Synthesis, structure, and properties of osmium complexes containing [Os(′S4′)] and [Os(′S2′)2] fragments (′S4′2- = 1,2-bis(2-mercaptophenylthio)-ethane(2-), ′S2′2- = 1,2-benzened

Article abstract of DOI:10.1002/(SICI)1099-0682(199806)1998:6<819::AID-EJIC819>3.0.CO;2-M

In search for osmium complexes with sulfur-dominated coordination spheres that potentially bind and activate or stabilize nitrogenase relevant small molecules, several osmium-sulfur complexes containing 1,2-bis(2-mercaptophenylthio)ethane(2-) (′S₄

Full text of DOI:10.1002/(SICI)1099-0682(199806)1998:6<819::AID-EJIC819>3.0.CO;2-M

FULL PAPER
Transition Metal Complexes with Sulfur Ligands, 131[᭛]
Synthesis, Structure, and Properties of Osmium Complexes Containing
[Os(ЈS4Ј)] and [Os(ЈS2Ј)2] Fragments (ЈS4Ј2؊ ؍ 1,2-Bis(2-mercaptophenylthio)-
ethane(2؊), ЈS2Ј2؊ ؍ 1,2-Benzenedithiolate)Ƞ
Dieter Sellmann*, Andreas C. Hennige, and Frank W. Heinemann
Institut für Anorganische Chemie der Universität Erlangen-Nürnberg,
Egerlandstr. 1, D-91058 Erlangen, Germany
Fax: (internat.) ϩ49(0)9131/857367
E-mail: sellmann@anorganik.chemie.uni-erlangen.de
Received December 22, 1997
Keywords: S ligands / P ligands / Osmium / Solvent effects
In search for osmium complexes with sulfur-dominated coor- (9a) were characterized by X-ray structure analysis, leading
dination spheres that potentially bind and activate or stabi-
lize nitrogenase relevant small molecules, several osmium centers, innocent dithiolate ligands are present. The
osmiumϪsulfur complexes containing 1,2-bis(2-mercapto-
stabilization of the OsIV centers is traced back to SǞM π do-
phenylthio)ethane(2Ϫ) (ЈS4Ј2Ϫ
and benzenedithiolate nation. Close inspection of 1 and 2 revealed a large influence
to the conclusion that despite the high oxidation state of the
)
(ЈS2Ј2Ϫ) ligands were synthesized. [OsII(PR3)2(ЈS4Ј)] [R = Ph
(1), Et (2)], [OsIV(PR3)2(ЈS2Ј)2] [R = Et (3), Pr(4), Me(5), Ph(6)],
[OsIV(PCy3)(ЈS2Ј)2] (7), (PHCy3)[OsIII(ЈS2Ј)2] (8a), (NMe4)-
[OsIII(ЈS2Ј)2] (8b), and (NBu4)2[OsIV(ЈS2Ј)3] (9b) were obtained
in reactions starting from commercially available osmium
compounds and the sulfur and phosphane ligands. The pres-
of the phosphane ligands on the stability of OsII thioether
complexes. While 1 is reasonable stable, 2 readily gives 3
and ethylene via intramolecular ЈS4Ј2Ϫ ligand reduction and
OsII Ǟ OsIV oxidation. UV-Vis spectra of 3Ϫ5 indicate phos-
phane dissociation in solution leading to pentacoordinate
[Os(PR3)(ЈS2Ј)2] complexes. This was confirmed by the syn-
ence or absence of reducing solvents strongly influenced thesis of pentacoordinate [Os(PCy3)(ЈS2Ј)2] (7).
these reactions. Octahedral (3), (4), and (PHCy3)2[OsIV(ЈS2Ј)3]
Introduction
Transition metals in sulfur-dominated coordination
spheres form the active centers of numerous oxidoreduct-
ases such as nitrogenases, hydrogenases and CO dehydro-
genase[1]. In the search for low-molecular compounds that
combine structural and reactivity features of these [MS] en-
zymes we have found that transition metal complexes con-
taining [M(ЈS4Ј)] (A) or [M(ЈS2Ј)2] fragments (B and C)
[ЈS4Ј2Ϫ
ϭ
1,2-bis(2-mercaptophenylthio)ethane(2Ϫ);
ЈS2Ј2Ϫ ϭ 1,2-benzenedithiolate(2Ϫ)] can bind and activate
or stabilize a considerable number of small molecules that
are key intermediates in enzymatic processes[2]. In a few
cases, catalytic reaction cycles could be developed[3]. For
example, [Rh(L)(ЈS4Ј)]ϩ complexes (L ϭ CO, PCy3) cata-
lyze the heterolytic cleavage of dihydrogen and D2/Hϩ ex-
rare. In fact, [Mo(N2)2(octamethyltetrathiacyclohexade-
cane)] is the only example for the coordination of N2 to a
metal center carrying exclusively sulfur coligands[5]
.
change that are features of hydrogenases[4]
Iron and ruthenium [M(ЈS4Ј)] complexes bind key inter-
.
For this reason, we have started to explore the osmium
chemistry of ЈS4Ј2Ϫ and ЈS2Ј2Ϫ ligands, anticipating that
with [Os(ЈS4Ј)] or [Os(ЈS2Ј)n] species complexes could be-
come accessible that proved inaccessible with the iron and
ruthenium homologues. [Os(ЈS4Ј)] complexes have been un-
known as yet, the chemistry of osmium benzene-1,2-dithiol-
ate and related ligands is largely unexplored[6]. No benzene-
dithiolate complex was known, and only a very few com-
plexes with toluenedithiolate, maleonitriledithiolate and
[2]
mediates of N2 fixation such as N2H2, N2H4 and NH3
.
However, attempts to coordinate also dinitrogen to such
fragments have as yet remained unsuccessful. In this context
it is to be noted that transition metal N2 complexes with
sulfur dominated coordination spheres are conspicuously
[᭛]
Part 130: D. Sellmann, T. Gottschalk-Gaudig, F. W. Heine-
mann, Inorg. Chem, submitted.
similar ligands have been described[7]
.
Eur. J. Inorg. Chem. 1998, 819Ϫ826
WILEY-VCH Verlag GmbH, D-69451 Weinheim, 1998
1434Ϫ1948/98/0606Ϫ0819 $ 17.50ϩ.50/0
819

D. Sellmann, A. C. Hennige, F. W. Heinemann
FULL PAPER
Results
Synthesis and Characterization of the Hexa- and Pentacoordinate
OsIV Complexes [Os(PR3)2(ЈS2Ј)2] (R ؍ Me, Et, Pr, Ph), and
[Os(PCy3)(ЈS2Ј)2]
[Os(ЈS4Ј)] Complexes
Two target complexes containing [Os(ЈS4Ј)] cores could
be obtained from commercially available OsCl3 ·x H2O by
the reaction according to eq. (1).
[Os(PR3)2(ЈS2Ј)2] complexes were obtained with various
PR3 ligands according to eq. (3).
The resultant complexes 3Ϫ6 are gray-black to black-vi-
olet and diamagnetic. While the PMe3 and PPh3 complexes
5 and 6 are only very sparingly soluble, the PEt3 and PPr3
complexes 3 and 4 readily dissolve in common organic sol-
vents. The complexes were characterized by elemental
analyses and spectroscopic methods, and 3 and 4 also by
X-ray structure analyses. The OsIV complexes 3 and 4 each
exhibit a characteristic low field shifted 31P-NMR signal in
the region of δ ϭ Ϫ200 and contrast in this respect the OsII
complexes 1 and 2 whose 31P-NMR signals appear at δ ca.
Ϫ20. No 31P-NMR spectrum could be recorded of the spar-
ingly soluble PMe3 complex 5. The 31P-NMR spectrum of
the PPh3 complex 6 revealed one broad signal at δ ϭ Ϫ46.5.
The shift of this signal indicates dissociation of 6 to give
pentacoordinate [Os(PPh3)(ЈS2Ј)2] (vide infra).
Heating to reflux, an excess of the respective phosphane,
and the use of the solvent mixture MeOH/THF proved
necessary. The excess of phosphane and the methanol prob-
ably serve as reducing reagents for OsCl3 ·x H2O. The meth-
anol additionally causes precipitation of the resultant yel-
low to yellow-green [Os(PR3)2(ЈS4Ј)] complexes 1 (PPh3)
and 2 (PEt3) from the reaction solutions. When pure THF
was used as solvent, neither 1 nor 2 could be isolated.
In these experiments, it was noted that 2 is rather thermo-
labile. The reaction leading to its formation according to
eq. (1) had to be quenched after ca. one hour of refluxing in
order to avoid a drastic decrease in yield. Already at room
temperature, [Os(PEt3)2(ЈS4Ј)] (2) slowly decomposes ac-
cording to eq. (2).
When the reaction according to eq. (3) was carried out
with the sterically very demanding phosphane PCy3, no
hexacoordinate complex but the pentacoordinate
[Os(PCy3)(ЈS2Ј)2] (7) formed. This even occurred when a
fourfold excess of PCy3 was applied. Complex 7 was ob-
tained as violet microcrystals that proved diamagnetic and
well soluble in organic solvents. The number and splitting
1
of the H- and 13C-NMR signals of 7 indicate that 7 pos-
sesses lateral symmetry. The 31P-NMR spectrum exhibits
one signal at δ ϭ Ϫ29.2 whose chemical shift contrasts the
31P-NMR shifts (Ϫ200 ppm) of the bisphosphane com-
plexes 3 and 4. The FD mass spectrum of 7 revealed the
molecular ion at m/z ϭ 752 and no ions of higher masses.
These results and, in addition, the UV-Vis-NIR spectro-
scopic properties of 7 versus those of 3Ϫ5 (vide infra) indi-
cate that 7 is mononuclear possessing the structure indi-
cated by formula D.
An intramolecular redox reaction leads to release of
C2H4 and formation of the OsIV complex [Os(PEt3)2(ЈS2Ј)2]
(3). The evolving ethylene could be detected by its 1H-NMR
signal at δ ϭ 5.24[8]
.
Complexes 1 and 2 were characterized by the common
1
spectroscopic methods. For example, the H-NMR spectra
of 1 and 2 exhibit signal patterns that are typical of C2
symmetrical [ML2(ЈS4Ј)][9] complexes. Cyclic voltammetry
of 2 further revealed two reversible redox waves at E1/2
ϭ
Ϫ20 mV and E1/2 ϭ 950 mV that can be assigned to the
formation of the [2]ϩ and [2]2ϩ cations.
Attempts to substitute one PPh3 ligand of 1 by N2H4 or
CO remained unsuccessful. Complex 1 proved substitution
inert even at elevated temperatures and pressures. In this
respect, 1 contrasts the homologous [Ru(PPh3)2(ЈS4Ј)]
which readily exchanges one PPh3 ligand for numerous two
electron donors at room temperature[10]
.
X-ray Structure Determination of [Os(PEt3)2(ЈS2Ј)2] (3) and
[Os(PPr3)2(ЈS2Ј)2] (4)
The facile formation of the OsIV complex [Os-
(PEt3)2(ЈS2Ј)2] (3) from the OsII complex [Os(PEt3)2(ЈS4Ј)]
The molecular structures of 3 and 4 are depicted in Fig-
(2) and the rareness of osmium benzene dithiolate com- ure 1.
plexes in higher oxidation states prompted us to investigate
Complexes 3 and 4 both possess crystallographically im-
these species more closely, which are also potentially suited posed inversion symmetry and exhibit pseudo-octrahedral
to yield complexes with [Os(ЈS4Ј)] cores via template alky- coordination with the phosphane ligands in trans positions.
lations[9]
820
.
The corresponding OsϪP and OsϪS distances in 3 and 4
Eur. J. Inorg. Chem. 1998, 819Ϫ826

Transition Metal Complexes with Sulfur Ligands, 131
FULL PAPER
Figure 1. ORTEP plots of a) [Os(PEt3)2(ЈS2Ј)2] (3) and b) and related species, which have been extensively discussed
previously[13]. They allow to conclude that benzenedithiol-
ate behaves as “innocent” dithiolate ligand such that stabi-
[Os(PPr3)2(ЈS2Ј)2] (4) drawn with 50% probability ellipsoids (H
atoms omitted)[a]
lization of higher metal oxidation states is rather due to
increasing SǞM π donation.
Reversible Dissociation of [Os(PR3)2(ЈS2Ј)2] Complexes;
UV-Vis-NIR Spectra
The UV-Vis-NIR spectra of the hexacoordinate com-
plexes 3Ϫ5 exhibit very intense absorptions (ε > 40000
l·molϪ1·cmϪ1) in the region of 950Ϫ1050 nm. These bands
can be assigned to sulfur-metal LMCT transitions, and they
slowly decrease in intensity when dilute solutions of 3Ϫ5
are kept at room temperature. Simultaneously, the solutions
change color from deep red to violet blue. Addition of the
respective phosphane reverses these effects (Figure 2).
Figure 2. UV-Vis-NIR spectra of a) 4 in CH2Cl2 (λmax ϭ 1043 nm,
ε ϭ 42740 lmolϪ1cmϪ1), b) after 12 h, c) after addition of excessive
PPr3
[a]
Selected distances [pm] and angles [°]: 3: Os(1)ϪS(1) 231.1(2),
Os(1)ϪS(2) 232.8(2), Os(1)ϪP(1) 244.8(2), S(1)ϪC(10) 174.8(8),
S(2)ϪC(15) 173.1(8), C(10)ϪC(11) 142.4(10), C(11)ϪC(12) 138(2),
C(12)ϪC(13) 130(3), C(14)ϪC(15) 141.2(9), C(10)ϪC(15)
139.0(11). S(1)ϪOs(1)ϪP(1) 90.58(7), S(2)ϪOs(1)ϪP(1) 90.46(7),
S(1)ϪOs(1)ϪS(2) 86.33(7). Ϫ 4: Os(1)ϪS(1) 231.2(2), Os(1)ϪS(2)
231.7(2), Os(1)ϪP(1) 244.2(2), S(1)ϪC(10) 172.8(11), S(2)ϪC(15)
These observations indicate that the hexa-coordinate
complexes reversibly dissociate in solution to yield penta-
coordinate species according to eq. (5).
172.6(9),
C(10)ϪC(11)
137.9(13),
C(11)ϪC(12)
137(2),
C(12)ϪC(13) 136(2), C(14)ϪC(15) 138.1(12), C(10)ϪC(15)
145.3(14), S(1)ϪOs(1)ϪP(1) 89.85(8), S(2)ϪOs(1)ϪP(1) 90.65(8),
S(1)ϪOs(1)ϪS(2) 86.29(8).
are identical within the 3σ criterion. The averaged OsϪS
distances of 3 and 4 [231.7(2) pm] are identical to the RuϪS
distances of the analogous [Ru(PMe3)2(ЈS2Ј)2] [231.7(1)
pm][11] and are in the usual range of osmium(IV) thiolate
complexes. OsϪS distances of osmium(IV) thiolate com-
plexes cover a range from 220 to 241 pm and depend on
This assumption is supported by the electronic spectrum
of the pentacoordinate complex [Os(PCy3)(ЈS2Ј)2] (7) which
does not exhibit an absorption in the NIR region. It is
further corroborated by the FD mass spectra of complexes
3Ϫ5, which all show intensive signals of the fragment ions
[Os(PR3)(ЈS2Ј)2]ϩ in addition to the molecular ions.
the coordination number and geometry[12]
.
Detailed inspection of the CϪC and CϪS bond distances
2Ϫ
in the C6H4S2 ligands revealed no evidence for a partial
oxidation of the benzenedithiolate ligands to give dithiocy-
clohexadiene units according to eq. (4).
Synthesis and Properties of the OsIII Complex
(PHCy3)[Os(ЈS2Ј)2] (8a)
The [Os(PR3)2(ЈS4Ј)] complexes 1 and 2 had shown that
the solvent and reaction time could markedly influence the
In this respect, the OsIV complexes 3 and 4 behave iden- course of synthesis reactions. This was also observed when
tical to the homologous FeIV complex [Fe(PMe3)2(ЈS2Ј)2] (NH4)2[OsBr6], ЈS2Ј-Li2 and an excess of PCy3 were com-
Eur. J. Inorg. Chem. 1998, 819Ϫ826
821

D. Sellmann, A. C. Hennige, F. W. Heinemann
FULL PAPER
bined not in THF as in the reaction according to eq. (3),
This reaction involves an OsIII Ǟ OsIV oxidation, but the
but in a mixture of THF and MeOH, and refluxed for three oxidizing reagent as well as the fate of the formally released
days. In this case, not the OsIV complex 7 but the OsIII proton and electron remain unknown. Evolution of H2
complex (PHCy3)[Os(ЈS2Ј)2] (8a) formed as major product could not be observed[16]
.
according to eq. (6).
Synthesis and Properties of (NBu4)2[Os(ЈS2Ј)3] and
(PHCy3)2[Os(ЈS2Ј)3]
Single crystals that precipitated in minor amounts from
the mother liquors of the [Os(PCy3)(ЈS2Ј)2] (7) synthesis
could be characterized by X-ray structure analysis revealing
that the crystals contained the salt (PHCy3)2[Os(ЈS2Ј)3] (9a).
The NBu4 salt (NBu4)2[Os(ЈS2Ј)3] (9b) was subsequently
obtained in the straight forward synthesis according to eq.
Complex 8a precipitated as orange micro-crystals from
the boiling reaction mixture. The violet-blue
[Os(PCy3)(ЈS2Ј)2] (7) formed only as minor by-product and
ϩ
(9).
could be isolated in negligible amounts when the mother
o
liquors were cooled to Ϫ20 C.
Apparently, in the reaction according to eq. (6) the sol-
vent MeOH and possibly also the excess PCy3 act as reduc-
ing reagents upon (NH4)2[OsBr6]. Complex 8a, whose el-
emental composition differs from that of the OsIV complex
[Os(PCy3)(ЈS2Ј)] (7) only by one proton, was identified by
its spectra, magnetism, and by the metathesis reaction with
9b was isolated in form of dark red crystals, which were
characterized by elemental analysis and spectroscopic meth-
ods. 9b is diamagnetic. Its cyclic voltammogramm shows
one irreversible (Ϫ580 mV) and two reversible anodic redox
waves (Ϫ80 mV and 180 mV). They can be assigned to the
redox steps indicated by eq. (10).
ϩ
NMe4OH yielding the NMe4 salt (NMe4)[Os(ЈS2Ј)2] (8b)
according to eq. (7).
ϩ
The presence of the PHCy3 cation in 8a could further
Figure 3 depicts the molecular structure of the anion of
(PHCy3)2[Os(ЈS2Ј)3] (9a).
1
be concluded from the H-NMR spectrum of 8a which re-
vealed the characteristic 1J(PH) coupling constant (475 Hz)
ϩ
Figure 3. ORTEP plot of the anion of (PHCy3)2[Os(ЈS2Ј)3] (9a)
of the PHCy3 cation.
drawn with 50% probability ellipsoids (H atoms omitted)[a]
8a is paramagnetic and exhibits a magnetic moment of
µeff ϭ 3.04 µB. The magnetic moment is compatible with
three unpaired electrons at OsIII centers in square planar or
tetragonal pyramidal coordination. In contrast octahedral
OsIII thiolate phosphane complexes with one unpaired elec-
tron exhibit magnetic moments in the range µeff
ϭ
1.85Ϫ1.98 µB[14]. The structure of the anion in 8a remains
unknown, however, the dinuclear structure of the homolo-
gous iron complex that was revealed by X-ray structure
analysis[15] suggests a similar structure for 8a as indicated
by formula E.
[a]
Selected distances [pm]: Os(1)ϪS(1) 236.6(2), Os(1)ϪS(2)
235.7(2), Os(1)ϪS(3) 235.6(2), Os(1)ϪS(4) 234.5(3), Os(1)ϪS(5)
235.0(3), Os(1)ϪS(6) 236.0(3), S(1)ϪC(10) 175.8(9), S(2)ϪC(15)
173.6(9), S(3)ϪC(20) 177.4(10), S(4)ϪC(25) 172.7(11), S(5)ϪC(30)
176.7(11), S(6)ϪC(35) 177.2(10); average SϪS(intra) 3.190,
SϪS(inter) 3.385.
167.40(9), S(2)ϪOs(1)ϪS(5) 163.53(9), S(3)ϪOs(1)ϪS(6) 168.23(8),
S(1)ϪOs(1)ϪS(2) 85.06(8), S(3)ϪOs(1)ϪS(4) 85.40(9),
S(5)ϪOs(1)ϪS(6) 85.23(10).
Complex 8a is sparingly soluble in THF or MeOH, but
readily dissolves in CH2Cl2. Also in the absence of air, the
resultant orange CH2Cl2 solutions are unstable and turn to
deep violet in the course of a few hours, because 8a spon-
taneously forms 7 according to eq. (8).
Ϫ Selected angles [°]: S(1)ϪOs(1)ϪS(4)
The average OsϪS distances in 9a [235.6(3) pm] are
longer than those in the neutral [Os(PR3)2(ЈS2Ј)2] complexes
3 and 4 [231.7(2) pm]. This can be traced back to reduced
822
Eur. J. Inorg. Chem. 1998, 819Ϫ826

Transition Metal Complexes with Sulfur Ligands, 131
FULL PAPER
SǞM π donation in 9a which unlike 3 and 4 does not exhi- [Os(PCy3)(ЈS2Ј)2] (7) could be isolated. The influence of sol-
bit π acceptor phosphane ligands. As for 3 and 4, scrutiniz- vents upon the course of reactions became particularly evi-
ing the CϪC and CϪS distances yielded no evidence for dent when the synthesis of (7) was tried in MeOH instead
cyclohexadienedithioketone-like structures of the C6H4S2 li- of THF. In this case, the OsIII complex (PHCy3)[Os(ЈS2Ј)2]
gands.
(8a) formed. Complex 8a probably possesses a dinuclear
An important structural feature of numerous dithiolene anion, is paramagnetic and spontaneously oxidizes in
type [M(S2C2R2)3] complexes (R ϭ H, Ph) is their trigonal CH2Cl2 to give 7. Cyclic voltammetry revealed redox ac-
prismatic coordination geometry. Potential factors, e.g., tivity also for 2, 3, and (NBu4)2[Os(ЈS2Ј)3] (9b) which forms
S···S interactions between vicinal S donors, metal-ligand π from stoichiometric amounts of [OsBr6]2Ϫ, NBu4ϩ, and
bonding and the overall charge of the complexes, stabilizing ЈS2Ј2Ϫ
.
X-ray structure analysis of the analogous
the trigonal pyramidal versus the octahedral coordination (PHCy3)2[Os(ЈS2Ј)3] (9a) revealed pseudo-octahedral coor-
geometry have been elucidated[17]. The analysis of the dination geometry of the [Os(ЈS2Ј)3]2Ϫ anion.
SϪOsϪS angles in 9a shows that 9a is best described to
Scrutinizing the CϪC and CϪS distances in the C6H4S2
possess pseudo-octahedral geometry. Due to the chelate
bite of the C6H4S2 units, the ideal SϪMϪS angle which can
units of 3, 4, and 9a corroborates previous results. They
indicate that benzenedithiolate behaves as “normal” dithiol-
ate also when binding to metal centers in higher oxidation
states. The stabilization of these oxidation states thus is bet-
be reached for ЈtransЈ sulfur donors in octahedral com-
plexes is 170° (instead of 180°)[18]. The corresponding angle
in trigonal prismatic complexes is 136°. The respective
ter traced back to increasing SǞM π donation than to a
SϪOsϪS angles in 9a vary between 163.5(1)° and 168.2(1)°
“non-innocence” of benzenedithiolate that involves a
break-up of the aromatic benzene system.
In summary, first examples of complexes containing
[Os(ЈS4Ј)] and [Os(ЈS2Ј)2)] fragments have been synthesized
and are thus close to the ideal angle for octahedral coordi-
nation.
A literature search revealed that there are only two other
dianionic [M(ЈS2Ј)3]2Ϫ complexes (M ϭ Ti[19], Zr[18]) that
and characterized. The complexes differ unexpectedly
exhibit
octahedral
geometry.
The
anion
in
strongly from their iron and ruthenium homologues. While
with ЈS4Ј2Ϫ or ЈS2Ј2Ϫ ligands the metal oxidation state ϩIV
is found only in very few iron and only unsignificantly more
ruthenium complexes, it is well accessible with Os com-
plexes.
(AsPh4)2[W(ЈS2Ј)3] shows average SϪWϪS angles of
151.6°[20]. It thus represents an intermediate between octa-
hedral and trigonal prismatic coordination comparable to
the structure of the monoanion in (AsPh4)[Nb(ЈS2Ј)3][21]
.
Discussion and Summary
Financial Support of this work by the Deutsche Forschungsge-
meinschaft and the Fonds der Chemischen Industrie is gratefully
acknowledged.
The OsII complexes [Os(PR3)2(ЈS4Ј)] (1) (R ϭ Ph) and
2 (R ϭ Et) could be directly synthesized from ЈS4Ј2Ϫ, the
respective phosphane and commercially available OsCl3 ·x
H2O. Complexes 1 and 2 revealed a remarkable influence
of the phosphane coligands upon the complex stability and
reactivity. 1 proved temperature stable and substitution in-
ert contrasting the homologous [Ru(PPh3)2(ЈS4Ј)], which re-
adily exchanges one PPh3 ligand. 2 is so labile that already
at room temperature it readily releases C2H4 and forms the
OsIV complex [Os(PEt3)2(ЈS2Ј)2] (3) via an intramolecular
redox reaction. Evidently, the strongly electron donating
PEt3 and the a priori high electron density of the OsII center
destabilize the ЈS4Ј2Ϫ-ligand to such an extent that its C2H4
bridge is reductively eliminated. Such C2H4 eliminations
from the ЈS4Ј2Ϫ-ligand have been observed previously with
electron rich Fe and Mo species[22]. In this respect, 2 unex-
pectedly strongly differs from its iron and ruthenium alkyl-
phosphane [M(PR3)2(ЈS4Ј)] counterparts which are perfectly
stable at ambient conditions. Complex 3 and the PMe3 5,
PPr3 4, and PPh3 6 analogues were directly obtained from
[OsBr6]2Ϫ, ЈS2Ј2Ϫ and the respective phosphanes. X-ray
structure analyses of 3 and 4 revealed that these complexes
possess planar [Os(ЈS2Ј)2] cores and trans phosphanes. UV-
Vis-NIR spectroscopy further showed that the hexaco-
ordinate complexes 3 to 5 have very intense NIR bands
and reversibly dissociate yielding pentacoordinate
[Os(PR3)(ЈS2Ј)2] complexes. When PR3 is the sterically
Experimental Section
General Methods: Unless noted otherwise, all reactions were car-
ried out under an atmosphere of dinitrogen at room temperature
by using standard Schlenk techniques. Solvents were dried and dis-
tilled before use. Ϫ Physical measurements were carried out with
the following instruments: IR spectra, Perkin Elmer 16PC FTIR
spectrometer (IR spectra of solutions were recorded in CaF2 cu-
vettes with compensation of the solvent bands, solids were meas-
ured as KBr pellets); mass spectra, Varian MAT 212; UV/Vis/NIR
spectra, Shimadzu UV3101 PC spectrometer; NMR spectra, Jeol
FT-JNM-GX 270, EX 270 and LA 400; Magnetic susceptibility:
Johnson Matthey susceptibility balance; Cyclic voltammograms,
EG&G potentiostat PAR model 264A with glassy carbon working
electrode, Pt counter electrode and Ag/AgCl reference electrode.
Conducting electrolyte: 0.1  NBu4PF6. Potentials are referred to
NHE via Cp2Fe0/ϩ as internal standard. Cp2Fe0/ϩ ϭ 0.40 V vs.
NHE[23]. Ϫ 1,2-benzenedithiol[24] and 1,2-bis(2-mercaptophenyl-
[25]
thio)ethane ЈS4Ј-H2
were prepared as described in the literature.
[Os(PPh3)2(ЈS4Ј)] (1): OsCl3 ·x H2O (335 mg, 1.1 mmol), PPh3
(1 g, 3.8 mmol), and ЈS4Ј-H2 (350 mg, 1.1 mmol) were suspended
in MeOH (20 ml) and THF (40 ml) and refluxed for 24 h. The
resultant suspension was cooled to room temperature, the precipi-
tating yellow-green crystals were separated, recrystallized from
CH2Cl2 (20 ml), and dried in vacuo. Yield: 500 mg of 1·0.25
CH2Cl2 (44%). Ϫ C50.25H42.5OsP2S4 (1044.5): calcd. C 57.78, H
4.10, S 12.28; found C 57.55, H 4.15, S 12.22. Ϫ 1H NMR
very bulky PCy3, only the pentacoordinate species (CD2Cl2): δ ϭ 6.4Ϫ7.5 (m, 38 H, C6H4, C6H5), 2.15Ϫ2.4 (m, 2 H,
Eur. J. Inorg. Chem. 1998, 819Ϫ826 823

D. Sellmann, A. C. Hennige, F. W. Heinemann
FULL PAPER
C2H4), 1.6Ϫ1.8 (m, 2 H, C2H4). Ϫ 13C{1H} NMR (CD2Cl2): δ ϭ
[Os(PEt3)2(ЈS2Ј)2] (3) from OsCl3 ·x H2O, ЈS4Ј-H2 and PEt3:
159.6, 136.2 (m), 135.4 (t), 133.1, 130.8, 129.8, 129.2, 128.1, 126.7 OsCl3 ·x H2O (360 mg, 1.2 mmol), PEt3 (4 ml, ca. 25 mmol), and
(t), 121.6 (C6H4, C6H5), 43.3 (C2H4). Ϫ 31P{1H} NMR (CD2Cl2) ЈS4Ј-H2 (380 mg, 1.2 mmol) were combined in MeOH (35 ml) and
δ ϭ Ϫ14.4 (s, PPh3).
THF (20 ml) and heated under reflux for 3 d. The resultant solu-
tion was filtered while hot and cooled to room temperature. Black
crystals precipitated that were collected after 7 d, washed with
MeOH (40 ml) and n-hexane (20 ml) and dried in vacuo. They were
identified by comparison with an authentic sample of 3. Yield: 620
mg of 3 (73%). Ϫ C24H38OsP2S4 (707.0): calcd. C 40.78, H 5.42, S
18.14; found C 40.80, H 5.67, S 18.36.
[Os(PEt3)2(ЈS4Ј)] (2): OsCl3 ·x H2O (360 mg, 1.2 mmol), PEt3
(4 ml, 26 mmol), and ЈS4Ј-H2 (380 mg, 1.2 mmol) were suspended
in MeOH (35 ml) and THF (20 ml) and refluxed for 1 h. The
resultant solution was filtered and cooled to Ϫ20°C. Yellow crys-
tals precipitated that were separated after one week, washed with
MeOH (50 ml) and n-hexane (20 ml), and dried in vacuo. Yield:
550 mg of 2 (62%). Ϫ C26H42OsP2S4 (735.0): calcd. C 42.49, H
5.76, S 17.45; found C 42.85, H 5.75, S 17.54. Ϫ FD MS (CH2Cl2);
m/z: 736 [Mϩ]. Ϫ 1H NMR (CD2Cl2), δ ϭ 7.3Ϫ7.6 (m, 4 H, C6H4),
6.65Ϫ7.0 (m, 4 H, C6H4), 2.45Ϫ2.7 (m, 2 H, C2H4), 1.7Ϫ2.2 (m,
12 H, CH2), 1.4Ϫ1.7 (m, 2 H, C2H4), 0.8Ϫ1.2 (m, 18 H, CH3). Ϫ
31P NMR (CD2Cl2), δ ϭ Ϫ26.3 (s, PEt3). Ϫ CV (CH2Cl2, room
temp., [mV]); E ϭ Ϫ20 (rev.), Ϫ950 (rev.).
[Os(PCy3)(ЈS2Ј)2] (7): At Ϫ78°C, 2.5  nBuLi in n-hexane (0.4
ml, 1 mmol) was added to a solution of ЈS2Ј-H2 (0.16 ml, 0.5 mmol)
in THF (10 ml). The solution was warmed to room temperature
and added to a suspension of (NH4)2[OsBr6] (176 mg, 0.25 mmol)
and PCy3 (280 mg, 1 mmol) in THF (20 ml). The resultant violet
suspension was heated under reflux for 19 h, filtered and cooled to
Ϫ20°C. The precipitating violet crystals were collected after 8 d,
washed with MeOH (20 ml) and dried in vacuo. When the THF/
MeOH mother liquor was kept at Ϫ20°C, a few single crystals
separated in the course of 14 d, which were identified as
(PHCy3)2[Os(ЈS2Ј)3] (8a) by X-ray structure determination. Yield:
125 mg of 7 (67%). Ϫ C30H41OsPS4 (751.1): calcd. C 47.98, H 5.50,
S 17.08; found C 47.88, H 5.51, S 17.27. Ϫ FD MS (CH2Cl2); m/z:
[Os(PR3)2(ЈS2Ј)2] with R ϭ Me, Et, Pr, Ph
General Procedure: At Ϫ78°C, 2.5  nBuLi in n-hexane (0.8 ml,
2 mmol) was added to a solution of ЈS2Ј-H2 (0.12 ml, 1 mmol) in
THF (10 ml). The solution was warmed to room temperature and
added to a suspension of (NH4)2[OsBr6] (350 mg, 0.5 mmol) and
PR3 (0.15 ml, 1 mmol) in MeOH or THF (10 ml). The resultant
suspension was heated under reflux for 19 h, filtered, and cooled
to room temperature or Ϫ20°C. The resultant complexes precipi-
tated as black crystals or gray-black powders that were collected
after one week, washed with MeOH (20 ml) and dried in vacuo.
Complex 6 required recrystallization from THF (20°C Ǟ Ϫ20°C)
in order to obtain correct elemental analyses.
1
752 [M]ϩ. Ϫ H NMR (CD2Cl2), δ ϭ 8.25Ϫ8.45 (m, 4 H, C6H4),
6.55Ϫ6.75 (m, 4 H, C6H4), 0.7Ϫ2.0 (m, 33 H, C6H11). Ϫ 13C{1H}
NMR (CD2Cl2), δ ϭ 164.4, 129.0, 123.7 (C6H4), 28.8, 28.1, 28.0,
26.4 (C6H11). Ϫ 31P{1H} NMR (CD2Cl2), δ ϭ Ϫ29.2 (s, PCy3). Ϫ
UV/VIS/NIR (CH2Cl2, λmax (lg ε) ϭ 563 nm (3.66), 753 (3.22).
(PHCy3)[Os(ЈS2Ј)2] (8a): At Ϫ78°C, 2.5  nBuLi in n-hexane
(0.8 ml, 2 mmol) was added to a solution of ЈS2Ј-H2 (0.12 ml, 1
mmol) in THF (10 ml). The solution was warmed to room tempera-
ture and added to a suspension of (NH4)2[OsBr6] (355 mg, 0.5
mmol) and PCy3 (560 mg, 2 mmol) in MeOH (10 ml) and THF
(10 ml). The resultant violet suspension was heated under reflux
for 3 d and cooled to room temperature. Orange crystals precipi-
tated that were separated, washed with MeOH (20 ml) and Et2O
(40 ml) and dried in vacuo. Yield: 195 mg of (8a) (52%). Ϫ
C30H42OsPS4 (752.1): calcd. C 47.91, H 5.63, S 17.05; found C
[Os(PEt3)2(ЈS2Ј)2] (3): Yield: 225 mg of
3 (50%). Ϫ
C24H38OsP2S4 (707.0): calcd. C 40.78, H 5.42, S 18.14; found C
40.66, H 5.72, S 18.10. Ϫ FD MS (CH2Cl2); m/z: 590 [Mϩ Ϫ PEt3].
1
Ϫ H NMR (CD2Cl2), δ ϭ 7.5Ϫ7.7 (m, 4 H, C6H4), 5.3Ϫ5.5 (m,
4 H, C6H4), 0.4Ϫ0.6 (quint, 18 H, CH3), Ϫ0.7 (m, 12 H, CH2). Ϫ
13C{1H} NMR (CD2Cl2), δ ϭ 148.0, 125.0, 120.7 (C6H4), 10.7 (t,
CH2), 6.7 (s, CH3). Ϫ 31P{1H} NMR (CD2Cl2), δ ϭ Ϫ195.4 (s,
PEt3). Ϫ UV/VIS/NIR (CH2Cl2): λmax (lg ε) ϭ 1043 nm (4.61), 765
(3.64), 626 (3.78), 531 (3.67). Ϫ CV (CH2Cl2, room temp., [mV]);
E ϭ 340 (rev.), Ϫ760 (rev.), 1030 (irrev.).
1
47.83, H 5.68, S 16.96. Ϫ H NMR (CD2Cl2), δ ϭ 7.4Ϫ7.6 (m, 4
1
H, C6H4), 6.55Ϫ6.75 (m, 4 H, C6H4), 5.46 (d, JPH ϭ 475 Hz, 1
H, PHCy3), 0.8Ϫ1.9 (m, 33 H, C6H11). Ϫ 13C{1H} NMR (CD2Cl2,
Ϫ70°C), δ ϭ 148.3, 127.7, 121.8 (C6H4), 26.1, 25.8, 25.5, 24.2
(C6H11). Ϫ 31P{1H} NMR (CD2Cl2), δ ϭ 20.7 (s, PHCy3).
[Os(PPr3)2(ЈS2Ј)2] (4): Yield: 290 mg of
4 (73%). Ϫ
C30H50OsP2S4 (791.1): calcd. C 45.55, H 6.37, S 16.21; found C
45.50, H 6.40, S 15.75. Ϫ FD MS (CH2Cl2); m/z: 792 [M]ϩ, 632
[Mϩ Ϫ PPr3]. Ϫ 1H NMR (CD2Cl2), δ ϭ 7.5Ϫ7.7 (m, 4 H, C6H4),
(NMe4)[Os(ЈS2Ј)2] (8b): An orange-brown suspension of (8a)
(75 mg, 0.1 mmol) in THF (5 ml) was treated with a 2.2  solution
of NMe4OH in MeOH (0.1 ml, 0.2 mmol). The resultant orange-
brown powder was separated, washed with MeOH (5 ml) and dried
in vacuo. Yield: 50 mg of (8b) (92%). Ϫ C16H20NOsS4 (544.8):
calcd. C 35.28, H 3.70, N 2.57; found C 35.52, H 3.46, N 2.47. Ϫ
1H NMR ([D6]DMSO), δ ϭ 7.30Ϫ7.45 (m, 4 H, C6H4), 6.55Ϫ6.70
(m, 4 H, C6H4), 3.1 (s, 12 H, NMe4ϩ).
β
5.35Ϫ5.55 (m, 4 H, C6H4), 0.6Ϫ0.9 (m, 12 H, CH2), 0.5 (t, 18 H,
CH3), Ϫ0.75Ϫ(Ϫ0.6) (m, 12 H, αCH2).
Ϫ
13C{1H} NMR
(CD2Cl2), δ ϭ 147.9, 124.9, 120.7 (C6H4), 21.1 (t, αCH2), 16.3 (s,
CH3), 16.0 (t, βCH2). Ϫ 31P{1H} NMR (CD2Cl2), δ ϭ Ϫ201.1 (s,
PPr3). Ϫ UV/VIS/NIR (CH2Cl2, λmax (lg ε) ϭ 1043 nm (4.63), 761
(3.74), 625 (3.88).
[Os(PMe3)2(ЈS2Ј)2] (5): Yield: 155 mg of
5 (50%). Ϫ
C18H26OsP2S4 (622.8): calcd. C 34.71, H 4.21; found C 34.96, H
4.17. Ϫ 1H NMR (C6D6), δ ϭ 7.9Ϫ8.1 (m, 4 H, C6H4), 5.4Ϫ5.6
(m, 4 H, C6H4), Ϫ1.2 (t, 18 H, CH3). Ϫ UV/VIS/NIR (CH2Cl2):
λmax (lg ε) ϭ 985 nm (4.53), 750(3.71), 622(3.56).
(NBu4)2[Os(ЈS2Ј)3] (9b): NBu4OH (3 ml of 1  solution in
MeOH, 3 mmol) ЈS2Ј-H2 (0.18 ml, 1.5 mmol), and (NH4)2[OsBr6]
(355 mg, 0.5 mmol) were combined in MeOH (50 ml) and heated
under reflux for 2 h. The resultant brown-red solution was filtered
while hot, and cooled to room temperature. Brown-red crystals pre-
[Os(PPh3)2(ЈS2Ј)2] (6): Yield: 410 mg of
6 (82%). Ϫ
C48H38OsP2S4 (995.2): calcd. C 57.93, H 3.85; found C 57.90, H cipitated that were separated after 4 h, washed with MeOH (30 ml)
3.84. Ϫ 1H NMR (CD2Cl2), δ ϭ 7.5Ϫ7.6 (m, 4 H, C6H4), 6.9Ϫ7.25 and Et2O (30 ml), and dried in vacuo. Yield: 500 mg of (9b) (91%).
(m, 30 H, C6H5), 5.9Ϫ6.05 (m, 4 H, C6H4). Ϫ 13C{1H} NMR Ϫ C50H84N2OsS6 (1095.8): calcd. C 54.80, H 7.73, N 2.56, S 17.56;
(CD2Cl2), δ ϭ 134.1 (d), 132.3 (d), 132.2, 129.4, 128.8 (d), 128.1,
found C 54.61, H 7.97, N 2.54, S 17.84. Ϫ 1H NMR (CD2Cl2), δ ϭ
122.8, 134.1 (d) (C6H4, C6H5). Ϫ 31P{1H} NMR (CD2Cl2), δ ϭ 6.55Ϫ7.90 (m, C6H4), 3.00 (m, 16 H, CH2), 1.70 (m, 16 H, CH2),
Ϫ46.5 (s, PPh3).
1.42 (m, 16 H, CH2), 1.0 (t, 24 H, CH3), 0.22 (s, C6H4), Ϫ0.90 (s,
Eur. J. Inorg. Chem. 1998, 819Ϫ826
824

Transition Metal Complexes with Sulfur Ligands, 131
Table 1. Selected crystallographic data for [Os(PEt3)2(ЈS2Ј)2] (3), [Os(PPr3)2(ЈS2Ј)2] (4), and (PHCy3)2[Os(ЈS2Ј)3] (9a)
FULL PAPER
compound
[Os(PEt3)2(ЈS2Ј)2]
(3)
[Os(PPr3)2(ЈS2Ј)2]
(4)
(PHCy3)2[Os(ЈS2Ј)3]
(9a)
Formula
MW [g/mol]
Crystal size. [mm]
F(000)
C24H38P2S4Os
706.92
C30H50P2S4Os
791.08
C54H78P2S6Os
1171.66
0.5 ϫ 0.2 ϫ 0.2
2416
0.4 ϫ 0.3 ϫ 0.2
704
0.3 ϫ 0.2 ϫ 0.1
800
Crystal system
Space group
a [pm]
monoclinic
P21/n
monoclinic
P21/c
monoclinic
P21/n
968.9(7)
1163.7(6)
1285.6(7)
93.38(5)
1.447(2)
2
1001.5(5)
1320.8(6)
1354.7(4)
95.09(3)
1.785(1)
2
1801.7(4)
1705.4(5)
1942.4(5)
112.72(2)
5.505(3)
4
b [pm]
c [pm]
β [°]
Cell volume [nm3]
Z
dcalcd. [g/cm3]
1.622
1.472
1.414
µ [mmϪ1
]
4.817
3.913
2.636
Temperature [K]
θ-range
293(2)
293(2)
200(2)
2.36Ϫ27.04
5442
2.04Ϫ27.05
4852
2.27Ϫ27.06
14605
Measured reflections
Independent reflections
Observed reflections
Refined parameters
R1 [F0 Ն 4σ (F)]
wR2 (all data)
3177
3354
11812
2169
1943
4086
145
169
605
0.0330
0.0434
0.0488
0.0865
0.1074
0.1115
[3]
[3a] D. Sellmann, B. Seubert, Angew. Chem. 1992, 104, 200Ϫ201;
C6H4). Ϫ CV (CH2Cl2, room temp., [mV]); E1 ϭ Ϫ80 (rev.), 180
(rev.), Ϫ580 (irrev.).
[3b]
Angew. Chem. Int. Ed. Engl. 1992, 31, 205Ϫ207. Ϫ
D.
Sellmann, D. Häußinger, F. Knoch, M. Moll, J. Am. Chem. Soc.
1996, 118, 5368Ϫ5374.
X-ray Structure Analysis of [Os(PEt3)2(ЈS2Ј)2] (3),
[Os(PPr3)2(ЈS2Ј)2] (4), and (PHCy3)2[Os(ЈS2Ј)3] (9a): Black sin-
gle crystals of [Os(PEt3)2(ЈS2Ј)2] (3) and [Os(PPr3)2(ЈS2Ј)2] (4) were
grown from MeOH (3) or MeOH/THF (4) solutions at Ϫ20°C. A
few black single crystals of (PHCy3)2[Os(ЈS2Ј)3] (9a) were obtained
as minor by-product from the THF/MeOH mother liquor resulting
from the synthesis of [Os(PCy3)(ЈS2Ј)2] (7). Suitable single crystals
were sealed under N2 in glass capillaries. The data were collected
using a Siemens P4 diffractometer. The structures were solved with
direct methods and refined using full-matrix least-squares pro-
cedures on F2 values (SHELXTL 5.03)[26]. Non-hydrogen atoms
were refined anisotropically, hydrogen positions were taken from
the difference Fourier synthesis and fixed on their positions with a
common isotropic thermal parameter in case of 4, while for 3 and
9a all H-atoms are geometrically positioned. One cyclohexyl group
(C70ϪC75) of the cation in 9a is disordered. Two different orien-
tations were refined, with a site occupancy of 50%. Table 1 lists
[4]
[5]
[6]
[7]
D. Sellmann, J. Käppler, M. Moll, J. Am. Chem. Soc. 1993,
115, 1830Ϫ1835.
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selected crystallographic data of 3, 4, and 9a[27]
.
[12] [12a]
Ƞ
Dedicated to Professor Heinrich Nöth on the occasion of his
[12b]
1994, 1819Ϫ1824. Ϫ
J. P. Collman, D. S. Bohle, A. K. Po-
70th birthday.
[12c]
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well, Inorg. Chem. 1993, 32, 4004Ϫ4011. Ϫ
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B. K. Burgess in Molybdenum Enzymes, Cofactors, and
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[1b]
ton), ACS Symposium Ser. 1993, 535, 144Ϫ170. Ϫ
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A. Earnshaw, Intro-
[2] [2a]
duction to magnetochemistry, Academic Press, London, 1968,
p. 70Ϫ71.
D. Sellmann, H. Friedrich, F. Knoch, M. Moll, Z. Natur-
[2b]
forsch. 1994, 48b, 76Ϫ88. Ϫ
D. Sellmann, M. Waeber, Z.
[15]
[16]
Naturforsch. 1986, 41b, 877Ϫ884. Ϫ [2c] D. Sellmann, E. Böhlen,
M. Waeber, G. Huttner, L. Zsolnai, Angew. Chem. 1985, 97,
984Ϫ985; Angew. Chem. Int. Ed. Engl. 1985, 24, 981Ϫ982. Ϫ
[2d] D. Sellmann in Molybdenum Enzymes, Cofactors, and Model
B. S. Kang, L. H. Weng, D. X. Wu, F. Wang, Z. Guo, L. R.
Huang, Z. Y. Huang, H. Q. Liu, Inorg. Chem. 1988, 27,
1128Ϫ1130.
D. Sellmann, M. Geck, M. Moll, J. Am. Chem. Soc. 1991,
113, 5259Ϫ5264.
Systems, (Eds.: E. I. Stiefel, D. Coucouvanis, W. E. Newton),
[2e]
[17] [17a]
ACS Symposium Ser. 1993, 535, 332Ϫ345. Ϫ
D. Sellmann
R. Eisenberg, E. I. Stiefel, R. C. Rosenberg, H. B. Gray, J.
[17b]
in Sulfur Coordinated Transition Metal Complexes: Biological
and Industrial Significance, (Eds.: E. I. Stiefel, K. Matsumoto),
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88, 2956Ϫ2966. Ϫ
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Eur. J. Inorg. Chem. 1998, 819Ϫ826
825

D. Sellmann, A. C. Hennige, F. W. Heinemann
FULL PAPER
[17d]
[23]
Soc. 1965, 87, 3776Ϫ3778. Ϫ
G. N. Schrauzer, V. P.
H. Koepp, H. Wendt, H. Strehlow, Z. Elektrochem. 1960, 64,
483Ϫ491.
J. Degani, R. Fochi, Synthesis 1976, 7, 471Ϫ472.
D. Sellmann, W. Reißer, Z. Naturforsch. 1984, 39b, 1268Ϫ1275.
SHELXTL 5.03 for Siemens Crystallographic Research Sys-
tems, Release 4 21/V, Copyright 1995 by Siemens Analytical X-
Ray Instruments Inc., Madison; WI.
Further details of the crystal structure investigations are avail-
able on request from Cambridge Crystallographic Data Cen-
tre, The Director, 12 Union Road, Cambridge CB2 1EZ (Tele-
fax: Int. ϩ 1223/336-033; E-mail: deposit@chemcrys.cam.a-
c.uk), on quoting the “supplementary publication no. CCDC-
100408”, the names of the authors, and the journal citation.
[97316]
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