Silylation, sulfidation, and benzene-1,2-dithiolate complexation reactions of oxo- and oxosulfidomolybdates(VI) and -tungstates(VI)

Article abstract of DOI:10.1021/ic701294y

The synthesis and structures of two types of molecules are presented: [M^VIO_{3 - n}S_n(OSiR₂R′)] ^1- (M = Mo, n = 0-3; M = W, n = 3) and [M^VIO ₂(OSiR₂R′)(bdt)]^1- (M = Mo, W; bdt = benzene-1,2-dithiolate). For both types, R₂R′ are Me ₃, Prⁱ₃, Ph₃, Me₂Bu ^t and Ph₂Bu^t. The complete series of oxo/sulfido/silyloxo molybdenum complexes has been prepared. Complexes with n = 0 are readily prepared by the silylation of Ag₂MoO₄ and sustain mono-or disulfidation with Ph₃SiSH to form a species with n = 1 and n = 2, respectively. Complexes with n = 3 are accessible by the silylation of [MOS₃]^2-. Structures of the representative series members [MoO₃(OSiPh₂Bu^t)]^1-, [MoO₂S(OSiPh₃)]^1-, [MoOS₂(OSiPr ⁱ₃)]^1-, [MoS₃(OSiPh ₂Bu^t)]^1-, and also [WS₃(OSiMe ₂Bu^t)]^1-, all with tetrahedral stereochemistry, are presented. Benzene-1,2-dithiolate complexes are prepared by the reaction of [MoO₃(OSiR₂R′)]^1- with the dithiol or by the silylation of previously reported [MO₃(bdt)]^2-. The structures of [MoO₂(OSiPh₂Bu^t)(bdt)] ^1- and [WO₂(OSiPrⁱ₃)(bdt)] ^1- conform to square-pyramidal stereochemistry with an oxo ligand in the apical position. The role of these complexes in the preparation of site analogues of the xanthine oxidoreductase enzyme family is noted. The sulfidation reactions reported here point to the utility of Ph₃SiSH and Pr ⁱ₃SiSH as reagents for Mo^VI-based oxo-for-sulfido conversions.

Full text of DOI:10.1021/ic701294y

Inorg. Chem. 2007, 46, 11156
−11164
Silylation, Sulfidation, and Benzene-1,2-dithiolate Complexation
Reactions of Oxo- and Oxosulfidomolybdates(VI) and -Tungstates(VI)
Jun-Jieh Wang and R. H. Holm*
Department of Chemistry and Chemical Biology, HarVard UniVersity,
Cambridge, Massachusetts 02138
Received June 30, 2007
−
The synthesis and structures of two types of molecules are presented: [MVIO3 nSn(OSiR2R
′
)]1 (M
)
Mo, n
)
-
−
0
−
3; M
R2R
has been prepared. Complexes with n
or disulfidation with Ph3SiSH to form a species with n
)
W, n
)
3) and [MVIO2(OSiR2R
′
)(bdt)]1 (M
)
Mo, W; bdt
)
benzene-1,2-dithiolate). For both types,
are Me3, Pri3, Ph3, Me2But and Ph2But. The complete series of oxo/sulfido/silyloxo molybdenum complexes
0 are readily prepared by the silylation of Ag2MoO4 and sustain mono-
′
)
)
1 and n
)
2, respectively. Complexes with n
)
3 are
accessible by the silylation of [MOS3]2−. Structures of the representative series members [MoO3(OSiPh2But)]1
,
−
[MoO2S(OSiPh3)]1−, [MoOS2(OSiPri3)]1−, [MoS3(OSiPh2But)]1−, and also [WS3(OSiMe2But)]1−, all with tetrahedral
stereochemistry, are presented. Benzene-1,2-dithiolate complexes are prepared by the reaction of [MoO3(OSiR2R′
)]1
−
with the dithiol or by the silylation of previously reported [MO3(bdt)]2−. The structures of [MoO2(OSiPh2But)(bdt)]1
−
and [WO2(OSiPri3)(bdt)]1 conform to square-pyramidal stereochemistry with an oxo ligand in the apical position.
The role of these complexes in the preparation of site analogues of the xanthine oxidoreductase enzyme family is
noted. The sulfidation reactions reported here point to the utility of Ph3SiSH and Pri3SiSH as reagents for MoVI-
based oxo-for-sulfido conversions.
−
Introduction
[MoVIO(OH)S(S2pd)], respectively.8 Appropriate structural
analogues of these sites are shown in Figure 1, together with
actual or projected methods of synthesis. In these molecules,
benzene-1,2-dithiolate models the cofactor ligand and sily-
lation simulates protonation. The approximate square-
pyramidal geometry with axial and basal oxo and basal
sulfido coordination follows from the X-ray structure of
Pseudomonas putida quinoline 2-oxidoreductase.9 Accurate
bond distances are available from the molybdenum EXAFS
analysis of bovine XO.10
The sulfidation method of synthesis has recently afforded,
among others, the complexes [WO2S(bdt)]2- and [WOS-
(OSiPri3)(bdt)]1-, which are the first structural analogues of
the oxidized XO sites.11 Tungsten is used without structural
compromise to stabilize the MVI state. In the course of this
and recent work, we have investigated silylation and sulfi-
dation reactions of oxomolybdates(VI) and oxotungstates-
We are engaged in research on the biomimetic chemistry
of molybdenum and tungsten directed at the attainment of
structural and functional analogues of the catalytic centers
of oxotransferase and hydroxylase enzymes. Results on
oxotransferase analogues have been summarized1 and are
augmented by more recent developments.2-4 Hydroxylases
are members of the xanthine oxidoreductase enzyme family,5
and utilize coordinated hydroxide as a nucleophile in
reactions with purines, aldehydes, and other substrates of
this family.6,7 A critical structural and mechanistic feature
of the apparently common, oxidized catalytic site is the
presence of a basal sulfido ligand in the square-pyramidal
unprotonated and protonated sites [MoVIO2S(S2pd)] and
* To whom correspondence should be addressed. E-mail: holm@
chemistry.harvard.edu.
(1) Enemark, J. H.; Cooney, J. J. A.; Wang, J.-J.; Holm, R. H. Chem.
ReV. 2004, 104, 1175-1200.
(2) Jiang, J.; Holm, R. H. Inorg. Chem. 2004, 43, 1302-1310.
(3) Jiang, J.; Holm, R. H. Inorg. Chem. 2005, 44, 1068-1072.
(4) Wang, J.-J.; Tessier, C.; Holm, R. H. Inorg. Chem. 2006, 45, 2979-
2988.
(5) Hille, R. Chem. ReV. 1996, 96, 2757-2816.
(6) Hille, R. Arch. Biochem. Biophys. 2005, 433, 107-116.
(7) Hille, R. Eur. J. Inorg. Chem. 2006, 1913-1926.
(8) Abbreviations are given in the chart.
(9) Bonin, I.; Martins, B. M.; Purvanov, V.; Fetzner, S.; Huber, R.;
Dobbek, H. Structure 2004, 12, 1425-1435.
(10) Doonan, C. J.; Stockert, A.; Hille, R.; George, G. N. J. Am. Chem.
Soc. 2005, 127, 4518-4522.
(11) Wang, J.-J.; Groysman, S.; Lee, S. C.; Holm, R. H. J. Am. Chem.
Soc. 2007, 129, 7512-7513.
11156 Inorganic Chemistry, Vol. 46, No. 26, 2007
10.1021/ic701294y CCC: $37.00
© 2007 American Chemical Society
Published on Web 11/29/2007

Oxo- and Oxosulfidomolybdates(VI) and -Tungstates(VI)
Figure 1. Synthetic analogues of the oxidized active sites in the xanthine oxidoreductase family of enzymes and their precursors.
R ) R′ ) Me. Needlelike crystals, 49%. IR: 955, 902,
(VI), leading to species of potential utility in the preparation
of XO site analogues. For example, the ions [MO3S]2- (M
) Mo, W), difficult to obtain as pure R4N+ salts by the
classical reaction of aqueous [MO4]2- with H2S, are readily
prepared by the more easily controlled reactions 1 and 2.12
Here, we describe the synthesis of a family of oxo/sulfido/
silyloxo complexes of MoVI and WVI comprised primarily
of previously unreported or incompletely characterized types,
and the structures of representative members. A later report
will enlarge on the use of such complexes in the synthesis
of oxo/sulfido site analogues.
1
878 cm-1. ES-MS: m/z 233 (M-). H NMR: δ 0.11 (s).
R ) R′ ) Pri. Platelike crystals, 59%. IR: 971, 906, 679 cm-1
.
ES-MS: m/z 317 (M-). H NMR: δ 0.14 (sept, 3), 1.07 (d, 18).
Anal. Calcd for C17H41MoNO4Si: C, 45.62; H, 9.23; N, 3.13.
Found: C, 45.48; H, 9.30; N, 3.09.
1
R ) Me, R′ ) But. Blocklike crystals, 55%. IR: 973, 907, 878,
1
678 cm-1. ES-MS: m/z 275 (M-). H NMR: δ 0.06 (s, 6), 0.92
(s, 9).
R ) Ph, R′ ) But. Platelike crystals, 67%. IR: 972, 904, 885,
1
703 cm-1. H NMR: δ 1.03 (s, 9), 7.39 (m, 6), 7.74 (m, 4). ES-
MS: m/z 399 (M-). Anal. Calcd for C24H39MoNO4Si: C, 54.43;
[MO4]2- + Ph3C+ + HS- f [MO3S]2- + Ph3COH (1)
H, 7.42; N, 2.64. Found: C, 54.38; H, 7.30; N, 2.69.
(Et4N)[MoO2S(OSiPh2But)]. The procedure was performed at
-20 °C. A solution of Ph3SiSH (112 mg, 0.383 mmol) in 2 mL of
THF was added dropwise to a solution of (Et4N)[MoO3(OSiPh2-
But)] (201 mg, 0.380 mmol) in 8 mL of acetonitrile. The reaction
mixture turned bright orange within 3 min, and stirring was
continued for 10 min. Solvents were removed, and the yellow-
orange solid was washed with hexanes and dissolved in 1.5 mL of
acetonitrile. The solution was filtered, and the filtrate was layered
with 20 mL of ether. Over 8 h, a solid separated, which was washed
with ether (2 × 3 mL) and dried, to afford the product as 171 mg
(83%) of yellow-orange crystals. Absorption spectrum: λmax (ꢀM)
256 (5820), 311 (6780), 399 (sh, 770), 455 (sh, 1100) nm. ES-
MS: m/z 415 (M-). 1H NMR: δ 1.04 (s, 9), 7.42 (m, 6), 7.75 (m,
4). Anal. Calcd for C24H39MoNO3SSi: C, 52.83; H, 7.20; N, 2.57;
S, 5.88. Found: C, 52.68; H, 7.10; N, 2.48; S, 5.86.
(Et4N)[MoO2S(OSiPri3)]. The previous procedure was followed
with the use of 0.40 mmol each of (Et4N)[MoO3(OSiPri3)] and Pri3-
SiSH. The product was obtained as 168 mg (90%) of yellow-orange
crystals. IR: 949, 901, 881, 500 cm-1. Absorption spectrum: λmax
(ꢀM) 255 (5370), 310 (4440), 350 (1860), 472 (280) nm. ES-MS
m/z 333 (M-). 1H NMR: δ 1.09 (d) (CH not detected). Anal. Calcd
for C17H41MoNO3SSi: C, 44.04; H, 8.91; N, 3.02; S, 6.92. Found:
C, 43.87; H, 9.02; N, 2.97; S, 6.85.
[MoO3(OSiPh3)]1- + HS- f [MoO3S]2- + R3SiOH
(2)
Experimental Section
Preparation of Compounds. All of the reactions and manipula-
tions were performed under a pure dinitrogen atmosphere using
either an inert atmosphere box or standard Schlenk techniques.
Acetonitrile, diethylether, dichloromethane, and THF were freshly
purified using an Innovative Technology solvent purification system
and stored over 4 Å molecular sieves. Benzene-1,2-dithiol (H2(bdt))
was prepared as described.13 1H NMR data for salts refer to anions
in CD3CN solutions. IR spectra were recorded in KBr pellets and
absorption spectra in acetonitrile solutions. All of the compounds
1
were characterized by a combination of IR, H NMR, UV-vis,
mass spectroscopy, and elemental analysis. Negative-ion electro-
spray mass spectra of all of the complex salts reveal a prominent
peak for the parent anion (M-). Certain compounds not subjected
to elemental analysis were identified by X-ray structure determina-
tions.
Oxo/Sulfido/Silyloxo Complexes. (Et4N)[MoO3(OSiR2R′)].
These compounds were prepared on a 5-8 mmol scale, by a method
analogous to that reported for (Et4N)[MoO3(OSiPh3)]12 but with
the use of R2R′SiCl. A solution of R2R′SiCl (1.0 equiv) in
dichloromethane was added dropwise to a suspension of Ag2MoO4
(2-3 g) in dichloromethane. The reaction mixture was stirred for
72 h and 1.0 equiv of Et4NCl was added. The mixture was stirred
for 8 h, filtered through Celite, and the filtrate was taken to dryness,
leaving a solid white residue. This material was dissolved in 20-
30 mL of dichloromethane, the solution was filtered, and the filtrate
solvent was removed. This step was repeated with the residue, the
resultant solid was extracted with acetonitrile, and the extract was
filtered through Celite. The filtrate was reduced to half-volume,
several volume equiv of ether were layered on the filtrate, and the
mixture was allowed to stand for 2 d. Products were isolated as
crystalline white solids in the indicated yields.
(Et4N)[MoOS2(OSiR2R′)]. To a solution of (Et4N)[MoO3-
(OSiR2R′)] (0.38-0.40 mmol) in 6 mL of acetonitrile was added
a solution of Ph3SiSH (2.0 equiv) in 2 mL of THF. The reaction
mixture turned bright orange within 1 min and was stirred for 10
min to give a deep-orange solution. The solution was filtered and
the solvents were removed. The orange solid was washed with
hexanes and ether and dissolved in 1.5 mL of acetonitrile. The
solution was filtered, and the filtrate was layered with 20 mL of
ether. The solid that separated over 8 h was washed with ether (2
× 3 mL) and dried to afford the products as orange platelike crystals
in the indicated yields.
R ) R′ ) Pri. 84%. IR: 938, 899, 507 cm-1. Absorption
spectrum: λmax (ꢀM) 289 (4120), 300 (sh, 3950), 350 (4400), 404
(12) Partyka, D. V.; Holm, R. H. Inorg. Chem. 2004, 43, 8609-8616.
(13) Giolando, D. M.; Kirschbaum, K. Synthesis 1992, 451-452.
1
(1260), 535 (190) nm. ES-MS: m/z 351 (M-). H NMR: δ 1.09
Inorganic Chemistry, Vol. 46, No. 26, 2007 11157

Wang and Holm
Table 1. Crystallographic Data for Compounds Containing [MO3 - nSn(OSiR2R′)]1- (M ) Mo, n ) 0-3; M ) W, n ) 3)a
(Et4N)[1d]‚CH2Cl2
(Et4N)[2b]
(Et4N)[3a]
(Et4N)[4e]
(Et4N)[5c]
formula
fw
C25H41Cl2 MoNO4Si
614.52
C26H35MoNO2SSi
565.64
C17H41MoNO2S2Si
479.66
C24H39MoNOS3Si
577.77
C14H35NOS3SiW
541.55
cryst syst
space group
Z
triclinic
P1h
2
triclinic
P1h
2
monoclinic
P21/c
4
monoclinic
P21/c
4
monoclinic
P21/c
4
a (Å)
b (Å)
c (Å)
9.830(2)
10.660(2)
15.920(3)
107.21(3)
103.20(3)
93.31(3)
1537.3(5)
1.328
0.667
1.39-27.90
1.042
3.10
8.33
8.5965(8)
9.2168(9)
19.4188(18)
100.911(2)
92.755(2)
113.094(2)
1376.9(2)
1.364
0.622
1.08-25.00
1.080
4.90
13.47
17.7637(14)
8.4492(7)
16.5049(14)
20.6752(16)
10.3777(8)
14.4721(11)
18.678(4)
8.1799(16)
16.724(3)
R (deg)
â (deg)
γ (deg)
V (Å3)
90.732(2)
110.422(1)
110.59(3)
2477.0(4)
1.286
0.756
1.15-25.00
1.089
2910.0(4)
1.319
0.723
1.05-28.28
1.107
2392.0(8)
1.504
5.141
1.16-27.89
1.176
d
calcd (g/cm3)
µ (mm-1
)
θ range (deg)
GOF (F 2)
R1b (%)
4.79
10.31
3.50
8.95
3.22
8.36
wR2c (%)
a Mo KR radiation, 193 K. b R1 ) ∑||Fo| - |Fc||/∑|Fo|. c wR2 ) [∑w(Fo - Fc )2/∑(Fo )2]1/2
.
2
2
2
Table 2. Crystallographic Data for Compounds Containing
[MO2(OSiR2R′)(bdt)]1- (M ) Mo, W) and [Mo2O3Cl2(bdt)2]2- a
(d) (CH not detected). Anal. Calcd for C17H41MoNO2S2Si: C, 42.57;
H, 8.62; N, 2.92; S, 13.37. Found: C, 42.45; H, 8.76; N, 2.85; S,
13.44.
(Et4N)[8d]
(Et4N)[9b]
(Et4N)2[10]
R ) R′ ) Ph. 88%. IR: 964, 906, 885, 510 cm-1. Absorption
spectrum: λmax (ꢀM) 260 (9280), 313 (6530), 352 (2830), 406 (sh,
formula
fw
C
30H43MoNO3S2Si
C23H45NOS2SiW C28H48Cl2Mo2N2O3S4
653.80
659.66
851.70
cryst syst
space group
Z
orthorhombic
Pna21
4
triclinic
P1h
4
monoclinic
P21/c
2
1
1530) nm. ES-MS: m/z 453 (M-). H NMR: δ 7.43 (m, 9), 7.62
(m, 6).
R ) Ph, R′ ) But. The procedure was conducted at 0 °C.; 82%.
IR: 972, 904, 885, 703 cm-1. Absorption spectrum: λmax (ꢀM) 256
(8500), 302 (sh, 4020), 350 (4400), 404 (sh, 1300), 470 (660) nm.
ES-MS: m/z 431 (M-). 1H NMR: δ 1.05 (s, 9), 7.42 (m, 6), 7.62
(m, 2), 7.76 (m, 2).
a (Å)
b (Å)
c (Å)
R (deg)
â (deg)
γ (deg)
V (Å3)
23.374(6)
8.965(2)
15.057(3)
8.4161(4)
17.3262(9)
19.9065(11)
84.9760(10)
88.8130(10)
89.7990(10)
2891.0(3)
1.516
4.204
1.18-27.91
1.089
4.71
9.54
8.3500(17)
16.477(3)
13.535(3)
104.00(3)
3155.3(13)
1806.9(6)
1.565
1.104
1.98-27.89
1.046
(Et4N)[MoOS2(OSiMe2But)]. A solution of Me2ButSiCl (57 mg,
0.39 mmol) in 2 mL of THF was added to a suspension of (Et4N)2-
[MoO3S]12 (166 mg, 0.38 mmol) in 8 mL of THF. The reaction
mixture became yellowish and then bright orange in 10 min and
was stirred for 30 min, resulting in a deep-orange solution and a
precipitate. The mixture was filtered, and the filtrate was taken to
dryness. The solid residue was washed with ether (3 × 3 mL) and
dissolved in 1.5 mL of acetonitrile. The solution was covered with
20 mL of ether, and the mixture was allowed to stand overnight.
The product was isolated as 78 mg (43%) of orange platelike
crystals. IR: 956, 882, 506 cm-1. Absorption spectrum: λmax (ꢀM)
288 (4020), 301 (sh, 3890), 350 (4380), 406 (sh, 1240), 438 (780),
d
calcd (g/cm3) 1.376
µ (mm-1
)
0.616
θ range (deg) 1.74-27.90
GOF (F 2)
R1b (%)
0.993
3.01
6.38
5.15
11.95
wR2c (%)
2
a Mo KR radiation, 193 K. b R1 ) ∑||Fo| - |Fc||/∑|Fo|. c wR2 ) [∑w(Fo
2
2
- Fc )2/∑(Fo )2]1/2
not detected). Anal. Calcd for C17H41MoNOS3Si: C, 41.19; H, 8.34;
N, 2.83; S, 19.40. Found: C, 41.31; H, 8.40; N, 2.76; S, 19.34.
This compound can also be prepared by the reaction of (Et4N)-
[MoO3(OSiPri3)] and g3 equiv of Pri3SiSH in acetonitrile.
R ) R′ ) Ph. 70%. ES-MS: m/z 467 (M-). IR: 946, 518,
500 cm-1. Absorption spectrum: λmax(ꢀM) 273 (4130), 291 (sh,
3900), 445 (2200) nm. 1H NMR: δ 7.42 (m, 9), 7.63 (m, 6). This
compound can also be prepared by the reaction of (Et4N)[MoO3-
(OSiPh3)] and g3 equiv of Ph3SiSH in acetonitrile.
R ) Me, R′ ) But. 55%. IR: 924, 508 cm-1. ES-MS: m/z 275
(M-). Absorption spectrum: λmax (ꢀM) 285 (5500), 347 (sh, 1360),
405 (2770), 437 (sh, 1200), 535 (600) nm. 1H NMR: δ 0.08 (s, 6),
0.92 (s, 9).
R ) Ph, R′ ) But. 68%. IR: 933, 508, 478 cm-1. ES-MS: m/z
399 (M-). Absorption spectrum: λmax (ꢀM) 271 (4060), 300 (sh,
2720), 382 (sh, 630), 448 (520) nm. 1H NMR: δ 1.06 (s, 9), 7.42
(m, 6), 7.74 (m, 4).
(Et4N)[WS3(OSiR2R′)]. These compounds were prepared on a
5-8 mmol scale in a procedure analogous to the preceding
preparations, but with (Et4N)2[WOS3],14 and were isolated as yellow
crystalline solids in the indicated yields.
R ) R′ ) Pri. 89%. IR: 936, 901, 490, 482 cm-1. ES-MS: m/z
453 (M-). Absorption spectrum: λmax (ꢀM) 254 (9000), 283 (sh,
1
536 (140) nm. ES-MS: m/z 307 (M-). H NMR: δ 0.06 (s, 6),
0.92 (s, 9).
(Et4N)[MoS3(OSiR2R′)]. These compounds were prepared by
a method and on a scale similar to the preceding preparation. A
solution of R2R′SiCl (1.0 equiv) in THF was added to a suspension
of (Et4N)2[MoOS3]14 (1.0 equiv) in THF. The reaction mixture
became orange within 5 min and was stirred for 30 min. Workup
was performed as in the preceding preparation, to afford the
products as red blocklike crystals in the indicated yields.
R ) R′ ) Me. 49%. IR: 921, 510, 502 cm-1. ES-MS: m/z 233
(M-). Absorption spectrum: λmax(ꢀM) 290 (4800), 347 (sh, 1300),
1
408 (2570), 535 (450) nm. H NMR: δ 0.13 (s). This compound
can also prepared by the reaction of (Et4N)[MoO3(OSiMe3)] and
g3 equiv of (Me3Si)2S in acetonitrile.
R ) R′ ) Pri. 69%. IR: 922, 507 cm-1. ES-MS: m/z 317 (M-
). Absorption spectrum: λmax (ꢀM) 287 (5000), 349 (sh, 960), 407
1
(2280), 440 (sh, 900), 534 (600) nm. H NMR: δ 1.06 (d) (CH
(14) McDonald, J. W.; Friesen, G. D.; Rosenhein, L. D.; Newton, W. E.
Inorg. Chim. Acta 1983, 72, 205-210.
11158 Inorganic Chemistry, Vol. 46, No. 26, 2007

Oxo- and Oxosulfidomolybdates(VI) and -Tungstates(VI)
1
2460), 345 (3870), 434 (970) nm. H NMR: δ 1.06 (d) (CH not
detected). Anal. Calcd for C17H41NOS3SiW: C, 34.94; H, 7.08; N,
2.40; S, 16.48. Found: C, 35.10; H, 7.02; N, 2.36; S, 16.34.
R ) R′ ) Ph. 77%. IR: 870, 484, 471 cm-1. ES-MS: m/z 555
(M-). Absorption spectrum: λmax (ꢀM) 385 (4500), 439 (sh, 1200)
1
nm. H NMR: δ 7.45 (m, 9), 7.66 (m, 6).
R ) Me, R′ ) But. 75%. IR: 927, 486 cm-1. ES-MS: m/z 411
(M-). Absorption spectrum: λmax (ꢀM) 254 (8600), 283 (sh, 2800),
1
341 (4120), 435 (1120) nm. H NMR: δ 0.06 (s, 6), 0.92 (s, 9).
R ) Ph, R′ ) But. 82%. IR: 905, 514, 503 cm-1. ES-MS: m/z
535 (M-). Absorption spectrum: λmax (ꢀM) 254 (10 200), 345
1
(4080), 438 (1070) nm. H NMR: δ 1.03 (s, 9), 7.43 (m,6), 7.75
(m, 2), 7.82 (m, 2).
Oxo/Sulfido/Silyloxo-Benzenedithiolate Complexes. (Et4N)-
[MoO2(OSiR2R′)(bdt)]. Method A. To a suspension of (Et4N)2-
[MoO3(bdt)]12 (120 mg, 0.221 mmol) in 20 mL of THF was added
a solution of R2R′SiCl (0.22-0.24 mmol) in 3 mL of THF. The
reaction mixture was stirred for the specified time and the solvent
was removed. The residue was washed with ether (3 × 3 mL),
dissolved in 3 mL of acetonitrile, the solution was filtered, and the
filtrate was layered with 20 mL of ether. After the mixture was
allowed to stand overnight, the solid material was collected, washed
with ether, and recrystallized from acetonitrile/ether to yield the
product as an orange crystalline solid in the indicated yield.
R ) R′ ) Me. The procedure was performed at -20 °C, 10
min, 47%. IR: 946, 913, 884 cm-1. ES-MS: m/z 357 (M-).
Absorption spectrum: λmax (ꢀM) 299 (4310), 335 (sh, 3060), 401
(sh, 1100), 727 (230) nm. H NMR: δ 0.16 (s, 9), 6.85 (dd, 2),
7.16 (dd, 2).
R ) R′ ) Pri. 50 min, 60%. IR: 944, 911, 884 cm-1. ES-MS:
m/z 441 (M-). Absorption spectrum: λmax (ꢀM) 301 (4500), 334
(sh, 2980), 399 (sh, 1070), 723 (240) nm. 1H NMR: δ 0.15 (m, 3),
1.18 (s, 18), 6.84 (dd, 2), 7.15 (dd, 2). Anal. Calcd for C23H45-
MoNO3S2Si: C, 48.31; H, 7.93; N, 2.45; S, 11.22. Found: C, 48.43;
H, 7.90; N, 2.39; S, 11.31.
Figure 2. Synthetic scheme affording oxo/sulfido/silyloxo molybdates
1-4, trisulfidosilyloxide tungstate 5, and bdt complexes 8 and 9.
1
R ) R′ ) Pri. Green-brown crystalline solid, 5 h, 68%. IR:
973, 920, 894 cm-1. ES-MS: m/z 529 (M-). Absorption spec-
1
trum: λmax (ꢀM) 304 (8300), 397 (320) nm. H NMR: δ 0.15 (m,
3); 1.13 (s, 18), 6.84 (dd, 2), 7.19 (dd, 2). Anal. Calcd for C23H45-
NO3S2SiW: C, 41.88; H, 6.88; N, 2.12; S, 9.72. Found: C, 41.97;
H, 6.81; N, 2.08; S, 9.52.
R ) Me, R′ ) But. Light-yellow crystalline solid, 5 h, 52%.
IR: 977, 923, 895 cm-1. ES-MS: m/z 487 (M-). Absorption
R ) Me, R′ ) But. 40 min, 48%. IR: 957, 908, 884 cm-1
.
1
spectrum: λmax (ꢀM) 303 (8150), 398 (360) nm. H NMR: δ 0.13
ES-MS: m/z 399 (M-). Absorption spectrum: λmax (ꢀM) 304 (4000),
(s, 6), 0.95 (s, 9), 6.84 (dd, 2), 7.20 (dd, 2).
1
338 (sh, 2870), 394 (1170) nm. H NMR: δ 0.12 (s, 6), 0.93 (s,
R ) Ph, R′ ) But. Green-yellow crystalline solid, 10 h, 58%.
IR: 977, 924, 890 cm-1. ES-MS: m/z 611 (M-). Absorption
9), 6.84 (dd, 2), 7.15 (dd, 2). Anal. Calcd for C20H39MoNO3S2Si:
C, 45.35; H, 7.42; N, 2.64; S, 12.11. Found: C, 45.48; H, 7.47; N,
2.71; S, 12.04.
1
spectrum: λmax (ꢀM) 303 (8900), 397 (600) nm. H NMR: δ 1.09
(s, 9), 6.87 (dd, 2), 7.21 (dd, 2), 7.42 (m, 6), 7.84 (m, 4). Anal.
Calcd for C30H43NO3S2SiW: C, 48.58; H, 5.84; N, 1.89; S, 8.65.
Found: C, 48.51; H, 5.89; N, 1.87; S, 8.47.
R ) Ph, R′ ) But. 60 min, 62%. IR: 952, 913, 883 cm-1. ES-
MS: m/z 523 (M-). Absorption spectrum: λmax (ꢀM) 300 (4930),
1
332 (sh, 3140), 399 (sh, 1430), 488 (sh, 540), 720 (500) nm. H
(Et4N)2[Mo2O2Cl2(bdt)2(µ2-O)]. To a suspension of (Et4N)2-
[MoO3(bdt)] (120 mg, 0.221 mmol) in 20 mL of THF was injected
dropwise a solution of Me3SiCl (50 mg, 0.45 mmol) in 4 mL of
THF. The reaction mixture become green-brown in 10 min and
was stirred for an additional 10 min. Solvent was removed, the
residue was washed with ether (3 × 3 mL), and was dissolved in
2 mL of acetonitrile. The solution was filtered, and the filtrate was
covered with 20 mL of ether. The mixture was allowed to stand
overnight, during which a red-brown crystalline solid separated.
1H NMR: δ 6.97 (dd, 2), 7.59 (dd, 2). This compound was
identified by an X-ray structure determination.
X-ray Structure Determinations. Structures of the eight
compounds in Tables 1 and 2 were determined. Diffraction-quality
crystals were obtained by layering several volume equiv of ether
onto acetonitrile solutions that were maintained thereafter at 243-
298 K for at least 12 h. Crystals were coated in paratone-N oil and
mounted on either a Bruker SMART 1K or APEX CCD-based
diffractometer equipped with a low temperature apparatus operating
at 193 K. Data were collected with ω scans of 0.3°/frame for 30 s,
NMR: δ 1.08 (s, 9), 6.87 (dd, 2), 7.17 (dd, 2), 7.42 (m ,6), 7.83
(m, 4).
Method B. These compounds were prepared on a 0.20 mmol
scale by the reaction of equimolar H2(bdt) and (Et4N)[MoO3-
(OSiR2R′)] in acetonitrile. The orange reaction mixture was reduced
in volume to 2 mL and was layered with 30 mL of ether, causing
an orange precipitate. The solid was washed with ether and dried,
affording the products (72-83%). Spectral properties are identical
to those of the products of Method A.
(Et4N)[WO2(OSiR2R′)(bdt)]. To a suspension of (Et4N)2[WO3-
(bdt)]12 (200 mg, 0.316 mmol) in 20 mL of THF was added a
solution of 0.32-0.34 mmol of R2R′SiCl in 3 mL of THF. After
the specified reaction times, the reaction mixtures were yellow or
yellow-green. Solvent was removed and the residue was collected,
washed with ether, and recrystallized from acetonitrile/ether.
R ) R′ ) Me. Green-brown crystalline solid, 2 h, 42%. ES-
MS: m/z 445 (M-). Absorption spectrum: λmax (ꢀM) 302 (8510),
1
399 (350) nm. H NMR: δ 0.l7 (m, 9), 6.84 (dd, 2), 7.20 (dd, 2).
Inorganic Chemistry, Vol. 46, No. 26, 2007 11159

Wang and Holm
Figure 3. Structures of [MoO3(OSiPh2But)]1- (left), [MoO2S(OSiPh3)]1- (right), and [MoOS2(OSiPri3)]1- (center). In this and the following structural
figures, 50% probability ellipsoids, the atom-labeling schemes, and selected (mean) bond distances (angstroms) and angles (degrees) are given. Left: mean
Mo-O1,2,3 1.721(2), Mo-O4 1.876(2), O4-Si 1.622(2), Si-C 1.876(2); O1-Mo-O2 109.3(1), O2-Mo-O3 108.8(1), O1-Mo-O3 109.3(1), O1-
Mo-O4 110.1(1), O2-Mo-O4 108.7(1), O3-Mo-O4 110.7(1), Mo-O4-Si 169.8 (1). Right: Mo-O1 1.792(4), Mo-O2 1.719(3), Mo-S1 2.104(2),
Mo-O3 1.883(3), O3-Si 1.622(3), Si-C 1.865; O1-Mo-O2 108.0(2), O1-Mo-S1 108.8(2), O2-Mo-S1 108.5(2), O1-Mo-O3 110.7(2), O2-Mo-
O3 107.7(2), S1-Mo-O3 113.0(1), Mo-O3-Si 161.2(2). Center: Mo-O1 1.70(2), Mo-S1 2.150(1), Mo-S2 2.06(1), Mo-O2 1.88(1), O2-Si 1.63(1),
Si-C 1.87(1); S1-Mo-S2A 110.6(1), O1A-Mo-S1 105.6(4), O1A-Mo-S2A 111.6(5), O1A-Mo-O2A 118.8(5), S1-Mo-O2A 106.4(4), S2A-Mo-
O2A 103.7(4), Mo-O2A-Si 156.3 (8).
such that 971-1647 frames were collected for a hemisphere of
data. The first 50 frames were recollected at the end of the data
collection to monitor for crystal decay; no significant decay was
detected for any compound. Cell parameters were retrieved using
SAINT software and refined with SAINT on all of the reflections.
Data integration was performed with SAINT, which corrects for
Lorentz polarization and decay. Absorption corrections were applied
with SADABS. Space groups were assigned unambiguously by
analysis of symmetry, and systematic absences were determined
by XPREP. All of the crystals were checked with PLATON for the
possibility of higher symmetry; none was found. Structures were
solved by direct methods and refined against all of the data by
full-matrix least-squares techniques on F 2 using the SHELXL-97
package. All of the non-hydrogen atoms were refined anisotropi-
cally. Isopropyl groups in anions 3a, 4b, 5a, 8b, and 9b were
disordered. The disorder was modeled effectively in all cases except
3a, for which no satisfactory description of the disorder was
obtained. Hydrogen atoms were placed in idealized positions on
carbon atoms and refined as a riding model. Crystal parameters
and agreement factors are collected in Tables 1 and 2.15
In addition to the compounds in Tables 1 and 2, several other
structures were determined. Owing to the close structural similarities
of their complexes to those described in full, only crystallographic
parameters are reported.15 (Et4N)[MoS3(OSiPri3)]: monoclinic, P21/
c, a ) 17.990(4) Å, b ) 8.490(2) Å, c ) 16.505(1) Å, â ) 90.79-
(3)°, Z ) 4, R1(wR2) ) 0.1030(0.2617). (Et4N)[WS3(OSiPri3)]:
monoclinic, P21/c, a ) 18.061(2) Å, b ) 8.523(1) Å, c ) 16.662-
(2) Å, â ) 91.032(2)°, Z ) 4, R1(wR2) ) 0.0559(0.1242). (Et4N)-
[MoO2(OSiPri3)(bdt)]: triclinic, P1h, a ) 8.400(2) Å, b ) 17.300(4)
Å, c ) 19.860(4) Å, R ) 85.08(3)°, â ) 88.78(3)°, γ ) 89.70(3)°,
Z ) 4, R1(wR2) ) 0.0495(0.1057). (Et4N)[WO2(OSiMe2But)(bdt)]:
monoclinic, P21/c, a ) 19.940(4) Å, b ) 7.830(2) Å, c ) 34.290-
(7) Å, â ) 92.17(3)°, Z ) 8, R1(wR2) ) 0.0593(0.1329).
Other Physical Measurements. All of the measurements were
made under anaerobic conditions. NMR spectra were recorded on
a Varian Mercury 300 and 400 spectrometers. Infrared spectra were
obtained on a Nicolet Nexus 470 FTIR spectrometer. Absorption
spectra were measured with a Varian Cary 50 Bio spectrophotom-
eter. Electrospray mass spectra were recorded on a Micromass
(16) Do, Y.; Simhon, E. D.; Holm, R. H. Inorg. Chem. 1985, 24, 1831-
1838.
(15) See paragraph at the end of this article for Supporting Information
available.
(17) Lim, B. S.; Willer, M. W.; Miao, M.; Holm, R. H. J. Am. Chem. Soc.
2001, 123, 8343-8349.
11160 Inorganic Chemistry, Vol. 46, No. 26, 2007

Oxo- and Oxosulfidomolybdates(VI) and -Tungstates(VI)
Chart 1. Designation of Complexes and Abbreviationsa
a
bdt ) benzene-1,2-dithiolate(2-); But3tach ) 1,3,5-tert-butyl-1,3,5-
triazacyclohexane; Cp* ) pentamethylcyclopentadienide(1-); S2pd )
pyranopterindithiolate(2-) cofactor ligand; Tp ) tris(pyrazolyl)hydrobo-
rate(1-); XO ) xanthine oxidoreductase.
succeeds with AgMO4, resulting in [Me3SiOMO3] (M ) Tc,20
Re21). The structure of 1d (Figure 3) reveals the expected
tetrahedral stereochemistry at the molybdenum atom (O-
Mo-O angles of 108.9(1)-110.7(1)°), a mean ModO
distance of 1.721(2) Å, a Mo-OSi distance of 1.876(2) Å,
and a nearly linear Mo-O-Si angle of 169.8(1)°. These
complexes are precursors to monosulfido species. Despite
repeated attempts under different conditions, no reaction was
observed between Ag2WO4 and silylchlorides. A route to
the complexes [WO3(OSiR2R′)]1- remains to be developed.
Ag2MoO4 + R2R′SiCl + Cl- f [MoO3(OSiR2R′)]1-
+
2AgCl (3)
Figure 4. Structures of [MoS3(OSiPh2But)]1- (upper): mean Mo-S1,2,3
2.150(1), Mo-O1 1.857(1), O1-Si 1.636(2), Si-C 1.875(2); S1-Mo-
S2 109.17(3), S1-Mo-S3 109.29(3), S2-Mo-S3 109.23(3), S1-Mo-
O1 108.91(5), S2-Mo-O1 109.93(5), S3-Mo-O1 110.30(6), Mo-O1-
Si 171.4(1). [WS3(OSiMe2But)]1- (lower): mean W-S1,2,3 2.154(1),
W-O1 1.858(4), O1-Si 1.634(4), Si-C 1.861(8); S1-W-S2 109.33(5),
S1-W-S3 109.33(6), S2-W-S3 109.40(6), S1-W-O1 110.0(2), S2-
W-O1 110.4(1), S3-W-O1 108.4(1), W-O1-Si 155.2(3).
Oxothiosilyloxomolybdates. Monosulfidation reaction 4a
was first used to prepare 2b from 1e.12 Application of this
reaction to 1d was successful, yielding 2c (83%). However,
this procedure was unsuccessful with the trialkylsilyloxides
1a, 1b, and 1c, affording instead 2b in good yield. This
species was identified by mass spectrometry and a crystal
structure determination (Figure 3). In these reactions, sulfi-
dation occurs but with apparent protonation of the bound
silyloxide group and its departure as the silanol, followed
by the coordination of Ph3SiS-, nucleophilic attack of an
oxo ligand at silicon, and Si-S bond breaking to generate
the product. Such a sequence is avoided in the formation of
2c because the capacious Ph2ButSiO group hinders the
encroachment of also bulky Ph3SiSH; additionally, the
silyloxo group contains only one electron-releasing alkyl
substituent. This situation can be avoided by the use of a
less acidic silylthiol and/or the same silyl substituents, as in
reaction 4b, which gives yellow-orange 2a (90%). The
structure of 2b resembles that of 1d, but with a ModS
distance of 2.144(3) Å and a Mo-O-Si angle of 160.4(5)°.
(Danvers, MA) Platform II quadrupole mass spectrometer. Elemen-
tal analyses were performed by H. Kolbe (Mu¨lheim, Germany).
Results and Discussion
Reactions 3-8 leading to oxo/sulfido/silyloxo molybdates-
(VI) and tungstates(VI) are summarized by the scheme in
Figure 2. All of the compounds were isolated as Et4N+ salts.
Structures of representative complexes are presented in
Figures 3 and 4 together with selected metric data. In the
sections that follow, complexes are numerically designated,
according to Chart 1. Complexes 1-4 constitute the series
[MoO3 - nSn(OSiR2R′)]1- (n ) 0-3).
Oxosilyloxomolybdates. The scheme is initiated by the
direct silylation reaction 3 of Ag2MoO4 in dichloromethane,
affording colorless complexes [MoO3(OSiR2R′)]1- as 1a-
1d in yields of 49-67%. 1e was prepared recently by this
method.12 The first examples of this type were obtained by
the silylation of [Mo2O7]2- with R3SiOH.18 Subsequently, it
was shown that excess Ph3SiCl with Ag2MoO4 yielded the
doubly silylated product [MoO2(OSiPh3)2].19 The method also
[MoO3(OSiR2R′)]1- + Ph3SiSH f [MoO2S(OSiR2R′)]1-
Ph3SiOH (4a)
+
[MoO3(OSiPri3)]1- + Pri3SiSH f [MoO2S(OSiPri3)]1-
+
Pri3SiOH (4b)
(18) Klemperer, W. G.; Mainz, V. V.; Wang, R.-C.; Shum, W. Inorg. Chem.
1985, 24, 1970-1971.
(19) Huang, M.; DeKock, C. W. Inorg. Chem. 1993, 32, 2287-2291.
(20) Nugent, W. A. Inorg. Chem. 2007, 22, 965-969.
(21) Schmidt, M.; Schmidbaur, H. Inorg. Synth. 1967, 9, 149-151.
Inorganic Chemistry, Vol. 46, No. 26, 2007 11161

Wang and Holm
average ModS distances of 1.880(4) and 2.13 Å, respec-
tively, and a Mo-O-Si angle of 159.1(4)°.
[MoO3(OSiR2R′)]1- + 2Ph3SiSH f [MoOS2(OSiR2R′)]1-
+ 2Ph3SiOH (6)
Trisulfido complexes are readily accessible by the silyla-
tion of the anions [MOS3]2- (M ) Mo, W) in reaction 8.
Molybdenum complexes 4a-4e were isolated as red crystals
(49-70%) and tungsten complexes 5a-5d as yellow crystals
(75-89%). 4a, 4b, and 4c were also prepared in high purity
and yield by the reaction of the corresponding trioxo
complexes with g3 equiv of (Me3Si)2S, Pri3SiSH, and Ph3-
SiSH, respectively, in acetonitrile. The first of these reactions
is precedented by the reaction of [Mo2O7]2- with excess
(Me3Si)2S to afford 4a.16 The MS3OSi fragments of 4e and
5c are isostructural and nearly isometric (Figure 4). Param-
eters of 4e include a mean ModS bond length of 2.150(1)
Å and a Mo-O-Si angle of 171.4(1)°. For 5c, the mean
WdS bond distance is 2.155(1) Å and the W-O-Si angle
is 155.2(3)° because of the smaller steric bulk of the
silyloxide substituents.
[MOS3]2- + R2R′SiCl f [MS3(OSiR2R′)]1- + Cl- (8)
Oxosilyloxobenzenedithiolate Complexes. Monoben-
zenedithiolate complexes were obtained by two related
methods (Figure 2). In reaction 9, bdt is introduced with the
elimination of an oxo ligand as water, to yield molybdenum
complexes 8a-8d as orange solids (72-83%). This reaction
is similar to the preparation of [MoO(bdt)(µ2-S)2CuL]2- from
[MoO2(µ2-S)2CuL]2- and the dithiol.22 Alternatively, trioxo
complexes 6 and 7 are silylated to form 8a-8d (47-62%)
and tungsten complexes 9a-9d (greeen-brown or light-
yellow, 42-68%), respectively, in reaction 10.
Figure 5. Structures of [MoO2(OSiPh2But)(bdt)]1- (upper): Mo-O1
1.700(2), Mo-O2 1.723(2), Mo-O3 1.911(2), Mo-S1 2.447(1), Mo-S2
2.472(1), S1-Mo-S2 79.47(2), θ ) 132.1, δ ) 0.56. [WO2(OSiPri3)(bdt)]1-
(lower): W-O1 1.724(4), W-O2 1.731(4), W-O3 1.886(4), W-S1 2.434-
(2), W-S2 2.476(1), S1-W-S2 80.07(5), θ ) 131.0, δ ) 0.57.
[MoO3(OSiR2R′)]1- +H2(bdt)f[MoO2(OSiR2R′)(bdt)]1- + H2O (9)
[MO3(bdt)]2- + R2R′SiCl f [MO2(OSiR2R′)(bdt)]1- + Cl- (10)
The structures of 8d and 9b are set out in Figure 5 with
selected dimensions. These complexes present isostructural
MO3(bdt) fragments with distorted square-pyramidal coor-
dination indicated by two basal angles S1-M-O3 and S2-
M-O2 in the range of 138-152°, dihedral angles θ between
MS1S2 and MO2O3 coordination planes, and displacements
δ of the metal atom toward the apical oxo ligand O1. Values
of the latter two parameters for 8d/9b are θ ) 132.1°/131.0°
and δ ) 0.56 Å/0.57 Å. Other bond distances and angles
are unexceptional. When trioxo complex 6 was treated with
2 equiv of Me3SiCl in THF, the only isolable product was
the MoV µ2-oxo dimer 10. The reaction proceeds with the
initial formation of 8a. The second equiv of the silyl chloride
apparently removes the silyloxide as the siloxane with
Figure 6. Structure of centrosymmetric [Mo2O3Cl2(bdt)2]2-
: Mo-O1
1.689(3), Mo-O2 1.877(1), Mo-Cl 2.395(1), Mo-S1 2.385(1), Mo-S2
2.393(1), S1-Mo-S2 83.14(4), θ ) 130.7, δ ) 0.68.
Attempts to prepare pure monosulfido 2 by the silylation
of [MoO3S]2- were not productive. In one case, reaction 5
with Me2ButSiCl (Figure 2) afforded the disulfido 3c (43%).
The course of this reaction is unclear. Subsequently, disulfido
3a, 3b, and 3d were obtained by double-sulfidation reaction
6 as orange solids in 82-88% yield. The obvious intermedi-
ate is a monosulfido complex, as demonstrated by the clean
conversions 2b f 3b and 2c f 3d with 1.0 equiv of Ph3-
SiSH in reaction 7 (Figure 2). The structure of 3a (Figure
3) closely resembles others in the series, with ModO and
(22) Takuma, M.; Ohki, Y.; Tatsumi, K. Inorg. Chem. 2005, 44, 6034-
6043.
11162 Inorganic Chemistry, Vol. 46, No. 26, 2007

Oxo- and Oxosulfidomolybdates(VI) and -Tungstates(VI)
Figure 7. UV-vis absorption spectra of 1.0 mM [MoVIO3 - nSn(OSiPri3)]1- (n ) 3, red solid line; n ) 2, blue solid line; n ) 1, green broken line; n )
0, brown broken line) in acetonitrile solutions.
coordination of chloride. The likely reductant is bdt. As seen
in Figure 6, the complex is centrosymmetric and contains
the ubiquitous OdMoV-O-MoVdO fragment. Coordination
at the molybdenum sites is approximately square pyramidal;
other metric features are normal.
Summary. The principal results of this work are sum-
marized in terms of two main classes of compounds. Multiple
examples within each class are provided to support the
generality of the synthetic procedures and the scope of the
stable compounds.
and [(But3tach)WOS2].25 Pyramidal MS3 units are more
common, having been found in [(But3tach)MoS3],25 [(Tp)-
WS3]1-,26 [Cp*MS3]1-,27,28 and [WS3(SR)]1-.29-32
•[MO2(OSiR2R′)(bdt)]1-. The complexes 8 are accessible
from 1 by the reaction with H2(bdt); silylation of trioxo
complexes 6 and 7 affords 8 and 9, respectively. They are
square pyramidal with an oxo ligand in the apical position.
As such, they are structural analogues of the inactive
protonated sites [MoO2(OH)(S2pd)] of the XO family. By
sulfidation with Ph3SiSH, they are immediate precursors to
square-pyramidal [WOS(OSiR2R′)(bdt)]1- with apical oxo
and basal sulfido ligation and are structural analogues of the
active protonated sites [MoOS(OH)(S2pd)].11,33 Further, 8 and
9 react with thiols to give [MO2(SR)(bdt)]1-,33 which like
the molybdenum complex with R ) C6H2-2,4,6-Pri3,17 are
analogues of the oxidized active site of sulfite oxidase.
The sulfidation reactions reported here call attention to
the utility of silylthiols, here Ph3SiSH and Pri3SiSH, com-
mercial compounds of moderate cost, as reagents for oxo-
for-sulfido conversions. In the exhaustive compilation of such
•[MO3 - nSn(OSiR2R′)]1-. Examples of all of the members
of the tetrahedral [MoO3 - nSn(OSiR2R′)]1- series (n ) 0-3)
have now been isolated and structurally characterized. Colors
range from nearly colorless (n ) 0) to bright red (n ) 3), as
seen by the progressive low-energy shifts of the LMCT bands
in Figure 7 as the sulfur content increases. The n ) 0
complexes 1 are obtained by silylation of Ag2MoO4. These
complexes undergo monosulfidation to give the n ) 1
complexes 2. These can be converted by further sulfidation
to the n ) 2 species 3, one of which can be obtained by the
silylation of [MoO3S]2-. Complexes 4 and 5 with n ) 3 are
accessible by the silylation of [MOS3]2-. The n ) 0 and 3
members are precedented by three examples (1e,12,18
[MoO3(OSiBut3)]1-,18 and 4a16), two of which were prepared
by different methods than employed here. The only previous
example of an n ) 1 complex is 2b.12 There has been no
prior report of an n ) 2 complex. Concerning the multiply
bonded pyramidal fragment MO3 - nSn (M ) Mo, W) in other
molecular types but excluding members of the set
(25) Partyka, D. V.; Staples, R. J.; Holm, R. H. Inorg. Chem. 2003, 42,
7877-7886.
(26) Seino, H.; Arai, Y.; Iwata, N.; Nagao, S.; Mizobe, Y.; Hidai, M. Inorg.
Chem. 2001, 40, 1677-1682.
(27) Rau, M. S.; Kretz, C. M.; Geoffroy, G. N. Organometallics 1993, 12,
3447-3460.
(28) Kawaguchi, H.; Yamada, K.; Lang, J.-P.; Tatsumi, K. J. Am. Chem.
Soc. 1997, 119, 10346-10358.
(29) Boorman, P. M.; Wang, M.; Parvez, M. J. Chem. Soc., Chem. Commun.
1994, 999-1000.
(30) Kruhlak, N. L.; Wang, M.; Boorman, P. M.; Parvez, M.; McDonald,
R. Inorg. Chem. 2001, 40, 3141-3148.
[MO4 - nSn]2- 12,23 there are no prior structurally characterized
,
(31) Lang, J.-P.; Kawaguchi, H.; Tatsumi, K. J. Chem. Soc., Dalton Trans.
2002, 2573-2580.
examples of n ) 1 and of n ) 2 other than [Cp*WOS2]1-24
(32) We note in passing that pyramidal MS3 groups are not confined to M
) Mo, W. Complexes of the type [MS3(SR)]2- (M ) Nb, Ta) have
been prepared: Coucouvanis, D.; Chen, S.-J.; Mandimutsira, B. S.;
Kim, C. G. Inorg. Chem. 1994, 33, 4429-4430.
(33) Wang, J.-J. Ph.D. Thesis, Harvard University, 2007.
(23) Mu¨ller, A.; Diemann, E.; Jostes, R.; Bo¨gge, H. Angew. Chem., Int.
Ed. Engl. 1981, 20, 934-955.
(24) Kawaguchi, H.; Tatsumi, K. Angew. Chem., Int. Ed. 2001, 40, 1266-
1267.
Inorganic Chemistry, Vol. 46, No. 26, 2007 11163

Wang and Holm
reactions by Donahue,34 only one compound is cited for only
one reaction, Ph3SiSH in the conversion 1e f 2b. The
minimal representation of these conversions is MVIdO +
Ph3SiSH f MVIdS + Ph3SiOH. On an enthalpic basis, the
reaction is favored in part by the ca. 25-40 kcal/mol
differenceinSi-OversusSi-Sbonddissociationenergies.35-37
Experimental MdO and MdS bond energies for M ) Mo
and W at constant structure and ligation are lacking. Density
functional theory results for [MVIQCl4] (Q ) O, S) with
optimized MdQ bond lengths close to those observed in the
present compounds indicate bond energy differences for Md
O versus MdS of 47 kcal/mol for M ) Mo and 42 kcal/
mol for M ) W.38 These results would appear to suggest
that enthalpy changes for the minimal reaction based on bond
energies are unfavorable. Experimental bond energies and
reaction enthalpies would be helpful in resolving this issue.
Acknowledgment. This research was supported by NSF
Grant CHE 0547734. We appreciate expert crystallographic
assistance from Dr. Douglas M. Ho.
Supporting Information Available: X-ray crystallographic files
in CIF format for the compounds in Tables 1 and 2.This material
is available free of charge via the Internet at http://pubs.acs.org.
(34) Donahue, J. P. Chem. ReV. 2006, 106, 4747-4783.
(35) Luo, Y.-R. Handbook of Bond Dissociation Energies in Organic
Compounds; CRC Press: New York, 2003, pp 287-299.
(36) Basch, H. Inorg. Chim. Acta 1996, 252, 265-279.
(37) Leroy, G.; Temsamani, D. R.; Wilante, C. J. Mol. Struct. 1994, 306,
21-39.
IC701294Y
(38) Gonsa´lez-Blanco, O.; Branchadell, V.; Monteyne, K.; Ziegler, T. Inorg.
Chem. 1998, 37, 1744-1748.
11164 Inorganic Chemistry, Vol. 46, No. 26, 2007