Gold(iii) compounds containing a chelating, dicarbanionic ligand derived from 4,4′-di-tert-butylbiphenyl

Article abstract of DOI:10.1039/c4dt00778f

An oligomeric gold(iii) compound containing dicarbanionic chelating 4,4′-di-tert-butylbiphenyl was prepared via transmetallation using the corresponding organotin(iv) compound. The reactivity of the chloro-bridged oligomer with various species including neutral N-, P-, and C-donor ligands as well as monoanionic S- and Se-ligands was investigated. Some of the products were characterised by X-ray crystallography. The photophysical properties of two derivatives were studied.

Full text of DOI:10.1039/c4dt00778f

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Gold(III) compounds containing a chelating,
dicarbanionic ligand derived from 4,4’-di-
tert-butylbiphenyl†
Cite this: Dalton Trans., 2014, 43,
11059
B. David,a U. Monkowius,b J. Rust,c C. W. Lehmann,c L. Hyzaka and F. Mohr*c
An oligomeric gold(III) compound containing dicarbanionic chelating 4,4’-di-tert-butylbiphenyl was
prepared via transmetallation using the corresponding organotin(IV) compound. The reactivity of the
chloro-bridged oligomer with various species including neutral N-, P-, and C-donor ligands as well as
monoanionic S- and Se-ligands was investigated. Some of the products were characterised by X-ray
crystallography. The photophysical properties of two derivatives were studied.
Received 14th March 2014,
Accepted 23rd May 2014
DOI: 10.1039/c4dt00778f
www.rsc.org/dalton
in the oxidation state +3 a MLCT is not favoured. For these
complexes containing ligands with an extended π-system an
Introduction
The transfer of an organic group to a gold centre is tradition- emissive IL excited state is feasible, but the energetically low
ally carried out using organolithium compounds, Grignard lying dd-states quench potential emissive states of most Au(III)
reagents or organomercurials.1,2 There are however alternative complexes. However, these dd-states can be destabilized by
transmetallation agents, which are particularly attractive strong field ligands diminishing the radiationless deactivation.
because of their insensitivity to air and moisture, their mild Consequently, several cyclometallated complexes of the
reaction conditions and simple work-up. These include general formula [Au(C–N)L2]n+ (C–N = 2-phenylpyridine type
organotin(IV) compounds and boronic acids.3–9 Whilst the ligand; L = acetylide, NHC; n = 0 or 2) and similar complexes
former have been used in the preparation of both gold(I) and bearing pincer type ligands including 2,6-diphenylpyridine or
gold(III) compounds, the latter are so far limited to gold(I). 6-phenyl-2,2′-bipyridine were reported to feature luminescence
Gold(III) compounds represent interesting alternatives to other even in fluid solution at room temperature. The emissions are
metal-based luminescent compounds with a d8 electron con- mostly assignable to an 3IL-transition and sometimes these
figuration.10,11 For Pd(II) and Pt(II) complexes (in the absence complexes also show a dual emission of both 1IL and 3IL char-
of metal–metal interactions) the emissive excited state is either acter.13 Luminescent cyclometallated Au(III) complexes were
a metal-to-ligand charge transfer (MLCT) or an intra-ligand reviewed in 201111 and since then, several new examples of
(IL) transition (or a mixture of both) and of triplet-character this type were published.14–22 To the best of our knowledge,
(phosphorescence).12 Their metal-centred transitions are there is only one report on a luminescent Au(III) complex
usually at high energy and do not strongly influence the lumi- bearing a biphenyl moiety: [Au(Ppy)(Bip)] (Ppy = 2-phenyl-
nescence properties, which is important as these dd-states pyridine; Bip = biphenyl).23 However, the second chromophore
usually lead to a very efficient radiationless deactivation of the (Ppy) complicates the precise assignment of the transition.
excited state. Au(III) complexes are much less investigated due Indeed, according to TD-DFT calculations, both a ligand-to-
to some preconditions which have to be fulfilled for an emis- ligand charge transfer (3LLCT) [π(Bip) → π*(Ppy)] and 3IL
sive behaviour: because of the high oxidation potential of gold [π(Bip) → π*(Bip)] contribute to the excited state. For this
reason, the complexes presented below are particularly valu-
able, because they allow the investigation of the discrete
chromophoric Au(III)-biphenyl moiety.
aFachbereich C, Anorganische Chemie, Bergische Universität Wuppertal, Gaußstr. 20,
42119 Wuppertal, Germany. E-mail: fmohr@uni-wuppertal.de
bInstitut für Anorganische Chemie, Johannes Kepler University Linz, Altenbergerstr.
69, 4040 Linz, Austria
In continuation of our work on the design of organogold(I)
compounds and their applications,8,24–28 we now wished to
extend this to gold(III) and report here the preparation of an
auracycle derived from 2,2′-dibromo-4,4′-di-tert-butylbiphenyl
and its derivatives as well as detailed photophysical studies of
some compounds.
cMax-Planck-Institut für Kohlenforschung, Kaiser-Wilhelm-Platz 1, 45470 Mülheim
an der Ruhr, Germany
†CCDC 973049, 973050, 973052 and 973053. For crystallographic data in CIF or
other electronic format see DOI: 10.1039/c4dt00778f
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analogous unsubstituted biphenyl species [AuCl(Bip)]n it was
also proposed that n = 2.4 Furthermore, the formation of a
halide bridged arylgold(III) dimer has been confirmed by a
Results and discussion
Synthesis and reactivity
The organotin(IV) heterocycle [Sn(tBu2Bip)(nBu)2] (1) (tBu2Bip = structural study of the mesityl gold compound [AuCl(mes)]2.29
4,4′-di-tert-butylbiphenyl-2,2′-diyl) was prepared in good yield Similarly to what was reported by Usón for the biphenyl deriva-
from the reaction of 2,2′-dibromo-4,4′-di-tert-butylbiphenyl tive,4 the addition of donor ligands including pyridine, PTA
n
with two equivalents of BuLi and subsequent addition of one (1,3,5-triaza-7-phosphaadamantane) or xylyl isonitrile to a
equivalent of nBu2SnCl2 according to a modified literature pro- CH2Cl2 suspension of 2 results in rapid dissolution of the
cedure (Scheme 1). An improved method for the preparation of dimer. Out of these solutions the monomeric gold(III) com-
2,2′-dibromo-4,4′-di-tert-butylbiphenyl which uses CH2Cl2 plexes [AuCl(tBu2Bip)(L)] [L = Py (3); PTA (4), XyNC (5)] were
instead of CCl4 was also developed. The tin species isolated as pale yellow solids in good yields. The Au(III) deriva-
[Sn(tBu2Bip)(nBu)2] (1) reacts with H[AuCl4] in refluxing aceto- tive containing the N-heterocyclic carbene donor ligand (7)
nitrile to give a cream coloured material in moderate yield was obtained by a transmetallation reaction of 2 with the
(Scheme 1). The same compound could also be obtained (in NHC-silver complex Cl2Me2ImAgI. The chlorido ligands in
similar yield) using [AuCl3(tht)]. However, commercial 2 can also be replaced by monoanionic chelating ligands as
H[AuCl4] was more convenient and also avoids use of malo- exemplified by compounds 8–10 which were obtained by
dorous tetrahydrothiophene.
addition of NaS2CNEt2 or the acylthio- and selenoureas
t
Our hope that the presence of the two Bu-groups on the 4-MeC6H4C(O)NHC(E)NEt2 (E = S, Se) to a suspension of 2 in
biphenyl unit might improve the solubility of the compound the presence of base (Scheme 1). These monomeric gold(III)
was unfortunately not realised. The cream coloured compound compounds were characterized by solution NMR spectroscopy
which we formulate as the oligomer [AuCl(tBu2Bip)]n (2) could and elemental analysis. In the case of complexes 3–5, 7 and
not be characterised by solution NMR spectroscopy due to its 9–10, there appear two sets of resonances for the Bu-biphenyl
insolubility in common solvents. However, MALDI mass groups in the H NMR spectra due to the non-equivalence of
t
1
spectra, recorded using a solvent-free sample preparation tech- the two aromatic rings. While it was easy to determine which
nique and the dried-droplet technique, showed signals corres- signals belong to the same ring using 2D NMR experiments, it
ponding to the dimer [AuCl(tBu2Bip)]2 as well as a fragment was not always possible to assign absolutely which proton
+
peak due to [{AuCl(tBu2Bip)}2–Cl]+. The fragment peak gives belongs to which ring. However, in the case of the pyridine
the most intense signal in all mass spectra recorded. The and NHC complexes (3 and 7), one set of doublets corres-
ionization in positive mode seems to favour the loss of one ponding to H-3 of the biphenyl ring is shifted considerably
chloride ion towards the formation of a radical cation of the upfield (to ca. 6.4 ppm). We attribute this shift to be caused by
aromatic system. This mass spectroscopic data suggests that the close proximity of the aromatic ring (Py or NHC), the
n = 2 i.e. compound 2 may be a chloro-bridged dimer. For the centre of which lies almost directly above this proton. With
this information we could subsequently assign all proton and
carbon signals unambiguously in these two compounds. In
the carbene complex 7 the resonance of the carbene-carbon
atom was observed at 186 ppm in the 13C NMR spectrum.30
For comparison, in NHC-AuCl3 complexes the chemical shifts
of the carbene-carbon atom fall within the range of 140 to
150 ppm. The gold(III) isonitrile complex (5) was reacted with
Et2NH at room temperature affording a gold(III) compound
containing an N-acyclic carbene (NAC) ligand [AuCl(tBu2Bip)-
{C(NEt2)(NHXy)}] (6) (Scheme 1). Whilst the proton NMR data
for this compound is not very diagnostic, the 13C NMR spec-
trum shows a resonance at 209 ppm due to the carbene-
carbon atom. Similar addition reactions of secondary amines
to chlorogold(I) isonitrile complexes giving chlorogold(I)-NAC
derivatives have previously been described.31 In these com-
pounds the resonance for the carbene-carbon atoms are
observed at around 190 ppm in the 13C NMR spectra. Unfortu-
nately, we were unable to obtain X-ray quality crystals of the
NAC derivative 6 despite numerous attempts to unambiguously
confirm the proposed structure.
Structural studies
We were able to obtain X-ray quality crystals of several of the
Scheme 1
gold(III) compounds reported here. The molecular structures of
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compounds 3, 5, 8 and 10 are shown in Fig. 1–4. Selected
bond lengths and angles are collected in Table 1.
In all of the compounds reported here, the gold atom is co-
ordinated by two carbon atoms of the biphenyl unit as well as
two other ligand atoms in a square planar arrangement, as
expected for gold(III). The carbon–gold bond-lengths are typical
for aromatic compounds bound to a gold(III) centre. Only one
other crystal structure of a gold(III) complex containing a
dicarbanionic, chelating biphenyl ligand has been reported so
far.12 The carbon–gold bond lengths show a narrow distri-
bution centered at 2.05 Å. The carbon–gold–carbon angle is
significantly smaller than 90° and comparable to the bite
angle in phenylpyridyl ligands. The acylselenoureato complex
(10) represents the only known example of a gold(III) com-
Fig. 4 Molecular structure of [Au(tBu2Bip){4-MeC6H4C(O)NC(Se)NEt2}]
(10). Only one of the two independent molecules of the asymmetric unit
is shown. Hydrogen atoms have been omitted for clarity. The disordered
tBu-groups are shown as spheres with arbitrary radii.
pound containing
a deprotonated acylselenourea ligand.
Table 1 Selected bond lengths and angles of the gold coordination
spherea
(3)
(5)
(8)
(10)
Au–C1
Au–C2
Au–L3
Au–L4
2.0233(1)
2.029(2)
2.024(2)
2.025(2)
2.038(3)
2.036(3)
2.0328(11)
2.0277(12)
2.0267(11)
2.0386(11)
2.048(6)
2.043(5)
2.022(6)
2.027(5)
2.3757(5) [Cl] 2.3762(7) [Cl] 2.3810(3) [S] 2.4551(10) [Se]
2.3686(5)
2.1326(17) [N] 2.069(3) [C]
2.1500(17)
2.4077(3)
2.3947(3) [S] 2.099(4) [O]
2.4599(9)
2.3802(3)
74.610(12)
74.315(13)
177.64(3)
174.08(3)
174.81(3)
178.26(3)
81.47(5)
2.084(4)
91.63(12)
93.30(11)
175.63(15)
176.28(15)
172.8(2)
171.19(19)
81.1(2)
L3–Au–L4 88.68(5)
87.77(5)
C1–Au–L3 176.81(6)
173.64(6)
C2–Au–L4 172.85(7)
177.18(8)
C1–Au–C2 80.85(8)
81.30(8)
85.95(8)
Fig. 1 Molecular structure of [Au(tBu2Bip)(Py)] (3). Only one of the two
independent molecules of the asymmetric unit is shown. Hydrogen
atoms have been omitted for clarity.
179.31(12)
175.85(8)
81.27(12)
81.29(5)
81.2(2)
a Standard uncertainties are given in parentheses. For ligands L3 and
L4 the atom type is given in square brackets. For those crystal
structures with more than one molecule in the asymmetric unit, bond
lengths and angles for both molecules are listed in separate rows.
Generally, attempts to react such organoselenium species with
gold(III) precursors have resulted in reduction to gold(I)
accompanied by oxidation of the selenium compound.32,33
The dianionic chelating carbon ligand is likely to be stabilising
this complex in the +3 oxidation state.
Fig. 2 Molecular structure of [Au(tBu2Bip)(XyNC)] (5). Hydrogen atoms
have been omitted for clarity.
Photophysical studies
The pyridyl and isonitrile complexes 3 and 5 displayed blue
luminescence upon irradiation with a UV lamp, therefore
more detailed photophysical studies were carried out with
these two compounds. For both complexes, comparable photo-
physical behaviour typical for Au complexes bearing a ligand
with an extended and rigid π-system could be observed.13,34–36
The electronic absorption spectra exhibit features at ∼250 nm
and a band centred around 300 nm (Fig. 5).
The high energy signals are superimposable with the
absorption of free biphenyl37 and can be assigned to a π–π*
transition. Frequently, IL bands are bathochromic shifted due
Fig. 3 Molecular structure of [Au(tBu2Bip)(S2CNEt2)] (8). Hydrogen
atoms have been omitted for clarity.
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a strong influence of the rigidity of the environment and/or of
the supramolecular arrangement of the molecules.
Formation of excimers can be ruled out due to the bulky
t-butyl substituents of the ligand. In addition, we could not
observe any evidence for excimer based absorption or emission
bands in solution. A detailed investigation in solution is some-
what hampered by the photosensitivity of the compounds. In
de-aerated solutions, the emission signals are very weak at
room temperature. The low emission intensity of solutions of
luminescent Au(III) complexes is well known and a result of the
photoreductive elimination of e.g. the halide ligands and of
low-energy non-radiative d–d LF states.10,11,13,34,40 On the other
hand, the luminescence of the complexes becomes more
intense in a glass matrix at 77 K or as neat powders, where
competing quenching processes are minimized. Both com-
pounds feature structured emission bands both in solid state
and solutions typical for an intraligand π–π* transition. Again,
there is no evidence for excimer based emissions. A huge
Stokes shift and a long emission decay time in the micro-
second regime indicate phosphorescence from a 3LC state
(Table 2).
This assignment is further supported be the vibrational
progressional spacing (e.g. 1351 and 1217 cm−1 for solid 3 at
r.t.; Fig. 6), which are similar to biphenyl (1055 and
1274 cm−1) and typical for vibrational stretching modes of aro-
matic ligands.41 It should be noted, that the homologous Au(I)
complex [Au(Bip)(PPh3)] features a very similar luminescence
behaviour with somewhat hypsochromic shifted emission
bands.42 It is instructive to compare these data with the iso-
electronic [Pt(Bip)L2] complexes (L = neutral ligands such as
CO, phosphines, COD).43 Whereas the wavelengths of the
emission bands are similar, their emission decay times are
almost one magnitude smaller. Due to the fact that the spin
orbit coupling (SOC) is slightly higher for gold than for plati-
num, the spin-forbidden T1→S0 transition for the gold com-
plexes should be at least as probable as for Pt(II) complexes.
This fact shines light on the different nature of the emissive
state: The d-orbitals of the highly oxidizing Au(III) ions do not
directly participate in the electronic transition rendering the
SOC rather low in spite of the high atomic number of the gold.
This interpretation is further supported by the very similar
photophysical behaviour of Au(I) complexes bearing ligands
Fig. 5 Electronic spectra of 3: (a) absorption spectrum, (b) emission
spectrum at r.t. in CH2Cl2 (c ≈ 10−5 mol L−1, degassed, λexc = 310 nm),
and (c) excitation spectrum (λdet = 520 nm), and emission spectrum at
77 K in MeTHF glass (c ≈ 10−5 mol L−1, λexc = 310 nm).
to metal coordination, i.e. the low energy bands might result
from further, metal perturbed IL transitions covering the Cl →
Au ligand-to-metal-charge-transfer (LMCT) states, which are
usually of lower intensity.36,38–40 Interestingly, these low energy
excited states are even further bathochromically shifted in the
solid state. In the excitation spectra of neat 3 intensive bands
reaching up to 400 nm (Fig. 6) are observed, clearly indicating
Fig. 6 Electronic spectra of neat 3: excitation (left, λdet = 480 nm) and
emission spectra (right, λexc = 310 nm) at r.t. (red) and at 77 K (blue).
Table 2 Photophysical data of compounds 3 and 5
Compound
Absorption λmax (lgε)
Medium
Emission λmax
Excitation λmax
τ [μs]
a
3
244 (4.36), 253 (4.38), 265 sh (3.75),
284 (3.75), 304 (3.77), 316 (3.76)
CH2Cl2 (r.t.)
MeTHF (77 K)
Solid (r.t.)
485, 517, 554
470, 506, 545
485, 519, 554
481, 517, 555
—
250, 274, 283, 300, 315
270, 330, 347
275, 326, 346
220
48
77
Solid (77 K)
a
5
254 (4.90), 275 sh (4.43),
286 sh (4.29), 305 (3.99), 317 (4.01)
CH2Cl2 (r.t.)
MeTHF (77 K)
Solid (r.t.)
501, 533, 576
483, 517, 553
492, 529, 568, 615 sh
484, 496, 523, 566, 613 sh
—
315, 302, 283 sh, 276
275, 331, 344
275, 325, 344
150
61
92
Solid (77 K)
a Due to the photosensitivity and low intensity of the emission, no reliable emission decay time could be measured in solution at r.t.
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with an extended π-system and leads to the conclusion that the The resulting orange solid was recrystallised from EtOH to
gold atom (regardless of its oxidation state) is modulating the afford yellow needles of 2,2′-dibromo-4,4′-di-tert-butylbiphenyl
electronic properties of the ligand according to the so called in 63% yield. GC-MS (m/z): 424 [M]+, 409 [M − CH3]+, 313 [M −
“external heavy atom effect”.44 In contrast, the metal character 2 tBu]+. 1H NMR (600 MHz, CDCl3): δ = 1.40 (s, 18 H, tBu), 7.21
of the excited triplet states of the Pt(II) complexes are high (d, J = 8.0 Hz, 2 H, H-6), 7.41 (dd, J = 8.8, 2.0 Hz, 2 H, H-5),
even in cases where the transitions are dominantly ligand 7.70 (d, J = 2.0 Hz, 2 H, H-3). 13C{1H} NMR (151 MHz, CDCl3):
centred. Therefore, the SOC is more effective resulting in δ = 31.23 (tBu), 34.70 (tBu), 123.40 (C-2), 124.14 (C-5), 129.48
shorter emission decay time.
(C-6), 130.72 (C-3), 139.01 (C-1), 152.65 (C-4). Elemental ana-
lysis calcd (%) for C20H24Br2: C 56.6, H 5.7; found: C 56.2, H 5.9.
[Sn(tBu2Bip)(nBu)2] (1). To a solution of 2,2′-dibromo-4,4′-di-
tert-butylbiphenyl (1.9 g, 4.4 mmol) in Et2O (20 mL) was slowly
Conclusions
n
added BuLi (3.7 mL of a 2.5 M solution in hexanes) at 0 °C.
A family of gold(III) compounds containing dicarbanionic che- After complete addition the mixture was allowed to warm to
lating ligands derived from 4,4′-di-tert-butylbiphenyl were pre- room temperature and was subsequently stirred for 2 h. To the
pared and fully characterised. The structures of several suspension of the dilithium salt was added a solution of
analogues were determined by X-ray crystallography. The pyri- nBu2SnCl2 (1.3 g, 4.2 mmol) in Et2O (10 mL). After stirring
dine and xylyl isonitrile compounds show interesting photo- overnight at room temperature the mixture was hydrolysed
physical properties, which were studied both in solution and with water. The phases were allowed to separate and the
solid-state.
organic phase was washed with water (3 × 20 mL). After drying
(MgSO4) and removal of the solvent, the resulting yellow oil
was triturated with MeOH and cooled. The resulting yellow
solid was isolated by filtration and was dried in air. The
product was obtained in 85% yield. GC-MS (m/z): 498 [M]+, 385
Experimental
General procedures
t
[M − 2 nBu]+, 272 [M − 2 Bu − 2 nBu]+. 1H NMR (600 MHz,
1H, 13C{1H} and 31P{1H} NMR spectra were recorded on a CDCl3): δ = 0.96 (t, J = 7.5 Hz, 6 H, nBu CH3), 1.40 (m, 4 H,
Bruker Avance ARX 400 (400 MHz) or a Bruker Avance III 600 SnCH2), 1.44 (s, 18 H, Bu), 1.45 (m, 4 H, nBu CH2CH3), 1.72
t
(600 MHz) spectrometer. Chemical shifts are quoted relative to (quint., J = 7.5 Hz, 4 H, nBu CH2CH2CH3), 7.46 (dd, J = 2.3,
external SiMe4 (1H, 13C), or H3PO4 (31P). Elemental analyses 8.3 Hz, 2 H, H-4), 7.70 (d, J = 2.3 Hz, 2 H, H-6), 7.90 (d, JHH
=
were performed by staff of the microanalysis laboratory of the 8,3 Hz, 2 H, H-3). 13C{1H} NMR (151 MHz, CDCl3): δ = 12.1
Technical University Dortmund. PTA, Cl2Me2ImAgI, 4,4′-di-tert- (JC–Sn = 178.8 Hz, nBu C-α), 13.6 (nBu C-δ), 27.1 (JC–Sn = 26.9
butylbiphenyl and 4-MeC6H4C(O)NHC(Se)NEt2 were prepared Hz, nBu C-γ), 29.1 (JC–Sn = 12.1 Hz, nBu C-β), 31.4 (tBu), 34.5
according to literature methods.45–48 All other chemicals and (tBu), 121.8 (JC–Sn = 35.5 Hz, C-3), 125.9 (C-4), 133.2 (JC–Sn
=
solvents (anhydrous grade) were sourced commercially and 42.9 Hz, C-6), 140.8 (C-5), 146.0 (JC–Sn = 58.3 Hz, C-1), 149.7
used as received. Reactions involving air- and moisture sensi- (JC–Sn = 37.4 Hz, C-2). Elemental analysis calcd (%) for
tive compounds were carried out under dry dinitrogen gas C28H42Sn: C 67.6, H 8.5; found: C 67.4, H 8.4.
using standard Schlenk techniques. MALDI and LDI analyses
[AuCl(tBu2Bip)]n (2). A solution containing H[AuCl4]·2H2O
were performed on a Shimadzu AXIMA-Performance MALDI (0.100 g, 0.27 mmol) and 1 (0.134 g, 0.27 mmol) in MeCN
instrument, equipped with a pulsed nitrogen laser (λ = (25 mL) was heated to reflux for ca. 24 h. The resulting solid
337 nm) delivering 3 ns laser pulses, a nominal energy of was isolated by filtration and was washed successively with
100 µJ per laser shot and a laser ablation width of 100 µm. H2O, MeCN and Et2O. A cream coloured solid was obtained in
The laser flux was adjusted to be slightly above the threshold 38% yield (0.050 g). MALDI-MS (pyrene matrix, m/z): 461.2
for the observation of MALDI ions. The instrument was [M − Cl]+, 957.3 [2M − Cl]+, 992.1 [2M]+. LDI-MS (matrix-free
adjusted to the positive-ion mode using the reflectron and an sample, m/z): 461.3 [M − Cl]+, 957.3 [2M − Cl]+, 992.2 [2M]+.
acceleration voltage of 20 kV. For the dried-droplet technique Elemental analysis calcd (%) for [C20H24AuCl]2: C 39.7, H 4.9;
pyrene 10 mg mL−1 was solved in CHCl3 and mixed with the found: C 40.1, H 4.6.
solid sample to give a suspension. Aliquots (0.5 µL) of the sus-
pension were spotted on the target and allowed to air-dry. For
Reactions of [AuCl(tBu2Bip)]n
the solvent-free technique the sample was pressed with a To a suspension of 2 in CH2Cl2 (8 mL) was added one equi-
spatula on a stainless steel target giving a thin film of sample valent of the appropriate ligand (Py, PTA, XyNC, NaDTC,
on the target.
Cl2MeImAgI). The mixture was left to stir at room temperature
2,2′-Dibromo-4,4′-di-tert-butylbiphenyl. To
a
solution of for ca. 2 h and subsequently passed through a pad of celite.
4,4′-di-tert-butylbiphenyl (2.5 g, 10.0 mmol) in CH2Cl2 (10 mL) The filtrate was taken to dryness and the resulting solids were
was added Fe powder (few mg) and bromine (2.8 mL, washed with water and Et2O and subsequently dried in air.
22.0 mmol). After ca. 2 h stirring at room temperature the
[AuCl(tBu2Bip)(Py)] (3). 28.4 mg, 84% yellow solid from 2
stirrer bar with the adhering iron powder was removed and (30.0 mg, 0.03 mmol) and pyridine (4.2 μL, 0.06 mmol). 1H
t
the deep orange solution was left to evaporate in the hood. NMR (600 MHz, CDCl3): δ = 1.11 (s, 9 H, Bu′), 1.39 (s, 9 H,
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tBu), 6.34 (d, J = 1.5 Hz, 1 H, H-6′), 7.18 (dd, J = 7.9 Hz, 1.2 Hz, 159.3 (C-1), 208.7 (C-7). Signals from the quaternary carbon
1 H, H-4′), 7.22 (dd, J = 7.9, 1.5 Hz, 1 H, H-4), 7.24 (d, J = atoms of the xylyl group were not observed. Elemental analysis
7.9 Hz, 1 H, H-3), 7.29 (d, J = 7.9 Hz, 1 H, H-3′), 7.74 (t, J = calcd (%) for C33H45N2AuCl: C 56.5, H 6.5, N 4.0; found: C
6.4 Hz, 2 H, m-Py), 8.11 (t, J = 7.9 Hz, 1 H, p-Py), 8.24 (d, J = 1.2 56.8, H 6.3, N 3.9.
Hz, 1 H, H-6), 8.88 (d, 2 H, J = 4.9 Hz, o-Py). 13C {1H} NMR
[AuCl(tBu2Bip)(Cl2MeIm)] (7). 35.7 mg, 89% yellow solid
(151 MHz, CDCl3): δ = 31.1 (tBu′); 31.4 (tBu), 34.73 (tBu′), 35.2 from 2 (0.03 mg, 0.03 mmol) and Cl2MeImAgI (23.9 mg,
(tBu), 120.8 (C-3), 121.2 (C-3′), 124.7 (C-4, C-4′), 126.5 (m-Py, 0.06 mmol). H NMR (400 MHz, CDCl3): δ = 1.19 (s, 9 H, Bu′),
C-6′), 131.26 (C-6), 140.0 (p-Py), 149.2 (C-5′), 149.4 (C-2′), 149.6 1.39 (s, 9 H, Bu), 3.90 (s, 6 H, CH3), 6.40 (d, J = 2.0 Hz, 1 H,
1
t
t
(C-5), 149.8 (C-2), 150.0 (C-1), 150.3 (o-Py) 155.7 (C-1′). Elemen- H-6′), 7.19 (dd, J = 8.1, 1 H, 1.8 Hz, H-4′), 7.22 (dd, J = 7.8, 1.8
tal analysis calcd (%) for C25H29NAuCl: C 34.2, H 5.9, N 2.4; Hz, 1 H, H-4), 7.30 (d, J = 8.1 Hz, 1 H, H-3), 7.34 (d, J = 7.8 Hz,
found: C 34.6, H 5.4, N 2.1.
1 H, H-3′), 8.27 (d, J = 2.0 Hz, 1 H, H-6). 13C{1H}-NMR
[AuCl(tBu2Bip)(PTA)] (4). 26.5 mg, 81% beige solid from 2 (101 MHz, CDCl3): δ = 31.2 (tBu′), 31.4 (tBu), 34.4 (tBu′), 35.2
(30.0 mg, 0.03 mmol) and PTA (9.4 mg, 0.06 mmol). H NMR (tBu), 36.2 (CH3), 118.8 (CCl), 120.2 (C-3), 121.5 (C-3′), 124.3
1
(600 MHz, CDCl3): δ = 1.37 (s, 9 H, tBu′), 1.41 (s, 9 H, tBu), 4.64 (C-4′), 124.5 (C-4), 128.9 (C-6′), 129.9 (C-6), 149.5 (C-5′), 149.7
(s, 6 H, NCH2N), 4.66 (s, 6 H, PCH2N), 7.19 (m, 2 H, H-4, H-6), (C-5), 149.9 (C-2′), 151.4, (C-2) 151.5 (C-1), 158.8 (C-1′), 186.2
7.25 (m, 2 H, H-6′, H-3), 7.33 (d, 1 H, J = 8.3 Hz, H-3′), 8.24 (dd, (C-Au). Elemental analysis calcd (%) for C25H31N2AuCl3: C
1 H, J = 9.8 Hz, 1.9 Hz, H-4′). 13C {1H} NMR (101 MHz, CDCl3): 45.3, H 4.7, N 4.2; found: C 45.5, H 4.4, N 4.3.
δ = 31.4 (tBu), 31.8 (tBu′), 35.0 (tBu), 35.4 (tBu′), 51.1 (d, JCP
9.9 Hz, PCH2N), 73.2 (d, JCP = 6.6 Hz, NCH2N), 120.7 (d, JCP
=
=
[Au(tBu2Bip)(SSCNEt2)] (8). 27.1 mg, 74% yellow solid from
2 (30.0 mg, 0.03 mmol) and NaDTC (13.5 mg, 0.06 mmol).
6.6 Hz, C-6′), 121.9 (C-3′), 124.7 (C-4), 124.9 (C-4′), 129.1 (C-3), 1H-NMR (400 MHz, CDCl3): δ = 1.37 (s, 18 H, Bu), 1.43 (t, J =
130.9 (d, JCP = 11.0 Hz, C-6), 148.9 (C-2′), 149.9 (C-5′), 150.0 7.1 Hz, 6 H, NCH2CH3), 3.84 (q, J = 7.1 Hz, 4 H, NCH2CH3),
(C-5), 51.2 (d, JCP = 4.4 Hz C-2), 154.4 (d, JCP = 7.7 Hz, C-1′), 7.30 (d, J = 1,8 Hz, 2 H, H-6), 7.36 (d, J = 8.1 Hz, 2 H, H-3), 7.42
165.8 (C-1). 31P{1H} NMR (162 MHz, CDCl3): δ = −54.41. (dd, J = 7.8, 2.0 Hz, 2 H, H-4). 13C{1H}-NMR (101 MHz, CDCl3):
Elemental analysis calcd (%) for C26H36N3PAuCl: C 47.8, H 5.6, δ = 12.4 (NCH2CH3), 31.4 (tBu), 34.9 (tBu), 46.4 (NCH2CH3),
t
N 6.4; found: C 48.0, H 5.8, N 6.3.
120.9 (C-3), 124.0 (C-4), 127.9 (C-6), 149.1 (C-2), 150.1 (C-5),
[AuCl(tBu2Bip)(XyNC)] (5). 36.1 mg, 95% colourless solid 153.4 (C-1), 203.4 (C-7). Elemental analysis calcd (%) for
from 2 (30.0 mg, 0.03 mmol) and XyNC (7.8 mg, 0.06 mmol). C25H34NS2Au: C 49.3, H 5.6, N 2.3; found: C 49.0, H 5.7, N 2.1.
t
1H NMR (600 MHz, CDCl3): δ = 1.35 (s, 9 H, Bu′), 1.39 (s, 9 H,
[Au(tBu2Bip){4-MeC6H4C(O)NC(S)NEt2}] (9). To a solution of
tBu), 2.66 (s, 6 H, CH3-Xy), 7.22 (dd, J = 8.3 Hz, 1.9 Hz, 4-MeC6H4C(O)NHC(S)NEt2 (11.3 mg, 0.05 mmol) in CH2Cl2
1 H, H-4), 7.26 (m, 4 H, H-3, H-4′, m-Xy), 7.31 (d, J = 8.3 Hz, (8 mL) was added a solution of NaOMe (2.8 mg, 0.05 mmol) in
1 H, H-3′), 7.42 (t, J = 7.9 Hz, 1 H, p-Xy), 7.65 (d, J = 1.9 Hz, 1 H, MeOH (6 mL). The mixture was stirred at room temperature
H-6′), 8.27 (d, J = 1.9 Hz, 1 H, H-6). 13C{1H}-NMR (151 MHz, for ca. 15 min before solid 2 (25.0 mg, 0.05 mmol) was added.
CDCl3): δ = 19.0 (2 × CH3-Xy), 31.3 (tBu′), 31.4 (tBu), 34.9 (tBu), After stirring for 2 hours at room temperature, the solution
35.3 (tBu′), 120.7 (C-3), 121.5 (C-3′), 124.2 (ipso-Xy), 124.9 (C-4′), was passed through celite and the filtrate was evaporated to
125.0 (C-4), 128.6 (m-Xy); 129.7 (C-6), 131.5 (p-Xy), 131.8 (C-6′), dryness. The resulting solid was washed with water, Et2O and
136.71 (o-Xy), 149.7 (C-5), 150.1 (C-2′), 150.3 (C-2, C-5′), 156.0 subsequently dried in air. A yellow solid was obtained in 73%
1
(C-2′), 156.5 (C-1). The signal due to the carbon atom of the yield (26.1 mg). H-NMR (400 MHz, CDCl3): δ = 1.35 (m, 3 H,
NuC group was not observed. Elemental analysis calcd (%) for NCH2CH3), 1.37 (s, 9 H, tBu), 1.45 (m, 3 HNCH2CH3), 1.65 (s, 9
t
C29H34NAuCl: C 55.4, H 5.5, N 2.2; found: C 55.2, H 5.6, N 2.0.
[AuCl(tBu2Bip){C(NEt2)(NHXy)}] (6). To
solution of
H, Bu′), 2.47 (s, 3 H, Me), 3.96 (q, J = 7.0 Hz, 4 H, NCH2CH3),
4.05 (q, J = 7.0 Hz, 4 H, NCH2CH3), 7.20 (d, J = 7.8 Hz, 1 H,
a
5
(25.0 mg, 0.04 mmol) in CH2Cl2 (6 mL) was added Et2NH H-4), 7.27–7.35 (m, 5 H, MeC6H4, H4′, H3, H3′), 7.62 (d, J =
(4.2 μL, 0.04 mmol). The solution was stirred at room tempera- 1.8 Hz, 1 H, H-6′), 8.17 (d, J = 1.8 Hz, 1 H, H-6), 8.25 (d, J = 8.3
ture for ca. 24 h and worked up as above to give 13.0 mg (47%) Hz, 2 H, MeC6H4). 13C{1H}-NMR (101 MHz, CDCl3): δ = 12.6
yellow solid. H-NMR (400 MHz, CDCl3): δ = 1.31 (s, 9 H, Bu), (NCH2CH3), 13.2 (NCH2CH3), 21.6 (Me), 31.4 (tBu), 31.5 (tBu′),
1.34 (s, 9 H, tBu′), 1.43 (t, 3 H, NCH2CH3), 1.59 (t, 3 H, 35.0 (tBu), 35.2 (tBu′), 46.2 (NCH2CH3), 47.4 (NCH2CH3), 120.5
NCH2CH3), 2.14 (br. s, 1 H, Xy CH3), 2.56 (br. s, 1 H, Xy CH3), (C-3), 121.0 (C-3′), 124.3 (C-4′), 124.4 (C-4), 125.0 (C-6), 128.5
3.63 (m, 1H, NCH2CH3), 3.76 (m, 2 H, NCH2CH3), 4.33 (m, 1 H, (C-6′), 128.9 (m-MeC6H4), 129.9 (o-MeC6H4), 133.4 (C-1, C-1′),
NCH2CH3), 6.92 (br. s, 1 H, p-Xy), 7.12 (m, 3 H, m-Xy, H-4), 145.4 (C-1, C-1′), 142.5 (m-MeC6H4), 148.3 (C-2′), 149.1 (C-5′),
7.20 (dd, J = 8.1, 2.3 Hz, 1 H, H-4′), 7.22 (d, J = 8.1 Hz, 1 H, 150.6 (C-2), 162.1 (ipso MeC6H4), 170.8 (C–S), 171.2 (C–O).
H-3), 7.30 (m, 2 H, H-3′, H-6′); 8.04 (d, J = 2.0 Hz, 1 H, H-6). Elemental analysis calcd (%) for C33H41N2OSAu: C 55.8, H 5.8,
The NH proton signal could not be observed. 13C{1H}-NMR N 3.9; found: C 56.0, H 5.9, N 4.0.
1
t
(101 MHz, CDCl3): δ = 12.6 (NCH2CH3), 13.8 NCH2CH3), 19.9
[Au(tBu2Bip){4-MeC6H4C(O)NC(Se)NEt2}] (10). This was pre-
(Xy CH3), 20.1 (Xy CH3), 31.4 (tBu), 34.8 (tBu′), 35.1 (tBu), 41.7 pared as described above using 4-MeC6H4C(O)NHC(Se)NEt2. A
(NCH2CH3), 52.2 (NCH2CH3), 119.7 (C-3), 120.8 (C-3′), 123.6 dark yellow solid was obtained in 87% yield (33.2 mg).
(C-4′, C-4), 128.6 (m-Xy), 129.0 (p-Xy), 130.2 (C-6), 131.0 (C-6′), 1H-NMR (400 MHz, CDCl3): δ = 1.30–1.57 (m, 24 H, NCH2CH3,
149.9 (C-2), 151.1 (C-2′), 148.2 (C-5′), 148.9 (C-5), 151.7 (C-1′), tBu), 2.46 (s, 3 H, Me), 3.97 (q, J = 6.8 Hz, 4 H, NCH2CH3), 4.08
11064 | Dalton Trans., 2014, 43, 11059–11066
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(q, J = 6.8 Hz, 4 H, NCH2CH3), 7.21 (d, J = 7.3 Hz, 1 H, H-4),
7.24–7.41 (m, 5 H, MeC6H4, H4′, H3, H3′), 7.53 (d, J = 1.8 Hz,
1 H, H-6′), 8.17 (d, J = 1.8 Hz, 1 H, H-6), 8.24 (d, J = 7.3 Hz, 2 H,
8 N. Meyer, C. W. Lehmann, T. K. M. Lee, J. Rust,
V. W. W. Yam and F. Mohr, Organometallics, 2009, 28,
2931–2934.
9 D. V. Partyka, M. Zeller, A. D. Hunter and T. G. Gray, Angew.
Chem., Int. Ed., 2006, 25, 8188–8191.
MeC6H4). 13C{1H}-NMR (101 MHz, CDCl3):
δ
=
13.1
(NCH2CH3), 13.2 (NCH2CH3), 21.6 (Me), 31.4 (tBu), 31.5 (tBu′),
35.0 (tBu), 35.2 (tBu′), 46.2 (NCH2CH3), 49.3 (NCH2CH3), 120.5 10 V. W. W. Yam and K. M. C. Wong, Chem. Commun., 2011,
(C-3), 121.2 (C-3′), 124.2 (C-4′), 124.3 (C-4), 124.7 (C-6), 128.9
(m-MeC6H4), 130.0 (o-MeC6H4), 130.1 (C-6′), 134.1 (C-1, C-1′), 11 C. Bronner and O. S. Wenger, Dalton Trans., 2011, 40,
145.1 (C-1, C-1′), 142.6 (p-MeC6H4), 148.1 (C-2′), 149.3 (C-5′), 12409–12420.
150.7 (C-2), 163.9 (ipso MeC6H4), 166.9 (C–Se), 171.4 (C–O). 12 H. Yersin, A. F. Rausch, R. Czerwieniec, T. Hofbeck and
47, 11579–11592.
Elemental analysis calcd (%) for C33H41N2OSeAu: C 52.3, H
5.5, N 3.7; found: C 52.1, H 5.5, N 3.9.
T. Fischer, Coord. Chem. Rev., 2011, 255, 2622–2652.
13 M. Kriechbaum, M. List, R. J. F. Berger, M. Patzschke and
U. Monkowius, Chem. – Eur. J., 2012, 18, 5506–5509.
14 V. K. M. Au, N. Zhu and V. W. W. Yam, Inorg. Chem., 2013,
52, 558–567.
Photophysical studies
Spectroscopic grade solvents were used throughout all
measurements. Absorption spectra were recorded with a
Varian Cary 300 double beam spectrometer. Emission spectra
at 300 and at 77 K were measured with a steady-state fluo-
rescence spectrometer (Jobin Yvon Fluorolog 3). Emission
decay times were measured with a pulsed UV xenon flash tube
using the R928P detector in the photon-counting mode
implemented in the fluorescence spectrometer. Fluid solutions
were degassed by three pump–freeze–thaw cycles.
15 W. P. To, K. T. Chan, G. S. M. Tong, C. Ma, W. M. Kwok,
X. Guan, K. H. Low and C. M. Che, Angew. Chem., Int. Ed.,
2013, 52, 6648–6652.
16 A. Szentkuti, M. Bachman, J. A. Garg, O. Blacque and
K. Venkatesan, Chem. – Eur. J., 2014, 20, 2585–2596.
17 Y. Tanaka, K. M. C. Wong and V. W. W. Yam, Chem. Sci.,
2012, 3, 1185–1191.
18 W. P. To, G. S. M. Tong, W. Lu, C. Ma, J. Liu, A. L. F. Chow
and C. M. Che, Angew. Chem., Int. Ed., 2012, 51, 2654–
2657.
19 D. A. Smith, D. A. Roşca and M. Bochmann, Organometal-
lics, 2012, 31, 5998–6000.
20 R. Muñoz-Rodríguez, E. Buñuel, J. A. G. Williams and
D. J. Cárdenas, Chem. Commun., 2012, 48, 5980–5982.
21 D. A. Roşca, D. A. Smith and M. Bochmann, Chem.
Commun., 2012, 48, 7247–7249.
22 W. Lu, K. T. Chan, S. X. Wu, Y. Chen and C. M. Che, Chem.
Sci., 2012, 3, 752–755.
23 J. A. Garg, O. Blacque, T. Fox and K. Venkatesan, Inorg.
Chem., 2010, 49, 11463–11472.
24 F. Mohr, S. H. Privér, S. K. Bhargava and M. A. Bennett,
Coord. Chem. Rev., 2006, 250, 1851–1888.
X-Ray crystallography
Suitable single crystals were picked under inert oil and cooled
to 100 K in a nitrogen cold gas stream using an Oxford Cryo-
systems cooler. Data were collected on a four circle diffracto-
meter equipped with a CCD detector using Mo-Kα radiation
generated by a rotating anode and a focussing graded multi-
layer mirror. Further details about the crystal structure deter-
minations have been included in the CIF files, which have
been deposited with the Cambridge Crystallographic Data
Centre and can be retrieved quoting CCDC numbers 973049
(8), 973050 (3), 973052 (5) and 973053 (10). The figures were
generated using OLEX2.49
25 E. Schuh, S. M. Valiahdi, M. A. Jakupec, B. K. Keppler,
P. Chiba and F. Mohr, Dalton Trans., 2009, 10841–10845.
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27 A. Molter, J. Rust, C. W. Lehmann and F. Mohr, Tetra-
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A. Bindoli, A. Casini and M. P. Rigobello, Metallomics,
2013, 5, 1006–1015.
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