Dinuclear Gold(I) dithiophosphonate complexes

Article abstract of DOI:10.1021/ic0201856

2,4-Diaryl- and 2,4-diferrocenyl-1,3-dithiadiphosphetane disulfide dimers (RP(S)S)2 (R = Ph (1a), 4-C₆H₄OMe (1b), FeC₁₀H₉ (Fc) (1c)) react with a variety of alcohols, silanols, and trialkylsilyl alcohols to form new dithiophosphonic acids in a facile manner. Their corresponding salts react with chlorogold(I) complexes in THF to produce dinuclear gold(I) dithiophosphonate complexes of the type [AuS₂PR(OR′)]₂ in satisfactory yield. The asymmetrical nature of the ligands allows for the gold complexes to form two isomers (cis and trans) as verified by solution ¹H and ³¹P{¹H} NMR studies. The X-ray crystal structures of [AuS₂PR(OR′)]₂ (R = Ph, R′ = C₅H₉ (2); R = 4-C₆H₄OMe, R′ = (1S,5R,2S)-(-)-menthyl (3); R = Fc, R′ = (CH₂)₂O(CH₂)₂OMe (4)) have been determined. In all cases only the trans isomer is obtained, consistent with solid state ³¹P NMR data obtained for the bulk powder of 3. Crystallographic data for 2 (213 K): orthorhombic, Ibam, a = 12.434(5) A, b = 19.029(9) A, c = 11.760(4) A, V = 2782(2) A³, Z = 4. Data for 3 (293 K): monoclinic, P2₁, a = 7.288(2) A, b = 12.676(3) A, c = 21.826(4) A, β = 92.04(3)°, V = 92.04(3)°, V = 2015.0(7) A³, Z = 2. Data for 4 (213 K): monoclinic, P2₁/n, a = 11.8564(7) A, b = 22.483(1) A, c = 27.840(2) A, β = 91.121(1)° V = 7419.8(8) A³, Z = 8. Moreover, 1a-c react with [Au₂(dppm)Cl₂] to form new heterobridged trithiophosphonate complexes of the type [Au₂(dppm)(S₂P(S)R)] (R = Fc (12)). The luminescence properties of several structurally characterized complexes have been investigated. Each of the title compounds luminesces at 77 K. The results indicate that the nature of Au...Au interactions in the solid state has a profound influence on the optical properties of these complexes.

Full text of DOI:10.1021/ic0201856

Inorg. Chem. 2002, 41, 4579−4589
Dinuclear Gold(I) Dithiophosphonate Complexes: Synthesis,
Luminescent Properties, and X-ray Crystal Structures of [AuS PR(OR′)]2
2
(R ) Ph, R′ ) C H ; R ) 4-C H OMe, R′ ) (1S,5R,2S)-(−)-Menthyl; R )
5 9
6 4
Fc, R′ ) (CH ) O(CH ) OMe)
2 2
2 2
Werner E. van Zyl,† Jose´ M. Lo´pez-de-Luzuriaga,‡ Ahmed A. Mohamed,† Richard J. Staples,§ and
,†
John P. Fackler, Jr.*
Department of Chemistry and Laboratory for Molecular Structure and Bonding,
Texas A&M UniVersity, P.O. Box 30012, College Station, Texas 77842-3012,
Departamento de Qu´ımica, Grupo de S´ıntesis Qu´ımica de La Rioja, UniVersidad de La Rioja,
Madre de Dios 51, E-26004 Logron˜o, Spain, and Department of Chemistry and Chemical Biology,
HarVard UniVersity, Cambridge, Massachusetts 02138
Received March 7, 2002
2,4-Diaryl- and 2,4-diferrocenyl-1,3-dithiadiphosphetane disulfide dimers (RP(S)S)2 (R ) Ph (1a), 4-C H OMe (1b),
6
4
FeC H (Fc) (1c)) react with a variety of alcohols, silanols, and trialkylsilyl alcohols to form new dithiophosphonic
10
9
acids in a facile manner. Their corresponding salts react with chlorogold(I) complexes in THF to produce dinuclear
gold(I) dithiophosphonate complexes of the type [AuS PR(OR′)]2 in satisfactory yield. The asymmetrical nature of
2
1
the ligands allows for the gold complexes to form two isomers (cis and trans) as verified by solution H and
31P{1H} NMR studies. The X-ray crystal structures of [AuS PR(OR′)]2 (R ) Ph, R′ ) C H (2); R ) 4-C H OMe,
2
5
9
6 4
R′ ) (1S,5R,2S)-(−)-menthyl (3); R ) Fc, R′ ) (CH ) O(CH ) OMe (4)) have been determined. In all cases only
2 2
2 2
the trans isomer is obtained, consistent with solid state 31P NMR data obtained for the bulk powder of 3.
Crystallographic data for 2 (213 K): orthorhombic, Ibam, a ) 12.434(5) Å, b ) 19.029(9) Å, c ) 11.760(4) Å, V
3
) 2782(2) Å , Z ) 4. Data for 3 (293 K): monoclinic, P21, a ) 7.288(2) Å, b ) 12.676(3) Å, c ) 21.826(4) A,
3
â ) 92.04(3)°, V ) 2015.0(7) Å , Z ) 2. Data for 4 (213 K): monoclinic, P21/n, a ) 11.8564(7) Å, b ) 22.483(1)
3
Å, c ) 27.840(2) Å, â ) 91.121(1)°, V ) 7419.8(8) Å , Z ) 8. Moreover, 1a−c react with [Au2(dppm)Cl2] to form
new heterobridged trithiophosphonate complexes of the type [Au2(dppm)(S P(S)R)] (R ) Fc (12)). The luminescence
2
properties of several structurally characterized complexes have been investigated. Each of the title compounds
luminesces at 77 K. The results indicate that the nature of Au‚‚‚Au interactions in the solid state has a profound
influence on the optical properties of these complexes.
Introduction
utilizing the related dithiophosphonate ligand, [S2PR(OR′)]-,
in metal complex formation has not been abundant. This is
exemplified by the fact that few compounds that contain this
ligand have been structurally characterized.8 This is surprising
since phosphorus-1,1-dithiolates as a general class of com-
pounds have been important as antiwear and antioxidant
additives in the oil and petroleum industry,9 as agricultural
insecticide derivatives,10 and as metal ore extraction re-
agents.11 As part of our ongoing studies of gold-sulfur
compounds, we report here the chemistry derived from the
reaction between these monoanionic, potentially bidentate
sulfur ligands and gold(I), yielding dinuclear gold(I) dithio-
In recent years, due to the potential application in
electrochemistry,1 microelectronics,2 catalysis,3 ion ex-
change,4 sensors,5 photophysics,6 and materials,7 metal
phosphonate chemistry has flourished. In contrast, research
* To whom correspondence should be addressed. E-mail:
fackler@mail.chem.tamu.edu.
† Texas A&M University.
‡ Universidad de La Rioja.
§ Harvard University.
(1) Murray, R. W. Acc. Chem. Res. 1980, 13, 135.
(2) Roberts, G. G. AdV. Phys. 1985, 34, 475.
(3) Cheng, S.; Peng, G.-Z.; Clearfield, A. Ind. Eng. Chem. Prod. Res.
DeV. 1984, 23, 2.
10.1021/ic0201856 CCC: $22.00 © 2002 American Chemical Society
Published on Web 08/02/2002
Inorganic Chemistry, Vol. 41, No. 17, 2002 4579

van Zyl et al.
phosphonate complexes. A general synthetic route for
dithiophosphonate salts has been described.12
Experimental Section
Caution! Tetrahydrothiophene has a foul smell and may cause
conjunctivitis. Several organophosphorus compounds described
herein are highly malodorous, and all are highly toxic. Manipula-
tions of these materials should be performed in a well-ventilated
fume hood. Hydrogen sulfide excess was destroyed by bubbling
the gas through a dilute NaClO (bleach) solution.
We found that dithiophosphonates form an interesting
modification of the known dithiophosphate chemistry. Al-
though the ligands are not commercially available, a variety
of new ligands is obtained in a facile manner from a common
precursor. The asymmetrical nature of the ligand allows for
two isomers (cis and trans) to be formed, a feature not
possible for the symmetrical dithiophosphinates, [S2PR2]-,13
or dithiophosphates, [S2P(OR)2]-. The ligand also facilitates
General Methods. Unless otherwise noted, all reactions and
manipulations were carried out under an inert atmosphere with a
positive nitrogen gas flow using standard Schlenk techniques.15
Diethyl ether, THF, benzene, and hexane were distilled under
dinitrogen over a Na/K alloy with the formation of a benzophenone
ketyl indicator. Dichloromethane was distilled over P4O10. Methanol
and ethanol were distilled from Mg turnings.16 The following
chemicals were purchased from Aldrich Chemical Co.: tetrahy-
drothiophene; tetraphosphorus decasulfide; ferrocene; bis(diphe-
nylphosphino)methane; cyclopentanol; cyclohexanol; allyl alcohol;
(1R,2S,5R)-(-)-menthol; 2-(2-methoxyethoxy)ethanol; 1-adaman-
tanol; trimethylsilyl alcohol; triphenylsilanol; 2,4,6 trimethylphenol.
Phenyldichlorophosphine was obtained from Strem Chemicals.
Hydrogen sulfide and ammonia gases were obtained from Matheson
Gas Products Co. The following compounds were prepared by
literature procedures: [PhP(S)S]2;17 [4-C6H4OMeP(S)S]2 (also
commercially available);18 [FcP(S)S]2.19 All chemicals were used
as received.
Instrumentation. Melting points were measured on a Unimelt
capillary melting point apparatus and are uncorrected. Positive fast
atom bombardment (+FAB/DIP) (DIP ) direct insertion probe)
mass spectrometry20 was carried out on a VG Analytical (Manches-
ter, U.K.) 70S high-resolution, double-focusing mass spectrometer.
Samples for analyses were prepared by dissolving the solid
compound in an appropriate solvent with a nitrobenzyl alcohol
(NBA) matrix added and placed on the DIP tip. The probe was
then inserted into the instrument through a vacuum interlock. The
sample was bombarded with 8 keV xenon primary particles from
an Ion Tech FAB gun operating at an emission current of 2 mA.
Data were collected by a VG11-250J data system. 1H NMR spectra
were obtained on a Varian XL-200 spectrometer or a Varian
the formation of an Au-S bond that is functionally well
suited for photoluminescence studies. Indeed, these com-
plexes possess a rich but complex photophysics. The results
described here indicate that dinuclear gold(I) complexes with
S-P-S bridging ligands have luminescent properties that
are influenced strongly by the presence or absence of
intermolecular Au‚‚‚Au interactions. This observation ap-
pears to provide a means to determine whether intermolecular
Au‚‚‚Au interactions are present in the bulk sample inde-
pendent of structural studies. Preliminary results related to
this study have been reported previously.14
(4) (a) Clearfield, A. In New DeVelopments in Ion Exchange Materials;
Abe, M., Kataoka, T., Suzuki, T.; Eds.; Kodansha, Ltd.: Tokyo, 1991.
(b) Wang, J. D.; Clearfield, A.; Peng. G.-Z. Mater. Chem. Phys. 1993,
35, 208.
(5) Alberti, G.; Casciola, M.; Palombari, R. Solid State Ionics 1993, 61,
241.
(6) (a) Vermeulen, L. A.; Thompson, M. E. Nature 1992, 358, 656. (b)
Vermeulen, L. A.; Snover, J. L.; Sapochak, L. S.; Thompson, M. E.
J. Am. Chem. Soc. 1993, 115, 11767.
(7) Cao, G.; Hong, H.; Mallouk, T. E. Acc. Chem. Res. 1992, 25, 420.
(8) (a) Fackler, J. P., Jr.; Thompson, L. D. Inorg. Chim. Acta 1981, 45.
(b) Murray, H. H.; Garzo´n, G.; Raptis, R. G.; Mazany, A. M.; Porter,
L. C.; Fackler, J. P., Jr. Inorg. Chem. 1988, 27, 836. (c) Bone, S. P.;
Constantinescu, R.; Haiduc, I. J. Chem. Res. 1979, S69. (d) Haiduc,
I.; Sowerby, D. B.; Lu, S. F. Polyhedron 1995, 14, 3389-3472. (e)
Fackler, J. P., Jr.; van Zyl, W. E.; Prihoda, B. A. In Gold: Progress
in Chemistry, Biochemistry and Technology; Schmidbaur, H., Ed.; John
Wiley & Sons: West Sussex, England, 1999; pp 795-840.
(9) (a) Klaman, D., Ed. Lubricants and Related Products; Verlag
Chemie: Weinheim, Germany, 1984. (b) Colclough T. Ind. Eng. Chem.
1987, 26, 1888. (c) Dumdum, J. M.; Mendelson, L. T.; Pilling, R. L.
U.S. Pat. 4,908,142; Chem. Abstr. 1990, 112, 201925k.
(10) Patnaik, P. A ComprehensiVe Guide to the Hazardous Properties of
Chemical Substances; Van Nostrand Reinhold: New York, 1992;
Chapter 40 and references therein.
1
UnityPlus-300 spectrometer. H NMR data are expressed in parts
per million (ppm) downfield shift referenced internally to the
residual proton impurity in the deuterated solvent and are reported
as chemical shift position (δH), multiplicity (s ) singlet, d )
doublet, t ) triplet, q ) quartet, and m ) multiplet), relative integral
intensity, and assignment. 31P{1H} NMR spectra were obtained on
a Varian XL 200 MHz broad-band spectrometer operating at 81
MHz or on a Varian UnityPlus-300 spectrometer operating at 121
MHz with chemical shifts reported relative to a 85% H3PO4 in D2O
external standard solution. The solid state 31P NMR spectrum of 3
was obtained using a Bruker MSL-300 spectrometer operating at
ambient temperature with a 7 mm magic angle spinning (MAS)
probe. Data were acquired using a 30° pulse for excitation with a
proton decoupled field of 62.5 kHz during acquisition. The sample
(15) Shriver D. F.; Drezdzon, M. A. The Manipulation of Air-SensitiVe
Compounds, 2nd ed.; John Wiley & Sons: New York, 1986.
(16) Perrin, D. D.; Armarego, W. L. F. Purification of Laboratory
Chemicals; Pergamon Press: New York, 1988.
(11) Miyake, Y.; Harada, M. ReV. Inorg. Chem. 1989, 10, 145.
(12) van Zyl, W. E.; Fackler, J. P., Jr. Phosphorus, Sulfur Silicon 2000,
167, 117-132.
(17) Chupp, J. P.; Newallis, P. E. J. Org. Chem. 1962, 3832.
(18) Pederson, B. S.; Scheibye, S.; Nilsson, N. H.; Lawesson, S. O. Bull.
Soc. Chim. Belg. 1978, 223.
(19) Foreman, M. R. St. J.; Slawin, A. M. Z.; Woollins, J. D. J. Chem.
Soc., Dalton Trans. 1996, 3653.
(20) (a) Barber, M.; Bordoli, R. S.; Elliot, G. J.; Sedgwick, R. D.; Tyler,
A. N. Anal. Chem. 1982, 54, 645A. (b) Aberth, W.; Straub, K. M.;
Burlingame, A. L. Anal. Chem. 1982, 54, 2029.
(13) van Zyl, W. E.; Lopez-de-Luzuriaga, J. M.; Fackler, J. P., Jr.; Staples,
R. J. Can J. Chem. 2001, 79, 896-903.
(14) (a) van Zyl, W. E.; Staples, R. J.; Fackler, J. P., Jr. Inorg. Chem.
Commun. 1998, 1, 51. (b) van Zyl, W. E.; Lopez-de-Luzuriaga, J.
M.; Fackler, J. P., Jr. J. Mol. Struct. 2000, 516, 99-106.
4580 Inorganic Chemistry, Vol. 41, No. 17, 2002

Dinuclear Gold(I) Dithiophosphonate Complexes
Table 1. Selected Bond Lengths (Å) and Angles (deg) for
[AuS2PPh(OC5H9)]2, 2
was spinning at 4083 Hz about the magic angle. Using a recycle
delay of 30 s, 16 scans were acquired for signal averaging.
Au(1)-Au(1B)
Au(1)-Au(1A)
Au(1)-S(1E)
Au(1)-S(1)
2.9261(11)
2.9538(11)
2.300(2)
S(1)-P(1)
P(1)-O(1)
P(1)-C(4)
O(1)-C(1)
2.002(2)
1.553(7)
1.811(10)
1.433(13)
Excitation and Emission Spectra. Excitation and emission
spectra were obtained using a SLM/AMINCO model 8100 spec-
trofluorometer using a xenon lamp. The radiation was filtered
through a 0.10 M KNO2 solution to reduce the amount of scattered
light. Low-temperature measurements were made in a cryogenic
device of local design. Collodion was used to attach the powder
samples to the holder. The collodion was scanned for baseline
subtraction.
2.300(2)
S(1E)-Au(1)-S(1)
169.09(7) P(1)-S(1)-Au(1) 104.38(9)
S(1E)-Au(1)-Au(1B)
S(1)-Au(1)-Au(1B)
S(1E)-Au(1)-Au(1A)
S(1)-Au(1)-Au(1A)
84.55(4) O(1)-P(1)-C(4)
84.55(4) O(1)-P(1)-S(1)
95.45(4) C(4)-P(1)-S(1)
101.0(4)
112.91(14)
106.4(2)
95.45(4) S(1)-P(1)-S(1B) 115.72 (13)
Au(1A)-Au(1)-Au(1B) 180.0
X-ray Crystallography. Crystals used in the diffraction mea-
surements at room temperature were mounted on the tip of a quartz
fiber with fast adhesive glue. Single-crystal diffraction analyses were
carried out on 3 using an automated Nicolet R3 diffractometer
utilizing the Wyckoff scanning technique with graphite-monochro-
mated Mo KR (λ ) 0.710 73 Å) radiation. The unit cell was
determined using search, center, index, and least-squares refine
routines. The Laue class and lattice dimensions were verified by
axial oscillation photography. The intensity data were corrected for
absorption, Lorentz, and polarization effects. An empirical absorp-
tion correction based on ψ scans of five strong reflections spanning
a range of 2θ values. All data processing were performed by a
Data General Eclipse S140 minicomputer using a SHELXTL
crystallographic computational package (version 5.1) and Siemens
SHELXTL PLUS (Micro Vax II).21 The systematic absences were
consistent with the space group assigned. The crystal structures
were solved using direct methods to determine the gold atom
positions, while other atoms were located on difference Fourier
maps. Structure refinements were carried out using SHELX-93. The
position of the hydrogen atoms were calculated by assuming
idealized geometries, C-H ) 0.93 Å. Crystal data for complexes
2 and 4 were collected on a Siemens (Bruker) SMART CCD
(charge-coupled device) based diffractometer equipped with a LT-2
low-temperature apparatus operating at 213 K. A suitable crystal
was chosen and mounted on a glass fiber using grease. Data were
measured using omega scans of 0.3°/frame for 30 s, such that a
hemisphere was collected. A total of 1271 frames were collected
with a final resolution of 0.75 Å. The first 50 frames were collected
at the end of the data collection to monitor for decay. Cell
parameters were retrieved using SMART software22 and refined
using SAINT on all observed reflections. Data reduction was
performed using SAINT software23 which corrects for Lorentz
polarization and decay. Absorption corrections were applied
(semiempirical from ψ scans) using SADABS24 supplied by G.
Sheldrick. The structures were solved by direct methods using the
SHELXS-9025 and SHELXS-97 programs and refined by least-
squares methods on F2.26 All non-hydrogen atoms were refined
anisotropically. The crystal used for the diffraction study showed
no decomposition during data collection. Crystallographic data and
results are listed in Table 4. Atomic coordinates and thermal
parameters for all structures are supplied as Supporting Information.
Table 2. Selected Bond Lengths (Å) and Angles (deg) for
[AuS2P(4-C6H4OMe)(O-menthyl)]2, 3
Au(1)-S(1A)
Au(1)-S(2A)
Au(1)-Au(2)
Au(2)-S(2)
Au(2)-S(1)
2.297(6)
2.303(6)
3.0432(13)
2.288(6)
2.295(6)
S(1)-P(1)
S(2)-P(2)
P(2)-O(2)
P(2)-C(21)
O(1)-C(1)
2.012(8)
2.000(8)
1.595(14)
1.83(2)
1.51(2)
S(1A)-Au(1)-S(2A) 167.8(2)
S(2)-Au(2)-Au(1)
88.91(14)
97.4(3)
109.2(8)
S(1A)-Au(1)-Au(2)
S(2A)-Au(1)-Au(2)
S(2)-Au(2)-S(1)
94.72(14) P(1)-S(1)-Au(2)
97.44(14) O(2)-P(2)-C(21)
176.4(2)
Table 3. Selected Bond Lengths (Å) and Angles (deg) for
[AuS2PFc(O(CH2)2O(CH2)2OMe)]2, 4
Au(1)-S(1)
Au(1)-S(3)
Au(2)-Au(3)
Au(1)-Au(2)
Au(3)-Au(4)
Au(2)-S(4)
Au(2)-S(2)
2.301(4)
2.318(4)
3.0396(10)
3.2355(9)
3.0791(9)
2.307(4)
2.312(4)
S(1)-P(1)
2.021(6)
P(1)-O(1)
P(1)-C(21)
O(1)-C(1)
Fe(2)-C(27)
Fe(2)-C(30)
1.611(10)
1.770(15)
1.450(16)
1.985(16)
2.047(17)
S(1)-Au(1)-S(3)
S(1)-Au(1)-Au(2)
176.09(16) S(3)-P(2)-S(4)
93.17(11) S(7)-P(4)-S(8)
118.00(3)
118.04(2)
83.57(11)
78.86(11)
Au(1)-Au(2)-Au(3) 171.19(3)
Au(2)-Au(3)-Au(4) 138.16(3)
S(2)-Au(2)‚‚‚Au(3)
Au(2)‚‚‚Au(3)-S(7)
Materials. The preparation of the ligand [NH4][S2PPh(OCH2-
CHdCH2)] is described below and is representative for preparing
all the dithiophosphonic salt derivatives from 1a,b precursors.12
It should be noted that analytical results were obtained12 for the
ammonium salt precursors to the gold products reported in this
study.
[NH4][S2PPh(OCH2CHdCH2)]. A 25 mL Schlenk tube was
charged with [PhP(S)S]2, 1a (2.08 g, 6.01 mmol), and placed under
vacuum for 30 min. The solid was heated to ∼70 °C, and allyl
alcohol (0.70 g, 12.02 mmol) was added and allowed to react. The
temperature was maintained at 70-75 °C until dissolution of all
the solids was observed and then stirred for an additional 20 min.
The acids are typically volatile, viscous yellow colored oils. No
attempt was made to isolate the acids. A small amount of benzene
was added to the acid. The solution was placed in an ice bath for
10 min. Anhydrous ammonia gas was slowly bubbled through the
solution with stirring. A colorless precipitate was formed im-
mediately. In cases where the salt was sparingly soluble in benzene,
precipitation was induced by evaporation of the solvent under
reduced pressure. The material was filtered under aerobic conditions
on a glass frit and washed with three 5 mL portions of cold hexane.
The salts were dried in air yielding a free flowing, odorless, and
colorless powder. In cases where the alcohol is a solid, it is dissolved
in a minimum amount of benzene prior to addition. A slight excess
of alcohol and/or a slightly elevated temperature (e85 °C) did not
negatively reduce product purity or yield. Yield: 1.30 g (88%).
Mp: 130 °C. The salts slowly hydrolyze in air and moisture but
can be safely stored in a vacuum desiccator.
(21) Sheldrick, G. M. SHELXTL-Plus User’s Manual; Nicolet XRD
Corp.: Madison, WI, 1988.
(22) SMART V 4.043 Software for the CCD Detector System; Bruker
Analytical X-ray Systems: Madison, WI, 1995.
(23) SAINT V 4.035 Software for the CCD Detector System; Bruker
Analytical X-ray Systems: Madison, WI, 1995.
(24) Blessing, R. H. SADABS. Program for absorption corrections using
Siemens CCD based on the method of Robert Blessing. Acta
Crystallogr. 1995, A51, 33.
(25) Sheldrick, G. M. SHELXS-90, Program for the Solution of Crystal
Structure; University of Go¨ttingen: Go¨ttingen, Germany, 1990.
(26) Sheldrick, G. M. SHELXL-97, Program for the Refinement of Crystal
Structure; University of Go¨ttingen: Go¨ttingen, Germany, 1997.
Inorganic Chemistry, Vol. 41, No. 17, 2002 4581

van Zyl et al.
Table 4. Crystal Data and Structure Refinement for Complexes 2-4
2
3
4
empirical formula
fw
C22H28Au2O2P2S4
908.56
C34H52Au2O4P2S4
1108.87
C30H40Au2O6P2S4Fe2
1192.43
temp (K)
213(2)
293(2)
213(2)
wavelength (Å)
cryst system
space group
0.710 73
0.710 73
0.710 73
orthorhombic
monoclinic
monoclinic
Ibam
P21
P21/n
unit cell dimens (Å, deg)
a ) 12.434(5), R ) 90
b ) 19.029(9), â ) 90
c ) 11.760(4), γ ) 90
2782(2), 4
a ) 7.288(2), R ) 90
b ) 12.676(3), â ) 92.04(3)
c ) 21.826(4), γ ) 90
2015.0(7), 2
a ) 11.8564(7), R ) 90
b ) 22.483(1), â ) 91.121(3)
c ) 27.840(2), γ ) 90
7419.8(8), 8
V (Å3), Z
D(calcd) (g/cm3)
2.169
1.828
2.135
abs coeff (mm-1
F(000)
cryst size (mm)
)
10.967
7.593
9.002
1712
1080
4576
0.15 × 0.10 × 0.05
0.20 × 0.20 × 0.15
0.05 × 0.10 × 0.30
θ range for data collcn (deg)
limiting indices
1.96-27.62
2.46-22.62
1.46-22.50
-15 e h e15, -24 e k e 21,
-12 e l e 14
0 e h e 7, 0 e k e 13,
-23 e l e 23
-12 e h e 10, -24 e k e 24,
-29 e l e 29
reflcns collcd
6374
2869
44 299
indpdt reflcns
1606 [R(int) ) 0.0419]
semiempirical from ψ scans
full-matrix least squares on F2
1606/0/81
2634 [R(int) ) 0.0389]
semiempirical from ψ scans
full-matrix least squares on F2
2634/97/406
9701 [R(int) ) 0.1592]
semiempirical from ψ scans
full-matrix least squares on F2
9701/14/481
abs corr
refinement method
data/restraints/params
goodness-of-fit on F2
final R indices [I > 2σ(I)]
R indices (all data)
largest diff peak and hole (e‚Å-3
1.151
1.191
1.030
R1 ) 0.0319, wR2 ) 0.0898
R1 ) 0.0390, wR2 ) 0.0952
1.099 and -0.894
R1 ) 0.0410, wR2 ) 0.0975
R1 ) 0.0458, wR2 ) 0.1015
1.058 and -0.800
R1 ) 0.0515, wR2 ) 0.0738
R1 ) 0.1300, wR2 ) 0.0838
1.420 and -1.224
)
The gold(I) complexes 3-11 are formed in a fashion similar to
the synthesis described for 2 given here.
of an initially dilute CH2Cl2 solution. Colorless crystals suitable
for X-ray studies were obtained from the slow evaporation of an
initially dilute CH2Cl2 solution.
[AuS2PPh(OC5H9)]2, 2. A 50 mL Schlenk tube was charged
with [NH4][S2PPh(OC5H9)] (88 mg, 0.32 mmol) and placed under
vacuum for 30 min. The salt was dissolved in 20 mL of THF, and
upon dissolution Au(THT)Cl (THT ) tetrahydrothiophene)27 (100
mg, 0.31 mmol) was added in one portion at room temperature.
An immediate white precipitate (NH4Cl) was observed. The mixture
was stirred for 40 min followed by removal of the solvent in vacuo.
The complex was extracted with CH2Cl2 (25 mL) and filtered
through anhydrous MgSO4 to remove NH4Cl. The filtrate was
evaporated under reduced pressure, which gave a pale yellow
powder. The crude material was washed with three 10 mL portions
of ether and dried under vacuum (10-2 Torr) for 1 h. Yield: 70%.
Mp: 186 °C (dec, green to brown). +FAB/DIP MS (NBA/CH2-
Cl2, m/z): 909 ([M + 1]+). 1H NMR data for cis and trans isomers
(chloroform-d, 300 MHz, 20 °C, δ): 8.12-8.02 (m, 4H, Ph), 7.54-
7.39 (m, 6H, Ph), 1.95-1.45 (m, 18H, C5H9). 31P{1H} NMR data
(chloroform-d, 300 MHz, 20 °C, δ): 102.25 (s), 99.32 (s). Green
crystals suitable for X-ray studies were obtained from the slow
diffusion of hexane into a concentrated CH2Cl2 solution. The
complex is soluble in chlorinated solvents.
[AuS2P(4-C6H4OCH3)(O-menthyl)]2, 3. Yield: 64%. Mp: 200
°C. +FAB/DIP MS (NBA/CHCl3, m/z): 1109 ([M + 1]+). 1H NMR
data for cis and trans isomers (chloroform-d, 300 MHz, 20 °C, δ):
8.18-7.90 (m, 2H, Ph), 7.00-6.85 (m, 2H, Ph), 3.87 (s-br, 3H,
OCH3), 2.52-2.08 (m, 2H, CH), 1.72-1.58 (m, 2H, CH), 1.48-
1.28 (m, 3H, CH), 1.20-0.98 (m, 3H, CH), 0.96-0.75 (m, 9H,
CH3). 31P{1H} NMR data (chloroform-d, 300 MHz, 20 °C, δ):
101.65 (s), 99.66 (s). 31P{1H} NMR data (chloroform-d, µ/D )
1.04 (g), 300 MHz, 20 °C, δ): 101.65 (s), 99.66 (s), with relative
intensities of 0.57 and 1.00, respectively. Upon dissolution of the
compound in acetonitrile (dipole moment, µ/D (g) ) 3.92), the 31P-
{1H} NMR spectrum at 20 °C produces resonances at 103.97 and
102.51 with relative intensities of 0.82 and 1.00. In DMSO, µ/D
(g) ) 3.96, and peaks at 103.65 and 102.18 are observed with
relative intensities of 0.77 and 1.00, respectively. Colorless crystals
suitable for X-ray studies were obtained from the slow evaporation
[AuS2P(Fc)(O(CH2)2O(CH2)2OCH3]2, 4. Yield: 58%. Mp: 106
1
°C. +FAB/DIP MS (NBA/CHCl3, m/z): 1192 ([M]+). H NMR
data for cis and trans isomers (chloroform-d, 300 MHz, 20 °C, δ):
4.69 (m, 2H, C5H4), 4.50 (m, 2H, C5H4), 4.38 (s, 5H, Cp), 3.95-
3.52 (m, 8H, O(CH2)2O(CH2)2). 31P{1H} NMR data (chloroform-
d, 300 MHz, 20 °C, δ): 110.89 (s), 106.94 (s). Orange needles
suitable for X-ray crystallographic study were obtained in a manner
similar to that for 2.
[AuS2P(4-C6H4OCH3)(OSiPh3)]2, 5. Yield: 77%. Mp: 202 °C
(dec). +FAB/DIP MS (NBA/CH2Cl2, m/z): 1349 ([M + 1]+), 1271
([M - Ph]+). 1H NMR data for the cis and trans isomers
(chloroform-d, 300 MHz, 20 °C, δ): 7.94-7.84 (m, 4H, HCCO),
7.74-7.62 (m, 12H, SiPh3), 7.48-7.32 (m, 18H, SiPh3), 6.76-
6.68 (m, 4H, HCCP), 3.81 (s, 6H, OCH3), 3.80 (s, 6H, OCH3).
31P{1H} NMR data (chloroform-d, 300 MHz, 20 °C, δ): 93.01 (s),
90.28 (s). Colorless block crystals were obtained from a CH2Cl2
solution layered with hexane within 24 h.
[AuS2PPh(OEt)]2, 6. Yield: 185 mg, colorless (72%). Mp: 171
°C. +FAB/DIP MS(NBA/CHCl3, m/z): 829 ([M + 1]+), 631 ([M
1
- Au]+). H NMR data for cis and trans isomers (chloroform-d,
300 MHz, 20 °C, δ): 8.13-8.02 (m, 4H, Ph), 7.62-7.45 (m, 6H,
Ph), 4.47 (q, 4H, OCH2), 4.42 (q, 4H, OCH2), 1.47 (t, 6H, CH3),
1.42 (t, 6H, CH3). 31P{1H} NMR data (chloroform-d, 300 MHz,
20 °C, δ): 104.59 (s), 101.86 (s).
[AuS2PPh(OCH2CHdCH2)]2, 7. Yield: 82%. Mp: 144 °C.
+FAB/DIP MS (NBA/CHCl3, m/z): 853 ([M + 1]+), 655 ([M -
Au]+), 427 ([M - AuL]+). 1H NMR data for cis and trans isomers
(chloroform-d, 300 MHz, 20 °C, δ): 8.11-8.01 (m, 4H, Ph), 7.61-
7.44 (m, 6H, Ph), 6.10-5.90 (m-br, 2H, CHdCH2), 5.46 (d, 4H,
OCH2), 5.30 (d, 4H, OCH2), 4.88 (s br, 4H, CdCH2). 31P{1H} NMR
data (δ): chloroform-d, 200 MHz, 19 °C, 106.18 (s), 103.37 (s);
dichloromethane-d2, 200 MHz, 19 °C, 106.67 (s), 104.12 (s);
deuterium oxide, 300 MHz, 22 °C, 106.72 (s), 104.21 (s). The pale
yellow complex is soluble in chlorinated solvents.
[AuS2PPh(OC6H11)]2, 8. Yield: 76%. Mp: 152 °C. +FAB/DIP
MS (NBA/Na/CH2Cl2, m/z): 956 ([M + Na]+), 935 ([M + 1]+).
(27) Uso´n, R.; Laguna, A.; Laguna, M. Inorg. Synth. 1986, 26, 85.
4582 Inorganic Chemistry, Vol. 41, No. 17, 2002

Dinuclear Gold(I) Dithiophosphonate Complexes
1H NMR data for cis and trans isomers (chloroform-d, 300 MHz,
20 °C, δ): 8.22-8.00 (m, 4H, Ph), 7.60-7.40 (m, 6H, Ph), 1.80-
1.20 (m, 22H, OC6H11). 31P{1H} NMR data (chloroform-d, 200
MHz, 20 °C, δ): 102.29 (s), 99.56 (s). The material is colorless
and soluble in chlorinated solvents.
OMe, 1b). The dimer 1b, known as Lawesson’s reagent, can
be readily prepared from P4S10 and anisole.18 Lawesson’s
reagent is routinely used as a thionation reagent,29 but its
utility as a potential dithiophosphonic complexing agent has
not been previously exploited. Woollins and co-workers
reported the electron-rich ferrocenyl dimer [FcP(S)S]2 (1c)
wherein Fc is the organometallic moiety.19 We have prepared
dithiophosphonic acid derivatives with each of the three
dimers 1a-c and alcohols and extended the chemistry further
by reaction with silanols and trialkylsilanols. Once isolated,
these dimers are microcrystalline solids that may be stored
indefinitely in an inert atmosphere. Unsaturated (allyl),
sterically demanding (adamantyl, SiPh3, mesityl), strained
(cyclopentyl), and chiral/cyclic (menthyl) are among the
variety of alcohol types that have been effectively utilized
in this respect. Halogen-containing and tertiary alcohols give
unsatisfactory results. The former indeed forms the acid, but
subsequent reaction with NH3 presumably dehydrohaloge-
nates the acid instead of simply removing the proton from
the acidic S-H moiety. The latter readily eliminates olefinic
species30 (Chugaev reaction) at elevated temperatures. For
example, ButOH eliminates isobutylene.
The acids were readily transformed to the corresponding
ammonium salts through reaction with dry NH3 bubbled
through a concentrated benzene solution at 0 °C. Formation
of the title compounds in a typical reaction was accomplished
by dissolving the dithiophosphonate salt in THF, followed
by addition of 1 equiv of Au(THT)Cl (molar ratio 1:1) at
ambient temperature. The compounds are all partly soluble
to very soluble (although prone to decomposition from within
a few hours to several days) in chlorinated solvents. The
reaction between the dithiadiphosphetanes 1a-c and [Au2-
(dppm)Cl2] (molar ratio 1:1) in THF after 18 h yields a
heterobridged dinuclear gold(I) trithiophosphonate complex
of the type which 12 (R ) Fc) is typical,14a through
asymmetric cleavage of the dimer31 shown as follows: The
[AuS2PPh(O-adamantyl)]2, 9. Yield: 77%, colorless. Mp: 200
°C (dec, starts to foam from ca. 150 °C). +FAB/DIP MS (NBA/
1
CHCl3, m/z): 1041 ([M + 1]+). H NMR data for cis and trans
isomers (chloroform-d, 200 MHz, 19.7 °C, δ): 8.30-8.08 (m, 4H,
Ph), 7.58-7.38 (m, 6H, Ph), 2.28-2.03 (m, 9H, adamantyl), 1.62-
1.44 (m, 6H, adamantyl). 31P{1H} NMR data (δ): chloroform-d,
300 MHz, 22 °C, 96.03 (s), 95.62 (s); chloroform-d, 300 MHz, 40
°C, 96.09 (s), 95.68 (s).
[AuS2P(4-C6H4OCH3)(OCH2SiMe3)]2, 10. Yield: 80%, pale
yellow. Mp: 158 °C. +FAB/DIP MS (NBA/EtOAc, m/z): 1005
1
([M + 1]+). H NMR data for cis and trans isomers (chloroform-
d, 200 MHz, 19.7 °C, δ): 8.10-7.88 (m, 4H, Ph), 7.00-6.88 (m,
4H, Ph), 4.00 (d, 4H, OCH2), 3.92 (d, 4H, OCH2), 3.84 (s, 6H,
OCH3), 3.83 (s, 6H, OCH3), 0.15 (s, 18H, Si(CH3)3). 31P{1H} NMR
data (chloroform-d, 200 MHz, 19 °C, δ): 109.99 (s), 106.73 (s).
[AuS2PPh(OC6H2(CH3)3)]2, 11. Yield: 62%, pale yellow. Mp:
214 °C. 1H NMR data for cis and trans isomers (chloroform-d, 300
MHz, 20 °C, δ): 8.26-8.14 (m, 2H, Ph), 7.60-7.40 (m, 3H, Ph),
6.81-6.79 (m, 2H, arom-mesityl), 2.34-2.20 (m, 9H, CH3). 31P-
{1H} NMR data (chloroform-d, 300 MHz, 20 °C, δ): 105.76 (s),
105.12 (s). No FAB MS data collection was attempted. The complex
is soluble in chlorinated solvents.
[Au2(dppm)(S2P(S)Fc)], 12. A 50 mL Schlenk tube was charged
with [FcP(S)S]2 (1.0 mmol), and 10 mL of THF was added. [Au2-
(dppm)Cl2] (1.1 mmol) was added in one portion. The mixture was
stirred for 18 h. The solution became clear after 1 h of stirring and
depending on the concentration of the solution either remains that
way (dilute solution) or yields a yellow precipitate (concentrated
solution) after ∼6 h of stirring. After 18 h, the THF was removed
in vacuo. When the solution became concentrated, ether was added
to induce complete precipitation of the product. The product was
filtered on a frit, washed with cold ether, and air-dried. Yield: 71%.
Mp: ∼180 °C. +FAB/DP MS (NBA/Na/CHCl3, m/z): 905 ([M
-FeC10H9]+), 811 ([M - S2P(FeC10H9)]+). 1H NMR data (dichlo-
romethane-d2, 300 MHz, 20 °C, δ): 7.70-7.59 (m, 8H, Ph), 7.44-
7.28 (m, 12H, Ph), 4.66 (q, 2H, C5H4), 4.47 (q, 2H, C5H4), 4.38 (s,
5H, Cp), 4.25 (t, 2H, PCH2P). A satisfactory 31P{1H} NMR
spectrum could not be obtained due to the poor solubility of the
complex. The product is orange in single crystal form and yellow
in powder form.
Results and Discussion
solvent was removed under vacuum, and precipitation was
induced by addition of ether. Although the reaction requires
considerable reaction time, it is highly efficient and the major
product can be easily isolated. Although Rauchfuss and co-
workers have studied reactions of Lawesson’s reagent, the
mechanism by which the reaction described here proceeds
has not been determined.32
Synthesis. A drawback in metal dithiophosphonate chem-
istry, and perhaps a reason for its paucity in the chemical
literature, is that (unlike the phosphonates) the ligands are
not readily available. It is known that 2,4-diaryl-1,3-
dithiadiphosphetane disulfide dimers, (RP(S)S)2 (R ) Ph,
1a), react with two stoichiometric equiv of alcohol (R′OH)
at elevated temperatures (60-80 °C) to form dithiophos-
phonic acids, HSP(S)R(OR′),28 through symmetric cleavage
of the dimer. However, 1a is formed from the reaction
between PhP(S)Cl2 and H2S gas which is introduced sub-
surface above 210 °C, with the ensuing reaction being very
exothermic. Formation of 1a through this route is thus
cumbersome and hazardous. An alternative less hazardous
route is to form the related dimer [RP(S)S]2 (R ) 4-C6H4-
(28) Newallis, P. E.; Chupp, J. P.; Groenweghe L. C. D. J. Org. Chem.
1962, 27, 3829 and ref 17.
(29) For reviews on Lawesson’s reagent, see: (a) Cava, M. P.; Levinson,
M. I. Tetrahedron 1985, 41, 5061. (b) Cherkasov, R. A.; Kutyrev, G.
A.; Pudovik, A. N. Tetrahedron 1985, 41, 2567. (c) Nizamov, I. S.;
Batyeva, E. S.; Al’fonsov, V. A. Russ. J. Gen. Chem. 1993, 63, 1840.
(30) Fackler, J. P., Jr.; Seidel, Wm. C.; Myron, M. Chem. Commun. 1969,
1133.
(31) (a) Jones, R.; Williams, D. J.; Wood, P. T.; Woollins, J. D. Polyhedron
1987, 539. (b) Wood, P. T.; Woollins, J. D. Transition Met. Chem.
1987, 403.
Inorganic Chemistry, Vol. 41, No. 17, 2002 4583

van Zyl et al.
Table 5. Dinuclear Gold(I)-Sulfur Compounds and Their Solid State Luminescence Spectral Datad
298 K
77 K
complex
excitatn (nm)
emission (nm)
excitatn (nm)
emission (nm)
Au‚‚‚Au (Å)
[AuS2PPh(OC3H5)]2, 7a
400
400
398
392
398
428
443
461
447
467
487
450
400
380
400
395
396
432
319
320
338
327
300
335
351
388
468
445, 491
451, 495
453, 496
453, 494
491, 530
468, 524
417
447
423
421
418
3.10, 3.12
2.96, 3.09
3.10, 3.12f
13 a
[AuS2PPh2]2
[AuS2PPh(OEt)]2, 6a
c
[AuS2P(4-C6H4OMe)(OEt)]2
[AuS2PPh(OC5H9)]2, 2a
2.93, 2.95
3.05, 3.10, 2.91e
3.14
3.04
3.18
[AuS2P(OiPr)2]2
42 a
[AuS2P(4-C6H4OMe)(OSiPh3)]2, 5b
[AuS2P(4-C6H4OMe)(O-menthyl)]2, 3b
[AuS2PEt2]13 b
43 b
[AuS2PMe2]2
3.19
13 c
[AuS2P(4-C6H4Me)2]2
[Au2{S2PPh2}{(CH2)2PMe2}]13 b
[Au2{S2PEt2}{(CH2)2PMe2}]13 c
[NBu4]2[Au2{S2CdC(CN)2]45 b
K2[S2CdC(CN)2]
451
437
495, 527
553
3.10
2.80
a Complexes with intermolecular Au‚‚‚Au (∼3.1 D) interactions. b Complexes with no intermolecular Au‚‚‚Au interactions. c Structure not determined.
For purposes of reading the text, other numbered compounds are the following: [PhP(S)S]2, 1a; [RP(S)S]2 (R ) 4-C6H4OMe), 1b; [AuS2P(Fc)(O(CH2)2O(CH2)2-
OCH3]2, 4; [AuS2PPh(OC6H11)]2, 8; [AuS2PPh(O-adamantyl)]2, 9; [AuS2P(4-C6H4OCH3)(OCH2SiMe3)]2, 10; [AuS2PPh(OC6H2(CH3)3)]2, 11; [Au2(dppm)(S2P(S)Fc)],
12. d Note that Table 4 in ref 14b incorrectly lists compound 2 and [AuS2P(OiPr)2]2 as compounds with no intermolecular interactions in the solid state. This
table also presents emission data for the latter compound somewhat different from the data here taken from van Zyl’s thesis. Data reported previously14b at
77 K with an excitation at 420 nm gave emission maxima at 435 and 610 nm. e The last listing is the intermolecular distance. f To be published.
Structure. The molecular structures of the title complexes
were probed both in solution and in the solid state. Due to
the asymmetry of the ligands, two different isomers (cis and
trans) are possible for each new dinuclear gold(I) complex
formed. Isomers are not observed for the related symmetri-
cal S-P-S bridging ligands such as dithiophosphates,
[S2P(OR)2]-, or dithiophosphinates, [S2PR2]-. The formation
of the isomers, shown above, requires a more extensive
structural analysis, both in solution and in the solid state.
Hence these ligands are not a simple extension of the
chemistry of the dithiophosphates and dithiophosphinates.
In the solid state, complexes 2-5 (see Table 5 for a listing
of all numbered compounds) have been analyzed with single-
crystal X-ray crystallography. Complexes 2-4 are described
Figure 1. Molecular structure of complex 2 showing transannular
in this study as they represent variations of both R and R′
Au‚‚‚Au interactions. Thermal ellipsoids are at the 30% probability level.
Hydrogen atoms are omitted for clarity.
groups. The structure of 5 has been previously reported.14
The complexes all have a neutral eight member metallacycle
present in the solid. Selected bond lengths and angles for 2
are shown in Table 1.
ring in an elongated chair conformation with short transan-
nular Au‚‚‚Au interactions. Complexes 2-4 crystallize with
close intramolecular Au‚‚‚Au interactions, with 2 by far the
shortest intra- [d(Au‚‚‚Au) ) 2.926(1) Å] and intermolecular
[d(Au‚‚‚Au) ) 2.954(1) Å] interaction observed to date for
any dinuclear Au(I) complex with a S-P-S bridging moiety
reported. The molecular structure of 2 is shown in Figure 1,
and its interesting crystal packing is shown in Figure 2.
Complex 3 contains no intermolecular Au‚‚‚Au interac-
tions as shown in its crystal structure, Figure 3. The molecule
crystallizes in the noncentric monoclinic space group P21.
The two S-Au-S linkages in the molecule are not “parallel”
to each other but induce a significant “crossover” effect or
twist as shown in Figure 4. The latter feature is common in
open-ended dinuclear complexes (unstrained) but has not
been previously observed in gold(I) metallacycles with
S-P-S bridging ligands.
In photochemical studies performed on these complexes
(vide infra), it was demonstrated that the room-temperature
luminescence of 2 is quenched in chloroform, presumably
by disruption of the intermolecular aurophilic interactions
It is noted that 3 satisfies an important requirement for
second-order NLO properties to appear with photolumines-
33,34
cent materials,
in that it crystallizes in the noncentric
(32) The expected major byproduct on the basis of stoichiometry is RP-
(S)Cl2. Although we obtained yields of the gold product as high as
72%, we did not look for RP(S)Cl2 in the reaction mixture. Rauchfuss
has discussed Lawesson’s reagent as an excellent electrophile in its
reaction with carbonyls and suggests it is in equilibrium with the
symmetrical cleavage of RP(S)2 species. Hence the mechanism for
this reaction remains obscure. (a) Zank, G. A.; Rauchfuss, T. B.
Organometallics 1984, 3, 1191. (b) Rauchfuss, T. B.; Zank, G. A.
Tetrahedron Lett. 1986, 27, 3445.
space group P21. Noncentric space groups are relatively
(33) (a) Lindsay, G. A.; Singer, K. D. Polymers for Second-Order Nonlinear
Optics; ACS Symposium Series 601; American Chemical Society:
Washington, DC, 1995. (b) Zyss, J. Molecular Nonlinear Optics;
Academic Press: New York, 1994. (c) Prasad, N. P.; Williams, D. J.
Introduction to Nonlinear Optical Effects in Molecules and Polymers;
Wiley: New York, 1991.
4584 Inorganic Chemistry, Vol. 41, No. 17, 2002

Dinuclear Gold(I) Dithiophosphonate Complexes
Figure 2. Crystal packing of complex 2.
Figure 4. View of the crystal structure of complex 3 showing the crossover
of the S-Au-P units.
Figure 5. Molecular structure of complex 4. Thermal ellipsoids are at the
Figure 3. Molecular structure of complex 3. Thermal ellipsoids are at the
30% probability level. Hydrogen atoms are omitted for clarity.
30% probability level. Hydrogen atoms are omitted for clarity.
uncommon for molecular inorganic compounds. In this case,
the chiral O-menthyl containing ligand is assumed to be
responsible for inducing the noncentric structure.
Complex 4 represents the first example of a ferrocenyl
derivative isolated as a dithiophosphonate salt and subse-
quently coordinated to a transition metal center. The ether
functionalities on this particular ligand may be further utilized
as additional coordination sites for other metal ions, although
such studies were not performed here. The molecular
structure of 4 is shown in Figure 5. The cyclopentadienyl
rings on both Fc groups are in the eclipsed conformation,
and both Fc groups are trans to each other. It is also notable
that the intramolecular Au‚‚‚Au distances (3.08, 3.23 Å) are
both different and longer than the intermolecular Au‚‚‚Au
distance (3.04 Å).
Figure 6. Solid state 31P NMR spectrum of complex 3.
Solid State 31P NMR Studies. Since the dinuclear gold-
(I) complexes can form geometric cis and trans isomers, solid
state 31P NMR studies were used to attempt to find any trace
of the cis isomer in the bulk powder. The trans isomer was
exclusively present in single crystals used for X-ray studies.
The solid state 31P NMR powder spectrum of the non-
centric 3 is shown in Figure 6. The spectrum shows singlet
peaks at 95.68 and 94.06 ppm. The spinning sidebands are
clearly distinguished from the relevant peaks by varying the
spin rate of the rotor in two consecutive experiments with
(34) For recent reviews on NLO organometallics, see: (a) Long, N. J.
Angew. Chem., Int. Ed. Engl. 1995, 34, 21. (b) Marder, S. R. In
Inorganic Materials; Bruce, D. W., O’Hare, D., Eds.; John Wiley &
Sons: New York, 1992; pp 115-164.
Inorganic Chemistry, Vol. 41, No. 17, 2002 4585

van Zyl et al.
the same sample. Complex 3 contains discrete, well-separated
dinuclear units in the solid state with negligible magnetic
influence on the P atoms caused by an adjacent molecule.
The structure refined in the monoclinic space group P21 as
one complete molecule in the asymmetric unit. The two
phosphorus atoms in the molecule are not crystallographically
nor magnetically equivalent; that is, the local environment
around each P center is different and reveals a single peak
for each, as is clearly the case. This is not the case in solution
where both the cis and trans species each have magnetically
equivalent P atoms which appear as singlets. On the basis
of these observations. it was concluded that the cis isomer
is not present in the bulk powder sample of 3 but rearrange-
ment in solution rapidly forms it.
energy barrier to isomerization. This observation was further
supported from force field calculations with the aid of CAChe
molecular package, indicating a very low energy difference
(<5 kcal/mol) between the two isomers.35 A specific isomer
thus could not unambiguously be assigned to its correspond-
ing NMR peak in this study. However, the peaks are not of
the same integrated intensity and remain that way within the
time of the experiment time (<40 min). For all complexes,
the downfield peak is always the smaller of the two.
Although solution equilibrium constants could not be
accurately measured, the solution 31P{1H}NMR intensity
changes of 3 in solvents of increasing polarity are consistent
with the conclusion that a rapid equilibrium between the two
isomers exists. The more polar cis isomer appears to be
present at ∼36% in the less polar solvent chloroform-d and
at ∼45% in the more polar acetonitrile. On the basis of this
peak intensity interpretation, the trans isomers appear at 99.7
ppm in chloroform-d and 102.5 ppm in acetonitrile with the
cis isomers at 102 and 104 ppm in these solvents, respec-
tively.
Luminescence Studies. The photophysics of d10 gold(I)
complexes has attracted a considerable attention over the past
few years.36 Of special interest is the relationship between
the observation of emission and the presence of weak
intermolecular bonding interactions between neighboring
gold centers.37 The presence of such weak intermolecular
metal-metal interactions has been implicated also in the
design of other electronic and sensor devices.38 Gold-sulfur
complexes often show weak intermolecular bonding interac-
tions (5-15 kcal/mol) between the closed-shell d10 gold
atoms. Crystal packing effects often compete with the
aurophilicity, however, and can dictate the presence or
absence of aurophilic interactions in the crystalline solids.
For this reason attempts have been made to determine by
spectroscopy the presence of such interactions. The relation-
ship between the observation of emission and the presence
of weak intermolecular aurophilic bonding interactions
between neighboring gold atoms has been addressed previ-
ously,39 but a conclusive answer that applies to gold-sulfur
compounds in general is yet to be obtained although some
progress has been realized.14b In particular, the photolumi-
None of the other compounds showed the presence of the
cis isomer in the solid state 31P NMR spectra.
Solution NMR Studies. Both trans and cis isomers are
formed and detected in solution by NMR spectroscopy. Since
the trans isomer has an inversion center and no dipole
moment, and the cis isomer has no inversion center and a
dipole moment, the phosphorus centers of each isomer are
chemically distinct. The 31P{1H} NMR spectrum for each
of the title compounds thus reveal a singlet peak for each of
the two isomers in the range 90-110 ppm, and the two peaks
1
are usually ∼1-3 ppm apart. As expected, the H NMR
spectrum for each complex shows the same feature as seen
in the 31P{1H} NMR spectra, namely, peaks for each isomer
can be separately observed. For complexes that contain a
P-Ph moiety, the phenyl group is split into two well-resolved
multiplets with overlap of the peaks of the two isomers. In
complexes that contain the C6H4OMe moiety (ligands derived
from Lawesson’s reagent), the OMe protons typically are
found at approximately 3.8 ppm as a characteristic singlet.
For 5, very good resolution resulted in singlets at 3.81 and
3.80 ppm corresponding to the OMe protons observed for
each isomer. For 4 the Cp ring attached to the phosphorus
atom resulted in narrow multiplets that were centered at 4.69
and 4.50 ppm. In complex 12 the Cp protons had better
resolution and similar protons were assigned as quartets (see
Experimental Section). Complex 6 shows two quartets and
1
two triplets in its 31P decoupled H NMR spectrum corre-
sponding to the protons of the P-O-Et moiety. The
spectrum shows each isomer (cis and trans) individually (as
also assigned in the Experimental Section). No three-bond
P-H coupling (300 MHz) was observed across the oxygen
atom in the P-O-C-H type moiety (e.g. 6) for any of the
complexes.
Although all peaks for both isomers can be separately
observed and accounted for in each spectrum, deciding which
set of peaks corresponds to which isomer (cis or trans) was
not readily possible (but see below). Variable-temperature
31P{1H} NMR experiments were conducted but did not
provide additional help. It was hoped that since the bulk
powder was the trans isomer (from the structure and the solid
state 31P NMR for 3), a solution could be formed and cooled
to prevent significant isomerization from occurring. However,
two singlets were observed within seconds after dissolution
at -80 °C, implying that, in solution, there is a Very low
(35) CAChe (Computer Aided Chemistry); CAChe Scientific, Inc., Teknotron-
ix Co.: Beaverton, OR 97077.
(36) (a) Roundhill, D. M. Photochemistry and Photophysics of Metal
Complexes; Plenum Press: New York, 1994. (b) King, C.; Wang, J.-
C.; Khan, M. N. I.; Fackler, J. P., Jr. Inorg. Chem. 1989, 28, 2145.
(c) Che, C. M.; Kwong, H. L.; Poon, C. K.; Yam, V. W. W. J. Chem.
Soc., Dalton Trans. 1990, 3215. (d) Li, D.; Che, C. M.; Kwong, H.
L.; Yam, V. W. W. J. Chem. Soc., Dalton Trans. 1992, 3235. (e)
Jaw, H. R. C.; Savas, M. M.; Rogers, R. D.; Mason, W. R. Inorg.
Chem. 1989, 28, 1028. (f) Hong, X.; Cheung, K. K.; Guo, C. X.; Che,
C. M. J. Chem. Soc., Dalton Trans. 1994, 1867. (f) Forward, J. M.;
Fackler, Jr., J. P.; Assefa, Z. In Optoelectronic Properties of Inorganic
Compounds; Roundhill, D. M., Fackler, J. P., Jr., Eds.; Plenum Press:
New York, 1999; pp 195-229.
(37) Rawashdeh-Omary, M. A.; Omary, M. A.; Patterson, H. H.; Fackler,
J. P., Jr. J. Am. Chem. Soc. 2001, 123, 11237.
(38) (a) Mansour, M. A.; Connick, W. B.; Lachicotte, R. J.; Gysling H. J.;
Eisenberg, R. J. Am. Chem. Soc. 1998, 120, 1329. (b) Miller, J. S.;
Epstein, A. J. Prog. Inorg. Chem. 1976, 20, 1. (c) Daws, C. A.;
Exstrom, C. L.; Sowa, J. R.; Mann, K. R. Chem. Mater. 1997, 9, 363.
(d) Konugi, Y.; Mann, K. R.; Miller, L. L.; Exstrom, C. L. J. Am.
Chem. Soc. 1998, 120, 589.
4586 Inorganic Chemistry, Vol. 41, No. 17, 2002

Dinuclear Gold(I) Dithiophosphonate Complexes
Figure 7. 3-D graphic of the emission spectra at 77 K of complex 2 obtained with excitations between 250 and 400 nm (increments of 5 nm).
nescence of dinuclear gold(I) dithiolate systems shows an
emission that arises from a S-Au charge-transfer transition,
LMCT, with contributions from the metal-metal bond
formed in the excited state, LMMCT. When substituents on
the sulfur ligands do not produce significant electronic
perturbations, the LMMCT emission bands become strongly
influenced by the intermetallic Au‚‚‚Au distances.
and without intermolecular interactions in the solid state.
These features allow direct comparisons to be made to
develop a more coherent understanding of the luminescence
properties of Au-S compounds. Additionally, the S-P-S
bridging ligands used have been chosen not only to see if
one can to predict the presence or absence of intermolecular
Au‚‚‚Au interactions but also to qualitatively estimate the
distances between the gold centers (using bulky substituents
to control the distances) in cases where the emission bands
have similar energies. This comparison is reliable only if
the S-P-S moiety is retained for different R and OR groups
attached to the phosphorus atom.
All complexes studied here luminesce at 77 K in the solid
state. Several complexes (e.g. 2, 6, and 7) luminesce at room
temperature also and show a similar excitation and emission
profile. Table 5 is a summary of the excitation and emission
data measured for the complexes. Note that Table 5 replaces
the Table 4 of ref 14b with better data. The observation that
the emission for certain complexes (2, 6, 7) is different from
that of others (3, 5) suggests that the emission involves the
sulfur atom of the dithiophosphonate ligand. It is not
associated with π orbitals of the phenyl group. A large
change in the energy of the emission would not be anticipated
if the latter were true. Thus, these emissions as seen in 2
(Figure 7) can be assigned as ligand to metal charge transfer
(LMCT), similar to results obtained with other dinuclear
gold(I)-sulfur complexes.39b,40 As seen in Figure 7, there
are two prominent excitation energies that give rise to the
two obvious emission bands, one at 360 nm and the other
near 400 nm.
Yam and co-workers40 carefully analyzed the question of
LMCT and LMMCT in a series of phosphine thiolates
recently. She finds that selected ligands also contribute to
the emission spectra observed, as we believe is the situation
with [Au(i-MNT)2]2, where there is no aurophilic intermo-
lecular interaction, Table 5. However, the extended chain
dithiophosphonates in our study show no ligand-based low-
energy emission. Hence it is reasonable to believe that
LMMCT is the dominant feature of the low-energy transition
observed in these extended chain species, with the M-M
bond formed in the excited state strongly perturbed by
intermolecular Au‚‚‚Au interactions. The excited state has
intermolecular contributions which lower its energy much
as found in exciplex formation studies described recently
for [Au(CN)2]-.37 It is not clear that Yam completely ruled
out a related interpretation of the solution spectra although
the bulky properties of the ligands may prevent association,
as found in the solid state.
This study aimed to find a clear correlation between the
emission profiles of gold-sulfur complexes and the presence
of weak intermolecular Au‚‚‚Au interactions. The complexes
studied represent a group of compounds which (i) have all
been structurally characterized, (ii) all contain S-P-S
bridging ligands, and (iii) are a distribution of structures with
The blue shift observed in the emission bands with
increasing temperature is consistent with an increase in
Au‚‚‚Au separation as a result of thermal expansion. This
suggests that the Au‚‚‚Au distance has a significant influence
on the HOMO-LUMO gap, which increases with increasing
Au‚‚‚Au distance. Another observation involving these
distances is that in 2, which has the shortest inter- and
intramolecular distance Au‚‚‚Au of all the dithiophosphonates
(39) (a) Forward, J. M.; Bohmann, D.; Fackler, J. P., Jr.; Staples, R. J.
Inorg. Chem. 1995, 34, 6330. (b) Narayanaswamy, R.; Young, M.
A.; Parkhurst, E.; Ouellette, M.; Kerr, M. E.; Ho, D. M.; Elder, R. C.;
Bruce, A. E.; Bruce, M. R. M. Inorg. Chem. 1993, 32, 2506. (c) Jones,
W. B.; Yuan, J.; Narayanaswamy, R.; Young, M.; Elder, R. C.; Bruce,
A. E.; Bruce, M. R. M. Inorg. Chem. 1995, 34, 1996.
(40) Yam, V. W.-W.; Chan, C.-L.; Li, C.-K.; Wong, K. M.-C. Coord. Chem.
ReV. 2001, 216-217, 173-194.
Inorganic Chemistry, Vol. 41, No. 17, 2002 4587

van Zyl et al.
Figure 8. Emission spectra of complexes 2 (right) and 7 (left) indicating a significant red shift for 2 as the Au‚‚‚Au interactions become closer in the solid
state.
examined (vide supra), the emission band is significantly red
shifted compared to 6 and 7. In 6 the Au‚‚‚Au distances are
3.096 and 3.123 Å; see Figure 8 and Table 5. The same trend
is also observed between 3 and 5 in which the emission for
3, with shorter intramolecular Au‚‚‚Au distances, is red
shifted with respect to 5. However, this paper will not address
this apparent relationship further. The donor property of the
substituents on the phosphorus centers in the compounds
reported here is similar; hence, they have about the same
influence on the shift. Dilute CHCl3 solutions (∼10-4 M) of
the colored complexes (excluding R ) Fc) show a disap-
pearance of the colors (e.g. yellow 6 and 7, green 2), and
the emission is quenched. However, concentrated solutions,
in which the molecules presumably remain associated, keep
their color and optical properties (Figure 8).
the z axis is along the direction of the metal-metal
interaction). These Au‚‚‚Au interactions can lead to a mixing
of the empty pz orbitals on the Au centers producing a
“bandlike” situation that stabilizes the LUMO. The net effect
is a lowering the energy of the transition, producing the
observed red shift of the emission energy. It appears
consistent that as the number of Au‚‚‚Au interactions
increase, the HOMO-LUMO gap is further reduced. Thus,
for example, 2, 6, and 7 have two different Au‚‚‚Au
interactions (inter and intra) in the solid state, while
complexes such as 3 and 5 have only intramolecular
interactions. The emissions of the latter are consequently blue
shifted compared to 2, 6, and 7. For 3 and 5 where the
HOMO-LUMO gap is large (see excitation energies, Table
5), a high-energy emission does not appear.
The absorption spectra of 7 measured at 0.1, 0.03, and
0.01 M concentrations show a progressive blue shift of the
charge-transfer absorption and the disappearance of a very
low intensity, broad band placed at ∼400 nm. This band
corresponds to the excitation frequency producing the
reported emission. Concentration-dependent UV-vis and
luminescence spectra in gold(I) compounds were previously
reported as evidence for molecular association in solution.40,41
All of these facts seem to indicate that although the emission
is related to a LMCT transition, the Au‚‚‚Au interactions
have a systematic influence on the energies of the frontier
orbitals responsible for the emission. The Au‚‚‚Au interac-
It is proposed that the high-energy bands result from
fluorescence (a small Stokes shift), while the lower energy
bands result from phosphorescence (a triplet excited state).
The latter band is presumably influenced strongly by the
close proximity of the gold centers of different molecules
because it disappears completely when there is no intermo-
lecular Au‚‚‚Au interaction. These results are supported by
preliminary lifetime measurements performed on 2, which
contains short (2.93-2.95 Å) intermolecular Au‚‚‚Au inter-
actions. The blue-shifted emission peak (observed at 77 K)
has a lifetime that is short (<100 ns) compared with the red-
shifted peak (>500 ns). To determine if there is a general
trend, the previously reported dithiophosphate complex
[AuS2P(OiPr)2]2, which shows intra- and intermolecular
Au‚‚‚Au interactions,42 and [AuS2PMe2]2, which shows only
intramolecular Au‚‚‚Au interactions,43 were investigated. The
2
tions produce a destabilization of the filled dz orbital (where
(41) (a) Feng, D.-F.; Tang, S. S.; Liu, C. W.; Lin, I. J. B.; Wen, Y.-S.;
Liu, L.-K. Organometallics 1997, 16, 909. (b) Fernandez, E. J.;
Gimeno, M. C.; Laguna, A.; Lopez de Luzuriaga, J. M.; Monge, M.;
Pyykko, P.; Sundholm, D. J. Am. Chem. Soc. 2000, 122, 7287.
4588 Inorganic Chemistry, Vol. 41, No. 17, 2002

Dinuclear Gold(I) Dithiophosphonate Complexes
luminescence properties of these complexes are consistent
with results obtained in this study. For [AuS2P(OiPr)2]2, the
room-temperature emission spectrum shows only one band,
while at 77 K it shows two. The latter complex is nonemis-
sive at room temperature, while at 77 K it shows one
emission band at 421 nm. Recently, Eisenberg and co-
workers38a reported two forms of a dinuclear gold(I) dithio-
carbamate complex. The one form contains intermolecular
Au‚‚‚Au interactions (solvated), and the other form contains
no intermolecular interactions (not solvated). The lumines-
cence properties of both forms are in accordance with the
results in this study. The solvated complex shows one
emission (630 nm) band and the latter shows no emission,
both at room temperature. Different results are expected at
77 K for both forms; that is, the form with the one emission
band at room temperature should reveal two bands, and the
nonluminescent form one band.44
The ability to predict the presence of weak intermolecular
Au‚‚‚Au interactions in other dinuclear gold-sulfur com-
plexes from the emission spectra was tested with the complex
[NBu4]2[Au2{S2CdC(CN)}2] for which the structure is
known.45 It shows no intermolecular Au‚‚‚Au interaction.
The complex has a S-C-S bridging moiety. Surprisingly
the complex shows two emission bands (495, 527 nm) at 77
K, a result that appeared to contradict the hypothesis
presented in this study. Subsequent studies of the ligand
showed, however, that the yellow potassium salt luminesces
at 77 K with an emission at 553 nm. The 527 nm emission
of the complex thus can be attributed to the ligand which
has the same emission profile. This phenomenon was not
seen for any of the other complexes investigated which all
had colorless, nonluminescent dithiolate ligands. Hence it
appears from this series of complexes studied that the
emission profile can be used to predict the presence of
intermolecular Au‚‚‚Au interactions, at least for dinuclear
gold(I)-sulfur compounds, provided that the ligand emission
spectrum is known. We expect that these results can be
extended to mononuclear gold(I) with sulfur ligands which
may or may not be aurophilically associated.
When we reported14b the spectrum of [AuS2P(OiPr)2]2, we
presented emission maxima different from those reported
here.46 From recent studies of Eisenberg,44 it now seems
likely that both data are correct and that the higher energy
excitation at 77 K produces the lower energy emission.14b
Similar multiple state behavior is not as apparent to date in
the gold dithiophosphonate studies.
Conclusions
This study demonstrates the facile formation of new
dinuclear gold(I) dithiophosphonates from the corresponding
ligand salts. The title complexes reveal two isomers in
solution (cis and trans) as verified by NMR, although only
the trans isomer has been found to date in the solid state.
Solid state 31P NMR studies performed on 3 indicate the
trans isomer exclusively is present in the bulk powder, a
result consistent with single-crystal structural studies. This
paper shows that there is a close relationship between the
structural features of the title complexes and their emission
spectral profiles.
Acknowledgment. The authors thank the Robert A.
Welch Foundation for financial support. J.M.L-d.-L. ac-
knowledges the University of La Rioja for financial support
and two visits to Texas A&M University. Howard Patterson
and C. Larochelle at the University of Maine are acknowl-
edged with thanks for some lifetime measurements, and R.
T. Stubbs (TAMU) is thanked for help with X-ray crystal-
lography in refining some structures. This paper was
abstracted in part from the Ph.D. thesis of W.v.Z., Texas
A&M University, Dec 1998. The authors also thank Richard
Eisenberg for a preprint of work he is doing on Au(I)
dithiophosphates and several helpful conversations about
emission spectra.
(42) Lawton, S. L.; Rohrbaugh, W. J.; Kokotailo, G. T. Inorg. Chem. 1972,
11, 2227.
(43) Preisenberger, M.; Bauer, A.; Schier, A.; Schmidbaur, H. J. Chem.
Soc., Dalton Trans. 1997, 4753.
(44) While this paper was in review, we became aware of a related study
by R. Eisenberg (private communication) on alkyl dithiophosphate
complexes. The structures of several dinuclear Au(I) complexes were
reported along with their luminescence properties. Multiple states
emission and thermochromism were observed. 1MC, 3MC, and 3LMCT
emitting states were suggested to be present from lifetime measure-
ments. However, no direct comparison could be made between
emission spectra obtained with and without intermolecular interac-
tions since each complex in that study showed an intermolecular
Au(I)‚‚‚Au(I) interaction in the solid state.
Supporting Information Available: Listings of X-ray crystal-
lographic data, all atomic coordinates, and equivalent isotropic and
anisotropic parameters. This material is available free of charge
via the Internet at http://pubs.acs.org.
IC0201856
(45) Khan, M. N. I.; Wang, S.; Fackler, J. P., Jr. Inorg. Chem. 1989, 28,
3579.
(46) van Zyl, W. E., Ph.D. Thesis, Texas A&M University, 1998.
Inorganic Chemistry, Vol. 41, No. 17, 2002 4589