Synthesis and properties of Rh(i) and Ir(i) distibine complexes with organometallic co-ligands

Article abstract of DOI:10.1039/b605198g

The first series of Rh(i) distibine complexes with organometallic co-ligands is described, including the five-coordinate [Rh(cod)(distibine)Cl], the 16-electron planar cations [Rh(cod)(distibine)]BF₄ and [Rh{Ph₂Sb(CH₂)₃SbPh₂} ₂]BF₄ and the five-coordinate [Rh(CO)(distibine) ₂][Rh(CO)₂Cl₂] (distibine = R ₂Sb(CH₂)₃SbR₂, R = Ph or Me, and o-C₆H₄(CH₂SbMe₂)₂). The corresponding Ir(i) species [Ir(cod)(distibine)]BF₄ and [Ir{Ph ₂Sb(CH₂)₃SbPh₂}₂]BF ₄ have also been prepared. The complexes have been characterised by ¹H and ¹³C{¹H} NMR and IR spectroscopy, electrospray mass spectrometry and microanalysis. The crystal structure of the anion exchanged [Rh(CO){Ph₂Sb(CH₂)₃SbPh ₂}₂]PF₆·3/4CH₂Cl₂ is also described. The methyl-substituted distibine complexes are less stable than the complexes of Ph₂Sb(CH₂)₃SbPh ₂, with C-Sb fission occurring in some of the complexes of the former. The salts [Rh(CO){Ph₂Sb(CH₂)₃SbPh ₂}₂]PF₆ and [Rh{Ph₂Sb(CH ₂)₃SbPh₂}₂]BF₄ undergo oxidative addition with Br₂ to give the known [RhBr ₂{Ph₂Sb(CH₂)₃SbPh₂} ₂]⁺, while using HCl gives the same hydride complex from both precursors, which is tentatively assigned as [RhHCl₂{Ph ₂Sb(CH₂)₃SbPh₂}]. An unexpected further Rh(iii) product from this reaction, trans-[RhCl₂{Ph ₂Sb(CH₂)₃SbPh₂}{PhClSb(CH ₂)₃SbClPh}]Cl, was identified by a crystal structure analysis and represents the first structurally characterised example of a chlorostibine coordinated to a metal. [Rh{Ph₂Sb(CH₂) ₃SbPh₂}₂]BF₄ reacts with CO to give [Rh(CO){Ph₂Sb(CH₂)₃SbPh₂} ₂]BF₄ initially, and upon further exposure this species undergoes further reversible carbonylation to give a cis-dicarbonyl species thought to be [Rh(CO)₂{Ph₂Sb(CH₂) ₃SbPh₂}{κ¹Sb-Ph₂Sb(CH ₂)₃SbPh₂}]BF₄ which converts back to the monocarbonyl complex when the CO atmosphere is replaced with N₂. The Royal Society of Chemistry 2006.

Full text of DOI:10.1039/b605198g

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www.rsc.org/dalton | Dalton Transactions
Synthesis and properties of Rh(I) and Ir(I) distibine complexes with
organometallic co-ligands
Michael D. Brown, William Levason, Gillian Reid* and Michael Webster
Received 11th April 2006, Accepted 26th May 2006
First published as an Advance Article on the web 9th June 2006
DOI: 10.1039/b605198g
The first series of Rh(I) distibine complexes with organometallic co-ligands is described, including the
five-coordinate [Rh(cod)(distibine)Cl], the 16-electron planar cations [Rh(cod)(distibine)]BF4 and
[Rh{Ph2Sb(CH2)3SbPh2}2]BF4 and the five-coordinate [Rh(CO)(distibine)2][Rh(CO)2Cl2] (distibine =
R2Sb(CH2)3SbR2, R = Ph or Me, and o-C6H4(CH2SbMe2)2). The corresponding Ir(I) species [Ir(cod)-
(distibine)]BF4 and [Ir{Ph2Sb(CH2)3SbPh2}2]BF4 have also been prepared. The complexes have been
1
characterised by 1H and 13C{ H} NMR and IR spectroscopy, electrospray mass spectrometry and micro-
analysis. The crystal structure of the anion exchanged [Rh(CO){Ph2Sb(CH2)3SbPh2}2]PF6·3/4CH2Cl2
is also described. The methyl-substituted distibine complexes are less stable than the complexes of
Ph2Sb(CH2)3SbPh2, with C–Sb fission occurring in some of the complexes of the former. The salts
[Rh(CO){Ph2Sb(CH2)3SbPh2}2]PF6 and [Rh{Ph2Sb(CH2)3SbPh2}2]BF4 undergo oxidative addition
with Br2 to give the known [RhBr2{Ph2Sb(CH2)3SbPh2}2]+, while using HCl gives the same hydride
complex from both precursors, which is tentatively assigned as [RhHCl2{Ph2Sb(CH2)3SbPh2}]. An
unexpected further Rh(III) product from this reaction, trans-[RhCl2{Ph2Sb(CH2)3SbPh2}-
{PhClSb(CH2)3SbClPh}]Cl, was identified by a crystal structure analysis and represents the first
structurally characterised example of a chlorostibine coordinated to a metal.
[Rh{Ph2Sb(CH2)3SbPh2}2]BF4 reacts with CO to give [Rh(CO){Ph2Sb(CH2)3SbPh2}2]BF4 initially, and
upon further exposure this species undergoes further reversible carbonylation to give a cis-dicarbonyl
species thought to be [Rh(CO)2{Ph2Sb(CH2)3SbPh2}{j1Sb-Ph2Sb(CH2)3SbPh2}]BF4 which converts
back to the monocarbonyl complex when the CO atmosphere is replaced with N2.
synthetic methods for distibines and have used the reaction of
Introduction
R2SbCl with a variety of di-Grignard reagents to produce m- and p-
phenylene and o-, m- and p-xylylene distibines in remarkably high
yields.7 Subsequently we have explored the ligating characteristics
of these compounds towards a range of transition metal carbonyls
and (mostly with o-C6H4(CH2SbMe2)2) with transition metal
halides.8 The o-xylyl distibine turns out to be a versatile ligand
With the exception of the commercially available triphenylstibine,
SbPh3, the coordination chemistry and organometallic chemistry
of organoantimony ligands has been relatively little studied
in comparison to the lighter Group 15 analogues, especially
phosphines.1,2 Traditionally stibines were regarded as ‘poorer’
ligands compared to phosphines and arsines. However, more
recently, work from a number of groups has shown that the
distinctly different electronic properties ofthe stibines can promote
markedly different reaction chemistry and, in fact they are superior
ligands for certain reactions. For example, the pioneering work
of Werner which led to the first discovery of bridging ER3
ligands, initially used SbiPr3, and was only later extended to
phosphines and arsines.3 The same group has also made signif-
icant contributions to organometallic Rh, Ir and Ru chemistry
with SbiPr3 and shown that these complexes exhibit different
reactivity to the PiPr3 and AsiPr3 species.4 Also, the nickel–
SbPh3 complexes [Ni(2-methylallyl)(SbPh3)3][BARF] (BARF =
[B{C6H3-3,5-(CF3)2}4]−) and trans-[Ni(C6Cl2F3)2(SbPh3)2] are ef-
ficient catalysts for styrene polymerization and norbornene inser-
tion polymerization respectively.5,6
˚
capable of adjusting its chelate bite, d(Sb · · · Sb), by ∼0.5 A
to accommodate the preferred geometry at the metal ion. Very
recently we have begun to explore the chemistry of these and
related distibines with organometallic reagents and have fully
characterised the first examples of stable Pt(IV) stibine complexes,
[PtMe3I(distibine)] and [(PtMe3)2(l-I)2(l-R2SbCH2SbR2)] (R =
Me or Ph) and shown that they undergo reductive elimination of
ethane upon thermolysis.9
In this paper we describe the coordination of the dis-
tibine ligands Ph2Sb(CH2)3SbPh2, Me2Sb(CH2)3SbMe2 and o-
C6H4(CH2SbMe2)2 with a range of Rh(I) and Ir(I) organometallic
species, including their syntheses and spectroscopic properties
and the crystal structure of [Rh(CO){Ph2Sb(CH2)3SbPh2}2]PF6.
Some reaction chemistry of Rh(I) and Ir(I) complexes containing
Ph2Sb(CH2)3SbPh2 is also described.
A number of Rh(I) complexes involving SbPh3 have been
described.1 Specifically, the interaction of SbPh3 with rhodium
carbonyl halides has been studied by several groups,10–13 and both
the yellow, planar, four-coordinate trans-[Rh(CO)(SbPh3)2Cl] and
the red, trigonal bipyramidal, five-coordinate [Rh(CO)(SbPh3)3Cl]
Only a limited range of distibine ligands are known and none
are available commercially. We have been interested in developing
School of Chemistry, University of Southampton, Highfield, Southampton,
UK SO17 1BJ. E-mail: gr@soton.ac.uk
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1
have been structurally characterised,11 as well as the planar
[Rh(CO)(SbPh3)2I].12 The five-coordinate [Rh(CO)(SbPh3)3Cl]
undergoes oxidative addition with various substrates, including
MeI which gives [Rh(CO)(SbPh3)2I2(Me)], whose structure shows
trans stibines and cis iodines.11,13–15
SbPh3 and [Rh(cod)Cl]2 are reported to give [Rh(SbPh3)2-
(cod)Cl] as an orange solid on the basis of spectroscopic and
analytical data.16 [Rh(CO)2Cl]2 also reacts with R2SbCH2SbR2
(R = Me or Ph) to give the ligand bridged dimers trans-
[{Rh(CO)Cl}2(l-R2SbCH2SbR2)2].17,18
but these compounds are spectroscopically simpler, with H and
13C{ H} NMR spectra consistent with static, planar cations, and
1
−
IR spectra revealing the ionic BF4 anion.
Rhodium(I)–bis(distibine) systems
In an effort to obtain [Rh(L–L)2]BF4, an acetone solution of
[Rh2Cl2(cod)2] was treated with two mol. equiv. AgBF4, filtered to
remove the AgCl, and then 4.1 mol. equiv. of Ph2Sb(CH2)3SbPh2
in toluene was added and the reaction mixture heated to 90 ◦C
for ca. 1 h. However, spectroscopic analysis of the resulting yellow
orange solid showed incomplete substitution of the cod ligand,
giving [Rh(cod){Ph2Sb(CH2)3SbPh2}]BF4 as the major product,
with the [Rh{Ph2Sb(CH2)3SbPh2}2]BF4 as a minor product. This
contrasts with the reaction chemistry of the analogous diphos-
phine ligands which readily produce [Rh(diphosphine)2]BF4 via
similar reactions even at room temperature.19,20 The complex
[Rh{Ph2Sb(CH2)3SbPh2}2]BF4 was however obtained in good
yield as a red solid from reaction of the more labile [Rh2Cl2(coe)4]
with two mol. equiv. AgBF4 in acetone, removal of the AgCl
by filtration, and addition of the resulting yellow solution to a
toluene solution of L–L at room temperature. The formulation
follows from the positive ion electrospray MS which shows
major peaks corresponding to [Rh{Ph2Sb(CH2)3SbPh2}2]+ ([M]+)
and loss of one SbPh2 unit, [M − SbPh2]+, microanalysis, IR
Results and discussion
Rhodium(I)–cod–stibine systems
The previously reported [Rh(SbPh3)2(cod)Cl]16 was re-prepared by
adding [Rh2Cl2(cod)2] to a refluxing solution of excess SbPh3 in dry
EtOH under argon. The reaction precipitated a red solid, in good
yield. The formulation of the product as the 1 : 2 Rh : SbPh3 species
follows from microanalysis, integration of the resonances in the 1H
NMR spectrum and mass spectrometry, which exhibits a cluster
of peaks centred at 917, corresponding to the [Rh(cod)(SbPh3)2]+
cation.
The five-coordinate 18-electron Rh(I) cod complexes in-
corporating distibine ligands, [Rh(cod){Ph2Sb(CH2)3SbPh2}Cl]
and [Rh(cod){Me2Sb(CH2)3SbMe2}Cl] were prepared by adding
[Rh2Cl2(cod)2] to a solution of the appropriate ligand (2 mol.
equiv.) in dry EtOH under argon. The reaction mixtures were
concentrated to dryness and triturated in hexane to afford orange
precipitates in good yield. The 1H NMR spectroscopic data
for both of the complexes show the presence of cod and the
distibine, and although the complexes appear to be fluxional
at 300 K, at 223 K the 1H NMR spectra show separate
peaks (broad) for the distinct environments of the cod protons
and the SbMe groups. The electrospray mass spectra exhibit
mass peaks (with the correct isotope distributions) at 805 and
557 corresponding to the ions [Rh(cod){Ph2Sb(CH2)3SbPh2}]+
and [Rh(cod){Me2Sb(CH2)3SbMe2}]+ respectively. Conductivity
measurements confirm that these are neutral, and hence 18-
electron, five-coordinate species. Attempts to obtain [Rh(cod){o-
C6H4(CH2SbMe2)2}Cl] similarly afforded a yellow orange solid,
the electrospray mass spectrum of which revealed the [Rh(cod){o-
C6H4(CH2SbMe2)2}]+ cation as the only significant species. How-
ever, even after recrystallisation we were unable to obtain an
and 1H and 13C{ H} NMR spectroscopy. Some reactions of
1
this compound are described below. Attempts to obtain [Rh{o-
C6H4(CH2SbMe2)2}2]BF4 both using the reaction conditions de-
scribed for [Rh{Ph2Sb(CH2)3SbPh2}2]+ or using TlPF6 in place of
AgBF4 were not successful.
Rhodium(I)–carbonyl–stibine systems
The known [Rh(CO)(SbPh3)2Cl] was synthesised by reaction of
[Rh2Cl2(CO)4] with 2 mol. equiv. of the appropriate ligand in dry
CH2Cl2. The reaction was monitored by solution IR spectroscopy,
and when the reaction was complete the solvent was removed in
vacuo and the resulting material was triturated with hexane to give
1
[Rh(CO)(SbPh3)2Cl] with H NMR and IR spectroscopic data
in line with the literature.11 The 13C{ H} NMR spectrum shows a
1
doublet due to the coordinated carbonyl at d 184.3 ppm (JRh–C = 57
Hz). Positive ion electrospray MS shows the major peaks centred
at 837 corresponding to [Rh(CO)(SbPh3)2]+.
Reaction of [Rh2Cl2(CO)4] with 2 mol. equiv. of Ph2Sb-
(CH2)3SbPh2 in dry, degassed CH2Cl2 solution gives [Rh(CO)-
{Ph2Sb(CH2)3SbPh2}2][Rh(CO)2Cl2] as an orange solid in good
yield. The IR spectrum shows three m(CO) bands both in CH2Cl2
solution and in the solid. The bands at 2068 (s) and 1989 (m) cm−1
(CH2Cl2) correspond to the [Rh(CO)2Cl2]− anion,22 while the
third band at 1968 (m) cm−1 corresponds to the [Rh(CO){Ph2Sb-
(CH2)3SbPh2}2]+ cation. The phosphine analogue, [Rh(CO)-
(dppp)2]+ has m(CO) = 1930 cm−1, i.e. significantly to low frequency
of the directly analogous distibine complex, and consistent with a
1
analytically pure sample and the H NMR spectrum was more
complicated than expected, hence this species was not pursued.
The five-coordinate Rh(I) distibine complexes described here are
expected to have a distorted trigonal bipyramidal geometry similar
to that observed for [Ir(C2H4)2(SbiPr3)2Cl], the crystal structure of
which shows equatorial olefins and one axial and one equatorial
stibine.4
The related planar 16-electron Rh(I) species [Rh(cod)(L–
L)]BF4 (L–L = Ph2Sb(CH2)3SbPh2, Me2Sb(CH2)3SbMe2, o-
C6H4(CH2SbMe2)2) were obtained in good yield as yellow orange
solids through reaction of acetone solutions of [Rh2Cl2(cod)2]
with two mol. equiv. AgBF4, removal of the AgCl precipitate by
filtration, and addition of a toluene solution of two mol. equiv.
of L–L. The positive ion electrospray MS of the isolated species
are indistinguishable from those of the neutral Rh(I) species above,
more electron rich Rh centre in the phosphine.21 The H NMR
1
spectrum shows coordinated ligand, while the 13C{ H} NMR
1
spectrum shows a doublet at d 182.3 ppm (JRh–C = 71 Hz)
indicating the presence of the anion, but the carbonyl group
on the cation was not evident, possibly due to fluxionality in
the five-coordinate species. The most significant feature in the
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Scheme 1 Summary of Rh chemistry.
positive ion electrospray MS is a cluster of peaks at ca.
1289 corresponding to [Rh{Ph2Sb(CH2)3SbPh2}2]+ with loss of
CO, with a much weaker feature (ca. 5%) corresponding to
[Rh(CO){Ph2Sb(CH2)3SbPh2}2]+. The only significant feature in
the negative ion electrospray MS is at 229 mass units, correspond-
ing to the rhodium anion [Rh(CO)2Cl2]−. The formulation was
also confirmed by microanalysis.
Crystals of [Rh(CO){Ph2Sb(CH2)3SbPh2}2]PF6·3/4CH2Cl2
were obtained by layering a solution of the complex in CH2Cl2
with hexane. The crystal structure shows two independent
cations and anions in the asymmetric unit and two partially
occupied CH2Cl2 solvent molecules. The two Rh(I) cations are
essentially indistinguishable (Fig. 1, Table 1), showing distorted
five-coordinate, trigonal bipyramidal coordination environments
based upon two chelating distibines and one CO ligand in an
The ionic [Rh(CO){Ph2Sb(CH2)3SbPh2}2][Rh(CO)2Cl2] species
was subsequently treated with 2 mol. equiv. of Ph2Sb(CH2)3SbPh2
in dry CH2Cl2 and stirred under argon. This led to loss of m(CO)
for the Rh(I) anion, leaving only the m(CO) band at 1966 cm−1
for the [Rh(CO){Ph2Sb(CH2)3SbPh2}2]+ cation. The presence
of this species was further confirmed by positive ion electro-
spray MS. In another experiment [Rh(CO){Ph2Sb(CH2)3SbPh2}2]-
[Rh(CO)2Cl2], 2 mol. equiv. of Ph2Sb(CH2)SbPh2 and 2 mol. equiv.
of NH4PF6 were dissolved in dry CH2Cl2 and stirred at room
temperature. The solution IR spectrum showed that the reaction
was complete within 10 min, and the NH4Cl was filtered off. The
orange solid was isolated by concentration of the reaction mixture
and precipitation with Et2O. The 1H NMR spectrum again showed
coordinated ligand, and the positive ion electrospray MS and
solution IR spectra were very similar to those above. The Nujol
mull IR spectrum showed one m(CO) band at 1952 cm−1, with
further bands at 837 and 557 cm−1 confirming the presence of ionic
PF6−. Similar complexes with diphosphines have been reported
previously, although these are typically obtained via bubbling
CO into solutions of the planar 16-electron [Rh(diphosphine)2]+
cations.19,20
˚
˚
equatorial position. The Rh–Sb distances (2.54–2.62 A) in this
Rh(I) species compare with 2.594(2) and 2.611(2) A in the
◦
˚
Table 1 Selected bond lengths (A) and angles ( ) for [Rh(CO){Ph2Sb-
(CH2)3SbPh2}2]PF6·3/4CH2Cl2
Rh1–Sb1
Rh1–Sb2
Rh1–Sb3
Rh1–Sb4
Rh1–C55
Sb–C
2.5404(6)
2.5967(7)
2.6062(7)
2.5579(6)
1.875(7)
2.119(7)–2.156(6) Sb–C
1.141(8) C110–O2
Rh2–Sb5
Rh2–Sb6
Rh2–Sb7
Rh2–Sb8
Rh2–C110
2.5588(7)
2.6173(7)
2.5585(7)
2.6080(7)
1.856(7)
2.116(6)–2.164(7)
1.151(8)
C55–O1
C55–Rh1–Sb1 88.67(19)
C55–Rh1–Sb2 128.5(2)
C55–Rh1–Sb3 125.2(2)
C55–Rh1–Sb4 91.36(19)
Sb1–Rh1–Sb2 87.70(2)
Sb1–Rh1–Sb3 91.26(2)
Sb1–Rh1–Sb4 177.99(2)
Sb2–Rh1–Sb3 106.16(2)
Sb2–Rh1–Sb4 93.85(2)
Sb3–Rh1–Sb4 87.08(2)
C110–Rh2–Sb5 89.4(2)
C110–Rh2–Sb6 133.8(2)
C110–Rh2–Sb7 90.1(2)
C110–Rh2–Sb8 126.4(2)
Sb5–Rh2–Sb6
87.04(2)
Sb5–Rh2–Sb7 178.53(3)
Sb5–Rh2–Sb8
Sb6–Rh2–Sb7
Sb6–Rh2–Sb8
Sb7–Rh2–Sb8
93.15(2)
92.33(2)
99.78(2)
88.26(2)
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Rhodium(I) reaction chemistry
Our investigations of the reaction chemistry have focused on the
Rh(I) complexes with Ph2Sb(CH2)3SbPh2, since these were found
to be more stable both in the solid and in solution compared to
the methyl-substituted distibine complexes.
Bubbling CO through a solution of [Rh{Ph2Sb(CH2)3SbPh2}2]-
BF4 in acetone leads initially to the appearance of a single
m(CO) band at 1966 cm−1, due to the monocarbonyl cation [Rh-
(CO){Ph2Sb(CH2)3SbPh2}2]+, providing an alternative synthesis
for this complex. Continued exposure to a CO atmosphere over
a period of ca. 1 h leads to this CO absorption band being replaced
by two new bands at 2020 and 1993 cm−1, consistent with a
cis-dicarbonyl Rh(I) complex. This species is unstable in
the absence of a CO atmosphere, reverting fully to [Rh(CO)-
{Ph2Sb(CH2)3SbPh2}2]+. The formation of the dicarbonyl complex
from the 18-electron monocarbonyl cation could occur via either
dissociation of a distibine (to give [Rh(CO)2{Ph2Sb(CH2)3-
SbPh2}]+ and free distibine) or via reversible chelate ring opening
(to give the five-coordinate [Rh(CO)2{Ph2Sb(CH2)3SbPh2}{j1Sb-
Ph2Sb(CH2)3SbPh2}]+). For comparison, the 16-electron planar
Fig. 1 View of the structure of [Rh(CO){Ph2Sb(CH2)3SbPh2}2]+ showing
the Rh1 centred cation with numbering scheme adopted. The second cation
in the structure is very similar. Ellipsoids are drawn at the 50% probability
level and H atoms are omitted for clarity.
cis-[Rh(CO)2{Ph2P(CH2)2PPh2}]+ gives m(CO)
=
2100 and
Rh(III) cation trans-[RhCl2{Ph2Sb(CH2)3SbPh2}2]+.23 The Rh–CO
2055 cm−1,24 while the dimeric five-coordinate Rh(I) dicarbonyl
complex [{(CO)2{Ph2P(CH2)4PPh2}Rh}2{l-Ph2P(CH2)4PPh2}]
gives m(CO) = 2020 and 1965 cm−1.20 Both on the basis of the
CO stretching frequencies and the observation that the distibine
complex converts reversibly to [Rh(CO){Ph2Sb(CH2)3SbPh2}2]+,
it seems more likely that the cis-dicarbonyl complex is the five-
coordinate [Rh(CO)2{Ph2Sb(CH2)3SbPh2}{j1Sb-Ph2Sb(CH2)3-
SbPh2}]+, although we have not been able to obtain crystals
to prove this unequivocally. Furthermore, Hieber and Frey
have described the five-coordinate dicarbonyl stibine complex
[Rh(CO)2(SbPh3)3][AlCl4] which has m(CO) = 2009 cm−1 (KBr).25
In CH2Cl2 solution [Rh(CO){Ph2Sb(CH2)3SbPh2}2]PF6 un-
dergoes oxidative addition with Br2 to give the known
Rh(III) complex cation trans-[RhBr2{Ph2Sb(CH2)3SbPh2}2]+ (IR,
MS and NMR evidence).23 However, no reaction was
apparent when either [Rh(CO){Ph2Sb(CH2)3SbPh2}2]PF6 or
[Rh{Ph2Sb(CH2)3SbPh2}2]BF4 were heated with MeI.
˚
distances of 1.875(7) and 1.856(7) A compare with d(Rh–CO) =
+19
˚
1.894(6) A in [Rh(CO)(Ph2PCH2PPh2)2] and 1.886(4), 1.922(5)
2+ 20
˚
A in [Rh2(CO)4{Ph2P(CH2)4PPh2}3] .
Under similar reaction conditions, treatment of [Rh2Cl2(CO)4]
with four mol. equiv. of Me2Sb(CH2)3SbMe2 or o-C6H4(CH2-
SbMe2)2 in dry CH2Cl2 solution leads to the formation of dark
brown materials over the period of a few minutes, with substantial
decomposition. No well-defined product was obtained from this
reaction (it has been noted previously that other rhodium(I)
complexes involving distibinomethanes also decompose readily
even in the solid state).18 However, repeating the reaction using
a 1 : 2 molar ratio of [Rh(CO)2Cl]2 : Me2Sb(CH2)3SbMe2 in
CH2Cl2 solution at ca. −15 ◦C for ∼30 min afforded the compound
[Rh(CO){Me2Sb(CH2)3SbMe2}2][Rh(CO)2Cl2] as a dark red solid,
1
as shown by electrospray mass spectrometry, IR, 1H and 13C{ H}
NMR spectroscopy and microanalysis. In contrast to the Rh–
carbonyl complex of the Ph2Sb(CH2)3SbPh2 analogue above, this
methyl-substituted ligand complex decomposes significantly in so-
lution at RT over a period of minutes, hence spectra were recorded
at −30 ◦C. Treatment of this complex with excess distibine or
Treatment of a CH2Cl2 solution of [Rh(CO){Ph2Sb(CH2)3-
SbPh2}2]PF6 with excess HCl saturated CH2Cl2 solution leads to
loss of the band due to the CO stretching vibration in the IR
spectrum. Spectroscopic analysis of the product obtained after
removal of the CH2Cl2 shows that there is a mixture of products,
one of which was identified by 1H NMR spectroscopy as a Rh(III)-
hydride, giving d −18.95 ppm, 1JRhH = 7.2 Hz. We tentatively assign
this to the neutral [RhHCl2{Ph2Sb(CH2)3SbPh2}] by comparison
of the spectroscopic data with those for the five-coordinate
[RhHCl2(SbPh3)2] (d1H = −18.3, 1JRhH = 7 Hz) reported by Mague
and Wilkinson.26
We were also able to grow a few small crystals of a sec-
ond species from a solution of the products in CHCl3 over a
few days. The crystal structure† shows (Fig. 2) a very unex-
pected Rh(III) species of formula [RhCl2{Ph2Sb(CH2)3SbPh2}-
{PhClSb(CH2)3SbClPh}]Cl·CHCl3. The Rh atom is surrounded
−
addition of PF6 did not result in complete replacement of the
[Rh(CO)2Cl2]− anion.
The corresponding [Rh(CO){o-C6H4(CH2SbMe2)2}2][Rh-
(CO)2Cl2] was obtained similarly, but decomposes very readily in
solution. [Rh(CO)2Cl]2 reacts with four mol. equiv. of Ph2SbCH2-
SbPh2 in CH2Cl2 to form the known dimer18 [Rh2(CO)2Cl2-
{Ph2SbCH2SbPh2}2] initially (mCO = 2000 cm−1). With continued
stirring at RT the reaction proceeds to afford another CO
containing species (mCO = 1970 cm−1), which may be a cationic
Rh(I) carbonyl, but even in the presence of NH4PF6 the reaction
is incomplete and a substantial amount of the dimer remains.
The positive ion electrospray MS supports these conclusions,
revealing peaks at m/z 1429 ([Rh2(CO)2Cl{Ph2SbCH2SbPh2}2]+)
and m/z 1263 ([Rh(CO){Ph2SbCH2SbPh2}2]+); however, we
were unable to isolate an analytically pure sample, and given
that distibinomethanes show a much lower tendency to chelate
compared to diphosphinomethanes, this was not pursued.
† The crystallographic data for this compound were rather weak, giving
higher than normal residuals. Hence detailed comparisons of geometric
parameters require caution.
4042 | Dalton Trans., 2006, 4039–4046
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produced clearly behaves as a ligand in the isolated Rh(III) species.
This reaction chemistry is different from that of phenylphosphines,
which do not undergo P–Ph cleavage by HCl.
The planar 16-electron [Rh{Ph2Sb(CH2)3SbPh2}2]BF4 was also
treated with HCl saturated acetone, and the same Rh–hydride
product (d1H = −18.95, J = 7.2 Hz) was identified from in situ 1H
NMR studies. A very weak feature in the IR spectrum at 1998 cm−1
is tentatively assigned to the Rh–H stretching vibration.
Iridium(I)–stibine complexes
Few examples of iridium(I) stibine complexes are known, and
none involve distibine coordination.1 The solution obtained
by treatment of [Ir2(cod)2Cl2] with two mol. equiv. of AgBF4
in acetone (following filtration to remove the AgCl) reacts
with two mol. equiv. of L–L (L–L = Ph2Sb(CH2)3SbPh2 or
o-C6H4(CH2SbMe2)2) to give the planar, 16-electron species
[Ir(cod)(L–L)]BF4 in an analogous manner to the Rh chemistry
described above. The identity of the light orange products
follow from positive ion electrospray MS, IR, H and 13C{ H}
NMR spectroscopy and microanalysis. Using [Ir2(coe)4Cl2] and
AgBF4 in acetone, followed by addition of a toluene solution of
Ph2Sb(CH2)3SbPh2 produces an orange solution from which the
planar Ir(I) species [Ir{Ph2Sb(CH2)3SbPh2}2]BF4 may be obtained
in good yield. NMR spectroscopy reveals adventitious CH2Cl2
in this sample. Bubbling CO gas through an acetone solution
of [Ir{Ph2Sb(CH2)3SbPh2}2]BF4 leads to the appearance of two
strong IR bands at 2018 and 1996 cm−1 attributed to a dicarbonyl
complex. The positive ion ES MS of this solution shows peaks at
m/z = 1435 and 1407 assigned to [Ir(CO)2{Ph2Sb(CH2)3SbPh2}2]+
and [Ir(CO){Ph2Sb(CH2)3SbPh2}2]+. The CO is lost on pumping
the solution to dryness in vacuo.
Fig. 2 View of the structure of [RhCl2{Ph2Sb(CH2)3SbPh2}{PhClSb-
(CH2)3SbClPh}]Cl with atom numbering scheme. Ellipsoids are drawn
at the 50% probability level and H atoms are omitted for clarity. Selected
◦
1
1
˚
bond lengths (A) and angles ( ): Rh1–Cl2 = 2.371(3), Rh1–Cl1 = 2.410(3),
Rh1–Sb1 = 2.5896(13), Rh1–Sb2 = 2.5920(14), Rh1–Sb4 = 2.6045(14),
Rh1–Sb3 = 2.6261(13), Sb3–Cl3 = 2.440(3), Sb3 · · · Cl5 = 2.736(3),
˚
Sb4–Cl4 = 2.435(4), Sb4 · · · Cl5 = 2.823(3) A; Cl2–Rh1–Cl1 = 174.86(11),
Sb1–Rh1–Sb2 = 89.56(4), Sb1–Rh1–Sb4 = 97.75(5), Sb2–Rh1–Sb4 =
170.86(5), Sb1–Rh1–Sb3
Sb4–Rh1–Sb3 = 81.90(4), Sb3 · · · Cl5 · · · Sb4 = 76.13(8).
=
176.92(5), Sb2–Rh1–Sb3
=
91.09(4),
by two trans Cl’s and four Sb atoms, two from a chelating
˚
Ph2Sb(CH2)3SbPh2 (d(Rh–Sb) = 2.590(1), 2.592(1) A) and two
from a bis(phenylchlorostibino)propane, (d(Rh–Sb) = 2.604(1),
−
˚
2.626(1) A). A Cl anion is also present to provide charge balance,
and this is involved in long range bridging secondary interactions
with the two Sb atoms of the modified ligand, d(Sb · · · Cl) =
◦
˚
2.736(3), 2.823(3) A, Sb · · · Cl · · · Sb = 76.13(8) . Thus, it is clear
that one of the Ph ring substituents on each Sb atom of one ligand
has undergone cleavage with HCl, being replaced by a Cl atom.
The crystal data were weak and hence the final residuals are rather
high, precluding detailed comparisons of the parameters.
Conclusions
These results show that a range of four- and five-coordinate
Rh(I) and Ir(I) distibine complexes involving various organometal-
lic co-ligands may be obtained through careful choice of the
metal precursor and the reaction conditions. The complexes of
Ph2Sb(CH2)3SbPh2 appear to be the most stable, presumably the
coordinated –SbPh2 units lead to less electron-rich, and hence less
reactive, complexes compared to the coordinated –SbMe2 units,
which appear to undergo Sb–C fission in some of the reac-
tions. [Rh(CO){Ph2Sb(CH2)3SbPh2}2]PF6 and [Rh{Ph2Sb(CH2)3-
SbPh2}2]BF4 undergo oxidative addition with Br2 and HCl.
The reaction with HCl also yields the very unexpected trans-
[RhCl2{Ph2Sb(CH2)3SbPh2}{PhClSb(CH2)3SbClPh}]Cl, which
represents the first structurally characterised example of a co-
ordinated chlorostibine. Work is underway in our laboratories
to investigate the reactions of organoantimony chlorides with
transition metals.
Secondary Sb · · · Cl interactions are well known in antimony
chloride anions, however, structural data on examples involving
R2SbCl units (as presented here) are very rare. A survey of the
Cambridge Crystallographic Database shows that the Sb · · · Cl
distances in the Rh complex described here lie at the short end of
the normal bond length range for secondary interactions in chloro-
˚
antimony anions, with values between 2.9 and 3.2 A being more
typical, e.g. in [Sb2Cl6{o-C6H4(AsMe2)2}] d(Sb · · · Cl) = 3.020(3),
27
˚
3.171(2), 3.267(3) A. The unusually short Sb · · · Cl distances in
this species could be a consequence of (i) the geometric constraints
imposed by the coordination of the Sb atoms to Rh, (ii) the
presence of the C3-unit linking the Sb atoms and (iii) the metal
coordination which will make the Sb atoms less electron rich and
hence promote stronger Sb · · · Cl interactions.
It is known that phenylstibines can undergo cleavage with HCl
gas to give chlorostibines (indeed we have used this reaction
regularly to prepare the distibine ligands in this work), however,
the chlorostibines are not generally considered as ligands for metal
centres, and in fact the Rh(III) complex reported here is the first
structurally characterized example of a metal coordinated to a
chlorostibine. We do not know whether the Ph cleavage occurs
while the distibine is coordinated to rhodium, but the chlorostibine
Experimental
Infrared spectra were recorded as Nujol mulls between CsI plates
using a Perkin-Elmer 983G spectrometer over the range 4000–
200 cm−1, or in chlorocarbon solution over the range 2300–
1700 cm−1. Mass spectra were run by positive ion or negative ion
electrospray (MeCN solution) using a VG Biotech platform. H
NMR spectra were recorded using a Bruker AV300 spectrometer.
1
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1
13C{ H} NMR spectra were recorded using a Bruker DPX400
filtered and added dropwise to a solution of Ph2Sb(CH2)3SbPh2
(0.225 g, 0.38 mmol) in degassed toluene (15 mL). The resulting
orange solution was stirred at room temperature for ca. 1 h and
then reduced to dryness in vacuo. The residues were recrystallised
in CH2Cl2/Et2O to give a yellow/orange solid, which was
filtered off and dried in vacuo. Yield 0.12 g, 74%. Required for
[C35H38BF4RhSb2]: C, 47.1; H, 4.3%. Found: C, 47.0; H, 4.1%. 1H
NMR (CDCl3): d 6.9–7.6 (m) [20H] (Ph), 4.2 (br) [4H] (cod CH),
spectrometer operating at 100.6 MHz and are referenced to
TMS. Microanalyses were undertaken by the University of
Strathclyde microanalytical service. Solvents were dried prior
to use and all preparations were undertaken using standard
Schlenk techniques under a N2 or Ar atmosphere. Percentage
yields are based upon the metal. The Rh(I) and Ir(I) precursors
[Rh2Cl2(CO)4],28 [M2Cl2(cod)2],29,30 [M2Cl2(coe)4] (M = Rh or Ir)31
and the ligands were prepared as described previously.7,32,33
1
2.3–2.5 (br) [14H] (CH2) ppm. 13C{ H} NMR (CDCl3): d 128.22–
133.40 (Ph), 80.98 (cod CH), 31.48 (cod CH2), 17.36, 17.15 (CH2)
ppm. ES+ MS (MeCN): m/z 805 [Rh(cod){Ph2Sb(CH2)3SbPh2}]+.
IR (Nujol mull): 1054 (BF4−) cm−1.
Rhodium(I) compounds
[Rh(cod)(SbPh3)2Cl]. [Rh2Cl2(cod)2] (0.049 g, 0.10 mmol) was
added to a refluxing solution of SbPh3 (1.0 g, 2.9 mmol)
in dry EtOH (10 mL) under argon. An orange precip-
itate formed immediately, was filtered off, washed with
CH2Cl2/hexane and dried in vacuo. Yield 0.2 g, 100%. Required
for [C44H42ClRhSb2]·1/2CH2Cl2: C, 53.7; H, 4.4%. Found: C,
[Rh(cod){Me2Sb(CH2)3SbMe2}]BF4. Method as above using
[Rh2Cl2(cod)2], AgBF4 and Me2Sb(CH2)3SbMe2. The product was
recrystallised from Me2CO and Et2O. Yield 56%. Required for
1
[C15H30BF4RhSb2]· toluene: C, 30.2; H, 4.8. Found: C, 30.1; H,
4
4.5%. 1H NMR ((CD3)2CO): d 4.0 (s) [4H] (cod CH), 2.4 (s)
[8H] (cod CH2), 2.1–2.4 (br) [6H] (CH2), 1.7 (br) (12H) (SbMe)
ppm (signals due to associated toluene solvent are also evident).
1
53.7; H, 3.8%. H NMR ((CD3)2CO, 300 K): d 7.50–7.30 (m)
[30H] (Ph), 5.43 (s) CH2Cl2, 4.25 (br) [4H] (cod CH), 2.45
1
13C{ H} NMR ((CD3)2CO): d 79.31 (d 15 Hz) (cod CH), 31.45 (cod
1
(m) [4H] (cod CH2), 1.85 (br) [4H] (cod CH2) ppm. 13C{ H}
CH2), 23.94 (CH2CH2CH2), 18.75 (SbCH2), −6.00 (SbMe) ppm.
ES+ MS (MeCN): m/z 557 [Rh(cod){Me2Sb(CH2)3SbMe2}]+. IR
(Nujol mull): 1054 (BF4−) cm−1.
NMR ((CD3)2CO, 225 K): d 136.3 (s), 135.7 (s), 134.8 (s), 129.1
(s), 128.8 (s) (Ph), 78.0 (d) J = 15 Hz (cod CH) (cod CH2
resonances obscured by solvent) ppm. ES+ MS (MeCN): m/z 563
[Rh(cod)(SbPh3)]+, 841 [Rh(SbPh3)2Cl2]+, 917 [Rh(cod)(SbPh3)2]+.
Conductivity KM/X−1 cm2 mol−1 (10−3 mol dm−3 in CH2Cl2): 1.39.
[Rh(cod){o-C6H4(CH2SbMe2)2}]BF4. Method as above using
[Rh2Cl2(cod)2], AgBF4 and o-C6H4(CH2SbMe2)2. Yield 60%.
Required for [C20H32BF4RhSb2]: C, 34.0; H, 4.6. Found: C, 33.4;
H, 4.5%. 1H NMR ((CD3)2CO): d 7.0–7.7 (m) [4H] (o-C6H4), 4.3
(br) [4H] (SbCH2), 4.1 (s) [4H] (cod CH), 2.4 (s) [8H] (cod CH2),
[Rh(cod){Ph2Sb(CH2)3SbPh2}Cl]. Reaction as above using
[Rh2Cl2(cod)2] (0.062 g, 0.126 mmol) and Ph2Sb(CH2)3SbPh2
(0.15 g, 0.25 mmol). The deep orange solution was reduced to
dryness and stirred in dry hexane until a precipitate formed. The
orange solid was filtered off and dried in vacuo. Yield 0.093 g,
44%. Required for [C35H38ClRhSb2]·CH2Cl2: C, 46.7; H, 4.4%.
1
1.7 (d) [12H] (SbMe2) ppm. 13C{ H} NMR ((CD3)2CO): d 124.74–
130.70 (o-C6H4), 78.34 (d 15 Hz) (cod CH), 30.57 (SbCH2), 29.80
(cod CH2), 0.89 (SbMe) ppm. IR (Nujol mull): 1054 (BF4−) cm−1.
1
Found: C, 47.4; H, 4.1%. H NMR ((CD3)2CO, 300 K): d 7.60–
[Rh{Ph2Sb(CH2)3SbPh2}2]BF4. [Rh2Cl2(coe)4]
(0.064
g,
7.20 (m) [20H] (Ph), 5.43 (s) CH2Cl2, 4.20 (br) [4H] (cod CH), 2.43
(br) [4H] (cod CH2), 2.33 (br) [6H] (CH2), 1.78 (br) [4H] (cod CH2)
ppm. ES+ MS (MeCN): m/z 805 [Rh(cod){Ph2Sb(CH2)3SbPh2}]+.
Conductivity KM/X−1 cm2 mol−1 (10−3 mol dm−3 in CH2Cl2): 4.68.
0.09 mmol) and AgBF4 (0.043 g, 0.22 mmol) were dissolved in
degassed acetone (10 mL) and stirred for 45 min at RT, where
upon a white precipitate formed. After filtering, the orange
solution was added drop-wise to a solution of Ph2Sb(CH2)3SbPh2
(0.225 g, 0.38 mmol) in degassed toluene (15 mL). The deep
red solution was left to stir for 30 min, and reduced to dryness.
The residues were dissolved in minimum acetone, and Et2O
(10 mL) was added to precipitate a solid. The red solid was
filtered off and dried in vacuo. Yield 0.2 g, 81%. Required for
[C54H52BF4RhSb4]·CH2Cl2: C, 45.2; H, 3.7. Found: C, 45.4; H,
[Rh(cod){Me2Sb(CH2)3SbMe2}Cl]. Reaction as above, except
at room temperature using [Rh2Cl2(cod)2] and Me2Sb(CH2)3-
SbMe2. The orange precipitate was dried in vacuo. Yield 46%.
Required for [C15H30ClRhSb2]·2CH2Cl2: C, 26.8; H, 4.5%. Found:
1
C, 27.2; H, 5.0%. H NMR ((CD3)2CO): d 5.43 (s) CH2Cl2, 4.18
(br) [4H] (cod CH), 2.43 (br) [4H] (cod CH2), 2.32 (br) [6H]
(CH2), 1.76 (br) [4H] (cod CH2), 1.35–1.20 (m) [12H] (SbMe) ppm.
ES+ MS (MeCN): m/z 557 [Rh(cod){Me2Sb(CH2)3SbMe2}]+.
Conductivity KM/X−1 cm2 mol−1 (10−3 mol dm−3 in CH2Cl2): 2.25.
1
3.9%. H NMR ((CD3)2CO): d 6.8–7.5 (m) [40H] (Ph), 5.43 (s)
CH2Cl2, 2.3–2.7 (br) [12H] (CH2) ppm (CH2Cl2 solvent is also
1
evident). 13C{ H} NMR ((CD3)2CO): d 129.42–137.07 (Ph), 24.71
(CH2CH2CH2), 21.62 (SbCH2) ppm. ES+ MS (MeCN): m/z 1291
[Rh{Ph2Sb(CH2)3SbPh2}2]+, 1013 [Rh{Ph2Sb(CH2)3SbPh2}2
−
[Rh(cod){o-C6H4(CH2SbMe2)2}Cl]. Prepared at room tem-
perature as above using [Rh2Cl2(cod)2] and o-C6H4(CH2SbMe2)2.
Orange solid. Yield 40%. ES+ MS (MeCN): m/z 619 [Rh(cod){o-
SbPh2]+. IR (Nujol mull): 1064 (BF4−) cm−1.
[Rh(CO)(SbPh3)2Cl]. [Rh2Cl2(CO)4] (0.082 g, 0.21 mmol) and
SbPh3 (0.30 g, 0.92 mmol) were dissolved in dry CH2Cl2 (10 mL)
and stirred for 2 h. The reaction was monitored by solution IR
spectroscopy, and the reaction mixture was reduced to dryness and
the residues were stirred in dry hexane (30 mL) until a dark red
precipitate was formed. This was filtered off and the red solid was
dried in vacuo. Yield 0.2 g, 100%. Required for [C37H30ClORhSb2]:
1
C6H4(CH2SbMe2)2}]+. H NMR ((CD3)2CO): d 7.0–7.4 (m) [4H]
(o-C6H4), 4.18 (br) [4H] (cod CH), 2.40 (br) [4H] (cod CH2), 2.32
(br) [6H] (CH2), 1.75 (br) [4H] (cod CH2), 1.30, 1.40 (m) [12H]
(SbMe) ppm.
[Rh(cod){Ph2Sb(CH2)3SbPh2}]BF4. [Rh2Cl2(cod)2] (0.047 g,
0.095 mmol) and AgBF4 (0.043 g, 0.22 mmol) were dissolved
in degassed acetone (20 mL) and heated to reflux for 30 min,
where upon a white precipitate formed. The yellow solution was
1
C, 50.9; H, 3.5. Found: C, 50.6; H, 3.1%. H NMR (CDCl3): d
1
7.90–7.30 (m) [30H] (Ph) ppm. 13C{ H} NMR (CDCl3): d 184.3
4044 | Dalton Trans., 2006, 4039–4046
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(d) J = 57 Hz (CO), 134.9, 130.7, 128.9, 127.9 (Ph) ppm. ES+
MS (MeCN): m/z 837 [Rh(CO)(SbPh3)2]+. IR (CH2Cl2): 1967 (s)
(CO) cm−1. IR (Nujol mull): 1952 (s) (CO) cm−1. Conductivity
KM/X−1 cm2 mol−1 (10−3 mol dm−3 in CH2Cl2): 0.
(SbMe). ES+ MS (MeCN): found m/z = 947 [Rh(CO){o-
C6H4(CH2SbMe2)2}2]+. ES− MS (MeCN): found m/z = 229
[Rh(CO)2Cl2]−. IR (Nujol mull): 2075, 2007 (v br), 1974 (sh)
(CO) cm−1.
[Rh(CO){Ph2Sb(CH2)3SbPh2}2][Rh(CO)2Cl2]. Reaction
as
Iridium(I) compounds
above with [Rh2Cl2(CO)4] (0.049 g, 0.126 mmol) and Ph2Sb-
(CH2)3SbPh2 (0.15 g, 0.25 mmol). The orange precipitate was
dried in vacuo. Yield 0.13 g, 68%. Required for [C57H52Cl2O3-
Rh2Sb4]: C, 44.2; H, 3.3. Found: C, 43.4; H, 3.0%. 1H NMR
((CD3)2CO): d 7.60–7.40 (m) [20H] (Ph), 2.85 (bs) [4H] (CH2Sb),
[Ir(cod){Ph2Sb(CH2)3SbPh2}]BF4. [Ir2Cl2(cod)2] (0.0806 g,
0.12 mmol) and AgBF4 (0.0493 g, 0.253 mmol) were dissolved in
degassed acetone (10 mL) and heated gently for 30 min, whereupon
a white precipitate formed. After filtering, the yellow solution
was added drop-wise to a solution of Ph2Sb(CH2)3SbPh2 (0.15 g,
0.253 mmol) in degassed toluene (15 mL). The resulting pink
solution was stirred for 30 min at room temperature and reduced
in volume to ca. 2 mL whereupon a pink/orange solid formed.
This was then filtered off and dried in vacuo. Yield 0.18 g, 76%.
Required for [C35H38BF4IrSb2]: C, 42.8; H, 3.9. Found: C, 43.6;
1
2.05 (s) [2H] (CH2) ppm. 13C{ H} NMR (CDCl3): d 182.3 (d
71 Hz) ([Rh(CO)2Cl2]−), 136.1, 134.7, 131.2, 129.9 (Ph), 23.7
(CH2), 18.9 (CH2Sb) ppm. ES+ MS (MeCN): m/z 1289 [Rh-
{Ph2Sb(CH2)3SbPh2}2]+, 1317 [Rh(CO){Ph2Sb(CH2)3SbPh2}2]+.
ES− MS (MeCN): m/z 229 [Rh(CO)2Cl2]−. IR (CH2Cl2): 2068 (s),
1989 (m), 1968 (m) (CO) cm−1. IR (Nujol mull): 2058 (s), 1977
(s), 1953 (s) (CO) cm−1.
1
H, 4.1%. H NMR (CDCl3): d 7.0–7.6 (m) [20H] (Ph), 3.76 (s)
[4H] (cod CH), 2.59 (br) [8H] (cod CH2), 2.00–2.15 (m) [6H]
[Rh(CO){Ph2Sb(CH2)3SbPh2}2]Cl. A further two mol. equiv-
alents of Ph2Sb(CH2)3SbPh2 were added to the [Rh(CO){Ph2-
Sb(CH2)3SbPh2}2][Rh(CO)2Cl2] prepared above, in dry CH2Cl2,
and the reaction was stirred under argon for 12 h and the
progress was monitored by solution IR spectroscopy. An or-
ange solid was isolated. IR (CH2Cl2): 1966 (s) (CO) cm−1.
ES+ MS (MeCN): m/z 1289 [Rh{Ph2Sb(CH2)3SbPh2}2]+, 1317
[Rh(CO){Ph2Sb(CH2)3SbPh2}2]+.
1
(CH2) ppm. 13C{ H} NMR (CDCl3): d 128.22–133.40 (Ph), 63.77
(cod CH), 36.53 (cod CH2), 23.37 (CH2CH2CH2), 19.59 (SbCH2)
ppm. ES+ MS (MeCN): m/z 895 [Ir(cod){Ph2Sb(CH2)3SbPh2}]+.
IR (Nujol mull): 1064 (BF4−) cm−1.
[Ir(cod){o-C6H4(CH2SbMe2)2}]BF4. Method as above using
[Ir2Cl2(cod)2], AgBF4 and o-C6H4(CH2SbMe2)2. Yield 65%. Re-
quired for [C20H32BF4IrSb2]: 30.2; H, 4.1. Found: C, 30.2; H, 4.1%.
1H NMR ((CD3)2CO): d 7.2–7.7 (m) [4H] (o-C6H4), 3.8 (br) [8H]
(cod CH, SbCH2), 2.5 (br) [8H] (cod CH2), 1.4 (s) [12H] (SbMe)
[Rh(CO){Ph2Sb(CH2)3SbPh2}2]PF6. [Rh(CO){Ph2Sb(CH2)3-
SbPh2}2][Rh(CO)2Cl2] (0.067 g, 0.043 mmol), Ph2Sb(CH2)3SbPh2
(0.051 g, 0.0865 mmol) and NH4PF6 (0.016 g, 0.0865 mmol)
were dissolved in dry CH2Cl2 (20 mL). Solution IR spectroscopy
indicated that the reaction was complete after 5 min. The fine
white precipitate (NH4Cl) was removed by filtration and the
resultant orange solution was concentrated to ca. 1 mL. Et2O
(10 mL) was added to precipitate an orange solid, which
was isolated by filtration and dried in vacuo. Yield 60%. 1H
NMR (CDCl3): d 7.40–7.05 (m) [20H] (Ph), 1.90 (bs) [2H]
(CH2CH2), 1.80 (bs) [4H] (CH2Sb) ppm. ES+ MS (MeCN): m/z
1291 [Rh{Ph2Sb(CH2)3SbPh2}2]+, 1317 [Rh(CO){Ph2Sb(CH2)3-
SbPh2}2]+. IR (CH2Cl2): 1967 (s) (CO) cm−1. IR (Nujol mull):
1952 (s) (CO), 837 (s) m(PF6−), 557 (s) d(PF6−) cm−1.
1
ppm. 13C{ H} NMR ((CD3)2CO): d 126.4–136.7 (o-C6H4), 59.16
(cod CH), 33.60 (cod CH2), 24.73 (SbCH2), −4.87 (SbMe) ppm.
ES+ MS (MeCN): m/z 707 [Ir(cod){o-C6H4(CH2SbMe2)2}]+. IR
(Nujol mull): 1064 (BF4−) cm−1.
[Ir{Ph2Sb(CH2)3SbPh2}2]BF4. [Ir2(coe)4Cl2]
(0.08
g,
0.09 mmol) and AgBF4 (0.043 g, 0.22 mmol) were dissolved in
degassed acetone (10 mL) and stirred at RT for 1 h. The white
precipitate was filtered off and the orange solution was added
dropwise to a solution of Ph2Sb(CH2)3SbPh2 (0.225 g, 0.38 mmol)
in degassed toluene (10 mL). The reaction was stirred for 30 min
and then the reaction was pumped to dryness. The yellow residues
were dissolved in minimum acetone, and Et2O (10 mL) was
added to precipitate a solid. The yellow solid was isolated by
filtration and dried in vacuo. Yield 0.19 g, 72%. Required for
[C54H52BF4IrSb4]·CH2Cl2: C, 42.5; H, 3.5. Found: C, 41.9; H,
3.7%. 1H NMR ((CD3)2CO): d 7.0–7.4 (m) [40H] (Ph), 5.43
[Rh(CO){Me2Sb(CH2)3SbMe2}2][Rh(CO)2Cl2]. Method as
for [Rh(CO){Ph2Sb(CH2)3SbPh2}2][Rh(CO)2Cl2] above, except
the solutions were maintained at ∼ −15 ◦C with an ice–salt bath.
Orange/brown solid. Yield 50%. Required for [C17H36Cl2O3-
Rh2Sb4]: C, 19.4; H, 3.5; found: C, 20.2; H, 3.6%. 1H NMR
1
(s) CH2Cl2, 2.8 (br) [4H] (CH2), 2.3 (br) [8H] (CH2). 13C{ H}
NMR ((CD3)2CO): d 130.0–136.6 (Ph), 25.0 (CH2CH2CH2), 23.1
1
(CDCl3): d 1.8–1.3 (br) [6H] (CH2), 1.22 (s) [12H] (SbMe). 13C{ H}
(SbCH2). IR (Nujol mull): 1067 (BF4−) cm−1.
NMR (CDCl3, 250 K): d 193.0 (d 65 Hz) [Rh(CO){Me2Sb-
(CH2)3SbMe2}2]+, 181.7 (d 79 Hz) ([Rh(CO)2Cl2]−), 23.04
(CH2), 16.89 (CH2), −0.16 (SbMe). ES+ MS (MeCN): m/z
865 [Rh(CO){Me2Sb(CH2)3SbMe2}2.MeCN]+, 795 [Rh{Me2Sb-
(CH2)3SbMe2}2]+, 641 [Rh{Me2Sb(CH2)3SbMe2}2 − SbMe2]+.
IR (CH2Cl2): 2069, 1988, 1966 (CO) cm−1. IR (Nujol mull): 2047
(sh), 1953 (v br) (CO) cm−1.
X-Ray crystallography
Details of the crystallographic data collection and refinement
parameters are given in Table 2. Crystals of [Rh(CO){Ph2Sb-
(CH2)3SbPh2}2]PF6·3/4CH2Cl2 and [RhCl2{Ph2Sb(CH2)3SbPh2}-
{PhClSb(CH2)3SbClPh}]Cl·CHCl3 were obtained by diffusion
of hexane into a CH2Cl2 solution of the compound, or slow
evaporation of CHCl3 from a solution of the compound in the
glove box, respectively. Data collection used a Nonius Kappa CCD
diffractometer (T = 120 K) and with graphite-monochromated
[Rh(CO){o-C6H4(CH2SbMe2)2}2][Rh(CO)2Cl2]. Method as
above using [Rh2Cl2(CO)4] and o-C6H4(CH2SbMe2)2. Orange/
1
brown solid. Yield 55%. H NMR (CDCl3, 210 K): d 7.0–7.5
˚
(m) [8H] (o-C6H4), 3.3–3.5 (m) [8H] (CH2), 1.15–1.22 (m) [24H]
Mo-Ka X-radiation (k = 0.71073 A). Structure solution and
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Table 2 Crystallographic parameters
Complex
[Rh(CO){Ph2Sb(CH2)3SbPh2}2]PF6·3/4CH2Cl2
[RhCl2{Ph2Sb(CH2)3SbPh2}{PhClSb(CH2)3SbClPh}]Cl·CHCl3
Formula
M
C55.75H53.5Cl1.5F6OPRhSb4
1527.54
C43H43Cl8RhSb4
1433.28
Monoclinic
P21/c (no.14)
28.147(6)
10.9609(16)
15.724(3)
90
104.095(8)
90
4705.2(15)
4
3.096
0.089
31249
9970
505
0.1057
0.1508
0.1492
Crystal system
Space group
Triclinic
¯
P1 (no. 2)
˚
a/A
13.5141(10)
20.129(3)
21.133(3)
74.016(5)
80.152(7)
82.929(7)
5427.5(10)
4
2.426
0.065
94727
24949
˚
b/A
˚
c/A
a/◦
b/◦
c /◦
U/A
Z
3
˚
l(Mo-Ka)/mm−1
Rint
Total no. reflections
Unique reflections
No. of parameters
R1a [Io > 2r(Io)]
R1a [all data]
1265
0.0509
0.0824
0.0996
b
wR2 [Io > 2r(Io)]
b
wR2 [all data]
0.1109
0.1730
ꢀ
ꢀ
ꢀ
ꢀ
2
4 1/2
a R1 = ꢀFo − |Fcꢀi/ |Fo|. b wR2 = [ w(Fo − Fc2)2/ wFoi
] .
refinement were routine.34,35 Selected bond lengths and angles are
presented in Table 1 and the Fig. 2 caption.
CCDC reference numbers 604224 and 604225.
For crystallographic data in CIF or other electronic format see
DOI: 10.1039/b605198g
8 W. Levason, M. L. Matthews, G. Reid and M. Webster, Dalton Trans.,
2004, 554.
9 M. D. Brown, W. Levason, G. Reid and M. Webster, Dalton Trans.,
2006, 1667.
10 L. M. Vallarino, J. Chem. Soc., 1957, 2287.
11 S. Otto and A. Roodt, Inorg. Chim. Acta, 2002, 331, 199.
12 S. Otto and A. Roodt, Acta Crystallogr., Sect. C, 2002, 58, m565.
13 A. Kayan, J. C. Gallucci and A. Wojcicki, Inorg. Chem. Commun., 1998,
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Acknowledgements
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We thank the EPSRC for support and access to the EPSRC’s
Chemical Database Service at Daresbury. We also thank Johnson-
Matthey plc for loans of precious metal salts.
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