Coinage metal complexes of tris(pyrazolyl)methanide [C(3,5-Me 2pz)3]-: κ3-coordination vs. backbone functionalisation

Article abstract of DOI:10.1039/b512309g

Tris(pyrazolyl)methanides, [C(3,5-R₂pz)₃] ^-, contain an unassociated tetrahedral carbanionic centre in the bridgehead position. In addition to nitrogen donor centres for transition metal coordination, an accessible reactive site for further manipulations is available in the backbone of the ligand. The coordination variability of the ambidental C^-/N ligand [C(3,5-Me₂pz)₃]^- was elucidated by investigating its coinage metal complexes. Two principle coordination modes were found for complexes of general formula [LMPR ₃] (with M = Cu^I, Ag^I, Au^I; L = [C(3,5-Me₂pz)₃]^-; R = Ph, OMe). While for Cu(i) (2, 3) and Ag(i) (4) complexes the anionic ligand acts as a face-capping, six electron N₃-donor, gold(i) (5) is coordinated by the bridging carbanion yielding a two coordinate Au(i) complex comprising a covalent Au-C bond. The complexes featuring the κ³-coordinated N ₃-donor ligand were investigated by ³¹P CP (MAS) NMR in the solid state. The Royal Society of Chemistry 2006.

Full text of DOI:10.1039/b512309g

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PAPER
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Coinage metal complexes of tris(pyrazolyl)methanide [C(3,5-Me2pz)3]−:
j3-coordination vs. backbone functionalisation
Ivo Krummenacher,a,b Heinz Ru¨eggera and Frank Breher*a,b
Received 31st August 2005, Accepted 31st October 2005
First published as an Advance Article on the web 28th November 2005
DOI: 10.1039/b512309g
Tris(pyrazolyl)methanides, [C(3,5-R2pz)3]−, contain an unassociated tetrahedral carbanionic centre in
the bridgehead position. In addition to nitrogen donor centres for transition metal coordination, an
accessible reactive site for further manipulations is available in the backbone of the ligand. The
coordination variability of the ambidental C−/N ligand [C(3,5-Me2pz)3]− was elucidated by
investigating its coinage metal complexes. Two principle coordination modes were found for complexes
of general formula [LMPR3] (with M = CuI, AgI, AuI; L = [C(3,5-Me2pz)3]−; R = Ph, OMe). While for
Cu(I) (2, 3) and Ag(I) (4) complexes the anionic ligand acts as a face-capping, six electron N3-donor,
gold(I) (5) is coordinated by the bridging carbanion yielding a two coordinate Au(I) complex
comprising a covalent Au–C bond. The complexes featuring the j3-coordinated N3-donor ligand were
investigated by 31P CP (MAS) NMR in the solid state.
Introduction
Important face-capping, six-electron N-donor ligands in coor-
dination chemistry are certainly tris(pyrazolyl)hydroborate (Tp)
ligands (I).1 First introduced by Trofimenko in 1967, Tp ligands
have become one of the most widely employed classes of lig-
and systems in coordination chemistry. Tris(pyrazolyl)methane
ligands of general formula II are the neutral analogues of
tris(pyrazolyl)hydroborates. These types of j3-coordinating N3-
donor ligands are formally derived by replacing the bridging (BH)−
moiety with the isoelectronic CH group. They have attracted con-
siderable interest mainly driven by the improved ligand syntheses
developed by Reger and co-workers.2 Recently, Mountford et al.
have summarised this emerging research field in a review article.3
As with the Tp ligands (I), the type II ligands can be considered
as the tripodal equivalent of pentamethylcyclopentadienide (Cp*)
and cyclopentadienide (Cp), acting as face-capping six electron
donors.4 However, their isoelectronic, uninegative analogues, that
is, tris(pyrazolyl)methanides [C(3,5-R2pz)3]− (III) containing a
cognize the true structure of, and the fascinating bonding situation
carbanionic centre in the bridgehead position are completely un-
within, this lithium organyl compound. Only recently were we able
derdeveloped in coordination chemistry. Thus, little information
to clarify the zwitterionic structure of [Li{C(3,5-Me2pz)3}(thf)]
is available from the literature about the properties of such ligands
(1) in solution and in the solid-state.6 Our investigations revealed
and their metal complexes.
that a suitable bridle, created by intramolecular chelation of the
To the best of our knowledge, only one transition metal complex
Li cation, and lack of p-delocalisation, led to the first monomeric
is known. Mountford and co-workers impressively succeeded in
lithium organyl compound containing an unassociated tetrahedral
isolating a zwitterionic titanium(IV) imido complex [Ti{C(3,5-
carbanionic centre. Apart from their usefulness as anion transfer
Me2pz)3}(Nt-Bu)Cl(thf)].5 It was formed by coincidental depro-
reagents, donor-functionalised ligands like 1 should have a high
tonation of the corresponding tris(pyrazolyl)methane complex.
potential as transition metal ligands. Therefore, stimulated by
This example contains the first structurally characterised “naked”
these recent results, we have begun to elaborate the coordinating
sp3-hybridised carbanion. Moreover, they described the possibility
abilities of 3,5-disubstituted tris(pyrazolyl)methanides towards
of cleanly deprotonating HC(3,5-Me2pz)3 with MeLi prior to com-
transition metals. We are particularly interested in anionic tripodal
plexation with a transition metal centre. However, they did not re-
ligand systems like III because alongside nitrogen donor centres
for transition metal coordination, an accessible reactive site for
aDepartment of Chemistry and Applied Biosciences (D-CHAB), ETH
further manipulations is available in the backbone of the ligand.
Ho¨nggerberg, Wolfgang-Pauli Str., CH-8093, Zu¨rich, Switzerland
Here we report our results on the syntheses and characterisa-
bInstitut fu¨r Anorganische Chemie, Universita¨t Karlsruhe (TH), Engesserstr.
tion of coinage metal complexes of the hexamethyl substituted
tris(pyrazolyl)methanide, [C(3,5-Me2pz)3]−.
15, D-76131, Karlsruhe, Germany. E-mail: breher@aoc1.uni-karlsruhe.de;
Fax: int. +(49) 721 608 84 40
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In previous papers several research groups have already sys-
tematically investigated the coordination chemistry of the related
Tp ligands and scorpionates towards coinage metals. Attention to
such systems mainly arises from their potential relevance to biolog-
ical systems and synthetic oxidative catalysis, which have received
significant interest over the past two decades. Alongside zinc com-
plexes developed by Vahrenkamp et al.,7 copper/Tp complexes8
have been employed as model compounds for active sites of
metalloproteins such as copper enzymes that activate O2 and
function as oxygenases or oxidases.9 Furthermore, Reger et al. have
prepared a number of tris(pyrazolyl)alkane silver complexes in
which the ligand is linked via the bridging carbon atom, resulting in
supramolecular complexes.10 Such coordination polymers are cur-
rently of interest because of their potential as functional materials.
Scheme 2 Synthesis of 4.
Results and discussion
In transition metal coordination chemistry “classical” tripodal
ligands like I and II are normally coordinated via the nitrogen
donor atoms. In contrast, ambidental C−/N ligands like III might
alternatively act as a two electron C-donor due to its isolobal
relationship to phosphines (i.e., R3C− ↔ R3P).11 According to
the HSAB (hard/soft acids/bases) principle for small, highly
charged metals a coordination using the “hard” N-donors would
be preferable, whereas the “soft” carbanionic centre may be the
more favourable ligand for larger, singly charged metals. In order
to shed some light on the coordination variability of the methyl
substituted tris(pyrazolyl)methanide [C(3,5-Me2pz)3]− we have
investigated its coinage metal complexes. Indeed, two principle
coordination modes were found for the coinage metal complex of
general formula [LMPR3] (with M = CuI, AgI, AuI; L = [C(3,5-
Me2pz)3]−; R = Ph, OMe). While for Cu(I) (2, 3) and Ag(I) (4) the
anionic tris(pyrazolyl)methanide acts as face-capping, six electron
N3-donor, gold(I) (5) is coordinated by the bridging carbanion
furnishing a two coordinate Au(I) complex comprising a covalent
Au–C bond (see Schemes 1 to 3).
Scheme 3 Synthesis of 5.
base for the deprotonation of the neutral precursor HC(3,5-
Me2pz)3. When a 1 : 1 mixture of both starting materials in
toluene is treated with one equiv. of trimethyl phosphite a slightly
colored reaction mixture is observed. 1H NMR spectroscopy
revealed incomplete deprotonation of the bridging CH moiety.
With detectable amounts of unreacted starting material present,
an apparent acid–base equilibrium between the involved species
in solution is suspected. Consequently, following this protocol the
copper complex 3 was isolated in only 29% yield.
In view of these results, the corresponding silver (4) and gold
(5) complexes were synthesised via salt elimination using suitable
precursors; Ph3PAgNO3 for the synthesis of 4 and Ph3PAuCl for
5, and the deprotonated ligand 1. Both compounds are accessible
in good yield (74% (4), 76% (5)) after recrystallisation from
hydrocarbon solvents.
Compounds 2 to 5 are colorless crystalline solids, which are
fairly air- and moisture-sensitive, but thermally stable with melting
points in excess of 131 ◦C. The silver complex 4 is sensitive to
daylight and decomposes immediately upon irradiation but can
be stored in the dark under argon at −30 ◦C without any signs
of decomposition. The IR spectra (solid, attenuated total reflex-
ion, ATR) show the characteristic stretching frequencies of the
pyrazole rings around 1553 (av.) cm−1. Hence, they are completely
invariant to metal substitution or the coordination mode.
Much more diagnostic are the NMR chemical shifts (Table 1). In
the case of j3-coordination of the tridentate ligand the 1H NMR
resonance of the heteroaromatic pyrazole, i.e., CHpz, is shifted
to lower frequency compared to the protonated ligand HC(3,5-
Me2pz)3 (d = 5.98 ppm) or the gold complex 5 (d = 5.94 ppm).
The separation between the resonances for the methyl substituents
at the 3- and 5-position (|Dd3,5| given in Table 1) is very diagnostic
for the bonding mode. While small |Dd3,5| values are observed when
the bridging carbon atom is coordinated (cf. 5: 0.08 ppm; HC(3,5-
Me2pz)3: 0.17 ppm), |Dd3,5| is much larger for the j3-bonding mode
Scheme 1 Syntheses of 2 and 3.
The zwitterionic copper(I) complex 2 can easily be synthesised
by using a classical metathesis approach. Reacting the lithium
organyl compound 1, which is straightforwardly accessible by
deprotonation of HC(3,5-Me2pz)3, with [Ph3PCuCl]4 directly
affords colorless crystalline material of 2 in moderate isolated
yield (64%, Scheme 1). An alternative method involves the use
of [CuOtBu]8 or [Cu{N(SiMe3)2}]4, which already contain the
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Table 1 Selected NMR chemical shifts; see Schemes for numbering12
Compound
Nucleus
1H
Moiety (site)
HC(Me2pz)3
1
2
3
4
5
CH3 (3)
CH3 (5)
2.20
2.03
0.17
5.89
81.2a
203.1
298.6
–
2.16
2.51
0.35
5.55
1.99
2.72
0.73
2.36
2.68
0.32
1.85
2.56
0.71
5.59
2.28
2.20
0.08
5.94
|Dd3,5
|
CHpz (4)
Canionic
5.75
5.77
13C
15N
73.6
73.4 (d)b
232.2
274.0
73.2 (d)c
73.4
111.8 (d)d
220.7
303.5
35.9
Npz (1)
Npz (2)
PR3
233.1
231.4
272.2
130 (br.)
–
232.1
285.9
19.2 (2d)f
945
285.5 (q)e
31P
–
–
7.8 (br.)
109Ag
pz3AgP
–
–
–
a HC(Me2pz)3. b 4J(31P,13C) = 1.7 Hz. c 4J(31P,13C) = 2.3 Hz. d 2J(31P,13C) = 120.2 Hz. e 1J(15N,7Li) = 10 Hz. f 1J(107Ag,31P) = 582 Hz, 1J(109Ag,31P) = 663 Hz.
with values up to 0.73 ppm. It seems likely that the large chemical
shift differences of the methyl resonances of 2 and 4 can be ascribed
to anisotropic shielding effects of the phenyl rings of the Ph3P
ligand in close spatial proximity to the methyl residues in the 3-
position.
The 13C NMR resonances of the “free” anionic carbon atoms are
more or less invariant for all coinage metal complexes containing
the j3-ligand, even compared to the lithium precursor 1.13 In
contrast, the corresponding 13C NMR signal of gold(I) compound
5 is shifted to higher frequency. While only very broad 31P
NMR signals were observed for the copper complexes 2 and 3
at room temperature, the 31P NMR solution spectra of 5 and 4
Fig. 1 109Ag,1H HMQC spectrum of 4 showing the doublet multiplicity
show a singlet (5) and two doublets with coupling constants of
due to the spin of 31P (d(109Ag) = 945 ppm; 1J(109Ag,31P) = 663 Hz). The
1J(107Ag,31P) = 582 Hz, 1J(109Ag,31P) = 663 Hz (4).
small additional 1H NMR resonances are due to decomposition of the
silver complex.
Furthermore, a 109Ag,1H correlation spectrum clearly demon-
strated that the silver cation in 4 is fixed in the N3 pocket of
the tris(3,5-dimethylpyrazolyl)methanide ligand. The spectrum
1
2
3
2
the spin 31P and spin 65Cu and 63Cu nuclei, which cannot be
1
revealed a doublet fine structure due to the spin nucleus of
2
31P (Fig. 1).
removed by magic angle spinning. In the high field approximation,
a first order analysis16,17 can generally be employed yielding a
parameter d, expressing how much the inner and outer line
pairs are shifted to higher and lower frequencies, respectively.
Deviations from this model can be accounted for by introducing
an additional parameter d1.18 The actual separations of the
quartet lines are then D21 = J − 2d − 2d1, D32 = J + 2d1, and
D43 = J + 2d − 2d1, respectively. A comparison of our data on
the tris(pyrazolyl)methanide complexes with the closely related
tris(pyrazolyl)hydroborates shows nosignificantdifferences within
the limits of reasonable experimental errors. Thus, for compound
2 we find J = 1772, d = 27, d1 = 13; whereas for the analogous
tris(pyrazolyl)hydroborates [Cu(L)PPh3] (with L = Tp, pzTp and
Tp*) these parameters vary in the ranges of J = 1750–1831, d =
23–54, and d1 = 5–22 Hz, respectively.24
Solid-state NMR spectroscopy
In order to elucidate the 31P NMR properties in the
solid-state, detailed CP (MAS) NMR experiments on the
tris(pyrozolyl)methanide complexes 2, 3 and 4 were performed
(Fig. 2–4). The relevant numerical data are compiled in Table 2.
Copper complexes. The spectra of the copper(I) complexes
recorded at high magnetic field, B0 = 11.7 T, under magic
angle spinning exhibit the usual pairs of overlapping asymmetric
quartets due to the copper isotopes 65Cu and 63Cu. The unequal
separations of the quartet lines arise from a quadrupolar per-
turbation of the scalar (J) and dipolar (D) interactions between
Table 2 Solid-state 31P NMR dataa
d
Compound
diso
4.3
129.5
20.3
d11
33
210
60
d22
33
210
30
d33
Jiso
DJ
Db
dc
d1
2
3
4
−53
−30
−30
−1772
−2640
629
2450
2400
−1240
−1284
170
27
32
13
22
a Chemical shifts in ppm relative to H3PO4, Coupling constants in Hz, for the copper complexes 2 and 3 the values for the 63Cu isotope are given, for
silver complex 4 the average of the 109Ag and 107Ag isotopes. Signs of coupling constants are according to the convention used in ref. 14. b Calculated from
the M–P bond lengths obtained by X-ray crystallography.15 c Calculated as d = (D43 − D21)/4.24 d Calculated as d1 = (D32 − Jiso)/2.24
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Fig. 4 Experimental 202.5 MHz 31P{ H} CP MAS spectra of compound
4 recorded with a spinning frequency of 2000 Hz and on the static sample
are shown in the bottom left and right traces, respectively. Corresponding
spectral simulations using SIMPSON14 and the NMR parameters given
in Table 2 are reproduced in the top traces. The additional lines present
to low frequency in the experimental spectrum are due to decomposition
products.19
1
1
Fig. 2 Experimental 202.5 MHz 31P{ H} CP MAS spectrum of com-
pound 2 recorded with a spinning frequency of 7692 Hz and an expansion
of its isotropic part shown in the bottom left and right traces, respectively.
Corresponding spectral simulations using SIMPSON14 and the NMR
parameters given in Table 2 are reproduced in the top trace.
the rotating and the static samples, were satisfactorily simulated
using the parameters given in Table 2. However, it should be
mentioned that in this analysis it was assumed that the 31P NMR
chemical shift, the scalar, and the dipolar coupling tensors were
all of axial symmetry and aligned co-axially. This is, of course, not
strictly the case, as there exists no point-group symmetry in the
molecules studied, which would justify this particular choice.
Silver complex. The 31P solid-state NMR spectra for 4 are
much simpler, consisting of two overlapping doublets due to
coupling to the 109Ag and 107Ag isotopes, which are not resolved
1
(Fig. 4). The observed average coupling constant J(109,107Ag,31P)
agrees well with the value obtained in solution for this complex
as well as with those obtained for analogous tris(pyrazolyl)borate
compounds.24 From the expected anisotropic interactions only the
31P NMR chemical shift anisotropy had to be taken into account in
order to accurately simulate the 31P NMR spectrum of the sample
spinning in the magic angle. In contrast to the analogous copper
complex 2, the chemical shift tensor in 4 deviates significantly
from axial symmetry. This difference originates mostly from the
orientation of the phenyl substituents, being closer to C3 symmetry
in 2 (torsion angles M–P–Cipso–Cortho: 26.7(1), 36.9(2), 46.6(2)◦)
than in 4 (3.1(3), 23.3(3), 74.7(3)◦).
X-Ray structure determination
The crystal structure determination of 2 (Fig. 5) and 3 (Fig. 6)
verified the formation of monomeric copper(I) complexes in which
the copper cations are tetrahedrally coordinated by three pyrazole
nitrogen atoms and one phosphine molecule.20 Compounds 2 and
3 can formally be described as zwitterions containing a spatially
separated anion (C1) and cation (Cu1). The N–C1–N angles
(108.2–109.3◦ for 2 and 108.2–108.6◦ for 3) are in agreement
with a (pseudo)tetrahedral environment at the carbanionic center
and compare well with those found for 1. The average bond
lengths within the pyrazole rings, the inner ring angles (C–N–
N at N1, see Schemes for numbering), and the average C1–N
distances of 145.0 pm (2) and 145.3 pm (3) prohibit a delocalisation
1
Fig. 3 Experimental 202.5 MHz 31P{ H} CP spectrum of compound 2
recorded on a static sample and the corresponding spectral simulations
using SIMPSON14 and the NMR parameters given in Table 2 are
reproduced in the bottom and top traces, respectively.
The anisotropy of the phosphorus chemical shift, characterised
by the span X = d11 − d33, manifests itself in the number and
intensity of the spinning side bands; the anisotropy (DJ) of the
scalar coupling constant 1J(65,63Cu,31P) affects the distribution
of the intensities of the individual lines within the asymmetric
quartets. The experimental 31P solid state NMR spectra, both for
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The X-ray structure analysis of the analogous silver(I) complex
4 revealed almost the same geometrical features compared to the
copper systems (Fig. 7).26 Although the N–C1–N angles widenend
by 1–2◦, the carbanionic centre at C1 still adopts a tetrahedral
geometry. The anionic [C(3,5-Me2pz)3]− ligand is coordinated to
the Ag(I) cation in a j3 fashion and the coordination sphere is com-
pleted by the additional phosphine ligand (Ag1–P1: 232.15 pm).
The distortion from the ideal tetrahedral environment around the
transition metal in 4 is slightly more pronounced compared to the
copper compounds (cf. C1 · · · Ag1 of 330.4 pm and the average N–
Ag1–N and P1–Ag1–N angles of 81.5◦ and 131.0◦, respectively).
Fig. 5 Molecular structure and numbering scheme for compound 2,
thermal ellipsoids are drawn at a 30% probability level, selected bond
lengths [pm] and angles [◦]: Cu1–P1 214.69(5), Cu1–N2 205.8(1), Cu1–N4
206.9(1), Cu1–N6 207.4(1), C1–N1 145.3(2), C1–N3 144.7(2), C1–N5
144.9(2), C1 · · · Cu1 304.2; N1–C1–N3 109.3(1), N1–C1–N5 108.2(1),
N3–C1–N5 109.1(1).
Fig. 7 Molecular structure and numbering scheme for compound 4,
thermal ellipsoids are drawn at a 30% probability level, selected bond
lengths [pm] and angles [◦]: Ag1–P1 232.15(8), Ag1–N2 232.1(3), Ag1–N4
228.4(3), Ag1–N6 232.9(3), C1–N1 144.2(4), C1–N3 143.8(4), C1–N5
144.3(4), C1 · · · Ag1 330.4; N1–C1–N3 110.7(3), N1–C1–N5 110.0(3),
N3–C1–N5 110.1(3).
Only recently, Zimmer et al. used CSD database analysis and
molecular mechanics to determine the conformational flexibility
of tridentate scorpionate ligands like I and II.27 They showed that
ligands of this type can accomodate a variety of metal sizes by
opening up the ligand. They undergo deformations similar to
that of a “jellyfish swimming through the water”, opening their
tripodal structure for larger metals and closing around smaller
metal ions. As the M–N distance increases the ligand opens up
and the bite size increases. The same tendency is obeserved for
the complexes reported in this paper, which can be seen from an
analysis of the structural parameters of all literature known metal
complexes containing the anionic, j3 coordinating ligand [C(3,5-
Me2pz)3]−. Although many more data need to be acquired in order
to corroborate reliable predictions, a general trend is anticipated.
The analysis shows that as the metal to nitrogen distance increases
the bite size and the distance between the plane and metal (a)
increases, while the distance between the anionic carbon atom
and the plane (b) shortens (see Chart 1 and Table 3). In response
to changing metal sizes our ligand undergoes structural changes
similar to those for the “classical” scorpionate ligands I (and II),27
although the steric repulsion of the lone pair of electrons at C1 and
the Me substituents in the 5-position may to some extent inhibit
an increase of the bite size. The observation that in contrast to the
Fig. 6 Molecular structure and numbering scheme for compound 3,
thermal ellipsoids are drawn at a 30% probability level, selected bond
lengths [pm] and angles [◦]: Cu1–P1 212.2(1), Cu1–N2 210.2(2), Cu1–N4
204.7(2), Cu1–N6 206.2(2), C1–N1 144.8(3), C1–N3 145.4(3), C1–N5
145.6(4), C1 · · · Cu1 306.6; N1–C1–N3 108.6(2), N1–C1–N5 108.2(2),
N3–C1–N5 108.4(2).
of the negative charge into the adjacent pyrazole rings. As
expected, these geometrical features clearly show an unassociated,
localised carbanionic center at C1.21 However, one would expect
an intramolecular electrostatic interaction between the regions of
negative and positive charge in these copper complexes. The degree
of interaction can be estimated from the C1 · · · Cu1 distances
of 304.2 pm (2) and 306.6 pm (3) (compare C1 · · · Li1 in 1:
289 pm), which are much longer than observed in copper(I) organyl
compounds containing a direct Cu–C bond.22 The geometries at
the copper atoms fit well to stretched tetrahedrons with acute
N–Cu1–N angles (average 89.4◦ for 2 and 88.7◦ for 3) and wide
P1–Cu1–N angles (average 125.6◦ for 2 and 126.1◦ for 3). The
Cu1–P1 distances of 214.69 pm (2) and 212.2 pm (3) fall into a
typical range found for other copper phosphine compounds.23–25
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Table 3 Selected structural parameters [pm] revealing a certain flexibility
compares well with those found for other gold(I)/phosphine
complexes. The same holds for the carbon–gold distance with a
value of 211.1 pm.29 As can be seen from the molecular structure
depicted in Fig. 8, two pyrazole substituents adopt a kind of
propeller arrangement in a way that two nitrogen donor centres
point away from the nobel metal while the N donor atom of
a third pz ligand is directed towards the Au atom (N2 · · · Au1:
286.6 ppm). The plane spanned by the atoms of the latter pz
moiety deviates only slightly from the ideal parallel alignment
with respect to the C1–Au1 vector. This may be attributed on the
one hand to steric interactions between the methyl substituents
attached to the heteroaromatic ring, or on the other hand, to
(weak) stabilising nitrogen gold interactions. Although the true
nature of these interactions remains speculative, the latter seems
to be more reasonable. Therefore, the ligand environment around
the Au atom in complex 5 can be described as that of a [2 + 1]
coordination sphere.
of tris(pyrazolyl)methanide acting as tripodal ligand
Parameter
[TiL4]a
1
2
3
4
a
148.7
184.1
219.2
235.8
216.8
223.9
282.3
292.0
294.6
289.6
108.2
180.9
202.9
203.4
200.6
202.3
298.8
290.4
298.9
296.0b
120.6
183.7
205.8
206.9
207.4
206.7
291.3
291.1
290.1
290.8
122.3
184.3
210.2
204.7
206.2
207.0
292.5
294.5
281.2
289.4
151.9
178.4
232.1
228.4
232.9
231.1
298.7
302.7
303.6
301.7
b
d(M–N)
Average
Bite size
Average
a [TiL4] = [Ti{C(3,5-Me2pz)3}(Nt-Bu)Cl(thf)].5 b The comparably large
bite size of the lithium complex may be attributed to electrostatic C− · · · Li+
interactions, hence relatively short distances a and b and steric repulsion
of the pz-ligands with the additional thf donor ligand at lithium.
Conclusions
The coordination variability of the ambidental C−/N ligand
tris(pyrazolyl)methanide [C(3,5-Me2pz)3]− was elucidated by in-
vestigating its coinage metal complexes. The suitable precursor
[Li{C(3,5-Me2pz)3}(thf)] (1) cleanly reacts with Ph3PAuCl under
salt elimination to yield the backbone functionalised gold(I)
complex 4.30 In contrast, the corresponding Ag(I) and Cu(I)
phosphine complexes adopt zwitterionic structures with a spatially
separated anion (C1) and cation (coinage metal) comprising the
anionic tris(pyrazolyl)methanide as j3 coordinated N3-ligand.
Owing to the outward pointing, unassociated carbanionic center
in the bridging position an accessible reactive site for further
manipulations (e.g., coordination to other transition metal centres,
functionalisation, etc.) is available in the backbone of the ligand.
Chart 1
lighter congeners, the corresponding gold(I) complex does not
consist of a tetrahedrally coordinated central metal atom might
already point in this direction (Fig. 8).28 The Au centre is two
coordinated by one phosphine ligand and the carbanionic moiety
of the tris(pyrazolyl)methanide with an almost linear P1–Au1–
C1 alignment (175.6◦). The Au1–P1 bond length of 227.4 pm
Experimental
Methods and techniques
NMR investigations. Solution NMR spectra were recorded
using Bruker Avance instruments operating at a 1H Larmor
frequency of 500 MHz and are referenced according to IUPAC
recommendation.31 Chemical shifts are given relative to AgNO3,
H3PO4 and TMS for 109Ag, 31P, 13C and 1H, respectively. Coupling
constants J are given in Hertz [Hz] as positive values regardless of
their real individual signs. The multiplicity of the signals is indi-
cated as s, d, or m for singlets, doublets, or multiplets, respectively.
The abbrevation br. is given for broadened signals. Quaternary
carbon atoms are indicated as Cquart, aromatic moieties as CHar and
pyrazole units as CHpz when not noted otherwise. 13C CP-MAS
and 31P CP-MAS solid-state spectra were acquired at room temper-
ature on a Bruker Avance instrument operating at a 1H Larmor fre-
quency of 500 MHz. Conventional cross-polarization and magic-
angle-spinning techniques were implemented using 4 mm rotors
with which frequencies of >11 kHz were achieved. The strength of
the magnetic field was adjusted such that the 13C NMR carboxylate
resonance of a-glycine appeared at 176.0 ppm. In consequence ref-
erencing of all isotopes could be achieved as for the solution NMR
using the unified N scale.31 Chemical shifts are expressed relative
to TMS and H3PO4, for the isotopes 13C and 31P, respectively.
Fig. 8 Molecular structure and numbering scheme for compound 5,
thermal ellipsoids are drawn at a 30% probability level, selected bond
lengths [pm] and angles [◦]: Au1–P1 227.4(1), Au1–C1 211.1(4), C1–N1
145.3(6), C1–N3 146.6(6), C1–N5 149.0(6), N2 · · · Au1 286.6; P1–Au1–C1
175.6(1), N1–C1–N3 107.6(3), N1–C1–N5 107.6(4), N3–C1–N5 107.2(3).
1078 | Dalton Trans., 2006, 1073–1081
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The Royal Society of Chemistry 2006
©

View Online
1
1.1 Hz, Cquart (3)). 31P{ H} NMR (C6D6): d ∼130 (br). 15N NMR
(C6D6): d 231.4 (1), 272.2 (2). IR (solid, ATR, cm−1): 2960w, 2923w
(t(CHpz, CH3)), 1558s (t(pyrazole ring)), 1447w, 1411m, 1319s,
1253s, 1097w, 1022s (d(CH, CH3), t(CC)), 881w, 862s, 826s, 776s,
699s, 625m (t(CC), d(CC), t(CuN)).
General techniques. All manipulations were performed un-
der an argon atmosphere using standard Schlenk techniques.
Chemicals were purchased from Aldrich and used without fur-
ther purification. [CuOtBu]8,32 [CuN(SiMe3)2]4,33 [AgNO3PPh3],34
[CuClPPh3]4,35 and [Li{C(3,5-Me2pz)3}(thf)] (1)6 were prepared
according to literature methods. All solvents were freshly distilled
under argon from sodium/benzophenone (thf, toluene), or from
sodium/diglyme/benzophenone (n-hexane) prior to use. Air sen-
sitive compounds were stored and weighed in a glove box (Braun
MB 150 B–G–II system). IR-spectra were measured with the ATR-
technique (attenuated total reflection) on a Perkin-Elmer 2000 FT-
IR spectrometer in the range from 4000 cm−1 to 550 cm−1 using a
KBr beamsplitter. The intensity of the absorption band is indicated
as w (weak), m (medium) and s (strong). Elemental analyses were
carried out at the Microanalytical Laboratory Pascher (Remagen,
Germany).
Synthesis of [Ag{C(3,5-Me2pz)3}(PPh3)] (4). A solution of
[Li{C(3,5-Me2pz)3}(thf)] (0.600 g, 1.57 mmol) in toluene (20 cm3)
was slowly added to a suspension of [AgNO3PPh3] (0.680 g,
1.57 mmol) in toluene (15 cm3) at ambient temperature. The
yellowish mixture was stirred for 20 min at this temperature.
After filtration over Celite the clear slightly yellow filtrate was
concentrated in vacuo to ca. 10 cm3 and n-hexane (30 cm3) was
added. Cooling to −18 ◦C afforded4 as colourless crystals (0.780 g,
74%). Found: C, 61.71; H, 5.87; N, 12.60. C34H36PAgN6 requires C,
61.20; H, 5.45; N, 12.59%; mp (decomposes upon light exposure).
1H NMR (d8-thf): d 1.85 (s, 9 H, CH3 (3)), 2.56 (s, 9 H, CH3 (5)),
5.59 (s, 3 H, CHpz (4)), 7.48–7.51 (m, 9 H, CHar), 7.71–7.75 (m,
6 H, CHar). 13C NMR (d8-thf): d 12.5 (CH3 (5)), 14.2 (CH3 (3)),
Syntheses
73.4 (Canionic), 101.5 (d, 4JPC = 1.3 Hz, CHpz (4)), 129.2 (d, 3JPC
=
=
=
=
=
The numbering in brackets of the assigned NMR resonances is in
accord with the Schemes.
4
1
10 Hz, CHar), 130.6 (d, JPC = 1.6 Hz, CHar), 134.1 (dd, JPC
31.3 Hz, 2JCAg = 3.7 Hz, Cipso), 134.5 (dd, 2JPC = 18.1 Hz, 3JCAg
2.3 Hz, CHar), 144.8 (Cquart (5)), 145.1 (dd, 2JCAg = 2.4 Hz, 3JPC
Synthesis of [Cu{C(3,5-Me2pz)3}(PPh3)] (2). A solution of
[Li{C(3,5-Me2pz)3}(thf)] (0.400 g, 1.05 mmol) in toluene (20 cm3)
was added to a suspension of [CuClPPh3]4 (0.380 g, 1.05 mmol) in
toluene (15 cm3) at ambient temperature. The mixture was stirred
for 1 h at this temperature. After careful filtration over Celite
the solvent was removed in vacuo. The obtained white solid was
recrystallised from toluene–n-hexane to afford 3 (0.420 g, 64%)
as large colourless blocks. Found: C 65.74; H 6.55; N 12.50%.
C34H36PCuN6·0.3 n-hexane requires C 66.23; H 6.25; N 12.90%;
mp 147 ◦C (decomp.). 1H NMR (C6D6): d 1.99 (s, 9 H, CH3 (3)),
2.72 (s, 9 H, CH3 (5)), 5.75 (s, 3 H, CHpz (4)), 7.09–7.17 (m, 9 H,
CHar), 7.91–7.95 (m, 6 H, CHar). 13C NMR (C6D6): d 12.9 (CH3
1
0.7 Hz, Cquart (3)). 31P{ H} NMR (d8-thf): d 19.2 (dd, 1J107Ag, 31P
582 Hz, 1J109Ag, 31P = 663 Hz, PPh3). 15N NMR (d8-thf): d 232.1 (1),
285.9 (2). 109Ag NMR (d8-thf): d 945 (d, 1J109Ag, 31P = 663 Hz). IR
(solid, ATR, cm−1): = 3072w, 2954w, 2920w (t(CHpz, CHar, CH3)),
1549m (t(pyrazole ring)), 1478w, 1434m, 1415m, 1396m, 1095s,
1034m (d(CH, CH3), t(CC)), 869m, 743s, 691s (t(CC), d(CC),
d(CHar), t(AgN)).
Synthesis of [Au(PPh3){C(3,5-Me2pz)3}] (5). The synthesis
was performed on a larger scale because we are interested in
exploring the coordination chemistry of 5. A solution of [Li{C(3,5-
Me2pz)3}(thf)] (0.900 g, 2.39 mmol) in toluene (15 cm3) was added
dropwise to a suspension of Ph3PAuCl (1.180 g, 2.39 mmol)
in toluene (15 cm3) at room temperature. In the course of
the addition the colorless Ph3PAuCl dissolved and the reaction
mixture turned orange. After stirring 1.5 h at this temperature
10 cm3 n-hexane was added. After filtration all volatile components
were removed in vacuo. The pale yellow residue was dissolved in
warm toluene and layered with n-hexane to precipitate 5 (1.370 g,
76%) overnight as yellowish crystals. Found: C, 53.36; H, 4.94;
N, 11.00. C34H36PAuN6 requires C, 53.97; H, 4.81; N, 11.11%; mp
179 ◦C. 1H NMR (CD2Cl2): d 2.20 (s, 9 H, CH3 (5)), 2.28 (s, 9 H,
CH3 (3)), 5.94 (s, 3 H, CH (4)), 7.51–7.61 (m, 9 H, CHar), 7.70–7.75
(m, 6 H, CHar). 13C NMR (CD2Cl2): d 12.7 (CH3 (3)), 14.0 (CH3
4
(5)), 14.7 (CH3 (3)), 73.4 (d, JPC = 1.7 Hz, Canionic), 102.8 (CHpz
(4)), 129.0 (d, 3JPC = 9.6 Hz, CHar), 130.0 (d, 4JPC = 1.6 Hz, CHar),
2
1
134.8 (d, JPC = 16.3 Hz, CHar), 135.9 (d, JPC = 32.6 Hz, Cipso),
144.8 (d, 4JPC = 0.6 Hz, Cquart (5)), 145.8 (d, 3JPC = 0.8 Hz, Cquart
1
(3)). 31P{ H} NMR (C6D6): d 7.8 (br). 15N NMR (C6D6): d 232.2
(1), 274.0 (2). IR (solid, ATR, cm−1): 3072w, 3054w, 2954w, 2922w
(t(CHpz, CHar, CH3)), 1553m (t(pyrazole ring)), 1478m, 1435m,
1401m, 1260w, 1204w, 1095s, 1037m (d(CH, CH3), t(CC)), 865m,
792m, 767m, 747m, 743m, 702w, 691s (t(CC), d(CC), t(CuN),
d(CHar)).
Synthesis of [Cu{C(3,5-Me2pz)3}{P(OMe)3}] (3). A solution
of HC(3,5-Me2pz)3 (0.133 g, 0.45 mmol) in toluene (10 cm3)
was added slowly to a suspension of [CuN(SiMe3)2]4 (0.100 g,
0.45 mmol) in toluene (10 cm3). The slightly yellow solution was
stirred for 30 min at room temperature. After addition of P(OMe)3
(0.055 mL, 0.45 mmol) the mixture was stirred for 4 h. Volatile
materials were removed in vacuo and the residue was extracted
into hot n-hexane. Filtration followed by cooling to 0 ◦C afforded
colourless needles of 2 (0.062 g, 29%). Found: C, 47.17; H, 6.45;
N, 17.30. C19H30PCuO3N6 requires C, 47.05; H, 6.25; N, 17.33%;
mp 131 ◦C (decomp.). 1H NMR (C6D6): d 2.36 (s, 9 H, CH3 (3)),
2.68 (s, 9 H, CH3 (5)), 3.61 (d, 3JPC = 12.5 Hz, OCH3), 5.77 (s, 3 H,
CHpz (4)). 13C NMR (C6D6): d 12.7 (CH3 (5)), 14.4 (CH3 (3)), 50.6
1
(5)), 106.8 (CHpz (4)), 111.8 (d, JPC = 120.2 Hz, Canionic), 129.5
3
1
(d, JPC = 11.2 Hz, CHar), 130.8 (d, JPC = 53.4 Hz, Cipso), 131.8
(d, JPC = 2.3 Hz, CHar), 134.6 (d, JPC = 13.7 Hz, CHar). 15N
4
2
NMR (CD2Cl2): d 220.7 (2), 303.5 (1). 31P{ H} NMR (CD2Cl2): d
1
35.9. IR (solid, ATR, cm−1): 3048w, 2916w (t(CHpz, CHar, CH3)),
1551m (t(pyrazole ring)), 1481w, 1435m, 1412m, 1341m, 1221w,
1215w, 1100s, 1026w (d(CH, CH3), t(CC)), 871m, 843m, 746m,
710w, 691s (t(CC), d(CC), d(CHar)).
X-Ray crystallographic investigations and crystal data
2
4
(d, JPC = 5.2 Hz, OCH3), 73.2 (d, JPC = 2.3 Hz, Canionic), 102.6
(CHpz (4)), 144.7 (d, JPC = 1.1 Hz, Cquart (5)), 145.6 (d, JPC
Crystals suitable for X-ray diffraction of 2, 3 and 5 were obtained
by crystallisation of a concentrated n-hexane solution at room
4
3
=
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Dalton Trans., 2006, 1073–1081 | 1079
©

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Table 4 Crystal data, data collection, and structure refinement for compounds 2, 3, 4 and 5
Compound
2
3
4
5
Empirical formula
M
C34H36N6PCu·0.5n-hexane
666.28
Monoclinic
C2/c (no. 15)
2660.3(2)
C19H30N6O3PCu
485.00
C34H36N6PAg·1.5C6H6
784.69
Monoclinic
P21/n (no. 14)
1353.9(1)
C34H36N6PAu
756.62
Crystal system
Space group36
a/pm
Triclinic
Triclinic
¯
¯
P1 (no. 2)
P1 (no. 2)
1039.2(2)
1106.9(3)
1170.5(3)
96.346(5)
104.986(5)
112.169(5)
1171.4(4)
1.032
909.6(1)
1181.0(1)
1644.1(1)
74.039(1)
80.507(1)
69.707(1)
1588.0(2)
4.716
b/pm
1775.5(1)
1848.9(1)
1433.5(1)
2045.5(1)
c/pm
a/◦
b/◦
125.483(1)
94.590(2)
c /◦
V/× 106 pm3
7111.1(8)
0.693
1.245
3957.3(4)
0.578
1.317
l/mm−1
D
calcd/g cm−3
1.375
1.582
Crystal dimensions/mm
Z
0.39 × 0.35 × 0.25
0.72 × 0.47 × 0.19 0.36 × 0.27 × 0.23
0.21 × 0.16 × 0.14
8
2
250
61.82
4
200
49.42
2
T/K
2h max
200
52.74
200
56.56
◦
/
Refls. measured
Refls. unique
31717
9733
6546
280/0
0.0593
0.1694
0.805/, −0.465
20175
16147
7263 (Rint = 0.0216)
6730 (Rint = 0.0540)
7717 (Rint = 0.0341)
Parameters/restraints
R1 [I ≥ 2r(I)]
407/1
465/0
385/0
0.0349
0.1016
0.379, −0.266
0.0398
0.0900
0.873, −0.242
0.0424
0.0951
2.555, −0.824
wR2 (all data)
Max., min. residual electron density/e ×10−6 pm−3
temperature. Those of 4 were grown from a benzene solution.
In order to avoid quality degradation the single crystals were
mounted in perfluoropolyalkylether oil on top of a glass fiber and
then brought into the cold nitrogen stream of a low-temperature
device so that the oil solidified. Data collection for the X-ray
structure determinations were performed on a Bruker SMART
Apex diffractometer system with CCD area detector by using
Liebig scholarship provided by the Fonds der Chemischen Indus-
trie and thanks Prof. H. Gru¨tzmacher for valuable discussions and
generous support.
References and notes
1 S. Trofimenko, Chem. Rev., 1993, 93, 943; S. Trofimenko, Scorpionates:
The Coordination Chemistry of Polypyrazolylborate Ligands, Imperial
College Press, London, 1999.
2 D. L. Reger, T. C. Grattan, K. J. Brown, C. A. Little, J. J. S. Lamba,
A. L. Rheingold and R. D. Sommer, J. Organomet. Chem., 2000, 607,
120. Concerning some recent results see:; C. Pettinari and R. Pettinari,
Coord. Chem. Rev., 2005, 249, 525.
˚
graphite-monochromated MoKa (0.71073 A) radiation and a low
temperature device. An empirical absorption correction using
SADABS (ver. 2.03) was applied to all structures except 4. All
calculations were performed by using SHELXTL (ver. 6.12) and
SHELXL-97. The structures were solved by direct methods and
successive interpretation of the difference Fourier maps, followed
by full matrix least-squares refinement (against F2). All atoms were
refined anisotropically, excluding the n-hexane solvent molecule
of 2. The contribution of the hydrogen atoms, in their calculated
positions, was included in the refinement using a riding model.
Upon convergence, the final Fourier difference map of the X-ray
structures of 2, 3 and 4 showed no significant peaks. For 5, some
residual electron density was located close to the heavy atom gold
3 H. R. Bigmore, S. C. Lawrence, P. Mountford and C. S. Tredget, Dalton
Trans., 2005, 635.
4 Although ligands like I or II are often compared with Cp (e.g., the same
number of electrons is donated upon facial coordination) the different
geometries of the orbitals may not be neglected. For a comparison of
isoelectronic Tp and Cp Ru complexes see: E. Ru¨ba, W. Simanko, K.
Mereiter, R. Schmid and K. Kirchner, Inorg. Chem., 2000, 39, 382.
5 S. C. Lawrence, M. E. G. Skinner, J. C. Green and P. Mountford, Chem.
Commun., 2001, 705. One closely related scandium complex is described
in ref. 3.
6 F. Breher, J. Grunenberg, S. C. Lawrence, P. Mountford and H. Ru¨egger,
Angew. Chem., Int. Ed., 2004, 43, 2521.
˚
(∼0.85 A) even when an absorption correction was applied. The
asymmetric unit of 2 contains one half of an n-hexane solvent
molecule which is disordered over two sites. The two positions
were refined against each other using one free variable (FVAR)
with an occupation factor of 46% for the disordered position.
Relevant data concerning crystallographic data, data collection,
and refinement details are summarized in Table 4.
7 H. Vahrenkamp, Acc. Chem. Res., 1999, 32, 589; J. Seebacher, M. H.
Shu and H. Vahrenkamp, Chem. Commun., 2001, 1026; D. Badura and
H. Vahrenkamp, Eur. J. Inorg. Chem., 2003, 3723; R. Walz, M. Ruf and
H. Vahrenkamp, Eur. J. Inorg. Chem., 2001, 139; see also; H. Boerzel,
M. Koeckert, W. Bu, B. Spingler and S. J. Lippard, Inorg. Chem., 2003,
42, 1604.
8 C. Mealli, C. S. Arcus, J. L. Wilkinson, T. J. Marks and J. A. Ibers, J. Am.
Chem. Soc., 1976, 98, 711; N. Kitajima, K. Fujisawa, C. Fujimoto, Y.
Moro-oka, S. Hashimoto, T. Kitagawa, K. Toriumi, K. Tatsumi and A.
Nakamural, J. Am. Chem. Soc., 1992, 114, 1277; Z. Hu, R. D. Williams,
D. Tran, T. G. Spiro and S. M. Gorun, J. Am. Chem. Soc., 2000, 122,
3556; B. S. Hammes, X. Luo, B. S. Chohan, M. W. Carrano and C. J.
Carrano, J. Chem. Soc., Dalton Trans., 2002, 3374.
CCDC reference numbers 282767–282770.
For crystallographic data in CIF or other electronic format see
DOI: 10.1039/b512309g
9 T. D. P. Stack, Dalton Trans., 2003, 1881; E. I. Solomon, P. Chen,
M. Metz, S.-K. Lee and A. E. Palmer, Angew. Chem., Int. Ed., 2001,
40, 4570; E. I. Solomon, U. M. Sundaram and T. E. Machonkin,
Chem. Rev., 1996, 96, 2563; A. G. Blackman and W. B. Tolman, Struct.
Bonding, 2000, 97, 179; E. A. Lewis and W. B. Tolman, Chem. Rev.,
Acknowledgements
This work is supported by the Swiss National Science Foundation
(SNF) and the ETH Zu¨rich. F. Breher gratefully acknowledges a
1080 | Dalton Trans., 2006, 1073–1081
This journal is
The Royal Society of Chemistry 2006
©

View Online
2004, 104, 1047; L. M. Mirica, X. Ottenwaelder and T. D. B. Stack,
Chem. Rev., 2004, 104, 1013; N. Kitajima and Y. Moro-oka, Chem.
Rev., 1994, 94, 737.
22 X. He, K. Ruhland-Senge and P. P. Power, J. Am. Chem. Soc., 1994,
116, 6963; J. Diez, M. P. Gasama, J. Gimeno, E. Lastra, A. Aguirre
and S. Garc´ıa-Granda, Organometallics, 1993, 12, 2213; V. W.-W. Yam,
W.-K. Lee and T.-F. Lai, Organometallics, 1993, 12, 2383; V. W.-W.
Yam, W. K.-M. Fung and K.-K. Cheung, Angew. Chem., Int. Ed. Engl.,
1996, 35, 1100.
23 C. Pettinari, A. Cingolani, G. G. Lobbia, F. Marchetti, D. Martini, M.
Pellei, R. Pettinari and C. Santini, Polyhedron, 2004, 23, 451.
24 G. G. Lobbia, J. V. Hanna, M. Pellei, C. Pettinari, C. Santini, B. W.
Skelton and A. H. White, Dalton Trans., 2004, 951.
25 N. Kitajima, T. Koda, S. Hashimoto, T. Kitagawa and Y. Moro-oka,
J. Am. Chem. Soc., 1991, 113, 5664; G. G. Lobbia, C. Pattinari, F.
Marchetti, B. Bovio and P. Cecchi, Polyhedron, 1996, 15, 881.
26 For silver/tris(pyrazolyl)methane complexes see: D. L. Reger, J. E.
Collins, A. L. Rheingold, L. M. Liable-Sands and G. P. A. Yap,
Organometallics, 1997, 16, 349; C. Santini, G. G. Lobbia, C.
Pettinari, M. Pellei, G. Valle and S. Calogero, Inorg. Chem., 1998,
37, 890, see also ref. 10 and cited literature. For structurally related
tris(pyrazolyl)hydroborate phosphine complexes of Ag(I) see for in-
stance:; C. Santini, C. Pettinari, G. G. Lobbia, D. Leonesi, G. Valle and
S. Calogero, Polyhedron, 1998, 17, 3201.
27 H. De Bari and M. Zimmer, Inorg. Chem., 2004, 43, 3344.
28 To the best of our knowledge, only one tris(pyrazolyl)methane
gold complex is known: A. J. Canty, N. J. Minchin, P. C. Healey
and A. H. White, J. Chem. Soc., Dalton Trans., 1982, 1795. For
tris(pyrazolyl)hydroborate complexes see ref. 24, 25 and references
therein.
29 H. Schmidbaur, F. P. Gabba¨ı, A. Schier and J. Riede, Organometallics,
1995, 14, 4969; M. C. Gimeno, P. G. Jones, A. Laguna and M. D.
Villacampa, Chem. Ber., 1996, 129, 585; E. J. Ferna´ndez, M. C. Gimeno,
P. G. Jones, A. Laguna, M. Laguna, J. M. Lo´pez-de-Luzuriaga and
M. A. Rodriguez, Chem. Ber., 1995, 128, 121; E. J. Ferna´ndez, M. C.
Gimeno, P. G. Jones, A. Laguna, M. Laguna and J. M. Lo´pez-de-
Luzuriaga, Angew. Chem., Int. Ed. Engl., 1994, 33, 87; F. Scherbaum,
A. Grohmann, B. Huber, C. Kru¨ger and H. Schmidbaur, Angew. Chem.,
Int. Ed. Engl., 1988, 27, 1544; M. Contel, J. Garrido, J. Jime´nez, P. G.
Jones, A. Laguna and M. Laguna, J. Organomet. Chem., 1997, 543, 71;
H. Schmidbaur, F. Scherbaum, B. Huber and G. Mu¨ller, Angew. Chem.,
Int. Ed. Engl., 1988, 27, 419; J. Vicente, M. T. Chicote, R. Guerrero and
P. G. Jones, J. Am. Chem. Soc., 1996, 118, 699.
30 The much desired functionalisation of tris(3,5-dimethyl-
pyrazolyl)methane at the central methine carbon atom under
any conditions with electrophilic reagents other than H2O, D2O, or
DCl has not been accomplished. It was surmised that the substituents
in the 5-position of the pyrazole rings block the methine carbon atom
from reaction with any electrophiles other than protic.
10 D. L. Reger, R. F. Semeniuc and M. D. Smith, Dalton Trans., 2003,
285; D. L. Reger, R. F. Semeniuc and M. D. Smith, Eur. J. Inorg.
Chem., 2002, 543; D. L. Reger, R. F. Semeniuc and M. D. Smith, Inorg.
Chem., 2003, 42, 8137; D. L. Reger, R. F. Semeniuc and M. D. Smith,
Eur. J. Inorg. Chem., 2003, 3480; D. L. Reger, R. F. Semeniuc and
M. D. Smith, Inorg. Chem. Commun., 2002, 5, 278; D. L. Reger, R. F.
Semeniuc, I. Silaghi-Dumitrescu and M. D. Smith, Inorg. Chem., 2003,
42, 3751; D. L. Reger, R. F. Semeniuc, V. Rassolov and M. D. Smith,
Inorg. Chem., 2004, 43, 537.
11 For closely related tris(pyrazolyl)phosphine ligands see: R. E.
Cobbledick and F. W. B. Einstein, Acta Crystallogr., Sect. B, 1975, 31,
2731; S. Fischer, J. Hoyano and L. K. Peterson, Can. J. Chem., 1976,
54, 2710; S. Fischer, L. K. Peterson and J. F. Nixon, Can. J. Chem.,
1974, 52, 3981.
12 Due to folding effects in the two-dimensional 15N1H correlation
spectrum one 15N resonance of 1 was mistakenly reported in ref. 6. The
current value of d = 233.1 ppm reported here is correct. We apologize
for this mistake.
13 For the copper systems 2 and 3 small 4J(31P,13C) coupling constants
around 2 Hz could be detected.
14 M. Bak, J. T. Rasmussen and N. C. Nielsen, J. Magn. Reson., 2000, 147,
296.
ꢀ
ꢁ ꢀ
ꢁ
ꢂ
ꢃ
l0
h
2p
−3
15 D =
c (31P)c (M) r
.
P,M
16 R. K. 4Hp arris and A. C. Olivieri, Prog. Nucl. Magn. Reson. Spectrosc.,
1992, 24, 435.
17 A. C. Olivieri, J. Magn. Reson., 1989, 81, 201.
18 A. C. Olivieri, J. Am. Chem. Soc., 1992, 114, 5758.
19 Immediately after refilling the MAS rotor no decomposition of the
product at this stage of the experiment could be detected.
20 Selected copper/tris(pyrazolyl)methane complexes: D. L. Reger, J. E.
Collins, A. L. Rheingold and L. M. Liable-Sands, Organometallics,
1996, 15, 2029; M. Cvetkovic, S. R. Batten, B. Moubaraki, K. S. Murray
and L. Spiccia, Inorg. Chim. Acta, 2001, 324, 131; E. R. Humphrey,
K. L. V. Mann, Z. R. Reeves, A. Behrendt, J. C. Jeffery, J. P. Maher,
J. A. McCleverty and M. D. Ward, New J. Chem., 1999, 23, 417; K. A.
van Langenberg, B. Moubaraki, K. S. Murray and E. R. T. Tiekink,
Z. Kristallogr.–New Cryst. Struct., 2002, 217, 223; B. Moubaraki, K. S.
Murray and E. R. T. Tiekink, Z. Kristallogr.–New Cryst. Struct., 2002,
217, 219; K. Fujisawa, T. Ono, H. Aoki, Y. Ishikawa, Y. Miyashita, K.
Okamoto, H. Nakazawa and H. Higashimura, Inorg. Chem. Commun.,
2004, 7, 330.
21 The main geometric feature of unassociated carbanions is the trigonal
planar coordinated central carbon atom. This is due to delocalisation
of the negative charge in the adjacent rings. See: U. Pieper and
D. Stalke, Organometallics, 1993, 12, 1201; H. Gornitzka and D.
Stalke, Angew. Chem., Int. Ed. Engl., 1994, 33, 636; H. Gornitzka
and D. Stalke, Organometallics, 1994, 13, 4398; I. Ferna´ndez, E.
Mart´ınez-Viviente, F. Breher and P. S. Pregosin, Chem. Eur. J., 2005,
11, 1495; M. M. Olmstead and P. P. Power, J. Am. Chem. Soc.,
1985, 107, 2174; P. P. Power, Acc. Chem. Res., 1988, 21, 147; J. S.
Alexander and K. Ruhland-Senge, Angew. Chem., Int. Ed., 2001,
40, 2658; S. Harder, Chem. Eur. J., 2002, 8, 3229 and references
therein.
31 R. K. Harris, E. D. Becker, S. M. Cabral, de Menezes, R. Goodfellow
and P. Granger, Pure Appl. Chem., 2001, 73, 1795.
32 M. Ha˚kansson, C. Lopes and S. Jagner, Inorg. Chim. Acta, 2000, 304,
178.
33 A. M. James, R. K. Laxman, F. R. Fronczek and A. W. Maverick, Inorg.
Chem., 1998, 37, 3785.
34 R. A. Stein and C. Knobler, Inorg. Chem., 1977, 16, 242.
35 D. J. Fife, W. M. Moore and K. W. Morse, Inorg. Chem., 1984, 23, 1684.
36 T. Hahn, International Tables for Crystallography – Volume A, Kluwer
Academic Publishers, Dordrecht, 5th edn, 2002.
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