COMMUNICATIONS
ꢀ
the well-known processes of S S bond formation from thiol
steric hindrance of the cyclohexyl groups. The three bond
lengths around the ylide carbon atom are slightly shorter than
functionalities, which stabilize the tertiary structure of many
proteins, take place by oxidative coupling,[9] whereas in our
ꢀ
ꢀ
expected for single bonds (P1 C5 1.756(7), P2 C5 1.744(7),
ꢀ
case oxidation of 1 (either with I2 or Ag ) results in the
C5 S 1.760(7) ). The P1-P2-C5 and C5-S-P3 planes are
ꢀ
scission of the S S bond.
almost mutually perpendicular (dihedral angle 79.0(3)8),
The thione in 5 undergoes thiophilic addition by treatment
with phosphanes, such as PCy3, to afford 6, a complex in which
the diphosphane ligand contains a unique thioxophosphorane
ylide functionality (Scheme 1). The same behavior is shown
by complex 2, which readily reacts with PCy3 by nucleophilic
substitution of Iꢀ to give 6. Similar types of 1,3-dipolar
molecules are assumed to be reaction intermediates in the
well-known desulfurization and coupling reactions of 1,3-
dithiole-2-thiones by trialkylphosphites, which led to tetra-
thiafulvalene derivatives (constituents of organic conductors,
Scheme 2),[10] as well as in the formation of phosphorus ylides
which minimizes the steric repulsions between the cyclohexyl
ꢀ
and phenyl rings. In the S PCy3 moiety the phosphorus atom
has a distorted tetrahedral coordination geometry, and the
ꢀ
P S distance (2.107 (3) ) is typical of a single bond.
The gentle warming of 6 in THF readily liberates SPCy3,
thus completing the sulfur extrusion process from 5. However,
the transient diphosphanylcarbene complex [Mn(CO)4-
:
{(PPh2)2C }] which should remain in the reaction mixture
was not detected; instead a complex mixture of manganese(i)
derivatives is found that still requires characterization.
In summary, the approach presented allows the reversible
ꢀ
scission and formation of the S S bond in the dinuclear
complex 1, which, in parallel, enables the generation of
unusual functionalities at the central carbon atom of the
diphosphane moiety. Preliminary results show that 2 and 5
undergo nucleophilic attack on the sulfur atom not only with
tertiary phosphanes, but also with a wide variety of nucleo-
philic reagents such as KCN, MgRCl, and NaSR. Thus these
complexes show great promise for synthetic applications.
S
S
S
S
S
S
S
S
P(OR)3
- SP(OR)3
C
S
C
S
C
C
P(OR)3
Scheme 2. Schematic representation of the desulfurization of 1,3-dithiole-
2-thiones by thiophilic addition of phosphites to give tetrathiafulvalene
derivatives.
from thiones.[11] However, this is the first time that such a
derivative has been isolated and fully structurally character-
ized. The structure of 6 ´ BF4, which has been elucidated
by X-ray crystallography (Figure 1),[12] clearly shows
the presence of the modified diphosphane ligand
[{(PPh2)2CSPCy3}h2(P, P')]-coordinated to the Mn(CO)4 moi-
ety. The P1-P2-C5-S skeleton departs appreciably from the
expected planar conformation (the sulfur atom is at
0.644(2) from the P1-P2-C5 plane), probably due to the
Experimental Section
2: I2 (0.022 g, 0.087 mmol) was added to a solution of 1 (0.1 g, 0.086 mmol)
in CH2Cl2. After the mixture had been stirred for 5 min at room
temperature, the solvent was evaporated to dryness, and the brown residue
was recrystallized from CH2Cl2/hexane to afford a red solid; yield 91%
(0.11 g). Elemental analysis (%) calcd for C29H20IMnO4P2S: C 49.18, H
2.85; found: C 48.87, H 2.82; IR (CH2Cl2): nÄ 2081 (s), 2011 (sh), 2001 (vs),
1982 (m) cmꢀ1 (CO); 31P{1H} NMR (121.5 MHz, CD2Cl2): d 36.5 (br);
FAB-MS (positive-ion): m/z: 708 [M ], 652 [M ꢀ 2CO].
4: IR (CH2Cl2): nÄ 2094 (s), 2036 (m), 2011 (vs) cmꢀ1 (CO); Raman (KBr):
nÄ 451 (s) cmꢀ1 (S S); 31P{1H} NMR (121.5 MHz, CD2Cl2): d 34.0 (br);
ꢀ
1H NMR (300 MHz, CD2Cl2): d 6.98 (t, JP,H 7 Hz, 2H; P2CH).
2
5 ´ BF4: AgBF4 (0.35 g, 0.18 mmol) was added to a solution of 1 (0.1 g,
0.086 mmol) in CH2Cl2. The resulting suspension, protected from light, was
stirred for 1 h. Then the solution was filtered off and evaporated to dryness.
The residue was recrystallized twice in CH2Cl2/hexane at ꢀ208C to afford
white crystals; yield 40% (0.054 g). Elemental analysis (%) calcd for
C29H20BF4MnO4P2S: C 52.13, H 3.02; found: C 52.03, H 2.96; IR (CH2Cl2):
nÄ 2093 (s), 2033 (m), 2011 (vs) cmꢀ1 (CO); 31P{1H} NMR (121.5 MHz,
CD2Cl2): d 44.0 (br); FAB-MS (positive-ion): m/z: 581 [M ꢀ BF4].
6 ´ BF4: PCy3 (0.025 g, 0.09 mmol) was added to a solution of 5 ´ BF4 (0.06 g,
0.09 mmol) in CH2Cl2. After the mixture had been stirred for 20 min at
room temperature, the solvent was evaporated to dryness. The residue was
washed with Et2O (20 mL) and recrystallized from CH2Cl2/Et2O to obtain
white crystals; yield 70% (0.06 g). Elemental analysis (%) calcd for
C47H53BF4MnO4P3S: C 59.51, H 5.63; found: C 59.10, H 5.88; IR (CH2Cl2):
nÄ 2079 (s), 2014 (s), 1988 (vs) cmꢀ1 (CO); 31P{1H} NMR (121.5 MHz,
3
CD2Cl2): d 32.4 (br), 53.5 (t, JP,P 7 Hz).
Received: July 31, 2000 [Z15557]
Â
Figure 1. Structure of the cationic complex
6
in the crystal (30%
[1] J. J. R. Frausto da Silva, R. J. P. Williams, The Biological Chemistry of
probability ellipsoids; hydrogen atoms are omitted for clarity). Selected
bond lengths [] and angles [8]: Mn-P1 2.342(2), Mn-P2 2.318(2), P1-C5
1.756(7), P2-C5 1.744(7), C5-S 1.760(7), S-P3 2.107(3); P1-Mn-P2 70.39(7),
Mn-P1-C5 93.4(2), Mn-P2-C5 94.5(2), P1-C5-P2 100.3(3), P1-C5-S 131.2(4),
P2-C5-S 121.9(4), C5-S-P3 116.0(2).
the Elements, Clarendon, Oxford, 1991, pp. 164 ± 170.
[2] P. Versloot, M. van Duin, J. G. Haasnoot, J. Reedijk, A. L. Spek, J.
Chem. Soc. Chem. Commun. 1993, 183 ± 184; K. Ganesh, K. Kishore,
Macromolecules 1996, 29, 26 ± 29.
[3] D. L. Rabenstein, P. L. Yeo, J. Org. Chem. 1994, 59, 4223 ± 4229.
Angew. Chem. Int. Ed. 2001, 40, No. 1
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