Tris(pyrazolyl)phosphine oxides. Synthesis and coordination chemistry with copper(I)

Article abstract of DOI:10.1021/om300051f

A set of substituted tris(pyrazolyl)phosphine oxides (OP(pz ^x)₃) has been prepared in high yield and applied as neutral scorpion-type ligands. The P apex provides a convenient spectroscopic handle. Substitution at the 3-position of the pyrazolyl ring influences the steric demands of the ligand, while substitution at the 5-position enhances the stability. Copper(I) acetonitrile complexes of the OP(pz^x) ₃ ligands were prepared and tested in ligand exchange reactions with PPh₃ and CO. The v(CO) values of the carbonyl complexes demonstrate the electron-withdrawing properties of the ligands. These observations show that OP(pz^x)₃ ligands are an interesting extension of the widely used scorpion-type ligands.

Full text of DOI:10.1021/om300051f

Article
pubs.acs.org/Organometallics
Tris(pyrazolyl)phosphine Oxides. Synthesis and Coordination
Chemistry with Copper(I)
Cornelis G. J. Tazelaar,† Volodymyr Lyaskovskyy,† Tom van Dijk,† Daniel L. J. Broere,†
̈
Ludo A. Kolfschoten,† Rima Osman Hassan Khiar,† Martin Lutz,‡ J. Chris Slootweg,*,†
and Koop Lammertsma*,†
†Department of Chemistry and Pharmaceutical Sciences, VU University Amsterdam, De Boelelaan 1083, 1081 HV Amsterdam, The
Netherlands
‡Bijvoet Center for Biomolecular Research, Crystal and Structural Chemistry, Utrecht University, Padualaan 8, 3584 CH Utrecht, The
Netherlands
S
* Supporting Information
ABSTRACT: A set of substituted tris(pyrazolyl)phosphine oxides
(OP(pzx)3) has been prepared in high yield and applied as neutral
scorpion-type ligands. The P apex provides a convenient spectroscopic
handle. Substitution at the 3-position of the pyrazolyl ring influences
the steric demands of the ligand, while substitution at the 5-position
enhances the stability. Copper(I) acetonitrile complexes of the
OP(pzx)3 ligands were prepared and tested in ligand exchange
reactions with PPh3 and CO. The ν(CO) values of the carbonyl
complexes demonstrate the electron-withdrawing properties of the ligands. These observations show that OP(pzx)3 ligands are an
interesting extension of the widely used scorpion-type ligands.
these neutral scorpion-type ligands. While the synthetic
protocols for preparing derivatized tris(pyrazolyl)methanes
have been improved greatly at the beginning of this century,
they remain far from ideal, especially for the more bulky
substituted ligands. For example, a yield of only 43.7% was
reported for the methane analogue of B and isolation required
several purification steps.15 Therefore, alternative neutral
scorpion-type ligands are desired, but these are scarce and
concern only the heavier tris(pyrazolyl)silane16−19 and the
phosphorus-centered analogues (D). Peterson and co-workers
were the first to report the isolation of both tris(pyrazolyl)-
phosphine (P(pz)3)20 and the corresponding phosphine oxide
(OP(pz)3).21 Their work on the metal complexes of these
ligands22,23 was extended by Joshi et al.24 with a single example
and by the group of Tolman, who in a series of papers focused
on the phosphine oxide apex in C3-chiral ligands containing
chiral pyrazolyl groups.25−28 The latest report on tris-
(pyrazolyl)phosphorus ligands was by the group of Ward,
who used pyridyl-substituted pyrazolyl rings to obtain a
phosphine sulfide with possible κ6 binding.29 The potential
applicability of phosphorus-centered tris(pyrazolyl) ligands is
evident from these studies. However, they did not provide a
systematic study that would facilitate the evaluation of the
ligand properties relative to those of other scorpion-type
ligands.
INTRODUCTION
■
Tris(pyrazolyl)methane (A) is a versatile ligand that complexes
with group 1−14 metals.1,2 Several of these complexes are
potent catalysts for reactions such as olefin polymerization,3
carbene transfer,4 and alkane oxidation.5 An important feature
of the tris(pyrazolyl)methane ligand is the possibility to adapt
the steric and electronic properties by selecting the proper
substituents. This versatility is shared with the established
anionic tris(pyrazolyl)borate analogue, developed and termed
the scorpionate ligand by Trofimenko.6−9 For these tris-
(pyrazolyl)borates it was shown that increased steric bulk at the
pyrazolyl 3-positions (as in B) can prevent disproportionation
and stabilize half-sandwich complexes with open coordination
sites available for further reactivity.10,11 Moreover, strongly
electron-withdrawing pyrazolyl substituents provide scorpio-
nate ligands (such as C), whose metal complexes can display
enhanced catalytic activity: e.g., in carbene transfer reac-
tions.12−14
For tris(pyrazolyl)methane the substituent effect has not
been fully exploited, probably due to the limited accessibility of
Received: February 16, 2012
Published: March 23, 2012
© 2012 American Chemical Society
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Here we report on the facile synthesis of a series of
tris(pyrazolyl)phosphine oxides with increasing bulk near the
binding pocket and their copper(I) acetonitrile complexes, as
well as substitution reactions of these complexes with PPh3 and
CO. IR spectroscopy of the resulting CO complexes
demonstrates the interesting electronic characteristics of these
ligands.
(for 2 h) and room temperature (for 1 h) and that of 1e at 60
°C (for 20 h), followed by workup, extraction into CH2Cl2,
removal of all volatiles, and column chromatographic
purification, the desired ligands 1d (30%, δ(31P) −10.3) and
1e (53%, δ(31P) −10.5) were obtained as colorless solids.
Exposure to air and addition of water to these methylated
ligands did not show any degradation, thereby confirming that
the methyl groups at the 5-position do indeed protect these
ligands from hydrolysis.
As these PO scorpion-type ligands are readily accessible, we
were eager to explore their coordination chemistry. Copper(I)
acetonitrile complexes were prepared from 1a−e by allowing a
1:1 mixture of the ligand and [Cu(NCMe)4][PF6] to react in
CH2Cl2 at room temperature (Scheme 2). The reaction with 1a
RESULTS AND DISCUSSION
■
We selected the PO analogues D of three key tris(pyrazolyl)-
methane ligands to study the effects of a change in apex.
OP(3,5-Me2pz)3 (1a)24 was chosen for direct comparison with
its frequently used tris(pyrazolyl)methane analogue HC(3,5-
Me2pz)3. OP(3-Phpz)3 (1b) and OP(3-t-Bupz)3 (1c)25
represent ligands with increasing bulk in the proximity of the
metal binding pocket; their borate analogues have been
successfully applied in catalysis.30−33 All three tris(pyrazolyl)-
phosphine oxides are readily prepared by addition of a
phosphoryl trichloride solution to an ice-cold solution of 3
equiv of the appropriate pyrazole and a slight excess (3.1 equiv)
of triethylamine in THF (Scheme 1); for 1a the best results
Scheme 2. Preparation and Reactivity of the CuI Complexes
2a−e
Scheme 1. Syntheses of the Tris(pyrazolyl)phosphine Oxide
Ligands 1a−e
gave, after stirring for 30 min, concentration, and crystal-
lization/precipitation by addition of pentane, the desired
complex [OP(3,5-Me2pz)3Cu(NCMe)][PF6] (2a) in 91%
yield (δ(31P) −19.8, −144.4 (septet, 1J(P,F) = 711 Hz,
PF6)). Likewise, stirring the reaction mixtures of 1b−e for 2
h, removing all volatiles, washing the residue with MTBE, and
drying at 70 °C gave excellent yields of [OP(3-Phpz)3Cu-
(NCMe)][PF6] (2b; 87%, δ(31P) −19.8), [OP(3-t-Bupz)3Cu-
(NCMe)][PF6] (2c; 85%, δ(31P) −20.7), [OP(3-Ph-5-
Mepz)3Cu(NCMe)][PF6] (2d; 98%, δ(31P) −18.0), and
[OP(3-t-Bu-5-Mepz)3Cu(NCMe)][PF6] (2e; 96%, δ(31P)
−17.1). Also for these reactions 31P NMR spectroscopy proved
to be an invaluable diagnostic tool, as upfield shifts of 5−8 ppm
were observed for the PO apex upon complexation. A single set
were obtained when phosphoryl trichloride was also present in
excess (1.1 equiv). After the reaction mixture was refluxed for
several hours, the triethylammonium salts were filtered off.
Removal of all volatiles (for 1a 8 h at 45 °C under high
vacuum) gave the ligands as colorless or slightly yellow (1b)
solids in high yields (1a, 90%; 1b, 86%; 1c, 93%).34 1H and 13
C
NMR spectra show a single set of signals for the pyrazolyl rings,
which indicates the attachment of all rings to the apex with
their substituent in the same position. This is in contrast with
the initial outcome of the coupling reaction for the methane
analogues that need an additional rearrangement step using p-
toluenesulfonic acid to obtain the C3-symmetric ligands.15 The
NMR resonances for 4-H and all ring carbons show coupling
with phosphorus (4J(H,P) = 3.6−3.8 Hz). The appearance of
the 31P NMR signal (δ −10.7 (1a), −14.8 (1b), and −14.4
(1c)) during the reaction proved to be an excellent tool to
follow its progress.35
While 1b,c are sensitive to moisture and decompose upon
exposure to air, liberating the corresponding pyrazole, a CDCl3
solution of 1a can be treated with water without any noticeable
change in the NMR spectra. We were curious whether the
presence of the methyl groups at the 5-position of the pyrazolyl
rings in 1a caused this enhanced stability. Therefore, OP(3-Ph-
5-Mepz)3 (1d) and OP(3-t-Bu-5-Mepz)3 (1e) were prepared
(Scheme 1), which are the methylated analogues of 1b,c. A
slight excess of phosphoryl trichloride (1.1 equiv) in THF was
added slowly to an ice-cold mixture of the corresponding
pyrazole (3 equiv) and potassium tert-butoxide (3.1−3.2 equiv)
in THF. After the reaction mixture of 1d was stirred at 0 °C
1
of H and 13C NMR signals was observed for the pyrazolyl
rings of all complexes, suggesting κ3 coordination of the ligands
in analogy to the reported CH analogues of complexes 2a−c.36
Crystal structure determinations of 2c,d (Figure 1, Table 1)
confirmed this coordination mode. Both molecular structures
display a distorted-tetrahedral geometry around copper. The
Cu−Npyrazolyl distance for 2c ranges between 2.089(2) and
2.134(2) Å, while the Cu−Nacetonitrile distance is shorter
(1.911(2) Å). The N−Cu−N angles between the pyrazolyl
rings range from 90.16(8) to 94.24(8)°, and those between
acetonitrile and the pyrazolyl donors range from 121.88(10) to
125.23(9)°. All these structural features compare very well with
those of its CH analogue,36 despite the significantly larger
phosphorus atom at the apex of the ligand (P−N distances in
2c from 1.670(2) to 1.675(2) Å, relative to C−N distances of
1.427(14) to 1.447(15) Å in [HC(3-t-Bupz)3Cu(NCMe)]-
[PF6]). In 2d all coordinating nitrogens are closer to the copper
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Figure 1. Displacement ellipsoid plots of 2c (left) and 2d (right) drawn at the 50% probability level. Hydrogen atoms, cocrystallized CH2Cl2 (for
2c), and the PF6 anion are omitted for clarity.
Table 1. Selected Bond Distances and Angles for 2c,d, 3a, and [HC(3-t-Bupz)3Cu(NCMe)][PF6]
a
2c
2d
3a
[HC(3-t-Bupz)3Cu(NCMe)][PF6]
Bond Distances (Å)
Cu1−N12
Cu1−N22
Cu1−N32
Cu1−L
2.089(2)
2.134(2)
2.101(2)
Cu1−N41
1.911(2)
P1−N
2.0710(13)
2.0863(17)
2.0843(18)
2.1039(17)
Cu1−P2
2.138(9)
2.122(9)
2.061(9)
Cu1− N41
1.873(9)
C1−N
2.0799(13)
2.0778(13)
Cu1−N41
1.8876(14)
P1−N
Cu1−L
2.1820(5)
A−N
P1−N
A−N11
A−N21
A−N31
1.675(2)
1.670(2)
1.672(2)
1.6828(14)
1.6801(14)
1.6889(14)
1.6808(18)
1.6729(18)
1.6781(18)
1.443(16)
1.447(15)
1.427(14)
Bond Angles (deg)
N−Cu1−L
N12−Cu1−L
N22−Cu1−L
N32−Cu1−L
N12−Cu1−N22
N−Cu1−N41
125.23(9)
121.88(10)
122.70(9)
90.16(8)
N−Cu1−N41
128.13(6)
122.17(6)
121.47(6)
92.30(5)
N−Cu1−P2
126.45(5)
125.39(5)
122.77(5)
90.00(7)
N−Cu1−N41
122.95(4)
125.7(4)
128.69(5)
89.0(4)
N12−Cu1−N32
N22−Cu1−N32
Cu1−N41−C41
93.90(8)
91.41(5)
89.74(7)
89.9(4)
94.24(8)
91.69(5)
91.91(7)
88.8(4)
176.6(2)
174.03(15)
174.1(14)
a
Data taken from ref 36.
center than in 2c (Cu−Npyrazolyl distances from 2.0709(14) to
2.0799(14) Å, Cu−Nacetonitrile distance: 1.8876(14) Å), while
the angles around the copper are comparable (N−Cu−N
angles between pyrazolyl rings 91.42(5)−92.30(5)° and
between acetonitrile and the pyrazolyl donors 121.47(6)−
128.13(6)°).
With this new set of tris(pyrazolyl)phosphine oxide
complexes at hand and their structures established unequiv-
ocally, we were interested in their reactivity. To start, we
investigated the ligand exchange reaction of 2a with the σ-
donor ligand PPh3, which is very common in CuI chemistry
(Scheme 2). After 3 h, full conversion in CH2Cl2 was observed
by 31P NMR spectroscopy, which showed the PO scorpion
ligand as a sharp singlet at δ −20.2, while the broad signal of
copper-bound PPh3 appeared at δ 6.8 (i.e., 12.1 ppm downfield
relative to free PPh3). Removal of all volatiles and washing with
Et2O gave the desired PPh3 adduct 3a as a colorless solid in
78% yield. The molecular structure of this complex (Figure 2,
Table 1) shows again the copper center in a distorted-
tetrahedral surrounding with N−N angles between 89.74(7)
and 91.91(7)° and P−N angles ranging from 122.77(5) to
126.45(5)°. The Cu−N distances fall between those found for
2c,d (i.e., from 2.0843(18) to 2.1039(17) Å); the Cu−P
distance of 2.1820(5) Å is within the range found in related
tris(pyrazolyl) copper complexes (from 2.1469(5) Å for C(3,5-
Me2pz)3Cu(PPh3)37 to 2.219(1) Å for HB(3,5-(CF3)2pz)3Cu-
(PPh3)38).
Having learned that ligand substitutions are feasible, we were
eager to explore the reactivity of the CuI complexes toward CO.
Attachment of this well-known π-acceptor to a metal complex
can provide insight into the electron density of the metal by
virtue of determining its ν(CO) IR frequency. This, in turn,
allows an evaluation of the effect of substituting the CH apex
for the PO apex on the electronic properties of the scorpion
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2137 cm−1 reported for the scorpionate copper(I) complex
with the very electron withdrawing HB(3,5-(CF3)2pz)3
ligand.41 It has been demonstrated that the corresponding Ag
complexes of this ligand benefit from the low electron density
on the metal center in several catalytic reactions.12 This holds
promise for the performance of our readily accessible PO
ligands in catalysis, which is under current investigation.
CONCLUSIONS
■
We have expanded the scope of a highly accessible neutral class
of scorpion-type ligands. These tris(pyrazolyl)phosphine oxides
are readily obtained in good yields. Their phosphorus apex
provides a convenient spectroscopic handle to monitor the
ligand synthesis and the fate of the ligand in complexation
reactions and follow-up chemistry. We have shown that these
ligands are suitable to support CuI complexes with different
ancillary ligands and have probed the CO stretching frequency
of their CO adducts. This showed the tris(pyrazolyl)phosphine
oxides to be on the low-donating side of the whole range of
scorpion-type ligands,12 which makes exploring their behavior
in catalysis highly interesting.
Figure 2. Displacement ellipsoid plot of 3a drawn at the 50%
probability level. Hydrogen atoms, cocrystallized CH2Cl2, and the PF6
anion are omitted for clarity.
EXPERIMENTAL SECTION
■
General Procedures. All experiments were performed under an
atmosphere of dry nitrogen. Solvents were purified, dried, and
degassed by standard techniques. 3-Phenylpyrazole,11 3-tert-butylpyr-
azole,11 3-methyl-5-phenylpyrazole,42 5,5-dimethylhexane-2,4-dione,43
and tetrakis(acetonitrile)copper(I) hexafluorophosphate44 were pre-
pared according to literature procedures. Triethylamine was dried over
sodium, and phosphoryl trichloride was distilled under nitrogen before
use. Other reagents were obtained commercially and used as received.
NMR spectra were recorded on a Bruker Avance 250, a Bruker Avance
400, or a Bruker Ultrashield 500 spectrometer. 1H and 13C NMR
spectra were referenced internally to residual solvent resonances
ligand. Exposing CH2Cl2 solutions of all copper acetonitrile
adducts 2a−e to a CO atmosphere for a prolonged time,
followed by precipitation on addition of pentane, gave mixed
results (Scheme 2). While [OP(3-Ph-5-Mepz)3Cu(CO)][PF6]
(4d) was obtained quantitatively after stirring for 64 h at room
temperature, 2e showed no conversion at all.39 The other
complexes gave partial conversions after 1 month (2a:4a,
0.3:1.0; 2c:4c, 4:1) while for [OP(3-Phpz)3Cu(CO)][PF6]
(4b) (after 18 h) the ratio could not be determined due to
overlap of the signals in the 1H NMR spectrum. IR
spectroscopy of all four CO complexes 4a−d showed ν(CO)
values that are at least 16 cm−1 higher than those for the
analogous CH-centered complexes (Table 2). This shows that
1
1
(CDCl3: H, 7.26 ppm (CHCl3), 13C{1H}, 77.16 ppm; CD2Cl2: H,
5.32 ppm (CDHCl2), 13C{1H}, 53.84 ppm). Other nuclei were
referenced to external standards: 19F, BF3·Et2O (0 ppm); 31P, 85%
H3PO4 (0 ppm). IR spectra were recorded on a Shimadzu FTIR-
84005 spectrophotometer, using the ATR technique. Peak intensities
are marked as follows: s = strong, m = medium, w = weak. High-
resolution electrospray ionization-mass spectrometry (HR ESI-MS)
was performed using a Bruker MicroTOFQ, ESI in positive mode
(capillary voltage 4.5 kV). Flash chromatography was performed using
SiliaFlash P60 (0.040−0.063 mm) silica gel with an overpressure of
about 0.5 bar. Melting points were measured on samples in unsealed
capillaries on a Stuart Scientific SMP3 melting point apparatus.
Preparation of 3-Methyl-5-tert-butylpyrazole. This compound
was prepared following the procedure reported for 3-methyl-5-
phenylpyrazole.42 Hydrazine hydrate (1.75 mL, 35.0 mmol) was
added dropwise to a solution of 5,5-dimethylhexane-2,4-dione (1.0 g,
7.0 mmol) in methanol (30 mL) at 0 °C. The reaction was slightly
exothermic and had a yellow hue. After 1 h all volatiles were removed
by rotary evaporation. The resulting solid was washed on a glass frit
with n-hexane and fully dried in vacuo. 3-Methyl-5-tert-butylpyrazole
Table 2. Carbonyl Stretching Frequencies for
Tris(pyrazolyl)phosphine Oxide and
Tris(pyrazolyl)methane Copper(I) Carbonyl Complexes
ν(CO) (cm−1
)
ref
[OP(3,5-Me2pz)3Cu(CO)][PF6] (4a)
[OP(3-Phpz)3Cu(CO)][PF6] (4b)
[OP(3-t-Bupz)3Cu(CO)][PF6] (4c)
[OP(3-Ph-5-Mepz)3Cu(CO)][PF6] (4d)
[HC(3,5-Me2pz)3Cu(CO)][PF6]
[HC(3-Phpz)3Cu(CO)][PF6]
2129
2121
2118
2111
2113
2104
2100
this work
this work
this work
this work
36
36
[HC(3-t-Bupz)3Cu(CO)][PF6]
36
1
was obtained as a colorless solid (0.99 g, 7.0 mmol, quantitative). H
the π back-donation to CO is much lower in our complexes,
thereby demonstrating a significant decrease in the electron
density of the metal centers. When the ν(CO) frequencies of
HB(3,5-Me2pz)3Cu(CO) (2066 cm−1),40 [HC(3,5-Me2pz)3Cu-
(CO)][PF6] (2113 cm−1),36 and 4a (2129 cm−1) are
compared, it is clear that not only the charge of the ligand
(the borate versus the last two) but also the nature of the apex
(the methane versus the phosphine oxide 4a, which are both
neutral ligands) influences the electron density of the
complexed metal. The CO stretching frequency of 4a has the
highest value of the complexes reported here. It approaches the
NMR (250.1 MHz, CDCl3): δ 1.30 (s, 9H, CMe3), 2.27 (s, 3H, 5-Me),
5.88 (s, 1H, 4-H); the signal for NH was not observed.
Preparation of Tris(3,5-dimethylpyrazolyl)phosphine Oxide
(1a).24 Phosphoryl trichloride (6.31 g, 41.1 mmol) in THF (30 mL)
was added dropwise (0.5 h) to a stirred solution of 3,5-
dimethylpyrazole (11.05 g, 114.9 mmol) and triethylamine (16.6
mL, 120 mmol) in THF (100 mL) at 0 °C. During the addition a
colorless solid was formed. After the addition was complete, the
reaction mixture was warmed to room temperature and was refluxed
for 3 h. After 1 h the mixture became slightly yellow. After 3 h, the
reaction mixture was filtered over silica and was washed with THF (3
× 15 mL). The combined filtrates were evaporated to dryness, and
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pentane was added to the residue. This was also removed in vacuo to
remove traces of solvent. Some byproducts remained, according to 1H
and 31P NMR spectra, and were removed by sublimation under
vacuum at 45 °C for 8 h. 1a was obtained as a colorless solid (11.4 g,
34.3 mmol, 89.6%). Mp: 91−93 °C. 1H NMR (500.2 MHz, CDCl3): δ
2.18 (s, 9H, Me), 2.29 (s, 9H, Me), 6.00 (d, 3H, 4J(H,P) = 3.8 Hz, pz).
13C{1H} NMR (125.8 MHz, CDCl3): δ 12.4 (s, Me), 14.1 (s, Me),
potassium tert-butyloxide (751 mg, 6.69 mmol) and 3-methyl-5-
phenylpyrazole (1.00 g, 6.32 mmol) in THF (10 mL) at 0 °C. The
mixture was stirred at 0 °C for 2 h, followed by 1 h at room
temperature. Water and CH2Cl2 were added, the organic phase was
separated, and the aqueous layer was extracted three times with
dichloromethane. The combined organic layers were dried over
MgSO4 and concentrated under reduced pressure. Column chromato-
graphic purification (SiO2, pentane/MTBE 10/5) gave 1d (328 mg,
3
2
111.1 (d, J(C,P) = 8.1 Hz, pz C-4), 148.2 (d, J(C,P) = 11.9 Hz, pz
1
3
C-5), 154.9 (d, J(C,P) = 15.7 Hz, pz C-3). 31P{1H} NMR (101.3
0.633 mmol, 30.0%) as a colorless solid. Mp: 169−171 °C. H NMR
4
(500 MHz, CDCl3): δ 2.43 (s, 9H, pz 5-Me), 6.61 (d, 3H, J(H,P) =
MHz, CDCl3): δ −10.7. IR: ν 3109 (w), 2993 (w), 2962 (w), 2928
(w), 1577 (m), 1408 (m), 1373 (w), 1284 (s), 1176 (s), 1141 (s),
1084 (m), 1041 (w), 1022 (m), 960 (s), 848 (m), 806 (m), 767 (m),
632 (m), 594 (s), 582 (s), 563 (s), 505 (m), 486 (m), 459 (m), 439
(m) cm−1. HR ESI-MS: m/z calcd for C15H22N6OP (M + H)
333.1587, found 333.1572.
3.5 Hz, pz 4-H), 7.30−7.37 (m, 9H, Hmeta,para), 7.67 (d, 6H, 3J(H,H) =
6.8 Hz, Hortho). 13C{1H} NMR (125.8 MHz, CDCl3): δ 12.5 (s, pz 5-
3
Me), 108.3 (d, J(C,P) = 7.6 Hz, pz C-4), 126.5 (s, Cortho), 128.7 (s,
Cmeta), 129.0 (s, Cpara), 132.0 (s, Cipso), 149.1 (d, 2J(C,P) = 11.8 Hz, pz
3
C-5), 156.7 (d, J(C,P) = 15.7 Hz, pz C-3). 31P{1H} NMR (101.3
MHz, CDCl3): δ −10.3. IR: ν 3113 (w), 2963 (w), 1570 (w), 1462
(w), 1400 (w), 1280 (m), 1261 (m), 1165 (s), 1095 (m), 1076 (m),
1041 (m), 1022 (m), 991 (m), 941 (m), 918 (w), 821 (m), 798 (m),
767 (m), 736 (m), 694 (s), 651 (m), 590 (s), 547 (m), 528 (w), 501
(w), 482 (m) cm−1. HR ESI-MS: m/z calcd for C30H28N6OP (M + H)
519.2057, found 519.2043.
Preparation of Tris(3-phenylpyrazolyl)phosphine Oxide
(1b). A solution of phosphoryl trichloride (1.82 g, 11.9 mmol) in
THF (10 mL) was added over 30 min to a stirred solution of 3-
phenylpyrazole (5.13 g, 35.6 mmol) and triethylamine (5.1 mL, 37
mmol) in THF (40 mL) at 0 °C. During the addition a colorless solid
formed. After the addition the solution was allowed to attain room
temperature, after which it was stirred overnight, refluxed for 4 h,
stirred overnight again, and refluxed for 3 h more, after which 31P
NMR showed the reaction to be complete. The reaction mixture was
filtered with a filter cannula and washed with THF (2 × 10 mL). All
Preparation of Tris(3-tert-butyl-5-methylpyrazolyl)-
phosphine Oxide (1e). A solution of phosphoryl trichloride (982
mg, 0.60 mL, 6.40 mmol) in THF (8 mL) was added dropwise to a
solution of potassium tert-butyloxide (2.02 g, 18.0 mmol) and 3-
methyl-5-tert-butylpyrazole (2.39 g, 17.3 mmol) in THF (16 mL) at 0
°C. The mixture was then heated to 60 °C and stirred at this
temperature for 20 h. After the mixture was cooled to ambient
temperature, water and CH2Cl2 were added, and the mixture was
filtered through Celite. The organic phase was separated, and the
aqueous layer was extracted three times with dichloromethane. The
combined organic layers were dried over MgSO4 and concentrated
under reduced pressure. Column chromatographic purification (SiO2,
pentane/MTBE 10/4; iodine was used to visualize TLC spots) gave 1e
(1.41 g, 3.07 mmol, 53.3%) as a colorless solid. Mp: 107−109 °C. 1H
NMR (400.1 MHz, CDCl3): δ 1.18 (s, 27H, CMe3), 2.19 (dd, 4J(H,H)
= 0.9 Hz, 4J(H,P) = 0.5 Hz, 9H, pz 5-Me), 6.04 (dd, 3H, 4J(H,P) = 3.8
Hz, 4J(H,H) = 0.9 Hz, pz 4-H). 13C{1H} NMR (100.6 MHz, CDCl3):
δ 12.0 (s, pz 5-Me), 29.9 (s, CMe3), 32.6 (s, CMe3), 107.7 (d, 3J(C,P)
1
volatiles were evaporated, and the residue was analyzed by H NMR
spectroscopy. As this showed the presence of some triethylammonium
chloride, the solid was dissolved in THF and filtered over silica. The
residue was washed with THF (2 × 10 mL), and all volatiles were
removed from the combined filtrates. This afforded 1b as a pale yellow
solid (4.88 g, 10.2 mmol, 86.0%). Mp: 175−180 °C. 1H NMR (500.2
MHz, CDCl3): δ 6.85 (dd, 3H, 4J(H,P) = 3.6 Hz, 3J(H,H) = 2.8 Hz, pz
3
4-H), 7.36−7.43 (m, 9H, Hmeta,para), 7.86 (d, 6H, J(H,H) = 6.6 Hz,
Hortho), 8.01 (d, 3H, 3J(H,H) = 2.8 Hz, pz 5-H). 13C{1H} NMR (125.8
MHz, CDCl3): δ 107.8 (d, 3J(C,P) = 7.2 Hz, pz C-4), 126.8 (s, Cortho),
2
128.9 (s, Cmeta), 129.5 (s, Cpara), 131.4 (s, Cipso), 137.6 (d, J(C,P) =
12.1 Hz, pz C-5), 159.1 (d, 3J(C,P) = 15.5 Hz, pz C-3). 31P{1H} NMR
(162.0 MHz, CDCl3): δ −14.8. IR: ν 1535 (m), 1500 (w), 1450 (w),
1381 (w), 1327 (m), 1300 (m), 1280 (w), 1215 (m), 1161 (m), 1091
(m), 1072 (m), 1030 (s), 952 (m), 756 (s), 694 (s), 609 (s), 586 (s),
520 (m), 505 (m) cm−1. HR ESI-MS: m/z calcd for C27H22N6OP (M
+ H) 477.1587, found 477.1576.
2
= 7.9 Hz, =CH), 147.9 (d, J(C,P) = 11.7 Hz, pz C-3), 166.9 (d,
3J(C,P) = 14.5 Hz, pz C-5). 31P{1H} NMR (162.0 MHz, CDCl3): δ
−10.5. IR: ν 2962 (w), 2928 (w), 2866 (w), 1573 (m), 1485 (w), 1458
(w), 1446 (w), 1404 (w), 1384 (w), 1361 (w), 1296 (s), 1234 (m),
1211 (w), 1165 (m), 1114 (w), 1099 (w), 1087 (w), 1068 (w), 960
(m), 802 (m), 725 (m), 636 (w), 594 (s), 578 (s), 536 (w), 513 (w)
cm−1. HR ESI-MS: m/z calcd for C24H40N6OP (M + H) 495.2996,
found 459.2985.
Preparation of Tris(3-tert-butylpyrazolyl)phosphine Oxide
(1c).25 A solution of phosphoryl trichloride (1.95 g, 12.7 mmol) in
THF (10 mL) was added over 30 min to a stirred solution of 3-tert-
butylpyrazole (4.74 g, 38.2 mmol) and triethylamine (5.5 mL, 40
mmol) in THF (40 mL) at 0 °C. During the addition a colorless solid
was formed. After the addition was complete, the reaction mixture was
warmed to room temperature, stirred overnight, and refluxed for 4 h,
after which 31P NMR showed the reaction to be complete. All solids
were removed by cannula filtration, and the residue was washed with
THF (2 × 10 mL). All volatiles were evaporated from the combined
filtrates, and pentane was added to the residue. This was also removed
in vacuo to remove the last trace of solvent, affording 1c as a colorless
solid (4.94 g, 11.9 mmol, 93.4%). Mp: 150−153 °C. 1H NMR (500.2
MHz, CDCl3): δ 1.27 (s, 27H, CMe3), 6.33 (dd, 3H, 4J(H,P) = 3.6 Hz,
Preparation of Copper(I) Acetonitrile Tris(3,5-
dimethylpyrazolyl)phosphine Oxide Hexafluorophosphate
(2a). Dichloromethane (5 mL) was added with stirring to a mixture
of 1a (175 mg, 0.527 mmol) and [Cu(NCMe)4][PF6] (197 mg, 0.528
mmol). Within a few minutes a clear reaction mixture resulted that was
stirred for 30 min. After concentration (∼4 mL) pentane (0.5 mL) was
added, and after brief heating, the resulting clear solution was stored at
−70 °C for crystallization, yielding 119 mg (0.205 mmol) of colorless
crystalline material after drying in vacuo. Treating the mother liquor
with pentane (10 mL) resulted in a second batch of colorless powder
(159 mg, 0.273 mmol) that was spectroscopically identical with the
first batch. Total yield: 278 mg, 0.478 mmol, 90.6%. Mp: 230−233 °C
dec. 1H NMR (500.2 MHz, CDCl3): δ 2.36 (s, 9H, 3-Me), 2.37 (s, 3H,
3
3J(H,H) = 2.8 Hz, pz 4-H), 7.65 (d, 3H, J(H,H) = 2.8 Hz, pz 5-H).
13C{1H} NMR (125.8 MHz, CDCl3): δ 30.0 (s, CMe3), 32.8 (s,
3
2
CMe3), 107.0 (d, J(C,P) = 7.6 Hz, pz C-4), 136.3 (d, J(C,P) = 12.0
Hz, pz C-5), 169.4 (d, J(C,P) = 13.8 Hz, pz C-3). 31P{1H} NMR
3
4
NCMe), 2.58 (s, 9H, 5-Me), 6.10 (d, 3H, J(H,P) = 5.2, pz 4-H).
(101.3 MHz, CDCl3): δ −14.4. IR: ν 3113 (w), 2958 (w), 2904. (w),
2866 (w), 1535 (m), 1500 (m), 1481 (m), 1462 (w), 1381 (w), 1365
(m), 1323 (m), 1296 (m), 1230 (m), 1211 (m), 1176 (m), 1141 (s),
1103 (s), 1041 (s), 972 (w), 952 (m), 883 (w), 829 (w), 798 (w), 775
(s), 725 (w), 694 (w), 678 (w), 628 (s), 605 (s), 563 (s), 513 (w), 493
cm−1. HR ESI-MS: m/z calcd for C20H34N6OP (M + H) 417.2526,
found 417.2511.
Preparation of Tris(3-phenyl-5-methylpyrazolyl)phosphine
Oxide (1d). A solution of phosphoryl trichloride (340 mg, 0.21 mL,
2.22 mmol) in THF (3 mL) was added dropwise to a solution of
13C{1H} NMR (125.8 MHz, CDCl3): δ 2.7 (NCMe), 13.7 (s, 5-
3
Me), 14.0 (s, 3-Me), 110.8 (d, J(C,P) = 9.8 Hz, pz C-4), 117.3 (s,
NC), 149.8 (d, 2J(C,P) = 11.5 Hz, pz C-5), 157.3 (d, 3J(C,P) = 11.4
Hz, pz C-3). 31P{1H} NMR (101.3 MHz, CDCl3): δ −144.4 (septet,
1P, 1J(P,F) = 712 Hz, PF6), −19.8 (s, 1P, PO). 19F{1H} NMR (235.4
1
MHz, CDCl3): δ −73.6 (d, J(F,P) = 712 Hz). IR: ν 3148 (w), 3090
(w), 2970 (w), 1574 (w), 1531 (w), 1497 (w), 1458 (w), 1408 (w),
1373 (w), 1319 (m), 1273 (m), 1169 (m), 1095 (w), 1076 (w), 1038
(m), 972 (w), 922 (w), 829 (vs), 764 (s), 690 (m), 621 (m), 579 (s),
3312
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Organometallics
Article
555 (s), 517 (m), 447 (m) cm−1. HR ESI-MS: m/z calcd for
C15H21CuN6OP (M − PF6 − CH3CN) 395.0805, found 395.0781.
General Procedure for the Preparation of the Other
Copper(I) Acetonitrile Complexes. Freshly deoxygenated dichloro-
methane was added to a mixture of the corresponding ligand (1.00
mmol) and [Cu(NCMe)4][PF6] (1.00 mmol) at 20 °C. The resulting
suspension was stirred at room temperature, which eventually gave a
clear solution. After 2 h of stirring 31P NMR indicated full conversion
to the target complex. The solvent was evaporated and the solid
washed with MTBE, filtered, and dried at 70 °C (in some cases a small
solvent signal was still observed by NMR) to give the target complexes
as colorless solids.
1234 (w), 1172 (m), 976 (w), 840 (s), 821 (s), 729 (s), 713 (w), 624
(w), 594 (s), 555 (m), 516 (w) cm−1. HR ESI-MS: m/z calcd for
C24H39CuN6OP (M − CH3CN − PF6) 521.2213, found 521.2197.
Preparation of Copper(I) Triphenylphosphine Tris(3,5-
dimethylpyrazolyl)phosphine Oxide Hexafluorophosphate
(3a). Dichloromethane (5 mL) was added with stirring to a mixture
of 2a (87 mg, 0.15 mmol) and triphenylphosphine (41 mg, 0.16
mmol). Within a few minutes a clear solution was obtained, which was
stirred for 3 h more. After removal of all volatiles, the residual colorless
solid was washed with diethyl ether (3 × 5 mL) and dried in vacuo for
5 h at 65 °C, yielding 94 mg (0.12 mmol, 78%) of 3a. Crystals, suitable
for X-ray structure analysis, were obtained by storing a saturated
solution of 3a in a dichloromethane/pentane mixture at 7 °C for 4
days. Mp: 226.1−226.5 °C. 1H NMR (250.1 MHz, CDCl3): δ 1.79 (s,
Copper(I) Acetonitrile Tris(3-phenylpyrazolyl)phosphine Oxide
Hexafluorophosphate (2b). Yield: 87%. Mp: 202−205 °C. 1H
NMR (400.1 MHz, CD2Cl2): δ 1.92 (s, 3H, NCMe), 6.94 (dd,
3H, 4J(H,P) = 4.5 Hz, 3J(H,H) = 2.9 Hz, pz 4-H), 7.46−7.57 (m, 9H,
Hmeta,para), 7.78 (m, 6H, Hortho), 8.43 (dd, 3H, 3J(H,H) = 2.9 Hz,
3J(H,P) = 0.8 Hz, pz 5-H). 13C{1H} NMR (100.6 MHz, CD2Cl2): δ
4
9H, 3-Me), 2.66 (s, 9H, 5-Me), 6.16 (d, 3H, J(H,P) = 5.2 Hz, pz 4-
H), 7.41−7.53 (m, 15H, Ph). 13C{1H} NMR (62.9 MHz, CDCl3): δ
3
13.9 (s, 5-Me), 14.3 (s, 3-Me), 111.5 (d, J(C,P) = 9.9 Hz, pz C-4),
129.6 (d, 3J(C,P) = 10.1 Hz, Cortho), 131.3 (d, 4J(C,P) = 1.8 Hz, Cpara),
132.0 (d, 1J(C,P) = 38.5 Hz, Cipso), 134.0 (d, 2J(C,P) = 15.2 Hz, Cmeta),
151.0 (d, 2J(C,P) = 11.7 Hz, pz C-5), 157.1 (d, 3J(C,P) = 11.4 Hz, pz
C-3). 31P{1H} NMR (101.3 MHz, CDCl3): δ −144.4 (septet, 1P,
1J(P,F) = 712 Hz, PF6), −20.2 (s, 1P, PO), 6.8 (broad s, 1P, PPh3).
3
2.51 (NCMe), 109.7 (d, J(C,P) = 8.9 Hz, pz C-4), 114.9 (s, N
C), 128.4 (s, Cortho), 129.2 (s, Cmeta), 129.8 (s, Cipso), 131.3 (s, Cpara),
137.3 (d, 2J(C,P) = 11.6 Hz, pz C-5), 161.2 (d, 3J(C,P) = 11.9 Hz, pz
C-3). 31P{1H} NMR (101.3 MHz, CD2Cl2): δ −144.3 (septet, 1P,
1J(P,F) = 711 Hz, PF6), −19.8 (s, 1P, PO). 19F{1H} NMR (235.4
MHz, CD2Cl2): δ −72.9 (d, 1J(F,P) = 711 Hz). IR: ν 3136 (w), 3117
(w), 3059 (w), 1535 (w), 1504 (w), 1454 (w), 1381 (w), 1327 (m),
1300 (m), 1280 (w), 1215 (m), 1161 (m), 1087 (w), 1072 (m), 1030
(s), 952 (m), 756 (s), 690 (s), 609 (s), 586 (s), 505 (m) cm−1. HR
ESI-MS: m/z calcd for C27H21CuN6OP (M − PF6 − CH3CN)
539.0805, found 539.0774.
1
19F{1H} NMR (235.4 MHz, CDCl3): δ −73.9 (d, J(F,P) = 712 Hz).
IR: ν 3653 (w), 3113 (w), 3078 (w), 2989 (w), 2935 (w), 2361 (w),
2322 (w), 1574 (m), 1477 (sh), 1462 (w), 1435 (m), 1412 (m), 1373
(w), 1315 (m), 1277 (m), 1177 (m), 1153 (m), 1095 (m), 1034 (w),
976 (w), 833 (vs), 748 (s), 698 (s), 656 (w), 625 (w), 590 (s), 555
(s), 521 (s), 505 (s), 451 (s), 428 (m), 405 (w) cm−1. HR ESI-MS: m/
z calcd for C33H36CuN6OP2 (M − PF6) 657.1722, found 657.1647.
General Procedure for MeCN−CO Exchange. A solution of the
Cu acetonitrile complex in degassed dichloromethane (5 mL) was
degassed by three freeze−pump−thaw cycles. Before thawing for the
third time, the flask was filled with CO gas (1 atm). After thawing, the
reaction mixture was stirred at room temperature for the indicated
time. Then, pentane (20 mL) was added and the solvent was removed
from the precipitated solid using a cannula filter. Subsequently, the
product was dried under a stream of nitrogen.
Copper(I) Acetonitrile Tris(3-tert-butylpyrazolyl)phosphine Oxide
1
Hexafluorophosphate (2c). Yield: 85%. Mp: 160−165 °C dec. H
NMR (500.2 MHz, CD2Cl2): δ 1.44 (s, 27H, CMe3), 2.34 (s, 3H, N
4
3
C−Me), 6.56 (dd, 3H, J(H,P) = 4.7 Hz, J(H,H) = 3.0 Hz, pz 4-H),
8.11 (d, 3H, 3J(H,H) = 3.0 Hz, pz 5-H). 13C{1H} NMR (125.8 MHz,
CD2Cl2): δ 2.9 (s, NC−Me), 30.0 (s, CMe3), 33.1 (s, CMe3), 108.0
3
2
(d, J(C,P) = 8.9 Hz, pz C-4)), 118.1 (NC), 136.2 (d, J(C,P) =
11.7 Hz, pz C-5), 171.7 (d, 3J(C,P) = 10.5 Hz, pz C-3). 31P{1H} NMR
1
(101.3 MHz, CD2Cl2): δ −144.4 (septet, 1P, J(P,F) = 711 Hz, PF6),
Copper(I) Carbonyl Tris(3,5-dimethylpyrazolyl)phosphine Oxide
−20.7 (s, 1P, PO). 19F{1H} NMR (235.4 MHz, CD2Cl2): δ −73.1 (d,
Hexafluorophosphate (4a). After stirring for 1 month, a mixture of 2a
1
1J(F,P) = 711 Hz). IR: ν 1531 (w), 1319 (w), 1230 (w), 1188 (w),
and the product was present in a 0.3:1.0 ratio, according to H NMR
integration. 1H NMR (500.2 MHz, CDCl3): δ 2.42 (s, 9H, 3-Me), 2.62
(s, 9H, 5-Me), 6.25 (d, 3H, 4J(H,P) = 4.6 Hz, pz 4-H). 13C{1H} NMR
(125.8 MHz, CDCl3): δ 13.6 (s, 5-Me), 14.4 (s, 3-Me), 111.2 (d,
3J(C,P) = 9.7 Hz, pz C-4), 151.4 (d, 2J(C,P) = 10.9 Hz, pz C-5), 158.4
1145 (w), 1049 (m), 837 (s), 783 (m), 729 (w), 628 (s), 570 (m), 555
(s), 524 (w), 509 (w), 455 (w), 420 (m) cm−1. HR ESI-MS: m/z calcd
for C21H33CuN6OP (M − CH3CN − PF6) 479.1744, found 479.1729.
Copper(I) Acetonitrile Tris(3-phenyl-5-methylpyrazolyl)-
phosphine Oxide Hexafluorophosphate (2d). Yield: 98%. Dec pt:
190−200 °C (no melting). 1H NMR (500.2 MHz, CD2Cl2): δ 1.85 (s,
3
(d, J(C,P) = 10.8 Hz, pz C-3). 31P{1H} NMR (101.3 MHz, CDCl3):
1
δ −144.4 (septet, 1P, J(P,F) = 712 Hz, PF6), −21.7 (s, 1P, PO).
4
1
19F{1H} NMR (235.4 MHz, CDCl3): δ −73.5 (d, J(F,P) = 712 Hz).
3H, NC−Me), 2.77 (s, 9H, pz 5-Me), 6.64 (d, 3H, J(H,P) = 4.8
Hz, pz 4-H), 7.41−7.47 (m, 6H, Hmeta), 7.47−7.52 (m, 3H, Hpara), 7.60
(d, 6H, 3J(H,H) = 7.1 Hz, Hortho). 13C{1H} NMR (125.8 MHz,
CD2Cl2): δ 2.3 (s, NC−Me), 14.0 (s, pz 5-Me), 110.0 (d, 3J(C,P) =
9.5 Hz, pz C-4), 116.6 (s, NC), 128.2 (s, Cortho), 129.0 (s, Cmeta),
130.0 (s, Cipso), 130.9 (s, Cpara), 151.8 (d, 2J(C,P) = 11.3 Hz, pz C-5),
IR: ν 3148 (w), 3128 (w), 3094 (w), 2129 (w), 1574 (m), 1535 (w),
1451 (w), 1458 (m), 1412 (w), 1377 (w), 1319 (m), 1277 (s), 1173
(s), 1153 (sh), 1099 (w), 1038 (m), 975 (m), 922 (w), 837 (vs), 814
(vs), 764 (s), 725 (m), 694 (m), 625 (m), 582 (vs), 555 (vs), 520
(sh), 451 (s), 420 (sh) cm−1. HR ESI-MS: m/z calcd for
C15H21CuN6OP (M − PF6 − CO) 395.0805, found 395.0777.
Copper(I) Carbonyl Tris(3-phenylpyrazolyl)phosphine Oxide
Hexafluorophosphate (4b). After stirring overnight, most of 2b
seemed not to have reacted according to NMR spectroscopy. The
actual conversion is difficult to estimate from the NMR spectra
because of the similarity of the chemical shifts of the product and the
starting compound. IR ν(CO): 2121 (w) cm−1. HR ESI-MS: m/z
calcd for C27H21CuN6OP (M − PF6 − CO) 539.0805, found
539.0774.
3
159.5 (d, J(C,P) = 11.9 Hz, pz C-3). 31P{1H} NMR (101.3 MHz,
CD2Cl2): δ −144.5 (septet, 1P, 1J(P,F) = 710 Hz, PF6), −18.0 (s, 1P,
PO). 19F{1H} NMR (235.4 MHz, CD2Cl2): δ −73.4 (d, 1J(F,P) = 710
Hz). IR: ν 1566 (w), 1462 (w), 1315 (w), 1292 (w), 1269 (w), 1161
(m), 952 (w), 833 (s), 767 (m), 736 (w), 694 (m), 648 (m), 621 (w),
586 (s), 555 (s) cm−1. HR ESI-MS: m/z calcd for C32H30CuN7OP (M
− PF6) 622.1540, found 622.1515.
Copper(I) Acetonitrile Tris(3-tert-butyl-5-methylpyrazolyl)-
phosphine Oxide Hexafluorophosphate (2e). Yield: 96%. Mp:
170−174 °C. 1H NMR (500.2 MHz, CDCl3): δ 1.35 (s, 27H,
CMe3), 2.34 (s, 3H, NC−Me), 2.50 (s, 9H, pz 5-Me), 6.28 (d, 3H,
4J(H,P) = 4.7 Hz, pz 4-H). 13C{1H} NMR (125.8 MHz, CDCl3): δ 2.5
Copper(I) Carbonyl Tris(3-tert-butylpyrazolyl)phosphine Oxide
Hexafluorophosphate (4c). After stirring for 1 month, most of the
isolated material was unreacted 2c. According to 1H NMR integration,
the ratio of 2c and the product was 4:1. 1H NMR (500.2 MHz,
CDCl3): δ 1.36 (s, 27H, CMe3), 6.30 (s, 3H, coupling constants are
not resolved, pz 4-H), 7.99 (d, 3H, 3J(H,H) = 2.4 Hz, pz 5-H).
13C{1H} NMR (125.8 MHz, CDCl3): δ 30.6 (s, CMe3), 32.5 (s,
(s, NC−Me), 13.5 (s, pz 5-Me), 29.9 (s, CMe3), 32.8 (s, CMe3),
109.2 (d, 3J(C,P) = 9.2 Hz, pz C-4), 118.3 (NC), 150.0 (d, 2J(C,P)
3
= 11.9 Hz, pz C-5), 169.5 (d, J(C,P) = 10.6 Hz, pz C-3). 31P{1H}
1
NMR (101.3 MHz, CDCl3): δ −144.3 (septet, 1P, J(P,F) = 712 Hz,
PF6), −17.1 (s, 1P, PO). 19F{1H} NMR (235.4 MHz, CDCl3): δ
CMe3), 107.2 (br s, pz C-4), 135.3 (br s, pz C-5), 166.9 (br s, pz C-3);
1
−73.2 (d, J(F,P) = 712 Hz). IR: ν 2974 (w), 1573 (w), 1284 (w),
coupling constants are not resolved. 31P{1H} NMR (101.3 MHz,
3313
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Article
Table 3. Experimental Details of the Crystal Structure Determinations
2c
2d
3a
formula
fw
[C23H36CuN7OP](PF6)·CH2Cl2
750.99
[C32H30CuN7OP](PF6)
768.11
[C33H36CuN6OP2](PF6)·2CH2Cl2
972.98
cryst size (mm3)
crystal color
T (K)
0.60 × 0.51 × 0.31
colorless
0.42 × 0.25 × 0.21
colorless
0.51 × 0.28 × 0.18
colorless
150(2)
150(2)
150(2)
cryst syst
space group
a (Å)
orthorhombic
P21212 (No. 18)
16.9778(6)
monoclinic
triclinic
P21/c (No. 14)
8.6120(3)
P1 (No. 2)
̅
11.0739(3)
12.6624(3)
15.9619(2)
102.223(1)
106.463(1)
91.278(1)
2089.69(8)
2
b (Å)
18.8108(7)
23.4829(9)
c (Å)
10.5559(4)
17.3556(6)
α (deg)
β (deg)
γ (deg)
V (Å3)
109.357(2)
3371.2(2)
4
3311.5(2)
4
Z
dcalcd (g/cm3)
1.480
1.541
1.546
μ (mm−1
)
0.965
0.829
0.958
abs cor type
multiscan50
0.67−0.75
0.65
multiscan50
0.68−0.75
0.65
multiscan50
0.70−0.84
0.65
abs cor range
(sin θ/λ)max (Å−1
)
no. of measd/unique rflns
no. of params/restraints
R1/wR2 (I > 2σ(I))
R1/wR2 (all rflns)
S
46 498/7748
401/91
57 072/7613
468/81
40 560/9572
531/42
0.0326/0.0925
0.0337/0.0936
1.023
0.0294/0.0761
0.0337/0.0795
1.032
0.0349/0.0887
0.0409/0.0937
1.032
Flack x51
−0.009(10)
−0.48/0.69
ρmin/max (e/Å3)
−0.41/0.63
−0.72/0.87
matrices to generate an HKLF5 file.49 Distance and angle restraints
were used for the CH2Cl2 solvent molecules. The Cl atoms were
restrained to approximate isotropic behavior.
1
CDCl3): δ −144.6 (septet, 1P, J(P,F) = 711 Hz, PF6), −19.4 (s, 1P,
PO). 19F{1H} NMR (235.4 MHz, CDCl3): δ −73.6 (br d, J(F,P) =
1
715 Hz). IR ν(CO): 2118 (w) cm−1.
Copper(I) Carbonyl Tris(3-phenyl-5-methylpyrazolyl)phosphine
Oxide Hexafluorophosphate (4d). Stirring for 64 h gave full
conversion, and 4d was isolated as a colorless solid in quantitative
ASSOCIATED CONTENT
* Supporting Information
Figures giving all reported NMR spectra and CIF files giving
crystallographic data for 2c,d and 3a. This material is available
free of charge via the Internet at http://pubs.acs.org.
■
S
1
yield. Mp: 170−177 °C dec. H NMR (400.1 MHz, CD2Cl2): δ 2.81
4
(s, 9H, pz 5-Me), 6.64 (d, 3H, J(H,P) = 5.0 Hz, pz 4-H), 7.44−7.62
(m, 15H, Ph). 13C{1H} NMR (125.8 MHz, CD2Cl2): 14.1 (s, pz 5-
Me), 110.6 (br s, pz C-4), 128.3 (s, Cortho), 129.5 (s, Cmeta), 130.1 (s,
Cipso), 131.1 (s, Cpara), 152.9 (br s, pz C-3), 161.1 (br s, pz C-5).
31P{1H} NMR (162.0 MHz, CD2Cl2): δ −144.4 (septet, 1P, 1J(P,F) =
711 Hz, PF6), −20.4 (s, 1P, PO). 19F{1H} NMR (235.4 MHz,
AUTHOR INFORMATION
Corresponding Author
*Fax: +31-20-5987488. E-mail: K.Lammertsma@vu.nl (K.L.); J.
C.Slootweg@vu.nl (J.C.S.).
■
1
CD2Cl2): δ −73.2 (d, J(F,P) = 711 Hz). IR: ν 2111 (w), 1565 (w),
1458 (w), 1407 (w), 1332 (w), 1271 (w), 1162 (m), 958 (w), 832 (s),
771 (m), 703 (m), 699 (m), 584 (s), 555 (s) cm−1. HR ESI-MS: m/z
calcd for C30H27CuN6OP (M − PF6 − CO) 581,1274, found
581.1241.
Notes
The authors declare no competing financial interest.
Crystal Structure Determinations. X-ray intensities were
measured on a Bruker Kappa ApexII diffractometer with sealed tube
and Triumph monochromator (λ = 0.710 73 Å) (compounds 2c,d) or
on a Nonius KappaCCD diffractometer with rotating anode and
graphite monochromator (λ = 0.710 73 Å) (compound 3a).
Integration was performed with Saint45 (2c,d) or Eval1546 (3a). The
structures were solved with direct methods using SHELXS-97.47 Least-
squares refinement was performed with SHELXL-9747 on F2 of all
reflections. Non-hydrogen atoms were refined with anisotropic
displacement parameters. Hydrogen atoms were introduced in
calculated positions (2c, 3a) or located in difference Fourier maps
(2d) and refined with a riding model. Structure calculations and
checking for higher symmetry were performed with PLATON.48
Further details are given in Table 3. For 2c,d, distance and angle
restraints were used for the PF6 anions. The F atoms were restrained
to approximate isotropic behavior. For 3a, the crystal appeared to be
cracked into two fragments related by a rotation of 1.5° about an
arbitrary axis. The integration was performed with two orientation
ACKNOWLEDGMENTS
■
This work was supported by the Council for Chemical Sciences
of The Netherlands Organization for Scientific Research
(NWO/CW) and benefitted from interactions within the
European PhoSciNet (COST Action CM0802). We thank M.
Smoluch and A. C. Janssen for measuring the high-resolution
mass spectra and J. Bouma for providing CO gas.
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