Synthesis and characterization of indium compounds with phosphinothiol ligands. (see abstract)

Article abstract of DOI:10.1021/ic980282s

The electrochemical oxidation of anodic indium metal in an acetonitrile solution of phosphinothiol ligands affords [In{2-(Ph₂P)C₆H₄S}₃] (1), [In{2-(Ph₂P)-6-(Me₃Si)C₆H₃S)} ₂{2-(Ph₂PO)-6-(Me₃Si)C₆H ₃S}] (2), [In{2-(Ph₂PO)-6-(Me₃Si)C₆H₃S} ₃] (3), and [NMe₄][In{PhP(C₆H₄S-2)₂} ₂]·CH₃CN (4) complexes exhibiting distorted six-coordinate geometries based on {InS₃P₃}, {InS₃P₂O}, and {InS₄P₂} cores, respectively. In all cases, the In - P bond distances are anomalously long, presumably as a consequence of steric crowding. The anion of 4 provides an unusual example of an In(III)-thiolate coordination complex ion. Crystal data: 1, C₅₄H₄₂InP₃S₃, monoclinic, P2₁/c, a = 16.6579(1) A?, b = 12.6628(2) A?, c = 22.5520(3) A?, β = 96.42(1)°, V = 4727.15(1) A?³, Z = 4, 6176 reflections, R = 0.0579; 2, C₆₃H₆₆InOP₃S₃Si₃, monoclinic, P2₁/c, a = 11.53090(10) A?, b = 26.2505(3) A?, c = 20.4206(2) A?, β = 94.0870(10)°, V = 6165.43(11) A?³, Z = 4, 10 699 reflections, R = 0.0621; 4, C₄₂H₄₁InN₂P₂S₄, monoclinic, P2(1), a = 13.0052(2) A?, b = 11.2240(2) A?, c = 14.3070(3) A?, β= 93.190(1)°, V = 2085.16(7) A?³, Z = 2, 6651 reflections, R = 0.0352.

Full text of DOI:10.1021/ic980282s

Inorg. Chem. 1999, 38, 1293-1298
1293
Synthesis and Characterization of Indium Compounds with Phosphinothiol Ligands. The
Crystal and Molecular Structures of [In{2-(Ph2P)C6H4S}3],
[In{2-(Ph2P)-6-(Me3Si)C6H3S}2{2-(Ph2PO)-6-(Me3Si)C6H3S}], and
[NMe4][In{PhP(C6H4S-2)2}2]‚CH3CN
Paulo Pe´rez-Lourido, Jaime Romero,* Jose´ Arturo Garc´ıa-Va´zquez, and Antonio Sousa*
Departamento de Qu´ımica Inorga´nica, Universidad de Santiago de Compostela,
15706 Santiago de Compostela, Spain
Kevin Maresca and Jon Zubieta*
Department of Chemistry, Syracuse University, Syracuse, New York 13244
ReceiVed March 12, 1998
The electrochemical oxidation of anodic indium metal in an acetonitrile solution of phosphinothiol ligands affords
[In{2-(Ph2P)C6H4S}3] (1), [In{2-(Ph2P)-6-(Me3Si)C6H3S)}2{2-(Ph2PO)-6-(Me3Si)C6H3S}] (2), [In{2-(Ph2PO)-6-
(Me3Si)C6H3S}3] (3), and [NMe4][In{PhP(C6H4S-2)2}2]‚CH3CN (4) complexes exhibiting distorted six-coordinate
geometries based on {InS3P3}, {InS3P2O}, and {InS4P2} cores, respectively. In all cases, the In-P bond distances
are anomalously long, presumably as a consequence of steric crowding. The anion of 4 provides an unusual
example of an In(III)-thiolate coordination complex ion. Crystal data: 1, C54H42InP3S3, monoclinic, P21/c, a )
16.6579(1) Å, b ) 12.6628(2) Å, c ) 22.5520(3) Å, â ) 96.42(1)°, V ) 4727.15(1) Å3, Z ) 4, 6176 reflections,
R ) 0.0579; 2, C63H66InOP3S3Si3, monoclinic, P21/c, a ) 11.53090(10) Å, b ) 26.2505(3) Å, c ) 20.4206(2)
Å, â ) 94.0870(10)°, V ) 6165.43(11) Å3, Z ) 4, 10 699 reflections, R ) 0.0621; 4, C42H41InN2P2S4, monoclinic,
P2(1), a ) 13.0052(2) Å, b ) 11.2240(2) Å, c ) 14.3070(3) Å, â ) 93.190(1)°, V ) 2085.16(7) Å3, Z ) 2, 6651
reflections, R ) 0.0352.
Introduction
of 111In or 113In γ emitters in medical imaging.5 As a continu-
ation of this work, we report the synthesis of indium phosphi-
The coordination chemistry of indium thiolates remains
relatively unexplored with only a handful of compounds
exhibiting In-S bonds having been structurally characterized.1,2
Since the pronounced tendency of sulfur to bridge metal centers
often produces insoluble polymers, one strategy for the synthesis
of low molecular weight compounds exploits bulky substituents
on the ligand to prevent the association process. This approach
has proved successful in the preparation and structural charac-
terization of dinuclear indium thiolates of the class [Mes2In(µ-
SR)]2 (R ) But, 2-ButC6H4, or SiPh3),3 which show potential
as precursors for the deposition of indium chalcogenides under
MOCVD conditions. Monomeric three-coordinated indium
thiolate complexes have also been obtained by Power using very
bulky ligands such as HS(2,4,6-But3C6H2).4 An alternative route
to molecular species involves the saturation of the metal
coordination sphere with other donor atoms in addition to the
thiolate groups; in the specific case of multidentate mixed-donor
ligands, complex stability is enhanced by the chelate effect. This
technique has been exploited to prepare monomeric and
binuclear indium compounds with pyridine-2-thione and its
derivatives with lipophilic characteristics as potential sources
noarenethiolate complexes, with ligands incorporating both
thiolate sulfur and tertiary phosphorus atoms as donor sites. The
synthesis involves an electrochemical procedure with the metal
acting as the anode of a cell containing the ligand in an
acetonitrile solution. This method has previously been employed
in the preparation of homoleptic indium thiolate complexes6 and
more generally for complexes with ligands containing weakly
acidic groups such as heterocyclic thiones and their derivatives.7-11
While coordination compounds of phosphinoarenethiol ligands
have been reported previously by Dilworth and Zubieta, mainly
with heavier transition metals, such as molybdenum,12 techne-
(5) (a) Rose, D. J.; Chang, Y. D.; Chem, Q.; Kettler, P. B.; Zubieta, J.
Inorg. Chem. 1995, 34, 3973. (b) Moore, D. A.; Fanwick, P. E.; Welch,
M. J. Inorg. Chem. 1990, 29, 672.
(6) Green, J. H.; Kumar, R.; Seudeal, N.; Tuck, D. G. Inorg. Chem. 1989,
28, 123.
(7) Castro, R.; Dura´n, M. L.; Garc´ıa-Va´zquez, J. A.; Romero, J.; Sousa,
A.; Castin˜eiras, A.; Hiller, W.; Stra¨hle, J. Z. Naturforsch 1992, 47b,
1067.
(8) Castro, R.; Garc´ıa-Va´zquez, J. A.; Romero, J.; Sousa, A.; Pritchard,
R.; McAulife, C. A. J. Chem. Soc., Dalton Trans. 1994, 1115.
(9) Castro, J. A.; Romero, J.; Garc´ıa-Va´zquez, J. A.; Castin˜eiras, A.; Sousa,
A.; Zubieta, J. Polyhedron 1995, 14, 2841.
* Authors to whom correspondence should be addressed.
(1) Einstein, F. W. B.; Jones, R. D. G. J. Chem. Soc. A 1971, 2762.
(2) Chadha, R. K.; Hayes, P. C.; Mabrouk, H. E.; Tuck, D. G. Can. J.
Chem. 1987, 65, 804.
(3) Rahbarnoohi, H.; Taghiof, M.; Heeg, M. J.; Dick, D. G.; Oliver J. P.
Inorg. Chem. 1994, 33, 6307.
(10) Tallo´n, J.; Garc´ıa-Va´zquez, J. A.; Romero, J.; Louro, M. S.; Sousa,
A.; Chem, Q.; Chang, Y.; Zubieta, J. Polyhedron 1995, 14, 2309.
(11) Pe´rez-Lourido, P. A.; Garc´ıa-Va´zquez, J. A.; Romero, J.; Louro, M.
L.; Sousa, A.; Chem, Q.; Chang, Y.; Zubieta, J. J. Chem. Soc., Dalton
Trans. 1996, 2047.
(12) Block, E.; Kang, H.; Ofori-Okai, G.; Zubieta, J. Inorg. Chim. Acta
1989, 166, 155.
(4) Ruhlandt-Senge, K.; Power, P. P. Inorg. Chem. 1993, 32, 3478.
10.1021/ic980282s CCC: $18.00 © 1999 American Chemical Society
Published on Web 03/04/1999

1294 Inorganic Chemistry, Vol. 38, No. 6, 1999
Pe´rez-Lourido et al.
tium and rhenium,13 ruthenium,14 and rhodium and iridium,15
materials with main group metals remain relatively unexplored,
and indium compounds of such ligand types have not been
reported to date.
Table 1. Summary of Crystallographic Data for the Compounds
[In{2-(Ph2P)C6H4S}3] (1),
[In{2-(Ph2P)-6-(Me3Si)C6H3S}2{2-(Ph2PO)-6-(Me3Si)C6H3S}] (2),
and [NMe4][In{PhP(C6H4S-2)2}2]‚CH3CN (4)
1
2
4
Experimental Section
empirical formula C54H42InP3S3 C63H66InOP3S3Si3 C42H41InN2P2S4
fw
994.79
monoclinic
P21/c
1227.34
monoclinic
P21/c
878.77
monoclinic
P21
General Considerations. All manipulations were carried out under
an inert atmosphere of dry nitrogen. Indium (Aldrich Chemie) was used
as plates (ca. 2 × 2 cm). Syntheses of ligands were carried out using
minor modifications of the standard literature procedures involving
lithiation of benzenethiol,16 using Schlenk techniques and dry solvents.
Elemental analysis were performed in a Carlo-Erba EA 1108 microana-
lyzer. IR spectra were recorded in KBr disks using a Bruker IFS 66v
spectrophotometer. 1H and 31P NMR spectra were recorded on a Bruker
AMX 300 MHz instrument using Cl3CD as solvent, except for 4, which
was recorded in DMSO-d6. 1H NMR chemical shifts were determined
against TMS as the internal standard. 31P NMR chemical shifts were
determined against 85% H3PO4. The FAB mass spectra were recorded
on a Kratos MS-50TC spectrophotometer, using 3-nitrobenzyl alcohol
(3-NOBA) as a matrix material.
cryst syst
space group
unit cell dimens
a, Å
16.6579(1)
12.6628(2)
22.5520(3)
96.42(1)
4727.15(1)
4
11.53090(10)
26.2505(3)
20.4206(2)
94.087(10)
6165.43(11)
4
13.0052(2)
11.2240(2)
14.3070(3)
93.19(1)
2085.16(7)
2
b, Å
c, Å
â, deg
vol, Å3
Z
d
calc, g cm-3
1.398
1.322
1.400
λ, Å (Mo KR
0.71073
0.71073
0.71073
radiation)
µ(Mo KR), cm-1
T, °C
no. of reflns
collected
7.70
25
19116
6.61
-123
31098
8.75
25
10546
Electrochemical Synthesis. The electrochemical procedure used in
the synthesis of the complexes was similar to that described by Tuck.17
The cell consisted of a metal anode suspended from a platinum wire
in a solution of the corresponding thiol ligand (and ca. 20 mg of
tetramethylammonium perchlorate as supporting electrolyte) in aceto-
no. of indep reflns 6176
10699
2544
0.0621
0.1683
6651
900
0.0352
0.0869
F(000)
2032
0.0579
0.1392
Ra
b
Rw
2
a R ) ∑(|Fo| - |Fc|)/∑|Fo|. b Rw ) [∑w(|Fo| - |Fc|)2/∑w|Fo| ]1/2
.
nitrile with a platinum cathode. The cells can be summarized as Pt(-)
/
CH3CN + RP-SH/In(+)
.
washed with cool acetonitrile and diethyl ether, and dried under vacuum
(260 mg, 0.207 mmol, 78%). Anal. Calcd for C63H66InP3S3Si3: C, 60.10;
H, 5.25; S, 7.63. Found: C, 60.28; H, 5.10; S, 7.20. IR (KBr, cm-1):
1554 (m), 1484 (w), 1437 (m), 1355 (s), 1244 (m), 1132 (s), 1072
[In{2-(Ph2P)C6H4S}3] (1). Electrochemical oxidation of an indium
anode in a solution of 2-(diphenylphosphinyl)benzenethiol, 2-(Ph2P)-
C6H4SH (0.330 g, 1.12 mmol), in acetonitrile (50 cm3), at 8 V and 5
mA for 2 h caused 43 mg of indium to be dissolved, Ef ) 1.0 mol F-1
.
1
(m), 853 (s), 749 (m), 693 (m), 557 (s). H NMR (CD3Cl, ppm): δ
During the electrolysis hydrogen was evolved at the cathode, and after
1 h, white crystalline needles appeared on the electrodes and at the
bottom of the vessel. The solid was filtered off, washed with acetonitrile
and ether, and dried under vacuum (313 mg, 0.315 mmol, 84%). Anal.
Calcd for C54H42InP3S3: C, 65.13; H, 4.22; S, 9.65. Found: C, 65.35;
H, 4.33; S, 9.61. IR (KBr, cm-1): 1573 (m), 1480 (m), 1438 (s), 1417
(m), 1121 (m), 1095 (m), 742 (s), 645 (s). 1H NMR (CD3Cl, ppm): δ
7.8-6.7 (m, 42 H). 31P NMR (CD3Cl, ppm): δ 40.1, 39.5, and 39.2.
[In{2-(Ph2P)-6-(Me3Si)C6H3S}2{2-(Ph2PO)-6-(Me3Si)C6H3S}] (2).
A solution of acetonitrile (50 cm3) containing 2-diphenylphosphino-
6-trimethylsilylbenzenethiol (0.270 g, 0.75 mmol) was electrolyzed at
5 mA for 2 h, during which time 42 mg of indium metal was dissolved
from the anode, Ef ) 0.98 mol F-1. The resulting microcrystalline
product was washed with acetonitrile and ethyl ether and dried (285
mg, 0.232 mmol, 63%). Colorless crystals suitable for X-ray studies
were obtained by recrystallization from methanol/chloroform and
identified by elemental analysis. Anal. Calcd for C63H66InOP3S3Si3: C,
61.17; H, 5.38; S, 7.83. Found: C, 61.22; H, 5.39; S, 7.42. IR (KBr,
cm-1): 1554 (m), 1481 (m), 1435 (m), 1353 (s), 1244 (m), 1128 (s),
1095 (w), 1039 (w), 850 (s), 741 (s), 692 (s). 1H NMR (CD3Cl, ppm):
δ 7.8-6.4 (m, 39H), 0.10 (s, 9H), 0.30 (s, 9H), 0.40 (s, 9H). 31P NMR
(CD3Cl, ppm): δ 40.9 and 43.7.
7.8-6.8 (m, 39 H), 0.10 (s, 9H), 0.20 (s, 9H), 0.40 (s, 9H). 31P NMR
(CD3Cl, ppm): δ 49.8, 50.0, and 50.7.
[NMe4][In{PhP(C6H4S-2)2}2]‚CH3CN (4). The electrochemical
oxidation of indium in a solution of PPh(C6H4SH-2)2 (0.17 g, 0.52
mmol) in acetonitrile (60 mL) containing tetramethylammonium
perchlorate (20 mg) as supporting electrolyte for 2 h at 4 V and 5 mA
resulted in the loss of 42 mg of indium from the anode, Ef ) 0.98 mol
F-1. A white solid of an uncharacterized compound precipitated in the
cell. Concentration of the solution yielded crystals of 4 suitable for
X-ray diffraction as a minor product. Anal. Calcd for C42H41N2P2S4In:
C, 61.36; H, 5.11; N, 3.49; S, 7.98. Found: C, 60.85; H, 5.05; N, 3.32;
S, 8.11. IR (KBr, cm-1): 1574 (s), 1481 (s), 1436 (s), 1246 (m), 1127
1
(m), 1096 (s), 999 (m), 741 (s), 695 (m). H NMR (DMSO-d6, ppm):
δ 7.6-6.8 (m, 26H), 3.1 (s, 12H). 31P NMR (DMSO-d6, ppm): δ 42.7.
X-ray Crystallography. Compounds 1 and 4 were studied on a
Rigaku AFC6S equipped with a conventional scintillation counter, and
compound 2 was studied on a Siemens Smart system with a CCD
detector. Data collection of 2 was carried out at low temperature while
that of 1 and 4 was carried out under ambient conditions, using graphite-
monocromated Mo KR radiation. The crystal parameters and other
experimental details of the data collection are summarized in Table 1.
A complete description of the details of the crystallographic methods
is given in the Supporting Information. The structures were solved by
direct methods.18 Neutral atom scattering factors were taken from
Cromer and Waber19 and anomalous dispersion factors were taken from
Cromer20 for 1 and 4 and Creagh and McAuley for 2.21 All calculations
were performed using the Texsan crystallographic sofware package22
for 1 and 4 and the SHELXTL crystallographic sofware package23 for
[In{2-(Ph2PO)-6-(Me3Si)C6H3S}3] (3). In a procedure similar to that
employed in the isolation of 2 (6 V, 5 mA, 2.0 h), 44 mg of indium
dissolved in the presence of the ligand 2-(Ph2PO)-6-(Me3Si)C6H3SH
(0.290 g, 0.56 mmol) in 50 cm3 of acetonitrile, Ef ) 1.02 mol F-1. A
white crystalline precipitate formed during the electrolysis at the anode,
and hydrogen was evolved at the cathode. The solid was collected,
(13) Dilworth, J. R.; Huston, A. J.; Morton, S.; Harman, M.; Hursthouse,
M. B.; Zubieta, J.; Archer, C. M.; Kelly, J. D. Polyhedron 1992, 11,
2151.
(18) Texsan: Texray structural Analysis Packge; Molecular Structure
Corporation: The Woodlands, TX, 1992.
(14) Dilworth, J. R.; Zheng, Y.; Lu, S.; Wu, Q. Transition Met. Chem.
(London) 1992, 17, 364.
(15) Dilworth, J. R.; Lu, S.; Miller, J. R.; Zheng, Y. J. Chem. Soc., Dalton
(19) Cromer, D. T.; Waber, J. T. International Tables for X-ray Crystal-
lography; Kynoch Press: Birmingham, England, 1974; Vol. 4.
(20) Cromer, D. T. International Tables for X-ray Crystallography; Kynoch
Press: Birmingham, England, 1974; Vol. 4, Table 2.3.1.
Trans. 1995, 1957.
(16) Block, E.; Ofori-Okai. G.; Zubieta, J. J. Am. Chem. Soc. 1989, 111,
(21) Creagh, D. C.; McAuley, J. W. J. International Tables for X-ray
Crystallography; Kluwer Academic: Boston, 1992; Vol. C, Table 4.
(22) TEXSAN-TEXRAY structure and analysis package; Molecular Structure
Corporation: The Woodlands, TX, 1985.
2327.
(17) Habeeb, J. J.; Tuck, D. G.; Walters, F. H. J. Coord. Chem. 1978, 8,
27.

Indium Compounds with Phosphinothiol Ligands
Inorganic Chemistry, Vol. 38, No. 6, 1999 1295
Table 2. Selected Bond Lengths (Å) and Angles (deg) for 1
compounds obtained in this fashion are crystalline solids soluble
in chloroform (except 4) and in other common organic solvents.
The electrochemical efficiency for the process, Ef, defined
as the number of moles of metal dissolved per faraday of charge,
was in all cases close to 1 mol F-1. These values demonstrate
that the anodic oxidation of the metal leads initially to In(I)
species, which are further oxidized to In(III) in solution. This
observation and the evolution of the hydrogen at the cathode
are compatible with the following mechanism:
In-S(1)
2.518(2)
2.557(2)
2.728(2)
1.777(6)
1.781(7)
1.775(6)
1.815(6)
1.822(6)
1.818(6)
In-S(2)
In-P(1)
2.550(2)
2.963(2)
2.812(2)
1.812(8)
1.821(7)
1.804(7)
1.820(7)
1.817(6)
1.825(6)
In-S(3)
In-P(3)
In-P(2)
S(1)-C(11)
S(2)-C(41)
S(3)-C(71)
P(2)-C(46)
P(2)-C(66)
P(3)-C(76)
P(1)-C(26)
P(1)-C(36)
P(1)-C(16)
P(2)-C(56)
P(3)-C(86)
P(3)-C(96)
S(1)-In-S(2)
S(2)-In-S(3)
S(2)-In-P(3)
S(1)-In-P(2)
S(3)-In-P(2)
S(1)-In-P(1)
S(3)-In-P(1)
P(2)-In-P(1)
161.91(6)
96.85(6)
90.02(5)
92.52(6)
100.53(5)
71.31(5)
158.60(5)
96.90(5)
S(1)-In-S(3)
S(1)-In-P(3)
S(3)-In-P(3)
S(2)-In-P(2)
P(3)-In-P(2)
S(2)-In-P(1)
P(3)-In-P(1)
95.50(5)
106.15(6)
73.60(5)
72.26(5)
160.77(5)
100.22(6)
93.50(5)
cathode: RP-SH + e- f RP-S- + 1/2H2
anode:
In + RP-S- f [In(S-PR)] + e-
[In(S-PR)] + 2[RP-SH] f [In(S-PR)3] + H2
where RP-SH stands for the neutral ligand. This behavior has
previously been observed in other indium systems in which low-
oxidation-state species are the initial electrochemical prod-
ucts.6,24
Table 3. Selected Bond Lengths (Å) and Angles (deg) for 2
In(1)-O(1)
In(1)-S(2)
In(1)-P(3)
S(1)-C(14)
S(3)-C(60)
P(1)-C(13)
P(1)-C(7)
P(2)-C(28)
P(3)-C(43)
P(3)-C(49)
2.198(5)
2.538(2)
2.827(2)
1.759(6)
1.774(6)
1.807(6)
1.811(7)
1.829(6)
1.827(6)
1.828(7)
In(1)-S(3)
In(1)-S(1)
In(1)-P(2)
S(2)-C(34)
P(1)-O(1)
P(1)-C(1)
P(2)-C(35
P(2)-C(22)
P(3)-C(55)
Si(1)-C(20)
2.531(2)
2.556(2)
2.840(2)
1.766(6)
1.468(5)
1.809(6)
1.822(6)
1.830(6)
1.828(7)
1.861(7)
The IR spectrum of 1 shows the absence of a band which
appears at 2943 cm-1 in the free ligand and is attributed to ν-
(S-H). This observation indicates that the ligand is in the
anionic thiolate form in the complex. The spectrum also shows
bands in the aromatic region characteristic of the coordinated
1
phosphinothiol ligand. The room temperature H NMR of 1
exhibits peaks in the aromatic region, and also the disappearance
of the signal attributable to SH hydrogen which appears at δ
4.1 ppm in the free ligand as a doublet as a result of the coupling
with the phosphorus atom. The 31P spectra of the complex shows
three separate signals at δ 40.1, 39.5, and 39.2 ppm, an
observation which is consistent with the compound in solution
adopting a mer disposition of the ligands in the octahedral
environment around the metal. This is also the structure observed
for the compound in the solid state (vide infra). The FAB mass
spectrum of this compound does not show the molecular ion,
and the highest m/e peak corresponds to [In{2-(Ph2P)C6H4S}2]+
(m/z 701, 40%). The spectrum also shows the peaks associated
with [In{2-(Ph2P)C6H4S}]2+ and [2-(Ph2P)C6H4S]- at m/z 407
(9%) and m/z 293 (100%), respectively. The peak clusters
display the appropriate isotope distributions.
O(1)-In(1)-S(3)
S(3)-In(1)-S(2)
S(3)-In(1)-S(1)
O(1)-In(1)-P(3)
S(2)-ln(1)-P(3)
99.72(13) O(1)-In(1)-S(2)
93.47(13)
86.71(13)
91.13(5)
74.22(5)
160.43(5)
93.26(5)
96.85(5)
163.03(6)
100.19(5)
O(1)-In(1)-S(1)
S(2)-In(1)-S(1)
76.03(13) S(3)-ln(1)-P(3)
98.94(5)
S(1)-ln(1)-P(3)
O(1)-In(1)-P(2) 165.73(14) S(3)-ln(1)-P(2)
S(2)-ln(1)-P(2)
P(3)-In(l)-P(2)
72.70(5)
102.14(5)
S(1)-In(1)-P(2)
C(14)-S(l)-In(1) 110.4(2)
Table 4. Selected Bond Lengths (Å) and Angles (deg) for 4
In-S(2)
2.5578(11)
2.5949(9)
2.6779(11)
1.818(5)
1.837(4)
1.823(5)
1.761(5)
1.776(4)
In-S(1)
2.5925(13)
2.6428(12)
2.7006(10)
1.820(5)
1.813(4)
1.832(5)
In-S(4)
In-S(3)
In-P(2)
In-P(1)
P(1)-C(16)
P(1)-C(6)
P(2)-C(46)
S(1)-C(11)
S(3)-C(41)
P(1)-C(26)
P(2)-C(56)
P(2)-C(36)
S(2)-C(21)
S(4)-C(51)
1.776(6)
1.774(5)
To evaluate possible steric effects upon the indium-phos-
phinothiolate coordination geometry, anodic indium was oxi-
dized in a solution of the sterically enhanced ligand 2-(diphen-
ylphosphinyl)-6-(trimethylsilyl)benzenethiol in acetonitrile. The
solid obtained was identified as [In{2-(Ph2P)-6-(Me3Si)C6H3S}2-
{2-(PhPO)-6-(Me3Si)C6H3S}] (2). X-ray studies confirmed the
presence of both the bidentate phosphinothiolate and oxophos-
phinothiolate forms of the ligands (vide infra). The oxygen atom
incorporated into the oxophosphinothiolate moiety most likely
originates from oxygen dissolved in the solvent. Such facile
oxidation of phosphine to phosphine oxides has been observed
for similar complexes.12 The IR spectrum of 2 is similar to that
S(2)-In-S(1)
S(1)-In-S(4)
S(1)-In-S(3)
S(2)-In-P(2)
S(4)-In-P(2)
S(2)-In-P(1)
99.01(4)
99.02(5)
151.22(5)
163.96(4)
74.63(3)
75.61(4)
S(2)-In-S(4)
S(2)-In-S(3)
S(4)-In-S(3)
S(1)-In-P(2)
S(3)-In-P(2)
S(1)-In-P(1)
90.63(4)
100.76(4)
101.47(4)
89.69(4)
76.61(4)
78.53(4)
2. No anomalies were encountered in the refinements of any of the
structures. Atomic position parameters and isotropic temperature factors
for the structures are presented in the Supporting Information. Selected
bond lengths and angles for 1, 2, and 4 are listed in Tables 2-4,
respectively.
of 1 with an additional medium-intensity band at 1128 cm-1
,
attributed to ν(P-O), and an intense band at 850 cm-1
1
Results and Discussion
characteristic of the Si-C group. The room temperature H
NMR of the complex shows signals from aromatic protons in
the range δ 7.8-6.4 ppm and three separate signals at δ 0.1,
0.3, and 0.4 ppm assigned to the three nonequivalent trimeth-
ylsilyl groups. The 31P NMR spectrum shows two signals for
the phosphorus atoms at δ 40.9 and 43.7 ppm. Of the several
The indium(III) phosphinothiolato complexes 1-3 are readily
prepared in good yield by oxidation of an indium anode in a
cell containing a solution of the ligand and tetramethylammo-
nium perchlorate as supporting electrolyte, while compound 4
could be obtained only as a minor product. The air-stable
(24) Romero, J.; Dura´n, M. L.; Castin˜eiras, A.; Garc´ıa-Va´zquez, J. A.;
Sousa, A.; Christiaens, L.; Zubieta, J. Inorg. Chim. Acta 1997, 225,
307.
(23) SHELXTL PC; Siemens Analytical X-ray Instruments, Inc.: Madison,
WI, 1990.

1296 Inorganic Chemistry, Vol. 38, No. 6, 1999
Pe´rez-Lourido et al.
Figure 1. View of the structure of [In{2-(Ph2P)C6H4S}3] (1), showing
the atom-labeling scheme and 50% thermal ellipsoids.
Figure 2. View of the structure of [In{2-(Ph2P)-6-(Me3Si)C6H3S}2{2-
(Ph2PO)-6-(Me3Si)C6H3S}] (2), showing the atom-labeling scheme and
50% thermal ellipsoids.
possible structures for the compound, the only one compatible
with these data contains the indium atom coordinated to three
sulfur atoms disposed in a meridional disposition and two
phosphorus atoms trans to each other, a structure at variance
with the solid state structure of this compound (vide infra). The
FAB mass spectrum of this compound shows a peak at m/z 845
due to the [In{2-(Ph2P)-6-(Me3Si)C6H4S}2]+ ion (10%), formed
by loss of the oxophosphinothiolate ligand, and also peaks
associated with [In{2-(Ph2P)-6-(Me3Si)C6H4S}]2+ at m/z 480
(4%) and [2-(Ph2P)-6-(Me3Si)C6H4S]- at m/z 365 (24%).
Compound 3 was obtained by oxidation of indium metal in
a cell containing 2-(diphenylphosphinyl)-6-(trimethylsilyl)-
benzenethiol. Attempts to obtain crystals suitable for X-ray
studies were unsuccessful. Analytical data confirms the presence
of an In(III) compound with three monoanionic ligands. The
IR spectrum shows the characteristic bands of the coordinated
ligand. Three signals for the trimethylsilyl groups at δ 0.1, 0.2,
1
and 0.4 ppm in the H NMR spectrum and three signals at δ
49.8, 50.0, and 50.7 ppm in the 31P NMR again confirm a
meridional disposition of the ligands in the octahedral arrange-
ment around the metal in the solution phase. The FAB mass
spectrum of this compound shows a peak at m/z 879 (53%),
attributed to the [In{2-(PhPO)-6-(Me3Si)C6H4S}2]+ ion, and also
peaks associated with [In{2-(Ph2PO)-6-(Me3Si)C6H4S}]2+ at
m/z 496 (21%) and [2-(Ph2PO)-6-(Me3Si)C6H4S]- at m/z 381
(4%).
Figure 3. View of the structure of the anion [In{PhP(C6H4S-2)2}2]-
of 4, showing the atom-labeling scheme and 50% thermal ellipsoids.
Description of the Structures. The molecular structure of
[In{2-(Ph2P)C6H4S}3] (1) is shown in Figure 1, together with
the atomic numbering scheme adopted. Selected bond distances
and angles are found in Table 2. In the case of compound 1,
the indium atom is coordinated to the phosphorus and sulfur
donor atoms of three monoanionic chelating ligands. The
environment around the indium can be described as possessing
a distorted octahedral P3S3 core with an average value of 73.39-
(5)° for the chelate bite angles of the ligands. The angles defined
by two trans atoms at the indium atom deviate considerably
from the idealized value of 180° (161.91(6)°, 160.77(5)°, and
158.60(5)°). The arrangement of the sulfur and phosphorus
atoms is such that the complex can be described as the
meridional isomer, a disposition which is maintained in solu-
tion. This donor group arrangement has also been observed in
other trischelate metal complexes involving this ligand, namely,
[Re{2-(Ph2P)C6H4S}3], [Tc{2-(Ph2P)C6H4S}3],13 Ir{2-(Ph2P)-
Compound 4 was obtained as a minor product in the oxidation
of an indium anode in the presence of PhP(C6H4SH-2)2. As the
electrolysis proceeded, an amorphous and uncharacterizable
solid precipitated in the cell. Concentration of the resulting
solution resulted in the formation of a small amount of crystals
containing the anionic species [In{PhP(C6H4SH-2)2}2]- and the
cation tetramethylammonium. The absence of bands in the IR
spectrum attributable to ν(SH) and the lack of signals for these
1
hydrogen atoms in the H NMR spectra in DMSO-d6 confirm
that the four thiol groups are deprotonated in the complex. The
1H NMR shows the presence of the methyl groups from the
tetramethylammonium cation at δ 3.1 ppm. The 31P NMR shows
one signal at δ 42.73 ppm, such that the phosphorus atoms are
equivalent, an observation consistent with the structure of the
compound in the solid state (vide infra).

Indium Compounds with Phosphinothiol Ligands
Inorganic Chemistry, Vol. 38, No. 6, 1999 1297
Table 5. Selected Structural Parameters for In(III)-Thiolate Complexes
compound
coord no.
In-S, Å
2.398(4)
2.619(5)
2.592(4)
2.621(1)
2.617(6)
2.418
2.450(4)
2.458(5)
2.443(4) × 3
2.649(3) × 1
2.511(2)
2.531(2)
2.539(3)
2.549(1)
2.542(3)
In-X (X), Å
S-C, Å
M-S-C, deg
ref
[In(SC5H2-2,4,6-But3)3]
3
4
4
4
4
4
4
5
5
1.81(1)
c
c
c
98.1(3)
c
c
c
4
3
3
3
3
29
2
30
31
[Mes2In(SBut)]2
2.107(8) (C)
2.22(1) (C)
2.176(4) (C)
2.12(1) (C)
2.244(6) (O)
2.527(1) (Br)
2.39(1) (N)
2.39(1) (N)
a
[Mes2In(S-amyl)]2
[Mes2In(SSiPh3)]2
[Mes2In(SSiPh3)]3
[In(SC6H2-2,4,6-(CF3)3)3(OEt2)]
[Ph4P][BrIn(SPh)3]
[In(SPh)3(NC5H5)2]
[In{(SCH2CH2)3N}]
c
c
1.786(8)
1.75(3)
1.77(1)
1.84(1)
104.1(3)
107.7(7)
104.9(7)
95.7(2)
[In(TS-TACN)]b
[In(SC4H4N)3]
[In(SC5H3N-3-SiMe3)3]
[In2(OC2H5)2(SC5H4N)4]
[In(PS)3] (1)
6
6
6
6
6
2.397(4) (N)
2.318(6) (N)
2.31(1) (N)
2.296(4) (N)
2.770(2) × 2 (P)
2.963(2) (P)
2.834(3) (P)
2.198 (O)
c
c
32
5
5
5
d
1.746(8)
1.76(1)
1.733(4)
1.774(8)
81.5(3)
82.5(4)
80.9(2)
98.5(3)
[In(PS)2(OPS)] (2)
6
6
2.542(3)
1.767(8)
1.772(8)
107.2(3)
104.5(4)
d
d
[NMe4][In(SPS)2] (4)
2.582(1) × 3
2.689(1) (P)
2.643(1)
a Mes ) 2,4,6-trimethylphenyl. b TS-TACN ) 1,4,7-tris(2-mercaptoethyl)-1,4,7-triazacyclononane. c Not reported. d This work.
C6H4S}3],15 and [Co{2-(Ph2P)C6H4S}3].25 The three In-S bond
distances are similar and fall in the range 2.518(2)-2.557(2)
Å, with an average value of 2.541(2) Å. These values are similar
to those found in indium complexes with heterocyclic thiones,
e.g., [In(pyt)3], 2.531(3) Å, [In(3-Me3Sipyt)3], 2.539(3) Å,5a and
[In(pymt)3], 2.522(1) Å26 (pyt ) pyridine-2-thionato, pymt )
pyrimidine-2-thionato). Curiously, the In-P(1) bond distance,
2.963(2) Å, is significantly longer than the other two In-P
distances, 2.812(2) and 2.728(2) Å for In-P(2) and In-P(3),
respectively. In the absence of additional structural data for In-P
bond distances in octahedral indium complexes for comparison
with 1, it is tempting to conclude that steric crowding is
responsible for the difference in these In-P bond lengths. The
significantly shorter In-P distance of 2.603(7) Å reported for
the four-coordinate InI3(PPh3)27 would seem to support this
analysis. The fact that the highest molecular peak in the mass
spectrum corresponds to the [In{2-(Ph2P)C6H4S}2]+ ion could
be indicative of the weakness of the In-P(1) bond.
The structure of [In{2-(Ph2P)-6-(Me3Si)C6H3S}2{2-(Ph2PO)-
6-(Me3Si)C6H3S}] (2), Figure 2, consists of discrete molecules
with the indium atom in a distorted octahedral [InOP2S3]
environment, coordinated by two anionic bidentate 2-(diphe-
nylphosphinyl)-6-(trimethylsilyl)benzenethiolate ligands bonding
through their sulfur and phosphorus atoms and one bidentate
anionic 2-(diphenylphosphinyl)-6-(trimethylsilyl)benzenethiolate
ligand which coordinates through the oxygen and sulfur atoms.
The phosphorus atoms exhibit a cis arrangement. The In-S
distances 2.556(2), 2.538(2), and 2.531(2) Å and the In-P
distances, 2.840(2) and 2.827(2) Å, Table 3, are similar to the
corresponding distances found in 1. The data reveal that the
introduction of a trialkylsilyl group in the ligand has a negligible
influence on the structural parameters of the compound. The
In-O bond distance 2.198(5) Å is similar to that found in [In-
(PT)3] (PT ) 1-oxopyridine-2-thionate anion), 2.203(5) Å
average value, an In(III) compound with an octahedral [InO3S3]
core.28
The structural analysis of 4 reveals that the compound
contains the anionic species [In{PhP(C6H4S)2}2]- and the cation
[NMe4]+ incorporated from the background electrolyte. As
shown in Figure 3, the complex anion consists of a distorted
octahedral [InP2S4] environment resulting from the coordination
of an indium atom to two tridentate bis(2-mercaptophenyl)phen-
ylphosphine ligands. The two sulfur donors and the phosphorus
atom of each ligand adopt a facial arrangement, such that the
phosphorus atoms are in the cis orientation. The In-S bond
distances, Table 4, fall in the range 2.558(1)-2.643(1) Å, with
an average value of 2.597(2) Å. The In-P bond distances 2.678-
(1) and 2.701(1) Å fall in the low range of values previously
observed for compounds 1 and 3.
The data summarized in Table 5 illustrate the remarkable
structural versatility exhibited by In(III)-thiolate complexes,
which display coordination numbers from three to six and often
highly distorted geometries. Both the presence of sterically
demanding groups and of auxiliary donor groups evidently
influence the geometry adopted by this class of compounds.
Not unexpectedly, bridging thiolate groups exhibit lengthened
In-S distances which fall in the range 2.59-2.65 Å. Excluding
such bridging types, there exists an apparent correlation of In-S
bond distance with coordination number. Thus, as the coordina-
tion number increases from three to six, the average In-S bond
distance increases monotonically with values of 2.398(3), 2.434-
(7), 2.493(4), and 2.542 Å observed for three, four, five, and
six coordination, respectively.
While the compounds of this study in general exhibit un-
exceptional In-S distances for six coordination, the In-P dis-
tances are significantly longer than anticipated from the sums
of the covalent radii of In(III) and phosphorus. The In-P dis-
tances would be expected to be on the order of 0.08-0.12 Å
longer than the In-S distances in the corresponding complex,
in the absence of other contributing factors. With the exception
of 4, which exhibits In-S distances of 2.582 and 2.643 Å and
In-P distances of 2.689 Å, the other compounds of this study
possess exceptionally elongated In-P bond distances. In fact,
(25) Pe´rez-Lourido, P.; Romero, J.; Garc´ıa-Va´zquez, J. A.; Sousa, A.;
Zubieta, J.; Maresca, K. Unpublished results.
(26) Romero, J.; Dura´n, M. L.; Rodr´ıguez, R.; Garc´ıa-Va´zquez, J. A.; Sousa,
A.; Rose, D. J.; Zubieta, J. Inorg. Chim. Acta, in press.
(27) Brown, M. A.; Tuck, D. G.; Wells, E. J. Can. J. Chem. 1996, 74,
1535.
(29) Bertel, N.; Notlemeyer, M.; Roesky, H. W. Z. Anorg. Allg. Chem.
1990, 588, 102.
(30) Annan, T. A.; Kumar, R.; Mabrouk, H. E.; Tuck, D. G.; Chadha, R.
K. Polyhedron 1989, 8, 865.
(31) Rose, D. J.; Zubieta, J.; Fischman, A. J.; Hillier, S.; Babich, J. W.
Unpublished results.
(32) Bossek, U.; Hanke, D.; Wieghardt, K. Polyhedron 1993, 12, 1.
(28) Rodriguez, A.; Romero, J.; Garc´ıa-Va´zquez, J. A.; Sousa, A.; Zubieta,
J.; Rose, D.; Maresca, K. Inorg. Chim. Acta, in press.

1298 Inorganic Chemistry, Vol. 38, No. 6, 1999
Pe´rez-Lourido et al.
the 2.963(2) Å In-P bond length of 2 represents approximately
0.1-0.2 of a bond according to valence sum calculations,
suggesting a negligible interaction between the metal and this
donor group. The highly distorted geometries associated with
all of the compounds of this study, in contrast to the more
uniform bond length distributions exhibited by six-coordinate
compounds with {InS3N3} cores, suggest that the origin of this
characteristic is steric, reflecting the constraints both of the
chelate rings and of the sterically demanding phosphine groups.
and solid state structures of 2, an observation which may reflect
the relative ease of bond breaking and rearrangement suggested
by the anomalous In-P bond distances in the solid state. The
electrochemical synthesis also affords the first example of a six-
coordinate In(III)-thiolate complex anion in compound 4. There
is only one other structurally characterized example of an In-
thiolate complex anion, the four-coordinate [BrIn(SPh)3]-
species. Since 4 could be prepared only by electrochemical
methods, we are investigating these for the preparation of other
complex ions of the In(III)-thiolate and Ga(III)-thiolate
families.
Conclusions
The isolation of 1-4 demonstrates that electrochemical
oxidation of In in the presence of thiolate ligands affords a facile
method for the preparation of In-thiolates. With the exception
of compound 4, monophasic materials were obtained in high
yield. Compounds 1, 2, and 4 represent the first structurally
characterized compounds of In with mixed thiolate-sulfur/
phosphine donors. The anomalously long In-P bond distances
associated with these compounds appear to reflect steric
constraints, as do the highly irregular geometries in general. A
curious feature of the chemistry is the variance of the solution
Acknowledgment. We thank the Xunta de Galicia (Spain)
(Xuga 20910B93) and the Petroleum Research Fund (PRF-
30651-AC5,3) for financial support.
Supporting Information Available: Tables in CIF format provid-
ing atomic positional parameters, bond distances and angles, anisotropic
thermal parameters and calculated hydrogen atoms positions for 1, 2,
and 4. This material is available free of charge via the Internet at
http://pubs.acs.org.
IC980282S