The preparation, properties and X-ray structures of gold(I) trithiophosphite complexes

Article abstract of DOI:10.1016/j.jorganchem.2006.07.034

The first gold(I) trithiophosphite complexes were synthesised and fully characterised. Reaction of (tht)AuX (X = Cl, C₆F₅; tht = tetrahydrothiophene) with trithiophosphites (RS)₃P (R = Me, Ph) and the bicyclic [(SCH₂CH₂S)PSCH₂]₂ (²L) afforded the corresponding molecular complexes (RS)₃PAuX [R = Me, X = Cl (1); R = Me, X = C₆F₅ (2); R = Ph, X = Cl (3); R = Ph, X = C₆F₅ (4)], and ²L(AuX)₂ [X = Cl (5), X = C₆F₅ (6)]. Reacting (tht)AuCl consecutively with two mole equivalents of (MeS)₃P and then AgOTf, gave the ionic compound {[(MeS)₃P]₂Au}OTf (7). The compounds were characterised by multinuclear NMR spectroscopy, IR measurements and mass spectrometry, and the crystal and molecular structures of 1, 3, 6, two polymorphs of 2 as well as the known (MeO)₃PAuCl (8) were determined by X-ray diffraction. The halide complexes 1 and 8 are isostructural and exhibit infinite chains of crossed-sword -type aurophilic interactions with Au?Au contact distances of 3.2942(3) and 3.1635(4) ?, respectively. Complex 6 exhibits a long Au?Au contact of 3.4671(9) ?. Au?S interactions between 3.3455(7) and 3.520(2) ? are present in the structures of 1 and one polymorph of 2.

Full text of DOI:10.1016/j.jorganchem.2006.07.034

Journal of Organometallic Chemistry 691 (2006) 4788–4796
www.elsevier.com/locate/jorganchem
The preparation, properties and X-ray structures of gold(I)
trithiophosphite complexes
*
Christoph E. Strasser, Stephanie Cronje, Hubert Schmidbaur, Helgard G. Raubenheimer
Department of Chemistry and Polymer Science, University of Stellenbosch, Private Bag X1, Matieland 7602, South Africa
Received 12 July 2006; accepted 28 July 2006
Available online 4 August 2006
Abstract
The first gold(I) trithiophosphite complexes were synthesised and fully characterised. Reaction of (tht)AuX (X = Cl, C6F5; tht =
tetrahydrothiophene) with trithiophosphites (RS)3P (R = Me, Ph) and the bicyclic [(SCH2CH2S)PSCH2]2 (2L) afforded the correspond-
ing molecular complexes (RS)3PAuX [R = Me, X = Cl (1); R = Me, X = C6F5 (2); R = Ph, X = Cl (3); R = Ph, X = C6F5 (4)], and
2L(AuX)2 [X = Cl (5), X = C6F5 (6)]. Reacting (tht)AuCl consecutively with two mole equivalents of (MeS)3P and then AgOTf, gave
the ionic compound {[(MeS)3P]2Au}OTf (7). The compounds were characterised by multinuclear NMR spectroscopy, IR measurements
and mass spectrometry, and the crystal and molecular structures of 1, 3, 6, two polymorphs of 2 as well as the known (MeO)3PAuCl (8)
were determined by X-ray diffraction. The halide complexes 1 and 8 are isostructural and exhibit infinite chains of ‘‘crossed-sword’’-type
˚
aurophilic interactions with Auꢀ ꢀ ꢀAu contact distances of 3.2942(3) and 3.1635(4) A, respectively. Complex 6 exhibits a long Auꢀ ꢀ ꢀAu
˚
˚
contact of 3.4671(9) A. Auꢀ ꢀ ꢀS interactions between 3.3455(7) and 3.520(2) A are present in the structures of 1 and one polymorph of 2.
ꢀ 2006 Elsevier B.V. All rights reserved.
Keywords: Gold(I) complexes; Trithiophosphite; X-ray crystal structure; Aurophilic interaction; Gold–sulphur interaction; Phosphorus–sulphur
heterocycle
1. Introduction
Addition compounds of AuCl3 with trithiophosphites
have been mentioned but have only been identified by their
melting points [7]. No other gold–trithiophosphite interac-
tions have been investigated.
In this study, we set out to further expand the
knowledge of the ligand properties of trithiophosphites
by preparing a series of gold(I) complexes with the three
ligands trimethyltrithiophosphite, triphenyltrithiophosph-
ite and 1,2-bis(1,3,2-dithiaphospholan-2-ylthio)ethane. To
our knowledge, no coordination compounds of the latter
ligand are known.
The trithiophosphite complexes prepared by us were
fully characterised by elemental analysis as well as NMR,
IR, FAB- and ESI-MS measurements, and, for several
compounds, X-ray structure determination. While this
work was in progress, we also noticed that the crystal
structure of chloro(trimethylphosphite)gold(I) (8) is not
known so this compound was prepared and its crystal
and molecular structures determined for comparison.
Even though trithiophosphites were reported for the
first time in 1872 [1], relatively little coordination chemistry
with these ligands is known. This may be in part owing to
the properties of trithiophosphites whose odour and
toxicity render them unattractive substrates of study. A
recent paper by Kataeva et al. summarises trithiophosphite
coordination chemistry [2]. A limited number of crystal
structures have been published for a series of trit-
hiophosphite (L) complexes of copper(I) halides and
pseudohalides [2,3], two CpMn(CO)2L-type compounds
[4], an (arene)Cr(CO)2L [5] and one each of di- and trinu-
clear iron carbonyl complexes [6].
*
Corresponding author. Tel.: +27 21 808 3850; fax: +27 21 808 3849.
E-mail address: hgr@sun.ac.za (H.G. Raubenheimer).
0022-328X/$ - see front matter ꢀ 2006 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2006.07.034

C.E. Strasser et al. / Journal of Organometallic Chemistry 691 (2006) 4788–4796
4789
2. Experimental
the solution. The obtained solid was again dissolved in
thf (15 mL), filtered through Celite and stripped of solvent
affording the target compound as a colourless microcrystal-
line solid in quantitative yield (0.342 g). Crystals suitable
for X-ray diffraction measurement were grown by layering
a deuteriochloroform solution with pentane, m.p. 114 ꢁC
(dec.) Anal. Calc. for C3H9AuClPS3: C, 8.90; H, 2.24.
Found: C, 8.7; H, 2.3%. IR (cmꢁ1): 2920 (CH3, s), 1415
(CH3, vs), 694 (s), 566 (vs), 512 (vs), 503 (vs), 315 (Au35Cl,
2.1. General
Solvents were freshly distilled from sodium (toluene,
pentane), sodium benzophenone ketyl radical (diethyl
ether, thf) or CaH2 (dichloromethane) under an atmo-
sphere of dry dinitrogen. All operations were conducted
in oven-dry Schlenk-type glassware under an atmosphere
of dry argon. (MeS)3P and (PhS)3P [8], (tht)AuCl [9,10]
and (tht)AuC6F5 [10] were synthesised following published
procedures. Melting points were determined in sealed cap-
illary on a Stuart Scientific SMP3 melting point apparatus
and are uncorrected. Elemental analyses and FAB mass
spectra (nitrobenzyl alcohol matrices) were performed by
the University of the Witwatersrand. Standard infrared
spectra were recorded at 4 cmꢁ1 resolution on a Nicolet
Avatar 300 FT-IR instrument equipped with a Smart
Performer ZnSe disk ATR accessory. The spectra were
corrected for ATR effects using Omnic software. Far-IR
spectra were recorded in polyethylene discs at 4 or
2 cmꢁ1 resolution on a Nicolet Nexus FT-IR spectrometer
using a solid substrate beam splitter and a DTGS polyeth-
ylene detector. The 1H, 13C, 19F and 31P NMR spectra (d in
ppm) were recorded on a Varian VXR 300 or a Varian
Unity INOVA 400 spectrometer at the indicated frequen-
cies. Solvent residual peaks were used to reference 1H
and 13C spectra. For 19F and 31P spectra, CFCl3 and
85% H3PO4, respectively, were used as external references.
1
s), 308 (Au37Cl, m). H NMR (300 MHz, CDCl3): d 2.43
3
1
(d, JPH 17.6, JCH 144). 13C{1H} NMR (75.4 MHz,
CDCl3): d 16.1 (s). 31P{1H} NMR (121 MHz, CDCl3): d
123.4 (s). MS (ESI): m/z 613 [62%, (LAu Æ AuSMe)+]; 567
(40), 541 (15, L2Au+), 369 (30, LAu+).
2.2.3. (Pentafluorophenyl)(trimethyltrithiophosphite)-
gold(I) (2)
A solution of (MeS)3P (0.107 g, 0.62 mmol) in diethyl
ether (30 mL) was cooled to 0 ꢁC and transferred via a tef-
lon cannula to a second Schlenk tube charged with
(tht)AuC6F5 (0.273 g, 0.60 mmol). The mixture was stirred
for 45 min at 0 ꢁC followed by filtration of the purplish
solution through Celite previously washed with diethyl
ether. After removal of the volatiles in vacuo a crude
purple product was obtained. The filtration procedure
was repeated to afford a colourless microcrystalline solid
(0.283 g, 87%). Crystals of polymorph A suitable for
X-ray diffraction measurement were grown by diffusing
pentane vapour into a diethyl ether solution. Polymorph
B crystallised from a thf solution layered with pentane,
m.p. 92 ꢁC (dec.) Anal. Calc. for C9H9AuF5PS3: C, 20.16;
H, 1.69. Found: C, 20.1; H, 1.7%. IR (cmꢁ1): 2917 (CH3,
s), 1634 (m), 1501 (s), 1454 (vs), 1419 (CH3, vs), 1061 (s),
1
Values for coupling constants are given in Hz, JCH cou-
pling constants were obtained from 13C satellites in the
1H spectra. ESI mass spectra were recorded on a Waters
API Quattro Micro instrument at 50 V cone voltage in
thf/acetonitrile solutions. Thermal gravimetric analysis
was conducted on a TA Instruments TGA Q500 device.
1
952 (vs), 790 (s) 693 (m). H NMR (400 MHz, CDCl3):
3
1
d
2.51 (d, JPH 16.4, JCH 143). 13C{1H} NMR
1
(75.4 MHz, CDCl3): d 149.3 (dm, JFC 229, ortho-C),
1
1
2.2. Preparation of the compounds
140.0 (dm, JFC 248, meta-C), 137.6 (dm, JFC 253, para-
C), 15.4 (s, CH3). 19F NMR (376 MHz, CDCl3): d
ꢁ116.7 (2F, m, ortho-F), ꢁ157.4 (1F, m, para-F), ꢁ162.2
(2F, m, meta-F). 31P{1H} NMR (121 MHz, CDCl3): d
144.3 (s). MS (FAB): m/z 536 (9%, M+), 522 [10, (M–
C6F5 + C7H7NO3)+], 369 [18, (M–C6F5)+].
2.2.1. 1,2-Bis(1,3,2-dithiaphospholan-2-ylthio)ethane
A diethyl ether solution (40 mL) of ethane-1,2-dithiol
(2.25 g, 24 mmol) was added dropwise to a stirred solution
of freshly distilled phosphorus trichloride (2.05 g, 15 mmol)
and pyridine (4.07 g, 52 mmol) in diethyl ether (60 mL) at
0 ꢁC. After 2 h pyridine hydrochloride was removed by
filtration and washed with dichloromethane (60 mL). The
solvents were removed in vacuo and the remaining
colourless solid extracted with toluene (100 mL) and again
filtered. Toluene was removed in vacuo affording a
colourless microcrystalline solid (0.789 g, 31%); m.p.
123 ꢁC.
2.2.4. Chloro(triphenyltrithiophosphite)gold(I) (3)
The complex was prepared in an analogous manner to 1
employing (PhS)3P (0.346 g, 0.97 mmol) and (tht)AuCl
(0.315 g, 0.98 mmol) affording a viscous colourless oil
which slowly crystallised over several days at ꢁ16 ꢁC yield-
ing a colourless solid (0.539 g, 95%). A crystal suitable for
X-ray structure determination was grown from a thf solu-
tion layered with diethyl ether at ꢁ16 ꢁC, dec. 63 ꢁC with-
out melting. Anal. Calc. for C18H15AuClPS3: C, 36.59; H,
2.56. Found: C, 36.4; H, 2.7%. IR (cmꢁ1): 3044 (CH, m),
1572 (m), 1470 (vs), 1436 (vs), 1082 (s), 1023 (s), 745 (vs),
687 (vs), 461 (vs), 339 (AuCl, s), 318 (s), 262 (m), 235
2.2.2. Chloro(trimethyltrithiophosphite)gold(I) (1)
(MeS)3P (0.146 g, 0.85 mmol) was dissolved in thf
(15 mL) and (tht)AuCl (0.272 g, 0.85 mmol) was added.
The resulting homogeneous slightly yellowish solution
was stirred for 1 h. All volatiles were removed in vacuo
during which the compound started to precipitate from
1
(m). H NMR (300 MHz, CD2Cl2): d 7.64 (6H, m, ortho-
H), 7.54 (3H, m, para-H), 7.46 (6H, m, meta-H). 13C{1H}

4790
C.E. Strasser et al. / Journal of Organometallic Chemistry 691 (2006) 4788–4796
2
NMR (75.4 MHz, CD2Cl2): d 136.9 (d, JPC 5.0, ipso-C),
1.13. Found: C, 20.4; H, 1.2%. IR (cmꢁ1): 2924 (CH2, w),
1638/1632 (m), 1502 (vs), 1452 (vs), 1357 (s), 1199 (m),
1061 (s), 952 (s), 789 (s). H NMR (400 MHz, thf-d8): d
3.65 (8H, m, ring-CH2), 3.46 (4H, m, bridge-CH2).
13C{1H} NMR (101 MHz, thf-d8): d 41.3 (s, ring-CH2),
36.6 (s br, bridge-CH2). 19F NMR (376 MHz, thf-d8): d
ꢁ115.4 (4F, m, ortho-F), ꢁ159.6 (2F, t, 3JFF 19.6, para-F),
ꢁ163.7 (4F, m, meta-F). 31P{1H} NMR (121 MHz, CDCl3):
d 134 (br s). MS (FAB): m/z 899 [1%, (M–C6F5)+], 595 (1),
535 [1, (M–AuC6F5–C6F5)+], 164 (15), 162 (24).
3
4
131.5 (d, JPC 3.6, ortho-C), 130.6 (d, JPC 2.8, meta-C),
129.0 (br s, para-C). 31P{1H} NMR (121 MHz, CD2Cl2):
d 142.1 (s). MS (ESI): m/z 1167 [30%, (LAu Æ 2AuSPh)+];
1123 (30), 913 (30, L2Au+), 861 [100, (LAu Æ AuSPh)+],
817 (70), 665 [30, (LAu Æ PhSH)+].
1
2.2.5. (Pentafluorophenyl)(triphenyltrithiophosphite)-
gold(I) (4)
The compound was prepared in an analogous manner to
2 employing (PhS)3P (0.145 g, 0.40 mmol) and (tht)AuC6F5
(0.189 g, 0.42 mmol). After evaporation of all volatiles a
colourless crystalline solid was obtained (0.283 g, 97%),
m.p. 86 ꢁC (dec.) Anal. Calc. for C24H15AuF5PS3: C,
39.90; H, 2.09. Found: C, 40.0; H, 2.1%. IR (cmꢁ1): 3054
(CH, m), 1638 (m), 1609 (m), 1503 (s), 1456 (vs), 1438
(vs), 1355 (s), 1060 (s), 952 (vs), 741 (s), 683 (s). 1H
NMR (400 MHz, CDCl3): d 7.60 (6H, m, ortho-H), 7.43
(3H, m, para-H), 7.37 (6H, m, meta-H). 13C{1H} NMR
2.2.8. Bis(trimethyltrithiophosphite)gold(I) triflate (7)
(MeS)3P (0.139 g, 0.81 mmol) was dissolved in aceto-
nitrile (10 mL) and (tht)AuCl (0.130 g, 0.41 mmol) was
added which yielded a yellow precipitate. After 1 h thf
(10 mL) was added which dissolved the precipitate afford-
ing a hazy yellowish solution. A solution of silver triflate
(0.102 g, 0.40 mmol) in acetonitrile (5 mL) was added caus-
ing immediate precipitation of AgCl. The suspension was
stirred for another hour and then filtered through Celite.
The filter was washed with thf (20 mL) and the filtrate
evaporated in vacuo affording a yellow oil which slowly
crystallised at ꢁ16 ꢁC. Treatment of the raw product with
diethyl ether (40 mL), inverse filtration and drying in vacuo
afforded a hygroscopic yellow solid (0.153 g, 56%) which is
very sensitive to moisture, m.p. 60 ꢁC with evolution of gas.
Anal. Calc. for C7H18AuF3O3P2S7: C, 12.17; H, 2.63.
Found: C, 12.5; H, 2.9%. IR (cmꢁ1): 2916 (CH3, m),
2847 (CH3, m), 1422/1418 (CH3, s), 1253 (CF3SO3, s),
1219 (CF3SO3, vs), 1155 (s), 1140 (s), 1026 (s), 955 (m).
1
(75.4 MHz, CDCl3): d 148.6 (dm, JFC 230, ortho-C6F5),
139.4 (dm, JFC 248, meta-C6F5), 137.0 (dm, JFC 253,
para-C6F5), 136.6 (d, JPC 3.7, ipso-C6H5), 130.7 (d, JPC
1
1
2
3
4
3.3, ortho-C6H5), 130.0 (d, JPC 2.8, meta-C6H5), 128.5
(br s, para-C6H5). 19F NMR (376 MHz, CDCl3): d
3
ꢁ115.9 (2F, m, ortho-C6F5), ꢁ158.2 (1F, t, JFF 20.0,
para-C6F5), ꢁ162.7 (2F, m, meta-C6F5). 31P{1H} NMR
(121 MHz, CDCl3): d 161.3 (s). MS (FAB): m/z 722
(15%, M+), 613 [5, (M–SPh)+], 555 [20, (M–C6F5)+], 446
[8, (M–C6F5–SPh)+], 249 {58, [P(SPh)2]+}.
3
1
2.2.6. Dichloro{l-[1,2-bis(1,3,2-dithiaphospholan-2-
ylthio)ethane]}digold(I) (5)
1H NMR (300 MHz, CDCl3): d 2.40 (d, JPH 14.7, JCH
144). 13C{1H} NMR (75.4 MHz, CDCl3): d 15.2 (d, JPC
2
A solution of (tht)AuCl (0.218 g, 0.68 mmol) and 1,2-
bis(1,3,2-dithiaphospholan-2-ylthio)ethane (0.115 g, 0.34
mmol) in thf (15 mL) was stirred at r.t. A precipitate was
observed and after 1.5 h the volatiles were removed in
vacuo affording a yellowish solid (0.263 g, 96%). Only lim-
ited analytical data could be obtained due to the insolubil-
ity of the material, m.p. dec. 95 ꢁC without melting. Anal.
Calc. for C6H12Au2Cl2P2S6: C, 8.97; H, 1.51. Found: C,
8.9; H, 1.5%. IR (cmꢁ1): 2958 (CH2, s), 2922 (CH2, s),
1416/1411 (CH2, vs), 1288 (m), 1202 (vs), 938 (s), 837
(vs), 728 (m), 673 (s), 433 (m), 371 (m), 323 (AuCl, s).
4.0). 31P{1H} NMR (121 MHz, CDCl3): d 128.1 (s). MS
(ESI): m/z 785 {7%, [(MeS)3P]2Au+ Æ AuSMe}, 583 (12),
541 {90, [(MeS)3P]2Au+}.
2.2.9. Chloro(trimethylphosphite)gold(I) (8)
In an analogous manner to the preparation of 1 the
reaction of trimethylphosphite (0.041 g, 0.33 mmol) and
(tht)AuCl (0.108 g, 0.34 mmol) afforded a crystalline pow-
der after evaporation of all volatiles. It was redissolved in
thf (7 mL), the solution layered with pentane and stored
at ꢁ16 ꢁC whereupon the target compound crystallised as
colourless needles (0.104 g, 90%). A suitable crystal was
mounted for X-ray diffraction; m.p. 101 ꢁC. 1H NMR
2.2.7. Bis(pentafluorophenyl){l-[1,2-bis(1,3,2-
dithiaphospholan-2-ylthio)ethane]}digold(I) (6)
3
1
(300 MHz, CDCl3): d 3.74 (d, JPH 14.0, JCH 150).
13C{1H} NMR (75.4 MHz, CDCl3): d 53.1 (br s).
31P{1H} NMR (121 MHz, CDCl3): d 121.0 (s).
A solution of 1,2-bis(1,3,2-dithiaphospholan-2-ylthio)-
ethane (0.077 g, 0.23 mmol) in thf (10 mL) was cooled to
0 ꢁC and (tht)AuC6F5 (0.210 g, 0.46 mmol) was added.
After stirring the homogeneous solution for 30 min the vol-
atiles were removed in vacuo during which the product
started to precipitate. The dry solid was again dissolved in
thf (30 mL), filtered through Celite and stripped of solvent
to afford a colourless crystalline product (0.216 g, 87%).
Crystals suitable for X-ray diffraction were obtained by lay-
ering a thf solution with pentane, m.p. dec. 158 ꢁC without
melting. Anal. Calc. for C18H12Au2F10P2S6: C, 20.27; H,
2.3. Crystal structure determinations
Intensity data were collected at T = 100 K with a Bruker
SMART Apex diffractometer [11] with graphite monochro-
˚
mated Mo Ka radiation (k = 0.71073 A). Intensities were
measured using the x-scan mode and were corrected for
Lorentz and polarisation effects. The structures were solved
by direct methods and refined by full-matrix least-squares

C.E. Strasser et al. / Journal of Organometallic Chemistry 691 (2006) 4788–4796
4791
on F2 using the SHELXL-97 software package and X-SEED
[12]. All non-hydrogen atoms were refined with anisotropic
displacement parameters and all hydrogens were placed in
calculated positions. Figures were created using POV-RAY
3.5 with thermal displacement ellipsoids at the 50% proba-
bility level, all hydrogen atoms were omitted for clarity.
Data and parameters of the crystal structure determina-
tions are shown in Table 1.
temperature however is lower and slow deterioration with
deposition of metallic gold occurs within days. Complexes
of the bicyclic ligand, 5 and 6, as well as the homoleptic 7
are more sensitive and turn yellow within weeks upon stor-
age in the freezer. This might be caused by P–S bond cleav-
age which was observed in the synthesis of iron carbonyl
complexes of trithiophosphites [6]. While 1 and 3 are solu-
ble in polar, aprotic solvents, complexes 2 and 4 are also
soluble in diethyl ether; all compounds are insoluble in ali-
phatic hydrocarbons. The solubility of the binuclear com-
plexes is poor; 5 does not dissolve at all and 6 only
dissolves in thf when freshly prepared but after prolonged
storage becomes insoluble. The complexes exhibit a faint
odour of the parent thiol and are decomposed slowly by
moisture. Protic solvents like methanol effect fast decom-
position indicating a destabilising effect of the coordinated
gold moiety on the ligand. This pathway has been used to
convert coordinated trithiophosphites into phosphonates
by hydrolysis of copper(I) halide complexes [15].
3. Results and discussion
The preparation of the complexes is outlined in Scheme
1. Syntheses of 1–6 were readily achieved in high yields by
replacing tetrahydrothiophene from either chloro(tetra-
hydrothiophene)gold(I) or (pentafluorophenyl)(tetrahydro-
thiophene)gold(I) with the respective trithiophosphite. The
substitutions were carried out in thf at room temperature
for the chloro complexes or in diethyl ether solution at
0 ꢁC for the pentafluorophenyl compounds. Evaporation
of all volatile matter afforded microcrystalline product mix-
tures that were, especially in the case of the pentafluorophe-
nyl derivatives, contaminated with metallic gold. Filtration
over Celite yielded the complexes as colourless microcrys-
talline compounds after stripping of solvent. Preparation
of (7) was effected by reacting two equivalents of (MeS)3P
with (tht)AuCl and AgOTf in acetonitrile/thf. The known
[13,14] phosphite complex 8 was prepared analogously to 1.
Compounds 1–4 are stable for months without any signs
of decomposition when stored at ꢁ16 ꢁC. Stability at room
3.1. Thermal gravimetric analysis
A crystalline sample of 1 (4.0 mg) was heated at a rate of
10 ꢁC minꢁ1 to 400 ꢁC. The sample mass was constant up
to the melting point (114 ꢁC) when rapid loss (44.3%) of
weight set in until 176 ꢁC was reached. Thereafter the mass
stayed fairly constant up to 400 ꢁC when a final loss of
45.7% occurred. A yellow solid remained in the pan. The
observed weight loss falls between the theoretical loss to
Table 1
Crystallographic and data collection parameters for compounds 1, 2A, 2B, 3, 6 and 8
Compound
(MeS)3PAuCl (1) (MeO)3PAuCl (8) (MeS)3PAuC6F5 (2A) (MeS)3PAuC6F5 (2B) (PhS)3PAuCl (3) 2L(AuC6F5)2a(6)
Empirical formula
Mr
C3H9AuClPS3
404.69
C3H9AuClO3P
356.49
C9H9AuF5PS3
536.30
C9H9AuF5PS3
536.30
C18H15AuClPS3 C18H12Au2F10P2S6
590.90
1066.5
Crystal habit
Crystal dimensions
(mm)
Needle
0.2 · 0.1 · 0.05
Needle
0.5 · 0.1 · 0.1
Block
0.05 · 0.04 · 0.03
Block
0.1 · 0.1 · 0.05
Block
0.2 · 0.2 · 0.15
Block
0.1 · 0.08 · 0.04
Crystal system
Space group
a (A)
Orthorhombic
Pbca (No. 61)
6.5671(6)
15.6506(15)
18.3143(17)
90
90
90
1882.3(3)
8, 2.856
16.670
Orthorhombic
Pbca (No. 61)
6.2810(8)
14.5070(18)
17.324(2)
90
90
90
1578.6(3)
8, 3.000
19.119
Triclinic
Triclinic
Monoclinic
P21/c (No. 14)
15.156(2)
13.1192(18)
10.1472(14)
90
100.834(2)
90
1981.7(5)
4, 1.980
Monoclinic
I2/a (No. 15)
9.0659(15)
17.155(3)
17.061(3)
90
94.020(4)
90
2646.8(8)
4, 2.676
11.749
ꢀ
ꢀ
P1 (No. 2)
P1 (No. 2)
˚
11.7392(16)
11.7574(16)
12.6724(17)
103.971(2)
105.090(2)
110.925(2)
1464.9(3)
4, 2.432
7.7052(13)
10.0602(17)
11.0138(19)
65.077(2)
82.579(3)
69.830(3)
726.6(2)
˚
b (A)
˚
c (A)
a (ꢁ)
b (ꢁ)
c (ꢁ)
3
˚
V (A )
Z, Dc (Mg mꢁ3
)
2, 2.451
10.699
l(Mo Ka) (mmꢁ1
)
10.614
7.953
Number of reflections, 10206, 2007
unique
8198, 1604
8780, 6057
7786, 2963
11766, 4510
7592, 2726
Rint
0.0259
0.0268
0.0201
0.0282
0.0443
0.0510
Data/restraints/
parameters
F (000)
R1, wR2 [I > 2r(I)]
R1, wR2 (all data)
1924/0/85
1514/0/85
5267/0/349
2770/0/175
3815/0/217
2308/0/172
1488
1296
1000
500
1128
1976
b
0.0163, 0.0395
0.0173, 0.0399
1.101
0.0218, 0.0446
0.0239, 0.0453
1.188
0.0341, 0.0813
0.0407, 0.0845
1.029
0.0279, 0.0632
0.0310, 0.0644
1.079
0.0462, 0.0856
0.0588, 0.0890
1.130
0.0531, 0.1002
0.0666, 0.1047
1.139
Goodness-of-fit
a
2L = 1,2-bis(1,3,2-dithiaphospholan-2-ylthio)ethane.
2
b
w ¼ 1=½r2ðF 2oÞ þ ðaPÞ þ bPꢂ where P ¼ ðF o2 þ 2F 2c Þ=3.

4792
C.E. Strasser et al. / Journal of Organometallic Chemistry 691 (2006) 4788–4796
Scheme 1. Preparation of the compounds: (i) thf, r.t. for X = Cl; diethyl ether, 0 ꢁC for X = C6F5. (ii) acetonitrile/thf, r.t.
afford the possible decomposition products Au2S (47.4%)
and AuCl (42.6%).
dination of (MeS)3P. The aromatic protons in 3 and 4 are
shifted to lower field by ca. 0.1–0.2 ppm vs. free ligand thus
allowing the discrimination of meta- and para-signals that
overlap in the spectrum of (PhS)3P.
3.2. Spectroscopic analyses
In the 13C spectra of 2 and 4 the ipso-carbon atoms of
the pentafluorophenyl group and the CF3-carbon in 7 were
not observed due to low intensity, 6 was not soluble
enough to detect any carbon resonances of the C6F5
groups. Unexpectedly, the JPC coupling constants of all
ligands decrease upon coordination, again showing dissim-
ilarity to the simple phosphanes [17]. Though the protons
of the trimethyltrithiophosphite complexes 1, 2 and 7 all
3.2.1. Nuclear magnetic resonance
The coordination of the trithiophosphite ligands to the
gold(I) centre could be verified by comparison of the H
1
and 31P NMR spectra of the free ligands and complexes.
Coordination to the AuCl moiety does not greatly affect
the 31P shift, Dd being ꢁ2.3 for 1 and +2.2 for 3, in contrast
to the large Dd (+38 to +48) observed for gold(I) chloride
adducts of simple tertiary phosphanes [16,17], and with the
31P upfield shift (Dd, ꢁ20) associated with normal phos-
phite coordination to AuCl [16]. Upon coordination to
the AuC6F5 fragment, however, a pronounced Dd, averag-
ing +20 for the trithiophosphite ligands, is observed. All
31P signals are sharp singlets except for complex 6, which
shows a broad peak; see Scheme 2.
2
indicate coupling with the 31P nucleus, a substantial JPC
in the 13C spectra is only observed for the free ligand
(18 Hz); the complexes with the exception of 7 (2JPC
4 Hz) only exhibit a sometimes broadened singlet for the
methyl carbon atoms, similar to the methyl resonance of
8. This could be due to fast ligand exchange in the com-
plexes as was observed earlier for phosphine and phosphite
complexes [13]. For the triphenyltrithiophosphite ligand
the 13C signals are split into doublets up to the meta carbon
atoms. The para carbons appear as broad singlets and the
values of the JPC coupling constants especially for the ipso
carbon (2JPC 5–6 Hz), are lower than for the free ligand
(13 Hz). With the bicyclic ligand, 1,2-bis(1,3,2-dithiaphos-
pholan-2-ylthio)ethane, the doublet of doublets of the
two bridging carbon atoms at higher field in the free ligand
spectrum [18] is again reduced to a broad singlet in 6.
In addition, the pentafluorophenyl groups of 2, 4 and 6
were examined by 19F NMR spectroscopy and the usual
pattern of shifts and multiplicities for the AuC6F5 moiety
is observed [19].
The proton spectra for 1, 2 and 7 show a downfield shift
1
of the methyl signal by 0.2–0.3 ppm. The JCH coupling
constants obtained from the 13C satellites remain essen-
tially unchanged at an average value of 143 Hz upon coor-
3.2.2. Infrared spectroscopy
Routine IR spectra essentially show the absorptions of
the ligand groups for complexes 1, 3 and 5. Compounds
Scheme 2. Possible dynamic homoleptic rearrangement of compound 6 to
a ionic species giving rise to the broad resonance in the 31P NMR
spectrum.

C.E. Strasser et al. / Journal of Organometallic Chemistry 691 (2006) 4788–4796
4793
2, 4 and 7, additionally, exhibit the characteristic vibrations
of the C6F5 or CF3SO3 groups.
molecules 2A-1 and 2A-2) was found by diffusing pentane
vapour into an diethyl ether solution of 2; later, crystals
of the more symmetric polymorph, B, with only one mole-
cule in the asymmetric unit (2B) were obtained by layering a
thf solution of 2 with pentane. Complex 1, the isostructural
8 as well as 6, exhibit Auꢀ ꢀ ꢀAu interactions. Important bond
lengths and angles are reported in Table 2.
In general, it was noted that even though it is potentially
possible for trithiophosphite ligands to adopt local C3 sym-
metry in the crystal, in agreement with gold(I) complexes of
tertiary phosphanes like chloro(triethylphosphane)gold(I)
[21], it was not observed. Two of the SMe or SPh moieties
are bent more or less towards the gold while the S–C axis of
the third group points away from the metal centre. This
observation is also echoed by the Au–P–S angles which
are in the order of 116–118ꢁ for the former and 108ꢁ for
the latter moieties.
In addition to these standard spectra, far-IR spectra in
the frequency range 600–200 cmꢁ1 of compounds 1, 3
and 5 were recorded in polyethylene discs to locate Au–
Cl vibrations. Compound 1 exhibits a sharp m(Au35Cl)
band at 315 cmꢁ1 with a m(Au37Cl) satellite at 308 cmꢁ1
consistent with theory; m(AuCl) for the phosphite complex
8 has been reported at 326 cmꢁ1 [20]. Combined with the
crystallographic findings (see below) this suggests that the
Auꢀ ꢀ ꢀS contacts in 1 could weaken both Au–P and Au–
Cl bonds compared to 8.
The spectrum of 3 shows two vibrations at 339 and
318 cmꢁ1, but only the band at higher wavenumber has a
shoulder indicative of a non-resolved m(Au37Cl) vibration.
The Au–Cl stretching band for (PhO)3PAuCl was reported
at 340 cmꢁ1 [20], suggesting that both ligands induce a
similar electronic effect since no close intermolecular con-
tacts are observed in the molecular structures of these com-
pounds (see below).
The crystal structures of 1 (Fig. 1), and 8 (Fig. 2), in the
orthorhombic space group Pbca are isostructural and exhi-
bit infinite, slightly bent chains owing to Auꢀ ꢀ ꢀAu interac-
tions. Au(1)–Au(10)–Au(100) angles are 170.783(8)ꢁ for 1
and 166.166(12)ꢁ for 8 along the a-axis, with the P–Au–Cl
axes oriented in the ‘‘crossed sword’’ motif (Fig. 3). The
Cl(1)–Au(1)ꢀ ꢀ ꢀAu(10)–Cl(10) torsion angles are 103.88(4)ꢁ
and 100.96(6)ꢁ, respectively. It is clear from Au–P bond
lengths that the trimethylphosphite ligand is both more
strongly bonded to the gold(I) centre and causes stronger
aurophilic interactions between the molecules. The differ-
ences in bond lengths are more pronounced than for the
triphenyltrithiophosphite and triphenylphosphite ligands
(see below). One sulphur atom of 1 is also involved in an
intermolecular sub van der Waals contact [Au(1)ꢀ ꢀ ꢀS(30)
0.5 + x, y, 0.5 ꢁ z] ‘‘supporting’’ the Au chain and may in
part be responsible for weakening the Au–P bond and
affording longer aurophilic interactions in 1. Auꢀ ꢀ ꢀS con-
tacts have previously been found to play a role in the pack-
ing of other gold(I) complexes [22]. The compounds
chloro(trimethylphosphane)gold(I) [23] [Auꢀ ꢀ ꢀAu distances
Compound 5 shows a broad m(AuCl) band at 323 cmꢁ1
suggesting that Auꢀ ꢀ ꢀAu interactions are present as would
be expected from the insolubility of the compound and the
effect of intermolecular contacts in 1.
3.2.3. Mass spectrometry
The FAB mass spectra of compounds 2, 4 and 6 show the
loss of a pentafluorophenyl unit but the molecular ion was
observed for 2 and 4. For compounds 1 and 3 FAB-MS
measurements failed to give interpretable patterns and
ESI-MS in thf/acetonitrile solution was employed. Frag-
mentation of the trithiophosphite ligand was observed lead-
ing to strong signals for [(RS)3PAu Æ AuSR]+ clusters along
with other ions. However, due to the insolubility of 5 no
mass spectrum could be obtained with any of above ionisa-
tion methods.
It is noteworthy that 1 does lose the ligand on heating
but rather loses the chloride in ionising conditions.
˚
3.271, 3.386 and 3.356 A] and chloro(triethylphos-
˚
3.2.4. Crystallography
Compounds 1, 2, 3, 6 and 8 furnished crystals suitable for
X-ray diffraction. For compound 2 two polymorphs both in
phane)gold(I) [21] [Auꢀ ꢀ ꢀAu distance 3.568 A] which have
tertiary phosphane ligands of similar or less steric require-
ment than (MeS)3P or (MeO)3P, crystallise in space groups
of lower symmetry suggesting that the sulphur and oxygen
lone pairs could be involved in directing the crystallisation
of compounds 1 and 8.
ꢀ
the space group P1 were discovered. First, a modification
with two independent molecules in the asymmetric unit
(referred to in the following discussion as polymorph A with
Table 2
˚
Selected bond angles (ꢁ) and distances (A) for compounds 1, 2A, 2B, 3, 6 and 8
1 (X = Cl)
2A (2A-1/2A-2) (X = C6F5)
2B (X = C6F5)
3 (X = Cl)
6 (X = C6F5)
8 (X = Cl)
Au–P
Au–X
2.2352(8)
2.3100(8)
3.2942(3)/3.3455(7)
178.55(3)
118.59(4)
119.37(4)
2.2662(14)/2.2724(16)
2.043(5)/2.049(6)
–/–
178.89(16)/174.21(17)
116.16(8)/112.87(8)
107.47(8)/121.42(8)
116.83(8)/108.08(8)
2.2704(14)
2.041(5)
–/3.5201(15)
178.61(15)
117.37(7)
2.2184(16)
2.2816(16)
–/–
176.99(6)
115.13(8)
114.64(9)
108.53(8)
2.271(3)
2.063(10)
3.4671(9)/–
171.7(3)
118.78(14)
114.72(13)
113.63(13)
2.2110(12)
2.3106(11)
3.1635(4)/–
175.90(4)
117.00(14)a
108.66(13)
118.98(14)
Auꢀ ꢀ ꢀAu/Auꢀ ꢀ ꢀS
P–Au–X
Au–P–S(1,2,3)
107.06(7)
118.34(7)
106.57(4)
a
Values for Au–P–O angles.

4794
C.E. Strasser et al. / Journal of Organometallic Chemistry 691 (2006) 4788–4796
Fig. 1. Molecular structure of 1. Auꢀ ꢀ ꢀAu and Auꢀ ꢀ ꢀS interactions are
indicated with dashed lines.
Fig. 3. Packing of 1 in the unit cell shown along the a-axis. Compound 8
has the same structure with slightly different cell dimensions.
Fig. 2. Molecular structure of 8. Auꢀ ꢀ ꢀAu interactions are shown with
dashed lines.
Triphenyltrithiophosphite crystallises in the space group
ꢀ
R3 and the molecules exhibit local C3 symmetry at the phos-
˚
phorus atom [24]. The P–S bond length is 2.126 A and the
P–S–C angle 99.6ꢁ. Upon coordination to AuCl, the P–S
bonds undergo a significant shortening to 2.094(2) [P(1)–
˚
S(1)], 2.090(2) [P(1)–S(2)] and 2.084(2) A [P(1)–S(3)] for
the three independent PhS groups in 3 (Fig. 4). The P–S–
C angles are not greatly affected by coordination and
remain at 99.1(2)ꢁ [P(1)–S(1)–C(11)] to 103.8(2)ꢁ [P(1)–
S(3)–C(31)]. In contrast to the isostructural 1 and 8, mono-
clinic 3 (space group P21/c) is not isostructural with triclinic
Fig. 4. Molecular structure of 3.
vail in the crystals and lead to different structures. The
Au–Cl and Au–P distances and the P–Au–Cl angles are
˚
ꢀ
chloro(triphenylphosphite)gold(I) (space group P1) [25].
comparable at 2.2816(16), 2.2184(16) A and 176.99(6)ꢁ for
˚
This may be due to the absence of Auꢀ ꢀ ꢀAu and Auꢀ ꢀ ꢀS
3 and 2.273(5), 2.192(5) A and 178.5(2)ꢁ for the oxo-
interactions in these structures. Thus, classical forces pre-
analogue.

C.E. Strasser et al. / Journal of Organometallic Chemistry 691 (2006) 4788–4796
4795
Fig. 5. Molecular structure of 2A. Both crystallographically independent molecules of the asymmetric unit are shown (2A-1 on the right, 2A-2 on the left).
In contrast to 1, polymorphs A and B (both in space
group P1, Z = 4 for A and Z = 2 for B) of 2 (Figs. 5
to the other molecule 2A-1 whose angle is close to the
expected 180ꢁ, as it is the case in 2B. The plane of the
C6F5 ring in 2A-1 is nearly eclipsed with the P(1)–S(13)
bond while the C6F5 ring in 2A-2 adopts a staggered con-
formation also found in polymorph B.
ꢀ
and 6) do not exhibit aurophilic interactions, which may
be due to the prevalence of other association phenomena
discussed below as steric factors are not likely to contrib-
ute. Instead, A exhibits infinite AA0BB0 stacks of penta-
fluorophenyl groups (distances between the0 phenyl-C6
The bond lengths in both polymorphs are the same
within experimental error, with only the Au(1)–P(1) bond
of 2A-1 somewhat shorter than in the other molecules
2A-2 and 2B. The Au–P distances in both polymorphs of
2 are longer than the Au–P distances of 1, resembling the
situation in chloro(triphenylphosphane)gold(I) (Au–P
0
0
0
˚
centroids AA = BB 3.668, A B 3.534, and B A 3.541 A)
for both crystallographically independent molecules run-
ning in the direction of the spatial vector defined by the
cell axes. The pentafluorophenyl groups of 2B on the
other hand exhibit no pꢀ ꢀ ꢀp interaction, but Auꢀ ꢀ ꢀS con-
tacts between the molecules related by an inversion centre
are observed which are in the range of the sum of the van
der Waals radii [Au(1)ꢀ ꢀ ꢀS(30) ꢁx, 1 ꢁ y, 1 ꢁ z]. Even
though the packing of the molecules in both polymorphs
is governed by different modes of interaction, the norma-
lised cell volumes differ by less than 1%. 2A-2 exhibits sig-
nificantly distorted geometry at the gold centre compared
˚
2.233 A) [26] and (pentafluorophenyl)(triphenylphos-
˚
phane)gold(I) (Au–P 2.273 A) [27].
The crystal structure of 1,2-bis(1,3,2-dithiaphospholan-
2-ylthio)ethane has been reported [28]. It crystallises in
the space group P21/c with two molecules in the unit cell.
Only half of the molecule is unique and an inversion centre
is located at the bridging C–C bond. Two P–S distances
˚
[2.120(3) and 2.126(3) A] and the exocyclic P–S–C angle
[98.7(3)ꢁ] are comparable to the values in (PhS)3P. In the
five-membered ring one P–S bond is shorter than expected
˚
[2.102(3) A] and the P–S–C angles [96.9(3)ꢁ and 101.8(3)ꢁ]
are slightly distorted. In the molecular structure of com-
pound 6 (Fig. 7), the conformation of the ligand has chan-
ged: instead of the arrangement with an inversion centre, a
structure with a C2 axis through the C(1)–C(10) and
Au(1)ꢀ ꢀ ꢀAu(10) bonds is observed which allows intramole-
cular aurophilic bonding. The P(1)–Au(1)ꢀ ꢀ ꢀAu(10)–P(10)
torsion angle is 110.19(13)ꢁ. Again, coordination causes
the P–S bonds to shorten to 2.067(4), 2.081(3) and
˚
2.086(4) A; the situation found in the free ligand, i.e., that
one of the cyclic P–S bonds is shorter than the other two, is
retained. The Au–P–S angles do not follow the trend of the
other compounds with two angles at 117ꢁ and one at 108ꢁ
but have intermediate values, probably caused by restraints
associated with the five-membered ring. The P(1)–Au(1)–
C(11) angle deviates from linearity, a result of the intramo-
lecular aurophilic attraction of the gold atoms.
Fig. 6. Molecular structure of 2B; Auꢀ ꢀ ꢀS interactions are indicated by
dashed lines.

4796
C.E. Strasser et al. / Journal of Organometallic Chemistry 691 (2006) 4788–4796
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4. Conclusion
The present study expands the scope of trithiophosphite
coordination chemistry and shows that gold(I) tri-
thiophosphite complexes are stable compounds and easily
accessible from common starting materials. The ligands
only being coordinated via their phosphorus atoms and
the gold(I) centres exhibiting the standard linear dicoordi-
nate geometry, though weak inter- and intramolecular
Auꢀ ꢀ ꢀS contacts are also observed. The simplest complex
chloro(trimethyltrithiophosphite)gold(I) and the isostruc-
tural chloro(trimethylphosphite)gold(I) aggregate in infi-
nite chains via Auꢀ ꢀ ꢀAu interactions.
[16] M.J. Mays, P.A. Vergnano, J. Chem. Soc., Dalton Trans. (1979)
1112–1115.
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Rosario Menezes, D.S. Raslan, E. de Souza, A.L.A.B. de Souza,
Phosphorus Sulfur Silicon Relat. Elem. 166 (2000) 1–14.
[19] F. Mohr, E. Cerrada, M. Laguna, Organometallics 25 (2006) 644–
648.
Appendix. Supplementary material
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3400.
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M. Preisenberger, A. Bauer, A. Schier, H. Schmidbaur, J. Chem.
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Katsyuba, Zh. Obshch. Khim. 65 (1995) 1129–1133;
Two other crystal structure determinations were published by:
N. Burford, B.W. Royan, P.S. White, Acta Crystallogr. Sec C 46
(1990) 274–276;
Crystallographic data for the structural analyses have
been deposited with the Cambridge Crystallographic Data
Centre, CCDC Nos. 609872–609877 for compounds 1, 2A,
2B, 3, 6, and 8. Copies of this information may be obtained
free of charge from the Director, CCDC, 12 Union Road,
Cambridge CB2 1EZ, UK (e-mail: deposit@ccdc.cam.a-
c.uk or http://www.ccdc.cam.ac.uk). Supplementary data
associated with this article can be found, in the online ver-
sion, at doi:10.1016/j.jorganchem.2006.07.034.
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