Structural and photophysical study on heterobimetallic complexes with d8-d10 interactions supported by carborane ligands: Theoretical analysis of the emissive behaviour

Article abstract of DOI:10.1002/chem.201303735

Heterobimetallic complexes of formula [M{(PPh₂) ₂C₂B₉H₁₀}(S₂C ₂B₁₀H₁₀)M'(PPh₃)] (M=Pd, Pt; M'=Au, Ag, Cu) and [Ni{(PPh₂)₂C₂B₉H ₁₀}(S₂C₂B₁₀H₁₀) Au(PPh₃)] were obtained from the reaction of [M{(PPh ₂)₂C₂B₁₀H₁₀}(S ₂C₂B₁₀H₁₀)] (M=Pd, Pt) with [M'(PPh₃)]⁺ (M'=Au, Ag, Cu) or by one-pot synthesis from [(SH)₂C₂B₁₀H₁₀], (PPh ₂)₂C₂B₁₀H₁₀, NiCl ₂×6 H₂O, and [Au(PPh₃)]⁺. They display d⁸-d¹⁰ intermetallic interactions and emit red light in the solid state at 77aK. Theoretical studies on [M{(PPh ₂)₂C₂B₉H₁₀}(S ₂C₂B₁₀H₁₀)Au(PPh₃)] (M=Pd, Pt, Ni) attribute the luminescence to ligand (thiolate, L)-to- P₂-M-S₂ (ML') charge-transfer (LML'CT) transitions for M=Pt and to metal (M)-to- P₂-M-S ₂ (ML') charge-transfer (MML′CT) transitions for M=Ni, Pd. A family of red emitters of formula [M{(PPh₂)₂C ₂B₉H₁₀}(S₂C₂B ₁₀H₁₀)M′(PPh₃)] (M=Pd, Pt; M′=Au, Ag, Cu) and [Ni{(PPh₂)₂C₂B₉H ₁₀}(S₂C₂B₁₀H₁₀) Au(PPh₃)] (see figure) was synthesised. Theoretical studies on [M{(PPh₂)₂C₂B₉H₁₀}(S ₂C₂B₁₀H₁₀)Au(PPh₃)] (M=Pd, Pt, Ni) attribute the luminescence to ligand (thiolate, L)-to- P₂-M-S₂ group (ML′) charge-transfer (LML′CT) transitions for M=Pt and to metal (M)-to- P₂-M-S₂ group (ML′) charge-transfer (MML′CT) transitions for M=Ni, Pd.

Full text of DOI:10.1002/chem.201303735

DOI: 10.1002/chem.201303735
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&
Heterometallic Complexes
Structural and Photophysical Study on Heterobimetallic
Complexes with d8–d10 Interactions Supported by Carborane
Ligands: Theoretical Analysis of the Emissive Behaviour
Olga Crespo,*[a] M. Concepciꢀn Gimeno,*[a] Antonio Laguna,[a] Olli Lehtonen,[b]
Isaura Ospino,[a] Pekka Pyykkç,[b] and M. Dolores Villacampa[a]
In memory of Marꢀa Pilar Garcꢀa Clemente
Abstract: Heterobimetallic complexes of formula [M-
{(PPh2)2C2B9H10}(S2C2B10H10)M’(PPh3)] (M=Pd, Pt; M’=Au, Ag,
Cu) and [Ni{(PPh2)2C2B9H10}(S2C2B10H10)Au(PPh3)] were ob-
tained from the reaction of [M{(PPh2)2C2B10H10}(S2C2B10H10)]
(M=Pd, Pt) with [M’(PPh3)]+ (M’=Au, Ag, Cu) or by one-pot
synthesis from [(SH)2C2B10H10], (PPh2)2C2B10H10, NiCl2·6H2O,
and [Au(PPh3)]+. They display d8–d10 intermetallic interac-
tions and emit red light in the solid state at 77 K. Theoretical
studies on [M{(PPh2)2C2B9H10}(S2C2B10H10)Au(PPh3)] (M=Pd,
Pt, Ni) attribute the luminescence to ligand (thiolate, L)-to-
“P2-M-S2” (ML’) charge-transfer (LML’CT) transitions for M=Pt
and to metal (M)-to-“P2-M-S2” (ML’) charge-transfer (MML’CT)
transitions for M=Ni, Pd.
Introduction
We have now combined these three SEOs in heterobimetal-
lic complexes. The rigidity and steric demand of the carborane
skeleton allowed us to synthesise a group of complexes that
display d8–d10 metal–metal interactions: [M{(PPh2)2C2B9H10}-
(S2C2B10H10)M’(PPh3)] [M=Pd, Pt; M’=Au, Ag, Cu] and [Ni-
{(PPh2)2C2B9H10}(S2C2B10H10)Au(PPh3)]. Figure 1 shows an exam-
New structural patterns that are expected to be luminescent
can be proposed on the basis of studies on the emissive prop-
erties of known coordination complexes. We call such patterns
structural emissive origins (SEO). Combining several SEOs in
the same compound could lead to tuneable emissions upon
small structural changes.
Some examples of SEOs are: 1) Metal–thiolate bonds, which
lead in many cases to ligand (thiolate)-to-metal charge-transfer
(LMCT) transitions that can cause emissions which stretch over
the green-red region in gold complexes;[1] 2) Metal–fluoro-
phore bonds, because the intrinsic fluorophore emissions may
be modified upon coordination to the metal. In this work, we
were especially interested in the nido bis-phosphane[2] [7,8-
(PPh2)2C2B9H10]ꢀ as fluorophore; 3) Metal–metal interactions,
which may be responsible for emissions that involve the elec-
tron density between the metal centres. Such emissions may
originate from metal-centred (MC) transitions or from charge-
transfer transitions [ligand-to-metal–metal (LMMCT) or metal–
metal-to-ligand (MMLCT)].[3]
Figure 1. Possible origins of the luminescence observed in the analysed
system and the regions in which the emissions are frequently observed. In
all three situations, M may be involved in the transitions, as the intraligand
(bis-phosphane) transitions may be modified upon coordination to the
metal atom.
[a] Dr. O. Crespo, Prof. M. C. Gimeno, Prof. A. Laguna, Dr. I. Ospino,
Dr. M. D. Villacampa
Departamento de Quꢀmica Inorgꢁnica, Universidad de Zaragoza-CSIC
Instituto de Sꢀntesis Quꢀmica y Catꢁlisis Homogꢂnea (ISQCH)
Pedro Cerbuna 12, 50009 Zaragoza (Spain)
Fax: (+34)976761187
ple of such structural motifs, which have scarcely been report-
ed in the literature. About 25 structures in which a metal M
(Ni, Pd, Pt) is coordinated by a dithiolate and two phosphorus
atoms of a bis- or mono-phosphane in square-planar geometry
and one or both sulfur centres form bridges to another metal
E-mail: ocrespo@unizar.es
gimeno@unizar.es
[b] Dr. O. Lehtonen, Prof. P. Pyykkç
Department of Chemistry, University of Helsinki
P.O.B 55 (A. I. Virtasen aukio 1), 00014 Helsinki (Finland)
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planar complexes [M{(PPh2)2C2B10H10}(S2C2B10H10)] [M=Pd (3),
M=Pt (4)]. The 31P{1H} NMR spectrum of complexes 3 and 4
display one signal at 68.6 (3) and 59.1 (4) ppm, which are shift-
ed by about 10 and 3 ppm to higher and lower field, respec-
tively, relative to those of the precursors [MCl2{(PPh2)2-
C2B10H10}].
Reaction of complexes 3 and 4 with [M’X(PPh3)n] (n=1: M’=
Au, X=Cl; M’=Ag, X=OTf. n=2: M’=Cu, X=NO3) in refluxing
ethanol led to partial degradation of the carborane cage of the
bis-phosphane ligand and coordination of the M’(PPh3) frag-
ment to afford complexes of formula [M{(PPh2)2C2B9H10}-
(S2C2B10H10)M’(PPh3)] [M=Pd, Pt; M’=Au, Ag, Cu] (Scheme 1).
Figure 2. Structural types of published crystal structures showing the struc-
tural motif represented in Figure 1.
Scheme 1. i) [MCl2(NCPh)2] (M=Pd, Pt); ii) K2CO3, (SH)2C2B10H10; iii) [AuCl-
(PPh3)], [Ag(OTf)(PPh3)], or [Cu(NO3)(PPh3)2]; iv) M=Ni, M’=Au; (SH)2C2B10H10,
[AuCl(PPh3)]; v) NiCl2·6H2O, (SH)2C2B10H10, [AuCl(PPh3)].
M’ (Cu, Ag, Au) were found in the CCDC.[4] The published struc-
tural types are summarised in Figure 2. Three points are nota-
ble: 1) About 15 of them show M(d8, Group 10)–M’(d10,
Group 11) interactions, about nine of which are Pt–Ag interac-
tions. 2) The structural types shown in Figure 2 are tri-, tetra-
or hexanuclear, with the sole exception of dinuclear complex
2c. 3) The emissive behaviour of these complexes is almost un-
explored.
These complexes contain a closo-carborane dithiolate and
a nido-carborane bis-phosphane ligand and exhibit MꢀAu (5,
6), MꢀAg (7, 8) or MꢀCu (9, 10) interactions. For complexes 3–
10 the n(BH) band is observed at about 2500 cmꢀ1. A multiplet
at about ꢀ2 ppm due to the bridging hydrogen atom in the
open face of the carborane resulting from the partial degrada-
Different origins have been proposed for the luminescence
observed for complexes 2a and 2b, in which diimine ligands
complete the M(d10) coordination sphere, depending on the
compound type and M(d10). Although the assignments of such
emissions are not based on theoretical studies, the proposed
origins of the luminescence include neither metal-centred (MC)
transitions nor metal–metal interactions.[4a]
1
tion process appears in the H NMR spectra of complexes 5–
10. Comparison of the integral of this signal with that of the
broad resonance in the aromatic region indicated that only
one carborane cage has been partially degraded. Nucleophilic
attack is expected to occur on the carborane cluster of the bis-
phosphane ligand, rather than on that of the dithiolate. We
confirmed this by X-ray studies (see below).
The phosphorus atoms of the bis-phosphane appear as sin-
glets in the 31P NMR spectra of complexes 5–10 at about 85
(M=Pd: 5, 7, and 9) or 65 ppm (M=Pt: 6, 8, and 10). These
resonances are shifted to lower field relative to the starting
material [M{(PPh2)2C2B10H10)}(S2C2B10H10)]. The chemical shift of
the PPh3 ligand depends on M’: about 35 ppm for M’=Au,
about 15 ppm for M’=Ag and 4 ppm (M=Pd: 9) or ꢀ4 ppm
(M=Pt: 10) for M’=Cu. Complexes 7 and 8 display one singlet
and two doublets in their 31P{1H} NMR spectra. The singlet cor-
responds to the bis-phosphane, and the two doublets are as-
Results and Discussion
Synthesis and characterization
The reaction of (PPh2)2C2B10H10 with [MCl2(NCPh)2] (M=Pd, Pt)
affords complexes [MCl2{(PPh2)2C2B10H10}] [M=Pd (1), M=Pt
(2)]. The synthesis of both complexes has been previously de-
scribed. By changing the solvent[5] from toluene or benzene to
dichloromethane, we have shortened the reaction times. Both
complexes react with the dithiol (SH)2C2B10H10 to afford square-
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signed to coupling of the P atoms of the PPh3 ligand to the
silver isotopes 109Ag and 107Ag.
Crystal structure determinations
With the aim of obtaining analogous complexes displaying
NiꢀM’ (M’=Au, Ag, Cu) interactions, we carried out the reac-
tion of [NiCl2{(PPh2)2C2B10H10}] with (SH)2C2B10H10. It led to a mix-
ture of complexes which included the expected product, but
partial degradation of the bis-phosphane was observed. As it
was not possible to obtain pure samples of [Ni-
{(PPh2)2C2B10H10}(S2C2B10H10)], we
The structures of complexes 5–7, 9, and 11 were determined
by X-ray crystallography (Figure 3). They confirmed partial deg-
radation of the carborane cage of the bis-phosphane ligand,
and all of them show d8–d10 metallophilic interactions[6]
(Table 1). The only crystal structures reported of heterometallic
complexes with carborane ligands containing Group 11 and
tried
a one-pot synthesis to
obtain complexes with NiꢀM’
(M’=Au, Ag, Cu) interactions.
The reaction of NiCl2·6H2O with
Table 1. Bond lengths [ꢂ] for [M{(PPh2)2C2B9H10}(S2C2B10H10)M’(PPh3)].
Bond
Compound (M/M’)
7 (Pd/Ag)
(PPh2)2C2B10H10,
(SH)2C2B10H10,
5 (Pd/Au)
6 (Pt/Au)
9 (Pd/Cu)
11 (Ni/Au)
and [AuCl(PPh3)] in refluxing
methanol gave the expected
product 11. The one-pot reac-
tion of [NiCl2{(PPh2)2C2B10H10}]
with (SH)2C2B10H10 and [AuCl-
(PPh3)] in refluxing methanol/
ethyl acetate gave similar yields.
The 31P{1H} NMR spectrum of 11
displays one resonance at
74.5 ppm, due to the phospho-
rus atoms of the bis-phosphane
and another at 34 ppm, corre-
sponding to the PPh3 ligand.
MꢀP[a]
MꢀS
2.2592(12),
2.2851(12)
2.3349(11),
2.3905(12)
2.2599(12)
2.3282(11)
2.2689(18),
2.2417(18)
2.3331(19),
2.3629(18)
2.242(2)
2.2517(11),
2.2600(11)
2.3846(13),
2.4035(11)
2.3577(11)
2.4918(10),
2.8336(13)
2.9498(8)
0.0311
2.2527(13),
2.2569(13)
2.4027(13),
2.4172(13)
2.1903(14)
2.3172(13),
2.4187(15)
2.7519(9)
0.0060
2.1700(12),
2.2023(13)
2.1894(12),
2.2296(12)
2.2659(12)
2.3488(11)
M’ꢀP[b]
M’ꢀS
2.3338(12)
MꢀM’
3.2618(12)
0.00609
93.8
3.2251(7)
0.0885
86.5
3.0206(8)
0.0746
84.5
M[c]
a[d]
76.9
104.1
[a] Phosphorus atoms of the bis-phosphane. [b] Phosphorus atom of PPh3. [c] Deviation of M from the plane
built from P2, S1, S2. [d] Angle between planes 1 and 2: plane 1, built from atoms P1, P2, S1, and S2; plane 2,
built from atoms: M’, P3, and S. P1 and P2: phosphorus atoms of the bis-phosphane; P3: phosphorous atom of
PPh3.
Figure 3. Molecular diagrams of complexes 5 (a), 6 (b), 7 (c), 9 (d), and 11 (e) showing the atom-labelling schemes. Hydrogen atoms have been omitted for
clarity. Ellipsoids represent 50% probability levels.
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Group 10 metal atoms are metallacarborane complexes[7] and
the species [AgNiCl2{(PPh2)2C2B10H10}{(PPh2)2C2B9H10}],[8] in which
both bis-phosphanes are coordinated in a chelating mode. The
nido bis-phosphane is coordinated to the silver centre and the
closo bis-phosphane to the Ni atom. No metal–metal interac-
tion was reported for any of them. The PtꢀAu distance in 6 re-
sembles the shortest PtꢀAu intermetallic interactions in the
complexes discussed in the introduction,[4] whereas the PdꢀCu
and PdꢀAg distances in 7 and 9 are shorter than those report-
ed for such complexes.
The M(d8) metal centres have a square-planar coordination
environment. The main distortion is due to the bite angles of
the chelating bis-phosphane and dithiolate ligands (Table 2).
Table 2. Bond angles [8] for complexes [M{(PPh2)2C2B9H10}(S2C2B10H10)M’-
(PPh3)].
Compound (M/M’)
P[a]-M-P[a]
S-M-S
S-M’-P[b]
5 (Pd/Au)
6 (Pt/Au)
7 (Pd/Ag)
9 (Pd/Cu)
11 (Ni/Au)
82.75(4)
83.82(7)
85.57(4)
85.47(5)
84.79(5)
90.75(4)
91.03(6)
87.73(4)
84.92(5)
95.41(5)
175.44(3)
176.67(7)
156.24(4), 126.96(4)
141.41(5), 131.82(5)
176.27(5)
[a] Phosphorus atoms of the bis-phosphane. [b] Phosphorus atom of
PPh3.
The S-M(d8)-S angles range between 95.41 and 84.928, and
the P(bis-phosphane)-M(d8)-P(bis-phosphane) angles between
85.55 and 82.758 (Table 2).
Figure 4. DRUV spectra of [M{(PPh2)2C2B9H10}(S2C2B10H10)M’(PPh3)].
The M(d10) centres in 5, 6, and 11 are coordinated to the
phosphorus atom of the PPh3 ligand and one of the sulfur
atoms of the dithiolate in a distorted linear coordination
mode. This distortion probably arises mainly from the M(d8)ꢀ
M(d10) metallophilic interaction (see Tables 1 and 2). For com-
pound 7 a short distance of the silver atom to the other sulfur
atoms of the dithiolate and a larger distortion from the linear
geometry are observed compared to those of complexes 5, 6,
and 11. In complex 9 the copper centre is coordinated to both
sulfur atoms of the dithiolate, and the geometry of the copper
centre can be described as highly distorted trigonal planar.
Table 3. DRUV maxima, steady-state luminescence data, and lifetimes for
complexes [M{(PPh2)2C2B9H10}(S2C2B10H10)M’(PPh3)] (5–11) in the solid state
at 77 K.
Complex (M/M’)
DRUV
[nm]
lEm[a](lEx)[b]
[nm]
t[c]
[ms]
5 (Pd/Au)
6 (Pt/Au)
11 (Ni/Au)
7 (Pd/Ag)
8 (Pt/Ag)
9 (Pd/Cu)
10 (Pt/Cu)
310, 420
279, 365
320, 400, 500
305, 400
300, 415
267, 324
300, 400
630 (420)
620 (400)
600 (420)
615 (420)
610 (420)
650 (380)
600 (400)
39.7
43.1
55.6
96.6
26.9
61.2
83.4
[a] lEm =emission maximum. [b] lEx =excitation maximum. [c] Data were
fitted to a first-order exponential decay (R2 =0.97–0.99).
Photophysical studies
The diffuse-reflectance (DR) UV spectra of complexes 5, 7, 8,
and 10 exhibit similar patterns. They show a broad band with
maxima between 267 and 320 nm and a shoulder with a maxi-
mum between 324 and 420 nm (Figure 4, Table 3). Complex 11
displays another shoulder at about 500 nm, which spreads to
610 nm. The spectra of complexes 6 and 9 follow the same
pattern, but are shifted to higher energies. The most intense
band appears at about 270 nm, and the shoulder at 324 nm.
The bands at higher energies may be attributed to the phos-
phane aryl substituents, whereas that at lower energies may
be due to metallophilic interactions or to charge-transfer tran-
sitions, which could involve the metal centres (d8 and/or d10)
and the ligands (bis-phosphane and/or dithiolate).
The mononuclear complexes 1–4 are non-luminescent. Com-
plexes 5–11 are not emissive in the solid state at room temper-
ature. At 77 K they display emissions in the red region
(ꢁ620 nm) upon excitation at about 400 nm (Table 3). The life-
times, in the microsecond range, and the Stokes shifts indicate
a phosphorescent nature of the emission. The emission spectra
display similar profiles for all complexes, although for com-
pound 11 a structured band which spreads to 800 nm is ob-
served (Figure 5). The analysis of the data in Table 3 suggests
that the emission is not dependent on the metallophilic d8–d10
interaction. Thus, we propose that charge-transfer transitions
are responsible for the luminescence. With the aim of elucidat-
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Figure 5. Emission spectra of [M{(PPh2)2C2B9H10}(S2C2B10H10)M’(PPh3)].
ing which ligand (dithiolate and/or bis-phosphane) and which
metal centre (d8 and/or d10) are involved in such transitions,
calculations were carried out in order to visualise the orbitals
and make a proposal of how the transitions take place.
Figure 6. Selection of frontier molecular orbitals in [M-
{(PPh2)2C2B9H10}{S2C2B10H10}Au(PPh3)].
the emissions, the TDDFT method was employed to analyse
the first singlet!triplet transitions for complexes 5, 6, and 11
and the molecular orbitals involved in such transitions. By
comparing the calculated vertical excitation and experimental
excitation wavelengths, we can propose that such a transition
is responsible for the luminescence. Table 4 lists the more im-
portant orbitals involved in this transition. We note that the
calculated singlet!triplet excitation energies are lower than
the corresponding experimental values. Calculations at this
qualitative level do not allow any definitive conclusion about
MO energy levels, and the relation between excitation energy
and differences in MO energies is only approximately correct.
From the data of Table 4 and Figure 6 we can attribute the
origin of the luminescence to a charge-transfer transition from
Theoretical studies
Complexes [M{(PPh2)2C2B9H10}(S2C2B10H10)Au(PPh3)] (5, 6, and
11) were selected for a computational analysis. For all of the
complexes, the crystallographic structures were used as
models. The electronic structures of the complexes were ob-
tained by single-point DFT calculations on model systems built
up from the X-ray structures with the aim of analysing the
frontier molecular orbitals involved in the electronic transitions
responsible for the phosphorescence. Figure 6 shows a selec-
tion of the frontier orbitals. The HOMOꢀ2 for 5 and 6 and
HOMO for 11 have thiolate and metal (d8) contributions. Elec-
tron delocalisation on the carborane cage was found for the
HOMO of 5 and 6 and HOMOꢀ2 of 11. A predominant contri-
bution of s-antibonding orbitals of the d8 metal centre and
the dithiolate and bis-phosphane ligands in the LUMO orbitals
is observed for the three complexes.
An important point is that the metallophilic d8–d10 interac-
tion does not make a relevant contribution to the frontier orbi-
tals. This is in agreement with the emissive behaviour observed
for the complexes, which does not seem to be dependent on
the substitution of the d8 or d10 metal centre. Since the life-
times and Stokes shifts point to a phosphorescent nature of
Table 4. Calculated vertical excitation (lT) and experimental excitation
(lEx) energies for complexes [M{(PPh2)2C2B9H10}(S2C2B10H10)Au(PPh3)].
Compound (M/M’)
lEx
lT
Transition
[nm/eV]
[nm/eV]
5 (Pd/Au)
6 (Pt/Au)
11 (Ni/Au)
420/2.95 587/2.10 HOMOꢀ1(269)!LUMO(271)
400/3.10 490/2.52 HOMO(270)!LUMO(271)
420/2.95 571/1.42 HOMOꢀ1(269)!LUMO(271)
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7.63–7.72 (brm, 4H, Ph), 8.21–8.27 (brm, 8H, Ph); 31P{1H} NMR
(CDCl3, ppm): 79.0 (s); IR (cmꢀ1): n˜(BH)=2560 (s). Data for 2: ele-
mental analysis calcd (%) for C26H30B10Cl2P2Pt: C 40.10, H 3.88;
the ligand (L, nido-carborane) to the metal–ligand group “S2-
M(d8)-P2” (ML’) (LML’CT transition) for complex 6 (M=Pt), and
for complexes 5 (M=Pd) and 11 (M=Ni) to charge transfer
from the metal [M(d8)] to the metal–ligand group “S2-M(d8)-P2”
(ML’) (MML’CT charge transfer). The different origins of the
emissive behaviour could be related to the different electronic
character of the d8 metal centre, as Pt has the more stable d
orbitals.
1
found: C 39.76, H 3.49; H NMR (CDCl3, ppm): d=1–3 (brm, 10H,
BH), 7.56–7.64 (brm, 8H, Ph), 7.72–7.82 (brm, 8H, Ph), 8.23–8.28
(brm, 4H, Ph); 31P{1H} NMR (CDCl3, ppm): d=56.4 (s, J(195Pt,P)=
1876.0 Hz); IR: n˜(BH)=2566 cmꢀ1 (s).
[M{(PPh2)2C2B10H10}(S2C2B10H10)] [M=Pd (3), M=Pt (4)]: An excess
of K2CO3 was added to a solution of (SH)2C2B9H10 (0.1 mmol,
20.8 mg) in dichloromethane (20 mL). The resulting suspension
was stirred for one hour, and [MCl2{(PPh2)2C2B10H10}] (0.1 mmol, M=
Pd: 68.6 mg, M=Pt: 77.6 mg) was added. The mixture was stirred
for 3.0 h (M=Pd) or 6.0 h (M=Pt) and filtered through Celite. The
resulting solution was concentrated to about 5 mL. Addition of n-
hexane led to the precipitation of 3 and 4 as pale yellow solids in
78 and 74% yield, respectively. Data for 3: elemental analysis calcd
(%) for C28H40B20P2PdS2: C 40.74, H 4.88, S 7.77; found: C 41.03, H,
Conclusion
A
new family of red emitters of formula [M-
{(PPh2)2C2B9H10}(S2C2B10H10)M’(PPh3)] [M=Pd, Pt; M’=Au, Ag,
Cu] and [Ni{(PPh2)2C2B9H10}(S2C2B10H10)Au(PPh3)] has been syn-
thesised. The complexes exhibit a fluorophore ligand (nido-car-
borane bis-phosphane), a dithiolate (which may be responsible
for metal-to-thiolate or thiolate-to-metal charge-transfer transi-
tions) and d8 M(Ni, Pd, Pt)–d10 M’(Cu, Ag, Au) interactions,
which also may lead to emissive behaviour. Calculations for [M-
{(PPh2)2C2B9H10}(S2C2B10H10)Au(PPh3)] (M=Pd, Pt, Ni) attribute
the luminescence to ligand (thiolate, L)-to-“P2-M(d8)-S2” group
(ML’) charge-transfer (LML’CT) transitions for M=Pt and to
metal [M(d8)]-to-“P2-M(d8)-S2” group (ML’) charge-transfer
(MML’CT) transitions for M=Ni, Pd.
1
4.98, S 7.70; H NMR (CDCl3, ppm): d=0–3.5 (brm, 20H, BH), 7.52–
7.55 (brm, 8H, Ph), 7.60–7.64 (brm, 4H, Ph), 8.05–8.10 (brm, 8H,
Ph); 31P{1H} NMR (CDCl3, ppm): d=68.6 (s); IR (cmꢀ1): n˜(BH)=2568
(s). Data for 4: elemental analysis calcd (%) for C28H40B20P2PtS2: C
1
36.79, H 4.41, S 7.01; found: C 36.16, H 3.91, S 6.87; H NMR (CDCl3,
ppm): 0–3 (brm, 20H, BH), 7.59–7.75 (brvm, 15H, Ph), 8.05–8.10
(brm, 5H, Ph); 31P{1H} NMR (CDCl3, ppm): 59.1 (s, J(195Pt,P)=
1469.2 Hz); IR (cmꢀ1): n˜(BH)=2561 (s).
[M{(PPh2)2C2B9H10}(S2C2B10H10)Au(PPh3)] [M=Pd (5), Pt (6)]: [AuCl-
(PPh3)] (0.1 mmol, 49.7 mg) was added to a solution of [M-
{(PPh2)2C2B10H10}{S2C2B10H10}] (0.10 mmol, M=Pd: 78.9 mg, M=Pt:
91.0 mg) in ethanol (20 mL). The mixture was heated to reflux for
2 h (M=Pd) or 3 h (M=Pt). The solids that precipitated were col-
lected by filtration and washed with n-hexane to give 5 (yellow,
81% yield) and 6 (pale yellow, 62% yield). Data for 5: elemental
analysis calcd (%) for C46H55AuB19P3PdS2: C 43.37, H 4.35, S 5.03;
found: C 43.09, H 4.00, S 4.75; 1H NMR (CDCl3, ppm): d=ꢀ2.19
(brs, 1H, B-H-B), 0–3 (brm, 19H, BH), 6.99–7.03 (brm, 5H, Ph),
7.29–7.42 (brm, 10H, Ph), 7.64–7.78 (brm, 15H, Ph), 8.02–8.05
(brm, 5H, Ph); 31P{1H} NMR (CDCl3, ppm): d=80.3 (s, bis-phos-
phane), 34.4 (s, PPh3); IR (cmꢀ1): n˜(BH)=2560 (s). Data for 6: ele-
mental analysis calcd (%) for C46H55AuB19P3PtS2: C 40.55, H 4.06, S
4.70; found: C 40.95, H 4.53, S 4.06; 1H NMR (CDCl3, ppm): d=
ꢀ2.30 (brs, 1H, B-H-B), 0–3.5 (brm, 19H, BH), 7.01–7.03 (brm, 5H,
Ph), 7.35–7.72 (brvm, 25H, Ph), 7.94–7.98 (brm, 5H, Ph); 31P{1H}
NMR (CDCl3, ppm): 60.1 (s, J(P,195Pt)=1528.4 Hz, bis-phosphane),
32.7 (s, PPh3); IR (cmꢀ1): n˜(BH)=2555 (s).
Experimental Section
General comments
(SH)2C2B10H10,[9] (PPh2)2C2B10H10,[10] [MCl2{(PPh2)2C2B10H10}] [M=Pd,[5a]
Pt,[5b] Ni[11]], [AuCl(PPh3)],[12] [Ag(OTf)(PPh3)],[13] and [Cu(NO3)-
(PPh3)2][14] were synthesised according to published procedures.
Other reagents and solvents were used as received. Solution 1H
and 31P NMR spectra were recorded with Bruker Avance 400 and
Bruker DPX 300 spectrometers. If not specified, the 400 MHz spec-
trometer was used. The chemical shifts were referenced to residual
1
resonances of protiated solvent and external 85% H3PO4 in the H
and 31P spectra, respectively. Mass spectra were determined on
a Bruker APEX-Qe ESI FT-ICR instrument in the ESI+ mode. DRUV
spectra were recorded on Unicam UV-4 spectrophotometer
equipped with a Spectralon RSA-UC-40 Labsphere integrating
sphere. The solid samples were mixed with dried KBr to obtain
a homogeneous powder. The mixtures were placed in a home-
made cell equipped with quartz window. The intensities are given
in Kubelka–Munk units. Steady-state photoluminescence spectra
were recorded on a HORIBA Jobin Yvon Fluorolog FL-3-11 spec-
trometer with band pathways of 3 nm for both excitation and
emission. Phosphorescence lifetimes were recorded with a Fluoro-
max phosphorimeter accessory containing an UV xenon flash tube.
[M{(PPh2)2C2B9H10}(S2C2B10H10)Ag(PPh3)] [M=Pd (7), Pt (8)]: [Ag-
(OTf)(PPh3)] (0.1 mmol, 51.8 mg) was added to a solution of [M-
{(PPh2)2C2B10H10}(S2C2B10H10)] (0.10 mmol, M=Pd: 78.9 mg; Pt:
91.0 mg) in ethanol (20 mL) . The mixture was heated to reflux for
2 h (M=Pd) or 5 h (M=Pt). During this period a yellow solid pre-
cipitated, which was filtered off and washed with n-hexane to give
7 (78% yield) and 8 (56% yield). Data for 7: elemental analysis
calcd (%) for C46H55AgB19P3PdS2: C 46.63, H 4.67, S 5.41; found: C
Synthesis
[PdCl2{(PPh2)2C2B10H10}][M=Pd (1), M=Pt (2)]: [MCl2(NCPh)2]
(0.1 mmol, M=Pd: 38.4 mg, M=Pt: 47.2 mg) was added to a solu-
tion of (PPh2)2C2B10H10 (0.1 mmol, 50.9 mg) in dichloromethane
(20 mL). The solution was stirred for 2 (M=Pd) or 6 h (M=Pt). Con-
centration of the solution under reduced pressure and addition of
n-hexane led to precipitation of 1 and 2 as yellow solids in 98 and
87% yield, respectively. Data for 1: elemental analysis calcd (%) for
1
46.82, H 4.78, S 5.10; H NMR (CDCl3, ppm): d=ꢀ2.08 (brs, 1H, B-
H-B), 0–3 (brm, 19H, BH), 6.91–6.94 (brm, 5H, Ph), 7.27–7.44 (brm,
10H, Ph), 7.60–7.69 (brm, 15H, Ph), 8.06–8.11 (brm, 5H, Ph); 31P{1H}
NMR (300 MHz, CDCl3, ppm): d=84.4 (s, bis-phosphane), 15.01 (td,
J(109Ag,P)=692.55, J(107Ag,P)=595.34 Hz, PPh3); IR (cmꢀ1): n˜(BH)=
2568 (s). Data for 8: elemental analysis calcd (%) for
C46H55AgB19P3PtS2: C 43.38, H 4.35, S 5.03; found: C 43.94, H 4.63, S
4.70; 1H NMR (CDCl3, ppm): ꢀ2.20 (brs, 1H, B-H-B), 0–3.5 (brm,
1
C26H30B10Cl2P2Pd: C 45.26, H 4.38; found: C 44.96, H 4.25; H NMR
(CDCl3, ppm): d=1–3 (brm, 10H, BH), 7.54–7.58 (brm, 8H, Ph),
Chem. Eur. J. 2014, 20, 3120 – 3127
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ꢁ 2014 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

Full Paper
19H, BH), 6.94–6.97 (brm, 5H, Ph), 7.29–7.39 (brm, 10H, Ph), 7.55–
7.67 (brm, 15H, Ph), 7.96–8.0 (brm, 5H, Ph); 31P{1H} NMR (300 MHz,
CDCl3, ppm): 62.5 (s J(195Pt,P)=1515.6 Hz, bis-phosphane), 12.7 (dd,
J(109Ag,P)=716.85, J(107Ag,P)=615.04 Hz, PPh3); IR (cmꢀ1): n˜(BH)=
2562 (s).
Crystallography
A crystal of each compound was mounted in inert oil on a glass
fibre and transferred to the cold gas stream of a Xcalibur Oxford
Diffraction diffractometer (5, 6, 7, 9, and 11) or Bruker Smart Apex
CCD (6) equipped with a low-temperature attachment. Data were
collected by using monochromated MoKa radiation (l=0.71073 ꢂ)
[M{(PPh2)2C2B9H10}(S2C2B10H10)Cu(PPh3)] [M=Pd (9), Pt
(10)]:
A suspension of [M{(PPh2)2C2B10H10}(S2C2B10H10)]
(0.10 mmol, M=Pd: 78.9 mg, M=Pt: 91.0 mg) and [Cu-
(NO3)(PPh3)2] (0.10 mmol, 64.9 mg) in ethanol (20 mL)
was heated to reflux for 2 h (M=Pd) or 3 h (M=Pt). The
solid that precipitated was filtered off and washed with
n-hexane to give 9 (yellow, 77% yield) or 10 (pale
yellow, 52% yield). Data for 9: elemental analysis calcd
(%) for C46H55CuB19S2P3Pd: C 48.44, H 4.86, S 5.62; found:
Table 5. X-ray data for complexes 5–7.
5
6
7
formula
crystal system
space group
a [ꢂ]
b [ꢂ]
c [ꢂ]
C46H54AuB19P3PdS2
triclinic
ꢀ
P1
C49H60AuB19P3PtS2
triclinic
ꢀ
P1
C48H57AgB19Cl6P3PdS2
triclinic
ꢀ
P1
1
11.432(2)
15.421(3)
16.144(3)
82.08(3)
84.36(3)
75.12(3)
2718.6(9)/2
1.555
11.575(3)
13.389(3)
19.235(5)
78.242(5)
85.205(4)
78.588(5)
2857.8(12)/2
1.631
12.184(2)
15.788(3)
17.317(4)
72.28(3)
85.81(3)
89.75(3)
3164.1(11)/2
1.494
C 48.14, H 4.53, S 5.86; H NMR (CDCl3, ppm): d=ꢀ2.05
(brs, 1H, B-H-B), 0–3.5 (brm, 19H, BH); 6.86–6.78 (brm,
5H, Ph); 7.38–7.66 (brvm, 25H, Ph), 8.05–8.10 (brm, 5H,
Ph), 31P{1H} NMR (CDCl3, ppm): d=87.3 (s, bis-phos-
phane), 3.9 (s, PPh3); IR (cmꢀ1): n˜(BH)=2560 (s). Data for
10: elemental analysis calcd (%) for C46H55CuB19P3PtS2: C
44.95, H 4.51, S 5.21; found: C 44.68, H,4.27, S 5.36;
1H NMR (CDCl3, ppm): d=ꢀ2.15 (brs,1H, B-H-B), 0–3.5
(brm, 19H, BH), 7.06–7.20 (brm, 10H, Ph), 7.29–7.75
(brvm, 20H, Ph), 7.99–8.05 (brm, 5H, Ph); 31P{1H} NMR
(CDCl3, ppm): 62.5 (s, J(195Pt,P)=1521.5 Hz, bis-phos-
phane), ꢀ3.3 (s, PPh3); IR (cmꢀ1): n˜(BH)=2578 (s).
a [8]
b [8]
g [8]
V [ꢂ3]/Z
1calcd [Mgmꢀ3
]
m [mmꢀ1
F(000)
T [8C]
]
3.225
1254
5.201
1366
1.024
1424
ꢀ173
ꢀ173
ꢀ173
2qmax
50
50
50
measured reflns
independent reflns
transmission
Rint
parameters
restraints
100882
9546
0.626–0.734
0.0494
653
22149
9988
0.530–0.746
0.0581
734
90662
11110
0.923–0.960
0.0246
807
[Ni{(PPh2)2C2B9H10}(S2C2B10H10)Au(PPh3)] (11): Method a:
(SH)2C2B10H10 (0.1 mmol 20.8 mg) and [AuCl(PPh3)]
(0.1 mmol 49.7 mg) were added to a solution of [NiCl2-
{(PPh2)2C2B10H10}] (0.10 mmol, 77.3 mg) in methanol
(20 mL). The solution was heated to reflux for 4 h.
During this time a red solid appeared which was filtered
off and washed with n-hexane (60% yield). Method b: A
solution of (PPh2)2C2B10H10 (0.10 mmol, 50.9 mg) and
NiCl2·6H2O (0.10 mmol, 23.7 g) in ethyl acetate/methanol
(10/10 mL) was stirred for 10 min, after which
21
18
21
wR(F2, all reflns)
R [I>2s(I)]
S
0.0692
0.0288
1.058
0.0947
0.0431
0.984
0.0891
0.0376
0.0827
1.599
D1max [eꢂꢀ3
]
1.219
1.449
Table 6. X-ray data for complexes 9 and 11.
(SH)2C2B10H10 (0.1 mmol, 20.8 mg) and [AuCl(PPh3)] (0.1 mmol,
49.7 mg) were added. The solution was heated to reflux for 4 h.
During this time a red solid appeared which was filtered off and
washed with n-hexane (90% yield). Elemental analysis calcd (%) for
C46H55AuB19NiP3S2: C 46.27, H 4.64, S 2.68; found: C 46.94, H 4.95, S
Compound
9
11
formula
crystal system
space group
a [ꢂ]
b [ꢂ]
c [ꢂ]
C48H57B19Cl6Cu P3PdS2
triclinic
ꢀ
P1
C46H55AuB19NiP3S2
monoclinic
P21/n
10.948(2)
28.848(6)
17.306(4)
90
90.53(3)
90
5465.5(19)/4
1.490
1
2.47; H NMR (CDCl3, ppm): d=ꢀ2.44 (brs,1H, B-H-B), 0–3.5 (brm,
12.103(2)
15.632(3)
17.342(4)
106.74(3)
93.14(3)
90.95(3)
3135.2(11)/2
1.461
19H, BH); 6.99–7.03 (brm, 5H, Ph); 7.19–7.23 (brm, 5H, Ph), 7.33–
7.38 (brm, 5H, Ph), 7.60–7.74 (brm, 15H, Ph), 8.04–8.08 (brm, 5H,
Ph); 31P{1H} NMR (CDCl3, ppm): d=74.5 (s, bis-phosphane); 34.6 (s,
PPh3); IR (cmꢀ1): n˜(BH)=2568 (s).
a [8]
b [8]
g [8]
V [ꢂ3]/Z
1calcd [Mgmꢀ3
]
m [mmꢀ1
F(000)
T [8C]
]
1.060
1388
3.224
2440
DFT and TDDFT calculations
ꢀ173
ꢀ173
In all calculations the PBE functional[15] and TURBOMOLE 6.0 pro-
gram[15c,16] were used. Single-point DFT[17] calculations were per-
formed on model systems built up from the X-ray structures. The
calculated vertical excitation energies were obtained by the time-
dependent (TD) DFT approach.[18] The Karlsruhe split-valence quali-
ty def2-SV(P) basis sets with additional polarization functions on
non-hydrogen atoms were used.[19] The resolution of the identity
method was used to speed up calculations.[20] The Stuttgart effec-
tive core potentials, which include scalar relativistic effects, were
used for Ni, Pd, Pt, and Au.[21] The calculations were performed
without symmetry constraints.
2qmax
50
50
measured reflns
independent reflns
transmission
Rint
parameters
restraints
88498
11008
0.857–0.949
0.0458
801
58474
8480
0.374–0.627
0.0776
729
21
0
wR(F2, all reflns)
R [I>2s(I)]
S
0.1295
0.0545
0.916
0.0648
0.0354
0.980
D1max [eꢂꢀ3
]
2.383
1.473
Chem. Eur. J. 2014, 20, 3120 – 3127
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3126
ꢁ 2014 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

Full Paper
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1983, 75, 51.
with scan type w. Absorption correction based on multiple scans
was applied with the program SADABS.[22] The structure was re-
fined on F2 by using the program SHELXL-97.[23] All non-hydrogen
atoms were refined anisotropically. Hydrogen atoms were included
by using a riding model. Further details of the data collection and
refinement are given in Tables 5 and 6. CCDC 961295 (5), 961296
(6), 961297 (7), 961298 (9), and 961299 (11) contain the supple-
mentary crystallographic data for this paper. These data can be ob-
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[13] a) M. Bardaji, O. Crespo, A. Laguna, K. Fischer, Inorg. Chim. Acta 2000,
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We thank the Ministerio de Economꢃa y Competitividad for
project MEC/FEDER CTQ2007-67273-C02-01 and grant BES-
2008002858 and the Academy of Finland for project 126905.
We also thank the Finnish Centre of Excellence in Computa-
tional Molecular Science (CMS) and the CSC-IT Centre for Sci-
ence, Espoo, Finland, for the computer resources provided.
[14] G. J. Kubas, Inorg. Synth. 1979, 19, 90.
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Keywords: carboranes
luminescence · metal–metal interactions · transition metals
·
heterometallic
complexes
·
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Received: September 24, 2013
Published online on February 13, 2014
Chem. Eur. J. 2014, 20, 3120 – 3127
www.chemeurj.org
3127
ꢁ 2014 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim