Synthesis and properties of new ditertiary stibines based upon o-, m- or p-xylyl and m- or p-phenylene backbones and their complexes with tungsten, iron and nickel carbonyls

Article abstract of DOI:10.1039/b312083j

High yield syntheses for 1,2-, 1,3-, and 1,4-xylyl distibines (1,2-C₆H₄(CH₂SbMe₂)₂, 1,3-C₆H₄(CH₂ SbMe₂)₂, 1,4-C₆H₄(CH₂ SbMe₂)₂, respectively) from Me₂SbCl (conveniently made in situ from Me₂PhSb and HCl_gas) and the appropriate di-Grignard are reported. The 1,3- and 1,4-phenylene distibines, 1,3-C₆H₄(SbMe₂)₂ and 1,4-C₆H₄(SbMe₂)₂, were made similarly. The new ligands have been characterised by mass spectrometry, ¹H and ¹³C{¹H} NMR spectroscopy, and by the preparation of methiodide derivatives. The crystal structures of 1,4-C₆H₄(CH₂ SbMe₂)₂ and [1,3-C₆H₄(CH₂ SbMe₃)₂]I₂ have been determined. The synthesis of 1,2-C₆H₄-(CH₂ SbPh₂)₂ has been achieved similarly in modest yield and the distibine converted into the tetra-iodo-derivative 1,2-C₆H₄(CH₂SbPh₂ I₂)₂. The coordination modes available to these ligands have been probed by the synthesis and characterisation of complexes with nickel, iron and tungsten carbonyls. The crystal structure of [{Fe(CO)₄}₂-{μ-1,3-C₆H₄ (CH₂SbMe₂)₂}] has been determined. The spectroscopic properties of these carbonyl derivatives have been compared with those of complexes of other antimony ligands, and in some cases with diphosphine and diarsine complexes, to probe the electronic properties of the new ligands.

Full text of DOI:10.1039/b312083j

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Synthesis and properties of new ditertiary stibines based upon
o-, m- or p-xylyl and m- or p-phenylene backbones and their
complexes with tungsten, iron and nickel carbonyls
William Levason, Melissa L. Matthews, Gillian Reid and Michael Webster
School of Chemistry, University of Southampton, Southampton, UK SO17 1BJ
Received 29th September 2003, Accepted 6th November 2003
First published as an Advance Article on the web 28th November 2003
High yield syntheses for 1,2-, 1,3-, and 1,4-xylyl distibines (1,2-C6H4(CH2SbMe2)2, 1,3-C6H4(CH2SbMe2)2,
1,4-C6H4(CH2SbMe2)2, respectively) from Me2SbCl (conveniently made in situ from Me2PhSb and HClgas
)
and the appropriate di-Grignard are reported. The 1,3- and 1,4-phenylene distibines, 1,3-C6H4(SbMe2)2 and
1,4-C6H4(SbMe2)2, were made similarly. The new ligands have been characterised by mass spectrometry, 1H
and 13C{1H} NMR spectroscopy, and by the preparation of methiodide derivatives. The crystal structures
of 1,4-C6H4(CH2SbMe2)2 and [1,3-C6H4(CH2SbMe3)2]I2 have been determined. The synthesis of 1,2-C6H4-
(CH2SbPh2)2 has been achieved similarly in modest yield and the distibine converted into the tetra-iodo-derivative
1,2-C6H4(CH2SbPh2I2)2. The coordination modes available to these ligands have been probed by the synthesis
and characterisation of complexes with nickel, iron and tungsten carbonyls. The crystal structure of [{Fe(CO)4}2-
{µ-1,3-C6H4(CH2SbMe2)2}] has been determined. The spectroscopic properties of these carbonyl derivatives have
been compared with those of complexes of other antimony ligands, and in some cases with diphosphine and diarsine
complexes, to probe the electronic properties of the new ligands.
reactions of conveniently prepared chlorostibines with di-Grig-
nards represents a significantly improved route for C–Sb bond
formation in polydentates and macrocycles. The m- and p-xylyl
and m- and p-phenylene backboned ligands should be suitable
for the construction of extended frameworks, whereas the
o-xylyl ligand is an antimony analogue of wide-angle diphos-
Introduction
A very large number of diphosphine and diarsine ligands is
known, and examples with higher denticities (up to eight) have
been prepared.1–3 Some tri- and tetra-tertiary phosphines are
commercially available. Similarly, whilst a moderately wide
range of hybrid donor polydentates containing one antimony
phines which are currently attracting great interest owing to the
centre in combination with phosphorus, arsenic, nitrogen, sul-
catalytic properties of their metal complexes.
fur etc., are known,4 ligands containing two antimony donor
atoms are much more difficult to obtain and correspondingly
their coordination chemistry has been neglected.3,4 The distib-
inoalkanes R2Sb(CH2)nSbR2 (R = Me or Ph; n = 1, 3 or 4) can
be made from NaSbR2 and the appropriate α,ω-dihaloalkane
in liquid ammonia, but the reaction of NaSbR2 with ClCH2-
Experimental
All preparations were conducted under a dry dinitrogen atmos-
phere. Tetrahydrofuran was distilled from sodium benzo-
phenoneketyl before use and toluene was distilled from sodium
wire. Other solvents were obtained commercially and used as
supplied. Liquid ammonia was condensed from the dry gas
(BDH) using CO2–acetone slush-baths, and hydrogen chloride
used as received (Aldrich). PhSbCl2 and Ph2SbCl were made as
described17 from SbCl3 and SbPh3 in the appropriate ratio.
W(CO)6, Fe2(CO)9 and Ni(CO)4 (Aldrich) were used as
received. CAUTION: Ni(CO)4 is volatile and extremely toxic;
all reactions (including the preparation of spectroscopic samples)
were carried out in a good fume hood, and syntheses were con-
ducted using closed systems fitted with bromine–water scrubbers.
Residues were destroyed using bromine. Physical measurements
were made as described in previous reports from these
laboratories.8–11
CH Cl results in elimination to form R Sb and CH ᎐CH .5,6
᎐
2
4
2
2
2
The coordination chemistry of these ligands reveals that they
are soft moderate σ donors, and in appropriate cases, weak π
acceptors, forming complexes with low valent metal carbonyls
and soft platinum group or Group 11 metals.4,7–12 These recent
detailed studies have revealed significant differences from their
much studied lighter analogues, which include a tendency to
promote higher coordination numbers, less dissociation from
metal centres, and the production of unusual geometric iso-
mers, whilst the weak C–Sb bond is easily broken in the pres-
ence of some metal centres, resulting in ligand fragmentation.
Other ditertiary stibines are rare: 1,2-bis(dimethylstibanyl)-
benzene, o-C6H4(SbMe2)2, the antimony analogue of the fam-
ous “diars”, (o-C6H4(AsMe2)2), has superior coordination
properties to other distibines above and for example, forms rel-
atively stable complexes with Ni()13 or Co(),14 but its prepar-
ation is difficult and yields are very poor.3,15 This has seriously
hindered its study as a ligand. Complexes of only one tritertiary
stibine, MeC(CH2SbPh2)3 have been described.16 The present
work was initiated with the aim of finding new routes to di- and
polytertiary stibines with other than alkane backbones, which
would produce the ligands from convenient starting materials
and in yields sufficient to allow their coordination chemistry to
be studied in some detail. Here, we describe our first results,
the syntheses and characterisation of o-, m-, and p-xylyl and
m- and p-phenylene backboned distibines and some complexes
with metal carbonyls, which illustrate the ligand properties and
bonding modes available. The new methodology utilising the
PhMe2Sb
Methylmagnesium iodide was prepared from methyl iodide
(42.6 g, 0.30 mmol) and magnesium turnings (7.7 g, 0.32 mmol)
in diethyl ether (1 L), and stirred for 45 min to ensure complete
reaction. Dichlorophenylstibine (40 g, 0.15 mol) in diethyl ether
(250 mL) was added dropwise with stirring, and the yellow
suspension stirred at room temperature for 3 h. The reaction
was hydrolysed with aqueous NH4Cl (∼1 mol dmϪ3, 300 mL)
and the organic layer separated. The aqueous layer was washed
with diethyl ether (3 × 100 mL) and the combined organics
dried over anhydrous MgSO4. The solvent was removed at
atmospheric pressure and the residual oil fractionated in vacuo.
The PhMe2Sb was obtained at 40–42 ЊC (0.3 mm Hg), yield
T h i s j o u r n a l i s © T h e R o y a l S o c i e t y o f C h e m i s t r y 2 0 0 4
D a l t o n T r a n s . , 2 0 0 4 , 5 1 – 5 8
51

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1
15.4 g (49%), and Ph2SbMe at 80 ЊC (0.3 mm Hg), yield 8.4 g
(24%).
yellow oil. Yield 2.0 g (56%). H NMR (CDCl3): 0.67(s) [12H]
CH3, 2.77(s) [4H] CH2, 6.84–7.41(m) [4H] aryl-CH. 13C{1H}
NMR (CDCl3): Ϫ3.3 CH3, 22.3 CH2, 123.7, 126.8, 128.3 aryl-
CH, 141.0 i-C. EI MS: m/z 408; calcd. for [C12H20121Sb123Sb]ϩ
408.
PhMe2Sb: 1H NMR (CDCl3): 1.15(s) [6H] CH3, 7.46(m)
[3H], 7.72(m) [2H], Ar–CH. 13C{1H} NMR (CDCl3): Ϫ0.9
CH3, 128.4, 128.8, 135.2 aryl-CH, 137.7 i-C. A methiodide was
obtained by reaction with excess MeI in acetone. Found: C,
29.23; H, 3.52. C9H14ISb requires C, 29.15; H, 3.81%. 1H NMR
(d6-DMSO): 1.83(s) [9H] CH3, 7.52–7.80(m) [5H] aryl-CH.
13C{1H} NMR (d6-DMSO): 3.64 CH3, 129.3, 131.3, 134.3 aryl-
CH. ESϩ MS (MeCN): m/z 243; calcd. for [C9H14121Sb]ϩ 243.
Ph2MeSb: 1H NMR (CDCl3): 1.27(s) [3H] CH3, 7.38–7.45(m)
[6H], 7.59–7.68(m) [4H], Ar–CH. 13C{1H} NMR (CDCl3): 0.71
CH3, 128.65, 128.9, 135.65 aryl-CH, 138.2 i-C.
A dimethiodide was prepared by quarternisation with excess
iodomethane in acetone and recrystallisation from acetone/
diethyl ether. Found: C, 25.49; H, 3.73. C14H26I2Sb2ؒ½Me2CO
requires C, 25.83; H, 4.05%. 1H NMR (d6-DMSO): 1.58(s)
[18H] CH3, 3.74(s) [4H] CH2, 7.24–7.43(m) [4H] aryl-CH.
13C{1H} NMR (d6-DMSO): 2.1 CH3, 26.8 CH2, 127.2, 128.7,
129.6 aryl-CH, 135.6 i-C. ESϩ MS (MeCN): m/z 219; calcd. for
[C12H26121Sb123Sb]2ϩ 219.
1,2-Bis(dimethylstibanylmethyl)benzene, 1,2-C6H4(CH2SbMe2)2
1,4-Bis(dimethylstibanylmethyl)benzene, 1,4-C6H4(CH2SbMe2)2
Method 1. Hydrogen chloride gas was bubbled through a solu-
tion of PhMe2Sb (7.0 g, 31 mmol) in dry toluene (50 mL) for ca.
15 min and then the solution was purged with N2 to remove any
excess hydrogen chloride. This solution was added dropwise to
a solution of sodium (1.4 g, 62 mmol) in liquid ammonia (250
mL) at Ϫ78 ЊC. The reaction was stirred for 2 h and a solution
of α,αЈ-dibromo-o-xylene (4.1 g, 15.5 mmol) in dry diethyl ether
(150 mL) was added dropwise. When addition was complete the
reaction was allowed to warm to room temperature, and then
hydrolysed with aqueous NH4Cl (∼1 mol dmϪ3, 200 mL). The
organic layer was separated and the aqueous layer washed with
diethyl ether (2 × 100 mL). The combined organics were dried
over anhydrous MgSO4. The solvent was removed in vacuo, and
the residual yellow oil purified via Kugelröhr distillation. The
ligand was obtained at 200 ЊC (0.5 mm Hg), yield 0.40 g (6%).
Method 2. 1,2-Bis(chloromagnesiomethyl)benzene was pre-
pared following the literature procedure,18 from magnesium
powder (1.7 g, 70 mmol) activated with 1,2-dibromoethane
(0.2 mL) in THF (5 mL). THF (15 mL) was then added, fol-
lowed by dropwise addition of α,αЈ-dichloro-o-xylene (3.1 g,
17.7 mmol). After 15 h, this solution was treated dropwise with
a toluene solution of Me2SbCl, prepared as above from
PhMe2Sb (8.0 g, 35 mmol), and stirred overnight. The reaction
The reaction was carried out as above using α,αЈ-dichloro-p-
xylene (1.53 g, 8.7 mmol). The ligand was purified via Kugel-
röhr distillation to give a white crystalline solid. Yield 1.8 g
1
(50%). H NMR (CDCl3): 0.5(s) [12H] CH3, 2.7(s) [4H] CH2,
6.7–7.2(m) [4H] aryl-CH. 13C{1H} NMR (CDCl3): Ϫ3.3 CH3,
21.8 CH2, 127.6 aryl-CH, 136.7 i-C. EI MS: m/z 408, 255;
calcd. for [C12H20121Sb123Sb]ϩ 408, [C10H14121Sb]ϩ 255.
A dimethiodide was prepared by quarternisation with excess
iodomethane in acetone and recrystallisation from diethyl
ether. Found: C, 24.06; H, 3.61. C14H26I2Sb2 requires C, 24.31;
1
H, 3.79%. H NMR (d6-DMSO): 1.4(s) [18H] CH3, 3.6(s) [4H]
CH2, 7.2(s) [4H] aryl-CH. 13C{1H} NMR (d6-DMSO): 1.9 CH3,
26.7 CH2, 129.3 aryl-CH, 133.2 i-C. ESϩ MS (MeCN): m/z 565;
calcd. for [C14H26I121Sb123Sb]ϩ 565.
1,2-Bis(diphenylstibanylmethyl)benzene, 1,2-C6H4(CH2SbPh2)2
A solution of α,αЈ-dichloro-o-xylene (1.53 g, 8.7 mmol) in dry
THF was added dropwise over 3.5 h to a suspension of mag-
nesium powder (0.85 g, 35.0 mmol) in dry THF (10 mL), and
the resulting mixture stirred at room temperature for 15 h. To
this was added a solution of Ph2SbCl (prepared from Ph3Sb
(4.1 g, 11.6 mmol) and SbCl3 (1.33 g, 5.8 mmol)) in dry toluene,
and the reaction was stirred at room temperature overnight.
mixture was hydrolysed with aqueous NH4Cl (∼1 mol dmϪ3
,
Hydrolysis was effected with aqueous NH4Cl (∼1 mol dmϪ3
,
50 mL), the organic layer separated and the aqueous layer
washed with diethyl ether (2 × 100 mL). The combined organics
were dried over anhydrous MgSO4, and the solvent removed
in vacuo to yield the ligand as a fawn oil which was pure by
NMR. Yield 6.3 g (88%). 1H NMR (CDCl3): 0.99(s) [12H] CH3,
3.07(s) [4H] CH2, 7.33–7.77 (m) [4H] CH. 13C{1H} NMR
(CDCl3): Ϫ3.1 CH3, 124.5, 128.5 aryl-CH, 137.6 i-C. EIϩ MS:
m/z 393, 255; calcd. for [C11H17121Sb123Sb]ϩ 393, [C10H14121Sb]ϩ
255.
A dimethiodide, o-C6H4(CH2SbMe3)2I2, was prepared by
quarternisation with excess iodomethane in acetone and re-
crystallisation from diethyl ether. Found: C, 24.18; H, 3.92.
C14H26I2Sb2 requires C, 24.31; H, 3.79%. 1H NMR (d6-DMSO):
1.61(s) [18H] CH3, 3.80(s) [4H] CH2, 7.33–7.42(m) [4H] aryl-
CH. ESϩ MS (MeCN): m/z 551, 219; calcd. for [C13H22I121Sb-
123Sb]ϩ 551, [C14H26121Sb123Sb]2ϩ 219.
150 mL). The organic layer was separated and the aqueous
washed with diethyl ether (2 × 100 mL). The combined organics
were filtered through celite and dried over anhydrous MgSO4.
The solvent was removed in vacuo to yield the ligand as a brown
waxy solid. Yield 0.78 g (13%). 1H NMR (CDCl3): 2.82(s) [4H]
CH2, 7.09–7.48(m) [24H] aryl-CH. 13C{1H} NMR (CDCl3):
34.3 CH2, 126.5, 128.8, 129.0, 129.3 aryl-CH, 134.6, 136.4 i-C.
The tetraiodo-derivative was made by dissolving a sample of
the ligand in CH2Cl2 and adding a diiodine solution in CH2Cl2
dropwise at 0 ЊC until the colour was no longer discharged. The
mixture was stirred for 1 h then refrigerated and the orange–
yellow solid filtered off, washed with ice-cold diethyl ether and
dried in vacuo. Found: C, 32.99; H, 2.60. C32H28I4Sb2 requires C,
33.03; H, 2.50%.
1,4-Bis(dimethylstibanyl)benzene, 1,4-C6H4(SbMe2)2
1,3-Bis(dimethylstibanylmethyl)benzene, 1,3-C6H4(CH2SbMe2)2
1,4-Bis(bromomagnesio)benzene was prepared19 from mag-
nesium powder (0.42 g, 17.3 mmol) and anthracene (0.31 g,
1.73 mmol) which was activated with 1,2-dibromoethane
(0.1 mL) in THF (5 mL). More THF (25 mL) was added and
then 1,4-dibromobenzene (1.03 g, 4.37 mmol) in THF (130 mL)
added dropwise. The mixture was refluxed for 3 h, cooled, and
Me2SbCl (prepared from PhMe2Sb, 2.0 g, 8.74 mmol) in tolu-
ene (15 mL) added, and the resulting solution stirred overnight.
A solution of α,αЈ-dichloro-m-xylene (1.53 g, 8.7 mmol) in dry
THF was added dropwise over 3.5 h to a suspension of mag-
nesium powder (0.85 g, 35.0 mmol) (previously activated with
0.1 mL of 1,2-dibromoethane) in dry THF (100 mL), and the
resulting mixture stirred at room temperature for 15 h. To this
was added a solution of Me2SbCl (prepared from PhMe2Sb
(4.0 g, 17.5 mmol) as above) in dry toluene (50 mL). The reac-
tion was stirred at room temperature for 15 h before hydrolysing
with aqueous NH4Cl (∼1 mol dmϪ3, 150 mL). The organic layer
was separated and the aqueous washed with diethyl ether (2 ×
100 mL). The combined organics were dried over anhydrous
MgSO4 and the solvent removed in vacuo to yield the ligand as a
The mixture was hydrolysed with aqueous NH4Cl (1 mol dmϪ3
,
50 mL), the organic layer separated, the aqueous layer extracted
with diethyl ether (2 × 100 mL), and the combined organics
dried with MgSO4. The solvent was removed under vacuum,
and the residue taken up in diethyl ether (10 mL), filtered to
D a l t o n T r a n s . , 2 0 0 4 , 5 1 – 5 8
52

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remove a white solid (anthracene), and the solvent was again
removed in vacuum. Yield 0.97 g (58%). Typically the product
contains small amounts of residual anthracene evident in the
NMR spectra and sometimes, small amounts of PhMe2Sb.
The latter could be removed by distillation in vacuum, but since
the subsequent distillation of the distibine resulted in consider-
[{184W(CO)5}2{1,4-C6H4(CH2121SbMe2)2}]ϩ 1055, [184W2(CO)9-
{1,4-C6H4(CH2121SbMe2)2}]ϩ 1027.
[W(CO)4{1,2-C6H4(CH2SbMe2)2}]
To a solution of [W(CO)4(piperidine)2] (0.11 g, 0.24 mmol) in
EtOH (25 mL) was added a solution of 1,2-C6H4(CH2SbMe2)2
(0.10 g, 0.24 mmol) in EtOH (10 mL). Reaction was heated to
reflux under N2 for 2 h. Solvent was removed in vacuo and the
resulting yellow residue triturated with ice-cold pentane to give
a fawn colored solid. Yield 0.075 g (43%). Found: C, 29.32; H,
1
able decomposition, the distibine was not usually distilled. H
NMR (CDCl3): 0.99(s) [12H] CH3, 7.52(s) [4H] aryl CH.
13C{1H} NMR (CDCl3): Ϫ1.49 CH3, 134.8 aryl CH, 136.4 i-C.
EI MS: m/z 380, 365, 350, 335; calcd. for [C10H16121Sb123Sb]ϩ
121
380, [C9H13121Sb123Sb]ϩ 365, [C8H10121Sb123Sb]ϩ 350, [C7H7
Sb123Sb]ϩ 335.
-
1
3.54. C16H20O4Sb2Wؒ½C5H12 requires C, 30.00; H, 3.51%. H
NMR (CDCl3): 1.31 (s) [12H] CH3, 3.34 (s) [4H] CH2, 7.00–7.28
(m) [4H] aryl-CH. 13C{1H} NMR (CH2Cl2/CDCl3): Ϫ1.1 CH3,
24.6 CH2, 123.4 aryl-CH, 129.7 aryl-CH, 140.0 i-C, 201.7
[1,4-C6H4(SbMe3)2]I2 was made by reaction of the ligand
1
with excess MeI in either acetone or methanol. H NMR (d6-
DMSO): 1.86(s) [18H] CH3, 7.89(s) [4H] aryl-CH. 13C{1H}
NMR (d6-DMSO): 4.65 CH3, 134.2 aryl-CH, 136.0 i-C. ESϩ
MS (MeCN): m/z 537, 204; calcd. for [C12H22I121Sb123Sb]ϩ 537,
[C12H22121Sb123Sb]2ϩ 204.
(J = 126 Hz), 206.1 (J = 160 Hz) CO. IR spectrum (ν(CO)/cmϪ1
,
CH2Cl2): 2012m, 1935sh, 1901vs, 1873sh. APCI MS (MeCN):
m/z 704; calcd. for [184W(CO)4{1,2-C6H4(CH2121SbMe2)2}]ϩ 702.
[{Fe(CO)4}2{1,3-C6H4(CH2SbMe2)2}]
1,3-Bis(dimethylstibanyl)benzene, 1,3-C6H4(SbMe2)2
To a solution of [Fe2(CO)9] (0.18 g, 0.49 mmol) in dry THF
(30 mL) was added a solution of 1,3-C6H4(CH2SbMe2)2 (0.10 g,
0.24 mmol) in dry THF (10 mL). The reaction was stirred under
N2 at RT for 15 h. The solvent was removed in vacuo and the
resulting orange residue taken up in CH2Cl2 (5 mL), and the
solution filtered. The solvent was removed in vacuo and the
residue triturated with ice-cold pentane to give the product as
an orange–brown solid. Yield 0.088 g (48%). Found: C, 30.97;
H, 2.73. C20H20O8Fe2Sb2ؒ½CH2Cl2 requires C, 31.26; H, 2.73%.
1H NMR (CDCl3): 1.23(s) [12H] CH3, 3.30(s) [4H] CH2, 6.90–
7.28(m) [4H] aryl-CH. 13C{1H} NMR (CH2Cl2/CDCl3): Ϫ1.3
CH3, 25.2 CH2, 126.5, 128.0, 129.8 aryl-CH, 137.5 i-C, 213.3
CO. IR spectrum (ν(CO)/cmϪ1, CH2Cl2): 2041s, 1964m, 1933s;
(Nujol mull) 2033s, 1964m, 1935s. APCI MS (MeCN): m/z 745,
This was made in a similar manner to the 1,4-analogue, using
magnesium powder (0.85 g, 35 mmol), anthracene ( 0.62 g, 3.5
mmol), 1,3-dibromobenzene (2.06 g, 8.75 mmol), and PhMe2Sb
(4.0 g, 17.5 mmol). Yield 2.0g (60%). The crude ligand again
retained some anthracene, and sometimes small amounts of
1
PhMe2Sb, which could be distilled off in vacuum. H NMR
(CDCl3): 1.01(s) [12H] CH3, 7.22–7.78(m) [4H] aryl-CH.
13C{1H} NMR (CDCl3): Ϫ1.28 CH3, 127.5, 128.7, 134.6 aryl-
CH, 141.4 i-C. EI MS: m/z 380, 365, 350, 335; calcd. for
[C10H16121Sb123Sb]ϩ 380, [C9H13121Sb123Sb]ϩ 365, [C8H10121Sb-
123Sb]ϩ 350, [C7H7121Sb123Sb]ϩ 335.
[1,3-C6H4(SbMe3)2]I2 was prepared from the ligand and
excess MeI and recrystallised from acetone/diethyl ether.
Found: C, 23.08; H, 3.52. C12H22I2Sb2 requires C, 21.72; H,
3.34%. 1H NMR (d6-DMSO): 2.19(s) [18H] CH3, 7.95–8.43(m)
[4H] aryl-CH. 13C{1H} NMR (d6-DMSO): 4.36 CH3, 129.6,
131.0, 136.6 aryl-CH, 139.0 i-C. ESϩ MS (MeCN): m/z
537, 393; calcd. for [C12H22I121Sb123Sb]ϩ 537, [C11H19121Sb123Sb]ϩ
393.
ϩ
577; calcd. for [{Fe(CO)4}2{1,3-C6H4(CH2121SbMe2)2}] 742,
[Fe(CO)4{1,3-C6H4(CH2 121SbMe2)2}]ϩ 575.
[{Fe(CO)4}2{1,4-C6H4(CH2SbMe2)2}]
The reaction was carried out as above using 1,4-C6H4-
(CH2SbMe2)2 (0.10 g, 0.24 mmol). Yield 0.055 g (30%). Found:
C, 32.19; H, 2.99; C20H20O8Fe2Sb2 requires C, 32.31; H, 2.70%.
1H NMR (CDCl3): 1.19(s) [12H] CH3, 3.30(s) [4H], CH2, 7.09(s)
[4H] aryl-CH. 13C{1H} NMR (CH2Cl2/CDCl3): Ϫ1.5 CH3,
25.0 CH2, 129.0 aryl-CH, 134.6 i-C, 213.4 CO. IR spectrum
(ν(CO)/cmϪ1, CH2Cl2): 2040s, 1963m, 1931s; (Nujol mull):
2043s, 1959sh, 1938s. APCI MS (MeCN): m/z 745, 577; calcd.
for [{Fe(CO)4}2{1,4-C6H4(CH2121SbMe2)2}]ϩ 743, [Fe(CO)4-
{1,4-C6H4(CH2 121SbMe2)2}]ϩ 575.
[W(CO)5{1,3-C6H4(CH2SbMe2)2}]
A solution of 1,3-C6H4(CH2SbMe2)2 (0.10 g, 0.24 mmol) in dry
THF (10 mL) was added to a solution of [W(CO)5(THF)] gen-
erated in situ by the photolysis of [W(CO)6] (0.22 g, 0.62 mmol)
in dry THF (50 mL). The reaction was stirred at room temper-
ature for 2 h. The reaction mixture was filtered and the solvent
removed in vacuo to give a brown residue. Trituration with ice-
cold pentane gave a brown gum. Yield 0.078 g (44%). Found: C,
30.92; H, 3.28. C17H20O5Sb2Wؒ½C5H12 requires C, 30.46; H,
3.38%. 1H NMR (CDCl3): 1.21 (s) [3H], 1.27 (s) [3H] CH3, 3.20
(s) [H], 3.21 (s) [H] CH2, 6.80–7.20(m) [2H] aryl-CH. 13C{1H}
NMR (CH2Cl2/CDCl3): Ϫ1.6, 1.6 CH3, 23.0, 24.2 CH2, 126.0,
127.9, 129.8 aryl-CH, 137.6, 138.6 i-C, 197.0 (J = 126 Hz),
199.7 (J = 163 Hz) CO. IR spectrum (ν(CO)/cmϪ1, CH2Cl2):
2069s, 1975vs, 1937vs. APCI MS (MeCN): m/z 704, 676; calcd.
for [184W(CO)5{1,3-C6H4(CH2121SbMe2)2}]ϩ 702, [184W(CO)4-
{1,3-C6H4(CH2121SbMe2)2}]ϩ 674.
[{Fe(CO)4}2{1,2-C6H4(CH2SbMe2)2}]
The reaction was carried out as above using 1,2-C6H4(CH2-
SbMe2)2 (0.10 g, 0.24 mmol) and Fe2(CO)9 (0.18 g, 0.49 mmol),
red–brown oil. Yield 0.074 g (40%). 1H NMR (CDCl3): 1.20 (s)
[12H] CH3, 3.29 (s) [4H] CH2, 7.15–7.20 (m) [4H] aryl-CH.
13C{1H} NMR (CH2Cl2/CDCl3): Ϫ1.1 CH3, 23.5 CH2, 127.6,
129.8 aryl-CH, 134.0 i-C, 213.3 CO. IR spectrum (ν(CO)/cmϪ1
,
CH2Cl2): 2041s, 1965m, 1932s; (thin film): 2038s, 1917s.
APCI MS (MeCN): m/z 744, 577; calcd. for [{Fe(CO)4}2-
{1,2-C6H4(CH2121SbMe2)2}]ϩ 742, [Fe(CO)4{1,2-C6H4(CH2-
121SbMe2)2}]ϩ 575.
[{W(CO)5}2{1,4-C6H4(CH2SbMe2)2}]
The reaction carried out as above using 1,4-C6H4(CH2SbMe2)2
(0.10 g, 0.24 mol) and [W(CO)6] (0.22 g, 0.62 mmol)]. The
product was a brown solid. Yield 0.20 g (77%). Found: C,
25.49; H, 2.02. C22H20O10Sb2W2 requires C, 25.03; H, 1.91%. 1H
NMR (CDCl3): 1.19(s) [12H] CH3, 3.22(s) [4H] CH2, 7.05(s)
[4H] aryl-CH. 13C{1H} NMR (CH2Cl2/CDCl3): 2.0 CH3, 23.8
CH2, 128.9 aryl-CH, 134.4 i-C, 197.0 (J = 128 Hz), 199.7
(J = 164 Hz) CO. IR spectrum (ν(CO)/cmϪ1, CH2Cl2): 2068s,
1975vs, 1937vs. APCI MS (MeCN): m/z 1055, 1027; calcd. for
[{Fe(CO)4}2{1,3-C6H4(SbMe2)2}]
The reaction was carried out as above using 1,3-C6H4(SbMe2)2
(0.10 g, 0.26 mmol) and [Fe2(CO)9] (0.19 g, 0.52 mmol), brown
1
wax. Yield 0.062 g (33%). H NMR (CDCl3): 1.57 (s) [12H]
CH3, 7.31–7.72 (m) [4H] aryl-CH. 13C{1H} NMR (CH2Cl2/
CDCl3): 0.8 CH3, 130.5, 135.7, 138.9 aryl-CH, 140.0 i-C, 213.3
CO. IR spectrum (ν(CO)/cmϪ1, CH2Cl2): 2043s, 1966m, 1932s;
D a l t o n T r a n s . , 2 0 0 4 , 5 1 – 5 8
53

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(thin film): 2041s, 1917vs. APCI MS (MeCN): m/z 716, 548;
calcd. for [{Fe(CO)4}2{1,3-C6H4(121SbMe2)2}]ϩ 714, [Fe(CO)4-
{1,3-C6H4(121SbMe2)2}]ϩ 546.
2070s, 2000s, 1995s, 1941w; (thin film): 2070vs, 2007s, 1985s,
1943s.
[Mo(CO)4{1,2-C6H4(CH2SbMe2)2}]
[Fe(CO)4{ꢀ1-1,4-C6H4(SbMe2)2}]
To a solution of [Mo(CO)4(nbd)] (0.10 g, 0.12 mmol) in CH2Cl2
(30 mL) was added a solution of 1,2-C6H4(CH2SbMe2)2 (0.14 g,
0.12 mmol) in CH2Cl2 (5 mL). The reaction was stirred for 2 h
The reaction was carried out as above using 1,4-C6H4(SbMe2)2
(0.10 g, 0.26 mmol) and [Fe2(CO)9] (0.19 g, 0.52 mmol), brown
wax. Yield 0.073 g (51%). 1H NMR (CDCl3): 0.98 (s) [6H]
CH3, 1.52 (s) [6H] CH3, 7.52–7.65 (m) [4H] aryl-CH. 13C{1H}
NMR (CH2Cl2/CDCl3): Ϫ1.4 CH3, 0.9 CH3, 133.3, 135.0 aryl-
under N2
until solution IR studies showed the absence of bands
associated with starting material. The solvent volume was
reduced in vacuo to ca. 5 mL and degassed hexane added to give
a pale brown precipitate. The product was isolated by filtration
and dried in vacuo. Yield 0.07 g (33%). Found: C, 31.6; H, 3.3.
CH, 135.9, 137.8 i-C, 213.3 CO. IR spectrum (ν(CO)/cmϪ1
,
CH2Cl2): 2043s, 1966 m, 1933s; (thin film): 2040s, 1963sh,
1927vs. APCI MS (MeCN): m/z 548; calcd. for [Fe(CO)4-
{1,4-C6H4(121SbMe2)2}]ϩ 546.
1
C16H20MoO4Sb2 requires C, 31.2; H, 3.3%. H NMR (CDCl3):
1.21(s) [12H] CH3
, 3.22 (s) [4H] CH , 6.99(m) [2H] aryl-CH,
2
7.05(m) [2H] aryl-CH. 13C{1H} NMR (CH2Cl2/CDCl3): Ϫ0.2
CH3, 24.4 CH2, 126.3, 129.2 aryl-CH, 137.0 i-C, 210.9, 215.5
CO. 95Mo NMR (CH2Cl2/CDCl3): Ϫ1798. IR spectrum (CsI
disk/ν(CO)/cmϪ1): 2017s, 1935bs, 1901s, 1867s.
[Ni(CO)3{1,3-C6H4(CH2SbMe2)2}]
Ni(CO)4 (0.10 g, 0.59 mmol) was injected into a solution of 1,3-
C6H4(CH2SbMe2)2 (0.10 g, 0.25 mmol) in CH2Cl2 (30 mL). The
reaction was stirred at RT under N2 for 3 h. The solvent was
removed in vacuo to yield a brown oil. 1H NMR (CDCl3):
0.80(s) [6H] CH3, 0.98(s) [6H] CH3, 2.87(s) [2H] CH2, 3.01(s)
[2H] CH2, 6.73–7.20(m) [4H] aryl-CH. 13C{1H} NMR (CH2Cl2/
CDCl3): Ϫ2.1, Ϫ0.6 CH3, 24.0, 25.2 CH2, 124.9, 125.2, 126.3,
127.4, 128.9 aryl-CH, 139.3, 139.6 i-C, 197.0 CO. IR spectrum
(ν(CO)/cmϪ1, CH2Cl2): 2068s, 1993s,br; (thin film); 2067s,
1987vs.
X-Ray crystallography
Crystal data and other details are presented in Table 1. Suitable
crystals of 1,4-C6H4(CH2SbMe2)2 were obtained from the
preparation, crystals of [1,3-C6H4(CH2SbMe3)2]I2 were grown
from acetone solution stored in the freezer, and those of
[{Fe(CO)4}2{1,3-C6H4(CH2SbMe2)2}] were grown from CH2Cl2
solution by slow evaporation in the freezer. Data were recorded
using a Nonius Kappa CCD diffractometer fitted with Mo–Kα
radiation and graphite monochromator with the crystals held at
120 K in a gas stream. An absorption correction using the
SORTAV procedure20 was used and the usual Lorentz and
polarization factors were applied.
[Ni(CO)3{1,4-C6H4(CH2SbMe2)2}]
The reaction carried out as above using 1,4-C6H4(CH2SbMe2)2
(0.10 g, 0.25 mmol). The product was a colourless oil. 1H NMR
(CDCl3): 0.79(s) [6H] CH3, 0.96(s) [6H] CH3, 2.89(s) [2H] CH2,
3.03(s) [2H] CH2, 6.92–7.11(m) [4H] Aryl-CH. 13C{1H} NMR
(CH2Cl2/CDCl3): Ϫ2.4, Ϫ0.8 CH3, 23.6, 24.8 CH2, 128.1, 128.3
The structures were solved using the direct methods option in
SHELXS-9721 and refined using SHELXL-97.22 Hydrogen
atoms were placed in idealised positions and given a common
refined isotropic displacement parameter. The systematic
absences for [1,3-C6H4(CH2SbMe3)2]I2 were consistent with
space groups C2/m, C2 and Cm. The normalized structure
factors favoured the centrosymmetric space group C2/m, how-
ever the presence of a few heavy atoms whose y coordinates are
very similar makes this result unreliable. A satisfactory dis-
ordered model in C2/m emerged with all the Sb and I and four
of the six Me groups in the asymmetric unit located on a mirror
plane. The mirror plane relationship between the two C6 rings
made some of the C atoms unreasonably close together and the
methylene C atom was disordered with one of the methyl C
atoms. A second solution emerged in C2 which is not dis-
ordered but did suffer from one unreasonably close H ؒ ؒ ؒ H
contact; the Flack parameter suggested some twinning and
inclusion of the TWIN command led to a modest improve-
ment. The two models: the higher symmetry (C2/m) with dis-
order of the light atoms or the lower symmetry (C2) with twin-
ning is a recognised problem. In chemical terms the models are
the same, confirming the ligand geometry. Partly because of the
short H ؒ ؒ ؒ H distance in C2 the C2/m model is reported here.
Hydrogen atoms were introduced in calculated positions except
for the disordered C(H2)/C(H3) in [1,3-C6H4(CH2SbMe3)2]I2.
Forthe[{Fe(CO)4}2{1,3-C6H4(CH2SbMe2)2}]theabsolutestruc-
ture was established from the Flack parameter23 (Ϫ0.01(6)).
CCDC reference numbers 220713 (1,4-C6H4(CH2SbMe2)2),
220714 (iodide) and 220715 (Fe complex).
aryl-CH, 136.4, 138.3 i-C, 197.1 CO. IR spectrum (ν(CO)/cmϪ1
CH2Cl2): 2068s, 1993vs; (thin film): 2067s, 1986vs.
,
[Ni(CO)2{1,2-C6H4(CH2SbMe2)2}]
The reaction was carried out as above using 1,2-C6H4-
(CH2SbMe2)2. Work up yielded a colourless solid. H NMR
1
(CDCl3): 1.09(s) [12H] CH3, 3.14(s) [4H] CH2, 6.96–7.02(m)
[4H] aryl-CH. 13C{1H} NMR (CH2Cl2/CDCl3): Ϫ1.1 CH3, 23.7
CH2, 125.5, 129.5 aryl-CH, 137.7 i-C, 201.0 CO. IR spectrum
(ν(CO)/cmϪ1, CH2Cl2): 2002s, 1939s; (thin film): 1997s, 1922s.
APCI MS (MeCN): m/z 508, 451; calcd. for [Ni(CO)2-
{1,2-C6H4(CH2121SbMe2)(CH2121SbMe)}]ϩ 505, [Ni{1,2-C6H4-
(CH2121SbMe2)(CH2121SbMe)}]ϩ 449.
Ni(CO)4 ؉1,3-C6H4(SbMe2)2
The reaction was conducted as above and produced an
inseparable mixture of three complexes (see text). [Ni(CO)3-
{η1-1,3-C6H4(SbMe2)2}], [{Ni(CO)3}2{1,3-C6H4(SbMe2)2}], and
[{Ni(CO)2{1,3-C6H4(SbMe2)2}}2]. 1H NMR (CDCl3): 1.10,
1.19, 1.28 1.30 [12H] CH3, 7.22–7.66 [4H] aryl-CH. 13C{1H}
NMR (CH2Cl2/CDCl3): Ϫ1.2, Ϫ0.1, 0.6, 1.2 CH3, 129.5–140.1
aryl-CH, 196.9, 201.0 CO. IR spectrum (ν(CO)/cmϪ1, CH2Cl2):
2070s, 2000s, 1995s, 1941w; (thin film): 2070vs, 2007s, 1985s,
1943s.
See http://www.rsc.org/suppdata/dt/b3/b312083j/ for crystal-
lographic data in CIF or other electronic format.
Ni(CO)4 ؉1,4-C6H4(SbMe2)2
The reaction was conducted as above and produced an
inseparable mixture of three complexes (see text). [Ni(CO)3-
{η1-1,4-C6H4(SbMe2)2}], [{Ni(CO)3}2{1,4-C6H4(SbMe2)2}], and
[{Ni(CO)2{1,4-C6H4(SbMe2)2}}2]. 1H NMR (CDCl3): 1.01,
1.16, 1.21, 1.27 [12H] CH3, 6.98–7.66 [4H] aryl-CH. 13C{1H}
NMR (CH2Cl2/CDCl3): Ϫ1.2, Ϫ0.1, 0.5, 1.1 CH3, 129.0–135.5
aryl-CH, 197.0, 201.0 CO. IR spectrum (ν(CO)/cmϪ1, CH2Cl2):
Results and discussion
Ligand syntheses
The literature route15 to 1,2-C6H4(SbMe2)2 illustrates many of
the problems experienced in obtaining di- and polydentate stib-
ines – it is lengthy, gives very poor overall yields, and involves
D a l t o n T r a n s . , 2 0 0 4 , 5 1 – 5 8
54

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Table 1 Crystal data and structure refinement detailsa
Compound
1,4-C6H4(CH2SbMe2)2
[1,3-C6H4(CH2SbMe3)2]I2
[{Fe(CO)4}2{1,3-
C6H4(CH2SbMe2)2}]
C20H20Fe2O8Sb2
743.56
Formula
FW
C12H20Sb2
407.78
C14H26I2Sb2
691.65
Crystal system
Space group
a/Å
b/Å
Monoclinic
P21/n (no. 14)
6.1174(12)
17.749(4)
6.7048(16)
100.766(8)
715.2(3)
Monoclinic
C2/m (no. 12)
22.721(4)
7.0975(15)
16.478(3)
121.006(7)
2277.5(7)
4
Tetragonal
P41212 (no. 92)
10.5264(16)
10.5264(16)
22.924(4)
—
2540.1(7)
c/Å
β/Њ
U/Å3
Z
2
4
µ/mmϪ1
3.745
5.072
3.263
Total no. of obsns (Rint
Unique obsns
R1, wR2 (I > 2σ(I ))b
R1, wR2 (all data)
)
5538 (0.078)
1621
0.034, 0.083
0.040, 0.087
9172 (0.069)
2803
0.042, 0.110
0.054, 0.116
8902 (0.071)
2902
0.047, 0.090
0.075, 0.099
4
a Common items: temperature = 120 K; wavelength (Mo–Kα) = 0.71073 Å; θ(max) = 27.5Њ. b R1 = Σ|| Fo| Ϫ |Fc||/Σ|Fo|. wR2 = [Σw(Fo2 Ϫ Fc2)2/ΣwFo ]1/2
.
handling hazardous intermediates on a moderately large scale.
In particular, the pyrophoric and volatile Me3Sb is a consider-
able fire-hazard and is not easily stored. Usually it is converted
by halogenation to the air and water stable Me3SbX2 (X = Cl
or Br) which are decomposed when required to Me2SbX
by pyrolysis under reduced pressure. However, this thermal
decomposition needs careful temperature and pressure control,
or substantial amounts of Me3SbX2 sublime unchanged and
some scrambling of the groups at antimony occurs.24,25 As an
alternative, we have used the method in Scheme 1, which uses
crude PhSbCl2 (from comproportionation of Ph3Sb and 2SbCl3
in the absence of a solvent),17 converted into Me2PhSb by
MeMgI. The Me2PhSb is only moderately air-sensitive, easily
purified by fractionation in vacuum, can be made on a large
scale and is easily stored until needed. The preparation also
yields smaller quantities of MePh2Sb which arise either from
Ph2SbCl impurity in the PhSbCl2 and/or from some substituent
scrambling in the reaction, but this is easily separated by frac-
tionation (and provides a source of MeSbCl2 by reaction with
ing in vacuo, obviating the need to distill it. The contrasting
yields of this distibine, <10% when an antimony nucleophile
(SbMe2Ϫ) reacts with a dihaloorganic reagent, and 88% when
the nucleophile (the di-Grignard) reacts with the electrophilic
antimony reagent (Me2SbCl) is striking, and consistent with
previous reports2–4,15 that antimony nucleophiles tend to
break existing Sb–C bonds as well as substitute C–X bonds.
The route utilising the appropriate di-Grignard was extended to
make 1,3-bis(dimethylstibanylmethyl)benzene and 1,4-bis(di-
methylstibanylmethyl)benzene in 56 and 50% yield, respectively.
The 1,2- and 1,3-compounds are air-sensitive oils, the 1,4-disti-
bine is a white solid. All were further characterised by reaction
with excess MeI in acetone, which afforded the corresponding
dimethiodides C6H4(CH2SbMe3)2I2 as crystalline solids. This
ready diquaternisation contrasts with the exclusive mono-
quaternisation observed for o-C6H4(EMe2)2 (E = P, As, Sb
etc.)15 attributed to deactivation of the second –EMe2 by
ϩ
inductive effects from the –EMe3
.
The reaction of NaSbPh2 28 in liquid NH3 with α,αЈ-dibromo-
o-xylene failed to give any 1,2-bis(diphenylstibanylmethyl)-
benzene, the major products being Ph3Sb, Ph2SbSbPh2 and
much black solid. However, reaction of Ph2SbCl17 with 1,2-
bis(chloromagnesiomethyl)benzene was more successful, giving
the waxy solid distibine in 13% yield. Samples of the latter
26
HCl – a useful synthon for polydentates). The Me2PhSb is
converted to Me2SbCl by treatment with HCl gas27 in CH2Cl2,
benzene or toluene and can be isolated by removing the solvent
in vacuum. However, it is usually easier to use toluene as sol-
vent, purge the excess HCl with N2 and use the toluene solution
directly. Reaction with Na/liquid NH3 gave NaSbMe2, which
reacted with α,αЈ-dibromo-o-xylene to afford 1,2-bis(di-
methylstibanylmethyl)benzene, but only in 6% yield after distil-
lation. However, when the same Me2SbCl solution in toluene
was added to the di-Grignard 1,2-bis(chloromagnesiomethyl)-
benzene, itself prepared18 from activated magnesium powder
and α,αЈ-dichloro-o-xylene in THF, the yield of 1,2-bis(di-
methylstibanylmethyl)benzene was 88%. Moreover, the product
was spectroscopically pure after removing all solvents by pump-
1
produced in this way appeared pure by H and 13C{1H} NMR
spectroscopy. Diarylalkylstibines do not quaternise with MeI,29
but reaction with diiodine gave 1,2-C6H4(CH2SbPh2I2)2 as an
orange–yellow powder.
The methodology was extended to the synthesis of 1,4-
and 1,3-bis(dimethylstibanyl)benzene, by using magnesium–
anthracene19 to prepare the phenylene-di-Grignards as des-
cribed in the Experimental, followed by reaction with Me2SbCl.
The two phenylene distibines were obtained as oils, along with
some PhMe2Sb, easily separated by distillation. Mass spectra
of the crude 1,3-C6H4(SbMe2)2 showed peaks at higher mass
which corresponded to the tristibine MeSb(C6H4SbMe2)2,
although this was not evident in the NMR spectra and is clearly
a minor by-product. The triarsine MeAs(o-C6H4AsMe2)2 was
previously identified as a very minor by-product of the syn-
thesis of 1,2-C6H4(AsMe2)2 from o-C6H4Cl2 and NaAsMe2.30
The 1,3-C6H4(SbMe2)2 and 1,4-C6H4(SbMe2)2 gave the expected
diquaternary derivatives.
The 1H NMR spectra of the distibines are consistent with the
formulations but unexceptional. The 13C{1H} NMR spectra are
more informative, and the characteristic δ(Me) resonances to
low frequency of TMS are notable, the effect being shared by
methyl groups on other heavy atoms such as I, Pb or Te, and
attributed to spin–orbit effects of the heavy atom.31 Quaternis-
ation of the antimony results in marked high frequency shifts in
the δ(Me) and δ(CH2) resonances in both 1H and 13C{1H}
NMR spectra.
Scheme 1
D a l t o n T r a n s . , 2 0 0 4 , 5 1 – 5 8
55

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Table 2 Selected bond lengths (Å) and angles (Њ) for 1,4-C6H4-
(CH2SbMe2)2
Sb(1)–C(1)
Sb(1)–C(2)
2.153(4)
2.148(4)
Sb(1)–C(3)
C(3)–C(4)
2.192(3)
1.497(5)
C(1)–Sb(1)–C(2)
C(2)–Sb(1)–C(3)
93.79(15)
97.12(14)
C(1)–Sb(1)–C(3)
Sb(1)–C(3)–C(4)
96.84(14)
114.8(2)
The EIϩ mass spectra of the distibines and ESϩ mass
spectra of their quaternary derivatives show characteristic
antimony isotope patterns (121Sb 57.3%, 123Sb 42.7%). For
1,2-C6H4(CH2SbMe2)2 there is no evidence for a parent peak,
major fragment ions being [PϪMe]ϩ and [PϪSbMe2]ϩ,
whereas both 1,3-C6H4(CH2SbMe2)2 and 1,4-C6H4(CH2-
SbMe2)2 show strong [P]ϩ ions. The fragmentation patterns of
the dimethiodides also differ: both 1,2-C6H4(CH2SbMe3)2I2 and
1,3-C6H4(CH2SbMe3)2I2 show [PϪ2I]2ϩ as expected, but for
1,4-C6H4(CH2SbMe3)2I2 the major feature is [PϪI]ϩ, whilst
1,2-C6H4(CH2SbMe3)2I2 uniquely shows an ion corresponding
to [PϪ(CH4I)]ϩ. The EI mass spectra of the two phenylene
distibines show parent ions and sequential loss of all four Me
groups as the major features.
Crystals of 1,4-C6H4(CH2SbMe2)2 were obtained from the
preparation and the structure (Fig. 1, Table 2) shows a centro-
symmetric molecule with an approximate mirror plane. The
d(Sb–C) and the C–Sb–C angles are unexceptional,4,10,32 but the
structure is confirmation of the identity of the new ligand. For
1,3-C6H4(CH2SbMe3)2I2 crystals were obtained from acetone
and show (Fig. 2, Table 3) the antimony in a distorted tetra-
hedral environment, although the d(Sb–C) on average are only
slighter shorter than in 1,4-C6H4(CH2SbMe2)2.
Fig. 2 Molecular structure of the disordered cation in [1,3-C6H4-
(CH2SbMe3)2]I2 solved in the space group C2/m. There is a crystallo-
graphic mirror plane passing through Sb1, C1, C2, Sb2, C11 and C12.
C3/C3a and C10/C10a are mirror related atoms (x, Ϫy, z) and represent
disordered C(H2)/C(H3) groups. The diagram shows one molecule in the
disordered cation with thermal ellipsoids drawn at the 50% probability
level.
Nickel
The reactions were carried out by stirring an excess of Ni(CO)4
with the ligands in CH2Cl2 at ambient temperature, and moni-
toring the progress of reaction by IR spectroscopy. After a few
hours when reaction had ceased, the excess Ni(CO)4 and the
solvent were removed in vacuum, and the residual oils exam-
1
ined by IR, H and 13C{1H} NMR spectroscopy to determine
the species present. With few exceptions, the products were
colourless oils, which darkened in a few hours at room temper-
ature, indicating decomposition, although they could be kept
for some weeks at Ϫ20 ЊC in the dark. Mass spectrometry also
gave little information, with one exception (below), the spectra
were dominated by low mass ligand fragments. The reaction of
1,2-bis(dimethylstibanylmethyl)benzene with Ni(CO)4 in a
1:2 molar ratio in CH2Cl2 at ambient temperature proceeded
smoothly, accompanied by visible gas evolution, and the reac-
tion was monitored by recording IR spectra of the solution in
the region 2200–1800 cmϪ1 at regular intervals. The t2 mode of
Ni(CO)4 at 2043 cmϪ1 diminished in intensity over time and two
modes at 2002, 1939 cmϪ1 assigned to the a1 ϩ b1 modes of a
dicarbonyl36 fragment increased in intensity. Removal of all
volatiles in vacuo left a fawn solid, identified as [Ni(CO)2{1,2-
C6H4(CH2SbMe2)2}], confirmed by the single Me and CH2
resonances in the 1H and 13C{1H} NMR spectra, both shifted to
high frequency from the values in the free ligand, and by a
single δ(CO) at 201.1. The ν(CO) 2002, 1939 cmϪ1 in this
complex may be compared with those in [Ni(CO)2(L–L)] (L–L
Fig. 1 Molecular structure of 1,4-C6H4(CH2SbMe2)2 showing the
atom labelling scheme. H atoms omitted for clarity and the thermal
ellipsoids are drawn at the 50% probability level. Symmetry operation:
a = 2Ϫx, Ϫy, 1Ϫz.
= o-C6H4(PMe2)2 1996, 1931 and o-C6H4(AsMe2)2 1996, 1931
36
cmϪ1
)
showing that the stibine is a significantly weaker
σ-donor than the diphosphine or diarsine.
Complexes
The reaction of 1,4-bis(dimethylstibanylmethyl)benzene with
Ni(CO)4 was conducted similarly using a 1:2.2 molar ratio of
reactants. In this case, new carbonyl stretches at 2068s, 1993vs
cmϪ1 developed, indicative of a Ni(CO)3 fragment,10 and pump-
ing to dryness in vacuo left a clear colourless oil. However both
the 1H and 13C{1H} NMR spectra of this oil showed two δ(Me)
resonances of equal intensity both slightly to high frequency of
the values in the “free” ligand, consistent with the formation
In order to establish the coordination modes possible for the
xylyl-based distibines, complexes were prepared using nickel,
iron and tungsten carbonyls. The carbonyl stretching vibrations
in their IR spectra and the 13C{1H} NMR carbonyl chemical
shifts, providing useful data on the ligand electronic properties
and permitting comparisons with other Group 15 donor lig-
ands.33–35
a
Table 3 Selected bond lengths (Å) and angles (Њ) for [1,3-C6H4(CH2SbMe3)2]I2
Sb(1)–C(1)
Sb(1)–C(2)
Sb(1)–C(3)
C(3)–C(4)
C–C (ring)
2.105(10)
2.103(7)
2.117(6)
1.449(12)
Sb(2)–C(10)
Sb(2)–C(11)
Sb(2)–C(12)
C(6)–C(10)
2.130(6)
2.101(7)
2.091(9)
1.442(13)
1.376(18)–1.414(16)
C(1)–Sb(1)–C(2)
C(1)–Sb(1)–C(3)
C(2)–Sb(1)–C(3)
C(3)–Sb(1)–C(3a)
Sb(1)–C(3)–C(4)
C–C–C (ring)
108.1(4)
106.6(3)
113.2(2)
108.6(4)
113.7(6)
117.1(11)–122.7(11)
C(11)–Sb(2)–C(12)
C(11)–Sb(2)–C(10)
C(12)–Sb(2)–C(10)
C(10)–Sb(2)–C(10a)
Sb(2)–C(10)–C(6)
107.9(4)
113.2(2)
107.4(3)
107.5(4)
114.2(6)
a Symmetry operation: a = x, Ϫy, z.
D a l t o n T r a n s . , 2 0 0 4 , 5 1 – 5 8
56

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Table 4 Selected spectroscopic data on some nickel carbonyl complexes
Complex
ν(CO)a/cmϪ1
δ(13CO)/ppm
Ref.
[Ni(CO)3(SbEt3)]
[Ni(CO)3(SbPh3)]
2067, 1996
2074, 2004
2067, 1994
2072, 2004
2068, 1993
2068, 1993
2070, 2000
2070, 2000
2064, 1982
2067, 1990
2068, 1990
2072, 1999
197.5
196.5
197.1
196.3
197.1
197.0
197.0
196.9
196.7
197.0
195.9
195.8
34,37
34,38
10
10
This work
This work
This work
This work
33,34
34,37
33,34
[{Ni(CO)3}2(Me2SbCH2SbMe2)]
[Ni(CO)3(η1-Ph2SbCH2SbPh2)]
[Ni(CO)3{η1-1,4-C6H4(CH2SbMe2)2}]
[Ni(CO)3{η1-1,3-C6H4(CH2SbMe2)2}]
[Ni(CO)3{η1-1,4-C6H4(SbMe2)2}]
[Ni(CO)3{η1-1,3-C6H4(SbMe2)2}]
[Ni(CO)3(PMe3)]
[Ni(CO)3(AsEt3)]
[Ni(CO)3(PPh3)]
[Ni(CO)3(AsPh3)]
34,37
a Chlorocarbon solvent.
Table 5 Selected bond lengths (Å) and angles (Њ) for [{Fe(CO)4}2{1,3-C6H4(CH2SbMe2)2}]
Sb(1)–Fe(1)
Sb(1)–C(5)
Sb(1)–C(6)
Sb(1)–C(7)
C(7)–C(8)
2.4901(11)
2.120(7)
2.129(6)
2.146(7)
1.505(9)
Fe(1)–C(1)
Fe(1)–C(2)
Fe(1)–C(3)
Fe(1)–C(4)
C(n)–O(n)
1.797(8)
1.784(8)
1.794(8)
1.783(8)
1.129(8)–1.152(8)
Fe(1)–Sb(1)–C(5)
Fe(1)–Sb(1)–C(6)
Fe(1)–Sb(1)–C(7)
Sb(1)–C(7)–C(8)
C(1)–Fe(1)–C(2)
C(1)–Fe(1)–C(3)
C(1)–Fe(1)–C(4)
C(5)–Sb(1)–C(6)
C(6)–Sb(1)–C(7)
116.1(2)
114.9(2)
115.9(2)
110.6(4)
94.0(3)
118.1(3)
118.7(3)
104.6(3)
101.4(3)
Sb(1)–Fe(1)–C(1)
Sb(1)–Fe(1)–C(2)
Sb(1)–Fe(1)–C(3)
Sb(1)–Fe(1)–C(4)
C(2)–Fe(1)–C(3)
C(2)–Fe(1)–C(4)
C(3)–Fe(1)–C(4)
C(5)–Sb(1)–C(7)
Fe(1)–C(n)–O(n)
86.6(3)
179.3(2)
88.8(2)
85.7(2)
91.3(3)
93.7(3)
122.4(3)
102.1(3)
177.7(7)–178.6(7)
of [Ni(CO)3{η1-1,4-C6H4(CH2SbMe2)2}]. Similarly 1,3-bis(di-
methylstibanylmethyl)benzene and Ni(CO)4 formed [Ni(CO)3-
{η1-1,3-C6H4(CH2SbMe2)2}]. However, in this case, longer
reaction times in the presence of excess Ni(CO)4 produced a
an Fe2(CO)9 :ligand mol. ratio of 2:1 (half the contained iron is
lost as Fe(CO)5 in these reactions39) led to complexes of stoi-
chiometry [{Fe(CO)4}2{C6H4(CH2SbMe2)2}]. The IR spectra
each show three ν(CO)s at ca. 2040, 1965, 1933 cmϪ1 (CH2Cl2
solutions) consistent with axially substituted trigonal bi-
pyramidal iron centres (C3v)40 (theory: 2a1 ϩ e). In all three
complexes the two Fe(CO)4 units are bridged by the distibine
ligand as confirmed by the crystal structure of [{Fe(CO)4}2-
{1,3-C6H4(CH2SbMe2)2}]. The geometry is also supported by
the NMR data which showed only single Me and CH2
environments, and as usual10,40 in iron carbonyl derivatives, the
CO groups are fluxional, giving a single 13C NMR resonance.
The tricarbonyl [Fe(CO)3{1,2-C6H4(CH2SbMe2)2}] does not
form under these conditions, attributable to the difficulty of
displacing a second carbonyl group from the iron in such
systems.41 In contrast to the mixtures produced with nickel,
the phenylene-distibines afforded [{Fe(CO)4}2{µ-1,3-C6H4-
(SbMe2)2}] and [Fe(CO)4{η1-1,4-C6H4(SbMe2)2}] cleanly as
brown solids.
second species, a dicarbonyl with ν(CO) 1997, 1938 cm .
Ϫ1 36 The
reaction did not go to completion and extensive decomposition
occurred on further reaction with much black solid produced.
Addition of Me3NO also failed to convert the mixture
completely to the dicarbonyl.
The two phenylene-backboned ligands gave mixtures on
reaction with Ni(CO)4, the products being identified by a
combination of IR, 1H and 13C{1H} NMR spectroscopy as
[{Ni(CO)3}2{µ-C6H4(SbMe2)2}], [Ni(CO)3{η1-C6H4(SbMe2)2}]
and [{Ni(CO)2{C6H4(SbMe2)2}}2], the last formulated as ligand
bridged dimers, since neither ligand can chelate. Despite the
relatively poor stability of these complexes, the spectroscopic
parameters needed to compare the electronic properties of the
distibines with those of other ligands were readily extracted and
a comparison is shown in Table 4. The data on the new distibine
complexes show the usual dependence upon both the donor
atom and the R-group.10,33,34,37 Comparison with Tolman’s
extensive listing10 of the ν1(a1) modes in Ni(CO)3L complexes
shows the electronic properties of the present ligands are typi-
cal of trialkylstibines, which place less electron density into the
π* CO orbitals than phosphine or arsine analogues. The 13C
NMR data on the Ni(CO)3 units reflect the same trends
although the numerical differences are small. Thus, one can
conclude that these distibine ligands are electronically typical
of their kind, but offer a range of architectures which will sup-
port a corresponding range of structures in metal complexes.
The crystal structure of [{Fe(CO)4}2{1,3-C6H4(CH2-
SbMe2)2}] was determined and consists of the distibine ligand
with each Sb bonded axially to an Fe(CO)4 residue (Fig. 3,
Table 5). The discrete molecule has 2-fold crystallographic
symmetry passing through C(10) and C(11). The Fe–Sb bond
Iron
Iron carbonyl complexes were readily isolated as red or brown
powders or oils, and these were stable at room temperature
under an inert atmosphere. The reaction of Fe2(CO)9 in THF at
ambient temperature39 with each of the three xylyl distibines in
Fig. 3 Molecular structure of [{Fe(CO)4}2{1,3-C6H4(CH2SbMe2)2}]
showing the atom labelling scheme. H atoms omitted for clarity and the
thermal ellipsoids are drawn at the 50% probability level. Symmetry
operation: a = yϩ1, xϪ1, 2Ϫz.
D a l t o n T r a n s . , 2 0 0 4 , 5 1 – 5 8
57

View Article Online
length may be compared with that reported10 in [Fe(CO)4-
(η1-Ph2SbCH2SbPh2)] (2.491(2) Å) and as noted before32 in
triphenylstibine complexes, there is an increase in the average
C–Sb–C on complexation; here we compare 1,4-C6H4-
(CH2SbMe2)2 (96Њ (av)) with the present iron complex (103Њ
2 W. Levason and C. A. McAuliffe, Phosphine, Arsine and
Stibine Complexes of the Transition Elements, Elsevier, New York,
1979.
3 W. Levason and G. Reid, Comprehensive Coordination Chemistry II,
ed. J. A. McCleverty and T. J. Meyer, Elsevier, Oxford, 2003, vol. 1,
in press.
(av)). The shortest intermolecular contact is 2.40
Å
4 W. Levason and N. R. Champness, Coord. Chem. Rev., 1994, 133,
115.
(O(4) ؒ ؒ ؒ H(6B)) and this may be the reason for the C–Sb(1)–
Fe(1)–Ceq torsion angles being displaced from the idealised
60Њ (the smallest is 33Њ).
5 W. Hewertson and H. R. Watson, J. Chem. Soc., 1962, 1490.
6 K. Issleib and B. Hamann, Z. Anorg. Allg. Chem., 1965, 339,
289; K. Issleib and B. Hamann, Z. Anorg. Allg. Chem., 1964, 332,
179.
7 T. Even, A. R. J. Genge, A. M. Hill, N. J. Holmes, W. Levason and
M. Webster, J. Chem. Soc., Dalton Trans., 2000, 655.
8 N. J. Holmes, W. Levason and M. Webster, J. Chem. Soc.,
Dalton Trans., 1998, 3457.
9 A. M. Hill, N. J. Holmes, A. R. J. Genge, W. Levason, M. Webster
and S. Rutschow, J. Chem. Soc., Dalton Trans., 1998, 825.
10 A. M. Hill, W. Levason, M. Webster and I. Albers, Organometallics,
1997, 16, 5641.
11 J. R. Black, W. Levason, M. D. Spicer and M. Webster, J. Chem.
Soc., Dalton Trans., 1993, 3129.
Tungsten
The reaction of 1,4-C6H4(CH2SbMe2)2 with 2.2 equivalents of
[W(CO)5(THF)], generated in situ by photolysis of W(CO)6 in
THF, gave [{W(CO)5}2{1,4-C6H4(CH2SbMe2)2}] as a white
powder. The dimer formulation with bridging distibine follows
from the APCI MS which showed a parent ion, and the IR
spectra which exhibited three ν(CO)s at ca. 2069, 1995, 1937
cmϪ1 consistent with a square pyramidal W(CO)5 moieties
(theory: 2a1 ϩ e) at energies similar to those in other tungsten
12 A. M. Hill, W. Levason and M. Webster, Inorg. Chem., 1996, 35,
1
stibines.9 The H and 13C{1H} NMR spectra are also consis-
3428.
tent with this formulation.9 However, for 1,3-C6H4(CH2SbMe2)2
the same reaction gave only [W(CO)5{η1-1,3-C6H4(CH2-
SbMe2)2}] even further treatment of the isolated complex with
[W(CO)5(THF)] did not attach a second tungsten centre. As
expected, the ligand 1,2-C6H4(CH2SbMe2)2 behaves differ-
ently in tungsten carbonyl systems. Photolysis of [W(CO)6] and
1,2-C6H4(CH2SbMe2)2 in THF solution gave [W(CO)4{1,2-
C6H4(CH2SbMe2)2}] in poor yield along with much black
decomposition product. The same complex was better made
from [W(CO)4(piperidine)2] and 1,2-C6H4(CH2SbMe2)2 in
ethanol, and the corresponding [Mo(CO)4{1,2-C6H4(CH2-
SbMe2)2}] was obtained from the ligand and [Mo(CO)4-
(norbornadiene)] in CH2Cl2. The IR spectra of these two com-
plexes are typical of cis tetracarbonyls showing four IR active
stretches (theory: 2a1 ϩ b1 ϩ b2). For the tungsten complex the
1J(183W–13C) coupling on the carbonyl resonance of the
COtransSb of 160 Hz is comparable with those observed in other
tungsten stibines,9 and in comparison with data on other Group
15 ligand complexes34 places the distibines low in the trans
influence series, attributable to poor σ donation by the
antimony.
13 E. Shewchuk and S. B. Wild, J. Organomet. Chem., 1977, 128,
115.
14 H. C. Jewiss, W. Levason and M. Webster, Inorg. Chem., 1986, 25,
1997.
15 W. Levason, K. G. Smith, C. A. McAuliffe, F. P. McCullough, R. D.
Sedgwick and S. G. Murray, J. Chem. Soc., Dalton Trans., 1979,
1718.
16 A. F. Chiffey, J. Evans, W. Levason and M. Webster,
Organometallics, 1996, 15, 1280.
17 M. Nunn, D. B. Sowerby and D. M. Wesolek, J. Organomet. Chem.,
1983, 251, C45; S. P. Bone and D. B. Sowerby, J. Chem. Soc.,
Dalton Trans., 1979, 715.
18 M. F. Lappert, T. R. Martin and C. L. Raston, Inorg. Synth., 1989,
26, 144.
19 L. Zhang, S. Liao, Y. X. M. Wang, Y. Zhang and D. Yu, Synth.
React. Inorg. Met. Org. Chem., 1996, 26, 809.
20 R. H. Blessing, J. Appl. Crystallogr., 1997, 30, 421.
21 G. M. Sheldrick, SHELXS-97, a program for crystal structure
solution, University of Göttingen, Germany, 1997.
22 G. M. Sheldrick, SHELXL-97, a program for crystal structure
refinement, University of Göttingen, Germany, 1997.
23 H. D. Flack, Acta Crystallogr., Sect. A, 1983, 39, 876.
24 G. T. Morgan and G. R. Davies, Proc. R. Soc. London, Ser. A, 1926,
110, 523.
25 H. J. Breunig and W. Kanig, Phosphorus Sulfur, 1982, 12, 149.
26 H. Althaus, H. J. Breunig and E. Lork, Organometallics, 2001, 20,
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Conclusions
27 H. J. Breunig, H. Althaus, R. Rosler and E. Lork, Z. Anorg. Allg.
Chem., 2000, 626, 1137.
28 K. K. Chow, W. Levason and C. A. McAuliffe, J. Chem. Soc.,
Dalton Trans., 1976, 1429.
29 G. O. Doak and L. D. Freedmann, Organometallic Compounds
of Arsenic, Antimony and Bismuth, Wiley, New York, 1970,
ch. 8.
30 R. D. Feltham, A. S. Kasenally and R. S. Nyholm, J. Organomet.
Chem., 1967, 7, 285.
31 A. A. Cheremisin and P. V. Schastnev, J. Magn. Res., 1980, 40,
459.
32 N. J. Holmes, W. Levason and M. Webster, J. Chem. Soc.,
Dalton Trans., 1997, 4223; G. Becker, O. Mundt, M. Sachs, H. J.
Breunig, E. Lork, J. Probst and A. Silvestru, Z. Anorg. Allg. Chem.,
2001, 627, 699.
33 C. A. Tolman, J. Am. Chem. Soc., 1970, 92, 2953.
34 G. M. Bodner, M. P. May and L. E. McKinney, Inorg. Chem., 1980,
19, 1951.
High yield syntheses from convenient starting materials have
been developed for five new distibines with xylyl or phenylene
backbones. The synthetic methodology, particularly the clean-
liness and high yields of the reactions used to establish Me–Sb–
C linkages represents a significant advance in this area and may
offer routes to polydentate and macrocyclic systems. These are
currently under study. The new ligands exhibit similar electro-
nic properties to alkyl stibines, but incorporate a range of lig-
and architectures. The metal carbonyl complexes in the present
work show that the m- and p-xylyl and m- and p-phenylene
ligands exhibit monodentate or bridging bidentate co-
ordination modes, while the 1,2-C6H4(CH2SbMe2)2 has pro-
duced both bridging bidentate and 7-membered chelate ring
complexes. Further studies on the reactions of 1,2-C6H4-
(CH2SbMe2)2 with transition metal halides are in progress.
35 W. Buchner and W. A. Schenk, Inorg. Chem., 1984, 23, 132.
36 J. Chatt and F. A. Hart, J. Chem. Soc., 1960, 1378.
37 D. Benlian and M. Bigorgne, Bull. Soc. Chim. Fr., 1963, 1583;
G. Bouquet and M. Bigorgne, Bull. Soc. Chim. Fr., 1962, 433.
38 F. T. Delbeke, G. P. Van der Kelen and Z. Eeckhout, J. Organomet.
Chem., 1974, 64, 265.
Acknowledgements
We thank EPSRC for support (MLM).
39 F. A. Cotton and J. M. Troup, J. Am. Chem. Soc., 1974, 96, 3438.
40 L. R. Martin, F. W. B. Einstein and R. K. Pomeroy, Inorg. Chem.,
1985, 24, 2777.
41 P. A. Wegner, L. F. Evans and J. Haddock, Inorg. Chem., 1975, 14,
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D a l t o n T r a n s . , 2 0 0 4 , 5 1 – 5 8
58