Synthesis, structure, and reactivity of novel dithiolato(oxo)rhenium(v) complexes

Full text of DOI:10.1021/ic981367w

1040
Inorg. Chem. 1999, 38, 1040-1041
Synthesis, Structure, and Reactivity of Novel Dithiolato(oxo)rhenium(V) Complexes
Josemon Jacob, Ilia A. Guzei, and James H. Espenson*
Ames Laboratory and Department of Chemistry, Iowa State University of Science and Technology, Ames, Iowa 50011
ReceiVed NoVember 30, 1998
Oxygen atom transfer catalyzed by transition metal complexes
holds great interest owing to its chemical and biological
relevance.1-8 The intriguing mechanisms of certain of these
reactions catalyzed by organorhenium oxides have been re-
vealed.9,10 As we became involved in certain sulfur atom transfer
reactions, it became important to synthesize stable thiolato
complexes derived from methyltrioxorhenium (CH3ReO3 or
MTO), in that they are related to important catalytic intermediates.
A tetrathiophenylato complex, unstable above 15 °C, has been
reported,11 as have anionic dithiolato complexes of rhenium(V)-
sulfides.12 Prompted by these reports, we sought to prepare new,
Figure 1. Perspective view of the dinuclear rhenium(V) compound D
thermally stable thiolato complexes derived from MTO.
with thermal ellipsoids at the 30% probability level. Selected bond lengths
(Å) and angles (deg): Re(1)-S(1) 2.386; Re(1)-S(3) 2.362; Re(1)-
S(4) 2.299; Re(1)-O(1) 1.670; Re(1)-C(1) 2.120; S(3)-Re(1)-S(1)
75.2; S(3)-Re(1)-S(4) 90.8; S(4)-Re(1)-S(1) 146.2; S(3)-Re(1)-O(1)
112.7; S(3)-Re(1)-C(1) 143.2; O(1)-Re(1)-C(1) 103.8.
The reaction of MTO (0.8 mmol, 200 mg) with a twofold
excess of the dithiol13,14 was carried out at 0 °C in toluene (10
mL); after 15 min, 5 mL of hexane was added, and the mixture
was kept in a freezer overnight. The product was a dimeric
dithiolato-dirhenium complex, D, that forms fine needles, isolated
in 88% yield. Its structure was determined from spectroscopic15
and X-ray data,16,17 as shown in eq 1 and Figure 1.
As depicted, D is a dinuclear compound held together with
coordinate bonds from the sulfur of one ligand to the rhenium of
the other. A dithiolate ligand chelates Re(V), which is also
coordinated by single oxo and methyl groups. Accompanying this
product is the cyclic organic disulfide, required to balance the
reduction of Re(VII) to Re(V). D contains a four-membered
heteroatomic ring composed of two rhenium and two sulfur atoms.
The two {Re, S, S} planes within the central Re2S2 core define
a dihedral angle of 19.2(2)°. The rhenium atoms exist in a severely
distorted trigonal bipyramid: two sulfur atoms lie in apical
positions, at an average angle of 148(2)°, considerably off
linearity. Sulfur, oxygen, and carbon atoms are found in the
equatorial plane. The distortions are such that, alternatively, the
coordination sphere of the rhenium atoms can be described as
distorted square pyramidal with a carbon and three sulfur atoms
in the basal plane and an oxygen atom at the apex. One set of
three sulfur atoms and carbon is coplanar within 0.01(1) Å; the
second within 0.09(1) Å. The rhenium-oxo vectors are almost
normal to those planes, at angles of 84.5(1)° and 83.9(1)°.
Although the rhenium-sulfur distance between the monomeric
units (av 2.373(11) Å) exceeds that found within each monomer
(av 2.294(8) Å), it falls well within similar rhenium-sulfur bond
(1) Holm, R. H. Chem. ReV. 1987, 87, 1401.
(2) Espenson, J. H.; Abu-Omar, M. M. AdV. Chem. Ser. 1997, 253, 99-
134.
(3) Sheldon, R. A.; Kochi, J. K. Metal-Catalyzed Oxidations of Organic
Compounds; Academic Press: New York, 1981.
(4) Abrams, M. J.; Davison, A.; Jones, A. G. Inorg. Chim. Acta 1984, 82,
125.
(5) Begnan, I. A.; Behm, J.; Cook, M. R.; Herrmann, W. A. Inorg. Chem.
1991, 30, 2165.
(6) Conry, R. R.; Mayer, J. M. Inorg. Chem. 1990, 29, 4862-4867.
(7) Schultz, B. E.; Gheller, S. F.; Muetterties, M. C.; Scott, M. J.; Holm, R.
H. J. Am. Chem. Soc. 1993, 115, 2714.
(8) Moyer, B. A.; Sipe, B. K.; Meyer, T. J. Inorg. Chem. 1981, 20, 1475.
(9) Abu-Omar, M. M.; Appleman, E. H.; Espenson, J. H. Inorg. Chem. 1996,
35, 7751-7757.
(10) Abu-Omar, M. M.; Espenson, J. H. Inorg. Chem. 1995, 34, 6239-6240.
(11) Takacs, J.; Cook, M. R.; Kiprof, P.; Kuchler, J. G.; Herrmann, W. A.
Organometallics 1991, 10, 316.
(16) X-ray crystal data for C16H18O2Re2S4‚C7H8: monoclinic, P21/c, a )
14.6264(8) Å, b ) 18.7219(10) Å, c ) 9.3664(5) Å, â ) 93.393(1)°, V
) 2560.3(2) Å3, Z ) 4, T ) 163(2) K, Dcalcd ) 2.166 Mg/m3, R(F) )
1.98% for 4407 independently observed (I g 2σ(I) reflections (4° e 2θ
e 53°).
(17) All atoms other than hydrogen were refined with anisotropic displacement
coefficients. All hydrogen atoms were included in the structure factor
calculation at idealized positions and were allowed to ride on the
neighboring atoms with relative isotropic displacement coefficients. The
software and sources of the scattering factors are contained in the
SHELXTL (version 5.1) program library (G. Sheldrick, Bruker Analytical
X-Ray Systems, Madison, WI). Absorption corrections were carried out
by programs SADABS (Blessing, R. H. Acta Crystallogr. 1995, A51,
33-38) for D and DIFABS (Walker, N.; Stuart, D. Acta Crystallogr.
1983, A39, 158) for M-L.
(12) Goodman, J. T.; Rauchfuss, T. B. Inorg. Chem. 1998, 37, 5040-5041.
(13) Klingsberg, E.; Schreiber, A. M. J. Am. Chem. Soc. 1962, 84, 2941-
2944.
(14) Hortmann, A. G.; Aron, A. J.; Bhattacharya, A. K. J. Org. Chem. 1978,
43, 3374-3378.
(15) Spectroscopic data for the dinuclear compound D are as follows. 1H
NMR: δ 7.52 (d, 2H, J ) 8 Hz), 7.03 (m, 2H), 6.91(m, 4H), 4.05 (d,
2H, J ) 10.8 Hz), 3.53 (d, 2H, J ) 10.8 Hz), and 2.91 (s, 6H) ppm. 13
C
(18) Tisato, F.; Bolzati, C.; Duatti, A.; Bandoli, G.; Refosco, F. Inorg. Chem.
1993, 32, 2042-2048.
(19) Tanner, L. D.; Haltiwanger, R. C.; DuBois, M. R. Inorg. Chem. 1988,
27, 1741-1746.
NMR: δ 141.94, 135.81, 130.62, 130.56, 130.18, 127.87, 36.91, 17.10
ppm. Elemental anal. Calcd: C, 25.85; H, 2.44; S, 17.27. Found: C,
26.68; H, 2.53; S, 17.33.
10.1021/ic981367w CCC: $18.00 © 1999 American Chemical Society
Published on Web 02/27/1999

Communications
Inorganic Chemistry, Vol. 38, No. 6, 1999 1041
molecules with virtually identical parameters in the asymmetric
unit; only one is shown. In the following discussion the structural
parameters have been averaged between two molecules. As in
the case of D, the molecular geometry of M-L can be viewed
as highly distorted trigonal bipyramidal with one sulfur and one
phosphorus atom in the apical positions (av P-Re-S angle is
149.4(4)°). Sulfur, carbon, and oxygen atoms lie in the equatorial
plane. Alternatively, the rhenium atom is in a distorted square
pyramidal environment with a phosphorus, a carbon, and two
sulfur atoms in the basal plane (planarity within 0.14(1) Å) and
an oxygen atom at the vertex. The oxygen-rhenium vector
intersected the basal plane at 84.6(1)°. The bond distances to
rhenium fall in the usual ranges. The similar structural features
of both complexes are noteworthy because the one is a dimer,
the other a monomer.
Figure 2. Perspective view of M-L with thermal ellipsoids at the 30%
probability level. Selected bond lengths (Å) and angles (deg) (corre-
sponding parameters for the second molecule in parentheses): Re(1)-
S(1) 2.283 (2.275); Re(1)-S(2) 2.329 (2.340); Re(1)-P(1) 2.452 (2.447);
Re(1)-O(1) 1.677 (1.696); Re(1)-C(1) 2.125 (2.131); S(2)-Re(1)-S(1)
91.0 (90.6); S(2)-Re(1)-C(1) 78.6 (78.8); S(2)-Re(1)-O(1) 108.9
(109.1); C(1)-Re(1)-P(1) 83.3 (83.0).
lengths.12,18 Mixed sulfido-oxo complexes of rhenium18 and
molybdenum19 have been reported.
Since complexes of methyldioxorhenium are known to abstract
oxygen from various oxidants to form MTO,9,22 we investigated
the reactivity of D toward various oxygen donors, XO. Addition
of 4 equiv of XO in benzene solution caused both the rhenium
and its dithiolate ligand to be oxidized:23,24
Most likely, a first-formed mononuclear Re(VII) chelate then
undergoes reductive elimination. Further ligand coordination and
dimerization yields the Re(V) dithiolato complex D. Although
excess dithiol was used in the synthesis, it did not monomerize
D and remained unreacted. A tetrathiophenolato complex of
MTO,11 stable at low temperatures, undergoes reductive elimina-
tion at higher temperature. In our study, low-temperature NMR
experiments did not detect any intermediary Re(VII) species.
However, the reactivity of D toward various two-electron oxidants
(vide infra) suggests the intermediacy of a Re(VII) species.
Given the dimeric structure, it seemed possible that a Re(V)
monomer might be formed by coordination of an exogenous Lewis
base, L. The addition of 2 equiv of Ph3P to the yellow dimer
resulted in the quantitative formation of the intensely green
mononuclear dithiolato complex (ꢀ606 ) 1.9 × 102 L mol-1 cm-1),
eq 2. The rhenium(V) phosphine compound M-L was character-
The reactions were monitored by 1H NMR.25 With XO ) pyridine
N-oxide, Me3NO, or Ph3AsO, complete reaction occurred within
5 min. Me2SO required 1.5 days for 81% conversion, whereas
Ph3SbO gave only 50% reaction in 3 days. The disulfide isolated
from this reaction and from eq 1 showed 1H and 13C NMR spectra
identical to those of a sample prepared independently.26 Perhaps
initial O transfer to form the Re(VII) thiolato is rate controlling;
detailed studies are now underway to define the differences in
reactivity of various oxidants.
In summary, we have synthesized, analyzed, and characterized
new oxorhenium(V) complexes containing a dithiolato ligand. The
dinuclear version of this complex is monomerized upon reaction
with triphenylphosphine. The dimer readily reacts with several
O-atom donors, undergoing oxidation both at the metal and at
the ligand. We are currently investigating the scope and mech-
anism of this reaction and further studying the reactivity of this
binuclear complex.
1
ized by H and 13C NMR spectroscopy, elemental analysis, and
(despite quite small crystals grown by the slow diffusion of hexane
into a toluene solution) single-crystal X-ray analysis.17,20,21 Its
molecular structure, presented in Figure 2, shows two independent
(20) 1H NMR: δ 7.84 (d, 1H, J ) 7.6 Hz), 7.67 (m, 6H), 7.11 (t, 1H, J )
7.6 Hz), 7.04 (d, 1H, J ) 7.6 Hz), 6.90 (m, 10H), 4.80 (d, 1H, J ) 10.6
Hz), 3.25 (d, 1H, J ) 10.6 Hz), 2.97(d, 3H, J ) 8.4 Hz) ppm. 13C
NMR: δ 142.66, 140.37, 137.84 (d, J ) 9.2 Hz), 134.62 (d, J ) 7.7
Hz), 133.99 (d, J ) 14.7 Hz), 131.14 (d, J ) 1.7 Hz), 130.98, 130.47,
129.29, 126.29, 42.54 (d, J ) 7.1 Hz,) 15.45 (d, J ) 3 Hz) ppm. 31P
NMR: δ 27.82 ppm. Elemental anal. Calcd: C, 49.25; H, 3.82; S, 10.12.
Found: C, 49.25; H, 3.60; S, 9.78.
(21) X-ray crystal data for C26H24O2PReS2: triclinic, P1h, a ) 11.7741(5) Å,
b ) 13.9288(6) Å, c ) 14.7608(7) Å, R ) 83.860(1)°, â ) 84.093(1)°,
γ ) 81.878(1)°, V ) 2373.23(18) Å3, Z ) 4, T ) 163(2) K, Dcalcd
)
1.774 Mg/m3, R(F) ) 5.01% for 7178 independent observed (I g 2σ(I)
reflections (4° e 2θ e 56°).
Acknowledgment. This research was supported by the U.S.
Department of Energy, Office of Basic Energy Sciences, Division
of Chemical Sciences, under Contract W-7405-Eng-82.
(22) Zhu, Z.; Espenson, J. H. J. Mol. Catal. 1995, 103, 87.
(23) Arterburn, J. B.; Perry, M. C.; Nelson, S. L.; Dible, B. R.; Holguin, M.
S. J. Am. Chem. Soc. 1997, 119, 9309.
(24) Abu-Omar, M. M.; Khan, S. I. Inorg. Chem. 1998, 37, 4979.
(25) In the case of Me3NO, the reaction proceeds with decomposition of the
product, MTO. Although free MTO has δ 1.20 ppm in C6D6, in all these
cases the MTO formed in the reaction showed a chemical shift 1.50 e
δ e 1.70 ppm due to the coordination of X formed in the reaction. See
also: Wang, W.-D, Espenson, J. H. J. Am. Chem. Soc. 1998, 120, 11335.
(26) Wallace, T. J. J. Org. Chem. 1966, 31, 1217-1221.
Supporting Information Available: Spectroscopic and analytical data
for the new complexes, X-ray diffraction data for D and M-L, and the
UV-vis changes accompanying the reaction between D and PPh3. This
material is available free of charge via the Internet at http://pubs.acs.org.
IC981367W