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A. Sil6estru et al. / Journal of Organometallic Chemistry 588 (1999) 256–259
Crystals of the title compound were obtained from a
monodentate fashion. This interpretation is also sup-
ported by the phosphorus–sulfur distances in the
diphenyldithiophosphinato units of 2, which are char-
acteristic for single, PꢀS (205.23(8) and 206.32(8) pm)
and double, PꢁS (195.95(8) and 195.97(8) pm) bonds
(c.f. 207.7(1) and 195.4(1) pm in the free acid, Ph2PS2H)
[14].
The equatorial positions in the trigonal bipyramidal
environment of antimony are occupied by the C(1),
C(2) and C(3) atoms of the organic groups attached to
the metal. The SbC3 unit is planar (the sum of the
CꢀSbꢀC angles is 360°), but the C(3)ꢀSb(1)ꢀC(1) angle
is somewhat enlarged (125.76(8)°) at the expense of the
C(2)ꢀSb(1)ꢀC(3) angle (114.31(8)°). The antimony–car-
bon distances (212 pm, mean value) are in the same
range as those found in other trimethylantimony(V)
derivatives (210 pm in Me3Sb(S2PMe2)2, and 208 pm in
Me3Sb(OSPPh2)2).
chloroform–n-hexane solution. The triclinic unit cell
contains monomeric units of 2 with no intermolecular
associations being observed. The molecular structure
with the atom numbering scheme is depicted in Fig. 2.
Both diphenyldithiophosphinato groups act as
monodentate ligands, being connected to the central
antimony atom through sulfur atoms occupying the
axial positions in a distorted trigonal bipyramidal envi-
ronment (S(1)ꢀSb(1)ꢀS(3) 175.098(16)°). The coordina-
tion polyhedron is less distorted than in
Me3Sb(S2PPh2)2 [9] where the corresponding SꢀSbꢀS
angle is smaller, i.e. 171.1(1)°. On the other hand, the
SꢀSbꢀS angle in 2 is of the same magnitude as the
OꢀSbꢀO angle (177.7(2)°) in the monothio derivative,
Me3Sb(OSPPh2)2 [13], where the ligand units exhibit a
similar monodentate coordination pattern. The
Sb(1)ꢀS(1) and Sb(1)ꢀS(3) distances are comparable in
both dithiophosphinato compounds: 263.69(8) and
261.37(8) pm in 2 and 261.1(5) pm in Me3Sb(S2PPh2)2
[9]. The distances between the antimony and the sulfur
atoms double bonded to phosphorus are much larger in
One of the three silicon atoms of the trimethylsilyl-
methyl groups lies practically in the Sb(1)C(1)C(2)C(3)
plane while the other two are almost symmetrically
located above and under this plane (mean deviation
from the SbC3 plane for Si(1), Si(2) and Si(3) are
2
(409.4 and 404.8 pm, respectively) than in
,
−0.962, 0.003 and 0.917 A respectively) (see Table 1).
Me3Sb(S2PPh2)2 (374.4 and 383.9 pm, respectively [9]).
Moreover they are longer than the sum of van der
Waals radii for S and Sb (ca. 400 pm). These data
prove that in 2 the dithiophosphinato ligand acts in a
3. Experimental
All the experiments were performed in an argon
atmosphere, using dried solvents distilled under argon.
3.1. Synthesis of bis(trimethylsilymethyl)antimony
tribromide (1)
At −20°C a solution of Br2 (0.28 g, 1.75 mmol) in
petroleum ether (20 ml) was added to (Me3SiCH2)2SbBr
(0.44 g, 1.17 mmol) in 10 ml petroleum ether. After the
addition the mixture was allowed to warm up to room
temperature. The solvent was removed at reduced pres-
sure yielding 0.62g (99%) of bis(trimethylsily-
methyl)antimony tribromide. Crystallization from
warm toluene afforded colorless crystals melting, with
decomposition beginning at 123–125°C. 1H-NMR
(C6D6, 200 MHz): 0.21 s (9H, CH3), 2.68 s (2H, CH2).
13C-NMR (C6D6, 50 MHz): 0.25 (CH3), 50.24 (CH2).
MS (EI, 70eV) m/z [fragment]: 517 [R2SbBr3ꢀMe]+,
455 [R2SbBr2]+, 376 [R2SbBr]+, 361 [R2SbBrꢀMe]+,
353 [RSbBr2ꢀMe]+, 289 [RSbBr]+ with R=
Me3SiCH2. Anal. found: C 17.68, H 3.99. Anal. Calc.
C8H22Br3SbSi2: C 17.93, H 4.14%.
Fig. 2. Structure of 2. Selected distances (pm) and angles (°)
Sb(1)ꢀC(1) 212.21(19), Sb(1)ꢀC(2) 211.92(19), Sb(1)ꢀC(3), 212.2(2),
Sb(1)ꢀS(1), 263.69(8), Sb(1)ꢀS(3), 261.37(8), P(1)ꢀS(1), 205.23(8),
P(2)ꢀS(3) 206.32(8), P(1)ꢀS(2) 195.95(8), P(2)ꢀS(4) 195.97(8);
C(1)ꢀSb(1)ꢀC(2)
119.92(8),
C(1)ꢀSb(1)ꢀC(3)
125.76(8),
C(2)ꢀSb(1)ꢀC(3) 114.31(8), S(1)ꢀSb(1)ꢀC(1) 92.46(6), S(3)ꢀSb(1)ꢀC(1)
90.82(6), S(1)ꢀSb(1)ꢀC(2) 94.24(6), S(3)ꢀSb(1)ꢀC(2) 87.27(6),
S(1)ꢀSb(1)ꢀC(3) 82.71(6), S(3)ꢀSb(1)ꢀC(3) 92.42(6), S(1)ꢀSb(1)ꢀS(3)
175.098(16), Sb(1)ꢀS(1)ꢀP(1) 111.91(3), Sb(1)ꢀS(3)ꢀP(2) 107.95(3),
S(1)ꢀP(1)ꢀS(2) 117.01(4), S(3)ꢀP(2)ꢀS(4) 117.62(4), C(40)ꢀP(1)ꢀC(46)
102.80(11), C(52)ꢀP(2)ꢀC(58) 102.44(9).
3.2. Synthesis of tris(trimethylsilymethyl)antimony
bis(diphenyldithiophosphinate) (2)
A stoichiometric mixture of (Me3SiCH2)3SbBr2 (0.45
g, 0.83 mmol) and Ph2PS2NH4 (0.45 g, 1.66 mmol) was