Trithio-chloro molybdate [MoClS3]-: A versatile precursor for molybdenum trisulfido complexes

Article abstract of DOI:10.1021/ic702397j

The reaction of trithiomolybdate [PPh₄]₂[MoOS ₃] (1) with 2 equiv of trimethylchlorosilane generated trithio-chloro molybdate [PPh₄][MoClS₃] (2) in high yield, by way of a siloxy complex [PPh₄][Mo(OSiMe₃)S₃] (3). This intriguing reaction provided us with a convenient entry into a series of mononuclear molybdenum trisulfido complexes, [PPh₄][MoS₃X] (4, X = Cp*; 6a, X = S^tBu; 6b, X = SPh; 6c, X = SMes (Mes = mesityl); 6d, X = STip (Tip = 2,4,6-triisopropylphenyl); 6e, X = SDmp (Dmp = 2,6-dimesitylphenyl); 7, X = NPh₂; 8a, X = O^tBu; 8b, X = OPh; 8c, X = OC(CH₂)^tBu; 8d, X = OC(CH₂)Ph), which were obtained by the reactions of 2 with the corresponding potassium salts. In a similar manner, a citrate complex [PPh₄][MoS ₃(Me₃cit)] (9, Me₃cit = OC(CH ₂CO₂Me)₂(CO₂Me)) was synthesized, which may model the molybdenum site of the nitrogenase FeMo-cofactor. The molecular structures of 2, 6c, 7, 8a, 8b, 8c, and 9 were determined by X-ray crystallography.

Full text of DOI:10.1021/ic702397j

Inorg. Chem. 2008, 47, 3763-3771
Trithio-Chloro Molybdate [MoClS3]-: A Versatile Precursor for
Molybdenum Trisulfido Complexes
Jun-ichi Ito, Yasuhiro Ohki, Masatoshi Iwata, and Kazuyuki Tatsumi*
Department of Chemistry, Graduate School of Science and Research Center for Materials Science,
Nagoya UniVersity, Furo-cho, Chikusa-ku, Nagoya 464-8602, Japan
Received December 11, 2007
The reaction of trithiomolybdate [PPh4]2[MoOS3] (1) with 2 equiv of trimethylchlorosilane generated trithio-chloro
molybdate [PPh4][MoClS3] (2) in high yield, by way of a siloxy complex [PPh4][Mo(OSiMe3)S3] (3). This intriguing
reaction provided us with a convenient entry into a series of mononuclear molybdenum trisulfido complexes,
[PPh4][MoS3X] (4, X ) Cp*; 6a, X ) StBu; 6b, X ) SPh; 6c, X ) SMes (Mes ) mesityl); 6d, X ) STip (Tip )
2,4,6-triisopropylphenyl); 6e, X ) SDmp (Dmp ) 2,6-dimesitylphenyl); 7, X ) NPh2; 8a, X ) OtBu; 8b, X ) OPh;
8c, X ) OC(CH2)tBu; 8d, X ) OC(CH2)Ph), which were obtained by the reactions of 2 with the corresponding
potassium salts. In a similar manner, a citrate complex [PPh4][MoS3(Me3cit)] (9, Me3cit ) OC(CH2CO2Me)2(CO2Me))
was synthesized, which may model the molybdenum site of the nitrogenase FeMo-cofactor. The molecular structures
of 2, 6c, 7, 8a, 8b, 8c, and 9 were determined by X-ray crystallography.
Introduction
against Wilson’s desease.6 Although mononuclear molyb-
denum complexes carrying ModS bond(s) provide an
important basis for the development of this area of chemistry,
those with two or more terminal sulfides remain scarce. We
have reported the synthesis of the first organometallic
trisulfido complexes [Cp*MS3] (M ) Mo, W),7 and they
have been used as convenient precursors for various hetero-
metallic sulfido clusters with late transition metals.8 The other
known examples of di and trisulfido complexes include
Thio/oxo complexes of molybdenum are important con-
stituents in the active sites of molybdo-enzymes, such as the
molybdopterin cofactors of oxidoreductases1 and the FeMo-
cofactor of nitrogenase.2 Thiomolybdate and oxothiomolyb-
dates have also received recent attention as precursors of
luminescent3 and nonlinear optical materials,4 and they have
been used in organic synthesis as sulfur transfer reagents5
and in medical applications such as anticopper therapy
(6) (a) Brewer, G. J. J. Cell. Mol. Med. 2003, 7, 11–20. (b) Brewer, G. J.;
Merajver, S. D. Integr. Cancer Ther. 2002, 1, 327–337. (c) Pan, Q.;
Kleer, C. G.; van Golden, K. L.; Irani, J.; Bottema, K. M.; Bias, C.;
De Carvalho, M.; Mesri, E. A.; Robins, D. M.; Dick, R. D.; Brewer,
G. J.; Merajver, S. D. Cancer Res. 2002, 62, 4854–4859. (d) Conrads,
T.; Hemann, C.; George, G. N.; Pickering, I. J.; Prince, R. C.; Hille,
R. J. Am. Chem. Soc. 2002, 124, 11276–11277.
* To whom correspondence should be addressed. E-mail: i45100a@
nucc.cc.nagoya-u.ac.jp. Fax: +81-52-789-2943.
(1) (a) Hille, R. Chem. ReV. 1996, 96, 2757–2816. (b) Enemark, J. H.;
Cooney, J. J. A.; Wang, J.-J.; Holm, R. H. Chem. ReV. 2004, 104,
1175–2000.
(7) (a) Kawaguchi, H.; Tatsumi, K. J. Am. Chem. Soc. 1995, 117, 3885–
3886. (b) Kawaguchi, H.; Yamada, K.; Lang, J.-P.; Tatsumi, K. J. Am.
Chem. Soc. 1997, 119, 10346–10358.
(2) Einsle, O.; Tezcan, F. A.; Andrade, S. L. A.; Schmid, B.; Yoshida,
M.; Howard, J. B.; Rees, D. C. Science 2002, 297, 1696–1700.
(3) Che, C.-M.; Xia, B.-H.; Huang, J.-S.; Chan, C.-K.; Zhou, Z.-Y.;
Cheung, K.-K. Chem.sEur. J. 2001, 7, 3999–4006.
(8) (a) Lang, J.-P.; Kawaguchi, H.; Tatsumi, K. J. Organomet. Chem.
1998, 569, 109–119. (b) Lang, J.-P.; Kawaguchi, H.; Ohnishi, S.;
Tatsumi, K. Inorg. Chim. Acta 1998, 283, 136–144. (c) Lang, J.-P.;
Tatsumi, K. Inorg. Chem. 1998, 37, 160–162. (d) Lang, J.-P.; Tatsumi,
K. Inorg. Chem. 1999, 38, 1364–1367. (e) Lang, J.-P.; Tatsumi, K. J.
Organomet. Chem. 1999, 579, 332–337. (f) Ohki, Y.; Matsuura, N.;
Marumoto, T.; Kawaguchi, H.; Tatsumi, K. J. Am. Chem. Soc. 2003,
125, 7978–7988. (g) Komuro, T.; Kawaguchi, H.; Lang, J.-P.;
Nagasawa, T.; Tatsumi, K. J. Organomet. Chem. 2007, 692, 1–9.
(9) (a) Krüss, G. Justus Liebigs Ann. Chem. 1884, 225, 1–57. (b) Müller,
A.; Diemann, E.; Jostes, R.; Bögge, H. Angew. Chem., Int. Ed. Engl.
1981, 20, 934–955. (c) McDonald, J. W.; Friesen, G. D.; Rosenhein,
L. D.; Newton, W. E. Inorg. Chim. Acta 1983, 72, 205–210. (d) Laurie,
S. H. Eur. J. Inorg. Chem. 2000, 2443, 2450.
(4) (a) Shi, S.; Ji, W.; Tang, S.-H.; Lang, J.-P.; Xin, X.-Q. J. Am. Chem.
Soc. 1994, 116, 3615–3616. (b) Lang, J.-P.; Tatsumi, K.; Kawaguchi,
H.; Lu, J.-M.; Ge, P.; Ji, W.; Shi, S. Inorg. Chem. 1996, 35, 7924–
7927. (c) Hou, H.-W.; Xin, X.-Q.; Shi, S. Coord. Chem. ReV. 1996,
153, 25–56. (d) Zhang, C.; Song, Y.; Jin, G.; Fang, G.; Wang, Y.;
Raj, S. S. S.; Fun, H.-K.; Xin, X. J. Chem. Soc., Dalton Trans. 2000,
1317, 1323. (e) Zhang, C.; Song, Y.; Fung, B. M.; Xue, Z.; Xin, X.
Chem. Commun. 2001, 843, 844. (f) Zhang, Q.-F.; Niu, Y.; Leung,
W. -H.; Song, Y.; Williams, I. D.; Xin, X. Chem. Commun. 2001,
1126, 1127.
(5) Sureshkumar, D.; Koutha, S. M.; Chandrasekaran, S. J. Am. Chem.
Soc. 2005, 127, 12760–12761.
10.1021/ic702397j CCC: $40.75  2008 American Chemical Society
Inorganic Chemistry, Vol. 47, No. 9, 2008 3763
Published on Web 03/18/2008

Ito et al.
[MoSnO4-n]
2- (n ) 1–4),9 [MoS3(OSiMe3)]-,10 cis-Mo(S)2(η2-
Scheme 1
C5H10NO)2,11 cis-Mo(S)2(η2-Et2NO)2,12 trans-Mo(PMe3)4-
(S)2,13 trans-Mo(diphosphine)2(S)2,14 trans-{Me8[16]aneS4}-
Mo(S)2,15 and (tBu3tacn)Mo(S)3.16 We and Boorman et al.
have independently demonstrated that alkylation reactions
of tetrathiomolybdate and tetrathiotungstate, [MS4]2- (M )
Mo, W), by alkylhalides give rise to trithio-thiolato com-
plexes [MS3(SR)]-.17 The related reaction of molybdate
[MoO4]2- with trialkylchlorosilane was reported to give
[MoO3(OSiR3)]- and [MoO2(OSiR3)2].18
teristic ModS stretching bands at νModS ) 517, 496 cm-1.
These frequencies are comparable to those of [MoS3-
(OSiMe3)]- (νModS ) 512, 503 cm-1).10 Whereas complex
2 is isolable in pure form from a tetrahydrofuran (THF)
solution at room temperature, the complex is not thermally
stable in THF, CH3CN, or dimethylformamide (DMF). For
instance, gentle heating of a THF solution of 2 to 40–50 °C
resulted in a gradual color change to dark brown, and
insoluble materials precipitated.
In this paper, we describe the facile synthesis and reactions
of trithio-chloro molybdate [MoClS3]- (2) from trithiomo-
lybdate [MoOS3]2- and trimethylchlorosilane. The unique
mononuclear molybdenum complex carrying only sulfide and
chloride was readily generated from trithiomolybdate
[MoOS3]2- and 2 equiv of trimethylchlorosilane, and com-
plex 2 was found to provide versatile synthetic routes to a
series of mononuclear trisulfido complexes of molybdenum.
For instance, the reaction of 2 with a citric acid ester
produced [MoS3{OCCH2CO2Me}2(CO2Me)]] (9), which is
relevant to the molybdenum site of the FeMo-cofactor of
nitrogenase.
The molecular structure of 2 was determined by X-ray
diffraction analysis. The crystals of 2 possess crystallographic
+
Td symmetry, where both phosphorus of PPh4 and molyb-
-
j
denum of MoClS3 sit at site of 4 (S4 point group) of
-
symmetry. Thus, three sulfides and one chloride of MoClS3
Results and Discussion
are fully disordered over four positions, as indicated in Figure
1. The ModS distances of the related trisulfido complexes
[MoS3X]- are 2.148(2) Å for X ) StBu17a and 2.154(6) Å
for X ) OSiMe3,10 while the Mo-Cl distances in the four-
coordinate (2,6-iPr2C6H3N)2Mo{Si(SiMe3)3}Cl and (2,6-
iPr2C6H3N)2Mo{N(SiMe3)2}Cl are in the range of 2.3093(14)–
2.3353(11) Å.19 The observed Mo-S/Cl distance of 2
(2.1727(1) Å) is close to a weighted average of the ModS
and Mo-Cl bond lengths.
Preparation and Characterization of [PPh4][MoClS3].
Treatment of trithiomolybdate [PPh4]2[MoOS3] with 2 equiv
of Me3SiCl in THF at -80 °C gave first a dark red solution
with precipitation of PPh4Cl. The color of the solution
gradually turned to dark green upon warming to room
temperature, and the trithio-chloro molybdate [PPh4]-
[MoClS3] (2) was isolated in 81% yield as green crystals
after a standard workup (Scheme 1). The complex anion of
2 was detected in the electrospray ionization (ESI)-mass
spectrum of the dark green reaction solution, where the
observed isotope pattern was consistent with calculations.
The IR spectrum of 2 isolated as crystals exhibits charac-
It is likely that the reaction of [MoOS3]2- with 2 equiv of
Me3SiCl was initiated by a nucleophilic attack of the terminal
oxo ligand at the silicon atom of Me3SiCl. A possible
intermediate of the formation of 2 would be the siloxy
compound [MoS3(OSiMe3)]- (3).10,18 To explore this pos-
sibility, complex 1 was treated with 1 equiv of Me3SiCl in
THF at -50 °C. The ESI-mass spectrum of the resultant
red solution showed an intense band of isotopic clusters
centered at m/z ) 282.7, in addition to the signals associated
with 2 (m/z ) 228.7), which fits the theoretical mass pattern
(10) Do, Y.; Simhon, E. D.; Holm, R. H. Inorg. Chem. 1985, 24, 1831–
1838.
(11) Wieghardt, K.; Hahn, M.; Weiss, J.; Swiridoff, W. Z. Anorg. Allg.
Chem. 1982, 492, 164–174.
(12) Gheller, S. F.; Hambley, T. W.; Traill, P. R.; Brownlee, R. T. C.;
O’Conner, M. J.; Snow, M. R.; Wedd, A. G. Aust. J. Chem. 1982, 35,
2183–2191.
(13) (a) Murphy, V. J.; Parkin, G. J. Am. Chem. Soc. 1995, 117, 3522–
3528. (b) Schwarz, D. E.; Rauchfuss, T. B.; Wilson, S. R. Inorg. Chem.
2003, 42, 2410–2417.
(14) (a) Cotton, F. A.; Schmid, G. Inorg. Chem. 1997, 36, 2267–2278. (b)
Smith, S. J.; Whaley, C. M.; Rauchfuss, T. B.; Wilson, S. R. Inorg.
Chem. 2006, 45, 679–687.
(15) Yoshida, T.; Adachi, T.; Matsumura, K.; Kawazu, K.; Baba, K. Chem.
Lett. 1991, 1067, 1070.
(16) Partyka, D. V.; Staples, R. J.; Holm, R. H. Inorg. Chem. 2003, 42,
7877–7886.
(17) (a) Kruhlak, N. L.; Wang, M.; Boorman, P. M.; Parvez, M.; McDonald,
R. Inorg. Chem. 2001, 40, 3141–3148. (b) Lang, J.-P.; Kawaguchi,
H.; Tatsumi, K. J. Chem. Soc., Dalton Trans. 2002, 2573, 2580.
(18) (a) Huang, M.; DeKock, C. W. Inorg. Chem. 1993, 32, 2287–2291.
(b) Partyka, D. V.; Holm, R. H. Inorg. Chem. 2004, 43, 8609–8616.
(c) Thapper, A.; Donahue, J. P.; Musgrave, K. B.; Willer, M. W.;
Nordlander, E.; Hedman, B.; Hodgson, K. O.; Holm, R. H. Inorg.
Chem. 1999, 38, 4104–4114.
(19) (a) Casty, G. L.; Tilley, T. D.; Yap, G. P. A.; Rheingold, A. L.
Organometallics 1997, 16, 4746–4754. (b) Chen, T.; Sorasaenee, K. R.;
Wu, Z.; Diminnie, J. B.; Xue, Z. Inorg. Chim. Acta 2003, 345, 113–
120.
Figure 1. Structure of the complex anion of [PPh4][MoClS3] (2) with
thermal ellipsoids at 50% probability level. Mo-S(Cl) 2.1727(1) Å.
3764 Inorganic Chemistry, Vol. 47, No. 9, 2008

Versatile Precursor for Molybdenum Trisulfido Complexes
Scheme 2
Scheme 3
of 3. Analytically pure 3 was isolated successfully in 47%
yield from the reaction mixture, after stirring the red solution
at -50 °C for 36 h. As expected, the reaction of 3 with 1
equiv of Me3SiCl in THF at room temperature immediately
afforded a green suspension, from which 2 was isolated in
73% yield. Thus, Me3SiCl attacked the siloxy group of 3,
presumably liberating Me3SiOSiMe3. In this regard, it is
interesting to note that the reaction of [MoO4]2- with 2 equiv
of triphenylchlorosilane was reported to give the doubly
silylated product MoO2(OSiPh3)2.18a An analogous reaction
of tetrathiomolybdate [PPh4]2[MoS4] with 2 equiv of Me3SiCl
resulted in an unidentifiable complex mixture and did not
show any sign of the formation of 2.
Table 1. Selected Bond Distances (Å) and Angles (°) for 5
Mo(1)-Mo(2)
Mo(1)-S(1)
Mo(1)-S(2)
Mo(1)-S(3)
Mo(2)-S(2)
Mo(2)-S(3)
Mo(2)-S(4)
Mo(2)-S(5)
Mo(2)-S(6)
S(5)-S(6)
2.8731(4)
2.148(1)
2.3158(9)
2.3231(9)
2.3121(9)
2.3028(9)
2.122(1)
2.382(1)
2.356(1)
2.068(2)
S(1)-Mo(1)-S(2)
S(1)-Mo(1)-S(3)
S(2)-Mo(1)-S(3)
Mo(1)-S(2)-Mo(2)
Mo(1)-S(3)-Mo(2)
S(2)-Mo(2)-S(3)
S(2)-Mo(2)-S(4)
S(2)-Mo(2)-S(5)
S(2)-Mo(2)-S(6)
S(3)-Mo(2)-S(4)
S(3)-Mo(2)-S(5)
S(3)-Mo(2)-S(6)
S(4)-Mo(2)-S(5)
S(4)-Mo(2)-S(6)
S(5)-Mo(2)-S(6)
104.27(4)
104.48(4)
102.51(3)
76.75(3)
76.79(3)
103.26(3)
105.81(4)
136.33(4)
90.88(4)
107.97(4)
91.62(4)
133.23(4)
108.11(4)
110.52(4)
51.73(4)
Synthesis and Characterization of A Series of Molyb-
denum Trisulfido Complexes. Using the trithio-chloro
molybdate 2, we examined the reactions leading to various
mononuclear trisulfido complexes of molybdenum.
4 with [MoClS3]- (2) and the reduction of the two Mo centers
accompanied by oxidative coupling of two thio ligands to
give S22-. It is known that dinuclear Mo(V) complexes are
occasionally generated in the reactions of [MoS4]2-, with
concomitant S-S bond formation.20 Complex 5 was selec-
tively generated in CH3CN, probably because KCp* is hardly
soluble in CH3CN while both 2 and 4 dissolve readily,
making the reaction between 2 and 4 feasible. On the other
hand, DMF dissolves KCp* well, leading to a high concen-
tration of KCp* which consumes all of 2 before it can react
with 4, so that DMF turned out to be the best solvent for the
synthesis of 4.
(1) Reaction of 2 with KCp*. The reaction of 2 with
KCp* in DMF at room temperature and subsequent crystal-
lization from DMF/ether produced [PPh4][Cp*MoS3]7b (4)
in 52% yield as reddish brown crystals (Scheme 2). We have
previously reported the synthesis of 4 in 51% yield, via C-S
bond cleavage of Cp*Mo(StBu)3,7b which itself requires five
steps starting from commercially available Mo(CO)6. The
use of 2 has advantages for the synthesis of 4 over the above
procedure, because the precursor 2 can be prepared in two
steps from inexpensive [MoO4]2-.
It was found, however, that the choice of solvent was
important for the successful isolation of 4. When the reaction
was carried out in CH3CN, the ESI-mass spectrum of the
reaction mixture indicated formation of the dinuclear com-
plex anion [Cp*Mo2S6]-. Interestingly, only a small signal
of [Cp*MoS3]- was seen in the spectrum. X-ray structure
analysis revealed that the product was [PPh4][Cp*Mo(S)(µ-
S)2Mo(S)(S2)] (5). As shown in Figure 2, complex 5 contains
a Cp*MoS3 fragment, to which MoS(S2) is connected via
two µ-S bridges and a Mo(V)-Mo(V) bond. The dinuclear
structure was perhaps produced by the reaction of preformed
(2) Reactions of 2 with Various Thiolates. Mononuclear
thiolate/sulfide complexes of Mo(VI) remain scarce. Thus,
we have investigated the synthesis of a series of thiolate
derivatives [MoS3(SR)]- from 2, taking an advantage of the
successful isolation of 2 (Scheme 3). Complex 2 was treated
with KStBu in THF at 0 °C, and [PPh4][MoS3(StBu)] (6a)
was isolated in 50% yield as dark brown crystals after
recrystallizaion of the crude product from ether/THF. This
complex was previously synthesized by the reaction between
17a
t
[PPh4]2[MoS4] and BuBr,
where the yield was lower
(20%) because of the tendency of [MoS3(StBu)]- to react
further with tBuBr leading to insoluble materials. Likewise,
various arylthiolato complexes [PPh4][MoS3(SAr)] {6b, Ar
) Ph; 6c, Ar ) Mes (Mes ) mesityl); 6d, Ar ) Tip (Tip )
2,4,6-triisopropylphenyl); 6e, Ar ) Dmp (Dmp ) 2,6-
dimesitylphenyl)} were synthesized readily by the reactions
of 2 with the corresponding potassium salts of these
arylthiolates. In all the reactions, the products were obtained
as dark brown crystals in moderate yields ranging from 57%
(20) (a) Müller, A.; Nole, W.-O.; Krebs, B, Angew. Chem., Int. Ed. Engl.
1978, 17, 279–279. (b) Draganjac, M.; Simhon, E.; Chan, L. T.;
Kanatzidis, M.; Baenziger, N. C.; Coucouvanis, D. Inorg. Chem. 1982,
21, 3321–3332. (c) Cohen, S. A.; Stiefel, E. I. Inorg. Chem. 1985,
24, 4657–46662. (d) Coyle, C. L.; Harmer, M. A.; George, G. N.;
Daage, M.; Stiefel, E. I. Inorg. Chem. 1990, 29, 14–19.
Figure 2. Structure of the complex anion of [PPh4][Cp*Mo(S)(µ-
S)2Mo(S)(S2)] (5) with thermal ellipsoids at 50% probability level.
Inorganic Chemistry, Vol. 47, No. 9, 2008 3765

Ito et al.
Scheme 4
(NPh2)2 by the substitution reaction of amides with a chiral
R-BINOL derivative to give Mo(NAr)(CHCMe2Ph)(Biphen)
(Biphen ) 3,3′-tBu2-5,5′,6,6′-Me4-1,1′-biphenyl-2,2′-di-
olate).23 We were thus interested in introducing amides into
the trisulfido molybdenum moiety, anticipating that the
resulting amide complexes may also serve as convenient
precursors, being alternatives to 2, for the synthesis of
trisulfido molybdenum complexes.
Figure 3. Structure of the complex anion of [PPh4][MoS3(SMes)] (6c) with
thermal ellipsoids at 50% probability level.
The reaction of 2 with KNPh2 was carried out at room
temperature in THF, and the subsequent workup and recrys-
tallization from THF/ether gave [PPh4][MoS3(NPh2)] (7) as
black crystals in 59% yield (Scheme 4). The ESI-mass
spectrum features the signal of the [MoS3(NPh2)]- anion at
m/z ) 361.7. Complex 7 is highly moisture sensitive, but
thermally stable at room temperature. Interestingly, a similar
reaction with KNEt2 resulted in a complex mixture of
products, and the desired diethylamide complex could not
be isolated. In the case of the reaction between 2 and
KN(SiMe3)2, the ESI-mass spectrum indicated that
[MoS3{N(SiMe3)2}]- was the major product. However,
isolation of the bis(trimethylsilyl)amide complex has not been
successful.
The molecular structure of 7 as determined by X-ray
diffraction is shown in Figure 4, and the selected bond
distances and angles are summarized in Table 2. In the
tetrahedral coordination geometry at molybdenum, the aver-
age S-Mo-S angle (108.72(4)°) is slightly smaller than the
average S-Mo-N angle (110.22(7)°), while the ModS
distances are normal. The sum of the bond angles at the
amide nitrogen is 359.8°, pointing to a planar geometry. The
maximum deviation from the planarity occurs at C(7)
(0.13(1) Å). The effective N pπ-Mo dπ interaction is also
incarnated in the short Mo-N distance of 2.004(2) Å,
although it is somewhat longer than those of the dimethyl-
amido molybdenum complexes, Mo(NMe2)4 (Mo-N (av) )
to 68%. Complexes 6b-e were characterized by NMR, IR,
and ESI-mass spectra, and the elemental analyses were
satisfactory. The ESI-mass spectra of 6b-e show isotope
patterns in accordance with those calculated for [MoS3-
(SAr)]- (Ar ) Ph, Mes, Tip, Dmp), respectively. The IR
spectra feature characteristic ModS stretching bands ap-
pearing at 507-514 cm-1 and at 482-486 cm-1, the
frequencies of which are somewhat lower than those of 2.
The crystal structure of 6c was determined, and the ORTEP
(Oak Ridge thermal ellipsoid plot) drawing and selected
metric parameters are given in Figure 3 and Table 2,
respectively. The ModS distances (2.1406(5)–2.1603(8) Å)
and the Mo-Sthiolate distance (2.3519(7) Å) are similar to
those of 6a,17a while the Mo(1)-S(4)-C(1) angle (108.54(8)°)
is slightly smaller than 6a (111.8(2)°).
This synthetic route to [MoS3(SR)]- starting from
[MoClS3] (2) is obviously advantageous over the alkylation
of [MoS4]2-. Complex 2 reacts with KSR cleanly, and
according to the ESI mass measurement of each reaction
solution, the only detectable product was the expected tris-
sulfido/thiolato complex. Furthermore, various potassium
salts of arylthiolates readily react with 2 to give [MoS3-
(SAr)]-, while [MoS4]2- does not react with arylhalides.
(3) Synthesis of [PPh4][MoS3(NPh2)]. Transition metal
amido complexes have been used as precursors for the
synthesis of a wide range of organometallic complexes under
mild conditions,21 and a series of intriguing 4-coordinate
molybenum complexes have also been synthesized from the
reactions of amide ligands. For instance, Cummins et al. have
prepared tris-alkoxide complexes Mo(X)(OAd)3 (X )
C{CH2(SiMe3)}, N, P; Ad ) adamantylidene) via protonation
of the amides in Mo(X)[N(iPr)(3,5-C6H3Me2)]3 by adaman-
tanol.22 Schrock et al. expanded the scope of their ring-
closing metathesis catalyst Mo{N(2,6-iPr2C6H3)}(CHCMe2Ph)-
(21) Gade, L. H.; Mountford, P. Coord. Chem. ReV. 2001, 216–217, 65–
97.
(22) (a) Tsai, Y.-C.; Diaconescu, P. L.; Cummins, C. C. Organometallics
2000, 19, 5260–5262. (b) Cherry, J.-P. F.; Stephens, F. H.; Johnson,
M. J. A.; Diaconescu, P. L.; Cummins, C. C. Inorg. Chem. 2001, 40,
6860–6862. (c) Stephens, F. H.; Figueroa, J. S.; Diaconescu, P. L.;
Cummins, C. C. J. Am. Chem. Soc. 2003, 125, 9264–9265.
(23) Sinha, A.; Schrock, R. R.; Müller, P.; Hoveyda, A. H. Organometallics
2006, 25, 4621–4626.
Figure 4. Structure of the complex anion of [PPh4][MoS3(NPh2)] (7) with
thermal ellipsoids at 50% probability level.
3766 Inorganic Chemistry, Vol. 47, No. 9, 2008

Versatile Precursor for Molybdenum Trisulfido Complexes
Table 2. Selected Bond Distances (Å) and Angles (°) for 6c and 7
or oxo-chlorido complexes of molybdenum, MoCl4(THF)2,
MoCl2O2, MoCl2O2(MeCN)2, and Tp*MoOCl2 with alkaline
metal salts of alkoxides have been reported to give corre-
sponding alkoxo complexes.25 The ESI-mass spectra of 8a
and 8b exhibited signals for anions centered at m/z ) 266.7
and 286.7, respectively; their isotope patterns fit well with
those of [MoS3(OR)]- (R ) tBu, Ph). The 1H NMR spectra
of 8a and 8b exhibited a singlet for the tBu group at δ 1.30
and the signals for the phenoxide group at δ 7.05 (2H), 6.98
(2H) and 6.79 (1H), respectively.
6c
7
Mo(1)-S(1)
Mo(1)-S(2)
Mo(1)-S(3)
Mo(1)-S(4)
S(4)-C(1)
S(1)-Mo(1)-S(2)
S(1)-Mo(1)-S(3)
S(2)-Mo(1)-S(3)
S(1)-Mo(1)-S(4)
S(2)-Mo(1)-S(4)
S(3)-Mo(1)-S(4)
Mo(1)-S(4)-C(1)
2.1422(8)
2.1603(8)
2.1406(5)
2.3519(7)
1.790(2)
Mo-S(1)
Mo-S(2)
Mo-S(3)
Mo-N
N-C(1)
N-C(7)
S(1)-Mo-S(2)
S(1)-Mo-S(3)
S(2)-Mo-S(3)
S(1)-Mo-N
S(2)-Mo-N
S(3)-Mo-N
Mo-N-C(7)
Mo-N-C(1)
C(1)-N-C(7)
2.1518(7)
2.1614(8)
2.1433(8)
2.004(2)
1.450(4)
1.423(3)
111.74(3)
111.17(2)
110.57(3)
100.50(3)
112.11(2)
110.40(2)
108.54(8)
110.46(3)
107.13(4)
108.57(4)
108.73(7)
109.50(7)
112.43(7)
133.1(2)
112.4(2)
114.4(2)
Transition metal enolate complexes have been postulated
as intermediates in metal-mediated catalytic C-C bond
formation.26 Enolate ligands feature diverse coordinaton
modes ranging from η1(O)-enolate, to η1(C)-2-oxoalkyl, and
to η3(O,C,C)-oxaallyl.27 The reaction between 2 and potas-
sium enolates resulted in the formation of the η1(O)-enolate
Scheme 5
t
complexes [PPh4][MoS3{OC(CH2)R}] (R ) Bu (8c), Ph
(8d)) in 51 and 29%. Consistent with the η1(O)-enolate
coordination, the signals for the terminal )CH2 group of 8c
and 8d were observed in the 1H NMR at δ 4.31, 3.94 and δ
4.74, 4.73, respectively, and no intense C)O stretching band
was found in the IR spectrum. The characteristic νModS bands
of 8a-d appeared at 503–515, 484–490 cm-1, which are
close to those for the relevant trisulfido complexes
[MoS3(StBu)]- and [MoS3(SC5H10O)]- (508–511, 482
cm-1)17 and [MoS3(OSiMe3)]- (512, 503 cm-1),10 and are
at higher frequencies than those for [Cp*MoS3]- (455, 445
cm-1),7 (tBu3tacn)Mo(S)3 (483,473cm-1),16 and[MoO4-nSn]2-
(460–470 cm-1).9
1.926(6) Å) and Mo2(NMe2)6 (Mo-N (av) ) 1.98 Å).24 The
slight elongation of the Mo-N bond in 7, relative to those
of Mo(NMe2)4 and Mo2(NMe2)6, is likely due to π-conjuga-
tion between a phenyl substituent and the amido nitrogen
leading to weaker π-donation interaction with Mo. In fact,
one phenyl ring orients in such a way that it sits coplanarly
with the molybdenum and nitrogen atoms (interplane angle
) 1.7(2)°), while the other phenyl ring is approximately
perpendicular to it (interplane angle ) 83.8(2)°). The
different orientation of the phenyl rings also makes the two
Mo-N-C angles distinct, Mo-N-C(1) ) 112.4(2)° versus
Mo-N-C(7) ) 133.1(2)°, and the shorter N-C(7) bond
(1.423(3) Å) relative to N-C(1) (1.450(4) Å) indicates the
presence of N-C(7) π bonding.
The molecular structures of 8a-8c were determined by
X-ray crystallography, and the perspective view of 8c is
shown in Figure 5. The selected bond lengths and angles of
8a-8c are listed in Table 3. The molybdenum centers in
the alkoxo complexes 8a and 8b are also tetrahedral like
the other [MoS3X]- (X ) Cl, SR, NPh2) complexes. The
ModS distances, 2.1535(8)–2.1623(7) Å for 8a and
2.1320(6)–2.1531(6) Å for 8b, are slightly shorter than those
(4) Synthesis of Alkoxide and Enolate Complexes.
Whereas molybdenum complexes containing both ModS and
MosOR groups are relevant to the active sites of xanthine
oxidase/dehydrogenase, aldehyde oxidoreductase,1 and ni-
trogenase,2 there have been no monomeric molybdenum
trisulfido complexes with alkoxy ligands. Thus, we inves-
tigated the substitution of the chloride in 2 with potassium
salts of t-butoxide and phenoxide, and these reactions were
found to proceed straightforwardly to give the desired
trisulfido/alkoxo complexes.
for thiomolybdates [MoOnS4-n]
2- (2.176(6)–2.2236(1) Å)28
and are comparable to those of [MoS3(OSiMe3)]- (2.154(6)
(25) (a) Soo, H. S.; Figueroa, J. S.; Cummins, C. C. J. Am. Chem. Soc.
2004, 126, 11370–11376. (b) Hanna, T. A.; Incarvito, C. D.;
Rheingold, A. L. Inorg. Chem. 2000, 39, 630–631. (c) Hanna, T. A.;
Ghosh, A. K.; Ibarra, C.; Mendez-Rojas, M. A.; Rheingold, A. L.;
Watson, W. H. Inorg. Chem. 2004, 43, 1511–1516. (d) Cleland, W. E.,
Jr.; Barnhart, K. M.; Yamanouchi, K.; Collison, D.; Mabbs, F. E.;
Ortega, R. B.; Enemark, J. H. Inorg. Chem. 1987, 26, 1017–1025.
(26) (a) Doney, J. J.; Bergmann, R. G.; Heathcock, C. H. J. Am. Chem.
Soc. 1985, 107, 3724–3726. (b) Burkhardt, E. R.; Doney, J. J.;
Bergmann, R. G.; Heathcock, C. H. J. Am. Chem. Soc. 1987, 109,
2022–2039. (c) Burkhardt, E. R.; Bergmann, R. G.; Heathcock, C. H.
Organometallics 1990, 9, 30–44. (d) Hartwig, J. F.; Bergman, R. G.;
Andersen, R. A. Organometallics 1991, 10, 3326–3344.
t
The reaction of 2 with KOR (R ) Bu, Ph) in THF
immediately proceeded at room temperature to afford
t
[PPh4][MoS3(OR)] (R ) Bu (8a), Ph (8b)), which were
isolated in 56 and 81% yields, respectively (Scheme 5). As
demonstrated in these reactions, both alkoxides and arylox-
ides are available for the replacement of the chloride in 2.
Such seemingly simple replacement of a chloride with an
alkoxide is rare. However, some related reactions of chloro
(27) (a) Slough, G. A.; Hayashi, R.; Ashbaugh, J. R.; Shamblin, S. L.;
Aukamp, A. M. Organometallics 1994, 13, 890–898. (b) Slough, G. A.;
Ashbaugh, J. R.; Zannoni, L. A. Organometallics 1994, 13, 3587–
3593. (c) Krug, C.; Hartwig, J. F. Organometallics 2004, 23, 4594–
4607.
(28) (a) For [MoO3S]2-, see ref 18b. For [MoO2S2]2-, see Kutzler, F. W.;
Scott, R. A.; Berg, J. M.; Hodgson, K. O.; Doniach, S.; Cramer, S. P.;
Chang, C. H. J. Am. Chem. Soc. 1981, 103, 6083–6088. (b) For
[MoOS3]2-, see Krebs, B.; Müller, A.; Kindler, E. Z. Naturforsch.
1970, 25B, 222. (c) For [MoS4]2-, see Lapasset, J.; Chezeau, N.;
Belounge, P. Acta Crystallogr. 1976, B32, 3087–3088. (d) Kanatzidis,
M.; Coucouvanis, D. Acta Crystallogr. 1983, C39, 835–838.
(24) (a) Chisholm, M. H.; Cotton, F. A.; Frenz, B. A.; Reichert, W. W.;
Shive, L. W.; Stults, B. R. J. Am. Chem. Soc. 1976, 98, 4469–4476.
(b) Chisholm, M. H.; Cotton, F. A.; Extine, M. W. Inorg. Chem. 1978,
17, 1329–1332.
Inorganic Chemistry, Vol. 47, No. 9, 2008 3767

Ito et al.
Figure 5. Structure of the complex anion of [PPh4][MoS3{OC(CH2)tBu}]
(8c) with thermal ellipsoids at 50% probability level.
Table 3. Selected Bond Distances (Å) and Angles (°) for 8a-c
8a
8b
8c
Figure 6. Structure of the complex anion of [PPh4][MoS3(Me3cit)] (9) with
thermal ellipsoids at 50% probability level.
Mo(1)-S(1)
Mo(1)-S(2)
Mo(1)-S(3)
Mo(1)-O(1)
O(1)-C(1)
O(1)-C(2)
C(1)-C(2)
2.1623(7)
2.1574(8)
2.1535(8)
1.870(2)
2.1471(6)
2.1531(6)
2.1320(6)
1.916(2)
1.377(3)
2.1448(7)
2.1442(7)
2.1559(5)
1.9108(18)
1.377(2)
Scheme 6
1.447(3)
1.316(4)
S(1)-Mo(1)-S(2)
S(1)-Mo(1)-S(3)
S(2)-Mo(1)-S(3)
S(1)-Mo(1)-O(1)
S(2)-Mo(1)-O(1)
S(3)-Mo(1)-O(1)
Mo(1)-O(1)-C(1)
Mo(1)-O(1)-C(2)
109.73(3)
110.57(2)
108.85(3)
108.64(3)
109.09(3)
107.94(6)
110.19(7)
111.23(7)
107.44(3)
109.39(3)
109.77(6)
108.62(5)
111.05(6)
128.7(1)
110.09(2)
110.24(2)
109.37(5)
108.03(6)
110.22(5)
129.08(16)
Table 4. Selected Bond Distances (Å) and Angles (°) for 9
Mo-S(1)
Mo-S(2)
Mo-S(3)
Mo-O(1)
O-C(3)
2.1538(7)
2.1447(6)
2.1553(7)
1.890(2)
1.408(3)
S(1)-Mo-S(2)
S(1)-Mo-S(3)
S(2)-Mo-S(3)
S(1)-Mo-O(1)
S(2)-Mo-O(1)
S(3)-Mo-O(1)
Mo-O(1)-C(3)
110.09(3)
109.31(3)
108.34(3)
107.89(5)
111.96(5)
109.22(5)
141.9(1)
139.1(2)
Å)10 and [MoS3(StBu)]- (2.148(2) Å).17a The short Mo-O
distances of 8a (1.870(2) Å) and 8b (1.916(2) Å) are
indicative of δ-donation from oxygen to molybdenum. The
Mo-O(alkoxo) distance of 8a is similar to those for
Mo2(OCH2CMe3)6 (Mo-O ) 1.88(2) Å)29 and Mo[OC-
(Ad)(Mes)]4 (Mo-O ) 1.866(3), 1.869(3) Å, Ad )
adamantylidene).25a A rather shorter Mo-O(alkoxo) bond
can be seen in Mo2(OiPr)6Br4 (Mo-O (av) ) 1.81 Å).30 As
indicated by the difference in the Mo-O distances between
8a and 8b, δ-donation from the electron rich tert-butoxide
group in 8a is more efficient than that from the phenoxide
in 8b. The weaker δ-donation in 8b possibly results from
conjugation within the -OPh ligand. In fact, the O-C(1)
distance of 8b (1.377(3) Å) is significantly shorter than the
corresponding O-C(2) bond in 8a (1.447(3) Å). Such a
structural feature is also found in the η1(O)-enolate complex
8c. As can be seen in Figure 5 and Table 3, the electronic
effect of the vinyl group on the Mo-O-C bonding array is
similar to that of a phenyl group, since the bond lengths of
Mo-O (1.9108(18) Å) and O-C(1) (1.377(2) Å) are close
to those for the phenoxide complex 8b. The Mo-O-R
angles parallel the trend of the Mo-O distances, in such a
way that the shorter Mo-O bond of 8a accompanies the
larger Mo-O-R angle.
(5) Synthesis of [PPh4][MoS3(Me3cit)] (Me3cit ) OC-
(CH2CO2Me)2(CO2Me)). The molybdenum site in the
nitrogenase FeMo-cofactor carries an R-homocitrate and a
histidine residue.2 Molybdenum trisulfide complexes with
citrate derivatives could serve as suitable building blocks
for structural models of the FeMo-cofactor and may provide
information regarding reactivity at the molybdenum site.
Thus, we have extended the reactions of 2 with alkoxides to
the introduction of a citric acid ester to the MoS3 unit.
Treatment of 2 with the potassium salt of citric acid
trimethyl ester led to the formation of a trisulfido complex
[PPh4][MoS3(Me3cit)] (9, Me3cit ) OC(CH2CO2Me)2-
1
(CO2Me)) in 73% yield as a red solid (Scheme 6). The H
NMR spectrum of 9 clearly indicated the presence of the
Me3cit moiety, showing two singlets for methyl groups at δ
3.67 and 3.49, and an AB-doublet for the methylenes at δ
3.07 and 2.99. The ESI mass spectrum confirmed the
formation of [MoS3(Me3cit)]-, showing a molecular ion peak
at m/z ) 426.7 with an appropriate isotope pattern.
The X-ray derived structure of the anion of 9 is shown in
Figure 6. The selected bond distances and angles are listed
in Table 4. The Me3cit group is bound to molybdenum at
the alkoxy-oxygen, and the ester portions do not interact with
molybdenum. As a result, complex 9 again possesses a
(29) Chisholm, M. H.; Cotton, F. A.; Murillo, C. A.; Reichert, W. W. Inorg.
Chem. 1977, 16, 1801–1808.
(30) Chisholm, M. H.; Kirkpatrick, C. C.; Huffman, J. C. Inorg. Chem.
1981, 20, 871–876.
3768 Inorganic Chemistry, Vol. 47, No. 9, 2008

Versatile Precursor for Molybdenum Trisulfido Complexes
t
t
t
(R ) Bu, Ph), KNPh2, and KOR′ (R′ ) Bu, Ph, C(CH2)2 Bu,
C(CH2)2Ph) were prepared in a similar manner from the reactions
of thiols, HNPh2, or alcohols, with KOtBu (for KStBu) or KH
(others). KSAr (Ar ) Mes, Tip, Dmp) were generated in situ and
used without purification: KSMes was generated from MesSH (300
mg, 1.97 mmol) and KH (80 mg, 2.0 mmol); KSTip was generated
from TipSH (486 mg, 2.06 mmol) and KH (83 mg, 2.1 mmol);
KSDmp was generated from DmpSH (500 mg, 1.44 mmol) with
KH (58 mg, 1.5 mmol). K(Me3cit) was prepared from citric acid
trimethyl ester (271 mg, 1.16 mmol) and a toluene solution of
KN(SiMe3)2 (0.5 M, 2.0 mL, 1.0 mmol) in THF at -80 °C, and
was purified by washing with hexane.
tetrahedral coordination geometry, and the ModS distances
are similar to those of 6c, 7, 8a, and 8b. The absence of
interactions between the ester-oxygens and molybdenum
points to coordinative saturation of 9 with three terminal
sulfides. It might be that coordination of the sulfides to iron(s)
would facilitate further coordination of one of the ester-
oxygens mimicking the geometry at the molybdenum of the
FeMo-cofactor. The Mo-O(1) bond is relatively short, that
is shorter than those for relevant citrate (cit4-) complexes
of molybdenum, [Mo(Hcit)(CO)3]3- (Mo-O ) 2.230(2) Å)31
and K4[MoO3(cit)] (Mo-O ) 2.052(2) Å).32 The Mo-O(1)
distance and the large Mo-O(1)-C(3) angle are similar to
those for 8a. Similarity between 8a and 9 can be also seen
in the IR spectrum, where the ModS bands appeared at 509,
490 cm-1 for 9 and at 503, 486 cm-1 for 8a.
Preparation of [PPh4][MoClS3] (2). Treatment of a THF
suspension of [PPh4]2[MoOS3] (555 mg, 0.626 mmol) with Me3SiCl
(185 µL, 1.46 mmol) at -80 °C gave a purple suspension. Upon
warming to room temperature, the color of the suspension gradually
turned dark green. After being centrifuged to remove insoluble
materials, the solution was evaporated to dryness. The resulting
green solid was extracted with THF (40 mL), and the extract was
centrifuged again. After concentration of the extract, ether was
layered. Slow diffusion of the layered solution led to the formation
of dark green (almost black) crystals of 2 (288 mg, 0.508 mmol,
81%). IR (KBr): 3054(w), 1585(w), 1483(m), 1437(s), 1338(w),
1311(w), 1190(w), 1169(w), 1107(s), 997(m), 923(w), 760(w),
746(m), 723(s), 687(s), 526(s), 517(s, ModS), 496(sh, ModS)
cm-1. ESI-TOF-MS (THF, rt): m/z ) 228.7. UV/vis (THF, rt): λmax
(ε) 581 (1.0 × 103), 425 (4.2 × 103), 315 nm (6.2 × 103). Elemental
analysis calcd for C24H20ClMoPS3: C 50.84, H 3.56, S 16.97; Found:
C 50.77, H 3.66, S 16.70.
Summary
The oxo ligand in [MoOS3]2- (1) was found to be
selectively replaced by chloride in the reaction with tri-
methylchlorosilane, giving rise to the molybdenum trisulfido-
chloro complex [MoClS3]- (2). This new complex was shown
to be a useful and versatile precursor for a series of monomeric
trisulfido complexes of molybdenum, and Cp*, thiolato, amido,
and alkoxo complexes were readily obtained from the substitu-
tion of the chloride with the corresponding alkaline metal
reagents. This synthetic method also allowed us to prepare a
citrate derivative of molybdenum trisulfide, which should serve
as a valuable building block for the synthesis of structural and
reaction models of the FeMo-cofactor.
Reaction of [PPh4][MoOS3] with one Equivalent of Me3SiCl.
To a THF suspension of [PPh4][MoOS3] (500 mg, 0.564 mmol)
was added Me3SiCl (75 µL, 0.60 mmol) at -80 °C. After stirring
for 36 h at -50 °C, the solvent was removed under reduced
pressure. The residue was extracted with THF (50 mL) and the
extract was centrifuged to remove insoluble materials. Concentration
of the solution followed by slow diffusion of ether gave red crystals
of [PPh4][MoS3(OSiMe3)] (3, 165 mg, 0.266 mmol, 47%). 1H NMR
(500 MHz, CDCl3, rt): δ 7.88 (m, 4H, PPh4), 7.77 (m, 8H, PPh4),
7.66 (m, 8H, PPh4), 0.14 (s, 9H, SiMe3). ESI-TOF-MS (CH3CN,
rt): 282.7. Elemental analysis calcd for C27H29MoOPS3Si: C 52.24,
H 4.71, S 15.50; Found: C 52.12, H 4.46, S 15.78.
Reaction of [PPh4][MoS3(OSiMe3)] (3) with Me3SiCl. To a
THF solution of [PPh4][MoS3(OSiMe3)] (72 mg, 0.12 mmol) was
added Me3SiCl (16 µL, 0.13 mmol) at room temperature. After
stirring for 30 min, the solution was centrifuged and evaporated to
dryness. The residue was extracted with THF, and the extract was
centrifuged again. After evaporation under reduced pressure, the green
solid was washed with ether (5 mL × 2) and dried under reduced
pressure to give [PPh4][MoClS3] (2, 48 mg, 0.084 mmol, 73%).
Preparation of [PPh4][Cp*MoS3] (4). To a DMF solution of 2
(173 mg, 0.305 mmol) was added a THF solution of KCp* (60
mg, 0.34 mmol) at room temperature. With vigorous stirring for
15 min, the reaction mixture afforded a reddish brown solution.
After addition of acetonitrile (30 mL) to precipitate KCl, the brown
suspension was centrifuged. The solution was concentrated, layered
with ether, and kept standing at -40 °C. Reddish brown crystals
of [PPh4][Cp*MoS3] (4, 106 mg, 0.159 mmol) were obtained in
52% yield. This compound gave identical spectral data with those
reported.7b
Experimental Section
General Procedures. All reactions were manipulated using
standard Schlenk and vacuum line techniques under a nitrogen
atmosphere. THF, CH3CN, ether, and hexane were purified by the
method of Grubbs, where the solvents were passed over columns
of activated alumina and a supported copper catalyst supplied by
Hansen & Co. Ltd. Degassed and distilled solvents from sodium
benzophenone ketyl (hexane, ether, toluene, THF) or from CaH2
(CH3CN) were also used. DMF was dried over Molecular Sieve
4A. CD3CN, CDCl3, CD2Cl2, tetrahydrofuran-d8, and trimethyl-
chlorosilane were dried by CaH2 and distilled prior to use. 1H NMR
spectra were recorded on a Varian INOVA-500 or a JEOL ECA600.
The signals were referenced to the residual proton peak of the
deuterated solvent. IR spectra were recorded on a JASCO FT/IR-
410. UV/vis spectra were recorded on a JASCO V560. ESI-TOF-
MS spectra were recorded on a Micromass LCT TOF-MS.
Elemental analyses were recorded on a LECO-CHNS-932 elemental
analyzer where the crystalline samples were sealed in silver capsules
under nitrogen. X-ray diffraction data were collected on a Rigaku
AFC7R, a Rigaku AFC8, or a Rigaku RA-Micro7 equipped with a
CCD area detector by using graphite-monochromated Mo KR
radiation. [PPh4]2[MoOS3] was prepared according to the literature
procedure.9b
All potassium salts of the ligands were prepared in THF. KCp*
was prepared from the reaction of C5Me5H with 1 equiv of KH.
After evaporation, KCp* was purified by washing with hexane. KSR
Reaction of 2 with KCp* in CH3CN. To an acetonitrile solution
(20 mL) of 2 (111 mg, 0.196 mmol) was added a THF (5 mL)
suspension of KCp* (38 mg, 0.218 mmol) at -20 °C. The reaction
mixture was vigorously stirred to give a dark brown suspension.
(31) Takuma, M.; Ohki, Y.; Tatsumi, K. Organometallics 2005, 24, 1344–
1347.
(32) Zhou, Z.; Wan, H.; Tsai, K. Inorg. Chem. 2000, 39, 59–64.
Inorganic Chemistry, Vol. 47, No. 9, 2008 3769

Ito et al.
After warming to room temperature, the suspension was centrifuged
to remove insoluble materials. The ESI-mass spectrum of the
J ) 6.7 Hz, 6H, CHMe2), 1.13 (d, J ) 6.9 Hz, 12H, CHMe2). IR
(KBr): 3053(w), 1585(w), 1483(m), 1460(w), 1437(s), 1360(w),
1311(w), 1186(w), 1163(w), 1107(s), 1059(w), 1028(w), 995(m),
883(w), 750(m), 723(s), 687(s), 526(s), 511(s, ModS), 484(m,
ModS) cm-1. ESI-TOF-MS (CH3CN): m/z ) 428.8. UV/vis (THF,
rt): λmax (ε) 509 (1.4 × 103), 443 (4.4 × 103), 277 nm (2.3 × 104).
Elemental analysis calcd for C39H43MoPS4: C 61.08, H 5.65, S
16.72; Found: C 61.38, H 5.56, S 16.72.
solution showed anionic signals at m/z
) 518.4 (100%,
[Cp*Mo2S6]-), 486.7 (20%, [Cp*Mo2S5]-), and 328.9 (5%,
[Cp*MoS3]-). After evaporation of the solvent, the dark brown
residue was extracted with THF (20 mL), and the extract was
centrifuged. The dark brown solution was concentrated and stored
at -20 °C to produce black crystals of [PPh4][Cp*Mo(S)(µ-
S)2Mo(S)(S2)] (5) and a dark brown powder. Single crystals of 5
for X-ray diffraction were manually separated from the precipitate.
Preparation of [PPh4][MoS3(StBu)] (6a). The following ma-
nipulations were carried out at 0 °C because of thermal instability
of the product. KStBu was prepared by the reaction of tBuSH with
KOtBu. To a THF solution of [PPh4][MoClS3] (200 mg, 0.353
mmol) was added a THF suspension of KStBu (59 mg, 0.46 mmol).
After stirring for 30 min, the suspension was centrifuged. The
resulting brown solution was diffused into ether at -40 °C to give
dark brown crystals of [PPh4][MoS3(StBu)] (6a, 112 mg, 0.177
mmol, 50%). The product gave identical spectral data with those
reported by Boorman.17a 1H NMR (500 MHz, CDCl3, rt): δ 7.87
(m, 4H, PPh4), 7.76 (m, 8H, PPh4), 7.63 (m, 8H, PPh4), 1.44 (s,
9H, tBu). ESI-TOF-MS (CH3CN): m/z ) 282.6. Elemental analysis
calcd for C28H29MoPS4: C 54.18, H 4.71, S 20.66; Found: C 53.86,
H 4.76, S 20.58.
Preparation of [PPh4][MoS3(SDmp)] (6e). The same procedure
as in the case of 6b was used. The reaction of [PPh4][MoClS3]
(800 mg, 1.41 mmol) with KSDmp (1.44 mmol) in THF at -80
°C gave a brown suspension, from which dark brown crystals of
[PPh4][MoS3(SDmp)] (6e, 777 mg, 0.886 mmol, 63%) were
1
isolated. H NMR (600 MHz, CD2Cl2, rt): δ 7.89 (m, 4H, PPh4),
7.72 (m, 8H, PPh4), 7.60 (m, 8H, PPh4), 7.22 (t, J ) 7.6 Hz, 1H,
p-C6H), 6.90 (d, J ) 7.6 Hz, 2H, m-C6H), 6.89 (s, 4H, C6H2Me3),
2.28 (s, 6H, p-C6Me), 2.10 (s, 12H, o-C6Me). IR (KBr): 3051(w),
1583(w), 1483(m), 1437(s), 1383(w), 1315(w), 1181(w), 1165(w),
1107(s), 1028(w), 995(m), 847(m), 800(m), 746(m), 723(s), 688(s),
526(s), 507(s, ModS), 484(m, ModS) cm-1. ESI-TOF-MS (THF):
m/z ) 538.7. UV/vis (THF, rt): λmax (ε) 516 (2.7 × 103), 458 (5.8
× 103), 276 nm (2.0 × 104). Elemental analysis calcd for
C48H45MoPS4: C 65.73, H 5.17, S 14.62; Found: C 65.65, H 5.27,
S 14.89.
Preparation of [PPh4][MoS3(SPh)] (6b). The reaction of
[PPh4][MoClS3] (122 mg, 0.215 mmol) with KSPh (47 mg, 0.31
mmol) in THF was initiated at -80 °C. After warming to room
temperature, the brown suspension was centrifuged, and the solution
was diffused into ether at -40 °C to give dark brown crystals of
[PPh4][MoS3(SPh)] (6b, 78 mg, 0.122 mmol, 57%). Satisfactory
1H NMR measurement was not available because of thermal
instability and low solubility in CDCl3 and CD3CN. IR (KBr):
3049(w), 1585(w), 1481(m), 1434(s), 1315(w), 1184(w), 1160(w),
1108(s), 1022(w), 997(m), 746(m), 723(s), 688(s), 528(s), 514(s,
ModS), 486(m, ModS) cm-1. ESI-TOF-MS (CH3CN): m/z )
302.7. UV/vis (CH3CN, rt): λmax (ε) 520 (1.0 × 103), 457 (5.0 ×
103), 269 nm (1.7 × 104). Elemental analysis calcd for
C30H25MoPS4: C 56.24, H 3.93, S 20.02; Found: C 56.62, H 3.98,
S 19.62.
Preparation of [PPh4][MoS3(NPh2)] (7). To a THF solution of
[PPh4][MoClS3] (200 mg, 0.353 mmol) was added a THF solution
of KNPh2 (103 mg, 0.498 mmol) at room temperature. After stirring
for 30 min, the solution was centrifuged and evaporated to dryness.
The residue was extracted with THF, and the extract was centrifuged
again. The resulting solution was diffused into ether to give black
crystals of [PPh4][MoS3(NPh2)] (7, 145 mg, 0.207 mmol, 59%).
1H NMR (500 MHz, CD3CN, rt): δ 7.92 (m, 4H, PPh4), 7.75 (m,
8H, PPh4), 7.69 (m, 8H, PPh4), 7.20 (t, J ) 8.0 Hz, 4H, NPh2),
7.16 (d, J ) 7.5 Hz, 4H, NPh2), 6.97 (t, J ) 7.3 Hz, 2H, NPh2). IR
(KBr): 3057(w), 1583(m), 1479(s), 1437(s), 1319(w), 1226(m),
1174(m), 1153(m), 1108(s), 1026(w), 995(m), 928(m), 873(m),
856(w), 761(s), 750(w), 719(s), 690(s), 524(s), 505(s, ModS),
482(m, ModS), 444(w), 417(w) cm-1. ESI-TOF-MS (CH3CN): m/z
) 361.7. UV/vis (CH3CN, rt): λmax (ε) 468 (8.1 × 103), 327 (9.3
× 103), 261 nm (1.8 × 104). Elemental analysis calcd for
C36H30MoNPS3: C 61.79, H 4.32, N 2.00, S 13.75; Found: C 61.43,
H 4.46, N 2.04, S 13.78.
Preparation of (PPh4)[MoS3(SMes)] (6c). A similar procedure
as that for 6b was used. The reaction of [PPh4][MoClS3] (1.00 g,
1.76 mmol) with KSMes (1.97 mmol) gave a brown suspension.
After addition of acetonitrile, the mixture was centrifuged. The
solution was concentrated, and then diffused into ether to give dark
brown crystals of [PPh4][MoS3(SMes)] (6c, 821 mg, 1.20 mmol,
Preparation of [PPh4][MoS3(OtBu)] (8a). To a THF solution
of [PPh4][MoClS3] (300 mg, 0.529 mmol) was added KOtBu (74
mg, 0.66 mmol) at room temperature. After stirring for 30 min,
the solution was centrifuged to remove insoluble materials. The
resulting dark red solution was concentrated and diffused into ether
to give red crystals of [PPh4][MoS3(OtBu)] (8a, 178 mg, 0.294
1
68%). H NMR (600 MHz, CD3CN, rt): δ 7.91 (m, 4H, PPh4),
7.74 (m, 8H, PPh4), 7.68 (m, 8H, PPh4), 6.82 (s, 2H, C6H2), 2.37
(s, 6H, o-C6Me2), 2.22 (s, 3H, p-C6Me). IR (KBr): 3055(w),
1583(w), 1481(m), 1462(w), 1437(s), 1373(w), 1313(w), 1184(w),
1161(w), 1101(s), 1051(w), 1026(w), 995(m), 860(w), 758(m),
719(s), 690(s), 528(s), 511(s, ModS), 482(m, ModS) cm-1. ESI-
TOF-MS (CH3CN): m/z ) 344.7. UV/vis (THF, rt): λmax (ε) 518
(3.1 × 103), 447 (6.2 × 103), 277 nm (2.1 × 104). Elemental
analysis calcd for C33H31MoPS4: C 58.05, H 4.58, S 18.79; Found:
C 57.75, H 4.62, S 18.74.
Preparation of (PPh4)[MoS3(STip)] (6d). The same procedure
as in the case of 6b was used. The reaction of [PPh4][MoClS3]
(1.10 g, 1.94 mmol) and KSTip (2.06 mmol) in THF at -80 °C
gave a brown suspension, from which dark brown crystals of
[PPh4][MoS3(STip)] (6d, 875 mg, 1.14 mmol, 59%) were isolated.
1H NMR (500 MHz, CDCl3, rt): δ 7.82 (m, 4H, PPh4), 7.70 (m,
8H, PPh4), 7.63 (m, 8H, PPh4), 6.84 (s, 2H, C6H2), 3.86 (sep, J )
6.9 Hz, 2H, CHMe2), 2.79 (sep, J ) 6.7 Hz, 1H, CHMe2), 1.19 (d,
1
mmol, 56%). H NMR (500 MHz, CD3CN, rt): δ 7.91 (m, 4H,
t
PPh4), 7.74 (m, 8H, PPh4), 7.69 (m, 8H, PPh4), 1.30 (s, 9H, Bu).
IR (KBr): 3053(w), 2970(w), 2915(w), 1585(w), 1483(w), 1435(s),
1385(w), 1359(w), 1342(w), 1315(w), 1232(w), 1161(m), 1107(s),
1025(w), 997(m), 931(s), 789(w), 752(m), 723(s), 688(s), 575(m),
526(s), 503(s, ModS), 486(sh, ModS) cm-1. ESI-TOF-MS (THF,
rt): m/z ) 266.7. UV/vis (THF, rt): λmax (ε) 541 (1.0 × 103), 411
(4.7 × 103), 283 nm (9.5 × 103). Elemental analysis calcd for
C28H29MoOPS3: C 55.62, H 4.83, S 15.91; Found: C 55.41, H 4.49,
S 16.37.
Preparation of [PPh4][MoS3(OPh)] (8b). The same procedure
as in the case of 8a was used. The reaction of [PPh4][MoClS3]
(222 mg, 0.392 mmol) with KOPh (71 mg, 0.54 mmol) gave a red
suspension, from which red crystals of [PPh4][MoS3(OPh)] (8b,
1
198 mg, 0.336 mmol, 81%) were isolated. H NMR (500 MHz,
3770 Inorganic Chemistry, Vol. 47, No. 9, 2008

Versatile Precursor for Molybdenum Trisulfido Complexes
Table 5. Crystal Data for 2, 5, 6c, 7, 8a-c, and 9
2
5
6c
7
8a
8b
8c
9
formula
mol wt (g mol-1) 566.97
C24H20ClMoPS C38H35Mo2OPS6 C33H31MoPS4 C36H30MoNPS3 C28H29MoOPS3 C30H25MoOPS3 C30H31MoOPS3 C33H33MoO7PS3
922.91
682.76
699.73
monoclinic
Cc (#9)
9.100(2)
16.719(4)
20.994(5)
604.63
624.62
630.69
764.71
crystal system
space group
a (Å)
tetragonal
I4 (#82)
12.9808(8)
triclinic
triclinic
monoclinic
P21/n (#14)
14.612(3)
11.813(2)
17.210(3)
monoclinic
P21/c (#14)
13.427(3)
11.008(2)
18.997(4)
monoclinic
P21/n (#14)
15.415(3)
12.054(2)
16.960(3)
monoclinic
P21/n (#14)
8.787(2)
17.862(4)
22.379(5)
j
j
j
P1 (#2)
P1 (#2)
10.956(2)
11.307(2)
18.199(3)
82.324(7)
84.800(7)
61.785(4)
1967.8(5)
2
11.187(2)
12.523(3)
12.906(3)
106.7794(7)
102.5378(17) 98.572(4)
109.067(2)
b (Å)
c (Å)
7.0844(8)
R (°)
ꢀ (°)
110.744(2)
93.868(3)
110.835(3)
94.839(2)
γ (°)
V (Å3)
Z
1193.7(2)
2
1.577
9.99
0.023
0.032
0.98
1536.1(6)
2
3158.4(13)
4
2777.9(9)
4
2801.5(10)
4
2945.2(10)
4
3499.9(1)
4
dcalc (g cm-3
)
1.557
10.25
0.052
0.059
1.476
7.721
0.028
0.035
1.04
1.471
6.91
0.026
0.029
1.02
1.446
7.74
0.045
0.052
1.29
1.481
7.70
0.033
0.043
1.14
1.422
7.329
0.035
0.043
1.02
1.451
6.43
0.032
0.047
1.08
µ (cm-1
Ra
)
Rwb
GOFc
1.35
a R ) Σ4Fo| - |Fc4/Σ|Fo|. b Rw ) [{Σw (|Fo| - |Fc|)2}/ΣwFo ]1/2
and parameters.
.
c GOF ) [{Σw(|Fo| - |Fc|)2}/(No - Np)]1/2, where No and Np denote the number of data
2
CD3CN, rt): δ 7.83 (m, 4H, PPh4), 7.72 (m, 8H, PPh4), 7.60 (m,
8H, PPh4), 7.05 (m, 2H, OPh), 6.98 (m, 2H, OPh), 6.79 (m, 1H,
OPh). IR (KBr): 3048(w), 1583(m), 1481(m), 1471(m), 1433(s),
1336(w), 1226(s), 1186(w), 1157(w), 1106(s), 997(m), 876(m),
752(m), 723(s), 687(s), 646(m), 526(s), 507(s, ModS), 487(m,
ModS) cm-1. ESI-TOF-MS (THF, rt): m/z ) 286.7. UV/vis
(CH3CN, rt): λmax (ε) 549 (1.6 × 103), 411 (5.4 × 103), 283 nm
(1.6 × 104). Elemental analysis calcd for C30H25MoOPS3: C 57.69,
H 4.03, S 15.40; Found: C 57.74, H 4.05, S 15.41.
[PPh4][MoS3(Me3cit)] (9, 491 mg, 0.643 mmol, 73%). Crystals for
the X-ray diffraction were obtained by slow diffusion of ether to a
THF solution of 9. 1H NMR (500 MHz, CD3CN, rt): δ 7.93 (m, 4H,
PPh4), 7.76 (m, 8H, PPh4), 7.69 (m, 8H, PPh4), 3.67 (s, 3H, OMe),
3.49 (s, 6H, OMe), 3.07 (d, J ) 16 Hz, 2H, CH2), 2.99 (d, J ) 16 Hz,
2H, CH2). IR (KBr): 1736 (vs, C)O), 1585(w), 1483(w), 1435(s),
1336(w), 1207(m), 1163(m), 1107(s), 1072(m), 997(m), 941(m),
835(w), 760(w), 721(s), 688(s), 530(s), 509(s, ModS), 490(s, ModS),
455(m) cm-1. ESI-TOF-MS (THF): m/z ) 426.7. UV/vis (THF, rt):
λmax (ε) 549 (1.1 × 103), 411 (3.7 × 103), 278 nm (9.5 × 103).
Elemental analysis calcd for C33H33MoO7PS3: C 51.83, H 4.35, S
12.58; Found: C 51.72, H 4.35, S 12.54.
X-ray Structural Determination. Crystal data and refinement
parameters of 2, 5, 6c, 7, 8a-c, and 9 were summarized in Table 5.
Single crystals were coated with oil (Immersion Oil, type B: Code
1248, Cargill Laboratories, Inc.) and mounted on loops. Diffraction
data were collected on a Rigaku Mercury CCD diffractometer (for 2,
5, 7, 8b, and 8c), Rigaku Saturn 70 CCD diffractometer (for 8a), and
Rigaku Saturn 70 CCD with Micromax (for 6c and 9), all equipped
with a graphite monochromatized Mo KR source (λ ) 0.71070 Å).
Data were collected on 676 oscillation images with oscillation range
of 0.5° (for 2), 720 oscillation images with oscillation range of 0.5°
(for 5, 6c, 7, 8a-c, and 9). Intensity data were corrected for Lorentz-
polarization effects and empirical absorption using the CrystalClear
program package. All structures were solved by direct methods (SIR-
92) using the TEXSAN or CrystalStructure program packages.
Anisotropic refinement was applied to all nonhydrogen atoms, and all
hydrogen atoms were placed at the calculated positions and were not
refined. The S and Cl atoms in 2 overlap because of the crystallographic
Td symmetry, and they were analyzed as 75%(S) and 25%(Cl). The
refinement was carried out by least-squares methods based on F with
all measured reflections.
Preparation of [PPh4][MoS3{OC(CH2)tBu}] (8c). A similar
procedure as that for 8a was used. The reaction of [PPh4][MoClS3]
(500 mg, 0.882 mmol) with KOC(CH2)tBu (130 mg, 0.940 mmol)
at -80 °C gave a red suspension, from which red crystals of
[PPh4][MoS3{OC(CH2)tBu}] (8c, 285 mg, 0.452 mmol, 51%) were
1
isolated. H NMR (600 MHz, THF-d8, rt): δ 7.91 (m, 4H, PPh4),
7.80 (m, 16H, PPh4), 4.31 (s, 1H, CH), 3.94 (s, 1H, CH), 1.01 (s,
9H, tBu). IR (KBr): 3045(w), 1585(m), 1481(m), 1435(s), 1340(w),
1275(m), 1186(w), 1163(s), 1107(s), 995(m), 980(s), 812(m),
750(m), 723(s), 688(s), 634(m), 526(s), 509(s, ModS), 484(m,
ModS) cm-1. ESI-TOF-MS (THF, rt): m/z ) 292.5. UV/vis (THF,
rt): λmax (ε) 550 (1.2 × 103), 410 (4.7 × 103), 287 nm (1.1 × 104).
Elemental analysis calcd for C30H31MoOPS3: C 57.13, H 4.95, S
15.25; Found: C 57.26, H 5.01, S 15.45.
Preparation of [PPh4][MoS3{OC(CH2)Ph}] (8d). The same
procedure as in the case of 8c was used. The reaction of
[PPh4][MoClS3] (500 mg, 0.882 mmol) with KOC(CH2)Ph (150
mg, 0.948 mmol) at -80 °C gave a red suspension, from which
red crystals of [PPh4][MoS3{OC(CH2)Ph}] (8d, 165 mg, 0.254
1
mmol, 29%) were isolated. H NMR (600 MHz, THF-d8, rt): δ
7.89 (m, 4H, PPh4), 7.78 (m, 16H, PPh4), 7.53 (d, 3JHH ) 7.6 Hz,
3
3
2H, o-Ph), 7.15 (t, JHH ) 7.6 Hz, 2H, m-Ph), 7.09 (t, JHH ) 7.6
Hz, 1H, p-Ph), 4.74 (s, 1H, CH), 4.73 (s, 1H, CH). IR (KBr):
3042(w), 1481(m), 1434(s), 1311(w), 1271(m), 1072(m), 1107(s),
985(s), 812(m), 773(w), 748(w), 721(s), 688(s), 634(m), 526(s),
515(s, ModS), 490(m, ModS) cm-1. ESI-TOF-MS (THF, rt): m/z
) 312.8. UV/vis (THF, rt): λmax (ε) 553 (1.3 × 103), 412 (5.5 ×
103), 284 nm (1.8 × 104). Elemental analysis calcd for
C32H27MoOPS3: C 59.07, H 4.18, S 14.78; Found: C 58.91, H 4.47,
S 14.91.
Acknowledgment. We thank Prof. Roger E. Cramer at
the University of Hawaii for helpful discussions. This
research was financially supported by a Grant-in-Aid for
Scientific Research (No.’s 18GS0207 and 18064009) from
the Ministry of Education, Culture, Sports, Science, and
Technology, Japan.
Preparation of [PPh4][MoS3(Me3cit)] (9) (Me3cit ) OC(CH2-
CO2Me)2(CO2Me)). A THF solution of K(Me3cit) (1.0 mmol) was
added to a THF solution of 2 (500 mg, 0.882 mmol) at room
temperature. After stirring for 30 min, the dark red suspension was
centrifuged to remove insoluble materials. The solution was evaporated
to dryness, and the resulting red solid was washed with ether to give
Supporting Information Available: X-ray crystallographic
information file (CIF). This material is available free of charge via
the Internet at http://pubs.acs.org.
IC702397J
Inorganic Chemistry, Vol. 47, No. 9, 2008 3771