Synthesis and characterization of ruthenium and osmium complexes of heterocyclic bidentate ligands (N, X), X = S, Se

Article abstract of DOI:10.1016/j.ica.2005.06.009

The reaction of [RuCl₂(PPh₃)₃] and [OsBr₂(PPh₃)₃] precursors with a series of heterocyclic bidentate (N, X) ligands, X = S, Se, gave complexes [M(R-pyS) ₂(PPh₃)₂], (R = H, 3-CF₃, 5-CF ₃, 3-Me₃Si); [M(R-pymS)₂(PPh₃) ₂], (R = 4-CF₃, 4,6-MeCF₃) and [M(R-pySe) ₂(PPh₃)₂], (R = H, 3-CF₃, 5-CF ₃), where M is Ru or Os, pyS and pymS the anions of pyridine-2-thione and pyrimidine-2-thione, respectively, and pySe is the anion produced by the reductive cleavage of the Se-Se bond in the dipyridyl-2,2′-diselenide. All of the compounds obtained were characterized by microanalysis, IR, FAB, NMR spectroscopy and by cyclic voltammetry. Compounds [Ru(3-CF₃-pyS) ₂(PPh₃)₂] ? 2(CH₂Cl ₂) (2), [Ru(3-Me₃Si-pyS)₂(PPh₃) ₂] (4), [Ru(4-CF₃-pymS)₂(PPh₃) ₂] (5), [Ru(3-CF₃-pySe)₂(PPh₃) ₂] ? 2(CH₂Cl₂) (8), [Os(3-CF ₃-pyS)₂(PPh₃)₂] ? (CHCl ₃) (11), [Os(3-Me₃Si-pyS)₂(PPh ₃)₂] (13), [Os(3-CF₃-pySe)₂(PPh ₃)₂] ? 2(CH₂Cl₂) (17), [Os(5-CF₃-pySe)₂(PPh₃)₂] ? 2(H₂O) (18) and [OsCl₂(4,6-MeCF₃-pymS)(PPh ₃)₂] (19) were also characterized by X-ray diffraction. In all cases, the metal is in a distorted octahedral environment with the heterocyclic ligand acting as a bidentate (N, S) chelate system.

Full text of DOI:10.1016/j.ica.2005.06.009

Inorganica Chimica Acta 359 (2006) 863–876
www.elsevier.com/locate/ica
Synthesis and characterization of ruthenium and osmium
complexes of heterocyclic bidentate ligands (N,X), X = S, Se
a
a
a
´
Antonio Sousa-Pedrares , Maria Luz Duran , Jaime Romero ,
a
b
a,
*
´
´
´
Jose Arturo Garcıa-Vazquez , Juan C. Monteagudo , Antonio Sousa
,
c
Jonathan R. Dilworth
a
Departamento de Quı´mica inorga´nica, Universidad de Santiago de Compostela, 15782 Santiago de Compostela, Spain
b
Departamento de Quı´mica Fı´sica, Universidad de Santiago de Compostela, 15782 Santiago de Compostela, Spain
c
Inorganic Chemistry Laboratory, University of Oxford, Oxford OXI 3QR, UK
Received 5 April 2005; accepted 11 June 2005
Available online 19 August 2005
Ruthenium and Osmium Chemistry Topical Issue.
Abstract
The reaction of [RuCl2(PPh3)3] and [OsBr2(PPh3)3] precursors with a series of heterocyclic bidentate (N,X) ligands, X = S, Se,
gave complexes [M(R-pyS)2(PPh3)2], (R = H, 3-CF3, 5-CF3, 3-Me3Si); [M(R-pymS)2(PPh3)2], (R = 4-CF3, 4,6-MeCF3) and [M(R-
pySe)2(PPh3)2], (R = H, 3-CF3, 5-CF3), where M is Ru or Os, pyS and pymS the anions of pyridine-2-thione and pyrimidine-2-thi-
one,respectively, and pySe is the anion produced by the reductive cleavage of the Se–Se bond in the dipyridyl-2,20-diselenide. All of
the compounds obtained were characterized by microanalysis, IR, FAB, NMR spectroscopy and by cyclic voltammetry.
Compounds [Ru(3-CF3-pyS)2(PPh3)2] Æ 2(CH2Cl2) (2), [Ru(3-Me3Si-pyS)2(PPh3)2] (4), [Ru(4-CF3-pymS)2(PPh3)2] (5), [Ru(3-CF3-
pySe)2(PPh3)2] Æ 2(CH2Cl2) (8), [Os(3-CF3-pyS)2(PPh3)2] Æ (CHCl3) (11), [Os(3-Me3Si-pyS)2(PPh3)2] (13), [Os(3-CF3-pySe)2(PPh3)2] Æ
2(CH2Cl2) (17), [Os(5-CF3-pySe)2(PPh3)2] Æ 2(H2O) (18) and [OsCl2(4,6-MeCF3-pymS)(PPh3)2] (19) were also characterized by X-ray
diffraction. In all cases, the metal is in a distorted octahedral environment with the heterocyclic ligand acting as a bidentate (N,S)
chelate system.
ꢀ 2005 Elsevier B.V. All rights reserved.
Keywords: Ruthenium complexes; Osmium complexes; Heterocyclic thiones; Selenolates
1. Introduction
or bridging between two [5] or three [6] metal atoms),
which gives rise to complexes with variable nuclearity
and a wide range of structural geometries [7]. The chem-
istry of Ru(II), and to a lesser extent Os(II), with the pyr-
idine-2-thione ligand is relatively well documented for
complexes with a variety of coligands such as phosphines,
carbonyls or others that complete the coordination
sphere around the metal [8–17]. Furthermore, the crystal
structure of [Ru(pyS)2(PPh3)2] has already been reported
[8]. However, there is experimental evidence that the
presence and location of a substituent in the heterocyclic
ring are important factors in determining the type of
Metal complexes with heterocyclic thiones, mainly
pyridine-2-thionato and pyrimidine-2-thionato com-
plexes, have been widely studied because of their rele-
vance to biological systems and the versatility in their
coordination forms (neutral monodentate [1], bridging
through S [2], anionic S-monodentate [3], chelating [4]
*
Corresponding author. Tel.: +34 981 563 100x14950; fax: +34 981
597 525.
´
´
E-mail addresses: qijagv@usc.es (J.A. Garcıa-Vazquez), qiansoal@
usc.es (A. Sousa).
0020-1693/$ - see front matter ꢀ 2005 Elsevier B.V. All rights reserved.
doi:10.1016/j.ica.2005.06.009

864
A. Sousa-Pedrares et al. / Inorganica Chimica Acta 359 (2006) 863–876
R
with an apparatus consisting of an EG&G Priceton Ap-
R
R
plied Research potentiostat (model 273) and an electro-
chemical cell consisting of a working electrode (graphite
disc), a reference electrode (saturated calomel) and an
auxiliary electrode (platinum wire). Dichloromethane
was used as the solvent to make the solutions and tetra-
butylammonium tetrafluoroborate (0.1 M) was used as
the electrolyte. In all cases, the concentration of the sam-
ples under investigation were 10ꢀ3 M.
N
N
H
S
N
H
S
N
Se
2
R-pySe-
R-pymSH
R-pySH
R= H, 3-CF3, 5-CF3, 3-Me3Si
R= H, 3-CF3, 5-CF3
R= 4-CF3, 4,6-MeCF3
Scheme 1.
2.2. Preparation of the complexes
coordination of the ligand and the structure and proper-
ties of the metal–pyridine-2-thionato complexes [18–20].
On the other hand, complexes of these metals with pyrim-
idine-2-thione ligands has been studied to a much lesser
extent [21–24] and compounds incorporating the pyri-
dine-2-selenolato ligand have not been reported at all.
Our continued interest in the coordination chemistry of
heterocyclic thionato or selenolato ligands led us to
investigate the synthesis and characterization of ruthe-
nium and osmium compounds with a series of heterocy-
clic bidentate ligands (N,X), X = S, Se (see Scheme 1).
The results of this study are reported here along with a
discussion concerning the influence of the nature and
the location of the substituent in the heterocyclic ring
on the structure and properties of the complexes.
2.2.1. [Ru(pyS)2(PPh3)2] (1)
Et3N (0.1 ml, 0.688 mmol) was added to a methanolic
solution of pySH (0.0696 g, 0.625 mmol). The resulting
solution was stirred for 1 h and
a solution of
[RuCl2(PPh3)3] (0.3 g, 0.313 mmol) in dichloromethane
was added. The reaction mixture was stirred for 2 h
and the resulting solid was filtered off, washed with
diethyl ether and dried under vacuum. Anal. Calc. for
C46H38N2P2S2Ru (mol. wt. 845.9): C, 65.3; H, 4.5; N,
3.3. Found: C, 64.8; H, 4.7; N, 3.3%. IR (KBr): 3049
(m), 1578 (m), 1545 (m), 1480 (m), 1432 (s), 1419 (s),
1311 (w), 1262 (m), 1190 (w), 1151 (m), 1137 (m), 1097
(w), 1088 (m), 1028 (w), 752 (m), 740 (s), 696 (s), 539
(m), 521 (s), 500 (m), 470 (m). 1H NMR (CDCl3,
ppm) 7.6 (H6, d, 1H), 6.8 (H3, d, 1H), 6.2 (H4, t, 1H),
6.0 (H5, t, 1H); 7.2–6.9 (m, 15H, PPh3); 13C NMR
(CDCl3, ppm) 181.2 (C2), 124.2 (C3), 136.1 (C4): 115.3
(C5), l46.0 (C6), 128.2 (Ca), 133.8 (Cb), 126.7 (Cc):
l26.8 (Cd). FAB (m/z): 846 (M+), 736 (M–pyS), 584
(M–PPh3) and 474 (M–pyS–PPh3).
2. Experimental
2.1. General procedures
All manipulations were carried out under an inert
atmosphere of dry nitrogen. RuCl3 Æ 3H2O, OsO4,
PPh3, 3-CF3-pySH, 5-CF3-pySH and other reagents
were commercial products and were used without fur-
ther purification. 3-Me3Si-pySH was prepared following
the method described by Block et al. [25]. 4,6-(Me,CF3)-
pymSH was synthesized by direct reaction of 1,1,1-tri-
fluoro-2,4-pentanedione and thiourea as described in
the literature [26]. The syntheses of (pySe)2, (3-CF3-
pySe)2 and (5-CF3-pySe)2 were carried out by reacting
sodium diselenide with the appropriate 2-bromopyridine
in dimethylformamide following a literature procedure
[27]. [RuCl2(PPh3)2] was prepared using a procedure
similar to that described by Hallman et al. [28] and
[OsBr2(PPh3)3] was obtained using a procedure similar
to that described by Hoffman and Caulton [29]. Elemen-
tal analyses were performed in a Carlo-Erba EA micro-
analyser. IR spectra were recorded on KBr discs using a
2.2.2. [Ru(3-CF3-pyS)2(PPh3)2] (2)
3-CF3-pySH (0.112 g, 0.625 mmol), Et3N (0.1 ml,
0.688 mmol) and [RuCl2(PPh3)3] (0.3 g, 0.313 mmol).
Anal. Calc. for C48H36F6N2P2S2Ru (mol. wt. 981.9):
C, 58.7; H, 3.7; N, 2.8. Found: C, 58.5; H, 3.6; N,
2.9%. IR (KBr): 3059 (m), 1578 (m), 1562 (m), 1481
(m), 1434 (m), 1404 (s), 1321 (s), 1259 (m), 1208 (m),
1165 (m), 1129 (m), 1110 (m), 1089 (m), 1066 (m),
1047 (m), 1001 (w), 972 (w), 813 (m), 797 (m), 740
(m), 721 (m), 696 (s), 535 (m), 521 (s), 497 (m). 1H
NMR (CDCl3, ppm) 7.8 (H6, d, 1H), 6.1 (H5, t, 1H);
7.2–6.9 (m, 16H, H4, PPh3); 13C NMR (CDCl3, ppm)
181.0 (C2), 131.1 (C3), 135.5 (C4): 113.9 (C5), l49.0
(C6), 128.5 (Ca), 133.9 (Cb), 127.0 (Cc): 127.0 (Cd).
FAB (m/z): 982 (M+), 804 (M–{3-CF3-pyS}), 720 (M–
PPh3) and 542 (M–{3-CF3-pyS}–PPh3). Crystals of
[Ru(3-CF3-pyS)2(PPh3)2] Æ 2(CH2Cl2) suitable for X-ray
studies were obtained by crystallisation of the initial
product from methanol/dichloromethane.
1
Bruker IFS 66v spectrophotometer. H and 13C spectra
were recorded on a Bruker AMX 300 MHz instrument
using CDCl3 as solvent. The chemical shifts for 1H
and 13C were determined against TMS as internal stan-
dard. The FAB mass spectra were recorded on a Micro-
mass Autospec instrument using 3-nitrobenzyl alcohol
as the matrix material. Voltammograms were obtained
2.2.3. [Ru(5-CF3-pyS)2(PPh3)2] (3)
5-CF3-pySH (0.112 g, 0.625 mmol), Et3N (0.1 ml,
0.688 mmol) and [RuCl2(PPh3)3] (0.3 g, 0.313 mmol).

A. Sousa-Pedrares et al. / Inorganica Chimica Acta 359 (2006) 863–876
865
Anal. Calc. for C48H36F6N2P2S2Ru (mol. wt. 981.9): C,
58.7; H, 3.7; N, 2.8. Found: C, 59.1; H, 3.8; N, 2.8%. IR
(KBr): 3052 (m), 1593 (s), 1548 (m), 1480 (m), 1460 (m),
1434 (m), 1383 (w), 1319 (s), 1269 (m), 1256 (m), 1170
(m), 1151 (s), 1116 (m), 1105 (m), 1072 (s), 1026 (w),
924 (w), 824 (m), 761 (m), 697 (s), 615 (w), 535 (m),
521 (s), 496 (m), 470 (m). 1H NMR (CDCl3, ppm)
7.68 (H6, s, 1H), 7.1 (H3, t, 1H), 6.3 (H4, d, 1H); 7.2–
6.9 (m, 15H, PPh3); l3C NMR (CDCl3, ppm) 186.6
(C2), 123.7 (C3), 135.2 (C4): 130.1 (C5), l43.2 (C6),
128.7 (Ca), 133.8 (Cb), 127.1 (Cc): l27.1 (Cd). FAB (m/
z): 982 (M+), 804 (M–{5-CF3-pyS}), 720 (M–PPh3)
and 542 (M–{5-CF3-pyS}–PPh3).
0.313 mmol). Anal. Calc. for C48H38F6N4P2S2Ru (mol.
wt. 1012.1): C, 56.9; H, 3.8; N, 5.5. Found: C, 56.9; H,
4.0; N, 5.4%. IR (KBr): 3449 (vb), 3058 (m), 1578 (m),
1542 (s), 1482 (m), 1434 (s), 1395 (s), 1311 (w), 1274
(s), 1233 (m), 1197 (m), 1172 (m), 1147 (m), 1114 (m),
1089 (m), 1027 (w), 992 (m), 929 (m), 855 (m), 746
(m), 697 (s), 536 (m), 523 (s), 497 (m), 466 (w). 1H
NMR (CDCl3, ppm) 6.13 (H5, s, 1H); 2.26 (CH3, s,
3H) 7.2–6.9 (m, 15H, PPh3); 13C NMR (CDCl3, ppm)
180.1 (C2), 135.0 (C4): 118.5 (C5), l71.4 (C6), 128.9
(Ca), 133.7 (Cb), 127.0 (Cc): l27.1 (Cd). FAB (m/z):
1012 (M+), 819 (M–{4,6-CF3Me-pymS}), 750 (M–
PPh3) and 557 (M–{4,6-CF3Me-pymS}–PPh3).
2.2.4. [Ru(3-Me3Si-pyS)2(PPh3)2] (4)
2.2.7. [Ru(pySe)2(PPh3)2] Æ (CH2Cl2) (7)
3-TMS-pySH (0.115 g, 0.625 mmol), Et3N (0.1 ml,
0.688 mmol) and [RuCl2(PPh3)3] (0.3 g, 0.313 mmol).
Anal. Calc. for C52H54N2P2S2Si2Ru (mol. wt. 990.3):
C, 63.0; H, 5.5; N, 2.8. Found: C, 63.0; H, 5.6; N,
2.7%. IR (KBr): 3048 (m), 1156 (m), 1541 (m), 1481
(m), 1432 (m), 1365 (s), 1261 (w), 1242 (m), 1221 (m),
1183 (w), 1135 (m), 1086 (m), 1072 (m), 1055 (m),
1027 (w), 840 (s), 746 (m), 695 (s), 625 (w), 536 (s),
A methanolic solution of dipyridyl-2,20-diselenide
(0.0983 g, 0.312 mmol) was treated with NaBH4
(0.026 g, 0.688 mmol). The mixture was stirred for 1 h
and a solution of [RuCl2(PPh3)3] (0.3 g, 0.313 mmol)
in dichloromethane was added. The reaction mixture
was stirred for 3 h and the resulting solid filtered off un-
der nitrogen, washed with diethyl ether and dried under
vacuum
(0.052 g,
30.4%).
Anal.
Calc.
for
1
523 (s), 498 (m), 468 (w). H NMR (CDCl3, ppm) 7.8
C47H40Cl2N2P2Se2Ru (dichloromethane solvate, mol.
wt. 1024.7): C, 55.0; H, 3.9; N, 2.7. Found: C, 54.0; H,
4.2; N, 2.7%. IR (KBr): 3049 (m), 1579 (m), 1544 (m),
1480 (m), 1432 (m), 1416 (m), 1311 (w), 1260 (m),
1247 (w), 1148 (m), 1121 (m), 1096 (m), 1087 (m), 752
(m), 738 (s), 697 (s), 538 (m), 521 (s), 499 (m). 1H
NMR (CDCl3, ppm) 8.0 (H6, d, 1H), 6.7 (H3, d, 1H),
6.4 (H4, d, 1H), 6.1 (H5, t, 1H); 7.2–6.9 (m, 15H,
PPh3); l3C NMR (CDCl3, ppm) 173.2 (C2), 136.9 (C4):
117.0 (C5), l48.7 (C6), 128.1 (Ca), 134.2 (Cb), 126.7
(Cc): l26.8 (Cd). FAB (m/z): 940 (M+), 784 (M–pySe),
678 (M–PPh3) and 522 (M–{pySe}–PPh3).
(H6, d, 1H), 6.2 (H4, t, 1H); 0.5 (CH3, s, 9H); 7.2–6.9
(m, 16H, H4, PPh3); l3C NMR (CDCl3, ppm) 187.4
(C2), 138.8 (C3), 136.6 (C4), 114.7 (C5), l46.2 (C6),
127.9 (Ca), 134.1 (Cb), 126.6 (Cc): l26.7 (Cd). FAB
(m/z): 990 (M+), 808 (M–{3-TMS-pyS}), 728 (M–
PPh3) and 546 (M–{3-TMS-pyS}–PPh3). Crystals of
[Ru(3-Me3Si-pyS)2(PPh3)2] suitable for X-ray studies
were obtained by crystallisation of the initial product
from methanol/dichloromethane.
2.2.5. [Ru(4-CF3-pymS)2(PPh3)2] (5)
4-CF3-pymSH (0.1125 g, 0.625 mmol), Et3N (0.1 ml,
0.688 mmol) and [RuCl2(PPh3)3] (0.3 g, 0.313 mmol).
Anal. Calc. for C46H34F6N4P2S2Ru (mol. wt. 983.9):
C, 56.1; H, 3.5; N, 5.7. Found: C, 56.3; H, 3.5; N,
5.6%. IR (KBr): 3450 (vb), 3047 (m), 1555 (m), 1481
(m), 1432 (m), 1347 (m), 1331 (s), 1265 (w), 1195 (s),
1163 (m), 1147 (m), 1113 (m), 1091 (m), 1026 (w),
1003 (m), 834 (m), 739 (m), 698 (s), 684 (m), 535 (s),
2.2.8. [Ru(3-CF3-pySe)2(PPh3)2] (8)
(3-CF3-pySe)2 (0.141 g, 0.312 mmol), NaBH4
(0.026 g, 0.688 mmol) and [RuCl2(PPh3)3] (0.3 g, 0.313
mmol). Anal. Calc. for C48H36F6N2P2Se2Ru (mol. wt.
1077.97): C, 53.4; H, 3.4; N, 2.6. Found: C, 53.2; H,
3.4; N, 2.6%. IR (KBr): 3051 (m), 1561 (m), 1542 (w),
1481 (m), 1433 (s), 1402 (s), 1319 (s), 1267 (w), 1247
(w), 1163 (m), 1128 (m), 1087 (m), 1058 (m), 1045 (m),
1
495 (m), 474 (w). H NMR (CDCl3, ppm) 7.7 (H6, d,
1H), 6.3 (H5, d, 1H); 7.2–6.9 (m, 15H, PPh3); 13C
NMR (CDCl3, ppm) 188.6 (C2), 153.0 (C4), 119.0 (C5),
l55.7 (C6), 129.0 (Ca), 134.6 (Cb), 127.3 (Cc): l27.4
(Cd). FAB (m/z): 984 (M+), 805 (M–{4-CF3-pymS}),
722 (M–PPh3) and 543 (M–{4-CF3-pymS}–PPh3). Crys-
tals of [Ru(4-CF3-pymS)2(PPh3)2] suitable for X-ray
studies were obtained by crystallisation of the initial
product from methanol/dichloromethane.
799 (m), 741 (s), 695 (s), 537 (m), 521 (s), 494 (m). H
1
NMR (CDCl3, ppm) 8.4 (H6, d, 1H), 7.4 (H4, d, 1H),
6.5 (H5, t, 1H), 7.3–7.1 (m, 15H, PPh3). FAB (m/z):
1076 (M+), 852 (M–{3-CF3-pySe}), 814 (M–PPh3) and
589 (M–{3-CF3-pySe}–PPh3). Crystals of [Ru(3-CF3-
pySe)2(PPh3)2] Æ 2(CH2Cl2) suitable for X-ray studies
were obtained by crystallisation of the initial product
from methanol/dichloromethane.
2.2.6. [Ru(4,6-CF3Me-pymS)2(PPh3)2] (6)
4,6-CF3Me-pymSH (0.1212 g, 0.625 mmol), Et3N
(0.1 ml, 0.688 mmol) and [RuCl2(PPh3)3] (0.3 g,
2.2.9. [Ru(5-CF3-pySe)2(PPh3)2] (9)
(5-CF3-pySe)2 (0.141 g, 0.312 mmol), NaBH4 (0.026 g,
0.688 mmol) and [RuCl2(PPh3)3] (0.3 g, 0.313 mmol).

866
A. Sousa-Pedrares et al. / Inorganica Chimica Acta 359 (2006) 863–876
Anal. Calc. for C48H36F6N2P2Se2Ru (mol. wt. 1077.97):
C, 53.4; H, 3.4; N, 2.6. Found: C, 53.1; H, 3.5; N, 2.7%.
IR (KBr): 3450 (b), 3053 (m), 1597 (m), 1549 (w), 1480
(m), 1459 (w), 1434 (m), 1377 (w), 1323 (s), 1265 (m),
1167 (m), 1137 (m), 1091 (s), 1071 (m), 1029 (w), 826
s, 1H), 6.6 (H3, t, 1H), 6.3 (H4, d, 1H); 7.2–6.9 (m,
15H, PPh3). FAB (m/z): 1072 (M+), 893 (M–{5-CF3-
pyS}), 810 (M–PPh3) and 632 (M–{5-CF3-pyS}–PPh3).
2.2.13. [Os(3-Me3Si-pyS)2(PPh3)2] (13)
1
(w), 742 (w), 697 (s), 536 (m), 521 (m), 496 (m). H
3-TMS-pySH (0.0483 g, 0.264 mmol), Et3N (0.04 ml,
0.276 mmol) and [OsBr2(PPh3)3] (0.15 g, 0.132 mmol).
Anal. Calc. for C52H54Si2N2P2S2Os (mol. wt. 1079.5):
C, 57.8; H, 5.0; N, 2.6. Found: C, 57.3; H, 4.9; N,
2.7%. IR (KBr): 3436 (vb), 3052 (m), 2954 (w), 1557
(w), 1480 (m), 1433 (m), 1364 (s), 1311 (w), 1247 (m),
1215 (m), 1184 (w), 1158 (m), 1134 (m), 1087 (m),
1033 (w), 845 (s), 749 (m), 697 (s), 619 (w), 522 (s),
NMR (CDCl3, ppm) 8.0 (H6, d, 1H), 6.8 (H3, d, 1H),
6.5 (H4, t, 1H), 7.2–6.9 (m, 15H, PPh3); l3C NMR (CDCl3,
ppm) 180.0 (C2), 127.7 (C3), 136.2 (C4): 129.5 (C5), l45.7
(C6), 128.5 (Ca), 133.8 (Cb), 127.1 (Cc): l27.0 (Cd). FAB
(m/z): 1076 (M+), 852 (M–5-CF3-pySe), 814 (M–PPh3)
and 589 (M–{5-CF3-pySe}–PPh3).
1
2.2.10. [Os(pyS)2(PPh3)2] (10)
427 (w). H NMR (CDCl3, ppm) 7.4 (H6, d, 1H), 7.1
Et3N (0.04 ml, 0.276 mmol) was added to a methan-
olic solution of pySH (0.0293 g, 0.264 mmol). The
resulting solution was stirred for 1 h and a solution of
[OsBr2(PPh3)3] (0.15 g, 0.132 mmol) in dichloromethane
was added. The reaction mixture was stirred for 2 h and
the resulting solid was filtered off, washed with diethyl
ether and dried under vacuum. Anal. Calc. for
C46H38N2P2S2Os (mol. wt. 934.9): C, 59.0; H, 4.1; N,
3.0. Found: C, 58.8; H, 4.1; N, 2.7%. IR (KBr): 3437
(vb), 3054 (m), 1580 (m), 1480 (m), 1434 (m), 1382
(w), 1315 (w), 1261 (w), 1184 (w), 1144 (m), 1087 (m),
(H4, d, 1H), 6.0 (H5, t, 1H); 0.3 (CH3, s, 9H); 7.3–7.2
(m, 15H, PPh3); 13C NMR (CDCl3, ppm) 185.5 (C2),
138.2 (C3), 135.1 (C4), 114.9 (C5), l44.2 (C6), 127.8
(Ca), 134.0 (Cb), 126.6 (Cc), l26.8 (Cd), –1.6 (CH3).
FAB (m/z): 1080 (M+), 897 (M–{3-TMS-pyS}), 818
(M–PPh3) and 633 (M–{3-TMS-pyS}–PPh3). Crystals
of [Os(3-TMS-pySe)2(PPh3)2] suitable for X-ray studies
were obtained by crystallisation of the initial product
from methanol/dichloromethane.
2.2.14. [Os(4-CF3-pymS)2(PPh3)2] (14)
1
1028 (w), 801 (w), 743 (m), 697 (s), 521 (s). H NMR
4-CF3-pymSH (0.0475 g, 0.264 mmol), Et3N (0.04 ml,
0.276 mmol) and [OsBr2(PPh3)3] (0.15 g, 0.132 mmol).
Anal. Calc. for C46H34F6N4P2S2Os (mol. wt. 1073.1):
C, 51.4; H, 3.2; N, 5.2. Found: C, 51.2; H, 3.3; N,
5.4%. IR (KBr): 3438 (vb), 3056 (m), 1543 (w), 1480
(m), 1434 (m), 1384 (w), 1348 (m), 1331 (m), 1187 (m),
1142 (m), 1114 (m), 1088 (m), 1028 (w), 990 (w), 819
(w), 746 (m), 696 (s), 544 (m), 521 (s), 430 (w). FAB
(m/z): 1072 (M+), 894 (M–{4-CF3-pymS}), 816 (M–
PPh3) and 633 (M–{4-CF3-pymS}–PPh3).
(CDCl3, ppm); 7.7 (H6, d, 1H), 6.8 (H3, d, 1H), 6.2
(H4, t, 1H), 6.0 (H5, t, 1H); 7.2–6.9 (m, 15H, PPh3).
FAB (m/z): 937 (M+), 826 (M–pyS), 675 (M–PPh3)
and 562 (M–{pyS}–PPh3).
2.2.11. [Os(3-CF3-pyS)2(PPh3)2] Æ (CH2Cl2) (11)
3-CF3-pySH (0.0472 g, 0.264 mmol), Et3N (0.04 ml,
0.276 mmol) and [OsBr2(PPh3)3] (0.15 g, 0.132 mmol).
Anal. Calc. for C49H38Cl2F6N2P2S2Os (mol. wt. 1155.2):
C, 50.9; H, 3.3; N, 2.4. Found: C, 51.2; H, 3.0; N, 2.2%.
IR (KBr): 3439 (vb), 3055 (m), 1578 (w), 1480 (m), 1433
(m), 1403 (m), 1320 (s), 1261 (w), 1201 (w), 1167 (m),
1123 (m), 1087 (m), 1047 (m), 1003 (w), 793 (w), 744
2.2.15. [Os(4 6-CF3Me-pymS)2(PPh3)2] (15)
4,6-CF3Me-pymSH (0.0512 g, 0.264 mmol), Et3N
(0.04 ml, 0.276 mmol) and [OsBr2(PPh3)3] (0.15 g,
0.132 mmol). Anal. Calc. for C48H38F6N4P2S2Os (mol.
wt. 1101.1): C, 52.3; H, 3.4; N, 5.1. Found: C, 52.6; H,
3.8; N, 5.0%. IR (KBr): 3433 (vb), 3055 (m), 2926 (m),
1631 (m), 1579 (w), 1537 (w), 1478 (m), 1434 (m), 1392
(m), 1310 (w), 1278 (m), 1232 (m), 1194 (m), 1147 (m),
1115 (m), 1086 (m), 800 (w), 746 (m), 698 (s), 520 (s),
1
(m), 697 (s), 521 (s), 432 (w). H NMR (CDCl3, ppm)
7.8 (H6, d, 1H), 6.2 (H5, t, 1H); 7.2–6.9 (m, 16H, H4,
PPh3). FAB (m/z): 1072 (M+), 893 (M–{3-CF3-pyS}),
810 (M–PPh3) and 632 (M–{3-CF3-pyS}–PPh3). Crystals
of [Os(3-CF3-pyS)2(PPh3)2] Æ (CHCl3) suitable for X-ray
studies were obtained by crystallisation of the initial prod-
uct from methanol/chloroform.
1
430 (w). H NMR (CDCl3, ppm) 6.1 (H5, s, 1H), 7.5–
7.7 (m, 15H, PPh3); 2.3 (CH3, s, 3H). FAB (m/z): 1103
(M+), 908 (M–{4,6-CF3Me-pymS}), 840 (M–PPh3)
and 647 (M–{4,6-CF3Me-pymS}–PPh3).
2.2.12. [Os(5-CF3-pyS)2(PPh3)2] (12)
5-CF3-pySH (0.0472 g, 0.264 mmol), Et3N (0.04 ml,
0.276 mmol) and [OsBr2(PPh3)3] (0.15 g, 0.132 mmol).
Anal. Calc. for C48H36F6N2P2S2Os (mol. wt. 1071.1):
C, 53.7; H, 3.4; N, 2.6. Found: C, 54.1; H, 3.7; N,
2.7%. IR (KBr): 3432 (vb), 3056 (m), 1593 (m), 1477
(m), 1434 (m), 1382 (w), 1322 (s), 1265 (w), 1152 (s),
1118 (m), 1079 (m), 1031 (m), 819 (w), 745 (m), 697
2.2.16. [Os(pySe)2(PPh3)2] (16)
A methanolic solution of dipyridyl-2,20-diselenide
(0.0414 g, 0.132 mmol) was treated with NaBH4
(0.011 g, 0.290 mmol). The mixture was stirred for 1 h
and a solution of [OsBr2(PPh3)3] (0.15 g, 0.132 mmol)
in dichloromethane was added. The reaction mixture
1
(s), 522 (s), 430 (w). H NMR (CDCl3, ppm) 7.7 (H6,

A. Sousa-Pedrares et al. / Inorganica Chimica Acta 359 (2006) 863–876
867
was stirred for 3 h and the resulting solid was filtered off
under nitrogen, washed with diethyl ether and dried un-
der vacuum (0.052 g, 30.4%). Anal. Calc. for
C46H38N2P2Se2Os (mol. wt. 1028.9): C, 53.6; H, 3.7;
N, 2.7. Found: C, 54.0; H, 3.7; N, 2.6%. IR (KBr):
3441 (vb), 3051 (m), 1580 (w), 1543 (w), 1480 (m),
1435 (m), 1311 (w), 1261 (w), 1187 (w), 1151 (w), 1121
(m), 1086 (m), 1026 (w), 851 (w), 745 (m), 698 (s), 521
(s), 432 (w). FAB (m/z): 1030 (M+), 871 (M–pySe),
767 (M–PPh3) and 609 (M–{pySe}-PPh3).
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 com-
pounds, except 2 and 4, were corrected using the pro-
gram SADABS [30]; absorption in 2 was corrected using
semiempirical w scans; absorption effects in 4 were disre-
garded due to its twinned nature. The crystal structures
of all compounds were solved by direct methods. Crys-
tallographic programs used for structure solution and
refinement were those in SHELX97 [31] and these were in-
stalled on a PC clone. Scattering factors were those pro-
vided with the SHELX program system. Missing atoms
were located in the difference Fourier map and included
in subsequent refinement cycles. The structures were re-
fined by full-matrix least-squares refinement on F2, using
anisotropic displacement parameters for all non-hydro-
gen atoms. Hydrogen atoms were placed geometrically
and refined using a riding model, including free rotation
about C–C bonds for methyl groups, with C–H dis-
2.2.17. [Os(3-CF3-pySe)2(PPh3)2 ] Æ 2(CH2Cl2) (17)
(3-CF3-pySe)2 (0.0593 g, 0.132 mmol), NaBH4
(0.011 g, 0.290 mmol) and [OsBr2(PPh3)3] (0.15 g,
0.132 mmol). Anal. Calc. for C52H40F6Cl4N2P2Se2Os
(mol. wt. 1382.13): C, 46.9; H, 2.9; N, 2.0. Found: C,
46.7; H, 2.5; N, 2.7%. IR (KBr): 3432 (vb), 3056 (m),
1573 (m), 1478 (m), 1435 (m), 1404 (s), 1320 (s), 1261
(m), 1205 (m), 1165 (m), 1130 (s), 1090 (m), 1054 (m),
1
˚
801 (m), 745 (m), 698 (s), 526 (m), 436 (w). H NMR
tances of 0.93–0.97 A. For all compounds, hydrogen
(CDCl3, ppm) 7.7 (H6, d, 1H), 6.9 (H4, d, 1H), 5.8
(H5, t, 1H), 7.5–7.0 (m, 15H, PPh3). FAB (m/z): 1166
(M+), 941 (M–{3-CF3-pySe}), 904 (M–PPh3) and 678
(M–{3-CF3-pySe}–PPh3). Crystals of [Os(3-CF3-py-
Se)2(PPh3)2] Æ 2(CH2Cl2) suitable for X-ray studies were
obtained by crystallisation of the initial product from
methanol/dichloromethane.
atoms were refined with Uiso constrained at 1.2 (for
non-methyl groups) and 1.5 (for methyl groups) times
Ueq of the carrier C atom. Disorder was typically han-
dled by introducing split positions for the affected
groups into the refinement of the respective occupancies.
Compound 4 was a merohedral twin, where the twin
law is a twofold axis along the bisector of the a and b axes.
This axis interchanges h and k and reverses l. The struc-
ture has heavy atoms such as ruthenium, so it should be
possible to determine the absolute structure. The absolute
structure Flack parameter x [32] refined to 0.37(6), so the
structure was refined as a four-component twin so as to
take racemic twinning into account. Only the ruthenium
atom was refined using anisotropic thermal parameters.
The crystallographic problems associated with this struc-
ture mean that geometrical parameters such as bond
lengths and angles will not be discussed. Compound 4 will
only be used to illustrate how the connectivity around the
metal centre is the same as for the rest of all the ruthenium
and osmium structures. On the other hand, the X-ray
crystal structure of the osmium analog of this compound
(compound 13) was studied. Compound 13 was found to
have an analogous unit cell and crystallises in the same
space group, P –4 2(1) c, as one would expect given the
similar covalent radii of ruthenium and osmium. This
proves that the unit cell found for the ruthenium com-
pound 4 is the correct one.
2.2.18. [Os(5-CF3-pySe)2(PPh3)2] Æ 2(CH2Cl2) (18)
(5-CF3-pySe)2 (0.0593 g, 0.132 mmol), NaBH4 (0.011
g, 0.290 mmol) and [OsBr2(PPh3)3] (0.15 g, 0.132 mmol).
Anal. Calc. for C52H40F6Cl4N2P2Se2Os (mol. wt.
1382.12): C, 46.9; H, 2.9; N, 2.0. Found: C, 46.7; H, 2.5;
N, 2.1%. IR (KBr): 3432 (vb), 3056 (m), 1594 (m), 1478
(m), 1434 (m), 1376 (w), 1323 (s), 1261 (m), 1164 (m),
1129 (s), 1088 (s), 1030 (m), 821 (w), 745 (m), 697 (s),
1
521 (s), 430 (w). H NMR (CDCl3, ppm) 7.7 (H6, d,
1H), 6.90 (H3, d, 1H), 6.50 (H4, t, 1H), 7.5–7.0 (m, 15H,
PPh3). FAB (m/z): 1166 (M+), 941 (M–{5-CF3-pySe}),
904 (M–PPh3) and 678 (M–{5-CF3-pySe}–PPh3).
Crystals of [Os(5-CF3-pySe)2(PPh3)2] Æ 2(H2O) suitable
for X-ray studies were obtained by crystallisation of the
initial product from methanol/dichloromethane.
2.3. X-ray crystallography studies
Intensity data for all compounds, except 2, were col-
lected using a Smart-CCD-1000 Bruker diffractometer
(Mo Ka radiation, k = 0.71073 A) equipped with a
graphite monochromator. Intensity data for compound
Pertinent details of the data collections and structure
refinements are summarized in Tables 1 and 2. Selected
bond distances and angles are given in Tables 4–11 and
a summary of the important geometrical data for all
compounds is given in Tables 12 and 13. Further details
regarding the data collections, structure solutions and
refinements are included in the Supporting Information.
Ortep3 [33] drawings with the numbering schemes used
are shown in Figs. 2–10.
˚
2 were collected using a MACH3 Enraf Nonius diffract-
˚
meter (Mo Ka radiation, k = 0.71073 A) equipped with
a graphite monochromator. All crystals were measured
at 293 K apart from compounds 13 and 18, which were
collected at 153 K. The x scan technique was employed
to measure intensities in all crystals. Decomposition of

868
A. Sousa-Pedrares et al. / Inorganica Chimica Acta 359 (2006) 863–876
Table 1
Summary of crystal data and structure refinement for ruthenium complexes
Compound 2
Compound 4
Compound 5
Compound 8
Formula
M
C25H20Cl2F3NPSRu0.5
575.89
C26H27NPSSiRu0.5
990.28
C46H34F6N4P2S2Ru
983.90
C25H20Cl2F3NPSeRu0.5
622.79
Crystal size (mm)
Temperature (K)
0.28 · 0.16 · 0.12
293(2)
0.250 · 0.15 · 0.10
293(2)
0.20 · 0.20 · 0.20
293(2)
0.35 · 0.30 · 0.20
293(2)
˚
Wavelength (A)
0.71073
monoclinic
C2/c
19.820(6)
11.426(3)
22.877(4)
90.00
106.91(2)
90.00
4957(2)
0.71073
tetragonal
0.71073
triclinic
0.17073
monoclinic
C2/c
19.5790(3)
11.4930(3)
22.5770(4)
90.00
107.270(2)
90.00
Crystal symmetry
Space group
ꢀ
ꢀ
P42ð1Þc
P1
˚
a (A)
14.9520
14.9520
21.7030(9)
90.00
13.7161(5)
13.8199(6)
13.9510(6)
101.665(1)
110.114(1)
106.264(1)
2247.50(16)
2
˚
b (A)
˚
c (A)
a (ꢁ)
b (ꢁ)
c (ꢁ)
90.00
90.00
4852.0(2)
8
0.562
3
˚
V (A )
4851.27(17)
8
2.172
Z
8
l (mmꢀ1
)
0.741
0.575
Colleted reflections
Data/restraints/parameters
Goodness-of-fit
5283
5133/0/313
0.932
0.0673
0.1262
11643
11643/0/148
0.487
0.0412
0.09011
15580
10721/0/604
0.972
0.0663
0.1136
9038
4891/0/383
1.060
0.0254
0.0662
R1(F),a/[I > 2r(I)]
wR2(F2),b/[I > 2r(I)]
P
P
a
R1= [jFoj ꢀ jFcj]/ [jFoj].
P
P
1=2
b
wR2 ¼ ½ ðF 2o ꢀ F c2Þꢁ= ðF 2oÞꢁ
.
Table 2
Summary of crystal data and structure refinement for osmium complexes
Compound 11
49H37Cl3F6N2P2S2Os
Compound 13
Compound 17
Compound 18
Compound 19
Formula
M
C
C26H27NPSSiOs0.5
539.71
C25H20Cl2F3NPSeOs0.5
667.35
C48H36F6N2P2O2Se2Os
1196.85
C42H34Cl2F3N2P2SOs
978.81
1190.42
Crystal size (mm)
Temperature (K)
Wavelength (A)
0.30 · 0.15 · 0.10
293(2)
0.71073
0.25 · 0.20 · 0.10
153(2)
0.71073
0.50 · 0.20 · 0.20
293(2)
0.71073
0.25 · 0.20 · 0.10
153(2)
0.71073
0.55 · 0.26 · 0.11
293(2)
0.71073
˚
Crystal symmetry
Space group
a (A)
triclinic
tetragonal
monoclinic
C2/c
19.7198(10)
11.5642(6)
22.9848(12)
90.00
106.7764(11)
90.00
5018.5(4)
8
monoclinic
P2(1)/c
23.781(9)
17.481(6)
11.234(4)
90.00
90.273(8)
90.00
4670(3)
monoclinic
P2(1)/c
9.8016(18)
35.142(7)
11.320(2)
90.00
98.380(3)
90.00
3857.6(12)
4
ꢀ
ꢀ
P1
P42ð1Þc
˚
12.3849(6)
13.5911(7)
15.1235(7)
89.5760(10)
87.8420(10)
69.9380(10)
2389.5(2)
2
14.967
14.967
21.771(5)
90.00
˚
b (A)
˚
c (A)
a (ꢁ)
b (ꢁ)
c (ꢁ)
90.00
90.00
4877.1(15)
8
2.852
3
˚
Volume (A )
Z
4
l (mmꢀ1
)
3.051
4.328
4.422
3.630
Collected reflections
Data/restraints/
parameters
17239
11618/0/586
25013
6018/0/276
17529
6239/0/303
23579
8201/12/568
7922
7922/0/478
Goodness-of-fit
R1(F),a/[I > 2r(I)]
wR2(F2),b/[I > 2r(I)]
1.166
0.0389
0.0966
0.902
0.0333
0.0589
1.033
0.0329
0.0814
0.972
0.0751
0.1831
1.003
0.0565
0.1086
P
P
a
R1 = [jFoj ꢀ jFcj]/ [jFoj].
P
3. Results and discussion
P
1=2
b
wR2 ¼ ½ ðF 2o ꢀ F c2Þ= ðF 2oÞꢁ
.
of the appropriate ligand and triethylamine to a stirred
solution of the precursor [MX2(PPh)3] in dichloro-
methane:
3.1. Synthesis
2½R-pySHꢁ þ 2Et3N þ ½MX2ðPPh3Þ3ꢁ
! ½MðR-pySÞ2ðPPh3Þ2ꢁ þ PPh3 þ 2Et3NHX
M ¼ Ru; X ¼ Cl; M ¼ Os; X ¼ Br
Ruthenium and osmium complexes with heterocy-
clic thiones R-pySH or R-pymSH were all obtained
in reasonable yields by adding a methanolic solution

A. Sousa-Pedrares et al. / Inorganica Chimica Acta 359 (2006) 863–876
869
In each case the resulting solid was filtered off
under nitrogen, washed with ether and dried under
vacuum. Crystalsof[Ru(3-CF3-pyS)2(PPh3)2] Æ 2(CH2Cl2)
(2), [Ru(3-Me3Si-pyS)2(PPh3)2] (4), [Ru(4-CF3-pymS)2-
(PPh3)2] (5), [Os(3-CF3-pyS)2(PPh3)2] Æ (CHCl3) (11),
[Os(3-Me3Si-pyS)2(PPh3)2] (13) and [OsCl2(4,6-Me-
CF3-pymS)(PPh3)2] (19) suitable for X-ray studies were
obtained by slow evaporation of solutions of the initial
product in a mixture of methanol/dichloromethane –
the exception being crystals of compound 11, which
were obtained by crystallisation from methanol/
chloroform.
In the synthesis of the selenium derivatives 7–9 and
16–18, the nucleophilic species was obtained by reduc-
tion of the corresponding diselenide with sodium
borohydride in methanol [34]. The product was subse-
quently reacted with the metal-containing precursor
[MX2(PPh3)3] according to the following general
process:
the presence of m(C@N) and m(C@C) in a non-aro-
matic system. In the complexes, however, these bands
appear in the region 1590–1545 cmꢀ1, which is charac-
teristic of stretching vibrations in an aromatic group
[36]. These observations confirm that the ligand is
present in the complexes in the thiolate form. The
spectra of the complexes also show bands due to
deformation of the aromatic ring, and these appear
in the regions 1110–990 and 750–620 cmꢀ1 [37]. The
presence of triphenylphosphine unit is confirmed by
a medium intensity band at 1000 cmꢀ1, which is due
to m(P–C). The spectra of trimethylsilyl derivatives 4
and 13 also show additional medium intensity bands
at 3100–2900 cmꢀ1, which correspond to the vibra-
tions of the methyl group, and a strong intensity band
in the rang 845–850 cmꢀ1, which is characteristic of
m(Si–C).
In all cases the FAB mass spectra of the compounds
show peaks due to the molecular ion. Signals corre-
sponding to the loss of one of the heterocyclic ligands
are also observed along with peaks corresponding to
ions formed by the loss of one of the thione or triphenyl-
phosphine molecules. The peak clusters have appropri-
ate isotope distributions.
½MX2ðPPh3Þ3ꢁ þ 2NaðR-pySeÞ
! ½MðR-pySeÞ2ðPPh3Þ2ꢁ þ PPh3 þ 2NaX
M ¼ Ru; X ¼ Cl; M ¼ Os; X ¼ Br
The triphenylphosphine proton signals in the 1H
NMR spectra of the compounds (see Section 2) appear
at relatively low field, with chemical shifts between 7.5
and 6.9 ppm. These signals appear as three triplets that
integrate to 6, 3 and 6 protons, respectively, and corre-
spond to the three different types of proton in this li-
gand. The other signals in the spectra are due to
protons in the thiolate or selenolate ligands. The most
deshielded of these signals corresponds to the ring pro-
ton ortho to the nitrogen atom and this appears at 7.6
and 8.4 ppm. This signal is shifted to higher field with
respect to that in the corresponding free ligands. The
same trend is observed for the other proton signals
for the aromatic rings in that they are shifted to
slightly higher field in the complexes as compared to
the ligands. The signals for these protons could be as-
signed in all cases, except in cases where the signal
overlapped the large triphenylphosphine signal. For
these signals it was necessary to study COSY spectra
to obtain the chemical shifts for these protons. The ali-
phatic proton signals – in ligands that contain such
substituents on the heterocyclic ring – appear at rela-
tively high field.
Crystallisation of the products from methanol/dichlo-
romethane gave crystals of [Ru(3-CF3-pySe)2(PPh3)2] Æ
2(CH2Cl2) (8), [Os(3-CF3-pySe)2(PPh3)2] Æ 2(CH2Cl2)
(17) and [Os(5-CF3-pySe)2(PPh3)2] Æ 2(H2O) (18) that
are suitable for X-ray studies.
The complexes reported here are air-stable in the
solid form and do not show any tendency to decompo-
sition or oxidation. The ruthenium complexes are also
relatively stable in solution but the osmium complex
decomposes slowly. This fact makes it difficult to study
solutions of these complexes by NMR spectroscopy or
cyclic voltammetry. It is worth noting that the crystal-
lisation of [Os(4,6-MeCF3-pymS)2(PPh3)2] (15) from a
mixture of dichloromethane/methanol allows the isola-
tion of the osmiun(III) complex [OsCl2(4,6-MeCF3-
pymS)(PPh3)2] (19). This finding can be rationalized
as being the result of nucleophilic attack of a coordi-
nated ligand to CH2Cl2. This behavior has been found
previously in the reaction between [Ag(6-tBuMe2Si-
pyS)] and CH2Cl2, for which the reaction products
were isolated and characterized by X-ray diffraction
[35].
3.2. Spectroscopy
The 13C spectra of the ruthenium complexes contain,
in all cases, signals corresponding to the different carbon
atoms in the molecule (see Section 2). In these spectra
the most deshielded signal is due to the carbon directly
attached to the sulfur. This signal is shifted to slightly
higher field in comparison to that in the free ligand. This
change in chemical shift is due to the reduction in the or-
der of the C–S bond that occurs in the transformation
from thione to thionate [38]. At higher field several
The IR spectra of the complexes confirm the pres-
ence of the ligands coordinated to the metal. For
example, the band attributable to the m(N–H), which
appears at 3200–3100 cmꢀ1 in the free thione ligands,
is absent and this indicates that the ligands are in the
deprotonated form in the complexes. The strong li-
gand bands in the range 1640–1660 cmꢀ1 are due to

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A. Sousa-Pedrares et al. / Inorganica Chimica Acta 359 (2006) 863–876
spectra contain signals due to the methyl groups present
in some of the ligands. However, the signals due to the
quaternary carbons of the CF3 groups – for those
compounds that contain them – are not observed due
to their low intensity. Poor solubility and a degree of
instability mean that raesonable 13C data could not be
obtained for the osmium complexes. However, the pres-
ence of the trimethylsilyl group in [Os(3-Me3Si-pyS)2-
(PPh3)2] increased the solubility and, in this case, the
spectrum could be recorded (see Section 2).
2.6E-05
1.6E-05
6.0E-06
-4.0E-06
-1.4E-05
-2.4E-05
-3.4E-05
Ic
Ia
0.000
0.200
0.400
0.600
0.800
1.000
3.3. Electrochemical behavior
E (V vs. ECS)
Fig. 1. Cyclic voltammogram of [Ru(3-Me3Si-pyS)2(PPh3)2] in
dichloromethane, scan rate 0.2 V/s.
The cyclic voltammetry results for the ruthenium
complexes are shown in Table 3. In addition, a typical
voltammogram for a ruthenium compound is shown in
Fig. 1. In all cases, an anodic and a cathodic peak are
observed and these have the characteristics of a quasi-
reversible monoelectronic process.
3.4. Structural characterization
3.4.1. Molecular structures of [Ru(3-CF3-
In the pyridine-2-thionato complexes, replacement of
hydrogen by a Me3Si group results in a slight decrease in
the oxidation potential. However, replacement of a
hydrogen by a CF3 group leads to a large increase in
the oxidation potential. This phenomenon could be
caused by a conventional substituent inductive effect
on coordinated metal potentials. In such a case, the elec-
tron-withdrawing effect of the CF3 group would make
the oxidation between Ru(II)/Ru(III) more difficult
and thereby shift E1/2 to higher values. The same expla-
nation may also apply to the complexes derived from
pyrimidine-2-thionato and pyridine-2-selenolato li-
gands. Comparison of the E1/2 values for the complexes
of pyridine-2-thionato and pyrimidine-2-thionato shows
that the these ligands are poorer electron donors than
the corresponding 2-pyridine-2-thione ligands.
pyS)2(PPh3)2] Æ 2(CH2Cl2) (2), [Ru(3-Me3Si-
pyS)2(PPh3)2] (4), [Ru(4-CF3-pymS)2(PPh3)2] (5)
and [Ru(3-CF3-pySe)2(PPh3)2] Æ 2(CH2Cl2) (8)
The crystal structures of the ruthenium complexes are
shown in Figs. 2–5 along with the numbering scheme;
solvent molecules are not shown. Crystallographic data
and selected distances and bond angles are given in
Tables 4–6.
The presence in compound 4 of twin-type crystals (see
Section 2) prevented good refinement of the structural
data. This means that, although it was possible to obtain
the connectivity between all the atoms in the complex,
the distance and bond angle values are associated with
sufficiently high level of error that they will not be in-
cluded in the discussion.
The compounds are structurally very similar regard-
less of the nature of the thione and the substituents on
the ring, which do not markedly affect the structural
parameters. All of the complexes consist of neutral
monomeric units with the ruthenium atom bonded to
two phosphorus atoms from the triphenylphosphine
Comparison of the results for the pyridine-2-thionato
complexes with those for the pyridine-2-selenolato com-
plexes shows a lower oxidation potential for the Ru/Se
system. This indicates that the HOMO (Se) is destabi-
lized relative to that of the corresponding Ru/S system.
Table 3
Cyclic voltammetric data for the ruthenium complexes
L
R
v = 0.2 V/s
v = 0.02 V/s
Epc
Epa
DEp
E1/2
Epc
Epa
DEp
E1/2
pyS
H
0.427
0.349
0.661
0.667
0.582
0.510
0.796
0.836
0.155
0.161
0.135
0.169
0.505
0.430
0.729
0.752
0.444
0.380
0.676
0.692
0.554
0.482
0.770
0.800
0.110
0.102
0.094
0.108
0.499
0.431
0.723
0.746
3-Me3 Si
3-CF3
5-CF3
pymS
pySe
4-CF3
4,6-MeCF3
0.851
0.783
1.028
0.908
0.177
0.125
0.940
0.846
0.880
0.792
0.988
0.886
0.108
0.094
0.934
0.839
H
3CF3
5CF3
0.371
0.549
0.603
0.530
0.780
0.766
0.159
0.231
0.163
0.451
0.665
0.685
0.392
0.590
0.628
0.498
0.724
0.724
0.106
0.134
0.096
0.445
0.657
0.676

A. Sousa-Pedrares et al. / Inorganica Chimica Acta 359 (2006) 863–876
871
Fig. 2. Molecular structure of [Ru(3-CF3-pyS)2(PPh3)2] Æ 2(CH2Cl2)
(2).
Fig. 4. Molecular structure of [Ru(4-CF3-pymS)2(PPh3)2] (5).
Fig. 3. Molecular structure of [Ru(3-Me3Si-pyS)2(PPh3)2] (4).
Fig. 5. Molecular structure of [Ru(3-CF3-pySe)2(PPh3)2] Æ 2(CH2Cl2)
(8).
molecules, which are cis with respect to one another.
The ruthenium is also bonded to two heterocyclic li-
gands that coordinate to the metal through their nitro-
gen and sulfur atoms – or selenium in the case of
compound 8 – with these latter two atoms arranged
trans with respect to one another.
The environment of the metal is distorted octahedral
in all cases and the bond angles between the atoms ar-
ranged trans are markedly different from the ideal value
of 180 ꢁ (see Table 12). The main cause of this distortion
is the low value for the chelate angle corresponding to
the four-membered ring formed by the bidentate ligand;
the values for these angles are in the range 67.21(19)–
68.46(4)ꢁ.
The Ru–S bond lengths in compounds 2 and 5 are
very similar and are in the range 2.416(7)–2.4327(12)
˚
A. These values are very close to those found in other
ruthenium(II) complexes with heterocyclic thione li-
˚
gands (2.39–2.45 A) [13]. The Ru–N bond lengths in
˚
all the complexes [2.086(4)–2.1467(16) A] and the Ru–
˚
P distances [ 2.2936(5)–2.3566(13) A] are also as one

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A. Sousa-Pedrares et al. / Inorganica Chimica Acta 359 (2006) 863–876
Table 4
means that it is impossible to make a direct comparison
between the structural parameters. For example, the
Ru–Se distance in 8, 2.52456(19) A, is markedly longer
˚
Selected bond distances (A) and angles (ꢁ) for [Ru(3-CF3-pyS)2-
(PPh3)2] Æ 2(CH2Cl2) (2)
˚
Ru(1)–N(1)
Ru(1)–P(1)
Ru(1)–S(1)
S(1)–C(1)
2.125(7)
2.300(2)
2.416(2)
1.729(8)
1.807(9)
P(1)–C(7)
P(1)–C(13)
N(1)–C(5)
N(1)–C(1)
1.820(9)
1.845(8)
1.334(9)
1.376(9)
than the average value found in the Ru(IV) complex
described above [2.365(3) A]. This difference is undoubt-
˚
edly due to the coordinative character of the ligand
involved in each complex and the difference in the oxida-
tion state of the metal. A better comparison is probably
that with the analogous osmium complex (17), which is
isostructural and has an analogous unit cell. The Os–Se
P(1)–C(19)
N(1)–Ru(1)–N(1)#1
N(1)–Ru(1)–P(1)
N(1)–Ru(1)–S(1)
S(1)–Ru(1)–P(1)
77.1(3)
P(1)–Ru(1)–S(1)#1
P(1)–Ru(1)–N(1)#1
N(1)–Ru(1)–S(1)#1
P(1)–Ru(1)–P(1)#1
98.66(8)
163.53(18)
67.21(19)
99.63(8)
93.67(17)
90.43(19)
98.28(12)
˚
distance in compound 17, 2.5314(4) A, is very similar to
Symmetry transformation used to generate equivalent atoms: #1:
that in complex 8 (see below).
ꢀx + 1, y, ꢀz + 1/2.
In these complexes the thiolate ligands are essentially
planar, with S–C bond distances in the range of 1.725 at
1.733 A (average value). These values are higher than
˚
those in the free thione [40] and this indicates that the
ligands are in the thiolate form in the complexes. Other
structural parameters for this ligand – as well as for the
triphenylphosphine molecule – are as one would expect
for this type of complex and do not warrant further
attention.
Solvent molecules, in those complexes that contain
them, are located within the network but do not interact
significantly with the complex.
Table 5
˚
Selected bond distances (A) and angles (ꢁ) for [Ru(4-CF3-
pymS)2(PPh3)2] (5)
Ru(1)–N(1)
Ru(1)–P(1)
Ru(1)–S(1)
2.087(3)
2.3518(12) Ru(1)–P(2)
2.4304(12) Ru(1)–S(2)
Ru(1)–N(3)
2.086(4)
2.3566(13)
2.4327(12)
N(1)–Ru(1)–N(3)
N(1)–Ru(1)–P(1)
N(1)–Ru(1)–P(2)
P(1)–Ru(1)–P(2)
N(3)–Ru(1)–S(1)
P(2)–Ru(1)–S(1)
N(3)–Ru(1)–S(2)
P(2)–Ru(1)–S(2)
82.10(14)
167.19(10)
87.80(11)
102.86(5)
91.51(10)
92.46(5)
S(1)–Ru(1)–S(2)
N(3)–Ru(1)–P(1)
N(3)–Ru(1)–P(2) 166.78(10)
N(1)–Ru(1)–S(1)
P(1)–Ru(1)–S(1)
N(1)–Ru(1)–S(2)
P(1)–Ru(1)–S(2)
152.14(5)
88.30(10)
67.36(10)
104.63(4)
90.99(10)
93.14(4)
3.4.2. Molecular structures of [Os(3-CF3-pyS)2
(PPh3)2] Æ (CHCl3) (11), [Os(3-Me3Si-pyS)2
(PPh3)2] (13), [Os(3-CF3-pySe)2(PPh3)2] Æ
67.38(10)
104.48(4)
2(CH2Cl2) (17), [Os(5-CF3-pySe)2(PPh3)2] Æ 2(H2O)
(18) and [OsCl2(4,6-MeCF3-pymS)(PPh3)2] (19)
The crystal structures of the compounds under inves-
tigation are shown in Figs. 6–10 along with the number-
ing scheme used. Solvent molecules are not shown in
these figures. Selected distances and angles for these
complexes are given in Tables 7–11.
would expect and are similar to those found in other
ruthenium(II) complexes with heterocyclic thiones and
triphenylphosphine; e.g., the aforementioned complex
[Ru(py)2(PPh3)2], whose crystal structure has been re-
ported (see Table 12) [8].
The structural determination of complex 8 represents
the first example of a monomeric ruthenium(II) complex
containing a selenolate ligand. Examples can be found
in the literature of oligomeric ruthenium(II) selenolate
structures in which the selenium atom acts as a bridge
between metal centers. However, the only monomeric
structure was reported for [Ru{Se(2,3,5,6-Me4C6H)}4-
(CH3CN)], in which the metal is in the oxidation state
IV [39] and the selenolate ligand is very hindered and
acts as a terminal monodentate system. This situation
All of the complexes have similar structures and these
consist of neutral monomeric units with the metal in a
distorted octahedral environment. As in the case of the
ruthenium complexes, the metal is coordinated by two
triphenylphosphine molecules in cis to one another.
The osmium is also coordinated by two bidentate
(N,X), X = S or Se, ligands, with the X donor atoms
trans to one another.
In a similar way to the ruthenium complexes,
compounds 17 and 18 represent the first examples of
Table 6
Selected bond distances (A) and angles (ꢁ) for [Ru(3-CF3-pySe)2(PPh3)2] Æ 2(CH2Cl2) (8)
˚
´
Ru(1)–N(1)
Ru(1)–Se(1)
Se(1)–C(1)
2.1467(16)
2.52456(19)
1.8834(19)
Ru(1)–P(1)
N(1)–C(5)
N(1)–C(1)
2.2936(5)
1.338(3)
1.350(2)
N(1)–Ru(1)–N(1)#1A
N(1)–Ru(1)–P(1)#1A
N(1)–Ru(1)–Se(1)
Se(1)–Ru(1)–Se(1)#1
P(1)–Ru(1)–P(1)#1
77.03(8)
93.77(4)
68.46(4)
153.241(12)
98.18(3)
P(1)–Ru(1)–Se(1)#1
N(1)–Ru(1)–P(1)
N(1)–Ru(1)–Se(1)#1A
Se(1)–Ru(1)–P(1)
99.064(13)
163.55(4)
90.29(4)
98.368(13)
Symmetry transformation used to generate equivalent atoms: #1: ꢀx, y, ꢀz + 1/2.

A. Sousa-Pedrares et al. / Inorganica Chimica Acta 359 (2006) 863–876
873
Fig. 8. Molecular structure of [Os(3-CF3-pySe)2(PPh3)2] Æ 2(CH2Cl2)
(17).
Fig. 6. Molecular structure of [Os(3-CF3-pyS)2(PPh3)2] Æ (CHCl3) (11).
Fig. 7. Molecular structure of [Os(3-Me3Si-pyS)2(PPh3)2] (13).
monomeric osmium(II) species containing selenolate li-
gands. A survey of the literature only reveals the crystal
structures of two oligomeric osmium complexes and these
contain phenylselenolate ligands. In these cases the sele-
nium acts as a bridge between different osmium atoms
[41].
The angles in the four-membered chelate rings are in
the range 66.48(15)–68.12(19)ꢁ, which is again markedly
different to the values one would expect for a regular
geometry. In addition, the distortion in the geometry
is clear from the bond angles between atoms that are
trans to one another; these angles have values that differ
significantly from the expected 180ꢁ.
Fig. 9. Molecular structure of [Os(5-CF3-pySe)2(PPh3)2] Æ 2(H2O) (18).
The Os–S bond lengths in complexes 11 and 13,
˚
2.4269(15) and 2.4218(13) A, respectively, are both sim-
ilar to those found in other monomeric osmium(II) com-
plexes with anionic heterocyclic thione N,S chelate
ligands. Examples of such complexes include [Os(g2-
˚
H2)(CO)(PPh3)2(pyS)](BF4) [42], 2.449 A, and [Os(CO)2-
˚
(pyS)2] [43], 2.411 and 2.419 A. The Os–N distances in
the complexes under investigation are in the range
˚
2.102(15)–2.159(6) A, and these values are very similar
to those found in the complexes discussed above, which

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A. Sousa-Pedrares et al. / Inorganica Chimica Acta 359 (2006) 863–876
Table 9
˚
´
Selected bond distances (A) and angles (ꢁ) for [Os(3-CF3-pySe)2(P-
Ph3)2] Æ 2(CH2Cl2) (17)
Os(1)–Se(1)
Os(1)–P(1)
2.5314(4) Os(1)–N(1)
2.2962(9) Se(1)–C(1)
2.159(3)
1.890(4)
N(1)–Os(1)–Se(1)
Se(1)–Os(1)–Se(1)#1 152.573(19) N(1)–Os(1)–P(1)
N(1)–Os(1)–P(1)#1
P(1)–Os(1)–Se(1)#1
P(1)a–Os(1)–P(1)
67.90(8)
N(1)–Os(1)–Se(1)#1
90.25(8)
162.93(9)
98.34(3)
93.85(8)
99.46(3)
98.54(5)
P(1)–Os(1)–Se(1)
N(1)–Os(1)–N(1)#1
76.74(16)
Symmetry transformation used to generate equivalent atoms: #1: ꢀx,
y, ꢀz + 1/2.
Table 10
˚
´
Selected bond distances (A) and angles (ꢁ) for [Os(5-CF3-pySe)2(P-
Ph3)2] Æ 2(H2O) (18)
Os(1)–Se(1)
Os(1)–N(1)
Os(1)–P(1)
Se(1)–C(1)
2.5443(17) Os(1)–Se(2)
2.5564(17)
2.13(2)
2.303(6)
1.89(2)
2.102(15)
2.303(6)
1.84(2)
Os(1)–N(2)
Os(1)–P(2)
Se(2)–C(7)
Fig. 10. Molecular structure of [OsCl2(4,6-MeCF3-pymS)(PPh3)2]
(19).
N(1)–Os(1)–Se(1)
N(1)–Os(1)–P(1)
N(1)–Os(1)–N(2)
N(2)–Os(1)–Se(2)
N(2)–Os(1)–P(2)
P(1)–Os(1)–Se(2)
P(2)–Os(1)–Se(1)
67.0(4)
92.2(5)
81.7(6)
68.1(4)
90.6(5)
N(1)–Os(1)–Se(2)
N(1)–Os(1)–P(2)
N(2)–Os(1)–Se(1)
N(2)–Os(1)–P(1)
P(1)–Os(1)–Se(1)
P(1)–Os(1)–P(2)
P(2)–Os(1)–Se(2)
90.6(5)
164.0(4)
90.4(4)
166.4(4)
98.36(15)
98.06(15)
99.56(15)
Table 7
˚
´
Selected bond distances (A) and angles (ꢁ) for [Os(3-CF3-
pyS)2(PPh3)2](CHCl3) (11)
Os(1)–S(1)
Os(1)–N(1)
Os(1)–P(1)
S(1)–C(1)
2.4270(15)
2.123(5)
2.3126(15)
1.742(7)
Os(1)–S(2)
Os(1)–N(2)
Os(1)–P(2)
S(2)–C(7)
2.4269(15)
2.122(5)
2.3244(16)
1.724(6)
100.05(15)
99.32(14)
Se(1)–Os(1)–Se(2) 151.39(7)
N(1)–Os(1)–S(1)
N(1)–Os(1)–N(2)
N(1)–Os(1)–P(2)
N(2)–Os(1)–S(2)
N(2)–Os(1)–P(2)
P(1)–Os(1)–S(1)
P(2)–Os(1)–S(1)
S(2)–Os(1)–S(1)
66.48(15)
81.4(2)
N(1)–Os(1)–S(2)
N(1)–Os(1)–P(1)
N(2)–Os(1)–S(1)
N(2)–Os(1)–P(1)
P(1)–Os(1)–P(2)
P(1)–Os(1)–S(2)
P(2)–Os(1)–S(2)
92.50(14)
170.91(15)
90.06(14)
91.71(15)
97.22(5)
Table 11
90.31(15)
66.50(14)
169.01(14)
107.81(5)
93.26(6)
Selected bond distances and angles for [OsCl2(4,6-MeCF3-
pymS)(PPh3)2] (19)
90.19(5)
106.92(5)
Os(1)–Cl(1)
Os(1)–Cl(2)
Os(1)–N(1)
Os(1)–S(1)
2.391(2)
2.381(2)
2.153(6)
2.363(2)
Os(1)–P(1)
Os(1)–P(2)
S(1)–C(1)
2.365(2)
2.414(2)
1.728(9)
151.18(5)
N(1)–Os(1)–S(1)
N(1)–Os(1)–Cl(1)
N(1)–Os(1)–Cl(2)
N(1)–Os(1)–P(1)
N(1)–Os(1)–P(2)
S(1)–Os(1)–Cl(1)
S(1)–Os(1)–Cl(2)
68.12(19)
81.8(2)
98.71(19)
166.8(2)
90.5(2)
S(1)–Os(1)–P(1)
S(1)–Os(1)–P(2)
P(1)–Os(1)–Cl(1)
P(1)–Os(1)–Cl(2)
Cl(1)–Os(1)–Cl(2)
P(1)–Os(1)–P(2)
Cl(1)–Os(1)–P(2)
103.58(7)
85.53(7)
87.92(7)
89.79(7)
91.00(8)
99.33(7)
171.97(7)
Table 8
˚
´
Selected bond distances (A) and angles (ꢁ) for [Os(3-Me3Si-pyS)2(PPh3)2]
(13)
Os(1)–N(1)
Os(1)–S(1)
N(1)–C(5)
2.129(4)
2.4218(13) S(1)–C(1)
1.341(5)
Os(1)–P(1)
2.2972(13)
1.750(5)
1.361(6)
89.43(8)
166.63(8)
N(1)–C(1)
N(1)–Os(1)–N(1)#1
S(1)–Os(1)–S(1)#1
N(1)–Os(1)–P(1)#1 165.12(10)
N(1)–Os(1)–S(1)#1
P(1)–Os(1)–S(1)
81.0(2)
149.83(6)
P(1)–Os(1)–P(1)#1
N(1)–Os(1)–P(1)
N(1)–Os(1)–S(1)
P(1)–Os(1)–S(1)
95.76(6)
93.07(11)
66.71(10)
100.25(5)
Table 12
89.98(10)
99.86(4)
˚
Summary of selected bond lengths [A] and angles [ꢁ] for the ruthenium
complexes (average values)
(1)a
(2)
2.125(7)
2.300(2)
2.416(2)
1.729(8)
(5)
2.086(4)
2.3542(12)
2.4315(12)
1.729(5)
(8)
2.1467(16)
2.2936(5)
2.52456(19)
1.8834(19)
Symmetry transformation used to generate equivalent atoms: #1: ꢀx,
ꢀy + 1, z.
Ru–N
Ru–P
Ru–Xb
C–X
2.124(6)
2.326(2)
2.436(2)
1.739(9)
˚
have values in the range 2.070–2.149 A. The Os–P bond
distances in the different complexes are very similar to
the average value found in complexes in which the
osmium is coordinated to triphenylphosphine units
[44]. Finally, as mentioned previously, the absence of
other structures for similar osmium selenolates makes
it impossible to compare bond distances.
N–Ru–X
P–Ru–N
67.1(2)
169.0(2)
171.6(2)
154.7(1)
67.21(19)
67.37(10)
68.46(4)
163.55(4)
163.55(4)
153.241(12)
163.53(18) 166.78(10)
163.53(18) 167.19(10)
151.88(12) 152.14(5)
X–Ru–X
a
From Ref. [8].
X = S or Se.
b

A. Sousa-Pedrares et al. / Inorganica Chimica Acta 359 (2006) 863–876
875
Table 13
Summary of selected bond lengths [A] and angles [ꢁ] for the osmium complexes (average values)
˚
(11) (13) (17)
(18)
2.116(15)
(19)
Os–N
Os–P
Os–Xa
C–X
2.122(5) 2.129(4) 2.159(3)
2.153(6)
2.389(2)
2.363(2)
1.728(9)
2.386(2)
2.3185(15)
2.4269(15)
1.743(7)
2.2972(13)
2.4218(13)
1.750(5)
2.2962(9)
2.5314(4)
1.890(4)
2.303(6)
2.5503(17)
1.86(2)
Os–Cl
N–Os–X
P–Os–N
66.49(15)
169.01(14)
170.91(15)
151.18(5)
67.71(10)
165.12(10)
165.12(10)
149.83(6)
67.90(8)
162.93(9)
162.93(9)
152.573(19)
67.5(4)
164.0(4)
166.4(4)
151.39(7)
68.12(19)
166.8(2)
X–Os–X
Cl–Os–P
Cl–Os–S
Cl–Os–Cl
a
171.97(7)
166.63(8)
91.00(8)
(S or Se).
Complex 19 was obtained during the crystallisation
of compound 15 and in this transformation one of the
pyrimidine-2-thiolate molecules was replaced by two
chloro ligands (vide infra). Compound 19 has a similar
structure to the other osmium complexes in that the me-
tal is in an octahedral environment and the two chloro
ligands are arranged cis with respect to one another.
Comparison of the structural data for this complex with
those discussed previously shows a shorter Os–S dis-
BQU2002-01819). We are grateful to Johnson and
Mathey for the loan of ruthenium and osmium salts.
Appendix A. Supplementary data
Crystallographic data for the structures reported in
this paper have been deposited at the Cambridge
Crystallographic Data Center as supplementary publi-
cation numbers CCDC 267446-267454. Copies of the
data can be obtained free of charge on application
to CCDC, 12 Union Road, Cambridge, CB2 1EZ,
UK [fax: +44-1223-336-033; e-mail deposit@ccdc.
cam.ac.uk]. Supplementary data associated with this
article can be found, in the online version, at
doi:10.1016/j.ica.2005.06.009.
˚
tance, 2.363(2) A, which is probably due to the differ-
ence in the oxidation state of the metal.
4. Conclusions
The work described in this paper involves the synthesis
and structural characterization of a series of ruthenium
and osmium complexes with heterocyclic bidentate
(N,S) and (N,Se) donor ligands and triphenylphosphine.
These ligands contain different substituents on the hetero-
cyclic ring but it appears that the steric hindrance pro-
duced by such substituents does not significantly
influence the structures of the complexes. Furthermore,
the nature of the donor atoms in the heterocyclic ligand
does not markedly influence the structure of the complex.
All of the complexes under investigation have an octahe-
dral structure, with the phosphorus atoms in a cis arrange-
ment and the sulfur (or selenium) atoms in trans positions.
These findings are in sharp contrast to the chemistry of
other elements, for which the presence and position of
substituents in the ring do have an influence on the struc-
tures of the complexes [19].
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