MS2(Me2PC2H4PMe 2)2 (M = Mo, W): Acid-base properties, proton transfer, and reversible protonolysis of sulfido ligands

Article abstract of DOI:10.1021/ic051443c

The acid-base reactivity of MS₂(dmpe)₂, where M = Mo (1) and W (2) and dmpe = Me₂PCH₂CH₂PMe ₂, was examined. Compounds 1 and 2 arise via the one-pot reaction of (NH₄)₂MS₄ and dmpe. Protonation of these species gives the stable salts [MS(SH)(dmpe)₂]X. The pK_a's of the Mo and W compounds are estimated to be 16.5 and 15.5, respectively. Protonation causes the M=S distances to diverge from 2.24 A to 2.06 and 2.57 A, whereas the Mo-P distances do not change appreciably. ¹H and ³¹P NMR studies for [1H]BAr^F₄ reveal that the proton exchange is competitive with the NMR time scale; at low temperatures, individual signals for both the parent disulfide and its conjugate acid can be observed. Treatment of 1 with excess HOTf liberates H₂S to afford [MoS(OTf)(dmpe)₂]OTf, which forms an adduct with CD ₃CN and regenerates 1 upon treatment with SH^-/Et ₃N solutions. Consistent with its ready protonation, complex 1 is methylated, and the use of excess MeOTf gives [MoS(OTf)(dmpe)₂] ⁺ and Me₂S in a rare example of double alkylation at a sulfido ligand.

Full text of DOI:10.1021/ic051443c

Inorg. Chem. 2006, 45, 679−687
MS2(Me2PC2H4PMe2)2 (M
) Mo, W): Acid−Base Properties, Proton
Transfer, and Reversible Protonolysis of Sulfido Ligands
Steven J. Smith, C. Matthew Whaley, Thomas B. Rauchfuss,* and Scott R. Wilson
Department of Chemistry, UniVersity of Illinois at Urbana-Champaign, Urbana, Illinois 61801
Received August 24, 2005
The acid−base reactivity of MS2(dmpe)2, where M ) Mo (1) and W (2) and dmpe ) Me2PCH2CH2PMe2, was
examined. Compounds 1 and 2 arise via the one-pot reaction of (NH4)2MS4 and dmpe. Protonation of these species
gives the stable salts [MS(SH)(dmpe)2]X. The pKa’s of the Mo and W compounds are estimated to be 16.5 and
15.5, respectively. Protonation causes the M
d
S distances to diverge from 2.24 Å to 2.06 and 2.57 Å, whereas the
1
Mo−
P distances do not change appreciably. H and 31P NMR studies for [1H]BArF reveal that the proton exchange
4
is competitive with the NMR time scale; at low temperatures, individual signals for both the parent disulfide and its
conjugate acid can be observed. Treatment of 1 with excess HOTf liberates H2S to afford [MoS(OTf)(dmpe)2]OTf,
which forms an adduct with CD3CN and regenerates 1 upon treatment with SH-/Et3N solutions. Consistent with its
ready protonation, complex 1 is methylated, and the use of excess MeOTf gives [MoS(OTf)(dmpe)2]+ and Me2S in
a rare example of double alkylation at a sulfido ligand.
Introduction
MoS2(Me8[16]-aneS4) via the reaction of trans-Mo(N2)2-
(Me8[16]-aneS4) with S8 or t-BuSH, where Me8[16]-aneS4
is a tetradentate thioether macrocycle.5 The species “(C5H5)2-
MoS”,6 which is related to the aforementioned series of trans-
MoS2L4 complexes in ostensibly being a d2, 18e MdS
complex, is unstable and of undefined nuclearity.
These reports comprise the foundation literature for d2
complexes containing “pure” MdE double bonds (E ) S,
Se, Te). The ModS bond lengths are 2.22-2.25 Å vs ∼2.15
Å, typical for the more pervasive bonds between Mo and S
that usually have triple-bond character.7 The bonding in these
18e species has been described using both qualitative and
Hartree-Fock molecular orbital theory; the trans geometry
is characteristic of the d2 configuration.4,8 The correlation
of bond order and bond lengths is confirmed by Yoshida’s
characterization of the methylated derivative trans-[MoS-
(SMe)(Me8[16]-aneS4)]I, wherein the Mo-S bonds diverge
from 2.24 Å to 2.14 and 2.44 Å.9 Thus, alkylation could be
In inorganic chemistry, many studies have focused on
basicity as it relates to reactions at the metal center, e.g.,
ligand substitution and protonation/alkylation at metals.
Fewer studies, however, have systematically examined the
basicity and nucleophilicity of coordinated ligands, especially
chalcogenide ligands.1 In this paper, we address this gap
through an examination of an important class of metal
dichalcogenides.
Starting in 1991, a series of publications have described
the 18e, d2 complexes of the type trans-ME2L4, where M )
Mo, W and E ) S, Se, Te and L ) 2e donor ligand (Figure
1). Parkin and co-workers developed MoS2(PMe3)42 and the
corresponding W analogues and Se and Te derivatives
thereof.3 Cotton and co-workers, using Mo(N2)2(diphos)2
precursors, prepared the corresponding series MoE2(diphos)2
for E ) O, S, Se, Te (diphos ) Ph2PCH2CH2PPh2, cis-Ph2-
PCHdCHPPh2).4 Yoshida and co-workers described trans-
* To whom correspondence should be addressed. E-mail: rauchfuz@
uiuc.edu.
(4) Cotton, F. A.; Schmid, G. Inorg. Chem. 1997, 36, 2267-2278.
(5) Yoshida, T.; Adachi, T.; Matsumura, K.; Kawazu, K.; Baba, K. Chem.
Lett. 1991, 1067-1070.
(1) Nugent, W. A.; Mayer, J. M. Metal-Ligand Multiple Bonds; John
Wiley: New York, 1988.
(6) Pilato, R. S.; Eriksen, K. A.; Stiefel, E. I.; Rheingold, A. L. Inorg.
Chem. 1993, 32, 3799-3800.
(2) Murphy, V. J.; Rabinovich, D.; Halkyard, S.; Parkin, G. J. Chem. Soc.,
Chem. Commun. 1995, 1099-1100.
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Rabinovich, D.; Parkin, G. J. Am. Chem. Soc. 1991, 113, 5904-5905.
Rabinovich, D.; Parkin, G. J. Am. Chem. Soc. 1993, 115, 9822-9823.
Rabinovich, D.; Parkin, G. Inorg. Chem. 1994, 33, 2313-2314.
Rabinovich, D.; Parkin, G. Inorg. Chem. 1995, 34, 6341-6361.
(7) Parkin, G. Prog. Inorg. Chem. 1998, 47, 1-165. Coucouvanis, D.
AdV. Inorg. Chem. 1998, 45, 1-73.
(8) Paradis, J. A.; Wertz, D. W.; Thorp, H. H. J. Am. Chem. Soc. 1993,
115, 5308-5309.
(9) Yoshida, T.; Adachi, T.; Matsumura, K.; Baba, K. Chem. Lett. 1992,
2447-2450.
10.1021/ic051443c CCC: $33.50
Published on Web 12/23/2005
© 2006 American Chemical Society
Inorganic Chemistry, Vol. 45, No. 2, 2006 679

Smith et al.
Figure 1. Prototypical d2 MoS2L4 complexes.
described as being “spring-loaded” because of the large
structural change that accompanies attachment of the elec-
trophile.
Results
Synthesis and Basic Properties of MoS2(dmpe)2. Par-
kin’s synthesis of MoS2(PMe3)4 involved the intermediacy
of Mo(PMe3)6, prepared via the Na/K reduction of MoCl5/
PMe3 mixtures at low temperatures.21 We recently found that
MoS2(PMe3)4 forms efficiently upon treatment of MeCN
slurries of (NH4)2MoS4 with PMe3 at room temperature (eq
1).22 Reflecting their high basicity (see below), the sulfido
ligands in MoS2(PMe3)4 resist further desulfurization by
PMe3. The coproducts, H2S, NH3, and even SPMe3, are
volatile; thus, reaction workup is convenient and efficient.
Peripherally related to the focus of this paper, numerous
d0 species also feature “pure” MdE double bonds, e.g.,
Cp*2M(S)(py) (M ) Ti, Zr, Hf),10 (triamine)MoE3 (E ) O,
S),11 (C5Me5)ReO3,12 [(C5Me5)MoS3]-,13 and [Cl3ReO3]2-.14
These d0 compounds might be expected to display diminished
basicity relative to the d2 MdE species. Other interesting
18e MdE species include the cationic d4 oxo-complexes.15
Compounds with pure MdS/Se/Te bonds may also be
viewed as transition-metal representatives of “heavy ke-
tones”, defined by Okazaki and Tokitoh to describe MdE-
bonded systems where E is S, Se, or Te and M is a main-
group atom heavier than the first row.16 Analogous to the
18e MdE species, the heavy ketones follow the octet rule.
+
A proton source, in this case NH4 , is essential to assist in
the elimination of H2S.22 Important to this paper, MoS2-
(dmpe)2 (1) can be prepared via ligand exchange from MoS2-
(PMe3)4 but also formed via the one-pot reaction of (NH4)2-
MoS4 and 2.5 equiv of dmpe (dmpe ) Me2PCH2CH2PMe2,
eq 2). We also found that MeCN solutions of either (NH4)2-
A theme that is relevant to basicity is, of course, the
behavior of the conjugate acid. The present cases are, in
principle, dibasic because of the presence of two equivalent
sites of protonation. Monoprotonation of such dibasic species
opens questions of degenerate proton exchange. Little
information exists on the proton-exchange dynamics of
M-S-H systems, which contrasts with the centrality of
Mo-S-H functionalities in catalytic H-atom transfers in
both enzymology and industrial hydrotreating catalysis.17-19
Slow proton transfer has been observed in oxides, such as
Re(O)(OH)(C2Me2)2,20 but not in sulfides.
(NH4)2MoS4 + 5PMe3 f
MoS2(PMe3)4 + H2S + 2NH3 + SPMe3 (1)
(NH4)2MoS4 + 2.5dmpe f
MoS2(dmpe)2 + H2S + 2NH3 + 0.5dmpeS2 (2)
MoS2O2 or (NH4)2MoS3O, PMe3, and dmpe produce 1 as
well. The intensely green species MoS2(dmpe)2 exhibits good
solubility in benzene and THF but is only poorly soluble in
MeCN and alkanes. Its solutions can be handled in air, at
least briefly, and show no tendency to dissociate ligands in
solution.
The analogous violet tungsten complex WS2(dmpe)2 (2)
was prepared similarly to the Mo compound. 23 Starting with
(PPh4)2MoSe4 and using NH4PF6 as the proton source, we
also synthesized the brown-colored MoSe2(dmpe)2, which
was crystallographically characterized.
(10) Sweeney, Z. K.; Polse, J. L.; Andersen, R. A.; Bergman, R. G.
Organometallics 1999, 18, 5502-10. Sweeney, Z. K.; Polse, J. L.;
Andersen, R. A.; Bergman, R. G. J. Am. Chem. Soc. 1998, 120, 7825-
7834. Howard, W. A.; Parkin, G. J. Am. Chem. Soc. 1994, 116, 606-
615.
(11) Partyka, D. V.; Staples, R. J.; Holm, R. H. Inorg. Chem. 2003, 42,
7877-7886.
(12) Romao, C. C.; Kuhn, F. E.; Herrmann, W. A. Chem. ReV. 1997, 97,
3197-3246.
(13) Kawaguchi, H.; Yamada, K.; Lang, J.; Tatsumi, K. J. Am. Chem. Soc.
1997, 119, 10346-10358. Cao, R.; Tatsumi, K. Inorg. Chem. 2002,
41, 4102-4104.
Protonation of MS2(dmpe)2 (M ) Mo, W). Upon the
addition of protic acids, green solutions of 1 changed to
orange or brown, depending on the strength of the reacting
acid. Treating 1 with 1 equiv of methanesulfonic acid
(14) Grove, D. E.; Johnson, N. P.; Wilkinson, G. Inorg. Chem. 1969, 8,
1196.
(15) Meyer, T. J.; Huynh, M. H. V. Inorg. Chem. 2003, 42, 8140-8160.
Bryant, J. R.; Matsuo, T.; Mayer, J. M. Inorg. Chem. 2004, 43, 1587-
1592. Klinker, E. J.; Kaizer, J.; Brennessel, W. W.; Woodrum, N. L.;
Cramer, C. J.; Que, L., Jr. Angew. Chem., Int. Ed. 2005, 44, 3690-
3694.
(16) Okazaki, R.; Tokitoh, N. Acc. Chem. Res. 2000, 33, 625-630.
(17) Stiefel, E. I. J. Chem. Soc., Dalton Trans. 1997, 3915-3923. Stiefel,
E. I. ACS Symp. Ser. 1996, 653, 2-38.
(18) Kuwata, S.; Hidai, M. Coord. Chem. ReV. 2001, 213, 211-305.
(19) Peruzzini, M.; de los Rios, I.; Romerosa, A. Prog. Inorg. Chem. 2001,
49, 169-543.
(20) Erikson, T. K. G.; Mayer, J. M. Angew. Chem., Int Ed. Engl. 1988,
100, 1527-1529. Kramarz, K. W.; Norton, J. R. Prog. Inorg. Chem.
1994, 42, 1-65.
(21) Murphy, V. J.; Parkin, G. J. Am. Chem. Soc. 1995, 117, 3522-3528.
(22) Schwarz, D. E.; Rauchfuss, T. B.; Wilson, S. R. Inorg. Chem. 2003,
42, 2410-2417.
(23) Curtis, C. J.; Miedaner, A.; Ciancanelli, R.; Ellis, W. W.; Noll, B. C.;
Rakowski DuBois, M.; DuBois, D. L. Inorg. Chem. 2003, 42, 216-
227.
680 Inorganic Chemistry, Vol. 45, No. 2, 2006

MS2(Me2PC2H4PMe2)2 (M ) Mo, W)
we considered the possibility that [1H]+ might undergo
exchange with D2, but exposure of either CD3CN or CD3-
NO2 solutions of [1H]BArF to ca. 1 atm of D2 resulted in
4
1
no change in the H NMR spectrum after 48 h.
Protonation of 2 with HOMs results in a color change from
deep purple to neon green (Figure 2). An equimolar mixture
of 1 and [2H]OMs in a CD3CN solution results in a dark-
orange solution, the 31P NMR spectrum of which reveals
two broad peaks, one at δ 29.5 for the average of 1 and
[1H]OMs and one at δ 2 for the average of 2 and [2H]OMs.
Analysis of chemical shifts in this mixture indicates that 1
is more basic than 2, with a Keq ) 10-11 (eq 3).
Compound 1 is protonated by NH4PF6 (pKa ) 16.5) and
subsequently deprotonated by Et3N (pKa of Et3NH+
)
18.7),24 as demonstrated by 1H and 31P NMR spectroscopy.
+
Because 2 is not protonated by NH4 , i.e., has a pKa < 16.5,
and because it is 10 times more weakly basic than 1, it
follows that the pKa of 1 is 16.5-17.5.
Figure 2. Optical spectra for various stages in the protonation of 1 (top)
and 2 (bottom) with HOMs in MeCN solution. The aliquot sizes for 1 were
0, 0.25, 0.5, 0.75, and 1.0 mol, and for 2, the aliquot sizes were 0, 0.3, 0.6,
and 1.0 mol.
Structural Studies on [M(S)(SR)(dmpe)2]+. Although
MoS2(Me8[16]-aneS4) can be alkylated,9 its protonation
results in immediate elimination of H2S to give trans-[Mo2S3-
(Me8[16]-aneS4)2]2+.25 Crystallographic characterization of
[1H]BArF4 reveals that protonation most significantly affects
the Mo-S bond lengths (Figure 4). In neutral trans-MoS2-
(dmpe)2, the two ModS bonds are 2.250(9) Å in length,
(HOMs; pKa ) 10.0 in MeCN; all pKa’s are quoted for a
MeCN solution unless otherwise noted) gives the bright-
orange salt [MoS(SH)(dmpe)2]OMs, [1H]OMs. Optical
measurements show that this reaction proceeds cleanly with
isosbestic points at 530 and 710 nm (Figure 2). The 1H NMR
spectrum of [1H]OMs in a CD3CN solution consists of a
quintet at δ -4.08 for the 31P-coupled SH group. The methyl
groups on the dmpe ligands are inequivalent, whereas the
single 31P NMR signal is consistent with C2V symmetry
(Figure 3).
To test the possibility that S protonation would suppress
dissociation of phosphine from the otherwise labile PMe3
species, MoS2(PMe3)4 was treated with 1 equiv of H(Et2O)2-
BArF4 (ArF ) 3,5-(CF3)2C6H3) in a THF-d8 solution at -70
°C to produce a bright-orange solution. The 1H NMR
spectrum reveals that protonation occurs analogously to that
of 1 with a quintet centered at δ -2.08 for the 31P-coupled
SH and a peak at δ 1.89 for the four equivalent PMe3 groups.
Upon warming to room temperature, the SH and PMe3
signals decreased concomitantly with an increase in the signal
for SPMe3. Thus, protonation does not suppress the lability
of the PMe3 ligands.
whereas in [1H]BArF , these distances have diverged to
4
2.062(7) and 2.573(7) Å. The Mo-P distances do not change
appreciably upon protonation; however, the StMo-P bond
angles increase from 91.1° to 95.4° as the diphosphine
ligands tilt away from the MotS.
Crystallographic results on [2H]OMs proved consistent
with the results for the Mo derivatives. In neutral WS2-
(PMe3)4, the WdS distance is 2.252 (3) Å, whereas in [2H]-
OMs, these distances diverge to 2.074(13) and 2.581(13) Å.
The StW-P bond angles again show that the diphosphine
ligands bend away from the more tightly bonded terminal
sulfido ligand.
Proton-Transfer Dynamics. Preliminary measurements
suggested that proton transfer in [1H]+ can be sluggish. For
1
example, the H NMR spectrum of [1H]OMs shows two
equally intense PMe signals, separated by 150 Hz (∆ν). On
the basis of the relation τ ) 21/2π(∆ν), the rate of site
(24) Izutsu, K. Acid-Base Dissociation Constants in Dipolar Aprotic
SolVents; Blackwell Scientific Publications: Oxford, U.K., 1990.
(25) Yoshida, T.; Adachi, T.; Matsumura, K.; Baba, K. Angew. Chem.,
Int. Ed. Engl. 1993, 32, 1621-1623.
The SH NMR signal in [1H]OMs disappears upon treat-
ment with D2O. On the basis of its formal 16e configuration,
Inorganic Chemistry, Vol. 45, No. 2, 2006 681

Smith et al.
1
Figure 3. 500-MHz H NMR spectrum of [MoS(SH)(dmpe)2]OMs in a CD3CN solution. The inset shows the SH signal, J(P,H) ) 13 Hz.
Figure 4. Molecular structure of the cation in [MoS(SH)(dmpe)2]BArF
4
with 50% thermal ellipsoids.
Figure 5. 200-MHz 31P NMR spectra of [MoS(SH)(dmpe)2]BArF in
4
acetone-d6 at various temperatures.
exchange is <1000 s-1. Furthermore, the 31P NMR spectrum
of an equimolar solution of [MoS(SH)(dmpe)2]OMs and
MoS2(dmpe)2 consists of a broad signal at the average of
the singlets for two individual components.
separate peaks for the P-methyl groups, indicating again
that the less basic solvent inhibits proton transfer.
[MoS(OTf)(dmpe)2]+. Treatment of 1 in a MeCN solution
with an excess of HOTf liberated H2S (δ 1.05). From the
resulting solution, we obtained a high yield of the salt [MoS-
(OTf)(dmpe)2]OTf ([3]OTf) as an analytically pure pale-
green solid. The rate of protonolysis of the sulfido ligand is,
however, sensitive to the acidity of the acid. The addition
of 2 equiv of HOMs (pKa ) 10.0)24 to a CD3CN solution of
1 liberated H2S only over the course of several hours.
The 19F NMR spectrum of [3]OTf in a CD2Cl2 solution
showed equally intense signals at δ -79.7 and -78.0 for
free and coordinated OTf-, respectively. In a CD3CN
solution, the 19F NMR spectrum simplified to a single peak
at δ -79.7, indicating that the MeCN displaced the coor-
dinated triflate. The addition of more than 2 equiv of MeOTf
to a MeCN solution of 1 also produced [3]OTf, via an
unusual example of a double alkylation of a sulfido ligand
(see below).
The optical spectrum of the salt with the ostensible formula
[1H]BArF indicated the presence of both [1H]+ (as for the
4
OMs- salt) and 1. The addition of 1 equiv of HOMs con-
verted the brown solution to bright orange, characteristic of
1
pure [1H]+. Ambient-temperature H and 31P NMR spectra
of [1H]BArF in a CD3CN solution are broadened relative
4
to the corresponding OMs- salt. Analysis of chemical shifts
established that Keq ) 2.3 at ca. 25 °C. Upon cooling of the
sample to -40 °C, the 31P NMR signal decoalesces to sing-
lets at δ 22.5 and 32.5, assignable to 1 and [1H]+, respec-
tively. Low-temperature (-80 °C) 31P NMR (Figure 5) ana-
lysis indicated that the 1/[1H+] ratio is higher in acetone-d6
vs CD3CN, consistent with the greater basicity26 of Me2CO.
The 1H NMR spectrum of [2H]OMs in a CD3CN solution
consists of a broad singlet for the P-methyl groups,
suggesting that proton exchange is more rapid for this species
vs the Mo analogue (see below). With the less basic solvent
Crystallographic analysis of [3]OTf showed that this
complex exhibits similarities to [2]+ in the MotS bond
length and the S-Mo-P bond angles (Tables 1-4). The
Mo-O bond length is comparable to those of other Mo(IV)
triflate complexes.
1
CD3NO2, the H NMR spectrum of [2H]OMs consists of
(26) Catala´n, J.; Diaz, C.; Lopez, V.; Pe´rez, P.; De Paz, J.-L. G.; Rodriguez,
J. G. Liebigs Ann. Chem. 1996, 1785-1794.
682 Inorganic Chemistry, Vol. 45, No. 2, 2006

MS2(Me2PC2H4PMe2)2 (M ) Mo, W)
Table 1. Selected Bond Lengths (Å) and Angles (deg) for 1 and
[1H]BArF
4
1
[1H]BArF
4
ModS or MotS
Mo-SH
2.2476(9)-2.2497(8)
2.062(7)
2.573(7)
2.491(2)
95.38(2)
98.02(8)
Mo-P
2.476(8)-2.488(8)
87.64(10)-93.6(4)
99.45(3)
Conclusions
SdMosP
P-Mo-P
Given their distinctive electronic structure and their
dramatic structural and electronic responses to S function-
alization, the trans-MS2L4 compounds are highly unusual
Lewis bases. Their reactivity has received little attention,
partially because of synthetic challenges that this and our
preceding report22 resolve. We have shown that a variety of
trans-MoE2(diphos)2 species could be prepared with diverse
diphosphines and chalcogenides. Because these complexes
are relatively kinetically stable, they lend themselves to
mechanistic and structural analysis.
Table 2. Selected Bond Lengths (Å) and Angles (deg) for
WS2(PMe3)4 and [2H]OMs
3
WS2(PMe3)4
2.252(3)
[2H]OMs
WdS or WtS
W-SH
2.074(13)
2.581(13)
2.493(17)
94.34(5)
99.0(5)
W-P
2.50(3)
82.8/90.6(1)
90.6(1)
SdWsP
P-W-P
Table 3. Selected Bond Lengths (Å) and Angles (deg) for [3]OTf
Basicity. MoS2(dmpe)2 is a relatively basic metal sulfide.
Its basicity exceeds that of the dianion [MoS4]2-, which is
not protonated by NH4+.22,27 2 is ca. 10 times less basic than
MoS2(dmpe)2. NMR evidence also points to the greater
acidity of the WSH versus MoSH complex in terms of more
rapid proton exchange and lower field NMR chemical shift
for WSH vs MoSH in [2H]OMs and [1H]OMs, respectively.
In contrast, for protonation at the metal, third-row metals
are considerably more basic than their lighter congeners; e.g.,
the pKa for HMn(CO)5 at 14 is 7 log units lower than that
for HRe(CO)5.28
The optical properties of metal complexes rarely are as
sensitive to protonation as the complexes described in this
work. The case of MoS2(dmpe)2 (and its analogues29) is
special because the ground electronic state is strongly altered
in the conversion from EdML4dE to [HEsML4tE]+. It is
also known that the optical properties of these complexes
are highly sensitive to the nature of the ligands8,29 as well as
small structural distortions.30 Optical changes in the attendant
protonation are comparable with those associated with
methylation at sulfur.
[MoS(OTf)(dmpe)2]OTf
MotS
Mo-O
Mo-P
SdMosP
P-Mo-P
2.0867(8)
2.2914(19)
2.5090/2.5318(8)
94.85/97.65(3)
79.67/100.51(2)
The protonation of the sulfido ligand in 1 to give [3]OTf
proved to be fully reversible: the addition of Et3N to a CD3-
CN solution containing [3]+ and 1 equiv of H2S gave [1H]+
over the course of 5 h (eq 4). As discussed above, this
MoSH+ species can be further deprotonated with Et3N to
give 1.
Slow Proton Transfer in Metal Sulfides. The proton-
transfer reactivity of metal sulfides and sulfhydryl com-
plexes18,19 is virtually unstudied. It has been reported that a
mixture of the d2 dimer [(C5R5)2Mo2(S)(SH)(S2CH2)]+ and
its conjugate base undergoes rapid proton exchange on the
NMR time scale.31 The 31P NMR spectrum of [Pt2(PR3)4(µ-
S)(µ-SH)]+ also indicates fast proton transfer following a
Further illustrating the displacement of OTf- by chalco-
genides, [3]OTf was treated with PPh4TeH/Et3N or 2 equiv
of Bu4NOH to give MoS(E)(dmpe)2 (E ) O, Te, respec-
tively). Spectroscopic and mass spectrometric data are
consistent with the formation of these mixed chalcogenide
species.
slower conversion from SHequatorial to SHaxial.
32 A potentially
interesting case is the d0 sulfide (C5Me4Et)2Nb(S)(SH),33
although its dynamic properties have not been reported.
Alkylation Studies. Consistent with its ready protonation,
complex 1 is methylated by MeI. Solutions of 1 do not,
however, react with PhBr or even PhCH2Cl. Analogous to
the protonations, the methylation was signaled by a green-
(27) Srinivasan, B. R.; Dhuri, S. N.; Na¨ther, C.; Bensch, W. Inorg. Chim.
Acta 2005, 358, 279-287.
(28) Moore, E. J.; Sullivan, J. M.; Norton, J. R. J. Am. Chem. Soc. 1986,
108, 2257-2263.
(29) Bendix, J.; Bøgevig, A. Inorg. Chem. 1998, 37, 5992-6001.
(30) Da Re, R. E.; Hopkins, M. D. Inorg. Chem. 2002, 41, 6973-6985.
(31) Birnbaum, J.; Godziela, G.; Maciejewski, M.; Tonker, T. L.;
Haltiwanger, R. C.; Rakowski DuBois, M. Organometallics 1990, 9,
394-401.
(32) Mas-Balleste´, R.; Aullo´n, G.; Champkin, P. A.; Clegg, W.; Me´gret,
C.; Gonzalez-Duarte, P.; Lledo´s, A. Chem. Eur. J. 2003, 9, 5023-
5035. Aullo´n, G.; Capdevila, M.; Clegg, W.; Gonza´lez-Duarte, P.;
Lledo´s, A.; Mas-Balleste´, R. Angew. Chem., Int. Ed. 2002, 41, 2776-
2778.
1
to-orange color change. The H NMR spectrum of [MoS-
(SMe)(dmpe)2]I ([1Me]I) shows two signals for the PMe
groups consistent with the conversion from D2h to idealized
C2V symmetry. The SMe group appears as a 31P-coupled
pentet at δ 1.38. The 31P NMR spectrum reveals one peak
for the four equivalent phosphorus atoms. Yoshida methy-
lated trans-MoS2(Me8[16]-aneS4) with MeI in a similar
fashion.9 Using MeOTf, one can doubly methylate 1 to give
high yields of both [3]OTf and Me2S (eq 5).
Inorganic Chemistry, Vol. 45, No. 2, 2006 683

Smith et al.
Table 4. Details of Data Collection and Structure Refinement for 1, [1H]BArF4, [2H]OMs, MoSe2(dmpe)2, [MoS(OTf)(dmpe)2]OTfa
1
[1H]BArF
[2H]OMs
MoSe2(dmpe)2
[MoS(OTf)(dmpe)2]OTf
4
formula‚solvate
cryst size (mm3)
space group
a (Å)
b (Å)
c (Å)
C12H32MoP4S2
0.11 × 0.16 × 0.3
P21/c
13.214(6)
12.385(5)
13.228(6)
90
92.733(7)
90
2162.6(16)
4
1.767
1.355
11336/3933
0/295
1.034
C44H45BF24MoP4S2
0.16 × 0.24 × 0.40
Pbca
19.531(4)
22.835(4)
24.407(5)
90
90
90
10885(4)
8
1.615
C15H39NO3P4S3W‚MeCN
C12H32MoP4 Se2
0.12 × 0.16 × 0.41
P21/n
8.801(2)
12.854(3)
9.771(3)
90
93.393(5)
90
1103.4(5)
2
1.668
4.172
10593/2731
284/258
1.041
C14H32O6F6MoP4S3
0.30 × 0.29 × 0.04
P21/c
19.195(2)
17.8704(19)
17.7886(19)
90
106.791(6)
90
5841.8(11)
8
1.652
0.948
139266/14956
1776/1076
1.024
0.14 × 0.22 × 0.26
Pnma
12.622(4)
20.482(6)
10.506(3)
90
90
90
2716.0(14)
4
1.676
4.735
20377/2568
0/142
R (deg)
â (deg)
γ (deg)
V (Å3)
Z
D
calcd (mg m-3
)
µ(Mo ΚR) (mm-1
)
0.550
reflns measd/indep
restraints/params
GOF
83270/10034
738/841
1.062
1.360
Rint
0.0297
0.0989
0.0441
0.0277
0.0422
R1 [I > 2σ(I)]
(all data)
0.0272 (0.0415)
0.0557 (0.0986)
0.0276 (0.0432)
0.0247 (0.0341)
0.0368 (0.0504)
wR2 [I > 2σ(I)]
(all data)
0.0645 (0.0699)
0.1440 (0.1602)
0.0683 (0.1001)
0.0610 (0.0640)
0.0917 (0.1007)
max peak/hole
0.618/-0.434
0.909/-0.559
0.678/-1.227
0.328/-0.446
1.328/-1.375
(e-/Å3)
2
2
2
a R1 ) ∑||Fo| - |Fc||/∑|Fo|; wR2 ) {∑[w(Fo - Fc )2]/∑[w(Fo )2]}1/2
.
The slow proton transfer in [MoS(SH)(dmpe)2]+ is con-
sistent with a substantial energetic barrier associated with
rehybridization of L4Mo(dS)2 into [L4Mo(tS)(-SH)]+.
Structural studies bear this out; protonation causes the two
ModS bond lengths of 2.24 Å to diverge to 2.06 and 2.57
Å, characteristic of triple and single bonds, respectively (eq
6).
In [MoS(SMe)(Me8[16]-aneS4)]+, the Mo-S distances are
also divergent at 2.14 and 2.44 Å vs ∼2.24 Å in the parent
trans-MoS2(Me8[16]-aneS4).9 Kubas has reported an Mo-
SH distance of 2.596(3) Å in the alkylidyne complex trans-
Mo(SH)(tCNMe2)(dppe)2.34 In [Mo(SH)O(Me8[16]-aneS4)]+,
the Mo-SH distance is 2.49 Å.35
Protonolysis and Methylation Reactions. trans-MoS2-
(dmpe)2 undergoes sequential double protonation or double
methylation at the same S atom. In a related finding, Bendix
and Bøgevig reported that MO2(dppe)2 (M ) Mo, W) reacts
with excess acid to give [MO(X)(dppe)2]+ (X ) Cl, Br, I,
OMe).29 The second protonation of [MoS(SH)(dmpe)2]+
occurs at SH. The sequential alkylation and protonation at a
sulfido ligand is a potentially useful method for the synthesis
of thiols. The advantages to the use of MoS2L4 complexes
for this transformation are that thioether formation is
noncompetitive and the spent molybdenum reagent can be
recycled. The reactivity of MoS2(dmpe)2 toward common
alkylating agents is, however, too low for practical use.
Presently, however, MoS2(dmpe)2 is insufficiently reactive
toward common alkylating agents.
Figure 6. Space-filling model of MoS2(dmpe)2.
In contrast to the apparent instability of [MoS(SH)(Me8-
[16]-aneS4)]+,25 [MoS(SH)(dmpe)2]+ is stable with respect
to loss of H2S. This enhanced stability may reflect the steric
protection afforded by the four P-Me groups that project
above and below the MoP4 plane (Figure 6).
[MoS(dmpe)2]2+, an Unusual 16e, π Acid. 16e fragments
have played useful roles in coordination chemistry, e.g., [Ru-
(NH3)5]2+, [CpFe(CO)2]+, Mo(CO)5, etc. These metal elec-
trophiles are, however, all π bases reflecting their d6
configuration. In contrast, [MS(dmpe)2]2+ (M ) Mo, W) is
a π acid, which suggests that it will be a novel platform for
examining π-basic ligands. The unusual character of [MS-
(dmpe)2]2+ is illustrated by its ability to accept S2- to re-
form MdE bonds, i.e., M-OTf+ f MdS. Halide complexes
can often be converted to the corresponding SH derivatives,19
i.e., step i in eq 7, but their further conversion into terminal
sulfido ligands remains otherwise unprecedented.
SH-
-H+
[LnM-X]+
8 [LnM-SH]+
8 LnMdS
(7)
i
ii
Experimental Section
(33) Brunner, H.; Gehart, G.; Meier, W.; Wachter, J.; Nuber, B. J.
Organomet. Chem. 1993, 454, 117-122.
General Procedures. As previously described,22 synthetic reac-
tions were conducted under a flowing N2 atmosphere. The following
reagents were synthesized by published procedures: (NH4)2MoS4
(34) Luo, X. L.; Kubas, G. J.; Burns, C. J.; Butcher, R. J. Organometallics
1995, 14, 3370-3376.
(35) DeSimone, R. E.; Glick, M. D. Inorg. Chem. 1978, 17, 3574-3577.
684 Inorganic Chemistry, Vol. 45, No. 2, 2006

MS2(Me2PC2H4PMe2)2 (M ) Mo, W)
and (NH4)2WS4,36 NaBArF4 and H(Et2O)2BArF ,37 (PPh4)2MoSe4,38
trans-[MoS(SH)(dmpe)2]OMs ([1H]OMs). A solution of 0.158
g (0.343 mmol) of 1 in 13 mL of MeCN was treated with 23 µL
(0.343 mmol) of HOMs. The resulting bright orange solution was
concentrated to ca. 5 mL, and 15 mL of Et2O was added to
precipitate an orange solid, which was washed with 20 mL of Et2O.
Yield: 0.178 g (93%). 1H NMR (CD3CN): δ 2.75 (s, 3H, MeSO3),
2.23 (t, 8H, CH2, JPH ) 7.5 Hz), 1.95 (s, 12H, CH3), 1.61 (s, 12H,
CH3), -4.08 (p, 1H, SH, JPH ) 13 Hz). 31P{1H} NMR (MeCN-
d3): δ 31.9. IR (KBr, cm-1): νSH ) 2562 (w). UV-vis (MeCN):
λmax (ꢀ) ) 756 (47), 430 (2590), 383 nm (2050 L mol-1 cm-1).
Anal. Calcd for C13H36MoO3P4S3 (found): C, 28.06 (27.94); H,
6.52 (6.46).
4
and MoS2(PMe3)4.22 Electronic and IR spectra were recorded on
Varian Cary 50Bio and Mattson Infinity Gold FTIR spectropho-
tometers, respectively.
trans-MoS2(dmpe)2 (1). A slurry of 0.500 g (1.92 mmol) of
(NH4)2MoS4 in 10 mL of MeCN was treated with 0.642 mL (3.85
mmol) of dmpe. The solution was frozen, evacuated, and then
treated with 0.7 mL (6.77 mmol) of PMe3, which was condensed
onto the frozen slurry. Note: the low solubility of (NH4)2MoS4 in
MeCN, along with the prompt freezing of the solution with dmpe
limits desulfurization by the chelating phosphine. The mixture was
allowed to warm to room temperature and stirred for 4 h. After the
resulting green slurry was purged for 1 h, solvent was removed
via a cannula and the microcrystals were washed with ca. 10 mL
of MeCN. X-ray-quality crystals were grown by cooling the mother
liquor at -20 °C. Yield: 300 mg (34%). An additional 130 mg of
product can be obtained by cooling the washings to -20 °C for a
combined yield of 430 mg (50%). 1H NMR (C6D6): δ 1.56 (t, 8H,
CH2, JPH ) 7 Hz), 1.53 (s, 24H, CH3). 31P{1H} (C6D6): δ 22. IR
(KBr, cm-1): νMoS ) 414 (s). ESI(+) MS (MeCN): m/z ) 462.9
[MoS2(dmpe)2+]. UV-vis (MeCN): λmax (ꢀ) ) 756 (47), 646 (85),
559 (108), 376 (26 800), 254 (12 160), 228 nm (17 820 L mol-1
cm-1). Anal. Calcd for C12H32MoP4S2 (found): C, 31.31 (31.29,
31.31); H, 7.01 (7.12, 7.01); Mo, 20.84 (20.90); P, 26.91 (25.34);
S, 13.93 (14.21). The basicity of 1 was approximated by the
following NMR experiment: ∼20 mg of 1 was treated with a
solution of ∼7 mg of NH4PF6 in 1 mL of CD3CN to give an orange
solution, showing signals assigned (see below) to [1H]+. The
addition of ∼6 µL of Et3N to this solution restored the green color
trans-[MoS(SH)(dmpe)2]OTf ([1H]OTf). To a solution of 0.353
g (0.767 mmol) of 1 in 30 mL of Et2O was added a solution of 68
µL (0.767 mmol) of HOTf in 10 mL of Et2O. The resulting bright
yellow solid was collected and washed with 10 mL of Et2O.
1
Yield: 0.416 g (89%). H NMR (CD3CN): δ 2.23 (t, 8H, CH2,
JPH ) 7.5 Hz), 1.95 (s, 12H, CH3), 1.61 (s, 12H, CH3), -4.08 (p,
1H, SH, JPH ) 13 Hz). 31P{1H} NMR (MeCN-d3): δ 31.9. Anal.
Calcd for C13H33F3MoO3P4S3 (found): C, 25.58 (25.72); H, 5.45
(5.48).
trans-[MoS(SH)(dmpe)2]BArF ([1H]BArF ). To a solution of
4
4
0.175 g (0.38 mmol) of 1 in 20 mL of Et2O was added a solution
of 0.382 g (0.38 mmol) of H(Et2O)2BArF in 8 mL of Et2O. The
4
volume of the resulting rust-colored solution was concentrated to
ca. 10 mL under vacuum. Using a cannula, solvent was removed
from the rust-colored solid. X-ray-quality crystals were grown from
1
a saturated Et2O solution at -20 °C. Yield: 0.300 g (60%). H
NMR (CD3CN): δ 7.68 (s, 12H, Ph), 7.66 (s, 4H, Ph), 2.09 (s,
8H, CH2), 1.70 (s, 24H, CH3), -4.08 (s, 1H, SH). 31P{1H} NMR
(CD3CN): δ 30. UV-vis (MeCN): λmax (ꢀ) ) 704 (77), 376 nm
(2670 L mol-1 cm-1). Analysis of chemical shifts established Keq
) 2.3 at ca. 25 °C in a CD3CN solution. The equilibrium constant
was determined by the percent shift of the 31P NMR signal versus
that for 1 and [1H]+.
1
and H NMR signals characteristic of 1.
trans-WS2(dmpe)2 (2). A slurry of 0.300 g (0.862 mmol) of
(NH4)2WS4 in 10 mL of MeCN was treated with 0.432 mL (2.59
mmol) of dmpe. After stirring for 1 h, the resulting purple solution
was filtered, and the solvent was removed in vacuo. The solid was
extracted with 10 mL of benzene; this extract was filtered, and the
solvent was removed in vacuo. The solid was recrystallized by
dissolution in a minimum amount of MeCN at room temperature
followed by cooling to -20 °C for 18 h to afford purple
trans-[WS(SH)(dmpe)2]OMs ([2H]OMs). To a deep purple
solution of 0.078 g (0.142 mmol) of 2 in 5 mL of MeCN was added
9.2 µL (0.142 mmol) of HOMs. The addition of 15 mL of Et2O to
the resulting neon-green solution gave a bright-green precipitate.
After removal of the solvent using a cannula, the solid was washed
with 20 mL of Et2O. X-ray-quality crystals were grown by
dissolving 0.070 g of the solid in 3 mL of MeCN and then adding
6 mL of Et2O, filtering, and storing the mixture at -20 °C overnight.
Yield: 0.082 g (90%). 1H NMR (CD3CN): δ 2.40 (s, 3H, MeSO3),
2.12 (t, 8H, CH2, JPH ) 7 Hz), 1.88 (s, 24H, CH3), -3.7 (1H,
quintet). 31P{1H} NMR (MeCN-d3): δ 8.4 [s and d, J(31P,183W) )
251 Hz]. The relative pKa of 1 vs [2H]OMs was determined in a
competition experiment in a sealable NMR tube fitted with a Teflon
screwcap. In a typical experiment, an equimolar mixture of 0.005
g (0.0109 mmol) of 1 and 0.007 g (0.0109 mmol) of the competing
acid was dissolved in ∼0.8 mL of CD3CN. The equilibrium constant
was obtained by the percent shift of 31P NMR peaks from 1 toward
[1H]+. The analogous trans-[WS(SH)(dmpe)2]BArF ([2H]BArF )
1
microcrystals. Yield: 0.042 g (0.175; 9%). H NMR (C6D6): δ
1.65 (s, 24H, CH3), 1.50 (t, 8H, CH2, JPH ) 6.5 Hz). 31P{1H} NMR
(C6D6): δ -0.5 [s and d, J(31P,183W) ) 264.2 Hz]. Anal. Calcd
for C12H32P4S2W (found): C, 26.29 (26.52); H, 5.88 (5.77).
trans-MoSe2(dmpe)2. To a suspension of 0.300 g (0.275 mmol)
of (PPh4)2MoSe4 in 7 mL of MeCN was added 0.058 g (0.551
mmol) of NH4BF4. The solution was frozen, evacuated, and then
treated with 0.2 mL (1.93 mmol) of PMe3, which was condensed
onto the frozen slurry. The mixture was allowed to warm to room
temperature and stirred for 10 min, at which point a brown solution
forms and 92 µL (0.551 mmol) of dmpe was added. The solution
was stirred under an N2 purge for 20 min. The solvent was removed
in vacuo, and the solid was extracted with 20 mL of Et2O and
filtered. The solvent was removed in vacuo, and the solid was
recrystallized from a saturated MeCN solution at -20 °C. X-ray-
quality crystals were grown by cooling a saturated MeCN solution
4
4
was prepared similarly by treatment of a suspension of 0.070 g
(0.128 mmol) of 2 in 10 mL of Et2O with a solution of 0.110 g
(0.128 mmol) of H(Et2O)2BArF4 in 10 mL of Et2O. Concentration
of the resulting homogeneous brown-green solution to ca. 10 mL
(0.035 g) precipitated a light-green solid, which was washed with
hexane. An additional 0.030 g was isolated upon cooling of the
filtrate to -20 °C for a total yield of 0.065 g (36%). Anal. Calcd
for C44H45BF24P4S2W (found): C, 37.42 (37.57); H, 3.21 (3.12).
trans-[MoS(OTf)(dmpe)2]OTf ([3]OTf). To a deep-green solu-
tion of 0.091 g (0.198 mmol) of 1 in 14 mL of MeCN was added
1
to -20 °C. Yield: 0.038 g (25%). H NMR (C6D6): δ 1.61 (s,
24H, CH3), 1.58 (t, 8H, CH2). 31P{1H} NMR (C6D6): δ 19.0 (s).
ESI(+) MS (MeCN): m/z ) 555.1 [MoSe2(dmpe)2+]. Anal. Calcd
for C12H32MoP4Se2 (found): C, 26.01 (25.79); H, 5.82 (5.44).
(36) McDonald, J. W.; Friesen, G. D.; Rosenhein, L. D.; Newton, W. E.
Inorg. Chim. Acta 1983, 72, 205-210.
(37) Reger, D. L.; Little, C. A.; Lamba, J. J. S.; Brown, K. J. Inorg. Synth.
2004, 34, 5-8.
(38) Howard, K. E.; Rauchfuss, T. B.; Wilson, S. R. Inorg. Chem. 1988,
27, 1710-1716.
Inorganic Chemistry, Vol. 45, No. 2, 2006 685

Smith et al.
40 µL (0.415 mmol) of HOTf in 10 mL of MeCN over the course
of 1 min. During the addition, the solution quickly became orange
followed by pale green. The solution was stirred under a slow N2
purge for 30 min and then concentrated to ca. 2 mL. The addition
of 8 mL of Et2O precipitated a green oil. The solvent was decanted
via a cannula, and the oil was washed with 20 mL of Et2O. Drying
under vacuum yielded a light-green solid. X-ray-quality crystals
were grown by vapor diffusion of hexane into a dichloromethane
1.6 (m, 8H, CH2), 1.44 (s, 12H, CH3), 1.23 (s, 12H, CH3). 31P{1H}
NMR (C6D6): δ 24.8. ESI(+) MS (MeCN): m/z ) 447.3 [MoSO-
(dmpe)2+]. An analogous experiment using 50 µL of Et3N and PPh4-
1
TeH39 afforded a dark-red solid. H NMR (C6D6): δ 1.8 (s, 12H,
CH3), 1.73 (m, 8H, CH2), 1.5 (s, 12H, CH3). 31P{1H} NMR
(C6D6): δ 16. ESI(+) MS (MeCN): m/z ) 558.1 [MoSTe-
(dmpe)2+].
trans-[MoS(SMe)(dmpe)2]I ([1Me]I). To a solution of 0.250 g
(0.543 mmol) of 1 in 10 mL of THF was added 37.3 µL (0.598
mmol) of MeI. The solution immediately assumed a dark-orange
color, and orange microcrystals precipitated. After removal of the
solvent via a cannula, the solid was washed with 20 mL of Et2O.
1
solution. Yield: 0.130 g (90%). H NMR (CD3CN): δ 2.42 (s,
8H, CH2), 2.16 (s, 12H, CH3), 1.63 (s, 12H, CH3). 31P{1H} NMR
(CD3CN): δ 37.5. 19F NMR (CD3CN): δ -79.7. 19F NMR (CD2-
Cl2): δ -78.0, -79.7. 1H NMR (CD2Cl2): δ 2.43 (br m, 8H, CH2),
2.13 (s, 12H, CH3), 1.82 (s, 12H, CH3). 31P{1H} NMR (CD2Cl2):
δ 37.0. 19F NMR (CD2Cl2): δ -78.0, -79.7. ESI(+) MS
(MeCN): m/z ) 579 [MoS(OTf)(dmpe)2+], 235.5 [MoS(MeCN)-
(dmpe)2+], 215.0 [MoS(dmpe)22+]. Anal. Calcd for C14H32F6-
MoO6P4S3 (found): C, 23.15 (23.43); H, 4.44 (4.32).
1
Yield: 0.304 g (93%). H NMR (CD3CN): δ 2.27 (t, 8H, CH2,
JPH ) 7 Hz), 1.89 (s, 12H, CH3), 1.68 (s, 12H, CH3), 1.39 (quintet,
3H, SMe, JPH ∼ 1 Hz). 31P{1H} NMR (CD3CN): δ 29.3. UV-vis
(MeCN): λmax (ꢀ) ) 438 (3280), 376 (3410), 244 nm (19 900 L
mol-1 cm-1). Anal. Calcd for C13H35IMoP4S2 (found): C, 25.92
(26.19); H, 5.86 (5.47).
(i) Conversion of [3]OTf into 1. in an NMR tube with a Teflon
screwcap, a frozen slurry of 19 mg (0.041 mmol) of 1 and 1 mL of
CD3CN was treated with 13 µL (0.151 mmol) of HOTf. The frozen
mixture was evacuated, sealed, and examined by NMR spectros-
copy. The reaction was complete upon warming to room temper-
ature as shown by 1H and 31P NMR spectroscopies, which showed
the presence of H2S and [MoS(CD3CN)(dmpe)2]+. The solution
was then refrozen and treated with 30 µL of Et3N. The frozen
mixture was evacuated and allowed to warm to ambient temper-
atures. 1H and 31P NMR measures showed that the signals for [1H]+
formed over the course of 5 h.
(ii) Reaction of 1 with 2 equiv of MeOTf. The addition of 0.98
mL of a 0.0884 M solution of MeOTf in CD3CN was added to
0.020 g (0.043 mmol) of 1. The 1H and 31P NMR spectra indicated
clean conversion to [3]OTf. The volatile components were vacuum
transferred from the light-green solution into a sealable NMR tube.
1H NMR analysis showed the formation of Me2S.
Crystallography. Crystals of 1, MoSe2(dmpe)2, [1H]BArF , [2H]-
4
OMs, and [MoS(OTf)(dmpe)2]OTf were mounted on thin glass
fibers by using oil (Paratone-N, Exxon) before being transferred
to the diffractometer. Data were collected on a Siemens CCD
automated diffractometer at 193 K. Data processing was performed
with the integrated program package SHELXTL.40 Selected aspects
of the refinement are discussed below.
(i) MoS2(dmpe)2 (1). Systematic conditions suggested the
unambiguous space group, and the structure was phased by direct
methods. The proposed model imposed inversion symmetry on the
two independent Mo sites and includes one chelate ligand disordered
over two sites for Mo1. Chemically similar bond lengths and bond
angles for disordered sites were restrained equivalent values with
effective standard deviations (esd’s) of 0.01 and 0.02 Å, respec-
tively. Displacement parameters for overlapping disordered sites
were restrained to be similar (esd 0.01). Methyl H-atom positions
were optimized by rotation about P-C bonds with idealized C-H,
C...H, and H...H distances. The remaining H atoms were included
as riding idealized contributors. Methyl H-atom U’s were assigned
as 1.5 times Ueq of the adjacent atom; the remaining H-atom U’s
were assigned as 1.2 times the adjacent Ueq. The space group choice
was confirmed by successful convergence of the full-matrix least-
squares refinement on F 2. The highest peaks in the final difference
Fourier map were near S1 and S2; the final map had no other
significant features. A final analysis of the variance between
observed and calculated structure factors showed little dependence
on amplitude or resolution.
Generation of MeSPr from 1. To a solution of 0.150 g (0.326
mmol) of 1 in 15 mL of THF was added 0.318 mL (0.326 mmol)
of PrI. The solution darkened to an orange-brown color and was
allowed to stir for 16 h while protected from light. The resulting
dark-orange suspension was concentrated to ca. 5 mL, and the solid
was filtered off and washed with 40 mL of Et2O. Yield: 0.184 g
1
(0.293 mmol, 90%). H NMR (CD3CN): δ 2.26 (t, 8H), 1.88 (s,
12H), 1.79 (t, 2H), 1.68 (s, 12H), 1.07 (m, 2H), 0.65 (t, 3H). 31P
NMR (CD3CN): δ 28.7. The iodide was converted to the BArF -
4
salt by the addition of 0.260 g (0.293 mmol) of NaBArF to a
4
solution of the iodide salt in 10 mL of MeCN. The mixture was
stirred for 10 min before being evaporated. The solid was extracted
into 30 mL of Et2O and filtered. Evaporation of the extract produced
(ii) MoSe2(dmpe)2. Systematic conditions suggested the unam-
biguous space group, and the structure was phased by direct
methods. The proposed model imposed inversion symmetry on
coordinated Se and dmpe ligands disordered over three sites. Owing
to high correlation coefficients, the C1-C2 bond length was
idealized using an esd of 0.01 Å, and the chemically similar
disordered ligands were restrained to similar geometry (esd 0.01).
Anisotropic displacement parameters for superimposed sites were
restrained to have similar rigid-bond values. Methyl H-atom
positions were optimized by rotation about R-C bonds with
idealized C-H, R‚‚‚H, and H‚‚‚H distances. The remaining H atoms
were included as riding idealized contributors. Methyl H-atom U’s
were assigned as 1.5 times Ueq of the adjacent atom; the remaining
H-atom U’s were assigned as 1.2 times the adjacent Ueq. The space
1
an orange powder. Yield: 0.360 g (0.264 mmol, 90%). H NMR
(CD3CN): δ 7.7 (m, 12H, BArF ), 2.29 (s, 8H), 1.91 (s, 12H), 1.83
4
(t, 2H), 1.71 (s, 12H), 1.11 (m, 2H), 0.69 (t, 3H). 31P NMR (CD3-
CN): δ 27.7. An NMR tube was charged with 0.020 g of [MoS-
(SPr)(dmpe)2]BArF4 and 0.5 mL of CD3CN followed by 0.165 mL
1
of 0.0884 M MeOTf in CD3CN. H NMR (CD3CN): δ 7.7 (m,
12H, BArF ), 2.80 (s, 3H), 2.47 (s, 8H), 2.19 (s, 12H), 1.79 (m,
4
2H), 1.67 (s, 12H), 1.05 (m, 5H). 31P NMR (CD3CN): δ 37.5.
Generation of trans-MoS(E)(dmpe)2 (E ) O, Te). To a light-
green solution of 0.070 g (0.096 mmol) of [3]OTf in 5 mL of MeCN
was added 0.193 mL of a 1.0 M solution of Bu4NOH in MeOH.
The solution quickly turned deep purple and then purple/orange.
The solvent was removed under reduced pressure to dryness. The
addition of 20 mL of Et2O followed by filtration resulted in a deep-
orange solution. Removal of the solvent to dryness produced an
orange oil contaminated by Bu4N+ salts. 1H NMR (C6D6): δ 1.8-
(39) Houser, E. J.; Rauchfuss, T. B.; Wilson, S. R. Inorg. Chem. 1993, 32,
4069-4076.
(40) Sheldrick, G. M. SHELXTL; Bruker AXS: Madison, WI, 1998.
686 Inorganic Chemistry, Vol. 45, No. 2, 2006

MS2(Me2PC2H4PMe2)2 (M ) Mo, W)
group choice was confirmed by successful convergence of the full-
matrix least-squares refinement on F 2. The highest peaks in the
final difference Fourier map were near C16, Se1, and Se2; the final
map had no other significant features. A final analysis of the
variance between observed and calculated structure factors showed
no dependence on the amplitude or resolution.
(v) [MoS(OTf)(dmpe)2]OTf. Systematic conditions suggested
the unambiguous space group, and the structure was phased by
direct methods. The proposed model included disordered sites for
one of two cations and both anions. The model for the disordered
cation included two sites for each chelate ligand and three sites for
the axial triflate ligand. Each disordered anion was refined over
two sites. Chemically equivalent 1,2 and 1,3 distances for disordered
sites were restrained to equal values using esd’s of 0.02 and 0.03
Å, respectively. The triflate anions were idealized (esd 0.02 Å).
Rigid-bond restraints (esd 0.01) were imposed on displacement
parameters for disordered sites. Disordered sites separated by less
than 1.7 Å were further restrained to have similar values. Methyl
H-atom positions, R-CH3, were optimized by rotation about R-C
bonds with idealized C-H, R-H, and H-H distances. The
remaining H atoms were included as riding idealized contributors.
Methyl H-atom U’s were assigned as 1.5 times Ueq of the adjacent
atom; the remaining H-atom U’s were assigned as 1.2 times the
adjacent Ueq. The space group choice was confirmed by successful
convergence of the full-matrix least-squares refinement on F 2. The
highest peaks in the final difference Fourier map were in the vicinity
of Mo atoms and the disordered anions; the final map had no other
significant features. A final analysis of the variance between
observed and calculated structure factors showed little dependence
on the amplitude or resolution.
(iii) [MoS(SH)(dmpe)2]BArF4 ([1H]BArF ). Systematic condi-
4
tions suggested the unambiguous space group, and the structure
was solved by direct methods. Inversion symmetry was imposed
on the proposed model, and the Mo atom was disordered above
and below the base plane of the complex. Six CF3 groups for the
anion were disordered about the mirror plane. Methyl H-atom U’s
were assigned as 1.5 times Ueq of the corresponding methyl C atom.
The remaining H atoms were included as riding idealized contribu-
tors with U’s assigned as 1.2 times Ueq of the adjacent non-H atoms.
The space group choice was confirmed by successful convergence
of the full-matrix least-squares refinement on F 2. The highest peaks
in the final difference Fourier map were near S1 and S2; the final
map had no other significant features. A final analysis of the
variance between observed and calculated structure factors showed
no dependence on the amplitude or resolution.
(iv) [WS(SH)(dmpe)2]OMs ([2H]OMs). Systematic conditions
suggested the ambiguous space group, and the structure was solved
by direct methods. Inversion symmetry was imposed on the
proposed model, and the W atom was disordered above and below
the base plane of the complex. H atoms for the MeCN solvate were
disordered about the mirror plane. MeCN and other Me-P H-atom
positions of the mirror were optimized by rotation about R-C bonds
with idealized C-H, R‚‚‚H, and H‚‚‚H distances. Methyl H-atom
U’s were assigned as 1.5 times Ueq of the corresponding methyl C
atom. The remaining H atoms were included as riding idealized
contributors with U’s assigned as 1.2 times Ueq of the adjacent
non-H atoms. The space group choice was confirmed by successful
convergence of the full-matrix least-squares refinement on F 2. The
highest peak in the final difference Fourier map was near S2; the
final map had no other significant features. A final analysis of the
variance between observed and calculated structure factors showed
no dependence on the amplitude or resolution.
Acknowledgment. This research was supported by the
National Science Foundation and the Department of Energy.
We thank Cameron Spahn for his help with refinements of
the crystallographic data.
Supporting Information Available: X-ray crystallographic data
for of 1, MoSe2(dmpe)2, [1H]BArF , [2H]OMs, and [MoS(OTf)-
4
(dmpe)2]OTf. This material is available free of charge via the
Internet at http//pubs.acs.org.
IC051443C
Inorganic Chemistry, Vol. 45, No. 2, 2006 687