Carbon-sulfur bond cleavage of S2CPR3 ligands in dinuclear complexes promoted by reduction and protonation

Article abstract of DOI:10.1021/om971074v

Complexes [Mn₂(CO)₆(μ-S₂CPR₃)] (R = Cy (1a), Prⁱ (1b)) are reduced with Na[Hg] in THF to afford the anions [Mn₂(CO)₆(μ-S₂CPR₃)]^2- (2a,b), which g

Full text of DOI:10.1021/om971074v

3448
Organometallics 1998, 17, 3448-3453
Ca r bon -Su lfu r Bon d Clea va ge of S2CP R3 Liga n d s in
Din u clea r Com p lexes P r om oted by Red u ction a n d
P r oton a tion
J ing Li, Daniel Miguel,*,† M. Dolores Morales, and V´ıctor Riera
Departamento de Quı´mica Orga´nica e Inorga´nica, IUQOEM-Unidad Asociada del CSIC,
Universidad de Oviedo, E-33071 Oviedo, Spain
Santiago Garc´ıa-Granda
Departamento de Quı´mica Fı´sica y Analı´tica, Universidad de Oviedo, 33071 Oviedo, Spain
Received December 8, 1997
Complexes [Mn2(CO)6(µ-S2CPR3)] (R ) Cy (1a ), Pri (1b)) are reduced with Na[Hg] in THF
to afford the anions [Mn2(CO)6(µ-S2CPR3)]2- (2a ,b), which give neutral unstable [Mn2(CO)6-
(µ-SH){µ-SC(H)PR3}(NH3)] (3a ,b) upon protonation with excess NH4PF6. The NH3 ligand
of 3a ,b is readily replaced by PEt3 to obtain [Mn2(CO)6(µ-SH){µ-SC(H)PR3}(PEt3)] (5a ,b) as
stable crystalline solids, which have been isolated and characterized. The same reduction/
protonation sequence when applied to the dirhenium analogue [Re2(CO)6(µ-S2CPCy3)] (1c)
affords stable crystalline [Re2(CO)6(µ-SH){µ-SC(H)PCy3}(NH3)] (6). An X-ray determination
revealed that 6 contains one bridging SH- and the novel ligand Cy3PC(H)S- which is bonded
as µ2-η1(S);η2(C,S′), donating 5e to the metals. Both bridging ligands are produced from the
cleavage of one C-S bond of the starting S2CPR3 during the reduction/protonation process,
which can be regarded globally as hydrogenolysis of the C-S bond. Additionally, the Re-
Re bond is also cleaved during the process. As their dimanganese analogues, 6 undergo
easy substitution of NH3 by PEt3 to give [Re2(CO)6(µ-SH){µ-SC(H)PCy3}(PEt3)] (7). Com-
parison of the spectroscopic data indicate that both series of compounds are isostructural,
with the only difference being the higher stability of the dirhenium complexes when compared
to those of dimanganese.
In tr od u ction
complexes,2c,d and the cleavage of C-S bonds of thiophene
has been attained within the coordination sphere of the
metal.3
The cleavage of carbon-sulfur bonds are of primary
importance in the process of hydrodesulfurization of
crude oils (HDS).1 It is well-known that, in this process,
compounds containing carbon-sulfur multiple bonds,
such as thiophene and its derivatives, are more difficult
to desulfurate than compounds which contain C-S with
a bond of order 1, such as thiols or thioethers. In
practice, the HDS process requires the use of hetero-
geneous catalysts which contain molybdenum and other
transition-metal oxides and sulfides. This has stimu-
lated many studies of the coordination of thiophenes to
transition metals, both on surfaces2a-c and in molecular
We have been interested in recent years in the
chemistry of mono- and dinuclear carbonyl complexes
containing S2CPR3 ligands. These compounds display
a wide range of reactions depending on the bonding
mode of the ligands. Thus, mononuclear complexes
containing the ligands as a η2(S,S′) chelate4 undergo
hydride addition to the central carbon;5 while those in
which the ligands are bonded as η3(S,C,S′) pseudoallyl
(3) See, for example: (a) Paneque, M.; Taboada, S.; Carmona, E.
Organometallics 1996, 15, 2678. (b) Bleeke, J . R.; Ortwerth, M. F.;
Rohde, A. M. Organometallics 1995, 14, 2813. (c) Feng, Q.; Rauchfuss,
T. B.; Wilson, S. R. Organometallics 1995, 14, 2923. (d) Krautscheid,
H.; Feng, Q.; Rauchfuss, T. B. Organometallics 1993, 12, 3273. (e)
J ones, W. D.; Chin, R. M. J . Am. Chem. Soc. 1994, 116, 198. (f) Ogilvy,
A. E.; Skaugset, A. E.; Rauchfuss, T. B. Organometallics 1989, 8, 2739.
(g) Dong, L.; Duckett, S. B.; Ohman, K. F.; J ones, W. D. J . Am. Chem.
Soc. 1992, 114, 151. (h) Bianchini, C.; Meli, A.; Peruzzini, M.; Vizza,
F.; Frediani, P.; Herrera, V.; Sa´nchez-Delgado, R. A. J . Am. Chem.
Soc. 1993, 115, 2731. (i) Chen, J .; Young, V. G., J r.; Angelici, R. J .
Organometallics 1996, 15, 2727. (j) Chen, J .; Angelici, R. J . Organo-
metallics 1989, 8, 2277. (k) Chen, J .; Daniels, L. M.; Angelici, R. J . J .
Am. Chem. Soc. 1990, 112, 199. (l) Choi, M. G.; Daniels, L. M.; Angelici,
R. J . Inorg. Chem. 1991, 30, 3647. (m) Spies, G. H.; Angelici, R. J .
Organometallics 1987, 6, 1897. (n) Hachgenei, J . W.; Angelici, R. J . J .
Organomet. Chem. 1988, 355, 359.
† Present address: Departamento de Quı´mica Inorga´nica, Facultad
de Ciencias, Universidad de Valladolid, 47071 Valladolid, Spain. E-mail
dmsj@cpd.uva.es.
(1) (a) Gates, B. C.; Katzer, J . R.; Schuit, G. C. A. Chemistry of
Catalytic Processes; McGraw-Hill: New York, 1979. (b) J ones, W. D.;
Chin, R. M. J . Am. Chem. Soc. 1994, 116, 198. (c) Angelici, R. J . Acc.
Chem. Res. 1988, 21, 387. (d) Rakowski-Dubois, M. Chem. Rev. 1989,
89, 1. (e) Rauchfuss, T. B. Prog. Inorg. Chem. 1991, 39, 259. (f)
Bianchini, C.; J ime´nez, A.; Meli, A.; Vizza, F. Organometallics 1995,
14, 4858.
(2) (a) Wiegand, B. C.; Friend, C. M. Chem. Rev. 1992, 92, 491. (b)
Calhorda, M. J .; Hoffmann, R.; Friend, C. M. J . Am. Chem. Soc. 1990,
112, 50. (c) Wiegand, B. C.; Napier, M. E.; Friend, C. M.; Uvdal, P. J .
Am. Chem. Soc. 1996, 118, 2962. (d) Ruette, F.; Valencia, N.; Sa´nchez-
Delgado, R. J . Am. Chem. Soc. 1989, 111, 40. (e) Harris, S. Organo-
metallics 1994, 13, 2628.
(4) Miguel, D.; Riera, V.; Miguel, J . A.; Bois, C.; Philoche-Levisalles,
M.; J eannin, Y. J . Chem. Soc. Dalton Trans. 1987, 2875.
(5) Miguel, D.; Miguel, J . A.; Riera, V.; Sola´ns, X. Angew. Chem.,
Int. Ed. Engl. 1989, 28, 1014. Barrado, G.; Miguel, D.; Miguel, J . A.;
Riera, V.; Sola´ns, X. Chem. Ber. 1996, 129, 1535.
S0276-7333(97)01074-1 CCC: $15.00 © 1998 American Chemical Society
Publication on Web 07/07/1998

C-S Bond Cleavage of S2CPR3 Ligands
Organometallics, Vol. 17, No. 16, 1998 3449
Sch em e 1
are able to add electrophiles to one of the sulfur atoms.6
In binuclear complexes containing η2(S,S′);η3(S,C,S′)
and halogen bridges,7 it is possible to create a metal-
metal bond by reduction with sodium amalgam, afford-
ing anions capable of undergoing addition of electro-
philes to the metals.8 Finally, dinuclear complexes
containing η2(S,S′);η3(S,C,S′) bridges spanning a direct
metal-to-metal bond9 undergo hydride addition on the
M-M bond to afford hydrido-bridged carbonylmetalate
anions.10 Subsequent addition of alkyl halides leads to
neutral complexes containing trialkylphosphonio-
dithioesters, while the reaction with CS2 produces
anionic complexes containing tralkylphosphonioethene-
trithiolate bridges formed through desulfurization and
C-C coupling.11
As an extension of these studies, we have found that
the reduction of S2CPR3 complexes containing metal-
metal bonds, followed by protonation, affords stable
neutral species containing new ligands produced through
cleavage of one C-S bond, thus splitting the starting
S2CPR3 ligand into two parts which remain both as
bridging ligands in the final complex: one hydrogeno-
sulfido SH- and one trialkylphosphoniothiolateylide
R3PC(H)S- attached as η2(C,S). Thus, the two-electron
reduction, followed by addition of two protons, can be
viewed globally as a formal hydrogenolysis of the C-S
bond.
Resu lts a n d Discu ssion
When [Mn2(CO)6(µ-S2CPR3)] (1a ,b in Scheme 1) was
treated with excess 1% sodium amalgam in THF at 0
°C, the IR spectra of the solutions, in the ν(CO) region,
showed the quick dissappearance of the bands of the
starting compounds while a new set of bands, shifted
to lower frequencies, developed over a period of 15 min.
The low position of the new bands suggests the forma-
tion of anionic species 2a ,b (see Scheme 1).
Unfortunately, all attempts to isolate and characterize
them as Na+ or NEt4+ salts led to extensive decomposi-
tion. It was not possible, therefore, to propose a
reasonable structure for these anions on the sole basis
of the IR spectra in solution. Aiming to obtain neutral,
isolable species, we attempted the protonation of the
anions under several conditions. When freshly prepared
solutions of the anions of 2a ,b were transferred over
solid NH4PF6 at low temperature (-78 °C), an instan-
taneous reaction was detected by IR monitoring to afford
a mixture of compounds. The minor compound was
readily identified by spectroscopic methods to be the
dithioformate complex [Mn2(CO)6(µ-S2CH)]- (3), which
had been previously isolated and structurally character-
ized by our group.10 The major compounds, 4a ,b in
Scheme 1, have been formulated as [Mn2(CO)6(µ-SH)-
{µ-SC(H)PR3}(NH3)] by their IR spectra in solution,
which correspond to that of the dirhenium analogue 6,
which will be described below. Unfortunately, the
dimanganese complexes 4a ,b decompose quickly in
solution and did not resist the necessary workup to
(6) Galindo, A.; Gutie´rrez-Puebla, E.; Monge, A.; Pastor, A.; Pizzano,
A.; Ruiz, C.; Sa´nchez, L., Carmona, E. Inorg. Chem. 1993, 32, 5569.
Galindo, A.; Mealli, C.; Cuya´s, J .; Miguel, D.; Riera, V.; Pe´rez-Mart´ınez,
J . A.; Bois, C.; J eannin, Y. Organometallics 1996, 15, 2735.
(7) Miguel, D.; Pe´rez-Mart´ınez, J . A.; Riera, V.; Garc´ıa-Granda, S.
J . Organomet. Chem. 1991, 420, C12. (b) Miguel, D.; Pe´rez-Mart´ınez,
J . A.; Riera, V.; Garc´ıa-Granda, S. Organometallics 1993, 12, 1394.
(8) Miguel, D.; Pe´rez-Mart´ınez, J . A.; Riera, V.; Garc´ıa-Granda, S.
Organometallics 1993, 12, 2888. Lo´pez, E. M.; Miguel, D.; Pe´rez-
Mart´ınez, J . A.; Riera, V.; Garc´ıa-Granda, S. Organometallics 1995,
14, 23. Miguel, D.; Pe´rez-Mart´ınez, J . A.; Riera, V.; Garc´ıa-Granda, S.
Organometallics 1994, 13, 4667.
(9) (a) Miguel, D.; Riera, V.; Miguel, J . A.; Sola´ns, X.; Font-Altaba,
M. J . Chem. Soc., Chem. Commun. 1987, 472. (b) Miguel, D.; Riera,
V.; Miguel, J . A.; Go´mez, M.; Sola´ns, X. Organometallics 1991, 10, 1683.
(10) Alvarez, B.; Garc´ıa-Granda, S.; J eannin, Y.; Miguel, D.; Miguel,
J . A.; Riera, V. Organometallics 1991, 10, 3005.
(11) Alvarez, B.; Garc´ıa-Granda, S.; Li, J .; Miguel, D.; Riera, V.
Organometallics 1994, 13, 16.

3450 Organometallics, Vol. 17, No. 16, 1998
Li et al.
Ta ble 1. Cr ysta l Da ta a n d Refin em en t Deta ils for
[Re2(CO)6(µ-SH){µ-SC(H)P Cy3}(NH3)]‚THF (6)
formula
fw
C29H46NO7PRe2S2
988.16
cryst syst
space group
a, Å
monoclinic
P21/c
10.111(2)
b, Å
22.531(4)
c, Å
15.896(4)
â, deg
V, Å3
Z
102.65(3)
3533(1)
4
T, K
293(2)
1.86
1920
F
calc, g cm-3
F(000)
λ (Mo KR), Å
0.710 73
cryst size, mm; color
0.35 × 0.15 × 0.15, pale yellow
µ, cm-1
7.051
method of collection
scan range, deg
no. of reflns measd
no. of reflns obsd, I g 2σ(I)
no. of params
goodness of fit
residuals R (observed)
wR2 (all)
ω/2θ scan
0 e θ e 25
6562
4064
393
0.977
0.036
0.090
F igu r e 1. Perspective view (EUCLID Package)17 of the
molecule of [Re2(CO)6(µ-SH){µ-SC(H)PCy3}(NH3)] (6), show-
ing the atom-numbering scheme.
Ta ble 2. Selected Bon d Len gth s (Å) a n d An gles
(d eg) for [Re2(CO)6(µ-SH){µ-SC(H)P Cy3}(NH3)] (6)
isolate them. After extensive decomposition, only minor
amounts (5-10%) of the starting 1a ,b complexes were
recovered. Nevertheless, the solutions of complexes
4a ,b can be used to obtain stable derivatives by replac-
ing NH3 with phosphines. Thus, treatment of solutions
of 4a ,b with 1 mol equiv of PEt3 affords derivatives
[Mn2(CO)6(µ-SH){µ-SC(H)PR3}(PEt3)] (5a ,b) in good
yield. The structures depicted for 5a ,b in Scheme 1 are
supported by the comparison of their analytical and
spectroscopic data (see Experimental Section) with those
obtained for the dirhenium derivatives described below.
In contrast with the instability of dimanganese com-
plexes 4a ,b, the reduction of the recently prepared
[Re2(CO)6(µ-S2CPCy3)] (1c)12 with sodium amalgam,
followed by protonation with excess NH4PF6, cleanly
affords a new complex 6, which could be isolated and
characterized by analytical and spectroscopic methods.
Additionally, the structure of 6 was determined by X-ray
crystallography. As with the dimanganese complexes
4a ,b, the NH3 ligand of 6 can be easily replaced by PEt3
to give [Re2(CO)6(µ-SH){SC(H)PCy3}(PEt3)] (7). Ana-
lytical and spectroscopic data indicate that 7 has es-
sentially the same structure as 6 and support the
structures proposed for the dimanganese derivatives
with NH3 (4a ,b) and PEt3 (5a ,b).
Re(1)-C(3)
Re(1)-C(2)
Re(1)-S(1)
Re(2)-C(5)
Re(2)-C(7)
Re(2)-S(1)
P(1)-C(1)
C(2)-O(2)
C(4)-O(4)
C(6)-O(6)
1.887(10)
1.903(8)
2.496(2)
1.881(11)
1.920(9)
2.505(2)
1.782(7)
1.154(9)
1.136(10)
1.155(13)
Re(1)-C(4)
Re(1)-C(1)
Re(1)-S(2)
Re(2)-C(6)
Re(2)-N(1)
Re(2)-S(2)
S(1)-C(1)
C(3)-O(3)
C(5)-O(5)
C(7)-O(7)
1.903(10)
2.187(7)
2.548(2)
1.899(12)
2.234(7)
2.522(2)
1.821(7)
1.168(11)
1.165(11)
1.137(10)
C(3)-Re(1)-C(4)
C(4)-Re(1)-C(2)
C(4)-Re(1)-C(1)
C(3)-Re(1)-S(1)
C(2)-Re(1)-S(1)
C(3)-Re(1)-S(2)
C(2)-Re(1)-S(2)
S(1)-Re(1)-S(2)
C(5)-Re(2)-C(7)
89.2(4)
89.7(3)
97.9(3)
155.1(2)
115.2(2)
93.2(3)
91.7(3)
79.41(7)
90.2(4)
C(3)-Re(1)-C(2)
C(3)-Re(1)-C(1)
C(2)-Re(1)-C(1)
C(4)-Re(1)-S(1)
C(1)-Re(1)-S(1)
C(4)-Re(1)-S(2)
C(1)-Re(1)-S(2)
C(5)-Re(2)-C(6)
C(6)-Re(2)-C(7)
C(6)-Re(2)-N(1)
C(5)-Re(2)-S(1)
C(7)-Re(2)-S(1)
88.6(3)
110.3(3)
159.6(3)
97.9(3)
45.16(18)
177.3(3)
80.02(19)
87.5(5)
88.9(5)
92.6(5)
93.7(3)
172.8(3)
94.5(3)
C(5)-Re(2)-N(1) 176.6(3)
C(7)-Re(2)-N(1)
C(6)-Re(2)-S(1)
N(1)-Re(2)-S(1)
C(6)-Re(2)-S(2)
N(1)-Re(2)-S(2)
Re(2)-S(2)-Re(1)
C(1)-P(1)-C(11) 106.7(4)
C(1)-P(1)-C(21) 114.6(3)
C(1)-S(1)-Re(2)
P(1)-C(1)-S(1)
S(1)-C(1)-Re(1)
93.2(3)
97.3(3)
82.92(19) C(5)-Re(2)-S(2)
176.5(4)
85.2(2)
C(7)-Re(2)-S(2)
S(1)-Re(2)-S(2)
C(1)-P(1)-C(31)
93.9(3)
79.75(7)
112.7(4)
96.70(8)
C(31)-P(1)-C(11) 105.6(4)
C(1)-S(1)-Re(1)
Re(1)-S(1)-Re(2)
P(1)-C(1)-Re(1)
O(2)-C(2)-Re(1)
O(4)-C(4)-Re(1)
O(6)-C(6)-Re(2)
58.4(2)
98.49(7)
129.6(4)
178.6(7)
176.7(8)
178.3(12)
Relevant crystal data and refinement details for the
structure of 6 are in Table 1, and selected bond distances
and angles are listed in Table 2.
106.7(2)
119.5(4)
76.5(2)
O(3)-C(3)-Re(1) 179.6(8)
O(5)-C(5)-Re(2) 179.2(9)
O(7)-C(7)-Re(2) 177.9(9)
As can be seen in Figure 1, the molecule of 6 consists
of two Re(CO)3 fragments which are held together by
two bridges: one of them is the well-known hydrogeno-
sulfido HS- and the other is the novel ligand tricyclo-
hexylphosphoniothiolateylide Cy3PC(H)S-, which is
bonded to one rhenium through the sulfur atom [S(1)-
Re(2) ) 2.504(2) Å] and to the other rhenium both
through the sulfur [S(1)-Re(1) ) 2.496(2) Å] and
through the carbon [C(1)-Re(1) ) 2.194(8) Å].
SC(H)PPh3}-3-(PPh3)-closo-3,1,2-RhC2B9H11], generated
by attack of PPh3 on a coordinated dithioformate.13
Complex 6 constitutes, therefore, the first example of
R3PC(H)S- acting as a bridging ligand. The interme-
tallic distance in 6 (3.788(1) Å) is too long to permit any
significant interaction between the two Re atoms (cf.
Re-Re 2.975(1) Å in the starting 1c). The central Re-
There is only one precedent for this ligand, bonded
in a η2(C,S) fashion in the mononuclear complex [3-{η2-
(13) Ferguson, G.; Gallagher, J . F.; J ennings, M. C.; Coughlan, S.;
Spalding, T. R.; Kennedy, J . D.; Fontaine, X. L. R. J . Chem. Soc., Chem.
Commun. 1994, 1595.
(12) Alvarez, B.; Miguel, D.; Li, J .; Morales, M. D.; Riera, V.; Garc´ıa-
Granda, S. Chem. Ber. 1997, 130, 1507.

C-S Bond Cleavage of S2CPR3 Ligands
Organometallics, Vol. 17, No. 16, 1998 3451
Sch em e 2
electron counting discussed above, in the protonated
intermediate C one of the metals possesses only 16e
and, thus, requires the coordination of an additional
ligand, in this case one molecule of the ammonia
liberated (2 mol equiv) in the protonation. It has been
mentioned above that in the case of the dimanganese
complexes, some amount of the starting complex 1a ,b
is found at the end of the reaction. This could result
from a partial oxidation of intermediate A by the
protons. Addition of one proton to intermediate A would
produce the previously known hydrido carbonyl anion
D.10 While it has not been possible to detect this
intermediate in the protonation of the anions, there is
some indirect evidence which support this hypothesis.
Spectroscopically pure hydridocarbonyl anion D can be
prepared in THF solution by addition of Li[BHEt3] to
1a at 0 °C. When this solution was transferred over
excess NH4PF6, the starting material 1a was produced
instantaneously in high yield. Additionally, it was
known previously10 that D rearranges spontaneously,
with loss of PR3, to give the dithioformate complex anion
[Mn2(CO)6(µ-S2CH)]- (3), which has also been found in
the reduction/protonation of the dimanganese com-
plexes.
(1)-S(1)-Re(2)-S(2) is not planar, adopting an enve-
lope conformation which is folded by an angle of 23.31°
with respect to the S(1)‚‚‚S(2) line. The geometry
around Re(1) can be described as octahedral by assum-
ing that the phosphoniothiolateylide ligand occupies two
coordination positions. Nevertheless, there is a severe
distortion of the geometry due to the angle S(1)-Re(1)-
C(1) of 45.16(18)°, which deviates greatly from the value
of 90° required for the ideal octahedral geometry.
Around Re(2), the three carbonyl groups in a facial
disposition, the two sulfurs, and one ammonia ligand
complete a fairly regular octahedral disposition, with
values of interligand angles ranging from 79.75(7)° to
97.3(3)°. Since there is no direct metal-metal bond, and
assuming that the SH- bridge donates 3e, the electron
counting in 6 requires the phosphoniothiolateylide to
donate five electrons to complete 18e around each metal,
as outlined in Scheme 2. In this fashion, the new ligand
supports a net charge of 1-, i.e., 1- in the sulfur, 1-
in the carbon, and 1+ in the phosphorus. This, together
with the negative charge of SH-, leads to the assign-
ment of a formal oxidation number (+1) to each Re
atom.
By comparing 6 with the precursor 1b, it is apparent
that the reduction/protonation sequence of reactions
produces the cleavage of the Re-Re and one C-S bonds
and the addition of hydrogen atoms to the split sulfur
and to the central carbon of the phosphoniothiolate
ligand. Due to the high reactivity of the anions 2, we
have not been able to obtain spectroscopic data apart
from their IR spectra in solution. Therefore, it is not
possible to propose, on safe grounds, a sensible structure
for these carbonyl anions. In view of the structure of
the final compounds, it is reasonable to question in
which of the two steps of the process the cleavage of
the bond has occurred. A tentative mechanism is
outlined in Scheme 3, supported by additional indirect
data.
We have previously found that hydride addition to the
starting complexes 1a ,b occurs at the metal-metal bond
to produce the carbonyl anions [Mn2(CO)6(µ-H)(µ-S2-
CPCy3]- (D in Scheme 3) without cleavage of the Mn-
Mn bond.10 This suggests that the LUMO of the
substrate 1 lies mainly on the metals. On the other
hand, it is well-known that reduction of binuclear
species with Na[Hg] usually produces cleavage of the
M-M bond. In the present case, this would lead to an
intermediate (A in Scheme 3) with the charges centered
on the metals. An intramolecular oxidative addition of
one C-S bond to one of the metal atoms in A would
produce the cleavage of the C-S bond, leading to
intermediate B with the charges now centered on the
two atoms of the split bond: C and S. Subsequent
protonation of these atoms forms the ligands SH- and
R3PC(H)S- of the final compounds. Consistent with the
The transformation of complexes 1 into their deriva-
tives containing R3PC(H)S- and SH- bridges involves
the addition of 2e in the reduction and 2H+ in the
protonation. Therefore, it can be regarded as hydro-
genolysis of a CdS bond π-coordinated to a Mn or Re
atom.
We have previously shown that complexes 1 could be
viewed as consisting of a manganadithiabutene ring
coordinated to a M(CO)3 fragment, with structural and
electronic features similar to those found in the well-
known cymantrene-like derivatives [M(η5-C5H5)(CO)3].9b
Pursuing this analogy one step further, the similarity
can be extended to isoelectronic [M(η5-thiophene)-
(CO)3]+, as shown in Scheme 4. In fact, the close
z+
relationship of the fragments “CpMLn
”
and
“(thiophene)MLn(z+1)+” has been supported by the results
of Fenske-Hall MO calculations.2e In this way, the
process described here may serve as a model for the
hydrogenolysis of a η5-coordinated thiophene. However,
the analogy is not limited to the structural or bonding
features, but it extends to some aspects of the reactivity.
It has been shown that the reduction of cationic com-
plexes of Rh and Ir is often followed by the opening of
the thiophene ring to afford a metallathiabenzene.3f,k
Calculations of the Fenske-Hall type show that this is
produced through an oxidative addition of a C-S bond
to the metal atom, such as the transformation from A
to B proposed in Scheme 3.2e Quite understandably, the
calculations also suggest that the metal center should
be more electron rich to promote the oxidative addition.
This is the case for the carbonyl anion A, and it can be
taken as additional support for the pathway proposed
in Scheme 3.
Apart from their interest as models for the ring
opening of thiophene and related molecules, compounds
4-7 represent the first examples of compounds contain-
ing the new bridging ligand Cy3PC(H)S-. Additionally,
complexes 4-7 and their very reactive, anionic precur-
sors 2 described here open new and unexpected syn-
thetic pathways which are currently being studied.

3452 Organometallics, Vol. 17, No. 16, 1998
Li et al.
Sch em e 3
tion of 2a , starting from [Re2(CO)6(µ-S2CPCy3)] (1c) (0.13 g,
0.15 mmol) and sodium amalgam (1% w/w, 10 g, excess) in
THF (10 mL). The reaction required 4 h to reach completion.
The solution was filtered as described above, to be used in the
preparation of derivative 6. IR (THF): ν(CO) 1985m, 1966vs,
Sch em e 4
1868vs, 1846s, cm-1
.
[Mn 2(CO)6(µ-SH){µ-SC(H)P Cy3}(NH3)] (4a ). A solution
of 2a (0.15 mmol) in THF (20 mL), prepared as described
above, was cooled to -78 °C and transferred through a cannula
into a Schlenck flask containing NH4PF6 (0.065 g, 4 mmol).
The reaction was clean and instantaneous, according to IR
monitoring, to give 4a together with some of the dithioformate
complex anion 3 (10-20%). Attempts at isolation led to
extensive decomposition of 4a to give only small amounts of
starting 1a (5-10%). However, the solution of 4a was used
successfully to prepare the PEt3 derivative 5a (see below). IR
(THF): ν(CO) 2009m, 1975vs, 1907s, 1882s, 1864m, cm-1
.
[Mn 2(CO)6(µ-SH){µ-SC(H)P P r i3}(NH3)] (4b). A solution
of 2b (0.23 mmol) in THF (10 mL), prepared as described
above, was cooled to -78 °C and transferred through a cannula
into a Schlenck flask containing NH4PF6 (0.065 g, 4 mmol).
Similarly to 4a , compound 4b could not be isolated and was
used in solution to prepare the derivative 5b (see below). IR
Exp er im en ta l Section
All reactions were carried out in dry solvents under a
nitrogen atmosphere. Details of the instrumentation and
experimental procedures have been given elsewhere.7b Lit-
erature procedures for the preparation of the starting materi-
als are quoted in each case. Ligands and other reagents were
purchased and used without purification unless otherwise
stated.
(THF): ν(CO) 2009m, 1975vs, 1908s, 1883s, 1864m, cm-1
.
[Mn 2(CO)6(µ-SH){µ-SC(H)P Cy3}(P Et3)] (5a ). To a cooled
(-78 °C) solution of 4a (0.15 mmol) in THF (20 mL), prepared
as described above, was added PEt3 (19 µL, 0.15 mmol). The
mixture was stirred for 20 min, and the solvent was evaporated
in vacuo. The residue, containing 5a together with minor
amounts (10-20%) of the dithioformate anionic complex 3
(sodium salt), was dissolved in a CH2Cl2/hexane mixture (1:3,
v:v) and filtered through a short column (2.5 × 10 cm) of
alumina (activation degree III). Under these conditions,
complex 3 remained adsorbed on the column. The filtrate
containing 5a was evaporated in vacuo, and the concentrated
solution was placed overnight in a refrigerator (-20 °C) to
afford compound 5a as a yellow microcrystalline solid. Yield:
0.052 g, 50.5% (with respect to starting [Mn2CO6)(µ-S2CPCy3)].
Anal. Calcd for C31H50Mn2O6P2S2: C, 49.34; H, 6.68. Found:
C, 49.31; H, 6.93. IR (THF): ν(CO) 2002m, 1976vs, 1912m,
Na 2[Mn 2(CO)6(µ-S2CP Cy3)] (2a ) in TH F Solu t ion .
[Mn2(CO)6(µ-S2CPCy3)] (1a ) (0.10 g, 0.15 mmol) was dissolved
in THF (20 mL), and the solution was cooled in an ice bath.
Freshly prepared sodium amalgam (1% w/w, 10 g, excess) was
then added, and the mixture was stirred for 15 min, when the
IR spectrum of the solution showed that all starting 1a had
been consumed. The mixture was decanted, and the solution
was filtered through a cannula over the appropriate reagent
to obtain the protonated derivatives. IR (THF): ν(CO) 1987m,
1946vs, 1917m, 1877vs, cm-1
.
Na 2[Mn 2(CO)6(µ-S2CP P r i3)] (2b) in THF Solu tion . The
procedure was similar to that described above for the prepara-
tion of 2a , starting from [Mn2(CO)6(µ-S2CPPri )] (1b) (0.12 g,
1902s, 1882m, 1866m, cm-1 1H NMR (CDCl3): δ 3.29 [s(br),
.
3
0.23 mmol) and sodium amalgam (1% w/w, 10 g, excess) in
THF (10 mL). The reaction was complete in 15 min, and the
solution was similarly filtered through a cannula to be used
in subsequent reactions. IR (THF): ν(CO) 1987m, 1947vs,
1H, SC(H)P)], 2.44-0.84 [m, 48 H, Cy, Et], -3.29 [d (16), 1H,
SH]. 31P{1H} NMR (CDCl3): δ 40.5 [s, SCP], 37.0 [s, PEt3].
13C{1H} NMR (C6D6): 229.2, 227.4, 223.4 [MnCO], 35.4 [d (43),
C1 of Cy)], 31.3 [dd(41 and 5), SC(H)P], 28.8 and 28.2 [2 × s,
C2 and C6 of Cy], 27.8 [d(11)] and 27.5 [d(11) (C3 and C5 of
Cy)], 26.6 (s, C4 of Cy), 17.8 [d(22), CH2 of Et], 8.8 (s, CH3 of
Et).
1917m, 1877vs, cm-1
.
Na 2[Re2(CO)6(µ-S2CP Cy3)] (2c) in THF Solu tion . The
procedure was similar to that described above for the prepara-

C-S Bond Cleavage of S2CPR3 Ligands
Organometallics, Vol. 17, No. 16, 1998 3453
[Mn 2(CO)6(µ-SH){µ-SC(H)P P r i3}(P Et3)] (5b). Compound
5b was prepared as described above for 5a , from a solution of
4b (ca. 0.23 mmol) and PEt3 (31 µL, 0.23 mmol) in THF (20
mL). The workup was as described for 5a , affording 5b as
yellow-orange microcrystals. Yield: 0.051 g, 41%. Anal.
Calcd for C22H38Mn2O6P2S2: C, 41.65; H, 6.04. Found: C,
41.34; H, 6.36. IR (THF): ν(CO) 2003s, 1977vs, 1914m,
sorption correction was applied with DIFABS.16 All non-
hydrogen atoms were refined anisotropically. Hydrogen atoms
were geometrically positioned, with a common isotropic tem-
perature factor which was refined. The perspective drawing
in Figure 1 was made with PLATON.17
[Re2(CO)6(µ-SH){µ-SC(H)P Cy3}(P Et3)] (7). To solution
of 6 (0.1 g, 0.1 mmol) in THF (15 mL) at 0 °C was added PEt3
(16 µL, 0.1 mmol), and the mixture was stirred for 10 min.
The solvent was evaporated in vacuo, the residue was ex-
tracted with CH2Cl2/hexane (2/1, v/v, 4 × 15 mL), and the
collected extracts were filtered through a short column of
alumina (2.5 × 5 cm, activation degree III). Slow concentra-
tion in vacuo afforded 7 as a creamy-white microcrystalline
solid. Yield: 0.07 g, 71%. Anal. Calcd for C31H50O6P2Re2S2:
C, 36.60; H, 4.95. Found: C, 36.87; H, 5.06. IR (THF): ν(CO)
1902m, 1884m, 1867m, cm-1 1H NMR (CD2Cl2): δ 3.32 [s(br),
.
1H, SC(H)P)], 2.41 [m, 3 H, CH of Pri], 1.55 [m, 24H, CH3 of
Pri and CH2 of Et], 1.22 [m, 9H, CH3 of Et], -2.29 [s(br), 1H,
SH]. 31P{1H} NMR (CDCl3): δ 49.9 [s, SCP], 36.9 [s, PEt3].
13C{1H} NMR (CD2Cl2): 227.9, 226.8, 226.7 [MnCO], 28.2 [dd-
(43 and 6), SC(H)P], 24.5 [d(45), CH of Pri], 18.2 [d(33), CH3
of Pri], 17.1 [d(22), CH2 of Et], 8.2 (s, CH3 of Et).
2013m, 1990vs, 1914s, 1897s, 1884s, 1868m, cm-1 1H NMR
.
[Re2(CO)6(µ-SH){µ-SC(H)P Cy3}(NH3)] (6). A solution of
2c (0.15 mmol) in THF (10 mL), prepared as described above,
was cooled to -78 °C and transferred through a cannula into
a Schlenck flask containing NH4PF6 (0.065 g, 4 mmol) at 0
°C. The mixture was stirred for 2 h, until the complete
dissappearance of the bands of the anion 2c. The solvent was
evaporated in vacuo, the solid residue was extracted with a
THF/hexane (1:1) mixture, and the extracts were filtered
through alumina (activation degree III). Evaporation of the
solvent in vacuo gave a yellow solid, which was recrystallized
from THF/hexane to obtain 6 as yellow crystals. Yield: 0.09
g, 65%. Anal. Calcd for C25H38NO6PRe2S2‚THF: C, 35.25; H,
4.69; N, 1.42. Found: C, 35.41; H, 4.82; N, 1.35. IR (THF):
(CDCl3): δ 2.43 [s, 1H, SC(H)P], 2.33-2.18 [m, 9H, CH of Cy
and CH2 of Et], 2.13-1.26 [m, 30H, CH2 of Cy], 1.18 [m, 9H,
CH3 of Et], -0.96 [s(br), 1H, SH]. 31P{1H} NMR (CD2Cl2): δ
36.3 [d(3.5), SCP], 0.7 [d(3.5), PEt3]. 13C{1H} NMR (CD2Cl2):
200.6 [s, ReCO], 200.5 [s, 2 × ReCO], 196.6 [s, ReCO], 195.2
[d(59), ReCO], 192.9 [dd (46 and 8), ReCO], 34.3 [d (43), C1 of
Cy)], 27.6 [d(4)] and 27.5 [d(4) [C2 and C6 of Cy]], 27.0 [d(12)]
and 26.5 [d(12) (C3 and C5 of Cy)], 25.7 (s, C4 of Cy), 24.1 [dd-
(35 and 5), SC(H)P], 16.6 [d(28), CH2 of PEt3], 8.0 [d(2.5), CH3
of PEt3].
Ack n ow led gm en t. We thank the Spanish Direccio´n
General de Investigacio´n Cient´ıfica y Te´cnica (Projects
PB94-1332, PB96-0317, and PB96-0556) for financial
support. We also thank CICYT for a grant to J .L.
ν(CO) 2015m, 1988vs, 1892vs, 1865m, cm-1
.
1H NMR
(CDCl3): δ 3.61 (THF), 3.10 [s, 3H, NH3], 2.30-1.29 [m, 36H,
THF, SC(H)P, and Cy], -1.13 [s(br), 1H, SH]. 31P{1H} NMR
(CD2Cl2): δ 36.5 [s, SCP]. 13C{1H} NMR (CD2Cl2): 202.4,
199.1, 197.2, 196.5, 192.9, 192.5 [ReCO], 68.0 (s, THF), 34.7
[d (43), C1of Cy)], 28.5 [d(3)] and 28.1 [d(2) [C2 and C6 of Cy]],
27.7 [d(11)] and 27.1 [d(11) (C3 and C5 of Cy)], 26.4 (s, C4 of
Cy), 21.6 [d(35), SC(H)P].
Su p p or tin g In for m a tion Ava ila ble: Complete tables of
atomic coordinates, anisotropic thermal parameters, bond
lengths and angles, torsion angles, and least squares planes
for the structure of 6 (8 pages). Ordering information is given
on any current masthead page. A list of structure factor
amplitudes is available from the authors.
X-r a y Diffr a ction Stu d y of 6. Crystals were grown by
slow difusion of hexane into a concentrated solution of 6 in
THF at -20 °C. Relevant crystallographic details are given
in Table 1. Unit cell parameters were determined from the
least-squares refinement of a set of 25 centered reflections in
the range 15° < θ < 18°. Three reflections were measured
every 1 h as orientation and intensity control. Significant
decay was not observed. The structure was solved by Patter-
son methods, phase expansion, and subsequent Fourier maps
with DIRDIF.14 Full-matrix least-squares refinement was
made with SHELX-93.15 After isotropic refinement, an ab-
OM971074V
(14) Beurskens, P. T.; Admiraal, G.; Bosman, W. P.; Beurskens, G.;
Doesburg, H. M.; Garc´ıa-Granda, S.; Gould, R. O.; Smits, J . M. M.;
Smikalla, C. The DIRDIF Program System; Technical Report of the
Crystallography Laboratory; University of Nijmegen: Nijmegen, The
Netherlands, 1992.
(15) Sheldrick, G. M. SHELXL-93; University of Go¨ttingen: Got-
tingen, Germany, 1993.
(16) Walker, N.; Stuart, D. Acta Crystallogr. 1983, A39, 158.
(17) Spek, A. L. The EUCLID Package. In Computational Crystal-
lography; Sayre, E., Ed.; Clarendon Press: Oxford, England, 1982; p
528.