Nitrogen-Phosphorus(III)-Chalcogen Macrocycles for the Synthesis of Polynuclear Silver(I) Sandwich Complexes

Article abstract of DOI:10.1021/acs.inorgchem.7b00141

The synthesis of inorganic N-P(III)-Ch-based macrocycles [-PhP-NMe-PPh-Ch-]₂ (8_Ch; Ch = S, Se) is presented by incorporating two nitrogen, two chalcogen, and four phosphorus atoms. The macrocycles are conveniently obtained via the cy

Full text of DOI:10.1021/acs.inorgchem.7b00141

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Nitrogen−Phosphorus(III)−Chalcogen Macrocycles for the Synthesis
of Polynuclear Silver(I) Sandwich Complexes
Sivathmeehan Yogendra, Felix Hennersdorf, and Jan J. Weigand*
Department of Chemistry and Food Chemistry, TU Dresden, 01062 Dresden, Germany
S
* Supporting Information
ABSTRACT: The synthesis of inorganic N−P(III)-Ch-based
macrocycles [−PhP−NMe−PPh−Ch−]2 (8Ch; Ch = S, Se) is
presented by incorporating two nitrogen, two chalcogen, and
four phosphorus atoms. The macrocycles are conveniently
obtained via the cyclocondensation reaction of Na2Ch (Ch =
S, Se) with the acyclic dichlorodiphosphazane ClPhP−NMe−
PClPh (9). Treatment with elemental sulfur (S8) or gray
selenium (Segray) results in an oxidative ring contraction to give
1,3,2,4-thiazadiphosphetidine 2,4-disulfide (10S) and 1,3,2,4-
selenazadiphosphetidine 2,4-diselenide (10Se), respectively.
Macrocycles 8Ch are excellent multidentate ligands for
transition metal complexation, as demonstrated by the
isolation of mono-, di- tri-, and tetranuclear silver sandwich
complexes. The polynuclear silver complexes are comprehen-
sively characterized, including detailed NMR and X-ray analysis.
Chart 1. Selected Macrocyclic Phosphachalcoganes 14+, 2, 3,
and 4; the N−P(III/V)−Ch-Based Macrocycles (5Ch)
INTRODUCTION
■
Organic macrocycles, such as crown ethers, cryptands, and
porphyrins are well developed and have become indispensable
as ligands in modern coordination chemistry, particularly in the
field of supramolecular chemistry.1 Macrocycles composed of
an entirely inorganic backbone are a rare class of compounds
and are only insufficiently investigated.2 Because inorganic
macrocycles can be composed of a large variety of elements and
structural functions, their development is of significant
interest.3 Our group particularly works in the field of
polyphosphorus derivatives and we recently reported on the
synthesis of the tetracationic imidazoliumyl-substituted phos-
phorus/sulfur heterocycles 14+ (Chart 1, Im = LR,Me
=
i
imidazolium-2-yl; R = Me, Pr), representing examples with
an inorganic P(III)/S core.4 Probably the most investigated
phosphorus chalcogen heterocycles are the P(V)-based Law-
esson reagent (Ch = S)5 and the Woollins reagent (Ch = Se),6
whereas P(III)/chalcogen heterocycles are less common.
However, they are very attractive as ligands for the coordination
of transition metals.7 Selected P(III)−chalcogen macrocycles,
also known as phosphachalcoganes, are the cyclic (RPCh)n
derivatives (Chart 1, n = 4, 2, R = Mes = 2,4,6-
trimethylphenyl;8 n = 3, 3, R = Mes* = 2,4,6-tert-butylphenyl;9
n = 2, 4Ch, Ch = S, Se, R = Ar* = 2,6-(2,4,6-trimethylphenyl)-
phenyl10).11 Phosphazanes also feature an inorganic P(III)
backbone and have proven to be robust building blocks for the
formation of macrocycles. This was demonstrated by Chivers
and Wright et al. by bridging cyclophosphazanes via amino
groups to yield macrocyclic phosphazanes.12 Subsequently,
Wright and co-workers interlinked cyclo-phosphazanes with
chalcogenes to yield the intriguing P(III)/P(V) mixed
macrocycles 5Ch (Ch = S,13 Se14). Coordination chemistry
toward soft metals of these hybrid macrocycles is not reported
so far. Recently, we reported a convenient condensation
reaction of chlorophosphanes R2PCl with chalcogenides (e.g.,
Na2Ch), representing a general synthesis method to form
selectively either the diphosphane monochalcogenides 6 (R =
Me, Et, Ph, Tol; Ch = S, Se) or the acyclic diphosphanylchal-
Special Issue: Advances in Main-Group Inorganic Chemistry
Received: January 20, 2017
© XXXX American Chemical Society
A
DOI: 10.1021/acs.inorgchem.7b00141
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t
coganes 7 (R = Bu, Mes, N(iPr)2, C6F5; Ch = S, Se, Te;
diffraction, confirming the presence of exclusively the meso-9
isomer in the solid state (Supporting Information, Figure S5).
Upon dissolving meso-9 at ambient temperature, it equilibrates
to a mixture of both diastereomers, as evidenced by 31P−31P
EXSY NMR spectroscopy (Supporting Information, Figure S4).
Compound 9 represents a rare example of an acyclic chloro-
functionalized diphosphazane and displays a suitable building
block for the targeted synthesis of N−P(III)−Ch-based
macrocycles.17,19 Cyclocondensation of 9 with Na2Ch (Ch =
S, Se) results in the formation of eight-membered macrocycles
of type 8Ch in good yields (Ch = S (73%), Se (74%); Scheme
2). The corresponding tellurium derivative 8Te could not be
prepared from the reaction of 9 with Na2Te or (Me3Si)2Te.
The formation of elemental tellurium was observed in both
cases (as observed as a metallic mirror and black precipitate),
presumably as a result of a complex redox reaction. The
corresponding 31P{1H} NMR spectrum indicates complex P−P
coupling reactions, which we did not further investigate. The
31P{1H} NMR spectra of 8Ch display singlets at δ(8S) = 107.8
Scheme 1).15 On the basis of our method, acyclic
Scheme 1. Condensation Reaction of R2PCl and Na2Ch To
Yield Either 6 (R = Me, Et, Ph, Tol) or 7 (R = Bu, Mes,
t
N(iPr)2, C6F5)
dichlorodiphosphazanes of type ClR′P−NR−PClR′ should
represent potential building blocks for the formation of N−
P(III)−Ch-based macrocycles [−R′P−NR−PR′−Ch−]n via
cyclocondensation reaction with Na2Ch.
In this context, we present the synthesis of the eight-
membered macrocycles 8Ch, which consist only of N, P(III),
and Ch atoms in the ring (Ch = S, Se). The use of 8Ch as
multidentate ligands for the preparation of polynuclear Ag(I)
sandwich complexes is presented.
ppm and δ(8Se) = 115.2 ppm, respectively. In addition, the 31
P
NMR spectrum of 8Se reveals an indefinable set of satellites that
can be attributed to the isotopologues containing 77Se isotope
(spin 1/2, natural isotopic abundance 7.6%).20 The 77Se NMR
spectrum of 8Se shows a pseudo-quintet at δ = 199.8 ppm,
caused by virtual coupling.21 The 1JSeP coupling constant of 125
Hz is typical for endocyclic P−Se−P fragments.15,22 Single
crystals suitable for X-ray analysis are obtained by vapor
diffusion of n-pentane into a saturated CH2Cl2 solution of 8Ch
(Figure 1). A trigonal planar geometry for the N atoms and a
trigonal pyramidal geometry for the P atoms are observed. All P
atoms in 8Ch have alternating configurations and are therefore
cis to each other, resulting a crown type conformation, as
observed for cyclo-S8. The P−N bond lengths in 8Ch (8S, P1A−
N1 1.722(2) Å, P4A−N1 1.713(2) Å; 8Se, P1A−N1 1.716(4)
Å, P4A−N1 1.704(4) Å) are comparable to those, observed in
precursor 9 (P1−N1 1.695(2) Å, P2−N1 1.702(2) Å). The P−
Ch bond lengths (8S, P1A−S1A 2.132(2) Å; 8Se, P1A−Se1A
2.282(2) Å) and the P−Ch−P angles (8S, P1A−S1A−P2A
94.86(66)°; 8Se, P1A−Se1A−P2A 92.33(6)°) are similar to
those in acyclic diphosphanylchalcoganes.15
Oxidative Ring Contraction of 8Ch To Yield 10Ch.
Reacting toluene solutions of 8Ch with elemental sulfur (S8) or
gray selenium (Segray) at 111 °C (boiling point of toluene) for
12 h result in an oxidative ring contraction to yield four-
membered rings of type 10Ch (Ch = S (73%), Se (82%);
Scheme 3).23 Few congeners of 10Ch are already literature
reported and are synthesized on the basis of reactions with
Lawesson’s24,25 and the Woollins’ reagent,26 respectively. The
31P NMR spectra of 10Ch display singlets at δ(10S) = 60.1 ppm
RESULTS AND DISCUSSION
■
Synthesis of Macrocycles 8Ch (Ch = S, Se). Reaction of
(Me3Si)2NMe with PhPCl2 under solvent free conditions gives
access to 9 as colorless crystals on multigram scale (91%,
Scheme 2).16,17 The 31P{1H} NMR spectrum of 9 reveals two
Scheme 2. Synthesis of Chlorophosphazane 9 and
a
Macrocycles 8Ch
a
(i) +(Me3Si)2NMe, −2Me3SiCl, 91%; (ii) 8S, EtCN, 10 d, rt, + Na2S,
−2NaCl, 73%; 8Se, MeCN, 4 h, rt, +Na2Se, −2NaCl, 74%.
singlets at δ = 137.1 and 134.8 ppm in an almost 1:1 ratio for
the two possible diastereomers ((R,R)/(S,S)- and meso-
isomers). The isomers are distinguishable in the 1H and
13C{1H} NMR spectra, which display two signal sets. Single
crystals of the meso-9 isomer suitable for X-ray analysis are
obtained from a saturated n-pentane solution of 9 at −35 °C,
and its molecular structure is depicted in Figure 1. A trigonal
planar geometry is observed for the N1 atom with typical P−N
bond lengths (P1−N1 1.695(2) Å, P2−N1 1.702(2) Å) being
comparable with other phosphazanes.18 The homogeneity of
the isolated bulk material was analyzed by powder X-ray
Figure 1. Molecular structures of 9, 8S, and 8Se (hydrogen atoms omitted for clarity and thermal ellipsoids displayed at 50% probability). Selected
bond lengths in Å and angles in deg: (9) P1−N1 1.695(2), P2−N1 1.702(2), P1−Cl1 2.1043(9), P1−N1−P2 111.8(1); (8S) P4A−N1 1.713(2),
P1A−N1 1.722(2), P1A−S1A 2.132(2), P1A−N1−P4A 112.1(1), P1A−S1A−P2A 94.86(6); (8Se) P4A−N1 1.704(4), P1A−N1 1.716(4), P1A−
Se1A 2.282(2), P4A−N1−P1A 113.2(2), P1A−Se1A−P2A 92.33(6).
B
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a
Scheme 3. Oxidation of 8Ch with S8 or Segray To Yield 10Ch
Figure 3. Molecular structures of 10S and 10Se (hydrogen atoms
omitted for clarity and thermal ellipsoids displayed at 50%
probability). Selected bond lengths in Å and angles in deg: (10S)
P1−N1 1.671(3), P1−S1 2.120(2), P1−S2 1.932(6), P1−N1−P2
106.7(2), P1−S1−P2 78.49(7); (10Se) P1−N1 1.691(4), P1−Se1
2.256(2), P1−Se2 2.097(6), P1−N1−P2 109.7(2), P1−Se1−P2
74.54(6).
a
Ch = S: (a) + 1/2 equiv of S8, toluene, 12 h, 111 °C, 73%; Ch = Se:
(a) + 4 equiv of Se, toluene, 12 h, 111 °C, 82%.
and δ(10Se) = 43.3 ppm. Figure 2 shows the 31P{1H} NMR
spectrum of 10Se, in which four different isotopologues are
ratios. Reacting a CH2Cl2 solution of 8Ch with AgOTf in a 2:1
ratio results in the selective formation of the mononuclear
sandwich complexes [Ag(8Ch)2]OTf (Ch = S (86%), Se (71%),
Scheme 4). The reactions of 8Ch with AgOTf in a 1:1 ratio
under the same conditions yield quantitatively the dinuclear
sandwich complexes [Ag2(8Ch)2][OTf]2 (Ch = S (87%), Se
(77%)). In the reaction of the selenium congener 8Se with
Scheme 4. Reaction of 8Ch with AgOTf in Different Ratios
a
To Give Complexes of Type [Agn(8Ch)2]OTf]n
Figure 2. Cutout of the 31P{1H} NMR spectrum of 10Se, displaying
the resonances for the different isotopologues (CD2Cl2, 300 K, 13C-
satellites are marked with “#”; unidentified species is marked with “*”).
identified (A−D). The isotopologue containing no 77Se isotope
(A) gives a singlet resonance. The isotopologue with an
endocyclic 77Se isotope (B) shows a doublet (1JPSe(endo) = 255
Hz). The isotopologue with an exocyclic 77Se isotope (C)
2
displays a dd resonance (1JPSe(exo) = 850 Hz, JPP = 7 Hz) and
a
the isotopologue with one exocyclic and one endocyclic 77Se
Yield: [Ag(8S)2]OTf, 86%; [Ag(8Se)2]OTf, 71%; [Ag2(8S)2][OTf]2,
87%; [Ag2(8Se)2][OTf]2, 77%; [Ag4(8S)2][OTf]4, 97%; [Ag3(8Se)2]-
[OTf]3, 51%.
isotope (D) is identified as a ddd (1JPSe(exo)) = 850 Hz,
1JPSe(endo) = 255 Hz, JPP = 7 Hz).27 The doublet resonance of
2
the isotopologue E with two exocyclic 77Se isotopes is expected
to be covered by the more intense signal of C due to a similar
1JPSe coupling constant, but lower abundancy. No resonance is
observed for the isotopologue F containing three 77Se isotopes
due to negligible abundance. The 77Se NMR spectrum of 10Se
shows a downfield shifted triplet at δ = 715.9 ppm for the
endocyclic Se atom due to the coupling to the two adjacent P
atoms (1JSeP = 255 Hz)15,22,26,23,28 and a dd resonance at δ =
AgOTf in a 2:3 ratio in CH2Cl2, the formation of the highly
reactive trinuclear sandwich complex [Ag3(8Se)2][OTf]3 is
observed (quantitative formation as determined by 31P NMR
spectroscopy; isolated yield 51%). However, a different reaction
outcome is observed when reacting the sulfur congener 8S with
AgOTf in CH2Cl2 with the same ratio, yielding the dinuclear
complex [Ag2(8S)2][OTf]2 as the major product. Reacting a
toluene/CH2Cl2 solution (2:1, v/v) of 8S with AgOTf in a 1:2
ratio gives the tetranuclear complex [Ag4(8S)2][OTf]4
selectively (yield 97%). When 8Se is reacted with AgOTf in a
1:2 ratio, the formation of the corresponding selenium
containing tetranuclear complex [Ag4(8Se)2][OTf]4 is not
observed, but the trinuclear complex [Ag3(8Se)2][OTf]3 is
formed quantitatively. The trinuclear complex [Ag3(8S)2]-
[OTf]3 and the tetranuclear complex [Ag4(8Se)2][OTf]4 are
not formed under these conditions.
NMR Spectroscopy of Complexes [Agn(8Ch)2]OTf]n.
The 31P NMR spectra of [Ag(8Ch)2]OTf in CD2Cl2 reveal an
A8X and a A8Z spin system (A = 31P, X = 107Ag, Z = 109Ag) due
to the two possible isotopologues containing either the 107Ag or
the 109Ag isotope. The resulting two sharp sets of doublets
indicate isochronic P atoms and consequently an equal
contribution of all P atoms in the coordination sphere of the
Ag atom in solution. The resulting two sharp sets of doublets
3
−16.1 ppm (1JSeP = 850 Hz, JSeP = 7 Hz) for the exocyclic Se
atoms.15,29 Molecular structures of 10S and 10Se were
confirmed by X-ray crystallography (Figure 3), showing
comparable structural parameters to those reported for other
congeners of 10S and 10Se, and therefore we abstain from a
detailed discussion.24,26
Synthesis of Polynuclear Silver Complexes
([Agn(8Ch)2][OTf]n). Macrocycles 8Ch represent short bite
chelates and are suitable ligands for the precise synthesis of
multinuclear metal complexes.30 Polynuclear Ag(I) complexes
represent potential catalysts,31 are interesting with respect to
their photophysical properties,32 and can be used as versatile
precursors for the synthesis of a variety of metal complexes via
transmetalation reactions.33 The presence of the additional N-
and Ch-donor sites in 8Ch may also allow the synthesis of more
complex polymetallic structures. To synthesize polynuclear
Ag(I) complexes, 8Ch were reacted with AgOTf in different
C
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indicating a suppression of the aforementioned dynamic
dissociation/association mechanism of the [OTf]− anion and
the CH3CN (Supporting Information, Figure S3).
Table 1. 31P NMR Data of Complexes [Agn(8Ch)2]n+ [300 K,
Single Crystal X-ray Diffraction of Complexes
[Agn(8Ch)2]OTf]n. The molecular structures of [Ag(8Ch)2]+,
[Ag2(8S)2]2+, [Ag2(8Se)2(EtCN)2]2+, [Ag3(8Se)2(MeCN)4]3+,
and [Ag4(8S)2][OTf]4 are displayed in Figure 4.36 Selected
geometric parameters are given in Table 2. Sandwich complexes
are observed in all cases in which the Ag atoms (n = 1−4) are
centered between two 8Ch ligands. The distances between the
ligands increases with a higher number of Ag atoms
([Ag(8S)2]+, 4.147 Å; [Ag(8Se)2]+, 4.191 Å; [Ag2(8S)2]2+,
4.565 Å; [Ag2(8Se)2(EtCN)2]2+, 4.408 Å; [Ag4(8S)4][OTf]4,
4.875 Å) but are far outside the Van-der-Waals radii of the P
atoms (ΣvdW(P−P) 3.60 Å).37 Unlike in solution, the solid state
structures of the mononuclear cations [Ag(8Ch)2]+ display the
contribution of only two P atoms of each macrocycles as the
donor for the Ag complexation. As a consequence, the Ag
atoms show a distorted tetrahedral bonding environment. The
centrosymmetric dinuclear dication [Ag2(8S)2]2+ shows also a
distorted tetrahedral geometry at both Ag atoms, in which all P
atoms of the two 8S ligands are coordinated to the Ag2 core.
Similarly, dication [Ag2(8Se)2(EtCN)2]2+ (EtCN was used as
solvent for crystallization)38 displays a centrosymmetric
dinuclear Ag complex with a distorted tetrahedral geometry
for the Ag atoms, in which each Ag atom is coordinated by
three P atoms (P2, P3, and P4 atom) and one EtCN donor.
Consequently, the P1 atom is not involved as a donor in the Ag
coordination sphere. Both [Ag 2 (8S )2 ]2 + and
[Ag2(8Se)2(EtCN)2]2+ display intramolecular π-stacking of the
phenyl substituents with an interplanar separation of 3.52 and
3.68 Å, respectively.3 9 The trinuclear cation
[Ag3(8Se)2(MeCN)4]3+ displays a triangular Ag3 core, in
which two Ag atoms are coordinated by two P atoms and
two acetonitrile molecules. The third Ag atom of the Ag3 core
coordinates to four P atoms. We abstain from a detailed
discussion of distances and angles due to the uncertainty caused
CD2Cl2 (n = 1, 2); CD3CN (n = 3, 4)]
[Agn(8S)2]n+
1J(PAg107/109), Hz
[Agn(8Se)2]n+
1J(PAg107/109), Hz
n
δ, ppm
δ, ppm
1
2
3
4
117.3
119.2
111/128
119/141
125.0
124.7
128.2
107/124
118/137
124.1
resonate at δ([Ag(8S)2]OTf) = 117.3 ppm and δ([Ag(8Se)2]-
OTf) = 124.5 ppm, respectively (Table 1). The relatively small
1JPAg coupling constants ([Ag(8S)2]OTf, JPAg(107) = 111 Hz,
1
1
1JPAg(109) = 128 Hz; [Ag(8Se)2]OTf, JPAg(107) = 107 Hz,
1JPAg(109) = 124 Hz) refer to tetracoordinated Ag atoms.34,35
CD2Cl2 solutions of the dinuclear complexes [Ag2(8Ch)2]-
[OTf]2 reveal in the 31P NMR spectra A8X2, A8Z2, and A8XZ
spin systems (A = 31P, X = 107Ag, Z = 109Ag) at
δ([Ag2(8S)2][OTf]2) = 119.2 ppm and δ[Ag2(8Se)2][OTf]2 =
124.7 ppm, respectively, due to the presence of eight isochronic
P atoms. The corresponding two triplets (A8X2, A8Z2 spin
systems) and the dd resonance (A8XZ spin system) display
1
slightly larger JPAg coupling constants than observed in the
mononuclear complexes [Ag(8Ch)2]OTf ([Ag2(8S)2][OTf]2,
1
1JPAg(107) = 119 Hz, JPAg(109) = 141 Hz; [Ag2(8Se)2][OTf]2,
1
1JPAg(107) = 118 Hz, JPAg(108) = 137 Hz). [Ag3(8Se)2][OTf]3 in
CH3CN (insoluble in CH2Cl2) displays a broad singlet at δ =
128.2 ppm. The broadening and absence of JPAg coupling might
be caused by a dynamic dissociation/association process of
CH3CN and [OTf]− anions serving as additional ligands for the
Ag atoms. Analogously, the tetranuclear complex [Ag4(8S)2]-
[OTf]4 in CH3CN (insoluble in CH2Cl2) displays a broad
singlet resonance at δ = 124.1 ppm. At lower temperatures
(+42 to −38 °C) the broad singlet splits into a multiplet,
Figure 4. Molecular structures of [Ag(8S)2]+, [Ag(8Se)2]+, [Ag2(8S)2]2+, [Ag2(8Se)2(EtCN)2]2+, [Ag3(8Se)2(MeCN)4]3+, and [Ag4(8S)2][OTf]4
(hydrogen atoms omitted for clarity and thermal ellipsoids displayed at 50% probability).
D
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Table 2. Selected Geometrical Parameters for the Crystallographically Characterized Silver Complexes [Ag(8S)2]+, [Ag(8Se)2]+,
[Ag2(8S)2]2+, [Ag2(8Se)2(EtCN)2]2+, and [Ag4(8S)2][OTf]4
Ag−P, Å
Ag−Ag, Å
P−Ch−P, deg
90.85(7)
P−N−P, deg
[Ag(8S)2]+
2.574(1)
2.574(1)
2.621(1)
2.621(1)
94.05(7)
94.73(7)
90.07(5)
113.4(3)
113.7(3)
114.1(2)
112.5(3)
113.45(9)
116.62(9)
113.8(1)
110.8(1)
120.4(2)
118.9(2)
93.64(7)
89.16(5)
[Ag(8Se)2]+
[Ag2(8S)2]2+
2.4246(4)
2.6874(5)
2.4174(6)
2.5593(6)
2.438(1)
2.6294(5)
2.6433(5)
2.5968(6)
2.9244(3)
2.9266(5)
91.23(2)
92.58(2)
100.45(6)
97.68(2)
88.93(2)
[Ag2(8Se)2(EtCN)2]2+
[Ag4(8S)2][OTf]4
2.455(1)
3.0053(5)
2.9448(5)
by severe disorder.38 In [Ag4(8S)4][OTf]4 the macrocycles 8S
are acting as tetradentate ligands to give a centrosymmetric
tetranuclear complex, where the Ag4 core forms a square plane
(sum of angles in plane, 360°; Ag1−Ag2−Ag1′, 95.95(2)°;
Ag2−Ag1−Ag2′, 84.05(2)°).
CONCLUSION
■
In conclusion, the inorganic N−P(III)−Ch-based macrocycles
8Ch were synthesized via a facile cyclocondensation reaction of
the acyclic chlorophosphazane 9 and Na2Ch (Ch = S, Se). The
oxidation reaction of 8Ch with S8 or Segray results in an
interesting ring contraction reaction to give the four-membered
P(V) rings 10Ch. The crown conformation observed in 8Ch
facilitates the preparation of transition metal sandwich
complexes, as demonstrated in the isolation of various silver
complexes including mono-, di-, tri-, and tetranuclear Ag
sandwich complexes. These complexes should facilitate trans-
metalation reactions to enable the preparation of a variety of
new inorganic homo- and heterometallic complexes, which are
part of our ongoing research.
The Ag2−O bonds (Ag2−O2, 2.731(3); Ag2−O5,
2.747(4)°) are longer than the Ag1−O bonds (Ag1−O1,
2.540(3)°; Ag1−O4, 2.573(4)°) but are still inside the Van-der-
Waals radii (ΣvdW(Ag−O) 3.24 Å).37 In consideration of the
Ag1···Ag2 interactions, the Ag atoms show a slightly distorted
octahedral bonding environment. Interestingly, obtuse P−S−P
and P−N−P angles are observed in [Ag4(8S)2][OTf]4
compared to the free ligand (P1−S1−P2, 94.86(6)°; P1−
N1−P4, 112.1(1)°) or the mono- and dinuclear complexes
[Ag(8S)2]+ and [Ag2(8S)2]2+ caused by the increased space
requirement of the Ag4 core. Attractive argentophilic
interactions can be anticipated in the dinuclear complexes, as
indicated by the short Ag···Ag distances in [Ag2(8S)2]2+ and
[Ag2(8Se)2(EtCN)2]2+ (ΣvdW(Ag−Ag) 3.44 Å37).40 Several, weak
argentophilic interactions are also observed in the Ag4 cluster in
complex [Ag4(8S)2][OTf]4 as evidenced by the short Ag1···Ag2
and Ag2′···Ag1′ distances.41 Some weak intermolecular π−π
interactions are observed (interplanar separation: 3.37−3.7 Å),
which result in the formation of one-dimensional strands
(Figure 5).
ASSOCIATED CONTENT
* Supporting Information
The Supporting Information is available free of charge on the
ACS Publications website at DOI: 10.1021/acs.inorg-
chem.7b00141.
■
S
Description of the materials and synthesis methods, 31P
NMR and 31P−31P EXSY NMR spectra, powder X-ray
diffractogram, description of X-ray structure refinement,
and crystallographic and structure refinement data
(PDF)
Crystal data in cif format (ZIP)
AUTHOR INFORMATION
Corresponding Author
*J. J. Weigand. E-mail: jan.weigand@tu-dresden.de.
■
ORCID
Jan J. Weigand: 0000-0001-7323-7816
Notes
The authors declare no competing financial interest.
ACKNOWLEDGMENTS
■
This work was supported by the Fonds der Chemischen
Industrie (FCI, scholarship for F.H.) and the European
research council (ERC, SynPhos 307616).
REFERENCES
■
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