Organoantimony ring-chain equilibria: Trapping of catena-tetrastibanes in cyclo-[Cr(CO)4(R′2Sb-SbR-SbR-SbR′2) ] (R′ = Me, Ph; R = Me3SiCH2) and related complexes

Article abstract of DOI:10.1021/om001085f

Ring-chain equilibria between cyclo-(Me₃SiCH₂Sb)_n (n = 4, 5) and R′₄Sb₂ (R′ = M Ph) contain the catena-tristibanes R′₂Sb-SbR-SbR′₂ (1, R′ = Me; 2, R′ = Ph, R = Me₃SiCH

Full text of DOI:10.1021/om001085f

1360
Organometallics 2001, 20, 1360-1364
Or ga n oa n tim on y Rin g-Ch a in Equ ilibr ia : Tr a p p in g of
ca ten a -Tetr a stiba n es in
cyclo-[Cr (CO)4(R′2Sb-SbR-SbR-SbR′2)] (R′ ) Me, P h ; R )
Me3SiCH2) a n d Rela ted Com p lexes
Hans J oachim Breunig,* Ioan Ghesner, and Enno Lork
Institut fu¨r Anorganische und Physikalische Chemie (FB 02) der Universita¨t Bremen,
D-28334 Bremen, Germany
Received December 22, 2000
Ring-chain equilibria between cyclo-(Me3SiCH2Sb)n (n ) 4, 5) and R′4Sb2 (R′ ) Me, Ph)
contain the catena-tristibanes R′2Sb-SbR-SbR′2 (1, R′ ) Me; 2, R′ ) Ph, R ) Me3SiCH2) as
the most abundant chain components. Addition of [nbdCr(CO)4] (nbd ) norbornadiene) to
the equilibrium mixture formed from cyclo-(Me3SiCH2Sb)n (n ) 4, 5) and R′4Sb2 (R′ ) Me,
Ph) gives cyclo-[Cr(CO)4(R′2Sb-SbR-SbR-SbR′2)] (3, R′ ) Me; 4, R′ ) Ph, R ) Me3SiCH2),
two complexes with catena-tetrastibane ligands. Reaction of 3 with [W(CO)5(thf)] (thf )
tetrahydrofuran) leads to cyclo-[Cr(CO)4(Me2Sb-SbR-SbR-SbMe2)W(CO)5] (R ) Me3SiCH2)
(5). The crystal structures of 3 and 5 have been determined by X-ray diffraction.
In tr od u ction
distibanes Me4Sb2 and Ph4Sb2 and the reactive ring
system cyclo-(Me3SiCH2Sb)n (n ) 4, 5), which is not too
difficult to prepare, and report here on the formation of
novel catena-tristibanes and on trapping reactions of
catena-tetrastibanes as ligands in metal carbonyl com-
plexes.
The chemistry of organometallic antimony chains
(catena-stibanes) has been investigated for a long time,1
but our knowledge of this highly diverse group of
compounds is still rather limited. Only three ionic
trimers, [R2Sb-Sb-SbR2]- (R ) Ph2, t-Bu3) and [R2Sb-
SbR2-SbR2]+ (R ) Me),4 were characterized by X-ray
crystallography. Neutral catena-stibanes have been
reported as tristibanes, R2Sb-SbR′-SbR2 (R ) Me, Et,
Ph; R′ ) Me, Et, t-Bu, (Me3Si)2CH, Ph),5 a tetrastibane,5
Ph2Sb-SbEt-SbEt-SbPh2, and several polymers,1 all
with unknown crystal structures. The tri- and tetra-
stibanes were identified by 1H NMR and mass spec-
trometry as components in equilibria mixtures with
distibanes and cyclo-stibanes. Complexes with homo-
nuclear organoantimony chain ligands are presented
here for the first time. However complexes with phos-
phorus or arsenic chains were reported before, and also
a phosphorus antimony chain, Me2P-SbMe-SbMe-
PMe2 was synthesized in the coordination sphere of a
transition metal carbonyl complex.6
Resu lts a n d Discu ssion
The trimethylsilylmethyl antimony rings cyclo-(Me3-
SiCH2Sb)n (n ) 4, 5)7 react instantaneously with Me4-
8
9
Sb2 or Ph4Sb2 in benzene with formation of the
tristibanes Me2Sb-SbR-SbMe2 (1) or Ph2Sb-SbR-
SbPh2 (2) (R ) Me3SiCH2) as major components of the
equilibria mixtures. The ring-chain equilibria involving
the tristibanes 1 and 2 are described in eq 1.
We have continued our investigations5 of ring chain
equilibria choosing the well-known and readily available
Even at low temperatures the equilibria reactions are
fast, and techniques allowing the isolation of 1 or 2 from
the mixtures are not available. Removal of the disti-
banes under reduced pressure gives the antimony rings
(1) (a) Schmidt, H. Liebigs Ann. Chem. 1920, 421, 174. (b) Wieber,
M. Gmelin Handbook of Inorganic Chemistry, Sb Organoantimony
Compounds, Part 2; Springer-Verlag: Berlin, 1981. (c) Breunig, H. J .;
Ro¨sler, R. Coord. Chem. Rev. 1997, 163, 33. (d) Breunig, H. J .; Ro¨sler,
R. Chem. Soc. Rev. 2000, 6, 403.
(2) Bartlett, R. A.; Rasika Dias, H. V.; Hope, H.; Murray, B. D.;
Olmstead, M. M.; Power, P. P. J . Am. Chem. Soc. 1986, 108, 6921.
(3) Althaus, H.; Breunig, H. J .; Probst, J .; Ro¨sler, R.; Lork, E. J .
Organomet. Chem. 1999, 585, 285.
(4) Breunig, H. J .; Denker, M.; Lork, E. Angew. Chem. 1996, 108,
1081; Angew. Chem., Int. Ed. Engl. 1996, 35, 1005.
(5) Ates, M.; Breunig, H. J .; Ebert, K.; Gu¨lec, S.; Kaller, R.; Dra¨ger,
M. Organometallics 1994, 11, 145.
(6) (a) J ohannes, G.; Stelzer, O.; Unger, E. Chem. Ber. 1975, 108,
1259. (b) Sheldrick, W. S. Chem. Ber. 1975, 108, 2242. (c) Sheldrick,
W. S. Acta Crystallogr. 1975, B31, 1789. (d) Stelzer, O.; Unger, E.
Chem. Ber. 1975, 108, 2232. (e) Sheldrick, W. S. Acta Crystallogr. 1976,
B32, 308. (f) Stelzer, O.; Unger, E.; Wray, V. Chem. Ber. 1977, 110,
3430. (g) J ones, R. A.; Whittlesey, B. R. Organometallics 1984, 3, 469.
(h) Reddy, V. S.; Katti, K. V. Inorg. Chem. 1994, 33, 2695. (i) Reddy,
V. S.; Katti, K. V.; Barnes, C. L. Chem. Ber. 1994, 127, 1355.
1
back. 1 and 2 were identified by H NMR spectroscopy
in C6D6 and by mass spectrometry in the case of 1. A
1
typical H NMR spectrum of the equilibrium mixture
obtained by the reaction of Me4Sb2 with cyclo-(Me3-
SiCH2Sb)n (n ) 4, 5) in C6D6 is depicted in Figure 1.
The most intensive signals stem from the starting
materials and from the tristibane, 1, for which the
singlet signals at 0.11 ppm for the SiMe3 protons and
(7) Silvestru, A.; Breunig, H. J .; Ebert, K. H.; Kaller, R. J . Orga-
nomet. Chem. 1995, 501, 117.
(8) Breunig, H. J .; Breunig-Lyriti, V.; Knobloch, T. P. Chem. Z. 1977,
101, 399.
(9) Hewertson, W.; Watson, H. R. J . Chem. Soc. 1962, 1490.
10.1021/om001085f CCC: $20.00 © 2001 American Chemical Society
Publication on Web 02/27/2001

Organoantimony Ring-Chain Equilibria
Organometallics, Vol. 20, No. 7, 2001 1361
F igu r e 1. 1H NMR spectrum of the components of the equilibrium mixture containing (Me3SiCH2Sb)5 (o), -Me4Sb2 (∼),
and Me2Sb-SbCH2SiMe3-SbMe2, 1, (x).
at 0.89 ppm for the methylene protons of the central
Me3SiCH2Sb group and two singlet signals of equal
intensity for the diastereotopic methyl substituents of
the terminal SbMe2 groups are characteristic. The low-
intensity signals probably result from catena-Me2Sb-
SbR-SbR-SbMe2 (R ) Me3SiCH2) and from longer
antimony chains. They disappear with excess distibane.
Estimations of the equilibrium constants for the
reaction according to eq 1 are based on the intensity of
but do not lead to complexes of other catena-stibanes.
The highly selective formation of 3 and 4 is remarkable
in view of the complexity of the initial mixture, which
contains the free tetrastibane at best as a minor
component. It reflects the high thermodynamic stability
of five-membered ring systems and the good fit between
the bite of the tetrastibane ligand and the chromium
center.
1
the H NMR signals of the most abundant components
using the C6H6 peak as internal standard. For K ) [Me2-
SbSbRSbMe2]5/[R5Sb5][Me4Sb2]5, R ) Me3SiCH2, we find
K ) 26. Analogous values for R ) Et or n-Pr are K )
120 or K ) 46.5 For K ) [Ph2SbSbRSbPh2]5/[R5Sb5][Ph4-
Sb2]5, R ) Me3SiCH2, we find K ) 8. These data reflect
a partial shift of the equilibria toward catena-stibanes
when bulkier substituents at the end and less bulky
groups in the center of the antimony chains are used.
A complete shift of the equilibria is achieved when
antimony chains are trapped as ligands in transition
metal carbonyl complexes.
Further complexation of 3 with [W(CO)5(thf)] gives
the complex cyclo-[Cr(CO)4(Me2Sb-SbR-SbR-SbMe2)W-
(CO)5] (R ) Me3SiCH2) (5) according to eq 3 in 79% yield
as orange crystals, soluble in aromatic and aliphatic
solvents. For a short time the complexes 3, 4, and 5 are
stable in air.
The equilibrium mixtures obtained by combining
solutions of Me4Sb2 or Ph4Sb2 with cyclo-(Me3SiCH2Sb)n
(n ) 4, 5) in toluene react with [Cr(CO)4(nbd)] (nbd )
norbornadiene) to give the tetrastibane complexes cyclo-
[Cr(CO)4(R’ Sb-SbR-SbR-SbR’ )] (3, R′ ) Me; 4, R′ )
2
2
Ph, R ) Me3SiCH2). Best yields (3, 69%; 4, 62%) are
obtained when the exact stoichiometry of eq 2 is used.
Variations of molar ratios reduce the yields of 3 and 4

1362 Organometallics, Vol. 20, No. 7, 2001
Breunig et al.
The NMR spectra of 3-5 are consistent with the
structures established by X-ray diffraction. They cor-
respond also to the spectra of analogous phosphorus
compounds.6a,d,f 1H NMR spectra of 3 and 4 exhibit one
singlet signal for the SiMe3 protons and two doublet
signals (AB spin system) for the methylene groups
bonded to one of the central antimony atoms, which are
both chiral. The organo groups bonded to the terminal
antimony atoms of the ligand are not equivalent, and
therefore two signals are observed for the SbMe2 groups
in 3. In the case of 4 the nonequivalency of the phenyl
groups is best reflected in the 13C NMR spectra, which
exhibit two singlet signals for each kind of carbon atom
of the phenyl rings. In 5 all the organic groups are
nonequivalent. The 1H NMR spectra of 5 show two
singlet signals for the SiMe3 groups, two AB spin
systems for the methylene groups, and four singlet
signals for the SbMe2 groups. The EI mass spectra of
3-5 contain molecular ions at highest mass and in the
case of 3 also with highest intensity. Fragmentation
occurs mainly by loss of the CO groups. The IR spectra
of 3 and 4 show in the region of the CO-stretching
vibrations the common pattern for complexes of the type
cis-L2Cr(CO)4. In the case of 5 instead of a strong signal
at 1945-1950 cm-1, which is common for complexes of
the type LW(CO)5, a shoulder was observed at 1952
cm-1. The composition of 3-5 has been proven by high-
resolution mass spectrometry and by elemental analy-
ses.
F igu r e 2. ORTEP representation at 50% probability of
the two possible conformers of 3 (ball-and-stick representa-
tion of Sb(2a) and Sb(3a)) and atom numbering scheme for
one of the d,l forms of 3. Important bond lengths (Å) and
angles (deg) are as follows: Sb(2)-Sb(3) 2.813(5), Sb(2)-
Sb(1) 2.828(5), Sb(4)-Sb(3) 2.822(5), Sb(2a)-Sb(3a) 2.800-
(2), Sb-Cr(1), 2.588(8)-2.596(8), Sb(1)-C 2.137(5)-2.144-
(5), Sb(2)-C(11) 2.189(5), Sb(3)-C(7) 2.178(5), Sb(4)-C
2.130(6)-2.139(6), Sb(4)-Cr(1)-Sb(1) 92.11(3), Cr(1)-Sb-
(4)-Sb(3) 121.55(2), Cr(1)-Sb(1)-Sb(2) 118.88(2), Sb(3)-
Sb(2)-Sb(1) 95.805(13), Sb(2)-Sb(3)-Sb(4) 94.947(13),
C(11)-Sb(2)-Sb(3) 98.05(16), C(11)-Sb(2)-Sb(1) 89.14-
(14), C(15)-Sb(4)-C(16) 97.6(3), C-Sb-Cr(1) 113.6(2)-
118.39(17), C-Sb(4)-Sb(3) 99.46(19)-102.86(18), C(6)-
Sb(1)-C(5) 98.5(3), C-Sb(1)-Sb(2) 96.52(17)-104.27(17),
C(7)-Sb(3)-Sb(2) 95.24(15), C(7)-Sb(3)-Sb(4) 90.06(14).
In an NMR-tube experiment we have also studied the
reactivity of 3 with tetramethyldistibane. The spectra
reveal that excess distibane leads to the formation of
the tristibane 1 and probably to [cis-(Me2SbSbMe2)2Cr-
(CO)4], a compound showing two singlet signals of equal
intensity in the region of the SbMe2 protons (0.87, 1.01
ppm).
in 3 and 88.6(3)-116.4(3)° in 5) correspond to p3
configurations for the three-coordinate antimony atoms
and to sp3 hybridization for the four-coordinate anti-
mony atoms. This view is also supported by the Sb-C
bond lengths of 3 and 5 (Sb(4-coordinate)-C 2.130(6)-
2.154(10) Å and Sb(3-coordinate)-C 2.149(8)-2.189(5)
Å). Close to the Sb(2) and Sb(3) atoms of 3 we found
two additional electron densities representing approxi-
mately 1.5 electron each. These electron densities were
assigned to antimony atoms from another conformation
of the five-membered CrSb4 ring. The crystal of 3
contains 98% of the main conformer and 2% of the
second conformer, the latter being formed by a ring
inversion process. Conformational effects of this kind
are not unusual for five-membered metal-containing
rings.11
Single crystals for X-ray diffraction studies have been
obtained by cooling solutions of 3 in petroleum ether to
-28 °C and solutions of 5 in petroleum ether/toluene
(5/1) to 7 °C. The crystal structures of 3 and 5 consist
of five-membered CrSb4 rings in which the Me2Sb-
SbR-SbR-SbMe2 (R ) Me3SiCH2) chain functions as
a chelating bidentate four-electron donor via lone pair
donation through the terminal Sb atoms. The structures
of 3 and 5 are depicted in Figures 2 and 3. In both
complexes the five-membered rings are nonplanar, the
Sb(2)-Sb(3) unit being twisted out of the Sb(1)-Cr(1)-
Sb(4) plane by 22.4° in the case of 5 and by 26.3° in the
case of the main conformer of 3. The trimethylsilyl-
methyl groups bound to Sb(2) and Sb(3) occupy trans
positions. For a catena-tetrastibane the meso and d,l
forms are possible; however only the d,l forms act as
ligand in 3 and 5.
Exp er im en ta l Section
The Sb-Cr bond lengths (2.596(8), 2.588(8) Å in 3 and
2.593(19), 2.575(15) Å in 5) lie in the usual range for
Sb-Cr distances ((cyclo-[(Me2SbOSbMe2Cr(CO)4]2, 2.566-
(3), 2.573(4) Å; cis-[(Me2SbSSbMe2)2Cr(CO)4], 2.5986-
(12), 2.5838(9) Å).10 The angles around the antimony
atoms (Sb(1) 96.52(17)-118.39(17)° in 3 and 100.0(5)-
118.73(4)° in 5, Sb(4) 97.6(3)-121.55(2)° in 3 and 95.9-
(5)-121.19(4)° in 5, Sb(2) 89.14(14)-98.05(16)° in 3 and
99.1(2)-118.49(3)° in 5, and Sb(3) 90.06(14)-95.24(15)°
Gen er a l Com m en t s. NMR spectra were run on Bruker
DPX 200 and AVANCE DRX-600 spectrometers. Chemical
shifts are reported in δ units (ppm) referenced to C6D5H (7.15
ppm, 1H) and C6D6 (128.0 ppm, 13C). The C, H correlation was
performed with the use of HSQC spectra. Mass spectra were
recorded on Finnigan MAT CH7 (A) and Finnigan MAT 8222
spectrometers. The pattern of antimony-containing ions was
compared with theoretical values. Elemental analyses were
performed by Mikroanalytisches Laboratorium Beller in Go¨t-
(10) Breunig, H. J .; J o¨nsson, M.; Ro¨sler R.; Lork, E. J . Organomet.
Chem. 1999, 588, 256.
(11) Corey, E. J .; Bailar, J . C. J . Am. Chem. Soc. 1959, 81, 2620.

Organoantimony Ring-Chain Equilibria
Organometallics, Vol. 20, No. 7, 2001 1363
g (2.36 mmol) of Me4Sb2 in 15 mL of toluene was added to 0.6
g (2.36 mmol) of nbdCr(CO)4 in toluene (10 mL). The reaction
mixture was stirred for 12 h at room temperature. Thereafter
the solution was reduced to 10 mL, combined with Al2O3 (2
g), dried to a flowing powder under reduced pressure, and
placed on a chromatography column (12 × 2 cm, Al2O3, activity
level II). With petroleum ether/toluene (1/1) an intense orange
fraction was eluted. Removal of the solvents under reduced
pressure gave 1.44 g (69%) of 3 as a orange microcrystalline
solid. Crystals were grown by keeping a solution of 3 in
petroleum ether for 2 days at -28 °C; mp 107 °C. Anal. Calcd
for C16H34Si2O4Cr1Sb4 (885.57): C, 21.70; H, 3.86. Found: C,
21.71; H, 3.82. 1H NMR (C6D6, 200 MHz): -0.04 (s, 18 H,
1
2
(CH3)3Si, J CH ) 136.9 Hz, J SiH ) 6.1 Hz), AB spin system
2
with A, 0.11; B, 0.19 (4 H, CH2, J HH ) 12.9 Hz), 1.09 (s, 6 H,
CH3Sb), 1.38 (s, 6 H, CH3Sb). 13C NMR (C6D6, 50 MHz): -9.34
(s, CH2), -2.56 (s, CH3Sb), -1.95 (s, CH3Sb), 0.62 (s, (CH3)3-
Si), 221.82 (s, COeq), 234.42 (s, COax). IR (toluene): 1998 s,
1988 sh, 1909 vs cm-1 (ν CO). HRMS (EI, 70 eV): 885.75616
(calcd 885.75617 amu, C16H34O4Si2Cr52Sb2121Sb2123, M+). MS
(EI, 70 eV, 204 °C): 886 (100) [M+], 802 (14) [M+ - 3 CO],
774 (47) [M+ - 4 CO], 740 (4) [M+ - (SiMe3)2], 686 (14) [Sb4-
+
Me6Cr(CO)2+], 670 (15) [(Me3SiCH2)4Sb3 - 3 Me], 540 (20)
F igu r e 3. ORTEP representation at 25% probability of 5
and atom-numbering scheme for one of the enantiomers
of 5. Important bond lengths (Å) and angles (deg) are as
follows: Sb(3)-Sb(2) 2.811(9), Sb(3)-Sb(4) 2.845(9), Sb-
(1)-Sb(2) 2.832(11), Sb-Cr(1) 2.576(15)-2.593(19), Sb(2)-
W(1) 2.791(6), Sb(4)-C 2.142(10)-2.145(10), Sb(2)-C(11)
2.149(8), Sb(3)-C(7) 2.177(9), Sb(1)-C 2.134(11)-2.154-
(10), Sb(1)-Cr(1)-Sb(4) 94.21(5), Cr(1)-Sb(1)-Sb(2) 118.73-
(4), Cr(1)-Sb(4)-Sb(3) 121.19(4), Sb(2)-Sb(3)-Sb(4) 94.780-
(3), Sb(3)-Sb(2)-Sb(1) 99.17(3), W(1)-Sb(2)-Sb(1) 99.17(3),
W(1)-Sb(2)-Sb(3) 118.49(3), C(11)-Sb(2)-Sb(3) 107.7(2),
C(11)-Sb(2)-Sb(1) 99.1(2), C(11)-Sb(2)-W(1) 116.4(3),
C(15)-Sb(1)-C(16) 100.0(5), C(6)-Sb(4)-C(5) 95.9(5), C-Sb-
(1)-Cr(1) 114.9(3)-118.5(3), C-Sb(4)-Cr(1) 114.0(4)-
117.3(3), C-Sb(1)-Sb(2) 100.4(3)-101.1(3), C-Sb(4)-Sb(3)
101.5(3)-102.9(3), C(7)-Sb(3)-Sb(2) 88.6(3), C(7)-Sb(3)-
Sb(4) 95.3(3).
[Sb4Cr+], 502 (33) [CH2Sb2Cr2(CO)5+], 446 (18) [(Me3SiCH2)4-
+
+
Sb2 - (SiMe3)2], 430 (23), 417 (20) [(Me3SiCH2)4Sb2 - CH2-
(SiMe3)2, - Me], 295 (11) [(Me3SiCH2)2Sb+], 225 (5) [(Me3-
SiCH2)MeSb+], 139 (29) [Me3SiCH2Cr+], 73 (58) [Me3Si+], 52
(18) [Cr+].
[Cr (CO)4(P h 2Sb-SbR-SbR-SbP h 2)] (R ) Me3SiCH2)
(4). The reaction of a mixture of 0.37 g (0.35 mmol) of (Me3-
SiCH2Sb)5 and 0.49 g (0.88 mmol) of Ph4Sb2 with 0.22 g (0.88
mmol) of nbdCr(CO)4 in 20 mL of toluene and the workup
procedures were performed in a manner analogous to that of
the synthesis of 3. However, after stirring for 12 h at room
temperature, the reaction mixture was heated under reflux
for 3 h. For the chromatography Al2O3, activity level III, 17 ×
2 cm was used. 4 was eluted with petroleum ether/toluene (19/
1) as a yellow fraction. Removal of the solvent under reduced
pressure gave 0.62 g (62%) of 4 as a yellow microcrystalline
solid, mp 181 °C. Anal. Calcd for C36H42Si2O4Cr1Sb4 (1133.86):
C, 38.13; H, 3.73. Found: C, 38.36; H, 3.82. 1H NMR (C6D6,
200 MHz): -0.02 (s, 18 H, (CH3)3Si, 1J CH ) 122.1 Hz), AB spin
tingen. The reactions and manipulations were performed
under an inert atmosphere of dry argon. (Me3SiCH2Sb)5,7 Me4-
Sb2,8 Ph4Sb2,9 and [Cr(CO)4(nbd)] (nbd ) norbornadiene)13 were
prepared according to reported procedures.
Rea ction s of cyclo-(Me3SiCH2Sb)n (n ) 4, 5) w ith Dis-
tiba n es. Solutions of distibanes in various concentrations in
C6D6 were added at room temperature to saturated solutions
of (Me3SiCH2Sb)5. The catena-stibanes 1 and 2 were formed
immediately in equilibria with the distibanes and the cy-
clostibane. The molar ratio of the components was determined
by integration of the NMR signals.
system with A, 0.08; B, 0.47 (4 H, CH2, 2J HH ) 12.8 Hz), 6.91-
3
7.08 (m, 12 H, C6H5 - m + p), 7.95 (d, 4 H, C6H5 - o, J HH
)
7.2 Hz), 8.10 (d, 4 H, C6H5 - o, 3J HH ) 7.2 Hz). 13C NMR (C6D6,
50 MHz): -8.45 (s, CH2), 0.23 (s, (CH3)3Si), 129.67 (s, C6H5
-
m), 129.74 (s, C6H5 - p), 129.83 (s, C6H5 - m), 129.87 (s,
C6H5 - p), 134.24 (s, C6H5 - ipso), 134.70 (s, C6H5 - ipso),
136.17 (s, C6H5 - o), 136.61 (s, C6H5 - o), 221.63 (s, COeq),
233.72 (s, COax). IR (toluene): 2003 vs, 1970 sh, 1909 vs cm-1
(ν CO). MS (EI, 70 eV, 230 °C): 1134 (22) [M+], 1022 (52)
1,1,3,3-Tetr a m eth yl-2-(tr im eth ylsilylm eth yl)tr istiba n
[M+ - 4 CO], 658 (14) [Sb3Ph(Me3SiCH2)3 - 3 Me], 648 (15)
+
1
2
(1). H NMR (C6D6, 600 MHz): 0.11 (s, 9 H, (CH3)3Si, J SiH
)
[Sb3Ph2(Me3SiCH2)2 - 3 Me], 604 (38) [Ph4Sb2Cr+], 552 (20)
+
6.4 Hz), 0.89 (s, 2 H, CH2), 1.05 (s, 6 H, CH3Sb), 1.08 (s, 6 H,
CH3Sb). 13C (C6D6, 50 MHz): -12.42 (CH2), -8.40 (CH3Sb),
-8.20 (CH3Sb), 1.33 ((CH3)3Si). MS (EI, 70 eV, 44 °C): 512 (2)
[M+], 497 (1) [M+ - Me], 440 (3.4) [M+ - Me3Si], 425 (2) ([Sb3-
Me2+], 409 (1.4) [Sb3Me3+], 395 (4.4) [Sb3Me2+], 376 (1.2) [Sb3-
Me+], 365 (1) [Sb3+].
[Ph4Sb2+], 502 (27) [CH2Sb2Cr2(CO)5+], 450 (26) [CH2Sb2Cr-
(CO)5+], 327 (29) [Ph2SbCr+], 295 (23) [(Me3SiCH2)2Sb+], 285
(25) [(Me3SiCH2)SbPh+], 275 (65) [Ph2Sb+], 205 (39) [Sb(CH2-
Si)2+], 154 (100) [Ph2+], 135 (96) [PhSiMe3+], 77 (20) [Ph+], 73
(98) [Me3Si+], 52 (34) [Cr+], 28 (9) [Si+].
[Cr (CO)4(Me2Sb-SbR-SbR-SbMe2)W(CO)5] (R ) Me3-
SiCH2) (5). A 0.5 g (0.56 mmol) sample of 3 and 0.22 g (0.56
mmol) of W(CO)5(thf) in 150 mL of THF were stirred for 12 h
at room temperature. Thereafter, the solution was reduced to
10 mL, combined with Al2O3 (1.5 g), dried to a flowing powder
under reduced pressure, and placed on a chromatography
column (20 × 2 cm, Al2O3, activity level III). With petroleum
ether/toluene (19/1) an orange fraction was eluted. Removal
of the solvents under reduced pressure gave 0.54 g (79%) of 5
as an orange microcrystalline solid. Crystals were grown by
storing a solution of 5 in petroleum ether/toluene (5/1) for 12
h at 7 °C, mp 146-147 °C. Anal. Calcd for C21H34Si2O9Cr1W1-
Sb4 (1209.47): C, 20.85; H, 2.83. Found: C, 21.10; H, 2.94. 1H
1,1,3,3-Tetr a p h en yl-2-(tr im eth ylsilylm eth yl)tr istiba n
(2). 1H NMR (C6D6, 600 MHz): -0.11 (s, 9 H, (CH3)3Si, 2J SiH
)
1
6.3 Hz, J CH ) 115.2 Hz), 0.90 (s, 2 H, CH2), 7.06 (m, 12
H, C6H5 - m + p), 7.72 (m, 8 H, C6H5 - o). 13C (C6D6, 50
MHz): -9.13 (CH2), 0.63 ((CH3)3Si), 128.56 (C6H5 - p), 128.72
(C6H5 - p), 129.31 (C6H5 - m), 129.37 (C6H5 - m), 138.08
(C6H5 - o), 138.27 (C6H5 - o).
[Cr (CO)4(Me2Sb-SbR-SbR-SbMe2)] (R ) Me3SiCH2)
(3). A mixture of 0.99 g (0.94 mmol) of (Me3SiCH2Sb)5 and 0.72
(12) Sheldrick, W. S. Acta Crystallogr. 1976, B32, 308.
(13) King, R. B. In Organometallic Synthesis; King, R. B., Eisch, J .
J . Eds.; 1965; Vol. 1, p 122.

1364 Organometallics, Vol. 20, No. 7, 2001
Breunig et al.
Ta ble 1. Cr ysta l Da ta , Da ta Collection , a n d
Str u ctu r e Refin em en t P a r a m eter s for 3 a n d 5
50 MHz): -8.01 (s, CH2), -4.95 (s, CH2), -2.46 (s, CH3Sb),
-1.95 (s, CH3Sb), -1.62, (s, CH3Sb), -0.13 (s, (CH3)3Si), 0.79
(s, CH3Sb), 1.16 (s, (CH3)3Si), 197.58, 198.47, 220.75, 232.21
(CO). IR (toluene): 2064 vs, 1999 s, 1977 sh, 1952 sh, 1914 s,
1900 s cm-1 (ν CO). HRMS (EI, 70 eV): 1203.67822 (calcd
1203.67826 amu, C21H34O9Si2Cr52Sb4121W182, M+). MS (EI, 70
eV, 237 °C): 1210(29) [M+], 1098 (26) [M+ - 4 CO], 886 (100)
3
5
formula
fw
color
C
16H34CrO4Sb4Si2
C21H34CrO9Sb4Si2W
1209.51
orange
885.61
orange
temp (K)
cryst size, mm
cryst syst
space group
a, Å
b, Å
c, Å
R, deg
â, deg
γ, deg
V, Å3
173(2)
298(2)
[M+ - W(CO)5], 802 (32) [M+ - W, - 8 CO], 774 (82) [M+
-
0.5 × 0.4 × 0.3
monoclinic
P21/n
15.8510(10)
10.1220(10)
20.436(3)
90
110.580(10)
90
3069.6(6)
4
0.7 × 0.5 × 0.5
monoclinic
P21/n
9.639(4)
21.484(3)
18.414(2)
90
90.56(2)
90
3813.1(17)
4
W, 9 CO], 742 (16) [M+ - W(CO)5, - (SiMe3)2], 686 (29) [Sb4-
+
Me6Cr(CO)2+], 670 (17) [(Me3SiCH2)4Sb3 - 3 Me], 540 (19)
[Sb4Cr+], 502 (29) [CH2Sb2Cr2(CO)5+], 446 (16) [(Me3SiCH2)4-
+
+
Sb2 - (SiMe3)2], 430 (18), 417 (17) [(Me3SiCH2)4Sb2 - CH2-
(SiMe3)2, - Me], 295 (8) [(Me3SiCH2)2Sb+], 139 (19) [Me3SiCH2-
Cr+], 73 (56) [Me3Si+], 52 (22) [Cr+].
X-r a y Cr ysta llogr a p h y. The details of the crystal structure
determination and refinement are given in Table 1. Data were
collected on a Siemens P4 four-circle diffractometer using
graphite-monochromated Mo KR radiation (λ ) 0.710 73 Å).
For this purpose the crystals were attached with Kel-F-oil to
a glass fiber and cooled under a nitrogen stream to 173 K in
the case of 3. The structures were refined with anisotropic
thermal parameters. The hydrogen atoms were refined with
a riding model and a mutual isotropic thermal parameter. For
structure solving and refinement the software package SHELX-
97 was used.14 The drawings were created with the DIAMOND
program.15
Z
d
calcd, g‚cm-3
1.916
3.911
ω/2θ
1672
2.107
6.172
ω/2θ
2248
µ(Mo KR), mm-1
scan method
F(000)
scan range (deg)
no. of measd data
2.75 e θ e 27.50
8799
2.56 e θ e 25
8544
no. of unique data 7032
6654
(R(int) ) 0.0259)
(R(int) ) 0.0198)
no. of params
abs corr
267
356
ψ-scans
0.0753
0.0470
0.0709
0.0337
DIFABS12
0.0942
0.0530
0.0894
0.0388
wR2a (all data)
R1a (all data)
wR2a (I>2σ(I))
R1a (I>2σ(I))
GOF on F2
Ack n ow led gm en t. The support of this work by the
Universita¨t Bremen and the Fonds der Chemischen
Industrie is gratefully acknowledged.
1.045
1.029
residual density,
+0.688; -0.638
+0.975; -0.995
Su p p or tin g In for m a tion Ava ila ble: Tables of crystal
data and refinement details, atom coordinates and U values,
bond distances and angles, anisotropic thermal parameters,
and dihedral angles. This material is available free of charge
via the Internet at http://pubs.acs.org.
e‚Å-3
a
Definition of the R values: R1 ) (∑||Fo| - |Fc||)/(∑|Fo|; wR2 )
2
{[w∑(Fo - Fc2)2]/∑[w(Fo2)2]}1/2 with w-1 ) σ2(Fo2) + (aP)2 + bP.
NMR (C6D6, 200 MHz): -0.06 (s, 9 H, (CH3)3Si), -0.04 (s, 9
H, (CH3)3Si), AB spin system with A, 0.08; B, 0.16 (2 H, CH2,
2J HH ) 12.7 Hz), AB spin system with A, 0.70; B, 0.82 (2 H,
OM001085F
(14) Sheldrick, G. M. SHELX-97; Universita¨t Go¨ttingen, 1997.
(15) DIAMOND-Visual Crystal Structure Information System;
CRYSTAL IMPACT: P.O.B. 1251, D-53002, Bonn.
2
CH2, J HH ) 12.9 Hz), 1.13 (s, 3 H, CH3Sb), 1.18 (s, 3 H, CH3-
Sb), 1.31 (s, 3 H, CH3Sb), 1.40 (s, 3 H, CH3Sb). 13C NMR (C6D6,