A fixation mode of gold from solutions using heterogeneous reaction of cadmium dicyclohexyl dithiophosphate with H[AuCl4]. Structural and (13C, 31P) CP/MAS NMR studies and thermal behaviour of crystalline polymeric gold(I) dicyclohexyl dithiophosphate and bis(dicyclohexylthiophosphoryl) disulphide

Article abstract of DOI:10.1016/j.molstruc.2012.08.052

Two novel compounds: polynuclear catena-poly[bis(μ₃-O, O′-di-cyclo-hexyldithiophosphato-S,S,S′)digold(I)] (AuAu) (1) and crystalline bis(O,O′-di-cyclo-hexylthiophosphoryl)disulphide, (cyclo-C₆H₁₁O)₂P(S)SS(S)P(O-cyclo-C ₆H₁₁)₂ (2) were prepared using heterogeneous reaction between freshly precipitated binuclear cadmium(II) dithiophosphate (Dtph), [Cd₂{S₂P(O-cyclo-C₆H₁₁} ₄] and H[AuCl₄] in 2 M hydrochloric acid. The isolated compounds 1 and 2 (the fixation mode of gold from the solution and the oxidised form of Dtph groups, respectively) have been studied by means of single-crystal X-ray diffraction, ¹³C and ³¹P cross-polarisation/magic- angle-spinning (CP/MAS) NMR spectroscopy and simultaneous thermal analysis (STA). Centrosymmetric binuclear molecule of 1, [Au₂{S ₂P(O-cyclo-C₆H₁₁)₂}₂] comprises a pair of μ-bridging di-cyclo-hexyl Dtph ligands, linking two neighbouring gold atoms, and displays additional intramolecular aurophilic bond Au?Au. At the supramolecular level of structural self-organisation of complex 1, infinite polymeric zigzag chains arise due to pairs of the secondary bonds Au···S between neighbouring binuclear molecules. Centrosymmetric molecule of 2 displays two O,O′-di-cyclo- hexythiophosphoryl fragments, which are connected by the chemical bond S(1)S(1)^a, and a planar zigzag array [SPSSPS] passing through the central part of the molecule. To characterise additionally the Dtph groups in both compounds 1 and 2, chemical shift anisotropy (CSA) parameters (δ_aniso and η) were calculated from spinning sideband manifolds in experimental ³¹P MAS NMR spectra. The thermal behaviour of complex 1 was studied using simultaneous thermal analysis (a combination of TG and DSC) under an argon atmosphere. The thermal behaviour displays stepwise mass loss, comprising thermal decompositions of the organic and inorganic parts of 1 with gold(I) dithio-meta-phosphate and reduced metallic gold as the intermediate and the final products, respectively.

Full text of DOI:10.1016/j.molstruc.2012.08.052

Journal of Molecular Structure 1034 (2013) 152–161
Contents lists available at SciVerse ScienceDirect
Journal of Molecular Structure
journal homepage: www.elsevier.com/locate/molstruc
A fixation mode of gold from solutions using heterogeneous reaction of
cadmium dicyclohexyl dithiophosphate with H[AuCl4]. Structural and (13C, 31P)
CP/MAS NMR studies and thermal behaviour of crystalline polymeric gold(I)
dicyclohexyl dithiophosphate and bis(dicyclohexylthiophosphoryl) disulphide
a
a
b
Alexander V. Ivanov a, , Eugenia V. Korneeva , Irina A. Lutsenko , Andrey V. Gerasimenko ,
⇑
Oleg N. Antzutkin c,d, Anna-Carin Larsson d, Valentin I. Sergienko b
a Institute of Geology and Nature Management, Far Eastern Branch of the Russian Academy of Sciences, 675000 Blagoveschensk, Amur Region, Russia
b Institute of Chemistry, Far Eastern Branch of the Russian Academy of Sciences, 690022 Vladivostok, Russia
c Department of Physics, Warwick University, Coventry CV47AL, UK
d Chemistry of Interfaces, Luleå University of Technology, S-97187 Luleå, Sweden
h i g h l i g h t s
"
"
"
"
"
Doubly-bridged binuclear gold(I) di-cyclo-hexyldithiophosphate comprising aurophilic bonds.
Supramolecular self-organisation of polymeric chains involving secondary bonds Auꢀ ꢀ ꢀS.
Thermal decomposition of the complex successively yields [Au2(S2PO)2] and metallic Au.
Centrosymmetric molecule of bis(O,O0-di-cyclo-hexylthiophosphoryl) disulphide.
13C and 31P CP/MAS NMR characteristics of di-cyclo-hexyldithiophosphate compounds.
a r t i c l e i n f o
a b s t r a c t
Two novel compounds: polynuclear catena-poly[bis(l
3-O,O0-di-cyclo-hexyldithiophosphato-S,S,S0)
Article history:
Received 26 April 2012
Received in revised form 30 August 2012
Accepted 31 August 2012
Available online 8 September 2012
digold(I)] (AuAAu) (1) and crystalline bis(O,O0-di-cyclo-hexylthiophosphoryl)disulphide, (cyclo-C6H11O)2-
P(S)SAS(S)P(O-cyclo-C6H11)2 (2) were prepared using heterogeneous reaction between freshly precipitated
binuclear cadmium(II) dithiophosphate (Dtph), [Cd2{S2P(O-cyclo-C6H11}4] and H[AuCl4] in 2 M hydrochlo-
ric acid. The isolated compounds 1 and 2 (the fixation mode of gold from the solution and the oxidised form
of Dtph groups, respectively) have been studied by means of single-crystal X-ray diffraction, 13C and 31
P
Keywords:
cross-polarisation/magic-angle-spinning (CP/MAS) NMR spectroscopy and simultaneous thermal analysis
(STA). Centrosymmetric binuclear molecule of 1, [Au2{S2P(O-cyclo-C6H11)2}2] comprises a pair of -bridg-
Polymeric gold(I) O,O0-di-cyclo-hexyl
dithiophosphate
l
ing di-cyclo-hexyl Dtph ligands, linking two neighbouring gold atoms, and displays additional intramolec-
ular aurophilic bond Auꢀ ꢀ ꢀAu. At the supramolecular level of structural self-organisation of complex 1,
infinite polymeric zigzag chains arise due to pairs of the secondary bonds AuꢀꢀꢀS between neighbouring
binuclear molecules. Centrosymmetric molecule of 2 displays two O,O0-di-cyclo-hexythiophosphoryl
Bis(O,O0-di-cyclo-hexylthiophosphoryl)
disulphide
Molecular and supramolecular structure
Aurophilic bonding
Multinuclear 13C, 31P CP/MAS NMR
spectroscopy
fragments, which are connected by the chemical bond S(1)AS(1)a, and
a
planar zigzag array
[S@PASASAP@S] passing through the central part of the molecule. To characterise additionally the Dtph
groups in both compounds 1 and 2, chemical shift anisotropy (CSA) parameters (daniso and ) were calcu-
Simultaneous thermal analysis
g
lated from spinning sideband manifolds in experimental 31P MAS NMR spectra. The thermal behaviour of
complex 1 was studied using simultaneous thermal analysis (a combination of TG and DSC) under an argon
atmosphere. The thermal behaviour displays stepwise mass loss, comprising thermal decompositions of the
organic and inorganic parts of 1 with gold(I) dithio-meta-phosphate and reduced metallic gold as the
intermediate and the final products, respectively.
Ó 2012 Elsevier B.V. All rights reserved.
⇑
Corresponding author. Tel.: +7 4162 225 329; fax: +7 4162 225 325.
E-mail address: alexander.v.ivanov@chemist.com (A.V. Ivanov).
0022-2860/$ - see front matter Ó 2012 Elsevier B.V. All rights reserved.
http://dx.doi.org/10.1016/j.molstruc.2012.08.052

A.V. Ivanov et al. / Journal of Molecular Structure 1034 (2013) 152–161
153
self-organisation of polymeric zigzag chains due to pairs of second-
ary bonds Auꢀ ꢀ ꢀS between neighbouring binuclear molecules of
[Au2{S2P(O-cyclo-C6H11)2}2] at the supramolecular level of com-
pound 1. To characterise quantitatively the phosphorous sites in
both species of Dtph ligands with different structural functions
(in compounds 1 and 2), isotropic 31P chemical shifts were used
1. Introduction
Ionic dialkyl substituted derivatives of phosphorous(V) dithioac-
ids (i.e., dialkyl dithiophosphates) are the main components of com-
mercial flotation reagents such as Aerofloats and Danafloats and,
therefore, are frequently used as selective collectors in froth flota-
tion enrichment of non-ferrous metal sulphide ores. Fixation modes
of the three main types of ionic dithioreagent collectors (such as
Dtphs, dialkyl dithiocarbamates and alkyl xanthates) at the surfaces
of sulphide minerals are one of the most important questions in the
flotation theory. In our previous works, we have studied surface
complexation of various dialkyl dithiophosphates and established
principally different fixation modes of ionic Dtph groups at the
surface of various synthetic metal sulphides: sphalerite, ZnS [1], ga-
lena, PbS [2] and stibnite, Sb2S3 [3]. The bridging coordination of
Dtph groups between either two neighbouring zinc or antimony
atoms was suggested at the mineral surface of ZnS [1] and Sb2S3
[3], respectively; while there is mainly the terminal S,S0-chelating
coordination of Dtph ions to one lead atom at a PbS surface [2].
Dithiophosphates of transition and post-transition metals are of
interest in coordination chemistry due to their abilities to form
mono-, bi-, tetra- hexa- and polynuclear molecular structures,
whereas bis(O,O0-dialkylthiophosphoryl) disulphides1 are impor-
tant compounds in preparations of metal complexes and organome-
tallic dithiophosphates. This structural diversity is defined by the
possibilities of dithiophosphate ligands to play various structural
functions, (i.e., unidentate, terminal chelating, bridging or combined
coordination). Previously, different dithiophosphate compounds
comprising cyclo-hexyl substituents have been characterised using
X-ray diffraction (XRD) and multinuclear (13C, 31P, 113Cd, 195Pt) CP/
MAS NMR: ammonium [5], potassium [6], nickel(II) [7–10], chro-
mium(III) [11], platinum(II) [12,13], zinc(II) [1], cadmium(II)
[14,15], lead(II) [16,17], thallium(I) [18] and antimony (III) [3]. (Di-
cyclo-pentyl dithiophosphate nickel(II) and mercury(II) complexes
have been also described [19,20].)
in combination with 31P CSA parameters (daniso and
g), which were
successfully calculated from spinning sideband manifolds in 31P CP/
MAS NMR spectra obtained at different spinning frequencies. The
thermal behaviour, molecular and supramolecular structures of
the isolated compounds are also discussed in detail.
2. Experimental
2.1. Materials
Symmetrically disubstituted potassium O,O0-di-cyclo-hexyl
dithiophosphate, K{S2P(O-cyclo-C6H11)2}, which constitute the
major component of the commercial Danafloat-569 K collector,
was provided to us by ‘CHEMINOVA AGRO A/S’. The original binu-
clear O,O0-di-cyclo-hexyldithiophosphate cadmium(II) complex,
[Cd2{S2P(O-cyclo-C6H11)2}4] [14] was prepared by metathesis of
the corresponding potassium dialkyl dithiophosphate with
Cd(ClO4)2ꢀ6H2O (Merck). The original cadmium(II) complex and
the crystalline potassium salt, KS2P(O-cyclo-C6H11)2 were identi-
fied using solid-state 13C CP/MAS NMR [15] (diso, ppm):
[Cd2{S2P(O-cyclo-C6H11)2}4]: 81.4, 79.7, 77.0, 75.2 (3:2:1:2,
AOCH@); 35.4, 34.0 (1:1, o-CH2A); 26.9, 25.8, 22.4 (1:1:1,
m-, p-CH2A).
KS2P(O-cyclo-C6H11)2: 79.9, 78.8, 78.1, 77.1 (1:1:1:1, AOCH@);
35.7, 35.2, 34.7, 33.9 (o-CH2A); 26.2 (m-, p-CH2A).
2.2. Synthesis of polycrystalline compounds 1 and 2
Recently, we reported the structural and 31P MAS NMR data and
thermal behaviour on polynuclear di-iso-propyl dithiophosphate
gold(I) complex, [Au2{S2P(O-iso-C3H7)2}2]n [21]. Two non-centro-
symmetric cyclic binuclear molecules, [Au2{S2P(O-iso-C3H7)2}2],
whose four structurally inequivalent dithiophosphate ligands exhi-
The syntheses of compounds 1, ([Au2{S2P(O-cyclo-C6H11)2}2])n
and 2, [(cyclo-C6H11O)2P(S)S]2 were carried out using heteroge-
neous reaction between freshly precipitated binuclear cadmium(II)
di-cyclo-hexyl dithiophosphate, [Cd2{S2P(O-cyclo-C6H11)2}4] and
solutions of gold(III) in 2 M HCl. This interaction follows an ion
exchange scenario and may be represented by the following
red-ox reaction:
bit the same
l2-bridging structural function between two gold
atoms, were discovered in the structure of the aforementioned com-
pound [21,22]. These four bridging Dtph groups have been charac-
terised in detail using full 31P chemical shift tensors (CSTs), i.e.
isotropic 31P chemical shifts, diso, and both CSA parameters: daniso
3½Cd2fS2PðO-cyclo-C6H11Þ2g4ꢂ þ 4H½AuCl4ꢂ
¼ 2½Au2fS2PðO-cyclo-C6H11Þ g2ꢂ
and g. At the supramolecular level, these isomeric binuclear mole-
cules form linear polymeric chains by means of relatively weak
intermolecular aurophilic bonds Auꢀ ꢀ ꢀAu, alternating along the
chain length. The similar structural organisation at the supramolec-
ular or/and molecular level has been also discovered for gold(I)
diethyl dithiophosphate [23] and related dialkyl dithiophosphonate
[24–28] and dialkyl dithiophosphinate [29–32] gold(I) complexes.
In continuation of our study on O,O0-di-cyclo-hexyl Dtph com-
pounds, this article reports on the chemisorption activity of the
binuclear cadmium(II) complex, [Cd2{S2P(O-cyclo-C6H11)2}4] with
respect to [AuCl4]ꢁ anions in 2 M hydrochloric acid. Two novel com-
pounds: polymeric dithiophosphate gold(I) complex, ([Au2{S2P(O-
cyclo-C6H11)2}2]n comprising two bridging dithiophosphate ligands
(compound 1) and crystalline bis(O,O0-di-cyclo-hexylthiophospho-
þ 4ðcyclo-C6H11OÞ PðSÞSASð2SÞPðO-cyclo-C6H11Þ þ 6CdCl2 þ 4HCl:
2
2
ðAu3þ þ 2ðROÞ2PðSÞSꢁ ¼ Auþ þ ½ðROÞ2PðSÞSꢂ2Þ
To 200 mg of cadmium(II) di-cyclo-hexyl dithiophosphate,
10 mL of a solution of AuCl3 in 2 M HCl containing 41.4 mg of gold,
was added dropwise and then the reaction mixture slurry was stir-
red for about one hour. The resulting yellowish-grey precipitate
was collected on a filter, washed with water and air dried. Complex
1 has a low solubility in acetone, and, therefore, it was separated as
a fine crystalline yellowish-white powder by washing with warm
acetone. To isolate compound 2 from the acetone solution, the fil-
trated organic phase was evaporated and then the prepared crude
material was dissolved in ethanol with following crystallisation of
2 using slow evaporation of the solvent.
ryl) disulphide, (cyclo-C6H11O)2P(S)SAS(S)P(O-cyclo-C6H11
) (2)
For X-ray diffraction studies, suitable single crystals of polynu-
were discovered as the fixation mode of gold from these solutions
and oxidised form of Dtph groups, respectively. There is a structural
clear catena-poly[bis(l
3-O,O0-di-cyclo-hexyldithiophosphato-S,S,S0)
digold(I)] (AuAAu) (1) and bis(O,O0-di-cyclo-hexylthiophosphoryl)
disulphide (2) were prepared using re-crystallisation of isolated
compounds from methylene chloride (1) and ethanol (2) at room
temperature. The compounds were prepared as transparent,
1
Complexation properties of bis(O,O-dialkylthiophosphoryl) disulphides with
metal species are in detail discussed in a review of Haiduc and Goh [4].

154
A.V. Ivanov et al. / Journal of Molecular Structure 1034 (2013) 152–161
Table 1
Selected crystal data for compounds 1 and 2.
Empirical formula
Formula weight
Crystal system
Space group
Crystal shape
Crystal size (mm)
Unit cell dimensions
a (Å)
C24H44O4P2S4Au2
C24H44O4P2S4
586.77
980.70
Monoclinic
C2/c
Prism
0.30 ꢃ 0.10 ꢃ 0.08
Triclinic
ꢀ
P1
Prism
0.40 ꢃ 0.14 ꢃ 0.05
23.5530(9)
6.6713(3)
22.3461(9)
90.000
114.2020(10)
90.000
3202.6(2)
4
2.034
8.829(1)
9.663(1)
10.069(1)
79.762(3)
75.051(3)
64.316(3)
745.8(2)
1
b (Å)
c (Å)
a
(°)
b (°)
c
(°)
V (Å3)
Z
Dcalc. (g cmꢁ3
)
1.307
Temperature (K)
(Mo K
) (mmꢁ1
h Range
203(2)
9.540
203(2)
0.453
l
a
)
2.00–28.32
ꢁ31 ? 20
ꢁ8 ? 8
ꢁ28 ? 29
1888
2.10–25.00
ꢁ9 ? 10
ꢁ11 ? 11
ꢁ11 ? 11
314
Range of h, k and l
F(000)
Rint
0.0219
0.025
Number of observations
Criterion of significance
Number of parameters
Weighting scheme
3367
2179
I > 2r(I)
155
I > 2r
(I)
163
2
2
w ¼ 1=½s2ðFo2Þ þ ð0:0218PÞ þ 0:0000Pꢂ; where P ¼ ðFo2 þ 2F2c Þ=3
w ¼ 1=½s2ðFo2Þ þ ð0:0440PÞ þ 0:6734Pꢂ; where P ¼ ðFo2 þ 2F2c Þ=3
S (goodness-of-fit)
0.996
0.0195, 0.0422
0.775, ꢁ0.574
1.189
0.0497, 0.1221
0.456, ꢁ0.284
R1, wR2 (F2 > 2
D
r
(F2))
qmax, D
qmin (e/Å3)
pale-yellow (1) and yellow (2) prisms. Yields of 81% (1) and 63% (2)
were obtained, respectively.
positions and line widths, as well as the Lorentzian and Gaussian
contributions to the line shapes. All 31P chemical shift data are given
with respect to 85.5% H3PO4 [36] (here, 0 ppm, externally
referenced), which was mounted in a short 1 mm glass tube and
placed in a 7.5 mm rotor to avoid errors due to differences in the
magnetic susceptibility. Drifts in the 13C/31P frequencies (B0-drift)
were 0.051/0.11 Hz hꢁ1, respectively. The homogeneity of the mag-
netic field was monitored by measuring the width of the reference
signal of crystalline adamantane at d(13C) = 38.48 ppm, which was
2.6 Hz.
Solid-state 13C CP/MAS NMR data (diso, ppm) for compounds 1
and 2 are given below:
(1) [Au2{S2P(O-cyclo-C6H11)2}2]n: 81.8, 81.0 (1:1, AOCH@); 36.2,
35.5, 35.2 (1:1:2, o-CH2A); 26.9, 26.2, 25.1 (m-,p-CH2A).
(2) [(cyclo-C6H11O)2P(S)S]2: 81.0, 80.7 (1:1, AOCH@); 36.5, 35.5,
34.7 (1:1:2, o-CH2A); 27.0, 26.5, 25.8 (m-,p-CH2A).
The anisotropy, daniso = dzz ꢁ diso, and the asymmetry parameter
of the 31P chemical shift tensor (CST),
g
= (dyy ꢁ dxx)/(dzz ꢁ diso),2
2.3. Physical measurements
were estimated from the determined ratios between integrated side-
band intensities for each phosphorous site in the NMR spectra re-
2.3.1. 13C and 31P CP/MAS NMR spectroscopy
Solid state 13C and 31P magic-angle-spinning (MAS) NMR spectra
were recorded on an Agilent/Varian/Chemagnetics InfinityPlus
CMX-360 (B0 = 8.46 T) spectrometer operating in the pulsed Fourier
transform mode, using cross-polarisation (CP) from the protons to-
corded at two different spinning frequencies [37,38] using
a
simulation program in the Mathematica front end [39]. To increase
the number of spinning sidebands (>10) in 31P NMR spectra, which
are needed for more accurate estimation of CSA parameters, spectra
were also recorded at relatively low spinning frequencies (2.15–
2.7 kHz).
gether with phase modulated proton decoupling [33]. The 13C/31
P
operating frequencies were 90.52/145.72 MHz, respectively. The
proton /2 pulse durations were 3.3–5.0/3.3–7.0 s, CP mixing
times were 1.7–2.5/2.5–3.0 ms and the nutation frequencies of pro-
tons during decoupling nut/2 = 35/32 kHz. For each sample,
p
l
x
p
2.3.2. Crystal structure determination
1360–12100/4–16 transients, spaced by relaxation delays of 3–
10/30–180 s, were accumulated. Polycrystalline samples (ca.
120 mg) were packed in zirconium dioxide standard double bearing
7.5 mm rotors. The spinning frequencies for studied samples ran-
ged from 5500 to 6000/2150 to 5850 Hz and were stabilised to
2 Hz using a built-in stabilisation device. All 13C and 31P NMR spec-
tra were recorded at room temperature (ca. 295 K).
Suitable single crystal of 1, [Au2{S2P(O-cyclo-C6H11)2}2]n and 2,
(cyclo-C6H11O)2P(S)SAS(S)P(O-cyclo-C6H11 2 were selected and
)
mounted on glass fibres with epoxy glue. Experimental intensity
data were collected at T = 203(2) K on a BRUKER SMART 1000
CCD diffractometer with graphite monochromated Mo K
tion (k = 0.71073 Å) in the range of a semi-sphere [40] (crystal-
detector distance 45 mm); scan with an increment of 0.2° and
a radia-
x
13C Isotropic chemical shifts (in the deshielding, d-scale) were
externally referenced to the least shielded resonance of solid ada-
mantane [34] at 38.48 ppm [35] relative to tetramethylsilane.
Chemical shifts and integrated intensity ratios for overlapping
signals in the 13C NMR spectra were additionally refined by
fragment-by-fragment simulations taking into account both line
an exposure time of 20 s per frame was used. Intensity data were
corrected for absorption using the crystal face indices (1) and the
indices of equivalent reflections (2). The unit cell dimensions,
2
The principal values of the CST: dxx
|dzz ꢁ diso| > |dxx ꢁ diso| > |dyy ꢁ diso|.
, dyy and dzz are defined as

A.V. Ivanov et al. / Journal of Molecular Structure 1034 (2013) 152–161
155
Table 2
Table 3
Selected bond lengths (Å), bond angles (°) and torsion angles (°) in the gold(I) complex 1.
Selected bond lengths (Å), bond angles (°) and torsion angles (°) in the molecule of 2.
Bond lengths
Bond lengths
Au(1)AS(1)
Au(1)AS(2)a
Au(1)ꢀ ꢀ ꢀS(1)b
Au(1)ꢀ ꢀ ꢀAu(1)a
S(1)AP(1)
2.3035(8)
2.3051(8)
3.4301(8)
3.0287(3)
2.0140(11) C(5)AC(6)
2.0028(11) C(7)AC(12)
1.570(2)
1.576(2)
1.479(4)
1.470(3)
1.500(4)
C(1)AC(6)
C(2)AC(3)
C(3)AC(4)
C(4)AC(5)
1.509(4)
1.523(5)
1.516(5)
1.520(5)
1.527(5)
1.508(4)
1.509(4)
1.518(4)
1.509(5)
1.518(5)
1.522(4)
S(1)AP(1)
S(1)AS(1)a
S(2)AP(1)
P(1)AO(1)
P(1)AO(2)
O(1)AC(1)
O(2)AC(7)
C(1)AC(2)
C(1)AC(6)
C(2)AC(3)
2.0871(8) C(3)AC(4)
2.115(1) C(4)AC(5)
1.9142(8) C(5)AC(6)
1.520(3)
1.517(3)
1.518(4)
1.511(3)
1.506(3)
1.526(3)
1.514(3)
1.519(4)
1.526(3)
1.572(2)
1.569(2)
1.479(3)
1.477(3)
1.506(3)
1.513(3)
1.528(3)
C(7)AC(8)
C(7)AC(12)
C(8)AC(9)
C(9)AC(10)
C(10)AC(11)
C(11)AC(12)
S(2)AP(1)
P(1)AO(1)
P(1)AO(2)
O(1)AC(1)
O(2)AC(7)
C(1)AC(2)
C(7)AC(8)
C(8)AC(9)
C(9)AC(10)
C(10)AC(11)
C(11)AC(12)
Bond angles
Bond angles
P(1)AS(1)AS(1)a
O(1)AP(1)AO(2)
O(1)AP(1)AS(2)
O(2)AP(1)AS(2)
O(1)AP(1)AS(1)
O(2)AP(1)AS(1)
S(2)AP(1)AS(1)
C(1)AO(1)AP(1)
C(7)AO(2)AP(1)
O(1)AC(1)AC(2)
O(1)AC(1)AC(6)
C(2)AC(1)AC(6)
C(1)AC(2)AC(3)
100.40(4)
97.43(8)
C(4)AC(3)AC(2)
C(5)AC(4)AC(3)
C(4)AC(5)AC(6)
C(1)AC(6)AC(5)
O(2)AC(7)AC(8)
O(2)AC(7)AC(12)
C(12)AC(7)AC(8)
C(7)AC(8)AC(9)
C(10)AC(9)AC(8)
C(9)AC(10)AC(11)
C(10)AC(11)AC(12)
C(7)AC(12)AC(11)
111.5(2)
S(1)AAu(1)AS(2)a
P(1)AS(1)AAu(1)
P(1)AS(2)AAu(1)a
S(2)AP(1)AS(1)
O(1)AP(1)AS(1)
O(1)AP(1)AS(2)
O(2)AP(1)AS(1)
O(2)AP(1)AS(2)
O(1)AP(1)AO(2)
C(1)AO(1)AP(1)
C(7)AO(2)AP(1)
O(1)AC(1)AC(2)
O(1)AC(1)AC(6)
C(2)AC(1)AC(6)
170.08(3)
102.65(4)
101.13(4)
116.42(5)
113.40(9)
107.43(9)
106.99(9)
109.17(9)
C(1)AC(2)AC(3)
C(1)AC(6)AC(5)
C(3)AC(4)AC(5)
C(4)AC(3)AC(2)
C(4)AC(5)AC(6)
O(2)AC(7)AC(8)
O(2)AC(7)AC(12)
C(7)AC(8)AC(9)
111.1(3)
109.5(3)
110.6(3)
111.4(3)
111.9(3)
106.4(2)
109.8(2)
110.6(3)
110.2(3)
110.7(3)
111.9(3)
111.9(3)
112.2(3)
111.1(2)
111.0(2)
110.0(2)
108.9(2)
107.7(2)
112.4(2)
109.4(2)
110.5(2)
110.7(2)
110.9(2)
110.2(2)
119.11(7)
118.92(7)
107.64(7)
107.68(6)
105.32(3)
119.12(12)
119.89(12)
108.2(2)
102.47(12) C(7)AC(12)AC(11)
120.8(2)
125.5(2)
107.6(3)
109.1(3)
112.4(3)
C(9)AC(10)AC(11)
C(10)AC(9)AC(8)
C(10)AC(11)AC(12)
C(12)AC(7)AC(8)
108.6(2)
112.0(2)
109.5(2)
Torsion angles
P(1)AS(1)AS(1)a–P(1)a 180.0
S(2)AP(1)AS(1)AS(1)a 179.61(4)
Torsion angles
a
S(1)AAu(1)AAu(1)aAS(1)a 180.0
S(2)AAu(1)AAu(1)aAS(2)a 180.0
S(1)AS(2)aAS(2)AS(1)a 180.0
S(2)AS(1)AS(1)aAS(2)a 180.0
ꢁx + 1, ꢁy, ꢁz + 1.
a
ꢁx + 1/2, ꢁy ꢁ 1/2, ꢁz + 1.
ꢁx + 1/2, ꢁy + 1/2, ꢁz + 1.
b
scanning electron microscope attached to an Oxford INCAEnergy
EDX instrument.
3. Results and discussion
additional crystallographic data and refinement results for com-
pounds 1 and 2 are given in Table 1.
3.1. Heteronuclear (13C, 31P) CP/MAS NMR data
The structure was solved using direct methods and refined by
least-squares calculation in anisotropic approximation for non-
hydrogen atoms. Hydrogen atoms were added at ideal positions
and refined using a riding model. Data collection and editing, as
well as refinement of unit cell parameters, was performed with
the SMART [40] and SAINT [41] program packages. Structure solu-
tion and refinement were performed with the SHELXTL/PC pro-
gram packages [42]. Selected bond lengths, bond angles and
torsion angles are listed in Tables 2 and 3. Complete crystallo-
graphic details are included in the Supporting information.
Fig. 1 shows 13C CP/MAS NMR spectra of crystalline gold(I) O,O0-
di-cyclo-hexyl dithiophosphate, 1 and bis(O,O0-di-cyclo-hexylthio-
phosphoryl) disulphide, 2. In both cases, discussed spectra com-
prise expected sets of 13C resonance lines due to AOCH@, o-, m-
and p-CH2A groups of cyclic substituents. Pairs of poorly shielded
13C resonances, appearing at 80.7–81.8 ppm (see Section 2.2), have
equal integral intensities (Fig. 1a and b). These suggest a structural
inequivalence of the AOCH@ groups in the neighbouring cyclic
moieties of Dtph ligands. Beside that, 31P CP/MAS NMR spectra
(Figs. 2 and 3), displaying single resonances for each of the di-
cyclo-hexyl dithiophosphate compounds, reveal structurally unique
Dtph ligands in both compounds 1 and 2. The individual nature of
the prepared compounds was established using a combination of
13C NMR data (Section 2.2 and Fig. 1) and corresponding 31P NMR
spectral patterns (Figs. 2 and 3) and characteristics (Table 4).
Figs. 2 and 3 exhibit 31P CP/MAS NMR spectral patterns of com-
pounds 1 (Fig. 2) and 2 (Fig. 3) observed at different spinning fre-
quencies. 31P isotropic chemical shifts of these compounds can be
established from the positions of the centrebands (marked by
asterisks in Figs. 2 and 3), which are flanked by spinning sidebands.
In each of the discussed 31P MAS NMR spectra, only one centreband
resonance line is discovered, which defines unique structural
states of Dtph groups in both compounds 1 and 2. Comparing iso-
tropic 31P chemical shifts for the above compounds and the original
potassium di-cyclo-hexyl dithiophosphate (see Table 4), more
shielded phosphorous sites (smaller values in the deshielding d-
scale) can be discerned in the former case. This is in a good agree-
ment with previous 31P NMR studies, which were carried out on
various di-cyclo-hexyl dithiophosphate complexes (see Table 4),
and 31P NMR data on different substituted bis(thiophosphoryl)
2.3.3. Thermal analysis
The thermal behaviour of complex 1 was studied using the
simultaneous thermal analysis (STA) technique for parallel
recording of TG (thermogravimetry) and DSC (differential scan-
ning calorimetry) curves. The study was performed on an STA
449C Jupiter instrument (‘NETZSCH’) in corundum crucibles under
a lid with a hole to ensure a vapour pressure of 1 atm during the
thermal decomposition of the samples. The rate of heating to
1100 °C was 5 °C minꢁ1 under an argon atmosphere. The sample
mass was in the range of 5.08–7.52 mg. The accuracy of temper-
ature measurements was 0.7 °C, and that of mass changes was
1 ꢃ 10ꢁ2 mg. In order to improve a detection of heat effects in
the low-temperature range (below 220 °C), aluminium crucibles
were also used.
2.3.4. Elemental microanalysis
Qualitative determination of elements was carried out on the
basis of electron-probe X-ray microanalysis. The energy dispersive
X-ray (EDX) spectra were recorded using a JEOL JSM-6390 LV

156
A.V. Ivanov et al. / Journal of Molecular Structure 1034 (2013) 152–161
Fig. 1. 90.52 MHz 13C CP/MAS NMR spectra of crystalline compounds 1 (a) and 2
(b). The MAS frequencies were 6.0 in (a) and 5.5 kHz in (b). The number of
transients was 12,100 (a) and 1360 (b). (The sideband is denoted by ‘s’.)
Fig. 3. 145.73 MHz 31P CP/MAS NMR spectra of compound 2. The MAS frequencies
were 3.8 (a) and 2.5 kHz (b). The number of transients was 16 in each case. (The
central bands are denoted by asterisks.)
Dtph ligands. Therefore, in order to distinguish between various
structural functions for the Dtph groups in the prepared compounds,
we used the 31P CSA parameters of phosphorous sites in 1 and 2: the
chemical shift anisotropy, daniso and the asymmetry parameter of the
CST,
g. (Note that
g = 0 corresponds to the axially symmetric CST. An
increase in
g
from 0 to 1 displays a corresponding increase in the
rhombicity of the tensor.) From the relative intensities of the side-
bands in the spinning sideband manifolds (Figs. 2 and 3), v2-statis-
tics as a function of the two aforementioned 31P CSA parameters
were calculated using a program of Levitt and co-workers [38] writ-
ten in the Mathematica front end [39]. The global minimum of this
statistics, v2min, gives values for the two CSA parameters, daniso and
g
, while the joint confidence limit is the measure of the joint-error
intervals forthese parameters[39]. Fig. 4 shows joint confidencelim-
its for daniso and
, while the 31P CSA data given in Table 4 correspond
to the minima of the v2-plots [39]. The 31P CSTs of phosphorous sites
in both compounds 1 and 2 are expectedly close to rhombic ( = 0.82
and 0.85, respectively). Beside that, for both studied compounds, the
daniso-values are characterised by the negative sign, i.e. dzz < diso
g
g
.
It has been established by our previous studies of dithiophos-
phate complexes that the positive sign of daniso (dzz > diso) correlates
well with the terminally chelating Dtph groups with relatively
small SAPAS angles [1–3,6,8,13,15], while the negative sign usually
correlates with either bridging or combined structural functions of
Dtph ligands displaying rather large SAPAS angles [1,6,15–18,21]
(see Table 4). Moreover, a correlation between the 31P CST principal
value dyy and the SAPAS angle in different metal Dtph complexes
(larger SAPAS angles define bigger dyy values and vice versa) has
been identified based on ab initio quantum mechanical calculations
[6,17]. Therefore, dyy-values have been additionally calculated for
compounds 1 and 2: dyy = 98.8 ppm and 88.0 ppm, respectively.
From these data, it can be concluded that substantially larger
SAPAS angle is expected in the bridging Dtph ligands of complex
1 compared to this in the Dtph groups of compound 2.
Fig. 2. 145.73 MHz 31P CP/MAS NMR spectra of complex 1. The MAS frequencies
were 5.85, 2.7 and 2.15 kHz in (a), (b), and (c), respectively. The number of
transients was 4 in each case. (The central bands are denoted by asterisks.)
disulphides [10,43–45]. Therefore, observed additional shielding
arises due to the covalent linkage of Dtph groups with gold atoms
(in complex 1) or between Dtph groups via a SAS linker (in com-
pound 2). Beside that, similarities in the shape of spinning side-
band patterns in 31P CP/MAS NMR spectra (Figs. 2 and 3) suggest
similar rhombicities (but different size) of the 31P CSTs of phospho-
rous sites in both compounds 1 and 2.
To validate this conclusion based on 31P CP/MAS NMR data, the
molecular structures of compounds 1 and 2 were solved by the di-
rect method, single-crystal X-ray diffraction data analysis.
Previously, using isotropic chemical shifts, diso, and CSA parame-
ters, daniso and g, we have quantitatively characterised Dtph ligands
with different structural function (terminal chelating, bidentate
bridging or combined coordination) in di-cyclo-hexyl dithiophos-
phate complexes of various transition and post-transition metals
[1–3,6,8,13,15–18] (see Table 4). It has been found that both the size
and the shape of the 31P CST exhibit a dependence on the SAPAS
bond angle, which, in turn, is defined by the structural function of
3.2. Structural descriptions
Polymeric dithiophosphate gold(I) complex, ([Au2{S2P(O-cyclo-
C6H11)2}2]) (compound 1) and bis(O,O0-di-cyclo-hexylthiophospho-
ryl) disulphide, (cyclo-C6H11O)2P(S)SAS(S)P(O-cyclo-C6H11 2 (2)
)

A.V. Ivanov et al. / Journal of Molecular Structure 1034 (2013) 152–161
157
Table 4
31P NMR chemical shift tensor parametersa for O,O’-di-cyclo-hexyl dithiophosphate compounds.
Compound
31P
diso (ppm)
daniso (ppm)b
gb
(1) [Au2{S2P(O-cyclo-C6H11)2}2]n
(2) [(cyclo-C6H11O)2P(S)S]2
K{S2P(O-cyclo-C6H11)2} [6]
94.8
79.8
ꢁ44.6 0.4
ꢁ109.5 0.4
ꢁ110.6 1.5
ꢁ109.1 1.7
0.82 0.02
0.85 0.01
0.14 0.10
0.21 0.06
109.3
105.0
(1:1)
[Cd2{S2P(O-cyclo-C6H11)2}4] [15]
[Pb{S2P(O-cyclo-C6H11)2}2]n [16,17]
101.8 (97)d
98.2
48.8
–58.4
0.74
0.00
(1:1)
99.6
95.6
(1:1)
93.5
96.7
99.3
98.0
ꢁ59.0 1.1
ꢁ64.4 1.2
0.83 0.05
0.88 0.04
[Tl2{S2P(O-cyclo-C6H11)2}2]n ‘A’c ‘B’c [18]
[Zn2{S2P(O-cyclo-C6H11)2}4] [1,6]
ꢁ71.5 0.3
ꢁ94.7 0.8
ꢁ54.3 1.6
ꢁ52.3 2.5
51.6 2.2
0.69 0.01
0.35 0.02
0.09 0.32
0.35 0.32
0.43 0.28
0.46 0.29
95.3
93.9
49.8 2.2
(1:1:1:1)
90.7
[Ni{S2P(O-cyclo-C6H11)2}2] [8]
[Pt{S2P(O-cyclo-C6H11)2}2] [13]
[Sb{S2P(O-cyclo-C6H11)2}3] [3]
55.9 1.4
30.8 0.2
82.5 0.6
82.2 0.7
80.8 0.6
0.35 0.15
0.98 0.02
0.20 0.03
0.29 0.03
0.13 0.05
d
99.0 (433.2)
92.6 0.4
90.5 0.3
89.3 0.6
(1:1:1)
103.0 (25)
102.0 (24)
97.3 (26)
96.2 (24)
d
[Au2{S2P(O-iso-C3H7)2}2]n [21]
ꢁ56.4 1.0
ꢁ54.7 1.0
–50.6 0.8
–47.9 1.0
0.54 0.07
0.50 0.08
0.43 0.10
0.30 0.17
d
d
d
(1:1:1:1)
a
b
c
Relative to 85.5% H3PO4, deshielding scale.
daniso = dzz ꢁ diso; g = (dyy ꢁ dxx)/(dzz ꢁ diso).
Two polymorphs: ‘A’ and ‘B’.
d
2J (31PA111,113Cd), 2J (31PA195Pt) and 4J (31PA31P), in Hz.
cell, respectively (see Table 1). In both compounds 1 and 2, each
of the Dtph groups comprises cyclo-hexyl rings, which are charac-
terised by the ‘chair’ conformation, with CAC bond lengths within
the range 1.500–1.528 Å and CACAC bond angles that are rather
close to the tetrahedral value: 106.4–112.4°. In Dtph groups, the
phosphorous atoms are tetrahedrally coordinated within the
[O2S2] neighbouring environment. The PAS bond lengths (2.0871
and 1.9142 Å) are well corresponding to hypothetical single
(2.14 Å) and double (1.94 Å) phosphorous–sulphur bonds [46–48]
in compound 2. While in compound 1 both PAS bonds (2.0140
and 2.0028 Å) are intermediate between the two above-mentioned
ideal values [46–48]. Selected bond lengths, angles and torsion an-
gles for 1 and 2 are given in Tables 2 and 3, respectively.
3.2.1. Complex 1, [Au2{S2P(O-cyclo-C6H11)2}2]n
The main structural unit of complex 1 is centrosymmetric dou-
bly-bridged binuclear molecule of [Au2{S2P(O-cyclo-C6H11)2}2]
(Fig. 5). The pairs of di-cyclo-hexyl dithiophosphate ligands, dis-
playing the same
l2-bridging structural function, combine two
neighbouring gold atoms forming extensive eight-membered
metallocycles [Au2S4P2] in the above-mentioned binuclear mole-
cules (Fig. 5). (Previously, eight-membered moieties [Au2S4P2]
have been also revealed in various gold(I) diethyl dithiophosphates
[21–23], dialkyl dithiophosphonates [24–28] and dialkyl dith-
iophosphinates [29–32].) Each of bridging Dtph ligands having,
therefore, the expectedly large SAPAS angle (116.42°) forms a cou-
ple of almost equal bonds SAAu with two gold atoms: 2.3035 and
2.3051 Å. In the binuclear molecule [Au2{S2P(O-cyclo-C6H11)2}2],
the central cyclic moiety is additionally stabilised by relatively
weak intramolecular secondary interactions Auꢀ ꢀ ꢀAu (i.e., by
Fig. 4. v2 Statistics as a function of the 31P CSA parameters daniso and
g
. Graphs for
compounds 1 (a) and 2 (b) are presented. The 68.3% joint confidence limit (solid)
and 95.4% joint confidence limit (dashed) for the two CSA parameters are shown. In
each case (a) and (b) simulations were performed for a P-site at two different
spinning frequencies: 2.15 (a) and 3.8 (b) kHz (thick lines) and 2.7 (a) and 5.2
(b) kHz (thin lines).
ꢀ
crystallise in the monoclinic, C2/c, and the triclinic, P1, space
groups with four and one crystallographic formula units per unit

158
A.V. Ivanov et al. / Journal of Molecular Structure 1034 (2013) 152–161
Fig. 5. Centrosymmetric binuclear molecule of [Au2{S2P(O-cyclo-C6H11)2}2]. Displacement ellipsoids are shown at the 50% probability level.
aurophilic bonding,3 3.0287 Å; cf. data for the sum of two van der
Waals radii of the gold atom, 3.32 Å [46–48]). The spatial configura-
tion of the cyclic moiety [Au2S4P2] does not correspond to any of the
ten canonical forms that have been calculated for possible stable
conformations of saturated eight-membered rings [50]. This new
cyclic formation is characterised by an important structural feature:
six atoms [Au2S4] are coplanar (corresponding torsion angle values
are equal to 180°, see Table 2), whereas two phosphorous atoms
symmetrically project out of the plane in opposite directions. There-
fore, the central eight-membered moiety [Au2S4P2] is the resulting
combination of two five-membered rings [Au2S2P] adopting the
same ‘envelope’ conformation and having the common side on the
line Auꢀ ꢀ ꢀAu. Due to the intramolecular secondary bond between
two gold atoms, the S(1)AAu(1)AS(2)a and S(1)aAAu(1)AS(2) angles
(170.08°) are noticeably less than 180°. Therefore, the discussed
common side of the two ‘envelopes’ (3.0287 Å) is essentially shorter
than the other side on the line S(1)AS(2) (3.414 Å; cf. datum for the
sum of two van der Waals radii of the sulphur atom, 3.60 Å [46–48]).
As a result, aurophilic bonding defines the distortion of these five-
membered metalocycles from the regular ‘envelope’ configuration.
At the supramolecular level, further structural self-organisation
of compound 1 is achieved due to the pairs of relatively weak non-
valence interactions (i.e., by secondary bonds4) between neigh-
bouring binuclear molecules of [Au2{S2P(O-cyclo-C6H11)2}2] (Fig. 6).
Thus, one of the sulphur atoms in each of Dtph ligands is additionally
coordinated by the gold atom of the neighbouring binuclear mole-
cule (Auꢀ ꢀ ꢀS 3.4301 Å, cf. datum for the sum of the van der Waals ra-
dii of the gold atom and the sulphur atom – 3.46 Å [46–48]) and,
therefore, infinite polynuclear zigzag chains, ([Au2{S2P(O-cyclo-
C6H11)2}2])n arise. In these chains, having an orientation along the
crystallographic b-axis, the AuAAuAAu angle value is equal to
137.39°, while the intermolecular distance of Auꢀ ꢀ ꢀAu is 4.119 Å. It
is worth noting that discussed complex 1 also exhibits the structural
type of polymeric zigzag chains, but with principally different mode
of structural organisation compared to the previously described
structures of dithiophosphate gold(I) complexes, ([Au2{S2P(OR)2}2])n
(R = C2H5 [23], iso-C3H7 [21,22]).
Hence, in contrast with two other coinage metals, silver(I) and
copper(I), which form either discrete tetra-, hexa- or octa-nuclear
molecules of dialkyl dithiophosphate complexes ([52–55] and
[56–61], respectively), gold(I) dithiophosphates are characterised
by the structural type of polynuclear chains [21–23 and this work].
3.2.2. Compound 2, [(cyclo-C6H11O)2P(S)S]2
The molecular structure solved for compound 2, (cyclo-C6H11O)2
P(S)SAS(S)P(O-cyclo-C6H11)2 is shown in Fig. 7. In this centrosym-
metric molecule, two structurally equivalent O,O0-di-cyclo-hexyl-
thiophosphoryl fragments are combined by the chemical bond
S(1)AS(1)a, whose length (2.115 Å) is noticeably longer compared
to these seen for most of presently known bis(organothiophospho-
ryl) disulphides [43–45,62,63].
A
planar zigzag array
[S@PASASAP@S] is passing through the central part in the mole-
cule of 2 (see Table 3). Therefore, the SASAP@S units are expect-
edly characterised by anti–anti geometry [54]. The latter
configuration exhibits the usual values of the torsion angle
SASAP@S (179.61°) and the bond PAS length (2.0871 Å). Beside
that, two PAS bond length values (2.0871 and 1.9142 Å) are very
close to these of hypothetical single (2.14 Å) and double (1.94 Å)
phosphorous–sulphur bonds [46], whereas the bond angle
S(1)AP(1)AS(2) is 105.32°.
3.3. Thermal analysis and elemental microanalysis data
In order to reveal optimal conditions for the regeneration of
bound gold, the thermal behaviour of complex 1 was studied by
the STA technique (parallel detection of the TG and DSC curves) un-
der an argon atmosphere. Fig. 8 displays both the TG and DSC
traces. Thermogravimetry data reveals the thermal stability of
complex 1 below 138 °C, while the stepwise mass loss is observed
in the range of 138–1100 °C. The first step of the TG curve reflects
the thermal decomposition in the organic parts of the binuclear
3
Theoretical concepts of the ‘aurophilicity phenomenon’ and ‘aurophilic interac-
tions’ are in detail discussed in a review of Schmidbaur [49].
4
The ‘secondary bond’ concept was suggested by Alcock [51] for the description of
interactions at interatomic distances longer than ordinary covalent bonds but shorter
than van der Waals distances.
molecule of [Au2{S2P(O-cyclo-C6H11)2}2]:
a 37.9% total loss

A.V. Ivanov et al. / Journal of Molecular Structure 1034 (2013) 152–161
159
Fig. 6. A view of a three-membered fragment of the [Au2{S2P(O-cyclo-C6H11)2}2]n chain. The secondary bonds Auꢀ ꢀ ꢀS and Auꢀ ꢀ ꢀAu are indicated by dashed lines. The cyclo-
C6H11OA groups of Dtph ligands are omitted for clarity.
Fig. 7. Centrosymmetric disulphide molecule of [(cyclo-C6H11O)2P(S)S]2. Displacement ellipsoids are shown at the 50% probability level.
corresponds to the relative mass of two cyclo-C6H11A and two
cyclo-C6H11OA groups (the calculated loss is 37.2%). The mass
remaining after the first step at 194 °C (62.1%) expectedly corre-
sponds to the mass of gold(I) dithio-meta-phosphate, [Au2(S2PO)2]
(calc. 62.8%) as the intermediate product. The formation of gold(I)
and platinum(II) dithio-meta-phosphates have been previously dis-
covered by thermal studies of various dialkyl dithiophosphate
complexes of the above metals [13,21,64–66]. Energy dispersive
X-ray analysis was employed in order to establish qualitatively
the elemental composition of this intermediate product. The EDX
spectral pattern (Fig. 9a) supports the existence of the [Au2(S2PO)2]
particles, which are characterised by the presence of the gold, sul-
phur, phosphorus and oxygen. From the SEM data, the discovered
particles of gold(I) dithio-meta-phosphate exist as microscopic hol-
low spheres (Fig. 9b).
138–1100 °C, the total mass loss is 20.1%. Therefore, the mass of
the metallic residue (42.0%) somewhat exceeds the theoretically
calculated mass of reduced gold (40.17%), most likely, due to the
accompanying formation of some amount of slag products (a
red-brawn5 slag is observed on the bottom of the crucible).
There are four consecutive endotherms at the low-temperature
region of the DSC trace (see Fig. 8b). The first one, in the thermal
stability region of complex 1 (i.e., before the beginning of mass
loss), is the melting endotherm (the extrapolated m.p. of 1 is
136.0 °C). The second, third and fourth endotherms (at 151.3 °C,
172.5 °C and 179.9 °C, respectively) illustrate the complicated
character of the thermal decomposition of complex 1. The fifth,
high-temperature endotherm reflects melting of reduced metallic
gold (the extrapolated m.p. 1063.0 °C). When the m.p. was
achieved, bright metallic yellow-gold beads from 0.005 to
The second (194–310 °C) and third (460–600 °C) distinctly dis-
cerning steps are defined by the thermal decomposition of the
intermediate compound [Au2(S2PO)2] that yields reduced metallic
gold as the main final product (Fig. 8c). In the range of
5
For interpretation of color in Fig. 8, the reader is referred to the web version of
this article.

160
A.V. Ivanov et al. / Journal of Molecular Structure 1034 (2013) 152–161
Fig. 8. TG (a) and DSC (b) curves of complex 1. A close-up view of the inner surface of the crucible with the end-product particles (c).
structural function, combine two neighbouring gold atoms forming
centrosymmetric doubly-bridged binuclear molecules of [Au2{S2-
P(O-cyclo-C6H11)2}2]. There is also additional intramolecular sec-
ondary bond Auꢀ ꢀ ꢀAu in molecules of 1. Therefore, the central
eight-membered moiety [Au2S4P2] is a combination of two five-
membered rings [Au2S2P] adopting the same distorted ‘envelope’
conformation. Further supramolecular self-organisation of com-
plex 1, resulting in formation of infinite polymeric zigzag chains,
is defined by the pairs of the secondary bonds Auꢀ ꢀ ꢀS between
neighbouring binuclear molecules of [Au2{S2P(O-cyclo-C6H11)2}2].
In centrosymmetric molecules of 2, pairs of O,O0-di-cyclo-hexyl-
thiophosphoryl fragments are combined by the chemical bond
S(1)AS(1)a and a planar zigzag array [S@PASASAP@S] passes
through their central part. In these molecular systems, both phos-
phorous sites having negative daniso-values (dzz < diso) are character-
ised by mainly rhombic 31P CSTs:
g = 0.82 (1) and 0.85 (2). At the
first stage of the thermal decomposition of complex 1, a 37.9%
mass loss, corresponding to the relative mass of two cyclo-
C6H11A and two cyclo-C6H11OA groups (the calc. loss is 37.2%), sug-
gests formation of gold(I) dithio-meta-phosphate, [Au2(S2PO)2]
(62.1%/calc. 62.8%), as the intermediate product; whereas reduced
metallic gold is the main final product.
Acknowledgements
We are grateful to ‘CHEMINOVA AGRO A/S’ (Denmark) for
potassium di-cyclo-hexyl dithiophosphate, which was kindly sup-
plied for this study. This work was financially supported by the
Presidium of Far Eastern Branch of the Russian Academy of Sci-
ences (Project Nos. 12-I-P8-01 and 12-III-A-04-040). The CMX-
360 NMR spectrometer has been purchased with a grant from
the Swedish Council for Planning and Coordination of Research
(FRN). We thank the foundation in memory of J.C. and Seth M.
Kempe for grants JCK-2003, JCK-2307 and JCK-2701 from which
some of the NMR equipment was purchased. Centre of Advanced
Mining and Metallurgy (CAMM) at Luleå University of Technology
(LTU) is acknowledged for the financial support.
Fig. 9. EDX spectrum (a) and SEM image (b) of the intermediate product particles of
[Au2(S2PO)2].
0.03 mm in diameter were discovered on the bottom, walls and
cover of the crucibles (Fig. 8c).
4. Conclusions
Crystalline polymeric gold(I) di-cyclo-hexyl dithiophosphate,
[Au2{S2P(O-cyclo-C6H11)2}]n (1) and bis(O,O0-di-cyclo-hexylthio-
phos-phoryl) disulphide, (cyclo-C6H11O)2P(S)SAS(S)P(O-cyclo-
Appendix A. Supplementary material
C6H11)2 (2) were prepared and studied by means of heteronuclear
13C, 31P CP/MAS NMR spectroscopy, single-crystal X-ray diffraction
and simultaneous thermal analysis. In complex 1, the pairs of
CCDC 870307 and 870308 contain the supplementary crystallo-
graphic data for compounds 1 and 2, respectively. These data can
be obtained free of charge via http://www.ccdc.cam.ac.uk/conts/
di-cyclo-hexyl Dtph ligands, displaying the same
l2-bridging

A.V. Ivanov et al. / Journal of Molecular Structure 1034 (2013) 152–161
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tre, 12 Union Road, Cambridge CB2 1EZ, UK; fax: (+44) 1223-336-
033; or e-mail: deposit@ccdc.cam.ac.uk. Supplementary data asso-
ciated with this article can be found, in the online version, at
http://dx.doi.org/10.1016/j.molstruc.2012.08.052. These data in-
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