1′-(diphenylphosphino)-1-cyanoferrocene: A simple ligand with complicated coordination behavior toward copper(I)

Article abstract of DOI:10.1021/ic4026848

1′-(Diphenylphosphino)-1-cyanoferrocene (3), a new donor-asymmetric ferrocene ligand obtained in two steps from 1′-(diphenylphosphino) ferrocene-1-carboxaldehyde, reacts with CuCl at a Cu/3 molar ratio of 1:1 to give the heterocubane complex [Cu(μ₃-Cl)(3-κP)]₄ (4). When the Cu/3 ratio is changed to 1:2 or 1:3, the reaction takes a different course, producing the P,N-bridged dimer [CuCl(3-κP)(μ(P,N)-3) ]₂ (5) after crystallization. Notably, CuBr and CuI behave differently, affording the corresponding 2D coordination polymers [CuX(μ(P,N)-3)]_n [X = I (7), and Br (8)], regardless of the Cu/3 ratio. Reaction of 3 with sources of naked Cu⁺, such as [Cu(MeCN)₄]⁺ salts or their synthetic equivalents, provides the 1D coordination polymer [Cu(MeCN-κN)(μ(P,N)-3)][BF ₄] (9) or salts of a quadruply bridged dicopper(I) cation, [Cu ₂(μ(P,N)-3)₄]X₂ ([10]X₂), depending on the Cu/3 molar ratio (1:1 vs 1:2 and 1:3). Except for 4, in which 3 binds as a simple P-monodentate ligand, the complexes reported here represent the first structurally characterized compounds in which a phosphinonitrile ligand coordinates through both of its soft donor moieties, thereby extending the coordination chemistry of these ligands.

Full text of DOI:10.1021/ic4026848

Article
pubs.acs.org/IC
1′-(Diphenylphosphino)-1-cyanoferrocene: A Simple Ligand with
Complicated Coordination Behavior toward Copper(I)
̌
̌
Karel Skoch, Ivana Císarova, and Petr Stepnicka*
̌
́
̌
̌
Department of Inorganic Chemistry, Faculty of Science, Charles University in Prague, Hlavova 2030, 12840 Prague 2, Czech Republic
S
* Supporting Information
ABSTRACT: 1′-(Diphenylphosphino)-1-cyanoferrocene (3),
a new donor-asymmetric ferrocene ligand obtained in two
steps from 1′-(diphenylphosphino)ferrocene-1-carboxalde-
hyde, reacts with CuCl at a Cu/3 molar ratio of 1:1 to give
the heterocubane complex [Cu(μ3-Cl)(3-κP)]4 (4). When the
Cu/3 ratio is changed to 1:2 or 1:3, the reaction takes a
different course, producing the P,N-bridged dimer [CuCl(3-
κP)(μ(P,N)-3)]2 (5) after crystallization. Notably, CuBr and
CuI behave differently, affording the corresponding 2D
coordination polymers [CuX(μ(P,N)-3)]n [X = I (7), and
Br (8)], regardless of the Cu/3 ratio. Reaction of 3 with
sources of naked Cu+, such as [Cu(MeCN)4]+ salts or their
synthetic equivalents, provides the 1D coordination polymer [Cu(MeCN-κN)(μ(P,N)-3)][BF4] (9) or salts of a quadruply
bridged dicopper(I) cation, [Cu2(μ(P,N)-3)4]X2 ([10]X2), depending on the Cu/3 molar ratio (1:1 vs 1:2 and 1:3). Except for
4, in which 3 binds as a simple P-monodentate ligand, the complexes reported here represent the first structurally characterized
compounds in which a phosphinonitrile ligand coordinates through both of its soft donor moieties, thereby extending the
coordination chemistry of these ligands.
the copper(I) complexes resulting from its reactions with Cu(I)
halides and [Cu(MeCN)4]+ salts or their synthetic equivalents.
Because the stoichiometries of copper(I) complexes usually
“give little clue to their structures, which can be very
complicated”,19 we have focused mainly on the structural
characterization of the prepared complexes and have thus
identified both conventional and novel compound types.
INTRODUCTION
■
In the vast majority of coordination compounds containing
simple (organic) phosphinonitrile donors, such as
Ph2PCH2CN,1 (Ph2P)2CHCN,2 Ph2PCH(CN)2,3 Ph3−nP-
(CH2CH2CN)n (n = 1−3),4,5 2- and 4-Ph2PC6H4CN,6−8 and
similar compounds,9 in their native (neutral) form,10 these
compounds coordinate as simple P-donors, with their cyano
groups acting as auxiliary substituents. Compounds in which
both functional groups are coordinated to a metal center remain
extremely rare and have not been definitively confirmed using
methods of direct structural analysis.1b,11
Given the numerous reports dealing with the multifaceted
coordination chemistry of 1′-functionalized ferrocene phos-
phines,12,13 we decided to prepare and study the new ferrocene-
based mixed-donor ligand 3, which combines the soft cyano
and phosphine donor groups and formally represents a
congener of the ubiquitous 1,1′-bis(diphenylphosphino)-
ferrocene (dppf).14 Compounds of this type are not entirely
unprecedented, even among ferrocene derivatives, being
represented by 1-(diphenylphosphino)-2-(cyanomethyl)-
ferrocene15 and its Cα-substituted derivatives,16 1-(diphenyl-
phosphino)-2-cyano-3-ethylferrocene,17 and 2-cyano-1-phos-
phaferrocene.18 However, only the last of these compounds
has been studied as a ligand in transition-metal complexes,
coordinating as a P-monodentate donor.18
RESULTS AND DISCUSSION
■
Synthesis of the Phosphinonitrile Ligand. 1′-(Diphe-
nylphosphino)-1-cyanoferrocene (3) was prepared in a stand-
ard manner starting from phosphinoaldehyde 120 (Scheme 1).
In the first step, the aldehyde was converted into the
corresponding oxime 2 by reaction with hydroxylamine in
methanol.21 The oxime was subsequently dehydrated with
a
Scheme 1. Preparation of Phosphinonitrile 3
a
BOP = (benzotriazol-1-yloxy)tris(dimethylamino)phosphonium hex-
afluorophosphate, DBU = 1,8-diazabicyclo[5.4.0]undec-7-ene.
In this contribution, we report the synthesis and structural
characterization of 1′-(diphenylphosphino)-1-cyanoferrocene
(3) as a new ferrocene-based donor-asymmetric ligand and
Received: October 25, 2013
Published: December 17, 2013
© 2013 American Chemical Society
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BOP/DBU22 to afford nitrile 3 as an orange, air-stable solid in a
good overall yield (73% from 1).23
potentials, which was tentatively attributed to a redox response
of a decomposition product (EC mechanism, Figure 1).26
The solid-state structures of compounds 2 and 3 and the
corresponding phosphine oxide 3O27 were determined by X-
ray diffraction analysis (Figure 2). The CHNOH moiety in
the structure of 2 was found to be disordered over the two
positions corresponding to the (E) and (Z) isomers [the
refined (E)/(Z) ratio was ca. 34:66], which corresponds with
the solution observations. The individual conformers assemble
through O−H···N hydrogen bonds, forming dimers around the
crystallographic inversion centers (see the Supporting In-
formation, Figure S1). A similar mode of assembly was
observed with FcCHNOH28 (Fc = ferrocenyl). Notably,
compounds 3 and 3O are practically isostructural. From a
formal viewpoint, they differ only in the occupancy of one of
the four compartments within the tetrahedron around the
phosphorus atom (oxygen vs lone electron pair29), which has a
rather minor impact on the overall molecular structure.
Oxidation of the phosphorus atom results in shortening of
the P−C bonds by ca. 0.03 Å, presumably due to an electron
density transfer from the aromatic rings toward the electron-
withdrawing phosphoryl moiety.30 The C−P−C angles in 3O
are increased (by ca. 4°) by the higher steric demands of the
fourth substituent (oxygen) at the phosphorus atom.
1
The H and 13C NMR spectra of 2 and 3 show four signals
typical for asymmetrically 1,1′-disubstituted ferrocene units and
a characteristic multiplet of the PPh2 substituents. The spectra
of 2 also display additional signals of two nonequivalent CH
NOH moieties attributable to the (E) and (Z) double-bond
isomers in a ca. 1:2 ratio. The 31P NMR resonances of 2 and 3
are observed at approximately δP −17, close to that of the
starting aldehyde.20 In addition, compound 3 shows a
characteristic CN stretching band at 2225 cm−1 in its IR
spectrum, well within the range typical for conjugated nitriles.24
A cyclic voltammetry study (Figure 1) showed that nitrile 3
The molecular parameters of 2, 3, and 3O presented in Table
1 are generally comparable with the corresponding data
reported for simple ferrocene derivatives such as fc(CH
31
NOH)2 (fc = ferrocene-1,1′-diyl; note that oxime FcCH
NOH is heavily disordered28), FcCN,32 and FcPPh2.33 The
ferrocene moieties exhibit balanced Fe−C distances and,
consequently, practically negligible tilting. The cyclopentadien-
yl rings in 3 and 3O are eclipsed, and their substituents assume
a synclinal orientation (see τ angle in Table 1). In contrast, the
substituents in 2 adopt an anti configuration, halfway between
the eclipsed anticlinal (τ = 144°) and the staggered
antiperiplanar (τ = 180°) conformations.
Figure 1. Cyclic voltammograms of 3, as recorded on a Pt disk
electrode in 1,2-dichloroethane (c = 0.5 mM). The scan direction
(arrow) and scan rates (in V s−1) are indicated in the figure.
Preparation of Complexes from Copper(I) Halides.
The copper(I) ion is a typical soft acid according to Pearson’s
hard and soft acids and bases concept.34 Nevertheless, its
character can be partly influenced by the attached donors (e.g.,
halides),35 and a previous study on Cu(I)/dppf/dppfO2
complexes (dppfO2 = 1,1′-bis(diphenylphosphinoyl)ferrocene)
becomes oxidized in a single irreversible step at Epa ≈ 0.48 V25
versus the ferrocene/ferrocenium reference. This primary,
presumably iron-centered (FeII/FeIII) oxidation shows signs
of electrochemical reversibility at higher scan rates and is
associated with another irreversible oxidation at more positive
Figure 2. PLATON plots of the molecular structures of 2, 3, and 3O showing the atom labeling scheme and the displacement ellipsoids at the 30%
probability level. For oxime 2, both orientations of the disordered OH group are shown.
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Table 1. Selected Distances (Å) and Angles (deg) for Compounds 2, 3, and 3O
a
b
c
parameter
2
3
3O
Fe−C (range)
Fe−Cg1
Fe−Cg2
∠Cp1, Cp2
τ
2.034(1)−2.057(1)
1.6507(6)
1.6531(6)
1.08(8)
2.024(2)−2.057(2)
1.6456(8)
1.6457(8)
0.9(1)
2.025(1)−2.062(1)
1.6469(6)
1.6422(6)
0.38(8)
162.13(9)
1.452(2)
69.8(1)
69.0(1)
C1−C11
C11−N
C1−C11−N
P−C6
P−C12
P−C18
1.430(2)
1.144(2)
177.3(2)
1.813(2)
1.842(2)
1.836(2)
1.430(2)
1.273(2)
1.143(2)
125.4(1)
177.5(2)
1.817(1)
1.786(1)
1.835(1)
1.809(1)
1.836(1)
1.806(1)
a
Ring planes are defined as follows: Cp1 = C(1−5), C2 = C(6−10). Cg1 and Cg2 are the respective ring centroids. Parameter τ stands for the
b
c
torsion angle C1−Cg1−Cg2−C6. Further data: N−O1 = 1.424(2) Å, N−O2 = 1.436(3) Å. Further data: P−O = 1.487(1) Å.
have suggested some borderline character for this metal ion.36
a
Scheme 2. Reactions of 3 with CuCl
Considering the nature of the donor groups available in 3 and
the coordination variability of Cu(I)-complexes,37 we decided
to study the interactions of the newly prepared ligand 3 with
Cu(I) by probing its reactivity toward copper(I) halides and
precursors of the free Cu+ ion.
Addition of ligand 3 (1, 2, or 3 molar equiv) to a suspension
of CuCl in CDCl3 led to complete dissolution of the solid
copper(I) salt within hours. NMR analysis of the resulting
solutions revealed that these reactions proceeded cleanly and
afforded three different products at the three mentioned metal-
to-ligand ratios (see the Supporting Information, Figure S2).
An ESI mass spectrometric analysis performed in parallel was
rather inconclusive. Regardless of the CuCl:3 molar ratio, the
mass spectra showed only fragments attributable to [Cu2Cl-
(3)2]+ (m/z 951; the heaviest ionic species observed),
[Cu(3)2]+ (m/z 853), [Cu2Cl(3)]+ (m/z 556), and [Cu(3)]+
(m/z 458). However, the absence of higher molecular weight
fragments is likely due to fragmentation during the ionization
process and/or disintegration in the highly polar solvent used
(methanol).
Subsequent evaporation and crystallization from an ethyl
acetate/hexane mixture produced air-stable crystalline solids.
The NMR spectra of the crystalline products isolated from the
reactions performed at Cu/3 ratios of 1:1 and 1:2 were
identical with those recorded in situ. The compounds were
characterized by X-ray diffraction analysis as a heterocubane
a
As formulated, compound 6 represents a plausible intermediate that
was characterized in solution but could not be isolated as a defined
comprising the ferrocene ligand as a P-monodentate donor,
[(μ3-Cl)4{Cu(3-κP)}4] (4), and the ligand-bridged dimer
[(μ(P,N)-3){CuCl(3-κP)}]2 (5), respectively (Scheme 2). In
contrast, the crystallization of the product obtained upon
addition of 3 molar equiv of 3 to CuCl afforded exclusively the
already mentioned dicopper(I) complex 5. Because complexes
of the type [CuCl(PR3)3] are relatively common among Cu(I)-
phosphine complexes,38 we assume that the reaction of CuCl
with 3 equiv of 3 indeed produced the tris-phosphine complex
[CuCl(3-κP)3] (6) in the solution (perhaps in equilibrium with
other species). However, upon crystallization, this species likely
dissociated to give the less soluble dimer 5, which then
separated from the reaction mixture in pure crystalline form.
The dissociative formation of 5 may be aided by steric
destabilization of intermediate 6, resulting from the presence of
the bulky phosphinoferrocene ligand,39 and the availability of
another, much less sterically demanding soft donor group
(nitrile).
solid substance.
The 31P NMR spectra of 4-6 showed broad singlets near δP =
−13 ppm, suggesting coordination of the phosphine groups in
all cases. The compounds were clearly distinguished by their 1H
NMR spectra, which showed the signals of the phosphino-
ferrocene ligand at different positions (Figure S2, Supporting
Information). The observation of a single set of resonances in
the 1H NMR spectrum of 5 corroborates the fluxional nature of
the Cu−3 complexes. The IR spectra of crystalline complexes 4
and 5 differed mainly in the fingerprint region and provided
limited diagnostic information. The spectrum of 5 showed a
strong νCN band (2224 cm−1) at a position identical to that
observed for uncoordinated 3 (2225 cm−1), whereas the νCN
band in the spectrum of complex 4 (2241 cm−1), which
contains only uncoordinated CN moieties, was shifted to
higher energies compared to free 3.40
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The crystal structures of 4 and 5 are presented in Figures 3
and 4 (for complete views, see the Supporting Information,
atom has a distorted Cl3P tetrahedral coordination environ-
ment. The heterocubane unit in 4 has an exact C2 symmetry,
residing on the crystallographic symmetry element. The
interatomic distances within the Cu4Cl4 cube in 4 are within
the range observed for other [CuCl(PR3)]4 complexes,42 while
the P−Cu bond lengths compare well with those reported for
the [CuI(L)]4 complexes obtained from phosphinoferrocene
donors.43 The faces of the heterocubane moiety (see the
Supporting Information, Figure S5) are distorted from the ideal
square shape. The intraface Cu···Cu contacts (3.1950(5)-
3.3332(5) Å) are shorter than the Cl···Cl distances (3.540(1)-
3.6634(8) Å), and the associated Cl−Cu−Cl angles (93.31(3)-
99.41(2)°) are less acute that the Cu−Cl−Cu angles (81.89(2)-
86.70(3)°). The ferrocene moieties that decorate the cubane
unit at its exterior maintain their regular geometry [tilt angles
ca. 2°; Fe−Cg 1.648(1)−1.653(2) Å] but assume different
conformations (τ = −162.5(2)° (Fe1) and −66.4(2)° (Fe2)),
which direct their arm-like cyano pendants into structural voids
and away from the Cu4Cl4 core.
Complex 5, obtained at CuCl:3 ratios of 1:2 and 1:3 (after
crystallization), is a dicopper(I) complex in which two
phosphinoferrocene ligands coordinate as P-monodentate
donors while the other two bridge the Cu(I) centers as P,N
donors, thus resulting in identical CuClP2N centers (Figure 4).
The symmetrical nature of the complex species is manifested in
the crystal structure, in which the complex molecules reside on
the crystallographic inversion centers.
The tetrahedral coordination environment of the Cu(I) ions
in 5 is distorted, reflecting the dissimilar steric demands of the
donor moieties attached to Cu(I) [cf. the interligand angles
ranging from 98.16(4)° (Cl1−Cu−N2′) to 117.62(2)° (P1−
Cu−P2)]. With respect to the Cu−donor distances, the
coordination can be described as 3 + 1 because the rather
similar Cu−Cl and Cu−P bonds are significantly longer that
the remaining Cu−N bond (by ca. 0.15−0.18 Å). The
ferrocene units are rotated into open intermediate conforma-
tions [τ = 159.0(1)° for Fe1, τ = −137.7(1)° for Fe2]. The
bridging ligand shows a larger tilt and slightly shorter Fe−Cg
distances [tilt 3.88(9)°, Fe−Cg 1.6475(7) and 1.6456(7) Å]
than the P-coordinated one [tilt 1.8(1)°, Fe−Cg 1.6515(8) and
1.6559(8) Å].
Figure 3. PLATON plot of the molecular structure of heterocubane 4
with 50% probability displacement ellipsoids. The phenyl ring carbons,
except for those in ipso positions, and all hydrogens were omitted to
simplify the figure. Atoms labeled with a prime are generated by the
(−x, y, 3/2 − z) symmetry operation. Selected distances (Å) and angles
(deg): Cu1−P1 2.1760(8), Cu1−Cl1 2.4431(7), Cu1−Cl2 2.3595(5),
Cu1−Cl2′ 2.4558(9), Cu2−P2 2.1856(8), Cu2−Cl1 2.5229(7), Cu2−
Cl2 2.4820(7), Cu2−Cl1′ 2.3412(9), Cl1−Cu1−Cl2 99.41(2), Cl1−
Cu1−Cl2′ 93.57(3), Cl2−Cu1−Cl2′ 96.36(2), Cl1−Cu2−Cl2
94.10(2), Cl1−Cu2−Cl1′ 93.31(3), Cl2−Cu2−Cl1′ 95.46(3), Cl−
Cu−P 115.30(3)−132.26(3).
Figures S3 and S4). As indicated above, complex 4 adopts a
typical37,41 heterocubane structure in which each copper(I)
As for the CuCl/3 system, the NMR spectra of CuX−3 (X =
Br and I) mixtures obtained by mixing the appropriate
copper(I) halide with 3 in CDCl3 at metal-to-ligand ratios of
1:1, 1:2, or 1:3 suggested the formation of distinct species in
each case. However, the subsequent crystallizations afforded
only the insoluble polymeric complexes [CuX(μ(P,N)-3)]n (7
X = Br, 8 X = I) instead of the heterocubanes analogous to 4.
This confirms the dynamic nature of the CuX(3)n species in
solution, which in turn enables the selective formation (upon
crystallization) of the most stable and/or the least soluble
product.
The crystal structures of 7 and 8 were determined by X-ray
crystallography. In contrast to the other crystal structures
reported in this paper, which were determined at 150 K, the
diffraction data for 7 were recorded at 250 K because this
compound undergoes a phase transition associated with a
roughly 3-fold increase in the length of the monoclinic (b) axis.
Differential scanning calorimetry (DSC) analysis demonstrated
that the compound undergoes a reversible second-order phase
transition at approximately −12 °C (see the Supporting
Information). In addition, while compounds 7 and 8 have
Figure 4. PLATON plot of the molecular structure of dimer 5 with
50% probability displacement ellipsoids. For clarity, the phenyl ring
carbons, except for the ipso ones, and all hydrogens were omitted. The
primed atoms are generated by crystallographic inversion. Selected
distances (Å) and angles (deg): Cu−Cl 2.2877(4), Cu−P1 2.2558(5),
Cu−P2 2.2673(4), Cu−N2′ 2.111(1), C111−N1 1.145(2), C211−N2
1.148(2), Cl−Cu−P1 113.38(1), Cl−Cu−P2 116.10(1), Cl−Cu−N2′
98.16(4), P1−Cu−P2 117.62(2), P1−Cu−N2′ 108.16(4), P2−Cu−
N2′ 99.97(4).
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very similar structures, they are not isostructural (Figure S6,
Supporting Information).44
intensity at 2314 and 2283 cm−1. The crystal structure of 9
(Figure 6) confirmed the presence of different nitrile groups,
The crystal structure of 8 is depicted in Figure 5, and the data
for both polymeric complexes are given in the figure caption.
Figure 6. Section of the polymeric chain in the structure of 9, in which
the “monomer units” are related by elemental translation along the a
−
axis. The counteranions (BF4 ), phenyl ring carbons (except for those
in ipso positions), and all hydrogens are omitted for clarity.
Displacement ellipsoids are scaled to the 50% probability level.
Selected distances (Å) and angles (deg): Cu−P 2.1985(5), Cu−N′
1.954(2), Cu−N90 1.956(2), C11−N 1.141(3), C90−N90 1.136(3),
P−Cu−N′ 120.19(5), P−Cu−N90 128.37(5), N′−Cu−N90
111.22(7).
Figure 5. Section of the 2D polymeric structure of 8, showing
displacement ellipsoids at the 30% probability level. The circles
indicate the atoms through which the propagation of the infinite
assembly occurs. Selected distances (Å) and angles (deg) for 7 (X =
Br) and [8 (X = I)]: Cu−X 2.4494(5) [2.6027(3)], Cu−X′ 2.5224(5)
[2.6857(3)], Cu−P 2.2169(9) [2.2394(6)], Cu−N″ 2.022(3)
[2.016(2)], C11−N 1.137(4) [1.144(3)], X−Cu−X′ 109.96(2)
[115.93(1)], X−Cu−P 118.25(2) [115.19(2)], X′−Cu−P 108.50(3)
[105.21(2)], X−Cu−N″ 109.06(8) [112.34(6)], X′−Cu−N″ 99.96(8)
[97.57(5)], Cu−X−Cu′ 70.04(1) [64.07(1)].
indicating that 9 is a coordination polymer in which ligand 3
bridges the adjacent Cu(MeCN) units. The copper(I) centers
are thus coordinated by two phosphinonitrile ligands and one
acetonitrile, constituting an irregular trigonal N2P donor set.
Because the disubstituted ferrocene unit [tilt 4.4(1)°, Fe−Cg
1.6474(9)/1.6398(9) Å] assumes a conformation similar to
synclinal eclipsed [τ = −63.8(1)°, ideal value = 72°], the
infinite chains are angular and, therefore, rather contracted
(note that, owing to the overall symmetry, the Cu···Cu
separation is exactly equal to the length of the crystallographic a
axis). The BF4− ions are located in between the chains and are
fixed by the soft F···H−C interactions.46
Each copper(I) ion in the structures of 7 and 8 is coordinated
by two ligands (one through the phosphorus and one through
its CN group), and the resulting Cu(3)2 units are connected
into a dimeric unit through asymmetric halide bridges45 that
complete the distorted tetrahedral coordination spheres around
the Cu(I) ions. Because each ligand acts as a P,N bridge
between two adjacent dicopper(I) units, the dimer units are
interlinked into infinite corrugated layers (see the Supporting
Information, Figure S7). The donor substituents in bridging 3
are rotated away from each other (τ = −158.9(2)° for 7 and
−157.9(1)° for 8). Otherwise, the ferrocene units remain
regular [7: Fe−Cg 1.644(2)/1.647(1) Å; 8: 1.647(1)/
1.6480(9) Å] and display negligible tilting (below 1°).
Rather unexpectedly, increasing the Cu/3 ratio to 1:2 and
1:347 in reactions of the phosphinonitrile with [Cu(MeCN)4]X
[X = BF4, PF6, CF3SO3, or B(C6F5)448] resulted in the selective
formation of the respective quadruply ligand-bridged dicopper-
(I) complex salts 10X2 (Scheme 3, route a). These complexes,
which were accessible equally well by the treatment of CuCl
with 2 equiv of 3 and then by a silver(I) salt (i.e., from AgX and
5 formed in situ, Scheme 3, route b) or, similarly, by halogen
removal from in situ generated 6 (Scheme 3, route c), represent
an unprecedented structural type among Cu(I) complexes
prepared from P,N donors. Previously structurally characterized
compounds49 in which a P,N donor bridges two discrete Cu(I)
centers devoid of any supporting halide ligands include only
asymmetric, triply bridged complexes of the type [(MeCN)-
Reactions of 3 with Precursors of Bare Cu+. Similar to
the above experiments, reactions were performed at metal-to-
ligand ratios of 1:1, 1:2, and 1:3 using [Cu(MeCN)4]+ salts as
the common precursors of Cu(I) ions devoid of any firmly
bound supporting ligands. The reaction of [Cu(MeCN)4][BF4]
with 1 molar equiv of 3 in dichloromethane produced an
orange precipitate, which redissolved upon addition of little
acetonitrile. Layering with hexane and crystallization by liquid-
phase diffusion afforded the catena-polymer [Cu(μ-3)-
(MeCN)]n[BF4]n (9).
Cu(μ-P−N)2 (μ-N−P)Cu]2 +
, where N−P is 2-
(diphenylphosphino)pyridine50 or 2-(diphenylphosphino)-1-
methylimidazole.51,52 The former ligand also forms a doubly
bridged dicopper(I) cation having two or four additional
acetonitrile ligands, viz. [(MeCN)nCu(μ-P−N)(μ-N−P)Cu-
(MeCN)n]2+ (n = 1 or 2).50,53 The different coordination
This compound was insoluble in common deuterated,
nondonor solvents and could therefore not be analyzed by
NMR spectroscopy. Its IR spectrum featured several νCN
bands: a strong band at 2249 cm−1 and two bands of medium
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S9), which also presents the structure of the less symmetric
solvate 10[SbF6]2·2Me2CO for comparison.
Scheme 3. Alternative Routes Leading to the Dicopper(I)
Salts 10X2
a
The structure of cation 102+ can be likened to a fragment of a
quadruple helix consisting of pairs of chains with opposite
polarity arranged around the central Cu1···Cu2 axis or, more
figuratively, to a propeller with four blades (see Figure S9,
Supporting Information). The compound crystallizes with the
symmetry of the chiral orthorhombic space group Aba2 such
that the copper atoms reside on the 2-fold axis. This “external”
symmetry renders only one-half of the complex cation and one
−
counterion (SbF6 ) structurally independent.
The Cu1···Cu2 separation in 10[SbF6]2 is 5.4820(5) Å,
which is considerably longer than the sum of covalent radii
(2.64 Å54) or the Cu···Cu distances in heterocubane 4
[3.1950(5)−3.3332(4) Å] and much less than the Cu···Cu′
distances in 5 [8.2816(8) Å] and 9 [7.9595(5) Å]. Each
copper(I) atom in 102+ forms two relatively shorter bonds to
the nitrile groups and two longer bonds to the phosphine
groups within a distorted tetrahedral coordination environ-
ment. The P−Cu−P angles are the largest, while the N−Cu−N
angles are the most acute, reflecting the different steric
properties of the donor moieties. The departure from the
ideal tetrahedral angles is larger for Cu1 than for Cu2. The
ferrocene units assume a synclinal eclipsed conformation [τ =
75.6(2)° for Fe1 and τ = 74.1(2)° for Fe2], which brings the
donor moieties into positions suitable for bridging the two
Cu(I) centers. However, this conformation of the donor units
results in a mutual rotation of the CuN2P2 units (P1−Cu1···
Cu2−N1 = 26.94(7)°, P2−Cu2···Cu1−N2 = 24.28(7)°) and,
consequently, the helical character of the dicopper(I) cation.
The νCN bands in the IR spectrum of the 102+ salts appear
shifted toward higher frequencies (2230 and 2237 cm−1 for
10[BF4]2 and 10[SbF6]2, respectively) compared with the free
ligand (2225 cm−1). Together with a marginal variation of the
lengths of the CN bonds,55 this shift is in line with the usual
trend, reflecting changes in the electronic structure of the nitrile
moiety upon coordination.40
a
−
−
−
−
Route a for X = BF4 , PF6 , CF3SO3 , and B(C6F5)4 ; route b for X
−
−
= SbF6 and (CF3SO2)2N−; and route c for X = SbF6 .
behavior of 3 is very likely due to the presence of the rather
small, rod-like CN donor unit, which cannot easily participate
in the chelation of the P-bonded metal ion but can be directed
to another metal center (through practically unrestricted
rotation of the ferrocene cyclopentadienyls) and thus supple-
ment the preferred tetrahedral coordination environment
around the “other” Cu(I) ion.
Although the salts of the cation 102+ crystallize readily, their
structural characterization proved difficult owing to the
presence of extensively disordered counteranions and/or
solvent molecules. Good-quality, disorder-free crystals were
ultimately obtained for 10[SbF6]2. The structure of the
complex cation in this salt is presented in Figure 7. A complete
view and a projection of the cation along the (Cu2, Cu1) vector
are available in the Supporting Information (Figures S8 and
CONCLUSIONS
■
The readily accessible phosphinonitrile 3 exhibits some unique
properties, primarily due to the presence of the ferrocene
moiety.56 As a ligand, it can rotate along the axis of the
ferrocene unit and thus undergo the rotational reorganization
of the donor moieties, but it remains inflexible with respect to
the tilting of the cyclopentadienyl rings. Furthermore, the entire
molecule of 3 is conjugated and, because of strong electron-
donating nature of the ferrocene unit, electron-rich. This results
in unprecedented coordination behavior, which is exemplified
herein for the soft Cu(I) ion.
In addition to conventional complexes in which the cyano
groups remain uncoordinated and thus serve as spectators,
albeit rather specific substituents, the structures determined for
the Cu(I) complexes with ligand 3 reported in this Article
demonstrate the ability of the phosphinonitrile donor to
coordinate as a P,N bridge through both soft donor sites. The
molecular structures of such complexes have been determined
for the first time. Although limited to Cu(I) and a few
coordination geometries (halide complexes PX3 or NPX2
tetrahedral donor sets, complexes without halide ligands PN2
trigonal or P2N2 tetrahedral coordination environments), the
results presented here demonstrate as yet undocumented
coordination behavior of phosphinonitrile donors and stress the
Figure 7. View of the complex cation in the structure of 10[SbF6]2,
showing the displacement ellipsoids at the 30% probability level. The
primed atoms are generated by the crystallographic 2-fold axis (−x, 2
− y, z). Selected distances (Å) and angles (deg): Cu1−P1 2.3069(5),
Cu1−N2 2.051(2), Cu2−P2 2.2807(5), Cu2−N1 2.016(2), C111−
N1 1.143(3), C211−N2 1.144(3), P1−Cu1−P1′ 124.05(3), P1−
Cu1−N2 104.52(5), P1−Cu1−N2′ 109.84(6), N2−Cu1−N2′
102.05(8), P2−Cu2−P2′ 119.18(2), P2−Cu2−N1 107.10(5), P2−
Cu2−N1′ 108.59(5), N1−Cu2−N1′ 105.49(7).
573
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Inorganic Chemistry
Article
Calcd for C23H20FeNOP·0.2CH3CO2Et (430.8): C 66.34, H 5.05, N
3.25%. Found: C 66.24, H 4.73, N 3.28%. The amount of clathrated
solvent was verified by NMR spectroscopy.
necessity of selecting the appropriate metal ions for evaluating
the coordination potential of these donors.
1′-(Diphenylphosphino)-1-cyanoferrocene (3). Oxime 2
(0.293 g, 0.71 mmol) and (benzotriazol-1-yloxy)tris(dimethylamino)-
phosphonium hexafluorophosphate (BOP; 0.628 g, 1.42 mmol) were
mixed in dry THF (15 mL). After the mixture had been stirred at
room temperature for 5 min, 1,8-diazabicyclo[5.4.0]undec-7-ene
(DBU; 0.25 mL, 1.7 mmol) dissolved in 5 mL of THF was added,
and the stirring was continued for another 2 h. The mixture was
washed with water (2× 5 mL) and brine (5 mL), and the organic
phase was dried over MgSO4 and evaporated with silica gel. The
preadsorbed product was transferred to the top of a chromatographic
column (silica gel; hexane/diethyl ether 1:1). Elution with the same
solvent mixture afforded a single red band, which was collected and
evaporated to give nitrile 3 as an orange microcrystalline solid (yield:
0.250 g, 89%). Crystals suitable for X-ray diffraction analysis were
grown from ethyl acetate/hexane.
EXPERIMENTAL SECTION
■
Materials and Methods. The syntheses of 2 and 3 were
performed in an argon atmosphere using standard Schlenk
techniques.57 Complexes with ligand 3 were prepared in argon-flushed
vessels and in the dark. Aldehyde 1 was prepared according to the
literature.20 Dichloromethane and tetrahydrofuran (THF) were dried
with a Pure Solv MD-5 Solvent Purification System (Innovative
Technology, Amesbury, MA). Other chemicals and solvents utilized
for crystallizations and chromatography were used as received (Sigma-
Aldrich; solvents from Lachner, Brno, Czech Republic).
NMR spectra were measured with a Varian UNITY Inova 400
spectrometer (1H 399.95, 13C 100.58, 31P 161.90 MHz) at 25 °C
unless noted otherwise. Chemical shifts (δ, ppm) are given relative to
internal tetramethylsilane (1H and 13C) or external 85% aqueous
H3PO4 (31P). In addition to the usual notation for signal multiplicity,
vt and vq are used to denote virtual triplets and quartets arising from
the AA′BB′ and AA′BB′X spin systems of the cyano- and PPh2-
substituted cyclopentadienyl rings, respectively (fc = ferrocene-1,1′-
diyl). IR spectra were recorded with an FTIR Nicolet 760 instrument
in the range 400−4000 cm−1. Conventional (low-resolution) electro-
spray ionization mass spectra (ESI MS) were recorded on a Bruker
Esquire 3000 spectrometer. The samples were dissolved in HPLC-
grade methanol. High-resolution (HR) ESI MS measurements were
obtained with an LTQ Orbitrap XL mass spectrometer. Elemental
analyses were determined by a conventional combustion method with
a PE 2400 Series II CHNS/O Elemental Analyzer (Perkin-Elmer).
Melting points were determined with a melting point B-540 apparatus
Mp 163−164 °C (ethyl acetate/hexane). 1H NMR (CDCl3): δ 4.26
(vq, J′ = 1.9 Hz, 2H, fc), 4.28 (vt, J′ = 1.9 Hz, 2H, fc), 4.53 (vt, J′ = 1.9
Hz, 2H, fc), 4.56 (vt, J′ = 1.9 Hz, 2H, fc), 7.32−7.37 (m, 10H, Ph).
13C{1H} NMR (CDCl3): δ 52.62 (C−CN of fc), 72.17 (d, JPC = 1 Hz,
CH of fc), 72.56 (CH of fc), 73.72 (d, JPC = 4 Hz, CH of fc), 74.87 (d,
1
JPC = 14 Hz, CH of fc), 79.29 (d, JPC = 10 Hz, C−P of fc), 119.60
2
(CN), 128.35 (d, JPC = 7 Hz, CHortho of Ph), 128.86 (CHpara of
3
1
Ph), 133.40 (d, J = 20 Hz, CHmeta of Ph), 138.03 (d, JPC = 10 Hz,
Cipso of Ph). 31P{1H} NMR (CDCl3): δ −17.7. IR (Nujol): νmax
(cm−1) 3114 w, 3100 w, 3082 w, 3055 w, 2225 m, 1232 w, 1194 w,
1160 m, 1090 w, 1232 w, 1032 m, 1027 m, 913 w, 848 w, 840 w, 823
m, 749 s, 699 s, 562 w, 555 w, 519 w, 510 m, 478 m, 495 m, 448 m,
450 m, 425 w. ESI+ MS: m/z 396 ([M + H]+), 418 ([M + Na]+), 434
([M + K]+). HR MS (ESI+): calcd for C23H19FeNP ([M + H]+)
396.0599, found 396.0599. Anal. Calcd for C23H18FeNP (395.2): C
69.90, H 4.59, N 3.55%. Found: C 69.60, H 4.44, N 3.45%.
Reactions of Ligand 3 with CuCl. A solution of phosphine 3 in
dichloromethane (1.5 mL) was added to a suspension of CuCl in the
same solvent (0.5 mL). The resulting mixture was stirred at room
temperature for 90 min, during which time all of the CuCl dissolved.
Following evaporation under a vacuum, the solid products were
analyzed by NMR spectroscopy and subsequently recrystallized by
liquid-phase diffusion from ethyl acetate/hexane or chloroform/
hexane.
(Buchi, Flawil, Switzerland).
̈
1′-(Diphenylphosphino)ferrocene-1-carboxaldehyde Oxime
(2). A solution of sodium ethoxide prepared separately by dissolving
sodium metal (0.063 g, 2.7 mmol) in anhydrous ethanol (5 mL) was
added to a solution of hydroxylamine hydrochloride (0.190 g, 2.7
mmol) in absolute ethanol (15 mL), whereupon a fine white
precipitate (NaCl) separated. The mixture was stirred for 10 min
and then filtered through a polytetrafluoroethylene (PTFE) syringe
filter into a suspension of 1′-(diphenylphosphino)ferrocene-1-
carboxaldehyde (1; 0.360 g, 0.90 mmol) in anhydrous ethanol (20
mL). The resulting mixture was stirred at 60 °C for 3 h, cooled to
room temperature, and diluted with brine (20 mL) and dichloro-
methane (20 mL). The organic layer was separated, washed with brine,
dried over MgSO4, and evaporated with chromatographic silica gel.
The preadsorbed crude product was transferred onto a silica gel
column packed in a hexane/diethyl ether (3:1) mixture. The same
mobile phase was used to remove nonpolar impurities. The red band
that eluted when the eluent was changed to hexane/diethyl ether (1:1)
was collected and evaporated to afford aldoxime 2 as an orange solid
(yield: 0.306 g, 82%). The compound was a mixture of (E) and (Z)
isomers in ca. 2:1 ratio. Crystals suitable for X-ray diffraction analysis
were grown by liquid-phase diffusion from an ethyl acetate/hexane
mixture.
Complex 4. Reaction between 3 (20 mg, 51 μmol) and CuCl (5.0
mg, 51 μmol) as described above gave 4 as a yellow microcrystalline
1
solid (yield: 16 mg, 64%). H NMR (CDCl3): δ 4.36 (br vt, J′ = 1.8
Hz, 2H, fc), 4.46 (vt, J′ =1.9 Hz, 2H, fc), 4.50−4.53 (br m, 4H, fc),
7.25−7.31 (m, 4H, Ph), 7.33−7.39 (m, 2H, Ph), 7.56−7.65 (m, 2H,
Ph). 31P{1H} NMR (CDCl3): δ −13.3 (br s). IR (Nujol): νmax (cm−1)
3109 w, 3065 w, 3039 w, 2241 m, 1232 w, 1194 w, 1160 w, 1090 w,
1032 m, 1027 m, 913 w, 848w, 839 w, 823 m, 749 s, 699 s, 562 w, 558
w, 519 w, 511 m, 495 m, 478 m, 450 m, 425 w. ESI+ MS: m/z 458
([Cu(3)]+), 516 ([CuCl(3) + Na]+), 558 ([Cu2Cl(3)]+), 853
([Cu(3)2]+), 911 ([CuCl(3)2 + Na]+), 953 ([Cu2Cl(3)2]+). Anal.
Calcd for (C23H18ClCuFeNP)4 (1976.8): C 55.89, H 3.67, N 2.83%.
Found: C 55.91, H 3.60, N 2.59%.
1H NMR (CDCl3): major isomer δ 4.13 (m, 2H, fc), 4.23 (vt, J′ =
1.9 Hz, 2H, fc), 4.43 (m, J′ = 1.8 Hz, 4H, fc), 7.30−7.39 (m, 10H, Ph),
7.71 (s, 1H, CHNOH), 7.96 (br s, 1H, CHNOH); minor isomer δ
4.11 (m, 2H, fc), 4.25 (vt, J′ = 1.9 Hz, 2H, fc), 4.41 (vt, J′ = 1.8 Hz,
2H, fc), 4.70 (vt, J′ = 1.9 Hz, 2H, fc), 6.96 (s, 1H, CHNOH), 7.30−
7.39 (m, 10H, Ph), 7.96 (br s, 1H, CHNOH). 13C{1H} NMR
(CDCl3): major isomer δ 68.44 (CH of fc), 71.28 (CH of fc), 72.16
(d, JPC = 4 Hz, CH of fc), 72.46 (d, JPC = 4 Hz, CH of fc), 73.88 (d,
Complex 5. Reaction of 3 (15 mg, 38 μmol) and CuCl (1.9 mg, 19
μmol) as described above produced 5 as a red crystalline solid (yield:
11 mg, 66%). 1H NMR (CDCl3): δ 4.34 (br vt, 2H, fc), 4.46 (vt, J′ =
2.0 Hz, 2H, fc), 4.51 (vt, J′ = 2.0 Hz, 2H, fc), 4.54 (vt, J′ = 1.9 Hz, 2H,
fc), 7.27−7.33 (m, 4H, Ph), 7.36−7.41 (m, 2H, Ph), 7.43−7.51 (br m,
4H, Ph). 31P{1H} NMR (CDCl3): δ −13.1 (br s). IR (Nujol): νmax
(cm−1) 3101 w, 3047 m, 2224 s, 1586 w, 1236 w, 1192 w, 1167 w,
1035 w, 1026 w, 846 w, 833 w, 755 m, 740 m, 696 s, 630 w, 595 w, 553
w, 530 m, 510 m, 476 m, 458 m, 425 w. ESI+ MS: m/z 458
([Cu(3)]+), 516 ([CuCl(3) + Na]+), 558 ([Cu2Cl(3)]+), 853
([Cu(3)2]+), 911 ([CuCl(3)2 + Na]+), 953 ([Cu2Cl(3)2]+). Anal.
Calcd for C46H36ClCuFe2N2P2 (889.4): C 62.12, H 4.08, N 3.15%.
Found: C 61.87, H 3.94, N 3.10%.
1JPC = 14 Hz, C−P of fc), 76.86 (C−CHN of fc), 128.20 (d, JPC = 7
2
Hz, CHortho of Ph), 128.62 (CHpara of Ph), 133.47 (d, JPC = 20 Hz,
3
1
CHmeta of Ph), 138.71 (d, JPC = 9 Hz, Cipso of Ph). 31P{1H} NMR
(CDCl3): −16.7 (major), −16.6 (minor). IR (Nujol): νmax (cm−1)
3280 br m, 3240 br m, 3160 br m, 3017 m, 1642 w, 1304 m, 1245 w,
1195 w, 1188 w, 1161 w, 1090 w, 1070 m, 1040 m, 997 w, 948 s, 897
m, 827 m, 783 m, 751 s, 703 m, 695 s, 636 w, 582 w, 569 w, 499 s, 453
w, 413 w. ESI+ MS: m/z 414 ([M + H]+), 436 ([M + Na]+). Anal.
According to monitoring by NMR spectroscopy, when the reaction
was performed similarly with 3 equiv of 3 (3: 15 mg, 38 μmol; CuCl
574
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Inorganic Chemistry
Article
1.3 mg, 13 μmol), it produced a different product (formulated as
[CuCl(3)3] (6)), which was converted completely to complex 5
during the subsequent crystallization from ethyl acetate/hexane (yield
red crystals, which separated over several days, were filtered off,
washed with pentane, and dried under a vacuum to afford analytically
pure 9 (yield: 25 mg, 84%).
IR (Nujol): νmax (cm−1) 3099 w, 3071 w, 3048 w, 2314 w, 2283 m,
2249 s, 1306 w, 1285 w, 1242 m, 1195 w, 1169 m, 1102 s, 1075 s, 1052
s, 1027 s, 997 m, 916 m, 845 m, 831 w, 749 s, 699 s, 538 s, 519 s, 488 s,
481 s, 464 m, 429 w. Anal. Calcd for C25H21N2BF4PFeCu (586.6) C
51.18, H 3.61, N 4.78%. Found: C 51.48, H 3.59, N 4.59%.
Complex 10[BF4]2 (Route a in Scheme 3). A solution of 3 (15 mg,
38 μmol) in dry dichloromethane was added to a suspension of
[Cu(MeCN)4][BF4] in the same solvent (6.0 mg, 19 μmol in 0.5 mL).
The resulting mixture was stirred for 1 h and evaporated under a
vacuum. The residue was taken up with acetone (5 mL) and filtered
through a syringe filter. Evaporation of the filtrate under vacuum gave
10[BF4]2 as a yellow solid (yield: 14 mg, 78%). IR (Nujol): νmax
(cm−1) 2230 s, 1712 w, 1618 w, 1237 m, 1166 m, 1071 s, 1044 s, 999
m, 913 w, 741 m, 722 m, 696 w, 635 w, 532 w, 511 s, 490 s, 476 s, 463
s, 433 m. ESI+ MS: m/z 458 [Cu(3)+]. Anal. Calcd for
C92H72B2Cu2F8Fe4N4P4·H2O (1899.6): C 58.17, H 3.93, N 2.95%.
Found: C 57.85, H 4.00, N 2.95%. (Note: Salts with other anions were
obtained similarly.)
1
of 5: 11 mg, 95%). Data recorded for 6 in situ. H NMR (CDCl3): δ
4.31 (br vt, J′ = 1.8 Hz, 2H, fc), 4.42 (br vt, J′ = 1.8 Hz, 2H, fc), 4.50
(vt, J′ = 1.9 Hz, 2H, fc), 4.56 (vt, J′ = 1.9 Hz, 2H, fc), 7.28−7.43 (m,
10H, Ph). 31P{1H} NMR (CDCl3): δ −15.0 (br s). ESI+ MS: m/z 458
([Cu(3)]+), 516 ([CuCl(3) + Na]+), 558 ([Cu2Cl(3)]+), 853
([Cu(3)2]+), 911 ([CuCl(3)2 + Na]+), 953 ([Cu2Cl(3)2]+). The
NMR and IR spectra of the crystallized samples were identical to those
of 5.
[CuBr(3)]n (7). CuBr (7.3 mg, 51 μmol) and 3 (20 mg, 51 μmol)
were reacted in dry chloroform (2 mL) for 1 h to afford a clear
solution, which was partly evaporated under a vacuum (to ca. 1 mL)
and filtered through a PTFE syringe filter. The filtrate was layered with
chloroform (1 mL) and hexane (10 mL), and the mixture was allowed
to crystallize by diffusion to produce 8 as an orange-red crystalline
solid (yield: 19 mg, 70%). Note: Complete solvent removal produces a
glassy solid, which can be dissolved in ethyl acetate. The solution,
however, rapidly deposits 8 as an orange precipitate.
1H NMR (in situ, CDCl3): δ 4.38 (vt, J′ = 1.9 Hz, 2H, fc), 4.40 (vt,
J′ =1.9 Hz, 2H, fc), 4.57 (vt, J′ = 1.7 Hz, 2H, fc), 4.59 (br s, 2H, fc),
7.28−7.34 (m, 4H, Ph), 7.36−7.42 (m, 2H, Ph), 7.56−7.63 (m, 4H,
Ph). 31P{1H} NMR (in situ, CDCl3): δ −16.1 (br s). IR (Nujol): νmax
(cm−1) 3112 w, 3103 w, 3061 w, 3040w, 2243 s, 1238 m, 1193 w, 1167
s, 1033 s, 914 s, 890 w, 753 s, 745 s, 697 s, 636 w, 535 s, 517 s, 509 m,
481 s, 457 m, 432 m. Anal. Calcd for C23H18BrCuFeNP (538.7): C
51.28, H 3.37, N 2.60%. Found: C 50.90, H 3.29, N 2.34%.
The NMR spectra recorded for the reaction mixtures obtained
similarly at Cu/3 molar ratios of 1:2 and 1:3 were different, but the
subsequent crystallization always produced only complex 8. Cu/3 =
1:2. 1H NMR (in situ, CDCl3): δ 4.39 (br vt, J′ = 1.7 Hz, 2H, fc), 4.45
(vt, J′ = 1.9 Hz, 2H, fc), 4.48 (vt, J′ = 1.9 Hz, 2H, fc), 4.54 (vt, J′ = 1.9
Hz, 2H, fc), 7.27−7.32 (m, 4H, Ph), 7.36−7.41 (m, 2H, Ph), 7.43−
7.48 (m, 4H, Ph). 31P{1H} NMR (in situ, CDCl3): δ −13.6 (br s).
Cu/3 = 1:3. 1H NMR (in situ, CDCl3): δ 4.35 (br vt, J′ = 1.8 Hz, 2H,
fc), 4.42 (br vt, J′ = 1.9 Hz, 2H, fc), 4.49 (vt, J′ = 1.9 Hz, 2H, fc), 4.56
(vt, J′ = 1.9 Hz, 2H, fc), 7.28−7.33 (m, 4H, Ph), 7.35−7.41 (m, 6H,
Ph). 31P{1H} NMR (in situ, CDCl3): δ −14.7 (br s).
Complex 10[SbF6]2 (Route c in Scheme 3). A solution of ligand 3
(30 mg, 76 μmol) in dichloromethane (3 mL) was added to a
suspension of CuCl (3.8 mg, 38 μmol) in the same solvent (1 mL).
After being stirred for 60 min, the resulting solution was treated with a
suspension of Ag[SbF6] (13 mg, 38 μmmol) in dichloromethane (3
mL), and the reaction mixture was stirred for another 30 min and
filtered through a PTFE syringe filter. The filtrate was evaporated
under a vacuum, and the residue was taken up with acetone (1.5 mL)
and filtered into a 5 mm NMR tube. The solution was carefully layered
with acetone (0.5 mL) and hexane (ca. 2 mL), and the mixture was
allowed to crystallize at room temperature. The separated crystalline
solid was filtered off, washed with pentane, and dried under a vacuum.
Yield of 10[SbF6]2: 34 mg (82%), red crystalline solid. IR (Nujol):
νmax (cm−1) 3122 w, 3055 w, 2237 s, 1587 w, 1481 m, 1435 s, 1238 m,
1196 w, 1099 m, 1041 m, 999 w, 912 w, 830 m, 741 m, 695 s, 659 s,
577 w, 531 w, 511 s, 487 s, 478 s, 466 m, 433 w. ESI+ MS: m/z 458
[Cu(3)+]. Anal. Calcd for C92H72Cu2F12Fe4P4N4Sb2 (2179.4) C 50.70,
H 3.33, N 2.57%. Found: C 50.43, H 3.33, N 2.36%.
[CuI(3)]n (8). Ligand 3 (50 mg, 0.13 mmol) and CuI (24 mg, 0.13
mmol) were reacted in dry CHCl3 as described above. After filtration,
the clear, orange solution was layered with chloroform (2 mL) and
hexane (20 mL) and set aside for crystallization to produce 8 in the
form of orange-red crystals (yield: 65 mg, 87%).
ASSOCIATED CONTENT
* Supporting Information
■
S
Additional structural diagrams, NMR spectra of CuCl/3
mixtures, results of DSC measurements for 7, description of
single-crystal X-ray diffraction analyses, and copies of NMR and
IR spectra. Complete crystallographic data in standard CIF
format (CCDC deposition numbers 966377−966386). This
material is available free of charge via the Internet at http://
pubs.acs.org.
1H NMR (in situ, CDCl3): δ 4.07 (br s, 2H, fc), 4.26 (br s, 2H, fc),
4.52−4.56 (m, 4H, fc), 7.39−7.45 (m, 4H, Ph), 7.47−7.60 (m, 6H,
Ph). 31P{1H} NMR (in situ, CDCl3): δ −27.9 (br s). IR (Nujol): νmax
(cm−1) 3112 w, 3103 m, 3089 w, 3065 m, 3041 m, 2242 s, 1586 w,
1237 m, 1193 m, 1165 s, 1098 m, 1070 w, 1050 w, 1033 s, 999 w, 987
w, 914 m, 889 w, 865 w, 839 s, 832 s, 809 m, 952 s, 744 s, 697 s, 635 w,
577 w, 534 s, 516 s, 509 m, 478 s, 459 s, 432 m. Anal. Calcd for
C23H18CuFeINP (585.7): C 47.17, H 3.10, N 2.39%. Found: C 46.90,
H 3.03, N 2.20%.
AUTHOR INFORMATION
Corresponding Author
*E-mail: stepnic@natur.cuni.cz.
Notes
■
Similar to the CuBr/3 system, the reaction mixtures obtained at
CuI/3 ratios of 1:2 and 1:3 gave different NMR spectra but provided
1
only complex 9 upon crystallization. CuI/3 = 1:2. H NMR (in situ,
The authors declare no competing financial interest.
CDCl3): δ 4.41−4.46 (m, 6H, fc), 4.54 (vt, J′ =1.9 Hz, 2H, fc), 7.26−
7.31 (m, 4H, Ph), 7.35−7.43 (m, 6H, Ph). 31P{1H} NMR (in situ,
1
ACKNOWLEDGMENTS
CDCl3): δ −14.8 (br s). CuI/3 = 1:3. H NMR (in situ, CDCl3): δ
■
4.39−4.42 (m, 4H, fc), 4.48 (vt, J′ =1.9 Hz, 2H, fc), 4.48 (vt, J′ =1.9
Hz, 2H, fc), 4.55 (vt, J′ =1.9 Hz, 2H, fc), 7.27−7.32 (m, 4H, Ph),
7.34−7.40 (m, 6H, Ph). 31P{1H} NMR (in situ, CDCl3): δ −14.9 (br
s).
This contribution is based on work supported by the Czech
Science Foundation (Project 13-08890S) and the Grant Agency
of Charles University in Prague (Project 108213).
Preparation of [Cu(3)(MeCN)]x[BF4]x (9). A solution of 3 (20 mg,
51 μmol) in dichloromethane (2 mL) was added to a suspension of
solid [Cu(MeCN)4][BF4] (16 mg, 51 μmol) in the same solvent (1
mL), and the resulting mixture was stirred for 1 h. The separated solid
was dissolved by addition of acetonitrile (2 drops), and the solution
was filtered through a syringe filter. The filtrate was layered with
hexane (ca. 6 mL) and set aside for crystallization. The dark orange-
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