II. Literature data [631870]

II. Literature data

Literature data 7

In this chapter a review of the structural types of organo antimony complexes
containing metal carbonyl fragments will be presented. Here in it is also presented a
class of organoantimony compounds containing aromatic organic groups with potential
to establish intramolecular N→Sb interactions and their corresponding complexes.
This chapter is based on up -to-date searches in Cambridge Structural Database
and Science Finder Database. Compounds are grouped as follows:

 Di- and t riorganoantimony (III) metal carbonyl complexes

 Com plexes of oligo stibanes and related organoantimony compounds

II.1. Di- and t riorganoantimony (III) metal carbonyl complexes

The chemistry of the metal carbonyl stibine complexes has been studied more
often in the last years .10,11,12,13,14,15 It was already kn own that the transition metal
compounds with organoantimony ligands mostly contain monodentate SbR 3 (R = alky l,
aryl); however, stibines have always been received much less attention than
phosphorus or arsine analogues.
The trend described for the group 15 compounds corresponds to the increasing s
character of the electron lone pair,16 although the behavior of the derivatives also
depends on the substituent effects. Thus electron -withdrawing organic groups
decrease the Lewis basicity whereas electron -releasi ng groups increase it.17

10 M. J. Aroney, I. E. Buys, M. S. Davies, T. W. Hambley, J. Chem. Soc., Dalton Trans ., 1994 , 2827 .
11 A. M. Hill, N. J. Holmes, A. R. J. Genge, W. Levason, M. Webster, S. Rutschow, J. Chem. Soc., Dalton
Trans ., 1998, 825 .
12 H. J. Breunig, T. Borrmann, E. Lork , C. I. Raț, J. Organomet. Chem ., 2007 , 692, 2593 .
13 H. J. Breunig , E. Lork, C. I. Raț, R. P. Wagner, J. Organomet. Chem ., 2007 , 692, 3430 .
14 H. J. Breunig, T. Borrmann , E. Lork, O. Moldovan , C. I. Raț, R. P. Wagner, J. Organomet. Chem ., 2009 ,
694, 427 .
15 W. L evason, M. L. Matthews, G. Reid, M. Webster, Dalton Trans ., 2004 , 51.
16 W. Kutzelnigg, Angew. Chem. Int. Ed. Engl. , 1984 , 23, 272.
17 N. R. Champness, W. Levason, Coord. Chem. Rev. , 1994 , 133, 115.

8 The structural types of organoantimony metal carbonyl complexes

This study on the metal carbonyl stibine complexes has been realized taking into
account the electronic and steric factors which affect metal -ligand interactions in
transition -metal complexes. This knowledge can be important in u nderstanding the
course of the metal -centered reactions in such complexes.

II.1. a. Preparation

The complexes 1–2, 4–10 were prepared by substitution of tetrahydrofuran (thf)
in reactions between organoantimony (III) derivatives such as Me 3Sb, tBu3Sb, Ph 3Sb,
Ph2SbX, and [M(CO) 5(thf)] to give [M(CO) 5(Me 3Sb)] [M = Cr ( 1), W ( 2)],14
[Cr(CO) 5(tBu3Sb)] (4),13 [M(CO) 5(Ph 3Sb)] [M = Cr ( 5), Mo ( 6), W (7)]10 and
[W(CO) 5(Ph 2SbX) ] [X = Cl ( 8), Br ( 9), I ( 10)].12 In the reaction between Me 3Sb and cis-
[Mo(CO) 4(piperid ine)2], the substitution of piperidine leads to the cis-
[Mo(CO) 4(Me 3Sb) 2] (3) complex (Scheme 1 ).14
The complex es 1–2, 4–10 were characterized by single -crystal X -ray diffraction
studies and the y cons ist of trigonal pyramidal R 3Sb or Ph 2SbX ligands coordi nated to
square pyramidal M(CO) 5 units .
The iron carbonyl complexes (Scheme 1 ) were obtained by reacting a thf solution
of Fe2(CO) 9 with 1,3 -C6H4(SbMe 2)2 (for 11), 1,4 -C6H4(SbMe 2)2 (for 12), 1,3 –
C6H4(CH 2SbMe 2)2 (for 17) and 1,4 -C6H4(CH 2SbMe 2)2 (for 18). The preparation s of
tungsten carbonyl complexes 13 and 14 were made by photolysis of [W(CO) 6] in situ
with 1,3-C6H4(CH 2SbMe 2)2 and 1,4 -C6H4(CH 2SbMe 2)2, respectively. By contrast , the
complexes 15 and 16 were obtained in CH 2Cl2 by reacting 1,2-C6H4(CH 2SbMe 2)2 and
[W(CO) 4(piperidine) 2] (for 15) and [Mo(CO) 4(nbd) 2] (nbd = norbornadiene) (for 16),
respectiv ely.15
The nickel carbonyl complexes 19–21 were obtained by injection of Ni(CO) 4 into
the solutions of organoantimony derivatives: 1,3 -C6H4(CH 2SbMe 2)2 (for 19), 1,4-
C6H4(CH 2SbMe 2)2 (for 20) and 1,2-C6H4(CH 2SbMe 2)2 (for 21).15
The complexes 1−21 are presented in Scheme 1 .

Literature data 9

Scheme 1 .

The complexes of the type [ M(CO) 5(η1-dpsm) ],11 [M = Cr (22), Mo (23) or W (24);
dpsm = bis( diphen ylstibino)methane ] were synthesi sed by photolysis of [M(CO) 6] in thf
to yield [M(CO) 5(thf)] in situ , followed by addition of dpsm. A better chemical route is
the reaction of dpsm with [NEt 4][M(CO) 5Br]18 in a 1 : 1 molar ratio in ethanol. Thermal
reactions of [M(CO) 5(η1-dpsm)] with [M (CO) 6] take place with low yields . When the
reaction between [M(CO) 5Br]⁻ with dpsm was made in a 2 : 1 molar ratio, only the

18 E. W. Abel, I. S. Butler, J. G. Reid, J. Chem. Soc. , 1963, 2068.

10 The structural types of organoantimony metal carbonyl complexes

[M(CO) 5(η1-dpsm)] (M = Mo or W) complexes were obtained. In the case of chromium
a mixture of [Cr(CO) 5(η1-dpsm)] and [{Cr(CO) 5}2(dpsm)] resulted.
The reaction between [M(CO) 5(η1-dpsm)] and [M(CO) 5(thf)] leads to the pure
[{M(CO) 5}2(dpsm)] [M = Cr ( 25) or W ( 26)].11
The dmsm compounds [dmsm = bis(dimethylstibino )methane] 27–29 were
obtained by reaction of [M(CO) 6] with dmsm in a 2 : 1 mol ar ratio in a high -boiling
solvent. The complexes of the type cis-[{M(CO) 4(L–L)}2] (M = Cr, Mo or W; L –L = dpsm
or dmsm) (see Scheme 2 , complexes 30–35) were prepared by the displacement of the
neutral ligands from [M(CO) 4(nbd) ] [M = Cr or Mo; nbd = n orbornadiene
(bicyclo[2.2.1]hepta -2,5-diene)] or [W(CO) 4(Me 2NCH 2CH 2CH 2NMe 2)]. In the solid state
the pure [{M(CO) 4(dmsm)} 2] complexes appear to be air stable, but in CH 2Cl2 solution
they decompose rapidly.11
The fac-[Mo(CO) 3(η1-dpsm) 3] (37) complex has been synthesis ed by reacting
[Mo(CO) 6] with dpsm in ethanol , with NaBH 4 as catalyst. The corresponding tungsten
38 and chromium 36 complexes do not form using this method . The fac-
[Cr(CO) 3(dpsm) 3] (36) was obtained in low yield by heating [Cr(CO) 4(nbd)] with an
excess of dpsm in ethanol or more slowly in methylcyclohexane, and fac-
[W(CO) 3(dpsm) 3] (38) from [W(CO) 3(MeCN) 3] and dpsm.11 The complexes 22−38 are
depicted in Scheme 2 .11
The distibinopropanes R 2Sb(CH 2)3SbR 2 were used t o obtain cis-
[M(CO) 4{R2Sb(CH 2)3SbR 2}] [R = Ph, M = Cr ( 39), Mo ( 40) or W ( 41); R = Me, M = Cr ( 42),
Mo ( 43) or W ( 44)], [{Fe(CO) 4}2{μ-R2Sb(CH 2)3SbR 2}], [R = Ph ( 45)], [{Ni(CO) 3}2{μ-
R2Sb(CH 2)3SbR 2}] [R = Ph ( 46), Me ( 47)], [Co 2(CO) 6{Ph 2Sb(CH 2)3SbPh 2}] ( 48),
[Co 2(CO) 4{Me 2Sb(CH 2)3SbMe 2}3][Co(CO) 4]2 (49). The preparation of complexes 39–48 is
shown in Scheme 3 .19 A few Group 6 metal carbonyl complexes of 1,2 -C6H4(SbMe 2)220
and Ph 2Sb(CH 2)3SbPh 221 were reported in the early 1970s, but with little
characterization da ta.

19 M. D. Brown, W. Levason, J. M. Manning, G. Reid, J. Organomet. Chem ., 2005 , 690, 1540.
20 E. Shewchuk, S. B. Wild, J. Organomet. Chem ., 1977 , 128, 115.
21 T. Fukumoto, Y. Matsumura, R. Okawara, Inorg. Nucl. Chem. Lett ., 1973 , 9, 711.

Literature data 11

Scheme 2.11

Reagents: I. [M(CO) 4(nbd)] (M = Cr, Mo) in EtOH, or [W(CO) 4(piperidine) 2] in EtOH; II. Ni(CO) 4 in CH 2Cl2; III.
Fe2(CO) 9 in thf; IV and V . Co 2(CO) 8 in toluene.

Scheme 3. Preparation of complexes 39−48.19

12 The structural types of organoantimony metal carbonyl complexes

The spectroscopic data used to characterize the metal carbonyl complexes
containing stibines as ligands are listed in Table 1 .

Table 1. Caracterization of compounds 1–49.
Compoun
d Spectroscopic data Compound Spectroscopic data
1 1H, 13C, MS, IR, X -ray [ 14] 26 1H, 13C, IR, MS, X -ray [11]
2 1H, 13C, MS, IR, X -ray [14] 27 1H, 13C, IR [ 11]
3 1H, 13C, MS, IR, X -ray [ 14] 28 1H, 13C, 95Mo, IR [11]
4 1H, 13C, MS, X -ray [13] 29 1H, 13C, MS, IR [ 11]
5 X-ray [10] 30 1H, 13C, MS, IR [11]
6 X-ray [10] 31 1H, 13C, 95Mo, MS, IR [11]
7 X-ray [10] 32 1H, 13C, MS, IR , X-ray [11]
8 1H, 13C, MS, IR, X -ray [ 12] 33 1H, 13C, MS, IR [11]
9 1H, 13C, MS, IR, X -ray [ 12] 34 1H, 13C, 95Mo, MS, IR [11]
10 1H, 13C, MS, IR, X -ray [ 12] 35 1H, 13C, MS, IR, X-ray [11]
11 1H, 13C, MS, IR [15] 36 1H, 13C, MS, IR [ 11]
12 1H, 13C, MS, IR [15] 37 1H, 13C, 95Mo, MS, IR [11]
13 1H, 13C, MS, IR [15] 38 1H, 13C, MS, IR [11]
14 1H, 13C, MS, IR [15] 39 1H, 13C, MS, IR [ 19]
15 1H, 13C, MS, IR [15] 40 1H, 13C, 95Mo, MS, IR [ 19]
16 1H, 13C, 95Mo, IR [15] 41 1H, 13C, MS, IR [ 19]
17 1H, 13C,MS, IR, X -ray [15] 42 1H, 13C, MS, IR [ 19]
18 1H, 13C,MS, IR [15] 43 1H, 13C, 95Mo, IR [ 19]
19 1H, 13C, IR [15] 44 1H, 13C, MS, IR [ 19]
20 1H, 13C, IR [15] 45 1H, 13C, MS, IR [ 19]
21 1H, 13C, IR [15] 46 1H, 13C, IR [ 19]
22 1H, 13C, MS, IR [11 ] 47 1H, 13C, IR [ 19]
23 1H, 13C, 95Mo, MS, IR [ 11] 48 1H, IR [ 19]
24 1H, 13C, MS, IR, X -ray [ 11] 49 1H, 59Co, MS, IR [ 19]
25 1H, 13C, MS, IR [11]

Literature data 13

II.1. b. Spectroscopic characterization

The 1H and 13C NMR spectra of the air -stable complexes formed as colourless ( 1,
4), brown ( 2, 3), yellow -green ( 8) and yellow ( 9, 10) products , show the expected
signals. In the infrared spectra, the patterns of the ν(CO) stretching vibrations are
typical for a C 4v local s ymmetry of the metal carbonyl fragments in the case of 1 and 2.
The IR spectra of the tungsten carbonyl comple x [{W(CO) 5}2{1,4-
C6H4(CH 2SbMe 2)2}] (14)15 exhibited three ν(CO) band s at ca. 2069, 1995, 1937 cm–1,
consistent with square pyramidal W(CO) 5 moieties (theory: 2 A1 + E), at energies sim ilar
to those in other carbonyltungsten -stibine complexes . Also the 1H and 13C NMR spectra
as well as APCI MS were consiste nt with this formulation .10
Iron carb onyl complexes of the type [{Fe(CO) 4}2{C6H4(CH 2SbR2)2}] were obtained
as red or brown powders or oils, which were found to be stable at room temperature
in an inert atmosphere. The NMR spectra show the singlet resonances for the CH 3 and
CH 2 protons in the case of [{Fe(CO) 4}2{C6H4(CH 2SbMe 2)2}]. The presence of a singlet
resonance in 13C NMR suggests that the CO groups are fluxional .15 The IR spectra of the
iron carbo nyl derivatives show three ν(CO) stretching vibration at ca. 2040, 1965, 1933
cm–1 (CH 2Cl2 solutions) , consistent with axially substituted trigonal bipyramidal iron
centres ( C3v)22 (theory: 2 A1 + E).
The 1H and 13C NMR spectra of the [Ni(CO) 2{1,2-C6H4(CH 2SbMe 2)2}] (21) complex
confirm ed the presence of single t CH 3 and CH 2 resonances, both shifted to high er
frequency from the values in the free ligand, and of a single t resonance for the
carbonyl groups at δ(CO) 201.1 ppm . The ν(CO) stretching vibrations in this complex
were found at the 2002 and 1939 cm–1 and were compared with those in [Ni(CO) 2(L–L)]
[L–L = o-C6H4(PMe 2)2 1996, 1931 cm–1, and o-C6H4(AsMe 2)2 1996, 1931 cm–1]23 showing
that the stibine is a si gnificantly weaker σ -donor than the diphosphine or diarsine
ligands . When the reaction of 1,2-C6H4(CH 2SbMe 2)2 with Ni(CO) 4 was performed, new
carbonyl stretches at 2068 and 1993 cm–1 were observed, corresponding to a Ni(CO) 3
fragment.24 After dryness in vac uum , the resulted product was a colourless oil and both
1H and 13C NMR spectra of this product were consistent with the formation of
[Ni(CO) 3{η1-1,4-C6H4(CH 2SbMe 2)2}] (20).15

22 L. R. Martin, F. W. B. Einstein and R. K. Pomeroy, Inorg. Chem. , 1985 , 24, 2777.
23 J. Chatt and F. A. Hart, J. Chem. Soc. , 1960 , 1378.
24 A. M. Hill, W. Levason, M. Webster, I. Albers, Organometallics , 1997 , 16, 5641.

14 The structural types of organoantimony metal carbonyl complexes

For the metal carbonyl complexes containing the dpsm ligand, 22–24,11 the three
ν(CO) vibration modes in the IR spectra (theory 2A 1 + E) and the two δ(CO) resonances
(1 : 4 ratio) in the 13C NMR spectra are consistent with the expected C4v structure This
was demonstrated also by a single -crystal X-ray study. The formulation for the
complexes 25–29 as [(OC) 5M(μ -dpsm)M(CO) 5]11 was confirmed by IR and MS
spectrometry . The formulation as [(OC) 4M(μ-L–L)2M(CO) 4] dimers in the case of the
complexes 30–35 was supported by FAB mass spectra which show the corresponding
ions for the dpsm and dmsm complexes , respectively. The singlet δ(CO) resonance in
the 13C NMR spectrum of each complex and the two ν(CO) bands in the IR spectra are
typical of the fac-M(CO) 3Sb3 arrangement in compounds 36–38, cf. fac-
[Mo(CO) 3{MeC(CH 2SbPh 2)3}].25
The Group 6 comple xes 39–4519 were investigated by NMR and IR spectroscopy.
The derivatives of Me 2Sb(CH 2)3SbMe 2 were poorly soluble in dichloromethane , but they
dissolved easily in DMSO, in which the 1H and 13C NMR studies have been recorded .
The spectra show the expected r esonances, including those fo r the CO groups . In the
case of the tungsten derivatives weak satellit es were observed due to the 1J183W–13C
couplings; the magnitude of the coupling trans to Sb (165 Hz) placing the stibines low
in the trans influence series26 and thus reflecting the weak σ -donation by the antimony.
The identity of [{Fe(CO) 4}{η1-Ph2Sb(CH 2)3SbPh 2}]19 was based on the presence of
three major CH 2 resonances in the NMR spectra (suggesting the monodentate
coord ination pattern of the distibine ligand ) and on the number of the ν(CO) bands the
IR spectrum. The pattern for the 13C resonances for the carbonyl groups in the NMR
spectrum of this complex are not significantly different from those in the
corresponding 2 : 1 complex (45).19
The formulation of the tricarbonyl nickel complexes 46 and 4719 was
demonstrated by the characteristic pattern of the resonances for the carbonyl groups
in the 13C NMR spectra and the two IR active carbonyl stretches (theory A 1 + E). Also
the presence of one CH 3 and two CH 2 (2:1 intensity ratio) resonances in the NMR
spectra confirm ed that the distibine is bidentate coordinated.
Due to its instability, t he complex [Co 2(CO) 4(Me 2Sb(CH 2)3SbMe 2)3][Co(CO) 4]2 (49)
has been identified immediately after isolation by spectroscopic meth ods. The IR
spectrum of the solid in the region characteristic for CO vibrations is very simple,
consisting of two strong broad absorptions at 1968 and 1876 cm–1. These are very

25 A. F. Chiffey, J. Evans, W. Levason, M. Webster, Organometallics , 1996 , 15, 1280 .
26 W. Buchner, W. A. Schenk, Inorg. Chem ., 1984 , 23, 132.

Literature data 15

similar to those reported for several diarsine complexes27 and consistent with the
formulation proposed.

II.1. c. Single -crystal X -ray diffraction studies

The complexes 1–10 were characterized by single -cystal X -ray diffraction studies
and their crystals contain molecular units with trigonal p yramidal ligands bonded
through the Sb atom to transition metal atom s.
The value of the coordinative bond length in complex 1 is Sb –Cr 2.6108(6) Å,14 in
comparison with the [ Cr(CO) 5(tBu3Sb)] (4) complex in which the coordinative bond [ Sb–
Cr 2. 7042(7) Å] is significantly longer.13
In the comp lex 4 is observed that t he environment of the Sb is distorted
tetraheadral with av. Cr–Sb–C 11 1.4(2 )° and av. C–Sb–C 103.8( 3)° angles. This
demonstrates that for the dative bond from antimony to the transition metal centre
hybrid orbitals with p orbital contribution are used. The structure of 4 is depic ted in
Figure 4.13

Figure 4. The molecular structure of [Cr(CO) 5(tBu3Sb)] (4).13

The molecules in complexes 8–10 are composed of pyramidal Ph 2SbX units
coordinated through the antimo ny atoms to tetragona l pyramidal W(CO) 5 fragments.

27 (a) D. J. Thornhill, A. R. Manning, J. Chem. Soc., Dalton Trans ., 1973 , 2086; (b) J. Ellermann, J.
Organomet. Chem ., 1975 , 94, 201.

16 The structural types of organoantimony metal carbonyl complexes

The Sb –W bonds in 8 [2.7184(10) Å], 9 [2.7243(8) Å] and 10 [2.7256(7) Å]12 are slightly
shorter than the corresponding bonds in [W(CO) 5(Ph 3Sb)] [2.745(1) Å]10 or
[{W(CO) 5}n(dpsm) ] [24, n = 1, 2.743(1) Å; 26, n = 2, 2.756(2) Å ].11
The crystal of 8 contains pairs of molecules, built through contact distances of
3.451(8) Å between an oxygen atom of a carbonyl group and the antimony atom of the
neighbouring molecules ( Figure 5).12 The distance between oxygen and antimony
atoms is close to the sum of van der Waals radii of antimony and oxygen [∑ rvdW(Sb,O)
3.60 Å].28

Figure 5. Dimeric association in the crystal of [W(CO) 5(Ph 2SbCl)] ( 8).12

The molecule s of all three iron complexes 11, 17 and 18 contain two Fe(CO) 4
units bridged by the distibine ligand . This fact is confirmed by the crystal structure of
[{Fe(CO) 4}2{1,3-C6H4(CH 2SbMe 2)2}] (17) (Figure 6).15 The discrete molecule exhibits a 2-
fold crystallographic symmetry passing through C(10) and C(11) atoms . The Fe –Sb bond
length [2.490(11) Å ] was similar to that observed in the related [Fe(CO) 4(η1-dpsm )]
[2.491(2) Å].24,29
The molecular structures of [W(CO) 5(dpsm)] ( 24), [{W(CO) 5}2(dpsm)] ( 26),
[{W(CO) 4(dpsm)} 2] (32) and [{W(CO) 4(dmsm)} 2] (35) were determined by single -crystal
X-ray diffraction.11

28 J. Emsley, Die El emente , Walter de Gruyter, Berlin, 1994 .
29 (a) N. J. Holmes, W. Levason and M. Webster, J. Chem. Soc., Dalton Trans. , 1997 , 4223; (b) G. Becker,
O. Mundt, M. Sachs, H. J. Breunig, E. Lork, J. Probst , A. Silvestru, Z. Anorg. Allg. Chem. , 2001 , 627, 699.

Literature data 17

Figure 6. Molecular structure of [{Fe(CO) 4}2{1,3-C6H4(CH 2SbMe 2)2}] (17).15

The molecules of complexes 24 and 26 show coordination by one or two Sb
atoms to square pyramidal W(CO) 5 units. In 24 the C –Sb–C angle [106.8(5) °] is smaller
than in the free dpsm [117.3 (2)⁰].24
The tetracarbonyl derivative s 32 and 35 are centrosymetric dimeric species in
which the Sb atoms are bonded to different W atoms. In complex [{W(CO) 4(dpsm)} 2]
(32) it was found that the Sb –C–Sb angle [125.4(5) °] is a little bit larger (3⁰) than that in
the derivative 26 and the C –Sb–C angles are as expected for a bonded Sb. The
molecular structures of tetracarbonyl derivatives 32 and 35 are presented in Figure 7.11
In addition to t he complex 35 only one other dmsm complex was described, i.e.
[Co 2(CO) 4(µ-CO) 2(µ-dmsm)]. For both compoun ds the C–Sb–C angle s are in the range
98 to 103 °, but the value for the Sb–C–Sb angle found in the tungsten complex
[119.7(8) °] is larger than in the cobalt com plex [114.5 (7)°].11

(a) (b)

Figure 7. The molec ular structures of [{W(CO) 4(dpsm)} 2] (32) (a) and [{W(CO) 4(dmsm)} 2]
(35) (b).11

18 The structural types of organoantimony metal carbonyl complexes

II.2. Complexes of catena -oligo stibanes and related
organoantimony compounds

The chemistry of organometallic antimony chains ( catena -stibanes) has been
investigated for a lon g time.30 Complexes with homonuclear organoantimony chain
ligands were reported for the first time by Breunig et al ., in 2001.31 More attention
have received the phosphorus analogues of catena -stibanes32,33 and also complexes
with catena –phospane or –arsane we re reported.34,35
The chemistry of complexes with antimony –group 4 metal bonds is very little
known. In this chapter there are also presented polynuclear titanium complexes with
antimony ligands.

II.2.a. Preparation

The combined solutions of Me 4Sb2 or Ph 4Sb2 with cyclo -(Me 3SiCH 2Sb) n (n = 4, 5)
in toluene react with [Cr(CO) 4(nbd)] (nbd = norbornadiene) to give the tetrastibane
complexes cyclo -[Cr(CO) 4(R’2Sb-SbR-SbR-SbR’2)] [R = Me 3SiCH 2, R’ = Me (50), Ph (51)].
The complexation of 50 with [W(CO) 5(thf)] lea ds to the complex cyclo -[Cr(CO) 4(Me 2Sb-
SbR-SbR-SbMe 2)W(CO) 5] (R = Me 3SiCH 2) (52), according to Scheme 4.31 The complex
[{Cr(CO) 5}2(Me 2Sb-SbMe 2)] (53) was obtain ed trying to isolate the tristibane derivative
by complexation with [Cr(CO) 5(thf)].36

30 (a) H. Sc hmidt, Liebigs Ann. Chem. , 1920 , 421, 174. (b) M. Wieber, Gmelin Handbook of Inorganic
Chemistry , Sb Organoantimony Compounds, Part 2; Springer -Verlag: Berlin, 1981 . (c) H. J. Bre unig, R.
Rösler, Coord. Chem. Rev. , 1997 , 163, 33. (d) H. J. Breuni g, R. Rösler, Chem. Soc. Rev. , 2000 , 6, 403.
31 H. J. Breunig, I. Ghesner, E. Lork, Organometallics , 2001 , 20, 1360 .
32 M. Baudler, G. Reuschenbach, D. Koch, B. Carlsoh n, Chem. Ber ., 1980 , 113, 1264.
33 E. Urnezius, K. -Ch. Lam, A.L. Rheingold, J. D. Protas iewicz, J. Organomet. Chem ., 2001 , 630, 193.
34 G. Johannes, O. Stelzer, E. Unger, Chem. Ber ., 1975 , 108, 1259.
35 O. Stelzer, E. Unger, V. Wray, Chem. Ber ., 1977 , 110, 3430.
36 H. J. Breunig, I. Ghesner, M. E. Ghesner, E. Lork, J. Organomet. Chem ., 2003 , 677, 15.

Literature data 19

Scheme 4. Preparation of compounds 50–52.31

The react ion produced by photochemically -induced substitution of [M(CO) 6] (in
thf) with the intact distibanes leads to the formation of the first mononuclear distibane
complexes of the type [M(CO) 5(Sb 2R4)] (M = Cr , W; R = CH 3, C 2H5, C 6H5) These type of
complexes were only spectroscopically characterized .37
The trans -[Fe(CO) 3(PPh 3)(Sb 2Ph4)] (54) complex38 was obtained by reaction of the
phosphane -substituted ferrate K 2[Fe(CO) 3(PPh 3)] with two equivalents of Ph 2SbCl
followed by the elimination of KCl to yield the first η1–coordinated
tetraphenyldistibane ligand by ferrate -assisted reductive Sb –Sb coupling of two
Ph2SbCl molecules.38
The antimony -iron complexes of the types [Fe 4(CO) 14(Et 2Sb) 4] ( 55),
[Fe 3(CO) 10(nPr2Sb) 4] ( 56), [Fe 2(CO) 6{(Me 3SiCH 2)2Sb} 4] ( 57), and [ {2-
(Me 2NCH 2)C6H4Sb}{Fe(CO) 4}2] (58) were prepared by reacting R2Sb–SbR2 [R = Et, nPr,
Me 3SiCH 2, 2-(Me 2NCH 2)C6H4] with [Fe2(CO) 9]. The compounds 55–58 represent novel
types of compounds in the chemistry of iron complexes with pnictogen ligands.39 The
red, air -sensi tive crystals 55–57 are supposed to be formed by addition of distibane or
of the previously described distibane complexes of types A and B to the central Fe –Fe
bond in an a ntimonido complex of type C (Scheme 5 ).39

37 H. J. Breunig, W. Fichtner, Z. Anorg. Allg. Chem. , 1979 , 454, 167.
38 I.-P Lorenz, S. Rudolph, H. Piotrowski, K. Polborn, Eur. J. Inorg. Chem. , 2005 , 82.
39 H. J. Breunig, E. Lork, O. Moldovan, C. I. Raț, Z. Anorg. Allg. Chem ., 2010 , 636, 1090 .

20 The structural types of organoantimony metal carbonyl complexes

Scheme 5. Preparation of compounds 55–58.39

The antimonido complex [(Cp 2Ti)2(SbEt2)2] (59)40 and t he polynuclear titanocene
complexes [(Cp 2Ti)3(SbR) 3Sb] ( 60)40 [R = 2 -(Me 2NCH 2)C6H4] and [(Cp 2Ti)5(SbR) 2Sb7] (61)40

40 H. J. Breunig, E. Lork, O. Moldovan, C. I. Ra ț, U. Rosenthal , C. Silvestru , Dalton Trans., 2009 , 5065 .

Literature data 21

(R = Me 3SiCH 2) were obtained by reacting three different tetraorganodistibanes R 2Sb–
R2Sb with [Cp 2Ti(btmsa)] (btmsa = Me 3SiC≡CSiMe 3) in benzene, at room temperature.
The reaction between t he ring−ring equilibrium mixture of cyclo -(RSbE) n [n = 2, 3;
R = CH(SiMe 3)2; E = S, Se] and [W(CO) 5(thf) ] leads to cyclo -[RSbS] 2[W(CO) 5]2 (62)41 and
cyclo -[RSbS e]2[W(CO) 5]2 (63) (Scheme 6 ).42 The brown crystals of 62 and 63 were grown
from a solution of petroleum ether at −28 °C. They are soluble in the aliphatic or
aromatic hydrocarbons, stable in the air for a short time and stable for several days
when kept under argon at room temperature (fo r 62) or −30 °C (for 63).
The stibinidene complex, [2-(Me 2NCH 2)C6H4Sb{W(CO) 5}2] (64) 43was isolated from
the reaction between [2 -(Me 2NCH 2)C6H4Sb] 4 and [W(CO) 5(thf) ] in thf. The same
compound was obtained when cyclo -[2-(Me 2NCH 2)C6H4SbS] 2 was reacted with
[W(CO) 5(thf) ]. The major product of this reaction was the cyclo -[2-
(Me 2NCH 2)C6H4SbS] 2[W(CO) 5] (65).43 The preparation of compounds 62−65 is presented
in Scheme 6 .

Scheme 6. Synthesis of complexes 62–65.41-43

41 H. J. Breunig, I. Ghesner, E. Lork, Appl. Organo met. Chem. , 2002 , 16, 547 .
42 H. J. Breunig, I. Ghesner, E. Lork, J. Organomet.Chem ., 2002 , 664, 130.
43 L. M. Opriș , A. Silvestru, C. Silvestru, H. J. Breunig, E. Lork, Dalton Trans. , 2004 , 3575 .

22 The structural types of organoantimony metal carbonyl complexes

The spectroscopic data used to characterize the metal carbonyl complexes
containing catena -oligo stibanes and related organoantimony as ligands are listed in
Table 2.

Table 2. Caracterization of compounds 50–65.
Compound Spectroscopic data Compound Spectroscopic data
50 1H, 13C, MS, X -ray [ 31] 58 MS, X-ray [ 39]
51 1H, 13C, MS , X-ray [31] 59 X-ray [40]
52 1H, 13C, MS, X -ray [ 31] 60 X-ray [40]
53 X-ray [36] 61 X-ray [40]
54 1H, 13C,31P, IR, X-ray [38] 62 1H, 13C, MS, IR , X-ray [41]
55 1H, MS, IR, X -ray [39] 63 1H, 13C, MS, IR, X -ray [42]
56 1H, MS, IR, X -ray [39] 64 1H, 13C, MS, IR, X -ray [43]
57 1H, MS,IR, X -ray [39] 65 1H, 13C, MS, IR, X -ray [43]

Literature data 23

II.2.b. Spectroscopic characterization

The compounds 50–52 were investigated by NMR spectroscopy and the data are
consistent with t he structures estab lished by X -ray diffraction.31 In the 1H NMR spectra
of these compounds were observed one singlet resonance for the Si Me 3 protons and
an AB spin system for the C H2 groups bonded to one of the antimony atoms, which are
both chiral. The or ganic groups which are bonded to the terminal antimony atoms are
non-equivalent. The 13C NMR spectrum of compound 51 is consistent with the
nonequ ivalen ce of the phenyl groups.
In the IR spectra of complexes 50 and 51 were ob served CO stretching vibratio ns
which are common for complexes of the type cis-[L2Cr(CO) 4].31 In the case of 52 a
shoulder signal was observed at 1952 cm–1. The identity of the complexes 50–52 was
confirmed also by high -resolution mass spectrometry and elemental analyses.
The identit y of complex es 5336 and 5438 was confirmed by 1H and 13C NMR as
well as IR spectroscopy. Also complexes 55–58 were investigated by mass
spectrometry , 1H NMR and IR spectroscopy.44
The IR spectrum ofcomplex 5438 show s the single absorption band ν (CO) at 188 3
cm–1 which was found to be similar with the ν(CO) absorption (1886 cm–1) of the
symmetrical species trans -[Fe(CO) 3(PPh 3)2].45 The 1H and 13C NMR spectra show the
expected resonances for the phenyl protons and phenyl carbons. The 31P resonance it
was found at δ 86.4 ppm.
The compounds 59–61 were found to be unstable under MS and NMR
conditions, probably due to their paramagnetic character.
The complexes 62–65 were investigated by IR, 1H and 13C NMR spec troscopies
and mass spectrometry [using desorptive ch emical ionization (DCI) techniques for 6241
and 6342 complexes, electron impact (EI) for 64 and chemical ionization (CI) technique
for 65], the results being consistent with the chemical formulation.43
The IR spectra indicated the presence of W(CO) 5 moiet ies in the case of all
compounds.
The 1H NMR spec tra of complexes cyclo -(RSbS) 2[W(CO) 5]2 (62)41 and cyclo –
(RSbSe) 2[W(CO) 5]2 (63)42 [R = CH(SiMe 3)2] showed the expected singlet signals for the

44 H. J. Breunig, W. Fichtner, T. P. Knobloch, Z. Anorg. Allg. Chem ., 1981 , 477, 126.
45 A. F. Clifford, A. K. Mu kherjee, Inorg. Synth ., 1966 , 8, 185 .

24 The structural types of organoantimony metal carbonyl complexes

SiMe 3 protons (0.22 ppm for 62 and 0.23 ppm for 63) and C H prot ons (0.38 ppm for 62
and 0.29 ppm for 63).
The 1H NMR spectrum (benzene -d6) of complex RSb[W(CO) 5]2 (64) [R = 2 –
(Me 2NCH 2)C6H4] exhibited in the aliphatic region the expected singlet resonances for
the methyl protons attached to nitrogen and methylene prot ons, respectively. The
aromatic region showed the four, well separated, multiplet resonances for the aryl
protons. In the 13C NMR spectrum of 64 the resonances corresponding to the carbonyl
groups could not be observed.43
The 1H NMR spectrum of compound cyclo-(RSbS) 2[W(CO) 5] (65) [R = 2 –
(Me 2NCH 2)C6H4] showed that the organic groups are equivalent and this was pro ven by
the presence of only one set of signals. In the aliphatic region was observed two singlet
resonances ( δ 2.45, 2.49 ppm) for the NMe 2 proton s and an AB spin system [ δ A: 3.92,
B: 4.14 ppm (2JHH = 13.9 Hz)] for the CH 2 protons. This suggest s either a strong
intramolecular N→Sb coordination in solution, at room temperature, and a bridging
coordination of the W(CO) 5 moiety to the sulph ur atoms of the Sb 2S2 ring ( Scheme 7) or
a dynamic process with rapid migration of W(CO) 5 between the sulph ur atoms.43

Scheme 7.43

Literature data 25

II.2.c. Single -crystal X -ray diffraction studies

The molecular structures of complexes cyclo -[Cr(CO) 4(Me 2Sb-SbR-SbR-SbMe 2)]
(50), cyclo -[Cr(CO) 4(Me 2Sb-SbR-SbR-SbMe 2)W(CO) 5] (52) (R = Me 3SiCH 2) and
[{Cr(CO) 5}2(Me 2Sb) 2] (53) were determinated by si ngle -crystal X -ray diffraction studies.
The molecular structures of complexes 50 (a) and 52 (b) are depic ted in Figure 8 . The
five m embered Sb4Cr rings are nonplanar , with the Sb 2–Sb3 unit being twisted out of
the Sb 1–Cr1–Sb4 plane 22.4 ° for 52 and 26.3 ° for the main conformer of 50,
respectively .31

(a) (b)

Figure 8. Molecular structures of complexes 50 (a) and 52 (b).31

The Sb -Cr bond lengths [ 2.596(8), 2.588(8) Å in 50 and 2.593(19), 2.575(15) Å in
52] lie in the usu al range for Sb -Cr distances, e.g. cyclo -[{Cr(CO) 4(Me 2Sb–O–SbMe 2)}2]
[2.566(3), 2.573(4) Å] or cyclo -[{Cr(CO) 4(Me 2Sb–S–SbMe 2)}2] [2.5986(12), 2.5838(9)
Å].46 The trimethylsilylmethyl groups bound to Sb(2) and Sb(3) are situated in trans
position s. In 50 and 52 the angles around the antimony atoms correspond to p3
configurations for the three -coordinate antimony atoms and to sp3 hybridization for
the four -coordinate antimony atoms.32 In the crystal of 50 it could be observe d that the
main conformer occupied 98% , while 2% being occupied by the second conformer. The

46 H. J. Breunig, M. Jönsson, R. Rösler, E. Lork, Z. Anorg. Allg. Chem., 1999 , 625, 2120 .

26 The structural types of organoantimony metal carbonyl complexes

latter is formed by a ring inversion process and these kind of conformational effects are
not unusual for five -membered metal -containing rings.47
The molecular structure of the first transition metal complex of
tetramethyldis tibane , [{Cr(CO) 5}2(Me 2Sb-SbMe 2)] (53)36 is depic ted in Figure 9. The
wider angles and shorter bonds at the antimony atoms in 53 [C–Sb–C, 99 .20(18)–
100.34(16) °, C–Sb–Sb, 96.41(11) –102.44(11) °; Sb–Sb 2.8097(9) Å ] in comparison with
Me 2Sb-SbMe 2 (C–Sb–C, 92.2 –95.2 °; C–Sb–Sb, 94.27 –94.65 °; Sb–Sb, 2.84 Å) are due to
the coordination of the distibane. The increase of s-orbital participation from the p3
configuration of the antimony atoms in Me 4Sb2 to closer to sp3 in 53 are probably
resulting from the changes tha t occurs in the geometry of 53. The Sb –Cr bond distance
is 2.625 Å and is comparable with those foun d in complexes 50 and 52.

Figure 9. Molecular structure of complex 53.36

The molecular structures of complexes 62 and 63 revealed that both antimony
atoms of the ring are coordinated to W(CO) 5 units which are positionated in cis
positions relative to the ring and trans to the alkyl groups. The molecular structure of
62 is depic ted in Figure 10 .41 The cent ral unit is formed by a four -membered Sb 2E2 (E =
S, Se) ring which contains alternati ng antimony and c halcogen atoms, in the case of
both 62 and 63. The Sb−S bond length s [2.425(1) Å and 2.428(1) Å in 62] are similar to
those found in other known complexes with Sb−S ligands , e.g. cyclo –
[Cr(CO) 4(Me 2Sb−S−SbMe−S−SbMe 2)]∙[Cr(CO) 4(nbd)] [2.433(9) Å and 2.412(8) Å ], cyclo –
[{Cr(CO) 4(Me 2Sb−S−SbMe 2)}2] [2.424(9 ) Å and 2.421(5) Å ],46 but are shorter than in the
case of the of the free Me 2Sb−S−SbMe 2 [2.498(1) Å].48

47 E. J. Corey, J. C. Bailar, J. Am. Chem. Soc ., 1959 , 81, 2620.
48 H. J. Breunig, E. Lork, R. Rösler , G. Becker, O. Mundt, W. Schwarz, Z. Anorg . Allg. Chem ., 2000 , 626,
1595.

Literature data 27

The Sb−W bond lengths in 62 [2.737(7) Å] were found to be similar to those
found in the complex 63 [2.749(5) Å] and shorter than those in the related cyclo-
[tBu4Sb4][W(CO) 5]2 [2.847(3) Å and 2.882(2) Å].28

Figure 10. Molecular structures of cyclo -[RSbS] 2[W(CO) 5]2 (62).41

The molecular structure of complex RSb[W(CO) 5]2 (64) [R = 2 -(Me 2NCH 2)C6H4],
(Figure 11 )43 revealed that two pentacarbonyl tungste n moieties are bridged by the
antimony atom of a [2 -(Me 2NCH 2)C6H4]Sb unit. This type of compound is within of the
famil ly of “open” systems of the type RE(ML n)2 (E = P, As, Sb, Bi; ML n = 16e– transition
metal fragment), which feature an sp2 σ-bonding framework and p -delocalisation of
the lone pair electrons of the pnicogen atom between the two transition metal
centres.49,50,51,52,53,54,55,56,57,58

49 G. Balázs, H. J. Breunig, E. Lork , S. A. Mason, Organometallics , 2003 , 22, 576.
50 L. Balázs, H. J. Breunig, E. Lork, C. Silvestru, Eur. J. Inorg. Chem. , 2003 , 7, 1361.
51 G. Huttner, in Multiple Bonds and Low Coordination in Phosphorus Chemistry , ed. M. Regitz and O. J.
Scherer, Thieme, Stuttgart, 1990 .
52 J. von Seyerl, G. Huttner, Angew. Chem. , 1978 , 90, 911; J. von Seyerl, G. Huttner, Angew. Chem. Int. Ed.
Engl. , 1978 , 17, 843.
53 U. Weber, L. Zsolnai , G. Huttner, J. Organomet. Chem. , 1984 , 260, 281.
54 A. H. Cowley, N. C. Norman , M. Pakulsky, J. Am. Chem. Soc. , 1984 , 106, 6844.
55 A. M. Arif, A. H. Cowley, N. C. Norman , M. Pakulsky, J. Am. Chem. Soc. , 1985 , 107, 1062.
56 A. H. Cowley, N. C. Norman, M. Pakulsky, D. L. Bricker, D. H. Russell, J. Am. Chem. Soc. , 1985 , 107,
8211.
57 M. Arif, A. H. Cowley, N. C. Norman , M. Pakulsky, Inorg. Chem. , 1986 , 25, 4836.
58 G. Balazs, H. J. Breunig , E. Lork, Z. Anorg. Allg. Chem. , 2003 , 629, 1937.

28 The structural types of organoantimony metal carbonyl complexes

The antimony atom is deviated 0.545 Å from the expected planar CSbW 2 system
for an “open” stibinidene com plex [the sum of angles around Sb in the CSbW 2
framework is 346.24°) . The nitrogen atom which belongs to the pendant arm is
strongly coordinated intramolecular ly to the antimony atom [ Sb(1) –N(1) 2.292(5) Å] .43
The Sb –W bond lengths [2.7547(10) and 2.7475(9 ) Å] were found to be longer than the
Sb–W bond lengths in the case of complex (Me 3Si)2CHSb[W(CO) 5]2 [2.687(1) Å],56 and
they are similar to the values found in [ {Ph2SbW(CO) 5}2] [2.749(1) Å],59
[(Ph 4Sb2CH 2)W(CO) 5] [2.743(1) Å],11 or [(Ph 4Sb2CH 2){W(CO) 5}2] [2.756(2) Å].11

Figure 11. The molecular structure of complex 64.43

The molecular structure of compound cyclo -[2-(Me 2NCH 2)C6H4SbS] 2[W(CO) 5] (65)
shows that the compound crystallizes as a 1:1 mixture of R,R and S, S isomers. Figure 12
shows the ( R,R)-65 isomer and reveals that a W(CO) 5 unit is coordinated to the cis
isomer of cyclo -[2-(Me 2NCH 2)C6H4SbS] 2 by one of the sulph ur atom of the Sb 2S2 ring
[S(2) –W(1) 2.5902(13) Å] and not to the metal atom as in the case of the
cyclo −[RSbS] 2[W(CO) 5]2 (62) [R = CH(SiMe 3)2] complex.41 This S–coordination of the
W(CO) 5 moiety, which occupies a trans position relative to the organic ligands , is
probably due to the N→Sb intramolecular interactions . In the molecule of 65 the four –
membered S b2S2 ring is slightly folded [fold angles: S(1)Sb(1)S(2)/S(1)Sb(2)S(2) 165.2,
Sb(1)S(1)Sb(2)/Sb(1)S(2)Sb(2) 164.7 °]. The transanular Sb(1) –Sb(2) non -bonding
distance [3.590(1) Å] in 65 is longer than in trans -(RSbS) 2 [3.549(3) Å]. The Sb(1) –S(2)
and Sb(2) –S(1) bonds [2.4480(14), 2.4109(15) Å] are shorter than Sb(1) –S(1) bond

59 H. J. Breunig, J. Pawlik, Z. Anorg. Allg. Chem ., 1995 , 621, 817.

Literature data 29

[2.4245(12) Å] in the free cyclo -(RSbS) 2. The longer Sb –S bond s are those which are
placed trans to the nitrogen atoms strongly coordinated to the antimony atoms.43

Figure 12. The m olecular structure of (R,R)-65 isomer .43