50% probability level and
hydrogen atoms are omitted for clarity.
In contrast to the free ligands, the palladium complexes
4h(Cu) crystallized from ethanol-containing solutions. The scarcely crystallize. However, small single crystals of 4h
copper(II) complex of 3h shows a distorted structure be- suitable for X-ray analysis by using synchrotron radiation
tween tetrahedral and square-planar conformation, with an were obtained by slow diffusion of pentane into a saturated
N–Cu–N plane twisted about 51.7° to the Cl–Cu–Cl plane, diethyl ether solution. As shown in Figure 3, two molecules
which is a known phenomena for κ2-LCuCl2 complexes but of the complex [Pd{(bcpz)1,1Ј-(p-tBuC6H4)2}] adopt a
less pronounced in related κ2-2,2Ј-copper(II) compounds[25] cagelike structure with its benzyl wingtips encapsulating
and hardly visible in κ2-2,2Ј-bipyridine copper(II) com- one single diethyl ether molecule. The Pd1 atom lies
plexes[26,27] (see Figure 2). To the best of our knowledge, 49.8 pm above the mean bipyrazole plane (Pd1 coordina-
Eur. J. Inorg. Chem. 2011, 5014–5024
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O. Trapp et al.
FULL PAPER
tion plane 20.5° out of bipyrazole plane; for Pd2 41.7 pm
and 16.5°, respectively) and the bite angle N–Pd–N is
78.3(1)° for Pd1 and 78.9(1)° for Pd2.
1
Figure 4. Distinctive H NMR spectroscopic pattern of 3a and 3j
showing splitting of wingtip methylene signals into a set of two
diastereotopic protons upon complexation to afford 4a and 4j (re-
corded after 16 h).
Figure 3. X-ray crystal structure of palladium 3,3Ј-bipyrazole com-
plex 4h showing the cisoid structure. Thermal ellipsoids are plotted
at 50% probability level and hydrogen atoms are omitted for clarity.
Selected bond lengths [pm]: Pd1–N2 206.4(3), Pd1–N2Ј 207.5(3),
N1–N2 136.5(4), N1Ј–N2Ј 137.3(4), N2–C3 133.6(5), N2Ј–C3Ј
136.8(5).
formation seems to dominate. Surprisingly, evaluation of
the CD spectra of the PdII complexes revealed a reverse
solution behavior exclusively for the 3,5-trifluorobenzyl-
The complex stability in solution, integrity of the cisoid substituted complex 4k, with a pronounced broad positive
structure, and the feasibility of rotating the wingtips are Cotton effect between 275 and 283 nm (see the Supporting
the prerequisite for any application as a catalytic system in Information).
homogeneous catalysis. Therefore solutions of the palladi-
With these ligands and complexes in hand, their catalytic
um(II) complexes 4d–k were studied by temperature-de- potential was screened in the copper-free catalytic oxidation
1
pendent H NMR spectroscopy. The two protons of each of terminal alkenes.[29–31] Compound 4h was arbitrarily
wingtip methylene group at C1 and C1Ј of the free ligands chosen as the model complex for preliminary catalytic
show a characteristic singlet between δ = 5.0 and 5.6 ppm screening.[32] For comparison, [PdCl2(3,3Ј-bpy)][33] (3,3Ј-
for arylated structures, as expected for two sets of enantio- bpy = 3,3Ј-bipyrazole) was synthesized and tested in paral-
topic protons, whereas complexation with PdII results in a lel as a benchmark under the same reaction conditions. Af-
distinct pattern for the cisoid structure. Splitting of the ter optimizing reaction conditions, the oxidations of alkenes
methylene signals with a downfield shift to δ = 5.8 and with molecular oxygen showed overall good conversions to
6.3 ppm is generally observed for the two sets of dia- the corresponding ketones (72–87%; see Table 1). These re-
stereotopic protons of arylated bcpz compounds including sults are noteworthy, even though prolonged reaction times
2
geminal JC,H couplings (δ = 13.8–14.1 ppm for alkyl; δ = were required, since no or very low conversions were ob-
15.6–16.7 ppm for benzylic protons). This is observed for served using molecular oxygen combined with [PdCl2(3,3Ј-
the proton spectra of N,NЈ-alkylated ligands 3a–c as well, bpy)] (5) as catalyst. Much shorter reaction times of 17 h
which undergo downfield shifts between δ = 4.3 and were obtained with benzoquinone (BQ) as the internal oxi-
6.0 ppm combined with more complex splitting patterns dant with overall conversions of 89–99%. To evaluate the
(see Figure 4).
performance of the catalysts with respect to their substitu-
Variable-temperature (VT) proton NMR spectra of 4h–j tion pattern, a test set of three catalysts (4h–k) as represen-
in 1,1,2,2-[D2]tetrachloroethane between 243 and 363 K did tatives for N,NЈ-arylated Pd(bcpz) compounds was chosen.
not indicate the presence of further conformations in solu- The most electron-deficient 3,5-bis(trifluoromethyl)-substi-
tion. The starting spectra remained unchanged, thus prov- tuted complex 4k showed only low conversions of 1-octene
ing complex stability over a broad temperature range. To and vinylcyclohexane, whereas catalysts 4h (p-tert-but-
investigate the influence of solvent, the CD spectra of 4h ylbenzyl-substituted) and 4i (mesitylene substituted) were
were recorded in various solvents. The CD spectra show much more active. With 4i, yields of 83–99% of the corre-
two strong absorptions with a maximum positive Cotton sponding ketones were obtained. We explain this by the
effect at 266–271 nm and a negative Cotton effect at 225– higher redox potential of the 3,3-bipyrazoles, which are in
227 nm in both THF and CH2Cl2 solutions, which are addition to electronic effects also strongly influenced by
larger than in the free ligand. The zero crossings in the CD steric effects, which may be enforced by the ligand back-
spectra are in satisfactory agreement with the maximum ab- bone. While still maintaining the structure, framework, and
sorptions of the complexes, as can be seen in the UV spec- coordination cavity, higher reactivities and conversions with
tra. By contrast, in CH3CN a more disordered random con- increasing electronic-donating properties of arylsubstituted
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Bulky and Modular 3,3Ј-Bipyrazoles as Ligands
bcpz-type catalysts in the range of mesitylene Ͼ p-tert-but- (CF3)2Bn] in the copper-free Wacker oxidation of terminal
ylbenzyl ϾϾ 3,5-bis(trifluoromethyl)benzyl were observed. alkenes. Furthermore, preliminary results in our laborato-
No conversion was achieved using the corresponding palla- ries showed excellent yields and selectivities in the PdII-cata-
dium(II) acetates of 4h and 5 as catalysts.[34] Secondary lyzed isomerization of allylbenzenes, which will be reported
alcohols as starting materials were not oxidized.[35,36] From in due course. Therefore, it can be envisaged that our short
our experimental experiences, we can exclude formation of and high-yielding synthetic protocol, combined with the
Pd black, and all catalysts showed activity even after two versatility of the system, which allows a systematic screen-
cycles, which underlines the stability and recyclability of the ing of steric as well as electronic effects, will give rise to a
catalysts investigated here.
number of new types of fused and even optional chiral 3,3Ј-
bipyrazoles in the near future. Further experiments on the
formation of tetradentate, bimetallic bcpz–metal complexes
and their application in catalysis are underway.
Table 1. Summarized results of the copper-free Wacker oxidation
of alkenes using Pd complexes 4h, 4i, 4k, and 5[a]
.
Substrate
Cat. Ox.[c]
Yield [%][b]
aldehyde ketone
Conv.
[%][b]
1
2
3
4
1-octene
5
4h
5
4h
5
4h
5
4k
4h
4i
5
O2
O2
O2
O2
O2
–
–
25
33
–
–
–
–
Ͻ1
2
35
80
1
27
3
67
2
19
99
97
3
36
94[c]
34
87
5
72
2
19
Ͼ99
Ͼ99
3
Experimental Section
General Remarks: All reagents and solvents were obtained from
Acros, ABCR, Alfa Aesar, Sigma–Aldrich or VWR and were used
without further purification unless otherwise noted. Dichlorometh-
ane was freshly distilled from calcium hydride under an argon at-
mosphere; THF was freshly distilled from sodium under argon at-
mosphere. Deuterated solvents were purchased from Euriso-Top.
Acetonitrile was dried by a MB SPS-800 with the aid of drying
columns. Handling of air- and moisture-sensitive materials was car-
ried out in flame-dried flasks under an atmosphere of argon using
Schlenk techniques. NMR spectra were recorded with Bruker Av-
ance 500, Bruker Avance 300, and Bruker ARX-250 spectrometers
at room temp. Chemical shifts (in ppm) were referenced to residual
solvent protons.[37] GC and GC–MS measurements were performed
with a Thermo PolarisQ Trace GC–MS equipped with split injector
(250 °C), free induction decay (FID; 250 °C), and a quadrupole
ion-trap MS (Thermo, San Jose, CA). MS spectra were recorded
with a Finnigan MAT TSQ 700 or a JEOL JMS-700 spectrometer.
IR spectra were recorded with a Bruker Vector 22 FTIR. Elemental
analyses were performed by the analytical laboratories of the chem-
ical institute of the University of Heidelberg. Melting points were
determined with a Büchi melting-point apparatus and temperatures
were uncorrected. Crystal-structure analysis was accomplished with
Bruker Smart CCD and Bruker APEX diffractometers.
4-methylstyrene
vinylcyclohexane
1-octene
O2
BQ
BQ
BQ
BQ
BQ
BQ
BQ
BQ
5
vinylcyclohexane
–
–
–
–
4k
4h
4i
6
61
83
6
62
83
[a] Reaction conditions: catalyst (5 mol-%), alkene (0.90 mm), O2
(1 atm) or benzoquinone (3.00 equiv.) and n-undecane (10.0 μL) as
internal standard in a dimethylacetamide (DMA)/water mixture
(6:1) at 70 °C stirred for 17 h in a cap sealed vial (3 d with O2).
[b] Reactions were monitored and yields determined by GC and
GC–MS analysis using a 25 m HP-5MS column and He as the inert
carrier gas. [c] 11% of 1-octene isomers detected.
Conclusion
In summary, we have described a novel class (bcpz) of a
sterically bulky ligand system, which features a rigid, bulky
backbone yet still maintains flexibility and diversity
through different substitution patterns (wingtips), thus al-
lowing electronic and steric tuning of the ligands. Since re-
dox potentials of transition-metal complexes are strongly
influenced by steric effects, which may be enforced by the
ligand backbone, the constant ligand sphere combined with
variable and tunable substituents and the smaller cavity of
3,3Ј-bipyrazoles compared to the widely used 2,2Ј-bipyr-
idines may help in developing new catalysts. The corre-
2,2-Bipyridinepalladium(II) chloride (5) was synthesized starting
from [PdCl2(MeCN)2][39] according to a literature procedure.[40]
Bis{(1R,4S)-7,7-dimethyl-3-oxobicyclo[2.2.1]heptan-2-ylidene}-
glyoxal (1): This compound was prepared using a modified pro-
cedure of the reported one.[38] Sodium hydride (0.87 g, 0.036 mol)
was slowly added to a solution of (+)-camphor (5.00 g, 0.033 mol)
in anhydrous THF (150 mL). The suspension was stirred under re-
flux heating (75 °C) for 3 d until the mixture turned into a yellow,
clear solution. The solution was allowed to cool down to room
temperature and half of the volume of diethyl oxalate (2.4 g,
0.016 mol) dissolved in anhydrous THF (100 mL) was added drop-
sponding CuII, CoII, and a series of PdII complexes were wise. After 2 h, the remaining diethyl oxalate solution was added
dropwise and the orange solution was stirred under reflux for one
day. The red solution was cooled to room temperature, and the
solvent was evaporated under reduced pressure. Dichloromethane
(200 mL) was added and the suspension was extracted three times
with water (200 mL). The aqueous layer was acidified with aqueous
1 n hydrochloric acid and extracted with diethyl ether until the
aqueous layer remained almost colorless. The organic layers were
combined, washed with brine, dried with sodium sulfate, and the
solvent removed under reduced pressure to obtain an orange pow-
der. Purification by washings with a small amount of acetone and
prepared and their conformational behavior was studied
with regard to substitution in the solid, as well as in solu-
tion state using X-ray, CD, and VT 1H NMR spectroscopic
analyses. To the best of our knowledge, these complexes of
3h represent the first examples of d8 (Pd) and d9 (Cu) 3,3Ј-
bipyrazole complexes that coordinate through bidentate
complexation. Initial catalytic investigations revealed that
these palladium complexes showed higher activities with in-
creasing electron donating properties induced by appropri-
ate wingtip substitution [–CH2R: Mes Ͼ p-tBuBn ϾϾ 3,5- drying under high vacuum yielded 1 as a bright yellow powder
Eur. J. Inorg. Chem. 2011, 5014–5024
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O. Trapp et al.
(5.47 g, 0.015 mmol, 93 %); m.p. 178–186 °C. 1 H NMR (75.46 MHz, CD3CN): δ = 11.9, 17.7, 20.2, 21.1, 28.7, 34.7, 46.1,
FULL PAPER
(500.13 MHz, CDCl3, TMS): δ = 0.84 [s, 6 H, 2ϫ (–CH3)], 0.93 [s,
6 H, 2ϫ (–CH3)], 0.99 [s, 6 H, 2ϫ (–CH2CCH3)], 1.40–1.51 [m, 4
49.5, 53.7, 63.9, 127.3, 138.9, 155.4 ppm. MS (EI): m/z (%) = 73
(26), 133 (14), 355 (13), 377 (75), 406 (14), 420 (33) [M – (n-pent-
H, 2ϫ (–CCH2–)], 1.69–1.79 [m, 2 H, 2ϫ (–CHCH2–)], 2.01–2.10 yl)]+, 434 (11) [M – (n-butyl)]+, 447 (73) [M – (3ϫCH3)]+, 420 (9)
[m, 2 H, 2ϫ (–CHCH2–)], 3.28 [d, J = 4.0 Hz, 2 H, 2ϫ (–CH)], [M – (ethyl)]+, 475 (9) [M – (CH3)]+, 490 (62) [M]+. HRMS (EI):
11.83 [br. s, 2 H, 2ϫ (–OH)] ppm. 13C NMR (125.75 MHz, CDCl3,
TMS): δ = 8.7, 18.6, 20.6, 27.1, 30.5, 48.5, 48.9, 57.9, 120.6, 155.3,
214.7 ppm. MS (EI): m/z (%) = 151 (15), 179 (100) [C11H15O2]+,
247 (94), 330 (54), 358 (34) [M]+. HRMS (EI): m/z calcd. for
m/z calcd. for C H N : 490.4035; found 490.4018. IR (KBr): ν =
˜
32 50 4
3428, 2957, 2870, 1632, 1504, 1451, 1386, 1378, 1365, 1352, 1310,
1282, 1247, 1133, 1107, 1082, 1060, 1049, 1029 cm–1.
1,1Ј-Diisopropyl Derivative 3b: Compound 3b was prepared follow-
ing the standard procedure using 2 (200 mg, 0.571 mmol), sodium
hydride (33 mg, 1.376 mmol), and isopropyl bromide (215 μL,
2.29 mmol) in anhydrous THF (90 mL). After 2 h at reflux tem-
perature, additional isopropyl bromide (215 μL) was added. Exten-
sive drying at elevated temperature under high vacuum yielded pure
3b (236 mg, 0.542 mmol, 95%) as a yellowish powder; m.p. 155–
C H O : 358.2144; found 358.2158. IR (KBr): ν = 3442, 2960,
˜
22 30
4
2871, 1661, 1579, 1456, 1390, 1376, 1337, 1269, 1225, 1179, 1155,
1146, 1106, 1069, 1027, 826, 815 cm–1. C22H30O4 (358.48): calcd.
C 73.71, H 8.44; found C 73.22, H 8.40.
7,7Ј,8,8,8Ј,8Ј-Hexamethyl-4,4Ј,5,5Ј,6,6Ј,7,7Ј-octahydro-1H,1ЈH-
3,3Ј-bi-4,7-methanoindazole (2): Hydrazinium hydroxide
(9.5 mLg–1, 9.22 g, 0.184 mol) was added to a boiling solution of
1 (3.50 g, 9.76 mmol) in absolute ethanol (200 mL) at once through
a short reflux condenser. After heating at reflux for two days, the
precipitate was collected by hot filtration. The filtrate was concen-
trated under reduced pressure at 70 °C, and the formed precipitates
were successively collected. Washings with ethyl acetate and drying
under high vacuum yielded pure 2 (3.13 g, 8.93 mmol, 91%) as a
fluffy, insoluble white powder; m.p. Ͼ 250 °C. MS (EI): m/z (%) =
55 (15), 77 (16), 67 (22), 121 (23), 133 (31), 159 (35), 176 (20)
1
162 °C. H NMR (300.13 MHz, CDCl3, TMS): δ = 0.74–0.68 [m,
2 H, 2ϫ (–CHCH2–)], 0.78 [s, 6 H, 2ϫ (–CH3)], 0.91 [s, 6 H, 2ϫ
(–CH3)], 1.02–1.10 [m, 2 H, 2ϫ (–CHCH2–)], 1.36 [s, 6 H, 2ϫ
(–CH2CCH3)], 1.50 [d, J = 6.9 Hz, 6 H, 2ϫ (–NCHCH3)], 1.53 [d,
J = 6.9 Hz, 6 H, 2 ϫ (–NCHCH3)], 1.90–1.73 [m, 2 H, 2 ϫ
(–CHCH2–)], 2.02–2.15 [m, 2 H, 2ϫ (–CHCH2–)], 2.85 [d, J =
5.0 Hz, 2 H, 2 ϫ (–CCH)], 4.47 [q, J = 6.8 Hz, 2 H, 2 ϫ
(–CH2CH3)] ppm. 13C NMR (125.75 MHz, CDCl3, TMS): δ =
12.5, 19.9, 20.6, 23.2, 23.4, 27.6, 34.1, 48.4, 51.9, 52.8, 62.4, 126.5,
[C11H16N2]+, 177 (69), 187 (19), 220 (19), 307 (32) [M – (3 ϫ 137.7, 152.7 ppm. MS (EI): m/z (%) = 307 (11), 349 (60) [M –
CH3)]+, 350 (17) [M]+. HRMS (EI): m/z calcd. for C22H30N4:
(2ϫiPr)]+, 355 (9), 377 (8), 391 (55) [M – (iPr)]+, 405 (8), 419 (20)
[M – (CH3)]+, 434 (58) [M+]. HRMS (EI): m/z calcd. for C28H42N4:
350.2470; found 350.2442. IR (KBr): ν = 3428, 3262, 2957, 2871,
˜
1632, 1473, 1453, 1418, 1388, 1375, 1367, 1270, 1237, 1180, 1170,
434.3409; found 434.3405. IR (KBr): ν = 3394, 2954, 2869, 1627,
˜
1129, 1083, 969, 950 cm–1. C22H30N4 (350.51): calcd. C 75.39, H 1474, 1452, 1386, 1373, 1366, 1269, 1250, 1234, 1082, 1058, 1020,
8.63, N 15.98; found C 75.18, H 8.88, N 15.77.
971, 954, 915 cm–1.
General Procedure for Alkylation and Arylation of Bicamphorpyr-
azole 2. Syntheses of 3a–k: Compound 2 (1.00 equiv.) and NaH
(2.30 equiv.) were suspended in anhydrous THF (10–50 mm, refer-
enced to 2), stirred for 30 min at room temperature, and heated at
reflux for 2 h until they turned into a clear colorless solution. The
solution was then cooled to room temperature and the appropriate
amount of arylhalogenide (2.05 equiv.) was added. The solution
was stirred at room temperature for 30 min and heated at reflux
1,1Ј-Dipentyl Derivative 3c: Compound 3 was prepared following
the standard procedure using 2 (150 mg, 0.427 mmol), sodium hy-
dride (25 mg, 1.024 mmol), and n-pentyl bromide (116 μL,
0.938 mmol) in anhydrous THF (80 mL). The solution was heated
at reflux for 16 h. Extensive drying at elevated temperature under
high vacuum yielded pure 3c (229 mg, 0.542 mmol, 97%) as a yel-
lowish, insoluble powder; m.p. Ͼ 250 °C. MS (EI): m/z (%) = 73
(26), 133 (14), 355 (13), 377 (75), 406 (14), 420 (33) [M – (n-pent-
for 4–16 h. The precipitate was filtered off, and the solvent was yl)]+, 434 (11) [M – (n-butyl)]+, 447 (73) [M – (3ϫCH3)]+, 420 (9)
evaporated under reduced pressure. The residue was taken up in
CH2Cl2 and washed with water and brine. The organic phase was
separated, dried with Na2SO4, and the solvent was evaporated un-
der reduced pressure to yield the corresponding arylated com-
pounds as analytically pure solids. In the case of alkylation, alkyl-
halogenides (2.20 equiv.) were added. Standard workup procedure
and drying at elevated temperatures under high vacuum yielded
pure alkylated compounds. Whenever necessary, the compounds
were washed with small amounts of pentane.
[M – (ethyl)]+, 475 (9) [M – (CH3)]+, 490 (62) [M]+. HRMS (EI):
m/z calcd. for C H N : 490.4035; found 490.4018. IR (KBr): ν =
˜
32 50
4
3431, 2956, 2871, 1627, 1511, 1454, 1387, 1375, 1366, 1286, 1277,
1260, 1135, 1109, 1084, 1058, 1043, 1015, 1000 cm–1.
1,1Ј-Bis(4-methoxybenzyl) Derivative 3d: Compound 3d was pre-
pared following the standard procedure using 2 (300 mg,
0.856 mmol), sodium hydride (45 mg, 1.883 mmol), and 4-meth-
oxybenzyl chloride (246 μL, 1.75 mmol) in anhydrous THF
(100 mL). The solution was heated at reflux for 4 h. After crystalli-
1,1Ј-Diethyl-7,7Ј,8,8,8Ј,8Ј-hexamethyl-4,4Ј,5,5Ј,6,6Ј,7,7Ј-octa- zation out of ethanol and washings with acetone, 3d (398 mg,
hydro-1H,1ЈH-3,3Ј-bi-4,7-methanoindazole (3a): Compound 3a was
prepared following the standard procedure using 2 (150 mg,
0.676 mmol, 79%) was obtained as a yellowish powder; m.p. 151–
154 °C. 1H NMR (500.13 MHz, CDCl3, TMS): δ = 0.78 [s, 6 H,
0.427 mmol), sodium hydride (25 mg, 1.024 mmol), and ethyl 2 ϫ (–CH3)], 0.87 [s, 6 H, 2 ϫ (–CH3)], 1.07–1.09 [m, 2 H,
bromide (116 μL, 0.938 mmol) in anhydrous THF (80 mL). The solu- 2ϫ (–CCH2–)], 1.10 [s, 6 H, 2ϫ (–CH2CCH3)], 1.18–1.23 [m, 4 H,
tion was heated at reflux for 16 h. Extensive drying at elevated tem-
perature under high vacuum yielded pure 3a (229 mg, 0.542 mmol,
97 %) as a yellowish powder; m.p. 132–148 °C. 1 H NMR
(300.13 MHz, CD3CN): δ = 0.73 [s, 6 H, 2ϫ (–CH3)], 0.93 [s, 6 H,
2ϫ (–CH3)], 1.02–1.10 [m, 2 H, 2ϫ (–CCH2–)], 1.16–1.20 [m, 2 H,
2ϫ (–CCH2–)], 1.65–1.70 [m, 2 H, 2ϫ (–CHCH2–)], 2.06–2.08 [m,
2 H, 2ϫ (–CHCH2–)], 2.92 [d, J = 3.7 Hz, 2 H, 2ϫ (–CCH)], 3.73
2
[s, 6 H, 2ϫ (–OCH3)], 5.32 (d, JH,H = 15.9 Hz, 2 H, –NCH2–),
2
5.36 (d, JH,H = 16.0 Hz, 2 H, –NCH2–), 6.68 [s, 2 H, 2ϫ (ArH)],
6.73–6.77 [m, 4 H, 2ϫ2(ArH)], 7.17–7.20 [m, 2 H, 2ϫ (ArH)] ppm.
2ϫ (–CCH2–)], 1.24 [t, J = 7.2 Hz, 6 H, 2ϫ (–CH2CH3)], 1.34 [s, 13C NMR (125.75 MHz, CDCl3, TMS): δ = 11.3, 19.6, 20.4, 27.3,
6 H, 2ϫ (–CH2CCH3)], 1.82–1.90 [m, 2 H, 2ϫ (–CHCH2–)], 2.08– 33.4, 48.4, 52.4, 54.0, 55.2, 62.6, 112.0, 13.0, 119.1, 127.2, 129.3,
2.17 [m, 2 H, 2 ϫ (–CHCH2–)], 2.90 [d, J = 3.9 Hz, 2 H, 2 ϫ
138.2, 140.2, 154.0, 159.7 ppm. MS (EI): m/z (%) = 121 (44)
(–CCH)], 4.01 [q, J = 7.2 Hz, 4 H, 2ϫ (–CH2CH3)] ppm. 13C NMR [C8H9O]+, 469 (94) [M – (methoxybenzyl)]+, 483 (17) [M –
5018
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© 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Inorg. Chem. 2011, 5014–5024

Bulky and Modular 3,3Ј-Bipyrazoles as Ligands
(C8H9O)]+, 547 (48), 575 (7) [M – (CH3)]+, 590 (100) [M]+. HRMS
(EI): m/z calcd. for C38H46O2N4: 590.3621; found 590.3585. IR
1504, 1493, 1455, 1435, 1424, 1386, 1374, 1365, 1347, 1275, 1117,
1081, 1045 cm–1.
(KBr): ν = 3436, 2955, 2871, 1602, 1587, 1491, 1455, 1437, 1387,
˜
1,1Ј-Bis(4-tert-butylbenzyl) Derivative 3h: Compound 3h was pre-
pared following the standard procedure using 2 (500 mg,
1.427 mmol), sodium hydride (82 mg, 3.424 mmol), and 4-tert-but-
ylbenzyl bromide (534 μL, 2.906 mmol) in anhydrous THF
(100 mL). The solution was heated at reflux for 4 h. Compound 3h
(887 mg, 1.380 mmol, 97%) was obtained as a yellowish powder;
1365, 1348, 1281, 1261, 1147, 1117, 1085, 1045, 999 cm–1.
1,1Ј-Dibenzyl Derivative 3e: Compound 3e was prepared following
the standard procedure using 2 (700 mg, 1.997 mmol), sodium hy-
dride (115 mg, 4.792 mmol), and benzyl bromide (484 μL,
4.093 mmol) in anhydrous THF (110 mL). The solution was heated
at reflux for 4 h. Compound 3e (1.002 g, 1.888 mmol, 94%) was
obtained as a yellowish powder; m.p. 151–161 °C. 1H NMR
(500.13 MHz, CDCl3, TMS): δ = 0.76 [s, 6 H, 2ϫ (–CH3)], 0.86 [s,
6 H, 2ϫ (–CH3)], 1.07 [s, 6 H, 2ϫ (–CH2CCH3)], 1.18–1.23 [m, 4
H, 2ϫ (–CCH2–)], 1.63–1.68 [m, 2 H, 2ϫ (–CHCH2–)], 2.02–2.07
[m, 2 H, 2ϫ (–CHCH2–)], 2.91 [d, J = 4.0 Hz, 2 H, 2ϫ (–CCH)],
1
m.p. 214–226 °C. H NMR (300.13 MHz, CDCl3, TMS): δ = 0.78
[s, 6 H, 2 ϫ (–CH3)], 0.87 [s, 6 H, 2 ϫ (–CH3)], 1.12 [s, 6 H,
2ϫ (–CH2CCH3)], 1.17–1.30 [m, 22 H, 2ϫ –tBu, 2ϫ (–CCH2–)],
1.63–1.71 [m, 2 H, 2 ϫ (–CHCH2–)], 2.00–2.10 [m, 2 H,
2ϫ (–CHCH2–)], 2.91 [d, J = 3.1 Hz, 2 H, 2ϫ (–CCH)], 5.28 (d,
2
2JH,H = 15.7 Hz, 2 H, –NCH2–), 5.36 (d, JH,H = 15.8 Hz, 2 H,
2
2
–NCH2–), 7.08–7.11 [m, 4 H, 2 ϫ 2(ArH)], 7.27–7.29 [m, 4 H,
2ϫ2(ArH)] ppm. 13C NMR (75.46 MHz, CDCl3, TMS): δ = 11.5,
19.8, 20.6, 27.5, 31.5, 33.6, 34.6, 48.5, 52.6, 53.9, 62.7, 125.3, 126.7,
127.2, 135.6, 138.3, 150.2, 154.1 ppm. MS (EI): m/z (%) = 147 (78)
[C11H15]+, 495 (100) [M – (C11H15)]+, 509 (13) [M – (C10H13)]+, 599
(19) [M – (3ϫCH3)]+, 627 (5) [M – (CH3)]+, 643 (91) [M]+. HRMS
(EI): m/z calcd. for C44H58N4: 642.4661; found 642.4662. IR (KBr):
5.35 (d, JH,H = 16.0 Hz, 2 H, –NCH2), 5.39 (d, JH,H = 16.0 Hz,
2 H, –NCH2), 7.13–7.22 [m, 10 H, 2ϫ5(ArH)] ppm. 13C NMR
(125.75 MHz, CDCl3, TMS): δ = 11.4, 19.8, 20.6, 27.5, 33.6, 48.6,
52.6, 54.2, 62.8, 126.9, 127.4, 128.5, 138.3, 138.8, 154.2 ppm. MS
(EI): m/z (%) = 91 (95) [C7H7]+, 439 (77) [M – (benzyl)]+, 453 (14)
[M – (C6H5)]+, 487 (86) [M – (3ϫCH3)]+, 515 (8) [M – (CH3)]+,
530 (100) [M]+. HRMS (EI): m/z calcd. for C36H42N4: 530.3409;
ν = 3455, 2952, 2869, 1609, 1504, 1493, 1455, 1435, 1424, 1386,
˜
found 530.3420. IR (KBr): ν = 3430, 2955, 2870, 1496, 1473, 1454,
˜
1374, 1365, 1347, 1275, 1117, 1081, 1045 cm–1.
1421, 1386, 1376, 1364, 1308, 1279, 1244, 1118, 1086, 1047, 1029,
999 cm–1.
1,1Ј-Bis(2,4,6-trimethylbenzyl) Derivative 3i: Compound 3i was pre-
pared following the standard procedure using 2 (244 mg,
0.695 mmol), sodium hydride (40 mg, 1.667 mmol), and 2,4,6-tri-
methylbenzyl chloride (240 mg, 1.423 mmol) in anhydrous THF
(50 mL). The solution was heated at reflux for 16 h. Compound 3i
(398 mg, 0.647 mmol, 93%) was obtained as a yellowish foam; m.p.
1,1Ј-Bis(4-methylbenzyl) Derivative 3f: Compound 3f was prepared
following the standard procedure using 2 (440 mg, 1.255 mmol),
sodium hydride (72 mg, 3.014 mmol), and 4-methylbenzyl bromide
(476 mg, 2.573 mmol) in anhydrous THF (100 mL). The solution
was heated at reflux for 4 h. Compound 3f (690 mg, 1.235 mmol,
98%) was obtained as a yellowish powder; m.p. 71–92 °C. 1H NMR
(300.13 MHz, CDCl3, TMS): δ = 0.77 [s, 6 H, 2ϫ (–CH3)], 0.86 [s,
6 H, 2ϫ (–CH3)], 1.09 [s, 6 H, 2ϫ (–CH2CCH3)], 1.16–1.31 [m, 4
H, 2ϫ (–CCH2–)], 1.61–1.70 [m, 2 H, 2ϫ (–CHCH2–)], 2.00–2.10
[m, 2 H, 2ϫ (–CHCH2–)], 2.30 (s, 6 H, ArCH3), 2.91 [d, J = 3.6 Hz,
1
153–179 °C. H NMR (500.13 MHz, CDCl3, TMS): δ = 0.78 [s, 6
H, 2 ϫ (CH3 )], 0.85 [s, 6 H, 2 ϫ (–CH3 )], 0.96 [s, 6 H,
2ϫ (–CH2CCH3)], 1.06–1.16 [m, 4 H, 2ϫ (–CCH2–)], 1.60–1.65
[m, 2 H, 2ϫ (–CHCH2–)], 1.98–2.03 [m, 2 H, 2ϫ (–CHCH2–)],
2.27 [s, 6 H, 2ϫ (ArCH3)], 2.29 [s, 12 H, 4ϫ (ArCH3)], 2.88 [d, J
= 3.5 Hz, 2 H, 2ϫ (–CCH)], 5.32 [s, 4 H, 2ϫ (–NCH2–)], 6.85 [s,
4 H, 4ϫ (ArH)] ppm. 13C NMR (125.75 MHz, CDCl3, TMS): δ =
11.5, 19.9, 20.6, 21.1, 27.4, 33.6, 48.2, 49.3, 53.3, 62.4, 127.1, 129.4,
130.6, 137.4, 138.1, 153.7 ppm. MS (EI): m/z (%) = 133 (100)
[C10H13]+, 481 (86) [M – (C10H13)]+, 495 (22) [M – (mesityl)]+, 571
(24) [M – (3ϫCH3)]+, 599 (5) [M – (CH3)]+, 614 (71) [M]+. HRMS
(EI): m/z calcd. for C42H54N4: 614.4348; found 614.4359. IR (KBr):
2
2 H, 2ϫ (–CCH)], 5.30 (d, JH,H = 15.7 Hz, 2 H, –NCH2–), 5.36
2
(d, JH,H = 15.9 Hz, 2 H, NCH2–), 7.03–7.09 [m, 8 H, 4ϫ2(ArH)]
ppm. 13C NMR (75.46 MHz, CDCl3, TMS): δ = 11.4, 19.8, 20.6,
21.2, 27.5, 33.5, 48.6, 52.5, 54.0, 62.7, 126.8, 127.3, 129.1, 135.7,
136.9, 138.2, 154.0 ppm. MS (EI): m/z (%) = 105 (100) [C8H9]+,
453 (90) [M – (p-xylenyl)]+, 467 (14) [M – (C7H7)]+, 515 (18) [M –
(3ϫCH3)]+, 543 (3) [M – (CH3)]+, 558 (65) [M]+. HRMS (EI): m/z
ν = 3442, 2956, 2869, 1614, 1487, 1463, 1425, 1386, 1375, 1365,
˜
calcd. for C38H46N : 558.3722; found 558.3704. IR (KBr): ν =
˜
4
1284, 1261, 1237, 1118, 1080, 1050, 1032, 997 cm–1.
3433, 2956, 2868 1515, 1472, 1453, 1422, 1386, 1375, 1364, 1352,
1309, 1298, 1280, 1118, 1085, 1046, 1020, 998 cm–1.
Crystal
Data
for
3i:
C42H54N4,
Mr
=
614.89,
0.39ϫ0.23ϫ0.06 mm3, triclinic, space group P1, a = 8.8223(13) Å,
b = 10.7579(16) Å, c = 11.2401(17) Å, α = 109.734(3)°, β =
1,1Ј-Bis(3-methylbenzyl) Derivative 3g: Compound 3g was prepared
following the standard procedure using 2 (500 mg, 1.427 mmol),
sodium hydride (82 mg, 3.424 mmol), and 3-methylbenzyl bromide
(541 mg, 2.923 mmol) in anhydrous THF (100 mL). The solution
was heated at reflux for 4 h. Compound 3g (730 g, 1.306 mmol,
92%) was obtained as a yellowish powder; m.p. 132–140 °C. 1H
NMR (300.13 MHz, CDCl3, TMS): δ = 0.78 [s, 6 H, 2ϫ (–CH3)],
0.87 [s, 6 H, 2ϫ (–CH3)], 1.07 [s, 6 H, 2ϫ (–CH2CCH3)], 1.09–
1.26 [m, 4 H, 2ϫ (–CCH2–)], 1.63–1.71 [m, 2 H, 2ϫ (–CHCH2–)],
2.01–2.11 [m, 2 H, 2ϫ (–CHCH2–)], 2.28 (s, 6 H, ArCH3), 2.92 [d,
109.934(4)°, γ = 99.710(4)°, V = 894.1(2) Å3, Z = 1, ρcalcd.
=
=
1.14 gcm–3, Mo-Kα radiation (graphite-monochromated,
λ
0.71073 Å), T = 200(2) K, θ range = 2.1–26.4°; reflections mea-
sured 8286, independent 3645, Rint = 0.026. Final R indices
[IϾ2σ(I)]: R1 = 0.057, wR2 = 0.126.
1,1Ј-Bis[(naphthalene-2-yl)methyl] Derivative 3j: Compound 3j was
prepared following the standard procedure using 2 (300 mg,
0.856 mmol), sodium hydride (49 mg, 2.043 mmol), and 2-(bromo-
J = 3.6 Hz, 2 H, 2ϫ (–CCH)], 5.34 [s, 4 H, 2ϫ (–NCH2–)], 6.92– methyl)naphthalene (382 mg, 1.728 mmol) in anhydrous THF
7.16 [m, 8 H, 2ϫ4(ArH)] ppm. 13C NMR (75.46 MHz, CDCl3, (80 mL). The solution was heated at reflux for 4 h. Compound 3j
TMS): δ = 11.4, 19.8, 20.6, 21.5, 27.5, 33.6, 48.6, 52.6, 54.2, 62.8,
124.0, 127.4, 127.6, 128.1, 128.4, 138.1, 138.2, 138.6, 154.1 ppm.
MS (EI): m/z (%) = 105 (92) [C8H9]+, 453 (100) [M – (m-xylen-
(519 mg, 0.823 mmol, 96%) was obtained as a white powder; m.p.
200–223 °C. H NMR (300.13 MHz, CDCl3, TMS): δ = 0.81 [s, 6
H, 2ϫ (–CH3)], 0.86 [s, 6 H, 2ϫ (–CH3)], 1.08 [s, 6 H,
1
yl)]+, 467 (14) [M – (C7H7)]+, 515 (19) [M – (3ϫCH3)]+, 543 (4) 2ϫ (–CH2CCH3)], 1.10–1.30 [m, 4 H, 2ϫ (–CCH2–)], 1.61–1.70
[M – (CH3)]+, 558 (94) [M]+. HRMS (EI): m/z calcd. for C38H46N4: [m, 2 H, 2ϫ (–CHCH2–)], 2.03–2.13 [m, 2 H, 2ϫ (–CHCH2–)],
558.3722; found 558.3690. IR (KBr): ν = 3435, 2952, 2869, 1609,
2.96 [d, J = 3.7 Hz, 2 H, 2ϫ (–CCH)], 5.57 [s, 4 H, 2ϫ (–NCH2–
˜
Eur. J. Inorg. Chem. 2011, 5014–5024
© 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjic.org
5019

O. Trapp et al.
FULL PAPER
)], 7.31–7.35 [m, 2 H, 2ϫ (ArH)], 7.42–7.47 [m, 4 H, 2ϫ2(ArH)],
2ϫ (–CCH3)], 0.76 [s, 6 H, 2ϫ (–CCH3)] ppm. 13C NMR
7.59 [s, 2 H, 2ϫ (ArH)], 7.75–7.82 [m, 6 H, 2ϫ3(ArH)] ppm. 13C (125.75 MHz, CDCl3, TMS): δ = 11.2, 17.5, 19.4, 20.4, 27.1, 33.6,
NMR (75.46 MHz, CDCl3, TMS): δ = 11.5, 19.8, 20.6, 27.5, 33.6,
48.6, 52.6, 54.4, 62.8, 125.1, 125.4, 125.9, 126.2, 127.6, 127.8, 128.0,
128.3, 132.9, 133.4, 136.3, 138.4, 154.3 ppm. MS (EI): m/z (%) =
141 (100) [C11H9]+, 489 (71) [M – (C11H9)]+, 503 (8) [M – (2-
naphthyl)]+, 587 (8) [M – 3ϫ (CH3)]+, 615 (2) [M – (CH3)]+, 630
(44) [M]+. HRMS (EI): m/z calcd. for C44H46N4: 630.3722; found
45.5, 47.9, 54.0, 63.2, 124.5, 138.6, 158.3 ppm. MS (FAB): m/z (%)
= 511 (100) [M – (HCl), – (Cl–)]+, 546 (8) [M – (Cl–)]+, 953 (51)
[M + (L), –(Cl–)]+, 1129 (13) [2ϫM – (Cl–)]+. HRMS (FAB): m/z
(%) calcd. for C26H37N4106Pd+ [M – (HCl), – (Cl–)]+: 511.2053;
found 511.2042. IR (KBr): ν = 3443, 2964, 2872, 1635, 1559, 1508,
˜
1466, 1390, 1380, 1306, 1287, 1276, 1247, 1206, 1182, 1137, 1100,
1082, 1063, 1015 cm–1. C26H38Cl2N4Pd·1/5CHCl3: calcd. C 51.37,
H 6.28, N 9.13, Cl 15.44, Pd 17.38; found C 51.25, H 6.46, N 9.28.
630.3679. IR (KBr): ν = 3425, 2956, 2870, 1509, 1453, 1438, 1419,
˜
1387, 1376, 1366, 1278, 1261, 1117, 1085, 1046, 1019, 999, 810
cm–1.
Pd Complex 4b: Compound 4b was prepared following the stan-
dard procedure using 3b (101 mg, 0.231 mmol) and bis(aceto-
nitrile)dichloropalladium(II) (60 mg, 0.231 mmol) in anhydrous
acetonitrile (10 mL) to yield 4b (134 mg, 0.219 mmol, 95%) as an
ochre-red powder; m.p. 170–179 °C. 1H NMR (500.13 MHz,
CDCl3, TMS): δ = 0.77 [s, 6 H, 2ϫ (–CCH3)], 0.96 [s, 6 H, 2ϫ
(–CCH3)], 1.10–1.15 [m, 2 H, 2ϫ (–CCH2–)], 1.27–1.33 [m, 2 H,
2ϫ (–CCH2–)], 1.40–1.47 {m, 18 H, 2ϫ[–CH2C(CH3)2], 2ϫ
–(CH2CCH3)}, 1.83–1.90 [m, 2 H, 2ϫ (–CHCH2–)], 2.11–2.16 [m,
2 H, 2ϫ (–CHCH2–)], 2.87 [d, J = 3.7 Hz, 2 H, 2ϫ (–CCH)], 5.84
[q, J = 6.9 Hz, 2 H, 2ϫ (–NCH–)] ppm. 13C NMR (125.75 MHz,
CDCl3, TMS): δ = 15.0, 19.8, 20.5, 22.5, 23.1, 27.0, 47.4, 54.4, 55.5,
62.9, 126.8, 137.8, 157.6 ppm. MS (FAB): m/z (%) = 539 (25) [M –
(HCl), – (Cl–)]+, 1010 (14) [M + (L), –(Cl–)]+. HRMS (FAB): m/z
(%) calcd. for C28H41N4106Pd+ [M – (HCl), – (Cl–)]+: 539.2377;
Crystal
Data
for
3j:
C44H46N4,
Mr
=
630.85,
0.27ϫ0.18ϫ0.06 mm3, triclinic, space group P1, a = 7.275984 Å,
b = 11.44737(7) Å, c = 12.4101(7) Å, α = 116.572(1)°, β =
99.604(2)°, γ = 93.301(2)°, V = 901.19(9) Å3, Z = 1, ρcalcd.
=
=
1.16 gcm–3, Mo-Kα radiation (graphite-monochromated,
λ
0.71073 Å), T = 200(2) K, θ range = 1.9–21.7°; reflections mea-
sured 5207, independent 2098, Rint = 0.075. Final R indices
[IϾ2σ(I)]: R1 = 0.072, wR2 = 0.167.
1,1Ј-Bis[3,5-bis(trifluoromethyl)benzyl] Derivative 3k: Compound
3k was prepared following the standard procedure using 2 (300 mg,
0.856 mmol), sodium hydride (45 mg, 1.88 mmol), and 3,5-bis(tri-
fluoromethyl)benzyl chloride (322 μL, 1.75 mmol) in anhydrous
THF (90 mL). The solution was heated at reflux for 4 h. After
crystallization out of diethyl ether and washings with pentane, 3k
(289 mg, 0.360 mmol, 42%) was obtained as a white powder; m.p.
155–158 °C. H NMR (500.13 MHz, CDCl3, TMS): δ = 0.80 [s, 6
H, 2ϫ (–CH3)], 0.90 [s, 6 H, 2ϫ (–CH3)], 1.08–1.25 [m, 8 H, 2ϫ
–CH2CCH3, 2ϫ (–CCH2–)], 1.19–1.25 [m, 2 H, 2ϫ (–CCH2–)],
found 539.2407. IR (KBr): ν = 3444, 2966, 2872, 1628, 1559, 1438,
˜
1389, 1369, 1331, 1288, 1277, 1259, 1207, 1181, 1136, 1104, 1083,
1049, 998 cm–1. C28H42Cl2N4Pd·1/3CHCl3: calcd. C 50.96, H 6.38,
N 8.34; found C 50.93, H 6.47, N 8.55.
1
1.75–1.80 [m, 2 H, 2ϫ (–CHCH2–)], 2.08–2.14 [m, 2 H, 2ϫ
Pd Complex 4c: Compound 4c was prepared following the standard
procedure using 3c (114 mg, 0.231 mmol) and bis(acetonitrile)-
dichloropalladium(II) (60 mg, 0.231 mmol) in anhydrous acetoni-
trile (10 mL) to yield 4c (134 mg, 0.211 mmol, 91%) as an ochre red
powder; m.p. 149–154 °C. 1H NMR (500.13 MHz, CDCl3, TMS): δ
= 0.76 [s, 6 H, 2ϫ (–CCH3)], 0.89 [t, J = 7.4 Hz, 6 H,
2ϫ (–CH2CH3)], 0.96 [s, 6 H, 2ϫ (–CCH3)], 1.13–1.17 [m, 2 H,
2ϫ (–CHCH–)], 1.26–1.37 [m, 16 H, 2ϫ (–CHCH2CH2–), 2ϫ
(–CHCH2CH2–), 2ϫ (–CH2CCH3)], 1.78–1.89 [m, 4 H, 2ϫ
(–CH2CH2CH3)], 2.00 (s, 2 H, –CH2CH2–), 2.11–2.16 [m, 2 H, 2ϫ
(–CH2CH2–)], 2.85 [d, J = 3.8 Hz, 2 H, 2ϫ (–CCH)], 4.52 (ddd, J
2
(–CHCH2–)], 3.00 [br. s, 2 H, 2ϫ (–CCH)], 5.46 (d, JH,H
=
2
16.5 Hz, 2 H, –NCH2–), 5.52 (d, JH,H = 16.3 Hz, 2 H, –NCH2–),
7.58 [s, 4 H, 4ϫ (ArH)], 7.77 [s, 2 H, 2ϫ (ArH)] ppm. 13C NMR
(125.75 MHz, CDCl3, TMS): δ = 11.28, 19.5, 20.1, 27.1, 33.6, 48.4,
52.6, 53.0, 62.9, 121.5, 122.0, 124.2, 126.9, 128,1. 131.9, 140.9,
154.7 ppm. MS (EI): m/z (%) = 227 (11) [C9H5F6]+, 575 (23) [M –
{3,5-bis(trifluormethyl)benzyl}]+, 589 (4) [M – (C9H5F6)]+, 759
(100), 787 (7) [M – (CH3)]+, 803 (24) [M]+. HRMS (EI): m/z calcd.
for C H F N : 802.2905; found 802.2914. IR (KBr): ν = 3447,
˜
40 38 12
4
2964, 2874, 1624, 1505, 1464, 1437, 1381, 1348, 1323, 1277, 1245,
1178, 1134, 1084, 1045, 906, 888 cm–1.
2
= 9.4 Hz, J = 6.0 Hz, JH,H = 13.8 Hz, 2 H, –NCH2–), 4.73 (ddd,
2
J = 9.4 Hz, J = 6.3 Hz, JH,H = 14.0 Hz, 2 H –NCH2–) ppm. 13C
General Procedure for the Preparation of bcpz–Palladium(II) Chlor-
ide Complexes 4a–k: [Pd(MeCN)2Cl2] (1.00 equiv.) was added to a
solution of the corresponding bipyrazole ligand 3 (1.00 equiv.) in
anhydrous CH2Cl2, and the solution was stirred for 16 h at room
temperature. The solvent was evaporated under reduced pressure,
and the product was taken up in a small amount of chloroform
and filtered though a short plug of silica. Evaporation and drying
under high vacuum yielded the corresponding Pd(bcpz) complexes
as deep orange to red microcrystalline solids.
NMR (125.75 MHz, CDCl3, TMS): δ = 11.3, 14.2, 19.4, 20.4, 22.5,
27.1, 28.8, 32.0, 33.6, 47.9, 50.4, 54.0, 63.2, 124.3, 138.6, 158.4 ppm.
MS (FAB): m/z (%) = 595 (84) [M – (HCl), – (Cl–)]+, 631 (4) [M –
(Cl–)]+, 1121 (1) [M + (L), –(Cl–)]+, 1297 (7) [2ϫM – (Cl–)]+.
HRMS (FAB): m/z (%) calcd. for C32H49N4106Pd+ [M – (HCl),
– (Cl–)]+: 595.2992; found 595.2990. IR (KBr): ν = 3445, 2959,
˜
2931, 2871, 1627, 1465, 1390, 1378, 1307, 1287, 1276, 1247, 1206,
1184, 1137, 1105, 1086, 1067, 1015, 1000 cm–1. C32H50Cl2N4Pd·
5/6CHCl3: calcd. C 51.38, H 6.68, N 7.63; found C 51.42, H 6.62,
N 7.72.
Pd Complex 4a: Compound 4a was prepared following the stan-
dard procedure using 3a (94 mg, 0.231 mmol) and bis(acetonitrile)-
dichloropalladium(II) (60 mg, 0.231 mmol) in anhydrous acetoni-
trile (10 mL) to yield 4 (132 mg, 0.226 mmol, 98%) as an ochre-red
Pd Complex 4d: Compound 4d was prepared following the stan-
dard procedure using 3d (114 mg, 0.193 mmol) and bis(aceto-
nitrile)dichloropalladium(II) (50 mg, 0.193 mmol) in anhydrous
acetonitrile (10 mL) to yield 4d (145 mg, 0.189 mmol, 97%) as a
deep orange powder; m.p. 218–222 °C. 1H NMR (500.13 MHz,
CDCl3, TMS): δ = 0.74 [s, 6 H, 2ϫ (–CCH3)], 0.92 [s, 6 H,
1
powder; m.p. 147–158 °C. H NMR (500.13 MHz, CDCl3, TMS):
δ = 4.84 [dddd, J = 7.1 Hz, J = 7.0 Hz, J = 7.0 Hz, 2JH,H = 14.1 Hz,
2 H, 2ϫ (–NCH2–)], 4.61 [dddd, J = 7.1 Hz, J = 7.0 Hz, J = 7.0 Hz,
2JH,H = 14.1 Hz, 2 H, 2ϫ (–NCH2–)], 2.86 [d, J = 3.4 Hz, 2 H, 2ϫ
(–CCH)], 2.11–2.16 [m, 2 H, 2ϫ (–CHCH2–)], 1.87–1.92 [m, 2 H, 2ϫ (–CCH3)], 1.06–1.15 [m,
4 H, 2ϫ (–CH2CH2–), 2ϫ
2ϫ (–CHCH2–)], 1.41 [dd, J = 7.0 Hz, J = 7.0 Hz, 6 H, 2ϫ (–CH2CH2–)], 1.23 [s, 6 H, 2ϫ (–CH2CCH3)], 1.72–1.76 [m, 2 H,
(–CH2CCH3)], 1.35 [s, 6 H, 2ϫ (–CH2CH3)], 1.26–1.31 [m, 2 H, 2ϫ (–CH2CH2–)], 2.08–2.13 [m, 2 H, 2ϫ (–CH2CH2–)], 2.87 [d, J
2
2ϫ (–CCH2–)], 1.12–1.17 [m, 2 H, 2ϫ (–CCH2–)], 0.96 [s, 6 H,
= 3.7 Hz, 2 H, 2ϫ (–CCH)], 5.83 (d, JH,H = 15.9 Hz, 2 H,
5020
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© 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Inorg. Chem. 2011, 5014–5024

Bulky and Modular 3,3Ј-Bipyrazoles as Ligands
2
2
–NCH2–), 6.18 (d, JH,H = 15.9 Hz, 2 H, –NCH2–), 6.78–6.87 [m, 3.7 Hz, 2 H, 2ϫ (–CCH)], 5.84 (d, JH,H = 15.9 Hz, 2 H,
2
4 H, 2ϫ2(ArH)], 6.86–6.87 [m, 2 H, 2ϫ (ArH)], 7.20–7.23 [m, 2
–NCH2–), 6.16 (d, JH,H = 15.9 Hz, 2 H, –NCH2–), 7.01–7.06 [m,
H, 2ϫ (ArH)] ppm. 13C NMR (125.75 MHz, CDCl3, TMS): δ =
6 H, 2ϫ (3ArH)], 7.17–7.20 [m, 2 H, 2ϫ (ArH)] ppm. 13C NMR
11.1, 19.2, 20.3, 26.8, 32.7, 47.7, 53.3, 54.0, 55.3, 63.2, 112.8, 113.3, (125.75 MHz, CDCl3, TMS): δ = 11.2, 19.4, 20.4, 21.6, 26.9, 32.8,
119.3, 125.5, 129.6, 138.3, 139.0, 159.5, 159.7 ppm. MS (FAB): m/z
47.9, 53.5, 54.1, 63.3, 124.2, 125.6, 127.8, 128.6, 128.7, 137.0, 138.3,
(%) = 695 (96) [M – (HCl), – (Cl–)]+, 733 (24) [M – (Cl–)]+, 1323 139.1, 159.6 ppm. MS (FAB): m/z (%) = 663 (25) [M – (HCl),
(19) [M + (L), – (Cl–)]+. HRMS (FAB): m/z (%) calcd. for – (Cl–)]+, 699 (30) [M – (Cl–)]+, 1259 (2) [M + (L), –(Cl–)]+, 1439
C38H4635ClN4O2108Pd+ [M]+: 733.2347; found 733.2348. IR (KBr):
(3) [2ϫM –
(Cl–)]+. HRMS (FAB): m/z (%) calcd. for
ν = 3427, 2962, 2874, 1602, 1586, 1491, 1456, 1437, 1390, 1369,
C38H4635ClN4106Pd+ [M]+: 699.2457; found 699.2478. IR (KBr): ν
˜
˜
1349, 1305, 1284, 1261, 1148, 1123, 1103, 1046, 1017 cm–1.
C38H46Cl2N4O2Pd·1/11CHCl3: calcd. C 57.93, H 5.88, N 7.07;
found C 57.43, H 6.06, N 6.84.
= 3453, 2963, 2871, 1609, 1490, 1456, 1390, 1378, 1369, 1348, 1306,
1287, 1276, 1248, 1184, 1123, 1104, 1092 cm–1. C38H46Cl2N4Pd·1/
8CHCl3: calcd. C 60.83, H 6.18, N 7.44; found C 60.69, H 6.36, N
7.41.
Pd Complex 4e: Compound 4e was prepared following the standard
procedure using 3e (123 mg, 0.231 mmol) and bis(acetonitrile)
dichloropalladium(II) (60 mg, 0.231 mmol) in anhydrous acetoni-
trile (10 mL) to yield 4e (158 mg, 0.223 mmol, 96%) as a deep
Pd Complex 4h: Compound 4h was prepared following the stan-
dard procedure using 3h (149 mg, 0.231 mmol) and bis(aceto-
nitrile)dichloropalladium(II) (60 mg, 0.231 mmol) in anhydrous
acetonitrile (10 mL) to yield 4h (187 mg, 0.224 mmol, 97%) as a
1
orange powder; m.p. 164–170 °C. H NMR (500.13 MHz, CDCl3,
TMS): δ = 0.72 [s, 6 H, 2ϫ (–CCH3)], 0.90 [s, 6 H, 2ϫ (–CCH3)], deep orange powder; m.p. 203–205 °C. 1H NMR (500.13 MHz,
1.00–1.14 [m, 4 H, 2ϫ (–CH2CH2–), 2ϫ (–CH2CH2–)], 1.19 [s, 6 CDCl3, TMS): δ = 0.74 [s, 6 H, 2ϫ (–CCH3)], 0.92 [s, 6 H, 2ϫ
H, 2ϫ (–CH2CCH3)], 1.68–1.73 [m, 2 H, 2ϫ (–CH2CH2–)], 2.06–
(–CCH3)], 1.05–1.14 [m, 4 H, 2ϫ (–CH2CH2–)], 1.24 [s, 6 H, 2ϫ
2.12 [m, 2 H, 2ϫ (–CH2CH2–)], 2.86 [d, J = 3.6 Hz, 2 H, 2ϫ (–CH2CCH3)], 1.29 {s, 18 H, 2ϫ[–C(CH3)3]}, 1.72–1.76 [m, 2 H,
2
2
(–CCH)], 5.85 (d, JH,H = 15.8 Hz, 2 H, –NCH2–), 6.23 (d, JH,H 2ϫ (–CH2CH2–)], 2.08–2.13 [m, 2 H, 2ϫ (–CH2CH2–)], 2.87 [d, J
2
= 15.9 Hz, 2 H, –NCH2–), 7.23–7.32 [m, 10 H, 2ϫ (ArH)] ppm.
13C NMR (125.75 MHz, CDCl3, TMS): δ = 11.2, 19.4, 20.4, 26.9,
32.8, 47.9, 53.6, 54.2, 63.4, 125.7, 127.3, 127.9, 128.7, 137.1, 139.1,
159.7 ppm. MS (FAB): m/z (%) = 635 (82) [M – (HCl), – (Cl–)]+,
= 3.7 Hz, 2 H, 2ϫ (–CCH)], 5.81 (d, JH,H = 15.8 Hz, 2 H
2
–NCH2–), 6.18 (d, JH,H = 15.8 Hz, 2 H, –NCH2–), 7.19 [d, J =
8.3 Hz, 4 H, 2ϫ (ArH)], 7.32 [d, J = 8.4 Hz, 4 H, 2ϫ (ArH)] ppm.
13C NMR (125.75 MHz, CDCl3, TMS): δ = 11.1, 19.2, 20.3, 26.8,
671 (26) [M – (Cl–)]+, 1203 (4) [M + (L), – (Cl–)]+, 1381 (6) [2ϫM – 32.7, 34.5, 47.8, 53.0, 54.0, 63.2, 125.4, 126.9, 133.7, 139.0, 150.7,
(Cl–)]+. HRMS (FAB): m/z (%) calcd. for C36H4235ClN4106Pd+
159.4 ppm. MS (FAB): m/z (%) = 747 (45) [M – (HCl), – (Cl–)]+,
783 (19) [M – (Cl–)]+, 1427 (3) [M + (L), –(Cl–)]+. HRMS (FAB):
m/z (%) calcd. for C44H5835ClN4106Pd+ [M]+: 783.3398; found
[M]+: 671.2143; found 699.2164. IR (KBr): ν = 3442, 2962, 2871,
˜
1626, 1606, 1497, 1454, 1391, 1379, 1369, 1315, 1287, 1276, 1247,
1182, 1124, 1103 cm–1. C36H42Cl2N4Pd·1/11CHCl3: calcd. C 60.22,
H 5.89, N 7.78; found C 60.17, H 6.06, N 7.87.
783.3434. IR (KBr): ν = 3445, 2961, 2871, 1622, 1514, 1458, 1415,
˜
1391, 1367, 1316, 1276, 1247, 1205, 1193, 1125, 1050, 1019, 1001
cm–1. C44H58Cl2N4Pd·1/9CHCl3: calcd. C 63.45, H 7.01, N 6.71;
found C 63.47, H 7.19, N 6.82.
Pd Complex 4f: Compound 4f was prepared following the standard
procedure using 3f (129 mg, 0.231 mmol) and bis(acetonitrile)
dichloropalladium(II) (60 mg, 0.231 mmol) in anhydrous acetoni-
trile (10 mL) to yield 4f (166 mg, 0.226 mmol, 98%) as a deep
Crystal Data for 4h: C38H46Cl2N4Pd, Mr
0.15ϫ0.14ϫ0.01 mm3, monoclinic, space group P21,
16.196(5) Å, b = 10.248(3) Å, c = 21.795(7) Å, α = 90°, β =
=
736.09,
a
=
1
orange powder; m.p. 151–160 °C. H NMR (500.13 MHz, CDCl3,
TMS): δ = 0.72 [s, 6 H, 2ϫ (–CCH3)], 0.90 [s, 6 H, 2ϫ (–CCH3)], 96.143(4)°, γ = 90°, V = 3596.6(19) Å3, Z = 4, ρcalcd. = 1.36 gcm–3,
1.02–1.11 [m,
4
H, 2ϫ (–CH2CH2–)], 1.22 [s,
6
H, 2ϫ
Mo-Kα radiation (synchrotron, λ = 0.80000 Å), T = 150 K, θ range
(–CH2CCH3)], 1.69–1.74 [m, 2 H, 2ϫ (–CH2CH2–)], 2.06–2.11 [m, = 1.86–31.57°; reflections measured 97835, independent 15609, Rint
2 H, 2ϫ (–CH2CH2–)], 2.31 [s, 6 H, 2ϫ (ArCH3)], 2.85 [d, J =
= 0.040. Final R indices [IϾ2σ(I)]: R1 = 0.027, wR2 = 0.057.
2
3.7 Hz, 2 H, 2ϫ (–CCH)], 5.77 (d, JH,H = 15.6 Hz, 2 H, –NCH2–
Pd Complex 4h(OAc): Compound 4h(OAc) was prepared following the
standard procedure using 3h (100 mg, 0.156 mmol) and palladi-
um(II) acetate (35 mg, 0.156 mmol) in anhydrous dichloromethane
(12 mL) to yield 4h(OAc) (129 mg, 0.149 mmol, 96%) as a white
powder. Decomp. Ͼ 170 °C. 1H NMR (399.89 MHz, CD2Cl2): δ =
0.75 [s, 6 H, 2ϫ (–CCH3)], 0.90 [s, 6 H, 2ϫ (–CCH3)], 1.08 [s, 6
H, 2ϫ (–CH2CCH3)], 1.12–1.20 [m, 4 H, 2ϫ (–CH2CH2–)], 1.30
{s, 18 H, 2ϫ[–C(CH3)3]}, 1.49 [s, 6 H, 2ϫ (–OAc)], 1.69–1.75 [m,
2 H, 2ϫ (–CH2CH2–)], 2.07–2.14 [m, 2 H, 2ϫ (–CH2CH2–)], 2.92
2
), 6.18 (d, JH,H = 15.5 Hz, 2 H, –NCH2–), 7.11 [d, J = 8.0 Hz, 4
H, 2ϫ (ArH)], 7.18 [d, J = 8.0 Hz, 4 H, 2ϫ (ArH)] ppm. 13C NMR
(125.75 MHz, CDCl3, TMS): δ = 11.3, 19.4, 20.4, 21.3, 26.9, 32.8,
47.9, 53.4, 54.1, 63.3, 125.6, 127.3, 129.4, 134.0, 137.6, 139.1, 159.5
ppm. MS (FAB): m/z (%) = 663 (91) [M – (HCl), – (Cl–)]+, 699 (30)
[M – (Cl–)]+, 1258 (19) [M + (L), – (Cl–)]+, 1438 (6) [2ϫM –
(Cl–)]+. HRMS (FAB): m/z (%) calcd. for C38H4635ClN4106Pd+
[M]+: 699.2457; found 699.2419. IR (KBr): ν = 3432, 2963, 2872,
˜
1617, 1516, 1457, 1390, 1369, 1316, 1287, 1276, 1248, 1205, 1184,
1124, 1103, 1072, 1050, 1018 cm–1. C38H46Cl2N4Pd·1/8CHCl3:
calcd. C 60.83, H 6.19, N 7.44; found C 60.89, H 6.37, N 7.30.
2
[d, J = 3.6 Hz, 2 H, 2ϫ (–CCH)], 5.35 (d, JH,H = 16.1 Hz, 2 H –
2
NCH2–), 5.47 (d, JH,H = 16.2 Hz, 2 H, –NCH2–), 7.06 [d, J =
8.3 Hz, 4 H, 2ϫ (ArH)], 7.37 [d, J = 8.3 Hz, 4 H, 2ϫ (ArH)] ppm.
13C NMR (125.75 MHz, CDCl3, TMS): δ = 11.0, 19.3, 20.4, 22.7,
27.0, 31.5, 32.9, 34.7, 47.9, 52.5, 53.9, 63.1, 125.7, 126.3, 133.4,
138.0, 150.8, 158.3, 179.1 ppm. MS (FAB): m/z (%) = 747 (100)
[M – (HOAc), – (OAc–)]+, 1391 (15) [M + (L), –2ϫ (OAc–)]+.
HRMS (FAB): m/z (%) calcd. for C44H57N4106Pd+ [M]+: 747.3634;
Pd Complex 4g: Compound 4g was prepared following the stan-
dard procedure using 3g (129 mg, 0.231 mmol) and bis(aceto-
nitrile)dichloropalladium(II) (60 mg, 0.231 mmol) in anhydrous
acetonitrile (10 mL) to yield 4g (166 mg, 0.224 mmol, 97%) as a
deep orange powder; m.p. 143–147 °C. 1H NMR (500.13 MHz,
CDCl3, TMS): δ = 0.73 [s, 6 H, 2ϫ (–CCH3)], 0.91 [s, 6 H, 2ϫ found 747.3631. IR (KBr): ν = 3432, 2961, 2871, 1638, 1581, 1515,
˜
(–CCH3)], 1.04–1.14 [m, 4 H, 2ϫ (–CH2CH2–)], 1.19 [s, 6 H, 2ϫ
(–CH2CCH3)], 1.70–1.75 [m, 2 H, 2ϫ (–CH2CH2–)], 2.08–2.13 [m, cm–1. C48H64N4O4Pd·1/9CHCl3: calcd. C 66.46, H 7.44, N 6.46;
2 H, 2ϫ (–CH2CH2–)], 2.31 [s, 6 H, 2ϫ (ArCH3)], 2.87 [d, J = found C 65.41, H 7.47, N 6.39.
1458, 1414, 1391, 1367, 1288, 1262, 1206, 1184, 1128, 1108, 1017
Eur. J. Inorg. Chem. 2011, 5014–5024
© 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjic.org
5021

O. Trapp et al.
FULL PAPER
Pd Complex 4h(OAc): Compound 4h(OAc) was prepared following the
standard procedure using 3h (100 mg, 0.156 mmol) and palladi-
um(II) acetate (35 mg, 0.156 mmol) in anhydrous dichloromethane
Pd Complex 4k: Compound 4k was prepared following the stan-
dard procedure using 3k (102 mg, 0.127 mmol) and bis(aceto-
nitrile)dichloropalladium(II) (33 mg, 0.127 mmol) in anhydrous
(12 mL) to yield 4h(OAc) (129 mg, 0.149 mmol, 96%) as a white acetonitrile (10 mL) to yield 4k (120 mg, 0.122 mmol, 96%) as a
powder. Decomp. Ͼ 170 °C. 1H NMR (399.89 MHz, CD2Cl2): δ = yellow powder; m.p. 145–148 °C. H NMR (500.13 MHz, CDCl3,
1
0.75 [s, 6 H, 2ϫ (–CCH3)], 0.90 [s, 6 H, 2ϫ (–CCH3)], 1.08 [s, 6
H, 2ϫ (–CH2CCH3)], 1.12–1.20 [m, 4 H, 2ϫ (–CH2CH2–)], 1.30
TMS): δ = 0.78 [s, 6 H, 2ϫ (–CCH3)], 0.96 [s, 6 H, 2ϫ (–CCH3)],
1.14 [s, 6 H, 2ϫ (–CH2CCH3)], 1.16–1.25 [m, 4 H, 2ϫ (–CH2CH2–),
{s, 18 H, 2ϫ[–C(CH3)3]}, 1.49 [s, 6 H, 2ϫ (–OAc)], 1.69–1.75 [m, 2ϫ (–CH2CH2–)], 1.84–1.89 [m, 2 H, 2ϫ (–CH2CH2–)], 2.17–2.23
2 H, 2ϫ (–CH2CH2–)], 2.07–2.14 [m, 2 H, 2ϫ (–CH2CH2–)], 2.92 [m, 2 H, 2ϫ (–CH2CH2–)], 2.97 [d, J = 3.7 Hz, 2 H, 2ϫ
2
2
2
[d, J = 3.6 Hz, 2 H, 2ϫ (–CCH)], 5.35 (d, JH,H = 16.1 Hz, 2 H
(–CCH)], 6.10 (d, JH,H = 16.7 Hz, 2 H, –NCH2–), 6.32 (d, JH,H
2
–NCH2–), 5.47 (d, JH,H = 16.2 Hz, 2 H, –NCH2–), 7.06 [d, J = = 16.7 Hz, 2 H, –NCH2–), 7.52 (s, 4 H, 4ϫ (ArH), 7.80 [s, 2 H,
8.3 Hz, 4 H, 2ϫ (ArH)], 7.37 [d, J = 8.3 Hz, 4 H, 2ϫ (ArH)] ppm.
13C NMR (125.75 MHz, CDCl3, TMS): δ = 11.0, 19.3, 20.4, 22.7,
27.0, 31.5, 32.9, 34.7, 47.9, 52.5, 53.9, 63.1, 125.7, 126.3, 133.4,
138.0, 150.8, 158.3, 179.1 ppm. MS (FAB): m/z (%) 747 (100) [M –
(HOAc), – (OAc–)]+, 1391 (15) [M + (L), –2ϫ (OAc–)]+. HRMS
2ϫ (ArH)] ppm. 13C NMR (125.75 MHz, CDCl3, TMS): δ = 10.9,
19.1, 20.0, 26.7, 33.0, 47.9, 52.5, 54.1, 63.6, 119.7, 121.7, 124.1,
126.3, 126.5, 132.1, 132.0, 139.3, 140.0, 159.9 ppm. MS (FAB): m/z
(%) = 907 (100) [M – (HCl), – (Cl–)]+, 945 (26) [M – (Cl–)]+. HRMS
(FAB): m/z (%) calcd. for C40H3835ClF12N4108Pd+ [M]+: 945.1632;
(FAB): m/z (%) calcd. for C44H57N4106Pd+ [M]+: 747.3634; found found 945.1594. IR (KBr): ν = 3446, 2965, 2026, 1973, 1624, 1457,
˜
747.3631. IR (KBr): ν = 3432, 2961, 2871, 1638, 1581, 1515, 1458,
1382, 1351, 1280, 1175, 1136, 1017, 907, 845 cm–1.
C36H42Cl2N4Pd·1/13CHCl3: calcd. C 48.63, H 3.88, N 5.66; found
C 48.39, H 4.02, N 5.54.
˜
1414, 1391, 1367, 1288, 1262, 1206, 1184, 1128, 1108, 1017 cm–1.
C48H64N4O4Pd·1/9CHCl3: calcd. C 66.46, H 7.44, N 6.46; found C
65.41, H 7.47, N 6.39.
Co Complex 4h(Co): Compound 4h(Co) was prepared following the
standard procedure using 3h (49.9 mg, 0.078 mmol) and cobalt(II)
chloride hexahydrate (18.5 mg, 0.078 mmol) in absolute ethanol
(3 mL) to yield 4h(Co) (54.2 mg, 0.070 mmol, 90%) as a fluffy, pale
purple solid; m.p. 170–178 °C. MS (FAB): m/z (%) = 700 (2) [M –
(HCl), – (Cl–)]+, 736 (100) [M – (Cl–)]+, 1378 (11) [M + (L),
– (Cl–)]+. HRMS (FAB): m/z (%) calcd. for C44H5835ClN4Co+
Pd Complex 4i: Compound 4i was prepared following the standard
procedure using 3i (142 mg, 0.231 mmol) and bis(acetonitrile)-
dichloropalladium(II) (60 mg, 0.231 mmol) in anhydrous acetoni-
trile (10 mL) to yield 4i (173 mg, 0.218 mmol, 95%) as an ochre red
powder; m.p. 162–172 °C. 1H NMR (500.13 MHz, CDCl3, TMS): δ
= 0.60 [s, 6 H, 2ϫ (–CCH3)], 0.68 [s, 6 H, 2ϫ (–CCH3)], 0.81 [s, 6
H, 2ϫ (–CH2CCH3)], 0.85–0.91 [m, 2 H, 2ϫ (–CH2CH2–)], 1.05–
1.10 [m, 2 H, 2ϫ (–CH2CH2–)], 1.47–1.52 [m, 2 H, 2ϫ (–CH2CH2–)],
2.02–2.07 [m, 2 H, 2ϫ (–CH2CH2–)], 2.10 [s, 12 H, 2ϫ (ArCH3)],
2.24 [s, 6 H, 2ϫ (ArCH3)], 2.81 [d, J = 3.6 Hz, 2 H, 2ϫ (–CCH)],
[M]+: 736.3682; found 736.3704. IR (KBr): ν = 3434, 2963, 2871,
˜
1619, 1516, 1455, 1427, 1391, 1366, 1337, 1319, 1273, 1248, 1204,
1183, 1129, 1107, 1017 cm–1. C44H58Cl2CoN4·1/15CHCl3: calcd. C
67.75, H 7.49, N 7.17; found C 67.87, H 7.59, N 7.19.
2
2
5.74 (d, JH,H = 16.6 Hz, 2 H, –NCH2–), 6.35 (d, JH,H = 16.6 Hz,
2 H, –NCH2–), 6.78 [s, 4 H, 2ϫ (ArH)] ppm. 13C NMR
(125.75 MHz, CDCl3, TMS): δ = 10.5, 19.5, 20.4, 20.5, 21.0, 27.2,
32.2, 47.7, 51.8, 55.3, 63.1, 126.7, 130.0, 137.3, 137.7, 137.8, 159.0
ppm. MS (FAB): m/z (%) = 719 (59) [M – (HCl), – (Cl–)]+, 754 (5)
[M – (Cl–)]+, 1371 (6) [M + (L), – (Cl–)]+. HRMS (FAB): m/z (%)
calcd. for C42H5435ClN4106Pd+ [M]+: 755.3084; found 755.3137. IR
Co Complex 4j(Co): Compound 4j(Co) was prepared following the
standard procedure using 3j (47.8 mg, 0.076 mmol) and cobalt(II)
chloride hexahydrate (18.0 mg, 0.076 mmol) in absolute ethanol
(3 mL) to yield 4j(Co) (53.7 mg, 0.071 mmol, 93%) as a fluffy, pale
purple solid; m.p. 145–151 °C. MS (FAB): m/z (%) = 688 (6) [M –
(HCl), – (Cl–)]+, 724 (93) [M – (Cl–)]+, 1354 (1) [M + (L),
– (Cl–)]+. HRMS (FAB): m/z (%) calcd. for C44H4635ClN463Co+
(KBr): ν = 3447, 2960, 2874, 1613, 1483, 1457, 1423, 1390, 1379,
˜
[M]+: 724.2743; found 724.2808. IR (KBr): ν = 3434, 3052, 2963,
˜
1323, 1288, 1277, 1261, 1246, 1182, 1125, 1099, 1031, 1016,
850 cm–1. C42H54Cl2N4Pd·1/4CHCl3: calcd. C 61.11, H 6.58, N
6.73; found C 61.01, H 6.66, N 6.85.
1689, 1635, 1558, 1542, 1509, 1455, 1372, 1329, 1287, 1274, 1248,
1126, 1103 cm–1. C44H46Cl2CoN4·1/5CHCl3: calcd. C 67.66, H
5.94, N 7.14; found C 67.52, H 6.07, N 7.11.
Pd Complex 4j: Compound 4j was prepared following the standard
procedure using 3j (150 mg, 0.238 mmol) and bis(acetonitrile)-
dichloropalladium(II) (62 mg, 0.238 mmol) in anhydrous acetoni-
trile (10 mL) to yield 4j (173 mg, 0.225 mmol, 95%) as a deep
orange powder; m.p. 158–170 °C. 1H NMR (500.13 MHz, CD2Cl2,
TMS): δ = 0.78 [s, 6 H, 2ϫ (–CCH3)], 0.91 [s, 6 H, 2ϫ (–CCH3)],
Cu Complex 4h(Cu): Compound 4h(Cu) was prepared following the
standard procedure using 3h (50.9 mg, 0.079 mmol) and copper(II)
chloride dihydrate (13.5 mg, 0.079 mmol) in absolute ethanol
(3 mL) to yield 4h(Cu) (53.7 mg, 0.071 mmol, 89%) as a fine, red
powder; m.p. 174–181 °C. MS (FAB): m/z (%) = 704 (11) [M –
(HCl), – (Cl–)]+, 740 (49) [M – (Cl–)]+, 1382 (9) [M + (L), – (Cl–)]+.
HRMS (FAB): m/z (%) calcd. for C44H5835ClN4Cu+
1.03–1.19 [m,
4 H, 2ϫ (–CH2CH2–)], 1.21 [s, 6 H, 2ϫ
(–CH2CCH3)], 1.69–1.77 [m, 2 H, 2ϫ (–CH2CH2–)], 2.07–2.17 [m,
2 H, 2ϫ (–CH2CH2–)], 2.96 [d, J = 3.7 Hz, 2 H, 2ϫ (–CCH)], 6.05
[M]+: 740.3646; found 736.3624. IR (KBr): ν = 3439, 2963, 2872,
˜
1626, 1558, 1542, 1515, 1456, 1391, 1365, 1339, 1319, 1275, 1248,
1183, 1129, 1017 cm–1. C44H58Cl2CuN4·1/6CHCl3: calcd. C 66.53,
H 7.35, N 7.03; found C 66.64, H 7.46, N 7.05.
2
2
(d, JH,H = 16.2 Hz, 2 H, –NCH2–), 6.40 (d, JH,H = 16.2 Hz, 2
H, –NCH2–), 7.41–7.52 [m, 6 H, 2ϫ (ArH)], 7.62 [s, 2 H, 2ϫ
(ArH)], 7.81–7.87 [m,
7
H, 2ϫ (ArH)] ppm. 13C NMR
(125.75 MHz, CD2Cl2, TMS): δ = 11.4, 19.5, 20.6, 27.2, 33.3, 48.5,
63.8, 125.3, 126.0, 126.4, 126.7, 126.9, 128.2, 128.4, 129.0, 133.4,
133.8, 135.4, 139.7, 160.4 ppm. MS (FAB): m/z (%) = 735 (63) [M –
(HCl), – (Cl–)]+, 771 (8) [M – (Cl–)]+, 1402 (4) [M + (L), – (Cl–)]+.
HRMS (FAB): m/z (%) calcd. for C44H4635ClN4106Pd+ [M]+:
Cu Complex 4j(Cu): Compound 4j(Cu) was prepared following the
standard procedure using 3j (54.1 mg, 0.086 mmol) and copper(II)
chloride dihydrate (14.6 mg, 0.086 mmol) in absolute ethanol
(3 mL) to yield 4j(Cu) (59.5 mg, 0.078 mmol, 91%) as a fine, red
powder; m.p. 131–138 °C. MS (FAB): m/z (%) = 692 (9) [M –
(HCl), – (Cl–)]+, 728 (44) [M – (Cl–)]+, 1358 (1) [M + (L),
– (Cl–)]+. HRMS (FAB): m/z (%) calcd. for C44H4635ClN463Cu+
771.2459; found 771.2455. IR (KBr): ν = 3446, 3115, 2963, 2872,
˜
1654, 1634, 1602, 1509, 1457, 1424, 1390, 1378, 1370, 1329, 1286,
1275, 1248, 1124 cm–1. C28H42Cl2N4Pd·1/8CHCl3: calcd. C 64.25,
H 5.64, N 6.79; found C 64.06, H 5.74, N 6.87.
[M]+: 728.2707; found 728.2678. IR (KBr): ν = 3431, 3053, 2963,
˜
2873, 1634, 1510, 1455, 1390, 1370, 1330, 1287, 1275, 1248, 1185,
5022
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© 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Inorg. Chem. 2011, 5014–5024

Bulky and Modular 3,3Ј-Bipyrazoles as Ligands
1126, 1102, 1017 cm–1. C44H58Cl2CuN4·1/3CHCl3: calcd. C 64.78, [M]+: 728.2707; found 728.2678. IR (KBr): ν = 3431, 3053, 2963,
˜
H 5.68, N 6.79; found C 64.91, H 5.79, N 6.97.
2873, 1634, 1510, 1455, 1390, 1370, 1330, 1287, 1275, 1248, 1185,
1126, 1102, 1017 cm–1. C44H58Cl2CuN4·1/3CHCl: calcd. C 64.78,
H 5.68, N 6.79; found C 64.91, H 5.79, N 6.97.
General Procedure for the Preparation of bcpz Cobalt(II) and Cop-
per(II) Complexes: Cobalt(II) chloride hexahydrate or copper(II)
chloride dihydrate (1 equiv.), respectively, were added to a solution
of the corresponding bipyrazole ligand (1 equiv.) in absolute etha-
nol. The solution lightened and became cloudy. After 16 h at room
temperature, the solvent was evaporated, and the residue was dis-
solved in a small amount of chloroform and filtered through a
short plug of neutral alumina. The filtrate was evaporated and the
product dried under high vacuum to yield the biindazole cobalt(II)
complexes as fluffy, pale purple solids and the biindazole copper(II)
complexes as red solids, respectively.
General Procedure for the Copper-Free Wacker Oxidation of Ter-
minal Alkenes: The catalyst (5 mol-%) was dissolved in a mixture
of DMA (2.5 mL) and water (6:1) in a cap-sealed vial, which was
in turn evacuated at –78 °C and refilled with oxygen for three times.
The solution was warmed to room temperature and the appropriate
alkene (0.89 mm) and of internal standard (undecane) (10 μL) were
added. Reaction control samples were taken out of the solution,
extracted with diethyl ether, filtered through a short plug of neutral
alumina to remove the catalyst, and analyzed by GC and GC–MS
(PolarisQ Trace GC–MS, Thermo, San Jose, CA) using a 25 m HP-
5MS column (Agilent Technologies, Palo Alto, CA, film thickness
250 nm).
Co Complex 4h(Co): Compound 4h(Co) was prepared following the
standard procedure using 3h (49.9 mg, 0.078 mmol) and cobalt(II)
chloride hexahydrate (18.5 mg, 0.078 mmol) in absolute ethanol
(3 mL) to yield 4h(Co) (54.2 mg, 0.070 mmol, 90%) as a fluffy, pale
purple solid; m.p. 170–178 °C. MS (FAB): m/z (%) = 700 (2) [M –
(HCl), – (Cl–)]+, 736 (100) [M – (Cl–)]+, 1378 (11) [M + (L),
– (Cl–)]+. HRMS (FAB): m/z (%) calcd. for C44H5835ClN4Co+
X-ray Crystallography: CCDC-822414 (for 3i), -832814 (for 3j),
-822413 (for 4h), and -832815 [for 4h(Cu)] contain the supplemen-
tary crystallographic data for this paper. These data can be ob-
tained free of charge from The Cambridge Crystallographic Data
Centre via www.ccdc.cam.ac.uk/data_request/cif.
[M]+: 736.3682; found 736.3704. IR (KBr): ν = 3434, 2963, 2871,
˜
1619, 1516, 1455, 1427, 1391, 1366, 1337, 1319, 1273, 1248, 1204,
1183, 1129, 1107, 1017 cm–1. C44H58Cl2CoN4·1/15CHCl: calcd. C
67.75, H 7.49, N 7.17; found C 67.87, H 7.59, N 7.19.
Supporting Information (see footnote on the first page of this arti-
cle): NMR spectroscopic data, UV/Vis spectra, CD spectra.
Co Complex 4j(Co): Compound 4j(Co) was prepared following the
standard procedure using 3j (47.8 mg, 0.076 mmol) and cobalt(II)
chloride hexahydrate (18.0 mg, 0.076 mmol) in absolute ethanol
(3 mL) to yield 4j(Co) (53.7 mg, 0.071 mmol, 93%) as a fluffy, pale
purple solid; m.p. 145–151 °C. MS (FAB): m/z (%) = 688 (6) [M –
(HCl), – (Cl–)]+, 724 (93) [M – (Cl–)]+, 1354 (1) [M + (L),
– (Cl–)]+. HRMS (FAB): m/z (%) calcd. for C44H4635ClN463Co+
Acknowledgments
We thank the Deutsche Forschungsgemeinschaft (DFG), (SFB 623:
Molecular Catalysts: Structure and Functional Design) for gener-
ous financial support and a doctoral fellowship (to M. J. S.,
GK 850 Molecular Modeling). We thank the Synchrotron Light
Source ANKA for the provision of measuring time at the SCD
beamline and Christian Lothschütz for fruitful discussions.
[M]+: 724.2743; found 724.2808. IR (KBr): ν = 3434, 3052, 2963,
˜
1689, 1635, 1558, 1542, 1509, 1455, 1372, 1329, 1287, 1274, 1248,
1126, 1103 cm–1. C44H46Cl2CoN4·1/5CHCl: calcd. C 67.66, H 5.94,
N 7.14; found C 67.52, H 6.07, N 7.11.
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Cu Complex 4h(Cu): Compound 4h(Cu) was prepared following the
standard procedure using 3h (50.9 mg, 0.079 mmol) and copper(II)
chloride dihydrate (13.5 mg, 0.079 mmol) in absolute ethanol
(3 mL) to yield 4h(Cu) (53.7 mg, 0.071 mmol, 89%) as a fine, red
powder; m.p. 174–181 °C. MS (FAB): m/z (%) = 704 (11) [M –
(HCl), – (Cl–)]+, 740 (49) [M – (Cl–)]+, 1382 (9) [M + (L),
– (Cl–)]+. HRMS (FAB): m/z (%) calcd. for C44H5835ClN4Cu+
[M]+: 740.3646; found 736.3624. IR (KBr): ν = 3439, 2963, 2872,
˜
1626, 1558, 1542, 1515, 1456, 1391, 1365, 1339, 1319, 1275, 1248,
1183, 1129, 1017 cm–1. C44H58Cl2CuN4·1/6CHCl: calcd. C 66.53,
H 7.35, N 7.03; found C 66.64, H 7.46, N 7.05.
Crystal Data for 4h(Cu)
:
C46H58Cl2CuN4, Mr
=
817.40,
0.20ϫ0.18ϫ0.16 mm3, triclinic, space group P1, a = 11.0049(3) Å,
b = 13.1228(3) Å, c = 16.7500(3) Å, α = 103.126(1)°, β = 95.282(1)°,
γ = 95.840(1)°, V = 2326.91(9) Å3, Z = 2, ρcalcd. = 1.167 g/cm3,
Mo-Kα radiation (graphite-monochromated, λ = 0.71073 Å), T =
200(2) K, θ range = 1.61–21.97°; reflections measured 14388, inde-
pendent 11090, Rint = 0.074. Final R indices [IϾ2σ(I)]: R1 = 0.10,
wR2 = 0.25.
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(3 mL) to yield 4j(Cu) (59.5 mg, 0.078 mmol, 91%) as a fine, red
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(HCl), – (Cl–)]+, 728 (44) [M – (Cl–)]+, 1358 (1) [M + (L),
– (Cl–)]+. HRMS (FAB): m/z (%) calcd. for C44H4635ClN463Cu+
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Received: July 6, 2011
Published Online: September 21, 2011
5024
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© 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Inorg. Chem. 2011, 5014–5024