New group 11 complexes with metal-selenium bonds of methyldiphenylphosphane selenide: A solid state, solution and theoretical investigation

Article abstract of DOI:10.1039/c1dt11268f

Reactions between methyldiphenylphosphane selenide, SePPh₂Me, and different group 11 metal starting materials {CuCl, [CuNO ₃(PPh₃)₂], AgOTf, [AgOTf(PPh₃)] (OTf = OSO₂CF₃), [AuCl(tht)], [Au(C₆F ₅)(tht)] and [Au(C₆F₅)₃(tht)] (tht = tetrahydrothiophene)} were performed in order to obtain several new species with metal-selenium bonds. The new complexes [CuCl(SePPh₂Me)] (1), [AgOTf(SePPh₂Me)] (2), [AuCl(SePPh₂Me)] (5), [Au(C ₆F₅)(SePPh₂Me)] (6) and [Au(C₆F ₅)₃(SePPh₂Me)] (7) were isolated and structurally characterized in solution by multinuclear NMR spectroscopy ( ¹H, ³¹P, ⁷⁷Se and ¹⁹F where appropriate). Solid products were isolated also from the reactions between SePPh₂Me and [CuNO₃(PPh₃)₂] or [AgOTf(PPh₃)], respectively. NMR experiments, including low temperature ¹H and ³¹P NMR, revealed for them a dynamic behaviour in solution, involving the transfer of selenium from PPh₂Me to PPh₃. In case of the isolated silver(i) containing solid an equilibrium between, respectively, monomeric [AgOTf(PPh₃)(SePPh ₂Me)] (3) and [AgOTf(PPh₂Me)(SePPh₃)] (4), and dimeric [Ag(PPh₃)(μ-SePPh₂Me)]₂(OTf) ₂ (3a) and [Ag(PPh₂Me)(μ-SePPh₃)] ₂(OTf)₂ (4a) species was observed in solution. In case of the isolated copper(i) containing solid the NMR studies brought no clear evidence for a similar behaviour, but it can not be excluded in a first stage of the reaction. However the transfer of selenium between the two triorganophosphanes takes place also in this case, but the NMR spectra suggest that the final reaction mixture contains the free triorganophospane selenides SePPh₂Me and SePPh₃ as well as the complex species [CuNO₃(PPh₃)₂], [CuNO₃(PPh ₂Me)₂] and [CuNO₃(PPh₃)(PPh ₂Me)] in equilibrium. Single-crystal X-ray diffraction studies revealed monomeric structures for the gold(i) 6 and gold(iii) 7 complexes. In case of compound 6 weak aurophilic gold(i)...gold(i) contacts were also observed in the crystal. DFT calculations were performed in order to understand the solution behaviour of the silver(I) and copper(i) species containing both P(iii) and P(v) ligands, to verify the stability of possible dimeric species and to account for the aurophilic interactions found for 6. In addition, the nature of the electronic transitions involved in the absorption/emission processes observed for 6 and 7 in the solid state were also investigated by means of TD-DFT calculations. The Royal Society of Chemistry.

Full text of DOI:10.1039/c1dt11268f

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PAPER
New group 11 complexes with metal–selenium bonds of
methyldiphenylphosphane selenide: a solid state, solution and theoretical
investigation†
Alexandra Pop,a Anca Silvestru,*a M. Concepcio´n Gimeno,b Antonio Laguna,b Monika Kulcsar,b
Massimiliano Arca,c Vito Lippolis*c and Anna Pintusc
Received 3rd July 2011, Accepted 2nd September 2011
DOI: 10.1039/c1dt11268f
Reactions between methyldiphenylphosphane selenide, SePPh2Me, and different group 11 metal
starting materials {CuCl, [CuNO3(PPh3)2], AgOTf, [AgOTf(PPh3)] (OTf = OSO2CF3), [AuCl(tht)],
[Au(C6F5)(tht)] and [Au(C6F5)3(tht)] (tht = tetrahydrothiophene)} were performed in order to obtain
several new species with metal–selenium bonds. The new complexes [CuCl(SePPh2Me)] (1),
[AgOTf(SePPh2Me)] (2), [AuCl(SePPh2Me)] (5), [Au(C6F5)(SePPh2Me)] (6) and
[Au(C6F5)3(SePPh2Me)] (7) were isolated and structurally characterized in solution by multinuclear
NMR spectroscopy (1H, 31P, 77Se and 19F where appropriate). Solid products were isolated also from the
reactions between SePPh2Me and [CuNO3(PPh3)2] or [AgOTf(PPh3)], respectively. NMR experiments,
including low temperature 1H and 31P NMR, revealed for them a dynamic behaviour in solution,
involving the transfer of selenium from PPh2Me to PPh3. In case of the isolated silver(I) containing
solid an equilibrium between, respectively, monomeric [AgOTf(PPh3)(SePPh2Me)] (3) and
[AgOTf(PPh2Me)(SePPh3)] (4), and dimeric [Ag(PPh3)(m-SePPh2Me)]2(OTf)2 (3a) and
[Ag(PPh2Me)(m-SePPh3)]2(OTf)2 (4a) species was observed in solution. In case of the isolated copper(I)
containing solid the NMR studies brought no clear evidence for a similar behaviour, but it can not be
excluded in a first stage of the reaction. However the transfer of selenium between the two
triorganophosphanes takes place also in this case, but the NMR spectra suggest that the final reaction
mixture contains the free triorganophospane selenides SePPh2Me and SePPh3 as well as the complex
species [CuNO3(PPh3)2], [CuNO3(PPh2Me)2] and [CuNO3(PPh3)(PPh2Me)] in equilibrium.
Single-crystal X-ray diffraction studies revealed monomeric structures for the gold(I) 6 and gold(III) 7
complexes. In case of compound 6 weak aurophilic gold(I) ◊ ◊ ◊ gold(I) contacts were also observed in the
crystal. DFT calculations were performed in order to understand the solution behaviour of the silver(I)
and copper(I) species containing both P(III) and P(V) ligands, to verify the stability of possible dimeric
species and to account for the aurophilic interactions found for 6. In addition, the nature of the
electronic transitions involved in the absorption/emission processes observed for 6 and 7 in the solid
state were also investigated by means of TD-DFT calculations.
Introduction
aFaculty of Chemistry and Chemical Engineering, “Babes-Bolyai” Univer-
Triorganophosphane chalcogenides (Se, Te) have attracted much
sity, RO-400028, Cluj-Napoca, Romania. E-mail: ancas@chem.ubbcluj.ro;
interest in recent years due to their ability to form complexes
Fax: 0040 264 590818; Tel: 0040 264 593833
with metal–chalcogen bonds,1–12 which are promising candidates as
bDepartamento de Qu´ımica Inorga´nica, Instituto de S´ıntesis Qu´ımica
precursors for semiconductors.3–6 The soft chalcogen and the polar
y
Cata´lisis Homoge´nea, Universidad de Zaragoza-C.S.I.C, E-50009,
Zaragoza, Spain
phosphorus–chalcogen bond make them suitable to coordinate
soft metal centres.
cDipartimento di Chimica Inorganica ed Analitica, Universita` degli Studi di
Cagliari, S.S. 554 Bivio per Sestu, 09042, Monserrato (CA), Italy
Several studies were reported in recent years related to metal
complexes of triorganophosphane chalcogenides. Few adducts
of main group metals of type [MX3(EPR3)] (M = Al; E = O,
† Electronic supplementary information (ESI) available: X-ray crystallo-
graphic data in CIF format for 6 and 7; Figures S1–S3 contain NMR
spectra revealing the solution behaviour of the solid species isolated in
reactions (iii) and (vii); Tables S1–S6 report the optimized geometries for
complexes 3, 3a, 6, 6¢, 7 and 8; Tables S7–S9 summarise the main electronic
transitions calculated at TD-DFT level for 6, 6¢, and 7. CCDC reference
numbers 827811 and 827812. For ESI and crystallographic data in CIF or
other electronic format see DOI: 10.1039/c1dt11268f
S, Se; X = Cl, Br,7,8 M = Sb, E = O, S, Se; X = Cl, Br, I13–17
)
and [SbCl5(EPR3)] (E = O, S, Se)18 were described. Among
the transition metal containing species only few triorganophos-
phane tellurides of tungsten, gold, silver and copper were either
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investigated in solution or isolated and structurally characterized
as short living species.1,9 In the presence of Lewis acids or free
phosphanes such metal complexes are kinetically labile and suffer
decomposition, depositing chalcogen and forming a more stable
triorganophosphane complex. Such a behaviour was observed
for [MCl(TePR3)] complexes (R = Pri, M = Cu, Au, Ag; R =
But, M = Ag).19 Dimeric or polymeric associations were found in
[Ag2(NMs2)2(TePPri3)2], [Ag2(NMs2)(TePPri3)4]+[NMs2]-·CH3CN
(NMs = dimethylsulfonylamide) and [Ag(EPPri3)2]+[SbF6]- (E = Se,
Te), respectively.19 Several group 11 complexes were described with
the flexible 1,1¢-bis(diphenylselenophosphoryl)ferrocene ligand
which was found to act as bridging or trans chelating moiety.20–22
Ligands of type Ph2P(Se)(CH2)nP(Se)Ph2 act as bridging units
towards copper or gold, involving either both chalcogen atoms or
only one of them in metal coordination.23–27
We report here on the synthesis and spectroscopic characteri-
zation of several new group 11 complexes with the neutral ligand
SePPh2Me. A deeper understanding of the coordination chemistry
of triorganophosphane selenides towards coinage metal ions (Cu,
Ag, Au) can open to future applications of the related complexes
featuring Cu–, Ag–, or Au–chalcogen bonds, which to date are
rather uncommon and not easy to handle.
With the exception of compound 5 which was isolated as a
brownish oil, all the other species described in this paper are
crystalline solids (colourless – species 1–4 and 7, or pale yellow
compound 6).
Spectroscopic characterization
1H and 31P NMR data for the complexes containing only one type
of organophosphorus ligand (SePPh2Me, i.e. compounds 1, 2, 5–7)
suggest the existence of only one species in solution, while for the
complexes containing more than one type of organophosphorus
ligands the NMR spectra suggest a dynamic behaviour. However,
for the phenyl and the methyl groups attached to phosphorus the
1H NMR spectra exhibit resonances with the expected pattern
due to the proton-proton and phosphorus-proton couplings,
respectively. The 31P NMR spectra of the complexes 1, 2 and 5–7
exhibit singlet resonances corresponding to the SePPh2Me moiety,
with characteristic 77Se and 13C satellites, (d 21.17 for 1, 23.1 for
5, 24.2 for 6 and 26.05 ppm for 7, respectively, in CDCl3 solutions
and 27.7 ppm for 2 in acetone-d6). A significant decrease of the
1J(SeP) coupling constant was observed in all these species (range
535.4–598.5 Hz) in comparison with the free ligand SePPh2Me [d
23.24 ppm, 1J(SeP) 717.3 Hz, in CDCl3 and d 23.26 ppm, 1J(SeP)
733.8 Hz in acetone-d6].
Results and discussion
In case of the gold complexes 6 and 7 the 19F NMR spectra
contain three resonances with the expected patterns for the C6F5
groups. In case of the square-planar compound 7 the three C6F5
groups attached to gold give two different 19F sets of resonances in
a 1 : 2 molar ratio for the non-equivalent C6F5 groups (one of them
trans to selenium and the other two trans each other, respectively).
Synthesis
The triorganophosphane selenide ligand SePPh2Me was reacted in
a 1 : 1 molar ratio with the appropriate group 11 metal containing
starting material as depicted in Scheme 1.
Scheme 1
12480 | Dalton Trans., 2011, 40, 12479–12490
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The ESI+ MS spectrum of compound 1 revealed two peaks
at m/z 720.8 (10%, [(CuSePPh2Me)2Cl+]) and at m/z 622.7
+
(100%, [Cu(SePPh2Me)2 + H]), while the ESI- MS spec-
trum presents a peak at m/z 613.7 (100%), corresponding to
-
the [Cu(PPh2Me)(SePPh2Me)Cl2 ] species. The silver complex 2
presents in the ESI+ spectrum a peak at m/z 559.4 (100%, [M+ +
Na]) and in the ESI- spectrum a peak at m/z 406.7 corresponding
-
to the anion [Ag(OTf)2 ].
This behaviour suggests in case of compounds 1 and 2 the
existence of only one species in solution, at least at room
temperature, either monomeric (Scheme 2, a), or dimeric with
either selenium (Scheme 2, b) or an anionic ligand (Cl- or OTf-)
(Scheme 2, c) bridging moieties, but with equivalent SePPh2Me
ligands.
Fig. 1 VT 31P NMR spectra (-15 ∏ +14 ppm region) of species 3 (A, *)
and 3a (A, ·) and 4 and 4a (B), respectively.
and d 9.64 ppm [1J(107Ag–31P) 526.3 Hz, 1J(109Ag–31P) 460.8 Hz],
and they correspond to the monomeric 3 and the dimeric 3a
species (Scheme 1), respectively. In accordance with the previously
reported observation that the 1J(107Ag–31P) coupling constants
increase with decreasing of the Ag–P distance32 and that they
are inversely proportional with the coordination number of the
silver atom,31 the resonance at d 8.61 ppm could be assigned
to a monomeric species containing a dicoordinate silver atom,
while the resonance at d 9.64 ppm could be assigned to a dimeric
species containing a tricoordinate silver atom. The second broad
resonance (d -7.3 ppm at room temperature) gives rise at low
temperature to a broad doublet [at -60 ◦C d -8.48 ppm, 1J(Ag–P)
594.8 Hz]. For the species 4 and 4a (Scheme 1) we presume a similar
behaviour with that one described before for species 3 and 3a
(Scheme 1), but the corresponding resonances are not well resolved
in this case. A further lowering of the temperature did not result
in a better separation of the resonances. By contrast, a broadening
in the base line of these resonances was observed. Using the
Eyring◦relation33 we determined at the coalescence temperature
Tc = 5 C a medium value for the free enthalpy DG# of 15.21 kcal
mol-1 for the equilibrium process between the monomeric 3 and
the dimeric 3a species depicted in Scheme 1. According to the
intensity of the resonances, the monomeric species is predominant
in solution at low temperature. Similarly, for the equilibrium
related to the monomeric [Ag(PPh2Me)(SePPh3)]+ (4) and the
dimeric [Ag(PPh2Me)(SePPh3)]22+ (4a) species a medium value for
the free enthalpy DG# of 11.96 kcal mol-1 was calculated at the
coalescence temperature Tc = -20 ◦C from the 31P NMR data.
The aliphatic region of the 1H NMR spectra changed at
low temperature to two broad resonances for the PPh2Me and
SePPh2Me protons, respectively (see ESI, Fig. S2†). The 1H NMR
resonances at low temperature, even for the methyl groups attached
to phosphorus in the two species, undergo a behaviour consistent
with a very slow rotation of the organic groups around the Se–Ag
and P–Ag bonds, respectively, the well defined doublet resonances
in the aliphatic region at room temperature become very large,
broad singlet signals at low temperature.
Scheme 2
The room temperature 31P NMR spectra of the solid products
isolated from reactions (iii) and (vii) (Scheme 1), respectively, both
in CDCl3 or acetone-d6 solution, show four different resonances,
two of them sharp, accompanied by 77Se satellites, corresponding
to the P(V) Se moieties and the other two broad, belonging
to P(III) environments (See ESI Fig. S1†). At a first glance, this
pattern suggest an equillibrium mixture of two species in each
case, containing both phosphorus(III) and phosphorus(V) ligands.
Solution behaviour of the silver(I) species of type
{[Ag(PPhxMe3 -x)(SePPhyMe3 -y)]OTf}n
In case of the solid product isolated from reaction (iii) (Scheme
1) the 1H NMR spectrum (acetone-d6) shows in the aliphatic
region two resonances (d 1.85 ppm, JPH 5.9 Hz and d 2.60
2
2
ppm, JPH 13.6 Hz). The observed coupling constants are in
accordance with the presence of both a P(III) and a P(V) species
containing PMe protons. Taking in account these results and the
fact that for phosphine complexes of coinage metals a dynamic
behaviour in solution, involving either M–PPh3 and/or S–MPPh3
bond dissociation, is well known,28–31 low temperature NMR
experiments were performed (Fig. 1), both for the isolated solid
product and for a 1 : 1 : 1 reaction mixture of PPh3 + AgOTf +
SePPh2Me realized directly in the NMR tube. We obtained the
same spectra in both cases. While the 31P resonances assigned
to the P Se moieties remained almost unchanged with the
temperature variation, the resonances assigned to Ag(PPh3) (d
10.5 ppm, broad) and Ag(PPh2Me) (d -7.3 ppm, broad), in
acetone-d6, changed according to an equilibrium between dimeric
and mono◦meric species, as depicted in Scheme 1.
At -60 C, instead of the large resonance at d 10.5 ppm, two
resonances were observed, with a pattern of doublet of doublets
each of them falling at d 8.61 and 9.64 ppm, respectively. This
pattern is determined by the 107Ag–31P and 109Ag–31P couplings. In
case of the discussed silver species the observed coupling constants
A coordination pattern of the triorganophosphane chalco-
genide ligand with the chalcogen atom bridging two metal centres
are: d 8.61 ppm [1J(107Ag–31P) 618.9 Hz, J(109Ag–31P) 539.6 Hz]
1
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Table 1 NMR data for starting materials and complexes involving Ag(I) and Cu(I) species
acetone-d6
CDCl3
Compound
d
31P [ppm]
1JSeP [Hz]
Compound
d
31P [ppm]
1JSeP [Hz]
PPh3
PPh2Me
SePPh3
SePPh2Me
[AgOTf(PPh3)]
[AgOTf(SePPh2Me)] (2)
[AgOTf(PPh3)] + SePPh2Me (solid product-reaction (iii), RT)
[AgOTf(PPh3)(SePPh2Me)] (3) +
[Ag(PPh3)(m-SePPh2Me)]2(OTf)2 (3a)
-5.81s
PPh3
PPh2Me
SePPh3
-6.0s
-26.84s
35.5s
35.14s
23.6s
12.53d, br.
27.7s
747.2
733.8
738
717.3
SePPh2Me
[CuNO3(PPh3)2]
[CuCl(SePPh2Me)] (1)
[CuNO3(PPh3)2] + SePPh2Me (solid product-reaction (vii), RT)
[CuNO3(PPh2Me)2]
[CuNO3(PPh3)2]
[CuNO3(PPh3)(PPh2Me)]
SePPh2Me
SePPh3
[CuNO3(PPh3)2] + SePPh2Me
(RT, NMR tube scale reaction)
23.24s
-1.87, br.
21.17s
535.4
598.5
10.5s
25.8s
-17.4s, br.
-1.2s, br.
595.4
[AgOTf(PPh2Me)(SePPh3)] (4) +
[Ag(PPh2Me)(m-SePPh3)]2(OTf)2 (4a)
PPh3 + AgOTf + SePPh2Me
-7.3s, br.
33.6s
10.3s, br.
25.8s
-7.4s,br.
33.7s
23.3s
35.4s
-17.9s, br.
-1.4s, br.
23.2s
715.3
728.0
625.0
602.9
629.4
564.0
(RT, NMR tube scale reaction)
715.5
728.1
35.3s
SePPh3 + AgOTf (RT, NMR tube scale reaction)
[AgOTf(SePPh3)] 38.3s
PPh3 + SePPh2Me (RT, NMR tube scale reaction)
PPh2Me
PPh3
SePPh2Me
SePPh3
-23.0s, br.
-5.5s, br.
23.2s
717.0
728.8
35.3s
was previously described in solid state for other sulfur, selenium
or tellurium containing ionic species.19,23,24,26,31
be considered as forming two sets of resonances, similarly to
the situation described before for the silver(I) complex species
3, 3a and 4, 4a. The 77Se NMR spectrum presents two doublets,
one of them at d -266.3 ppm [1J(SeP) 728.8 Hz] and the other
at d -275.2 ppm [1J(SeP) 715.5 Hz]. These values are almost
identical to those found for the free triorganophosphane selenides
SePPh2Me and SePPh3 (Table 1). Moreover, the31P NMR chemical
shifts are similar to those observed for the species SePPh2Me,
SePPh3 and [CuNO3(PPh3)2], respectively (Table 1). The fourth
resonance at d -17.4 ppm (in acetone-d6) was tentatively assigned
to [CuNO3(PPh2Me)2]. Taking in account this similarity, we
presume that even if in reaction (vii) an equilibrium process
involving both transfer of selenium from SePPh2Me to PPh3 and
association in dimeric units can take place in a first instance, as
depicted in Scheme 1, due to the high lability of the resulted
copper(I) species and the overcrowded metal center, subsequent
processes of dissociation/recombination occurred, resulting in
SePPh2Me, SePPh3, [CuNO3(PPh2Me)2], [CuNO3(PPh3)2] and
[CuNO3(PPh3)(PPh2Me)] species (Scheme 1). An evidence in this
sense is also the fact that attempts to grow single-crystals of the
solid isolated from this reaction resulted in the isolation of SePPh3
or [CuNO3(PPh3)2].
Low temperature 31P NMR spectra of the copper species
brought no clear evidence for an equilibrium between a mixture of
monomeric (8 and 9) and dimeric (8a and 9a) species, as was de-
scribed above for the silver(I) complex species 3 and 4, respectively,
but such a dimerization process can not be excluded as occurring
in the first stage of the reaction. At -75 ◦C, the two 31P resonances
corresponding to the phosphines, PPh3 and PPh2Me, respectively,
attached to copper have an aspect of multiplets. This aspect
suggests the existence of a third bis(triorganophosphane)copper(I)
species in solution, i.e. [CuNO3(PPh3)(PPh2Me)], and it might be
determined by very close chemical shift values of the PPh3 and
PPh2Me ligands in the three types of bis(triorganophosphane)
copper(I) complexes and by the fact that at such low temperature
The 19F NMR spectrum of the solid product isolated from
reaction (iii) exhibits only one singlet resonance (d -78.5 ppm),
close to the value found in the 19F NMR spectrum of com-
plex 2 (-79.8 ppm) and to that found for the ionic species
[Ag(PPh3)(SCN4Me)]2(OTf)2 (-77.9 ppm).31 The IR spectra of the
silver containing species show bands at 1280(vs), 1218(vs), 1155(s)
and 1021(vs) cm-1 (compound 2) and at 1262(vs), 1223(s), 1151(s)
and 1024(s) cm-1 (the solid isolated from reaction iii), respectively,
suggesting a ionic character for the triflate group.22,34
The 77Se NMR spectra for the solid isolated from reaction
(iii) (Scheme 1) exhibit two doublet resonances, low field shifted
in comparison with the free ligand (d -250.3 and -241.2 ppm
vs. -294.0 ppm for the free ligand). A significant difference
1
was also observed in the coupling constant J(77Se–31P) for the
free ligands (SePPh2Me and SePPh3) and the silver complex
species detected in solution ([AgOTf(PPh3)(SePPh2Me)] and
[AgOTf(PPh2Me)(SePPh3)]), as can be seen from the NMR data
listed in Table 1.
The mass spectra (APCI+) of the solid isolated from
reaction (iii) present peaks corresponding to the ion
[AgOTf(PPh3)(SePPh2Me)+] [m/z 800.9(80%)] as well as the ion
[Ag(PPh3)(SePPh2Me)+ + Se] [m/z 729.6(100%)].
Solution behaviour of the solid isolated from the reaction between
[CuNO3(PPh3)2] and SePPh2Me
Apparently, the solid isolated from reaction (vii) (Scheme 1) proved
to have a similar behaviour in solution as it was described above
for the silver species {[Ag(PPhxMe3 -x)(SePPhyMe3 -y)]OTf}n. The
1H and 31P NMR spectra recorded at room temperature either
in CDCl3 or acetone-d6 solution present four resonances, two
of them at high field, sharp and accompanied by 77Se satellites,
and the other two broad, at low field. These four signals might
12482 | Dalton Trans., 2011, 40, 12479–12490
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◦
˚
Table 2 Selected bond distances (A) and angles ( ) for compounds 6
and 7
even the two phosphorus atoms in species containing the same
triorganophosphanes attached to the metal center are no more
equivalent (see ESI, Fig. S3†).
The room temperature 77Se NMR spectrum for the solid isolated
from reaction (vii) in Scheme 1, as well as for a reaction mixture
of [CuNO3(PPh3)2] and SePPh2Me in a 1 : 1 molar ratio realized
directly in the NMR tube, presents two doublets, one of them at
d -266.3 ppm [1J(PSe) 728.8 Hz] and the other at d -275.2 ppm
[1J(PSe) 715.5 Hz].
In order to bring more arguments in the favour of the dynamic
processes described before, for both the silver(I) and the copper(I)
species containing both P(III) and P(V) ligands, we performed
further NMR experiments reacting directly in the NMR tube
(a) a 1 : 1 reaction mixture of SePPh3 and AgOTf and (b) a 1 : 1
reaction mixture of PPh3 and SePPh2Me. In first case the d(31P)
and d(77Se) values for the P(V) species are shifted in comparison
with those observed for the Ag(I) species described above, while in
the second case the d(31P) and d(77Se) values are almost identical
to those observed for the Cu(I) species (Table 1). Reaction (b)
revealed that the transfer of selenium from a P(V) to a P(III) species
according to eqn (1) takes place even in the absence of a metal
center, as it was previously described and documented both by
experimental and computational methods for few other couples
of organophosphorus species of type EPR3 and PR¢3 (E = O, S,
Se).35–37
6
7
Au1–C1
Au1–Se1
Au1 ◊ ◊ ◊ Au1¢
Se1–P1
P1–C10
P1–C21
P1–C11
2.059(7)
Au1–C1
Au1–C11
Au1–C21
Au1–Se1
Se1–P1
P1–C30
P1–C31
P1–C41
2.073(5)
2.055(5)
2.070(5)
2.5128(7)
2.1787(14)
1.794(5)
1.811(5)
1.805(5)
2.4353(11)
3.3387(7)
2.1769(18)
1.798(7)
1.804(7)
1.819(7)
C1–Au1–Se1
C1–Au1 ◊ ◊ ◊ Au1¢
Se1–Au1 ◊ ◊ ◊ Au1¢
P1–Se1–Au1
C10–P1–C21
C10–P1–C11
C21–P1–C11
C10–P1–Se1
C21–P1–Se1
C11–P1–Se1
176.72(16)
108.06(16)
75.22(2)
94.05(5)
106.5(3)
107.8(3)
108.3(3)
112.4(2)
107.9(2)
113.8(2)
C11–Au1–Se1
C21–Au1–Se1
C1–Au1–Se1
C11–Au1–C21
C11–Au1–C1
C21–Au1–C1
P1–Se1–Au1
C30–P1–C41
C30–P1–C31
C41–P1–C31
C30–P1–Se1
C41–P1–Se1
C31–P1–Se1
174.00(14)
92.88(13)
89.21(13)
89.40(19)
88.63(19)
177.63(19)
102.98(4)
110.1(3)
107.5(2)
106.6(2)
110.34(18)
114.05(17)
108.02(17)
(1)
PPh3 + SePPh2Me ꢀ SePPh3 + PPh2Me
The mass spectra (ESI+) of the solid resulted from re-
action (vii) contains peaks corresponding to the species
[CuNO3(PPh3)(SePPh2Me)+] (m/z 667.5, 5%), [Cu(PPh3)-
(SePPh2Me)+] (m/z 605.5, 72%) and [CuNO3(PPh3)(PPh2Me)+]
(m/z 588.5, 100%).
Crystal and molecular structure of compounds 6 and 7
The ORTEP-like representations for compounds 6 and 7 are
depicted in Fig. 2 and Fig. 3, respectively, while relevant bond
distances and angles are given in Table 2.
Fig. 3 ORTEP plot of [Au(C6F5)3(SePPh2Me)] (7). The atoms are drawn
with 50% probability ellipsoids.
The organophosphorus(V) ligand SePPh2Me behaves as a
monometallic monoconnective moiety in both gold complexes,
being attached to the metal centre through selenium. In complex 6
the coordination geometry about the gold(I) atom is linear, slightly
distorted [C1–Au1–Se1 176.72(16)◦].
Fig. 2 ORTEP plot of [Au(C6F5)(SePPh2Me)] (6). The atoms are drawn
with 50% probability ellipsoids.
Taking into account the weak Au ◊ ◊ ◊ Au contact, a T-shaped co-
ordination geometry can be assigned [Se1–Au1 ◊ ◊ ◊ Au1¢ 75.22(2)◦
and C1–Au1 ◊ ◊ ◊ Au1¢ 108.06(16)◦]. In complex 7 the gold atom
has a square planar geometry. The C6F5 group trans to se-
lenium is twisted to almost 90◦ with respect to the other
two pentafluorophenyl rings. The phosphorus atoms have tetra-
hedral coordination geometries in both complexes, while the
selenium atoms have distorted pseudo tetrahedral coordination
The gold complexes 6 and 7 are essentially monomeric species,
although in complex 6 the gold–gold distance between two
neighbouring molecules is just at the limit below the sum of the
˚
van der Waals radii for gold [3.3387(7) A vs. RrvdW(Au,Au) 3.40
A ].
38
˚
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◦
˚
Table 3 Luminescent spectral data for the ligand SePPh2Me and com-
pounds 6 and 7 in solid state
Table 4 Selected bond distances (A) and angles ( ) calculated for 3 (M =
Ag) and 8 (M = Cu) at DFT level
lmax (298 K)
lmax (77 K)
3a
3b
8a
8b,c
Compound
emission (excitation) emission (excitation)
P1–M
Se–M
P2–Se
P2–Se–M
P1–M–Se
2.411
2.518
2.191
97.64
177.39
2.419
2.542
2.193
96.19
176.67
2.232
2.323
2.194
95.52
177.28
2.233
2.328
2.201
95.75
177.76
SePPh2Me
448 (398)
—
440 (385)
480 shoulder (385)
500 (395)
[Au(C6F5)(SePPh2Me)] (6)
[Au(C6F5)3(SePPh2Me)] (7) 396, 482 (283)
360, 446 broad (310)
a Calculated in the gas phase. b Calculated in acetone (PCM-IEF). c P–Se
distance = 2.126 A for SePPh2Me in the gas phase.
geometries [P1–Se1–Au1 94.05(5)◦ in 6 and 102.98(4)◦ in 7,
˚
˚
respectively]. The P Se distances [P Se 2.1769(18) A in 6 and
˚
2.1787(14) A in 7, respectively] are of similar magnitude to those
found in [Au(C6F5)2{SePPh2CHPPh2SeAu(C6F5)3}] [2.1814(8)
only one emission is observed and it is shifted towards low energy,
indicating that the origin of the emission is probably intraligand
but modified due to the coordination to the metal and the presence
of gold(I) ◊ ◊ ◊ gold(I) interactions in the structure.
27
˚
and 2.1716(10) A] or [Au(C6F5)2{(SePPh2)2N}] [2.1970(6) and
13
˚
2.1953(7) A], but longer than in (Se PPh2)2NH [2.085(1) and
39
˚
2.101(1) A].
˚
The selenium-gold distances [2.4353(11) A in 6 and 2.5128(7)
˚
A in 7, respectively], are close to those found in other gold(I)
˚
Theoretical calculations on 3, 8, 3a, and 8a
or gold(III) complexes with P–Se–Au bonds, i.e. 2.4352(3) A
˚
in [Au2{(SePPh2)2N}(PPh3)2]OTf, 2.4808(3) and 2.4832(3) A
One of the most intriguing results arising from the spectroscopic
NMR measurements discussed above is the alleged tendency of
both species 3 and 4 to dimerize in solution to give 3a and 4a,
respectively. In order to ascertain the nature of such dimers, DFT
calculations have been carried out on 3 and 3a.
in [Au(C6F5)2{(SePPh2)2N}],13 2.4639(4) and 2.4940(4) A in
˚
[Au(C6F5)2{SePPh2CHPPh2SeAu(C6F5)3}].27
Luminescence studies
The diffuse reflectance ultraviolet visible spectra (DRUV) were
recorded for the gold complexes 6 and 7. The spectrum of complex
6 consists of a band with two maxima at 231 and 260 nm and
that of 7 of a band with a maximum at 276 nm. Both complexes
are weakly emissive in the solid state, complex 6 only at 77 K
and complex 7 at room temperature and at 77 K too. Complex 6
displays one emission (Table 3) at 500 nm (Fig. 4) and complex
7 shows two emissions, one at 360 and the other one, a not well
resolved structured band, at about 446 nm.
The optimized structure of 3 shows the silver(I) cation
linearly coordinated by the triphenylphosphine and the
methyldiphenylphosphine selenide (Se–Ag–P angle = 177.39◦),
with the P Se bond disposed almost orthogonally to the P1–
Ag–Se fragment (Table 4).
NBO charge distribution shows that the chalcogen atom
features the most negative charge (QSe = -0.396 e in 3 as compared
to QSe = -0.499 e in SePPh2Me), while the silver atom is positively
charged (QAg = 0.373 e). In addition, the Kohn–Sham Highest
Occupied Molecular Orbital (KS-HOMO) calculated for 3 shows a
large contribution from the lone pair located on the selenium atom
(Fig. 5), while the LUMO is mainly built up of the antibonding s-
in-nature MO of the P Se bond. Interestingly, LUMO+1 shows a
large contribution from the empty 5s orbital of the silver atom. In
order to verify whether the electronic structure calculated for 3 is
preserved in the solvent medium (acetone) adopted for 1H-NMR
measurements, the geometry optimization was also performed
according to the IEF-PCM approach.
Fig. 4 Excitation (dashed line) and emission (straight line) spectrum of
complex 6 at 77 K.
The ligand SePPh2Me is also emissive at room temperature and
at 77 K. At room temperature it shows an emission at 448 nm and at
77 K there is a maximum at 440 nm with a shoulder at 480 nm. The
emissions observed in the gold(III) derivative 7 resembles those of
the ligand, then the origin of the emissions is based on intraligand
transitions (IL), whereas in complex 6 with a gold(I) fragment
Fig. 5 KS-HOMO drawing calculated for 3 in the gas phase. Cutoff value
0.05 e.
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Table 5 Selected bond distances (A) and angles ( ) calculated for 3a at
Ag ◊ ◊ ◊ Se distance between the two monomers is remarkably
shortened (2.998 A) and the distortions in the two units of 3a
DFT level. Atom labeling as in Fig. 6
˚
with respect to the optimized structure of 3 are more pronounced,
with the coordination sphere around the AgA ion involved into
the interaction with the triorganophosphane chalcogenide ligand
tending to a trigonal planar three-coordination.
The head-to-tail conformation calculated for 3a supports the
hypothesis that indeed both Ag centers could be alternatively
involved in the Ag ◊ ◊ ◊ Se contact discussed above, so that a fast
equilibrium on NMR time scale between the dimer featuring the
AgA ◊ ◊ ◊ SeB interaction and the dimer featuring the AgB ◊ ◊ ◊ SeA
contact would justify the presence in the 31P NMR spectrum at
room temperature of only two 31P resonances for the dimeric
species.
3aa,c
3aa,d
3ab,c
3ab,d
P1–Ag
2.421
2.534
2.197
2.414
2.535
2.204
3.281a
97.45
178.52
2.443
2.585
2.190
2.424
2.561
2.205
2.998b
98.09
177.70
Se–Ag
P2–See
AgA . . . SeB, f
P2–Se–Ag
P1–Ag–Se
99.08
170.88
99.57
157.91
a Calculated in the gas phase. b Calculated in acetone (PCM-IEF). c Unit
A of the dimer (See Fig. 6). d Unit B of the dimer (see Fig. 6). e P–Se
distance = 2.126 A for SePPh2Me in the gas phase. Distance between the
silver atoms belonging to the two interacting units A and B.
f
˚
Analogous calculations were carried out for the copper complex
8. The complex features the copper ion dicoordinated in a linear
Se–Cu–P geometry closely resembling that of the silver homologue
3 (Table 4). Also the composition of the KS-HOMO, mainly
due to a lone pair localized on the selenium atom, with a minor
contribution from the copper ion, is very similar to that calculated
for 3. This notwithstanding, the virtual MO’s in the range LUMO-
LUMO+5 (about 0.22 eV), contrary to what observed for 3, show
only very small contributions from the metal ion. This could
possibly prevent those intramolecular interactions, between the
Se donor atom of a unit and the metal ion of another unit,
which the dimer formation is based on in the case of 3a. Notably,
the calculation including the effect of the solvent (acetone),
implicitly taken into account, does not affect remarkably neither
the molecular geometry (Table 4) nor the composition of the
frontier KS-MO’s of 8.
An examination of the bond lengths and angles shows only small
variations as compared to the corresponding ones calculated in the
gas phase (Table 4).
The nature of the KS-HOMO and the natural charge distribu-
tion (QSe = -0.463, QAg = 0.481 e) indicate that the polarisation
of the Ag–Se bond is remarkably increased (DQAg–Se = 0.769 and
0.943 e in the gas phase and in acetone, respectively) and confirm
the selenium atom as the most donor site.
The optimized structure of 3a in the gas phase (Fig. 6, Table
5) shows that, in agreement with natural atomic charges and the
composition of HOMO and LUMO+1, the compound is formed
by a head-to-tail combination of the two molecular units by a
single interaction between the selenium donor site of one unit and
the Ag center of a second one (units B and A, respectively, in Fig. 6)
˚
with a Ag ◊ ◊ ◊ Se contact of 3.281 A (sum of van der Waals contact
˚
3.62 A). The triorganophosphane chalcogenide ligand, therefore,
An attempt to optimise a hypothetical dimer 8a showing
structural features similar to those calculated for 3a was carried
out. The optimization steps led to the elimination of PPh2Me, with
formation of a dinuclear species [Cu2(PPh3)2(SePPh2Me)(Se)]2+,
would not bridge symmetrically the two metal centres. Notably,
the molecular unit whose silver atom is involved in the contact
(unit A) undergoes a distortion resulting in a bending of the P–
Ag–Se fragment (by about 7◦) and small elongations in the P–Ag
˚
featuring a Cu–Cu bond [d(Cu–Cu) = 2.908 A; WBI (Cu–Cu) =
˚
and Se–Ag bonds, by 0.010 and 0.016 A, respectively (Tables 4
0.145] and a selenide bridge between the two metal ions, which
show different charges (+0.232 and +0.018 e) suggesting a mixed-
valence nature for the compound. It is worth noting that copper-
copper interactions of the same order of magnitude as those
calculated for [Cu2(PPh3)2(SePPh2Me)(Se)]2+ have been reported in
several cases of cluster compounds featuring phosphanes and sele-
nated ligands.40–42 Although [Cu2(PPh3)2(SePPh2Me)(Se)]2+ might
be unstable, and possibly prelude to the formation of other
species, the calculation allows confirming the instability of 8a,
in agreement with the experimental NMR data discussed before.
DFT calculations were extended to gold(I) and gold(III) com-
plexes 6 and 7 in order to investigate their electronic structure and
the spectroscopic features discussed above.
and 5). On passing from the gas phase to the acetone solution,
the optimized metric parameters indicate that the interaction
between the two units of 3 is strengthened. Accordingly, the
In the case of 6, whose X-ray diffraction analysis showed
Au(I) ◊ ◊ ◊ Au(I) interactions between couples of molecular com-
plexes, both the isolated molecular unit (6) and a couple of
units (6¢), kept together by the aurophilic interactions, were
optimized starting from structural data. In Table 6, some selected
bond distances and angles are summarised for the two optimized
structures. It is remarkable that 6 and 6¢ show metric parameters
very close to each other, and in very good agreement with the
structural data obtained by single crystal X-ray diffraction (Table
2). In particular, it should be underlined that the calculated
Au ◊ ◊ ◊ Au distance in 6¢, related to the evaluation of the aurophilic
Fig. 6 Ball and stick drawing of the molecular structure of 3a optimized
at DFT level in the gas phase. Hydrogen atoms have been omitted for
clarity.
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˚
Table 6 Selected bond distances (A) and angles ( ) calculated for6, 6¢, and
7 at DFT level. Atom labeling as in Fig. 2 and Fig. 3. The corresponding
structural values are listed in Table 2
6
6¢
7
Au1–C1
2.029
2.504
—
2.181
1.816
1.816
1.821
2.031
2.503
3.360
2.181
1.819
1.819
1.820
Au1–C1
Au1–C11
Au1–C21
Au1–Se1
Se1–P1
P1–C30
P1–C31
P1–C41
C11–Au1–Se1
C21–Au1–Se1
C1–Au1–Se1
C11–Au1–C21
C11–Au1–C1
C21–Au1–C1
P1–Se1–Au1
C30–P1–C41
C30–P1–C31
C41–P1–C31
C30–P1–Se1
C41–P1–Se1
C31–P1–Se1
2.069
2.034
2.075
2.569
2.192
1.813
1.820
1.813
174.62
96.15
86.28
88.59
88.99
177.57
102.34
109.56
106.24
107.06
112.20
114.55
106.71
Au1–Se1
Au1 ◊ ◊ ◊ Au1¢¢
Se1–P1
P1–C10 (Me)
P1–C21
P1–C11
C1–Au1–Se1
C1–Au1 ◊ ◊ ◊ Au1¢
Se1–Au1 ◊ ◊ ◊ Au1¢
P1–Se1–Au1
C10–P1–C21
C10–P1–C11
C21–P1–C11
C10–P1–Se1
C21–P1–Se1
C11–P1–Se1
178.12
—
—
94.72
106.13
107.93
106.11
112.28
108.82
115.19
179.71
89.36
90.58
94.85
106.62
106.69
107.73
112.16
108.75
114.52
interaction, is very close to the experimental value (3.360 and
˚
3.3387(7) A, respectively), directly confirming the choice of the
RECP adopted for the gold species.
In Fig. 7 the orbital energy diagram calculated for 6 along with
the isosurfaces of selected frontier Kohn–Sham molecular orbitals,
ranging between HOMO-6 (MO 100) and LUMO+9 (MO 115),
are depicted. Worthy of note, gold(I) contributes with the 5d AO’s
to the highest filled orbitals (see MO’s 100, 104 and 106 in Fig.
7), while the lowest unoccupied ones are mainly localised on the
phenyl groups.
The pattern of molecular orbitals of 6¢ derives directly from the
overlap of the MO of each molecular unit. Optimized structural
data and the comparison of the molecular orbitals calculated for 6
and 6¢ contribute to indicate that the Au(I) ◊ ◊ ◊ Au(I) interaction
does not affect significantly the electronic structure of each
interacting unit. Accordingly, the Wiberg bond index calculated
for the Au ◊ ◊ ◊ Au system (0.118) indicates a weak interaction,
confirmed by a stabilisation in the electronic energy of about 6.6
kcal mol-1 (DHf = 5.92 kcal mol-1 at 298 K taking into account
Zero Point Energy and thermal corrections).
Fig. 7 Energy diagram and KS-MO isosurface drawings of the frontier
orbitals calculated for 6. HOMO = MO 106, LUMO = MO 107. Cutoff
value = 0.05 e.
peculiar to 6¢ and therefore directly related to the aurophilic
interaction, can be envisaged in the electronic transition involving
ES S3, calculated at 4.026 eV (f = 0.103), largely due to the
HOMO–LUMO monoelectronic excitation (Fig. 8).
TD-DFT calculations were exploited to simulate the electronic
absorption spectrum of the complexes in the UV-Vis region
and to get a deeper insight into the emission processes. A
comparison of the spectra calculated for 6 and 6¢ shows that
in both cases the absorption spectra in the region 230–500 nm
are dominated by electronic transitions falling at about 250 nm, in
very good agreement with diffuse reflectance experiments showing
absorption maxima between 230 and 260 nm. Such absorption can
be attributed to the vertical transitions to the singlet excited states
(ES’s) S38 and S39, in turn due to monoelectronic excitations
having a large MLCT character (S38: MO 212 → MO 219, f =
0.084, E = 4.850 eV; S39: 205 → 214 and 203 → 213, f = 0.134, E =
4.888 eV). This notwithstanding, experimental excitation spectra
recorded at 77 K for compound 6 in the solid-state (Table 3) clearly
show that a weaker absorption at 395 nm is responsible for the
fluorescent emission observed at 500 nm. Such an absorption,
Fig. 8 KS-HOMO (left) and LUMO (right) calculated for 6¢ in the gas
phase. Cutoff value = 0.05 e.
TD-DFT calculations were also carried out on the complex
7, fluorescent both at 77 K and at room temperature (Table 3),
whose optimized geometry (Table 6) is in excellent agreement with
the structural data (Table 2). As mentioned above, the DRUV
spectrum recorded for 7 at 298 K clearly shows a structured
band featuring an absorption maximum at 276 nm. The excitation
spectrum at 298 K features a maximum at roughly the same energy
(283 nm, Table 3).
A comparison between the experimental UV-Vis spectrum and
the simulated spectrum based on TD-DFT calculations shows
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that the absorption band derives from three main contributions,
involving the singlet ES’s S40, S47, and S59. The electronic
transition featuring the highest oscillator strength is that involving
S40 (5.494 eV, f = 0.497), largely (40%) due to a monoelectronic
excitation from KS-MO 180 (corresponding to the LP localised on
the chalcogen atom of the SePPh2Me ligand) to MO 189 [involving
the Se atom, the p* system of one of the phenyl groups of the same
ligand, and to a lesser extent a 5d AO of the Au(III) ion]. Therefore,
the main absorption in the UV region is ILCT in nature and
regards an excitation process localised on the SePPh2Me ligand,
in perfect agreement with the conclusions drawn on the basis of
the luminescence studies discussed above.
Experimental
General procedures
All synthetic manipulations were carried out under argon
atmosphere using Schlenk techniques. Solvents were
dried and freshly distilled prior to use. The starting
materials, [AuCl(tht)],43 [Au(C6F5)(tht)], [Au(C6F5)3(tht)],44
[AgOTf(PPh3)],45 [CuNO3(PPh3)2]46 and SePPh2Me,47 were
prepared according to literature methods. The commercial
reagents AgOTf, CuCl, Cu(NO3)2, PPh3 and PPh2Me were
purchased from Sigma Aldrich and used without further
purification. Elemental analyses were performed on a VarioEL
analyser. Infrared spectra were recorded on a Jasco FT-IR
machine, as KBr pellets. NMR spectra were recorded on a
BRUKER Avance 300 instrument (1H, 31P and 77Se) and a
VARIAN GEMINI 400S instrument (19F) operating at 300,
121.5, 57.2 and 376.5 MHz, respectively, in CDCl3 or acetone-d6
solutions. Chemical shifts are reported in ppm relative to TMS
(1H), trifluoracetic acid (19F) and H3PO4 85% (31P). The 77Se
spectra were obtained using diphenyl diselenide as external
standard. Chemical shifts are reported relative to dimethyl
selenide (d 0 ppm) by assuming that the resonance of the standard
is at d 461 ppm.48 2D heteronuclear 31P-1H NMR correlation
experiments (HMQC) were used to assign the resonances for the
copper(I) and silver(I) complexes in solution. Mass spectra were
recorded on an Agilent 6320 Ion Trap instrument. DRUV spectra
were recorded with a UnicamUV-4 spectrophotometer equipped
with a Spectralon RSA-UC-40 Labsphere integrating sphere. The
intensities were recorded in Kubelka-Munk units. Steady-state
photoluminescence spectra were recorded with a Jobin–Yvon
Horiba Fluorolog FL-3-11 spectrometer using band pathways of
3 nm for both excitation and emission.
Conclusions
Several group 11 metal complexes ([CuCl(SePPh2Me)]
(1),
[AgOTf(SePPh2Me)]
(2),
[AuCl(SePPh2Me)]
(5),
[Au(C6F5)(SePPh2Me)] (6) and [Au(C6F5)3(SePPh2Me)] (7)
were isolated and structurally characterized in solution by
multinuclear NMR spectroscopy. For the gold complexes 6 and
7 monomeric structures were determined by single-crystal X-ray
diffraction, and they were further optimized by DFT calculations.
In case of compound 6 weak aurophilic gold(I) ◊ ◊ ◊ gold(I) contacts
were also observed in the crystal.
The DRUV spectra have shown that complexes 6 and 7, as well
as the ligand SePPh2Me are emissive in the solid state, complex
6 only at 77 K and complex 7 and the free ligand both at room
temperature and at 77 K. TD-DFT calculations were performed
in order to investigate the electronic properties which determin
the luminescence of complexes 6 and 7, as well as of the ligand
SePPh2Me in the solid state.
The products isolated from the reactions between SePPh2Me
and [CuNO3(PPh3)2] or [AgOTf(PPh3)] prooved to have a dy-
namic solution behavior involving the transfer of selenium
from the P(V) species SePPh2Me to the P(III) phosphane
PPh3. In case of the silver(I) species the NMR experiments
brought further evidence for dimerization processes resulting
in {[Ag(PPh3)(m-SePPh2Me)]2(OTf)2 (3a) and [Ag(PPh2Me)(m-
SePPh3)]2(OTf)2 (4a)}, while in case of the Cu(I) species the NMR
experiments suggest the formation of decomposition products,
i.e. the copper(I) complexes [CuNO3(PPh3)2], [CuNO3(PPh2Me)2]
and [CuNO3(PPh3)(PPh2Me)] and the triorganophosphane se-
lenides SePPh2Me and SePPh3 in equilibrium, even if in
the first stage of the reaction the formation of monomeric
{[CuNO3(PPh3)2(SePPh2Me)] (8) and [CuNO3(PPh2Me)(SePPh3)]
(9)}, and dimeric {[Cu(PPh3)(m-SePPh2Me)]2(NO3)2 (8a) and
[Cu(PPh2Me)(m-SePPh3)]2(NO3)2 (9a)} might be also envisaged.
DFT calculations are in accordance with a head-to-tail con-
formation for 3a, thus supporting the hypothesis that both Ag
centers in a dimeric unit could be alternatively involved in
the Ag ◊ ◊ ◊ Se contact so that a fast equilibrium on NMR time
scale between the dimer featuring the AgA ◊ ◊ ◊ SeB interaction
and the dimer featuring the AgB ◊ ◊ ◊ SeA contact takes place, in
accordance with the 31P NMR spectrum at room temperature. The
attempt to optimize a hypothetical dimer 8a showing structural
features similar to those calculated for 3a suggest the elimination
of PPh2Me, with formation of an unstable dinuclear species
[Cu2(PPh3)2(SePPh2Me)(Se)]2+, which might prelude the further
decomposition, in accordance with the NMR spectra.
Synthesis of [CuCl(SePPh2Me)] (1). A mixture of SePPh2Me
(0.115 g, 0.41 mmol) and CuCl (0.041 g, 0.41 mmol) in 20 mL
anhydrous CH2Cl2 was stirred for 1 h at room temperature. The
solvent was removed in vacuum and addition of n-hexane afforded
the title product as a colorless solid. Yield 0.134 g (86%). Anal.
Calc. for C13H13ClCuPSe (MW 378.18): C, 41.29; H, 3.46; Found:
C, 41.32; H, 3.61; 1H NMR (CDCl3): d 2.83 (3H, d, CH3, 2JPH 13.7
Hz), 7.47 (4H, m, C6H5-meta), 7.54 (2H, m, C6H5-para), 7.74 (4H,
ddd, C6H5-ortho, 3JPH = 13.7, 3JHH = 7.4, 4JHH = 1.6 Hz); 31P NMR
(CDCl3): d 21.17 (s, 1JSeP 598.5 Hz). ESI+ MS m/z(%): 720.8 (10)
[(CuSePPh2Me)2Cl+], 622.8 (100) [Cu(SePPh2Me)2 + H]; ESI-
+
-
MS m/z(%):613.8 (100) [(Cu(PPh2Me) (SePPh2Me)2Cl2 ].
Synthesis of [AgOTf(SePPh2Me)] (2). A mixture of SePPh2Me
(0.092 g, 0.33 mmol) and AgOTf (0.085 g, 0.33.mmol) in 20 mL
anhydrous CH2Cl2 was stirred for 2 h at room temperature. The
solvent was removed in vacuum and addition of n-hexane afforded
the title product as a colorless powder. Yield 0.127 g (72%). Anal.
Calc. for C14H13AgF3O3PSSe (MW 536.11): C, 31.36; H, 2.44.
1
Found: C, 31.29; H, 2.42. H NMR (acetone-d6): d 2.95 (3H, d,
CH3, 2JPH 13.8 Hz), 7.64 (4H, dt, PC6H5-meta, 3JHH 7.8, 4JHH 3.6
3
4
Hz), 7.74 (2H, dt, PC6H5-para, JHH 7.5, JHH 2.1 Hz), 7.92 (4H,
3
4
3
ddd, PC6H5-ortho, JHH 7.2, JHH 1.4, JPH 14.3 Hz). 31P NMR
(acetone-d6): d 27.7 (s, 1JSeP 535.4 Hz). 19F NMR (acetone-d6): d
-79.8 (s, OTf). ESI+ MS m/z(%): 559.4 (100) [M+ + Na]; ESI- MS
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m/z(%): 406.7 (100) [Ag(OTf)2 ]. IR (n, cm-1): 1280(vs), 1218(vs),
1155(s) and 1021(vs).
d -162.73 (m, AuC6F5-meta), -160.14 (t, AuC6F5-para, 2JFF 20.2
Hz), -116.32 (m, AuC6F5-ortho).
-
Preparation of [Au(C6F5)3(SePPh2Me)] (7). 7 was prepared
similarly to 5 and 6 from SePPh2Me (0.233 g, 0.83 mmol) and
[(C6F5)3Au(tht)] (0.656 g, 0.83 mmol) in 20 mL anhydrous CH2Cl2,
as a colorless powder. Yield 0.621 g (76%). Anal. Calc. for
C31H13AuF15PSe (MW 977.31): C, 38.10; H, 1.34. Found: C, 38.18;
Reaction between [AgOTf(PPh3)] and SePPh2Me. A mixture
of [AgOTf(PPh3)] (0.332 g, 0.64.mmol) and SePPh2Me (0.179 g,
0.64 mmol) was stirred for 2 h at room temperature in 20 mL ace-
tone and then worked up as described for compound 1. A colorless
powder was finally isolated. Yield 0.347 g (68%). Anal. Calc. for
C32H28AgF3O3P2SSe (MW 798.40): C, 48.14; H, 3.53. Found: C,
1
2
H, 1.41. H NMR (CDCl3): d 2.66 (3H, d, CH3, JPH 13.5 Hz),
7.51–7.56 (8H, m, PC6H5-ortho+meta, 7.62–7.66 (2H, m, PC6H5-
para); 31P NMR (CDCl3): d 26.05 (s, 1JSeP 553, 1JPC(Ph) 76.0, 1JPC(Me)
50.0 Hz). 19F NMR (CDCl3): d -161.34 (2F, m, AuC6F5-meta),
1
48.22; H, 3.42. H, 13C, 31P, 19F and 77Se NMR spectra evidence
the presence of two sets of resonances which can be assigned
to the species [AgOTf(PPh3)(SePPh2Me)] (3) and [Ag(PPh3)(m-
SePPh2Me)]2(OTf)2 (3a), and [AgOTf(PPh2Me)(SePPh3)] (4) and
2
-160.95 (4F, m, AuC6F5-meta), -157.3 (1F, t, AuC6F5-para, JFF
20.0 Hz), -157.16 (2F, t, AuC6F5-para, 2JFF 20 Hz), -122.22 (2F,
m, AuC6F5-ortho), -119.78 (4F, m, AuC6F5-ortho).
1
[Ag(PPh2Me)(m-SePPh3)]2(OTf)2 (4a). 3/3a: H NMR (acetone-
2
d6, 293 K): d 2.60 (3H, d, SePCH3, JPH 13.6 Hz), 7.29–7.48
(15H, m, PPh3 ortho+meta+para) 7.48–7.53 (6H, m, PPh2Me
Reaction between [CuNO3(PPh3)2] and SePPh2Me. A mixture
of SePPh2Me (0.117 g, 0.42 mmol) and CuNO3(PPh3)2 (0.272 g,
0.42 mmol) was stirred for 2 h at room temperature in 30 mL
anhydrous CH2Cl2 and then worked up as described for compound
1. A colorless powder was finally isolated. Yield 0.255 g (66%).
Anal. Calc. for C49H43CuNO3P3Se (MW 929.30): C, 63.33; H, 4.66;
3
3
meta+para), 7.81 (4H, dd, PPh2Me ortho, JHH 7.7, JPH 14.1
Hz). 31P NMR (acetone-d6, 293 K): d 10.5 (s, br., PPh3), 25.8 (s,
SePPh2Me, 1JSeP 595.4, 1JPC(Me) 52.7, 1JPC(Ph) 75.4 Hz). 77Se (acetone-
d6, 293 K): d -250.3 (d, AgSePPh2Me, 1JSeP 595.7 Hz). 19F NMR
(acetone-d6, 293 K): d -78.5 (s, OTf). 31P NMR (acetone-d6, 213
1
1
K): d 8.61 (3, d, AgPPh3, J107Ag–31P 618.9, J109Ag–31P 539.6 Hz),
9.64 (3a, d, AgPPh3, 1J107Ag–31P 526.3, 1J109Ag–31P 460.8 Hz), 26.4 (s,
AgSePPh2Me, 1JPSe 576.5 Hz). 77Se (acetone-d6, 243 K): d 259.1 (d,
AgSePPh2Me, 1JPSe 584.6 Hz). 4/4a: 1H NMR (acetone-d6, 293 K):
d 1.85 (3H, d, CH3, 2JPH 5.9 Hz), 7.48–7.53 (m, 10H, PPh2Me or-
tho+meta+para + 9H, SePPh3meta+para), 7.66 (4H, dd, PPh2Me
ortho, 3JHH 7.8, 3JPH 13.6 Hz). 31P NMR (acetone-d6, 293 K): d -7.3
1
N, 1.51. Found: C, 63.27; H, 4.61; N, 1.54. H NMR (acetone-
2
d6, 293 K): d 1.6 (3H, d, CuPPh2Me, JPH = 4.0 Hz), 2.51 (3H,
2
d, CuSePPh2Me, JPH = 13.4 Hz), 7.19–7.44 (m, 30H, CuPPh3-
ortho+meta+para + 10H CuPPh2Me-meta+para), 7.53 (m, 9H
CuSePPh3-meta+para + 6H CuSePPh2Me-meta+para), 7.77 (4H,
3
3
dd, CuSePPh3-ortho, JPH = 13.2, JHH = 7.4 Hz), 7.94 (4H, ddd,
3
3
4
CuSePPh2Me-ortho, JPH = 13.4, JHH = 7.0, JHH = 1.6 Hz). 31P
NMR (acetone-d6, 293 K): d -18.8 (s, br., CuPPh2Me), -2.25 (s,
br., CuPPh3), 23.6 (s, SePPh2Me, 1JSeP 731.8, 1JPC 74 Hz), 35.2 (s,
SePPh3, 1JSeP 746.3 Hz). 31P NMR (acetone-d6, 198 K): d -18.8 (m,
CuPPh2Me), -1.27 (d, CuPPh3, 2JPP 83.5 Hz), 24.5 (s, SePPh2Me,
1
1
(s, br., AgPPh2Me), 33.6 (s, AgSePPh3, JSeP 625.0, JPC(Me) 52.7,
1JPC(Ph) 77.4 Hz). 77Se (acetone-d6, 293 K): d -241.2 (d, AgSePPh3,
1JSeP 626.7 Hz). 19F NMR (acetone-d6, 293 K): d -78.7 (s, br.,
OTf). 31P NMR (acetone-d6, 213 K): d -8.48 (d, br., AgPPh2Me,
1
1JAgP 594.8 Hz), 32.5 (s, br., 4 + 4a, AgSePPh3, JSeP 616 Hz).
1
1
1
1JSeP 719.7, JPC(Ph) 73.0, JPC(Me) 53.0 Hz), 35.3 (s, SePPh3, JSeP
MS (APCI+) m/z(%): 800.9 (80) [AgOTf(PPh3)(SePPh2Me)+],
729.6 (100) [Ag(PPh3)(SePPh2Me)+ + Se]. IR (n, cm-1): 1262 (vs),
1223(s), 1151(s) and 1024(s).
1
1
736.8, JPC 76.8 Hz). H NMR (CDCl3, 293 K): d 1.59 (3H, d,
CuPPh2Me, JPH = 2.54 Hz), 2.46 (3H, d, CuSePPh2Me, JPH
2
2
=
13.3 Hz), 7.35–7.14 (m, 15H, CuPPh3-ortho+meta+para + 6H,
CuPPh2Me-meta+para), 7.47 (m, 9H, CuSePPh3-meta+para +
6H, CuSePPh2Me-meta+para), 7.75 (6H, dd, CuSePPh3-ortho,
Preparation of [AuCl(SePPh2Me)] (5).
A
mixture of
3JPH = 13.6, JHH = 6.8 Hz), 7.83 (4H ddd, CuSePPh2Me-ortho,
SePPh2Me (0.049 g, 0.18 mmol) and [AuCl(tht)] (0.056 g, 0.18
mmol) in 20 mL anhydrous CH2Cl2 was stirred for 30 min. at
room temperature. The solvent was removed in vacuum and then
the oily product was treated with n-hexane. A brown oily product
was obtained. Yield: 0.052 g (58%). Anal. Calc. for C13H13AuClPSe
3
3JPH = 13.5, 3JHH = 7.3, 4JHH = 1.5 Hz). 31P NMR (CDCl3, 293 K): d
-17.4 (s, br., CuPPh2Me), -1.2 (s, br., CuPPh3), 23.3 (s, SePPh2Me,
1JSeP 715.3, 1JPC 74 Hz), 35.4 (s, SePPh3, 1JSeP 728.0 Hz). 31P NMR
(CDCl3, 198 K): d -17.3 (m, CuPPh2Me), -0.75 (m, CuPPh3),
23.8 (s, SePPh2Me, 1JSeP 692.0 Hz), 35.4 (s, SePPh3, 1JSeP 709, 1JPC
77.2 Hz). 77Se NMR (CDCl3, 293 K): d -266.3 (d, CuSePPh2Me,
1
(MW 511.60): C, 30.52; H, 2.56; Found: C, 30.42; H, 2.61; H
2
NMR (CDCl3): d 2.61 (3H, d, CH3, JPH 13.6 Hz), 7.55 (4H, m,
3
1JPSe = 728.8 Hz), -275.2 (d, CuSePPh3, JPSe = 715.5 Hz). MS
PC6H5-meta), 7.63 (2H, t, PC6H5-para, JHH 5.48 Hz), 7.79 (4H,
1
3
3
dd, PC6H5-ortho, JHH 7.3, JPH 14.2 Hz). 31P NMR (CDCl3): d
(ESI+) m/z(%): 667.5 (5), [CuNO3(PPh3)(SePPh2Me)+] 605.5 (72)
23.1 (s, 1JPC 75.8, 1JSeP 544.8 Hz).
[Cu(PPh3)(SePPh2Me)+], 588.5 (100) [CuNO3(PPh3)(PPh2Me)+].
Preparation of [Au(C6F5)(SePPh2Me)] (6). 6 was prepared
similarly to 5 from SePPh2Me (0.202 g, 0.72 mmol) and
[(C6F5)Au(tht)] (0.327 g, 0.72 mmol) in 40 mL anhydrous CH2Cl2,
as a microcrystalline pale yellow powder. Yield: 0.302 g, (65%).
Anal. Calc. for C19H13AuF5PSe (MW 643.20): C, 35.48; H, 2.04.
Found: C, 35.63; H, 2.11. 1H NMR (CDCl3): d 2.68 (3H, d, CH3,
Crystal structures
Single-crystals of compounds 6 (pale yellow) and 7 (colorless) were
grown by slow diffusion in CH2Cl2/n-hexane (1/5, v/v) systems.
Details of the crystal structure determination and refinement for
compounds 6 and 7 are given in Table 7.
Data were measured using Mo-Ka radiation (l = 0.71073)
on a Xcalibur Oxford Diffraction diffractometer. Absorption
corrections were based on multiple scans (program SADABS).49
The structures were solved by Direct Methods, and refined by
3
4
2JPH 13.5 Hz), 7.55 (4H, dt, PC6H5-meta, JHH 7.6, JPH 3.2 Hz),
3
4
7.63 (2H, dt, PC6H5-para, JHH 7.2, JHH 2.1 Hz), 7.71 (4H, dd,
3
3
PC6H5-ortho, JHH 7.4, JPH 14.2 Hz). 31P NMR (CDCl3): d 24.2
(s, JSeP 556.5, JPC(Ph) 76.1, JPC(Me) 50.8 Hz). 19F NMR (CDCl3):
1
1
1
12488 | Dalton Trans., 2011, 40, 12479–12490
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The Royal Society of Chemistry 2011
©

View Article Online
Table 7 Crystalllographic data for compounds 6 and 7
Acknowledgements
6
7
Financial support from the Ministry of Education and Research
of Romania (CNCSIS, Research Project ID-2404/2008) and the
Ministerio de Ciencia e Innovacio´n (CTQ2010-20500-C02-01) is
greatly appreciated. A. Pop thanks the European Social Fund
for a Scholarship (Education and Training Program 2008-2013,
POSDRU/6/1.5/S/3). We warmly acknowledge Prof. Konstantin
Karaghiosoff for helpful discussions.
Empirical formula
M
T
C19H13AuF5PSe
643.19
100(2)
Monoclinic
P21/c
9.0631(18)
21.657(4)
9.6803(19)
90
C31H13AuF15PSe
977.31
100(2)
Monoclinic
P21/c
10.848(2)
20.482(4)
13.523(3)
90
Crystal system
Space group
˚
a/A
˚
b/A
˚
c/A
a (◦)
b (◦)
g (◦)
96.97(3)
90
1886.0(6)
Multi-Scan49
9.863
0.0383
0.0736
97.75(3)
90
2977.3(10)
Multi-Scan49
6.336
0.0310
0.0655
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