Zinc(II), cadmium(II), mercury(II), and ethylmercury(II) complexes of phosphinothiol ligands

Article abstract of DOI:10.1021/ic7005925

Neutral zinc, cadmium, mercury(II), and ethylmercury(II) complexes of a series of phosphinothiol ligands, Ph_nP(C₆H ₃(SH-2)(R-3))_3-n (n = 1, 2; R = H, SiMe₃) have been synthesized and characterized by IR and NMR (¹H, ¹³C, and ³¹P) spectroscopy, FAB mass spectrometry, and X-ray structural analysis. The compounds [Zn{PhP(C₆H₄S-2)₂}] (1) and [Cd{Ph₂PC₆H₄S-2}₂] (2) have been synthesized by electrochemical oxidation of anodic metal (zinc or cadmium) in an acetonitrile solution of the appropriate ligand. The presence of pyridine in the electrolytic cell affords the mixed complexes [Zn{PhP(C₆H ₄S-2)₂}(py)] (3) and [Cd{PhP(C₆H ₄S-2)₂}(py)] (4). [Hg{Ph₂PC₆H ₄S-2}₂] (5) and [Hg{Ph₂PC₆H ₃(S-2)(SiMe₃-3)}₂] (6) were obtained by the addition of the appropriate ligand to a solution of mercury(II) acetate in methanol in the presence of Methylamine. [EtHg{Ph₂PC ₆H₄S-2}] (7), [EtHg{Ph₂P(O)C₆H ₃(S-2)(SiMe₃-3)}] (8), [{EtHg}₂{PhP(C ₆H₄S-2)₂}] (9), and [{EtHg} ₂{PhP(C₆H₃(S-2)(SiMe₃-3)) ₂}] (10) were obtained by reaction of ethylmercury(II) chloride with the corresponding ligand in methanol. In addition, in the reactions of EtHgCl with Ph₂PC₆H₄SH-2 and with the potentially tridentate ligand PhP(C₆H₃(SH-2)(SiMe₃-3)) ₂, cleavage of the Hg-C bond was observed with the formation of [Hg{Ph₂PC₆H₄S-2}₂] (5) and [Hg(EtHg)₂{PhP(O)(C₆H₃(S-2)(SiMe ₃-3))₂}₂] (11), respectively, and the corresponding hydrocarbon. The crystal structures of [Zn₃{PhP(C ₆H₄S-2)₂}₂{PhP(O)(C ₆H₄S-2)₂}] (1*), [Cd₂{Ph ₂PC₆H₄S-2}₃{Ph₂P(O)C ₆H₄S-2}] (2*), 3, 5, 6, [EtHg{Ph₂P(O) C₆H₄S-2}] (7*), 8, 9, [{EtHg}₂{PhP(O) (C₆H₃(S-2)(SiMe₃-3))₂}] (10*), and 11 are discussed. The molecular structures of 1, 2, 4, 7, and 10 have also been studied by means of density functional theory (DFT) calculations.

Full text of DOI:10.1021/ic7005925

Inorg. Chem. 2008, 47, 2121-2132
Zinc(II), Cadmium(II), Mercury(II), and Ethylmercury(II) Complexes of
Phosphinothiol Ligands
P. Fernández,† A. Sousa-Pedrares,† J. Romero,† J. A. García-Vázquez,*,† A. Sousa,†
and P. Pérez-Lourido‡
Departamento de Química Inorgánica, UniVersidad de Santiago de Compostela, 15782, Santiago
de Compostela, Spain, and Departamento de Química Inorgánica, UniVersidad de Vigo,
36200 Vigo, Spain
Received March 29, 2007
Neutral zinc, cadmium, mercury(II), and ethylmercury(II) complexes of a series of phosphinothiol ligands,
PhnP(C6H3(SH-2)(R-3))3-n (n ) 1, 2; R ) H, SiMe3) have been synthesized and characterized by IR and NMR
(1H, 13C, and 31P) spectroscopy, FAB mass spectrometry, and X-ray structural analysis. The compounds
[Zn{PhP(C6H4S-2)2}] (1) and [Cd{Ph2PC6H4S-2}2] (2) have been synthesized by electrochemical oxidation of anodic
metal (zinc or cadmium) in an acetonitrile solution of the appropriate ligand. The presence of pyridine in the electrolytic
cell affords the mixed complexes [Zn{PhP(C6H4S-2)2}(py)] (3) and [Cd{PhP(C6H4S-2)2}(py)] (4). [Hg{Ph2PC6H4S-
2}2] (5) and [Hg{Ph2PC6H3(S-2)(SiMe3-3)}2] (6) were obtained by the addition of the appropriate ligand to a solution
of mercury(II) acetate in methanol in the presence of triethylamine. [EtHg{Ph2PC6H4S-2}] (7), [EtHg{Ph2P(O)C6H3(S-
2)(SiMe3-3)}] (8), [{EtHg}2{PhP(C6H4S-2)2}] (9), and [{EtHg}2{PhP(C6H3(S-2)(SiMe3-3))2}] (10) were obtained by reaction
of ethylmercury(II) chloride with the corresponding ligand in methanol. In addition, in the reactions of EtHgCl with
Ph2PC6H4SH-2 and with the potentially tridentate ligand PhP(C6H3(SH-2)(SiMe3-3))2, cleavage of the Hg-C bond
was observed with the formation of [Hg{Ph2PC6H4S-2}2] (5) and [Hg(EtHg)2{PhP(O)(C6H3(S-2)(SiMe3-3))2}2] (11),
respectively, and the corresponding hydrocarbon. The crystal structures of [Zn3{PhP(C6H4S-2)2}2{PhP(O)(C6H4S-
2)2}] (1*), [Cd2{Ph2PC6H4S-2}3{Ph2P(O)C6H4S-2}] (2*), 3, 5, 6, [EtHg{Ph2P(O)C6H4S-2}] (7*), 8, 9, [{EtHg}2{PhP(O)(C6H3(S-
2)(SiMe3-3))2}] (10*), and 11 are discussed. The molecular structures of 1, 2, 4, 7, and 10 have also been studied
by means of density functional theory (DFT) calculations.
Introduction
sulfur atoms is related to mercury-cysteine thionato interac-
tions in the toxicological behavior of this metal,8 in detoxi-
fication of the mercury by metallothioneins9 in a DNA-
binding protein,10 and in mercury reductase and related
proteins.6,11
Zinc and cadmium metals with thiolate ligands usually
form polymeric species as a consequence of the tendency
of thiolato ligands to bridge metal centers. Thus, neutral
thiolate [M(SR)2] complexes of zinc or cadmium generally
The chemistry of metal-sulfur complexes has attracted a
great deal of interest over the past decade because of the
potential relevance of such compounds to active sites in
metalloenzymes and their ability to adopt geometries of
variable nuclearity and great structural complexity.1–7 The
chemistry of mercury complexes containing ligands bearing
* To whom correspondence should be addressed. Tel: +34-981563100,
ext 14950. Fax: + 34-(9)81 594912. E-mail: qijagv@usc.es.
†
Universidad de Santiago de Compostela.
Universidad de Vigo.
‡
(8) Cheesman, B. V.; Arnold, A. P.; Rabenstein, D. L. J. Am. Chem. Soc.
1988, 110, 6359–6364.
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(4) Krebs, B.; Henkel, G. Angew. Chem., Int. Ed. Engl. 1991, 30, 769–
788.
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260, 5342–5350. (b) Stillman, M. J.; Law, A. Y. C.; Szymanska, J. A.
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10.1021/ic7005925 CCC: $40.75
Published on Web 02/14/2008
2008 American Chemical Society
Inorganic Chemistry, Vol. 47, No. 6, 2008 2121

Fernández et al.
form infinite lattices with bridging ligands and tetrahedral
metal centers.12 The polymeric nature of these systems leads
to insoluble compounds that are difficult to isolate as crystals
suitable for X-ray studies, and they are also unsuitable as
precursors for metal calcogenides under typical metal-organic
chemical vapor deposition (MOCVD) conditions. The ag-
gregation phenomena can be controlled by steric constraints
produced by appropriate ligand design13 or by saturation of
the metal coordination sphere with other donor atoms in
addition to the thiolate group. In the specific cases of
multidentate mixed-donor ligands, complex stability is
enhanced by chelating effects. In previous studies, we have
used this strategy for the synthesis of monomeric14 and
dimeric compounds15 of zinc and cadmium with sterically
hindered heterocyclic thiones.
Inorganic mercury(II) complexes exhibit a wide range of
coordination numbers and environments, while organomer-
cury [RHg]+ compounds (e.g., ethylmercury(II) complexes)
almost invariably contain the metal in a linear two coordinate
geometry16 with, in some cases, additional weak secondary
bonds.17 It is well-known that the metal–carbon bond in
[RHg]+ compounds is rather stable,18 and this stability under
physiological conditions, along with its lipophilic nature,
leads to a strong tendency toward bioaccumulation in the
food chain. However, the bacterial enzyme organomercurial
lyase (MerB) catalyzes the protonolytic cleavage of [RHg]+
cations to yield the parent hydrocarbon and inorganic Hg(II),
which is complexed through thiolate groups.19 It seems that
the initial formation of an enzyme–substrate complex in the
organomercurial lyase active site polarizes the Hg-C bond,
favoring attack by the electrophilic agent and cleavage of
the bond itself. Some recent studies have confirmed that the
activation of the Hg-C bond and its cleavage is related to
the coordination of mercury by strongly donating ligands
such as N(CH2CH2PPh2)3,20 2-(2′-pyridyl)quinoxaline,21
diphenyldithiophosphinic acid,22 and thioethers.23
Polydentate ligands incorporating both thiolate and tertiary
phosphine donor atoms form stable complexes with a wide
range of metals including lanthanides and transition and post-
transition metals. To date, most studies have focused on
bidentate Ph2PCH2CH2SH or Ph2PC6H4SH-2 ligands,24 while
the potentially tridentate ligand PhP(C6H4SH-2)2 has received
less attention. Some studies on the chemistry of zinc and
cadmium with these ligands have already been published,25
but mercury(II) or ethylmercury(II) complexes with phos-
phinothiol ligands have not been reported.
In this paper, we describe the electrochemical synthesis
and characterization of new zinc and cadmium compounds
with arenephosphinothiol ligands in which the polydentate
behavior of the ligand and the presence of additional
coligands allows the preparation of low molecular species.
In addition, the chemistry of Hg(II) and [EtHg]+ with these
ligands is also explored. In the reaction of EtHgCl with some
of these ligands, the initial products are unstable in solution
and undergo oxidation and cleavage processes leading to the
formation of inorganic mercury(II) thiolates.
Experimental Section
General Considerations. All manipulations were carried out
under an inert atmosphere of dry nitrogen. Zinc and cadmium
(Aldrich Chemie) were used as plates (ca. 2 × 2 cm). Mercury
acetate and ethylmercury chloride (Aldrich Chemie) were used as
provided. All other reagents were used as supplied. Synthesis of
ligands was carried out using slight modifications of the standard
literature procedure.26 Elemental analyses were performed using a
Perkin-Elmer 240B microanalyzer. IR spectra were recorded as KBr
1
discs using a Perkin-Elmer spectrophotometer. H, 13C, and 31P
spectra were recorded on a Bruker WM 350 MHz instrument using
CDCl3 as solvent. 1H NMR and 13C chemical shifts were determined
against trimethylsilane (TMS) as internal standard and those of 31
P
against 85% H3PO4. The mass spectra (FAB) were recorded on a
Micromass Autospec spectrometer using 3-nitrobenzyl alcohol as
the matrix material.
Electrochemical Synthesis of Zinc and Cadmium Com-
pounds. The zinc and cadmium complexes 1–4 were obtained using
an electrochemical procedure.27 The cell consisted of an anode
suspended from a platinum wire, and the cathode was also a
platinum wire. The ligand was dissolved in acetonitrile and a small
amount of tetramethylammonium perchlorate was added to the
solution as a supporting electrolyte (Caution: perchlorate com-
pounds are potentially explosiVe and should be handled in small
quantities and with great care). For the synthesis of mixed
complexes, pyridine was also added to the solution. Applied
voltages of 10–15 V allowed sufficient current flow for smooth
dissolution of the metal. During electrolysis, nitrogen was bubbled
(12) (a) Craig, D. C.; Dance, I. G.; Garbutt, R. G. Angew. Chem., Int. Ed.
Engl. 1986, 98, 178–179. (b) Dance, I. G.; Garbutt, R. G.; Graig, D. C.;
Scudder, M. L. Inorg. Chem. 1987, 26, 4057–4064.
(13) Bochman, M.; Bwembya, G.; Grinter, R. R.; Lu, J.; Webb, K.;
Willianson, D. J.; Hursthouse, M. H.; Mazid, M. Inorg. Chem. 1993,
32, 532–537.
(14) Castro, R.; Durán, M. L.; García-Vázquez, J. A.; Romero, J.; Sousa,
A.; Castiñeiras, A.; Hiller, W.; Strahle, J. Z. Naturforsch. 1992, 47b,
1067–1074.
(15) Castro, R.; García-Vázquez, J. A.; Romero, J.; Sousa, A.; Castiñeiras,
A.; Hiller, W.; Strahle, J. Inorg. Chim. Acta 1993, 211, 47–54.
(16) Wardell, J. L. In ComprehensiVe Organometallic Chemistry; Wilkin-
son, G., Ed.; Pergamon Press: Oxford, U.K., 1982; Vol. 2 p 901.
(17) (a) Casas, J. S.; García-Tasende, M. S.; Sordo, J. Coord. Chem. ReV.
1999, 193–195, 283–359. (b) Holloway, C. E.; Melnik, M. J.
Organomet. Chem. 1995, 495, 1–31. (c) Tallon, J.; García-Vázquez,
J. A.; Romero, J.; Louro, M. S.; Sousa, A. Polyhedron 1995, 114,
2309–2317. (d) Atwood, J. O.; Berry, D. E.; Stobard, S. R;.;
Zoworotko, M. J. Inorg. Chem. 1983, 22, 3480–3482. (e) Black, D.
St.; Deacon, G. B.; Edwards, G. L.; Gatehouse, M. Aust. J. Chem.
1993, 46, 1323–1326.
(22) Casas, J. S.; García-Tasende, M. S.; Sánchez, A.; Sordo, J.; Vázquez-
López, E. M. Inorg. Chim. Acta 1997, 256, 211–216.
(23) Wilhelm, M.; Deeken, S.; Berssen, E.; Saak, W.; Lützen, A.; Koch,
R.; Strasdeit, H. Eur. J. Inorg. Chem. 2004, 2301–2312.
(24) Dilworth, J. R.; Wheatley, N. Coord. Chem. ReV. 2000, 199, 89–158,
and references therein.
(18) Bloodworth, A. J. In The Chemistry of Mercury; McAuliffe, C. A.,
Ed.; Mc Millan Press: London, 1977; Chapter 22, pp 209–233.
(19) Moore, M. J.; Distefano, M. D.; Zydowsky, L. D.; Cummings, R. T.;
Walsh, C. T. Acc. Chem. Res. 1990, 23, 301–308.
(25) Pérez-Lourido, P.; Romero, J.; García-Vázquez, J. A.; Sousa, A.;
Maresca, K.; Zubieta, J. Inorg. Chem. 1999, 38, 3709–3715.
(26) Block, E.; Ofori-Okai, G.; Zubieta, J. J. Am. Chem. Soc. 1989, 111,
2327–2329.
(27) (a) Tuck, D. G. Pure Appl. Chem. 1979, 51, 2005–2018. (b)
Chakravorti, M. C.; Subrahmanyam, G. V. B. Coord. Chem ReV. 1994,
135–136, 65–92. (c) Vecchio-Sadus, A. M. J. Appl. Electrochem. 1993,
23, 401–416.
(20) Barbaro, P.; Cecconi, F.; Ghilardi, C. A.; Midollini, S.; Orlandini,
A.; Vacca, A. Inorg. Chem. 1994, 33, 6163–6170.
(21) Garoufis, A.; Perlepes, S. S.; Scheiber, A.; Bau, R.; Hadjiliadis, N.
Polyhedron 1996, 15, 177–180.
2122 Inorganic Chemistry, Vol. 47, No. 6, 2008

Complexes of Phosphinothiol Ligands
through the solution to provide an inert atmosphere and also to stir
the reaction mixture. In these conditions, the electrochemical cell
can be summarized as
of a solution of mercury acetate (for the synthesis of complexes 5
and 6) or a solution of ethylmercury(II) chloride in the same solvent
(for complexes 7–10).
Synthesis of [Hg{Ph2PC6H4S-2}2] (5). To a stirred solution of
Ph2PC6H4SH-2 (0.10 g, 0.34 mmol) and NEt3 (0.048 mL, 0.35
mmol) in methanol (25 mL) was added slowly a solution of
mercuric acetate (0.054 g, 0.17 mmol) in methanol (15 mL) at room
temperature. In a few minutes, a white solid was formed. The solid
was filtered off, washed with methanol, and dried in Vacuo. Anal.
Calcd for C36H28P2S2Hg (mol wt 788.1): C, 54.82; H, 3.58; S, 8.11.
Found: C, 55.12; H, 3.61; S, 7.88%. IR (KBr, cm-1): 1573(m),
1478(m), 1437(s), 1415(m), 1093(s), 743(s), 695(s), 523(s), 502(m),
Pt(-)/CH3CN + PhnP(C6H3(SH-2)(R-3))3 - n/M(+); M ) Zn,Cd
(1)
Synthesis of [Zn{PhP(C6H4S-2)2}] (1). Electrochemical oxida-
tion of a zinc anode in a solution of PhP(C6H4SH-2)2 (0.122 g,
0.374 mmol) in acetonitrile (50 mL) at 12 V, 10 mA, for 2 h caused
24.0 mg of zinc to be dissolved; Ef ) 0.49 mol F-1. During the
electrolysis, hydrogen was evolved at the cathode, and at the end
of the reaction, a white crystalline solid appeared at the bottom of
the vessel. The solid was filtered off, washed with acetonitrile and
ether, and dried under vacuum. Anal. Calcd for C18H13PS2Zn (mol
wt 387.9): C, 55.67; H, 3.38; S, 16.48. Found: C, 54.97; H, 3.50;
S, 15.98%. IR (cm-1): 1574(m), 1440(s), 1421(s), 1253(m), 1101(s),
1
470(m). H NMR (CDCl3, ppm): δ 7.7–6.9 (m, 28H). 13C NMR
(CDCl3, ppm): δ 134–124. 31P NMR (CDCl3, ppm): δ 33.5. Slow
concentration of the mother liquor gave crystals that were suitable
for X-ray studies.
Synthesis of [Hg{Ph2PC6H3(S-2)(SiMe3-3)}2] (6). To a solution
of Ph2PC6H3(SH-2)(SiMe3-3) (0.050 g, 0.136 mmol) and NEt3
(0.020 g, 0.136 mmol) in methanol (25 mL) was added a solution
of mercury acetate (0.021 g, 0.066 mmol) in methanol (5 mL). The
solution was stirred at room temperature for several hours, but a
solid did not separate. The solvent was removed, and the resulting
solid was dissolved in chloroform to yield a compound characterized
as [Hg{Ph2PC6H3(S-2)(SiMe3-3)}2] · CHCl3. Anal. Calcd for
C43H45Cl3P2S2Si2Hg (mol wt 1050.1): C, 49.14, H, 4.32; S, 6.10.
Found: C, 50.87; H, 4.58; S, 6.58. IR 3053(m), 2949(m), 2893(m),
1555(m), 1482(m), 1436(m), 1352(s), 1243(m), 1096(m), 853(s),
1
744(s), 694(m). H NMR (CDCl3, ppm): δ 7.9–6.6 (m, 13H). 31P
NMR (CDCl3, ppm): δ 29.3. FAB MS: m/z 389 (ZnL+); 778
(Zn2L2+); 1167 (Zn3L3+). Crystals of [Zn3{PhP(C6H4S-
2)2}2{PhP(O)(C6H4S-2)2}] (1*) suitable for X-ray analysis were
obtained by concentration of the mother liquor.
Synthesis of [Cd{Ph2PC6H4S-2}2] (2). A similar experiment (13
V, 10 mA, 2 h) with cadmium as the anode and Ph2PC6H4SH-2
(0.220 g, 0.748 mmol) in acetonitrile (50 mL) dissolved 40 mg of
metal (Ef ) 0.47 mol F-1). At the end of the electrolysis, the white
crystals deposited in the cell were recovered, washed with cool
acetonitrile and diethyl ether, and dried under vacuum. Anal. Calcd
for C36H28P2S2Cd (mol wt 700.0): C, 61.71; H, 4.03; S, 9.13. Found:
C, 62.80; H, 4.20; S, 9.33%. IR (KBr, cm-1): 1570(m), 1479(m),
1435(s), 1418(m), 1247(m), 1094(m), 743(s), 693(s). 1H NMR
(CD3Cl, ppm): δ 8.0–6.8 (m, 28H). 31P NMR (CDCl3, ppm): δ
35.2. Crystals of [Cd2{Ph2PC6H4S-2}3{Ph2P(O)C6H4S-2}]·CH3CN
(2*) suitable for X-ray studies were obtained by concentration of
the mother liquor.
Synthesis of [Zn{PhP(C6H4S-2)2}(py)] (3). Electrolysis of an
acetonitrile solution (50 mL) containing PhP(C6H4SH-2)2 (0.124
g, 0.378 mmol) and pyridine (0.031 g, 0.380 mmol) using a current
of 10 mA (12 V) for 2 h led to the dissolution of 25 mg of zinc (Ef
) 0.50 mol F-1). The crystalline solid obtained was washed with
acetonitrile and ether and dried under vacuum. Anal. Calcd for
C23H18NPS2Zn·CH3CN (mol wt 508.0): C, 59.05; H, 4.17; S, 12.59;
N, 5.51. Found: C, 58.55; H, 4.06; S, 12.66, N, 5.31%. IR (cm-1):
1605(m), 1573(m), 1447(s), 1438(s), 1417(s), 1247(m), 1220(m),
1156(s), 1134(s), 998(m), 743(s), 665(m). 1H NMR (CDCl3, ppm):
δ 8.0–6.8(m, 18 H). 31P NMR (CDCl3, ppm): δ 39.9. FAB MS:
m/z 389 (ZnL+); 778 (Zn2L2+); 1167 (Zn3L3+). Crystals of
[Zn2{PhP(C6H4S-2)2}2(py)2] · 2CH3CN suitable for X-ray studies
were obtained directly from the cell.
Synthesis of [Cd{PhP(C6H4S-2)2}(py)] (4). The same procedure
was used for the synthesis of this compound. A solution of the
ligand (0.122 g, 0.374 mmol) and pyridine (0.030 g, 0.379 mmol)
in acetonitrile (50 mL) was electrolyzed at 10 mA during 1 h, and
21 mg of the metal was dissolved from the anode (Ef ) 0.50 mol
F-1). Anal. Calcd for C23H18NPS2Cd (mol wt 516.9): C, 53.54; H,
3.51; S, 12.41; N, 2.71. Found: C, 53.84; H, 3.80; S, 12.50, N,
2.90%. IR (KBr, cm-1): 1630(m), 1581(m), 1437(m), 1418(m),
1227(m), 1121(s), 1107(s), 997(m), 745(s), 694(m).1H NMR
(CDCl3, ppm): δ 8.0–6.8 (m, 18 H). 31P NMR (CDCl3, ppm): δ
39.9. FAB MS: m/z 436 (CdL+), 872 (Cd2L2+).
1
743(s), 692(s). H NMR (CDCl3, ppm): δ 7.8–6.6 (m, 26H), 0.42
(s, 18H). 13C NMR (CDCl3, ppm): δ 138–128. 31P NMR (CDCl3,
ppm): 36.1. Crystals of [Hg{Ph2PC6H3(S-2)(SiMe3-3}2]·0.75CH2Cl2
suitable for X-ray studies were obtained by crystallization from
methanol/dichloromethane.
Synthesis of [EtHg{Ph2PC6H4S-2}] (7). To a refluxing solution
of Ph2PC6H4SH-2 (0.055 g, 0.187 mmol) and NEt3 (0.026 mL,
0.186 mmol) in methanol (25 mL) was added a solution of
ethylmercury(II) chloride (0.055 g, 0.18 mmol) in methanol (15
mL). The solution was stirred at room temperature, and within a
few minutes a white solid had formed. The solid was filtered off,
washed, dried, and characterized as [EtHg{Ph2PC6H4S-2}] (7).
Anal. Calcd for C20H19PSHg (mol wt 524.0); C, 45.80; H, 3.65; S,
6.10. Found: C, 45.67; H, 3.53, S, 5.96.%. IR (KBr, cm-1): 3067(m),
3054(m), 2967(m), 2935(m), 2850(m), 1583(m), 1477(m) 1433(s),
1419(m), 1396(m), 1170(s), 1094(s), 753(s), 744(s), 719(s), 541(m),
500(m), 466(m). 1H NMR (CDCl3, ppm): δ 7.9–6.6 (m, 14H), 1.8
(q, 2H), 1.5 (t, 3H). 13C NMR (CDCl3, ppm): δ 134–124, 25.1,
15.0. 31P NMR (CDCl3, ppm): δ 17.7. FAB MS: m/z 522 (M+).
The mother liquor was left to stand and slowly crystallize for several
months. Crystals suitable for X-ray studies formed and were
identified as [Hg{Ph2PC6H4S-2}2] (5) and [EtHg{Ph2P(O)C6H4S-
2}] (7*).
Synthesis of [EtHg{Ph2P(O)C6H3(S-2)(SiMe3-3)}] (8). Com-
pound 8 was synthesized following a similar procedure as that for
7, starting from Ph2P(O)C6H3(SH-2)(SiMe3-3) (0.164 g, 0.43 mmol),
NEt3 (0.057 mL, 0.43 mmol) in methanol (20 mL), and EtHgCl
(0.115 g, 0.43 mmol) in methanol (2 mL). The mixture was stirred,
and a white solid formed. The solid was isolated, dried, and
characterized as [EtHg{Ph2P(O)C6H3(S-2)(SiMe3-3)}] (8). Anal.
Calcd for C23H27POSSiHg (mol wt 613.1): C, 45.02; H, 4.60; S
5.21. Found: C, 44.95; H, 4.43; S, 5.26%. IR (KBr, cm-1): 3043(m),
2958(s) 2854(m), 1546(m), 1434(s), 1356(s), 1246(m), 1174(s),
1117(m), 1039(m), 856(s), 840(s), 749(m), 691(s). 1H NMR (CDCl3,
Synthesis of Mercury Compounds. Mercury(II) and ethylm-
ercury(II) complexes were obtained by slow addition to a stirred
solution of the appropriate ligand and triethylamine in methanol
ppm): δ 7.8–6.5 (m, 13H), 1.8 (q, 2H), 1.4 (t, 3H), 0.5 (s, 9H). 13
C
NMR (CDCl3, ppm): δ 138–124, 25.4, 14.4, -0.86. 31P NMR
Inorganic Chemistry, Vol. 47, No. 6, 2008 2123

Fernández et al.
(CDCl3, ppm): δ 33.3. FAB MS: m/z 612 (M+). Slow concentration
of the mother liquor gave crystals of [EtHg{Ph2P(O)C6H3(S-
2)(SiMe3-3}]·CH3OH suitable for X-ray studies.
larger P-Cd distance of the carrier phosphorus support this
statement. The large Uiso suggests that this position is only partially
occupied by an oxygen atom. The occupancy parameter for this
oxygen was explored using two different approaches. One of them
was to refine simultaneously the occupancy and the Uiso. Upon
convergence, the occupancy parameter obtained was 0.675 and the
Uiso was 0.09256. A second approach was to fix the Uiso at a value
of 0.045, which is comparable to the value found in other complexes
and to the value of the neighbor atoms. The occupancy parameter
obtained was 0.65. So, the second approach should be preferred.
This indicates that only the 65% of the molecules in the crystal
structure are oxidized. In the remaining nonoxidized 35% of the
molecules, the phosphorus atoms are expected to be coordinated
to the cadmium atoms. However, the lack of residual electronic
density in the vicinity of the phosphorus atom suggests that this
unoxidized phosphorus atom is not coordinated to the cadmium
atom. This does not seem too likely. All the residual electronic
density is around the cadmium atoms so the possibility of further
disorder could not be explored. In conclusion, we believe that the
unoxidized phosphorus atom of the remaining 35% of the molecules
present in the crystal structure should be coordinated to the cadmium
atom, but this cannot be proven with the available crystallographic
data. Therefore, only the oxidized units will be discussed.
Synthesis of [{EtHg}2{PhP(C6H4S-2)2} (9). Compound 9 was
synthesized following a similar procedure as that for 7 starting from
PhP(C6H4SH-2)2 (0.060 g, 0.184 mmol), Et3N (0.051 mL, 0.36
mmol) in methanol (30 mL), and EtHgCl (0.100 g, 0.370 mmol)
in methanol (5 mL). A white solid formed immediately. The solid
was isolated, washed with methanol, dried, and characterized as 9.
Anal. Calcd for C22H23PS2Hg2 (mol wt 784.0): C, 33.75; H, 2.94;
S, 8.18. Found: C, 33.55; H, 2.93; S, 8.061%. IR (KBr, cm-1):
3067(m), 3047(m), 3006(m), 2959(m), 1570(m), 1442(s), 1423(s),
1247(m), 1090(s), 749(s), 695(m). 1H NMR (CDCl3, ppm): δ
7.6–6.6 (m, 13H), 1.5 (q, 4H), 1.3 (t, 6H). 13C NMR (CDCl3, ppm):
δ 147–125, 25.8(s), 14.9(s). 31P(CDCl3, ppm): δ 18.7. FAB MS:
m/z 784(M+); 522 (M - EtHg). Crystallization of the initial product
from dichloromethane/methanol gave crystals suitable for X-ray
diffraction.
Synthesis of [{EtHg}2{PhP(C6H3(S-2)(SiMe3-3))2}] (10). Com-
pound 10 was synthesized following a similar procedure as that
for 7 , starting from PhP{C6H3(SH-2)(SiMe3-3)}2 (0.080 g, 0.21
mmol), EtN3 (0.055 mL, 0.38 mmol) in methanol (20 mL), and
EtHgCl (0.105 g, 0.396 mmol) in methanol (5 mL). After a few
minutes, a white solid formed, and this was filtered off, washed
with diethyl ether, dried under vacuum, and characterized as 10.
Anal. Calcd for C28H39PS2Si2Hg2 (mol wt 928.1): C, 36.28; H, 4.21;
S, 6.91. Found: C, 36.39; H, 4.30; S, 6.44%. IR 3039(m), 2968(m),
2939(m), 1586(m), 1435(s), 1395(m), 1356(s), 1244(m), 1106(s),
846(s), 755(s), 697(m). 1H NMR (CDCl3, ppm): δ 7.9–6.6 (m, 11H),
1.8 (q, 4H), 1.4 (t, 6H), 0.4 (s, 18H). FAB MS: m/z 928 (M+); 699
(M - EtHg). Slow crystallization over several months from the
mother liquor gave crystals of [{EtHg}2{PhP(O)(C6H3(S-2)(SiMe3-
3))2}] (10*) and [Hg(EtHg)2{PhP(O)(C6H3(S-2)(SiMe3-3))2}2] (11)
suitable for X-ray diffraction.
For all structures, except for compound 6, non-hydrogen atoms
were anisotropically refined. The intensity data set for compound
7* was too weak to allow anisotropic refinement of all non-
hydrogen atoms. In this case, only the heavy atoms (Hg, S, and P)
were anisotropically refined. Due to the poor quality of the data
for compound 7*, geometrical parameters are not discussed, and
these data will only be used to show the connectivity around the
metal center. In the last cycles of refinement of all structures a
weighting scheme was used with weights calculated using the
2
2
following formula w ) 1/[σ2(Fo ) + (aP)2 + bP], where P ) (Fo
+ 2Fc2)/3.
X-ray Crystallographic Studies. Intensity data sets for all
compounds were collected using a Smart-CCD-1000 Bruker dif-
fractometer (Mo KR radiation, λ ) 0.71073 Å) equipped with a
graphite monochromator. All crystals were measured at 293 K
except compound 1, which was measured at 150 K. The ω scan
technique was employed to measure intensities in all crystals.
Decomposition of the crystals did not occur during data collection.
The intensities of all data sets were corrected for Lorentz and
polarization effects. Absorption effects in all compounds were
corrected using the program SADABS.28 The crystal structures of
all compounds were solved by direct methods. Crystallographic
programs used for structure solution and refinement were those of
SHELX97.29 Scattering factors were those provided with the
SHELX program system. Missing atoms were located in the
difference Fourier map and included in subsequent refinement
cycles. The structures were refined by full-matrix least-squares
refinement on F2. Hydrogen atoms were placed geometrically and
refined using a riding model with Uiso constrained at 1.2 (for
nonmethyl groups) and 1.5 (for methyl groups) times Ueq of the
carrier C atom. In compound 2*, the refinement of the oxygen O1
as one full oxygen atom gives a Uiso too large in comparison to the
rest of the atoms in the complex. However, from a chemical point
of view, we do not have any doubt that this position is actually
occupied by an oxygen atom. Besides, the P-O distance and the
Pertinent details of the data collections and structure refinements
are collected in Tables 1 and 2. Further details regarding the data
collections, structure solutions, and refinements are included in the
Supporting Information. ORTEP3 drawings30 with the numbering
schemes used are shown in Figures 1-3 and 5-9.
Crystallographic data (excluding structure factors) for the
structures reported in this paper have been deposited with the
Cambridge Crystallographic Data Centre as supplementary publica-
tion no. CCDC 642063–642072. Copies of the data can be obtained
free of charge on application to CCDC, 12 Union Road, Cambridge
CB21EZ,UK(fax:(/44)1223-336-033;e-mail:deposit@ccdc.cam.ac.uk).
Computational Methods. Geometry optimizations of the struc-
tures investigated in this study were carried out by density functional
theory (DFT) calculations, using the Gaussian03 package31 and the
X-ray crystallographic data as starting points. In particular, we
employed the B3LYP method, which combines Becke’s three-
(30) ORTEP3 for Windows. Farrugia, L. J. J. Appl. Crystallogr. 1997, 30,
565.
(31) Frisch, M. J.; Trucks, G. W.; Schlegel, H. B.; Scuseria, G. E.; Robb,
M. A.; Cheeseman, J. R.; Zakrzewski, V. G.; Montgomery, J. A.;
Stratmann, R. E. ; Burant, J. C. ; Dapprich, S.; Millam, J. M.; Daniels,
A. D.; Kudin, K. N.; Strain, M. C.; Farkas, O.; Tomasi, J.; Barone,
V.; Cossi, M.; Cammi, R.; Mennucci, B.; Pomelli, C.; Adamo, C.;
Clifford, S.; Ochterski, J.; Petersson, G. A.; Ayala, P. Y.; Cui Q.;
Morokuma, K.; Malick, D. K. ; Rabuck, A. D.; Raghavachari, K.;
Foresman, J. B.; Cioslowski, J.; Ortiz, J. V.; Stefanov, B. B.; Liu, G.;
Liashenko, A.; Piskorz, P.; Komaromi, I.; Gomperts, R.; Martin, R. L.;
Fox, D. J.; Keith, T.; Al-Laham, M. A.; Peng, C. Y.; Nanayakkara,
A.; Gonzalez, C.; Challacombe, M.; Gill, P. M. W.; Johnson, B. G.;
Chen, W.; Wong, M. W.; Andres, J. L.; Head-Gordon, M.; Replogle,
E. S.; Pople, J. A. Gaussian 98, Revision A.7; Gaussian, Inc.:
Pittsburgh PA, 1998.
(28) Sheldrick, G. M. SADABS: Program for absorption correction using
area detector data; University of Göttingen: Go¨ttingen, Germany,
1996.
(29) Sheldrick, G. M. SHELX97 [Includes SHELXS97, SHELXL97, CIFT-
AB] - Programs for Crystal Structure Analysis, Release 97-2; Institüt
für Anorganische Chemie der Universität: Göttingen, Germany, 1998.
2124 Inorganic Chemistry, Vol. 47, No. 6, 2008

Complexes of Phosphinothiol Ligands
Table 1. Summary of Crystallographic Data and Refinement for Zinc
values, along with the evolution of hydrogen at the cathode,
are compatible with the following mechanism:
and Cadmium Compounds
compound
1*
2*
3
Cathode: PhP(C6H4SH-2)2 + 2e-
f
empirical
formula
fw
C54H39P3OS6Zn3 C74H59Cd2NOP4S4 C50H42N4P2S4Zn2
{PhP(C6H4S-2)2}2- + H2
1185.23
1.01 × 0.19 ×
0.15
1455.14
0.30 × 0.22 ×
0.13
1019.80
0.31 × 0.13 ×
0.11
cryst size,
Anode: M f M2+ + 2e-
Solution: M2+ + {PhP(C6H4S-2)2}2-
mm3
temp, K
wavelength
cryst syst
space group
unit cell
dimens
a, Å
150(2)
293(2)
293(2)
f
0.71073
triclinic
j
P1
0.71073
monoclinic
P2(1)/n
0.71073
monoclinic
P2(1)/c
[M{PhP(C6H4S-2)2}] M ) Zn, Cd
A similar mechanism can be proposed for the synthesis
of metal complexes with the ligand Ph2PC6H4SH-2.
The spectroscopic data for 1–4 (Experimental Section) are
indicative of the presence of the coordinated phosphinothi-
olate ligands in the complexes. Slow concentration of the
mother liquors from the syntheses of complexes 1, 2, and 3
yielded crystals suitable for X-ray studies of [Zn3{PhP(C6H4S-
2)2}2{PhP(O)(C6H4S-2)2}] (1*), [Cd2{Ph2PC6H4S-2}3{Ph2-
P(O)C6H4S-2}]· CH3CN (2*), and [Zn2{PhP(C6H4S-2)2}2-
(py)2] · 2CH3CN (3). The structural resolutions of 1* and 2*
show the presence of both phosphinothiolate and oxophos-
phinothiolate forms of the ligand (Vide infra). The oxygen
in the oxophosphinothiolate moieties in 1* and 2* may
originate from the incorporation of adventitious oxygen from
the solvent during the crystallization process. Such facile
oxidations have been observed in other compounds contain-
ing this type of ligand.38
However, all efforts to isolate crystals of [Zn{PhP(C6H4S-
2)2}] (1), [Cd{Ph2PC6H4S-2}2] (2), and [Cd{PhP(C6H4S-
2)2}(py)] (4) were unsuccessful. For this reason, the structures
of these compounds were optimized by DFT calculations.
The results of these calculations are discussed below.
Description of Structures. Compounds 1*, 2*, and 3 were
studied by X-ray diffraction. The crystal parameters, experi-
mental details for data collection, and bond distances and
angles for these compounds are provided as Supporting
Information.
The molecular structure of [Zn3{PhP(C6H4S-2)2}2{PhP-
(O)(C6H4S-2)2}] (1*) is shown in Figure 1, together with
the atomic numbering scheme adopted. Selected bond
distances and angles with estimated deviations are listed in
Table 3.
The structure consists of trimeric species in which three
zinc atoms are coordinated to two bis(2-mercaptophenyl)phe-
nylphosphine ligands and one bis(2-mercaptophenyl)pheny-
loxophosphine ligand, with three thiolate sulfur atoms of two
different ligands bridging the zinc atoms. This gives rise to
the formation of a central six-membered [Zn3S3] ring. The
ligands are all tridentate, but they show different coordination
behavior. A first ligand acts as an OS2 donor and is
coordinated to the Zn(1) atom through O(1) and S(1) and to
Zn(2) through S(2). A second ligand behaves as a P(µ-S)2
donor with the P(2) atom coordinated to Zn(2) and the two
sulfur donors, S(3) and S(4), forming a bridge between two
11.292(11)
14.233(14)
20.05(2)
109.455(15)
97.335(16)
99.492(16)
2938(5)
2
22.1791(18)
12.8523(10)
24.002(2)
90.00
101.395(2)
90.00
6706(9)
4
0.889
11.283(2)
18.627(4)
23.290(4)
90.00
103.548(4)
90.00
4758.9(15)
4
1.290
b, Å
c, Å
R, deg
ꢁ, deg
γ, deg
vol, Å3
Z
µ, mm-1
no. reflns
collected
no.
1.544
32654
23237
30492
11882
7976
9748
independent
reflns
[R(int) ) 0.0280] [R(int) ) 0.0716] [R(int) ) 0.0427]
data/restraints/ 11882/0/604
params
7976/0/776
9748/ 0/561
GOF
1.056
0.790
1.049
final R indices R ) 0.0310
[I > 2σ(I)] wR ) 0.0794
R ) 0.0415
Rw ) 0.0486
R ) 0.0380
wR ) 0.0817
parameter nonlocal hybrid exchange potential32 with the nonlocal
correlation functional of Lee, Yang, and Parr.33 The basis set used
in the calculations was the standard LanL2DZ, which consists of
the Dunning/Huzinaga full double-ꢀ (D95)34 for first row and Los
Alamos effective core potentials plus double-ꢀ functions on
Na-Bi.35–37
Results and Discussion
Zinc and Cadmium Compounds. Zinc and cadmium
phosphinothiolate complexes [Zn{PhP(C6H4S-2)2}] (1) and
[Cd{Ph2PC6H4S-2}2] (2) were easily prepared in good yield
by oxidation of a metal anode in a cell containing a solution
of the corresponding ligand in acetonitrile and a small amount
of tetramethylammonium perchlorate as an electrolytic
carrier. The incorporation of pyridine as an additional
coligand in the cell allowed the synthesis of mixed complexes
such as [Zn{PhP(C6H4S-2)2}(py)] (3) and [Cd{PhP(C6H4S-
2)2}(py)] (4). These compounds were moderately soluble in
the reaction solvent and were obtained as air-stable white
crystalline solids in the bottom of the cell. The complexes
are soluble in chloroform and in a range of other chlorinated
organic solvents.
The electrochemical efficiency for these processes, Ef,
defined as the number of moles of metal dissolved per
faraday of charge, was always close to 0.5 mol F-1. These
(32) (a) Becke, A. D. J. Chem. Phys. 1993, 98, 5648. (b) Becke, A. D.
J. Chem. Phys. 1992, 96, 2155–2160.
(33) Lee, C.; Yang, W.; Parr, R. G. Phys. ReV. 1988, B37, 785–789.
(34) Dunning, T. H., Jr.; Hay, P. J. In Modern Theoretical Chemistry;
Schaefer, H. F., Ed.; PlenumNew York, 1976; Vol. 3, p 1.
(35) Hay, P. J.; Wadt, W. R. J. Chem. Phys. 1985, 82, 270–283.
(36) Wadt, W. R.; Hay, P. J. J. Chem. Phys. 1985, 82, 284–298.
(37) Hay, P. J.; Wadt, W. R. J. Chem. Phys. 1985, 82, 299–310.
(38) (a) Block, E.; Kang, H. Y.; Ofori-Okai, G.; Zubieta, J. Inorg. Chim.
Acta 1989, 166, 155–157. (b) Pérez-Lourido, P.; Romero, J.; García-
Vázquez, J. A.; Sousa, A.; Maresca, K.; Rose, D. G.; Zubieta, J. Inorg.
Chem. 1998, 37, 3331–3336.
Inorganic Chemistry, Vol. 47, No. 6, 2008 2125

Fernández et al.
Table 2. Summary of Crystallographic Data and Refinement for Mercury Compounds
compound
5
6
7*
8
9
10*
11
empirical formula C36H28P2S2Hg
C
171H182Cl6P8S8- C20H19OPSHg
C24H31O2-
PSSiHg
643.20
C22H23PS2Hg2
C28H39OPS2Si2- C52H68O2P2S4Si4-
Si8Hg4
3981.19
0.45 × 0.16 ×
0.05
Hg2
Hg3
fw
787.23
0.31 × 0.20 ×
538.97
783.67
944.04
1629.37
0.46 × 0.09 ×
0.07
cryst size, mm3
0.53 × 0.05 ×
0.47 × 0.25 ×
0.40 × 0.12 ×
0.66 × 0.36 ×
0.08
0.05
0.06
0.06
0.33
temp, K
wavelength
cryst syst
space group
unit cell dimens
a, Å
293(2)
293(2)
293(2)
293(2)
293(2)
293(2)
293(2)
0.71073
monoclinic
C2/c
0.71073
monoclinic
C2/c
0.71073
monoclinic
P2(1)/c
0.71073
triclinic
j
P1
0.71073
triclinic
j
P1
0.71073
monoclinic
P2(1)/c
0.71073
monoclinic
P2(1)/n
16.322(3)
9.2713(16)
20.907(4)
90.00
98.067(3)
90.00
3132.3(9)
4
5.174
51.447(4)
11.8702(8)
33.296(2)
90.00
114.6160(10)
90.00
18485(2)
4
3.656
12.645(6)
8.614(4)
34.752(16)
90.00
96.035(9)
90.00
3764(3)
8
8.377
10.0294(18)
11.224(2)
12.005(2)
99.942(3)
101.184(3)
91.568(3)
1303.3(4)
2
8.7029(17)
11.429(2)
12.764(3)
110.978(3)
97.386(3)
100.074(3)
1141.6(4)
2
12.472(3)
19.760(5)
14.744(4)
90.00
111.260(4)
90.00
3393.0(15)
4
9.298
11.5787(17)
28.822(4)
20.742(3)
90.00
101.891(4)
90.00
6773.5(17)
4
7.057
b, Å
c, Å
R, deg
ꢁ, deg
γ, deg
vol, Å3
Z
µ, mm-1
no. reflns
collected
6.110
14986
13.690
9744
4242
83214
31445
20666
42799
no. independent 3192 [R(int) )
13353 [R(int) ) 3939 [R(int) )
5327 [R(int) )
0.0357]
4608 [R(int) )
0.0365]
6923 [R(int) )
0.0394]
9715 [R(int) )
0.0547]
reflns
0.0252]
0.0863]
0.2109]
data/restraints/
params
3192/0/186
13353/4/955
3939/6/223
5327/0/273
4608/0/244
6923/0/325
9715/0/604
GOF
1.087
1.036
1.210
0.998
1.046
0.934
0.940
final R indices
[I > 2σ(I)]
R ) 0.0206
wR ) 0.0478
R ) 0.0442
wR ) 0.1021
R ) 0.1507
wR ) 0.3329
R ) 0.0291
wR ) 0.0720
R ) 0.0357
wR ) 0.0690
0.0386
wR ) 0.0930
0.0531
wR ) 0.1267
metal centers. The third ligand behaves as a PS(µ-S) system
in that its P(3) and S(6) are coordinated to Zn(3) while the
other sulfur acts as a bridge. The presence of an oxophos-
phine group in one of the ligands leads to different environ-
ments around the zinc atoms, [OS3] for Zn(1) and [PS3] for
both Zn(2) and Zn(3).
Every zinc atom is in a distorted tetrahedral environment
with bond angles in the range 132.11(6)°–80.79(6)°. The
lower values in this range correspond to donor atoms in five-
membered chelate rings. All of the Zn-S bond lengths are
similar to one another and are in the range 2.431(2)-2.238(2)
Å regardless of the terminal or bridging nature of the sulfur,
a situation that indicates the presence of a fairly symmetrical
thiolate bridge. These values are comparable to those found
in other tetrahedral zinc complexes with thiolate ligands that
contain five-membered chelate rings, for example, 2.266 Å
(average value) found in [Zn{SCH2CH2N(CH3)2}2].39 In
addition, the Zn-P bond distances, 2.358(2) and 2.437(2)
Å, are also close to those found in tetrahedral zinc complexes
with tertiary phosphines, for example, 2.376(1) Å (average
value) found in [ZnCl2(PMe3)2].40 Both of these bond
distances are similar to those found in the compound
[Zn{Ph2PC6H3(S-2)(SiMe3-3)}2], 2.2791(9) and 2.387(1) Å,
Figure 1. ORTEP diagram of the molecular structure of 1* with 50%
thermal ellipsoid probability.
Figure 2. ORTEP diagram of the molecular structure of 2* with 50%
thermal ellipsoid probability.
2126 Inorganic Chemistry, Vol. 47, No. 6, 2008

Complexes of Phosphinothiol Ligands
Figure 3. ORTEP diagram of the molecular structure of 3 with 50% thermal ellipsoid probability.
Table 4. Selected Bond Lengths [Å] and Angles [deg] for 2*
Cd(1)-O(1)
Cd(1)-S(1)
Cd(1)-S(2)
Cd(1)-S(3)
Cd(1)-P(2)
O(1)-Cd(1)-S(1)
2.172(7)
2.546(2)
2.862(2)
Cd(2)-S(2)
Cd(2)-S(3)
Cd(2)-S(4)
2.5232(17)
2.9684(19)
2.566(2)
2.6270(19)
2.674(2)
2.5356(16) Cd(2)-P(3)
2.6447(19) Cd(2)-P(4)
90.3(2)
S(1)-Cd(1)-S(2) 167.21(6)
O(1)-Cd(1)-S(3) 112.06(18)
O(1)-Cd(1)-P(2) 112.24(17)
S(1)-Cd(1)-P(2) 101.90(6)
S(3)-Cd(1)-S(1) 104.66(6)
S(3)-Cd(1)-P(2) 127.45(6)
O(1)-Cd(1)-S(2)
P(2)-Cd(1)-S(2)
P(4)-Cd(2)-S(3)
84.8(2)
69.35(6)
96.47(6)
S(3)-Cd(1)-S(2)
88.13(6)
S(2)-Cd(2)-S(4) 107.87(6)
S(2)-Cd(2)-P(3) 122.24(6)
S(2)-Cd(2)-P(4) 115.91(6)
P(3)-Cd(2)-P(4) 117.86(6)
S(4)-Cd(2)-S(3) 166.01(5)
S(4)-Cd(2)-P(3) 103.64(6)
S(4)-Cd(2)-P(4)
S(2)-Cd(2)-S(3)
P(3)-Cd(2)-S(3)
76.42(6)
86.04(6)
68.72(6)
Table 5. Bond Lengths [Å] and Angles [deg] for 3
Zn(1)-N(1)
Zn(1)-S(1)
Zn(2)-N(2)
Zn(2)-S(3)
N(1)-Zn(1)-S(4) 104.90(8)
S(4)-Zn(1)-S(1) 131.41(4)
S(4)-Zn(1)-P(1) 122.86(4)
N(2)-Zn(2)-S(2) 103.58(8)
S(2)-Zn(2)-S(3) 131.06(4)
S(2)-Zn(2)-P(2) 122.47(4)
2.124(3)
2.2932(11) Zn(1)-P(1)
2.132(3) Zn(2)-S(2)
2.2899(11) Zn(2)-P(2)
Zn(1)-S(4)
2.2841(10)
2.4172(10)
2.2760(10)
2.3941(11)
Figure 4. The optimized structure of 4.
N(1)-Zn(1)-S(1) 102.95(8)
Table 3. Selected Bond Lengths [Å] and Angles [deg] for 1*
N(1)-Zn(1)-P(1)
S(1)-Zn(1)-P(1)
99.35(8)
90.25(3)
Zn(1)-O(1)
Z(1)-S(1)
Zn(1)-S(5)
Zn(1)-S(4)
Zn(2)-S(2)
Zn(2)-S(4)
2.007(2)
Zn(2)-S(3)
2.431(2)
2.437(2)
2.275(2)
2.2910(18)
2.358(2)
2.412(2)
N(2)-Zn(2)-S(3) 102.93(8)
2.2739(15) Zn(2)-P(2)
2.3207(17) Zn(3)-S(6)
2.3585(17) Zn(3)-S(3)
2.238(2)
2.3569(18) Zn(3)-S(5)
N(2)-Zn(2)-P(2) 101.93(8)
S(3)-Zn(2)-P(2)
90.70(4)
Zn(3)-P(3)
structure consists of dimers in which two thiolate sulfur
atoms from two ligands bridge the two cadmium atoms. In
addition, Cd(1) is coordinated to a phosphorus atom of the
bridging ligand and to the thiolate sulfur atom and the oxygen
atom of an additional chelating ligand; Cd(2) is coordinated
to a phosphorus atom of another bridging ligand and to a
sulfur and a phosphorus atom of a chelating ligand. Analysis
of the shape-determining bond angles, using the geometrical
parameter τ [τ ) (ꢁ - R)/60],41 gives values of 0.66 and
0.77 and suggests that the cadmium atoms are in distorted
O(1)-Zn(1)-S(1) 102.56(8)
S(1)-Zn(1)-S(5) 123.69(6)
S(1)-Zn(1)-S(4) 109.87(6)
S(2)-Zn(2)-S(4) 122.27(3)
S(4)-Zn(2)-S(3) 113.82(6)
O(1)-Zn(1)-S(5) 104.57(9)
O(1)-Zn(1)-S(4) 99.51(8)
S(5)-Zn(1)-S(4) 112.92(6)
S(2)-Zn(2)-S(3) 113.43(5)
S(2)-Zn(2)-P(2) 132.11(6)
S(3)-Zn(2)-P(2)
S(6)-Zn(3)-P(3)
S(6)-Zn(3)-S(5) 111.82(3)
P(3)-Zn(3)-S(5) 84.34(7)
S(4)-Zn(2)-P(2)
86.59(6)
80.79(6)
91.11(4)
S(6)-Zn(3)-S(3) 122.85(5)
S(3)-Zn(3)-P(3) 118.86(4)
S(3)-Zn(3)-S(5) 118.15(6)
respectively, in which the metal atom is in a [P2S2] tetrahedral
environment.25
A view of [Cd2{Ph2P(C6H4S-2)}3{Ph2P(O)(C6H4S-2)}]
(2*) is shown in Figure 2, together with the atomic
numbering scheme. Bond lengths and angles with the
estimated standard deviations are listed in Table 4. The
(39) Casals, C. I.; Gonzalez-Duarte, P.; López, C.; Solans, X. Polyhedron
1990, 9, 763–768.
(40) Cotton, F. A.; Schmid, G. Polyhedron 1996, 15, 4053–4059.
(41) Addison, A. W.; Rao, T. N.; Reedijk, J.; van Rinj, J.; Verschoor, G. C.
J. Chem. Soc., Dalton Trans. 1984, 1349–1356.
Inorganic Chemistry, Vol. 47, No. 6, 2008 2127

Fernández et al.
in dinitrato bis(2-methylmercaptoaniline)Cd(II).45 The Cd-P
bond distances, 2.6270(19) and 2.674(2) Å, are similar to
those found in cadmium complexes with tertiary phosphines.46
The compound crystallizes with one acetonitrile solvent
molecule, which does not interact with the cadmium complex
in any significant manner, and there are no noteworthy
intermolecular contacts.
The molecular structure of [Zn2{PhP(C6H4S-2)2}2(py)2] ·
2CH3CN (3) is shown in Figure 3, together with the atomic
numbering scheme adopted. Selected bond distances and
angles with estimated deviations are listed Table 5. The
structural analysis reveals that the compound is a dimer, with
each of the zinc atoms in an [NPS2] environment formed by
a phosphorus atom and a sulfur atom from one ligand, a
sulfur atom from the second ligand, and the nitrogen from
a pyridine molecule. In this way, each of the ligands acts in
a PS chelate manner toward a zinc atom, while the other
sulfur atom is used to bind the other metal center. This
arrangement gives rise to the formation of a ten-membered
ring.
Figure 5. ORTEP diagram of the molecular structure of 5 with 50% thermal
ellipsoid probability.
Scheme 1. Schematic Representation of the Routes Employed in the
Synthesis of Hg(II) Complexes
Each Zn atom is in a highly distorted tetrahedral environ-
mentwithbondangles(Table5)intherange131.41(4)°–90.25(3)°
for the Zn(1) environment and 131.06(4)°–90.70(4)° for
Zn(2). The presence of five-membered chelate rings is the
main source of distortion. The bond distances are as one
would expect with an average value for the Zn-S distance
of 2.2858(10) Å and 2.4172(10) and 2.3941(11) Å for
the Zn-P bonds. These values are similar to those found in
the previously described zinc compound and also to those
in other zinc complexes that contain phosphinothiolato
ligands.25 The Zn-N bond distances, 2.124(3) and 2.132(3)
Å, are longer than those reported for several tetrahedral
pyridine complexes of zinc(II), in which the Zn-N bond
distances are in the range 2.040–2.060 Å.47 The zinc
compound crystallizes with two acetonitrile molecules that
are located within the network but do not interact signifi-
cantly with the complex.
DFT calculations were performed for structural optimiza-
tions of complexes 1, 2, and 4. In all cases, the atomic
coordinates of the molecules obtained in the crystal structures
of the related compounds 1*, 2*, and 3, respectively, were
used as the starting points and references for geometry
optimization. In the case of the homoleptic species 1 and 2,
the optimized structures, included in the Supporting Informa-
tion, are similar to those found in the related compounds 1*
and 2* by X-ray diffraction. The results for 1 show that the
trimer is 35 kcal mol-1 lower in energy than the sum of the
energy of the monomer and the dimer. Therefore, from the
theoretical point of view a structure of trimer should be
preferred for 1. Such trimeric species contains a central Zn3S3
[CdPOS3] and [CdP2S3] trigonal bipyramidal environments
with two sulfur atoms in axial sites and O(1), P(2), and S(3)
for Cd(1) and P(3), P(4), and S(2) for Cd(2) in the equatorial
plane. Angular distortions are observed in the equatorial
plane of each cadmium atom, with bond angles in the range
112.06(18)°–127.45(6)°, and along the axial direction of the
bipyramid, with angles of 167.21(7)° and 166.01(5)°.
The four-membered ring Cd(1)-S(2)-S(3)-Cd(2) is
nearly planar with the two metal atoms 0.1282(6) and
0.1327(7) Å above and the two sulfur atoms -0.1273(6) and
-0.1331(7) below the best plane containing the four atoms
in question (rms 0.132). The thiolate bridge is clearly
asymmetric with two short bond distances, Cd(1)-S(3)
2.5356(16) Å and Cd(2)-S(2) 2.5232(17) Å, and two longer
bond distances, Cd(1)-S(2) 2.862(2) and Cd(2)-S(3)
2.9684(17) Å. The latter values are larger than the sum of
the covalent radii of tetrahedral cadmium and sulfur atoms,
2.52 Å,42 and this is indicative of weaker interactions
between the metal and these donor atoms. The other bridging
bond distances and the cadmium terminal sulfur bond
distances, Cd(1)-S(1) 2.546(2) Å and Cd(2)-S(4) 2.566(2)
Å, are as expected and are consistent with those found in
other dimeric cadmium complexes with pentacoordinated
environments around the cadmium and with Cd(µ-SR) bond
distances in general.43 The Cd(1)-O bond distance, 2.172(7)
Å, is shorter than those found in other pentacoordinated
cadmium complexes involving O-donor ligands, for example,
2.34 Å [Cd(thiourea)3(SO4)]44 or 2.387(9) and 2.353(9) Å
(44) Corao, E.; Baggio, S. Inorg. Chim. Acta 1969, 3, 617–622.
(45) Griffith, E. A. H.; Charles, N. G.; Rodesiler, P. F.; Amma, E. L.
Polyhedron 1985, 4, 615–620.
(46) (a) Dean, P. A. W.; Payne, N. C.; Vitale, P. J.; Wu, Y. Inorg. Chem.
1993, 32, 4632. (b) Abrahams, B. F.; Corbell, M.; Dakternieks, D.;
Gable, R. W.; Hoskins, B. F.; Tiekimg, E. R. T.; Winter, G. Aust.
J. Chem. 1986, 39, 1993.
(42) Pauling, L. The Nature of the Chemical Bond, 3rd ed.; Cornell
University Press: Ithaca, NY, 1960; p 246.
(47) (a) Lynton, H.; Sears, M. C. Can. J. Chem. 1971, 49, 3418. (b) Stephan,
W. L.; Palenik, C. J. Acta Crystallogr. 1976, B32, 298. (c) Stephan,
W. L.; Palenik, C. J. Inorg. Chem. 1977, 16, 741.
(43) Gonzalez-Duarte, P.; Clegg, W.; Casals, I.; Sola, J.; Ruis, J. J. Am.
Chem. Soc. 1998, 120, 1260–1266.
2128 Inorganic Chemistry, Vol. 47, No. 6, 2008

Complexes of Phosphinothiol Ligands
Scheme 2. Schematic Representation of the Routes Employed in the Synthesis of EtHg(II) Complexes
Table 6. Selected Bond Lengths [Å] and Angles (deg) for 5
The spectroscopic data confirm the presence of the coordinate
ligands in both complexes. The room temperature 31P NMR
spectrum shows a single peak at δ 33.5 and 36.1 ppm for 5
and 6, which are consistent with data reported for four-
coordinate phosphine mercury complexes48 and show that in
solution the ligand is coordinated through the phosphorus atom
as confirmed by X-ray diffraction studies (Vide infra).
The routes employed in the synthesis of ethylmercury
complexes are shown in Scheme 2. The reaction of ethyl-
mercury chloride with Ph2PC6H4SH-2 in the presence of
triethylamine gave a white solid, the analytical data of which
are consistent with the formula [EtHg{Ph2PC6H4S-2}] (7).
Hg(1)-S(1)
2.4986(7) Hg(1)-P(1)
2.5085(7)
1.808(3)
C(2)-S(1)
1.762(3)
84.28(3)
P(1)-C(1)
S(1)-Hg(1)-P(1)
S(1)-Hg(1)-S(1)a 125.47(4)
S(1)-Hg(1)-P(1)a 119.24(3)
P(1)-Hg(1)-P(1)a 129.77(3)
a
Symmetry transformation used to generated equivalent atoms: 1, -x,
3
y, -z + /2.
Table 7. Selected Bond Lengths [Å] and Angles (deg) for 6
molecule A molecule B
Hg(1)-S(1)
2.553(2)
2.512(3)
2.455(3)
2.467(2)
81.26(8)
137.08(9)
83.51(9)
111.27(9)
122.58(10)
123.53(8)
Hg(2)-S(3)
2.489(3)
2.537(3)
2.492(2)
Hg(1)-S(2)
Hg(2)-S(4)
Hg(1)-P(1)
Hg(1)-P(2)
Hg(2)-P(3)
Hg(2)-P(4)
2.462(3)
S(1)-Hg(1)-P(1)
P(1)-Hg(1)-P(2)
P(2)-Hg(1)-S(2)
S(1)-Hg(1)-S(2)
P(1)-Hg(1)-S(2)
P(2)-Hg(1)-S(1)
P(4)-Hg(2)-S(3)
P(4)-Hg(2)-P(3)
S(3)-Hg(2)-P(3)
P(4)-Hg(2)-S(4)
S(3)-Hg(2)-S(4)
P(3)-Hg(2)-S(4)
126.49(3)
127.76(9)
84.21(8)
82.02(9)
118.07(10)
123.32(9)
ring with all of the zinc atoms having the same [PS3]
tetrahedral environment. In the case of compound 2, the
optimized structure is dimeric and is similar to that of 2*,
with two sulfur atoms acting as bridges and the cadmium
centers in pentacoordinated [P2S3] environments.
The structure of the mixed complex 4, Figure 4, shows
the presence of dimeric species in which the ligand acts in
a terdentate manner, with the sulfur atom acting as a bridge
and the other as a terminal atom. In this case, the cadmium
is in a pentacoordinate [PS3N] environment. It is worth noting
in this case that the geometry of 4 and the coordination of
the ligand are clearly different from those found in zinc
complex 3, which has an analogous composition.
Mercury(II) and Ethylmercury(II) Compounds. The
reaction of mercury(II) acetate with Ph2PC6H5SH-2 and
Ph2PC6H3(SH-2)(MeSi3-3) in methanol in the presence of
triethylamine led to the formation of solids for which the
analytical data are consistent with [Hg{Ph2PC6H4S-2}2]
(5) and [Hg{Ph2PC6H3(S-2)(SiMe3-3)}2] · CHCl3 (6) (Sch-
eme 1).
Figure 6. ORTEP diagram of the molecular structure of 8 with 50% thermal
ellipsoid probability.
Table 8. Selected Bond Lengths [Å] and Angles (deg) for 8
Hg(1)-S(1)
2.3739(12)
1.483(3)
175.2(2)
Hg(1)-C(22)
C(1)-S(1)
2.076(6)
1.779(4)
P(1)-O(1)
C(22)-Hg(1)-S(1)
Inorganic Chemistry, Vol. 47, No. 6, 2008 2129

Fernández et al.
Table 9. Selected Bond Lengths [Å] and Angles (deg) for 9 and 10*
9
10*
Hg(1)-S(1)
Hg(1)-P(1)
Hg(2)-S(2)
C(19)-Hg(1)-S(1) 166.2(3)
S(1)-Hg(1)-P(1) 80.27(7)
C(19)-Hg(1)-P(1) 111.6(3)
C(21)-Hg(2)-S(2) 178.7(3)
2.386(3) Hg(1)-S(1)
2.807(2) Hg(2)-S(2)
2.368(2) Hg(1)-C(25)
2.390(2)
2.362(2)
2.108(10)
2.067(10)
Hg(2)-C(27)
C(25)-Hg(1)-S(1) 174.0(4)
C(27)-Hg(2)-S(2) 175.7(3)
Table 10. Selected Bond Lengths [Å] and Angles (deg) for 11
Hg(1)-S(1)
Hg(2)-S(3)
Hg(3)-S(2)
C(25)-Hg(1)-S(1) 177.9(5)
S(2)-Hg(3)-S(4) 169.45(13)
2.372(4) Hg(1)-C(25)
2.380(4) Hg(2)-C(51)
2.326(4) Hg(3)-S(4)
2.099(15)
2.131(18)
2.328(4)
C(51)-Hg(2)-S(3) 178.3(6)
starting material. It has been demonstrated that the coordina-
tion of organomercury derivatives by strongly chelating
ligands polarizes and activates the carbon-mercury bond for
protonolysis under these mild conditions.20–23
Figure 7. ORTEP diagram of the molecular structure of 9 with 50% thermal
ellipsoid probability.
The analytical data for the compound obtained in the
reaction between ethylmercury chloride and Ph2P(O)C6H3(SH-
2)(Me3Si-3) are consistent with the formula [EtHg{Ph2P(O)-
C6H3(S-2)(Me3Si-3)}] (8). A study of a solution of this
compound indicated its stability, as evidence for cleavage
1
processes was not observed in this case. The H NMR
spectrum shows characteristic signals for the ligands coor-
dinate, and the single signal at δ 33.3 ppm in the 31P spectrum
can be assigned to the presence of a PO group that is not
coordinated to the metal. These data all demonstrate that in
solution the complex has the same structure as in the solid
state, as established by X-ray diffraction (Vide infra).
The chemistry of the related tridentate ligand PhP(C6H4SH-
2)2 was also investigated in order to evaluate the influence
of ligand denticity on the reaction chemistry and product
identity. The reaction of this ligand with ethylmercury
chloride in methanol in the presence of Et3N gave a white
solid, the analytical data of which are consistent with a
compound of general formula [{EtHg}2{PhP(C6H4S-2)2}]
(9). The spectroscopic data confirm the presence of a
coordinated ligand and evidence for oxidized phosphorus
atoms was not seen. NMR 31P spectrum again shows a
relatively broad signal at δ 18.7 ppm, which can be assigned
to the phosphorus atom coordinated to mercury. These data
confirm the structure found by X-ray diffraction in the solid
state.
The reaction between EtHgCl and PhP{C6H3(SH-2)(SiMe3-
3)}2 initially gave an insoluble white solid in the reaction
medium. The analytical data for this compound are consistent
with the formula [{EtHg}2{PhP(C6H3(S-2)(SiMe3-3))2}] (10).
The spectroscopic data confirm the presence of the coordi-
nated ligand, and the FAB spectrum shows a molecular ion
peak at m/z 928. Crystals of 10 suitable for X-ray diffraction
could not be obtained, and the structure of this compound
was optimized by DFT calculations. The results of these
calculations are shown below. Crystallization of the com-
pound discussed above gave two different products. In the
first product, oxidation of the phosphorus atom of the ligand
hadoccurredandledtotheformationof[{EtHg}2{PhP(O)(C6H3(S-
2)(SiMe3-3))2}] (10*). The crystal structure of this compound
Figure 8. ORTEP diagram of the molecular structure of 10* with 50%
thermal ellipsoid probability.
The IR and NMR studies are compatible with the formula
proposed. We were unable to obtain crystals of 7 suitable
for X-ray studies, but the structure was optimized using
theoretical methods, and the results are shown below.
Concentration of the mother liquors from the reaction mixture
gave two new compounds. The major isolated component
was [EtHg{Ph2P(O)C6H4S-2}] (7*), the structure of which
was determined by X-ray diffraction (Vide infra). A second
crystalline compound was obtained from the same solution
andX-rayanalysis(Videinfra)confirmedthistobe[Hg{Ph2PC6H4S-
2}2], the preparation of which from mercury acetate has
already been described above, and contains a mercury atom
coordinated to two monoanionic bidentate ligands. The
formation of this compound suggests the occurrence of a
cleavage process on the C-Hg bond in the organomercury
(48) Allam, T.; Goel, R. G. Can. J. Chem. 1984, 62, 615.
2130 Inorganic Chemistry, Vol. 47, No. 6, 2008

Complexes of Phosphinothiol Ligands
Figure 9. ORTEP diagram of the molecular structure of 11 with 50% thermal ellipsoid probability.
was studied by X-ray diffraction (Vide infra) and was found to
be similar to that of compound 9. The crystallization process
also gave a minor component. X-ray analysis (Vide infra) of
this compound showed the presence of a species of formula
[Hg{EtHg}2{PhP(O)(C6H3(S-2)(SiMe3-3)2}2] (11). In this case,
cleavage of the Hg-C bond had taken place.
Description of the Structures. The molecular structure
of [Hg{Ph2PC6H4S-2}2] (5) is shown in Figure 5. The
compound possess a 2-fold rotation axis that passes through
the mercury atom. Selected bond distances and angles are
given in Table 6. The asymmetric unit of compound
Hg{Ph2PC6H3(S-2)(SiMe3-3)}2] (6) contains two molecules
of the complex and 1.5 molecules of CH2Cl2, and the
molecular structure of one of the two molecules is included
in the Supporting Information. Selected bond distances and
angles are given in Table 7.
Both compounds consist of discrete molecules in which
the mercury atoms are coordinated to two monoanionic
bidentate (η2-P,S) ligands. The geometry around the metal
in both cases is distorted tetrahedral with bond angles
corresponding to five-membered chelate rings, 84.28(3)° in
5 and 82.38(9)° (average value) in 6.
The Hg-S bond distances, 2.4986(7) Å for 5 and 2.523(3)
Å (average value) for 6, are very similar to one another and
close to those found in other mercury thiolates in which the
metal atom is tetracoordinated in a tetrahedral environment,
for example, 2.537(1) and 2.552(1) Å in [Hg(SC6H4Cl)4]2–49
Supporting Information. Unfortunately, the X-ray diffraction
data are of poor quality, and for this reason, the structure is
shown only to demonstrate the connectivity of the atoms
around the metal center (see X-ray Crystallographic Studies).
As a result, the geometrical parameters for this compound
will not be discussed. The molecular structure of [EtHg{Ph2-
P(O)C6H3(S-2)(Me3Si-6)}]· CH3OH (8) is shown in Figure
6, together with the atomic numbering scheme adopted. A
selection of bond distances and angles for this complex are
given in Table 8.
The structures of both compounds are similar consisting
of monomeric species in which the mercury is coordinated
to a carbon atom of the ethyl group and the thiolate sulfur
of the ligand. In both compounds, the geometry around the
metal atom is essentially linear with S-Hg-C bond angles
close to the ideal value of 180°. The Hg-C bond length,
2.076(6) Å, and the Hg-S bond length, 2.3739(12) Å, for 8
are within the expected range for linear organomercury
compounds coordinated with thiolate ligands.51,52 The value
of the distance between the mercury atom and the oxygen
atom of the oxophosphine ligand, 2.713 Å, is larger than
the normal covalent bond between the two atoms, 2.00–2.30
Å,53 but is shorter than the sum of the van der Waals radii,
3.00–3.23 Å,54 and may be considered as indicative of some
interaction.55 Compound 8 crystallizes with a molecule of
methanol, which maintains a hydrogen-bonding interaction
with the oxygen atom of the ligand.
or 2.543(7)
Å
in [(np3)Hg(SC6H4CH3)]+ (np3
)
N(CH2CH2PPh2)3).20 The Hg-P bond distances are relatively
short at 2.5085(7) and 2.469(3) Å (average value) for 5 and
6, respectively. These values are slightly shorter than those
found in [(np3)Hg(SC6H4CH3)]+, which are in the range
2.593(7)–2.633(8) Å, and in [HgX2(PPh3)2] complexes, which
are in the range 2.45–2.91 Å.50
(50) Guergi, H. B.; Fischere, E.; Kunz, R. W.; Parvez, M.; Pregosin, P. S.
Inorg. Chem. 1982, 21, 1246–1256.
(51) Castiñeiras, A.; Hiller, W.; Strahle, J.; Bravo, J.; Casas, J. S.; Gayoso,
M.; Sordo, J. J. Chem. Soc., Dalton Trans. 1986, 1945–1948.
(52) Block, E.; Brito, M.; Gernon, M.; McGowty, D.; Zubieta, J. Inorg.
Chem. 1990, 29, 3172–3181, and references therein.
(53) (a) Taylor, N. J.; Wong, Y. S.; Chieh, P. C.; Carthy, A. J. J. Chem.
Soc., Dalton Trans. 1975, 438–442. (b) Dittmar, G.; Hellmer, E.
Angew. Chem., Int. Ed. Engl. 1969, 8, 679.
The structure of one of the two molecules of [EtHg{Ph2P(O)-
C6H4S-2}] (7*) in the asymmetric unit is include in the
(54) (a) Grdenic, D. Q. ReV. 1965, 303–328. (b) Bondi, A. J. Chem. Phys.
1964, 68, 441–451.
(49) Choudhury, S.; Dance, I. G.; Guerney, P. J.; Rae, A. D. Inorg. Chim.
Acta 1983, 70, 227–230.
(55) Barbaro, P.; Ghilardi, C. A.; Midollini, S.; Orlandini, A.; Ramirez,
J. A.; Scapacci, G. J. Organomet. Chem. 1998, 555, 255–262.
Inorganic Chemistry, Vol. 47, No. 6, 2008 2131

Fernández et al.
The molecular structures of [{EtHg}2{PhP(C6H4S-2)2}] (9)
and [{EtHg}2{PhP(O){C6H3(S-2)2(SiMe3-3)}2}] (10*) are
shown in Figures 7 and 8, along with the atom labeling
schemes. Selected bond distances and angles are given in
Table 9. The two structures can be considered to be related,
although the presence in the second compound of an oxidized
phosphorus atom gives rise to structural differences between
the two complexes. In compound 9, the two mercury atoms
have different coordination behavior and different geometries.
The Hg(2) center is coordinated in a linear manner to a
carbon from the ethyl group and a sulfur atom, with a
C-Hg-S(2) bond angle of 178.7(3)°.
Compound 10* consists of two EtHg- units that are
bonded to two thiolate sulfur atoms from the dianionic ligand.
Both mercury atoms have a linear coordination in which the
metal is only bonded to a carbon atom from the ethyl group
and the anionic sulfur. The oxygen atoms from the PO groups
are sufficiently remote that the existence of interactions with
the mercury atom can be ruled out.
The bond distances in the S-Hg-C fragment are as one
would expect for covalent bonds. However, the Hg(1) atom,
in addition to the strong covalent Hg-C and Hg-S bonds,
is also linked to the phosphorus atom of the ligand. The
Hg-P bond distance is 2.807(2) Å, which is shorter than
the sum of the van der Waals radii of mercury and
phosphorus42 (3.4 Å) and is characteristic of the presence
of a weak interaction.56 In this case, the C-Hg-S bond angle
is closed and has a value of 166.2(3)°, the lowest value in
the organomercury compounds discussed here and charac-
teristic of complexes in which secondary coordination occurs.
The molecular structure of [Hg{EtHg}2{PhP(O)(C6H3(S-
2)(SiMe3-3))2}2 (11) is shown in Figure 9 along with the
atom labeling scheme. Selected bond distances and angles
are given in Table 10. The compound is trinuclear and
contains mercury atoms of different natures. The atoms Hg(1)
and Hg(2) are coordinated in a linear fashion with a carbon
atom of the ethyl group and the sulfur of a phosphinothiolate
ligand. In addition, the oxygen atom from the PO group of
the ligand is 2.622(7) and 2.674(9) Å away from the mercury,
a situation that seems to indicate the presence of a weak
interaction between these atoms. The Hg(3) atom is coor-
dinated in a linear manner with two sulfur atoms from
different thiolate ligands, and there are also weak interactions
with the oxygen atoms of the two ligands, bond distances
2.617(7) and 2.689(8) Å, in a coordination that can be
considered as 2 + 2, which is characteristic of some Hg(II)
compounds. In all three cases, regardless of the presence of
possible secondary interactions, the bond angles around the
metal are in the range 169.45(13)°–178.3° and Hg-S bond
distances in the range 2.326(4)–2.380(4) Å, values similar
to those found in the previously described mercury com-
pounds, and therefore do not warrant further discussion.
The structures of 7 and 10 were optimized by DFT
calculations. The results obtained are shown in the Support-
ing Information. In these compounds, and in relation to the
structures of compounds 7* and 10*, the presence of a
bonding interaction can be seen between the metal and the
phosphorus, which in this case is not oxidized. This situation
is consistent with the softer character of this atom. Whereas
the structures of complexes 7* and 10*, obtained by X-ray
diffraction, have the mercury in a digonal coordination, in 7
the metal center is tricoordinated and in 10 the two mercury
atoms have different environments, with one coordinated to
the phosphorus of the ligand.
Acknowledgment. This work was supported by Xunta de
Galicia (Spain) and by the Ministerio de Ciencia y Tec-
nología (Spain) (Grant No. CTQ2006-05298).
Supporting Information Available: Crystallographic data in
cif format, optimized structures of 1, 2, 7, 10, and ORTEP diagrams
of 6 and 7*. This material is available free of charge via the Internet
at http://pubs.acs.org.
(56) Cecconi, F.; Ghilardi, C. A.; Ienco, A.; Midollini, S.; Orlandini, A. J.
Organomet. Chem. 1999, 575, 119–125.
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2132 Inorganic Chemistry, Vol. 47, No. 6, 2008